On measuring surface wave phase velocity from station–station cross-correlation of ambient signal

DEFF Research Database (Denmark)

Boschi, Lapo; Weemstra, Cornelis; Verbeke, Julie

2012-01-01

We apply two different algorithms to measure surface wave phase velocity, as a function of frequency, from seismic ambient noise recorded at pairs of stations from a large European network. The two methods are based on consistent theoretical formulations, but differ in the implementation: one met...

3D shear wave velocity structure revealed with ambient noise tomography on a DAS array

Science.gov (United States)

Zeng, X.; Thurber, C. H.; Wang, H. F.; Fratta, D.

2017-12-01

An 8700-m Distributed Acoustic Sensing (DAS) cable was deployed at Brady's Hot Springs, Nevada in March 2016 in a 1.5 by 0.5 km study area. The layout of the DAS array was designed with a zig-zag geometry to obtain relatively uniform areal and varied angular coverage, providing very dense coverage with a one-meter channel spacing. This array continuously recorded signals of a vibroseis truck, earthquakes, and traffic noise during the 15-day deployment. As shown in a previous study (Zeng et al., 2017), ambient noise tomography can be applied to DAS continuous records to image shear wave velocity structure in the near surface. To avoid effects of the vibroseis truck operation, only continuous data recorded during the nighttime was used to compute noise cross-correlation functions for channel pairs within a given linear segment. The frequency band of whitening was set at 5 to 15 Hz and the length of the cross-correlation time window was set to 60 second. The phase velocities were determined using the multichannel analysis of surface waves (MASW) methodology. The phase velocity dispersion curve was then used to invert for shear wave velocity profiles. A preliminarily velocity model at Brady's Hot Springs (Lawrence Livermore National Laboratory, 2015) was used as the starting model and the sensitivity kernels of Rayleigh wave group and phase velocities were computed with this model. As the sensitivity kernel shows, shear wave velocity in the top 200 m can be constrained with Rayleigh wave group and phase velocities in our frequency band. With the picked phase velocity data, the shear wave velocity structure can be obtained via Occam's inversion (Constable et al., 1987; Lai 1998). Shear wave velocity gradually increases with depth and it is generally faster than the Lawrence Livermore National Laboratory (2015) model. Furthermore, that model has limiting constraints at shallow depth. The strong spatial variation is interpreted to reflect the different sediments and

Shear-wave velocity of marine sediments offshore Taiwan using ambient seismic noise

Science.gov (United States)

Lin, Yu-Tse; Lin, Jing-Yi; Kuo-Chen, Hao; Yeh, Yi-Chin; Cheng, Win-Bin

2017-04-01

Seismic ambient noise technology has many advantages over the traditional two-station method. The most important one is that noise is happening all the time and it can be widely and evenly distributed. Thus, the Green's Function of any station pair can be obtained through the data cross-correlation process. Many related studies have been performed to estimate the velocity structures based on the inland area. Only a few studies were reported for the marine area due to the relatively shorter recording time of ocean bottom seismometers (OBS) deployment and the high cost of the marine experiment. However, the understanding about the shear-wave velocity (Vs) of the marine sediments is very crucial for the hazard assessment related to submarine landslides, particularly with the growing of submarine resources exploration. In this study, we applied the ambient noise technique to four OBS seismic networks located offshore Taiwan in the aim of getting more information about the noise sources and having the preliminary estimation for the Vs of the marine sediments. Two of the seismic networks were deployed in the NE part of Taiwan, near the Ryukyu subduction system, whereas the others were in the SW area, on the continental margin rich in gas hydrate. Generally, ambient seismic noise could be associated with wind, ocean waves, rock fracturing and anthropogenic activity. In the southwestern Taiwan, the cross-correlation function obtained from two seismic networks indicate similar direction, suggestion that the source from the south part of the network could be the origin of the noise. However, the two networks in the northeastern Taiwan show various source direction, which could be caused by the abrupt change of bathymetry or the volcanic degassing effect frequently observed by the marine geophysical method in the area. The Vs determined from the dispersion curve shows a relatively higher value for the networks in the Okinawa Trough (OT) off NE Taiwan than that in the

THE TRANSVERSE PECULIAR VELOCITY OF THE Q2237+0305 LENS GALAXY AND THE MEAN MASS OF ITS STARS

International Nuclear Information System (INIS)

Poindexter, Shawn; Kochanek, Christopher S.

2010-01-01

Using 11 years of OGLE V-band photometry of Q2237+0305, we measure the transverse velocity of the lens galaxy and the mean mass of its stars. We can do so because, for the first time, we fully include the random motions of the stars in the lens galaxy in the analysis of the light curves. In doing so, we are also able to correctly account for Earth's parallax motion and the rotation of the lens galaxy, further reducing systematic errors. We measure a lower limit on the transverse speed of the lens galaxy, v t > 338 km s -1 (68% confidence) and find a preferred direction to the east. The mean stellar mass estimate, including a well-defined velocity prior, is 0.12 ≤ (M/M sun ) ≤ 1.94 at 68% confidence, with a median of 0.52 M sun . We also show for the first time that analyzing subsets of a microlensing light curve, in this case the first and second halves of the OGLE V-band light curve, gives mutually consistent physical results.

Directional Transverse Oscillation Vector Flow Estimation

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt

2017-01-01

A method for estimating vector velocities using transverse oscillation (TO) combined with directional beamforming is presented. In Directional Transverse Oscillation (DTO) a normal focused field is emitted and the received signals are beamformed in the lateral direction transverse to the ultrasound...... beam to increase the amount of data for vector velocity estimation. The approach is self-calibrating as the lateral oscillation period is estimated from the directional signal through a Fourier transform to yield quantitative velocity results over a large range of depths. The approach was extensively...... simulated using Field IIpro and implemented on the experimental SARUS scanner in connection with a BK Medical 8820e convex array transducer. Velocity estimates for DTO are found for beam-to-flow angles of 60, 75, and 90, and vessel depths from 24 to 156 mm. Using 16 emissions the Standard Deviation (SD...

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...... search can also yield the direction, and the full velocity vector is thereby found. An examples from a flow rig is shown....

Crustal structure of Australia from ambient seismic noise tomography

Science.gov (United States)

Saygin, Erdinc; Kennett, B. L. N.

2012-01-01

Surface wave tomography for Australian crustal structure has been carried out using group velocity measurements in the period range 1-32 s extracted from stacked correlations of ambient noise between station pairs. Both Rayleigh wave and Love wave group velocity maps are constructed for each period using the vertical and transverse component of the Green's function estimates from the ambient noise. The full suite of portable broadband deployments and permanent stations on the continent have been used with over 250 stations in all and up to 7500 paths. The permanent stations provide a useful link between the various shorter-term portable deployments. At each period the group velocity maps are constructed with a fully nonlinear tomographic inversion exploiting a subspace technique and the Fast Marching Method for wavefront tracking. For Rayleigh waves the continental coverage is good enough to allow the construction of a 3D shear wavespeed model in a two stage approach. Local group dispersion information is collated for a distribution of points across the continent and inverted for a 1D SV wavespeed profile using a Neighbourhood Algorithm method. The resulting set of 1D models are then interpolated to produce the final 3D wavespeed model. The group velocity maps show the strong influence of thick sediments at shorter periods, and distinct fast zones associated with cratonic regions. Below the sediments the 3D shear wavespeed model displays significant heterogeneity with only moderate correlation with surface tectonic features. For example, there is no evident expression of the Tasman Line marking the eastern edge of Precambrian outcrop. The large number of available inter-station paths extracted from the ambient noise analysis provide detailed shear wavespeed information for crustal structure across the Australian continent for the first time, including regions where there was no prior sampling because of difficult logistics.

High resolution Rayleigh wave group velocity tomography in North-China from ambient seismic noise

International Nuclear Information System (INIS)

Fang Lihua; Wu Jianping; Ding Zhifeng; Panza, G.F.

2009-03-01

This study presents the results of the Rayleigh wave group velocity tomography in North-China performed using ambient seismic noise observed at 190 broadband and 10 very broadband stations of the North-China Seismic Array. All available vertical component time-series for the 14 months span between January, 2007 and February, 2008 are cross-correlated to obtain empirical Rayleigh wave Green functions that are subsequently processed, with the multiple filter method, to isolate the group velocity dispersion curves of the fundamental mode of Rayleigh wave. Tomographic maps, with a grid spacing of 0.25 deg. x 0.25 deg., are computed at the periods of 4.5s, 12s, 20s, 28s. The maps at short periods reveal an evident lateral heterogeneity in the crust of North-China, quite well in agreement with known geological and tectonic features. The North China Basin is imaged as a broad low velocity area, while the Taihangshan and Yanshan uplifts and Ordos block are imaged as high velocity zones, and the Quaternary intermountain basins show up as small low-velocity anomalies. The group velocity contours at 4.5s, 12s and 20s are consistent with the Bouguer gravity anomalies measured in the area of the Taihangshan fault, that cuts through the lower crust at least. Most of the historical strong earthquakes (M≥6.0) are located where the tomographic maps show zones with moderate velocity gradient. (author)

Velocity, bathymetry, and transverse mixing characteristics of the Ohio River upstream from Cincinnati, Ohio, October 2004-March 2006

Science.gov (United States)

Koltun, G.F.; Ostheimer, Chad J.; Griffin, Michael S.

2006-01-01

Velocity, bathymetry, and transverse (cross-channel) mixing characteristics were studied in a 34-mile study reach of the Ohio River extending from the lower pool of the Captain Anthony Meldahl Lock and Dam, near Willow Grove, Ky, to just downstream from the confluence of the Licking and Ohio Rivers, near Newport, Ky. Information gathered in this study ultimately will be used to parameterize hydrodynamic and water-quality models that are being developed for the study reach. Velocity data were measured at an average cross-section spacing of about 2,200 feet by means of boat-mounted acoustic Doppler current profilers (ADCPs). ADCP data were postprocessed to create text files describing the three-dimensional velocity characteristics in each transect. Bathymetry data were measured at an average transect spacing of about 800 feet by means of a boat-mounted single-beam echosounder. Depth information obtained from the echosounder were postprocessed with water-surface slope and elevation information collected during the surveys to compute stream-bed elevations. The bathymetry data were written to text files formatted as a series of space-delimited x-, y-, and z-coordinates. Two separate dye-tracer studies were done on different days in overlapping stream segments in an 18.3-mile section of the study reach to assess transverse mixing characteristics in the Ohio River. Rhodamine WT dye was injected into the river at a constant rate, and concentrations were measured in downstream cross sections, generally spaced 1 to 2 miles apart. The dye was injected near the Kentucky shoreline during the first study and near the Ohio shoreline during the second study. Dye concentrations were measured along transects in the river by means of calibrated fluorometers equipped with flow-through chambers, automatic temperature compensation, and internal data loggers. The use of flow-through chambers permitted water to be pumped continuously out of the river from selected depths and through the

Rayleigh wave group-velocity across the Dominican Republic and Puerto Rico from ambient noise tomography

Science.gov (United States)

Quiros, D.; Pulliam, J.; Polanco Rivera, E.; Huerfano Moreno, V. A.

2017-12-01

The eastern North America-Caribbean (NA-CAR) plate boundary near the islands of Hispaniola (which is comprised of the Dominican Republic and Haiti) and Puerto Rico is a complex transition zone in which strain is accommodated by two transform fault systems and oblique subduction. In 2013, scientists from Baylor University, the Autonomous University of Santo Domingo, and the Puerto Rico Seismic Network deployed 16 broadband stations on the Dominican Republic to expand the local permanent network. The goal of the Greater Antilles Seismic Program (GrASP) is to combine its data with that from permanent networks in Puerto Rico, Haiti, Cuba, the Cayman Islands, and Jamaica to develop a better understanding of the crust and upper mantle structure in the Northeastern Caribbean (Greater Antilles). One important goal of GrASP is to develop robust velocity models that can be used to improve earthquake location and seismic hazard efforts. In this study, we focus on obtaining Rayleigh wave group velocity maps from ambient noise tomography. By cross-correlating ambient seismic noise recorded at 53 stations between 2010 to present, we obtain Green's functions between 1165 pairs of stations. From these, we obtain dispersion curves by the application of FTAN methods with phase-matched filtering. Selection criteria depend on the signal-to-noise ratio and seasonal variability, with further filtering done by rejecting velocities incompatible with maps produced from overdamped tomographic inversions. Preliminary dispersion maps show strong correlations with large-scale geological and tectonic features for periods between 5 - 20 s, such as the Cordillera Central in both the Dominican Republic and Puerto Rico, the Mona Passage, and the NA-CAR subduction zone. Ongoing efforts focus on including shorter periods in Puerto Rico as its denser station distribution could allow us to retrieve higher resolution group velocity maps.

Drift velocity, longitudinal and transverse diffusion in hydrocarbons derived from distributions of single electrons

International Nuclear Information System (INIS)

Schmidt, B.; Roncossek, M.

1992-01-01

A time of flight method is described which allows the simultaneous measurement of drift velocity w and the ratios of the longitudinal and transverse diffusion coefficients to mobility (D L /μ, D T /μ) of electrons in gases. The accuracy achieved in this omnipurpose experiment is comparable with that of specialised techniques and is estimated to be ±1% for w and ±5% for the d/μ measurements. Results for methane, ethane, ethene, propane, propene and cyclopropane for values of E/N (the electric field strength divided by the number density) ranging from 0.02 to 15 Td are presented and discussed (1 Td = 10 21 V m 2 ). 13 refs., 4 tabs., 7 figs

Algorithms for estimating blood velocities using ultrasound

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt

2000-01-01

Ultrasound has been used intensively for the last 15 years for studying the hemodynamics of the human body. Systems for determining both the velocity distribution at one point of interest (spectral systems) and for displaying a map of velocity in real time have been constructed. A number of schemes...... have been developed for performing the estimation, and the various approaches are described. The current systems only display the velocity along the ultrasound beam direction and a velocity transverse to the beam is not detected. This is a major problem in these systems, since most blood vessels...... are parallel to the skin surface. Angling the transducer will often disturb the flow, and new techniques for finding transverse velocities are needed. The various approaches for determining transverse velocities will be explained. This includes techniques using two-dimensional correlation (speckle tracking...

Demonstration of a Vector Velocity Technique

DEFF Research Database (Denmark)

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

2011-01-01

With conventional Doppler ultrasound it is not possible to estimate direction and velocity of blood flow, when the angle of insonation exceeds 60–70°. Transverse oscillation is an angle independent vector velocity technique which is now implemented on a conventional ultrasound scanner. In this pa......With conventional Doppler ultrasound it is not possible to estimate direction and velocity of blood flow, when the angle of insonation exceeds 60–70°. Transverse oscillation is an angle independent vector velocity technique which is now implemented on a conventional ultrasound scanner...

Migration velocity analysis using a transversely isotropic medium with tilt normal to the reflector dip

KAUST Repository

Alkhalifah, T.

2010-06-13

A transversely isotropic model in which the tilt is constrained to be normal to the dip (DTI model) allows for simplifications in the imaging and velocity model building efforts as compared to a general TTI model. Though this model, in some cases, can not be represented physically like in the case of conflicting dips, it handles all dips with the assumption of symmetry axis normal to the dip. It provides a process in which areas that meet this feature is handled properly. We use efficient downward continuation algorithms that utilizes the reflection features of such a model. For lateral inhomogeneity, phase shift migration can be easily extended to approximately handle lateral inhomogeneity, because unlike the general TTI case the DTI model reduces to VTI for zero dip. We also equip these continuation algorithms with tools that expose inaccuracies in the velocity. We test this model on synthetic data of general TTI nature and show its resilience even couping with complex models like the recently released anisotropic BP model.

A First Layered Crustal Velocity Model for the Western Solomon Islands: Inversion of Measured Group Velocity of Surface Waves using Ambient Noise Cross-Correlation

Science.gov (United States)

Ku, C. S.; Kuo, Y. T.; Chao, W. A.; You, S. H.; Huang, B. S.; Chen, Y. G.; Taylor, F. W.; Yih-Min, W.

2017-12-01

Two earthquakes, MW 8.1 in 2007 and MW 7.1 in 2010, hit the Western Province of Solomon Islands and caused extensive damage, but motivated us to set up the first seismic network in this area. During the first phase, eight broadband seismic stations (BBS) were installed around the rupture zone of 2007 earthquake. With one-year seismic records, we cross-correlated the vertical component of ambient noise recorded in our BBS and calculated Rayleigh-wave group velocity dispersion curves on inter-station paths. The genetic algorithm to invert one-dimensional crustal velocity model is applied by fitting the averaged dispersion curves. The one-dimensional crustal velocity model is constituted by two layers and one half-space, representing the upper crust, lower crust, and uppermost mantle respectively. The resulted thickness values of the upper and lower crust are 6.4 and 14.2 km, respectively. Shear-wave velocities (VS) of the upper crust, lower crust, and uppermost mantle are 2.53, 3.57 and 4.23 km/s with the VP/VS ratios of 1.737, 1.742 and 1.759, respectively. This first layered crustal velocity model can be used as a preliminary reference to further study seismic sources such as earthquake activity and tectonic tremor.

Exploration of Wave Development during Yarn Transverse Impact

Directory of Open Access Journals (Sweden)

Matthew Hudspeth

2017-05-01

Full Text Available Single yarns have been impacted in a transverse fashion so as to probe the characteristics of resulting wave development. Longitudinal wave speeds were tracked in efforts to directly measure the yarn tensile stiffness, resulting in a slight increase in the modulus of Kevlar® KM2 and Dyneema® SK76. Additionally, the load developed in AuTx® and Kevlar® KM2 yarns behind the longitudinal wave front has been recorded, providing additional verification for the Smith relations. Further effort to bolster the Smith equations has been successfully performed via tracking transverse wave speeds in AuTx® yarns over a range of impacting velocities. Additional emphasis has been placed at understanding the transverse wave development around the yarn critical velocity, demonstrating that there is a velocity zone where partial yarn failure is detected. Above the critical velocity, measurement of early time transverse wave speeds also agrees with the Smith solution, though the wave speed quickly reduces in value due to the drop in tensile stresses resulting from filament rupture. Finally, the Smith equations have been simplified and are compared to the Cunniff equation, which bear a striking resemblance. Due to such a resemblance, it is suggested that yarn critical velocity experiments can be performed on trial yarn material, and the effect of modifying yarn mechanical properties is discussed.

Experimental investigation of transverse flow estimation using transverse oscillation

DEFF Research Database (Denmark)

Udesen, Jesper; Jensen, Jørgen Arendt

2003-01-01

Conventional ultrasound scanners can only display the blood velocity component parallel to the ultrasound beam. Introducing a laterally oscillating field gives signals from which the transverse velocity component can be estimated using 2:1 parallel receive beamformers. To yield the performance...... perpendicular to the ultrasound beam. The velocity profile of the blood is parabolic, and the speed of the blood in the center of the vessel is 1.1 m/s. An extended autocorrelation algorithm is used for velocity estimation for 310 trials, each containing 32 beamformed signals. The velocity can be estimated.......0% and the relative mean standard deviation is found to be 9.8%. With the Compuflow 1000 programmable flow pump a color flow mode image is produced of the experimental setup for a parabolic flow. Also the flow of the human femoralis is reproduced and it is found that the characteristics of the flow can be estimated....

Upper and Middle Crustal Velocity Structure of the Colombian Andes From Ambient Noise Tomography: Investigating Subduction-Related Magmatism in the Overriding Plate

Science.gov (United States)

Poveda, Esteban; Julià, Jordi; Schimmel, Martin; Perez-Garcia, Nelson

2018-02-01

New maps of S velocity variation for the upper and middle crust making up the northwestern most corner of South America have been developed from cross correlation of ambient seismic noise at 52 broadband stations in the region. Over 1,300 empirical Green's functions, reconstructing the Rayleigh wave portion of the seismic wavefield, were obtained after time and frequency-domain normalization of the ambient noise recordings and stacking of 48 months of normalized data. Interstation phase and group velocity curves were then measured in the 6-38 s period range and tomographically inverted to produce maps of phase and group velocity variation in a 0.5° × 0.5° grid. Velocity-depth profiles were developed for each node after simultaneously inverting phase and group velocity curves and combined to produce 3-D maps of S velocity variation for the region. The S velocity models reveal a 7 km thick sedimentary cover in the Caribbean region, the Magdalena Valley, and the Cordillera Oriental, as well as crustal thicknesses in the Pacific and Caribbean region under 35 km, consistent with previous studies. They also display zones of slow velocity at 25-35 km depth under regions of both active and inactive volcanism, suggesting the presence of melts that carry the signature of segmented subduction into the overriding plate. A low-velocity zone in the same depth range is imaged under the Lower Magdalena Basin in the Caribbean region, which may represent either sublithospheric melts ponding at midcrustal levels after breaching through a fractured Caribbean flat slab or fluid migration through major faults within the Caribbean crust.

Phased-array vector velocity estimation using transverse oscillations

DEFF Research Database (Denmark)

Pihl, Michael Johannes; Marcher, Jønne; Jensen, Jørgen Arendt

2012-01-01

.79 to 0.92, indicating a correlation between the performance metrics of the TO spectrum and the velocity estimates. Because these performance metrics are much more readily computed, the TO fields can be optimized faster for improved velocity estimation of both simulations and measurements. For simulations......, but with a poorer performance compared with a 128-element transducer. The simulation and experimental results demonstrate that the TO method is suitable for use in conjunction with a phased-array transducer, and that 2-D vector velocity estimation is possible down to a depth of 15 cm....

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...

Positive and negative streamers in ambient air: measuring diameter, velocity and dissipated energy

International Nuclear Information System (INIS)

Briels, T M P; Kos, J; Van Veldhuizen, E M; Ebert, U; Winands, G J J

2008-01-01

Positive and negative streamers are studied in ambient air at 1 bar; they emerge from a needle electrode placed 40 mm above a planar electrode. The amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses have rise times of 30 ns or shorter. Diameters, velocities and energies of the streamers are measured. Two regimes are identified; a low voltage regime where only positive streamers appear and a high voltage regime where both positive and negative streamers exist. Below 5 kV, no streamers emerge. In the range from 5 to 40 kV, positive streamers form, while the negative discharges only form a glowing cloud at the electrode tip, but no streamers. For 5-20 kV, diameters and velocities of the positive streamers have the minimal values of d = 0.2 mm and v ∼ 10 5 m s -1 . For 20-40 kV, their diameters increase by a factor of 6 while the voltage increases only by a factor of 2. Above the transition value of 40 kV, streamers of both polarities form; they strongly resemble each other, though the positive ones propagate further; their diameters continue to increase with applied voltage. For 96 kV, positive streamers attain diameters of 3 mm and velocities of 4 x 10 6 m s -1 ; negative streamers are about 20% slower and thinner. An empirical fit formula for the relation between velocity v and diameter d is v = 0.5d 2 mm -1 ns -1 for both polarities. Streamers of both polarities dissipate energies of the order of several millijoules per streamer while crossing the gap.

Performance of a vector velocity estimator

DEFF Research Database (Denmark)

Munk, Peter; Jensen, Jørgen Arendt

1998-01-01

tracking can be found in the literature, but no method with a satisfactory performance has been found that can be used in a commercial implementation. A method for estimation of the velocity vector is presented. Here an oscillation transverse to the ultrasound beam is generated, so that a transverse motion...... in an autocorrelation approach that yields both the axial and the lateral velocity, and thus the velocity vector. The method has the advantage that a standard array transducer and a modified digital beamformer, like those used in modern ultrasound scanners, is sufficient to obtain the information needed. The signal...

Validation of Transverse Oscillation Vector Velocity Estimation In-Vivo

DEFF Research Database (Denmark)

Hansen, Kristoffer Lindskov; Udesen, Jesper; Thomsen, Carsten

2007-01-01

Conventional Doppler methods for blood velocity estimation only estimate the velocity component along the ultrasound (US) beam direction. This implies that a Doppler angle under examination close to 90deg results in unreliable information about the true blood direction and blood velocity. The novel...... the presented angle independent 2-D vector velocity method. The results give reason to believe that the TO method can be a useful alternative to conventional Doppler systems bringing forth new information to the US examination of blood flow....

Role of Inelastic Transverse Compressive Behavior and Multiaxial Loading on the Transverse Impact of Kevlar KM2 Single Fiber

Directory of Open Access Journals (Sweden)

Subramani Sockalingam

2017-02-01

Full Text Available High-velocity transverse impact of ballistic fabrics and yarns by projectiles subject individual fibers to multi-axial dynamic loading. Single-fiber transverse impact experiments with the current state-of-the-art experimental capabilities are challenging due to the associated micron length-scale. Kevlar® KM2 fibers exhibit a nonlinear inelastic behavior in transverse compression with an elastic limit less than 1.5% strain. The effect of this transverse behavior on a single KM2 fiber subjected to a cylindrical and a fragment-simulating projectile (FSP transverse impact is studied with a 3D finite element model. The inelastic behavior results in a significant reduction of fiber bounce velocity and projectile-fiber contact forces up to 38% compared to an elastic impact response. The multiaxial stress states during impact including transverse compression, axial tension, axial compression and interlaminar shear are presented at the location of failure. In addition, the models show a strain concentration over a small length in the fiber under the projectile-fiber contact. A failure criterion, based on maximum axial tensile strain accounting for the gage length, strain rate and multiaxial loading degradation effects are applied to predict the single-fiber breaking speed. Results are compared to the elastic response to assess the importance of inelastic material behavior on failure during a transverse impact.

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....

Crustal surface wave velocity structure of the east Albany-Fraser Orogen, Western Australia, from ambient noise recordings

Science.gov (United States)

Sippl, C.; Kennett, B. L. N.; Tkalčić, H.; Gessner, K.; Spaggiari, C. V.

2017-09-01

Group and phase velocity maps in the period range 2-20 s for the Proterozoic east Albany-Fraser Orogen, Western Australia, are extracted from ambient seismic noise recorded with the 70-station ALFREX array. This 2 yr temporary installation provided detailed coverage across the orogen and the edge of the Neoarchean Yilgarn Craton, a region where no passive seismic studies of this scale have occurred to date. The surface wave velocities are rather high overall (>3 km s-1 nearly everywhere), as expected for exposed Proterozoic basement rocks. No clear signature of the transition between Yilgarn Craton and Albany-Fraser Orogen is observed, but several strong anomalies corresponding to more local geological features were obtained. A prominent, NE-elongated high-velocity anomaly in the northern part of the array is coincident with a Bouguer gravity high caused by the upper crustal metamorphic rocks of the Fraser Zone. This feature disappears towards longer periods, which hints at an exclusively upper crustal origin for this anomaly. Further east, the limestones of the Cenozoic Eucla Basin are clearly imaged as a pronounced low-velocity zone at short periods, but the prevalence of low velocities to periods of ≥5 s implies that the uppermost basement in this area is likewise slow. At longer periods, slightly above-average surface wave velocities are imaged below the Eucla Basin.

South Ilan Plain High-Resolution 3-D S-Wave Velocity from Ambient Noise Tomography

Directory of Open Access Journals (Sweden)

Kai-Xun Chen

2016-06-01

Full Text Available The Ilan Plain in northeastern Taiwan is located at a pivotal point where the Ryukyu trench subduction zone, the northern Taiwan crustal stretching zone, and the ongoing arc-continent collision zone converge. In contrast to the North Ilan Plain, the South Ilan Plain exhibits a thin unconsolidated sedimentary layer with depths ranging from 0 - 1 km, high on-land seismicity and significant SE movements relative to Penghu island. We deployed a dense network of 43 short-period vertical component Texan instruments from June to November 2013 in this study, covering most of the South Ilan Plain and its vicinity. We then used the ambient noise tomography method for simultaneous phase and group Rayleigh wave velocity measurements to invert a high-resolution 3-D S-wave for shallow structures (up to a depth of 2.5 km in the South Ilan Plain. We used the fast marching method for ray tracing to deal with ray bending in an inhomogeneous medium. The resulting rays gradually bend toward high velocity zones with increasing number of iterations. The high velocity zone results are modified by more iterations and the resolutions become higher because ray crossings are proportional to ray densities for evenly distributed stations. The final results agreed well with known sedimentary basement thickness patterns. We observed nearly EW trending fast anomalies beneath the mountainous terrain abutting to the South Ilan Plain. The Chingshui location consistently exhibited a low S-wave velocity zone to a depth of 1.5 km.

An Experimental Measurement on Laminar Burning Velocities and Markstein Length of Iso-Butane-Air Mixtures at Ambient Conditions

Directory of Open Access Journals (Sweden)

Yousif Alaeldeen Altag

2016-01-01

Full Text Available In the present work, experimental investigation on laminar combustion of iso-butane-air mixtures was conducted in constant volume explosion vessel. The experiments were conducted at wide range of equivalence ratios ranging between Ф = 0.6 and 1.4 and atmospheric pressure of 0.1 MPa and ambient temperature of 303K. Using spherically expanding flame method, flame parameters including stretched, unstretched flame propagation speeds, laminar burning velocities and Markstein length were calculated. For laminar burning velocities the method of error bars of 95% confidence level was applied. In addition, values of Markstein lengths were measured in wide range of equivalence ratios to study the influence of stretch rate on flame instability and burning velocity. It was found that the stretched flame speed and laminar burning velocities increased with equivalence ratios and the peak value was obtained at equivalence ratio of Ф = 1.1. The Markstein length decreased with the increases in equivalence ratios, which indicates that the diffusion thermal flame instability increased at high equivalence ratios in richer mixture side. However, the total deviations in the laminar burning velocities have discrepancies of 1.2-2.9% for all investigated mixtures.

Method to measure a relative transverse velocity of a source-lens-observer system using gravitational lensing of gravitational waves

International Nuclear Information System (INIS)

Itoh, Yousuke; Futamase, Toshifumi; Hattori, Makoto

2009-01-01

Gravitational waves propagate along null geodesics like light rays in the geometrical optics approximation, and they may have a chance to suffer from gravitational lensing by intervening objects, as is the case for electromagnetic waves. Long wavelengths of gravitational waves and compactness of possible sources may enable us to extract information in the interference among the lensed images. We point out that the interference term contains information of relative transverse velocity of the source-lens-observer system, which may be obtained by possible future space-borne gravitational wave detectors such as BBO/DECIGO.

Positive and negative streamers in ambient air: measuring diameter, velocity and dissipated energy

Energy Technology Data Exchange (ETDEWEB)

Briels, T M P; Kos, J; Van Veldhuizen, E M; Ebert, U [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600 MB Eindhoven (Netherlands); Winands, G J J [Department of Electrical Engineering, Technische Universiteit Eindhoven, PO Box 513, 5600 MB Eindhoven (Netherlands)], E-mail: e.m.v.veldhuizen@tue.nl, E-mail: ebert@cwi.nl

2008-12-07

Positive and negative streamers are studied in ambient air at 1 bar; they emerge from a needle electrode placed 40 mm above a planar electrode. The amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses have rise times of 30 ns or shorter. Diameters, velocities and energies of the streamers are measured. Two regimes are identified; a low voltage regime where only positive streamers appear and a high voltage regime where both positive and negative streamers exist. Below 5 kV, no streamers emerge. In the range from 5 to 40 kV, positive streamers form, while the negative discharges only form a glowing cloud at the electrode tip, but no streamers. For 5-20 kV, diameters and velocities of the positive streamers have the minimal values of d = 0.2 mm and v {approx} 10{sup 5} m s{sup -1}. For 20-40 kV, their diameters increase by a factor of 6 while the voltage increases only by a factor of 2. Above the transition value of 40 kV, streamers of both polarities form; they strongly resemble each other, though the positive ones propagate further; their diameters continue to increase with applied voltage. For 96 kV, positive streamers attain diameters of 3 mm and velocities of 4 x 10{sup 6} m s{sup -1}; negative streamers are about 20% slower and thinner. An empirical fit formula for the relation between velocity v and diameter d is v = 0.5d{sup 2} mm{sup -1} ns{sup -1} for both polarities. Streamers of both polarities dissipate energies of the order of several millijoules per streamer while crossing the gap.

Comparative study of methods for blood flow measurement within transverse sinuses by using MR

International Nuclear Information System (INIS)

Gao Gejun; Feng Xiaoyuan; Yang Bojie; Geng Daoying

2003-01-01

Objective: To assess the accuracy of two-dimensional phase contrast (2D-PC) MR method for blood flow measurement within transverse sinuses by comparing this method with cine phase contrast (cine-PC) MR and Doppler in volunteers and patients. Methods: (1) A total of 12 transverse sinuses were examined in 8 healthy volunteers. 2D-PC MR and cine-PC MR were used respectively to measure the transverse area of flow, the flow velocities, and the volumetric flow rates in the same position in every transverse sinus. Paired t-test was used for comparison between the results determined by 2D-PC MR and that determined by cine-PC MR. (2) A total of 6 transverse sinuses were examined in 5 patients who needed operation. 2D-PC MR was used to determine the blood flow velocity of transverse sinus before operation, and Doppler was used to determine the blood flow velocity of the same transverse sinus during operation. The linear regression analysis was used for statistical analysis. Results: (1) Statistical analysis indicated that there were no significant difference among the transverse area of flow (t = -1.106, P = 0.293), the flow velocities (t = 0.262, P = 0.798), and the volumetric flow rates (t = 0.439, P = 0.669) measured by using 2D-PC MR and cine PC MR, respectively. (2) The correlation between flow velocities determined by 2D-PC MR imaging before operation and that determined by Doppler during operation was in excellent agreement (Y-circumflex = 1.303 x + 0.62, r 2 = 0.88). Conclusion: 2D-PC MR may be a practical convenient method for blood flow measurement within transverse sinuses system

On the velocity of the Vela pulsar

OpenAIRE

Gvaramadze, Vasilii

2000-01-01

It is shown that if the shell of the Vela supernova remnant is responsible for nearly all the scattering of the Vela pulsar, then the scintillation and proper motion velocities of the pulsar can only be reconciled with each other in the case of nonzero transverse velocity of the scattering material. A possible origin of large-scale transverse motions in the shell of the Vela supernova remnant is discussed.

On the velocity of the Vela pulsar

Science.gov (United States)

Gvaramadze, V.

2001-04-01

It is shown that if the shell of the Vela supernova remnant is responsible for nearly all the scattering of the Vela pulsar, then the scintillation and proper motion velocities of the pulsar can only be reconciled with each other in the case of nonzero transverse velocity of the scattering material. A possible origin of large-scale transverse motions in the shell of the Vela supernova remnant is discussed.

3D velocity structure of upper crust beneath NW Bohemia/Vogtland

Science.gov (United States)

Javad Fallahi, Mohammad; Mousavi, Sima; Korn, Michael; Sens-Schönfelder, Christoph; Bauer, Klaus; Rößler, Dirk

2013-04-01

surrounding area. Surface wave tomography using ambient noise provides additional constraints on shear velocities. The detailed knowledge of the 3D structure is essential to select the optimal future borehole locations. we use the vertical and transverse component ambient noise data to estimate both Rayleigh and Love waves from ambient noise cross-correlation waveforms to investigate the crustal seismic structure of W-Bohemia/Vogtland. More than 2000 Rayleigh and Love group-velocity dispersion curves are obtained by time-frequency analysis of stacked ambient noise cross-correlation functions between station pairs. We used the data between 2002 and 2004 recorded at 43 seismic stations from BOHEMA experiment and between 2006 and 2008 recorded at 79 seismic stations from permanent station networks of Germany, Czech Academy of Sciences (WEBNET) and PASSEQ experiments. At each period between 1 and 10 s, group velocity maps are constructed, all corresponding to different sampling depths, and thus together giving an indication of the 3D shear wave velocity structure extending to a depth of about 15 km.

CFD analysis of transverse flow in a wire-wrapped hexagonal seven-pin bundle

International Nuclear Information System (INIS)

Zhao, Pinghui; Liu, Jiaming; Ge, Zhihao; Wang, Xi; Cheng, Xu

2017-01-01

Highlights: • Transverse flow in a wire-wrapped hexagonal seven-pin bundle are simulated. • Four kinds of subchannels are taken as the object. • Effects of wire number and position on transverse velocities are studied. • Parameter studies reveal P/D and H/D have a great influence than Re. • Present transverse velocity correlations need to be modified. - Abstract: Transverse flow induced by helical spacer wires has important effects on the flow and heat transfer behavior of reactor core. In this paper, transverse flow in a wire-wrapped hexagonal seven-pin bundle was simulated by the open source code, OpenFOAM, based on computational fluid dynamic (CFD) method. The Shear Stress Transport (SST) k-ω model and Spalding wall function were used to resolve the momentum field. Hexahedral dominated meshes were generated to achieve high grid quality. Periodic boundary condition and parallel processing were adopted to save the computational cost. Transverse velocity distributions in four different kinds of subchannel gaps were analyzed. The results show that the influence of wire number and position on the transverse velocity distribution is obvious. For an interior gap, transverse flow seems to be dominated by wires near the gap, and its direction changes periodically in one helical pitch. However, for a peripheral gap, transverse velocity is affected by more wires and its direction is decided by the direction of wire rotation. Parameter studies reveal that the Reynolds number (Re, at the range of 6000–100,000) has little effect on the normalized transverse flow, while the pitch to pin diameter ratio (P/D, at the range of 1.11–1.22) and the helical pitch to pin diameter ratio (H/D, at the range of 12–24) have a great influence on it, especially the P/D. Large discrepancies between our simulation results and some existing correlations were observed. This indicates that new correlations comprehensively considering both P/D and H/D effects need to be developed

CFD analysis of transverse flow in a wire-wrapped hexagonal seven-pin bundle

Energy Technology Data Exchange (ETDEWEB)

Zhao, Pinghui, E-mail: phzhao@mail.ustc.edu.cn [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Liu, Jiaming; Ge, Zhihao [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Wang, Xi; Cheng, Xu [Karlsruhe Institute of Technology, Institute of Fusion and Reactor Technologies, Kaiserstrasse 12, Karlsruhe (Germany)

2017-06-15

Highlights: • Transverse flow in a wire-wrapped hexagonal seven-pin bundle are simulated. • Four kinds of subchannels are taken as the object. • Effects of wire number and position on transverse velocities are studied. • Parameter studies reveal P/D and H/D have a great influence than Re. • Present transverse velocity correlations need to be modified. - Abstract: Transverse flow induced by helical spacer wires has important effects on the flow and heat transfer behavior of reactor core. In this paper, transverse flow in a wire-wrapped hexagonal seven-pin bundle was simulated by the open source code, OpenFOAM, based on computational fluid dynamic (CFD) method. The Shear Stress Transport (SST) k-ω model and Spalding wall function were used to resolve the momentum field. Hexahedral dominated meshes were generated to achieve high grid quality. Periodic boundary condition and parallel processing were adopted to save the computational cost. Transverse velocity distributions in four different kinds of subchannel gaps were analyzed. The results show that the influence of wire number and position on the transverse velocity distribution is obvious. For an interior gap, transverse flow seems to be dominated by wires near the gap, and its direction changes periodically in one helical pitch. However, for a peripheral gap, transverse velocity is affected by more wires and its direction is decided by the direction of wire rotation. Parameter studies reveal that the Reynolds number (Re, at the range of 6000–100,000) has little effect on the normalized transverse flow, while the pitch to pin diameter ratio (P/D, at the range of 1.11–1.22) and the helical pitch to pin diameter ratio (H/D, at the range of 12–24) have a great influence on it, especially the P/D. Large discrepancies between our simulation results and some existing correlations were observed. This indicates that new correlations comprehensively considering both P/D and H/D effects need to be developed

An investigation of time-frequency domain phase-weighted stacking and its application to phase-velocity extraction from ambient noise's empirical Green's functions

Science.gov (United States)

Li, Guoliang; Niu, Fenglin; Yang, Yingjie; Xie, Jun

2018-02-01

The time-frequency domain phase-weighted stacking (tf-PWS) technique based on the S transform has been employed in stacking empirical Green's functions (EGFs) derived from ambient noise data, mainly due to its superior power in enhancing weak signals. Questions such as the induced waveform distortion and the feasibility of phase-velocity extraction are yet to be thoroughly explored. In this study, we investigate these issues by conducting extensive numerical tests with both synthetic data and USArray transportable array (TA) ambient noise data. We find that the errors in the measured phase velocities associated with waveform distortion caused by the tf-PWS depend largely on the way of how the inverse S transform (IST) is implemented. If frequency IST is employed in tf-PWS, the corresponding errors are generally less than 0.1 per cent, sufficiently small that the measured phase velocities can be safely used in regular surface wave tomography. On the other hand, if a time IST is used in tf-PWS, then the extracted phase velocities are systematically larger than those measured from linearly stacked ones, and the discrepancy can reach as much as ˜0.4 per cent at some periods. Therefore, if tf-PWS is used in stacking EGFs, then frequency IST is preferred to transform the stacked S spectra back to the time domain for the stacked EGFs.

Shear velocity model for the westernmost Mediterranean from ambient noise and ballistic finite-frequency Rayleigh wave tomography

Science.gov (United States)

Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; Harnafi, M.

2014-12-01

The westernmost Mediterranean comprises the Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin. From north to south this region consists of the Pyrenees, resulting from Iberia-Eurasia collision; the Iberian Massif, which has been undeformed since the end of the Paleozoic; the Central System and Iberian Chain, regions with intracontinental Oligocene-Miocene deformation; the Gibraltar Arc (Betics, Rif and Alboran terranes), resulting from post-Oligocene subduction roll-back; and the Atlas Mountains. We analyzed data from recent broad-band array deployments and permanent stations in the area (IberArray and Siberia arrays, the PICASSO array, the University of Munster array, and the Spanish, Portuguese and Moroccan National Networks) to characterize its lithospheric structure. The combined array of 350 stations has an average interstation spacing of ~60 km. We calculated the Rayleigh waves phase velocities from ambient noise (periods 4 to 40 s) and teleseismic events (periods 20 to 167 s). We inverted the phase velocities to obtain a shear velocity model for the lithosphere to ~200 km depth. Our results correlate well with the surface expression of the main structural units with higher crustal velocity for the Iberian Massif than for the Alpine Iberia and Atlas Mountains. The Gibraltar Arc has lower crustal shear velocities than the regional average at all crustal depths. It also shows an arc shaped anomaly with high upper mantle velocities (>4.6 km/s) at shallow depths (volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths, and suggesting that the lithosphere has been removed beneath these areas.

The effect of gradational velocities and anisotropy on fault-zone trapped waves

Science.gov (United States)

Gulley, A. K.; Eccles, J. D.; Kaipio, J. P.; Malin, P. E.

2017-08-01

Synthetic fault-zone trapped wave (FZTW) dispersion curves and amplitude responses for FL (Love) and FR (Rayleigh) type phases are analysed in transversely isotropic 1-D elastic models. We explore the effects of velocity gradients, anisotropy, source location and mechanism. These experiments suggest: (i) A smooth exponentially decaying velocity model produces a significantly different dispersion curve to that of a three-layer model, with the main difference being that Airy phases are not produced. (ii) The FZTW dispersion and amplitude information of a waveguide with transverse-isotropy depends mostly on the Shear wave velocities in the direction parallel with the fault, particularly if the fault zone to country-rock velocity contrast is small. In this low velocity contrast situation, fully isotropic approximations to a transversely isotropic velocity model can be made. (iii) Fault-aligned fractures and/or bedding in the fault zone that cause transverse-isotropy enhance the amplitude and wave-train length of the FR type FZTW. (iv) Moving the source and/or receiver away from the fault zone removes the higher frequencies first, similar to attenuation. (v) In most physically realistic cases, the radial component of the FR type FZTW is significantly smaller in amplitude than the transverse.

Kinetic transverse dispersion relation for relativistic magnetized electron-positron plasmas with Maxwell-Jüttner velocity distribution functions

Energy Technology Data Exchange (ETDEWEB)

López, Rodrigo A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile); Moya, Pablo S. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Department of Physics, Catholic University of America, Washington DC, DC 20064 (United States); Muñoz, Víctor [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Valdivia, J. Alejandro [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Santiago (Chile)

2014-09-15

We use a kinetic treatment to study the linear transverse dispersion relation for a magnetized isotropic relativistic electron-positron plasma with finite relativistic temperature. The explicit linear dispersion relation for electromagnetic waves propagating along a constant background magnetic field is presented, including an analytical continuation to the whole complex frequency plane for the case of Maxwell-Jüttner velocity distribution functions. This dispersion relation is studied numerically for various temperatures. For left-handed solutions, the system presents two branches, the electromagnetic ordinary mode and the Alfvén mode. In the low frequency regime, the Alfvén branch has two dispersive zones, the normal zone (where ∂ω/∂k > 0) and an anomalous zone (where ∂ω/∂k < 0). We find that in the anomalous zone of the Alfvén branch, the electromagnetic waves are damped, and there is a maximum wave number for which the Alfvén branch is suppressed. We also study the dependence of the Alfvén velocity and effective plasma frequency with the temperature. We complemented the analytical and numerical approaches with relativistic full particle simulations, which consistently agree with the analytical results.

Transverse Oscillations for Phased Array Vector Velocity Imaging

DEFF Research Database (Denmark)

Pihl, Michael Johannes; Jensen, Jørgen Arendt

2010-01-01

of superficial blood vessels. To broaden the usability of the method, it should be expanded to a phased array geometry enabling vector velocity imaging of the heart. Therefore, the scan depth has to be increased to 10-15 cm. This paper presents suitable pulse echo fields (PEF). Two lines are beamformed...... (correlation coefficient, R: -0.76), and therefore predict estimator performance. CV is correlated with the standard deviation (R=0.74). The results demonstrate the potential for using a phased array for vector velocity imaging at larger depths, and potentially for imaging the heart....

Improving the shear wave velocity structure beneath Bucharest (Romania) using ambient vibrations

Science.gov (United States)

Manea, Elena Florinela; Michel, Clotaire; Poggi, Valerio; Fäh, Donat; Radulian, Mircea; Balan, Florin Stefan

2016-11-01

Large earthquakes from the intermediate-depth Vrancea seismic zone are known to produce in Bucharest ground motion characterized by predominant long periods. This phenomenon has been interpreted as the combined effect of both seismic source properties and site response of the large sedimentary basin. The thickness of the unconsolidated Quaternary deposits beneath the city is more than 200 m, the total depth of sediments is more than 1000 m. Complex basin geometry and the low seismic wave velocities of the sediments are primarily responsible for the large amplification and long duration experienced during earthquakes. For a better understanding of the geological structure under Bucharest, a number of investigations using non-invasive methods have been carried out. With the goal to analyse and extract the polarization and dispersion characteristics of the surface waves, ambient vibrations and low-magnitude earthquakes have been investigated using single station and array techniques. Love and Rayleigh dispersion curves (including higher modes), Rayleigh waves ellipticity and SH-wave fundamental frequency of resonance (f0SH) have been inverted simultaneously to estimate the shear wave velocity structure under Bucharest down to a depth of about 8 km. Information from existing borehole logs was used as prior to reduce the non-uniqueness of the inversion and to constrain the shallow part of the velocity model (array (the URS experiment) installed by the National Institute for Earth Physics and by the Karlsruhe Institute of Technology during 10 months in the period 2003-2004. The array consisted of 32 three-component seismological stations, deployed in the urban area of Bucharest and adjacent zones. The large size of the array and the broad-band nature of the available sensors gave us the possibility to characterize the surface wave dispersion at very low frequencies (0.05-1 Hz) using frequency-wavenumber techniques. This is essential to explore and resolve the deeper

Blood flow measurement of transverse sinuses by using MR: a phantom study of its influence factors

International Nuclear Information System (INIS)

Gao Gejun; Feng Xiaoyuan; Li Yuan; Geng Daoying; Yao Zhengyu

2003-01-01

Objective: (1) To determine the relationship between the MR signal intensity and the actual flow velocity under steady flow condition. (2) to analyze the influence produced by the angle (θ) between the flow direction and the velocity-encoded gradient direction, and flip angle as well as section thickness on the velocity measurement under oblique flow condition. (3) to develop a suitable protocol for using this method to measure volumetric flow rate in the transverse sinus system. Methods: Flow phantom, which simulated blood-flow conditions in the transverse sinus system, consisted of a fluid-filled cylinder and a bent tube with a 3.4 mm internal diameter. A 1.5 T superconductive MR imager and VIGRE sequence were used for these studies. A suitable protocol was based on consideration of the effects of (1) the accuracy of velocity and transverse area measurement of flow, and (2) signal-to-noise ratio (SNR). Results: (1) Signal intensity (y) determined by MR and the actual flow velocity (x) showed straight-line correlation, y=68.914x + 357.206, R 2 =0.998. (2) As the angle (θ) increased, the transverse area of the signal determined by MR also increased, but the value of flow velocity decreased. (3) As the flip angle increased, the SNR varied from 5.7 to 11.2. The maximum SNR was obtained with 30 degree flip angle. (4) As the section thickness increased, the SNR and the transverse area of the signal determined by MR slightly increased. Conclusions: Phase-contrast MR imaging is a practical method for measuring volumetric flow rates. The angle (θ influenced the accuracy of flow velocity and the measurement of transverse area of flow whereas the flip angle and the section thickness substantially influenced the signal-to-noise ratio and the transverse area of flow

Application of the Spatial Auto-Correlation Method for Shear-Wave Velocity Studies Using Ambient Noise

Science.gov (United States)

Asten, M. W.; Hayashi, K.

2018-05-01

Ambient seismic noise or microtremor observations used in spatial auto-correlation (SPAC) array methods consist of a wide frequency range of surface waves from the frequency of about 0.1 Hz to several tens of Hz. The wavelengths (and hence depth sensitivity of such surface waves) allow determination of the site S-wave velocity model from a depth of 1 or 2 m down to a maximum of several kilometres; it is a passive seismic method using only ambient noise as the energy source. Application usually uses a 2D seismic array with a small number of seismometers (generally between 2 and 15) to estimate the phase velocity dispersion curve and hence the S-wave velocity depth profile for the site. A large number of methods have been proposed and used to estimate the dispersion curve; SPAC is the one of the oldest and the most commonly used methods due to its versatility and minimal instrumentation requirements. We show that direct fitting of observed and model SPAC spectra generally gives a superior bandwidth of useable data than does the more common approach of inversion after the intermediate step of constructing an observed dispersion curve. Current case histories demonstrate the method with a range of array types including two-station arrays, L-shaped multi-station arrays, triangular and circular arrays. Array sizes from a few metres to several-km in diameter have been successfully deployed in sites ranging from downtown urban settings to rural and remote desert sites. A fundamental requirement of the method is the ability to average wave propagation over a range of azimuths; this can be achieved with either or both of the wave sources being widely distributed in azimuth, and the use of a 2D array sampling the wave field over a range of azimuths. Several variants of the method extend its applicability to under-sampled data from sparse arrays, the complexity of multiple-mode propagation of energy, and the problem of precise estimation where array geometry departs from an

3-D Upper-Mantle Shear Velocity Model Beneath the Contiguous United States Based on Broadband Surface Wave from Ambient Seismic Noise

Science.gov (United States)

Xie, Jun; Chu, Risheng; Yang, Yingjie

2018-05-01

Ambient noise seismic tomography has been widely used to study crustal and upper-mantle shear velocity structures. Most studies, however, concentrate on short period (structure on a continental scale. We use broadband Rayleigh wave phase velocities to obtain a 3-D V S structures beneath the contiguous United States at period band of 10-150 s. During the inversion, 1-D shear wave velocity profile is parameterized using B-spline at each grid point and is inverted with nonlinear Markov Chain Monte Carlo method. Then, a 3-D shear velocity model is constructed by assembling all the 1-D shear velocity profiles. Our model is overall consistent with existing models which are based on multiple datasets or data from earthquakes. Our model along with the other post-USArray models reveal lithosphere structures in the upper mantle, which are consistent with the geological tectonic background (e.g., the craton root and regional upwelling provinces). The model has comparable resolution on lithosphere structures compared with many published results and can be used for future detailed regional or continental studies and analysis.

A model for the Lin-Shu type density-wave structure of our Galaxy: Line-of-sight and transverse-longitudinal velocities of 242 optically visible open clusters

Science.gov (United States)

Griv, E.; Jiang, I.-G.

2015-02-01

In this paper, the fourth in a series, we examine again one of the implications of the Lin-Shu density-wave theory, specifically, the noncircular systematic motion of the Galactic objects. Our previous investigation is extended by analyzing simultaneously both the line-of-sight and transversal velocities of a sample of open clusters for which velocities, distances and ages are available. The ordinary equations of the Oort-Lindblad theory of galactic differential rotation are used. The minor effects caused by the two-dimensional tightly-wound density waves are also taken into account. The published data of 242 currently known optically visible clusters having distances rsight and transversal along the Galactic longitude velocities are nearly equal. We argue that the resemblance of these Galactic wave structures is so remarkable that no doubt is felt as to the theory's truth with respect to these data. The results obtained allow us to conclude that several low-m trailing density-wave patterns with different number of spiral arms m (say, m=1, 2, 3, and 4), pitch angles (about 5o, 8o, 11o, and 14o, respectively) and amplitudes of the perturbed gravitational potential may coexist in the Galaxy. The latter suggests the asymmetric multiarm, not well-organized (``flocculent'') spiral structure of the system. In memory of Professors Alexei M. Fridman (1940-2010) and Chi Yuan (1937-2008)

LONGITUDINAL AND TRANSVERSAL PLASMA WAVE INSTABILITIES IN TWO COUNTERSTREAMING PLASMAS WITHOUT EXTERNAL FIELDS

Energy Technology Data Exchange (ETDEWEB)

Buenemann, D

1963-03-15

Some aspects of the theory of longitudinal and transversal waves in a collisionless nonrelativistic plasma are treated. A dispersion relation for multicomponent plasmas is derived from the linearized Boltzmann-Vlasov equation using the full set of Maxwell's equations without an external field. The velocity distributions of the plasma streams are assumed to be Maxwellian. For the particular case of two counterstreaming plasmas it is shown that there exists transversal instabilities for all counterstreaming velocities whereas the well known two stream instabilities only exist for velocities greater than a critical velocity. Exact solutions for the onset of the instabilities can be given. This kind of instability may occur for any nonisotropic velocity distribution in a collisionless plasma. (auth)

A STATISTICAL STUDY OF TRANSVERSE OSCILLATIONS IN A QUIESCENT PROMINENCE

Energy Technology Data Exchange (ETDEWEB)

Hillier, A. [Kwasan and Hida Observatories, Kyoto University, Kyoto 607-8471 (Japan); Morton, R. J. [Mathematics and Information Science, Northumbria University, Pandon Building, Camden Street, Newcastle upon Tyne NE1 8ST (United Kingdom); Erdélyi, R., E-mail: andrew@kwasan.kyoto-u.ac.jp [Solar Physics and Space Plasma Research Centre (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

2013-12-20

The launch of the Hinode satellite has allowed for seeing-free observations at high-resolution and high-cadence making it well suited to study the dynamics of quiescent prominences. In recent years it has become clear that quiescent prominences support small-amplitude transverse oscillations, however, sample sizes are usually too small for general conclusions to be drawn. We remedy this by providing a statistical study of transverse oscillations in vertical prominence threads. Over a 4 hr period of observations it was possible to measure the properties of 3436 waves, finding periods from 50 to 6000 s with typical velocity amplitudes ranging between 0.2 and 23 km s{sup –1}. The large number of observed waves allows the determination of the frequency dependence of the wave properties and derivation of the velocity power spectrum for the transverse waves. For frequencies less than 7 mHz, the frequency dependence of the velocity power is consistent with the velocity power spectra generated from observations of the horizontal motions of magnetic elements in the photosphere, suggesting that the prominence transverse waves are driven by photospheric motions. However, at higher frequencies the two distributions significantly diverge, with relatively more power found at higher frequencies in the prominence oscillations. These results highlight that waves over a large frequency range are ubiquitous in prominences, and that a significant amount of the wave energy is found at higher frequency.

A STATISTICAL STUDY OF TRANSVERSE OSCILLATIONS IN A QUIESCENT PROMINENCE

International Nuclear Information System (INIS)

Hillier, A.; Morton, R. J.; Erdélyi, R.

2013-01-01

The launch of the Hinode satellite has allowed for seeing-free observations at high-resolution and high-cadence making it well suited to study the dynamics of quiescent prominences. In recent years it has become clear that quiescent prominences support small-amplitude transverse oscillations, however, sample sizes are usually too small for general conclusions to be drawn. We remedy this by providing a statistical study of transverse oscillations in vertical prominence threads. Over a 4 hr period of observations it was possible to measure the properties of 3436 waves, finding periods from 50 to 6000 s with typical velocity amplitudes ranging between 0.2 and 23 km s –1 . The large number of observed waves allows the determination of the frequency dependence of the wave properties and derivation of the velocity power spectrum for the transverse waves. For frequencies less than 7 mHz, the frequency dependence of the velocity power is consistent with the velocity power spectra generated from observations of the horizontal motions of magnetic elements in the photosphere, suggesting that the prominence transverse waves are driven by photospheric motions. However, at higher frequencies the two distributions significantly diverge, with relatively more power found at higher frequencies in the prominence oscillations. These results highlight that waves over a large frequency range are ubiquitous in prominences, and that a significant amount of the wave energy is found at higher frequency

Examples of in-vivo blood vector velocity estimation

DEFF Research Database (Denmark)

Udesen, Jesper; Nielsen, Michael Bachmann; Nielsen, Kristian R.

2007-01-01

In this paper examples of in-vivo blood vector velocity images of the carotid artery are presented. The transverse oscillation (TO) method for blood vector velocity estimation has been used to estimate the vector velocities and the method is first evaluated in a circulating flowrig where...

Shear wave velocity structure of the Anatolian Plate and surrounding regions using Ambient Noise Tomography

Science.gov (United States)

Delph, J. R.; Beck, S. L.; Zandt, G.; Biryol, C. B.; Ward, K. M.

2013-12-01

The Anatolian Plate consists of various lithospheric terranes amalgamated during the closure of the Tethys Ocean, and is currently extruding to the west in response to a combination of the collision of the Arabian plate in the east and the roll back of the Aegean subduction zone in the west. We used Ambient Noise Tomography (ANT) at periods structure of the Anatolian Plate. We computed a total of 13,779 unique cross-correlations using one sample-per-second vertical component broadband seismic data from 215 stations from 8 different networks over a period of 7 years to compute fundamental-mode Rayleigh wave dispersion curves following the method of Benson et al. (2007). We then inverted the dispersion data to calculate phase velocity maps for 11 periods from 8 s - 40 s throughout Anatolia and the Aegean regions (Barmin et al. 2001). Using smoothed Moho values derived from Vanacore et al. (2013) in our starting models, we inverted our dispersion curves using a linear least-squares iterative inversion scheme (Herrmann & Ammon 2004) to produce a 3-D shear-wave velocity model of the crust and uppermost mantle throughout Anatolia and the Aegean. We find a good correlation between our seismic shear wave velocities and paleostructures (suture zones) and modern deformation (basin formation and fault deformation). The most prominent crustal velocity contrasts occur across intercontinental sutures zones, resulting from the juxtaposition of the compositionally different basements of the amalgamated terranes. At shallow depths, seismic velocity contrasts correspond closely with surficial features. The Thrace, Cankiri and Tuz Golu basins, and accretionary complexes related to the closure of the Neotethys are characterized by slow shear wave velocities, while the Menderes and Kirsehir Massifs, Pontides, and Istanbul Zone are characterized by fast velocities. We find that the East Anatolia Plateau has slow shear-wave velocities, as expected due to high heat flow and active

Multi-component pre-stack time-imaging and migration-based velocity analysis in transversely isotropic media; Imagerie sismique multicomposante et analyse de vitesse de migration en milieu transverse isotrope

Energy Technology Data Exchange (ETDEWEB)

Gerea, C.V.

2001-06-01

Complementary to the recording of compressional (P-) waves, the observation of P-S converted waves has recently been receiving specific attention. This is mainly due to their tremendous potential as a tool for fracture and lithology characterization, imaging sediments in gas saturated rocks, and imaging shallow sediments with higher resolution than conventional P-P data. In a conventional marine seismic survey, we cannot record P-to-S converted-wave energy since the fluids cannot support shear-wave strain. Thus, to capture the converted-wave energy, we need to record it at the water-bottom casing an ocean-bottom cable (OBC). The S-waves recorded at the seabed are mainly converted from P to S (i.e., PS-waves or C-waves) at the subsurface reflectors. The most accurate way to image seismic data is pre-stack depth migration. In this thesis, I develop a numerically efficient 2.5-D true-amplitude elastic Kirchhoff pre-stack migration algorithm designed to handle OBC data gathered along a single line. All the kinematic and dynamic elastic Green's functions required in the computation of true-amplitude weight term of Kirchhoff summation, are based on the non-hyperbolic explicit approximations of P- and SV-wave travel-times in layered transversely isotropic (VTI) media. Hence, this elastic imaging algorithm is very well-suited for migration-based velocity analysis techniques, for which fast, robust and iterative pre-stack migration is desired. In this thesis, I approach also the topic of anisotropic velocity model building for elastic pre-stack time-imaging. and propose an original methodology for joint PP-PS migration-based velocity analysis (MVA) in layered VTI anisotropic media. Tests on elastic synthetic and real OBC seismic data ascertain the validity of the pre-stack migration algorithm and velocity analysis methodology. (author)

Superconducting RF for Low-Velocity and Intermediate-Velocity Beams

CERN Document Server

Grimm, Terry L

2005-01-01

Existing superconducting radio frequency (SRF) linacs are used to accelerate ions (protons through uranium) with velocities less than about 15% the speed of light, or electrons with velocities approximately equal to the speed of light. In the last ten years, prototype SRF cavities have completely covered the remaining range of velocities. They have demonstrated that SRF linacs will be capable of accelerating electrons from rest up to the speed of light, and ions from less than 1% up to the speed of light. When the Spallation Neutron Source is operational, SRF ion linacs will have covered the full range of velocities except for v/c ~ 0.15 to v/c ~ 0.5. A number of proposed projects (RIA, EURISOL) would span the latter range of velocities. Future SRF developments will have to address the trade-offs associated with a number of issues, including high gradient operation, longitudinal and transverse acceptance, microphonics, Lorentz detuning, operating temperature, cryogenic load, number of gaps or cells per cavity...

Transverse and Longitudinal Doppler Effects of the Sunbeam Spectra and Earth-Self Rotation and Orbital Velocities, the Mass of the Sun and Others

OpenAIRE

Nam, Sang Boo

2009-01-01

The transverse and longitudinal Doppler effects of the sunbeam spectra are shown to result in the earth parameters such as the earth-self rotation and revolution velocities, the earth orbit semi-major axis, the earth orbital angular momentum, the earth axial tilt, the earth orbit eccentricity, the local latitude and the mass of the sun. The sunbeam global positioning scheme is realized, including the earth orbital position. PACS numbers: 91.10.Fc, 95.10.Km, 91.10.Da, 91.10.Jf.

The Utility of the Extended Images in Ambient Seismic Wavefield Migration

Science.gov (United States)

Girard, A. J.; Shragge, J. C.

2015-12-01

Active-source 3D seismic migration and migration velocity analysis (MVA) are robust and highly used methods for imaging Earth structure. One class of migration methods uses extended images constructed by incorporating spatial and/or temporal wavefield correlation lags to the imaging conditions. These extended images allow users to directly assess whether images focus better with different parameters, which leads to MVA techniques that are based on the tenets of adjoint-state theory. Under certain conditions (e.g., geographical, cultural or financial), however, active-source methods can prove impractical. Utilizing ambient seismic energy that naturally propagates through the Earth is an alternate method currently used in the scientific community. Thus, an open question is whether extended images are similarly useful for ambient seismic migration processing and verifying subsurface velocity models, and whether one can similarly apply adjoint-state methods to perform ambient migration velocity analysis (AMVA). Herein, we conduct a number of numerical experiments that construct extended images from ambient seismic recordings. We demonstrate that, similar to active-source methods, there is a sensitivity to velocity in ambient seismic recordings in the migrated extended image domain. In synthetic ambient imaging tests with varying degrees of error introduced to the velocity model, the extended images are sensitive to velocity model errors. To determine the extent of this sensitivity, we utilize acoustic wave-equation propagation and cross-correlation-based migration methods to image weak body-wave signals present in the recordings. Importantly, we have also observed scenarios where non-zero correlation lags show signal while zero-lags show none. This may be a valuable missing piece for ambient migration techniques that have yielded largely inconclusive results, and might be an important piece of information for performing AMVA from ambient seismic recordings.

New Observations of Seismic Group Velocities in the Western Solomon Islands from Cross-Correlation of Ambient Seismic Noise

Science.gov (United States)

Ku, C. S.; You, S. H.; Kuo, Y. T.; Huang, B. S.; Wu, Y. M.; Chen, Y. G.; Taylor, F. W.

2015-12-01

A MW 8.1 earthquake occurred on 1 April 2007 in the western Solomon Islands. Following this event, a damaging tsunami was induced and hit the Island Gizo where the capital city of Western Province of Solomon Islands located. Several buildings of this city were destroyed and several peoples lost their lives during this earthquake. However, during this earthquake, no near source seismic instrument has been installed in this region. The seismic evaluations for the aftershock sequence, the possible earthquake early warning and tsunami warning were unavailable. For the purpose of knowing more detailed information about seismic activity in this region, we have installed 9 seismic stations (with Trillium 120PA broadband seismometer and Q330S 24bit digitizer) around the rupture zone of the 2007 earthquake since September of 2009. Within a decade, it has been demonstrated both theoretically and experimentally that the Green's function or impulse response between two seismic stations can be retrieved from the cross-correlation of ambient noise. In this study, 6 stations' observations which are more complete during 2011/10 ~ 2012/12 period, were selected for the purpose of the cross-correlation analysis of ambient seismic noise. The group velocities at period 2-20 seconds of 15 station-pairs were extracted by using multiple filter technique (MFT) method. The analyzed results of this study presented significant results of group velocities with higher frequency contents than other studies (20-60 seconds in usually cases) and opened new opportunities to study the shallow crustal structure of the western Solomon Islands.

Crustal and upper mantle shear velocities of Iberia, the Alboran Sea, and North Africa from ambient noise and ballistic finite-frequency Rayleigh wave tomography

Science.gov (United States)

Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; mimoun, H.

2013-12-01

The complex Mesozoic-Cenozoic Alpine deformation in the western Mediterranean extends from the Pyrenees in northern Spain to the Atlas Mountains in southern Morocco. The Iberian plate was accreted to the European plate in late Cretaceous, resulting in the formation of the Pyrenees. Cenozoic African-European convergence resulted in subduction of the Tethys oceanic plate beneath Europe. Rapid Oligocene slab rollback from eastern Iberia spread eastward and southward, with the trench breaking into three segments by the time it reached the African coast. One trench segment moved southwestward and westward creating the Alboran Sea, floored by highly extended continental crust, and building the encircling Betics Rif mountains comprising the Gibraltar arc, and the Atlas mountains, which formed as the inversion of a Jurassic rift. A number of recent experiments have instrumented this region with broad-band arrays (the US PICASSO array, Spanish IberArray and Siberia arrays, the University of Munster array), which, including the Spanish, Portuguese, and Moroccan permanent networks, provide a combined array of 350 stations having an average interstation spacing of ~60 km. Taking advantage of this dense deployment, we have calculated the Rayleigh waves phase velocities from ambient noise for short periods (4 s to 40 s) and teleseismic events for longer periods (20 s to 167 s). Approximately 50,000 stations pairs were used to measure the phase velocity from ambient noise and more than 160 teleseismic events to measure phase velocity for longer periods. The inversion of the phase velocity dispersion curves provides a 3D shear velocity for the crust and uppermost mantle. Our results show differences between the various tectonic regions that extend to upper mantle depths (~200 km). In Iberia we obtain, on average, higher upper mantle shear velocities in the western Variscan region than in the younger eastern part. We map high upper mantle velocities (>4.6 km/s) beneath the

Efficient focusing scheme for transverse velocity estimation using cross-correlation

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt

2001-01-01

simulations with Field II. A 64-elements, 5 MHz linear array was used. A parabolic velocity profile with a peak velocity of 0.5 m/s was considered for different angles between the flow and the ultrasound beam and for different emit foci. At 60 degrees the relative standard deviation was 0.58 % for a transmit...

Construindo cidadania ambiental na escola

Directory of Open Access Journals (Sweden)

Cibele Schwanke

2014-03-01

Full Text Available http://dx.doi.org/10.5007/1807-0221.2013v10n16p14 O forte componente transversal da Educação Ambiental possibilita sua inserção em vários espaços e níveis de escolaridade. No ensino fundamental, constitui-se em uma importante ferramenta para criar espaços que permitam a abordagem de temáticas socioambientais atuais, de forma crítica e participativa. O presente trabalho tem como objetivo apresentar o Projeto Construindo Cidadania Ambiental, executado por bolsistas do Grupo PET - Conexões Gestão Ambiental em unidades escolares, explicitando sua filosofia de implantação e resultados obtidos até o momento. Verifica-se que sua natureza interdisciplinar e integrada permite uma efetiva interação com o corpo docente e discente da escola, bem como permite a prática de uma educação ambiental crítica e transformadora.

Shallow velocity structure above the Socorro Magma Body from ambient noise tomography using the large-N Sevilleta array, central Rio Grande Rift, New Mexico

Science.gov (United States)

Worthington, L. L.; Ranasinghe, N. R.; Schmandt, B.; Jiang, C.; Finlay, T. S.; Bilek, S. L.; Aster, R. C.

2017-12-01

The Socorro Magma Body (SMB) is one of the largest recognized active mid-crustal magma intrusions globally. Inflation of the SMB drives sporadically seismogenic uplift at rates of up to of few millimeters per year. We examine the upper crustal structure of the northern section of the SMB region using ambient noise seismic data collected from the Sevilleta Array and New Mexico Tech (NMT) seismic network to constrain basin structure and identify possible upper crustal heterogeneities caused by heat flow and/or fluid or magma migration to shallower depths. The Sevilleta Array comprised 801 vertical-component Nodal seismic stations with 10-Hz seismometers deployed within the Sevilleta National Wildlife Refuge in the central Rio Grande rift north of Socorro, New Mexico, for a period of 12 days during February 2015. Five short period seismic stations from the NMT network located south of the Sevilleta array are also used to improve the raypath coverage outside the Sevilleta array. Inter-station ambient noise cross-correlations were computed from all available 20-minute time windows and stacked to obtain estimates of the vertical component Green's function. Clear fundamental mode Rayleigh wave energy is observed from 3 to 6 s period. Beamforming indicates prominent noise sources from the southwest, near Baja California, and the southeast, in the Gulf of Mexico. The frequency-time analysis method was implemented to measure fundamental mode Rayleigh wave phase velocities and the resulting inter-station travel times were inverted to obtain 2-D phase velocity maps. One-dimensional sensitivity kernels indicate that the Rayleigh wave phase velocity maps are sensitive to a depth interval of 1 to 8 km, depending on wave period. The maps show (up to 40%) variations in phase velocity within the Sevilleta Array, with the largest variations found for periods of 5-6 seconds. Holocene to upper Pleistocene, alluvial sediments found in the Socorro Basin consistently show lower phase

A New Method for Estimation of Velocity Vectors

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt; Munk, Peter

1998-01-01

The paper describes a new method for determining the velocity vector of a remotely sensed object using either sound or electromagnetic radiation. The movement of the object is determined from a field with spatial oscillations in both the axial direction of the transducer and in one or two...... directions transverse to the axial direction. By using a number of pulse emissions, the inter-pulse movement can be estimated and the velocity found from the estimated movement and the time between pulses. The method is based on the principle of using transverse spatial modulation for making the received...

Response of a swirl-stabilized flame to transverse acoustic excitation

Science.gov (United States)

O'Connor, Jacqueline

This work addresses the issue of transverse combustion instabilities in annular gas turbine combustor geometries. While modern low-emissions combustion strategies have made great strides in reducing the production of toxic emissions in aircraft engines and power generation gas turbines, combustion instability remains one of the foremost technical challenges in the development of next generation combustor technology. To that end, this work investigates the response of a swirling flow and swirl-stabilized flame to a transverse acoustic field is using a variety of high-speed laser techniques, especially high-speed particle image velocimetry (PIV) for detailed velocity measurements of this highly unsteady flow phenomenon. Several important issues are addressed. First, the velocity-coupled pathway by which the unsteady velocity field excites the flame is described in great detail. Here, a transfer function approach has been taken to illustrate the various pathways through which the flame is excited by both acoustic and vortical velocity fluctuations. It has been shown that while the direct excitation of the flame by the transverse acoustic field is a negligible effect in most combustor architectures, the coupling between the transverse acoustic mode in the combustor and the longitudinal mode in the nozzle is an important pathway that can result in significant flame response. In this work, the frequency response of this pathway as well as the resulting flame response is measured using PIV and chemiluminescence measurements, respectively. Next, coupling between the acoustic field and the hydrodynamically unstable swirling flow provides a pathway that can lead to significant flame wrinkling by large coherent structures in the flow. Swirling flows display two types of hydrodynamic instability: an absolutely unstable jet and convectively unstable shear layers. The absolute instability of the jet results in vortex breakdown, a large recirculation zone along the centerline of

Ambient Temperature and Cerebrovascular Hemodynamics in the Elderly.

Science.gov (United States)

Pan, Wen-Chi; Eliot, Melissa N; Koutrakis, Petros; Coull, Brent A; Sorond, Farzaneh A; Wellenius, Gregory A

2015-01-01

Some prior studies have linked ambient temperature with risk of cerebrovascular events. If causal, the pathophysiologic mechanisms underlying this putative association remain unknown. Temperature-related changes in cerebral vascular function may play a role, but this hypothesis has not been previously evaluated. We evaluated the association between ambient temperature and cerebral vascular function among 432 participants ≥65 years old from the MOBILIZE Boston Study with data on cerebrovascular blood flow, cerebrovascular resistance, and cerebrovascular reactivity in the middle cerebral artery. We used linear regression models to assess the association of mean ambient temperature in the previous 1 to 28 days with cerebrovascular hemodynamics adjusting for potential confounding factors. A 10°C increase in the 21-day moving average of ambient temperature was associated with a 10.1% (95% confidence interval [CI], 2.2%, 17.3%) lower blood flow velocity, a 9.0% (95% CI, 0.7%, 18.0%) higher cerebrovascular resistance, and a 15.3% (95%CI, 2.7%, 26.4%) lower cerebral vasoreactivity. Further adjustment for ozone and fine particulate matter (PM2.5) did not materially alter the results. However, we found statistically significant interactions between ambient temperature and PM2.5 such that the association between temperature and blood flow velocity was attenuated at higher levels of PM2.5. In this elderly population, we found that ambient temperature was negatively associated with cerebral blood flow velocity and cerebrovascular vasoreactivity and positively associated with cerebrovascular resistance. Changes in vascular function may partly underlie the observed associations between ambient temperature and risk of cerebrovascular events.

New technology - demonstration of a vector velocity technique

DEFF Research Database (Denmark)

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

2011-01-01

With conventional Doppler ultrasound it is not possible to estimate direction and velocity of blood flow, when the angle of insonation exceeds 60-70°. Transverse oscillation is an angle independent vector velocity technique which is now implemented on a conventional ultrasound scanner. In this pa...

Instability of shallow open channel flow with lateral velocity gradients

Energy Technology Data Exchange (ETDEWEB)

Lima, A C; Izumi, N, E-mail: adriano@eng.hokudai.ac.jp, E-mail: nizumi@eng.hokudai.ac.jp [River and Watershed Engineering Laboratory, Hokkaido University, Sapporo, 060-8628 (Japan)

2011-12-22

The turbulent flow in a wide rectangular open channel partially covered with vegetation is studied using linear stability analysis. In the base state normal flow condition, the water depth is constant and the transverse velocity vanishes, while there is a lateral gradient in the streamwise velocity with an inflexion point at the boundary between the vegetated zone and the main channel. The Reynolds stress is expressed by introducing the eddy viscosity, which is obtained from assuming a logarithmic distribution of the velocity near the bed. Perturbation expansions are introduced to the streamwise and transverse velocities, as well as to the water depth. The system of governing equations was solved in order to determine the maximum growth rate of the perturbations as a function of parameters which describe physical characteristics of the channel and the flow.

Nondestructive evaluation of green wood using stress wave and transverse vibration techniques

Science.gov (United States)

Udaya B. Halabe; Gangadhar M. Bidigalu; Hota V.S. GangaRao; Robert J. Ross

1997-01-01

Longitudinal stress wave and transverse vibration nondestructive testing (NDT) techniques have proven to be accurate means of evaluating the quality of wood based products. Researchers have found strong relationships between stress wave and transverse vibration parameters (e.g., wave velocity and modulus of elasticity predicted using NDT measurements) with the actual...

Measurement of Ambient Air Motion of D. I. Gasoline Spray by LIF-PIV

Science.gov (United States)

Yamakawa, Masahisa; Isshiki, Seiji; Yoshizaki, Takuo; Nishida, Keiya

Ambient air velocity distributions in and around a D. I. gasoline spray were measured using a combination of LIF and PIV techniques. A rhodamine and water solution was injected into ambient air to disperse the fine fluorescent liquid particles used as tracers. A fuel spray was injected into the fluorescent tracer cloud and was illuminated by an Nd: YAG laser light sheet (532nm). The scattered light from the spray droplets and tracers was cut off by a high-pass filter (>560nm). As the fluorescence (>600nm) was transmitted through the high-pass filter, the tracer images were captured using a CCD camera and the ambient air velocity distribution could be obtained by PIV based on the images. This technique was applied to a D. I. gasoline spray. The ambient air flowed up around the spray and entered into the tail of the spray. Furthermore, the relative velocity between the spray and ambient air was investigated.

A new estimator for vector velocity estimation [medical ultrasonics

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt

2001-01-01

A new estimator for determining the two-dimensional velocity vector using a pulsed ultrasound field is derived. The estimator uses a transversely modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation...... be introduced, and the velocity estimation is done at a fixed depth in tissue to reduce the influence of a spatial velocity spread. Examples for different velocity vectors and field conditions are shown using both simple and more complex field simulations. A relative accuracy of 10.1% is obtained...

Numerical study of ambient pressure for laser-induced bubble near a rigid boundary

Science.gov (United States)

Li, BeiBei; Zhang, HongChao; Han, Bing; Lu, Jian

2012-07-01

The dynamics of the laser-induced bubble at different ambient pressures was numerically studied by Finite Volume Method (FVM). The velocity of the bubble wall, the liquid jet velocity at collapse, and the pressure of the water hammer while the liquid jet impacting onto the boundary are found to increase nonlinearly with increasing ambient pressure. The collapse time and the formation time of the liquid jet are found to decrease nonlinearly with increasing ambient pressure. The ratios of the jet formation time to the collapse time, and the displacement of the bubble center to the maximal radius while the jet formation stay invariant when ambient pressure changes. These ratios are independent of ambient pressure.

An In-vivo investigation of transverse flow estimation

DEFF Research Database (Denmark)

Udesen, Jesper; Jensen, Jørgen Arendt

2004-01-01

, and 1.4 seconds of data is acquired. Using 2 parallel receive beamformers a transverse oscillation is introduced with an oscillation period 1.2 mm. The velocity estimation is performed using an extended autocorrelation algorithm. The volume flow can be estimated with a relative standard deviation of 13...

Estimates of ambient groundwater velocity in the alluvium south of Yucca Mountain from single-well tracer tests

International Nuclear Information System (INIS)

Reimus, P.W.; Umari, M.J.; Roback, R.; Earle, John; Darnell, Jon; Farnham, Irene

2002-01-01

The saturated alluvium located south of Yucca Mountain, Nevada is expected to serve as the final barrier to radionuclide transport from the proposed high-level nuclear waste repository at Yucca Mountain. The alluvium will act as a barrier if radionuclides breach the engineered barriers in the repository, move through the unsaturated zone beneath the repository to the water table, and then migrate through saturated volcanic tuffs to the alluvium. Three single-well injection-withdrawal tracer tests were conducted between December 2000 and April 2001 in the saturated alluviuni at NC-EWDP-19D1, a Nye County-Early Warning Drilling Program well located about 18 km south of Yucca Mountain. The tests had the objectives of (1) distinguishing between a single- and a dual-porosity conceptual radionuclide transport model for the alluvium, and (2) obtaining estimates of ambient groundwater velocity in the alluvium.

Prominent transverse flow of clusters in stopped Au(150AMeV)+Au reactions

International Nuclear Information System (INIS)

Coffin, J.P.; Kuhn, C.; Roy, C.; Cerruti, C.; Crochet, P.; Fintz, P.; Guillaume, G.; Houari, A.; Jundt, F.; Rami, F.; Tizniti, L.; Wagner, P.; Konopka, J.; Stoecker, H.

1995-01-01

Stopped Au(150AMeV)+Au collisions have been measured with the FOPI-Detector at GSI by imposing an upper limit on the ratio of the global longitudinal momentum to the collected charge within an event. The ejectiles, in particular those with Z>3, have a rapidity close to mid-rapidity and exhibit angular distributions in the centre-of-mass strongly peaking around 90 thus suggesting an enhancement of the flow in the transverse direction. Fits to the data and comparisons with QMD calculations indicate an averaged collective velocity in the transverse direction equal to 0.12c. Significance of the determined velocity and temperature values is discussed. ((orig.))

General planar transverse domain walls realized by optimized transverse magnetic field pulses in magnetic biaxial nanowires

Science.gov (United States)

Li, Mei; Wang, Jianbo; Lu, Jie

2017-02-01

The statics and field-driven dynamics of transverse domain walls (TDWs) in magnetic nanowires (NWs) have attracted continuous interests because of their theoretical significance and application potential in future magnetic logic and memory devices. Recent results demonstrate that uniform transverse magnetic fields (TMFs) can greatly enhance the wall velocity, meantime leave a twisting in the TDW azimuthal distribution. For application in high-density NW devices, it is preferable to erase the twisting so as to minimize magnetization frustrations. Here we report the realization of a completely planar TDW with arbitrary tilting attitude in a magnetic biaxial NW under a TMF pulse with fixed strength and well-designed orientation profile. We smooth any twisting in the TDW azimuthal plane thus completely decouple the polar and azimuthal degrees of freedom. The analytical differential equation describing the polar angle distribution is derived and the resulting solution is not the Walker-ansatz form. With this TMF pulse comoving, the field-driven dynamics of the planar TDW is investigated with the help of the asymptotic expansion method. It turns out the comoving TMF pulse increases the wall velocity under the same axial driving field. These results will help to design a series of modern magnetic devices based on planar TDWs.

Turbine airfoil with ambient cooling system

Science.gov (United States)

Campbell, Jr, Christian X.; Marra, John J.; Marsh, Jan H.

2016-06-07

A turbine airfoil usable in a turbine engine and having at least one ambient air cooling system is disclosed. At least a portion of the cooling system may include one or more cooling channels configured to receive ambient air at about atmospheric pressure. The ambient air cooling system may have a tip static pressure to ambient pressure ratio of at least 0.5, and in at least one embodiment, may include a tip static pressure to ambient pressure ratio of between about 0.5 and about 3.0. The cooling system may also be configured such that an under root slot chamber in the root is large to minimize supply air velocity. One or more cooling channels of the ambient air cooling system may terminate at an outlet at the tip such that the outlet is aligned with inner surfaces forming the at least one cooling channel in the airfoil to facilitate high mass flow.

Performance of the Transverse Oscillation method using beamformed data from a commercial scanner

DEFF Research Database (Denmark)

Pihl, Michael Johannes; Nikolov, S.; Haugaard, P.

2009-01-01

Blood velocity estimates using conventional color flow imaging (CFI) or Doppler techniques are angle dependent. One of the proposed techniques to overcome this limitation is the Transverse Oscillation (TO) method, which also estimates the lateral velocity components. The performance of this is ev......Blood velocity estimates using conventional color flow imaging (CFI) or Doppler techniques are angle dependent. One of the proposed techniques to overcome this limitation is the Transverse Oscillation (TO) method, which also estimates the lateral velocity components. The performance...... deviation and bias of the velocity components. The relative mean standard deviation decreases as the number of shots per estimate increases and a value of 5% is obtained for 64 shots per estimate. For a center frequency of 5 MHz at 60°, 75°, and 90°, the relative mean bias varies from 21% to 27......% and is lowest at a transmit focal depth close to the center of the vessel. The present performance is comparable with the results from the experimental scanner and simulations. It is obtained with only few changes to the conventional CFI setup and further optimization can improve the performance...

Observations of transverse ion acceleration in the topside auroral ionosphere

International Nuclear Information System (INIS)

Garbe, G.P.; Arnoldy, R.L.; Moore, T.E.; Kintner, P.M.; Vago, J.L.

1992-01-01

Data obtained from a sounding rocket flight which reached an apogee of 927 km and passed through several auroral arcs are reported. During portions of the flight when the rocket was not in an energetic auroral structure, the ion data are fit to a Maxwellian function which yields the plasma parameters. Throughout the middle portion of the flight when above 700 km altitude, ion distributions having a superthermal tail were measured. These ion distributions generally coexisted with a cold thermal core distribution and peaked at pitch angles slightly greater than 90 degree, which identifies them as conic distributions. These ions can be modeled using a bi-Maxwellian distribution function with a perpendicular (to B) temperature about 10 times greater than the parallel temperature of 0.15 eV. When the rocket was immersed in energetic auroral electron precipitation, two other ion distributions were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed continuously in these arcs. The characteristic perpendicular energy of the transversely bulk heated ions reached as high as 3 eV compared to typically less than 0.4 eV during nonauroral times. Cold ions flowing down the magnetic field were also continuously observed when the rocket was immersed in auroral electron precipitation and had downward speeds between 3 and 5 km/s. If one balances electric and collisional forces, these speeds translate to an electric field pointing into the atmosphere of magnitude 0.01 mV/m. A close correlation between auroral electron precipitation, measured electrostatic oxygen cyclotron waves, cold downflowing ions and transversely bulk heated ions will be shown

A Potential Method for Body and Surface Wave Propagation in Transversely Isotropic Half- and Full-Spaces

Directory of Open Access Journals (Sweden)

Mehdi Raoofian Naeeni

2016-12-01

Full Text Available The problem of propagation of plane wave including body and surface waves propagating in a transversely isotropic half-space with a depth-wise axis of material symmetry is investigated in details. Using the advantage of representation of displacement fields in terms of two complete scalar potential functions, the coupled equations of motion are uncoupled and reduced to two independent equations for potential functions. In this paper, the secular equations for determination of body and surface wave velocities are derived in terms of both elasticity coefficients and the direction of propagation. In particular, the longitudinal, transverse and Rayleigh wave velocities are determined in explicit forms. It is also shown that in transversely isotropic materials, a Rayleigh wave may propagate in different manner from that of isotropic materials. Some numerical results for synthetic transversely isotropic materials are also illustrated to show the behavior of wave motion due to anisotropic nature of the problem.

Influence of transverse reinforcement on perforation resistance of reinforced concrete slabs under hard missile impact

International Nuclear Information System (INIS)

Orbovic, Nebojsa; Sagals, Genadijs; Blahoianu, Andrei

2015-01-01

This paper describes the work conducted by the Canadian Nuclear Safety Commission (CNSC) related to the influence of transverse reinforcement on perforation capacity of reinforced concrete (RC) slabs under “hard” missile impact (impact with negligible missile deformations). The paper presents the results of three tests on reinforced concrete slabs conducted at VTT Technical Research Centre (Finland), along with the numerical simulations as well as a discussion of the current code provisions related to impactive loading. Transverse reinforcement is widely used for improving the shear and punching strength of concrete structures. However, the effect of this reinforcement on the perforation resistance under localized missile impact is still unclear. The goal of this paper is to fill the gap in the current literature related to this topic. Based on similar tests designed by the authors with missile velocity below perforation velocity, it was expected that transverse reinforcement would improve the perforation resistance. Three slabs were tested under almost identical conditions with the only difference being the transverse reinforcement. One slab was designed without transverse reinforcement, the second one with the transverse reinforcement in form of conventional stirrups with hooks and the third one with the transverse reinforcement in form of T-headed bars. Although the transverse reinforcement reduced the overall damage of the slabs (the rear face scabbing), the conclusion from the tests is that the transverse reinforcement does not have important influence on perforation capacity of concrete slabs under rigid missile impact. The slab with T-headed bars presented a slight improvement compared to the baseline specimen without transverse reinforcement. The slab with conventional stirrups presented slightly lower perforation capacity (higher residual missile velocity) than the slab without transverse reinforcement. In conclusion, the performed tests show slightly

Suggestions for new transverse oscillations damping systems in large synchrotrons and colliders

International Nuclear Information System (INIS)

Ivanov, I.N.; Melnikov, V.A.

1994-01-01

Due to the high requirements on beam quality, modern synchrotrons and colliders require special systems for transverse oscillation damping (TDS). New system for the correction of injection errors and multibunch instabilities is proposed. The special beam monitor on the basis of the axial-slotted lines is developed for the transverse beam velocity measuring. The special nonlinear regime of damping is suggested to decrease the operating time of TDS. 2 refs., 4 figs., 2 tabs

Real-Time GPU Implementation of Transverse Oscillation Vector Velocity Flow Imaging

DEFF Research Database (Denmark)

Bradway, David; Pihl, Michael Johannes; Krebs, Andreas

2014-01-01

Rapid estimation of blood velocity and visualization of complex flow patterns are important for clinical use of diagnostic ultrasound. This paper presents real-time processing for two-dimensional (2-D) vector flow imaging which utilizes an off-the-shelf graphics processing unit (GPU). In this work...... vector flow acquisition takes 2.3 milliseconds seconds on an Advanced Micro Devices Radeon HD 7850 GPU card. The detected velocities are accurate to within the precision limit of the output format of the display routine. Because this tool was developed as a module external to the scanner’s built...

Upper crustal structure of Madeira Island revealed from ambient noise tomography

Science.gov (United States)

Matos, Catarina; Silveira, Graça; Matias, Luís; Caldeira, Rita; Ribeiro, M. Luísa; Dias, Nuno A.; Krüger, Frank; Bento dos Santos, Telmo

2015-06-01

We present the first image of the Madeira upper crustal structure, using ambient seismic noise tomography. 16 months of ambient noise, recorded in a dense network of 26 seismometers deployed across Madeira, allowed reconstructing Rayleigh wave Green's functions between receivers. Dispersion analysis was performed in the short period band from 1.0 to 4.0 s. Group velocity measurements were regionalized to obtain 2D tomographic images, with a lateral resolution of 2.0 km in central Madeira. Afterwards, the dispersion curves, extracted from each cell of the 2D group velocity maps, were inverted as a function of depth to obtain a 3D shear wave velocity model of the upper crust, from the surface to a depth of 2.0 km. The obtained 3D velocity model reveals features throughout the island that correlates well with surface geology and island evolution.

Geotail observations of FTE velocities

Directory of Open Access Journals (Sweden)

G. I. Korotova

2009-01-01

Full Text Available We discuss the plasma velocity signatures expected in association with flux transfer events (FTEs. Events moving faster than or opposite the ambient media should generate bipolar inward/outward (outward/inward flow perturbations normal to the nominal magnetopause in the magnetosphere (magnetosheath. Flow perturbations directly upstream and downstream from the events should be in the direction of event motion. Flows on the flanks should be in the direction opposite the motion of events moving at subsonic and subAlfvénic speeds relative to the ambient plasma. Events moving with the ambient flow should generate no flow perturbations in the ambient plasma. Alfvén waves propagating parallel (antiparallel to the axial magnetic field of FTEs may generate anticorrelated (correlated magnetic field and flow perturbations within the core region of FTEs. We present case studies illustrating many of these signatures. In the examples considered, Alfvén waves propagate along event axes away from the inferred reconnection site. A statistical study of FTEs observed by Geotail over a 3.5-year period reveals that FTEs within the magnetosphere invariably move faster than the ambient flow, while those in the magnetosheath move both faster and slower than the ambient flow.

La educación ambiental como tema transversal en el área de conocimiento del medio

OpenAIRE

Pérez Rojo, Patricia

2013-01-01

La problemática ambiental constituye un tema de interés social a día de hoy, pues es el ser humano el responsable del deterioro de los hábitats y las condiciones ambientales de nuestro planeta. Por ello, es necesario potenciar la educación ambiental en la escuela como medio para transmitir una serie de valores y hábitos que encaminen a las generaciones hacia una forma de vida respetuosa con el medio ambiente consiguiéndose así la formación de una conciencia social basada en el cuidado del en...

In-vivo studies of new vector velocity and adaptive spectral estimators in medical ultrasound

DEFF Research Database (Denmark)

Hansen, Kristoffer Lindskov

In this PhD project new ultrasound techniques for blood flow measurements have been investigated in-vivo. The focus has mainly been on vector velocity techniques and four different approaches have been examined: Transverse Oscillation, Synthetic Transmit Aperture, Directional Beamforming and Plane...... in conventional Doppler ultrasound. That is angle dependency, reduced temporal resolution and low frame rate. Transverse Oscillation, Synthetic Transmit Aperture and Directional Beamforming can estimate the blood velocity angle independently. The three methods were validated in-vivo against magnetic resonance...... phase contrast angiography when measuring stroke volumes in simple vessel geometry on 11 volunteers. Using linear regression and Bland-Altman analyses good agreements were found, indicating that vector velocity methods can be used for quantitative blood flow measurements. Plane Wave Excitation can...

Transverse Oscillation Vector Velocity Estimation using a Phased Array Transducer

DEFF Research Database (Denmark)

Marcher, Jønne; Pihl, Michael Johannes; Seerup, Gert

2012-01-01

greater than 100 mm. Tests at depths of 72 mm and 82 mm with a peak velocity of 0.5 m/s, showed a relative mean bias ~Bvx that varied from 0 % and to 21 % and a relative mean standard deviation ~vx that varied from 18 % and to 51 %. The investigation showed an increasing bias with respect to depth, which...

In-Situ Characterization of Isotropic and Transversely Isotropic Elastic Properties Using Ultrasonic Wave Velocities

NARCIS (Netherlands)

Pant, S; Laliberte, J; Martinez, M.J.; Rocha, B.

2016-01-01

In this paper, a one-sided, in situ method based on the time of flight measurement of ultrasonic waves was described. The primary application of this technique was to non-destructively measure the stiffness properties of isotropic and transversely isotropic materials. The method consists of

Ion temperature gradient driven mode in presence of transverse velocity shear in magnetized plasmas

DEFF Research Database (Denmark)

Chakrabarti, N.; Juul Rasmussen, J.; Michelsen, Poul

2005-01-01

The effect of sheared poloidal flow on the toroidal branch of the ion temperature gradient driven mode of magnetized nonuniform plasma is studied. A novel "nonmodal" calculation is used to analyze the problem. It is shown that the transverse shear flow considerably reduced the growth...

Comparison of high group velocity accelerating structures

International Nuclear Information System (INIS)

Farkas, Z.D.; Wilson, P.B.

1987-02-01

It is well known that waveguides with no perturbations have phase velocities greater than the velocity of light c. If the waveguide dimensions are chosen so that the phase velocity is only moderately greater than c, only small perturbations are required to reduce the phase velocity to be synchronous with a high energy particle bunch. Such a lightly loaded accelerator structure will have smaller longitudinal and transverse wake potentials and hence will lead to lower emittance growth in an accelerated beam. Since these structures are lightly loaded, their group velocities are only slightly less than c and not in the order of 0.01c, as is the case for the standard disk-loaded structures. To ascertain that the peak and average power requirements for these structures are not prohibitive, we examine the elastance and the Q for several traveling wave structures: phase slip structures, bellows-like structures, and lightly loaded disk-loaded structures

Nonlinear effects in the propagation of shortwave transverse sound in pure superconductors

International Nuclear Information System (INIS)

Gal'perin, Y.

1982-01-01

Various mechanisms are analyzed which lead to nonlinear phenomena (e.g., the dependence of the absorption coefficient and of the velocity of sound on its intensity) in the propagation of transverse shortwave sound in pure superconductors (the wavelength of the sound being much less than the mean free path of the quasiparticles). It is shown that the basic mechanism, over a wide range of superconductor parameters and of the sound intensity, is the so-called momentum nonlinearity. The latter is due to the distortion (induced by the sound wave) of the quasimomentum distribution of resonant electrons interacting with the wave. The dependences of the absorption coefficient and of the sound velocity on its intensity and on the temperature are analyzed in the vicinity of the superconducting transition point. The feasibility of an experimental study of nonlinear acoustic phenomena in the case of transverse sound is considered

Transverse jet-cavity interactions with the influence of an impinging shock

International Nuclear Information System (INIS)

Zare-Behtash, H.; Lo, K.H.; Kontis, K.; Ukai, T.; Obayashi, S.

2015-01-01

Highlights: • Experimental study of shock-jet-cavity in a supersonic freestream is conducted. • Shock impingement at the cavity leading edge lifts the shear layer, encouraging momentum transfer. • Shock impingement close to the jet location increases the number of smaller turbulent structures. - Abstract: For high-speed air breathing engines, fuel injection and subsequent mixing with air is paramount for combustion. The high freestream velocity poses a great challenge to efficient mixing both in macroscale and microscale. Utilising cavities downstream of fuel injection locations, as a means to hold the flow and stabilise the combustion, is one mechanism which has attracted much attention, requiring further research to study the unsteady flow features and interactions occurring within the cavity. In this study we combine the transverse jet injection upstream of a cavity with an impinging shock to see how this interaction influences the cavity flow, since impinging shocks have been shown to enhance mixing of transverse jets. Utilising qualitative and quantitative methods: schlieren, oilflow, PIV, and PSP the induced flowfield is analysed. The impinging shock lifts the shear layer over the cavity and combined with the instabilities generated by the transverse jet creates a highly complicated flowfield with numerous vertical structures. The interaction between the oblique shock and the jet leads to a relatively uniform velocity distribution within the cavity

Entropic transport of active particles driven by a transverse ac force

Energy Technology Data Exchange (ETDEWEB)

Wu, Jian-chun, E-mail: wjchun2010@163.com; Chen, Qun; Ai, Bao-quan, E-mail: aibq@scnu.edu.cn

2015-12-18

Transport of active particles is numerically investigated in a two-dimensional period channel. In the presence of a transverse ac force, the directed transport of active particles demonstrates striking behaviors. By adjusting the amplitude and the frequency of the transverse ac force, the average velocity will be influenced significantly and the direction of the transport can be reversed several times. Remarkably, it is also found that the direction of the transport varies with different self-propelled speeds. Therefore, particles with different self-propelled speeds will move to the different directions, which is able to separate particles of different self-propelled speeds. - Highlights: • A transverse ac force strongly influence the transport of active particles. • The direction of the transport can be reversed several times. • Active particles with different self-propelled speeds can be separated.

Ambient Seismic Noise Interferometry on the Island of Hawai`i

Science.gov (United States)

Ballmer, Silke

Ambient seismic noise interferometry has been successfully applied in a variety of tectonic settings to gain information about the subsurface. As a passive seismic technique, it extracts the coherent part of ambient seismic noise in-between pairs of seismic receivers. Measurements of subtle temporal changes in seismic velocities, and high-resolution tomographic imaging are then possible - two applications of particular interest for volcano monitoring. Promising results from other volcanic settings motivate its application in Hawai'i, with this work being the first to explore its potential. The dataset used for this purpose was recorded by the Hawaiian Volcano Observatory's permanent seismic network on the Island of Hawai'i. It spans 2.5 years from 5/2007 to 12/2009 and covers two distinct sources of volcanic tremor. After applying standard processing for ambient seismic noise interferometry, we find that volcanic tremor strongly affects the extracted noise information not only close to the tremor source, but unexpectedly, throughout the island-wide network. Besides demonstrating how this long-range observability of volcanic tremor can be used to monitor volcanic activity in the absence of a dense seismic array, our results suggest that care must be taken when applying ambient seismic noise interferometry in volcanic settings. In a second step, we thus exclude days that show signs of volcanic tremor, reducing the dataset to three months, and perform ambient seismic noise tomography. The resulting two-dimensional Rayleigh wave group velocity maps for 0.1 - 0.9 Hz compare very well with images from previous travel time tomography, both, for the main volcanic structures at low frequencies as well as for smaller features at mid-to-high frequencies - a remarkable observation for the temporally truncated dataset. These robust results suggest that ambient seismic noise tomography in Hawai'i is suitable 1) to provide a three-dimensional S-wave model for the volcanoes and 2

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

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt

2013-01-01

A method for making Vector Flow Images using the transverse oscillation (TO) approach on a convex array is presented. The paper presents optimization schemes for TO fields for convex probes and evaluates their performance using Field II simulations and measurements using the SARUS experimental...... from 90 to 45 degrees in steps of 15 degrees. The optimization routine changes the lateral oscillation period lx to yield the best possible estimates based on the energy ratio between positive and negative spatial frequencies in the ultrasound field. The basic equation for lx gives 1.14 mm at 40 mm...

Modulation of energetic particle fluxes by a mixed mode of transverse and compressional waves

International Nuclear Information System (INIS)

Lin, C.S.; Parks, G.K.

1982-01-01

Modulation characteristics of particle fluxes in the presence of a mixed mode of compressional and transverse magnetic waves at hydromagnetic frequencies have been studied by means of kinetic perturbation of the distribution function. The magnetospheric medium in which the particles are modulated contains both the magnetic and pressure gradients. It is found that the modulation features are strongly dependent on the energy and pitch angle of the particles. Drifting particles can resonate with waves whose phase velocities are near their drift velocities. When this happens, the amplitude of the modulations become significantly large and large phase shifts will occur. Resonance is important for particles with mid pitch angles (40 0 --70 0 ). The phase shift between the particle modulations and the magnetic field oscillations are strongly controlled by combined effects of transverse and compressional wave components and/or the occurrence of drift resonance. We have performed numerical calculations by using the dispersion relation of drift mirror Alfven waves as an example of waves with both compressional and transverse components. The results derived in this study may be of importance in studying the relationship of particles and Pc 4--5 waves that are observed during magnetically disturbed times

Toward predicting clay landslide with ambient seismic noise

Science.gov (United States)

Larose, E. F.; Mainsant, G.; Carriere, S.; Chambon, G.; Michoud, C.; Jongmans, D.; Jaboyedoff, M.

2013-12-01

Clay-rich pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity, which could be detected by monitoring shear wave velocity variations, The ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010, and then again from fall 2011 on. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results are confirmed by analogous small-scale experiments in the laboratory. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

Scanning anisotropy parameters in horizontal transversely isotropic media

KAUST Repository

Masmoudi, Nabil

2016-10-12

The horizontal transversely isotropic model, with arbitrary symmetry axis orientation, is the simplest effective representative that explains the azimuthal behaviour of seismic data. Estimating the anisotropy parameters of this model is important in reservoir characterisation, specifically in terms of fracture delineation. We propose a travel-time-based approach to estimate the anellipticity parameter η and the symmetry axis azimuth ϕ of a horizontal transversely isotropic medium, given an inhomogeneous elliptic background model (which might be obtained from velocity analysis and well velocities). This is accomplished through a Taylor\\'s series expansion of the travel-time solution (of the eikonal equation) as a function of parameter η and azimuth angle ϕ. The accuracy of the travel time expansion is enhanced by the use of Shanks transform. This results in an accurate approximation of the solution of the non-linear eikonal equation and provides a mechanism to scan simultaneously for the best fitting effective parameters η and ϕ, without the need for repetitive modelling of travel times. The analysis of the travel time sensitivity to parameters η and ϕ reveals that travel times are more sensitive to η than to the symmetry axis azimuth ϕ. Thus, η is better constrained from travel times than the azimuth. Moreover, the two-parameter scan in the homogeneous case shows that errors in the background model affect the estimation of η and ϕ differently. While a gradual increase in errors in the background model leads to increasing errors in η, inaccuracies in ϕ, on the other hand, depend on the background model errors. We also propose a layer-stripping method valid for a stack of arbitrary oriented symmetry axis horizontal transversely isotropic layers to convert the effective parameters to the interval layer values.

Fluid flow in a porous medium with transverse permeability discontinuity

Science.gov (United States)

Pavlovskaya, Galina E.; Meersmann, Thomas; Jin, Chunyu; Rigby, Sean P.

2018-04-01

Magnetic resonance imaging (MRI) velocimetry methods are used to study fully developed axially symmetric fluid flow in a model porous medium of cylindrical symmetry with a transverse permeability discontinuity. Spatial mapping of fluid flow results in radial velocity profiles. High spatial resolution of these profiles allows estimating the slip in velocities at the boundary with a permeability discontinuity zone in a sample. The profiles are compared to theoretical velocity fields for a fully developed axially symmetric flow in a cylinder derived from the Beavers-Joseph [G. S. Beavers and D. D. Joseph, J. Fluid Mech. 30, 197 (1967), 10.1017/S0022112067001375] and Brinkman [H. C. Brinkman, Appl. Sci. Res. A 1, 27 (1947), 10.1007/BF02120313] models. Velocity fields are also computed using pore-scale lattice Boltzmann modeling (LBM) where the assumption about the boundary could be omitted. Both approaches give good agreement between theory and experiment, though LBM velocity fields follow the experiment more closely. This work shows great promise for MRI velocimetry methods in addressing the boundary behavior of fluids in opaque heterogeneous porous media.

Acoustic reflection log in transversely isotropic formations

Science.gov (United States)

Ronquillo Jarillo, G.; Markova, I.; Markov, M.

2018-01-01

We have calculated the waveforms of sonic reflection logging for a fluid-filled borehole located in a transversely isotropic rock. Calculations have been performed for an acoustic impulse source with the characteristic frequency of tens of kilohertz that is considerably less than the frequencies of acoustic borehole imaging tools. It is assumed that the borehole axis coincides with the axis of symmetry of the transversely isotropic rock. It was shown that the reflected wave was excited most efficiently at resonant frequencies. These frequencies are close to the frequencies of oscillations of a fluid column located in an absolutely rigid hollow cylinder. We have shown that the acoustic reverberation is controlled by the acoustic impedance of the rock Z = Vphρs for fixed parameters of the borehole fluid, where Vph is the velocity of horizontally propagating P-wave; ρs is the rock density. The methods of waveform processing to determine the parameters characterizing the reflected wave have been discussed.

Ambient Noise Tomography at Regional and Local Scales in Southern California using Rayleigh Wave Phase Dispersion and Ellipticity

Science.gov (United States)

Berg, E.; Lin, F. C.; Qiu, H.; Wang, Y.; Allam, A. A.; Clayton, R. W.; Ben-Zion, Y.

2017-12-01

Rayleigh waves extracted from cross-correlations of ambient seismic noise have proven useful in imaging the shallow subsurface velocity structure. In contrast to phase velocities, which are sensitive to slightly deeper structure, Rayleigh wave ellipticity (H/V ratios) constrains the uppermost crust. We conduct Rayleigh wave ellipticity and phase dispersion measurements in Southern California between 6 and 18 second periods, computed from multi-component ambient noise cross-correlations using 315 stations across the region in 2015. Because of the complimentary sensitivity of phase velocity and H/V, this method enables simple and accurate resolution of near-surface geological features from the surface to 20km depth. We compare the observed H/V ratios and phase velocities to predictions generated from the current regional models (SCEC UCVM), finding strong correspondence where the near-surface structure is well-resolved by the models. This includes high H/V ratios in the LA Basin, Santa Barbara Basin and Salton Trough; and low ratios in the San Gabriel, San Jacinto and southern Sierra Nevada mountains. Disagreements in regions such as the Western Transverse Ranges, Salton Trough, San Jacinto and Elsinore fault zones motivate further work to improve the community models. A new updated 3D isotropic model of the area is derived via a joint inversion of Rayleigh phase dispersions and H/V ratios. Additionally, we examine azimuthal dependence of the H/V ratio to ascertain anisotropy patterns for each station. Clear 180º periodicity is observed for many stations suggesting strong shallow anisotropy across the region including up to 20% along the San Andreas fault, 15% along the San Jacinto Fault and 25% in the LA Basin. To better resolve basin structures, we apply similar techniques to three dense linear geophone arrays in the San Gabriel and San Bernardino basins. The three arrays are composed by 50-125 three-component 5Hz geophones deployed for one month each with 15-25km

Principle and performance of the transverse oscillation vector velocity technique in medical ultrasound

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt; Pihl, Michael Johannes; Udesen, Jesper

2010-01-01

Medical ultrasound systems measure the blood velocity by tracking the blood cells motion along the ultrasound field. The is done by pulsing in the same direction a number of times and then find e.q. the shift in phase between consecutive pulses. Properly normalized this is directly proportional...... a double oscillating field. A special estimator is then used for finding both the axial and lateral velocity component, so that both magnitude and phase can be calculated. The method for generating double oscillating ultrasound fields and the special estimator are described and its performance revealed...

Quantum Criticality of an Ising-like Spin-1 /2 Antiferromagnetic Chain in a Transverse Magnetic Field

Science.gov (United States)

Wang, Zhe; Lorenz, T.; Gorbunov, D. I.; Cong, P. T.; Kohama, Y.; Niesen, S.; Breunig, O.; Engelmayer, J.; Herman, A.; Wu, Jianda; Kindo, K.; Wosnitza, J.; Zherlitsyn, S.; Loidl, A.

2018-05-01

We report on magnetization, sound-velocity, and magnetocaloric-effect measurements of the Ising-like spin-1 /2 antiferromagnetic chain system BaCo2V2O8 as a function of temperature down to 1.3 K and an applied transverse magnetic field up to 60 T. While across the Néel temperature of TN˜5 K anomalies in magnetization and sound velocity confirm the antiferromagnetic ordering transition, at the lowest temperature the field-dependent measurements reveal a sharp softening of sound velocity v (B ) and a clear minimum of temperature T (B ) at B⊥c,3 D=21.4 T , indicating the suppression of the antiferromagnetic order. At higher fields, the T (B ) curve shows a broad minimum at B⊥c=40 T , accompanied by a broad minimum in the sound velocity and a saturationlike magnetization. These features signal a quantum phase transition, which is further characterized by the divergent behavior of the Grüneisen parameter ΓB∝(B -B⊥c)-1. By contrast, around the critical field, the Grüneisen parameter converges as temperature decreases, pointing to a quantum critical point of the one-dimensional transverse-field Ising model.

Turbulent flow velocity distribution at rough walls

International Nuclear Information System (INIS)

Baumann, W.

1978-08-01

Following extensive measurements of the velocity profile in a plate channel with artificial roughness geometries specific investigations were carried out to verify the results obtained. The wall geometry used was formed by high transverse square ribs having a large pitch. The measuring position relative to the ribs was varied as a parameter thus providing a statement on the local influence of roughness ribs on the values measured. As a fundamental result it was found that the gradient of the logarithmic rough wall velocity profiles, which differs widely from the value 2.5, depends but slightly on the measuring position relative to the ribs. The gradients of the smooth wall velocity profiles deviate from 2.5 near the ribs, only. This fact can be explained by the smooth wall shear stress varying with the pitch of the ribs. (orig.) 891 GL [de

Seismic Tomography and the Development of a State Velocity Profile

Science.gov (United States)

Marsh, S. J.; Nakata, N.

2017-12-01

Earthquakes have been a growing concern in the State of Oklahoma in the last few years and as a result, accurate earthquake location is of utmost importance. This means using a high resolution velocity model with both lateral and vertical variations. Velocity data is determined using ambient noise seismic interferometry and tomography. Passive seismic data was acquired from multiple IRIS networks over the span of eight years (2009-2016) and filtered for earthquake removal to obtain the background ambient noise profile for the state. Seismic Interferometry is applied to simulate ray paths between stations, this is done with each possible station pair for highest resolution. Finally the method of seismic tomography is used to extract the velocity data and develop the state velocity map. The final velocity profile will be a compilation of different network analyses due to changing station availability from year to year. North-Central Oklahoma has a dense seismic network and has been operating for the past few years. The seismic stations are located here because this is the most seismically active region. Other parts of the state have not had consistent coverage from year to year, and as such a reliable and high resolution velocity profile cannot be determined from this network. However, the Transportable Array (TA) passed through Oklahoma in 2014 and provided a much wider and evenly spaced coverage. The goal of this study is to ultimately combine these two arrays over time, and provide a high quality velocity profile for the State of Oklahoma.

Skin effect of microwaves and transverse pseudowaves in plasmas

International Nuclear Information System (INIS)

Minami, Kazuo

1977-09-01

Using linearized Vlasov-Maxwell equations, the skin effect of microwaves and transverse pseudowaves excited by an idealized grid antenna in plasmas are analyzed. It is shown that the latter is predominant over the former, in such a plasma that ω sub(p) v sub(t)/ωc >= 1, where ω sub(p) and ω are the plasma and microwave angular frequencies, v sub(t) and c are the electron thermal and light velocities, respectively. (auth.)

Transverse momentum in high-energy nuclear collisions: Collective expansion

International Nuclear Information System (INIS)

Wang, X.; Hwa, R.C.

1987-01-01

Hadron production in the central region in high-energy nuclear collisions is investigated. The hydrodynamical expansion of a locally thermalized system is studied for both the cases with and without phase transition. The case with phase transition is considered by using a sound-velocity function c/sub s/(T) parametrized to fit the energy density determined in a lattice gauge calculation. The effect of a transverse rarefaction wave is included in the calculation of the temperature profile of the expanding fluid. The transverse-momentum distribution of hadrons is calculated by collecting all the hadrons produced when the hadron gas is cooled down to a freeze-out temperature at different times in the expansion. Fluctuation in initial temperature and radius is allowed due to variation in impact parameter. On the basis of a study of the thermalization process in the parton model we impose a constraint on the initial temperature and the thermalization time, the simultaneous variation of both of which gives rise to a relationship between the average transverse momentum and rapidity density. We have found that there is no so-called ''plateau'' region in that relationship. The implication on the diagnostics of a quark-gluon plasma is discussed

Ambient noise tomography of Lo'ihi

Science.gov (United States)

McClement, K.; Thurber, C. H.; Teel, A.; Caplan-Auerbach, J.

2012-12-01

Lo'ihi seamount, the youngest volcano in the Hawaiian-Emperor chain, lies approximately 30 km south of Hawai'i Island with its summit still approximately 1 km below sea level. Lo'ihi offers a unique opportunity to study the early formation of a hotspot volcano and can provide insight into the deep internal structure of the other volcanoes that make up the Hawaiian Islands. This study uses Ambient Noise Tomography (ANT) to create a 3D tomographic image of Lo'ihi's S-wave velocity structure from ocean bottom seismometer (OBS) data. ANT has been used in many subaerial studies but has seen very few applications to OBS data. This study uses continuous data recorded in 2010 to 2011 from 12 short-period OBS instruments deployed on and around Lo'ihi. With the farthest distance between stations being just over 30 km, the stations provide a fairly dense coverage mainly for the northern half of the volcano. Following the approach of Masterlark et al. [2010], we computed vertical-vertical and vertical-radial cross-correlations using 97 days of continuous data from the 12 stations to produce the ambient noise Green's functions. From these, dispersion curves were produced over a frequency range from .04 Hz to 0.65 Hz . After a quality control analysis, checkerboard tests were used to determine a suitable cell size for the 2D group velocity inversions. The final step is the inversion of the group velocity dispersion curves to create a 3D Vs model. The 3D Vs image produced through this method does not provide clear evidence of a shallow magma chamber; however, when compared to a previous P-wave velocity (Vp) model [Caplan-Auerbach, 2001], a high Vp/Vs ratio is evident especially at depths from 1 km to 5 km, indicating the presence of highly fractured rock.

La literatura infantil como recurso para desarrollar el eje de educación ambiental : proyectos dirigidos a niños y niñas de tercero de EGB

OpenAIRE

Narváez Rodríguez, Verónica Alexandra

2008-01-01

La Reforma Curricular de la Educación básica ecuatoriana ha considerado necesario incrementar el tema de la Educación Ambiental dentro del currículo escolar como eje transversal. “La Educación Ambiental se constituye en eje Transversal del Currículo, como respuesta urgente a los graves problemas ambientales que están afectando a nuestro planeta y a la inaplazable necesidad de enfrentarlos con el desarrollo de una conciencia activa de conservación y protección de nuestro medi...

Contribution to the study of transverse turbulent diffusion in streams

International Nuclear Information System (INIS)

Masson, Olivier

1991-01-01

In this research our objective is to study the turbulent diffusion in a water flow, in particular the transverse diffusion. According to formulae reviewed in literature the diffusion coefficients (K) may be expressed as a function of several velocity parameters. A synthetic formula depending on a macro-scale length of turbulence L x and a turbulent intensity √(u' 2 ) is proposed: K = β.L x .U-bar.(√(u' 2 /U-bar)) 2 . In order to validate this expression we performed two in situ experiments (one in a wide river and the other in an irrigation canal) with a double set of measurements: turbulent velocities and concentrations of a diffusing tracer. The first set gives us usable data in our formula. The results, compared with values available in literature, give a good agreement. Moreover it appears that it is possible to roughly divide the data in two groups according to (1) the cross section shape and (2) the bed roughness. The second set allows us to evaluate a global turbulent mixing coefficient. The coefficients calculated by the two methods are in accordance so our formula is validated. Nevertheless some problems appear because of what is called secondary currents and coherent structures as those seen above bed cracks in the Garonne river. Those phenomenon may play a major part upon turbulent diffusion in real streams. Although they were made conspicuous by an analysis of transverse velocity component, it has not been yet possible to quantify their effects. (author) [fr

Generalized multidemensional propagation velocity equations for pool-boiling superconducting windings

International Nuclear Information System (INIS)

Christensen, E.H.; O'Loughlin, J.M.

1984-09-01

Several finite difference, finite element detailed analyses of propagation velocities in up to three dimensions in pool-boiling windings have been conducted for different electromagnetic and cryogenic environments. Likewise, a few full scale simulated winding and magnet tests have measured propagation velocities. These velocity data have been correlated in terms of winding thermophysical parameters. This analysis expresses longitudinal and transverse propagation velocities in the form of power function regression equations for a wide variety of windings and electromagnetic and thermohydraulic environments. The generalized velocity equations are considered applicable to well-ventilated, monolithic conductor windings. These design equations are used piecewise in a gross finite difference mode as functions of field to predict the rate of normal zone growth during quench conditions. A further check of the validity of these predictions is available through total predicted quench durations correlated with actual quench durations of large magnets

Electrical modulation and switching of transverse acoustic phonons

Science.gov (United States)

Jeong, H.; Jho, Y. D.; Rhim, S. H.; Yee, K. J.; Yoon, S. Y.; Shim, J. P.; Lee, D. S.; Ju, J. W.; Baek, J. H.; Stanton, C. J.

2016-07-01

We report on the electrical manipulation of coherent acoustic phonon waves in GaN-based nanoscale piezoelectric heterostructures which are strained both from the pseudomorphic growth at the interfaces as well as through external electric fields. In such structures, transverse symmetry within the c plane hinders both the generation and detection of the transverse acoustic (TA) modes, and usually only longitudinal acoustic phonons are generated by ultrafast displacive screening of potential gradients. We show that even for c -GaN, the combined application of lateral and vertical electric fields can not only switch on the normally forbidden TA mode, but they can also modulate the amplitudes and frequencies of both modes. By comparing the transient differential reflectivity spectra in structures with and without an asymmetric potential distribution, the role of the electrical controllability of phonons was demonstrated as changes to the propagation velocities, the optical birefringence, the electrically polarized TA waves, and the geometrically varying optical sensitivities of phonons.

3-D Vector Velocity Estimation with Row-Column Addressed Arrays

DEFF Research Database (Denmark)

Holbek, Simon; Christiansen, Thomas Lehrmann; Rasmussen, Morten Fischer

2015-01-01

-D velocity vector in a 15◦ rotated vessel with a 75◦ beam-to-flow angle. In the experimental setup with a 90◦ beam-to-flow angle, the relative mean biases were (-2.6%, -1.3% , 1.4%) with a relative standard deviation of (5.0%, 5.2%, 1.0%) for the respective transverse, lateral and axial velocity...... mm) containing a laminar parabolic flow and a peak velocity of 0.54 m/s. Data was sampled and stored on the experimental ultrasound scanner SARUS. Simulations yields relative mean biases at (- 1.1%, -1.5%, -1.0%) with mean standard deviations of σ˜ were (8.5%, 9.0%, 1.4%) % for (vx, vy, vz) from a 3...

Dynamic Behavior of Spicules Inferred from Perpendicular Velocity Components

Energy Technology Data Exchange (ETDEWEB)

Sharma, Rahul; Verth, Gary; Erdélyi, Robertus [Solar Physics and Space Plasma Research Centre, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

2017-05-10

Understanding the dynamic behavior of spicules, e.g., in terms of magnetohydrodynamic (MHD) wave mode(s), is key to unveiling their role in energy and mass transfer from the photosphere to corona. The transverse, torsional, and field-aligned motions of spicules have previously been observed in imaging spectroscopy and analyzed separately for embedded wave-mode identification. Similarities in the Doppler signatures of spicular structures for both kink and torsional Alfvén wave modes have led to the misinterpretation of the dominant wave mode in these structures and is a subject of debate. Here, we aim to combine line- of-sight (LOS) and plane-of-sky (POS) velocity components using the high spatial/temporal resolution H α imaging-spectroscopy data from the CRisp Imaging SpectroPolarimeter based at the Swedish Solar Telescope to achieve better insight into the underlying nature of these motions as a whole. The resultant three-dimensional velocity vectors and the other derived quantities (e.g., magnetic pressure perturbations) are used to identify the MHD wave mode(s) responsible for the observed spicule motion. We find a number of independent examples where the bulk transverse motion of the spicule is dominant either in the POS or along the LOS. It is shown that the counterstreaming action of the displaced external plasma due to spicular bulk transverse motion has a similar Doppler profile to that of the m = 0 torsional Alfvén wave when this motion is predominantly perpendicular to the LOS. Furthermore, the inferred magnetic pressure perturbations support the kink wave interpretation of observed spicular bulk transverse motion rather than any purely incompressible MHD wave mode, e.g., the m = 0 torsional Alfvén wave.

The drift velocity monitoring system of the CMS barrel muon chambers

CERN Document Server

Altenhoefer, Georg Friedrich; Heidemann, Carsten Andreas; Reithler, Hans; Sonnenschein, Lars; Teyssier, Daniel Francois

2017-01-01

The drift velocity is a key parameter of drift chambers. Its value depends on several parameters: electric field, pressure, temperature, gas mixture, and contamination, for example, by ambient air. A dedicated Velocity Drift Chamber (VDC) with 1-L volume has been built at the III. Phys. Institute A, RWTH Aachen, in order to monitor the drift velocity of all CMS barrel muon Drift Tube chambers. A system of six VDCs was installed at CMS and has been running since January 2011. We present the VDC monitoring system, its principle of operation, and measurements performed.

The drift velocity monitoring system of the CMS barrel muon chambers

Science.gov (United States)

Altenhöfer, Georg; Hebbeker, Thomas; Heidemann, Carsten; Reithler, Hans; Sonnenschein, Lars; Teyssier, Daniel

2018-04-01

The drift velocity is a key parameter of drift chambers. Its value depends on several parameters: electric field, pressure, temperature, gas mixture, and contamination, for example, by ambient air. A dedicated Velocity Drift Chamber (VDC) with 1-L volume has been built at the III. Phys. Institute A, RWTH Aachen, in order to monitor the drift velocity of all CMS barrel muon Drift Tube chambers. A system of six VDCs was installed at CMS and has been running since January 2011. We present the VDC monitoring system, its principle of operation, and measurements performed.

Ambient Noise Tomography in Koyna-Warna region.

Science.gov (United States)

Rohilla, S.; Rao, N. P.; Gerstoft, P.; Yao, H.; Fang, H.; Davulluri, S.

2017-12-01

In the present study Ambient Noise tomography has been done in the Koyna-Warna region of western India to decipher the complex structural setting and its linkage to the seismogenesis in this unique Reservoir Triggered Seismicity zone. The 3-D velocity model obtained from the study clearly brings out the lateral and vertical variations of shear velocity in the region down to a depth of about 10 km. In the Koyna region, seismicity distribution along the NNE-SSW trending Donachiwada fault zone is seen coinciding with a low velocity zone between two competent zones with a very high velocity > 4.0 km/s. The seismicity between the Koyna and Warna regions roughly trending NW-SE can be clearly seen in the NE-SW depth sections coinciding with a low velocity zone interspersed between two high velocity zones. The most active seismicity cluster south of the Warna Lake correlates with a near-vertical velocity discontinuity with a contrast of about 0.5 km/s is seen in an EW depth section. The study has helped in delineating the major fault zones of the Koyna-Warna region and enabled understanding the seismogenesis with respect to the structural controls in a RTS enviroment.

The preliminary results: Seismic ambient noise Rayleigh wave tomography around Merapi volcano, central Java, Indonesia

International Nuclear Information System (INIS)

Trichandi, Rahmantara; Yudistira, Tedi; Nugraha, Andri Dian; Zulhan, Zulfakriza; Saygin, Erdinc

2015-01-01

Ambient noise tomography is relatively a new method for imaging the shallow structure of the Earth subsurface. We presents the application of this method to produce a Rayleigh wave group velocity maps around the Merapi Volcano, Central Java. Rayleigh waves group velocity maps were reconstructed from the cross-correlation of ambient noise recorded by the DOMERAPI array which consists 43 broadband seismometers. In the processing stage, we first filtered the observation data to separatethe noise from the signal that dominated by the strong volcanic activities. Next, we cross-correlate the filtered data and stack to obtain the Green’s function for all possible station pairs. Then we carefully picked the peak of each Green’s function to estimate the dispersion trend and appliedMultiple Filter Technique to obtain the dispersion curve. Inter-station group velocity curvesare inverted to produceRayleigh wave group velocity maps for periods 1 to 10 s. The resulted Rayleigh group velocity maps show the interesting features around the Merapi Volcano which generally agree with the previous studies. Merapi-Lawu Anomaly (MLA) is emerged as a relatively low anomaly in our group velocity maps

The preliminary results: Seismic ambient noise Rayleigh wave tomography around Merapi volcano, central Java, Indonesia

Energy Technology Data Exchange (ETDEWEB)

Trichandi, Rahmantara, E-mail: rachmantara.tri@gmail.com [Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, 40132, Bandung (Indonesia); Yudistira, Tedi; Nugraha, Andri Dian [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, 40132 (Indonesia); Zulhan, Zulfakriza [Earth Science Graduate Program, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Bandung, 40132 (Indonesia); Saygin, Erdinc [Research School of Earth Sciences, The Australian National University, Canberra ACT 0200 (Australia)

2015-04-24

Ambient noise tomography is relatively a new method for imaging the shallow structure of the Earth subsurface. We presents the application of this method to produce a Rayleigh wave group velocity maps around the Merapi Volcano, Central Java. Rayleigh waves group velocity maps were reconstructed from the cross-correlation of ambient noise recorded by the DOMERAPI array which consists 43 broadband seismometers. In the processing stage, we first filtered the observation data to separatethe noise from the signal that dominated by the strong volcanic activities. Next, we cross-correlate the filtered data and stack to obtain the Green’s function for all possible station pairs. Then we carefully picked the peak of each Green’s function to estimate the dispersion trend and appliedMultiple Filter Technique to obtain the dispersion curve. Inter-station group velocity curvesare inverted to produceRayleigh wave group velocity maps for periods 1 to 10 s. The resulted Rayleigh group velocity maps show the interesting features around the Merapi Volcano which generally agree with the previous studies. Merapi-Lawu Anomaly (MLA) is emerged as a relatively low anomaly in our group velocity maps.

CRECIMIENTO ECONÓMICO Y MEDIO AMBIENTE EN MÉXICO

Directory of Open Access Journals (Sweden)

Claudia S. Gómez-López

2011-01-01

Full Text Available El artículo hace un análisis de la relación entre crecimiento económico y medio ambiente para las 32 entidades federativas de la República Mexicana. La curva ambiental de Kuznets (CAK sugiere la existencia de una relación entre crecimiento económico y medio ambiente. A medida que las economías disfrutan un mayor crecimiento económico, se presenta una degradación ambiental y una vez que se alcanza cierto crecimiento, aumenta la disponibilidad a pagar por la conservación del medio ambiente. En el caso de la economía mexicana, al aplicar el análisis de convergencia por medio de datos de corte transversal y datos de panel, se encuentra que: i existe β convergencia en árboles plantados, áreas naturales protegidas, licencias ambientales y volumen de tratamiento de aguas en sus niveles per capita; ii no hay evidencia de σ-convergencia en las variables medio ambientales para los estados de la economía mexicana, excepto en áreas naturales protegidas, árboles plantados y licencias ambientales; iii no existe una relación entre crecimiento económico y aumento en el cuidado de las variables medioambientales, excepto para el volumen de recolección de basura y el volumen de aguas residuales; iv los resultados sugieren que el medio ambiente no está entre las prioridades de la economía mexicana de acuerdo con la hipótesis de la CAK.

Finite element modelling of aluminum alloy 2024-T3 under transverse impact loading

Science.gov (United States)

Abdullah, Ahmad Sufian; Kuntjoro, Wahyu; Yamin, A. F. M.

2017-12-01

Fiber metal laminate named GLARE is a new aerospace material which has great potential to be widely used in future lightweight aircraft. It consists of aluminum alloy 2024-T3 and glass-fiber reinforced laminate. In order to produce reliable finite element model of impact response or crashworthiness of structure made of GLARE, one can initially model and validate the finite element model of the impact response of its constituents separately. The objective of this study was to develop a reliable finite element model of aluminum alloy 2024-T3 under low velocity transverse impact loading using commercial software ABAQUS. Johnson-Cook plasticity and damage models were used to predict the alloy's material properties and impact behavior. The results of the finite element analysis were compared to the experiment that has similar material and impact conditions. Results showed good correlations in terms of impact forces, deformation and failure progressions which concluded that the finite element model of 2024-T3 aluminum alloy under low velocity transverse impact condition using Johnson-Cook plastic and damage models was reliable.

First results of cross-correlation analysis of ambient seismic noise from the Hellenic Unified Seismic Network

NARCIS (Netherlands)

Panou, Areti; Paulssen, Hanneke; Hatzidimitriou, Panagiotis

2015-01-01

In this study we present phase velocity maps that were obtained from the cross-correlation analysis of ambient seismic noise recorded in the region of Greece.We used one year (2013) of ambient seismic data obtained from the vertical component of 64 broadband permanent seismological stations that are

A Generalized Version of a Low Velocity Impact between a Rigid Sphere and a Transversely Isotropic Strain-Hardening Plate Supported by a Rigid Substrate Using the Concept of Noninteger Derivatives

Directory of Open Access Journals (Sweden)

Abdon Atangana

2013-01-01

Full Text Available A low velocity impact between a rigid sphere and transversely isotropic strain-hardening plate supported by a rigid substrate is generalized to the concept of noninteger derivatives order. A brief history of fractional derivatives order is presented. The fractional derivatives order adopted is in Caputo sense. The new equation is solved via the analytical technique, the Homotopy decomposition method (HDM. The technique is described and the numerical simulations are presented. Since it is very important to accurately predict the contact force and its time history, the three stages of the indentation process, including (1 the elastic indentation, (2 the plastic indentation, and (3 the elastic unloading stages, are investigated.

Operation of the transverse feedback system at the CERN SPS

International Nuclear Information System (INIS)

Bossart, R.; Louwerse, R.; Mourier, J.; Vos, L.

1987-01-01

To prevent transverse instabilities at high beam intensity in the SPS, the transverse feedback system for damping the betatron oscillations has been upgraded for larger damping decrements and for increased system's bandwidth. The feedback loop now contains a digital delay line cancellor, so that the damper works with a velocity feedback Δx/Δt, unaffected by the closed orbit position x at the pick-up station. The digital processing of the feedback signal facilitates nonlinear feedback techniques such as antidamping and ''band-bang'' feedback. The ''bang-bang'' feedback provides the maximum possible damping rate of the injection oscillations in the SPS-collider, in order to minimize the emittance increase caused by filamentation. The antidamping nonlinearity provides small continuous beam oscillations of 50 μm amplitude for tracking the machine tune Q with a phase locked loop

Longitudinal and transverse structure functions in decaying nearly homogeneous and isotropic turbulence

International Nuclear Information System (INIS)

Ahmad Imtiaz; Lu Zhi-Ming; Liu Yu-Lu

2014-01-01

Streamwise evolution of longitudinal and transverse velocity structure functions in a decaying homogeneous and nearly isotropic turbulence is reported for Reynolds numbers Re λ up to 720. First, two theoretical relations between longitudinal and transverse structure functions are examined in the light of recently derived relations and the results show that the low-order transverse structure functions can be well approximated by longitudinal ones within the sub-inertial range. Reconstruction of fourth-order transverse structure functions with a recently proposed relation by Grauer et al. is comparatively less valid than the relation already proposed by Antonia et al. Secondly, extended self-similarity methods are used to measure the scaling exponents up to order eight and the streamwise evolution of scaling exponents is explored. The scaling exponents of longitudinal structure functions are, at first location, close to Zybin's model, and at the fourth location, close to She—Leveque model. No obvious trend is found for the streamwise evolution of longitudinal scaling exponents, whereas, on the contrary, transverse scaling exponents become slightly smaller with the development of a steamwise direction. Finally, the stremwise variation of the order-dependent isotropy ratio indicates the turbulence at the last location is closer to isotropic than the other three locations. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

3-D Velocity Estimation for Two Planes in vivo

DEFF Research Database (Denmark)

Holbek, Simon; Pihl, Michael Johannes; Ewertsen, Caroline

2014-01-01

3-D velocity vectors can provide additional flow information applicable for diagnosing cardiovascular diseases e.g. by estimating the out-of-plane velocity component. A 3-D version of the Transverse Oscillation (TO) method has previously been used to obtain this information in a carotid flow...... and stored on the experimental scanner SARUS. The full 3-D velocity profile can be created and examined at peak-systole and end-diastole without ECG gating in two planes. Maximum out-of-plane velocities for the three peak-systoles and end-diastoles were 68.5 5.1 cm/s and 26.3 3.3 cm/s, respectively....... In the longitudinal plane, average maximum peak velocity in flow direction was 65.2 14.0 cm/s at peak-systole and 33.6 4.3 cm/s at end-diastole. A commercial BK Medical ProFocus UltraView scanner using a spectral estimator gave 79.3 cm/s and 14.6 cm/s for the same volunteer. This demonstrates that real-time 3-D...

Relative Seismic Velocity Variations Correlate with Deformation at Kīlauea Volcano.

Science.gov (United States)

Donaldson, C.; Caudron, C.; Green, R. G.; White, R. S.

2016-12-01

Passive interferometry using ambient seismic noise is an appealing monitoring tool at volcanoes. The continuous nature of seismic noise provides better temporal resolution than earthquake interferometry and ambient noise may be sensitive to changes at depths that do not deform the volcano surface. Despite this, to our knowledge, no studies have yet comprehensively compared deformation and velocity at a volcano over a significant length of time. We use a volcanic tremor source (approximately 0.3 - 1.0 Hz) at Kīlauea volcano as a source for interferometry to measure relative velocity changes with time. The tremor source that dominates the cross correlations is located under the Halema'uma'u caldera at Kīlauea summit. By cross-correlating the vertical component of day-long seismic records between 200 pairs of stations, we extract coherent and temporally consistent coda wave signals with time lags of up to 70 seconds. Our resulting time series of relative velocity shows a remarkable correlation with the tilt record measured at Kīlauea summit. Kīlauea summit is continually inflating and deflating as the level of the lava lake rises and falls. During these deflation-inflation (DI) events the tilt increases (inflation), as the velocity increases, on the scale of days to weeks. In contrast, we also detect a longer-term velocity decrease between 2011-2015 as the volcano slowly inflates. We suggest that variations in velocity result from opening and closing cracks and pores due to changes in magma pressurization. Early modeling results indicate that pressurizing magma reservoirs at different depths can result in opposite changes in compression/extension at the surface. The consistent correlation of relative velocity and deformation in this study provides an opportunity to better understand the mechanism causing velocity changes, which currently limits the scope of passive interferometry as a monitoring tool.

Blood flow velocity measurements in chicken embryo vascular network via PIV approach

Science.gov (United States)

Kurochkin, Maxim A.; Stiukhina, Elena S.; Fedosov, Ivan V.; Tuchin, Valery V.

2018-04-01

A method for measuring of blood velocity in the native vasculature of a chick embryo by the method of micro anemometry from particle images (μPIV) is improved. A method for interrogation regions sorting by the mask of the vasculature is proposed. A method for sorting of the velocity field of capillary blood flow is implemented. The in vitro method was evaluated for accuracy in a glass phantom of a blood vessel with a diameter of 50 μm and in vivo on the bloodstream of a chicken embryo, by comparing the transverse profile of the blood velocity obtained by the PIV method with the theoretical Poiseuille laminar flow profile.

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...

GSpecDisp: A matlab GUI package for phase-velocity dispersion measurements from ambient-noise correlations

Science.gov (United States)

Sadeghisorkhani, Hamzeh; Gudmundsson, Ólafur; Tryggvason, Ari

2018-01-01

We present a graphical user interface (GUI) package to facilitate phase-velocity dispersion measurements of surface waves in noise-correlation traces. The package, called GSpecDisp, provides an interactive environment for the measurements and presentation of the results. The selection of a dispersion curve can be done automatically or manually within the package. The data are time-domain cross-correlations in SAC format, but GSpecDisp measures phase velocity in the spectral domain. Two types of phase-velocity dispersion measurements can be carried out with GSpecDisp; (1) average velocity of a region, and (2) single-pair phase velocity. Both measurements are done by matching the real part of the cross-correlation spectrum with the appropriate Bessel function. Advantages of these two types of measurements are that no prior knowledge about surface-wave dispersion in the region is needed, and that phase velocity can be measured up to that period for which the inter-station distance corresponds to one wavelength. GSpecDisp can measure the phase velocity of Rayleigh and Love waves from all possible components of the noise correlation tensor. First, we briefly present the theory behind the methods that are used, and then describe different modules of the package. Finally, we validate the developed algorithms by applying them to synthetic and real data, and by comparison with other methods. The source code of GSpecDisp can be downloaded from: https://github.com/Hamzeh-Sadeghi/GSpecDisp

In-vivo studies of new vector velocity and adaptive spectral estimators in medical ultrasound

DEFF Research Database (Denmark)

Hansen, Kristoffer Lindskov

2010-01-01

New ultrasound techniques for blood flow estimation have been investigated in-vivo. These are vector velocity estimators (Transverse Oscillation, Synthetic Transmit Aperture, Directional Beamforming and Plane Wave Excitation) and adaptive spectral estimators (Blood spectral Power Capon and Blood...

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

Science.gov (United States)

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

2015-04-01

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

Transverse Resonant Vibration of Non-Bearing Structures Caused by Wind

Science.gov (United States)

Jendzelovsky, Norbert; Antal, Roland

2017-10-01

Nowadays, there are increasing use of very thin, subtle and light structures in the field of building constructions. We can find such a structures as part of roofs or design facades. By using these lamellas like, non-bearing structures as a part of architectural design of buildings, it is necessary to consider wind effects on these structures. Subtle structures of this type are prone to vibration in the transverse direction of the wind flow. The fact that the vibration occurs depends on wind parameters (wind velocity, direction of an air flow) and it also depends on the properties of lamella (shape, length, mass, natural frequency, support type). The principal idea of this article is to show susceptibility of lamellae-like structures to transverse resonant vibration caused by the phenomenon called Von Karman effect. Comparison of susceptibility to transverse resonance vibration was analysed on the different shapes of lamellas loaded by different wind speed. Analysis was based on usage of empirically derived equations. Von Karman effect arise from wind flow past an object. Turbulence in the form of vortices are formed at the object and shed into the flowing stream intermittently. The potential problem is that this turbulence can induce vibrations into the lamella itself. In terms of this vibration problem, two frequencies are interesting. Von Karman shedding frequency is the frequency at which the vortices are formed and shed at the object. The vortex-shedding frequency increases with the velocity of the wind flow and decreases with the size of the object. Natural frequency of the object depends on the construction of the lamella itself. Parameters of lamella as a shape, mass, length, elasticity modulus of material and support types are directly involved in the calculation of natural frequency. Worst case scenario in the term of transverse resonant vibration occurs when the natural frequency of lamella is equal to the vortex-shedding frequency. In this case

El ruido en el ambiente laboral estomatológico

OpenAIRE

Grass Martínez, Yadia; Castañeda Deroncelé, Mario; Pérez Sánchez, Glenda; Rosell Valdenebro, Leyxi; Roca Serra, Lisandra

2017-01-01

Se realizó un estudio observacional, descriptivo y transversal de 59 trabajadores que se encontraban laborando físicamente en el Servicio de Estomatología del Policlínico Docente "Julián Grimau García" de Santiago de Cuba, desde julio de 2015 hasta igual mes de 2016, con el objetivo de identificar los niveles de ruido existentes en el ambiente laboral de dicho Servicio. En la serie se obtuvo que los departamentos de mayor nivel de ruido resultaron ser: Prótesis (73,2 dB), Ortodoncia y Periodo...

An Automated Algorithm for Identifying and Tracking Transverse Waves in Solar Images

Science.gov (United States)

Weberg, Micah J.; Morton, Richard J.; McLaughlin, James A.

2018-01-01

Recent instrumentation has demonstrated that the solar atmosphere supports omnipresent transverse waves, which could play a key role in energizing the solar corona. Large-scale studies are required in order to build up an understanding of the general properties of these transverse waves. To help facilitate this, we present an automated algorithm for identifying and tracking features in solar images and extracting the wave properties of any observed transverse oscillations. We test and calibrate our algorithm using a set of synthetic data, which includes noise and rotational effects. The results indicate an accuracy of 1%–2% for displacement amplitudes and 4%–10% for wave periods and velocity amplitudes. We also apply the algorithm to data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and find good agreement with previous studies. Of note, we find that 35%–41% of the observed plumes exhibit multiple wave signatures, which indicates either the superposition of waves or multiple independent wave packets observed at different times within a single structure. The automated methods described in this paper represent a significant improvement on the speed and quality of direct measurements of transverse waves within the solar atmosphere. This algorithm unlocks a wide range of statistical studies that were previously impractical.

Pure air-plasma bullets propagating inside microcapillaries and in ambient air

KAUST Repository

Lacoste, Deanna; Bourdon, Anne; Kuribara, Koichi; Urabe, Keiichiro; Stauss, Sven; Terashima, Kazuo

2014-01-01

This paper reports on the characterization of air-plasma bullets in microcapillary tubes and in ambient air, obtained without the use of inert or noble gases. The bullets were produced by nanosecond repetitively pulsed discharges, applied in a dielectric barrier discharge configuration. The anode was a tungsten wire with a diameter of 50 μm, centered in the microcapillary, while the cathode was a silver ring, fixed on the outer surface of the fused silica tube. The effects of the applied voltage and the inner diameter of the microcapillary tube on the plasma behavior were investigated. Inside the tubes, while the topology of the bullets seems to be strongly dependent on the diameter, their velocity is only a function of the amplitude of the applied voltage. In ambient air, the propagation of air bullets with a velocity of about 1.25 ×105 m s-1 is observed.

Pure air-plasma bullets propagating inside microcapillaries and in ambient air

KAUST Repository

Lacoste, Deanna

2014-11-04

This paper reports on the characterization of air-plasma bullets in microcapillary tubes and in ambient air, obtained without the use of inert or noble gases. The bullets were produced by nanosecond repetitively pulsed discharges, applied in a dielectric barrier discharge configuration. The anode was a tungsten wire with a diameter of 50 μm, centered in the microcapillary, while the cathode was a silver ring, fixed on the outer surface of the fused silica tube. The effects of the applied voltage and the inner diameter of the microcapillary tube on the plasma behavior were investigated. Inside the tubes, while the topology of the bullets seems to be strongly dependent on the diameter, their velocity is only a function of the amplitude of the applied voltage. In ambient air, the propagation of air bullets with a velocity of about 1.25 ×105 m s-1 is observed.

Ambient Space and Ambient Sensation

DEFF Research Database (Denmark)

Schmidt, Ulrik

The ambient is the aesthetic production of the sensation of being surrounded. As a concept, 'ambient' is mostly used in relation to the music genre 'ambient music' and Brian Eno's idea of environmental background music. However, the production of ambient sensations must be regarded as a central...... aspect of the aesthetization of modern culture in general, from architecture, transport and urbanized lifeforms to film, sound art, installation art and digital environments. This presentation will discuss the key aspects of ambient aesthetization, including issues such as objectlessness...

Ambient seismic noise monitoring of a clay landslide: Toward failure prediction

Science.gov (United States)

Mainsant, Guénolé; Larose, Eric; Brönnimann, Cornelia; Jongmans, Denis; Michoud, Clément; Jaboyedoff, Michel

2012-03-01

Given that clay-rich landslides may become mobilized, leading to rapid mass movements (earthflows and debris flows), they pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones, which could be detected by monitoring shear wave velocity variations. With this purpose in mind, the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

Charge Inversion Effects in Electrophoresis of Polyelectrolytes in the Presence of Multivalent Counterions and Transversal Electric Fields

Directory of Open Access Journals (Sweden)

Sorin Nedelcu

2014-12-01

Full Text Available By molecular dynamics simulations we investigate the transport of charged polymers in confinement, under externally applied electric fields, in straight cylinders of uniform diameter and in the presence of monovalent or multivalent counterions. The applied electric field has two components; a longitudinal component along the axis of the cylinder and a transversal component perpendicular to the cylinder axis. The direction of electrophoretic velocity depends on the polyelectrolyte length, valency of the counterions present in solution and transversal electric field value. A statistical model is put forward in order to explain these observations.

MHD modeling of ATLAS experiments to study transverse shear interface interactions

CERN Document Server

Faehl, R J; Keinigs, R K; Lindemuth, I R

2001-01-01

Summary form only given. The transverse shear established at the interface of two solids moving at differential velocities on the order of the sound speed is being studied in experiments on the ATLAS capacitor bank at Los Alamos, beginning in August 2001. The ATLAS bank has finished certification tests and has demonstrated peak currents of 27.5 MA with a 5 microsecond risetime into an inductive load. One- and two-dimensional MHD calculations have been performed in support of these "friction-like" ATLAS experiments. Current flowing along the outer surface of a thick aluminum liner, roughly 8 mm thick, accelerates the solid liner to velocities ~1 km/s. This cylindrically imploding liner then impacts a target assembly, composed of alternating regions of high and low density materials. The different shock speeds in the two materials leads to a differential velocity along the interface. Shock heating, elastic- plastic flow, and stress transport are included in the calculations. Material strength properties are tre...

Transverse dispersion in heterogeneous fractures

International Nuclear Information System (INIS)

Dershowitz, Bill; Shuttle, Dawn; Klise, Kate; Outters, Nils; Hermanson, Jan

2004-12-01

breakthrough curves are much more strongly affected by transverse dispersivity, with t 95 delayed by up to almost 50%. This is because when aperture is held constant, velocity varies directly with transmissivity, such that flow outside the high transmissivity channel is slower. However, even for these cases, the effect of transverse dispersivity in these single fracture studies was to increase transport times. Studies of sorbing tracer transport (Case 3) produced results similar to those found with conservative tracers, in which the magnitude of changes in breakthrough statistics due to transverse dispersion was on the same order as the changes between stochastic realizations of the spatial fields. Similarly, simulations with larger tracer release area (Case 2) also produced variations due to transverse dispersion within the range defined by stochastic realizations

Operative Method for Transverse Colon Carcinoma: Transverse Colectomy Versus Extended Colectomy.

Science.gov (United States)

Chong, Choon Seng; Huh, Jung Wook; Oh, Bo Young; Park, Yoon Ah; Cho, Yong Beom; Yun, Seong Hyeon; Kim, Hee Cheol; Lee, Woo Yong

2016-07-01

The type of surgery performed for primary transverse colon cancer varies based on tumor characteristics and surgeon perspective. The optimal oncological outcome following different surgical options has not been clearly established, and transverse colectomy has shown oncological equivalence only in small cohort studies. Our aim was to compare long-term oncological outcomes after transverse colectomy versus extended resection for transverse colon cancer. This study is a retrospective review of prospectively collected data. This study was conducted at a tertiary care hospital. All patients treated for transverse colon cancer at the Samsung Medical Center between 1995 and 2013 were included. Oncological outcomes were compared between 2 groups of patients: a transverse colectomy group and an extended colectomy group (which included extended right hemicolectomy and left hemicolectomy). A total of 1066 patients were included, of whom 750 (70.4%) underwent extended right hemicolectomy, 127 (11.9%) underwent transverse colectomy, and 189 (17.7%) underwent left hemicolectomy. According to univariate analysis, surgical approach, histological type, tumor morphology, cancer T and N stage, cancer size, and lymphovascular invasion were significant factors contributing to disease-free survival (DFS). However, as seen in multivariate analysis, only node-positive disease (HR = 2.035 (1.188-3.484)), tumors with ulcerative morphology (HR = 3.643 (1.132-11.725)), and the presence of vascular invasion (HR = 2.569 (1.455-4.538)) were significant factors for DFS. Further analysis with a propensity-matched cohort between the transverse and extended colectomy groups demonstrated no significant differences in DFS and overall survival. This study was limited because it was performed at a single institution and it was retrospective in nature. In terms of perioperative and oncological outcomes, transverse colectomy and extended colectomy did not differ despite a shorter specimen length and

3D Vector Velocity Estimation using a 2D Phased Array

DEFF Research Database (Denmark)

Pihl, Michael Johannes; Jensen, Jørgen Arendt

2011-01-01

of using the TO method for estimation 3D velocity vectors, and the proposed decoupling is demonstrated. A 64x64 and a 32x32 elements transducer are emulated using Field II. Plug flow with a speed of 1 m/s in a small region is rotated in the XY -plane. A binary flow example with [vx,vy]=[1,0] and [0,1] m......A method to estimate the three dimensional (3D) velocity vector is presented is this paper. 3D velocity vector techniques are needed to measure the full velocity and characterize the complicated flow patterns in the human body. The Transverse Oscillation (TO) method introduces oscillations...... matrix transducer. For the 32x32 transducer, the mean and standard deviation for the speed are 0.94 0.11 m/s and for the angle bias -0.487.7. The simulation study clearly demonstrates, that the new method can be used to estimate the 3D velocity vector using a 2D phased matrix array, and that the velocity...

Influence of velocity shear on the Rayleigh-Taylor instability

International Nuclear Information System (INIS)

Guzdar, P.N.; Satyanarayana, P.; Huba, J.D.; Ossakow, S.L.

1982-01-01

The influence of a transverse velocity shear on the Rayleigh-Taylor instability is investigated. It is found that a sheared velocity flow can substantially reduce the growth rate of the Rayleigh-Taylor instability in short wavelength regime (i.e., kL>1 where L is the scale length of the density inhomogeneity), and causes the growth rate to maximize at kL<1.0. Applications of this result to ionospheric phenomena [equatorial spread F (ESF) and ionospheric plasma clouds] are discussed. In particular, the effect of shear could account for, at times, the 100's of km modulation observed on the bottomside of the ESF ionosphere and the km scale size wavelengths observed in barium cloud prompt striation phenomena

Ambient noise adjoint tomography for a linear array in North China

Science.gov (United States)

Zhang, C.; Yao, H.; Liu, Q.; Yuan, Y. O.; Zhang, P.; Feng, J.; Fang, L.

2017-12-01

Ambient noise tomography based on dispersion data and ray theory has been widely utilized for imaging crustal structures. In order to improve the inversion accuracy, ambient noise tomography based on the 3D adjoint approach or full waveform inversion has been developed recently, however, the computational cost is tremendous. In this study we present 2D ambient noise adjoint tomography for a linear array in north China with significant computational efficiency compared to 3D ambient noise adjoint tomography. During the preprocessing, we first convert the observed data in 3D media, i.e., surface-wave empirical Green's functions (EGFs) from ambient noise cross-correlation, to the reconstructed EGFs in 2D media using a 3D/2D transformation scheme. Different from the conventional steps of measuring phase dispersion, the 2D adjoint tomography refines 2D shear wave speeds along the profile directly from the reconstructed Rayleigh wave EGFs in the period band 6-35s. With the 2D initial model extracted from the 3D model from traditional ambient noise tomography, adjoint tomography updates the model by minimizing the frequency-dependent Rayleigh wave traveltime misfits between the reconstructed EGFs and synthetic Green function (SGFs) in 2D media generated by the spectral-element method (SEM), with a preconditioned conjugate gradient method. The multitaper traveltime difference measurement is applied in four period bands during the inversion: 20-35s, 15-30s, 10-20s and 6-15s. The recovered model shows more detailed crustal structures with pronounced low velocity anomaly in the mid-lower crust beneath the junction of Taihang Mountains and Yin-Yan Mountains compared with the initial model. This low velocity structure may imply the possible intense crust-mantle interactions, probably associated with the magmatic underplating during the Mesozoic to Cenozoic evolution of the region. To our knowledge, it's first time that ambient noise adjoint tomography is implemented in 2D media

Experimental 3-D Vector Velocity Estimation with Row-Column Addressed Arrays

DEFF Research Database (Denmark)

Holbek, Simon; Stuart, Matthias Bo; Jensen, Jørgen Arendt

2016-01-01

Experimental 3-D vector flow estimates obtained with a 62+62 2-D row-column (RC) array with integrated apodization are presented. A transverse oscillation (TO) velocity estimator is implemented on a 3.0 MHz RC array, to yield realtime 3-D vector flow in a cross-sectional scan plane at 750 frames...... per second. The method is validated in a straight-vessel phantom (Ø = 8 mm) connected to a flow pump capable of generating timevarying carotid waveforms. The out-of-plane velocity component perpendicular to the cross section of the vessel and the crosssectional area is used to estimate volumetric flow...

On the weakly nonlinear, transversal vibrations of a conveyor belt with a low and time-varying velocity

NARCIS (Netherlands)

Suweken, G.; van Horssen, W.T.

2002-01-01

In this paper the weakly nonlinear, transversal vibrations of a conveyor belt will be considered. The belt is assumed to move with a low and time-varying speed. Using Kirchhoff's approach a single equation of motion will be derived from a coupled system of partial differential equations describing

Transverse spin and transverse momentum in scattering of plane waves

OpenAIRE

Saha, Sudipta; Singh, Ankit K.; Ray, Subir K.; Banerjee, Ayan; Gupta, Subhasish Dutta; Ghosh, Nirmalya

2016-01-01

We study the near field to the far field evolution of spin angular momentum (SAM) density and the Poynting vector of the scattered waves from spherical scatterers. The results show that at the near field, the SAM density and the Poynting vector are dominated by their transverse components. While the former (transverse SAM) is independent of the helicity of the incident circular polarization state, the latter (transverse Poynting vector) depends upon the polarization state. It is further demon...

The Main Principles of Formation of the Transverse Modes in the Multilayered Waveguides of Surface Acoustic Waves

Science.gov (United States)

Sveshnikov, B. V.; Bagdasaryan, A. S.

2016-07-01

We develop a self-consistent model allowing one to analyze the properties of the interdigital transducer of the surface acoustic waves as a symmetric five-layered waveguide on a piezoelectric substrate with three possible values of the phase velocity of the acoustic-wave propagation along the longitudinal axis of the system. The transcendental dispersion relation for describing the waves in such a system is derived and the method for its instructive graphic analysis is proposed. The condition under which only the fundamental transverse mode is excited in the waveguide is formulated. The method for calculating the normalized power and the transverse distribution of the field of the continuous-spectrum waves radiated from the considered waveguide is described. It is shown that the characteristic spatial scale of the longitudinal damping of the amplitude of this field at the waveguide center can be a qualitative estimate of the transverse-mode formation length. The efficiency of a new method for suppressing the higher-order transverse waveguide modes is demonstrated.

Joint inversion of high resolution S-wave velocity structure underneath North China Basin

Science.gov (United States)

Yang, C.; Li, G.; Niu, F.

2017-12-01

North China basin is one of earthquake prone areas in China. Many devastating earthquakes occurred in the last century and before, such as the 1937 M7.0 Heze Earthquake in Shandong province, the 1966 M7.2 Xingtai Earthquake and 1976 Tangshan Earthquake in Hebei province. Knowing the structure of the sediment cover is of great importance to predict strong ground motion caused by earthquakes. Unconsolidated sediments are loose materials, ranging from clay to sand to gravel. Earthquakes can liquefy unconsolidated sediments, thus knowing the distribution and thickness of the unconsolidated sediments has significant implication in seismic hazard analysis of the area. Quantitative estimates of the amount of extension of the North China basin is important to understand the thinning and evolution of the eastern North China craton and the underlying mechanism. In principle, the amount of lithospheric stretching can be estimated from sediment and crustal thickness. Therefore an accurate estimate of the sediment and crustal thickness of the area is also important in understanding regional tectonics. In this study, we jointly invert the Rayleigh wave phase-velocity dispersion and Z/H ratio data to construct a 3-D S-wave velocity model beneath North China area. We use 4-year ambient noise data recorded from 249 temporary stations, and 139 earthquake events to extract Rayleigh wave Z/H ratios. The Z/H ratios obtained from ambient noise data and earthquake data show a good agreement within the overlapped periods. The phase velocity dispersion curve was estimated from the same ambient noise data. The preliminary result shows a relatively low Z/H ratio and low velocity anomaly at the shallow part of sediment basins.

The crustal structure beneath The Netherlands derived from ambient seismic noise

NARCIS (Netherlands)

Yudistira, Tedi; Paulssen, Hanneke; Trampert, Jeannot

2017-01-01

This work presents the first comprehensive 3-D model of the crust beneath The Netherlands. To obtain this model, we designed the NARS-Netherlands project, a dense deployment of broadband stations in the area. Rayleigh and Love wave group velocity dispersion was measured from ambient noise

Field Testing of an In-well Point Velocity Probe for the Rapid Characterization of Groundwater Velocity

Science.gov (United States)

Osorno, T.; Devlin, J. F.

2017-12-01

Reliable estimates of groundwater velocity is essential in order to best implement in-situ monitoring and remediation technologies. The In-well Point Velocity Probe (IWPVP) is an inexpensive, reusable tool developed for rapid measurement of groundwater velocity at the centimeter-scale in monitoring wells. IWPVP measurements of groundwater speed are based on a small-scale tracer test conducted as ambient groundwater passes through the well screen and the body of the probe. Horizontal flow direction can be determined from the difference in tracer mass passing detectors placed in four funnel-and-channel pathways through the probe, arranged in a cross pattern. The design viability of the IWPVP was confirmed using a two-dimensional numerical model in Comsol Multiphysics, followed by a series of laboratory tank experiments in which IWPVP measurements were calibrated to quantify seepage velocities in both fine and medium sand. Lab results showed that the IWPVP was capable of measuring the seepage velocity in less than 20 minutes per test, when the seepage velocity was in the range of 0.5 to 4.0 m/d. Further, the IWPVP estimated the groundwater speed with a precision of ± 7%, and an accuracy of ± 14%, on average. The horizontal flow direction was determined with an accuracy of ± 15°, on average. Recently, a pilot field test of the IWPVP was conducted in the Borden aquifer, C.F.B. Borden, Ontario, Canada. A total of approximately 44 IWPVP tests were conducted within two 2-inch groundwater monitoring wells comprising a 5 ft. section of #8 commercial well screen. Again, all tests were completed in under 20 minutes. The velocities estimated from IWPVP data were compared to 21 Point Velocity Probe (PVP) tests, as well as Darcy-based estimates of groundwater velocity. Preliminary data analysis shows strong agreement between the IWPVP and PVP estimates of groundwater velocity. Further, both the IWPVP and PVP estimates of groundwater velocity appear to be reasonable when

Mechanism to synthesize a ‘moving optical mark’ at solid-ambient interface for the estimation of thermal diffusivity of solid

Directory of Open Access Journals (Sweden)

Settu Balachandar

2016-01-01

Full Text Available A novel mechanism is proposed, involving a novel interaction between solid-sample supporting unsteady heat flow with its ambient-humidity; invokes phase transformation of water-vapour molecule and synthesize a ‘moving optical-mark’ at sample-ambient-interface. Under tailored condition, optical-mark exhibits a characteristic macro-scale translatory motion governed by thermal diffusivity of solid. For various step-temperature inputs via cooling, position-dependent velocities of moving optical-mark are measured at a fixed distance. A new approach is proposed. ‘Product of velocity of optical-mark and distance’ versus ‘non-dimensional velocity’ is plotted. The slope reveals thermal diffusivity of solid at ambient-temperature; preliminary results obtained for Quartz-glass is closely matching with literature.

How to measure propagation velocity in cardiac tissue: a simulation study

Directory of Open Access Journals (Sweden)

Andre C. Linnenbank

2014-07-01

Full Text Available To estimate conduction velocities from activation times in myocardial tissue, the average vector method computes all the local activation directions and velocities from local activation times and estimates the fastest and slowest propagation speed from these local values. The single vector method uses areas of apparent uniform elliptical spread of activation and chooses a single vector for the estimated longitudinal velocity and one for the transversal. A simulation study was performed to estimate the influence of grid size, anisotropy, and vector angle bin size. The results indicate that the average vector method can best be used if the grid- or bin-size is large, although systematic errors occur. The single vector method performs better, but requires human intervention for the definition of fiber direction. The average vector method can be automated.

A compact fiber optics-based heterodyne combined normal and transverse displacement interferometer.

Science.gov (United States)

Zuanetti, Bryan; Wang, Tianxue; Prakash, Vikas

2017-03-01

While Photonic Doppler Velocimetry (PDV) has become a common diagnostic tool for the measurement of normal component of particle motion in shock wave experiments, this technique has not yet been modified for the measurement of combined normal and transverse motion, as needed in oblique plate impact experiments. In this paper, we discuss the design and implementation of a compact fiber-optics-based heterodyne combined normal and transverse displacement interferometer. Like the standard PDV, this diagnostic tool is assembled using commercially available telecommunications hardware and uses a 1550 nm wavelength 2 W fiber-coupled laser, an optical focuser, and single mode fibers to transport light to and from the target. Two additional optical probes capture first-order beams diffracted from a reflective grating at the target free-surface and deliver the beams past circulators and a coupler where the signal is combined to form a beat frequency. The combined signal is then digitized and analyzed to determine the transverse component of the particle motion. The maximum normal velocity that can be measured by this system is limited by the equivalent transmission bandwidth (3.795 GHz) of the combined detector, amplifier, and digitizer and is estimated to be ∼2.9 km/s. Sample symmetric oblique plate-impact experiments are performed to demonstrate the capability of this diagnostic tool in the measurement of the combined normal and transverse displacement particle motion.

Statistics of a mixed Eulerian-Lagrangian velocity increment in fully developed turbulence

International Nuclear Information System (INIS)

Friedrich, R; Kamps, O; Grauer, R; Homann, H

2009-01-01

We investigate the relationship between Eulerian and Lagrangian probability density functions obtained from numerical simulations of two-dimensional as well as three-dimensional turbulence. We show that in contrast to the structure functions of the Lagrangian velocity increment δ τ v(y)=u(x(y, τ), τ)- u(y, 0), where u(x, t) denotes the Eulerian velocity and x(y, t) the particle path initially starting at x(y, 0)=y, the structure functions of the velocity increment δ τ w(y)=u(x(y, τ), τ)- u(y, τ) exhibit a wide range of scaling behavior. Similar scaling indices are detected for the structure functions for particles diffusing in frozen turbulent fields. Furthermore, we discuss a connection to the scaling of Eulerian transversal structure functions.

Offshore Rayleigh Group Velocity Observations of the South Island, New Zealand, from Ambient Noise Data

KAUST Repository

Yeck, William L.; Sheehan, Anne F.; Stachnik, Joshua C.; Lin, Fan-Chi

2017-01-01

We present azimuthally anisotropic Rayleigh group velocity models from 8 - 35 s both offshore and onshore of the South Island of New Zealand. We use MOANA (Marine Observations of Anisotropy Near Aotearoa) broadband ocean seismic data in combination with on land data from the New Zealand National Seismography Network (NZNSN) to investigate the seismic structure of the flanks of the Australian-Pacific plate boundary. At 8 s, we observe low offshore group velocities best explained by the influence of the water layer and thick water-laden sediments. At long periods (20-30 s), group velocities are lower on the South Island relative to its offshore flanks, due to thickened crust beneath the island, with the lowest velocities primarily beneath the Southern Alps. Group velocity azimuthal anisotropy fast directions near the Alpine Fault align with the direction of relative plate motion between the Australian and Pacific plates. In the southern portion of the island, fast directions rotate anticlockwise, likely in response to a decrease in dextral shearing away from the plate boundary. Azimuthal anisotropy fast directions align with absolute plate motion offshore on the Pacific plate. Based on the depth sensitivity of our observations, we suggest diffuse deformation occurs throughout the crust. Our observations match trends in previous Pn anisotropy and SKS shear wave splitting observations, and therefore suggest a consistent pattern of distributed deformation throughout the lithosphere.

Offshore Rayleigh Group Velocity Observations of the South Island, New Zealand, from Ambient Noise Data

KAUST Repository

Yeck, William L.

2017-02-15

We present azimuthally anisotropic Rayleigh group velocity models from 8 - 35 s both offshore and onshore of the South Island of New Zealand. We use MOANA (Marine Observations of Anisotropy Near Aotearoa) broadband ocean seismic data in combination with on land data from the New Zealand National Seismography Network (NZNSN) to investigate the seismic structure of the flanks of the Australian-Pacific plate boundary. At 8 s, we observe low offshore group velocities best explained by the influence of the water layer and thick water-laden sediments. At long periods (20-30 s), group velocities are lower on the South Island relative to its offshore flanks, due to thickened crust beneath the island, with the lowest velocities primarily beneath the Southern Alps. Group velocity azimuthal anisotropy fast directions near the Alpine Fault align with the direction of relative plate motion between the Australian and Pacific plates. In the southern portion of the island, fast directions rotate anticlockwise, likely in response to a decrease in dextral shearing away from the plate boundary. Azimuthal anisotropy fast directions align with absolute plate motion offshore on the Pacific plate. Based on the depth sensitivity of our observations, we suggest diffuse deformation occurs throughout the crust. Our observations match trends in previous Pn anisotropy and SKS shear wave splitting observations, and therefore suggest a consistent pattern of distributed deformation throughout the lithosphere.

Magnetic field-aligned plasma expansion in critical ionization velocity space experiments

International Nuclear Information System (INIS)

Singh, N.

1989-01-01

Motivated by the recent Critical Ionization Velocity (CIV) experiments in space, the temporal evolution of a plasma cloud released in an ambient plasma is studied. Time-dependent Vlasov equations for both electrons and ions, along with the Poisson equation for the self-consistent electric field parallel to the ambient magnetic field, are solved. The initial cloud is assumed to consist of cold, warm, and hot electrons with temperatures T/sub c/ ≅ 0.2 eV, T/sub w/ ≅ 2 eV, and T/sub h/ ≅ 10 eV, respectively. It is found that the minor hot electrons escape the cloud, and their velocity distribution function shows the typical time-of-flight dispersion feature - that is, the larger the distance from the cloud, the larger is the average drift velocity of the escaping electrons. The major warm electrons expand along the magnetic field line with the corresponding ion-acoustic speed. The combined effect of the escaping hot electrons and the expanding warm ones sets up an electric potential structure which accelerates the ambient electrons into the cloud. Thus, the energy loss due to the electron escape is partly replenished. The electric field distribution in the potential structure depends on the stage of the evolution; before the rarefaction waves propagating from the edges of the cloud reach its center, the electric fields point into the cloud. After this stage the cloud divides into two subclouds, with each having their own bipolar electric fields. Effects of collisions on the evolution of plasma clouds are also discussed. The relevance of the results seen from the calculations are discussed in the context of recent space experiments on CIV

Enhancing PIV image and fractal descriptor for velocity and shear stresses propagation around a circular pier

Directory of Open Access Journals (Sweden)

Alireza Keshavarzi

2017-07-01

Full Text Available In this study, the fractal dimensions of velocity fluctuations and the Reynolds shear stresses propagation for flow around a circular bridge pier are presented. In the study reported herein, the fractal dimension of velocity fluctuations (u′, v′, w′ and the Reynolds shear stresses (u′v′ and u′w′ of flow around a bridge pier were computed using a Fractal Interpolation Function (FIF algorithm. The velocity fluctuations of flow along a horizontal plane above the bed were measured using Acoustic Doppler Velocity meter (ADV and Particle Image Velocimetry (PIV. The PIV is a powerful technique which enables us to attain high resolution spatial and temporal information of turbulent flow using instantaneous time snapshots. In this study, PIV was used for detection of high resolution fractal scaling around a bridge pier. The results showed that the fractal dimension of flow fluctuated significantly in the longitudinal and transverse directions in the vicinity of the pier. It was also found that the fractal dimension of velocity fluctuations and shear stresses increased rapidly at vicinity of pier at downstream whereas it remained approximately unchanged far downstream of the pier. The higher value of fractal dimension was found at a distance equal to one times of the pier diameter in the back of the pier. Furthermore, the average fractal dimension for the streamwise and transverse velocity fluctuations decreased from the centreline to the side wall of the flume. Finally, the results from ADV measurement were consistent with the result from PIV, therefore, the ADV enables to detect turbulent characteristics of flow around a circular bridge pier.

Efeito das dimensões da seção transversal e da frequência do transdutor na velocidade de propagação de ondas de ultra-som na madeira Effect of the transversal section dimensions and transducer frequency on ultrasound wave propagation velocity in wood

Directory of Open Access Journals (Sweden)

Alex Julio Trinca

2009-02-01

Full Text Available Diversas pesquisas vêm sendo realizadas com o uso da velocidade de propagação de ondas de ultra-som como parâmetro para estimar propriedades mecânicas da madeira. Tendo em vista que essa velocidade pode ser influenciada pela forma da peça ensaiada, bem como pela frequência do transdutor utilizado no ensaio, conhecer essas fontes de influência é fator importante para a obtenção de resultados confiáveis. Durante estudo mais amplo sobre a influência da dimensão do corpo-de-prova em ensaios destrutivos de compressão paralela às fibras, os corpos-de-prova de 0,03 x 0,03 x 0,09 m e de 0,05 x 0,05 x 0,15 m foram também utilizados para avaliar a variação da velocidade de propagação de ondas de ultrassom em razão da dimensão da peça ensaiada. Para a avaliação da influência da frequência, os ensaios foram realizados com transdutores de onda longitudinal (compressão de 25 kHz, 45 kHz, 80 kHz, 100 kHz, 500 kHz e 1 MHz, em 119 corpos-de-prova de Pinus elliottii e 244 de Eucalyptus grandis. Os resultados indicaram que, em ambas as espécies, a seção transversal exerceu influência na propagação da onda de ultrassom e que a velocidade longitudinal foi fortemente afetada pela frequência do transdutor para frequências abaixo de 500 kHz, corroborando a importância de sempre se adotarem, nos ensaios, relações de comprimento de percurso/comprimento de onda superiores a 3,0.Several works use the ultrasound wave propagation velocity as the main parameter to determine the mechanical properties of wood. Since this velocity can be influenced by the specimen's dimension or by the transducer's frequency, this influence must be known to obtain reliable results. During research on the influence of specimen dimension on destructive testing of the compression parallel to the grain, 0.03 x 0.03 x 0.09 m and 0.05 x 0.05 x 0.15 m specimens were tested to evaluate the variation in wave propagation velocity as a function of specimen dimension

Development of a low cost method to estimate the seismic signature of a geothermal field form ambient noise analysis.

Energy Technology Data Exchange (ETDEWEB)

Tibuleac, Ileana [Univ. of Nevada, Reno, NV (United States)

2016-06-30

A new, cost effective and non-invasive exploration method using ambient seismic noise has been tested at Soda Lake, NV, with promising results. The material included in this report demonstrates that, with the advantage of initial S-velocity models estimated from ambient noise surface waves, the seismic reflection survey, although with lower resolution, reproduces the results of the active survey when the ambient seismic noise is not contaminated by strong cultural noise. Ambient noise resolution is less at depth (below 1000m) compared to the active survey. In general, the results are promising and useful information can be recovered from ambient seismic noise, including dipping features and fault locations.

A software to measure phase-velocity dispersion from ambient-noise correlations and its application to the SNSN data

Science.gov (United States)

Sadeghisorkhani, Hamzeh; Gudmundsson, Ólafur

2017-04-01

Graphical software for phase-velocity dispersion measurements of surface waves in noise-correlation traces, called GSpecDisp, is presented. It is an interactive environment for the measurements and presentation of the results. It measures phase-velocity dispersion curves in the frequency domain based on matching of the real part of the cross-correlation spectrum with the appropriate Bessel function. The inputs are time-domain cross-correlations in SAC format. It can measure two types of phase-velocity dispersion curves; 1- average phase-velocity of a region, and 2- single-pair phase velocity. The average phase-velocity dispersion curve of a region can be used as a reference curve to automatically select the dispersion curves from each single-pair cross-correlation in that region. It also allows the users to manually refine the selections. Therefore, no prior knowledge is needed for an unknown region. GSpecDisp can measure the phase velocity of Rayleigh and Love waves from all possible components of the noise correlation tensor, including diagonal and off-diagonal components of the tensor. First, we explain how GSpecDisp is applied to measure phase-velocity dispersion curves. Then, we demonstrate measurement results on synthetic and real data from the Swedish National Seismic Network (SNSN). We compare the results with two other methods of phase-velocity dispersion measurements. Finally, we compare phase-velocity dispersion curves of Rayleigh waves obtained from different components of the correlation tensor.

Electron velocity distributions near collisionless shocks

International Nuclear Information System (INIS)

Feldman, W.C.

1984-01-01

Recent studies of the amount of electron heating and of the shapes of electron velocity distributions across shocks near the earth are reviewed. It is found that electron heating increases with increasing shock strength but is always less than the ion heating. The scale length of electron heating is also less than that for the ions. Electron velocity distributions show characteristic shapes which depend on the strength of the shocks. At the weaker shocks, electron heating is mostly perpendicular to the ambient magnetic field, bar B, and results in Gaussian-shaped velocity distributions at low-to-moderate energies. At the stronger shocks, parallel heating predominates resulting in flat-topped velocity distributions. A reasonable interpretation of these results indicates that at the weaker shocks electron heating is dominated by a tendency toward conservation of the magnetic moment. At the stronger fast-mode shocks, this heating is thought to be dominated by an acceleration parallel to bar B produced by the macroscopic shock electric field followed by beam driven plasma instabilities. Some contribution to the heating at the stronger shocks from conservation of the magnetic moment and cross-field current-driven instabilities cannot be ruled out. Although the heating at slow-mode shocks is also dominated by instabilities driven by magnetic field-aligned electron beams, their acceleration mechanism is not yet established

Transverse thermopherotic MHD Oldroyd-B fluid with Newtonian heating

Science.gov (United States)

Mehmood, R.; Rana, S.; Nadeem, S.

2018-03-01

Hydromagnetic transverse flow of an Oldroyd-B type fluid with suspension of nanoparticles and Newtonian heating effects is conferred in this article. Relaxation and Retardation time effects are taken into consideration. Using suitable transformations physical problem is converted into non-linear ordinary differential equations which are tackled numerically via Runge-Kutta Fehlberg integration scheme. Illustration of embedded constraints on flow characteristics are extracted through graphs. The physical response of velocity, temperature and concentration are investigated computationally. Momentum boundary layer thickness decreases but local heat and mass flux rises for Deborah number and Hartman number. The results provide interesting insights into certain applicable transport phenomena involving hydromagnetic rheological fluids.

Deformation and velocity measurements at elevated temperature in a fractured 0.5 M block of tuff

International Nuclear Information System (INIS)

Blair, S.C.; Berge, P.A.

1996-01-01

This paper presents preliminary results of laboratory tests conducted on small block samples of Topopah Spring tuff, in support of the Yucca Mountain Site Characterization Project. The overall objective of these tests is to investigate the thermal-mechanical, thermal-hydrological, and thermal-chemical response of the rock to conditions similar to the near-field environment (NFE) of a potential nuclear waste repository. We present preliminary results of deformation and elastic wave velocity measurements on a 0.5-m-scale block of Topopah Spring tuff tested in uniaxial compression to 8.5 MPa and at temperatures to 85 degree C. The Young's modulus was found to be about 7 to 31 GPa for vertical measurements parallel to the stress direction across parts of the block containing no fractures or a few fractures, and 0.5 to 0.9 GPA for measurements across individual fractures, at ambient temperature and 8.5 MPa maximum stress. During stress cycles between 5 and 8.5 MPa, the deformation modulus values for the matrix with fractures were near 15-20 GPa at ambient temperature but dropped to about 10 GPa at 85 degree C. Compressional wave velocities were found to be about 3.6 to 4.7 km/s at ambient temperature and stress. After the stress was cycled, velocities dropped to values as low as 2.6 km/s in the south end of the block where vertical cracks developed. Heating the block to about 85 degree C raised velocities to as much as 5.6 km/s in the upper third of the block

Application of the time dependent suction to free convection laminar flow in the presence of transverse magnetic field

International Nuclear Information System (INIS)

Agrawal, H.L.; Ram, P.C.

1980-01-01

The laminar unsteady free convection and heat transfer of an electrically conducting fluid past a porous vertical flat plate in the presence of uniform transverse magnetic field is investigated when the free stream velocity and suction at the plate are oscillatory functions of time, viscous dissipation term and Joul's dissipation term have been neglected at low velocity. Expressions for velocity and temperature distributions have been obtained in the non-dimensional forms and the skin-friction has been calculated. The skin-friction decreases by increasing Hartmann number. The suction is applied to check the growth of the boundary layer. This study is likely to have bearing on the problem of boundary layer control and transpiration cooling. (author)

Transversity: Theory and phenomenology

Energy Technology Data Exchange (ETDEWEB)

D' Alesio, Umberto [Dipartimento di Fisica, Universita di Cagliari, Cittadella Universitaria, and Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari, C. P. 170, I-09042 Monserrato (Italy)

2013-04-15

The distribution of transversely polarized quarks inside a transversely polarized nucleon, known as transversity, encodes a basic piece of information on the nucleon structure, sharing the same status with the more familiar unpolarized and helicity distributions. I will review its properties and discuss different ways to access it, with highlights and limitations. Recent phenomenological extractions and perspectives are also presented.

Transversity: Theory and phenomenology

International Nuclear Information System (INIS)

D'Alesio, Umberto

2013-01-01

The distribution of transversely polarized quarks inside a transversely polarized nucleon, known as transversity, encodes a basic piece of information on the nucleon structure, sharing the same status with the more familiar unpolarized and helicity distributions. I will review its properties and discuss different ways to access it, with highlights and limitations. Recent phenomenological extractions and perspectives are also presented.

Drift velocity and pressure monitoring of the CMS muon drift chambers

CERN Document Server

Sonnenschein, Lars

2011-01-01

The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers. The differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest drift velocity monitoring results are discussed.

3D Crust and Uppermost Mantle Structure beneath Tian Shan Region from ambient noise and earthquake surface waves

Science.gov (United States)

Xiao, X.; Wen, L.

2017-12-01

As a typical active intracontinental mountain range in Central Asia, Tian Shan Mt serves as the prototype in studying geodynamic processes and mechanism of intracontinental mountain building. We study 3D crust and the uppermost mantle structure beneath Tian Shan region using ambient noise and earthquake surface waves. Our dataset includes vertical component records of 62 permanent broadband seismic stations operated by the Earthquake Administration of China. Firstly, we calculate two-year stacked Cross-Correlation Functions (CCFs) of ambient noise records between the stations. The CCFs are treated as the Empirical Green's Functions (EGFs) of each station pair, from which we measured phase velocities of fundamental-mode Rayleigh wave in the period of 3-40 s using a frequency-time analysis method. Secondly, we collect surface wave data from tele-seismic events with Mw > 5.5 and depth shallower than 200 km and measure phase velocities of the fundamental-mode of Rayleigh wave in the period of 30-150 s using a two-station method. Finally, we combine the phase velocity measurements from ambient noise and earthquake surface waves, obtain lateral isotropic phase velocity maps at different periods based on tomography and invert a 3D Vsv model of crust and uppermost mantle down to about 150 km using a Monte Carlo Inversion method. We will discuss our inversion results in detail, as well as their implications to the tectonics in the region.

Quasi-Rayleigh waves in transversely isotropic half-space with inclined axis of symmetry

International Nuclear Information System (INIS)

Yanovskaya, T.B.; Savina, L.S.

2003-09-01

A method for determination of characteristics of quasi-Rayleigh (qR) wave in a transversely isotropic homogeneous half-space with inclined axis of symmetry is outlined. The solution is obtained as a superposition of qP, qSV and qSH waves, and surface wave velocity is determined from the boundary conditions at the free surface and at infinity, as in the case of Rayleigh wave in isotropic half-space. Though the theory is simple enough, a numerical procedure for the calculation of surface wave velocity presents some difficulties. The difficulty is conditioned by necessity to calculate complex roots of a non-linear equation, which in turn contains functions determined as roots of nonlinear equations with complex coefficients. Numerical analysis shows that roots of the equation corresponding to the boundary conditions do not exist in the whole domain of azimuths and inclinations of the symmetry axis. The domain of existence of qR wave depends on the ratio of the elastic parameters: for some strongly anisotropic models the wave cannot exist at all. For some angles of inclination qR wave velocities deviate from those calculated on the basis of the perturbation method valid for weak anisotropy, though they have the same tendency of variation with azimuth. The phase of qR wave varies with depth unlike Rayleigh wave in isotropic half-space. Unlike Rayleigh wave in isotropic half-space, qR wave has three components - vertical, radial and transverse. Particle motion in horizontal plane is elliptic. Direction of the major axis of the ellipsis coincide with the direction of propagation only in azimuths 0 deg. (180 deg.) and 90 deg. (270 deg.). (author)

Displacement of an electric arc by a stationary transverse magnetic field to different pressures of the ionized gas

International Nuclear Information System (INIS)

Ramos, J.

1987-01-01

The displacement of a wall-stabilized electric arc by a stationary transverse magnetic field is measured to different pressures of the ionized gas. The increase of the pressure makes the heat transfer function and the mass flow velocity in the arc column to raise, and it makes the arc displacement to decrease. (author)

ENERGY CONTENT AND PROPAGATION IN TRANSVERSE SOLAR ATMOSPHERIC WAVES

Energy Technology Data Exchange (ETDEWEB)

Goossens, M.; Van Doorsselaere, T. [Centre for mathematical Plasma Astrophysics, Mathematics Department, Celestijnenlaan 200B bus 2400, B-3001 Heverlee (Belgium); Soler, R. [Solar Physics Group, Departament de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain); Verth, G., E-mail: tom.vandoorsselaere@wis.kuleuven.be [Solar Physics and Space Plasma Research Centre (SP2RC), School of Mathematics and Statistics, University of Sheffield, Hounsfield Road, Hicks Building, Sheffield S3 7RH (United Kingdom)

2013-05-10

Recently, a significant amount of transverse wave energy has been estimated propagating along solar atmospheric magnetic fields. However, these estimates have been made with the classic bulk Alfven wave model which assumes a homogeneous plasma. In this paper, the kinetic, magnetic, and total energy densities and the flux of energy are computed for transverse MHD waves in one-dimensional cylindrical flux tube models with a piecewise constant or continuous radial density profile. There are fundamental deviations from the properties for classic bulk Alfven waves. (1) There is no local equipartition between kinetic and magnetic energy. (2) The flux of energy and the velocity of energy transfer have, in addition to a component parallel to the magnetic field, components in the planes normal to the magnetic field. (3) The energy densities and the flux of energy vary spatially, contrary to the case of classic bulk Alfven waves. This last property has the important consequence that the energy flux computed with the well known expression for bulk Alfven waves could overestimate the real flux by a factor in the range 10-50, depending on the flux tube equilibrium properties.

Rayleigh wave tomography of the British Isles from ambient seismic noise

Science.gov (United States)

Nicolson, Heather; Curtis, Andrew; Baptie, Brian

2014-08-01

We present the first Rayleigh wave group speed maps of the British Isles constructed from ambient seismic noise. The maps also constitute the first surface wave tomography study of the crust under the British Isles at a relatively high resolution. We computed interferometric, interstation Rayleigh waves from vertical component records of ambient seismic noise recorded on 63 broad-band and short-period stations across the UK and Ireland. Group velocity measurements were made from the resulting surface wave dispersion curves between 5 and 25 s using a multiple phase-matched filter method. Uncertainties in the group velocities were computed by calculating the standard deviation of four dispersion curves constructed by stacking a random selection of daily cross-correlations. Where an uncertainty could not be obtained for a ray path using this method, we estimated it as a function of the interreceiver distance. Group velocity maps were computed for 5-25-s period using the Fast Marching forward solution of the eikonal equation and iterative, linearized inversion. At short and intermediate periods, the maps show remarkable agreement with the major geological features of the British Isles including: terrane boundaries in Scotland; regions of late Palaeozoic basement uplift; areas of exposed late Proterozoic/early Palaeozoic rocks in southwest Scotland, northern England and northwest Wales and, sedimentary basins formed during the Mesozoic such as the Irish Sea Basin, the Chester Basin, the Worcester Graben and the Wessex Basin. The maps also show a consistent low-velocity anomaly in the region of the Midlands Platform, a Proterozoic crustal block in the English Midlands. At longer periods, which are sensitive velocities in the lower crustal/upper mantle, the maps suggest that the depth of Moho beneath the British Isles decreases towards the north and west. Areas of fast velocity in the lower crust also coincide with areas thought to be associated with underplating of the

La educación ambiental como base cultural y estrategia para el desarrollo sostenible

Directory of Open Access Journals (Sweden)

Carlos Severiche-Sierra

2016-05-01

Full Text Available En la actualidad se habla de educación ambiental como el medio más efectivo para concienciar a la población sobre la necesidad de preservar el ambiente con miras a lograr una mejor calidad de vida en las generaciones actuales y por venir. Pese a los esfuerzos por conservar los recursos naturales no se ha podido frenar el deterioro ambiental, debido, posiblemente, a que no logramos tener conciencia y actitud de respeto hacia la naturaleza. Se hizo una revisión sobre las investigaciones más recientes acerca de la trascendencia de la educación ambiental como base para optimizar la cultura presente y futura. El presente artículo de revisión tiene como principal analizar cualitativamente la literatura científica disponible en las bases de datos Science Direct, Scielo, Redalyc y páginas Web oficiales, empleando como palabras de búsqueda: ambiente, cultura, educación, sociedad, sostenibilidad. Se obtuvo información pertinente relacionada con el objetivo propuesto, la cual se presenta en 3 secciones: la educación ambiental, un eje transversal, cultura y educación ambiental y educación para el desarrollo sostenible, estableciendo además la dimensión ambiental como estrategia para el avance en aspectos sociales, económicos y su contribución al desarrollo sostenible de nuestra sociedad. La educación ambiental es pilar fundamental de la generación de cambios de actitud y aptitud y de lograr un equilibrio entre el ser humano y su entorno. Se requiere del apoyo de casi todas las disciplinas, por lo que la resolución de los problemas ambientales debe contar con la participación activa de un amplio conjunto de personas e instituciones.

Determination of the Ion Velocity Distribution in a Rotating Plasma from Measurements of Doppler Broadening

DEFF Research Database (Denmark)

Jørgensen, L. W.; Sillesen, Alfred Hegaard

1979-01-01

The Doppler-broadened profile of the He II 4685.75 AA line was measured along a chord in a rotating plasma, transverse to the magnetic field. Using a single-particle orbit picture, the corresponding velocity spectrum of ions confirm the measurements, so it can be concluded that the single-particl...

Modeling continuous seismic velocity changes due to ground shaking in Chile

Science.gov (United States)

Gassenmeier, Martina; Richter, Tom; Sens-Schönfelder, Christoph; Korn, Michael; Tilmann, Frederik

2015-04-01

In order to investigate temporal seismic velocity changes due to earthquake related processes and environmental forcing, we analyze 8 years of ambient seismic noise recorded by the Integrated Plate Boundary Observatory Chile (IPOC) network in northern Chile between 18° and 25° S. The Mw 7.7 Tocopilla earthquake in 2007 and the Mw 8.1 Iquique earthquake in 2014 as well as numerous smaller events occurred in this area. By autocorrelation of the ambient seismic noise field, approximations of the Green's functions are retrieved. The recovered function represents backscattered or multiply scattered energy from the immediate neighborhood of the station. To detect relative changes of the seismic velocities we apply the stretching method, which compares individual autocorrelation functions to stretched or compressed versions of a long term averaged reference autocorrelation function. We use time windows in the coda of the autocorrelations, that contain scattered waves which are highly sensitive to minute changes in the velocity. At station PATCX we observe seasonal changes in seismic velocity as well as temporary velocity reductions in the frequency range of 4-6 Hz. The seasonal changes can be attributed to thermal stress changes in the subsurface related to variations of the atmospheric temperature. This effect can be modeled well by a sine curve and is subtracted for further analysis of short term variations. Temporary velocity reductions occur at the time of ground shaking usually caused by earthquakes and are followed by a recovery. We present an empirical model that describes the seismic velocity variations based on continuous observations of the local ground acceleration. Our hypothesis is that not only the shaking of earthquakes provokes velocity drops, but any small vibrations continuously induce minor velocity variations that are immediately compensated by healing in the steady state. We show that the shaking effect is accumulated over time and best described by

Doppler lidar investigation of wind turbine wake characteristics and atmospheric turbulence under different surface roughness.

Science.gov (United States)

Zhai, Xiaochun; Wu, Songhua; Liu, Bingyi

2017-06-12

Four field experiments based on Pulsed Coherent Doppler Lidar with different surface roughness have been carried out in 2013-2015 to study the turbulent wind field in the vicinity of operating wind turbine in the onshore and offshore wind parks. The turbulence characteristics in ambient atmosphere and wake area was analyzed using transverse structure function based on Plane Position Indicator scanning mode. An automatic wake processing procedure was developed to determine the wake velocity deficit by considering the effect of ambient velocity disturbance and wake meandering with the mean wind direction. It is found that the turbine wake obviously enhances the atmospheric turbulence mixing, and the difference in the correlation of turbulence parameters under different surface roughness is significant. The dependence of wake parameters including the wake velocity deficit and wake length on wind velocity and turbulence intensity are analyzed and compared with other studies, which validates the empirical model and simulation of a turbine wake for various atmosphere conditions.

Preliminary Estimates of Specific Discharge and Transport Velocities near Borehole NC-EWDP-24PB

International Nuclear Information System (INIS)

Freifeld, Barry; Doughty, Christine; Finsterle, Stefan

2006-01-01

This report summarizes fluid electrical conductivity (FEC) and thermal logging data collected in Borehole NC-EWDP-24PB, located approximately 15 km south of the proposed repository at Yucca Mountain. Preliminary analyses of a small fraction of the FEC and temperature data indicate that relatively large, localized fluid fluxes are likely to exist at this location. The implication that considerable flow is induced by small gradients, and that flow is highly localized, is significant for the estimation of groundwater transport velocities and radionuclide travel times. The sensitivity of the data to potential perturbations during testing (i.e., internal wellbore flow in the case of FEC data, and buoyancy effects in the case of thermal logging data) make it difficult to conclusively derive fluid fluxes and transport velocities without a detailed analysis of all data and processes involved. Such a comprehensive analysis has not yet been performed. However, the preliminary results suggest that the ambient component of the estimated flow rates is significant and on the order of liters per minute, yielding groundwater transport velocities in the range of kilometers per year. One particular zone in the Bullfrog tuff exhibits estimated velocities on the order of 10 km/yr. Given that the preliminary estimates of ambient flow rates and transport velocities are relatively high, and considering the potential impact of high rates and velocities on saturated-zone flow and transport behavior, we recommend that a comprehensive analysis of all the available data be performed. Moreover, additional data sets at other locations should be collected to examine whether the current data set is representative of the regional flow system near Yucca Mountain

Doppler velocity measurements from large and small arteries of mice

Science.gov (United States)

Reddy, Anilkumar K.; Madala, Sridhar; Entman, Mark L.; Michael, Lloyd H.; Taffet, George E.

2011-01-01

With the growth of genetic engineering, mice have become increasingly common as models of human diseases, and this has stimulated the development of techniques to assess the murine cardiovascular system. Our group has developed nonimaging and dedicated Doppler techniques for measuring blood velocity in the large and small peripheral arteries of anesthetized mice. We translated technology originally designed for human vessels for use in smaller mouse vessels at higher heart rates by using higher ultrasonic frequencies, smaller transducers, and higher-speed signal processing. With these methods one can measure cardiac filling and ejection velocities, velocity pulse arrival times for determining pulse wave velocity, peripheral blood velocity and vessel wall motion waveforms, jet velocities for the calculation of the pressure drop across stenoses, and left main coronary velocity for the estimation of coronary flow reserve. These noninvasive methods are convenient and easy to apply, but care must be taken in interpreting measurements due to Doppler sample volume size and angle of incidence. Doppler methods have been used to characterize and evaluate numerous cardiovascular phenotypes in mice and have been particularly useful in evaluating the cardiac and vascular remodeling that occur following transverse aortic constriction. Although duplex ultrasonic echo-Doppler instruments are being applied to mice, dedicated Doppler systems are more suitable for some applications. The magnitudes and waveforms of blood velocities from both cardiac and peripheral sites are similar in mice and humans, such that much of what is learned using Doppler technology in mice may be translated back to humans. PMID:21572013

Drift velocity and pressure monitoring of the CMS muon drift chambers

CERN Document Server

Sonnenschein, Lars

2010-01-01

The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers because the drift velocity depends on it. Furthermore the differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest pressure monitoring results are discussed.

Amphibious Shear Velocity Structure of the Cascadia Subduction Zone

Science.gov (United States)

Janiszewski, H. A.; Gaherty, J. B.; Abers, G. A.; Gao, H.

2017-12-01

The amphibious Cascadia Initiative crosses the coastline of the Cascadia subduction zone (CSZ) deploying seismometers from the Juan de Fuca ridge offshore to beyond the volcanic arc onshore. This allows unprecedented seismic imaging of the CSZ, enabling examination of both the evolution of the Juan de Fuca plate prior to and during subduction as well as the along strike variability of the subduction system. Here we present new results from an amphibious shear velocity model for the crust and upper mantle across the Cascadia subduction zone. The primary data used in this inversion are surface-wave phase velocities derived from ambient-noise Rayleigh-wave data in the 10 - 20 s period band, and teleseismic earthquake Rayleigh wave phase velocities in the 20 - 160 s period band. Phase velocity maps from these data reflect major tectonic structures including the transition from oceanic to continental lithosphere, Juan de Fuca lithosphere that is faster than observations in the Pacific for oceanic crust of its age, slow velocities associated with the accretionary prism, the front of the fast subducting slab, and the Cascades volcanic arc which is associated with slower velocities in the south than in the north. Crustal structures are constrained by receiver functions in the offshore forearc and onshore regions, and by active source constraints on the Juan de Fuca plate prior to subduction. The shear-wave velocities are interpreted in their relationships to temperature, presence of melt or hydrous alteration, and compositional variation of the CSZ.

Design and laboratory testing of a new flow-through directional passive air sampler for ambient particulate matter.

Science.gov (United States)

Lin, Chun; Solera Garcia, Maria Angeles; Timmis, Roger; Jones, Kevin C

2011-03-01

A new type of directional passive air sampler (DPAS) is described for collecting particulate matter (PM) in ambient air. The prototype sampler has a non-rotating circular sampling tray that is divided into covered angular channels, whose ends are open to winds from sectors covering the surrounding 360°. Wind-blown PM from different directions enters relevant wind-facing channels, and is retained there in collecting pools containing various sampling media. Information on source direction and type can be obtained by examining the distribution of PM between channels. Wind tunnel tests show that external wind velocities are at least halved over an extended area of the collecting pools, encouraging PM to settle from the air stream. Internal and external wind velocities are well-correlated over an external velocity range of 2.0-10.0 m s⁻¹, which suggests it may be possible to relate collected amounts of PM simply to ambient concentrations and wind velocities. Measurements of internal wind velocities in different channels show that velocities decrease from the upwind channel round to the downwind channel, so that the sampler effectively resolves wind directions. Computational fluid dynamics (CFD) analyses were performed on a computer-generated model of the sampler for a range of external wind velocities; the results of these analyses were consistent with those from the wind tunnel. Further wind tunnel tests were undertaken using different artificial particulates in order to assess the collection performance of the sampler in practice. These tests confirmed that the sampler can resolve the directions of sources, by collecting particulates preferentially in source-facing channels.

Kinematics of Local, High-Velocity K dwarfs in the SUPERBLINK Proper Motion Catalog

Science.gov (United States)

Kim, Bokyoung; Lepine, Sebastien

2018-01-01

We present a study of the kinematics of 345,480 K stars within 2 kpc of the Sun, based on data from the SUPERBLINK catalog of stars with high proper motions (> 40 mas/yr), combined with data from the 2MASS survey and from the first GAIA release, which together yields proper motions accurate to ~2 mas/yr. All K dwarfs were selected based on their G-K colors, and photometric distances were estimated from a re-calibrated color-magnitude relationship for K dwarfs. We plot transverse velocities VT in various directions on the sky, to examine the local distribution of K dwarfs in velocity space. We have also obtained radial velocity information for a subsample of 10,128 stars, from RAVE and SDSS DR12, which we use to construct spatial velocity (U, V, W) plots. About a third (123,350) of the stars are high-velocity K dwarfs, with motions consistent with the local Galactic halo population. Our kinematic analysis suggests that their velocity-space distribution is very uniform, and we find no evidence of substructure that might arise, e.g., from local streams or moving groups.

A program to calculate pulse transmission responses through transversely isotropic media

Science.gov (United States)

Li, Wei; Schmitt, Douglas R.; Zou, Changchun; Chen, Xiwei

2018-05-01

We provide a program (AOTI2D) to model responses of ultrasonic pulse transmission measurements through arbitrarily oriented transversely isotropic rocks. The program is built with the distributed point source method that treats the transducers as a series of point sources. The response of each point source is calculated according to the ray-tracing theory of elastic plane waves. The program could offer basic wave parameters including phase and group velocities, polarization, anisotropic reflection coefficients and directivity patterns, and model the wave fields, static wave beam, and the observed signals for pulse transmission measurements considering the material's elastic stiffnesses and orientations, sample dimensions, and the size and positions of the transmitters and the receivers. The program could be applied to exhibit the ultrasonic beam behaviors in anisotropic media, such as the skew and diffraction of ultrasonic beams, and analyze its effect on pulse transmission measurements. The program would be a useful tool to help design the experimental configuration and interpret the results of ultrasonic pulse transmission measurements through either isotropic or transversely isotropic rock samples.

Assimilation of ambient seismic noise in hydrological models allows estimation of hydraulic conductivity in unsaturated media

Science.gov (United States)

Fores, B.; Champollion, C.; Mainsant, G.; Fort, A.; Albaric, J.

2016-12-01

Karstic hydrosystems represent one of the main water resources in the Mediterranean area but are challenging for geophysical methods. The GEK (Geodesy in Karstic Environment) observatory has been setup in 2011 to study the unsaturated zone of a karstic system in the south of France. The unsaturated zone (the epikarst) is thick and up to 100m on the site. Since 2011, gravity, rainfall and evapotranspiration are monitored. Together, they allow precise estimation of the global water storage changes but lack depth resolution. Surface waves velocity variations, obtained from ambient seismic noise monitoring are used here to overcome this lack. Indeed, velocities depend on saturation and the depths where changes occur can be defined as surface waves are dispersive. From October 2014 to November 2015, two seismometers have been recording noise. Velocity changes at a narrow frequency band (6-8 Hz) have shown a clear annual cycle. Minimum velocity is several months late on precipitations, which is coherent with a slow infiltration and a maximum sensitivity at -40m for these frequencies and this site. Models have been made with the Hydrus-1D software which allows modeling 1D-flow in variably saturated media. With a stochastic sampling, we have researched the underground parameters that reproduce the most the different observations (gravity, evapotranspiration and rainfall, and velocity changes). We show that velocity changes clearly constrain the hydraulic conductivity of the medium. Ambient seismic noise is therefore a promising method to study unsaturated zone which are too deep or too heterogeneous for classic methods.

Laparoscopic colectomy for transverse colon carcinoma.

Science.gov (United States)

Zmora, O; Bar-Dayan, A; Khaikin, M; Lebeydev, A; Shabtai, M; Ayalon, A; Rosin, D

2010-03-01

Laparoscopic resection of transverse colon carcinoma is technically demanding and was excluded from most of the large trials of laparoscopic colectomy. The aim of this study was to assess the safety, feasibility, and outcome of laparoscopic resection of carcinoma of the transverse colon. A retrospective review was performed to identify patients who underwent laparoscopic resection of transverse colon carcinoma. These patients were compared to patients who had laparoscopic resection for right and sigmoid colon carcinoma. In addition, they were compared to a historical series of patients who underwent open resection for transverse colon cancer. A total of 22 patients underwent laparoscopic resection for transverse colon carcinoma. Sixty-eight patients operated for right colon cancer and 64 operated for sigmoid colon cancer served as comparison groups. Twenty-four patients were identified for the historical open group. Intraoperative complications occurred in 4.5% of patients with transverse colon cancer compared to 5.9% (P = 1.0) and 7.8% (P = 1.0) of patients with right and sigmoid colon cancer, respectively. The early postoperative complication rate was 45, 50 (P = 1.0), and 37.5% (P = 0.22) in the three groups, respectively. Conversion was required in 1 (5%) patient in the laparoscopic transverse colon group. The conversion rate and late complications were not significantly different in the three groups. There was no significant difference in the number of lymph nodes harvested in the laparoscopic and open groups. Operative time was significantly longer in the laparoscopic transverse colectomy group when compared to all other groups (P = 0.001, 0.008, and transverse colectomy, respectively). The results of laparoscopic colon resection for transverse colon carcinoma are comparable to the results of laparoscopic resection of right or sigmoid colon cancer and open resection of transverse colon carcinoma. These results suggest that laparoscopic resection of transverse

Optimal Surgery for Mid-Transverse Colon Cancer: Laparoscopic Extended Right Hemicolectomy Versus Laparoscopic Transverse Colectomy.

Science.gov (United States)

Matsuda, Takeru; Sumi, Yasuo; Yamashita, Kimihiro; Hasegawa, Hiroshi; Yamamoto, Masashi; Matsuda, Yoshiko; Kanaji, Shingo; Oshikiri, Taro; Nakamura, Tetsu; Suzuki, Satoshi; Kakeji, Yoshihiro

2018-04-02

Although the feasibility and safety of laparoscopic surgery for transverse colon cancer have been shown by the recent studies, the optimal laparoscopic approach for mid-transverse colon cancer is controversial. We retrospectively analyzed the data of patients with the mid-transverse colon cancer at our institutions between January 2007 and April 2017. Thirty-eight and 34 patients who received extended right hemicolectomy and transverse colectomy, respectively, were enrolled. There were no significant differences in operating time, blood loss, and hospital stay between the two groups. Postoperative complications developed in 10 of 34 patients (29.4%; wound infection: 2 cases, anastomotic leakage: 2 cases, bowel obstruction: 1 case, incisional hernia: 2 cases, others: 3 cases) for the transverse colectomy group and in 4 of 38 patients (10.5%; wound infection: 1 case, anastomotic leakage: 0 case, bowel obstruction: 2 cases, incisional hernia: 0 case, others: 1 case) for the extended right hemicolectomy group (P = 0.014). Although the median number of harvested #221 and #222 LNs was similar between the two groups (6 vs. 8, P = 0.710, and 3 vs. 2, P = 0.256, respectively), that of #223 was significantly larger in extended right hemicolectomy than in transverse colectomy (3 vs. 1, P = 0.038). The 5-year disease-free and overall survival rates were 92.4 and 90.3% for the extended right hemicolectomy group, and 95.7 and 79.6% for the transverse colectomy group (P = 0.593 and P = 0.638, respectively). Laparoscopic extended right hemicolectomy and laparoscopic transverse colectomy offer similar oncological outcomes for mid-transverse colon cancer. Laparoscopic extended right hemicolectomy might be associated with fewer postoperative complications.

Research Note: The sensitivity of surface seismic P-wave data in transversely isotropic media to reflector depth

KAUST Repository

Alkhalifah, Tariq Ali

2016-12-17

The leading component of the high-frequency asymptotic description of the wavefield, given by the travel time, is governed by the eikonal equation. In anisotropic media, traveltime measurements from seismic experiments conducted along one surface cannot constrain the long-wavelength attribute of the medium along the orthogonal-to-the-surface direction, as anisotropy introduces an independent parameter controlling wave propagation in the orthogonal direction. Since travel times measured on the Earth\\'s surface in transversely isotropic media with a vertical symmetry axis are mainly insensitive to the absolute value of the anisotropic parameter responsible for relating these observations to depth δ, the travel time was perturbed laterally to investigate the traveltime sensitivity to lateral variations in δ. This formulation can be used to develop inversion strategies for lateral variations in δ in acoustic transversely isotropic media, as the surface-recorded data are sensitive to it even if the model is described by the normal moveout velocity and horizontal velocity, or the anellipticity parameter η. Numerical tests demonstrate the enhanced sensitivity of our data when the model is parameterised with a lateral change in δ.

Migration using a transversely isotropic medium with symmetry normal to the reflector dip

KAUST Repository

Alkhalifah, Tariq Ali; Sava, P.

2011-01-01

A transversely isotropic (TI) model in which the tilt is constrained to be normal to the dip (DTI model) allows for simplifications in the imaging and velocity model building efforts as compared to a general TI (TTI) model. Although this model cannot be represented physically in all situations, for example, in the case of conflicting dips, it handles arbitrary reflector orientations under the assumption of symmetry axis normal to the dip. Using this assumption, we obtain efficient downward continuation algorithms compared to the general TTI ones, by utilizing the reflection features of such a model. Phase-shift migration can be easily extended to approximately handle lateral inhomogeneity using, for example, the split-step approach. This is possible because, unlike the general TTI case, the DTI model reduces to VTI for zero dip. These features enable a process in which we can extract velocity information by including tools that expose inaccuracies in the velocity model in the downward continuation process. We test this model on synthetic data corresponding to a general TTI medium and show its resilience. 2011 Tariq Alkhalifah and Paul Sava.

Ambient Seismic Noise Tomography of a Loess High Bank at Dunaszekcső (Hungary)

Czech Academy of Sciences Publication Activity Database

Szanyi, G.; Gráczer, Z.; Györi, E.; Kaláb, Zdeněk; Lednická, Markéta

2016-01-01

Roč. 173, č. 8 (2016), s. 2913-2928 ISSN 0033-4553 Institutional support: RVO:68145535 Keywords : seismic interferometry * ambient noise * group velocity * tomography * landslide * high bank Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.591, year: 2016 http://link.springer.com/article/10.1007/s00024-016-1304-1

Comparison of extended hemicolectomy versus transverse colectomy in patients with cancer of the transverse colon.

Science.gov (United States)

van Rongen, I; Damhuis, R A M; van der Hoeven, J A B; Plaisier, P W

2013-01-01

Cancer of the transverse colon is rare and postoperative mortality tends to be high. Standard surgical treatment involves either extended hemicolectomy or transverse colectomy, depending on the location of the tumour. The aim of the present study was to compare postoperative mortality and five-year survival between these types of surgery. For this observational study, data on patients with a tumour of the transverse colon, treated by open resection in the Dordrecht Hospital from 1989 through 2003, were derived from the database of the regional cancer registry. Information on type of resection, tumour stage, complications, postoperative mortality (30-day) and survival was abstracted from the medical files. Patients with multi-organ surgery, (sub)total colectomy or stage IV disease were excluded from the analysis, leaving a total series of 103 patients. Transverse colectomy comprised one third of operations, predominantly involving partial resections. Postoperative mortality was 6% (2/34) after transverse colectomy and 7% (5/69) after extended hemicolectomy. Five-year survival was slightly higher for the hemicolectomy group (61% versus 50%), but this difference did not reach statistical significance (p = 0.34). Our results confirm the high postoperative risk after surgery for cancer of the transverse colon and show that this risk does not depend on the type of surgery. Considering the satisfactory results after partial transverse colectomy, segmental resections may be considered as an option for the treatment of localised tumours of the transverse colon.

Appraisal of transverse nasal groove: a study.

Science.gov (United States)

Sathyanarayana, Belagola D; Basavaraj, Halevoor B; Nischal, Kuchangi C; Swaroop, Mukunda R; Umashankar, Puttagangu N; Agrawal, Dhruv P; Swamy, Suchetha S; Okram, Sarda

2012-01-01

Transverse nasal groove is a condition of cosmetic concern which awaits due recognition and has been widely described as a shallow groove that extends transversely over the dorsum of nose. However, we observed variations in the clinical presentations of this entity, hitherto undescribed in literature. We conducted a clinicoepidemiological study of transverse nasal lesions in patients attending our outpatient department. We conducted a prospective observational study. We screened all patients attending our out-patient department for presence of transverse nasal lesions, signs of any dermatosis and associated other skin conditions. One hundred patients were recruited in the study. Females (80%) predominated over males. Most patients were of 15-45 years age group (70%). Majority of the transverse nasal lesions were classical transverse nasal groove (39%) and others included transverse nasal line (28%), strip (28%), ridge (4%) and loop (1%). Seborrhoeic diathesis was the most common condition associated with transverse nasal lesion. Occurrence of transverse nasal line, strip, ridge and loop, in addition to classical transverse nasal groove implies that latter is actually a subset of transverse nasal lesions. Common association of this entity with seborrheic dermatitis, seborrhea and dandruff raises a possibility of whether transverse nasal lesion is a manifestation of seborrheic diathesis.

An Interpretation of the Laminar-Turbulent Transition Startup against the Consideration of the Transverse Viscosity Factor

Science.gov (United States)

Kolodezhnov, V. N.

2018-03-01

This paper proposes a rheological model of a fluid having the Newtonian model applicability limit and a potential for further “addition” of the transverse viscosity factor. The dynamic equations for a fluid that has such rheological model are discussed, the analysis of which demonstrates the possibility of “generating” the cross stream velocity components. The transition to the dimensionless notation introduces four dimensionless complexes of local characterization for the transition conditions in the neighborhood of the flow region point in question. Based on such dimensionless complexes and using the known experimental data, the empiric conditions of “generating” the cross stream velocity components and starting the laminar-turbulent transition are proposed.

Surface-wave tomography of Ireland and surroundings using ambient noise and teleseismic data

Science.gov (United States)

Bonadio, Raffaele; Arroucau, Pierre; Lebedev, Sergei; Meier, Thomas; Schaeffer, Andrew; Licciardi, Andrea; Piana Agostinetti, Nicola

2016-04-01

Ireland's geology is dominated by northeast-southwest structural trends and suture zones, mostly inferred from geological mapping and a few active source seismic experiments. However, their geometry and extent at depth and their continuity across the Irish Sea are still poorly known. Important questions also remain unanswered regarding the thickness and bulk properties of the sedimentary cover at the regional scale, the deformation and flow of the deep crust during the formation of Ireland, the thickness of Ireland's lithosphere today, and the thermal structure and dynamics of the asthenosphere beneath Ireland. In this work, we take advantage of abundant, newly available broadband data from temporary array deployments and permanent seismic networks in Ireland and Great Britain to produce high-resolution models of seismic velocity structure and anisotropy of the lithosphere. We combine Rayleigh and Love phase velocity measurements from waveform cross-correlation using both ambient noise and teleseismic data in order to produce high-quality dispersion curves for periods ranging from 1 to 300 s. The phase velocity measurement procedures are adapted from Meier et al.[2], Lebedev et al.[1] and Soomro et al.[3] and are automated in order to deal with the large amount of data and ensure consistency and reproducibility. For the nearly 200 stations used in this study, we obtain a very large number of dispersion curves from both ambient noise and teleseimic data. Dispersion measurements are then inverted in a tomographic procedure for surface-wave phase velocity maps in a very broad period range. The maps constrain the 3D seismic-velocity structure of the crust and upper mantle underlying Ireland and the Irish Sea. {9} Lebedev, S., T. Meier, R. D. van der Hilst. Asthenospheric flow and origin of volcanism in the Baikal Rift area, Earth Planet. Sci. Lett., 249, 415-424, 2006. Meier, T., K. Dietrich, B. Stockhert, H.P. Harjes, One-dimensional models of shear wave velocity for

Ambient noise tomography across Mount St. Helens using a dense seismic array

KAUST Repository

Wang, Yadong

2017-05-08

We investigated upper crustal structure with data from a dense seismic array deployed around Mount St. Helens for 2 weeks in the summer of 2014. Interstation cross correlations of ambient seismic noise data from the array were obtained, and clear fundamental mode Rayleigh waves were observed between 2.5 and 5 s periods. In addition, higher-mode signals were observed around 2 s period. Frequency-time analysis was applied to measure fundamental mode Rayleigh wave phase velocities, which were used to invert for 2-D phase velocity maps. An azimuth-dependent traveltime correction was implemented to mitigate potential biases introduced due to an inhomogeneous noise source distribution. Reliable phase velocity maps were only obtained between 3 and 4 s periods due to limitations imposed by the array aperture and higher-mode contamination. The phase velocity tomography results, which are sensitive to structure shallower than 6 km depth, reveal an ~10–15% low-velocity anomaly centered beneath the volcanic edifice and peripheral high-velocity anomalies that likely correspond to cooled igneous intrusions. We suggest that the low-velocity anomaly reflects the high-porosity mixture of lava and ash deposits near the surface of the edifice, a highly fractured magmatic conduit and hydrothermal system beneath the volcano, and possibly a small contribution from silicate melt.

Det Ambiente

DEFF Research Database (Denmark)

Schmidt, Ulrik

Det ambiente er iscenesættelsen af en karakteristisk sanseoplevelse, der er kendetegnet ved fornemmelsen af at være omgivet. I dag bliver begrebet om det ambiente mest anvendt i forbindelse med musikgenren ’ambient musik’. Det ambiente er dog ikke essentielt knyttet til det musikalske, men må...... forstås som et betydeligt bredere fænomen i den moderne æstetiske kultur, der spiller en væsentlig rolle i oplevelsen af moderne transportformer, arkitektur, film, lydkunst, installationskunst og digitale multimedieiscenesættelser. En forståelse af det ambiente er derfor centralt for forståelsen af en...... moderne æstetiseret oplevelseskultur i almindelighed. Da det ambiente ikke hidtil har været gjort til genstand for en mere indgående teoretisk behandling, er der dog stor usikkerhed omkring, hvad fænomenet overhovedet indebærer. Hovedformålet med Det ambiente – Sansning, medialisering, omgivelse er derfor...

Transverse Localization of Light

NARCIS (Netherlands)

Raedt, Hans De; Lagendijk, Ad; Vries, Pedro de

1989-01-01

We study the propagation of light through a semi-infinite medium with transverse disorder (that is, disorder in two directions only). We show that such a system exhibits strong two-dimensional localization by demonstrating that on propagation a beam expands until the transverse localization length

Fast imaging of the laser-blow-off plume driven shock wave: Dependence on the mass and density of the ambient gas

Energy Technology Data Exchange (ETDEWEB)

George, Sony [ISP, Cochin University of Science and Tech., Cochin 682 022 (India); Singh, R.K., E-mail: rajesh@ipr.res.in [Institute for Plasma Research, Gandhinagar 382 428 (India); Nampoori, V.P.N. [ISP, Cochin University of Science and Tech., Cochin 682 022 (India); Kumar, Ajai [Institute for Plasma Research, Gandhinagar 382 428 (India)

2013-01-17

A systemic investigation of expansion dynamics of plasma plume, produced by laser-blow-off of LiF–C thin film has been done with emphasis on the formation of shock wave and their dependence on the pressure and nature of the ambient gas. The present results demonstrate that highly directional plume produces a strong shock wave in comparison to shock produced by the diverging plume. Shock-velocity, strength and its structure are strongly dependent on ambient environment; maximum shock velocity is observed in helium whereas shock strength is highest in argon environment. The role of chemically reactive processes was not observed in the present case as the plume structure is almost similar in argon and oxygen.

Transverse baryon flow as possible evidence for a quark-gluon-plasma phase

International Nuclear Information System (INIS)

Levai, P.; Mueller, B.

1991-01-01

In order to investigate the coupling between collective flow of nucleons and pions in hot pion-dominated hadronic matter, we calculate the pion-nucleon drag coefficient in linearized transport theory. We find that the characteristic time for flow equalization is longer than the time scale of the expansion of a hardonic fireball created in high-energy collisions. The analysis of transverse-momentum data from p+bar p collisions at √s =1.8 TeV reveals the same flow velocity for mesons and antinucleons. We argue that this may be evidence for the formation of a quark-gluon plasma in these collisions

Transversely Compressed Bonded Joints

DEFF Research Database (Denmark)

Hansen, Christian Skodborg; Schmidt, Jacob Wittrup; Stang, Henrik

2012-01-01

The load capacity of bonded joints can be increased if transverse pressure is applied at the interface. The transverse pressure is assumed to introduce a Coulomb-friction contribution to the cohesive law for the interface. Response and load capacity for a bonded single-lap joint was derived using...

Power spectrum, growth velocities and cross-correlations of longitudinal and transverse oscillations of individual Nicotiana tabacum pollen tube.

Science.gov (United States)

Haduch-Sendecka, Aleksandra; Pietruszka, Mariusz; Zajdel, Paweł

2014-08-01

We report on our results concerning growth rate and oscillation modes of the individual pollen tube apex. The observed volumetric growth and growth rate periodicity in the longitudinal (axial) direction are accompanied by transverse oscillations with similar frequencies but higher energies than the axial modes. Examination of the time-domain coherence between oscillations in mutually perpendicular directions revealed minimal energy dissipation in the unperturbed (isotonic) case, opposite to the two remaining cases (hypertonic, hypotonic) with notable correlations. We conjecture that the minimal energy loss is therefore optimal in the natural growth conditions. The longitudinal growth velocity is also found to be the fastest in the unperturbed case. As a result, the isolated system (pollen tube tip) is conserving energy by transforming it from elastic potential energy of extending apical wall to the kinetic energy of periodical motion. The energy dissipation is found to be about 20 % smaller in axial direction than in lateral one, indicating that the main energy consumption is dedicated to the elongation. We further observe that the hypertonic spectrum is shifted towards lower and the hypotonic towards higher frequencies with respect to the isotonic spectrum. In consequence, the turgor pressure inside the growing cell influences monotonically the frequency of both modes of oscillations. The calculated power spectrum seen as a measure of the overall energy efficiency of tip growth under hypertonic, hypotonic and isotonic conditions implies that the biochemistry has been fine tuned to be optimal under normal growth conditions, which is the developmental implication of this work. A simple theoretical extension of the Ortega equation is derived and analysed with respect to its contribution to power spectrum. We show that the plastic term, related to the effective turgor pressure, with maximum contribution at frequency f = 0 is responsible for the steady growth. In turn

TRANSVERSELY POLARIZED Λ PRODUCTION

International Nuclear Information System (INIS)

BORER, D.

2000-01-01

Transversely polarized Λ production in hard scattering processes is discussed in terms of a leading twist T-odd fragmentation function which describes the fragmentation of an unpolarized quark into a transversely polarized Λ. We focus on the properties of this function and its relevance for the RHIC and HERMES experiments

High-resolution 3-D S-wave Tomography of upper crust structures in Yilan Plain from Ambient Seismic Noise

Science.gov (United States)

Chen, Kai-Xun; Chen, Po-Fei; Liang, Wen-Tzong; Chen, Li-Wei; Gung, YuanCheng

2015-04-01

The Yilan Plain (YP) in NE Taiwan locates on the western YP of the Okinawa Trough and displays high geothermal gradients with abundant hot springs, likely resulting from magmatism associated with the back-arc spreading as attested by the offshore volcanic island (Kueishantao). YP features NS distinctive characteristics that the South YP exhibits thin top sedimentary layer, high on-land seismicity and significant SE movements, relative those of the northern counterpart. A dense network (~2.5 km station interval) of 89 Texan instruments was deployed in Aug. 2014, covering most of the YP and its vicinity. The ray path coverage density of each 0.015 degree cells are greater than 150 km that could provide the robustness assessment of tomographic results. We analyze ambient noise signals to invert a high-resolution 3D S-wave model for shallow velocity structures in and around YP. The aim is to investigate the velocity anomalies corresponding to geothermal resources and the NS geological distinctions aforementioned. We apply the Welch's method to generate empirical Rayleigh wave Green's functions between two stations records of continuous vertical components. The group velocities of thus derived functions are then obtained by the multiple-filter analysis technique measured at the frequency range between 0.25 and 1 Hz. Finally, we implement a wavelet-based multi-scale parameterization technique to construct 3D model of S-wave velocity. Our first month results exhibit low velocity in the plain, corresponding existing sediments, those of whole YP show low velocity offshore YP and those of high-resolution south YP reveal stark velocity contrast across the Sanshin fault. Key words: ambient seismic noises, Welch's method, S-wave, Yilan Plain

[Clinical auxiliary diagnosis value of high frequency ultrasonographic measurements of the thickness of transverse carpal ligaments in carpal tunnel syndrome patients].

Science.gov (United States)

Xu, L; Chen, F M; Wang, L; Zhang, P X; Jiang, X R

2016-04-18

To evaluate the meaning and value of high-frequency ultrasound in the diagnosis of carpal tunnel syndrome (CTS). In this study, 48 patients (unilateral hand) with CTS were analyzed. The thickness of transverse carpal ligaments at the pisiform bone was measured using high-frequency ultrasound. Open carpal tunnel release procedure was performed in the 48 CTS patients, and the thickness of transverse carpal ligaments at the hamate hook bone measured using vernier caliper under direct vision. The accuracy of thickness of transverse carpal ligaments was evaluated using high-frequency ultrasound. high-frequency ultrasound measurement of thickness of transverse carpal ligaments at the hamate hook bone and pisiform bone, and determination of the diagnostic threshold measurement index using receiver operating characteristic (ROC) curve, sensitivity and specificity were performed and the correlation between the thickness of transverse carpal ligaments and nerve conduction study (NCS) analyzed. The thickness of transverse carpal ligaments in the CTS patients were (0.42±0.08) cm (high-frequency ultrasound) and (0.41±0.06) cm (operation) at hamate hook bone, and there was no significant difference between the two ways (t=0.672, P>0.05). The optimal cut-off value of the transverse carpal ligaments at hamate hook bone was 0.385 cm, the sensitivity 0.775, and the specificity 0.788. The optimal cut-off value of the transverse carpal ligaments at the pisiform bone was 0.315 cm, the sensitivity 0.950, and the specificity 1.000. The transverse carpal ligaments thickness and wrist-index finger sensory nerve conduction velocity (SCV), wrist-middle finger SCV showed a negative correlation. High frequency ultrasound measurements of thickness of transverse carpal ligaments is a valuable method for the diagnosis of CTS.

High transverse momentum events in Kr+Au, Th central collisions at 43 MeV/u

International Nuclear Information System (INIS)

Bougault, R.; Colin, J.; Delaunay, F.; Genoux-Lubain, A.; Le Brun, C.; Lecolley, J.F.; Lefebvres, F.; Louvel, M.; Steckmeyer, J.C.

1992-05-01

The multi-fragment production of the systems Kr+(Ag,Au,Th) is studied at 43 A.MeV. Heavy fragments (Z ≥ 6) were identified in coincidence by 4 π arrangement of low threshold detectors. Up to six fragments have been detected per event. An analysis based on relative velocities between the detected fragments allowed us to separate peripheral reactions from central collisions. For the central events large transverse energy values, clue for dynamical effects, are observed for Au- and Th-system

Decoupled equations for reverse time migration in tilted transversely isotropic media

KAUST Repository

Zhan, Ge; Pestana, Reynam C.; Stoffa, Paul L.

2012-01-01

Conventional modeling and migration for tilted transversely isotropic (TTI) media may suffer from numerical instabilities and shear wave artifacts due to the coupling of the P-wave and SV-wave modes in the TTI coupled equations. Starting with the separated P- and SV-phase velocity expressions for vertical transversely isotropic (VTI) media, we extend these decoupled equations for modeling and reverse time migration (RTM) in acoustic TTI media. Compared with the TTI coupled equations published in the geophysical literature, the new TTI decoupled equations provide a more stable solution due to the complete separation of the P-wave and SV-wave modes. The pseudospectral method is the most convenient method to implement these equations due to the form of wavenumber expressions and has the added benefit of being highly accurate and thus avoiding numerical dispersion. The rapid expansion method (REM) in time is employed to produce a broad band numerically stable time evolution of the wavefields. Synthetic results validate the proposed TTI decoupled equations and show that modeling and RTM in TTI media with the decoupled equations remain numerically stable even for models with strong anisotropy and sharp contrasts. © 2012 Society of Exploration Geophysicists.

Transverse wave propagation in [ab0] direction of silicon single crystal

Energy Technology Data Exchange (ETDEWEB)

Yun, Sang Jin; Kim, Hye Jeong; Kwon, Se Ho; Kim, Young H. [Applied Acoustics Lab, Korea Science Academy of KAIST, Busan(Korea, Republic of)

2015-12-15

The speed and oscillation directions of elastic waves propagating in the [ab0] direction of a silicon single crystal were obtained by solving Christoffel's equation. It was found that the quasi waves propagate in the off-principal axis, and hence, the directions of the phase and group velocities are not the same. The maximum deviation of the two directions was 7.2 degree angle. Two modes of the pure transverse waves propagate in the [110] direction with different speeds, and hence, two peaks were observed in the pulse echo signal. The amplitude ratio of the two peaks was dependent on the initial oscillating direction of the incident wave. The pure and quasi-transverse waves propagate in the [210] direction, and the oscillation directions of these waves are perpendicular to each other. The skewing angle of the quasi wave was calculated as 7.14 degree angle, and it was measured as 9.76 degree angle. The amplitude decomposition in the [210] direction was similar to that in the [110] direction, since the oscillation directions of these waves are perpendicular to each other. These results offer useful information in measuring the crystal orientation of the silicon single crystal.

Decoupled equations for reverse time migration in tilted transversely isotropic media

KAUST Repository

Zhan, Ge

2012-03-01

Conventional modeling and migration for tilted transversely isotropic (TTI) media may suffer from numerical instabilities and shear wave artifacts due to the coupling of the P-wave and SV-wave modes in the TTI coupled equations. Starting with the separated P- and SV-phase velocity expressions for vertical transversely isotropic (VTI) media, we extend these decoupled equations for modeling and reverse time migration (RTM) in acoustic TTI media. Compared with the TTI coupled equations published in the geophysical literature, the new TTI decoupled equations provide a more stable solution due to the complete separation of the P-wave and SV-wave modes. The pseudospectral method is the most convenient method to implement these equations due to the form of wavenumber expressions and has the added benefit of being highly accurate and thus avoiding numerical dispersion. The rapid expansion method (REM) in time is employed to produce a broad band numerically stable time evolution of the wavefields. Synthetic results validate the proposed TTI decoupled equations and show that modeling and RTM in TTI media with the decoupled equations remain numerically stable even for models with strong anisotropy and sharp contrasts. © 2012 Society of Exploration Geophysicists.

Epicenter Location of Regional Seismic Events Using Love Wave and Rayleigh Wave Ambient Seismic Noise Green's Functions

Science.gov (United States)

Levshin, A. L.; Barmin, M. P.; Moschetti, M. P.; Mendoza, C.; Ritzwoller, M. H.

2011-12-01

We describe a novel method to locate regional seismic events based on exploiting Empirical Green's Functions (EGF) that are produced from ambient seismic noise. Elastic EGFs between pairs of seismic stations are determined by cross-correlating long time-series of ambient noise recorded at the two stations. The EGFs principally contain Rayleigh waves on the vertical-vertical cross-correlations and Love waves on the transverse-transverse cross-correlations. Earlier work (Barmin et al., "Epicentral location based on Rayleigh wave empirical Green's functions from ambient seismic noise", Geophys. J. Int., 2011) showed that group time delays observed on Rayleigh wave EGFs can be exploited to locate to within about 1 km moderate sized earthquakes using USArray Transportable Array (TA) stations. The principal advantage of the method is that the ambient noise EGFs are affected by lateral variations in structure similarly to the earthquake signals, so the location is largely unbiased by 3-D structure. However, locations based on Rayleigh waves alone may be biased by more than 1 km if the earthquake depth is unknown but lies between 2 km and 7 km. This presentation is motivated by the fact that group time delays for Love waves are much less affected by earthquake depth than Rayleigh waves; thus exploitation of Love wave EGFs may reduce location bias caused by uncertainty in event depth. The advantage of Love waves to locate seismic events, however, is mitigated by the fact that Love wave EGFs have a smaller SNR than Rayleigh waves. Here, we test the use of Love and Rayleigh wave EGFs between 5- and 15-sec period to locate seismic events based on the USArray TA in the western US. We focus on locating aftershocks of the 2008 M 6.0 Wells earthquake, mining blasts in Wyoming and Montana, and small earthquakes near Norman, OK and Dallas, TX, some of which may be triggered by hydrofracking or injection wells.

The offset-midpoint traveltime pyramid in 3D transversely isotropic media with a horizontal symmetry axis

KAUST Repository

Hao, Qi

2014-12-30

Analytic representation of the offset-midpoint traveltime equation for anisotropy is very important for prestack Kirchhoff migration and velocity inversion in anisotropic media. For transversely isotropic media with a vertical symmetry axis, the offset-midpoint traveltime resembles the shape of a Cheops’ pyramid. This is also valid for homogeneous 3D transversely isotropic media with a horizontal symmetry axis (HTI). We extended the offset-midpoint traveltime pyramid to the case of homogeneous 3D HTI. Under the assumption of weak anellipticity of HTI media, we derived an analytic representation of the P-wave traveltime equation and used Shanks transformation to improve the accuracy of horizontal and vertical slownesses. The traveltime pyramid was derived in the depth and time domains. Numerical examples confirmed the accuracy of the proposed approximation for the traveltime function in 3D HTI media.

Weighted Maximum-Clique Transversal Sets of Graphs

OpenAIRE

Chuan-Min Lee

2011-01-01

A maximum-clique transversal set of a graph G is a subset of vertices intersecting all maximum cliques of G. The maximum-clique transversal set problem is to find a maximum-clique transversal set of G of minimum cardinality. Motivated by the placement of transmitters for cellular telephones, Chang, Kloks, and Lee introduced the concept of maximum-clique transversal sets on graphs in 2001. In this paper, we study the weighted version of the maximum-clique transversal set problem for split grap...

The correlation between the transverse polarization and transverse momentum of lambda produced in relativistic nucleus-nucleus collisions

International Nuclear Information System (INIS)

Ye Yunxiu; Zhou Xin; Ji Gang; Su Shufang; Zhu Guohuai

1996-01-01

The transverse polarization of lambda produced in relativistic nucleus-nucleus collisions is determined. The effect from the interaction between spin moment and magnetic field is corrected. The near zero transverse polarization and non-correlation between transverse polarization and transverse momentum are obtained and compared to ones obtained from the nucleus-nucleus interactions at lower energies. This comparison shows that the production mechanism of lambdas in the relativistic nucleus-nucleus collisions is different from one in the nucleus-nucleus reactions at lower energies

Ambiente da prática profissional e burnout em enfermeiros

Directory of Open Access Journals (Sweden)

Renata Cristina Gasparino

2015-01-01

Full Text Available evaluar el ambiente de la práctica profesional del enfermero, su relación con burnout y diferencias entre tres instituciones. Método: estudio transversal, desarrollado en hospitales (dos de tercer nivel y un secundario, con 278 enfermeros que respondieron a los instrumentos Nursing Work Index Revised – Versión Brasileña e Inventario de Burnout de Maslach. Resultados: de las instituciones, la mayoría de los enfermeros demostró satisfacción con el trabajo, buena calidad de la atención y, la minoría, intención de abandonar el trabajo. Comparándose las instituciones, la de nivel secundario presentó práctica de enfermería con más autonomía, control sobre el ambiente y buenas relaciones con el equipo médico y menores niveles de burnout. Conclusión: estos hallazgos podrán contribuir en la implementación de cambios que favorezcan la práctica profesional del enfermero, lo que permite lograr la satisfacción de implicados en el proceso, como pacientes, enfermeros e instituciones.

A transversely isotropic medium with a tilted symmetry axis normal to the reflector

KAUST Repository

Alkhalifah, Tariq Ali

2010-05-01

The computational tools for imaging in transversely isotropic media with tilted axes of symmetry (TTI) are complex and in most cases do not have an explicit closed-form representation. Developing such tools for a TTI medium with tilt constrained to be normal to the reflector dip (DTI) reduces their complexity and allows for closed-form representations. The homogeneous-case zero-offset migration in such a medium can be performed using an isotropic operator scaled by the velocity of the medium in the tilt direction. For the nonzero-offset case, the reflection angle is always equal to the incidence angle, and thus, the velocities for the source and receiver waves at the reflection point are equal and explicitly dependent on the reflection angle. This fact allows for the development of explicit representations for angle decomposition as well as moveout formulas for analysis of extended images obtained by wave-equation migration. Although setting the tilt normal to the reflector dip may not be valid everywhere (i.e., on salt flanks), it can be used in the process of velocity model building, in which such constrains are useful and typically are used. © 2010 Society of Exploration Geophysicists.

A transversely isotropic medium with a tilted symmetry axis normal to the reflector

KAUST Repository

Alkhalifah, Tariq Ali; Sava, Paul C.

2010-01-01

The computational tools for imaging in transversely isotropic media with tilted axes of symmetry (TTI) are complex and in most cases do not have an explicit closed-form representation. Developing such tools for a TTI medium with tilt constrained to be normal to the reflector dip (DTI) reduces their complexity and allows for closed-form representations. The homogeneous-case zero-offset migration in such a medium can be performed using an isotropic operator scaled by the velocity of the medium in the tilt direction. For the nonzero-offset case, the reflection angle is always equal to the incidence angle, and thus, the velocities for the source and receiver waves at the reflection point are equal and explicitly dependent on the reflection angle. This fact allows for the development of explicit representations for angle decomposition as well as moveout formulas for analysis of extended images obtained by wave-equation migration. Although setting the tilt normal to the reflector dip may not be valid everywhere (i.e., on salt flanks), it can be used in the process of velocity model building, in which such constrains are useful and typically are used. © 2010 Society of Exploration Geophysicists.

P-wave Velocity Structure Across the Mariana Trench and Implications for Hydration

Science.gov (United States)

Eimer, M. O.; Wiens, D.; Lizarralde, D.; Cai, C.

2017-12-01

Estimates of the water flux at subduction zones remain uncertain, particularly the amount of water brought into the trench by the subducting plate. Normal faulting related to the bending of the incoming plate has been proposed to provide pathways for water to hydrate the crust and upper mantle. A passive and active source seismic experiment spanning both the incoming plate and forearc was conducted in 2012 in central Mariana to examine the role of hydration at subduction zones. The active-source component of the survey used the R/V M.G. Langsethairgun array and 68 short period sensors, including suspended hydrophones, deployed on 4 transects. This study at the Mariana trench offers a comparison to related studies of incoming plate hydration in Middle America, where differing thermal structures related to plate age predict different stability fields for hydrous minerals. The forearc structure is also of interest, since Mariana is characterized by large serpentine seamounts and may have a serpentinized mantle wedge. The velocity structure will also be important for the relocation of earthquakes in the incoming plate, since the seismicity can offer a constraint for the depth extent of these bending faults. We examine the P-wave velocity structure along a 400-km long wide-angle refraction transect perpendicular to the trench and spanning both the forearc and incoming plate. Preliminary results indicate a velocity reduction in the crust and uppermost mantle at the bending region of the incoming plate, relative to the plate's structure away from the trench. This reduction suggests that outer-rise faults extend into the upper mantle and may have promoted serpentinization of that material. Mantle Pn refraction phases are not observed in the forearc, consistent with the ambient noise tomography results that show upper-mantle velocities similar to that of the lower crust. The lack of contrast between the upper mantle and crustal velocities from the ambient noise has been

Velocity auto-correlation and hot-electron diffusion constant in GaAs and InP

International Nuclear Information System (INIS)

Deb Roy, M.

1982-01-01

Auto-correlation functions of the fluctuations in the electron velocities transverse and parallel to the applied electric field are calculated by the Monte Carlo method for GaAs and InP at three different values of field strength which are around three times the threshold field for negative differential mobility in each case. From these the frequency-dependent diffusion coefficients transverse and parallel to the applied field and the figure of merit for noise performance when used in a microwave amplifying device are determined. The results indicate that the transverse auto-correlation function Csub(t)(s) falls nearly exponentially to zero with increasing interval s while the parallel function Csub(p)(s) falls sharply, attains a minimum and then rises towards zero. In each case a higher field gives a higher rate of fall and makes the correlation functions zero within a shorter interval. The transverses diffusion coefficient falls monotonically with the frequency but the parallel diffusion coefficient generally starts with a low value at low frequencies, rises to a maximum and then falls. InP, with a larger separation between the central and the satellite valleys, has a higher value of the low frequency transverse diffusion coefficient and a lower value of its parallel counterpart. The noise performance of microwave semiconductor amplifying devices depends mainly on the low frequency parallel diffusion constant and consequently devices made out of materials like InP with a large separation between valleys are likely to have better noise characteristics. (orig.)

Implication of Broadband Dispersion Measurements in Constraining Upper Mantle Velocity Structures

Science.gov (United States)

Kuponiyi, A.; Kao, H.; Cassidy, J. F.; Darbyshire, F. A.; Dosso, S. E.; Gosselin, J. M.; Spence, G.

2017-12-01

Dispersion measurements from earthquake (EQ) data are traditionally inverted to obtain 1-D shear-wave velocity models, which provide information on deep earth structures. However, in many cases, EQ-derived dispersion measurements lack short-period information, which theoretically should provide details of shallow structures. We show that in at least some cases short-period information, such as can be obtained from ambient seismic noise (ASN) processing, must be combined with EQ dispersion measurements to properly constrain deeper (e.g. upper-mantle) structures. To verify this, synthetic dispersion data are generated using hypothetical velocity models under four scenarios: EQ only (with and without deep low-velocity layers) and combined EQ and ASN data (with and without deep low-velocity layers). The now "broadband" dispersion data are inverted using a trans-dimensional Bayesian framework with the aim of recovering the initial velocity models and assessing uncertainties. Our results show that the deep low-velocity layer could only be recovered from the inversion of the combined ASN-EQ dispersion measurements. Given this result, we proceed to describe a method for obtaining reliable broadband dispersion measurements from both ASN and EQ and show examples for real data. The implication of this study in the characterization of lithospheric and upper mantle structures, such as the Lithosphere-Asthenosphere Boundary (LAB), is also discussed.

Transverse Spin Physics: Recent Developments

International Nuclear Information System (INIS)

Yuan, Feng

2008-01-01

Transverse-spin physics has been very active and rapidly developing in the last few years. In this talk, I will briefly summarize recent theoretical developments, focusing on the associated QCD dynamics in transverse spin physics

Development of Hydroxyl Tagging Velocimetry for Low Velocity Flows

Science.gov (United States)

Andre, Matthieu A.; Bardet, Philippe M.; Burns, Ross A.; Danehy, Paul M.

2016-01-01

Hydroxyl tagging velocimetry (HTV) is a molecular tagging technique that relies on the photo-dissociation of water vapor into OH radicals and their subsequent tracking using laser induced fluorescence. Velocities are then obtained from time-of-flight calculations. At ambient temperature in air, the OH species lifetime is relatively short (<50 µs), making it suited for high speed flows. Lifetime and radicals formation increases with temperature, which allows HTV to also probe low-velocity, high-temperature flows or reacting flows such as flames. The present work aims at extending the domain of applicability of HTV, particularly towards low-speed (<10 m/s) and moderate (<500 K) temperature flows. Results are compared to particle image velocimetry (PIV) measurements recorded in identical conditions. Single shot and averaged velocity profiles are obtained in an air jet at room temperature. By modestly raising the temperature (100-200 degC) the OH production increases, resulting in an improvement of the signal-to-noise ratio (SNR). Use of nitrogen - a non-reactive gas with minimal collisional quenching - extends the OH species lifetime (to over 500 µs), which allows probing of slower flows or, alternately, increases the measurement precision at the expense of spatial resolution. Instantaneous velocity profiles are resolved in a 100degC nitrogen jet (maximum jet-center velocity of 6.5 m/s) with an uncertainty down to 0.10 m/s (1.5%) at 68% confidence level. MTV measurements are compared with particle image velocimetry and show agreement within 2%.

Transverse vibration of pipe conveying fluid made of functionally graded materials using a symplectic method

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhong-Min, E-mail: wangzhongm@xaut.edu.cn; Liu, Yan-Zhuang

2016-03-15

Highlights: • We investigate the transverse vibration of FGM pipe conveying fluid. • The FGM pipe conveying fluid can be classified into two cases. • The variations between the frequency and the power law exponent are obtained. • “Case 1” is relatively more reasonable than “case 2”. - Abstract: Problems related to the transverse vibration of pipe conveying fluid made of functionally graded material (FGM) are addressed. Based on inside and outside surface material compositions of the pipe, FGM pipe conveying fluid can be classified into two cases. It is hypothesized that the physical parameters of the material along the direction of the pipe wall thickness change in the simple power law. A differential equation of motion expressed in non-dimensional quantities is derived by using Hamilton's principle for systems of changing mass. Using the assuming modal method, the pipe deflection function is expanded into a series, in which each term is expressed to admissible function multiplied by generalized coordinate. Then, the differential equation of motion is discretized into the two order differential equations expressed in the generalized coordinates. Based on symplectic elastic theory and the introduction of dual system and dual variable, Hamilton's dual equations are derived, and the original problem is reduced to eigenvalue and eigenvector problem in the symplectic space. Finally, a symplectic method is employed to analyze the vibration and stability of FGM pipe conveying fluid. For a clamped–clamped FGM pipe conveying fluid in “case 1” and “case 2”, the dimensionless critical flow velocity for first-mode divergence and the critical coupled-mode flutter flow velocity are obtained, and the variations between the real part and imaginary part of dimensionless complex frequency and fluid velocity, mass ratio and the power law exponent (or graded index, volume fraction) for FGM pipe conveying fluid are analyzed.

Transverse vibration of pipe conveying fluid made of functionally graded materials using a symplectic method

International Nuclear Information System (INIS)

Wang, Zhong-Min; Liu, Yan-Zhuang

2016-01-01

Highlights: • We investigate the transverse vibration of FGM pipe conveying fluid. • The FGM pipe conveying fluid can be classified into two cases. • The variations between the frequency and the power law exponent are obtained. • “Case 1” is relatively more reasonable than “case 2”. - Abstract: Problems related to the transverse vibration of pipe conveying fluid made of functionally graded material (FGM) are addressed. Based on inside and outside surface material compositions of the pipe, FGM pipe conveying fluid can be classified into two cases. It is hypothesized that the physical parameters of the material along the direction of the pipe wall thickness change in the simple power law. A differential equation of motion expressed in non-dimensional quantities is derived by using Hamilton's principle for systems of changing mass. Using the assuming modal method, the pipe deflection function is expanded into a series, in which each term is expressed to admissible function multiplied by generalized coordinate. Then, the differential equation of motion is discretized into the two order differential equations expressed in the generalized coordinates. Based on symplectic elastic theory and the introduction of dual system and dual variable, Hamilton's dual equations are derived, and the original problem is reduced to eigenvalue and eigenvector problem in the symplectic space. Finally, a symplectic method is employed to analyze the vibration and stability of FGM pipe conveying fluid. For a clamped–clamped FGM pipe conveying fluid in “case 1” and “case 2”, the dimensionless critical flow velocity for first-mode divergence and the critical coupled-mode flutter flow velocity are obtained, and the variations between the real part and imaginary part of dimensionless complex frequency and fluid velocity, mass ratio and the power law exponent (or graded index, volume fraction) for FGM pipe conveying fluid are analyzed.

Seismic structure of the upper crust in the Albertine Rift from travel-time and ambient-noise tomography - a comparison

Science.gov (United States)

Jakovlev, Andrey; Kaviani, Ayoub; Ruempker, Georg

2017-04-01

Here we present results of the investigation of the upper crust in the Albertine rift around the Rwenzori Mountains. We use a data set collected from a temporary network of 33 broadband stations operated by the RiftLink research group between September 2009 and August 2011. During this period, 82639 P-wave and 73408 S-wave travel times from 12419 local and regional earthquakes were registered. This presents a very rare opportunity to apply both local travel-time and ambient-noise tomography to analyze data from the same network. For the local travel-time tomographic inversion the LOTOS algorithm (Koulakov, 2009) was used. The algorithm performs iterative simultaneous inversions for 3D models of P- and S-velocity anomalies in combination with earthquake locations and origin times. 28955 P- and S-wave picks from 2769 local earthquakes were used. To estimate the resolution and stability of the results a number of the synthetic and real data tests were performed. To perform the ambient noise tomography we use the following procedure. First, we follow the standard procedure described by Bensen et al. (2007) as modified by Boué et al. (2014) to compute the vertical component cross-correlation functions between all pairs of stations. We also adapted the algorithm introduced by Boué et al. (2014) and use the WHISPER software package (Briand et al., 2013) to preprocess individual daily vertical-component waveforms. On the next step, for each period, we use the method of Barmin et al. (2001) to invert the dispersion measurements along each path for group velocity tomographic maps. Finally, we adapt a modified version of the algorithm suggested by Macquet et al. (2014) to invert the group velocity maps for shear velocity structure. We apply several tests, which show that the best resolution is obtained at a period of 8 seconds, which correspond to a depth of approximately 6 km. Models of the seismic structure obtained by the two methods agree well at shallow depth of about

Numerical simulation of plasma processes driven by transverse ion heating

Science.gov (United States)

Singh, Nagendra; Chan, C. B.

1993-01-01

The plasma processes driven by transverse ion heating in a diverging flux tube are investigated with numerical simulation. The heating is found to drive a host of plasma processes, in addition to the well-known phenomenon of ion conics. The downward electric field near the reverse shock generates a doublestreaming situation consisting of two upflowing ion populations with different average flow velocities. The electric field in the reverse shock region is modulated by the ion-ion instability driven by the multistreaming ions. The oscillating fields in this region have the possibility of heating electrons. These results from the simulations are compared with results from a previous study based on a hydrodynamical model. Effects of spatial resolutions provided by simulations on the evolution of the plasma are discussed.

Possibilities for reduction of transverse projected emittances by partial removal of transverse to longitudinal beam correlations

International Nuclear Information System (INIS)

Balandin, V.; Decking, W.; Golubeva, N.

2014-09-01

We show that if in the particle beam there are linear correlations between energy of particles and their transverse positions and momenta (linear beam dispersions), then the transverse projected emittances always can be reduced by letting the beam to pass through magnetostatic system with specially chosen nonzero lattice dispersions. The maximum possible reduction of the transverse projected emittances occurs when all beam dispersions are zeroed, and the values of the lattice dispersions required for that are completely defined by the values of the beam dispersions and the beam rms energy spread and are independent from any other second-order central beam moments. Besides that, we prove that, alternatively, one can also use the lattice dispersions to remove linear correlations between longitudinal positions of particles and their transverse coordinates (linear beam tilts), but in this situation solution for the lattice dispersions is nonunique and the reduction of the transverse projected emittances is not guaranteed.

Transversal lightlike submanifolds of indefinite sasakian manifolds

OpenAIRE

YILDIRIM, Cumali; Yıldırım, Cumali; Şahin, Bayram

2014-01-01

We study both radical transversal and transversal lightlike submanifolds of indefinite Sasakian manifolds. We give examples, investigate the geometry of distributions and obtain necessary and sufficient conditions for the induced connection on these submanifolds to be metric connection. We also study totally contact umbilical radical transversal and transversal lightlike submanifolds of indefinite Sasakian manifolds and obtain a classification theorem for totally contact umbilical tr...

Transversal lightlike submanifolds of indefinite sasakian manifolds

OpenAIRE

YILDIRIM, Cumali

2010-01-01

We study both radical transversal and transversal lightlike submanifolds of indefinite Sasakian manifolds. We give examples, investigate the geometry of distributions and obtain necessary and sufficient conditions for the induced connection on these submanifolds to be metric connection. We also study totally contact umbilical radical transversal and transversal lightlike submanifolds of indefinite Sasakian manifolds and obtain a classification theorem for totally contact umbilical tr...

La interacción en el b-learning como posibilitadora de ambientes de aprendizaje constructivistas: perspectiva de estudiantes

OpenAIRE

Islas Torres, Claudia

2015-01-01

El blearning se ha convertido en una modalidad de enseñanza-aprendizaje prometedora puesto que el hibrido de presencialidad y virtualidad incrementa las opciones para la construcción de conocimiento. El objetivo de la investigación, fue conocer las formas de interacción en modalidad blended que posibilitan la configuración de ambientes de aprendizaje constructivistas. Los resultados derivan de un estudio cuantitativo, no experimental transversal, de alcance descriptivo correlacional, en el qu...

Mapping of moveout in tilted transversely isotropic media

KAUST Repository

Stovas, A.; Alkhalifah, Tariq Ali

2013-01-01

The computation of traveltimes in a transverse isotropic medium with a tilted symmetry axis tilted transversely isotropic is very important both for modelling and inversion. We develop a simple analytical procedure to map the traveltime function from a transverse isotropic medium with a vertical symmetry axis (vertical transversely isotropic) to a tilted transversely isotropic medium by applying point-by-point mapping of the traveltime function. This approach can be used for kinematic modelling and inversion in layered tilted transversely isotropic media. © 2013 European Association of Geoscientists & Engineers.

Mapping of moveout in tilted transversely isotropic media

KAUST Repository

Stovas, A.

2013-09-09

The computation of traveltimes in a transverse isotropic medium with a tilted symmetry axis tilted transversely isotropic is very important both for modelling and inversion. We develop a simple analytical procedure to map the traveltime function from a transverse isotropic medium with a vertical symmetry axis (vertical transversely isotropic) to a tilted transversely isotropic medium by applying point-by-point mapping of the traveltime function. This approach can be used for kinematic modelling and inversion in layered tilted transversely isotropic media. © 2013 European Association of Geoscientists & Engineers.

SIMULATIONS OF HIGH-VELOCITY CLOUDS. I. HYDRODYNAMICS AND HIGH-VELOCITY HIGH IONS

International Nuclear Information System (INIS)

Kwak, Kyujin; Henley, David B.; Shelton, Robin L.

2011-01-01

We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities, and velocities. In all cases, the cloud-halo interaction ablates material from the clouds. The ablated material falls behind the clouds where it mixes with the ambient medium to produce intermediate-temperature gas, some of which radiatively cools to less than 10,000 K. Using a non-equilibrium ionization algorithm, we track the ionization levels of carbon, nitrogen, and oxygen in the gas throughout the simulation period. We present observation-related predictions, including the expected H I and high ion (C IV, N V, and O VI) column densities on sightlines through the clouds as functions of evolutionary time and off-center distance. The predicted column densities overlap those observed for Complex C. The observations are best matched by clouds that have interacted with the Galactic environment for tens to hundreds of megayears. Given the large distances across which the clouds would travel during such time, our results are consistent with Complex C having an extragalactic origin. The destruction of HVCs is also of interest; the smallest cloud (initial mass ∼ 120 M sun ) lost most of its mass during the simulation period (60 Myr), while the largest cloud (initial mass ∼ 4 x 10 5 M sun ) remained largely intact, although deformed, during its simulation period (240 Myr).

Average Transverse Momentum Quantities Approaching the Lightfront

OpenAIRE

Boer, Daniel

2015-01-01

In this contribution to Light Cone 2014, three average transverse momentum quantities are discussed: the Sivers shift, the dijet imbalance, and the $p_T$ broadening. The definitions of these quantities involve integrals over all transverse momenta that are overly sensitive to the region of large transverse momenta, which conveys little information about the transverse momentum distributions of quarks and gluons inside hadrons. TMD factorization naturally suggests alternative definitions of su...

Very low sound velocities in iron-rich (Mg,Fe)O: Implications for the core-mantle boundary region

International Nuclear Information System (INIS)

Wicks, J.K.; Jackson, J.M.; Sturhahn, W.

2010-01-01

The sound velocities of (Mg .16 Fe .84 )O have been measured to 121 GPa at ambient temperature using nuclear resonant inelastic x-ray scattering. The effect of electronic environment of the iron sites on the sound velocities were tracked in situ using synchrotron Moessbauer spectroscopy. We found the sound velocities of (Mg .16 Fe .84 )O to be much lower than those in other presumed mantle phases at similar conditions, most notably at very high pressures. Conservative estimates of the effect of temperature and dilution on aggregate sound velocities show that only a small amount of iron-rich (Mg,Fe)O can greatly reduce the average sound velocity of an assemblage. We propose that iron-rich (Mg,Fe)O be a source of ultra-low velocity zones. Other properties of this phase, such as enhanced density and dynamic stability, strongly support the presence of iron-rich (Mg,Fe)O in localized patches above the core-mantle boundary.

Zero sound velocity in π, ρ mesons at different temperatures

International Nuclear Information System (INIS)

Dey, J.; Dey, M.; Tomio, L.; Araujo, C.F. de Jr.

1994-07-01

Sharp transitions are perhaps absent in QCD, so that one looks for physical quantities which may reflect the phase change. One such quantity is the sound velocity which was shown in lattice theory to become zero at the transition point for pure glue. We show that even in a simple bag model the sound velocity goes to zero at temperature T=T ν ≠ 0 and that the numerical value of this T ν depends on the nature of the meson. The average thermal energy of mesons go linearly with T near T ν , with much smaller slope for the pion. The T ν - s can be connected with the Boltzmann temperatures obtained from transverse momentum spectrum of these mesons in heavy ion collision at mid-rapidity. It would be interesting to check the presence of different T ν - s in present day finite T lattice theory. (author). 22 refs, 1 fig., 2 tabs

Phase velocity of nonlinear plasma waves in the laser beat-wave accelerator

International Nuclear Information System (INIS)

Spence, W.L.

1985-01-01

The suggested plasma-laser accelerator is an attempt to achieve a very high energy gradient by resonantly exciting a longitudinal wave traveling at close to the speed of light in cold plasma by means of the beat-wave generated by the transverse fields in two laser beams. Previous calculations to all orders in v/sub z/ have been done essentially from the laboratory frame point of view and have treated the plasma wave as having sharply defined phase velocity equal to the speed of light. However a high energy particle beam undergoing acceleration sees the plasma wave from a nearly light-like frame of reference and hence is very sensitive to small deviations in its phase velocity. Here the authors introduce a calculational scheme that includes all orders in v/sub z/ and in the plasma density, and additionally takes into account the influence of plasma nonlinearities on the wave's phase velocity. The main assumption is that the laser frequencies are very large compared to the plasma frequency - under which they are able to in essence formally sum up all orders of forward Raman scattering. They find that the nonlinear plasma wave does not have simply a single phase velocity - it is really a superposition of many - but that the beat-wave which drives it is usefully described by a non-local effective phase velocity function

Experimental study on physiological responses and thermal comfort under various ambient temperatures.

Science.gov (United States)

Yao, Ye; Lian, Zhiwei; Liu, Weiwei; Shen, Qi

2008-01-28

This study mainly explored the thermal comfort from the perspective of physiology. Three physiological parameters, including skin temperature (local and mean), electrocardiograph (ECG) and electroencephalogram (EEG), were investigated to see how they responded to the ambient temperature and how they were related to the thermal comfort sensation. A total of four ambient temperatures (21 degrees C, 24 degrees C, 26 degrees C and 29 degrees C) were created, while the other thermal conditions including the air velocity (about 0.05+/-0.01 m/s) and the air humidity (about 60+/-5 m/s) were kept as stable as possible throughout the experiments. Twenty healthy students were tested with questionnaire investigation under those thermal environments. The statistical analysis shows that the skin temperature (local and mean), the ratio of LF(norm) to HF(norm) of ECG and the global relative power of the different EEG frequency bands will be sensitive to the ambient temperatures and the thermal sensations of the subjects. It is suggested that the three physiological parameters should be considered all together in the future study of thermal comfort.

Cladding for transverse-pumped solid-state laser

Science.gov (United States)

Byer, Robert L. (Inventor); Fan, Tso Y. (Inventor)

1989-01-01

In a transverse pumped, solid state laser, a nonabsorptive cladding surrounds a gain medium. A single tranverse mode, namely the Transverse Electromagnetic (TEM) sub 00 mode, is provided. The TEM sub 00 model has a cross sectional diameter greater than a transverse dimension of the gain medium but less than a transverse dimension of the cladding. The required size of the gain medium is minimized while a threshold for laser output is lowered.

Transverse Momentum Distributions for Heavy Quark Pairs

OpenAIRE

Berger, Edmond L.; Meng, Ruibin

1993-01-01

We study the transverse momentum distribution for a $pair$ of heavy quarks produced in hadron-hadron interactions. Predictions for the large transverse momentum region are based on exact order $\\alpha_s^3$ QCD perturbation theory. For the small transverse momentum region, we use techniques for all orders resummation of leading logarithmic contributions associated with initial state soft gluon radiation. The combination provides the transverse momentum distribution of heavy quark pairs for all...

Thermal Cracking in Westerly Granite Monitored Using Direct Wave Velocity, Coda Wave Interferometry, and Acoustic Emissions

Science.gov (United States)

Griffiths, L.; Lengliné, O.; Heap, M. J.; Baud, P.; Schmittbuhl, J.

2018-03-01

To monitor both the permanent (thermal microcracking) and the nonpermanent (thermo-elastic) effects of temperature on Westerly Granite, we combine acoustic emission monitoring and ultrasonic velocity measurements at ambient pressure during three heating and cooling cycles to a maximum temperature of 450°C. For the velocity measurements we use both P wave direct traveltime and coda wave interferometry techniques, the latter being more sensitive to changes in S wave velocity. During the first cycle, we observe a high acoustic emission rate and large—and mostly permanent—apparent reductions in velocity with temperature (P wave velocity is reduced by 50% of the initial value at 450°C, and 40% upon cooling). Our measurements are indicative of extensive thermal microcracking during the first cycle, predominantly during the heating phase. During the second cycle we observe further—but reduced—microcracking, and less still during the third cycle, where the apparent decrease in velocity with temperature is near reversible (at 450°C, the P wave velocity is decreased by roughly 10% of the initial velocity). Our results, relevant for thermally dynamic environments such as geothermal reservoirs, highlight the value of performing measurements of rock properties under in situ temperature conditions.

Source-to-target simulation of simultaneous longitudinal and transverse focusing of heavy ion beams

Directory of Open Access Journals (Sweden)

D. R. Welch

2008-06-01

Full Text Available Longitudinal bunching factors in excess of 70 of a 300-keV, 27-mA K^{+} ion beam have been demonstrated in the neutralized drift compression experiment [P. K. Roy et al., Phys. Rev. Lett. 95, 234801 (2005PRLTAO0031-900710.1103/PhysRevLett.95.234801] in rough agreement with particle-in-cell source-to-target simulations. A key aspect of these experiments is that a preformed plasma provides charge neutralization of the ion beam in the last one meter drift region where the beam perveance becomes large. The simulations utilize the measured ion source temperature, diode voltage, and induction-bunching-module voltage waveforms in order to determine the initial beam longitudinal phase space which is critical to accurate modeling of the longitudinal compression. To enable simultaneous longitudinal and transverse compression, numerical simulations were used in the design of the solenoidal focusing system that compensated for the impact of the applied velocity tilt on the transverse phase space of the beam. Complete source-to-target simulations, that include detailed modeling of the diode, magnetic transport, induction bunching module, and plasma neutralized transport, were critical to understanding the interplay between the various accelerator components in the experiment. Here, we compare simulation results with the experiment and discuss the contributions to longitudinal and transverse emittance that limit the final compression.

Transversal infinitesimal automorphisms on K\\"ahler foliations

OpenAIRE

Jung, Seoung Dal

2011-01-01

Let F be a K\\"ahler foliation on a compact Riemannian manifold M. we study the properties of infinitesimal automorphisms on (M,F), and in particular we concentrate on the transversal conformal field, transversal projective field and transversally holomorphic field

Periodismo ambiental

Directory of Open Access Journals (Sweden)

Lucía Lemos

2015-01-01

Full Text Available Los periodistas toman el tema del medio ambiente cada vez más en serio. El uso de temas relacionados con el medio ambiente, debe estar ligado al análisis socio-económico y a las posibilidades de comunicación y educación de diferentes regiones del mundo. A continuación se presenta un resumen de la situación ambiental, las acciones de prensa y comunicación que se llevan a cabo en América Central (Panamá, El Salvador, Costa Rica y en Sudamérica Brasil,Colombia, Chile, México, y Perú. Se concluye en la necesidad de formar hábitos ecológicos. Los comunicadores deben presentar soluciones a los problemas, fomentar campañas comunes, compartir información y velar por el ambiente ambiente para que las generaciones futuras no tengan que perecer.

46 CFR 154.174 - Transverse contiguous hull structure.

Science.gov (United States)

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Transverse contiguous hull structure. 154.174 Section... Equipment Hull Structure § 154.174 Transverse contiguous hull structure. (a) The transverse contiguous hull...) The transverse contiguous hull structure of a vessel having cargo containment systems with secondary...

Significance of geological units of the Bohemian Massif, Czech Republic, as seen by ambient noise interferometry

Czech Academy of Sciences Publication Activity Database

Růžek, Bohuslav; Valentová, L.; Gallovič, F.

2016-01-01

Roč. 173, č. 5 (2016), s. 1663-1682 ISSN 0033-4553 R&D Projects: GA ČR GAP210/12/2336; GA MŠk LM2010008 Institutional support: RVO:67985530 Keywords : ambient noise * geological units * Bohemian Massif * velocity model Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.591, year: 2016

Velocity bunching of high-brightness electron beams

Directory of Open Access Journals (Sweden)

S. G. Anderson

2005-01-01

Full Text Available Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly

Transverse spin physics

CERN Document Server

Barone, Vicenzo

2001-01-01

This book is devoted to the theory and phenomenology of transverse-spin effects in high-energy hadronic physics. Contrary to common past belief, it is now rather clear that such effects are far from irrelevant. A decade or so of intense theoretical work has shed much light on the subject and brought to surface an entire class of new phenomena, which now await thorough experimental investigation. Over the next few years a number of experiments world-wide (at BNL, CERN, DESY and JLAB) will run with transversely polarised beams and targets, providing data that will enrich our knowledge of the tra

Resolution enhancement of slam using transverse wave

International Nuclear Information System (INIS)

Ko, Dae Sik; Moon, Gun; Kim, Young H.

1997-01-01

We studied the resolution enhancement of a novel scanning laser acoustic microscope (SLAM) using transverse waves. Mode conversion of the ultrasonic wave takes place at the liquid-solid interface and some energy of the insonifying longitudinal waves in the water will convert to transverse wave energy within the solid specimen. The resolution of SLAM depends on the size of detecting laser spot and the wavelength of the insonifying ultrasonic waves. Since the wavelength of the transverse wave is shorter than that of the longitudinal wave, we are able to achieve the high resolution by using transverse waves. In order to operate SLAM in the transverse wave mode, we made wedge for changing the incident angle. Our experimental results with model 2140 SLAM and an aluminum specimen showed higher contrast of the SLAM Image In the transverse wave mode than that in the longitudinal wave mode.

Chiral dynamics and peripheral transverse densities

Energy Technology Data Exchange (ETDEWEB)

Granados, Carlos G. [Uppsala University (Sweden); Weiss, Christian [JLAB, Newport News, VA (United States)

2014-01-01

In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M{sub {pi}}{sup -1}) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two--pion threshold at timelike t = 4 M{ sub {pi}}{sup 2}, which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M{sub {pi}}{sup -1}) and the "molecular" region b = O(M{sub N}{sup 2}/M{sub {pi}}{sup 3}); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N{ sub c} limit of QCD; (e) quantify the region of transverse distances where the chiral components of the densities are numerically dominant; (f) calculate the chiral divergences of the b{sup 2}-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M{sub {pi}} -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes.

Longitudinal and transverse polarizations in the deep inelastic reactions; Polarisations longitudinale et transverse dans les reactions inelastiques profondes

Energy Technology Data Exchange (ETDEWEB)

Bressan, A.

1996-07-01

This course is an introduction to the dominant effects of longitudinal and transverse spin in deep inelastic reactions. Only the effects present to the `leading twist` are attacked. The mass and transverse impulsion of partons are neglected. We will attach to bring out the respective specificities of longitudinal and transverse polarizations. (N.C.).

High-frame-rate Imaging of a Carotid Bifurcation using a Low-complexity Velocity Estimation Approach

DEFF Research Database (Denmark)

di Ianni, Tommaso; Villagómez Hoyos, Carlos Armando; Ewertsen, Caroline

2017-01-01

In this paper, a 2-D vector flow imaging (VFI) method developed by combining synthetic aperture sequential beamforming and directional transverse oscillation is used to image a carotid bifurcation. Ninety-six beamformed lines are sent from the probe to the host system for each VFI frame, enabling...... the possibility of wireless transmission. The velocity is estimated using a relatively inexpensive 2-D phase-shift approach, and real-time performance can be achieved in mobile devices. However, high-frame-rate velocities can be obtained by sending the data to a cluster of computers. The objective of this study...... is to demonstrate the scalability of the method’s performance according to the needs of the user and the processing capabilities of the host system. In vivo measurements of a carotid bifurcation of a 54-year-old volunteer were conducted using a linear array transducer connected to the SARUS scanner. The velocities...

Transverse electron resonance accelerator

International Nuclear Information System (INIS)

Osonka, P.L.

1985-01-01

Transverse (to the velocity, v-bar, of the particles to be accelerated) electron oscillations are generated in high (e.g. solid) density plasms by either an electromagnetic wave or by the field of charged particles traveling parallel to v-bar. The generating field oscillates with frequency ω = ω/sub p/, where ω/sub p/ is the plasma frequency. The plasma is confined to a sequence of microstructures with typical dimensions of d≅2πc/ω/sub p/, allowing the generating fields to penetrate. Since ω/sub p/ is now high, the time scales, T, are correspondingly reduced. The microstructures are allowed to explode after t = T, until then they are confined by ion inertia. As a result of resonance, the electric field, E, inside the microstructures can exceed the generating field E/sub L/. The generating force is proportional to E/sub L/ (as opposed to E 2 /sub L/). Phase matching of particles is possible by appropriate spacing of the microstructures or by a gas medium. The generating beam travels outside the plasma, filamentation is not a problem. The mechanism is relatively insensitive to the exact shape and position of the microstructures. This device contains features of various earlier proposed acceleration mechanisms and may be considered as the limiting case of several of those for small d, T and high E

Transverse electron resonance accelerator

International Nuclear Information System (INIS)

Csonka, P.L.

1985-01-01

Transverse (to the velocity, v, of the particles to be accelerated) electron oscillations are generated in high (e.g. solid) density plasmas by either an electromagnetic wave or by the field of charged particles traveling parallel to v. The generating field oscillates with frequency ω = ω/sub p/, where ω/sub p/ is the plasma frequency. The plasma is confined to a sequence of microstructures with typical dimensions of d approx. = 2πc/ω/sub p/, allowing the generating fields to penetrate. Since ω/sub p/ is now high, the time scales, T, are correspondingly reduced. The microstructures are allowed to explode after t = T, until then they are confined by ion inertia. As a result of resonance, the electric field, E, inside the microstructures can exceed the generating field E/sub L/. The generating force is proportional to E/sub L/ (as opposed to E/sub L/ 2 ). Phase matching of particles is possible by appropriate spacing of the microstructures or by a gas medium. The generating beam travels outside the plasma, filamentation is not a problem. The mechanism is relatively insensitive to the exact shape and position of the microstructures. This device contains features of various earlier proposed acceleration mechanisms and may be considered as the limiting case of several of those for small d, T and high E

Kinetic theory of the positive column of a low-pressure discharge in a transverse magnetic field

International Nuclear Information System (INIS)

Londer, Ya. I.; Ul’yanov, K. N.

2011-01-01

The influence of a transverse magnetic field on the characteristics of the positive column of a planar low-pressure discharge is studied theoretically. The motion of magnetized electrons is described in the framework of a continuous-medium model, while the ion motion in the ambipolar electric field is described by means of a kinetic equation. Using mathematical transformations, the problem is reduced to a secondorder ordinary differential equation, from which the spatial distribution of the potential is found in an analytic form. The spatial distributions of the plasma density, mean plasma velocity, and electric potential are calculated, the ion velocity distribution function at the plasma boundary is found, and the electron energy as a function of the magnetic field is determined. It is shown that, as the magnetic field rises, the electron energy increases, the distributions of the plasma density and mean plasma velocity become asymmetric, the maximum of the plasma density is displaced in the direction of the Ampère force, and the ion flux in this direction becomes substantially larger than the counter-directed ion flux.

Deuteron transverse densities in holographic QCD

Energy Technology Data Exchange (ETDEWEB)

Mondal, Chandan [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China); Indian Institute of Technology Kanpur, Department of Physics, Kanpur (India); Chakrabarti, Dipankar [Indian Institute of Technology Kanpur, Department of Physics, Kanpur (India); Zhao, Xingbo [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China)

2017-05-15

We investigate the transverse charge density in the longitudinally as well as transversely polarized deuteron using the recent empirical description of the deuteron electromagnetic form factors in the framework of holographic QCD. The predictions of the holographic QCD are compared with the results of a standard phenomenological parameterization. In addition, we evaluate GPDs and the gravitational form factors for the deuteron. The longitudinal momentum densities are also investigated in the transverse plane. (orig.)

A Study of Large Transverse Momentum Phenomena

CERN Multimedia

2002-01-01

This experiment studies the structure of those p-p and @*-p collisions which are characterized by a very high transverse momentum flow in the central region. Some specific items studied are:\\\\ \\\\ \\item -~~Structure of events, where the high transverse momentum is shared by charged and neutral hadron (``jets''). Transverse momentum distribution, correlations and momentum balance for such events. \\item -~~Structure of events, where the high transverse momentum is mostly carried by one identified particle. Quantum number dependence and quantum number correlations of the high transverse momentum events. \\item -~~Structure of events containing large transverse momentum leptons or lepton pairs or direct photons. \\end{enumerate}.sk -~~Study of low momentum electrons and photons. -~~Search for gluonium states. -~~Search for new and rare particles. \\\\ \\\\ A conventional C-type magnet with a 0.5 T field in the direction of the beams together with a 42-layer cylindrical drift chamber detector is used for momentum analysi...

Transverse mass and rapidity distributions and space dispersion plots of (net-)protons in Pb-Pb collisions at SPS energies

International Nuclear Information System (INIS)

Liu, Fu-Hu; Tian, Tian; Wen, Xin-Jian

2014-01-01

The transverse mass and rapidity distributions of (net-)protons produced in Pb-Pb collisions with different centrality intervals at 40A and 158A GeV have been analyzed by using the multisource thermal model in which the whole interacting system and then the sources are described by the Tsallis statistics. The modelling results are in agreement with the experimental data of the NA49 Collaboration. The dispersion plots (or scatter plots) of (net-)protons at the stage of freeze-out in the momentum space, velocity space, and transverse momentum and rapidity space in Pb-Pb collisions at 40A and 158A GeV in different centrality intervals are obtained. We see the differences in density distributions in the dispersion plots for different origins, centrality intervals, and incident energies for the considered collisions. (orig.)

Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

Directory of Open Access Journals (Sweden)

P. Guio

Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.

Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

Directory of Open Access Journals (Sweden)

P. Guio

1998-10-01

Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

Effects of closed immersion filtered water flow velocity on the ablation threshold of bisphenol A polycarbonate during excimer laser machining

International Nuclear Information System (INIS)

Dowding, Colin; Lawrence, Jonathan

2010-01-01

A closed flowing thick film filtered water immersion technique ensures a controlled geometry for both the optical interfaces of the flowing liquid film and allows repeatable control of flow-rate during machining. This has the action of preventing splashing, ensures repeatable machining conditions and allows control of liquid flow velocity. To investigate the impact of this technique on ablation threshold, bisphenol A polycarbonate samples have been machined using KrF excimer laser radiation passing through a medium of filtered water flowing at a number of flow velocities, that are controllable by modifying the liquid flow-rates. An average decrease in ablation threshold of 7.5% when using turbulent flow velocity regime closed thick film filtered water immersed ablation, compared to ablation using a similar beam in ambient air; however, the use of laminar flow velocities resulted in negligible differences between closed flowing thick film filtered water immersion and ambient air. Plotting the recorded threshold fluence achieved with varying flow velocity showed that an optimum flow velocity of 3.00 m/s existed which yielded a minimum ablation threshold of 112 mJ/cm 2 . This is attributed to the distortion of the ablation plume effected by the flowing immersion fluid changing the ablation mechanism: at laminar flow velocities Bremsstrahlung attenuation decreases etch rate, at excessive flow velocities the plume is completely destroyed, removing the effect of plume etching. Laminar flow velocity regime ablation is limited by slow removal of debris causing a non-linear etch rate over 'n' pulses which is a result of debris produced by one pulse remaining suspended over the feature for the next pulse. The impact of closed thick film filtered water immersed ablation is dependant upon beam fluence: high fluence beams achieved greater etch efficiency at high flow velocities as the effect of Bremsstrahlung attenuation is removed by the action of the fluid on the plume; low

A note on fractional disjoint transversals in hypergraphs

DEFF Research Database (Denmark)

Henning, Michael A.; Yeo, Anders

2017-01-01

A transversal in a hypergraph H is a subset of vertices that has a nonempty intersection with every edge of H. A transversal family F of H is a family of (not necessarily distinct) transversals of H. The effective transversal-ratio of the family F is the ratio of the number of sets in F over the ...

Transversals in non-discrete groups

Indian Academy of Sciences (India)

Transversals in non-discrete groups. RAMJI LAL and R P SHUKLA. Department of Mathematics, University of Allahabad, Allahabad 211 002, India. E-mail: ramjilal@mri.ernet.in; rps@mri.ernet.in. MS received 2 August 2004; revised 4 August 2005. Abstract. The concept of 'topological right transversal' is introduced to study ...

Apparatus and method for determining movements and velocities of moving objects

DEFF Research Database (Denmark)

1998-01-01

in the apparatus is applicable where wave energy is used to sense or detect an object by its scattering properties when using either sound waves or electro-magnetic waves. The movement can be detected according to the field properties. The field represented by the sampling pulse must feature a spatial oscillation...... in the directions, where the velocity components are of interest. Such a transversely oscillating field is e.g. generated by using apodization on individual transducer elements and a special focusing scheme. The apparatus uses waves of either sound or electro-magnetic radiation. The temporal characteristics...

High resolution 3-D shear wave velocity structure in South China from surface wave tomography

Science.gov (United States)

Ning, S.; Guo, Z.; Chen, Y. J.

2017-12-01

Using continuous data from a total of 638 seismic stations, including 484 from CEArray between 2008 and 2013 and 154 from SINOPROBE between 2014 and 2015, we perform both ambient noise and earthquake Rayleigh wave tomography across South China. Combining Rayleigh wave phase velocity between 6and 40s periods from ambient noise tomography and Rayleigh wave phase velocity between 20and 140s from teleseismic two-plane-wave tomography, we obtain phase velocity maps between 6 and140 s periods. We then invert Rayleigh wave phase velocity to construct a 3-D shear wave velocity structure of South China by Markov Chain Monte Carlo method. Similar to other inversion results, our results correspond topography well. Moreover, our results also reveal that velocity structure of the eastern South China in mantle depth is similar to eastern North China, the core of the western South China, Sichuan Block (SB),still exists thick lithosphere. However, owing to much more data employed and some data quality control techniques in this research, our results reveal more detailed structures. Along Qinling-Dabie Orogenic Belt (QDOB), North-South Gravity Lineament (NSGL) and the Sichuan-Yunnan Rhombic Block (SYRB), there are obvious high speed anomalies in depths of 10-20 km, which possibly imply ancient intrusions. Moreover, it seems that Tancheng-Lujiang Fault Zone (TLFZ) has already cut through QDOB, forming a deep fracture cutting through the crust of the whole China continent. Although SB still exists thick lithosphere, there are indications for thermal erosion. At the same time, the lithosphere of the central SYRB seems to be experiencing delamination process, obviously forming a barrier to prevent the hot Tibetan Plateau (TP) mantle material from flowing further southeast. Upwelling hot mantle material possibly triggered by this delamination process might be the cause of the Emeishan Large Igneous Province. There exists an intercontinental low velocity layer in the crust of the TP

Growth of transverse coherence in SASE FELs

International Nuclear Information System (INIS)

Kumar, Vinit; Krishnagopal, Srinivas

2000-01-01

We introduce the correlation function between the electric field at two different points in the transverse plane as a parameter to quantify the degree of transverse coherence. We also propose a more realistic model for the initialization of the radiation in computer codes used to study SASE FELs. We make these modifications in the code TDA and use it to study the growth of transverse coherence as a function of electron beam size, beam current and transverse emittance. Our results show explicitly that the onset of full transverse coherence in SASE takes place much before the power saturates. With the more realistic model the onset of the exponential growth regime is delayed, and to get a given power from the FEL one needs a longer undulator than would be predicted by the original TDA code

Missing transverse energy performance of the CMS detector

Energy Technology Data Exchange (ETDEWEB)

Chatrchyan, Serguei [Yerevan Physics Inst. (Armenia); et al.

2011-09-01

During 2010 the LHC delivered pp collisions with a centre-of-mass energy of 7 TeV. In this paper, the results of comprehensive studies of missing transverse energy as measured by the CMS detector are presented. The results cover the measurements of the scale and resolution for missing transverse energy, and the effects of multiple pp interactions within the same bunch crossings on the scale and resolution. Anomalous measurements of missing transverse energy are studied, and algorithms for their identification are described. The performances of several reconstruction algorithms for calculating missing transverse energy are compared. An algorithm, called missing-transverse-energy significance, which estimates the compatibility of the reconstructed missing transverse energy with zero, is described, and its performance is demonstrated.

Missing transverse energy performance of the CMS detector

International Nuclear Information System (INIS)

2011-01-01

During 2010 the LHC delivered pp collisions with a centre-of-mass energy of 7 TeV. In this paper, the results of comprehensive studies of missing transverse energy as measured by the CMS detector are presented. The results cover the measurements of the scale and resolution for missing transverse energy, and the effects of multiple pp interactions within the same bunch crossings on the scale and resolution. Anomalous measurements of missing transverse energy are studied, and algorithms for their identification are described. The performance of several reconstruction algorithms for calculating missing transverse energy are compared. An algorithm, called missing-transverse-energy significance, which estimates the compatibility of the reconstructed missing transverse energy with zero, is described, and its performance is demonstrated.

Post-seismic velocity changes following the 2010 Mw 7.1 Darfield earthquake, New Zealand, revealed by ambient seismic field analysis

Science.gov (United States)

Heckels, R. EG; Savage, M. K.; Townend, J.

2018-05-01

Quantifying seismic velocity changes following large earthquakes can provide insights into fault healing and reloading processes. This study presents temporal velocity changes detected following the 2010 September Mw 7.1 Darfield event in Canterbury, New Zealand. We use continuous waveform data from several temporary seismic networks lying on and surrounding the Greendale Fault, with a maximum interstation distance of 156 km. Nine-component, day-long Green's functions were computed for frequencies between 0.1 and 1.0 Hz for continuous seismic records from immediately after the 2010 September 04 earthquake until 2011 January 10. Using the moving-window cross-spectral method, seismic velocity changes were calculated. Over the study period, an increase in seismic velocity of 0.14 ± 0.04 per cent was determined near the Greendale Fault, providing a new constraint on post-seismic relaxation rates in the region. A depth analysis further showed that velocity changes were confined to the uppermost 5 km of the subsurface. We attribute the observed changes to post-seismic relaxation via crack healing of the Greendale Fault and throughout the surrounding region.

Ambient Seismic Imaging of Hydraulically Active Fractures at km Depths

Science.gov (United States)

Malin, P. E.; Sicking, C.

2017-12-01

Streaming Depth Images of ambient seismic signals using numerous, densely-distributed, receivers have revealed their connection to hydraulically active fractures at 0.5 to 5 km depths. Key for this type of imaging is very high-fold stacking over both multiple receives and periods of a few hours. Also important is suppression of waveforms from fixed, repeating sources such as pumps, generators, and traffic. A typical surface-based ambient SDI survey would use a 3D seismic receiver grid. It would have 1,000 to 4,000 uniformly distributed receivers at a density of 50/km2over the target. If acquired by borehole receivers buried 100 m deep, the density can be dropped by an order of magnitude. We show examples of the acquisition and signal processing scenarios used to produce the ambient images. (Sicking et al., SEG Interpretation, Nov 2017.) While the fracture-fluid source connection of SDI has been verified by drilling and various types of hydraulic tests, the precise nature of the signal's origin is not clear. At the current level of observation, the signals do not have identifiable phases, but can be focused using P wave velocities. Suggested sources are resonances of pressures fluctuations in the fractures, or small, continuous, slips on fractures surfaces. In either case, it appears that the driving mechanism is tectonic strain in an inherently unstable crust. Solid earth tides may enhance these strains. We illustrate the value of the ambient SDI method in its industrial application by showing case histories from energy industry and carbon-capture-sequestration projects. These include ambient images taken before, during, and after hydraulic treatments in un-conventional reservoirs. The results show not only locations of active fractures, but also their time responses to stimulation and production. Time-lapse ambient imaging can forecast and track events such as well interferences and production changes that can result from nearby treatments.

Transverse spin correlations of the random transverse-field Ising model

Science.gov (United States)

Iglói, Ferenc; Kovács, István A.

2018-03-01

The critical behavior of the random transverse-field Ising model in finite-dimensional lattices is governed by infinite disorder fixed points, several properties of which have already been calculated by the use of the strong disorder renormalization-group (SDRG) method. Here we extend these studies and calculate the connected transverse-spin correlation function by a numerical implementation of the SDRG method in d =1 ,2 , and 3 dimensions. At the critical point an algebraic decay of the form ˜r-ηt is found, with a decay exponent being approximately ηt≈2 +2 d . In d =1 the results are related to dimer-dimer correlations in the random antiferromagnetic X X chain and have been tested by numerical calculations using free-fermionic techniques.

Collisionless coupling of a high- β expansion to an ambient, magnetized plasma. II. Experimental fields and measured momentum coupling

Science.gov (United States)

Bonde, Jeffrey; Vincena, Stephen; Gekelman, Walter

2018-04-01

The momentum coupled to a magnetized, ambient argon plasma from a high- β, laser-produced carbon plasma is examined in a collisionless, weakly coupled limit. The total electric field was measured by separately examining the induced component associated with the rapidly changing magnetic field of the high- β (kinetic β˜106), expanding plasma and the electrostatic component due to polarization of the expansion. Their temporal and spatial structures are discussed and their effect on the ambient argon plasma (thermal β˜10-2) is confirmed with a laser-induced fluorescence diagnostic, which directly probed the argon ion velocity distribution function. For the given experimental conditions, the electrostatic field is shown to dominate the interaction between the high- β expansion and the ambient plasma. Specifically, the expanding plasma couples energy and momentum into the ambient plasma by pulling ions inward against the flow direction.

A generalized formulation for noise-based seismic velocity change measurements

Science.gov (United States)

Gómez-García, C.; Brenguier, F.; Boué, P.; Shapiro, N.; Droznin, D.; Droznina, S.; Senyukov, S.; Gordeev, E.

2017-12-01

The observation of continuous seismic velocity changes is a powerful tool for detecting seasonal variations in crustal structure, volcanic unrest, co- and post-seismic evolution of stress in fault areas or the effects of fluid injection. The standard approach for measuring such velocity changes relies on comparison of travel times in the coda of a set of seismic signals, usually noise-based cross-correlations retrieved at different dates, and a reference trace, usually a averaged function over dates. A good stability in both space and time of the noise sources is then the main assumption for reliable measurements. Unfortunately, these conditions are often not fulfilled, as it happens when ambient-noise sources are non-stationary, such as the emissions of low-frequency volcanic tremors.We propose a generalized formulation for retrieving continuous time series of noise-based seismic velocity changes without any arbitrary reference cross-correlation function. We set up a general framework for future applications of this technique performing synthetic tests. In particular, we study the reliability of the retrieved velocity changes in case of seasonal-type trends, transient effects (similar to those produced as a result of an earthquake or a volcanic eruption) and sudden velocity drops and recoveries as the effects of transient local source emissions. Finally, we apply this approach to a real dataset of noise cross-correlations. We choose the Klyuchevskoy volcanic group (Kamchatka) as a case study where the recorded wavefield is hampered by loss of data and dominated by strongly localized volcanic tremor sources. Despite the mentioned wavefield contaminations, we retrieve clear seismic velocity drops associated with the eruptions of the Klyuchevskoy an the Tolbachik volcanoes in 2010 and 2012, respectively.

Tomographic Rayleigh wave group velocities in the Central Valley, California, centered on the Sacramento/San Joaquin Delta

Science.gov (United States)

Fletcher, Jon B.; Erdem, Jemile; Seats, Kevin; Lawrence, Jesse

2016-04-01

If shaking from a local or regional earthquake in the San Francisco Bay region were to rupture levees in the Sacramento/San Joaquin Delta, then brackish water from San Francisco Bay would contaminate the water in the Delta: the source of freshwater for about half of California. As a prelude to a full shear-wave velocity model that can be used in computer simulations and further seismic hazard analysis, we report on the use of ambient noise tomography to build a fundamental mode, Rayleigh wave group velocity model for the region around the Sacramento/San Joaquin Delta in the western Central Valley, California. Recordings from the vertical component of about 31 stations were processed to compute the spatial distribution of Rayleigh wave group velocities. Complex coherency between pairs of stations was stacked over 8 months to more than a year. Dispersion curves were determined from 4 to about 18 s. We calculated average group velocities for each period and inverted for deviations from the average for a matrix of cells that covered the study area. Smoothing using the first difference is applied. Cells of the model were about 5.6 km in either dimension. Checkerboard tests of resolution, which are dependent on station density, suggest that the resolving ability of the array is reasonably good within the middle of the array with resolution between 0.2 and 0.4°. Overall, low velocities in the middle of each image reflect the deeper sedimentary syncline in the Central Valley. In detail, the model shows several centers of low velocity that may be associated with gross geologic features such as faulting along the western margin of the Central Valley, oil and gas reservoirs, and large crosscutting features like the Stockton arch. At shorter periods around 5.5 s, the model's western boundary between low and high velocities closely follows regional fault geometry and the edge of a residual isostatic gravity low. In the eastern part of the valley, the boundaries of the low-velocity

Tomographic Rayleigh-wave group velocities in the Central Valley, California centered on the Sacramento/San Joaquin Delta

Science.gov (United States)

Fletcher, Jon Peter B.; Erdem, Jemile; Seats, Kevin; Lawrence, Jesse

2016-01-01

If shaking from a local or regional earthquake in the San Francisco Bay region were to rupture levees in the Sacramento/San Joaquin Delta then brackish water from San Francisco Bay would contaminate the water in the Delta: the source of fresh water for about half of California. As a prelude to a full shear-wave velocity model that can be used in computer simulations and further seismic hazard analysis, we report on the use of ambient noise tomography to build a fundamental-mode, Rayleigh-wave group velocity model for the region around the Sacramento/San Joaquin Delta in the western Central Valley, California. Recordings from the vertical component of about 31 stations were processed to compute the spatial distribution of Rayleigh wave group velocities. Complex coherency between pairs of stations were stacked over 8 months to more than a year. Dispersion curves were determined from 4 to about 18 seconds. We calculated average group velocities for each period and inverted for deviations from the average for a matrix of cells that covered the study area. Smoothing using the first difference is applied. Cells of the model were about 5.6 km in either dimension. Checkerboard tests of resolution, which is dependent on station density, suggest that the resolving ability of the array is reasonably good within the middle of the array with resolution between 0.2 and 0.4 degrees. Overall, low velocities in the middle of each image reflect the deeper sedimentary syncline in the Central Valley. In detail, the model shows several centers of low velocity that may be associated with gross geologic features such as faulting along the western margin of the Central Valley, oil and gas reservoirs, and large cross cutting features like the Stockton arch. At shorter periods around 5.5s, the model’s western boundary between low and high velocities closely follows regional fault geometry and the edge of a residual isostatic gravity low. In the eastern part of the valley, the boundaries

GDI fuel sprays of light naphtha, PRF95 and gasoline using a piezoelectric injector under different ambient pressures

KAUST Repository

Wu, Zengyang; Wang, Libing; Badra, Jihad A.; Roberts, William L.; Fang, Tiegang

2018-01-01

This study investigates fuel sprays of light naphtha (LN), primary reference fuel (PRF) and gasoline under different ambient pressures with an outwardly opening piezo gasoline direct injection (GDI) fuel injector. The tested gasoline fuel (regular grade with up to 10% ethanol, E10) was obtained by mixing fuels with AKI (the average of the research octane number (RON) and the motor octane number (MON)) of 87 from three local gas stations. Primary reference fuel (PRF) is commonly used as gasoline surrogate fuel and is blended by iso-octane and n-heptane. PRF95 is the blend of 95% iso-octane and 5% n-heptane by volume. LN fuel was provided by Saudi Aramco Oil Company. Five different ambient pressure conditions varied from 1 bar to 10 bar were tested. The spray was visualized by applying a Mie-scattering technique and a high-speed camera was employed to capture the spray images. The spray structure, spray angle, spray penetration length and spray front fluctuation were analyzed and compared among three fuels. Spray images show that a clear filamentary hollow-cone spray structure is formed for all three fuels at atmospheric conditions, and toroidal recirculation vortexes are observed at the downstream spray edges. A higher ambient pressure leads to a stronger vortex located closer to the injector outlet. Generally speaking, larger spray angles are found under higher ambient pressure conditions for all three fuels. Gasoline fuel always has the largest spray angle for each ambient pressure, while PRF95 has the smallest at most time. For each fuel, the spray front penetration length and spray front penetration velocity decrease with increasing ambient pressure. LN, PRF95 and gasoline show similar penetration length and velocity under the tested conditions. A two-stage spray front fluctuation pattern is observed for all three fuels. Stage one begins from the start of the injection and ends at 450–500 μs after the start of the injection trigger (ASOIT) with a slow

GDI fuel sprays of light naphtha, PRF95 and gasoline using a piezoelectric injector under different ambient pressures

KAUST Repository

Wu, Zengyang

2018-03-20

This study investigates fuel sprays of light naphtha (LN), primary reference fuel (PRF) and gasoline under different ambient pressures with an outwardly opening piezo gasoline direct injection (GDI) fuel injector. The tested gasoline fuel (regular grade with up to 10% ethanol, E10) was obtained by mixing fuels with AKI (the average of the research octane number (RON) and the motor octane number (MON)) of 87 from three local gas stations. Primary reference fuel (PRF) is commonly used as gasoline surrogate fuel and is blended by iso-octane and n-heptane. PRF95 is the blend of 95% iso-octane and 5% n-heptane by volume. LN fuel was provided by Saudi Aramco Oil Company. Five different ambient pressure conditions varied from 1 bar to 10 bar were tested. The spray was visualized by applying a Mie-scattering technique and a high-speed camera was employed to capture the spray images. The spray structure, spray angle, spray penetration length and spray front fluctuation were analyzed and compared among three fuels. Spray images show that a clear filamentary hollow-cone spray structure is formed for all three fuels at atmospheric conditions, and toroidal recirculation vortexes are observed at the downstream spray edges. A higher ambient pressure leads to a stronger vortex located closer to the injector outlet. Generally speaking, larger spray angles are found under higher ambient pressure conditions for all three fuels. Gasoline fuel always has the largest spray angle for each ambient pressure, while PRF95 has the smallest at most time. For each fuel, the spray front penetration length and spray front penetration velocity decrease with increasing ambient pressure. LN, PRF95 and gasoline show similar penetration length and velocity under the tested conditions. A two-stage spray front fluctuation pattern is observed for all three fuels. Stage one begins from the start of the injection and ends at 450–500 μs after the start of the injection trigger (ASOIT) with a slow

Propagation behavior of two transverse surface waves in a three-layer piezoelectric/piezomagnetic structure

Science.gov (United States)

Nie, Guoquan; Liu, Jinxi; Liu, Xianglin

2017-10-01

Propagation of transverse surface waves in a three-layer system consisting of a piezoelectric/piezomagnetic (PE/PM) bi-layer bonded on an elastic half-space is theoretically investigated in this paper. Dispersion relations and mode shapes for transverse surface waves are obtained in closed form under electrically open and shorted boundary conditions at the upper surface. Two transverse surface waves related both to Love-type wave and Bleustein-Gulyaev (B-G) type wave propagating in corresponding three-layer structure are discussed through numerically solving the derived dispersion equation. The results show that Love-type wave possesses the property of multiple modes, it can exist all of the values of wavenumber for every selected thickness ratios regardless of the electrical boundary conditions. The presence of PM interlayer makes the phase velocity of Love-type wave decrease. There exist two modes allowing the propagation of B-G type wave under electrically shorted circuit, while only one mode appears in the case of electrically open circuit. The modes of B-G type wave are combinations of partly normal dispersion and partly anomalous dispersion whether the electrically open or shorted. The existence range of mode for electrically open case is greatly related to the thickness ratios, with the thickness of PM interlayer increasing the wavenumber range for existence of B-G type wave quickly shortened. When the thickness ratio is large enough, the wavenumber range of the second mode for electrically shorted circuit is extremely narrow which can be used to remove as an undesired mode. The propagation behaviors and mode shapes of transverse surface waves can be regulated by the modification of the thickness of PM interlayer. The obtained results provide a theoretical prediction and basis for applications of PE-PM composites and acoustic wave devices.

Transverse structure of the QCD string

International Nuclear Information System (INIS)

Meyer, Harvey B.

2010-01-01

The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length β defined from the slope of its gravitational form factor, is given by (d-1/2πσ)log(β/4r 0 ) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2πσ)log(r/r 0 ). We also obtain predictions for transition form factors among closed-string states.

Lithospheric shear velocity structure of South Island, New Zealand, from amphibious Rayleigh wave tomography

Science.gov (United States)

Ball, Justin S.; Sheehan, Anne F.; Stachnik, Joshua C.; Lin, Fan-Chi; Yeck, William L.; Collins, John A.

2016-05-01

We present a crust and mantle 3-D shear velocity model extending well offshore of New Zealand's South Island, imaging the lithosphere beneath the South Island as well as the Campbell and Challenger Plateaus. Our model is constructed via linearized inversion of both teleseismic (18-70 s period) and ambient noise-based (8-25 s period) Rayleigh wave dispersion measurements. We augment an array of 4 land-based and 29 ocean bottom instruments deployed off the South Island's east and west coasts in 2009-2010 by the Marine Observations of Anisotropy Near Aotearoa experiment with 28 land-based seismometers from New Zealand's permanent GeoNet array. Major features of our shear wave velocity (Vs) model include a low-velocity (Vs 50 km) beneath the central South Island exhibits strong spatial correlation with upper mantle earthquake hypocenters beneath the Alpine Fault. The ~400 km long low-velocity zone we image beneath eastern South Island and the inner Bounty Trough underlies Cenozoic volcanics and the locations of mantle-derived helium measurements, consistent with asthenospheric upwelling in the region.

A Transverse Colectomy is as Safe as an Extended Right or Left Colectomy for Mid-Transverse Colon Cancer.

Science.gov (United States)

Leijssen, Lieve G J; Dinaux, Anne M; Amri, Ramzi; Kunitake, Hiroko; Bordeianou, Liliana G; Berger, David L

2018-03-19

Although extended colectomy is often chosen for patients with transverse colon cancer, the optimal surgical approach for mid-transverse colon cancer has not been established. We identified patients who underwent a transverse (TC) or an extended colectomy (EC) for mid-transverse colon cancer between 2004 and 2014. To adjust for potential selection bias between the groups, a propensity score matching analysis was performed. A total of 103 patients were included, of whom 63% underwent EC (right 47%, left 17%) and 37% TC. EC patients tend to have worse short-term outcomes. Although fewer lymph nodes were harvested after TC, 5-year overall (OS) ad disease-free survival (DFS) was comparable between the groups. When comparing long-term outcomes stage-by-stage, worse OS and DFS were seen in stage-II. All stage-II patients died of a non-cancer-related cause and recurrence occurred in pT4 TC patients who did not receive adjuvant therapy. The propensity-matched cohort demonstrated similar postoperative morbidity, but more laparoscopic procedures in EC. Additionally, TC tumors were correlated with poorer histopathological features and disease recurrence was only seen after TC. Our study underlines the oncological safety of a transverse colectomy for mid-transverse colon cancer. Although TC tumors were associated with poorer histopathological features, survival rates were comparable.

Numerical performance analysis of acoustic Doppler velocity profilers in the wake of an axial-flow marine hydrokinetic turbine

Energy Technology Data Exchange (ETDEWEB)

Richmond, Marshall C.; Harding, Samuel F.; Romero Gomez, Pedro DJ

2015-09-01

The use of acoustic Doppler current profilers (ADCPs) for the characterization of flow conditions in the vicinity of both experimental and full scale marine hydrokinetic (MHK) turbines is becoming increasingly prevalent. The computation of a three dimensional velocity measurement from divergent acoustic beams requires the assumption that the flow conditions are homogeneous between all beams at a particular axial distance from the instrument. In the near wake of MHK devices, the mean fluid motion is observed to be highly spatially dependent as a result of torque generation and energy extraction. This paper examines the performance of ADCP measurements in such scenarios through the modelling of a virtual ADCP (VADCP) instrument in the velocity field in the wake of an MHK turbine resolved using unsteady computational fluid dynamics (CFD). This is achieved by sampling the CFD velocity field at equivalent locations to the sample bins of an ADCP and performing the coordinate transformation from beam coordinates to instrument coordinates and finally to global coordinates. The error in the mean velocity calculated by the VADCP relative to the reference velocity along the instrument axis is calculated for a range of instrument locations and orientations. The stream-wise velocity deficit and tangential swirl velocity caused by the rotor rotation lead to significant misrepresentation of the true flow velocity profiles by the VADCP, with the most significant errors in the transverse (cross-flow) velocity direction.

Studies of the hydrodynamic evolution of matter produced in fluctuations in p-barp collisions and in ultrarelativistic nuclear collisions. II. Transverse-momentum distributions

International Nuclear Information System (INIS)

Kataja, M.; Ruuskanen, P.V.; McLerran, L.D.; von Gersdorff, H.

1986-01-01

We study solutions to the hydrodynamic equations appropriate for ultrarelativistic nuclear collisions. We find that the matter produced in such collisions spends time t>30 fm/c at temperatures larger than 150 MeV. The transverse momentum of protons, kaons, and pions is computed in the central region of ultrarelativistic nuclear collisions. Assuming Bjorken's initial conditions for the hydrodynamic equations, and a bag-model equation of state, we show that the transverse-momentum distribution as a function of dN/dy does reflect properties of the equation of state. We demonstrate that such a distribution approximately scales as a function of (1/A)dN/dy. The relation between p/sub t/ and dN/dy is shown to be significantly altered under different assumptions about the equation of state. The transverse-momentum distribution of heavy hadrons is shown to be much enhanced relative to that of light pions. These distributions are little changed by differences in the assumptions about the initial transverse density and velocity profile. We are unable to fit the observed correlation between p/sub t/ and dE/dy observed in the Japanese-American Cooperative Emulsion Experiment

Transverse angular momentum in topological photonic crystals

Science.gov (United States)

Deng, Wei-Min; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

2018-01-01

Engineering local angular momentum of structured light fields in real space enables applications in many fields, in particular, the realization of unidirectional robust transport in topological photonic crystals with a non-trivial Berry vortex in momentum space. Here, we show transverse angular momentum modes in silicon topological photonic crystals when considering transverse electric polarization. Excited by a chiral external source with either transverse spin angular momentum or transverse phase vortex, robust light flow propagating along opposite directions is observed in several kinds of sharp-turn interfaces between two topologically-distinct silicon photonic crystals. A transverse orbital angular momentum mode with alternating phase vortex exists at the boundary of two such photonic crystals. In addition, unidirectional transport is robust to the working frequency even when the ring size or location of the pseudo-spin source varies in a certain range, leading to the superiority of the broadband photonic device. These findings enable one to make use of transverse angular momentum, a kind of degree of freedom, to achieve unidirectional robust transport in the telecom region and other potential applications in integrated photonic circuits, such as on-chip robust delay lines.

Evaluation of the photocathode laser transverse distribution

Energy Technology Data Exchange (ETDEWEB)

Saisa-ard, Chaipattana [DESY, Zeuthen (Germany); Chiang Mai Univ., Chiang Mai (Thailand); Krasilnikov, Mikhail; Vashchenko, Grygorii [DESY, Zeuthen (Germany)

2016-07-01

Many years experience of electron source developments at the photo injector test facility at DESY in Zeuthen (PITZ) show that the photocathode laser is the one of major tools to produce high brightness electron beams. The transverse distribution of the laser on the photocathode plays a significant role in the high brightness photo injector optimization. However, the imperfections in the laser beam profile according to the deviation from a radially homogeneous profile directly result in transversely distorted charged particle distributions. This includes inhomogeneous core as well as transverse halo which is due to not sharp edges around the core. The laser transverse distribution is measured at PITZ using a virtual cathode:this is a CCD camera located at the position which is optically equivalent to the photocathode position (so called virtual cathode). An algorithm is developed for the evaluation of the experimentally obtained transverse profiles. It fits a flat-top or an inhomogeneous rotational symmetric core with exponentially decaying tails to an experimental distribution. The MATLAB script with implemented algorithm is applied to a set of measured transverse laser distributions. Results of the analysis will be presented.

Generalized Transversal Lightlike Submanifolds of Indefinite Sasakian Manifolds

OpenAIRE

Yaning Wang; Ximin Liu

2012-01-01

We introduce and study generalized transversal lightlike submanifold of indefinite Sasakian manifolds which includes radical and transversal lightlike submanifolds of indefinite Sasakian manifolds as its trivial subcases. A characteristic theorem and a classification theorem of generalized transversal lightlike submanifolds are obtained.

Velocity variations associated with the large 2010 eruption of Merapi volcano, Java, retrieved from seismic multiplets and ambient noise cross-correlation

Science.gov (United States)

Budi-Santoso, Agus; Lesage, Philippe

2016-07-01

We present a study of the seismic velocity variations that occurred in the structure before the large 2010 eruption of Merapi volcano. For the first time to our knowledge, the technique of coda wave interferometry is applied to both families of similar events (multiplets) and to correlation functions of seismic noise. About half of the seismic events recorded at the summit stations belong to one of the ten multiplets identified, including 120 similar events that occurred in the last 20 hr preceding the eruption onset. Daily noise cross-correlation functions (NCF) were calculated for the six pairs of short-period stations available. Using the stretching method, we estimate time-series of apparent velocity variation (AVV) for each multiplet and each pair of stations. No significant velocity change is detected until September 2010. From 10 October to the beginning of the eruption on 26 October, a complex pattern of AVV is observed with amplitude of up to ±1.5 per cent. Velocity decrease is first observed from families of deep events and then from shallow earthquakes. In the same period, AVV with different signs and chronologies are estimated from NCF calculated for various station pairs. The location in the horizontal plane of the velocity perturbations related with the AVV obtained from NCF is estimated by using an approach based on the radiative transfer approximation. Although their spatial resolution is limited, the resulting maps display velocity decrease in the upper part of the edifice in the period 12-25 October. After the eruption onset, the pattern of velocity perturbations is significantly modified with respect to the previous one. We interpret these velocity variations in the framework of a scenario of magmatic intrusion that integrates most observations. The perturbation of the stress field associated with the magma migration can induce both decrease and increase of the seismic velocity of rocks. Thus the detected AVVs can be considered as precursors of

Magnetohydrodynamic simulations of hypersonic flow over a cylinder using axial- and transverse-oriented magnetic dipoles.

Science.gov (United States)

Guarendi, Andrew N; Chandy, Abhilash J

2013-01-01

Numerical simulations of magnetohydrodynamic (MHD) hypersonic flow over a cylinder are presented for axial- and transverse-oriented dipoles with different strengths. ANSYS CFX is used to carry out calculations for steady, laminar flows at a Mach number of 6.1, with a model for electrical conductivity as a function of temperature and pressure. The low magnetic Reynolds number (<1) calculated based on the velocity and length scales in this problem justifies the quasistatic approximation, which assumes negligible effect of velocity on magnetic fields. Therefore, the governing equations employed in the simulations are the compressible Navier-Stokes and the energy equations with MHD-related source terms such as Lorentz force and Joule dissipation. The results demonstrate the ability of the magnetic field to affect the flowfield around the cylinder, which results in an increase in shock stand-off distance and reduction in overall temperature. Also, it is observed that there is a noticeable decrease in drag with the addition of the magnetic field.

Magnetohydrodynamic Simulations of Hypersonic Flow over a Cylinder Using Axial- and Transverse-Oriented Magnetic Dipoles

Directory of Open Access Journals (Sweden)

Andrew N. Guarendi

2013-01-01

Full Text Available Numerical simulations of magnetohydrodynamic (MHD hypersonic flow over a cylinder are presented for axial- and transverse-oriented dipoles with different strengths. ANSYS CFX is used to carry out calculations for steady, laminar flows at a Mach number of 6.1, with a model for electrical conductivity as a function of temperature and pressure. The low magnetic Reynolds number (≪1 calculated based on the velocity and length scales in this problem justifies the quasistatic approximation, which assumes negligible effect of velocity on magnetic fields. Therefore, the governing equations employed in the simulations are the compressible Navier-Stokes and the energy equations with MHD-related source terms such as Lorentz force and Joule dissipation. The results demonstrate the ability of the magnetic field to affect the flowfield around the cylinder, which results in an increase in shock stand-off distance and reduction in overall temperature. Also, it is observed that there is a noticeable decrease in drag with the addition of the magnetic field.

Atmosphere and Ambient Space

DEFF Research Database (Denmark)

Schmidt, Ulrik

Atmosphere and Ambient Space This paper explores the relation between atmosphere and ambient space. Atmosphere and ambient space share many salient properties. They are both ontologically indeterminate, constantly varying and formally diffuse and they are both experienced as a subtle, non......-signifying property of a given space. But from a certain point of view, the two concepts also designate quite dissimilar experiences of space. To be ’ambient’ means to surround. Accordingly, ambient space is that space, which surrounds something or somebody. (Gibson 1987: 65) Since space is essentially...... of a surrounding character, all space can thus be described as having a fundamentally ambient character. So what precisely is an ambient space, then? As I will argue in my presentation, ambient space is a sensory effect of spatiality when a space is experienced as being particularly surrounding: a ‘space effect...

Seismic imaging of the southern California plate-boundary around the South-Central Transverse Ranges using double-difference tomography

Science.gov (United States)

Share, P. E.; Ben-Zion, Y.; Thurber, C. H.; Zhang, H.; Guo, H.

2017-12-01

We derive P and S seismic velocities within and around the South-Central Transverse Ranges section of the San Andreas Fault (SAF), using a new double-difference tomography algorithm incorporating both event-pair and station-pair differential times. The event-pair data can determine high-resolution relative earthquake locations and resolve fine-scale structure in seismogenic zones, whereas station-pair data allow for better absolute locations and higher resolution of structure near the surface where stations are most dense. The tomographic results are based on arrival times of P and S waves generated by 17,753 M>1 local events from 1/1/2010 to 6/30/2015 recorded by 259 stations within a 222 km x 164 km region. The resulting P and S velocity models include low velocities along major fault segments and across-fault velocity contrasts. For example, at depths 50 km parallel to the SAF around Coachella Valley but offset to the NE by 13 km. This is interpreted to mark a dipping section of the SAF that separates granites at depth in the SW from gneisses and schists in the NE. Analysis of fault zone head waves propagating along these sections of the SAF and SJFZ show that major bimaterial interfaces are associated with the observed velocity contrasts. Additional features within the models include elongated low velocity anomalies extending from the SJFZ trifurcation area, which itself has associated low velocity at great depth (>14 km), to the Elsinore Fault in the SW. Moreover, a deep (>13 km) velocity contrast appears beneath the SBB with an east-west strike oblique to both the northern SJFZ and SAF traces. The latter is potentially related to the ancestral Banning Fault, which dips to the north, separating low velocity Pelona schist in the north from high velocity granites in the south.

Growth responses of male broilers subjected to increasing air velocities at high ambient temperatures and a high dew point.

Science.gov (United States)

Dozier, W A; Lott, B D; Branton, S L

2005-06-01

This study examined live performance responses of male broilers to increasing air velocity of 120 and 180 m/min reared under high cyclic temperatures (25-35-25 degrees C) with a 23 degrees C dew point from 21 to 49 d. Birds were reared in an environmental facility containing 2 wind tunnels (4 pens/tunnel) and 6 floor pens (control). At 21 d, 53 birds were placed in each pen of the wind tunnels and control group, respectively, and growth performance was determined weekly. Increasing air velocity from 120 to 180 m/min improved BW and BW gain from 29 to 35, 36 to 42, and 43 to 49 d of age leading to a cumulative advantage of 287 g in BW gain and a 10-point difference in feed conversion from 21 to 49 d of age. Subjecting birds to air velocity improved growth rate, feed consumption, and feed conversion at each weekly interval from 28 to 49 d over the control birds. These results indicate that male broilers approximating 2.0 to 3.0 kg respond to an air velocity of 180 m/min when exposed to high cyclic temperatures.

Chaotic behavior in a relativistic electron beam interacting with a transverse slow electromagnetic wave

International Nuclear Information System (INIS)

Serbeto, A.; Alves, M.V.

1993-01-01

Using a nonlinear set of equations which describes the excitation of a purely transverse slow electromagnetic wave by a relativistic electron beam, it is shown that the system runs from chaotic behavior to a regular stable state due to crisis phenomenon and from stabilized soliton and repeated stabilized explosive solutions to a temporal chaos. These behaviors suggest that the primary mechanism for the saturation of the explosive instability is not only the cubic nonlinear frequency shift as pointed out by many authors until now. The inclusion of the velocity perturbation in the beam charge initial equilibrium state leads the system to these strange behaviors. (author)

Ambient Noise Green's Function Simulation of Long-Period Ground Motions for Reverse Faulting

Science.gov (United States)

Miyake, H.; Beroza, G. C.

2009-12-01

Long-time correlation of ambient seismic noise has been demonstrated as a useful tool for strong ground motion prediction [Prieto and Beroza, 2008]. An important advantage of ambient noise Green's functions is that they can be used for ground motion simulation without resorting to either complex 3-D velocity structure to develop theoretical Green’s functions, or aftershock records for empirical Green’s function analysis. The station-to-station approach inherent to ambient noise Green’s functions imposes some limits to its application, since they are band-limited, applied at the surface, and for a single force. We explore the applicability of this method to strong motion prediction using the 2007 Chuetsu-oki, Japan, earthquake (Mw 6.6, depth = 9 km), which excited long-period ground motions in and around the Kanto basin almost 200 km from the epicenter. We test the performance of ambient noise Green's function for long-period ground motion simulation. We use three components of F-net broadband data at KZK station, which is located near the source region, as a virtual source, and three components of six F-net stations in and around the Kanto basin to calculate the response. An advantage to applying this approach in Japan is that ambient-noise sources are active in diverse directions. The dominant period of the ambient noise for the F-net datasets is mostly 7 s over the year, and amplitudes are largest in winter. This period matches the dominant periods of the Kanto and Niigata basins. For the 9 components of the ambient noise Green’s functions, we have confirmed long-period components corresponding to Love wave and Rayleigh waves that can be used for simulation of the 2007 Chuetsu-oki earthquake. The relative amplitudes, phases, and durations of the ambient noise Green’s functions at the F-net stations in and around the Kanto basin respect to F-net KZK station are fairly well matched with those of the observed ground motions for the 2007 Chuetsu

Natural Frequencies Evaluation on Partially Damaged Building using Ambient Vibration Technique

Science.gov (United States)

Kamarudin, A. F.; Zainal Abidin, M. H.; Daud, M. E.; Noh, M. S. Md; Madun, A.; Ibrahim, A.; Matarul, J.; Mokhatar, S. N.

2018-04-01

Severe damages observed on the school blocks, roads, retaining walls and drainage within the compound of SMK Kundasang Sabah possibly due to the ground movements triggered by the Ranau earthquake in 1991. Ambient vibration measurements were carried on the remaining demolished 3-storey building which partially damaged in order to measure the predominant building frequencies using tri-axial 1 Hz seismometer sensors. Popular methods of Horizontal-to-vertical spectral ratios (HVSR) and Fourier amplitude spectra (FAS) were used to compute the ambient vibration wave fields of each building axes (Transverse or North-South (NS), Longitudinal or East-West (EW) and vertical) into Fourier spectra. Two main modes of translation and torsion were observed from the peaks frequencies obtained at 2.99 to 3.10 Hz (1st mode), 4.85 Hz (2nd mode) and 5.63 to 5.85 Hz (3rd mode). The building experiencing translation modes of bending and shear in the NS and EW directions. It could be seen when the amplitudes tends to increase when the floor are increased. Meanwhile, the torsional bending mode is expected to occur when the deformation amplitudes are found to be increasing horizontally, when moving into partially structural damaged section located on the East wing of building.

Licenciamento ambiental e sustentabilidade

Directory of Open Access Journals (Sweden)

Marcelo Macedo Valinhas

2011-12-01

Full Text Available A sustentabilidade está apoiada principalmente nas dimensões econômica, ambiental e social. No entanto, sem a dimensão política ela não se constrói. Um dos principais instrumentos de comando e controle da política nacional de meio ambiente, o licenciamento ambiental é um processo contínuo de gestão ambiental pública e privada. Analisou-se o processo de licenciamento ambiental como acoplamento estrutural entre os sistemas social, econômico e ambiental. Apesar da constatação de críticas aos mecanismos de comando e controle dos últimos anos, foi verificado que o Estado do Rio de Janeiro tem buscado integrar a política ambiental do Estado à gestão ambiental privada e que esta integração busca atender às demandas dos sistemas sociais e econômicos para as questões ambientais. Em linhas gerais, este caminho segue as estratégias e ações propostas na Agenda 21 brasileira.

Full-Wave Ambient Noise Tomography of the Long Valley Volcanic Region (California)

Science.gov (United States)

Flinders, A. F.; Shelly, D. R.; Dawson, P. B.; Hill, D. P.; Shen, Y.

2017-12-01

In the late 1970s, and throughout the 1990s, Long Valley Caldera (California) experienced intense periods of unrest characterized by uplift of the resurgent dome, earthquake swarms, and CO2 emissions around Mammoth Mountain. While modeling of the uplift and gravity changes support the possibility of new magmatic intrusions beneath the caldera, geologic interpretations conclude that the magmatic system underlying the caldera is moribund. Geophysical studies yield diverse versions of a sizable but poorly resolved low-velocity zone at depth (> 6km), yet whether this zone is indicative of a significant volume of crystal mush, smaller isolated pockets of partial melt, or magmatic fluids, is inconclusive. The nature of this low-velocity zone, and the state of volcano's magmatic system, carry important implications for the significance of resurgent-dome inflation and the nature of associated hazards. To better characterize this low-velocity zone we present preliminary results from a 3D full-waveform ambient-noise seismic tomography model derived from the past 25 years of vertical component broadband and short-period seismic data. This new study uses fully numerical solutions of the wave equation to account for the complex wave propagation in a heterogeneous, 3D earth model, including wave interaction with topography. The method ensures that wave propagation is modeled accurately in 3D, enabling the full use of seismic records. By using empirical Green's functions, derived from ambient noise and modeled as Rayleigh surface waves, we are able to extend model resolution to depths beyond the limits of previous local earthquake studies. The model encompasses not only the Long Valley Caldera, but the entire Long Valley Volcanic Region, including Mammoth Mountain and the Mono Crater/Inyo Domes volcanic chain.

Robotic transverse colectomy for mid-transverse colon cancer: surgical techniques and oncologic outcomes.

Science.gov (United States)

Jung, Kyung Uk; Park, Yoonah; Lee, Kang Young; Sohn, Seung-Kook

2015-06-01

Robot-assisted surgery for colon cancer has been reported in many studies, most of which worked on right and/or sigmoid colectomy. The aim of this study was to report our experience of robotic transverse colectomy with an intracorporeal anastomosis, provide details of the surgical technique, and present the theoretical benefits of the procedure. This is a retrospective review of prospectively collected data of robotic surgery for colorectal cancer performed by a single surgeon between May 2007 and February 2011. Out of 162 consecutive cases, we identified three robotic transverse colectomies, using a hand-sewn intracorporeal anastomosis. Two males and one female underwent transverse colectomies for malignant or premalignant disease. The mean docking time, time spent using the robot, and total operative time were 5, 268, and 307 min, respectively. There were no conversions to open or conventional laparoscopic technique. The mean length of specimen and number of lymph nodes retrieved were 14.1 cm and 6.7, respectively. One patient suffered from a wound seroma and recovered with conservative management. The mean hospital stay was 8.7 days. After a median follow-up of 72 months, there were no local or systemic recurrences. Robotic transverse colectomy seems to be a safe and feasible technique. It may minimize the necessity of mobilizing both colonic flexures, with facilitated intracorporeal hand-sewn anastomosis. However, further prospective studies with a larger number of patients are required to draw firm conclusions.

Signals for transversity and transverse-momentum-dependent quark distribution functions studied at the HERMES experiment

Energy Technology Data Exchange (ETDEWEB)

Diefenthaler, Markus

2010-08-15

Intention of the present thesis was the study of transverse-momentum dependent quark distribution functions. In the focus stood the Fourier analysis of azimutal single-spin asymmetries of pions and charged kaons performed within the HERMES experiment. These asymmetries were reconstructed from deep-inelastic scattering events on a transversely polarized proton target and decomposed in Fourier components. In the framework of quantum chromodynamics such components can be interpreted as folding of quark distribution and fragmentation functions. By the analysis of the transverse-momentum dependent quark distribution functions the study of spin-orbit correlations in the internal of the nucleon was made possible. By this conclusions on the orbital angular momentum of the quarks can be drawn. The extracted Fourier components extend the hitherto available informations on the transverse-momentum dependent quark distribution functions remarkably. The presented Fourier analysis made not only a detection of the Collins and Sivers effects possible, but beyond the extraction of the signals of the pretzelosity and worm-gear distributions. The so obtained results will conclusively contribute to the understanding of future measurements in this field and furthermore make possible a test of fundamental predictions of quantum chromodynamics.

Ferroelectric Cathodes in Transverse Magnetic Fields

International Nuclear Information System (INIS)

Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

2002-01-01

Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode

Improved accuracy in the estimation of blood velocity vectors using matched filtering

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt; Gori, P.

2000-01-01

the flow and the ultrasound beam (30, 45, 60, and 90 degrees). The parabolic flow has a peak velocity of 0.5 m/s and the pulse repetition frequency is 3.5 kHz. Simulating twenty emissions and calculating the cross-correlation using four pulse-echo lines for each estimate, the parabolic flow profile...... is found with a standard deviation of 0.014 m/s at 45 degrees (corresponding to an accuracy of 2.8%) and 0.022 m/s (corresponding to an accuracy of 4.4%) at 90 degrees, which is transverse to the ultrasound beam....

Percepción de los riesgos psicosociales ocasionados por el medio ambiente laboral en la profesión docente colombiana

OpenAIRE

Torres Gómez, Ana C.

2013-01-01

Tesis (Maestría en Gerencia del Talento Humano). Universidad de Manizales. Facultad de Psicología, 2013 La siguiente alternativa de investigación se enmarca en el macroproyecto WONPUM y su objetivo principal es describir la percepción que tienen los docentes de algunas instituciones educativas colombianas acerca del ambiente laboral o entorno físico. Contó con un diseño descriptivo, transversal y relacional que pretendió caracterizar algunos aspectos cualitativos y cuantitativos de la perc...

Nucleon Spin Structure: Longitudinal and Transverse

International Nuclear Information System (INIS)

Chen, Jian-Ping

2011-01-01

Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinal polarized parton (quark and gluon) distributions in the nucleon. It has becoming clear that transverse spin and transverse momentum dependent distributions (TMDs) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction. The transverse spin structure and the TMDs are the subject of increasingly intense theoretical and experimental study recently. With a high luminosity electron beam facility, JLab has played a major role in the worldwide effort to study both the longitudinal and transverse spin structure. Highlights of recent results will be presented. With 12-GeV energy upgrade, JLab will provide the most precise measurements in the valence quark region to close a chapter in longitudinal spin study. JLab will also perform a multi-dimensional mapping of the transverse spin structure and TMDs in the valence quark region through Semi-Inclusive DIS (SIDIS) experiments, providing a 3-d partonic picture of the nucleon in momentum space and extracting the u and d quark tensor charges of the nucleon. The precision mapping of TMDs will also allow a detailed study of the quark orbital motion and its dynamics.

Saúde Ambiental: uma Análise dos Resultados das Conferências Nacionais de Meio Ambiente, Saúde e Saúde Ambiental

Directory of Open Access Journals (Sweden)

Maria Beatriz Maury de Carvalho

2010-08-01

Full Text Available A representação nas políticas públicas do conceito de saúde ambiental, como expressão do equilíbrio da rede de conexões entre a sociedade humana e a natureza é discutida neste trabalho, no intuito de demonstrar o status quo da saúde ambiental nas políticas públicas no país. Primeiro foi traçado o histórico da “ambientalização na saúde”, do conceito de saúde ambiental e da institucionalização das políticas ambientais e de saúde ambiental no âmbito dos Ministérios do Meio Ambiente e da Saúde. As interações entre as políticas de Saúde e de Meio Ambiente para a efetivação de uma Política Nacional de Saúde Ambiental e as intersecções dos resultados das Conferências Nacionais de Saúde, Meio Ambiente e Saúde Ambiental foram analisadas; concluindo- se com os avanços conseguidos pelos dois setores, os desafios para a articulação intersetorial e a participação social para a construção de políticas públicas de saúde ambiental.

Transversity GPD in photo- and electroproduction of two vectormesons

Energy Technology Data Exchange (ETDEWEB)

Enberg, Rikard; Pire, Bernard; Szymanowski, Lech

2006-01-17

The chiral-odd generalized parton distribution (GPD), or transversity GPD, of the nucleon can be accessed experimentally through the photo- or electroproduction of two vector mesons on a polarized nucleon target, {gamma}{sup (*)}N {yields} {rho}{sub 1}{rho}{sub 2}N', where {rho}{sub 1} is produced at large transverse momentum, {rho}{sub 2} is transversely polarized, and the mesons are separated by a large rapidity gap. We predict the cross section for this process for both transverse and longitudinal {rho}{sub 2} production. To this end we propose a model for the transversity GPDH{sub T}(x,{zeta},t), and give an estimate of the relative sizes of the transverse and longitudinal {rho}{sub 2}cross sections. We show that a dedicated experiment at high energy should be able to measure the transversity content of the proton.

A transverse lattice QCD model for mesons

Energy Technology Data Exchange (ETDEWEB)

Patel, Apoorva D.; Ratabole, Raghunath

2004-03-01

QCD is analysed with two light-front continuum dimensions and two transverse lattice dimensions. In the limit of large number of colours and strong transverse gauge coupling, the contributions of light-front and transverse directions factorise in the dynamics, and the theory can be analytically solved in a closed form. An integral equation is obtained, describing the properties of mesons, which generalises the 't Hooft equation by including spin degrees of freedom. The meson spectrum, light-front wavefunctions and form factors can be obtained by solving this equation numerically. These results would be a good starting point to model QCD observables which only weakly depend on transverse directions, e.g. deep inelastic scattering structure functions.

Constituent models and large transverse momentum reactions

International Nuclear Information System (INIS)

Brodsky, S.J.

1975-01-01

The discussion of constituent models and large transverse momentum reactions includes the structure of hard scattering models, dimensional counting rules for large transverse momentum reactions, dimensional counting and exclusive processes, the deuteron form factor, applications to inclusive reactions, predictions for meson and photon beams, the charge-cubed test for the e/sup +-/p → e/sup +-/γX asymmetry, the quasi-elastic peak in inclusive hadronic reactions, correlations, and the multiplicity bump at large transverse momentum. Also covered are the partition method for bound state calculations, proofs of dimensional counting, minimal neutralization and quark--quark scattering, the development of the constituent interchange model, and the A dependence of high transverse momentum reactions

Transverse magnetization and giant magnetoimpedance in amorphous ribbons

International Nuclear Information System (INIS)

Orue, I.; Garcia-Arribas, A.; Saad, A.; Cos, D. de; Barandiaran, J.M.

2005-01-01

In the classical approach giant magnetoimpedance (GMI) is driven by the transverse permeability of the sample, as excited by the current flowing through it. Transverse permeability is usually taken as a constant, while detailed magnetization processes are important for the interpretation of GMI data. In most cases the transverse permeability (or magnetization) is only guessed by looking at the longitudinal magnetization curve and direct determinations of such parameter are scarce in the literature. In this work we report on the operation of a simple setup which provides the transverse magnetization of amorphous ribbons as a function of the current intensity flowing through it, by means of the magnetooptical kerr effect (MOKE). The system has been tested on low magnetostriction amorphous ribbons of very soft character with both longitudinal and transverse anisotropy. The transverse magnetization as a function of both the current and a DC longitudinal field applied, was compared with magneto impedance measurements

Ambient Noise in an Urbanized Tidal Channel

Science.gov (United States)

Bassett, Christopher

levels that shows good agreement with 85% of the temporal data. Bed stresses associated with currents can produce propagating ambient noise by mobilizing sediments. The strength of the tidal currents in northern Admiralty Inlet produces bed stresses in excess of 20 Pa. Significant increases in noise levels at frequencies from 4-30 kHz, with more modest increases noted from 1-4 kHz, are attributed to mobilized sediments. Sediment-generated noise during strong currents masks background noise from other sources, including vessel traffic. Inversions of the acoustic spectra for equivalent grain sizes are consistent with qualitative observations of the seabed composition. Bed stress calculations using log layer, Reynolds stress, and inertial dissipation techniques generally agree well and are used to estimate the shear stresses at which noise levels increase for different grain sizes. Ambient noise levels in one-third octave bands with center frequencies from 1 kHz to 25 kHz are dominated by sediment-generated noise and can be accurately predicted using the near-bed current velocity above a critical threshold. When turbulence is advected over a pressure sensitive transducer, the turbulent pressure fluctuations can be measured as noise, though these pressure fluctuations are not propagating sound and should not be interpreted as ambient noise. Based on measurements in both Admiralty Inlet, Puget Sound and the Chacao Channel, Chile, two models are developed for flow-noise. The first model combined measurements of mean current velocities and turbulence and agrees well with data from both sites. The second model uses scaling arguments to model the flow-noise based solely on the mean current velocity. This model agrees well with the data from the Chacao Channel but performs poorly in Admiralty Inlet, a difference attributed to differences turbulence production mechanisms. At both sites, the spectral slope of flow noise follows a f-3.2 dependence, suggesting partial cancellation of

The transverse momenta in the exclusive reactions at intermediate energies a parameter to mesure the transversity

International Nuclear Information System (INIS)

Armenise, N.; Fogli Muciaccia, M.T.; Nuzzo, S.

1977-01-01

The definition of a parameter usefull to measure the transversity is given. Some reactions at 9GeV/c are examined and the channels are selected looking at the behaviour of global transverse momenta of the event. A few comparisons with other variables, used to select the channels characterized by different production processes are reported

An Ice Track Equipped with Optical Sensors for Determining the Influence of Experimental Conditions on the Sliding Velocity

Science.gov (United States)

Lungevics, J.; Jansons, E.; Gross, K. A.

2018-02-01

The ability to slide on ice has previously focused on the measurement of friction coefficient rather than the actual sliding velocity that is affected by it. The performance can only be directly measured by the sliding velocity, and therefore the objective was to design and setup a facility to measure velo-city, and determine how experimental conditions affect it. Optical sensors were placed on an angled ice track to provide sliding velocity measurements along three sections and the velocity for the total sliding distance. Experimental conditions included the surface roughness, ambient temperature and load. The effect of roughness was best reported with a Criterion of Contact that showed a similar sliding velocity for metal blocks abraded with sand paper smoother than 600 grit. Searching for the effect of temperature, the highest sliding velocity coincided with the previously reported lowest coefficient of ice friction. Load showed the greatest velocity increase at temperatures closer to the ice melting point suggesting that in such conditions metal block overcame friction forces more easily than in solid friction. Further research needs to be conducted on a longer ice track, with larger metal surfaces, heavier loads and higher velocities to determine how laboratory experiments can predict real-life situations.

An Ice Track Equipped with Optical Sensors for Determining the Influence of Experimental Conditions on the Sliding Velocity

Directory of Open Access Journals (Sweden)

Lungevics J.

2018-02-01

Full Text Available The ability to slide on ice has previously focused on the measurement of friction coefficient rather than the actual sliding velocity that is affected by it. The performance can only be directly measured by the sliding velocity, and therefore the objective was to design and setup a facility to measure velo-city, and determine how experimental conditions affect it. Optical sensors were placed on an angled ice track to provide sliding velocity measurements along three sections and the velocity for the total sliding distance. Experimental conditions included the surface roughness, ambient temperature and load. The effect of roughness was best reported with a Criterion of Contact that showed a similar sliding velocity for metal blocks abraded with sand paper smoother than 600 grit. Searching for the effect of temperature, the highest sliding velocity coincided with the previously reported lowest coefficient of ice friction. Load showed the greatest velocity increase at temperatures closer to the ice melting point suggesting that in such conditions metal block overcame friction forces more easily than in solid friction. Further research needs to be conducted on a longer ice track, with larger metal surfaces, heavier loads and higher velocities to determine how laboratory experiments can predict real-life situations.

Time dependent response of low velocity impact induced composite conical shells under multiple delamination

Science.gov (United States)

Dey, Sudip; Karmakar, Amit

2014-02-01

This paper presents the time dependent response of multiple delaminated angle-ply composite pretwisted conical shells subjected to low velocity normal impact. The finite element formulation is based on Mindlin's theory incorporating rotary inertia and effects of transverse shear deformation. An eight-noded isoparametric plate bending element is employed to satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. A multipoint constraint algorithm is incorporated which leads to asymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark's time integration algorithm. Parametric studies are conducted with respect to triggering parameters like laminate configuration, location of delamination, angle of twist, velocity of impactor, and impactor's displacement for centrally impacted shells.

Factors affecting the transverse force measurements of an optical trap: I

Science.gov (United States)

Wood, Tiffany A.; Wright, Amanda; Gleeson, Helen F.; Dickenson, Mark; Mullin, Tom; Murray, Andrew

2002-03-01

The transverse force of an optical trap is usually measured by equating the trapping force to the viscous drag force applied to the trapped particle according to Stokes' Law. Under normal conditions, the viscous drag force on a trapped particle is proportional to the fluid velocity of the medium. In this paper we show that an increase of particle concentration within the medium affects force measurements. In order to trap the particle, 1064 nm light from a Nd:YVO4 laser was brought to a focus in a sample slide, of thickness around 380 microns, by using an inverted Zeiss microscope objective, with NA equals 1.3. The slide was filled with distilled water containing 6 micron diameter polystyrene spheres. Measurements were taken at a fluid velocity of 0.75 microns/sec, achieved by moving the sample stage with a piezo-electric transducer whilst a particle was held stationary in the trap. The laser power required to hold a sphere at different trap depths for various concentrations was measured. Significant weakening of the trap was found for concentrations >0.03% solids by weight, becoming weaker for higher trap depths. These results are explained in terms of aberrations, particle-particle interactions and distortion of the beam due to particle-light interactions.

Eurisol-DS Multi MW Target Preliminary Study of the Windlowless Transverse Film (WTF) Liquid Metal Proton-to Neutron Converter

CERN Document Server

Kadi, Y; Rocca, R; Samec, K

2008-01-01

This technical note summarises the design calculations performed within Task#2 of the European Isotope Separation On-Line Radioactive Ion Beam Facility Design Study (EURISOL-DS) for the WTF (Windowless Transverse Film) mercur converter. A preliminary study was carried out in order to determine the heat deposition within the mercury and estimate the mercury velocity needed in the film. The geometry used is based on previous analysis simulated using the Monte Carlo code FLUKA. The results of these calculations show the baseline parameters, which will be used for the detailed design. Particularly, with a 1 GeV proton beam with a $\\sigma$ ~2 mm Gaussian distribution on a 4x30x40cm long target and with a 5m/s velocity at the peak power density region seems a suitable solution.

Normal forms for Poisson maps and symplectic groupoids around Poisson transversals.

Science.gov (United States)

Frejlich, Pedro; Mărcuț, Ioan

2018-01-01

Poisson transversals are submanifolds in a Poisson manifold which intersect all symplectic leaves transversally and symplectically. In this communication, we prove a normal form theorem for Poisson maps around Poisson transversals. A Poisson map pulls a Poisson transversal back to a Poisson transversal, and our first main result states that simultaneous normal forms exist around such transversals, for which the Poisson map becomes transversally linear, and intertwines the normal form data of the transversals. Our second result concerns symplectic integrations. We prove that a neighborhood of a Poisson transversal is integrable exactly when the Poisson transversal itself is integrable, and in that case we prove a normal form theorem for the symplectic groupoid around its restriction to the Poisson transversal, which puts all structure maps in normal form. We conclude by illustrating our results with examples arising from Lie algebras.

Det ambiente

DEFF Research Database (Denmark)

Schmidt, Ulrik

Om begrebet "det ambiente", der beskriver, hvad der sker, når vi fornemmer baggrundsmusikkens diskrete beats, betragter udsigten gennem panoramavinduet eller tager 3D-brillerne på og læner os tilbage i biografsædet. Bogen analyserer, hvorfan ambiente oplevelser skabes, og hvilke konsekvenser det...

Ambient Sensors

NARCIS (Netherlands)

Börner, Dirk; Specht, Marcus

2014-01-01

This software sketches comprise two custom-built ambient sensors, i.e. a noise and a movement sensor. Both sensors measure an ambient value and process the values to a color gradient (green > yellow > red). The sensors were built using the Processing 1.5.1 development environment. Available under

Transverse deflections of an elastic spherical shell as a function of transverse and tangential loads

DEFF Research Database (Denmark)

Niordson, Christian F.; Nielsen, S.B.

2006-01-01

of the transverse deflection is modified by in-plane tectonic forces originating e.g. at plate boundaries. However, geoscience applications of the coupling between transverse deflections and boundary conditions have been restricted to the one-dimensional thin-plate model. In this paper we extend the model...

Transverse betatron tune measurements

International Nuclear Information System (INIS)

Serio, M.

1989-01-01

In this paper the concept of the betatron tune and the techniques to measure it are discussed. The smooth approximation is introduced along with the terminology of betatron oscillations, phase advance and tune. Single particle and beam spectra in the presence of synchro-betatron oscillations are treated with emphasis on the consequences of sampling the beam position. After a general presentation of various kinds of beam position monitors and transverse kickers, the time domain and frequency domain analysis of the beam response to a transverse excitation are discussed and several methods and applications of the tune measurements are listed

Pedagogía ambiental y didáctica ambiental como fundamentos del currículo para la formación ambiental

OpenAIRE

Julio César Tovar-Gálvez

2013-01-01

Se trata el problema de la fundamentación del currículo para la formación ambiental en la educación superior, frente a lo cual es necesario construir los conceptos de pedagogía ambiental y de didáctica ambiental. El marco teórico permite definir las categorías "lo pedagógico" y "lo didáctico", a partir de lo cual se analiza la literatura y con ello definir pedagogía ambiental y didáctica ambiental. El estado del arte permite establecer que existen dos sustentos teóricos: a) uno que se cimenta...

Observations of high-velocity molecular gas near Herbig-Haro objects: HH 24--27 and HH 1--2

International Nuclear Information System (INIS)

Snell, R.L.; Edwards, S.

1982-01-01

High-velocity CO has been detected in the vicinity of the Herbig-Haro objects HH 24--27. These observations indicate that there are two sources of high-velocity outflow; one centered on an infrared source near HH 26, and the second centered roughly 2' south of HH 24. The redshifted and blueshifted wings in both sources are spatially separated suggesting that the high-velocity gas is due to energetic bipolar outflow from young stars embedded in the molecular cloud. The association of Herbig-Haro objects with regions of high-velocity gas suggests a common origin for both in the interaction of a stellar wind with the ambient molecular cloud. The mass loss rates implied by our observations, assuming that the rate of mass loss has been constant throughout the dynamical lifetime of the bipolar lobes, are roughly 10 -6 M/sub sun/ yr -1 for both sources. We have also searched for high-velocity gas near HH 1--2 but found no evidence for mass outflow in this region

Large transverse momentum behavior of gauge theories

International Nuclear Information System (INIS)

Coquereaux, Robert; De Rafael, Eduardo.

1977-05-01

The large transverse momentum behavior of Compton scattering and Moeller scattering in Quantum Electrodynamics; and of elastic quark-quark scattering in Quantum Chromodynamics are examined in perturbation theory. The results strongly suggest that the large transverse momentum regime in gauge theories is governed by a differential equation of the Callan-Symanzik type with a suitable momentum dependent anomalous dimension term. An explicit solution for the quark-quark elastic scattering amplitude at large transverse momentum is given

Longitudinal and transverse wake potentials in SLAC

International Nuclear Information System (INIS)

Bane, K.; Wilson, P.

1980-01-01

In a machine with short bunches of high peak currents, such as the SLAC collider, one needs to know the longitudinal wake potential, for the higher mode losses, and the transverse wake potential, since, for bunches passing slightly off axis, the induced transverse forces will tend to cause beam break up. The longitudinal and transverse wakes of the SLAC structure presented here, were calculated by computer using the modal method, and including an analytic extension for higher modes. (Auth.)

Numerical investigation of a plasma beam entering transverse magnetic fields

International Nuclear Information System (INIS)

Koga, J.; Geary, J.L.; Tajima, T.; Rostoker, N.

1988-11-01

We study plasma beam injection into transverse magnetic fields using both electrostatic and electromagnetic particle-in-cell (PIC) codes. In the case of small beam momentum or energy (low drift kinetic /beta/) we study both large and small ion gyroradius beams. Large ion gyroradius beams with a large dielectric constant /epsilon/ /muchreverse arrowgt/ (M/m)/sup /1/2// are found to propagate across the magnetic field via E /times/ B drifts at nearly the initial injection velocity, where /epsilon/ = 1 + (/omega//sup pi//sup 2/)/(/Omega//sub i//sup 2/) and (M/m) is the ion to electron mass ratio. Beam degradation and undulations are observed in agreement with previous experimental and analytical results. When /epsilon/ is on the order of (M/m)/sup /1/2//, the plasma beam propagates across field lines at only half its initial velocity and loses its coherent structure. When /epsilon/ is much less than (M/m)/sup /1/2//, the beam particles decouple at the magnetic field boundary, scattering the electrons and slightly deflecting the ions. For small ion gyroradius beam injection a flute type instability is observed at the beam magnetic fields interface. In the case of large beam momentum or energy (high drift kinetic /beta/) we observe good penetration of a plasma beam which shields the magnetic field from the interior of the beam (diagmagnetism). 25 refs., 13 figs., 1 tab

MR imaging of alar and transverse atlantal ligament injuries

Energy Technology Data Exchange (ETDEWEB)

Echigoya, Naoki; Harata, Seiko; Ueyama, Kazumasa (Hirosaki Univ., Aomori (Japan). School of Medicine); Nakano, Keisuke

1992-06-01

Autopsy findings of ligaments of the upper cervical spine were compared with magnetic resonance imaging (MRI) findings. Ligaments were clearly shown as hypointensity on T1-weighted images and proton density images. Transverse images were useful in diagnosing alar and transverse atlantal ligament injuries. When there is a bilateral difference in the alar ligaments, ruptured ligament is suspected. Transverse ligament rupture was shown on interrupted hypointensity and as hyperintensity. MRI was capable of diagnosing alar ligament rupture in 8 of 11 patients, and transverse ligament rupture in all 3 patients. In 2 patients having Jefferson's fracture and injuried atlanoaxial subluxation encountered in the clinical practice, transverse ligament rupture was similarly observed as that in autopsy cases on MR images. Hyperintensity in the transverse ligament rupture area was seen even one year after injury. Injured transverse ligament was seen as swollen hyperintensity on sagittal images; and the hyperintensity was gradually decreased with the process of healing. (N.K.).

Strange hadron production at low transverse momenta

Science.gov (United States)

Veres, Gábor I.; PHOBOS Collaboration; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Becker, B.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Harrington, A. S.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Lee, J. W.; Lin, W. T.; Manly, S.; Mignerey, A. C.; Noell, A.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Roland, C.; Roland, G.; Sagerer, J.; Sarin, P.; Sawicki, P.; Sedykh, I.; Skulski, W.; Smith, C. E.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Teng, R.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wadsworth, B.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wyslouch, B.; Zhang, J.

2004-01-01

Some of the latest results of the PHOBOS experiment from the \\sqrt{s_{NN}}= 200\\ GeV Au+Au data are discussed. Those relevant to strangeness production are emphasized. These observations relate to the nature of the matter created when heavy ions collide at the highest achieved energy. The invariant yields of strange and non-strange charged hadrons at very low transverse momentum have been measured, and used to differentiate between different dynamical scenarios. In the intermediate transverse momentum range, the measured ratios of strange and anti-strange kaons approach one, while the antibaryon to baryon ratio is still significantly less, independent of collision centrality and transverse momentum. At high transverse momenta, we find that central and peripheral Au+Au collisions produce similar numbers of charged hadrons per participant nucleon pair, rather than per binary nucleon-nucleon collision. Finally, we describe the upgrades of PHOBOS completed for the 2003 d+Au and p+p run, which extend the transverse momentum range over which particle identification is possible and, at the same time, implement a trigger system selective for high-pT particles.

How does tissue preparation affect skeletal muscle transverse isotropy?

Science.gov (United States)

Wheatley, Benjamin B.; Odegard, Gregory M.; Kaufman, Kenton R.; Haut Donahue, Tammy L.

2016-01-01

The passive tensile properties of skeletal muscle play a key role in its physiological function. Previous research has identified conflicting reports of muscle transverse isotropy, with some data suggesting the longitudinal direction is stiffest, while others show the transverse direction is stiffest. Accurate constitutive models of skeletal muscle must be employed to provide correct recommendations for and observations of clinical methods. The goal of this work was to identify transversely isotropic tensile muscle properties as a function of post mortem handling. Six pairs of tibialis anterior muscles were harvested from Giant Flemish rabbits and split into two groups: fresh testing (within four hours post mortem), and non-fresh testing (subject to delayed testing and a freeze/thaw cycle). Longitudinal and transverse samples were removed from each muscle and tested to identify tensile modulus and relaxation behavior. Longitudinal non-fresh samples exhibited a higher initial modulus value and faster relaxation than longitudinal fresh, transverse fresh, and transverse rigor samples (p<0.05), while longitudinal fresh samples were less stiff at lower strain levels than longitudinal non-fresh, transverse fresh, and transverse non-fresh samples (p<0.05), but exhibited more nonlinear behavior. While fresh skeletal muscle exhibits a higher transverse modulus than longitudinal modulus, discrepancies in previously published data may be the result of a number of differences in experimental protocol. Constitutive modeling of fresh muscle should reflect these data by identifying the material as truly transversely isotropic and not as an isotropic matrix reinforced with fibers. PMID:27425557

Radical Transversal Lightlike Submanifolds of Indefinite Para-Sasakian Manifolds

OpenAIRE

Shukla S.S.; Yadav Akhilesh

2014-01-01

In this paper, we study radical transversal lightlike submanifolds and screen slant radical transversal lightlike submanifolds of indefinite para-Sasakian manifolds giving some non-trivial examples of these submanifolds. Integrability conditions of distributions D and RadTM on radical transversal lightlike submanifolds and screen slant radical transversal lightlike submanifolds of indefinite para-Sasakian manifolds, have been obtained. We also study totally contact umbilical radical transvers...

TWITCH PARAMETERS IN TRANSVERSAL AND LONGITUDINAL BICEPS BRACHII RESPONSE

Directory of Open Access Journals (Sweden)

Boštjan Šimunič

2010-01-01

Full Text Available Assessment of the contractile properties of skeletal muscles is continuing to be an important issue and a difficult task methodologically. Longitudinal direction of skeletal muscle contraction blurs intrinsic muscle belly contractile properties with many factors. This study evaluates and explains contractile properties such as: delay time (Td, contraction time (Tc, half relaxation time (Tr and maximal amplitude (Dm extracted from twitch transversal response and compare them with torque response. In fifteen healthy males (age 23.7 ± 3.4 years isometric twitch transversal and torque responses were simultaneously recorded during graded electrically elicited contractions in the biceps brachii muscle. The amplitude of electrical stimulation was increased in 5 mA steps from a threshold up to a maximal response. The muscles’ belly transversal response was measured by a high precision mechanical displacement sensor while elbow joint torque was calculated from force readings. Results indicate a parabolic relation between the transversal displacement and the torque Dm. A significantly shorter Tc was found in transversal response without being correlated to torque Tc (r = -0.12; > 0.05. A significant correlation was found between torque Tc and the time occurrence of the second peak in the transversal response (r = 0.83; < 0.001. Electrical stimulation amplitude dependant variation of the Tc was notably different in transversal than in torque response. Td was similar at submaximal and maximal responses but larger in transversal at just above threshold contractions. Tr has a similar linear trend in both responses, however, the magnitude and the slope are much larger in the transversal response. We could conclude that different mechanisms affect longitudinal and transversal twitch skeletal muscle deformations. Contractile properties extracted from the transversal response enable alternative insights into skeletal muscle contraction mechanics.

Cladding For Transversely-Pumped Laser Rod

Science.gov (United States)

Byer, Robert L.; Fan, Tso Yee

1989-01-01

Combination of suitable dimensioning and cladding of neodymium:yttrium aluminum garnet of similar solid-state laser provides for more efficient utilization of transversely-incident pump light from diode lasers. New design overcomes some of limitations of longitudinal- and older transverse-pumping concepts and promotes operation at higher output powers in TEM00 mode.

Types for BioAmbients

Directory of Open Access Journals (Sweden)

Sara Capecchi

2010-02-01

Full Text Available The BioAmbients calculus is a process algebra suitable for representing compartmentalization, molecular localization and movements between compartments. In this paper we enrich this calculus with a static type system classifying each ambient with group types specifying the kind of compartments in which the ambient can stay. The type system ensures that, in a well-typed process, ambients cannot be nested in a way that violates the type hierarchy. Exploiting the information given by the group types, we also extend the operational semantics of BioAmbients with rules signalling errors that may derive from undesired ambients' moves (i.e. merging incompatible tissues. Thus, the signal of errors can help the modeller to detect and locate unwanted situations that may arise in a biological system, and give practical hints on how to avoid the undesired behaviour.

Design Strategy for CO2 Adsorption from Ambient Air Using a Supported Amine Based Sorbent in a Fixed Bed Reactor

NARCIS (Netherlands)

Yu, Qian; Brilman, D. W.F.

In this work, a fixed bed reactor is evaluated for CO2 capture from ambient air using an amine based ion exchange resin. Using adsorption experiments, the effect of superficial velocity and bed length on process economics is investigated. It is shown that the optimal conditions are found at an

Structure of Kinetic Alfvén Waves of Small Transverse Scale

Science.gov (United States)

Morales, G. J.; Maggs, J. E.

1996-11-01

This analytical study illustrates the spatial pattern of kinetic Alfvén waves excited by a current-modulating disk whose dimension R transverse to the confining magnetic field is comparable to cs / Ω_i. The radial structure of the wave azimuthal magnetic field consists of 3 regions: a Bessel function behavior for r > R. The pattern spreads at an angle given by tan θ = (ω/Ω_i)(c_s/V_A)/(2 \\cdot 6), where ω is the modulation frequency and VA the Alfvén speed. This arises because there is a maximum value at finite k_⊥ for the ratio of the perpendicular to parallel group velocity, which differs from the cone spreading(G.J. Morales, R.S. Loritsch, and J.E. Maggs, Phys. Plasmas) 1, 3765 (1994) associated with inertial Alfvén waves. Sponsored by ONR

The Potential for Ambient Plasma Wave Propulsion

Science.gov (United States)

Gilland, James H.; Williams, George J.

2016-01-01

A truly robust space exploration program will need to make use of in-situ resources as much as possible to make the endeavor affordable. Most space propulsion concepts are saddled with one fundamental burden; the propellant needed to produce momentum. The most advanced propulsion systems currently in use utilize electric and/or magnetic fields to accelerate ionized propellant. However, significant planetary exploration missions in the coming decades, such as the now canceled Jupiter Icy Moons Orbiter, are restricted by propellant mass and propulsion system lifetimes, using even the most optimistic projections of performance. These electric propulsion vehicles are inherently limited in flexibility at their final destination, due to propulsion system wear, propellant requirements, and the relatively low acceleration of the vehicle. A few concepts are able to utilize the environment around them to produce thrust: Solar or magnetic sails and, with certain restrictions, electrodynamic tethers. These concepts focus primarily on using the solar wind or ambient magnetic fields to generate thrust. Technically immature, quasi-propellantless alternatives lack either the sensitivity or the power to provide significant maneuvering. An additional resource to be considered is the ambient plasma and magnetic fields in solar and planetary magnetospheres. These environments, such as those around the Sun or Jupiter, have been shown to host a variety of plasma waves. Plasma wave propulsion takes advantage of an observed astrophysical and terrestrial phenomenon: Alfven waves. These are waves that propagate in the plasma and magnetic fields around and between planets and stars. The generation of Alfven waves in ambient magnetic and plasma fields to generate thrust is proposed as a truly propellantless propulsion system which may enable an entirely new matrix of exploration missions. Alfven waves are well known, transverse electromagnetic waves that propagate in magnetized plasmas at

Recent advances in blood flow vector velocity imaging

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt; Nikolov, Svetoslav; Udesen, Jesper

2011-01-01

tracking. The key advantages of these techniques are very fast imaging that can attain an order of magnitude higher precision than conventional methods. SA flow imaging was implemented on the experimental scanner RASMUS using an 8-emission spherical emission sequence and reception of 64 channels on a BK...... investigated using both simulations, flow rig measurements, and in-vivo validation against MR scans. The TO method obtains a relative accuracy of 10% for a fully transverse flow in both simulations and flow rig experiments. In-vivo studies performed on 11 healthy volunteers comparing the TO method...... been acquired using a commercial implementation of the method (BK Medical ProFocus Ultraview scanner). A range of other methods are also presented. This includes synthetic aperture imaging using either spherical or plane waves with velocity estimation performed with directional beamforming or speckle...

Rayleigh and Love Wave Phase Velocities in the Northern Gulf Coast of the United States

Science.gov (United States)

Li, A.; Yao, Y.

2017-12-01

The last major tectonic event in the northern Gulf Coast of the United States is Mesozoic continental rifting that formed the Gulf of Mexico. This area also experienced igneous activity and local uplifts during Cretaceous. To investigate lithosphere evolution associated with the rifting and igneous activity, we construct Rayleigh and Love wave phase velocity models at the periods of 6 s to 125 s in the northern Gulf Coast from Louisiana to Alabama including the eastern Ouachita and southern Appalachian orogeny. The phase velocities are derived from ambient noise and earthquake data recorded at the 120 USArray Transportable Array stations. At periods below 20 s, phase velocity maps are characterized by significant low velocities in the Interior Salt Basin and Gulf Coast Basin, reflecting the effects of thick sediments. The northern Louisiana and southern Arkansas are imaged as a low velocity anomaly in Rayleigh wave models but a high velocity anomaly of Love wave at the periods of 14 s to 30 s, indicating strong lower crust extension to the Ouachita front. High velocity is present in the Mississippi Valley Graben from period 20 s to 35 s, probably reflecting a thin crust or high-velocity lower crust. At longer periods, low velocities are along the Mississippi River to the Gulf Coast Basin, and high velocity anomaly mainly locates in the Black Warrior Basin between the Ouachita Belt and Appalachian Orogeny. The magnitude of anomalies in Love wave images is much smaller than that in Rayleigh wave models, which is probably due to radial anisotropy in the upper mantle. A 3-D anisotropic shear velocity model will be developed from the phase velocities and will provide more details for the crust and upper mantle structure beneath the northern Gulf of Mexico continental margin.

The relationship between VHF radar auroral backscatter amplitude and Doppler velocity: a statistical study

Directory of Open Access Journals (Sweden)

B. A. Shand

Full Text Available A statistical investigation of the relationship between VHF radar auroral backscatter intensity and Doppler velocity has been undertaken with data collected from 8 years operation of the Wick site of the Sweden And Britain Radar-auroral Experiment (SABRE. The results indicate three different regimes within the statistical data set; firstly, for Doppler velocities <200 m s^–1, the backscatter intensity (measured in decibels remains relatively constant. Secondly, a linear relationship is observed between the backscatter intensity (in decibels and Doppler velocity for velocities between 200 m s^–1 and 700 m s^–1. At velocities greater than 700 m s^–1 the backscatter intensity saturates at a maximum value as the Doppler velocity increases. There are three possible geophysical mechanisms for the saturation in the backscatter intensity at high phase speeds: a saturation in the irregularity turbulence level, a maximisation of the scattering volume, and a modification of the local ambient electron density. There is also a difference in the dependence of the backscatter intensity on Doppler velocity for the flow towards and away from the radar. The results for flow towards the radar exhibit a consistent relationship between backscatter intensity and measured velocities throughout the solar cycle. For flow away from the radar, however, the relationship between backscatter intensity and Doppler velocity varies during the solar cycle. The geometry of the SABRE system ensures that flow towards the radar is predominantly associated with the eastward electrojet, and flow away is associated with the westward electrojet. The difference in the backscatter intensity variation as a function of Doppler velocity is attributed to asymmetries between the eastward and westward electrojets and the geophysical parameters controlling the backscatter amplitude.

The relationship between VHF radar auroral backscatter amplitude and Doppler velocity: a statistical study

Directory of Open Access Journals (Sweden)

B. A. Shand

1996-08-01

Full Text Available A statistical investigation of the relationship between VHF radar auroral backscatter intensity and Doppler velocity has been undertaken with data collected from 8 years operation of the Wick site of the Sweden And Britain Radar-auroral Experiment (SABRE. The results indicate three different regimes within the statistical data set; firstly, for Doppler velocities <200 m s–1, the backscatter intensity (measured in decibels remains relatively constant. Secondly, a linear relationship is observed between the backscatter intensity (in decibels and Doppler velocity for velocities between 200 m s–1 and 700 m s–1. At velocities greater than 700 m s–1 the backscatter intensity saturates at a maximum value as the Doppler velocity increases. There are three possible geophysical mechanisms for the saturation in the backscatter intensity at high phase speeds: a saturation in the irregularity turbulence level, a maximisation of the scattering volume, and a modification of the local ambient electron density. There is also a difference in the dependence of the backscatter intensity on Doppler velocity for the flow towards and away from the radar. The results for flow towards the radar exhibit a consistent relationship between backscatter intensity and measured velocities throughout the solar cycle. For flow away from the radar, however, the relationship between backscatter intensity and Doppler velocity varies during the solar cycle. The geometry of the SABRE system ensures that flow towards the radar is predominantly associated with the eastward electrojet, and flow away is associated with the westward electrojet. The difference in the backscatter intensity variation as a function of Doppler velocity is attributed to asymmetries between the eastward and westward electrojets and the geophysical parameters controlling the backscatter amplitude.

Transverse and longitudinal angular momenta of light

Energy Technology Data Exchange (ETDEWEB)

Bliokh, Konstantin Y., E-mail: k.bliokh@gmail.com [Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama 351-0198 (Japan); Nonlinear Physics Centre, RSPhysE, The Australian National University, Canberra, ACT 0200 (Australia); Nori, Franco [Center for Emergent Matter Science, RIKEN, Wako-shi, Saitama 351-0198 (Japan); Physics Department, University of Michigan, Ann Arbor, MI 48109-1040 (United States)

2015-08-26

We review basic physics and novel types of optical angular momentum. We start with a theoretical overview of momentum and angular momentum properties of generic optical fields, and discuss methods for their experimental measurements. In particular, we describe the well-known longitudinal (i.e., aligned with the mean momentum) spin and orbital angular momenta in polarized vortex beams. Then, we focus on the transverse (i.e., orthogonal to the mean momentum) spin and orbital angular momenta, which were recently actively discussed in theory and observed in experiments. First, the recently-discovered transverse spin  angular momenta appear in various structured fields: evanescent waves, interference fields, and focused beams. We show that there are several kinds of transverse spin angular momentum, which differ strongly in their origins and physical properties. We describe extraordinary features of the transverse optical spins and overview recent experiments. In particular, the helicity-independent transverse spin inherent in edge evanescent waves offers robust spin–direction coupling at optical interfaces (the quantum spin Hall effect of light). Second, we overview the transverse orbital angular momenta of light, which can be both extrinsic and intrinsic. These two types of the transverse orbital angular momentum are produced by spatial shifts of the optical beams (e.g., in the spin Hall effect of light) and their Lorentz boosts, respectively. Our review is underpinned by a unified theory of the angular momentum of light based on the canonical momentum and spin densities, which avoids complications associated with the separation of spin and orbital angular momenta in the Poynting picture. It allows us to construct a comprehensive classification of all known optical angular momenta based on their key parameters and main physical properties.

Data based ambient lighting control

NARCIS (Netherlands)

2012-01-01

In controlling an ambient lighting element, a category of data being rendered by a host is identified, ambient lighting data associated with the identified category is retrieved, and the retrieved ambient lighting data is rendered in correspondence with the rendered data. The retrieved ambient

Phase diagrams of diluted transverse Ising nanowire

International Nuclear Information System (INIS)

Bouhou, S.; Essaoudi, I.; Ainane, A.; Saber, M.; Ahuja, R.; Dujardin, F.

2013-01-01

In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J cs exchange interaction are studied using the effective field theory with a probability distribution technique, in the presence of transverse fields in the core and in the surface shell. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms, the exchange interaction core/shell, the exchange in surface and the transverse fields in core and in surface shell of phase diagrams are investigated. - Highlights: ► We use the EFT to investigate the phase diagrams of Ising transverse nanowire. ► Ferrimagnetic and ferromagnetic cases are investigated. ► The effects of the dilution and the transverse fields in core and shell are studied. ► Behavior of the transition temperature with the exchange interaction is given

Low-Frequency Oscillations and Transport Processes Induced by Multiscale Transverse Structures in the Polar Wind Outflow: A Three-Dimensional Simulation

Science.gov (United States)

Ganguli, Supriya B.; Gavrishchaka, Valeriy V.

1999-01-01

Multiscale transverse structures in the magnetic-field-aligned flows have been frequently observed in the auroral region by FAST and Freja satellites. A number of multiscale processes, such as broadband low-frequency oscillations and various cross-field transport effects are well correlated with these structures. To study these effects, we have used our three-dimensional multifluid model with multiscale transverse inhomogeneities in the initial velocity profile. Self-consistent-frequency mode driven by local transverse gradients in the generation of the low field-aligned ion flow and associated transport processes were simulated. Effects of particle interaction with the self-consistent time-dependent three-dimensional wave potential have been modeled using a distribution of test particles. For typical polar wind conditions it has been found that even large-scale (approximately 50 - 100 km) transverse inhomogeneities in the flow can generate low-frequency oscillations that lead to significant flow modifications, cross-field particle diffusion, and other transport effects. It has also been shown that even small-amplitude (approximately 10 - 20%) short-scale (approximately 10 km) modulations of the original large-scale flow profile significantly increases low-frequency mode generation and associated cross-field transport, not only at the local spatial scales imposed by the modulations but also on global scales. Note that this wave-induced cross-field transport is not included in any of the global numerical models of the ionosphere, ionosphere-thermosphere, or ionosphere-polar wind. The simulation results indicate that the wave-induced cross-field transport not only affects the ion outflow rates but also leads to a significant broadening of particle phase-space distribution and transverse particle diffusion.

What do we learn from transverse energy distributions?

International Nuclear Information System (INIS)

Baym, G.; Friedman, G.; Heiselberg, H.

1990-01-01

Transverse energy measurements provide a wealth of information on the physics of ultrarelativistic heavy-ion collisions. To begin with they tell one the degree to which the colliding nuclei transfer energy and stop each other. With information about the space-time dynamics of the collisions, transverse energy data enables one to estimate the evolving energy density in the collision volume, a quantity needed to assess the likelihood of quark-gluon plasma formation. Furthermore, since the transverse energy distribution is to a large extent determined by the geometry of the collision, transverse energy is a useful indicator of centrality of collisions. It also provides considerable evidence for the rescattering of secondaries in the medium. Finally, fluctuations in the tails of the transverse energy distributions are an important probe of the independence of or possible coherence among the nucleon-nucleon subcollisions that constitute the first stage of heavy-ion collisions. Since the experimental talks in this workshop have done a rather complete job of presenting the transverse energy data from both BNL and CERN, the focus, as the authors discuss these topics in turn, will be on the theoretical interpretation of the data

Biotecnologia Ambiental. Aplicacions biotecnològiques a la millora del medi ambient

OpenAIRE

Blanch i Gisbert, Anicet

2010-01-01

La biotecnología ambiental comprende el conjunto de actividades tecnológicas que facilitan la comprensión y la gestión de los sistemas biológicos en el medio ambiente, con el fin de proveer productos y servicios. Actualmente, la gestión del medio ambiente y de sus recursos naturales no se comprende si no se realiza de manera sostenible. Los avances científicos y tecnológicos le están permitiendo a la biotecnología ambiental, el desarrollo de nuevas herramientas y aplicaciones con los que resp...

Scaling properties of the transverse mass spectra

International Nuclear Information System (INIS)

Schaffner-Bielich, J.

2002-01-01

Motivated from the formation of an initial state of gluon-saturated matter, we discuss scaling relations for the transverse mass spectra at BNL's relativistic heavy-ion collider (RHIC). We show on linear plots, that the transverse mass spectra for various hadrons can be described by an universal function in m t . The transverse mass spectra for different centralities can be rescaled into each other. Finally, we demonstrate that m t -scaling is also present in proton-antiproton collider data and compare it to m t -scaling at RHIC. (orig.)

The future is 'ambient'

Science.gov (United States)

Lugmayr, Artur

2006-02-01

The research field of ambient media starts to spread rapidly and first applications for consumer homes are on the way. Ambient media is the logical continuation of research around media. Media has been evolving from old media (e.g. print media), to integrated presentation in one form (multimedia - or new media), to generating a synthetic world (virtual reality), to the natural environment is the user-interface (ambient media), and will be evolving towards real/synthetic undistinguishable media (bio-media or bio-multimedia). After the IT bubble was bursting, multimedia was lacking a vision of potential future scenarios and applications. Within this research paper the potentials, applications, and market available solutions of mobile ambient multimedia are studied. The different features of ambient mobile multimedia are manifold and include wearable computers, adaptive software, context awareness, ubiquitous computers, middleware, and wireless networks. The paper especially focuses on algorithms and methods that can be utilized to realize modern mobile ambient systems.

Disentangling random thermal motion of particles and collective expansion of source from transverse momentum spectra in high energy collisions

Science.gov (United States)

Wei, Hua-Rong; Liu, Fu-Hu; Lacey, Roy A.

2016-12-01

In the framework of a multisource thermal model, we describe experimental results of the transverse momentum spectra of final-state light flavor particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead (p-Pb), and proton-proton (p -p) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, by using the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein), Tsallis, and two- or three-component standard distributions which can be in fact regarded as different types of ‘thermometers’ or ‘thermometric scales’ and ‘speedometers’. A central parameter in the three distributions is the effective temperature which contains information on the kinetic freeze-out temperature of the emitting source and reflects the effects of random thermal motion of particles as well as collective expansion of the source. To disentangle both effects, we extract the kinetic freeze-out temperature from the intercept of the effective temperature (T) curve as a function of particle’s rest mass (m 0) when plotting T versus m 0, and the mean transverse flow velocity from the slope of the mean transverse momentum ( ) curve as a function of mean moving mass (\\overline{m}) when plotting versus \\overline{m}.

Towards New Ambient Light Systems: a Close Look at Existing Encodings of Ambient Light Systems

Directory of Open Access Journals (Sweden)

Andrii Matviienko

2015-10-01

Full Text Available Ambient systems provide information in the periphery of a user’s attention. Their aim is to present information as unobtrusively as possible to avoid interrupting primary tasks (e.g. writing or reading. In recent years, light has been used to create ambient systems to display information. Examples of ambient light systems range from simple notification systems such as displaying messages or calendar event reminders, to more complex systems such as focusing on conveying information regarding health activity tracking. However, for ambient light systems, there is a broad design space that lacks guidelines on when to make use of light displays and how to design them. In this paper we provide a systematic overview of existing ambient light systems over four identified information classes derived from 72 existing ambient light systems. The most prominent encoding parameters among the surveyed ambient light systems are color, brightness, and their combination. By analyzing existing ambient light systems, we provide a first step towards developing guidelines for designing future ambient light systems.

Pseudoscalar Meson Electroproduction and Transversity

International Nuclear Information System (INIS)

Goldstein, G.; Liuti, S.

2011-01-01

Exclusive meson leptoproduction from nucleons in the deeply virtual exchanged boson limit can be described by generalized parton distributions (GPDs). Including spin dependence in the description requires 8 independent quark-parton and gluon-parton functions. The chiral even subset of 4 quark-nucleon GPDs are related to nucleon form factors and to parton distribution functions. The chiral odd set of 4 quark-nucleon GPDs are related to transversity, the tensor charge, and other quantities related to transversity. Different meson or photon production processes access different combinations of GPDs. This is analyzed in terms of t-channel exchange quantum numbers, J PC and it is shown that pseudoscalar production can isolate chiral odd GPDs. There is a sensitive dependence in various cross sections and asymmetries on the tensor charge of the nucleon and other transversity parameters. In a second section, analyticity and completeness are shown to limit the partonic interpret ation of the GPDs in the ERBL region.

Transverse jets and their control

Energy Technology Data Exchange (ETDEWEB)

Karagozian, Ann R. [Department of Mechanical and Aerospace Engineering, University of California, 48-121 Engineering IV, Los Angeles, CA 90095 (United States)

2010-10-15

The jet in crossflow or transverse jet has been studied extensively because of its relevance to a wide variety of flows in technological systems, including fuel or dilution air injection in gas turbine engines, thrust vector control for high speed airbreathing and rocket vehicles, and exhaust plumes from power plants. These widespread applications have led over the past 50+ years to experimental, theoretical, and numerical examinations of this fundamental flowfield, with and without a combustion reaction, and with single or multi-phase flow. The complexities in this flowfield, whether the jet is introduced flush with respect to the injection wall or from an elevated pipe or nozzle, present challenges in accurately interrogating, analyzing, and simulating important jet features. This review article provides a background on these studies and applications as well as detailed features of the transverse jet, and mechanisms for its control via active means. Promising future directions for the understanding, interrogation, simulation, and control of transverse jet flows are also identified and discussed. (author)

Optimizing the longitudinal and transverse electroosmotic pumping in a rectangular channel with horizontal baffle plates

Science.gov (United States)

Lai, Anison K. R.; Chang, Chien-Cheng; Wang, Chang-Yi

2018-04-01

This paper presents a continued study to our previous work on electroosmotic (EO) flow in a channel with vertical baffle plates by further investigating EO flow through an array of baffle plates arranged in parallel to the channel walls. The flow may be driven either in the direction along or in the direction transverse to the plates, thus distinguishing the longitudinal EO pumping (LEOP) and the transverse EO pumping (TEOP). In both types of EO pumping, it is more interesting to examine the cases when the baffle plates develop a higher zeta potential (denoted by α) than that on the channel walls (β). This semi-analytical study enables us to compare between LEOP and TEOP in the pumping efficiency under similar conditions. The TEOP case is more difficult to solve due to the higher order governing partial differential equations caused by the induced non-uniform pressure gradient distribution. In particular, we examine how the EO pumping rates deviate from those predicted by the Helmholtz-Smoluchowski velocity and illustrate the general trend of optimizing the EO pumping rates with respect to the physical and geometric parameters involved.

Shallow crustal radial anisotropy beneath the Tehran basin of Iran from seismic ambient noise tomography

Science.gov (United States)

Shirzad, Taghi; Shomali, Z. Hossein

2014-06-01

We studied the shear wave velocity structure and radial anisotropy beneath the Tehran basin by analyzing the Rayleigh wave and Love wave empirical Green's functions obtained from cross-correlation of seismic ambient noise. Approximately 199 inter-station Rayleigh and Love wave empirical Green's functions with sufficient signal-to-noise ratios extracted from 30 stations with various sensor types were used for phase velocity dispersion analysis of periods ranging from 1 to 7 s using an image transformation analysis technique. Dispersion curves extracted from the phase velocity maps were inverted based on non-linear damped least squares inversion method to obtain a quasi-3D model of crustal shear wave velocities. The data used in this study provide an unprecedented opportunity to resolve the spatial distribution of radial anisotropy within the uppermost crust beneath the Tehran basin. The quasi-3D shear wave velocity model obtained in this analysis delineates several distinct low- and high-velocity zones that are generally separated by geological boundaries. High-shear-velocity zones are located primarily around the mountain ranges and extend to depths of 2.0 km, while the low-shear-velocity zone is located near regions with sedimentary layers. In the shallow subsurface, our results indicate strong radial anisotropy with negative magnitude (VSV > VSH) primarily associated with thick sedimentary deposits, reflecting vertical alignment of cracks. With increasing depth, the magnitude of the radial anisotropy shifts from predominantly negative (less than -10%) to predominantly positive (greater than 5%). Our results show a distinct change in radial anisotropy between the uppermost sedimentary layer and the bedrock.

Optimized simultaneous transverse and longitudinal focusing of intense ion beam pulses for warm dense matter applications

International Nuclear Information System (INIS)

Sefkow, Adam B.; Davidson, Ronald C.; Kaganovich, Igor D.; Gilson, Erik P.; Roy, Prabir K.; Seidl, Peter A.; Yu, Simon S.; Welch, Dale R.; Rose, David V.; Barnard, John J.

2007-01-01

Intense, space-charge-dominated ion beam pulses for warm dense matter and heavy ion fusion applications must undergo simultaneous transverse and longitudinal bunch compression in order to meet the requisite beam intensities desired at the target. The longitudinal compression of an ion bunch is achieved by imposing an initial axial velocity tilt on the drifting beam and subsequently neutralizing its space-charge and current in a drift region filled with high-density plasma. The Neutralized Drift Compression Experiment (NDCX) at Lawrence Berkeley National Laboratory has measured a sixty-fold longitudinal current compression of an intense ion beam with pulse duration of a few nanoseconds, in agreement with simulations and theory. A strong solenoid is modeled near the end of the drift region in order to transversely focus the beam to a sub-millimeter spot size coincident with the longitudinal focal plane. The charge and current neutralization provided by the background plasma is critical in determining the total achievable transverse and longitudinal compression of the beam pulse. Numerical simulations show that the current density of an NDCX ion beam can be compressed over a few meters by factors greater than 10 5 with peak beam density in excess of 10 14 cm -3 . The peak beam density sets a lower bound on the local plasma density required near the focal plane for optimal beam compression, since the simulations show stagnation of the compression when n beam >n plasma . Beam-plasma interactions can also have a deleterious effect on the compression physics and lead to the formation of nonlinear wave excitations in the plasma. Simulations that optimize designs for the simultaneous transverse and longitudinal focusing of an NDCX ion beam for future warm dense matter experiments are discussed

Temporal Variability in Seismic Velocity at the Salton Sea Geothermal Field

Science.gov (United States)

Taira, T.; Nayak, A.; Brenguier, F.

2015-12-01

We characterize the temporal variability of ambient noise wavefield and search for velocity changes associated with activities of the geothermal energy development at the Salton Sea Geothermal Field. The noise cross-correlations (NCFs) are computed for ~6 years of continuous three-component seismic data (December 2007 through January 2014) collected at 8 sites from the CalEnergy Subnetwork (EN network) with MSNoise software (Lecocq et al., 2014, SRL). All seismic data are downloaded from the Southern California Earthquake Data Center. Velocity changes (dv/v) are obtained by measuring time delay between 5-day stacks of NCFs and the reference NCF (average over the entire 6 year period). The time history of dv/v is determined by averaging dv/v measurements over all station/channel pairs (252 combinations). Our preliminary dv/v measurement suggests a gradual increase in dv/v over the 6-year period in a frequency range of 0.5-8.0 Hz. The resultant increase rate of velocity is about 0.01%/year. We also explore the frequency-dependent velocity change at the 5 different frequency bands (0.5-2.0 Hz, 0.75-3.0 Hz, 1.0-4.0 Hz, 1.5-6.0 Hz, and 2.0-8.0 Hz) and find that the level of this long-term dv/v variability is increased with increase of frequency (i.e., the highest increase rate of ~0.15%/year at the 0.5-2.0 Hz band). This result suggests that the velocity changes were mostly occurred in a depth of ~500 m assuming that the coda parts of NCFs (~10-40 s depending on station distances) are predominantly composed of scattered surface waves, with the SoCal velocity model (Dreger and Helmberger, 1993, JGR). No clear seasonal variation of dv/v is observed in the frequency band of 0.5-8.0 Hz.

Transversally extended string

International Nuclear Information System (INIS)

Akama, Keiichi

1988-01-01

Starting with the space-time action of the transversally extended string, we derive its world-sheet action, which is that of a gravitational and gauge theory with matter fields on the world-sheet, with additional effects of the second fundamental quantity. (author)

Velocity diagnostics of electron beams within a 140 GHz gyrotron

International Nuclear Information System (INIS)

Polevoy, J.T.

1989-06-01

Experimental measurements of the average axial velocity v parallel of the electron beam within the M.I.T. 140 GHz MW gyrotron have been performed. The method involves the simultaneous measurement of the radial electrostatic potential of the electron beam V p and the beam current I b . V p is measured through the use of a capacitive probe installed near or within the gyrotron cavity, while I b is measured with a previously installed Rogowski coil. Three capacitive probes have been designed and built, and two have operated within the gyrotron. The probe results are repeatable and consistent with theory. The measurements of v parallel and calculations of the corresponding transverse to longitudinal beam velocity ratio α = v perpendicular /v parallel at the cavity have been made at various gyrotron operation parameters. These measurements will provide insight into the causes of discrepancies between theoretical rf interaction efficiencies and experimental efficiencies obtained in experiments with the M.I.T. 140 GHz MW gyrotron. The expected values of v parallel and α are determined through the use of a computer code entitled EGUN. EGUN is used to model the cathode and anode regions of the gyrotron and it computes the trajectories and velocities of the electrons within the gyrotron. There is good correlation between the expected and measured values of α at low α, with the expected values from EGUN often falling within the standard errors of the measured values. 10 refs., 29 figs., 2 tabs

Phase diagrams of diluted transverse Ising nanowire

Energy Technology Data Exchange (ETDEWEB)

Bouhou, S.; Essaoudi, I. [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Ainane, A., E-mail: ainane@pks.mpg.de [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Saber, M. [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Ahuja, R. [Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala (Sweden); Dujardin, F. [Laboratoire de Chimie et Physique des Milieux Complexes (LCPMC), Institut de Chimie, Physique et Matériaux (ICPM), 1 Bd. Arago, 57070 Metz (France)

2013-06-15

In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J{sub cs} exchange interaction are studied using the effective field theory with a probability distribution technique, in the presence of transverse fields in the core and in the surface shell. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms, the exchange interaction core/shell, the exchange in surface and the transverse fields in core and in surface shell of phase diagrams are investigated. - Highlights: ► We use the EFT to investigate the phase diagrams of Ising transverse nanowire. ► Ferrimagnetic and ferromagnetic cases are investigated. ► The effects of the dilution and the transverse fields in core and shell are studied. ► Behavior of the transition temperature with the exchange interaction is given.

Curative resection of transverse colon cancer via minilaparotomy.

Science.gov (United States)

Ishida, Hideyuki; Ishiguro, Tohru; Ishibashi, Keiichiro; Ohsawa, Tomonori; Okada, Norimichi; Kumamoto, Kensuke; Haga, Norihiro

2011-01-01

Minilaparotomy has been reported to be a minimally invasive alternative to laparoscopically assisted surgery. We retrospectively evaluated the usefulness of minilaparotomy for the resection of transverse colon cancer, which has generally been considered difficult to resect laparoscopically. Patients for whom curative resection was attempted for transverse colon cancer (n = 21) or sigmoid colon cancer (n = 81) via minilaparotomy (skin incision, transverse colon cancer as well as those with sigmoid colon cancer.

Collins Fragmentation and the Single Transverse Spin Asymmetry

OpenAIRE

Yuan, Feng; Zhou, Jian

2009-01-01

We study the Collins mechanism for the single transverse spin asymmetry in the collinear factorization approach. The correspondent twist-three fragmentation function is identified. We show that the Collins function calculated in this approach is universal. We further examine its contribution to the single transverse spin asymmetry of semi-inclusive hadron production in deep inelastic scattering and demonstrate that the transverse momentum dependent and twist-three collinear approaches are con...

Studying the instantaneous velocity field in gas-sheared liquid films in a horizontal duct

Science.gov (United States)

Vasques, Joao; Tokarev, Mikhail; Cherdantsev, Andrey; Hann, David; Hewakandamby, Buddhika; Azzopardi, Barry

2016-11-01

In annular flow, the experimental validation of the basic assumptions on the liquid velocity profile is vital for developing theoretical models of the flow. However, the study of local velocity of liquid in gas-sheared films has proven to be a challenging task due to the highly curved and disturbed moving interface of the phases, small scale of the area of interrogation, high velocity gradients and irregular character of the flow. This study reports on different optical configurations and interface-tracking methods employed in a horizontal duct in order to obtain high-resolution particle image velocimetry (PIV) data in such types of complex flows. The experimental envelope includes successful measurements in 2D and 3D waves regimes, up to the disturbance wave regime. Preliminary data show the presence of complex structures in the liquid phase, which includes re-circulation areas below the liquid interface due to the gas-shearing action, together with non-uniform transverse movements of the liquid phase close to the wall due to the presence of 3D waves at the interface. With the aid of the moving interface-tracking, PIV, time-resolved particle-tracking velocimetry and vorticity measurements were performed.

Stability aspects of plasmas penetrated by neutral gas with respect to velocity driven modes

International Nuclear Information System (INIS)

Ohlsson, D.

1978-08-01

A study of the stability properties of dense partially ionized plasmas immersed in strong magnetic fields with respect to velocity driven modes are presented. First we consider modes driven by mass motion perpendicular to the lines of force and the unperturbed density and temperature gradients. The presence of a third fluid, neutral gas, gives under certain conditions rise to unstable modes. This type of instability arises independently or whether the applied electric field transverse to the lines of force, driving the mass motion, being parallel or antiparallel to the unperturbed density and temperature gradient. The presence of neutral gas also corresponds to stabilizing effects which, in certain parameter regions, result in a quenching of this instability. It is shown that modes driven by velocity shear perpendicular to the lines of force are effectively stabilized by viscous and resistive effects. These effects are in certain parameter ranges strongly enhanced on account of plasma-neutral gas interaction effects. In collisionless plasmas, modes driven by velocity shear parallel to the lines of force are stabilized by compressibility effects parallel to the magnetic field and by finite Larmor radius effects. (author)

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

Directory of Open Access Journals (Sweden)

A. Marchaudon

2009-03-01

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

Vertical compared with transverse incisions in abdominal surgery

DEFF Research Database (Denmark)

Grantcharov, T P; Rosenberg, J

2001-01-01

, and late complications (incisional hernia). RESULTS: Eleven randomised controlled trials and seven retrospective studies were identified. The transverse incision offers as good an access to most intra-abdominal structures as a vertical incision. The transverse incision results in significantly less......OBJECTIVE: To reach an evidence-based consensus on the relative merits of vertical and transverse laparotomy incisions. DESIGN: Review of all published randomised controlled trials that compared the postoperative complications after the two main types of abdominal incisions, vertical and transverse....... SETTING: Teaching hospital, Denmark. SUBJECTS: Patients undergoing open abdominal operations. INTERVENTIONS: For some of the variables (burst abdomen and incisional hernia) it was considered adequate to include retrospective studies. Studies were identified through Medline, Cochrane library, Embase...

Experimental investigation of a reacting transverse jet in a high pressure oscillating vitiated crossflow

Science.gov (United States)

Fugger, Christopher A.

Staged combustion is one design approach in a gas turbine engine to reduce pollutant emission levels. In axially staged combustion, portions of the air and fuel are injected downstream of a lean premixed low NOx primary combustion zone. The gas residence time at elevated temperatures is decreased resulting in lower thermal NOx, and the reduced oxygen and high temperature vitiated primary zone flow further help to reduce pollutant emissions and quickly complete combustion. One implementation of axially staged combustion is transverse fuel jet injection. An important consideration for staged combustion systems, though, is how the primary and secondary combustion zones can couple through the acoustic resonances of the chamber. These couplings can lead to additional source terms that pump energy into the resonant acoustic field and help sustain the high-amplitude combustor pressure oscillations. An understanding of these couplings is important so that it may be possible to design a secondary combustion system that provides inherent damping to the combustor system. To systematically characterize the coupling of a reacting jet in unsteady crossflow in detail, the effects of an an unsteady pressure flowfield and an unsteady velocity flowfield are separately investigated. An optically accessible resonant combustion chamber was designed and built as part of this work to generate a standing wave unsteady vitiated crossflow at a chamber pressure of 0.9 MPa. The location of transverse jet injection corresponds to one of two locations, where one location is the pressure node and the other location the pressure anti-node of the resonant chamber acoustic mode. The injection location is optically accessible, and the dynamic interactions between the transverse jet flow and the 1st and 2nd axial combustor modes are measured using 10 kHz OH-PLIF and 2D PIV. This document analyzes five test cases: two non-reacting jets and three reacting jets. All cases correspond to jet injection

Ambient Dried Aerogels

Science.gov (United States)

Jones, Steven M.; Paik, Jong-Ah

2013-01-01

A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network.

Highlights from PHENIX transverse spin program at RHIC

International Nuclear Information System (INIS)

Liu, M.

2013-01-01

In recent years, there has been exciting development in both experimental and theoretical studies of transverse spin phenomena in high energy polarized p+p and polarized DIS collisions. In the p+p frontier, the polarized p+p collider at RHIC provides a unique opportunity to investigate the novel physics that causes the large spin effects seen in the transversely polarized p+p collisions over the past 30 years, particularly in the forward rapidity. Since the beginning, PHENIX has been conducting a very active transverse spin physics program to study Sivers, Collins and other novel spin effects at RHIC, including measurements of transverse single spin asymmetry (TSSA) in light and heavy quark productions, leading neutron TSSA in the very forward rapidity, and di-hadron (and 'jet') spin correlations in a wide kinematics range, just to name a few. In 2012, PHENIX collected transversely polarized 200 GeV p+p data with a record high luminosity of 9.24 pb −1 , with an average beam polarization of 58%. In this talk, I highlight the recent results from the PHENIX experiment, and also briefly discuss the near-term prospects of new transverse spin measurements only possible with the latest (forward) silicon vertex detectors, (F)VTX, and the upcoming forward MPC-EX upgrade detectors.

Observation of transverse patterns in an isotropic microchip laser

International Nuclear Information System (INIS)

Chen, Y.F.; Lan, Y.P.

2003-01-01

An isotropic microchip laser is used to study the characteristics of high-order wave functions in a two-dimensional (2D) quantum harmonic oscillator based on the identical functional forms. With a doughnut pump profile, the spontaneous transverse modes are found to, generally, be elliptic and hyperbolic transverse modes. Theoretical analyses reveal that the elliptic transverse modes are analogous to the coherent states of a 2D harmonic oscillator; the formation of hyperbolic transverse modes is a spontaneous mode locking between two identical Hermite-Gaussian modes

Unsteady three dimensional flow of Casson liquid film over a porous stretching sheet in the presence of uniform transverse magnetic field and suction/injection

Energy Technology Data Exchange (ETDEWEB)

Maity, S., E-mail: susantamaiti@gmail.com [Department of Mathematics, National Institute of Technology, Arunachal Pradesh, Yupia, Papumpare 791112 (India); Singh, S.K. [Engineering Mechanics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Kumar, A.V. [Department of Mathematics, National Institute of Technology, Arunachal Pradesh, Yupia, Papumpare 791112 (India)

2016-12-01

Three dimensional flow of thin Casson liquid film over a porous unsteady stretching sheet is investigated under assumption of initial uniform film thickness. The effects of the uniform transverse magnetic field, suction and injection are also considered for investigation. The nonlinear governing set of equations and film evolution equation are solved analytically by using singular perturbation technique. It is found that the film thickness decreases with the increasing values of the Casson parameter. The Hartmann number and porosity parameter resist the film thinning process. It is also observed that the film thickness increases with the increasing values of the suction velocity whereas it decreases for increasing values of the injection velocity at the stretching surface.

Limitations on Transversal Computation through Quantum Homomorphic Encryption

OpenAIRE

Newman, Michael; Shi, Yaoyun

2017-01-01

Transversality is a simple and effective method for implementing quantum computation fault-tolerantly. However, no quantum error-correcting code (QECC) can transversally implement a quantum universal gate set (Eastin and Knill, Phys. Rev. Lett., 102, 110502). Since reversible classical computation is often a dominating part of useful quantum computation, whether or not it can be implemented transversally is an important open problem. We show that, other than a small set of non-additive codes ...

CUIDADO AMBIENTAL E RESPONSABILIDADE: POSSÍVEL DIÁLOGO ENTRE PSICOLOGIA AMBIENTAL E LOGOTERAPIA

Directory of Open Access Journals (Sweden)

Diogo Arnaldo Corrêa

2016-05-01

Full Text Available O cuidado ambiental vem sendo marcado pela tônica da conservação e da promoção da sustentabilidade. A premente necessidade de um dado compromisso e educação ambiental e de condutas pró-ambientais vem sendo defendida em vários contextos: na mídia, nas políticas públicas, por meio de campanhas sazonais. Todavia, pouco se descreve acerca do sentido presente nos modos de cuidado configurados a partir da inter-relação pessoa-ambiente. Nesta perspectiva, este estudo objetivou promover um possível diálogo a partir das contribuições da Psicologia Ambiental e da Logoterapia visando aproximar a noção de cuidado ambiental, delineada pela Psicologia Ambiental, à ideia de responsabilidade, como defendida pela Logoterapia, por meio de uma revisão bibliográfica. As articulações propositadas corroboraram, portanto, para acenar que a relação pessoa-ambiente pode ser arraigada em qualidade se a responsabilidade é reconhecida em sua propriedade de potencial humano, o que pode favorecer na emergência do sentido das atitudes e condutas pró-ambientais e explicitar o caráter de tarefa única e irrepetível inerente à vida.

Numerical modelling of flow structures over idealized transverse aeolian dunes of varying geometry

Science.gov (United States)

Parsons, Daniel R.; Walker, Ian J.; Wiggs, Giles F. S.

2004-04-01

A Computational Fluid Dynamics (CFD) model (PHOENICS™ 3.5) previously validated for wind tunnel measurements is used to simulate the streamwise and vertical velocity flow fields over idealized transverse dunes of varying height ( h) and stoss slope basal length ( L). The model accurately reproduced patterns of: flow deceleration at the dune toe; stoss flow acceleration; vertical lift in the crest region; lee-side flow separation, re-attachment and reversal; and flow recovery distance. Results indicate that the flow field over transverse dunes is particularly sensitive to changes in dune height, with an increase in height resulting in flow deceleration at the toe, streamwise acceleration and vertical lift at the crest, and an increase in the extent of, and strength of reversed flows within, the lee-side separation cell. In general, the length of the separation zone varied from 3 to 15 h from the crest and increased over taller, steeper dunes. Similarly, the flow recovery distance ranged from 45 to >75 h and was more sensitive to changes in dune height. For the range of dune shapes investigated in this study, the differing effects of height and stoss slope length raise questions regarding the applicability of dune aspect ratio as a parameter for explaining airflow over transverse dunes. Evidence is also provided to support existing research on: streamline curvature and the maintenance of sand transport in the toe region; vertical lift in the crest region and its effect on grainfall delivery; relations between the turbulent shear layer and downward forcing of flow re-attachment; and extended flow recovery distances beyond the separation cell. Field validation is required to test these findings in natural settings. Future applications of the model will characterize turbulence and shear stress fields, examine the effects of more complex isolated dune forms and investigate flow over multiple dunes.

Survey of high-velocity molecular gas in the vicinity of Herbig-Haro objects. I

International Nuclear Information System (INIS)

Edwards, S.; Snell, R.L.

1983-01-01

A survey of high-velocity molecular gas toward 49 Herbig-Haro objects is presented. Observations of the 12 CO J = 1-0 transition obtained with the 14 m telescope of the Five College Radio Astronomy Observatory reveal three new spatially extended high-velocity molecular outflows. One is in the NGC 1333 region near HH 12, and two are in the NGC 7129 region, the first near LkHα 234 and the second near a far-infrared source. The relationship between optical Herbin-Haro emission knots and large-scale motions of the ambient molecular material is investigated, and the properties of high-velocity molecular outflows in the vicinity of Herbig-Haro objects are discussed. Of 11 energetic outflows in the vicinity of Herbig-Haro objects, eight are found in four pairs separated by 0.2-1.0 pc. We estimate that energetic outflows characterized by mass loss rates > or =10 -7 M/sub sun/ yr -1 occur for at least 10 4 yr once in the lifetime of all stars with masses greater than 1M/sub sun/

Relation between intraocular pressure and size of transverse sinuses

Energy Technology Data Exchange (ETDEWEB)

Kantarci, Mecit; Onbas, Omer; Alper, Fatih; Okur, Adnan [Atatuerk University, Department of Radiology, Medical Faculty, Erzurum (Turkey); Dane, Senol; Gumustekin, Kenan [Atatuerk University, Department of Physiology, Medical Faculty, Erzurum (Turkey); Aslankurt, Murat [Atatuerk University, Department of Ophtalmatology, Medical Faculty, Erzurum (Turkey); Yazici, Ahmet Taylan [Beyoglu Goez Egitim ve Arastirma Hastanesi, Istanbul (Turkey)

2005-01-01

There are asymmetries in the sizes of transverse sinus and intraocular pressure. The purpose of this study was to investigate possible relationships between the asymmetry of transverse sinuses in TOF MR venography and intraocular pressures of right and left eyes. In this study, subjects were 63 male and 42 female medical school students, aged 18-21 years (mean{+-}SD; 19.72{+-}0.67 years). Subjects with neurological and ophthalmologic disease, particularly dural sinus thrombosis, myopia, trauma and glaucoma, were excluded the study. Subjects were divided into five groups according to the magnitudes of the right- and left-transverse sinuses in MR venography results. There is a functional relation between intraocular pressures of the right and left eyes and asymmetry of the transverse sinus. If the transverse sinus on one side is larger and its venous drainage is greater, the intraocular pressure of the eye on this side is lower. It can be speculated that the transverse sinus size may be associated with pathogenesis of diseases with increased intraocular pressure such as glaucoma. We aim to determine the relation between the size and drainage of transverse sinuses in TOF MR venography and intraocular pressure in patients with open-angle glaucoma in our next study. (orig.)

Relation between intraocular pressure and size of transverse sinuses

International Nuclear Information System (INIS)

Kantarci, Mecit; Onbas, Omer; Alper, Fatih; Okur, Adnan; Dane, Senol; Gumustekin, Kenan; Aslankurt, Murat; Yazici, Ahmet Taylan

2005-01-01

There are asymmetries in the sizes of transverse sinus and intraocular pressure. The purpose of this study was to investigate possible relationships between the asymmetry of transverse sinuses in TOF MR venography and intraocular pressures of right and left eyes. In this study, subjects were 63 male and 42 female medical school students, aged 18-21 years (mean±SD; 19.72±0.67 years). Subjects with neurological and ophthalmologic disease, particularly dural sinus thrombosis, myopia, trauma and glaucoma, were excluded the study. Subjects were divided into five groups according to the magnitudes of the right- and left-transverse sinuses in MR venography results. There is a functional relation between intraocular pressures of the right and left eyes and asymmetry of the transverse sinus. If the transverse sinus on one side is larger and its venous drainage is greater, the intraocular pressure of the eye on this side is lower. It can be speculated that the transverse sinus size may be associated with pathogenesis of diseases with increased intraocular pressure such as glaucoma. We aim to determine the relation between the size and drainage of transverse sinuses in TOF MR venography and intraocular pressure in patients with open-angle glaucoma in our next study. (orig.)

Longitudinal and transverse polarizations in the deep inelastic reactions

International Nuclear Information System (INIS)

Bressan, A.

1996-07-01

This course is an introduction to the dominant effects of longitudinal and transverse spin in deep inelastic reactions. Only the effects present to the 'leading twist' are attacked. The mass and transverse impulsion of partons are neglected. We will attach to bring out the respective specificities of longitudinal and transverse polarizations. (N.C.)

Jet axes and universal transverse-momentum- dependent fragmentation

International Nuclear Information System (INIS)

Neill, Duff; Scimemi, Ignazio; Waalewijn, Wouter J.

2017-01-01

We study the transverse momentum spectrum of hadrons in jets. By measuring the transverse momentum with respect to a judiciously chosen axis, we find that this observable is insensitive to (the recoil of) soft radiation. Furthermore, for small transverse momenta we show that the effects of the jet boundary factorize, leading to a new transverse-momentum-dependent (TMD) fragmentation function. In contrast to the usual TMD fragmentation functions, it does not involve rapidity divergences and is universal in the sense that it is independent of the type of process and number of jets. These results directly apply to sub-jets instead of hadrons. We discuss potential applications, which include studying nuclear modification effects in heavy-ion collisions and identifying boosted heavy resonances.

Remote determination of the velocity index and mean streamwise velocity profiles

Science.gov (United States)

Johnson, E. D.; Cowen, E. A.

2017-09-01

When determining volumetric discharge from surface measurements of currents in a river or open channel, the velocity index is typically used to convert surface velocities to depth-averaged velocities. The velocity index is given by, k=Ub/Usurf, where Ub is the depth-averaged velocity and Usurf is the local surface velocity. The USGS (United States Geological Survey) standard value for this coefficient, k = 0.85, was determined from a series of laboratory experiments and has been widely used in the field and in laboratory measurements of volumetric discharge despite evidence that the velocity index is site-specific. Numerous studies have documented that the velocity index varies with Reynolds number, flow depth, and relative bed roughness and with the presence of secondary flows. A remote method of determining depth-averaged velocity and hence the velocity index is developed here. The technique leverages the findings of Johnson and Cowen (2017) and permits remote determination of the velocity power-law exponent thereby, enabling remote prediction of the vertical structure of the mean streamwise velocity, the depth-averaged velocity, and the velocity index.

Anaesthetic considerations in patients with transverse myelitis ...

African Journals Online (AJOL)

Transverse myelitis is an acute or subacute inflammatory disorder involving the spinal cord. Clinical signs are due to the involvement of the ascending and descending tracts in the transverse plane of the spinal cord. The most common cause is autoimmune. These patients may present with various clinical findings with ...

Transverse momentum distributions of identified particles produced ...

Indian Academy of Sciences (India)

We assume that the transverse momentum distributions of identified particles measured in final state are contributed by a few energy sources which can be regarded as partons or quarks in the interacting system. The particle is contributed by each source with gluons which have transverse momentum distributions in an ...

Algorithmic fundamentals of computerized tomography and of transverse analogue tomography

International Nuclear Information System (INIS)

Heckmann, K.

1981-01-01

Computerized tomography and transverse analogue tomography are two different approaches to the same goal, namely, transverse tomography. The algorithm is discussed and compared. Transverse tomography appears capable of further development, judging by this comparison. (orig.) [de

A Low-cost Environmental Control System for Precise Radial Velocity Spectrometers

Science.gov (United States)

Sliski, David H.; Blake, Cullen H.; Halverson, Samuel

2017-12-01

We present an environmental control system (ECS) designed to achieve milliKelvin (mK) level temperature stability for small-scale astronomical instruments. This ECS is inexpensive and is primarily built from commercially available components. The primary application for our ECS is the high-precision Doppler spectrometer MINERVA-Red, where the thermal variations of the optical components within the instrument represent a major source of systematic error. We demonstrate ±2 mK temperature stability within a 0.5 m3 thermal enclosure using resistive heaters in conjunction with a commercially available PID controller and off-the-shelf thermal sensors. The enclosure is maintained above ambient temperature, enabling rapid cooling through heat dissipation into the surrounding environment. We demonstrate peak-to-valley (PV) temperature stability of better than 5 mK within the MINERVA-Red vacuum chamber, which is located inside the thermal enclosure, despite large temperature swings in the ambient laboratory environment. During periods of stable laboratory conditions, the PV variations within the vacuum chamber are less than 3 mK. This temperature stability is comparable to the best stability demonstrated for Doppler spectrometers currently achieving m s-1 radial velocity precision. We discuss the challenges of using commercially available thermoelectrically cooled CCD cameras in a temperature-stabilized environment, and demonstrate that the effects of variable heat output from the CCD camera body can be mitigated using PID-controlled chilled water systems. The ECS presented here could potentially provide the stable operating environment required for future compact “astrophotonic” precise radial velocity (PRV) spectrometers to achieve high Doppler measurement precision with a modest budget.

Imaging Subsurface Structure of Central Zagros Zone/Iran Using Ambient Noise Tomography

Science.gov (United States)

Vahidravesh, Shaghayegh; Pakzad, Mehrdad, ,, Dr.; Hatami, Mohammad Reza, ,, Dr.

2017-04-01

The Central Zagros zone, of west Iran & east Iraq, is surrounded by many active faults (including Main Zagros Reversed Fault, Main Recent Fault, High Zagros Fault, Zagros Fold, & Thrust Belt). Recent studies show that cross-correlation of a long-term ambient seismic noise data recorded in station-pair, includes important information regarding empirical Green's functions (EGFs) between stations. Hence, ambient seismic noise carries valuable information of the wave propagation path (which can be extracted). The 2D model of surface waves (Rayleigh & Love) velocities for the studied area is obtained by seismic ambient noise tomography (ANT) method. Throughout this research, we use continuous records of all three vertical, radial, and tangential components (obtained by rotation) recorded by IRSC (Iranian Seismological Center) and IIEES (International Institute of Earthquake Engineering) networks for this area of interest. The IRSC & IIEES networks are equipped by SS-1 kinematics and Guralp CMG-3T sensors respectively. Data of 20 stations were used for 12 months from 2014/Nov. to 2015/Nov. The performed data processing is similar to the one, put into words in detail by Bensen et al. (2007) including the processed daily base data. Mean, trend, and instrument response were removed and the data were decimated to 5 sps (sample per second) to reduce the amount of storage space and computational time required. We then applied merge to handle data gaps. One-bit time-domain normalization was also applied to suppress the influence of instrument irregularities and earthquake signals followed by spectral (frequency-domain) normalization between 0.05-0.2 Hz (period 5-20 sec). After cross-correlation (processing step), we perform rms stacking (new approach of stacking) to stack many cross-correlation functions based on the highest energy in a time interval which we accordingly anticipate to receive Rayleigh & Love waves fundamental modes. To evaluate quality of the stacking process

On the structure and origin of HH jets.

Science.gov (United States)

De Colle, Fabio

2011-10-01

The goal of this proposal is to study the structure and origin of jets from young stellar objects by using HST observations of T Tauri jets. To this end, we propose to use three different but complementary approaches: tomographic reconstruction to recover the jet velocity cross-section, numerical simulations to compare the predictions of jet ejection models with the observations, and a statistical analysis of the data. First, we plan to use standard tomographic reconstruction techniques to derive the cross-section {i.e. perpendicular to the jet axis} velocity and physical parameters {electron density, temperature and ionization fraction} of the jets. This will allow a reliable estimation of mass- and momentum-flux from the central star-disk system, which, together with the cross-sectional velocity constraints, will help to distinguish between different jet ejection models. Second, we will focus our study on understanding recent observations of stellar jets showing transverse velocity shifts in several emission lines. The origin of these velocity shift is still debated: they can be interpreted as evidence of rotation, or they can be originated by side-to-side asymmetries in the flow or in the ambient medium. To distinguish between these two scenarios, we plan to uncover the origin of transverse velocity shift by a statistical approach based on the presence {or absence} of correlations between the velocity shifts and the degree of asymmetries in the flow. Finally, we will use our adaptive mesh refinement code to compare the observations with a large number of numerical simulations constructed on different jet ejection mechanisms.

The transverse field Richtmyer-Meshkov instability in magnetohydrodynamics

KAUST Repository

Wheatley, V.; Samtaney, Ravi; Pullin, D. I.; Gehre, R. M.

2014-01-01

The magnetohydrodynamic Richtmyer-Meshkov instability is investigated for the case where the initial magnetic field is unperturbed and aligned with the mean interface location. For this initial condition, the magnetic field lines penetrate the perturbed density interface, forbidding a tangential velocity jump and therefore the presence of a vortex sheet. Through simulation, we find that the vorticity distribution present on the interface immediately after the shock acceleration breaks up into waves traveling parallel and anti-parallel to the magnetic field, which transport the vorticity. The interference of these waves as they propagate causes the perturbation amplitude of the interface to oscillate in time. This interface behavior is accurately predicted over a broad range of parameters by an incompressible linearized model derived presently by solving the corresponding impulse driven, linearized initial value problem. Our use of an equilibrium initial condition results in interface motion produced solely by the impulsive acceleration. Nonlinear compressible simulations are used to investigate the behavior of the transverse field magnetohydrodynamic Richtmyer-Meshkov instability, and the performance of the incompressible model, over a range of shock strengths, magnetic field strengths, perturbation amplitudes and Atwood numbers.

The transverse field Richtmyer-Meshkov instability in magnetohydrodynamics

KAUST Repository

Wheatley, V.

2014-01-10

The magnetohydrodynamic Richtmyer-Meshkov instability is investigated for the case where the initial magnetic field is unperturbed and aligned with the mean interface location. For this initial condition, the magnetic field lines penetrate the perturbed density interface, forbidding a tangential velocity jump and therefore the presence of a vortex sheet. Through simulation, we find that the vorticity distribution present on the interface immediately after the shock acceleration breaks up into waves traveling parallel and anti-parallel to the magnetic field, which transport the vorticity. The interference of these waves as they propagate causes the perturbation amplitude of the interface to oscillate in time. This interface behavior is accurately predicted over a broad range of parameters by an incompressible linearized model derived presently by solving the corresponding impulse driven, linearized initial value problem. Our use of an equilibrium initial condition results in interface motion produced solely by the impulsive acceleration. Nonlinear compressible simulations are used to investigate the behavior of the transverse field magnetohydrodynamic Richtmyer-Meshkov instability, and the performance of the incompressible model, over a range of shock strengths, magnetic field strengths, perturbation amplitudes and Atwood numbers.

Transverse spin of the quarks inside the baryon

International Nuclear Information System (INIS)

Artru, X.; Mekhfi, M.

1990-04-01

We give a brief apercu of transverse polarisation of quarks at short distance. We first show on a simple model that the quark a priori remembers transverse polarisation of its parent hadron. Then we show how to measure the transversely polarized quark density at leading order in 1/Q 2 and α s . Using a t-channel approach, we are led to the following subprocesses: qantiq annihilation, qq scattering of identical quarks (with polarized beam and target) and lepton-quark scattering (with polarized target and analysis of the final quark polarisation by its fragmentation into a Λ). We list some feasible experiments. The transversely polarized quark distibution Δ 1q (x, Q 2 ) evolves according to a Gribov-Lipatov-Altarelli-Parisi equation, with no coupling to the gluonic distributions; all its moments are decreasing

Measurement of Rayleigh wave Z/H ratio and joint inversion for a high-resolution S wave velocity model beneath the Gulf of Mexico passive margin

Science.gov (United States)

Miao, W.; Li, G.; Niu, F.

2016-12-01

Knowledge on the 3D sediment structure beneath the Gulf of Mexico passive margin is not only important to explore the oil and gas resources in the area, but also essential to decipher the deep crust and mantle structure beneath the margin with teleseismic data. In this study, we conduct a joint inversion of Rayleigh wave ellipticity and phase velocity at 6-40 s to construct a 3-D S wave velocity model in a rectangular area of 100°-87° west and 28°-37° north. We use ambient noise data from a total of 215 stations of the Transportable Array deployed under the Earthscope project. Rayleigh wave ellipticity, or Rayleigh wave Z/H (vertical to horizontal) amplitude ratio is mostly sensitive to shallow sediment structure, while the dispersion data are expected to have reasonably good resolution to uppermost mantle depths. The Z/H ratios measured from stations inside the Gulf Coastal Plain are distinctly lower in comparison with those measured from the inland stations. We also measured the phase velocity dispersion from the same ambient noise dataset. Our preliminary 3-D model is featured by strong low-velocity anomalies at shallow depth, which are spatially well correlated with Gulf Cost, East Texas, and the Lower Mississippi basins. We will discuss other features of the 3-D models once the model is finalized.

Non-gyrotropic pressure anisotropy induced by velocity shear.

Science.gov (United States)

Tenerani, A.; Del Sarto, D.; Pegoraro, F.; Califano, F.

2015-12-01

We discuss how, in a collisionless magnetized plasma, a sheared velocity field may lead to the anisotropization of an initial Maxwellian state. By including the full pressure tensor dynamics in a fluid plasma model, we show, analytically and numerically, that a sheared velocity field makes an initial isotropic state anisotropic and non-gyrotropic [1], i.e., makes the plasma pressure tensor anisotropic also in the plane perpendicular to the magnetic field. The propagation of transverse magneto-elastic waves in the anisotropic plasma affects the process of formation of a non-gyrotropic pressure and can lead to its spatial filamentation. This plasma dynamics implies in particular that isotropic MHD equilibria cease to be equilibria in presence of a stationary sheared flow. Similarly, in the case of turbulence, where small-scale spatial inhomogeneities are naturally developed during the direct cascade, we may expect that isotropic turbulent states are not likely to exist whenever a full pressure tensor evolution is accounted for. These results may be relevant to understanding the agyrotropic pressure configurations which are well documented in solar wind measurements and possibly correlated to plasma flows (see e.g. Refs.[2,3]), and which have also been measured in Vlasov simulations of Alfvenic turbulence [4]. [1] D. Del Sarto, F. Pegoraro, F. Califano, "Pressure anisotropy and small spatial scales induced by a velocity shear", http://arxiv.org/abs/1507.04895 [2] H.F. Astudillo, E. Marsch, S. Livi, H. Rosenbauer, "TAUS measurements of non-gyrotropic distribution functions of solar wind alpha particles", AIP Conf. Proc. 328, 289 (1996). [3] A. Posner, M.W. Liemhon, T.H. Zurbuchen, "Upstream magnetospheric ion flux tube within a magnetic cloud: Wind/STICS", Geophys. Res. Lett. 30, (2003). [4] S. Servidio, F. Valentini, F. Califano, P. Veltri, "Local kinetic effects in Two-Dimensional Plasma Turbulence", Phys. Rev. Lett. 108, 045001 (2012).

Evolution of transverse modes in FELIX macropulses

International Nuclear Information System (INIS)

Weits, H.H.; Lin, L.; Werkhoven, G.H.C. van

1995-01-01

We present ringdown measurements of both the intracavity beam, using a low reflection beamsplitter, as well as the hole-outcoupled beam of FELIX, the intracavity measurements being taken at various sets of transverse coordinates. Recent measurements show a significant difference in the decay of the signals at different radial positions, suggesting the presence of higher order transverse modes. The formation of transverse modes depends on the properties of the cold cavity and its losses (i.e. resonator parameters, diffraction and outcoupling at the hole, absorption and edge losses on the mirrors, waveguide clipping), as well as on the gain mechanism. Both simulations with the axisymmetric ELIXER code and previous hole-outcoupled measurements indicated a substantial energy content of the 2nd or 4th Gauss-Laguerre (GL) mode for the 20-30 μm regime of FELIX. Moreover, as FELIX has a phase degenerate cavity, the fundamental and higher order transverse modes can interplay to create a reduced outcoupling efficiency at the hole. For example, in contrast to the decay rate of 13% per roundtrip that we would expect for a pure gaussian beam when we include a loss of 6% for the reflection at the intracavity beamsplitter, recent simulations indicate a decay rate as high as 23% of the hole-outcoupled signal. In this case the 2nd order GL mode contains 30% of the total intracavity power. The effect of transverse modes on subpulses in the limit cycle regime is an interesting aspect. As soon as a subpulse is losing contact with the electrons, its transverse pattern will exhibit an on-axis hole after a few roundtrips, according to the simulations. This process could mean that the subpulses are less pronounced in the hole-outcoupled signal of FELIX 1

Measurement of the transverse energy spectrum in proton-nucleon collisions

International Nuclear Information System (INIS)

Bettoni, D.

1988-01-01

The author describes a measurement of the transverse energy spectrum in proton-nucleon interactions carried out at the CERN SPS using the HELIOS spectrometer. The measurement is of particular interest in that it is performed in a rapidity region away from central rapidity, where experimental data is scarce. In this rapidity region very interesting physics is anticipated and the measurement of the proton-nucleon collisions is essential as a basis to understand the more complicated proton-nucleus and nucleus-nucleus interactions. Both these topics are part of the experimental program of HELIOS. The measurement was done using a deuterium target enclosed in an iron tube. The contribution to the transverse energy spectrum from the p-Fe events is discriminated against by reconstructing the primary interaction vertex using drift chamber information. The measured spectrum is corrected via Monte Carlo to deconvolute the effect of reinteractions. High spatial resolution and multi-track resolving power are achieved with the use of a cool gas, such that the electron characteristic energy is close to the thermal limit: this implies a small diffusion coefficient and a consequently good positional accuracy. Of vital importance are the low value of the drift velocity, the fast, differentiating electronics and a careful shaping of the electric field configuration to improve the isochrony of the drift collection. The author reports on the design and tests of drift chamber prototypes built along the above lines, with which a spatial accuracy of 0.06 mm and a double track resolution of 0.6 mm were measured. He also describes the final drift chamber system and its operation in HELIOS

Pedagogía ambiental y didáctica ambiental: tendencias en la educación superior

Directory of Open Access Journals (Sweden)

Julio César Tovar-Gálvez

2017-01-01

Full Text Available El artículo aborda el problema del currículo de educación ambiental en la educación superior, para lo que se centra en los conceptos pedagogía ambiental y didáctica ambiental. La metodología consiste en realizar un estado del arte para identificar las tendencias existentes sobre pedagogía ambiental y didáctica ambiental, para desde allí diseñar una encuesta que es dirigida a profesores y estudiantes de programas con formación en lo ambiental, de algunas universidades en Bogotá, con el objetivo de identificar sus opiniones como expertos en lo ambiental. Los resultados muestran un especial énfasis en las tendencias sobre la complejidad, pero así mismo plantean la posibilidad de múltiples modelos según los contextos y necesidades.

VELOCITY FIELD OF COMPRESSIBLE MAGNETOHYDRODYNAMIC TURBULENCE: WAVELET DECOMPOSITION AND MODE SCALINGS

International Nuclear Information System (INIS)

Kowal, Grzegorz; Lazarian, A.

2010-01-01

We study compressible magnetohydrodynamic turbulence, which holds the key to many astrophysical processes, including star formation and cosmic-ray propagation. To account for the variations of the magnetic field in the strongly turbulent fluid, we use wavelet decomposition of the turbulent velocity field into Alfven, slow, and fast modes, which presents an extension of the Cho and Lazarian decomposition approach based on Fourier transforms. The wavelets allow us to follow the variations of the local direction of the magnetic field and therefore improve the quality of the decomposition compared to the Fourier transforms, which are done in the mean field reference frame. For each resulting component, we calculate the spectra and two-point statistics such as longitudinal and transverse structure functions as well as higher order intermittency statistics. In addition, we perform a Helmholtz- Hodge decomposition of the velocity field into incompressible and compressible parts and analyze these components. We find that the turbulence intermittency is different for different components, and we show that the intermittency statistics depend on whether the phenomenon was studied in the global reference frame related to the mean magnetic field or in the frame defined by the local magnetic field. The dependencies of the measures we obtained are different for different components of the velocity; for instance, we show that while the Alfven mode intermittency changes marginally with the Mach number, the intermittency of the fast mode is substantially affected by the change.

Resolution Enhancement of Scanning Laser Acoustic Microscope Using Transverse Wave

International Nuclear Information System (INIS)

Ko, D. S.; Park, J. S.; Kim, Y. H.

1997-01-01

We studied the resolution enhancement of a novel scanning laser acoustic microscope (SLAM) using transverse waves. Mode conversion of the ultrasonic wave takes place at the liquid-solid interface and some energy of the insonifying longitudinal waves in the water will convert to transverse wave energy within the solid specimen. The resolution of SLAM depends on the size of detecting laser spot and the wavelength of the insonifying ultrasonic waves. Science the wavelength of the transverse wave is shorter than that of the longitudinal wave, we are able to achieve the high resolution by using transverse waves. In order to operate SLAM in the transverse wave mode, we made wedge for changing the incident angle. Our experimental results with model 2140 SLAM and an aluminum specimen showed higher contrast of the SLAM image in the transverse wave mode than that in the longitudinal wave mode

Non-Boussinesq turbulent buoyant jet of a low-density gas leaks into high-density ambient

KAUST Repository

El-Amin, Mohamed

2010-12-01

In this article, we study the problem of low-density gas jet injected into high-density ambient numerically which is important in applications such as fuel injection and leaks. It is assumed that the local rate of entrainment is consisted of two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. The integral models of the mass, momentum and concentration fluxes are obtained and transformed to a set of ordinary differential equations using some similarity transformations. The resulting system is solved to determine the centerline quantities which are used to get the mean axial velocity, mean concentration and mean density of the jet. Therefore, the centerline and mean quantities are used together with the governing equation to determine some important turbulent quantities such as, cross-stream velocity, Reynolds stress, velocity- concentration correlation, turbulent eddy viscosity and turbulent eddy diffusivity. Throughout this paper the developed model is verified by comparing the present results with experimental results and jet/plume theory from the literature. © 2010 Elsevier Inc. All rights reserved.

Non-Boussinesq turbulent buoyant jet of a low-density gas leaks into high-density ambient

KAUST Repository

El-Amin, Mohamed; Sun, Shuyu; Kanayama, Hiroshi

2010-01-01

In this article, we study the problem of low-density gas jet injected into high-density ambient numerically which is important in applications such as fuel injection and leaks. It is assumed that the local rate of entrainment is consisted of two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. The integral models of the mass, momentum and concentration fluxes are obtained and transformed to a set of ordinary differential equations using some similarity transformations. The resulting system is solved to determine the centerline quantities which are used to get the mean axial velocity, mean concentration and mean density of the jet. Therefore, the centerline and mean quantities are used together with the governing equation to determine some important turbulent quantities such as, cross-stream velocity, Reynolds stress, velocity- concentration correlation, turbulent eddy viscosity and turbulent eddy diffusivity. Throughout this paper the developed model is verified by comparing the present results with experimental results and jet/plume theory from the literature. © 2010 Elsevier Inc. All rights reserved.

Control of transversal instabilities in reaction-diffusion systems

Science.gov (United States)

Totz, Sonja; Löber, Jakob; Totz, Jan Frederik; Engel, Harald

2018-05-01

In two-dimensional reaction-diffusion systems, local curvature perturbations on traveling waves are typically damped out and vanish. However, if the inhibitor diffuses much faster than the activator, transversal instabilities can arise, leading from flat to folded, spatio-temporally modulated waves and to spreading spiral turbulence. Here, we propose a scheme to induce or inhibit these instabilities via a spatio-temporal feedback loop. In a piecewise-linear version of the FitzHugh–Nagumo model, transversal instabilities and spiral turbulence in the uncontrolled system are shown to be suppressed in the presence of control, thereby stabilizing plane wave propagation. Conversely, in numerical simulations with the modified Oregonator model for the photosensitive Belousov–Zhabotinsky reaction, which does not exhibit transversal instabilities on its own, we demonstrate the feasibility of inducing transversal instabilities and study the emerging wave patterns in a well-controlled manner.

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.

Velocity diagnostics of electron beams within a 140 GHz gyrotron

Science.gov (United States)

Polevoy, Jeffrey Todd

1989-06-01

Experimental measurements of the average axial velocity v(sub parallel) of the electron beam within the M.I.T. 140 GHz MW gyrotron have been performed. The method involves the simultaneous measurement of the radial electrostatic potential of the electron beam V(sub p) and the beam current I(sub b). The V(sub p) is measured through the use of a capacitive probe installed near or within the gyrotron cavity, while I(sub b) is measured with a previously installed Rogowski coil. Three capacitive probes have been designed and built, and two have operated within the gyrotron. The probe results are repeatable and consistent with theory. The measurements of v(sub parallel) and calculations of the corresponding transverse to longitudinal beam velocity ratio (alpha) = v(sub perpendicular)/v(sub parallel) at the cavity have been made at various gyrotron operation parameters. These measurements will provide insight into the causes of discrepancies between theoretical RF interaction efficiencies and experimental efficiencies obtained in experiments with the M.I.T. 140 GHz MW gyrotron. The expected values of v(sub parallel) and (alpha) are determined through the use of a computer code (EGUN) which is used to model the cathode and anode regions of the gyrotron. It also computes the trajectories and velocities of the electrons within the gyrotron. There is good correlation between the expected and measured values of (alpha) at low (alpha), with the expected values from EGUN often falling within the standard errors of the measured values.

POLÍTICA PÚBLICA AMBIENTAL Y AMBIENTE EN EL VALLE DEL CAUCA, 1991-2010

Directory of Open Access Journals (Sweden)

Álvaro Quiceno Martínez

2010-01-01

Full Text Available La política pública ambiental en el Valle del Cauca, a partir de 1991, va en contravía de la conservación ambiental al enfatizar en el crecimiento económico, la generación de plusvalía y la ampliación de la tasa de ganancia. Para la realización de esta investigación se adoptó como herramienta metodológica la revisión bibliográfica. Se halló que la política pública ambiental en el Valle se ha orientado a subsidiar monetaria, ecológica, ambiental y socialmente al sector cañicultor. Se concluye que dicha política ha contribuido al desequilibrio ecológico y al deterioro ambiental.

Ambiente e justiça: sobre a utilidade do conceito de racismo ambiental no contexto brasileiro

OpenAIRE

Silva, Lays Helena Paes e

2013-01-01

A ideia de crise ambiental suscita discussões a respeito de distintas concepções de natureza e de ambiente e das disputas simbólicas e materiais neste meio. Uma concepção que toma sociedade e ambiente como pares inseparáveis levou à emergência, nos Estados Unidos, de movimentos que introduziram conceitos como justiça ambiental e racismo ambiental. No Brasil, surgiram movimentos e estudos focados nas mesmas bandeiras de luta e nos mesmos conceitos. Considerando as especificidades do racismo no...

Evolution of microstructure and elastic wave velocities in dehydrated gypsum samples

Science.gov (United States)

Milsch, Harald; Priegnitz, Mike

2012-12-01

We report on changes in P and S-wave velocities and rock microstructure induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air, at ambient pressure, and temperatures between 378 and 423 K. Dehydration did not proceed homogeneously but via a reaction front moving sample inwards separating an outer highly porous rim from the remaining gypsum which, above approximately 393 (±5) K, concurrently decomposed into hemihydrate. Overall porosity was observed to continuously increase with reaction progress from approximately 2% for fully hydrated samples to 30% for completely dehydrated ones. Concurrently, P and S-wave velocities linearly decreased with porosity from 5.2 and 2.7 km/s to 1.0 and 0.7 km/s, respectively. It is concluded that a linearized empirical Raymer-type model extended by a critical porosity term and based on the respective time dependent mineral and pore volumes reasonably replicates the P and S-wave data in relation to reaction progress and porosity.

Structure of kinetic Alfvacute en waves with small transverse scale length

International Nuclear Information System (INIS)

Morales, G.J.; Maggs, J.E.

1997-01-01

This analytical study illustrates the spatial pattern of kinetic Alfvacute en waves excited by a current-modulating disk whose dimension a, transverse to the confining magnetic field, is comparable to the ion sound gyroradius c s /Ω i , where c s is the sound speed and Ω i the ion cyclotron frequency. The radial structure of the wave azimuthal magnetic field is found to consist of four regions: a Bessel function behavior for r a which merges onto the 1/r asymptotic region. The pattern spreads at an angle given by tanθ=(ω/Ω i )(c s /v A )/2.6, where ω is the modulation frequency and v A is the Alfvacute en speed. This behavior arises because there is a maximum value at finite k perpendicular for the ratio of the perpendicular to parallel group velocity, which differs from the cone spreading [G. J. Morales et al., Phys. Plasmas 1, 3765 (1994)] associated with inertial Alfvacute en waves. copyright 1997 American Institute of Physics

Local transport in multi-filamentary superconductors: longitudinal versus transverse dissipation

International Nuclear Information System (INIS)

Borroto, A; Del Rio, L; Altshuler, E; Arronte, M; Mikheenko, P; Qviller, A; Johansen, T H

2013-01-01

Little is known on the electrical properties of superconducting tapes and coatings in the direction transverse to the long dimension of the composite. However, transverse dissipation can eventually determine the fate of a transmission line in the case of failure due to the presence of transversal cracks, and is also crucial in the AC regime. In this paper we present a detailed experimental study of the electrical transport properties along the transverse direction of Bi 2 Sr 2 Ca 2 Cu 3 O 10+x -Ag tapes, and compare them with those measured along the long axis of the material. We study in detail the influence of the tape’s microstructure on electrical properties along both directions by using sliding electrodes. Our measurements suggest that there is always dissipation in the transverse direction for any value of the current. We also demonstrate that the local dissipation in the transverse direction has a nontrivial correlation with the local density of superconducting filaments. (paper)

Anomalous resistivity due to low-frequency turbulence. [of collisionless plasma with limited acceleration of high velocity runaway electrons

Science.gov (United States)

Rowland, H. L.; Palmadesso, P. J.

1983-01-01

Large amplitude ion cyclotron waves have been observed on auroral field lines. In the presence of an electric field parallel to the ambient magnetic field these waves prevent the acceleration of the bulk of the plasma electrons leading to the formation of a runaway tail. It is shown that low-frequency turbulence can also limit the acceleration of high-velocity runaway electrons via pitch angle scattering at the anomalous Doppler resonance.

Psychophysics of a nociceptive test in the mouse: ambient temperature as a key factor for variation.

Directory of Open Access Journals (Sweden)

Ivanne Pincedé

Full Text Available The mouse is increasingly used in biomedical research, notably in behavioral neurosciences for the development of tests or models of pain. Our goal was to provide the scientific community with an outstanding tool that allows the determination of psychophysical descriptors of a nociceptive reaction, which are inaccessible with conventional methods: namely the true threshold, true latency, conduction velocity of the peripheral fibers that trigger the response and latency of the central decision-making process.Basically, the procedures involved heating of the tail with a CO(2 laser, recording of tail temperature with an infrared camera and stopping the heating when the animal reacted. The method is based mainly on the measurement of three observable variables, namely the initial temperature, the heating rate and the temperature reached at the actual moment of the reaction following random variations in noxious radiant heat. The initial temperature of the tail, which itself depends on the ambient temperature, very markedly influenced the behavioral threshold, the behavioral latency and the conduction velocity of the peripheral fibers but not the latency of the central decision-making.We have validated a psychophysical approach to nociceptive reactions for the mouse, which has already been described for rats and Humans. It enables the determination of four variables, which contribute to the overall latency of the response. The usefulness of such an approach was demonstrated by providing new fundamental findings regarding the influence of ambient temperature on nociceptive processes. We conclude by challenging the validity of using as "pain index" the reaction time of a behavioral response to an increasing heat stimulus and emphasize the need for a very careful control of the ambient temperature, as a prevailing environmental source of variation, during any behavioral testing of mice.

Effects of Surface Nonuniformities on the Mean Transverse Energy from Photocathodes

Science.gov (United States)

Karkare, Siddharth; Bazarov, Ivan

2015-08-01

The performance of photoinjectors is limited by the lowest value of the mean transverse energy of the electrons obtained from photocathodes. The factors that influence the mean transverse energy are poorly understood. In this paper, we develop models to calculate the effect of spatial work-function variations and subnanometer-scale roughness and surface defects on the mean transverse energy. We show that these can limit the lowest value of mean transverse energy achieved and that atomically perfect surfaces will be required to further reduce the mean transverse energy obtained from photocathodes.

Local velocity measurements in lead-bismuth and sodium flows using the ultrasound doppler velocimetry

International Nuclear Information System (INIS)

Eckert, S.; Gerbeth, G.

2003-01-01

We will present measurements of the velocity profiles in liquid sodium and eutectic lead-bismuth by means of the Ultrasonic Doppler Velocimetry (UDV). A sodium flow in a rectangular duct exposed to an external, transverse magnetic field has been examined. To demonstrate the capability of UDV the transformation of the well-known turbulent, piston-like profile to an M-shaped velocity profile for growing magnetic field strength was observed. The significance of artifacts such as caused by the existence of reflecting interfaces in the measuring domain will be discussed. In the sodium case, the measurements were performed through the channel wall. An integrated ultrasonic sensor with acoustic wave-guide has been developed to overcome the limitation of ultrasonic transducers to temperatures lower than 200 .deg. C. This sensor can presently be applied at maximum temperatures up to 800 .deg. C. Stable and robust measurements have been performed in various PbBi flows in our laboratory at FZR as well as at the THESYS loop of the KALLA laboratory of the ForschungsZentrum Karlsruhe (FZK). We will also present experimental results obtained in a PbBi bubbly flow at 250...300 .deg. C. Argon bubbles were injected through a single orifice in a cylindrical container filled with stagnant PbBi. Velocity profiles were measured in the bubble plume. Mean values of the liquid as well as the bubble velocity were extracted from the data and will be presented as function of the gas flow rate

Transverse tomography and radiotherapy

International Nuclear Information System (INIS)

Leer, J.W.H.

1982-01-01

This study was intended to delineate the indications for radiotherapy treatment-planning with the help of computerized axial tomography (C.T.) and transverse analog tomography (T.A.T.). Radiotherapy localisation procedures with the conventional method (simulator), with the CT-scanner and with the transverse analog tomograph (T.A.T., Simtomix, Oldelft) were compared. As criterium for evaluation differences in reconstruction drawing based on these methods were used. A certain method was judged ''superior'' to another if the delineation of the target volume was more accurate, if a better impression was gained of the site of (for irradiation) organs at risk, or if the localisation could only be performed with that method. The selected group of patients consisted of 120 patients for whom a reconstruction drawing in the transverse plane was made according to the treatment philosophy. In this group CT-assisted localisation was judged on 68 occasions superior to the conventional method. In a number of cases it was found that a ''standard'' change in a standard target volume, on the base of augmented anatomical knowledge, made the conventional method sufficient. The use of CT-scanner for treatment planning was estimated. For ca. 270/1000 new patients a CT-scan is helpful (diagnostic scan), for 140 of them the scan is necessary (planning scan). The quality of the anatomical information obtained with the T.A.T. does not yet fall within acceptable limits, but progress has been made. (Auth.)

Competencias instrumentales del docente universitario en la gestión de la educación ambiental

Directory of Open Access Journals (Sweden)

Nelson Romero Parra

2013-01-01

Full Text Available El propósito principal de la investigación fue analizar las competencias instrumentales del docente universitario en la gestión de la educación ambiental en instituciones de educación superior del Estado Zulia. La investigación fue de tipo descriptiva de campo, con un diseño no experimental-transversal. La muestra estuvo constituida por 328 estudiantes y docentes de las universidades Rafael María Baralt, Dr. José Gregorio Hernández y la Universidad del Zulia. La información se obtuvo mediante la aplicación de un cuestionario reorientado bajo la escala tipo Likert con 5 alternativas de respuestas. La confiabilidad del mismo se calculó mediante el método de Alpha Cronbach, obteniendo un valor de 0.88. Para el análisis cualitativo y cuantitativo se utilizó la estadística descriptiva inferencial para ambas muestras, pudiéndose concluir que existe baja presencia de las competencias instrumentales docentes, observándose debilidades en la implementación de instrumentos de gestión ambiental.

Entanglement of transverse modes in a pendular cavity

OpenAIRE

Mancini, Stefano; Gatti, Alessandra

2001-01-01

We study the phenomena that arise in the transverse structure of electromagnetic field impinging on a linear Fabry-Perot cavity with an oscillating end mirror. We find quantum correlations among transverse modes which can be considered as a signature of their entanglement.

A&T Sector Note on the PS transverse feedback

CERN Document Server

Coly, Marcel; Blas, Alfred; Sterbini, Guido; CERN. Geneva. ATS Department

2017-01-01

In a particle accelerator, several contributions can degrade the beam quality and particularly the beam transverse emittance. In this document we will describe a system used in the CERN Proton Synchrotron (PS) to cope with the injection steering errors and the transverse instabilities: the PS transverse feedback (PS TFB). As time progresses, this system is also being used for other purpose, to increase in a controlled way the beam transverse emittance and to excite the beam for the Multi-Turn-Extraction (MTE). In 2016, it has been successfully used on some operational beams to damp injection oscillations. This allowed to test the reliability of the system for its operational deployment. A piquet service is available in case of problem.

Interplay among transversity induced asymmetries in hadron leptoproduction

CERN Document Server

Adolph, C.; Alexeev, M.G.; Alexeev, G.D.; Amoroso, A.; Andrieux, V.; Anosov, V.; Augustyniak, W.; Austregesilo, A.; Azevedo, C.D.R.; Badelek, B.; Balestra, F.; Barth, J.; Beck, R.; Bedfer, Y.; Bernhard, J.; Bicker, K.; Bielert, E.R.; Birsa, R.; Bisplinghoff, J.; Bodlak, M.; Boer, M.; Bordalo, P.; Bradamante, F.; Braun, C.; Bressan, A.; Buchele, M.; Burtin, E.; Chang, W.C.; Chiosso, M.; Choi, I.; Chung, S.U.; Cicuttin, A.; Crespo, M.L.; Curiel, Q.; d'Hose, N.; Dalla Torre, S.; Dasgupta, S.S.; Dasgupta, S.; Denisov, O.Yu.; Dhara, L.; Donskov, S.V.; Doshita, N.; Duic, V.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P.D.; Eyrich, W.; Ferrero, A.; Finger, M.; M. Finger jr; Fischer, H.; Franco, C.; von Hohenesche, N. du Fresne; Friedrich, J.M.; Frolov, V.; Fuchey, E.; Gautheron, F.; Gavrichtchouk, O.P.; Gerassimov, S.; Giordano, F.; Gnesi, I.; Gorzellik, M.; Grabmuller, S.; Grasso, A.; Grosse-Perdekamp, M.; Grube, B.; Grussenmeyer, T.; Guskov, A.; Haas, F.; Hahne, D.; von Harrach, D.; Hashimoto, R.; Heinsius, F.H.; Herrmann, F.; Hinterberger, F.; Horikawa, N.; Hsieh, C.Yu; Huber, S.; Ishimoto, S.; Ivanov, A.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jorg, P.; Joosten, R.; Kabuss, E.; Ketzer, B.; Khaustov, G.V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koivuniemi, J.H.; Kolosov, V.N.; Kondo, K.; Konigsmann, K.; Konorov, I.; Konstantinov, V.F.; Kotzinian, A.M.; Kouznetsov, O.; Kramer, M.; Kremser, P.; Krinner, F.; Kroumchtein, Z.V.; Kuchinski, N.; Kunne, F.; Kurek, K.; Kurjata, R.P.; Lednev, A.A.; Lehmann, A.; Levillain, M.; Levorato, S.; Lichtenstadt, J.; Longo, R.; Maggiora, A.; Magnon, A.; Makins, N.; Makke, N.; Mallot, G.K.; Marchand, C.; Marianski, B.; Martin, A.; Marzec, J.; Matousek, J.; Matsuda, H.; Matsuda, T.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu. V.; Miyachi, Y.; Montuenga, P.; Nagaytsev, A.; Nerling, F.; Neyret, D.; Nikolaenko, V.I.; Novy, J.; Nowak, W.D.; Nukazuka, G.; Nunes, A.S.; Olshevsky, A.G.; Orlov, I.; Ostrick, M.; Panzieri, D.; Parsamyan, B.; Paul, S.; Peng, J.C.; Pereira, F.; Pesaro, G.; Pesek, M.; Peshekhonov, D.V.; Platchkov, S.; Pochodzalla, J.; Polyakov, V.A.; Pretz, J.; Quaresma, M.; Quintans, C.; Ramos, S.; Regali, C.; Reicherz, G.; Riedl, C.; Rossiyskaya, N.S.; Ryabchikov, D.I.; Rychter, A.; Samoylenko, V.D.; Sandacz, A.; Santos, C.; Sarkar, S.; Savin, I.A.; Sbrizzai, G.; Schiavon, P.; Schmidt, K.; Schmieden, H.; Schonning, K.; Schopferer, S.; Selyunin, A.; Shevchenko, O.Yu.; Silva, L.; Sinha, L.; Sirtl, S.; Slunecka, M.; Sozzi, F.; Srnka, A.; Stolarski, M.; Sulc, M.; Suzuki, H.; Szabelski, A.; Szameitat, T.; Sznajder, P.; Takekawa, S.; Wolbeek, J. ter; Tessaro, S.; Tessarotto, F.; Thibaud, F.; Tosello, F.; Tskhay, V.; Uhl, S.; Veloso, J.; Virius, M.; Weisrock, T.; Wilfert, M.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zink, A.

2016-01-01

In the fragmentation of a transversely polarized quark several left-right asymmetries are possible for the hadrons in the jet. When only one unpolarized hadron is selected, it exhibits an azimuthal modulation known as Collins effect. When a pair of oppositely charged hadrons is observed, three asymmetries can be considered, a di-hadron asymmetry and two single hadron asymmetries. In lepton deep inelastic scattering on transversely polarized nucleons all these asymmetries are coupled with the transversity distribution. From the high statistics COMPASS data on oppositely charged hadron-pair production we have investigated for the first time the dependence of these three asymmetries on the difference of the azimuthal angles of the two hadrons. The similarity of transversity induced single and di-hadron asymmetries is discussed. A phenomenological analysis of the data allows to establish quantitative relationships among them, providing strong indication that the underlying fragmentation mechanisms are all driven ...

Auto-correlation of velocity-fluctuations and frequency-dependent diffusion constant for hot electrons

International Nuclear Information System (INIS)

Roy, M.D.; Nag, B.R.

1981-01-01

A method has been developed for determining the auto-correlation functions of the fluctuations in the transverse and the parallel components of hot carrier-velocity in a semiconductor by Monte Carlo simulation. The functions for electrons in InSb are determined by this method for applied electric fields of 50 V/cm, 75 V/cm, and 100 V/cm. With increasing value of the time interval the transverse auto-correlation function fall nearly exponentially to zero, but the parallel function falls sharply to a negative peak, then rises to positive values and finally becomes zero. The interval beyond which the auto-correlation function is zero and the correlation time are also evaluated. The correlation time is found to be approximately 1.6 times the relaxation time calculated from the chord mobility. The effect of the flight sampling time on the value of variance of the displacement, is investigated in terms of the low frequency diffusion constants, determined from the variation of the correlation functions. It is found that the diffusion constants become independent of the sampling time if it is of the order of one hundred times the relaxation time. The frequency-dependent diffusion constants are calculated from the correlation functions. The transverse diffusion constant falls monotonically with frequency for all the field strengths studied. The parallel diffusion constant has similar variation for the lower fields (50 V/cm and 75 V/cm) but it has a peak at about 44 GHz for the field of 100 V/cm. (orig.)

A new fifth parameter for transverse isotropy III: reflection and transmission coefficients

Science.gov (United States)

Kawakatsu, Hitoshi

2018-04-01

The effect of the newly defined fifth parameter, ηκ, of transverse anisotropy to the reflection and transmission coefficients, especially for P-to-S and S-to-P conversion coefficients, is examined. While ηκ systematically affects the P-to-S and S-to-P conversions, in the incidence angle range of the practical interest of receiver function studies, the effect may be asymmetric in a sense that P-wave receiver function is affected more than S-receiver function in terms of amplitude. This asymmetry may help resolving ηκ via extensive receiver function analysis. It is also found that P-wave anisotropy significantly influences P-to-S and S-to-P conversion coefficients that complicates the interpretation of receiver functions, because, for isotropic media, we typically attribute the primary receiver function signals to S-wave velocity changes but not to P-wave changes.

Launch Velocities in Successful Golf Putting: An Analytical Analysis

Directory of Open Access Journals (Sweden)

John F. Mahoney

2017-04-01

Full Text Available Background: This study is concerned with the special case of a putted ball intersecting a standard golf hole at its diameter. The velocity of the ball at the initial rim of the hole is termed the launch velocity and depending upon its value the ball may either be captured or it may escape capture by jumping over the hole. The critical value of the launch velocity (V is such that lesser values result in capture while greater values produce escape. Purpose: Since the value of the V entered prominently in some theoretical studies of putting, the aim of the current study is to provide an original re-evaluation of V and to contrast our results with existing results. Method: This analytical analysis relies on trigonometry in conjunction with Newtonian mechanics and the mathematics of projectiles. The results of a recent study into the mathematics of a bouncing ball which included the notions of restitution and friction were also employed in the analysis. Results: If bouncing and slipping do not occur when the ball hits the far rim of the hole our analysis produces a value of V of 1.356 m/s. When bouncing and slipping are present we find that V is at least 1.609 m/s but increases beyond this value as slipping and friction become greater. Useful relations which relate the dynamics and geometry of the ball to V are provided. Conclusion: Since ambient conditions may influence the extent of bounce and slippage we conjecture that the value of V is not unique.

New sensor for measurement of low air flow velocity. Phase I final report

International Nuclear Information System (INIS)

Hashemian, H.M.; Hashemian, M.; Riggsbee, E.T.

1995-08-01

The project described here is the Phase I feasibility study of a two-phase program to integrate existing technologies to provide a system for determining air flow velocity and direction in radiation work areas. Basically, a low air flow sensor referred to as a thermocouple flow sensor has been developed. The sensor uses a thermocouple as its sensing element. The response time of the thermocouple is measured using an existing in-situ method called the Loop Current Step Response (LCSR) test. The response time results are then converted to a flow signal using a response time-versus-flow correlation. The Phase I effort has shown that a strong correlation exists between the response time of small diameter thermocouples and the ambient flow rate. As such, it has been demonstrated that thermocouple flow sensors can be used successfully to measure low air flow rates that can not be measured with conventional flow sensors. While the thermocouple flow sensor developed in this project was very successful in determining air flow velocity, determining air flow direction was beyond the scope of the Phase I project. Nevertheless, work was performed during Phase I to determine how the new flow sensor can be used to determine the direction, as well as the velocity, of ambient air movements. Basically, it is necessary to use either multiple flow sensors or move a single sensor in the monitoring area and make flow measurements at various locations sweeping the area from top to bottom and from left to right. The results can then be used with empirical or physical models, or in terms of directional vectors to estimate air flow patterns. The measurements can be made continuously or periodically to update the flow patterns as they change when people and objects are moved in the monitoring area. The potential for using multiple thermocouple flow sensors for determining air flow patterns will be examined in Phase II

Optical observations on the CRIT-II Critical Ionization Velocity Experiment

International Nuclear Information System (INIS)

Stenbaek-Nielsen, H.C.; Wescott, E.M.; Haerendel, G.; Valenzuela, A.

1990-01-01

A rocket borne Critical Ionization Velocity (CIV) experiment was carried out from Wallops Island at dusk on May 4, 1989. Two barium shaped charges were released below the solar terminator (to prevent photoionization) at altitudes near 400 km. The ambient ionospheric electron density was 5x10 5 cm -3 . The neutral barium jet was directed upwards and at an angle of nominally 45 degrees to B which gives approximately 3x10 23 neutrals with super critical velocity. Ions created by a CIV process in the region of the neutral jet would travel up along B into sunlight where they can be detected optically. Well defined ion clouds (max. brightness 750 R) were observed in both releases. An ionization rate of 0.8%s -1 (125s ionization time constant) can account for the observed ion cloud near the release field line, but the ionization rate falls off with increasing distance from the release. It is concluded that a CIV process was present in the neutral jet out to about 50 km from the release, which is significantly further than allowed by current theories

Integral Analysis of Seismic Refraction and Ambient Vibration Survey for Subsurface Profile Evaluation

Science.gov (United States)

Hazreek, Z. A. M.; Kamarudin, A. F.; Rosli, S.; Fauziah, A.; Akmal, M. A. K.; Aziman, M.; Azhar, A. T. S.; Ashraf, M. I. M.; Shaylinda, M. Z. N.; Rais, Y.; Ishak, M. F.; Alel, M. N. A.

2018-04-01

Geotechnical site investigation as known as subsurface profile evaluation is the process of subsurface layer characteristics determination which finally used for design and construction phase. Traditionally, site investigation was performed using drilling technique thus suffers from several limitation due to cost, time, data coverage and sustainability. In order to overcome those problems, this study adopted surface techniques using seismic refraction and ambient vibration method for subsurface profile depth evaluation. Seismic refraction data acquisition and processing was performed using ABEM Terraloc and OPTIM software respectively. Meanwhile ambient vibration data acquisition and processing was performed using CityShark II, Lennartz and GEOPSY software respectively. It was found that studied area consist of two layers representing overburden and bedrock geomaterials based on p-wave velocity value (vp = 300 – 2500 m/s and vp > 2500 m/s) and natural frequency value (Fo = 3.37 – 3.90 Hz) analyzed. Further analysis found that both methods show some good similarity in term of depth and thickness with percentage accuracy at 60 – 97%. Consequently, this study has demonstrated that the application of seismic refractin and ambient vibration method was applicable in subsurface profile depth and thickness estimation. Moreover, surface technique which consider as non-destructive method adopted in this study was able to compliment conventional drilling method in term of cost, time, data coverage and environmental sustainaibility.

Transverse colon cancer with Krukenberg tumor : A case report

OpenAIRE

東門, 敦子; 松原, 洋孝; 下地, 英明; 伊佐, 勉; 濱安, 俊吾; 仲地, 厚; 宮里, 浩; 白石, 祐之; 武藤, 良弘; Tomon, Atsuko; Matsubara, Hirotaka; Shimoji, Hideaki; Isa, Tsutomu; Nakachi, Atsushi; Miyazato, Hiroshi

1999-01-01

A case of Krukenberg tumor in a 30-year-old woman with transverse colon cancer is reported herein. The patient was found to have bilateral ovarian tumors and abnormal elevation of serum CEA at a community hospital. Subsequently, she was referred to the University Hospital for further work. Diagnostic examinations including US, CT and colonoscopy demonstrated transverse colon cancer and bilateral ovarian tumors. Exploratory laparotomy showed the growth of transverse colon cancer over the perit...

Analysis of transverse field distributions in Porro prism resonators

Science.gov (United States)

Litvin, Igor A.; Burger, Liesl; Forbes, Andrew

2007-05-01

A model to describe the transverse field distribution of the output beam from porro prism resonators is proposed. The model allows the prediction of the output transverse field distribution by assuming that the main areas of loss are located at the apexes of the porro prisms. Experimental work on a particular system showed some interested correlations between the time domain behavior of the resonator and the transverse field output. These findings are presented and discussed.

Transverse momentum in semi-inclusive deep inelastic scattering

International Nuclear Information System (INIS)

Ceccopieri, Federico Alberto; Trentadue, Luca

2006-01-01

Within the framework of perturbative quantum chromodynamics we derive the evolution equations for transverse momentum dependent distributions and apply them to the case of semi-inclusive deep inelastic scattering. The evolution equations encode the perturbative component of transverse momentum generated by collinear parton branchings. The current fragmentation is described via transverse momentum dependent parton densities and fragmentation functions. Target fragmentation instead is described via fracture functions. We present, to leading logarithmic accuracy, the corresponding semi-inclusive deep inelastic scattering cross-section, which applies to the entire phase space of the detected hadron. Some phenomenological implications and further developments are briefly outlined

Transverse myelitis

International Nuclear Information System (INIS)

Black, M.J.; Motaghedi, B.; Robitaille, Y.

1980-01-01

Transverse myelitis is a known complication of radiation treatment for carcinoma of the heat and neck. In a five year period, 1970 to 1975, 120 patients with head and neck cancer received radiation as part of their treatment in this hospital. A review of the records of these patients showed only two cases of myelitis, an incidence of about 2%. This paper reviews the clinical syndrome; treatment and preventive measures are discussed and a survey of the literature is presented

Combined threshold and transverse momentum resummation for inclusive observables

International Nuclear Information System (INIS)

Muselli, Claudio; Forte, Stefano; Ridolfi, Giovanni

2017-01-01

We present a combined resummation for the transverse momentum distribution of a colorless final state in perturbative QCD, expressed as a function of transverse momentum p T and the scaling variable x. Its expression satisfies three requirements: it reduces to standard transverse momentum resummation to any desired logarithmic order in the limit p T →0 for fixed x, up to power suppressed corrections in p T ; it reduces to threshold resummation to any desired logarithmic order in the limit x→1 for fixed p T , up to power suppressed correction in 1−x; upon integration over transverse momentum it reproduces the resummation of the total cross cross at any given logarithmic order in the threshold x→1 limit, up to power suppressed correction in 1−x. Its main ingredient, and our main new result, is a modified form of transverse momentum resummation, which leads to threshold resummation upon integration over p T , and for which we provide a simple closed-form analytic expression in Fourier-Mellin (b,N) space. We give explicit coefficients up to NNLL order for the specific case of Higgs production in gluon fusion in the effective field theory limit. Our result allows for a systematic improvement of the transverse momentum distribution through threshold resummation which holds for all p T , and elucidates the relation between transverse momentum resummation and threshold resummation at the inclusive level, specifically by providing within perturbative QCD a simple derivation of the main consequence of the so-called collinear anomaly of SCET.

Combined threshold and transverse momentum resummation for inclusive observables

Energy Technology Data Exchange (ETDEWEB)

Muselli, Claudio; Forte, Stefano [Tif Lab, Dipartimento di Fisica, Università di Milano and INFN, Sezione di Milano,Via Celoria 16, I-20133 Milano (Italy); Ridolfi, Giovanni [Dipartimento di Fisica, Università di Genova and INFN, Sezione di Genova,Via Dodecaneso 33, I-16146 Genova (Italy)

2017-03-21

We present a combined resummation for the transverse momentum distribution of a colorless final state in perturbative QCD, expressed as a function of transverse momentum p{sub T} and the scaling variable x. Its expression satisfies three requirements: it reduces to standard transverse momentum resummation to any desired logarithmic order in the limit p{sub T}→0 for fixed x, up to power suppressed corrections in p{sub T}; it reduces to threshold resummation to any desired logarithmic order in the limit x→1 for fixed p{sub T}, up to power suppressed correction in 1−x; upon integration over transverse momentum it reproduces the resummation of the total cross cross at any given logarithmic order in the threshold x→1 limit, up to power suppressed correction in 1−x. Its main ingredient, and our main new result, is a modified form of transverse momentum resummation, which leads to threshold resummation upon integration over p{sub T}, and for which we provide a simple closed-form analytic expression in Fourier-Mellin (b,N) space. We give explicit coefficients up to NNLL order for the specific case of Higgs production in gluon fusion in the effective field theory limit. Our result allows for a systematic improvement of the transverse momentum distribution through threshold resummation which holds for all p{sub T}, and elucidates the relation between transverse momentum resummation and threshold resummation at the inclusive level, specifically by providing within perturbative QCD a simple derivation of the main consequence of the so-called collinear anomaly of SCET.

Variations in Transverse Foramina of Cervical Vertebrae: Morphology & Clinical Importance

Directory of Open Access Journals (Sweden)

Vaishakhi Gonsai

2015-12-01

Full Text Available Background: The purpose of this study is to investigate variations in transverse foramina in the cervical vertebrae and its morphological and clinical importance. Materials and Method : The variations in the number and size of transverse foramina was studied in total 200 human dried cervical vertebrae, which were taken from the Department of Anatomy, B.J.Medical College, Ahmedabad. All the vertebrae were observed for variation in number and size of transverse foramina. Results: Out of 200 cervical vertebrae, complete double transverse foramina were observed in 40 vertebrae (20%, among them unilateral double foramina were found in 31 vertebrae (15.5% and the bilateral double foramina were found in 9 vertebrae (4.5%. Incomplete double transverse foramina were observed in 22 vertebrae (11%, among them unilateral double foramina were found in 16 vertebrae (8% and bilateral double foramina were observed in 6 vertebrae (3%. Conclusion: Complete unilateral double transverse foramina of cervical vertebrae were more common than bilateral. Also unilateral small size transverse foramina of cervical vertebrae were also common. This variation is important for the neurosurgeon during cervical surgery. Under such condition the course of the vertebral artery may be distorted. It is also useful for Radiologist during CT and MRI scan.

Observation of Single Isolated Electrons of High Transverse Momentum in Events with Missing Transverse Energy at the CERN pp Collider

DEFF Research Database (Denmark)

Banner, M.; Kofoed-Hansen, O.

1983-01-01

We report the results of a search for single isolated electrons of high transverse momentum at the CERN collider. Above 15 GeV/c, four events are found having large missing transverse energy along a direction opposite in azimuth to that of the high-pT electron. Both the configuration of the events...

Transverse momentum signatures for heavy Higgs bosons

International Nuclear Information System (INIS)

Cahn, R.N.; Ellis, S.D.; Kleiss, R.; Stirling, W.J.

1986-01-01

Heavy Higgs bosons produced by WW fusion at the SSC will have transverse mementum of order M/sub w/. The background due to q anti q → ZZ will produce pairs with characteristically less transverse momentum. This provides a useful discriminator. It may be possible to tag the WW fusion events in a manner analogous to that used in two photon physics. 12 refs., 4 figs

Three-component ambient noise beamforming in the Parkfield area

Science.gov (United States)

Löer, Katrin; Riahi, Nima; Saenger, Erik H.

2018-06-01

We apply a three-component beamforming algorithm to an ambient noise data set recorded at a seismic array to extract information about both isotropic and anisotropic surface wave velocities. In particular, we test the sensitivity of the method with respect to the array geometry as well as to seasonal variations in the distribution of noise sources. In the earth's crust, anisotropy is typically caused by oriented faults or fractures and can be altered when earthquakes or human activities cause these structures to change. Monitoring anisotropy changes thus provides time-dependent information on subsurface processes, provided they can be distinguished from other effects. We analyse ambient noise data at frequencies between 0.08 and 0.52 Hz recorded at a three-component array in the Parkfield area, California (US), between 2001 November and 2002 April. During this time, no major earthquakes were identified in the area and structural changes are thus not expected. We compute dispersion curves of Love and Rayleigh waves and estimate anisotropy parameters for Love waves. For Rayleigh waves, the azimuthal source coverage is too limited to perform anisotropy analysis. For Love waves, ambient noise sources are more widely distributed and we observe significant and stable surface wave anisotropy for frequencies between 0.2 and 0.4 Hz. Synthetic data experiments indicate that the array geometry introduces apparent anisotropy, especially when waves from multiple sources arrive simultaneously at the array. Both the magnitude and the pattern of apparent anisotropy, however, differ significantly from the anisotropy observed in Love wave data. Temporal variations of anisotropy parameters observed at frequencies below 0.2 Hz and above 0.4 Hz correlate with changes in the source distribution. Frequencies between 0.2 and 0.4 Hz, however, are less affected by these variations and provide relatively stable results over the period of study.

Relating seismicity to the velocity structure of the San Andreas Fault near Parkfield, CA

Science.gov (United States)

Lippoldt, Rachel; Porritt, Robert W.; Sammis, Charles G.

2017-06-01

The central section of the San Andreas Fault (SAF) displays a range of seismic phenomena including normal earthquakes, low-frequency earthquakes (LFE), repeating microearthquakes (REQ) and aseismic creep. Although many lines of evidence suggest that LFEs are tied to the presence of fluids, their geological setting is still poorly understood. Here, we map the seismic velocity structures associated with LFEs beneath the central SAF using surface wave tomography from ambient seismic noise to provide constraints on the physical conditions that control LFE occurrence. Fault perpendicular sections show that the SAF, as revealed by lateral contrasts in relative velocities, is contiguous to depths of 50 km and appears to be relatively localized at depths between about 15 and 30 km. This is consistent with the hypothesis that LFEs are shear-slip events on a deep extension of the SAF. We find that along strike variations in seismic behaviour correspond to changes in the seismic structure, which support proposed connections between fluids and seismicity. LFEs and REQs occur within low-velocity structures, suggesting that the presence of fluids, weaker minerals, or hydrous phase minerals may play an important role in the generation of slow-slip phenomena.

Interplay among transversity induced asymmetries in hadron leptoproduction

Directory of Open Access Journals (Sweden)

C. Adolph

2016-02-01

Full Text Available In the fragmentation of a transversely polarized quark several left–right asymmetries are possible for the hadrons in the jet. When only one unpolarized hadron is selected, it exhibits an azimuthal modulation known as the Collins effect. When a pair of oppositely charged hadrons is observed, three asymmetries can be considered, a di-hadron asymmetry and two single hadron asymmetries. In lepton deep inelastic scattering on transversely polarized nucleons all these asymmetries are coupled with the transversity distribution. From the high statistics COMPASS data on oppositely charged hadron-pair production we have investigated for the first time the dependence of these three asymmetries on the difference of the azimuthal angles of the two hadrons. The similarity of transversity induced single and di-hadron asymmetries is discussed. A new analysis of the data allows quantitative relationships to be established among them, providing for the first time strong experimental indication that the underlying fragmentation mechanisms are all driven by a common physical process.

Salud ambiental: conceptos y actividades

Directory of Open Access Journals (Sweden)

Gonzalo A. Ordóñez

2000-03-01

Full Text Available La finalidad del trabajo es aportar información y propuestas conceptuales que faciliten la tarea de quienes tienen a su cargo la sistematización institucional de la salud ambiental. Se hace un análisis de la noción de "ambiente" para la cual se sugiere una definición, y se examina el lugar de la salud ambiental en el contexto de los problemas ambientales y sus vertientes "verde" y "azul". Se examinan denominaciones equivalentes de salud ambiental y se introducen los servicios de salud ambiental. Se proporcionan varias definiciones y se da la oficial de salud ambiental adoptada por la OMS en Sofía, Bulgaria (1993. A continuación se transcriben las áreas básicas que a la salud ambiental le han asignado diversas organizaciones o reuniones, como la OPS, la OMS, el Programa 21 y otros. A partir de aquí se construye un repertorio bastante completo de áreas y subáreas y se encuentra que todos los listados son, en realidad, una reunión asistemática de tres tipos de constituyentes: determinantes (factores o hechos de la realidad física, procesos (conjuntos de intervenciones y funciones (conjuntos de acciones de gestión, los cuales pueden enfocarse matricialmente y llevan a individualizar actividades de los servicios de salud ambiental. Se proponen unas reglas de operación que permiten, en una especie de álgebra, construir expresiones para especificar con precisión las actividades y sus agregados. De este modo se logra disponer de un lenguaje simbólico común que puede ayudar a la intercomunicación, enseñanza e investigación en el ámbito de la salud ambiental.

Transverse intrinsic localized modes in monatomic chain and in graphene

Energy Technology Data Exchange (ETDEWEB)

Hizhnyakov, V. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Klopov, M. [Department of Physics, Faculty of Science, Tallinn University of Technology, Ehitajate 5, 19086 Tallinn (Estonia); Shelkan, A., E-mail: shell@ut.ee [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia)

2016-03-06

In this paper an analytical and numerical study of anharmonic vibrations of monatomic chain and graphene in transverse (perpendicular) with respect to the chain/plane direction is presented. Due to the lack of odd anharmonicities and presence of hard quartic anharmonicity for displacements in this direction, there may exist localized anharmonic transverse modes with the frequencies above the spectrum of the corresponding phonons. Although these frequencies are in resonance with longitudinal (chain) or in-plane (graphene) phonons, the modes can decay only due to a weak anharmonic process. Therefore the lifetime of these vibrations may be very long. E.g. in the chain, according to our theoretical and numerical calculations it may exceed 10{sup 10} periods. We call these vibrations as transverse intrinsic localized modes. - Highlights: • In a stretched monatomic chain, long-living nonlinear transverse localized modes may exist. • Transverse vibrations of a chain slowly decay due to creation of longitudinal phonons. • Lifetime of transverse vibrations of a chain may exceed billion periods of vibrations. • In stretched graphene, long-living out-of-plain localized vibrations may exist.

Transversal Lines of the Debates

Directory of Open Access Journals (Sweden)

Yolanda Onghena

1998-12-01

Full Text Available The Transversal Lines of the Debates gathers for publication the presentations of the scholars invited to the seminar. In the papers, Yolanda Onghena observes that the evolution from the cultural to the inter-cultural travels along four axes: the relations between cultureand society; the processes of change within identity-based dynamics; the representations of the Other; and, interculturality. Throughout the presentations and subsequent debates, whenever the different participants referred to aspects of the cultural identity problematic--”angst”, “obsession”, “deficit”, manipulation”, and others, these same participants in the Transversal Lines of the Debates also showed that, in certain areas, an optimistic viewpoint is not out of the question.

Transverse momentum correlations of quarks in recursive jet models

Science.gov (United States)

Artru, X.; Belghobsi, Z.; Redouane-Salah, E.

2016-08-01

In the symmetric string fragmentation recipe adopted by PYTHIA for jet simulations, the transverse momenta of successive quarks are uncorrelated. This is a simplification but has no theoretical basis. Transverse momentum correlations are naturally expected, for instance, in a covariant multiperipheral model of quark hadronization. We propose a simple recipe of string fragmentation which leads to such correlations. The definition of the jet axis and its relation with the primordial transverse momentum of the quark is also discussed.

Spin versus helicity in processes involving transversity

CERN Document Server

Mekhfi, Mustapha

2011-01-01

We construct the spin formalism in order to deal in a direct and natural way with processes involving transversity which are now of increasing popularity. The helicity formalism which is more appropriate for collision processes of definite helicity has been so far used also to manage processes with transversity, but at the price of computing numerous helicity amplitudes generally involving unnecessary kinematical variables.In a second step we work out the correspondence between both formalisms and retrieve in another way all results of the helicity formalism but in simpler forms.We then compute certain processes for comparison.A special process:the quark dipole magnetic moment is shown to be exclusively treated within the spin formalism as it is directly related to the transverse spin of the quark inside the baryon.

Probing Transverse Momentum Dependent Parton Distributions in Charmonium and Bottomonium Production

OpenAIRE

Mukherjee, Asmita; Rajesh, Sangem

2015-01-01

We propose the study of unpolarized transverse momentum dependent gluon parton distributions as well as the effect of linearly polarized gluons on transverse momentum and rapidity distributions of $J/\\psi$ and $\\Upsilon$ production within the framework of transverse momentum dependent factorization employing color evaporation model (CEM) in unpolarized proton-proton collision. We estimate the transverse momentum and rapidity distributions of $J/\\psi$ and $\\Upsilon$ at LHCb, RHIC and AFTER ene...

MODIFICANDO O AMBIENTE ESCOLAR ATRAVÉS DO PROJETO MEIO AMBIENTE: CULTIVANDO E CONHECENDO AS PLANTAS

Directory of Open Access Journals (Sweden)

Letícia Caroline Lopes

2011-07-01

Full Text Available O presente trabalho intitulado “MODIFICANDO O AMBIENTE ESCOLAR ATRAVÉS DO PROJETO MEIO AMBIENTE: CULTIVANDO E CONHECENDO AS PLANTAS” tem como desígnio apresentar o desenvolvimento do projeto “meio ambiente: cultivando e conhecendo as plantas”, no qual teve como proposta sensibilizar os alunos sobre a importância e preservação do meio ambiente através da prática e modificação do ambiente escolar, onde procurou-se utilizar materiais reciclados, tais como, garrafas pet, pneus velhos, carreteis de fios de eletricidade, e também mudas de arvore, plantas e hortaliças. Desta forma buscou se utilizar da criatividade dos envolvidos no processo para a transformação do ambiente escolar seco e vazio, para uma ambiente alegre, e acolhedor. O projeto foi elaborado pelas professoras da Extensão Betel, e aplicado em parceria com acadêmicos do sexto semestre do curso de Licenciatura em Pedagogia da Universidade do Estado do Mato Grosso (UNEMAT, campus de Sinop. Tendo como proposta a interdisciplinaridade, o projeto foi divido em três eixos orientados pelas professoras Edneuza Alves Trugillo, Sinóvia Rauber e Mariza Kreinner, abrangendo assim alunos e professoras de duas turmas de 2º Ano do Ensino Fundamental, e acadêmicos e professores da Universidade, os eixos foram arborização, jardinagem e horta, onde teve a duração de aproximadamente dois meses. A finalização das práticas obteve resultados satisfatórios e objetivos alcançados, tanto pela sensibilização dos alunos sobre a preservação e importância do meio-ambiente, quanto pela prática de intervenção pelos acadêmicos envolvidos no processo, que em coletividade conseguiram modificar o ambiente escolar através do objetivo do projeto, meio-ambiente, proporcionando assim um enriquecimento na formação acadêmica enquanto práticas pedagógicas.

Efficient sub-Doppler transverse laser cooling of an indium atomic beam

International Nuclear Information System (INIS)

Kim, Jae-Ihn

2009-01-01

Laser cooled atomic gases and atomic beams are widely studied samples in experimental research in atomic and optical physics. For the application of ultra cold gases as model systems for e.g. quantum many particle systems, the atomic species is not very important. Thus this field is dominated by alkaline, earthalkaline elements which are easily accessible with conventional laser sources and have convenient closed cooling transition. On the other hand, laser cooled atoms may also be interesting for technological applications, for instance for the creation of novel materials by atomic nanofabrication (ANF). There it will be important to use technologically relevant materials. As an example, using group III atoms of the periodical table in ANF may open a route to generate fully 3D structured composite materials. The minimal requirement in such an ANF experiment is the collimation of an atomic beam which is accessible by one dimensional laser cooling. In this dissertation, I describe transverse laser cooling of an Indium atomic beam. For efficient laser cooling on a cycling transition, I have built a tunable, continuous-wave coherent ultraviolet source at 326 nm based on frequency tripling. For this purpose, two independent high power Yb-doped fiber amplifiers for the generation of the fundamental radiation at λ ω = 977 nm have been constructed. I have observed sub-Doppler transverse laser cooling of an Indium atomic beam on a cycling transition of In by introducing a polarization gradient in the linear-perpendicular-linear configuration. The transverse velocity spread of a laser-cooled In atomic beam at full width at half maximum was achieved to be 13.5±3.8 cm/s yielding a full divergence of only 0.48 ± 0.13 mrad. In addition, nonlinear spectroscopy of a 3-level, Λ-type level system driven by a pump and a probe beam has been investigated in order to understand the absorption line shapes used as a frequency reference in a previous two-color spectroscopy experiment

Efficient sub-Doppler transverse laser cooling of an indium atomic beam

Energy Technology Data Exchange (ETDEWEB)

Kim, Jae-Ihn

2009-07-23

Laser cooled atomic gases and atomic beams are widely studied samples in experimental research in atomic and optical physics. For the application of ultra cold gases as model systems for e.g. quantum many particle systems, the atomic species is not very important. Thus this field is dominated by alkaline, earthalkaline elements which are easily accessible with conventional laser sources and have convenient closed cooling transition. On the other hand, laser cooled atoms may also be interesting for technological applications, for instance for the creation of novel materials by atomic nanofabrication (ANF). There it will be important to use technologically relevant materials. As an example, using group III atoms of the periodical table in ANF may open a route to generate fully 3D structured composite materials. The minimal requirement in such an ANF experiment is the collimation of an atomic beam which is accessible by one dimensional laser cooling. In this dissertation, I describe transverse laser cooling of an Indium atomic beam. For efficient laser cooling on a cycling transition, I have built a tunable, continuous-wave coherent ultraviolet source at 326 nm based on frequency tripling. For this purpose, two independent high power Yb-doped fiber amplifiers for the generation of the fundamental radiation at {lambda}{sub {omega}} = 977 nm have been constructed. I have observed sub-Doppler transverse laser cooling of an Indium atomic beam on a cycling transition of In by introducing a polarization gradient in the linear-perpendicular-linear configuration. The transverse velocity spread of a laser-cooled In atomic beam at full width at half maximum was achieved to be 13.5{+-}3.8 cm/s yielding a full divergence of only 0.48 {+-} 0.13 mrad. In addition, nonlinear spectroscopy of a 3-level, {lambda}-type level system driven by a pump and a probe beam has been investigated in order to understand the absorption line shapes used as a frequency reference in a previous two

Educação ambiental na escola: a perspectiva estudantil sobre o meio ambiente e a propaganda ambiental na internet

Directory of Open Access Journals (Sweden)

Fernanda Reis de Pinho Tavares

2005-01-01

Full Text Available Este trabalho visa mostrar as idéias dos estudantes sobre um tema - a propaganda - refletindo como ela se insere na questão ambiental. Também abordamos como os alunos percebem questões como as relações, empresa, meio ambiente e sociedade. Foi realizado em uma oficina de Educação Ambiental, em uma escola particular de Lagoa Santa - MG, durante os meses de junho e julho de 2004. Analisaram-se sites de diversas empresas e ONG's (Organizações Não Governamentais. Em sua maioria os estudantes conseguiram posicionar-se criticamente em relação às entidades investigadas.