54,376 research outputs found

    Simulation of the small punch creep test with consideration of variation of material properties

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    A new finite element model of the small punch creep test is described. The material constitutive relationship for creep considered is a simple Norton power law: in this study the exponent in the power law is varied for each element to simulate the random behaviour of creep. The influence of this random variation, and the effect of the friction factor between the punch and specimen, on the deformation and stress field has been investigated

    Macroscopic Kinetic Effect of Cell-to-Cell Variation in Biochemical Reactions

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    Genetically identical cells under the same environmental conditions can show strong variations in protein copy numbers due to inherently stochastic events in individual cells. We here develop a theoretical framework to address how variations in enzyme abundance affect the collective kinetics of metabolic reactions observed within a population of cells. Kinetic parameters measured at the cell population level are shown to be systematically deviated from those of single cells, even within populations of homogeneous parameters. Because of these considerations, Michaelis-Menten kinetics can even be inappropriate to apply at the population level. Our findings elucidate a novel origin of discrepancy between in vivo and in vitro kinetics, and offer potential utility for analysis of single-cell metabolomic data

    Scalable Breadth-First Search on a GPU Cluster

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    On a GPU cluster, the ratio of high computing power to communication bandwidth makes scaling breadth-first search (BFS) on a scale-free graph extremely challenging. By separating high and low out-degree vertices, we present an implementation with scalable computation and a model for scalable communication for BFS and direction-optimized BFS. Our communication model uses global reduction for high-degree vertices, and point-to-point transmission for low-degree vertices. Leveraging the characteristics of degree separation, we reduce the graph size to one third of the conventional edge list representation. With several other optimizations, we observe linear weak scaling as we increase the number of GPUs, and achieve 259.8 GTEPS on a scale-33 Graph500 RMAT graph with 124 GPUs on the latest CORAL early access system.Comment: 12 pages, 13 figures. To appear at IPDPS 201


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    Consumers in the United States consume 53 pounds of pork per capita per year. Forty percent of that pork enters the market by way of a contract with a packer or an integrated supply chain arrangement. Chinese consumers consume 37 pounds per capita. Eighty percent of that pork is produced in the backyards of millions of households all over the countryside. The supply chain that brings pork from hog to human is clearly different in these two countries, but both are moving in the same direction. In the United States, pork breeding produced leaner but heavier hogs by the late 1990's. This was largely in response to consumer demand for leaner meat and processors demand for less waste. Stricter sanitation regulation and quality control by food manufacturers led to a more integrated supply chain. Food companies contract with farmers for hogs with particular characteristics being demanded by consumers and retailers. Half of fresh pork and forty percent of processed pork is sold through foodservice establishments in the U.S. Consumers need for time-saving food is revealed by the portion of pork they eat away from home (42% of $35 billion sales) and by the mix of fresh (27%) and processed (73%) pork purchased in retail stores. The emphasis in the U.S. supply chain for pork is on delivering consistent quality of safe meat to consumers all the time. There is considerable research into new pork products. The top ten processing plants handle 43 percent of the total output. China is the largest pork producer in the world slaughtering 526.7 million hogs in 2000, over five times as many as the United States. Although commercial operations and specialized households are growing they provide only about twenty percent of all China's pork. Lower quality and sanitation standards prevent pork produced in backyards from entering the westernized/commercial supply chain but it is an important source of meat in the inland and rural areas of China. Coastal cities have more commercial and imported pork. For example, in Beijing sixty percent of production is from commercial farms. The advent of retail supermarkets and higher incomes in China foretell an increase in commercial pork operations. Direct foreign investment by key Western food companies and retailers are leading the standards for food safety and handling in the larger cities. Based on current pork consumption at various income levels, it is estimated that pork consumption will grow more than seven percent in Chinese cities and 1.5 percent in the countryside over the next ten years. This translates into an additional 12 million pounds of pork in 2011 with the urban consumption surpassing the rural consumption. The pork industry will be driven to emphasize quality, sanitation, and convenience in China as they already do in the United States. With China entering the World Trade Organization (WTO) more pork imports can be expected. Exports will depend on meeting the quality and safety standards of importing countries.Industrial Organization, Livestock Production/Industries,

    Higher Spin Interactions in Four Dimensions: Vasiliev vs. Fronsdal

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    We consider four-dimensional Higher-Spin Theory at the first nontrivial order corresponding to the cubic action. All Higher-Spin interaction vertices are explicitly obtained from Vasiliev's equations. In particular, we obtain the vertices that are not determined solely by the Higher-Spin algebra structure constants. The dictionary between the Fronsdal fields and Higher-Spin connections is found and the corrections to the Fronsdal equations are derived. These corrections turn out to involve derivatives of arbitrary order. We observe that the vertices not determined by the Higher-Spin algebra produce naked infinities, when decomposed into the minimal derivative vertices and improvements. Therefore, standard methods can only be used to check a rather limited number of correlation functions within the HS AdS/CFT duality. A possible resolution of the puzzle is discussed.Comment: 56 pages=40+Appendices; 1 figure; typos fixed, one ref adde
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