University of Maryland, Baltimore County
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Analysis of Routing and Wavelength Assignment in Large WDM Networks
No full textIn Wavelength Division Multiplexing (WDM) network, for a given connection request, a route has to be found, and a dedicated wavelength has to be assigned along that route. This problem of assigning route and wavelength to the connection request, using minimum network resources, is called Routing and Wavelength Assignment (RWA) Problem. This thesis focuses on the analysis of proposed RWA algorithms in large WDM networks. We use simulations and analysis of randomly generated large networks under dynamic traffic and static traffic, with and without protection of the connection request. The protection of the primary route between source and destination is considered by setting up a dedicated backup path in case of failures. The wavelength requirements are analyzed using different wavelength assignment heuristics under different routing techniques for a set of connection requests. We find that, the fixed alternate routing packs the connection requests into less number of wavelengths than the fixed routing and most-used performs slightly better than the first-fit heuristic
Experimental and Theoretical Investigation of Laser Photothermal Therapy for Prostate Cancer Treatment Using Gold Nanorods
No full textGold-based nanoparticles have gained prominence in recent years for use in clinical applications such as imaging, drug delivery, hyperthermia, and tissue ablation. In laser photothermal therapy using gold nanorods, the challenges are unknown distribution of gold nanorod deposition in tumors and treatment efficacy assessment. This dissertation establishes a streamline process of investigating the thermal effects in laser photothermal therapy. It eventually leads to identifying heating protocols for treating prostatic tumors embedded in tissue. It starts with microCT quantification of gold nanorod distribution in tumors after an intratumoral injection to determine the volumetric heat generation rate induced by laser and enhanced by gold nanorods. In vivo animal experiments are performed to measure intratumoral temperature elevations in PC3 xenograft tumors implanted in mice during laser photothermal therapy. The temperature profile suggests that normal tumor tissue still absorbs some amount of the laser energy without nanorod presence; however, the injected nanorods ensure almost all the laser energy is confined to the targeted tumors. It is sufficient to elevate the tumor temperature above 50�C using only 0.1 cc of a nanorod solution at a low laser irradiance of 1.6 W/cm2 on the tumor surface. The observed uniform deposition of nanorods in the tumors would simplify theoretical simulation of temperature elevations in tumor during laser photothermal therapy. The second part of this dissertation is dedicated to measure tumor shrinkage and to perform histologic analyses after laser irradiation to evaluate whether an administered laser photothermal treatment protocol induces adequate thermal damage to tumors. By average, the tumors shrink to less than 7% of its original volume within 25 days after the heating treatment. The tumors without heating continue to grow and double their sizes within 18 days. The histological analyses also show tumor necrosis events surrounding the tumor center after the heating. However, the extent of thermal damage to the tumor is not uniform throughout. The effects of radiation properties of tumor tissue containing gold nanorods at various concentration levels are then evaluated. A computational algorithm of Monte Carlo method is developed to determine the specific absorption rate (SAR) distribution in a spherical tumor containing gold nanorods at specific concentration. The SAR distribution is utilized as a source term in the Pennes bioheat equation to simulate temperature elevations in a spherical tumor implanted in mice. The radiation properties are then extracted via comparing the theoretically predicted temperature profiles in the tumor to that measured in our previous in vivo experiments. The final part of this study is focused on designing a treatment protocol to induced reasonable thermal damage to a tumor embedded in a prostate model, while protecting its surrounding healthy tissue. Monte Carlo and 3-D finite element computational modeling strategies are utilized to evaluate spatiotemporal temperature elevation distribution and thermal damage regions. This leads to identification of heating protocols to induce 100% damage to the tumor, while resulting in less than 5% damage to the surrounding sensitive prostatic tissue
ELLIPSOIDAL TOLERANCE REGIONS AND SIMULTANEOUS TOLERANCE INTERVALS FOR SOME MULTIVARIATE NORMAL POPULATIONS
No full textA tolerance region for a population is a region computed using a random sample, so that the region will include a specified proportion or more of the population, with a given confidence level. The theory of statistical tolerance regions has undergone vigorous development during the last several years. In particular, the computation of satisfactory tolerance regions for multivariate normal populations and multivariate regression models have been investigated, and approximations have been developed for computing the required tolerance factor. The available literature in the case of multivariate normal populations deal with the derivation of ellipsoidal tolerance regions only. The present research is motivated by several observations: for ellipsoidal tolerance regions, the available numerical methods to compute the tolerance factor are unsatisfactory, and the available approximations are not always accurate. Furthermore, the literature does not address the computation of simultaneous tolerance intervals. For computing the tolerance factor required to obtain an ellipsoidal tolerance region, an approximation coupled with Monte Carlo simulation is investigated. The methodology is developed when the unknown population covariance matrix does not have any specific structure, and when it has the intra-class covariance structure. Numerical results show that this approach results in an accurate tolerance factor. The methodology is extended to the case of a multivariate linear regression model for obtaining an ellipsoidal tolerance region under a fixed set of values of the covariates. The second part of the research deals with the derivation of simultaneous tolerance intervals and simultaneous prediction intervals. This is motivated by the fact that an ellipsoidal tolerance region cannot provide information on the distribution of the individual components of the response vector. The case of a general covariance matrix, and that of the intra-class covariance matrix are separately considered, and the derivation of both one-sided and two-sided tolerance intervals are addressed. In the case of the intra-class covariance structure, the derivation of a tolerance rectangle is also investigated. Numerical results are given to assess the accuracy of the proposed solutions, and illustrative examples and applications are provided
The Impacts of Service-Learning Participation upon Post-Secondary Students' Academic and Social Development
No full textService-Learning is a form of applied learning that engages students in solving social problems within community-based settings. It is rooted in the social and educational philosophy of John Dewey's Pragmatism. As a pedagogy, service-learning presents students with opportunities for social and intellectual growth by complementing classroom learning with community-based experiential learning. This research aims to improve our understanding of the academic and social impacts of service-learning participation in higher education. This study incorporates a mixed methodological design comprised of a primary quantitative study that meets a gap in the service-learning research, and a complementary qualitative study that allows for additional themes to emerge and illustrate findings of the primary study. The University of Maryland, Baltimore County is an ideal location for this research because of its history of service-learning leadership. Through rigorous, quasi-experimental, longitudinal analysis of a robust data set, the quantitative analysis investigates the relationship between service-learning participation and diverse measures of student academic development. A fixed effects design limits the potential bias stemming from non-random selection into service-learning. Qualitative research complements the quantitative study and provides an in-depth understanding of students' development, with a particular focus upon analyzing academic and pro-social growth through service-learning (e.g., voluntary behavior intended to benefit another such as altruism [Eisenberg, et al., 2006, p. 646]). The qualitative study consists of a non-probability, purposive sample of students (Singleton & Straits, 2005) participating in semi-structured interviews (Singleton & Straits, 2005), followed by thematic analysis (Marks & Yardley, 2004). This research makes methodological contributions and strengthens our understanding of applied and service-learning, particularly as implemented through the innovative institutional practices at the studied university. The quantitative study is strengthened by modeling that addresses threats to internal validity from students' self-selection (i.e., endogenous bias; Meyer, 1995) and allows for significant analytical conclusions. Additionally, the mixed methodological design illustrates student pro-social growth through a number of emergent themes (Johnson & Onwuegbuzie, 2004). The scale and design of this study increases our understanding of the impact of service-learning and the conclusions suggest it deserves further institutional attention as a core pedagogy in higher education
THE OUTCOMES OF TRANSLATING NEOLIBERAL ENVIRONMENTAL THEORY: A CRITICAL ANAYLSIS OF PAYMENTS FOR ECOSYSTEM SERVICES
No full textPayments for ecosystem services (PES) is a conservation mechanism that aims to commodify ecosystems based on the services they provide. PES programs represent a neoliberal approach to conservation by expanding the economy into environmental management. The successful creation of markets in which ecosystem services are valued and sold is thought to ensure their future sustainability. This market-based approach to conservation is considered to be more efficient, transparent, simple, and apolitical than alternative conservation mechanisms. However these benefits are contingent upon the successful establishment of free markets for completely commodified ecosystem services. As PES programs have been implemented, they have consistently failed to create free markets. In this thesis I argue that the requirements of markets and the process of commodification are incompatible with the characteristics of ecosystems. Due to this incompatibility, policymakers are forced to alter the design of PES programs in such a way that they are not demand generating, self-sufficient free markets as anticipated by theory. The success of PES programs in maintaining or increasing the provision of ecosystem services is unclear, as is the claim that they will simultaneously reduce rural poverty. In this thesis, I provide a critical analysis of Costa Rica's PES program to demonstrate the translation of neoliberal economic theory to state environmental policy
Essays on health insurance for immigrants in the United States: An examination of federal and state policies
No full textThe working–age, adult immigrant population living in the United States is often left out of health policy initiatives and consequentially is more likely to be uninsured. In my dissertation, I provide an analysis of why immigrants are more likely to be uninsured as well as an analysis of what factors make them likely to be covered by Medicaid or private health insurance. In the first essay, I estimate the effects of state generosity on the likelihood of an immigrant being uninsured, having Medicaid, employer–sponsored insurance (ESI) or other private health insurance (OPHI). I explore the determinants of lacking health insurance and the probability of having Medicaid, ESI or OPHI using a multinomial probit model, focusing on the variable of interest indicating whether or not a state is generous in accepting eligible, recent immigrants who have lived in the U.S. for fewer than 5 years into the Medicaid program. In the second essay, I research the effect of residency restrictions on immigrants' health insurance coverage rates through the use of a regression discontinuity design. The Personal Responsibility and Work Opportunity Reconciliation Act (PRWORA) passed in 1996 requires eligible immigrants to live in the U.S. for five years before they can qualify for Medicaid. My research analyzes the effects of this federal policy on Medicaid rates and explores how PRWORA continues to impact immigrants and their health insurance coverage options. In the final essay, I use a difference–in–differences (DID) approach to examine how simplifying the Medicaid application/renewal process affects health insurance coverage rates for both natives and immigrants. In recent years, some states have chosen to modify the Medicaid application and/or renewal process in order to make the process easier and break down one of the many barriers to obtain Medicaid benefits. My research evaluates whether simplification policies affect potentially eligible immigrants and natives differently and analyzes the effect of these simplifications on Medicaid coverage rates and rates of ESI, OPHI and uninsurance
AN INVESTIGATION ON THE CRACK GROWTH RESISTANCE OF HUMAN TOOTH ENAMEL: ANISOTROPY, MICROSTRUCTURE AND TOUGHENING
No full textThe enamel of human teeth is generally regarded as a brittle material with low fracture toughness. Consequently, the contributions of this tissue in resisting tooth fracture and the importance of its complex microstructure have been largely overlooked. The primary objective of this dissertation is to characterize the role of enamel's microstructure and degree of decussation on the fracture behavior of human enamel. The importance of the protein content and aging on the fracture toughness of enamel were also explored. Incremental crack growth in sections of human enamel was achieved using a special inset Compact Tension (CT) specimen configuration. Crack extension was achieved in two orthogonal directions, i.e. longitudinal and transverse to the prism axes. Fracture surfaces and the path of crack growth path were evaluated using scanning electron microscopy (SEM) to understand the fundamental mechanisms of crack growth extension. Furthermore, a hybrid approach was adopted to quantify the contribution of toughening mechanisms to the overall toughness. Results of this investigations showed that human enamel exhibits rising R-curve for both directions of crack extension. Cracks extending transverse to the rods in the outer enamel achieved lower rise in toughness with crack extension, and significantly lower toughness (1.23 � 0.20 MPa*m0.5) than in the inner enamel (1.96 � 0.28 MPa*m0.5) and in the longitudinal direction (2.01 � 0.21 MPa*m0.5). The crack growth resistance exhibited both anisotropy and inhomogeneity, which arise from the complex hierarchical microstructure and the decussated prism structure. Decussation causes deflection of cracks extending from the enamel surface inwards, and facilitates a continuation of transverse crack extension within the outer enamel. This process dissipates fracture energy and averts cracks from extending toward the dentin and vital pulp. This study is the first to investigate the importance of proteins and the effect of aging on the fracture resistance of this highly mineralized tissue. Results showed that although the organic content is small, it plays an important role in the toughness of enamel. The deproteinized enamel underwent a significant reduction in the crack growth resistance with respect to proteinized control, with fracture toughness in the longitudinal (1.24 � 0.24 MPa*m0.5) and transverse directions (0.95 � 0.20 MPa*m0.5) approximately 40% lower than the control. Removal of the proteins also resulted in a loss of anisotropy, which reduces enamel's unique ability to invoke crack deflection. Additionally, results showed that aging results in a significant reduction in the fracture toughness. In the longitudinal direction the fracture toughness of old enamel was 1.38 � 0.35 MPa*m0.5, which is more than 30% lower than that of the control. Microscopic observation of crack extension in the enamel specimens showed that crack growth toughening occurred by a combination of extrinsic toughening mechanism including crack bridging, crack deflection and crack bifurcation. The cohesive zone analysis confirmed that enamel is primarily extrinsically toughened, with intrinsic and extrinsic toughening contributing approximately 5% and 30% of the total energy to fracture in the decussated enamel, respectively. However, the contribution of the extrinsic toughening in the outer enamel was negligible. For the deproteinized and old enamel, the degree of extrinsic toughening was 75%, and 30% lower, respectively, in comparison to the young proteinized enamel. The degradation in extrinsic toughening was attributed to embrittlement of the bridging ligaments. The organic substance at the rod boundaries was found to be essential in the crack growth toughening of enamel through the formation of unbroken ligaments and crack bridging, microcracking along the rod boundaries and in the process of crack bifurcation. The effectiveness of these mechanisms is most dominant in the decussated enamel due to the higher organic content. Through these findings the present investigation provides new understanding on the fracture resistance of enamel, which is essential to advancements in the field of restorative dentistry, as well as in the design of new restorative and bio-inspired materials
The Vietnam War: Communist Mass Mobilization at the National and Provincial Level in the Mekong Delta
No full textThe following study is an examination of Communist and Nationalist mass mobilization tactics during the Second Indochina Conflict. How did the use of violent and non-violent methods of mass mobilization and population control vary from region to reion in the context of local and national events, and what effect did these patterns have on communist and revolutionary efforts to gain popular support? How did these local practices influence the outcome of the conflict? The present study examines macro-level political trends and local case studies to investigate the development of communist mass mobilization strategy. The present study argues that Communist and Nationalist revolutionary leaders adapted mass mobilization techniques to the particular geographic and political realities of different regions, thereby enhancing the effectiveness of their efforts amongst the peasantry. The role of the Central Committee, the National Liberation Front, and the Southern Communist will be analyzed against the backdrop of national and local circumstances facilitated by the Republic of South Vietnam and the United States of America
Classification Using the ROC Curve Analysis and Testing Non-equivalence
No full textThe dissertation consists of two different topics. The first topic is to develop the methodologies in optimizing the ROC (Receiver Operating Characteristic) curve with variable selection based on group sparsity. An ROC curve is a popular tool in the classification of two populations. The nonparametric additive model is used to construct a classifier which is estimated by maximizing the U-statistic type of empirical AUC (Area Under Curve). In particular, the sparsity situation is considered in the sense that only a small number of variables is significant in the classification, so it is demanded that lots of noisy variables will be removed. Some theoretical result on the necessity of variable selection under the sparsity condition is provided since the AUC of the classifier from maximization of empirical AUC is not guaranteed to be optimal. To select significant variables in the classification, the grouped lasso which has been widely used when groups of parameters need to be either selected or discarded simultaneously is used. In addition, the performance of the proposed method is evaluated by numerical studies including simulation and real data examples compared with other existing approaches. The second topic is developing the hypothesis test for non-equivalence. We consider the problem of testing the non-equivalence of several independent normal population means. Testing homogeneity of several population means usually refers to testing the exact equality of population means. Instead of determining the exact homogeneity or equality, one may consider more flexible homogeneity which allows a predetermined level of difference. This problem is known as testing the non-homogeneity of populations. We propose the plug-in tests for three different measures of variability: the sum of the absolute deviations, the maximum of the absolute deviations, and the range for testing non-equivalence. For each test, the least favorable configuration (LFC) to ensure the maximum rejection probability under the null hypothesis is investigated. Furthermore, we demonstrate the numerical studies based on both simulations and real data to evaluate the plug-in tests and compare our proposed tests with other possible tests
PERCEIVED FAULTLINE IMPACT IN TEMPORARY DISTRIBUTED TEAMS: EXAMINING THE ROLE OF NORMS OF TECHNOLOGY USE
No full text As distributed teams are inherently heterogeneous, they have a greater tendency to fracture into subgroups which result from the misalignment of demographics, geography, or values of the team members. This is referred in the literature as a faultline. Current studies of faultline have focused on collocated teams, which differ from distributed teams in terms of their primary mechanism of interaction: face-to-face vs. computer-mediated. As distributed teams mainly rely on computer mediated communication, there is greater possibility of members making inaccurate and stereotyped impressions that can negatively affect them in working together as a team. Additionally, current faultline research has fixated on demographic attributes. Although these studies are insightful, there are other attributes that are more pertinent in influencing subgroups on distributed teams, specifically. This study extends the body of knowledge on faultline and distributed teams through the development of a model that systematically investigates antecedents of subgroup processes and team performance. The model was empirically tested with survey data collected from 225 graduate students in 53 distributed project teams, using Partial Least Squares method. Research results demonstrated several novel insights into how perceived faultlines impact team performances. Firstly, in temporary distributed teams, the alignment of time orientation attributes and relationship values, also known as dormant faultlines, are positively correlated with the sense of division among team members (a perceived faultine). Secondly, this perceived faultline is negatively related to perceived team performance through the presence of task and relationship conflicts. In other words, both relationship and task conflict mediated the relationship of perceived faultline and perceived team performance. Thirdly, while this perceived faultline negatively correlates with team performance, the norms of technology significantly moderate the negative relationship of task conflict on team performance. The results suggest that the negative relationship between task conflict and team performance was reduced in teams having higher norms of technology use for supporting task awareness, task coordination, and interactions. Finally, implications for research and practice are presented with potential avenues for future research. </bold