Block Layout Research Articles

Effect of Subsurface Drip Irrigation System Uniformity on Cotton Production in the Texas High Plains

Planned reductions in subsurface drip irrigation (SDI) system uniformity in the semi-arid environment of West Texas could reduce installation costs. A SDI system was installed and cotton production experiment conducted from 2001 to 2006 to evaluate irrigation system water distribution uniformities having flow variations (Qvar) = 5%, 15%, and 27% at both moderate and near full irrigation levels. Flow variation treatments were established by installing and irrigating cotton with different diameter drip laterals in field plots in a complete block layout. Subsurface drip laterals with diameters of 17, 22, and 25 mm, pressurized at 72, 83, and 45 kPa, respectively, resulted in different irrigation uniformity treatments defined as poor (POOR), very good (VGD), and acceptable (ACC).

Manufacturing facilities layout design using Genetic Algorithm

In this paper, a multiobjective machine layout problem with unequal area and fixed shape is solved by using Genetic Algorithm (GA). The proposed model minimises the cost associated with material handling during normal and breakdown periods and the cost of unusable space. The shape-based block layout approach, which is capable of changing the orientation of facilities to increase the space utilisation, is used to place the machines in the given building area, based on the layout string generated by the GA optimiser. The mathematical formulation, the details of solution methodology, the illustrative example and the computational results are presented.

Developing exact and Tabu search algorithms for simultaneously determining AGV loop and P/D stations in single loop systems

There are some issues which have to be addressed when designing an automated guided vehicles system (AGVS) such as flow-path layout, traffic management, the number and the location of pick up and delivery points, vehicle routing and so on. One of the AGVS guide path configurations discussed in the previous researches includes a single-loop which is the subject of this paper. In unidirectional single loop systems, determining the loop for the motion of an AGV, and the location of pick up and delivery (P/D) stations in the cells, are prominent points which, when considered simultaneously, lead to better results than determining each one independently. However, in the literature it is proved that the problem of separately determining the shortest feasible loop is a NP-complete problem. In this paper, by considering a from-to chart and a block layout as the input of problem, we try to determine: (1) a single loop, with at least one shared edge with each cell, (2) the direction of the flow and (3) the location of P/D stations on the loop, all at the same time, in a way that the total travel distance on the loop be minimised. In this regard, first a new exact algorithm is presented and then three heuristic algorithms are developed utilising a Tabu search (TS) method. Solving randomly generated test problems shows that our exact algorithm is capable of solving small size problems; also all three TS algorithms work efficiently in solving problems that could not be solved by exact algorithms.

T-shape homogenous block patterns for the two-dimensional cutting problem

This paper presents an algorithm for unconstrained T-shape homogenous block cutting patterns of rectangular pieces. A vertical cut divides the stock sheet into two segments. Each segment consists of sections that have the same length and direction. A section contains a row of homogenous blocks. A homogenous block consists of homogenous strips of the same piece type. Each cut on the block produces just one strip. The directions of two strips cut successively from a block are either parallel or orthogonal. The algorithm uses a dynamic programming recursion to generate optimal blocks, solves knapsack problems to obtain the block layouts on the sections and the section layout on segments of various lengths, and optimally selects two segments to compose the cutting pattern. The computational results indicate that the algorithm is efficient in improving material usage, and the computation time is reasonable.

Comparison of Nodal Distribution of Soybean Cultivars' Yield Components in Different Planting Dates

Aim of this study was to determine planting date effects on Nodal distribution of yield and its components in nine indeterminate soybean cultivars. To meet such a purpose, a split plot design based on a randomized complete block layout with six planting dates (24th April, 10th and 27th May, 10th and 26th June and 11th July) as main plots and nine cultivars (Williams, Clark 63, SRF 450, Steele, Hark, Corsoy, Blackhawk, Woodworth and Bonus) as sub plots have been used in five replications. The results have clarified that height, branch number, pod number, grain number and seed weight plays an important role on yield increasing. So that, medium maturity cultivars have producing maximum number of pods, grains and seed weight in their upper two third of canopy. Also, various cultivars have indicated different reactions for yield components, so that, Williams and Woodworth (medium maturity cultivars), Steele and Bonus (early maturity cultivars) have produced larger seeds in different planting dates. Generally, Woodworth, in comparison with the other cultivars, demonstrating superiorities in all the considered traits. Maximum amount of pod number, grain number and seed weight in early maturity cultivars was belong to 27th of May planting date, however, for Woodworth and Clark 63 (medium maturity) it was 24th of April and 27th of May, respectively. The highest 100 seed weight per node were produced at 26th of June and 27th of May planting dates by Woodworth and Corsoy, respectively. Differences between planting dates for 100 seed weight in Clark 63 and Bonus were not significant.

Design and analysis of efficacy evaluation trials

Design and analysis of efficacy evaluation trials

Toward guiding the selection of a layout procedure

PurposeThe purpose of this paper is to assist facility designers decide when to use the graph‐theoretic (GTH) approach to develop a block layout and when to seek another alternative that requires a lesser effort. Difficulties encountered when a GTH block layout is developed from an adjacency graph could force designers to sacrifice or change some of the adjacencies of the adjacency graph in the GTH block layout. Consequently, the value of the objective function of a GTH block layout could become less than what would be expected from the GTH approach.Design/methodology/approachA computational study is performed to assess the value of the objective function of block layouts produced by the GTH approach when adjacencies of the adjacency graph are deleted or changed in the GTH block layout and two of the procedures in the literature.FindingsThe computational study reveals that the magnitude of the decline in the value of the objective function of the GTH block layout renders it comparable to values obtained by the two procedures selected from the literature.Originality/valueThe results of the study could motivate layout designers to resort to various approaches to develop a block layout rather than sacrifice some adjacencies of the adjacency graph in the GTH block layout, which would adversely affect its objective function value.

Designing an efficient method for simultaneously determining the loop and the location of the P/D stations using genetic algorithm

There are some issues which have to be addressed when designing an automated guided vehicles system (AGVS) such as flow-path layout, traffic management, the number and the location of pick-up and delivery points, vehicle routing and so on. One of the AGVS guide path configurations discussed in the previous researches includes a single-loop which is the subject of this paper. Many researchers have worked on the subject of finding the shortest single loop in a given block layout. This problem has been already proved to be NP-complete. Finding the location of pick-up/drop-off (P/D) stations on a given loop is what is typically done, but locating the loop and the P/D stations simultaneously is actually more realistic. In this paper, a genetic algorithm (GA) has been developed to determine these two simultaneously. The algorithm only reproduces the feasible solutions. The objective is to minimize the total traveled distance. A from-to chart and a block layout are the inputs and a unidirectional loop including its corresponding direction and along with the locations of the P/D stations on the loop are the outputs. To show the efficiency of the algorithm, the associated results for some sample problems have been compared with the results generated by LINGO for the equivalent mixed integer programming (MIP) problem. Computational results show the efficiency of the algorithm in solving relatively large size problem.

Detailed layout planning for irregularly-shaped machines with transportation path design

In order to obtain a competitive level of productivity in a manufacturing system, efficient machine or department arrangements and appropriate transportation path structures are of considerable importance. By defining a production system’s basic structure and material flows, the layout determines its operational performance over the long term. However, most approaches proposed in the literature provide only a block layout, which neglects important operational details. By contrast, in this paper, we introduce approaches to planning layouts at a more detailed level. Hence, this present paper introduces an integrated approach which allows a more detailed layout planning by simultaneously determining machine arrangement and transportation paths. Facilities to be arranged as well as the entire layout may have irregular shapes and sizes. By assigning specific attributes to certain layout subareas, application-dependent barriers within the layout, like existing walls or columns, can be incorporated. We introduce a new mathematical layout model and develop several improvement procedures. An analysis of the computational experiments shows that more elaborate heuristics using variable neighborhoods can generate promising layout configurations.

Coordinated Multilevel Buffer Cache Management with Consistent Access Locality Quantification

This paper proposes a protocol for effective coordinated buffer cache management in a multilevel cache hierarchy typical of a client/server system. Currently, such cache hierarchies are managed suboptimally-decisions about block placement and replacement are made locally at each level of the hierarchy without coordination between levels. Though straightforward, this approach has several weaknesses: 1) Blocks may be redundantly cached, reducing the effective total cache size, 2) weakened locality at lower-level caches makes recency-based replacement algorithms such as LRU less effective, and 3) high-level caches cannot effectively identify blocks with strong locality and may place them in low-level caches, The fundamental reason for these weaknesses is that the locality information embedded in the streams of access requests from clients is not consistently analyzed and exploited, resulting in globally nonsystematic, and therefore suboptimal, placement and replacement of cached blocks across the hierarchy. To address this problem, we propose a coordinated multilevel cache management protocol based on consistent access-locality quantification. In this protocol, locality is dynamically quantified at the client level to direct servers to place or replace blocks appropriately at each level of the cache hierarchy. The result is that the block layout in the entirely hierarchy dynamically matches the locality of block accesses. Our simulation experiments on both synthetic and real-life traces show that the protocol effectively ameliorates these caching problems. As anecdotal evidence, our protocol achieves a reduction of block accesses of 11 percent to 71 percent, with an average of 35 percent, over uniLRU, a unified multilevel cache scheme

Coordinated Multilevel Buffer Cache Management with Consistent Access Locality Quantification

This paper proposes a protocol for effective coordinated buffer cache management in a multilevel cache hierarchy typical of a client/server system. Currently, such cache hierarchies are managed suboptimally-decisions about block placement and replacement are made locally at each level of the hierarchy without coordination between levels. Though straightforward, this approach has several weaknesses: 1) Blocks may be redundantly cached, reducing the effective total cache size, 2) weakened locality at lower-level caches makes recency-based replacement algorithms such as LRU less effective, and 3) high-level caches cannot effectively identify blocks with strong locality and may place them in low-level caches, The fundamental reason for these weaknesses is that the locality information embedded in the streams of access requests from clients is not consistently analyzed and exploited, resulting in globally nonsystematic, and therefore suboptimal, placement and replacement of cached blocks across the hierarchy. To address this problem, we propose a coordinated multilevel cache management protocol based on consistent access-locality quantification. In this protocol, locality is dynamically quantified at the client level to direct servers to place or replace blocks appropriately at each level of the cache hierarchy. The result is that the block layout in the entirely hierarchy dynamically matches the locality of block accesses. Our simulation experiments on both synthetic and real-life traces show that the protocol effectively ameliorates these caching problems. As anecdotal evidence, our protocol achieves a reduction of block accesses of 11 percent to 71 percent, with an average of 35 percent, over uniLRU, a unified multilevel cache scheme

A two-stage simulated annealing procedure for block layout problems

Rules for setting simulated annealing control parameters are proposed for block layout problems where different material-handling devices are dynamically assigned to individual material movements as layout solutions are perturbed. Recognizing the high cost of computing materials-handling cost in this type of problem, the rules are based on adapting an existing two-stage simulated annealing procedure to accelerate convergence. Experimental results suggest that the application of these rules yields solution quality comparable with other single and two-stage simulated annealing algorithms but with significantly fewer re-evaluations of the objective function.

Ant colony algorithm for the shortest loop design problem

In this paper, a new algorithm for solving the shortest loop design problem is presented. The shortest loop design problem is to find the shortest loop for an automated guided vehicle covering at least one edge of each department of a block layout. In this paper, first it is shown that this problem can be represented as a graph model. The properties of the presented model enable us to design a meta-heuristic based on ant colony system algorithm for solving the shortest loop design problem. Computational results show the efficiency of our algorithm in compare to the other techniques.

A Mixed Integer Programming Model to Modify a Block Layout for Obtaining Smooth Material Flow Paths

The conceptual block layouts generated by layout software packages very often yield detailed layouts with non-smooth material flow paths that have an excessive number of turns. Such non-smooth flow paths are not acceptable or feasible for actual construction. The automatically generated block layouts almost always have to be adjusted by layout design engineer in a labor intensive process. This paper presents a mixed integer programming model to modify a given block layout into a layout that allows the construction of smooth flow paths, while preserving the relative positions of the departments in the original block layout. Results of the computational experiments show that much smoother flow paths can be generated in the modified block layouts than those in the original block layouts. The suggested model can be solved within short computational time even for large industrial-sized block layout problems and can be executed without human intervention.

Two-stage general block patterns for the two-dimensional cutting problem

This paper presents an algorithm for the unconstrained two-dimensional cutting problem of rectangular pieces. It proposes the two-stage general block pattern that can be cut into general blocks in two stages, with another two or more stages being required to cut the blocks into pieces. Firstly vertical cuts divide the stock sheet into segments, and then horizontal cuts divide the segments into general blocks. A general block contains general strips, and each cut on the block produces just one strip. The directions of two strips cut successively from a block are either parallel or perpendicular to each other. The algorithm uses a dynamic programming recursion to determine the strip layout on each block, solves knapsack problems to obtain the block layout on each segment and the segment layout on the sheet. The computational results indicate that the algorithm is highly efficient in improving material usage, and the computation time is reasonable.

A new mixed integer programming formulation for facility layout design using flexible bays

This paper presents a mixed-integer programming formulation to find optimal solutions for the block layout problem with unequal departmental areas arranged in flexible bays. The nonlinear department area constraints are modeled in a continuous plane without using any surrogate constraints. The formulation is extensively tested on problems from the literature.

Improving WCET by applying a WC code-positioning optimization

Applications in embedded systems often need to meet specified timing constraints. It is advantageous to not only calculate the worst-case execution time (WCET) of an application, but to also perform transformation, which reduce the WCET, since an application with a lower WCET will be less likely to violate its timing constraints. Some processors incur a pipeline delay whenever an instruction transfers control to a target that is not the next sequential instruction. Code-positioning optimizations attempt to reduce these delays by positioning the basic blocks to minimize the number of unconditional jumps and taken conditional branches that occur. Traditional code-positioning algorithms use profile data to find the frequently executed edges between basic blocks, then minimize the transfers of control along these edges to reduce the average case execution time (ACET). This paper introduces a WCET code-positioning optimization, driven by the worst-case (WC) path information from a timing analyzer, to reduce the WCET instead of ACET. This WCET optimization changes the layout of the code in memory to reduce the branch penalties along the WC paths. Unlike the frequency of edges in traditional profile-driven code positioning, the WC path may change after code-positioning decisions are made. Thus, WCET code positioning is inherently more challenging than ACET code positioning. The experimental results show that this optimization typically finds the optimal layout of the basic blocks with the minimal WCET. The results show over a 7% reduction in WCET is achieved after code positioning is performed.

An Incremental Placement Algorithm for Building Block Layout Design Based on the O-Tree Representation

Incremental modification and optimization in VLSI physical design is of fundamental importance. Based on the O-tree (ordered tree) representation which has more prominent advantages in comparison with other topological representations of non-slicing floorplans, in this paper, we present an incremental placement algorithm for BBL (Building Block Layout) design in VLSI physical design. The good performance of experimental results in dealing with some instances proves the effectiveness of our algorithm.

Optimization of block layout design problems with unequal areas: A comparison of MILP and MINLP optimization methods

The block layout design problem with unequal areas, which was originally formulated by Armour and Buffa in the early 1960s, is a fundamental optimization problem encountered in many manufacturing and service organizations. In this paper, we present a new modelling framework for effectively finding global optimal solutions for the block layout design problem with unequal areas. The most fundamental aspect of the framework consists of an exact representation of the underlying area restrictions. Our computational results consistently yield optimal solutions on several well-known test problems from the published literature. Furthermore, different mixed-integer linear and mixed-integer nonlinear optimization methods are compared. Our study indicates that the new modeling framework together with simple constraints to avoid symmetric layout solutions can be successfully used to find optimal layout solutions; therefore, seriously challenging other optimization methods on this important class of hard, fundamental problems. The new modeling framework may easily be applied in the context of the process plant layout and piping design problems.

Layout design for flexible manufacturing systems considering single-loop directional flow patterns

To achieve high productivity in a flexible manufacturing system (FMS), an efficient layout arrangement and material flow path design are important due to the large percentage of product cost that is related to material handling. The layout design problem addressed in this paper has departments with fixed shapes and pick-up/drop-off points. It is an open-field type layout with single-loop directed flow path. A two-step heuristic is proposed to solve the problem. It first solves a traditional block layout with directed-loop flow path to minimize material handling costs by using a combined spacefilling curve and simulated annealing algorithm. The second step of the proposed methodology uses the resulting flow sequence and relative positioning information from the first step as input to solve the detailed FMS layout, which includes the spatial coordinates and orientation of each FMS cell. This detailed FMS layout problem is formulated and solved as a mixed integer program. Empirical illustrations show promising results for the proposed methodology in solving real-world type problems.