基于损失函数的随机设施布局优化分析

现有的随机设施布局问题的优化方法或是优化总物料处理成本的均值以获得最鲁棒的布局,或是优化其方差以获得最稳定的布局,但两者均只优化了总物料处理成本随机特征中的一个方面.通过引入田口损失函数的概念,建立了新的随机设施布局优化模型,对总物料处理成本的均值和方差同时进行优化求解,相比于现有的优化方法,新方法得到的布局形式能够使系统同时获得较好的鲁棒性和稳定性.     

A cross-entropy approach to the single row facility layout problem

The single row facility layout problem is to arrange a given number of facilities along a straight line so as to minimise the total cost associated with the interactions between the facilities. In this paper, a metaheuristic algorithm based on the cross-entropy method, incorporating a local search procedure and symmetry-breaking techniques, is developed to solve this problem. The proposed algorithm has been tested on some widely used benchmark instances. The computational results show that the proposed algorithm has found the optimal or the best solutions known so far for the instances of size with up to 100 facilities and is competitive with some existing algorithms.     

Heuristic approach for solving the multi-objective facility layout problem

A new heuristic approach for the generation of preferred objective weights to solve the multi-objective facility layout problem is presented. By applying a multi-pass halving and doubling procedure, a paired comparison method based on the strength of preference among objectives given by the decision-maker is developed. Furthermore, a ‘prior test’ is proposed to examine the consistency of the paired comparison matrix. An efficient method to transform the inconsistent matrix into a consistent one so the result can closely approximate the decision-maker's original assessments is also offered. The geometric mean method is then employed to obtain the objective weights and the final solution. There are five phases in the proposed heuristic approach. The first generates a basic solution; the second involves constructing a paired comparison matrix by using the multi-pass halving and doubling procedure; the third identifies the consistency of the paired comparison matrix; the fourth transforms the inconsistent matrix into a consistent one; and the fifth generates the preferred weights and obtains the facility layout solution. An illustrative example is given to demonstrate an application of the proposed approach for solving the multi-objective facility layout problem.     

A two-step heuristic algorithm for layout design of unequal-sized facilities with input/output points

The facility layout problem (FLP) is to arrange facilities within a given area so as to minimise the total material-handling cost. An efficient arrangement of facilities plays an important part in the achievement of high productivity in a manufacturing system. This paper focuses on the layout design of unequal-sized facilities with fixed shapes and input/output (I/O) points. A mixed-integer programming (MIP) model is developed to obtain optimal solutions. Since the MIP model is not applicable to large-sized problems, a two-step heuristic algorithm is developed to solve the FLPs. In the first step, a layout solution with moderate quality is generated by using an interconnected zone algorithm and a simulated annealing (SA) algorithm. The zone algorithm is a newly developed layout construction technique which places facilities successively within designated zones according to a placing sequence. The zone concept is introduced to reduce the solution space such that the computational effort is decreased, while SA is used to search for the placing sequences. The second step improves that solution further using the reduced MIP by employing the relative position information obtained from the first step. Computational experiments indicate that the algorithm in the first step can yield on average a 1.048% improvement on the best solutions obtained by the existing algorithms. The second step can further improve the solutions obtained in the first step by 0.484% on average. Compared to the commercial software VIP-PLANOPT 2006 (Engineering Optimization Software 2005 Engineering Optimization Software. 2005. PLANOPT User’s Manual, Florida: Deltona.  [Google Scholar]), the proposed two-step algorithm improves the solutions by 9.113% on average.     

A simulated annealing algorithm based on a closed loop layout for facility layout design in flexible manufacturing systems

Facility layout design problems in flexible manufacturing systems (FMS) differ from traditional facility design problems and are more difficult to solve because there are more constraints that must be considered (i.e., cell shape, cell orientation, pick-up and drop-off point positions). The focus of this paper is on the closed loop type layout, which is based on a predetermined layout pattern. This layout pattern is commonly found in manufacturing settings since it requires a simplified material handling system configuration and since it facilitates a modular and expandable layout structure. The open-field type layout problem, where there is no predetermined layout pattern, may potentially have a more efficient configuration, since there are fewer restrictions. However, this problem is more difficult to solve and may result in configurations that are not desirable due to the lack of structure or modularity. The procedure developed in this paper improves the efficiency of the closed loop configuration by changing the rectangular shape of the loop to different sizes. In many cases, the resulting closed loop layout proves to be as efficient as the open field layout. A simulated annealing procedure (SA-CL) is used to search for the configuration that minimizes the total material handling costs. A comparison of the results with existing methods indicates that, based on solution quality and computational time, the SA-CL offers a favourable alternative for efficient layout design.     

A sequence-pair representation and MIP-model-based heuristic for the facility layout problem with rectangular departments

In Facility Layout Problem (FLP) research, the continuous-representation-based FLP can consider all feasible all-rectangular-department solutions. Given this flexibility, this representation has become the representation of choice in FLP research. Much of this research is based on a methodology of Mixed-Integer Programming (MIP) models. However, these MIP-FLP models can only solve problems with a limited number of departments to optimality due to the large number of combinations of the binary variables used in the models to maintain feasibility with respect to departments overlapping. Our research centers around the sequence-pair representation, a concept that originated in the Very Large Scale Integration (VLSI) design literature. We show that an exhaustive search of the sequence-pair solution space will result in finding the optimal layout of the MIP-FLP and that every sequence-pair solution is position consistent (although possibly not layout feasible) in the MIP-FLP. We propose a genetic-algorithm-based heuristic that combines the sequence-pair representation with the MIP-FLP model. Numerical experiments based on different sized test problems from both the literature and industrial applications are provided and the solutions are compared with both the optimal solutions and the solutions from other heuristics to show the effectiveness and efficiency of our heuristic. For 11 data sets from the literature we provide solutions better than those previously found. For two large industrial application data sets we perform a sensitivity analysis with respect to the department aspect ratio constraint.     

A multi-improved genetic algorithm for facility layout optimisation based on slicing tree

For the facility layout optimisation problem, we use the slicing tree structure based on the order of traversal to form a new chromosome encoding system demonstrating facilities’ order, the relationship and the location. We generate the initial solution based on two principles namely the facilities’ adjacency and random generation. The structure of chromosome is made up with three sections in the research so that we can do the genetic operations to these three sections respectively, and we use dynamic and feedback mechanisms to improve the penalty function. As a result, the analysis of typical cases shows that there are certain improvements to this algorithm both in effectiveness and efficiency.     

A corrected formulation for the double row layout problem

This paper presents a corrected formulation to the mixed integer programming model of the double-row layout problem (DRLP), first proposed by Chung and Tanchoco (2010 Chung, J and Tanchoco, J. 2010. The double row layout problem. International Journal of Production Research, 48(3): 709–727. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar], The double row layout problem. International Journal of Production Research, 48 (3), 709–727). In the DRLP, machines are placed along two rows of a corridor, where the objective is to minimise the total cost of material handling for products that move between these machines. We highlight the errors in the original formulation, propose corrections to the formulation, and provide an analytical validation of the corrections.     

A machine-to-loop assignment and layout design methodology for tandem AGV systems with single-load vehicles

In this paper, we propose a method for design of tandem automated guided vehicle (AGV) systems with single-load vehicles. We consider the concurrent design of machines layout and AGV guide paths for a tandem system. Our goal is to devise a method that can achieve the following objectives: (1) maximise the workload balance between loops; (2) minimise the inter-loop flow; and (3) minimise the total flow distance. Our method solves the problem in four stages, considering the machines layout and the tandem paths at the same time. It assigns machines to loops, determines the layout of each loop, arranges loops on the floor, and finally designs a transportation centre to link the loops. We compare the performance of our method with a sequential design method that first determines the layout and then assigns the machines to loops. We solve a number of randomly generated problems for both methods. Results indicate that the proposed algorithm performs faster and achieves lower values of inter-loop flows and inter-loop flow distances.     

Integration of occupational health and safety in the facility layout planning,part II: design of the kitchen of a hospital

Facility layout design has an important effect on the performance of manufacturing systems. It intends to determine relative location of departments and machines within a plant. A good layout design must ensure that a set of criteria and objectives are met and optimised, e.g. area requirements, cost, communication and safety. The most common objective used in facility planning methods is to minimise the transportation cost. However, factors such as the plant safety, flexibility for future design changes, noise and aesthetics must be considered as well. In this paper, a case study is carried out to investigate the safety concerns in facility layout design. In this regard, a facility layout planning methodology, integrating occupational health and safety (OHS) is presented. This methodology considers transportation cost as well as safety in the facility design. By this means, OHS issues are considered at the design stage of the facility. In other words, this research demonstrates the improvements in the layout design by integrating safety aspects.     

An integrated approach to determine the block layout,AGV flow path and the location of pick-up/delivery points in single-loop systems

Layout design and material handling system design are two of the major aspects of facility planning. Although both aspects directly influence each other, the classical approach to the layout design is carried out in two separate steps: in the first step the block layout, i.e. the location of the departments in the workshop, is constructed, and in the second step, the material handling system is designed. The separate optimisation of these two aspects of the problem leads to solutions that can be far from the global optimum. In this paper, we develop an integrated algorithm to design the facilities and material handling systems. We focus on single-loop AGV systems. The proposed algorithm determines the block layout, AGV single-loop flow path and pick-up delivery stations, simultaneously. The associated from–to chart and the area of departments are the principal inputs of the algorithm. The objective is minimising total material flow distance among all departments. The results of our computational experiments show the algorithm was coded using MATLAB 7.0, and that our integrated algorithm is more efficient in terms of both the objective function value and the runtime.     

A game theory based approach for emergy analysis of industrial ecosystem under uncertainty

A well-designed and operated industrial ecological system should be able to utilize effectively the generated wastes from one member as the feed to another member. Nevertheless, due to heavy interactions among the member entities, particularly with various uncertainties, the coordinative material and energy reuse is a very complex task. In this paper, the issues of optimal operation of an industrial ecosystem under uncertainty are addressed. A game theory based approach is then introduced to derive an economically and environmentally optimal status of an industrial ecosystem. The effectiveness of the approach is demonstrated by tackling a case study problem, where the Nash Equilibrium for the profit payoff and sustainability payoff of the member entities is identified. The possible conflicts of the profit and sustainability objectives of the member entities in the ecosystem are resolved.     

An integrated approach for the concurrent determination of the block layout and the input and output point locations based on the contour distance

This paper presents an integrated approach for the facilities design problem. It develops a method for the concurrent determination of the block layout, the locations of departmental input and output (I/O) points using the contour distances between the I/O points, and the material flow paths between the I/O points. The topology of block layouts is represented using two linear sequences (sequence-pair), which allows the layout to have either a slicing or a non-slicing structure. The block layout is obtained from the sequence-pair with a linear programming formulation. Three heuristic methods are then presented to determine for a given block layout the locations of the I/O points on the perimeters of the departments. The flow paths from output to input points are found by determining the shortest paths that follow the perimeters of the departments. The linear programming algorithm, the shortest path algorithm, and the I/O point location heuristics are embedded into a simulated annealing algorithm that modifies the sequence-pair to obtain a high-quality layout based on the contour distances between the I/O points. Results of computational experiments show that the performance of this integrated algorithm compares favourably with those of algorithms using a sequential approach and is capable of solving industrial-sized problems in acceptable computation time.     

A nonlinear thick plate formulation based on the modified strain gradient theory

A geometric nonlinear first-order shear deformation theory-based formulation is presented to analyze microplates. The formulations derived herein are based on a modified strain gradient theory and the von Karman nonlinear strains. The modified strain gradient theory includes five material length scale parameters capable to capture the size effects in small scales. The governing equations of motion and the most general form of boundary conditions of an arbitrary-shaped plate are derived using the principle of virtual displacements. The analysis is general and can be reduced to the modified couple stress plate model or the classical plate model.     

A flexible labour division approach to the polygon packing problem based on space allocation

This paper deals with the two-dimensional satellite module polygon packing problem. Based on the duality of material and space, it regards the polygon packing problem as a space allocation problem, which involves allocating the container space to the given polygons reasonably and efficiently. Ant colony’s labour division is essentially a kind of task allocation. Using this task allocation to achieve the space allocation in polygon packing problems, a flexible labour division approach (FLD) is proposed based on the response threshold model. According to the characteristics of space allocation in polygon packing problems, FLD designs three actions for polygons to occupy the container space. With the interaction between environmental stimulus and response threshold, each polygon takes an appropriate action to complete the space allocation and a layout that meets the requirements of satellite module layout is obtained. The results of standard test instances demonstrate the effectiveness of FLD when compared with self-organisation emergence algorithm. Moreover, experiments on the general polygon packing problem also show that FLD is competitive with other existing algorithms.     

A new discrete Kirchhoff quadrilateral element based on the third-order theory for composite plates

A new discrete Kirchhoff quadrilateral element based on the refined third-order theory is developed for the analysis of composite plates. The element has seven degrees of freedom per node, namely, the three displacements, two rotations and two transverse shear strain components at the mid-surface. The inplane displacements and the shear strains are interpolated using bilinear interpolation functions and the mid-surface rotations are interpolated using bi-quadratic functions based on the discrete Kirchhoff technique. The element stiffness matrix and the consistent load vector are developed using the principle of virtual work. The finite element formulation is validated by comparing the results for simply-supported plate with the analytical Navier solution. Comparison of the present results with those using other available elements based on the TOT establishes the superiority of the present element in respect of simplicity, accuracy and computational efficiency. The element is free from shear locking     

基于贝叶斯理论及MCMC-MH算法推演地基土材料阻尼比的概率分布模型

浅层土壤的材料阻尼比参数分布可以通过多通道表面波(MASW)分析法提取的表面波衰减曲线来反演识别,但是衰减曲线对于较大深度和小空间尺度土壤性质的变化不敏感,反演的土壤材料阻尼比分布是非唯一的和不确定的.基于该研究建立了土体材料阻尼比随深度变化的先验概率分布模型,利用Nataf变换和Karhunen-Loeve将其分解为...     

A new FE model based on higher order zigzag theory for the analysis of laminated sandwich beam with soft core

A new finite element (FE) model has been developed based on higher order zigzag theory (HOZT) for the static analysis of laminated sandwich beam with soft core. In this theory, the in-plane displacement variation is considered to be cubic for both the face sheets and the core. The transverse displacement is assumed to vary quadratically within the core while it remains constant in the faces beyond the core. The proposed model satisfies the condition of transverse shear stress continuity at the layer interfaces and the zero transverse shear stress condition at the top and bottom of the beam. The nodal field variables are chosen in an efficient manner to overcome the problem of continuity requirement of the derivatives of transverse displacements. A C₀ quadratic beam finite element is implemented to model the HOZT for the present analysis. Numerical examples covering different features of laminated composite and sandwich beams are presented to illustrate the accuracy of the present model. Many new results are also presented which should be useful for future research.     

Magnetic dependence of cyclotron transition absorption in piezoelectric materials based on the quantum transport theory

We investigated theoretically the magnetic field dependence of the quantum optical transition of quasi 2-Dimensional Landau splitting system, in CdS and ZnO. Through the analysis of the current work, we found the increasing properties of the optical Quantum Transition Line Shapes (QTLSs) which show the absorption power and the Quantum Transition Line Widths(QTLWs) with the magnetic-field in CdS and ZnO. We also found that QTLW, γ(B)_total of CdS < γ(B)_total of ZnO in the magnetic field region B < 25 Tesla.