Analytical investigation of squeeze film dampers

Squeeze film damping effects naturally occur if structures are subjected to loading situations such that a very thin film of fluid is trapped within structural joints, interfaces, etc. An accurate estimate of squeeze film effects is important to predict the performance of dynamic structures. Starting from linear Reynolds equation which governs the fluid behavior coupled with structure domain which is modeled by Kirchhoff plate equation, the effects of nondimensional parameters on the damped natural frequencies are presented using boundary characteristic orthogonal functions. For this purpose, the nondimensional coupled partial differential equations are obtained using Rayleigh-Ritz method and the weak formulation, are solved using polynomial and sinusoidal boundary characteristic orthogonal functions for structure and fluid domain respectively. In order to implement present approach to the complex geometries, a two dimensional isoparametric coupled finite element is developed based on Reissner-Mindlin plate theory and linearized Reynolds equation. The coupling between fluid and structure is handled by considering the pressure forces and structural surface velocities on the boundaries. The effects of the driving parameters on the frequency response functions are investigated. As the next logical step, an analytical method for solution of squeeze film damping based upon Green’s function to the nonlinear Reynolds equation considering elastic plate is studied. This allows calculating modal damping and stiffness force rapidly for various boundary conditions. The nonlinear Reynolds equation is divided into multiple linear non-homogeneous Helmholtz equations, which then can be solvable using the presented approach. Approximate mode shapes of a rectangular elastic plate are used, enabling calculation of damping ratio and frequency shift as well as complex resistant pressure. Moreover, the theoretical results are correlated and compared with experimental results both in the literature and in-house experimental procedures including comparison against viscoelastic dampers.

Numerical modeling of the failure mechanisms in Si thin film anode for Li-ion batteries

In recent times, the demand for the storage of electrical energy has grown rapidly for both static applications and the portable electronics enforcing the substantial improvement in battery systems, and Li-ion batteries have been proven to have maximum energy storage density in all rechargeable batteries. However, major breakthroughs are required to consummate the requirement of higher energy density with lower cost to penetrate new markets. Graphite anode having limited capacity has become a bottle neck in the process of developing next generation batteries and can be replaced by higher capacity metals such as Silicon. In the present study we are focusing on the mechanical behavior of the Si-thin film anode under various operating conditions. A numerical model is developed to simulate the intercalation induced stress and the failure mechanism of the complex anode structure. Effect of the various physical phenomena such as diffusion induced stress, plasticity and the crack propagation are investigated to predict better performance parameters for improved design.

Not your mother's Latinas : film representations for a new millennium

This dissertation seeks to contribute to film, feminist and Latino/a studies by exploring the construction and ideological implications of representations of Latinas in four recent, popular U.S. films: Girlfight (Kusama 2000), Maid in Manhattan (Wang 2002), Real Women Have Curves (Cardoso 2002) and Spanglish (Brooks 2004). These films were released following a time of tremendous growth in the population and the political and economic strength of the Latina/o community as well as a rise in popularity and visibility in the 1990s of entertainers like Selena and actresses such as Jennifer Lopez and Salma Hayek. Drawing on the critical concepts of hybridity, Latinidad, and Bakhtinian dialogism, I analyze these films from a cultural and historical perspective to consider whether and to what degree, assuming changes in the situation of Latinas/os in the 1990’s, representations of Latinas have also changed. Specifically, in this dissertation I consider the ways in which the terrain of the Latina body is articulated in these films in relation to competing societal, cultural and familial conflicts, focusing on the body as a site of struggle where relationships collide, interact and are negotiated. In this dissertation I argue that most of the representations of Latinas in these films defy easy categorization, featuring complex characters grappling with economic issues, intergenerational differences, abuse, mother-daughter relationships, notions of beauty, familial expectations and the very real tensions between Latina/o cultural beliefs and practices and the dominant Anglo culture of the United States. Specifically, I argue that narrative and visual representation of Latina bodies in these films reflects a change in the Latinas offered for consumption to film viewers, presenting us with what some critics have called ‘emergent’ Latinas: conflicted and multilayered representations that in some cases challenge dominant ideologies and offer new demonstrations of Latina agency.