Seismic imaging is a technique that uses seismic echoes to map and detect underground geological structures. The conventional seismic image has the resolution limit of λ/2, where λ is the wavelength associated with the seismic waves propagating in the subsurface. To exceed this resolution limit, this thesis develops a new imaging method using resonant multiples, which produces superresolution images with twice or even more the spatial resolution compared to the conventional primary reflection image. A resonant multiple is defined as a seismic reflection that revisits the same subsurface location along coincident reflection raypath. This reverberated raypath is the reason for superresolution imaging because it increases the differences in reflection times associated with subtle changes in the spatial location of the reflector. For the practical implementation of superresolution imaging, I develop a post-stack migration technique that first enhances the signal-to-noise ratios (SNRs) of resonant multiples by a moveout-correction stacking method, and then migrates the post-stacked resonant multiples with the associated Kirchhoff or wave-equation migration formula. I show with synthetic and field data examples that the first-order resonant multiple image has about twice the spatial resolution compared to the primary reflection image. Besides resolution, the correct estimate of the subsurface velocity is crucial for determining the correct depth of reflectors. Towards this goal, wave-equation migration velocity analysis (WEMVA) is an image-domain method which inverts for the velocity model that maximizes the similarity of common image gathers (CIGs). Conventional WEMVA based on subsurface-offset, angle domain or time-lag CIGs requires significant computational and memory resources because it computes higher dimensional migration images in the extended image domain. To mitigate this problem, I present a new WEMVA method using plane-wave CIGs. Plane-wave CIGs reduce the computational cost and memory storage because they are directly calculated from prestack plane-wave migration, and the number of plane waves is often much smaller than the number of shots. In the case of an inaccurate migration velocity, the moveout of plane-wave CIGs is automatically picked by a semblance analysis method, which is then linked to the migration velocity update by a connective function. Numerical tests on synthetic and field datasets validate the efficiency and effectiveness of this method.

Diploma thesis is about application of ultrasonic pulse velocity method to determinate the strengths of cements, if there is a relevant calibration relation.

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Previous research efforts have shown that fish and macroinvertebrates are responsive to fine sediment in streambeds. Excess fine sediment (<2mm in diameter) impairs over 40,000 miles of streams in the U.S., degrading habitat quality for many aquatic species. Embeddedness (emb, %), a measure of fine sediment in gravel bed streams, is negatively correlated with bankfull shear velocity (u*, m/s). This relationship can be modeled by emb = au*b, with baseline coefficient values of a = 10 and b = –1. The purpose of this thesis was to investigate the applicability of this relationship across the U.S., to begin to quantify the variation of embeddedness in time, and to determine the applicability of embeddedness as a habitat metric for lotic biota. The areas that were studied included Stroubles Creek at the Virginia Tech Stream Lab, the Upper Roanoke River Basin in southwest Virginia, and Level II and III ecoregions nationwide with the U.S. EPA National Rivers and Streams Assessment dataset. Nationally, measurements of embeddedness were higher than modeled in areas with higher sediment supply, and lower than modeled in regions with low fine sediment supply. By calculating shear velocity through remotely sensed channel geometry metrics, embeddedness may be predicted throughout a stream network. Various biotic metrics were found to be correlated to embeddedness, with regional variation. Burrowing macroinvertebrate taxa, which may use increased sand to escape predation, increased with increasing embeddedness while the number of Ephemeroptera, Plecoptera, Trichoptera (EPT) taxa, the number of lithophilic spawning fish, and the number of salmonid taxa decreased with increasing embeddedness. Highly embedded substrate is generally considered poor habitat, which was supported by a trend of decreasing intolerant fish taxa with increasing embeddedness. Richness (total number of taxa) did not show a significant correlation, indicating that embeddedness, and fine sediment in general, is not necessarily an impairment to all stream habitat, but is impactful for particular taxa. / Master of Science / Previous research has shown that fish and macroinvertebrates are responsive to fine sediment in streambeds. Excess fine sediment (sand, silt, and clay) impairs over 40,000 miles of streams in the U.S., degrading habitat quality for many aquatic species. Embeddedness (emb, %), a measure of fine sediment in gravel bed streams, decreases with increasing bankfull shear velocity (u*, m/s), a measure of a stream's ability to move a particular size of sediment. The purpose of this thesis was to investigate the relationship between embeddedness and shear velocity in varying areas, to begin to quantify the variation of embeddedness in time, and to determine the applicability of embeddedness as a habitat metric for stream biota. The areas that were studied included Stroubles Creek at the Virginia Tech Stream Lab, the Upper Roanoke River Basin in southwest Virginia, and Level II and III ecoregions nationwide with the U.S. EPA National Rivers and Streams Assessment dataset. Nationally, measurements of embeddedness were higher in areas that may have higher sediment supply, and lower in regions with low fine sediment supply. By calculating shear velocity with remotely available stream data, embeddedness may be predicted throughout a stream network and compared with biota in those locations. Various biotic metrics were found to be correlated to embeddedness, with regional variation. Burrowing macroinvertebrate taxa, which may use increased sand to escape predation, increased with increasing embeddedness while the number of Ephemeroptera, Plecoptera, Trichoptera (EPT) taxa, the number of lithophilic spawning fish, and the number of salmonid taxa decreased. Highly embedded substrate is generally considered poor habitat, which was supported by a trend of decreasing intolerant fish taxa with increasing embeddedness.

The purpose of this study was to evaluate the effects of same-day strength training on velocity and accuracy of a tennis serve among five female Division I intercollegiate athletes at the second and sixth week of a strength training program. Velocity and accuracy of 20 tennis serves were measured approximately four hours after a morning split-body (lower legs and trunk) strength training session termed the lift-day (LD) and were compared to measures taken on days that no lifting took place, termed the non-lift day (NLD). For each test day, velocity was multiplied by accuracy to provide an overall serve performance score for each NLD and LD. An ANOVA revealed that there was no significant difference in any of the measured variables between the NLD and the LD at any time period throughout the study. A mean serve performance score difference between NLD (77.56) and LD (78.05) of 0.49 was not statistically different [p = 0.84]. The results of this study suggest that female collegiate tennis players may strength-train with no significant effect on same-day serve performance following adequate recovery.

Observational data are analyzed and decomposed to reveal internal ocean waves and their interactions with one another. Particularly, the interaction of small-scale internal waves with a large inertia wave packet is examined. Using the governing internal wave equations, an analysis is made of the energy propagation of a small scale internal wave with a large-scale inertia wave. With that, an assessment is made of the frequency of occurrence of various encounter types. Next, the possibility of energy transfer during an interaction is explored. The relative energy of the small wave before interacting with the large-scale inertia wave is calculated and compared to the relative energy during and after the interaction. Performing this analysis on multiple wave-wave interactions seen within the observational data set provides a look into the behavior of these wave types. Additionally, the dissipation within each of the corresponding time-space regions is calculated, giving an alternative explanation other than energy transfer among waves for the disparity in energy. Dissipation estimates and energy results are extrapolated to create a general energy transfer and dissipation estimate in the ocean resultant from these interaction types. A two dimensional non-linear method presents a comparison between the observational data findings and the expected computed result. From there, conclusions are drawn synthesizing the results from the observational and numerical analyses. It was concluded that for observational small waves propagating in the same direction as the background shear, a loss was seen in the wave's energy. For interactions wherein the small wave propagated in the opposite direction, the observational small wave energy increased through the interaction. Within the numerical findings, the small wave energy in same direction interactions was partially lost while the small wave energy in opposite direction interactions was both lost and gained depending on the encounter type which encounter types could be confirmed in observations. The dissipation analysis showed the greatest dissipation during the interaction between a small wave and background shear so the gains seen occurred when the types of encounters expecting a gain were present.

Quantum coherence and interference (QCI) is a phenomenon that takes place in all multi-level atomic systems interacting with multiple lasers. In this work QCI is used to create several interesting effects like lasing without inversion (LWI), controlling group velocity of light to extreme values, controlling the direction of propagation through non-linear phase matching condition and for controlling the correlations in field fluctuations. Controlling group velocity of light is very interesting because of many novel applications it can offer. One of the unsolved problems in this area is to achieve a slow and fast light which can be tuned continuously as a function of frequency. We describe a method for creation of tunable slow and fast light by controlling intensity of incident laser fields using QCI effects. Lasers are not new to the modern world but an extreme ultra-violet laser or a x-ray laser is definitely one of the most desirable technologies today. Using QCI, we describe a method to realize lasing at high frequencies by creating lasing without inversion. Role of QCI in creating correlations and anti-correlations, which are generated by vacuum fluctuations, in a three level lambda system coupled to two strong fields is discussed.

This research presents a novel capacitive-sensing-based method to measure fluid velocity for microfluidics devices. To illustrate the importance of fluid velocity measurement, a case study was first conducted for a split and recombine micromixer. The study underscored the influence of fluid velocity on micromixer efficiency and mixing quality. The proposed fluid velocity measurement method employs two capacitance sensing electrodes placed along the fluid channel, capable of detecting small capacitance changes as fluid passing through the sensing area. The relation between capacitance changes and fluid velocity in the proposed sensing structures was developed and hence used to estimate fluid velocity. The proposed technique does not require extensive bench equipment and is suitable for point-of-care applications. To validate our approach, we implemented a two-step 3D printing process, creating a Polylactic acid (PLA) micro platform with embedded graphene–PLA composite electrodes. The accuracy of the developed method was investigated by cross-verifying the obtained velocities with an optical measurement method. Most absolute percentage discrepancies between the results from the proposed method and the optical method are under 12%, validating the precision of the proposed method. Future research will focus on integrating this velocity measurement method into microfluidic devices produced using advanced microfabrication technologies.

Engineering design is a decision-making process. Optimization techniques can be used to insure that better decisions are made. One design of great interest to engineers is that of high-velocity channels used for routing floodwater out of urban areas. In the design of these channels it is very important to avoid such hydraulic phenomena as standing waves, hydraulic jumps, and shocks. These will require higher wall heights and more expense. These channels can be modeled with physical models, but they are expensive and time consuming. To minimize the cost of building and changing the physical models and the time required to perform the study, an automated numerical model can be used to test a range of designs before construction of the physical model. The resulting design can be used as an initial design, which is close to the desired design requiring fewer changes to the physical model, saving time and money.