3-D Container Packing Heuristics

In this paper, we study the 3-D container packing problem. The problem is divided into box selection, space selection, box orientation and new space generation sub-problems. As a first step, a basic heuristic is devised. From results using this heuristic, problems are categorized as homogeneous and heterogeneous. Two augmenting heuristics are then formulated to deal with these categories. They are complementary in their capabilities in dealing with a range of practical problems, and in terms of their computational consumption. Results using our algorithmsexceed the benchmark by 4.5% on average.     

SizeScale:求解旅行商问题(TSP)的新算法

旅行商（TSP）问题是组合优化中最典型的NP－Hard问题之一,目前关于该问题的启发式算法主要分布为两类：环路构造算法和环路改进算法,对于第1类算法,首次提出了在环路构造中成批加入顶点,同时在构造过程对环路进行局部优化的思想,由上得到了一种新的算法：SizeScale-Construct,它的解质量极大地改进了现有的环路构造算法,对于2类算法,在分析局部最优解与全局最优解之间关系的基础上,提出了另一个采用局部最优解的交集作为初始环路的新算法：SizeScale-Improve,实验结果表明该算法在解的质量和求解速度上都较大地改进了现有最好的环路改进算法;另一方面,理论上对于最坏情况和平均情况时间复杂度的分析表明这两个算法是实用的。     

A Survey of Automated Timetabling

The timetabling problem consists in scheduling a sequence of lectures between teachers and students in a prefixed period of time (typically a week), satisfying a set of constraints of various types. A large number of variants of the timetabling problem have been proposed in the literature, which differ from each other based on the type of institution involved (university or school) and the type of constraints. This problem, that has been traditionally considered in the operational research field, has recently been tackled with techniques belonging also to Artificial Intelligence (e.g., genetic algorithms, tabu search, and constraint satisfaction). In this paper, we survey the various formulations of the problem, and the techniques and algorithms used for its solution.     

Query Optimization in Multidatabase Systems

Global query execution in a multidatabase system can be done parallelly, as all the local databases are independent. In this paper, a cost model that considers parallel execution of subqueries for a global query is developed. In order to obtain maximum parallelism in query execution, it is required to find a query execution plan that is represented in the form of a bushy tree and this query tree should be balanced to the maximal possible extent with respect to execution time. A new bottom up approach called Agglomerative Approach (AA) is proposed to construct balanced bushy trees with respect to execution time. By the deterministic nature of this approach, it generates local optimal solutions. This local minima problem will be severe in the case of graph queries, i.e., queries that are represented with a graph structure. A Simulated annealing Approach (SA) is employed to obtain a (near) optimal solution. These approaches (AA and SA) are suitable for handling on-line and off-line queries respectively. A Hybrid Approach (HA), that is an integration of AA and SA, is proposed to optimize queries for which the estimated time to be spent on optimization is known a priori. Results obtained with AA and SA on both tree and graph structured queries are presented.     

Designing tributary networks with multiple ring families

Advances in telecommunication technology result in improved service, but can also lead to difficult and challenging network design problems. For example, networks in which nodes are connected by rings of optical fiber can now be used to provide rapid service restoration in the event of a failure. However, as a result, network designers are faced with the new problem of designing networks based on topological ring structures. In this paper, we consider the particular case of tributary network design. In a tributary network, a group of nodes are connected to a hub node, which is used as a point of interconnection with other parts of the network. For a particular network architecture, we describe an algorithm to determine how many topological ring structures are required, and which nodes should be included on each. We highlight connections between this problem and problems in vehicle routing.A common architecture for a telecommunications network consists of several tributary (often called access) networks, which connect locations to hubs, and a backbone network, which interconnects the hubs. This paper describes a heuristic approach for designing tributary networks based on self-healing rings (SHRs). The tributary network consists of multiple ring families, and each of those is comprised of one or more SHRs, called “stacked” rings. The SHRs in a given ring family are routed over the same cycle of optical fiber cables, but each SHR serves only a subset of the locations along the cycle. Each demand location is assigned to a single SHR on one of the ring families, whereas the hub is assigned to all SHRs on all ring families. A link that is used by some ring family incurs a fixed cost plus a variable cost per SHR associated with that family. Each SHR is constrained by the demand volume it can handle and by the number of locations it can serve. This tributary ring network design problem can be viewed as a complex version of a vehicle routing problem with a single-depot andmultiple vehicles. Our algorithm is initiated with numerous ring families. It then attempts to merge these families, while ensuring that savings are realized in terms of the sum of fixed and variable costs.     

Subclasses of solvable problems from classes of combinatorial optimization problems

Well-known subclasses of solvable problems from classes of combinatorial optimization are reviewed. For solvable problems such as the traveling salesman problem, location problem, assignment problem, and clustering problem, the changes in the objective function on a given ordering of combinatorial configurations are analyzed. Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 97–105, March–April 2009.     

生物能源生产多目标优化模型的研究

一个能够同时优化生物能源的生产供应链,包括环境、经济和社会方面影响的多目标优化模型,模拟和优化了综合的生物能生产系统,即用数种不同类的生物质原料以生产电能、热能和可燃气的系统。该系统包含可供用户选择的多种技术,以模块的形式体现在单元过程中。通过模型生命周期的评价(LCA),最终优化目标确定为解决最小化能量生产成本、最大化节能潜力、最小化环境负担、根据用户选择最大或最小化工人数和最大化生物能系统总效率。通过平衡环境和社会责任,本研究结果可帮助计划和生产人员有效地提高生物质系统的经济竞争力。     

粒子群算法在组合优化问题上的研究与发展

粒子群优化算法是一种新兴的基于群智能搜索的优化技术。该算法简单、易实现、参数少,具有较强的全局优化能力,可有效应用于科学与工程实践中。介绍了算法的基本原理和算法在组合优化上一些改进方法的主要应用形式。最后,对粒子群算法作了一些深入分析并在此基础上对粒子群算法应用于组合优化问题做了一些总结。     

Design and analysis of stochastic local search for the multiobjective traveling salesman problem

Stochastic local search (SLS) algorithms are typically composed of a number of different components, each of which should contribute significantly to the final algorithm's performance. If the goal is to design and engineer effective SLS algorithms, the algorithm developer requires some insight into the importance and the behavior of possible algorithmic components. In this paper, we analyze algorithmic components of SLS algorithms for the multiobjective travelling salesman problem. The analysis is done using a careful experimental design for a generic class of SLS algorithms for multiobjective combinatorial optimization. Based on the insights gained, we engineer SLS algorithms for this problem. Experimental results show that these SLS algorithms, despite their conceptual simplicity, outperform a well-known memetic algorithm for a range of benchmark instances with two and three objectives.     

Methods of Constructing Argument of Objective Function in Combinatorial Optimization Problems

Combinatorial configurations of different types are studied. A new point of view is proposed for their classification. Three recurrent combinatorial operators are introduced, and used to form different types of combinatorial configurations.     

Boolean query optimization and the 0-1 hyperbolic sum problem

An intelligent front-end or logic assistant is an interactive program devised to assist the users of an information retrieval system in the formulation of their queries. In order to provide knowledge usable in such a program, we study a problem of query optimization with an average efficiency criterion. We formulate it as a new combinatorial optimization problem, which we call 0-1 hyperbolic sum, and provide an exact branch-and-bound algorithm and two heuristics (of simulated annealing and tabu search type) to solve it. Computational experience illustrating the effectiveness of the tabu search technique is reported.This research was done in part during a visit of the first author to the Pontifical Catholic University of Rio de Janeiro in July and August 1987, sponsored by CNPq. It was also supported in part by grants 0271 and 0066 of AFOSR to Rutgers University.