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.
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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.
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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.
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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.
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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.
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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.
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Cao, Weimin. "Theoretical and experimental studies of surface and interfacial phenomena involving steel surfaces." Doctoral thesis, KTH, Materialens processvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-26194.
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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.
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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=7We 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.
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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.
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Cunanan, Aaron J., W. Guy Hornsby, Mark A. South, Alex Perkins, Kyle C. Pierce, Kimitake Sato, and Michael H. Stone. "Training Implications of Peak Barbell Velocity Differences among Elite Men and Women Weightlifters." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/5095.
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Peak barbell velocity is an important determinant of weightlifting performance 2 . However, direct comparisons of this measure between elite men and women weightlifters is limited 7,8 . Therefore, the present study sought to establish a reference of the current status and trajectory of sexbased peak barbell velocity differences among elite weightlifters. This study examined performances of men and women in the 69 kg weight class in order to obviate the influence of body mass on performance. The purpose of this investigation was to help practitioners identify training needs of elite men and women weightlifters to improve weightlifting performance based upon between-group differences in peak barbell velocity.
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Abo, Abdulla. "A three-dimensional flow model for different cross-section high-velocity channels." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/2852.
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High velocity channels are typically designed to discharge surplus water during severe flood events, and these types of flow are distinguished by high velocity, usually supercritical. A major challenge in high velocity channel design is to predict the free surface flow. Being able to predict the free surface flow profile beforehand can assist in selecting the best design for the channel as a whole. When the flow encounters a bridge pier, the streamline of the flow is separated and pressure may drop to a minimum; in contrast, velocity rises to its maximum value. As a result, cavitation damage may occur. The present study has used the computational fluid dynamics code ANSYS-CFX to investigate a full scale, three-dimensional engineering flow simulation of high velocity channels with different cross sections. The simulations were carried out on a high performance computing HPC cluster with 32 nodes. The code is based on the finite volume method and the Volume of Fluid (VOF) method was used to predict the position of the free surface profile. The impact of variation of the following parameters was investigated in terms of the free surface flow profile, both along the centreline and the wall of the channel: the minimum cavity index, and maximum shear stress on both bed and wall of the channel and on bridge pier; aspect ratio (channel bed width/flow depth), bed and side slopes of the channel, different discharges, which are represented by Froude numbers; the length and thickness of the bridge pier. First, the code sensitivity tools for convergence were examined. For this purpose, cases with different mesh sizes were examined and the best size chosen, depending on computation expense and convergence. Then, different turbulence models, such as the standard k-ε, RNG k-ε, and SST turbulence models were tested. The results show that the standard k-ε gives satisfactory results. Next, efforts were made to establish whether the flow achieved steady state conditions. This involved simulating two cases, one with steady state and the other with a transient state. Comparison of the two results shows that the flow properties do not change after three seconds and stay stable thereafter, so the flow can be considered as attaining a steady state. Finally, symmetry within the model geometry was tested, as this would allow a reduction in computation time, with only one side of the symmetrical model needing to be simulated. Two cases were investigated: firstly a simulation of only half of the channel geometry, and secondly a full geometry simulation. A comparison of the results of each case showed that the flow can be considered symmetrical along the centreline of the channel. Next, the code was validated against both numerical and experimental published results. For the free surface flow profile and velocity distribution the published experimental and numerical work of Stockstill (1996) was used; the ANSYS-CFX code results agree more closely with Stockstill’s experimental data than Stockstill’s numerical data. To test for shear stress distribution on the wall, uniform flow within a trapezoidal cross section channel was investigated and the results compared with those presented in the literature. The comparison shows good agreement between the ANSYS-CFX and published experimental works, for the predicted shear stress distributions on the walls and the bed of the channel. In total, sixty cases were simulated in order to investigate the impact of variations in the aforementioned parameters on maximum flow depth (both along the centreline and the wall of the channel) minimum cavity index, and maximum shear stress on both bed and wall of the channel and on bridge pier. Finally, non-dimensional curves are provided in addition to formulae derived from the data regression, which are intended to provide useful guidelines for designers.
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Chiang, Gilbert W. (Gilbert Wang Jit). "A comparison of the velocity fields associated with vorticities of three different origins." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/45729.
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Shah, Amy S. M. D. "Racial Differences in Arterial Stiffness Among Adolescents and Young Adults with Type 2 Diabetes." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1298040943.
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Mahmoud, S. A. "Motion detection and velocity computation of moving objects in time-varying image sequences : Application of the exponential area transform in computation of presence and velocity of objects of different sizes and occurences." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379903.
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Wu, Chunquan. "Temporal change of seismic velocity and site response for different scales and implications for nonlinearity." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24619.
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Grafton, Catherine E. "Binocular vision and three-dimensional motion perception : the use of changing disparity and inter-ocular velocity differences." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/1922.
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This thesis investigates the use of binocular information for motion-in-depth (MID) perception. There are at least two different types of binocular information available to the visual system from which to derive a perception of MID: changing disparity (CD) and inter-ocular velocity differences (IOVD). In the following experiments, we manipulate the availability of CD and IOVD information in order to assess the relative influence of each on MID judgements. In the first experiment, we assessed the relative effectiveness of CD and IOVD information for MID detection, and whether the two types of binocular information are processed by separate mechanisms with differing characteristics. Our results suggest that, both CD and IOVD information can be utilised for MID detection, yet, the relative dependence on either of these types of MID information varies between observers. We then went on to explore the contribution of CD and IOVD information to time-to-contact (TTC) perception, whereby an observer judges the time at which an approaching stimulus will contact them. We confirmed that the addition of congruent binocular information to looming stimuli can influence TTC judgements, but that there is no influence from binocular information indicating no motion. Further to this, we found that observers could utilise both CD and IOVD for TTC judgements, although once again, individual receptiveness to CD and/or IOVD information varied. Thus, we demonstrate that the human visual system is able to process both CD and IOVD information, but the influence of either (or both) of these cues on an individual’s perception has been shown to be mutually independent.
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Lepore, Jason. "Experiments on passive scalar mixing in turbulent flows with different velocity- and scalar-field boundary conditions." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119387.
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An experimental investigation of the influence of the large-scale features of turbulent flows on the mixing of a passive scalar therein is presented. Given the direct relationship between the large scales of turbulent flows and the geometrical configuration of the flow, two distinct sets of experiments are conducted in which the dependence of the scalar mixing on the (i) scalar- and (ii) velocity-field boundary conditions is studied. The first set of experiments is conducted in the plane wake downstream of a circular cylinder. To vary the scalar-field boundary conditions, while maintaining a hydrodynamically identical flow field, two different heat injection mechanisms are employed. First, a heating element is embedded within the cylinder that generates the hydrodynamic wake. When the element is energized, the wake is therefore heated by means of a "heated cylinder." Second, an array of fine, Nichrome wires is installed downstream of the cylinder. This configuration, known as a "mandoline," has been demonstrated to have a negligible influence on the velocity field, due to the small diameter of the wires. Using this apparatus, multiple velocity and passive-scalar statistics are examined. The measurements suggest that certain small-scale statistics may be contaminated by the large-scale features of the scalar field. Consequently, it is of interest to determine why such statistics exhibit these dependencies. In particular, the passive scalar structure functions, and their inertial-convective-range scaling exponents, along with the mixed velocity-temperature structure functions and the (non-centered) autocorrelations of the dissipation rate of scalar variance are employed to obtain quantitative estimates of the internal intermittency of the passive scalar field. It is revealed that the high-order passive scalar structure function scaling exponents display a significant difference when comparing the results generated using different heat injection mechanisms. Upon examination of the kurtosis structure functions of the temperature difference, the present work suggests that passive scalar structure function scaling exponents exhibit a dependence on the scalar-field boundary conditions due to the finite (and different) Péclet numbers of the flows under consideration — an effect that is significantly less prominent in the measurements of the mixed velocity-temperature structure functions and the (non-centered) autocorrelations of the dissipation rate of scalar variance. The second set of experiments consists of a study of the scalar field downstream of a concentrated line source within a fully-developed, high-aspect-ratio channel flow. However, unlike previous dispersion measurements employing concentrated sources, the current research employs a line source oriented in the direction of the inhomogeneity of the velocity field. Consequently, the resulting wake downstream of the line source is statistically three-dimensional. In such an arrangement, the velocity field at each wall-normal position is different, since the velocity field in the current configuration is solely a function of the wall-normal distance. The resultant mixing is studied using a variety of statistics, including the mean and root-mean-square temperature distributions, probability density functions of the temperature fluctuations, as well as the (turbulent) intensity of the scalar fluctuations. These results are contrasted with prior transverse dispersion measurements in which the scalar dispersion remains statistically two-dimensional, in an attempt to elucidate the effect of the velocity-field boundary conditions. The findings suggest that both the mean flow shear and turbulence intensity of the velocity field play an important role in determining the mixedness of the scalar field.Une étude expérimentale de l'effet des caractéristiques à grandes-échelles des écoulements turbulents sur le mélange d'un scalaire passif y est présentée. Étant donné la relation directe entre les grandes échelles des écoulements turbulents et la configuration géométrique de l'écoulement, deux ensembles d'expériences distincts sont menés dans lesquels la dépendance du mélange d'un scalaire sur les conditions limites du (i) champ scalaire et (ii) champ de vitesse est étudiée. Le premier ensemble d'expériences est réalisé dans le sillage d'un cylindre circulaire. Pour varier les conditions limites du champ scalaire, tout en gardant le même écoulement hydrodynamique, deux mécanismes d'injection de chaleur différents sont utilisés. Premièrement, un élément chauffant est incorporé dans le cylindre qui génère le sillage hydrodynamique. Lorsque l'élément est mis sous tension, le sillage est donc chauffé au moyen d'un « cylindre chauffé ». Deuxièmement, un ensemble de fils fins est installé en aval du cylindre. Cette configuration, connue sous le nom de « mandoline, » s'est avérée d'avoir une influence négligeable sur le champ de vitesse, en raison du faible diamètre des fils. Par conséquent, l'une des deux configurations peut être utilisée pour chauffer le sillage, sans modifier le champ de vitesse, et de nombreuses statistiques du champ scalaire et du champ de vitesse sont examinées. En particulier, les fonctions de structure du champ scalaire (et leurs exposants d'échelle), ainsi que les fonctions de structure mixte vitesse-température et les autocorrélations (non-centrées) du taux de dissipation de la variance scalaire, sont utilisées pour obtenir des estimations quantitatives de l'intermittence interne du champ scalaire. Il est conclu que les exposants d'échelle des fonctions de structure du champ scalaire passif présentent une différence importante lorsque l'on compare les résultats obtenus en utilisant de différents mécanismes d'injection de chaleur. Lorsque l'on examine les fonctions de structure du coefficient d'aplatissement de la différence de température, ce mémoire suggère que les exposants d'échelle des fonctions de structure démontrent une dépendance aux conditions limites du champ scalaire en raison des nombres de Péclet finis (et différents) des écoulements étudiés — un effet qui est nettement moins important dans les fonctions de structure mixte vitesse-température et les autocorrélations du taux de dissipation de la variance scalaire.Le deuxième ensemble d'expériences consiste d'une étude du champ scalaire en aval d'une source concentrée linéaire dans un écoulement de canal pleinement développé, ayant un rapport hauteur-largeur élevé. Contrairement à des mesures de dispersion précédentes utilisant des sources concentrées, ce travail emploie une source linéaire orientée dans la direction de l'inhomogénéité du champ de vitesse. Par conséquent, le panache thermique créé par la source linéaire est (statistiquement) tridimensionnel. Dans une tel configuration, le champ de vitesse à chaque distance du mur est différent, puisque le champ de vitesse dans la configuration actuelle est uniquement une fonction de la distance du mur. Le mélange du scalaire passif est étudié en utilisant une variété de statistiques, incluant la moyenne et la moyenne quadratique du champ de température, des fonctions de densité de probabilité des fluctuations de température, ainsi que l'intensité (turbulent) des fluctuations scalaires. Ces résultats (i) exposent les différences entre ces mésures et celles de dispersion transverse, dans lesquelles la dispersion du scalaire reste statistiquement bidimensionel, et (ii) facilitent l'élucidation des effets des conditions limites du champ de vitesse sur le mélange d'un scalaire passif. Les résultats suggèrent que le cisaillement de l'écoulement moyen et l'intensité turbulent du champ de vitesse jouent un rôle important dans la détermination du niveau de mélange du champ scalaire.
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Levernier, Guillaume. "Déterminants biomécaniques de la performance en escalade : étude de la force des membres supérieurs et de la relation force-vitesse chez les sportifs de haut niveau Four Weeks of Finger Grip Training Increases the Rate of Force Development and the Maximal Force in Elite and Top World-Ranking Climbers Rate of Force Development and Maximal Force : Reliability and Difference between Non-Climbers , Skilled and International Climbers Force-Velocity-Power profile in high elite boulder, lead, speed climbers competitors." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS604.
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Ce travail de thèse s’est intéressé à la production de force externe ainsi qu’à la relation force-vitesse-puissance des membres supérieurs chez les sportifs de haut niveau en escalade.La première partie de l'étude s'est focalisée sur deux aspects clefs dans la performance : la force maximale volontaire (FMV) des muscles fléchisseurs des doigts ainsi que le taux de développement de la force (RFD). Un protocole de mesure a été mis au point et sa fiabilité a été vérifiée. Cela a permis de montrer qu'un entrainement spécifique de seulement 4 semaines permettait déjà d'engendrer des évolutions spécifiques au niveau du RFD.Ce protocole a également vérifié l'hypothèse que la force maximale et le RFD étaient supérieurs chez les grimpeurs de haut niveau : la différence par rapport aux autres sportifs, y compris les grimpeurs confirmés, est significative. De même, ce protocole a confirmé que la force maximale des muscles fléchisseurs des doigts ainsi que le RFD diffèrent significativement selon la discipline : ils sont plus élevés chez les grimpeurs de bloc que chez les spécialistes de la difficulté. La seconde partie de ce travail a étudié un troisième déterminant clef de la performance en escalade : la production de force externe des muscles fléchisseurs des bras à différentes vitesse. Un test de tractions lestées a été mené sur des groupes de grimpeurs de haut niveau représentatifs de chacune des 3 disciplines : bloc, difficulté et vitesse. Il a ainsi été montré qu'il existe d'importantes différences, du point de vue de la relation force-vitesse-puissance, selon la discipline. Les grimpeurs de bloc présentent notamment une production de force à vitesse rapide significativement supérieure à celles des deux autres disciplines. Par contre, la production de force à vitesse lente n'est pas discriminante entre les 3 groupes.En conclusion, ce travail a démontré que l'évaluation quantitative des facteurs déterminants biomécaniques pourrait compléter utilement les outils qualitatifs à la disposition de l'entraineur. Ainsi, selon la discipline et les prochaines échéances sportives, il pourra définir un entrainement spécifique et suivre de façon objective les résultats obtenus par le grimpeurThis PhD work was interested in the production of force output and the force-velocity-power relationship of the upper limb in high-level climbing athletes.The first part of the study focused on two key aspects of performance: the maximal voluntary contraction (MVC) of fingers' flexor muscles and the rate of force development (RFD). A measurement protocol was set up and its trustworthiness proof checked. This showed that a 4-weeks-only specific training has an impact on RFD evolution.This protocol also checked the fact that high-level climbers have higher MVC and RFD: the difference between them and other athletes, including advanced climbers, is significant. Likewise, this protocol confirmed that fingers flexor muscles maximum contraction and RFD significantly differ depending on the discipline: they are higher in bouldering climbers than in lead climbing ones.The second part of this work studied a third key determinant of performance in climbing: the arms flexor muscles external force production at different speeds. A test was run on panels of high-level climbers representatives of the three disciplines: bouldering, lead climbing and speed climbing. It resulted in major differences in the force-velocity-power relationship depending on the discipline. Bouldering climbers notably showed a force production at high speed rate significantly higher than the two other groups. However, at lower speed rate, the force production was not a discriminative criteria between the three groups.To conclude, this work showed that the quantitative assessment of determinant biomechanical factors could be beneficial as a complement to qualitative tools available to coaches/trainers. Thus, depending on the discipline and upcoming sport deadlines, a specific training could be set up and an unbiased follow-up of the climbers' performances could be obtained
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Rouhnia, Mohamad. "Vertical Transport of Sediment from Muddy Buoyant River Plumes in the Presence of Different Modes of Interfacial Instabilities." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82506.
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This study focuses on deposition processes from sediment laden buoyant river plumes in deltaic regions. The goal is to experimentally examine the effects of various physical phenomena influencing the rate at which sediment is removed from the plume. Previous laboratory and field measurements have suggested that, at times, sedimentation can take place at rates higher than that expected from individual particle settling (i.e., C{W}_{s}). Two potential drivers of enhanced sedimentation are flocculation and interfacial instabilities. We experimentally measured the sediment fluxes from each of these processes using two sets of laboratory experiments that investigate two different modes of instability, one driven by sediment settling and one driven by fluid shear. The settling-driven and shear-driven instability sets of experiments were carried out in a stagnant stratification tank and a stratification flume respectively. In both sets, continuous interface monitoring and concentration measurement were made to observe developments of instabilities and their effects on the removal of sediment. Floc size was measured during the experiments using a separate floc camera setup and image analysis routines. Results from the stratification tank experiments suggest that the settling-driven gravitational instabilities do occur in the presence of flocs, and that they can produce sedimentation rates higher than those predicted from floc settling. A simple cylinder based force balance approach adopting the concept of critical Grashof number was used to develop a model for the effective settling velocity under settling-driven instabilities that is a function of sediment concentration in the plume only. Results from the stratification flume experiments show that under shear instabilities, the effective settling velocity is greater than the floc settling velocity, and increases with plume velocity and interface mixing. The difference between effective and floc settling velocity was denoted as the shear-induced settling velocity. This settling rate was found to be a strong function of the Richardson number, and was attributed to mixing processes at the interface. Conceptual and empirical analysis shows that the shear-induced settling velocity is proportional to U{Ri}^{-2}.
Following the experiments, analyses were made among contributions of different mechanisms on the total deposition rate, and the locations that the various mechanisms may be active in the length of a plume. This analysis leads to a conceptual discretization of a plume into three zones of sedimentation behavior and Richardson number. The first zone is the supercritical near-field plume with intense interface mixing. Zone two represents the subcritical region where interface mixing still occurs, and zone three is the high Richardson number zone where mixing at the interface is effectively nonexistent. In zones one and two, individual floc settling and shear-induced settling mechanisms play the major roles in removing sediment from the plume. While, shear-induced settling rate was found to be maximum near the river mouth, its share of the total settling rate increases in the crossshore direction, since sand and large particulates deposit near the inlet and only small particles (with relatively low settling velocity) remain as the plume propagates. The third zone, starts when the interfacial mixing diminishes and leaking commences.Ph. D.
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Doldo, Neil Anthony. "Racial and sex differences in strength, peak power, movement velocity, and functional ability in middle aged and older adults." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/2331.
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Thesis (M.A.) -- University of Maryland, College Park, 2004.Thesis research directed by: Kinesiology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Ryberg, Anders T. "On the autonomic control of blood flow and secretion in salivary glands : functional and morphological aspects of muscarinic receptor subtypes in different species /." Göteborg : Institute of Neuroscience and Physiology, Department of Pharmacology, the Sahlgrenska Academy at Göteborg University, 2007. http://hdl.handle.net/2077/9596.
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Wong, Hanson. "The Effects of Different Set Configurations on Concentric Velocities in the Barbell Back Squat." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etd/3788.
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The purpose of this study was to determine if concentric velocities of lighter loads of could be augmented if they are performed heavier working sets. Twelve trained males with experience in the barbell back squat performed a 5RM and completed two separate squat training session conditions that consisted of three sets of five repetitions with 85% of their 5RM. Both conditions differed in the placement of a reduced-load set that was either performed after the working sets or during the warm-up period. No significant differences were observed in the working set MCVs in both conditions. Additionally, no significant differences were observed amongst MCVs in the Down Set and equivalent warm-up set loads. The results of this study suggest that postactivation potentiation may not occur using a similar set-load scheme.
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Mitschke, Christian, Matthias Öhmichen, and Thomas L. Milani. "A Single Gyroscope Can Be Used to Accurately Determine Peak Eversion Velocity during Locomotion at Different Speeds and in Various Shoes." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-226795.
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Gyroscopes have been used in previous studies to measure the peak angular velocity of the shoe or foot in the frontal plane (evVel). However, it is not clear whether different test conditions (footwear hardness or locomotion speed) can influence the accuracy of evVel. The purpose of the present study was to compare the accuracy of gyroscopes and electrogoniometers when measuring evVel and the time until evVel (t_evVel) in 12 different conditions using a single axis gyroscope attached to the heel cap. Twenty-four recreational runners were instructed to walk and run on a 15-m indoor track at four locomotion speeds (1.5, 2.5, and 3.5 m/s, and individual running speed) and in three footwear conditions (low to high hardness). The gyroscope data and electrogoniometer data were sampled at a rate of 1000 Hz. Comparisons between both measurement devices showed small mean differences up to 49.8 ± 46.9 deg/s for evVel and up to 5.3 ± 3.5 ms for t_evVel. Furthermore, strong relationships between gyroscope and electrogoniometer data were found for evVel as well as for t_evVel for all conditions. It can be concluded that gyroscopes can be used to accurately determine evVel and t_evVel under a variety of conditions.
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Manseck, Andreas, Christian Pilarsky, Stefan E. Froschermaier, Mario Menschikowski, and Manfred P. Wirth. "Diagnostic Significance of Prostate-Specific Antigen Velocity at Intermediate PSA Serum Levels in Relation to the Standard Deviation of Different Test Systems." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-133947.
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Serial prostate-specific antigen (PSA) measurements (PSA velocity) as an additional instrument to detect prostatic cancer was introduced in 1992. It has previously been reported that PSA increase per year differed in the last 5 years prior to diagnosis in patients with benign prostatic hyperplasia (0.18 ng/ml/year), locally confined (0.75 ng/ml/year) and metastasized (4.4 ng/ml/year) cancer of the prostate (CaP) in contrast to healthy men (0.04 ng/ml/year). The ability of PSA velocity to detect organ-confined CaP in patients with intermediate PSA serum values depends therefore on a reliable and reproducible PSA result. The present study comprised 85 men with PSA values between 3 and 8 ng/ml (Abbott IMx). PSA measurements were repeated with Abbott IMx (n = 85 patients) and Hybritech Tandem-E (n = 59 patients) assays. The PSA serum values differed from one examination to the other from 0.02 to 2.74 ng/ml with the Abbott IMx. Standard deviation amounted to 0.35 ng/ml with the Abbott IMx PSA assay. Using the Hybritech Tandem-E assay, mean standard deviation was 1.15 ng/ml and therefore higher than with the Abbott IMx assay. The difference from one test to the other ranged from 0.05 to 4.05 ng/ml with the Hybritech Tandem-E. Using the Abbott IMx assay, 10.6% of all repeat measurements exceeded 1 ng/ml whereas in the Hybritech Tandem-E assay 62.7% of the second measurements differed >1 ng/ml from the first PSA result. An increase in PSA serum values may therefore be due to intratest variation, physiological day-to-day variation as well as prostatic disease. It is important to notice that the intra-assay variation may be greater than the PSA increase per year in a patient with CaP. Therefore, PSA velocity seems to be of limited valueDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Manseck, Andreas, Christian Pilarsky, Stefan E. Froschermaier, Mario Menschikowski, and Manfred P. Wirth. "Diagnostic Significance of Prostate-Specific Antigen Velocity at Intermediate PSA Serum Levels in Relation to the Standard Deviation of Different Test Systems." Karger, 1998. https://tud.qucosa.de/id/qucosa%3A27551.
Full textAbstract:
Serial prostate-specific antigen (PSA) measurements (PSA velocity) as an additional instrument to detect prostatic cancer was introduced in 1992. It has previously been reported that PSA increase per year differed in the last 5 years prior to diagnosis in patients with benign prostatic hyperplasia (0.18 ng/ml/year), locally confined (0.75 ng/ml/year) and metastasized (4.4 ng/ml/year) cancer of the prostate (CaP) in contrast to healthy men (0.04 ng/ml/year). The ability of PSA velocity to detect organ-confined CaP in patients with intermediate PSA serum values depends therefore on a reliable and reproducible PSA result. The present study comprised 85 men with PSA values between 3 and 8 ng/ml (Abbott IMx). PSA measurements were repeated with Abbott IMx (n = 85 patients) and Hybritech Tandem-E (n = 59 patients) assays. The PSA serum values differed from one examination to the other from 0.02 to 2.74 ng/ml with the Abbott IMx. Standard deviation amounted to 0.35 ng/ml with the Abbott IMx PSA assay. Using the Hybritech Tandem-E assay, mean standard deviation was 1.15 ng/ml and therefore higher than with the Abbott IMx assay. The difference from one test to the other ranged from 0.05 to 4.05 ng/ml with the Hybritech Tandem-E. Using the Abbott IMx assay, 10.6% of all repeat measurements exceeded 1 ng/ml whereas in the Hybritech Tandem-E assay 62.7% of the second measurements differed >1 ng/ml from the first PSA result. An increase in PSA serum values may therefore be due to intratest variation, physiological day-to-day variation as well as prostatic disease. It is important to notice that the intra-assay variation may be greater than the PSA increase per year in a patient with CaP. Therefore, PSA velocity seems to be of limited value.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Abraham, Rohit Mathew. "An Experimental Study of Scuffing Performance of a Helical Gear Pair Subjected to Different Lubrication Methods." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397228984.
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Rezailashkajani, Mohammadreza. "Cardiovascular risk in ageing men of different ethnicities : inter-relationships between imaging and endocrine markers." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/cardiovascular-risk-in-ageing-men-of-different-ethnicities-interrelationships-between-imaging-and-endocrine-markers(504c0fa3-280e-4206-94b6-e6093fb5e87b).html.
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Cardiovascular disease varies by ethnicity in the UK. South Asians (SA) have higher coronary heart disease (CHD) and diabetes prevalence, while African-Caribbeans (AfC) have greater stroke, but intriguingly lower CHD rates despite higher blood pressures and diabetes risk than Europeans. Conventional risk factors do not fully explain such differences. This cross-sectional study tested the hypothesis that the hormones, vitamin D measured as 25(OH)D and aldosterone, would be independently associated with intermediate cardiovascular outcome markers in these ethnic groups. Community-dwelling men 40-80 years old (AfC: n=67, 55±10yr; SA: n=68, 55±10yr; European: n=63, 57±8yr) were sampled from Greater Manchester’s multi-ethnic population. The intermediate markers examined were aortic pulse wave velocity (aPWV), left ventricular (LV) mass and function, and carotid intima media thickness (CIMT), measured non-invasively by ultrasound, and hemodynamic profiling methods (the Arteriograph) in the total sample and by magnetic resonance imaging (MRI) in a subsample of 50. Adjusted for age, systolic blood pressure and diabetes, mean(SE) aPWV by the Arteriograph, was 0.5(0.2) m/s higher in SA than AfC and Europeans (p=0.01), which paralleled known cross-ethnic CHD risk differences in the UK. By MRI, aPWV along the descending aorta in SA was 0.7(0.3) and 0.8(0.3) m/s higher than that in AfC and Europeans, but aPWV along the aortic arch was not significantly different. Unlike aldosterone, 25(OH)D was independently and inversely correlated with aPWV (unstandardised B(SE)=-0.013[0.004] m/s, p<0.001), and partly explained the ethnic variation in aPWV. Similar inverse correlations were found between 25(OH)D and LV concentricity measured by echocardiography and MRI. Compared to Europeans, SA and AfC, had 21(3) and 14(3) nmol/L lower mean(SE) 25(OH)D, respectively (p<0.01). Mean(SE) of relative wall thickness, an index of LV concentricity by echocardiography, was 0.05(0.01) higher in SA and AfC than Europeans. Lower 25(OH)D levels were also associated with higher myocardial deformation rates measured by MRI myocardial tagging (n=50), supporting previous animal experimental evidence. A one standard deviation (SD) decrease in 25(OH)D was associated with a 0.38 SD increase in absolute systolic strain rate (p=0.003) and 0.22 SD rise in diastolic strain rate (p=0.04). Right and left CIMT showed different relations with 25(OH)D and aldosterone. Left-right CIMT differences varied by ethnicity and were related to SA ethnicity and aldosterone levels. Two related technical studies investigated the relatively new method of hemodynamic profiling, the Arteriograph, used here. The results suggested a standardisation method of aortic length estimation for purely central aPWV, which significantly improved aPWV agreement between the Arteriograph and MRI (reference method here), and was used for calibrating the Arteriograph aPWV in the above-mentioned results for the total sample. Future well-designed trials are necessary to investigate any cause-effect relationship between vitamin D deficiency and the unfavourable cardiovascular intermediate outcomes found here in a cross-sectional design and multi-ethnic background.
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Czuba, Thaddeus Bradley. "Binocular mechanisms underlying the processing of three-dimensional visual motion." 2012. http://hdl.handle.net/2152/19449.
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In this dissertation, I examine binocular 3D motion processing through a series of psychophysical and neuroimaging experiments aimed at uncovering the neural computations involved and their interaction with the known hierarchy of visual motion processing. Two primary binocular cues could be used to compute 3D motion: one based on changing disparities over time (CD), the other based on interocular velocity differences (IOVD). Under normal viewing conditions, both cues coexist and (potentially) provide the same 3D direction information, yet whether CD, IOVD, or both mechanisms exist has distinct implications for how 3D motion is processed along the visual stream.
First, I measured 3D direction discrimination sensitivity is measured for isolated binocular cues under a range of 3D motion speeds and visual eccentricities. Comparison of isolated-cue sensitivity to corresponding combined cue sensitivity (i.e. concurrent IOVD & CD cue stimuli) provided an estimate of relative cue contributions under normal viewing conditions. Second, I conducted a series of motion adaptation experiments to differentiate the neural representation of 2D and 3D directions of motion, and examine the degree to which IOVD or CD mechanisms can account for 3D motion adaptation. Third, I examined the neural locus of 3D motion processing by measuring 3D direction- selectivity throughout a range of visual cortical areas using functional neuroimaging in an event-related paradigm that parallels psychophysical adaptation experiments. Finally, I discuss the broader implications for the neural mechanisms of binocular 3D motion processing and future experimental directions.
Together, these results reveal that: (1) the IOVD cue is the dominant cue to 3D motion processing across the majority of natural speeds & eccentricities, (2) neural tuning for 3D motion is distinct from 2D motion and can be fully explained by an IOVD mechanism, and (3) the IOVD cue is computed relatively late in the visual processing stream, in areas MT & MST— cortical areas primarily associated with 2D/retinal motion and thought to be beyond the point of binocular combination. The significance of IOVD —but not CD—cues to 3D motion perception motivates a drastic modification to canonical models of motion processing to include the late-stage comparison of eye- specific motion signals.text
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Peng, Cheng-Chi, and 彭成麒. "The Study of Using Finite Difference Method and Back-propagation Neural Networks to Evaluate Shear Wave Velocity." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/83wy69.
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Chang, Chien-Chung, and 張建忠. "Generalized finite difference method for two-dimensional velocity-vorticity formulation and the assessment of its parallel efficiency." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/xdb9qq.
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碩士國立臺灣海洋大學
河海工程學系
103
In this study, we use the generalized finite difference method (GFDM) to simulate the two-dimensional fluid fields of incompressible viscous fluid. In order to accelerate the computational speed, we parallelize our program on a multithreading computer which has shared memory architecture. To validate the feasibility, accuracy and the parallel efficiency of the meshless method proposed in this article, we provided three numerical examples. The velocity-vorticity formulation are solved in this study and it is another form of the standard Navier-Stokes equations. The problem of the pressure term and the pressure boundary condition in the primary-variable formulation of the Navier-Stokes equations can be overcame. In addition, the number of the unknown variables in the velocity-vorticity formulation is the same as the primary-variable formulation in two-dimensional fluid fields. Therefore, the velocity-vorticity formulation has great potential to be used in engineering applications. The methods, used for flow fields, usually require grids in the computational domain, such as the finite difference method and the finite volume method. Instead, we adopt the GFDM, a novel meshless method. It can get rid of mesh generation and numerical quadrature as well as construct a sparse matrix by introducing the localized concept. Moreover, we used the parallelizable non-symmetric sparse matrix direct solver to solve the resultant linear algebraic system. The GFDM is based on the moving-least-square method to approximate the derivatives at every node in computational domain by linear summation of nodal values. Therefore, the programming by using the GFDM is quite easy and convenient and can reduce the probability of ill-conditioned matrix. On the other hand, we use the implicit Euler method on the time quadrature, so we can adopt larger time step to acquire the stable result. To apply the above methods will result in non-linear algebraic equations. We solve it by the Newton’s method because its convergence is at least quadratic. In this paper, we analyze the two-dimensional flow fields of incompressible viscous fluid, described by the velocity-vorticity formulation, by using the GFDM, the implicit Euler method and the Newton’s method. To verify the accuracy and the stability of our model, we simulated some examples include cavity flow, rectangular cavity flow, and staggered double cavity flow. The results of these examples are very similar to previous work, so we can deduce that our model has the ability for accurately solving flow-field problems. We also examine the influence of the variables in our model, such as, the number of total nodes, the number of nodes in the sub-domain and the length of time steps. All these results and comparisons can verify the accuracy, consistency, and stability of our model. We also parallelized the developed model by OpenMP and test the efficiency on a shared memory computer. According to the results, our parallelized model provided a satisfying efficiency when four threads are used.
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Torres, Daniel E. "Evaluation of the Procedure Used to Determine Nonlinear Soil Properties In Situ." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8818.
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Soil properties (shear modulus and damping) are normally determined from laboratory tests. These tests provide both values of the shear modulus in the linear elastic range for very small levels of strain, and its variation with the level of strain. It has become more common to measure the maximum shear modulus at low levels of strain directly in the field, using geophysical techniques. The values obtained in situ can differ significantly in some cases from those determined in the laboratory, and a number of reasons and correction factors have been proposed in the literature to account for this variation. As a result, when in situ properties are available, it is normal to use these values for very low levels of strain, but still assume that the variation of the ratio G/Gmax (normalized shear modulus) with shear strain is the same as determined in the laboratory.
Recently, tests have been performed using large vibrators (the Thumper and Tyrannosaurus Rex of the University of Texas at Austin) to determine soil properties in situ for larger strains, and the variation of G/Gmax obtained from these tests has been compared to that reported in the literature from lab tests. Observation indicates some generally good agreement, but also some minor variations. One must take into account, however, that in the determination of the shear modulus versus strain in the field from vibration records, a number of approximations are introduced. The objective of this work is to evaluate the accuracy of some the procedures used and to assess the validity of the simplifying assumptions which are made.
For this purpose, a shear cone that would reproduce correctly the horizontal stiffness of a circular mat foundation on the surface of an elastic, homogeneous half space, was considered. The cone was discretized using both a system of lumped masses and springs and a finite difference, using second-order central difference formulation, verifying that in the linear elastic range the results were accurate. A number of studies were conducted next, increasing the level of the applied force and using nonlinear springs that would reproduce a specified G/Gmax vs. γ curve. Using a similar procedure to that used in the field tests, the shear wave velocity between hypothetical receivers and the levels of strain were determined. The resulting values of G/Gmax vs. γ were then compared with the assumed curve to assess the accuracy of the estimated values.
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CHIN, PENG SHAO, and 彭紹錦. "Numerical Modeling of Three-Dimensional Flow Field in a Cylindrical Combustor of Co-Flow Jets with Large Velocity Difference." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/98153530515843015181.
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碩士元智大學
機械工程研究所
87
The three-dimensional flow fields in a cylindrical combustor of co-flow jets with large velocity difference are investigated numerically. Prediction results show presence of a large central recirculation zone and its remarkable effect on rapid heating, flame stabilization and combustion intensification, although its strength, size, and location are changed with the flow parameters. The jet hole location and the velocity difference between the high velocity and primary jets play the most important role in inducing the central recirculation zone.
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Lin, Shu-Heng, and 林樞衡. "A development of double-difference earthquake location program using three-dimensional velocity model and its application to the 2013 Ruisui, Taiwan, earthquake sequence." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/33323854158021536661.
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碩士國立臺灣大學
地質科學研究所
102
Double-difference algorithm is one of the methods used in earthquake relocation. The widely used double-difference relocation program is hypoDD (Waldhauser and Ellsworth, 2000; Waldhauser, 2001). It only supports using layered velocity model in the relocation process. To improve the relocation result by using higher resolution velocity model, we developed a double-difference earthquake relocation program using three-dimensional velocity model (3D-DD). Moreover, we also joint single-event relocation method with double-difference location algorithm during the inversion procedure, in order to prevent losing the relocation results when double-difference location algorithm is only used. The performance of the program was tested by a series of synthetic data tests, and the location error of 3D-DD is smaller than the error of hypoDD and a three-dimensional single event earthquake relocation program. We also apply our method on the relocation of Ruisui, Taiwan, earthquake sequence occurred on October 31st, 2013. The relocated hypocentral distribution is much more concentrated and linear. The location error and residual also became smaller after relocated by this method. By relocated hypocenters and velocity structure of Taiwan area, the cause of Ruisui earthquake may be the tectonic activity of the Luzon forearc crust.
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Hutchinson, David Karel. "Wind Stress Parameterisation in the Southern Ocean." Thesis, 2008. http://hdl.handle.net/1885/47691.
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Wind stress is often parameterised in ocean-atmosphere coupled models by a quadratic function of atmosphere velocity. Strictly speaking, this drag law should be a quadratic function of the difference between the ocean and atmosphere velocities. The two schemes give very similar magnitudes of stress, however the power input is significantly reduced under the velocity difference stress. This work is the first to model this effect in the Southern Ocean. The velocity difference stress is found to reduce power input, but paradoxically the circumpolar transport is increased. The increase in transport is a consequence of two main factors: eddy saturation of the Antarctic Circumpolar Current, and eddy damping under the velocity difference stress.
¶
The wind stress parameterisation is also modified, by coupling the quadratic drag law to the temperature difference between the ocean and atmosphere. This simple representation is shown to be consistent with scatterometer observations, and the coupling constant is calibrated using known correlations between gradients of stress and sea surface temperature. Unlike the velocity difference stress, the temperature coupled stress is found to have a negligible effect on the mean flow in this model.
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Chun-Lin, Huang, and 黃春霖. "Study on Deposition Effect in Different Velocity of Different Dry Masonary Work." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/27281576236292301676.
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碩士中原大學
土木工程研究所
102
ABSTRACT In recent years, due to the rise of ecological awareness of conservation, ecological and environmental problems has been regarded as an important river issues, application of ecological engineering required to consider local conditions and local materials, and the need to make the overall system considerations. Domestic dikes and revetments, the use of concrete flood wall, although able to reach flood prevention effect, but this construction method tends to destroy the natural ecology. In this study, based on Beinan River actual flow rate, sand grain size, slope and switchgrass workers materials such as information model test. Use hydraulic flume tests to analyzes vertical-scale structure, positive-scale structure and inverse-scale structure three in different stone masonry works to execute the hydraulic model test of clean water and Sand Filled test. To investigate this in three different stone masonry works, the change of Manning coefficient and physical parameters of the water under different velocity of flow for future references. This study know, inverse-scale structure velocity of flow is the biggest changing in vertical section,the second is vertical-scale structure,the least is positive-scale structure；Manning coefficient of three masonary work the biggest is inverse-scale structure, second one is ertical-scale structure, the least is positive-scale structure. When the flow changes from small to large, inverse-scale structure and positive-scale structure sediment size distribution will change, when low flow, large particles of sand will be deposited in the preceding of test section, when the flow becomes large, large particles of sand will be deposited in the rear of test section; But the vertical-scale structure of deposition gravel size distribution won't change ,when the flow changing.
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Lin, Ya-Han, and 林雅涵. "The Effect of Different Stiffness and Balance Point on Badminton Racket’s Swing Velocity and Ball Velocity." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/75219565668238260856.
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碩士國立臺灣師範大學
運動科學研究所
98
Purpose ：To understand the effect of four different kinds of stiffness and three different swing-weight on swing-velocity, ball-velocity and coefficient of restitution. The result of the study will be taken as index to the selection and design of badminton racket in the future. Methods: Two experiments were conducted in the study; In the first experiment, the ball was served and then collided the racket; in the second experiment, the ball is fastened with clamping, hanging in the air, and hit by players. The results were recorded by 10000 Hz high speed video camera, and analyzed by video analysis software, which helped researcher to compare swing velocity and ball velocity between pre-test and post-test. Statistical analysis were conducted by two-way ANOVA to examine the effects of stiffness and swing-weight on swing-velocity, ball-velocity and coefficient of restitution. The significant level was set at α<.05. Results: In the group impacted by server, the coefficient of restitution was in direct proportion to impact velocity, and the coefficient of restitution of middle swing weight was significantly higher than that of low swing weight. In the group hit by player, the swing velocity was in reverse proportion to swing weight, and the swing velocity of low swing weight was significantly faster than that of middle swing weight. Ball velocity was effected by the stiffness of the racket when swing velocity exceed 90 km; the Swing Velocity of high swing weight is slow, but its COR was higher than those of low swing weight and middle swing weight. Conclusion: The swing weight that significantly impacted on swing velocity, ball velocity and COR, and the influence of stiffness is comparatively less than swing weight. The users and designers would be advised to choose the racket with low swing weight in order to increase swing velocity, or high swing weight in order to increase COR.
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Wang, Shiu-horng, and 王旭虹. "Application of Different Critical Velocity in Distance Running Pace." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/35296602535282920543.
Full textAbstract:
碩士國立體育學院
運動科學研究所
92
Application of Different Critical Velocity in Distance Running Pace Abstract The purposes of this study were to investigate the difference 5000 m performance among critical velocity (CV) pace, 95﹪CV pace, and the maximal 5000 m effort test; to assess the relationship among CV, 1500 m, 3000 m, and 5000 m best performance; to use the simple regression to find CV predict equation from 1500 m, 3000 m and 5000 m performance as well. Eleven elite males distance runners volunteered as study subject. The CV was used the V-T mode to evaluate subjects best score of 1500 m, 3000 m, and 5000 m in recent three months. All of the test paces had to finish in 6 weeks. The subjects were divided into two groups according to their running pace. In order to avoid disturbed running performance, each group had its difference pace during the test. One-way repented ANOVA and Turkey post hot t-comparison were used to analyze the difference among the CV, 95﹪CV, and the maximal effort; Pearson product-moment correlation was used to test relationship between CV and 1500 m; CV and 3000 m; and CV and 5000 m test. Furthermore, the simple linear regression was used to find out the CV predict equation. The alpha level was set at .05. The findings are as follow: No significant different difference was found on the CV, 95﹪CV, and the maximal 5000 m performance. The correlation coefficients between CV and 1500 m; CV and 3000 m; CV and 5000 m were -.52, -.81, and -.99, respectively. Meanwhile, CV with 3000 m; CV with 5000 m had reached significant level; and the predict formula were Ŷ (CV)＝-0.01314×3000 m (s)＋12.169 with Ŷ (CV)＝-0.06239×5000 m (s)＋10.933 respectively. Predicted accuracy were 67﹪and 98﹪. Therefore, both CV pace and 95﹪CV pace can be applied on 5000 m competition and training strategy except 1500 m. Since every athlete has its own peculiarity, coach can choose most suitable way on practice. Key words：long distance, runner, critical velocity, pace
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Huang, Kuei-Yu, and 黃貴裕. "Comparison of Swing Velocity Among Three Different Level Baseball Players." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/58814328885094756184.
Full textAbstract:
碩士輔仁大學
體育學系碩士班
101
Abstract This study mainly discussed the differences of the swiping speed between the players in junior baseball league, senior baseball league and adult baseball league. According to individual defense places, we divided the players into infielders and outfielders to compare the differences of swiping speed of players at different defense places. We took 17 players in Taipei City Baseball Team, 16 senior-baseball-league players in Yang-Ming Senior High Baseball Team, and 13 junior-baseball-league players in Chongqing Junior High School for subjects. We used swiping speed test system to get the parameters of swiping speed of players from each rank which will be statistically analyzed through SPSS 14.0 for Windows. This research mainly compared the differences of swiping speed between adult baseball league, senior baseball league and junior baseball league with one-way analysis of variance of independent sample. And then, independent samples, t-test, were used to compare the infielders’ and outfielders’ differences of swiping speed. The standard of significant difference was α<.05. Please see the result of the study below: First, Among baseball players of different levels, in the result of swiping speed, the swiping speed of players in adult league was 90.7±10.4 km/hr; senior league was 83.4±8.8 km/hr ; junior league was 78.4±8.8 km/hr. After comparing the three different groups, the obvious difference (p＜.05) indicated that the swiping speed of players in adult league was apparently faster than that in junior league (p＜.05). Second, the swiping speeds of infielders and outfielders in adult league were respectively 90.8±11.7 km/hr and 90.6±6.2 km/hr. The result wasn’t notable(p＞.05). Third, the swiping speeds of infielders and outfielders in senior league were respectively 81.9±7.2 km/hr and 86.6±11.8 km/hr. The result wasn’t notable(p＞.05). Fourth, the swiping speeds of infielders and outfielders in junior league were respectively 80.7±6.3 km/hr and 76.5±7.6 km/hr. The result wasn’t notable(p＞.05).
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Chang, Chien Hsu-Fang, and 張簡旭芳. "Relationships between Body Acceleration and Velocity during Different Gait Pattern." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/58617477424997359847.
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碩士國立臺灣師範大學
運動競技學系
104
Introduction：The population engaged in exercise increases annually. One of the main reasons for exercising is for promoting overall health; therefore, the accuracy of measuring physical activity is critical. In recent years, the electronic industry has been booming and wearable technology is getting increasingly mature. The accelerometer has made a big breakthrough in accuracy, volume and convenience and is now a necessity for recording physical activity. Although accelerometers are commonly used in measuring physical activity, the algorithms are quite diverse and not yet standardized. The moving speed is an index of exercise intensity but the correlations between the physical acceleration and moving speed are not yet clear. Purpose: The purpose of this study is to examine: 1) the correlations between the physical acceleration, moving speed and heart rate reserve (HRR%)； 2） a better algorithm for estimating physical acceleration at different walking and running speeds. Method: This study recruited 19 healthy males who were asked to wear a heart rate monitor and a tri-axis accelerometer to perform walking and running at different speeds. Each speed was tested for 3 minutes followed by a rest until the participants returned to their standing rest heart rate. A one-minute stable heart rate of each trial was gathered for data analysis. After being processed with different algorithms the acceleration values were analyzed with moving speeds and HRR% respectively. The Pearson product-moment correlation coefficient was used to examine the relationships between walking, running, the entire walking-running period, physical acceleration, moving speeds and HRR%. Result: In the walking, running, and the entire walking-running period, the peak values of resultant acceleration and the MAD values of anterior-posterior acceleration showed significant correlations with moving speeds (r=.829**、.514**、.836**； r=.833**、.637**、.780**) and HRR% (r=.771**、.517**、.856**； r= .837**、.651**、.787**). Conclusion: It is feasible to estimate the exercise intensity for walking, running and the entire walking-running period with the peak values of resultant acceleration and the MAD values of anterior-posterior acceleration. The results can be used as a foundation for the future application in measuring physical activity.
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Liu, Kang-cheng, and 劉康丞. "Shallow crustal velocity structures inferred from different microtremor array methods." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/37963880288135235828.
Full textAbstract:
碩士國立中正大學
地震研究所暨應用地球物理研究所
98
Several techniques, such as the spatial autocorrelation (SPAC) , the centerless cicular array (CCA) , the spatial autocorrelation method along a linear array using vertical component data as well as the SPAC+L, SPAC-L and CCA-L methods using only horizontal component data, which are wildly applied in studying subsurface shear-wave velocity structures. The main purpose of this research is to use the above methods to obtain dispersion curves which are further used to infer the phase velocities of Rayleigh waves and Love waves recorded by a circular array deployed at Tapo, Chiayi city, Taiwan. Despite of the above, the other important task of this study is to investigate the resolution in different wavelengths for each method, which can play an important information for future study in deployment different sizes of array. Our results indicate that each method has different ranges of wavelength of good resolution.The SPAC method shows good resolution on short-wavelength side, while the CCA method show good resolution on long-wavelength side. For a linear array, the results obtained from the SPAC method are similar to other methods. We also compare the velocity structures derived from each method with the velocity structured obtained from PS-logging data and seismic exploration data. We find that our results agree well with both studies.
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李政翰. "River Velocity Measurement Techniques by Using Microwave Radar in Different Frequencies." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/2c229b.
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碩士逢甲大學
水利工程與資源保育學系
102
Observing the flow discharge of Taiwanese rivers is difficult because of high-intensity rainfall during typhoons, which results in high silt-content flooding and high cross-section scour and deposition variation. Traditional manual observation methods are time and labor consuming, hazardous, and inaccurate. Therefore, to achieve a breakthrough in current flow-volume observation technology, this study project in cooperation with domestic firms was proposed for developing a noncontact automatic river discharge radar observation device suitable for Taiwan. This study is using a water surface velocity radar to measure the velocity. A 24.125 GHz surface water flow meter was developed and tested at the Water Resources Planning Institute and at on-site locations. Integrating the laboratory and on-site testing results indicated that the 10.525 GHz and 24.125 GHz surface water flow meters were the most accurate when placed at a 30-degree angle of depression. The measurement errors of the two meters were respectively ± 7 % and ± 3 %. The relative expanded uncertainty were respectively 2 ~ 9% and 2 ~ 8%; because the suitable application angle of depression of the 24.125 GHz surface water flow meter is broader, this meter can be used to compensate for the deficiencies of the 10.525 GHz flow meter for conditions with flow speeds lower than 0.5 m/s and angles of depression greater than 40 degrees. The maximum measured flow velocity of the surface water flow meters was 9.93 m/s. To conduct on-site observations, the Ximen Bridge (Zhongshan Bridge) station on Ilan River of the Lan-Yang river basin and the Wanli River Bridge station on Wanli River were selected for northern and eastern area testing, respectively, the Dali River Xinan Bridge station of the Wu river basin and the Jishui River Sinying (formerly the Jishui River Bridge) station of the Jishui river basin were selected for central and southern area testing, respectively. The natural observation site testing results indicated that the instrument measurements yielded results that exhibited errors within a range of ± 10 %.
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Wu, Xin-shi, and 吳欣蒔. "The Study of Critical Velocity of Male Different Distance Speed Skating." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/51309935792090611260.
Full textAbstract:
碩士國立屏東教育大學
體育學系
99
This study was aimed at discussing about the establishment of critical velocity mode of male long-distance speed skating players, in order to help coaches and players to draft t programs. Meanwhile, Take 18 long-distance critical velocity players of Ping-Tung county skating committee to proceed maximal oxygen consumption test to find out anaerobic threshold and proceed different- distance with the greatest efforts test to calculate personal critical velocity mode through linear mathematic formula of critical velocity of the score. Results in this research: the average of maximal oxygen consumption was 65.0±8.6 ml‧kg-1‧min-1 , the average of maximal heart rate 191.7±7.2 time/ minute, and the average of heart rate of anaerobic threshold was 152.5±11.6 time/ minute, however, all above in order to set up each player''s exclusive speed training goal, and the suggestion of goal palpitation rate training, making coaches can constitute the goal more efficiently while training. The critical velocity in long-distance speed skating items has apparent relevance, thus, there is the same result with the research of other long distance items. Coaches can introduce this idea into training, promoting the efficiency of training, but does not go on steadily in the contest of the speed skating, therefore, it often has component that a need vies for assigning to with higher speed, and this is also a restriction between this research and actual contest.
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(6504827), Boon Him Lim. "Critical Velocity of High-Performance Yarn Transversely Impacted by Different Indenters." Thesis, 2019.
Find full textAbstract:
Critical velocity is defined as projectile striking velocity that causes instantaneous rupture of the specimen under transverse impact. The main goal of this dissertation was to determine the critical velocities of a Twaron® 2040 warp yarn impacted by different round indenters. Special attention was placed to develop models to predict the critical velocities when transversely impacted by the indenters. An MTS 810 load frame was utilized to perform quasi-static transverse and uniaxial tension experiments to examine the stress concentration and the constitutive mechanical properties of the yarn which were used as an input to the models. A gas/powder gun was utilized to perform ballistic experiments to evaluate the critical velocities of a Twaron® 2040 warp yarn impacted by four different type of round projectiles. These projectiles possessed a radius of curvature of 2 μm, 20 μm, 200 μm and 2 mm. The results showed that as the projectile radius of curvature increased, the critical velocity also increased. However, these experimental critical velocities showed a demonstrated reduction as compared to the classical theory. Post-mortem analysis via scanning electron microscopy on the recovered specimens revealed that the fibers failure surfaces changed from shear to fibrillation as the radius of curvature of the projectile increased. To improve the prediction capability, two additional models, Euler-Bernoulli beam and Hertzian contact, were developed to predict the critical velocity. For the Euler–Bernoulli beam model, the critical velocity was obtained by assuming the specimen ruptured instantaneously when the maximum flexural strain reached the ultimate tensile strain of the yarn upon impact. On the other hand, for the Hertzian contact model, the yarn was assumed to fail when the indentation depth was equivalent to the diameter of the yarn. Unlike Smith theory, the Euler-Bernoulli beam model underestimated the critical velocity for all cases. The Hertzian model was capable of predicting the critical velocities of a Twaron® 2040 yarn transversely impacted by 2 μm and 20 μm round projectiles.
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Li, Siwei 1987. "Seismic imaging and velocity model building with the linearized eikonal equation and upwind finite-differences." Thesis, 2014. http://hdl.handle.net/2152/24990.
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Ray theory plays an important role in seismic imaging and velocity model building. Although rays are the high-frequency asymptotic solutions of the wave equation and therefore do not usually capture all details of the wave physics, they provide a convenient and effective tool for a wide range of geophysical applications. Especially, ray theory gives rise to traveltimes. Even though wave-based methods for imaging and model building had attracted significant attentions in recent years, traveltime-based methods are still indispensable and should be further developed for improved accuracy and efficiency. Moreover, there are possibilities for new ray theoretical methods that might address the difficulties faced by conventional traveltime-based approaches. My thesis consists of mainly four parts. In the first part, starting from the linearized eikonal equation, I derive and implement a set of linear operators by upwind finite differences. These operators are not only consistent with fast-marching eikonal solver that I use for traveltime computation but also computationally efficient. They are fundamental elements in the numerical implementations of my other works. Next, I investigate feasibility of using the double-square-root eikonal equation for near surface first-break traveltime tomography. Compared with traditional eikonal-based approach, where the gradient in its adjoint-state tomography neglects information along the shot dimension, my method handles all shots together. I show that the double-square-root eikonal equation can be solved efficiently by a causal discretization scheme. The associated adjoint-state tomography is then realized by linearization and upwind finite-differences. My implementation does not need adjoint state as an intermediate parameter for the gradient and therefore the overall cost for one linearization update is relatively inexpensive. Numerical examples demonstrate stable and fast convergence of the proposed method. Then, I develop a strategy for compressing traveltime tables in Kirchhoff depth migration. The method is based on differentiating the eikonal equation in the source position, which can be easily implemented along with the fast-marching method. The resulting eikonal-based traveltime source-derivative relies on solving a version of the linearized eikonal equation, which is carried out by the upwind finite-differences operator. The source-derivative enables an accurate Hermite interpolation. I also show how the method can be straightforwardly integrated in anti-aliasing and Kirchhoff redatuming. Finally, I revisit the classical problem of time-to-depth conversion. In the presence of lateral velocity variations, the conversion requires recovering geometrical spreading of the image rays. I recast the governing ill-posed problem in an optimization framework and solve it iteratively. Several upwind finite-differences linear operators are combined to implement the algorithm. The major advantage of my optimization-based time-to-depth conversion is its numerical stability. Synthetic and field data examples demonstrate practical applicability of the new approach.text
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Huang, hsiang-yen, and 黃香燕. "Measure the wave velocity of sand under different condition by piezoelectric ceramics." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/19563038708819260991.
Full textAbstract:
碩士國立中央大學
土木工程學系
86
Taiwan is located on the Circum-Pacific Earthquake Zone in whichgreat earthquakes occur frequently. Liquefaction of sand induced byearthquakes may cause severe damage to the civil structures rested onthe loose sandy soil. The complicated mechanical behavior of sandduring shearing must be thoroughly studied from the microscopicview for prevention of earthquake disaster.A set of compression wave transducers and shear wave transducersmanufactured respectively from two different types of piezoelectricceramics were designed to be transmitters and receivers. The transmitters were mounted in the cap and the receivers in the base,while a soil sample sit between them. The receivers can receive asignal with an oscilloscope after the transmitters driven by a functiongenerator generates a wave and the wave propagates through the soilsample. Vs and Vp can be calculated for a soil sample during thetriaxial test at the different stress paths. The test results show that determination of arrival time will beinterfered with near field effect. A criterion of determination ofarrival time and the suitable working frequency are proposed to avoidmisjudging the arrival time. For measuring Vs on a sample of 15 cmheight, the arrival time keeps constant and high-voltage output onlyin a narrower frequency range of 4KHz-25KHz in the case of thetransmitter driven with a sine wave, while the arrival time still keepsconstant and high-voltage output in a wider frequency range of4kHz~50kHz in the case of the transmitter driven a square pulse. Therefore, a square pulse of 10 kHz is deliberately chosen as a drivenwaveform in the tests. For measuring Vp, a square pulse of 10 kHzis also chosen at the same consideration. The measured Vs for a remolded sample having the identical drydensity as in-situ compare considerable well with that measured withcross hole test. It is noted that Vp and Vs for a sample can becontinuously measured at different stress states during shearing. The new index of Vs/Vp is proposed to describe the change of fabric indirectly for sand subjected cyclic loading. The index of Vs/Vp is agood indicator of fabric.
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Da, Chiang Kun, and 江昆達. "The effects of throwing different weight baseball on pitching velocity and movement." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/00705023284577960432.
Full textAbstract:
碩士臺北巿立體育學院
運動科學研究所
96
The purpose of this research was to investigate the effects of throwing 50, 75, 100, 125, 150, 175, 200, 225, 250, 275 and 300 gram baseballs on pitching velocity, shoulder abduction, external rotation, flexion angle and elbow flexion angle. Five college pitchers (training 9.2±2.17 year) were analyzed by 3-D Motion Analysis system with ten cameras (200 Hz). The results indicated that (1) throwing less than 100 gram baseball increased pitching velocity, time to maximum shoulder external rotation angle and maximum shoulder flexion became early. (2) throwing 100 and 125 gram baseball increased pitching velocity about 6.15% and 4.04%, but the other kinematic and temporal had no significance. (3) throwing 175 gram baseball decreased pitching velocity about 0.56%, but the other kinematic and temporal had no significance. (4) throwing more than 175 gram baseball decreased pitching velocity and maximum shoulder external rotation angle and time to maximum shoulder external rotation angle became early. This research suggested that 100-175 gram was appropriate baseball weight for college pitchers.
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Chen, Jong-Ren, and 陳仲仁. "The Study of Variation on Baseballs'' COR Curves in Different Velocity Impact." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/73388296837978340076.
Full textAbstract:
碩士國立體育學院
教練研究所
89
Although baseball is a very popular source of recreational activity throughout the world, safety of baseball exercise is still a concern. Results of previous studies showed that the properties of baseball were highly correlated with safety of baseball. The objective of this study was to investigate baseball’s coefficient of restitution (COR) in different impacting velocities. Another purpose was to find the relation between peak force, impulse of impact, and COR while baseball hitting the wall. In this study, the subjects were 20 trademarks baseballs, 16 trademarks were traditional baseballs and 4 trademarks were modified baseballs. Fourteen testing velocities were used in the experiment. JVC high speed video camera was used to film the ball’s impact process. In order to measure the peak force and impulse while impacting, force plant was fixed on the wall to be hit by the baseballs. The results showed that the peak force and impulse of impact were positively significantly correlated with the impact velocity, but COR was negatively significantly correlated with the impact velocity. In testing velocities 62∼80 mph, the curve of peak force, impulse, and COR curves of traditional baseballs were nonlinear and unstable. COR curves of traditional baseball were increasing in this interval, differing from decreasing in another intervals. In addition, the traditional baseballs’ COR didn’t correlate with the peak force and impulse of impact in all testing velocities. Most of the modified baseballs’ COR significantly correlated with the peak force and impulse of impact in testing velocities 71∼89 mph. Based on the results of this study, in different impact velocities, traditional baseballs’ COR curves were nonlinear and unstable. To make conjectures, this result was caused of change on the rebound model while ball impacting in high speed. Because of low correlation between impulse of impact and COR, it was difficult to find an effective method to project traditional baseballs’ COR. Modified baseball had a more simple structure, therefore each curve of parameter was relatively stable.
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Chuang, Yu-Jen, and 莊昱仁. "Measurements of flow velocity by Using UAV-LSPIV in different flow conditions." Thesis, 2019. http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107NCHU5080046%22.&searchmode=basic.
Full textAbstract:
碩士國立中興大學
水土保持學系所
107
Previously, LSPIV analysis was affected by poor mobility of the vehicle, which made it limited in image capture. In recent years, with the advancement of technology, the development of unmanned aerial vehicles (UAV) as a photographic equipment for field survey has been developed. UAV has the characteristics of small volume and high mobility, which can penetrate deep into the areas or river sections that are difficult to arrive. Therefore, UAV are be chosen as the photographic vehicle for LSPIV flow velocity analysis in this study. In LSPIV analysis, imagery of tracking particle is an important factor affecting the accuracy of its analysis. Due to the changes of UAV’s flight height or shooting angle, the resolution and deformation of particles in the image will be different. Therefore, this study simulates the change of different shooting conditions through UAV, analyzes the flow rate with LSPIV under different flow conditions, and compares it with the ADCP measurement results. In addition, this study introduces the concept of outliers in calculations to determine the appropriate IA size for different flow conditions and to improve the defect of previous judgments on IA size. In the comparison of LSPIV flow velocity analysis, the difference between the using artificial particles or not is 30%, which is the biggest difference among all the shooting factors. The increase in shooting height and angle will result in a decrease in image resolution and an increase in the amount of deformation, resulting in an increase of 2% to 10% in the analysis result compared with the measured value. Through the interpretation of IA and the comparison between various factors, it is hoped that the analysis efficiency of relevant LSPIV outdoor experiments will be improved.
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Chang, Yu Chin, and 張予親. "The acute response of pulse wave velocity following different models of aerobic exercise." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/09695963228249821613.
Full textAbstract:
碩士國立中正大學
運動與休閒教育研究所
101
Purpose: The purpose of the study is to compare the region pulse wave velocity (PWV) after aerobic exercises using treadmills, elliptical machines and Core X. Method: The participants, including 30 college students (age 19.87 ± 1.68 yrs, height 167.45 ± 7.20 cm, weight 63.16 ± 11.60 kg), received incremental maximal exercise to exhaustion to obtain the heart rate maximal. According to the balance way of order, the participants accepted three kinds of aerobic exercise (70% HRR HRC with treadmill, 70% HRR HRC fixed frequency 50rpm with elliptical machine and 40rpm fixed frequency with Core X) respectively for 30 minutes. After 30 minutes of rest after exercise, Ultrasonic Doppler Flow Detector was used to measure pulse wave velocity. Data was progressed by One-way ANOVA to compare the difference among the effects of 3 aerobic exercise on the carotid-femoral (cf), brachial-ankle (ba) and femoral-ankle (fa) PWV. The significant level was set at α=.05. Result: There were no significant differences on pulse wave velocity of resting and after aerobic exercise from cfPWV, baPWV and faPWV cfPWV after elliptical machines and Core X aerobic exercise were significant different (p<.05). Both baPWV and faPWV after aerobic exercise of treadmills, elliptical machines and Core X had no significant difference. Conclusion: Central arterial compliance was indices with elliptical aerobic training. The effect of arterial compliance with Core X and treadmill aerobic exercise that no difference.