Finite-Difference Modeling of 2-D Compressional Wavefield

This project discusses the derivation of the 2-D compressional wavefield (P-wave) and its finite-difference approximation. In developing this wavefield, we have two approximations. First, the subsurface density is assumed to be a constant. Second, the angle of wave propagation is less than 150 with respect to the surface (horizontal direction). The algorithms are used to demonstrate the propagation of P-wave through a simple subsurface model. Although not discussed in this project, the same algorithms are also able to model the propagation of P-wave in another complex model and the success of depthimaging algorithms in recovering the subsurface structures indicates the accuracy of the approximations for most modeling purposes. Future studies include modeling P-wave in 3-D, modeling elastic wavefield in 2/3-D, and extending the angle of propagation to more accurately model incoming waves at the edge of the computational grid

The Ekeland variational principle for set-valued maps involving coderivatives

AbstractIn this paper we use the Fréchet, Clarke, and Mordukhovich coderivatives to obtain variants of the Ekeland variational principle for a set-valued map F and establish optimality conditions for set-valued optimization problems. Our technique is based on scalarization with the help of a marginal function associated with F and estimates of subdifferentials of this function in terms of coderivatives of F

Piezoelectric Energy Harvesting System

This project investigates the behavior of two types of piezoelectric harvester in response to different applied strains. Three tests are performed: two Deflection Amplitude vs. Voltage Generation tests and an Energy Charging Rate test. The two deflection tests are done on a Volture energy harvester and a piezoelectric disk. The energy charging rate test is done on a pair of piezoelectric disks. The strain test on the Volture energy harvester show inconsistent relationships between a piezoelectric harvester’s natural frequency and its ability to generate voltage. The strain test on the piezoelectric disk are also not clear either since the voltage generated varies greatly after each tap. The results from the energy charging rate test indicate that a piezoelectric harvester generates energy at a higher rate when subjected to a higher-frequency vibration source than to a lower-frequency one. Future studies are recommended to make comprehensive conclusions regarding the relationships between a piezoelectric harvester’s natural frequency and its ability to generate voltage. Further researches regarding vibration sources are also recommended as finding a suitable vibration source is found to be the most challenging part of this project

Cost-effectiveness analysis of interventions to prevent cardiovascular disease in Vietnam

Background Vietnam is in the process of an epidemiological transition, with cardiovascular disease (CVD) now ranked as the leading cause of death. The burden of CVD will continue to rise unless effective interventions for addressing its underlying risk factors are put in place. Objectives To assess the costs, health effects and cost-effectiveness of a set of personal and non-personal prevention strategies to reduce CVD in Vietnam, including mass media campaigns for reducing consumption of salt and tobacco, drugs for lowering blood pressure or cholesterol, and combined pharmacotherapy for people at varying levels of absolute risk of a cardiovascular event. Methods WHO-CHOICE methods and analytical models were employed, using local data to estimate the costs, effects and cost-effectiveness of 12 population and individual interventions implemented singly or in combination. Costs were measured in Vietnamese Dong for the year 2007 (discounted at a rate of 3% per year), while health effects were expressed in age-weighted and discounted disability-adjusted life years (DALYs) averted. Results A health education programme to reduce salt intake (VND 1 945 002 or US$118 per DALY averted) and individual treatment of systolic blood pressure above 160 mmHg (VND 1 281 596 or US$78 per DALY averted) were found to be the most cost-effective measures for population- and individual-based approaches, respectively. Where budget is very limited, a mass media education programme on salt intake and a combination mass media programme addressing salt intake, cholesterol and tobacco should be selected first. If more resources become available, greatest population health gains can be achieved via individual treatment of systolic blood pressure and the absolute risk approach to CVD prevention. Conclusions Contextualization of WHO-CHOICE using local data provides health decision-makers with more sound economic evidence for policy debates on prioritizing health interventions to reduce cardiovascular diseases in Vietnam. When used, cost-effectiveness analysis could increase efficiency in allocating scare resource

Characterization of Dyspnea in Veteran Lung Cancer Survivors Following Curative-Intent Therapy.

PurposeDyspnea is highly prevalent in lung cancer survivors following curative-intent therapy. We aimed to identify clinical predictors or determinants of dyspnea and characterize its relationship with functional exercise capacity (EC).MethodsIn an analysis of data from a cross-sectional study of lung cancer survivors at the VA San Diego Healthcare System who completed curative-intent therapy for stage I-IIIA disease ≥1 mo previously, we tested a thorough list of comorbidities, lung function, and lung cancer characteristics. We assessed dyspnea using the European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire Lung Cancer Module 13 (LC13) and functional EC using the 6-minute walk. We replicated results with the University of California San Diego Shortness of Breath Questionnaire.ResultsIn 75 participants at a median of 12 mo since treatment completion, the mean ± SD LC13-Dyspnea score was 35.3 ± 26.2; 60% had abnormally high dyspnea. In multivariable linear regression analyses, significant clinical predictors or determinants of dyspnea were (β [95% CI]) psychiatric illness (-20.8 [-32.4 to -9.09]), heart failure with reduced ejection fraction (-15.5 [-28.0 to -2.97]), and forced expiratory volume in the first second of expiration (-0.28 [-0.49 to -0.06]). Dyspnea was an independent predictor of functional EC (-1.54 [-2.43 to -0.64]). These results were similar with the University of California San Diego Shortness of Breath Questionnaire.ConclusionWe identified clinical predictors or determinants of dyspnea that have pathophysiological bases. Dyspnea was independently associated with functional EC. These results have implications in efforts to reduce dyspnea and improve exercise behavior and functional EC in lung cancer survivors following curative-intent therapy

Vai trò của nhóm nghiên cứu đối với việc công bố quốc tế trong lĩnh vực khoa học tự nhiên và kỹ thuật

Công bố khoa học được xem là một trong những thước đo trình độ phát triển khoa học công nghệ và sức cạnh tranh của mỗi một quốc gia do đó nó luôn là chủ đề gây chú ý đối với toàn xã hội trong những năm gần đây. Nâng cao số lượng và chất lượng nghiên cứu khoa học, công bố quốc tế được xem là một trong những yếu tố quan trọng quyết định đến sự hình thành và phát triển của các nhóm nghiên cứu cũng như quyết định cho sự thành công của các hoạt động khoa học công nghệ của bất kỳ cơ quan tổ chức nghiên cứu, giáo dục nào. Nghiên cứu này được thực hiện nhằm đánh giá vai trò của các nhóm nghiên cứu đối với việc công bố quốc tế riêng trong lĩnh vực khoa học tự nhiên và kỹ thuật