弹性介质中正交各向异性微管的屈曲分析

已有实验表明,处于细胞质中的微管可以比自由微管承受更大的压力而不发生屈曲．基于嵌入式碳纳米管屈曲的Winkler模型,利用正交各向异性情形的Winkler模型研究了细胞质中充当细胞骨架的微管的屈曲行为．计算表明,本模型可以较好地预测嵌入弹性介质中的微管较自由微管承受更大屈曲压力这一现象,而且所得到的临界屈曲压力与微管受压屈曲的实验值吻合\．同时,所得的结果也表明周围介质与微管的相互作用可以极大地提高微管抵抗屈曲的能力,该结果很好地阐释了介质与微管相互作用从而提高微管抗屈曲压力的相互作用机制\．模拟结果表明,所给出的模型可以对嵌入弹性介质中的微管的屈曲行为进行很好地模拟．     

Busy period distribution in state-dependent queues

We consider a state-dependent M/M/1 queue in which the arrival rate is a function of the instantaneous unfinished work (work backlog) in the system, and the customer's exponential service time distribution is allowed to depend on the unfinished work in the system at the instant that customer arrived. We obtain asymptotic approximations to both the busy period distributions as well as the residual busy period distribution. Our approximations are valid for systems with a rapid arrival rate and small mean service times.This research was supported in part by NSF Grants DMS-84-06110 and DMS-86-20267 and grants from the U.S. Israel Binational Science Foundation and the Israel Academy of Sciences. C. Knessl was partially supported by an I.B.M. Graduate Fellowship.     

Mazur's Incidence Structure for Projective Varieties (I)

Let X be an m dimensional smooth projective variety with a Kähler metric. We construct a metrized line bundle with a rational section s over the product of Chow varieties such that

A note on polylinking flow networks

This is a supplementary note on M. X. Goemans, S. Iwata, and R. Zenklusen’s paper that proposes a flow model based on polylinking systems. Their flow model is a series (or tandem) connection of polylinking systems. We can consider an apparently more general model of a polylinking flow network which consists of an ordinary arc-capacitated network endowed with polylinking systems on the vertex set, one for each vertex of the network. This is a natural, apparent generalization of polymatroidal flow model of E. L. Lawler and C. U. Martel and of generalized-polymatroidal flow model of R. Hassin. We give a max-flow min-cut formula for the polylinking network flow problem and discuss some acyclic flow property of polylinking flows.     

Random walks in quenched i.i.d. space-time random environment are always a.s. diffusive

We consider a general model of discrete-time random walk X_t on the lattice , = 1,..., in a random environment ={(t,x):(t,x)⁺¹} with i.i.d. components (t,x). Previous results on the a.s. validity of the Central Limit Theorem for the quenched model required a small stochasticity condition. In this paper we show that the result holds provided only that an obvious non-degeneracy condition is met. The proof is based on the analysis of a suitable generating function, which allows to estimate L₂ norms by contour integrals.Partially supported by C.N.R. (G.N.F.M.) and M.U.R.S.T. research funds.Partially supported by C.N.R. (G.N.F.M.) and M.U.R.S.T. research funds, by R.F.F.I. grants n. 99-01-00284, 97-01-00714, and CRDF research funds N RM1-2085.Partially supported by C.N.R. (G.N.F.M.) and M.U.R.S.T. research funds.Mathematics Subject Classification (2000): 60J15, 60F05, 60G60, 82B41     

关于$3\times 3$阶三角矩阵环上模的研究

文章对$3\times 3$阶三角矩阵环$$\Gamma = \left(\begin{array}{ccc}T & 0 & 0 \\M & U & 0\\{N \otimes _U M} & N & V \\\end{array}\right)$$上的模作了研究,其中T,U,V均是环, M,N分别是U-T, V-U双模.通过用一个五元组$(A,B,C;f,g)$来描述一个左$\Gamma$-模 (其中$A \in \mod T, B\in {\rm mod} U, C \in {\rm mod} V$, $f:M \otimes _T A \to B \in {\rm mod} U, g:N \otimes _U B \to C \in {\rm mod} V$), 文章分别刻画了$\Gamma$上的一致模、空的模、有限嵌入模,并且确定了${ }_\Gamma (A \oplus B \oplus C)$的根和基座．     

Automorphisms of (B)-geometries

(B)-Geometries are incidence structures arising from permutation sets. The present paper studies the automorphism groups of (B)-Geometries. In certain cases these automorphisms yield examples of inversive planes and of subplanes which are embedded in Minkowski planes (chapter 2). In chapter 3 we describe the automorphism groups of the (B)-Geometries arising from the groups PL(2, pⁿ) and AL(1, pⁿ) in their natural representations on the points of the projective and affine line.Dedicated to Prof.Dr. Walter Benz on his 60th birthdayWork done within the activity of G.N.S.A.G.A. of C.N.R. and supported by the 40% grants of M.U.R.S.T.     

Christoffel functions,orthogonal polynomials,and Nevai's conjecture for Freud weights

We obtain upper and lower bounds for Christoffel functions for Freud weights by relatively new methods, including a new way to estimate discretization of potentials. We then deduce bounds for orthogonal polynomials on thereby largely resolving a 1976 conjecture of P. Nevai. For example, let W:=e ^–Q, whereQ: is even and continuous in, Q^" is continuous in (0, ) andQ ^'>0 in (0, ), while, for someA, B,

Asymmetric response and interaction of U.S. and local news in financial markets

This paper examines the extent to which financial returns on market indices exhibit mean and volatility asymmetries, as a response to past information from both the U.S. market and the local market itself. In particular, we wish to assess the asymmetric effect of a combination of local and U.S. market news on volatility. To the best of the authors knowledge, this joint effect has not been considered previously. We propose a double threshold non‐linear heteroscedastic model, combined with a GJR‐GARCH effect in the conditional volatility equation, to capture jointly both mean and volatility asymmetric behaviours and the interactive effect of U.S. and local market news. In an application to five major international market indices, clear evidence of threshold non‐linearity is discovered, supporting the hypothesis of an uneven mean‐reverting pattern and volatility asymmetry, both in reaction to U.S. market news and news from the local market itself. Significant, but somewhat different, interactive effects between local and U.S. news are observed in all markets. An asymmetric pattern in the exogenous relationship between the local market and the U.S. market is also found. Copyright © 2005 John Wiley & Sons, Ltd.     

U.S. and Chinese Teachers' Constructing, Knowing, and Evaluating Representations to Teach Mathematics

This study examined U.S. and Chinese teachers' constructing, knowing, and evaluating representations to teach mathematics. All Chinese lesson plans are very similar, because they are all based on the Chinese national unified curriculum in mathematics. However, the U.S. lesson plans are extremely varied, even for those teachers from the same school. The Chinese teachers' lessons are very detailed; the U.S. teachers' lesson plans have exclusively adopted the “outline and worksheet” format. In the Chinese lesson plans, concrete representations are used exclusively to mediate students' understanding of the concept of average. In U.S. lessons, concrete representations are not only used to model the averaging processes to foster students' understanding of the concept, but they are also used to generate data. The U.S. teachers are much more likely than the Chinese teachers to predict drawing and guess-and-check strategies. For some problems, the Chinese teachers are much more likely than are the U.S. teachers to predict algebraic approaches. For the responses using conventional strategies, both the U.S. and Chinese teachers gave them high and almost identical scores. If a response involved a drawing or an estimate of an answer, the Chinese teachers usually gave a relatively lower score, even though the strategy is appropriate for the correct answer, because it is less generalizable. This study contributed to our understanding of the cross-national differences between U.S. and Chinese students' mathematical thinking. It also contributed to our understanding about teachers' beliefs from a cross-cultural perspective.     

On the dual risk model with tax payments

In this paper, we study the dual risk process in ruin theory (see e.g. Cramér, H. 1955. Collective Risk Theory: A Survey of the Theory from the Point of View of the Theory of Stochastic Processes. Ab Nordiska Bokhandeln, Stockholm, Takacs, L. 1967. Combinatorial methods in the Theory of Stochastic Processes. Wiley, New York and Avanzi, B., Gerber, H.U., Shiu, E.S.W., 2007. Optimal dividends in the dual model. Insurance: Math. Econom. 41, 111–123) in the presence of tax payments according to a loss-carry forward system. For arbitrary inter-innovation time distributions and exponentially distributed innovation sizes, an expression for the ruin probability with tax is obtained in terms of the ruin probability without taxation. Furthermore, expressions for the Laplace transform of the time to ruin and arbitrary moments of discounted tax payments in terms of passage times of the risk process are determined. Under the assumption that the inter-innovation times are (mixtures of) exponentials, explicit expressions are obtained. Finally, we determine the critical surplus level at which it is optimal for the tax authority to start collecting tax payments.     

U.S. and Chinese Teachers' Constructing,Knowing, and Evaluating Representations to Teach Mathematics

This study examined U.S. and Chinese teachers' constructing, knowing, and evaluating representations to teach mathematics. All Chinese lesson plans are very similar, because they are all based on the Chinese national unified curriculum in mathematics. However, the U.S. lesson plans are extremely varied, even for those teachers from the same school. The Chinese teachers' lessons are very detailed; the U.S. teachers' lesson plans have exclusively adopted the "outline and worksheet" format. In the Chinese lesson plans, concrete representations are used exclusively to mediate students' understanding of the concept of average. In U.S. lessons, concrete representations are not only used to model the averaging processes to foster students' understanding of the concept, but they are also used to generate data. The U.S. teachers are much more likely than the Chinese teachers to predict drawing and guess-and-check strategies. For some problems, the Chinese teachers are much more likely than are the U.S. teachers to predict algebraic approaches. For the responses using conventional strategies, both the U.S. and Chinese teachers gave them high and almost identical scores. If a response involved a drawing or an estimate of an answer, the Chinese teachers usually gave a relatively lower score, even though the strategy is appropriate for the correct answer, because it is less generalizable. This study contributed to our understanding of the cross-national differences between U.S. and Chinese students' mathematical thinking. It also contributed to our understanding about teachers' beliefs from a cross-cultural perspective.     

BOOK REVIEWS

Book reviewed in this article: Physics, A Basic Science, by Elmer E. Burns, Teacher of Physics (Emeritus), Austin High School, Chicago; Frank L. Verwiebe, Associate Professor of Physics, Hamilton College, Research Associate, Army Institute; and Herbert C. Hazel, Major, U. S. Marine Corps. Practical Radio Communication, by Arthur R. Nilson, Chief Instructor, Nilson Radio School, New York, N. Y. Lieutenant (Tecknicist) (Communications) U.S.N.R. (Retired); Member Institute of Radio Engineers, and J. L. Hornung, Lieutenant A-V (R.S) U.S.N.R.; Member Institute of Radio Engineers; Formerly Radio Instructor, New York University. Machines, by Charles R. Wallendorf, Administrative Assistant, Woodrow Wilson Vocational High School, Jamaica, N. Y., Frank Stewart, Department of Applied Physics, Brooklyn Technical High School, N. Y., George Luedeke, Supervisor of Shop Subjects in Vocational High Schools, Board of Education, New York, N. Y., and Dominic M. Chiarello, Department of Applied Electricity, Brooklyn Technical High School, N. Y. Systematics and the Origin of Species, by Ernst Mayr Common Edible Mushrooms, by Clyde M. Christensen Handbook of Microscopic Characteristics of Tissues and Organs, 2nd edition, by Karl A. Stiles Plane Trigonometry, by Arthur W. Weeks, M.A., The Phillips Exeter Academy, and H. Gray Funkhouser, Ph.D. Analytic Geometry, by Frederick H. Steen, Ph.D., Associate Professor of Mathematics, Allegheny College, and Donald H. Ballou, Ph.D., Assistant Professor of Mathematics, Middlebury College. Electricity, by Charles A. Rirsde. Principles and Practice of Radio Servicing, by H. J. Hicks, M.S. Experimental Electronics, by Ralph H. Müller, Professor of Chemistry, New York University; R. L. Carman, Assistant Professor of Chemistry, New York University; and M. E. Droz, Assistant Professor of Chemistry, New York University. Simplified Industrial Mathematics, by John H. Wolfe, Ph.D., Supervisor of Ford Apprentice Training, Ford Motor Company, Dearborn, Michigan; William F. Mueller, A.B., Principal of Ford Aircraft Apprentice School, Ford Motor Company, Dearborn, Michigan; and Seibert D. Mullikin, B.S., Principal of Ford Airplane Apprentice School, Ford Motor Company, Willow Run, Michigan.     

环上可加左导子的刻画

令A与B是含单位元的环,M是(A,B)-双模,U=Tri(A,M,B)是三角环.在一些附加假设条件下,本文从几个不同的角度给出了U上可加左导子的结构性质.此外,也得到了满足一定条件的环上可加左导子的两个不同刻画.     

Formulating an objective for an economy

This paper is dedicated to the memory of E.M.L. Beale. Not a small part of Martin Beale's success in developing and solving large-scale mathematical programs is attributed to the care he took in properly formulating his models.Our presentation concerns our efforts to also properly formulate a model. Our model is an economic model used for technology assessment. In order for it to be useful, it is important that the dual variables represent as realistically as possible real world prices. This required us to formulate the model as a time-staged economic equilibrium model. Our main result is a proof that an equilibrium formulation using expected aggregate demand can under certain conditions be replaced by one in which the economy is driven by an aggregate utility or objective function, one that promotes economic growth subject to physical flow constraints. We show that such an objective function always exists except for populations consisting of significantly large classes of people whose consumption patterns differ radically one from another. Assuming that the latter is not the case, this equivalent formulation means that mathematical programming software can be applied to efficiently solve the model. This paper summarizes an extensive paper entitled Deriving a Utilty Function for the U.S. Economy [3]. The main theorems are stated without proof.The authors wish to thank Kenneth Arrow, Gerard Debreu, Robert Dorfman, Dale Jorgenson and Lawrence J. Lau for their helpful comments.Research of this report was partially supported by the National Science Foundation Grants DMS-8420623, SES-8518662 and ECS-8617905; U.S. Department of Energy Grant DE-FG03-87ER25028; Office of Naval Research Contract N0004-85-K-0343, Electric Power Research Institute Contract RP 5006-01, and the Center for Economic Policy Research at Stanford University.     

On two-point boundary-value problems

Summary Boundary-value problems are considered for systems of m ordinary linear differential equations of order n. For such a problem L, a canonically associated first-order problem M, with mn equations, is introduced in such a may that associates of adjoint problems are adjoint first-order problems. The solution of a boundary-value problem L is given in terms of a generalized Green's function. This work has been supported by Sandia Corporation, a prime contractor to the U. S. Atomic Energy Commission.     

可分解半群的Morita等价

设S,R是可分解半群.记US-FAct={sM∈S-Act|SM=M且SHoms(S,M)≌M],给出了范畴US-FAct与UR-FAct等价的刻划;S分别强Morita等价于一个夹层半群、局部单位半群、幺半群和群的条件;S是完全单半群当且仅当S强Morita等价于一个群且对任何指标集I,S SHoms(S,i∈I S)→i∈I S,s t·f→(st)f,是同构.     

3-Manifold Containing Separating Incompressible Surfaces of All Positive Genera

In this paper, we shall prove that for any orientable 3-manifold M, there is a link L - K U K1 U K2 U K3 with four components in M, such that the complement of L, say ML, contains separating essential closed surfaces of all positive genera.     

HMO市场结构影响下的美国医疗费用预测分析

分析了美国HMO（Health Maintenance Organization）市场结构主要指标及部分医疗和社会经济指标对美国医疗费用的影响,采用1995-2007年数据,利用主成分分析（PCA）方法与BP神经网络构建预测模型,对美国支出在医院方面的医疗费用进行拟合及预测,预测结果与实际值之间的相对误差小于0.25%,表明可基于该模型考察在HMO市场结构影响下的美国医疗费用.