The aim of this study is to offer useful correlation equations to the designer for the optimum design of annular fins with thermal properties varying with temperature. In order to obtain the optimum size of the fins, the heat transfer from the fin must be calculated with the least assumptions possible. Therefore, the variation of the heat transfer coefficient and thermal conductivity with the temperature are considered in this study and a nonlinear fin equation is solved with the variation of parameters method, which is quite new in the solution of nonlinear heat transfer problems. Heat transfer rate from the fin to the environment is calculated in terms of dimensionless problem parameters with the help of the obtained temperature distribution. Fin geometries maximizing the heat transfer rate are determined for the given problem parameters. These results, which can be used for nucleate boiling, natural convection and forced convection heat transfer modes, are offered to the designer with two identical correlation equations.

In this paper, a seawater source heat pump system is designed for a bridge heating in winters. It is probable to freeze of the ways and bridges which may cause many accidents in the cold and snowy weathers. Snow melting system is necessary to prevent the possible accidents and privative situations. Design of the optimum pipe length of seawater heat exchanger is a critical issue to transfer the maximum heat from the sea. Effects of the pipe diameter, wall thickness, radius of the coil and coil pitch on the heat transfer were shown in this paper. Moreover, friction factor of the helicoidal pipes and energy consumption of pumps were also calculated.

In this study, the flow past a cylinder which is forced to oscillate in a free stream is numerically investigated using a solver developed within the framework of the open-source toolbox OpenFOAM. Governing equations are written in the non-inertial reference frame fixed to the cylinder and solved using the finite volume method. Flow is assumed to be incompressible, unsteady and two-dimensional. Harmonic oscillation of the cylinder is considered separately for each degree-of-freedom (heaving, surging and pitching). By spanning several oscillation frequencies, the lock-in behavior is captured. The agreement obtained in the moving cylinder problem demonstrates the convenience of the approach in the general flow simulations of moving rigid bodies.

In this study, wall shear stress and pressure difference values for a pure water flow in various microchannel configurations are obtained numerically. Through simulations, physical effects of various flow rates on endothelium and immune system cells are predicted and case studies are carried out to investigate the behavior of such cells under similar laboratory conditions. In-vivo physiological behavior of endothelium and monocyte cells under real conditions can be predicted by pressure differences and wall shear stresses calculated for various flowrates. In this concept, various microchannel configurations such as sudden expanding microchannels with different expansion ratios, microchannels with cavities on one side and symmetrically curved microchannels are designed and CFD simulations are carried out to obtain computational values of the pressure drops between the inlet and outlet of the microchannels as well as wall shear stress distributions on the bottom walls of the configurations.

Performance assessment of a cold thermal energy storage (ITES – Ice thermal Energy Storage) system with ice slurry generation for closed space air conditioning purposes is conducted. A detailed energy and exergy analysis are performed for the baseline system and some parametric studies are also presented for varying environmental conditions. Exergy definition is linked to sustainability and reported with graphical representations. A compressor & condenser unit linked to an ice slurry generator and generated ice is stored at storage tank for specific hours of a day. Stored energy is then discharged to the building through a flat-plate heat exchanger. Thermodynamic analysis results suggest that high capacity cooling can be conducted with low capacity vapor compression refrigeration systems (VCR) by integrating ITES systems, leading to a signifýcantly lower size and lower cost HVAC systems.

In this study, the lithium fluid was numerically analyzed in a three-dimensional circular channel exposed to external magnetic field induction. The magnetic field is applied perpendicular to the flow direction of the channel. Re = 2250 and the magnetic field strength was selected as 0T, 0.04T, 0.08T and 0.12T, respectively. Besides, while the fluid temperature is 473.15 K, the wall temperature is 373.15 K. Calculations were performed with ANSYS-Fluent commercial software. The effect of the magnetic field on the fluid velocity, pressure and temperature has presented graphically. While the magnetic field seriously has reduced the fluid velocity, the pressure has observed to increase. Also, it has been observed that the magnetic field affects the temperature differently in different regions of the channel along the pipe length.

The growth of global human population has increased the world energy demand and made it necessary to evaluate effectively and efficiently usage of energy sources. According to the international energy research projections’ data, world’s energy reserves will be ended in the next 100 years. The fact that the large portion of energy consumption is used in buildings for heating. Therefore, saving that energy is so important in buildings and the need for thermal insulation materials has increased day by day. The investigation of new technologies and new materials has already been continued for thermal insulation. In this study, using of the perlite, whose 74% of the world reserves are in Turkey, in building sector directly as an insulation material and/or reinforcing material in other building materials has been investigated.

In this study, several reverse engineering applications which mainly being used in many industrial areas have been investigated and a workflow has been formed. According to this workflow, a bus turbo unit outlet/connection with both surface and solid model capabilities has been scanned by a three dimension (3D) laser scanner integrated to a portable coordinate measuring machine (CMM) and a digital model has been created. A 1/1 scale three dimension part has been printed via computer aided design (CAD) model created from the point cloud acquired from laser scanning operation. This application has been evaluated according to the workflow. Therefore, it has seen that surface modelling and solid design methods can be integrated with reverse engineering software in various applications. In addition, it has seen that 3D printers can be adopt easily to the applications of reverse engineering of the parts having freeform surfaces and the use of 3D printers can be a standard part of the reverse engineering process.

Active wrist orthosis is an electromechanical device which can work interacting with forearm and wrist, and this device is especially designed for the ones who should perform excessively repetitive wrist motions due to their profession. In the scope of this study, kinematics and kinetics analyses of the active wrist orthosis,which is designed for the rehabilitation and the continuance of daily and professional activities of patients having a tendon torn at their elbow location, are realized in order to show the performance of the device. Furthermore, the performance of the device under the control of two different control architectures (admittance and empedance) is also tested in a simulation environment. The results of the performance tests and the analyses show that the design process has been successfully accomplished and it can pass through the production stage of the device for the future work studies.

In this study, DP 800, Usibor 1500 and Ductibor 500P three different high strength steel sheet materials with different thicknesses were joined with electrical resistance spot welding. Welding process is carried out in different material combinations under constant parameters such as electric current, pressure and duration. Tensile specimens for the same and different material pairs welded by resistance spot welding in the form of overlay were prepared according to the standards. Mechanical properties of the welded specimens were evaluated by hardness and tensile-shear tests. The results show that Ductibor 500P material has the highest strength and hardness values. Furthermore, when different types of steels are welded together, the maximum tensile-shear force and elongation achieved are higher than those of the same type of materials.

Machining accuracy is one of the most important criteria of electro discharge drilling (EDD) processes and this phenomenon is serious due to excessive electrode wears. In this study, the workpieces were machined with regard to EDD parameters to obtain blind holes. The machining accuracy was analyzed experimentally based on machining depth and shape of the holes. Experimental results were assessed by statistical methods such as analysis of variance and regression analysis. In addition, grey relation analysis was used to determine optimal machining condition and to improve the machining accuracy. It has been observed that working current is the determinative parameter. The lower working current and the higher pulse time are suggested to obtain the more accurate shape of the drilled holes in EDD of materials.

Among network optimization problems, travelling salesman problem is widely studied one in the literature. Since the problem is computationally hard, many heuristics have been developed to obtain the optimal solution in reasonable time. This paper introduces a hybrid electromagnetism-like heuristics to solve symmetric travelling salesman problems. Originally, electromagnetism-like heuristic is a population based global search algorithm that is inspired by electromagnetism theory in Physics. The proposed mechanism is based on the principle of encouraging randomly generated particles to move toward to optimal solution in the feasible area. In this paper, random-key approach is adapted to electromagnetism-like heuristic to solve vehicle routing problems. Regarding 15 benchmark instances, proposed heuristic procedure produces optimal solutions for small instances. Moreover, as the number of vertices increase in the network, the proposed algorithm generates near optimal solutions. Efficiency of results shows that the proposed algorithm can be evaluated for the solution of combinatorial optimization problems.

Demand forecasting studies are one of the strategic issues which are considered as significant for academicians and decision makers. Constantly changing political, cultural, legal and economic developments have pushed the companies to predict under uncertainty. It is very difficult to model some problems with traditional methods in complex, multi-dimensional and highly uncertain environment. Fuzzy approaches provide an easier modelling owing to their flexible nature. In this study, a demand forecasting study in a FMCG (fast-moving consumer goods) company has been applied using a rule based fuzzy logic approach which utilizes fuzzy set theory, fuzzy if-else rules and fuzzy inference concepts. The obtained results have been compared with real demands and low MAPE (mean absolute percentage error) values have been calculated. Also the obtained results have been compared with time series approach and the superiorities of the methods are discussed.

The problem of locating naval platforms in the operation region with the aim of maximizing both total radar coverage and critical radar coverage is solved by using Multiobjective Evolutionary Algorithms (MOEA). Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) and S-Metric Selection Evolutionary Multiobjective Optimization Algorithm (SMS-EMOA) procedures are implemented. Experiments show that evolutionary algorithms provide good and diverse alternatives that are considered to be very close to Pareto-optimal front. The performances of NSGA-II and SMS-EMOA approaches are compared employing the hypervolume indicator technique. The performance of NSGA-II is found better in terms of both convergence and diversity.

Traffic flow in urban areas is one of the major problems both for drivers and pedestrians. Traffic congestion and traffic lights constitute a large portion of the time spent in traffic. This wasted time for waiting in traffic also costs countries considerable amount of wasted fuel and hence considerable amount of money. In this study, traffic flow of a road in Izmir, Turkey is considered. In order to decrease all the wasted resources in urban traffic, an experimental design is conducted on the factors affecting the signal controlled traffic flow. The design factors are determined to be signal times of traffic lights, traffic intensity and the speed of vehicles. The effects of these factors on the three performance measures of time in system, waiting time in red light and number of vehicles going out of the system are analyzed. A fractional factorial design is carried out on the 486 design points evaluated using simulation modeling. In results, among the design points, best level of factors to minimize total waiting time in traffic flow are determined.

Machine scheduling in the production planning activities of enterprises is an activity that is frequently repeated in short periods and is very important in terms of efficient use of resources. It is necessary to solve a parallel machine scheduling problem regardless of the workshop environment in workshops where more than one machine that can do the same job to increase the capacity and solve the bottleneck problems. Especially in non-identical parallel machines, it is desired to determine which machine will process the job depending on many factors. A general software cannot respond to such situations. In addition, it is important for planners to prepare charts that take into account sequence dependent setup times in parallel machine environments such as plastic injection and oven scheduling problems. In this context, the study is focused on designing a decision support system for non-identical parallel machine scheduling problems with sequence dependent setup times. By using the decision support system, the decision maker can obtain the schedule for the jobs need to be scheduled for the relevant period and purpose according to situation of workshop. The system makes it possible to find and compare schedules for different objective functions such as minimizing makespan and minimizing the number of tardy jobs. On the basis of the model of the decision support system, meta-heuristic algorithms that can produce a solution to large scale real-life scheduling problems in a short time have been used.

Materials, products and workers have to move in order to perform the daily schedule of the organizations. This movement which is done by vehicles or material handling systems is an important cost element for the organizations. A good facility layout design may reduce this cost by minimizing the interdepartmental flow. Till today, most of the facility layout planning studies have been focused on production facilities. On the other hand, having vehicles with high fuel consumption and having continuously moving personnel makes facility layout important for also military facilities. In this study, in order to remedy this deficiency in the literature, we focused on military facilities. In addition to conventional transportation costs, the allocation of infirmary and quick reaction team which affects human health and personnel safety has also considered. We presented a multi-objective mixed integer programming model for this bi-objective facility layout problem. We applied this model on a military facility problem which is created by utilizing real data.

While investors used to create their portfolios according to traditional portfolio theory in the past, today modern portfolio approach is widely preferred. The basis of the modern portfolio theory was suggested by Harry Markowitz with the mean variance model. A greater number of securities in a portfolio is difficult to manage and has an increased transaction cost. Therefore, the number of securities in the portfolio should be restricted. The problem of portfolio optimization with cardinality constraints is NP-Hard. Meta-heuristic methods are generally preferred to solve since problems in this class are difficult to be solved with exact solution algorithms within acceptable times. In this study, a particle swarm optimization algorithm has been adapted to solve the portfolio optimization problem and applied to Istanbul Stock Exchange. The experiments show that while in low risk levels it is required to invest into more number of assets in order to converge unconstrained efficient frontier, as risk level increases the number of assets to be held is decreased.

An assembly line is a flow-oriented production system in which the productive units performing the operations, referred to as stations, are aligned in a serial manner. Design of efficient assembly lines has considerable importance for the production of high-quantity standardized products. In this paper, a differential evolution algorithm is proposed to solve simple straight and U-type assembly line balancing problems. As a population-based evolutionary algorithm, differential evolution algorithm is seen as an effective method to solve optimization problems in recent years. A computational study is conducted by solving a large number of benchmark problems available in the literature to compare the performance of the proposed approach. The results show that the proposed approach performs quite effectively.

Two-sided assembly lines are heavily used in automotive industry for producing large-sized products such as buses, trucks and automobiles. Mixed-model lines help manufacturers satisfy customized demands at a reasonable cost with desired quality. This paper addresses to mixed-model two-sided lines incorporating incompatible task groups and proposes a new method for minimizing two conflicting objectives, namely cycle time and the number of workstations, to maximize line efficiency. While such an approach yields to a so-called type-E problem in the line balancing domain, the proposed nondominated sorting ant colony optimization (NSACO) approach provides a set of solutions dominating others in terms of both objectives (pareto front solutions). The solution which has the highest line efficiency among pareto front solutions is then determined as the best solution. An additional performance criterion is also applied when two different solutions have the same values for both objectives. The solution which has the smoother workload distribution is favoured when both criteria are the same. NSACO is described and a numerical example is provided to exhibit its running mechanism. The performance of the algorithm is tested through test problems in two cases, i.e. incompatible task sets are considered and not considered, and computational results are presented for the first time. The results indicate that NSACO has a promising solution capacity.

The use of Operations Research techniques for problems in healthcare systems is observed to get remarkable attention in recent years. In this study, problems encountered in healthcare systems are taken into consideration and are classified under the headings of planning, management and application. In order to guide the researchers who will work on these issues, studies published between the years 2007-2017 are evaluated according to their headings, solution methods and applications on real life problems, and the applicability of Operation Research over these problems is presented.