具有素中心环的若干性质(英文)

给出了素中心环的若干新的性质 ,在具有素中心的条件下 ,我们证明了 :环的幂零元与强幂零元是一致的 ;环的素根与诣零根是相同的 ;环的满自同态是自同构 ;对于每个 a∈ R,序列 Ra Ra2 …是稳定的当且仅当对于每个 a∈ R,存在自然数 n使得 an是一个正则元 .研究了某些具有素中心的特殊环     

Twisted rational functions and series

We study rings of twisted rational functions and twisted Laurent series over simple artinian rings. We determine the centers of such rings and investigate the structure of subalgebras of these rings. We extend to infinite dimensional division rings and to simple artinian rings results proven in a previous paper for finite dimensional division algebras. We investigate “Galois subrings” of rings of fractions.     

Possibilistic clustering approach to trackless ring Pattern Recognition in RICH counters

The pattern recognition problem in Ring Imaging CHerenkov (RICH) counters concerns the identification of an unknown number of rings whose centers and radii are assumed to be unknown. In this paper we present an algorithm based on the possibilistic approach to clustering that automatically finds both the number of rings and their position without any a priori knowledge. The algorithm has been tested on realistic Monte Carlo LHCb simulated events and it has been shown very powerful in detecting complex images full of rings. The tracking-independent algorithm could be usefully employed after a track based approach to identify remaining trackless rings.     

Location of Service Facilities for the Elderly

Senior centers provide a variety of supportive services for independent elderly adults. In many metropolitan areas, the elderly population is growing and redistributing from central cities to suburbs, where accessibility to senior centers is limited. Policy analysts need to locate senior centers to best meet changing demands for service. We present alternative hierarchical facility location models for senior centers applied to Allegheny County, Pennsylvania. We find that a model that minimizes consumer disutility and unserved demands is preferred to one that maximizes utility alone, and that the former model is well-behaved in response to changes in structural parameters.     

A Property Satisfying Reducedness over Centers

This article concerns a ring property called pseudo-reduced-over-center that is satisfied by free algebras over commutative reduced rings.The properties of radicals of pseudo-reduced-over-center rings are investigated,especially related to polynomial rings.It is proved that for pseudo-reduced-over-center rings of nonzero characteristic,the centers and the pseudo-reduced-over-center property are preserved through factor rings modulo nil ideals.For a locally finite ring R,it is proved that if R is pseudo-reduced-over-center,then R is commutative and R/J(R) is a commutative regular ring with J(R) nil,where J(R) is the Jacobson radical of R.     

How to improve the performance of ATM multiplexers

We consider an ATM multiplexer with a finite or infinite buffer and stochastic output rate. There are independent, identical sources connected to this multiplexer which transmit fluid directly into the buffer. We show that the throughput of the multiplexer is increasing in the number of sources connected, where we scale the cell stream process in such a way that the mean and peak input rate stays unchanged. In the finite buffer case, the cell loss is decreasing in the number of sources connected. Hence more links improve the performance of ATM multiplexers. In the last part, we prove that correlations within cell stream processes have a negative effect on the performance of ATM multiplexers. These investigations provide easily computable lower bounds to performance measures.     

On the Krull―Schmidt Theorem for Artinian Modules

A property of rings generalizing commutativity is introduced. If a ring satisfies this property, then the Krull--Schmidt theorem holds for Artinian modules over the ring. In particular, this property is fulfilled for local rings of finite rank and for rings such that their centers are surjectively mapped by the natural projection onto the factor with respect to the radical of the ring. A local ring for which the property fails is constructed; for the direct decompositions of Artinian modules over this ring there appear anomalies similar to the anomalies of direct decompositions of torsion-free Abelian groups of finite rank. Bibliography: 6 titles.     

The Placing of Multiplexers to Minimise Cable Distance

Journal of the Operational Research Society - We wish to site a given number of multiplexers, used in communication networks to cut cable costs, so that the main cable distance between a terminal...     

Assignment of add–drop multiplexer (ADM) rings and digital cross-connect system (DCS) mesh in telecommunication networks

This paper discusses a design of a hybrid ring–mesh network in a survivable communication network. Given a set of traffic demands, the problem is to assign each traffic demand to rings and mesh such that the cost of add–drop multiplexer (ADM) and digital cross-connect system (DCS) equipment required is minimized. This assignment problem can be considered together with the fibre routing of nodes on rings and mesh. As a solution procedure, a tabu search is developed with recency-based short-term and frequency-based long-term memory structures. In computational experiments, the proposed tabu search is compared with the solutions obtained by the branch and bound procedure of CPLEX. We see that the tabu search provides a nearly optimal solution within sufficiently short time periods for all test problems with a gap of approximately 1–4% from the lower bound.     

Central elements of integral group rings

Centers of integral group rings are studied. The notion of a class character ring is introduced and made use of in describing centers of integral group rings. With every automorphism of a character field, associated is an automorphism of the center of an integral group ring. The norm of a central element of an integral group ring is determined and used to obtain invertibility criteria for central elements. Supported by RFFR grant No. 99-01-00550. Translated fromAlgebra i Logika, Vol. 39, No. 5, pp. 513–525, September–October, 2000.     

Simple transitive 2-representations and Drinfeld center for some finitary 2-categories

We classify all simple transitive 2-representations for two classes of finitary 2-categories associated with tree path algebras and also for one class of fiat 2-categories associated with truncated polynomial rings. Additionally, we compute the Drinfeld centers for all these 2-categories.     

Two-stage stochastic modeling of transportation outsourcing plans for transshipment centers

In this study, we deal with the problem of short-term transportation outsourcing for transshipment centers. The carrier needs to determine the numbers of outsourced and self-run trips for the different types of transportation tasks. Stochastic demands which are likely to occur in actual operation are considered. Different trip numbers need to be determined in sequence, so a two-stage stochastic programming technique is applied to formulate the problem. Two models are developed based upon practical considerations to help determine the optimal transportation outsourcing plan. A case study regarding the operations of a logistics carrier in Taiwan is performed. Several tests are also performed considering the number of demand scenarios, optimality gaps, variations in demands, outsourcing cost variations, and problem dimensions in order to better understand the performance of the two models.     

A bi-level stochastic optimization model for reliable supply chain in competitive environments: Hybridizing exact method and genetic algorithm

Managing supply chain operations in a reliable manner is a significant concern for decision-makers in competitive industries. In this article, two mathematical models considering competition and integrity in a three-echelon supply chain under uncertainty are proposed. The competition is formulated as a Stackelberg game such that the distribution centers have more power than the retailers. In the first model, decisions are made about the location and number of distribution centers (DCs), allocation of retailers, and the selling price of products. In the second model, based on the real world, the probability of risk and failure for the distribution centers are considered. Backup facilities should be established for unreliable facilities to meet the demands of retailers during disruption. To capture uncertainty, a two-stage stochastic approach is applied to model the problems. The first stage of the model belongs to the strategic planning and is not affected by randomness, while the second stage deals with tactical decisions depending on the realization of the first stage's random vector. In order to solve the problem, a hybrid genetic algorithm has been applied to large-scale problems. Numerical experiments have been conducted to assess the effectiveness of the proposed algorithm. Next, a sensitivity analysis is performed to recognize the most important parameters and evaluate the accuracy of our approach. Finally, to demonstrate the applicability of the model, the proposed model was implemented on the data of Alborz Pharmaceutical Company.     

Supply chain network competition among blood service organizations: a Generalized Nash Equilibrium framework

In this paper we present a Generalized Nash Equilibrium model of supply chain network competition among blood service organizations which compete not only for blood donors but also for business from hospitals and medical centers. The model incorporates not only link capacities and associated arc multipliers to capture perishability, but also bounds on the number of donors in regions as well as lower and upper bounds on the demands at the demand points in order to ensure needed amounts for surgeries, treatments, etc., while reducing wastage. The concept of a variational equilibrium is utilized to transform the problem into a variational inequality problem, and alternative formulations are given. A Lagrange analysis yields economic insights. The proposed algorithmic procedure is then applied to a series of numerical examples in order to illustrate the impacts of disruptions in the form of a reduction on the number of donors as well as that of decreases in capacities of critical links such as testing and processing on RBC prices, demands, net revenues of the blood service organizations, and their overall utilities.

     

The Markov modulated regulated Brownian motion: A second-order fluid flow model of a finite buffer

A second-order fluid flow model of a queue with finite capacity buffer and variable net input process is presented, based on the previous work of Karandikar and Kulkarni (1995). Queue length is modelled as a Brownian motion whose parameters are controlled by a finite state Markov chain. The process, termed a Markov modulated regulated Brownian motion (MMRBM), provides analytical solutions for steady state queue length distributions, overflow losses and idleness probabilities using boundary regulators. Applications of the model include queues with failure-prone servers and ATM statistical multiplexers with variable traffic loads. This revised version was published online in June 2006 with corrections to the Cover Date.     

A scatter search heuristic for the capacitated clustering problem

This paper proposes a scatter search-based heuristic approach to the capacitated clustering problem. In this problem, a given set of customers with known demands must be partitioned into p distinct clusters. Each cluster is specified by a customer acting as a cluster center for this cluster. The objective is to minimize the sum of distances from all cluster centers to all other customers in their cluster, such that a given capacity limit of the cluster is not exceeded and that every customer is assigned to exactly one cluster. Computational results on a set of instances from the literature indicate that the heuristic is among the best heuristics developed for this problem.     

Guaranteed approximation of Markov chains with applications to multiplexer engineering in ATM networks

Discrete Markov chains are applied widely for analysis and design of high speed ATM networks due to their essentially discrete nature. Unfortunately, their use is precluded for many important problems due to explosion of the state space cardinality. In this paper we propose a new method for approximation of a discrete Markov chain by a chain of considerably smaller dimension which is based on the duality theory of optimization. A novel feature of our approach is that it provides guaranteed upper and lower bounds for the performance indices defined on the steady state distribution of the original system. We apply our method to the problem of engineering multiplexers for ATM networks.     

On Two Families of Hopf Algebras of Dimension 2 m

Abstract

In this paper we construct two families of semisimple Hopf algebras of dimension 2 ⁿ⁺¹, n ≥ 3. They are all constructed as Radford's biproducts. For these examples and their duals we compute their grouplike elements, centers, character algebras and Grothendieck rings. Comparing these facts we are able to show that depending on the dimension, representatives of one of the families are selfdual. We also prove that Hopf algebras from these families are neither triangular nor cotriangular and that their cocycle deformations are trivial.     

An internal characterisation of structural matrix rings

It is known that structural matrix rings pro-vide a natural passage from complete matrix rings to upper and lower triangular matrix rings, and they often explain the peculiarities regarding certain properties of complete matrix rings on the one hand and of triangular matrix rings on the other hand. In this paper the concept of a set of matrix units in a ring associated with a quasi-order relation is introduced and used to provide an internal char-acterisation of structural matrix rings.     

Rotator design

The authors study the design of rotators (i.e. networks whose outputs are obtained by a cyclic permutation of their inputs). A direct design can be built with multiplexers. The expansion of rotators (i.e. the building of a large rotator by an interconnection of several smaller rotators) is studied, and three designs are given for it: the common factor, prime factor and near prime factor designs.