Imran Ali Chaudhry

A research survey: review of flexible job shop scheduling techniques

In the last 25 years, extensive research has been carried out addressing the flexible job shop scheduling (JSS) problem. A variety of techniques ranging from exact methods to hybrid techniques have been used in this research. The paper aims at presenting the development of flexible JSS and a consolidated survey of various techniques that have been employed since 1990 for problem resolution. The paper comprises evaluation of publications and research methods used in various research papers. Finally, conclusions are drawn based on performed survey results.

Object Oriented Case Representation for CBR Application in Structural Analysis

Knowledge representation is an essential element of a problem-solving technique through computational work. This article describes the knowledge representation scheme formulated to represent a problem in the structural analysis domain for solution through case-based reasoning (CBR). The numerical knowledge is extracted from a real-life problem that can be used as an input in a case-based reasoner. The geometric topology, loading, and mesh distribution for structure from a solved problem is represented in the form of numerical values for easy adaptation by the new problem. The representation scheme is a step forward in development of a system to be utilized for the time-consuming structural analysis requiring heavy computational power, such as an aircraft wing and fuselage components. The success of the representation strategy is a proof that CBR can work as a powerful problem-solving tool in this domain.Knowledge representation is an essential element of a problem-solving technique through computational work. This article describes the knowledge representation scheme formulated to represent a problem in the structural analysis domain for solution through case-based reasoning CBR. The numerical knowledge is extracted from a real-life problem that can be used as an input in a case-based reasoner. The geometric topology, loading, and mesh distribution for structure from a solved problem is represented in the form of numerical values for easy adaptation by the new problem. The representation scheme is a step forward in development of a system to be utilized for the time-consuming structural analysis requiring heavy computational power, such as an aircraft wing and fuselage components. The success of the representation strategy is a proof that CBR can work as a powerful problem-solving tool in this domain.

Collaborative Product Development in Extended Enterprise

Excessive market competition, mass customization, growing product complexity is forcing enterprises to look for new initiatives. To take the lead in new product development, mergers and joint ventures are a common strategy. As the companies do not possess all the knowledge with in, they need to instead rely on other organizations, the result is, need of distance product development, which in turn requires huge efforts for collaborative product development, especially in case of aerospace and automotive. In this paper we investigate into the collaborative product development for complex products like aeroplane in an extended enterprise and also examine product design approaches being adopted by leading giants of the industry. There are claims of high gains by those who have adopted the systems(i.e. PLM solutions) that helped collaboration. We propose PLM based framework to enable collaborative product development. In this paper we also introduce a brief concept of design flow process activities for collaborative development

Genetic Algorithm to minimize flowtime in a no-wait flowshop scheduling problem

No-wait flowshop is an important scheduling environment having application in many industries. This paper addresses a no-wait flowshop scheduling problem, where the objective function is to minimise total flowtime. A Genetic Algorithm (GA) optimization approach implemented in a spreadsheet environment is suggested to solve this important class of problem. The proposed algorithm employs a general purpose genetic algorithm which can be customised with ease to address any objective function without modifying the optimization routine. Performance of the proposed approach is compared with eight previously reported algorithms for two sets of benchmark problems. Experimental analysis shows that the performance of the suggested approach is comparable with earlier approaches in terms of quality of solution.

Identical Parallel-Machine Scheduling and Worker Assignment Problem Using Genetic Algorithms to Minimize Makespan

Identical parallel machine scheduling problem for minimizing the makespan is a very important production scheduling problem which has been proven to be NP-hard. The problem further compounds with additional constraints. Genetic algorithms (GA) have shown great advantages in solving the combinatorial optimization problem in view of its characteristic that has high efficiency and that is fit for practical application. In this chapter we present a spreadsheet based GA approach for minimizing the makespan for scheduling of a set of tasks for identical parallel machines and worker assignment to machines. The results obtained from the proposed approach are compared with two sets of benchmark problems consisting of 100 problems each. It has been demonstrated that the performance of proposed approach is superior to the results that have been obtained earlier. The proposed approach produces optimal solution for almost 95% of the problems demonstrating the effectiveness of the proposed approach. An empirical analysis of GA parameters has also been carried out to see the effect on the performance of the proposed algorithm.

Tensile Behavior of Unidirectional Carbon Reinforced Composites for Aerospace Structures under Varying Strain Rates

This paper focuses on progressive damage investigation and failure analysis of carbon fiber reinforced laminates under varying strain rates in tensile mode. Samples specimen prepared for experiments were made from unidirectional ply with 70/30 fiber-matrix volume fraction and cross-ply (0°-90°) balanced stacking. These laminates were subjected to uniaxial longitudinal tensile loading in a Universal Testing Machine (UTM) with varying strain rates. Results acquired from the experiments were used to plot stress versus strain curves for different strain rates. These plots were subsequently analyzed to investigate the effect of varying loading rates on the mechanical properties and failure behavior of these composites. Experimental data revealed a considerable increase in the tensile strength with increasing strain rate. The tensile modulus and strain to failure were also found to exhibit slight increase with the increasing strain rate.

AIRCRAFT FAULT IDENTIFICATION AND DIAGNOSIS USING AN EXPERT SYSTEM: A CASE STUDY

Artificial intelligence (Al) technology is widely suggested for systematic diagnosis of faults where the amount of well-defined diagnosis knowledge is vast and the sequence of steps required to identify the fault is very long. This paper addresses the practical use of Expert System (ES) for aircraft fault identification and diagnosis. A prototype Expert System has been developed using Microsoft Windows® based K-Vision® software, a freely available expert system development tool and run on a PC. The heart of the ES i.e., the knowledge base has been developed from interviewing the experts, existing aircraft manuals and maintenance history. It has been demonstrated that expert systems can be employed effectively for aircraft fault identification and diagnosis as well as for any other problem area. The result of this development is expected to introduce a systematic and intelligent method in aircraft fault identification and diagnosis and also act as a tutor for inexperienced aircraft technicians and engineers. The paper gives brief theory of the Expert Systems and then a demonstration of the software is presented.

REVIEW OF SCHEDULING TECHNIQUES IN A MANUFACTURING ENVIRONMENT

Scheduling theory is concerned with the optimal allocation of scarce resources to activities over time. Scheduling in the manufacturing environment can be defined as the process of deciding what happens when and where. The purpose of this paper is to apprise the reader of the various scheduling techniques used for scheduling in the manufacturing environment. Strengths and weaknesses of the reviewed techniques are also given. This paper will also serve the purpose of tutorial and a starting point to select the appropriate technique to suit a particular domain.