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Sample records for vertical velocity due

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  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. 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...

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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…

  15. 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.

  16. 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.

  17. 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.

  18. Analysis of debris-flow velocities due to superelevation

    Science.gov (United States)

    Scheidl, C.; Rickenmann, D.; McArdell, B. W.

    2012-12-01

    For debris flows the estimation of the maximum flow-velocity is considered to be essential. Often the runout or the degree of exposure of a debris-flow event can only be predicted, based on the assessment of the maximum velocity. In practice, geomorphologic traces like flood marks on banks provide important information about the flowing process of a debris flow. A possible approach to estimate maximum flow velocities is based on the vortex equation by using superelevation marks. Superelevation can be observed in bending channels, where the flow-height of the inner-curvature is lower than the flow-height of the outer-curvature, caused by the centrifugal acceleration of the flow. For the estimation of debris-flow velocities with the vortex equation, a correction factor (>1) is often introduced, accounting for the viscosity and vertical sorting of the bulk mixture. Several studies show that the correction factor may be as high as 10 and may depend on bend geometry and debris flow material properties. The objective of this work is therefore to analyze the influence of channel geometry and material properties on the vortex equation when applying to debris flows. In particular, the project aims to compare observed flow velocities from physical modeling in flume experiments with observations from debris-flow field sites. In a first step experimental investigations are done at the laboratory of the Swiss Federal Institute WSL, Birmensdorf. The flume consists of a flexible plastic half-pipe and is mounted on a wooden plane construction. At the moment two different bend radii (1.0 m and 3.0 m) with a bend angle of 60° are implemented. The total length of the flume is further covered with 40 grit silicon carbide sandpaper reflecting a constant basal friction layer. To apply for the complexity of a debris-flow process, three different material mixtures based on three different grain size distributions, were defined. Superelevation is measured by using high speed cameras

  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

  20. 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.

  1. 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.

  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. 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. 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

  7. 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.

  8. 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.

  9. 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.

  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. SIMULATION OF SCOURING AROUND A VERTICAL CYLINDER DUE TO TSUNAMI

    Directory of Open Access Journals (Sweden)

    Kuswandi

    2017-06-01

    Full Text Available Local scour due to tsunami is damaging especially on shallow foundation. Although relatively in a short duration, tsunami attack may scour material around buildings that led to destruction. A number of formulae on local scouring due to flood and tsunami have been available. The local scouring pattern and depth produced by tsunami may be affected by tsunami duration and tsunami surge Froude number and hence different to that resulted by flood which normally have much longer duration and lower Froude number. The research used a relatively short flume to create short duration tsunami surge that run-up on 1:20 beach slope and hit a vertical cylinder on land. Both the pattern and the depth of local scouring around the cylinder were observed and the results were compared with similar research but with different tsunami surge characteristic. It was shown that the maximum scour depth was significantly deeper than the final scour depth. When compared with other experimental study of local scour due to tsunami, the present local scour maximum depth seemed to be slightly less. This could have been caused by the relatively short duration of the present experiment. It was also found that the sidewall effect was insignificant when the ratio of cylinder diameter to the flume width was less then approximately 0.15.

  12. 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.

  13. 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.

  14. 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.

  15. 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 ...

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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....

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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?

  17. Modifications of the optimal velocity traffic model to include delay due to driver reaction time

    Science.gov (United States)

    Davis, L. C.

    2003-03-01

    Straightforward inclusion of a delay time due to driver reaction time in the optimal velocity (OV) model reveals an unphysical sensitivity to driver reaction times. For delay times of nearly 1 s, which are typical for most drivers, oscillations in vehicle velocity induced by encountering a slower vehicle grow until limited by non-linear effects. Simulations demonstrate that unrealistically small delay times are needed for lengthy platoons of vehicles to avoid collisions. This is a serious limitation of the OV model. Other models, such as the inertial car-following model, allow somewhat larger delay times, but also show unphysical effects. Modifications of the OV model to overcome this deficiency are demonstrated. In addition, unphysical short-period oscillations of vehicle velocity are eliminated by introducing partial car-following into the model. Traffic jams are caused primarily by the delay due to driver reaction time in the modified OV model.

  18. 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.

  19. Drag and power-loss in rowing due to velocity fluctuations

    NARCIS (Netherlands)

    Greidanus, A.J.; Delfos, R.; Westerweel, J.; Jansen, A.J.

    2016-01-01

    The flow motions in the turbulent boundary layer between water and a rowing boat initiate a turbulent skin friction. Reducing this skin friction results in better rowing performances. A Taylor-Couette (TC) facility was used to verify the power losses due to velocity fluctuations PV′ in

  20. 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

  1. 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...

  2. 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.

  3. 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

  4. 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...

  5. 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%.

  6. Vertical transmission of the hip rolls due to wearing of TLSO for scoliosis.

    Science.gov (United States)

    Korovessis, P; Stamatakis, M; Baikousis, A; Kirkos, C; Kavouris, A

    1996-08-01

    Cosmesis is important in the treatment of adolescent patients with idiopathic scoliosis. It has been shown that although bracing reduces the rib hump, it induces several complications. The aim of this study was to describe a new disturbing complication due to wearing a thoracolumbosacral orthosis (TLSO) for adolescent idiopathic scoliosis: the vertical transmission of the hip rolls (trochanteric lipomatosis) in girls and its pathogenetic mechanisms. Trochanteric lipomatosis is common in the female population, particularly after adolescence, and is responsible for the characteristic appearance of the hip rolls. No data have been reported concerning vertical transmission of normal trochanteric lipomatosis with subsequent disturbance of aesthetic appearance while wearing the TLSO. In this prospective study, 300 consecutive adolescent girls who were treated with the TLSO for progressive idiopathic scoliosis were followed and evaluated for development of any vertical transmission of the hip rolls after application of the brace for an average of 2.5 years after termination of the treatment. Almost simultaneously, 290 age-matched, randomly selected adolescent girls served as controls and were examined by two unbiased observers during the school screening program to estimate the prevalence of trochanteric lipomatosis in female adolescents of the same geographic area. In this series, bracing reduced the thoracic scoliosis from 34.4 +/- 5 degrees to 18.5 +/- 6 degrees and the lumbar scoliosis from 29.4 +/- 4 degrees to 16.7 +/- 4 degrees 6 months after initiation of brace wearing. The average prevalence of normal trochanteric lipomatosis in girls in the control group was 26% (range, 12.2-68.4%) for the ages 9-14 years and was increasing with the age and weight. No correlation was found between amount of reduction of scoliosis and prevalence of the complication. Vertical transmission of the hip rolls was observed in 69 (23%) of the girls with scoliosis 6 months after

  7. Unrecognized ligamentous instability due to high-energy, low-velocity mechanism of injury.

    Science.gov (United States)

    Dusseldorp, J R; Ow-Yang, M; Mobbs, R J

    2010-01-01

    We report a unique mechanism of injury and illustrate the difficulties of diagnosing purely ligamentous injuries to the cervical spine. To our knowledge, there have been no previous reports of this type of high-energy, low-velocity mechanism of injury. The pattern of injury is also unusual, consisting of anterolisthesis of L4 on L5 with bilateral perched facet joints, atlantoaxial instability and bilateral lower limb fractures. We present a 49-year-old man who experienced a high-energy, low-velocity crush injury that led to extreme hyperflexion of his spine. Standard trauma protocols were carried out, yet atlantoaxial instability was not diagnosed until 3 days post-operatively, when the patient went into respiratory failure due to high spinal cord compression. We fused the C1/2 vertebral bodies using Harm's technique; the patient exhibited no long-term spinal cord dysfunction. Although uncommon, if left undiagnosed or not considered, purely ligamentous injuries to the cervical spine can result in catastrophic complications. Such injuries are an important subgroup to be considered at the time of initial assessment. Furthermore, when managing the multi-trauma patient, clinicians must remember not to overlook the atlantoaxial joint, as high-energy, low-velocity injury to the cervical spine may lead to silent, life-threatening instability that may not be apparent on routine imaging. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

  8. 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.

  9. 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.

  10. Bio-mixing due to Diel Vertical Migration of Daphnia spp. in a Small Lake

    Science.gov (United States)

    Simoncelli, Stefano; Wain, Danielle; Thackeray, Stephen

    2016-04-01

    Bio-turbulence or bio-mixing refers to the contribution of living organisms towards the mixing of waters in oceans and lakes. Experimental measurements in an unstratified tank by Wilhelmus & Dabiri (2014) show that zooplankton can trigger fluid instabilities through collective motions and that energy is imparted to scales bigger than organism's size of few mm. Length scales analysis, for low-Reynolds-number organisms in stratified water by Leshansky & Pismen (2010) and Kunze (2011), estimate eddy diffusivity up two orders of magnitude larger than the molecular thermal diffusivity. Very recently, Wand & Ardekani (2015) showed a maximum diffusivity of 10-5 m2/s for millimetre-sized organisms from numerical simulations in the intermediate Reynolds number regime. Here we focus our attention on turbulence generated by the vertical migration of zooplankton in a small lake, mostly populated by Daphnia spp. This very common species, belonging to Cladocera order, is engaged in a vertical migration (DVM) at sunset, with many organisms crossing the thermocline despite the density stratification. During the ascension they may create hydrodynamic disturbances in the lake interior where the stratification usually suppresses the vertical diffusion. We have conducted five turbulence experiments in Vobster Quay, a small (area ˜ 59,000 m2), deep (40m) man-made basin with small wind fetch and steep sides, located in the South West UK. Turbulence was measured with a temperature microstructure profiler. To asses the zooplankton vertical concentration we used a 100 μm mesh net, by collecting and analyzing samples in 8 layers of the lake. A bottom-mounted acoustic Doppler current profiler was also employed to track their concentration and migration with the measured backscatter strength. Measured dissipation rates ɛ during the day showed low turbulence level (<= 10-8 W/Kg) in the thermocline and in the zooplankton layer. Turbulence, during the DVM in two different days, is highest on

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. Acrodermatitis due to zinc deficiency after combined vertical gastroplasty with jejunoileal bypass: case report

    Directory of Open Access Journals (Sweden)

    Selma Freire de Carvalho Cunha

    Full Text Available CONTEXT: Nutritional complications may occur after bariatric surgery, due to restriction of food intake and impaired digestion or absorption of nutrients. CASE REPORT: After undergoing vertical gastroplasty and jejunoileal bypass, a female patient presented marked weight loss and protein deficiency. Seven months after the bariatric surgery, she presented dermatological features compatible with acrodermatitis enteropathica, as seen from the plasma zinc levels, which were below the reference values (34.4 mg%. The skin lesions improved significantly after 1,000 mg/day of zinc sulfate supplementation for one week. CONCLUSIONS: The patient's evolution shows that the multidisciplinary team involved in surgical treatment of obesity should take nutritional deficiencies into consideration in the differential diagnosis of skin diseases, in order to institute early treatment.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Real-Time Vertical Temperature, and Velocity Profiles from a Wave Glider

    Science.gov (United States)

    2014-09-30

    as well as notes on the spurious stalls incurred due to the mechanical braking system. The second generation UWW was delivered by MacArtney in May...power system was developed for the UWW to limit back electromotive force (back- EMF ) induced by current surges from the UWW’s motor. Majority of the

  1. 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.

  2. Stresses due to vertical subsurface loading for an inhomogeneous cross-anisotropic half-space

    Science.gov (United States)

    Wang, Cheng-Der; Pan, Ernian

    2004-10-01

    In this article, we present the solutions for the stresses induced by four different loads associated with an axially loaded pile in a continuously inhomogeneous cross-anisotropic half-space. The planes of cross-anisotropy are parallel to the horizontal surface of the half-space, and the Young's and shear moduli are assumed to vary exponentially with depth. The four loading types are: an embedded point load for an end-bearing pile, uniform skin friction, linear variation of skin friction, and non-linear parabolic variation of skin friction for a friction pile. The solutions for the stresses due to the pile load are expressed in terms of the Hankel integral and are obtained from the point load solutions of the same inhomogeneous cross-anisotropic half-space which were derived recently by the authors (Int. J. Rock Mech. Min. Sci. 2003; 40(5):667-685). A numerical procedure is proposed to carry out the integral. For the special case of homogeneous isotropic and cross-anisotropic half-space, the stresses predicted by the numerical procedure agree well with the solutions of Geddes and Wang (Geotechnique 1966; 16(3):231-255; Soils Found. 2003; 43(5):41-52). An illustrative example is also given to investigate the effect of soil inhomogeneity, the type and degree of soil anisotropy, and the four different loading types on the vertical normal stress. The presented solutions are more realistic in simulating the actual stratum of loading problem in many areas of engineering practice. Copyright

  3. 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

  4. Assessment of brine migration risks along vertical pathways due to CO2 injection

    Science.gov (United States)

    Kissinger, Alexander; Class, Holger

    2015-04-01

    Global climate change, shortage of resources and the growing usage of renewable energy sources has lead to a growing demand for the utilization of subsurface systems. Among these competing uses are Carbon Capture and Storage (CCS), geothermal energy, nuclear waste disposal, 'renewable' methane or hydrogen storage as well as the ongoing production of fossil resources like oil, gas and coal. Additionally, these technologies may also create conflicts with essential public interests such as water supply. For example, the injection of CO2 into the subsurface causes an increase in pressure reaching far beyond the actual radius of influence of the CO2 plume, potentially leading to large amounts of displaced salt water. In this work we focus on the large scale impacts of CO2 storage on brine migration but the methodology and the obtained results may also apply to other fields like waste water disposal, where large amounts of fluid are injected into the subsurface. In contrast to modeling on the reservoir scale the spatial scale required for this work is much larger in both vertical and lateral direction, as the regional hydrogeology has to be considered. Structures such as fault zones, hydrogeological windows in the Rupelian clay or salt domes are considered as potential pathways for displaced fluids into shallow systems and their influence has to be taken into account. We put the focus of our investigations on the latter type of scenario, since there is still a poor understanding of the role that salt diapirs would play in CO2 storage projects. As there is hardly any field data available on this scale, we compare different levels of model complexity in order to identify the relevant processes for brine displacement and simplify the modeling process wherever possible, for example brine injection vs. CO2 injection, simplified geometries vs. the complex formation geometry and the role of salt induced density differences on flow. Further we investigate the impact of the

  5. Near-surface seismic velocity changes in a salt-dominated environment due to shaking and thermal stressing

    Science.gov (United States)

    Richter, Tom; Sens-Schönfelder, Christoph; Kind, Rainer; Asch, Günter

    2014-05-01

    We report on results from a seismic station of the Integrated Plate Boundary Observatory Chile (IPOC) showing a superior sensitivity of seismic velocity changes in the surrounding medium to shaking and temperature. 5 years of daily autocorrelations of the IPOC network are analyzed with passive image interferometry. Due to the particular geological conditions we observe a high sensitivity of the medium around the station near Patache (PATCX) resulting in annual periodic velocity variations and temporary velocity reductions induced by ground shaking. We observe a linear relationship between the amplitude of the velocity reductions and the peak ground acceleration (PGA) of nearby earthquakes at station PATCX. Although velocity reductions are also observed at other stations of the IPOC array for the Mw 7.7 Tocopilla earthquake a clear relationship between the PGA of this earthquake and the induced velocity reductions at the different stations is not visible. Furthermore, we observe velocity variations with an annual and daily period. We present different arguments that these periodic changes are caused by variations of the atmospheric temperature. In this context we construct a model that starts at observed temperature variations and evaluates thermal stresses induced by the temperature gradients. Using radiative transfer based sensitivity kernels and third order elastic constants we relate the distribution of thermal stress in the subsurface to observable time shifts of coda waves. The model is able to reproduce the major features confirming that stress changes in the subsurface can be detected with noise based monitoring.

  6. Damage Accumulation in Vertical Breakwaters due to Combined Impact Loading and Pulsating Wave Loads

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Nielsen, Søren R. K.

    1999-01-01

    Vertical wall breakwaters used to protect for example an harbour from large waves usually consist of large concrete caissons placed on the seabed. The wave loads can be divided in two types, pulsating and impact loads. For some types of breakwaters especially the impact wave loads can be very large...

  7. 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...

  8. 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

  9. 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.

  10. Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy

    Science.gov (United States)

    Morawski, Wojciech

    2009-12-01

    Geological mapping in combination with geophysical investigations and borehole analyses show differences of the Pleistocene between the Warmia and Mazury palaeogeographic provinces in NE Poland. The (more western) Warmia province has a crystalline basement that is covered by a folded sedimentary succession of 2-4 km thick. The (more eastern) Mazury province (eastern) has a basement that forms part of the rigid East European crystalline craton, which is covered by a sedimentary cover of only 1-1.5 km thick. Cyclic loading by the Pleistocene ice sheets in this area induced glacioisostatic processes of different intensities, resulting in changing palaeogeographic conditions. The changes were increased by intense neotectonic activity that was induced by the ice sheets in the intermediate zone between the two provinces, stretching along the western slope of the crystalline craton. Significant part of intermediate zone forms a belt of crevasse-infill landforms deposited between the Warmia and Mazury lobes of the last glaciation. Studied deposits reveal a cyclic reactivation of the interlobe zone during the successive Pleistocene glaciations. Considerable variations of the relief of the top-Neogene, vertical discontinuities cutting the Pleistocene and Neogene, stratigraphic gaps within the Pleistocene succession, and thick glaciolacustrine successions result from the vertical neotectonic movements in the intermediate area between the two provinces.

  11. The velocity dependence of X-ray emission due to Charge Exchange in the Cygnus Loop

    Science.gov (United States)

    Cumbee, Renata; Lyons, David; Mullen, Patrick Dean; Shelton, Robin L.; Stancil, Phillip C.; Schultz, David R.

    2016-01-01

    The fundamental collisional process of charge exchange (CX) has been been established as a primary source of X-ray emission from the heliosphere [1], planetary exospheres [2], and supernova remnants [3,4]. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly-excited, high charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays.To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross-sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics for collisions of bare and H-like C to Al ions with H, He, and H2. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant will be shown as an example with ion velocity dependence.[1] Henley, D. B. & Shelton, R. L. 2010, ApJSS, 187, 388[2] Dennerl, K. et al. 2002, A&A 386, 319[3] Katsuda, S. et al. 2011, ApJ 730 24[4] Cumbee, R. S. et al. 2014, ApJ 787 L31This work was partially supported by NASA grant NNX09AC46G.

  12. Anomalous diffusion due to the non-Markovian process of the dust particle velocity in complex plasmas

    Science.gov (United States)

    Ghannad, Z.; Hakimi Pajouh, H.

    2017-12-01

    In this work, the motion of a dust particle under the influence of the random force due to dust charge fluctuations is considered as a non-Markovian stochastic process. Memory effects in the velocity process of the dust particle are studied. A model is developed based on the fractional Langevin equation for the motion of the dust grain. The fluctuation-dissipation theorem for the dust grain is derived from this equation. The mean-square displacement and the velocity autocorrelation function of the dust particle are obtained in terms of the Mittag-Leffler functions. Their asymptotic behavior and the dust particle temperature due to charge fluctuations are studied in the long-time limit. As an interesting result, it is found that the presence of memory effects in the velocity process of the dust particle as a non-Markovian process can cause an anomalous diffusion in dusty plasmas. In this case, the velocity autocorrelation function of the dust particle has a power-law decay like t - α - 2, where the exponent α take values 0 < α < 1.

  13. 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.

  14. Effects on Chilean Vertical Reference Frame due to the Maule Earthquake co-seismic and post-seismic effects

    Science.gov (United States)

    Montecino, Henry D.; de Freitas, Silvio R. C.; Báez, Juan C.; Ferreira, Vagner G.

    2017-12-01

    The Maule Earthquake (Mw = 8.8) of February 27, 2010 is among the strongest earthquakes that occurred in recent years throughout the world. The crustal deformation caused by this earthquake has been widely studied using GNSS, InSAR and gravity observations. However, there is currently no estimation of the possible vertical deformations produced by co-seismic and post-seismic effects in segments of the Chilean Vertical Reference Frame (CHVRF). In this paper, we present an estimation of co-seismic and post-seismic deformations on the CHVRF using an indirect approach based on GNSS and Gravity Recovery and Climate Experiment (GRACE) data as well as by applying a trajectory model. GNSS time series were used from 10 continuous GNSS stations in the period from 2007 to 2015, as well as 28 GNSS temporary stations realized before and after the earthquake, and 34 vertical deformation vectors in the region most affected by the earthquake. We considered a set of 147 monthly solutions of spherical harmonic gravity field that were expanded up to degree, as well as order 96 of the GRACE mission provided by Center for Space Research, University of Texas at Austin (UT-CSR) process center. The magnitude of vertical deformation was estimated in part of the Chilean vertical network due to the co-seismic and post-seismic effects. Once we evaluated the hydrological effect, natural and artificial jumps, and the effect of glacial isostatic adjustment in GNSS and GRACE time series, the maximum values associated to co- and post-seismic deformations on orthometric height were found to be ∼-34 cm and 5 cm, respectively. Overall, the deformation caused by the Maule earthquake in orthometric heights is almost entirely explained by the variation in the ellipsoidal heights (over 85% in co-seismic jump); however, coseismic jump in the geoid reached -3.3 mm, and could influence the maintenance of a modern vertical reference network in a medium to long term. We evaluated the consistency for a

  15. 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,...

  16. 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.

  17. 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.

  18. 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.

  19. A Study on Distribution Measurement and Mechanism of Deformation due to Water Loss of Overburden Layer in Vertical Shaft

    Directory of Open Access Journals (Sweden)

    Chunde Piao

    2015-01-01

    Full Text Available Based on FBG fiber Bragg grating technology and BOTDA distributed optical fiber sensing technology, this study uses fine sand to simulate overburden layer in vertical shaft model equipment. It studies the placing technique and test method for optical fiber sensors in the overburden layer, combined with MODFLOW software to simulate the change of the water head value when the overburden layer is losing water, and obtains the deformation features of overburden layer. The results show, at the beginning of water loss, the vertical deformation increases due to larger hydraulic pressure drop, while the deformation decreases gradually and tends to be stable with the hydraulic pressure drop reducing. The circumferential deformation is closely related to such factors as the distance between each drainage outlet, the variations of water head value, and the method of drainage. The monitoring result based on optical fiber sensing technology is consistent with the characteristics of water loss in overburden layer simulated by MODFLOW software, which shows that the optical fiber sensing technology applied to monitor shaft overburden layer is feasible.

  20. 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

  1. 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.

  2. Regional-scale brine migration along vertical pathways due to CO2 injection - Part 1: The participatory modeling approach

    Science.gov (United States)

    Scheer, Dirk; Konrad, Wilfried; Class, Holger; Kissinger, Alexander; Knopf, Stefan; Noack, Vera

    2017-06-01

    Saltwater intrusion into potential drinking water aquifers due to the injection of CO2 into deep saline aquifers is one of the potential hazards associated with the geological storage of CO2. Thus, in a site selection process, models for predicting the fate of the displaced brine are required, for example, for a risk assessment or the optimization of pressure management concepts. From the very beginning, this research on brine migration aimed at involving expert and stakeholder knowledge and assessment in simulating the impacts of injecting CO2 into deep saline aquifers by means of a participatory modeling process. The involvement exercise made use of two approaches. First, guideline-based interviews were carried out, aiming at eliciting expert and stakeholder knowledge and assessments of geological structures and mechanisms affecting CO2-induced brine migration. Second, a stakeholder workshop including the World Café format yielded evaluations and judgments of the numerical modeling approach, scenario selection, and preliminary simulation results. The participatory modeling approach gained several results covering brine migration in general, the geological model sketch, scenario development, and the review of the preliminary simulation results. These results were included in revised versions of both the geological model and the numerical model, helping to improve the analysis of regional-scale brine migration along vertical pathways due to CO2 injection.

  3. 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.

  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. 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

  6. 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

  7. 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.

  8. Off-line algorithm for calculation of vertical tracer transport in the troposphere due to deep convection

    NARCIS (Netherlands)

    Belikov, D.A.; Maksyutov, S.; Krol, M.C.; Fraser, A.; Rigby, M.; Bian, H.; Agusti-Panareda, A.; Bergmann, D.; Bousquet, P.; Cameron-Smith, P.; Chipperfield, M.P.; Fortems-Cheiney, A.; Gloor, E.; Haynes, K.; Hess, P.; Houweling, S.; Kawa, S.R.; Law, R.M.; Loh, Z.; Meng, L.; Palmer, P.I.; Patra, P.K.; Prinn, R.G.; Saito, R.; Wilson, C.

    2013-01-01

    A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical

  9. 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

  10. The Vertical Expandable Prosthetic Titanium Rib in the treatment of spinal deformity due to progressive early onset scoliosis.

    Science.gov (United States)

    Ramirez, Norman; Flynn, John M; Serrano, Jose Anibal; Carlo, Simon; Cornier, Alberto S

    2009-07-01

    The Vertical Expandable Prosthetic Titanium Rib (VEPTR) is a technique developed for the treatment of progressive early onset scoliosis. This vertically placed device uses distraction to indirectly elongate the spine and chest, stabilizing the progression of the spinal deformity while preserving spinal growth. Thoracic spine and chest wall deformity are usually correlated; therefore, elongation of the chest wall will increase the space available for the lung and improve respiratory mechanics in patients with early onset scoliosis. We conducted a retrospective study of 17 patients with early onset scoliosis treated with the VEPTR technique. The medical records, imaging studies, and follow-up physical examinations were evaluated. The patient population consisted of 17 primary VEPTR implantations and 33 expansion surgeries with a mean follow-up of 25 months. Our results show that there was an improvement in the coronal plane deformity between the presurgical and postsurgical Cobb angles, preoperative Cobb angle of 59 degrees (range 38-77) to postoperative 35 degrees (range 10-70), resulting in an average decrease of 59% in the Cobb angle (PVEPTR implantation is a safe and efficient method for the treatment of early onset scoliosis.

  11. 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.

  12. 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.

  13. The velocity dependence of X-ray emission due to Charge Exchange: Applications in the Cygnus Loop

    Science.gov (United States)

    Cumbee, Renata; Lyons, David; Mullen, Patrick; Shelton, Robin L.; Stancil, Phillip C.; Schultz, David R.

    2016-04-01

    The fundamental collisional process of charge exchange (CX) has been been established as a primary source of X-ray emission from the heliosphere [1], planetary exospheres [2], and supernova remnants [3,4]. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly-excited, high charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays.To provide reliable CX-induced X-ray spectral models to realistically simulate high-energy astrophysical environments, line ratios and spectra are computed using theoretical CX cross-sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for various collisional velocities. Collisions of bare and H-like C to Al ions with H, He, and H2 are considered. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant will be shown as an example with ion velocity dependence.[1] Henley, D. B. & Shelton, R. L. 2010, ApJSS, 187, 388[2] Dennerl, K. et al. 2002, A&A 386, 319[3] Katsuda, S. et al. 2011, ApJ 730 24[4] Cumbee, R. S. et al. 2014, ApJ 787 L31

  14. Traction Induced Vertical Displacement of Odontoid due to Type III Odontoid Fracture with Unrecognized Ligamentous Injury: A Case Report

    Science.gov (United States)

    Jung, Min-Ho; Hur, Hyuk; Jang, Jae-Won; Kim, Jae-Hyoo; Kim, Soo-Han

    2014-01-01

    Dens fractures are a common traumatic cervical spine injury. Among them, a type III fracture is the second common fracture. Although there are several treatment options, it has been accepted that type III fracture is usually healed by non-surgical method. After adequate reduction with traction, subsequent external immobilization has been associated with successful union rates. However, in the review of literatures, there are some cases with neurological deterioration after application of skull traction. So, the authors report a case of type III dens fracture with initially unrecognized ligamentous injury in which vertical dissociation and quadriplegia occurred after only five-pound Gardner-Well tongs traction. And also, the authors raise awareness of this potentially injury. PMID:27169054

  15. Velocity-measurement bias of the ambient noise method due to source directivity: a case study for the Swedish National Seismic Network

    Science.gov (United States)

    Sadeghisorkhani, Hamzeh; Gudmundsson, Ólafur; Roberts, Roland; Tryggvason, Ari

    2017-06-01

    The bias of velocity measurements from ambient-noise covariograms due to an anisotropic distribution of noise sources is studied assuming that the noise field consists of planar surface waves from large distance. First, general characteristics of the bias are described in terms of their dependence on wavelength, source-anomaly amplitude and width. Second, the expected bias of measurements in Sweden based on a noise-source model for the adjacent regions is analysed. The bias is conceptually explained and described in terms of two regimes, namely a high-frequency and a finite-frequency regime and their parameter domains quantified. Basic scaling laws are established for the bias. It is generally found to be small compared to lateral heterogeneity, except in the finite-frequency regime when interstation distance is small compared to a wavelength and in regions of low levels of heterogeneity. The potential bias, that is, its peak-to-peak variation, is generally higher for group-velocity than phase-velocity measurements. The strongly varying noise-source distribution as seen from Sweden results in predictions of relatively strong bias in the area at relevant frequencies and interstation distances. Levels of heterogeneity in the Baltic shield are relatively low, rendering the potential bias significant. This highlights the need for detailed studies of source anisotropy before application of ambient-noise tomography, particularly in regions with weak velocity heterogeneity. Predicted bias only partially explains deviations of phase-velocity measurements from a regional average for individual station pairs. Restricting measurements to station pairs with interstation distance exceeding five wavelengths limits the potential velocity bias in the area to within 1 per cent. This rather dramatic restriction can be relaxed by directional analysis of the noise-source field and application of azimuthal restrictions to the selected station pairs for measurement.

  16. Off-line algorithm for calculation of vertical tracer transport in the troposphere due to deep convection

    Directory of Open Access Journals (Sweden)

    D. A. Belikov

    2013-02-01

    Full Text Available A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical transport within the scheme includes entrainment and detrainment processes in convective updrafts and downdrafts. Output from the proposed parametrisation scheme is employed in the National Institute for Environmental Studies (NIES global chemical transport model driven by JRA-25/JCDAS reanalysis. The simulated convective precipitation rate and mass fluxes are compared with observations and reanalysis data. A simulation of the short-lived tracer 222Rn is used to further evaluate the performance of the cumulus convection scheme. Simulated distributions of 222Rn are evaluated against observations at the surface and in the free troposphere, and compared with output from models that participated in the TransCom-CH4 Transport Model Intercomparison. From this comparison, we demonstrate that the proposed convective scheme in general is consistent with observed and modeled results.

  17. Reflected solar radiation from horizontal, vertical and inclined surfaces: ultraviolet and visible spectral and broadband behaviour due to solar zenith angle, orientation and surface type.

    Science.gov (United States)

    Turner, J; Parisi, A V; Turnbull, D J

    2008-07-24

    Ultraviolet (UV) radiation affects human life and UV exposure is a significant everyday factor that individuals must be aware of to ensure minimal damaging biological effects to themselves. UV exposure is affected by many complex factors. Albedo is one factor, involving reflection from flat surfaces. Albedo is defined as the ratio of reflected (upwelling) irradiance to incident (downwelling) irradiance and is generally accepted only for horizontal surfaces. Incident irradiance on a non horizontal surface from a variety of incident angles may cause the reflectivity to change. Assumptions about the reflectivity of a vertical surface are frequently made for a variety of purposes but are rarely quantified. As urban structures are dominated by vertical surfaces, using albedo to estimate influence on UV exposure is limiting when incident (downwelling) irradiance is not normal to the surface. Changes to the incident angle are affected by the solar zenith angle, surface position and orientation and surface type. A new characteristic describing reflection from a surface has been used in this research. The ratio of reflected irradiance (from any surface position of vertical, horizontal or inclined) to global (or downwelling) irradiance (RRG) has been calculated for a variety of metal building surfaces in winter time in the southern hemisphere for both the UV and visible radiation spectrum, with special attention to RRG in the UV spectrum. The results show that the RRG due to a vertical surface can exceed the RRG due to a horizontal surface, at smaller solar zenith angles as well as large solar zenith angles. The RRG shows variability in reflective capacities of surface according to the above mentioned factors and present a more realistic influence on UV exposure than albedo for future investigations. Errors in measuring the RRG at large solar zenith angles are explored, which equally highlights the errors in albedo measurement at large solar zenith angles.

  18. [Increases of intracranial pressure and changes of blood flow velocity due to acupressure, needle and laser needle acupuncture?].

    Science.gov (United States)

    Litscher, Gerhard; Wang, Lu; Schwarz, Gerhard; Schikora, Detlef

    2005-08-01

    Pressure on the acupoints St.7 and SJ.22 can lead to significant, reversible increases in intracranial pressure (ICP) in patients with elevated ICP. In this study, we investigated whether changes in cerebral parameters in healthy volunteers can also be registered, when the mentioned acupoints associated with ICP, are stimulated. We investigated a total of 34 volunteers (24 females, 10 males) and a 15-year-old intensive care patient after severe head injury. The mean age of volunteers was 25.2 +/- 3.4 years (range 20-35). Stimulation was performed using acupressure techniques, manual needle and laser needle methods. We evaluated the main parameter of mean blood flow velocity in the middle cerebral artery (left and right) as well as the pulsatility index. In addition, near infrared spectroscopy and blood pressure parameters were registered. Acupressure, manual needle acupuncture and laser needle acupuncture partially led to significant changes in the main goal values. Acupressure as well as acupuncture (needle and laser needle) can evoke reproducible functional changes in the brain. These accompanying effects are not to be ignored, in particular in patients with increased ICP.

  19. Pulse splitting in light propagation through N -type atomic media due to an interplay of Kerr nonlinearity and group-velocity dispersion

    Science.gov (United States)

    Rajitha K., V.; Dey, Tarak N.; Evers, Jörg; Kiffner, Martin

    2015-08-01

    We investigate the spatiotemporal evolution of a Gaussian probe pulse propagating through a four-level N -type atomic medium. At two-photon resonance of probe and control fields, weaker probe pulses may propagate through the medium with low absorption and pulse shape distortion. In contrast, we find that increasing the probe pulse intensity leads to a splitting of the initially Gaussian pulse into a sequence of subpulses in the time domain. The number of subpulses arising throughout the propagation can be controlled via a suitable choice of the probe and control field parameters. Employing a simple theoretical model for the nonlinear pulse propagation, we conclude that the splitting occurs due to an interplay of Kerr nonlinearity and group-velocity dispersion.

  20. 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...

  1. 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.

  2. 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.

  3. 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.

  4. Magnetohydrodynamic and thermal radiation effects on the boundary-layer flow due to a moving extensible surface with the velocity slip model: A comparative study of four nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Aly, Emad H., E-mail: efarag@uj.edu.sa [Department of Mathematics, Faculty of Science, University of Jeddah, Jeddah 21589 (Saudi Arabia); Department of Mathematics, Faculty of Education, Ain Shams University, Roxy, Cairo 11757 (Egypt); Sayed, Hamed M. [Department of Mathematics, Faculty of Education, Ain Shams University, Roxy, Cairo 11757 (Egypt); Department of Mathematics, Faculty of Sciences, Taibah University, Yanbu (Saudi Arabia)

    2017-01-15

    In the current work, we investigated effects of the velocity slip for the flow and heat transfer of four nanofluids over a non-linear stretching sheet taking into account the thermal radiation and magnetic field in presence of the effective electrical conductivity. The governing partial differential equations were transformed into a set of nonlinear ordinary differential equation using similarity transformations before being solved numerically by the Chebyshev pseudospectral differentiation matrix (ChPDM). It was found that the investigated parameters affect remarkably on the nanofluid stream function for the whole investigated nanoparticles. In addition, velocity and skin friction profiles of the four investigated nanofluids decreases and increases, respectively, with the increase of the magnetic parameter, first-order and second-order velocity slips. Further, the flow velocity, surface shear stress and temperature are strongly influenced on applying the velocity slip model, where lower values of the second-order imply higher surface heat flux and thereby making the fluid warmer. - Highlights: • A comparative study for four nanoparticles with MHD and thermal radiation effects was studied. • The effective electrical conductivity is mandatory; otherwise a spurious physical sight will be gained. • The investigated parameters affect remarkably on the nanofluids' flow. • The flow velocity, surface shear stress and temperature are strongly influenced by the slip model. • Lower values of the second-order imply higher surface heat flux and thereby making the fluid warmer.

  5. 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

  6. Results of revisional operation following vertical banded gastroplasty performed due to morbid obesity--comparison between restoration of vertical banded gastroplasty and conversion of gastric bypass up to three years.

    Science.gov (United States)

    Wylezol, M; Pardela, M

    2005-12-01

    The aim of this study was to analyse incidence and efficacy of revisional surgery for failed vertical banded gastroplasty among 458 patients who underwent primary surgery between 1993 and 2003. Staple line disruption was diagnosed in 29 patients and was an indication for restoration of gastroplasty in 10 cases and a conversion to Roux-en-Y gastric bypass in 19 patients. In two cases of outlet stenosis the band was exchanged to enlarge the collar. In two cases of psychological intolerance of restriction the band was removed because of refusion by patients the conversion to Roux-en-Y gastric bypass. A substantial weight reduction without statistical differences between restoration and conversion group was recognized. In two patients (20%) after restoration and three patients (15.8%) after conversion we observed weight regain (p=0.57). In cases with removed band weight regained up to its value recorded before surgery. In patients with exchanged band weight was under control. No serious complications were observed. We could conclude that patients with weight regain after vertical banded gastroplasty should be offered conversion to Roux-en-Y gastric bypass. When malabsorption is refused, restoration of vertical banded gastroplasty could be also performed. Both of procedures are technically difficult but safe.

  7. 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.

  8. 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.

  9. Anisotropic parameter estimation using velocity variation with offset analysis

    Energy Technology Data Exchange (ETDEWEB)

    Herawati, I.; Saladin, M.; Pranowo, W.; Winardhie, S.; Priyono, A. [Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, 40132 (Indonesia)

    2013-09-09

    Seismic anisotropy is defined as velocity dependent upon angle or offset. Knowledge about anisotropy effect on seismic data is important in amplitude analysis, stacking process and time to depth conversion. Due to this anisotropic effect, reflector can not be flattened using single velocity based on hyperbolic moveout equation. Therefore, after normal moveout correction, there will still be residual moveout that relates to velocity information. This research aims to obtain anisotropic parameters, ε and δ, using two proposed methods. The first method is called velocity variation with offset (VVO) which is based on simplification of weak anisotropy equation. In VVO method, velocity at each offset is calculated and plotted to obtain vertical velocity and parameter δ. The second method is inversion method using linear approach where vertical velocity, δ, and ε is estimated simultaneously. Both methods are tested on synthetic models using ray-tracing forward modelling. Results show that δ value can be estimated appropriately using both methods. Meanwhile, inversion based method give better estimation for obtaining ε value. This study shows that estimation on anisotropic parameters rely on the accuracy of normal moveout velocity, residual moveout and offset to angle transformation.

  10. Comparison of Vertical Ionospheric Drifts Obtained by Different Techniques

    Science.gov (United States)

    Kouba, D.

    2016-12-01

    Since 2004 the ionospheric observatory in Pruhonice (Czech Republic, 50N, 14.9E) provides regular ionospheric sounding using Digisonde. In addition to classical ionograms the drift velocities in both E and F region using DDA method are measured routinely. However, vertical component of the drift velocity vector can be estimated by several different methods which can be found in the literature; for example the indirect estimation based on the temporal evolution of measured ionospheric characteristics is often used for calculation of the vertical drift component. The vertical velocity is thus estimated according to the change of characteristics scaled from the classical quarter-hour ionograms. In present paper the direct drift measurement is compared with technique based on measuring of the virtual height at fixed frequency from the F-layer trace on ionogram, technique based on variation of h`F and hmF. The ionospheric observatory in Pruhonice is midlatitudinal station and typicaly provides measurements in 15 minutes cadence. Due to the fact that the most papers use different indirect methods use equatorial data, we also focuse on results of equatorial stations and other stations that carry out measurements with higher cadence (5 minutes). Our comparison shows possibility of using different methods for calculating vertical drift velocity and their relationship to the direct measurement used by Digisondes.

  11. Unsteady mixed convection of a micropolar fluid past a circular cylinder due to time-dependent free stream velocity and temperature

    Directory of Open Access Journals (Sweden)

    Nepal C. Roy

    2016-06-01

    Full Text Available Unsteady mixed convection boundary-layer flow of an electrically conducting micropolar fluid past a circular cylinder is investigated taking into account the effect of thermal radiation and heat generation or absorption. The reduced non-similar boundary-layer equations are solved using the finite difference method. It is found that the magnitude of the friction factor and the couple stress significantly increases due to the increase of the mixed convection parameter, the conduction-radiation parameter, the surface temperature parameter, the heat absorption parameter and the frequency parameter. However the magnitude of the heat transfer rate decreases with these parameters. The converse characteristics are observed for the Prandtl number. The magnitude of the couple stress and the heat transfer rate is seen to decrease whereas the magnitude of the skin factor increases with increasing the vortex viscosity parameter. The magnetic field parameter reduces the skin factor, couple stress and heat transfer rate. The amplitude of oscillation of the transient skin factor and couple stress gradually increases owing to an increase of $\\xi$. But the transient heat transfer rate is found to be oscillating with almost the same amplitude for any value of $\\xi$. The amplitude of oscillation of the transient skin factor and couple stress increases with an increase of $S$ and $\\xi$ while the amplitude of the transient heat transfer rate increases with increasing Pr and $S$.

  12. 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.

  13. Uncertainty analysis of the external gamma-dose rate due to the variability of the vertical distribution of 137Cs in the soil.

    Science.gov (United States)

    Bunzl, K; Schimmack, W; Jacob, P

    2001-01-01

    The external gamma-dose rate at 1 m height above a flat area due to the presence of fallout radiocesium in the soil is frequently calculated from the observed depth profile of the 137Cs activity as well as the soil mass per unit area. At a given site, these depth profiles may, however, vary considerably, thus introducing an uncertainty to the external gamma-dose calculated in this way. To assess this source of uncertainty for a typical grassland site, the activity of Chernobyl-derived 137Cs and the wet bulk density in the three upper soil layers at 100 plots in a 100 m x 100 m pasture were determined. Analysis of these data shows that the frequency distribution of the dose rates calculated from the corresponding depth profiles of all plots is similar to a log-normal distribution (mean 25 nGy h-1, median 22 nGy h-1, standard deviation 11 nGy h-1; range 1.6-56 nGy h-1). The various sources which contribute to the uncertainty of the dose rate are quantified. The semi-variogram indicates that any spatial dependence of the dose rates occurs on this pasture only over distances that are smaller than the shortest sampling interval (here about 10 m). It is estimated which errors have to be expected for the median dose rate when the depth profiles of 137Cs and of the wet bulk density are determined only for a small number of plots. It is preferable to calculate the mean dose rate as a mean from the n individual dose rates rather than from an averaged 137Cs depth profile of the n plots.

  14. 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.

  15. Conventional Point-Velocity Records and Surface Velocity Observations for Estimating High Flow Discharge

    Directory of Open Access Journals (Sweden)

    Giovanni Corato

    2014-10-01

    Full Text Available Flow velocity measurements using point-velocity meters are normally obtained by sampling one, two or three velocity points per vertical profile. During high floods their use is inhibited due to the difficulty of sampling in lower portions of the flow area. Nevertheless, the application of standard methods allows estimation of a parameter, α, which depends on the energy slope and the Manning roughness coefficient. During high floods, monitoring of velocity can be accomplished by sampling the maximum velocity, umax, only, which can be used to estimate the mean flow velocity, um, by applying the linear entropy relationship depending on the parameter, M, estimated on the basis of historical observed pairs (um, umax. In this context, this work attempts to analyze if a correlation between α and M holds, so that the monitoring for high flows can be addressed by exploiting information from standard methods. A methodology is proposed to estimate M from α, by coupling the “historical” information derived by standard methods, and “new” information from the measurement of umax surmised at later times. Results from four gauged river sites of different hydraulic and geometric characteristics have shown the robust estimation of M based on α.

  16. Regional-scale brine migration along vertical pathways due to CO2 injection – Part 2: A simulated case study in the North German Basin

    Directory of Open Access Journals (Sweden)

    A. Kissinger

    2017-06-01

    Full Text Available Saltwater intrusion into potential drinking water aquifers due to the injection of CO2 into deep saline aquifers is one of the hazards associated with the geological storage of CO2. Thus, in a site-specific risk assessment, models for predicting the fate of the displaced brine are required. Practical simulation of brine displacement involves decisions regarding the complexity of the model. The choice of an appropriate level of model complexity depends on multiple criteria: the target variable of interest, the relevant physical processes, the computational demand, the availability of data, and the data uncertainty. In this study, we set up a regional-scale geological model for a realistic (but not real onshore site in the North German Basin with characteristic geological features for that region. A major aim of this work is to identify the relevant parameters controlling saltwater intrusion in a complex structural setting and to test the applicability of different model simplifications. The model that is used to identify relevant parameters fully couples flow in shallow freshwater aquifers and deep saline aquifers. This model also includes variable-density transport of salt and realistically incorporates surface boundary conditions with groundwater recharge. The complexity of this model is then reduced in several steps, by neglecting physical processes (two-phase flow near the injection well, variable-density flow and by simplifying the complex geometry of the geological model. The results indicate that the initial salt distribution prior to the injection of CO2 is one of the key parameters controlling shallow aquifer salinization. However, determining the initial salt distribution involves large uncertainties in the regional-scale hydrogeological parameterization and requires complex and computationally demanding models (regional-scale variable-density salt transport. In order to evaluate strategies for minimizing leakage into shallow aquifers

  17. 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.

  18. Transverse vertical dispersion in groundwater and the capillary fringe.

    Science.gov (United States)

    Klenk, I D; Grathwohl, P

    2002-09-01

    Transverse dispersion is the most relevant process in mass transfer of contaminants across the capillary fringe (both directions), dilution of contaminants, and mixing of electron acceptors and electron donors in biodegrading groundwater plumes. This paper gives an overview on literature values of transverse vertical dispersivities alpha(tv) measured at different flow velocities and compares them to results from well-controlled laboratory-tank experiments on mass transfer of trichloroethene (TCE) across the capillary fringe. The measured values of transverse vertical dispersion in the capillary fringe region were larger than in fully saturated media, which is credited to enhanced tortuosity of the flow paths due to entrapped air within the capillary fringe. In all cases, the values observed for alpha(tv) were model, based on the mean square displacement and the pore size accounting for only partial diffusive mixing at increasing flow velocities, shows very good agreement with measured and published data.

  19. 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.

  20. 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

  1. Seismic Velocity Gradients Across the Transition Zone

    Science.gov (United States)

    Escalante, C.; Cammarano, F.; de Koker, N.; Piazzoni, A.; Wang, Y.; Marone, F.; Dalton, C.; Romanowicz, B.

    2006-12-01

    One-D elastic velocity models derived from mineral physics do a notoriously poor job at predicting the velocity gradients in the upper mantle transition zone, as well as some other features of models derived from seismological data. During the 2006 CIDER summer program, we computed Vs and Vp velocity profiles in the upper mantle based on three different mineral physics approaches: two approaches based on the minimization of Gibbs Free Energy (Stixrude and Lithgow-Bertelloni, 2005; Piazzoni et al., 2006) and one obtained by using experimentally determined phase diagrams (Weidner and Wang, 1998). The profiles were compared by assuming a vertical temperature profile and two end-member compositional models, the pyrolite model of Ringwood (1979) and the piclogite model of Anderson and Bass (1984). The predicted seismic profiles, which are significantly different from each other, primarily due to different choices of properties of single minerals and their extrapolation with temperature, are tested against a global dataset of P and S travel times and spheroidal and toroidal normal mode eigenfrequencies. All the models derived using a potential temperature of 1600K predict seismic velocities that are too slow in the upper mantle, suggesting the need to use a colder geotherm. The velocity gradient in the transition zone is somewhat better for piclogite than for pyrolite, possibly indicating the need to increase Ca content. The presence of stagnant slabs in the transition zone is a possible explanation for the need for 1) colder temperature and 2) increased Ca content. Future improvements in seismic profiles obtained from mineral physics will arise from better knowledge of elastic properties of upper mantle constituents and aggregates at high temperature and pressure, a better understanding of differences between thermodynamic models, and possibly the effect of water through and on Q. High resolution seismic constraints on velocity jumps at 400 and 660 km also need to be

  2. 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.

  3. 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.

  4. Vertical Heat Flux in the Ocean: Estimates from Observations, and Comparisons with a Coupled General Circulation Model

    Science.gov (United States)

    Cummins, P. F.; Masson, D.; Saenko, O.

    2016-02-01

    The net heat uptake by the ocean in a changing climate involves small imbalances between the advective and diffusive processes that transport heat vertically. Generally, it is necessary to rely on global climate models to study these processes in detail. In the present study, it is shown that a key component of the vertical heat flux, namely that associated with the large-scale mean vertical circulation, can be diagnosed over extra-tropical regions from global observational data sets. This component is estimated based on the vertical velocity obtained from the geostrophic vorticity balance, combined with estimates of the absolute geostrophic flow. Results are compared with a non-eddy resolving, coupled atmosphere-ocean general circulation model. This shows reasonable agreement in the latitudinal distribution of the heat flux, along with net integrated vertical heat flux below about 300 meters depth. The mean vertical heat flux is shown to be dominated by the downward contribution from the southern hemisphere and, in particular, the Southern Ocean. This is driven by the Ekman vertical velocity which induces an upward vertical transport of seawater that is cold relative to the lateral average at a given depth. The correspondence with the coupled model breaks down at depths shallower than 300 m due to the dominant contribution of equatorial regions which have been excluded from the calculation. It appears that the vertical transport of heat by the large-scale mean circulation is consistent with simple linear vorticity dynamics over much of the ocean.

  5. Is Fish Response related to Velocity and Turbulence Magnitudes? (Invited)

    Science.gov (United States)

    Wilson, C. A.; Hockley, F. A.; Cable, J.

    2013-12-01

    Riverine fish are subject to heterogeneous velocities and turbulence, and may use this to their advantage by selecting regions which balance energy expenditure for station holding whilst maximising energy gain through feeding opportunities. This study investigated microhabitat selection by guppies (Poecilia reticulata) in terms of the three-dimensional velocity structure generated by idealised boulders in an experimental flume. Velocity and turbulence influenced intra-species variation in swimming behaviour with respect to size, sex and parasite intensity. With increasing body length, fish swam further and more frequently between boulder regions. Larger guppies spent more time in the high velocity and low turbulence region, whereas smaller guppies preferred the low velocity and high shear stress region directly behind the boulders. Male guppies selected the region of low velocity, indicating a possible reduced swimming ability due to hydrodynamic drag imposed by their fins. With increasing parasite (Gyrodactylus turnbulli) burden, fish preferentially selected the region of moderate velocity which had the lowest bulk measure of turbulence of all regions and was also the most spatially homogeneous velocity and turbulence region. Overall the least amount of time was spent in the recirculation zone which had the highest magnitude of shear stresses and mean vertical turbulent length scale to fish length ratio. Shear stresses were a factor of two greater than in the most frequented moderate velocity region, while mean vertical turbulent length scale to fish length ratio were six times greater. Indeed the mean longitudinal turbulent scale was 2-6 times greater than the fish length in all regions. While it is impossible to discriminate between these two turbulence parameters (shear stress and turbulent length to fish length ratio) in influencing the fish preference, our study infers that there is a bias towards fish spending more time in a region where both the bulk

  6. 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.

  7. 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.

  8. Influence of Compression and Stiffness Apparel on Vertical Jump Performance.

    Science.gov (United States)

    Wannop, John W; Worobets, Jay T; Madden, Ryan; Stefanyshyn, Darren J

    2016-04-01

    Compression apparel alters both compression of the soft tissues and the hip joint stiffness of athletes. It is not known whether it is the compression elements, the stiffness elements, or some combination that increases performance. Therefore, the purpose of this study was to determine how systematically increasing upper leg compression and hip joint stiffness independently from one another affects vertical jumping performance. Ten male athletes performed countermovement vertical jumps in 8 concept apparel conditions and 1 control condition (loose fitting shorts). The 8 apparel conditions, 4 that specifically altered the amount of compression exerted on the thigh and 4 that altered the hip joint stiffness by means of elastic thermoplastic polyurethane bands, were tested on 2 separate testing sessions (one testing the compression apparel and the other testing the stiffness apparel). Maximum jump height was measured, while kinematic data of the hip, knee, and ankle joint were recorded with a high-speed camera (480 Hz). Both compression and stiffness apparel can have a positive influence on vertical jumping performance. The increase in jump height for the optimal compression was due to increased hip joint range of motion and a trend of increasing the jump time. Optimal stiffness also increased jump height and had the trend of decreasing the hip joint range of motion and hip joint angular velocity. The exact mechanisms by which apparel interventions alter performance is not clear, but it may be due to alterations to the force-length and force-velocity relationships of muscle.

  9. Vertical heat flux in the ocean: Estimates from observations and from a coupled general circulation model

    Science.gov (United States)

    Cummins, Patrick F.; Masson, Diane; Saenko, Oleg A.

    2016-06-01

    The net heat uptake by the ocean in a changing climate involves small imbalances between the advective and diffusive processes that transport heat vertically. Generally, it is necessary to rely on global climate models to study these processes in detail. In the present study, it is shown that a key component of the vertical heat flux, namely that associated with the large-scale mean vertical circulation, can be diagnosed over extra-tropical regions from global observational data sets. This component is estimated based on the vertical velocity obtained from the geostrophic vorticity balance, combined with estimates of absolute geostrophic flow. Results are compared with the output of a non-eddy resolving, coupled atmosphere-ocean general circulation model. Reasonable agreement is found in the latitudinal distribution of the vertical heat flux, as well as in the area-integrated flux below about 250 m depth. The correspondence with the coupled model deteriorates sharply at depths shallower than 250 m due to the omission of equatorial regions from the calculation. The vertical heat flux due to the mean circulation is found to be dominated globally by the downward contribution from the Southern Hemisphere, in particular the Southern Ocean. This is driven by the Ekman vertical velocity which induces an upward transport of seawater that is cold relative to the horizontal average at a given depth. The results indicate that the dominant characteristics of the vertical transport of heat due to the mean circulation can be inferred from simple linear vorticity dynamics over much of the ocean.

  10. 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 ...

  11. 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

  12. The soil moisture velocity equation

    Science.gov (United States)

    Ogden, Fred L.; Allen, Myron B.; Lai, Wencong; Zhu, Jianting; Seo, Mookwon; Douglas, Craig C.; Talbot, Cary A.

    2017-06-01

    Numerical solution of the one-dimensional Richards' equation is the recommended method for coupling groundwater to the atmosphere through the vadose zone in hyperresolution Earth system models, but requires fine spatial discretization, is computationally expensive, and may not converge due to mathematical degeneracy or when sharp wetting fronts occur. We transformed the one-dimensional Richards' equation into a new equation that describes the velocity of moisture content values in an unsaturated soil under the actions of capillarity and gravity. We call this new equation the Soil Moisture Velocity Equation (SMVE). The SMVE consists of two terms: an advection-like term that accounts for gravity and the integrated capillary drive of the wetting front, and a diffusion-like term that describes the flux due to the shape of the wetting front capillarity profile divided by the vertical gradient of the capillary pressure head. The SMVE advection-like term can be converted to a relatively easy to solve ordinary differential equation (ODE) using the method of lines and solved using a finite moisture-content discretization. Comparing against analytical solutions of Richards' equation shows that the SMVE advection-like term is >99% accurate for calculating infiltration fluxes neglecting the diffusion-like term. The ODE solution of the SMVE advection-like term is accurate, computationally efficient and reliable for calculating one-dimensional vadose zone fluxes in Earth system and large-scale coupled models of land-atmosphere interaction. It is also well suited for use in inverse problems such as when repeat remote sensing observations are used to infer soil hydraulic properties or soil moisture.Plain Language SummarySince its original publication in 1922, the so-called Richards' equation has been the only rigorous way to couple groundwater to the land surface through the unsaturated zone that lies between the water table and land surface. The soil moisture distribution and

  13. 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

    Full Text Available When the internal waves break, they are one of the sources of small-scale turbulence. Small-scale turbulence causes the vertical exchange in the ocean. However, internal waves with regard to the Earth rotation in the presence of vertically inhomogeneous two-dimensional current are able to contribute to the vertical transport. Free inertial-gravity internal waves in a baroclinic current in a boundless basin of a constant depth are considered in the Bussinesq approximation. Boundary value problem of linear approximation for the vertical velocity amplitude of internal waves has complex coefficients when current velocity component, which is transversal to the wave propagation direction, depends on the vertical coordinate (taking into account the rotation of the Earth. Eigenfunction and wave frequency are complex, and it is shown that a weak wave damping takes place. Dispersive relation and wave damping decrement are calculated in the linear approximation. At a fixed wave number damping decrement of the second mode is larger (in the absolute value than the one of the first mode. The equation for vertical velocity amplitude for real profiles of the Brunt – Vaisala frequency and current velocity are numerically solved according to implicit Adams scheme of the third order of accuracy. The dispersive curves of the first two modes do not reach inertial frequency in the low-frequency area due to the effect of critical layers in which wave frequency of the Doppler shift is equal to the inertial one. Termination of the second mode dispersive curves takes place at higher frequency than the one of the first mode. In the second order of the wave amplitude the Stokes drift speed is determined. It is shown that the Stokes drift speed, which is transversal to the wave propagation direction, differs from zero if the transversal component of current velocity depends on the vertical coordinate. In this case, the Stokes drift speed in the second mode is lower than

  14. 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.

  15. Streamwise decrease of the 'unsteady' virtual velocity of gravel tracers

    Science.gov (United States)

    Klösch, Mario; Gmeiner, Philipp; Habersack, Helmut

    2017-04-01

    Gravel tracers are usually inserted and transported on top of the riverbed, before they disperse vertically and laterally due to periods of intense bedload, the passage of bed forms, lateral channel migration and storage on bars. Buried grains have a lower probability of entrainment, resulting in a reduction of overall mobility, and, on average, in a deceleration of the particles with distance downstream. As a consequence, the results derived from tracer experiments and their significance for gravel transport may depend on the time scale of the investigation period, complicating the comparison of results from different experiments. We developed a regression method, which establishes a direct link between the transport velocity and the unsteady flow variables to yield an 'unsteady' virtual velocity, while considering the tracer slowdown with distance downstream in the regression. For that purpose, the two parameters of a linear excess shear velocity formula (the critical shear velocity u*c and coefficient a) were defined as functions of the travelled distance since the tracer's insertion. Application to published RFID tracer data from the Mameyes River, Puerto Rico, showed that during the investigation period the critical shear velocity u*c of tracers representing the median bed particle diameter (0.11 m) increased from 0.36 m s-1 to 0.44 m s-1, while the coefficient a decreased from the dimensionless value of 4.22 to 3.53, suggesting a reduction of the unsteady virtual velocity at the highest shear velocity in the investigation period from 0.40 m s-1 to 0.08 m s-1. Consideration of the tracer slowdown improved the root mean square error of the calculated mean displacements of the median bed particle diameter from 8.82 m to 0.34 m. As in previous work these results suggest the need of considering the history of transport when deriving travel distances and travel velocities, depending on the aim of the tracer study. The introduced method now allows estimating the

  16. Velocities of Subducted Sediments and Continents

    Science.gov (United States)

    Hacker, B. R.; van Keken, P. E.; Abers, G. A.; Seward, G.

    2009-12-01

    shallow depths through trench-parallel at moderate depths to down-dip approaching sub-arc depths. Vertically incident waves have VP/ VS of 1.7-1.3 over the same range of depths, waves propagating up dip have VP/ VS of 1.7-1.3, and waves propagating along the slab at constant depth have VP/ VS of 1.7-1.45. These remarkably low VP/ VS ratios are due to the anomalous elastic behavior of quartz. More aluminous lithologies have elevated VP/ VS ratios: 1.85 for slab-normal waves, 1.75 for trench-parallel waves, and 1.65 for down-dip waves. Subducted continental crust that is too dry to transform to high-pressure minerals has relatively ordinary VP/ VS ratio of 1.71-1.75 for vertically incident waves, 1.6-1.7 for waves propagating up dip, and 1.65-1.75 for waves propagating along the slab. Thus, subducted mica-rich sediments can have high VP/ VS ratios, whereas quartzose lithologies generate low VP/ VS ratios.

  17. 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.

  18. 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.

  19. 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…

  20. PREDICTION OF POWER GENERATION OF SMALL SCALE VERTICAL AXIS WIND TURBINE USING FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Altab Md. Hossain

    2009-12-01

    Full Text Available Renewable energy from the wind turbine has been focused for the alternative source of power generation due to the following advances of the of the wind turbine. Firstly, the wind turbine is highly efficient and eco-friendly. Secondly, the turbine has the ability to response for the changeable power generation based on the wind velocity and structural framework. However, the competitive efficiency of the wind turbine is necessary to successfully alternate the conventional power sources. The most relevant factor which affects the overall efficiency of the wind turbine is the wind velocity and the relative turbine dimensions. Artificial intelligence systems are widely used technology that can learn from examples and are able to deal with non-linear problems. Compared with traditional approach, fuzzy logic approach is more efficient for the representation, manipulation and utilization. Therefore, the primary purpose of this work was to investigate the relationship between wind turbine power generation and wind velocity, and to illustrate how fuzzy expert system might play an important role in prediction of wind turbine power generation. The main purpose of the measurement over the small scaled prototype vertical axis wind turbine for the wind velocity is to predict the performance of full scaled H-type vertical axis wind turbine. Prediction of power generation at the different wind velocities has been tested at the Thermal Laboratory of Faculty of Engineering, Universiti Industri Selangor (UNISEL and results concerning the daily prediction have been obtained.

  1. PREDICTION OF POWER GENERATION OF SMALL SCALE VERTICAL AXIS WIND TURBINE USING FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Altab Hossain

    2009-01-01

    Full Text Available Renewable energy from the wind turbine has been focused for the alternative source of power generation due to the following advances of the of the wind turbine. Firstly, the wind turbine is highly efficient and eco-friendly. Secondly, the turbine has the ability to response for the changeable power generation based on the wind velocity and structural framework. However, the competitive efficiency of the wind turbine is necessary to successfully alternate the conventional power sources. The most relevant factor which affects the overall efficiency of the wind turbine is the wind velocity and the relative turbine dimensions. Artificial intelligence systems are widely used technology that can learn from examples and are able to deal with non-linear problems. Compared with traditional approach, fuzzy logic approach is more efficient for the representation, manipulation and utilization. Therefore, the primary purpose of this work was to investigate the relationship between wind turbine power generation and wind velocity, and to illustrate how fuzzy expert system might play an important role in prediction of wind turbine power generation. The main purpose of the measurement over the small scaled prototype vertical axis wind turbine for the wind velocity is to predict the performance of full scaled H-type vertical axis wind turbine. Prediction of power generation at the different wind velocities has been tested at the Thermal Laboratory of Faculty of Engineering, Universiti Industri Selangor (UNISEL and results concerning the daily prediction have been obtained.

  2. Experimental study of low-velocity impact on foam-filled Kraft paper honeycomb structure

    Science.gov (United States)

    Kadir, N. Abd; Aminanda, Y.; Ibrahim, M. S.; Mokhtar, H.

    2018-01-01

    Low-velocity impact tests of unfilled and foam-filled Kraft paper honeycomb are carried out to investigate the effect of foam, indenter size and location of indentation on maximum or peak force and energy absorption capability. In this study, three indenter sizes (10mm, 12mm, 15mm) and three different locations of indentation (vertical edge, double wall and single wall) were used and compared. The test results show that the foam is given a significant increment of peak force and specific energy absorption to the honeycomb structure subjected to indentation load. The peak force and energy absorption capability also effected by indenter size which due to the contact area of indentation. As for the location of indentation, vertical edge gives highest peak force and energy absorption by the fact that vertical edge is the intersection of three walls of honeycomb cell.

  3. 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.

  4. 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.

  5. 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...

  6. 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 accommodation by 3 diopters induced a vertical vergence of 10 degrees. This observation proves that the miswiring responsible for vertical accommodative vergence must not necessarily be congenital, but can be acquired. The cause and the mechanism leading to vertical accommodative vergence are yet unknown.

  7. Laboratory Evaluation of Aggregate Polishing as a function of Load and Velocity : Application to the Prediction of Damages on Skid Resistance of Pavement Surface due to Trucks and Passenger Cars

    OpenAIRE

    KANE, Malal; ZHAO, Dan; DE LARRARD, François; DO, Minh Tan

    2012-01-01

    Skid resistance of road surfaces depends mostly on pavement texture. This texture is usually divided to two components:microtexture and macrotexture. Microtexture refers to the smallscale texture of the road aggregate component while macrotexture refers to the large-scale texture of the road as a whole due to the aggregate particle arrangement. Both components contribute to the generation of friction between tyre and road. However, due to traffic, the firstcited component is continuously poli...

  8. Effects of Isometric Scaling on Vertical Jumping Performance

    NARCIS (Netherlands)

    Bobbert, M.F.

    2013-01-01

    Jump height, defined as vertical displacement in the airborne phase, depends on vertical takeoff velocity. For centuries, researchers have speculated on how jump height is affected by body size and many have adhered to what has come to be known as Borelli's law, which states that jump height does

  9. Lateral and vertical thermal diffusivities in a dense fluidized bed with tubes bundle

    Energy Technology Data Exchange (ETDEWEB)

    Collantes, M.A.; Martin, G.; Le Gal, J.H. [Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France)

    1995-07-01

    Dense fluidized beds are acknowledge as homogeneous systems from both temperature and composition aspects. However, some situation such as very large units or fluidized beds with tubes bundle lead to thermal gradients within the bed. These thermal gradients are due to solids motion limitation and may have detrimental effects on the process. This paper relates investigations aiming an determining lateral and vertical thermal diffusivities in a dense fluidized bed with an without a tubes bundle. These investigations have been carried out with an experimental setup of significant size (bed size = 0.6 x 1.1 x 1.3) and with small particles (less 500 microns) so as to fill some gaps of the literature. Thermal diffusivities have been deduced from temperature gradients measured between a hot wall and a cold wall in a perpendicular fluidized bed and by applying a conventional 2-D conduction model. Lateral thermal conductivities as well as vertical thermal conductivities increase with the gas velocity and the height of the bed, and when the particle size decreases. Immersing a vertical tube bundle into the fluidized bed leads to a significant reduction of the lateral thermal diffusivity, while there is no effect on the vertical thermal diffusivity. Correlations have been drawn from the experimental results. They would have to be applied for calculation of any system running at gas velocity ranging from 0.05 to 0.3 m/s and with particle size between 50 and 300 microns. (authors). 14 refs., 14 figs., 2 tabs.

  10. Free Convective Flow of a Reacting Fluid between Vertical Porous ...

    African Journals Online (AJOL)

    This study investigates free convective flow between vertical porous plates. The energy and momentum equations which arise from the definitions of temperature and velocity are written in dimensionless forms. The resulting second order equations are solved to obtain expressions for the velocity, temperature, mass transfer ...

  11. Numerical Investigation of the Tip Vortex of a Straight-Bladed Vertical Axis Wind Turbine with Double-Blades

    Directory of Open Access Journals (Sweden)

    Yanzhao Yang

    2017-10-01

    Full Text Available Wind velocity distribution and the vortex around the wind turbine present a significant challenge in the development of straight-bladed vertical axis wind turbines (VAWTs. This paper is intended to investigate influence of tip vortex on wind turbine wake by Computational Fluid Dynamics (CFD simulations. In this study, the number of blades is two and the airfoil is a NACA0021 with chord length of c = 0.265 m. To capture the tip vortex characteristics, the velocity fields are investigated by the Q-criterion iso-surface (Q = 100 with shear-stress transport (SST k-ω turbulence model at different tip speed ratios (TSRs. Then, mean velocity, velocity deficit and torque coefficient acting on the blade in the different spanwise positions are compared. The wind velocities obtained by CFD simulations are also compared with the experimental data from wind tunnel experiments. As a result, we can state that the wind velocity curves calculated by CFD simulations are consistent with Laser Doppler Velocity (LDV measurements. The distribution of the vortex structure along the spanwise direction is more complex at a lower TSR and the tip vortex has a longer dissipation distance at a high TSR. In addition, the mean wind velocity shows a large value near the blade tip and a small value near the blade due to the vortex effect.

  12. Vertical axis wind turbines

    Science.gov (United States)

    Krivcov, Vladimir [Miass, RU; Krivospitski, Vladimir [Miass, RU; Maksimov, Vasili [Miass, RU; Halstead, Richard [Rohnert Park, CA; Grahov, Jurij [Miass, RU

    2011-03-08

    A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

  13. Yielding transition of Carbopol gel in a vertical pipe

    Science.gov (United States)

    Liu, Yang; de Bruyn, John R.; John de Bruyn Team

    2016-11-01

    We have investigated the yielding transition of a simple yield-stress fluid (Carbopol 940) in a vertical pipe. The Carbopol gel was displaced by a Newtonian liquid injected at a constant, controlled rate at the bottom of the pipe. Rough- and smooth-walled pipes were used to study the effects of wall boundary conditions. The pressure in the Carbopol was measured by a pressure gauge fixed on the pipe wall, and the velocity profile in the Carbopol was measured by particle-image velocimetry (PIV). When the Newtonian liquid was injected, the rate of pressure increase was initially high, then decreased to a constant slow rate at later times. A time tc was defined by the intersection of straight lines fit to the pressure-time data at early and late times. In the rough pipe, the wall shear stress at tc is equal to the yield stress, suggesting that this time corresponds to yielding of the fluid. The velocity profiles were parabolic before yielding, and nearly a plug-like afterwards. In the smooth pipe, the pressure and velocity profiles appeared to show similar behavior to that in the rough pipe, but the wall shear stress at tc is substantially smaller than the yield stress and fluid motion was due to wall slip. NSERC.

  14. Exact solutions in a model of vertical gas migration

    Energy Technology Data Exchange (ETDEWEB)

    Silin, Dmitriy B.; Patzek, Tad W.; Benson, Sally M.

    2006-06-27

    This work is motivated by the growing interest in injectingcarbon dioxide into deep geological formations as a means of avoidingatmospheric emissions of carbon dioxide and consequent global warming.One of the key questions regarding the feasibility of this technology isthe potential rate of leakage out of the primary storage formation. Weseek exact solutions in a model of gas flow driven by a combination ofbuoyancy, viscous and capillary forces. Different combinations of theseforces and characteristic length scales of the processes lead todifferent time scaling and different types of solutions. In the case of athin, tight seal, where the impact of gravity is negligible relative tocapillary and viscous forces, a Ryzhik-type solution implies square-rootof time scaling of plume propagation velocity. In the general case, a gasplume has two stable zones, which can be described by travelling-wavesolutions. The theoretical maximum of the velocity of plume migrationprovides a conservative estimate for the time of vertical migration.Although the top of the plume has low gas saturation, it propagates witha velocity close to the theoretical maximum. The bottom of the plumeflows significantly more slowly at a higher gas saturation. Due to localheterogeneities, the plume can break into parts. Individual plumes alsocan coalesce and from larger plumes. The analytical results are appliedto studying carbon dioxide flow caused by leaks from deep geologicalformations used for CO2 storage. The results are also applicable formodeling flow of natural gas leaking from seasonal gas storage, or formodeling of secondary hydrocarbon migration.

  15. On the axis ratio of the stellar velocity ellipsoid in disks of spiral galaxies

    NARCIS (Netherlands)

    van der Kruit, PC; de Grijs, R

    1999-01-01

    The spatial distribution of stars in a disk of a galaxy can be described by a radial scale length and a vertical scale height. The ratio of these two scale parameters contains information on the axis ratio of the velocity ellipsoid, i.e. the ratio of the vertical to radial stellar velocity

  16. Geophysical aspects of vertical streamer seismic data

    Energy Technology Data Exchange (ETDEWEB)

    Sognnes, Walter

    1998-12-31

    Vertical cable acquisition is performed by deploying a certain number of vertical hydrophone arrays in the water column, and subsequently shooting a source point on top of it. The advantage of this particular geometry is that gives a data set with all azimuths included. Therefore a more complete 3-D velocity model can be derived. In this paper there are presented some results from the Fuji survey in the Gulf of Mexico. Based on these results, improved geometries and review recommendations for future surveys are discussed. 7 figs.

  17. Probability distribution of vertical longitudinal shear fluctuations.

    Science.gov (United States)

    Fichtl, G. H.

    1972-01-01

    This paper discusses some recent measurements of third and fourth moments of vertical differences (shears) of longitudinal velocity fluctuations obtained in unstable air at the NASA 150 m meteorological tower site at Cape Kennedy, Fla. Each set of measurements consisted of longitudinal velocity fluctuation time histories obtained at the 18, 30, 60, 90, 120 and 150 m levels, so that 15 wind-shear time histories were obtained from each set of measurements. It appears that the distribution function of the longitudinal wind fluctuations at two levels is not bivariate Gaussian. The implications of the results relative to the design and operation of aerospace vehicles are discussed.-

  18. Aerodynamic Interactions between Pairs of Vertical-Axis Wind Turbines

    Science.gov (United States)

    Brownstein, Ian; Dabiri, John

    2017-11-01

    Increased power production has been observed in downstream vertical-axis wind turbines (VAWTs) when positioned offset from the wake of upstream turbines. This effect was found to exist in both laboratory and field environments with pairs of co- and counter-rotating turbines. It is hypothesized that the observed power production enhancement is due to flow acceleration adjacent to the upstream turbine caused by bluff body blockage, which increases the incident freestream velocity on appropriately positioned downstream turbines. This type of flow acceleration has been observed in computational and laboratory studies of VAWTs and will be further investigated here using 3D-PTV measurements around pairs of laboratory-scale VAWTs. These measurements will be used to understand the mechanisms behind the performance enhancement effect and seek to determine optimal separation distances and angles between turbines based on turbine design parameters. These results will lead to recommendations for optimizing the power production of VAWT wind farms which utilize this effect.

  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. Stagnation-Point Flow towards a Stretching Vertical Sheet with Slip Effects

    Directory of Open Access Journals (Sweden)

    Khairy Zaimi

    2016-04-01

    Full Text Available The effects of partial slip on stagnation-point flow and heat transfer due to a stretching vertical sheet is investigated. Using a similarity transformation, the governing partial differential equations are reduced into a system of nonlinear ordinary differential equations. The resulting equations are solved numerically using a shooting method. The effect of slip and buoyancy parameters on the velocity, temperature, skin friction coefficient and the local Nusselt number are graphically presented and discussed. It is found that dual solutions exist in a certain range of slip and buoyancy parameters. The skin friction coefficient decreases while the Nusselt number increases as the slip parameter increases.

  1. Ballistics Model for Particles on a Horizontal Plane in a Vacuum Propelled by a Vertically Impinging Gas Jet

    Science.gov (United States)

    Lane, J. E.; Metzger, P. T.

    2010-01-01

    A simple trajectory model has been developed and is presented. The particle trajectory path is estimated by computing the vertical position as a function of the horizontal position using a constant horizontal velocity and a vertical acceleration approximated as a power law. The vertical particle position is then found by solving the differential equation of motion using a double integral of vertical acceleration divided by the square of the horizontal velocity, integrated over the horizontal position. The input parameters are: x(sub 0) and y(sub 0), the initial particle starting point; the derivative of the trajectory at x(sub 0) and y(sub 0), s(sub 0) = s(x(sub 0))= dx(y)/dy conditional expectation y = y((sub 0); and b where bx(sub 0)/y(sub 0) is the final trajectory angle before gravity pulls the particle down. The final parameter v(sub 0) is an approximation to a constant horizontal velocity. This model is time independent, providing vertical position x as a function of horizontal distance y: x(y) = (x(sub 0) + s(sub 0) (y-y(sub 0))) + bx(sub 0) -(s(sub 0)y(sub 0) ((y - y(sub 0)/y(sub 0) - ln((y/y(sub 0)))-((g(y-y(sub 0)(exp 2))/ 2((v(sub 0)(exp 2). The first term on the right in the above equation is due to simple ballistics and a spherically expanding gas so that the trajectory is a straight line intersecting (0,0), which is the point at the center of the gas impingement on the surface. The second term on the right is due to vertical acceleration, which may be positive or negative. The last term on the right is the gravity term, which for a particle with velocities less than escape velocity will eventually bring the particle back to the ground. The parameters b, s(sub 0), and in some cases v(sub 0), are taken from an interpolation of similar parameters determined from a CFD simulation matrix, coupled with complete particle trajectory simulations.

  2. Solenoidal filtering of volumetric velocity measurements using Gaussian process regression

    NARCIS (Netherlands)

    Azijli, I.; Dwight, R.P.

    2015-01-01

    Volumetric velocity measurements of incompressible flows contain spurious divergence due to measurement noise, despite mass conservation dictating that the velocity field must be divergence-free (solenoidal). We investigate the use of Gaussian process regression to filter spurious divergence,

  3. INTERNATIONAL SPECIALIZATION AND VERTICAL DIFFERENTIATION

    Directory of Open Access Journals (Sweden)

    Furia Donatella

    2010-07-01

    Full Text Available During the last decades, market segmentation and intra-industry trade have become increasingly relevant. The underlying hypothesis of our work is that distinct articles have heterogeneous potential for vertical differentiation, implying that different patterns of international specialization should be identifiable. We carry out an analysis on revealed comparative advantage (through the Lafay Index in specific sectors of interest. Then we highlight the emergence of diverse degrees of product quality differentiation among sectors (through the Relative Quality Index. Results confirm our hypothesis. Indeed it appears that only certain goods, for which the pace of either creative or technological innovation (or both is particularly fast, present a high degree of vertical differentiation and market segmentation. This allows countries to specialize in a particular product variety and gain market power position for that variety. These findings should be taken in due consideration when designing trade policies.

  4. An Experimental Investigation of Passive Variable-Pitch Vertical-Axis Ocean Current Turbine

    Directory of Open Access Journals (Sweden)

    Ridho Hantoro

    2011-04-01

    Full Text Available Vertical-axis hydrokinetic turbines with fixed pitch blades typically suffer from poor starting torque, low efficiency and shaking due to large fluctuations in both radial and tangential force with azimuth angle. Maximizing the turbine power output can be achieved only if the mechanism of generation of the hydrodynamic force on the blades is clearly identified and tools to design high-performance rotors are developed. This paper describes an initial experimental investigation to understand more of the performance on vertical-axis turbine related to the effect of fixed-pitch and passive variable-pitch application using airfoil NACA 0018. Comparative analysis according to aspects of rotation and tip speed ratios was discussed. Information regarding the changes of foil position in passive variable-pitch during rotation at a limited range of flow velocity variations test was obtained and analyzed.

  5. Intuitive Mechanics: Inferences of Vertical Projectile Motion

    Directory of Open Access Journals (Sweden)

    Milana Damjenić

    2016-07-01

    Full Text Available Our intuitive knowledge of physics mechanics, i.e. knowledge defined through personal experience about velocity, acceleration, motion causes, etc., is often wrong. This research examined whether similar misconceptions occur systematically in the case of vertical projectiles launched upwards. The first experiment examined inferences of velocity and acceleration of the ball moving vertically upwards, while the second experiment examined whether the mass of the thrown ball and force of the throw have an impact on the inference. The results showed that more than three quarters of the participants wrongly assumed that maximum velocity and peak acceleration did not occur at the initial launch of the projectile. There was no effect of object mass or effect of the force of the throw on the inference relating to the velocity and acceleration of the ball. The results exceed the explanatory reach of the impetus theory, most commonly used to explain the naive understanding of the mechanics of object motion. This research supports that the actions on objects approach and the property transmission heuristics may more aptly explain the dissidence between perceived and actual implications in projectile motion.

  6. Vertical and radial motions of the body during the take-off phase of high jumping.

    Science.gov (United States)

    Dapena, J; Chung, C S

    1988-06-01

    By placing the muscles of the take-off leg in faster eccentric or slower concentric conditions, a high jumper can increase the ground reaction force and the height of the jump. Film analysis of seven high jumpers showed that the radial velocity of the center of mass with respect to the supporting foot was more negative or less positive than the vertical velocity throughout the take-off phase. This favored faster eccentric or slower concentric conditions of the leg muscles. The radial distance from the hip of the take-off leg to the center of mass (RG/H) first decreased by 0.030 m, due to negative radial motions of the arms and swinging leg. This contributed to a smaller negative radial velocity of the hip (VRH), and thus to slower eccentric conditions of the muscles of the take-off leg. Therefore, it may have helped to cushion the initial impact with the ground. Subsequently, RG/H increased by 0.120 m, due to positive radial velocities of the arms, the swinging leg, and the head and trunk. This contributed first to larger negative (and later to smaller positive) VRH values, and thus to faster eccentric and slower concentric conditions of the muscles of the take-off leg.

  7. High-Velocity Clouds

    NARCIS (Netherlands)

    Wakker, Bart P.; Woerden, Hugo van; Oswalt, Terry D.; Gilmore, Gerard

    2013-01-01

    The high-velocity clouds (HVCs) are gaseous objects that do not partake in differential galactic rotation, but instead have anomalous velocities. They trace energetic processes on the interface between the interstellar material in the Galactic disk and intergalactic space. Three different processes

  8. Measurements of ammonia concentrations, fluxes and dry deposition velocities to a spruce forest 1991-1995

    DEFF Research Database (Denmark)

    Andersen, H.V.; Hovmand, M.F.; Hummelshøj, P.

    1999-01-01

    The dry deposition velocities and fluxes of ammonia have been estimated from measurements of the vertical gradient of ammonia and micrometeorology above a spruce forest in western Jutland, Denmark. Measurements have been made in seven periods, each lasting about one week and covering all seasons......, i.e. an ammonia concentration below which the trees and/or the surface emit ammonia due to an equilibrium with the ammonia inside the needles or on the surface. Emission of ammonia was also observed at relatively high ammonia concentration levels (above 2 mu g NH3-N m(-3)), mainly during one...... measuring period characterized by easterly winds with dry conditions and high ammonia concentrations, and the emissions might relate to evaporation from ammonia saturated surfaces or emission from mineralization in the forest soil. In general, relatively high net deposition velocities were observed during...

  9. Numerical simulations of thermospheric dynamics: divergence as a proxy for vertical winds

    Directory of Open Access Journals (Sweden)

    S. L. Cooper

    2009-06-01

    Full Text Available A local scale, time dependent three-dimensional model of the neutral thermosphere was used to test the applicability of two previously published empirical relations between thermospheric vertical wind and velocity divergence, i.e., those due to Burnside et al. (1981 and Brekke (1997. The model self-consistently solves for vertical winds driven by heat and momentum deposited into the neutral atmosphere by high latitude ion convection. The Brekke condition accurately mimicked the overall "shape" of the three-dimensional model vertical wind field although, as written, it consistently overestimated the vertical wind magnitude by a factor of approximately 5/3, for the heating scenarios that we considered. This same general behavior was observed regardless of whether the forcing was static or rapidly changing with time. We discuss the likely reason for the Brekke condition overestimating the magnitude of our vertical winds, and suggest an alternative condition that should better describe vertical winds that are driven by local heating. The applicability of the Burnside condition was, by contrast, quite variable. During static heating, both the magnitude and the sign of the model vertical winds were predicted reliably at heights above those of maximum energy and momentum deposition per unit mass. However, below the thermal forcing, the Burnside condition predicted vertical winds of the wrong sign. It also introduced significant artefacts into the predicted vertical wind field when the forcing changed suddenly with time. If these results are of general applicability (which seems likely, given the way these relations are derived then the Burnside condition could usually be used safely at altitudes above hmF2. But it should be avoided below this height at all times, and even at high altitudes during periods of dynamic forcing. While the Brekke condition (or our modified version of it could likely be used in all circumstances

  10. Vertical atlantoaxial dislocation

    OpenAIRE

    Ramaré, S.; Lazennec, J. Y.; Camelot, C.; Saillant, G.; Hansen, S.; Trabelsi, R.

    1999-01-01

    An unusual case of vertical atlantoaxial dislocation without medulla oblongata or spinal cord injury is reported. The pathogenic process suggested occipito-axial dislocation. The case was treated surgically with excellent results on mobility and pain.

  11. Coordination in vertical jumping

    NARCIS (Netherlands)

    Bobbert, Maarten F.; van Ingen Schenau, Gerrit Jan

    1988-01-01

    The present study was designed to investigate for vertical jumping the relationships between muscle actions, movement pattern and jumping achievement. Ten skilled jumpers performed jumps with preparatory countermovement. Ground reaction forces and cinematographic data were recorded. In addition,

  12. Hybrid vertical cavity laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2010-01-01

    A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide.......A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide....

  13. Composition of vertical gardens

    OpenAIRE

    Sandeva, Vaska; Despot, Katerina

    2013-01-01

    Vertical gardens are fully functional gardens in areas where there is less oxygen and space, ideal for residential and urban cities where there is no vegetation; occupy a special place in interiors furniture. The gardens occupy an important aesthetic problem. Aesthetic task in vertical gardens can be achieved by forming sectors of identification in the urban landscape through the choice of a particular plant spatial composition and composition, to create comfort and representation in commu...

  14. PICASSO: Shear velocities in the Western Mediterranean from Rayleigh Wave tomography

    Science.gov (United States)

    Palomeras, I.; Thurner, S.; Levander, A.

    2012-12-01

    The Western Mediterranean has been affected by complex subduction and slab rollback, simultaneously with compression due to African-European convergence. The deformed region occupies a wide area from the intra-continental Atlas mountain belt in Morocco to the southern Iberian Massif in Spain. Evolutionary models of the Western Mediterranean invoke extensive slab rollback and compression in the Cenozoic, as well as likely upper mantle delamination scenarios during formation of the Alboran domain, the Betics, Rif, and Atlas Mountains. PICASSO (Program to Investigate Convective Alboran Sea System Overturn) is a multidisciplinary, international investigation of the Alboran System and surrounding areas. In this study we have analyzed data from the 95 PICASSO broadband stations with data from the Spanish IberArray and Siberia Array in Spain and Morocco, the University of Muenster array in the Atlas Mountains and the permanent Spanish and Portuguese networks. We present Rayleigh wave tomography results made from 168 teleseimic events recorded by 237 stations from April 2009 to April 2011. We measured Rayleigh phase velocities using the two-plane-wave method to remove complications due to multi-pathing, and finite-frequency kernels to improve lateral resolution. Phase velocities were then inverted for shear velocity structure on a grid of 0.5 by 0.5 degree to form a well-resolved 3D shear velocity model to 230 km depth. Our results show low S-velocities (2.9 km/s) in the crust beneath the Gibraltar Strait. Low upper mantle S-velocities are mapped beneath the Middle and High Atlas at ~60 km depth suggesting an elevated asthenosphere beneath these young mountain belts, in agreement with receiver functions analysis (Thurner et al, this session). Beneath the Western Alboran Sea, upper-mantle velocities change laterally from high velocities (>4.5 km/s) in the east to lower velocities to the west (~4.3 km/s). The Rayleigh wave tomography is consistent with P-tomography that

  15. Eccentricity samples: Implications on the potential and the velocity distribution

    Directory of Open Access Journals (Sweden)

    Cubarsi R.

    2017-01-01

    Full Text Available Planar and vertical epicycle frequencies and local angular velocity are related to the derivatives up to the second order of the local potential and can be used to test the shape of the potential from stellar disc samples. These samples show a more complex velocity distribution than halo stars and should provide a more realistic test. We assume an axisymmetric potential allowing a mixture of independent ellipsoidal velocity distributions, of separable or Staeckel form in cylindrical or spherical coordinates. We prove that values of local constants are not consistent with a potential separable in addition in cylindrical coordinates and with a spherically symmetric potential. The simplest potential that fits the local constants is used to show that the harmonical and non-harmonical terms of the potential are equally important. The same analysis is used to estimate the local constants. Two families of nested subsamples selected for decreasing planar and vertical eccentricities are used to borne out the relation between the mean squared planar and vertical eccentricities and the velocity dispersions of the subsamples. According to the first-order epicycle model, the radial and vertical velocity components provide accurate information on the planar and vertical epicycle frequencies. However, it is impossible to account for the asymmetric drift which introduces a systematic bias in estimation of the third constant. Under a more general model, when the asymmetric drift is taken into account, the rotation velocity dispersions together with their asymmetric drift provide the correct fit for the local angular velocity. The consistency of the results shows that this new method based on the distribution of eccentricities is worth using for kinematic stellar samples. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. No 176011: Dynamics and Kinematics of Celestial Bodies and Systems

  16. Eccentricity Samples: Implications on the Potential and the Velocity Distribution

    Science.gov (United States)

    Cubarsi, R.; Stojanović, M.; Ninković, S.

    2017-06-01

    Planar and vertical epicycle frequencies and local angular velocity are related to the derivatives up to the second order of the local potential and can be used to test the shape of the potential from stellar disc samples. These samples show a more complex velocity distribution than halo stars and should provide a more realistic test. We assume an axisymmetric potential allowing a mixture of independent ellipsoidal velocity distributions, of separable or Staeckel form in cylindrical or spherical coordinates. We prove that values of local constants are not consistent with a potential separable in addition in cylindrical coordinates and with a spherically symmetric potential. The simplest potential that fits the local constants is used to show that the harmonical and non-harmonical terms of the potential are equally important. The same analysis is used to estimate the local constants. Two families of nested subsamples selected for decreasing planar and vertical eccentricities are used to borne out the relation between the mean squared planar and vertical eccentricities and the velocity dispersions of the subsamples. According to the first-order epicycle model, the radial and vertical velocity components provide accurate information on the planar and vertical epicycle frequencies. However, it is impossible to account for the asymmetric drift which introduces a systematic bias in estimation of the third constant. Under a more general model, when the asymmetric drift is taken into account, the rotation velocity dispersions together with their asymmetric drift provide the correct fit for the local angular velocity. The consistency of the results shows that this new method based on the distribution of eccentricities is worth using for kinematic stellar samples.

  17. Analyses of Current And Wave Forces on Velocity Caps

    OpenAIRE

    Christensen, Erik Damgaard; Buhrkall, Jeppe; Eskesen, Mark C. D.; Jensen, Bjarne

    2015-01-01

    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 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...

  18. Coding of Velocity Storage in the Vestibular Nuclei

    Directory of Open Access Journals (Sweden)

    Sergei B. Yakushin

    2017-08-01

    Full Text Available Semicircular canal afferents sense angular acceleration and output angular velocity with a short time constant of ≈4.5 s. This output is prolonged by a central integrative network, velocity storage that lengthens the time constants of eye velocity. This mechanism utilizes canal, otolith, and visual (optokinetic information to align the axis of eye velocity toward the spatial vertical when head orientation is off-vertical axis. Previous studies indicated that vestibular-only (VO and vestibular-pause-saccade (VPS neurons located in the medial and superior vestibular nucleus could code all aspects of velocity storage. A recently developed technique enabled prolonged recording while animals were rotated and received optokinetic stimulation about a spatial vertical axis while upright, side-down, prone, and supine. Firing rates of 33 VO and 8 VPS neurons were studied in alert cynomolgus monkeys. Majority VO neurons were closely correlated with the horizontal component of velocity storage in head coordinates, regardless of head orientation in space. Approximately, half of all tested neurons (46% code horizontal component of velocity in head coordinates, while the other half (54% changed their firing rates as the head was oriented relative to the spatial vertical, coding the horizontal component of eye velocity in spatial coordinates. Some VO neurons only coded the cross-coupled pitch or roll components that move the axis of eye rotation toward the spatial vertical. Sixty-five percent of these VO and VPS neurons were more sensitive to rotation in one direction (predominantly contralateral, providing directional orientation for the subset of VO neurons on either side of the brainstem. This indicates that the three-dimensional velocity storage integrator is composed of directional subsets of neurons that are likely to be the bases for the spatial characteristics of velocity storage. Most VPS neurons ceased firing during drowsiness, but the firing

  19. Coding of Velocity Storage in the Vestibular Nuclei

    Science.gov (United States)

    Yakushin, Sergei B.; Raphan, Theodore; Cohen, Bernard

    2017-01-01

    Semicircular canal afferents sense angular acceleration and output angular velocity with a short time constant of ≈4.5 s. This output is prolonged by a central integrative network, velocity storage that lengthens the time constants of eye velocity. This mechanism utilizes canal, otolith, and visual (optokinetic) information to align the axis of eye velocity toward the spatial vertical when head orientation is off-vertical axis. Previous studies indicated that vestibular-only (VO) and vestibular-pause-saccade (VPS) neurons located in the medial and superior vestibular nucleus could code all aspects of velocity storage. A recently developed technique enabled prolonged recording while animals were rotated and received optokinetic stimulation about a spatial vertical axis while upright, side-down, prone, and supine. Firing rates of 33 VO and 8 VPS neurons were studied in alert cynomolgus monkeys. Majority VO neurons were closely correlated with the horizontal component of velocity storage in head coordinates, regardless of head orientation in space. Approximately, half of all tested neurons (46%) code horizontal component of velocity in head coordinates, while the other half (54%) changed their firing rates as the head was oriented relative to the spatial vertical, coding the horizontal component of eye velocity in spatial coordinates. Some VO neurons only coded the cross-coupled pitch or roll components that move the axis of eye rotation toward the spatial vertical. Sixty-five percent of these VO and VPS neurons were more sensitive to rotation in one direction (predominantly contralateral), providing directional orientation for the subset of VO neurons on either side of the brainstem. This indicates that the three-dimensional velocity storage integrator is composed of directional subsets of neurons that are likely to be the bases for the spatial characteristics of velocity storage. Most VPS neurons ceased firing during drowsiness, but the firing rates of VO

  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. Thermal vertical bimorph actuators and their applications

    CERN Document Server

    Sehr, H J

    2002-01-01

    In this thesis, a novel concept for lateral actuators based on vertical bimorphs is presented. Vertical bimorphs consist of silicon beams side-coated with aluminium, which bend when heated due to the different thermal expansion coefficients of the two materials causing a displacement in the wafer plane. The heating of the actuator is provided by an electrical current through the silicon beam. The simplest implementation of a vertical bimorph actuator is a clamped-clamped beam. To obtain higher deflections, a meander shaped actuator has been designed. By combining four meander actuators, a two-dimensional positioning stage has been realised. The meander actuator has also been applied for normally closed and normally open micro-relays. Analytical calculations and ANSYS simulations have been carried out to predict the physical behaviour of the bimorph devices, including temperature distribution, static deflection, vertical stiffness, thermal time constant and lateral resonances. For both the clamped-clamped beam...

  2. Antarctic Ice Velocity Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This compilation of recent ice velocity data of the Antarctic ice sheet is intended for use by the polar scientific community. The data are presented in tabular form...

  3. Transverse spectral velocity estimation.

    Science.gov (United States)

    Jensen, Jørgen

    2014-11-01

    A transverse oscillation (TO)-based method for calculating the velocity spectrum for fully transverse flow is described. Current methods yield the mean velocity at one position, whereas the new method reveals the transverse velocity spectrum as a function of time at one spatial location. A convex array probe is used along with two different estimators based on the correlation of the received signal. They can estimate the velocity spectrum as a function of time as for ordinary spectrograms, but they also work at a beam-to-flow angle of 90°. The approach is validated using simulations of pulsatile flow using the Womersly-Evans flow model. The relative bias of the mean estimated frequency is 13.6% and the mean relative standard deviation is 14.3% at 90°, where a traditional estimator yields zero velocity. Measurements have been conducted with an experimental scanner and a convex array transducer. A pump generated artificial femoral and carotid artery flow in the phantom. The estimated spectra degrade when the angle is different from 90°, but are usable down to 60° to 70°. Below this angle the traditional spectrum is best and should be used. The conventional approach can automatically be corrected for angles from 0° to 70° to give fully quantitative velocity spectra without operator intervention.

  4. Vertical jump coordination: fatigue effects.

    Science.gov (United States)

    Rodacki, André Luiz Felix; Fowler, Neil E; Bennett, Simon J

    2002-01-01

    The aim of this study was to investigate the segmental coordination of vertical jumps under fatigue of the knee extensor and flexor muscles. Eleven healthy and active subjects performed maximal vertical jumps with and without fatigue, which was imposed by requesting the subjects to extend/flex their knees continuously in a weight machine, until they could not lift a load corresponding to approximately 50% of their body weight. Knee extensor and flexor isokinetic peak torques were also measured before and after fatigue. Video, ground reaction forces, and electromyographic data were collected simultaneously and used to provide several variables of the jumps. Fatiguing the knee flexor muscles did not reduce the height of the jumps or induce changes in the kinematic, kinetic, and electromyographic profiles. Knee extensor fatigue caused the subjects to adjust several variables of the movement, in which the peak joint angular velocity, peak joint net moment, and power around the knee were reduced and occurred earlier in comparison with the nonfatigued jumps. The electromyographic data analyses indicated that the countermovement jumps were performed similarly, i.e., a single strategy was used, irrespective of which muscle group (extensor or flexors) or the changes imposed on the muscle force-generating characteristics (fatigue or nonfatigue). The subjects executed the movements as if they scaled a robust template motor program, which guided the movement execution in all jump conditions. It was speculated that training programs designed to improve jump height performance should avoid severe fatigue levels, which may cause the subjects to learn and adopt a nonoptimal and nonspecific coordination solution. It was suggested that the neural input used in the fatigued condition did not constitute an optimal solution and may have played a role in decreasing maximal jump height achievement.

  5. A due

    DEFF Research Database (Denmark)

    to acknowledge the excellence of these two scholars by a double Festschrift, "A due". Both have been working at the Music Department of the University of Copenhagen and have collaborated with The Royal Library on various projects. This publication contains contributions from 44 colleagues, who thus - in topics...

  6. What is the velocity profile of debris flows?

    Science.gov (United States)

    Walter, Fabian; McArdell, Brian

    2015-04-01

    The distribution of flow velocity within a debris flow is difficult to determine at full scale in the field due to the large forces and inherently destructive nature of the flow. However, knowledge of the distribution of velocity within a flow would be helpful to constrain rheological models and to better understand the internal dynamics of such flows. Here we describe recent efforts to determine the velocity of debris flows as a function of distance from the channel bed. Measurements were made at the Illgraben, Switzerland, which exhibits a wide variety of flows, ranging from turbulent debris floods to flows which resemble laminar mud flows to more classical debris flows with a clear granular front. The Illgraben observation station is therefore an ideal location to investigate debris flow dynamics. Our measurements were made using sensors embedded on a 14 m long, 2.5 m tall steel-reinforced concrete wall constructed flush with the torrent channel walls. The main instrumentation consists of 18 geophones (10 Hz natural frequency) installed on square steel plates with a side length of 0.3 m. Each steel plate is acoustically isolated from the wall and the other plates through the use of elastomer elements. The geophone plates are arranged in six rows of three sensors with a dimension of 1.8 m in the vertical direction and 1.5 m in the horizontal direction (i.e. parallel to the flow direction). A sensorless plate separates each plate in the horizontal direction. The data are collected at 2 kHz using a high-speed (synchronous) capture card in a pc. The elevation of the flow surface is determined at a cross-stream distance 1 m away from the wall, using a laser sensor installed on a bridge above the wall. We present a processing approach for the geophone data with the goal to track particle sliding across the sensor plates. For signals near or above the sensors' natural frequency (10 Hz), the measured time series are poorly correlated between sensors. Therefore, we use a

  7. 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.

  8. 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.

  9. The vertical structure of gaseous galaxy discs in cold dark matter haloes

    Science.gov (United States)

    Benítez-Llambay, Alejandro; Navarro, Julio F.; Frenk, Carlos S.; Ludlow, Aaron D.

    2018-01-01

    We study the vertical structure of polytropic centrifugally supported gaseous discs embedded in cold dark matter (CDM) haloes. At fixed radius, R, the shape of the vertical density profile depends weakly on whether the disc is self-gravitating (SG) or non-self-gravitating (NSG). The disc 'characteristic' thickness, zH, set by the midplane sound speed and circular velocity, zNSG = (cs/Vc)R, in the NSG case, and by the sound speed and surface density, z_SG = c_s^2/GΣ, in SG discs, is smaller than zSG and zNSG. SG discs are typically Toomre unstable, NSG discs are stable. Exponential discs in CDM haloes with roughly flat circular velocity curves 'flare' outwards. Flares in mono abundance or coeval populations in galaxies like the Milky Way are thus not necessarily due to radial migration. For the polytropic equation of state of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations, discs that match observational constraints are NSG for Md < 3 × 109 M⊙ and SG at higher masses, if fully gaseous. We test these analytic results using a set of idealized smoothed particle hydrodynamic simulations and find excellent agreement. Our results clarify the role of the gravitational softening on the thickness of simulated discs, and on the onset of radial instabilities. EAGLE low-mass discs are NSG so the softening plays no role in their vertical structure. High-mass discs are expected to be SG and unstable, and may be artificially thickened and stabilized unless gravity is well resolved. Simulations with spatial resolution high enough to not compromise the vertical structure of a disc also resolve the onset of their instabilities, but the converse is not true.

  10. High-velocity penetrators

    Science.gov (United States)

    Lundgren, Ronald G.

    This paper summarizes the results of studies, coupled with a series of tests, that investigated rigid-body projectiles (penetrators) at high (up to 5500 ft/sec) velocities. Before these studies, it had been hypothesized that a velocity limit would be reached at which increasing the velocity would not commensurately increase depth of penetration into a target. It was further inferred that a given velocity/ penetration depth curve would avalanche into the hydrodynamic regime; that is, increasing the velocity past a certain point would decrease penetration performance. The test series utilized 1/2-in., 3-in., and 5 1/2-in. diameter, ogive-nose steel projectiles and grout and concrete targets. The tests confirmed that penetration depth increased as striking velocity increased to 4000 ft/sec. However, beyond striking velocities of 4000 ft/sec, asymmetric erosion and indentation of the projectile nose from the aggregate caused the projectile trajectories to deviate severely from the target centerline. These trajectory deviations caused the projectile to exit the side of the target, severely bend, break, or exhibit decreased penetration performance, confirming the hypothesis. Clearly, these results were dependent on the specific material and geometric parameters. The projectiles had 3.0 and 4.25 CRH (Caliber-Radius-Head) nose shapes and were heat-treated to R(sub c) 38-40. The grout targets had a maximum aggregate diameter of 3/16 in. and a nominal unconfined compressive strength of 2.5 ksi. The concrete targets had a maximum aggregate diameter of 3/4 in. and unconfined compressive strength of 5.5 ksi.

  11. Experimental study of ``laminar'' bubbly flows in a vertical pipe

    Science.gov (United States)

    Kashinsky, O. N.; Timkin, L. S.; Cartellier, A.

    1993-09-01

    Measurement of bubbly two-phase flow parameters in a vertical pipe were performed. To keep the pipe Reynolds number below that for single-phase turbulent transition, a water-glycerin solution was used as the test liquid. Local void fraction and liquid velocity profiles along with the wall shear stress were measured by an electrochemical method. Experiments were made with bubbles of two different sizes. As the gas flow rate was increased, a gradual development of the liquid velocity profile from the parabolic Poiseuille flow to a flattened two-phase profile was observed. The evolution of the wall shear stress and of the velocity fluctuations were also quantified.

  12. Diel vertical migrat..

    African Journals Online (AJOL)

    2002-01-24

    Jan 24, 2002 ... crustacean zooplankton but also in a Wide array of different marine zooplankton groups. (Russell 1927, McLaren 1963). Thus there is no doubt that ..... cooperation during field work and for their fruitful discussion on the draft manuscript. REFERENCES. Bayly lAE 1986 Aspects of diel vertical migration in ...

  13. Vertical market participation

    DEFF Research Database (Denmark)

    Schrader, Alexander; Martin, Stephen

    1998-01-01

    Firms that operate at both levels of vertically related Cournot oligopolies will purchase some input supplies from independent rivals, even though they can produce the good at a lower cost, driving up input price for nonintegrated firms at the final good level. Foreclosure, which avoids this stra...... this strategic behavior, yields better market performance than Cournot beliefs...

  14. Hunting Voronoi vertices

    NARCIS (Netherlands)

    Ferrucci, V.; Overmars, Mark; Rao, A.; Vleugels, J.

    1994-01-01

    Given three objects in the plane, a Voronoi vertex is a point that is equidistant simultaneously from each. In this paper, we consider the problem of computing Voronoi vertices for planar objects of xed but possibly unknown shape; we only require the ability to query the closest point on an object

  15. A dynamical approach to identify vertices' centrality in complex networks

    Science.gov (United States)

    Guo, Long; Zhang, Wen-Yao; Luo, Zhong-Jie; Gao, Fu-Juan; Zhang, Yi-Cheng

    2017-12-01

    In this paper, we proposed a dynamical approach to assess vertices' centrality according to the synchronization process of the Kuramoto model. In our approach, the vertices' dynamical centrality is calculated based on the Difference of vertices' Synchronization Abilities (DSA), which are different from traditional centrality measurements that are related to the topological properties. Through applying our approach to complex networks with a clear community structure, we have calculated all vertices' dynamical centrality and found that vertices at the end of weak links have higher dynamical centrality. Meanwhile, we analyzed the robustness and efficiency of our dynamical approach through testing the probabilities that some known vital vertices were recognized. Finally, we applied our dynamical approach to identify community due to its satisfactory performance in assessing overlapping vertices. Our present work provides a new perspective and tools to understand the crucial role of heterogeneity in revealing the interplay between the dynamics and structure of complex networks.

  16. Assimilation of Sonic Velocity and Thin-Section Measurements from the NEEM Ice-Core

    Science.gov (United States)

    Hay, M.; Pettit, E. C.; Waddington, E. D.

    2016-12-01

    We examine the measurement of crystal orientation fabric (COF) in ice cores using thin sections and sound-wave velocities, focusing on the NEEM core in Greenland. Ice crystals have substantial plastic anisotropy, with shear orthogonal to the crystallographic c-axis occurring far more easily than deformation in other orientations. Due to strain-induced grain-rotation, COFs can become highly anisotropic, resulting in bulk anisotropic flow. Thin-section measurements taken from ice cores allow sampling of the crystal fabric distribution. Thin-section measurements, however, suffer from sampling error, as they sample a small amount of ice, usually on the order of a hundred grans. They are typically only taken at intervals of several meters, which means that meter-scale variations in crystal fabric are difficult to capture. Measuring sonic velocities in ice cores provides an alternate method of determining crystal fabric. The speed of vertical compression waves is affected by the vertical clustering of c-axes, but is insensitive to azimuthal fabric anisotropy. By measuring splitting between the fast and slow shear-wave directions, information on the azimuthal distribution of orientations can be captured. Sonic-velocity measurements cannot capture detailed information on the orientation distribution of the COF, but they complement thin-section measurements with several advantages. Sonic-logging measurements can be taken at very short intervals, eliminating spatial gaps. In addition, sonic logging samples a large volume of ice with each measurement, reducing sampling error. Our logging tool has a depth resolution of around 3m/s, and can measure velocity features on the order of 1m/s. Here, we show the results of compression-wave measurements at NEEM. We also assimilate the sonic measurements with the thin-section data using a Bayesian inference procedure. This procedure allows us to combine the respective strengths of the two fabric measurement methods, to produce a more

  17. Approximation of wave action flux velocity in strongly sheared mean flows

    Science.gov (United States)

    Banihashemi, Saeideh; Kirby, James T.; Dong, Zhifei

    2017-08-01

    Spectral wave models based on the wave action equation typically use a theoretical framework based on depth uniform current to account for current effects on waves. In the real world, however, currents often have variations over depth. Several recent studies have made use of a depth-weighted current U˜ due to [Skop, R. A., 1987. Approximate dispersion relation for wave-current interactions. J. Waterway, Port, Coastal, and Ocean Eng. 113, 187-195.] or [Kirby, J. T., Chen, T., 1989. Surface waves on vertically sheared flows: approximate dispersion relations. J. Geophys. Res. 94, 1013-1027.] in order to account for the effect of vertical current shear. Use of the depth-weighted velocity, which is a function of wavenumber (or frequency and direction) has been further simplified in recent applications by only utilizing a weighted current based on the spectral peak wavenumber. These applications do not typically take into account the dependence of U˜ on wave number k, as well as erroneously identifying U˜ as the proper choice for current velocity in the wave action equation. Here, we derive a corrected expression for the current component of the group velocity. We demonstrate its consistency using analytic results for a current with constant vorticity, and numerical results for a measured, strongly-sheared current profile obtained in the Columbia River. The effect of choosing a single value for current velocity based on the peak wave frequency is examined, and we suggest an alternate strategy, involving a Taylor series expansion about the peak frequency, which should significantly extend the range of accuracy of current estimates available to the wave model with minimal additional programming and data transfer.

  18. APPLICATION OF A HEURISTIC METHOD FOR THE ESTIMATION OF S-WAVE VELOCITY STRUCTURE

    Directory of Open Access Journals (Sweden)

    Alfaro Castillo Andrés José

    2006-08-01

    Full Text Available The assessment of local site effects is one of the most important subjects in Engineering Seismology. In order to perform an assessment, it is necessary to determine the S-wave velocity structure of the site. Additionally, in some basins, it is very important to know the deep sedimentary structure, due to the amplification phenomena of low frequency waves. There are several techniques to achieve this purpose; probably the most inexpensive technique is using the vertical component of microtremors measured with an array of seismographs. The phase velocity of Rayleigh waves is inverted to an S-wave velocity (Vs profile  using optimization techniques. Most of the time, least square methods have been applied in the inversion.Recently, heuristic methods have also been used for the estimation of the S-wave velocity structure from microtremor.In this study seven arrays of microtremors in the city of Tsukuba city were performed, located to the NE edge of Kanto Basin, in order to estimate the deep S-wave velocity structure. The spatial autocorrelationmethod SPAC was used to determine phase velocity dispersion curves in the frequency range from 0.3-2.5 Hz. The determination of Vs profiles reached a depth of 750 m. Two methods were used to estimate the Swavevelocity structure: Inversion method and a heuristic method via the combination of Downhill Simplex Algorithm with a Very Fast Simulated Annealing Method. Comparisons with Vs from the existent resultsfrom PS-logging tests at the center of the array showed the reliability of the heuristic method.

  19. Similarity solution for rarefied flow over a vertical stretched surface

    Science.gov (United States)

    Al-Kouz, W.; Kiwan, S.; Sari, M.; Alkhalidi, A.

    2017-07-01

    Similarity technique is used to solve for the laminar natural convection heat transfer for rarefied flows over a linearly vertical stretched surface. Such flows have significant importance in many engineering and manufacturing applications. It is found that the flow is affected by flow parameters, namely, velocity slip (K1), temperature jump (K2), and the Prandtl number (Pr).

  20. Vertical gastroplasty: evolution of vertical banded gastroplasty.

    Science.gov (United States)

    Mason, E E; Doherty, C; Cullen, J J; Scott, D; Rodriguez, E M; Maher, J W

    1998-09-01

    The objective of this paper is to summarize the goals, technical requirements, advantages, and potential risks of gastroplasty for treatment of severe obesity. Gastroplasty is preferred to more complex operations, as it preserves normal digestion and absorption and avoids complications that are peculiar to exclusion operations. The medical literature and a 30-year experience at the University of Iowa Hospitals and Clinics (UIHC) provides an overview of vertical banded gastroplasty (VBG) evolution. Preliminary 10-year results with the VBG technique currently used at UIHC are included. At UIHC the VBG is preferred to other gastroplasties because it provides weight control that extends for at least 10 years and the required objective, intraoperative quality control required for a low rate of reoperation. It is recommended that modifications of the operative technique not be attempted until a surgeon has had experience with the standardized operation--and then only under a carefully designed protocol. Realistic goals for surgery and criteria of success influence the choice of operation and the optimum, lifelong risk/benefit ratio. In conclusion, VBG is a safe, long-term effective operation for severe obesity with advantages over complex operations and more restrictive simple operations.

  1. Velocity pump reaction turbine

    Science.gov (United States)

    House, P.A.

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  2. Density - Velocity Relationships in Explosive Volcanic Plumes

    Science.gov (United States)

    Fisher, M. A.; Kobs-Nawotniak, S. E.

    2015-12-01

    Positively buoyant volcanic plumes rise until the bulk density of the plume is equal to the density of the ambient atmosphere. As ambient air mixes with the plume, it lowers the plume bulk density; thus, the plume is diluted enough to reach neutral density in a naturally stratified atmospheric environment. We produced scaled plumes in analogue laboratory experiments by injecting a saline solution with a tracer dye into distilled water, using a high-pressure injection system. We recorded each eruption with a CASIO HD digital camera and used ImageJ's FeatureJ Edge toolbox to identify individual eddies. We used an optical flow software based off the ImageJ toolbox FlowJ to determine the velocities along the edge of each eddy. Eddy densities were calculated by mapping the dye concentration to the RGB digital color value. We overlaid the eddy velocities over the densities in order to track the behavioral relationship between the two variables with regard to plume motion. As an eddy's bulk density decreases, the vertical velocity decreases; this is a result of decreased mass, and therefore momentum, in the eddy. Furthermore as the density rate of change increases, the eddy deceleration increases. Eddies are most dense at their top and least dense at their bottom. The less dense sections of the eddies have lower vertical velocities than the sections of the eddies with the higher densities, relating to the expanding radial size of an eddy as it rises and the preferential ingestion of ambient air at the base of eddies. Thus the mixing rate in volcanic plumes fluctuates not only as a function of height as described by the classic 1D entrainment hypothesis, but also as a function of position in an eddy itself.

  3. 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...

  4. The Prescribed Velocity Method

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm

    The- velocity level in a room ventilated by jet ventilation is strongly influenced by the supply conditions. The momentum flow in the supply jets controls the air movement in the room and, therefore, it is very important that the inlet conditions and the numerical method can generate a satisfactory...

  5. Contemporary Surface Seasonal Oscillation and Vertical Deformation in Tibetan Plateau and Nepal Derived from the GPS, Leveling and GRACE Data

    Science.gov (United States)

    Shen, W.; Pan, Y.; Hwang, C.; Ding, H.

    2015-12-01

    We use 168 Continuous Global Positioning System (CGPS) stations distributed in the Tibetan Plateau (TP) and Nepal from lengths of 2.5 to 14 years to estimate the present-day velocity field in this area, including the horizontal and vertical deformations under the frame ITRF2008. We estimate and remove common mode errors in regional GPS time series using the principal component analysis (PCA), obtaining a time series with high signal to noise ratio. Following the maximum estimation analysis, a power law plus white noise stochastic model are adopted to estimate the velocity field. The highlight of Tibetan region is the crust vertical deformation. GPS vertical time series present seasonal oscillations caused by temporal mass loads, hence GRACE data from CSR are used to study the mass loads change. After removing the mass load deformations from GPS vertical rates, the results are improved. Leveling data about 48 years in this region are also used to estimate the rates of vertical movements. Our study suggests that the boundary of south Nepal is still sinking due to the fact that the India plate is crashing into the Eurasian plate. The uplift rates from south to north of TP reduce gradually. Himalayas region and north Nepal uplift around 6 mm/yr in average. The uplift rate along East TP in Qinhai is around 2.7 mm/yr in average. In contrast, the southeast of Tibetan Plateau, south Yunnan and Tarim in Xinjiang sink with different magnitudes. Our observation results suggest complicated mechanism of the mass migration in TP. This study is supported by National 973 Project China (grant Nos. 2013CB733302 and 2013CB733305), NSFC (grant Nos. 41174011, 41429401, 41210006, 41128003, 41021061).

  6. 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.

  7. 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.

  8. HUNTING PHENOMENON STUDY OF RAILWAY CONVENTIONAL TRUCK ON TANGENT TRACKS DUE TO CHANGE IN RAIL WHEEL GEOMETRY

    Directory of Open Access Journals (Sweden)

    KARIM H. ALI ABOOD

    2011-04-01

    Full Text Available A mathematical dynamic model of railway conventional truck is presented with 12 degrees of freedom equations of motion. The presented dynamic system consists of conventional truck attached with two single wheelsets in which equipped with lateral, longitudinal and vertical linear stiffness and damping primary and secondary suspensions. This investigated model governs lateral displacement, vertical displacement, roll yaw angles of each of wheelset and the lateral displacement, vertical displacement, roll and yaw angle of conventional truck. Kalker's linear theory has been adopted to evaluate the creep forces which are introduced on rail wheels due to rail wheel contact. The railway truck mathematical equations of motion are solved using fourth order Rung-Kutta method which requires that differential equations to be transformed into a set of first order differential equations. The transformed state space equations are simulated with computer aided simulation to represent the dynamic behavior and time solution of dynamics of conventional truck moving on tangent tracks. Influences of the geometric parameters of the rail wheel such as wheel conicity and nominal rolling radius on the dynamic stability of the system are investigated. It is concluded that the geometric parameters of the rail wheel have different effects on the hunting instability and on the change of the critical hunting velocity of the system. In addition critical hunting velocity of rail trucks is proportional inversely with the square roots of wheel conicity but high critical hunting velocity obtained by increasing the nominal rolling radius of the rail wheel.

  9. Certified standards and vertical coordination in aquaculture

    DEFF Research Database (Denmark)

    Trifkovic, Neda

    2014-01-01

    the application of standards and contract farming, processing companies prefer to vertically integrate primary production largely due to concerns over the stable supply of pangasius with satisfactory quality and safety attributes. These tendencies increase the market dominance of industrial farming and worsen......This paper explores the interaction between food standards and vertical coordination in the Vietnamese pangasius sector. For farmers and processors alike, the adoption of standards is motivated by a desire to improve market access by ensuring high quality supply. Instead of encouraging...

  10. Wave propagation and group velocity

    CERN Document Server

    Brillouin, Léon

    1960-01-01

    Wave Propagation and Group Velocity contains papers on group velocity which were published during the First World War and are missing in many libraries. It introduces three different definitions of velocities: the group velocity of Lord Rayleigh, the signal velocity of Sommerfeld, and the velocity of energy transfer, which yields the rate of energy flow through a continuous wave and is strongly related to the characteristic impedance. These three velocities are identical for nonabsorbing media, but they differ considerably in an absorption band. Some examples are discussed in the last chapter

  11. A space vehicle rotating with a uniform angu- lar velocity about a ...

    Indian Academy of Sciences (India)

    IAS Admin

    A space vehicle rotating with a uniform angu- lar velocity about a vertical axis fixed to it is falling freely vertically downwards, say, with its engine shut off. It carries two astronauts inside it. One astronaut throws a tiny tool towards the other astronaut. The motion of the tiny tool with reference to a rotating frame rigidly fixed.

  12. Optimum Tuning of a Gyroscopic Vibration Absorber Using Coupled Gyroscopes for Vibration Control of a Vertical Cantilever Beam

    Directory of Open Access Journals (Sweden)

    F. Ünker

    2016-01-01

    Full Text Available This paper deals with the investigation of optimum values of the stiffness and damping which connect two gyroscopic systems formed by two rotors mounted in gimbal assuming negligible masses for the spring, damper, and gimbal support. These coupled gyroscopes use two gyroscopic flywheels, spinning in opposing directions to have reverse precessions to eliminate the forces due to the torque existing in the torsional spring and the damper between gyroscopes. The system is mounted on a vertical cantilever with the purpose of studying the horizontal and vertical vibrations. The equation of motion of the compound system (gyro-beam system is introduced and solved to find the response measured on the primary system. This is fundamental to design, in some way, the dynamic absorber or neutralizer. On the other hand, the effect of the angular velocities of the gyroscopes are studied, and it is shown that the angular velocity (spin velocity of a gyroscope has a significant effect on the behavior of the dynamic motion. Correctness of the analytical results is verified by numerical simulations. The comparison with the results from the derivation of the corresponding frequency equations shows that the optimized stiffness and damping values are very accurate.

  13. Retrieval of vertical wind profiles during monsoon from satellite ...

    Indian Academy of Sciences (India)

    The aim of this paper is to study the feasibility of deriving vertical wind profiles from current satellite .... It is clear that the satellite derived winds are not sufficient by themselves for the NWP requirements, due to poor vertical resolution. In the present study we attempt to derive the ..... The solution of matrix equation (7) leads to ...

  14. Transverse Spectral Velocity Estimation

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2014-01-01

    array probe is used along with two different estimators based on the correlation of the received signal. They can estimate the velocity spectrum as a function of time as for ordinary spectrograms, but they also work at a beam-to-flow angle of 90°. The approach is validated using simulations of pulsatile...... flow using the Womersly–Evans flow model. The relative bias of the mean estimated frequency is 13.6% and the mean relative standard deviation is 14.3% at 90°, where a traditional estimator yields zero velocity. Measurements have been conducted with an experimental scanner and a convex array transducer....... A pump generated artificial femoral and carotid artery flow in the phantom. The estimated spectra degrade when the angle is different from 90°, but are usable down to 60° to 70°. Below this angle the traditional spectrum is best and should be used. The conventional approach can automatically be corrected...

  15. Plasmonic Properties of Vertically Aligned Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Hua Qi

    2012-01-01

    Full Text Available Nanowires (NWs/Ag sheath composites were produced to investigate plasmonic coupling between vertically aligned NWs for surface-enhanced Raman scattering (SERS applications. In this investigation, two types of vertical NW arrays were studied; those of ZnO NWs grown on nanosphere lithography patterned sapphire substrate via vapor-liquid-solid (VLS mechanism and Si NW arrays produced by wet chemical etching. Both types of vertical NW arrays were coated with a thin layer of silver by electroless silver plating for SERS enhancement studies. The experimental results show extremely strong SERS signals due to plasmonic coupling between the NWs, which was verified by COMSOL electric field simulations. We also compared the SERS enhancement intensity of aligned and random ZnO NWs, indicating that the aligned NWs show much stronger and repeatable SERS signal than those grown in nonaligned geometries.

  16. High-Velocity Clouds

    CERN Document Server

    Woerden, Hugo; Schwarz, Ulrich J; Boer, Klaas S

    2005-01-01

    This book contains 17 chapters reviewing our knowledge of the high-velocity clouds (HVCs) as of 2004, bringing this together in one place for the first time. Each of the many different aspects of HVC research is addressed by one of the experts in that subfield. These include a historical overview of HVC research and analyses of the structure and kinematics of HVCs. Separate chapters address the intermediate-velocity clouds, the Magellanic Stream, and neutral hydrogen HVCs discovered in external galaxies. Reviews are presented of the Ha emission and of optical and UV absorption-line studies, followed by discussions of the hot Galactic Halo and of the interactions between HVCs and their surroundings. Four chapters summarize the ideas about the origin of the high-velocity gas, with detailed discussions of connections between HVCs and the Galactic Fountain, tidally-stripped material, and remnants of the Milky Way's formation. A chapter outlining what we do not know completes the book. The book comes at a time whe...

  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. Mixed convection of micropolar fluid in a vertical double-passage ...

    African Journals Online (AJOL)

    The effect of the presence of a thin perfectly conductive baffle on the fully developed laminar mixed convection in a vertical channel containing micropolar fluid is analyzed. The channel has different constant wall temperatures. Analytical expressions for velocity and microrotation velocity are obtained. The solutions are ...

  19. Stationary bottom generated velocity fluctuations in one-dimensional open channel flow

    NARCIS (Netherlands)

    de Jong, B.

    1994-01-01

    Statistical characteristics are calculated for stationary velocity fluctuations in a one-dimensional open channel flow with a given vertical velocity profile and with one-dimensional irregular bottom waves, characterized by a spectral density function. The calculations are based on an approximate

  20. Modelling Velocity Spectra in the Lower Part of the Planetary Boundary Layer

    DEFF Research Database (Denmark)

    Olesen, H.R.; Larsen, Søren Ejling; Højstrup, Jørgen

    1984-01-01

    Principles used when constructing models for velocity spectra are reviewed. Based upon data from the Kansas and Minnesota experiments, simple spectral models are set up for all velocity components in stable air at low heights, and for the vertical spectrum in unstable air through a larger part of...

  1. GPS, su datum vertical.

    Directory of Open Access Journals (Sweden)

    Esteban Dörries

    2016-03-01

    Full Text Available La introducción de la metodología GPS en aplicaciones topográficas y geodésicas pone en notoria evidencia la clásica separación de sistemas de referencia en horizontal y vertical. Con GPS el posicionamiento es tridimensional, pero el concepto de altura difiere del clásico. Si se desea utilizar la información altimétrica debe contemplarse la ondulación del geoide.

  2. Cavity Enhanced Velocity Modulation Spectroscopy

    Science.gov (United States)

    Siller, Brian; Mills, Andrew; Porambo, Michael; McCall, Benjamin

    2010-11-01

    Over the past several decades, velocity modulation spectroscopy has been used to study dozens of molecular ions of astronomical importance. This technique has been so productive because it provides the advantage of ion-neutral discrimination, which is critically important when interfering neutral molecules are many orders of magnitude more abundant, and when combined with heterodyne techniques, its sensitivity can approach the shot noise limit. Traditionally, velocity modulation experiments have utilized unidirectional multipass White cells to achieve up to about 8 passes through a positive column discharge cell. But by positioning the cell within an optical cavity, it is possible to obtain an effective path length orders of magnitude longer than was previously possible. We have demonstrated this novel technique using a Ti:Sapp laser in the near-IR to observe rovibronic transitions of N2+. By demodulating at twice the modulation frequency, 2nd derivative-like lineshapes are observed for ions that are velocity-modulated, while Gaussian lineshapes are observed for excited neutral that are concentration-modulated. The signals for N2+ and N2+* have been observed to be 78° out of phase with one another, so ion-neutral discrimination is retained. And due to the laser power enhancement and geometry of the optical cavity, Doppler-free saturation spectroscopy is now possible. Observed Lamb dips have widths of 50 MHz, and when combined with calibration by an optical frequency comb, this allows for determination of line centers to within 1 MHz. In our original demonstration of this technique, our sensitivity was limited by noise in the laser-cavity lock. Since then, we have integrated Noise Immune Cavity Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS) by adding sidebands to the laser at an exact multiple of the cavity free spectral range, and demodulating at the sideband frequency before sending the signal to a lock-in amplifier for demodulating at twice the

  3. Remarks on the Definition and Estimation of Friction Velocity

    Science.gov (United States)

    Weber, Rudolf O.

    One of the mainscaling parameters in similarity theory of the atmospheric boundary layer is friction velocity. Unfortunately, several definitions of friction velocity exist in the literature. Some authors use the component of the horizontal Reynolds stress vector in the direction of the mean wind vector to define friction velocity. Others define the friction velocity by means of the absolute value of the horizontal Reynolds stress vector. The two definitions coincide only if the direction of the mean wind vector is parallel to the horizontal Reynolds stress vector. In general, the second definition gives larger values for the friction velocity. Over complex terrain the situation is further complicated by the fact that the terrain following flow is not necessarily horizontal. Thus, several authors have proposed to use terrain following coordinate systems for the definition of friction velocity. By means of a large dataset of fast-response wind measurements with an ultrasonic anemometer the friction velocities resulting from the different definitions are compared. Furthermore, it is shown that friction velocity can be well estimated from horizontal wind speed, and even better from simple horizontal or vertical turbulence parameters.

  4. Integrative velocity model building for imaging a geothermal reservoir in southern Tuscany, Italy

    Science.gov (United States)

    Schreiter, Lena; Loch, Felix; Ciuffi, Simonetta; Buske, Stefan

    2017-04-01

    Deep geothermal reservoirs are generally characterized by high temperatures and pressures, sometimes located in hard rock environments and even close to a super-critical state. For characterization of such a deep super-critical geothermal reservoir, the imaging of the subsurface at the highest possible resolution is required to reduce the uncertainties in exploration prior to the drilling phase. Several seismic surveys were carried out for characterization of a possible drilling target within a deep super-critical geothermal reservoir in Tuscany (project DESCRAMBLE). Seismic data were acquired in the form of 2D seismic reflection surveys as well as Vertical Seismic Profiling (VSP), the latter complemented by simultaneous recording of the source signals by a surface network covering an area of approximately 6 km x 6 km around the drill site. The investigation area itself is characterized by a complex geology with strong velocity contrasts, near-surface inhomogeneities and fracture zones. At first, the processing of the recorded seismic wavefields aimed at the determination of a seismic velocity model by a multidisciplinary approach. The application of conventional methods is limited due to the low resolution of the stacking velocities, significant lateral velocity changes and strong influence of noise. We performed first-arrival traveltime tomography and derived borehole velocities to tackle the complexity of the geology. Below the bottom of the borehole, results from laboratory measurements of rock samples from deeper neighboring wells were integrated into the velocity model. This approach limits the ambiguity, which depends on the existence and distribution of the neighboring wells in the investigation area. The results contribute to a robust migration velocity model used for an uncertainty depth analysis at the target horizon. In a next step, the influence of the velocity model on imaging is tested within an advanced seismic imaging workflow for several 2D

  5. A non-hydrostatic global spectral dynamical core using a height-based vertical coordinate

    Directory of Open Access Journals (Sweden)

    Juan Simarro

    2013-06-01

    Full Text Available Most of the dynamical cores of operational global models can be broadly classified according to the spatial discretisation into two categories: spectral models with mass-based vertical coordinate and grid point models with height-based vertical coordinate. This article describes a new non-hydrostatic dynamical core for a global model that uses the spectral transform method for the horizontal directions and a height-based vertical coordinate. Velocity is expressed in the contravariant basis (instead of the geographical orthonormal basis pointing to the East, North and Zenith directions so that the expressions of the boundary conditions and the divergence of the velocity are simpler. Prognostic variables in our model are the contravariant components of the velocity, the logarithm of pressure and the logarithm of temperature. Covariant tensor analysis is used to derive the differential operators of the prognostic equations, such as the curl, gradient, divergence and covariant derivative of the contravariant velocity. A Lorenz type grid is used in the vertical direction, with the vertical contravariant velocity staggered with respect to the other prognostic variables. High-order vertical operators are constructed following the finite difference technique. Time stepping is semi-implicit because it allows for long time steps that compensates the cost of the spectral transformations. A set of experiments reported in the literature is implemented so as to confirm the accuracy and efficiency of the new dynamical core.

  6. On the turbulent heating and the threshold condition in the critical ionization velocity interaction

    Science.gov (United States)

    Moebius, E.; Papadopoulos, K.; Piel, A.

    1987-01-01

    On the basis of the nonlinear treatment of the ion beam instability and the modified two-stream instability, threshold conditions for the critical ionization velocity interaction are derived. There are three different regimes of interaction: (1) additional ionization for relative velocities smaller than the critical velocity, (2) the self-sustained discharge for velocities greater than the critical velocity which indeed turns out as a sharp threshold, and (3) an explosive growth regime for velocities exceeding 1.5 times the critical velocity. Additional charge exchange collisions of ions and energy loss of electrons due to excitation do not change the basic threshold behavior but modify the value of the critical velocity.

  7. Rigid Ankle Foot Orthosis Deteriorates Mediolateral Balance Control and Vertical Braking during Gait Initiation

    Directory of Open Access Journals (Sweden)

    Arnaud Delafontaine

    2017-04-01

    Full Text Available Rigid ankle-foot orthoses (AFO are commonly used for impeding foot drop during the swing phase of gait. They also reduce pain and improve gait kinematics in patients with weakness or loss of integrity of ankle-foot complex structures due to various pathological conditions. However, this comes at the price of constraining ankle joint mobility, which might affect propulsive force generation and balance control. The present study examined the effects of wearing an AFO on biomechanical variables and electromyographic activity of tibialis anterior (TA and soleus muscles during gait initiation (GI. Nineteen healthy adults participated in the study. They initiated gait at a self-paced speed with no ankle constraint as well as wearing an AFO on the stance leg, or bilaterally. Constraining the stance leg ankle decreased TA activity ipsilaterally during the anticipatory postural adjustment (APA of GI, and ipsilateral soleus activity during step execution. In the sagittal plane, the decrease in the stance leg TA activity reduced the backward displacement of the center of pressure (CoP resulting in a reduction of the forward velocity of the center of mass (CoM measured at foot contact (FC. In the frontal plane, wearing the AFO reduced the displacement of the CoP in the direction of the swing leg during the APA phase. The mediolateral velocity of the CoM increased during single-stance prompting a larger step width to recover balance. During step execution, the CoM vertical downward velocity is normally reduced in order to lessen the impact of the swing leg with the floor and facilitates the rise of the CoM that occurs during the subsequent double-support phase. The reduction in stance leg soleus activity caused by constraining the ankle weakened the vertical braking of the CoM during step execution. This caused the absolute instantaneous vertical velocity of the CoM at FC to be greater in the constrained conditions with respect to the control condition. From

  8. Subduction and vertical coastal motions in the eastern Mediterranean

    Science.gov (United States)

    Howell, Andy; Jackson, James; Copley, Alex; McKenzie, Dan; Nissen, Ed

    2017-10-01

    Convergence in the eastern Mediterranean of oceanic Nubia with Anatolia and the Aegean is complex and poorly understood. Large volumes of sediment obscure the shallow structure of the subduction zone, and since much of the convergence is accommodated aseismically, there are limited earthquake data to constrain its kinematics. We present new source models for recent earthquakes, combining these with field observations, published GPS velocities and reflection-seismic data to investigate faulting in three areas: the Florence Rise, SW Turkey and the Pliny and Strabo Trenches. The depths and locations of earthquakes reveal the geometry of the subducting Nubian plate NE of the Florence Rise, a bathymetric high that is probably formed by deformation of sediment at the surface projection of the Anatolia-Nubia subduction interface. In SW Turkey, the presence of a strike-slip shear zone has often been inferred despite an absence of strike-slip earthquakes. We show that the GPS-derived strain-rate field is consistent with extension on the orthogonal systems of normal faults observed in the region and that strike-slip faulting is not required to explain observed GPS velocities. Further SW, the Pliny and Strabo Trenches are also often interpreted as strike-slip shear zones, but almost all nearby earthquakes have either reverse-faulting or normal-faulting focal mechanisms. Oblique convergence across the trenches may be accommodated either by a partitioned system of strike-slip and reverse faults or by oblique slip on the Aegean-Nubia subduction interface. The observed late-Quaternary vertical motions of coastlines close to the subduction zone are influenced by the interplay between: (1) thickening of the material overriding the subduction interface associated with convergence, which promotes coastal uplift; and (2) subsidence due to extension and associated crustal thinning. Long-wavelength gravity data suggest that some of the observed topographic contrasts in the eastern

  9. Adaptation of the vertical vestibulo-ocular reflex in cats during low-frequency vertical rotation.

    Science.gov (United States)

    Fushiki, Hiroaki; Maruyama, Motoyoshi; Shojaku, Hideo

    2017-04-27

    We examined plastic changes in the vestibulo-ocular reflex (VOR) during low-frequency vertical head rotation, a condition under which otolith inputs from the vestibular system are essential for VOR generation. For adaptive conditioning of the vertical VOR, 0.02Hz sinusoidal pitch rotation for one hour about the earth's horizontal axis was synchronized with out-of-phase vertical visual stimulation from a random dot pattern. A vertical VOR was well evoked when the upright animal rotated around the earth-horizontal axis (EHA) at low frequency due to the changing gravity stimulus and dynamic stimulation of the otoliths. After adaptive conditioning, the amplitude of the vertical VOR increased by an average of 32.1%. Our observations showing plasticity in the otolithic contribution to the VOR may provide a new strategy for visual-vestibular mismatch training in patients with otolithic disorders. This low-frequency vertical head rotation protocol also provides a model for investigating the mechanisms underlying the adaptation of VORs mediated by otolith activation. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. 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.

  11. The vertical distribution of buoyant plastics at sea

    Science.gov (United States)

    Reisser, J.; Slat, B.; Noble, K.; du Plessis, K.; Epp, M.; Proietti, M.; de Sonneville, J.; Becker, T.; Pattiaratchi, C.

    2014-11-01

    Millimeter-sized plastics are numerically abundant and widespread across the world's ocean surface. These buoyant macroscopic particles can be mixed within the upper water column due to turbulent transport. Models indicate that the largest decrease in their concentration occurs within the first few meters of water, where subsurface observations are very scarce. By using a new type of multi-level trawl at 12 sites within the North Atlantic accumulation zone, we measured concentrations and physical properties of plastics from the air-seawater interface to a depth of 5 m, at 0.5 m intervals. Our results show that plastic concentrations drop exponentially with water depth, but decay rates decrease with increasing Beaufort scale. Furthermore, smaller pieces presented lower rise velocities and were more susceptible to vertical transport. This resulted in higher depth decays of plastic mass concentration (mg m-3) than numerical concentration (pieces m-3). Further multi-level sampling of plastics will improve our ability to predict at-sea plastic load, size distribution, drifting pattern, and impact on marine species and habitats.

  12. Characteristics of Vertical Mantle Heat Exchangers for Solar Water Heaters

    DEFF Research Database (Denmark)

    Shah, Louise Jivan; Morrison, G.L.; Behnia, M.

    1999-01-01

    - The flow structure in vertical mantle heat exchangers was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the mantle were measured using a particle Image Velocimetry (PIV) system. A CFD simulation model of vertical mantle heat...... exchangers was also developed for detailed evaluation of the heat flux distribution over the mantle surface. Both the experimental and simulation results indicate that distribution of the flow around the mantle gap is governed by buoyancy driven recirculation in the mantle. The operation of the mantle...

  13. Vertical Protocol Composition

    DEFF Research Database (Denmark)

    Groß, Thomas; Mödersheim, Sebastian Alexander

    2011-01-01

    composition, and it is truly commonplace in today’s communication with the diversity of VPNs and secure browser sessions. In fact, it is normal that we have several layers of secure channels: For instance, on top of a VPN-connection, a browser may establish another secure channel (possibly with a different...... end point). Even using the same protocol several times in such a stack of channels is not unusual: An application may very well establish another TLS channel over an established one. We call this selfcomposition. In fact, there is nothing that tells us that all these compositions are sound, i.......e., that the combination cannot introduce attacks that the individual protocols in isolation do not have. In this work, we prove a composability result in the symbolic model that allows for arbitrary vertical composition (including self-composition). It holds for protocols from any suite of channel and application...

  14. Vertical cavity laser

    DEFF Research Database (Denmark)

    2016-01-01

    The present invention provides a vertical cavity laser comprising a grating layer comprising an in-plane grating, the grating layer having a first side and having a second side opposite the first side and comprising a contiguous core grating region having a grating structure, wherein an index......, an index of refraction of the second low-index layer or air being less than 2; and a thickness of the cap layer and a thickness of the grating layer, and a pitch and a duty cycle of the grating structure are selected to obtain a resonance having a free-space resonance wavelength in the interval 300 nm to 3...... microns, the cap layer comprises an active region configured to generate or absorb photons at the free-space resonance wavelength by stimulated emission or absorption when a sufficient forward or reverse bias voltage is applied across the active region, a thickness of the first low-index layer is less...

  15. Tomographic Inversion for Shear Velocity Beneath the North American Plate

    Science.gov (United States)

    Grand, Stephen P.

    1987-12-01

    A tomographic back projection scheme has been applied to S and SS travel times to invert for shear velocity below the North American plate. The data range in distance from 8° to 80°, and a total of 3923 arrival times were used. First arrivals were measured directly off the seismograms, while the arrival times of later arrivals were found by a waveform correlation technique using synthetic seismograms. The starting model was laterally heterogeneous in the upper 400 km to account for the first-order differences in ray paths already known. The model was divided into blocks with horizontal dimensions of 500 km by 500 km and varying vertical thicknesses. Good resolution was obtained for structure from just below the crust to about 1700 km depth in the mantle. In the upper mantle a high-velocity root was found directly beneath the Canadian shield to about 400 km depth with the Superior province having the highest velocity and deepest root. The east coast of the United States was found to have intermediate velocities from 100 to 350 km depth and the western United States the slowest velocities at these depths. Below 400 km depth the most significant structure found is a slab-shaped high-velocity anomaly from the eastern Carribean to the northern United States. Beneath the Carribean this anomaly is almost vertical and extends from about 700 km to 1700 km depth. Further to the north, the anomaly dips to the east with high velocities at 700 km depth in the central United States and high velocities below 1100 km depth beneath the east coast. The anomaly is about 1% in magnitude. This lower-mantle anomaly may be associated with past subduction of the Farallon plate beneath North America.

  16. Direct Observation of Ultralow Vertical Emittance using a Vertical Undulator

    Energy Technology Data Exchange (ETDEWEB)

    Wootton, Kent

    2015-09-17

    In recent work, the first quantitative measurements of electron beam vertical emittance using a vertical undulator were presented, with particular emphasis given to ultralow vertical emittances [K. P. Wootton, et al., Phys. Rev. ST Accel. Beams, 17, 112802 (2014)]. Using this apparatus, a geometric vertical emittance of 0.9 ± 0.3 pm rad has been observed. A critical analysis is given of measurement approaches that were attempted, with particular emphasis on systematic and statistical uncertainties. The method used is explained, compared to other techniques and the applicability of these results to other scenarios discussed.

  17. Examples of Vector Velocity Imaging

    DEFF Research Database (Denmark)

    Hansen, Peter M.; Pedersen, Mads M.; Hansen, Kristoffer L.

    2011-01-01

    To measure blood flow velocity in vessels with conventional ultrasound, the velocity is estimated along the direction of the emitted ultrasound wave. It is therefore impossible to obtain accurate information on blood flow velocity and direction, when the angle between blood flow and ultrasound wa...

  18. Validation of the iPhone app using the force platform to estimate vertical jump height.

    Science.gov (United States)

    Carlos-Vivas, Jorge; Martin-Martinez, Juan P; Hernandez-Mocholi, Miguel A; Perez-Gomez, Jorge

    2016-09-22

    Vertical jump performance has been evaluated with several devices: force platforms, contact mats, Vertec, accelerometers, infrared cameras and high-velocity cameras; however, the force platform is considered the gold standard for measuring vertical jump height. The purpose of this study was to validate the iPhone app, My Jump, that measures vertical jump height by comparing it with other methods that use the force platform to estimate vertical jump height, namely, vertical velocity at take-off and time in the air. A total of 40 sport sciences students (age 21.4 ± 1.9 years) completed five countermovement jumps (CMJs) over a force platform. Thus, 200 CMJ heights were evaluated from the vertical velocity at take-off and the time in the air using the force platform, and from the time in the air with the mobile application My Jump. The height obtained was compared using the intraclass correlation coefficient (ICC). Correlation between APP and force platform using the time in the air was perfect (ICC = 1.000, P Jump, is an appropriate method to evaluate the vertical jump performance; however, vertical jump height is slightly overestimated compared with that of the force platform.

  19. Characteristics of slug flow in narrow rectangular channels under vertical condition

    Science.gov (United States)

    Wang, Yang; Yan, Changqi; Sun, Licheng; Xing, Dianchuan; Yan, Chaoxing; Tian, Daogui

    2013-07-01

    Gas-liquid slug flow is widely encountered in many practical industrial applications. A detailed understanding of the hydrodynamics of gas slug has important significance for modeling of the slug flow. Non-intrusive flow visualization using a high speed video camera system is applied to study characteristics of slug flow in a vertical narrow rectangular channel (3.25×40 mm2). Ideal Taylor bubbles are hardly observed, and most of the gas slugs are deformed, much more seriously at high liquid superficial velocity. The liquid film thicknesses of left and right narrow sides surrounding gas slug are divergent and wavy, but it has weak effect on liquid film velocity. The gas and liquid velocity as well as the length of gas slug have significant effect on the separating liquid film thickness. The separating liquid film velocity is decreased with the increase of gas superficial velocity at low liquid velocity, and increased with the increase of liquid superficial velocity. The film stops descending and the gas superficial velocity has no significant effect on liquid film separating velocity at high liquid velocity (jL≥1.204 m/s), and it is mainly determined by the liquid flow rate. The shape of slug nose has a significant effect on its velocity, while the effect of its length is very weak. The Ishii&Jones-Zuber drift flux correlation could predict slug velocity well, except at low liquid superficial velocity by reason of that the calculated drift velocity is less than experimental values.

  20. Constraining fault interpretation through tomographic velocity gradients: application to northern Cascadia

    Directory of Open Access Journals (Sweden)

    K. Ramachandran

    2012-02-01

    Full Text Available Spatial gradients of tomographic velocities are seldom used in interpretation of subsurface fault structures. This study shows that spatial velocity gradients can be used effectively in identifying subsurface discontinuities in the horizontal and vertical directions. Three-dimensional velocity models constructed through tomographic inversion of active source and/or earthquake traveltime data are generally built from an initial 1-D velocity model that varies only with depth. Regularized tomographic inversion algorithms impose constraints on the roughness of the model that help to stabilize the inversion process. Final velocity models obtained from regularized tomographic inversions have smooth three-dimensional structures that are required by the data. Final velocity models are usually analyzed and interpreted either as a perturbation velocity model or as an absolute velocity model. Compared to perturbation velocity model, absolute velocity models have an advantage of providing constraints on lithology. Both velocity models lack the ability to provide sharp constraints on subsurface faults. An interpretational approach utilizing spatial velocity gradients applied to northern Cascadia shows that subsurface faults that are not clearly interpretable from velocity model plots can be identified by sharp contrasts in velocity gradient plots. This interpretation resulted in inferring the locations of the Tacoma, Seattle, Southern Whidbey Island, and Darrington Devil's Mountain faults much more clearly. The Coast Range Boundary fault, previously hypothesized on the basis of sedimentological and tectonic observations, is inferred clearly from the gradient plots. Many of the fault locations imaged from gradient data correlate with earthquake hypocenters, indicating their seismogenic nature.

  1. Vehicle Ride Height Change Due To Radial Expansion Of Tires

    Directory of Open Access Journals (Sweden)

    Čavoj Ondřej

    2015-11-01

    Full Text Available In general, tire deformations caused by wheel rotation are not taken into account when developing vehicle aerodynamics. On the road the tires radially expand as speed increases, which affects the actual ride height of a vehicle. In turn this often increases the real aerodynamic drag compared to values obtained using CFD or a wind tunnel as the mass flow across the relatively rough underbody increases with ground clearance. In this study, on-road ride heights were measured while running a vehicle in a straight line with fixed velocity whilst the aerodynamic lift of the vehicle was determined in a wind tunnel. Subsequently, the relationships between ride height and axle load were obtained by loading the vehicle at standstill with ballast. By comparing the ride heights at high and very low velocities with expected vertical displacement caused purely by aerodynamic lift force as computed according to the ride height - axle load equations, the ride height change due to tire radial expansion was determined.

  2. Vertical and Interfacial Transport in Wetlands (Invited)

    Science.gov (United States)

    Variano, E. A.

    2010-12-01

    The objective of this work is to understand the fluxes connecting the water column, substrate, and atmosphere in wetland environments. To do this, analytical, numerical, and laboratory models have been used to quantify the hydrodynamic contributions to vertical fluxes. A key question is whether the hydrodynamic transport can be modeled as a diffusivity, and, if so, what the vertical structure of this diffusivity is. This question will be addressed in a number of flow types and for a number of fluxes. The fluxes of interest are heat, sediment, dissolved gases (such as methane and oxygen) and other dissolved solutes (such as nutrients and pollutants). The flows of interest include: unidirectional current, reversing flow (under waves, seiches, and tides), wind-sheared surface flows, and thermal convection. Rain and bioturbation can be important, but are not considered in the modeling work discussed herein. Specifically, we will present results on gas transport at wind-sheared free surface, sediment transport in unidirectional flow, and heat transfer in an oscillating flow cause by a seiche. All three of these will be used to consider the question of appropriate analytical models for vertical transport. The analytic models considered here are all 1D models that assume homogeneity in the horizontal plane. The numerical models use finite element methods and resolve the flow around individual vegetation stems in an idealized geometry. Laboratory models discussed herein also use an idealized geometry. Vegetation is represented by an array of cylinders, whose geometry is modeled after Scirpus spp. wetlands in Northern California. The laboratory model is constructed in a way that allows optical access to the flow, even in dense vegetation and far from boundaries. This is accomplished by using fluoropolymer plastics to construct vegetation models. The optical access allows us to employ particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) to measure

  3. Vertical Motion Determined Using Satellite Altimetry and Tide Gauges

    Directory of Open Access Journals (Sweden)

    Chung-Yen Kuo

    2008-01-01

    Full Text Available A robust method to estimate vertical crustal motions by combining geocentric sea level measurements from decadal (1992 - 2003 TOPEX/POSEIDON satellite altimetry and long-term (> 40 years relative sea level records from tide gauges using a novel Gauss-Markov stochastic adjustment model is presented. These results represent an improvement over a prior study (Kuo et al. 2004 in Fennoscandia, where the observed vertical motions are primarily attributed to the incomplete Glacial Isostatic Adjustment (GIA in the region since the Last Glacial Maximum (LGM. The stochastic adjustment algorithm and results include a fully-populated a priori covariance matrix. The algorithm was extended to estimate vertical motion at tide gauge locations near open seas and around semi-enclosed seas and lakes. Estimation of nonlinear vertical motions, which could result from co- and postseismic deformations, has also been incorporated. The estimated uncertainties for the vertical motion solutions in coastal regions of the Baltic Sea and around the Great Lakes are in general < 0.5 mm yr-1, which is a significant improvement over existing studies. In the Baltic Sea, the comparisons of the vertical motion solution with 10 collocated GPS radial rates and with the BIFROST GIA model show differences of 0.2 _ 0.9 and 1.6 _ 1.8 mm yr-1, respectively. For the Great Lakes region, the comparisons with the ICE-3G model and with the relative vertical motion estimated using tide gauges only (Mainville and Craymer 2005 show differences of -0.2 _ 0.6 and -0.1 _ 0.5 mm yr-1, respectively. The Alaskan vertical motion solutions (linear and nonlinear models have an estimated uncertainty of ~1.2 - 1.6 mm yr-1, which agree qualitatively with GPS velocity and tide gauge-only solutions (Larsen et al. 2003. This innovative technique could potentially provide improved estimates of the vertical motion globally where long-term tide gauge records exist.

  4. Entropy generation in hydrodynamic slip flow over a vertical plate with convective boundary

    Energy Technology Data Exchange (ETDEWEB)

    Butt, Adnan Saeed; Munawar, Sufian; Ali, Asif [Quaid i Azam Univ., Islamabad (Pakistan); Meh Mood, Ahmer [International Islamic Univ., Islamabad (Pakistan)

    2012-09-15

    The present article aims to report the effects of hydrodynamic slip on entropy generation in the boundary layer flow over a vertical surface with convective boundary condition. Suitable similarity transformations are used to transform the fundamental equations of hydrodynamic and thermal boundary layer flow into ordinary differential equations. The governing equations are then solved numerically using the shooting method and the velocity and the temperature profiles are obtained for various values of parameters involved in the governing equations. The expressions for the entropy generation number and the Bejan number are presented and the results are discussed graphically and quantitatively for the slip parameter, the local Grashof number, the Prandtl number, the local convective heat transfer parameter, the group parameter and the local Reynolds number. It is observed that due to the presence of slip, entropy production in a thermal system can be controlled and reduced.

  5. A Tall-Tower Instrument for Mean and Fluctuating Velocity, Fluctuating Temperature and Sensible Heat Flux Measurements

    DEFF Research Database (Denmark)

    Gryning, Sven-Erik; Thomson, D. W.

    1979-01-01

    For an ongoing elevated-source, urban-scale tracer experiment, an instrument system to measure the three-dimensional wind velocity and the turbulent sensible heat flux was developed. The wind velocity was measured with a combination of cup anemometer, propeller (vertical) and vane sensor. The tem......For an ongoing elevated-source, urban-scale tracer experiment, an instrument system to measure the three-dimensional wind velocity and the turbulent sensible heat flux was developed. The wind velocity was measured with a combination of cup anemometer, propeller (vertical) and vane sensor...

  6. Vertical allometry: fact or fiction?

    Science.gov (United States)

    Mahmood, Iftekhar; Boxenbaum, Harold

    2014-04-01

    In pharmacokinetics, vertical allometry is referred to the clearance of a drug when the predicted human clearance is substantially higher than the observed human clearance. Vertical allometry was initially reported for diazepam based on a 33-fold higher human predicted clearance than the observed human clearance. In recent years, it has been found that many other drugs besides diazepam, can be classified as drugs which exhibit vertical allometry. Over the years, many questions regarding vertical allometry have been raised. For example, (1) How to define and identify the vertical allometry? (2) How much difference should be between predicted and observed human clearance values before a drug could be declared 'a drug which follows vertical allometry'? (3) If somehow one can identify vertical allometry from animal data, how this information can be used for reasonably accurate prediction of clearance in humans? This report attempts to answer the aforementioned questions. The concept of vertical allometry at this time remains complex and obscure but with more extensive works one can have better understanding of 'vertical allometry'. Published by Elsevier Inc.

  7. Impact of different vertical transport representations on simulating processes in the tropical tropopause layer (TTL)

    Energy Technology Data Exchange (ETDEWEB)

    Ploeger, Felix

    2011-07-06

    trajectories are highly correlated, rendering ozone an interesting tracer for aspects of transport in the TTL where water vapour is not sensitive. Consequently, dispersion and mean upwelling have similar effects on ozone profiles, with slower upwelling and larger dispersion both leading to higher ozone concentrations. Analyses of tropical upwelling based on mean transport characteristics (e.g., mean ascent rates) and model validation have to take into account this ambiguity. Predicted ozone concentrations for kinematic transport are robustly higher than for diabatic transport, due to larger trajectory dispersion caused by the larger inhomogeneity in the kinematic vertical velocity field. During the tropical SCOUT-O3 campaign, kinematic ozone predictions show an extreme high bias compared to in-situ observations. The high sensitivity of many characteristics of transport to the choice of the transport representation, demonstrates the need to better constrain transport in the TTL. Consequently, estimates of exact numbers from models, e.g., for timescales of transport, are not reliable and only a range of values can be given. However, there are robust features of tropical transport, not depending on the transport representation, as for example, a significant impact of monsoon driven horizontal in-mixing from the extratropics on the composition of the TTL. In fact, the annual cycle of ozone above the tropical tropopause is attributed, at least in 'ECMWF-world', to in-mixing of ozone-rich extratropical air during summer. (orig.)

  8. Factors Affecting Seismic Velocity in Alluvium

    Science.gov (United States)

    Huckins-Gang, H.; Mercadante, J.; Prothro, L.

    2015-12-01

    Yucca Flat at the Nevada National Security Site has been selected as the Source Physics Experiment (SPE) Dry Alluvium Geology Phase II site. The alluvium in this part of Yucca Flat is typical of desert basin fill, with discontinuous beds that are highly variable in clast size and provenance. Detailed understanding of the subsurface geology will be needed for interpretation of the SPE seismic data. A 3D seismic velocity model, created for Yucca Flat using interval seismic velocity data, shows variations in velocity within alluvium near the SPE Phase II site beyond the usual gradual increase of density with depth due to compaction. In this study we examined borehole lithologic logs, geophysical logs, downhole videos, and laboratory analyses of sidewall core samples to understand which characteristics of the alluvium are related to these variations in seismic velocity. Seismic velocity of alluvium is generally related to its density, which can be affected by sediment provenance, clast size, gravel percentage, and matrix properties, in addition to compaction. This study presents a preliminary subdivision of the alluvial strata in the SPE Phase II area into mappable units expected to be significant to seismic modeling. Further refinements of the alluvial units may be possible when seismic data are obtained from SPE Phase II tests. This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy.

  9. Vertical distribution of natural radionuclides in soils

    Directory of Open Access Journals (Sweden)

    Lozano J. C.

    2012-04-01

    Full Text Available Low-level alpha spectrometry techniques using semiconductor detectors (PIPS and liquid scintillation counters (LKB Quantulus 1220™ were used in order to determine the activity concentration of 238U, 232Th, 234U, 230Th, 226Ra, and 210Pb in soil samples. The soils were collected from an old disused uranium mine located in southwest Spain. The soils were selected with different levels of influence from the installation, in such a way that they had different levels of radioactive contamination. The vertical profiles in the soils (down to 40 cm depth were studied in order to evaluate the vertical distribution of the natural radionuclides. The possible contamination of subsurface waters depends strongly on vertical migration, and the transfer to plants (herbs, shrubs, and trees also will depend on the distribution of the radionuclides in the root zone. The study of the activity ratios between radionuclides belonging to the same series allowed us to assess the differing behaviour of the radionuclides involved. The vertical profiles for these radionuclides were different at each sampling point, showing the local impact of the installation. However, the profiles per point were similar for the long-lived radionuclides of the 238TJ series (238U, 234U, 230Th, and 226Ra. Also, a major disequilibrium was observed between 210Pb and 226Ra in the surface layer, due to 222Rn emanation and subsequent surface deposition of 210Pb.

  10. Counter-rotating vortex pairs in the wake of a vertical axis wind turbine

    Science.gov (United States)

    Rolin, Vincent; Porté-Agel, Fernando

    2017-04-01

    Despite the rising popularity of vertical axis wind turbines, or VAWTs, the wakes behind these machines is much less well understood than those behind horizontal axis wind turbines, or HAWTs. A thorough understanding of wakes is important as they can cause turbines in wind farms to produce less power than anticipated and increase the fatigue loading on turbines due to vibrations. In order to gain a deeper understanding of the wake behind a vertical axis wind turbine in atmospheric flow stereo-PIV is implemented in a boundary-layer wind tunnel to produce snapshots of the 3-component velocity field in the wake at various downstream positions. The boundaries of the wake are readily observed due to the high velocity gradients and turbulence present here. Two pairs of counter-rotating vortices similar to those in the wake of yawed HAWTs are also observed. An examination of the momentum fluxes behind the turbine demonstrates that the mean flow induced by these vortices entrains a large quantity of momentum from the unperturbed boundary layer flow above the wake. This effect proves to play an even more significant role than turbulence in reintroducing momentum into the wake. In order to comprehend why the VAWT produces these vortices we modify the double-multiple stream-tube model typically used to predict VAWT performance to incorporate crosswind forces. The similarity between VAWT and yawed HAWT wakes is found not to be coincidental as both cases feature rotors which exert a lateral thrust on the incoming wind which leads to the creation of counter-rotating vortex pairs.

  11. 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...

  12. 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...

  13. Train velocity estimation method based on an adaptive filter with fuzzy logic

    Science.gov (United States)

    Pichlík, Petr; Zděnek, Jiří

    2017-03-01

    The train velocity is difficult to determine when the velocity is measured only on the driven or braked locomotive wheelsets. In this case, the calculated train velocity is different from the actual train velocity due to slip velocity or skid velocity respectively. The train velocity is needed for a locomotive controller proper work. For this purpose, an adaptive filter that is tuned by a fuzzy logic is designed and described in the paper. The filter calculates the train longitudinal velocity based on locomotive wheelset velocity. The fuzzy logic is used for the tuning of the filter according to actual wheelset acceleration and wheelset jerk. The simulation results are based on real measured data on a freight train. The results show that the calculated velocity corresponds to the actual train velocity.

  14. Simulation Of Single Channel Length Vertical Silicon MOSFET

    Science.gov (United States)

    Ooi, P. K.; Ibrahim, K.

    2008-05-01

    Vertical MOSFET has been introduced in the last few decades. As planar devices become smaller and smaller, vertical MOS transistor is one of the solutions for surpassing the short channel effects and pattern transfer. Thus, it is a promising approach to achieve channel lengths between 100 nm and 25 nm. In this work, we simulate sub-100 nm single channel length vertical silicon MOSFET. The simulations are done with using ATHENA, DEVEDIT and ATLAS from SILVACO International. Input and output electrical characteristics of the vertical MOS transistors are investigated. The short channel effects of the vertical MOSFETs are explored. Due to the structure is not symmetry, source at top and bottom is also considered. The results also compared with experimental results from other researcher.

  15. Quantifying Ice-sheet/Ice-shelf Dynamics and Variability with Meter-scale DEM and Velocity Timeseries

    Science.gov (United States)

    Shean, D. E.; Joughin, I. R.; Smith, B. E.; Moratto, Z. M.; Porter, C.; Morin, P. J.

    2012-12-01

    Both the Antarctic and Greenland ice sheets are losing mass at an increasing rate, although loss due to accelerating flow and dynamic thinning remains poorly understood. We are using complementary data from repeat satellite and airborne observations to investigate the relationship between ice-sheet/ice-shelf dynamics and geometry on seasonal to interannual timescales. High-resolution along-track stereo imagery from commercial satellite vendors DigitalGlobe and GeoEye provides unprecedented spatial (~0.5 m/px with ~17 km swath width) and temporal (weekly/monthly) resolution for these efforts. We have developed an automated pipeline using open-source software to produce orthoimage, DEM, and surface velocity products from DigitalGlobe imagery. High-contrast surface texture (e.g. sastrugi, crevasses) visible at sub-meter resolution provides near-perfect image correlation (~99% success rate) during DEM and velocity map derivation. Elevation data from IceBridge ATM/LVIS, ICESat GLAS, and GPS campaigns are used to correct DEMs and perform accuracy assessment. Preliminary tests over exposed bedrock provide relative vertical accuracy estimates of <1-2 m for Worldview-1/2 DEMs. Velocity data from TerraSAR-X and GPS campaigns provide validation for surface velocity products, with horizontal error estimates of <10 m. Velocity and elevation change products with 2-4 m/px spatial resolution allow for unprecedented 3D dynamic characterization of sub-km flow transition zones (e.g. grounding lines, shear margins), capturing both local and regional variations due to melting and dynamic thinning. We present timeseries for West Greenland (Jakobshavn front - 20 observations, Jakobshavn south catchment - 10) and West Antarctica (Pine Island and Thwaites - 5 each) from 2009-2012. These observations complement ongoing efforts to measure and model outlet glacier dynamics, with implications for future ice-sheet mass balance estimates.

  16. 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.

  17. Protected Vertices in Motzkin trees

    OpenAIRE

    Van Duzer, Anthony

    2017-01-01

    In this paper we find recurrence relations for the asymptotic probability a vertex is $k$ protected in all Motzkin trees. We use a similar technique to calculate the probabilities for balanced vertices of rank $k$. From this we calculate upper and lower bounds for the probability a vertex is balanced and upper and lower bounds for the expected rank of balanced vertices.

  18. Investigating the effect of tractive parameters on imposed vertical stresses under driving wheel using a soil bin test rig facility

    Directory of Open Access Journals (Sweden)

    H Taghavifar

    2015-09-01

    relationship between traction and the soil vertical stress in a soil profile using a single-wheel tester and a soil bin facility. Materials and methods: The soil bin in Department of Mechanical Engineering of Urmia University was used in this study. This soil bin is featured 24 m in length, 2 m in width and 1 m in depth including a single-wheel tester and the carriage. A chain system was used for the power transmission from the electromotor to the carriage. The carriage was able to move alongside the soil bin through four ball bearings which also hold the weight of the carriage. The utilized tire in the study was a 220/65R21 driving wheel. One load cell was situated vertically to measure the wheel load and four S-shaped load cells were horizontally situated between the single-wheel tester and the carriage to measure the traction force. An electric motor was used to empower the carriage while another electric motor was used to empower the wheel tester. The difference between the linear velocities of the carriage and the wheel-tester provided the desired levels of slip. A housing including four load cells situated at the distances of 12.5 cm was used to measure the soil vertical stress transmission in the soil profile. The system was buried at the desired depth in the path of wheel traversal. Under the aforesaid treatments, the experiments were undertaken with the purpose of simultaneous measurement of soil stress propagation and traction force and finally the correlation between these parameters. Results and discussion: The results were analyzed using the statistical analysis at 1% significance level. The results showed that an increase in traction force leads to an increment of vertical soil stress. It was also recognized that the reduction in the velocity leads to the increase in soil stress which is due to the greater contact duration between the soil and the tire. Also, an increase in wheel load results in an increase of soil stress which has a linear correlation with the

  19. 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

  20. Waveform inversion of lateral velocity variation from wavefield source location perturbation

    KAUST Repository

    Choi, Yun Seok

    2013-09-22

    It is challenge in waveform inversion to precisely define the deep part of the velocity model compared to the shallow part. The lateral velocity variation, or what referred to as the derivative of velocity with respect to the horizontal distance, with well log data can be used to update the deep part of the velocity model more precisely. We develop a waveform inversion algorithm to obtain the lateral velocity variation by inverting the wavefield variation associated with the lateral shot location perturbation. The gradient of the new waveform inversion algorithm is obtained by the adjoint-state method. Our inversion algorithm focuses on resolving the lateral changes of the velocity model with respect to a fixed reference vertical velocity profile given by a well log. We apply the method on a simple-dome model to highlight the methods potential.

  1. Analytic solutions for seismic travel time and ray path geometry through simple velocity models.

    Energy Technology Data Exchange (ETDEWEB)

    Ballard, Sanford

    2007-12-01

    The geometry of ray paths through realistic Earth models can be extremely complex due to the vertical and lateral heterogeneity of the velocity distribution within the models. Calculation of high fidelity ray paths and travel times through these models generally involves sophisticated algorithms that require significant assumptions and approximations. To test such algorithms it is desirable to have available analytic solutions for the geometry and travel time of rays through simpler velocity distributions against which the more complex algorithms can be compared. Also, in situations where computational performance requirements prohibit implementation of full 3D algorithms, it may be necessary to accept the accuracy limitations of analytic solutions in order to compute solutions that satisfy those requirements. Analytic solutions are described for the geometry and travel time of infinite frequency rays through radially symmetric 1D Earth models characterized by an inner sphere where the velocity distribution is given by the function V (r) = A-Br{sup 2}, optionally surrounded by some number of spherical shells of constant velocity. The mathematical basis of the calculations is described, sample calculations are presented, and results are compared to the Taup Toolkit of Crotwell et al. (1999). These solutions are useful for evaluating the fidelity of sophisticated 3D travel time calculators and in situations where performance requirements preclude the use of more computationally intensive calculators. It should be noted that most of the solutions presented are only quasi-analytic. Exact, closed form equations are derived but computation of solutions to specific problems generally require application of numerical integration or root finding techniques, which, while approximations, can be calculated to very high accuracy. Tolerances are set in the numerical algorithms such that computed travel time accuracies are better than 1 microsecond.

  2. Analysis of vertical stability limits and vertical displacement event behavior on NSTX-U

    Science.gov (United States)

    Boyer, Mark; Battaglia, Devon; Gerhardt, Stefan; Menard, Jonathan; Mueller, Dennis; Myers, Clayton; Sabbagh, Steven; Smith, David

    2017-10-01

    The National Spherical Torus Experiment Upgrade (NSTX-U) completed its first run campaign in 2016, including commissioning a larger center-stack and three new tangentially aimed neutral beam sources. NSTX-U operates at increased aspect ratio due to the larger center-stack, making vertical stabilization more challenging. Since ST performance is improved at high elongation, improvements to the vertical control system were made, including use of multiple up-down-symmetric flux loop pairs for real-time estimation, and filtering to remove noise. Similar operating limits to those on NSTX (in terms of elongation and internal inductance) were achieved, now at higher aspect ratio. To better understand the observed limits and project to future operating points, a database of vertical displacement events and vertical oscillations observed during the plasma current ramp-up on NSTX/NSTX-U has been generated. Shots were clustered based on the characteristics of the VDEs/oscillations, and the plasma parameter regimes associated with the classes of behavior were studied. Results provide guidance for scenario development during ramp-up to avoid large oscillations at the time of diverting, and provide the means to assess stability of target scenarios for the next campaign. Results will also guide plans for improvements to the vertical control system. Work supported by U.S. D.O.E. Contract No. DE-AC02-09CH11466.

  3. Vertical motion of particles in vibration-induced granular capillarity

    Directory of Open Access Journals (Sweden)

    Fan Fengxian

    2017-01-01

    Full Text Available When a narrow tube inserted into a static container filled with particles is subjected to vertical vibration, the particles rise in the tube, much resembling the ascending motion of a liquid column in a capillary tube. To gain insights on the particle dynamics dictating this phenomenon – which we term granular capillarity – we numerically investigate the system using the Discrete Element Method (DEM. We reproduce the dynamical process of the granular capillarity and analyze the vertical motion of the individual particles in the tube, as well as the average vertical velocities of the particles. Our simulations show that the height of the granular column fluctuates in a periodic or period-doubling manner as the tube vibrates, until a steady-state (capillary height is reached. Moreover, our results for the average vertical velocity of the particles in the tube at different radial positions suggest that granular convection is one major factor underlying the particle-based dynamics that lead to the granular capillarity phenomenon.

  4. Vertical and horizontal seismometric observations of tides

    Science.gov (United States)

    Lambotte, S.; Rivera, L.; Hinderer, J.

    2006-01-01

    Tidal signals have been largely studied with gravimeters, strainmeters and tiltmeters, but can also be retrieved from digital records of the output of long-period seismometers, such as STS-1, particularly if they are properly isolated. Horizontal components are often noisier than the vertical ones, due to sensitivity to tilt at long periods. Hence, horizontal components are often disturbed by local effects such as topography, geology and cavity effects, which imply a strain-tilt coupling. We use series of data (duration larger than 1 month) from several permanent broadband seismological stations to examine these disturbances. We search a minimal set of observable signals (tilts, horizontal and vertical displacements, strains, gravity) necessary to reconstruct the seismological record. Such analysis gives a set of coefficients (per component for each studied station), which are stable over years and then can be used systematically to correct data from these disturbances without needing heavy numerical computation. A special attention is devoted to ocean loading for stations close to oceans (e.g. Matsushiro station in Japon (MAJO)), and to pressure correction when barometric data are available. Interesting observations are made for vertical seismometric components; in particular, we found a pressure admittance between pressure and data 10 times larger than for gravimeters for periods larger than 1 day, while this admittance reaches the usual value of -3.5 nm/s 2/mbar for periods below 3 h. This observation may be due to instrumental noise, but the exact mechanism is not yet understood.

  5. The dependence of sheet erosion velocity on slope angle

    Directory of Open Access Journals (Sweden)

    Chernyshev Sergey Nikolaevich

    2014-09-01

    Full Text Available The article presents a method for estimating the erosion velocity on forested natural area. As a research object for testing the methodology the authors selected Neskuchny Garden - a city Park on the Moskva river embankment, named after the cognominal Palace of Catherine's age. Here, an almost horizontal surface III of the Moskva river terrace above the flood-plain is especially remarkable, accentuated by the steep sides of the ravine parallel to St. Andrew's, but short and nameless. The crests of the ravine sides are sharp, which is the evidence of its recent formation, but the old trees on the slopes indicate that it has not been growing for at least 100 years. Earlier Russian researchers defined vertical velocity of sheet erosion for different regions and slopes with different parent (in relation to the soil rocks. The comparison of the velocities shows that climatic conditions, in the first approximation, do not have a decisive influence on the erosion velocity of silt loam soils. The velocities on the shores of Issyk-Kul lake and in Moscow proved to be the same. But the composition of the parent rocks strongly affects the sheet erosion velocity. Even low-strength rock material reduces the velocity by times. Phytoindication method gives a real, physically explainable sheet erosion velocities. The speed is rather small but it should be considered when designing long-term structures on the slopes composed of dispersive soils. On the slopes composed of rocky soils sheet erosion velocity is so insignificant that it shouldn't be taken into account when designing. However, there may be other geological processes, significantly disturbing the stability of slopes connected with cracks.

  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. New Urban Vertical Axis Wind Turbine Design

    Directory of Open Access Journals (Sweden)

    Alexandru-Mihai CISMILIANU

    2015-12-01

    Full Text Available This paper develops a different approach for enhancing the performance of Vertical Axis Wind Turbines for the use in the urban or rural environment and remote isolated residential areas. Recently the vertical axis wind turbines (VAWT have become more attractive due to the major advantages of this type of turbines in comparison to the horizontal axis wind turbines. We aim to enhance the overall performance of the VAWT by adding a second set of blades (3 x 2=6 blades following the rules of biplane airplanes. The model has been made to operate at a maximum power in the range of the TSR between 2 to 2.5. The performances of the VAWT were investigated numerically and experimentally and justify the new proposed design.

  8. Response of polymer composites to high and low velocity impact

    Science.gov (United States)

    Hsieh, C. Y.; Mount, A.; Jang, B. Z.; Zee, R. H.

    1990-01-01

    The present investigation of fiber-reinforced polymer matrix composites' impact characteristics employed a drop tower for the low-velocity impact case and a novel, projectile instantaneous velocity-measuring sensor for high-velocity impact. Attention was given to the energy loss of projectiles in composites reinforced with polyethylene, kevlar, and graphite. Two distinct energy-loss mechanisms are noted, the first of which is due to the actual fracture process while the other is due to the generation of friction heat. The drop-tower impact-test results furnish the strain-rate dependence of the energy loss.

  9. Optimal Design of Magnetohydrodynamic Mixed Convection Flow in a Vertical Channel with Slip Boundary Conditions and Thermal Radiation Effects by Using an Entropy Generation Minimization Method

    Directory of Open Access Journals (Sweden)

    Mohamad Yaghoub Abdollahzadeh Jamalabadi

    2015-02-01

    Full Text Available Investigation of the effect of thermal radiation on a fully developed magnetohydrodynamic (MHD convective flow of a Newtonian, incompressible and electrically conducting fluid in a vertical microchannel bounded by two infinite vertical parallel plates with constant temperature walls through a lateral magnetic field of uniform strength is presented. The Rosseland model for the conduction radiation heat transfer in an absorbing medium and two plates with slip-flow and no-slip conditions are assumed. In addition, the induced magnetic field is neglected due to the assumption of a small magnetic Reynolds number. The non-dimensional governing equations are solved numerically using Runge–Kutta–Fehlberg method with a shooting technique. The channel is optimized based on the Second Law of Thermodynamics by changing various parameters such as the thermal radiation parameter, the temperature parameter, Hartmann number, Grashof to Reynolds ratio, velocity slip length, and temperature jump.

  10. Training methods to improve vertical jump performance.

    Science.gov (United States)

    Perez-Gomez, J; Calbet, J A L

    2013-08-01

    This study aims to review the main methods used to improve vertical jump performance (VJP). Although many training routines have been proposed, these can be grouped into four main categories: plyometric training (PT), weight training (WT), whole body vibration training (VT) and electromyostimulation training (ET). PT enhances muscular force, the rate of force development (RFD), muscular power, muscle contraction velocity, cross-sectional area (CSA), muscle stiffness allowing greater storage and release of elastic energy. WT improve muscular force, velocity, power output, and RFD during jumping on a force plate, muscle hypertrophy and neural adaptations. One of the most effective methods to improve VJP is the combination of PT with WT, which takes advantage of the enhancement of maximal dynamic force through WT and the positive effects of PT on speed and force of muscle contraction through its specific effect on type II fibers. Some authors have found an increase in VJP with the use of VT while other did not see such an effect. However, it remains unknown by which mechanisms VT could enhance VJP. ET has been shown to elicit muscle hypertrophy. The VJP may be improved when ET is applied concomitantly with PT or practice of sports. In summary, scientific evidence suggests that the best way to improve VJP is through the combination of PT with WT. Further research is needed to establish if better results are possible by more complex strategies.

  11. High velocity impact experiment (HVIE)

    Energy Technology Data Exchange (ETDEWEB)

    Toor, A.; Donich, T.; Carter, P.

    1998-02-01

    The HVIE space project was conceived as a way to measure the absolute EOS for approximately 10 materials at pressures up to {approximately}30 Mb with order-of-magnitude higher accuracy than obtainable in any comparable experiment conducted on earth. The experiment configuration is such that each of the 10 materials interacts with all of the others thereby producing one-hundred independent, simultaneous EOS experiments The materials will be selected to provide critical information to weapons designers, National Ignition Facility target designers and planetary and geophysical scientists. In addition, HVIE will provide important scientific information to other communities, including the Ballistic Missile Defense Organization and the lethality and vulnerability community. The basic HVIE concept is to place two probes in counter rotating, highly elliptical orbits and collide them at high velocity (20 km/s) at 100 km altitude above the earth. The low altitude of the experiment will provide quick debris strip-out of orbit due to atmospheric drag. The preliminary conceptual evaluation of the HVIE has found no show stoppers. The design has been very easy to keep within the lift capabilities of commonly available rides to low earth orbit including the space shuttle. The cost of approximately 69 million dollars for 100 EOS experiment that will yield the much needed high accuracy, absolute measurement data is a bargain!

  12. Top or Bottom-Heavy? Observational Constraints on the Vertical Structure of the Eastern Pacific ITCZ

    Science.gov (United States)

    Takahashi, K.; Huaman, L.

    2015-12-01

    The Intertropical Convergence Zone (ITCZ) is a key component of the eastern Pacific ocean-atmosphere system and its variability on seasonal to inter-annual and longer time scales. This feature is generally misrepresented in climate models, which show an excessively strong branch south of the equator. On the other hand, there is debate on what is the structure of the ITCZ in nature, particularly whether the latent heating and vertical velocity profiles are top or bottom-heavy. This knowledge is probably key to validate and improve the models. Most methods for estimating the vertical structure of the rate of latent heating
rely on profiles from field campaigns in other regions, combined with convective/stratiform fractions from the TRMM satellite.
In this study we use the precipitation profiles from the TRMM Precipitation Radar (PR), with approximations to the moisture conservation equation and the first law of thermodynamic, to directly estimate the vertical profiles of latent heating and vertical air velocity, respectively, in the ITCZ for the period 1998-2010. Due to limitations in the PR sensitivity and the inability to quantify solid precipitation, our results are restricted to the layer between the altitudes of 2 and 2.75 km. Nevertheless, we show that our results provide a strong constraint on the profiles and help determine which of the other estimates are more realistic. Our preliminary results for the northern hemisphere ITCZ in austral winter/spring are closer to the top-heavy estimations using TRMM-based algorithms (CSH, SLH and PRH) than to the bottom-heavy atmospheric reanalysis (ERA Interim and NCEP-NCAR), providing indirect evidence for a top-heavy profile. However, using the meridional wind measurements during the EPIC field campaign we find evidence that shallow ascent does exist below 2 km, consistent with the previously reported shallow meridional circulation but not as strong as the Reanalysis products indicate. Thus, our results support the

  13. 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.

  14. Sodium Velocity Maps on Mercury

    Science.gov (United States)

    Potter, A. E.; Killen, R. M.

    2011-01-01

    The objective of the current work was to measure two-dimensional maps of sodium velocities on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The velocity shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial velocity of the Earth. The difference between the observed and calculated velocity shift was taken to be the velocity vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of velocities across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward velocities over the surface of Mercury. The velocity map shows patches of higher velocity in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward velocity occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a velocity map that is similar.

  15. Kaleidoscopic motion and velocity illusions

    NARCIS (Netherlands)

    Helm, P.A. van der

    2007-01-01

    A novel class of vivid motion and velocity illusions for contrast-defined shapes is presented and discussed. The illusions concern a starlike wheel that, physically, rotates with constant velocity between stationary starlike inner and outer shapes but that, perceptually, shows pulsations, jolts

  16. 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.

  17. Study of nitrogen two-phase flow pressure drop in horizontal and vertical orientation

    Science.gov (United States)

    Koettig, T.; Kirsch, H.; Santandrea, D.; Bremer, J.

    2017-12-01

    The large-scale liquid argon Short Baseline Neutrino Far-detector located at Fermilab is designed to detect neutrinos allowing research in the field of neutrino oscillations. It will be filled with liquid argon and operate at almost ambient pressure. Consequently, its operation temperature is determined at about 87 K. The detector will be surrounded by a thermal shield, which is actively cooled with boiling nitrogen at a pressure of about 2.8 bar absolute, the respective saturation pressure of nitrogen. Due to strict temperature gradient constraints, it is important to study the two-phase flow pressure drop of nitrogen along the cooling circuit of the thermal shield in different orientations of the flow with respect to gravity. An experimental setup has been built in order to determine the two-phase flow pressure drop in nitrogen in horizontal, vertical upward and vertical downward direction. The measurements have been conducted under quasi-adiabatic conditions and at a saturation pressure of 2.8 bar absolute. The mass velocity has been varied in the range of 20 kg·m‑2·s‑1 to 70 kg·m‑2·s‑1 and the pressure drop data has been recorded scanning the two-phase region from vapor qualities close to zero up to 0.7. The experimental data will be compared with several established predictions of pressure drop e.g. Mueller-Steinhagen and Heck by using the void fraction correlation of Rouhani.

  18. Augmentation of heat transfer in a bubble agitated vertical rectangular channel

    Science.gov (United States)

    Mitra, Asish; Dutta, Tapas Kumar; Ghosh, Dibyendu Narayan

    2012-04-01

    This paper presents the results of an experimental study of convective heat transfer between three parallel vertical plates symmetrically spaced with and without bubble agitation to ascertain the degree of augmentation of the heat transfer coefficients due to agitation. The centre plate was electrically heated, while the other side plates were water-cooled forming two successive parallel vertical rectangular channels of dimensions 20 cm × 3.5 cm × 35 cm (length W, gap L, height H) each. At the bottom of the hot and cold plates air spargers were fitted. Water/ethylene glycol (100%) was used to fill the channels. The superficial gas velocity ranged from 0.0016 to 0.01 m/s. Top, bottom and sides of the channels were open to the water/ethylene glycol in the chamber which is the novel aspect of this study. Experimental data have been correlated as under: Natural convective heat transfer: Nu = 0.60 Gr 0.29, r = 0.96, σ = 0.186, 1.17 E6 < Gr < 1.48 E7; Bubble agitated heat transfer: St = 0.11( ReFrPr 2)-0.23, r = 0.82, σ = 0.002, 1.20 E-2 < ( ReFrPr 2) < 1.36 E2.

  19. Investigation of the effect of inflow turbulence on vertical axis wind turbine wakes

    Science.gov (United States)

    Chatelain, P.; Duponcheel, M.; Zeoli, S.; Buffin, S.; Caprace, D.-G.; Winckelmans, G.; Bricteux, L.

    2017-05-01

    The aerodynamics of Vertical Axis Wind Turbines (VAWTs) is inherently unsteady, which leads to vorticity shedding mechanisms due to both the lift distribution along the blade and its time evolution. In this paper, we perform large-scale, fine-resolution Large Eddy Simulations of the flow past Vertical Axis Wind Turbines by means of a state-of-the-art Vortex Particle-Mesh (VPM) method combined with immersed lifting lines. Inflow turbulence with a prescribed turbulence intensity (TI) is injected at the inlet of the simulation either from a precomputed synthetic turbulence field obtained using the Mann algorithm [1] or generated on the-fly using time-correlated synthetic velocity planes. The wake of a standard, medium-solidity, H-shaped machine is simulated for several TI levels. The complex wake development is captured in details and over long distances: from the blades to the near wake coherent vortices, then through the transitional ones to the fully developed turbulent far wake. Mean flow and turbulence statistics are computed over more than 10 diameters downstream of the machine. The sensitivity of the wake topology and decay to the TI and to the operating conditions is then assessed.

  20. The significance of vertical moisture diffusion on drifting snow sublimation near snow surface

    Science.gov (United States)

    Huang, Ning; Shi, Guanglei

    2017-12-01

    Sublimation of blowing snow is an important parameter not only for the study of polar ice sheets and glaciers, but also for maintaining the ecology of arid and semi-arid lands. However, sublimation of near-surface blowing snow has often been ignored in previous studies. To study sublimation of near-surface blowing snow, we established a sublimation of blowing snow model containing both a vertical moisture diffusion equation and a heat balance equation. The results showed that although sublimation of near-surface blowing snow was strongly reduced by a negative feedback effect, due to vertical moisture diffusion, the relative humidity near the surface does not reach 100 %. Therefore, the sublimation of near-surface blowing snow does not stop. In addition, the sublimation rate near the surface is 3-4 orders of magnitude higher than that at 10 m above the surface and the mass of snow sublimation near the surface accounts for more than half of the total snow sublimation when the friction wind velocity is less than about 0.55 m s-1. Therefore, the sublimation of near-surface blowing snow should not be neglected.

  1. Trade Liberalisation and Vertical Integration

    DEFF Research Database (Denmark)

    Bache, Peter Arendorf; Laugesen, Anders Rosenstand

    producers face decisions on exporting, vertical integration of intermediate-input production, and whether the intermediate-input production should be offshored to a low-wage country. We find that the fractions of final-good producers that pursue either vertical integration, offshoring, or exporting are all......We build a three-country model of international trade in final goods and intermediate inputs and study the relation between four different types of trade liberalisation and vertical integration. Firms are heterogeneous with respect to both productivity and factor (headquarter) intensity. Final-good...... increasing when intermediate-input trade or final-goods trade is liberalised. Finally, we provide guidance for testing the open-economy property rights theory of the firm using firm-level data and surprisingly show that the relationship between factor (headquarter) intensity and the likelihood of vertical...

  2. Horizontal and Vertical Line Designs.

    Science.gov (United States)

    Johns, Pat

    2003-01-01

    Presents an art lesson in which students learn about the artist Piet Mondrian and create their own abstract artworks. Focuses on geometric shapes using horizontal and vertical lines. Includes background information about the artist. (CMK)

  3. Vertical axis wind turbine airfoil

    Science.gov (United States)

    Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

    2012-12-18

    A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

  4. Electromagnetic field generated by a finite fault due to electrokinetic effect

    Science.gov (United States)

    Hu, Hengshan; Gao, Yongxin

    2011-08-01

    This work investigates surface electromagnetic wavefields generated by a finite fault due to electrokinetic effect with Pride's theory as the governing equations. A finite fault is discretized into a series of small subfaults, each of which is taken as a point source with different initiation time. The wavefields generated by the whole fault are then synthesized by stacking those generated by all the subfaults. Numerical simulations of a vertical strike-slip fault with a constant rupturing velocity are then conducted on the basis of the derived formalism. Simulation results show that the rupturing fault generates observable permanent ground motions and electromagnetic field disturbances. Two types of electric field characters are observed in simulations: the coseismic oscillatory variation and the postseismic decaying variation. When the fault rupturing stops and the seismic waves pass far away, the magnetic field vanishes while the electric field remains, decaying slowly and lasting for hundreds of seconds. Adjacent to the free surface the vertical electric field is about 100 times larger than the horizontal one. When the receiving depth increases, the amplitudes of the horizontal electric fields in both the oscillatory and decaying components increase while those of the vertical electric fields decrease. It is also shown that there is no horizontal electric field remnant right at the free surface after the seismic perturbations decay away. The near-fault electric fields simulated in this paper hold similar features to some field observations in literature.

  5. Effects of Foam Rolling on Vertical Jump Performance

    Directory of Open Access Journals (Sweden)

    Andrew Jones

    2015-07-01

    Full Text Available Background: Foam rolling is a popular activity utilized by strength and conditioning coaches as it is believed to increase muscle length and break up fibrous adhesions located in connective tissue. However, there is little research investigating the effects of foam rolling on athletic performance. Objective: The purpose of this study was to investigate the effects of lower body foam rolling on vertical jump performance. Methods: Twenty males (age 24.05 ± 2.02 years; height 177.43 ± 6.31 cm; mass 81.41 ± 8.76 kg volunteered to participate. Subjects completed three days of testing, separated by at least twenty-four hours. Day one consisted of baseline vertical jumps on a force plate, followed by familiarization with foam rolling and control protocols. Subjects returned on days two and three and performed 30-second bouts of lower body foam rolling or mimicked foam rolling movements on a skateboard followed by vertical jumps on a force plate. The highest jump from each day was used for statistical analyses. Results: Repeated measures ANOVAs revealed no significant differences in Jump height, impulse, relative ground reaction force, or take-off velocity between conditions. Conclusion: 30-second bouts of lower body foam rolling do not improve vertical jump performance. Keywords: Dynamic Warm-Up, Foam Rolling, Vertical Jump

  6. Vertical slice modelling of nonlinear Eady waves using a compatible finite element method

    Science.gov (United States)

    Yamazaki, Hiroe; Shipton, Jemma; Cullen, Michael J. P.; Mitchell, Lawrence; Cotter, Colin J.

    2017-08-01

    A vertical slice model is developed for the Euler-Boussinesq equations with a constant temperature gradient in the direction normal to the slice (the Eady-Boussinesq model). The model is a solution of the full three-dimensional equations with no variation normal to the slice, which is an idealised problem used to study the formation and subsequent evolution of weather fronts. A compatible finite element method is used to discretise the governing equations. To extend the Charney-Phillips grid staggering in the compatible finite element framework, we use the same node locations for buoyancy as the vertical part of velocity and apply a transport scheme for a partially continuous finite element space. For the time discretisation, we solve the semi-implicit equations together with an explicit strong-stability-preserving Runge-Kutta scheme to all of the advection terms. The model reproduces several quasi-periodic lifecycles of fronts despite the presence of strong discontinuities. An asymptotic limit analysis based on the semi-geostrophic theory shows that the model solutions are converging to a solution in cross-front geostrophic balance. The results are consistent with the previous results using finite difference methods, indicating that the compatible finite element method is performing as well as finite difference methods for this test problem. We observe dissipation of kinetic energy of the cross-front velocity in the model due to the lack of resolution at the fronts, even though the energy loss is not likely to account for the large gap on the strength of the fronts between the model result and the semi-geostrophic limit solution.

  7. 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.

  8. Backward integration, forward integration, and vertical foreclosure

    OpenAIRE

    Spiegel, Yossi

    2013-01-01

    I show that partial vertical integration may either alleviates or exacerbate the concern for vertical foreclosure relative to full vertical integration and I examine its implications for consumer welfare.

  9. Soil-Pile Interaction in the Pile Vertical Vibration Based on Fictitious Soil-Pile Model

    OpenAIRE

    Deng, Guodong; Zhang, Jiasheng; Wu, Wenbing; Shi, Xiong; Meng, Fei

    2014-01-01

    By introducing the fictitious soil-pile model, the soil-pile interaction in the pile vertical vibration is investigated. Firstly, assuming the surrounding soil of pile to be viscoelastic material and considering its vertical wave effect, the governing equations of soil-pile system subjected to arbitrary harmonic dynamic force are founded based on the Euler-Bernoulli rod theory. Secondly, the analytical solution of velocity response in frequency domain and its corresponding semianalytical solu...

  10. Explosive movement in the older men: analysis and comparative study of vertical jump.

    Science.gov (United States)

    Argaud, Sébastien; Pairot de Fontenay, Benoit; Blache, Yoann; Monteil, Karine

    2017-10-01

    Loss of power has been demonstrated to have severe functional consequences to perform physical daily living tasks in old age. This study aimed to assess how moment and velocity were affected for each joint of the lower limbs during squat jumping for older men in comparison with young adults. Twenty-one healthy older men (74.5 ± 4.6 years) and 22 young men (21.8 ± 2.8 years) performed maximal squat jumps. Inverse dynamics procedure was used to compute the net joint power, moment and velocity produced at the hip, knee and ankle joints. Vertical jump height of the elderly was 64 % lower than the young adults. The maximal power of the body mass center (P maxbmc ) was 57 % lower in the older population. For the instant at P maxbmc , the vertical ground reaction force and the vertical velocity of the body mass center were 26 % and 35 % less in the older adults than in the young adults, respectively (p vertical ground reaction force; p vertical jump. This smaller power resulted from both a lower moment and angular velocity produced at each joint.

  11. A Newly Reanalyzed Dataset of GPS-determined Antarctic Vertical Rates

    Science.gov (United States)

    Thomas, I.; King, M.; Clarke, P. J.; Penna, N. T.; Lavallee, D. A.; Whitehouse, P.

    2010-12-01

    Accurate and precise measurements of vertical crustal motion offer useful constraints on glacial isostatic adjustment (GIA) models. Here we present a newly reprocessed data set of GPS-determined vertical rates for Antarctica. We give details of the global reanalysis of 15-years of GPS data, the overarching aim of which is to achieve homogeneous station coordinate time series, and hence surface velocities, for GPS receivers that are in regions of GIA interest in Antarctica. The means by which the reference frame is realized is crucial to obtaining accurate rates. Considerable effort has been spent on achieving a good global distribution of GPS stations, using data from IGS and other permanently recording stations, as well as a number of episodic campaigns in Antarctica. Additionally, we have focused on minimizing the inevitable imbalance in the number of sites in the northern and southern hemispheres. We align our daily non-fiducial solutions to ITRF2005, i.e. a CM frame. We present the results of investigations into the reference frame realization, and also consider a GPS-derived realization of the frame, and its effect on the vertical velocities. Vertical velocities are obtained for approximately 40 Antarctic locations. We compare our GPS derived Antarctic vertical rates with those predicted by the Ivins and James and ICE-5G models, after converting to a CE frame. We also compare to previously published GPS rates. Our GPS velocities are being used to help tune, and bound errors of, a new GIA model also presented in this session.

  12. Vertically Polarized Omnidirectional Printed Slot Loop Antenna

    DEFF Research Database (Denmark)

    Kammersgaard, Nikolaj Peter Iversen; Kvist, Søren H.; Thaysen, Jesper

    2015-01-01

    A novel vertically polarized omnidirectional printed slot loop antenna has been designed, simulated, fabricated and measured. The slot loop works as a magnetic loop. The loop is loaded with inductors to insure uniform and in-phase fields in the slot in order to obtain an omnidirectional radiation...... pattern. The antenna is designed for the 2.45 GHz Industrial, Scientific and Medical band. Applications of the antenna are many. One is for on-body applications since it is ideal for launching a creeping waves due to the polarization....

  13. Vertical CNT-Si photodiode array.

    Science.gov (United States)

    Ahnood, Arman; Zhou, Hang; Dai, Qing; Vygranenko, Yuri; Suzuki, Yuji; Esmaeili-Rad, Mr; Amaratunga, Gehan; Nathan, Arokia

    2013-09-11

    A photodiode consisting of nanopillars of thin-film silicon p-i-n on an array of vertically aligned carbon nanotubes (CNTs) with a noncontinuous cathode electrode is demonstrated. The structure exploits the intrinsic enhancement of the CNTs' electric field, which leads to reduction in the photodiode's operating voltage and response time and enhancement of optical coupling due to better light trapping, as compared with the conventional planar photodiode. These improvements translate to higher resolution and higher frame rate flat-panel imaging systems for a broad range of applications, including computed tomography and particle detection.

  14. Kinematics and dynamics of a solitary wave interacting with varying bathymetry and/or a vertical wall

    Science.gov (United States)

    Papoutsellis, Christos; Athanassoulis, Gerassimos; Charalampopoulos, Alexis-Tzianni

    2017-04-01

    In this work, we investigate the transformations that solitary surface waves undergo during their interaction with uneven seabed and/or fully reflective vertical boundaries. This is accomplished by performing simulations using a non-local Hamiltonian formulation, taking into account full nonlinearity and dispersion, in the presence of variable seabed [1]. This formulation is based on an exact coupled-mode representation of the velocity potential, leading to efficient and accurate computations of the Dirichlet to Neumann operator, required in Zakharov/Craig-Sulem formulation [2], [3]. In addition, it allows for the efficient computation of wave kinematics (velocity, acceleration) and the pressure field, in the time-dependent fluid domain, up to its physical boundaries. Such computations are performed for the case of high-amplitude solitary waves interacting with varying bathymetry and/or a vertical wall, shedding light to their kinematics and dynamics. More specifically, we first consider two benchmark cases, namely the transformation of solitary waves over a plane beach [4], and the reflection of solitary waves on a vertical wall [5]. As a further step, results on the scattering/reflection of a solitary wave due to an undulating seabed, and on the disintegration of a solitary wave travelling form shallow to deep water are also presented. References:[1] G.A. Athanassoulis. & Ch.E. Papoutsellis, in Volume 7: Ocean Engineering, ASME, OMAE2015-41452, p. V007T06A029 (2015)[2] W. Craig, C. Sulem, J. Comp. Phys. 108, 73-83 (1993) [3] V. Zakharov, J. Appl. Mech. Tech. Phys 9, 86-94 (1968)[4] S. Grilli, R. Subramanya, T. Svendsen. & J. Veeramony, J. Waterway, Port, Coastal, Ocean Eng. 120(6), 609-628. (1994)[5] Y.Y. Chen, C. Kharif , J.H. Yang, H.C. Hsu, J. Touboul & J. Chambarel, Eur. J. Mech B-Fluid 49, 20-28 (2015)

  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. Method of design for vertical oil shale retorting vessels and retorting therewith

    Science.gov (United States)

    Reeves, Adam A.

    1978-01-03

    A method of designing the gas flow parameters of a vertical shaft oil shale retorting vessel involves determining the proportion of gas introduced in the bottom of the vessel and into intermediate levels in the vessel to provide for lateral distribution of gas across the vessel cross section, providing mixing with the uprising gas, and determining the limiting velocity of the gas through each nozzle. The total quantity of gas necessary for oil shale treatment in the vessel may be determined and the proportion to be injected into each level is then determined based on the velocity relation of the orifice velocity and its feeder manifold gas velocity. A limitation is placed on the velocity of gas issuing from an orifice by the nature of the solid being treated, usually physical tests of gas velocity impinging the solid.

  17. Inertial Effects on the Vertical Transport of Suspended Particles in a Turbulent Boundary Layer

    Science.gov (United States)

    Richter, David; Chamecki, Marcelo

    2017-11-01

    In many atmospheric flows, a dispersed phase is actively suspended by turbulence, whose competition with gravitational settling ultimately dictates its vertical distribution. Examples of dispersed phases include snow, sea-spray droplets, dust, or sand, where individual elements of much larger density than the surrounding air are carried by turbulent motions after emission from the surface. In cases where the particle is assumed to deviate from local fluid motions only by its gravitational settling (i.e., they are inertialess), traditional flux balances predict a power-law dependence of particle concentration with height. It is unclear, however, how particle inertia influences this relationship, and this question is the focus of this work. Direct numerical simulations are conducted of turbulent open-channel flow, laden with Lagrangian particles of specified inertia; in this way the study focuses on the turbulent transport which occurs in the lowest few meters of the planetary boundary layer, in regions critical for connecting emission fluxes to the fluxes felt by the full-scale boundary layer. Simulations over a wide range of particle Stokes number, while holding the dimensionless settling velocity constant, are performed to understand the role of particle inertia on vertical dispersion. It is found that particles deviate from their inertialess behaviour in ways that are not easily captured by traditional theory; concentrations are reduced with increasing Stokes number. Furthermore, a similarity-based eddy diffusivity for particle concentration fails as particles experience inertial acceleration, precluding a closed-form solution for particle concentration as in the case of inertialess particles. The primary consequence of this result is that typical flux parametrizations connecting surface emission models (e.g., saltation models or sea-spray generation functions) to elevated boundary conditions may overestimate particle concentrations due to the reduced vertical

  18. Variation of Crustal Shear Velocity Structure Along the Eastern Lau Back-Arc Spreading Center Constrained By Seafloor Compliance

    Science.gov (United States)

    Zha, Y.; Webb, S. C.; Dunn, R. A.

    2014-12-01

    Measurements of seafloor compliance, the deformation under long period (typically 30-300 s) ocean wave forcing, are primarily sensitive to crustal shear velocity structure. We analyze seafloor compliance from data collected from a subset of 50 broadband Ocean Bottom Seismographs (OBS) deployed at the Eastern Lau spreading center (ELSC) from 2009 to 2010. The ELSC is a 400-km-long back-arc spreading center lying closely to the Tonga subduction trench in the southwestern Pacific. Seafloor morphology, crustal seismic structure and lava composition data show rapid variations along the ridge as the ridge migrates away from the volcanic arc front to the north, indicating a decreasing influence of the subducting slab. We calculate seafloor compliance functions by taking the spectral transfer function between the vertical displacement and pressure signal recorded by the 4-component OBSs, which are equipped with differential pressure gauges (DPGs). In the ridge perpendicular direction, compliance amplitude vary by more than an order of magnitude from the ridge crest to older seafloor covered by sediment. Along the spreading ridge, compliance measured from on-axis sites increases southwards, indicative of a decrease in the upper crustal shear velocity possibly due to increasing porosity and a thickening extrusive layer [Jacobs et al., 2007; Dunn et al., 2013]. We apply a Markov Chain Monte Carlo method to invert the compliance functions for crustal shear velocities at various locations along the ELSC.

  19. Lapse-time-dependent coda-wave depth sensitivity to local velocity perturbations in 3-D heterogeneous elastic media

    Science.gov (United States)

    Obermann, Anne; Planès, Thomas; Hadziioannou, Céline; Campillo, Michel

    2016-10-01

    In the context of seismic monitoring, recent studies made successful use of seismic coda waves to locate medium changes on the horizontal plane. Locating the depth of the changes, however, remains a challenge. In this paper, we use 3-D wavefield simulations to address two problems: first, we evaluate the contribution of surface- and body-wave sensitivity to a change at depth. We introduce a thin layer with a perturbed velocity at different depths and measure the apparent relative velocity changes due to this layer at different times in the coda and for different degrees of heterogeneity of the model. We show that the depth sensitivity can be modelled as a linear combination of body- and surface-wave sensitivity. The lapse-time-dependent sensitivity ratio of body waves and surface waves can be used to build 3-D sensitivity kernels for imaging purposes. Second, we compare the lapse-time behaviour in the presence of a perturbation in horizontal and vertical slabs to address, for instance, the origin of the velocity changes detected after large earthquakes.

  20. The vertical structure of the boundary layer around compact objects

    Science.gov (United States)

    Hertfelder, Marius; Kley, Wilhelm

    2017-09-01

    Context. Mass transfer due to Roche lobe overflow leads to the formation of an accretion disk around a weakly magnetized white dwarf (WD) in cataclysmic variables. At the inner edge of the disk, the gas comes upon the surface of the WD and has to get rid of its excess kinetic energy in order to settle down on the more slowly rotating outer stellar layers. This region is known as the boundary layer (BL). Aims: In this work we investigate the vertical structure of the BL, which is still poorly understood. We shall provide details of the basic structure of the two-dimensional (2D) BL and how it depends on parameters such as stellar mass and rotation rate, as well as the mass-accretion rate. We further investigate the destination of the disk material and compare our results with previous one-dimensional (1D) simulations. Methods: We solve the 2D equations of radiation hydrodynamics in a spherical (r-ϑ) geometry using a parallel grid-based code that employs a Riemann solver. The radiation energy is considered in the two-temperature approach with a radiative flux given by the flux-limited diffusion approximation. Results: The BL around a non-rotating WD is characterized by a steep drop in angular velocity over a width of only 1% of the stellar radius, a heavy depletion of mass, and a high temperature ( 500 000 K) as a consequence of the strong shear. Variations in Ω∗,M∗, and Ṁ influence the extent of the changes of the variables in the BL but not the general structure. Depending on Ω∗, the disk material travels up to the poles or is halted at a certain latitude. The extent of mixing with the stellar material also depends on Ω∗. We find that the 1D approximation matches the 2D data well, apart from an underestimated temperature.

  1. A Controlled Laboratory Environment to Study EO Signal Degradation Due to Underwater Turbulence

    Science.gov (United States)

    2015-05-11

    Executive Services and Communications Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person...concerns which have been communicated ) been incorporated in an official NRL Silvia Matt, 7333 Auther) erne of Record Signature Name and Code...along -tank velocity 0.02 20 40 60 80 lime (s) across -tank velocity 100 120 -0 02 0.02 t. IJ WLi 1. 20 40 60 80 100 120 time (s) vertical velocity 20 40

  2. 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.

  3. Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. II Spatiotemporal properties of the adapted slow-phase eye velocity

    Science.gov (United States)

    Angelaki, D. E.; Hess, B. J.

    1996-01-01

    position in these planes and response phase varied significantly as a function of head orientation. 2) The peak horizontal response amplitude shifted spatially over time, such that 5-10 mo after plugging it was maximal during rotations at head positions close to upright. 4. In parallel to these unique spatiotemporal response properties characterizing the adapted horizontal VOR, torsional slow-phase velocity also exhibited small spatiotemporal changes after lateral canal inactivation that tended to precede in time the changes associated with the horizontal response components. In contrast, vertical slow-phase velocity in the plugged animals was unaltered and continued to be characterized by cosine-tuned spatial properties in three dimensions. 5. Recovery of the horizontal response gain during yaw oscillations in upright position, as well as the unique, noncosine spatiotemporal characteristics of the adapted horizontal VOR, were also observed in an animal with all but one vertical semicircular canals inactivated. There was, however, no sign of VOR gain recovery up to 2 mo after all semicircular canals were inactivated. These results suggest that the observed recovery of horizontal VOR is at least partly due to signals originating from the remaining intact vertical canal(s). Even in the presence of a single intact vertical canal, the improvement in horizontal gaze stability is at least partly restored through spatiotemporal changes in the processing of vestibuloocular signals that improve the gain and spatial tuning of horizontal VOR at the expense of temporal response properties.

  4. A Method for Modeling of Floating Vertical Axis Wind Turbine

    DEFF Research Database (Denmark)

    Wang, Kai; Hansen, Martin Otto Laver; Moan, Torgeir

    2013-01-01

    It is of interest to investigate the potential advantages of floating vertical axis wind turbine (FVAWT) due to its economical installation and maintenance. A novel 5MW vertical axis wind turbine concept with a Darrieus rotor mounted on a semi-submersible support structure is proposed in this paper....... In order to assess the technical and economic feasibility of this novel concept, a comprehensive simulation tool for modeling of the floating vertical axis wind turbine is needed. This work presents the development of a coupled method for modeling of the dynamics of a floating vertical axis wind turbine....... This integrated dynamic model takes into account the wind inflow, aerodynamics, hydrodynamics, structural dynamics (wind turbine, floating platform and the mooring lines) and a generator control. This approach calculates dynamic equilibrium at each time step and takes account of the interaction between the rotor...

  5. Introduction to vector velocity imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Udesen, Jesper; Hansen, Kristoffer Lindskov

    over the full region of interest and a real time image at a frame rate of 20 Hz can be displayed. Real time videos have been obtained from both our research systems and from commercial BK Medical scanners. The vector velocity images reveal the full complexity of the human blood flow. It is easy to see...... direction and the correct velocity magnitude for any orientation of the vessels. At complex geometries like bifurcations, branching and for valves the approach reveals how the velocity changes magnitude and direction over the cardiac cycle. Vector velocity reveals a wealth of new information that now...... is accessible to the ultrasound community. The displaying and studying of this information is challenging as complex flow changes rapidly over the cardiac cycle....

  6. 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.

  7. Contribución segmentaria de los saltos con contramovimiento en vertical y en horizontal. [Segmental contribution on countermovement vertical and horizontal jumps].

    Directory of Open Access Journals (Sweden)

    Marcos Gutiérrez-Dávila

    2014-10-01

    , time-synchronized to a video camera that recorded at 210 Hz the sagital plane of the jumps performed on the platform. The jumps have been considered as a symmetrical movement taking place in a plane, with a mechanical coordinated model of eight segments. In the SV condition, participants had to perform a maximum vertical jump, starting from a standing position on the force platform. In the SH condition, participants had to perform a maximal horizontal jump starting from the same position. The results show a greater time for the jump in SH, (0.898 vs 1.056 s using a strategy extension-rotation in the horizontal jumps. The net force exerted during the braking impulse is higher for SV due to the greater velocity at the beginning of this phase (-1.166 vs -0.992 m/s. There was a greater involvement of the ankle and hip in SH, with a higher contribution of the trunk during the jump, also there was a greater contribution of the arms to the vertical displacement of the CM in SV.

  8. Online Wavelet Complementary velocity Estimator.

    Science.gov (United States)

    Righettini, Paolo; Strada, Roberto; KhademOlama, Ehsan; Valilou, Shirin

    2018-01-02

    In this paper, we have proposed a new online Wavelet Complementary velocity Estimator (WCE) over position and acceleration data gathered from an electro hydraulic servo shaking table. This is a batch estimator type that is based on the wavelet filter banks which extract the high and low resolution of data. The proposed complementary estimator combines these two resolutions of velocities which acquired from numerical differentiation and integration of the position and acceleration sensors by considering a fixed moving horizon window as input to wavelet filter. Because of using wavelet filters, it can be implemented in a parallel procedure. By this method the numerical velocity is estimated without having high noise of differentiators, integration drifting bias and with less delay which is suitable for active vibration control in high precision Mechatronics systems by Direct Velocity Feedback (DVF) methods. This method allows us to make velocity sensors with less mechanically moving parts which makes it suitable for fast miniature structures. We have compared this method with Kalman and Butterworth filters over stability, delay and benchmarked them by their long time velocity integration for getting back the initial position data. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  9. Effect of flow distributors on uniformity of velocity profile in a baghouse

    Energy Technology Data Exchange (ETDEWEB)

    Chi-Jen Chen; Man-Ting Cheng [Tajen Institute of Technology, Ping-Tung Hsien (Taiwan). Department of Environmental Engineering and Science

    2005-07-01

    In recent years, baghouses have been used as an alternative technology for particulate emission control from pulverized-coal-fired power plants. One of the more significant issues is to improve poor gas distribution that causes bag failures in baghouse operation. Bag failures during operation are almost impossible to prevent, but proper flow design can help in their prevention. This study investigated vertical velocity profiles below the bags in a baghouse (the hopper region) to determine whether flow could be improved with the installation of flow distributors in the hopper region. Three types of flow distributors were used to improve flow distribution and were compared with the original baghouse without flow distributors. Velocity profiles were measured by a hot-wire anemometer at an inlet velocity of 18 m/sec. Uniformity of flow distribution was calculated by the uniformity value U for the velocity profile of each flow distributor. Experimental results showed that the velocity profile of the empty configuration (without flow distributors) was poor because the uniformity value was 2.048. The uniformity values of type 1 (flow distributor with three vertical vanes), type 2 (flow distributor with one vertical and one inclined vane), and type 3 (flow distributor with two inclined vanes) configurations were reduced to 1.051, 0.617, and 0.526, respectively. These results indicate that the flow distributors designed in this study made significant improvements in the velocity profile of a baghouse, with the type 3 configuration having the best performance. 11 refs., 10 figs.

  10. Effect of flow distributors on uniformity of velocity profile in a baghouse.

    Science.gov (United States)

    Chen, Chi-Jen; Cheng, Man-Ting

    2005-07-01

    In recent years, the utility industry has turned to baghouses as an alternative technology for particulate emission control from pulverized-coal-fired power plants. One of the more significant issues is to improve poor gas distribution that causes bag failures in baghouse operation. Bag failures during operation are almost impossible to prevent, but proper flow design can help in their prevention. This study investigated vertical velocity profiles below the bags in a baghouse (the hopper region) to determine whether flow could be improved with the installation of flow distributors in the hopper region. Three types of flow distributors were used to improve flow distribution and were compared with the original baghouse without flow distributors. Velocity profiles were measured by a hot-wire anemometer at an inlet velocity of 18 m/sec. Uniformity of flow distribution was calculated by the uniformity value U for the velocity profile of each flow distributor. Experimental results showed that the velocity profile of the empty configuration (without flow distributors) was poor because the uniformity value was 2.048. The uniformity values of type 1 (flow distributor with three vertical vanes), type 2 (flow distributor with one vertical and one inclined vane), and type 3 (flow distributor with two inclined vanes) configurations were reduced to 1.051, 0.617, and 0.526, respectively. These results indicate that the flow distributors designed in this study made significant improvements in the velocity profile of a baghouse, with the type 3 configuration having the best performance.

  11. Vertical Motions of Oceanic Volcanoes

    Science.gov (United States)

    Clague, D. A.; Moore, J. G.

    2006-12-01

    lasting a few hundred thousand years as the island migrates over a broad flexural arch related to isostatic compensation of a nearby active volcano. The arch is located about 190±30 km away from the center of volcanic activity and is also related to the rejuvenated volcanic stage on the islands. Reefs on Oahu that are uplifted several tens of m above sea level are the primary evidence for uplift as the islands over-ride the flexural arch. At the other end of the movement spectrum, both in terms of magnitude and length of response, are the rapid uplift and subsidence that occurs as magma is accumulated within or erupted from active submarine volcanoes. These changes are measured in days to years and are of cm to m variation; they are measured using leveling surveys, tiltmeters, EDM and GPS above sea level and pressure gauges and tiltmeters below sea level. Other acoustic techniques to measure such vertical movement are under development. Elsewhere, evidence for subsidence of volcanoes is also widespread, ranging from shallow water carbonates on drowned Cretaceous guyots, to mapped shoreline features, to the presence of subaerially-erupted (degassed) lavas on now submerged volcanoes. Evidence for uplift is more limited, but includes makatea islands with uplifted coral reefs surrounding low volcanic islands. These are formed due to flexural uplift associated with isostatic loading of nearby islands or seamounts. In sum, oceanic volcanoes display a long history of subsidence, rapid at first and then slow, sometimes punctuated by brief periods of uplift due to lithospheric loading by subsequently formed nearby volcanoes.

  12. Seismic velocity, attenuation and rheology of the upper mantle

    Science.gov (United States)

    Anderson, D. L.; Minster, J. B.

    1980-01-01

    Seismic and rheological properties of the upper mantle in the vicinity of the low-velocity zone are expressed in terms of relaxation by dislocation glide. Dislocation bowing in the glide plane explains seismic velocities and attenuation. Climbing at higher stresses for longer periods of time give the observed viscosity, and explain the low velocity and high temperature attenuation found at seismic frequencies. Due to differing parameters, separate terms for thermal, seismic and rheological lithospheres are proposed. All three lithospheres, however, are related and are functions of temperature, and must be specified by parameters such as period, stress, and stress duration.

  13. Calibrating the Planck Cluster Mass Scale with Cluster Velocity Dispersions

    Science.gov (United States)

    Amodeo, Stefania; Mei, Simona; Stanford, Spencer A.; Bartlett, James G.; Melin, Jean-Baptiste; Lawrence, Charles R.; Chary, Ranga-Ram; Shim, Hyunjin; Marleau, Francine; Stern, Daniel

    2017-08-01

    We measure the Planck cluster mass bias using dynamical mass measurements based on velocity dispersions of a subsample of 17 Planck-detected clusters. The velocity dispersions were calculated using redshifts determined from spectra that were obtained at the Gemini observatory with the GMOS multi-object spectrograph. We correct our estimates for effects due to finite aperture, Eddington bias, and correlated scatter between velocity dispersion and the Planck mass proxy. The result for the mass bias parameter, (1-b), depends on the value of the galaxy velocity bias, {b}{{v}}, adopted from simulations: (1-b)=(0.51+/- 0.09){b}{{v}}3. Using a velocity bias of {b}{{v}}=1.08 from Munari et al., we obtain (1-b)=0.64+/- 0.11, i.e., an error of 17% on the mass bias measurement with 17 clusters. This mass bias value is consistent with most previous weak-lensing determinations. It lies within 1σ of the value that is needed to reconcile the Planck cluster counts with the Planck primary cosmic microwave background constraints. We emphasize that uncertainty in the velocity bias severely hampers the precision of the measurements of the mass bias using velocity dispersions. On the other hand, when we fix the Planck mass bias using the constraints from Penna-Lima et al., based on weak-lensing measurements, we obtain a positive velocity bias of {b}{{v}}≳ 0.9 at 3σ .

  14. Velocity Tomography Imaging Method with Variable Grid spacing/Interval

    OpenAIRE

    Guangnan, Huang; Yang, Liu; Tryggvason, Ari; Guangyi, Hu; Tingen, Fan; Jianhua, Dong

    2013-01-01

    In variable grid spacing tomography the underground velocity distribution is parameterized with model cells of different sizes. This method can simultaneously take into account the spatially varying resolution inherent in most datasets. E.g., due to experimental design or logistic constraints, the shallow and deep subsurface velocity distribution may be very differently determined by the available data. The variable grid spacing tomography and regular grid spacing tomography are similar in mo...

  15. 3-D crustal velocity structure of western Turkey: Constraints from full-waveform tomography

    Science.gov (United States)

    Çubuk-Sabuncu, Yeşim; Taymaz, Tuncay; Fichtner, Andreas

    2017-09-01

    The Sea of Marmara and western Turkey are characterized by intense seismicity and crustal deformation due to transition tectonics between the North Anatolian Fault Zone (NAFZ) and the extensional Aegean. Seismic imaging of the crust and uppermost mantle in W-NW Turkey is crucial to obtain a better understanding of its seismotectonics and geodynamics. So far, the Sea of Marmara and surroundings were considered in various active and passive seismic experiments providing significant information on crustal properties. Here, we further investigate the 3-D seismic velocity structure in this rapidly deforming region using non-linear full-waveform tomography based on the adjoint method. Our model is constrained by complete waveforms of 62 regional earthquakes (epicentral distance data uncertainties. Furthermore, quantitative resolution analyses yield 15 to 35 km horizontal resolution lengths in the shallow and deep crust beneath well-covered areas of W-NW Turkey. Our full-waveform tomography results indicate the presence of strong lateral and vertical velocity variations (2.55 ≤ VS ≤ 4.0 km/s) down to depths of ∼35 km. The seismic velocity distribution is characteristic of highly deformed and distributed crustal features along major fault zones (e.g. NAFZ and its branches), historic and recent regional volcanism (e.g. Kula volcanic province), and metamorphic core complex developments (e.g. Menderes and Kazdağ massifs). Radial anisotropy is very strong (around 20%) throughout the crust, further attesting to strong deformation and heterogeneity. Generally, our 3-D model is overall consistent with the active tectonics of western Turkey.

  16. Gait phase varies over velocities.

    Science.gov (United States)

    Liu, Yancheng; Lu, Kun; Yan, Songhua; Sun, Ming; Lester, D Kevin; Zhang, Kuan

    2014-02-01

    We sought to characterize the percent (PT) of the phases of a gait cycle (GC) as velocity changes to establish norms for pathological gait characteristics with higher resolution technology. Ninety five healthy subjects (49 males and 46 females with age 34.9 ± 11.8 yrs, body weight 64.0 ± 11.7 kg and BMI 23.5 ± 3.6) were enrolled and walked comfortably on a 10-m walkway at self-selected slower, normal, and faster velocities. Walking was recorded with a high speed camera (250 frames per second) and the eight phases of a GC were determined by examination of individual frames for each subject. The correlation coefficients between the mean PT of the phases of the three velocities gaits and PT defined by previous publications were all greater than 0.99. The correlation coefficient between velocity and PT of gait phases is -0.83 for loading response (LR), -0.75 for mid stance (MSt), and -0.84 for pre-swing (PSw). While the PT of the phases of three velocities from this study are highly correlated with PT described by Dr. Jacquenlin Perry decades ago, actual PT of each phase varied amongst these individuals with the largest coefficient variation of 24.31% for IC with slower velocity. From slower to faster walk, the mean PT of MSt diminished from 35.30% to 25.33%. High resolution recording revealed ambiguity of some gait phase definitions, and these data may benefit GC characterization of normal and pathological gait in clinical practice. The study results indicate that one should consider individual variations and walking velocity when evaluating gaits of subjects using standard gait phase classification. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Effects of Hall current, radiation and rotation on natural convection heat and mass transfer flow past a moving vertical plate

    Directory of Open Access Journals (Sweden)

    G.S. Seth

    2014-06-01

    Full Text Available An investigation of the effects of Hall current and rotation on unsteady hydromagnetic natural convection flow with heat and mass transfer of an electrically conducting, viscous, incompressible and optically thick radiating fluid past an impulsively moving vertical plate embedded in a fluid saturated porous medium, when temperature of the plate has a temporarily ramped profile, is carried out. Exact solution of the governing equations is obtained in closed form by Laplace transform technique. Exact solution is also obtained in case of unit Schmidt number. Expressions for skin friction due to primary and secondary flows and Nusselt number are derived for both ramped temperature and isothermal plates. Expression for Sherwood number is also derived. The numerical values of primary and secondary fluid velocities, fluid temperature and species concentration are displayed graphically whereas those of skin friction are presented in tabular form for various values of pertinent flow parameters.

  18. Vertical Motion Determined Using Satellite Altimetry and Tide Gauges

    Directory of Open Access Journals (Sweden)

    Chung-Yen Kuo

    2008-01-01

    Full Text Available A robust method to estimate vertical crustal motions by combining geocentric sea level measurements from decadal (1992 - 2003 TOPEX/POSEIDON satellite altimetry and long-term (> 40 years relative sea level records from tide gauges using a novel Gauss-Markov stochastic adjustment model is presented. These results represent an improvement over a prior study (Kuo et al. 2004 in Fennoscandia, where the observed vertical motions are primarily attributed to the incomplete Glacial Isostatic Adjustment (GIA in the region since the Last Glacial Maximum (LGM. The stochastic adjustment algorithm and results include a fully-populated a priori covariance matrix. The algorithm was extended to estimate vertical motion at tide gauge locations near open seas and around semi-enclosed seas and lakes. Estimation of nonlinear vertical motions, which could result from co- and postseismic deformations, has also been incorporated. The estimated uncertainties for the vertical motion solutions in coastal regions of the Baltic Sea and around the Great Lakes are in general < 0.5 mm yr-1, which is a significant improvement over existing studies. In the Baltic Sea, the comparisons of the vertical motion solution with 10 collocated GPS radial rates and with the BIFROST GIA model show differences of 0.2 ¡_ 0.9 and 1.6 ¡_ 1.8 mm yr-1, respectively. For the Great Lakes region, the comparisons with the ICE-3G model and with the relative vertical motion estimated using tide gauges only (Mainville and Craymer 2005 show differences of -0.2 ¡_ 0.6 and -0.1 ¡_ 0.5 mm yr-1, respectively. The Alaskan vertical motion solutions (linear and nonlinear models have an estimated uncertainty of ~1.2 - 1.6 mm yr-1, which agree qualitatively with GPS velocity and tide gauge-only solutions (Larsen et al. 2003. This innovative technique could potentially provide improved estimates of the vertical motion globally where long-term tide gauge records exist.

  19. Stabilization and Riesz basis property for an overhead crane model with feedback in velocity and rotating velocity

    Directory of Open Access Journals (Sweden)

    Toure K. Augustin

    2014-06-01

    Full Text Available This paper studies a variant of an overhead crane model's problem, with a control force in velocity and rotating velocity on the platform. We obtain under certain conditions the well-posedness and the strong stabilization of the closed-loop system. We then analyze the spectrum of the system. Using a method due to Shkalikov, we prove the existence of a sequence of generalized eigenvectors of the system, which forms a Riesz basis for the state energy Hilbert space.

  20. From Surface Flow Velocity Measurements to Discharge Assessment by the Entropy Theory

    Directory of Open Access Journals (Sweden)

    Tommaso Moramarco

    2017-02-01

    Full Text Available A new methodology for estimating the discharge starting from the monitoring of surface flow velocity, usurf, is proposed. The approach, based on the entropy theory, involves the actual location of maximum flow velocity, umax, which may occur below the water surface (dip phenomena, affecting the shape of velocity profile. The method identifies the two-dimensional velocity distribution in the cross-sectional flow area, just sampling usurf and applying an iterative procedure to estimate both the dip and umax. Five gage sites, for which a large velocity dataset is available, are used as a case study. Results show that the method is accurate in simulating the depth-averaged velocities along the verticals and the mean flow velocity with an error, on average, lower than 12% and 6%, respectively. The comparison with the velocity index method for the estimation of the mean flow velocity using the measured usurf, demonstrates that the method proposed here is more accurate mainly for rivers with a lower aspect ratio where secondary currents are expected. Moreover, the dip assessment is found more representative of the actual location of maximum flow velocity with respect to the one estimated by a different entropy approach. In terms of discharge, the errors do not exceed 3% for high floods, showing the good potentiality of the method to be used for the monitoring of these events.

  1. Transient natural convection in a vertical channel filled with nanofluids in the presence of thermal radiation

    Directory of Open Access Journals (Sweden)

    S. Das

    2016-03-01

    Full Text Available The transient natural convection in a vertical channel filled with nanofluids has been studied when thermal radiation is taken into consideration. The equations governing the flow are solved by employing the Laplace transform technique. Exact solutions for the velocity and temperature of nanofluid are obtained in cases of both prescribed surface temperature (PST and prescribed heat flux (PHF. The numerical results for the velocity and temperature of nanofluid are presented graphically for the pertinent parameters and discussed in detail. The fluid velocity is greater in the case of PST than that of PHF.

  2. Hybrid Vertical-Cavity Laser

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention provides a light source (2) for light circuits on a silicon platform (3). A vertical laser cavity is formed by a gain region (101) arranged between a top mirror (4) and a bottom grating-mirror (12) in a grating region (11) in a silicon layer (10) on a substrate. A waveguide...

  3. Physics and the Vertical Jump

    Science.gov (United States)

    Offenbacher, Elmer L.

    1970-01-01

    The physics of vertical jumping is described as an interesting illustration for motivating students in a general physics course to master the kinematics and dynamics of one dimensional motion. The author suggests that mastery of the physical principles of the jump may promote understanding of certain biological phenomena, aspects of physical…

  4. Multiservice Vertical Handoff Decision Algorithms

    Directory of Open Access Journals (Sweden)

    Zhu Fang

    2006-01-01

    Full Text Available Future wireless networks must be able to coordinate services within a diverse-network environment. One of the challenging problems for coordination is vertical handoff, which is the decision for a mobile node to handoff between different types of networks. While traditional handoff is based on received signal strength comparisons, vertical handoff must evaluate additional factors, such as monetary cost, offered services, network conditions, and user preferences. In this paper, several optimizations are proposed for the execution of vertical handoff decision algorithms, with the goal of maximizing the quality of service experienced by each user. First, the concept of policy-based handoffs is discussed. Then, a multiservice vertical handoff decision algorithm (MUSE-VDA and cost function are introduced to judge target networks based on a variety of user- and network-valued metrics. Finally, a performance analysis demonstrates that significant gains in the ability to satisfy user requests for multiple simultaneous services and a more efficient use of resources can be achieved from the MUSE-VDA optimizations.

  5. Advanced high performance vertical hybrid synthetic jet actuator

    Science.gov (United States)

    Xu, Tian-Bing (Inventor); Jiang, Xiaoning (Inventor); Su, Ji (Inventor)

    2011-01-01

    The present invention comprises a high performance, vertical, zero-net mass-flux, synthetic jet actuator for active control of viscous, separated flow on subsonic and supersonic vehicles. The present invention is a vertical piezoelectric hybrid zero-net mass-flux actuator, in which all the walls of the chamber are electrically controlled synergistically to reduce or enlarge the volume of the synthetic jet actuator chamber in three dimensions simultaneously and to reduce or enlarge the diameter of orifice of the synthetic jet actuator simultaneously with the reduction or enlargement of the volume of the chamber. The jet velocity and mass flow rate for the present invention will be several times higher than conventional piezoelectric synthetic jet actuators.

  6. ISAL experiment documentation of vertical tail and OMS pods

    Science.gov (United States)

    1983-01-01

    Investigation of Space Transportation System (STS) Atmospheric Luminosities (ISAL) experiment documentation includes vertical tail and orbital maneuvering system (OMS) pods with surface glow against the blackness of space. This glowing scene was provided by a long duration exposure with a 35mm camera aimed toward the tail of the Earth-orbiting Challenger, Orbiter Vehicle (OV) 099. OV-099 was maneuvered to a 120-nautical-mile altitude and flown with open payload bay (PLB) in the velocity vector for the conducting of a test titled, 'Evaluation of Oxygen Interaction with Materials (EOIM)'. Atomic oxygen within the low orbital environment is known to be extremely reactive when in contact with solid surfaces. In the darkened area between the camera and the glowing OMS pods and vertical stabilizer are two trays of test materials.

  7. Galactic Subsystems on the Basis of Cumulative Distribution of Space Velocities

    Directory of Open Access Journals (Sweden)

    Vidojević, S.

    2008-12-01

    Full Text Available A sample containing $4,614$ stars with available space velocities and high-quality kinematical data from the Arihip Catalogue is formed. For the purpose of distinguishing galactic subsystems the cumulative distribution of space velocities is studied. The fractions of the three subsystems are found to be: thin disc 92\\%, thick disc 6\\% and halo 2\\%. These results are verified by analysing the elements of velocity ellipsoids and the shape and size of the galactocentric orbits of the sample stars, i.e. the planar and vertical eccentricities of the orbits.

  8. Theory and experiment on electromagnetic-wave-propagation velocities in stacked superconducting tunnel structures

    DEFF Research Database (Denmark)

    Sakai, S.; Ustinov, A. V.; Kohlstedt, H.

    1994-01-01

    focused on. Furthermore, under the assumption that all parameters of the layers are equal, analytic solutions for a generic N-fold stack are presented. The velocities of the waves in two- and three-junction stacks by Nb-Al-AlOx-Nb systems are experimentally obtained by measuring the cavity resonance......Characteristic velocities of the electromagnetic waves propagating in vertically stacked Josephson transmission are theoretically discussed. An equation for solving n velocities of the waves in an n Josephson-junction stack is derived. The solutions of two- and threefold stacks are especially...

  9. Galactic subsystems on the basis of cumulative distribution of space velocities

    Directory of Open Access Journals (Sweden)

    Vidojević S.

    2008-01-01

    Full Text Available A sample containing 4 614 stars with available space velocities and high-quality kinematical data from the Arihip Catalogue is formed. For the purpose of distinguishing galactic subsystems the cumulative distribution of space velocities is studied. The fractions of the three subsystems are found to be: thin disc 92%, thick disc 6% and halo 2%. These results are verified by analyzing the elements of velocity ellipsoids and the shape and size of the galactocentric orbits of the sample stars, i.e. the planar and vertical eccentricities of the orbits.

  10. Variable velocity in solar external receivers

    Science.gov (United States)

    Rodríguez-Sánchez, M. R.; Sánchez-González, A.; Acosta-Iborra, A.; Santana, D.

    2017-06-01

    One of the major problems in solar external receivers is tube overheating, which accelerates the risk of receiver failure. It can be solved implementing receivers with high number of panels. However, it exponentially increases the pressure drop in the receiver and the parasitic power consumption of the Solar Power Tower (SPT), reducing the global efficiency of the SPT. A new concept of solar external receiver, named variable velocity receiver, is able to adapt their configuration to the different flux density distributions. A set of valves allows splitting in several independent panels those panels in which the wall temperature is over the limit. It increases the velocity of the heat transfer fluid (HTF) and its cooling capacity. This receiver does not only reduce the wall temperature of the tubes, but also simplifies the control of the heliostat field and allows to employ more efficient aiming strategies. In this study, it has been shown that variable velocity receiver presents high advantages with respect to traditional receiver. Nevertheless, more than two divisions per panels are not recommendable, due to the increment of the pressure drop over 70 bars. In the design point (12 h of the Spring Equinox), the use of a variable number of panels between 18 and 36 (two divisions per panel), in a SPT similar to Gemasolar, improves the power capacity of the SPT in 5.7%, with a pressure drop increment of 10 bars. Off-design, when the flux distribution is high and not symmetric (e.g. 10-11 h), the power generated by the variable velocity receiver is 18% higher than the generated by the traditional receiver, at these hours the pressure drop increases almost 20 bars.

  11. Multi-Joint Coordination of Vertical Arm Movement

    Directory of Open Access Journals (Sweden)

    Ajay Seth

    2003-01-01

    Full Text Available A model of the human arm was developed to study coordination of multi-joint movement in the vertical plane. The arm was represented as a two-segment, two-degree of freedom dynamic system with net muscle torques acting at the shoulder and elbow. Kinematic data were collected from a subject who performed unrestrained vertical movements with only the initial and final hand elevations prescribed. Movements were performed with and without a hand-held load. The method of computed torques was implemented to obtain net muscle torques, which enables position and velocity feedback to be used to estimate joint angular accelerations that produce a more stable simulation of arm movement. The model simulation was then used to calculate the contributions of the net muscle torques, gravitational torques and velocity-interaction torques to the angular accelerations of the shoulder and elbow and also to the vertical acceleration of the hand. The net muscle torques and gravity were the prime movers of the arm. The velocity-dependent effects contributed little to the dynamics of arm movement and were, in fact, insignificant when the hand was loaded. The muscles of the shoulder and elbow acted synergistically to elevate the arm in the sagittal plane. The hand was accelerated upward by the elbow first, until the point of maximum elbow flexion, after which the shoulder became the prime mover. Gravity acted consistently to accelerate the hand downward. Coordination was notably invariant to changes in external load. Some compensation for load was observed in the control, and these differences were attributed mainly to an increase in system inertia.

  12. Signal velocity in oscillator arrays

    Science.gov (United States)

    Cantos, C. E.; Veerman, J. J. P.; Hammond, D. K.

    2016-09-01

    We investigate a system of coupled oscillators on the circle, which arises from a simple model for behavior of large numbers of autonomous vehicles where the acceleration of each vehicle depends on the relative positions and velocities between itself and a set of local neighbors. After describing necessary and sufficient conditions for asymptotic stability, we derive expressions for the phase velocity of propagation of disturbances in velocity through this system. We show that the high frequencies exhibit damping, which implies existence of well-defined signal velocitiesc+ > 0 and c- < 0 such that low frequency disturbances travel through the flock as f+(x - c+t) in the direction of increasing agent numbers and f-(x - c-t) in the other.

  13. Comparing reading speed for horizontal and vertical English text.

    Science.gov (United States)

    Yu, Deyue; Park, Heejung; Gerold, David; Legge, Gordon E

    2010-02-23

    There are three formats for arranging English text for vertical reading-upright letters arranged vertically (marquee), and horizontal text rotated 90 degrees clockwise or counterclockwise. Previous research has shown that reading is slower for all three vertical formats than for horizontal text, with marquee being slowest (M. D. Byrne, 2002). It has been proposed that the size of the visual span-the number of letters recognized with high accuracy without moving the eyes-is a visual factor limiting reading speed. We predicted that reduced visual-span size would be correlated with the slower reading for the three vertical formats. We tested this prediction with uppercase and lowercase letters. Reading performance was measured using two presentation methods: RSVP (Rapid Serial Visual Presentation) and flashcard (a block of text on four lines). On average, reading speed for horizontal text was 139% faster than marquee text and 81% faster than the rotated texts. Size of the visual span was highly correlated with changes in reading speed for both lowercase and uppercase letters and for both RSVP and flashcard reading. Our results are consistent with the view that slower reading of vertical text is due to a decrease in the size of the visual span for vertical reading.

  14. 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) ...

  15. Noninvasive monitoring of vocal fold vertical vibration using the acoustic Doppler effect.

    Science.gov (United States)

    Tao, Chao; Jiang, Jack J; Wu, Dan; Liu, Xiaojun; Chodara, Ann

    2012-11-01

    To validate a proposed method of noninvasively monitoring vocal fold vertical vibration through utilization of the acoustic Doppler effect and the waveguide property of the vocal tract. Validation case-control study. In this device, an ultrasound beam is generated and directed into the mouth. The vocal tract, acting as a natural waveguide, guides the ultrasound beam toward the vibrating vocal folds. The vertical velocity of vocal fold vibration is then recovered from the Doppler frequency of the reflected ultrasound. One subject (age 32, male) was studied and measurements were taken under three modes of vocal fold vibration: breathing (no vibration), whispering (irregular vibration), and normal phonation (regular vibration). The peak-to-peak amplitude of the measured velocity of vocal fold vertical vibration was about 0.16 m/s, and the fundamental frequency was 172 Hz; the extracted velocity information showed a reasonable waveform and value in comparison with the previous studies. In all three modes of phonation, the Doppler frequencies derived from the reflected ultrasound corresponded with the vertical velocity of vocal fold vibration as expected. The proposed method can accurately represent the characteristics of different phonation modes such as no phonation, whisper and normal phonation. The proposed device could be used in daily monitoring and assessment of vocal function and vocal fold vibration. Copyright © 2012 The Voice Foundation. Published by Mosby, Inc. All rights reserved.

  16. 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...

  17. High-reliability vertical-axis wind turbine

    Science.gov (United States)

    Noll, R. B.; Zvara, J.

    A review of the design and development of a 1-kW high-reliability vertical-axis small wind energy conversion system (SWECS) is presented. The SWECS is a straight-bladed version of the Darrieus design. It incorporates high-reliability components in order to obtain a design value of mean time between failures of ten years based on one maintenance day a year. Design features are described, automatic control of the turbine is discussed, and typical results from controlled velocity testing are presented.

  18. 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.

  19. Velocity potential formulations of highly accurate Boussinesq-type models

    DEFF Research Database (Denmark)

    Bingham, Harry B.; Madsen, Per A.; Fuhrman, David R.

    2009-01-01

    processes on the weather side of reflective structures. Coast. Eng. 53, 929-945). An exact infinite series solution for the potential is obtained via a Taylor expansion about an arbitrary vertical position z=(z) over cap. For practical implementation however, the solution is expanded based on a slow...... variation of (z) over cap and terms are retained to first-order. With shoaling enhancement, the new models obtain a comparable accuracy in linear shoaling to the original velocity formulation. General consistency relations are also derived which are convenient for verifying that the differential operators...

  20. Maximum height and minimum time vertical jumping.

    Science.gov (United States)

    Domire, Zachary J; Challis, John H

    2015-08-20

    The performance criterion in maximum vertical jumping has typically been assumed to simply raise the center of mass as high as possible. In many sporting activities minimizing movement time during the jump is likely also critical to successful performance. The purpose of this study was to examine maximum height jumps performed while minimizing jump time. A direct dynamics model was used to examine squat jump performance, with dual performance criteria: maximize jump height and minimize jump time. The muscle model had activation dynamics, force-length, force-velocity properties, and a series of elastic component representing the tendon. The simulations were run in two modes. In Mode 1 the model was placed in a fixed initial position. In Mode 2 the simulation model selected the initial squat configuration as well as the sequence of muscle activations. The inclusion of time as a factor in Mode 1 simulations resulted in a small decrease in jump height and moderate time savings. The improvement in time was mostly accomplished by taking off from a less extended position. In Mode 2 simulations, more substantial time savings could be achieved by beginning the jump in a more upright posture. However, when time was weighted more heavily in these simulations, there was a more substantial reduction in jump height. Future work is needed to examine the implications for countermovement jumping and to examine the possibility of minimizing movement time as part of the control scheme even when the task is to jump maximally. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Relationship between vertical and horizontal jump variables and muscular performance in athletes.

    Science.gov (United States)

    Dobbs, Caleb W; Gill, Nicholas D; Smart, Daniel J; McGuigan, Michael R

    2015-03-01

    This study investigated the relationship between vertical and horizontal measures in bilateral and unilateral countermovement jump, drop jump and squat jump (SJ), and sprinting speed and muscle architecture of both the vastus lateralis and gastrocnemius. Subjects (n = 17) completed a 30-m sprint test, muscle stiffness test; ultrasound measures, and a jump testing session. Measures of horizontal peak and mean force, in both bilateral and unilateral jumps, tended to have greater relationships to sprint speeds (R = 0.132-0.576) than peak and mean force in the vertical plane (R = 0.008-0.504). Vertical velocity variables also showed some large and very large correlations to sprint speed (R = 0.062-0.635). Unilateral measures of velocity tended to have larger correlations to sprint performance than their bilateral counterparts across all jump types and peak and mean velocity in SJ showed large and very large correlations to sprint speed (bilateral R = 0.227-0.635; unilateral 0.393-0.574). Few large correlations were shown between muscle stiffness measures of muscle architecture and kinetic and kinematic variables in either vertical or horizontal jumps. The present findings suggest that sport scientists and strength and conditioning practitioners concerned with the prognostic value of kinetic variables to functional movements such as sprint speed should also use horizontal jumps in addition to vertical jumps in testing and training.

  2. Angle independent velocity spectrum determination

    DEFF Research Database (Denmark)

    2014-01-01

    An ultrasound imaging system (100) includes a transducer array (102) that emits an ultrasound beam and produces at least one transverse pulse-echo field that oscillates in a direction transverse to the emitted ultrasound beam and that receive echoes produced in response thereto and a spectral vel...... velocity estimator (110) that determines a velocity spectrum for flowing structure, which flows at an angle of 90 degrees and flows at angles less than 90 degrees with respect to the emitted ultrasound beam, based on the received echoes....

  3. Turbulent mixed convection in asymmetrically heated vertical channel

    Directory of Open Access Journals (Sweden)

    Mokni Ameni

    2012-01-01

    Full Text Available In this paper an investigation of mixed convection from vertical heated channel is undertaken. The aim is to explore the heat transfer obtained by adding a forced flow, issued from a flat nozzle located in the entry section of a channel, to the up-going fluid along its walls. Forced and free convection are combined studied in order to increase the cooling requirements. The study deals with both symmetrically and asymmetrically heated channel. The Reynolds number based on the nozzle width and the jet velocity is assumed to be 3 103 and 2.104; whereas, the Rayleigh number based on the channel length and the wall temperature difference varies from 2.57 1010 to 5.15 1012. The heating asymmetry effect on the flow development including the mean velocity and temperature the local Nusselt number, the mass flow rate and heat transfer are examined.

  4. Real-Time Vertical Temperature, and Velocity Profiles from a Wave Glider

    Science.gov (United States)

    2012-09-30

    Liquid Robotics navigated a Wave Glider from San Diego to Hawaii on a 82 day-long voyage that covered approximately 2500 nautical miles (http...Gawarkiewicz, G., et al. (2011), Circulation and Intrusions Northeast of Taiwan: Chasing and Predicting Uncertainty in the Cold Dome ., Oceanography, 24(4), 110...121. Lee, D.-K., and P. Niiler (2010), Influence of warm SST anomalies formed in the eastern Pacific subduction zone on recent El Nino events, J Mar Res, 68(3-4), 459-477.

  5. Horizontal and Vertical Structure of Velocity, Potential Vorticity and Energy in the Gulf Stream.

    Science.gov (United States)

    1985-02-01

    Number OCE-8208 746; and by the Office of Naval Research under contract Number NOOG 14-82-C -0019, NR 083-004. Reproduction in whole or in part is...The first term on the RHiS can be written 1 (p(0)+ :1)( ufO )+eufl)) 1 (0+P 1 *l 1O)CUI) 0 0 -H 1 HI () (-) pi O / V.1 (pa) +ft w 01 0j~ EoPO o1 1

  6. Inferring regional vertical crustal velocities from averaged relative sea level trends: A proof of concept

    Science.gov (United States)

    Bâki Iz, H.; Shum, C. K.; Zhang, C.; Kuo, C. Y.

    2017-11-01

    We report the design of a high-throughput gradient hyperbolic lenslet built with real-life materials and capable of focusing a beam into a deep sub-wavelength spot of λ/23. This efficient design is achieved through high-order transformation optics and circular effective-medium theory (CEMT), which are used to engineer the radially varying anisotropic artificial material based on the thin alternating cylindrical metal and dielectric layers. The radial gradient of the effective anisotropic optical constants allows for matching the impedances at the input and output interfaces, drastically improving the throughput of the lenslet. However, it is the use of the zeroth-order CEMT that enables the practical realization of a gradient hyperlens with realistic materials. To illustrate the importance of using the CEMT versus the conventional planar effective-medium theory (PEMT) for cylindrical anisotropic systems, such as our hyperlens, both the CEMT and PEMT are adopted to design gradient hyperlenses with the same materials and order of elemental layers. The CEMT- and PEMT-based designs show similar performance if the number of metal-dielectric binary layers is sufficiently large (9+ pairs) and if the layers are sufficiently thin. However, for the manufacturable lenses with realistic numbers of layers (e.g. five pairs) and thicknesses, the performance of the CEMT design continues to be practical, whereas the PEMT-based design stops working altogether. The accurate design of transformation optics-based layered cylindrical devices enabled by CEMT allow for a new class of robustly manufacturable nanophotonic systems, even with relatively thick layers of real-life materials.

  7. Wind stress, curl and vertical velocity in the Bay of Bengal during southwest monsoon, 1984

    Digital Repository Service at National Institute of Oceanography (India)

    Babu, M.T.; Heblekar, A.K.; Murty, C.S.

    Wind distribution observed during southwest monsoon of 1984 has used to derive the mean wind stress for the season at every 1 degree square grid and curl over the Bay of Bengal. Two regions of maximum wind stress are present over the Bay of Bengal...

  8. The Risk of Airborne Cross-Infection in a Room with Vertical Low-Velocity Ventilation

    DEFF Research Database (Denmark)

    Olmedo, Inés; Nielsen, Peter V.; Adana, M. Ruiz de

    2013-01-01

    Downward flow ventilation systems are one of the most recommended ventilation strategies when contaminants in rooms must be removed and people must be protected from the risk of airborne cross-infection. This study is based on experimental tests carried out in a room with downward flow ventilation....... Two breathing thermal manikins are placed in a room face to face. One manikin’s breathing is considered to be the contaminated source to simulate a risky situation with airborne cross-infection. The position of the manikins in relation to the diffuser and the location of diffuser in the room as well...

  9. Modelling vertical uniform contact stress of heavy vehicle tyres

    CSIR Research Space (South Africa)

    Steenkamp, Anton J

    2016-07-01

    Full Text Available over the selected operating range of 25 kN to 45 kN which is the typical load range for heavy vehicle tyres due to legal axle load limits. The polynomial formulas require only the tyre inflation pressure and vertical tyre load as inputs, in order...

  10. Experimental characterization of individual pitch controlled vertical axis wind turbine

    NARCIS (Netherlands)

    LeBlanc, B.P.; Simao Ferreira, C.

    2017-01-01

    Research into the Vertical Axis Wind Turbine (VAWT) has been progressing over the last few years due to
    the large shift in design constraints for large floating offshore wind turbines by leveraging tools and experience
    from research beginning in the 1970s and lasting until the HAWT

  11. Streaming Velocities and the Baryon Acoustic Oscillation Scale.

    Science.gov (United States)

    Blazek, Jonathan A; McEwen, Joseph E; Hirata, Christopher M

    2016-03-25

    At the epoch of decoupling, cosmic baryons had supersonic velocities relative to the dark matter that were coherent on large scales. These velocities subsequently slow the growth of small-scale structure and, via feedback processes, can influence the formation of larger galaxies. We examine the effect of streaming velocities on the galaxy correlation function, including all leading-order contributions for the first time. We find that the impact on the baryon acoustic oscillation (BAO) peak is dramatically enhanced (by a factor of ∼5) over the results of previous investigations, with the primary new effect due to advection: if a galaxy retains memory of the primordial streaming velocity, it does so at its Lagrangian, rather than Eulerian, position. Since correlations in the streaming velocity change rapidly at the BAO scale, this advection term can cause a significant shift in the observed BAO position. If streaming velocities impact tracer density at the 1% level, compared to the linear bias, the recovered BAO scale is shifted by approximately 0.5%. This new effect, which is required to preserve Galilean invariance, greatly increases the importance of including streaming velocities in the analysis of upcoming BAO measurements and opens a new window to the astrophysics of galaxy formation.

  12. REVEL: A model for Recent plate velocities from space geodesy

    Science.gov (United States)

    Sella, Giovanni F.; Dixon, Timothy H.; Mao, Ailin

    2002-04-01

    We present a new global model for Recent plate velocities, REVEL, describing the relative velocities of 19 plates and continental blocks. The model is derived from publicly available space geodetic (primarily GPS) data for the period 1993-2000. We include an independent and rigorous estimate for GPS velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates. The velocity fields for North America, Eurasia, and Antarctica clearly show the effects of glacial isostatic adjustment, and Australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field. Two thirds of tested plate pairs agree with the NUVEL-1A geologic (3 Myr average) velocities within uncertainties. Three plate pairs (Caribbean-North America, Caribbean-South America, and North America-Pacific) exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in NUVEL-1A due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities. Most other differences probably reflect real velocity changes over the last few million years. Several plate pairs (Arabia-Eurasia, Arabia-Nubia, Eurasia-India) move more slowly than the 3 Myr NUVEL-1A average, perhaps reflecting long-term deceleration associated with continental collision. Several other plate pairs, including Nazca-Pacific, Nazca-South America and Nubia-South America, are experiencing slowing that began ~25 Ma, the beginning of the current phase of Andean crustal shortening.

  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. 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.

  15. Roles of Wind Shear at Different Vertical Levels, Part I: Cloud System Organization and Properties

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qian; Fan, Jiwen; Hagos, Samson M.; Gustafson, William I.; Berg, Larry K.

    2015-07-07

    Understanding of critical processes that contribute to the organization of mesoscale convective systems is important for accurate weather forecast and climate prediction. In this study, we investigate the effects of wind shear at different vertical levels on the organization and properties of cloud systems using the Weather Research & Forecasting (WRF) model with a spectral-bin microphysical scheme. The sensitivity experiments are performed by increasing wind shear at the lower (0-5 km), middle (5-10 km), upper (> 10 km) and the entire troposphere, respectively, based on a control run for a mesoscale convective system (MCS) with weak wind shear. We find that increasing wind shear at the both lower and middle vertical levels reduces the domain-accumulated precipitation and the occurrence of heavy rain, while increasing wind shear at the upper levels changes little on precipitation. Although increasing wind shear at the lower-levels is favorable for a more organized quasi-line system which leads to enlarged updraft core area, and enhanced updraft velocities and vertical mass fluxes, the precipitation is still reduced by 18.6% compared with the control run due to stronger rain evaporation induced by the low-level wind shear. Strong wind shear in the middle levels only produces a strong super-cell over a narrow area, leading to 67.3% reduction of precipitation over the domain. By increasing wind shear at the upper levels only, the organization of the convection is not changed much, but the increased cloudiness at the upper-levels leads to stronger surface cooling and then stabilizes the atmosphere and weakens the convection. When strong wind shear exists over the entire vertical profile, a deep dry layer (2-9 km) is produced and convection is severely suppressed. There are fewer very-high (cloud top height (CTH) > 15 km) and very-deep (cloud thickness > 15 km) clouds, and the precipitation is only about 11.8% of the control run. The changes in cloud microphysical

  16. Evaluation of Aesthetic Function and Thermal Modification of Vertical Greenery at Bogor City, Indonesia

    Science.gov (United States)

    Sulistyantara, B.; Sesara, R.

    2017-10-01

    Bogor city currently develops vertical greenery due to counter the decreasing of green space quantity. Vertical greenery is a planting method using vertical structure similar to retaining walls. There are some benefits of vertical greenery, such as providing aesthetics value of the landscape, to protect from the heat, to reduce noise, and to reduce pollution. The purpose of this study were to identify thermal modification by vertical greenery in Bogor city, to assess the aesthetics value from vertical greenery, and to provide a recommendation in attempt to manage and improve the quality of vertical greenery in Bogor city. The study was conducted using Scenic Beauty Estimation method, and was done by providing questionnaires to the respondents in order to assess the aesthetics value of vertical greenery. Infrared thermometer was also used to measure the surface’s temperature to evaluate thermal modification function of the vertical greenery. The result of study proved that vertical greenery in the Bogor city has considerably good aesthetic. It also showed that there is a decreasing in surface temperature of the vertical greenery structure.

  17. Coexistence of Strategic Vertical Separation and Integration

    DEFF Research Database (Denmark)

    Jansen, Jos

    2003-01-01

    This paper gives conditions under which vertical separation is chosen by some upstream firms, while vertical integration is chosen by others in the equilibrium of a symmetric model. A vertically separating firm trades off fixed contracting costs against the strategic benefit of writing a (two......-part tariff, exclusive dealing) contract with its retailer. Coexistence emerges when more than two vertical Cournot oligopolists supply close substitutes. When vertical integration and separation coexist, welfare could be improved by reducing the number of vertically separating firms. The scope...

  18. The capillary interaction between two vertical cylinders

    KAUST Repository

    Cooray, Himantha

    2012-06-27

    Particles floating at the surface of a liquid generally deform the liquid surface. Minimizing the energetic cost of these deformations results in an inter-particle force which is usually attractive and causes floating particles to aggregate and form surface clusters. Here we present a numerical method for determining the three-dimensional meniscus around a pair of vertical circular cylinders. This involves the numerical solution of the fully nonlinear Laplace-Young equation using a mesh-free finite difference method. Inter-particle force-separation curves for pairs of vertical cylinders are then calculated for different radii and contact angles. These results are compared with previously published asymptotic and experimental results. For large inter-particle separations and conditions such that the meniscus slope remains small everywhere, good agreement is found between all three approaches (numerical, asymptotic and experimental). This is as expected since the asymptotic results were derived using the linearized Laplace-Young equation. For steeper menisci and smaller inter-particle separations, however, the numerical simulation resolves discrepancies between existing asymptotic and experimental results, demonstrating that this discrepancy was due to the nonlinearity of the Laplace-Young equation. © 2012 IOP Publishing Ltd.

  19. Novel Small-scale Technique for Determining Detonation Velocity

    Science.gov (United States)

    Preston, Daniel; Hill, Larry; Tappan, Bryce

    2013-06-01

    Measuring the local detonation velocity of an explosive has been limited to rate stick and cylinder tests. These tests traditionally used break wires, pins, and more recently PDV as a velocity diagnostic. These experimental techniques can be very accurate at measuring detonation velocities but are costly and require tens to hundreds of grams of material. This paper presents a novel small-scale technique for inferring detonation velocity from a modest sized pellet of explosive. A streak image is taken of the breakout shock on the flat output side of the pellet. Assuming a spherical shock wave, one can show that the breakout trace is of hyperbolic form. From this, one can simultaneously infer detonation velocty and apparent center. This method is ideal for energetic formulation and synthesis development due to the small amount of material required. Furthermore, this paper discusses the accuracy and limitations of this technique.

  20. Kinematic Fitting of Detached Vertices

    Energy Technology Data Exchange (ETDEWEB)

    Mattione, Paul [Rice Univ., Houston, TX (United States)

    2007-05-01

    The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the $\\Xi_{5}$ pentaquarks and investigate the excited $\\Xi$ states. Specifically, the exotic $\\Xi_{5}^{--}$ pentaquark will be sought by first reconstructing the $\\Xi^{-}$ particle through its weak decays, $\\Xi^{-}\\to\\pi^{-}\\Lambda$ and $\\Lambda\\to\\pi^{-}$. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction $\\gamma D\\rightarrow pp\\pi^{-}$ was studied in order to correct the track measurements and covariance matrices of the charged particles. The $\\Lambda\\rightarrow p\\pi^{-}$ and $\\Xi^{-}\\to\\pi^{-}\\Lambda$ decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.

  1. Vertical distribution of Arctic methane

    Science.gov (United States)

    Tukiainen, Simo; Karppinen, Tomi; Hakkarainen, Janne; Kivi, Rigel; Heikkinen, Pauli; Tamminen, Johanna

    2017-04-01

    In this study we show the vertical distribution of atmospheric methane (CH4) measured in Sodankylä, Northern Finland. The CH4 profiles are retrieved from the direct Sun FTS measurements using the dimension reduction retrieval method. In the retrieval method, we have a few degrees of freedom about the profile shape. The data set covers years 2010-2016 (from February to November) and altitudes 0-40 km. The retrieved FTS profiles are validated against ACE satellite measurements and AirCore balloon measurements. The total columns derived from the FTS profiles are compared to the official TCCON XCH4 data. A vertically resolved methane data set can be used, e.g., to study stratospheric methane during the polar vortex.

  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. 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.

  4. 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.

  5. Poligonación Vertical

    Directory of Open Access Journals (Sweden)

    Esteban Dörries

    2016-03-01

    Full Text Available La poligonación vertical es un método de medición de diferencias de altura que aprovecha las posibilidades de las estaciones totales. Se presta fundamentalmente para líneas de nivelación entre nodos formando red. El nombre se debe a que las visuales sucesivas se proyectan sobre aristas verticales en lugar de un plano horizontal, como ocurre en la poligonación convencional.

  6. Vertical Launch System Loadout Planner

    Science.gov (United States)

    2015-03-01

    United States Navy USS United States’ Ship VBA Visual Basic for Applications VLP VLS Loadout Planner VLS Vertical Launch System...mathematically complex and require training to operate the software. A Visual Basic for Applications ( VBA ) Excel (Microsoft Corporation, 2015...lockheed/data/ms2/documents/laun chers/MK41 VLS factsheet.pdf Microsoft Excel version 14.4.3, VBA computer software. (2011). Redmond, WA: Microsoft

  7. Trade Liberalisation and Vertical Integration

    DEFF Research Database (Denmark)

    Bache, Peter Arendorf; Laugesen, Anders

    We build a three-country model of international trade in final goods and intermediate inputs and study the relation between different types of trade liberalisation and vertical integration. Firms are heterogeneous with respect to both productivity and factor intensity as observed in data. Final......-economy property rights theory of the firm using firm-level data. Finally, we notice that our model's sorting pattern is in line with recent evidence when the wage difference across countries is not too big....

  8. Influence of Lorentz force, Cattaneo-Christov heat flux and viscous dissipation on the flow of micropolar fluid past a nonlinear convective stretching vertical surface

    Science.gov (United States)

    Gnaneswara Reddy, Machireddy

    2017-12-01

    The problem of micropolar fluid flow over a nonlinear stretching convective vertical surface in the presence of Lorentz force and viscous dissipation is investigated. Due to the nature of heat transfer in the flow past vertical surface, Cattaneo-Christov heat flux model effect is properly accommodated in the energy equation. The governing partial differential equations for the flow and heat transfer are converted into a set of ordinary differential equations by employing the acceptable similarity transformations. Runge-Kutta and Newton's methods are utilized to resolve the altered governing nonlinear equations. Obtained numerical results are compared with the available literature and found to be an excellent agreement. The impacts of dimensionless governing flow pertinent parameters on velocity, micropolar velocity and temperature profiles are presented graphically for two cases (linear and nonlinear) and analyzed in detail. Further, the variations of skin friction coefficient and local Nusselt number are reported with the aid of plots for the sundry flow parameters. The temperature and the related boundary enhances enhances with the boosting values of M. It is found that fluid temperature declines for larger thermal relaxation parameter. Also, it is revealed that the Nusselt number declines for the hike values of Bi.

  9. Prophylaxis of vertical HBV infection.

    Science.gov (United States)

    Pawlowska, Malgorzata; Pniewska, Anna; Pilarczyk, Malgorzata; Kozielewicz, Dorota; Domagalski, Krzysztof

    2016-10-01

    An appropriate management of HBV infection is the best strategy to finally reduce the total burden of HBV infection. Mother-to-child transmission (MTCT) is responsible for more than one third of chronic HBV infections worldwide. Because HBV infection in infancy or early childhood often leads to chronic infection, appropriate prophylaxis and management of HBV in pregnancy is crucial to prevent MTCT. The prevention of HBV vertical transmission is a complex task and includes: universal HBV screening of pregnant women, administration of antivirals in the third trimester of pregnancy in women with high viral load and passive-active HBV immunoprophylaxis with hepatitis B vaccine and hepatitis B immune globulin in newborns of all HBV infected women. Universal screening of pregnant women for HBV infection, early identification of HBV DNA level in HBV-infected mothers, maternal treatment with class B according to FDA antivirals and passive/active anti-HBV immunoprophylaxis to newborns of HBV-positive mothers are crucial strategies for reducing vertical HBV transmission rates. Consideration of caesarean section in order to reduce the risk of vertical HBV transmission should be recommend in HBV infected pregnant women with high viral load despite antiviral therapy or when the therapy in the third trimester of pregnancy is not available.

  10. Application of Refraction Microtremor (ReMi) technique for determination of 1-D shear wave velocity in a landslide area

    Science.gov (United States)

    Coccia, S.; Del Gaudio, V.; Venisti, N.; Wasowski, J.

    2010-06-01

    The application of the Refraction Microtremor (ReMi) method on slopes affected by or prone to landsliding is complicated by the presence of lateral lithological heterogeneities and irregular topography, which may hinder the extension of the geophone array to the minimum lengths (100-200 m) usually adopted in standard applications of this technique. We focus on deriving one-dimensional shear-wave velocity (Vs) vertical profiles from the analysis of microtremor recordings carried out in the municipality of Caramanico Terme (central Italy) where the seismic response has been monitored with a local accelerometer network since 2002. The stability of the ReMi data acquisitions and the reliability of the results in irregular landslide terrain were tested by using ReMi campaigns in three different periods and different acquisition parameters (seismograph channel number, geophone frequency and spacing). We also investigated the possible presence of directional variations in soil properties by carrying out noise recordings along L-shaped arrays. The influence of changing environmental conditions and of different acquisition parameters was tested by comparing the data obtained from different campaigns, using the same acquisition parameters, with the data from simultaneous acquisitions using different parameters. The tests showed that stable results can be obtained under different acquisition conditions provided that i) the ratio between the coherent and incoherent part of ambient noise is sufficiently high and ii) spatial aliasing does not contaminate the signal in the p (slowness)- f (frequency) matrix near the picking area: the latter condition can be satisfied by selecting geophone frequency and spacing appropriate for the site characteristics and for the investigation purpose. The differences in Vs measured in two orthogonal directions did not exceed 10-20 % and their analysis suggests that these directional variations are most likely due to anisotropy in noise source

  11. Vertical Capacity of Bucket Foundations in Undrained Soil

    DEFF Research Database (Denmark)

    Barari, Amin; Ibsen, Lars Bo

    2014-01-01

    Offshore wind turbine structures are traditionally founded on gravity concrete foundations or mono-piles. Bucket foundations were developed for the offshore oil and gas industry and are now being used in wind turbine construction. The loading in this application is characterized by a vertical load...... due to the slender construction combined with horizontal forces inducing a large overturning moment. Field tests on bucket foundations were performed to gain insight into the vertical load response of bucket foundations in clay soils. The field tests were accompanied by finite element numerical...... simulations in order to provide a better understanding of the parameters influencing bucket foundation behavior....

  12. Tissue motion in blood velocity estimation and its simulation

    DEFF Research Database (Denmark)

    Schlaikjer, Malene; Torp-Pedersen, Søren; Jensen, Jørgen Arendt

    1998-01-01

    . The motion due to the heart, when the volunteer was asked to hold his breath, gave a peak velocity of 4.2±1.7 mm/s. The movement of the carotid artery wall due to changing blood pressure had a peak velocity of 8.9±3.7 mm/s over the cardiac cycle. The variations are due to differences in heart rhythm......Determination of blood velocities for color flow mapping systems involves both stationary echo cancelling and velocity estimation. Often the stationary echo cancelling filter is the limiting factor in color flow mapping and the optimization and further development of this filter is crucial...... to the improvement of color flow imaging. Optimization based on in-vivo data is difficult since the blood and tissue signals cannot be accurately distinguished and the correct extend of the vessel under investigation is often unknown. This study introduces a model for the simulation of blood velocity data in which...

  13. PREDICTING THE INTRA-CYCLIC VARIATION OF THE VELOCITY OF THE CENTRE OF MASS FROM SEGMENTAL VELOCITIES IN BUTTERFLY STROKE: A PILOT STUDY

    Directory of Open Access Journals (Sweden)

    Joao P. Vilas-Boas

    2008-06-01

    end of the underwater path, should increase the vertical velocity during the downbeats and decrease the velocity during the hand's entry.

  14. Rayleigh-Wave Group-Velocity Tomography of Saudi Arabia

    Science.gov (United States)

    Tang, Zheng; Mai, P. Martin; Chang, Sung-Joon; Zahran, Hani

    2017-04-01

    We use surface-wave tomography to investigate the lithospheric structure of the Arabian plate, which is traditionally divided into the Arabian shield in the west and the Arabian platform in the east. The Arabian shield is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks. The Arabian platform is primarily covered by very thick Paleozoic, Mesozoic and Cenozoic sediments. We develop high-resolution tomographic images from fundamental-mode Rayleigh-wave group-velocities across Saudi Arabia, utilizing the teleseismic data recorded by the permanent Saudi National Seismic Network (SNSN). Our study extends previous efforts on surface wave work by increasing ray path density and improving spatial resolution. Good quality dispersion measurements for roughly 3000 Rayleigh-wave paths have been obtained and utilized for the group-velocity tomography. We have applied the Fast Marching Surface Tomography (FMST) scheme of Rawlinson (2005) to obtain Rayleigh-wave group-velocity images for periods from 8 s to 40 s on a 0.8° 0.8° grid and at resolutions approaching 2.5° based on the checkerboard tests. Our results indicate that short-period group-velocity maps (8-15 s) correlate well with surface geology, with slow velocities delineating the main sedimentary features including the Arabian platform, the Persian Gulf and Mesopotamia. For longer periods (20-40 s), the velocity contrast is due to the differences in crustal thickness and subduction/collision zones. The lower velocities are sensitive to the thicker continental crust beneath the eastern Arabia and the subduction/collision zones between the Arabian and Eurasian plate, while the higher velocities in the west infer mantle velocity.

  15. Maintenance of Vertical Scales under Conditions of Item Parameter Drift and Rasch Model-Data Misfit

    Science.gov (United States)

    O'Neil, Timothy P.

    2010-01-01

    With scant research to draw upon with respect to the maintenance of vertical scales over time, decisions around the creation and performance of vertical scales over time necessarily suffers due to the lack of information. Undetected item parameter drift (IPD) presents one of the greatest threats to scale maintenance within an item response theory…

  16. Design Of Rotor Blade For Vertical Axis Wind Turbine Using Double Aerofoil

    DEFF Research Database (Denmark)

    Chougule, Prasad; Ratkovich, Nicolas Rios; Kirkegaard, Poul Henning

    Nowadays, small vertical axis wind turbines are receiving more attention compared to horizontal wind turbines due to their suitability in urban use because they generate less noise, have bird free turbines and lower cost. There is few vertical axis wind turbines design with good power curve...

  17. 3D isotropic shear wave velocity structure of the lithosphere-asthenosphere system underneath the Alpine-Mediterranean Mobile belt

    Science.gov (United States)

    El-Sharkawy, Amr; Weidle, Christian; Christiano, Luigia; Lebedev, Sergei; Meier, Thomas

    2017-04-01

    The Alpine-Mediterranean mobile belt is, tectonically, one of the most complicated and active regions in the world. Since the Mesozoic, collisions between Gondwana-derived continental blocks and Eurasia, due to the closure of a number of rather small ocean basins, have shaped the Mediterranean geology. During the late Mesozoic, it was dominated by subduction zones (e.g., in Anatolia, the Dinarides, the Carpathians, the Alps, the Apennines, and the Betics), which inverted the extensional regime, consuming the previously formed oceanic lithosphere, the adjacent passive continental margins and presumably partly also continental lithosphere. The location, distribution, and evolution of these subduction zones were mainly controlled by the continental or oceanic nature, density, and thickness of the lithosphere inherited from the Mesozoic rift after the European Variscan Orogeny. Despite the numerous studies that have attempted to characterize the lithosphere-asthenosphere structure in that area, details of the lithospheric structure and dynamics, as well as flow in the asthenosphere are, however, poorly known. A 3D shear-wave velocity structure of the lithosphere-asthenosphere system in the Mediterranean is investigated using new tomographic images obtained from surface wave tomography. An automated algorithm for inter-station phase velocity measurements is applied here to obtain both Rayleigh and Love fundamental mode phase velocities. We utilize a database consisting of more than 4000 seismic events recorded by more than 2000 broadband seismic stations within the area, provided by the European Integrated Data Archive (WebDc/EIDA) and IRIS. Moreover, for the first time, data from the Egyptian National Seismological Network (ENSN), recorded by up to 25 broad band seismic stations, are also included in the analysis. For each station pair, approximately located on the same great circle path, the recorded waveforms are cross correlated and the dispersion curves of

  18. [Vertical fractures: apropos of 2 clinical cases].

    Science.gov (United States)

    Félix Mañes Ferrer, J; Micò Muñoz, P; Sánchez Cortés, J L; Paricio Martín, J J; Miñana Laliga, R

    1991-01-01

    The aim of the study is to present a clinical review of the vertical root fractures. Two clinical cases are presented to demonstrates the criteria for obtaining a correct diagnosis of vertical root fractures.

  19. Determinations of vertical stroke V{sub cb} vertical stroke and vertical stroke V{sub ub} vertical stroke from baryonic Λ{sub b} decays

    Energy Technology Data Exchange (ETDEWEB)

    Hsiao, Y.K. [Shanxi Normal University, School of Physics and Information Engineering, Linfen (China); National Tsing Hua University, Department of Physics, Hsinchu (China); Geng, C.Q. [Shanxi Normal University, School of Physics and Information Engineering, Linfen (China); National Tsing Hua University, Department of Physics, Hsinchu (China); Hunan Normal University, Synergetic Innovation Center for Quantum Effects and Applications (SICQEA), Changsha (China)

    2017-10-15

    We present the first attempt to extract vertical stroke V{sub cb} vertical stroke from the Λ{sub b} → Λ{sub c}{sup +}l anti ν{sub l} decay without relying on vertical stroke V{sub ub} vertical stroke inputs from the B meson decays. Meanwhile, the hadronic Λ{sub b} → Λ{sub c}M{sub (c)} decays with M = (π{sup -},K{sup -}) and M{sub c} =(D{sup -},D{sup -}{sub s}) measured with high precisions are involved in the extraction. Explicitly, we find that vertical stroke V{sub cb} vertical stroke =(44.6 ± 3.2) x 10{sup -3}, agreeing with the value of (42.11 ± 0.74) x 10{sup -3} from the inclusive B → X{sub c}l anti ν{sub l} decays. Furthermore, based on the most recent ratio of vertical stroke V{sub ub} vertical stroke / vertical stroke V{sub cb} vertical stroke from the exclusive modes, we obtain vertical stroke V{sub ub} vertical stroke = (4.3 ± 0.4) x 10{sup -3}, which is close to the value of (4.49 ± 0.24) x 10{sup -3} from the inclusive B → X{sub u}l anti ν{sub l} decays. We conclude that our determinations of vertical stroke V{sub cb} vertical stroke and vertical stroke V{sub ub} vertical stroke favor the corresponding inclusive extractions in the B decays. (orig.)

  20. 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...

  1. Critical velocity experiments in space

    Science.gov (United States)

    Torbert, R. B.

    1988-01-01

    Published data from active space experiments designed to demonstrate the Alfven critical-velocity effect are compiled in graphs and compared with the predictions of numerical simulations. It is found that the discrepancies in the ionization yields obtained in shaped-charge releases of alkali metals are related to the macroscopic limits of time and energy in such releases. It is argued that the total ionization yield is an inadequate measure of the critical-velocity effect, and a new criterion based on eta, the efficiency of energy transfer from the recently ionized neutrals to a heated electron population, is proposed: the effect would be verified if eta values of 10 percent or greater were observed.

  2. Design of h-Darrieus vertical axis wind turbine

    Science.gov (United States)

    Parra, Teresa; Vega, Carmen; Gallegos, A.; Uzarraga, N. C.; Castro, F.

    2015-05-01

    Numerical simulation is used to predict the performance of a Vertical Axis Wind Turbine (VAWT) H-Darrieus. The rotor consists of three straight blades with shape of aerofoil of the NACA family attached to a rotating vertical shaft. The influence of the solidity is tested to get design tendencies. The mesh has two fluid volumes: one sliding mesh for the rotor where the rotation velocity is established while the other is the environment of the rotor. Bearing in mind the overall flow is characterized by important secondary flows, the turbulence model selected was realizable k-epsilon with non-equilibrium wall functions. Conservation equations were solved with a Third-Order Muscl scheme using SIMPLE to couple pressure and velocity. During VAWT operation, the performance depends mainly on the relative motion of the rotating blade and has a fundamental period which depends both on the rate of rotation and the number of blades. The transient study is necessary to characterise the hysteresis phenomenon. Hence, more than six revolutions get the periodic behaviour. Instantaneous flows provide insight about wake structure interaction. Time averaged parameters let obtain the characteristic curves of power coefficient.

  3. Design of h-Darrieus vertical axis wind turbine

    Directory of Open Access Journals (Sweden)

    Parra Teresa

    2015-01-01

    Full Text Available Numerical simulation is used to predict the performance of a Vertical Axis Wind Turbine (VAWT H-Darrieus. The rotor consists of three straight blades with shape of aerofoil of the NACA family attached to a rotating vertical shaft. The influence of the solidity is tested to get design tendencies. The mesh has two fluid volumes: one sliding mesh for the rotor where the rotation velocity is established while the other is the environment of the rotor. Bearing in mind the overall flow is characterized by important secondary flows, the turbulence model selected was realizable k-epsilon with non-equilibrium wall functions. Conservation equations were solved with a Third-Order Muscl scheme using SIMPLE to couple pressure and velocity. During VAWT operation, the performance depends mainly on the relative motion of the rotating blade and has a fundamental period which depends both on the rate of rotation and the number of blades. The transient study is necessary to characterise the hysteresis phenomenon. Hence, more than six revolutions get the periodic behaviour. Instantaneous flows provide insight about wake structure interaction. Time averaged parameters let obtain the characteristic curves of power coefficient.

  4. 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.

  5. 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.

  6. 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.

  7. Topographic enhancement of vertical turbulent mixing in the Southern Ocean

    Science.gov (United States)

    Mashayek, A.; Ferrari, R.; Merrifield, S.; Ledwell, J. R.; St Laurent, L.; Garabato, A. Naveira

    2017-03-01

    It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation.

  8. Geological affinity of reflecting boundaries in the intermediate structural stage of the Chu Sarysuyskiy depression based on results of vertical seismic profilling

    Energy Technology Data Exchange (ETDEWEB)

    Davydov, N.G.; Kiselevskiy, Yu.N.

    1983-01-01

    A computer (EVM) and an ASOI-VSP-SK program complex are used to analyze data from seismic exploration and acoustical logging with interval by interval calculation of the velocity every four meters. Vertical seismic profilling (VSP) results are used to identify all the upper layers as reference layers. The basic reference level, the third, which corresponds to the floor of the carbonate middle to upper Visean series, is not sustained due to the thin layered state of the terrigeneous section. Based on data from vertical seismic profilling, the reflected wave method (MOV) and the common depth point method (MOGT), the reference 3-a and 6-a levels are identified. Deep reflections of the seventh, 7-a and Rf, approximately confined to the roof and floor of the lower Paleozoic deposits and the upper part of the upper reef series, are noted in the series of the Caledonian cap of the Prebaykal massifs based on vertical seismic profilling. Collector levels are noted on the basis of the frequency of the wave spectra and from the absorption coefficient in the Testas structure and in other low amplitude structures. The insufficiency of the depth capability of the common depth point method and the poor knowledge level of seismic exploration of the section of the lower Paleozoa and the upper Proterozoa of the Chu Sarysuyskiy depresion are noted.

  9. Development of Vertical Cable Seismic System (3)

    Science.gov (United States)

    Asakawa, E.; Murakami, F.; Tsukahara, H.; Mizohata, S.; Ishikawa, K.

    2013-12-01

    The VCS (Vertical Cable Seismic) is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. We carried out several VCS surveys combining with surface towed source, deep towed source and ocean bottom source. The water depths of the survey are from 100m up to 2100m. The target of the survey includes not only hydrothermal deposit but oil and gas exploration. Through these experiments, our VCS data acquisition system has been completed. But the data processing techniques are still on the way. One of the most critical issues is the positioning in the water. The uncertainty in the positions of the source and of the hydrophones in water degraded the quality of subsurface image. GPS navigation system are available on sea surface, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging. We have developed another approach to determine the positions in water using the travel time data from the source to VCS hydrophones. In the data acquisition stage, we estimate the position of VCS location with slant ranging method from the sea surface. The deep-towed source or ocean bottom source is estimated by SSBL/USBL. The water velocity profile is measured by XCTD. After the data acquisition, we pick the first break times of the VCS recorded data. The estimated positions of

  10. Interpretation of deformed ionograms induced by vertical ground motion of seismic Rayleigh waves and infrasound in the thermosphere

    Directory of Open Access Journals (Sweden)

    T. Maruyama

    2016-02-01

    Full Text Available The vertical ground motion of seismic surface waves launches acoustic waves into the atmosphere and induces ionospheric disturbances. Disturbances due to Rayleigh waves near the short-period Airy phase appear as wavy fluctuations in the virtual height of an ionogram and have a multiple-cusp signature (MCS when the fluctuation amplitude is increased. An extremely developed MCS was observed at Kazan, Russia, after the 2010 M 8.8 Chile earthquake. The ionogram exhibited steep satellite traces for which the virtual heights increased rapidly with frequency starting near the top of cusps and continuing for 0.1–0.2 MHz. This complicated ionogram was analyzed by applying a ray tracing technique to the radio wave propagation in the ionosphere that was perturbed by acoustic waves. Acoustic wavefronts were inclined by the effects of finite Rayleigh wave velocity and sound speed in the thermosphere. The satellite echo traces were reproduced by oblique returns from the inclined wavefronts, in addition to the nearly vertical returns that are responsible for the main trace.

  11. Monitoring for vertical creep in concrete in two silos at Wivenhoe pumped storage hydro power station

    Energy Technology Data Exchange (ETDEWEB)

    Harris, M.W. [Queensland Univ. of Technology, Brisbane (Australia). School of Surveying

    1996-12-31

    The need for structural monitoring is generated by expected or unexpected (newly discovered in the life of the structure) behaviour. Due to the long vertical driveshafts involved at Wivenhoe the phenomenon of `concrete creep` which, if it is occurring, could contribute to shaft misalignment and unscheduled bearing wear or failure, was used as a motivation to establish a vertical monitoring system. The particular system developed for this site is traceable, replaceable, expandable and inexpensive. Measurements are obtained by precise levelling and the use of specially calibrated vertically suspended tapes. The analysis of the vertical loops is performed using constrained variance estimation and `robust` inter-epoch comparison. (orig.)

  12. Determination of station positions and velocities from laser ranging observations to Ajisai, Starlette and Stella satellites

    Science.gov (United States)

    Lejba, P.; Schillak, S.

    2011-02-01

    The positions and velocities of the four Satellite Laser Ranging (SLR) stations: Yarragadee (7090), Greenbelt (7105), Graz (7839) and Herstmonceux (7840) from 5-year (2001-2005) SLR data of low orbiting satellites (LEO): Ajisai, Starlette and Stella were determined. The orbits of these satellites were computed from the data provided by 20 SLR stations. All orbital computations were performed by means of NASA Goddard’s GEODYN-II program. The geocentric coordinates were transformed to the topocentric North-South, East-West and Vertical components in reference to ITRF2005. The influence of the number of normal points per orbital arc and the empirical acceleration coefficients on the quality of station coordinates was studied. To get standard deviation of the coordinates determination lower than 1 cm, the number of the normal points per site had to be greater than 50. The computed positions and velocities were compared to those derived from LAGEOS-1/LAGEOS-2 data. Three parameters were used for this comparison: station coordinates stability, differences from ITRF2005 positions and velocities. The stability of coordinates of LEO satellites is significantly worse (17.8 mm) than those of LAGEOS (7.6 mm), the better results are for Ajisai (15.4 mm) than for Starlette/Stella (20.4 mm). The difference in positions between the computed values and ITRF2005 were little bit worse for Starlette/Stella (6.6 mm) than for LAGEOS (4.6 mm), the results for Ajisai were five times worse (29.7 mm) probably due to center of mass correction of this satellite. The station velocities with some exceptions were on the same level (≈1 mm/year) for all satellites. The results presented in this work show that results from Starlette/Stella are better than those from Ajisai for station coordinates determination. We can applied the data from LEO satellites, especially Starlette and Stella for determination of the SLR station coordinates but with two times lower accuracy than when using LAGEOS

  13. A study of the river velocity measurement techniques and analysis methods

    Science.gov (United States)

    Chung Yang, Han; Lun Chiang, Jie

    2013-04-01

    Velocity measurement technology can be traced back to the pitot tube velocity measurement method in the 18th century and today's velocity measurement technology use the acoustic and radar technology, with the Doppler principle developed technology advances, in order to develop the measurement method is more suitable for the measurement of velocity, the purpose is to get a more accurate measurement data and with the surface velocity theory, the maximum velocity theory and the indicator theory to obtain the mean velocity. As the main research direction of this article is to review the literature of the velocity measurement techniques and analysis methods, and to explore the applicability of the measurement method of the velocity measurement instruments, and then to describe the advantages and disadvantages of the different mean velocity profiles analysis method. Adequate review of the references of this study will be able to provide a reference for follow-up study of the velocity measurement. Review velocity measurement literature that different velocity measurement is required to follow the different flow conditions measured be upgraded its accuracy, because each flow rate measurement method has its advantages and disadvantages. Traditional velocity instrument can be used at low flow and RiverRAD microwave radar or imaging technology measurement method may be applied in high flow. In the tidal river can use the ADCP to quickly measure river vertical velocity distribution. In addition, urban rivers may be used the CW radar to set up on the bridge, and wide rivers can be used RiverRAD microwave radar to measure the velocities. Review the relevant literature also found that using Ultrasonic Doppler Current Profiler with the Chiu's theory to the velocity of observing automation work can save manpower and resources to improve measurement accuracy, reduce the risk of measurement, but the great variability of river characteristics in Taiwan and a lot of drifting floating

  14. Coastal Vertical Land motion in the German Bight

    Science.gov (United States)

    Becker, Matthias; Fenoglio, Luciana; Reckeweg, Florian

    2017-04-01

    In the framework of the ESA Sea Level Climate Change Initiative (CCI) we analyse a set of GNSS equipped tide gauges at the German Bight. Main goals are the determination of tropospheric zenith delay corrections for altimetric observations, precise coordinates in ITRF2008 and vertical land motion (VLM) rates of the tide gauge stations. These are to be used for georeferencing the tide gauges and the correction of tide gauge observations for VLM. The set of stations includes 38 GNSS stations. 19 stations are in the German Bight, where 15 of them belong to the Bundesanstalt für Gewässerkunde, 3 to EUREF and 1 to GREF. These stations are collocated with tide gauges (TGs). The other 19 GNSS stations in the network belong to EUREF, IGS and GREF. We analyse data in the time span from 2008 till the end of 2016 with the Bernese PPP processing approach. Data are partly rather noisy and disturbed by offsets and data gaps at the coastal TG sites. Special effort is therefore put into a proper estimation of the VLM. We use FODITS (Ostini2012), HECTOR (Bos et al, 2013), CATS (Williams, 2003) and the MIDAS approach of Blewitt (2016) to robustly derive rates and realistic error estimates. The results are compared to those published by the European Permanent Network (EPN), ITRF and the Système d'Observation du Niveau des Eaux Littorales (SONEL) for common stations. Vertical motion is small in general, at the -1 to -2 mm/yr level for most coastal stations. A comparison of the standard deviations of the velocity differences to EPN with the mean values of the estimated velocity standard deviations for our solution shows a very good agreement of the estimated velocities and their standard deviations with the reference solution from EPN. In the comparison with results by SONEL the standard deviation of the differences is slightly higher. The discrepancies may arise from differences in the time span analyzed and gaps, offsets and data preprocessing. The combined estimation of functional

  15. ?Vertical Sextants give Good Sights?

    Science.gov (United States)

    Richey, Michael

    Mark Dixon suggests (Forum, Vol. 50, 137) that nobody thus far has attempted to quantify the errors from tilt that arise while observing with the marine sextant. The issue in fact, with the related problem of what exactly is the axis about which the sextant is rotated whilst being (to define the vertical), was the subject of a lively controversy in the first two volumes of this Journal some fifty years ago. Since the consensus of opinion seems to have been that the maximum error does not necessarily occur at 45 degrees, whereas Dixon's table suggests that it does, some reiteration of the arguments may be in order.

  16. BATCH SETTLING IN VERTICAL SETTLERS

    OpenAIRE

    Lama Ramirez, R.; Universidad Nacional Mayor De San Marcos Facultad de Química e Ingeniería Química Departamento de Operaciones Unitarias Av. Venezuela cdra. 34 sin, Lima - Perú; Condorhuamán Ccorimanya, C.; Universidad Nacional Mayor De San Marcos Facultad de Química e Ingeniería Química Departamento de Operaciones Unitarias Av. Venezuela cdra. 34 sin, Lima - Perú

    2014-01-01

    lt has been studied the batch sedimentation of aqueous suspensions of precipitated calcium carbonate, barium sulphate and lead oxide , in vertical thickeners of rectangular and circular cross sectional area. Suspensions vary in concentration between 19.4 and 617.9 g/I and the rate of sedimentation obtained between 0.008 and 7.70 cm/min. The effect of the specific gravity of the solid on the rate of sedimentation is the same for all the suspensions, that is, the greater the value of the specif...

  17. Binocular responses and vertical strabismus

    Directory of Open Access Journals (Sweden)

    Risović Dušica

    2007-01-01

    Full Text Available Background/Aim. Elevation in adduction is the most common pattern of vertical strabismus, and it is mostly treated with surgery. The results of weaking of inferior oblique muscle are very changeable. The aim of this study was to evaluate binocular vision using sensory tests before and one and six months after the surgery. Methods. A total of 79 children were divided in two groups: the first, with inferior oblique muscle of overaction (n = 52, and the second with dissociated vertical deviation (DVD, and primary inferior oblique muscle overaction (n = 27. We tested them by polaroid mirror test (PMT, Worth test at distance and near, fusion amplitudes on sinoptofore, Lang I stereo test and Wirt-Titmus stereo test. We examined our patients before and two times after the surgery for vertical strabismus. Results. Foveal suppression in the group I was found in 60.5% of the patients before, and in 56.4% after the surgery. In group II Foveal suppression was detected in 64.7% of the patients before, but in 55.6% 6 months after the surgery with PMT. Worth test revealed suppression in 23.5% of the patients before, and in 40.7% after the vertical muscle surgery. Parafoveal fussion persisted in about 1/3 of the patients before the surgery, and their amplitudes were a little larger after the surgery in the group I patients. Lang I stereo test was negative in 53.9% before and 51.9% after the surgery in the group I, and in 48.2% of the patients before and after the surgery in the group II patients. Wirt-Titmus stereo test was negative in 74.5% of the patients before and in 72.9% after the surgery in the group I, but in the group II it was negative in 70.8% before and in 68.0% of the patients 6 months after the surgery. Conclusion. Binocular responses were found after surgery in 65.7% of the patients the group I and in 55.6% patients the group II. There was no significant difference between these two groups, but binocular responses were more often in the patients

  18. A novel velocity estimator using multiple frequency carriers

    DEFF Research Database (Denmark)

    Zhang, Zhuo; Jakobsson, Andreas; Nikolov, Svetoslav

    2004-01-01

    Most modern ultrasound scanners use the so-called pulsed-wave Doppler technique to estimate the blood velocities. Among the narrowband-based methods, the autocorrelation estimator and the Fourier-based method are the most commonly used approaches. Due to the low level of the blood echo, the signal...

  19. The microflown : a true particle velocity microphone; sound intensity application

    NARCIS (Netherlands)

    de Bree, H.E.

    1998-01-01

    The Microflown is world's first particle velocity microphone that enables numerous new acoustical applications, due to the combination of its unique acoustical performance and small dimensions. Several patents have been granted since its invention in 1994. This abstract will focus on one

  20. Movement velocity vs. strength training

    Directory of Open Access Journals (Sweden)

    Mário C. Marques

    2017-06-01

    practice in strength training, but increasing evidence (Sanborn et al., 2000; Folland et al., 2002; Izquierdo et al., 2006; Drinkwater et al., 2007 shows that training to repetition failure does not necessarily produce better strength gains and that may even be counterproductive by inducing excessive fatigue, mechanical and metabolic strain (Fry, 2004. In fact, fatigue associated with training to failure not only significantly reduces the force that a muscle can generate, but also the nervous system’s ability to voluntarily activate the muscles (Häkkinen, 1993. Consequently, this approach, besides being very tiring and having shown no advantage over other lower effort types of training, it is unrealistic because it is practically impossible to know exactly how many repetitions can be done with a given absolute load without any initial reference. In addition, if in the first set the subject has completed the maximum number of repetitions, it will be very difficult or even impossible to perform properly the same number of reps in the following sets. Movement velocity is another variable which could be of great interest for monitoring exercise intensity, but surprisingly it has been vaguely mentioned in most studies to date. The importance that monitoring movement velocity for strength training programming have already been noticed in 1991 (González-Badillo, 1991. More recently, González-Badillo and Sánchez-Medina (2010, 2011 studied this hypothesis and confirmed that movement velocity provides as a determinant of the level of effort during resistance training as well as an indicator of the degree of fatigue. Unfortunately, the lack of use of this variable is likely because until recently it was not possible to accurately measure velocity in isoinertial strength training exercises/movements.  Indeed, most research that has addressed movement velocity in strength training was basically conducted using isokinetic apparatus which, unfortunately, is not an ideal or common

  1. Gestation and the evolution of vertical stance bipedal humans

    Directory of Open Access Journals (Sweden)

    D.S. Robertson

    2011-12-01

    Full Text Available During mammalian gestation a change in maternal stance alters the velocities of maternal blood flows and results in a changed rate of delivery and distribution of nutrients required to form the bone and tissue in various parts of a developing foetus. The latter in turn results in change in the extent and position of tissue and bone formation in the foetus. It is shown that such changes would, over many generations, alter the physical characteristics of the ancestor offspring under conditions where the pregnant maternal ancestor normally exhibiting horizontal stance was constrained to adopt a vertical stance for all or most of the gestation period. This behaviour produced the physical characteristics seen in humans and other Hominidae primates, including the vertical stance and bipedalism of the former accompanied by increase in skull and brain size. The manner in which difficulties of giving birth as the change from horizontal stance to vertical stance proceeded from generation to generation, limited survival is discussed andreasons for the adoption of this behaviour are proposed. The induction of evolutionary change and the operation of natural selection through alterations in the characteristics of embryo/foetus of an animal, induced by physical, chemical, mechanical or behavioural means, is shown to be feasible. The changes are not related to the Lamarckian principle of inheritance of acquired characteristics as the changes described occurred before birth and are not related to any physical or mental characteristics already present in or acquired during the lifetime of the breeding pair.

  2. Design analysis of vertical wind turbine with airfoil variation

    Science.gov (United States)

    Maulana, Muhammad Ilham; Qaedy, T. Masykur Al; Nawawi, Muhammad

    2016-03-01

    With an ever increasing electrical energy crisis occurring in the Banda Aceh City, it will be important to investigate alternative methods of generating power in ways different than fossil fuels. In fact, one of the biggest sources of energy in Aceh is wind energy. It can be harnessed not only by big corporations but also by individuals using Vertical Axis Wind Turbines (VAWT). This paper presents a three-dimensional CFD analysis of the influence of airfoil design on performance of a Darrieus-type vertical-axis wind turbine (VAWT). The main objective of this paper is to develop an airfoil design for NACA 63-series vertical axis wind turbine, for average wind velocity 2,5 m/s. To utilize both lift and drag force, some of designs of airfoil are analyzed using a commercial computational fluid dynamics solver such us Fluent. Simulation is performed for this airfoil at different angles of attach rearranging from -12°, -8°, -4°, 0°, 4°, 8°, and 12°. The analysis showed that the significant enhancement in value of lift coefficient for airfoil NACA 63-series is occurred for NACA 63-412.

  3. Soret and dufour effects on free convection flow of a couple stress fluid in a vertical channel with chemical reaction

    OpenAIRE

    Srinivasacharya D.; Kaladhar K.

    2013-01-01

    The Soret and Dufour effects in the presence of chemical reaction on natural convection heat and mass transfer of a couple stress fluid in a vertical channel formed by two vertical parallel plates is presented. The governing non-linear partial differential equations are transformed into a system of ordinary differential equations using similarity transformations. The resulting equations are then solved using Homotopy Analysis Method (HAM). Profiles of dimensionless velocity, temperature...

  4. Three-dimensional surface velocities of Storstrømmen glacier, Greenland, derived from radar interferometry and ice-sounding radar measurements

    DEFF Research Database (Denmark)

    Reeh, Niels; Mohr, Johan Jacob; Madsen, Søren Nørvang

    2003-01-01

    in substantial errors (up to 20%) also on the south-north component of horizontal velocities derived by satellite synthetic aperture radar interferometry (InSAR) measurements. In many glacier environments, the steady-state vertical velocity component required to balance the annual ablation rate is 5-10 m a(-1...... tracks with airborne ice-sounding radar measurement of ice thickness. The results are compared to InSAR velocities previously derived by using the SPF assumption, and to velocities obtained by in situ global positioning system (GPS) measurements. The velocities derived by using the MC principle...

  5. Convective flow, heat and mass transfer of Ostwald-de Waele fluid over a vertical stretching sheet

    Directory of Open Access Journals (Sweden)

    K. Vajravelu

    2017-01-01

    Full Text Available In this paper we study the combined buoyancy (due to thermal and species diffusion effects on the flow, heat and mass transfer of a viscous, incompressible, Ostwald-de Waele fluid over a vertical stretching surface in the presence of a chemical reaction. The effects of variable thermal conductivity and the variable mass diffusivity are also considered. A similarity transformation is used to convert the partial differential equations into coupled nonlinear ordinary differential equations. Numerical solutions are obtained by the Keller-box method. The influences of sundry parameters on the velocity, temperature and the concentration fields are presented in figures and discussed in detail. The values of the skin friction coefficient, Nusselt number and the surface mass transfer for various values of the governing parameters are presented in tables. One of the interesting observations is that the influence of the buoyancy parameters increases the velocity. However, quite the opposite is true with the temperature and the mass concentration, for all values of the power law index and the reaction rate parameter. The results obtained reveal many interesting behaviors that warrant a further study of the non-Newtonian fluid phenomena, especially shear thinning phenomena. Shear thinning reduces the wall shear stress.

  6. A comparison of two landing styles in a two-foot vertical jump.

    Science.gov (United States)

    Gutiérrez-Davila, Marcos; Campos, José; Navarro, Enrique

    2009-01-01

    In team sports, such as basketball and volleyball, the players use different takeoff styles to make the vertical jump. The two-foot vertical jump styles have been classified according to the landing style and identified as hop style, when both feet touch the ground at the same time, and step-close style, when there is a slight delay between the first and second foot making contact with the ground. The aim of this research is to identify the differences between the two styles. Twenty-three subjects participated in the study, of whom 14 were volleyball players and 9 were basketball players. The jumps were video recorded and synchronized with two force platforms at 250 Hz. Two temporal periods of the takeoff were defined according to the reduction or increase in the radial distance between the center of gravity (CG) and the foot support (T - RDCG and T + RDCG, respectively). The findings produced no specific advantages when both styles were compared with respect to takeoff velocity and, consequently, to jump height, but takeoff time was significantly shorter (p vertical velocity of CG at the beginning of the takeoff is significantly lower. Moreover, the mean vertical force developed during T - RDCG was reduced by -627.7 +/- 251.1 N, thus lessening impact on landing. Horizontal velocity at the end of the takeoff is less when the step-close style is used (p jumps where it is necessary to move horizontally during the flight against an opponent.

  7. DESIGN AND DEVELOPMENT OF A 1/3 SCALE VERTICAL AXIS WIND TURBINE FOR ELECTRICAL POWER GENERATION

    OpenAIRE

    Altab Hossain; A.K.M.P. Iqbal; Ataur Rahman; M. Arifin; M. Mazian

    2007-01-01

    This research describes the electrical power generation in Malaysia by the measurement of wind velocity acting on the wind turbine technology. The primary purpose of the measurement over the 1/3 scaled prototype vertical axis wind turbine for the wind velocity is to predict the performance of full scaled H-type vertical axis wind turbine. The electrical power produced by the wind turbine is influenced by its two major part, wind power and belt power transmission system. The blade and the drag...

  8. Ultrasonic Measurement of Velocity Profile on Bubbly Flow Using Fast Fourier Transform (FFT) Technique

    Science.gov (United States)

    Wongsaroj, W.; Hamdani, A.; Thong-un, N.; Takahashi, H.; Kikura, H.

    2017-10-01

    In two-phase bubbly flow, measurement of liquid and bubble velocity is a necessity to understand fluid characteristic. The conventional ultrasonic velocity profiler (UVP), which has been known as a nonintrusive measurement technique, can measure velocity profile of liquid and bubble simultaneously by applying a separation technique for both phases (liquid and bubble) and transparent test section is unnecessary. The aim of this study was to develop a new technique for separating liquid and bubble velocity data in UVP method to measure liquid and bubble velocity profiles separately. The technique employs only single resonant frequency transducer and a simple UVP system. An extra equipment is not required. Fast Fourier Transform (FFT) based frequency estimator paralleled with other signal processing techniques, which is called as proposed technique, was proposed to measure liquid and bubble velocity separately. The experimental facility of two-phase bubbly flow in the vertical pipe was constructed. Firstly, the Doppler frequency estimation by using the FFT technique was evaluated in single-phase liquid flow. Results showed that FFT technique showed a good agreement with autocorrelation and maximum likelihood estimator. Then, separation of liquid and bubble velocity was demonstrated experimentally in the two-phase bubbly flow. The proposed technique confirmed that liquid and bubble velocity could be measured efficiently.

  9. Throwing velocity and jump height in female water polo players: performance predictors.

    Science.gov (United States)

    McCluskey, Lisa; Lynskey, Sharon; Leung, Chak Kei; Woodhouse, Danielle; Briffa, Kathy; Hopper, Diana

    2010-03-01

    Throwing velocity and vertical jumping ability are essential components for shooting and passing in water polo. The purpose of this study was to determine whether there is a relationship between throwing velocity and water jump height in highly skilled female water polo players. Throwing velocity and head height at ball release were measured in twenty-two female players (age 20.41 years (6.16); weight 68.28 kg (8.87)) with two 50 frames per second cameras while shooting at goal. Water jump height was also measured with a modified Yardstick device. Multiple regression analyses showed that peak lower limb power was the most significant predictor of maximal velocity. Power alone accounted for 62% of the variance in maximum velocity (pheight and anthropometry) made a significant contribution to throwing velocity. After controlling for the effect of power, head height at ball release accounted for an additional significant proportion of the variance in maximal velocity (R(2) change 7%; p=0.049). Lower body power was a significant predictor of higher throwing velocity in highly skilled female water polo players. Players with relatively higher underlying levels of lower limb power who are able to generate greater elevation out of the water are able to throw the ball faster. Copyright 2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  10. Vertically stacked nanocellulose tactile sensor.

    Science.gov (United States)

    Jung, Minhyun; Kim, Kyungkwan; Kim, Bumjin; Lee, Kwang-Jae; Kang, Jae-Wook; Jeon, Sanghun

    2017-11-16

    Paper-based electronic devices are attracting considerable attention, because the paper platform has unique attributes such as flexibility and eco-friendliness. Here we report on what is claimed to be the firstly fully integrated vertically-stacked nanocellulose-based tactile sensor, which is capable of simultaneously sensing temperature and pressure. The pressure and temperature sensors are operated using different principles and are stacked vertically, thereby minimizing the interference effect. For the pressure sensor, which utilizes the piezoresistance principle under pressure, the conducting electrode was inkjet printed on the TEMPO-oxidized-nanocellulose patterned with micro-sized pyramids, and the counter electrode was placed on the nanocellulose film. The pressure sensor has a high sensitivity over a wide range (500 Pa-3 kPa) and a high durability of 10(4) loading/unloading cycles. The temperature sensor combines various materials such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), silver nanoparticles (AgNPs) and carbon nanotubes (CNTs) to form a thermocouple on the upper nanocellulose layer. The thermoelectric-based temperature sensors generate a thermoelectric voltage output of 1.7 mV for a temperature difference of 125 K. Our 5 × 5 tactile sensor arrays show a fast response, negligible interference, and durable sensing performance.

  11. Upper-crustal velocity structure along 150 km of the Mendeleev Ridge from tomographic inversion of long-offset refraction data collected during HLY0602

    Science.gov (United States)

    Vermeesch, P. M.; van Avendonk, H. J.; Lawver, L. A.

    2007-12-01

    In the summer of 2006 we acquired a unique seismic refraction data set on the Chukchi Borderlands and Mendeleev Ridge utilizing USCGC Healy and two helicopters. The array on the Mendeleev Ridge consisted of 14 instrument sites with 12 km spacing between instruments. On every site we deployed a Sea-Ice Seismometer (S- IS) especially designed for this experiment in the ice-covered part of the Arctic Ocean. Each S-IS contained a vertical component geophone that was buried in the ice and a hydrophone that was hanging from the ice edge in the water. From the 14 instrument sites, 10 contained useful data with refracted crustal arrivals up to offsets of 40 km. Because of extensive drifting of the receivers (40 km in 5 days and containing numerous loops), and because of the irregular geometry of airgun shots due to the problems of sailing through ice-covered seas, a 3D ray-shooting code was developed to calculate ray paths within a 3D velocity model that extends along 150 km in the X- direction and along 35 km in the Y-direction. Using the velocity model proposed by Lebedeva-Ivanova et al. (2006) we observe that the maximum depth of our calculated ray paths is 11 km below sealevel. Using all the available data, the Root Mean Square (RMS) difference between observed and calculated travel-times is of the order of 500 ms. Initially a simple 1D travel-time inversion was developed to constrain the velocity structure of the basement underneath a layer of water (3D) and a layer of sediment (1D). This inversion was carried out on 2 pairs of receivers: one pair in the NNE and one more towards the SSW part of the line. Inversion of S-IS 45N-42 (NNE) results in a model with a velocity of 5.5 km s-1 at the top of the basement, slowly increasing to a velocity of 5.7 km s-1 at 3 km below the top of the basement (RMS = 117 ms). Inversion of S-IS 49-45S (SSW) results in a model with a velocity of 4.8 km s-1 at the top of the basement, increasing to a velocity of 5.9 km s-1 at 3 km below

  12. Decreased Nerve Conduction Velocity in Football Players

    Directory of Open Access Journals (Sweden)

    Daryoush Didehdar

    2014-06-01

    Full Text Available Background: Lower limbs nerves are exposed to mechanical injuries in the football players and the purpose of this study is to evaluate the influence of football on the lower leg nerves. Materials and Methods: Nerve conduction studies were done on 35 male college students (20 football players, 15 non active during 2006 to 2007 in the Shiraz rehabilitation faculty. Standard nerve conduction techniques using to evaluate dominant and non dominant lower limb nerves. Results: The motor latency of deep peroneal and tibial nerves of dominant leg of football players and sensory latency of superficial peroneal, tibial and compound nerve action potential of tibial nerve of both leg in football players were significantly prolonged (p<0.05. Motor and sensory nerve conduction velocity of tibial and common peroneal in football players were significant delayed (p<0.05. Conclusion: It is concluded that football is sport with high contact and it causes sub-clinical neuropathies due to nerve entrapment.

  13. Modal Parameter Identification of New Design of Vertical Axis Wind Turbine

    DEFF Research Database (Denmark)

    Chougule, Prasad; Nielsen, Søren R.K.

    2013-01-01

    Vertical axis wind turbines have lower power efficiency than the horizontal axis wind turbines. However vertical axis wind turbines are proven to be economical and noise free on smaller scale. A new design of three bladed vertical axis wind turbine by using two airfoils in construction of each...... blade has been proposed to improve power efficiency. The purpose of two airfoils in blade design of vertical axis wind turbine is to create high lift which in turns gives higher power output. In such case the structural parameter identification is important to understand the system behavior due to its...... first kind of design before experimental analysis. Therefore a study is carried out to determine the natural frequency to avoid unstable state of the system due to rotational frequency of rotor. The present paper outlines a conceptual design of vertical axis wind turbine and a modal analysis by using...

  14. Free convective flow of a stratified fluid through a porous medium bounded by a vertical plane

    Directory of Open Access Journals (Sweden)

    H. K. Mondal

    1994-01-01

    Full Text Available Steady two-dimensional free convection flow of a thermally stratified viscous fluid through a highly porous medium bounded by a vertical plane surface of varying temperature, is considered. Analytical expressions for the velocity, temperature and the rate of heat transfer are obtained by perturbation method. Velocity distribution and rate of heat transfer for different values of parameters are shown in graphs. Velocity distribution is also obtained for certain values of the parameters by integrating the coupled differential equations by Runge-Kutta method and compared with the analytical solution. The chief concern of the paper is to study the effect of equilibrium temperature gradient on the velocity and the rate of heat transfer.

  15. Effects of parabolic motion on an isothermal vertical plate with constant mass flux

    Directory of Open Access Journals (Sweden)

    R. Muthucumaraswamy

    2014-12-01

    Full Text Available An analytical study of free convection flow near a parabolic started infinite vertical plate with isothermal in the presence of uniform mass flux was considered. The mathematical model is reduced to a system of linear partial differential equations for the velocity, the concentration and the temperature; the closed form exact solutions were obtained by the Laplace transform technique. The velocity, temperature and concentration profiles for the different parameters as thermal Grashof number Gr, mass Grashof number Gc, Prandtl number Pr, Schmidt number Sc and time t were graphed and the numerical values for the skin friction were as tabulated. It is observed that the velocity is enhanced as the time increased and the velocity is decreased as the Prandtl number increased.

  16. Initial velocity V-shapes of young asteroid families

    Science.gov (United States)

    Bolin, Bryce T.; Walsh, Kevin J.; Morbidelli, Alessandro; Delbó, Marco

    2018-01-01

    Ejection velocity fields of asteroid families are largely unconstrained due to the fact that members disperse relatively quickly on Myr time-scales by secular resonances and the Yarkovsky effect. The spreading of fragments in a by the Yarkovsky effect is indistinguishable from the spreading caused by the initial ejection of fragments. By examining families Asteroid families that are asteroid families including the 1993 FY12, Aeolia, Brangane, Brasilia, Clarissa, Iannini, Karin, Konig, Koronis(2), Theobalda and Veritas asteroid families. We find that the majority of asteroid families have initial ejection velocity fields consistent with ∼D-1 supporting laboratory impact experiments and computer simulations of disrupting asteroid parent bodies.

  17. Ultrasonic velocity and adiabatic compressibility in dioxane-water mixtures

    Science.gov (United States)

    Ciupe, A.; Auslaender, D.

    1974-01-01

    Using a method of diffraction of light on an ultrasonic beam, the velocity of ultrasounds and the adiabatic compressibility in dioxane-water mixtures were determined. The dependence of these quantities on the temperature (in the 15-50 C range) and on the concentration (0-100%) were studied. For each temperature there was found a velocity maximum and a compressibility minimum for a given value of the dioxane concentration. The different behavior of these mixtures is due to intense interactions between the molecules of the two liquids composing the mixture.

  18. Volume-of-fluid simulations of bubble dynamics in a vertical Hele-Shaw cell

    Science.gov (United States)

    Wang, Xue; Klaasen, Bart; Degrève, Jan; Mahulkar, Amit; Heynderickx, Geraldine; Reyniers, Marie-Françoise; Blanpain, Bart; Verhaeghe, Frederik

    2016-05-01

    Bubbles in confined geometries serve an important role for industrial operations involving bubble-liquid interactions. However, high Reynolds number bubble dynamics in confined flows are still not well understood due to experimental challenges. In the present paper, combined experimental and numerical methods are used to provide a comprehensive insight into these dynamics. The bubble behaviour in a vertical Hele-Shaw cell is investigated experimentally with a fully wetting liquid for a variety of gap thicknesses. A numerical model is developed using the volume of fluid method coupled with a continuum surface force model and a wall friction model. The developed model successfully simulates the dynamics of a bubble under the present experimental conditions and shows good agreement between experimental and simulation results. It is found that with an increased spacing between the cell walls, the bubble shape changes from oblate ellipsoid and spherical-cap to more complicated shapes, while the bubble path changes from only rectilinear to a combination of oscillating and rectilinear; the bubble drag coefficient decreases and this results in a higher bubble velocity caused by a lower pressure exerted on the bubble; the wake boundary and wake length evolve gradually accompanied by vortex formation and shedding.

  19. Natural Convection Flow along an Isothermal Vertical Flat Plate with Temperature Dependent Viscosity and Heat Generation

    Directory of Open Access Journals (Sweden)

    Md. Mamun Molla

    2014-01-01

    Full Text Available The purpose of this study is to investigate the natural convection laminar flow along an isothermal vertical flat plate immersed in a fluid with viscosity which is the exponential function of fluid temperature in presence of internal heat generation. The governing boundary layer equations are transformed into a nondimensional form and the resulting nonlinear system of partial differential equations is reduced to a convenient form which are solved numerically using an efficient marching order implicit finite difference method with double sweep technique. Numerical results are presented in terms of the velocity and temperature distribution of the fluid as well as the heat transfer characteristics, namely, the wall shear stress and the local and average rate of heat transfer in terms of the local skin-friction coefficient, the local and average Nusselt number for a wide range of the viscosity-variation parameter, heat generation parameter, and the Rayleigh number. Increasing viscosity variation parameter and Rayleigh number lead to increasing the local and average Nusselt number and decreasing the wall shear stress. Wall shear stress and the rate of heat transfer decreased due to the increase of heat generation.

  20. Wind tunnel study of a vertical axis wind turbine in a turbulent boundary layer flow

    Science.gov (United States)

    Rolin, Vincent; Porté-Agel, Fernando

    2015-04-01

    Vertical axis wind turbines (VAWTs) are in a relatively infant state of development when compared to their cousins the horizontal axis wind turbines. Very few studies have been carried out to characterize the wake flow behind VAWTs, and virtually none to observe the influence of the atmospheric boundary layer. Here we present results from an experiment carried out at the EPFL-WIRE boundary-layer wind tunnel and designed to study the interaction between a turbulent boundary layer flow and a VAWT. Specifically we use stereoscopic particle image velocimetry to observe and quantify the influence of the boundary layer flow on the wake generated by a VAWT, as well as the effect the VAWT has on the boundary layer flow profile downstream. We find that the wake behind the VAWT is strongly asymmetric, due to the varying aerodynamic forces on the blades as they change their position around the rotor. We also find that the wake adds strong turbulence levels to the flow, particularly on the periphery of the wake where vortices and strong velocity gradients are present. The boundary layer is also shown to cause greater momentum to be entrained downwards rather than upwards into the wake.

  1. Simulations of Vertical Axis Wind Turbine Farms in the Atmospheric Boundary Layer

    Science.gov (United States)

    Hezaveh, Seyed Hossein; Bou-Zeid, Elie; Lohry, Mark; Martinelli, Luigi

    2014-11-01

    Wind power is an abundant and clean source of energy that is increasingly being tapped to reduce the environmental footprint of anthropogenic activities. The vertical axis wind turbine (VAWT) technology is now being revisited due to some important advantages over horizontal axis wind turbines (HAWTS) that are particularly important for farms deployed offshore or in complex terrain. In this talk, we will present the implementation and testing of an actuator line model (ALM) for VAWTs in a large eddy simulation (LES) code for the atmospheric boundary layer, with the aim of optimizing large VAWT wind farm configurations. The force coefficients needed for the ALM are here obtained from blade resolving RANS simulations of individual turbines for each configuration. Comparison to various experimental results show that the model can very successfully reproduce observed wake characteristic. The influence of VAWT design parameters such as solidity, height to radius ratio, and tip speed ratio (TSR) on these wake characteristics, particularly the velocity deficit profile, is then investigated.

  2. Further development of the attitude difference method for estimating deflections of the vertical in real time

    Science.gov (United States)

    Zhu, Jing; Zhou, Zebo; Li, Yong; Rizos, Chris; Wang, Xingshu

    2016-07-01

    An improvement of the attitude difference method (ADM) to estimate deflections of the vertical (DOV) in real time is described in this paper. The ADM without offline processing estimates the DOV with a limited accuracy due to the response delay. The proposed model selection-based self-adaptive delay feedback (SDF) method takes the results of the ADM as the a priori information, then uses fitting and extrapolation to estimate the DOV at the current epoch. The active region selection factor F th is used to take full advantage of the Earth model EGM2008 and the SDF with different DOV exhibitions. The factors which affect the DOV estimation accuracy are analyzed and modeled. An external observation which is specified by the velocity difference between the global navigation satellite system (GNSS) and the inertial navigation system (INS) with DOV compensated is used to select the optimal model. The response delay induced by the weak observability of an integrated INS/GNSS to the violent DOV disturbances in the ADM is compensated. The DOV estimation accuracy of the SDF method is improved by approximately 40% and 50% respectively compared to that of the EGM2008 and the ADM. With an increase in GNSS accuracy, the DOV estimation accuracy could improve further.

  3. Concentration and vertical distribution of 137Cs in the undisturbed soil of southwestern Nigeria.

    Science.gov (United States)

    Ajayi, I R; Fischer, H W; Burak, A; Qwasmeh, A; Tabot, B

    2007-01-01

    The results of measurements of 137Cs in soil profiles that were sampled in undisturbed soil in Ondo, Ekiti, and Oyo states in the southwestern area of Nigeria are presented in this paper. Samples were collected from nine soil profiles. The vertical distributions of 137Cs in the soil profiles have been determined. Cesium concentration ranged from 0.31 +/- 0.10 Bq kg(-1) in the 0-2 cm depth to a maximum of 1.25 +/- 0.21 Bq kg(-1) in the 6-8 cm depth at some sites and from 3.16 +/- 0.16 Bq kg(-1) in 0-5 cm depth to below detection limit (BDL) at 20-25 cm at another site. 137Cs total deposition in 0-10 cm depth was found to be greatest at Ikogosi site with a value of 90.30 Bq m(-2). The results generally showed that more than 40 y after the first nuclear weapon tests, 137Cs still remains within the 25 cm upper layer of soil in the region with a migration velocity of 0.17-0.18 cm y(-1). The mean value of effective dose commitment due to the presence of cesium in soil in the entire region was found to be 10.77 microSv.

  4. Capillary holdup between vertical spheres

    Directory of Open Access Journals (Sweden)

    S. Zeinali Heris

    2009-12-01

    Full Text Available The maximum volume of liquid bridge left between two vertically mounted spherical particles has been theoretically determined and experimentally measured. As the gravitational effect has not been neglected in the theoretical model, the liquid interface profile is nonsymmetrical around the X-axis. Symmetry in the interface profile only occurs when either the particle size ratio or the gravitational force becomes zero. In this paper, some equations are derived as a function of the spheres' sizes, gap width, liquid density, surface tension and body force (gravity/centrifugal to estimate the maximum amount of liquid that can be held between the two solid spheres. Then a comparison is made between the result based on these equations and several experimental results.

  5. Vertical air motion retrievals in deep convective clouds using the ARM scanning radar network in Oklahoma during MC3E

    Science.gov (United States)

    North, Kirk W.; Oue, Mariko; Kollias, Pavlos; Giangrande, Scott E.; Collis, Scott M.; Potvin, Corey K.

    2017-08-01

    The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Southern Great Plains (SGP) site includes a heterogeneous distributed scanning Doppler radar network suitable for collecting coordinated Doppler velocity measurements in deep convective clouds. The surrounding National Weather Service (NWS) Next Generation Weather Surveillance Radar 1988 Doppler (NEXRAD WSR-88D) further supplements this network. Radar velocity measurements are assimilated in a three-dimensional variational (3DVAR) algorithm that retrieves horizontal and vertical air motions over a large analysis domain (100 km × 100 km) at storm-scale resolutions (250 m). For the first time, direct evaluation of retrieved vertical air velocities with those from collocated 915 MHz radar wind profilers is performed. Mean absolute and root-mean-square differences between the two sources are of the order of 1 and 2 m s-1, respectively, and time-height correlations are of the order of 0.5. An empirical sensitivity analysis is done to determine a range of 3DVAR constraint weights that adequately satisfy the velocity observations and anelastic mass continuity. It is shown that the vertical velocity spread over this range is of the order of 1 m s-1. The 3DVAR retrievals are also compared to those obtained from an iterative upwards integration technique. The results suggest that the 3DVAR technique provides a robust, stable solution for cases in which integration techniques have difficulty satisfying velocity observations and mass continuity simultaneously.

  6. Relação dos saltos vertical, horizontal e sêxtuplo com a agilidade e velocidade em crianças Relationship of vertical, horizontal and sextuple jumps with agility and speed in children

    Directory of Open Access Journals (Sweden)

    Diogo Henrique Constantino Coledam

    2013-03-01

    Full Text Available Os objetivos do presente estudo foram: 1 verificar a relação dos saltos vertical, horizontal e sêxtuplo com a agilidade e velocidade de 5, 10 e 25 m; 2 verificar a capacidade desses saltos em predizer o desempenho da agilidade e velocidade de 5, 10 e 25 m em crianças. Vinte e oito meninos (9,47 ± 0,64 anos e 30 meninas (9,69 ± 0,70 anos foram avaliados. Os valores de correlação entre a agilidade, velocidade de 5, 10 e 25 m foram, respectivamente, r = 0,63, 0,51, 0,44 e 0,64 com o salto vertical, r = 0,68, 0,62, 0,28 e 0,62 com o salto sêxtuplo, e r = 0,60, 0,50, 0,26 e 0,57 com o salto horizontal. O salto vertical e o salto sêxtuplo foram capazes de predizer o desempenho da agilidade e da velocidade de 25 m (p The aim of the present study were: 1 To verify the relationship of vertical, horizontal and sextuple jumps with agility and velocity of 5, 10 and 25 m; 2 To verify the capacity of these jumps to predict the agility and 5, 10 and 25 m velocity performance in children. Twenty eight boys (9.47 ± 0.64 years and thirty girls (9.69 ± 0.70 years were evaluated. The correlation values between agility and velocity on 5, 10 and 25 m velocity were, respectively, r = 0.63, 0.51, 0.44 and 0.64 with vertical jump, r = 0.68, 0.62, 0.28 and 0.62 with sextuple jump, and r = 0.60, 0.50, 0.26 and 0.57 with horizontal jump. The vertical and sextuple jumps were able to predict the agility and 25 m velocity performance (p < 0.05. Furthermore, they demonstrated capacity to predict 5 and 10 m velocity, respectively (p < 0.05. The vertical and sextuple jump tests may be used for assessment and control of training with children practicing activities that require agility and velocity, since both jumps predicted the agility and velocity performance, which did not occur with the horizontal jump.

  7. 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....

  8. Characteristics of Wind Velocity and Temperature Change Near an Escarpment-Shaped Road Embankment

    Directory of Open Access Journals (Sweden)

    Young-Moon Kim

    2014-01-01

    Full Text Available Artificial structures such as embankments built during the construction of highways influence the surrounding airflow. Various types of damage can occur due to changes in the wind velocity and temperature around highway embankments. However, no study has accurately measured micrometeorological changes (wind velocity and temperature due to embankments. This study conducted a wind tunnel test and field measurement to identify changes in wind velocity and temperature before and after the construction of embankments around roads. Changes in wind velocity around an embankment after its construction were found to be influenced by the surrounding wind velocity, wind angle, and the level difference and distance from the embankment. When the level difference from the embankment was large and the distance was up to 3H, the degree of wind velocity declines was found to be large. In changes in reference wind velocities around the embankment, wind velocity increases were not proportional to the rate at which wind velocities declined. The construction of the embankment influenced surrounding temperatures. The degree of temperature change was large in locations with large level differences from the embankment at daybreak and during evening hours when wind velocity changes were small.

  9. Hall current effect on radiating span-wise fluctuating MHD convective flow through porous medium in a vertical porous channel

    Directory of Open Access Journals (Sweden)

    Dev Krishan Singh

    2015-01-01

    Full Text Available An analysis of an unsteady MHD convective flow of an electrically conducting viscous incompressible fluid through porous medium filled in a vertical porous channel is carried out. The two porous plates are subjected to a constant injection and suction velocity as shown in Fig. 1a, b. The temperature of the plate at y*= + 9 2 is assumed to be varying in space and time as T*(y*, z*, t* = T1 (y* + (T2 - T1COS (πz*d -ω*t*. A magnetic field of uniform strength is applied perpendicular to the plates of the channel. The temperature difference between the plates is high enough to induce the heat due to radiation. It is also assumed that the conducting fluid is opticallythin gray gas, absorbing/ emitting radiation and non-scattering. The Hall current effects have also been taken into account. Exact solution of the partial differential equations governing the flow under the prescribed boundary conditions has been obtained for the velocity and the temperature fields. The primary and secondary velocities, temperature and the skin-friction and Nusselt number for the rate of heat transfer in terms of their amplitudes and phase angles have been shown graphically to observe the effects of suction parameter λ, Grashof number Gr, Hartmann number M, Hall parameter H, the permeability of the porous medium K, Prandtl number Pr, radiation parameter N, pressure gradient A and the frequency of oscillation ω. The final results are then discussed in detail in the last section of the paper with the help of figures.

  10. Shear-wave velocity structure of the Tongariro Volcanic Centre, New Zealand: Fast Rayleigh and slow Love waves indicate strong shallow anisotropy

    Science.gov (United States)

    Godfrey, Holly J.; Fry, Bill; Savage, Martha K.

    2017-04-01

    frequency range of 0.25-1 Hz. First-higher mode Love-waves are similarly slower than first-higher mode Rayleigh waves. This is incompatible with synthetic dispersion curves we calculate using isotropic, layered velocity models appropriate for Ruapehu and Tongariro, in which Love waves travel more quickly than Rayleigh waves of the same period. The Love-Rayleigh discrepancy is likely due to structures such as dykes or cracks in the vertical plane having increased influence on surface-wave propagation. However, several measurements at Ruapehu have Love-wave group velocities that are faster than Rayleigh-wave group velocities. The differences between the Love- and Rayleigh-wave dispersion curves also vary with the azimuth of the interstation path across Ruapehu and Tongariro Volcanoes. Significant azimuthal dependence of both Love and Rayleigh-wave velocities are also observed. This suggests azimuthal anisotropy within the volcanic structures, which coupled with radial anisotropy, makes the Vs structures of Ruapehu and Tongariro Volcanoes anisotropic with orthorhombic or lower order symmetry. We suggest that further work to determine three-dimensional volcanic structures should include provisions for such anisotropy.

  11. Velocity and Drag Evolution From the Leading Edge of a Model Mangrove Forest

    Science.gov (United States)

    Maza, Maria; Adler, Katherine; Ramos, Diogo; Garcia, Adrian Mikhail; Nepf, Heidi

    2017-11-01

    An experimental study of unidirectional flow through a model mangrove forest measured both velocity and forces on individual trees. The individual trees were 1/12th scale models of mature Rhizophora, including 24 prop roots distributed in a three-dimensional layout. Thirty-two model trees were distributed in a staggered array producing a 2.5 m long forest. The velocity evolved from a boundary layer profile at the forest leading edge to a vertical profile determined by the vertical distribution of frontal area, with significantly higher velocity above the prop roots. Fully developed conditions were reached at the fifth tree row from the leading edge. Within the root zone the velocity was reduced by up to 50% and the TKE was increased by as much as fivefold, relative to the upstream conditions. TKE in the root zone was mainly produced by root and trunk wakes, and it agreed in magnitude with the estimation obtained using the Tanino and Nepf (2008) formulation. Maximum TKE occurred at the top of the roots, where a strong shear region was associated with the change in frontal area. The drag measured on individual trees decreased from the leading edge and reached a constant value at the fifth row and beyond, i.e., in the fully developed region. The drag exhibited a quadratic dependence on velocity, which justified the definition of a quadratic drag coefficient. Once the correct drag length-scale was defined, the measured drag coefficients collapsed to a single function of Reynolds number.

  12. Correlation between spin structure oscillations and domain wall velocities

    Science.gov (United States)

    Bisig, André; Stärk, Martin; Mawass, Mohamad-Assaad; Moutafis, Christoforos; Rhensius, Jan; Heidler, Jakoba; Büttner, Felix; Noske, Matthias; Weigand, Markus; Eisebitt, Stefan; Tyliszczak, Tolek; van Waeyenberge, Bartel; Stoll, Hermann; Schütz, Gisela; Kläui, Mathias

    2013-08-01

    Magnetic sensing and logic devices based on the motion of magnetic domain walls rely on the precise and deterministic control of the position and the velocity of individual magnetic domain walls in curved nanowires. Varying domain wall velocities have been predicted to result from intrinsic effects such as oscillating domain wall spin structure transformations and extrinsic pinning due to imperfections. Here we use direct dynamic imaging of the nanoscale spin structure that allows us for the first time to directly check these predictions. We find a new regime of oscillating domain wall motion even below the Walker breakdown correlated with periodic spin structure changes. We show that the extrinsic pinning from imperfections in the nanowire only affects slow domain walls and we identify the magnetostatic energy, which scales with the domain wall velocity, as the energy reservoir for the domain wall to overcome the local pinning potential landscape.

  13. Measurement of Poloidal Velocity on the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ronald E. Bell and Russell Feder

    2010-06-04

    A diagnostic suite has been developed to measure impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both active emission in the plane of the neutral heating beams and background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent chargeexchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. Local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. Radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.

  14. Motion of Euglena gracilis: Active fluctuations and velocity distribution

    Science.gov (United States)

    Romanczuk, P.; Romensky, M.; Scholz, D.; Lobaskin, V.; Schimansky-Geier, L.

    2015-07-01

    We study the velocity distribution of unicellular swimming algae Euglena gracilis using optical microscopy and active Brownian particle theory. To characterize a peculiar feature of the experimentally observed distribution at small velocities we use the concept of active fluctuations, which was recently proposed for the description of stochastically self-propelled particles [Romanczuk, P. and Schimansky-Geier, L., Phys. Rev. Lett. 106, 230601 (2011)]. In this concept, the fluctuating forces arise due to internal random performance of the propulsive motor. The fluctuating forces are directed in parallel to the heading direction, in which the propulsion acts. In the theory, we introduce the active motion via the depot model [Schweitzer, et al., Phys. Rev. Lett. 80(23), 5044 (1998)]. We demonstrate that the theoretical predictions based on the depot model with active fluctuations are consistent with the experimentally observed velocity distributions. In addition to the model with additive active noise, we obtain theoretical results for a constant propulsion with multiplicative noise.

  15. Variation of Quench Propagation Velocities in YBCO Cables

    CERN Document Server

    Härö, E.; Stenvall, A.; 10.1007/s10948-015-2976-y

    2015-01-01

    changes during the quench. Due to the large temperature margin between the operation and the current sharing temperatures, the normal zone does not propagate with the temperature front. This means that the temperature will rise in a considerably larger volume when compared to the quenched volume. Thus, the evolution of the temperature distribution below current sharing temperature Tcs after the quench onset affects the normal zone propagation velocity in HTS more than in LTS coils. This can be seen as an acceleration of the quench propagation velocities while the quench evolves when margin to Tcs is high. In this paper we scrutinize quench propagation in a stack of YBCO cables with an in-house finite element method software which solves the heat diffusion equation. We compute the longitudinal and transverse normal zone propagation velocities at various distances from the hot spot to demonstrate the distance-variation...

  16. A simulation study of the critical ionization velocity process

    Science.gov (United States)

    Machida, S.; Goertz, C. K.

    1986-01-01

    The critical ionization velocity process is studied by first investigating a coupled system of equations describing the production of several ion species and electrons by impact ionization, their collisions with neutrals, and the heating of electrons. Analytic relations derived from this were tested with the help of a particle simulation, including collisional processes between neutrals and plasma particles. It was found that resistive heating of electrons plays an important role when the density of the neutrals is high, and that electron heating due to lower hybrid waves is significant when the neutral density is low. In both cases, the control of the plasma production rate by the ratio of the beam velocity to the critical velocity was verified.

  17. Vertical groundwater flow in Permo-Triassic sediments underlying two cities in the Trent River Basin (UK)

    Science.gov (United States)

    Taylor, R. G.; Cronin, A. A.; Trowsdale, S. A.; Baines, O. P.; Barrett, M. H.; Lerner, D. N.

    2003-12-01

    The vertical component of groundwater flow that is responsible for advective penetration of contaminants in sandstone aquifers is poorly understood. This lack of knowledge is of particular concern in urban areas where abstraction disrupts natural groundwater flow regimes and there exists an increased density of contaminant sources. Vertical hydraulic gradients that control vertical groundwater flow were investigated using bundled multilevel piezometers and a double-packer assembly in dedicated boreholes constructed to depths of between 50 and 92 m below ground level in Permo-Triassic sediments underlying two cities within the Trent River Basin of central England (Birmingham, Nottingham). The hydrostratigraphy of the Permo-Triassic sediments, indicated by geophysical logging and hydraulic (packer) testing, demonstrates considerable control over observed vertical hydraulic gradients and, hence, vertical groundwater flow. The direction and magnitude of vertical hydraulic gradients recorded in multilevel piezometers and packers are broadly complementary and range, within error, from +0.1 to -0.7. Groundwater is generally found to flow vertically toward transmissive zones within the hydrostratigraphical profile though urban abstraction from the Sherwood Sandstone aquifer also influences observed vertical hydraulic gradients. Bulk, downward Darcy velocities at two locations affected by abstraction are estimated to be in the order of several metres per year. Consistency in the distribution of hydraulic head with depth in Permo-Triassic sediments is observed over a one-year period and adds support the deduction of hydrostratigraphic control over vertical groundwater flow.

  18. Local Lorentz force and ultrasound Doppler velocimetry in a vertical convection liquid metal flow

    Science.gov (United States)

    Zürner, Till; Vogt, Tobias; Resagk, Christian; Eckert, Sven; Schumacher, Jörg

    2018-01-01

    We report velocity measurements in a vertical turbulent convection flow cell that is filled with the eutectic liquid metal alloy gallium-indium-tin by the use of local Lorentz force velocimetry (LLFV) and ultrasound Doppler velocimetry. We demonstrate the applicability of LLFV for a thermal convection flow and reproduce a linear dependence of the measured force in the range of micronewtons on the local flow velocity magnitude. Furthermore, the presented experiment is used to explore scaling laws of the global turbulent transport of heat and momentum in this low-Prandtl-number convection flow. Our results are found to be consistent with theoretical predictions and recent direct numerical simulations.

  19. Shuttle vertical fin flowfield by the direct simulation Monte Carlo method

    Science.gov (United States)

    Hueser, J. E.; Brock, F. J.; Melfi, L. T.

    1985-01-01

    The flow properties in a model flowfield, simulating the shuttle vertical fin, determined using the Direct Simulation Monte Carlo method. The case analyzed corresponds to an orbit height of 225 km with the freestream velocity vector orthogonal to the fin surface. Contour plots of the flowfield distributions of density, temperature, velocity and flow angle are presented. The results also include mean molecular collision frequency (which reaches 1/60 sec near the surface), collision frequency density (approaches 7 x 10 to the 18/cu m sec at the surface) and the mean free path (19 m at the surface).

  20. 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.

  1. Structure of central and southern Mexico from velocity and attenuation tomography

    OpenAIRE

    Chen, Ting; Robert W. Clayton

    2012-01-01

    The 3D V_p, V_p/_Vs, P- and S-wave attenuation structure of the Cocos subduction zone in Mexico is imaged using earthquakes recorded by two temporary seismic arrays and local stations. Direct P wave arrivals on vertical components and direct S wave arrivals on transverse components from local earthquakes are used for velocity imaging. Relative delay times for P and PKP phases from teleseismic events are also used to obtain a deeper velocity structure beneath the southern seismic array. Using ...

  2. Modeling Travel-Time Correlations Based on Sensitivity Kernels and Correlated Velocity Anomalies

    Science.gov (United States)

    2008-09-01

    sensitivity of 1-Hz Pn arrivals are sensitive to the entire velocity profile between the Moho and a maximum depth that reaches 200 km for an arrival at 15...the Earth’s surface, (2) de-correlation of velocity anomalies across interfaces, such as the Moho , and (3) allowing spatial dependence of σ, λ1 and λ2...the Moho down to a depth that increases with distance, with the vertical extent of significant sensitivity (τ ≤ 0.5 s) eventually exceeding our

  3. The influence of chemical reaction and viscous dissipation on unsteady MHD free convection flow past an exponentially accelerated vertical plate with variable surface conditions

    Directory of Open Access Journals (Sweden)

    Kishore P.M.

    2013-01-01

    Full Text Available A numerical study is presented on the effects of chemical reaction and magnetic field on the unsteady free convection flow, heat and mass transfer characteristics in a viscous, incompressible and electrically conducting fluid past an exponentially accelerated vertical plate by taking into account the heat due to viscous dissipation. The problem is governed by coupled non-linear partial differential equations. The dimensionless equations of the problem have been solved numerically by the implicit finite difference method of Crank - Nicolson’s type. The effects of governing parameters on the flow variables are discussed quantitatively with the aid of graphs for the flow field, temperature field, concentration field, skin-friction, Nusselt number and Sherwood number. It is found that under the influence of chemical reaction, the flow velocity as well as concentration distributions reduce, while the viscous dissipation parameter leads to increase the temperature.

  4. A new numerical investigation of some thermo-physical properties on unsteady MHD non-Darcian flow past an impulsively started vertical surface

    Directory of Open Access Journals (Sweden)

    Motsa Sandile Sydney

    2015-01-01

    Full Text Available The behaviour of unsteady non-Darcian magnetohydrodynamic fluid flow past an impulsively started vertical porous surface is investigated. The effect of thermophoresis due to migration of colloidal particles in response to a macroscopic temperature gradient is taken into account. It is assumed that both dynamic viscosity and thermal conductivity are linear functions of temperature. The governing equations are non-dimensionalized by using suitable similarity transformation which can unravel the behaviour of the flow at short time and long time periods. A novel iteration scheme, called bivariate spectral local linearization method is developed for solving the corresponding systems of highly non-linear partial differential equations. The results of the numerical solutions obtained are presented graphically and analyzed for the effects of the various important parameters entering into the problem on velocity, temperature, and concentration field within the boundary layer.

  5. Vector blood velocity estimation in medical ultrasound

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Gran, Fredrik; Udesen, Jesper

    2006-01-01

    Two methods for making vector velocity estimation in medical ultrasound are presented. All of the techniques can find both the axial and transverse velocity in the image and can be used for displaying both the correct velocity magnitude and direction. The first method uses a transverse oscillation...... in the ultrasound field to find the transverse velocity. In-vivo examples from the carotid artery are shown, where complex turbulent flow is found in certain parts of the cardiac cycle. The second approach uses directional beam forming along the flow direction to estimate the velocity magnitude. Using a correlation...

  6. Aggregate Settling Velocities in San Francisco Estuary Margins

    Science.gov (United States)

    Allen, R. M.; Stacey, M. T.; Variano, E. A.

    2015-12-01

    One way that humans impact aquatic ecosystems is by adding nutrients and contaminants, which can propagate up the food web and cause blooms and die-offs, respectively. Often, these chemicals are attached to fine sediments, and thus where sediments go, so do these anthropogenic influences. Vertical motion of sediments is important for sinking and burial, and also for indirect effects on horizontal transport. The dynamics of sinking sediment (often in aggregates) are complex, thus we need field data to test and validate existing models. San Francisco Bay is well studied and is often used as a test case for new measurement and model techniques (Barnard et al. 2013). Settling velocities for aggregates vary between 4*10-5 to 1.6*10-2 m/s along the estuary backbone (Manning and Schoellhamer 2013). Model results from South San Francisco Bay shoals suggest two populations of settling particles, one fast (ws of 9 to 5.8*10-4 m/s) and one slow (ws of Brand et al. 2015). While the open waters of San Francisco Bay and other estuaries are well studied and modeled, sediment and contaminants often originate from the margin regions, and the margins remain poorly characterized. We conducted a 24 hour field experiment in a channel slough of South San Francisco Bay, and measured settling velocity, turbulence and flow, and suspended sediment concentration. At this margin location, we found average settling velocities of 4-5*10-5 m/s, and saw settling velocities decrease with decreasing suspended sediment concentration. These results are consistent with, though at the low end of, those seen along the estuary center, and they suggest that the two population model that has been successful along the shoals may also apply in the margins.

  7. Slope-Velocity-Equilibrium and evolution of surface roughness on a stony hillslope

    Science.gov (United States)

    Slope-velocity equilibrium is hypothesized as a state that evolves naturally over time due to the interaction between overland flow and bed morphology, wherein steeper areas develop a relative increase in physical and hydraulic roughness such that flow velocity is a unique function of overland flow ...

  8. High-Velocity Paint Gun Injuries.

    Science.gov (United States)

    Wohltmann, Wendi E; Wisell, Joshua A; Lafrades, Celina M C; Cramer, Daniel M; Ragsdale, Bruce D

    2017-08-01

    Cutaneous injuries due to industrial high-pressure paint guns are well-documented in the literature; however, the histologic characteristics are uncommonly described, and facial involvement has not been previously reported. Histopathologic features of paint gun injuries vary depending on the time since injection and type of material. Early lesions display an acute neutrophilic infiltrate, edema, and thrombosis, with varying degrees of skin, fat, and muscle necrosis. More developed lesions (120-192 hours after injury) have prominent histiocytes and fibrosis around necrotic foci, possibly with the pitfall of muscle regenerative giant cells that could be mistaken for sarcoma. Continuing inflammation, swelling, and resultant vascular compression could explain ongoing necrosis months after the accident. The histopathologic differential diagnosis in the absence of clinical history includes paint in an abrasion, foreign body reaction to tattoo, giant cell tumor of tendon sheath, and various neoplasms. If available, radiologic studies can substitute for clinical photographs to indicate the extent of injury. The radiologic differential, uninformed by history, may include calcific periarthritis, gouty tophus, and tumoral calcinosis. Seven cases of injury due to high-velocity paint guns are presented with 4 additional cases mimicking paint gun injury and with review of the literature.

  9. 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).

  10. Ion velocities in a micro-cathode arc thruster

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang Taisen; Shashurin, Alexey; Keidar, Michael [The George Washington University, Washington, DC 22202 (United States); Beilis, Isak [Tel Aviv University, Tel Aviv (Israel)

    2012-06-15

    Ion velocities in the plasma jet generated by the micro-cathode arc thruster are studied by means of time-of-flight method using enhanced ion detection system (EIDS). The EIDS triggers perturbations (spikes) on arc current waveform, and the larger current in the spike generates denser plasma bunches propagating along with the mainstream plasma. The EIDS utilizes double electrostatic probes rather than single probes. The average Ti ion velocity is measured to be around 2 Multiplication-Sign 10{sup 4} m/s without a magnetic field. It was found that the application of a magnetic field does not change ion velocities in the interelectrode region while leads to ion acceleration in the free expanding plasma plume by a factor of about 2. Ion velocities of about 3.5 Multiplication-Sign 10{sup 4} m/s were detected for the magnetic field of about 300 mT at distance of about 100-200 mm from the cathode. It is proposed that plasma is accelerated due to Lorentz force. The average thrust is calculated using the ion velocity measurements and the cathode mass consumption rate, and its increase with the magnetic field is demonstrated.

  11. Shrubline but not treeline advance matches climate velocity in montane ecosystems of south-central Alaska.

    Science.gov (United States)

    Dial, Roman J; Smeltz, T Scott; Sullivan, Patrick F; Rinas, Christina L; Timm, Katriina; Geck, Jason E; Tobin, S Carl; Golden, Trevor S; Berg, Edward C

    2016-05-01

    Tall shrubs and trees are advancing into many tundra and wetland ecosystems but at a rate that often falls short of that predicted due to climate change. For forest, tall shrub, and tundra ecosystems in two pristine mountain ranges of Alaska, we apply a Bayesian, error-propagated calculation of expected elevational rise (climate velocity), observed rise (biotic velocity), and their difference (biotic inertia). We show a sensitive dependence of climate velocity on lapse rate and derive biotic velocity as a rigid elevational shift. Ecosystem presence identified from recent and historic orthophotos ~50 years apart was regressed on elevation. Biotic velocity was estimated as the difference between critical point elevations of recent and historic logistic fits divided by time between imagery. For both mountain ranges, the 95% highest posterior density of climate velocity enclosed the posterior distributions of all biotic velocities. In the Kenai Mountains, mean tall shrub and climate velocities were both 2.8 m y(-1). In the better sampled Chugach Mountains, mean tundra retreat was 1.2 m y(-1) and climate velocity 1.3 m y(-1). In each mountain range, the posterior mode of tall woody vegetation velocity (the complement of tundra) matched climate velocity better than either forest or tall shrub alone, suggesting competitive compensation can be important. Forest velocity was consistently low at 0.1-1.1 m y(-1), indicating treeline is advancing slowly. We hypothesize that the high biotic inertia of forest ecosystems in south-central Alaska may be due to competition with tall shrubs and/or more complex climate controls on the elevational limits of trees than tall shrubs. Among tall shrubs, those that disperse farthest had lowest inertia. Finally, the rapid upward advance of woody vegetation may be contributing to regional declines in Dall's sheep (Ovis dalli), a poorly dispersing alpine specialist herbivore with substantial biotic inertia due to dispersal reluctance. © 2015

  12. 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.

  13. Relative seismic velocity variations correlate with deformation at Kīlauea volcano.

    Science.gov (United States)

    Donaldson, Clare; Caudron, Corentin; Green, Robert G; Thelen, Weston A; White, Robert S

    2017-06-01

    Seismic noise interferometry allows the continuous and real-time measurement of relative seismic velocity through a volcanic edifice. Because seismic velocity is sensitive to the pressurization state of the system, this method is an exciting new monitoring tool at active volcanoes. Despite the potential of this tool, no studies have yet comprehensively compared velocity to other geophysical observables on a short-term time scale at a volcano over a significant length of time. We use volcanic tremor (~0.3 to 1.0 Hz) at Kīlauea as a passive source for interferometry to measure relative velocity changes with time. By cross-correlating the vertical component of day-long seismic records between ~230 station pairs, we extract coherent and temporally consistent coda wave signals with time lags of up to 120 s. Our resulting time series of relative velocity shows a remarkable correlation between relative velocity and the radial tilt record measured at Kīlauea summit, consistently correlating on a time scale of days to weeks for almost the entire study period (June 2011 to November 2015). As the summit continually deforms in deflation-inflation events, the velocity decreases and increases, respectively. Modeling of strain at Kīlauea suggests that, during inflation of the shallow magma reservoir (1 to 2 km below the surface), most of the edifice is dominated by compression-hence closing cracks and producing faster velocities-and vice versa. The excellent correlation between relative velocity and deformation in this study provides an opportunity to understand better the mechanisms causing seismic velocity changes at volcanoes, and therefore realize the potential of passive interferometry as a monitoring tool.

  14. Vertical distraction osteogenesis of fibular bone flap in reconstructed mandible.

    Science.gov (United States)

    Eski, Muhitdin; Turegun, Murat; Deveci, Mustafa; Gokce, Hasan Suat; Sengezer, Mustafa

    2006-12-01

    Excellent functional and aesthetic results can be achieved in mandibular reconstructions with using free fibular bone flap. However, the vertical deficiency between the reconstructed segment and the occlusal plane made dental rehabilitation impossible in some cases. We encountered this problem in our 3 patients who had mandibular reconstruction with fibular flap due to extensive bone defect result from gunshot injury. To overcome this segmental vertical distraction of the reconstructed mandible was performed. Fibular bone segments (40-70 mm) were distracted with using extraoral distraction device after a latency period of 5-7 days. The rate of distraction was 1 mm/day, and the rhythm was 4 times (4 x 0.25 mm). Distraction was continued until the desired height was achieved, and the distractor left in place for 12 weeks for bony consolidation. No minor or major complications were encountered. The increase of vertical height was between 9 and 13 mm, and it was stable during the follow-up period (7-22 months). Following the vertical distraction and vestibuloplasty operations, the dental restoration of the patients was performed with mandibular removable partial dentures.

  15. Measurement of the Vertical Distribution of Reflected Solar Radiation

    Directory of Open Access Journals (Sweden)

    Tetsu Aoki

    2015-05-01

    Full Text Available The purpose of this study was to develop a devicefor measuring the vertical distribution of the reflected radiation to the inside of a room from terrace to building.The proposed device is attached to aluminum plates that are painted matte black at intervals of 20 cm on polystyrene insulation. The surface temperature of the aluminum plate, called the SAT (sol-air temperature, is used as an indicator of the quantity of solar radiation. In order to compare terrace materials, two of the measuring devices were located facing south.Concrete tile, artificial turf, and wood chips were selected as materials to be comparedfor the surface of the terrace and were laid in front of the measuring devices. The results indicate that the SAT reflected onto a vertical plane was higher closer to the ground for all materials. Hourly fluctuations of the vertical distribution of the reflected solar radiation differed, depending on the terrace surface material. When concrete tiles of different thicknesses were compared, the temporal heating patterns varied due to differences in heat capacity. These results lead us to the conclusion that using the developed measuringdevice enables grasping the effect of vertical distribution of reflected solar radiation from a terrace.

  16. Uplift Capacity of Inclined Underreamed Piles Subjected to Vertical Load

    Science.gov (United States)

    Rahman, Md. Akilur; Sengupta, Siddhartha

    2017-12-01

    Many offshore structures are subjected to overturning moments due to wind load, wave pressure, and ship impacts. Inclined (batter) piles are used to support such structures, and to carry the horizontal and vertical loads resulted from the overturning moments. Though studies have been done with inclined piles having no underream bulb, little information is available in the literature about estimating the uplift capacity of inclined underreamed piles. In the present study laboratory experiments have been done with vertically loaded model piles having no underream as well as with one and two underreams. The piles were positioned at angle of inclination of θ = 0°, 10°, 20°, 30° (with vertical); and placed in locally available sand under vertical uplift load. Three different pile stem diameters (D = 20, 25, and 35 mm) were used. The corresponding pile length to stem diameter (l/D) ratio were 18, 14, and 10 respectively. Experiments had been conducted with two relative different densities (45 and 70%) of sand. The failure uplift loads were obtained in each case. It had been found that for inclined piles increase in number of underream bulbs from 0 to 2 was quite effective in resisting uplift loads corresponding to piles having l/D equals to 10. The percentage decreases in uplift capacity corresponding to increase in inclination angle were more pronounced for piles with double underreams.

  17. 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.

  18. Multi Electrode Geoelectric on the Borehole Wall. Determination of Groundwater Velocity and Dispersion Parameters

    Science.gov (United States)

    Kessels, W.; Thorenz, C.; Rifai, H.

    2002-05-01

    A single well technique to determine groundwater flow and transport parameters is presented. Multi-electrode arrays are placed on a borehole wall by an inflatable packer or are installed behind the plastic casing. For measurements, a salt tracer is injected between the electrodes. This salt tracer cloud is afterwards moving in the natural groundwater flow field. The observation of this movement by geoelectric measurements is the basis for the determination of groundwater velocity and the dispersion parameters. The geoelectric observations are performed with n borehole electrodes and one earth connection. Thus, either n independent two point measurements or n*(n-1)/2 pole-to-pole measurements can be performed. The whole procedure consists of three phases: 1. Measurement of the basic conductivity without tracer. 2. Measurement during the injection. 3. Measurement after injection To test the method, measurements in a lab aquifer filled with sand are carried out. The results are discussed and the limitations of the method are shown. Here, the interpretation is restricted on two point geoelectric measurements and the transport equation for NaCl-tracered water. Due to the density contrast, the tracer shows a vertical movement which is not related to the natural velocity field. Numerical calculations with the finite-element-method simulator ROCKFLOW (Kolditz et al., 1999) reproduced this behaviour. The currently used interpretation code is based on an analytic solution of the transport equation. The parameters velocity and dispersion length are calculated by inversion. In the two scientific drillings CAT-LUD1 and CAT-LUD1A in the northern part of Germany multi-electrode installations behind the casing are tested in situ. A multi-electrode packer system is designed and build. References: Kessels, W., Zoth, G.(1997): Doppelmantel - Packers mit geoelektrischer Meßtechnik zur Bestimmung der Abstandsgeschwindigkeit des Grundwassers, Patentanmeldung Az:19855048.0 NLf

  19. Assessing Land Motion of Venice, Italy with GPS: Effects of Regional Filtering on Vertical Rate Estimates

    Science.gov (United States)

    Hammond, W. C.; Plag, H.

    2005-12-01

    We evaluate the vertical land motion in the city of Venice, Italy with data from 36 continuous Global Positioning System (GPS) receivers of the IGS, EUREF and FREDNET networks. This analysis has been undertaken in support of the Appraisal of Relative Sea Level Rise for Venice Project, which aims to define possible future relative sea level change scenarios for this World Heritage site over the next 100 years. Our objective is to quantify the present land surface vertical velocity in a geocentric reference frame so that the results can be combined with the other factors that contribute to the relative sea level rise. Vertical GPS velocities for the sites in the city and lagoon of Venice have been estimated from processing the daily continuous files with the GIPSY/OASIS II software package. Time series that are free of equipment changes or other apparent offsets are ~3.5 years long. We find their motion is significantly downward with respect to other GPS sites on the stable European plate that have long and linear time series. When cast in the ITRF2000 reference frame, however, their sense of motion is uniformly upward by an average of 0.5±0.2 mm/yr, but uncertainty of the motion of ITRF2000 with respect to the geocenter is on the order of 1 mm/yr, and dominates the error budget. To better resolve changes in the regional network shape over time, filtering is applied to mitigate the effects of daily reference frame noise. The filter assumes constant velocities and applies a daily Helmert transformation to minimize the misfit between the expected and actual positions. Generally, the filtering produces velocities that are better resolved, and time series that have ~35% less residual RMS scatter. After regional filtering the Venice city and lagoon sites move vertically downward at -2.7±0.2 mm/yr with respect to the geocenter and thus filtering strongly affects the perception of vertical motion. Results from numerical tests on subsets of the longer time series show that

  20. Measurement of the velocity of a quantum object: A role of phase and group velocities

    Science.gov (United States)

    Lapinski, Mikaila; Rostovtsev, Yuri V.

    2017-08-01

    We consider the motion of a quantum particle in a free space. Introducing an explicit measurement procedure for velocity, we demonstrate that the measured velocity is related to the group and phase velocities of the corresponding matter waves. We show that for long distances the measured velocity coincides with the matter wave group velocity. We discuss the possibilities to demonstrate these effects for the optical pulses in coherently driven media or for radiation propagating in waveguides.

  1. Broadband wavelength conversion in a silicon vertical-dual-slot waveguide

    DEFF Research Database (Denmark)

    Guo, Kai; Lin, Li; Christensen, Jesper Bjerge

    2017-01-01

    We propose a silicon waveguide structure employing silica-filled vertical-dual slots for broadband wavelength conversion, which can be fabricated using simple silicon-on-insulator technology. We demonstrate group-velocity dispersion tailoring by varying the width of the core, the slots and the si...... to significantly broaden the bandwidth of wavelength conversion via four-wave mixing, which is validated with experimentally measured 3 dB bandwidth of 76 nm....

  2. Urticaria due to antihistamines

    National Research Council Canada - National Science Library

    Sánchez Morillas, L; Rojas Pérez-Ezquerra, P; Reaño Martos, M; Sanz, M L; Laguna Martínez, J J

    2011-01-01

    .... We report a patient with urticaria due to ingestion of ebastine and fexofenadine. Skin prick tests, patch tests, and basophil activation tests with the implicated drugs and antihistamines from other families were negative...

  3. 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.

  4. An Analytical Model of Wake Deflection Due to Shear Flow

    NARCIS (Netherlands)

    Micallef, D.; Simao Ferreira, C.J.; Sant, T.; Van Bussel, G.J.W.

    2010-01-01

    The main motivation behind this work is to create a purely analytical engineering model for wind turbine wake upward deflection due to shear flow, by developing a closed form solution of the velocity field due to an oblique vortex ring. The effectiveness of the model is evaluated by comparing the

  5. Evaluation of an Extended Autocorrelation Phase Estimator for Ultrasonic Velocity Profiles Using Nondestructive Testing Systems.

    Science.gov (United States)

    Ofuchi, César Yutaka; Coutinho, Fabio Rizental; Neves, Flávio; de Arruda, Lucia Valéria Ramos; Morales, Rigoberto Eleazar Melgarejo

    2016-08-09

    In this paper the extended autocorrelation velocity estimator is evaluated and compared using a nondestructive ultrasonic device. For this purpose, three velocity estimators are evaluated and compared. The autocorrelation method (ACM) is the most used and well established in current ultrasonic velocity profiler technology, however, the technique suffers with phase aliasing (also known as the Nyquist limit) at higher velocities. The cross-correlation method (CCM) is also well known and does not suffer with phase aliasing as it relies on time shift measurements between emissions. The problem of this method is the large computational burden due to several required mathematical operations. Recently, an extended autocorrelation method (EAM) which combines both ACM and CCM was developed. The technique is not well known within the fluid engineering community, but it can measure velocities beyond the Nyquist limit without the ACM phase aliasing issues and with a lower computational cost than CCM. In this work, all three velocity estimation methods are used to measure a uniform flow of the liquid inside a controlled rotating cylinder. The root-mean-square deviation variation coefficient (CVRMSD) of the velocity estimate and the reference cylinder velocity was used to evaluate the three different methods. Results show that EAM correctly measures velocities below the Nyquist limit with less than 2% CVRMSD. Velocities beyond the Nyquist limit are only measured well by EAM and CCM, with the advantage of the former of being computationally 15 times faster. Furthermore, the maximum value of measurable velocity is also investigated considering the number of times the velocity surpasses the Nyquist limit. The combination of number of pulses and number of samples, which highly affects the results, are also studied in this work. Velocities up to six times the Nyquist limit could be measurable with CCM and EAM using a set of parameters as suggested in this work. The results validate

  6. TRUE MASSES OF RADIAL-VELOCITY EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Robert A., E-mail: rbrown@stsci.edu [Space Telescope Science Institute (United States)

    2015-06-01

    We study the task of estimating the true masses of known radial-velocity (RV) exoplanets by means of direct astrometry on coronagraphic images to measure the apparent separation between exoplanet and host star. Initially, we assume perfect knowledge of the RV orbital parameters and that all errors are due to photon statistics. We construct design reference missions for four missions currently under study at NASA: EXO-S and WFIRST-S, with external star shades for starlight suppression, EXO-C and WFIRST-C, with internal coronagraphs. These DRMs reveal extreme scheduling constraints due to the combination of solar and anti-solar pointing restrictions, photometric and obscurational completeness, image blurring due to orbital motion, and the “nodal effect,” which is the independence of apparent separation and inclination when the planet crosses the plane of the sky through the host star. Next, we address the issue of nonzero uncertainties in RV orbital parameters by investigating their impact on the observations of 21 single-planet systems. Except for two—GJ 676 A b and 16 Cyg B b, which are observable only by the star-shade missions—we find that current uncertainties in orbital parameters generally prevent accurate, unbiased estimation of true planetary mass. For the coronagraphs, WFIRST-C and EXO-C, the most likely number of good estimators of true mass is currently zero. For the star shades, EXO-S and WFIRST-S, the most likely numbers of good estimators are three and four, respectively, including GJ 676 A b and 16 Cyg B b. We expect that uncertain orbital elements currently undermine all potential programs of direct imaging and spectroscopy of RV exoplanets.

  7. Mandible vertical height correction using lingual bone-split pedicle onlay graft technique

    Directory of Open Access Journals (Sweden)

    Coen Pramono D

    2006-09-01

    Full Text Available As edentulous mandible become atrophic, a denture bearing area will also be reduced. Difficulty in the removable prosthesis rehabilitation will be present as well. The purpose of this paper reports an innovative surgical technique to cope a problem of unstable complete lower denture due to bone atrophy and resulted of vertical height reduction of the anterior region of the mandible necessary for denture retention. Vertical advancement of the lower jaw using lingual bone split pedicle onlay graft technique in the anterior region of the mandible and followed by secondary epithelization vestibuloplasty in achieving the vertical height dimension. The surgery was achieved satisfactorily as the vertical dimension of the mandible anterior region had increased and the denture seated more stable comparing with the previous denture worn by the patient. It concluded that the surgery was achieved with a great result as the vertical height of the anterior region of the mandible had increased positively therefore lead the denture seated more stable.

  8. Vertical barriers with increased sorption capacities

    Energy Technology Data Exchange (ETDEWEB)

    Bradl, H.B. [Bilfinger + Berger Bauaktiengesellschaft, Mannheim (Germany)

    1997-12-31

    Vertical barriers are commonly used for the containment of contaminated areas. Due to the very small permeability of the barrier material which is usually in the order of magnitude of 10-10 m/s or less the advective contaminant transport can be more or less neglected. Nevertheless, there will always be a diffusive contaminant transport through the barrier which is caused by the concentration gradient. Investigations have been made to increase the sorption capacity of the barrier material by adding substances such as organoclays, zeolites, inorganic oxides and fly ashes. The contaminants taken into account where heavy metals (Pb) and for organic contaminants Toluole and Phenantrene. The paper presents results of model calculations and experiments. As a result, barrier materials can be designed {open_quotes}tailor-made{close_quotes} depending on the individual contaminant range of each site (e.g. landfills, gasworks etc.). The parameters relevant for construction such as rheological properties, compressive strength and permeability are not affected by the addition of the sorbents.

  9. Lidar measured vertical atmospheric scattering profiles

    NARCIS (Netherlands)

    Kunz, G.J.

    1985-01-01

    The vertical structure of the atmosphere, which is of invaluable interest to meteorologists, geo-physicists and environmental researchers, can be measured with LIDAR. A method has been proposed and applied to invert lidar signals from vertical soundings to height resolved scattering coefficients. In

  10. Vertical integration from the large Hilbert space

    Science.gov (United States)

    Erler, Theodore; Konopka, Sebastian

    2017-12-01

    We develop an alternative description of the procedure of vertical integration based on the observation that amplitudes can be written in BRST exact form in the large Hilbert space. We relate this approach to the description of vertical integration given by Sen and Witten.

  11. Plasmon Modes of Vertically Aligned Superlattices

    DEFF Research Database (Denmark)

    Filonenko, Konstantin; Duggen, Lars; Willatzen, Morten

    2017-01-01

    By using the Finite Element Method we visualize the modes of vertically aligned superlattice composed of gold and dielectric nanocylinders and investigate the emitter-plasmon interaction in approximation of weak coupling. We find that truncated vertically aligned superlattice can function as plas...

  12. A vertically resolved model for phytoplankton aggregation

    Indian Academy of Sciences (India)

    components undergo vertical mixing, and phytoplank- ton sink. Phytoplankton growth is limited by the product of nutrient and light terms. The equations for nitrate (NO3) and ... resolved model there is an extra complication: the largest particles that sink out of ...... and biogeochemistry with satellite ocean colour data. Vertically ...

  13. Plasmon Modes of Vertically Aligned Superlattices

    DEFF Research Database (Denmark)

    Filonenko, Konstantin; Duggen, Lars; Willatzen, Morten

    By using the Finite Element Method we visualize the modes of vertically aligned superlattice composed of gold and dielectric nanocylinders and investigate the emitter-plasmon interaction in approximation of weak coupling. We find that truncated vertically aligned superlattice can function as plas...

  14. DESIGN, CONSTRUCTION AND EVALUATION OF A VERTICAL ...

    African Journals Online (AJOL)

    Vertical plate metering device is intended to minimize seed damage during planting while improving metering efficiency and field capacity. A vertical plate maize seed planter which is adapted for gardens and small holder farmers cultivating less than two hectares has been designed, constructed and tested. The major ...

  15. The green building envelope : Vertical greening

    NARCIS (Netherlands)

    Ottelé, M.

    2011-01-01

    Planting on roofs and façades is one of the most innovative and fastest developing fields of green technologies with respect to the built environment and horticulture. This thesis is focused on vertical greening of structures and to the multi-scale benefits of vegetation. Vertical green can improve

  16. Vertical Integration, Monopoly, and the First Amendment.

    Science.gov (United States)

    Brennan, Timothy J.

    This paper addresses the relationship between the First Amendment, monopoly of transmission media, and vertical integration of transmission and content provision. A survey of some of the incentives a profit-maximizing transmission monopolist may have with respect to content is followed by a discussion of how vertical integration affects those…

  17. Effects of flapless bur decortications on movement velocity of dogs′ teeth

    Directory of Open Access Journals (Sweden)

    Seyed Mohammadreza Safavi

    2012-01-01

    Conclusion: (1 Corticotomy facilitated orthodontic tooth movement is achievable with flapless bur decortication technique. (2 Velocity of tooth movement decreases in later stages of treatment due to maturation of newly formed bone at decortication sites.

  18. Velocity bias induced by flow patterns around ADCPs and associated deployment platforms

    Science.gov (United States)

    Mueller, David S.

    2015-01-01

    Velocity measurements near the Acoustic Doppler Current Profiler (ADCP) are important for mapping surface currents, measuring velocity and discharge in shallow streams, and providing accurate estimates of discharge in the top unmeasured portion of the water column. Improvements to ADCP performance permit measurement of velocities much closer (5 cm) to the transducer than has been possible in the past (25 cm). Velocity profiles collected by the U.S. Geological Survey (USGS) with a 1200 kHz Rio Grande Zedhead ADCP in 2002 showed a negative bias in measured velocities near the transducers. On the basis of these results, the USGS initiated a study combining field, laboratory, and numerical modeling data to assess the effect of flow patterns caused by flow around the ADCP and deployment platforms on velocities measured near the transducers. This ongoing study has shown that the negative bias observed in the field is due to the flow pattern around the ADCP. The flow pattern around an ADCP violates the basic assumption of flow homogeneity required for an accurate three-dimensional velocity solution. Results, to date (2014), have indicated velocity biases within the measurable profile, due to flow disturbance, for the TRDI 1200 kHz Rio Grande Zedhead and the SonTek RiverSurveyor M9 ADCPs. The flow speed past the ADCP, the mount and the deployment platform have also been shown to play an important role in the magnitude and extent of the velocity bias.

  19. Seismic velocity site characterization of 10 Arizona strong-motion recording stations by spectral analysis of surface wave dispersion

    Science.gov (United States)

    Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.

    2017-10-19

    Vertical one-dimensional shear wave velocity (VS) profiles are presented for strong-motion sites in Arizona for a suite of stations surrounding the Palo Verde Nuclear Generating Station. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS30), the average velocity for the entire profile (VSZ), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The VS profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean-square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

  20. Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy

    OpenAIRE

    Morawski, Wojciech

    2009-01-01

    Geological mapping in combination with geophysical investigations and borehole analyses show differences of the Pleistocene between the Warmia and Mazury palaeogeographic provinces in NE Poland. The (more western) Warmia province has a crystalline basement that is covered by a folded sedimentary succession of 2-4 km thick. The (more eastern) Mazury province (eastern) has a basement that forms part of the rigid East European crystalline craton, which is covered by a sedimentary cover of only 1...