Mechanical Behavior of Gas Metal Arc Welds and Lithium-Ion Battery Modules.

The first part of the dissertation is related to a study of the failure mechanisms of gas metal arc welds. Cost savings can be gained by minimizing the weld length. However, improperly sized welds can result in the loss of structural integrity of the welded components. The necking/shear failure modes for the mid-sections of gas metal arc welds in lap-shear specimens of HSLA steel are investigated. Three-dimensional finite element models were developed with the geometric characteristics of the heat affected zones (HAZ) designed to match the micrographs of the cross sections for the welds. The distributions of the void volume fraction near the welds shown from the finite element analyses are consistent with the failure modes observed in the experiments. Further finite element analyses showed that the geometric characteristics of the HAZ are key factors for the resulting failure location. The mode I and mode II stress intensity factor (SIF) solutions for gas metal arc welds in lap-shear specimens are investigated by the analytical solutions and by finite element analyses. The computational results indicate that the SIF solutions for realistic welds are lower than the analytical solutions for idealized weld geometry. Further finite element analyses were carried out in order to obtain the computational SIF solutions for the realistic weld geometries with dissimilar sheet thicknesses. Finally, three-dimensional computational results indicate that the distributions of the SIF solutions for discontinuous welds are different from those for continuous welds. In the second part, a computational model is developed for simulations of representative volume element specimens of lithium-ion battery modules under in-plane constrained compression tests. The model allows for computational efficiency while simulating the overall mechanical response of battery modules and the deformation patterns of the heat dissipater. The model is based on the properties of the heat dissipater, the foam, and the macro behavior of the cell components. The computational results compare fairly well with the experimental results. Further finite element analyses showed the increase in the initial nominal buckling stress under dynamic loading conditions.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111520/1/aed_1.pd

A web-based Alcohol Clinical Training (ACT) curriculum: Is in-person faculty development necessary to affect teaching?

<p>Abstract</p> <p>Background</p> <p>Physicians receive little education about unhealthy alcohol use and as a result patients often do not receive efficacious interventions. The objective of this study is to evaluate whether a free web-based alcohol curriculum would be used by physician educators and whether in-person faculty development would increase its use, confidence in teaching and teaching itself.</p> <p>Methods</p> <p>Subjects were physician educators who applied to attend a workshop on the use of a web-based curriculum about alcohol screening and brief intervention and cross-cultural efficacy. All physicians were provided the curriculum web address. Intervention subjects attended a 3-hour workshop including demonstration of the website, modeling of teaching, and development of a plan for using the curriculum. All subjects completed a survey prior to and 3 months after the workshop.</p> <p>Results</p> <p>Of 20 intervention and 13 control subjects, 19 (95%) and 10 (77%), respectively, completed follow-up. Compared to controls, intervention subjects had greater increases in confidence in teaching alcohol screening, and in the frequency of two teaching practices – teaching about screening and eliciting patient health beliefs. Teaching confidence and teaching practices improved significantly in 9 of 10 comparisons for intervention, and in 0 comparisons for control subjects. At follow-up 79% of intervention but only 50% of control subjects reported using any part of the curriculum (p = 0.20).</p> <p>Conclusion</p> <p>In-person training for physician educators on the use of a web-based alcohol curriculum can increase teaching confidence and practices. Although the web is frequently used for disemination, in-person training may be preferable to effect widespread teaching of clinical skills like alcohol screening and brief intervention.</p

Effects of chronic ethanol exposure on neuronal function in the prefrontal cortex and extended amygdala

Chronic alcohol consumption and withdrawal leads to anxiety, escalated alcohol drinking behavior, and alcohol dependence. Alterations in the function of key structures within the cortico-limbic neural circuit have been implicated in underlying the negative behavioral consequences of chronic alcohol exposure in both humans and rodents. Here, we used chronic intermittent ethanol vapor exposure (CIE) in male C57BL/6J mice to evaluate the effects of chronic alcohol exposure and withdrawal on anxiety-like behavior and basal synaptic function and neuronal excitability in prefrontal cortical and extended amygdala brain regions. Forty-eight hours after four cycles of CIE, mice were either assayed in the marble burying test (MBT) or their brains were harvested and whole-cell electrophysiological recordings were performed in the prelimbic and infralimbic medial prefrontal cortex (PLC and ILC), the lateral and medial central nucleus of the amygdala (lCeA and mCeA), and the dorsal and ventral bed nucleus of the stria terminalis (dBNST and vBNST). Ethanol-exposed mice displayed increased anxiety in the MBT compared to air-exposed controls, and alterations in neuronal function were observed in all brain structures examined, including several distinct differences between subregions within each structure. Chronic ethanol exposure induced hyperexcitability of the ILC, as well as a shift toward excitation in synaptic drive and hyperexcitability of vBNST neurons; in contrast, there was a net inhibition of the CeA. This study reveals extensive effects of chronic ethanol exposure on the basal function of cortico-limbic brain regions, suggests that there may be complex interactions between these regions in the regulation of ethanol-dependent alterations in anxiety state, and highlights the need for future examination of projection-specific effects of ethanol in cortico-limbic circuitry