Comparison among three pull control policies: kanban, base stock, and generalized kanban

This paper is concerned with maketostock pull control policies. A classical policy is the kanban policy. Another policy, very easy to implement, is the base stock policy. These two policies contain one design parameter per stage. A general control policy, known as the generalized kanban policy, can also be used to implement the pull mechanism. The generalized kanban policy includes, as special cases, the kanban and the base stock policies. This policy uses two parameters for each stage of the production system. The aim of this paper is to provide qualitative and quantitative comparisons of these three policies. The results of our study will help to choose the policy to implement in order to control a production system. We give practical rules. We also show that if there is no delay in filling orders, all three policies have similar costs. However, for the systems studied, we show that, if there is a delay in filling orders, generalized kanban systems and base stock systems yield close to optimal costs, which are lower than costs of kanban systems for the same service quality.     

Scheduler – A System for Staff Planning

In this paper we propose a unified formulation based on (min?,+) algebra to express the dynamics of pull control policies for serial single product manufacturing systems. For policies such as basestock, kanban, extended kanban and generalized kanban, the formulation has the same parametric form with different parameters for each policy. To calculate these parameters efficiently, (min?,+) algebra tools are used. This formulation allows us to identify under what parameter values two different policies have the same dynamics behavior. This has been applied to extended kanban and generalized kanban.     

随机生产系统安全库存的ЛТ控制策略

本文研究了随机工件加工时间的生产系统在ЛТ（Ｊｕｓｔ－Ｉｎ一Ｔｉｍｅ）控制策略下的运行机制．基于文［１］所提出的看板控制生产系统的生产率与其马尔柯夫模型的状态空间相对应的理论．本文探讨了在ЛТ控制策略下生产系统的看板在安全库存受限的条件下的最优配置问题，并给出了工作站数目小于５的生产系统看板最优配置公式．     

Ramanujan-type congruences modulo 8 for 7- and 23-core partition functions

Recently, Radu and Sellers proved numerous congruences modulo powers of 2 for \( (2k+1)\)-core partition functions by employing the theory of modular forms. In this paper, employing Ramanujan’s theta function identities, we prove many infinite families of congruences modulo 8 for 7-core partition function. Our results generalize the congruences modulo 8 for 7-core partition function discovered by Radu and Sellers. Furthermore, we present new proofs of congruences modulo 8 for 23-core partition function. These congruences were first proved by Radu and Sellers.     

A branch-reduce-cut algorithm for the global optimization of probabilistically constrained linear programs

We consider probabilistically constrained linear programs with general distributions for the uncertain parameters. These problems involve non-convex feasible sets. We develop a branch-and-bound algorithm that searches for a global optimal solution to this problem by successively partitioning the non-convex feasible region and by using bounds on the objective function to fathom inferior partition elements. This basic algorithm is enhanced by domain reduction and cutting plane strategies to reduce the size of the partition elements and hence tighten bounds. The proposed branch-reduce-cut algorithm exploits the monotonicity properties inherent in the problem, and requires solving linear programming subproblems. We provide convergence proofs for the algorithm. Some illustrative numerical results involving problems with discrete distributions are presented.     

样条变差缩减算子迭代极限的一个简单证明

一、引言在[1]和[2]中,胡莹生、徐叔贤利用 Markov 链终极条件概率的有关结果,确定了一类变差缩减算子的迭代极限.本文采用作者在[3]中使用的技巧,利用多项式样条的若干基本知识,不但简单地得出了[1,2]的结果,并且给出了迭代收敛速度的估计.对于等距分划的三次样条,所给的误差估计在某种意义上是最好的.     

Some new identities for colored partition

In this paper, we discover several new identities on colored partitions and provide proofs for them. Many colored partition identities presented in the paper do not belong to the general and unified combinatorial framework provided by Sandon and Zanello. Most of our proofs depend upon new modular equations given by employing the method of reciprocation.     

Independence of inadmissible strategies and best reply stability: a direct proof

Hillas (1990) introduced a definition of strategic stability based on perturbations of the best reply correspondence that satisfies all of the requirements given by Kohlberg and Mertens (1986). Hillas et al. (2001) point out though that the proofs of the iterated dominance and forward induction properties were not correct. They also provide a proof of the IIS property, a stronger version of both iterated dominance and forward induction, using the results of that paper. In this note we provide a direct proof of the IIS property.Received February 2002     

A single-stage supply chain system controlled by kanban under just-in-time philosophy

The production system using kanban was pioneered by Toyota Motor Company in Japan and subsequently it was adopted by numerous other Japanese and US companies for applying the just-in-time manufacturing principles. This research studies a single-stage supply chain system that is controlled by kanban mechanism. The supply chain system is modelled as a mixed-integer nonlinear programming (MINLP) problem. It is solved optimally by branch-and-bound method to determine the number of kanbans, batch size, number of batches, and the total quantity over one period. Meanwhile, the kanban operation between two adjacent plants is worked out considering the factors of loading and unloading time, and transport time. Coupled with plant-wide efforts for cost control and management commitment to enhance other measures of performance, a logistics system for controlling the production as well as the supply chain system is developed, which results in minimizing the total cost of the supply chain system. The results show that the improvements in reduction of inventory, wasted labour, and customer service in a supply chain are accomplished through the kanban mechanism.     

Bijective proofs of some classical partition identities

A bijective proof of a general partition theorem is given which has as direct corollaries many classical partition theorems due to Euler, Glaisher, Schur, Andrews, Subbarao, and others. It is shown that the bijective proof specializes to give bijective proofs of these classical results and moreover the bijections which result often coincide with bijections which have occurred in the literature. Also given are some sufficient conditions for when two classes of words omitting certain sequences of words are in bijection.     

An elementary,illustrative proof of the Rado–Horn theorem

The Rado–Horn theorem provides necessary and sufficient conditions for when a family of vectors can be partitioned into a fixed number of linearly independent sets. Such partitions exist if and only if every subfamily of the vectors satisfies the so-called Rado–Horn inequality. In this paper we provide an elementary proof of the Rado–Horn theorem as well as results for the redundant case. Previous proofs give no information about how to actually partition the vectors; we use ideas present in our proof to find subfamilies of vectors which may be used to construct a kind of “optimal” partition.     

On Ramanujan’s modular identities

For Ramanujan’s modular identities connected with his well-known partition congruences for the moduli 5 or 7, we had given, in an earlier paper, natural and uniform proofs through the medium of modular forms. Analogous (modular) identities corresponding to the (more difficult) case of the modulus 11 are provided here, with the consequent partition congruences; the relationship with relevant results of N J Fine is also sketched.     

Optimal models for a multi-stage supply chain system controlled by kanban under just-in-time philosophy

This research studies a multi-stage supply chain system that operates under a JIT (just-in-time) delivery policy. Kanbans play an important role in the information and material flows in a supply chain system. Thus, a kanban mechanism is employed to assist in linking different production processes in a supply chain system to implement the scope of JIT philosophy. For a multi-stage supply chain system, a mixed-integer nonlinear programming (MINLP) problem is formulated from the perspective of JIT delivery policy where a kanban may reflect to a transporter such as a truck or a fork-lifter. The number of kanbans, the batch size, the number of batches and the total quantity over one period are determined optimally. It is solved optimally by branch and bound method. A greedy heuristic to avoid the large computational time in branch-and-bound algorithm is developed for solving a large MINLP. Coupled with plant-wide efforts for cost control and management commitment, a logistic system for controlling the production as well as the supply chain is built, which results in minimizing the total cost of the supply chain system. The results show that the improvements in reduction of inventory, wasted labor and customer service in a supply chain are significantly accomplished through the kanban mechanism.     

Bijective proofs of partition identities arising from modular equations

We establish generalizations of certain partition theorems originating with modular equations and give bijective proofs for them. As a special case, we give a bijective proof of the Farkas and Kra partition theorem modulo 7.     

Density theorems and extremal hypergraph problems

We present alternative proofs of density versions of some combinatorial partition theorems originally obtained by E. Szemerédi, H. Furstenberg and Y. Katznelson. These proofs are based on an extremal hypergraph result which was recently obtained independently by W. T. Gowers and B. Nagle, V. Rödl, M. Schacht, J. Skokan by extending Szemerédi’s regularity lemma to hypergraphs.     

Identities and congruences for the general partition and Ramanujan’s tau functions

We present some identities and congruences for the general partition function p _r (n). In particular, we deduce some known identities for Ramanujan’s tau function and find simple proofs of Ramanujan’s famous partition congruences for modulo 5 and 7. Our emphasis throughout this paper is to exhibit the use of Ramanujan’s theta functions to generate identities and congruences for general partition function.     

An assembly-type supply chain system controlled by kanbans under a just-in-time delivery policy

This research studies the assembly-type supply chain system controlled by kanban mechanism. First, a supply chain system is modeled as a mixed-integer nonlinear programming (MINLP) problem. A composite formulation of the assembly-type supply chain system is developed by appropriately aggregating the individual branch models as a whole system. The batch size, the number of batches, and the total quantity over one period in the mainline and each branch line are determined. The small size MINLP problems are solved optimally by a branch-and-bound method. For the large size MINLP problems, a heuristic is developed which divides the ATSCS into several small size problems, and then conquers them individually. Next, the kanban operation between two adjacent plants is developed to schedule the loading and unloading, and transportation. Coupled with plant-wide efforts for cost control and management commitment, a logistics system is built for controlling the production as well as the supply chain system, which results in minimizing the total cost of the supply chain system. Numerical examples are presented to illustrate the two heuristic procedures and a better solution is obtained for the ATSCS problem.     

Some remarks on lengths of propositional proofs

We survey the best known lower bounds on symbols and lines in Frege and extended Frege proofs. We prove that in minimum length sequent calculus proofs, no formula is generated twice or used twice on any single branch of the proof. We prove that the number of distinct subformulas in a minimum length Frege proof is linearly bounded by the number of lines. Depthd Frege proofs ofm lines can be transformed into depthd proofs ofO(m ^d+1) symbols. We show that renaming Frege proof systems are p-equivalent to extended Frege systems. Some open problems in propositional proof length and in logical flow graphs are discussed. Supported in part by NSF grant DMS-9205181