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中国力学学会学术大会'2005

作者： Yong Yook Kong patel mihir Rutgers University Civil and Environmental EngineeringPiscatawayNJUSA

We present a new analytical tool for estimating the quartz resonator Q and other figures of merit by an energy sink method. Currently there are no analytical tools for estimating the Q of a resonator without an apriori assumption of the resonator impedance or damping. At the present time, the finite element software require an assumption of either the resistance of the resonator, or the Q value, in order to get good agreement with the measured data. We propose an energy sink method for evaluating resonator designs and their figures of merits. Results for quartz thickness shear, AT-cut resonators are presented. Our energy sink method is more realistic

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QUARTZ RESONATORS WITH MECHANICAL DAMPING AND RESISTANCE IN CURRENT CONDUCTION

QUARTZ RESONATORS WITH MECHANICAL DAMPING AND RESISTANCE IN ...

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中国力学学会学术大会'2005

作者： Yong Yook-Kong patel mihir Lam CS Rutgers University Civil and Environmental EngineeringPiscatawayNJUSA TXC Corporation Ping Cheng CityTaoyuan CountyTaiwanChina

Lee, Liu and Ballato presented the 3-D equations of linear piezoelectricity with quasi-electrostatic approximation which include losses attributed to mechanical damping in solid and resistance in current conduction. Lamb and Richter measured the first set of values of the viscosity tensor for quartz, and Ballato, by using these values, calculated the Q factor for various cuts of quartz. There is a necessity for better and more realistic modeling of resonators and filters due mainly to miniaturizations, and the rapid advances in frequency ranges in telecommunication Unfortunately, there is currently no finite element software for estimating the Q of

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Gut sterilization in experimental colitis leukocyte mediated colon injury, and effects on angiogenesis/lymphangiogenesis

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Open Journal of Gastroenterology 2013年第1期3卷 12-24页

作者： mihir patel Justin Olinde Allison Tatum Chaitanya V. Ganta Walter E. Cromer Ankur R. Sheth Merilyn H. Jennings J. Michael Mathis Traci Testerman Paul A. Jordan Kenneth Manas Christopher P. Monceaux J. Steven Alexander Department of Cellular Biology and Anatomy LSU Health Shreveport Shreveport USA Department of Gastroenterology and Hepatology LSU Health Shreveport Shreveport USA Department of Microbiology and Immunology LSU Health Shreveport Shreveport USA Department of Molecular and Cellular Physiology LSU Health Shreveport Shreveport USA

Inappropriate responses to normal commensal bacteria trigger immune activation in both inflammatory bowel disease and experimental colitis. How gut flora contribute to the pathogenesis of inflammatory bowel disease is unclear, but may involve entrapment of leukocytes and remodeling of the vascular system. Here we evaluated how the progression and tissue remodeling in experimental colitis differ in a germ- free model of mouse colitis. Four treatment groups were used: control, antibiotic-treated (ABX), dextran sulfate colitis (DSS) and DSS pre- and co-treated with antibiotics (DSS + ABX). In days 0 - 3 of the study, germ-free mice received antibiotics (vancomycin, neomycin, and metronidazole). During the next 11 days, antibiotics were continued and DSS (3%) added to “colitis” groups. Disease activity, weight, stool form and blood were monitored daily. Mice were sacrificed and tissue samples harvested. Histopathological scores in controls (0.00) and in ABX (1.0+/–0.81) were significantly (p –0). Extents of injury, inflammation and crypt damage were all improved in DSS + ABX. The Disease Activity Index score (day 11) was significantly worse in the DSS group compared to the DSS + ABX group. Stool blood and form scores were also significantly improved among these groups. Importantly, myeloper- oxidase was significantly reduced in DSS + ABX, indicating that neutrophil infiltration was blocked. Colitis was associated with an increase in blood and lymphatic vessels;both of these events were also significantly reduced by gut sterilization. Our experiment shows that clinical and histopathological severity of colitis was significantly worse in the DSS colitis group compared to the DSS + ABX group, supporting the hypothesis that development of IBD is likely to be less severe with appropriate antibiotic treatment. In particular, gut sterilization effectively reduces leuko- cyte-dependent (PMN) injury to improve outcomes and may be an important target for therapy.

关键词： Crohn’s Disease Antibiotics Myeloperoxidase Lymphatics Angiogenesis

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Piezoelectric resonators with mechanical damping and resistance in current conduction

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Science China(Physics,Mechanics & Astronomy) 2007年第5期50卷 650-672页

作者： Yook-Kong YONG mihir S patel Department of Civil and Environmental Engineering Rutgers University Piscataway NJ 08854 USA

A novel design method for high Q piezoelectric resonators was presented and proposed using the 3-D equations of linear piezoelectricity with quasi-electrostatic approximation which include losses attributed to mechanical damping in solid and resistance in current conduction. There is currently no finite element software for estimating the Q of a resonator without apriori assumptions of the resonator im- pedance or damping. There is a necessity for better and more realistic modeling of resonators and filters due to miniaturization and the rapid advances in frequency ranges in telecommunication. We presented new three-dimensional finite element models of quartz and barium titanate resonators with mechanical damping and resistance in current conduction. Lee, Liu and Ballato’s 3-D equations of linear piezoelectricity with quasi-electro- static approximation which include losses attributed to mechanical damping in solid and resistance in current conduction were formulated in a weak form and implemented in COMSOL. The resulting finite element model could predict the Q and other electrical parameters for any piezoelectric resonator without apriori as- sumptions of damping or resistance. Forced and free vibration analyses were per- formed and the results for the Q and other electrical parameters were obtained. Comparisons of the Q and other electrical parameters obtained from the free vibra- tion analysis with their corresponding values from the forced vibration analysis were found to be in excellent agreement. Hence, the frequency spectra obtained from the free vibration analysis could be used for designing high Q resonators. Results for quartz thickness shear AT-cut and SC-cut resonators and thickness stretch poled barium titanate resonators were presented. An unexpected benefit of the model was the prediction of resonator Q with energy losses via the mounting supports.

关键词： quality factor, energy sink, MEMS, mechanical dissipation and viscosity, electrical conductivity, piezoelectric materials

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