Simulation and Optimization Of Ant Colony Optimization Algorithm For The Stochiastic Uncapacitated Location-Allocation Problem

This study proposes a novel methodology towards using ant colony optimization (ACO) with stochastic demand. In particular, an optimizationsimulation-optimization approach is used to solve the Stochastic uncapacitated location-allocation problem with an unknown number of facilities, and an objective of minimizing the fixed and transportation costs. ACO is modeled using discrete event simulation to capture the randomness of customers’ demand, and its objective is to optimize the costs. On the other hand, the simulated ACO’s parameters are also optimized to guarantee superior solutions. This approach’s performance is evaluated by comparing its solutions to the ones obtained using deterministic data. The results show that simulation was able to identify better facility allocations where the deterministic solutions would have been inadequate due to the real randomness of customers’ demands

Metaheuristic Method Selection using Fuzzy Analytical Hierarchy Process to Solve The Design Problem of PRocess Oriented Facility Layout

Abstrak Pendekatan metaheuristik telah banyak diterapkan untuk memecahkan masalah optimasi. Meskipun terdapat kelebihan yang diperoleh melalui pendekatan ini, banyak penelitian yang menghadapi masalah untuk memilih kinerja pengukuran kriteria dan metode yang paling tepat. Penelitian ini mengusulkan pendekatan fuzzy Analytical Hierarchy Process (AHP) untuk melakukan pemilihan metode metaheuristik terbaik dalam studi kasus perancangan tata letak fasilitas. Fuzzy Analytical Hierarchy Process digunakan untuk menentukan bobot masing-masing kriteria dan alternatif. Penelitian ini menggambarkan suatu kerangka metodologi berdasarkan kriteria yang sesuai dan teknik fuzzy Analytical Hierarchy Process untuk memilih metode metaheuristik yang optimal. Metode yang dipilih dalam penelitian ini digunakan untuk menyelesaikan masalah fasilitas tata letak berorientasi proses. Hasil menunjukkan bahwa metode yang dipilih mampu menghasilkan kinerja yang lebih baik dari penelitian sebelumnya.Kata Kunci: metaheuristik, fuzzy AHP, perancangan tata letak   Abstract Metaheuristic approaches have been widely implemented to solve optimization problems. Despite the advantages of these approaches, previous research encountered problems in determining the most appropriate performance measurement criteria and method. This study proposed a fuzzy Analytical Hierarchy Process (AHP) approach to select the best metaheuristic method for facility layout design. Fuzzy Analytical Hierarchy Process was used to determine the weight of each criteria and alternative. This paper provides a practical framework based on appropriate criteria and fuzzy Analytical Hierarchy Process technique to selecting the optimal metaheuristic method. The method chosen in this study was used to solve the process-oriented facility layout problems. The results suggested that the selected method could produce better performance than that of the previous studies. Keywords: metaheuristic, fuzzy AHP, layout desig

A Two-Stage Queue Model to Optimize Layout of Urban Drainage System considering Extreme Rainstorms

Extreme rainstorm is a main factor to cause urban floods when urban drainage system cannot discharge stormwater successfully. This paper investigates distribution feature of rainstorms and draining process of urban drainage systems and uses a two-stage single-counter queue method M/M/1→M/D/1 to model urban drainage system. The model emphasizes randomness of extreme rainstorms, fuzziness of draining process, and construction and operation cost of drainage system. Its two objectives are total cost of construction and operation and overall sojourn time of stormwater. An improved genetic algorithm is redesigned to solve this complex nondeterministic problem, which incorporates with stochastic and fuzzy characteristics in whole drainage process. A numerical example in Shanghai illustrates how to implement the model, and comparisons with alternative algorithms show its performance in computational flexibility and efficiency. Discussions on sensitivity of four main parameters, that is, quantity of pump stations, drainage pipe diameter, rainstorm precipitation intensity, and confidence levels, are also presented to provide guidance for designing urban drainage system