International Journal of Applied Operational Research

Mathematical Modeling for an Integrated Inventory System with Two-level Trade Credit and Random Defectiveness in Transport

A. Thangam

Modern business environment focuses on improving the operational efficiency of supplier, retailer and customers through integrating their inventory. Although a smoothly running integrated inventory system is ideal, the reality is to deal with imperfectness in transportation. In actual production environments, inventory items are not perfect and defectiveness occurs in a random process. In this paper, we propose an integrated supplier–retailer inventory model in which both supplier and retailer have adopted trade credit policies, and the retailer receives an arriving lot which contains random defectiveness in quality of items. This paper proposes a mathematical model considering two situations such as (a) risk neutral and (b) risk-averse case and the solution procedures are described with computational algorithm. The optimization procedures are discussed for determining optimal cycle time and the optimal number of shipments by minimizing the expected joint total cost in the integrated inventory system. Numerical examples are provided to illustrate the theoretical results, and sensitivity analysis is made for major inventory parameters.

A novel cooperative game between client and subcontractors based on technical characteristics

M. Moradi

Large projects often have several activities which are performed by some subcontractors with several skills. Costs and time reduction and quality improvement of the project are very important for client and subcontractors. Therefore, in real large projects, subcontractors join together and form coalitions for improving the project profit. A key question is how an extra profit of cooperation among subcontractors should be assigned to them. This paper tries to address this question by proposing a cooperative game model based on technical characteristics of subcontractors. Technical characteristics of each contractor specify its value in the coalitions that it may join. Fair and appropriate allocation of profit among subcontractors is suggested by adopting cooperative game theory methods such as the Core method, Shapley method, Equal Profit Method (EPM) and the t-value.

Performance assessment of in-pipe inspection microrobots by FAHP method

M. Ghandehari

Since the issue of low diameter in-pipe inspection microrobots is particularly important in microrobotics field, in this paper, the results of a study on the various built or designed microrobots are presented. The objective of our paper is the prioritizing of in-pipe microrobots because that is an important tool in medical and industrial applications. This study , which includes 7 types of in-pipe microrobots such as Dielectric, Ionic Polymeric Metal Composite, Electromagnetic, Phase-change actuator , Piezoelectric actuator, Pneumatic actuator and Shape Memory Alloy actuator compares with some criteria such as the consuming power, response time, efficiency, dynamical modeling, producing force and manufacturing. These criteria are provided by specialists in standard organizations. In here, Fuzzy Analytic Hierarchy Process method is used for the best mechanisms determination in each field and weight of each criteria and their importance is determined. This study assists the design of a novel microrobotic system based on Fuzzy Analytic Hierarchy Process method with the design criteria consideration.

Proof of a conjecture of Yuan and Zontini on preconditioned methods for M-matrices

S. A. Edalatpanah

Systems of linear equations are ubiquitous in science and engineering, and iterative methods are indispensable for the numerical treatment of such systems. When we apprehend what properties of the coefficient matrix account for the rate of convergence, we may multiply the original system by some nonsingular matrix, called a preconditioner, so that the new coefficient matrix possesses better properties. Recently, some scholars presented several preconditioners and based on numerical tests proposed some conjectures for preconditioned iterative methods. In this paper, we prove one conjecture on the preconditioned Gauss–Seidel iterative method for solving linear systems whose coefficient matrix is an M-matrix.