Experiences in Expert Systems

This paper describes some work carried out in the Scientific Research and Development Branch (SRDB) of the Home Office, intended to contribute to an overall aim of building up internal expertise in the field of expert systems. This was done by carrying out a number of pilot and demonstrator projects, two of which are described in some detail. The plan, which proved successful, was to build as far as possible on the relevant skills already possessed by an OR group in the branch. The lessons learned from these are summarized in the hope that they will be of use to other groups who wish to become involved in this important area.     

Multi-Item Scheduling by Benders' Decomposition

Scheduling the production of several items requires the determination of production quantities in different periods in the presence of resource constraints. Several approximate and heuristic algorithms have been proposed to solve this problem. However, no method for finding an optimal solution has as yet been developed. It is shown that the problem may be solved advantageously using Benders' decomposition. The subproblem in Benders' decomposition is shown to be a transportation problem, and some strategies for solving the master problem are indicated. The paper concludes with a sample problem demonstrating the application of the method.     

Interactive Compromise Programming

The purpose of this paper is to introduce a solution method for multiple objective linear programming (MOLP) problems. The method, called interactive compromise programming (ICP), offers a practical solution to MOLP problems by combining judgement with an automatic optimization technique in decision-making. This is realised by using the method of compromise programming and the method of a two-person zero-sum game in an iterative way. The method is illustrated by a numerical example.     

Cost Comparisons for Out-of-Phase Inventory Models

Inventory costs for a fixed time period have traditionally been determined by allocating total costs per cycle uniformly throughout that cycle as well as any partial cycles. This procedure for cost allocation has led to the solution of numerous inventory problems, most notable of which is the anticipated price-increase model. When comparing two out-of-phase inventory models, if costs are accounted for when they occur over a fixed planning horizon, inventory policies should be changed to reflect the impact of this different cost-allocation procedure. For the anticipated price-increase model, the ‘optimal’ order quantity as well as the implied savings in inventory costs will be different when cost models are developed based on these different cost-allocation methods. If the objective is to maximize over a fixed planning horizon the actual savings in inventory costs as they occur, the cost models presented here should be used.     

Combined Routeing and Scheduling for the Transportation of Containerized Cargo

A tractor-trailer problem, with full load, from the class of combined routeing and scheduling problems is described. Distinctive features of the problem are: movements must be carried out within certain time windows; subsets of movements are linked in the sense that they must be executed in a certain order; and different priorities are attached to different movements. A new bidirectional sequential constructive heuristic is developed for the solution of this problem. The method constructs routes and schedules for the available tractor fleet. The algorithm attempts to minimize the total time for all the movements by minimizing the time taken up by unproductive movements (so-called deadhead) and waiting time between movements. Some practical aspects of the implementation of the approach are discussed.     

An effective interference suppression algorithm for visible light communication system based on DBSCAN

In order to improve the signal-to-noise ratio and mitigate the damage of noise to the communication quality,an effective interference suppression algorithm,which is based on the improved density-based spatial clustering of applications with noise algorithms,is proposed for visible light communication systems using the complementary metal–oxide–semiconductor image sensor as the receiver.Experimental results show that the algorithm can learn the region where the payload data is located,filter out the noise data,and greatly decrease the interference.The effect of the algorithm is also studied through bit error ratio performance.     

Dynamic relaxation process of a 3D super crystal structure in a Cu:KTN crystal

In this Letter,we report the existence and relaxation properties of a critical phenomenon on called a 3D super crystal that emerges at T=TC?3.5℃,that is,in the proximity of the Curie temperature of a Cu:KTN sample.The dynamics processes of a 3D super crystal manifest in its formation containing polarized nanometric regions and/or polarized clusters.However,with strong coupling and interaction of microcomponents,the characteristic relaxation time measured by dynamic light scattering demonstrates a fully new relaxation mechanism with a much longer relaxation time.As the relaxation mechanism of a relaxator is so-far undetermined,this research provides a novel perspective.These results can help structure a fundamental theory of ferroelectric relaxation.     

空中目标多波段红外辐射特性描述与仿真分析

针对空中目标在复杂背景下的探测需求,根据实际目标的运动特性,分析目标在飞行高度、飞行姿态角改变时的辐射特点,基于MODTRAN计算得到大气辐射和衰减数据,建立目标的三维模型、热辐射和反射模型,搭建空中目标的红外成像仿真系统.分析和仿真结果表明:在中波波段,目标尾焰的红外辐射比蒙皮强很多,在长波波段,蒙皮的红外辐射比较强,仿真图像的细节比较多,尾焰的红外辐射虽然有所减弱,红外成像效果依旧很好;相同探测条件下,由于位置越高大气越稀薄,探测器的可探测距离会变得比较远.目标红外辐射特性的分析和红外仿真系统的搭建对缩短红外探测器的研制周期和进一步确定探测器波段和系统分辨率等指标提供了参考依据.