WorldWideScience

Sample records for vertical velocity field

  1. Some numerical calculations of the vertical velocity field in hurricanes

    OpenAIRE

    Krishnamurti, T. N.

    2011-01-01

    The commonly observed crescent-shaped geometry of the tangential wind field in hurricanes is imposed on the primitive equations of atmospheric motion, and solutions for the vertical velocity field are obtained. It is shown that the numerically computed vertical motion field exhibits a spiral form, very similar to what is observed in radar pictures in individual hurricanes. Aircraft flight data from the National Hurricane Research Project are utilized to carry out the numerical calculations i...

  2. Magnetic and velocity fields MHD flow of a stretched vertical ...

    African Journals Online (AJOL)

    Analytical solutions for heat and mass transfer by laminar flow of Newtonian, viscous, electrically conducting and heat generation/absorbing fluid on a continuously moving vertical permeable surface with buoyancy in the presence of a magnetic field and a first order chemical reaction are reported. The solutions for magnetic ...

  3. Superposed epoch analysis of vertical ion velocity, electron temperature, field-aligned current, and thermospheric wind in the dayside auroral region as observed by DMSP and CHAMP

    Science.gov (United States)

    Kervalishvili, G.; Lühr, H.

    2016-12-01

    This study reports on the results obtained by a superposed epoch analysis (SEA) method applied to the electron temperature, vertical ion velocity, field-aligned current (FAC), and thermospheric zonal wind velocity at high-latitudes in the Northern Hemisphere. The SEA study is performed in a magnetic latitude versus magnetic local time (MLat-MLT) frame. The obtained results are based on observations collected during the years 2001-2005 by the CHAMP and DMSP (F13 and F15) satellites. The dependence on interplanetary magnetic field (IMF) orientations is also investigated using data from the NASA/GSFC's OMNI database. Further, the obtained results are subdivided into three Lloyd seasons of 130 days each, which are defined as follows: local winter (1 January ± 65 days), combined equinoxes (1 April and 1 October ± 32days), and local summer (1 July ± 65 days). A period of 130 days is needed by the CHAMP satellite to pass through all local times. The time and location of the electron temperature peaks from CHAMP measurements near the cusp region are used as the reference parameter for the SEA method to investigate the relationship between the electron temperature and other ionospheric quantities. The SEA derived MLat profiles of the electron temperature show a seasonal dependence, increasing from winter to summer, as expected. But, the temperature rise (difference between the reference temperature peak and the background electron temperature) strongly decreases towards local summer. The SEA derived MLat profiles of the ion vertical velocity at DMSP altitude show the same seasonal behaviour as the electron temperature rice. There exists a clear linear relation between these two variables with a quiet large correlation coefficient value, >0.9. The SEA derived MLat profiles of both, thermospheric zonal wind velocity and FAC, show a clear IMF By orientation dependence for all local seasons. The zonal wind velocity is prominently directed towards west in the MLat-MLT frame

  4. Predicting vertical jump height from bar velocity.

    Science.gov (United States)

    García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

    2015-06-01

    The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s(-2)). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r(2) = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r(2) = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key pointsVertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer.The relationship between the point at which bar acceleration is less than -9.81 m·s(-2) and the real take-off is affected by the velocity of movement.Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance.

  5. On the measurement of vertical velocity by MST radar

    Science.gov (United States)

    Gage, K. S.

    1983-01-01

    An overview is presented of the measurement of atmospheric vertical motion utilizing the MST radar technique. Vertical motion in the atmosphere is briefly discussed as a function of scale. Vertical velocity measurement by MST radars is then considered from within the context of the expected magnitudes to be observed. Examples are drawn from published vertical velocity observations.

  6. Difference of horizontal-to-vertical spectral ratios of observed earthquakes and microtremors and its application to S-wave velocity inversion based on the diffuse field concept

    Science.gov (United States)

    Kawase, Hiroshi; Mori, Yuta; Nagashima, Fumiaki

    2018-01-01

    We have been discussing the validity of using the horizontal-to-vertical spectral ratios (HVRs) as a substitute for S-wave amplifications after Nakamura first proposed the idea in 1989. So far a formula for HVRs had not been derived that fully utilized their physical characteristics until a recent proposal based on the diffuse field concept. There is another source of confusion that comes from the mixed use of HVRs from earthquake and microtremors, although their wave fields are hardly the same. In this study, we compared HVRs from observed microtremors (MHVR) and those from observed earthquake motions (EHVR) at one hundred K-NET and KiK-net stations. We found that MHVR and EHVR share similarities, especially until their first peak frequency, but have significant differences in the higher frequency range. This is because microtremors mainly consist of surface waves so that peaks associated with higher modes would not be prominent, while seismic motions mainly consist of upwardly propagating plain body waves so that higher mode resonances can be seen in high frequency. We defined here the spectral amplitude ratio between them as EMR and calculated their average. We categorize all the sites into five bins by their fundamental peak frequencies in MHVR. Once we obtained EMRs for five categories, we back-calculated EHVRs from MHVRs, which we call pseudo-EHVRs (pEHVR). We found that pEHVR is much closer to EHVR than MHVR. Then we use our inversion code to invert the one-dimensional S-wave velocity structures from EHVRs based on the diffuse field concept. We also applied the same code to pEHVRs and MHVRs for comparison. We found that pEHVRs yield velocity structures much closer to those by EHVRs than those by MHVRs. This is natural since what we have done up to here is circular except for the average operation in EMRs. Finally, we showed independent examples of data not used in the EMR calculation, where better ground structures were successfully identified from p

  7. Orthogonal Vertical Velocity Dispersion Distributions Produced by Bars

    Science.gov (United States)

    Du, Min; Shen, Juntai; Debattista, Victor P.; de Lorenzo-Cáceres, Adriana

    2017-02-01

    In barred galaxies, the contours of stellar velocity dispersions (σ) are generally expected to be oval and aligned with the orientation of bars. However, many double-barred (S2B) galaxies exhibit distinct σ peaks on the minor axis of the inner bar, which we termed “σ-humps,” while two local σ minima are present close to the ends of inner bars, I.e., “σ-hollows.” Analysis of numerical simulations shows that {σ }z-humps or hollows should play an important role in generating the observed σ-humps+hollows in low-inclination galaxies. In order to systematically investigate the properties of {σ }z in barred galaxies, we apply the vertical Jeans equation to a group of well-designed three-dimensional bar+disk(+bulge) models. A vertically thin bar can lower {σ }z along the bar and enhance it perpendicular to the bar, thus generating {σ }z-humps+hollows. Such a result suggests that {σ }z-humps+hollows can be generated by the purely dynamical response of stars in the presence of a sufficiently massive, vertically thin bar, even without an outer bar. Using self-consistent N-body simulations, we verify the existence of vertically thin bars in the nuclear-barred and S2B models that generate prominent σ-humps+hollows. Thus, the ubiquitous presence of σ-humps+hollows in S2Bs implies that inner bars are vertically thin. The addition of a bulge makes the {σ }z-humps more ambiguous and thus tends to somewhat hide the {σ }z-humps+hollows. We show that {σ }z may be used as a kinematic diagnostic of stellar components that have different thicknesses, providing a direct perspective on the morphology and thickness of nearly face-on bars and bulges with integral field unit spectroscopy.

  8. Diagnosis of hydrometeor profiles from area-mean vertical-velocity data

    Science.gov (United States)

    Braun, Scott A.; Houze, Robert A., Jr.

    1995-01-01

    A simple one-dimensional microphysical retrieval model is developed for estimating vertical profiles of liquid and frozen hydrometeor mixing ratios from observed vertical profiles of area-mean vertical velocity in regions of convective and/or stratiform precipitation. The mean vertical-velocity profiles can be obtained from Doppler radar (single and dual) or other means. The one-dimensional results are shown to be in good agreement with two-dimensional microphysical fields from a previous study. Sensitivity tests are performed.

  9. Parachute landing fall characteristics at three realistic vertical descent velocities.

    Science.gov (United States)

    Whitting, John W; Steele, Julie R; Jaffrey, Mark A; Munro, Bridget J

    2007-12-01

    Although parachute landing injuries are thought to be due in part to a lack of exposure of trainees to realistic descent velocities during parachute landing fall (PLF) training, no research has systematically investigated whether PLF technique is affected by different vertical descent conditions, with standardized and realistic conditions of horizontal drift. This study was designed to determine the effects of variations in vertical descent velocity on PLF technique. Kinematic, ground reaction force, and electromyographic data were collected and analyzed for 20 paratroopers while they performed parachute landings, using a custom-designed monorail apparatus, with a constant horizontal drift velocity (2.3 m x s(-1)) and at three realistic vertical descent velocities: slow (2.1 m x s(-1)), medium (3.3 m x s(-1)), and fast (4.6 m x s(-1)). Most biomechanical variables characterizing PLF technique were significantly affected by descent velocity. For example, at the fast velocity, the subjects impacted the ground with 123 degrees of plantar flexion and generated ground reaction forces averaging 13.7 times body weight, compared to 106 degrees and 6.1 body weight, respectively, at the slow velocity. Furthermore, the subjects activated their antigravity extensor muscles earlier during the fast velocity condition to eccentrically control the impact absorption. As vertical descent rates increased, the paratroopers displayed a significantly different strategy when performing the PLF. It is therefore recommended that PLF training programs include ground training activities with realistic vertical descent velocities to better prepare trainees to withstand the impact forces associated with initial aerial descents onto the Drop Zone and, ultimately, minimize the potential for injury.

  10. Kriging interpolating cosmic velocity field

    Science.gov (United States)

    Yu, Yu; Zhang, Jun; Jing, Yipeng; Zhang, Pengjie

    2015-10-01

    Volume-weighted statistics of large-scale peculiar velocity is preferred by peculiar velocity cosmology, since it is free of the uncertainties of galaxy density bias entangled in observed number density-weighted statistics. However, measuring the volume-weighted velocity statistics from galaxy (halo/simulation particle) velocity data is challenging. Therefore, the exploration of velocity assignment methods with well-controlled sampling artifacts is of great importance. For the first time, we apply the Kriging interpolation to obtain the volume-weighted velocity field. Kriging is a minimum variance estimator. It predicts the most likely velocity for each place based on the velocity at other places. We test the performance of Kriging quantified by the E-mode velocity power spectrum from simulations. Dependences on the variogram prior used in Kriging, the number nk of the nearby particles to interpolate, and the density nP of the observed sample are investigated. First, we find that Kriging induces 1% and 3% systematics at k ˜0.1 h Mpc-1 when nP˜6 ×1 0-2(h-1 Mpc )-3 and nP˜6 ×1 0-3(h-1 Mpc )-3 , respectively. The deviation increases for decreasing nP and increasing k . When nP≲6 ×1 0-4(h-1 Mpc )-3 , a smoothing effect dominates small scales, causing significant underestimation of the velocity power spectrum. Second, increasing nk helps to recover small-scale power. However, for nP≲6 ×1 0-4(h-1 Mpc )-3 cases, the recovery is limited. Finally, Kriging is more sensitive to the variogram prior for a lower sample density. The most straightforward application of Kriging on the cosmic velocity field does not show obvious advantages over the nearest-particle method [Y. Zheng, P. Zhang, Y. Jing, W. Lin, and J. Pan, Phys. Rev. D 88, 103510 (2013)] and could not be directly applied to cosmology so far. However, whether potential improvements may be achieved by more delicate versions of Kriging is worth further investigation.

  11. Orographic precipitation and vertical velocity characteristics from drop size and fall velocity spectra observed by disdrometers

    Science.gov (United States)

    Lee, Dong-In; Kim, Dong-Kyun; Kim, Ji-Hyeon; Kang, Yunhee; Kim, Hyeonjoon

    2017-04-01

    During a summer monsoon season each year, severe weather phenomena caused by front, mesoscale convective systems, or typhoons often occur in the southern Korean Peninsula where is mostly comprised of complex high mountains. These areas play an important role in controlling formation, amount, and distribution of rainfall. As precipitation systems move over the mountains, they can develop rapidly and produce localized heavy rainfall. Thus observational analysis in the mountainous areas is required for studying terrain effects on the rapid rainfall development and its microphysics. We performed intensive field observations using two s-band operational weather radars around Mt. Jiri (1950 m ASL) during summertime on June and July in 2015-2016. Observation data of DSD (Drop Size Distribution) from Parsivel disdrometer and (w component) vertical velocity data from ultrasonic anemometers were analyzed for Typhoon Chanhom on 12 July 2015 and the heavy rain event on 1 July 2016. During the heavy rain event, a dual-Doppler radar analysis using Jindo radar and Gunsan radar was also conducted to examine 3-D wind fields and vertical structure of reflectivity in these areas. For examining up-/downdrafts in the windward or leeward side of Mt. Jiri, we developed a new scheme technique to estimate vertical velocities (w) from drop size and fall velocity spectra of Parsivel disdrometers at different stations. Their comparison with the w values observed by the 3D anemometer showed quite good agreement each other. The Z histogram with regard to the estimated w was similar to that with regard to R, indicating that Parsivel-estimated w is quite reasonable for classifying strong and weak rain, corresponding to updraft and downdraft, respectively. Mostly, positive w values (upward) were estimated in heavy rainfall at the windward side (D1 and D2). Negative w values (downward) were dominant even during large rainfall at the leeward side (D4). For D1 and D2, the upward w percentages were

  12. Muscle activation history at different vertical jumps and its influence on vertical velocity

    NARCIS (Netherlands)

    Kopper, Bence; Csende, Zsolt; Safar, Sandor; Hortobagyi, Tibor; Tihanyi, Jozsef

    In the present study we investigated displacement, time, velocity and acceleration history of center of mass (COM) and electrical activity of knee extensors to estimate the dominance of the factors influencing the vertical velocity in squat jumps (SJs), countermovement jumps (CMJs) and drop jumps

  13. Wind Velocity Vertical Extrapolation by Extended Power Law

    Directory of Open Access Journals (Sweden)

    Zekai Şen

    2012-01-01

    Full Text Available Wind energy gains more attention day by day as one of the clean renewable energy resources. We predicted wind speed vertical extrapolation by using extended power law. In this study, an extended vertical wind velocity extrapolation formulation is derived on the basis of perturbation theory by considering power law and Weibull wind speed probability distribution function. In the proposed methodology not only the mean values of the wind speeds at different elevations but also their standard deviations and the cross-correlation coefficient between different elevations are taken into consideration. The application of the presented methodology is performed for wind speed measurements at Karaburun/Istanbul, Turkey. At this location, hourly wind speed measurements are available for three different heights above the earth surface.

  14. Terminal velocity of a shuttlecock in vertical fall

    Science.gov (United States)

    Peastrel, Mark; Lynch, Rosemary; Armenti, Angelo

    1980-07-01

    We have performed a straightforward vertical fall experiment for a case where the effects of air resistance are important and directly measurable. Using a commonly available badminton shuttlecock, a tape measure, and a millisecond timer, the times required for the shuttlecock to fall given distances (up to almost ten meters) were accurately measured. The experiment was performed in an open stairwell. The experimental data was compared to the predictions of several models. The best fit was obtained with the model which assumes a resistive force quadratic in the instantaneous speed of the falling object. This model was fitted to the experimental data enabling us to predict the terminal velocity of the shuttlecock (6.80 m/sec). The results indicate that, starting from rest, the vertically falling shuttlecock achieves 99% of its terminal velocity in 1.84 sec, after falling 9.2 m. The relative ease in collecting the data, as well as the excellent agreement with theory, make this an ideal experiment for use in physics courses at a variety of levels.

  15. New GNSS velocity field and preliminary velocity model for Ecuador

    Science.gov (United States)

    Luna-Ludeña, Marco P.; Staller, Alejandra; Gaspar-Escribano, Jorge M.; Belén Benito, M.

    2016-04-01

    In this work, we present a new preliminary velocity model of Ecuador based on the GNSS data of the REGME network (continuous monitoring GNSS network). To date, there is no velocity model available for the country. The only existing model in the zone is the regional model VEMOS2009 for South America and Caribbean (Drewes and Heidbach, 2012). This model was developed from the SIRGAS station positions, the velocities of the SIRGAS-CON stations, and several geodynamics projects performed in the region. Just two continuous GNSS (cGNSS) stations of Ecuador were taking into account in the VEMOS2009 model. The first continuous station of the REGME network was established in 2008. At present, it is composed by 32 continuous GNSS stations, covering the country. All the stations provided data during at least two years. We processed the data of the 32 GNSS stations of REGME for the 2008-2014 period, as well as 20 IGS stations in order to link to the global reference frame IGb08 (ITRF2008). GPS data were processed using Bernese 5.0 software (Dach et al., 2007). We obtained and analyzed the GNSS coordinate time series of the 32 REGME stations and we calculated the GPS-derived horizontal velocity field of the country. Velocities in ITRF2008 were transformed into a South American fixed reference frame, using the Euler pole calculated from 8 cGNSS stations throughout this plate. Our velocity field is consistent with the tectonics of the country and contributes to a better understanding of it. From the horizontal velocity field, we determined a preliminary model using the kriging geostatistical technique. To check the results we use the cross-validation method. The differences between the observed and estimated values range from ± 5 mm. This is a new velocity model obtained from GNSS data for Ecuador.

  16. Velocity measurements in the wake of laboratory-scale vertical axis turbines and rotating circular cylinders

    Science.gov (United States)

    Araya, Daniel; Dabiri, John

    2014-11-01

    We present experimental data to compare the wake characteristics of a laboratory-scale vertical-axis turbine with that of a rotating circular cylinder. The cylinder is constructed to have the same diameter and height as the turbine in order to provide a comparison that is independent of the tunnel boundary conditions. Both the turbine and cylinder are motor-driven to tip-speed ratios based on previous experiments. An analysis of the effect of the motor-driven flow is also presented. These measurements are relevant for exploring the complex structure of the vertical axis turbine wake relative to the canonical wake of a circular cylinder. 2D particle image velocimetry is used to measure the velocity field in a two-dimensional plane normal to the axis of rotation. This velocity field is then used to compare time-averaged streamwise velocity, phase-averaged vorticity, and the velocity power spectrum in the wake of the two configurations. The results give insight into the extent to which solid cylinders could be used as a simplified model of the flow around vertical axis turbines in computational simulations, especially for turbine array optimization.

  17. Vertical velocity distribution in open-channel flow with rigid vegetation.

    Science.gov (United States)

    Zhu, Changjun; Hao, Wenlong; Chang, Xiangping

    2014-01-01

    In order to experimentally investigate the effects of rigid vegetation on the characteristics of flow, the vegetations were modeled by rigid cylindrical rod. Flow field is measured under the conditions of submerged rigid rod in flume with single layer and double layer vegetations. Experiments were performed for various spacings of the rigid rods. The vegetation models were aligned with the approaching flow in a rectangular channel. Vertical distributions of time-averaged velocity at various streamwise distances were evaluated using an acoustic Doppler velocimeter (ADV). The results indicate that, in submerged conditions, it is difficult to described velocity distribution along the entire depth using unified function. The characteristic of vertical distribution of longitudinal velocity is the presence of inflection. Under the inflection, the line is convex and groove above inflection. The interaction of high and low momentum fluids causes the flow to fold and creates strong vortices within each mixing layer. Understanding the flow phenomena in the area surrounding the tall vegetation, especially in the downstream region, is very important when modeling or studying the riparian environment. ADV measures of rigid vegetation distribution of the flow velocity field can give people a new understanding.

  18. Using Smartphone Pressure Sensors to Measure Vertical Velocities of Elevators, Stairways, and Drones

    Science.gov (United States)

    Monteiro, Martín; Martí, Arturo C.

    2017-01-01

    We measure the vertical velocities of elevators, pedestrians climbing stairs, and drones (flying unmanned aerial vehicles), by means of smartphone pressure sensors. The barometric pressure obtained with the smartphone is related to the altitude of the device via the hydrostatic approximation. From the altitude values, vertical velocities are…

  19. The Effect of Atmospheric Cooling on Vertical Velocity Dispersion and Density Distribution of Brown Dwarfs

    Science.gov (United States)

    Ryan, Russell E., Jr.; Thorman, Paul A.; Schmidt, Sarah J.; Cohen, Seth H.; Hathi, Nimish P.; Holwerda, Benne W.; Lunine, Jonathan I.; Pirzkal, Nor; Windhorst, Rogier A.; Young, Erick

    2017-09-01

    We present a Monte Carlo simulation designed to predict the vertical velocity dispersion of brown dwarfs in the Milky Way. We show that since these stars are constantly cooling, the velocity dispersion has a noticeable trend with the spectral type. With realistic assumptions for the initial mass function, star formation history, and the cooling models, we show that the velocity dispersion is roughly consistent with what is observed for M dwarfs, decreases to cooler spectral types, and increases again for the coolest types in our study (˜T9). We predict a minimum in the velocity dispersions for L/T transition objects, however, the detailed properties of the minimum predominately depend on the star formation history. Since this trend is due to brown dwarf cooling, we expect that the velocity dispersion as a function of spectral type should deviate from the constancy around the hydrogen-burning limit. We convert from velocity dispersion to vertical scale height using standard disk models and present similar trends in disk thickness as a function of spectral type. We suggest that future, wide-field photometric and/or spectroscopic missions may collect sizable samples of distant (˜ 1 kpc) dwarfs that span the hydrogen-burning limit. As such, we speculate that such observations may provide a unique way of constraining the average spectral type of hydrogen burning. Support for program #13266 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under the NASA contract NAS 5-26555.

  20. Vertical Velocities in Cumulus Convection: Implications for Climate and Prospects for Realistic Simulation at Cloud Scale

    Science.gov (United States)

    Donner, Leo

    2014-05-01

    Cumulus mass fluxes are essential controls on the interactions between cumulus convection and large-scale flows. Cumulus parameterizations have generally been built around them, and these parameterizations are basic components of climate models. Several important questions in climate science depend also on cumulus vertical velocities. Interactions between aerosols and convection comprise a prominent example, and scale-aware cumulus parameterizations that require explicit information about cumulus areas are another. Basic progress on these problems requires realistic characterization of cumulus vertical velocities from observations and models. Recent deployments of dual-Doppler radars are providing unprecedented observations, which can be compared against cloud-resolving models (CRMs). The CRMs can subsequently be analyzed to develop and evaluate parameterizations of vertical velocities in climate models. Vertical velocities from several cloud models will be compared against observations in this presentation. CRM vertical velocities will be found to depend strongly on model resolution and treatment of sub-grid turbulence and microphysics. Although many current state-of-science CRMs do not simulate vertical velocities well, recent experiments with these models suggest that with appropriate treatments of sub-grid turbulence and microphysics robustly realistic modeling of cumulus vertical velocities is possible.

  1. Diagnosing ocean vertical velocities off New Caledonia from a SPRAY glider

    Science.gov (United States)

    Fuda, Jean-Luc; Marin, Frédéric; Durand, Fabien; Terre, Thierry

    2013-04-01

    A SPRAY glider has been operated in the Coral Sea (South-Western tropical Pacific ocean) since 2011, with the primary goal of monitoring the boundary currents and jets. In this presentation, we will describe how oceanic vertical velocities can be estimated from SPRAY glider measurements, with application to the observation of internal waves off New Caledonia in May-June 2012. Pressure measurements by the glider allow estimating the vertical velocities of the glider (relative to ocean bottom) at each time. These vertical velocities are the sum of the vertical velocities of the glider relative to the water body (governed by the laws of motion of the glider) and of the oceanic vertical velocities (due to ocean internal dynamics). If we solve the laws of motion of the glider (via an adequate flight model), we can thus retrieve oceanic vertical velocities. On account of their small magnitude, the retrieval of ocean vertical velocities would be tricky - if not impossible - through other conventional instruments such as ADCPs. Following a couple of similar previous studies on the SLOCUM and SEAGLIDER gliders, we describe a simplified flight model for the SPRAY glider. This model has three parameters that only depend on the characteristics of the glider: the compressibility and thermal expansion coefficients (that are constant) and the drag coefficient (that is allowed to change dive after dive, because of potential fouling of the hull). We estimate these parameters under the assumption that the absolute vertical water velocity average to zero over a long enough spatio-temporal window (typically: a profile or a group of profiles). Unlike previous studies, our flight model takes into account the vehicle roll to assess its impact on the flight model and oceanic vertical velocity retrieval. We apply this approach to a 40-day/250 dives/800km mission performed in May-June 2012 along 167°E south of New Caledonia. Dramatic water vertical velocities variations (up to 3-4 cm

  2. Velocity field calculation for non-orthogonal numerical grids

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-03-01

    -orthogonal grid, Darcy velocity components are rigorously derived in this study from normal fluxes to cell faces, which are assumed to be provided by or readily computed from porous-medium simulation code output. The normal fluxes are presumed to satisfy mass balances for every computational cell, and if so, the derived velocity fields are consistent with these mass balances. Derivations are provided for general two-dimensional quadrilateral and three-dimensional hexagonal systems, and for the commonly encountered special cases of perfectly vertical side faces in 2D and 3D and a rectangular footprint in 3D.

  3. Intraseasonal vertical velocity variation caused by the equatorial wave in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Horii, T.; Masumoto, Y.; Ueki, I.; PrasannaKumar, S.; Mizuno, K.

    for African-Asian-Australian Monsoon Analysis and Prediction, in October-November 2006. Using an array of four subsurface moored acoustic Doppler current profilers, we estimated vertical velocity by applying the continuity equation. Results indicated...

  4. Estimates of vertical velocities and eddy coefficients in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.; Sastry, J.S.

    Vertical velocities and eddy coefficients in the intermediate depths of the Bay of Bengal are calculated from mean hydrographic data for 300 miles-squares. The linear current density (sigma- O) versus log-depth plots show steady balance between...

  5. Determination of vertical velocities in the equatorial part of the western Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Bahulayan, N.; Varadachari, V.V.R.

    Using steady state two-dimensional turbulent diffusion equations of salt and heat some important characteristics of vertical circulation in the equatorial part of the Indian Ocean have been evaluated and discussed. Upwelling and sinking velocities...

  6. Vertically Integrated Multiple Nanowire Field Effect Transistor.

    Science.gov (United States)

    Lee, Byung-Hyun; Kang, Min-Ho; Ahn, Dae-Chul; Park, Jun-Young; Bang, Tewook; Jeon, Seung-Bae; Hur, Jae; Lee, Dongil; Choi, Yang-Kyu

    2015-12-09

    A vertically integrated multiple channel-based field-effect transistor (FET) with the highest number of nanowires reported ever is demonstrated on a bulk silicon substrate without use of wet etching. The driving current is increased by 5-fold due to the inherent vertically stacked five-level nanowires, thus showing good feasibility of three-dimensional integration-based high performance transistor. The developed fabrication process, which is simple and reproducible, is used to create multiple stiction-free and uniformly sized nanowires with the aid of the one-route all-dry etching process (ORADEP). Furthermore, the proposed FET is revamped to create nonvolatile memory with the adoption of a charge trapping layer for enhanced practicality. Thus, this research suggests an ultimate design for the end-of-the-roadmap devices to overcome the limits of scaling.

  7. The Vertical Variation of HI Velocity Dispersion in Disk Galaxies

    NARCIS (Netherlands)

    Peters, Stephan Pieter Cornelis; Freeman, Ken; van der Kruit, Pieter C.

    2010-01-01

    One of the key assumptions in dynamical applications of the HI velocity dispersion in disk galaxies (e.g. to the flattening of the dark halo) has always been the isothermal nature of the HI distribution. There is no physical reason for this assumption: it is made because until now it has not been

  8. Evaluation of gridded scanning ARM cloud radar reflectivity observations and vertical doppler velocity retrievals

    Science.gov (United States)

    Lamer, K.; Tatarevic, A.; Jo, I.; Kollias, P.

    2014-04-01

    The scanning Atmospheric Radiation Measurement (ARM) cloud radars (SACRs) provide continuous atmospheric observations aspiring to capture the 3-D cloud-scale structure. Sampling clouds in 3-D is challenging due to their temporal-spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a suggested scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range-Height Indicator - CW-RHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Southern Great Plains and Cape Cod sites are post-processed (detection mask, gaseous attenuation correction, insect filtering and velocity de-aliasing). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimensions. Next the Cartesian-gridded Doppler velocity fields are decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith-pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D cloud dynamical representations up to 25-30 degrees off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics and anisotropy and lead to more realistic 3-D radiative transfer calculations.

  9. Cloud base vertical velocity statistics: a comparison between an atmospheric mesoscale model and remote sensing observations

    Directory of Open Access Journals (Sweden)

    J. Tonttila

    2011-09-01

    Full Text Available The statistics of cloud base vertical velocity simulated by the non-hydrostatic mesoscale model AROME are compared with Cloudnet remote sensing observations at two locations: the ARM SGP site in central Oklahoma, and the DWD observatory at Lindenberg, Germany. The results show that AROME significantly underestimates the variability of vertical velocity at cloud base compared to observations at their nominal resolution; the standard deviation of vertical velocity in the model is typically 4–8 times smaller than observed, and even more during the winter at Lindenberg. Averaging the observations to the horizontal scale corresponding to the physical grid spacing of AROME (2.5 km explains 70–80 % of the underestimation by the model. Further averaging of the observations in the horizontal is required to match the model values for the standard deviation in vertical velocity. This indicates an effective horizontal resolution for the AROME model of at least 10 km in the presented case. Adding a TKE-term on the resolved grid-point vertical velocity can compensate for the underestimation, but only for altitudes below approximately the boundary layer top height. The results illustrate the need for a careful consideration of the scales the model is able to accurately resolve, as well as for a special treatment of sub-grid scale variability of vertical velocities in kilometer-scale atmospheric models, if processes such as aerosol-cloud interactions are to be included in the future.

  10. Turbulence velocity profiling for high sensitivity and vertical-resolution atmospheric characterization with Stereo-SCIDAR

    Science.gov (United States)

    Osborn, J.; Butterley, T.; Townson, M. J.; Reeves, A. P.; Morris, T. J.; Wilson, R. W.

    2017-02-01

    As telescopes become larger, into the era of ˜40 m Extremely Large Telescopes, the high-resolution vertical profile of the optical turbulence strength is critical for the validation, optimization and operation of optical systems. The velocity of atmospheric optical turbulence is an important parameter for several applications including astronomical adaptive optics systems. Here, we compare the vertical profile of the velocity of the atmospheric wind above La Palma by means of a comparison of Stereo-SCIntillation Detection And Ranging (Stereo-SCIDAR) with the Global Forecast System models and nearby balloon-borne radiosondes. We use these data to validate the automated optical turbulence velocity identification from the Stereo-SCIDAR instrument mounted on the 2.5 m Isaac Newton Telescope, La Palma. By comparing these data we infer that the turbulence velocity and the wind velocity are consistent and that the automated turbulence velocity identification of the Stereo-SCIDAR is precise. The turbulence velocities can be used to increase the sensitivity of the turbulence strength profiles, as weaker turbulence that may be misinterpreted as noise can be detected with a velocity vector. The turbulence velocities can also be used to increase the altitude resolution of a detected layer, as the altitude of the velocity vectors can be identified to a greater precision than the native resolution of the system. We also show examples of complex velocity structure within a turbulent layer caused by wind shear at the interface of atmospheric zones.

  11. The elastic wave velocity response of methane gas hydrate formation in vertical gas migration systems

    Science.gov (United States)

    Bu, Q. T.; Hu, G. W.; Ye, Y. G.; Liu, C. L.; Li, C. F.; Best, A. I.; Wang, J. S.

    2017-06-01

    Knowledge of the elastic wave velocities of hydrate-bearing sediments is important for geophysical exploration and resource evaluation. Methane gas migration processes play an important role in geological hydrate accumulation systems, whether on the seafloor or in terrestrial permafrost regions, and their impact on elastic wave velocities in sediments needs further study. Hence, a high-pressure laboratory apparatus was developed to simulate natural continuous vertical migration of methane gas through sediments. Hydrate saturation (S h) and ultrasonic P- and S-wave velocities (V p and V s) were measured synchronously by time domain reflectometry (TDR) and by ultrasonic transmission methods respectively during gas hydrate formation in sediments. The results were compared to previously published laboratory data obtained in a static closed system. This indicated that the velocities of hydrate-bearing sediments in vertical gas migration systems are slightly lower than those in closed systems during hydrate formation. While velocities increase at a constant rate with hydrate saturation in the closed system, P-wave velocities show a fast-slow-fast variation with increasing hydrate saturation in the vertical gas migration system. The observed velocities are well described by an effective-medium velocity model, from which changing hydrate morphology was inferred to cause the fast-slow-fast velocity response in the gas migration system. Hydrate forms firstly at the grain contacts as cement, then grows within the pore space (floating), then finally grows into contact with the pore walls again. We conclude that hydrate morphology is the key factor that influences the elastic wave velocity response of methane gas hydrate formation in vertical gas migration systems.

  12. Role of Vertical Jumps and Anthropometric Variables in Maximal Kicking Ball Velocities in Elite Soccer Players

    Directory of Open Access Journals (Sweden)

    Rodríguez-Lorenzo Lois

    2016-12-01

    Full Text Available Kicking is one of the most important skills in soccer and the ability to achieve ma ximal kicking velocity with both legs leads to an advantage for the soccer player. This study examined the relationship be tween kicking ball velocity with both legs using anthropometric measurements and vertical jumps (a squat jump (SJ; a countermovement jump without (CMJ and with the arm swing (CMJA and a reactive jump (RJ. Anthropome tric measurements did not correlate with kicking ball velocity. Vertical jumps correlated significantly with kicking ball velocity using the dominant leg only (r = .47, r = .58, r = .44, r = .51, for SJ, CMJ, CMJA and RJ, respectively . Maximal kicking velocity with the dominant leg was significantly higher than with the non-dominant leg (t = 18.0 4, p < 0.001. Our results suggest that vertical jumps may be an optimal test to assess neuromuscular skills involved in kicking at maximal speed. Lack of the relationship between vertical jumps and kicking velocity with the non-dominant leg may reflect a difficulty to exhibit the neuromuscular skills during dominant leg kicking.

  13. Vertical rise velocity of equatorial plasma bubbles estimated from Equatorial Atmosphere Radar (EAR) observations and HIRB model simulations

    Science.gov (United States)

    Tulasi Ram, S.; Ajith, K. K.; Yokoyama, T.; Yamamoto, M.; Niranjan, K.

    2017-06-01

    The vertical rise velocity (Vr) and maximum altitude (Hm) of equatorial plasma bubbles (EPBs) were estimated using the two-dimensional fan sector maps of 47 MHz Equatorial Atmosphere Radar (EAR), Kototabang, during May 2010 to April 2013. A total of 86 EPBs were observed out of which 68 were postsunset EPBs and remaining 18 EPBs were observed around midnight hours. The vertical rise velocities of the EPBs observed around the midnight hours are significantly smaller ( 26-128 m/s) compared to those observed in postsunset hours ( 45-265 m/s). Further, the vertical growth of the EPBs around midnight hours ceases at relatively lower altitudes, whereas the majority of EPBs at postsunset hours found to have grown beyond the maximum detectable altitude of the EAR. The three-dimensional numerical high-resolution bubble (HIRB) model with varying background conditions are employed to investigate the possible factors that control the vertical rise velocity and maximum attainable altitudes of EPBs. The estimated rise velocities from EAR observations at both postsunset and midnight hours are, in general, consistent with the nonlinear evolution of EPBs from the HIRB model. The smaller vertical rise velocities (Vr) and lower maximum altitudes (Hm) of EPBs during midnight hours are discussed in terms of weak polarization electric fields within the bubble due to weaker background electric fields and reduced background ion density levels.type="synopsis">type="main">Plain Language SummaryEquatorial plasma bubbles are plasma density irregularities in the ionosphere. The radio waves passing through these irregular density structures undergo severe degradation/scintillation that could cause severe disruption of satellite-based communication and augmentation systems such as GPS navigation. These bubbles develop at geomagnetic equator, grow vertically, and elongate along the field lines to latitudes away from the equator. The knowledge on bubble rise velocities and their maximum attainable

  14. Using smartphones' pressure sensors to measure vertical velocities in elevators, stairways and drones

    CERN Document Server

    Monteiro, Martin

    2016-01-01

    By means of smartphones' pressure sensors we measure vertical velocities of elevators, pedestrians climbing stairways and flying unmanned aerial vehicles (or \\textit{drones}). The barometric pressure obtained with the smartphone is related, thanks to the hydrostatic approximation, to the altitude of the device. From the altitude values, the vertical velocity is accordingly derived. The approximation considered is valid in the first hundreds meters of the inner layers of the atmosphere. Simultaneously to the pressure, the acceleration values, reported by the buit-in accelerometers, are also recorded. Integrating numerically the acceleration, vertical velocity and altitude are also obtained. We show that data obtained with the pressure sensor is considerable less noisy than that obtained with the accelerometer in the experiments proposed here. Accumulatioin of errors are also evident in the numerical integration of the acceleration values. The comparison with reference values taken from the architectural plans ...

  15. Lagrangian temperature and vertical velocity fluctuations due to gravity waves in the lower stratosphere

    Science.gov (United States)

    Podglajen, Aurélien; Hertzog, Albert; Plougonven, Riwal; Legras, Bernard

    2016-04-01

    Wave-induced Lagrangian fluctuations of temperature and vertical velocity in the lower stratosphere are quantified using measurements from superpressure balloons (SPBs). Observations recorded every minute along SPB flights allow the whole gravity wave spectrum to be described and provide unprecedented information on both the intrinsic frequency spectrum and the probability distribution function of wave fluctuations. The data set has been collected during two campaigns coordinated by the French Space Agency in 2010, involving 19 balloons over Antarctica and 3 in the deep tropics. In both regions, the vertical velocity distributions depart significantly from a Gaussian behavior. Knowledge on such wave fluctuations is essential for modeling microphysical processes along Lagrangian trajectories. We propose a new simple parameterization that reproduces both the non-Gaussian distribution of vertical velocities (or heating/cooling rates) and their observed intrinsic frequency spectrum.

  16. Personal Exposure to Contaminant Sources in a Uniform Velocity Field

    DEFF Research Database (Denmark)

    Brohus, Henrik; Nielsen, Peter V.

    The objective of this study has been to determine the personal exposure to a contaminant source in a uniform velocity field. This was done by full-scale measurements and computer simulations. The results showed a significant dependence on the velocity field both regarding the direction and the ma...... the usual operation range. Guidelines for personal exposure reduction in a uniform velocity field are discussed.......The objective of this study has been to determine the personal exposure to a contaminant source in a uniform velocity field. This was done by full-scale measurements and computer simulations. The results showed a significant dependence on the velocity field both regarding the direction...

  17. Radial Velocity Variability of Field Brown Dwarfs

    Science.gov (United States)

    Prato, L.; Mace, G. N.; Rice, E. L.; McLean, I. S.; Kirkpatrick, J. Davy; Burgasser, A. J.; Kim, Sungsoo S.

    2015-07-01

    We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R ˜ 20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph at the W. M. Keck Observatory. With a radial velocity (RV) precision of ˜2 km s-1, we are sensitive to brown dwarf companions in orbits with periods of a few years or less given a mass ratio of 0.5 or greater. We do not detect any spectroscopic binary brown dwarfs in the sample. Given our target properties, and the frequency and cadence of observations, we use a Monte Carlo simulation to determine the detection probability of our sample. Even with a null detection result, our 1σ upper limit for very low mass binary frequency is 18%. Our targets included seven known, wide brown dwarf binary systems. No significant RV variability was measured in our multi-epoch observations of these systems, even for those pairs for which our data spanned a significant fraction of the orbital period. Specialized techniques are required to reach the high precisions sensitive to motion in orbits of very low-mass systems. For eight objects, including six T dwarfs, we present the first published high-resolution spectra, many with high signal to noise, that will provide valuable comparison data for models of brown dwarf atmospheres.

  18. Vertical velocity and turbulence aspects during Mistral events as observed by UHF wind profilers

    Directory of Open Access Journals (Sweden)

    J.-L. Caccia

    2004-11-01

    Full Text Available The general purpose of this paper is to experimentally study mesoscale dynamical aspects of the Mistral in the coastal area located at the exit of the Rhône-valley. The Mistral is a northerly low-level flow blowing in southern France along the Rhône-valley axis, located between the French Alps and the Massif Central, towards the Mediterranean Sea. The experimental data are obtained by UHF wind profilers deployed during two major field campaigns, MAP (Mesoscale Alpine Program in autumn 1999, and ESCOMPTE (Expérience sur Site pour COntraindre les Modèles de Pollution atmosphériques et de Transports d'Emission in summer 2001. Thanks to the use of the time evolution of the vertical profile of the horizontal wind vector, recent works have shown that the dynamics of the Mistral is highly dependent on the season because of the occurrence of specific synoptic patterns. In addition, during summer, thermal forcing leads to a combination of sea breeze with Mistral and weaker Mistral due to the enhanced friction while, during autumn, absence of convective turbulence leads to substantial acceleration as low-level jets are generated in the stably stratified planetary boundary layer. At the exit of the Rhône valley, the gap flow dynamics dominates, whereas at the lee of the Alps, the dynamics is driven by the relative contribution of "flow around" and "flow over" mechanisms, upstream of the Alps. This paper analyses vertical velocity and turbulence, i.e. turbulent dissipation rate, with data obtained by the same UHF wind profilers during the same Mistral events. In autumn, the motions are found to be globally and significantly subsident, which is coherent for a dry, cold and stable flow approaching the sea, and the turbulence is found to be of pure dynamical origin (wind shears and mountain/lee wave breaking, which is coherent with non-convective situations. In summer, due to the ground heating and to the interactions with thermal circulation, the

  19. EnKF assimilation of simulated spaceborne Doppler observations of vertical velocity: impact on the simulation of a supercell thunderstorm and implications for model-based retrievals

    Directory of Open Access Journals (Sweden)

    W. E. Lewis

    2006-01-01

    Full Text Available Recently, a number of investigations have been made that point to the robust effectiveness of the Ensemble Kalman Filter (EnKF in convective-scale data assimilation. These studies have focused on the assimilation of ground-based Doppler radar observations (i.e. radial velocity and reflectivity. The present study differs from these investigations in two important ways. First, in anticipation of future satellite technology, the impact of assimilating spaceborne Doppler-retrieved vertical velocity is examined; second, the potential for the EnKF to provide an alternative to instrument-based microphysical retrievals is investigated. It is shown that the RMS errors of the analyzed fields produced by assimilation of vertical velocity alone are in general better than those obtained in previous studies: in most cases assimilation of vertical velocity alone leads to analyses with small errors (e.g. <1 ms-1 for velocity components after only 3 or 4 assimilation cycles. The microphysical fields are notable exceptions, exhibiting lower errors when observations of reflectivity are assimilated together with observations of vertical velocity, likely a result of the closer relationship between reflectivity and the microphysical fields themselves. It is also shown that the spatial distribution of the error estimates improves (i.e. approaches the true errors as more assimilation cycles are carried out, which could be a significant advantage of EnKF model-based retrievals.

  20. Effective diffusion equation in a random velocity field

    Science.gov (United States)

    Vinals, Jorge; Sekerka, Robert F.

    1992-01-01

    The effects are studied of assumed random velocity fields on diffusion in a binary fluid. Random velocity fields can result, for example, from the high-frequency components of residual accelerations onboard spacecraft (often called g-jitter). An effective diffusion equation is derived for an average concentration which includes spatial and temporal correlations induced by the fluctuating velocity fields assumed to be Gaussianly distributed. The resulting equation becomes nonlocal, and if correlations between different components of the velocity field exist, it is also anisotropic. The simple limiting case of short correlation times is discussed and an effective diffusivity is obtained which reflects the enhanced mixing caused by the velocity fields. The results obtained in the limit of short correlation times are valid even if the probability distribution of the velocity field is not Gaussian.

  1. Second vertical derivative of potential fields using an adaptation of ...

    African Journals Online (AJOL)

    The second vertical derivative of magnetic fields is commonly used for resolution of anomalies in gravity and magnetic fields. It is also commonly used as an aid to geologic mapping i.e. for the delineation of geological discontinuities in the subsurface. Frequency domain methods for calculating second vertical derivatives ...

  2. Water Velocity Measurements on a Vertical Barrier Screen at the Bonneville Dam Second Powerhouse

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, James S.; Deng, Zhiqun; Weiland, Mark A.; Martinez, Jayson J.; Yuan, Yong

    2011-11-22

    Fish screens at hydroelectric dams help to protect rearing and migrating fish by preventing them from passing through the turbines and directing them towards the bypass channels by providing a sweeping flow parallel to the screen. However, fish screens may actually be harmful to fish if they become impinged on the surface of the screen or become disoriented due to poor flow conditions near the screen. Recent modifications to the vertical barrier screens (VBS) at the Bonneville Dam second powerhouse (B2) intended to increase the guidance of juvenile salmonids into the juvenile bypass system (JBS) have resulted in high mortality and descaling rates of hatchery subyearling Chinook salmon during the 2008 juvenile salmonid passage season. To investigate the potential cause of the high mortality and descaling rates, an in situ water velocity measurement study was conducted using acoustic Doppler velocimeters (ADV) in the gatewell slot at Units 12A and 14A of B2. From the measurements collected the average approach velocity, sweep velocity, and the root mean square (RMS) value of the velocity fluctuations were calculated. The approach velocities measured across the face of the VBS varied but were mostly less than 0.3 m/s. The sweep velocities also showed large variances across the face of the VBS with most measurements being less than 1.5 m/s. This study revealed that the approach velocities exceeded criteria recommended by NOAA Fisheries and Washington State Department of Fish and Wildlife intended to improve fish passage conditions.

  3. Using smartphone pressure sensors to measure vertical velocities of elevators, stairways, and drones

    Science.gov (United States)

    Monteiro, Martín; Martí, Arturo C.

    2017-01-01

    We measure the vertical velocities of elevators, pedestrians climbing stairs, and drones (flying unmanned aerial vehicles), by means of smartphone pressure sensors. The barometric pressure obtained with the smartphone is related to the altitude of the device via the hydrostatic approximation. From the altitude values, vertical velocities are derived. The approximation considered is valid in the first hundred meters of the inner layers of the atmosphere. In addition to pressure, acceleration values were also recorded using the built-in accelerometer. Numerical integration was performed, obtaining both vertical velocity and altitude. We show that data obtained using the pressure sensor is significantly less noisy than that obtained using the accelerometer. Error accumulation is also evident in the numerical integration of the acceleration values. In the proposed experiments, the pressure sensor also outperforms GPS, because this sensor does not receive satellite signals indoors and, in general, the operating frequency is considerably lower than that of the pressure sensor. In the cases in which it is possible, comparison with reference values taken from the architectural plans of buildings validates the results obtained using the pressure sensor. This proposal is ideally performed as an external or outreach activity with students to gain insight about fundamental questions in mechanics, fluids, and thermodynamics.

  4. Sidewall containment of liquid metal with vertical alternating magnetic fields

    Science.gov (United States)

    Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.; Battles, James E.; Hull, John R.; Rote, Donald M.

    1990-01-01

    An apparatus for containing molten metal using a magnet producing vertical alternating magnetic field positioned adjacent the area in which the molten metal is to be confined. This invention can be adapted particularly to the casting of metal between counter-rotating rollers with the vertical alternating magnetic field used to confine the molten metal at the edges of the rollers. Alternately, the vertical alternating magnetic field can be used as a flow regulator in casting molten metal from an opening in a channel.

  5. Continuous model of the regional velocity field for Poland

    Science.gov (United States)

    Bogusz, J.; Figurski, M.; Kontny, B.; Grzempowski, P.; Klos, A.

    2012-04-01

    The poster presents modern determinations of the regional velocity field for Poland. The research is based on the ASG-EUPOS, Polish multifunctional GNNS network and performed within the developmental project of the Polish Ministry of Science and Higher Education. The network of the satellite-based sites consisted of above 130 Polish sites together with the selected number of European sites operating within EPN (EUREF Permanent Network). Data came from three-year period, which is the minimum number for the horizontal velocity determinations. The velocities were calculated within the discrete network related to the GNSS sites' distribution and then interpolated to the regular grid. The discussion on the interpolation methods is also included. To the interpolation of the velocity field kriging, spline and other functions were used. Assessment of the accuracy of the velocity on the interpolated points and tests of significance were also described. Developed models of the velocities field could indicate geodynamical activity on the area of Poland.

  6. Variability of Vertical Velocity Statistics in the Cloud-Free Convective Boundary Layer as Revealed by Doppler Lidar

    Science.gov (United States)

    Berg, L. K.; Newsom, R. K.; Turner, D. D.

    2016-12-01

    The majority of our understanding of the behavior of vertical velocity in the convective boundary layer is based on a small number of short-term observations made using either in situ or with remote sensing techniques over a limited number of sites. Analysis of long-term statistics have been lacking due to the scarcity of appropriate measurements. The US Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility is addressing this shortcoming through the deployment of a suite of scanning Doppler Lidars at a number of locations, associated with reconfiguration of the ARM Southern Great Plains site and the recent Holistic Interaction of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) field campaign. In this study, we utilize data collected by a Doppler Lidar system that has operated continuously from 2011 to the present at a location in north-central Oklahoma to examine the long-term behavior of the vertical velocity variance, skewness, and kurtosis. The application of standard normalization techniques, such as the mixed-layer depth and Deardorff convective velocity scale, do a good job in collapsing the data onto a single curve during periods in which the boundary layer is well developed, albeit with considerable amounts of scatter. During non-steady conditions, such as those found in the morning, scaling using the Deardorff convective velocity scale is found to work poorly. This behavior is likely due to the eddy turnover time and the growth rate of the boundary-layer depth. Systematic differences in the turbulence statistics are found by season, for non-stationary conditions, or periods with relatively small and large values of the surface friction velocity measured at the surface, amount of static instability, and wind shear across the boundary-layer top.

  7. Vertical velocity and turbulence aspects during Mistral events as observed by UHF wind profilers

    Directory of Open Access Journals (Sweden)

    J.-L. Caccia

    2004-11-01

    Full Text Available The general purpose of this paper is to experimentally study mesoscale dynamical aspects of the Mistral in the coastal area located at the exit of the Rhône-valley. The Mistral is a northerly low-level flow blowing in southern France along the Rhône-valley axis, located between the French Alps and the Massif Central, towards the Mediterranean Sea. The experimental data are obtained by UHF wind profilers deployed during two major field campaigns, MAP (Mesoscale Alpine Program in autumn 1999, and ESCOMPTE (Expérience sur Site pour COntraindre les Modèles de Pollution atmosphériques et de Transports d'Emission in summer 2001.

    Thanks to the use of the time evolution of the vertical profile of the horizontal wind vector, recent works have shown that the dynamics of the Mistral is highly dependent on the season because of the occurrence of specific synoptic patterns. In addition, during summer, thermal forcing leads to a combination of sea breeze with Mistral and weaker Mistral due to the enhanced friction while, during autumn, absence of convective turbulence leads to substantial acceleration as low-level jets are generated in the stably stratified planetary boundary layer. At the exit of the Rhône valley, the gap flow dynamics dominates, whereas at the lee of the Alps, the dynamics is driven by the relative contribution of "flow around" and "flow over" mechanisms, upstream of the Alps. This paper analyses vertical velocity and turbulence, i.e. turbulent dissipation rate, with data obtained by the same UHF wind profilers during the same Mistral events.

    In autumn, the motions are found to be globally and significantly subsident, which is coherent for a dry, cold and stable flow approaching the sea, and the turbulence is found to be of pure dynamical origin (wind shears and mountain/lee wave breaking, which is coherent with non-convective situations.

    Estimation of vertical migration velocity of (137)Cs in the Mount IDA/Kazdagi, Turkey.

    Science.gov (United States)

    Karadeniz, Özlem; Çakır, Rukiye; Karakurt, Hidayet

    2015-08-01

    This paper presents the results obtained from a radioecological study carried out in the forest sites of Mount IDA (Kazdagi)/Edremit, Turkey. For 118 soil profiles, the depth distribution of (137)Cs activity was established by fitting the experimental points to an exponential, a gaussian or a log-normal function. The relaxation lengths were in the range of 1.09-16.7 cm with a mean of 5.73 cm, showing a slow transport and a strong retention capacity of (137)Cs even after the 26-y period of Chernobyl accident. From the data for the vertical distribution of (137)Cs in soil profiles, the mean annual migration velocity of (137)Cs was in the range of 0.11-0.62 cm year(-1) with a mean of 0.30 cm year(-1). Statistically significant correlations between the thickness of the humus layer and the mean annual velocity of (137)Cs were found for both coniferous and mixed forest sites. The mean annual velocity of (137)Cs in the forests sites with Pinus nigra var pallasiana was significantly higher than sites with Pinus brutia. External dose-rates from the (137)Cs in forest soils were estimated using a conversion factor used in many studies and comprised with the external dose-rates determined according to the vertical distribution of (137)Cs within the soil depth profiles. It is clearly seen that both levels and spatial distribution patterns of the external dose-rates from (137)Cs were influenced considerably with the vertical migration rate and the vertical distribution of (137)Cs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Influence of running velocity on vertical, leg and joint stiffness : modelling and recommendations for future research.

    Science.gov (United States)

    Brughelli, Matt; Cronin, John

    2008-01-01

    Human running can be modelled as either a spring-mass model or multiple springs in series. A force is required to stretch or compress the spring, and thus stiffness, the variable of interest in this paper, can be calculated from the ratio of this force to the change in spring length. Given the link between force and length change, muscle stiffness and mechanical stiffness have been areas of interest to researchers, clinicians, and strength and conditioning practitioners for many years. This review focuses on mechanical stiffness, and in particular, vertical, leg and joint stiffness, since these are the only stiffness types that have been directly calculated during human running. It has been established that as running velocity increases from slow-to-moderate values, leg stiffness remains constant while both vertical stiffness and joint stiffness increase. However, no studies have calculated vertical, leg or joint stiffness over a range of slow-to-moderate values to maximum values in an athletic population. Therefore, the effects of faster running velocities on stiffness are relatively unexplored. Furthermore, no experimental research has examined the effects of training on vertical, leg or joint stiffness and the subsequent effects on running performance. Various methods of training (Olympic style weightlifting, heavy resistance training, plyometrics, eccentric strength training) have shown to be effective at improving running performance. However, the effects of these training methods on vertical, leg and joint stiffness are unknown. As a result, the true importance of stiffness to running performance remains unexplored, and the best practice for changing stiffness to optimize running performance is speculative at best. It is our hope that a better understanding of stiffness, and the influence of running speed on stiffness, will lead to greater interest and an increase in experimental research in this area.

  9. Field Emission of ITO-Coated Vertically Aligned Nanowire Array.

    KAUST Repository

    Lee, Changhwa

    2010-04-29

    An indium tin oxide (ITO)-coated vertically aligned nanowire array is fabricated, and the field emission characteristics of the nanowire array are investigated. An array of vertically aligned nanowires is considered an ideal structure for a field emitter because of its parallel orientation to the applied electric field. In this letter, a vertically aligned nanowire array is fabricated by modified conventional UV lithography and coated with 0.1-μm-thick ITO. The turn-on electric field intensity is about 2.0 V/μm, and the field enhancement factor, β, is approximately 3,078 when the gap for field emission is 0.6 μm, as measured with a nanomanipulator in a scanning electron microscope.

  10. Measuring Oscillatory Velocity Fields Due to Swimming Algae

    CERN Document Server

    Guasto, Jeffrey S; Gollub, J P

    2010-01-01

    In this fluid dynamics video, we present the first time-resolved measurements of the oscillatory velocity field induced by swimming unicellular microorganisms. Confinement of the green alga C. reinhardtii in stabilized thin liquid films allows simultaneous tracking of cells and tracer particles. The measured velocity field reveals complex time-dependent flow structures, and scales inversely with distance. The instantaneous mechanical power generated by the cells is measured from the velocity fields and peaks at 15 fW. The dissipation per cycle is more than four times what steady swimming would require.

  11. Water Velocity Measurements on a Vertical Barrier Screen at the Bonneville Dam Second Powerhouse

    Directory of Open Access Journals (Sweden)

    Yong Yuan

    2011-11-01

    Full Text Available Fish screens at hydroelectric dams help to protect rearing and migrating fish by preventing them from passing through the turbines and directing them towards the bypass channels by means of a sweeping flow parallel to the screen. However, fish screens may actually be harmful to fish if the fish become impinged on the surface of the screen or become disoriented due to poor flow conditions near the screen. Recent modifications to the vertical barrier screens (VBS in the gate wells at the Bonneville Dam second powerhouse (B2 were intended to increase the guidance of juvenile salmonids into the juvenile bypass system but have resulted in higher mortality and descaling rates of hatchery subyearling Chinook salmon during the 2008 juvenile salmonid passage season. To investigate the potential cause of the high mortality and descaling rates, an in situ water velocity measurement study was conducted using acoustic Doppler velocimeters in the gate well slots at turbine units 12A and 14A of B2. From the measurements collected, the average approach velocity, sweep velocity, and the root mean square value of the velocity fluctuations were calculated. The approach velocities measured across the face of the VBS were variable and typically less than 0.3 m/s, but fewer than 50% were less than or equal to 0.12 m/s. There was also large variance in sweep velocities across the face of the VBS with most measurements recorded at less than 1.5 m/s. Results of this study revealed that the approach velocities in the gate wells exceeded criteria intended to improve fish passage conditions that were recommended by National Marine Fisheries Service and the Washington State Department of Fish and Wildlife. The turbulence measured in the gate well may also result in suboptimal fish passage conditions but no established guidelines to contrast those results have been published.

  12. The boundary condition for vertical velocity and its interdependence with surface gas exchange

    Science.gov (United States)

    Kowalski, Andrew S.

    2017-07-01

    The law of conservation of linear momentum is applied to surface gas exchanges, employing scale analysis to diagnose the vertical velocity (w) in the boundary layer. Net upward momentum in the surface layer is forced by evaporation (E) and defines non-zero vertical motion, with a magnitude defined by the ratio of E to the air density, as w = E/ρ. This is true even right down at the surface where the boundary condition is w|0 = E/ρ|0 (where w|0 and ρ|0 represent the vertical velocity and density of air at the surface). This Stefan flow velocity implies upward transport of a non-diffusive nature that is a general feature of the troposphere but is of particular importance at the surface, where it assists molecular diffusion with upward gas migration (of H2O, for example) but opposes that of downward-diffusing species like CO2 during daytime. The definition of flux-gradient relationships (eddy diffusivities) requires rectification to exclude non-diffusive transport, which does not depend on scalar gradients. At the microscopic scale, the role of non-diffusive transport in the process of evaporation from inside a narrow tube - with vapour transport into an overlying, horizontal airstream - was described long ago in classical mechanics and is routinely accounted for by chemical engineers, but has been neglected by scientists studying stomatal conductance. Correctly accounting for non-diffusive transport through stomata, which can appreciably reduce net CO2 transport and marginally boost that of water vapour, should improve characterisations of ecosystem and plant functioning.

  13. The boundary condition for vertical velocity and its interdependence with surface gas exchange

    Directory of Open Access Journals (Sweden)

    A. S. Kowalski

    2017-07-01

    Full Text Available The law of conservation of linear momentum is applied to surface gas exchanges, employing scale analysis to diagnose the vertical velocity (w in the boundary layer. Net upward momentum in the surface layer is forced by evaporation (E and defines non-zero vertical motion, with a magnitude defined by the ratio of E to the air density, as w = E/ρ. This is true even right down at the surface where the boundary condition is w|0 = E/ρ|0 (where w|0 and ρ|0 represent the vertical velocity and density of air at the surface. This Stefan flow velocity implies upward transport of a non-diffusive nature that is a general feature of the troposphere but is of particular importance at the surface, where it assists molecular diffusion with upward gas migration (of H2O, for example but opposes that of downward-diffusing species like CO2 during daytime. The definition of flux–gradient relationships (eddy diffusivities requires rectification to exclude non-diffusive transport, which does not depend on scalar gradients. At the microscopic scale, the role of non-diffusive transport in the process of evaporation from inside a narrow tube – with vapour transport into an overlying, horizontal airstream – was described long ago in classical mechanics and is routinely accounted for by chemical engineers, but has been neglected by scientists studying stomatal conductance. Correctly accounting for non-diffusive transport through stomata, which can appreciably reduce net CO2 transport and marginally boost that of water vapour, should improve characterisations of ecosystem and plant functioning.

  14. Alignment of stress, mean wind, and vertical gradient of the velocity vector

    DEFF Research Database (Denmark)

    Berg, Jacob; Mann, Jakob; Patton, E.G.

    2012-01-01

    In many applications in the atmospheric surface layer the turbulent-viscosity hypothesis is applied, i.e. the stress vector can be described through the vertical gradient of velocity. In the atmospheric surface layer, where the Coriolis force and baroclinic effects are considered negligible...... of atmospheric boundary layer modeling. The measurements are from the Danish wind turbine test sites at Høvsøre. With theWindCube lidar we are able to reach heights of 250 meters and hence capture the entire atmospheric surface layer both in terms of wind speed and the direction of the mean stress vector....

  15. Conservative solute approximation to the transport of a remedial reagent in a vertical circulation flow field

    Science.gov (United States)

    Chen, Jui-Sheng; Jang, Cheng-Shin; Cheng, Chung-Ting; Liu, Chen-Wuing

    2010-09-01

    SummaryThis study presents a novel mathematical model for describing the transport of the remedial reagent in a vertical circulation flow field in an anisotropic aquifer. To develop the mathematical model, the radial and vertical components of the pore water velocity are calculated first by using an analytical solution for steady-state drawdown distribution near a vertical circulation well. Next, the obtained radial and vertical components of the pore water velocity are then incorporated into a three-dimensional axisymmetrical advection-dispersion equation in cylindrical coordinates from which to build the reagent transport equation. The Laplace transform finite difference technique is applied to solve the three-dimensional axisymmetrical advection-dispersion equation with spatial variable-dependent coefficients. The developed mathematical model is used to investigate the effects of various parameters such as hydraulic conductivity anisotropy, longitudinal and transverse dispersivities, the placement of the extraction and injection screened intervals of the vertical circulation well and the injection modes on the transport regime of the remedial reagent. Results show that those parameters have different degrees of impacts on the distribution of the remedial reagent. The mathematical model provides an effective tool for designing and operating an enhanced groundwater remediation in an anisotropic aquifer using the vertical circulation well technology.

  16. Evidence for thermospheric gravity waves in the southern polar cap from ground-based vertical velocity and photometric observations

    Directory of Open Access Journals (Sweden)

    J. L. Innis

    Full Text Available Zenith-directed Fabry-Perot Spectrometer (FPS and 3-Field Photometer (3FP observations of the λ630 nm emission (~240 km altitude were obtained at Davis station, Antarctica, during the austral winter of 1999. Eleven nights of suitable data were searched for significant periodicities common to vertical winds from the FPS and photo-metric variations from the 3FP. Three wave-like events were found, each of around one or more hours in duration, with periods around 15 minutes, vertical velocity amplitudes near 60 ms–1 , horizontal phase velocities around 300 ms–1 , and horizontal wavelengths from 240 to 400 km. These characteristics appear consistent with polar cap gravity waves seen by other workers, and we conclude this is a likely interpretation of our data. Assuming a source height near 125 km altitude, we determine the approximate source location by calculating back along the wave trajectory using the gravity wave property relating angle of ascent and frequency. The wave sources appear to be in the vicinity of the poleward border of the auroral oval, at magnetic local times up to 5 hours before local magnetic midnight.

    Key words. Meteorology and atmospheric dynamics (thermospheric dynamics; waves and tides

  17. Velocity and strain-rate analyses of the SCEC 3.0 velocity field

    Science.gov (United States)

    Wdowinski, S.; Bock, Y.

    2003-04-01

    The pre-released SCEC 3.0 velocity field consists of 845 velocity vectors, covering the entire Southern California region. It is about 3 times larger than the SCEC 2.0 field, which was released in 1998 and contains 343 velocity vectors. We analyze the new SCEC 3.0 velocity field following and improving the quasi-two-dimensional analyses developed by Wdowinski et al. [2001] for the 2.0 velocity field. The new analyses include the following steps: (1) Pole of Deformation (PoD) calculation; the PoD is a point on the Earth’s surface, in which small circles about this point are best, aligned with the velocity vectors of the deforming zone. (2) Transforming the velocity field into the PoD reference frame. (3) Characterization of the velocity field by segments of similar velocity transition between the Pacific and North American plates and orthogonal profiles along the plate boundary region. (4) Calculating velocity and velocity gradient for all segments and profiles using zero-phase digital filters and numerical derivation, respectively. (5) Calculation of regional strain-rate maps, and (6) back-transformation of the strain-rate maps into the regular north-pole reference frame. The results of our analyses show that shear deformation with high strain-rate is detected along a dozen narrow belts, which coincide with active geologic fault segments and high level of seismicity along the San Andreas Fault System. In the highly populated Los Angeles area, our analyses detected high strain-rate localization along the Newport-Inglewood fault and across the Ventura Basin. In the regional scale, our analyses show that the interseismic deformation of the wide diffused deforming NA-PA plate boundary region is localized along a finite number of narrow belts. Because no prior assumptions were made regarding the geology, tectonics, or seismicity of the region, our analysis demonstrates that geodetic observations alone can be used to detect active fault segments.

  18. Automated topology classification method for instantaneous velocity fields

    Energy Technology Data Exchange (ETDEWEB)

    Depardon, S. [Direction de la Recherche et de l' Innovation Automobile, PSA Peugeot Citroen, Velizy-Villacoublay Cedex (France); Laboratoire d' Etudes Aerodynamiques, Teleport 2, 1 Av. Clement Ader, BP 40109, Futuroscope Chasseneuil (France); Lasserre, J.J. [Direction de la Recherche et de l' Innovation Automobile, PSA Peugeot Citroen, Velizy-Villacoublay Cedex (France); Brizzi, L.E.; Boree, J. [Laboratoire d' Etudes Aerodynamiques, Teleport 2, 1 Av. Clement Ader, BP 40109, Futuroscope Chasseneuil (France)

    2007-05-15

    Topological concepts provide highly comprehensible representations of the main features of a flow with a limited number of elements. This paper presents an automated classification method of instantaneous velocity fields based on the analysis of their critical points distribution and feature flow fields. It uses the fact that topological changes of a velocity field are continuous in time to extract large scale periodic phenomena from insufficiently time-resolved datasets. This method is applied to two test-cases: an analytical flow field and PIV planes acquired downstream a wall-mounted cube. (orig.)

  19. The large low velocity province and the vertical flow beneath the Pacific

    Science.gov (United States)

    Kawai, K.; Geller, R. J.; Tsuchiya, T.

    2010-12-01

    Since tomographic studies found the large low velocity province (LLVP) (degree-2 pattern) in the lowermost mantle in 1980's, it has been controversial whether it is due to thermal effects, chemical heterogeneity, or both. Geodynamical studies have suggested that both effects can explain the LLVP but that the large thermo-chemical pile model is preferred (e.g., Bull et al. 2009). Our seismological group has developed waveform inversion techniques and applied them to data from recently deployed broad-band seismic arrays such as US-Array. We found that there are notable S-velocity decreases beneath the D" discontinuity as the CMB is approached within the high average velocity regions such as the lowermost mantle beneath Central America, the Arctic, and Siberia (Kawai et al. 2007a,b, 2009). We also found "S-shaped" velocity models in the lowermost mantle in regions with low average S-velocity such as beneath the western Pacific and the Pacific (Konishi et al. 2009; Kawai & Geller 2010a). We performed analyses based on ab-initio mineral physics (Kawai & Tsuchiya 2009), which showed that these velocity profiles can be explained by a simple thermal boundary layer (TBL) model with a CMB temperature of about 3800 K. The TBL model can also explain most of the important seismological properties in the lowermost mantle such as the LLVP, so that the large thermo-chemical pile model appears to be inappropriate. On the other hand, the S-velocity model beneath Hawaii requires the existence of localized chemical heterogeneity (Kawai & Geller 2010b), which could be due to an accumulated Fe-rich dense pile (Kawai & Tsuchiya in prep.). To better constrain the nature of the LLVP, we inverted the horizontal components of observed radial and transverse waveforms of S and ScS phases to determine the radial profile of TI shear wave velocity at the northeastern edge of the LLVP in the lowermost mantle beneath the Pacific (Kawai & Geller 2010c). We find that the radial (SV) component is 3

  1. Measuring average angular velocity with a smartphone magnetic field sensor

    Science.gov (United States)

    Pili, Unofre; Violanda, Renante

    2018-02-01

    The angular velocity of a spinning object is, by standard, measured using a device called a tachometer. However, by directly using it in a classroom setting, the activity is likely to appear as less instructive and less engaging. Indeed, some alternative classroom-suitable methods for measuring angular velocity have been presented. In this paper, we present a further alternative that is smartphone-based, making use of the real-time magnetic field (simply called B-field in what follows) data gathering capability of the B-field sensor of the smartphone device as the timer for measuring average rotational period and average angular velocity. The in-built B-field sensor in smartphones has already found a number of uses in undergraduate experimental physics. For instance, in elementary electrodynamics, it has been used to explore the well-known Bio-Savart law and in a measurement of the permeability of air.

  2. Three-dimensional instantaneous velocity field measurement using ...

    Indian Academy of Sciences (India)

    2014-02-13

    Feb 13, 2014 ... In the present study, a digital holography microscope has been developed to study instantaneous 3D velocity field in a square channel of 1000 × 1000 2 cross-section. The flow field is seeded with polystyrene microspheres of size d p = 2.1 m. The volumetric flow rate is set equal to 20 l/min.

  3. Patch near field acoustic holography based on particle velocity measurements

    DEFF Research Database (Denmark)

    Zhang, Yong-Bin; Jacobsen, Finn; Bi, Chuan-Xing

    2009-01-01

    Patch near field acoustic holography (PNAH) based on sound pressure measurements makes it possible to reconstruct the source field near a source by measuring the sound pressure at positions on a surface. that is comparable in size to the source region of concern. Particle velocity is an alternative...... input quantity for NAH, and the advantage of using the normal component of the particle velocity rather than the sound pressure as the input of conventional spatial Fourier transform based NAH and as the input of the statistically optimized variant of NAH has recently been demonstrated. This paper......, PNAH based on particle velocity measurements can give better results than the pressure-based PNAH with a reduced number of iterations. A simulation study, as well as an experiment carried out with a pressure-velocity sound intensity probe, demonstrates these findings....

  4. The statistical properties of sea ice velocity fields

    Science.gov (United States)

    Agarwal, S.; Wettlaufer, J. S.

    2016-12-01

    Thorndike and Colony (1982) showed that more than 70% of the variance of the ice motion can be explained by the geostrophic winds. This conclusion was reached by analyzing only 2 years of data. Due to the importance of ice motion in Arctic climate we ask how persistent is such a prediction. In so doing, we study and develop a stochastic model for the Arctic sea ice velocity fields based on the observed sea ice velocity fields from satellites and buoys for the period 1978 - 2012. Having previously found that the Arctic Sea Equivalent Ice Extent (EIE) has a white noise structure on annual to bi-annual time scales (Agarwal et. al. 2012), we assess the connection to ice motion. We divide the Arctic into dynamic and thermodynamic components, with focus on the dynamic part i.e. the velocity fields of sea ice driven by the geostrophic winds over the Arctic. We show (1) the stationarity of the spatial correlation structure of the velocity fields, and (2) the robustness of white noise structure present in the velocity fields on annual to bi-annual time scales, which combine to explain the white noise characteristics of the EIE on these time scales. S. Agarwal, W. Moon and J.S. Wettlaufer, Trends, noise and reentrant long-term persistence in Arctic sea ice, Proc. R. Soc. A, 468, 2416 (2012). A.S. Thorndike and R. Colony, Sea ice motion in response to geostrophic winds, J. Geophys. Res. 87, 5845 (1982).

  5. Horizontal and Vertical Velocities Derived from the IDS Contribution to ITRF2014, and Comparisons with Geophysical Models

    Science.gov (United States)

    Moreaux, G.; Lemoine, F. G.; Argus, D. F.; Santamaria-Gomez, A.; Willis, P.; Soudarin, L.; Gravelle, M.; Ferrage, P.

    2016-01-01

    In the context of the 2014 realization of the International Terrestrial Reference Frame (ITRF2014), the International DORIS Service (IDS) has delivered to the IERS a set of 1140 weekly SINEX files including station coordinates and Earth orientation parameters, covering the time period from 1993.0 to 2015.0. From this set of weekly SINEX files, the IDS Combination Center estimated a cumulative DORIS position and velocity solution to obtain mean horizontal and vertical motion of 160 stations at 71 DORIS sites. The main objective of this study is to validate the velocities of the DORIS sites by comparison with external models or time series. Horizontal velocities are compared with two recent global plate models (GEODVEL 2010 and NNR-MORVEL56). Prior to the comparisons, DORIS horizontal velocities were corrected for Global Isostatic Adjustment (GIA) from the ICE-6G (VM5a) model. For more than half of the sites, the DORIS horizontal velocities differ from the global plate models by less than 2-3 mm/yr. For five of the sites (Arequipa, Dionysos/Gavdos, Manila, Santiago) with horizontal velocity differences wrt these models larger than 10 mm/yr, comparisons with GNSS estimates show the veracity of the DORIS motions. Vertical motions from the DORIS cumulative solution are compared with the vertical velocities derived from the latest GPS cumulative solution over the time span 1995.0-2014.0 from the University of La Rochelle (ULR6) solution at 31 co-located DORIS-GPS sites. These two sets of vertical velocities show a correlation coefficient of 0.83. Vertical differences are larger than 2 mm/yr at 23 percent of the sites. At Thule the disagreement is explained by fine-tuned DORIS discontinuities in line with the mass variations of outlet glaciers. Furthermore, the time evolution of the vertical time series from the DORIS station in Thule show similar trends to the GRACE equivalent water height.

  6. Reaching saturation in patterned source vertical organic field effect transistors

    Science.gov (United States)

    Greenman, Michael; Sheleg, Gil; Keum, Chang-min; Zucker, Jonathan; Lussem, Bjorn; Tessler, Nir

    2017-05-01

    Like most of the vertical transistors, the Patterned Source Vertical Organic Field Effect Transistor (PS-VOFET) does not exhibit saturation in the output characteristics. The importance of achieving a good saturation is demonstrated in a vertical organic light emitting transistor; however, this is critical for any application requiring the transistor to act as a current source. Thereafter, a 2D simulation tool was used to explain the physical mechanisms that prevent saturation as well as to suggest ways to overcome them. We found that by isolating the source facet from the drain-source electric field, the PS-VOFET architecture exhibits saturation. The process used for fabricating such saturation-enhancing structure is then described. The new device demonstrated close to an ideal saturation with only 1% change in the drain-source current over a 10 V change in the drain-source voltage.

  7. Clogging of granular material in vertical pipes discharged at constant velocity

    Directory of Open Access Journals (Sweden)

    López-Rodríguez Diego

    2017-01-01

    Full Text Available We report an experimental study on the flow of spherical particles through a vertical pipe discharged at constant velocity by means of a conveyor belt placed at the bottom. For a pipe diameter 3.67 times the diameter of the particles, we observe the development of hanging arches that stop the flow as they are able to support the weight of the particles above them. We find that the distribution of times that it takes until a stable clog develops, decays exponentially. This is compatible with a clogging probability that remains constant during the discharge. We also observe that the probability of clogging along the pipe decreases with the height, i.e. most of the clogs are developed near the bottom. This spatial dependence may be attributed to different pressure values within the pipe which might also be related to a spontaneous development of an helical structure of the grains inside the pipe.

  8. Evolution of Area-Averaged Vertical Velocity in the Convective Region of a Midlatitude Squall Line

    Science.gov (United States)

    1992-12-01

    Ms. Svetla Veleva, Mr. Rusty Billingsly, and Capt. Kevin Mattison for their help in unfolding the raw Doppler-velocity fields; Mr. Robert Barritt for...and evolution of this important class of mesoscale convective system (MCS) (e.g., Zipser 1969, 1977; Houze 1977; LeMonc and Zipser 1980; Ogura and Liou...1980; Zipser and LeMone 1980; Gamache and ltouze 1982, 1985; Houze and Rappaport 1984; Heymsfield and Schotz 1985; Smull and Houze 1985, 1987a,b

  9. Relations between Lagrangian models and synthetic random velocity fields.

    Science.gov (United States)

    Olla, Piero; Paradisi, Paolo

    2004-10-01

    The authors propose an alternative interpretation of Markovian transport models based on the well-mixed condition, in terms of the properties of a random velocity field with second order structure functions scaling linearly in the space-time increments. This interpretation allows direct association of the drift and noise terms entering the model, with the geometry of the turbulent fluctuations. In particular, the well-known nonuniqueness problem in the well-mixed approach is solved in terms of the antisymmetric part of the velocity correlations; its relation with the presence of nonzero mean helicity and other geometrical properties of the flow is elucidated. The well-mixed condition appears to be a special case of the relation between conditional velocity increments of the random field and the one-point Eulerian velocity distribution, allowing generalization of the approach to the transport of nontracer quantities. Application to solid particle transport leads to a model satisfying, in the homogeneous isotropic turbulence case, all the conditions on the behavior of the correlation times for the fluid velocity sampled by the particles. In particular, correlation times in the gravity and in the inertia dominated case, respectively, longer and shorter than in the passive tracer case; in the gravity dominated case, correlation times longer for velocity components along gravity, than for the perpendicular ones. The model produces, in channel flow geometry, particle deposition rates in agreement with experiments.

  10. The velocity field induced by a helical vortex tube

    DEFF Research Database (Denmark)

    Fukumoto, Y.; Okulov, Valery

    2005-01-01

    The influence of finite-core thickness on the velocity field around a vortex tube is addressed. An asymptotic expansion of the Biot-Savart law is made to a higher order in a small parameter, the ratio of core radius to curvature radius, which consists of the velocity field due to lines of monopoles...... and dipoles arranged on the centerline of the tube. The former is associated with an infinitely thin core and is featured by the circulation alone. The distribution of vorticity in the core reflects on the strength of dipole. This result is applied to a helical vortex tube, and the induced velocity due...... to a helical filament of the dipoles is obtained in the form of the Kapteyn series, which augments Hardin's [Phys. Fluids 25, 1949 (1982)] solution for the monopoles. Using a singularity-separation technique, a substantial part of the series is represented in a closed form for both the mono- and the dipoles...

  11. Vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2012-10-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been developed using pure semiconducting carbon nanotubes. The source and drain were vertically stacked, separated by a dielectric, and the carbon nanotubes were placed on the sidewall of the stack to bridge the source and drain. Both the effective gate dielectric and gate electrode were normal to the substrate surface. The channel length is determined by the dielectric thickness between source and drain electrodes, making it easier to fabricate sub-micrometer transistors without using time-consuming electron beam lithography. The transistor area is much smaller than the planar CNTFET due to the vertical arrangement of source and drain and the reduced channel area. © 2012 Elsevier Ltd. All rights reserved.

  12. Effects of volume averaging on the line spectra of vertical velocity from multiple-Doppler radar observations

    Science.gov (United States)

    Gal-Chen, T.; Wyngaard, J. C.

    1982-01-01

    Calculations of the ratio of the true one-dimensional spectrum of vertical velocity and that measured with multiple-Doppler radar beams are presented. It was assumed that the effects of pulse volume averaging and objective analysis routines is replacement of a point measurement with a volume integral. A u and v estimate was assumed to be feasible when orthogonal radars are not available. Also, the target fluid was configured as having an infinite vertical dimension, zero vertical velocity at the top and bottom, and having homogeneous and isotropic turbulence with a Kolmogorov energy spectrum. The ratio obtained indicated that equal resolutions among radars yields a monotonically decreasing, wavenumber-dependent response function. A gain of 0.95 was demonstrated in an experimental situation with 40 levels. Possible errors introduced when using unequal resolution radars were discussed. Finally, it was found that, for some flows, the extent of attenuation depends on the number of vertical levels resolvable by the radars.

  13. Transformations Based on Continuous Piecewise-Affine Velocity Fields

    DEFF Research Database (Denmark)

    Freifeld, Oren; Hauberg, Søren; Batmanghelich, Kayhan

    2017-01-01

    We propose novel finite-dimensional spaces of well-behaved transformations. The latter are obtained by (fast and highly-accurate) integration of continuous piecewise-affine velocity fields. The proposed method is simple yet highly expressive, effortlessly handles optional constraints (e.g., volume...

  14. A non-parametric model for the cosmic velocity field

    NARCIS (Netherlands)

    Branchini, E; Teodoro, L; Frenk, CS; Schmoldt, [No Value; Efstathiou, G; White, SDM; Saunders, W; Sutherland, W; Rowan-Robinson, M; Keeble, O; Tadros, H; Maddox, S; Oliver, S

    1999-01-01

    We present a self-consistent non-parametric model of the local cosmic velocity field derived from the distribution of IRAS galaxies in the PSCz redshift survey. The survey has been analysed using two independent methods, both based on the assumptions of gravitational instability and linear biasing.

  15. Reconstructing the velocity field beyond the local universe

    CSIR Research Space (South Africa)

    Johnston, R

    2014-10-01

    Full Text Available an estimate of the velocity field derived from the galaxy over-density d(sub g) and the second makes use of the matter linear density power spectrum P(sub k). Using N-body simulations we find, with an SDSS-like sample (N(sub gal) 33 per deg(sup 2...

  16. Channel flow analysis. [velocity distribution throughout blade flow field

    Science.gov (United States)

    Katsanis, T.

    1973-01-01

    The design of a proper blade profile requires calculation of the blade row flow field in order to determine the velocities on the blade surfaces. An analysis theory is presented for several methods used for this calculation and associated computer programs that were developed are discussed.

  17. Near field acoustic holography with particle velocity transducers

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Liu, Yang

    2005-01-01

    Near field acoustic holography is usually based on measurement of the pressure. This paper describes an investigation of an alternative technique that involves measuring the normal component of the acoustic particle velocity. A simulation study shows that there is no appreciable difference between...... by an experimental investigation made with a p-u sound intensity probe produced by Microflown....

  18. Three-dimensional instantaneous velocity field measurement using ...

    Indian Academy of Sciences (India)

    2014-02-13

    Feb 13, 2014 ... Abstract. In the present study, a digital holography microscope has been developed to study instantaneous 3D velocity field in a square channel of 1000 × 1000 μm2 cross-section. The flow field is seeded with polystyrene microspheres of size dp = 2.1 μm. The volumetric flow rate is set equal to 20 μl/min.

  19. Vertical profiles of the 3-D wind velocity retrieved from multiple wind lidars performing triple range-height-indicator scans

    Science.gov (United States)

    Debnath, Mithu; Valerio Iungo, G.; Ashton, Ryan; Brewer, W. Alan; Choukulkar, Aditya; Delgado, Ruben; Lundquist, Julie K.; Shaw, William J.; Wilczak, James M.; Wolfe, Daniel

    2017-02-01

    Vertical profiles of 3-D wind velocity are retrieved from triple range-height-indicator (RHI) scans performed with multiple simultaneous scanning Doppler wind lidars. This test is part of the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign carried out at the Boulder Atmospheric Observatory. The three wind velocity components are retrieved and then compared with the data acquired through various profiling wind lidars and high-frequency wind data obtained from sonic anemometers installed on a 300 m meteorological tower. The results show that the magnitude of the horizontal wind velocity and the wind direction obtained from the triple RHI scans are generally retrieved with good accuracy. However, poor accuracy is obtained for the evaluation of the vertical velocity, which is mainly due to its typically smaller magnitude and to the error propagation connected with the data retrieval procedure and accuracy in the experimental setup.

  20. An experimental study of wave propagation and velocity distributions in a vertically driven time-dependent granular gas

    Science.gov (United States)

    Perez, John Anthony

    Averaged over appropriate space and time scales the dynamics of highly fluidized granular systems are often reminiscent of molecular fluid flows. As a result, theoretical efforts to describe these systems have borrowed heavily from continuum mechanics, particularly hydrodynamics. This has led to various proposed granular hydrodynamic theories which have been used to simulate granular materials in various states of confinement and excitation. These studies suggest that a continuum model for granular gasses can accurately reproduce the mean density, velocity and temperature profiles for an experimental granular gas. This thesis contributes to this body of work by presenting an experimental study of the hydrodynamic fields and velocity distributions within a vertically driven quasi-2D granular gas. We have taken pictures as fast as possible of a time-dependent granular gas using a high-speed CCD camera. We have extracted the positions and velocities of 57-564 particles per frame over 400 GB of raw images collected at 3700 fps. We used this data to compute the density, velocity and temperature fields as functions of time and space to a very high resolution. This approach led to the discovery of novel substructures within the hydrodynamic fields which would have been overlooked had we chosen to average over a drive cycle as earlier studies have done. In particular, the high spatial resolution available from our measurements reveals a serrated substructure in the shock waves which has not been reported before. This substructure is the result of collisional momentum transport . One of the current issues in formulating a granular continuum model is how to incorporate local and non-local dependencies between stress and strain correctly. In this thesis we demonstrate that the collisional transfer of momentum produces a non-local effect in the stress tensor which plays a major role in determining the mean flow. Current models have incorporated only the collisional or

  1. Effect of Induced Magnetic Field on MHD Mixed Convection Flow in Vertical Microchannel

    Science.gov (United States)

    Jha, B. K.; Aina, B.

    2017-08-01

    The present work presents a theoretical investigation of an MHD mixed convection flow in a vertical microchannel formed by two electrically non-conducting infinite vertical parallel plates. The influence of an induced magnetic field arising due to motion of an electrically conducting fluid is taken into consideration. The governing equations of the motion are a set of simultaneous ordinary differential equations and their exact solutions in dimensionless form have been obtained for the velocity field, the induced magnetic field and the temperature field. The expressions for the induced current density and skin friction have also been obtained. The effects of various non-dimensional parameters such as rarefaction, fluid wall interaction, the Hartmann number and the magnetic Prandtl number on the velocity, the induced magnetic field, the temperature, the induced current density, and skin friction have been presented in a graphical form. It is found that the effect of the Hartmann number and magnetic Prandtl number on the induced current density is found to have a decreasing nature at the central region of the microchannel.

  2. Numerical study of effect of induced magnetic field on transient natural convection over a vertical cone

    Directory of Open Access Journals (Sweden)

    Vanita

    2016-06-01

    Full Text Available In the present paper, an analysis has been performed to study the influence of induced magnetic field on the transient free convective flow of an electrically conducting and viscous incompressible fluid over a vertical cone. The coupled nonlinear partial differential equations governing the transient flow have been solved numerically by using the implicit finite difference method of Crank–Nicolson type. The influence of magnetic parameter, magnetic Prandtl number and semi-vertical angle of the cone on the velocity and induced magnetic field profiles has been illustrated graphically. Also, the local as well as average skin-friction and Nusselt number has been presented graphically. For result validation, we have done a comparative study and the present results are found to be in very good agreement with available results.

  3. Sound field separation with sound pressure and particle velocity measurements

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn; Leclère, Quentin

    2012-01-01

    and the velocity in a single layer are proposed. The two methods use an equivalent source formulation with separate transfer matrices for the outgoing and incoming waves, so that the sound from the two sides of the array can be modeled independently. A weighting scheme is proposed to account for the distance......In conventional near-field acoustic holography (NAH) it is not possible to distinguish between sound from the two sides of the array, thus, it is a requirement that all the sources are confined to only one side and radiate into a free field. When this requirement cannot be fulfilled, sound field...... separation techniques make it possible to distinguish between outgoing and incoming waves from the two sides, and thus NAH can be applied. In this paper, a separation method based on the measurement of the particle velocity in two layers and another method based on the measurement of the pressure...

  4. A dissipative random velocity field for fully developed fluid turbulence

    CERN Document Server

    Pereira, Rodrigo M; Chevillard, Laurent

    2015-01-01

    We investigate the statistical properties, based on numerical simulations and analytical calculations, of a recently proposed stochastic model for the velocity field of an incompressible, homogeneous, isotropic and fully developed turbulent flow. A key step in the construction of this model is the introduction of some aspects of the vorticity stretching mechanism that governs the dynamics of fluid particles along their trajectory. An additional further phenomenological step aimed at including the long range correlated nature of turbulence makes this model depending on a single free parameter $\\gamma$ that can be estimated from experimental measurements. We confirm the realism of the model regarding the geometry of the velocity gradient tensor, the power-law behaviour of the moments of velocity increments (i.e. the structure functions), including the intermittent corrections, and the existence of energy transfers across scales. We quantify the dependence of these basic properties of turbulent flows on the free...

  5. The influence of the tangential velocity of inner rotating wall on axial velocity profile of flow through vertical annular pipe with rotating inner surface

    Directory of Open Access Journals (Sweden)

    Sharf Abdusalam M.

    2014-03-01

    Full Text Available In the oil and gas industries, understanding the behaviour of a flow through an annulus gap in a vertical position, whose outer wall is stationary whilst the inner wall rotates, is a significantly important issue in drilling wells. The main emphasis is placed on experimental (using an available rig and computational (employing CFD software investigations into the effects of the rotation speed of the inner pipe on the axial velocity profiles. The measured axial velocity profiles, in the cases of low axial flow, show that the axial velocity is influenced by the rotation speed of the inner pipe in the region of almost 33% of the annulus near the inner pipe, and influenced inversely in the rest of the annulus. The position of the maximum axial velocity is shifted from the centre to be nearer the inner pipe, by increasing the rotation speed. However, in the case of higher flow, as the rotation speed increases, the axial velocity is reduced and the position of the maximum axial velocity is skewed towards the centre of the annulus. There is a reduction of the swirl velocity corresponding to the rise of the volumetric flow rate.

  6. The influence of the tangential velocity of inner rotating wall on axial velocity profile of flow through vertical annular pipe with rotating inner surface

    Science.gov (United States)

    Sharf, Abdusalam M.; Jawan, Hosen A.; Almabsout, Fthi A.

    2014-03-01

    In the oil and gas industries, understanding the behaviour of a flow through an annulus gap in a vertical position, whose outer wall is stationary whilst the inner wall rotates, is a significantly important issue in drilling wells. The main emphasis is placed on experimental (using an available rig) and computational (employing CFD software) investigations into the effects of the rotation speed of the inner pipe on the axial velocity profiles. The measured axial velocity profiles, in the cases of low axial flow, show that the axial velocity is influenced by the rotation speed of the inner pipe in the region of almost 33% of the annulus near the inner pipe, and influenced inversely in the rest of the annulus. The position of the maximum axial velocity is shifted from the centre to be nearer the inner pipe, by increasing the rotation speed. However, in the case of higher flow, as the rotation speed increases, the axial velocity is reduced and the position of the maximum axial velocity is skewed towards the centre of the annulus. There is a reduction of the swirl velocity corresponding to the rise of the volumetric flow rate.

  7. A Sensor Fusion Method for Tracking Vertical Velocity and Height Based on Inertial and Barometric Altimeter Measurements

    Directory of Open Access Journals (Sweden)

    Angelo Maria Sabatini

    2014-07-01

    Full Text Available A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU. An Extended Kalman Filter (EKF estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally, a complementary filter driven by the vertical linear acceleration and the measured pressure altitude produced estimates of height and vertical velocity. A method was also developed to condition the measured pressure altitude using a whitening filter, which helped to remove the short-term correlation due to environment-dependent pressure changes from raw pressure altitude. The sensor fusion method was implemented to work on-line using data from a wireless baro-IMU and tested for the capability of tracking low-frequency small-amplitude vertical human-like motions that can be critical for stand-alone inertial sensor measurements. Validation tests were performed in different experimental conditions, namely no motion, free-fall motion, forced circular motion and squatting. Accurate on-line tracking of height and vertical velocity was achieved, giving confidence to the use of the sensor fusion method for tracking typical vertical human motions: velocity Root Mean Square Error (RMSE was in the range 0.04–0.24 m/s; height RMSE was in the range 5–68 cm, with statistically significant performance gains when the whitening filter was used by the sensor fusion method to track relatively high-frequency vertical motions.

  8. A sensor fusion method for tracking vertical velocity and height based on inertial and barometric altimeter measurements.

    Science.gov (United States)

    Sabatini, Angelo Maria; Genovese, Vincenzo

    2014-07-24

    A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU) and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU). An Extended Kalman Filter (EKF) estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally, a complementary filter driven by the vertical linear acceleration and the measured pressure altitude produced estimates of height and vertical velocity. A method was also developed to condition the measured pressure altitude using a whitening filter, which helped to remove the short-term correlation due to environment-dependent pressure changes from raw pressure altitude. The sensor fusion method was implemented to work on-line using data from a wireless baro-IMU and tested for the capability of tracking low-frequency small-amplitude vertical human-like motions that can be critical for stand-alone inertial sensor measurements. Validation tests were performed in different experimental conditions, namely no motion, free-fall motion, forced circular motion and squatting. Accurate on-line tracking of height and vertical velocity was achieved, giving confidence to the use of the sensor fusion method for tracking typical vertical human motions: velocity Root Mean Square Error (RMSE) was in the range 0.04-0.24 m/s; height RMSE was in the range 5-68 cm, with statistically significant performance gains when the whitening filter was used by the sensor fusion method to track relatively high-frequency vertical motions.

  9. The Local Stellar Velocity Field via Vector Spherical Harmonics

    Science.gov (United States)

    Makarov, V. V.; Murphy, D. W.

    2007-01-01

    We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism.We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (V(sub X), V(sub Y), V(sub Z)) = (10.5, 18.5, 7.3) +/- 0.1 km s(exp -1) not for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (V(sub X), V(sub Y), V(sub Z)) = (9.9, 15.6, 6.9) +/- 0.2 km s(exp -1). The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star...

  10. Anomalous fluctuations of vertical velocity of Earth and their possible implications for earthquakes.

    Science.gov (United States)

    Manshour, Pouya; Ghasemi, Fatemeh; Matsumoto, T; Gómez, J; Sahimi, Muhammad; Peinke, J; Pacheco, A F; Tabar, M Reza Rahimi

    2010-09-01

    High-quality measurements of seismic activities around the world provide a wealth of data and information that are relevant to understanding of when earthquakes may occur. If viewed as complex stochastic time series, such data may be analyzed by methods that provide deeper insights into their nature, hence leading to better understanding of the data and their possible implications for earthquakes. In this paper, we provide further evidence for our recent proposal [P. Mansour, Phys. Rev. Lett. 102, 014101 (2009)10.1103/PhysRevLett.102.014101] for the existence of a transition in the shape of the probability density function (PDF) of the successive detrended increments of the stochastic fluctuations of Earth's vertical velocity V_{z} , collected by broadband stations before moderate and large earthquakes. To demonstrate the transition, we carried out extensive analysis of the data for V_{z} for 12 earthquakes in several regions around the world, including the recent catasrophic one in Haiti. The analysis supports the hypothesis that before and near the time of an earthquake, the shape of the PDF undergoes significant and discernable changes, which can be characterized quantitatively. The typical time over which the PDF undergoes the transition is about 5-10 h prior to a moderate or large earthquake.

  11. The longitudinal variability of equatorial electrojet and vertical drift velocity in the African and American sectors

    Directory of Open Access Journals (Sweden)

    E. Yizengaw

    2014-03-01

    Full Text Available While the formation of equatorial electrojet (EEJ and its temporal variation is believed to be fairly well understood, the longitudinal variability at all local times is still unknown. This paper presents a case and statistical study of the longitudinal variability of dayside EEJ for all local times using ground-based observations. We found EEJ is stronger in the west American sector and decreases from west to east longitudinal sectors. We also confirm the presence of significant longitudinal difference in the dusk sector pre-reversal drift, using the ion velocity meter (IVM instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in the west American sector compared to the African sector. Previous satellite observations have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This study's results raises the question if the vertical drift, which is believed to be the main cause for the enhancement of Rayleigh–Taylor (RT instability growth rate, is stronger in the American sector and weaker in the African sector – why are the occurrence and amplitude of equatorial irregularities stronger in the African sector?

  12. Vertical structure of internal wave induced velocity for mode I and II solitary waves in two- and three-layer fluid

    Science.gov (United States)

    Gigiyatullin, Ayrat; Kurkin, Andrey; Kurkina, Oxana; Rouvinskaya, Ekaterina; Rybin, Artem

    2017-04-01

    With the use of the Gardner equation, or its variable-coefficient forms, the velocity components of fluid particles in the vertical section induced by a passage of internal waves can be estimated in weakly nonlinear limit. The horizontal velocity gives the greatest contribution into the local current speed. This is a typical property of long waves. This feature of an internal wave field may greatly contribute to the local sediment transport and/or resuspension. The velocity field induced by mode I and II internal solitary waves are studied. The contribution from second-order terms in asymptotic expansion into the horizontal velocity is estimated for the models of two- and three-layer fluid density stratification for solitons of positive and negative polarity, as well as for breathers of different shapes and amplitudes. The influence of the nonlinear correction manifests itself firstly in the shape of the lines of zero horizontal velocity: they are curved and the shape depends on the soliton amplitude and polarity while for the leading-order wave field they are horizontal. Also the wavefield accounting for the nonlinear correction for mode I waves has smaller maximal absolute values of negative velocities (near-surface for the soliton of elevation, and near-bottom for the soliton of depression) and larger maximums of positive velocities. Thus for the solitary internal waves of positive polarity weakly nonlinear theory overestimates the near-bottom velocities and underestimates the near-surface current. For solitary waves of negative polarity, which are the most typical for hydrological conditions of low and middle latitudes, the situation is the opposite. Similar estimations are produced for mode II waves, which possess more complex structure. The presented results of research are obtained with the support of the Russian Foundation for Basic Research grant 16-35-00413.

  13. Newly velocity field of Sulawesi Island from GPS observation

    Science.gov (United States)

    Sarsito, D. A.; Susilo, Simons, W. J. F.; Abidin, H. Z.; Sapiie, B.; Triyoso, W.; Andreas, H.

    2017-07-01

    Sulawesi microplate Island is located at famous triple junction area of the Eurasian, India-Australian, and Philippine Sea plates. Under the influence of the northward moving Australian plate and the westward motion of the Philippine plate, the island at Eastern part of Indonesia is collide and with the Eurasian plate and Sunda Block. Those recent microplate tectonic motions can be quantitatively determine by GNSS-GPS measurement. We use combine GNSS-GPS observation types (campaign type and continuous type) from 1997 to 2015 to derive newly velocity field of the area. Several strategies are applied and tested to get the optimum result, and finally we choose regional strategy to reduce error propagation contribution from global multi baseline processing using GAMIT/GLOBK 10.5. Velocity field are analyzed in global reference frame ITRF 2008 and local reference frame by fixing with respect alternatively to Eurasian plate - Sunda block, India-Australian plate and Philippine Sea plates. Newly results show dense distribution of velocity field. This information is useful for tectonic deformation studying in geospatial era.

  14. A dissipative random velocity field for fully developed fluid turbulence

    Science.gov (United States)

    Chevillard, Laurent; Pereira, Rodrigo; Garban, Christophe

    2016-11-01

    We investigate the statistical properties, based on numerical simulations and analytical calculations, of a recently proposed stochastic model for the velocity field of an incompressible, homogeneous, isotropic and fully developed turbulent flow. A key step in the construction of this model is the introduction of some aspects of the vorticity stretching mechanism that governs the dynamics of fluid particles along their trajectory. An additional further phenomenological step aimed at including the long range correlated nature of turbulence makes this model depending on a single free parameter that can be estimated from experimental measurements. We confirm the realism of the model regarding the geometry of the velocity gradient tensor, the power-law behaviour of the moments of velocity increments, including the intermittent corrections, and the existence of energy transfers across scales. We quantify the dependence of these basic properties of turbulent flows on the free parameter and derive analytically the spectrum of exponents of the structure functions in a simplified non dissipative case. A perturbative expansion shows that energy transfers indeed take place, justifying the dissipative nature of this random field.

  15. Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

    Energy Technology Data Exchange (ETDEWEB)

    Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; Chilson, Phillip B.; Wharton, Sonia

    2016-01-01

    Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w'2) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w'2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w'2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w'2. Through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w'2. After the autocovariance technique is applied, values of w'2 from the Doppler lidars are generally in close agreement (R2≈0.95-0.98) with those calculated from sonic anemometer measurements.

  16. Thermal stability effects on the structure of the velocity field above an air-water interface

    Science.gov (United States)

    Papadimitrakis, Y. A.; Hsu, Y.-H. L.; Wu, J.

    1987-01-01

    Mean velocity and turbulence measurements are described for turbulent flows above laboratory water waves, under various wind and thermal stratification conditions. Experimental results, when presented in the framework of Monin-Obukhov (1954) similarity theory, support local scaling based on evaluation of stratification effects at the same nondimensional distance from the mean water surface. Such scaling allows an extension of application of the above theory to the outer region of the boundary layer. Throughout the fully turbulent region, ratios of mean velocity gradients, eddy viscosities, and turbulence intensities under nonneutral and neutral conditions correlate well with the parameter z/Lambda (Lambda being a local Obukhov length and z the vertical coordinate of the mean air flow) and show good agreement with established field correlations. The influence of stratification on the wind-stress coefficient can be estimated from an empirical relationship in terms of its value under neutral conditions and a bulk Richardson number.

  17. Shear velocity of the Rotokawa geothermal field using ambient noise

    Science.gov (United States)

    Civilini, F.; Savage, M. K.; Townend, J.

    2014-12-01

    Ambient noise correlation is an increasingly popular seismological technique that uses the ambient seismic noise recorded at two stations to construct an empirical Green's function. Applications of this technique include determining shear velocity structure and attenuation. An advantage of ambient noise is that it does not rely on external sources of seismic energy such as local or teleseismic earthquakes. This method has been used in the geothermal industry to determine the depths at which magmatic processes occur, to distinguish between production and non-production areas, and to observe seismic velocity perturbations associated with fluid extraction. We will present a velocity model for the Rotokawa geothermal field near Taupo, New Zealand, produced from ambient noise cross correlations. Production at Rotokawa is based on the "Rotokawa A" combined cycle power station established in 1997 and the "Nga Awa Purua" triple flash power plant established in 2010. Rotokawa Joint Venture, a partnership between Mighty River Power and Tauhara North No. 2 Trust currently operates 174 MW of generation at Rotokawa. An array of short period seismometers was installed in 2008 and occupies an area of roughly 5 square kilometers around the site. Although both cultural and natural noise sources are recorded at the stations, the instrument separation distance provides a unique challenge for analyzing cross correlations produced by both signal types. The inter-station spacing is on the order of a few kilometers, so waves from cultural sources generally are not coherent from one station to the other, while the wavelength produced by natural noise is greater than the station separation. Velocity models produced from these two source types will be compared to known geological models of the site. Depending on the amount of data needed to adequately construct cross-correlations, a time-dependent model of velocity will be established and compared with geothermal production processes.

  18. High-resolution Vertical Profiling of Ocean Velocity and Water Properties Under Hurricane Frances in September 2004

    Science.gov (United States)

    Sanford, T. B.; D'Asarp, E. A.; Girton, J. B.; Price, J. F.; Webb, D. C.

    2006-12-01

    In ONR's CBLAST Hurricane research program observations were made of the upper ocean's response to Hurricane Frances. Three EM-APEX floats (velocity sensing versions of Webb Research APEX floats) and two Lagrangian floats were deployed north of Hispaniola from a C-130 aircraft ahead of Hurricane Frances in September 2004. The EM-APEX floats measured T, S and V over the upper 500 m starting about a day before the storm's arrival. The Lagrangian floats measured temperature and salinity while following the three- dimensional boundary layer turbulence in the upper 40 m. One EM-APEX float was directly under the track of the storm's eye, another EM-APEX and two Lagrangian floats went in about 50 km to the right of the track (where the surface winds are strongest) and the third float was about 100 km to the right. The EM-APEX floats profiled for 10 hours from the surface to 200 m, then continued profiling between 35 and 200 m with excursions to 500 m every half inertial period. After 5 days, the EM-APEX floats surfaced and transmitted the accumulated processed observations, then the floats profiled to 500 m every half inertial period until recovered early in October aided by GPS and Iridium. The float array sampled in unprecedented detail the upper-ocean turbulence, momentum, and salt and heat changes in response to the hurricane. The buildup of surface gravity waves in advance of the storm was also observed in the velocity profiles, with significant wave heights of up to 11 m. Rapid acceleration of inertial currents in the surface mixing layer (SML) to over 1 m/s stimulated vertical mixing by shear instability at the SML base, as indicated by low Richardson numbers and SML deepening from about 40 m to 120 m under the strongest wind forcing. Surface cooling of about 2.5 C was primarily due to the SML deepening and entrainment of colder water, with a small contribution from surface heat flux. Intense inertial pumping was observed under the eye, with vertical excursions of

  19. Vertical Electric Field Measurements with Copper Plates by Sounding Balloon

    Science.gov (United States)

    Wen, Shao-Chun; Chiu, Cheng-Hsiu; Bing-Chih Chen, Alfred; Hsu, Rue-Ron; Su, Han-Tzong

    2015-04-01

    The vertical electric field plays an important role in driving the circulation of the global electric circuit, and crucial to the formation of the transient luminous events (TLEs). The in-situ measurement of the electric field in the upper atmosphere, especially from cloud top to the bottom of the ionosphere is very challenging but essential. Limited by the flight vehicle, the measurements of the electric field in and above cloud, especiall thundercloud, is rare up to now. A light-weight electric field meter was developed independently and sent to 30 km height by small meteorological balloons successfully. Other than the existing long-spaced, spherical probe design, an improved electric field meter has been built and tested carefully. A new circuit with ultra high input impedance and a high voltage amplifier is implemented to reduce the AC noise induced by the voltage divider. Two copper plates are used to replace the double spherical probes which is spaced by a long fiberglass boom. The in-lab calibration and tests show that this new model is superior to the existing design and very sensitive to the variation of the DC electric field. In this poster, the design and the in-lab tests will be presented, and preliminary results of the flight experiments are also discussed.

  20. On vertical velocity fluctuations and internal tides in an upwelling region off the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.; Antony, M.K.

    of flow and wind and temperature oscillations at a mooring site in the shelf waters off the west coast of India are discussed. The vertical velocities were computed from a time series of vertical temperature profiles assuming that horizontal advection... of tem- perature is negligible. The computed values at a depth of 40 m during the 72-h period of observation were of the order of 10-l to lo-* cm s-i, with a mean value of - 2.77 x lo-* cm s-i indicating a net upward movement of water. The com- puted...

  1. Measurements of the fluctuating liquid velocity of a bidisperse suspension of bubbles rising in a vertical channel

    Science.gov (United States)

    Serrano, Juan Carlos; Mendez, Santos; Zenit, Roberto

    2009-11-01

    Experiments were performed in a vertical channel to study the behaviour of a bidisperse suspension of bubbles. Bubbles were produced using capillaries of two distinct inner diameters. The capillaries are small enough to generate bubbles in the range of 1 to 6 mm in diameter. Using water and water-glycerin mixtures, the vertical component of the fluctuating liquid velocity was obtained using a flying hot wire anemometer technique. The system is characterized by the dimensionless Reynolds and Weber numbers in the range of 22bubble concentration. We also found that the variance, normalized with the mean bubble velocity squared, Tf% =Uf^^'2/Ub^2, increased as the Reynolds number decreased. Bidisperse flows, in general, show larger values of fluctuation.

  2. Full field gas phase velocity measurements in microgravity

    Science.gov (United States)

    Griffin, Devon W.; Yanis, William

    1995-01-01

    Measurement of full-field velocities via Particle Imaging Velocimetry (PIV) is common in research efforts involving fluid motion. While such measurements have been successfully performed in the liquid phase in a microgravity environment, gas-phase measurements have been beset by difficulties with seeding and laser strength. A synthesis of techniques developed at NASA LeRC exhibits promise in overcoming these difficulties. Typical implementation of PIV involves forming the light from a pulsed laser into a sheet that is some fraction of a millimeter thick and 50 or more millimeters wide. When a particle enters this sheet during a pulse, light scattered from the particle is recorded by a detector, which may be a film plane or a CCD array. Assuming that the particle remains within the boundaries of the sheet for the second pulse and can be distinguished from neighboring particles, comparison of the two images produces an average velocity vector for the time between the pulses. If the concentration of particles in the sampling volume is sufficiently large but the particles remain discrete, a full field map may be generated.

  3. Rayleigh-Bénard convection with uniform vertical magnetic field.

    Science.gov (United States)

    Basak, Arnab; Raveendran, Rohit; Kumar, Krishna

    2014-09-01

    We present the results of direct numerical simulations of Rayleigh-Bénard convection in the presence of a uniform vertical magnetic field near instability onset. We have done simulations in boxes with square as well as rectangular cross sections in the horizontal plane. We have considered the horizontal aspect ratio η=L(y)/L(x)=1 and 2. The onset of the primary and secondary instabilities are strongly suppressed in the presence of the vertical magnetic field for η=1. The Nusselt number Nu scales with the Rayleigh number Ra close to the primary instability as [{Ra-Ra(c)(Q)}/Ra(c)(Q)](0.91), where Ra(c)(Q) is the threshold for onset of stationary convection at a given value of the Chandrasekhar number Q. Nu also scales with Ra/Q as (Ra/Q)(μ). The exponent μ varies in the range 0.39≤μ≤0.57 for Ra/Q≥25. The primary instability is stationary as predicted by Chandrasekhar. The secondary instability is temporally periodic for Pr=0.1 but quasiperiodic for Pr=0.025 for moderate values of Q. Convective patterns for higher values of Ra consist of periodic, quasiperiodic, and chaotic wavy rolls above the onset of the secondary instability for η=1. In addition, stationary as well as time-dependent cross rolls are observed, as Ra is further raised. The ratio r(o)/Pr is independent of Q for smaller values of Q. The delay in the onset of the oscillatory instability is significantly reduced in a simulation box with η=2. We also observe inclined stationary rolls for smaller values of Q for η=2.

  4. An algorithm to estimate unsteady and quasi-steady pressure fields from velocity field measurements.

    Science.gov (United States)

    Dabiri, John O; Bose, Sanjeeb; Gemmell, Brad J; Colin, Sean P; Costello, John H

    2014-02-01

    We describe and characterize a method for estimating the pressure field corresponding to velocity field measurements such as those obtained by using particle image velocimetry. The pressure gradient is estimated from a time series of velocity fields for unsteady calculations or from a single velocity field for quasi-steady calculations. The corresponding pressure field is determined based on median polling of several integration paths through the pressure gradient field in order to reduce the effect of measurement errors that accumulate along individual integration paths. Integration paths are restricted to the nodes of the measured velocity field, thereby eliminating the need for measurement interpolation during this step and significantly reducing the computational cost of the algorithm relative to previous approaches. The method is validated by using numerically simulated flow past a stationary, two-dimensional bluff body and a computational model of a three-dimensional, self-propelled anguilliform swimmer to study the effects of spatial and temporal resolution, domain size, signal-to-noise ratio and out-of-plane effects. Particle image velocimetry measurements of a freely swimming jellyfish medusa and a freely swimming lamprey are analyzed using the method to demonstrate the efficacy of the approach when applied to empirical data.

  5. Operating length and velocity of human M. vastus lateralis fascicles during vertical jumping

    Science.gov (United States)

    Nikolaidou, Maria Elissavet; Marzilger, Robert; Bohm, Sebastian; Mersmann, Falk

    2017-01-01

    Humans achieve greater jump height during a counter-movement jump (CMJ) than in a squat jump (SJ). However, the crucial difference is the mean mechanical power output during the propulsion phase, which could be determined by intrinsic neuro-muscular mechanisms for power production. We measured M. vastus lateralis (VL) fascicle length changes and activation patterns and assessed the force–length, force–velocity and power–velocity potentials during the jumps. Compared with the SJ, the VL fascicles operated on a more favourable portion of the force–length curve (7% greater force potential, i.e. fraction of VL maximum force according to the force–length relationship) and more disadvantageous portion of the force–velocity curve (11% lower force potential, i.e. fraction of VL maximum force according to the force–velocity relationship) in the CMJ, indicating a reciprocal effect of force–length and force–velocity potentials for force generation. The higher muscle activation (15%) could therefore explain the moderately greater jump height (5%) in the CMJ. The mean fascicle-shortening velocity in the CMJ was closer to the plateau of the power–velocity curve, which resulted in a greater (15%) power–velocity potential (i.e. fraction of VL maximum power according to the power–velocity relationship). Our findings provide evidence for a cumulative effect of three different mechanisms—i.e. greater force–length potential, greater power–velocity potential and greater muscle activity—for an advantaged power production in the CMJ contributing to the marked difference in mean mechanical power (56%) compared with SJ. PMID:28573027

  6. Addition of Vertical Velocity to a One-Dimensional Aerosol and Trace Gas Model

    National Research Council Canada - National Science Library

    Hoppel, William A; Caffrey, Peter; Frick, Glendon M

    2005-01-01

    ... (Coupled Ocean Atmosphere Meteorological Prediction System). The aerosol model is run along an air-mass trajectory generated from the output of COAMPS that includes vertical profiles of meteorological data required by the aerosol model...

  7. Vertical E × B drift velocity variations and associated low-latitude ionospheric irregularities investigated with the TOPEX and GPS satellite data

    Directory of Open Access Journals (Sweden)

    I. Horvath

    2003-04-01

    Full Text Available With a well-selected data set, the various events of the vertical E × B drift velocity variations at magnetic-equator-latitudes, the resultant ionospheric features at low-and mid-latitudes, and the practical consequences of these E × B events on the equatorial radio signal propagation are demonstrated. On a global scale, the development of a equatorial anomaly is illustrated with a series of 1995 global TOPEX TEC (total electron content maps. Locally, in the Australian longitude region, some field-aligned TOPEX TEC cross sections are combined with the matching Guam (144.86° E; 13.59° N, geographic GPS (Global Positioning System TEC data, covering the northern crest of the equatorial anomaly. Together, the 1998 TOPEX and GPS TEC data are utilized to show the three main events of vertical E × B drift velocity variations: (1 the pre-reversal enhancement, (2 the reversal and (3 the downward maximum. Their effects on the dual-frequency GPS recordings are documented with the raw Guam GPS TEC data and with the filtered Guam GPS dTEC/min or 1-min GPS TEC data after Aarons et al. (1997. During these E × B drift velocity events, the Port Moresby (147.10° E; - 9.40° N, geographic virtual height or h'F ionosonde data (km, which cover the southern crest of the equatorial anomaly in the Australian longitude region, show the effects of plasma drift on the equatorial ionosphere. With the net (D horizontal (H magnetic field intensity parameter, introduced and called DH or Hequator-Hnon-equator (nT by Chandra and Rastogi (1974, the daily E × B drift velocity variations are illustrated at 121° E (geographic in the Australian longitude region. The results obtained with the various data show very clearly that the development of mid-latitude night-time TEC increases is triggered by the westward electric field as the appearance of such night-time TEC increases coincides with the E × B drift velocity reversal. An explanation is offered with the F

  8. Velocity field measurements of electrokinetic flow past a conductive cylinder

    Science.gov (United States)

    Canpolat, Cetin; Beskok, Ali

    2011-11-01

    Using the micro particle-image-velocimetry technique, electrokinetic (EK) flow past a conductive circular cylinder (D=0.67 mm) is measured in a rectangular cross-section PDMS/glass microchannel (H=0.1 mm, W=1.0 mm and L=5.3 mm). EK transport in such a system experiences electrophoresis (EP) of the PIV particles, electroosmotic flow (EOF) due to the channel walls, and induced charge electroosmotic (ICEO) flow due to the conductive cylinder. Experiments are conducted using 1xPBS buffer diluted in DI water, and the buffer pH is fixed at 2.05 using HCl solution. This pH value is shown to nearly eliminate the electrophoresis of 0.5 micron carboxylate modified spherical micro-particles used in the PIV studies. Suppression of EP enabled direct measurements of local ICEO flow and its interaction with the global EOF in the channel. By systematically varying the applied electric field from 5 V to 40 V, changes in the velocity field are recorded and correlated with the theoretical trends of EOF and ICEO flow. C.C. acknowledges the support of TUBITAK for this study.

  9. A simple algorithm to estimate pressure fields from velocity field measurements

    CERN Document Server

    Dabiri, John O

    2014-01-01

    This note briefly describes and characterizes a method for estimating the pressure field corresponding to instantaneous velocity field measurements. The algorithm is based on median polling of several integration paths through the measurement domain in order to reduce the effect of measurement errors that accumulate along individual integration paths. Integration paths are restricted to the nodes of the measured velocity field, thereby eliminating the need for measurement interpolation during integration of the pressure gradient field and significantly reducing the computational cost of the algorithm relative to previous approaches. The algorithm is validated using a numerically-simulated bluff-body flow to study the effects of spatial resolution, domain size, and signal-to-noise ratio.

  10. Variable Field Analytical Ultracentrifugation: II. Gravitational Sweep Sedimentation Velocity.

    Science.gov (United States)

    Ma, Jia; Zhao, Huaying; Sandmaier, Julia; Alexander Liddle, J; Schuck, Peter

    2016-01-05

    Sedimentation velocity (SV) analytical ultracentrifugation is a classical biophysical technique for the determination of the size-distribution of macromolecules, macromolecular complexes, and nanoparticles. SV has traditionally been carried out at a constant rotor speed, which limits the range of sedimentation coefficients that can be detected in a single experiment. Recently we have introduced methods to implement experiments with variable rotor speeds, in combination with variable field solutions to the Lamm equation, with the application to expedite the approach to sedimentation equilibrium. Here, we describe the use of variable-field sedimentation analysis to increase the size-range covered in SV experiments by ∼100-fold with a quasi-continuous increase of rotor speed during the experiment. Such a gravitational-sweep sedimentation approach has previously been shown to be very effective in the study of nanoparticles with large size ranges. In the past, diffusion processes were not accounted for, thereby posing a lower limit of particle sizes and limiting the accuracy of the size distribution. In this work, we combine variable field solutions to the Lamm equation with diffusion-deconvoluted sedimentation coefficient distributions c(s), which further extend the macromolecular size range that can be observed in a single SV experiment while maintaining accuracy and resolution. In this way, approximately five orders of magnitude of sedimentation coefficients, or eight orders of magnitude of particle mass, can be probed in a single experiment. This can be useful, for example, in the study of proteins forming large assemblies, as in fibrillation process or capsid self-assembly, in studies of the interaction between very dissimilar-sized macromolecular species, or in the study of broadly distributed nanoparticles. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  11. Step-Wise Velocity of an Air Bubble Rising in a Vertical Tube Filled with a Liquid Dispersion of Nanoparticles.

    Science.gov (United States)

    Cho, Heon Ki; Nikolov, Alex D; Wasan, Darsh T

    2017-03-21

    The motion of air bubbles in tubes filled with aqueous suspensions of nanoparticles (nanofluids) is of practical interest for bubble jets, lab-on-a-chip, and transporting media. Therefore, the focus of this study is the dynamics of air bubbles rising in a tube in a nanofluid. Many authors experimentally and analytically proposed that the velocity of rising air bubbles is constant for long air bubbles suspended in a vertical tube in common liquids (e.g. an aqueous glycerol solution) when the capillary number is larger than 10-4. For the first time, we report here a systematic study of an air bubble rising in a vertical tube in a nanofluid (e.g. an aqueous silica dioxide nanoparticle suspension, nominal particle size, 19 nm). We varied the bubble length scaled by the diameter of the tubes (L/D), the concentration of the nanofluid (10 and 12.5 v %), and the tube diameter (0.45, 0.47, and 0.50 cm). The presence of the nanoparticles creates a significant change in the bubble velocity compared with the bubble rising in the common liquid with the same bulk viscosity. We observed a novel phenomenon of a step-wise increase in the air bubble rising velocity versus bubble length for small capillary numbers less than 10-7. This step-wise velocity increase versus the bubble length was not observed in a common fluid. The step-wise velocity increase is attributed to the nanoparticle self-layering phenomenon in the film adjacent to the tube wall. To elucidate the role of the nanoparticle film self-layering on the bubble rising velocity, the effect of the capillary number, the tube diameter (e.g. the capillary pressure), and nanofilm viscosity are investigated. We propose a model that takes into consideration the nanoparticle layering in the film confinement to explain the step-wise velocity phenomenon versus the length of the bubble. The oscillatory film interaction energy isotherm is calculated and the Frenkel approach is used to estimate the film viscosity.

  12. Vertically coupled double quantum rings at zero magnetic field

    Science.gov (United States)

    Malet, F.; Barranco, M.; Lipparini, E.; Mayol, R.; Pi, M.; Climente, J. I.; Planelles, J.

    2006-06-01

    Within local-spin-density functional theory, we have investigated the “dissociation” of few-electron circular vertical semiconductor double quantum ring artificial molecules at zero magnetic field as a function of inter-ring distance. In a first step, the molecules are constituted by two identical quantum rings. When the rings are quantum mechanically strongly coupled, the electronic states are substantially delocalized, and the addition energy spectra of the artificial molecule resemble those of a single quantum ring in the few-electron limit. When the rings are quantum mechanically weakly coupled, the electronic states in the molecule are substantially localized in one ring or the other, although the rings can be electrostatically coupled. The effect of a slight mismatch introduced in the molecules from nominally identical quantum wells, or from changes in the inner radius of the constituent rings, induces localization by offsetting the energy levels in the quantum rings. This plays a crucial role in the appearance of the addition spectra as a function of coupling strength particularly in the weak coupling limit.

  13. Case studies of the impact of orbital sampling on stratospheric trend detection and derivation of tropical vertical velocities: solar occultation vs. limb emission sounding

    Directory of Open Access Journals (Sweden)

    L. F. Millán

    2016-09-01

    Full Text Available This study investigates the representativeness of two types of orbital sampling applied to stratospheric temperature and trace gas fields. Model fields are sampled using real sampling patterns from the Aura Microwave Limb Sounder (MLS, the HALogen Occultation Experiment (HALOE and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS. The MLS sampling acts as a proxy for a dense uniform sampling pattern typical of limb emission sounders, while HALOE and ACE-FTS represent coarse nonuniform sampling patterns characteristic of solar occultation instruments. First, this study revisits the impact of sampling patterns in terms of the sampling bias, as previous studies have done. Then, it quantifies the impact of different sampling patterns on the estimation of trends and their associated detectability. In general, we find that coarse nonuniform sampling patterns may introduce non-negligible errors in the inferred magnitude of temperature and trace gas trends and necessitate considerably longer records for their definitive detection. Lastly, we explore the impact of these sampling patterns on tropical vertical velocities derived from stratospheric water vapor measurements. We find that coarse nonuniform sampling may lead to a biased depiction of the tropical vertical velocities and, hence, to a biased estimation of the impact of the mechanisms that modulate these velocities. These case studies suggest that dense uniform sampling such as that available from limb emission sounders provides much greater fidelity in detecting signals of stratospheric change (for example, fingerprints of greenhouse gas warming and stratospheric ozone recovery than coarse nonuniform sampling such as that of solar occultation instruments.

  14. VELOCITY FIELD COMPUTATION IN VIBRATED GRANULAR MEDIA USING AN OPTICAL FLOW BASED MULTISCALE IMAGE ANALYSIS METHOD

    Directory of Open Access Journals (Sweden)

    Johan Debayle

    2011-05-01

    Full Text Available An image analysis method has been developed in order to compute the velocity field of a granular medium (sand grains, mean diameter 600 μm submitted to different kinds of mechanical stresses. The differential method based on optical flow conservation consists in describing a dense motion field with vectors associated to each pixel. A multiscale, coarse-to-fine, analytical approach through tailor sized windows yields the best compromise between accuracy and robustness of the results, while enabling an acceptable computation time. The corresponding algorithmis presented and its validation discussed through different tests. The results of the validation tests of the proposed approach show that the method is satisfactory when attributing specific values to parameters in association with the size of the image analysis window. An application in the case of vibrated sand has been studied. An instrumented laboratory device provides sinusoidal vibrations and enables external optical observations of sand motion in 3D transparent boxes. At 50 Hz, by increasing the relative acceleration G, the onset and development of two convective rolls can be observed. An ultra fast camera records the grain avalanches, and several pairs of images are analysed by the proposed method. The vertical velocity profiles are deduced and allow to precisely quantify the dimensions of the fluidized region as a function of G.

  15. Differences in vertical jumping and mae-geri kicking velocity between international and national level karateka

    Directory of Open Access Journals (Sweden)

    Carlos Balsalobre-Fernández

    2013-04-01

    Full Text Available Aim: Lower limb explosive strength and mae-geri kicking velocity are fundamental in karate competition; although it is unclear whether these variables could differentiate the high-level athletes. The objective of this research is to analyze the differences in the mae-geri kicking velocity and the counter-movement jump (CMJ between a group of international top level karateka and another group of national-level karateka.Methods: Thirteen international-level karateka and eleven national-level karateka participated in the study. After a standard warm-up, CMJ height (in cm and mae-geri kicking velocity (in m/s was measured using an IR-platform and a high-speed camera, respectively.Results: Proceeding with MANCOVA to analyze the differences between groups controlling the effect of age, the results show that the international-level karateka demonstrated significantly higher levels of CMJ than national-level competitors (+22.1%, F = 9.47, p = 0.006, η2 = 0.311. There were no significant differences between groups in the mae-geri kicking velocity (+5,7%, F=0.80; p=0.38; η2=0.03.Conclusion: Our data shows, first, the importance of CMJ assessment as a tool to detect talent in karate and, second, that to achieve international-level in karate it may be important to increase CMJ levels to values ​​similar to those offered here.

  16. Year-Long Vertical Velocity Statistics Derived from Doppler Lidar Data for the Continental Convective Boundary Layer

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Larry K. [Pacific Northwest National Laboratory, Richland, Washington; Newsom, Rob K. [Pacific Northwest National Laboratory, Richland, Washington; Turner, David D. [Global Systems Division, NOAA/Earth System Research Laboratory, Boulder, Colorado

    2017-09-01

    One year of Coherent Doppler Lidar (CDL) data collected at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) site in Oklahoma is analyzed to provide profiles of vertical velocity variance, skewness, and kurtosis for cases of cloud-free convective boundary layers. The variance was scaled by the Deardorff convective velocity scale, which was successful when the boundary layer depth was stationary but failed in situations when the layer was changing rapidly. In this study the data are sorted according to time of day, season, wind direction, surface shear stress, degree of instability, and wind shear across the boundary-layer top. The normalized variance was found to have its peak value near a normalized height of 0.25. The magnitude of the variance changes with season, shear stress, and degree of instability, but was not impacted by wind shear across the boundary-layer top. The skewness was largest in the top half of the boundary layer (with the exception of wintertime conditions). The skewness was found to be a function of the season, shear stress, wind shear across the boundary-layer top, with larger amounts of shear leading to smaller values. Like skewness, the vertical profile of kurtosis followed a consistent pattern, with peak values near the boundary-layer top (also with the exception of wintertime data). The altitude of the peak values of kurtosis was found to be lower when there was a large amount of wind shear at the boundary-layer top.

  17. Monte Carlo-based subgrid parameterization of vertical velocity and stratiform cloud microphysics in ECHAM5.5-HAM2

    Directory of Open Access Journals (Sweden)

    J. Tonttila

    2013-08-01

    Full Text Available A new method for parameterizing the subgrid variations of vertical velocity and cloud droplet number concentration (CDNC is presented for general circulation models (GCMs. These parameterizations build on top of existing parameterizations that create stochastic subgrid cloud columns inside the GCM grid cells, which can be employed by the Monte Carlo independent column approximation approach for radiative transfer. The new model version adds a description for vertical velocity in individual subgrid columns, which can be used to compute cloud activation and the subgrid distribution of the number of cloud droplets explicitly. Autoconversion is also treated explicitly in the subcolumn space. This provides a consistent way of simulating the cloud radiative effects with two-moment cloud microphysical properties defined at subgrid scale. The primary impact of the new parameterizations is to decrease the CDNC over polluted continents, while over the oceans the impact is smaller. Moreover, the lower CDNC induces a stronger autoconversion of cloud water to rain. The strongest reduction in CDNC and cloud water content over the continental areas promotes weaker shortwave cloud radiative effects (SW CREs even after retuning the model. However, compared to the reference simulation, a slightly stronger SW CRE is seen e.g. over mid-latitude oceans, where CDNC remains similar to the reference simulation, and the in-cloud liquid water content is slightly increased after retuning the model.

  18. METALLICITY DISTRIBUTION FUNCTIONS, RADIAL VELOCITIES, AND ALPHA ELEMENT ABUNDANCES IN THREE OFF-AXIS BULGE FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Christian I.; Rich, R. Michael [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Kobayashi, Chiaki [Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Kunder, Andrea; De Propris, Roberto [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile); Pilachowski, Catherine A. [Department of Astronomy, Indiana University, Swain West 319, 727 East Third Street, Bloomington, IN 47405-7105 (United States); Koch, Andreas, E-mail: cijohnson@astro.ucla.edu, E-mail: rmr@astro.ucla.edu, E-mail: c.kobayashi@herts.ac.uk, E-mail: akunder@ctio.noao.edu, E-mail: catyp@astro.indiana.edu, E-mail: akoch@lsw.uni-heidelberg.de [Zentrum fuer Astronomie der Universitaet Heidelberg, Landessternwarte, Koenigstuhl 12, Heidelberg (Germany)

    2013-03-10

    We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe], [Si/Fe], and [Ca/Fe] for 264 red giant branch stars in three Galactic bulge off-axis fields located near (l, b) = (-5.5, -7), (-4, -9), and (+8.5, +9). The results are based on equivalent width and spectrum synthesis analyses of moderate resolution (R Almost-Equal-To 18,000), high signal-to-noise ratio (S/N {approx} 75-300 pixel{sup -1}) spectra obtained with the Hydra spectrographs on the Blanco 4 m and WIYN 3.5 m telescopes. The targets were selected from the blue side of the giant branch to avoid cool stars that would be strongly affected by CN and TiO; however, a comparison of the color-metallicity distribution in literature samples suggests that our selection of bluer targets should not present a significant bias against metal-rich stars. We find a full range in metallicity that spans [Fe/H] Almost-Equal-To -1.5 to +0.5, and that, in accordance with the previously observed minor-axis vertical metallicity gradient, the median [Fe/H] also declines with increasing Galactic latitude in off-axis fields. The off-axis vertical [Fe/H] gradient in the southern bulge is estimated to be {approx}0.4 dex kpc{sup -1}; however, comparison with the minor-axis data suggests that a strong radial gradient does not exist. The (+8.5, +9) field exhibits a higher than expected metallicity, with a median [Fe/H] = -0.23, that might be related to a stronger presence of the X-shaped bulge structure along that line-of-sight. This could also be the cause of an anomalous increase in the median radial velocity for intermediate metallicity stars in the (+8.5, +9) field. However, the overall radial velocity and dispersion for each field are in good agreement with recent surveys and bulge models. All fields exhibit an identical, strong decrease in velocity dispersion with increasing metallicity that is consistent with observations in similar minor-axis outer bulge fields. Additionally, the [O/Fe], [Si/Fe], and [Ca

  19. Dynamic aeroelastic stability of vertical-axis wind turbines under constant wind velocity

    Science.gov (United States)

    Nitzsche, Fred

    1994-05-01

    The flutter problem associated with the blades of a class of vertical-axis wind turbines called Darrieus is studied in detail. The spinning blade is supposed to be initially curved in a particular shape characterized by a state of pure tension at the blade cross section. From this equilibrium position a three-dimensional linear perturbation pattern is superimposed to determine the dynamic aeroelastic stability of the blade in the presence of free wind speed by means of the Floquet-Lyapunov theory for periodic systems.

  20. Defining the Velocity Field of Root Cells in Arabidopsis Seedlings Using Open Source Image Processing Tools

    Science.gov (United States)

    Craig, Amy E.; Higgins, Brad R.; Guy, Tracy; Durham Brooks, Tessa; Wentworth, Christopher D.

    2011-11-01

    The velocity field for cells in a growing root is a function of a cell's position with respect to the root apex and time. For many species of plant this function has the same general sigmoid shape described by a modified logistics curve. In this investigation we obtain microscopic images of Arabidopsis seedling roots over a 20 minute period of time, measure the velocity field for root cells using an application developed with the open source mathematics application Octave, and test whether the velocity field can be described by the modified logistics function. We find support for describing the velocity field by the modified logistics function.

  1. Numerical Simulations of Wave-Induced Flow Fields around Large-Diameter Surface-Piercing Vertical Circular Cylinder

    Directory of Open Access Journals (Sweden)

    Giancarlo Alfonsi

    2015-08-01

    Full Text Available A computational analysis is performed on the diffraction of water waves induced by large-diameter, surface-piercing, vertical circular cylinder. With reference to linear-wave cases, the phenomenon is preliminarly considered in terms of velocity potential, a simplified theoretical framework in which both hypotheses of inviscid fluid and irrotational flow are incorporated. Then, and as a first-approximation analysis, the Euler equations in primitive variables are considered (a framework in which the fluid is still handled as inviscid, but the field can be rotational. Finally, the real-fluid behavior is analyzed, by numerically integrating the full Navier-Stokes equations (viscous fluid and rotational field in their velocity-pressure formulation, by following the approach of the Direct Numerical Simulation (DNS, no models are used for the fluctuating portion of the velocity field. For further investigation of the flow fields, the swirling-strength criterion for flow-structure extraction, and the Karhunen-Loève (KL decomposition technique for the extraction of the most energetic flow modes respectively, are applied to the computed fields. It is found that remarkable differences exist between the wave-induced fields, as derived within the different computing frameworks tested.

  2. Migration velocity analysis using pre-stack wave fields

    KAUST Repository

    Alkhalifah, Tariq Ali

    2016-08-25

    Using both image and data domains to perform velocity inversion can help us resolve the long and short wavelength components of the velocity model, usually in that order. This translates to integrating migration velocity analysis into full waveform inversion. The migration velocity analysis part of the inversion often requires computing extended images, which is expensive when using conventional methods. As a result, we use pre-stack wavefield (the double-square-root formulation) extrapolation, which includes the extended information (subsurface offsets) naturally, to make the process far more efficient and stable. The combination of the forward and adjoint pre-stack wavefields provides us with update options that can be easily conditioned to improve convergence. We specifically use a modified differential semblance operator to split the extended image into a residual part for classic differential semblance operator updates and the image (Born) modelling part, which provides reflections for higher resolution information. In our implementation, we invert for the velocity and the image simultaneously through a dual objective function. Applications to synthetic examples demonstrate the features of the approach.

  3. On the effects of vertical air velocity on winter precipitation types

    Directory of Open Access Journals (Sweden)

    J. M. Thériault

    2007-01-01

    Full Text Available The various precipitation types formed within winter storms (such as snow, wet snow and freezing rain often lead to very hazardous weather conditions. These types of precipitation often occur during the passage of a warm front as a warm air mass ascends over a cold air mass. To address this issue further, we used a one-dimensional kinematic cloud model to simulate this gentle ascent (≤10 cm/s of warm air. The initial temperature profile has an above 0°C inversion, a lower subfreezing layer, and precipitation falls from above the temperature inversion. The cloud model is coupled to a double-moment microphysics scheme that simulates the production of various types of winter precipitation. The results are compared with those from a previous study carried out in still air. Based on the temporal evolution of surface precipitation, snow reaches the surface significantly faster than in still air whereas other precipitation types including freezing rain and ice pellets have a shorter duration. Overall, even weak background vertical ascent has an important impact on the precipitation reaching the surface, the time of the elimination of the melting layer, and also the evolution of the lower subfreezing layer.

  4. Analysis of Vertical Velocities and Elevated Instability in the Comma-Head of Continental Winter Cyclones

    Science.gov (United States)

    Rosenow, Andrew

    The vertical motion and physical structure of elevated convection and generating cells within the comma heads of three continental winter cyclones are investigated using the Wyoming W-band Cloud Radar mounted on the NSF/NCAR C-130, supplemented by analyses from the Rapid Update Cycle model and WSR-88D data. The cyclones followed three distinct archetypical tracks and were typical of those producing winter weather in the Midwestern United States. In two of the cyclones, dry air in the middle and upper troposphere behind the Pacific cold front intruded over moist Gulf of Mexico air at lower altitudes within the comma head, separating the comma head into two zones. Elevated convection in the southern zone extended from the cold frontal surface to the tropopause. The stronger convective updrafts ranged from 2 to 7 m s-1 and downdrafts from -2 to -6 m s-1. The horizontal scale of the convective cells was ˜5 km. The poleward zone of the comma head was characterized by deep stratiform clouds topped by cloud top generating cells that reached the tropopause. Updrafts and downdrafts within the generating cells ranged from 1-2 m s-1, with the horizontal scale of the cells ˜1-2 km. Precipitation on the poleward side of the comma head conformed to a seeder-feeder process, the generating cells seeding the stratiform cloud, which was forced by synoptic scale ascent. In one case, shallow clouds behind the cyclone's cold front were also topped by cloud top generating cells, with vertical motions ranging from 1 2 m s-1. The development and distribution of potential instability in the elevated convective region of one of these cyclones is examined using a Weather Research and Forecasting (WRF) model simulation. The strong 8-9 December 2009 cyclone is simulated with a large outer domain and convection-allowing nest to simulate the convective region of the cyclone. The distribution of Most Unstable Convective Available Potential Energy (MUCAPE) is presented, with MUCAPE values up to

  5. Magnetic Geared Radial Axis Vertical Wind Turbine for Low Velocity Regimes

    Directory of Open Access Journals (Sweden)

    Wei Wei Teow

    2018-01-01

    Full Text Available In the 21st century, every country is seeking an alternative source of energy especially the renewable sources. There are considerable developments in the wind energy technology in recent years and in more particular on the vertical axis wind turbine (VAWT as they are modular, less installation cost and portable in comparison with that of the horizontal axis wind turbine (HAWT systems. The cut-in speed of a conventional wind turbine is 3.5 m/s to 5 m/s. Mechanical geared generators are commonly found in wind technology to step up power conversion to accommodate the needs of the generator. Wind turbine gearboxes suffer from overload problem and frequent maintenance in spite of the high torque density produced. However, an emerging alternative to gearing system is Magnetic Gear (MG as it offers significant advantages such as free from maintenance and inherent overload protection. In this project, numerical analysis is done on designed magnetic gear greatly affects the performance of the generator in terms of voltage generation. Magnetic flux density is distributed evenly across the generator as seen from the uniform sinusoidal output waveform. Consequently, the interaction of the magnetic flux of the permanent magnets has shown no disturbance to the output of the generator as the voltage generated shows uniform waveform despite the rotational speed of the gears. The simulation is run at low wind speed and the results show that the generator starts generating a voltage of 240 V at a wind speed of 1.04 m/s. This shows great improvement in the operating capability of the wind turbine.

  6. Three-Dimensional Velocity Field of the Yellowstone Deformation from Ascending and Descending ENVISAT Observations

    Science.gov (United States)

    Aly, M. H.; Cochran, E. S.

    2009-05-01

    The complex Yellowstone volcanic system is characterized by episodic crustal deformation that occurs on a decadal scale. Previous geodetic studies indicated that the 640 k year-old Yellowstone Caldera was recently subsiding until mid 2004, and then a new episode of uplift has occurred with rapid rates up to 7 cm/yr. However, Synthetic Aperture Radar Interferometry (InSAR) from either ascending or descending orbits permits measurements only in the line-of-sight (LOS) direction; and the Global Positioning System (GPS) provides point measurements and thus a limited spatial view of the ongoing deformation. In this study, we present the three-dimensional velocity field of Yellowstone deformation constructed from ascending and descending ENVISAT LOS components. Based on the ENVISAT satellite imaging and the Digital Elevation Model (DEM) geometries, we calculated the look vector, the elevation angle (the angle between the look vector and the horizontal surface plane), and the orientation angle (the angle between the projection of the look vector on the horizontal surface plane and the East direction) for each InSAR image pixel. The outputs indicate that the majority of observed deformation across the Yellowstone Caldera (approximately 7 cm/yr) and near the Norris Geyser Basin (approximately 4 cm/yr) occurred in the vertical direction during July 2005 - August 2006; however, significant horizontal deformation in the East-West direction occurred at the southeastern rim of the caldera and around Hebgen Lake, and slight deformation in the North-South direction occurred across the caldera during the same time period. The constructed three-dimensional velocity field provides new constraints on the depth and geometry of the Yellowstone magma chamber.

  7. Loss of exploratory vertical saccades after unilateral frontal eye field damage

    OpenAIRE

    Pflugshaupt, Tobias; Nyffeler, Thomas; Von Wartburg, Roman; Hess, Christian W; Müri, René M.

    2009-01-01

    Despite their relevance for locomotion and social interaction in everyday situations, little is known about the cortical control of vertical saccades in humans. Results from microstimulation studies indicate that both frontal eye fields (FEFs) contribute to these eye movements. Here, we present a patient with a damaged right FEF, who hardly made vertical saccades during visual exploration. This finding suggests that, for the cortical control of exploratory vertical saccades, integrity of both...

  8. Temperature Field-Wind Velocity Field Optimum Control of Greenhouse Environment Based on CFD Model

    Directory of Open Access Journals (Sweden)

    Yongbo Li

    2014-01-01

    Full Text Available The computational fluid dynamics technology is applied as the environmental control model, which can include the greenhouse space. Basic environmental factors are set to be the control objects, the field information is achieved via the division of layers by height, and numerical characteristics of each layer are used to describe the field information. Under the natural ventilation condition, real-time requirements, energy consumption, and distribution difference are selected as index functions. The optimization algorithm of adaptive simulated annealing is used to obtain optimal control outputs. A comparison with full-open ventilation shows that the whole index can be reduced at 44.21% and found that a certain mutual exclusiveness exists between the temperature and velocity field in the optimal course. All the results indicate that the application of CFD model has great advantages to improve the control accuracy of greenhouse.

  9. Mean-field theory for a passive scalar advected by a turbulent velocity field with a random renewal time.

    Science.gov (United States)

    Elperin, T; Kleeorin, N; Rogachevskii, I; Sokoloff, D

    2001-08-01

    Mean-field theory for turbulent transport of a passive scalar (e.g., particles and gases) is discussed. Equations for the mean number density of particles advected by a random velocity field, with a finite correlation time, are derived. Mean-field equations for a passive scalar comprise spatial derivatives of high orders due to the nonlocal nature of passive scalar transport in a random velocity field with a finite correlation time. A turbulent velocity field with a random renewal time is considered. This model is more realistic than that with a constant renewal time used by Elperin et al. [Phys. Rev. E 61, 2617 (2000)], and employs two characteristic times: the correlation time of a random velocity field tau(c), and a mean renewal time tau. It is demonstrated that the turbulent diffusion coefficient is determined by the minimum of the times tau(c) and tau. The mean-field equation for a passive scalar was derived for different ratios of tau/tau(c). The important role of the statistics of the field of Lagrangian trajectories in turbulent transport of a passive scalar, in a random velocity field with a finite correlation time, is demonstrated. It is shown that in the case tau(c)field equation for a passive scalar is independent of the statistics of the velocity field, where tau(N) is the characteristic time of variations of a mean passive scalar field.

  10. Global Neuromagnetic Cortical Fields Have Non-Zero Velocity.

    Directory of Open Access Journals (Sweden)

    David M Alexander

    Full Text Available Globally coherent patterns of phase can be obscured by analysis techniques that aggregate brain activity measures across-trials, whether prior to source localization or for estimating inter-areal coherence. We analyzed, at single-trial level, whole head MEG recorded during an observer-triggered apparent motion task. Episodes of globally coherent activity occurred in the delta, theta, alpha and beta bands of the signal in the form of large-scale waves, which propagated with a variety of velocities. Their mean speed at each frequency band was proportional to temporal frequency, giving a range of 0.06 to 4.0 m/s, from delta to beta. The wave peaks moved over the entire measurement array, during both ongoing activity and task-relevant intervals; direction of motion was more predictable during the latter. A large proportion of the cortical signal, measurable at the scalp, exists as large-scale coherent motion. We argue that the distribution of observable phase velocities in MEG is dominated by spatial filtering considerations in combination with group velocity of cortical activity. Traveling waves may index processes involved in global coordination of cortical activity.

  11. Magnetic domain-wall velocity enhancement induced by a transverse magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jusang, E-mail: jsyang@physics.utexas.edu [Department of Physics, The University of Texas at Austin, Austin, TX 78712-1081 (United States); Beach, Geoffrey S.D. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Knutson, Carl; Erskine, James L. [Department of Physics, The University of Texas at Austin, Austin, TX 78712-1081 (United States)

    2016-01-01

    Spin dynamics of field-driven domain walls (DWs) guided by permalloy nanowires are studied by high-speed magneto-optic polarimetry and numerical simulations. DW velocities and spin configurations are determined as functions of longitudinal drive field, transverse bias field, and nanowire width. Nanowires having cross-sectional dimensions large enough to support vortex wall structures exhibit regions of drive-field strength (at zero bias field) that have enhanced DW velocity resulting from coupled vortex structures that suppress oscillatory motion. Factor of 10 enhancements of the DW velocity are observed above the critical longitudinal drive-field (that marks the onset of oscillatory DW motion) when a transverse bias field is applied. Nanowires having smaller cross-sectional dimensions that support transverse wall structures also exhibit a region of higher mobility above the critical field, and similar transverse-field induced velocity enhancement but with a smaller enhancement factor. The bias-field enhancement of DW velocity is explained by numerical simulations of the spin distribution and dynamics within the propagating DW that reveal dynamic stabilization of coupled vortex structures and suppression of oscillatory motion in the nanowire conduit resulting in uniform DW motion at high speed. The enhanced velocity and drive field range are achieved at the expense of a less compact DW spin distribution. - Highlights: • The transverse magnetic fields can dramatically enhance the domain wall velocity. • The numerical simulation exhibits the four distinct dynamic modes. • Coupled multiple vortex structures within the domain wall become dynamically stable. • The enhanced domain wall velocity is explained by numerical simulations.

  12. Sound field separation with a double layer velocity transducer array (L)

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn

    2011-01-01

    In near-field acoustic holography sound field separation techniques make it possible to distinguish between sound coming from the two sides of the array. This is useful in cases where the sources are not confined to only one side of the array, e.g., in the presence of additional sources...... or reflections from the other side. This paper examines a separation technique based on measurement of the particle velocity in two closely spaced parallel planes. The purpose of the technique is to recover the particle velocity radiated by a source in the presence of disturbing sound from the opposite side...... of the array. The technique has been examined and compared with direct velocity based reconstruction, as well as with a technique based on the measurement of the sound pressure and particle velocity. The double layer velocity method circumvents some of the drawbacks of the pressure-velocity based...

  13. Research on Far-Field Wavelet's Extraction and Application of Vertical Cable System

    Science.gov (United States)

    Wang, Xiangchun; Xiao, Qingsong; Xia, Changliang; Wu, Zhongliang; Xie, Chengliang

    2017-04-01

    In marine seismic exploration, ghost wave and bubble effect reduce the vertical resolution and interpretation accuracy seriously. Here firstly the far-field wavelet including source wavelet, ghost wave and bubble effect recorded by the vertical cable system (VCS) is extracted. Then, filters are designed using the extracted far-field wavelet to eliminate ghost wave, bubble effect and source wavelet. At last, the designed filters are applied to the seismic data of VCS. The results show that this method can eliminate ghost wave, bubble effect and source wavelet effectively and the vertical resolution of the seismic data is improved obviously.

  14. Far field velocity potential induced by a rapidly decaying vorticity distribution

    Science.gov (United States)

    Klein, Rupert; Ting, LU

    1990-01-01

    The velocity field induced by a vorticity distribution decaying rapidly in the distance from the origin is investigated. It is shown that the sum of vector potentials for the velocity field can be expressed as a linear combination of Mn values, where Mn denotes the number of linearly independent vector functions of nth order. It is then shown that only the linear combinations 2n + 1 of these Mn vector functions contribute to the far field velocity which is irrotational, and that the corresponding scalar potential is then represented by a linear combination of 2n + 1 spherical harmonics of nth order whose coefficients are linear combinations of nth moments of vorticity.

  15. A Study of Three Dimensional Bubble Velocities at Co-current Gas-liquid Vertical Upward Bubbly Flows

    CERN Document Server

    Kuntoro, Hadiyan Yusuf; Deendarlianto,

    2015-01-01

    Recently, experimental series of co-current gas-liquid upward bubbly flows in a 6 m-height and 54.8 mm i.d. vertical titanium pipe had been conducted at the TOPFLOW thermal hydraulic test facility, Helmholtz-Zentrum Dresden-Rossendorf, Germany. The experiments were initially performed to develop a high quality database of two-phase flows as well as to validate new CFD models. An ultrafast dual-layer electron beam X-ray tomography, named ROFEX, was used as measurement system with high spatial and temporal resolutions. The gathered cross sectional grey value image results from the tomography scanning were reconstructed, segmented and evaluated to acquire gas bubble parameters for instance bubble position, size and holdup. To assign the correct paired bubbles from both measurement layers, a bubble pair algorithm was implemented on the basis of the highest probability values of bubbles in position, volume and velocity. Hereinafter, the individual characteristics of bubbles were calculated include instantaneous th...

  16. HF Radar Observation of Velocity Fields Induced by Tsunami Waves in the Kii Channel, Japan

    OpenAIRE

    日向, 博文; 藤, 良太郎; 藤井, 智史; 藤田, 裕一; 花土, 弘; 片岡, 智哉; 水谷, 雅裕; 高橋, 智幸

    2012-01-01

    High frequency ocean surface radar observation reveals the velocity fields of propagating tsunami waves and subsequent 30-40 minute period natural oscillation in the Kii Channel, Japan induced by the March 11, 2011 moment magnitude 9.0 Tohoku-Oki earthquake. Technical issues of the ocean surface radar sysytem concerning the detection of tsunami waves and natural oscillation velocities are also discussed.

  17. Ultrasonic velocity and amplitude characterization of magnetorheological fluids under magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Lopez, J., E-mail: jaimerl@caend.upm-csic.es [Centro de Acustica Aplicada y Ensayos No Destructivos, UPM-CSIC, 28006 Madrid (Spain); Elvira Segura, L.; Montero de Espinosa Freijo, F. [Centro de Acustica Aplicada y Ensayos No Destructivos, UPM-CSIC, 28006 Madrid (Spain)

    2012-01-15

    Variations in velocity of sound and amplitude of the signal of a commercial magnetorheological fluid under different magnetic fields are studied experimentally. Different factors such as orientation, uniformity, geometry and intensity of the magnetic field are investigated. An increase in the change of MR fluid acoustical properties is obtained when the magnetic field intensity is risen. In addition, these properties show an opposite behavior when a magnetic field is applied parallel or perpendicular to the ultrasound propagation. Experiments using an electromagnet and permanent magnets as the source of magnetic field are also compared. Properties such as anisotropy in sound velocity and amplitude make these materials interesting regarding applications. - Highlights: > First sound attenuation measurements as function of the magnetic field in MR fluids. > Sound velocity and attenuation anisotropy due to the microstructure is detected. > Geometry, intensity and uniformity of the magnetic field affect sound propagation.

  18. Magnetic field alignment of randomly oriented, high aspect ratio silicon microwires into vertically oriented arrays.

    Science.gov (United States)

    Beardslee, Joseph A; Sadtler, Bryce; Lewis, Nathan S

    2012-11-27

    External magnetic fields have been used to vertically align ensembles of silicon microwires coated with ferromagnetic nickel films. X-ray diffraction and image analysis techniques were used to quantify the degree of vertical orientation of the microwires. The degree of vertical alignment and the minimum field strength required for alignment were evaluated as a function of the wire length, coating thickness, magnetic history, and substrate surface properties. Nearly 100% of 100 μm long, 2 μm diameter, Si microwires that had been coated with 300 nm of Ni could be vertically aligned by a 300 G magnetic field. For wires ranging from 40 to 60 μm in length, as the length of the wire increased, a higher degree of alignment was observed at lower field strengths, consistent with an increase in the available magnetic torque. Microwires that had been exposed to a magnetic sweep up to 300 G remained magnetized and, therefore, aligned more readily during subsequent magnetic field alignment sweeps. Alignment of the Ni-coated Si microwires occurred at lower field strengths on hydrophilic Si substrates than on hydrophobic Si substrates. The magnetic field alignment approach provides a pathway for the directed assembly of solution-grown semiconductor wires into vertical arrays, with potential applications in solar cells as well as in other electronic devices that utilize nano- and microscale components as active elements.

  19. Hα LINE PROFILE ASYMMETRIES AND THE CHROMOSPHERIC FLARE VELOCITY FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Kuridze, D.; Mathioudakis, M.; Kennedy, M.; Keenan, F. P. [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast BT7 1NN (United Kingdom); Simões, P. J. A.; Voort, L. Rouppe van der; Fletcher, L. [SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Carlsson, M.; Jafarzadeh, S. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Allred, J. C.; Kowalski, A. F. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Graham, D. [INAF-Ossevatorio Astrofisico di Arcetri, I-50125 Firenze (Italy)

    2015-11-10

    The asymmetries observed in the line profiles of solar flares can provide important diagnostics of the properties and dynamics of the flaring atmosphere. In this paper the evolution of the Hα and Ca ii λ8542 lines are studied using high spatial, temporal, and spectral resolution ground-based observations of an M1.1 flare obtained with the Swedish 1 m Solar Telescope. The temporal evolution of the Hα line profiles from the flare kernel shows excess emission in the red wing (red asymmetry) before flare maximum and excess in the blue wing (blue asymmetry) after maximum. However, the Ca ii λ8542 line does not follow the same pattern, showing only a weak red asymmetry during the flare. RADYN simulations are used to synthesize spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. We show that the red asymmetry observed in Hα is not necessarily associated with plasma downflows, and the blue asymmetry may not be related to plasma upflows. Indeed, we conclude that the steep velocity gradients in the flaring chromosphere modify the wavelength of the central reversal in the Hα line profile. The shift in the wavelength of maximum opacity to shorter and longer wavelengths generates the red and blue asymmetries, respectively.

  20. Rotation and strain rate of Sulawesi from geometrical velocity field

    Science.gov (United States)

    Sarsito, D. A.; Susilo, Simons, W. J. F.; Abidin, H. Z.; Sapiie, B.; Triyoso, W.; Andreas, H.

    2017-07-01

    One of methods that can be used to determine the tectonic deformation status is rate estimation from geometric rotation and strain using quantitative velocity data from GPS observations. Microplate Sulawesi region located in the zone of triple junction (Eurasia, Australia and Philippine Sea Plates) has very complex tectonic and seismic condition, which is why become very important to know its recent deformation status in order to study neo-tectonic and disaster mitigation. Deformation rate quantification is estimated in two parameters: rotation and geodetic strain rate of each GPS station Delaunay triangle in the study area. The analysis in this study is not done using the grids since there is no rheological information at location that can be used as the interpolation-extrapolation constraints. Our analysis reveals that Sulawesi is characterized by rapid rotation in several different domains and compression-strain pattern that varies depending on the type and boundary conditions of microplate. This information is useful for studying neo tectonic deformation status and earthquake disaster mitigation.

  1. Mixed Convective Flow of an Elastico-Viscous Fluid Past a Vertical Plate in the Presence of Thermal Radiation and Chemical Reaction with an Induced Magnetic Field

    Science.gov (United States)

    Das, Utpal Jyoti

    2016-01-01

    The purpose of the study is to investigate the steady, two-dimensional, hydromagnetic, mixed convection heat and mass transfer of a conducting, optically thin, incompressible, elastico-viscous fluid (characterized by the Walters' B' model) past a permeable, stationary, vertical, infinite plate in the presence of thermal radiation and chemical reaction with account for an induced magnetic field. The governing equations of the flow are solved by the series method, and expressions for the velocity field, induced magnetic field, temperature field, and the skin friction are obtained.

  2. Image registration using stationary velocity fields parameterized by norm-minimizing Wendland kernel

    DEFF Research Database (Denmark)

    Pai, Akshay Sadananda Uppinakudru; Sommer, Stefan Horst; Sørensen, Lauge

    Interpolating kernels are crucial to solving a stationary velocity field (SVF) based image registration problem. This is because, velocity fields need to be computed in non-integer locations during integration. The regularity in the solution to the SVF registration problem is controlled by the re...... that Wendland SVF based measures separate (Alzheimer's disease v/s normal controls) better than both B-Spline SVFs (pamygdala) and B-Spline freeform deformation (pamygdala and cortical gray matter)....

  3. Clear and Measurable Signature of Modified Gravity in the Galaxy Velocity Field

    Science.gov (United States)

    Hellwing, Wojciech A.; Barreira, Alexandre; Frenk, Carlos S.; Li, Baojiu; Cole, Shaun

    2014-06-01

    The velocity field of dark matter and galaxies reflects the continued action of gravity throughout cosmic history. We show that the low-order moments of the pairwise velocity distribution v12 are a powerful diagnostic of the laws of gravity on cosmological scales. In particular, the projected line-of-sight galaxy pairwise velocity dispersion σ12(r) is very sensitive to the presence of modified gravity. Using a set of high-resolution N-body simulations, we compute the pairwise velocity distribution and its projected line-of-sight dispersion for a class of modified gravity theories: the chameleon f(R) gravity and Galileon gravity (cubic and quartic). The velocities of dark matter halos with a wide range of masses would exhibit deviations from general relativity at the (5-10)σ level. We examine strategies for detecting these deviations in galaxy redshift and peculiar velocity surveys. If detected, this signature would be a "smoking gun" for modified gravity.

  4. Near field acoustic holography based on the equivalent source method and pressure-velocity transducers

    DEFF Research Database (Denmark)

    Zhang, Y.-B.; Chen, X.-Z.; Jacobsen, Finn

    2009-01-01

    The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has...... on particle velocity input data than when it is based on measurements of sound pressure data, and this is confirmed by a simulation study and by experimental results. A method that combines pressure- and particle velocity-based reconstructions in order to distinguish between contributions to the sound field...

  5. Vertical Jump Height is more Strongly Associated with Velocity and Work Performed Prior to Take-off

    Science.gov (United States)

    Bentley, J. R.; Loehr, J. A.; DeWitt, J. K.; Lee, S. M. C.; English, K. L.; Nash, R. E.; Leach, M. A.; Hagan, R. D.

    2008-01-01

    Vertical jump (VJ) height is commonly used as a measure of athletic capability in strength and power sports. Although VJ has been shown to be a predictor of athletic performance, it is not clear which kinetic ground reaction force (GRF) variables, such as peak force (PF), peak power (PP), peak velocity (PV), total work (TW) or impulse (Imp) are the best correlates. To determine which kinetic variables (PF, PP, PV, TW, and Imp) best correlate with VJ height. Twenty subjects (14 males, 6 females) performed three maximal countermovement VJs on a force platform (Advanced Mechanical Technology, Inc., Watertown, MA, USA). VJ jump height was calculated as the difference between standing reach and the highest reach point measured using a Vertec. PF, PP, PV, TW, and Imp were calculated using the vertical GRF data sampled at 1000 Hz from the lowest point in the countermovement through the concentric portion until take-off. GRF data were normalized to body mass measured using a standard scale (Detecto, Webb City, MO, USA). Correlation coefficients were computed between each GRF variable and VJ height using a Pearson correlation. VJ height (43.4 plus or minus 9.1 cm) was significantly correlated (p less than 0.001) with PF (998 plus or minus 321 N; r=0.51), PP (1997 plus or minus 772 W; r=0.69), PV (2.66 plus or minus 0.40 m (raised dot) s(sup -1); r=0.85), TW (259 plus or minus 93.0 kJ; r=0.82), and Imp (204 plus or minus 51.1 N(raised dot)s; r=0.67). Although all variables were correlated to VJ height, PV and TW were more strongly correlated to VJ height than PF, PP, and Imp. Therefore, since TW is equal to force times displacement, the relative displacement of the center of mass along with the forces applied during the upward movement of the jump are critical determinants of VJ height. PV and TW are key determinants of VJ height, and therefore successful training programs to increase VJ height should focus on rapid movement (PV) and TW by increasing power over time rather

  6. Sensitivity of the near-surface vertical electric field land Controlled-Source Electromagnetic monitoring

    NARCIS (Netherlands)

    Schaller, A.M.; Hunziker, J.W.; Streich, R.; Drijkoningen, G.G.

    2014-01-01

    We investigate potential benefits of measuring the vertical electric field component in addition to the routinely measured horizontal electric field components in onshore time-lapse controlled-source electromagnetics. Synthetic electromagnetic data based on a model of the Schoonebeek onshore oil

  7. Sensitivity of the near-surface vertical electric field land Controlled-Source Electromagnetic monitoring

    NARCIS (Netherlands)

    Schaller, A.M.; Hunziker, J.W.; Streich, R.; Drijkoningen, G.G.

    We investigate potential benefits of measuring the vertical electric field component in addition to the routinely measured horizontal electric field components in onshore time-lapse controlled-source electromagnetics. Synthetic electromagnetic data based on a model of the Schoonebeek onshore oil

  8. Vertical Distribution of the Plant-Parasitic Nematode, Pratylenchus penetrans, Under Four Field Crops

    NARCIS (Netherlands)

    Pudassaini, M.P.; Schomaker, C.H.; Been, T.H.; Moens, M.

    2006-01-01

    The vertical distribution of Pratylenchus penetrans was monitored in four fields cropped with maize, black salsify, carrot, or potato. Soil samples were collected at 21-day intervals from May 2002 until April 2003 from five plots (2 × 5 m(^2)) per field. Per plot, 15 cores were taken to a depth of

  9. Stabilization of the Vertical Mode in Tokamaks by Localized Nonaxisymmetric Fields

    Energy Technology Data Exchange (ETDEWEB)

    A. Reiman

    2007-10-02

    Vertical instability of a tokamak plasma can be controlled by nonaxisymmetric magnetic fields localized near the plasma edge at the bottom and top of the torus. The required magnetic fields can be produced by a relatively simple set of parallelogram-shaped coils.

  10. Magnetic field effect on Poiseuille flow and heat transfer of carbon nanotubes along a vertical channel filled with Casson fluid

    Directory of Open Access Journals (Sweden)

    Sidra Aman

    2017-01-01

    Full Text Available Applications of carbon nanotubes, single walls carbon nanotubes (SWCNTs and multiple walls carbon nanotubes (MWCNTs in thermal engineering have recently attracted significant attention. However, most of the studies on CNTs are either experimental or numerical and the lack of analytical studies limits further developments in CNTs research particularly in channel flows. In this work, an analytical investigation is performed on heat transfer analysis of SWCNTs and MWCNTs for mixed convection Poiseuille flow of a Casson fluid along a vertical channel. These CNTs are suspended in three different types of base fluids (Water, Kerosene and engine Oil. Xue [Phys. B Condens. Matter 368, 302–307 (2005] model has been used for effective thermal conductivity of CNTs. A uniform magnetic field is applied in a transverse direction to the flow as magnetic field induces enhancement in the thermal conductivity of nanofluid. The problem is modelled by using the constitutive equations of Casson fluid in order to characterize the non-Newtonian fluid behavior. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the perturbation method is utilized to solve the governing equations with some physical conditions. Velocity and temperature solutions are obtained and discussed graphically. Expressions for skin friction and Nusselt number are also evaluated in tabular form. Effects of different parameters such as Casson parameter, radiation parameter and volume fraction are observed on the velocity and temperature profiles. It is found that velocity is reduced under influence of the exterior magnetic field. The temperature of single wall CNTs is found greater than MWCNTs for all the three base fluids. Increase in volume fraction leads to a decrease in velocity of the fluid as the nanofluid become more viscous by adding CNTs.

  11. Magnetic field effect on Poiseuille flow and heat transfer of carbon nanotubes along a vertical channel filled with Casson fluid

    Science.gov (United States)

    Aman, Sidra; Khan, Ilyas; Ismail, Zulkhibri; Salleh, Mohd Zuki; Alshomrani, Ali Saleh; Alghamdi, Metib Said

    2017-01-01

    Applications of carbon nanotubes, single walls carbon nanotubes (SWCNTs) and multiple walls carbon nanotubes (MWCNTs) in thermal engineering have recently attracted significant attention. However, most of the studies on CNTs are either experimental or numerical and the lack of analytical studies limits further developments in CNTs research particularly in channel flows. In this work, an analytical investigation is performed on heat transfer analysis of SWCNTs and MWCNTs for mixed convection Poiseuille flow of a Casson fluid along a vertical channel. These CNTs are suspended in three different types of base fluids (Water, Kerosene and engine Oil). Xue [Phys. B Condens. Matter 368, 302-307 (2005)] model has been used for effective thermal conductivity of CNTs. A uniform magnetic field is applied in a transverse direction to the flow as magnetic field induces enhancement in the thermal conductivity of nanofluid. The problem is modelled by using the constitutive equations of Casson fluid in order to characterize the non-Newtonian fluid behavior. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the perturbation method is utilized to solve the governing equations with some physical conditions. Velocity and temperature solutions are obtained and discussed graphically. Expressions for skin friction and Nusselt number are also evaluated in tabular form. Effects of different parameters such as Casson parameter, radiation parameter and volume fraction are observed on the velocity and temperature profiles. It is found that velocity is reduced under influence of the exterior magnetic field. The temperature of single wall CNTs is found greater than MWCNTs for all the three base fluids. Increase in volume fraction leads to a decrease in velocity of the fluid as the nanofluid become more viscous by adding CNTs.

  12. Radiography by selective detection of scatter field velocity components

    Science.gov (United States)

    Jacobs, Alan M. (Inventor); Dugan, Edward T. (Inventor); Shedlock, Daniel (Inventor)

    2007-01-01

    A reconfigurable collimated radiation detector, system and related method includes at least one collimated radiation detector. The detector has an adjustable collimator assembly including at least one feature, such as a fin, optically coupled thereto. Adjustments to the adjustable collimator selects particular directions of travel of scattered radiation emitted from an irradiated object which reach the detector. The collimated detector is preferably a collimated detector array, where the collimators are independently adjustable. The independent motion capability provides the capability to focus the image by selection of the desired scatter field components. When an array of reconfigurable collimated detectors is provided, separate image data can be obtained from each of the detectors and the respective images cross-correlated and combined to form an enhanced image.

  13. A simple measuring technique of surface flow velocity to analyze the behavior of velocity fields in hydraulic engineering applications.

    Science.gov (United States)

    Tellez, Jackson; Gomez, Manuel; Russo, Beniamino; Redondo, Jose M.

    2015-04-01

    An important achievement in hydraulic engineering is the proposal and development of new techniques for the measurement of field velocities in hydraulic problems. The technological advances in digital cameras with high resolution and high speed found in the market, and the advances in digital image processing techniques now provides a tremendous potential to measure and study the behavior of the water surface flows. This technique was applied at the Laboratory of Hydraulics at the Technical University of Catalonia - Barcelona Tech to study the 2D velocity fields in the vicinity of a grate inlet. We used a platform to test grate inlets capacity with dimensions of 5.5 m long and 4 m wide allowing a zone of useful study of 5.5m x 3m, where the width is similar of the urban road lane. The platform allows you to modify the longitudinal slopes from 0% to 10% and transversal slope from 0% to 4%. Flow rates can arrive to 200 l/s. In addition a high resolution camera with 1280 x 1024 pixels resolution with maximum speed of 488 frames per second was used. A novel technique using particle image velocimetry to measure surface flow velocities has been developed and validated with the experimental data from the grate inlets capacity. In this case, the proposed methodology can become a useful tools to understand the velocity fields of the flow approaching the inlet where the traditional measuring equipment have serious problems and limitations. References DigiFlow User Guide. (2012), (June). Russo, B., Gómez, M., & Tellez, J. (2013). Methodology to Estimate the Hydraulic Efficiency of Nontested Continuous Transverse Grates. Journal of Irrigation and Drainage Engineering, 139(10), 864-871. doi:10.1061/(ASCE)IR.1943-4774.0000625 Teresa Vila (1), Jackson Tellez (1), Jesus Maria Sanchez (2), Laura Sotillos (1), Margarita Diez (3, 1), and J., & (1), M. R. (2014). Diffusion in fractal wakes and convective thermoelectric flows. Geophysical Research Abstracts - EGU General Assembly 2014

  14. Estimations of Vertical Velocities Using the Omega Equation in Different Flow Regimes in Preparation for the High Resolution Observations of the SWOT Altimetry Mission

    Science.gov (United States)

    Pietri, A.; Capet, X.; d'Ovidio, F.; Le Sommer, J.; Molines, J. M.; Doglioli, A. M.

    2016-02-01

    Vertical velocities (w) associated with meso and submesoscale processes play an essential role in ocean dynamics and physical-biological coupling due to their impact on the upper ocean vertical exchanges. However, their small intensity (O 1 cm/s) compared to horizontal motions and their important variability in space and time makes them very difficult to measure. Estimations of these velocities are thus usually inferred using a generalized approach based on frontogenesis theories. These estimations are often obtained by solving the diagnostic omega equation. This equation can be expressed in different forms from a simple quasi geostrophic formulation to more complex ones that take into account the ageostrophic advection and the turbulent fluxes. The choice of the method used generally depends on the data available and on the dominant processes in the region of study. Here we aim to provide a statistically robust evaluation of the scales at which the vertical velocity can be resolved with confidence depending on the formulation of the equation and the dynamics of the flow. A high resolution simulation (dx=1-1.5 km) of the North Atlantic was used to compare the calculations of w based on the omega equation to the modelled vertical velocity. The simulation encompasses regions with different atmospheric forcings, mesoscale activity, seasonality and energetic flows, allowing us to explore several different dynamical contexts. In a few years the SWOT mission will provide bi-dimensional images of sea level elevation at a significantly higher resolution than available today. This work helps assess the possible contribution of the SWOT data to the understanding of the submesoscale circulation and the associated vertical fluxes in the upper ocean.

  15. A Method for Retrieving Vertical Air Velocities in Convective Clouds over the Tibetan Plateau from TIPEX-III Cloud Radar Doppler Spectra

    Directory of Open Access Journals (Sweden)

    Jiafeng Zheng

    2017-09-01

    Full Text Available In the summertime, convective cells occur frequently over the Tibetan Plateau (TP because of the large dynamic and thermal effects of the landmass. Measurements of vertical air velocity in convective cloud are useful for advancing our understanding of the dynamic and microphysical mechanisms of clouds and can be used to improve the parameterization of current numerical models. This paper presents a technique for retrieving high-resolution vertical air velocities in convective clouds over the TP through the use of Doppler spectra from vertically pointing Ka-band cloud radar. The method was based on the development of a “small-particle-traced” idea and its associated data processing, and it used three modes of radar. Spectral broadening corrections, uncertainty estimations, and results merging were used to ensure accurate results. Qualitative analysis of two typical convective cases showed that the retrievals were reliable and agreed with the expected results inferred from other radar measurements. A quantitative retrieval of vertical air motion from a ground-based optical disdrometer was used to compare with the radar-derived result. This comparison illustrated that, while the data trends from the two methods of retrieval were in agreement while identifying the updrafts and downdrafts, the cloud radar had a much higher resolution and was able to reveal the small-scale variations in vertical air motion.

  16. Spatial resolution and velocity field improvement of 4D-flow MRI.

    Science.gov (United States)

    Callaghan, Fraser M; Grieve, Stuart M

    2017-11-01

    4D-flow MRI obtains a time-dependent 3D velocity field; however, its use for the calculation of higher-order parameters is limited by noise. We present an algorithm for denoising 4D-flow data. By integrating a velocity field and eliminating streamlines in noisy flow, depicted by high curvature, a denoised dataset may be extracted. This method, defined as the velocity field improvement (VFIT) algorithm, was validated in an analytical dataset and using in vivo data in comparison with a computation fluid dynamics (CFD) simulation. As a proof of principal, wall shear stress (WSS) measurements in the descending aorta were compared with those defined by CFD. The VFIT algorithm achieved a >100% noise reduction of a corrupted analytical dataset. In addition, 4D-flow data were cleaned to show improved spatial resolution and near wall velocity representation. WSS measures compared well with CFD data and bulk flow dynamics were retained (flow measurements). This study presents a method for denoising 4D-flow datasets with improved spatial resolution. Bulk flow dynamics are accurately conserved while velocity and velocity gradient fields are improved; this is important in the calculation of higher-order parameters such as WSS, which are shown to be more comparable to CFD measures. Magn Reson Med 78:1959-1968, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  17. Creating analytically divergence-free velocity fields from grid-based data

    Science.gov (United States)

    Ravu, Bharath; Rudman, Murray; Metcalfe, Guy; Lester, Daniel R.; Khakhar, Devang V.

    2016-10-01

    We present a method, based on B-splines, to calculate a C2 continuous analytic vector potential from discrete 3D velocity data on a regular grid. A continuous analytically divergence-free velocity field can then be obtained from the curl of the potential. This field can be used to robustly and accurately integrate particle trajectories in incompressible flow fields. Based on the method of Finn and Chacon (2005) [10] this new method ensures that the analytic velocity field matches the grid values almost everywhere, with errors that are two to four orders of magnitude lower than those of existing methods. We demonstrate its application to three different problems (each in a different coordinate system) and provide details of the specifics required in each case. We show how the additional accuracy of the method results in qualitatively and quantitatively superior trajectories that results in more accurate identification of Lagrangian coherent structures.

  18. Near-field acoustic holography with sound pressure and particle velocity measurements

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren

    Near-field acoustic holography (NAH) is a powerful sound source identification technique that makes it possible to reconstruct and extract all the information of the sound field radiated by a source in a very efficient manner, readily providing a complete representation of the acoustic field under...... examination. This is crucial in many areas of acoustics where such a thorough insight into the sound radiated by a source can be essential. This study examines novel acoustic array technology in near-field acoustic holography and sound source identification. The study focuses on three aspects, namely the use...... of particle velocity measurements and combined pressure-velocity measurements in NAH, the relation between the near-field and the far-field radiation from sound sources via the supersonic acoustic intensity, and finally, the reconstruction of sound fields using rigid spherical microphone arrays. Measurement...

  19. Quantum sensing of rotation velocity based on transverse field Ising model

    Science.gov (United States)

    Ma, Yu-Han; Sun, Chang-Pu

    2017-10-01

    We study a transverse-field Ising model (TFIM) in a rotational reference frame. We find that the effective Hamiltonian of the TFIM of this system depends on the system's rotation velocity. Since the rotation contributes an additional transverse field, the dynamics of TFIM sensitively responses to the rotation velocity at the critical point of quantum phase transition. This observation means that the TFIM can be used for quantum sensing of rotation velocity that can sensitively detect rotation velocity of the total system at the critical point. It is found that the resolution of the quantum sensing scheme we proposed is characterized by the half-width of Loschmidt echo of the dynamics of TFIM when it couples to a quantum system S. And the resolution of this quantum sensing scheme is proportional to the coupling strength δ between the quantum system S and the TFIM, and to the square root of the number of spins N belonging the TFIM.

  20. Kinematics of the Suez-Sinai area from combined GPS velocity field

    Science.gov (United States)

    Pietrantonio, G.; Devoti, R.; Mahmoud, S.; Riguzzi, F.

    2016-12-01

    A combined GPS velocity solution covering a wide area from Egypt to Middle East allowed us to infer the current rates across the main, already well known, tectonic features. We have estimated 126 velocities from time series of 90 permanent and 36 non permanent GPS sites located in Africa (Egypt), Eurasia and Arabia plates in the time span 1996-2015, the largest available for the Egyptian sites. We have combined our velocity solution in a least-squares sense with two other recent velocity solutions of networks located around the eastern Mediterranean, obtaining a final IGb08 velocity field of about 450 sites. Then, we have estimated the IGb08 Euler poles of Africa, Sinai and Arabia, analyzing the kinematics of the Sinai area, particular velocity profiles, and estimating the 2D strain rate field. We show that it is possible to reliably model the rigid motion of Sinai block only including some GPS sites located south of the Carmel Fault. The estimated relative motion with respect to Africa is of the order of 2-3 mm/yr, however there is a clear mismatch between the modeled and the observed velocities in the southern Sinai sites. We have also assessed the NNE left shear motion along the Dead Sea Transform Fault, estimating a relative motion between Arabia and Africa of about 6 mm/yr in the direction of the Red Sea opening.

  1. Quantum mechanical grad-B drift velocity operator in a weakly non-uniform magnetic field

    Science.gov (United States)

    Chan, Poh Kam; Oikawa, Shun-ichi; Kosaka, Wataru

    2016-02-01

    This paper presents the analytical solution for quantum mechanical grad-B drift velocity operator by solving the Heisenberg equation of motion. Using the time dependent operators, it is shown the analytical solution of the position operators in x ̂(t ) and y ̂(t ) of the particle in the presence of a weakly non-uniform magnetic field. It is also shown numerically that the grad-B drift velocity operator agrees with the classical counterpart.

  2. Magnetic field effects on unsteady convective flow along a vertical porous flat surface embedded in a porous medium with constant suction and heat sink

    Energy Technology Data Exchange (ETDEWEB)

    Das, S.S.; Das, P. [Department of Pysics, K B D A B College, Nirakarpur, Khurda-752 019 (Orissa) (India); Mohanty, J. [Department of Physics, ABIT, CDA, Sector-I, Bidanasi, Cuttack-753 014, (Orissa) (India)

    2011-07-01

    The magnetohydrodynamic unsteady convective flow of a viscous incompressible fluid along a vertical porous plate embedded in a porous medium with constant suction and heat sink is considered. Approximate solutions for velocity, temperature, skin friction and rate of heat transfer are obtained by solving the governing equations of the flow field using multi parameter perturbation technique. The effects of various flow parameters affecting the flow field are discussed with the help of figures and table. It is observed that a growing magnetic parameter or heat sink parameter retards the transient velocity of the flow field while the Grashof number or permeability parameter reverses the effect. Further, an increase in magnetic parameter or Prandtl number or heat sink parameter decreases the transient temperature of the flow field. A growing permeability parameter enhances the magnitude of skin friction and the rate of heat transfer at the wall, while the magnetic parameter reverses the effect.

  3. Buoyant flow in long vertical enclosures in the presence of a strong horizontal magnetic field. Part 2. finite enclosures

    CERN Document Server

    Authie, G; Tagawa, T

    2003-01-01

    Numerical computations and experiments were carried out for a buoyant flow of liquid metal (mercury in the experiments) in a long vertical enclosure of square cross-section, in the presence of a uniform horizontal magnetic field. A strong emphasis is put on the case of a magnetic field perpendicular to the applied temperature gradient for two reasons: (1) the MHD damping is smaller than with any other orientation, and (2) the quasi-two-dimensionality of the flow in this case yields a quite efficient velocity measurement technique. The enclosure is heated by a thermally controlled flow of water from one of the vertical walls and cooled by a similar technique from the facing wall. Those two walls are good thermal conductors (thick copper plates in the experiments), whereas the four other walls are thermally insulating. All walls are electrically insulated from the fluid. In this paper, as well as in the companion paper by Tagawa et al. (Eur. J. Mech. B Fluids 21 (4) (2002) 383-398), we model analytically the Ha...

  4. Escape Velocity

    Directory of Open Access Journals (Sweden)

    Nikola Vlacic

    2010-01-01

    Full Text Available In this project, we investigated if it is feasible for a single staged rocket with constant thrust to attain escape velocity. We derived an equation for the velocity and position of a single staged rocket that launches vertically. From this equation, we determined if an ideal model of a rocket is able to reach escape velocity.

  5. Group velocity effect on resonant, long-range wake-fields in slow wave structures

    CERN Document Server

    Smirnov, A V

    2002-01-01

    Synchronous wake-fields in a dispersive waveguide are derived in a general explicit form on the basis of a rigorous electro-dynamical approach using Fourier transformations. The fundamental role of group velocity in wake-field propagation, calculation of attenuation, amplitudes, form-factors and loss-factors is analyzed for single bunch radiation. Adiabatic tapering of the waveguide and bunch density variation is taken into account analytically for the time-domain fields. Effects of field 'compression/expansion' and group delays are demonstrated. The role of these effects is discussed for single bunch wake-fields, transient beam loading, BBU and HOMs. A novel waveguide structure with central rf coupling and both positive and negative velocities is proposed. It can be used effectively in both high-energy accelerators and single-section linacs.

  6. Numerical Investigation of Viscous Flow Velocity Field around a Marine Cavitating Propeller

    Directory of Open Access Journals (Sweden)

    Zhifeng Zhu

    2014-11-01

    Full Text Available Velocity field around a ship cavitating propeller is investigated based on the viscous multiphase flow theory. Using a hybrid grid, the unsteady Navier-stokes (N-S and the bubble dynamics equations are solved in this paper to predict the velocity in a propeller wake and the vapor volume fraction on the back side of propeller blade for a uniform inflow. Compared with experimental results, the numerical predictions of cavitation and axial velocity coincide with the measured data. The evolution of tip vortex is shown, and the interaction between the tip vortex of the current blade and the wake of the next one occurs in the far propeller wake. The frequency of velocity signals changes from shaft rate to blade rate. The phenomena reflect the instability of propeller wake.

  7. Full-field velocity imaging of red blood cells in capillaries with spatiotemporal demodulation autocorrelation.

    Science.gov (United States)

    Wang, Mingyi; Zeng, Yaguang; Dong, Nannan; Liao, Riwei; Yang, Guojian

    2016-03-01

    We propose a full-field optical method for the label-free and quantitative mapping of the velocities of red blood cells (RBCs) in capillaries. It integrates spatiotemporal demodulation and an autocorrelation algorithm, and measures RBC velocity according to the ratio of RBC length to lag time. Conventionally, RBC length is assumed to be a constant and lag time is taken as a variable, while our method treats both of them as variables. We use temporal demodulation and the Butterworth spatial filter to separate RBC signal from background signal, based on which we obtain the RBC length by image segmentation and lag time by autocorrelation analysis. The RBC velocity calculated now is more accurate. The validity of our method is verified by an in vivo experiment on a mouse ear. Owing to its higher image signal-to-noise ratio, our method can be used for mapping RBC velocity in the turbid tissue case.

  8. A Sensor Fusion Method for Tracking Vertical Velocity and Height Based on Inertial and Barometric Altimeter Measurements

    OpenAIRE

    Angelo Maria Sabatini; Vincenzo Genovese

    2014-01-01

    A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU) and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU). An Extended Kalman Filter (EKF) estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally,...

  9. Quantum mechanical E × B drift velocity in a weakly inhomogeneous electromagnetic field

    Science.gov (United States)

    Chan, Poh Kam; Oikawa, Shun-ichi; Kosaka, Wataru

    2017-07-01

    The analytical solution for the quantum mechanical drift velocity for a non-relativistic spinless charged particle of E × B drift in the presence of a weakly inhomogeneous electric and magnetic field for the magnetized plasma is presented. Using the Heisenberg equation of motion, the time evolution of the position and momentum operators for the charged particle is solved. From the time dependent operators, the analytical solution of the time dependent momenta operators and position operators is derived. The quantum mechanical expansion rates of variances are shown to agree with the numerical results. Most importantly, the quantum mechanical E × B drift velocity coincides perfectly with the classical drift velocity in the limit of Planck's constant being zero. With higher order electric field inhomogeneity, low energy particles would drift faster than what the classical drift theory predicts.

  10. Integrating carbon nanotubes into silicon by means of vertical carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2014-01-01

    Single-walled carbon nanotubes have been integrated into silicon for use in vertical carbon nanotube field-effect transistors (CNTFETs). A unique feature of these devices is that a silicon substrate and a metal contact are used as the source and drain for the vertical transistors, respectively. These CNTFETs show very different characteristics from those fabricated with two metal contacts. Surprisingly, the transfer characteristics of the vertical CNTFETs can be either ambipolar or unipolar (p-type or n-type) depending on the sign of the drain voltage. Furthermore, the p-type/n-type character of the devices is defined by the doping type of the silicon substrate used in the fabrication process. A semiclassical model is used to simulate the performance of these CNTFETs by taking the conductance change of the Si contact under the gate voltage into consideration. The calculation results are consistent with the experimental observations. This journal is © the Partner Organisations 2014.

  11. Integrating carbon nanotubes into silicon by means of vertical carbon nanotube field-effect transistors.

    Science.gov (United States)

    Li, Jingqi; Wang, Qingxiao; Yue, Weisheng; Guo, Zaibing; Li, Liang; Zhao, Chao; Wang, Xianbin; Abutaha, Anas I; Alshareef, H N; Zhang, Yafei; Zhang, X X

    2014-08-07

    Single-walled carbon nanotubes have been integrated into silicon for use in vertical carbon nanotube field-effect transistors (CNTFETs). A unique feature of these devices is that a silicon substrate and a metal contact are used as the source and drain for the vertical transistors, respectively. These CNTFETs show very different characteristics from those fabricated with two metal contacts. Surprisingly, the transfer characteristics of the vertical CNTFETs can be either ambipolar or unipolar (p-type or n-type) depending on the sign of the drain voltage. Furthermore, the p-type/n-type character of the devices is defined by the doping type of the silicon substrate used in the fabrication process. A semiclassical model is used to simulate the performance of these CNTFETs by taking the conductance change of the Si contact under the gate voltage into consideration. The calculation results are consistent with the experimental observations.

  12. Filament formation in wind-cloud interactions- II. Clouds with turbulent density, velocity, and magnetic fields

    Science.gov (United States)

    Banda-Barragán, W. E.; Federrath, C.; Crocker, R. M.; Bicknell, G. V.

    2018-01-01

    We present a set of numerical experiments designed to systematically investigate how turbulence and magnetic fields influence the morphology, energetics, and dynamics of filaments produced in wind-cloud interactions. We cover 3D, magnetohydrodynamic systems of supersonic winds impacting clouds with turbulent density, velocity, and magnetic fields. We find that lognormal density distributions aid shock propagation through clouds, increasing their velocity dispersion and producing filaments with expanded cross-sections and highly magnetized knots and subfilaments. In self-consistently turbulent scenarios, the ratio of filament to initial cloud magnetic energy densities is ∼1. The effect of Gaussian velocity fields is bound to the turbulence Mach number: Supersonic velocities trigger a rapid cloud expansion; subsonic velocities only have a minor impact. The role of turbulent magnetic fields depends on their tension and is similar to the effect of radiative losses: the stronger the magnetic field or the softer the gas equation of state, the greater the magnetic shielding at wind-filament interfaces and the suppression of Kelvin-Helmholtz instabilities. Overall, we show that including turbulence and magnetic fields is crucial to understanding cold gas entrainment in multiphase winds. While cloud porosity and supersonic turbulence enhance the acceleration of clouds, magnetic shielding protects them from ablation and causes Rayleigh-Taylor-driven subfilamentation. Wind-swept clouds in turbulent models reach distances ∼15-20 times their core radius and acquire bulk speeds ∼0.3-0.4 of the wind speed in one cloud-crushing time, which are three times larger than in non-turbulent models. In all simulations, the ratio of turbulent magnetic to kinetic energy densities asymptotes at ∼0.1-0.4, and convergence of all relevant dynamical properties requires at least 64 cells per cloud radius.

  13. Comparison of the ENEAR peculiar velocities with the PSCz gravity field

    NARCIS (Netherlands)

    Nusser, A; da Costa, LN; Branchini, E; Bernardi, M; Alonso, MV; Wegner, G; Willmer, CNA; Pellegrini, PS

    2001-01-01

    We present a comparison between the peculiar velocity field measured from the ENEAR all-sky D-n-sigma catalogue and that derived from the galaxy distribution of the IRAS Point Source Catalog Redshift Survey (PSCz). The analysis is based on a modal expansion of these data in redshift space by means

  14. Wet and gassy zones in a municipal landfill from P- and S-wave velocity fields

    NARCIS (Netherlands)

    Konstantaki, L.A.; Ghose, R.; Draganov, D.S.; Heimovaara, T.J.

    2016-01-01

    The knowledge of the distribution of leachate and gas in a municipal landfill is of vital importance to the landfill operators performing improved landfill treatments and for environmental protection and efficient biogas extraction. We have explored the potential of using the velocity fields of

  15. An integrated shear-wave velocity model for the Groningen gas field, The Netherlands

    NARCIS (Netherlands)

    Kruiver, Pauline P.; van Dedem, Ewoud; Romijn, Remco; de Lange, Ger; Korff, M.; Stafleu, Jan; Gunnink, Jan L.; Rodriguez-Marek, Adrian; Bommer, Julian J.; van Elk, Jan; Doornhof, Dirk

    2017-01-01

    A regional shear-wave velocity (VS) model has been developed for the Groningen gas field in the Netherlands as the basis for seismic microzonation of an area of more than 1000 km2. The VS model, extending to a depth of almost 1 km, is an essential input to the

  16. A sound field separation technique based on measurements with pressure-velocity probes

    DEFF Research Database (Denmark)

    Zhang, Yong-Bin; Chen, Xin-Zhao; Jacobsen, Finn

    2009-01-01

    It has recently been shown that statistically optimized near field acoustic holography based on measurement with an array of pressure-velocity transducers makes it possible to distinguish between sources on the two sides of the array and thus suppress the influence of a disturbing source [F...

  17. Mobility Engineering in Vertical Field Effect Transistors Based on Van der Waals Heterostructures.

    Science.gov (United States)

    Shin, Yong Seon; Lee, Kiyoung; Kim, Young Rae; Lee, Hyangsook; Lee, I Min; Kang, Won Tae; Lee, Boo Heung; Kim, Kunnyun; Heo, Jinseong; Park, Seongjun; Lee, Young Hee; Yu, Woo Jong

    2018-01-15

    Vertical integration of 2D layered materials to form van der Waals heterostructures (vdWHs) offers new functional electronic and optoelectronic devices. However, the mobility in vertical carrier transport in vdWHs of vertical field-effect transistor (VFET) is not yet investigated in spite of the importance of mobility for the successful application of VFETs in integrated circuits. Here, the mobility in VFET of vdWHs under different drain biases, gate biases, and metal work functions is first investigated and engineered. The traps in WSe 2 are the main source of scattering, which influences the vertical mobility and three distinct transport mechanisms: Ohmic transport, trap-limited transport, and space-charge-limited transport. The vertical mobility in VFET can be improved by suppressing the trap states by raising the Fermi level of WSe 2 . This is achieved by increasing the injected carrier density by applying a high drain voltage, or decreasing the Schottky barrier at the graphene/WSe 2 and metal/WSe 2 junctions by applying a gate bias and reducing the metal work function, respectively. Consequently, the mobility in Mn vdWH at +50 V gate voltage is about 76 times higher than the initial mobility of Au vdWH. This work enables further improvements in the VFET for successful application in integrated circuits. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Acute Effect of Biomechanical Muscle Stimulation on the Counter-Movement Vertical Jump Power and Velocity in Division I Football Players.

    Science.gov (United States)

    Jacobson, Bert H; Monaghan, Taylor P; Sellers, John H; Conchola, Eric C; Pope, Zach K; Glass, Rob G

    2017-05-01

    Jacobson, BH, Monaghan, TP, Sellers, JH, Conchola, EC, Pope, ZK, and Glass, RG. Acute effect of biomechanical muscle stimulation on the counter-movement vertical jump power and velocity in division I football players. J Strength Cond Res 31(5): 1259-1264, 2017-Research regarding whole body vibration (WBV) largely supports such training augmentation in attempts to increase muscle strength and power. However, localized biomechanical vibration has not received the same attention. The purpose of this study was to assess peak and average power before and after acute vibration of selected lower-body sites in division I athletes. Twenty-one subjects were randomly assigned to 1 of 2 conditions using a cross-over design. Pretest consisted of a counter-movement vertical jump (VJ) followed by either localized vibration (30 Hz) to 4 selected lower-body areas or 4 minutes of moderately low-resistance stationary cycling (70 rpm). Vibration consisted of 1 minute bouts at each lower-leg site for a total of 4 minutes followed by an immediate post-test VJ. Repeated measures analysis of variance yielded no significant differences (p > 0.05) in either peak power or peak velocity. Similarly, no significant differences were found for average power and velocity between conditions. It should be noted that, while not significant, the vibration condition demonstrated an increase in peak power and velocity while the bike condition registered slight decreases. Comparing each of the post-VJ repetitions (1, 2, and 3) the vibration condition experienced significantly greater peak power and velocity from VJ 1 to VJ 3 compared with the bike condition which demonstrated no significant differences among the post-test VJs. These results yielded similar, although not statistically significant outcomes to previous studies using WBV. However, the novelty of selected site biomechanical vibration merits further investigation with respect to frequency, magnitude, and duration of vibration.

  19. Kinematics of the Suez-Sinai area from an updated combined GPS velocity field

    Science.gov (United States)

    Pietrantonio, Grazia; Devoti, Roberto; Mahmoud, Salah; Riguzzi, Federica

    2017-04-01

    Many studies based on GPS data, have been carried out to shed light on the current kinematics of the Suez-Sinai area, where the interaction of the African and Arabian plates is active. A combined GPS velocity solution covering a wide area from Egypt to Middle East allowed us to infer the current rates across the plate margins. We have estimated 126 velocities from time series of 90 permanent and 36 non permanent GPS sites located in Africa (Egypt), Eurasia and Arabia plates in the time span 1996-2015, the largest available for the Egyptian sites. We have combined our velocity solution in a least-squares sense with two other recent velocity solutions of networks located around the eastern Mediterranean, obtaining a final IGb08 velocity field of about 450 sites. Then, we have estimated the IGb08 Euler poles of Africa, Sinai and Arabia, analyzing the kinematics of the Sinai area, particular velocity profiles, and estimating the 2D strain rate field. We show that it is possible to reliably model the rigid motion of Sinai block only including some GPS sites located south of the Carmel Fault. The estimated relative motion with respect to Africa is of the order of 2-3 mm/yr, however there is a clear mismatch between the modeled and the observed velocities in the southern Sinai sites. We have also assessed the NNE left shear motion along the Dead Sea Transform Fault, estimating a relative motion between Arabia and Africa of about 6 mm/yr in the direction of the Red Sea opening.

  20. Two different approaches for creating a prescribed opposed-flow velocity field for flame spread experiments

    Directory of Open Access Journals (Sweden)

    Carmignani Luca

    2015-01-01

    Full Text Available Opposed-flow flame spread over solid fuels is a fundamental area of research in fire science. Typically combustion wind tunnels are used to generate the opposing flow of oxidizer against which a laminar flame spread occurs along the fuel samples. The spreading flame is generally embedded in a laminar boundary layer, which interacts with the strong buoyancy-induced flow to affect the mechanism of flame spread. In this work, two different approaches for creating the opposed-flow are compared. In the first approach, a vertical combustion tunnel is used where a thin fuel sample, thin acrylic or ashless filter paper, is held vertically along the axis of the test-section with the airflow controlled by controlling the duty cycles of four fans. As the sample is ignited, a flame spreads downward in a steady manner along a developing boundary layer. In the second approach, the sample is held in a movable cart placed in an eight-meter tall vertical chamber filled with air. As the sample is ignited, the cart is moved downward (through a remote-controlled mechanism at a prescribed velocity. The results from the two approaches are compared to establish the boundary layer effect on flame spread over thin fuels.

  1. Two different approaches for creating a prescribed opposed-flow velocity field for flame spread experiments

    Science.gov (United States)

    Carmignani, Luca; Celniker, Greg; Bussett, Kyle; Paolini, Christopher; Bhattacharjee, Subrata

    2015-05-01

    Opposed-flow flame spread over solid fuels is a fundamental area of research in fire science. Typically combustion wind tunnels are used to generate the opposing flow of oxidizer against which a laminar flame spread occurs along the fuel samples. The spreading flame is generally embedded in a laminar boundary layer, which interacts with the strong buoyancy-induced flow to affect the mechanism of flame spread. In this work, two different approaches for creating the opposed-flow are compared. In the first approach, a vertical combustion tunnel is used where a thin fuel sample, thin acrylic or ashless filter paper, is held vertically along the axis of the test-section with the airflow controlled by controlling the duty cycles of four fans. As the sample is ignited, a flame spreads downward in a steady manner along a developing boundary layer. In the second approach, the sample is held in a movable cart placed in an eight-meter tall vertical chamber filled with air. As the sample is ignited, the cart is moved downward (through a remote-controlled mechanism) at a prescribed velocity. The results from the two approaches are compared to establish the boundary layer effect on flame spread over thin fuels.

  2. Maximal power and force-velocity relationships during cycling and cranking exercises in volleyball players. Correlation with the vertical jump test.

    Science.gov (United States)

    Driss, T; Vandewalle, H; Monod, H

    1998-12-01

    The aim of this study was to propose a test battery adjusted to volleyball players and to study the links between dynamic (vertical jump, force-velocity relationships and maximal anaerobic power in cranking and cycling) and static (maximal voluntary force and rate of force development in isometric conditions) performances. The relationships between braking force (F) and peak velocity (V) have been determined for cycling and cranking exercises in 18 male volleyball players of a district league. According to previous studies, these F-V relationships were assumed to be linear and were expressed as follows: V = V0(1-F/F0), where V0 should be an estimate of the maximal velocity at zero braking force whereas F0 is assumed to be a braking force corresponding to zero velocity. Maximal anaerobic power in cycling (Pmax leg) and cranking (Pmax arm) were calculated as equal to 0.25 V0F0. The same subjects performed a vertical jump test (VJ) and a strength test on an isometric leg press with the measurement of the unilateral isometric maximal voluntary force (MVF) and indices of rate of isometric force development (RFD): maximal rate of force development (MRFD) and the time from 25% to 50% of MVF (T25-50). Pmax leg (15.8 +/- 1.4 W.kg-1) and V0 arm (259.6 +/- 13.1 rpm) were high but similar to the results of elite athletes, previously collected with the same protocols and the same devices. VJ was significantly with F0 leg, Pmax leg and Pmax arm related to body mass. The performances of the dynamic tests were significantly correlated and especially the parameters (V0, F0, Pmax) of the force velocity tests in cycling were significantly correlated with the same parameters in cranking. The results of the isometric tests (MVF, MRFD) were not correlated with VJ, except T25-50 of the left leg. A vertical jump test and a force velocity test with the arms are proposed for a test battery in volleyball players.

  3. Field test and theoretical analysis of electromagnetic pulse propagation velocity on crossbonded cable systems

    DEFF Research Database (Denmark)

    Jensen, Christian Flytkjær; Bak, Claus Leth; Gudmundsdottir, Unnur Stella

    2014-01-01

    In this paper, the electromagnetic pulse propagation velocity on a three-phase cable system, consisting of three single core (SC) cables in flat formation with an earth continuity conductor is under study. The propagation velocity is an important parameter for most travelling wave off- and online...... fault location methods and needs to be exactly known for optimal performance of these algorithm types. Field measurements are carried out on a 6.9 km and a 31.4 km 245 kV crossbonded cable system, and the results are analysed using the modal decomposition theory. Several ways for determining...

  4. The effect of spatially varying velocity field on the transport of radioactivity in a porous medium.

    Science.gov (United States)

    Sen, Soubhadra; Srinivas, C V; Baskaran, R; Venkatraman, B

    2016-10-01

    In the event of an accidental leak of the immobilized nuclear waste from an underground repository, it may come in contact of the flow of underground water and start migrating. Depending on the nature of the geological medium, the flow velocity of water may vary spatially. Here, we report a numerical study on the migration of radioactivity due to a space dependent flow field. For a detailed analysis, seven different types of velocity profiles are considered and the corresponding concentrations are compared. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Potential, velocity, and density fields from sparse and noisy redshift-distance samples - Method

    Science.gov (United States)

    Dekel, Avishai; Bertschinger, Edmund; Faber, Sandra M.

    1990-01-01

    A method for recovering the three-dimensional potential, velocity, and density fields from large-scale redshift-distance samples is described. Galaxies are taken as tracers of the velocity field, not of the mass. The density field and the initial conditions are calculated using an iterative procedure that applies the no-vorticity assumption at an initial time and uses the Zel'dovich approximation to relate initial and final positions of particles on a grid. The method is tested using a cosmological N-body simulation 'observed' at the positions of real galaxies in a redshift-distance sample, taking into account their distance measurement errors. Malmquist bias and other systematic and statistical errors are extensively explored using both analytical techniques and Monte Carlo simulations.

  6. Transition of equilibrium stochastic to unidirectional velocity vectors in a nanowire subjected to a towering electric field

    Science.gov (United States)

    Arora, Vijay K.; Chek, Desmond C. Y.; Tan, Michael L. P.; Hashim, Abdul Manaf

    2010-12-01

    The equilibrium Fermi-Dirac distribution is revealed to transform to an asymmetric distribution in a very high electric field where the energy gained (or lost) in a mean free path is of paramount importance. The equilibrium stochastic velocity vectors randomly oriented in and opposite to the quasifree direction of a nanowire are shown to streamline in the presence of an extremely high electric field. The complete velocity-field characteristics are acquired. The ultimate directed drift velocity in a towering field is shown to be limited to the appropriately averaged Fermi velocity in the strongly degenerate limit where only half of the quantum states are accessible to electrons. This unidirectional velocity does not sensitively depend on the low-field Ohmic mobility. The emission of a quantum in the form of a phonon or photon lowers the saturation velocity from its ultimate unidirectional limit.

  7. Three-dimensional flow field around and downstream of a subscale model rotating vertical axis wind turbine

    Science.gov (United States)

    Ryan, Kevin J.; Coletti, Filippo; Elkins, Christopher J.; Dabiri, John O.; Eaton, John K.

    2016-03-01

    Three-dimensional, three-component mean velocity fields have been measured around and downstream of a scale model vertical axis wind turbine (VAWT) operated at tip speed ratios (TSRs) of 1.25 and 2.5, in addition to a non-rotating case. The five-bladed turbine model has an aspect ratio (height/diameter) of 1 and is operated in a water tunnel at a Reynolds number based on turbine diameter of 11,600. Velocity fields are acquired using magnetic resonance velocimetry (MRV) at an isotropic resolution of 1/50 of the turbine diameter. Mean flow reversal is observed immediately behind the turbine for cases with rotation. The turbine wake is highly three-dimensional and asymmetric throughout the investigated region, which extends up to 7 diameters downstream. A vortex pair, generated at the upwind-turning side of the turbine, plays a dominant role in wake dynamics by entraining faster fluid from the freestream and aiding in wake recovery. The higher TSR case shows a larger region of reverse flow and greater asymmetry in the near wake of the turbine, but faster wake recovery due to the increase in vortex pair strength with increasing TSR. The present measurement technique also provides detailed information about flow in the vicinity of the turbine blades and within the turbine rotor. The details of the flow field around VAWTs and in their wakes can inform the design of high-density VAWT wind farms, where wake interaction between turbines is a principal consideration.

  8. Particle Velocity Distributions and Large-Scale Electric Field in Solar Wind

    Science.gov (United States)

    Pavan, J.; Vinas, A. F.

    2016-12-01

    Velocity distributions of particles are key elements in the study of solar wind. The physical mechanisms that regulate their many features are a matter of debate. The present work addresses the subject with a fully analytical method in order to establish the shape of particle velocity distributions in solar wind. The method consists in solving the steady-state kinetic equation for particles and the related fluid equations, assigning spatial profiles for density and temperature matching observational data. The model is one-dimensional in configuration-space and two-dimensional in velocity-space, and accounts for large-scale processes, namely, advection, gravity, magnetic mirroring and the large-scale ambipolar electric field, without the aid of wave-particle interactions or collisions. The findings reported add to the general understanding of regulation of particle distributions in solar wind and to the predictions of their shape in regions restricted for in situ measurements.

  9. Daytime, low latitude, vertical ExB drift velocities, inferred from ground-based magnetometer observations in the Peruvian, Philippine and Indian longitude sectors under quiet and disturbed conditions

    CERN Document Server

    Anderson, D; Chau, J; Yumoto, K; Bhattacharya, A; Alex, S

    2006-01-01

    Daytime, low latitude, vertical ExB drift velocities, inferred from ground-based magnetometer observations in the Peruvian, Philippine and Indian longitude sectors under quiet and disturbed conditions

  10. Second-order velocity slip with axisymmetric stagnation point flow and heat transfer due to a stretching vertical plate in a Copper-water nanofluid

    Science.gov (United States)

    Kardri, M. A.; Bachok, N.; Arifin, N. M.; Ali, F. M.

    2017-09-01

    The steady axisymmetric stagnation point flow with second-order velocity slip due to a stretching vertical plate with the existence of copper-water nanofluid was investigated. Similarity transformation has been applied to reduce the governing partial differential equations to ordinary differential equations. Then the self-similar equations are solved numerically using solver bvp4c available in Matlab with Prandtl number, Pr = 6.2. It is found that the dual solutions exist for the certain range of mixed convection parameter. The effects of the governing parameters on the velocity and temperature profile, skin friction coefficient and the local Nusselt number are observed. The results show that the inclusion of nanoparticle copper, will increase the shear stress on the stretching sheet and decrease the heat transfer rate for the slip parameters.

  11. Field Emission Characteristics of the Structure of Vertically Aligned Carbon Nanotube Bundles.

    Science.gov (United States)

    Lin, Pao-Hung; Sie, Cong-Lin; Chen, Ching-An; Chang, Hsuan-Chen; Shih, Yi-Ting; Chang, Hsin-Yueh; Su, Wei-Jhih; Lee, Kuei-Yi

    2015-12-01

    In this study, we performed thermal chemical vapor deposition for growing vertically aligned carbon nanotube (VACNT) bundles for a field emitter and applied photolithography for defining the arrangement pattern to simultaneously compare square and hexagonal arrangements by using two ratios of the interbundle distance to the bundle height (R) of field emitters. The hexagon arrangement with R = 2 had the lowest turn-on electric field (E to) and highest enhancement factor, whereas the square arrangement with R = 3 had the most stable field emission (FE) characteristic. The number density can reveal the correlation to the lowest E to and highest enhancement factor more effectively than can the R or L. The fluorescent images of the synthesized VACNT bundles manifested the uniformity of FE currents. The results of our study indicate the feasibility of applying the VACNT field emitter arrangement to achieve optimal FE performance.

  12. Interpretation of the electric fields measured in an ionospheric critical ionization velocity experiment

    Science.gov (United States)

    Brenning, N.; Faelthammar, C.-G.; Marklund, G.; Haerendel, G.; Kelley, M. C.; Pfaff, R.

    1991-01-01

    The quasi-dc electric fields measured in the CRIT I ionospheric release experiment are studied. In the experiment, two identical barium shaped charges were fired toward a main payload, and three-dimensional measurements of the electric field inside the streams were made. The relevance of proposed mechanisms for electron heating in the critical ionization velocity (CIV) mechanism is addressed. It is concluded that both the 'homogeneous' and the 'ionizing front' models probably are valid, but in different parts of the streams. It is also possible that electrons are directly accelerated by a magnetic field-aligned component of the electric field. The coupling between the ambient ionosphere and the ionized barium stream is more complicated that is usually assumed in CIV theories, with strong magnetic-field-aligned electric fields and probably current limitation as important processes.

  13. Contribution of Field Strength Gradients to the Net Vertical Current of Active Regions

    Science.gov (United States)

    Vemareddy, P.

    2017-12-01

    We examined the contribution of field strength gradients for the degree of net vertical current (NVC) neutralization in active regions (ARs). We used photospheric vector magnetic field observations of AR 11158 obtained by Helioseismic and Magnetic Imager on board SDO and Hinode. The vertical component of the electric current is decomposed into twist and shear terms. The NVC exhibits systematic evolution owing to the presence of the sheared polarity inversion line between rotating and shearing magnetic regions. We found that the sign of shear current distribution is opposite in dominant pixels (60%–65%) to that of twist current distribution, and its time profile bears no systematic trend. This result indicates that the gradient of magnetic field strength contributes to an opposite signed, though smaller in magnitude, current to that contributed by the magnetic field direction in the vertical component of the current. Consequently, the net value of the shear current is negative in both polarity regions, which when added to the net twist current reduces the direct current value in the north (B z > 0) polarity, resulting in a higher degree of NVC neutralization. We conjecture that the observed opposite signs of shear and twist currents are an indication, according to Parker, that the direct volume currents of flux tubes are canceled by their return currents, which are contributed by field strength gradients. Furthermore, with the increase of spatial resolution, we found higher values of twist, shear current distributions. However, the resolution effect is more useful in resolving the field strength gradients, and therefore suggests more contribution from shear current for the degree of NVC neutralization.

  14. Measurement of electroosmotic and electrophoretic velocities using pulsed and sinusoidal electric fields.

    Science.gov (United States)

    Sadek, Samir H; Pimenta, Francisco; Pinho, Fernando T; Alves, Manuel A

    2017-04-01

    In this work, we explore two methods to simultaneously measure the electroosmotic mobility in microchannels and the electrophoretic mobility of micron-sized tracer particles. The first method is based on imposing a pulsed electric field, which allows to isolate electrophoresis and electroosmosis at the startup and shutdown of the pulse, respectively. In the second method, a sinusoidal electric field is generated and the mobilities are found by minimizing the difference between the measured velocity of tracer particles and the velocity computed from an analytical expression. Both methods produced consistent results using polydimethylsiloxane microchannels and polystyrene micro-particles, provided that the temporal resolution of the particle tracking velocimetry technique used to compute the velocity of the tracer particles is fast enough to resolve the diffusion time-scale based on the characteristic channel length scale. Additionally, we present results with the pulse method for viscoelastic fluids, which show a more complex transient response with significant velocity overshoots and undershoots after the start and the end of the applied electric pulse, respectively. © 2016 The Authors. Electrophoresis published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Magnetic Field - Secular Variation of the Vertical Component of the Total Field Intensity for the Epoch 2010.0 - Direct Download

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This map layer shows lines of equal annual change (secular variation) in the vertical component of the total field intensity of the Earth's magnetic field, derived...

  16. Possible relationship between the equatorial electrojet (EEJ) and daytime vertical E × B drift velocities in F region from ROCSAT observations

    Science.gov (United States)

    Kumar, Sandeep; Veenadhari, B.; Tulasi Ram, S.; Su, S.-Y.; Kikuchi, T.

    2016-10-01

    The vertical E × B drift is very important parameter as its day to day variability has great influence on the variability in the low latitude F-region ion and electron density distributions. The measurements of vertical ion velocity from the first Republic of China Satellite (ROCSAT-1) provide a unique data base for the development of possible relationship between vertical E × B drifts and ground based magnetometer observation. An attempt has been made to derive quantitative relationship between F-region vertical E × B drifts measured by ROCSAT-1 (600 km) and ground measured equatorial electrojet for the solar maximum period 2001-2003 for Indian and Japanese sectors. The results consistently indicate existence of linear relationship between the measured vertical E × B drifts at topside F-region and EEJ for both the sectors, with a moderate to high correlation coefficients. The linear relationship between ROCSAT-1 measured E × B drifts and EEJ for Indian and Japanese sectors has been compared with a similar relationship with Jicamarca Unattended Long-term Ionosphere Atmosphere Radar (JULIA) measured E × B drifts (150 km echos) and EEJ strength from Peruvian sector during 2003. It has been found that ROCSAT-1 measured E × B drifts shows linear relationship with EEJ, however, exhibits a larger scatter unlike JULIA radar observed E × B drifts. This may be attributed to the large height difference as ROCSAT-1 measures E × B drifts at 600 km altitude and the EEJ is E-region (110 km) phenomenon.

  17. Investigation of Horizontal Velocity Fields in Stirred Vessels with Helical Coils by PIV

    Directory of Open Access Journals (Sweden)

    Volker Bliem

    2014-01-01

    Full Text Available Horizontal velocity flow fields were measured by particle image velocimetry for a stirred vessel with baffles and two helical coils for enlargement of heat transfer area. The investigation was carried out in a cylindrical vessel with flat base and two different stirrers (radial-flow Rushton turbine and axial-flow propeller stirrer. Combined velocity plots for flow fields at different locations are presented. It was found that helical coils change the flow pattern significantly. Measurements for the axial-flow Rushton turbine showed a strong deflection by the coils, leading to a mainly tangential flow pattern. Behind baffles large areas of unused heat transfer area were found. First results for the axial-flow propeller reveal an extensive absence of fluid movement in the horizontal plane. Improved design considerations for enhanced heat transfer by more compatible equipment compilation are proposed.

  18. Mathematical Modeling of Temperature and Velocity Fields in a Closed-Type Sloped Greenhouse

    OpenAIRE

    関, 平和; 木村, 達郎; 宮本, 暁人; 菅谷, 博; 佐々木, 華織; 猪之奥, 康治

    2001-01-01

    A mathematical model was developed for predicting air temperature, humidity and velocity fields in a closed-type sloped greenhouse. Calculated results of air temperature profile along the slope agreed well with the experimental results except in the daytime when the air temperature was high, and it seemed that the model would be useful for environment analysis in the sloped greenhouse. This model would be better if three-dimensional heat flow had been taken into account in the daytime. Both t...

  19. Determining Effects of Wagon Mass and Vehicle Velocity on Vertical Vibrations of a Rail Vehicle Moving with a Constant Acceleration on a Bridge Using Experimental and Numerical Methods

    Directory of Open Access Journals (Sweden)

    C. Mızrak

    2015-01-01

    Full Text Available Vibrations are vital for derailment safety and passenger comfort which may occur on rail vehicles due to the truck and nearby conditions. In particular, while traversing a bridge, dynamic interaction forces due to moving loads increase the vibrations even further. In this study, the vertical vibrations of a rail vehicle at the midpoint of a bridge, where the amount of deflection is expected to be maximum, were determined by means of a 1 : 5 scaled roller rig and Newmark-β numerical method. Simulations for different wagon masses and vehicle velocities were performed using both techniques. The results obtained from the numerical and experimental methods were compared and it was demonstrated that the former was accurate with an 8.9% error margin. Numerical simulations were performed by identifying different test combinations with Taguchi experiment design. After evaluating the obtained results by means of an ANOVA analysis, it was determined that the wagon mass had a decreasing effect on the vertical vibrations of the rail vehicle by 2.087%, while rail vehicle velocity had an increasing effect on the vibrations by 96.384%.

  20. Peculiarities of heat transfer at the liquid metal flow in a vertical channel in a coplanar magnetic field

    Science.gov (United States)

    Razuvanov, N. G.; Poddubnyi, I. I.; Kostychev, P. V.

    2017-11-01

    The research of hydrodynamics and heat transfer at the liquid metal (LM) downward flow and upflow in a vertical duct of a rectangular cross section with a ratio of sides ∼1/3 in a coplanar magnetic field (MF) under conditions of bilateral symmetrical heating is performed. The problem simulates the LM flow in the heat exchange channels for cooling the liquid metal module of the blanket of the thermonuclear reactor (TNR) of the TOKAMAK type. The experiments were carried out on the basis of the mercury magnetohydrodynamic test-bed (MHD) Moscow Power Engineering Institute (MPEI) – Joint Institute for High Temperatures of the Russian Academy of Sciences (JIHT RAS). The probe measurement technique was used in the flow. Profiles of averaged velocity and averaged temperature, as well as profiles of temperature pulsations in the axial planes of the channel cross-section, are obtained; the distribution of the dimensionless wall temperature along the perimeter unfolding of the channel in the section and along the length of the channel. A significant effect of thermogravitational convection (TGC), which leads to unexpected effects, is found. At the downflow in a magnetic field, in some modes, low-frequency pulsations of anomalously high intensity occur.

  1. Repeating firing fields of CA1 neurons shift forward in response to increasing angular velocity.

    Science.gov (United States)

    Cowen, Stephen L; Nitz, Douglas A

    2014-01-01

    Self-motion information influences spatially-specific firing patterns exhibited by hippocampal neurons. Moreover, these firing patterns can repeat across similar subsegments of an environment, provided that there is similarity of path shape and head orientations across subsegments. The influence of self-motion variables on repeating fields remains to be determined. To investigate the role of path shape and angular rotation on hippocampal activity, we recorded the activity of CA1 neurons from rats trained to run on spiral-shaped tracks. During inbound traversals of circular-spiral tracks, angular velocity increases continuously. Under this condition, most neurons (74%) exhibited repeating fields across at least three adjacent loops. Of these neurons, 86% exhibited forward shifts in the angles of field centers relative to centers on preceding loops. Shifts were absent on squared-spiral tracks, minimal and less reliable on concentric-circle tracks, and absent on outward-bound runs on circular-spiral tracks. However, outward-bound runs on the circular-spiral track in the dark were associated with backward shifts. Together, the most parsimonious interpretation of the results is that continuous increases or decreases in angular velocity are particularly effective at shifting the center of mass of repeating fields, although it is also possible that a nonlinear integration of step counts contributes to the shift. Furthermore, the unexpected absence of field shifts during outward journeys in light (but not darkness) suggests visual cues around the goal location anchored the map of space to an allocentric reference frame.

  2. Velocity field and coherent structures in the near wake of a utility-scale wind turbine

    Science.gov (United States)

    Hong, Jiarong; Dasari, Teja; Wu, Yue; Liu, Yun

    2017-11-01

    Super-large-scale particle image velocity (SLPIV) and the associated flow visualization technique using natural snowfall have been shown as an effective tool to probe turbulent velocity field and coherent structures around utility-scale wind turbines (Hong et al. Nature Comm. 2014). Here we present a follow-up study using the data collected during multiple deployments from 2014 to 2016 around the 2.5 MW turbine at EOLOS field station. The data include SLPIV measurements in the near wake of the turbine in a field of view of 120 m (height) x 60 m (width), and the visualization of tip vortex behavior near the bottom blade tip over a broad range of turbine operational conditions. SLPIV results indicate a highly intermittent flow field in the near wake, consisting of both intense wake expansion and contraction events. Such intermittent states of the near wake are shown to be influenced by both the incoming wind conditions and the turbine operation. The visualization of tip vortex behavior demonstrates the presence of the state of consistent vortex formation as well as various types of disturbed vortex states. The occurrence of these states is statistically analyzed and is shown to be correlated with turbine operational and response parameters under different field conditions. National Science Foundation Fluid Dynamics Program.

  3. Electrokinetics of scalable, electric-field-assisted fabrication of vertically aligned carbon-nanotube/polymer composites

    Science.gov (United States)

    Castellano, Richard J.; Akin, Cevat; Giraldo, Gabriel; Kim, Sangil; Fornasiero, Francesco; Shan, Jerry W.

    2015-06-01

    Composite thin films incorporating vertically aligned carbon nanotubes (VACNTs) offer promise for a variety of applications where the vertical alignment of the CNTs is critical to meet performance requirements, e.g., highly permeable membranes, thermal interfaces, dry adhesives, and films with anisotropic electrical conductivity. However, current VACNT fabrication techniques are complex and difficult to scale up. Here, we describe a solution-based, electric-field-assisted approach as a cost-effective and scalable method to produce large-area VACNT composites. Multiwall-carbon nanotubes are dispersed in a polymeric matrix, aligned with an alternating-current (AC) electric field, and electrophoretically concentrated to one side of the thin film with a direct-current (DC) component to the electric field. This approach enables the fabrication of highly concentrated, individually aligned nanotube composites from suspensions of very dilute ( ϕ = 4 × 10 - 4 ) volume fraction. We experimentally investigate the basic electrokinetics of nanotube alignment under AC electric fields, and show that simple models can adequately predict the rate and degree of nanotube alignment using classical expressions for the induced dipole moment, hydrodynamic drag, and the effects of Brownian motion. The composite AC + DC field also introduces complex fluid motion associated with AC electro-osmosis and the electrochemistry of the fluid/electrode interface. We experimentally probe the electric-field parameters behind these electrokinetic phenomena, and demonstrate, with suitable choices of processing parameters, the ability to scalably produce large-area composites containing VACNTs at number densities up to 1010 nanotubes/cm2. This VACNT number density exceeds that of previous electric-field-fabricated composites by an order of magnitude, and the surface-area coverage of the 40 nm VACNTs is comparable to that of chemical-vapor-deposition-grown arrays of smaller-diameter nanotubes.

  4. Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

    Science.gov (United States)

    Allam, A. A.; Schulte-Pelkum, V.; Ben-Zion, Y.; Tape, C.; Ruppert, N.; Ross, Z. E.

    2017-11-01

    We examine the structure of the Denali fault system in the crust and upper mantle using double-difference tomography, P-wave receiver functions, and analysis (spatial distribution and moveout) of fault zone head waves. The three methods have complementary sensitivity; tomography is sensitive to 3D seismic velocity structure but smooths sharp boundaries, receiver functions are sensitive to (quasi) horizontal interfaces, and fault zone head waves are sensitive to (quasi) vertical interfaces. The results indicate that the Mohorovičić discontinuity is vertically offset by 10 to 15 km along the central 600 km of the Denali fault in the imaged region, with the northern side having shallower Moho depths around 30 km. An automated phase picker algorithm is used to identify 1400 events that generate fault zone head waves only at near-fault stations. At shorter hypocentral distances head waves are observed at stations on the northern side of the fault, while longer propagation distances and deeper events produce head waves on the southern side. These results suggest a reversal of the velocity contrast polarity with depth, which we confirm by computing average 1D velocity models separately north and south of the fault. Using teleseismic events with M ≥ 5.1, we obtain 31,400 P receiver functions and apply common-conversion-point stacking. The results are migrated to depth using the derived 3D tomography model. The imaged interfaces agree with the tomography model, showing a Moho offset along the central Denali fault and also the sub-parallel Hines Creek fault, a suture zone boundary 30 km to the north. To the east, this offset follows the Totschunda fault, which ruptured during the M7.9 2002 earthquake, rather than the Denali fault itself. The combined results suggest that the Denali fault zone separates two distinct crustal blocks, and that the Totschunda and Hines Creeks segments are important components of the fault and Cretaceous-aged suture zone structure.

  5. Integration of Dense Velocity Fields in the ITRF: Quantification and Mitigation of Inconsistencies Between Individual Solutions

    Science.gov (United States)

    Legrand, Juliette; Bruyninx, Carine; Saria, Elifuraha; Griffiths, Jake; Craymer, Michael; Dawson, John; Kenyeres, Ambrus; Santamaría-Gómez, Alvaro; Sanchez, Laura; Altamimi, Zuheir

    2013-04-01

    The objective of the IAG Working Group "Integration of Dense Velocity Fields in the ITRF" is to provide a GNSS-based dense, unified and reliable velocity field globally referenced in the ITRF (International Terrestrial Reference Frame) and useful for geodynamical and geophysical interpretations. The WG is embedded in IAG Sub-Commission 1.3 "Regional Reference Frames" where it coexists with the Regional Reference Frame Sub-Commissions AFREF (Africa), APREF (Asia & Pacific), EUREF (Europe), NAREF (North America), SCAR (Antarctica), SIRGAS (Latin America & Caribbean). These IAG Regional Reference Frame sub-commissions are responsible for providing GNSS-based densified weekly solutions for their region. In addition, the ULR consortium is also a contributor to the WG. To obtain such a densified velocity field, the WG will combine the individual weekly solutions from different contributors and then stack these weekly combined solutions in order to derive a cumulative position and velocity solution as well as the associated residual position time series. The preliminary weekly combinations include 8 individual solutions (AFREF, APREF, EUREF, NAREF (NGS, GSB), SIRGAS, IGS, ULR) and contain about two thousand stations in addition to the ITRF2008. The agreement between the solutions is promising and leads to weekly RMS ranging from 2 to 8 mm. However, this agreement is presently limited by inconsistencies at the modeling and meta data level: 1) the meta data need to be verified as systematic biases occur, probably due to wrong antenna eccentricities and 2) different antenna calibration models have been used by the contributors: some solutions use igs08.atx, while others use igs05.atx or even individual calibrations. In addition, an optimal rescaling of the covariance matrices during the weekly combination is still under investigation. This poster will focus on the quantification and, if possible, the mitigation of these inconsistencies and on the improvement of the

  6. High-speed non-intrusive measurements of fuel velocity fields at high-pressure injectors

    Science.gov (United States)

    Gürtler, Johannes; Schlüßler, Raimund; Fischer, Andreas; Czarske, Jürgen

    2017-03-01

    Using a single high-speed camera and a frequency modulated laser, a novel approach is presented for fast velocity field measurements in unsteady spray flows. The velocity range is from zero up to several 100 m/s, which requires a high measurement rate and a large dynamic. Typically, flow measurements require to seed tracer particles to the fluid. A paradigm shift to seeding-free measurements is presented. The light scattered at the phase boundaries of the fluid droplets is evaluated. In order to validate the high-speed measurement system, a detailed uncertainty analysis is performed by means of measurements as well as simulations. Thereby, variations of the scattered light intensity, which are based on the high temporal velocity gradients, are found to be the main contribution to the uncertainty. The eventually measurement results, obtained at a measurement rate of 500 kHz, exhibit spray velocities ranging from 0 m/s up to 400 m/s in less than 1 ms, and the detection of unsteady and irregular flow phenomena with a characteristic time of several μs is achieved. This demonstrates the high measurement rate, the high temporal resolution and the large measurement range of the proposed high-speed measurement system.

  7. IGS Working Group "Regional Dense Velocity Fields": Objectives and Work Plan

    Science.gov (United States)

    Bruyninx, C.; Altamimi, Z.; Becker, M.; Craymer, M.; Combrinck, L.; Combrink, A.; Fernandes, R.; Govind, R.; Herring, T.; Kenyeres, A.; King, B.; Kreemer, C.; Lavallee, D.; Legrand, J.; Moore, M.; Sanchez, L.; Sella, G.; Woppelmann, G.

    2008-12-01

    The IAG Working Group (WG) on "Regional Dense Velocity Fields" was created within IAG sub-commission 1.3 "Regional Reference Frames" at the IUGG General Assembly in Perugia in 2007. The goal of the Working Group is to densify the latest realization of the ITRS and provide regional dense velocity information in a common global reference frame. For that purpose, working group members join efforts with the regional sub-commissions (AFREF, NAREF, SIRGAS, EUREF, ·s ) and analysis groups processing data from local/regional continuous and episodic GNSS stations. In a first step, dedicated region coordinators will gather as many as possible velocity solutions for their region (in accordance with the WG requirements) and combine these solutions with the sub-commission regional solutions to produce a regional cumulative combined solution in the SINEX format. In a second step, combination coordinators will perform combinations of the regional SINEX submissions and SINEX solutions from global GNSS networks like e.g. TIGA. The purpose of multiple combination coordinators is to evaluate both the results and different approaches. To assist in this task regional coordinators will solicit discontinuity tables in addition to the weekly SINEX solutions. At the same time, the WG will also study the strengths and shortcomings of local/regional and continuous/episodic GNSS solutions to determine site velocities, and define optimal strategies for the combination of regional and global SINEX solutions.

  8. Organic-inorganic proximity effect in the magneto-conductance of vertical organic field effect transistors

    Science.gov (United States)

    Khachatryan, B.; Greenman, M.; Devir-Wolfman, A. H.; Tessler, N.; Ehrenfreund, E.

    2016-07-01

    Vertical organic field effect transistors having a patterned source electrode and an a-SiO2 insulation layer show high performance as a switching element with high transfer characteristics. By measuring the low field magneto-conductance under ambient conditions at room temperature, we show here that the proximity of the inorganic a-SiO2 insulation to the organic conducting channel affects considerably the magnetic response. We propose that in n-type devices, electrons in the organic conducting channel and spin bearing charged defects in the inorganic a-SiO2 insulation layer (e.g., O2 = Si+.) form oppositely charged spin pairs whose singlet-triplet spin configurations are mixed through the relatively strong hyperfine field of 29Si. By increasing the contact area between the insulation layer and the conducting channel, the ˜2% magneto-conductance response may be considerably enhanced.

  9. Convenient method for estimating underground s-wave velocity structure utilizing horizontal and vertical components microtremor spectral ratio; Bido no suiheido/jogedo supekutoru hi wo riyoshita kan`i chika s ha sokudo kozo suiteiho

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, H.; Yoshioka, M.; Saito, T. [Iwate University, Iwate (Japan). Faculty of Engineering

    1996-05-01

    Studies were conducted about the method of estimating the underground S-wave velocity structure by inversion making use of the horizontal/vertical motion spectral ratio of microtremors. For this purpose, a dynamo-electric velocity type seismograph was used, capable of processing the east-west, north-south, and vertical components integratedly. For the purpose of sampling the Rayleigh wave spectral ratio, one out of all the azimuths was chosen, whose horizontal motion had a high Fourier frequency component coherency with the vertical motions. For the estimation of the underground S-wave velocity structure, parameters (P-wave velocity, S-wave velocity, density, and layer thickness) were determined from the minimum residual sum of squares involving the observed microtremor spectral ratio and the theoretical value calculated by use of a model structure. The known boring data was utilized for the study of the S-wave velocity in the top layer, and it was determined using an S-wave velocity estimation formula for the Morioka area constructed using the N-value, depth, and geological classification. It was found that the optimum S-wave velocity structure even below the top layer well reflects the S-wave velocity obtained by the estimation formula. 5 refs., 6 figs.

  10. NGS2008-beta: A preliminary estimate of an update to the North America CORS velocity field

    Science.gov (United States)

    Rohde, J. R.; Griffiths, J.; Cline, M.; Dulaney, R. L.; Hilla, S.; Kass, W. G.; Ray, J.; Sella, G.; Snay, R. A.

    2009-12-01

    The National Geodetic Survey (NGS) has reanalyzed the history of Global Positioning System (GPS) data collected by the North America network of about 1,625 Continuously Operating Reference Stations (CORS). The RINEX data have been reduced using the latest version of the PAGES software, resulting in a fully consistent, long-term set of station coordinates in a global framework. Station coordinate estimates are presented in weekly SINEX files, along with the full variance-covariance information. The goal for this paper is to assess the quality of the reprocessed time series and to present a preliminary estimate of the velocity field obtained by stacking the weekly SINEX files using the CATREF software from the Institut Géographique National. The stacking software works by aligning each weekly solution to the current IGS terrestrial frame, resulting in regularized coordinates and secular velocities for each CORS, and a time series of station coordinate residuals and Helmert transformation parameters. Analysis of the residuals and transformation parameters can yield useful information about the quality and consistency of the stacked solution. The completed velocity field from this reanalysis will provide the foundation for an update of the geometric component of the U.S. National Spatial Reference System (i.e., NAD83).

  11. Buoyancy effects in vertical rectangular duct with coplanar magnetic field and single sided heat load

    Science.gov (United States)

    Kostichev, P. I.; Poddubnyi, I. I.; Razuvanov, N. G.

    2017-11-01

    In some DEMO blanket designs liquid metal flows in vertical ducts of rectangular cross-section between ceramic breeder units providing their cooling. Heat exchange in these conditions is governed by the influence of magnetic field (coplanar) and by buoyancy effects that depend on the flow orientation to the gravity vector (downward and upward flow). Magnetohydrodynamic and heat transfer of liquid metal in vertical rectangular ducts is not well researched. Experimental study of buoyancy effects in rectangular duct with coplanar magnetic field for one-sided heat load and downward and upward flowsis presented in this paper. The detail research with has been done on mercury MHD close loop with using of the probe technique allow to discover several advantageous and disadvantageous effects. The intensive impact of buoyancy force has been observed in a few regime of downward flow which has been laminarized by magnetic field. Due to the development in the flow of the secondary large-scale vortices heat transfer improved and the temperature fluctuations of the abnormally high intensity have been fixed. On the contrary, in the upward flow the buoyancy force stabilized the flow which lead to decreasing of the turbulence heat transfer ratio and, consequently, deterioration of heat transfer.

  12. Tuning vertical alignment and field emission properties of multi-walled carbon nanotube bundles

    Science.gov (United States)

    Sreekanth, M.; Ghosh, S.; Srivastava, P.

    2018-01-01

    We report the growth of vertically aligned carbon nanotube bundles on Si substrate by thermal chemical vapor deposition technique. Vertical alignment was achieved without any carrier gas or lithography-assisted deposition. Growth has been carried out at 850 °C for different quantities of solution of xylene and ferrocene ranging from 2.25 to 3.00 ml in steps of 0.25 ml at a fixed concentration of 0.02 gm (ferrocene) per ml. To understand the growth mechanism, deposition was carried out for different concentrations of the solution by changing only the ferrocene quantity, ranging from 0.01 to 0.03 gm/ml. A tunable vertical alignment of multi-walled carbon nanotubes (CNTs) has been achieved by this process and examined by scanning and transmission electron microscopic techniques. Micro-crystalline structural analysis has been done using Raman spectroscopy. A systematic variation in field emission (FE) current density has been observed. The highest FE current density is seen for the film grown with 0.02 gm/ml concentration, which is attributed to the better alignment of CNTs, less structural disorder and less entanglement of CNTs on the surface. The alignment of CNTs has been qualitatively understood on the basis of self-assembled catalytic particles.

  13. Numerical simulation of velocity and temperature fields in natural circulation loop

    Science.gov (United States)

    Sukomel, L. A.; Kaban’kov, O. N.

    2017-11-01

    Low flow natural circulation regimes are realized in many practical applications and the existence of the reliable engineering and design calculation methods of flows driven exclusively by buoyancy forces is an actual problem. In particular it is important for the analysis of start up regimes of passive safety systems of nuclear power plants. In spite of a long year investigations of natural circulation loops no suitable predicting recommendations for heat transfer and friction for the above regimes have been proposed for engineering practice and correlations for forced flow are commonly used which considerably overpredicts the real flow velocities. The 2D numerical simulation of velocity and temperature fields in circular tubes for laminar flow natural circulation with reference to the laboratory experimental loop has been carried out. The results were compared with the 1D modified model and experimental data obtained on the above loop. The 1D modified model was still based on forced flow correlations, but in these correlations the physical properties variability and the existence of thermal and hydrodynamic entrance regions are taken into account. The comparison of 2D simulation, 1D model calculations and the experimental data showed that even subject to influence of liquid properties variability and entrance regions on heat transfer and friction the use of 1D model with forced flow correlations do not improve the accuracy of calculations. In general, according to 2D numerical simulation the wall shear stresses are mainly affected by the change of wall velocity gradient due to practically continuous velocity profiles deformation along the whole heated zone. The form of velocity profiles and the extent of their deformation in its turn depend upon the wall heat flux density and the hydraulic diameter.

  14. Antarctic Glaciological Data at NSIDC: field data, temperature, and ice velocity

    Science.gov (United States)

    Bauer, R.; Bohlander, J.; Scambos, T.; Berthier, E.; Raup, B.; Scharfen, G.

    2003-12-01

    An extensive collection of many Antarctic glaciological parameters is available for the polar science community upon request. The National Science Foundation's Office of Polar Programs funds the Antarctic Glaciological Data Center (AGDC) at the National Snow and Ice Data Center (NSIDC) to archive and distribute Antarctic glaciological and cryospheric system data collected by the U.S. Antarctic Program. AGDC facilitates data exchange among Principal Investigators, preserves recently collected data useful to future research, gathers data sets from past research, and compiles continent-wide information useful for modeling and field work planning. Data sets are available via our web site, http://nsidc.org/agdc/. From here, users can access extensive documentation, citation information, locator maps, derived images and references, and the numerical data. More than 50 Antarctic scientists have contributed data to the archive. Among the compiled products distributed by AGDC are VELMAP and THERMAP. THERMAP is a compilation of over 600 shallow firn temperature measurements ('10-meter temperatures') collected since 1950. These data provide a record of mean annual temperature, and potentially hold a record of climate change on the continent. The data are represented with maps showing the traverse route, and include data sources, measurement technique, and additional measurements made at each site, i.e., snow density and accumulation. VELMAP is an archive of surface ice velocity measurements for the Antarctic Ice Sheet. The primary objective of VELMAP is to assemble a historic record of outlet glaciers and ice shelf ice motion over the Antarctic. The collection includes both PI-contributed measurements and data generated at NSIDC using Landsat and SPOT satellite imagery. Tabular data contain position, speed, bearing, and data quality information, and related references. Two new VELMAP data sets are highlighted: the Mertz Glacier and the Institute Ice Stream. Mertz Glacier ice

  15. Temperature and velocity fields in natural convection by PIV and LIF

    DEFF Research Database (Denmark)

    Meyer, Knud Erik; Larsen, Poul Scheel; Westergaard, C. H.

    2002-01-01

    Natural convection in a cubical cavity (L = 250 mm) filled with water is created by heating a square plate (0.5 L) centred in the bottom wall and by cooling the sidewalls, while the remaining walls are insulated. The Rayleigh number based on cavity side length and temperature difference between...... plate and cooled walls is 1.4×10^10. The flow is turbulent and is similar to some indoor room flows. Combined Particle Image Velocimetry (PIV) and Planar Light Induced Fluorescence (LIF) are used to measure local velocities and temperatures. Data measured in a symmetry plane parallel to a sidewall...... are presented in terms of mean velocities and temperature and in terms turbulent quantities including Reynolds fluxes. The flow consists a plume rising above the heated plate into an almost stagnant fluid with a weakly stratified temperature field, as well as thin buoyancy driven boundary layers down...

  16. Doppler-shifted fluorescence imaging of velocity fields in supersonic reacting flows

    Energy Technology Data Exchange (ETDEWEB)

    Allen, M.G.; Davis, S.J.; Kessler, W.J.; Sonnenfroh, D.M. (Physical Sciences, Inc., Andover, MA (United States))

    1992-07-01

    The application of Doppler-shifted fluorescence imaging of velocity fields in supersonic reacting flows is analyzed. Focussing on fluorescence of the OH molecule in typical H2-air Scramjet flows, the effects of uncharacterized variations in temperature, pressure, and collisional partner composition across the measurement plane are examined. Detailed measurements of the (1,0) band OH lineshape variations in H2-air combustions are used, along with single-pulse and time-averaged measurements of an excimer-pumped dye laser, to predict the performance of a model velocimeter with typical Scramjet flow properties. The analysis demonstrates the need for modification and control of the laser bandshape in order to permit accurate velocity measurements in the presence of multivariant flow properties. 13 refs.

  17. River-ice and sea-ice velocity fields from near-simultaneous satellite imagery

    Science.gov (United States)

    Kaeaeb, A.; Leprince, S.; Prowse, T. D.; Beltaos, S.; Lamare, M.; Abrams, M.

    2013-12-01

    Satellite stereo and satellites that follow each other on similar orbits within short time periods produce near-simultaneous space imagery, a kind of data that is little exploited. In this study, we track river-ice and sea-ice motion over time periods of tens of seconds to several minutes, which is the typical time lag between the two or more images of such near-simultaneous acquisition constellations. Using this novel approach, we measure and visualize for the first time the almost complete two-dimensional minute-scale velocity fields over several thousand square-kilometers of sea ice cover or over up to several hundred kilometers long river reaches. We present the types of near-simultaneous imagery and constellations suitable for the measurements and discuss application examples, using a range of high and medium resolution imagery such as from ASTER, ALOS PRISM, Ikonos, WorldView-2, Landsat and EO-1. The river ice velocities obtained provide new insights into ice dynamics, river flow and river morphology, in particular during ice breakup. River-ice breakup and the associated downstream transport of ice debris is often the most important hydrological event of the year, producing flood levels that commonly exceed those for the open-water period and dramatic consequences for river infrastructure and ecology. We also estimate river discharge from ice/water surface velocities using near-simultaneous satellite imagery. Our results for sea ice complement velocity fields typically obtained over time-scales of days and can thus contribute to better understanding of a number of processes involved in sea ice drift, such as wind impact, tidal currents and interaction of ice floes with each other and with obstacles.

  18. Gummel Symmetry Test on charge based drain current expression using modified first-order hyperbolic velocity-field expression

    Science.gov (United States)

    Singh, Kirmender; Bhattacharyya, A. B.

    2017-03-01

    -order derivative and for weak inversion it is shown till fifth-order derivative. In the expression of drain current major short channel phenomena like vertical field mobility reduction, velocity saturation and velocity overshoot have been taken into consideration.

  19. A new car-following model for autonomous vehicles flow with mean expected velocity field

    Science.gov (United States)

    Wen-Xing, Zhu; Li-Dong, Zhang

    2018-02-01

    Due to the development of the modern scientific technology, autonomous vehicles may realize to connect with each other and share the information collected from each vehicle. An improved forward considering car-following model was proposed with mean expected velocity field to describe the autonomous vehicles flow behavior. The new model has three key parameters: adjustable sensitivity, strength factor and mean expected velocity field size. Two lemmas and one theorem were proven as criteria for judging the stability of homogeneousautonomous vehicles flow. Theoretical results show that the greater parameters means larger stability regions. A series of numerical simulations were carried out to check the stability and fundamental diagram of autonomous flow. From the numerical simulation results, the profiles, hysteresis loop and density waves of the autonomous vehicles flow were exhibited. The results show that with increased sensitivity, strength factor or field size the traffic jam was suppressed effectively which are well in accordance with the theoretical results. Moreover, the fundamental diagrams corresponding to three parameters respectively were obtained. It demonstrates that these parameters play almost the same role on traffic flux: i.e. before the critical density the bigger parameter is, the greater flux is and after the critical density, the opposite tendency is. In general, the three parameters have a great influence on the stability and jam state of the autonomous vehicles flow.

  20. The interseismic velocity field of the central Apennines from a dense GPS network

    Directory of Open Access Journals (Sweden)

    Alessandro Galvani

    2013-02-01

    Full Text Available Since 1999, we have repeatedly surveyed the central Apennines through a dense survey-style geodetic network, the Central Apennines Geodetic Network (CAGeoNet. CAGeoNet consists of 123 benchmarks distributed over an area of ca. 180 km × 130 km, from the Tyrrhenian coast to the Adriatic coast, with an average inter-site distance of 3 km to 5 km. The network is positioned across the main seismogenic structures of the region that are capable of generating destructive earthquakes. Here, we show the horizontal GPS velocity field of both CAGeoNet and continuous GPS stations in this region, as estimated from the position–time series in the time span from 1999 to 2007. We analyzed the data using both the Bernese and GAMIT software, rigorously combining the two solutions to obtain a validated result. Then, we analyzed the strain-rate field, which shows a region of extension along the axis of the Apennine chain, with values from 2 × 10–9 yr–1 to 66·× 10–9 yr–1, and a relative minimum of ca. 20 × 10–9 yr–1 located in the L'Aquila basin area. Our velocity field represents an improved estimation of the ongoing elastic interseismic deformation of the central Apennines, and in particular relating to the area of the L'Aquila earthquake of April 6, 2009.

  1. Galaxy Transformation as probed by Morphology and Velocity Fields of Distant Cluster Galaxies

    Science.gov (United States)

    Ziegler, Bodo

    2005-07-01

    We seek to obtain ACS imaging of four distant {0.3images. The velocity field and the morphology in restframe-UV light will reveal possible transformation mechanisms affecting not only the stellar populations but also the mass distribution of the galaxies. Additionally, it will be possible to pin down the nature of the interaction {e.g. tidally or ram-pressure induced}. This assessment gets supported by our N-body/SPH simulations {including star formation} of different interaction processes that allow the direct comparison of structural and kinematical characteristics at each time step with the observations on an individual basis taking into account all observational constraints for a given galaxy. All together, we will be able to explore the relative efficiency of the various proposed transformation phenomena. In the case of non-disturbed spirals, a rotation curve can be extracted from the full 2D velocity field with unprecedented quality, from which the maximum rotation speed can be derived with high confidence. In combination with accurate size and luminosity determinations from the ACS images, we will be able to establish the Tully-Fisher and Fundamental Plane relations of cluster spiral members at cosmological epochs. At these distances cluster assembly is predicted to peak and we can probe the galaxies' luminosity, size and mass evolution with robust methods. Together with our already existing sample of 200 distant {z<=1} spiral galaxies in the field, we will put strong constraints on current theories of galaxy formation and evolution in different environments.

  2. Velocity and magnetic field measurements of Taylor plumes in SSX under different boundary conditions

    Science.gov (United States)

    Kaur, Manjit; Brown, M. R.; Han, J.; Shrock, J. E.; Schaffner, D. A.

    2016-10-01

    The SSX device has been modified by the addition of a 1 m long glass extension for accommodating pulsed theta pinch coils. The Taylor plumes are launched from a magnetized plasma gun and flow to an expansion volume downstream. The time of flight (TOF) measurements of these plumes are carried out using a linear array of Ḃ probes (separated by 10cm). TOF of the plasma plumes from one probe location to the next is determined by direct comparison of the magnetic field structures as well as by carrying out a cross-correlation analysis. With the glass boundary, the typical velocity of the Taylor plumes is found to be 25km /s , accompanied by a fast plasma (>= 50km /s) at the leading edge. Magnetic field embedded in the Taylor plumes is measured in the expansion chamber using a three-dimensional array of Ḃ probes and is found to be 700G . Some flux conservation of the Taylor plumes is provided by using a resistive (soak time 3 μs) and a mesh (soak time 170 μs > discharge time) liner around the glass tube for improving the downstream Taylor state velocity as well as the magnetic field. The results from these different boundary conditions will be presented. Work supported by DOE OFES and ARPA-E ALPHA programs.

  3. Vertical electric field stimulated neural cell functionality on porous amorphous carbon electrodes.

    Science.gov (United States)

    Jain, Shilpee; Sharma, Ashutosh; Basu, Bikramjit

    2013-12-01

    We demonstrate the efficacy of amorphous macroporous carbon substrates as electrodes to support neuronal cell proliferation and differentiation in electric field mediated culture conditions. The electric field was applied perpendicular to carbon substrate electrode, while growing mouse neuroblastoma (N2a) cells in vitro. The placement of the second electrode outside of the cell culture medium allows the investigation of cell response to electric field without the concurrent complexities of submerged electrodes such as potentially toxic electrode reactions, electro-kinetic flows and charge transfer (electrical current) in the cell medium. The macroporous carbon electrodes are uniquely characterized by a higher specific charge storage capacity (0.2 mC/cm(2)) and low impedance (3.3 kΩ at 1 kHz). The optimal window of electric field stimulation for better cell viability and neurite outgrowth is established. When a uniform or a gradient electric field was applied perpendicular to the amorphous carbon substrate, it was found that the N2a cell viability and neurite length were higher at low electric field strengths (≤ 2.5 V/cm) compared to that measured without an applied field (0 V/cm). While the cell viability was assessed by two complementary biochemical assays (MTT and LDH), the differentiation was studied by indirect immunostaining. Overall, the results of the present study unambiguously establish the uniform/gradient vertical electric field based culture protocol to either enhance or to restrict neurite outgrowth respectively at lower or higher field strengths, when neuroblastoma cells are cultured on porous glassy carbon electrodes having a desired combination of electrochemical properties. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. On the interaction between the external magnetic field and nanofluid inside a vertical square duct

    Directory of Open Access Journals (Sweden)

    Kashif Ali

    2015-10-01

    Full Text Available In this paper, we numerically study how the external magnetic field influences the flow and thermal characteristics of nanofluid inside a vertical square duct. The flow is considered to be laminar and hydrodynamically as well as thermally developed, whereas the thermal boundary condition of constant heat flux per unit axial length with constant peripheral temperature at any cross section, is assumed. The governing equations are solved using the spectral method and the finite difference method. Excellent comparison is noted in the numerical results given by the two methods but the spectral method is found to be superior in terms of both efficiency and accuracy. We have noted that the flow reversal due to high Raleigh number may be controlled by applying an external magnetic field of suitable strength. Moreover, the Nusselt number is found to be almost a linear function of the nanoparticle volume fraction parameter, for different values of the Raleigh number and the magnetic parameter.

  5. On the interaction between the external magnetic field and nanofluid inside a vertical square duct

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Kashif; Ahmad, Shabbir; Ahmad, Shahzad, E-mail: shahzadahmadbzu@gmail.com; Ashraf, Muhammad; Asif, Muhammad [Centre for Advanced Studies in Pure and Applied Mathematics, Bahauddin Zakariya University, Multan (Postal Code: 60800) (Pakistan)

    2015-10-15

    In this paper, we numerically study how the external magnetic field influences the flow and thermal characteristics of nanofluid inside a vertical square duct. The flow is considered to be laminar and hydrodynamically as well as thermally developed, whereas the thermal boundary condition of constant heat flux per unit axial length with constant peripheral temperature at any cross section, is assumed. The governing equations are solved using the spectral method and the finite difference method. Excellent comparison is noted in the numerical results given by the two methods but the spectral method is found to be superior in terms of both efficiency and accuracy. We have noted that the flow reversal due to high Raleigh number may be controlled by applying an external magnetic field of suitable strength. Moreover, the Nusselt number is found to be almost a linear function of the nanoparticle volume fraction parameter, for different values of the Raleigh number and the magnetic parameter.

  6. Green's function of a massless scalar field in curved space-time and superluminal phase velocity of the retarded potential

    Science.gov (United States)

    Dai, De-Chang; Stojkovic, Dejan

    2012-10-01

    We study a retarded potential solution of a massless scalar field in curved space-time. In a special ansatz for a particle at rest whose magnitude of the (scalar) charge is changing with time, we found an exact analytic solution. The solution indicates that the phase velocity of the retarded potential of a nonmoving scalar charge is position-dependent and may easily be greater than the speed of light at a given point. In the case of the Schwarzschild space-time, at the horizon, the phase velocity becomes infinitely faster than the coordinate speed of light at that point. Superluminal phase velocity is a relatively common phenomenon, with the phase velocity of the massive Klein-Gordon field as the best known example. We discuss why it is possible to have modes with superluminal phase velocity even for a massless field.

  7. The Continuous Monitoring of Flash Flood Velocity Field based on an Automated LSPIV System

    Science.gov (United States)

    Li, W.; Ran, Q.; Liao, Q.

    2014-12-01

    Large-scale particle image velocimetry (LSPIV) is a non-intrusive tool for flow velocity field measurement and has more advantages against traditional techniques, with its applications on river, lake and ocean, especially under extreme conditions. An automated LSPIV system is presented in this study, which can be easily set up and executed for continuous monitoring of flash flood. The experiment site is Longchi village, Sichuan Province, where 8.0 magnitude earthquake occurred in 2008 and debris flow happens every year since then. The interest of area is about 30m*40m of the channel which has been heavily destroyed by debris flow. Series of videos obtained during the flood season indicates that flood outbreaks after rainstorm just for several hours. Measurement is complete without being influenced by this extreme weather condition and results are more reliable and accurate due to high soil concentration. Compared with direct measurement by impellor flow meter, we validated that LSPIV works well at mountain stream, with index of 6.7% (Average Relative Error) and 95% (Nash-Sutcliffe Coefficient). On Jun 26, the maximum flood surface velocity reached 4.26 m/s, and the discharge based on velocity-area method was also decided. Overall, this system is safe, non-contact and can be adjusted according to our requirement flexibly. We can get valuable data of flood which is scarce before, which will make a great contribution to the analysis of flood and debris flow mechanism.

  8. Tuning the Fermi velocity in Dirac materials with an electric field.

    Science.gov (United States)

    Díaz-Fernández, A; Chico, Leonor; González, J W; Domínguez-Adame, F

    2017-08-14

    Dirac materials are characterized by energy-momentum relations that resemble those of relativistic massless particles. Commonly denominated Dirac cones, these dispersion relations are considered to be their essential feature. These materials comprise quite diverse examples, such as graphene and topological insulators. Band-engineering techniques should aim to a full control of the parameter that characterizes the Dirac cones: the Fermi velocity. We propose a general mechanism that enables the fine-tuning of the Fermi velocity in Dirac materials in a readily accessible way for experiments. By embedding the sample in a uniform electric field, the Fermi velocity is substantially modified. We first prove this result analytically, for the surface states of a topological insulator/semiconductor interface, and postulate its universality in other Dirac materials. Then we check its correctness in carbon-based Dirac materials, namely graphene nanoribbons and nanotubes, thus showing the validity of our hypothesis in different Dirac systems by means of continuum, tight-binding and ab-initio calculations.

  9. Capabilities of optical SIV technique in measurements of flow velocity vector field dynamics

    Science.gov (United States)

    Mikheev, N. I.; Dushin, N. S.; Saushin, I. I.

    2017-11-01

    The main difference between Smoke Image Velocimetry (SIV) technique and the conventional PIV is that higher concentration of tracer particles typical of smoke visualization techniques is used in SIV. Not separate particles but smoke structures with continuous pixel intensity are visible in the recorded images. Owing to better smoke reflectivity, higher spatial and temporal resolution is obtained in the case when relatively simple equipment (camera and laser) is used. It is simple enough to perform SIV measurements of velocity vector field dynamics at the frequency exceeding 15000 Hz, which offers new opportunities in unsteady flow examination. The paper describes fundamentals of SIV technique and gives some new results obtained using this method for the measurements that require high spatial and temporal resolution. The latter include frequency spectra of turbulent velocity fluctuations, turbulence dissipation profiles in the boundary layer and higher-order moments of velocity fluctuations. It has been shown that SIV technique considerably extends the potential of experimental studies of turbulence and flow structure in high-speed processes.

  10. Dilution and Mixing in transient velocity fields: a first-order analysis

    Science.gov (United States)

    Di Dato, Mariaines; de Barros, Felipe, P. J.; Fiori, Aldo; Bellin, Alberto

    2017-04-01

    An appealing remediation technique is in situ oxidation, which effectiveness is hampered by difficulties in obtaining good mixing of the injected oxidant with the contaminant, particularly when the contaminant plume is contained and therefore its deformation is physically constrained. Under such conditions (i.e. containment), mixing may be augmented by inducing temporal fluctuations of the velocity field. The temporal variability of the flow field may increase the deformation of the plume such that diffusive mass flux becomes more effective. A transient periodic velocity field can be obtained by an engineered sequence of injections and extractions from wells, which may serve also as a hydraulic barrier to confine the plume. Assessing the effectiveness of periodic flows to maximize solute mixing is a difficult task given the need to use a 3D setup and the large number of possible flow configurations that should be analyzed in order to identify the optimal one. This is the typical situation in which analytical solutions, though approximated, may assist modelers in screening possible alternative flow configurations such that solute dilution is maximized. To quantify dilution (i.e. a precondition that enables reactive mixing) we utilize the concept of the dilution index [1]. In this presentation, the periodic flow takes place in an aquifer with spatially variable hydraulic conductivity field which is modeled as a Stationary Spatial Random Function. We developed a novel first-order analytical solution of the dilution index under the hypothesis that the flow can be approximated as a sequence of steady state configurations with the mean velocity changing with time in intensity and direction. This is equivalent to assume that the characteristic time of the transient behavior is small compared to the period characterizing the change in time of the mean velocity. A few closed paths have been analyzed quantifying their effectiveness in enhancing dilution and thereby mixing

  11. Constructing 3D isotropic and azimuthally anisotropic crustal models across USArray using Rayleigh wave phase velocity and ellipticity: inferring continental stress field

    Science.gov (United States)

    Lin, F. C.; Schmandt, B.; Tsai, V. C.

    2014-12-01

    The EarthScope USArray Transportable Array (TA) has provided a great opportunity for imaging the detailed lithospheric structure beneath the continental US. In this presentation, we will report our recent progress on constructing detailed 3D isotropic and anisotropic crustal models of the contiguous US using Rayleigh wave phase velocity and ellipticity measurements across TA. In particular, we will discuss our recent methodology development of extracting short period Rayleigh wave ellipticity, or Rayleigh-wave H/V (horizontal to vertical) amplitude ratios, using multicomponent noise cross-correlations. To retain the amplitude ratio information between vertical and horizontal components, for each station, we perform daily noise pre-processing (temporal normalization and spectrum whitening) simultaneously for all three components. For each station pair, amplitude measurements between cross-correlations of different components (radial-radial, radial-vertical, vertical-radial and vertical-vertical) are then used to determine the Rayleigh-wave H/V ratios at the two station locations. Measurements from all available station pairs are used to determine isotropic and directionally dependent Rayleigh-wave H/V ratios at each location between 8- and 24-second period. The isotropic H/V ratio maps, combined with previous longer period Rayleigh-wave H/V ratio maps from earthquakes and Rayleigh-wave phase velocity maps from both ambient noise and earthquakes, are used to invert for a new 3-D isotropic crustal and upper-mantle model in the western United States. The new model has an outstanding vertical resolution in the upper crust and tradeoffs between different parameters are mitigated. A clear 180-degree periodicity is observed in the directionally dependent H/V ratio measurements for many locations where upper crustal anisotropy is likely strong. Across the US, good correlation is observed between the inferred fast directions in the upper crust and documented maximum

  12. Estimating a continuous p-wave velocity profile with constant squared-slowness gradient models from seismic field data

    NARCIS (Netherlands)

    Ponomarenko, A.V.; Kashtan, B.M.; Troyan, V.N.; Mulder, W.A.

    2015-01-01

    We inverted seismic field data for a continuous, laterally invariant P-wave velocity profile. Instead of the usual approach that involves horizontal layers with piecewise constant densities and velocities, we consider models of one or two layers with a constant gradient of the squared slowness above

  13. Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

    Science.gov (United States)

    Chaffin, deceased, Roger J.; Dawson, Ralph; Fritz, Ian J.; Osbourn, Gordon C.; Zipperian, Thomas E.

    1989-01-01

    A field effect transistor comprises a semiconductor having a source, a drain, a channel and a gate in operational relationship. The semiconductor is a strained layer superlattice comprising alternating quantum well and barrier layers, the quantum well layers and barrier layers being selected from the group of layer pairs consisting of InGaAs/AlGaAs, InAs/InAlGaAs, and InAs/InAlAsP. The layer thicknesses of the quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice which has a superlattice conduction band energy level structure in k-vector space which includes a lowest energy .GAMMA.-valley and a next lowest energy L-valley, each k-vector corresponding to one of the orthogonal directions defined by the planes of said layers and the directions perpendicular thereto. The layer thicknesses of the quantum well layers are selected to provide a superlattice L.sub.2D -valley which has a shape which is substantially more two-dimensional than that of said bulk L-valley.

  14. Measuring curvature and velocity vector fields for waves of cardiac excitation in 2-D media.

    Science.gov (United States)

    Kay, Matthew W; Gray, Richard A

    2005-01-01

    Excitable media theory predicts the effect of electrical wavefront morphology on the dynamics of propagation in cardiac tissue. It specifies that a convex wavefront propagates slower and a concave wavefront propagates faster than a planar wavefront. Because of this, wavefront curvature is thought to be an important functional mechanism of cardiac arrhythmias. However, the curvature of wavefronts during an arrhythmia are generally unknown. We introduce a robust, automated method to measure the curvature vector field of discretely characterized, arbitrarily shaped, two-dimensional (2-D) wavefronts. The method relies on generating a smooth, continuous parameterization of the shape of a wave using cubic smoothing splines fitted to an isopotential at a specified level, which we choose to be -30 mV. Twice differentiating the parametric form provides local curvature vectors along the wavefront and waveback. Local conduction velocities are computed as the wave speed along lines normal to the parametric form. In this way, the curvature and velocity vector field for wavefronts and wavebacks can be measured. We applied the method to data sampled from a 2-D numerical model and several examples are provided to illustrate its usefulness for studying the dynamics of cardiac propagation in 2-D media.

  15. New vertical cryostat for the high field superconducting magnet test station at CERN

    Science.gov (United States)

    Vande Craen, A.; Atieh, S.; Bajko, M.; Benda, V.; de Rijk, G.; Favre, G.; Giloux, C.; Hanzelka, P.; Minginette, P.; Parma, V.; Perret, P.; Pirotte, O.; Ramos, D.; Viret, P.

    2014-01-01

    In the framework of the R&D program for new superconducting magnets for the Large Hadron Collider accelerator upgrades, CERN is building a new vertical test station to test high field superconducting magnets of unprecedented large size. This facility will allow testing of magnets by vertical insertion in a pressurized liquid helium bath, cooled to a controlled temperature between 4.2 K and 1.9 K. The dimensions of the cryostat will allow testing magnets of up to 2.5 m in length with a maximum diameter of 1.5 m and a mass of 15 tons. To allow for a faster insertion and removal of the magnets and reducing the risk of helium leaks, all cryogenics supply lines are foreseen to remain permanently connected to the cryostat. A specifically designed 100 W heat exchanger is integrated in the cryostat helium vessel for a controlled cooling of the magnet from 4.2 K down to 1.9 K in a 3 m3 helium bath. This paper describes the cryostat and its main functions, focusing on features specifically developed for this project. The status of the construction and the plans for assembly and installation at CERN are also presented.

  16. Influence of contact height on the performance of vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2013-01-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been experimentally demonstrated (J. Li et al., Carbon, 2012, 50, 4628-4632). The source and drain contact heights in vertical CNTFETs could be much higher than in flat CNTFETs if the fabrication process is not optimized. To understand the impact of contact height on transistor performance, we use a semi-classical method to calculate the characteristics of CNTFETs with different contact heights. The results show that the drain current decreases with increasing contact height and saturates at a value governed by the thickness of the oxide. The current reduction caused by the increased contact height becomes more significant when the gate oxide is thicker. The higher the drain voltage, the larger the current reduction. It becomes even worse when the band gap of the carbon nanotube is larger. The current can differ by a factor of more than five between the CNTEFTs with low and high contact heights when the oxide thickness is 50 nm. In addition, the influence of the contact height is limited by the channel length. The contact height plays a minor role when the channel length is less than 100 nm. © 2013 The Royal Society of Chemistry.

  17. 3D velocity field characterization of prosthetic heart valve with two different valve testers by means of stereo-PIV.

    Science.gov (United States)

    D'Avenio, Giuseppe; Grigioni, Mauro; Daniele, Carla; Morbiducci, Umberto; Hamilton, Kathrin

    2015-01-01

    Prosthetic heart valves can be associated to mechanical loading of blood, potentially linked to complications (hemolysis and thrombogenicity) which can be clinically relevant. In order to test such devices in pulsatile mode, pulse duplicators (PDs) have been designed and built according to different concepts. This study was carried out to compare anemometric measurements made on the same prosthetic device, with two widely used PDs. The valve (a 27-mm bileaflet valve) was mounted in the aortic section of the PD. The Sheffield University PD and the RWTH Aachen PD were selected as physical models of the circulation. These two PDs differ mainly in the vertical vs horizontal realization, and in the ventricular section, which in the RWTH PD allows for storage of potential energy in the elastic walls of the ventricle. A glassblown aorta, realized according to the geometric data of the same anatomical district in healthy individuals, was positioned downstream of the valve, obtaining 1:1 geometric similarity conditions. A NaI-glycerol-water solution of suitable kinematic viscosity and, at the same time, the proper refractive index, was selected. The flow field downstream of the valve was measured by means of the stereo-PIV (Particle Image Velocimetry) technique, capable of providing the complete 3D velocity field as well as the entire Reynolds stress tensor. The measurements were carried out at the plane intersecting the valve axis. A three-jet profile was clearly found in the plane crossing the leaflets, with both PDs. The extent of the typical recirculation zone in the Valsalva sinus was much larger in the RWTH PD, on account of the different duration of the swirling motion in the ventricular chamber, caused by the elasticity of the ventricle and its geometry. The comparison of the hemodynamical behaviour of the same bileaflet valve tested in two PDs demonstrated the role of the mock loop in affecting the valve performance.

  18. Exciton in vertically coupled type II quantum dots in threading magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza-Cantillo, J., E-mail: jhofry@gmail.com [Group of Investigation in Condensed Matter Theory, Universidad del Magdalena, Carrera 32 No 22-08, Santa Marta (Colombia); Universidad de la Guajira, Riohacha (Colombia); Escorcia-Salas, G. Elizabeth, E-mail: elizabethescorcia@gmail.com [Group of Investigation in Condensed Matter Theory, Universidad del Magdalena, Carrera 32 No 22-08, Santa Marta (Colombia); Mikhailov, I.D., E-mail: mikhail2811@gmail.com [Universidad Industrial de Santander, A. A. 678, Bucaramanga (Colombia); Sierra-Ortega, J., E-mail: jsierraortega@gmail.com [Group of Investigation in Condensed Matter Theory, Universidad del Magdalena, Carrera 32 No 22-08, Santa Marta (Colombia)

    2014-11-15

    We analyze the energy spectrum of a neutral exciton confined in a semiconductor heterostructure formed by two vertically coupled axially symmetrical type II quantum dots located close to each other. The electron in the structure is mainly located inside dots tunneling between them while the hole generally is placed in the exterior region close to the symmetry axis. Solutions of the Schrödinger equation are obtained by a variational separation of variables in the adiabatic limit. Numerical results are presented for the energies of bonding and anti-bonding lowest-lying of the exciton states and for the density of states for different InP/GaInP quantum dots' morphologies and the magnetic field strength values.

  19. Removing the current-limit of vertical organic field effect transistors

    Science.gov (United States)

    Sheleg, Gil; Greenman, Michael; Lussem, Bjorn; Tessler, Nir

    2017-11-01

    The reported Vertical Organic Field Effect Transistors (VOFETs) show either superior current and switching speeds or well-behaved transistor performance, especially saturation in the output characteristics. Through the study of the relationship between the device architecture or dimensions and the device performance, we find that achieving a saturation regime in the output characteristics requires that the device operates in the injection limited regime. In current structures, the existence of the injection limited regime depends on the source's injection barrier as well as on the buried semiconductor layer thickness. To overcome the injection limit imposed by the necessity of injection barrier, we suggest a new architecture to realize VOFETs. This architecture shows better gate control and is independent of the injection barrier at the source, thus allowing for several A cm-2 for a semiconductor having a mobility value of 0.1 cm2 V-1 s-1.

  20. Numerical investigation of MHD heat transfer in a vertical round tube affected by transverse magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zikanov, Oleg [University of Michigan - Dearborn, MI 48128-1491 (United States); Listratov, Yaroslav [Moscow Power Engineering Institute, 14 Karsnokazarmennaya St., Moscow 111250 (Russian Federation)

    2016-12-15

    Numerical simulations of the flow of a liquid metal in a vertical pipe are performed. The configuration reproduces the test section of the recent experiment . The mean flow is directed downward, a half of the pipe's wall is heated, and a strong horizontal magnetic field perpendicular to the temperature gradient is imposed. The simulations produce results in good agreement with the experiment and lead us to an explanation of the observed phenomenon of anomalous high-amplitude temperature fluctuations. The fluctuations are caused by growth and quasi-periodic breakdown of the pairs of ascending and descending jets related to the elevator-mode thermal convection. Implications for operation of liquid metal blankets with poloidal ducts are discussed.

  1. Direct growth of vertically-oriented graphene for field-effect transistor biosensor.

    Science.gov (United States)

    Mao, Shun; Yu, Kehan; Chang, Jingbo; Steeber, Douglas A; Ocola, Leonidas E; Chen, Junhong

    2013-01-01

    A sensitive and selective field-effect transistor (FET) biosensor is demonstrated using vertically-oriented graphene (VG) sheets labeled with gold nanoparticle (NP)-antibody conjugates. VG sheets are directly grown on the sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method and function as the sensing channel. The protein detection is accomplished through measuring changes in the electrical signal from the FET sensor upon the antibody-antigen binding. The novel biosensor with unique graphene morphology shows high sensitivity (down to ~2 ng/ml or 13 pM) and selectivity towards specific proteins. The PECVD growth of VG presents a one-step and reliable approach to prepare graphene-based electronic biosensors.

  2. Direct Growth of Vertically-oriented Graphene for Field-Effect Transistor Biosensor

    Science.gov (United States)

    Mao, Shun; Yu, Kehan; Chang, Jingbo; Steeber, Douglas A.; Ocola, Leonidas E.; Chen, Junhong

    2013-04-01

    A sensitive and selective field-effect transistor (FET) biosensor is demonstrated using vertically-oriented graphene (VG) sheets labeled with gold nanoparticle (NP)-antibody conjugates. VG sheets are directly grown on the sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method and function as the sensing channel. The protein detection is accomplished through measuring changes in the electrical signal from the FET sensor upon the antibody-antigen binding. The novel biosensor with unique graphene morphology shows high sensitivity (down to ~2 ng/ml or 13 pM) and selectivity towards specific proteins. The PECVD growth of VG presents a one-step and reliable approach to prepare graphene-based electronic biosensors.

  3. Radiative Walter's memory flow along a vertical cone in induced magnetic field with thermophoretic effect

    Science.gov (United States)

    Islam, Md. Manjiul; Haque, Md. Mohidul

    2017-06-01

    A radiative heat and mass transfer study of Walter's memory flow along a vertical cone with thermophoresis is completed in the presence of induced magnetic field. A mathematical model of Walter's memory flow is developed from the basis of studying Magnetohydrodynamics(MHD). Some dimensionless quantities have been used to transform the model to non-dimensional system of equations. The dimensionless unsteady, coupled and non-linear partial differential conservation equations for the boundary layer regime are solved by an efficient, accurate and unconditionally stable finite difference scheme of the Crank-Nicolson type. The features of the flow, heat and mass transfer characteristics within the boundary layer are analyzed by plotting graphs and the physical aspects are discussed in detail. The obtained results show that the impact of flow variables plays an important role in the Walter's memory flow. Last of all, some important findings of the present problem are concluded in this work.

  4. Improvement of vertical organic field-effect transistors by surface modification of metallic source electrodes

    Science.gov (United States)

    Chang, Jui-Fen; Lai, Yi-Chien; Yang, Rui-Hao; Yang, Yaw-Wen; Wang, Chia-Hsin

    2017-11-01

    A proper design of the injection barrier between a source electrode and an active layer is essential to achieve high-performance vertical organic field-effect transistors (VOFETs). Here, we show that a modification of metallic source electrodes with thiol-based self-assembled monolayers (SAMs) is effective in controlling the electrode work function and injection barrier into the active layer, leading to a significantly reduced off-current and undegraded on-current in an optimized VOFET. For the studied C60 VOFETs with Ag electrodes, the on/off ratio improves from <10 to 103-104 when the injection barrier is varied from 0.02 to 0.33 eV by SAM modification.

  5. Application of acoustic tomography to reconstruct the horizontal flow velocity field in a shallow river

    Science.gov (United States)

    Razaz, Mahdi; Kawanisi, Kiyosi; Kaneko, Arata; Nistor, Ioan

    2015-12-01

    A novel acoustic tomographic measurement system capable of resolving sound travel time in extremely shallow rivers is introduced and the results of an extensive field measurements campaign are presented and further discussed. Acoustic pulses were transmitted over a wide frequency band of 20-35 kHz between eight transducers for about a week in a meandering reach of theBāsen River, Hiroshima, Japan. The purpose of the field experiment was validating the concept of acoustic tomography in rivers for visualizing current fields. The particular novelty of the experiment resides in its unusual tomographic features: subbasin scale (100 m × 270 m) and shallowness (0.5-3.0 m) of the physical domain, frequency of the transmitted acoustic signals (central frequency of 30 kHz), and the use of small sampling intervals (105 s). Inverse techniques with no a priori statistical information were used to estimate the depth-average current velocity components from differential travel times. Zeroth-order Tikhonov regularization, in conjunction with L-curve method deployed to stabilize the solution and to determine the weighting factor appearing in the inverse analysis. Concurrent direct environmental measurements were provided in the form of ADCP readings close to the right and left bank. Very good agreement found between along-channel velocities larger than 0.2 m/s obtained from the two techniques. Inverted quantities were, however, underestimated, perhaps due to vicinity of the ADCPs to the banks and strong effect of river geometry on the readings. In general, comparing the visualized currents with direct nodal measurements illustrate the plausibility of the tomographically reconstructed flow structures.

  6. SAR-based Estimation of Glacial Extent and Velocity Fields on Isanotski Volcano, Aleutian Islands, Alaska

    Science.gov (United States)

    Sousa, D.; Lee, A.; Parker, O. P.; Pressler, Y.; Guo, S.; Osmanoglu, B.; Schmidt, C.

    2012-12-01

    Global studies show that Earth's glaciers are losing mass at increasing rates, creating a challenge for communities that rely on them as natural resources. Field observation of glacial environments is limited by cost and inaccessibility. Optical remote sensing is often precluded by cloud cover and seasonal darkness. Synthetic aperture radar (SAR) overcomes these obstacles by using microwave-frequency electromagnetic radiation to provide high resolution information on large spatial scales and in remote, atmospherically obscured environments. SAR is capable of penetrating clouds, operating in darkness, and discriminating between targets with ambiguous spectral signatures. This study evaluated the efficacy of two SAR Earth observation methods on small (Unimak Island, Aleutian Archipelago, USA. The local community on the island, the City of False Pass, relies on glacial melt for drinking water and hydropower. Two methods were used: (1) velocity field estimation based on Repeat Image Feature Tracking (RIFT) and (2) glacial boundary delineation based on interferometric coherence mapping. NASA Uninhabited Aerial Vehicle SAR (UAVSAR) single-polarized power images and JAXA Advanced Land Observing Satellite Phased Array type L-band SAR (ALOS PALSAR) single-look complex images were analyzed over the period 2008-2011. UAVSAR image pairs were coregistered to sub-pixel accuracy and processed with the Coregistration of Optically Sensed Images and Correlation (COSI-Corr) feature tracking module to derive glacial velocity field estimates. Maximum glacier velocities ranged from 28.9 meters/year to 58.3 meters/year. Glacial boundaries were determined from interferometric coherence of ALOS PALSAR data and subsequently refined with masking operations based on terrain slope and segment size. Accuracy was assessed against hand-digitized outlines from high resolution UAVSAR power images, yielding 83.0% producer's accuracy (errors of omission) and 86.1% user's accuracy (errors of

  7. Simultaneous measurement of 3D zooplankton trajectories and surrounding fluid velocity field in complex flows.

    Science.gov (United States)

    Adhikari, Deepak; Gemmell, Brad J; Hallberg, Michael P; Longmire, Ellen K; Buskey, Edward J

    2015-11-01

    We describe an automated, volumetric particle image velocimetry (PIV) and tracking method that measures time-resolved, 3D zooplankton trajectories and surrounding volumetric fluid velocity fields simultaneously and non-intrusively. The method is demonstrated for groups of copepods flowing past a wall-mounted cylinder. We show that copepods execute escape responses when subjected to a strain rate threshold upstream of a cylinder, but the same threshold range elicits no escape responses in the turbulent wake downstream. The method was also used to document the instantaneous slip velocity of zooplankton and the resulting differences in trajectory between zooplankton and non-inertial fluid particles in the unsteady wake flow, showing the method's capability to quantify drift for both passive and motile organisms in turbulent environments. Applications of the method extend to any group of organisms interacting with the surrounding fluid environment, where organism location, larger-scale eddies and smaller-scale fluid deformation rates can all be tracked and analyzed. © 2015. Published by The Company of Biologists Ltd.

  8. Filaments from the galaxy distribution and from the velocity field in the local universe

    Science.gov (United States)

    Libeskind, Noam I.; Tempel, Elmo; Hoffman, Yehuda; Tully, R. Brent; Courtois, Hélène

    2015-10-01

    The cosmic web that characterizes the large-scale structure of the Universe can be quantified by a variety of methods. For example, large redshift surveys can be used in combination with point process algorithms to extract long curvilinear filaments in the galaxy distribution. Alternatively, given a full 3D reconstruction of the velocity field, kinematic techniques can be used to decompose the web into voids, sheets, filaments and knots. In this Letter, we look at how two such algorithms - the Bisous model and the velocity shear web - compare with each other in the local Universe (within 100 Mpc), finding good agreement. This is both remarkable and comforting, given that the two methods are radically different in ideology and applied to completely independent and different data sets. Unsurprisingly, the methods are in better agreement when applied to unbiased and complete data sets, like cosmological simulations, than when applied to observational samples. We conclude that more observational data is needed to improve on these methods, but that both methods are most likely properly tracing the underlying distribution of matter in the Universe.

  9. Comparison of pressure reconstruction approaches based on measured and simulated velocity fields

    Directory of Open Access Journals (Sweden)

    Manthey Samuel

    2017-09-01

    Full Text Available The pressure drop over a pathological vessel section can be used as an important diagnostic indicator. However, it cannot be measured non-invasively. Multiple approaches for pressure reconstruction based on velocity information are available. Regarding in-vivo data introducing uncertainty these approaches may not be robust and therefore validation is required. Within this study, three independent methods to calculate pressure losses from velocity fields were implemented and compared: A three dimensional and a one dimensional method based on the Pressure Poisson Equation (PPE as well as an approach based on the work-energy equation for incompressible fluids (WERP. In order to evaluate the different approaches, phantoms from pure Computational Fluid Dynamics (CFD simulations and in-vivo PC-MRI measurements were used. The comparison of all three methods reveals a good agreement with respect to the CFD pressure solutions for simple geometries. However, for more complex geometries all approaches lose accuracy. Hence, this study demonstrates the need for a careful selection of an appropriate pressure reconstruction algorithm.

  10. Frequency, delay and velocity analysis for intrinsic channel region of carbon nanotube field effect transistors

    Directory of Open Access Journals (Sweden)

    P. Geetha

    2014-03-01

    Full Text Available Gate wrap around field effect transistor is preferred for its good channel control. To study the high frequency behaviour of the device, parameters like cut-off frequency, transit or delay time, velocity are calculated and plotted. Double-walled and array of channels are considered in this work for enhanced output and impedance matching of the device with the measuring equipment terminal respectively. The perfomance of double-walledcarbon nanotube is compared with single-walled carbon nanotube and found that the device with double-wall shows appreciable improvement in its characteristics. Analysis of these parameters are done with various values of source/drain length, gate length, tube diameters and channel densities. The maximum cut-off frequency is found to be 72.3 THz with corresponding velocity as 5x106 m/s for channel density as 3 and gate length as 11nm. The number of channel is varied from 3 to 21 and found that the perfromance of the device containing double-walled carbon nano tube is better for channel number lesser than or equal to 12. The proposed modelling can be used for designing devices to handle high speed applications of future generation.

  11. Field-programmable gate array-controlled sweep velocity-locked laser pulse generator

    Science.gov (United States)

    Chen, Zhen; Hefferman, Gerald; Wei, Tao

    2017-05-01

    A field-programmable gate array (FPGA)-controlled sweep velocity-locked laser pulse generator (SV-LLPG) design based on an all-digital phase-locked loop (ADPLL) is proposed. A distributed feedback laser with modulated injection current was used as a swept-frequency laser source. An open-loop predistortion modulation waveform was calibrated using a feedback iteration method to initially improve frequency sweep linearity. An ADPLL control system was then implemented using an FPGA to lock the output of a Mach-Zehnder interferometer that was directly proportional to laser sweep velocity to an on-board system clock. Using this system, linearly chirped laser pulses with a sweep bandwidth of 111.16 GHz were demonstrated. Further testing evaluating the sensing utility of the system was conducted. In this test, the SV-LLPG served as the swept laser source of an optical frequency-domain reflectometry system used to interrogate a subterahertz range fiber structure (sub-THz-FS) array. A static strain test was then conducted and linear sensor results were observed.

  12. A new method to disentangle the rotational velocities of stars: Application to main-sequence field Stars

    Science.gov (United States)

    Curé, M.; Rial, D. F.; Cassetti, J.; Christen, A.

    2014-10-01

    The projected rotational velocity v sin i is a fundamental observable quantity. In order to obtain the rotational velocity distribution of a sample of v sin i, Chandrasekhar & Münch (1950) developed a formalism to obtain this distribution under the assumption that rotational axes are uniformly distributed, but this method is not usually applied due to an intrinsic numerical problem associated to the derivative of an Abel's integral. An alternative iterative method was developed by Lucy (1974) to disentangle the distribution function of this kind of inverse problem, but this method has no convergence criteria. Here we present a new method to disentangle the distribution of rotational velocities, based on Chandrasekhar & Münch (1950) formalism. We obtain the cumulative distribution function (CDF) of the rotational velocities from projected velocities (v sin i) under the standard assumption of uniform distributed rotational axes. Through simulations the method is tested using a) theoretical Maxwellian distribution functions for the rotational velocity distribution and b) with a sample of about 12.500 main-sequence field stars. Our main results are: The method is robust and in just one step gives the cumulative distribution function of rotational velocities. When applied to theoretical distributions it recovers the CDF with very high confidence. When applied to real data, we recover the results from Carvalho et al. (2009) proving that the velocity distribution function of main-sequence field stars is non-Maxwellian and are better described by Tsallis or Kaniadakis distribution functions.

  13. Propagation of a squeezed optical field in a medium with superluminal group velocity.

    Science.gov (United States)

    Romanov, Gleb; Horrom, Travis; Novikova, Irina; Mikhailov, Eugeniy E

    2014-02-15

    We investigated the propagation of a squeezed optical field, generated via the polarization self-rotation effect, with a sinusoidally modulated degree of squeezing through an atomic medium with anomalous dispersion. We observed the advancement of the signal propagating through a resonant Rb vapor compared to the reference signal, propagating in air. The measured advancement time grew linearly with atomic density, reaching a maximum of 11±1  μs, which corresponded to a negative group velocity of v(g)≈-7,000  m/s. We also confirmed that the increasing advancement was accompanied by a reduction of output squeezing levels due to optical losses, in good agreement with theoretical predictions.

  14. Extraction of 3D velocity and porosity fields from GeoPET data sets

    Energy Technology Data Exchange (ETDEWEB)

    Lippmann-Pipke, Johanna; Kulenkampff, Johannes [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Reactive Transport; Eichelbaum, S. [Nemtics Visualization, Leipzig (Germany)

    2017-06-01

    Geoscientific process monitoring with positron emission tomography (GeoPET) is proven to be applicable for quantitative tomographic transport process monitoring in natural geological materials. We benchmarked GeoPET by inversely fitting a numerical finite element model to a diffusive transport experiment in Opalinus clay. The obtained effective diffusion coefficients, D{sub e}, parallel and D{sub e}, perpendicular to, are well in line with data from literature. But more complex, heterogeneous migration, and flow patterns cannot be similarly evaluated by inverse fitting using optimization tools. Alternatively, we started developing an algorithm that allows the quantitative extraction of velocity and porosity fields, v{sub i=x,y,z} (x,y,z) and n(x,y,z) from GeoPET time series, c{sub PET}(x,y,z,t). They may serve as constituent data sets for reactive transport modelling.

  15. Optimization of Transverse Oscillating Fields for Vector Velocity Estimation with Convex Arrays

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2013-01-01

    from 90 to 45 degrees in steps of 15 degrees. The optimization routine changes the lateral oscillation period lx to yield the best possible estimates based on the energy ratio between positive and negative spatial frequencies in the ultrasound field. The basic equation for lx gives 1.14 mm at 40 mm......, and 1.51 mm from the simulated point spread function. This results in a bias of 35% as lx directly scales the estimated velocities. Optimizing the focusing yields a lx of 1.61 mm. The energy ratio is reduced from -12.8 dB to -20.1 dB and the spectral bandwidth from 115.1 m􀀀1 to 96.5 m􀀀...

  16. Technique for velocity vector field dynamics measurement on the basis of smoke visualization of flow

    Science.gov (United States)

    Mikheev, N. I.; Dushin, N. S.; Saushin, I. I.

    2017-09-01

    The main difference between Smoke Image Velocimetry (SIV) technique and traditional PIV is that the smoke with continuous intensity in the image is seeded into the flow instead of separate particles. Owing to better smoke reflectivity, relatively primitive equipment is enough to measure the dynamics of velocity vector fields with the frequency of 25 kHz and higher. The image processing algorithm is adapted to high tracer concentration and relatively large displacement of smoke patches between two consecutive frames. The results of SIV testing are presented, including the estimations of the most measurement noise sensitive characteristics of turbulence calculated from spatial derivatives of fluctuations of small-scale turbulence. The measurement results have been shown to agree well with the data obtained by other methods. Application of SIV technique opens new possibilities in the research of flow pattern and turbulence in unsteady and fast processes.

  17. Experimental Investigation of Dynamic Wetting Models: Interface Shapes and Velocity Fields Near the Moving Contact Line.

    Science.gov (United States)

    Chen, Qun

    Dynamic wetting is the displacement of one fluid by another immiscible fluid across a solid surface as it spreads. Such processes control many natural phenomena and technological applications. The spreading dynamics of macroscopic fluid bodies are dictated by the hydrodynamics in a microscopic region near the moving contact line. Analytical models have been developed to describe the interface shape and velocity field near the contact line. Using videomicroscopy, particle image velocimetry, and digital image analysis, we make simultaneous measurements of the fluid/fluid interface shape and fluid flow field within the first few hundred microns near a moving contact line. Our experiments establish the validity and limitations of these analytical models. This work extensively tests assumptions embedded in the models and sets up bounds on the parameter space in which the models are valid. The models successfully describe the hydrodynamics near the contact line up to a capillary number ~0.10 but break down at higher capillary number. We determine the origins of this breakdown. We also carefully probe those regions near the contact line where the interface shape and flow field are independent of the macroscopic geometry. Our experimental technique provides a means of obtaining such material-dependent,, geometry-independent information about the system. Such information serves as boundary conditions transferable among different macroscopic geometries. It is an essential ingredient for numerical calculations of the spreading dynamics. The work reported in this thesis sets the stage for predictive modeling of dynamic wetting.

  18. "Ghost transients" in the southern California GPS velocity field: An investigation using finite-fault earthquake cycle models

    Science.gov (United States)

    Hearn, E. H.; Pollitz, F. F.; Thatcher, W. R.; Onishi, C. T.

    2011-12-01

    Elastic block models are generally used to infer slip rates on fault segments in tectonically complex areas, such as southern California (e.g. McCaffrey, 2005; Meade et al., 2005). These models implicitly assume steady-state deformation. However, owing to viscoelastic effects of past large earthquakes, deformation rates and patterns around major faults are expected to vary with time. Where viscoelasticity has been incorporated into block models, differences in inferred slip rates have resulted (Johnson et al., 2007). Here, we investigate the extent to which viscoelastic velocity perturbations (or "ghost transients") from individual earthquakes can affect elastic block model-based inferences of fault slip rates from GPS velocity fields. We focus on the southern California GPS velocity field, exploring the effects of known, large earthquakes for end-member rheological structures. For selected faults, an idealized earthquake history is constructed, consisting of a sequence of periodic, identical repeating slip events. For each earthquake, we first calculate average velocities and time-dependent perturbations relative to this average at all GPS sites in the neighborhood of an earthquake. (We deal with perturbations because to recover the velocities, we would have to compute and sum cycle-average velocities and perturbations for all fault segments in the region.) Next, we invert two GPS velocity fields for slip rates using a block modeling approach: one field that has been corrected for the perturbation, and one which has not, and we compare the resulting slip rates. For now, the viscoelastic models are simple (layers with linear rheologies), and locking depth is fixed in the block models. We find that if asthenosphere viscosities are low enough (3 x 10**18 Pa-s) the current GPS velocity field is significantly perturbed by the 1857 M 7.9 San Andreas Fault (SAF) earthquake sequence; that is, current strain rates around the SAF are lower than their average values

  19. Reliability of a field-based drop vertical jump screening test for ACL injury risk assessment.

    Science.gov (United States)

    Redler, Lauren H; Watling, Jonathan P; Dennis, Elizabeth R; Swart, Eric; Ahmad, Christopher S

    2016-01-01

    There is an epidemic of anterior cruciate ligament (ACL) injuries in youth athletes. Poor neuromuscular control is an easily modifiable risk factor for ACL injury, and can be screened for by observing dynamic knee valgus on landing in a drop vertical jump test. This study aims to validate a simple, clinically useful population-based screening test to identify at-risk athletes prior to participation in organized sports. We hypothesized that both physicians and allied health professionals would be accurate in subjectively assessing injury risk in real-time field and office conditions without motion analysis data and would be in agreement with each other. We evaluated the inter-rater reliability of risk assessment by various observer groups, including physicians and allied health professionals, commonly involved in the care of youth athletes. Fifteen athletes age 11-17 were filmed performing a drop vertical jump test. These videos were viewed by 242 observers including orthopaedic surgeons, orthopaedic residents/fellows, coaches, athletic trainers (ATCs), and physical therapists (PTs), with the observer asked to subjectively estimate the risk level of each jumper. Objective injury risk was calculated using normalized knee separation distance (measured using Dartfish, Alpharetta, GA), based on previously published studies. Risk assessments by observers were compared to each other to determine inter-rater reliability, and to the objectively calculated risk level to determine sensitivity and specificity. Seventy one observers repeated the test at a minimum of 6 weeks later to determine intra-rater reliability. Between groups, the inter-rater reliability was high, κ = 0.92 (95% CI 0.829-0.969, p vertical jump screening test to identify athletes at risk for ACL injury. Our study shows good inter- and intra-rater reliability and high sensitivity and suggests that screening can be performed without significant training by physicians as well as allied health professionals

  20. Anomalous field-induced effects in the sound velocity in lead magnesium niobate probed by micro-Brillouin scattering

    OpenAIRE

    Lushnikov, S. G.; Ko, Jae-Hyeon; Kojima, Seiji

    2004-01-01

    Field-induced changes in Brillouin scattering spectra of the PbMg1/3Nb2/3O3 relaxor ferroelectric have been examined in the vicinity of a diffuse phase transition under a dc electric field oriented along the [111] direction. It has been established that the transition into an electric-field-induced ferroelectric phase is accompanied by a step-like anomaly in the sound velocity of the quasilongitudinal acoustic phonon (QLA) propagating along the [110] direction. The changes in QLA phonon veloc...

  1. Remote Sensing Data in Wind Velocity Field Modelling: a Case Study from the Sudetes (SW Poland)

    Science.gov (United States)

    Jancewicz, Kacper

    2014-06-01

    The phenomena of wind-field deformation above complex (mountainous) terrain is a popular subject of research related to numerical modelling using GIS techniques. This type of modelling requires, as input data, information on terrain roughness and a digital terrain/elevation model. This information may be provided by remote sensing data. Consequently, its accuracy and spatial resolution may affect the results of modelling. This paper represents an attempt to conduct wind-field modelling in the area of the Śnieżnik Massif (Eastern Sudetes). The modelling process was conducted in WindStation 2.0.10 software (using the computable fluid dynamics solver Canyon). Two different elevation models were used: the Global Land Survey Digital Elevation Model (GLS DEM) and Digital Terrain Elevation Data (DTED) Level 2. The terrain roughness raster was generated on the basis of Corine Land Cover 2006 (CLC 2006) data. The output data were post-processed in ArcInfo 9.3.1 software to achieve a high-quality cartographic presentation. Experimental modelling was conducted for situations from 26 November 2011, 25 May 2012, and 26 May 2012, based on a limited number of field measurements and using parameters of the atmosphere boundary layer derived from the aerological surveys provided by the closest meteorological stations. The model was run in a 100-m and 250-m spatial resolution. In order to verify the model's performance, leave-one-out cross-validation was used. The calculated indices allowed for a comparison with results of former studies pertaining to WindStation's performance. The experiment demonstrated very subtle differences between results in using DTED or GLS DEM elevation data. Additionally, CLC 2006 roughness data provided more noticeable improvements in the model's performance, but only in the resolution corresponding to the original roughness data. The best input data configuration resulted in the following mean values of error measure: root mean squared error of velocity

  2. Evolution of Mass and Velocity Field in the Cosmic Web: Comparison between Baryonic and Dark Matter

    Science.gov (United States)

    Zhu, Weishan; Feng, Long-Long

    2017-03-01

    We investigate the evolution of the cosmic web since z = 5 in grid-based cosmological hydrodynamical simulations, focusing on the mass and velocity fields of both baryonic and cold dark matter. The tidal tensor of density is used as the main method for web identification, with λ th = 0.2-1.2. The evolution trends in baryonic and dark matter are similar, although moderate differences are observed. Sheets appear early, and their large-scale pattern may have been set up by z = 3. In terms of mass, filaments supersede sheets as the primary collapsing structures from z ˜ 2-3. Tenuous filaments assembled with each other to form prominent ones at z dark matter field, and is even moderately stronger between {\\boldsymbol{ω }} and {{\\boldsymbol{e}}}1, and ω and {{\\boldsymbol{e}}}3. Compared with dark matter, there is slightly less baryonic matter found residing in filaments and clusters, and its vorticity developed more significantly below 2-3 Mpc. These differences may be underestimated because of the limited resolution and lack of star formation in our simulation. The impact of the change of dominant structures in overdense regions at z ˜ 2-3 on galaxy formation and evolution is shortly discussed.

  3. Semi-automatic measurement of visual verticality perception in humans reveals a new category of visual field dependency

    Directory of Open Access Journals (Sweden)

    C.R. Kaleff

    2011-08-01

    Full Text Available Previous assessment of verticality by means of rod and rod and frame tests indicated that human subjects can be more (field dependent or less (field independent influenced by a frame placed around a tilted rod. In the present study we propose a new approach to these tests. The judgment of visual verticality (rod test was evaluated in 50 young subjects (28 males, ranging in age from 20 to 27 years by randomly projecting a luminous rod tilted between -18 and +18° (negative values indicating left tilts onto a tangent screen. In the rod and frame test the rod was displayed within a luminous fixed frame tilted at +18 or -18°. Subjects were instructed to verbally indicate the rod’s inclination direction (forced choice. Visual dependency was estimated by means of a Visual Index calculated from rod and rod and frame test values. Based on this index, volunteers were classified as field dependent, intermediate and field independent. A fourth category was created within the field-independent subjects for whom the amount of correct guesses in the rod and frame test exceeded that of the rod test, thus indicating improved performance when a surrounding frame was present. In conclusion, the combined use of subjective visual vertical and the rod and frame test provides a specific and reliable form of evaluation of verticality in healthy subjects and might be of use to probe changes in brain function after central or peripheral lesions.

  4. Simultaneous volume-velocity measurements in the near field of atomizing sprays

    Science.gov (United States)

    Pham, Phuong X.; Kourmatzis, Agisilaos; Masri, Assaad R.

    2017-11-01

    Direct visualization of atomizing sprays using backlight imaging is commonly used to obtain both qualitative and quantitative information on spray morphology. Recently, the standard backlight technique was extended to ‘dual-angle’ imaging by the authors (Kourmatzis et al 2017 Meas. Sci. Technol. 28 035302), to enable quantification of the volume of arbitrarily shaped fragments to accuracies of the order of 10% . In this contribution, dual-angle particle-tracking velocimetry (PTV) has been developed, hence extending our capability to measure volume, velocity, and flow rate of atomizing fragments simultaneously, regardless of their shapes. The experimental layout consists of two time-shifted lasers, where each beam is split in two, two long-distance microscope lenses and two cameras oriented 90 degrees towards each other, operating in particle image velocimetry mode. The accuracy of the joint volume-velocity measurements has been carefully assessed using mono-dispersed droplets and microspheres of known size. The technique has also been examined for different air-assisted sprays covering regimes from Rayleigh to multi-mode breakup. By introducing terminologies such as ‘fragment residence time’ and ‘fragment-specific volume flow rate’, the overall volume flow rate of both the mono-dispersed drops as well as low Weber number air-assisted sprays may be recovered. This PTV method is a powerful diagnostic tool to simultaneously track and size arbitrarily shaped liquid fragments. It also provides a viable technique to measure liquid mass flux in the near field of sprays.

  5. A New Velocity Field from a Dense GPS Array in the Southernmost Longitudinal Valley, Southeastern Taiwan

    Directory of Open Access Journals (Sweden)

    Horng-Yue Chen

    2013-01-01

    Full Text Available In the southernmost Longitudinal Valley (LV, Taiwan, we analyzed a dense GPS array composed of 10 continuous stations and 86 campaign-mode stations. By removing the effects of the four major earthquakes (one regional and three local occurred during the 1992 - 2010 observation period, we derived a new horizontal velocity field in this area, which then allows better locating the surface traces of the major active faults, including the Longitudinal Valley Fault (LVF system and the Central Range Fault, and characterizing the slip behaviors along the faults. Note that LVF reveals two sub-parallel strands in the study area: the Luyeh Fault to the west and the Lichi Fault to the east. Based on the results of strain analyses, including dilatation and shear strain, and projected vectors of station velocities across the major faults, we came to the following geological interpretations. During the inter-seismic periods, the surface deformation of the southernmost LV is mainly accommodated by the faulting on the two branches of the LVF; there is very little surface deformation on the Central Range Fault. The Luyeh River appears to act as a boundary to divide the LVF to behave differently to its northern and southern sides. The Lichi Fault reveals a change of slip kinematics from an oblique shearing/thrusting in the north to a nearly pure shearing with minor extension to the south. Regarding the slip behavior of the Luyeh Fault, it exhibits a creeping behavior in the north and a partially near-surface-locked faulting behavior in the south. We interpret that the two strands of the LVF merge together in the northern Taitung alluvial plain and turns to E-W trend toward the offshore area.

  6. A 5-min running field test as a measurement of maximal aerobic velocity.

    Science.gov (United States)

    Berthon, P; Fellmann, N; Bedu, M; Beaune, B; Dabonneville, M; Coudert, J; Chamoux, A

    1997-01-01

    Based on a theoretical approach from world record running data, we have previously calculated that the most suitable duration for measuring maximal aerobic velocity (Vamax) by a field test was 5 min (Vamax(5)). The aim of this study was, therefore, to check this hypothesis on 48 men of various levels of physical fitness by comparing (Vmax(5)) with (Vamax) determined at the last step of a progressive treadmill exercise test when the subject felt exhausted (Vamax(t)) and during a test on a running track, behind a cyclist (following an established protocol) (Vamax(c)). For each test, (VO2max) was also measured by a direct method on a treadmill (VO2max(1)) and calculated by an equation for field tests (VO2max(5) and VO2max(c)). The Vamax(5) [17.1 (SD 2.2) km.h-1] and (Vamax(c)) [(18.2 (SD 2.4) km.h-1] were significantly higher than (Vamax(t)) [16.9 (SD 2.6) km.h-1; P < 0.001]. The (Vamax(t)) was strongly correlated with (Vamax(5)) (r = 0.94) and (Vamax(c)) (r = 0.95) (P < 0.001). The best identity and correlation between (Vamax(5)) and track performances were found in the runners (n = 9) with experience over a distance of 3,000 m. The VO2max(5) and (VO2max(c)) were higher than VO2max(t) (+ 5.0% and + 13.7%, respectively; P < 0.001) and VO2max(t) was highly correlated with Vamax(5) (r = 0.90; P < 0.001). These results suggest that the 5-min field test, easy to apply, provided precise information on Vamax and to a lesser degree on VO2max.

  7. Relativistic derivations of the electric and magnetic fields generated by an electric point charge moving with constant velocity

    OpenAIRE

    Rothenstein, Bernhard; Popescu, Stefan; Spix, George J.

    2006-01-01

    We propose a simple relativistic derivation of the electric and the magnetic fields generated by an electric point charge moving with constant velocity. Our approach is based on the radar detection of the point space coordinates where the fields are measured. The same equations were previously derived in a relatively complicated way2 based exclusively on general electromagnetic field equations and without making use of retarded potentials or relativistic equations

  8. VTP as an Active Layer in a Vertical Organic Field Effect Transistor

    Science.gov (United States)

    Roslan, Nur Adilah; Abdullah, Shahino Mah; Halizan, Muhammad Zharfan Mohd; Bawazeer, Tahani M.; Alsenany, Nourah; Alsoufi, Mohammad S.; Majid, Wan Haliza Abdul; Supangat, Azzuliani

    2017-12-01

    In this letter, a p-type organic material from metal phthalocyanine (MPc) derivative, vanadyl 3,10,17,24-tetra-tert-butyl-1,8,15,22-tetrakis (dimethylamino)-29H,31H-phthalocyanine (VTP) has been utilized for fabrication of an organic electronic device. Prior to the fabrication of a vertical organic field effect transistor (VOFET), fundamental work in investigating the energy level of VTP has been done through determination of oxidation and reduction potentials. Energy levels of VTP were calculated based on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of cyclic voltammetry (CV) and UV-vis analyses. Subsequently, the soluble VTP was employed as an active layer in VOFET with different thicknesses of 90.4 nm, 66.4 nm, and 52.1 nm. It is found that a device with 66.4 nm VTP's thickness showed the optimum performance, by giving the maximum current density and lowest threshold voltage of around 37 mA/cm2 and 7.1 V, respectively. The effects of the channel thickness on the semi-transparent VOFET devices are explained in this work.

  9. Unique Characteristics of Vertical Carbon Nanotube Field-effect Transistors on Silicon

    KAUST Repository

    Li, Jingqi

    2014-07-01

    A vertical carbon nanotube field-effect transistor (CNTFET) based on silicon (Si) substrate has been proposed and simulated using a semi-classical theory. A single-walled carbon nanotube (SWNT) and an n-type Si nanowire in series construct the channel of the transistor. The CNTFET presents ambipolar characteristics at positive drain voltage (Vd) and n-type characteristics at negative Vd. The current is significantly influenced by the doping level of n-Si and the SWNT band gap. The n-branch current of the ambipolar characteristics increases with increasing doping level of the n-Si while the p-branch current decreases. The SWNT band gap has the same influence on the p-branch current at a positive Vd and n-type characteristics at negative Vd. The lower the SWNT band gap, the higher the current. However, it has no impact on the n-branch current in the ambipolar characteristics. Thick oxide is found to significantly degrade the current and the subthreshold slope of the CNTFETs.

  10. Studies In Field Theories: Mhv Vertices, Twistor Space, Recursion Relations And Chiral Rings

    CERN Document Server

    Svrcek, P

    2005-01-01

    In this thesis we study different aspects of four dimensional field theories. In the first chapter we give introduction and overview of the thesis. In the second chapter we review the connection between perturbative Yang-Mills and twistor string theory. Inspired by this, we propose a new way of constructing Yang-Mills scattering amplitudes from Feynman graphs in which the vertices are off-shell continuations of the tree level MHV amplitudes. The MHV diagrams lead to simple formulas for tree-level amplitudes. We then give a heuristic derivation of the diagrams from twistor string theory. In the third chapter, we explore the twistor structure of scattering amplitudes in theories for which a twistor string theory analogous to the one for N = 4 gauge theory has not yet been proposed. We study the differential equations of one-loop amplitudes of gluons in gauge theories with reduced supersymmetry and of tree level and one-loop amplitudes of gravitons in general relativity and supergravity. We find that the scat...

  11. Kinematic modeling of Neotectonic velocity field of the Persia-Tibet-Burma Orogen

    Science.gov (United States)

    Liu, Z.; Bird, P.

    2003-12-01

    New kinematic finite-element program NeoKinema has been applied to compute the long-term-average velocity field and fault slip rates in the Persia-Tibet-Burma orogen using the Maximum-likelihood criterion. The orogen extends from east Turkey on the west, to Burma and Laos on the south, to east and southeast China on the east, and to Mongolia on the north. We use three data sets in our modeling: 1497 GPS benchmark solutions compiled from published sources, 366 geologic slip rates with standard deviations, 876 most compressive horizontal principal stress directions from the World Stress Map 2003 [Mueller et al., 2003]. Faults and potentially active faults are included. But faults of less constrained slip rates, e.g., faults in Iran, are assigned with large uncertainty. An iterative procedure is used to correct for transient fault locking effects on geodetic data. We use an updated plate model PB2002 to approximate the velocity boundary conditions from surrounding rigid plates (Anatolia, Arabia, India, Burma, Sunda, Yangtze, Amur) and the rigid part of the Eurasia plate in a Eurasia-fixed reference frame [Bird, 2003]. We also test various Sunda-Eurasia Euler poles and their effects on our modeling results. The F-E grid has 1564 nodes and 1964 triangular elements. So far 26 models have been computed with various background strain rates and weighting of GPS data. Initial results show a good correspondence between predicted strain rate and Harvard CMT earthquake catalogue with m>5.5. The preferred fault slip rates in central and southeast Asia are generally less than the geologic estimates but within +/-2σ error bounds. The strain rate field and optimal fault slip rate estimates suggest that crustal deformation in the Persia-Tibet-Burma orogen is a mixture of distributed and quasi-rigid block deformation. A few such blocks are central Iran and southern Caspian basin, Tarim basin and Gobi platform, Qaidam basin, Ordos block and north of Tienshan in central Asia.

  12. Velocity and Vorticity Fields of a Turbulent Plume under different experimental conditions

    Science.gov (United States)

    Matulka, A. M.; Gonzalez-Nieto, P. L.; Redondo, J. M.; Tarquis, A. M.

    2012-04-01

    The geophysical and practical importance and the applications of turbulent plumes as generators of strong dispersion processes are clearly recognized. In geophysics and astrophysics, it is usual to model as a jet or plume the generation mechanism of turbulent mixing as a part of a dispersion process [1-3]. An interesting geophysical problem is the study of volcanic plumes [2], which are columns of hot volcanic ash and gas emitted into the atmosphere during an explosive volcanic eruption. Another interesting like-plume phenomenon can be observed where a stream, usually a river, empties into a lake, sea or ocean, generating a river plume [3,4]. Turbulent plumes are fluid motions whose primary source of kinetic energy and momentum flux is due to body forces that arise from density inhomogeneities. The plume boundary acts as an interface across which ambient fluid is entrained, and the plume boundary moves at the velocity of the plume fluid. The difference between the plume-fluid radial velocity and the total fluid velocity quantifies in a natural way the purely horizontal entrainment flux of ambient fluid into the plume across the phase boundary at the plume edge [5,6]. We show some results of research on a single turbulent plume as well as on the structure of the interaction between different plumes and jets, We measure and compare velocity and vorticity fields occurring in different experimental configurations (Parametrized by the Atwood number and the initial potential energy as well as the Plume-Jet length scale). This work is based on experiments that have been performed in GFD laboratories (IPD and UPC) using visualizations methods (LIF,PIV) and advanced multiscaling techniques. We calculate velocity and vorticity PDFs and the evolution of the structure of stratified decaying, with DigFlow and Imacalc programs (Matulka 2010)[7], where video sequence processing provides a range of global and local descriptor features designed specifically for analysing fluid

  13. Predicting present-day rates of glacial isostatic adjustment using a smoothed GPS velocity field for the reconciliation of NAD83 reference frames in Canada

    Science.gov (United States)

    Craymer, M. R.; Henton, J. A.; Piraszewski, M.

    2008-12-01

    Glacial isostatic adjustment following the last glacial period is the dominant source of crustal deformation in Canada east of the Rocky Mountains. The present-day vertical component of motion associated with this process may exceed 1 cm/y and is being directly measured with the Global Positioning System (GPS). A consequence of this steady deformation is that high accuracy coordinates at one epoch may not be compatible with those at another epoch. For example, modern precise point positioning (PPP) methods provide coordinates at the epoch of observation while NAD83, the officially adopted reference frame in Canada and the U.S., is expressed at some past reference epoch. The PPP positions are therefore incompatible with coordinates in such a realization of the reference frame and need to be propagated back to the frame's reference epoch. Moreover, the realizations of NAD83 adopted by the provincial geodetic agencies in Canada are referenced to different coordinate epochs; either 1997.0 or 2002.0. Proper comparison of coordinates between provinces therefore requires propagating them from one reference epoch to another. In an effort to reconcile PPP results and different realizations of NAD83, we empirically represent crustal deformation throughout Canada using a velocity field based solely on high accuracy continuous and episodic GPS observations. The continuous observations from 2001 to 2007 were obtained from nearly 100 permanent GPS stations, predominately operated by Natural Resources Canada (NRCan) and provincial geodetic agencies. Many of these sites are part of the International GNSS Service (IGS) global network. Episodic observations from 1994 to 2006 were obtained from repeated occupations of the Canadian Base Network (CBN), which consists of approximately 160 stable pillar-type monuments across the entire country. The CBN enables a much denser spatial sampling of crustal motions although coverage in the far north is still rather sparse. NRCan solutions of

  14. Gate Tunable Transport in Graphene/MoS2/(Cr/Au Vertical Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Ghazanfar Nazir

    2017-12-01

    Full Text Available Two-dimensional materials based vertical field-effect transistors have been widely studied due to their useful applications in industry. In the present study, we fabricate graphene/MoS2/(Cr/Au vertical transistor based on the mechanical exfoliation and dry transfer method. Since the bottom electrode was made of monolayer graphene (Gr, the electrical transport in our Gr/MoS2/(Cr/Au vertical transistors can be significantly modified by using back-gate voltage. Schottky barrier height at the interface between Gr and MoS2 can be modified by back-gate voltage and the current bias. Vertical resistance (Rvert of a Gr/MoS2/(Cr/Au transistor is compared with planar resistance (Rplanar of a conventional lateral MoS2 field-effect transistor. We have also studied electrical properties for various thicknesses of MoS2 channels in both vertical and lateral transistors. As the thickness of MoS2 increases, Rvert increases, but Rplanar decreases. The increase of Rvert in the thicker MoS2 film is attributed to the interlayer resistance in the vertical direction. However, Rplanar shows a lower value for a thicker MoS2 film because of an excess of charge carriers available in upper layers connected directly to source/drain contacts that limits the conduction through layers closed to source/drain electrodes. Hence, interlayer resistance associated with these layers contributes to planer resistance in contrast to vertical devices in which all layers contribute interlayer resistance.

  15. Large-scale vertical velocity, diabatic heating and drying profiles associated with seasonal and diurnal variations of convective systems observed in the GoAmazon2014/5 experiment

    Directory of Open Access Journals (Sweden)

    S. Tang

    2016-11-01

    Full Text Available This study describes the characteristics of large-scale vertical velocity, apparent heating source (Q1 and apparent moisture sink (Q2 profiles associated with seasonal and diurnal variations of convective systems observed during the two intensive operational periods (IOPs that were conducted from 15 February to 26 March 2014 (wet season and from 1 September to 10 October 2014 (dry season near Manaus, Brazil, during the Green Ocean Amazon (GoAmazon2014/5 experiment. The derived large-scale fields have large diurnal variations according to convective activity in the GoAmazon region and the morning profiles show distinct differences between the dry and wet seasons. In the wet season, propagating convective systems originating far from the GoAmazon region are often seen in the early morning, while in the dry season they are rarely observed. Afternoon convective systems due to solar heating are frequently seen in both seasons. Accordingly, in the morning, there is strong upward motion and associated heating and drying throughout the entire troposphere in the wet season, which is limited to lower levels in the dry season. In the afternoon, both seasons exhibit weak heating and strong moistening in the boundary layer related to the vertical convergence of eddy fluxes. A set of case studies of three typical types of convective systems occurring in Amazonia – i.e., locally occurring systems, coastal-occurring systems and basin-occurring systems – is also conducted to investigate the variability of the large-scale environment with different types of convective systems.

  16. Large-scale vertical velocity, diabatic heating and drying profiles associated with seasonal and diurnal variations of convective systems observed in the GoAmazon2014/5 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Shuaiqi; Xie, Shaocheng; Zhang, Yunyan; Zhang, Minghua; Schumacher, Courtney; Upton, Hannah; Jensen, Michael P.; Johnson, Karen L.; Wang, Meng; Ahlgrimm, Maike; Feng, Zhe; Minnis, Patrick; Thieman, Mandana

    2016-01-01

    This study describes the characteristics of large-scale vertical velocity, apparent heating source (Q1) and apparent moisture sink (Q2) profiles associated with seasonal and diurnal variations of convective systems observed during the two intensive operational periods (IOPs) that were conducted from 15 February to 26 March 2014 (wet season) and from 1 September to 10 October 2014 (dry season) near Manaus, Brazil, during the Green Ocean Amazon (GoAmazon2014/5) experiment. The derived large-scale fields have large diurnal variations according to convective activity in the GoAmazon region and the morning profiles show distinct differences between the dry and wet seasons. In the wet season, propagating convective systems originating far from the GoAmazon region are often seen in the early morning, while in the dry season they are rarely observed. Afternoon convective systems due to solar heating are frequently seen in both seasons. Accordingly, in the morning, there is strong upward motion and associated heating and drying throughout the entire troposphere in the wet season, which is limited to lower levels in the dry season. In the afternoon, both seasons exhibit weak heating and strong moistening in the boundary layer related to the vertical convergence of eddy fluxes. A set of case studies of three typical types of convective systems occurring in Amazonia – i.e., locally occurring systems, coastal-occurring systems and basin-occurring systems – is also conducted to investigate the variability of the large-scale environment with different types of convective systems.

  17. Influence of initial velocity on trajectories of a charged particle in uniform crossed electric and magnetic fields

    Science.gov (United States)

    Nurul Khotimah, Siti; Viridi, Sparisoma; Widayani

    2017-03-01

    Magnetic and electric fields can cause a charged particle to form interesting trajectories. In general, each trajectory is discussed separately in university physics textbooks for undergraduate students. In this work, a solution of a charged particle moving in a uniform electric field at right angles to a uniform magnetic field (uniform crossed electric and magnetic fields) is reported; it is limited to particle motion in a plane. Specific solutions and their trajectories are obtained only by varying the initial particle velocity. The result shows five basic trajectory patterns, i.e., straight line, sinusoid-like, cycloid, cycloid-like with oscillation, and circle-like. The region of each trajectory is also mapped in the initial velocity space of the particle. This paper is intended for undergraduate students and describes further the trajectories of a charged particle through the regions of electric and magnetic fields influenced by initial condition of the particle, where electromagnetic radiation of an accelerated particle is not considered.

  18. Ion velocity distribution function and electric field measurements in a dual-frequency rf sheath

    Science.gov (United States)

    Moore, Nathaniel; Gekelman, Walter; Prybil, Patrick; Zhang, Yiting; Kushner, Mark

    2013-10-01

    Ion dynamics are investigated in a dual-frequency rf sheath above a 300 mm diameter biased silicon wafer in an industrial inductively coupled (440 kHz, 500 W) plasma etch tool. Ion velocity distribution (IVD) function measurements in the argon plasma are taken using laser induced fluorescence (LIF). Planar sheets of laser light enter the chamber both parallel and perpendicular to the surface of the wafer in order to measure both parallel and perpendicular IVDs at thousands of spatial positions. A fast (30 ns exposure) CCD camera measures the resulting fluorescence with a spatial resolution of 0.4 mm. The dual-frequency bias on the wafer is comprised of a 2 MHz low frequency bias and an adjustable 10-20 MHz high frequency bias. The bias voltages may be switched on and off (frep up to 1 kHz, duty cycle 10-90%). IVDs are measured with several different bias and timing combinations. For the 2 MHz bias, it was found that the IVD is uniform to within 5% across the wafer. IVDs as a function of phase of the bias were also measured. The electric field in the sheath was measured volumetrically over the wafer at thousands of positions using an emissive probe. The experimental results are compared with a simulation specifically designed for this particular plasma tool. Work supported by the NSF and DOE.

  19. Application of a simplified calculation for full-wave microtremor H/ V spectral ratio based on the diffuse field approximation to identify underground velocity structures

    Science.gov (United States)

    Wu, Hao; Masaki, Kazuaki; Irikura, Kojiro; Sánchez-Sesma, Francisco José

    2017-12-01

    Under the diffuse field approximation, the full-wave (FW) microtremor H/ V spectral ratio ( H/ V) is modeled as the square root of the ratio of the sum of imaginary parts of the Green's function of the horizontal components to that of the vertical one. For a given layered medium, the FW H/ V can be well approximated with only surface waves (SW) H/ V of the "cap-layered" medium which consists of the given layered medium and a new larger velocity half-space (cap layer) at large depth. Because the contribution of surface waves can be simply obtained by the residue theorem, the computation of SW H/ V of cap-layered medium is faster than that of FW H/ V evaluated by discrete wavenumber method and contour integration method. The simplified computation of SW H/ V was then applied to identify the underground velocity structures at six KiK-net strong-motion stations. The inverted underground velocity structures were used to evaluate FW H/ Vs which were consistent with the SW H/ Vs of corresponding cap-layered media. The previous study on surface waves H/ Vs proposed with the distributed surface sources assumption and a fixed Rayleigh-to-Love waves amplitude ratio for horizontal motions showed a good agreement with the SW H/ Vs of our study. The consistency between observed and theoretical spectral ratios, such as the earthquake motions of H/ V spectral ratio and spectral ratio of horizontal motions between surface and bottom of borehole, indicated that the underground velocity structures identified from SW H/ V of cap-layered medium were well resolved by the new method.[Figure not available: see fulltext.

  20. Characteristics of the Taylor microscale in the solar wind/foreshock. Magnetic field and electron velocity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Gurgiolo, C. [Bitterroot Basic Research, Hamilton, MT (United States); Goldstein, M.L.; Vinas, A. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Heliospheric Physics Lab.; Matthaeus, W.H. [Delaware Univ., Newark, DE (United States). Bartol Research Foundation; Fazakerley, A.N. [University College London, Dorking (United Kingdom). Mullard Space Science Lab.

    2013-07-01

    The Taylor microscale is one of the fundamental turbulence scales. Not easily estimated in the interplanetary medium employing single spacecraft data, it has generally been studied through two point correlations. In this paper we present an alternative, albeit mathematically equivalent, method for estimating the Taylor microscale ({lambda}{sub T}). We make two independent determinations employing multi-spacecraft data sets from the Cluster mission, one using magnetic field data and a second using electron velocity data. Our results using the magnetic field data set yields a scale length of 1538{+-}550 km, slightly less than, but within the same range as, values found in previous magnetic-field-based studies. During time periods where both magnetic field and electron velocity data can be used, the two values can be compared. Relative comparisons show {lambda}{sub T} computed from the velocity is often significantly smaller than that from the magnetic field data. Due to a lack of events where both measurements are available, the absolute {lambda}{sub T} based on the electron fluid velocity is not able to be determined.

  1. Velocities in Solar Pores

    Science.gov (United States)

    Balasubramaniam, K. S.; Keil, S. L.; Smaldone, L. A.

    1996-05-01

    We investigate the three dimensional structure of solar pores and their surroundings using high spatial and spectral resolution data. We present evidence that surface velocities decrease around pores with a corresponding increase in the line-of-sight (LOS) velocities. LOS velocities in pores increase with the strength of the magnetic field. Surface velocities show convergence toward a weak downflow which appear to trace boundaries resembling meso-granular and super granular flows. The observed magnetic fields in the pores appear near these boundaries. We analyze the vertical velocity structure in pores and show that they generally have downflows decreasing exponentially with height, with a scale height of about 90 km. Evidence is also presented for the expanding nature of flux tubes. Finally we describe a phenomenological model for pores. This work was supported by AFOSR Task 2311G3. LAS was partially supported by the Progetto Nazionale Astrofisica e Fisica Cosmica of MURST and Scambi Internazionali of the Universita degli Studi di Napoli Frederico II. National Solar Observatory, NOAO, is operated for the National Science Foundation by AURA, Inc.

  2. Study on high breakdown voltage GaN-based vertical field effect transistor with interfacial charge engineering for power applications

    Science.gov (United States)

    Du, Jiangfeng; Liu, Dong; Liu, Yong; Bai, Zhiyuan; Jiang, Zhiguang; Liu, Yang; Yu, Qi

    2017-11-01

    A high voltage GaN-based vertical field effect transistor with interfacial charge engineering (GaN ICE-VFET) is proposed and its breakdown mechanism is presented. This vertical FET features oxide trenches which show a fixed negative charge at the oxide/GaN interface. In the off-state, firstly, the trench oxide layer acts as a field plate; secondly, the n-GaN buffer layer is inverted along the oxide/GaN interface and thus a vertical hole layer is formed, which acts as a virtual p-pillar and laterally depletes the n-buffer pillar. Both of them modulate electric field distribution in the device and significantly increase the breakdown voltage (BV). Compared with a conventional GaN vertical FET, the BV of GaN ICE-VFET is increased from 1148 V to 4153 V with the same buffer thickness of 20 μm. Furthermore, the proposed device achieves a great improvement in the tradeoff between BV and on-resistance; and its figure of merit even exceeds the GaN one-dimensional limit.

  3. Exploiting LSPIV to assess debris-flow velocities in the field

    Directory of Open Access Journals (Sweden)

    J. I. Theule

    2018-01-01

    Full Text Available The assessment of flow velocity has a central role in quantitative analysis of debris flows, both for the characterization of the phenomenology of these processes and for the assessment of related hazards. Large-scale particle image velocimetry (LSPIV can contribute to the assessment of surface velocity of debris flows, provided that the specific features of these processes (e.g. fast stage variations and particles up to boulder size on the flow surface are taken into account. Three debris-flow events, each of them consisting of several surges featuring different sediment concentrations, flow stages, and velocities, have been analysed at the inlet of a sediment trap in a stream in the eastern Italian Alps (Gadria Creek. Free software has been employed for preliminary treatment (orthorectification and format conversion of video-recorded images as well as for LSPIV application. Results show that LSPIV velocities are consistent with manual measurements of the orthorectified imagery and with front velocity measured from the hydrographs in a channel recorded approximately 70 m upstream of the sediment trap. Horizontal turbulence, computed as the standard deviation of the flow directions at a given cross section for a given surge, proved to be correlated with surface velocity and with visually estimated sediment concentration. The study demonstrates the effectiveness of LSPIV in the assessment of surface velocity of debris flows and permit the most crucial aspects to be identified in order to improve the accuracy of debris-flow velocity measurements.

  4. Exploiting LSPIV to assess debris-flow velocities in the field

    Science.gov (United States)

    Theule, Joshua I.; Crema, Stefano; Marchi, Lorenzo; Cavalli, Marco; Comiti, Francesco

    2018-01-01

    The assessment of flow velocity has a central role in quantitative analysis of debris flows, both for the characterization of the phenomenology of these processes and for the assessment of related hazards. Large-scale particle image velocimetry (LSPIV) can contribute to the assessment of surface velocity of debris flows, provided that the specific features of these processes (e.g. fast stage variations and particles up to boulder size on the flow surface) are taken into account. Three debris-flow events, each of them consisting of several surges featuring different sediment concentrations, flow stages, and velocities, have been analysed at the inlet of a sediment trap in a stream in the eastern Italian Alps (Gadria Creek). Free software has been employed for preliminary treatment (orthorectification and format conversion) of video-recorded images as well as for LSPIV application. Results show that LSPIV velocities are consistent with manual measurements of the orthorectified imagery and with front velocity measured from the hydrographs in a channel recorded approximately 70 m upstream of the sediment trap. Horizontal turbulence, computed as the standard deviation of the flow directions at a given cross section for a given surge, proved to be correlated with surface velocity and with visually estimated sediment concentration. The study demonstrates the effectiveness of LSPIV in the assessment of surface velocity of debris flows and permit the most crucial aspects to be identified in order to improve the accuracy of debris-flow velocity measurements.

  5. H0, q0 and the local velocity field. [Hubble and deceleration constants in Big Bang expansion

    Science.gov (United States)

    Sandage, A.; Tammann, G. A.

    1982-01-01

    An attempt is made to find a systematic deviation from linearity for distances that are under the control of the Virgo cluster, and to determine the value of the mean random motion about the systematic flow, in order to improve the measurement of the Hubble and the deceleration constants. The velocity-distance relation for large and intermediate distances is studied, and type I supernovae are calibrated relatively as distance indicators and absolutely to obtain a new value for the Hubble constant. Methods of determining the deceleration constant are assessed, including determination from direct measurement, mean luminosity density, virgocentric motion, and the time scale test. The very local velocity field is investigated, and a solution is preferred with a random peculiar radial velocity of very nearby field galaxies of 90-100 km/s, and a Virgocentric motion of the local group of 220 km/s, leading to an underlying expansion rate of 55, in satisfactory agreement with the global value.

  6. Study of flow field of burning particles in a pyrotechnic flame based on particle image and particle velocity

    Science.gov (United States)

    Xue, R.; Xu, H. Q.; Li, Y.; Zhu, C. G.

    2014-11-01

    Studying the burning particles in the pyrotechnic flame is important to acquire the decomposition mechanism and spectral radiance of pyrotechnics. The high speed video (HSV) and particle image velocimetry (PIV) were used in this paper to analyze the flow field and velocity of burning particles in the flame of pyrotechnics. The binary image was obtained through gray scale treatment and adaptive threshold segmentation from HSV and PIV data, by which the coordinate of each particle was marked. On the basis, the movement trajectory of each particle during combustion was pursued by the most recent guidelines algorithm of cancroids matching. Through the method proposed in this study, the velocity variation of each particle was obtained, the approximate distribution of particle quantity at each zone was visualized and the mathematical model of pyrotechnic particle velocity flow field was established.

  7. Magnetic and velocity fluctuations from nonlinearly coupled tearing modes in the reversed field pinch with and without the reversal surface

    Science.gov (United States)

    Craig, D.; Martin, D.; Den Hartog, D. J.; Nornberg, M. D.; Reusch, J. A.

    2017-08-01

    We investigate the role of poloidal mode number m = 0 fluctuations on m = 1 velocity and magnetic field fluctuations in the Reversed Field Pinch (RFP). Removing the m = 0 resonant surface in the Madison Symmetric Torus (MST), results in suppressed m = 0 activity without a reduction in m = 1 magnetic activity. However, the m = 1 velocity fluctuations and fluctuation-induced mean emf are reduced as m = 0 modes are suppressed. Velocity fluctuations are measured directly using fast Doppler spectroscopy. Similar results are seen in visco-resistive MHD simulation with the DEBS code. An artificial line-averaged velocity diagnostic is developed for DEBS simulations to facilitate direct comparisons with experimental measurements. The sensitivity of the m = 1 velocity fluctuations and corresponding emf to changes in m = 0 mode activity is a feature of tearing modes in the nonlinear regime with a spectrum of interacting modes. These results have implications for RFP sustainment strategies and inform our understanding of the role of magnetic turbulence in astrophysical contexts.

  8. Search for auroral belt E-parallel fields with high-velocity barium ion injections

    Science.gov (United States)

    Heppner, J. P.; Ledley, B. G.; Miller, M. L.; Marionni, P. A.; Pongratz, M. B.

    1989-01-01

    In April 1984, four high-velocity shaped-charge Ba(+) injections were conducted from two sounding rockets at 770-975 km over northern Alaska under conditions of active auroral and magnetic disturbance. Spatial ionization (brightness) profiles of high-velocity Ba(+) clouds from photometric scans following each release were found to be consistent with the 28-sec theoretical time constant for Ba photoionization determined by Carlsten (1975). These observations therefore revealed no evidence of anomalous fast ionization predicted by the Alfven critical velocity hypothesis.

  9. Non-uniform velocity of homogeneous DNA in a uniform electric field: consequence of electric-field-induced slow dissociation of highly stable DNA-counterion complexes.

    Science.gov (United States)

    Musheev, Michael U; Kanoatov, Mirzo; Krylov, Sergey N

    2013-05-29

    Identical molecules move with identical velocities when placed in a uniform electric field within a uniform electrolyte. Here we report that homogeneous DNA does not obey this fundamental rule. While most DNA moves with similar velocities, a fraction of DNA moves with velocities that vary within a multiple-fold range. The size of this irregular fraction increases several orders of magnitude when exogenous counterions are added to DNA. The irregular fraction decreases several orders of magnitude when DNA counterions are removed by dialysis against deionized water in the presence of a strong electric field (0.6 kV/cm). Dialysis without the field is ineffective in decreasing the size of irregular fraction. These results suggest that (i) DNA can form very stable complexes with counterions, (ii) these complexes can be dissociated by an electric field, and (iii) the observed non-uniform velocity of DNA is caused by electric-field-induced slow dissociation of these stable complexes. Our findings help to better understand a fundamental property of DNA: its interaction with counterions. In addition, these findings suggest a practical way of making electromigration of DNA more uniform: removal of strongly bound DNA counterions by electro-dialysis against deionized water.

  10. Simulation-Based Optimization of a Vector Showerhead System for the Control of Flow Field Profile in a Vertical Reactor Chamber

    Directory of Open Access Journals (Sweden)

    Huanxiong Xia

    2014-03-01

    Full Text Available Optimization of a vector showerhead in a vertical reactor involves thousands of holes on the showerhead face plate and the spatial distribution of physical fields, so parameterizing the geometry configuration of the holes in high resolution is very difficult, which makes the conventional optimization methods hard to deal with. To solve this problem, a profile error feedback (PEF optimization solution was proposed to optimize a vector showerhead gas delivery system for the control of mass transport. The gas velocity profile in the reactor and the continuous-feature impedance distribution profile on the showerhead face plate are defined as design objective and variables, respectively. A cyclic iterative approximation idea was implemented in this solution. The algorithm was started from a guessed initial design model and then cyclically adjusted the design variables by the constructed PEF iterative formula to generate a better model and to make the gas velocity profile in the critical domain of the new model continually approximate to the expected profile, until it could be accepted. Finally, the optimized impedance profile was mapped to the holes geometry configuration through the established equivalent impedance model for the showerhead face plate.

  11. [Distribution of Regional Pollution and the Characteristics of Vertical Wind Field in the Pearl River Delta].

    Science.gov (United States)

    Liu, Jian; Wu, Dui; Fan, Shao-jia

    2015-11-01

    Based on the data of hourly PM2.5 concentration of 56 environmental monitoring stations and 9 cities over the Pearl River Delta (PRD) region, the distributions of PM2.5 pollution in PRD region were analyzed by systematic cluster analysis and correlational analysis. It was found that the regional pollution could be divided into 3 types. The first type was the pollution occurred in Dongguan, Guangzhou, Foshan and Jiangmen (I type), and the second type was the pollution occurred in Zhongshan, Zhuhai, Shenzhen and Huizhou (II type), while the last type was the pollution only occurred in Zhaoqing (III type). During the study period, they occurred 47, 7 and 128 days, respectively. During events of pollution type I, except Zhuhai, Shenzhen and Huizhou, the PM2.5 concentrations of other cities were generally high, while the PM2.5 concentration in whole PRD region was over 50.0 μg x m(-3) during events of pollution type II. The regions with higher PM2.5 concentration was mainly concentrated in Zhaoqing, Guangzhou and Foshan during events of pollution type III. The wind data from 4 wind profile radars located in PRD region was used to study the characteristics of vertical wind field of these 3 pollution types. It was found that the wind profiles of type I and III were similar that low layer and high layer were controlled by the southeast wind and the southwest wind, respectively. For type II, the low layer and high layer were influenced by northerly wind and westerly wind, respectively. Compared with other types, the wind speed and ventilation index of type II. were much higher, and the variation of wind direction at lower-middle-layer was much smaller. When PRD region was influenced by northerly winds, the PM2.5 concentration in the entire PRD region was higher. When PRD region was controlled by southeast wind, the PM2.5 concentrations of I and II areas were relatively lower, while the pollution in III area was relatively heavier.

  12. Prediction of Fluid Velocity in Highly Heterogeneous Conductivity Fields Using a Genetic Algorithm-Designed Artificial Neural Network

    Science.gov (United States)

    Shirley, C.

    2003-12-01

    A genetic algorithm (GA) is used to select the operational parameters of artificial neural networks (ANN) which are trained to predict fluid velocity. Populations of three-layer, feedforward backpropagation ANN's with varying numbers of hidden nodes, types and slopes of activation functions, alpha and beta learning rates and initial distributions of weights for both the input and hidden layers are created by the GA. The GA- defined ANN's are trained with inputs-output pairs of hydraulic conductivity neighborhoods and resulting fluid velocities at certain points in the simulation domain. The hydraulic conductivity fields are highly heterogeneous with an ensemble log conductivity variance of 1.0. Results of the GA are defined and selected ANN velocity predictions are presented.

  13. Distinguished hyperbolic trajectories in time-dependent fluid flows: analytical and computational approach for velocity fields defined as data sets

    Directory of Open Access Journals (Sweden)

    K. Ide

    2002-01-01

    Full Text Available In this paper we develop analytical and numerical methods for finding special hyperbolic trajectories that govern geometry of Lagrangian structures in time-dependent vector fields. The vector fields (or velocity fields may have arbitrary time dependence and be realized only as data sets over finite time intervals, where space and time are discretized. While the notion of a hyperbolic trajectory is central to dynamical systems theory, much of the theoretical developments for Lagrangian transport proceed under the assumption that such a special hyperbolic trajectory exists. This brings in new mathematical issues that must be addressed in order for Lagrangian transport theory to be applicable in practice, i.e. how to determine whether or not such a trajectory exists and, if it does exist, how to identify it in a sequence of instantaneous velocity fields. We address these issues by developing the notion of a distinguished hyperbolic trajectory (DHT. We develop an existence criteria for certain classes of DHTs in general time-dependent velocity fields, based on the time evolution of Eulerian structures that are observed in individual instantaneous fields over the entire time interval of the data set. We demonstrate the concept of DHTs in inhomogeneous (or "forced" time-dependent linear systems and develop a theory and analytical formula for computing DHTs. Throughout this work the notion of linearization is very important. This is not surprising since hyperbolicity is a "linearized" notion. To extend the analytical formula to more general nonlinear time-dependent velocity fields, we develop a series of coordinate transforms including a type of linearization that is not typically used in dynamical systems theory. We refer to it as Eulerian linearization, which is related to the frame independence of DHTs, as opposed to the Lagrangian linearization, which is typical in dynamical systems theory, which is used in the computation of Lyapunov exponents. We

  14. Shape, size, velocity and field-aligned currents of dayside plasma injections: a multi-altitude study

    Directory of Open Access Journals (Sweden)

    A. Marchaudon

    2009-03-01

    Full Text Available On 20 February 2005, Cluster in the outer magnetosphere and Double Star-2 (TC-2 at mid-altitude are situated in the vicinity of the northern cusp/mantle, with Cluster moving sunward and TC-2 anti-sunward. Their magnetic footprints come very close together at about 15:28 UT, over the common field-of-view of SuperDARN radars. Thanks to this conjunction, we determine the velocity, the transverse sizes, perpendicular and parallel to this velocity, and the shape of three magnetic flux tubes of magnetosheath plasma injection. The velocity of the structures determined from the Cluster four-spacecraft timing analysis is almost purely antisunward, in contrast with the antisunward and duskward convection velocity inside the flux tubes. The transverse sizes are defined from the Cluster-TC-2 separation perpendicular to the magnetic field, and from the time spent by a Cluster spacecraft in one structure; they are comprised between 0.6 and 2 RE in agreement with previous studies. Finally, using a comparison between the eigenvectors deduced from a variance analysis of the magnetic perturbation at the four Cluster and at TC-2, we show that the upstream side of the injection flux tubes is magnetically well defined, with even a concave front for the third one giving a bean-like shape, whereas the downstream side is far more turbulent. We also realise the first quantitative comparison between field-aligned currents at Cluster calculated with the curlometer technique and with the single-spacecraft method, assuming infinite parallel current sheets and taking into account the velocity of the injection flux tubes. The results agree nicely, confirming the validity of both methods. Finally, we compare the field-aligned current distribution of the three injection flux tubes at the altitudes of Cluster and TC-2. Both profiles are fairly similar, with mainly a pair of opposite field-aligned currents, upward at low-latitude and downward at high

  15. Shape, size, velocity and field-aligned currents of dayside plasma injections: a multi-altitude study

    Directory of Open Access Journals (Sweden)

    A. Marchaudon

    2009-03-01

    Full Text Available On 20 February 2005, Cluster in the outer magnetosphere and Double Star-2 (TC-2 at mid-altitude are situated in the vicinity of the northern cusp/mantle, with Cluster moving sunward and TC-2 anti-sunward. Their magnetic footprints come very close together at about 15:28 UT, over the common field-of-view of SuperDARN radars. Thanks to this conjunction, we determine the velocity, the transverse sizes, perpendicular and parallel to this velocity, and the shape of three magnetic flux tubes of magnetosheath plasma injection. The velocity of the structures determined from the Cluster four-spacecraft timing analysis is almost purely antisunward, in contrast with the antisunward and duskward convection velocity inside the flux tubes. The transverse sizes are defined from the Cluster-TC-2 separation perpendicular to the magnetic field, and from the time spent by a Cluster spacecraft in one structure; they are comprised between 0.6 and 2 RE in agreement with previous studies. Finally, using a comparison between the eigenvectors deduced from a variance analysis of the magnetic perturbation at the four Cluster and at TC-2, we show that the upstream side of the injection flux tubes is magnetically well defined, with even a concave front for the third one giving a bean-like shape, whereas the downstream side is far more turbulent. We also realise the first quantitative comparison between field-aligned currents at Cluster calculated with the curlometer technique and with the single-spacecraft method, assuming infinite parallel current sheets and taking into account the velocity of the injection flux tubes. The results agree nicely, confirming the validity of both methods. Finally, we compare the field-aligned current distribution of the three injection flux tubes at the altitudes of Cluster and TC-2. Both profiles are fairly similar, with mainly a pair of opposite field-aligned currents, upward at low-latitude and downward at high-latitude. In terms of

  16. Factors controlling the field settling velocity of cohesive sediment in estuaries

    DEFF Research Database (Denmark)

    Pejrup, Morten; Mikkelsen, Ole

    2010-01-01

    this paper expressed as the root mean square [rms] velocity gradient, [G]) in the water on the W-50 in situ. There is a strong need to establish algorithms based on in situ measurements describing the dual impact of both SSC and G on the flocculation process, and hence, W-50. The present paper addresses......It has long been recognized that the suspended sediment concentration (SSC) is one of the major determinants for the flocculation of cohesive particles into sediment flocs in estuaries. It is furthermore well known that the turbulent shear of the water significantly influences the flocculation...... process and the equilibrium settling velocity of flocculated sediment in a turbulent flow. A vast number of authors have reported algorithms relating the median settling velocity (W-50) to suspended sediment concentration. However, only a few studies have dealt with the impact of the turbulent shear (in...

  17. Non-Gaussian Statistics and Stellar Rotational Velocities of Main-Sequence Field Stars

    Science.gov (United States)

    Carvalho, J. C.; do Nascimento, J. D.; Silva, R.; DeMedeiros, J. R.

    2009-05-01

    In this Letter, we study the observed distributions of rotational velocity in a sample of more than 16,000 nearby F and G dwarf stars, magnitude complete, and presenting high-precision Vsin i measurements. We show that the velocity distributions cannot be fitted by a Maxwellian. In addition, an analysis based on both Tsallis and Kaniadakis power-law statistics is by far the most appropriate statistics and gives a very good fit. It is also shown that single and binary stars have similar rotational distributions. This is the first time, to our knowledge, that these two new statistics have been tested for the rotation of such a large sample of stars, pointing solidly to a solution of the puzzling problem of the function governing the distribution of stellar rotational velocity.

  18. Depression storage and infiltration effects on overland flow depth-velocity-friction at desert conditions: field plot results and model

    Science.gov (United States)

    Rossi, M. J.; Ares, J. O.

    2012-09-01

    Water infiltration and overland flow are relevant in considering water partition among plant life forms, the sustainability of vegetation and the design of sustainable hydrological models and management. In arid and semi-arid regions, these processes present characteristic trends imposed by the prevailing physical conditions of the upper soil as evolved under water-limited climate. A set of plot-scale field experiments at the semi-arid Patagonian Monte (Argentina) were performed in order to estimate the effect of depression storage areas and infiltration rates on depths, velocities and friction of overland flows. The micro-relief of undisturbed field plots was characterized at z-scale 1 mm through close-range stereo-photogrammetry and geo-statistical tools. The overland flow areas produced by controlled water inflows were video-recorded and the flow velocities were measured with image processing software. Antecedent and post-inflow moisture were measured, and texture, bulk density and physical properties of the upper soil were estimated based on soil core analyses. Field data were used to calibrate a physically-based, mass balanced, time explicit model of infiltration and overland flows. Modelling results reproduced the time series of observed flow areas, velocities and infiltration depths. Estimates of hydrodynamic parameters of overland flow (Reynolds-Froude numbers) are informed. To our knowledge, the study here presented is novel in combining several aspects that previous studies do not address simultaneously: (1) overland flow and infiltration parameters were obtained in undisturbed field conditions; (2) field measurements of overland flow movement were coupled to a detailed analysis of soil microtopography at 1 mm depth scale; (3) the effect of depression storage areas in infiltration rates and depth-velocity friction of overland flows is addressed. Relevance of the results to other similar desert areas is justified by the accompanying biogeography analysis

  19. Hyperfine-induced hysteretic funnel structure in spin blockaded tunneling current of coupled vertical quantum dots at low magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Leary, A.; Wicha, A.; Harack, B.; Coish, W. A.; Hilke, M. [Department of Physics, McGill University, Ernest Rutherford Building, 3600 rue University, Montreal, Quebec H3A 2T8 (Canada); Yu, G.; Gupta, J. A. [National Research Council of Canada, M50, Montreal Road, Ottawa, Ontario K1A 0R6 (Canada); Payette, C.; Austing, D. G. [Department of Physics, McGill University, Ernest Rutherford Building, 3600 rue University, Montreal, Quebec H3A 2T8, Canada and National Research Council of Canada, M50, Montreal Road, Ottawa, Ontario K1A 0R6 (Canada)

    2013-12-04

    We outline the properties of the hyperfine-induced funnel structure observed in the two-electron spin blockade region of a weakly coupled vertical double quantum dot device. Hysteretic steps in the leakage current occur due to dynamic nuclear polarization when either the bias voltage or the magnetic field is swept up and down. When the bias voltage is swept, an intriguing ∼3 mT wide cusp near 0 T appears in the down-sweep position, and when the magnetic field is swept, the current at 0 T can be switched from 'low' to 'high' as the bias is increased.

  20. Continuos incremental field test to estimate velocity and maximal oxygen consumption in non-expert runners

    OpenAIRE

    José A. Bragada; Moreno, R.; Barbosa, Tiago M.

    2009-01-01

    Parameters such as a maximal oxygen uptake (VO2max) and velocity at which VO2max occurs (VelVO2max) are often used to training control purposes to enhance runner’s performance. This study had two purposes: (i) determine the relationship between VelVO2max obtained in continuous incremental filed test (CIFT) and VelVO2max determined on a treadmill in a laboratory; and (II) verify if it is possible to estimate the VO2max based on CIFT velocity

  1. Dissipated power and induced velocity fields data of a micro single dielectric barrier discharge plasma actuator for active flow control.

    Science.gov (United States)

    Pescini, E; Martínez, D S; De Giorgi, M G; Francioso, L; Ficarella, A

    2015-12-01

    In recent years, single dielectric barrier discharge (SDBD) plasma actuators have gained great interest among all the active flow control devices typically employed in aerospace and turbomachinery applications [1,2]. Compared with the macro SDBDs, the micro single dielectric barrier discharge (MSDBD) actuators showed a higher efficiency in conversion of input electrical power to delivered mechanical power [3,4]. This article provides data regarding the performances of a MSDBD plasma actuator [5,6]. The power dissipation values [5] and the experimental and numerical induced velocity fields [6] are provided. The present data support and enrich the research article entitled "Optimization of micro single dielectric barrier discharge plasma actuator models based on experimental velocity and body force fields" by Pescini et al. [6].

  2. Potential, velocity, and density fields from redshift-distance samples: Application - Cosmography within 6000 kilometers per second

    Science.gov (United States)

    Bertschinger, Edmund; Dekel, Avishai; Faber, Sandra M.; Dressler, Alan; Burstein, David

    1990-01-01

    A potential flow reconstruction algorithm has been applied to the real universe to reconstruct the three-dimensional potential, velocity, and mass density fields smoothed on large scales. The results are shown as maps of these fields, revealing the three-dimensional structure within 6000 km/s distance from the Local Group. The dominant structure is an extended deep potential well in the Hydra-Centaurus region, stretching across the Galactic plane toward Pavo, broadly confirming the Great Attractor (GA) model of Lynden-Bell et al. (1988). The Local Supercluster appears to be an extended ridge on the near flank of the GA, proceeding through the Virgo Southern Extension to the Virgo and Ursa Major clusters. The Virgo cluster and the Local Group are both falling toward the bottom of the GA potential well with peculiar velocities of 658 + or - 121 km/s and 565 + or - 125 km/s, respectively.

  3. Velocity flow field and water level measurements in shoaling and breaking water waves

    CSIR Research Space (South Africa)

    Mukaro, R

    2010-01-01

    Full Text Available In this paper we report on the laboratory investigations of breaking water waves. Measurements of the water levels and instantaneous fluid velocities were conducted in water waves breaking on a sloping beach within a glass flume. Instantaneous water...

  4. Correction of the closed orbit and vertical dispersion and the tuning and field correction system in ISABELLE

    Energy Technology Data Exchange (ETDEWEB)

    Parzen, G.

    1979-01-01

    Each ring in ISABELLE will have 10 separately powered systematic field correction coils to make required corrections which are the same in corresponding magnets around the ring. These corrections include changing the ..nu..-value, shaping the working line in ..nu..-space, correction of field errors due to iron saturation effects, the conductor arrangements, the construction of the coil ends, diamagnetic effects in the superconductor and to rate-dependent induced currents. The twelve insertion quadrupoles in the insertion surrounding each crossing point will each have a quadrupole trim coil. The closed orbit will be controlled by a system of 84 horizontal dipole coils and 90 vertical dipole coils in each ring, each coil being separately powered. This system of dipole coils will also be used to correct the vertical dispersion at the crossing points. Two families of skew quadrupoles per ring will be provided for correction of the coupling between the horizontal and vertical motions. Although there will be 258 separately powered correction coils in each ring.

  5. Autonomous Observations of the Upper Ocean Stratification and Velocity Fields About the Seasonally-Retreating Marginal Ice Zone

    Science.gov (United States)

    2015-09-30

    Stratification and Velocity Fields About the Seasonally-Retreating Marginal Ice Zone John M. Toole MS 21/354 Clark Laboratory, WHOI Woods Hole, MA 02543...OBJECTIVES As a contribution to the Marginal Ice Zone DRI, this research element is designed to observe the seasonal evolution of the upper-ocean...Figure 4. Drift tracks of the 5 ITP-V systems deployed during the Marginal Ice Zone DRI program. RESULTS Analysis of the MIZ

  6. Autonomous Observations of the Upper Ocean Stratification and Velocity Field about the Seasonality Retreating Marginal Ice Zone

    Science.gov (United States)

    2016-12-30

    stratification and velocity field about the seasonality-retreating marginal ice zone 5b. GRANT NUMBER N00014-12-1-0140 Sc. PROGRAM ELEMENT NUMBER 6...STATEMENT UNLIMITED - UNCLASSIFIED 13. SUPPLEMENTARY NOTES 14. ABSTRACT As a contribution to the Marginal Ice Zone ORI, this research element was...understanding of the Arctic air-ice-ocean system. 15. SUBJECT TERMS Arctic Ocean Air-Ice-Ocean Interaction Marginal Ice Zone 16. SECURITY

  7. Autonomous Observations of the Upper Ocean Stratification and Velocity Field about the Seasonally-Retreating Marginal Ice Zone

    Science.gov (United States)

    2016-12-30

    stratification and velocity field about the seasonality-retreating marginal ice zone Sb. GRANT NUMBER N00014-12-1 -0140 Sc. PROGRAM ELEMENT NUMBER 6...STATEMENT UNLIMITED- UNCLASSIFIED 13. SUPPLEMENTARY NOTES 14. ABSTRACT As a contribution to the Marginal Ice Zone DRI , this research element was...understanding of the Arctic air-ice-ocean system. 15. SUBJECT TERMS Arctic Ocean Air-Ice-Ocean Interaction Marginal Ice Zone 16. SECURITY

  8. Vertically integrated logic circuits constructed using ZnO-nanowire-based field-effect transistors on plastic substrates.

    Science.gov (United States)

    Kang, Jeongmin; Moon, Taeho; Jeon, Youngin; Kim, Hoyoung; Kim, Sangsig

    2013-05-01

    ZnO-nanowire-based logic circuits were constructed by the vertical integration of multilayered field-effect transistors (FETs) on plastic substrates. ZnO nanowires with an average diameter of -100 nm were synthesized by thermal chemical vapor deposition for use as the channel material in FETs. The ZnO-based FETs exhibited a high I(ON)/I(OFF) of > 10(6), with the characteristic of n-type depletion modes. For vertically integrated logic circuits, three multilayer FETs were sequentially prepared. The stacked FETs were connected in series via electrodes, and C-PVPs were used for the layer-isolation material. The NOT and NAND gates exhibited large logic-swing values of -93%. These results demonstrate the feasibility of three dimensional flexible logic circuits.

  9. Stresses of PTT, Giesekus, and Oldroyd-B fluids in a Newtonian velocity field near the stick-slip singularity

    Science.gov (United States)

    Evans, J. D.; Palhares Junior, I. L.; Oishi, C. M.

    2017-12-01

    We characterise the stress singularity of the Oldroyd-B, Phan-Thien-Tanner (PTT), and Giesekus viscoelastic models in steady planar stick-slip flows. For both PTT and Giesekus models in the presence of a solvent viscosity, the asymptotics show that the velocity field is Newtonian dominated near to the singularity at the join of the stick and slip surfaces. Polymer stress boundary layers are present at both the stick and slip surfaces. By integrating along streamlines, we verify the polymer stress behavior of r-4/11 for PTT and r-5/16 for Giesekus, where r is the radial distance from the singularity. These asymptotic results for PTT and Giesekus do not hold in the limit of vanishing quadratic stress terms for Oldroyd-B. However, we can consider the Oldroyd-B model in the fixed kinematics of a prescribed Newtonian velocity field. In contrast to PTT and Giesekus, this is not the correct balance for the momentum equation but does allow insight into the behavior of the Oldroyd-B equations near the singularity. A three-region asymptotic structure is again apparent with now a polymer stress singularity of r-4/5. The high Weissenberg boundary layer equations are found to manifest themselves at the stick surface and are of thickness r3/2. At the slip surface, dominant balance between the upper convected stress and rate-of-strain terms gives a slip boundary layer of thickness r2. The solution of the slip boundary layer shows that the polymer stress is now singular along the slip surface. These results are supported through numerical integration along streamlines of the Oldroyd-B equations in a Newtonian velocity field. The Oldroyd-B model thus extends the point singularity at the join of the stick and slip surfaces to the whole of slip surface. As such, it does not have a physically meaningful solution in a Newtonian velocity field. We would expect a similar stress behavior for this model in the true viscoelastic velocity field.

  10. The superluminal velocities as the consequence of non-classical states of electromagnetic field

    Science.gov (United States)

    Veklenko, B. A.

    2017-06-01

    It was shown within the framework of conventional quantum electrodynamics, and without using perturbation theory, the presence of superluminal signals, transferring the information, while investigating the scattering of quantum electromagnetic field by excited atom. The superluminal signals are impossible in the theory of free fields, but their existence is predicted by the theory of interacting fields.

  11. Experimental investigation of MHD heat transfer in a vertical round tube affected by transverse magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, I.A., E-mail: corpuskula@gmail.com; Sviridov, E.V.; Sviridov, V.G.; Razuvanov, N.G.

    2016-11-15

    Highlights: • Local and averaged heat transfer coefficient are measured. • Free convection influence on MHD-flow is investigated. • The region with the free convection effect of MHD-heat transfer is found. • Temperature low-frequency fluctuations of abnormally high amplitude are detected. • Analysis of the MHD-heat transfer experimental data is performed. - Abstract: The article is devoted to the results of experimental investigation of heat transfer for a downward mercury flow in a vertical round tube in the presence of a transverse magnetic with non-uniform heat flux along the tube circumference.

  12. The DC field components of horizontal and vertical electric dipole sources immersed in three-layered stratified media

    Directory of Open Access Journals (Sweden)

    D. Llanwyn Jones

    Full Text Available Formulas for computing the Cartesian components of the static (DC fields of horizontal electric dipoles ( HEDs and vertical electric dipoles ( VEDs located in the central zone of a three-layer horizontally stratified medium are derived and presented in a summary form suitable for immediate computation. Formulas are given for the electric and magnetic field components in the upper and central regions. In the general case the computation involves the summation of a convergent infinite series. For the particular case of an infinitely thick central region (corresponding to the two-layer problem, the analysis produces relatively simple closed-form equations for the field components which are suitable for a 'hand calculation'. Specimen calculations for dipoles in seawaters are included and the derived results are compared with computations made using an ac model.

  13. The DC field components of horizontal and vertical electric dipole sources immersed in three-layered stratified media

    Directory of Open Access Journals (Sweden)

    D. Llanwyn Jones

    1997-04-01

    Full Text Available Formulas for computing the Cartesian components of the static (DC fields of horizontal electric dipoles ( HEDs and vertical electric dipoles ( VEDs located in the central zone of a three-layer horizontally stratified medium are derived and presented in a summary form suitable for immediate computation. Formulas are given for the electric and magnetic field components in the upper and central regions. In the general case the computation involves the summation of a convergent infinite series. For the particular case of an infinitely thick central region (corresponding to the two-layer problem, the analysis produces relatively simple closed-form equations for the field components which are suitable for a 'hand calculation'. Specimen calculations for dipoles in seawaters are included and the derived results are compared with computations made using an ac model.

  14. Study of the velocity field of surface currents in the South Atlantic Ocean derived from drifting buoy data

    Directory of Open Access Journals (Sweden)

    Eduardo Marone

    2011-12-01

    Full Text Available A total of 1442 data series of 996 drifters from public and research databases were analyzed in order to decompose and to estimate the velocity field of surface currents between 30º S and 50º S in the South Atlantic Ocean, with emphasis on the South Atlantic Current (SAC. The SAC is the southernmost limit of the South Atlantic Subtropical Gyre and presents strong interaction with other currents such as the Antarctic Circumpolar Current (ACC. The data were processed according to the Taylor's theory. The velocity field map for the study area as well as the mean values of the current intensity and associated standard deviation are presented and discussed. The highest estimated values of the average current velocity are located at the origin of the SAC and at the Malvinas Current (MC. The mean intensity of the SAC is approximately 30 cm.s-1 and the highest intensity values are observed at its origin decaying towards east. The SAC comprises a system containing a main axis and two branches, north and south. The N-SAC feeds the Benguela Current and the S-SAC leaks to the east towards the Indian Ocean. The flow pattern observed for the SAC presents a meandering characteristics and high variability in the regions where it interacts with other currents and mesoscale features.

  15. High Vertical Resolution Full-Field Reflection-Type Three-Dimensional Angle-Deviation Microscope with Nonlinear Error Compensation.

    Science.gov (United States)

    Chiu, Ming-Hung; Tan, Chen-Tai; Huang, Shih-Feng; Chen, Jhao-An

    2015-06-01

    This study examines the use of reflectivity-height transformation in full-field angle-deviation microscopes (ADM). In such microscopes, two light intensity distribution images of a prism's total internal reflection and critical angle are obtained separately with two charge-coupled devices (CCDs), and are converted into a reflectivity profile point-to-point and then into angle of deviation matrix after the beam is reflected by the test sample; finally, the surface height of the sample is found through the triangular geometrical relationship. This method obtains the image through the effective imaging area of CCD. Once the two-dimensional (2D) image is obtained, the third dimension, height, is added to create a full-field 3D surface profile. Its conversion process is nonlinear; therefore, compensation must be made to reduce measurement errors. The optical magnification of high vertical resolution full-field 3D reflection-type ADM could reach >250 times, thus providing submicron measurements with nanometer vertical resolution and allowing for the simultaneous measurement of 2D and 3D images. Small defects on both transparent and nontransparent surfaces can be rapidly detected.

  16. Vertical InAs/InGaAs Heterostructure Metal-Oxide-Semiconductor Field-Effect Transistors on Si.

    Science.gov (United States)

    Kilpi, Olli-Pekka; Svensson, Johannes; Wu, Jun; Persson, Axel R; Wallenberg, Reine; Lind, Erik; Wernersson, Lars-Erik

    2017-10-11

    III-V compound semiconductors offer a path to continue Moore's law due to their excellent electron transport properties. One major challenge, integrating III-V's on Si, can be addressed by using vapor-liquid-solid grown vertical nanowires. InAs is an attractive material due to its superior mobility, although InAs metal-oxide-semiconductor field-effect transistors (MOSFETs) typically suffer from band-to-band tunneling caused by its narrow band gap, which increases the off-current and therefore the power consumption. In this work, we present vertical heterostructure InAs/InGaAs nanowire MOSFETs with low off-currents provided by the wider band gap material on the drain side suppressing band-to-band tunneling. We demonstrate vertical III-V MOSFETs achieving off-current below 1 nA/μm while still maintaining on-performance comparable to InAs MOSFETs; therefore, this approach opens a path to address not only high-performance applications but also Internet-of-Things applications that require low off-state current levels.

  17. Dissipated power and induced velocity fields data of a micro single dielectric barrier discharge plasma actuator for active flow control

    Directory of Open Access Journals (Sweden)

    E. Pescini

    2015-12-01

    Full Text Available In recent years, single dielectric barrier discharge (SDBD plasma actuators have gained great interest among all the active flow control devices typically employed in aerospace and turbomachinery applications [1,2]. Compared with the macro SDBDs, the micro single dielectric barrier discharge (MSDBD actuators showed a higher efficiency in conversion of input electrical power to delivered mechanical power [3,4]. This article provides data regarding the performances of a MSDBD plasma actuator [5,6]. The power dissipation values [5] and the experimental and numerical induced velocity fields [6] are provided. The present data support and enrich the research article entitled “Optimization of micro single dielectric barrier discharge plasma actuator models based on experimental velocity and body force fields” by Pescini et al. [6].

  18. Orientation of cosmic web filaments with respect to the underlying velocity field

    OpenAIRE

    Tempel, E.; Libeskind, N. I.; Hoffman, Y.; Liivamägi, L. J.; Tamm, A

    2013-01-01

    The large-scale structure of the Universe is characterised by a web-like structure made of voids, sheets, filaments, and knots. The structure of this so-called cosmic web is dictated by the local velocity shear tensor. In particular, the local direction of a filament should be strongly aligned with e3, the eigenvector associated with the smallest eigenvalue of the tensor. That conjecture is tested here on the basis of a cosmological simulation. The cosmic web delineated by the halo distributi...

  19. Relationships among seismic velocity, metamorphism, and seismic and aseismic fault slip in the Salton Sea Geothermal Field region

    Science.gov (United States)

    McGuire, Jeffrey J.; Lohman, Rowena B.; Catchings, Rufus D.; Rymer, Michael J.; Goldman, Mark R.

    2015-01-01

    The Salton Sea Geothermal Field is one of the most geothermally and seismically active areas in California and presents an opportunity to study the effect of high-temperature metamorphism on the properties of seismogenic faults. The area includes numerous active tectonic faults that have recently been imaged with active source seismic reflection and refraction. We utilize the active source surveys, along with the abundant microseismicity data from a dense borehole seismic network, to image the 3-D variations in seismic velocity in the upper 5 km of the crust. There are strong velocity variations, up to ~30%, that correlate spatially with the distribution of shallow heat flow patterns. The combination of hydrothermal circulation and high-temperature contact metamorphism has significantly altered the shallow sandstone sedimentary layers within the geothermal field to denser, more feldspathic, rock with higher P wave velocity, as is seen in the numerous exploration wells within the field. This alteration appears to have a first-order effect on the frictional stability of shallow faults. In 2005, a large earthquake swarm and deformation event occurred. Analysis of interferometric synthetic aperture radar data and earthquake relocations indicates that the shallow aseismic fault creep that occurred in 2005 was localized on the Kalin fault system that lies just outside the region of high-temperature metamorphism. In contrast, the earthquake swarm, which includes all of the M > 4 earthquakes to have occurred within the Salton Sea Geothermal Field in the last 15 years, ruptured the Main Central Fault (MCF) system that is localized in the heart of the geothermal anomaly. The background microseismicity induced by the geothermal operations is also concentrated in the high-temperature regions in the vicinity of operational wells. However, while this microseismicity occurs over a few kilometer scale region, much of it is clustered in earthquake swarms that last from

  20. Study of thermal-field emission properties and investigation of temperature dependent noise in the field emission current from vertical carbon nanotube emitters

    Science.gov (United States)

    Kolekar, Sadhu; Patole, S. P.; Patil, Sumati; Yoo, J. B.; Dharmadhikari, C. V.

    2017-10-01

    We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well-defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The real-time field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD) in order to understand the effect of temperature on distribution of electron emission spots and ring like structures in Field Emission Microscope (FEM) image. The FEM images could be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 from FEM image is typically, 4.5 × 107 and the actual number emitters per cm2 present as per Atomic Force Microscopy (AFM) data is 1.2 × 1012. The measured Current-Voltage (I-V) characteristics exhibit non linear Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current were recorded at different temperatures and Fast Fourier transformed into temperature dependent power spectral density. The latter was found to obey power law relation S(f) = A(Iδ/fξ), where δ and ξ are temperature dependent current and frequency exponents respectively.

  1. Velocity and temperature field characteristics of water and air during natural convection heating in cans.

    Science.gov (United States)

    Erdogdu, Ferruh; Tutar, Mustafa

    2011-01-01

    Presence of headspace during canning is required since an adequate amount allows forming vacuum during the process. Sealing technology may not totally eliminate all entrapped gases, and headspace might affect heat transfer. Not much attention has been given to solve this problem in computational studies, and cans, for example, were mostly assumed to be fully filled with product. Therefore, the objective of this study was to determine velocity and temperature evolution of water and air in cans during heating to evaluate the relevance of headspace in the transport mechanism. For this purpose, canned water samples with a certain headspace were used, and required governing continuity, energy, and momentum equations were solved using a finite volume approach coupled with a volume of fluid element model. Simulation results correlated well with experimental results validating faster heating effects of headspace rather than insulation effects as reported in the literature. The organized velocity motions along the air-water interface were also shown. Practical Application: Canning is a universal and economic method for processing of food products, and presence of adequate headspace is required to form vacuum during sealing of the cans. Since sealing technology may not totally eliminate the entrapped gases, mainly air, headspace might affect heating rates in cans. This study demonstrated the increased heating rates in the presence of headspace in contrast with some studies in the literature. By applying the effect of headspace, required processing time for thermally processed foods can be reduced leading to more rapid processes and lower energy consumptions.

  2. Experimental measurements on a powder avalanche impacting an obstacle: 3D velocity field and exerted pressures

    Science.gov (United States)

    Caccamo, P.; Naaim-Bouvet, F.; Bellot, H.; Ousset, F.; Faug, T.

    2012-04-01

    In the framework of the Alcotra DYNAVAL Interreg project, this experimental study aims at investigating the dynamical behaviour of a powder snow avalanche impacting an obstacle. Tests have been realised in a water tank where a salty water solution (rho=1.2kg m-3) flows down in a channel and impacts an obstacle at a distance d=1m from the releasing gate. The set-up geometry reproduces a simplified small-scale model of the real avalanche site of Taconnaz (Chamonix, France). A high-resolution acoustic velocimeter allows measurements on the 3D flow velocity. By measuring the velocity just upstream and downstream of the obstacle, it is possible to determine the influence of the obstacle on the flow. In a lack of suitable sensors, the pressure exerted on the obstacle is calculated using the classical formula P=1/2rhoU2. Then, density values are required. A new method to measure the flow density is advanced and preliminary results are presented.

  3. Field test report of the Department of Energy's 100-kW vertical axis wind turbine

    Science.gov (United States)

    Nellums, R. O.

    1985-02-01

    Three second generation Darrieus type vertical axis wind turbines of approximately 120 kW capacity per unit were installed in 1980-1981. Through March 1984, over 9000 hours of operation had been accumulated, including 6600 hours of operation on the unit installed in Bushland, Texas. The turbines were heavily instrumented and have yielded a large amount of test data. Test results of this program, including aerodynamic, structural, drive train, and economic data are presented. Among the most favorable results were an aerodynamic peak performance coefficient of 0.41; fundamental structural integrity requiring few repairs and no major component replacements as of March 1984; and an average prototype fabrication cost of approximately $970 per peak kilowatt of output. A review of potential design improvements is presented.

  4. Modulation of Electronic and Optical Anisotropy Properties of ML-GaS by Vertical Electric Field

    Science.gov (United States)

    Guo, Fei; Wu, Yaping; Wu, Zhiming; Ke, Congming; Zhou, Changjie; Chen, Ting; Li, Heng; Zhang, Chunmiao; Fu, Mingming; Kang, Junyong

    2017-06-01

    We investigate the electric-field-dependent optical properties and electronic behaviors of GaS monolayer by using the first-principles calculations. A reversal of the dipole transition from E//c to E⊥c anisotropy is found with a critical external electric field of about 5 V/nm. Decomposed projected band contributions exhibit asymmetric electronic structures in GaS interlayers under the external electric field, which explains the evolution of the absorption preference. Spatial distribution of the partial charge and charge density difference reveal that the strikingly reversed optical anisotropy in GaS ML is closely linked to the additional crystal field originated from the external electric field. These results pave the way for experimental research and provide a new perspective for the application of the monolayer GaS-based two-dimensional electronic and optoelectronic devices.

  5. Study of the Vertical Magnetic Field in Face-on Galaxies Using Faraday Tomography

    Science.gov (United States)

    Ideguchi, Shinsuke; Tashiro, Yuichi; Akahori, Takuya; Takahashi, Keitaro; Ryu, Dongsu

    2017-07-01

    Faraday tomography allows astronomers to probe the distribution of the magnetic field along the line of sight (LOS), but that can be achieved only after the Faraday spectrum is interpreted. However, the interpretation is not straightforward, mainly because the Faraday spectrum is complicated due to a turbulent magnetic field; it ruins the one-to-one relation between the Faraday depth and the physical depth, and appears as many small-scale features in the Faraday spectrum. In this paper, by employing “simple toy models” for the magnetic field, we describe numerically as well as analytically the characteristic properties of the Faraday spectrum. We show that the Faraday spectrum along “multiple LOSs” can be used to extract the global properties of the magnetic field. Specifically, considering face-on spiral galaxies and modeling turbulent magnetic field as a random field with a single coherence length, we numerically calculate the Faraday spectrum along a number of LOSs and its shape-characterizing parameters, that is, the moments. When multiple LOSs cover a region of ≳(10 coherence length)2, the shape of the Faraday spectrum becomes smooth and the shape-characterizing parameters are well specified. With the Faraday spectrum constructed as a sum of Gaussian functions with different means and variances, we analytically show that the parameters are expressed in terms of the regular and turbulent components of the LOS magnetic field and the coherence length. We also consider the turbulent magnetic field modeled with a power-law spectrum, and study how the magnetic field is revealed in the Faraday spectrum. Our work suggests a way to obtain information on the magnetic field from a Faraday tomography study.

  6. How does an asymmetric magnetic field change the vertical structure of a hot accretion flow?

    Science.gov (United States)

    Samadi, M.; Abbassi, S.; Lovelace, R. V. E.

    2017-09-01

    This paper explores the effects of large-scale magnetic fields in hot accretion flows for asymmetric configurations with respect to the equatorial plane. The solutions that we have found show that the large-scale asymmetric magnetic field can significantly affect the dynamics of the flow and also cause notable outflows in the outer parts. Previously, we treated a viscous resistive accreting disc in the presence of an odd symmetric B-field about the equatorial plane. Now, we extend our earlier work by taking into account another configuration of large-scale magnetic field that is no longer symmetric. We provide asymmetric field structures with small deviations from even and odd symmetric B-field. Our results show that the disc's dynamics and appearance become different above and below the equatorial plane. The set of solutions also predicts that even a small deviation in a symmetric field causes the disc to compress on one side and expand on the other. In some cases, our solution represents a very strong outflow from just one side of the disc. Therefore, the solution may potentially explain the origin of one-sided jets in radio galaxies.

  7. Mass Transfer Process by Magneto-convection at a Solid-liquid Interface in a Heterogeneous Vertical Magnetic Field

    Science.gov (United States)

    Sugiyama, Atsushi; Morisaki, Shigeyoshi; Aogaki, Ryoichi

    2003-08-01

    When an external magnetic field is vertically imposed on a solid-liquid interface, the mass transfer process of a solute dissolving from or depositing on the interface was theoretically examined. In a heterogeneous vertical magnetic field, a material receives a magnetic force in proportion to the product of the magnetic susceptibility, the magnetic flux density B and its gradient (dB/dz). As the reaction proceeds, a diffusion layer of the solute with changing susceptibility is formed at the interface because of the difference of the the magnetic susceptibility on the concentration of the solute. In the case of an unstable condition where the dimensionless number of magneto-convection S takes a positive value, the magnetic force is applied to the layer and induces numerous minute convection cells. The mass transfer of the solute is thus accelerated, so that it is predicted that the mass flux increases with the 1/3rd order of B(dB/dz) and the 4/3rd order of the concentration. The experiment was then performed by measuring the rate of the dissolution of copper sulfate pentahydrate crystal in water.

  8. Quantitative Velocity Field Measurements in Reduced-Gravity Combustion Science and Fluid Physics Experiments

    Science.gov (United States)

    Greenberg, Paul S.; Wernet, Mark P.

    1999-01-01

    Systems have been developed and demonstrated for performing quantitative velocity measurements in reduced gravity combustion science and fluid physics investigations. The unique constraints and operational environments inherent to reduced-gravity experimental facilities pose special challenges to the development of hardware and software systems. Both point and planar velocimetric capabilities are described, with particular attention being given to the development of systems to support the International Space Station laboratory. Emphasis has been placed on optical methods, primarily arising from the sensitivity of the phenomena of interest to intrusive probes. Limitations on available power, volume, data storage, and attendant expertise have motivated the use of solid-state sources and detectors, as well as efficient analysis capabilities emphasizing interactive data display and parameter control.

  9. NUMERICAL STUDY OF MICROPOLAR FLUID FLOW HEAT AND MASS TRANSFER OVER VERTICAL PLATE: EFFECTS OF THERMAL RADIATION AND MAGNETIC FIELD

    Directory of Open Access Journals (Sweden)

    REDHA ALOUAOUI

    2015-06-01

    Full Text Available In this paper, we examine the thermal radiation effect on heat and mass transfer in steady laminar boundary layer flow of an incompressible viscous micropolar fluid over a vertical flat plate, with the presence of a magnetic field. Rosseland approximation is applied to describe the radiative heat flux in the energy equation. The resulting similarity equations are solved numerically. Many results are obtained and representative set is displayed graphically to illustrate the influence of the various parameters on different profiles. The conclusion is drawn that the flow field, temperature, concentration and microrotation  as well as the skin friction coefficient and the both  local Nusselt and Sherwood numbers  are significantly influenced by Magnetic parameter, material parameter  and thermal radiation parameter.

  10. Stable field emission from arrays of vertically aligned free-standing metallic nanowires

    DEFF Research Database (Denmark)

    Xavier, S.; Mátéfi-Tempfli, Stefan; Ferain, E.

    2008-01-01

    the nanowire surface is developed to explain this particular field emission behaviour. Finally, we present an in situ cleaning procedure by ion bombardment that collectively removes this oxide layer, leading to a stable and reproducible emission behaviour. After treatment, the emission current density is ∼1 m...... fabrication and large surfaces. This technique offers an excellent control of the orientation, shape and nanowires density. It is applied to fabricate field emission arrays with a good control of the emission site density. We have prepared Co, Ni, Cu and Rh nanowires with a height of 3 μm, a diameter of 80 nm...... and a density of ∼10 cm. The electron field emission measurements and total energy distributions show that the as-grown nanowires exhibit a complex behaviour, first with emission activation under high field, followed by unstable emission. A model taking into account the effect of an oxide layer covering...

  11. Using micro-seismicity and seismic velocities to map subsurface geologic and hydrologic structure within the Coso geothermal field, California

    Science.gov (United States)

    Kaven, Joern Ole; Hickman, Stephen H.; Davatzes, Nicholas C.

    2012-01-01

    Geothermal reservoirs derive their capacity for fluid and heat transport in large part from faults and fractures. Micro-seismicity generated on such faults and fractures can be used to map larger fault structures as well as secondary fractures that add access to hot rock, fluid storage and recharge capacity necessary to have a sustainable geothermal resource. Additionally, inversion of seismic velocities from micro-seismicity permits imaging of regions subject to the combined effects of fracture density, fluid pressure and steam content, among other factors. We relocate 14 years of seismicity (1996-2009) in the Coso geothermal field using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. We utilize over 60,000 micro-seismic events using waveform cross-correlation to augment to expansive catalog of P- and S-wave differential travel times recorded at Coso. We further carry out rigorous uncertainty estimation and find that our results are precise to within 10s of meters of relative location error. We find that relocated micro-seismicity outlines prominent, through-going faults in the reservoir in some cases. We also find that a significant portion of seismicity remains diffuse and does not cluster into more sharply defined major structures. The seismic velocity structure reveals heterogeneous distributions of compressional (Vp) and shear (Vs) wave speed, with Vp generally lower in the main field when compared to the east flank and Vs varying more significantly in the shallow portions of the reservoir. The Vp/Vs ratio appears to outline the two main compartments of the reservoir at depths of -0.5 to 1.5 km (relative to sea-level), with a ridge of relatively high Vp/Vs separating the main field from the east flank. In the deeper portion of the reservoir this ridge is less prominent. Our results indicate that high-precision relocations of micro-seismicity can provide

  12. Effect of an external electric field on the propagation velocity of premixed flames

    KAUST Repository

    Sánchez-Sanz, Mario

    2015-01-01

    © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. There have been many experimental investigations into the ability of electric fields to enhance combustion by acting upon ion species present in flames [1]. In this work, we examine this phenomenon using a one-dimensional model of a lean premixed flame under the influence of a longitudinal electric field. We expand upon prior two-step chain-branching reaction laminar models with reactions to model the creation and consumption of both a positively-charged radical species and free electrons. Also included are the electromotive force in the conservation equation for ion species and the electrostatic form of the Maxwell equations in order to resolve ion transport by externally applied and internally induced electric fields. The numerical solution of these equations allows us to compute changes in flame speed due to electric fields. Further, the variation of key kinetic and transport parameters modifies the electrical sensitivity of the flame. From changes in flame speed and reactant profiles we are able to gain novel, valuable insight into how and why combustion can be controlled by electric fields.

  13. Formation of damage zone and seismic velocity variations during hydraulic stimulation: numerical modelling and field observations

    Science.gov (United States)

    Shalev, Eyal; Calò, Marco; Lyakhovsky, Vladimir

    2013-11-01

    During hydraulic stimulations, a complex interaction is observed between the injected flux and pressure, number and magnitude of induced seismic events, and changes in seismic velocities. In this paper, we model formation and propagation of damage zones and seismicity patterns induced by wellbore fluid injection. The model includes the coupling of poroelastic deformation and groundwater flow with damage evolution (weakening and healing) and its effect on the elastic and hydrologic parameters of crystalline rocks. Results show that three subsequent interactions occur during stimulation. (1) Injected flux-pressure interaction: typically, after a flux increase, the wellbore pressure also rises to satisfy the flux conditions. Thereafter, the elevated pore pressure triggers damage accumulation and seismic activity, that is, accompanied by permeability increase. As a result, wellbore pressure decreases retaining the target injected flux. (2) Wellbore pressure-seismicity interaction: damage processes create an elongated damage zone in the direction close to the main principal stress. The rocks within the damage zone go through partial healing and remain in a medium damage state. Damage that originates around the injection well propagates within the damage zone away from the well, raising the damage state of the already damaged rocks, and is followed by compaction and fast partial healing back to a medium damage state. This `damage wave' behaviour is associated with the injected flux changes only in early stages while fracture's height (h) is larger than its length (l). The ratio h/l controls the deformation process that is responsible for several key features of the damage zone. (3) Stress- and damage-induced variations of the seismic P-wave velocities (Vp). Vp gradually decreases as damage is accumulated and increases after rock failure as the shear stress is released and healing and compaction are dominant. Typically, Vp decreases within the damage zone and increases in

  14. Leading edge velocity field of an oscillating airfoil in compressible dynamic stall

    Science.gov (United States)

    Vandyken, R. D.; Chandrasekhara, M. S.

    1992-01-01

    Phase-averaged mean-velocity and turbulence data are obtained and analyzed for the leading-edge region of an oscillating airfoil under compressibility conditions. A two-component laser-Doppler velocimetry system was used to make the measurements. Results are compared for the two Mach numbers 0.3 and 0.4 at a reduced frequency of 0.05 with varying airfoil angles of attack. For a Mach number of 0.3, a separation bubble is present on the airfoil throughout the oscillation cycle and no dynamic stall occurs as the peak angle of attack is below the static stall angle. However, a slight imprint of vortical structures is seen in the shear layer enveloping the bubble at the top of the cycle, a result confirmed also by the vorticity contours and in agreement with the earlier stroboscopic schlieren studies. When the Mach number is 0.4, dynamic stall occurs with its origin in the break-up of the separation bubble. Turbulence intensities in the bubble were found to be very large.

  15. Effect of cavitation on velocity in the near-field of a diesel nozzle

    CERN Document Server

    Purwar, Harsh; Idlahcen, Saïd; Roze, Claude; Blaisot, Jean-Bernard; Meès, Loïc; Michard, Marc

    2016-01-01

    The entire process of atomization of the fuel in an internal combustion engine plays a very important role in determining the overall efficiency of these engines. A good atomization process could help the fuel to mix with the air properly leading to its efficient combustion, thereby reducing the emitted pollutants as well. The recent trend followed by the engineers focused on designing fuel injectors for more efficient atomization is to increase the atomization pressure while decreasing the nozzle orifice diameter. A consequence of this is the development of cavitation (formation of vapor cavities or bubbles in the liquid) inside the injector close to the nozzle. The main reason behind this is the sudden changes in the pressure inside the injector and these cavities or bubbles are usually formed where the pressure is relatively low.This work mainly focuses on studying the formation of cavitation and its effect on the velocity of the spray in the near nozzle region using asymmetrical transparent nozzle equippe...

  16. Velocity fields of a bed-load layer under a turbulent liquid flow

    CERN Document Server

    Penteado, Marcos Roberto Mendes

    2016-01-01

    The transport of sediments by a fluid flow is commonly found in nature and in industry. In nature, it is found in rivers, oceans, deserts, and other environments. In industry, it is found in petroleum pipelines conveying grains, in sewer systems, and in dredging lines, for example. This study investigates experimentally the transport of the grains of a granular bed sheared by a turbulent liquid flow. In our experiments, fully developed turbulent water flows were imposed over a flat granular bed of known granulometry. Under the tested conditions, the grains were transported as bed load, i.e., they became entrained by rolling and sliding over each other, forming a moving granular layer. The present experiments were performed close to incipient bed load, a case for which experimental data on grains velocities are scarce. Distinct from previous experiments, an entrance length assured that the water stream over the loose bed was fully developed. At different water flow rates, the moving layer was filmed using a hi...

  17. Estimation of a Plate Motion Model From the ITRF2014 Horizontal Velocity Field

    Science.gov (United States)

    Altamimi, Z.; Metivier, L.; Rebischung, P.; Rouby, H.; Collilieux, X.

    2016-12-01

    For various geodetic and geophysical applications, users need to have access to a Plate Motion Model (PMM) that is consistent with the ITRF2014 frame. The aim of this paper is to discriminate between the different possible approaches for determining a PMM from the horizontal velocities of a subset of the ITRF2014 sites away from plate boundaries, Glacial Isostatic Adjustment regions and other deformation zones. We show that it is necessary to include in the global inversion model of all plates, a translation rate vector between the ITRF2014 origin (long-term averaged center of mass of the Earth as sensed by SLR) and the center of tectonic plate motion. Although including that translation rate vector in our inversion model has statistically negligible impact on the estimated Euler poles, it should nevertheless be taken into account when using the ITRF2014 PMM. We additionally assess the impact of the site distribution (i.e. network effect) on both the estimated Euler poles and translation rate vector.

  18. Restricting the vertical and horizontal extent of the Field-of-View: Effects on manoeuvring performance

    NARCIS (Netherlands)

    Jansen, S.E.M.; Toet, A.; Delleman, N.J.

    2010-01-01

    It is known that Field-of-view restrictions affect distance estimation, postural equilibrium, and the ability to control heading. These are all important factors when manoeuvring on foot through complex structured environments. Although considerable research has been devoted to the horizontal

  19. Dark Matter Profiles in Dwarf Galaxies: A Statistical Sample Using High-Resolution Hα Velocity Fields from PCWI

    Science.gov (United States)

    Relatores, Nicole C.; Newman, Andrew B.; Simon, Joshua D.; Ellis, Richard; Truong, Phuongmai N.; Blitz, Leo

    2018-01-01

    We present high quality Hα velocity fields for a sample of nearby dwarf galaxies (log M/M⊙ = 8.4-9.8) obtained as part of the Dark Matter in Dwarf Galaxies survey. The purpose of the survey is to investigate the cusp-core discrepancy by quantifying the variation of the inner slope of the dark matter distributions of 26 dwarf galaxies, which were selected as likely to have regular kinematics. The data were obtained with the Palomar Cosmic Web Imager, located on the Hale 5m telescope. We extract rotation curves from the velocity fields and use optical and infrared photometry to model the stellar mass distribution. We model the total mass distribution as the sum of a generalized Navarro-Frenk-White dark matter halo along with the stellar and gaseous components. We present the distribution of inner dark matter density profile slopes derived from this analysis. For a subset of galaxies, we compare our results to an independent analysis based on CO observations. In future work, we will compare the scatter in inner density slopes, as well as their correlations with galaxy properties, to theoretical predictions for dark matter core creation via supernovae feedback.

  20. Absolute and convective instabilities of a film flow down a vertical fiber subjected to a radial electric field

    Science.gov (United States)

    Liu, Rong; Chen, Xue; Ding, Zijing

    2018-01-01

    We consider the motion of a gravity-driven flow down a vertical fiber subjected to a radial electric field. This flow exhibits rich dynamics including the formation of droplets, or beads, driven by a Rayleigh-Plateau mechanism modified by the presence of gravity as well as the Maxwell stress at the interface. A spatiotemporal stability analysis is performed to investigate the effect of electric field on the absolute-convective instability (AI-CI) characteristics. We performed a numerical simulation on the nonlinear evolution of the film to examine the transition from CI to AI regime. The numerical results are in excellent agreement with the spatiotemporal stability analysis. The blowup behavior of nonlinear simulation predicts the formation of touchdown singularity of the interface due to the effect of electric field. We try to connect the blowup behavior with the AI-CI characteristics. It is found that the singularities mainly occur in the AI regime. The results indicate that the film may have a tendency to form very sharp tips due to the enhancement of the absolute instability induced by the electric field. We perform a theoretical analysis to study the behaviors of the singularities. The results show that there exists a self-similarity between the temporal and spatial distances from the singularities.

  1. Vertical GPS ground motion rates in the Euro-Mediterranean region: New evidence of velocity gradients at different spatial scales along the Nubia-Eurasia plate boundary

    OpenAIRE

    Serpelloni, Enrico; Faccenna, Claudio; Spada, Giorgio; DONG Danan; Williams, Simon D.P.

    2013-01-01

    We use 2.5 to 14 years long position time series from >800 continuous Global Positioning System (GPS) stations to study vertical deformation rates in the Euro-Mediterranean region. We estimate and remove common mode errors in position time series using a principal component analysis, obtaining a significant gain in the signal-to-noise ratio of the displacements data. Following the results of a maximum likelihood estimation analysis, which gives a mean spectral index ~ −0.7, we adopt a power l...

  2. Vestibulo-Ocular Responses to Vertical Translation using a Hand-Operated Chair as a Field Measure of Otolith Function

    Science.gov (United States)

    Wood, S. J.; Campbell, D. J.; Reschke, M. F.; Prather, L.; Clement, G.

    2016-01-01

    The translational Vestibulo-Ocular Reflex (tVOR) is an important otolith-mediated response to stabilize gaze during natural locomotion. One goal of this study was to develop a measure of the tVOR using a simple hand-operated chair that provided passive vertical motion. Binocular eye movements were recorded with a tight-fitting video mask in ten healthy subjects. Vertical motion was provided by a modified spring-powered chair (swopper.com) at approximately 2 Hz (+/- 2 cm displacement) to approximate the head motion during walking. Linear acceleration was measured with wireless inertial sensors (Xsens) mounted on the head and torso. Eye movements were recorded while subjects viewed near (0.5m) and far (approximately 4m) targets, and then imagined these targets in darkness. Subjects also provided perceptual estimates of target distances. Consistent with the kinematic properties shown in previous studies, the tVOR gain was greater with near targets, and greater with vision than in darkness. We conclude that this portable chair system can provide a field measure of otolith-ocular function at frequencies sufficient to elicit a robust tVOR.

  3. Quantifying scaling in the velocity field of the anisotropic\\ud turbulent solar wind

    OpenAIRE

    Chapman, Sandra C.; Hnat, B.

    2007-01-01

    Solar wind turbulence is dominated by Alfvénic fluctuations with power spectral exponents that somewhat surprisingly evolve toward the Kolmogorov value of −5/3, that of hydrodynamic turbulence. We analyze in situ satellite observations at 1AU and show that the turbulence decomposes linearly into two coexistent components perpendicular and parallel to the local average magnetic field and determine their distinct intermittency independent scaling exponents. The first of these is consistent with...

  4. Correlation analysis of spatio-temporal images for estimating two-dimensional flow velocity field in a rotating flow condition

    Science.gov (United States)

    Yu, Kwonkyu; Kim, Seojun; Kim, Dongsu

    2015-10-01

    Flow velocity estimation in actual rivers using image processing technique has been highlighted for hydrometric communities in the last decades, and this technique is called Large Scale Particle Image Velocimetry (LSPIV). Although LSPIV has been successfully tested in many flow conditions, it has addressed several limitations estimating mean flow field because of difficult flow conditions such as rotating, lack of light and seeds, and noisy flow conditions. Recently, an alternative technique named STIV to use spatio-temporal images based on successively recorded images has been introduced to overcome the limitations of LSPIV. The STIV was successfully applied to obtain one-dimensional flow component in the river for estimating streamflow discharge, where the main flow direction is known. Using the 5th order of central difference scheme, the STIV directly calculated the mean angle of slopes which appeared as strips in the spatio-temporal images and has been proved to be more reliable and efficient for the discharge estimation as compared with the conventional LSPIV. However, yet it has not been sufficiently qualified to derive two-dimensional flow field in the complex flow, such as rotating or locally unsteady flow conditions. We deemed that it was because the strips in the given spatio-temporal images from not properly oriented for main flow direction are not narrow enough or clearly visible, thus the direct estimating strip slope could give erroneous results. Thereby, the STIV has been mainly applied for obtaining one-dimensional flow component. In this regard, we proposed an alternative algorithm to estimate the mean slope angle for enhancing the capability of the STIV, which used correlation coefficient between odd and even image splits from the given spatio-temporal image. This method was named CASTI (Correlation Analysis of Spatio-Temporal Image). This paper described the step-by-step procedure of the CASTI and validated its capability for estimating two

  5. Hydrogen-terminated diamond vertical-type metal oxide semiconductor field-effect transistors with a trench gate

    Energy Technology Data Exchange (ETDEWEB)

    Inaba, Masafumi, E-mail: inaba-ma@ruri.waseda.jp; Muta, Tsubasa; Kobayashi, Mikinori; Saito, Toshiki; Shibata, Masanobu; Matsumura, Daisuke; Kudo, Takuya; Hiraiwa, Atsushi [Graduate School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kawarada, Hiroshi [Graduate School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, 2-8-26 Nishiwaseda, Shinjuku, Tokyo 169-0051 (Japan)

    2016-07-18

    The hydrogen-terminated diamond surface (C-H diamond) has a two-dimensional hole gas (2DHG) layer independent of the crystal orientation. A 2DHG layer is ubiquitously formed on the C-H diamond surface covered by atomic-layer-deposited-Al{sub 2}O{sub 3}. Using Al{sub 2}O{sub 3} as a gate oxide, C-H diamond metal oxide semiconductor field-effect transistors (MOSFETs) operate in a trench gate structure where the diamond side-wall acts as a channel. MOSFETs with a side-wall channel exhibit equivalent performance to the lateral C-H diamond MOSFET without a side-wall channel. Here, a vertical-type MOSFET with a drain on the bottom is demonstrated in diamond with channel current modulation by the gate and pinch off.

  6. Hydrogen-terminated diamond vertical-type metal oxide semiconductor field-effect transistors with a trench gate

    Science.gov (United States)

    Inaba, Masafumi; Muta, Tsubasa; Kobayashi, Mikinori; Saito, Toshiki; Shibata, Masanobu; Matsumura, Daisuke; Kudo, Takuya; Hiraiwa, Atsushi; Kawarada, Hiroshi

    2016-07-01

    The hydrogen-terminated diamond surface (C-H diamond) has a two-dimensional hole gas (2DHG) layer independent of the crystal orientation. A 2DHG layer is ubiquitously formed on the C-H diamond surface covered by atomic-layer-deposited-Al2O3. Using Al2O3 as a gate oxide, C-H diamond metal oxide semiconductor field-effect transistors (MOSFETs) operate in a trench gate structure where the diamond side-wall acts as a channel. MOSFETs with a side-wall channel exhibit equivalent performance to the lateral C-H diamond MOSFET without a side-wall channel. Here, a vertical-type MOSFET with a drain on the bottom is demonstrated in diamond with channel current modulation by the gate and pinch off.

  7. Quantifying scaling in the velocity field of the anisotropic turbulent solar wind

    Science.gov (United States)

    Chapman, S. C.; Hnat, B.

    2007-09-01

    Solar wind turbulence is dominated by Alfvénic fluctuations with power spectral exponents that somewhat surprisingly evolve toward the Kolmogorov value of -5/3, that of hydrodynamic turbulence. We analyze in situ satellite observations at 1AU and show that the turbulence decomposes linearly into two coexistent components perpendicular and parallel to the local average magnetic field and determine their distinct intermittency independent scaling exponents. The first of these is consistent with recent predictions for anisotropic MHD turbulence and the second is closer to Kolmogorov-like scaling.

  8. Effects of light-load maximal lifting velocity weight training vs. combined weight training and plyometrics on sprint, vertical jump and strength performance in adult soccer players.

    Science.gov (United States)

    Rodríguez-Rosell, David; Torres-Torrelo, Julio; Franco-Márquez, Felipe; González-Suárez, José Manuel; González-Badillo, Juan José

    2017-07-01

    The purpose of this study was to compare the effects of combined light-load maximal lifting velocity weight training (WT) and plyometric training (PT) with WT alone on strength, jump and sprint performance in semiprofessional soccer players. Experimental, pre-post tests measures. Thirty adult soccer players were randomly assigned into three groups: WT alone (FSG, n=10), WT combined to jump and sprint exercises (COM, n=10) and control group (CG, n=10). WT consisted of full squat with low load (∼45-60% 1RM) and low volume (4-6 repetitions). Training program was performed twice a week for 6 weeks of competitive season in addition to 4 soccer sessions a week. Sprint time in 10 and 20m, jump height (CMJ), estimated one-repetition maximum (1RM est ) and velocity developed against different absolute loads in full squat were measured before and after training period. Both experimental groups showed significant improvements in 1RM est (17.4-13.4%; p<0.001), CMJ (7.1-5.2%; p<0.001), sprint time (3.6-0.7%; p<0.05-0.001) and force-velocity relationships (16.9-6.1%; p<0.05-0.001), whereas no significant gains were found in CG. No significant differences were found between FSG and COM. Despite FSG resulted of greater increases in strength variables than COM, this may not translate into superior improvements in the sport-related performance. In fact, COM showed higher efficacy of transfer of strength gains to sprint ability. Therefore, these findings suggest that a combined WT and PT program could represent a more efficient method for improving activities which involve acceleration, deceleration and jumps compared to WT alone. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  9. Image-guided spinal injection procedures in open high-field MRI with vertical field orientation: feasibility and technical features

    Energy Technology Data Exchange (ETDEWEB)

    Streitparth, F.; Walter, T.; Wonneberger, U.; Wagner, M.; Hermann, K.G.; Hamm, B.; Teichgraeber, U. [Charite, Humboldt-Universitaet zu Berlin, Department of Radiology, Berlin (Germany); Chopra, S. [Charite-Universitaetsmedizin Berlin, Campus Virchow Klinikum, Department of General, Visceral, and Transplantation Surgery, Berlin (Germany); Wichlas, F. [Charite-Universitaetsmedizin Berlin, Campus Virchow Klinikum, Center for Musculoskeletal Surgery, Berlin (Germany)

    2010-02-15

    We prospectively evaluated the feasibility and technical features of MR-guided lumbosacral injection procedures in open high-field MRI at 1.0 T. In a CuSO{sub 4}.5H{sub 2}O phantom and five human cadaveric spines, fluoroscopy sequences (proton-density-weighted turbo spin-echo (PDw TSE), T1w TSE, T2w TSE; balanced steady-state free precession (bSSFP), T1w gradient echo (GE), T2w GE) were evaluated using two MRI-compatible 20-G Chiba-type needles. Artefacts were analysed by varying needle orientation to B{sub 0}, frequency-encoding direction and slice orientation. Image quality was described using the contrast-to-noise ratio (CNR). Subsequently, a total of 183 MR-guided nerve root (107), facet (53) and sacroiliac joint (23) injections were performed in 53 patients. In vitro, PDw TSE sequence yielded the best needle-tissue contrasts (CNR = 45, 18, 15, 9, and 8 for needle vs. fat, muscle, root, bone and sclerosis, respectively) and optimal artefact sizes (width and tip shift less than 5 mm). In vivo, PDw TSE sequence was sufficient in all cases. The acquisition time of 2 s facilitated near-real-time MRI guidance. Drug delivery was technically successful in 100% (107/107), 87% (46/53) and 87% (20/23) of nerve root, facet and sacroiliac joint injections, respectively. No major complications occurred. The mean procedure time was 29 min (range 19-67 min). MR-guided spinal injections in open high-field MRI are feasible and accurate using fast TSE sequence designs. (orig.)

  10. Field estimates of floc dynamics and settling velocities in a tidal creek with significant along-channel gradients in velocity and SPM

    Science.gov (United States)

    Schwarz, C.; Cox, T.; van Engeland, T.; van Oevelen, D.; van Belzen, J.; van de Koppel, J.; Soetaert, K.; Bouma, T. J.; Meire, P.; Temmerman, S.

    2017-10-01

    A short-term intensive measurement campaign focused on flow, turbulence, suspended particle concentration, floc dynamics and settling velocities were carried out in a brackish intertidal creek draining into the main channel of the Scheldt estuary. We compare in situ estimates of settling velocities between a laser diffraction (LISST) and an acoustic Doppler technique (ADV) at 20 and 40 cm above bottom (cmab). The temporal variation in settling velocity estimated were compared over one tidal cycle, with a maximum flood velocity of 0.46 m s-1, a maximum horizontal ebb velocity of 0.35 m s-1 and a maximum water depth at high water slack of 2.41 m. Results suggest that flocculation processes play an important role in controlling sediment transport processes in the measured intertidal creek. During high-water slack, particles flocculated to sizes up to 190 μm, whereas at maximum flood and maximum ebb tidal stage floc sizes only reached up to 55 μm and 71 μm respectively. These large differences indicate that flocculation processes are mainly governed by turbulence-induced shear rate. In this study, we specifically recognize the importance of along-channel gradients that places constraints on the application of the acoustic Doppler technique due to conflicts with the underlying assumptions. Along-channel gradients were assessed by additional measurements at a second location and scaling arguments which could be used as an indication whether the Reynolds-flux method is applicable. We further show the potential impact of along-channel advection of flocs out of equilibrium with local hydrodynamics influencing overall floc sizes.

  11. A Unified Global Reference Frame of Vertical Crustal Movements by Satellite Laser Ranging

    Directory of Open Access Journals (Sweden)

    Xinhui Zhu

    2016-02-01

    Full Text Available Crustal movement is one of the main factors influencing the change of the Earth system, especially in its vertical direction, which affects people’s daily life through the frequent occurrence of earthquakes, geological disasters, and so on. In order to get a better study and application of the vertical crustal movement,as well as its changes, the foundation and prerequisite areto devise and establish its reference frame; especially, a unified global reference frame is required. Since SLR (satellite laser ranging is one of the most accurate space techniques for monitoring geocentric motion and can directly measure the ground station’s geocentric coordinates and velocities relative to the centre of the Earth’s mass, we proposed to take the vertical velocity of the SLR technique in the ITRF2008 framework as the reference frame of vertical crustal motion, which we defined as the SLR vertical reference frame (SVRF. The systematic bias between other velocity fields and the SVRF was resolved by using the GPS (Global Positioning System and VLBI (very long baseline interferometry velocity observations, and the unity of other velocity fields and SVRF was realized,as well. The results show that it is feasible and suitable to take the SVRF as a reference frame, which has both geophysical meanings and geodetic observations, so we recommend taking the SLR vertical velocity under ITRF2008 as the global reference frame of vertical crustal movement.

  12. The Effect of "Pumping" and "Nonpumping" Techniques on Velocity Production and Muscle Activity During Field-Based BMX Cycling.

    Science.gov (United States)

    Rylands, Lee P; Hurst, Howard T; Roberts, Simon J; Graydon, Robert W

    2017-02-01

    Rylands, LP, Hurst, HT, Roberts, SJ, and Graydon, RW. The effect of "pumping" and "nonpumping" techniques on velocity production and muscle activity during field-based BMX cycling. J Strength Cond Res 31(2): 445-450, 2017-The aim of the current study was to determine if a technique called "pumping" had a significant effect on velocity production in Bicycle Motocross (BMX) cycling. Ten National standard male BMX riders fitted with surface electromyography (sEMG) sensors completed a timed lap of an indoor BMX track using the technique of pumping, and a lap without pumping. The lap times were recorded for both trials and their surface sEMG was recorded to ascertain any variation in muscle activation of the biceps brachii, triceps brachii, vastus lateralis, and medial gastrocnemius. The findings revealed no significant differences between any of muscle groups (p > 0.05). However, significant differences (p muscle activity. From a physiological and technical perspective, coaches and riders should prioritize this technique when devising training regimes.

  13. Accurate Determination of Glacier Surface Velocity Fields with a DEM-Assisted Pixel-Tracking Technique from SAR Imagery

    Directory of Open Access Journals (Sweden)

    Shiyong Yan

    2015-08-01

    Full Text Available We obtained accurate, detailed motion distribution of glaciers in Central Asia by applying digital elevation model (DEM assisted pixel-tracking method to L-band synthetic aperture radar imagery. The paper firstly introduces and analyzes each component of the offset field briefly, and then describes the method used to efficiently and precisely compensate the topography-related offset caused by the large spatial baseline and rugged terrain with the help of DEM. The results indicate that the rugged topography not only forms the complex shapes of glaciers, but also affects the glacier velocity estimation, especially with large spatial baseline. The maximum velocity, 0.85 m∙d−1, was observed in the middle part on the Fedchenko Glacier, which is the world’s longest mountain glacier. The motion fluctuation on its main trunk is apparently influenced by mass flowing in from tributaries, as well as angles between tributaries and the main stream. The approach presented in this paper was proved to be highly appropriate for monitoring glacier motion and will provide valuable sensitive indicators of current and future climate change for environmental analysis.

  14. Integral Field Spectroscopy of Markarian 273: Mapping High-Velocity Gas Flows and an Off-Nucleus Seyfert 2 Nebula.

    Science.gov (United States)

    Colina; Arribas; Borne

    1999-12-10

    Integral field optical spectroscopy with the INTEGRAL fiber-based system is used to map the extended ionized regions and gas flows in Mrk 273, one of the closest ultraluminous infrared galaxies. The Hbeta and [O iii] lambda5007 maps show the presence of two distinct regions separated by 4&arcsec; (3.1 kpc) along position angle (P.A.) 240 degrees. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [O iii] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [O iii] ionized gas shows (1) the presence of highly disturbed gas in the regions around the LINER nucleus, (2) a high-velocity gas flow with a peak-to-peak amplitude of 2.4x103 km s-1, and (3) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst and that the quiescent gas is directly ionized by a nuclear source, similar to the ionization cones typically seen in Seyfert galaxies.

  15. InSAR, GPS, triangulation and EDM combination in a 3D velocity field: Insight from Arenal volcano

    Science.gov (United States)

    Muller, Cyril; del Potro, Rodrigo; Biggs, Juliet; Gottsmann, Joachim; Ebmeier, Susanna; Van der Laat, Rodolfo

    2014-05-01

    Geodetic techniques provide useful information to detect and assess geophysical processes occurring at volcanoes. When the deformation signal is large, standard analyses and modelling can be carried out. However, when surface movements are subtle and several processes occur simultaneously, stochastic and multi-techniques assessment is required. Here we present a methodology that combines GPS, triangulation, trilateration and InSAR in a 3D velocity surface without any prior specific source assumption. The methodology is in 5 steps: design of the geodetic monitoring network, acquisition and post-processing of deformation observations, spatial integration, time series computation and finally spatial and temporal measurement integration. We apply this methodology to Arenal volcano in Costa Rica and provide an unprecedented insight of the volcano's deformation. The most significant improvements of this method are the reduction of campaign logistics, the unambiguous detection of the outliers, an increase in accuracy, a 3D velocity field accounting for all techniques and measurements. Although, the methodology is applied to GPS, triangulation, trilateration and INSAR geodetic networks with a steady motion, it has the potential to be extended to other geodetic techniques and where transient deformations are ongoing. The described methodology can be applied in volcano monitoring worldwide.

  16. Dynamical properties for the problem of a particle in an electric field of wave packet: Low velocity and relativistic approach

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Diego F.M., E-mail: diegofregolente@gmail.com [Institute for Multiscale Simulations, Friedrich-Alexander Universität, D-91052, Erlangen (Germany); Leonel, Edson D., E-mail: edleonel@rc.unesp.br [Departamento de Estatística, Matemática Aplicada e Computação, UNESP, Univ. Estadual Paulista, Av. 24A, 1515, Bela Vista, 13506-900, Rio Claro, SP (Brazil); Departamento de Física, UNESP, Univ. Estadual Paulista, Av. 24A, 1515, 13506-900, Rio Claro, SP (Brazil)

    2012-11-01

    We study some dynamical properties for the problem of a charged particle in an electric field considering both the low velocity and relativistic cases. The dynamics for both approaches is described in terms of a two-dimensional and nonlinear mapping. The structure of the phase spaces is mixed and we introduce a hole in the chaotic sea to let the particles to escape. By changing the size of the hole we show that the survival probability decays exponentially for both cases. Additionally, we show for the relativistic dynamics, that the introduction of dissipation changes the mixed phase space and attractors appear. We study the parameter space by using the Lyapunov exponent and the average energy over the orbit and show that the system has a very rich structure with infinite family of self-similar shrimp shaped embedded in a chaotic region.

  17. Effects of Unsteady Flow Past An Infinite Vertical Plate With Variable ...

    African Journals Online (AJOL)

    The effects of unsteady flow past an infinite vertical plate with variable temperature and constant mass flux are investigated. Laplace transform technique is used to obtain velocity and concentration fields. The computation of the results indicates that the velocity profiles increase with increase in Grashof numbers, mass ...

  18. LARGE-EDDY SIMULATIONS OF A SEPARATION/REATTACHMENT BUBBLE IN A TURBULENT-BOUNDARY-LAYER SUBJECTED TO A PRESCRIBED UPPER-BOUNDARY, VERTICAL-VELOCITY PROFILE

    KAUST Repository

    Cheng, Wan

    2015-06-30

    We describe large-eddy simulations of turbulent boundary-layer flow over a flat plate at high Reynolds number in the presence of an unsteady, three-dimensional flow separation/reattachment bubble. The stretched-vortex subgrid-scale model is used in the main flow domain combined with a wall-model that is a two-dimensional extension of that developed by Chung & Pullin (2009). Flow separation and re-attachment of the incoming boundary layer is induced by prescribing wall-normal velocity distribution on the upper boundary of the flow domain that produces an adverse-favorable stream-wise pressure distribution at the wall. The LES predicts the distribution of mean shear stress along the wall including the interior of the separation bubble. Several properties of the separation/reattachment flow are discussed.

  19. Horizontal/vertical differences in range and upper/lower visual field differences in the midpoints of sensory fusion limits of oriented lines.

    Science.gov (United States)

    Grove, Philip M; Ono, Hiroshi

    2012-01-01

    O'Shea and Crassini (1982, Perception & Psychophysics 32 195-196) demonstrated that fusion persists for vertical lines with an orientation disparity of 8 degrees, but diplopia is experienced in simultaneously presented horizontal lines with the same disparity. They concluded that the neural fusion process fuses larger horizontal disparities than vertical disparities. Kertesz criticised their demonstration because it did not quantify the possible motor component associated with fusing their counter-rotated images. Krekling and Blika argued that the demonstrated anisotropy is due to a disparity bias in the visual system, owing to the temporalward tilt of corresponding vertical meridians. We addressed these criticisms with a novel stimulus and presentation protocol, that rendered compensatory cyclovergence eye movements unlikely and explored a wide range of orientation disparities. We confirmed O'Shea and Crassini's vertical/horizontal anisotropy in orientation fusion limits. In addition, our measurements of vertical lines showed that the distributions of fused responses as a function of orientation disparity in the upper and lower visual fields were shifted relative to each other. Therefore, the distributions of fusible orientation disparities are wider for vertical lines than horizontal lines and are relatively shifted as predicted if the fusional range is centred around the vertical horopter.

  20. Wind tunnel investigation of a 14 foot vertical axis windmill

    Science.gov (United States)

    Muraca, R. J.; Guillotte, R. J.

    1976-01-01

    A full scale wind tunnel investigation was made to determine the performance characteristics of a 14 ft diameter vertical axis windmill. The parameters measured were wind velocity, shaft torque, shaft rotation rate, along with the drag and yawing moment. A velocity survey of the flow field downstream of the windmill was also made. The results of these tests along with some analytically predicted data are presented in the form of generalized data as a function of tip speed ratio.

  1. Vertical electric sounding of selected Arctic and Antarctic soils: advances in express field investigation of the Cryosols

    Science.gov (United States)

    Abakumov, Evgeny

    2016-04-01

    Physical properties of the soils of the cold environments are underestimated. Soil and permafrost border and active layer thickness are the key classification indicators for the polar soils. That is why electrophysical research has been conducted with aim to determine the soil-permafrost layer heterogeneity and the depth of the uppermost permafrost layer on examples of selected plots in Antarctic region and Russian Arctic. The electric resistivity (ER) was measured directly in the soil profiles using the vertical electrical sounding (VERS) method, which provides data on the changes in the electrical resistivity throughout the profile from the soil surface without digging pits or drilling. This method allows dividing the soil layer vertically into genetic layers, which are different on main key properties and characteristics Different soil layers have different ER values, that is why the sharp changes in ER values in soil profile can be interpreted as results of transition of one horizon to another. In our study, the resistivity measurements were performed using four-electrode (AB + MN) arrays of the AMNB configuration with use of the Schlumberger geometry. A Landmapper ERM-03 instrument (Landviser, USA) was used for the VES measurements in this study. Electrodes were situated on the soil surface, distance between M and N was fixes, while distance from A to B were changed during the sounding. Vertical Electrical Resistivity Soundings (VERS) using Schlumberger array were carried out at stations, situated on the different plots of terrestrial ecosystems of Arctic and Antarctic. The resistance readings at every VERS point were automatically displayed on the digital readout screen and then written down on the field note book. The soils had been 'sounded' thoroughly and found to vary between 5 cm and 3-5 m in A-B distances. It was shown that use of VES methodology in soil survey is quite useful for identification of the permafrost depth without digging of soil pit. This

  2. Analysis of altimeter data jointly with seafloor electric data (vertically integrated velocity) and VCTD-yoyo data (detailed profiles of VCTD)

    Science.gov (United States)

    Tarits, Pascal D.; Menvielle, M.; Provost, C.; Filloux, J. H.

    1991-01-01

    We propose simultaneous analyses of the TOPEX/POSEIDON altimetry data, in situ data--mainly permanent seafloor electric recordings--and velocity, conductivity, temperature, density (VCTD)-yoyo data at several stations in areas of scientific interest. We are planning experiments in various areas of low and high energy levels. Several complementary and redundant methods will be used to characterize the ocean circulation and its short- and long-term variability. We shall emphasize long-term measurement using permanent stations. Our major initial objectives with the TOPEX/POSEIDON mission are the Confluence area in the Argentine Basin and the Circumpolar Antarctic Current. An early experiment was carried out in the Confluence zone in 1988 and 1990 (Confluence Principal Investigators, 1990) to prepare for an intensive phase later one. This intensive phase will include new types of instrumentation. Preliminary experiments will be carried out in the Mediterranean Sea (in 1991) and in the North Atlantic Ocean (in 1992, north of the Canary Islands) to test the new instrumentation.

  3. Using remotely sensed data to estimate river characteristics including water-surface velocity and discharge

    Science.gov (United States)

    Nelson, Jonathan M.; Kinzel, Paul J.; Legleiter, Carl; McDonald, Richard R.; Overstreet, Brandon; Conaway, Jeff

    2017-01-01

    This paper describes a project combining field studies and analyses directed at providing an assessment of the accuracy of remotely sensed methods for determining river characteristics such as velocity and discharge. In particular, we describe a remote sensing method for surface velocities using mid-wave thermal camera videography combined with image analysis. One of the critical problems in this work is determining a method for relating remotely measured water-surface velocities to vertically averaged velocities through a velocity index. We explore three similarity profiles that allow a relationship between surface and vertically averaged velocity to be found either using empirical results or simple roughness-to-depth ratios. To test the approaches we compare them in a situation where vertical structure is known over most of the flow depth through ADCP measurements. By determining best-fit profiles through the ADCP profiles, average values of the velocity index are found for the cross-sections where measurement were made. By comparing these to the predicted velocity indices from the three similarity profiles, we find that, although the differences between the various similarity profiles are substantial, they are smaller than differences associated with local nonuniformity and nonhydrostatic flow. Nevertheless, the velocity indices are accurate to about +/-5%, meaning that remotely sensed vertically averaged velocities can be computed to well within the current accuracy standard for such values when used for river gaging.

  4. A comparison of low-latitude cloud properties and their response to climate change in three AGCMs sorted into regimes using mid-tropospheric vertical velocity

    Energy Technology Data Exchange (ETDEWEB)

    Wyant, Matthew C.; Bretherton, Christopher S. [University of Washington, Department of Atmospheric Sciences, Box 351640, Seattle, WA (United States); Bacmeister, Julio T. [Goddard Spaceflight Center, NASA Global Modeling and Assimilation Office, Greenbelt, MD (United States); Kiehl, Jeffrey T. [National Center for Atmospheric Research, Boulder, CO (United States); Held, Isaac M.; Zhao, Ming [NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ (United States); Klein, Stephen A. [NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ (United States); Lawrence Livermore National Laboratory, The Atmospheric Science Division, Livermore, CA (United States); Soden, Brian J. [NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ (United States); University of Miami, Division of Meteorology and Physical Oceanography, Rosenstiel School of Marine and Atmospheric Science, Miami, FL (United States)

    2006-08-15

    Low-latitude cloud distributions and cloud responses to climate perturbations are compared in near-current versions of three leading U.S. AGCMs, the NCAR CAM 3.0, the GFDL AM2.12b, and the NASA GMAO NSIPP-2 model. The analysis technique of Bony et al. (Clim Dyn 22:71-86, 2004) is used to sort cloud variables by dynamical regime using the monthly mean pressure velocity {omega} at 500 hPa from 30S to 30N. All models simulate the climatological monthly mean top-of-atmosphere longwave and shortwave cloud radiative forcing (CRF) adequately in all {omega}-regimes. However, they disagree with each other and with ISCCP satellite observations in regime-sorted cloud fraction, condensate amount, and cloud-top height. All models have too little cloud with tops in the middle troposphere and too much thin cirrus in ascent regimes. In subsidence regimes one model simulates cloud condensate to be too near the surface, while another generates condensate over an excessively deep layer of the lower troposphere. Standardized climate perturbation experiments of the three models are also compared, including uniform SST increase, patterned SST increase, and doubled CO{sub 2} over a mixed layer ocean. The regime-sorted cloud and CRF perturbations are very different between models, and show lesser, but still significant, differences between the same model simulating different types of imposed climate perturbation. There is a negative correlation across all general circulation models (GCMs) and climate perturbations between changes in tropical low cloud cover and changes in net CRF, suggesting a dominant role for boundary layer cloud in these changes. For some of the cases presented, upper-level clouds in deep convection regimes are also important, and changes in such regimes can either reinforce or partially cancel the net CRF response from the boundary layer cloud in subsidence regimes. This study highlights the continuing uncertainty in both low and high cloud feedbacks simulated by GCMs

  5. Numerical modelling of temperature fields in the flow boiling liquid through a vertical minichannel with an enhanced heating surface

    Directory of Open Access Journals (Sweden)

    Hożejowska Sylwia

    2014-03-01

    Full Text Available The paper presents results of heat transfer research on flow boiling in a rectangular minichannel positioned vertically, with an enhanced surface. One of the channel walls was made of thin foil powered by direct current. This foil is enhanced on the side contacting fluid in the minichannel. It is possible to observe both surfaces of the minichannel through two openings covered with glass panes. One allows detecting temperature of the plain side of the foil by liquid crystal thermography. The opposite surface of the minichannel (from the enhanced side of the foil can be observed through the other glass pane. The observations of the flow structures allowed to calculate the void fraction for some cross-sections of selected two phase flow images. In mathematical modelling of the considered process stationary heat transfer in a glass pane, heating foil and boiling liquid can be described with Laplace equation, Poisson equation and energy equation, respectively. For completeness of the model a corresponding system of boundary conditions was given. The two-dimensional temperature fields of glass pane, heating foil and fluid was computed with the Trefftz method. The equalizing calculus used to smooth the measured data has reduced errors.

  6. Vertical distribution of heavy metals in soil profile in a seasonally waterlogging agriculture field in Eastern Ganges Basin.

    Science.gov (United States)

    Rajmohan, N; Prathapar, S A; Jayaprakash, M; Nagarajan, R

    2014-09-01

    The accumulation of heavy metals in soil and water is a serious concern due to their persistence and toxicity. This study investigated the vertical distribution of heavy metals, possible sources and their relation with soil texture in a soil profile from seasonally waterlogged agriculture fields of Eastern Ganges basin. Fifteen samples were collected at ~0.90-m interval during drilling of 13.11 mbgl and analysed for physical parameters (moisture content and grain size parameters: sand, silt, clay ratio) and heavy metals (Fe, Mn, Cr, Cu, Pb, Zn, Co, Ni and Cd). The average metal content was in the decreasing order of Fe > Mn > Cr > Zn > Ni > Cu > Co > Pb > Cd. Vertical distribution of Fe, Mn, Zn and Ni shows more or less similar trends, and clay zone records high concentration of heavy metals. The enrichment of heavy metals in clay zone with alkaline pH strongly implies that the heavy metal distributions in the study site are effectively regulated by soil texture and reductive dissolution of Fe and Mn oxy-hydroxides. Correlation coefficient analysis indicates that most of the metals correlate with Fe, Mn and soil texture (clay and silt). Soil quality assessment was carried out using geoaccumulation index (I(geo)), enrichment factor (EF) and contamination factor (CF). The enrichment factor values were ranged between 0.66 (Mn) and 2.34 (Co) for the studied metals, and the contamination factor values varied between 0.79 (Mn) and 2.55 (Co). Results suggest that the elements such as Cu and Co are categorized as moderate to moderately severe contamination, which are further confirmed by I(geo) values (0.69 for Cu and 0.78 for Co). The concentration of Ni exceeded the effects-range median values, and the biological adverse effect of this metal is 87%. The average concentration of heavy metals was compared with published data such as concentration of heavy metals in Ganga River sediments, Ganga Delta sediments and upper continental crust (UCC

  7. A Study into the Impact of Physical Structures on the Runway Velocity Field at the Atlantic City International Airport

    Science.gov (United States)

    King, David, Jr.; Manson, Russell; Trout, Joseph; Decicco, Nicholas; Rios, Manny

    2015-04-01

    Wake vortices are generated by airplanes in flight. These vortices decay slowly and may persist for several minutes after their creation. These vortices and associated smaller scale turbulent structures present a hazard to incoming flights. It is for this reason that incoming flights are timed to arrive after these vortices have dissipated. Local weather conditions, mainly prevailing winds, can affect the transport and evolution of these vortices; therefore, there is a need to fully understand localized wind patterns at the airport-sized mircoscale. Here we have undertaken a computational investigation into the impacts of localized wind flows and physical structures on the velocity field at Atlantic City International Airport. The simulations are undertaken in OpenFOAM, an open source computational fluid dynamics software package, using an optimized geometric mesh of the airport. Initial conditions for the simulations are based on historical data with the option to run simulations based on projected weather conditions imported from the Weather Research & Forcasting (WRF) Model. Sub-grid scale turbulence is modeled using a Large Eddy Simulation (LES) approach. The initial results gathered from the WRF Model simulations and historical weather data analysis are presented elsewhere.

  8. THE PHOTOMETRIC AND KINEMATIC STRUCTURE OF FACE-ON DISK GALAXIES. III. KINEMATIC INCLINATIONS FROM H{alpha} VELOCITY FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, David R. [NRC Herzberg Institute of Astrophysics, 5071 W Saanich Road, Victoria, BC V9E 2E7 (Canada); Bershady, Matthew A., E-mail: david.andersen@nrc-cnrc.gc.ca, E-mail: mab@astro.wisc.edu [Department of Astronomy, University of Wisconsin, 475 N Charter Street, Madison, WI 53706 (United States)

    2013-05-01

    Using the integral field unit DensePak on the WIYN 3.5 m telescope we have obtained H{alpha} velocity fields of 39 nearly face-on disks at echelle resolutions. High-quality, uniform kinematic data and a new modeling technique enabled us to derive accurate and precise kinematic inclinations with mean i{sub kin} = 23 Degree-Sign for 90% of these galaxies. Modeling the kinematic data as single, inclined disks in circular rotation improves upon the traditional tilted-ring method. We measure kinematic inclinations with a precision in sin i of 25% at 20 Degree-Sign and 6% at 30 Degree-Sign . Kinematic inclinations are consistent with photometric and inverse Tully-Fisher inclinations when the sample is culled of galaxies with kinematic asymmetries, for which we give two specific prescriptions. Kinematic inclinations can therefore be used in statistical ''face-on'' Tully-Fisher studies. A weighted combination of multiple, independent inclination measurements yield the most precise and accurate inclination. Combining inverse Tully-Fisher inclinations with kinematic inclinations yields joint probability inclinations with a precision in sin i of 10% at 15 Degree-Sign and 5% at 30 Degree-Sign . This level of precision makes accurate mass decompositions of galaxies possible even at low inclination. We find scaling relations between rotation speed and disk-scale length identical to results from more inclined samples. We also observe the trend of more steeply rising rotation curves with increased rotation speed and light concentration. This trend appears to be uncorrelated with disk surface brightness.

  9. Anomalous scaling of a passive scalar advected by a turbulent velocity field with finite correlation time and uniaxial small-scale anisotropy.

    Science.gov (United States)

    Jurcisinová, E; Jurcisin, M

    2008-01-01

    The influence of uniaxial small-scale anisotropy on the stability of the scaling regimes and on the anomalous scaling of the structure functions of a passive scalar advected by a Gaussian solenoidal velocity field with finite correlation time is investigated by the field theoretic renormalization group and operator product expansion within one-loop approximation. Possible scaling regimes are found and classified in the plane of exponents epsilon-eta , where epsilon characterizes the energy spectrum of the velocity field in the inertial range E proportional, variantk;{1-2epsilon} , and eta is related to the correlation time of the velocity field at the wave number k which is scaled as k;{-2+eta} . It is shown that the presence of anisotropy does not disturb the stability of the infrared fixed points of the renormalization group equations, which are directly related to the corresponding scaling regimes. The influence of anisotropy on the anomalous scaling of the structure functions of the passive scalar field is studied as a function of the fixed point value of the parameter u , which represents the ratio of turnover time of scalar field and velocity correlation time. It is shown that the corresponding one-loop anomalous dimensions, which are the same (universal) for all particular models with a concrete value of u in the isotropic case, are different (nonuniversal) in the case with the presence of small-scale anisotropy and they are continuous functions of the anisotropy parameters, as well as the parameter u . The dependence of the anomalous dimensions on the anisotropy parameters of two special limits of the general model, namely, the rapid-change model and the frozen velocity field model, are found when u-->infinity and u-->0 , respectively.

  10. Maximal aerobic velocity measured by the 5-min running field test on two different fitness level groups.

    Science.gov (United States)

    Berthon, P; Dabonneville, M; Fellmann, N; Bedu, M; Chamoux, A

    1997-12-01

    The aim of the study was to verify the validity and the accuracy of the 5-min running field test (5RFT) relatively to the classical treadmill test. Two groups of subjects were tested, the first one being made of sub-elite runners (G1, n = 18) and the second one of athletes of other individual or collective disciplines (G2, n = 23). To check the field technique, maximal aerobic velocity (vamax) and an approached VO2max calculated from vamax during the 5RFT were compared with the corresponding values directly determined during a treadmill test. vamax obtained on treadmill (vamax(t)) or during a 5RFT (vamax(5)) were significantly higher in G1 than in G2 (+3.7 km.h-1 and +3.6 km.h-1 among the test). In each group, the difference between vamax(t) and vamax(5) was not significant (19.4 +/- 1.0 vs 19.5 +/- 0.9 km.h-1 in G1; 15.7 +/- 2.2 vs 15.9 +/- 1.2 km.h-1 in G2). A significant correlation was found between vamax(t) and vamax(5) (slope = 0.92; r = 0.86 in G1; slope = 0.71; r = 0.84 in G2). In each group, the approached VO2max(5) was significantly higher than VO2max(t) (respectively 67.8 +/- 2.9 vs 63.7 +/- 3.5 in G1; 54.8 +/- 3.9 vs 52.0 +/- 3.2 ml.min-1.kg-1 in G2. Weak but significant correlations were found between VO2(t) and vamax(5) (r = 0.69 and r = 0.56 respectively in G1 and G2). In conclusion, the 5RFT allows to measure vamax accurately whatever the physical fitness of the subjects but more closely in runners than in non-runners. The low correlation between VO2max(t) and vamax(5) for both groups indicates that a vamax running field test is specific and cannot evaluate VO2max with reasonable accuracy whatever the group, runners or non-runners.

  11. Visualisation of the velocity field in a scaled water model for validation of numerical calculations for a powder fuelled boiler

    Energy Technology Data Exchange (ETDEWEB)

    Dumortier, Laurent [Luleaa Univ. of Technology (Sweden)

    2001-01-01

    Validation of numerical predictions of the flow field in a powder fired industry boiler by flow visualisation in a water model has been studied. The bark powder fired boiler at AssiDomaen Kraftliner in Piteaa has been used as a case study. A literature study covering modelling of combusting flows by water models and different flow visualisation techniques has been carried out. The main conclusion as regards the use of water models is that only qualitative information can be expected. As far as turbulent flow is assured in the model as well as the real furnace, the same Reynolds number is not required. Geometrical similarity is important but modelling of burner jets requires adaptation of the jet diameters in the model. Guidelines for this are available and are presented in the report. The review of visualisation techniques shows that a number of methods have been used successfully for validation of flow field predictions. The conclusion is that the Particle Image Velocimetry and Particle Tracking Velocimetry methods could be very suitable for validation purposes provided that optical access is possible. The numerical predictions include flow fields in a 1130 scale model of the AssiDomaen furnace with water flow as well as flow and temperature fields in the actual furnace. Two burner arrangements were considered both for the model and the actual furnace, namely the present configuration with four front burners and a proposed modification where an additional burner is positioned at a side wall below the other burners. There are many similarities between the predicted flow fields in the model and the full scale furnace but there are also some differences, in particular in the region above the burners and the effects of the low region re-circulation on the lower burner jets. The experiments with the water model have only included the arrangement with four front burners. There were problems determining the velocities in the jets and the comparisons with predictions are

  12. Phase-Contrast MRI measurements in intra-cranial aneurysms in-vivo of flow patterns, velocity fields and wall shear stress: A comparison with CFD

    Science.gov (United States)

    Boussel, Loic; Rayz, Vitaliy; Martin, Alastair; Acevedo-Bolton, Gabriel; Lawton, Michael T.; Higashida, Randall; Smith, Wade S.; Young, William L.; Saloner, David

    2010-01-01

    Evolution of intracranial aneurysms is known to be related to hemodynamic forces such as Wall Shear Stress (WSS) and Maximum Shear Stress (MSS). Estimation of these parameters can be performed using numerical simulations (computational fluid dynamics - CFD) but can also be directly measured with MRI using a time-dependent 3D phase-contrast sequence with encoding of each of the three components of the velocity vectors (7D-MRV). In order to study the accuracy of 7D-MRV in estimating these parameters in–vivo, in comparison with CFD, 7D-MRV and patient-specific CFD modeling was performed for three patients who had intracranial aneurysms. A visual and a quantitative analysis of the flow pattern and the distribution of velocities, MSS, and WSS were performed between the two techniques. Spearman's coefficients of correlation between the two techniques were 0.56 for the velocity field, 0.48 for MSS and 0.59 for WSS. Visual analysis and Bland-Altman plots showed a good agreement for flow pattern and velocities but large discrepancies for MSS and WSS. In conclusion, these results indicate that in-vivo 7D-MRV can be used to measure velocity flow fields and to estimate MSS and WSS but is not currently able to provide accurate quantification of these two last parameters. PMID:19161132

  13. Excellent scalability including self-heating phenomena of vertical-channel field-effect-diode type capacitor-less one transistor dynamic random access memory cell

    Science.gov (United States)

    Imamoto, Takuya; Endoh, Tetsuo

    2014-01-01

    The scalability study and the impact of the self-heating effect (SHE) on memory operation of the bulk vertical-channel field effect diode (FED) type capacitorless one transistor (1T) dynamic random access memory (DRAM) cell are investigated via device simulator for the first time. The vertical-channel FED type 1T-DRAM cell shows the excellent hold characteristics (100 ms at 358 K of ambient temperature) with large enough read current margin (1 µA/cell) even when silicon pillar diameter (D) is scaled down from 20 to 12 nm. It is also shown that by employing the vertical-channel FED type, maximum lattice temperature in the memory cell due to SHE (T_{\\text{L}}^{\\text{Max}}) can be suppressed to a negligible small value and only reach 300.6 from 300 K ambient temperature due to the low lateral electric field, while the vertical-channel bipolar junction transistor (BJT) type 1T-DRAM shows significant SHE (T_{\\text{L}}^{\\text{Max}} = 330.6 K). Moreover, this excellent thermal characteristic can be maintained even when D is scaled down from 20 to 12 nm.

  14. Auroral E-region electron density height profile modificationby electric field driven vertical plasma transport:some evidence in EISCAT CP-1 data statistics

    Directory of Open Access Journals (Sweden)

    T. Bösinger

    2004-03-01

    Full Text Available A model developed several years ago by Huuskonen et al. (1984 predicted that vertical transport of ions in the nocturnal auroral E-region ionosphere can shift the electron density profiles in altitude during times of sufficiently large electric fields. If the vertical plasma transport effect was to operate over a sufficiently long enough time, then the real height of the E-region electron maximum should be shifted some km upwards (downwards in the eastward (westward auroral electrojet, respectively, when the electric field is strong, exceeding, say, 50 mV/m. Motivated by these predictions and the lack of any experimental verification so far, we made use of the large database of the European Incoherent Scatter (EISCAT radar to investigate if the anticipated vertical plasma transport is at work in the auroral E-region ionosphere and thus to test the Huuskonen et al. (1984 model. For this purpose a new type of EISCAT data display was developed which enabled us to order a large number of electron density height profiles, collected over 16 years of EISCAT operation, according to the electric field magnitude and direction as measured at the same time at the radar's magnetic field line in the F-region. Our analysis shows some signatures in tune with a vertical plasma transport in the auroral E-region of the type predicted by the Huuskonen et al. model. The evidence brought forward is, however, not unambiguous and requires more rigorous analysis.

    Key words. Ionosphere (auroral ionosphere; plasma convection; electric fields and currents

  15. Analysis of thin film flow over a vertical oscillating belt with a second grade fluid

    Directory of Open Access Journals (Sweden)

    Taza Gul

    2015-06-01

    Full Text Available An analysis is performed to study the unsteady thin film flow of a second grade fluid over a vertical oscillating belt. The governing equation for velocity field with appropriate boundary conditions is solved analytically using Adomian decomposition method (ADM. Expressions for velocity field have been obtained. Optimal asymptotic method (OHAM has also been used for comparison. The effects of Stocks number, frequency parameter and pressure gradient parameters have been sketched graphically and discussed.

  16. Vertical shaft windmill

    Science.gov (United States)

    Grana, D. C.; Inge, S. V., Jr. (Inventor)

    1983-01-01

    A vertical shaft has several equally spaced blades mounted. Each blade consists of an inboard section and an outboard section skew hinged to the inboard section. The inboard sections automatically adjust their positions with respect to the fixed inboard sections with changes in velocity of the wind. This windmill design automatically governs the maximum rotational speed of shaft.

  17. Six years after the El Mayor-Cucapah earthquake: Transient far-field postseismic vertical motion observed by tide gauges and GPS

    Science.gov (United States)

    Smith-Konter, B. R.; Gonzalez-Ortega, J. A.; Merrifield, M. A.; Tong, X.; Sandwell, D. T.; Hardy, S.; Howell, S. M.

    2016-12-01

    On April 4, 2010, the El Mayor-Cucapah earthquake (Mw 7.2) ruptured a 120 km long set of faults of the southernmost San Andreas Fault System in northeastern Baja California, Mexico. Near-field coseismic GPS observations revealed up to 1.1 m of horizontal surface slip and 0.6 m of vertical subsidence at near-field stations. Early near-field InSAR and GPS time series postseismic observations also suggested several tens of centimeters of afterslip occurred within the first two years, however postseismic transients due to viscoelastic or poroelastic relaxation have also been offered as candidate models. Here we investigate the role of viscoelastic transients from six years of regional far-field ( 200 km from rupture) tide gauge and vertical GPS time series observations to further constrain postseismic deformation mechanisms. Vertical viscoelastic postseismic models of the El Mayor-Cucapah earthquake suggest alternating quadrants of uplift and subsidence straddling the rupture, with uplift to the north near the Salton Trough and subsidence to the west spanning the San Diego and Ensenada regions. These decaying transient motions are confirmed by both vertical postseismic GPS and tide gauge-altimetry observations, in both the near- and far fields. For example, tide gauge data in San Diego, which typically record vertical land motions on the order of a few millimeters per year, recorded nearly 30 mm of transient land subsidence over the first 3 years. We find that the magnitude and decay of far-field postseismic subsidence can be attributed to viscoelastic relaxation of the mantle assuming a temporally varying rheology; viscosities as low as 1017 Pa-s for at least the first 6-12 months, followed by an increasing viscosity on the order of 1018 Pa-s in the years following, best fit the data. While transient viscosity anomalies have been previously suggested from GPS data spanning the first 1.5 years following the earthquake [Pollitz et al., 2012], the combined results from

  18. Note: Development of a compact x-ray particle image velocimetry for measuring opaque flows. II. Three-dimensional velocity field reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Sung Yong [Center for Biofluid and Biomimic Research, Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyojadong, Pohang 790-784 (Korea, Republic of); Lee, Sang Joon [Center for Biofluid and Biomimic Research, Department of Mechanical Engineering, Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), San 31, Hyojadong, Pohang 790-784 (Korea, Republic of)

    2012-04-15

    An x-ray particle image velocimetry (PIV) system using a cone-beam type x-ray was developed. The field of view and the spatial resolution are 36 x 24.05 mm{sup 2} and 20 {mu}m, respectively. The three-dimensional velocity field was reconstructed by adopting the least squares minimum residue and simultaneous multiplicative algebraic reconstruction techniques. According to a simulation study with synthetic images, the reconstructions were acceptable with 7 projections and 50 iterations. The reconstructed and supplied flow rates differed by only about 6.49% in experimental verification. The x-ray tomographic PIV system would be useful for 3D velocity field information of opaque flows.

  19. Estimation of vector velocity

    DEFF Research Database (Denmark)

    2000-01-01

    Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...... estimator automatically compensates for the axial velocity, when determining the transverse velocity by using fourth order moments rather than second order moments. The estimation is optimized by using a lag different from one in the estimation process, and noise artifacts are reduced by using averaging...... of RF samples. Further, compensation for the axial velocity can be introduced, and the velocity estimation is done at a fixed depth in tissue to reduce spatial velocity dispersion....

  20. A Study of the Effect of the Fringe Fields on the Electrostatic Force in Vertical Comb Drives

    Directory of Open Access Journals (Sweden)

    Else Gallagher

    2014-10-01

    Full Text Available The equation that describes the relationship between the applied voltage and the resulting electrostatic force within comb drives is often used to assist in choosing the dimensions for their design. This paper re-examines how some of these dimensions—particularly the cross-sectional dimensions of the comb teeth—affect this relationship in vertical comb drives. The electrostatic forces in several vertical comb drives fabricated for this study were measured and compared to predictions made with four different mathematical models in order to explore the amount of complexity required within a model to accurately predict the electrostatic forces in the comb drives.

  1. Postseismic velocity changes following the 2010 Mw 7.1 Darfield earthquake, New Zealand, revealed by ambient seismic field analysis

    Science.gov (United States)

    Heckels, R. E. G.; Savage, M. K.; Townend, J.

    2018-01-01

    Quantifying seismic velocity changes following large earthquakes can provide insights into fault healing and reloading processes. This study presents temporal velocity changes detected following the September 2010 Mw 7.1 Darfield event in Canterbury, New Zealand. We use continuous waveform data from several temporary seismic networks lying on and surrounding the Greendale Fault, with a maximum inter-station distance of 156 km. Nine-component, day-long Green's functions were computed for frequencies between 0.1 and 1.0 Hz for continuous seismic records from immediately after the 4 September 2010 earthquake until 10 January 2011. Using the moving-window cross-spectral method seismic velocity changes were calculated. Over the study period, an increase in seismic velocity of 0.14 % ± 0.04 % was determined near the Greendale Fault, providing a new constraint on postseismic relaxation rates in the region. A depth analysis further showed that velocity changes were confined to the uppermost 5 km of the subsurface. We attribute the observed changes to postseismic relaxation via crack-healing of the Greendale Fault and throughout the surrounding region.

  2. Understanding the Structure of the Subsurface of the El Tatio Geyser field: A Velocity Model of the El Jefe Geyser from Ambient Seismic Noise

    Science.gov (United States)

    LongJohn, T.; Kelly, C.; Seats, K.; Lawrence, J.

    2013-12-01

    Hydrothermal system studies are important for geothermal energy exploration and geysers are also believed to be functional analogues of volcanoes. However, the mechanism of eruption and the characteristics of the plumbing system of most geysers are poorly understood given their subsurface location and sparse global distribution. An accurate acoustic velocity model could yield important insight into subsurface density and thermal variations in a geyser system. Passive seismic data was collected at El Jefe geyser in El Tatio Geyser Field, northern Chile during October of 2012. An array of 6 broadband seismometers and 51 high frequency geophones were deployed for ~1 week in a grid array with station spacing of 2-10 meters (geophones) and 3-50 meters (broadbands) centered around El Jefe Geyser. Using ambient seismic noise generated by the geyser system, I constructed a preliminary subsurface velocity model for El Jefe Geyser. As a result of the close station spacing, the seismic signals sampled shallow depths corresponding to high frequency waves. Coherent seismic records from different seismic station pairs were cross correlated to produce noise correlation functions (NCF). Adaptive covariance filtering and stacking techniques were utilized to amplify the signal of the NCFs and one-dimensional velocities between station pairs at varying depths were determined. Next, a tomographic inversion was done to interpolate between the one-dimensional velocities and produce a three-dimensional velocity model for the entire geyser area. From the velocity model, we can identify regions of low and high acoustic velocity that potentially represent water reservoirs and bedrock respectively.

  3. Experimental study of the possibility of reducing the resistance and unevenness of output field of velocities in flat diffuser channels with large opening angles

    Science.gov (United States)

    Dmitriev, S. S.; Vasil'ev, K. E.; Mokhamed, S. M. S. O.; Gusev, A. A.; Barbashin, A. V.

    2017-11-01

    In modern combined cycle gas turbines (CCGT), when designing the reducers from the output diffuser of a gas turbine to a boiler-utilizer, wide-angle diffusers are used, in which practically from the input a flow separation and transition to jet stream regime occurs. In such channels, the energy loss in the field of velocities sharply rise and the field of velocities in the output from them is characterized by considerable unevenness that worsens the heat transfer process in the first by motion tube bundles of the boiler-utilizer. The results of experimental research of the method for reducing the energy loss and alignment of the field of velocities at the output from a flat asymmetrical diffuser channel with one deflecting wall with the opening angle of 40° by means of placing inside the channel the flat plate parallel to the deflecting wall are presented in the paper. It is revealed that, at this placement of the plate in the channel, it has a chance to reduce the energy loss by 20%, considerably align the output field of velocities, and decrease the dynamic loads on the walls in the output cross-section. The studied method of resistance reduction and alignment of the fields of velocities in the flat diffuser channels was used for optimization of the reducer from the output diffuser of the gas turbine to the boiler-utilizer of CCGT of PGU-450T type of Kaliningrad Thermal Power Plant-2. The obtained results are evidence that the configuration of the reducer installed in the PGU-450T of Kaliningrad Thermal Power Plant-2 is not optimal. It follows also from the obtained data that working-off the reducer should be necessarily conducted by the test results of the channel consisting of the model of reducer with the model of boiler-utilizer installed behind it. Application of the method of alignment of output field of velocities and reducing the resistance in the wide-angle diffusers investigated in the work made it possible—when using the known model of diffusion

  4. Co-integration of nano-scale vertical- and horizontal-channel metal-oxide-semiconductor field-effect transistors for low power CMOS technology.

    Science.gov (United States)

    Sun, Min-Chul; Kim, Garam; Kim, Sang Wan; Kim, Hyun Woo; Kim, Hyungjin; Lee, Jong-Ho; Shin, Hyungcheol; Park, Byung-Gook

    2012-07-01

    In order to extend the conventional low power Si CMOS technology beyond the 20-nm node without SOI substrates, we propose a novel co-integration scheme to build horizontal- and vertical-channel MOSFETs together and verify the idea using TCAD simulations. From the fabrication viewpoint, it is highlighted that this scheme provides additional vertical devices with good scalability by adding a few steps to the conventional CMOS process flow for fin formation. In addition, the benefits of the co-integrated vertical devices are investigated using a TCAD device simulation. From this study, it is confirmed that the vertical device shows improved off-current control and a larger drive current when the body dimension is less than 20 nm, due to the electric field coupling effect at the double-gated channel. Finally, the benefits from the circuit design viewpoint, such as the larger midpoint gain and beta and lower power consumption, are confirmed by the mixed-mode circuit simulation study.

  5. Measurement of flow velocity fields in small vessel-mimic phantoms and vessels of small animals using micro ultrasonic particle image velocimetry (micro-EPIV)

    Energy Technology Data Exchange (ETDEWEB)

    Qian Ming; Niu Lili; Jiang Bo; Jin Qiaofeng; Jiang Chunxiang; Zheng Hairong [Paul C. Lauterbur Research Center for Biomedical Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen (China); Wang Yanping, E-mail: hr.zheng@siat.ac.c [Medical School of Jinan University, Guangzhou (China)

    2010-10-21

    Determining a multidimensional velocity field within microscale opaque fluid flows is needed in areas such as microfluidic devices, biofluid mechanics and hemodynamics research in animal studies. The ultrasonic particle image velocimetry (EchoPIV) technique is appropriate for measuring opaque flows by taking advantage of PIV and B-mode ultrasound contrast imaging. However, the use of clinical ultrasound systems for imaging flows in small structures or animals has limitations associated with spatial resolution. This paper reports on the development of a high-resolution EchoPIV technique (termed as micro-EPIV) and its application in measuring flows in small vessel-mimic phantoms and vessels of small animals. Phantom experiments demonstrate the validity of the technique, providing velocity estimates within 4.1% of the analytically derived values with regard to the flows in a small straight vessel-mimic phantom, and velocity estimates within 5.9% of the computationally simulated values with regard to the flows in a small stenotic vessel-mimic phantom. Animal studies concerning arterial and venous flows of living rats and rabbits show that the micro-EPIV-measured peak velocities within several cardiac cycles are about 25% below the values measured by the ultrasonic spectral Doppler technique. The micro-EPIV technique is able to effectively measure the flow fields within microscale opaque fluid flows.

  6. Vertical cross-spectral phases in neutral atmospheric flow

    DEFF Research Database (Denmark)

    Chougule, Abhijit S.; Mann, Jakob; Kelly, Mark C.

    2012-01-01

    The cross-spectral phases between velocity components at two heights are analyzed from observations at the Hovsore test site and from the field experiments under the Cooperative Atmosphere-Surface Exchange Study in 1999. These phases represent the degree to which turbulence sensed at one height...... leads (or lags) in time the turbulence sensed at the other height. The phase angle of the cross-wind component is observed to be significantly greater than the phase for the along-wind component, which in turn is greater than the phase for the vertical component. The cross-wind and along-wind phases...... increase with stream-wise wavenumber and vertical separation distance, but there is no significant change in the phase angle of vertical velocity, which remains close to zero. The phases are also calculated using a rapid distortion theory model and large-eddy simulation. The results from the models show...

  7. Rotating optical tubes for vertical transport of atoms

    Science.gov (United States)

    Al Rsheed, Anwar; Lyras, Andreas; Aldossary, Omar M.; Lembessis, Vassilis E.

    2016-12-01

    The classical dynamics of a cold atom trapped inside a vertical rotating helical optical tube (HOT) is investigated by taking also into account the gravitational field. The resulting equations of motion are solved numerically. The rotation of the HOT induces a vertical motion for an atom initially at rest. The motion is a result of the action of two inertial forces, namely, the centrifugal force and the Coriolis force. Both inertial forces force the atom to rotate in a direction opposite to that of the angular velocity of the HOT. The frequency and the turning points of the atom's global oscillation can be controlled by the value and the direction of the angular velocity of the HOT. However, at large values of the angular velocity of the HOT the atom can escape from the global oscillation and be transported along the axis of the HOT. In this case, the rotating HOT operates as an optical Archimedes' screw for atoms.

  8. MHD dissipative flow and heat transfer of Casson fluids due to metachronal wave propulsion of beating cilia with thermal and velocity slip effects under an oblique magnetic field

    Science.gov (United States)

    Akbar, Noreen Sher; Tripathi, D.; Bég, O. Anwar; Khan, Z. H.

    2016-11-01

    A theoretical investigation of magnetohydrodynamic (MHD) flow and heat transfer of electrically-conducting viscoplastic fluids through a channel is conducted. The robust Casson model is implemented to simulate viscoplastic behavior of fluids. The external magnetic field is oblique to the fluid flow direction. Viscous dissipation effects are included. The flow is controlled by the metachronal wave propagation generated by cilia beating on the inner walls of the channel. The mathematical formulation is based on deformation in longitudinal and transverse velocity components induced by the ciliary beating phenomenon with cilia assumed to follow elliptic trajectories. The model also features velocity and thermal slip boundary conditions. Closed-form solutions to the non-dimensional boundary value problem are obtained under physiological limitations of low Reynolds number and large wavelength. The influence of key hydrodynamic and thermo-physical parameters i.e. Hartmann (magnetic) number, Casson (viscoplastic) fluid parameter, thermal slip parameter and velocity slip parameter on flow characteristics are investigated. A comparative study is also made with Newtonian fluids (corresponding to massive values of plastic viscosity). Stream lines are plotted to visualize trapping phenomenon. The computations reveal that velocity increases with increasing the magnitude of Hartmann number near the channel walls whereas in the core flow region (center of the channel) significant deceleration is observed. Temperature is elevated with greater Casson parameter, Hartmann number, velocity slip, eccentricity parameter, thermal slip and also Brinkmann (dissipation) number. Furthermore greater Casson parameter is found to elevate the quantity and size of the trapped bolus. In the pumping region, the pressure rise is reduced with greater Hartmann number, velocity slip, and wave number whereas it is enhanced with greater cilia length.

  9. Study of Thermal-Field Emission Properties and Investigation of Temperature dependent Noise in the Emission Current form vertical Carbon nanotube emitters

    KAUST Repository

    Kolekar, Sadhu

    2017-05-05

    We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The real-time field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD), in order to understand the effect of temperature on electron emission spots in image morphology (as indicated by ring like structures) and electron emission spot intensity of the emitters. Moreover, the field electron emission images can be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 is 4.5x107 and, the actual number emitters per cm2 present for electron emission calculated from Atomic Force Microscopy (AFM) data is 1.2x1012. The measured Current-Voltage (I-V) characteristics obey the Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current are recorded at different temperatures and, temperature dependence of power spectral density obeys power law relation s(f)=I2/f2 with that of emission current and frequency.

  10. Development of site class and site coefficient maps of Semarang, Indonesia using field shear wave velocity data

    OpenAIRE

    Partono Windu; Irsyam Masyhur; Prabandiyani Retno Wardani Sri

    2017-01-01

    The new Indonesian National Code for seismic resistance design (SNI-03-1726-2012) issued recently utilizes seismic response spectra for the whole area of the country. Site class and site coefficient are two parameters needed for designing response spectra. Site class can be estimated using average standard penetration test (N-SPT), average shear wave velocity (Vs) and average un-drained shear strength (Su) of top 30 meter soil deposit. Site coefficients can be predicted using probabilistic se...

  11. Crustal velocity and strain rate fields in the Balearic Islands based on continuous GPS time series from the XGAIB network (2010-2013)

    Science.gov (United States)

    Sánchez-Alzola, Alberto; Sánchez, Carlos; Giménez, Jordi; Alfaro, Pedro; Gelabert, Bernadí; Borque, María J.; Gil, Antonio J.

    2014-12-01

    In this paper, we present a first estimation, using the GIPSY-OASIS software, of the crustal velocity and strain rate fields in the Balearic Islands (Spain), based on continuous GPS observations from the XGAIB network spanning the period 2010-2013. The XGAIB network consists of nine permanent, widely distributed stations that have operated continuously since 2010. In this paper, we describe the XGAIB network and the CGPS data processing and present our principle results in terms of the position time series and velocities of all of the sites, which were observed for more than three and a half years. In addition, strain tensors were estimated from the velocity field to obtain the first realistic crustal deformation model of the archipelago. The strains exhibit gradual variation across the Balearic Islands, from WNW-ESE extension in the southwest (Ibiza and Formentera) to NW-SE compression in the northeast (Menorca). These results constitute an advance in our knowledge of the tectonics of the western Mediterranean region.

  12. Vertical phase separation of 6,13-bis(triisopropylsilylethynyl) pentacene/poly(methyl methacrylate) blends prepared by electrostatic spray deposition for organic field-effect transistors

    Science.gov (United States)

    Onojima, Norio; Hara, Kazuhiro; Nakamura, Ayato

    2017-05-01

    Blend films composed of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) and poly(methyl methacrylate) (PMMA) were prepared by electrostatic spray deposition (ESD). ESD is considered as an intermediate process between dry and wet processes since the solvent present in small droplets can almost be evaporated before arriving at the substrate. Post-drying treatments with the time-consuming evaporation of residual solvents can be omitted. However, it is still not clear that a vertically phase-separated structure can be formed in the ESD process since the vertical phase separation of the blend films is associated with the solvent evaporation. In this study, we fabricated bottom-gate, top-contact organic field-effect transistors based on the blend films prepared by ESD and the devices exhibited transistor behavior with small hysteresis. This result demonstrates that the vertical phase separation of a blend film (upper TIPS pentacene active layer/bottom PMMA gate insulator) can occur in the facile one-step ESD process.

  13. Operation in the turbulent jet field of a linear array of multiple rectangular jets using a two-dimensional jet (Variation of mean velocity field

    Directory of Open Access Journals (Sweden)

    Fujita Shigetaka

    2016-01-01

    Full Text Available The mean flowfield of a linear array of multiple rectangular jets run through transversely with a two-dimensional jet, has been investigated, experimentally. The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle promoted the inward secondary flows strongly on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≅ 39 m / s was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (lh = 3.1 μm in diameter, dh = 0.6 mm effective length : dh / lh = 194 operated by the linearized constant temperature anemometers (DANTEC, and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a two-dimensional jet which run through transversely perpendicular to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets.

  14. Experimental analysis of turbulence effect in settling velocity of suspended sediments

    Directory of Open Access Journals (Sweden)

    H. Salinas–Tapia

    2008-01-01

    Full Text Available Settling velocities of sediment particles for different size ranges were measured in this work using PIV with the help of discriminatory filters. An experimental channel 10x15 cm cross section was used in order to obtain two set of turbulent characteristics corresponding with two different flow rates. The purpose was to analyze the effect of turbulence on the solids settling velocity. The technique allowed us to measure the individual settling velocity of the particles and the flow velocity field of the fluid. Capture and image analysis was performed with digital cameras (CCD using the software Sharp–provision PIV and the statistical cross correlation technique. Results showed that settling velocity of particles is affected by turbulence which enhances the fluid drag coefficient. Physical explanation of this phenomenon is related with the magnitude of the vertical fluctuating velocity of the fluid. However, more research is needed in order to define settling velocity formulas that takes into account this effect

  15. Detecting spectrally localized components of lunar tide-frequency in time-series of the electric field vertical component of the earth atmosphere boundary layer

    CERN Document Server

    Isakevich, V V; Isakevich, D V

    2016-01-01

    Using the signal eigenvectors and components analyser (Grunskaya L.V., Isakevich V.V., Isakevich D.V. the RF Utility Model Patent 116242 of 30.09.2011) made it possible to detect non-coherent complex-period components localized at lunar tide frequencies in the time-series of the electric field vertical component of the Earth atmosphere boundary layer. The detected components are unobservable by means of spectral analysis quadrature scheme. The probability of the detected effects being pseudo-estimates is not more than 0.00025

  16. Field tests with vertical perforated drain pipes used for beach protection at Southern Holmsland Barrier on the Danish North Sea Coast (half year report)

    DEFF Research Database (Denmark)

    Burcharth, Hans F.; Fredsøe, Jørgen

    In accordance with the agreement of 18 August 2004 between Skagen Innovation Center (SIC) and the Danish Governmental Coastal Authority (KDI) a field test with the purpose of demonstrating the efficiency of the SIC vertical drain method as a mean for coastal protecting was initiated in a meeting 24...... August 2004. The test period is three years after which a final report has to be presented. The report shall contain an evaluation of the drain system with respect to qualitative and quantitative efficiency and environmental impact, as well as a related comparison with conventional coastal protection...

  17. Field tests with vertical perforated drain pipes used for beach protection at Southern Holmsland Barrier on the Danish North Sea Coast

    DEFF Research Database (Denmark)

    Burcharth, Hans F.; Fredsøe, Jørgen

    In accordance with the agreement of 18 August 2004 between Skagen Innovation Center (SIC) and the Danish Governmental Coastal Authority (KDI) a field test with the purpose of demonstrating the efficiency of the SIC vertical drain method as a mean for coastal protecting was initiated in a meeting 24...... August 2004. The test period is three years after which a final report has to be presented. The report shall contain an evaluation of the drain system with respect to qualitative and quantitative fficiency and environmental impact, as well as a related comparison with conventional coastal protection...

  18. Time-Synchronized Continuous Wave Laser-Induced Fluorescence Velocity Measurements of a Diverging Cusped Field Thruster

    Science.gov (United States)

    2012-10-01

    comparator signal and raw emission plus fluorescence signal from the PMT are then fed into an SRS SR-250 Boxcar Averager Time-Sync CW-LIF Velocity...the comparator signal, the boxcar averager samples the PMT signal for a period of time defined by the gate width. The last sampled value of the PMT...signal is held until the next comparator trigger, at which point the boxcar averager re-samples and holds the PMT signal. Fig. 5 provides an example of

  19. Evidence for instability-waves in the velocity-field of a fully developed turbulent channel-flow

    Science.gov (United States)

    Hofbauer, M.

    1980-01-01

    The results from hot film measurements and quantitative visual investigations, performed in the turbulent flow of an oil-channel at a low Reynolds number (Re = 8000), are discussed. The main result of the hot film measurements is the power spectrum of the v-component of the fluctuating velocity. The power spectrum has regular maxima and minima. The frequencies corresponding to the maxima of the power spectrum are plotted as a function of the order n of the maxima. This graph demonstrates that the frequencies of the maxima are the harmonics of a fundamental frequency which are determined to be about 0.15 Hz. An estimation shows that the fundamental frequency is of the same order of magnitude as the roughly calculated unstable Tollmien-Schlichting frequencies of the mean turbulent velocity profile. This fundamental frequency is interpreted as the most excited frequency of Tollmien-Schlichting-like instability waves. The harmonics are believed to be due to a nonlinear amplification of the primarily excited instability waves. The evidence of regular oscillations in the near-wall region of the fully developed turbulent flow from the visual studies is examined.

  20. Field measurements of the atmospheric dry deposition fluxes and velocities of polycyclic aromatic hydrocarbons to the global oceans.

    Science.gov (United States)

    González-Gaya, Belén; Zúñiga-Rival, Javier; Ojeda, María-José; Jiménez, Begoña; Dachs, Jordi

    2014-05-20

    The atmospheric dry deposition fluxes of 16 polycyclic aromatic hydrocarbons (PAHs) have been measured, for the first time, in the tropical and subtropical Atlantic, Pacific, and Indian Oceans. Depositional fluxes for fine (0.7-2.7 μm) and coarse (>2.7 μm) aerosol fractions were simultaneously determined with the suspended aerosol phase concentrations, allowing the determination of PAH deposition velocities (vD). PAH dry deposition fluxes (FDD) bound to coarse aerosols were higher than those of fine aerosols for 83% of the measurements. Average FDD for total (fine + coarse) Σ16PAHs (sum of 16 individual PAHs) ranged from 8.33 ng m(-2)d(-1) to 52.38 ng m(-2)d(-1). Mean FDD for coarse aerosol's individual PAHs ranged between 0.13 ng m(-2)d(-1) (Perylene) and 1.96 ng m(-2)d(-1) (Methyl Pyrene), and for the fine aerosol fraction these ranged between 0.06 ng m(-2)d(-1) (Dimethyl Pyrene) and 1.25 ng m(-2)d(-1) (Methyl Chrysene). The estimated deposition velocities went from the highest mean vD for Methyl Chrysene (0.17-13.30 cm s(-1)), followed by Dibenzo(ah)Anthracene (0.29-1.38 cm s(-1)), and other high MW PAHs to minimum values of vD for Dimethyl Pyrene (oceans.

  1. Pulsejet engine dynamics in vertical motion using momentum conservation

    OpenAIRE

    Cheche, Tiberius O.

    2017-01-01

    The momentum conservation law is applied to analyse the dynamics of pulsejet engine in vertical motion in a uniform gravitational field in the absence of friction. The model predicts existence of a terminal speed given frequency of the short pulses. The conditions that the engine does not return to the starting position are identified. The number of short periodic pulses after which the engine returns to the starting position is found to be independent of the exhaust velocity and gravitationa...

  2. A simple method for assessment and minimization of errors in determination of electrophoretic or electroosmotic mobilities and velocities associated with the axial electric field distortion.

    Science.gov (United States)

    Nowak, Paweł Mateusz; Woźniakiewicz, Michał; Kościelniak, Paweł

    2015-12-01

    It is commonly accepted that the modern CE instruments equipped with efficient cooling system enable accurate determination of electrophoretic or electroosmotic mobilities. It is also often assumed that velocity of migration in a given buffer is constant throughout the capillary length. It is simultaneously neglected that the noncooled parts of capillary produce extensive Joule heating leading to an axial electric field distortion, which contributes to a difference between the effective and nominal electric field potentials and between velocities in the cooled and noncooled parts of capillary. This simplification introduces systematic errors, which so far were however not investigated experimentally. There was also no method proposed for their elimination. We show a simple and fast method allowing for estimation and elimination of these errors that is based on combination of a long-end and short-end injections. We use it to study the effects caused by variation of temperature, electric field, capillary length, and pH. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Drift velocity of charged particles in magnetic fields and its relation to the direction of the source current

    Science.gov (United States)

    Essén, Hanno; Nordmark, Arne B.

    2016-10-01

    Integrable motion of charged particles in magnetic fields produced by stationary current distributions is investigated. We treat motion in the magnetic field from an infinite flat current sheet, a Harris current sheath, an infinite rectilinear current, and a dipole in its equatorial plane. We find that positively charged particles as a rule will drift in the same direction as the current that is the source of the magnetic field in question. The conclusion is that charged particles moving under the influence of current distributions tend to enhance the current and that this indicates current self-amplification.

  4. Numerical calculation of gas and liquid velocities along a vertical flat plate immersed in turbulent tow-phase bubbly flow. Kihoryuchu ni okareta suichoku heiban mawari no ranryu kieki 2 soryu ni kansuru suchi kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Matsuura, A.; Nakamura, H. (Daido Inst. of Technology, Nagoya (Japan)); Hiraoka, S.; Tada, Y.; Kato, Y. (Nagoya Inst. of Tech. (Japan))

    1993-11-10

    A numerical calculation was made on the bubbly flow using the Prandtl's mixing length theory. The calculation results agreed well with the experimental results in the turbulent flow rather than in the laminar flow. The necessity of discussion on the turbulent flow analysis was clarified. It was elucidated that the experimental results could be explained sufficiently even by the simplest mixing model. The liquid phase velocity vector was aligned on the same direction when the bubbly flow length exceeded 1 cm, and little change took place in the velocity distribution shape. In the analysis of laminar flow, the velocity boundary layer was developed together with tie bubbly flow length, while in the analysis of turbulent flow, such change did not take place. The liquid phase velocity in the vicinity of the inlet had a velocity component which directed to the outside of the wall at the wall side. It was quite different from the analytical result of the laminar flow. The gas phase velocity vector behaved in the similar way to the liquid phase. The velocity direction at the periphery of the velocity distribution in the vicinity of tie inlet was toward the wall surface, and the inlet velocity was rapidly accelerated. 12 refs., 4 figs.

  5. Finite Difference Study of MHD Stokes Problem for a Vertical Infinite ...

    African Journals Online (AJOL)

    The explicit finite difference method is employed to study the effects of both the Hall and ionslip currents on a free convective flow of a viscous heat generating rotating fluid past an impulsively started infinite vertical plate, to which a strong magnetic field is applied perpendicularly. The velocity (both primary and secondary) ...

  6. Electrical guidance efficiency of downstream-migrating juvenile Sea Lamprey decreases with increasing water velocity

    Science.gov (United States)

    Miehls, Scott M.; Johnson, Nicholas; Haro, Alexander

    2017-01-01

    We tested the efficacy of a vertically oriented field of pulsed direct current (VEPDC) created by an array of vertical electrodes for guiding downstream-moving juvenile Sea Lampreys Petromyzon marinus to a bypass channel in an artificial flume at water velocities of 10–50 cm/s. Sea Lampreys were more likely to be captured in the bypass channel than in other sections of the flume regardless of electric field status (on or off) or water velocity. Additionally, Sea Lampreys were more likely to be captured in the bypass channel when the VEPDC was active; however, an interaction between the effects of VEPDC and water velocity was observed, as the likelihood of capture decreased with increases in water velocity. The distribution of Sea Lampreys shifted from right to left across the width of the flume toward the bypass channel when the VEPDC was active at water velocities less than 25 cm/s. The VEPDC appeared to have no effect on Sea Lamprey distribution in the flume at water velocities greater than 25 cm/s. We also conducted separate tests to determine the threshold at which Sea Lampreys would become paralyzed. Individuals were paralyzed at a mean power density of 37.0 µW/cm3. Future research should investigate the ability of juvenile Sea Lampreys to detect electric fields and their specific behavioral responses to electric field characteristics so as to optimize the use of this technology as a nonphysical guidance tool across variable water velocities.

  7. VELOCITY ANISOTROPY IN THE NIGER VDELTTXFSEDIMENTS ...

    African Journals Online (AJOL)

    Keywords: Intrinsic velocity anisotropy, Niger Delta, Thomsen's parameters, vertical i transverse isotropy (VT!) Introduction. In seismology, a layer is anisotropic if seismic waves propagate through it at different velocities in different directions. Sedimentary rocks possess some degree of intrinsic velocity anisotropy (Jones and.

  8. Characterization of vertical GaN p-n diodes and junction field-effect transistors on bulk GaN down to cryogenic temperatures

    Science.gov (United States)

    Kizilyalli, I. C.; Aktas, O.

    2015-12-01

    There is great interest in wide-bandgap semiconductor devices and most recently in vertical GaN structures for power electronic applications such as power supplies, solar inverters and motor drives. In this paper the temperature-dependent electrical behavior of vertical GaN p-n diodes and vertical junction field-effect transistors fabricated on bulk GaN substrates of low defect density (104 to 106 cm-2) is described. Homoepitaxial MOCVD growth of GaN on its native substrate and the ability to control the doping in the drift layers in GaN have allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 μm and net carrier electron concentrations as low as 1 × 1015 cm-3. This parameter range is suitable for applications requiring breakdown voltages of 1.2 kV to 5 kV. Mg, which is used as a p-type dopant in GaN, is a relatively deep acceptor (E A ≈ 0.18 eV) and susceptible to freeze-out at temperatures below 200 K. The loss of holes in p-GaN has a deleterious effect on p-n junction behavior, p-GaN contacts and channel control in junction field-effect transistors at temperatures below 200 K. Impact ionization-based avalanche breakdown (BV > 1200 V) in GaN p-n junctions is characterized between 77 K and 423 K for the first time. At higher temperatures the p-n junction breakdown voltage improves due to increased phonon scattering. A positive temperature coefficient in the breakdown voltage is demonstrated down to 77 K; however, the device breakdown characteristics are not as abrupt at temperatures below 200 K. On the other hand, contact resistance to p-GaN is reduced dramatically above room temperature, improving the overall device performance in GaN p-n diodes in all cases except where the n-type drift region resistance dominates the total forward resistance. In this case, the electron mobility can be deconvolved and is found to decrease with T -3/2, consistent with a phonon scattering model. Also, normally-on vertical junction

  9. Role of work function in field emission enhancement of Au island decorated vertically aligned ZnO nanotapers

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Avanendra [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India); Senapati, Kartik, E-mail: kartik@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India); Kumar, Mohit; Som, Tapobrata [SUNAG Laboratory, Institute of Physics, Bhubaneswar 751005, Odisha (India); Sinha, Anil K. [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India); Sahoo, Pratap K., E-mail: pratap.sahoo@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India)

    2017-07-31

    Highlights: • Hydrothermally synthesized nanotapers were decorated by gold corrugation using simple evaporation techniques for large area applications. • A significantly enhanced field emission properties of nanotapers were achieved. • The metal induced midgap states formed at the ZnO-Au interface and the reduced effective work function are responsible for low turn-on field. • TUNA measurements revealed a very uniform spatial emission profile in the Au decorated nanotapers. - Abstract: In this report, we demonstrate significantly enhanced field emission properties of ZnO nanotapers achieved via a corrugated decoration of Au. Field emission experiments on these Au-decorated ZnO nanotapers showed emission current densities comparable to the best results in the literature. Au decoration of 5 nm also reduced the effective turn-on field to ∼0.54 V/μm, compared to the as grown ZnO nanotapers, which showed a turn-on field of ∼1.1 V/μm. Tunneling atomic force microscopy measurements revealed a very uniform spatial emission profile in the 5 nm Au decorated nanotapers, which is a basic requirement for any large scale application. We believe that metal induced mid-gap states formed at the ZnO–Au interface are responsible for the observed low turn-on field because such interface states are known to reduce the effective work function. A direct measurement of effective work function using Kelvin probe force microscopy indeed showed more than 1.1 eV drop in the case of 5 nm Au decorated ZnO nanotapers compared to the pristine nanotapers, supporting the above argument.

  10. The relationship between running speed and measures of vertical jump in professional basketball players: a field-test approach.

    Science.gov (United States)

    Shalfawi, Shaher A I; Sabbah, Ammar; Kailani, Ghazi; Tønnessen, Espen; Enoksen, Eystein

    2011-11-01

    The purpose of this study was to examine the relationship between vertical jump measures and sprint speed over 10, 20, and 40 m in professional basketball players. Thirty-three professional basketball players aged (±SD) (27.4 ± 3.3 years), body mass (89.8 ± 11.1 kg), and stature (192 ± 8.2 cm) volunteered to participate in this study. All participants were tested on squat jump, countermovement jump, and 40-m running speed. The results show that all jump measures in absolute terms were correlated significantly to running performance over 10-, 20-, and 40-m sprint times. None of the jumping performance peak powers and reactive strength were found to have a correlation to running speed times in absolute term. Furthermore, all jump height measures relative to body mass except reactive strength had a marked and significant relationship with all sprint performance times. The results of this study indicate that while there is a strong and marked relationship between 10-, 20-, and 40-m sprint, there is also a considerable variation within the factors that contribute to performance over these distances. This may indicate that, separate training strategies could be implemented to improve running speed over these distances.

  11. Role of work function in field emission enhancement of Au island decorated vertically aligned ZnO nanotapers

    Science.gov (United States)

    Singh, Avanendra; Senapati, Kartik; Kumar, Mohit; Som, Tapobrata; Sinha, Anil K.; Sahoo, Pratap K.

    2017-07-01

    In this report, we demonstrate significantly enhanced field emission properties of ZnO nanotapers achieved via a corrugated decoration of Au. Field emission experiments on these Au-decorated ZnO nanotapers showed emission current densities comparable to the best results in the literature. Au decoration of 5 nm also reduced the effective turn-on field to ∼0.54 V/μm, compared to the as grown ZnO nanotapers, which showed a turn-on field of ∼1.1 V/μm. Tunneling atomic force microscopy measurements revealed a very uniform spatial emission profile in the 5 nm Au decorated nanotapers, which is a basic requirement for any large scale application. We believe that metal induced mid-gap states formed at the ZnO-Au interface are responsible for the observed low turn-on field because such interface states are known to reduce the effective work function. A direct measurement of effective work function using Kelvin probe force microscopy indeed showed more than 1.1 eV drop in the case of 5 nm Au decorated ZnO nanotapers compared to the pristine nanotapers, supporting the above argument.

  12. GPS Imaging of vertical land motion in California and Nevada: Implications for Sierra Nevada uplift

    Science.gov (United States)

    Hammond, William C.; Blewitt, Geoffrey; Kreemer, Corné

    2016-10-01

    We introduce Global Positioning System (GPS) Imaging, a new technique for robust estimation of the vertical velocity field of the Earth's surface, and apply it to the Sierra Nevada Mountain range in the western United States. Starting with vertical position time series from Global Positioning System (GPS) stations, we first estimate vertical velocities using the MIDAS robust trend estimator, which is insensitive to undocumented steps, outliers, seasonality, and heteroscedasticity. Using the Delaunay triangulation of station locations, we then apply a weighted median spatial filter to remove velocity outliers and enhance signals common to multiple stations. Finally, we interpolate the data using weighted median estimation on a grid. The resulting velocity field is temporally and spatially robust and edges in the field remain sharp. Results from data spanning 5-20 years show that the Sierra Nevada is the most rapid and extensive uplift feature in the western United States, rising up to 2 mm/yr along most of the range. The uplift is juxtaposed against domains of subsidence attributable to groundwater withdrawal in California's Central Valley. The uplift boundary is consistently stationary, although uplift is faster over the 2011-2016 period of drought. Uplift patterns are consistent with groundwater extraction and concomitant elastic bedrock uplift, plus slower background tectonic uplift. A discontinuity in the velocity field across the southeastern edge of the Sierra Nevada reveals a contrast in lithospheric strength, suggesting a relationship between late Cenozoic uplift of the southern Sierra Nevada and evolution of the southern Walker Lane.

  13. GPS Imaging of vertical land motion in California and Nevada: Implications for Sierra Nevada uplift.

    Science.gov (United States)

    Hammond, William C; Blewitt, Geoffrey; Kreemer, Corné

    2016-10-01

    We introduce Global Positioning System (GPS) Imaging, a new technique for robust estimation of the vertical velocity field of the Earth's surface, and apply it to the Sierra Nevada Mountain range in the western United States. Starting with vertical position time series from Global Positioning System (GPS) stations, we first estimate vertical velocities using the MIDAS robust trend estimator, which is insensitive to undocumented steps, outliers, seasonality, and heteroscedasticity. Using the Delaunay triangulation of station locations, we then apply a weighted median spatial filter to remove velocity outliers and enhance signals common to multiple stations. Finally, we interpolate the data using weighted median estimation on a grid. The resulting velocity field is temporally and spatially robust and edges in the field remain sharp. Results from data spanning 5-20 years show that the Sierra Nevada is the most rapid and extensive uplift feature in the western United States, rising up to 2 mm/yr along most of the range. The uplift is juxtaposed against domains of subsidence attributable to groundwater withdrawal in California's Central Valley. The uplift boundary is consistently stationary, although uplift is faster over the 2011-2016 period of drought. Uplift patterns are consistent with groundwater extraction and concomitant elastic bedrock uplift, plus slower background tectonic uplift. A discontinuity in the velocity field across the southeastern edge of the Sierra Nevada reveals a contrast in lithospheric strength, suggesting a relationship between late Cenozoic uplift of the southern Sierra Nevada and evolution of the southern Walker Lane.

  14. New GPS velocity field in the northern Andes (Ecuador - Colombia) : partial locking along the subduction and northeastward escape of the Northern Andean Block

    Science.gov (United States)

    Nocquet, Jean-Mathieu; Mothes, Patricia; Mohamed, Chlieh; Jarrin, Paul; Martin, Vallee; Rui, Gorki; Regnier, Marc

    2010-05-01

    Rapid subduction of the Nazca plate beneath the Ecuador-Colombia margin (~58 mm/yr) results in two different processes: (1) elastic stress is accumulating along the Nazca/South America plate interface which is responsible of one of the largest megathrust earthquake sequence during the last century (1906, Mw = 8.8, 1942 Mw = 7.8, 1958 Mw = 7.7, and 1979 Mw = 8.2) (2) the Northern Andean Block (NAB) moves northeastward with respect to Stable South America. However, kinematics of the NAB and its level of internal deformation has yet to be quantified. We present a new GPS velocity field covering the northern Andes from south of the Gulf of Guyaquil to the Carribean plate. Our velocity field includes new continuously-recording GPS stations installed along the Ecuadorian coast, together with campaign sites observed since 1994. The observed velocity field confirms that the current surface deformation results from the superimposition of a NNE motion the crustal North Andean Block occurring at ~8 mm/yr and the elastic deformation induced by partial locking of the subduction interface. We first estimate the long-term kinematics of the North Andean block in a joint inversion including GPS data, earthquake slip vectors and quaternary slip rates on major faults. The inversion provides an Euler pole located at long. -107.8°E, lat. 36.2°N, 0.091°/Ma and indicates little internal deformation of the North Andean Block (wrms of residual velcoties is 1.3 mm/yr). As a consequence, 30% of the obliquity of the Nazca/South America motion is accommodated by transcurrent deformation along the eastern boundary of the NAB. Residual velocities with respect to the North Andean Block are then modelled in terms of elastic locking along the subduction interface. Models indicate that the subduction interface is partially locked (50%) up to a depth of 40 km over the area of rupture of the 1906 earthquake. Further south, coupling decreases with latitude, with no coupling detected at the latitude

  15. Development of site class and site coefficient maps of Semarang, Indonesia using field shear wave velocity data

    Directory of Open Access Journals (Sweden)

    Partono Windu

    2017-01-01

    Full Text Available The new Indonesian National Code for seismic resistance design (SNI-03-1726-2012 issued recently utilizes seismic response spectra for the whole area of the country. Site class and site coefficient are two parameters needed for designing response spectra. Site class can be estimated using average standard penetration test (N-SPT, average shear wave velocity (Vs and average un-drained shear strength (Su of top 30 meter soil deposit. Site coefficients can be predicted using probabilistic seismic hazard analysis (PSHA by implementing total probability theorem. To perform PSHA, Vs30 is a parameter needed for calculating ground motion at bedrock elevation. This paper presents the results of PSHA and site class analysis using Vs30 values estimated based on N-SPT results collected from 265 boring locations in Semarang. Seismic data in a radius of 500 km from Semarang were collected for PSHA. Site class and site coefficient maps are then developed for the whole study area.

  16. Experimental results showing the internal three-component velocity field and outlet temperature contours for a model gas turbine combustor

    CSIR Research Space (South Africa)

    Meyers, BC

    2011-09-01

    Full Text Available A three-component flow field inside a can-type, forward flow experimental combustor was measured under non-reacting conditions. The combustor was run at atmospheric conditions with the air flow supplied from a fan and the outlet was straight...

  17. An analytical expression for ion velocities at the wall including the sheath electric field and surface biasing for erosion modeling at JET ILW

    Directory of Open Access Journals (Sweden)

    I. Borodkina

    2017-08-01

    Full Text Available For simulation of plasma-facing component erosion in fusion experiments, an analytical expression for the ion velocity just before the surface impact including the local electric field and an optional surface biasing effect is suggested. Energy and angular impact distributions and the resulting effective sputtering yields were produced for several experimental scenarios at JET ILW mostly involving PFCs exposed to an oblique magnetic field. The analytic solution has been applied as an improvement to earlier ERO modelling of localized, Be outer limiter, RF-enhanced erosion, modulated by toggling of a remote, however magnetically connected ICRH antenna. The effective W sputtering yields due to D and Be ion impact in Type-I and Type-III ELMs and inter-ELM conditions were also estimated using the analytical approach and benchmarked by spectroscopy. The intra-ELM W sputtering flux increases almost 10 times in comparison to the inter-ELM flux.

  18. Optimization of Vertical Well Placement for Oil Field Development Based on Basic Reservoir Rock Properties using Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Tutuka Ariadji

    2012-07-01

    Full Text Available Comparing the quality of basic reservoir rock properties is a common practice to locate new infills or development wells for optimizing an oil field development using a reservoir simulation. The conventional technique employs a manual trial and error process to find new well locations, which proves to be time-consuming, especially, for a large field. Concerning this practical matter, an alternative in the form of a robust technique was introduced in order that time and efforts could be reduced in finding best new well locations capable of producing the highest oil recovery. The objective of the research was to apply Genetic Algorithm (GA in determining wells locations using reservoir simulation to avoid the manual conventional trial and error method. GA involved the basic rock properties, i.e., porosity, permeability, and oil saturation, of each grid block obtained from a reservoir simulation model, which was applied into a newly generated fitness function formulated through translating the common engineering practice in the reservoir simulation into a mathematical equation and then into a computer program. The maximum of the fitness value indicated a final searching of the best grid location for a new well location. In order to evaluate the performance of the generated GA program, two fields that had different production profile characteristics, namely the X and Y fields, were applied to validate the proposed method. The proposed GA method proved to be a robust and accurate method to find the best new well locations for field development. The key success of this proposed GA method is in the formulation of the objective function.

  19. WIND VELOCITIES AND SAND FLUXES IN MESQUITE DUNE-LANDS IN THE NORTHERN CHIHUAHUAN DESERT: A COMPARISON BETWEEN FIELD MEASUREMENTS AND THE QUIC (QUICK URBAN AND INDUSTRIAL COMPLEX) MODEL

    Science.gov (United States)

    The poster shows comparisons of wind velocities and sand fluxes between field measurements and a computer model, called QUIC (Quick Urban & Industrial Complex). The comparisons were made for a small desert region in New Mexico.

  20. A self-consistent two-dimensional resistive fluid theory of field-aligned potential structures including charge separation and magnetic and velocity shear

    Science.gov (United States)

    Hesse, Michael; Birn, Joachim; Schindler, Karl

    1990-01-01

    A self-consistent two-fluid theory that includes the magnetic field and shear patterns is developed to model stationary electrostatic structures with field-aligned potential drops. Shear flow is also included in the theory since this seems to be a prominent feature of the structures of interest. In addition, Ohmic dissipation, a Hall term, and pressure gradients in a generalized Ohm's law, modified for cases without quasi-neutrality, are included. In the analytic theory, the electrostatic force is balanced by field-aligned pressure gradients (i.e., thermal effects in the direction of the magnetic field) and by pressure gradients and magnetic stresses in the perpendicular direction. Within this theory, simple examples of applications are presented to demonstrate the kind of solutions resulting from the model. The results show how the effects of charge separation and shear in the magnetic field and the velocity can be combined to form self-consistent structures such as are found to exist above the aurora, suggested also in association with solar flares.

  1. Engineering the interface characteristics on the enhancement of field electron emission properties of vertically aligned hexagonal boron nitride nanowalls

    Energy Technology Data Exchange (ETDEWEB)

    Sankaran, K.J.; Hoang, D.Q.; Drijkoningen, S.; Pobedinskas, P.; Haenen, K. [Institute for Materials Research (IMO), Hasselt University, Diepenbeek (Belgium); IMOMEC, IMEC vzw, Diepenbeek (Belgium); Srinivasu, K.; Leou, K.C. [Department of Engineering and System Science, National Tsing Hua University, Hsinchu (China); Korneychuk, S.; Turner, S.; Verbeeck, J. [Electron Microscopy for Materials Science (EMAT), University of Antwerp (Belgium); Lin, I.N. [Department of Physics, Tamkang University, Tamsui (China)

    2016-10-15

    Utilization of Au and nanocrystalline diamond (NCD) as interlayers noticeably modifies the microstructure and field electron emission (FEE) properties of hexagonal boron nitride nanowalls (hBNNWs) grown on Si substrates. The FEE properties of hBNNWs on Au could be turned on at a low turn-on field of 14.3 V μm{sup -1}, attaining FEE current density of 2.58 mA cm{sup -2} and life-time stability of 105 min. Transmission electron microscopy reveals that the Au-interlayer nucleates the hBN directly, preventing the formation of amorphous boron nitride (aBN) in the interface, resulting in enhanced FEE properties. But Au forms as droplets on the Si substrate forming again aBN at the interface. Conversely, hBNNWs on NCD shows superior in life-time stability of 287 min although it possesses inferior FEE properties in terms of larger turn-on field and lower FEE current density as compared to that of hBNNWs-Au. The uniform and continuous NCD film on Si also circumvents the formation of aBN phases and allows hBN to grow directly on NCD. Incorporation of carbon in hBNNWs from the NCD-interlayer improves the conductivity of hBNNWs, which assists in transporting the electrons efficiently from NCD to hBNNWs that results in better field emission of electrons with high life-time stability. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. A Comparison of Flow Field Characteristics from PIV Experiment Measurement to Numerical Simulation behind a Spacer in a Vertical Pipe

    Directory of Open Access Journals (Sweden)

    Lávička D.

    2010-07-01

    Full Text Available This paper describes the topic of measurement using a modern laser method (PIV in an annular channel of very small dimensions. The annular channel simulates the flow area around a model of a fuel rod in the VVER nuclear reactor. The annular channel holds spacers which create obstacles to fluid flow. The spacers serve a number of important purposes. In the real nuclear reactor, the spacer holds a fuel rod in the fuel rod bundle. Another important function of the spacer is to influence the flow field characteristics, especially turbulence size, by the shape of the spacer. The value of the turbulence regulates the intensity of heat transfer between the fuel rod and the fluid. Therefore, it is very important to provide a correct description and analysis of the flow field behind the obstacle the spacer generates. The paper further looks into the solution of the same task using numerical simulation. The solution of this task consisted of setting the suitable boundary conditions and of setting the turbulence model for the numerical simulation. The result is a comparison of the flow field characteristics from the experimental measurement and the findings of the numerical simulation. The numerical simulation was carried out using commercial CFD software package, FLUENT.

  3. Mixed convective magnetohydrodynamic flow in a vertical channel filled with nanofluids

    Directory of Open Access Journals (Sweden)

    S. Das

    2015-06-01

    Full Text Available The fully developed mixed convection flow in a vertical channel filled with nanofluids in the presence of a uniform transverse magnetic field has been studied. Closed form solutions for the fluid temperature, velocity and induced magnetic field are obtained for both the buoyancy-aided and -opposed flows. Three different water-based nanofluids containing copper, aluminium oxide and titanium dioxide are taken into consideration. Effects of the pertinent parameters on the nanofluid temperature, velocity, and induced magnetic field as well as the shear stress and the rate of heat transfer at the channel wall are shown in figures and tables followed by a quantitative discussion. It is found that the magnetic field tends to enhance the nanofluid velocity in the channel. The induced magnetic field vanishes in the cental region of the channel. The critical Rayleigh number at onset of instability of flow is strongly dependent on the volume fraction of nanoparticles and the magnetic field.

  4. Changes in hydrocarbon groups, soil ecotoxicity and microbiology along horizontal and vertical contamination gradients in an old landfarming field for oil refinery waste.

    Science.gov (United States)

    Mikkonen, Anu; Hakala, Kati P; Lappi, Kaisa; Kondo, Elina; Vaalama, Anu; Suominen, Leena

    2012-03-01

    Horizontal and vertical contaminant gradients in an old landfarming field for oil refinery waste were characterised with the aim to assess parallel changes in hydrocarbon groups and general, microbiological and ecotoxicological soil characteristics. In the surface soil polar compounds were the most prevalent fraction of heptane-extractable hydrocarbons, superseding GC-FID-resolvable and high-molar-mass aliphatics and aromatics, but there was no indication of their relatively higher mobility or toxicity. The size of the polar fraction correlated poorly with soil physical, chemical and microbiological properties, which were better explained by the total heptane-extractable and total petroleum hydrocarbons (TPH). Deleterious effects on soil microbiology in situ were observed at surprisingly low TPH concentrations (0.3%). Due to the accumulation of polar and complexed degradation products, TPH seems an insufficient measure to assess the quality and monitor the remediation of soil with weathered hydrocarbon contamination. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Evidence of vertical transmission and co-circulation of chikungunya and dengue viruses in field populations of Aedes aegypti (L.) from Guerrero, Mexico.

    Science.gov (United States)

    Dzul-Manzanilla, Felipe; Martínez, Norma E; Cruz-Nolasco, Maximina; Gutiérrez-Castro, Cipriano; López-Damián, Leonardo; Ibarra-López, Jesús; Martini-Jaimes, Andres; Bibiano-Marín, Wilbert; Tornez-Benitez, Citlalli; Vazquez-Prokopec, Gonzalo M; Manrique-Saide, Pablo

    2016-02-01

    We report results of the entomo-virological surveillance system in Aedes aegypti local populations performed by the Ministry of Health of Guerrero. Indoor-adult Ae. aegypti collected at Acapulco, Zihuatanejo, Coyuca de Benitez and Atoyac de Alvarez (dry season, 2015) were processed for dengue virus (DENV) and chikungunya virus (CHIKV) using RT-PCR. We identified different seroptypes of DENV (2, 3 and 4), CHIKV and their co-circulation in field-caught mosquitoes across a significant geographic area. Pools of males were positive for CHIKV and DENV 3 and 4 suggesting vertical transmission. Entomo-virological surveillance in Guerrero has identified early circulation of CHIKV and DENV and provided a trigger for timely and focalized vector control actions. © The Author 2015. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  6. Vertical deformation at western part of Sumatra

    Energy Technology Data Exchange (ETDEWEB)

    Febriyani, Caroline, E-mail: caroline.fanuel@students.itb.ac.id; Prijatna, Kosasih, E-mail: prijatna@gd.itb.ac.id; Meilano, Irwan, E-mail: irwan.meilano@gd.itb.ac.id

    2015-04-24

    This research tries to make advancement in GPS signal processing to estimate the interseismic vertical deformation field at western part of Sumatra Island. The data derived by Continuous Global Positioning System (CGPS) from Badan Informasi Geospasial (BIG) between 2010 and 2012. GPS Analyze at Massachusetts Institute of Technology (GAMIT) software and Global Kalman Filter (GLOBK) software are used to process the GPS signal to estimate the vertical velocities of the CGPS station. In order to minimize noise due to atmospheric delay, Vienna Mapping Function 1 (VMF1) is used as atmospheric parameter model and include daily IONEX file provided by the Center for Orbit Determination in Europe (CODE) as well. It improves GAMIT daily position accuracy up to 0.8 mm. In a second step of processing, the GLOBK is used in order to estimate site positions and velocities in the ITRF08 reference frame. The result shows that the uncertainties of estimated displacement velocity at all CGPS stations are smaller than 1.5 mm/yr. The subsided deformation patterns are seen at the northern and southern part of west Sumatra. The vertical deformation at northern part of west Sumatra indicates postseismic phase associated with the 2010 and 2012 Northern Sumatra earthquakes and also the long-term postseismic associated with the 2004 and 2005 Northern Sumatra earthquakes. The uplifted deformation patterns are seen from Bukit Tinggi to Seblat which indicate a long-term interseismic phase after the 2007 Bengkulu earthquake and 2010 Mentawai earthquake. GANO station shows a subsidence at rate 12.25 mm/yr, indicating the overriding Indo-Australia Plate which is dragged down by the subducting Southeast Asian Plate.

  7. Assessing Stride Variables and Vertical Stiffness with GPS-Embedded Accelerometers: Preliminary Insights for the Monitoring of Neuromuscular Fatigue on the Field

    Science.gov (United States)

    Buchheit, Martin; Gray, Andrew; Morin, Jean-Benoit

    2015-01-01

    The aim of the present study was to examine the ability of a GPS-imbedded accelerometer to assess stride variables and vertical stiffness (K), which are directly related to neuromuscular fatigue during field-based high-intensity runs. The ability to detect stride imbalances was also examined. A team sport player performed a series of 30-s runs on an instrumented treadmill (6 runs at 10, 17 and 24 km·h-1) with or without his right ankle taped (aimed at creating a stride imbalance), while wearing on his back a commercially-available GPS unit with an embedded 100-Hz tri-axial accelerometer. Contact (CT) and flying (FT) time, and K were computed from both treadmill and accelerometers (Athletic Data Innovations) data. The agreement between treadmill (criterion measure) and accelerometer-derived data was examined. We also compared the ability of the different systems to detect the stride imbalance. Biases were small (CT and K) and moderate (FT). The typical error of the estimate was trivial (CT), small (K) and moderate (FT), with nearly perfect (CT and K) and large (FT) correlations for treadmill vs. accelerometer. The tape induced very large increase in the right - left foot ∆ in CT, FT and K measured by the treadmill. The tape effect on CT and K ∆ measured with the accelerometers were also very large, but of lower magnitude than with the treadmill. The tape effect on accelerometer-derived ∆ FT was unclear. Present data highlight the potential of a GPS-embedded accelerometer to assess CT and K during ground running. Key points GPS-embedded tri-axial accelerometers may be used to assess contact time and vertical stiffness during ground running. These preliminary results open new perspective for the field monitoring of neuromuscular fatigue and performance in run-based sports PMID:26664264

  8. Tuning electronic and optical properties of arsenene/C3N van der Waals heterostructure by vertical strain and external electric field.

    Science.gov (United States)

    Zeng, Hui; Zhao, Jun; Cheng, Ai-Qiang; Zhang, Lei; He, Zi; Chen, Ru-Shan

    2018-02-16

    Searching for new van der Waals (vdW) heterostructure with novel electronic and optical properties is of great interest and importance for the next generation of devices. By using first-principles calculations, we show that the electronic and optical properties of the arsenene/C3N vdW heterostructure can be effectively modulated by applying vertical strain and external electric field. Our results suggest that this heterostructure has an intrinsic type-II band alignment with an indirect bandgap of 0.16 eV, facilitating the separation of photogenerated electron-hole pairs. The bandgap in the heterostructure can be tuned from 0-0.35 eV via the strain, experiencing an indirect-to-direct bandgap transition. Moreover, the bandgap of the heterostructure varies linearly with respect to a moderate external electric field, and the semiconductor-to-metal transition can be realized in the presence of a strong electric field. The calculated band alignment and the optical absorption reveal that the arsenene/C3N heterostructure could present excellent light-harvesting performance. Our designed vdW heterostructure is expected to have great potential applications in nanoelectronic devices and photovoltaics.

  9. Tuning electronic and optical properties of arsenene/C3N van der Waals heterostructure by vertical strain and external electric field

    Science.gov (United States)

    Zeng, Hui; Zhao, Jun; Cheng, Ai-Qiang; Zhang, Lei; He, Zi; Chen, Ru-Shan

    2018-02-01

    Searching for new van der Waals (vdW) heterostructure with novel electronic and optical properties is of great interest and importance for the next generation of devices. By using first-principles calculations, we show that the electronic and optical properties of the arsenene/C3N vdW heterostructure can be effectively modulated by applying vertical strain and external electric field. Our results suggest that this heterostructure has an intrinsic type-II band alignment with an indirect bandgap of 0.16 eV, facilitating the separation of photogenerated electron–hole pairs. The bandgap in the heterostructure can be tuned from 0–0.35 eV via the strain, experiencing an indirect-to-direct bandgap transition. Moreover, the bandgap of the heterostructure varies linearly with respect to a moderate external electric field, and the semiconductor-to-metal transition can be realized in the presence of a strong electric field. The calculated band alignment and the optical absorption reveal that the arsenene/C3N heterostructure could present excellent light-harvesting performance. Our designed vdW heterostructure is expected to have great potential applications in nanoelectronic devices and photovoltaics.

  10. Optimization of the Vertical Bridgman Method and the Vertical Gradient Method for CdZnTe Single Crystal Production

    Directory of Open Access Journals (Sweden)

    A. Kalbáč

    2000-01-01

    Full Text Available In designing optimum parameters of advanced crystal growth techniques, computer modeling has become an important tool owing to the fact that computer simulation is much cheaper than many experimental techniques based on the trial and error method. In this paper, the application of computational modeling in the optimization of experimental setups for the production of CdZnTe single crystals from the melt is demonstrated on two characteristic examples, namely on the vertical Bridgman and vertical gradient method. The influence of adjustable parameters on the temperature, concentration and velocity fields, and on the positions and velocities of the moving interface is studied. Finally, the effect of uncertainty in material parameters on computed results is analyzed.

  11. Waves, circulation and vertical dependence

    Science.gov (United States)

    Mellor, George

    2013-04-01

    Longuet-Higgins and Stewart (J Fluid Mech 13:481-504, 1962; Deep-Sea Res 11:529-562, 1964) and later Phillips (1977) introduced the problem of waves incident on a beach, from deep to shallow water. From the wave energy equation and the vertically integrated continuity equation, they inferred velocities to be Stokes drift plus a return current so that the vertical integral of the combined velocities was nil. As a consequence, it can be shown that velocities of the order of Stokes drift rendered the advective term in the momentum equation negligible resulting in a simple balance between the horizontal gradients of the vertically integrated elevation and wave radiation stress terms; the latter was first derived by Longuet-Higgins and Stewart. Mellor (J Phys Oceanogr 33:1978-1989, 2003a), noting that vertically integrated continuity and momentum equations were not able to deal with three-dimensional numerical or analytical ocean models, derived a vertically dependent theory of wave-circulation interaction. It has since been partially revised and the revisions are reviewed here. The theory is comprised of the conventional, three-dimensional, continuity and momentum equations plus a vertically distributed, wave radiation stress term. When applied to the problem of waves incident on a beach with essentially zero turbulence momentum mixing, velocities are very large and the simple balance between elevation and radiation stress gradients no longer prevails. However, when turbulence mixing is reinstated, the vertically dependent radiation stresses produce vertical velocity gradients which then produce turbulent mixing; as a consequence, velocities are reduced, but are still larger by an order of magnitude compared to Stokes drift. Nevertheless, the velocity reduction is sufficient so that elevation set-down obtained from a balance between elevation gradient and radiation stress gradients is nearly coincident with that obtained by the aforementioned papers. This paper

  12. Nitrification cessation and recovery in an aerated saturated vertical subsurface flow treatment wetland: Field studies and microscale biofilm modeling.

    Science.gov (United States)

    Murphy, Clodagh; Rajabzadeh, Amin R; Weber, Kela P; Nivala, Jaime; Wallace, Scott D; Cooper, David J

    2016-06-01

    In aerated treatment wetlands, oxygen availability is not a limiting factor in sustaining a high level of nitrification in wastewater treatment. In the case of an air blower failure, nitrification would cease, potentially causing adverse effects to the nitrifying bacteria. A field trial was completed investigating nitrification loss when aeration is switched off, and the system recovery rate after the aeration is switched back on. Loss of dissolved oxygen was observed to be more rapid than loss of nitrification. Nitrate was observed in the effluent long after the aeration was switched off (48h+). A complementary modeling study predicted nitrate diffusion out of biofilm over a 48h period. After two weeks of no aeration in the established system, nitrification recovered within two days, whereas nitrification establishment in a new system was previously observed to require 20-45days. These results suggest that once established resident nitrifying microbial communities are quite robust. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Vertical water and DOC/DIC flux estimates in a hummocky soil landscape - from pedon to field scale

    Science.gov (United States)

    Rieckh, Helene; Gerke, Horst H.

    2017-04-01

    Arable hummocky soil landscapes of formerly glaciated terrains are characterized by 3D spatial patterns of soil types resulting from tillage and water erosion. Erosion and deposition processes have implication for the water and carbon (C) balance of the hummocky soil landscape. The objective of this study was to estimate the leaching of dissolved C as a crucial component to the terrestrial net ecosystem C balance for (i) pedon scale at different terrain positions and (ii) field scale. At pedon scale, the interactions between erosion affected soil properties, the water balances, and the crop growth and feedback effects of erosion on the leaching rates were studied. The 1D water movements were described using the Richards equation as implemented using the numerical solution in the HYDRUS program. Measured DOC/DIC concentrations were combined with calculated water fluxes to obtain the solute fluxes for certain depth and positions. For the field scale estimation dissolved carbon fluxes a weight average per soil type was chosen, whereas soil types were determined by characteristic multi-parameter delineating landform units and by soil soundings. For a typical section of the hummocky soil landscape, i.e. the CarboZALF-D plot, the average seepage water flux for the three years period 2010-2012 was 96 mm yr-1, the average leaching of DOC 0.6 g m-2 yr-1 and of DIC 7.0 g m-2 yr-1 below the root zone at approximately 200 cm depth. The water and dissolved carbon fluxes varied in direction and magnitude depending on terrain position and erosion history. The depth of the water table was identified as a major influential factor. The temporal variations of dissolved carbon fluxes seem to be dominantly controlled by water fluxes rather than by temporal varying dissolved carbon concentrations. The consideration of soil-crop interactions lead to more spatial differences of water and dissolved carbon fluxes as well as to faster soil development.

  14. Analysis of P- and S-wave VSP (vertical seismic profile) data from the Salton Sea Geothermal Field

    Energy Technology Data Exchange (ETDEWEB)

    Daley, T.M.

    1987-09-01

    To understand any geophysical data, geologic information is necessary. This thesis will begin with a summary of the geology of the Salton Trough region and the Salton Sea Geothermal Field (SSGF). The information available from the SSSDP will also be summarized. After the geologic summary, the design of the VSP will be discussed, including acquisition equipment and procedures. The data processing procedures and software used will be discussed as a separate section. Processing procedures will also be described at various times in the thesis where more specialized procedures are used. Data analysis makes up the bulk of the thesis and it is divided into a number of sections detailing the basic VSP interpretation, the anisotropy analysis and the fracture detection and orientation analysis. A combined interpretation of the results, with probable geologic causes for observed events, is presented as a separate section from the data analysis. Finally, a summary of results for each of the goals stated above will be given. The reader should note that a large volume of data were collected and various display methods were used (from the standard wiggle-trace to three-component hodographs). Much of these data are left in the appendices with important or representative figures given in the body of the thesis. Also given in the appendices are listings of FORTRAN programs developed in conjunction with the thesis work. 46 refs., 63 figs., 12 tabs.

  15. Dayside ionospheric convection changes in response to long-period interplanetary magnetic field oscillations: Determination of the ionospheric phase velocity

    Energy Technology Data Exchange (ETDEWEB)

    Saunders, M.A.; Freeman, M.P.; Southwood, D.J.; Cowley, S.W.H. (Imperial College of Science, Technology and Medicine, London (United Kingdom)); Lockwood, M. (Rutherford Appleton Lab., Oxfordshire (United Kingdom)); Samson, J.C. (Univ. of Alberta, Edmonton (Canada)); Farrugia, C.J. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Hughes, T.J. (National Research Council of Canada, Ottawa, Ontario (Canada))

    1992-12-01

    Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-hour interval in question IMF B[sub z] oscillates between [plus minus] 7 nT with about a 1-hour period. Corresponding variations in the ground magnetic disturbance are observed which the authors infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5[degrees] magnetic latitude, but separated by [approximately]2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector ([approximately]10 MLT) and then spread outward toward dawn and dusk with a phase speed of [approximately]5 km s[sup [minus]1] over the longitude range [approximately]8 to 12 MLT, slowing to [approximately] 2 km s[sup [minus]1] outside this range. Cross correlating the data from these ground stations with IMP 8 IMF B[sub z] records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds. The authors interpret these observations in terms of the ionospheric response to the onset, expansion and decay of magnetic reconnection at the dayside magnetopause.

  16. MHD Natural Convection Flow of an incompressible electrically conducting viscous fluid through porous medium from a vertical flat plate

    Directory of Open Access Journals (Sweden)

    Dr. G. Prabhakara Rao,

    2015-04-01

    Full Text Available We consider a two-dimensional MHD natural convection flow of an incompressible viscous and electrically conducting fluid through porous medium past a vertical impermeable flat plate is considered in presence of a uniform transverse magnetic field. The governing equations of velocity and temperature fields with appropriate boundary conditions are solved by the ordinary differential equations by introducing appropriate coordinate transformations. We solve that ordinary differential equations and find the velocity profiles, temperature profile, the skin friction and nusselt number. The effects of Grashof number (Gr, Hartmann number (M and Prandtl number (Pr, Darcy parameter (D-1 on velocity profiles and temperature profiles are shown graphically.

  17. Simultaneous three-dimensional temperature and velocity field measurements using astigmatic imaging of non-encapsulated thermo-liquid crystal (TLC) particles.

    Science.gov (United States)

    Segura, Rodrigo; Rossi, Massimiliano; Cierpka, Christian; Kähler, Christian J

    2015-02-07

    A combination of cutting edge developments is presented to characterize three-dimensional (3D) temperature and velocity fields in microscopic flows. An emulsion of non-encapsulated thermo-liquid crystal (TLC) micro spheres, with a narrow size distribution is used to track the flow's motion and temperature distribution. A state-of-the-art light engine, which combines the spectrum of six light pipes, provides a balanced illumination which allows for strong and detectable color patterns across the TLC's temperature response range. Lastly, the ability of the TLC material to reflect select wavelength bands with an unchanging and independent circular polarization chirality is exploited by a filter that blocks background noise, while exclusively transmitting the color signal of the TLC particles. This approach takes advantage of the peculiar physical properties of TLCs to allow the estimation of individual TLC particle's 3D position, for the first time, using Astigmatism Particle Tracking Velocimetry (APTV).

  18. Evaluation of a Magneto-optical Filter and a Fabry-perot Interferometer for the Measurement of Solar Velocity Fields from Space

    Science.gov (United States)

    Rhodes, E. J., Jr.; Cacciani, A.; Blamont, J.; Tomczyk, S.; Ulrich, R. K.; Howard, R. F.

    1984-01-01

    A program was developed to evaluate the performance of three different devices as possible space-borne solar velocity field imagers. Two of these three devices, a magneto-optical filter and a molecular adherence Fabry-Perot interferometer were installed in a newly-constructed observing system located at the 60-foot tower telescope at the Mt. Wilson Observatory. Time series of solar filtergrams and Dopplergrams lasting up to 10 hours per day were obtained with the filter while shorter runs were obtained with the Fabry-Perot. Two-dimensional k (sub h)-omega power spectra which show clearly the well-known p-mode ridges were computed from the time series obtained with the magneto-optical filter. These power spectra were compared with similar power spectra obtained recently with the 13.7-m McMath spectrograph at Kitt Peak.

  19. A free software for pore-scale modelling: solving Stokes equation for velocity fields and permeability values in 3D pore geometries

    KAUST Repository

    Gerke, Kirill

    2015-04-01

    In this contribution we introduce a novel free software which solves the Stokes equation to obtain velocity fields for low Reynolds-number flows within externally generated 3D pore geometries. Provided with velocity fields, one can calculate permeability for known pressure gradient boundary conditions via Darcy\\'s equation. Finite-difference schemes of 2nd and 4th order of accuracy are used together with an artificial compressibility method to iteratively converge to a steady-state solution of Stokes\\' equation. This numerical approach is much faster and less computationally demanding than the majority of open-source or commercial softwares employing other algorithms (finite elements/volumes, lattice Boltzmann, etc.) The software consists of two parts: 1) a pre and post-processing graphical interface, and 2) a solver. The latter is efficiently parallelized to use any number of available cores (the speedup on 16 threads was up to 10-12 depending on hardware). Due to parallelization and memory optimization our software can be used to obtain solutions for 300x300x300 voxels geometries on modern desktop PCs. The software was successfully verified by testing it against lattice Boltzmann simulations and analytical solutions. To illustrate the software\\'s applicability for numerous problems in Earth Sciences, a number of case studies have been developed: 1) identifying the representative elementary volume for permeability determination within a sandstone sample, 2) derivation of permeability/hydraulic conductivity values for rock and soil samples and comparing those with experimentally obtained values, 3) revealing the influence of the amount of fine-textured material such as clay on filtration properties of sandy soil. This work was partially supported by RSF grant 14-17-00658 (pore-scale modelling) and RFBR grants 13-04-00409-a and 13-05-01176-a.

  20. Effects of impurity and composition profiles on electrical characteristics of GaAsSb/InGaAs hetero-junction vertical tunnel field effect transistors

    Science.gov (United States)

    Gotow, Takahiro; Mitsuhara, Manabu; Hoshi, Takuya; Sugiyama, Hiroki; Takenaka, Mitsuru; Takagi, Shinichi

    2017-11-01

    We fabricated and characterized GaAs0.51Sb0.49/In0.53Ga0.47As hetero-junction vertical tunnel field effect transistors (TFETs) on InP substrates in order to examine the effects of the structural characteristics of GaAsSb/InGaAs hetero-structures on the electrical properties of the TFETs. The operation of the fabricated GaAs0.51Sb0.49/In0.53Ga0.47As TFET was confirmed with the ION/IOFF ratio of ˜102 over VG swing of 1.25 V at 297 K. This ION/IOFF ratio was improved up to ˜104 at 20 K, thanks to the suppression of the leakage current in the source junction. The secondary ion mass spectrometry analyses for the present hetero-structures have revealed that the concentration of the p-type dopant (Be) atoms, doped in the GaAsSb source regions, decreases in the InGaAs channel regions at an inverse slope of ˜11 nm/dec. Also, the scanning transmission electron microscope-energy dispersive X-ray spectroscopy has shown that group III and V compositions change abruptly in a region within 10 nm from the interface between the Be-doped GaAsSb source and the undoped InGaAs channel. We performed the 2-dimensional device simulation based on the device structure and the experimentally obtained composition and impurity profiles, and we found that the composition profile had little effect on the S.S. values. The device simulation also revealed that both the optimization of the concentration and the profile of the p-type doping of GaAsSb, and thinning of the effective oxide thickness (EOT) of the gate stacks could effectively improve the inherent S.S. values of the present GaAs0.51Sb0.49/In0.53Ga0.47As hetero-junction vertical TFETs. When 1.0 nm EOT and NA = 1 × 1020 cm-3 are used under the present impurity abruptness, S.S. < 40 mV/dec. can be achieved for the vertical GaAsSb/InGaAs TFETs, which is promising for an ultralow power switching device.

  1. Low-voltage operating flexible ferroelectric organic field-effect transistor nonvolatile memory with a vertical phase separation P(VDF-TrFE-CTFE)/PS dielectric

    Science.gov (United States)

    Xu, Meili; Xiang, Lanyi; Xu, Ting; Wang, Wei; Xie, Wenfa; Zhou, Dayu

    2017-10-01

    Future flexible electronic systems require memory devices combining low-power operation and mechanical bendability. However, high programming/erasing voltages, which are universally needed to switch the storage states in previously reported ferroelectric organic field-effect transistor (Fe-OFET) nonvolatile memories (NVMs), severely prevent their practical applications. In this work, we develop a route to achieve a low-voltage operating flexible Fe-OFET NVM. Utilizing vertical phase separation, an ultrathin self-organized poly(styrene) (PS) buffering layer covers the surface of the ferroelectric polymer layer by one-step spin-coating from their blending solution. The ferroelectric polymer with a low coercive field contributes to low-voltage operation in the Fe-OFET NVM. The polymer PS contributes to the improvement of mobility, attributing to screening the charge scattering and decreasing the surface roughness. As a result, a high performance flexible Fe-OFET NVM is achieved at the low P/E voltages of ±10 V, with a mobility larger than 0.2 cm2 V-1 s-1, a reliable P/E endurance over 150 cycles, stable data storage retention capability over 104 s, and excellent mechanical bending durability with a slight performance degradation after 1000 repetitive tensile bending cycles at a curvature radius of 5.5 mm.

  2. Engineering of optical modes in vertical-cavity microresonators by aperture placement: applications to single-mode and near-field lasers

    Science.gov (United States)

    Shchukin, V. A.; Ledentsov, N. N.; Kropp, J.-R.; Steinle, G.; Ledentsov, N. N.; Choquette, K. D.; Burger, S.; Schmidt, F.

    2015-03-01

    Oxide-confined vertical cavity surface emitting lasers (VCSEL) are inherently leaky structures, despite the fact that the oxidized periphery region surrounding the all-semiconductor core has a lower refractive index. The reason is that the VCSEL modes in the non-oxidized core region can be coupled to tilted modes in the selectively oxidized periphery as the orthogonality between the core mode and the modes at the periphery is broken by the oxidation-induced optical field redistribution. Engineered VCSEL designs show that the overlap between the VCSEL mode of the core and the tilted mode in the periphery can reach >30% resulting in significant leakage. Three-dimensional modeling confirms that the leakage losses are much stronger for high order transverse modes which have a higher field intensity close to the oxidized region. Single mode lasing in the fundamental mode can thus proceed up to large aperture diameters. A 850-nm GaAlAs leaky VCSEL based on this concept is designed, modeled and fabricated, showing single-mode lasing with aperture diameters up to 5 μm. Side mode suppression ratio >20dB is realized at the current density of 10kA/cm2 in devices with the series resistance of 90 Ω.

  3. Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity

    Directory of Open Access Journals (Sweden)

    M. L. Parkinson

    2006-03-01

    Full Text Available Akasofu's solar wind ε parameter describes the coupling of solar wind energy to the magnetosphere and ionosphere. Analysis of fluctuations in ε using model independent scaling techniques including the peaks of probability density functions (PDFs and generalised structure function (GSF analysis show the fluctuations were self-affine (mono-fractal, single exponent scaling over 9 octaves of time scale from ~46 s to ~9.1 h. However, the peak scaling exponent α0 was a function of the fluctuation bin size, so caution is required when comparing the exponents for different data sets sampled in different ways. The same generic scaling techniques revealed the organisation and functional form of concurrent fluctuations in azimuthal magnetospheric electric fields implied by SuperDARN HF radar measurements of line-of-sight Doppler velocity, vLOS, made in the high-latitude austral ionosphere. The PDFs of vLOS fluctuation were calculated for time scales between 1 min and 256 min, and were sorted into noon sector results obtained with the Halley radar, and midnight sector results obtained with the TIGER radar. The PDFs were further sorted according to the orientation of the interplanetary magnetic field, as well as ionospheric regions of high and low Doppler spectral width. High spectral widths tend to occur at higher latitude, mostly on open field lines but also on closed field lines just equatorward of the open-closed boundary, whereas low spectral widths are concentrated on closed field lines deeper inside the magnetosphere. The vLOS fluctuations were most self-affine (i.e. like the solar wind ε parameter on the high spectral width field lines in the noon sector ionosphere (i.e. the greater cusp, but suggested multi-fractal behaviour on closed field lines in the midnight sector (i.e. the central plasma sheet. Long tails in the PDFs imply that "microbursts" in ionospheric convection

  4. Development of an optimal velocity selection method with velocity obstacle

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Geuk; Oh, Jun Ho [KAIST, Daejeon (Korea, Republic of)

    2015-08-15

    The Velocity obstacle (VO) method is one of the most well-known methods for local path planning, allowing consideration of dynamic obstacles and unexpected obstacles. Typical VO methods separate a velocity map into a collision area and a collision-free area. A robot can avoid collisions by selecting its velocity from within the collision-free area. However, if there are numerous obstacles near a robot, the robot will have very few velocity candidates. In this paper, a method for choosing optimal velocity components using the concept of pass-time and vertical clearance is proposed for the efficient movement of a robot. The pass-time is the time required for a robot to pass by an obstacle. By generating a latticized available velocity map for a robot, each velocity component can be evaluated using a cost function that considers the pass-time and other aspects. From the output of the cost function, even a velocity component that will cause a collision in the future can be chosen as a final velocity if the pass-time is sufficiently long enough.

  5. Orbital velocity

    OpenAIRE

    Modestino, Giuseppina

    2016-01-01

    The trajectory and the orbital velocity are determined for an object moving in a gravitational system, in terms of fundamental and independent variables. In particular, considering a path on equipotential line, the elliptical orbit is naturally traced, verifying evidently the keplerian laws. The case of the planets of the solar system is presented.

  6. Buoyancy induced Couette-Poiseuille flow in a vertical microchannel

    Science.gov (United States)

    Narahari, M.

    2017-10-01

    The fully developed buoyancy-induced (natural convective) Couette-Poiseuille flow in a vertical microchannel is investigated with the velocity slip and temperature jump boundary conditions. Closed form analytical solutions for the velocity and temperature fields are obtained. The effects of the fluid-wall interaction parameter, wall-ambient temperature difference ratio, Knudsen number, mixed convection parameter, and the dimensionless pressure gradient on the velocity, temperature, volume flow rate, heat flux between the plates and the Nusselt number have been discussed in detail through graphs. The outcomes of the investigation indicate that the volume flow rate increases with increasing values of mixed convection parameter, wall-ambient temperature difference ratio, and Knudsen number.

  7. Numerical Analysis of a Small-Size Vertical-Axis Wind Turbine Performance and Averaged Flow Parameters Around the Rotor

    Directory of Open Access Journals (Sweden)

    Rogowski Krzysztof

    2017-06-01

    Full Text Available Small-scale vertical-axis wind turbines can be used as a source of electricity in rural and urban environments. According to the authors’ knowledge, there are no validated simplified aerodynamic models of these wind turbines, therefore the use of more advanced techniques, such as for example the computational methods for fluid dynamics is justified. The paper contains performance analysis of the small-scale vertical-axis wind turbine with a large solidity. The averaged velocity field and the averaged static pressure distribution around the rotor have been also analyzed. All numerical results presented in this paper are obtained using the SST k-ω turbulence model. Computed power coeffcients are in good agreement with the experimental results. A small change in the tip speed ratio significantly affects the velocity field. Obtained velocity fields can be further used as a base for simplified aerodynamic methods.

  8. InSAR velocity field across the North Anatolian Fault (eastern Turkey): Implications for the loading and release of interseismic strain accumulation

    KAUST Repository

    Cakir, Ziyadin

    2014-10-01

    We use the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique with the European Space Agency\\'s Envisat and ERS SAR data acquired on three neighboring descending tracks (T350, T078, and T307) to map the interseismic strain accumulation along a ~225 km long, NW-SE trending section of the North Anatolian Fault that ruptured during the 1939, 1942, and 1943 earthquakes in eastern Turkey. We derive a line-of-sight velocity map of the region with a high spatial resolution and accuracy which, together with the maps of earthquake surface ruptures, shed light on the style of continental deformation and the relationships between the loading and release of interseismic strain along segmented continental strike-slip faults. In contrast with the geometric complexities at the ground surface that appear to control rupture propagation of the 1939 event, modeling of the high-resolution PS-InSAR velocity field reveals a fairly linear and narrow throughgoing shear zone with an overall 20 ± 3 mm/yr slip rate above an unexpectedly shallow 7 ± 2 km locking depth. Such a shallow locking depth may result from the postseismic effects following recent earthquakes or from a simplified model that assumes a uniform degree of locking with depth on the fault. A narrow throughgoing shear zone supports the thick lithosphere model in which continental strike-slip faults are thought to extend as discrete shear zones through the entire crust. Fault segmentation previously reported from coseismic surface ruptures is thus likely inherited from heterogeneities in the upper crust that either preexist and/or develop during coseismic rupture propagation. The geometrical complexities that apparently persist for long periods may guide the dynamic rupture propagation surviving thousands of earthquake cycles.

  9. Performance Enhancement of a GaAs Detector with a Vertical Field and an Embedded Thin Low-Temperature Grown Layer

    Science.gov (United States)

    Currie, Marc; Dianat, Pouya; Persano, Anna; Martucci, Maria Concetta; Quaranta, Fabio; Cola, Adriano; Nabet, Bahram

    2013-01-01

    Low temperature growth of GaAs (LT-GaAs) near 200 °C results in a recombination lifetime of nearly 1 ps, compared with approximately 1 ns for regular temperature ∼600 °C grown GaAs (RT-GaAs), making it suitable for ultra high speed detection applications. However, LT-GaAs detectors usually suffer from low responsivity due to low carrier mobility. Here we report electro-optic sampling time response measurements of a detector that employs an AlGaAs heterojunction, a thin layer of LT-GaAs, a channel of RT-GaAs, and a vertical electric field that together facilitate collection of optically generated electrons while suppressing collection of lower mobility holes. Consequently, these devices have detection efficiency near that of RT-GaAs yet provide pulse widths nearly an order of magnitude faster—∼6 ps for a cathode-anode separation of 1.3 μm and ∼12 ps for distances more than 3 μm. PMID:23429510

  10. Vertical compact torus injection into the STOR-M tokamak

    Science.gov (United States)

    Liu, Dazhi

    Central fuelling is a fundamental issue in the next generation tokamak-ITER (International Thermonuclear Experimental Reactor). It is essential for optimization of the bootstrap current which is proportional to the pressure gradient of trapped particles. The conventional fusion reactor fuelling techniques, such as gas puffing and cryogenic pellet injection, are considered inadequate to fulfill this goal due to premature ionization caused by high plasma temperature and density. Compact Torus (CT) injection is a promising fuelling technique for central fuelling a reactor-grade tokamak. An accelerated CT is expected to penetrate into the core region and deposit fuel there provided the CT kinetic energy density exceeds the magnetic energy density in a target plasma. This process is complicated and involves CT penetration into an external magnetic field, a CT stopping mechanism, magnetic reconnection, and excitation of plasma waves. CTs can be injected at different angles with respect to the tokamak toroidal magnetic field, either horizontally or vertically. Normally, CTs are injected radially in the mid-plane of a tokamak. In this configuration, CTs will undergo a decelerating force due to the gradient of the tokamak toroidal magnetic field. CTs will stop inside the tokamak chamber or bunce back depending on the relation between kinetic energy density of injected CTs and the tokamak toroidal magnetic field energy density. In the case of vertical injection, deeper penetration is expected due to the absence of the gradient of the tokamak toroidal field in that direction. Experimental investigations on vertical CT injection into a tokamak will be of great significance. The aim of this thesis is to experimentally investigate the feasibility of vertical CT injection into a tokamak and effects of CTs on tokamak plasma confinements. The Saskatchewan Torus-Modified (STOR-M) tokamak is currently the only tokamak equipped with a CT injector in the world. Vertical CT injection

  11. Influence of band offset, nanostructuring, and applied electric field on the optoelectronic properties of vertically stacked MoS2/WS2 materials

    Science.gov (United States)

    Mlinar, Vladan

    2017-12-01

    We theoretically investigate the electronic and optical properties of multilayer vertically stacked MoS2/WS2 heterostructures, focusing on the role of the MoS2-WS2 band offset, number of monolayers in the heterostructure, effects of an applied electric field, and size reduction in lateral direction, leading to MoS2/WS2 -based nanowires and nanoplatelets. Given that different values of the MoS2-WS2 band offset have been reported, we show that the band offset determines the ordering of the energy levels in the valence band and spin projections at the K point of the Brillouin zone. These variations as function of the value of the band offset are suppressed in an external electric field. For multilayer MoS2/WS2 -based nanostructures, our calculations reveal nanowires and nanoplatelets with S-atom edges exhibit a metallic character, but nanowires with one S-atom and other Mo/W edge show the band gap with electrons located in MoS2 and holes in WS2 layer. The band gap can be controlled by the size of the nanowire in lateral direction and number of layers. The calculated real part of optical conductivity show that the lowest optical transitions originate from the optical transitions in MoS2 layers. The electronic structure is obtained from a parametrized tight-binding model that includes nonorthogonal sp 3d5 orbitals and spin orbit coupling. Our results are gauged with respect to those extracted from density functional theory and G W methods to ensure the high quality of our predictions.

  12. A relaxed eddy accumulation system for measuring vertical fluxes of nitrous acid

    Directory of Open Access Journals (Sweden)

    X. Ren

    2011-10-01

    Full Text Available A relaxed eddy accumulation (REA system combined with a nitrous acid (HONO analyzer was developed to measure atmospheric HONO vertical fluxes. The system consists of three major components: (1 a fast-response sonic anemometer measuring both vertical wind velocity and air temperature, (2 a fast-response controlling unit separating air motions into updraft and downdraft samplers by the sign of vertical wind velocity, and (3 a highly sensitive HONO analyzer based on aqueous long path absorption photometry that measures HONO concentrations in the updrafts and downdrafts. A dynamic velocity threshold (±0.5σw, where σw is a standard deviation of the vertical wind velocity was used for valve switching determined by the running means and standard deviations of the vertical wind velocity. Using measured temperature as a tracer and the average values from two field deployments, the flux proportionality coefficient, β, was determined to be 0.42 ± 0.02, in good agreement with the theoretical estimation. The REA system was deployed in two ground-based field studies. In the California Research at the Nexus of Air Quality and Climate Change (CalNex study in Bakersfield, California in summer 2010, measured HONO fluxes appeared to be upward during the day and were close to zero at night. The upward HONO flux was highly correlated to the product of NO2 and solar radiation. During the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX 2009 at Blodgett Forest, California in July 2009, the overall HONO fluxes were small in magnitude and were close to zero. Causes for the different HONO fluxes in the two different environments are briefly discussed.

  13. Velocity Structure and Spatio-temporal Evolution in the Head Turbidity Currents based on Ultrasound Doppler Velocity Profiling

    Science.gov (United States)

    Nomura, Shun; Cesare Giovanni, De; Takeda, Yasushi; Yoshida, Taiki; Tasaka, Yuji; Sakaguchi, Hide

    2017-04-01

    Particle laden flow or turbidity current along the sea floor are important as a sediment conveyer and a formation factor of the submarine topography in the geological field. Especially, in the head of the flow, the kinematic energy is frequently exchanged through the boundary of the ambient water and the seabed floor, and it dominants the substantial dynamics of turbidity currents. An understanding of its turbulence structure helps to predict the sediment transport and layer development processes. To comprehend its dynamics precisely, flume test were conducted with continuously fed fluid quartz flour mixture supply. The flow velocities were measured at two different angles by the ultrasound Doppler velocity profiler UVP and both velocity components, in flow direction and on the vertical axis, were extracted. The fundamental velocity structure corresponds to the theories found in literature. Its spatio-temporal evolution was examined from the velocity distribution profiles along the downstream directions. Additionally, developing processes of head structures were also discussed through hydraulic statistic values such as mean velocity, Reynolds stress, and turbulent kinematic energy.

  14. Vertical saccades in dyslexic children.

    Science.gov (United States)

    Tiadi, Aimé; Seassau, Magali; Bui-Quoc, Emmanuel; Gerard, Christophe-Loïc; Bucci, Maria Pia

    2014-11-01

    Vertical saccades have never been studied in dyslexic children. We examined vertical visually guided saccades in fifty-six dyslexic children (mean age: 10.5±2.56 years old) and fifty-six age matched non dyslexic children (mean age: 10.3±1.74 years old). Binocular eye movements were recorded using an infrared video-oculography system (mobileEBT®, e(ye)BRAIN). Dyslexic children showed significantly longer latency than the non dyslexic group, also the occurrence of anticipatory and express saccades was more important in dyslexic than in non dyslexic children. The gain and the mean velocity values were significantly smaller in dyslexic than in non dyslexic children. Finally, the up-down asymmetry reported in normal population for the gain and the velocity of vertical saccades was observed in dyslexic children and interestingly, dyslexic children also reported an up-down asymmetry for the mean latency. Taken together all these findings suggested impairment in cortical areas responsible of vertical saccades performance and also at peripheral level of the extra-ocular oblique muscles; moreover, a visuo-attentionnal bias could explain the up-down asymmetry reported for the vertical saccade triggering. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. A 3D numerical simulation of mixed convection of a magnetic nanofluid in the presence of non-uniform magnetic field in a vertical tube using two phase mixture model

    Energy Technology Data Exchange (ETDEWEB)

    Aminfar, Habib, E-mail: hh_aminfar@tabrizu.ac.i [Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of); Mohammadpourfard, Mousa, E-mail: Mohammadpour@azaruniv.ed [Department of Mechanical Engineering, Azarbaijan University of Tarbiat Moallem, Tabriz, P.O. Box 53751-71379 (Iran, Islamic Republic of); Narmani Kahnamouei, Yousef, E-mail: Narmani87@ms.tabrizu.ac.i [Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2011-08-15

    In this paper, results of applying a non-uniform magnetic field on a ferrofluid (kerosene and 4 vol% Fe{sub 3}O{sub 4}) flow in a vertical tube have been reported. The hydrodynamics and thermal behavior of the flow are investigated numerically using the two phase mixture model and the control volume technique. Two positive and negative magnetic field gradients have been examined. Based on the obtained results the Nusselt number can be controlled externally using the magnetic field with different intensity and gradients. It is concluded that the magnetic field with negative gradient acts similar to Buoyancy force and augments the Nusselt number, while the magnetic field with positive gradient decreases it. Also with the negative gradient of the magnetic field, pumping power increases and vice versa for the positive gradient case. - Highlights: We model hydrothermal behavior of a ferrofluid flow using two phase mixture model. Various external non-uniform magnetic fields were implemented in a vertical tube. Nusselt number can be controlled using the magnetic field with different gradients. The magnetic field is more effective in low Reynolds numbers. Heat transfer enhancement using the magnetic field needs high pumping power.

  16. Ring-shaped velocity distribution functions in energy-dispersed structures formed at the boundaries of a proton stream injected into a transverse magnetic field: Test-kinetic results

    CERN Document Server

    Voitcu, Gabriel

    2016-01-01

    In this paper, we discuss the formation of ring-shaped and gyro-phase restricted velocity distribution functions (VDFs) at the edges of a cloud of protons injected into non-uniform distributions of the electromagnetic field. The velocity distribution function is reconstructed using the forward test-kinetic method. We consider two profiles of the electric field: (1) a non-uniform E-field obtained by solving the Laplace equation consistent with the conservation of the electric drift and (2) a constant and uniform E-field. In both cases, the magnetic field is similar to the solutions obtained for tangential discontinuities. The initial velocity distribution function is Liouville mapped along numerically integrated trajectories. The numerical results show the formation of an energy-dispersed structure due to the energy-dependent displacement of protons towards the edges of the cloud by the gradient-B drift. Another direct effect of the gradient-B drift is the formation of ring-shaped velocity distribution functio...

  17. Velocity anisotropy in the Niger Delta sediments derived from ...

    African Journals Online (AJOL)

    Seismic velocities decrease and increase laterally and vertically, respectively, towards the coast. These variations are attributable to the lateral and vertical changes in the degrees of compaction coastward and reduction in porosity with depth. Three zones of steep, moderate and slow velocity gradients, respectively, have ...

  18. The usage of velocity deviation log (VDL) in order to recognize porosity types and trends in permeability of the Asmari and Jahrum reservoirs units in the KHESHT oil field (Kazeroon)

    Science.gov (United States)

    Morshedi Pour, Amin; Lotfpour, Masoud; Enayati, Aliasghar

    2010-05-01

    Porosity value is one of the most important factors which determine the oil volume and also basis of economical or uneconomical calculation of a distinct oil field. By combining the logs, nowadays, very detailed and precise issues could be recognized, for instance we could point examining of porosity types and trends in permeability by using the velocity deviation log (VDL). Velocity devotion log which is calculated by combination sonic log with the Norton porosity or density log provides tool to obtain down hole information on the predominate pore type in carbonates the log can be use to trace the down hole distribution of digenetic processes and to estimate trends in permeability. Generally speaking, porosity and velocity have inverted relationship; nevertheless the type of porosity changes this relationship. In order to establish the velocity deviation log at first; by using the Wyllie equation, porosity log was exchanged to synthetic velocity log, acquired real velocity difference from sonic log and the acquired synthetic velocity from the porosity log is expressed as velocity deviation log. With log being deviated to left and right, the type of porosity would be identified .this method is applied for the Asmari and Jahrum reservoirs units of the Khesht oil field in Kazeroon (Fars),And in one of the wells. This log approves the boundary of Formations which is along with unconformities and even zoning whether is based on porosity value or change of lithology, and also the results which are gotten from the log have close similarities with the results of thin section studies in terms of porosity. Drawing of log and calculation of petrophysic parameters are done by Geolog software.

  19. Vertical and Interfacial Transport in Wetlands (Invited)

    Science.gov (United States)

    Variano, E. A.

    2010-12-01

    the velocity and scalar fields, respectively. To study sediment transport, an additional step is needed. Idealized sediment grains are manufactured, again using fluoropolymers. This allows the sediment and fluid phase to be resolved simultaneously, and the velocities of each to be determined independently of the other. The use of fluoropolymers means that the laboratory imaging techniques do not suffer from blockage during laser light delivery or during image capture by digital cameras. Cameras are paired and run in stereoscopic mode to allow three-dimensional velocities to be determined. This is important given the 3D nature of flow through vegetation. Current results from ongoing laboratory, field, and modeling efforts will be discussed, as well as the upcoming steps.

  20. Premixed flame propagation in vertical tubes

    CERN Document Server

    Kazakov, Kirill A

    2015-01-01

    Analytical treatment of premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations describing quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds, and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by the gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are ide...

  1. Predicting Vertical Motion within Convective Storms

    Science.gov (United States)

    van den Heever, S. C.

    2016-12-01

    Convective storms are both beneficial in the fresh water they supply and destructive in the life-threatening extreme weather they produce. They are found throughout the tropics and midlatitudes, vary in structure from isolated to highly organized systems, and are the sole source of precipitation in many regions of Earth. Convective updrafts and downdrafts plays a crucial role in cloud and precipitation formation, latent heating, water vapor transport, storm organization, and large-scale atmospheric circulations such as the Hadley and Walker cells. These processes, in turn, impact the strength and longevity of updrafts and downdrafts through complex, non-linear feedbacks. In spite of the significant influence of convective updrafts and downdrafts on the weather and climate system, accurately predicting vertical motion using numerical models remains challenging. In high-resolution cloud-resolving models where vertical motion is normally resolved, significant biases exist in the predicted profiles of updraft and downdraft velocities, at least for the limited cases where observational data have been available for model evaluation. It has been suggested that feedbacks between the vertical motion and microphysical processes may be one cause of these discrepancies, however, our understanding of these feedbacks remains limited. In this talk, the results of a small field campaign conducted over northeastern Colorado designed to observe storm vertical motion and cold pool characteristics within isolated and organized deep convective storms will be described. High frequency radiosonde, radar and drone measurements of a developing through mature supercell storm updraft and cold pool will be presented and compared with RAMS simulations of the same supercell storm. An analysis of the feedbacks between the storm dynamical and microphysical processes will be presented, and implications for regional and global modeling of severe storms will be discussed.

  2. Depth-dependent Vertical-to-Horizontal (V/H) Ratios of Free-Field Ground Motion Response Spectra for Deeply Embedded Nuclear Structures

    Energy Technology Data Exchange (ETDEWEB)

    Wei, X. [Brookhaven National Lab. (BNL), Upton, NY (United States); Braverman, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Miranda, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Rosario, M. E. [Brookhaven National Lab. (BNL), Upton, NY (United States); Costantino, C. J. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-02-01

    This report documents the results of a study to determine the depth-dependent V/H ratios of ground motion response spectra in the free field. The V/H ratios reported herein were developed from a worldwide database of surface and downhole acceleration recordings obtained from 45 vertical array stations. This database was specifically compiled for this project, and includes information from a diversity of active tectonic regions (California, Alaska, Taiwan, Japan), site conditions (rock to soft soil), ground motion intensity levels (PGAs between 0.01 g and 0.50 g), magnitudes (between ML 2.78 and JMA 8.1), epicentral distances (between 3.2 km and 812 km), and source depths (between 1.2 km and 112 km), as well as sensors at surface and at a wide range of depths relevant to the project. To study the significance of the depth effect, V/H ratios from all the records were sorted into a number of depth bins relevant to the project, and statistics (average, standard deviation, coefficient of variation, 16th, 50th, and 84th percentiles) of the V/H ratios within each bin were computed. Similar analyses were repeated, controlling for different site conditions, ground motion intensity levels, array locations, and source depths, to study their relative effect on the V/H ratios. Our findings confirm the importance of the depth effect on the V/H ratios. The research findings in this report can be used to provide guidance on the significance of the depth effect, and the extent to which this effect should be considered in the seismic design of deeply embedded SMR structures and NPP structures in general.

  3. Assessing Stride Variables and Vertical Stiffness with GPS-Embedded Accelerometers: Preliminary Insights for the Monitoring of Neuromuscular Fatigue on the Field

    Directory of Open Access Journals (Sweden)

    Martin Buchheit, Andrew Gray, Jean-Benoit Morin

    2015-12-01

    Full Text Available The aim of the present study was to examine the ability of a GPS-imbedded accelerometer to assess stride variables and vertical stiffness (K, which are directly related to neuromuscular fatigue during field-based high-intensity runs. The ability to detect stride imbalances was also examined. A team sport player performed a series of 30-s runs on an instrumented treadmill (6 runs at 10, 17 and 24 km·h-1 with or without his right ankle taped (aimed at creating a stride imbalance, while wearing on his back a commercially-available GPS unit with an embedded 100-Hz tri-axial accelerometer. Contact (CT and flying (FT time, and K were computed from both treadmill and accelerometers (Athletic Data Innovations data. The agreement between treadmill (criterion measure and accelerometer-derived data was examined. We also compared the ability of the different systems to detect the stride imbalance. Biases were small (CT and K and moderate (FT. The typical error of the estimate was trivial (CT, small (K and moderate (FT, with nearly perfect (CT and K and large (FT correlations for treadmill vs. accelerometer. The tape induced very large increase in the right - left foot ∆ in CT, FT and K measured by the treadmill. The tape effect on CT and K ∆ measured with the accelerometers were also very large, but of lower magnitude than with the treadmill. The tape effect on accelerometer-derived ∆ FT was unclear. Present data highlight the potential of a GPS-embedded accelerometer to assess CT and K during ground running.

  4. Determining the group velocity dispersion by field analysis for the LP0X, LP1X, and LP2X mode groups independently of the fiber length: applications to step-index fibers

    DEFF Research Database (Denmark)

    Israelsen, Stine Møller; Usuga Castaneda, Mario A.; Rottwitt, Karsten

    2017-01-01

    By knowing the electric field distribution of a guided mode in an optical fiber, we are able to evaluate the group velocity dispersion in a weakly guiding step-index fiber for a pure mode in the LP0X, LP1X, and LP2X mode groups independently of the fiber length. We demonstrate the method...

  5. Effect of radiation on free convection heat and mass transfer flow through porous medium in a vertical channel with heat absorption/generation and chemical reaction

    Science.gov (United States)

    Lavanya, B.

    2017-07-01

    The present paper analyses a solution for the transient free flow on a viscous and incompressible fluid between two vertical walls as a result of heta and mass transfer. The perturbation technique ahs been used to find the solutions for the velocity and temperature fields by solving the governing partial differential equations. The temperature of the one plate is assumed to be fluctuating. The effcets of the various parametrs entering into the problem, on the velocity and the temprature are depivted graphically. The impact of various parameters (Da, Rv, Pr, R and S) on velocity and temperature fields are shown graphically. The expressions for skin friction at both walls are also obtained.

  6. Vertical pressure gradient and particle motions in wave boundary layers

    DEFF Research Database (Denmark)

    Jensen, Karsten Lindegård

    and its role in the fully turbulent boundary layer. The pressure in the flow is obtained from the flow fields of the oscillatory boundary layer. What differs, the vertical pressure gradient, from other turbulent quantities, like e.g. velocity fluctuations is that it can detect newly generated turbulence....... The experiment is conducted in a oscillating water tunnel, for both smooth bed and rough bed. The particle motion is determined by utilizing particle tracking base on a video recording of the particle motion in the flow. In the oscillatory flow, in contrast to steady current, the particle motion is a function...

  7. Heat Transfer in MHD Mixed Convection Flow of a Ferrofluid along a Vertical Channel.

    Directory of Open Access Journals (Sweden)

    Aaiza Gul

    Full Text Available This study investigated heat transfer in magnetohydrodynamic (MHD mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4 was selected as a conventional base fluid. In addition, non-magnetic (Al2O3 aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published work.

  8. Heat Transfer in MHD Mixed Convection Flow of a Ferrofluid along a Vertical Channel.

    Science.gov (United States)

    Gul, Aaiza; Khan, Ilyas; Shafie, Sharidan; Khalid, Asma; Khan, Arshad

    2015-01-01

    This study investigated heat transfer in magnetohydrodynamic (MHD) mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4) was selected as a conventional base fluid. In addition, non-magnetic (Al2O3) aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published work.

  9. Loading effects in GPS vertical displacement time series

    Science.gov (United States)

    Memin, A.; Boy, J. P.; Santamaría-Gómez, A.; Watson, C.; Gravelle, M.; Tregoning, P.

    2015-12-01

    Surface deformations due to loading, with yet no comprehensive representation, account for a significant part of the variability in geodetic time series. We assess effects of loading in GPS vertical displacement time series at several frequency bands. We compare displacement derived from up-to-date loading models to two global sets of positioning time series, and investigate how they are reduced looking at interannual periods (> 2 months), intermediate periods (> 7 days) and the whole spectrum (> 1day). We assess the impact of interannual loading on estimating velocities. We compute atmospheric loading effects using surface pressure fields from the ECMWF. We use the inverted barometer (IB) hypothesis valid for periods exceeding a week to describe the ocean response to the pressure forcing. We used general circulation ocean model (ECCO and GLORYS) to account for wind, heat and fresh water flux. We separately use the Toulouse Unstructured Grid Ocean model (TUGO-m), forced by air pressure and winds, to represent the dynamics of the ocean response at high frequencies. The continental water storage is described using GLDAS/Noah and MERRA-land models. Non-hydrology loading reduces the variability of the observed vertical displacement differently according to the frequency band. The hydrology loading leads to a further reduction mostly at annual periods. ECMWF+TUGO-m better agrees with vertical surface motion than the ECMWF+IB model at all frequencies. The interannual deformation is time-correlated at most of the locations. It is adequately described by a power-law process of spectral index varying from -1.5 to -0.2. Depending on the power-law parameters, the predicted non-linear deformation due to mass loading variations leads to vertical velocity biases up to 0.7 mm/yr when estimated from 5 years of continuous observations. The maximum velocity bias can reach up to 1 mm/yr in regions around the southern Tropical band.

  10. Vertical Transport of Momentum by the Inertial-Gravity Internal Waves in a Baroclinic Current

    Directory of Open Access Journals (Sweden)

    A. A. Slepyshev

    2017-08-01

    in the first mode only in the pycnocline, outside the pycnocline their values are comparable in absolute value. The longitudinal component of the Stokes drift velocity of 15-min second mode internal waves observed in the field experiment during the 44th voyage of R/V “Mikhail Lomonosov” on the northwestern shelf of the Black Sea is by an order of magnitude greater than the transversal one. Vertical wave fluxes of the momentum also differ from zero and can be either comparable with the corresponding turbulent fluxes or exceed them.

  11. Thermal diffusion effects on free convection and mass transfer flow for an infinite vertical plate

    CERN Document Server

    Abdel-Khalek, M M

    2003-01-01

    A theoretical study is performed to examine the effects of thermal diffusion on free convection and mass transfer flow for an infinite vertical plate. The governing equations for the fluid flow and the heat transfer are solved subject to the relevant boundary conditions. A perturbation technique is used to obtain expressions for the velocity field and skin friction. An analysis of the effects of the parameters on the concentration, velocity and temperature profiles as well as skin friction and the rate of mass and heat transfer is done with the aid of graphs.

  12. 4D left ventricular resultant wall motion and blood flow assessed by phase-shift velocity mapping at high-field 3T MRI.

    Science.gov (United States)

    Samnøy, Stig F; Cuypers, Jochem; Greve, Gottfried; Larsen, Terje H

    2017-11-01

    Contractility and elasticity of the myocardium are important variables for detecting anomalies that may influence pump function. It is important to assess both wall motion and blood flow to detect regional left ventricular (LV) dysfunction and abnormal flow patterns. This study discusses four-dimensional (4D) phase-contrast magnetic resonance imaging (MRI) for simultaneous quantification and visualization of LV wall motion and blood flow. In thirteen healthy subjects, a three-directional retrospective cardiac triggered phase-shift velocity mapping technique was used to acquire velocity data of the LV throughout the cardiac cycle. All short-axis slices of the LV wall were segmented in six sectors of 60° starting from the anterior hinge point between the right and left ventricles, from base to apex. Velocity data in resultant, radial, circumferential and longitudinal directions were calculated and presented as coloured three-directional vectors. Our findings showed a reduction in maximum wall velocities from base to apex, whereas for the radial and circumferential directions no significant differences were noted (13·1 ± 2·7 and 13·0 ± 2·9 cm s(-1) , respectively. P = 0·9). The longitudinal maximum velocities (21·0 ± 0·6 cm s(-1) ) were significantly higher than the radial and circumferential components (P = 0·002). We found that the inclination angle of the resultant blood flow was changed towards the left ventricular outflow tract during systole. Using this 4D MRI velocity mapping technique, we present an improved method for quantification and visualization of ventricular wall velocities in the radial, circumferential and longitudinal directions, as well as for the intracavity blood flow. © 2016 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  13. Vertical variations of coral reef drag forces

    Science.gov (United States)

    Asher, Shai; Niewerth, Stephan; Koll, Katinka; Shavit, Uri; LWI Collaboration; Technion Collaboration

    2017-11-01

    Corals rely on water flow for the supply of nutrients, particles and energy. Therefore, modeling of processes that take place inside the reef, such as respiration and photosynthesis, relies on models that describe the flow and concentration fields. Due to the high spatial heterogeneity of branched coral reefs, depth average models are usually applied. Such an average approach is insufficient when the flow spatial variation inside the reef is of interest. We report on measurements of vertical variations of drag force that are needed for developing 3D flow models. Coral skeletons were densely arranged along a laboratory flume. Two corals were CT-scanned and replaced with horizontally sliced 3D printed replicates. Drag profiles were measured by connecting the slices to costume drag sensors and velocity profiles were measured using a LDV. The measured drag of whole colonies was in excellent agreement with previous studies; however, these studies never showed how drag varies inside the reef. In addition, these distributions of drag force showed an excellent agreement with momentum balance calculations. Based on the results, we propose a new drag model that includes the dispersive stresses, and consequently displays reduced vertical variations of the drag coefficient.

  14. Vertical profiles of aerosol and black carbon in the Arctic: a seasonal phenomenology along 2 years (2011–2012 of field campaigns

    Directory of Open Access Journals (Sweden)

    L. Ferrero

    2016-10-01

    Full Text Available We present results from a systematic study of vertical profiles of aerosol number size distribution and black carbon (BC concentrations conducted in the Arctic, over Ny-Ålesund (Svalbard. The campaign lasted 2 years (2011–2012 and resulted in 200 vertical profiles measured by means of a tethered balloon (up to 1200 m a.g.l. during the spring and summer seasons. In addition, chemical analysis of filter samples, aerosol size distribution and a full set of meteorological parameters were determined at ground. The collected experimental data allowed a classification of the vertical profiles into different typologies, which allowed us to describe the seasonal phenomenology of vertical aerosol properties in the Arctic. During spring, four main types of profiles were found and their behavior was related to the main aerosol and atmospheric dynamics occurring at the measuring site. Background conditions generated homogenous profiles. Transport events caused an increase of aerosol concentration with altitude. High Arctic haze pollution trapped below thermal inversions promoted a decrease of aerosol concentration with altitude. Finally, ground-based plumes of locally formed secondary aerosol determined profiles with decreasing aerosol concentration located at different altitude as a function of size. During the summer season, the impact from shipping caused aerosol and BC pollution plumes to be constrained close to the ground, indicating that increasing shipping emissions in the Arctic could bring anthropogenic aerosol and BC in the Arctic summer, affecting the climate.

  15. Similarity Solutions of MHD Mixed Convection Flow with Variable Reactive Index, Magnetic Field, and Velocity Slip Near a Moving Horizontal Plate: A Group Theory Approach

    Directory of Open Access Journals (Sweden)

    W. A. Khan

    2012-01-01

    Full Text Available The mixed convection of Newtonian fluid flow along a moving horizontal plate with higher-order chemical reaction, variable concentration reactant, and variable wall temperature and concentration is considered. Velocity slip and the thermal convective boundary conditions are applied at the plate surface. The governing partial differential equations are transformed into similarity equations via dimensionless similarity transformations developed by one-parameter continuous group method. The numerical solutions of the transformed ordinary differential equations are constructed for velocity, temperature and concentration functions, the skin friction factor, the rate of heat, and the rate of mass transfer using an implicit finite difference numerical technique. The investigated parameters are buoyancy parameters , , chemical reaction parameter , suction/injection parameter , velocity slip parameter convective heat transfer parameter , magnetic parameter , Prandtl number Pr and Schmidt number, Sc. Comparison with results from the open literature shows a very good agreement.

  16. Salt Interval Velocities vs Latitude in the Deepwater Gulf of Mexico: Keathley Canyon and Walker Ridge Areas

    Science.gov (United States)

    Cornelius, S.; Castagna, J. P.

    2016-12-01

    ABSTRACT A well log database of approximately 300 well logs from the Keathley Canyon and Walker Ridge areas of the Gulf of Mexico plus Mad Dog Field and Mission Deep Field in Green Canyon has been created for the purpose of building a geologically based 3D velocity model. While in the process of calibrating the finished velocity model, a scatter plot was made of all salt interval velocities versus latitude and an unexpected correlation was observed. Five different interval velocity zones have been identified with each having certain associated mineralogies within a latitude range. The salt interval velocity in the southern limits of the study area is higher than 15,000 ft/sec (4572 m/sec) due to the presence of gypsum. The northern most wells in the project area have anhydrite present inside the salt matrix such that their interval velocity can be as high as 18,535 ft/sec (5650 m/sec). In the mid-latitude zones, sylvite, siltstone, claystone, shale, tar and bitumen, with small traces of both anhydrite and gypsum, are found within the salt, yielding salt interval velocity variation from 14,388 ft/sec to 14,909 ft/sec (4386 m/sec to 4544 m/sec). The mineralogical content of the salt in each well was roughly estimated from mud logs and the corresponding interval velocities were determined from vertical seismic profiles, checkshot surveys, and sonic logs. Both geothermal gradients and overburden geopressure gradients between the mudline and the true vertical depth at well bottom calculated from this well database do not show the same correlation with latitude as the salt interval velocities. Mineralogical modeling of the salt composition using Hashin-Shtrikman bounds shows that these various inclusions within the salt matrix can be the cause of the observed variations in the salt interval velocities.

  17. MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.

    Science.gov (United States)

    Uddin, Md Jashim; Khan, Waqar A; Ismail, A I Md

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m) whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1)/2) where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory.

  18. Diffraction imaging and velocity analysis using oriented velocity continuation

    KAUST Repository

    Decker, Luke

    2014-08-05

    We perform seismic diffraction imaging and velocity analysis by separating diffractions from specular reflections and decomposing them into slope components. We image slope components using extrapolation in migration velocity in time-space-slope coordinates. The extrapolation is described by a convection-type partial differential equation and implemented efficiently in the Fourier domain. Synthetic and field data experiments show that the proposed algorithm is able to detect accurate time-migration velocities by automatically measuring the flatness of events in dip-angle gathers.

  19. Balance velocities of the Greenland ice sheet

    DEFF Research Database (Denmark)

    Joughin, I.; Fahnestock, M.; Ekholm, Simon

    1997-01-01

    We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetery data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail......, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning....

  20. Distribution and arrest of vertical through-going joints in shallow-water carbonates: Insights from an integrated virtual outcrop - field structural analysis of a reservoir-scale exposure (Sorrento Peninsula, Italy)

    Science.gov (United States)

    Corradetti, Amerigo; Tavani, Stefano; Parente, Mariano; Iannace, Alessandro; Vinci, Francesco; Pirmez, Carlos; Torrieri, Stefano; Giorgioni, Maurizio; Pignalosa, Antonio; Mazzoli, Stefano

    2017-04-01

    Through-going joints cutting across several beds are often invoked to match large-scale permeability patterns in tight carbonate reservoirs. However, despite the importance of these structures for fluid flow, only few field studies focused on the understanding and estimation of through-going joint dimensional parameters, including spacing and vertical extent in relation to stratigraphy. Recent improvements in the construction of virtual models of outcrops can greatly help to overcome many logistic issues, favoring the evaluation of relationships between jointing and stratigraphy at the reservoir scale. In this study, we present the results obtained from integrating field measurements and stratigraphic logs with a virtual outcrop model of a carbonate platform reservoir analogue in the Sorrento peninsula (Italy). The outcrop consists of a nearly vertical cliff exposing a monocline of alternating gently-dipping shallow-water limestones and dolostones, crossed by several vertical joints of different size. This study allowed us to define how major through-going joints pass across thick beds (bed thickness > 30 cm), while they arrest against packages made of thinly stratified layers. In essence, through-going joints arrest on "weak" levels, consisting of thinly bedded layers interposed between packages made of thick beds, in the same manner as bed-confined joints arrest on less competent interlayers.

  1. Heat and mass transfer in a vertical channel under heat-gravitational convection conditions

    Science.gov (United States)

    Petrichenko, Michail; Nemova, Darya; Reich, Elisaveta; Subbotina, Svetlana; Khayrutdinova, Faina

    2016-03-01

    Heat-gravitational motion of an air flow in a vertical channel with one-sided heating in an area with low Reynolds number is stated in Boussinesq approximation. Hydraulic variables field in a heat-gravitational motion is modeled with the application of ANSYS-FLUENT. It is converted to average velocity and temperature values in a cross section of the channel. The value of an average velocity is determined by rate of heat supply in a barotropic flow with a polytropic coefficient nventilated vertical channel with free air access and in the absence of gaps. In a channel with closed air access inleakage of the cold air through gaps on an unheated side leads to decrease in an average speed at least twice in comparison to channel with free air access.

  2. The effect of vertical advection and diffusion on nutrient supply to the euphotic zone: a model study of the Iceland-Faeroes Front

    Science.gov (United States)

    Popova, E.; Srokosz, M.

    2006-12-01

    This paper examines the effect of vertical advection and vertical diffusion on the supply of nutrients to the euphotic zone. This is done using a high resolution coupled biological-physical model, that has previously been used to reproduce in situ and satellite observations of physical and biological variability at the Iceland Faeroes Front (IFF). Oligotrophic conditions are imposed in the model in order to examine the vertical flux of nutrients.The results show that, while instantaneous vertical advective fluxes of nutrients can be much larger than vertical diffusive ones, over a period of days the latter act consistently to supply nutrients to the euphotic zone. In contrast, the spatially and temporally varying nature of the vertical velocity field means that there is no consistent vertical advective flux of nutrients. This suggests that for real "messy" complex flows, such as the one modelled here, ageostrophic vertical velocities induced by eddies and frontal meanders may not play as important a role in supplying nutrient to the euphotic zone, and in enhancing biological production there, as has previously been thought.

  3. Numerical optimization of a three-channel radiofrequency coil for open, vertical-field, MR-guided, focused ultrasound surgery using the hybrid method of moment/finite difference time domain method.

    Science.gov (United States)

    Xin, Xuegang; Wang, Di; Han, Jijun; Feng, Yanqiu; Feng, Qianjin; Chen, Wufan

    2012-07-01

    The numerical optimization of a three-channel radiofrequency (RF) coil with a physical aperture for the open, vertical-field, MR-guided, focused ultrasound surgery (MRgFUS) system using the hybrid method of moment (MoM)/finite difference time domain (FDTD) method is reported. The numerical simulation of the current density distribution on an RF coil with a complicated irregular structure was performed using MoM. The electromagnetic field simulation containing the full coil-tissue interactions within the region of interest was accomplished using the FDTD method. Huygens' equivalent box with six surfaces smoothly connected the MoM and FDTD method. An electromagnetic model of the human pelvic region was reconstructed and loaded in the FDTD zone to optimize the three-channel RF coil and compensate for the lower sensitivity at the vertical field. In addition, the numerical MoM was used to model the resonance, decoupling and impedance matching of the RF coil in compliance with engineering practices. A prototype RF coil was constructed to verify the simulation results. The results demonstrate that the signal-to-noise ratio and the homogeneity of the B(1) field were both greatly improved compared with previously published results. Copyright © 2011 John Wiley & Sons, Ltd.

  4. Segmental and Kinetic Contributions in Vertical Jumps Performed with and without an Arm Swing

    Science.gov (United States)

    Feltner, Michael E.; Bishop, Elijah J.; Perez, Cassandra M.

    2004-01-01

    To determine the contributions of the motions of the body segments to the vertical ground reaction force ([F.sub.z]), the joint torques produced by the leg muscles, and the time course of vertical velocity generation during a vertical jump, 15 men were videotaped performing countermovement vertical jumps from a force plate with and without an arm…

  5. Vertical saccades in children: a developmental study.

    Science.gov (United States)

    Bucci, Maria Pia; Seassau, Magali

    2014-03-01

    There are no studies exploring the development of vertical saccades in large populations of children. In this study, we examined the development of vertical saccades in sixty-nine children. Binocular eye movements were recorded using an infrared video oculography system [Mobile EBT(®), e(ye)BRAIN], and movements from both eyes had been analyzed. The gain and the peak velocity of vertical saccades show an up-down asymmetry. Latency value decreases with the age of children, and it does not depend on the direction of the saccades; in contrast, the gain and the peak velocity values of vertical saccades are stable during childhood. We suggest that the up-down asymmetry is developed early, or is innate, in humans. Latencies of vertical saccades develop with the age of children, in relationship with the development of the cortical network responsible for the saccade preparation. In contrast, the precision and the peak velocity are not age-dependent as they are controlled by the cerebellum and brainstem structures.

  6. Pulsejet engine dynamics in vertical motion using momentum conservation

    Science.gov (United States)

    Cheche, Tiberius O.

    2017-03-01

    The momentum conservation law is applied to analyse the dynamics of a pulsejet engine in vertical motion in a uniform gravitational field in the absence of friction. The model predicts the existence of a terminal speed given the frequency of the short pulses. The conditions where the engine does not return to the starting position are identified. The number of short periodic pulses after which the engine returns to the starting position is found to be independent of the exhaust velocity and gravitational field intensity for a certain frequency of pulses. The pulsejet engine and turbojet engine aircraft models of dynamics are compared. Also the octopus dynamics is modelled. The paper is addressed to intermediate undergraduate students of classical mechanics and aerospace engineering.

  7. A comprehensive statistical investigation of schlieren image velocimetry (SIV) using high-velocity helium jet

    Science.gov (United States)

    Biswas, Sayan; Qiao, Li

    2017-03-01

    A detailed statistical assessment of seedless velocity measurement using Schlieren Image Velocimetry (SIV) was explored using open source Robust Phase Correlation (RPC) algorithm. A well-known flow field, an axisymmetric turbulent helium jet, was analyzed near and intermediate region (0≤ x/d≤ 20) for two different Reynolds numbers, Re d = 11,000 and Re d = 22,000 using schlieren with horizontal knife-edge, schlieren with vertical knife-edge and shadowgraph technique, and the resulted velocity fields from SIV techniques were compared to traditional Particle Image Velocimetry (PIV) measurements. A novel, inexpensive, easy to setup two-camera SIV technique had been demonstrated to measure high-velocity turbulent jet, with jet exit velocities 304 m/s (Mach = 0.3) and 611 m/s (Mach = 0.6), respectively. Several image restoration and enhancement techniques were tested to improve signal to noise ratio (SNR) in schlieren and shadowgraph images. Processing and post-processing parameters for SIV techniques were examined in detail. A quantitative comparison between self-seeded SIV techniques and traditional PIV had been made using correlation statistics. While the resulted flow field from schlieren with horizontal knife-edge and shadowgraph showed excellent agreement with PIV measurements, schlieren with vertical knife-edge performed poorly. The performance of spatial cross-correlations at different jet locations using SIV techniques and PIV was evaluated. Turbulence quantities like turbulence intensity, mean velocity fields, Reynolds shear stress influenced spatial correlations and correlation plane SNR heavily. Several performance metrics such as primary peak ratio (PPR), peak to correlation energy (PCE), the probability distribution of signal and noise were used to compare capability and potential of different SIV techniques.

  8. Numerical study on small scale vertical axis wind turbine

    Science.gov (United States)

    Parra-Santos, Teresa; Gallegos, Armando; Uzarraga, Cristóbal N.; Rodriguez, Miguel A.

    2016-03-01

    The performance of a Vertical Axis Wind Turbine (VAWT) is numerically analyzed. The set-up is Hdarrieus with three straight blades airfoils NACA attached to a rotating vertical shaft. The wind turbine has solidity equals to the unity operating with wind velocity of 7 m/s. Influence of pitch angle is tested to get design tendencies. 2D, transient, Navier Stokes equations are solved using the code Ansys-Fluent. Conservation equations were solved with a Third-Order MUSCL scheme using SIMPLE to couple pressure and velocity. More than six revolutions must be simulated to get the periodic behavior. Two models of turbulence have been contrasted Realizable k-epsilon and Transition SST concluding the last one show more realistic flow features. Pitch angles of 0º, -6º and -10º have been tested with Tip Speed Ratios ranging from 0.7 and 1.6. The no null pitch angles improve the performance of the wind turbine. Instantaneous and averaged power coefficients as well as detailed flow field around the airfoils are showed.

  9. Numerical study on small scale vertical axis wind turbine

    Directory of Open Access Journals (Sweden)

    Parra-Santos Teresa

    2016-01-01

    Full Text Available The performance of a Vertical Axis Wind Turbine (VAWT is numerically analyzed. The set-up is Hdarrieus with three straight blades airfoils NACA attached to a rotating vertical shaft. The wind turbine has solidity equals to the unity operating with wind velocity of 7 m/s. Influence of pitch angle is tested to get design tendencies. 2D, transient, Navier Stokes equations are solved using the code Ansys-Fluent. Conservation equations were solved with a Third-Order MUSCL scheme using SIMPLE to couple pressure and velocity. More than six revolutions must be simulated to get the periodic behavior. Two models of turbulence have been contrasted Realizable k-epsilon and Transition SST concluding the last one show more realistic flow features. Pitch angles of 0º, -6º and -10º have been tested with Tip Speed Ratios ranging from 0.7 and 1.6. The no null pitch angles improve the performance of the wind turbine. Instantaneous and averaged power coefficients as well as detailed flow field around the airfoils are showed.

  10. Analysis of unsteady natural convective radiating gas flow in a vertical channel by employing the Caputo time-fractional derivative

    Science.gov (United States)

    Ahmad, Bakhtiar; Ali Shah, Syed Inayat; Ul Haq, Sami; Ali Shah, Nehad

    2017-09-01

    In this paper the exact solution of the unsteady natural convection radiating flow in an open ended vertical channel is studied. The channel is stationary with non-uniform temperature. The governing equations are fractional differential equations with the Caputo time-fractional derivative. Closed form analytical solutions for the temperature and velocity fields are obtained by using the Laplace transform technique. These solutions are expressed with the Wright function, the Robotnov and Hartley function. The effects of the fractional order and physical parameters on temperature and fluid velocity are presented graphically.

  11. Analyses of Current And Wave Forces on Velocity Caps

    DEFF Research Database (Denmark)

    Christensen, Erik Damgaard; Buhrkall, Jeppe; Eskesen, Mark C. D.

    2015-01-01

    leads the water into another pipe or tunnel system. A pressure gradient generated by the water level difference between the sea and basin drives the flow through the tunnel system. The tunnel system is often in the order of a couple kilometers long. Based on CFD analyses (computational fluid dynamics......Velocity caps are often used in connection with for instance offshore intake sea water for the use of for cooling water for power plants or as a source for desalinization plants. The intakes can also be used for river intakes. The velocity cap is placed on top of a vertical pipe. The vertical pipe......) this paper investigates the current and wave forces on the velocity cap and the vertical cylinder. The Morison’s force model was used in the analyses of the extracted force time series in from the CFD model. Further the distribution of the inlet velocities around the velocity cap was also analyzed in detail...

  12. Acquired vertical accommodative vergence.

    Science.gov (United States)

    Klein-Scharff, Ulrike; Kommerell, Guntram; Lagrèze, Wolf A

    2008-03-08

    Vertical accommodative vergence is an unusual synkinesis in which vertical vergence is modulated together with accommodation. It results from a supranuclear miswiring of the network normally conveying accommodative convergence. So far, it is unknown whether this condition is congenital or acquired. We identified an otherwise healthy girl who gradually developed vertical accommodative vergence between five to 13 years of age. Change of accommoda