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Physical Review E 2009年第4期79卷 041309-041309页

作者： Y. Jiao F. H. Stillinger S. Torquato Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08540 USA

Dense hard-particle packings are intimately related to the structure of low-temperature phases of matter and are useful models of heterogeneous materials and granular media. Most studies of the densest packings in three dimensions have considered spherical shapes, and it is only more recently that nonspherical shapes (e.g., ellipsoids) have been investigated. Superballs (whose shapes are defined by |x1|2p+|x2|2p+|x3|2p≤1) provide a versatile family of convex particles (p≥0.5) with both cubic-like and octahedral-like shapes as well as concave particles (0

关键词： Temperature

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Interactions leading to disordered ground states and unusual low-temperature behavior

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Physical Review E 2009年第3期80卷 031105-031105页

作者： Robert D. Batten Frank H. Stillinger Salvatore Torquato Department of Chemical Engineering Princeton University Princeton New Jersey 08544 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Princeton Materials Institute Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08544 USA

We have shown that any pair potential function v(r) possessing a Fourier transform V(k) that is positive and has compact support at some finite wave number K yields classical disordered ground states for a broad density range [R. D. Batten, F. H. Stillinger, and S. Torquato, J. Appl. Phys. 104, 033504 (2008)]. By tuning a constraint parameter χ (defined in the text), the ground states can traverse varying degrees of local order from fully disordered to crystalline ground states. Here, we show that in two dimensions, the “k-space overlap potential,” where V(k) is proportional to the intersection area between two disks of diameter K whose centers are separated by k, yields anomalous low-temperature behavior, which we attribute to the topography of the underlying energy landscape. At T=0, for the range of densities considered, we show that there is continuous energy degeneracy among Bravais-lattice configurations. The shear elastic constant of ground-state Bravais-lattice configurations vanishes. In the harmonic regime, a significant fraction of the normal modes for both amorphous and Bravais-lattice ground states have vanishing frequencies, indicating the lack of an internal restoring force. Using molecular-dynamics simulations, we observe negative thermal-expansion behavior at low temperatures, where upon heating at constant pressure, the system goes through a density maximum. For all temperatures, isothermal compression reduces the local structure of the system unlike typical single-component systems.

关键词： Ground state

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Dense packings of polyhedra: Platonic and Archimedean solids

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Physical Review E 2009年第4期80卷 041104-041104页

作者： S. Torquato Y. Jiao Department of Chemistry Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08540 USA Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544 USA

Understanding the nature of dense particle packings is a subject of intense research in the physical, mathematical, and biological sciences. The preponderance of previous work has focused on spherical particles and very little is known about dense polyhedral packings. We formulate the problem of generating dense packings of nonoverlapping, nontiling polyhedra within an adaptive fundamental cell subject to periodic boundary conditions as an optimization problem, which we call the adaptive shrinking cell (ASC) scheme. This optimization problem is solved here (using a variety of multiparticle initial configurations) to find the dense packings of each of the Platonic solids in three-dimensional Euclidean space R3, except for the cube, which is the only Platonic solid that tiles space. We find the densest known packings of tetrahedra, icosahedra, dodecahedra, and octahedra with densities 0.823…, 0.836…, 0.904…, and 0.947…, respectively. It is noteworthy that the densest tetrahedral packing possesses no long-range order. Unlike the densest tetrahedral packing, which must not be a Bravais lattice packing, the densest packings of the other nontiling Platonic solids that we obtain are their previously known optimal (Bravais) lattice packings. We also derive a simple upper bound on the maximal density of packings of congruent nonspherical particles and apply it to Platonic solids, Archimedean solids, superballs, and ellipsoids. Provided that what we term the “asphericity” (ratio of the circumradius to inradius) is sufficiently small, the upper bounds are relatively tight and thus close to the corresponding densities of the optimal lattice packings of the centrally symmetric Platonic and Archimedean solids. Our simulation results, rigorous upper bounds, and other theoretical arguments lead us to the conjecture that the densest packings of Platonic and Archimedean solids with central symmetry are given by their corresponding densest lattice packings. This can be regarded to be

关键词： Optimization

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Optimal Packings of Superdisks and the Role of Symmetry

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Physical Review Letters 2008年第24期100卷 245504-245504页

作者： Y. Jiao F. H. Stillinger S. Torquato Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08540 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA

Almost all studies of the densest particle packings consider convex particles. Here, we provide exact constructions for the densest known two-dimensional packings of superdisks whose shapes are defined by |x1|2p+|x2|2... 详细信息

关键词： Condensed matter physics

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A scholarship recruitment and selection strategy that successfully attracts diverse and academically talented freshmen

A scholarship recruitment and selection strategy that succes...

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114th Annual ASEE Conference and Exposition, 2007

作者： Papadopoulos, Chris Brucks, Karen Key, Eric Munson, Ethan Vairavan, K. University of Wisconsin Milwaukee United States Department of Civil Engineering and Mechanics University of Wisconsin Milwaukee United States UWM Computer Science Engineering and Mathematics Scholarship Program Brazil Department of Mathematical Sciences University of Wisconsin Milwaukee United States Mathematical Science Department UWM's Actuarial Science Program Department of Electrical Engineering and Computer Science University of Wisconsin-Milwaukee United States ACM SIGWEB Group on Hypertext Hypermedia and the Web Department of Electrical Engineering and Computer Science Department of Medical Informatics

We describe recruitment and selection procedures of the Computer Science, engineering, and mathematics Scholarship (CSEMS) program at the University of Wisconsin-Milwaukee that are designed to attract students who are academically talented, financially needy, and diverse. In particular, we address the possible exclusion of underrepresented minority students that could result if standardized test scores are used indiscriminately as metrics of student performance in both recruitment and selection procedures. We describe a "conditional award" process that enables students whose calculus placement is moderately below calculus to competitively apply for and receive scholarships;awards to such students are activated on the condition that they attempt to attain calculus placement prior to matriculation. We present data that demonstrate moderate effectiveness of these methods in fostering diversity among our scholars and reasonably encouraging retention and estimated graduation rates. We discuss areas of improvement for future program years, such as forging new partnerships with local Project Lead The Way high schools to recruit higher numbers of females and minorities, and developing new mentoring opportunities to reduce attrition, especially among underrepresented minority students. © American Society for engineering Education, 2007.

关键词： Social aspects

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Tibet air shower array: results and future plan

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Journal of Physics: Conference Series 2008年第6期120卷

作者： M Amenomori X J Bi D Chen S W Cui Danzengluobu L K Ding X H Ding C Fan C F Feng Z Feng Z Y Feng X Y Gao Q X Geng H W Guo H H He M He K Hibino N Hotta H Hu H B Hu J Huang Q Huang H Y Jia F Kajino K Kasahara Y Katayose C Kato K Kawata Labaciren G M Le A F Li J Y Li Y -Q Lou H Lu S L Lu X R Meng K Mizutani J Mu K Munakata A Nagai H Nanjo M Nishizawa M Ohnishi I Ohta H Onuma T Ouchi S Ozawa J R Ren T Saito T Y Saito M Sakata T K Sako M Shibata A Shiomi T Shirai H Sugimoto M Takita Y H Tan N Tateyama S Torii H Tsuchiya S Udo B Wang H Wang X Wang Y Wang Y G Wang H R Wu L Xue Y Yamamoto C T Yan X C Yang S Yasue Z H Ye G C Yu A F Yuan T Yuda H M Zhang J L Zhang N J Zhang X Y Zhang Y Zhang Zhaxisangzhu X X Zhou (The Tibet ASγ Collaboration) Department of Physics Hirosaki University Hirosaki 036-8561 Japan Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China Faculty of Engineering Yokohama National University Yokohama 240-8501 Japan Department of Physics Hebei Normal University Shijiazhuang 050016 China Department of Mathematics and Physics Tibet University Lhasa 850000 China Department of Physics Shandong University Jinan 250100 China Institute of Modern Physics SouthWest Jiaotong University Chengdu 610031 China Department of Physics Yunnan University Kunming 650091 China Faculty of Engineering Kanagawa University Yokohama 221-8686 Japan Faculty of Education Utsunomiya University Utsunomiya 321-8505 Japan Institute for Cosmic Ray Research University of Tokyo Kashiwa 277-8582 Japan Department of Physics Konan University Kobe 658-8501 Japan Research Institute for Science and Engineering Waseda University Tokyo 169-8555 Japan Department of Physics Shinshu University Matsumoto 390-8621 Japan Center of Space Science and Application Research Chinese Academy of Sciences Beijing 100080 China Physics Department and Tsinghua Center for Astrophysics Tsinghua University Beijing 100084 China Advanced Media Network Center Utsunomiya University Utsunomiya 321-8585 Japan National Institute of Informatics Tokyo 101-8430 Japan Tochigi Study Center University of the Air Utsunomiya 321-0943 Japan Department of Physics Saitama University Saitama 338-8570 Japan Tokyo Metropolitan College of Industrial Technology Tokyo 116-8523 Japan Max-Planck-Institut für Physik München D-80805 Deutschland Shonan Institute of Technology Fujisawa 251-8511 Japan RIKEN Wako 351-0198 Japan School of General Education Shinshu University Matsumoto 390-8621 Japan Paper presented at the conference by K. Kawata

The Tibet air shower array, which has an effective area of 36,900 m2, has been in operation at Yangbajing in Tibet, China at an altitude of 4,300 m above sea level. In this paper, we will briefly introduce the recent gamma-ray observation with the present Tibet air shower array and our future plan which is called the Tibet muon detector (MD) project.

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Implication of the sidereal anisotropy of ∼5 TeV cosmic ray intensity observed with the Tibet III air shower array

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AIP Conference Proceedings 2007年第1期932卷 283-289页

作者： Amenomori, M. Ayabe, S. Bi, X.J. Chen, D. Cui, S.W. Danzengluobu Ding, L.K. Ding, X.H. Feng, C.F. Feng, Zhaoyang Feng, Z.Y. Gao, X.Y. Geng, Q.X. Guo, H.W. He, H.H. He, M. Hibino, K. Hotta, N. Hu, Haibing Hu, H.B. Huang, J. Huang, Q. Jia, H.Y. Kajino, F. Kasahara, K. Katayose, Y. Kato, C. Kawata, K. Labaciren Le, G.M. Li, A.F. Li, J.Y. Lou, Y.-Q. Lu, H. Lu, S.L. Meng, X.R. Mizutani, K. Mu, J. Munakata, K. Nagai, A. Nanjo, H. Nishizawa, M. Ohnishi, M. Ohta, I. Onuma, H. Ouchi, T. Ozawa, S. Ren, J.R. Saito, T. Saito, T.Y. Sakata, M. Sako, T.K. Sasaki, T. Shibata, M. Shiomi, A. Shirai, T. Sugimoto, H. Takita, M. Tan, Y.H. Tateyama, N. Torii, S. Tsuchiya, H. Udo, S. Wang, B. Wang, H. Wang, X. Wang, Y.G. Wu, H.R. Xue, L. Yamamoto, Y. Yan, C.T. Yang, X.C. Yasue, S. Ye, Z.H. Yu, G.C. Yuan, A.F. Yuda, T. Zhang, H.M. Zhang, J.L. Zhang, N.J. Zhang, X.Y. Zhang, Y. Zhaxisangzhu Zhou, X.X. Department of Physics Hirosaki University Hirosaki 036-8561 Japan Department of Physics Saitama University Saitama 338-8570 Japan Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China Faculty of Engineering Yokohama National University Yokohama 240-8501 Japan Department of Physics Hebei Normal University Shijiazhuang 050016 China Department of Mathematics and Physics Tibet University Lhasa 850000 China Department of Physics Shandong University Jinan 250100 China Institute of Modern Physics SouthWest Jiaotong University Chengdu 610031 China Department of Physics Yunnan University Kunming 650091 China Faculty of Engineering Kanagawa University Yokohama 221-8686 Japan Faculty of Education Utsunomiya University Utsunomiya 321-8505 Japan Institute for Cosmic Ray Research University of Tokyo Kashiwa 277-8582 Japan Department of Physics Konan University Kobe 658-8501 Japan Faculty of Systems Engineering Shibaura Institute of Technology Saitama 337-8570 Japan Department of Physics Shinshu University Matsumoto 390-8621 Japan Center of Space Science and Application Research Chinese Academy of Sciences Beijing 100080 China Physics Department Tsinghua University Beijing 100084 China Tsinghua Center for Astrophysics Tsinghua University Beijing 100084 China Advanced Research Institute for Science and Engineering Waseda University Tokyo 169-8555 Japan Advanced Media Network Center Utsunomiya University Utsunomiya 321-8585 Japan National Institute of Informatics Tokyo 101-8430 Japan Tochigi Study Center University of the Air Utsunomiya 321-0943 Japan Tokyo Metropolitan College of Industrial Technology Tokyo 116-8523 Japan Shonan Institute of Technology Fujisawa 251-8511 Japan RIKEN Wako 351-0198 Japan School of General Education Shinshu University Matsumoto 390-8621 Japan

We show that the large-scale anisotropy of ∼5 TeV galactic cosmic ray (GCR) intensity observed by Tibet Air Shower experiment can be reproduced by the superposition of a bi-directional and uni-directional flows (UDF and BDF) of GCRs. The heliosphere is located inside the local interstellar cloud (LIC) very close to the inner edge of the LIC. If the GCR population is lower inside the LIC than outside, the BDF flow is expected from the parallel diffusion of GCRs into LIC along the local interstellar magnetic field (LISMF) connecting the heliosphere with the region outside the LIC, where the GCR population is higher. A type of the UDF, on the other hand, is expected from the B×n drift flux driven by a gradient of GCR density (n) in the LISMF (B). The LISMF orientation deduced from the best-fit direction of the BDF is almost parallel to the galactic plane and more consistent with the suggestion of Frisch (1996) than that of Lallement et al. (2005). We note that the model, if holds, yields the LISMF polarity together with its orientation. © 2007 American Institute of Physics.

关键词： Cosmic rays Extensive air shower

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Implication of the sidereal anisotropy of ∼5 TeV cosmic ray intensity observed with the Tibet III air shower array

Implication of the sidereal anisotropy of ∼5 TeV cosmic ray...

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30th International Cosmic Ray Conference, ICRC 2007

作者： Amenomori, M. Bi, X.J. Chen, D. Cui, S.W. Danzengluobu Ding, L.K. Ding, X.H. Fan, C. Feng, C.F. Feng, Zhaoyang Feng, Z.Y. Gao, X.Y. Geng, Q.X. Guo, H.W. He, H.H. He, M. Hibino, K. Hotta, N. Hu, Haibing Hu, H.B. Huang, J. Huang, Q. Jia, H.Y. Kajino, F. Kasahara, K. Katayose, Y. Kato, C. Kawata, K. Labaciren Le, G.M. Li, A.F. Li, J.Y. Lou, Y.-Q. Lu, H. Lu, S.L. Meng, X.R. Mizutani, K. Mu, J. Munakata, K. Nagai, A. Nanjo, H. Nishizawa, M. Ohnishi, M. Ohta, I. Onuma, H. Ouchi, T. Ozawa, S. Ren, J.R. Saito, T. Saito, T.Y. Sakata, M. Sako, T.K. Shibata, M. Shiomi, A. Shirai, T. Sugimoto, H. Takita, M. Tan, Y.H. Tateyama, N. Torii, S. Tsuchiya, H. Udo, S. Wang, B. Wang, H. Wang, X. Wang, Y. Wang, Y.G. Wu, H.R. Xue, L. Yamamoto, Y. Yan, C.T. Yang, X.C. Yasue, S. Ye, Z.H. Yu, G.C. Yuan, A.F. Yuda, T. Zhang, H.M. Zhang, J.L. Zhang, N.J. Zhang, X.Y. Zhang, Y. Zhang, Yi Zhaxisangzhu Zhou, X.X. Department of Physics Hirosaki University Hirosaki 036-8561 Japan Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China Faculty of Engineering Yokohama National University Yokohama 240-8501 Japan Department of Physics Hebei Normal University Shijiazhuang 050016 China Department of Mathematics and Physics Tibet University Lhasa 850000 China Department of Physics Shandong University Jinan 250100 China Institute of Modern Physics SouthWest Jiaotong University Chengdu 610031 China Department of Physics Yunnan University Kunming 650091 China Faculty of Engineering Kanagawa University Yokohama 221-8686 Japan Faculty of Education Utsunomiya University Utsunomiya 321- 8505 Japan Institute for Cosmic Ray Research University of Tokyo Kashiwa 277-8582 Japan Department of Physics Konan University Kobe 658-8501 Japan Research Institute for Science and Engineering Waseda University Tokyo 169-8555 Japan Department of Physics Shinshu University Matsumoto 390-8621 Japan Center of Space Science and Application Research Chinese Academy of Sciences Beijing 100080 China Physics Department and Tsinghua Center for Astrophysics Tsinghua University Beijing 100084 China Department of Physics Saitama University Saitama 338-8570 Japan Advanced Media Network Center Utsunomiya University Utsunomiya 321-8585 Japan National Institute of Informatics Tokyo 101-8430 Japan Tochigi Study Center University of the Air Utsunomiya 321-0943 Japan Tokyo Metropolitan College of Industrial Technology Tokyo 116-8523 Japan Max-Planck-Institut fur Physik Munchen D-80805 Deutschland Germany Shonan Institute of Technology Fujisawa 251-8511 Japan RIKEN Wako 351-0198 Japan School of General Education Shinshu University Matsumoto 390-8621 Japan

We show that the large-scale anisotropy of ∼5 TeV galactic cosmic ray (GCR) intensity observed by Tibet Air Shower experiment can be reproduced by the superposition of a bi-directional and uni-directional flows (BDF and UDF) of GCRs. The heliosphere is located inside the local interstellar cloud (LIC) very close to the inner edge of the LIC. If the GCR population is lower inside the LIC than outside, the BDF flow is expected from the parallel diffusion of GCRs into LIC along the local interstellar magnetic field (LISMF) connecting the heliosphere with the region outside the LIC, where the GCR population is higher. A type of the UDF, on the other hand, is expected from the B×δN drift flux driven by a gradient of GCR density (N) in the LISMF (B). The LISMF orientation deduced from the best-fit direction of the BDF is almost parallel to the galactic plane and more consistent with the suggestion of Frisch (1996) than that of Lallement et al. (2005). We note that the model gives the information on the LISMF polarity together with its orientation.

关键词： Anisotropy

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Parameter Stability of the Structural-Functional Model GREENLAB-Tomato as Affected by Plant Density and Biomass Data Acquisition

Parameter Stability of the Structural-Functional Model GREEN...

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International Symposium on Plant Growth Modeling and Applications (PMA)

作者： G. Louarn Q.X. Dong Y.M. Wang J.F. Barczi P. de Reffye Sino-French Laboratory of Informatics Automation and Applied Mathematics (LIAMA) Chinese Academy and Sciences Beijing China Department of Electronic Information College of Information and Electrical Engineering China Agricultural University Beijing China CIRAD UMR AMAP Montpellier France Digiplant Program INRIA Rocquencourt Le Chesnay France

In this study, we assessed the possibility of using the GREENLAB model to quantitatively simulate adaptive responses of tomato plants competing for light. The model was able to reproduce modifications induced by a reduction of plant spacing in dry matter production and in the allocation pattern. However, the analysis of parameter stability showed that some parameters were environment dependent and that an adjustment of model formalisms was required to explicitly represent the plant response. Model parameters also proved to be sensitive to the data acquisition procedure. We confirmed that target files composed of dry matter records lead to parameters that were better indicators of the carbohydrates metabolism at all densities.

关键词： Stability Bioinformatics Biomass Crops Predictive models Irrigation Production Data visualization Educational institutions Laboratories

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An Exponential Matrix Product Based Representation for Generalized Hypergeometric Functions of TypepFp

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Applied Numerical Analysis & Computational mathematics 2005年第1期2卷

作者： N. A. Baykara İrem Yaman Metin Demiralp Mathematics Department Faculty of Sciences and Letters Marmara University Göztepe 34722 İstanbul Turkey Group for Science and Methods of Computing Computational Science and Engineering Program Informatics Institute İstanbul Technical University Maslak 34469 İstanbul Turkey Phone: +90 212 285 70 77 Fax: +90 212 285 70 73 Phone: +90 212 285 70 82 Fax: +90 212 285 70 73

In this work, a new representation is developed for generalized hypergeometric functions of type p F p . To this end a first order vector differential equation is constructed in a way such that the derivative of the unknown vector has unit matrix coefficient. The solution vector differential equation is rewritten in the form of a series expansion. An infinite process of factor extractions and annihilations is employed to construct finally a vector differential equation that can be easily solved. Truncation of this scheme can be used to get approximations to hypergeometric functions of type p F p . A simple, yet meaningful, implementation seems to give quite promising results. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

关键词： Exponential matrix factorization generalized hypergemetric function

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