A new approximation algorithm for the multilevel facility location problem

In this paper we propose a new integer programming formulation for the multilevel facility location problem and a novel 3-approximation algorithm based on LP-rounding. The linear program that we use has a polynomial number of variables and constraints, thus being more efficient than the one commonly used in the approximation algorithms for these types of problems.     

Computing a maxian point of a simple rectilinear polygon

Let P be a simple rectilinear polygon with n vertices. There are k points in P. The maxian problem is to locate a single facility in P so as to maximize the sum of its distance from it to the k points. We present an O((n×k)logn) time algorithm for this problem.     

An algorithm for solving the multi-period online fulfillment assignment problem

This paper develops an optimal solution procedure for the multi-period online fulfillment assignment problem to determine how many and which of a retailer/e-tailer’s capacitated regional warehouse locations should be set up to handle online sales over a finite planning horizon. To reduce the number of candidate solutions in each period, dominance rules from the facility location literature are extended to handle the nonlinear holding and backorder cost implications of our problem. Computational results indicate that multi-period considerations can play a major role in determining the optimal set of online fulfillment locations. In 92% of our test problems, the multi-period solution incorporated fewer openings and closings than myopic single period solutions. To illustrate the use of the model under changing demands, the multi-period solution yielded different supply chain configurations than the myopic single period solution in over 37% of the periods.     

Applying fuzzy weighted average approach to evaluate office layouts with Feng–Shui consideration

Office layout is an important issue, especially in China and the Asian countries, where the Feng–Shui theory frequently plays a vital role. Yet, in the literature, Feng–Shui theory has seldom been discussed. Another problem is the imprecise or vague satisfaction level of the linguistic expression used in this theory. In this article, the fuzzy set theory is applied to deal with this aspect of the problem. Using an improved and efficient fuzzy weighted average (EFWA) algorithm, which has been shown to be more advantageous than the existing FWA algorithms, an empirical study of an office-layout design problem with the consideration of Feng–Shui is presented to illustrate the EFWA approach. The results and the criteria developed, based on the interpretation of the Form school concept of the Feng–Shui are reported.     

Approximate hierarchical facility location and applications to the bounded depth Steiner tree and range assignment problems

The paper concerns a new variant of the hierarchical facility location problem on metric powers (HFL_β[h]), which is a multi-level uncapacitated facility location problem defined as follows. The input consists of a set F of locations that may open a facility, subsets D₁,D₂,…,D_h−1 of locations that may open an intermediate transmission station and a set D_h of locations of clients. Each client in D_h must be serviced by an open transmission station in D_h−1 and every open transmission station in D_l must be serviced by an open transmission station on the next lower level, D_l−1. An open transmission station on the first level, D₁ must be serviced by an open facility. The cost of assigning a station j on level l1 to a station i on level l−1 is c_ij. For iF, the cost of opening a facility at location i is f_i0. It is required to find a feasible assignment that minimizes the total cost. A constant ratio approximation algorithm is established for this problem. This algorithm is then used to develop constant ratio approximation algorithms for the bounded depth Steiner tree problem and the bounded hop strong-connectivity range assignment problem.     

上海光源储存环工作点测量系统

报道了工作点测量技术的研究现状,对束流频谱分析用于工作点测量的方法进行了详细说明。介绍了上海光源储存环工作点测量系统的物理需求、方案设计、硬件结构及关键设备选型。采用束流实验的方法对系统配置参数进行优化,对系统测量误差及分辨力进行测试评估,讨论了测量系统不同工作模式的优缺点,并给出加速器不同运行阶段应该采用的运行模式。优化后的上海光源工作点测量系统,其系统测量误差小于0.000 1,测量分辨力好于0.000 05,测量过程对束流轨道及等效束斑尺寸的扰动控制在μm量级,现已在上海光源运行及机器研究中投入实用。     

用束流位置监测器精确测量储存环流强

 束流位置监测器（BPM）是粒子加速器束测系统中最为常见的元件,该探头输出信号中除包含束流位置信息外还包含电荷量等其它信息,可作为多参数束流诊断设备。采用BPM理论分析和数值仿真分析相结合的方法讨论了该种探头同时用于束流流强测量的可行性。在上海光源储存环上进行了束流试验,测定了全环140个BPM的流强标定系数,对BPM用于流强测量的分辨率、束流位置依赖性、频率依赖特性进行了测试,根据实验结果讨论了该方法在当前技术条件下所能达到的性能及其局限性。     

On finding the most BCC-efficient DMU: A new integrated MIP–DEA model

This paper proposes a new integrated mixed integer programing – data envelopment analysis (MIP–DEA) model to improve the integrated DEA model which was introduced by Toloo & Nalchigar [M. Toloo, S. Nalchigar. A new integrated DEA model for finding most BCC–efficient DMU. Appl. Math. Model. 33 (2009) 597–60]. In this study some problems of applying Toloo & Nalchigar’s model are addressed. A new integrated MIP–DEA model is then introduced to determine the most BCC-efficient decision making unit (DMU). Moreover, it is mathematically proved that the new model identifies only a single BCC-efficient DMU by a common set of optimal weights. To show applicability of proposed models, a numerical example is used which contains a real data set of nineteen facility layout designs (FLDs).     

A bi-objective modeling approach applied to an urban semi-desirable facility location problem

This paper introduces a mixed-integer, bi-objective programming approach to identify the locations and capacities of semi-desirable (or semi-obnoxious) facilities. The first objective minimizes the total investment cost; the second one minimizes the dissatisfaction by incorporating together in the same function “pull” and “push” characteristics of the decision problem (individuals do not want to live too close, but they do not want to be too far, from facilities). The model determines the number of facilities to be opened, the respective capacities, their locations, their respective shares of the total demand, and the population that is assigned to each candidate site opened. The proposed approach was tested with a case study for a particular urban planning problem: the location of sorted waste containers. The complete set of (supported or unsupported) non-inferior solutions, consisting of combinations of multi-compartment containers for the disposal of four types of sorted waste in nineteen candidate sites, and population assignments, was generated. The results obtained for part of the historical center of an old European city (Coimbra, Portugal) show that this approach can be applied to a real-world planning scenario.