Seqential approach in job shop scheduling

Abstract

This study investigats a new approach‐the sequential approach‐ in job shop scheduling. The objective is to minimize the total of lateness cost and set‐up cost in job shops. Whenever a scheduling decision has to be made as to which job should receive the next processing, this approach considers each cost sequentially. One of the two costs is considered first, and every time all waiting jobs must be examined in terms of this cost, and only those jobs qualified would the second cost apply to and from which a job would be selected for processing. This investigation was carried out by using GASP IV simulation under a variety of job shop situations. The effectiveness of this approach and job selection mechanism constitute the main theme of this study.     

Geographical characterisation of honeys according to their mineral content and antioxidant activity using a chemometric approach

In this article, discrimination models are presented, relating the origin of honey samples to several variables, being the concentrations of different cations and anions in the honey samples measured by ion chromatography, and parameters that measure/reflect the antioxidant activity of the honey samples. The unsupervised method, principal component analysis, and supervised discrimination methods, such as linear and quadratic discriminant analysis, and classification and regression trees (CART), were applied to evaluate the existence of data patterns and the relationship between geographical origin and the measured parameters. The model with the best predictive ability (%CCR_TEST = 66.67%), the best overall % specificity (80%) and the best overall % sensitivity (67%) was found to be CART. It was proven that the mineral content and parameters analysed can provide enough information for the geographical characterisation and discrimination of honey.     

水利工程移民分散安置点基础设施规划设计探析——以广东省西江干流治理工程为例

以广东省西江干流治理工程为例,选取具有代表性的分散安置点基础设施进行典型设计,从而类比其他分散安置点得到基础设施建设工程量,为后期移民安置投资补偿概算提供合理依据,对同类型工程移民分散安置点基础设施规划设计提供借鉴。     

摩擦接触系统多极边界元法二次建模与数值优化

讨论了摩擦接触系统的建模与求解问题。将系统方程组的多极边界元法求解归结为变分问题并证明其等价性。在系统最优化数学模型的基础上,通过引入严格凸二次函数建立系统的二次规划模型,证明其最优解存在且唯一,并给出模型求解的最优性条件。     

A numerical method for multipoint boundary value problems with application to a restricted three body problem

A type of parallel shooting method is proposed for the solution of nonlinear multipoint boundary value problems. It extends the usual quasilinearization method and a previous shooting method developed for such problems, and reduces to usual multiple shooting techniques for two point boundary value problems. The effectiveness of the method for stiff problems is illustrated by an application to the problem of finding periodic solutions of a restricted three body problem with given Jacobian constant and unknown period.     

Optimal capacitor placement for enhancing voltage stability in distribution systems using analytical algorithm and Fuzzy-Real Coded GA

Two algorithms for optimal capacitor placement, with a view to enhance voltage stability are introduced. In the analytical algorithm the nodes, whose voltage stability index values are lower than a threshold value, are ranked in ascending order as the candidate nodes for compensation. The additional reactive power compensation to be provided at a node is obtained by solving linearized VSI formula. The maximum compensation at each node is limited to the initial reactive power delivered by the respective node prior to compensation for avoiding over-dimensioning of the capacitor banks. However, capacitor placement based on voltage stability index has proven less than satisfactory and not always indicated the appropriate placement.As an alternative a fuzzy expert system is used for extracting suitability of capacitor location from power loss reduction index and improving the voltage profile within voltage constraints. A combination of fuzzy expert system for capacitor placement and real coded GA for capacitor sizing, with a view to enhance voltage stability is proposed for optimal capacitor placement. The result is enhancement of the overall system stability index and potential achievement of maximum net money savings due to power and energy loss reduction vs. expenditure in capacitors.The overall accuracy and reliability of the proposed Fuzzy-Real Coded GA algorithm has been validated and tested on 33-node radial distribution system. Comparison of obtained results with those in recent publications showed that the Fuzzy-Real Coded GA algorithm is capable of producing high-quality solutions with good performance of convergence, and demonstrated viability.     

纤维铺放虚拟数控系统设计

根据复合材料纤维自动铺放的原理,基于VC++编程搭建纤维铺放虚拟数控系统,主要包括三维模型的建立、虚拟数控单元的构建和运动仿真的实现。在虚拟数控单元中加入速度处理模块,符合实际,能得到比较好的铺放效果。最后通过一个实例对软件仿真效果进行验证。     

Optimization of multi-product economic production quantity model with partial backordering and physical constraints: SQP,SFS, SA,and WCA

A multi-product economic production quantity model with several real-world technical and physical constraints is developed in this paper. The cost function includes ordering, holding, backordering, lost sale, and the cost caused by unused space in the warehouse. The goal is to minimize the total inventory cost, where shortages are allowed and partially backordered with fixed and linear costs. The aim is to determine the length of the inventory cycle, the length of positive inventory period, and the backordering rates of the products during the shortage period in order to minimize the total inventory costs while satisfying all constraints. Due to complexity and non-linearity of the proposed model, sequential quadratic programming (SQP), stochastic fractal search (SFS), simulated annealing (SA), and water cycle algorithm (WCA) are utilized for solution. Ninety numerical examples in small, medium, and large sizes are solved to evaluate the efficiency of the solution methods. The performances of the solution methods are compared statistically. Besides, sensitivity analysis is performed to determine the effect of change in the main parameters of the problem on the objective function value and decision variables.     

变工况条件下Bang-Bang控制与常规PID控制的集成设计与分析

将Bang-Bang控制与常规PID控制集成,研究了一种适用于大范围工况变化的变工况控制方法。对于非线性二阶系统,采用相轨迹法求解Bang-Bang控制的一次最优切换点;通过设置切换动作的最短响应时间来计算变工况控制的启动阈值。实例仿真结果表明:以变工况控制作为补充的集成控制方案,对全范围的工况变化具有良好的控制效果。     

Feasibility study of robotic fibre placement on intersecting multi-axial revolution surfaces

In this paper, the first steps towards using a robotic workcell for the automated fibre placement (AFP) manufacturing of Y-shaped tubes are proposed. The proposed workcell is constituted of a standard serial manipulator holding the fibre placement toolhead combined to a rotary table on which the part where the fibres must be laid out is attached. The investigations carried out in this work explore the feasibility of this setup and more precisely the path planning aspect. To this aim two novel path planning algorithms are presented generalizing the techniques proposed in the literature for open-contoured and cylindrical surfaces. In the first, the maximal geodesic curvature typically allowed in AFP is disregarded to generate continuous paths with a constant placement angle on the branches without any gaps or overlaps. Subsequently, a second algorithm, taking into account this curvature constraint, is presented. These algorithms were implemented in a software using the MATLAB™ suite. Finally, an algorithm to optimize the motion of the robotic system is presented and simulations are discussed.