Effect of dislocation density on residual stress in polycrystalline silicon wafers

The goal of this research was to examine the relationship between dislocation density and in-plane residual stress in edge-defined film-fed growth (EFG) silicon wafers. Previous research has shown models for linking dislocation density and residual stress based on temperature gradient parameters during crystal growth. Residual stress and dislocation density have a positive relationship for wafers with very low dislocation density such as Cz wafers. There has been limited success in experimental verifications of residual stress for EFG wafers, without any reference to dislocation density. No model of stress relaxation has been verified experimentally in post production wafers. A model that assumes stress relaxation and links residual stress and dislocation density without growth parameters will be introduced here. Dislocation density and predominant grain orientation of EFG wafers have been measured by the means of chemical etching/optical microscope and x-ray diffraction, respectively. The results have been compared to the residual stress obtained by a near infrared transmission polariscope. A model was established to explain the results linking dislocation density and residual stress in a randomly selected EFG wafer.M.S.Committee Chair: Danyluk, Steven; Committee Member: Melkote, Shreyes; Committee Member: Rohatgi, Ajee

The Impact of Stress on Graduate Students’ Organizational Citizenship Behavior: the Moderating Role of Mentorship

Stress is one of the most researched topics in organizational psychology because of the important implications for overall health. Graduate school has many different stressors that put that specific population at a higher risk for the adverse effects of stress. Stress not only has implications for health but specific behaviors like organizational citizenship behaviors. The present study surveyed a sample of graduate students and examined ways in which mentorship can moderate the relation between stress, workload, physical symptoms, and OCBs. Eighty-five graduate students completed an anonymous survey. Results indicated that stress significantly predicted OCBs in graduate students. Also, mentorship was found to significantly moderate the relation between workload and OCBs. These findings provide added information on the impact of stress on graduate students as well as practical implications for mentorship

Technological learning for innovating towards sustainable cultivation practices: the Vietnamese smallholder rose sector

Deregulation and globalisation has altered the views of public involvement in development and led to strategies focusing on private sector participation. An implicit assumption seems to be that these linkages will enhance the technological capacity of smallholder producers by way of more cost-efficient technologies trickling down through the value chain or by quality requirements inducing best practices. The argument put forward in this paper is that sustainable non traditional agricultural chain development requires more purposeful actions and institutional transitions, both in the public and private spheres, targeting improved upstream innovative capacities. Empirical findings from a Dutch-Vietnamese partnership on sustainable floriculture development are used. Research revealed that the pest and disease control solutions applied by smallholder rose growers were incremental adaptations of experiences obtained in former food crop cultivation practices. Floriculture however may require more drastic changes in cultivation practices to make the sector more environmentally benign. In the case of smallholder Vietnamese flower producers, this implies adaptation of knowledge and skills currently not present. An important hindrance in promoting this knowledge and skills appears to be the weak vertical linkages between flower growers and public and private research and development organizations

Bladschade bij Monocotylen: Verslag van een workshop/thema bijeenkomst

Veel siergewassen krijgen bladschade bij veranderende groeiomstandigheden (bv. overgang licht/donker bij CAM planten, geremde verdamping bij C3 planten). Bladschade vermindert de sierwaarde en is daarmee een belangrijke kostenpost in de sierteelt. In het verleden is veel onderzoek gedaan om methodes te vinden om de schade te verminderen. Voor veel gewassen is dit helaas nog niet met de gewenste reproduceerbaarheid gelukt. Onderzoek van de Katholieke Universiteit Leuven heeft aangetoond dat de gevoeligheid voor bladschade bij Aechmea tussen rassen varieert. Dit wordt in de praktijk ook bij andere gewassen gezien. Uit dit onderzoek blijkt dat de gevoeligheid voor een groot gedeelte bepaald wordt door de chemische samenstelling van de celwand. In planten bestaan wel grofweg twee type celwanden. In de dicotylen komen vooraal celwanden voor waarbij een cellulose net versterkt wordt door een pectine netwerk, die calcium ionen kunnen binden. Monocotylen planten blijken vaak celwanden te hebben waarbij pectine en calcium een heel beperkte rol spelen, en waar de functie van de pectine overgenomen wordt door andere stoffen, GAX’s genoemd. De mate waarin deze GAX’s vertakt zijn bepaalt de flexibiliteit van de celwand. Gevoelige rassen hebben minder flexibele celwanden, die breken als de inwendige spanning te hoog wordt, en dat geeft bladschade. Rassen met een flexibele celwand vangen veranderingen in de inwendige spanning beter op en hebben daarom veel minder bladschade

Victoria Ordaz Garcia

Spotlight: Udoc-U Otters Portraits Created by CSUMB Undoc-U Otter students, Maria Lopez-Cabrera, Marisol Cruz, Daniella Lopez, Juan Pacheco Marcial, Jesus Loza-Mendez, Victoria Ordaz Garcia, Mirla Ramirez, and Adriana Ramirez Altamirano, these portraits are an interdisciplinary collaboration between the School of Humanities and Communication (HCOM) and the Visual and Public Art Dept. (VPA), and are part of a series of screenings, panels, and workshops made possible through funding from the National Endowment for the Humanities (NEH). Led by Dionicio Mendoza, Assistant Professor of Visual and Public Art, I AM WHO I AM…SO WHAT is a series of mixed-media workshops that aim to raise awareness about the urgent issues facing our undocumented community by emphasizing art as a tool for empowerment and community-building

Flexible Methods for Accounting for Distributional Misspecification of the Response-Adaptive Randomization Ratio in Two-Arm Clinical Trials with Continuous or Survival Outcomes

Optimal response-adaptive randomization (RAR) is used in clinical trials (CTs) to balance ethics and power by randomizing patients according to the unknown population parameters of an assumed parametric response distribution selected prior to data collection. If the distribution of the observed response data is misspecified, the resulting randomization may produce unanticipated trial characteristics. This dissertation introduces flexible estimators of the optimal RAR ratio that adjust for such misspecification. When observed response data were continuous in nature, sample moments were estimated from a continuous fit of the empirical CDF. These sample moments then served as the operands for the first flexible estimator of the RAR ratio presented in this work. The second estimator utilized a weighted-average approach. An array of RAR ratios corresponding to a set of candidate response distributions were estimated from the observed response data. These were then weighted by that distribution’s fit to the observed response data, and the resulting products were summed. These methods produced the desired randomization results in simulated CTs. However, they were computationally expensive, required large lead-ins, and did not consistently outperform the conventional normality assumption, even in small samples. Where a number of optimal RAR design exist for CTs with continuous outcomes, there is a paucity of the same for CTs with survival outcomes. Thus, convention for such trials is the optimal RAR framework constructed by Zhang and Rosenberger (ZR RAR), which has limitations. It relies upon the distributional specification of survival times and uses proxy metrics to define the RAR ratio, where only two cases (exponential and Weibull) have been addressed. It was hypothesized that the ZR RAR convention may be highly susceptible to distributional misspecification for these reasons. Thus, its behavior was examined under increasingly severe deviations from correct specification in the present work. A novel RAR ratio based on the cumulative hazard (H-RAR) was then developed using the ZR optimal RAR framework. Randomization results produced by H-RAR were compared to those obtained from (a) correctly-specified ZR RAR, (b) misspecified ZR RAR using well-behaved survival times, and (c) severely misspecified ZR RAR using change-point survival times. H-RAR recreated the correctly-specified ZR RAR and outperformed ZR RAR when misspecified. These results are promising and demonstrate a computationally straightforward and accurate estimator of the optimal RAR ratio for CTs with survival outcomes