Recognition of triangles by covariogram

The paper considers the problem of recognition of triangles by orientation-dependent chord length distribution. The following results are obtained: 1. The explicit form of the covariogram and orientation-dependent chord length distribution function for a triangle. 2. The explicit form for the chord length distribution function for a triangle. 3. The length of the maximal chord of a triangle is continuous function on direction u ∈ S ¹ (S ¹ is the space of all directions in the plane). 4. If we have orientation-dependent chord length distribution function for an everywhere dense set of S ¹, then we can uniquely recognize the triangle with respect to reflections and translations. 5. For any finite subset A ? S ¹, there are two non-congruent triangles with the same values of orientationdependent chord length distribution functions on A.     

Orientation-dependent section distributions for convex bodies

In the paper the orientation dependent chord length distribution functions for some bounded convex domains are obtained. In particular, formulae for the orientation dependent chord length distributions for a regular polygon and an ellipse are obtained. Explicit forms of the orientation dependent chord length distributions were known only in the cases of a disc and a triangle. We also obtain the cross-section area distribution functions for an ellipsoid and a cylinder. The cross-section area distribution function was known only in the case of a ball.     

Comparison of classical Winter's bracing requirements of compressed truss chord with stability analysis of 3D truss-model

Most code requirements concerning bracing are based on principles developed by Winter. The present research is devoted to study a lateral buckling of truss with linear elastic side supports. The classical Winter's model of truss chord in the case of out of the truss plane buckling is compared with nonlinear analysis of 3D truss model. Full bracing condition, that permits the truss chord to support load level corresponding to an unbraced length equal to the distance between braces is calculated. Then an approximate buckling load with less than full bracing is developed and the model is modified to account for unequal normal force distribution in compressed chord. The coefficient of buckling length related to side support distance in function of bracing stiffness is also calculated. The results are compared to design code requirements. It is shown that buckling length of truss chord with side supports considered as elastic elements is larger than assumed in design codes. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinematic measure of segments lying in a domain

The paper proves a formula for calculation of the kinematic measure K(D, l) of set of segments with constant length l, entirely contained in a bounded convex domainDof the Euclidean space. The obtained formula permits to find an explicit form for the kinematic measure K(D, l) for the domains D with known chord length distribution. In particular, application of the obtained formula gives explicit expressions for K(D, l) in the disc, regular triangle, rectangle and regular pentagon.     

Generalized Pleijel identity

A family of identities primarily associated with isoperimetric inequalities for planar convex domains was discovered by Pleijel in 1956. We call these identities classical Pleijel identities. R. V. Ambartzumian gave combinatorial proof of these identities and pointed out that they can be applied to find chord length distribution functions for convex domains. In the classical Pleijel identities integration is over the measure in the space \(\mathbb{G}\) of lines which is invariant with respect to the all Euclidean motions. In the present paper they are considered for any locally-finite measure in the space \(\mathbb{G}\). These identities are applied to find the so-called orientation-dependent chord length distribution (or density) functions for bounded convex domains.     

Algorithmic and explicit determination of the Lovász number for certain circulant graphs

We consider the problem of computing the Lovász theta function for circulant graphs C_n,J of degree four with n vertices and chord length J, 2?J?n. We present an algorithm that takes O(J) operations if J is an odd number, and O(n/J) operations if J is even. On the considered class of graphs our algorithm strongly outperforms the known algorithms for theta function computation. We also provide explicit formulas for the important special cases J=2 and J=3.     

Random copy of a segment within a convex domain

Under the assumption that S is a segment of the length l and D is a bounded, convex domain in the Euclidean plane ℝ², the paper considers the randomly moving copy L of S, under the condition that it hits D. Denote by L| the length of L ∩ D. In the paper an elementary expression for the distribution function F _L (x) of the random variable L| is obtained. Note that F _L (x) can have a jump at the point l or can be a continuous function depending on l and the domainD. In particular, a relation between chord length distribution functions of D and F _L (x) is given. Moreover, we derive explicit forms of F _L (x) for the disk and regular n-gons with n = 3÷7.     

ON GENERALIZED BUFFON NEEDLE PROBLEM FOR LATTICES

Two new concepts, the generalized support function and restricted chord function, both referring to a convex set, were introduced in [1]. General formulae to yield the kinematic measure of a segment of fixed length in a convex set were established based on these concepts. In this article , using the partial intersection method, we consider the generalized Buffon problem for three kinds of lattices. We determine the probability of intersection of a body test needle of length l, l < a.     

Pore structures: Measurement,characterization and relevance for flow and transport in soils

The geometry of the pore space determines the flow and transport properties of a soil under water saturated and unsaturated conditions. The spatial arrangement of the pores can be mapped using the appropriate tomographic technique. To understand the effect of the pore space on flow and transport, the complex pore structures must be quantified. To reveal the importance of various geometrical properties, porous media with well defined geometrical properties were numerically generated and were compared with a sand medium containing sphere-like particles with sizes ranging from 80 to 1.250 µm. The spatial distribution of water and air was calculated for the optimized media and the sand packing to quantify the relevance of the geometric properties. In a first test, the sand packing was compared with a generated medium with identical Minkowski functionals. The resulting pores of the generated media were too large and the water retention was underestimated. In a second test, a medium with an optimized chord length distribution was generated and a good agreement with respect to water distribution was found. The chord length distribution is a more relevant property, because it takes into account the correlation of the system over large spatial distances. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

随机弦长矩与弦幂积分

本文研究了凸体的五种类型的随机弦长分布.利用限弦投影原理和运动测度积分的方法,揭示了凸体的弦幂积分与随机弦长的矩之间的本质联系.     

On two-queue Markovian polling systems with exhaustive service

We consider a class of two-queue polling systems with exhaustive service, where the order in which the server visits the queues is governed by a discrete-time Markov chain. For this model, we derive an expression for the probability generating function of the joint queue length distribution at polling epochs. Based on these results, we obtain explicit expressions for the Laplace–Stieltjes transforms of the waiting-time distributions and the probability generating function of the joint queue length distribution at an arbitrary point in time. We also study the heavy-traffic behaviour of properly scaled versions of these distributions, which results in compact and closed-form expressions for the distribution functions themselves. The heavy-traffic behaviour turns out to be similar to that of cyclic polling models, provides insights into the main effects of the model parameters when the system is heavily loaded, and can be used to derive closed-form approximations for the waiting-time distribution or the queue length distribution.     

On a logarithmic integral and the moments of order statistics from the Weibull-geometric and half-logistic families of distributions

We provide an explicit analytical solution for a logarithmic integral in terms of the Lerch transcendent function together with the generalized Stirling numbers of the first kind. For some special cases of interest in statistical applications, the explicit solution can be expressed in terms of the polylogarithm function together with the aforementioned Stirling numbers. As a consequence, we obtain explicit expressions for the moments of order statistics from the half-logistic distribution, the Weibull-geometric distribution and the long-term Weibull-geometric distribution, which include as particular cases the extended exponential-geometric distribution and the long-term extended exponential-geometric distribution, among others. These analytical expressions are useful for computational purposes.     

在D-策略控制下服务员单重休假且休假不中断的M/G/1排队系统分析

该文研究在D-策略控制下服务员单重休假且休假不中断的M/G/1 排队系统,其中当服务员休假结束归来时,如果系统中等待服务的顾客所需的总服务时间之和不小于事先给定的正数阀值D,服务员就立即开始服务.运用全概率分解技术、更新过程理论和拉普拉斯变换工具,本文在任意初始状态下讨论了队长的瞬态分布,导出了队长瞬态分布的拉普拉斯变...     

Trapezoid Order Classification

In this paper we show the nonequivalence of combinations of several natural geometric restrictions on trapezoid representations of trapezoid orders. Each of the properties unit parallelogram, unit trapezoid and proper parallelogram, unit trapezoid and parallelogram, unit trapezoid, proper parallelogram, proper trapezoid and parallelogram, proper trapezoid, parallelogram, and trapezoid is shown to be distinct from each of the others. Additionally, interval orders are shown to be both unit trapezoid and proper parallelogram orders.     

Packet Models Revisited: Tandem and Priority Systems

We examine two extensions of traditional single-node packet-scale queueing models: tandem networks and (strict) priority systems. Two generic input processes are considered: periodic and Poisson arrivals. For the two-node tandem, an exact expression is derived for the joint distribution of the total queue length, and the queue length of the first queue, implicitly determining the distribution of the second queue. Similarly we derive the distribution of the low-priority queue in a two-class priority system. We also provide explicit approximations based on the Brownian bridge.     

Iterative learning control for linear discrete delay systems via discrete matrix delayed exponential function approach

ABSTRACT

This paper proposes iterative learning control (ILC) for linear discrete delay systems with randomly varying trial lengths without knowing prior information on the probability distribution of random iteration length. Based on matrix delayed exponential function approach, an explicit solution to the linear discrete delay controlled systems is used to generate a sequence of outputs that approximate the desired reference by adopting two ILC update laws in the presence of randomly iteration-varying lengths. A new and direct mathematical technique is explored to deal with ILC for linear discrete delay systems. Two illustrative examples are provided to verify the theoretical results.     

完备图分拆为带一条弦的(2k-1)-长圈

本文给出了构造G-设计的一个统一方法及当v≡1(mod 4k)时的C_(2k-1)~((r))-GD(v)的存在性,其中C_(10)~((r)),1≤r≤k-2表示带一条弦的2k-1长圈,r表示弦两个端点间的顶点个数。     

非寿险费率厘定中的平行四边形法则的数学原理

给出了非寿险精算费率厘定中的平行四边形法的一个数学模型,应用此模型对CAS方法和SOA方法计算等水平已赚保费做出了合理的数学解释,并比较了分别用CAS方法与SOA方法计算等水平已赚保费结果的大小.     

Enumeration of parallelogram polyominoes with given bond and site perimeter

We give the generating function for parallelogram polyominoes according to the bond perimeter and the site perimeter. In this last case, we give an asymptotic evaluation for their number. According to the two parameters an exact formula for their number is found which gives some numbers closed to the Narayana's numbers.