Integrated force method versus displacement method for finite element analysis

A novel formulation termed the integrated force method (IFM) has been developed in recent years for analyzing structures. In this method all the internal forces are taken as independent variables, and the system equilibrium equations (EE's) are integrated with the global compatibility conditions (CC's) to form the governing set of equations. In IFM the CC's are obtained from the strain formulation of St. Venant, and no choices of redundant load systems have to be made, in constrast to the standard force method (SFM). This property of IFM allows the generation of the governing equation to be automated straightforwardly, as it is in the popular stiffness method (SM). In this report IFM and SM are compared relative to the structure of their respective equations, their conditioning, required solution methods, overall computational requirements, and convergence properties as these factors influence the accuracy of the results. Overall, this new version of the force method produces more accurate results than the stiffness method for comparable computational cost

Compatibility conditions of structural mechanics for finite element analysis

The equilibrium equations and the compatibility conditions are fundamental to the analyses of structures. However, anyone who undertakes even a cursory generic study of the compatibility conditions can discover, with little effort, that historically this facet of structural mechanics had not been adequately researched by the profession. Now the compatibility conditions (CC's) have been researched and are understood to a great extent. For finite element discretizations, the CC's are banded and can be divided into three distinct categories: (1) the interface CC's; (2) the cluster or field CC's; and (3) the external CC's. The generation of CC's requires the separating of a local region, then writing the deformation displacement relation (ddr) for the region, and finally, the eliminating of the displacements from the ddr. The procedure to generate all three types of CC's is presented and illustrated through examples of finite element models. The uniqueness of the CC's thus generated is shown

Subharmonics, Chaos, and Beyond

While studying finite amplitude ultrasonic wave resonance in a one dimensional liquid-filled cavity, which is formed by a narrow band transducer and a plane reflector, subharmonics of the driver's frequency were observed in addition to the expected harmonic structure. Subsequently it was realized that the system was one of the many examples where parametric resonance takes place and in which the observed subharmonics are parametrically generated. Parametric resonance occurs in any physical system which has a periodically modulated natural frequency. The generation mechanism also requires a sufficiently high threshold value of the driving amplitude so that the system becomes increasingly nonlinear in response. The nonlinear features were recently investigated and are the objective of this presentation. An ultrasonic interferometer with optical precision was built. The transducers were compressional undamped quartz and Lithium Niobate crystals ranging from 1-10 Mhz, and driven by a high power amplifier. Both an optical diffraction system and a receive transducer attached to an aligned reflector with lapped flat and parallel surfaces were used to observe the generated frequency components in the cavity

Near-infrared optical properties and proposed phase-change usefulness of transition metal disulfides

The development of photonic integrated circuits would benefit from a wider selection of materials that can strongly-control near-infrared (NIR) light. Transition metal dichalcogenides (TMDs) have been explored extensively for visible spectrum opto-electronics, but the NIR properties of these layered materials have been less-studied. The measurement of optical constants is the foremost step to qualify TMDs for use in NIR photonics. Here we measure the complex optical constants for select sulfide TMDs (bulk crystals of MoS2, TiS2 and ZrS2) via spectroscopic ellipsometry in the visible-to-NIR range. Through Mueller matrix measurements and generalized ellipsometry, we explicitly measure the direction of the ordinary optical axis. We support our measurements with density functional theory (DFT) calculations, which agree with our measurements and predict giant birefringence. We further propose that TMDs could find use as photonic phase-change materials, by designing alloys that are thermodynamically adjacent to phase boundaries between competing crystal structures, to realize martensitic (i.e. displacive, order-order) switching.Comment: supplementary at end of document. 6 main figure

Contrôle da origem e pureza de gordura bovina comercial brasileira, visando sua possível participação no mercado internacional.

bitstream/item/65356/1/CTAA-DOCUMENTOS-2-CONTROLE-DA-ORIGEM-E-PUREZA-DE-GORDURA-BOVINA-COMERCIAL-BRASILEIRA-VISANDO-SUA-.pd

Moduli Stacks of Vector Bundles and Frobenius Morphisms

We describe the action of the different Frobenius morphisms on the cohomology ring of the moduli stack of algebraic vector bundles of fixed rank and determinant on an algebraic curve over a finite field in characteristic p and analyse special situations like vector bundles on the projective line and relations with infinite Grassmannians.Comment: 19 page

Where did all the irrigators go? Trends in irrigation and demographics in Kansas

Presented at the 2006 Central Plains irrigation conference on February 21-22 in Colby, Kansas.The 2000 United States Census indicated that Kansas had grown by 8.51 percent in population since 1990, compared to the national average growth rate of 13.15 percent. Only nine (9) of 105 counties in Kansas experienced growth equal to or greater than the national average growth rate. From 2000-2004 only 8 counties grew at or above the national average growth rate. In 1990, Kansans were 1.00 percent of the U.S. population, in 2004 only 0.94% of the population. The 2004 population estimates had 56 of 105 counties in Kansas declining in population since 2000. Of the 54 counties overlying the High Plains aquifer, only three (3) counties had equal or greater growth than the national average. In addition the census also indicated a cultural transition as many counties experienced domestic out-migration and foreign immigration. Agricultural Census data document a 5.26 percent decrease in the total market value of agricultural products from 1997 to 2002, while the total number of farms increased 4.58 percent in Kansas during the same period. The number of Irrigated farms decreased by 3.58 percent with total irrigated acres declining by only 1.07 percent to 2.678 million acres over the same five year period. Total acreage in crop production declined 1.59 percent, while the market value of crops sold decreasing 24.9% from $3.22 billion in 1997 to$2.42 billion in 2002. Since 1990, irrigation technology has dramatically changed to more efficient low pressure pivot and SDI (subsurface drip irrigation) systems. With more efficient water use, irrigators have been able to grow significantly more corn and other water intensive crops. Given the 3.5 percent decrease in the number of irrigated farms since 1997, the resulting 1.08 percent decline in irrigated acres indicates increased acreage efficiency by remaining irrigators. This presentation intends to demonstrate spatial and temporal trends in irrigation and demographics for Kansas, with focus on the 54 counties overlying the High Plains Aquifer