A公司电商仓库选址研究

文章研究了B2C电子商务环境下的仓库选址问题,提出了以总快递费用最优和总运输时效最少为目标,基于0-1整数规划的选址模型。最后,文章结合某体育运动品牌A公司的实例进行了验证,取得良好的效果。     

The flow-refueling location problem for alternative-fuel vehicles

Beginning with Hodgson (Geogr.Anal.22(1990) 270), several researchers have been developing a new kind of location-allocation model for “flow capturing.” Instead of locating central facilities to serve demand at fixed points in space, their models aim to serve demand consisting of origin-destination flows along their shortest paths. This paper extends flow-capturing models to optimal location of refueling facilities for alternative-fuel (alt-fuel) vehicles, such as hydrogen fuel cells or natural gas. Existing flow-capturing models assume that if a flow passes just one facility along its path, it is covered. This assumption does not carry over to vehicle refueling because of the limited range of vehicles. For refueling, it may be necessary to stop at more than one facility in order to successfully refuel the entire path, depending on the vehicle range, the path length, and the node spacing. The Flow Refueling Location Model (FRLM) optimally locates p refueling stations on a network so as to maximize the total flow volume refueled. This paper presents a mixed-integer programming formulation for the nodes-only version of the problem, as well as an algorithm for determining all combinations of nodes that can refuel a given path. A greedy-adding approach is demonstrated to be suboptimal, and the tradeoff curve between number of facilities and flow volume refueled is shown to be nonconvex.     

Some new mathematical methods in dynamic programming over infinite horizon

Two properties of the potentialsU(x, y) are studied. They are the acyclicity and the strong convexity. By mean of them, information on the dynamic behavior of the optimal choice functions is obtained. The previous results are then applied,via Dynamic Programming, to the models of optimization over an infinite horizon (discounted Ramsey models). Qualitative information on the dynamics in such models is derived and some new stability results are given.

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Riassunto Nel presente lavoro vengono proposte due proprietà dei potenzialiU(x, y): l'aciclicità e la convessità forte. Entrambe permettono di ottenere informazioni sul comportamento dinamico delle funzioni di scelta ottimale .La precedente teoria viene poi applicata, utilizzando la programmazione dinamica, al problema di dedurre informazioni qualitative sulle dinamiche nei modelli di ottimizzazione ad orizzonte infinito (modelli di Ramsey con utilità scontate). Si ottengono in questo modo alcuni nuovi risultati di stabilità delle soluzioni in questo modello.

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The research of the author was partially supported by a grant from the «Ministero della Pubblica Istruzione». A first version of this paper was delivered at the «VIII Convegno A.M.A. S.E.S., Modena 26–29 September 1984». In am grateful to E. Castagnoli and P. Mazzoleni for helpful suggestions. For any remaining errors, I am entirely responsible.     

The solution of the infinite horizon tracking problem for discrete time systems possessing an exogenous component

In this paper we derive an algorithm that yields, for a discrete-time system, a control minimizing a quadratic cost functional. The system considered is linear and possesses an exogenous component. The cost functional is a quadratic tracking equation over an infinite time horizon with positive semi-definite weighting matrices such that a weighted sum of these matrices is positive definite. The infinite planning horizon Minimum Variance cost criterion and the Linear Quadratic regulator are special cases. For stabilizable systems we give a characterization of the asymptotically admissible reference trajectories.     

时变环境下选址问题的一个启发式算法

配送中心选址作为物流管理中的一个重要研究问题受到广泛重视。然而,文献中所涉及的选址模型大都是静态的,即沿一条路径行进时所需的成本(或时间)是与出发时间无关的函数。但在实际生活中,它往往是会随时间的变化而变化的,这类问题被称为时变环境下的选址问题。文中讨论了时变环境下的单配送中心到多个零售点带容量约束的选址问题。由于该问题是NP-完备的,我们给出了一个启发式算法。     

Numerical and analytical results for the transportation problem of Monge-Kantorovich

The Monge-Kantorovich transportation problem has a long and interesting history and has found a great variety of applications (see Rachev and Rüschendorf (1998a,b)). Some interesting characterizations of optimal solutions to the transportation problem (resp. coupling problems) have been found recently. For the squared distance and discrete distributions they relate optimal solutions to generalized Voronoi diagrams. Numerically we investigate the dependence of optimal couplings on variations of the coupling function. Numerical results confirm also a conjecture on optimal couplings in the one-dimensional case for nonconvex coupling functions. A proof of this conjecture is given under some technical conditions. Received: November 1999     

A continuous location problem with different norms

This paper considers a set of problems of fixing the number and location of facilities to cover a given set of demand points, such that each demand point is served within a range of known distance standards, where each facility can be located on the entire plane and the distance can be either measured in rectilinear, Euclidean or Tchebycheff units. It is shown that an optimum solution can always be found on a small finite set of points. Thus the optimum itself can be found by either complete enumeration of these points or by zero one integer linear programming techniques. Furthermore, it is shown that the least and the largest number of facilities are required for the rectilinear and the Tchebycheff cases respectively.     

上海城市开发中的规划控制与区位选择

以城市开发中一个最基本的影响开发决策与规划管理的要素--区位(开发选址)作为研究的楔入点,通过对上海城市开发中区位选择表征和机制的分析,揭示目前上海城市开发中所存在的深层次矛盾,并在城市开发的运作过程中寻找问题的症结,提出城市规划在这个方面可能有的改进和控制方法.     

Booking horizon forecasting with dynamic updating: A case study of hotel reservation data

A highly accurate demand forecast is fundamental to the success of every revenue management model. As is often required in both practice and theory, we aim to forecast the accumulated booking curve, as well as the number of reservations expected for each day in the booking horizon. To reduce the dimensionality of this problem, we apply singular value decomposition to the historical booking profiles. The forecast of the remaining part of the booking horizon is dynamically adjusted to the earlier observations using the penalized least squares and historical proportion methods. Our proposed updating procedure considers the correlation and dynamics of bookings both within the booking horizon and between successive product instances. The approach is tested on real hotel reservation data and shows a significant improvement in forecast accuracy.     

The approximate solution of finite‐horizon discrete‐choice dynamic programming models

The estimation of finite‐horizon discrete‐choice dynamic programming (DCDP) models is computationally expensive. This limits their realism and impedes verification and validation efforts. Keane and Wolpin (Review of Economics and Statistics, 1994, 76(4), 648–672) propose an interpolation method that ameliorates the computational burden but introduces approximation error. I describe their approach in detail, successfully recompute their original quality diagnostics, and provide some additional insights that underscore the trade‐off between computation time and the accuracy of estimation results.     

“拐点”即将来临——大整合时代的房地产企业发展之道

中国房地产会不会出现“泡沫”？这个目前地产市场最敏感的话题，在不久前举办的“房地产创新论坛”上再次成为论争的焦点。 “其兴也勃焉，其衰也忽焉”——管理学专家岳川博的“大胆假设“，来源于对美、日等国房地产数据的“小心求证”。然而在经济学家赵晓看来，所谓周期、规律，在中国“非典型性市场”中都可能水土不服——基于工业化、城市化等宏观层面的认识，房地产“泡沫”才刚刚开始。 此番唇枪舌剑，只是目前有关房地产“泡沫”问题争论的一个缩影。本刊对此暂不评论，个中三昧还可由读者自己品味。 本刊还将陆续刊发一系列地产市场相关热点话题的争论及评点。欢迎读者踊跃参评。     

Comparison of exact and approximate methods of solving the uncapacitated plant location problem

This study was prompted by a recently published article in this journal on facility location by D. R. Sule. We show that the claim made by Sule of a novel and extremely simple algorithm yielding optimum solutions is not true. Otherwise, the algorithm would represent a breakthrough in decision-making for which a number of notoriously hard problems could be efficiently recast as location problems and easily solved.In addition, several variants of common location problems addressed by Sule are reviewed. In the last twenty years, many methods of accurately solving these problems have been proposed. In spite of their increased sophistication and efficiency, none of them claims to be a panacea. Therefore, researchers have concurrently developed a battery of fast but approximate solution techniques. Sule's method was essentially proposed by Kuehn and Hamburger in 1963, and has been adapted many times since.We exhibit several examples (including the one employed by Sule) in which Sule's algorithms lead to nonoptimal solutions. We present computational results on problems of size even greater than those utilized by Sule, and show that a method devised by Erlenkotter is both faster and yields better results.In a cost-benefit analysis of exact and approximate methods, we conclude that planning consists of generating an array of corporate scenarios, submitting them to the “optimizing black box,” and evaluating their respective merits. Therefore, much is to be gained by eliminating the vagaries of the black box—that is, by using an exact method—even if the data collection and the model representation introduce sizable inaccuracies. Ironically, large problems (those that typically require most attention) cannot be solved exactly in acceptable computational times. Pending the imminent design of a new generation of exact algorithms, the best heuristics are those that guarantee a certain degree of accuracy of their solutions.     

On the generalized principal-agent problem: Decomposition and existence results

This paper addresses the class of generalized agency problems: situations in which adverse selection and moral hazard are jointly present. We present a decomposition of the principal's optimization problem under the first-order approach that sheds light on the interactions between the two types of private information, and also significantly improves tractability. We use the decomposition to (1) provide examples of closed form solutions of the optimal contract, and (2) analyze the existence of optimal contracts. We also show that the first-order approach is valid in generalized agency problems if the production technology satisfies the linear distribution function condition (LDFC) in actions and types. For more general production technologies the Mirrlees-Rogerson sufficient conditions need to be extended to include restrictions on the form of the optimal contract. Received: 11 August 1997 / 26 September 1999     

Coalitional stability in the location problem with single-dipped preferences: An application of the minimax theorem

This study considers a situation in which agents choose the location of a public facility from a street according to a given mechanism. Agents have single-dipped preferences over a set of feasible locations. We analyze coalitional behavior for any given mechanism for this situation. We identify a necessary and sufficient condition for a mechanism to possess a strong Nash equilibrium by applying the minimax theorem of von Neumann and Morgenstern (1944). We introduce a class of core solutions and show that these solutions are characterized by strong Nash implementability. As a byproduct of these results, we propose a simple mechanism that implements any core solution in strong Nash equilibria.     

The general dynamic factor model: One-sided representation results

Recent dynamic factor models have been almost exclusively developed under the assumption that the common components span a finite-dimensional vector space. However, this finite-dimension assumption rules out very simple factor-loading patterns and is therefore severely restrictive. The general case has been studied, using a frequency domain approach, in Forni et al. (2000). That paper produces an estimator of the common components that is consistent but is based on filters that are two-sided and therefore unsuitable for prediction. The present paper, assuming a rational spectral density for the common components, obtains a one-sided estimator without the finite-dimension assumption.     

数据仓库设计方法研究

文章描述了数据仓库(DW)设计过程的几个常规阶段并给出了改进。类似于传统的数据库设计,数据仓库设计过程分为4个阶段。第一阶段指定相关操作型数据库的属性;概念设计把需求分析和规格说明的结果转换为满足第三多维范式的事实图;逻辑设计阶段采用概念设计生成的图表并产生一组视图定义;最后一阶段为数据仓库的物理设计阶段。     

重力式自动系统在成品仓库的运用

当企业产能达到一定程度．原来的成品仓库及其运作方式成为发展瓶颈时．企业的管理者必须对现有成品仓库进行突破性改造。     

标准化推动现代仓储业发展

<通用仓库等级>和<仓储眼务质量要求>两项国家标准的实施,为仓储(物流)企业提高仓库的技术条件与管理水平提出了目标,也为货主企业选择不同等级的仓库提供了依据.