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Journal articles on the topic "Velocity difference":
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Strumpf, C., M. L. Braunstein, C. W. Sauer, and G. J. Andersen. "Velocity difference and velocity ratio in structure-from-motion." Journal of Vision 1, no. 3 (March 15, 2010): 330. http://dx.doi.org/10.1167/1.3.330.
Many existing migration schemes cannot simultaneously handle the two most important problems of migration: imaging of steep dips and imaging in media with arbitrary velocity variations in all directions. For example, phase‐shift (ω, k) migration is accurate for nearly all dips but it is limited to very simple velocity functions. On the other hand, finite‐difference schemes based on one‐way wave equations consider arbitrary velocity functions but they attenuate steeply dipping events. We propose a new hybrid migration method, named “Fourier finite‐difference migration,” wherein the downward‐continuation operator is split into two downward‐continuation operators: one operator is a phase‐shift operator for a chosen constant background velocity, and the other operator is an optimized finite‐difference operator for the varying component of the velocity function. If there is no variation of velocity, then only a phase‐shift operator will be applied automatically. On the other hand, if there is a strong variation of velocity, then the phase‐shift component is suppressed and the optimized finite‐difference operator will be fully applied. The cascaded application of phase‐shift and finite‐difference operators shows a better maximum dip‐angle behavior than the split‐step Fourier migration operator. Depending on the macro velocity model, the Fourier finite‐difference migration even shows an improved performance compared to conventional finite‐difference migration with one downward‐continuation step. Finite‐difference migration with two downward‐continuation steps is required to reach the same migration performance, but this is achieved with about 20 percent higher computation costs. The new cascaded operator of the Fourier finite‐difference migration can be applied to arbitrary velocity functions and allows an accurate migration of steeply dipping reflectors in a complex macro velocity model. The dip limitation of the cascaded operator depends on the variation of the velocity field and, hence, is velocity‐adaptive.
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Coombs, Earl. "Demonstrating the difference between velocity and acceleration." Physics Teacher 28, no. 8 (November 1990): 546–47. http://dx.doi.org/10.1119/1.2343146.
WANG, Tao, and Jing ZHANG. "Property Analysis of Multiple Velocity Difference Model." Systems Engineering - Theory & Practice 28, no. 10 (October 2008): 150–55. http://dx.doi.org/10.1016/s1874-8651(10)60005-1.
Braunstein, Myron L., Craig W. Sauer, Cary Strumpf Feria, and George J. Andersen. "Perceived Internal Depth in Rotating and Translating Objects." Perception 31, no. 8 (August 2002): 943–54. http://dx.doi.org/10.1068/p3294.
Previous research has indicated that observers use differences between velocities and ratios of velocities to judge the depth within a moving object, although depth cannot in general be determined from these quantities. In four experiments we examined the relative effects of velocity difference and velocity ratio on judged depth within a transparent object that was rotating about a vertical axis and translating horizontally, examined the effects of the velocity difference for pure rotations and pure translations, and examined the effect of the velocity difference for objects that varied in simulated internal depth. Both the velocity difference and the velocity ratio affected judged depth, with difference having the larger effect. The effect of velocity difference was greater for pure rotations than for pure translations. Simulated depth did not affect judged depth unless there was a corresponding change in the projected width of the object. Observers appear to use the velocity difference, the velocity ratio, and the projected width of the object heuristically to judge internal object depth, rather than using image information from which relative depth could potentially be recovered.
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Zhou, Jie, and Zhong-Ke Shi. "A modified full velocity difference model with the consideration of velocity deviation." International Journal of Modern Physics C 27, no. 06 (May 13, 2016): 1650069. http://dx.doi.org/10.1142/s0129183116500698.
In this paper, a modified full velocity difference model (FVDM) based on car-following theory is proposed with the consideration of velocity deviation which represents the inexact judgement of velocity. The stability condition is obtained by the use of linear stability analysis. It is shown that the stability of traffic flow varies with the deviation extent of velocity. The Burgers, Korteweg-de Vries (KdV) and modified K-dV (MKdV) equations are derived to describe the triangular shock waves, soliton waves and kink–antikink waves in the stable, metastable and unstable region, respectively. The numerical simulations show a good agreement with the analytical results, such as density wave, hysteresis loop, acceleration, deceleration and so on. The results show that traffic congestion can be suppressed by taking the positive effect of velocity deviation into account. By taking the positive effect of high estimate of velocity into account, the unrealistic high deceleration and negative velocity which occur in FVDM will be eliminated in the proposed model.
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Min, I. A., I. Mezić, and A. Leonard. "Lévy stable distributions for velocity and velocity difference in systems of vortex elements." Physics of Fluids 8, no. 5 (May 1996): 1169–80. http://dx.doi.org/10.1063/1.868908.
Dissertations / Theses on the topic "Velocity difference":
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Zha, Wuyi. "Velocity-difference induced focusing in capillary electrophoresis and preparative capillary electrophoresis." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/448.
Velocity-difference induced focusing (V-DIF) with a dynamic pH junction in capillary electrophoresis (CE) using a sample with a pH different from that of the background electrolyte (BGE) was developed in our group, but the mechanism was not well understood. In this work, the mechanism of this focusing technique was first studied using an appropriate dye to monitor the pH of the BGE and the sample during the focusing process. A mechanism was proposed based on the experimental results. This technique was then applied to serotonin to improve the detection limit when CE was used with a UV absorption detector. It was also applied to focus amino acids, peptides, and proteins to improve the concentration sensitivity. It is found that the pKa rather than the pI of the analytes is the key criterion for selecting the pH for the sample and for the BGE to obtain the optimum focusing for these molecules. Since UV detection only provides migration time information, more structure information is obtained by using a photodiode array (PDA) and mass spectrometer (MS) for peak identification. Comparisons were made between the PDA detection and MS detection for aromatic amino acids with V-DIF using a dynamic pH junction. This V-DIF technique was then applied to non-aromatic amino acids with MS detection. It was used at low pH with positive ESI-MS detection and at high pH with negative ESI-MS ionization. The results of the two methods were compared and discussed. Finally, the preparative operation of continuous flow counterbalanced CE (FCCE) was studied. The effects of larger sample volumes and multiple capillary systems on improving the purification yield were investigated.
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Staley, Alan Joseph. "A Finite Difference Approach to Modeling High Velocity/Variable Loads using the Timoshenko Beam Model." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76954.
Electromagnetic launchers (railguns) are set to replace traditional large caliber ship mounted cannons in the near future. The success of the railgun depends heavily upon a comprehensive understanding of beam behavior during periods of heavy dynamic loading. It is hypothesized that the combination of velocity transition effects, electromagnetic loading, and other non-linear or design specific effects contribute to areas of high stresses/strains over the length of the rail/beam during launch.
This paper outlines the use of the Timoshenko beam model, a model which builds upon the traditional Bernoulli-Euler beam theory with the addition of shear deformation and rotary inertia effects, a necessity for high wave velocities. Real-world experimental setups are simplified and approximated by a series of linear springs and dampers for model prediction and validation.
The Timoshenko beam model is solved using finite difference (FD) methods for the approximation of spatial derivatives and MATLAB ordinary differential equation (ODE) solvers. The model shows good convergence and precision over a large range of system parameters including load velocities, foundation stiffness values, and beam dimensions. Comparison to experimental strain data has validated model accuracy to an acceptable level. Accuracy is further enhanced with the inclusion of damping and non-linear or piecewise effects used to mimic experimental observations. The MATLAB software package presents a valid preliminary analysis tool for railgun beam and foundation design while offering advantages in ease of use, computation time, and system requirements when compared to traditional FEA tools. Master of Science
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Ma, Xu. "Passive Seismic Tomography and Seismicity Hazard Analysis in Deep Underground Mines." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51266.
Seismic tomography is a promising tool to help understand and evaluate the stability of a rock mass in mining excavations. Lab measurements give evidence that velocities of seismic wave propagations increase in high stress areas of rock samples. It is well known that closing effects of cracks under compressive pressures tend to increase the effective elastic moduli of rocks. Tomography can map stress transfer and redistribution and further forecast rock burst potential and other seismic hazards, which are influenced by mining. Recorded by seismic networks in multiple underground mines, arrival time of seismic waves and locations of seismic events are used as sources of tomographic imaging survey. An initial velocity model is established according to properties of a rock mass, then velocity structure is reconstructed by velocity inversion to reflect the anomalies of the rock mass. Mining-induced seismicity and double-difference tomographic images of rock mass in mining areas are coupled to show how stress changes with microseismic activities. Especially, comparisons between velocity structures of different periods (before and after rock burst) are performed to analyze effects of rock burst on stress distribution. Tomographic results show that high velocity anomalies form in the vicinity of rock burst before the occurrence, and velocity subsequently experiences a significant drop after the occurrence of rock burst. In addition, regression analysis of travel time and distance indicates that the average velocity of all the monitored region appears to increase before rock burst and reduce after them. A reasonable explanation is that rock bursts tend to be triggered in highly stressed rock masses. After the energy release of rock bursts, stress relief is expected to exhibit within rock mass. Average velocity significantly decreases because of lower stresses and as a result of fractures in the rock mass that are generated by shaking-induced damage from nearby rock burst zones. Mining-induced microseismic rate is positively correlated with stress level. The fact that highly concentrated seismicity is more likely to be located in margins between high-velocity and low-velocity regions manifests that high seismic rates appear to be along with high stress in rock masses. Statistical analyses were performed on the aftershock sequence in order to generate an aftershock decay model to detect potential hazards and evaluate stability of aftershock activities. Ph. D.
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Wu, Jiedi. "New Constraints on Fault-Zone Structure from Seismic Guided Waves." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28873.
The structure of fault zones (FZs) plays an important role in understanding fault mechanics, earthquake rupture and seismic hazards. Fault zone seismic guided waves (GW) carry important information about internal structure of the low-velocity fault damage zone. Numerical modeling of observed FZGWs has been used to construct models of FZ structure. However, the depth extent of the waveguide and the uniqueness of deep structure in the models have been debated. Elastic finite-difference synthetic seismograms were generated for FZ models that include an increase in seismic velocity with depth both inside and outside the FZ. Strong GWs were created from sources both in and out of the waveguide, in contrast with previous homogenous-FZ studies that required an in-fault source to create GW. This is because the frequency-dependent trapping efficiency of the waveguide changes with depth. The near-surface fault structure efficiently guides waves at lower frequencies than the deeper fault. Fault structure at seismogenic depth requires the analysis of data at higher frequencies than the GWs that dominate at the surface. Adapting a two-station technique from surface wave studies, dispersive differential group arrival times between two earthquakes can be used to solve for FZ structures between the earthquakes. This method was tested with synthetic data and shallow events recorded in the SAFOD borehole in the San Andreas Fault. A pair of deep earthquakes recorded in the SAFOD borehole indicate a ~150 m wide San Andreas Fault waveguide with >20% velocity contrast at 10-12 km depth. With additional earthquakes, the full FZ structure at seismogenic depth could be imaged. Subsurface FZ structure can also be derived from a surface source and receiver array analogous to a body-wave refraction survey. Synthetic seismograms for such source-receiver geometry were generated and verified that FZGWs are refracted by the increase in velocity with depth. Synthetic data from a surface array were successfully inverted to derive FZ structure in the subsurface. The new methods presented in this dissertation extend the potential of FZGWs to image deeper FZ structure than has been uniquely constrained in the past. Ph. D.
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Tew, David Early. "A computational study of mixing downstream of a lobed mixer with a velocity difference between the co-flowing streams." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/43265.
Cao, Weimin. "Adsorption of surface active elements on the iron (100) surface a study based on ab initio calculations /." Licentiate thesis, Stockholm : Skolan för industriell teknik och management, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11234.
The present work was initiated to investigate the surface- and interfacial phenomena for iron and slag/iron systems. The aim was to understand the mechanism of the effect of surface active elements on surface and interfacial properties. In the present work, the adsorption of oxygen and sulfur on iron surface as well as adatom surface movements were studied based on the ab initio method. BCC iron melting phenomena and sulfur diffusion in molten iron were investigated by Monte Carlo simulations. The impact of oxygen potential on interfacial mass transfer was carried out by X-ray sessile drop method. Firstly, the structural, electronic and magnetic properties as well as thermodynamic stability were studied by Density functional theory (DFT). The hollow site was found to be the most stable adsorption site both for oxygen and sulfur adsorbed on iron (100) surface, which is in agreement with the experiment. The relaxation geometries and difference charge density of the different adsorption systems were calculated to analyze the interaction and bonding properties between Fe and O/S. It can be found that the charge redistribution was related to the geometry relaxation. In addition, the sulfur coverage is considered from a quarter of one monolayer (1ML) to a full monolayer. It was found that the work function and its change Δφ increased with S coverage, in very good agreement with experiment. Due to a recent discussion regarding the influence of charge transfer on Δφ, it is shown in the present work that the increase in Δφ can be explained by the increasing surface dipole moment as a function of S coverage. S strongly interacts with the surface Fe layer and decreases the surface magnetic moment as the S coverage increases. Secondly, a two dimensional (2D) gas model based on density functional calculations combined with thermodynamics and statistical physics, was proposed to simulate the movement of the surface active elements, viz. oxygen and sulfur atoms on the Fe(100) surface. The average velocity of oxygen and sulfur atoms was found to be related to the vibration frequencies and energy barrier in the final expression developed. The calculated results were based on the density function and thermodynamics & statistical physics theories. In addition, this 2D gas model can be used to simulate and give an atomic view of the complex interfacial phenomena in the steelmaking refining process. A distance dependent atomistic Monte Carlo model was developed for studying the iron melting phenomenon as well as effect of sulfur on molten iron surface. The effect of boundary conditions on the melting process of an ensemble of bcc iron atoms has been investigated using a Lennard-Jones distance dependent pair potential. The stability of melting process was energetically and spatially analyzed under fixed wall and free surface conditions and the effects of short and long-range interactions were discussed. The role of boundary conditions was significantly reduced when long-range interactions were used in the simulation. This model was further developed for investigating the effect of sulfur on molten iron surface. A combination of fixed wall and free surface boundary condition was found to well-represent the molten bath configuration while considering the second nearest neighbor interactions. Calculations concerning the diffusion of sulfur on molten surface were carried out as a function of temperature and sulfur concentration. Our results show that sulfur atoms tended to diffuse away from the surface into the liquid bulk and the diffusion rate increased by increasing temperature. Finally, impact of oxygen potential on sulfur mass transfer at slag/metal interface, was carried out by X-ray sessile drop method. The movement of sulfur at the slag/metal interface was monitored in dynamic mode at temperature 1873 K under non-equilibrium conditions. The experiments were carried out with pure iron and CaO-SiO2-Al2O3-FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. As the partial pressure of oxygen increased, it was found that interfacial velocity as well as the oscillation amplitude increased. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity. QC 20101123
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Adiya, Munkhsaikhan. "Seismic activity near Ulannbaatar : implication for seismic hazard assessment." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAH007/document.
On observe depuis 2005 une sismicité intense à 10 km d'Oulan Bator ce qui a permis d'identifier une faille active, Emeelt, sur le terrain. Après le calcule d'un modèle de vitesse 3D, j'ai appliqué la tomographie double différence pour obtenir une localisation précise des séismes. Ils marquent au moins trois branches parallèles orientées N147° comme la faille vue en surface. L'activité sur la faille principale d'Emeelt (MEF) s’étend sur 15 km, les branches Ouest et Est, moins actives, sur 10 km. La profondeur de l'activité s'étend entre 4 et 15 km. L'activité sismique semble concentrée à l'intersection avec des failles Mésozoïques et les contrastes Vs/Vs suggèrent la présence de fluides. Les 10 essaims identifiés montrent une activité croissante et une migration spatiale avec le temps. Le calcul de 2 scénarios possibles, un M ~ 6.4 et un M ~ 7, indique un important impact sur la ville d'Oulan Bator, avec une intensité minimum de VIII et localement IX pour M=6.4 et X pour M=7 We observe since 2005 a high seismic activity at 10 km from Ulaanbaatar that allowed us to identify a new active fault, Emeelt, in the field. After computing a 3D velocity model, I applied Double-Difference tomography to obtain a precise localization of earthquakes. They trace at least three parallel branches oriented N147° like the fault seen at surface. The seismic activity on the Main Emeelt Fault (MEF) is along at least 15 km, on the West and East branches, less active, along 10 km. The depth of the seismicity extends between 4 and 15 km. The activity seems concentrated at the intersection with Mesozoic faults and Vp/Vs contrast suggests the presence of fluids. The 10 swarms identified show an increasing activity and a spatial migration with time. The calculation of 2 possible scenarios, one M ~ 6.4 and one M ~ 7, shows an important impact on Ulaanbaatar, with a minimum intensity of VIII and IX for M=6.4 and X for M=7
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Ehrlich, Elizabeth R. "Sex Differences in Arterial Destiffening with Weight Loss." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/43707.
Given the current obesity epidemic in tandem with the aging US population, it is imperative to identify methods for reducing cardiovascular disease (CVD) risk that will be efficacious for both sexes. Arterial stiffness (AS) is an independent risk factor for a first cardiovascular event that increases with advancing age and obesity. Previous studies have found that modest weight loss (WL) of 5 to 10 percent successfully reduces AS and other risk factors for CVD. However, it remains unclear whether WL via caloric restriction reduces AS similarly among sexes. We tested the hypothesis that WL via caloric restriction would reduce AS more in men than women because men accumulate more abdominal visceral fat (VF) and lose more with WL compared with women of similar age and adiposity. To test our hypothesis AS was assessed from measurements of pulse wave velocity and ultrasonography of the carotid artery (Ã -SI). Total body and VF were measured using dual energy x-ray absorptiometry and computed tomography scans, respectively. Subjects underwent a 12-week WL intervention. No baseline differences in AS were observed between sexes. However, men were heavier and demonstrated higher levels of VF while women were fatter and had higher levels of abdominal subcutaneous fat. Contrary to our hypothesis both sexes experienced similar decreases in AS with WL despite greater reductions in VF in men. Our findings suggest that VF loss is not the primary mechanism mediating reductions in AS with WL. Future studies are needed to determine the mechanisms of arterial destiffening with WL. Master of Science
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Smith, Rachel K. "The Effect of Coaching on Two-Handed Catching: Looking at Developmental Differences and Time from Initial Movement to Peak Hand Velocity in College Aged Females." University of Toledo Honors Theses / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=uthonors1239740440.
Yu, S. C. M. Velocity measurements downstream of a lobed forced mixer with different trailing edge configurations. Washington, D. C: American Institute of Aeronautics and Astronautics, 1994.
Frenje, Lena. Scattering of Seismic Waves in Random Velocity Models: Finite Difference Simulations (Comprehensive Summaries of Uppsala Dissertations from the Faculty ... the Faculty of Science and Technology, 519). Coronet Books, 1999.
Di Paolo, Ezequiel A., Thomas Buhrmann, and Xabier E. Barandiaran. Representational pull, enactive escape velocity. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780198786849.003.0002.
Two different paths have been taken by researchers who argue that embodiment is crucial for understanding the mind. The first path is embodied functionalism, essentially the claim that traditional cognitivism needs to take into account the lessons of cognitive linguistics, dynamical systems explanations, and autonomous robotics seriously, so as to include bodily structures and processes in accounts of cognition. However, what it means to be a cognitive system remains unchanged and ruled by the computer metaphor. The other path rejects this metaphor and proposes that the self-organizing living body is constitutive of what it is to be a mind. This path, represented by enactivism, is not committed to a representational view of the mind, but rather understands it as an emergent, relational, world-involving phenomenon. The sensorimotor approach to perception may be interpreted in these terms; however, this approach requires a nonrepresentational account of sensorimotor mastery and a theory of agency.
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Wittman, David M. A First Look at Relativity. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199658633.003.0001.
The heart of relativity is the supposition that the laws of physics are the same in all coordinate systems. This chapter builds a foundation by defining coordinate systems (also called frames of reference or simply frames) and examining some quantities that are coordinate‐dependent and others that are coordinate‐independent; the latter turn out to be more physically meaningful. Galileo first considered relationships between coordinate systems moving at different veloCities; in modern terms this could relate a coordinate system attached to the ground to one attached to a moving train. Given your velocity relative to the train, and the train‐ground relative velocity, Galileo developed a law for inferring your velocity relative to the ground. If this Galilean velocity addition law is correct, there are profound implications: nature must have no speed limit, and the laws of motion must be the same in any constant‐velocity frame.
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The effects of different types of softball covers on velocity and rotation of pitches. 1987.
Isett, Philip. Checking Frequency Energy Levels for the Velocity and Pressure. Princeton University Press, 2017. http://dx.doi.org/10.23943/princeton/9780691174822.003.0024.
This chapter checks frequency energy levels for the velocity and pressure. It begins by comparing the different estimates obtained for the corrections to the velocity and the pressure with the Main Lemma. It then considers bounds that will be established for a particular constant C once the constant Bsubscript Greek Small Letter Lamda has been chosen. It also checks whether the frequency and energy levels of the new velocity and pressure are consistent with the claims of the Main Lemma (10.1). To complete the proof of the Main Lemma (10.1), it now only remains to choose a constant Bsubscript Greek Small Letter Lamda so that (243) and (244) can be verified for the new energy levels. This choice of Bλ is the last step of the proof.
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Voigt, Jens-Uwe. Quantification of left ventricular function and synchrony using tissue Doppler, strain imaging, and speckle tracking. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780199599639.003.0006.
Modern echocardiographic systems allow the quantitative and qualitative assessment of regional myocardial function by measuring velocity, motion, deformation, and other parameters of myocardial function.Both colour Doppler (CD) and spectral Doppler modes provide one-dimensional estimates of velocity. From CD data only, further parameters can be derived. Tracking techniques have recently been introduced which provide all parameters two-dimensionally, but at the cost of lower temporal resolution.Several clinical applications have been proposed, including regional and global systolic function assessment, evaluation of diastolic cardiac properties, and assessment of ventricular dyssynchrony.This chapter provides an introduction to the method of Doppler- and tracking-based function assessment and provides a basis for understanding its different clinical applications.
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Cameli, Matteo, Partho Sengupta, and Thor Edvardsen. Deformation echocardiography. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780198726012.003.0004.
Echocardiographic strain imaging, also known as deformation imaging, has been developed as a means to objectively quantify regional and global myocardial function. First introduced as a post-processing feature of tissue Doppler imaging velocity converted to strain and strain rate, strain imaging has more recently also been derived from speckle tracking analysis. Tissue Doppler imaging yields velocity information from which strain and strain rate are mathematically derived whereas two-dimensional speckle tracking yields strain information from which strain rate and velocity data are derived. Data obtained from these two different techniques may not be equivalent due to limitations inherent with each technique. Speckle tracking analysis can generate longitudinal, circumferential, and radial strain measurements and left ventricular twist. Although potentially useful, these measurements are also complicated and frequently displayed as difficult-to-interpret waveforms. Strain imaging is now considered a robust research tool and has great potential to play many roles in routine clinical practice. This chapter explains the fundamental concepts of deformation imaging, the technical features of strain imaging using tissue Doppler imaging and speckle tracking, and the strengths and weaknesses of these methods.
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Rajeev, S. G. Boundary Layers. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198805021.003.0007.
It is found experimentally that all the components of fluid velocity (not just thenormal component) vanish at a wall. No matter how small the viscosity, the large velocity gradients near a wall invalidate Euler’s equations. Prandtl proposed that viscosity has negligible effect except near a thin region near a wall. Prandtl’s equations simplify the Navier-Stokes equation in this boundary layer, by ignoring one dimension. They have an unusual scale invariance in which the distances along the boundary and perpendicular to it have different dimensions. Using this symmetry, Blasius reduced Prandtl’s equations to one dimension. They can then be solved numerically. A convergent analytic approximation was also found by H. Weyl. The drag on a flat plate can now be derived, resolving d’Alembert’s paradox. When the boundary is too long, Prandtl’s theory breaks down: the boundary layer becomes turbulent or separates from the wall.
Yeliu, Mo, Yu Xue, Shi Wei, and Liu Zhang. "Optimal Velocity Model Via Considering Multi-Velocity Difference Ahead." In Traffic and Granular Flow ’07, 181–88. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-77074-9_16.
Tashirova, Ekaterina. "The Numerical Solution of Wave Equation with Delay for the Case of Variable Velocity Coefficient." In Differential and Difference Equations with Applications, 181–93. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-56323-3_15.
Lazar, Hajar, Khadija Rhoulami, and Moulay Driss Rahmani. "A Novel Velocity-Separation Difference Model for Traffic Flow Theory." In Lecture Notes in Electrical Engineering, 3–10. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-30298-0_1.
Bognár, Gabriella. "Magnetohydrodynamic Flow of a Power-Law Fluid over a Stretching Sheet with a Power-Law Velocity." In Differential and Difference Equations with Applications, 131–39. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32857-7_13.
Wang, Lipo. "Two Point Velocity Difference Scaling along Scalar Gradient Trajectories in Turbulence." In Springer Proceedings in Physics, 45–48. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-02225-8_10.
Yang, Rui-Qiang, Peng Zhang, Xing-Wang Zhong, Deng-feng Wang, and Nian-Ke Zong. "Research on Ranging Algorithm Based on Combined-Process Method Using Frequency-Difference, Time-Difference and Relative-Velocity." In Lecture Notes in Electrical Engineering, 249–58. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-46632-2_21.
Skullerud, H. R., and S. Holmstrom. "Retarding Potential Difference Analysis of Ion Swarm Velocity Distributions: A Computer Simulation Study." In Swarm Studies and Inelastic Electron-Molecule Collisions, 79. New York, NY: Springer New York, 1987. http://dx.doi.org/10.1007/978-1-4612-4662-6_8.
AbstractIn this chapter, we experimentally demonstrate that the geometric phase can also emerge in a macroscopic thermal convection-conduction system. Following Li et al. [Science 364, 170–173 (2019)], we study two moving rings with equal-but-opposite velocities, joined together by a stationary intermediate layer. We first confirm an exceptional point of velocity that separates a stationary temperature profile and a moving one. We then investigate a cyclic path of time-varying velocity containing the exceptional point, and an extra phase difference of $$\pi $$ π appears (say, the geometric phase). These results broaden the scope of the geometric phase and provide insights into the thermal topology.
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Lim, Sheh Hong, Mohd Azrul Hisham Mohd Adib, Mohd Shafie Abdullah, Nur Hartini Mohd Taib, Radhiana Hassan, and Azian Abd Aziz. "Investigate the Velocity Difference Between MRI Measurement and CFD Simulation on Patient-Specific Blood Flow Analysis." In 6th Kuala Lumpur International Conference on Biomedical Engineering 2021, 453–60. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-90724-2_49.
Li, Chenggang, Hongwei Guo, Wuhong Wang, and Xiaobei Jiang. "Stabilization Analysis of Mixed Traffic Flow with Electric Vehicles Based on the Modified Multiple Velocity Difference Model." In Green Intelligent Transportation Systems, 251–61. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-0302-9_25.
Conference papers on the topic "Velocity difference":
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Nguyen, Thanh T., J. C. Devlin, D. M. Elton, G. Deng, and E. Custovic. "Spectrum Difference Function technique for measuring velocity." In 2014 Pan African Conference on Science, Computing and Telecommunications (PACT). IEEE, 2014. http://dx.doi.org/10.1109/scat.2014.7055120.
Levander, Alan R. "Fourth‐order velocity stress finite‐difference scheme." In SEG Technical Program Expanded Abstracts 1987. Society of Exploration Geophysicists, 1987. http://dx.doi.org/10.1190/1.1892060.
Shariat, Mohammad Hassan, Saeed Gazor, and Damian Redfearn. "Modified maximum time difference intracardiac conduction velocity estimation." In 2016 IEEE Canadian Conference on Electrical and Computer Engineering (CCECE). IEEE, 2016. http://dx.doi.org/10.1109/ccece.2016.7726764.
Bush, Robert, Harry Culver, Nicholas Georgiadis, and Dave Weissbein. "Low Velocity Difference Thermal Shear Layer Mixing Rate Measurements." In 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-1074.
Manning, Peter M., and Gary F. Margrave. "Finite‐difference modelling with correction filters in variable velocity." In SEG Technical Program Expanded Abstracts 2004. Society of Exploration Geophysicists, 2004. http://dx.doi.org/10.1190/1.1839682.
Mamutov, Alexander V. "Finite difference analysis of high-velocity plastic forming of shells." In Fourth International Workshop on Nondestructive Testing and Computer Simulations in Science and Engineering. SPIE, 2001. http://dx.doi.org/10.1117/12.417678.
Jiang, Nan, Weihua Zhang, and Xiaolong Feng. "Research of Energy Consumption Based on Full Velocity Difference Model." In The Twelfth COTA International Conference of Transportation Professionals. Reston, VA: American Society of Civil Engineers, 2012. http://dx.doi.org/10.1061/9780784412442.287.
Tan, Yuyang, Chuan He, and Hongliang Zhang. "Time difference-based velocity model inversion for microseismic event location." In SEG Technical Program Expanded Abstracts 2013. Society of Exploration Geophysicists, 2013. http://dx.doi.org/10.1190/segam2013-0165.1.
Guang Yang and Bo Dai. "The velocity characteristics analysis of pressure difference pipeline inner detector." In 2015 Chinese Automation Congress (CAC). IEEE, 2015. http://dx.doi.org/10.1109/cac.2015.7382793.
Chen Jian, Zhao Shen, Huang Zhigang, and Qiao Chunjie. "Acoustic velocity measurement in seawater based on phase difference of signal." In Instruments (ICEMI). IEEE, 2011. http://dx.doi.org/10.1109/icemi.2011.6037883.
Minkoff, S. E. Spatial parallelism of a 3D finite difference, velocity-stress elastic wave propagation code. Office of Scientific and Technical Information (OSTI), December 1999. http://dx.doi.org/10.2172/750170.
McKnight, C., David May, and Keaton Jones. Numerical analysis of dike effects on the Mississippi River using a two-dimensional Adaptive Hydraulics model (AdH). Engineer Research and Development Center (U.S.), November 2022. http://dx.doi.org/10.21079/11681/46120.
This report describes the hydraulic effects of dikes on water surface elevation (WSE) and velocities in the Mississippi River near Vicksburg, MS, from Interstate 20 to Highway 80 using a previously calibrated 2D Adaptive Hydraulics numerical model. Dike heights and their associated hydraulic roughness values were varied to quantify the overall effects of adjustments to dike fields. Steady flows characterized as low, medium, and high conditions were simulated. The WSE and velocity difference plots were generated to illustrate the hydraulic effects on the river under all scenarios discussed above. Overall, the dike adjustments had negligible impacts on WSEs and showed minimal effects on velocities on a system-wide scale.
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Ostashev, Vladimir, Michael Muhlestein, and D. Wilson. Extra-wide-angle parabolic equations in motionless and moving media. Engineer Research and Development Center (U.S.), September 2021. http://dx.doi.org/10.21079/11681/42043.
Wide-angle parabolic equations (WAPEs) play an important role in physics. They are derived by an expansion of a square-root pseudo-differential operator in one-way wave equations, and then solved by finite-difference techniques. In the present paper, a different approach is suggested. The starting point is an extra-wide-angle parabolic equation (EWAPE) valid for small variations of the refractive index of a medium. This equation is written in an integral form, solved by a perturbation technique, and transformed to the spectral domain. The resulting split-step spectral algorithm for the EWAPE accounts for the propagation angles up to 90° with respect to the nominal direction. This EWAPE is also generalized to large variations in the refractive index. It is shown that WAPEs known in the literature are particular cases of the two EWAPEs. This provides an alternative derivation of the WAPEs, enables a better understanding of the underlying physics and ranges of their applicability, and opens an opportunity for innovative algorithms. Sound propagation in both motionless and moving media is considered. The split-step spectral algorithm is particularly useful in the latter case since complicated partial derivatives of the sound pressure and medium velocity reduce to wave vectors (essentially, propagation angles) in the spectral domain.
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Malchenko, Svitlana L., Davyd V. Mykoliuk, and Arnold E. Kiv. Using interactive technologies to study the evolution of stars in astronomy classes. [б. в.], February 2020. http://dx.doi.org/10.31812/123456789/3752.
In astrophysics, a significant role is played by observations. During astronomy classes in the absence of surveillance tools interactive programmes such as an interactive programme for space objects simulation can be used as Universe Sandbox2. The aim of this work is to implement interactive programmes for effective astronomy teaching, understanding material and increasing cognitive interest. We observe the evolution of stars while using Universe Sandbox2 during the study of the topic “Evolution of stars”. Using this programme students have an opportunity to get acquainted with the existence of stars with different masses, their differences, to observe changes in the physical characteristics of stars such as: mass, temperature, speed velocity, luminosity, radius and gravity. It will help to develop the ability to analyze, to compare, to form scientific worldview, to develop the attraction for research, to raise the interest for studying astronomy.
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Haering, S., R. Balakrishnan, and R. Kotamarthi. A computational study of turbulent separated flow over a wall-mounted cube at two different Reynolds numbers and incoming velocity profiles. Office of Scientific and Technical Information (OSTI), July 2021. http://dx.doi.org/10.2172/1810324.
Russo, David, and William A. Jury. Characterization of Preferential Flow in Spatially Variable Unsaturated Field Soils. United States Department of Agriculture, October 2001. http://dx.doi.org/10.32747/2001.7580681.bard.
Preferential flow appears to be the rule rather than the exception in field soils and should be considered in the quantitative description of solute transport in the unsaturated zone of heterogeneous formations on the field scale. This study focused on both experimental monitoring and computer simulations to identify important features of preferential flow in the natural environment. The specific objectives of this research were: (1) To conduct dye tracing and multiple tracer experiments on undisturbed field plots to reveal information about the flow velocity, spatial prevalence, and time evolution of a preferential flow event; (2) To conduct numerical experiments to determine (i) whether preferential flow observations are consistent with the Richards flow equation; and (ii) whether volume averaging over a domain experiencing preferential flow is possible; (3) To develop a stochastic or a transfer function model that incorporates preferential flow. Regarding our field work, we succeeded to develop a new method for detecting flow patterns faithfully representing the movement of water flow paths in structured and non-structured soils. The method which is based on application of ammonium carbonate was tested in a laboratory study. Its use to detect preferential flow was also illustrated in a field experiment. It was shown that ammonium carbonate is a more conservative tracer of the water front than the popular Brilliant Blue. In our detailed field experiments we also succeeded to document the occurrence of preferential flow during soil water redistribution following the cessation of precipitation in several structureless field soils. Symptoms of the unstable flow observed included vertical fingers 20 - 60 cm wide, isolated patches, and highly concentrated areas of the tracers in the transmission zone. Soil moisture and tracer measurements revealed that the redistribution flow became fingered following a reversal of matric potential gradient within the wetted area. Regarding our simulation work, we succeeded to develop, implement and test a finite- difference, numerical scheme for solving the equations governing flow and transport in three-dimensional, heterogeneous, bimodal, flow domains with highly contrasting soil materials. Results of our simulations demonstrated that under steady-state flow conditions, the embedded clay lenses (with very low conductivity) in bimodal formations may induce preferential flow, and, consequently, may enhance considerably both the solute spreading and the skewing of the solute breakthrough curves. On the other hand, under transient flow conditions associated with substantial redistribution periods with diminishing water saturation, the effect of the embedded clay lenses on the flow and the transport might diminish substantially. Regarding our stochastic modeling effort, we succeeded to develop a theoretical framework for flow and transport in bimodal, heterogeneous, unsaturated formations, based on a stochastic continuum presentation of the flow and a general Lagrangian description of the transport. Results of our analysis show that, generally, a bimodal distribution of the formation properties, characterized by a relatively complex spatial correlation structure, contributes to the variability in water velocity and, consequently, may considerably enhance solute spreading. This applies especially in formations in which: (i) the correlation length scales and the variances of the soil properties associated with the embedded soil are much larger than those of the background soil; (ii) the contrast between mean properties of the two subdomains is large; (iii) mean water saturation is relatively small; and (iv) the volume fraction of the flow domain occupied by the embedded soil is relatively large.
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Allen, Jeffrey, Robert Moser, Zackery McClelland, Md Mohaiminul Islam, and Ling Liu. Phase-field modeling of nonequilibrium solidification processes in additive manufacturing. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/11681/42605.
This project models dendrite growth during nonequilibrium solidification of binary alloys using the phase-field method (PFM). Understanding the dendrite formation processes is important because the microstructural features directly influence mechanical properties of the produced parts. An improved understanding of dendrite formation may inform design protocols to achieve optimized process parameters for controlled microstructures and enhanced properties of materials. To this end, this work implements a phase-field model to simulate directional solidification of binary alloys. For applications involving strong nonequilibrium effects, a modified antitrapping current model is incorporated to help eject solute into the liquid phase based on experimentally calibrated, velocity-dependent partitioning coefficient. Investigated allow systems include SCN, Si-As, and Ni-Nb. The SCN alloy is chosen to verify the computational method, and the other two are selected for a parametric study due to their different diffusion properties. The modified antitrapping current model is compared with the classical model in terms of predicted dendrite profiles, tip undercooling, and tip velocity. Solidification parameters—the cooling rate and the strength of anisotropy—are studied to reveal their influences on dendrite growth. Computational results demonstrate effectiveness of the PFM and the modified antitrapping current model in simulating rapid solidification with strong nonequilibrium at the interface.
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Tremblay, T., and M. Lamothe. New contributions to the ice-flow chronology in the Boothia-Lancaster Ice Stream catchment area. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/331062.
Within the Boothia-Lancaster Ice Stream (BLIS) catchment area, ice flow patterns were reconstructed based on the synthesis of striation directions and cross-cutting relationships, transport patterns of erratic boulders, glacial landforms, cold-based glacial landsystems, and ice-retreat chronology. New ArcticDEM data, high-definition satellite imagery and multibeam echosounder bathymetric datasets provided increased details on ice flow indicators. Convergent high-velocity ice flows through the BLIS main axis were major, persistent features in the northeastern Laurentide Ice Sheet through the last glaciation, and this study highlights intensity fluctuations and ice flow pattern variations that occurred during that time. Highly contrasting glacial geomorphology, notably in the abundance of moraines, reflects marked differences in ice-margin retreat rates and patterns during deglaciation between the western and eastern sides of the BLIS.
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Si, Hongjun, Saburoh Midorikawa, and Tadahiro Kishida. Development of NGA-Sub Ground-Motion Model of 5%-Damped Pseudo-Spectral Acceleration Based on Database for Subduction Earthquakes in Japan. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, December 2020. http://dx.doi.org/10.55461/lien3652.
Presented within is an empirical ground-motion model (GMM) for subduction-zone earthquakesin Japan. The model is based on the extensive and comprehensive subduction database of Japanese earthquakes by the Pacific Engineering Research Center (PEER). It considers RotD50 horizontal components of peak ground acceleration (PGA), peak ground velocity (PGV), and 5%-damped elastic pseudo-absolute acceleration response spectral ordinates (PSA) at the selected periods ranging from 0.01 to 10 sec. The model includes terms and predictor variables considering tectonic setting (i.e., interplate and intraslab), hypocentral depths (D), magnitude scaling, distance attenuation, and site response. The magnitude scaling derived in this study is well constrained by the data observed during the large-magnitude interface events in Japan (i.e., the 2003 Tokachi-Oki and 2011 Tohoku earthquakes) for different periods. The developed ground-motion prediction equation (GMPE) covers subduction-zone earthquakes that have occurred in Japan for magnitudes ranging from 5.5 to as large as 9.1, with distances less than 300 km from the source.
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Madrzykowski, Daniel. Firefighter Equipment Operational Environment: Evaluation of Thermal Conditions. UL Firefighter Safety Research Institute, August 2017. http://dx.doi.org/10.54206/102376/igfm4492.
The goal of this study was to review the available literature to develop a quantitative description of the thermal conditions firefighters and their equipment are exposed to in a structural fire environment. The thermal exposure from the modern fire environment was characterized through the review of fire research studies and fire-ground incidents that provided insight and data to develop a range of quantification. This information was compared with existing standards for firefighting protective equipment to generate a sense of the gap between known information and the need for improved understanding. The comparison of fire conditions with the thermal performance requirements of firefighter protective gear and equipment demonstrates that a fire in a compartment can generate conditions that can fail the equipment that a firefighter wears or uses. The review pointed out the following: 1. The accepted pairing of gas temperature ranges with a corresponding range of heat fluxes does not reflect all compartment fire conditions. There are cases in which the heat flux exceeds the hazard level of the surrounding gas temperature. 2. Thermal conditions can change within seconds. Experimental conditions and incidents were identified in which firefighters would be operating in thermal conditions that were safe for operation based on the temperature and heat flux, but then due to a change in the environment the firefighters would be exposed to conditions that could exceed the protective capabilities of their PPE. 3. Gas velocity is not explicitly considered within the thermal performance requirements. Clothing and equipment tested with a hot air circulating (convection) oven are exposed to gas velocities that measure approximately 1.5 m/s (3 mph). In contrast, the convected hot gas flows within a structure fire could range from 2.3 m/s (5 mph) to 7.0 m/s (15 mph). In cases where the firefighter or equipment would be located in the exhaust portion of a flow path, while operating above the level of the fire, the hot gas velocity could be even higher. This increased hot gas velocity would serve to increase the convective heat transfer rate to the equipment and the firefighter, thereby reducing the safe operating time within the structure. 4. Based on the limited data available, it appears currently available protective clothing enables firefighters to routinely operate in conditions above and beyond the "routine" conditions measured in the fire-ground exposure studies conducted during the 1970s. The fire service and fire standards communities could benefit from an improved understanding of: • real world fire-ground conditions, including temperatures, heat flux, pressure, and chemical exposures; • the impact of convection on the thermal resistance capabilities of firefighting PPE and equipment; and • the benefits of balancing the thermal exposures (thermal performance requirements) across different components of firefighter protective clothing and safety equipment. Because it is unlikely due to trade offs in weight, breathe-ability, usability, cost, etc., that fireproof PPE and equipment will ever be a reality, fire officers and fire chiefs need to consider the capabilities of the protection that their firefighters have when determining fire attack strategies and tactics to ensure that the PPE and equipment is kept within its design operating environment, and that the safety buffer it provides is maintained.
