Dynamics of Shape Memory Alloys Patches with Mechanically Induced Transformations

A mathematical model is constructed for the modelling of two di- mensional thermo-mechanical behavior of shape memory alloy patches. The model is constructed on the basis of a modified Landau-Ginzburg theory and includes the coupling effect between thermal and mechanical fields. The free energy functional for the model is exemplified for the square to rectangular transformations. The model, based on nonlinear coupled partial differential equations, is reduced to a system of differential-algebraic equations and the backward differentiation methodology is used for its numerical analysis. Computational experiments with representative distributed mechanical loadings are carried out for patches of different sizes to analyze thermo-mechanical waves, coupling effects, and 2D phase transformations

Green Card, Blood Card, or June 4 Card: The Chinese Student Protection Act of 1992

This thesis will detail the actual reasons behind the passage of the Chinese Student Protection Act (CSPA) of 1992. It will demonstrate that the passage of this act is rooted in American political desires, American partisan conflicts, and a sophisticated lobbying effort on the part of Chinese students and scholars, who had their own, often complicated, reasons for not wishing to return to China. To set the stage for this work, it will provide significant background information on three topics: Chinese-American immigration history prior to 1989, the Crisis of 1989 itself, and the respective responses of the American Congress and the Bush administration to the Tiananmen Square tragedy. This wall provide the backdrop against which the most important parts of this thesis will be set: the response of Chinese-American students to the Tiananmen Square tragedy and their lobbying efforts for legislative protection in the U.S.; and a critical evaluation of the CSPA and its actual results. Both quantitative and qualitative research methods were employed to analyze the various primary sources used in this thesis, including one source—the China News Digest—which is the most popular, and for its time, the most important electronic news forum for Chinese students in North America

Finite Volume Analysis of Nonlinear Thermo-mechanical Dynamics of Shape Memory Alloys

In this paper, the finite volume method is developed to analyze coupled dynamic problems of nonlinear thermoelasticity. The major focus is given to the description of martensitic phase transformations essential in the modelling of shape memory alloys. Computational experiments are carried out to study the thermo-mechanical wave interactions in a shape memory alloy rod, and a patch. Both mechanically and thermally induced phase transformations, as well as hysteresis effects, in a one-dimensional structure are successfully simulated with the developed methodology. In the two-dimensional case, the main focus is given to square-to-rectangular transformations and examples of martensitic combinations under different mechanical loadings are provided.Comment: Keywords: shape memory alloys, phase transformations, nonlinear thermo-elasticity, finite volume metho

Numerical Model For Vibration Damping Resulting From the First Order Phase Transformations

A numerical model is constructed for modelling macroscale damping effects induced by the first order martensite phase transformations in a shape memory alloy rod. The model is constructed on the basis of the modified Landau-Ginzburg theory that couples nonlinear mechanical and thermal fields. The free energy function for the model is constructed as a double well function at low temperature, such that the external energy can be absorbed during the phase transformation and converted into thermal form. The Chebyshev spectral methods are employed together with backward differentiation for the numerical analysis of the problem. Computational experiments performed for different vibration energies demonstrate the importance of taking into account damping effects induced by phase transformations.Comment: Keywords: martensite transformation, thermo-mechanical coupling, vibration damping, Ginzburg-Landau theor

Thermo-Mechanical Wave Propagation In Shape Memory Alloy Rod With Phase Transformations

Many new applications of ferroelastic materials require a better understanding of their dynamics that often involve phase transformations. In such cases, an important prerequisite is the understanding of wave propagation caused by pulse-like loadings. In the present study, a mathematical model is developed to analyze the wave propagation process in shape memory alloy rods. The first order martensite transformations and associated thermo-mechanical coupling effects are accounted for by employing the modified Ginzburg-Landau-Devonshire theory. The Landau-type free energy function is employed to characterize different phases, while a Ginzburg term is introduced to account for energy contributions from phase boundaries. The effect of internal friction is represented by a Rayleigh dissipation term. The resulted nonlinear system of PDEs is reduced to a differential-algebraic system, and Chebyshev's collocation method is employed together with the backward differentiation method. A series of numerical experiments are performed. Wave propagations caused by impact loadings are analyzed for different initial temperatures. It is demonstrated that coupled waves will be induced in the material. Such waves will be dissipated and dispersed during the propagation process, and phase transformations in the material will complicate their propagation patterns. Finally, the influence of internal friction and capillary effects on the process of wave propagation is analyzed numerically.Comment: Keywords: nonlinear waves, thermo-mechanical coupling, martensite transformations, Ginzburg-Landau theory, Chebyshev collocation metho

Single-molecule FRET investigation of SNARE-mediated exocytosis regulation

In the neuron, neurotransmitter release is mediated by SNARE (soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor) proteins. SNARE-dependent synaptic vesicle membrane and plasma membrane fusion is a multiple-step event and a tightly regulated process. Vesicle-anchored (v-) SNARE from synaptic vesicles associates with target plasma membrane-anchored (t-) SNARE to form a trans-SNAREpin complex. When the triggering signal arrives, v-SNARE and t-SNARE mediate the membrane full fusion and extend on one side of the membrane, forming a cis-conformation. During the whole process, SNARE complex with the help of regulators overcomes the energy barriers to fuse two apposed membranes and ensures that fusion proceeds at the correct time and place. Currently, there are some key questions that remain regarding SNARE-mediated exocytosis regulation. First, among the SNARE regulators, complexin is a small SNARE-binding protein that is thought to inhibit membrane fusion before Ca2+ triggering signal arrives. Although such an inhibitory role of complexin has been reported, its structural basis is very controversially discussed. Second, as the central machinery of neurotransmitters release, all three SNARE proteins are targets of different botulinum neurotoxins (BoNTs). Even though BoNT A and E cleave SNAP-25 at the C-terminus to inhibit SNARE-dependent membrane fusion, the detailed effects of BoNT A and E cleavage on SNARE complex folding pathway, conformation and function remain largely elusive. Third, the cis-SNARE complex contains 16 layers. BoNT E and A cleave SNAP-25 at residue 180 within layer \u27+2\u27 and residue 197 within layer \u27+7\u27, separately. The effect of SNAP-25 layers on SNARE complex formation has not been systematically studied. Also, another knowledge gap is why naturally selected BoNT E and A choose to cleave SNAP-25 at residue 180 and 197. In this thesis, to solve the aforementioned questions, we primarily used single-molecule fluorescence resonance energy transfer (smFRET) to investigate the trans-SNAREpin and cis-SNARE complex formation and structure in the presence of SNARE regulators. Our results demonstrate that complexin splits the SNARE core in the C-terminal region to inhibit further SNARE zippering. We also conclude that the two membranes are necessary for the proper complexin function and are an integral part of the synaptic vesicle fusion regulatory machinery. SNAP-25E, the cleavage product by BoNT E, significantly decreases t- and v-SNARE pairing. The cleavage product by BoNT A SNAP-25A, however, does not affect the t- and v-SNARE pairing but mildly decreases SNARE zippering. In addition, our results unveil a delicate alpha-helix nucleation process at the SNAP-25 C-terminal motif (SC) downstream layers. The results also shed light on why BoNT E but not BoNT A can induce neuron degeneration

Two Rules on the Protein-Ligand Interaction

So far, we still lack a clear molecular mechanism to explain the protein-ligand interaction on the basis of electronic structure of a protein. By combining the calculation of the full electronic structure of a protein along with its hydrophobic pocket and the perturbation theory, we found out two rules on the protein-ligand interaction. One rule is the interaction only occurs between the lowest unoccupied molecular orbitals (LUMOs) of a protein and the highest occupied molecular orbital (HOMO) of its ligand, not between the HOMOs of a protein and the LUMO of its ligand. The other rule is only those residues or atoms located both on the LUMOs of a protein and in a surface pocket of a protein are activity residues or activity atoms of the protein and the corresponding pocket is the ligand binding site. These two rules are derived from the characteristics of energy levels of a protein and might be an important criterion of drug design

Innovative Bathtub Shower Chair for Geriatric

ME450 Capstone Design and Manufacturing Experience: Winter 2010Showering in a bathtub is a key barrier for the rapidly growing geriatric generation. Based on previous ME 450 projects of designing a shower chair our team will improve the chair to prepare it for commercial use. This project is sponsored by Albert Shih, Naomi Gilbert, and Susan Murphy. The new shower chair should allow independence for an elderly person to get into and out of the bath safely. It will also be able to fold up in the shower to allow others to use the shower as well. The device will help geriatric patients safely bathe while maintaining privacy and stability.http://deepblue.lib.umich.edu/bitstream/2027.42/109370/1/me450w10project13_report.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109370/2/me450w10project13_photo.jp