Salih O. Duffuaa

A linear programming approach for the weighted graph matching problem

A linear programming (LP) approach is proposed for the weighted graph matching problem. A linear program is obtained by formulating the graph matching problem in L/sub 1/ norm and then transforming the resulting quadratic optimization problem to a linear one. The linear program is solved using a simplex-based algorithm. Then, approximate 0-1 integer solutions are obtained by applying the Hungarian method on the real solutions of the linear program. The complexity of the proposed algorithm is polynomial time, and it is O(n/sup 6/L) for matching graphs of size n. The developed algorithm is compared to two other algorithms. One is based on an eigendecomposition approach and the other on a symmetric polynomial transform. Experimental results showed that the LP approach is superior in matching graphs than both other methods. >

Maintenance and quality: the missing link

Focuses on the relationship between maintenance and quality. Then briefly reviews models relating production and quality on the one hand, and production and maintenance on the other. Using concepts from predictive maintenance and the measure of equipment effectiveness from total productive maintenance (TPM), identifies explicit links between maintenance and quality. Emphasizes the need to develop adequate models relating maintenance and quality. Presents two approaches for modelling the link between maintenance and quality. The first approach is based on the concept of imperfect maintenance and the second one uses the Taguchi approach to quality and maintenance.

A Tabu search algorithm for maintenance scheduling of generating units

Abstract A new heuristic algorithm based on the Tabu search has been proposed for the maintenance schedule (MS) of electric generation units. The algorithm was developed, implemented and tested on an integrated model for the MS problem. The model used two criteria: minimizing the total generator operating cost and levering the reserve. Each of the above criteria is used with the following constraints: maintenance completion, crew size, precedence, reserve and reserve constants. The performance of the Tabu search algorithm is promising. The Tabu search algorithm solved two power system problems, 4 units and 22 units. The implicit enumeration algorithm was used to check the validity and the quality of the Tabu search solution.

A generic conceptual simulation model for maintenance systems

Maintenance is a complex process that is triggered by equipment failure or planned repair. This process requires planning, scheduling, control and the deployment of maintenance resources to perform necessary maintenance activities. In this paper a generic conceptual model for maintenance systems has been developed. The conceptual model consists of seven modules. The first one is the input module in which the characteristic of the maintenance system is specified. The second module is concerned with modeling the maintenance load. The third module is the planning and scheduling. This module is the most critical, since it controls the maintenance process. The fourth module is the material and spare parts supply, followed by the equipment availability module. The sixth module is the quality control module and the performance measures are the seventh module. The specification of such a conceptual model lays the ground for developing a realistic simulation model.

Maintenance, modeling, and optimization

List of Figures. List of Tables. Preface. Contributing Authors. Part I: Introduction. 1. Maintenance Modeling Areas M. Ben-Daya, S.O. Duffuaa. Part II: Maintenance Planning & Scheduling. 2. Mathematical Models in Maintenance Planning and Scheduling S.O. Duffuaa. 3. Electric Generator Maintenance Scheduling I. El-Amin. 4. Reliability Based Spare Parts Forecasting and Procurement Strategies A.K. Sheikh, et al. 5. Maintenance Service Contracts D.N.P. Murthy. 6. Simulation Metamodeling of a Maintenance Float System C.N. Madu. Part III: Preventive Maintenance. 7. Basic Preventive Maintenance Policies and their Variations T. Dohi, et al. 8. A General Framework for Analyzing Maintenance Policies V. Makis, et al. 9. Imperfect Preventive Maintenance Models T. Nakagawa. 10. Singel Machine Inspection Problem M.H. Mohammad, A. Al-Fawzan. 11. A General Approach for the Coordination of Maintenance Frequencies R. Dekker, et al. 12. Maintenance Grouping in Production Systems G. van Dijkhuizen. Part IV: Condition Based Maintenance. 13. One-Line Surveillance and Monitoring H.S.J. Elsayed, A. Elsayed. 14. Maintenance Scheduling Using Monitored Parameter Values D. Kumar. Part V: Integrated Maintenance, Production and Quality Models. 15. A General EMQ Model with Machine Breakdowns V. Makis, et al. 16. Stochastic Manufacturing Systems: Production and Maintenance Control E.K. Boukas, Q. Zhang. Part VI: Maintenance & New Technologies. 17. JIT and Maintenance G. Waeyenbergh, et al. Index.

Performance measures for academic departments

Measuring the performance of academic departments received little attention compared to other industries due to their complex nature and difficulty in measuring their outputs. However, measures of performance are needed to assess whether they meet their set objectives and foster an environment of continuous improvement. The objective of this paper is to develop a performance measurement system for educational institutions. It outlines the properties of adequate performance measures and the steps for developing such measures in an educational environment. Three types of performance measures are proposed. These are outcomes, inputs and process measures. Suggestions are made to select the most appropriate and relevant performance measures pertinent to academic departments’ goals and objectives. Also the need, relevance and implementation issues in the context of the Saudi Arabian educational system has been discussed and highlighted in the paper.

An optimal sequence in multicharacteristics inspection

Given a component withN critical characteristics, each characteristici has a cost of inspectionCi>0 and a probability of rejectionRi, 0<Ri<1. An optimal sequence for ordering these critical characteristics for inspection is found. This sequence minimizes the total expected cost of inspection. The implications and the applications of this sequence are examined.

The use of an analytical hierarchy process in pavement maintenance priority ranking

This paper describes the use of an analytical hierarchy process (AHP) in determining the rational weights of importance of pavement maintenance priority ranking factors. These weights were obtained by capturing the local people’s perception towards this vital part of the pavement management system (PMS). In this regard, different groups of individuals were asked to estimate the weight of importance in pavement maintenance of different factors for ranking pavement sections. These factors were road class, pavement condition, operating traffic, riding quality, safety condition, maintenance cost, and the overall importance of the road section to the community. The AHP method of pair‐wise comparison was employed to get the factor weights, which were compared with the weights obtained from the direct assignment method. It was concluded that the two methods were statistically similar which confirms that the results of the direct assignment method can be used safely with a sound reliability and consistency. This conclusion comes from the fact that the AHP method has a high reputation and applications, and it uses a high‐precision technique for obtaining the weights (priorities) of alternatives or items. Priority factor weights were used in developing a pavement maintenance priority ranking procedure for a road network. This procedure was validated by real case studies, and found to be logically and efficiently able to handle the ranking of a huge number of pavement sections for maintenance and repair.

Mathematical programming approaches for the management of maintenance planning and scheduling

Addresses the problem of maintenance planning and scheduling and reviews pertinent literature. Discusses the characteristics and the complexity of the problem. Advocates mathematical programming approaches for addressing the maintenance scheduling problem. Gives examples to demonstrate the utility of these approaches. Proposes expansion of the state‐of‐the‐art maintenance management information system to utilize the mathematical programming approaches and to have better control over the maintenance scheduling problem.

Integration of Taguchi's loss function approach in the economic design of x¯‐chart

In this paper we incorporate Taguchis loss function in the economic design of the control chart. This is done by redefining the in‐control and out‐of‐control costs using Taguchis loss function. The new model brings Taguchis off‐line concepts to the classical SPC approach and continues to have the advantages of the economic design model by taking into consideration the cost consequences of the design. Sensitivity analysis with respect to important model parameters is discussed.