Dynamics of Decision Making in Animal Group Motion

We analyze a continuous-time model of a multi-agent system motivated by simulation studies on dynamics of decision making in animal groups in motion. Each individual moves at constant speed in the plane and adjusts its heading in response to relative headings of others in the population. The population includes two subgroups that are “informed” such that individuals in each subgroup have a preferred direction of motion. The model exhibits fast and slow time scales allowing for a reduction in the dimension of the problem. The stable solutions for the reduced model correspond to compromise by individuals with conflicting preferences. We study the global phase space for the proposed reduced model by computing equilibria and exploring stability and bifurcations. B. Nabet’s and N.E. Leonard’s work is supported in part by AFOSR grant FA9550-07-1-0-0528 and ONR grants N00014-02-1-0826 and N00014-04-1-0534. I.D. Couzin’s work was supported by the Royal Society, Balliol College and EPSRC grants GR/S04765/01 and GR/T11234/01, a Searle Scholar Award and DARPA grant HR001-05-1-0057. S.A. Levin’s work was supported in part by DARPA grant HR0011-05-1-0057 and NSF grant EF-0434319.     

《地震战线》与地震预报知识的普及

"文革"十年,中国大陆经历了新中国成立以后的第一个地震活跃期。为了减少地震造成的破坏,全国范围内开展了以"群测群防、专群结合"为特点的大规模地震预报工作。但是在科技水平还无法准确预报地震的情况下,如何开展地震预报,如何在大众中普及预报方法,成为这项工作面临的首要问题。在此背景下,《地震战线》应运而生。文章在分析了《地震战线》的创刊背景、出版经过和该刊的主要内容及其特点的基础上,探讨了"文革"期间《地震战线》在地震预报知识普及中的作用和特点。     

论集体林权制度改革中的公平与效率

分析集体林权制度改革中不完善引发的种种矛盾对公平与效率的影响,提出完善集体林权制度,推进公平与效率实现的前提和对策：在确立农民经营林业的主体地位的平等,保证农民基本生活的前提下,追求林业土地生产效率;加强系统性地深化推进林业产权改革,加快对产权的界定、流转,保障产权利益的实现。     

论我国劳动者集体劳动权的特点及其实现路径

完善集体劳动关系是我国现代化建设中的重大课题,集体劳动关系的实质是劳动者集体劳动权的形成。我国集体劳动权的特点是工会体制一元化、注重集体协商、罢工权不明确和重视劳动者的民主参与权,它体现了国家的政体性质和文化传统。当前要通过增强工会集体谈判和集体争议职能,借助三方协商机制和基层党组织的纽带作用,强化法制等措施来实现劳动者的集体劳动权。     

Coexisting oblate and strongly triaxial structures in <Superscript>191</Superscript>Pt

Excited states in ¹⁹¹Pt have been populated using the reaction ¹⁸⁶W + ¹¹B at 85MeV beam energy. Gamma-ray coincidences were measured using the EUROGAM-II spectrometer array. The level scheme has been extended considerably. Evidence for favoured structures of highly triaxial shape with -90^° coexisting with oblate structures has been obtained by comparison with total Routhian surface and cranked shell model calculations. The presence of proton excitations in both positive- and negative-parity states has been confirmed.     

Mean-field limit for the stochastic Vicsek model

We consider the continuous version of the Vicsek model with noise, proposed as a model for collective behaviour of individuals with a fixed speed. We rigorously derive the kinetic mean-field partial differential equation satisfied when the number N of particles tends to infinity, quantifying the convergence of the law of one particle to the solution of the PDE. For this we adapt a classical coupling argument to the present case in which both the particle system and the PDE are defined on a surface rather than on the whole space R^d. As part of the study we give existence and uniqueness results for both the particle system and the PDE.     

Collective excitations in a confined,interacting dilute Bose-condensed fluid

In the Thomas–Fermi (TF) regime, S. Stringari [Phys. Rev. Lett., 77, 2360 (1996)] established the hydrodynamic normal modes of an interacting dilute Bose-condensed fluid confined in an isotropic harmonic trap. Here, we extend this treatment beyond the TF condensate using the work of B. Hu, G. Huang and Y. Ma [Phys. Rev. A, 69, 063608 (2004)] as a starting point. Both numerical results for low-lying eigenfrequencies, for various angular momentum quantum numbers???and n?=?0, and also samples of corresponding eigenfunctions, are presented. Finally, eigenfrequencies are also given for some collective excitations in an axially symmetrical trap.     

浅析影响大学生集体责任感形成的心理因素

责任意识、责任情感和责任意志是影响大学生集体责任感形成的三个心理因素。导致当代大学生集体责任感淡薄的主要原因是集体责任意识缺失、责任情感培育不够和责任意志缺乏磨练。大学生集体责任感的培养应该遵循心理发展规律,有效整合知、情、意、行,提高教育的实效性。     

Multiexciton molecules in the hexaborides

We investigate multiexciton bound states in a semiconducting phase of divalent hexaborides. Due to three degenerate valleys in both the conduction and valence bands the binding energy of a 6-exciton molecule is greatly enhanced by the shell effect. The ground state energies of multiexciton molecules are calculated using the density functional formalism. We also show that charged impurities stabilize multiexciton complexes leading to condensation of localized excitons. These complexes can act as nucleation centers of local moments. Received 24 October 2000