Flexible Model for Time/Cost Tradeoff Problem

This paper presents a flexible mixed integer-programming model for the solution of the time/cost tradeoff problem encountered in project management. Whereas it is commonly assumed that the time/cost function is linear, the model presented in this paper makes minimal assumptions and accommodates any type of cost function that is linear, piecewise linear or discrete. The model can be used for answering various “what if” questions that may be very helpful to a project manager in making rational decisions. The basic model minimizes the total cost which is the sum of direct and indirect costs, subject to a project deadline constraint. A simple modification in the model changes the focus from minimizing total cost to minimizing project completion time subject to a resource constraint. The models of this paper can be set up and run very easily on commercially available optimization packages with an integer-programming module. These models provide a viable alternative to more specialized algorithms developed for the time/cost tradeoff problem simply because a typical project manager may not have the necessary skills or resources to implement specialized algorithms.     

Fuzzy performance evaluation in Turkish Banking Sector using Analytic Hierarchy Process and TOPSIS

The performance evaluation of banks has important results for creditors, investors and stakeholders since it determines banks’ capabilities to compete in the sector and has a critical importance for the development of the sector. The aim of this study is to propose a fuzzy multi-criteria decision model to evaluate the performances of banks.The largest five commercial banks of Turkish Banking Sector are examined and these banks are evaluated in terms of several financial and non-financial indicators. Fuzzy Analytic Hierarchy Process (FAHP) and Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) methods are integrated in the proposed model. After the weights for a number of criteria are determined based on the opinions of experts using the FAHP method, these weights are input to the TOPSIS method to rank the banks. The results show that not only financial performance but also non-financial performance should be taken into account in a competitive environment.     

A comparative analysis for multiattribute selection among renewable energy alternatives using fuzzy axiomatic design and fuzzy analytic hierarchy process

Renewable energy is the energy generated from natural resources such as sunlight, wind, rain, tides and geothermal heat which are renewable. Energy resources are very important in perspective of economics and politics for all countries. Hence, the selection of the best alternative for any country takes an important role for energy investments. Among decision-making methodologies, axiomatic design (AD) and analytic hierarchy process (AHP) are often used in the literature. The fuzzy set theory is a powerful tool to treat the uncertainty in case of incomplete or vague information. In this paper, fuzzy multicriteria decision- making methodologies are suggested for the selection among renewable energy alternatives. The first methodology is based on the AHP which allows the evaluation scores from experts to be linguistic expressions, crisp, or fuzzy numbers, while the second is based on AD principles under fuzziness which evaluates the alternatives under objective or subjective criteria with respect to the functional requirements obtained from experts. The originality of the paper comes from the fuzzy AD application to the selection of the best renewable energy alternative and the comparison with fuzzy AHP. In the application of the proposed methodologies the most appropriate renewable energy alternative is determined for Turkey.     

Secondary flow and forced convection heat transfer near endwall boundary layer fences in a 90° turning duct

The present study deals with the secondary flow and heat transfer aspects of endwall boundary layer fences in 90° turning ducts. Boundary layer fences have recently been re-introduced as additional components to achieve favorable aerothermal effects in turbine/compressor passages and internal cooling systems. The turbine passage or internal coolant channel is simulated by a 90° turning duct (Re_D=360,000) to study the aerothermal interaction of the boundary layer fence and the passage flow that is dominated by the passage vortices. Specifically, a single boundary layer fence of varying dimensions is attached to a heated endwall of the duct. The current study adds to the currently small number of investigations on the use of endwall boundary layer fences and their aerothermal interaction with the passage flow system.     

A novel strategy for cartilage tissue engineering: Collagenase-loaded cryogel scaffolds in a sheep model

In this study, we developed a novel strategy, through which cartilage tissue pieces were placed in a sheep cartilage defect model and covered with a collagenase incorporated cryogel scaffold (in vivo cartilage tissue engineering, IVCTE group). While applying this strategy, the chondrocytes could be isolated inside the body and the treatment could be accomplished in one session. To compare our strategy, to another group, in which we used cultured cells and Chondro-gide, standard matrix-induced autologous chondrocyte implantation (MACI) was applied. Although the MACI applied group demonstrated better healing than IVCTE, the type II collagen synthesis was better in the IVCTE group compared to MACI applied group. Collagenase did not have detrimental effect on surrounding cartilage in IVCTE group. The preliminary results of the novel strategy applied group (IVCTE) were promising.