P. Simin Pulat

Bicriteria network flow problems: integer case

Abstract We consider a bicriteria network flow problem with flow variables restricted to integer values. The set of efficient solutions to the problem can be obtained by adopting a bicriteria integer programming technique. The purpose of this paper is to present a new technique which capitalizes on the network structure and the unimodular property of the incidence matrix. The procedure uses efficient solutions to the continuous version of the bicriteria network flow problem and parametric programming in order to generate the efficient solutions to the bicriteria integer network flow problem. The performance of the algorithm is also discussed.

Bicriteria Network Flow Problems : Continuous Case

Abstract An algorithm for bicriteria network flow problems is developed. It deals with a broader class of minimum cost network flow problems which include transportation, maximum flow, assignment, shortest path, and transshipment problems rather than a specific one. The algorithm integrates bicriteria mathematical programming theory with the out-of-kilter method.

DDM: decision support system for hierarchical dynamic decision making

Abstract A simulation-based decision support system for AHP (Analytic Hierarchy Process) is presented in this paper. The software, named DDM (Dynamic Decision Making), is applicable to dynamic decision scenarios where probabilistic interactions exist between the factors in the AHP hierarchy. Decision scenarios are generated using probability information specified by the user. The output of the simulation is the relative frequency of the selection of each alternative rather than a single final selection. The decision maker will evaluate the distribution histogram and make final selection based on his or her own inherent disposition to risk. DDM can be used for forecasting or for evaluating strategic planning options.

Efficient solutions for the bicriteria network flow problem

Abstract This paper discusses the generation of efficient basic feasible solutions for the bicriteria network flow problem. Alternate optima and degeneracy are also discussed. Computational performance of the algorithm is demonstrated using BINET code generated by the authors. The code includes cycle prevention and anti-stalling rules. It uses augmented threaded index list structures to update the bases. Computational results indicate the efficiency of the algorithm.

Experimental Analysis of Search-Based Selection of Sample Points for Straightness and Flatness Estimation

In earlier work [Bader et al., ASME J. Manuf Sci. Eng. 125(2), pp. 263-271 (2003); Int. J. Mach. Tools Manuf. 45(1), pp. 63-75 (2005)] the authors have presented an adaptive sampling method utilizing manufacturing error patterns and optimization search techniques for straightness and flatness evaluation. The least squares method was used to compute a tolerance zone. In this paper, experimental analysis is performed to verify the sturdiness of the adaptive sampling procedure. Experiments are carried out to investigate the effects of different factors on the sample size and absolute percent error of the estimated tolerance from that of a large population sample. Twelve 7075-T6 aluminum plates are end-milled and 12 cast iron plates are face-milled. Two sets of four plates from each lot are selected randomly, one each for straightness and flatness estimation. Factor A used in both straightness and flatness analyses is manufacturing process (i.e., surface error profile). Factor B for straightness is step size whereas for flatness it is search strategy (i.e., number of bad moves and restart allowed). Factor C for flatness is search algorithm (i.e tabu and hybrid). Plates are nested within the levels of manufacturing process. The results have been analyzed and compared with other sampling methods. The analyses reveal that the current approach is more efficient and reliable.

A Slope-Based Method for Least Cost Tolerance Allocation

In this paper, a new methodology is presented to solve the tolerance allocation-process selection problem simultaneously The prob lem is modeled using discrete and continuous variables and is transformed into a model with only continuous variables by defining an efficient tolerance-cost curve for each component Since the efficient tolerance-cost curve is neither convex nor concave, nonlinear programming method ologies cannot be directly applied The tolerance-cost curve is piecewise linearly approximated and an efficient methodology is developed to solve the problem The method starts with a solution which minimizes the objective function value but is not feasible The infeasibility is iteratively reduced in a way that the increase in the objective function value is minimal Computational analysis indicates that the method is very robust and requires negligible CPU time

Throughput analysis in an automated material handling system

Throughput analysis in an automated material handling system, such as an Automated Storage and Retrieval System(AS/RS), may be a complex problem. In the past, several approaches have been used for such an analysis. This paperpresents a combinatorial ap proach to evaluating the throughput performance of a mini-load system, with simulation as the primary method of investigation.

The shifting bottleneck procedure for job-shops with parallel machines

The shifting bottleneck (SB) heuristic has been successfully applied to the job-shop scheduling problem. In this paper, the shifting bottleneck heuristic has been extended to solve job-shop problems with parallel machine workcentres. The efficient shifting bottleneck heuristic was developed to reduce the number of subproblems and provide tradeoff results between the computation time and the solution quality. The effect of bottleneck machine selection and reoptimisation procedures on the computational time is discussed. Moreover, a procedure is developed to achieve the desired makespan with near optimal number of machines of each machine type. The tradeoff between the makespan and the minimal number of machines required to achieve the makespan is also illustrated on few job-shop problems.

Methodology for tolerance design using quality loss function

Abstract In this paper, we develop a methodology for tolerance design that focuses on total variability from the target value. A general optimization model is developed to allocate tolerances to assembly parts. The constraint for the optimization model is the requirment for assembly tolerances or variability and cost is related to the total cost to reduce variance for the components and loss due to variation from target for the assembly. Different quality loss functions are also discussed.

Computer-aided tolerance assignment procedure (CATAP) for design dimensioning

SUMMARY The manual procedure of drafting engineering designs is fast becoming obsolete. Newer systems for computer-aided design (CAD) drafting are emerging everyday. However, the process of including tolerance details in these CAD drawings is extremely complex and has very little evidence of existence in past literature. This paper identifies and computerizes a procedure for automatic tolerance assignment in CAD drawings. The procedure developed envelopes three major stages: feature extraction, feature infcrcncing, and rule-based tolerance allocation. The system was implemented on an IBM-PC compatible. The results established through example analysis verify the utility of the system.