Dissertations / Theses on the topic 'Wake recover'
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1
Sadler, Heidi D. "Disaster's wake role of architecture in trauma recovery /." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1082909131.
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SADLER, HEIDI D. "DISASTER'S WAKE: THE ROLE OF ARCHITECTURE IN TRAUMA RECOVERY." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1082909131.
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Du, Chenguang. "How Well Can Two-Wave Models Recover the Three-Wave Second Order Latent Model Parameters?" Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103856.
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Although previous studies on structural equation modeling (SEM) have indicated that the
second-order latent growth model (SOLGM) is a more appropriate approach to
longitudinal intervention effects, its application still requires researchers to collect at least
three-wave data (e.g. randomized pretest, posttest, and follow-up design). However, in
some circumstances, researchers can only collect two-wave data for resource limitations.
With only two-wave data, the SOLGM can not be identified and researchers often choose
alternative SEM models to fit two-wave data. Recent studies show that the two-wave
longitudinal common factor model (2W-LCFM) and latent change score model
(2W-LCSM) can perform well for comparing latent change between groups. However, there
still lacks empirical evidence about how accurately these two-wave models can estimate the
group effects of latent change obtained by three-wave SOLGM (3W-SOLGM). The main
purpose of this dissertation, therefore, is trying to examine to what extent the fixed effects
of the tree-wave SOLGM can be recovered from the parameter estimates of the two-wave
LCFM and LCSM given different simulation conditions.
Fundamentally, the supplementary study (study 2) using three-wave LCFM was
established to help justify the logistics of different model comparisons in our main study
(study 1). The data generating model in both studies is 3W-SOLGM and there are in total
5 simulation factors (sample size, group differences in intercept and slope, the covariance
between the slope and intercept, size of time-specific residual, change the pattern of
time-specific residual). Three main types of evaluation indices were used to assess the
quality of estimation (bias/relative bias, standard error, and power/type I error rate). The
results in the supplementary study show that the performance of 3W-LCFM and
3W-LCSM are equivalent, which further justifies the different models' comparison in the
main study. The point estimates for the fixed effect parameters obtained from the two-wave
models are unbiased or identical to the ones from the three-wave model. However, using
two-wave models could reduce the estimation precision and statistical power when the
time-specific residual variance is large and changing pattern is heteroscedastic
(non-constant). Finally, two real datasets were used to illustrate the simulation resultsDoctor of Philosophy
To collect and analyze the longitudinal data is a very important approach to understand the phenomenon of development in the real world. Ideally, researchers who are interested in using a longitudinal framework would prefer collecting data at more than two points in time because it can provide a deeper understanding of the developmental processes. However, in real scenarios, data may only be collected at two-time points. With only two-wave data, the second-order latent growth model (SOLGM) could not be used. The current dissertation compared the performance of two-wave models (longitudinal common factor model and latent change score model) with the three-wave SOLGM in order to better understand how the estimation quality of two-wave models could be comparable to the tree-wave model. The results show that on average, the estimation from two-wave models is identical to the ones from the three-wave model. So in real data analysis with only one sample, the point estimate by two-wave models should be very closed to that of the three-wave model. But this estimation may not be as accurate as it is obtained by the three-wave model when the latent variable has large variability in the first or last time point. This latent variable is more likely to exist as a statelike construct in the real world. Therefore, the current study could provide a reference framework for substantial researchers who could only have access to two-wave data but are still interested in estimating the growth effect that supposed to obtain by three-wave SOLGM.
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Zhang, Liang. "Energy recovery system for a gyrotron backward wave oscillator." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18933.
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This thesis is based on the research project of a W-band gyrotron backward wave oscillator (gyro-BWO) using a helically corrugated waveguide which is currently being built and upgraded in the University of Strathclyde. The gyro-BWO was optimally designed through numerical simulations to achieve an output maximum power of ~ 10 kW with a -3 dB frequency tuning range of 84 - 104 GHz. To increase the overall efficiency of the W-band gyro-BWO, an energy recovery system of four-stage depressed collector was designed, numerically optimized and fabricated on the gyro-BWO. Microwave components including the Bragg reflectors, the side-wall coupler, the three-layer microwave window and the pillbox window were designed, simulated and measured to facilitate the practical use of the energy recovery system. This thesis includes the analytically calculated results, the numerical simulations as well as the experimental results of the said components and system. A 14-section Bragg reflector together with the side-wall coupler located at the upstream of the helically corrugated interaction cavity was used to couple the microwave radiation out. This allowed the installation of the depressed collector at the downstream side of the gyro-BWO. The transmission coefficient of the coupler was numerically optimized to achieve -1.0 dB over the frequency tuning range, from 84 - 104 GHz. The Bragg reflector measurement agrees well with the simulation. The input coupler achieves an average -13 dB reflection over the frequency in the measurement. Theoretical analysis of the pillbox type window and multi-layer window based on mode-matching method was carried out. The simulation and optimization of the pillbox window achieved a reflection of less than -15 dB in the whole operating frequency range of 84 - 104 GHz. The three-layer window can achieve less than 30 dB reflection in the frequency range of 84 - 104 GHz in the simulation. A three-layer window and a pillbox window which particularly optimized in frequency range of 90 - 100 GHz (the operating frequency range of the gyro- TW A that shares the same experimental setup as the gyro-BWO) were fabricated. With manufacturing constraints the design of the three-layer window achieved an average -10 dB measured reflection in 84 - 104 GHz and better than -15 dB in 90 - 100 GHz. In the downstream side of the gyro-BWO, another 18-section Bragg reflector was used to reflect the radiation back into the upstream interaction cavity. And the transmission coefficient of -30 dB was obtained in the microwave measurements using a VNA, which means the microwave power leakage was less than 1%. The measurement results agreed well with the simulations. A four-stage depressed collector was designed to recover the energy from the spent electrons. The 3D PlC code MAGIC and a genetic algorithm were used to simulate and optimize the geometry of the electrodes. Secondary electron emissions were simulated and a few emission models were compared to investigate their effects on the overall recovery efficiency and the backstreaming rate for the multistage collector. The optimization of the shape and dimensions of each stage of the collector using a genetic algorithm achieved an overall recovery efficiency of about 70%, with a minimized backstreaming rate of 4.9%. The heat distribution on the collector was calculated and the maximum heat density on the electrodes was 240W/cm2 and the generation of "hot spots" could be avoided. The electric field distribution inside the depressed collector was calculated and the geometries of these electrodes were properly shaped to avoid the voltage breakdown in vacuum.
5
Jones, Garrett Collier. "Skeletal Muscle Recovery and Vibration." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8285.
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In the past decade there has been a significant increase in focus on the effect upper body vibration (UBV) has on the recovery of skeletal muscle after exercise-induced muscle damage. Recovery can be defined and investigated using a wide variety of methods. This study used three different measurements to track muscle recovery over 7 days following an exercise muscle damage protocol and applied vibration to a mathematical model. A visual analog scale (VAS) was used to measure muscle pain, a strain gauge was used to obtain maximum voluntary isometric contraction (MVIC) strength measurements, and shear wave elastography (SWE) represented muscle stiffness over the 7-day experiment. Thirty-three participants were divided into three groups. The first was a control group (C) that experienced no exercise and no therapy. The no vibration group (NV) performed the damage an exercise protocol but received no therapy. The vibration group (V) performed the same exercise protocol but also received vibration therapy. The exercise protocol consisted of 100 dumbbell curls at starting at 50% of their MVIC with one minute of rest after each set of ten. The data provided convincing evidence (27.2%, p < 0.0001) that group NV was not back to its normal stiffness after 7 days unlike group V, which was shown not to be any different from its baseline at the end of the week (9.15%, p = 0.137). Three vibration factors (����1, ����2, ����3) were added to a skeletal muscle regeneration model (SK) to simulate how vibration affects muscle regeneration. The three factors were determined by analyzing previous research to understand how vibration affects cells in the regeneration process. Adding these into SK decreased the time to recovery from about 13 days to about 7 days. Recovery was defined by reaching 10% of the original number of myofibers within the damaged muscle.
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Elliott, Brian B. "Flexural wave propagation in anisotropic laminates and inversion algorithms to recover elastic constants." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23679.
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Mcclay, Borawski Beverly Lynn. "The Construction of Adversarial Growth in the Wake of a Hurricane." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3241.
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This study employed a qualitative approach to explore the factors that contribute to positive change and growth following a natural disaster. The qualitative methodology included narrative interviews and family group interviews that were conducted with six families in Florida that had experienced two or three hurricanes within six weeks in 2004. Narrative analysis and thematic analysis were used to discover what factors contributed to participants experiencing positive growth.
Participants described the experience of surviving and coping with the hurricane. Participants reported that preparation before a hurricane was a three-part process that involved physical, mental, and emotional preparation. Four actions were referred to as helpful to stay positive during a hurricane: (a) drawing on family, friends, and neighbors for continual emotional support; (b) keeping occupied with a fun activity; (c) leaning on religious faith; (d) and listening to up-to-date information. Families described nine sources of support that enabled them to cope after the hurricane: (a) the government, (b) charitable organizations, (c) homeowner's insurance, (d) family, (e) friends, (f) religious faith, (g) stories, (h) life perspective, and (i) music.
Participants reported eight factors that encouraged adversarial growth. Communicating emotional support within relationships was the most commonly cited factor in recovery and growth after a hurricane, followed by worldview, appreciation, religious faith, patience, self-reliance, teamwork, and creativity.
A holistic approach to disaster planning that includes consideration of those elements that contribute to positive growth for the survivor is recommended. Further research is needed to understand how to facilitate adversarial growth among disaster survivors through emotional support and interpersonal networks.
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Herrmann, Felix J., Peyman P. Moghaddam, and Christiaan C. Stolk. "Just diagonalize: a curvelet-based approach to seismic amplitude recovery." European Association of Geoscientists & Engineers, 2007. http://hdl.handle.net/2429/523.
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Samarawickrama, Mahendra. "Acceleration Techniques for Sparse Recovery Based Plane-wave Decomposition of a Sound Field." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17302.
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Plane-wave decomposition by sparse recovery is a reliable and accurate technique for plane-wave decomposition which can be used for source localization, beamforming, etc. In this work, we introduce techniques to accelerate the plane-wave decomposition by sparse recovery. The method consists of two main algorithms which are spherical Fourier transformation (SFT) and sparse recovery. Comparing the two algorithms, the sparse recovery is the most computationally intensive. We implement the SFT on an FPGA and the sparse recovery on a multithreaded computing platform. Then the multithreaded computing platform could be fully utilized for the sparse recovery. On the other hand, implementing the SFT on an FPGA helps to flexibly integrate the microphones and improve the portability of the microphone array. For implementing the SFT on an FPGA, we develop a scalable FPGA design model that enables the quick design of the SFT architecture on FPGAs. The model considers the number of microphones, the number of SFT channels and the cost of the FPGA and provides the design of a resource optimized and cost-effective FPGA architecture as the output. Then we investigate the performance of the sparse recovery algorithm executed on various multithreaded computing platforms (i.e., chip-multiprocessor, multiprocessor, GPU, manycore). Finally, we investigate the influence of modifying the dictionary size on the computational performance and the accuracy of the sparse recovery algorithms. We introduce novel sparse-recovery techniques which use non-uniform dictionaries to improve the performance of the sparse recovery on a parallel architecture.
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D'Addato, Matteo. "Progetto di un PLL analogico a bassissimo consumo per sistemi wake-up radio." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17477/.
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Nei nodi wireless per applicazioni IoT, i ricetrasmettitori (transceiver) a radio-frequenza (RF) sono responsabili della maggior parte del consumo di potenza. Inoltre, se da un lato il picco di potenza assorbita avviene in corrispondenza degli istanti di trasmissione, dall’altro il ricevitore, che deve essere mantenuto sempre attivo anche quando il resto del sistema è in stato di “idle”, consuma una buona frazione dell’energia totale. Al fine di ridurre questo consumo, una particolare tipologia di ricevitori detti di “wake-up” sono tra i principali oggetti di ricerca nell’ambito dell’IoT. Essi hanno prestazioni ridotte e consumo molto basso, poiché devono restare sempre attivi mentre il resto del nodo è in stato di “idle”. Tale Wake-Up Radio (WUR) ha il compito di “ascoltare” il canale e attivare il ricevitore principale ed il microcontrollore solo quando c’è qualche richiesta in arrivo. Una parte integrante del ricevitore Wake-Up è il circuito per la decodifica dei byte trasmessi, che di solito comprendono almeno un codice d’indirizzo, che deve essere estratto e confrontato con l’indirizzo memorizzato nel ricevitore. Soltanto se questo confronto ha esito positivo viene attivato il resto del sistema.
L’obiettivo di questo lavoro di tesi è il progetto di un sistema di clock recovery basato su PLL analogico a bassissimo consumo per sistemi Wake-Up Radio di tipo short-range caratterizzati da una bit rate di 1 kbps. Tale sistema deve fornire alla rete di controllo un clock allineato in fase e frequenza con i dati ricevuti. Rispetto ad altri sistemi in cui si deve semplicemente decodificare un indirizzo, la soluzione basata su PLL oggetto di questo studio (poiché implica consumi e tempi di aggancio non trascurabili) è particolarmente adatta per lunghe trasmissioni. Nel progetto di un PLL a basso consumo l’obiettivo consiste nell’ottimizzare il trade-off tra consumo (con correnti nell’ordine del nanowatt) e tempo di aggancio.
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Morris, Ceri. "Influence of solidity on the performance, swirl characteristics, wake recovery and blade deflection of a horizontal axis tidal turbine." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/60952/.
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The main focus of this thesis was to investigate the influence of solidity on the performance, swirl characteristics, wake length and blade deflection of a Horizontal Axis Tidal Turbine (HATT) using the simulation software package Ansys. An existing laboratory scale prototype HATT was modified to improve upon previously gathered experimental data and provide further confidence of the validity of the numerical models. The solidity was varied by altering the number of blades in the numerical models. The work presented in this thesis shows that, for this blade profile, increasing the solidity increases the peak Cθ and peak Cp and reduces the λ at which these occur. Ct was found to be approximately the same at peak Cp, which was assumed to be the normal operating condition. At λ above peak Cp, near freewheeling, Ct continued to increase for the 2 bladed turbine, remained approximately constant for the 3 bladed turbine and decreased for the 4 bladed turbine, due to the change in pitch angle required to maintain optimum power. This indicates that higher solidity rotors would have to withstand lower loads in the event of a failure. In addition, the thrust per blade was shown to increase with reducing number of blades. The swirl characteristics in the wake were found to agree with swirl theory and the swirl was found to increase with solidity whilst being weak or very weak in each case. Swirl number was found to be dependent on solidity only up to distances of 10 diameters downstream. At higher turbulent intensities, the wake recovery was only influenced by solidity up to 15 diameters downstream of the HATT but at low turbulence intensities the wake length increased with solidity indicating that low solidity rotors may offer higher overall array efficiencies in areas of low turbulent intensity. Blade deflection was shown to increase with a reduction in the number of blades, due to the increased thrust per blade. The power output of the 3 bladed turbine was shown to decrease by 0.4% with a deflection of 0.12 m. However, the power output of the 2 and 4 bladed turbines was found to increase with deflections as it was subsequently found that the pitch settings found in a previous study were not fully optimised for a rigid blade. At deflections above 0.20 m the power output of the 4 bladed turbine was found to decrease. It is expected that the power output of the 2 bladed turbine would eventually decrease with further deflections but no decrease was found for the maximum deflection considered, of 0.35m. This thesis therefore shows that the optimum number of blades may vary from site to site and even from one location within an array to another. It also shows that blade deflection will alter the power output and that blades could be designed so as to reach their optimum setting at a given blade deflection.
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Jasim, Mohammed. "Initial Beam Access Schemes for Millimeter Wave Cellular Networks." Thesis, University of South Florida, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10791507.
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Millimeter wave technologies present an appealing solution for increasing data throughputs as they provide abundant contiguous channel bandwidths as compared to conventional microwave networks. However, millimeter wave technologies suffer from severe propagation limitations and channel impairments such as atmospheric attenuation and absorption, path and penetration losses, and blockage sensitivity. Therefore, phased arrays and beamforming technologies are necessary to compensate for the degraded signal levels due to the aforementioned factors. Namely, base stations and mobile stations utilize directional transmission in the control- and data- plane for an enhanced channel capacity, which results in initial access challenges due to the absence of omni-directional transmission. Here the base station and mobile station are compelled to exhaustively search the entire spatial domain, i.e., in order to determine the best beamforming and combining vectors that yield the highest received signal level.
Overall, a wide range of studies have looked at the initial beam access challenges in millimeter wave networks, with most efforts focusing on iterative and exhaustive search procedures, as well as subarrays schemes and out-of-band beam access. However, these studies suffer from significant signaling overhead attributed to the prolonged beam scanning cycle. In particular, access times here are excessively high that exceed control plane latencies and coherence times. Furthermore, existing work suffer from high computational complexity, power consumption, energy inefficiency, as well as low directivities and high outage probabilities.
In light of the above, the contributions in this dissertation propose fast initial beam access schemes based upon novel meta-heuristic search schemes and beamforming architectures. These contributions include modified search procedures inspired by Nelder Mead, Luss-Jaakola, divide-and-conquer with Tabu search, generalized pattern search, and Hooke Jeeves methods.
Furthermore, efficient and highly-directive access schemes are also developed in this dissertation levering sidelobe emissions, grating lobes and Hamming codes. The overall performance of the proposed solutions here is extensively evaluated versus traditional access schemes and incorporating different channel and path loss models.
Finally, this dissertation addresses the problem of link sensitivity and blockage effects in millimeter wave networks, a subsequent stage to beam access and link association. Nevertheless, a novel link recovery procedure is proposed here that features instantaneous link-recovery and high signal levels.
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Parks, Jason C. "EFFECTS OF A PROPER COOL-DOWN AFTER SUPRAMAXIMAL INTERVAL EXERCISE ON PULSE WAVE REFLECTION, AORTIC STIFFNESS, AND AUTONOMIC MODULATION." Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent158448596372427.
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Yasui, Etsuko. "Community vulnerability and capacity in post-disaster recovery: the cases of Mano and Mikura neighbourhoods in the wake of the 1995 Kobe earthquake." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/213.
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This is a study of how two small neighbourhoods, Mano and Mikura, recovered from the 1995 Kobe (Japan) earthquake, with a particular focus on the relationship between community vulnerability and capacity. Few studies have examined these interactions, even though vulnerability reduction is recognized to be a vital component of community recovery. Drawing from literature on disaster recovery, community development, vulnerability analysis, community capacity building and the Kobe earthquake, a community vulnerability and capacity model is elaborated from Blaikie et al.’s Pressure and Release Model (1994) to analyze the interactions. The Mano and Mikura cases are analyzed by applying this model and relating outcomes to the community’s improved safety and quality of community lives. Based on the experience of Mano, appropriate long-term community development practices as well as community capacity building efforts in the past can contribute to the reduction of overall community vulnerability in the post-disaster period, while it is recovering. On the other hand, the Mikura case suggests that even though the community experiences high physical and social vulnerability in the pre-disaster period, if the community is able to foster certain conditions, including active CBOs, adequate availability and accessibility to resources, and a collaborative working relationship with governments, the community can make progress on recovery. Although both Mano and Mikura communities achieved vulnerability reduction as well as capacity building, the long-term sustainability of the two communities remains uncertain, as issues and challenges, such as residual and newly emerging physical vulnerability, negative or slow population growth and aging, remained to create vulnerability to future disasters. The case studies reveal the interactions of community vulnerability and capacity to be highly complex and contingent on many contextual considerations.
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Rocolle, Guillaume. "Simulation and Experimental Verification of the Flooding and Draining Process of the Tidal Energy Converter “Deltastream” during Deployment and Recovery." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9206.
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Deltastream is an on-going project carried by Tidal Energy Limited since almost
twenty years. It is a tidal energy converter with a triangular shape and one
turbine on each tower. It has gone through many evolutions of design but a first
prototype will be installed in the end of 2014 at Ramsey Sound.
The deployment and recovery operations will be carried out with a single lift
point through a heavy lift frame. Two issues have to be tackled during the
operation: the rate of flooding of the ballasts and the tension on the lift crane
cable. The most favourable sea state must be found in order to minimise the
crane cable tension as well as the best inlets and outlets configuration for the
ballasts system.
In order to tackle those issues, preliminary analytical work was conducted on
the demonstrator to assess the stability during the flooding process. A scaled
model was designed and built in order to be tested in a wave-towing tank.
The results from the tests highlight that the deployment and the recovery
operations are safe for both the barge and Deltastream for the range of wave
conditions tested in the tank. However, the sea state has an important impact
on the proceeding of the operations, especially the period of the waves.
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Smallwood, Cameron David. "Frequency Response and Recovery of Muscles and Effects of Wrapping the Lower Leg on Surface Velocity Measurements." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7503.
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This thesis is comprised of two studies. The objective of the first study was to find the frequency response and stiffness of the biceps brachii muscle group during recovery from exercise induced damage and to determine whether these data could be used to track muscle recovery by correlating changes in the frequency response with changes in muscle stiffness. Stiffness moduli were collected using Shear Wave Elastography (SWE) which were then applied to a proportional first mode frequency analysis. Data were collected for the muscle stiffness and frequency response for fifteen subjects (25.6 +- 4.5). By comparing the proportion of the square root of the SWE results, the variation in stiffness showed a less than 2 Hz change in first mode resonance for the control group. Frequency response results for the control group agreed with the modified SWE results and the proportion analysis. SWE results for the damage protocol group showed an average increase of 4 Hz. Frequency response results for the damage protocol group were sorted into three categories: three subjects had a change in frequency of peaks of at least 4 Hz in the positive direction; four subjects had an increase in amplitude, but no change in frequency of peaks; three subjects showed mixed responses like fewer resonance peaks, variable amplitudes, changes in peak bandwidth. This research allowed for the documentation of the in-vivo frequency response of the biceps brachii muscle. We believe that the frequency response of a muscle group may be used in the future to evaluate recovery from exercise induced damage. Lessons learned were also recorded for helping future studies in their efforts using an SLDV with human body testing.The second study focused on finding the effects on the surface velocity of tissue above and below a region of the lower leg wrapped in an elastic band when excited by an external source. Ten male subjects between the ages of 18-25 were seated in a chair with one foot placed on a vibrating platform. Two excitation frequencies were separately applied while three points along the leg were measured. A repeatability analysis, using results without the leg wrap, showed a 6.5%, 2.5%, and 10.5% variance in the x-, y-, and z-directions respectively, applying a 20 Hz frequency. With a 40 Hz frequency, the variations were 24%, 23.8%, and 28.4% respectively. A change in displacement of +38% and +10% occurred above the knee in the x-direction with 40 Hz and in the y-direction with 20 Hz, respectively. A change in displacement of -20% occurred below the knee in the x-direction with 20 Hz. A change in displacement of -24% occurred below the wrap location in the y-direction with 40Hz. With a confidence interval of 93%, surface velocity of the tissue located above the wrap increased, while the surface velocity of the tissue below the wrap decreased.
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Gardner, Robert Matthew. "Conditioning of FNET Data and Triangulation of Generator Trips in the Eastern Interconnected System." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34338.
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Using data from the frequency disturbance recorders (FDRs) that comprise the nation-wide frequency monitoring network known as FNET, disturbances in the eastern interconnected system (EI) have been monitored and recorded over the past several years. Analysis of this and other data by a wide variety of research scientists and engineers has rendered the idea that frequency disturbances from generator trips, transmission line trips, load trips, and other events, travel with finite speed as electromechanical waves throughout any power system (in this case the EI). Using FNET data as a tool, it is possible to measure and output the arrival times of these disturbance waves with a time resolution of 100 ms.
To observe with certainty the arrival time of the frequency disturbance waves, field data collected by the FDRs must first be conditioned in a robust manner. The current method that uses the moving mean of raw FDR data is analyzed and two computationally efficient robust methods are suggested in this report. These new methods that rely on robust statistics are more resistant to the effect of outliers contained within the raw FDR data. Furthermore, like the moving mean, these methods smooth the raw data without removing the general trend.
Having recorded and conditioned the FDR data, three conventional triangulation techniques taken from the field of seismology are proposed and analyzed. This study reconfirms the fact that the EI is not a medium of continuous elasticity though which the frequency perturbations travel but rather a discontinuous patchwork of varying elasticities. Within this report, nine generator trip events are analyzed and the aforementioned triangulation methods are applied. The advantages and disadvantages of each method are discussed. To conclude, axioms of future research are proposed and delineated.
Master of Science
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Herrmann, Felix J., Gilles Hennenfent, and Peyman P. Moghaddam. "Seismic imaging and processing with curvelets." European Association of Geoscientists & Engineers, 2007. http://hdl.handle.net/2429/552.
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In this paper, we present a nonlinear curvelet-based sparsity-promoting formulation for
three problems in seismic processing and imaging namely, seismic data regularization
from data with large percentages of traces missing; seismic amplitude recovery for subsalt
images obtained by reverse-time migration and primary-multiple separation, given
an inaccurate multiple prediction. We argue why these nonlinear formulations are beneficial.
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Brown, Vickie McConnell. "Perceptions of the Implementation of the Online Credit Recovery Dropout Prevention and Alternative Education Program Odyssey Ware In Lee County Virginia Public Schools." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etd/1318.
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Schools in the United States have struggled with graduation rates for nearly 140 years. School divisions are continuously searching for new and creative curriculums to address changing student needs. From the U.S. Department of Education to local school board members, educators are working to discover creative and accountable alternatives to address these issues.
Development of online programs continues to offer students some of the curriculum resources they need for success and provides an alternative way to approach instruction for school systems. Educators in Lee County are researching new policies and programs to assist students in obtaining their high school diplomas. Understanding perceptions of the administrative staff plays a key role in program development and implementation of programs for students. This qualitative case study addresses the particular issue of perception in relation to the implementation of a new form of instruction. By understanding staff perceptions education leaders can develop plans and procedures to address issues related to staff development and program implementation. The following set of policies and procedures were necessary for the online program: Each individual school needed the opportunity to use the program as they deemed necessary for student needs.The online program would be used as a secondary curriculum to assist students in the areas of dropout prevention, alternative education and credit recovery.Administrators provide consistency of the implementation to all students in the county.
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Shabara, Yahia. "Establishing Large-Scale MIMO Communication: Coding for Channel Estimation." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618578732285999.
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Park, DongGook. "Cryptographic protocols for third generation mobile communication systems." Thesis, Queensland University of Technology, 2001.
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Nowicki, Robert J. "Effects of Catastrophic Seagrass Loss and Predation Risk on the Ecological Structure and Resilience of a Model Seagrass Ecosystem." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2994.
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As climate change continues, climactic extremes are predicted to become more frequent and intense, in some cases resulting in dramatic changes to ecosystems. The effects of climate change on ecosystems will be mediated, in part, by biotic interactions in those ecosystems. However, there is still considerable uncertainty about where and how such biotic interactions will be important in the context of ecosystem disturbance and climactic extremes.
Here, I review the role of consumers in seagrass ecosystems and investigate the ecological impacts of an extreme climactic event (marine heat wave) and subsequent widespread seagrass die-off in Shark Bay, Western Australia. Specifically, I compare seagrass cover, shark catch rates, and encounter rates of air breathing fauna in multiple habitat types before and after the seagrass die-off to describe post-disturbance dynamics of the seagrass community, shifts in consumer abundances, and changes in risk-sensitive habitat use patterns by a variety of mesoconsumers at risk of predation from tiger sharks (Galeocerdo cuvier). Finally, I conducted a 16 month field experiment to assess whether xi loss of top predators, and predicted shifts in dugong foraging, could destabilize remaining seagrass.
I found that the previously dominant temperate seagrass Amphibolis antarctica is stable, but not increasing. Conversely, an early-successional tropical seagrass, Halodule uninervis, is expanding. Following the die-off, the densities of several consumer species (cormorants, green turtles, sea snakes, and dugongs) declined, while others (Indo-Pacific bottlenose dolphins, loggerhead sea turtles, tiger sharks) remained stable. Stable tiger shark abundances following the seagrass die-off suggest that the seascape of fear remains intact in this system. However, several consumers (dolphins, cormorants) began to use dangerous but profitable seagrass banks more often following seagrass decline, suggesting a relaxation of anti-predator behavior. Experimental results suggest that a loss of tiger sharks would result in a behaviorally mediated trophic cascade (BMTC) in degraded seagrass beds, further destabilizing them and potentially resulting in a phase shift. My work shows that climactic extremes can have strong but variable impacts on ecosystems mediated in part by species identity, and that maintenance of top predator populations may by important to ecological resilience in the face of climate change.
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Mansutti, Giulia. "Analysis and design of innovative antenna systems for telecommunications and health applications." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421863.
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In this thesis the study of different innovative antenna systems is presented. The antenna designs that have been analyzed and that are described in this thesis can be divided in three main groups based on their application: phased-array antennas working on surfaces that change shape in time, millimeter-wave antennas for skin cancer diagnosis, and gaseous plasma antennas for satellite communications.
As far as the first topic is concerned, the research activity presented in this thesis focuses on the study of the strengths and limitations of a specific pattern recovery technique: the projection method. This technique has been adopted to retrieve the radiation properties of linear and planar arrays placed on surfaces whose shape changes in time according to different geometrical deformation; moreover, its effectiveness was assessed for both broadside and beam steering arrays, leading to a novel and simpler formulation of this pattern recovery technique for arrays whose beam is tilted towards different directions. The results have been obtained both through full-wave numerical simulations in CST Microwave Studio and through measurements performed in collaboration with the North Dakota State University (NDSU), Fargo, North Dakota, USA.
Regarding skin cancer diagnosis, a novel substrate integrated waveguide probe for early-stage skin cancer detection has been designed as well: this probe is cheap and easy to fabricate and can achieve high accuracy in detecting small early-stage skin cancer, thus providing a tool with the potential of being adopted as a real aid for skin cancer diagnosis. The probe has been tested both through full-wave numerical simulations and through measurements on a skin phantom realized at The University of Queensland with the support of the Microwave Team.
The study about gaseous plasma antennas for satellite communications has been mainly numerical. Different designs have been conceived with the aim of exploiting the advantages of using plasma elements while at the same time avoiding the limitations related to this novel technology. A practical implementation of these designs is now the subject of a collaboration with CISAS B. Colombo, an aerospace research center of the University of Padova.
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Ercolanelli, Julien. "Étude numérique et expérimentale d'un système couplé stabilisateur et récupérateur d'énergie des vagues Experimental and numerical investigation of sloshing in anti-roll tank using effective gravity angle Experimental and numerical assessment of the performance of a new type passive anti-roll stabilisation system." Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2019. http://www.theses.fr/2019ENTA0008.
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Le développement de Geps Techno est basé sur un concept innovant de structure flottante destinée à produire de l'énergie électrique à partir de plusieurs sources d'énergies marines renouvelables dont la source houlomotrice. Le système houlomoteur développé par Geps Techno repose sur la mise en circulation d'eau et la création d'un tourbillon en son sein. En profitant du phénomène de carène liquide, le concept est également déclinable en un système de stabilisation de navire ou de toute autre plateforme flottante. L'objectif à court terme de la société est le développement de cette technologie permettant la stabilisation et la récupération de l'énergie des vagues et pour lequel il reste des verrous technologiques à lever afin d'arriver à la viabilité et la rentabilité du système. Pour cela, Geps Techno a lancé en octobre 2015 le projet IHES (Integrated Harvesting Energy System) qui consiste à construire un démonstrateur de son concept de plateforme houlomotrice. Le projet IHES est un des projets de la feuille de route du plan "Navires écologiques" de la Nouvelle France Industrielle. Il est soutenu par Bpifrance dans le cadre du programme d'Investissements d'Avenir - Projets Industriels d'Avenir. Afin de maîtriser les objectifs de stabilisation et de récupération d'énergie, Geps Techno étudie les volets technologiques nécessaires permettant de passer de l'énergie disponible au niveau des vagues jusqu'à celle disponible au niveau de la turbine du houlomoteur. Les travaux de thèse soutenus par Fourestier en mai 2017 portaient sur un premier volet "Définition et contrôle des écoulements internes au système houlomoteur". A l'aide d'une modélisation des fluides numériques, ces derniers ont abouti à des modèles opérationnels caractérisant les écoulements internes. La présente thèse Cifre s'inscrit dans la continuité des travaux de Fourestier et traite d'un second volet "Modélisation du système couplé plateforme / houlomoteur". L'ensemble de ces travaux devra aboutir à un code de calcul opérationnel et corrélé à des résultats expérimentaux permettant d'étudier l'écoulement interne et le comportement du flotteur soumis à la houleGeps Techno's development is based on an innovative concept of a floating structure intended to produce electrical energy from several renewable marine energy sources, including wave power. The wave power system developed by Geps Techno is based on circulating water and creating a vortex within it. By taking advantage of the liquid hull phenomenon, the concept can also be used as a stabilization system for a ship or any other floating platform. The short-term objective of the company is the development of this technology allowing the stabilization and recovery of wave energy and for which there remain technological obstacles to be removed in order to achieve the viability and profitability of the system. To do this, in October 2015 Geps Techno launched the IHES (Integrated Harvesting Energy System) project, which consists of building a demonstrator of its wave power platform concept. The IHES project is one of the projects of the roadmap of the "Ecological ships" plan of New Industrial France. It is supported by Bpifrance within the framework of the Investments for the Future - Industrial Projects for the Future program. In order to master the objectives of stabilization and energy recovery, Geps Techno is studying the technological aspects necessary to switch from the energy available at wave level to that available at the wave turbine turbine. The Ph.D. thesis work supported by Fourestier in May 2017 focused on a first part "Definition and control of internal flows in the wave power system". Using CFD modeling, the latter resulted in operational models characterizing internal flows. This Cifre Ph.D. thesis follows on from Fourestier's work and deals with a second part "Modeling of the coupled platform / wave power system". All of this work should lead to an operational computer code correlated with experimental results making it possible to study the internal flow and the behavior of the float subjected to swell
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Ware, Cédric. "Récupération d'horloge par boucle à verrouillage de phase utilisant le mélange à quatre ondes dans un amplificateur optique à semi-conducteurs." Phd thesis, Télécom ParisTech, 2003. http://tel.archives-ouvertes.fr/tel-00005767.
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Dans le contexte des réseaux de transmission optiques à haut débit, l'on s'intéresse à la récupération d'horloge, fonction critique au niveau de la réception et de la régénération des signaux. À plusieurs dizaines de gigabits par seconde par canal, les boucles à verrouillage de phase électroniques remplissant traditionnellement cette tâche sont difficiles à réaliser. Or il est possible d'en reproduire le schéma à l'aide de composants optiques non-linéaires plus rapides, notamment les amplificateurs optiques à semi-conducteurs.Après une mise en contexte et quelques généralités sur le principe de fonctionnement desdits boucles de phase et amplificateurs optiques, nous présentons deux systèmes de récupération d'horloge utilisant le mélange à quatre ondes dans ces derniers. Cet effet non-linéaire est observé et étudié, ainsi que les dispositifs de récupération d'horloge, dont le fonctionnement est démontré expérimentalement sur des signaux optiques de type RZ et NRZ à 10 Gbps. Des mesures de taux d'erreurs montrent une pénalité négligeable ; on obtient une bande d'accrochage de l'ordre de quelques dizaines de kilohertz, et une gigue de l'ordre de la picoseconde.
Bien que ce débit ne soit plus très impressionnant de nos jours, ces schémas, reposant sur des effets non-linéaires ultrarapides, peuvent être étendus à une utilisation à des débits beaucoup plus élevés (de l'ordre de plusieurs centaines de gigabits par seconde voire au-delà) et à la récupération d'horloge fractionnelle, pour des applications de démultiplexage temporel. Les expériences correspondantes restent à effectuer, ainsi que l'utilisation de composants non-linéaires à faible bruit tels que les fibres optiques microstructurées et le niobate de lithium périodiquement orienté.
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Zwicke, Marine. "Impacts d'une canicule sécheresse sur le fonctionnement et la structure des communautés végétales de l'écosystème prairial." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-01020033.
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En Europe, les prairies permanentes représentent l'une des principales formes d'utilisation des terres. La durabilité des services rendus par ces écosystèmes est étroitement liée à la structure et au fonctionnement des communautés végétales qui les composent. La stabilité des processus écosystémiques, sous l'impact des fluctuations environnementales, va alors dépendre des mécanismes de résistance et de récupération propres à ces communautés. Les risques d'apparition d'extrêmes climatiques liés à l'évolution du climat, rendent nécessaire une adaptation des agro-écosystèmes à cette fluctuation climatique accrue. Cela implique de mieux comprendre les mécanismes par lesquels la variabilité du climat influe sur le fonctionnement et la structure des communautés végétales, et comment les pratiques agricoles impactent ces réponses. Cette thèse à pour objectif d'évaluer la vulnérabilité des prairies permanentes à un extrême climatique combinant une canicule et une sécheresse, dans un contexte de changement climatique. Afin d'identifier et de caractériser les mécanismes intrinsèques de la résistance à la sécheresse des communautés végétales, une démarche expérimentale mobilisant les concepts de l'écologie fonctionnelle a été développée. Les effets de la variabilité climatique sur la structure (diversité, composition) et le fonctionnement des communautés végétales ont d'abord été analysés in situ pendant 3 ans, après simulation d'une canicule-sécheresse dans les conditions climatiques actuelles et sous climat modifié (réchauffement et réduction des précipitations). Pour évaluer l'influence de la gestion sur la réponse des communautés végétales aux perturbations climatiques, deux fréquences de fauches ont été appliquées. Ce travail présente l'originalité d'avoir étudié conjointement le fonctionnement aérien et souterrain de la végétation. Sont considérées la production de biomasse, la démographie et la durée de vie des racines, afin de déterminer le rôle du système racinaire dans la résistance et la récupération des communautés végétales après une canicule sécheresse. Nous montrons un effet direct de l'extrême climatique sur la sénescence aérienne et la croissance racinaire dans les deux régimes de fauches. En réponse à un déficit hydrique modéré, la stratégie d'évitement au stress par le maintien de la croissance racinaire a été favorisée par des fauches non fréquentes. A l'automne suivant, les précipitations ont permis un reverdissement rapide de la couverture végétale et la production de nouvelles racines. Une baisse significative de la production de biomasse aérienne annuelle sous climat modifié, et suite à l'application de l'extrême climatique, a été observée pendant les 3 années d'expérimentation. En revanche, la production racinaire n'a pas été significativement affectée. Néanmoins une acclimatation de la croissance racinaire a été mise en évidence un an après l'extrême, en particulier dans les communautés de fauches non fréquemment. Ces changements de fonctionnement aériens et souterrains peuvent s'expliquer en partie par des modifications de la composition botanique. De plus, en réponse aux perturbations climatiques, la mortalité racinaire a été interrompue. Ces résultats inattendus ont donc entrainé une augmentation de la durée de vie des racines et suggèrent un effet négatif sur le turnover racinaire et les cycles biogéochimiques. Une expérimentation complémentaire à l'étude in situ a été menée en conditions semicontrôlées pour déterminer les mécanismes intrinsèques de la résistance à la sécheresse de la prairie permanente. Des traits morphologiques et physiologiques, aériens et souterrains, ont été mesurés sur des monocultures de sept populations prairiales en conditions optimales, puis en conditions de sécheresse afin de caractériser leurs stratégies de survie. Les résultats ont mis en évidence le rôle du système racinaire dans la survie des plantes. (...)
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De, Cillis Giovanni. "Numerical study of wind turbine wakes using modal-decomposition techniques and stability analysis." Doctoral thesis, 2021. http://hdl.handle.net/11589/213808.
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This thesis is focused on numerical analysis of wind turbines wakes. The flow over wind turbines is simulated performing Large Eddy Simulations (LES), where the rotor blades are modeled using the Actuator Line Method, whereas the Immersed Boundary Method is employed for tower and nacelle. The effect of tower and nacelle on wake dynamics is investigated by means of Proper Orthogonal Decomposition (POD) of numerical velocity data produced by two LES of a model wind turbine: one accounts only for the blades effect; the other includes also tower and nacelle. The turbine operates at Reynolds number Re = 6.3 × 10^5 and tip-speed ratio λ = 3. The two simulations are analysed and compared in terms of mean flow fields and POD modes that mainly characterize the wake dynamics. In the rotor-only case, the most energetic modes in the near wake are composed of high-frequency tip and root vortices, whereas in the far wake, low-frequency modes, mostly located in the wake shear layer region, are found. When tower and nacelle are included, low-frequency POD modes are present already in the near wake, linked to the von Karman vortices shed by the tower. These modes interact non linearly with the tip vortices in the far wake, generating new low-frequency POD modes, some of them lying in the frequency range of wake meandering. An analysis of the mean kinetic energy entrainment of each POD mode shows that tip vortices sustain the wake mean shear, whereas low-frequency modes contribute to wake recovery. This explains why tower and nacelle induce a faster wake recovery. The proper orthogonal decomposition, despite being able to isolate energetic flow structures in the wake, does not provide any physical information on their origin.
In an attempt to determine the physical mechanisms responsible for the emergence of these flow structures, the numerical data obtained without tower and nacelle are further analyzed performing two-dimensional modal and non-modal stability analysis of the turbulent mean flow developing downstream of a wind turbine rotor. Linear stability and optimal forcing analyses have been carried out in different cross-sections sufficiently far from the rotor, where nonparallel effects are rather weak. The frequency content and spatial structure of the most amplified perturbations are compared with that of the most energetic coherent structures recovered by POD analysis. Results show that most unstable modes computed relatively close to the rotor resemble large-scale oscillations isolated by the POD. Moving downstream, this matching is no longer verified; however, restricting the stability analysis to waves having streamwise wavenumber consistent with that of the POD analysis, we find three slightly stable eigenmodes bearing a strong resemblance with the most energetic POD modes.
The analyses described above are based on a model wind turbine; however utility-scale wind turbines operate at far larger Reynolds number, of the order of 10^8 and higher
tip-speed ratio. These differences can lead to a different wake dynamics. For this reason a reference utility-scale wind turbine (i.e. the NREL 5-MW) is simulated and analyzed using Proper Orthogonal Decomposition and Dynamic Mode Decomposition (DMD) in its sparsity promoting variant, which selects a limited subset of dynamically relevant modes. In contrast to the model wind turbine, the wake meanflow is, in this case, essentially aligned with the rotor axis and axisymmetric, suggesting a weaker impact of the tower. The coherent structures isolated by the two modal decomposition
techniques are similar to those observed for the model turbine, but a weaker interaction of tower’s wake and tip vortices is confirmed and a faster breakdown of the latter is reported. Furthermore, POD and DMD of the flow field provide rather different results. Large-scale, low-frequency oscillations are not present among the most energetic POD modes. On the contrary, sparsity-promoting dynamic mode
decomposition suggests that large-scale structures, developing far from the rotor, are relevant to the flow dynamics, despite their energetic content is not sufficiently high to overcome that of the tip vortices and their harmonics, which are among the first POD modes. This result demonstrates that while Proper Orthogonal Decomposition is efficient at identifying coherent structures, it may not be suitable for building a low-dimensional model of a wind turbine wake, while sparsity-promoting DMD can be a better choice.
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Tang, Shih-Tse, and 唐世澤. "Water Surface Elevation Recovery from Wave Pressure Signals." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/32610434592276746584.
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碩士國立交通大學
土木工程學系
84
In the present study an empirical transfer function between the wave pressure and wave height,which was established by Kuo and Chiu(1994) ,was applied to predict the history signals of the free water surface elevation from the wave pressure beneath the still water level.The Fast Fourier Transform(FFT) method is used to calculate the power spectral and history signals of wave height.The FFT method is compared with LCM method developed by Nielsen(1986) in this paper.It is found that both of FFT method and LCM method are accurately calculated when the pressure gages are locatted near the still water level.However, when the distance between the pressure gage and the still water level is longer,the FFT method with the empirical transfer function is more efficient and accurate than the LCM method. Furtherwore,the present study has decided on the cutoff frequency range,the weak point of the power spectral analisis which was resolved in this paper. Furthermore,the present study used the physical model test to investigate the transfer function between the wave pressure and the wave height in shallow water. By the analysis from the experimental data, we can find the transfer function is concern with the wave frequency and pressure gage locations. In addition ,the transfer functions of each older nonlinear components seem to be the same.
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Chen, Chia-Chi, and 陳加奇. "Community Variation and 921 Earthquake Recovery in Neo-Ware Village." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/63935549574459709953.
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碩士國立臺灣大學
地理環境資源學研究所
90
The Chi Chi Earthquake, occurred on September 21 in the year of 1999, has caused dramatic trauma and serious hazards in Neo-Ware Village. It force the community to face the problem of recovery right away. The rebuilding process, however, does not mean to rebuild material space only. It is the process of reproduction of social space at the same time. For the resident, it means that if the community could hold their social network and recover their normal life. For the community workers, it tests that if the community empowerment is possible, and if the marginality in space could be revised. All the social agent exhaust their entire social networks for rebuilding their homes and communities. And maybe we could find the most important social mechanism for community development during the pro-quake recovery process. So it is important to realize the locality of Neo-Ware before 921 earthquake. Besides, in this research, the author tries to utilize Lefebvre''s concepts of social space as tools for exploring the material, imaginational, and lived space in Neo-Ware village pro-quake recovery and to scrutinize the nature of local society, and the cause of problem during the rebuilding process. By scrutinizing community variation of Neo-Ware in the past 100 years and the production of space after 921 earthquake, it is argued in this thesis that the locality of village plays important role during the pro-quake recovery. It helps Neo-Ware people to confront the hazards. However, it causes contradiction and conflict inside the community at the same time. Besides, through re-establish the history of village, we realize that the difficulties of rebuilding. First, it is relationship to the land ownership transition from local people to special population outside the village in 1980s. Second, the new social relations of production in 1990s are also relevance. Besides, the possibility of rebuilding is not only to depend on the awareness of grassroots or to make use of community organization, which is proposed by that the community workers. This research finds that the daily life practice of local people helps them to reconstruct and survive themselves. It''s the most important agent for pro-quake recovery. It constructs the meaning of home, community and hold the social network at the same time. However, there are some limitations still. First, the recall of cultural identity is not enough to construct local agency of Neo-Ware village. Second, the lack of communication inside the community organization makes them evading the issue, when they confront the contradiction and conflict.
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Wiseman-Hakes, Catherine. "Sleep and Wake Disorders Following Traumatic Brain Injury: Impact on Recovery of Cognition and Communication." Thesis, 2012. http://hdl.handle.net/1807/34966.
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Objective: To examine sleep and wake disorders following traumatic brain injury (TBI) and their impact on recovery of cognition, communication and mood. Research Design: This three-manuscript thesis comprises an introduction to sleep in the context of human function and development. It is followed by a systematic review of the literature pertaining to sleep and wake disorders following TBI, and then explores the relationship between sleep and arousal disturbance and functional recovery of cognitive-communication through a single case study, pre–post intervention. Finally, a larger study longitudinally explores the impact of treatment to optimize sleep and wakefulness on recovery of cognition, communication and mood through objective and subjective measures, pre-post intervention. The thesis concludes with a chapter that addresses the implications of findings for rehabilitation from the perspective of the International Classification of Functioning, Disability and Health (ICF), and a presentation of future research directions for the field Methods: The first manuscript involved a systematic review and rating of the quality of evidence. The second manuscript involved the evaluation of sleep and wakefulness by objective measures, and longitudinally by self-report through the Daily Cognitive-Communication and Sleep Profile (DCCASP, © Wiseman-Hakes 2008, see Appendix S). Cognitive-communication abilities were also measured by the DCCASP. The third manuscript utilized a single case series and cohort design to evaluate sleep and wakefulness, and to examine cognition, communication and mood at baseline and following optimization of sleep and wakefulness. Results: For Manuscript One, 43 articles were reviewed for levels and quality of evidence across 5 domains: epidemiology, pathophysiology, neuropsychological implications, intervention and paediatrics. In Manuscript Two, we showed that there was a statistically and functionally significant relationship between perceived quality of sleep and language processing, attention and memory, seen across the phases of the intervention. In Manuscript Three, we showed that there were statistically and functionally significant improvements across several domains of cognition, communication and mood in response to treatment. Conclusions: Sleep and wake disorders after TBI are pervasive, and can negatively impact rehabilitation and recovery. There is a need for systematic evaluation and intervention for these disorders in all persons with TBI.
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Ying, Chang Chung, and 張炯殷. "Surface Wave Recovery from Subsurface Pressure Record Based on Field Observation." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/89285520524439573818.
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Jeong, Chanseok 1981. "On an inverse-source problem for elastic wave-based enhanced oil recovery." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-4027.
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Despite bold steps taken worldwide for the replacement or the reduction of the world’s dependence on fossil fuels, economic and societal realities suggest that a transition to alternative energy forms will be, at best, gradual. It also appears that exploration for new reserves is becoming increasingly more difficult both from a technical and an economic point of view, despite the advent of new technologies. These trends place renewed emphasis on maximizing oil recovery from known fields. In this sense, low-cost and reliable enhanced oil recovery (EOR) methods have a strong role to play.
The goal of this dissertation is to explore, using computational simulations, the feasibility of the, so-called, seismic or elastic-wave EOR method, and to provide the mathematical/computational framework under which the method can be systematically assessed, and its feasibility evaluated, on a reservoir-specific basis. A central question is whether elastic waves can generate sufficient motion to increase oil mobility in previously bypassed reservoir zones, and thus lead to increased production rates, and to the recovery of otherwise unexploited oil.
To address the many questions surrounding the feasibility of the elastic-wave EOR method, we formulate an inverse source problem, whereby we seek to determine the excitations (wave sources) one needs to prescribe in order to induce an a priori selected maximization mobility outcome to a previously well-characterized reservoir. In the industry’s parlance, we attempt to address questions of the form: how does one shake a reservoir?, or what is the “resonance” frequency of a reservoir?.
We discuss first the case of wellbore wave sources, but conclude that surface sources have a better chance of focusing energy to a given reservoir. We, then, discuss a partial-differential-equation-constrained optimization approach for resolving the inverse source problem associated with surface sources, and present a numerical algorithm that robustly provides the necessary excitations that maximize a mobility metric in the reservoir. To this end, we form a Lagrangian encompassing the maximization goal and the underlying physics of the problem, expressed through the side imposition of the governing partial differential equations. We seek to satisfy the first-order optimality conditions, whose vanishing gives rise to a systematic process that, in turn, leads to the prescription of the wave source signals.
We explore different (indirect) mobility metrics (kinetic energy or acceleration field maximization), and report numerical experiments under three different settings: (a) targeted formations within one-dimensional multi-layered elastic solids system of semi-infinite extent; (b) targeted formations embedded in a two-dimensional semi-infinite heterogeneous elastic solid medium; and (c) targeted poroelastic formations embedded within elastic heterogeneous surroundings in one dimension.
The numerical experiments, employing hypothetical subsurface formation models subjected to, initially unknown, ground surface wave sources, demonstrate that the numerical optimizer leads robustly to optimal loading signals and the illumination of the target formations. Thus, we demonstrate that the theoretical framework for the elastic wave EOR method developed in this dissertation can systematically address the application of the method on a reservoir-specific basis. From an application point of view and based on the numerical experiments reported herein, for shallow reservoirs there is strong promise for increased production. The case of deeper reservoirs can only be addressed with further research that builds on the findings of this work, as we report in the last chapter.text
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CHEN, ZHI-MING, and 陳志明. "Recovery of an optical wave in a turbulent medium by phase conjugation." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/01728261097544547306.
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Tietjen, Kristina. "Implications of heat stress and local human disturbance on early life stage corals." Thesis, 2020. http://hdl.handle.net/1828/11523.
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Coral reef recovery following a disturbance relies heavily on the restoration of coral cover, via growth of existing colonies and the successful recruitment of new corals. In well-connected reef networks, recruits may be sourced from neighboring reefs. In contrast, coral recruitment on geographically isolated reefs is reliant on adult corals at that location, which may limit recovery rates following mass coral mortality events. Such mortality events are increasingly caused by climate change induced temperature anomalies, which are overlaid on the local chronic human disturbances that already affect most of the world’s coral reefs. In this thesis, I exploit a natural ecosystem-scale experiment to examine how multiple anthropogenic stressors impact densities of coral recruits and small corals (e.g., juveniles; 5 cm) on Kiritimati (Christmas Island, Republic of Kiribati), an isolated atoll in the central equatorial Pacific Ocean. Specifically, I used benthic survey videos from before, during, and one year following the 2015-2016 El Niño and coral settlement tiles deployed during the three years after the event at 22 sites across the island, to quantify small corals and coral recruits, respectively. Local chronic stress negatively impacted small corals, with densities 47% lower at sites exposed to very high levels of chronic stress prior to the heat stress. The El Niño further resulted in a 56% loss of small corals, particularly for competitive coral species. Following the event, stress tolerant small corals rebounded to pre-El Niño densities within a year, whereas competitive and small corals overall had non-significant increases. I also quantified a low recruitment rate of 8.31 recruits m-2 per year (± 1.9 SE) during the three years following the El Niño compared to previous studies around the Pacific; recruits were genetically identified as primarily belonging to the stress tolerant family Agariciidae and the competitive genus Pocillopora. Local human disturbance also impacted coral recruitment with densities significantly lower at those with the greatest local chronic disturbance, together suggesting that local disturbance impedes post-settlement survival of recruits and the resilience of young corals during acute stress events. With increased net primary productivity, densities of both small corals and recruits (non-significant) also increased, which could reflect the positive influence of coral heterotrophic nutrition supplements during and after stress events, increasing survivability. Despite very low overall coral recruitment, all island regions did have some recruits, but Vaskess Bay (a bay region on the southern part of the island) had the highest densities. Overall these results indicate the negative consequences combined chronic and acute stressors can have on coral recruits, small corals, and accompanying coral resilience. When viewed together, this work suggests how the resilience is compromised by chronic stressors on Kiritimati and that the recovery trajectory may be variable across the disturbance gradient. Thus, local reef management may provide an avenue for enhancing recovery rates as acute temperature anomalies increase in frequency under our current climate trajectory.Graduate
2021-01-14
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Chandran, Sriram R. "Ultrasound-Assisted Diffuse Correlation Spectroscopy : Recovery of Local Dynamics and Mechanical Properties in Soft Condensed Matter Materials." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2753.
Full textAbstract:
This thesis describes the development and applications of an extension of DWS which enables the recovery of ‘localized’ mechanical properties, in a specified region of a complex jelly-like object which is inhomogeneous, marked out by the focal volume of an ultrasound transducer, also called the region-of-interest (ROI). Introduction of the sinusoidal forcing creates a sinusoidal phase variation in the detected light in a DWS experiment which modulates the measured intensity autocorrelation, g2 (τ ). Decay in the modulation depth with τ is used to recover the visco-elastic spectrum of the material in the ROI. En route to this, growth of the mean-squared dis- placement (MSD) with time is extracted from the modulation depth decay, which was verified first by the usual DWS experimental data from an homogeneous object with properties matching those in the ROI of the inhomogeneous object and then those obtained by solving the generalized Langevin equation (GLE) modelling the dynamics of a typical scattering centre in the ROI. A region-specific visco-elastic spectral map was obtained by scanning the inhomogeneous object by the ultrasound focal volume. Further, the resonant modes of the vibrating ROI were measured by locating the peaks of the modulation depth variation in g2(τ ) with respect to the ultrasound frequency. These resonant modes were made use of to recover elasticity of the material of the object in the ROI. Using a similar strategy, it was also shown that flow in pipe can be detected and flow rate computed by ‘tagging’ the photons passing through the pipe with a focussed ultrasound beam. It is demonstrated, both through experiments and simulations that the ultrasound-assisted technique devel- oped is better suited to both detect and quantitatively assess flow in a background of Brownian dynamics than the usual DWS. In particular, the MSD of particles in the flow, which shows forth a super-diffusive dynamics with MSD growing following τ α with α < 2, is captured over larger intervals of τ than was possible using existing methods. On the theoretical front, the main contribution is the derivation of the GLE, with multiplicative noise modulating the interaction ‘spring constant’. The noise is derived as an average effect of the micropolar rotations suffered by the
‘bath’ particles on the ‘system’ particle modelled. It has been shown that the ‘local’ dynamics of the system particle is nontrivially influenced by the dynamics, both translation and rotation, of ‘nonlocal’ bath particles.
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Roach, Lisa Aretha Nyala. "Temporal Variations in the Compliance of Gas Hydrate Formations." Thesis, 2012. http://hdl.handle.net/1807/44081.
Full textAbstract:
Seafloor compliance is a non-intrusive geophysical method sensitive to the shear modulus of the sediments below the seafloor. A compliance analysis requires the computation of the frequency dependent transfer function between the vertical stress, produced at the seafloor by the ultra low frequency passive source-infra-gravity waves, and the resulting displacement, related to velocity through the frequency. The displacement of the ocean floor is dependent on the elastic structure of the sediments and the compliance function is tuned to different depths, i.e., a change in the elastic parameters at a given depth is sensed by the compliance function at a particular frequency. In a gas hydrate system, the magnitude of the stiffness is a measure of the quantity of gas hydrates present. Gas hydrates contain immense stores of greenhouse gases making them relevant to climate change science, and represent an important potential alternative source of energy. Bullseye Vent is a gas hydrate system located in an area that has been intensively studied for over 2 decades and research results suggest that this system is evolving over time.
A partnership with NEPTUNE Canada allowed for the investigation of this possible evolution. This thesis describes a compliance experiment configured for NEPTUNE Canada’s seafloor observatory and its failure. It also describes the use of 203 days of simultaneously logged pressure and velocity time-series data, measured by a Scripps differential pressure gauge, and a Güralp CMG-1T broadband seismometer on NEPTUNE Canada’s seismic station, respectively, to evaluate variations in sediment stiffness near Bullseye. The evaluation resulted in a (- 4.49 x10-3± 3.52 x 10-3) % change of the transfer function of 3rd October, 2010 and represents a 2.88% decrease in the stiffness of the sediments over the period. This thesis also outlines a new algorithm for calculating the static compliance of isotropic layered sediments.