Raad Yahya Qassim

Synthesis of utility systems by simulated annealing

A combinatorial optimization approach is proposed to derive flowsheets for systems that satisfy fixed demands of steam, electricity and mechanical power. This approach allows the selection of equipment available in standard capacities by handling discrete variables and discontinuous cost functions. Simulated annealing is a combinatorial optimization technique that has been efficiently applied to several areas, including process design. Two annealing schedules are compared by means of a numerical example that also demonstrates the importance of considering discrete equipment capacities.

Activity-based costing for production learning

Learning has long been established as a phenomenon of great interest in operations management. Cost reduction through task learning has a great potential. Its quantitative determination is performed in this work using activity-based costing (ABC) and compared with traditional costing, employing a practical example in a mechanical workshop. Results obtained by these two techniques may be significantly different.

Synthesis of utility systems with variable demands using simulated annealing

A combinatorial optimization approach is proposed to design systems that satisfy time-varying utility demands. A numerical example illustrates the application of the procedure and is used to compare the traditional simulated annealing algorithm with a nonequilibrium version.

Selection of postharvest technology routes by mixed-integer linear programming

Abstract A mixed-integer linear programming model is proposed for the selection of technology routes for fruit and vegetable crops between harvest and market. The objective is to optimize capital investment in food preservation facilities under uncertainties, based on alternative routes and a set of crop and market scenarios. A case-study illustrates the application of the model.

Application of the Davies—Taylor equation to a large bubble rise in liquid-fluidized beds

Abstract The Davies—Taylor equation is used to correlate the velocity of rise with the radius of curvature of circular-cap gas bubbles in liquid-fluidized bed

Application of data envelopment analysis in the performance evaluation of electricity distribution: a review

The objective of this paper is to review the application of data envelopment analysis to performance evaluation of electricity distribution. After introducing the basic concepts and models of data envelopment analysis, work on its application in electricity distribution is discussed via a number of case studies. Suggestions for further research are presented, with a view to enhancing the use of data envelopment analysis in electrical energy distribution.

Minimum cost safety stocks for frequent delivery manufacturing

Abstract The lot-size reduction in production and purchasing intensifies the exposure to stockouts. Material and product safety stocks must be held to prevent production hampering and poor delivery performance to customers. Safety stocks reduce opportunity costs caused by delayed deliveries but significantly increase inventory costs. This paper presents an analytical solution for an optimization model that determines whenever it is preferable to incur inventory or opportunity costs. An application is presented to illustrate the solution.

Effect of voidage variation on flow past a fluidisation bubble

Abstract The motion of the particle—fluid mixture around a gas bubble rising in an incipiently gas-fluidised bed is studied using a potential-flow theory for the solid particles and allowing for observed void variation. The principal conclusion of this work is that the agreement between the Davidson theory and the theory based on observed void profiles is very good, though in the case of the fluid stream function the values are different.

A kaizen budgeting model

In addition to high quality, low cost and frequent on-time delivery, management accounting methods have been shown to be factors behind Japanese manufacturing excellence. A prominent example is Toyotas cost management system based on kaizen budgeting. In this paper, a quantitative model based on linear programming is developed as a decision support tool for determining the distribution of kaizen values through company processes and plants.

Risk-based inspection of flexible pipes using Bayesian updating

Flexible pipes can experience different failure mechanisms during their operational life. Internal sheath ageing, external sheath damage, bird caging, kinks due to overbending and corrosion-or fatigue-induced damage to the tensile armours are some of the most common defects that can eventually cause failure. Nowadays, a large portion of operational costs is devoted to pipe inspection and maintenance. Risk-Based Inspection (RBI) planning can establish a cost-effective inspection strategy while maintaining the desired level of safety. However, the complexity and variety of flexible pipe multi-layer structures with their interacting failure mechanisms, the somewhat poor defect capability of the existing inspection techniques and the lack of broad, long-term inspection data hamper the development of an effective RBI planning for the integrity management of flexible pipes. In this paper, Bayesian updating is employed as a tool reducing for RBI planning of flexible pipe systems. The focus of this work is on the uncertainties in the model parameters of loading and the two failure initiation mechanisms: internal sheath ageing and fatigue crack initiation and propagation in the armour layers. The method will be applied to simple models in order to assess the feasibility of its use in the development of a practical RBI planning for flexible pipes.