In this study, a prototype that works in accordance with the working principles of thermoelectric generator has been applied to the exhaust system of an internal combustion diesel engine. The aim is to transform heat energy that is discharged into the atmosphere into a usable electrical energy. Two different fluids have been used in the systems in order to create different temperatures that constitute the working conditions of thermoelectric module. One of them is the exhaust gases that are used to create a hot surface. The other fluid is cooling water that enables to create differential temperature that is necessary for thermoelectric module. 40 thermoelectric modules that are placed on octagonal structure composed of aluminum alloy material are connected to each other electrically. The performance of thermoelectric generation systems has been examined in terms of changing speed and load in the engine. At the same time, the vehicle battery has been charged by transferring the electrical energy to converters.

In this study, wind speed characteristics and wind energy potential were analyzed by using the wind speed data from the meteorological station of Bandýrma, Turkey. The hourly time-series wind speed data and wind direction were collected for 30 years between 1975 and 2005. The measured wind speed data were processed for 30 years and seasonal. Weibull and Rayleigh probability density functions were obtained from the observed data and Weibull shape parameter c and the scale parameter k were found as 4.55 and 1.66 for 30 years. The wind energy potentials of 30 years were compared according to Weibull distribution and actual data. The most frequent wind direction was found from NNE direction with the highest mean wind speed value of 4.78 m/s. Seasonal wind speed characteristics were also calculated. The highest mean wind speed value was found for summer season with 4.40 m/s.

Renewable energy sources are energy clean sources and according to other energy sources has a much lower environmental impact. Renewable energy has evolved rapidly over the past decade in Turkey. Renewable energy generation related with solar and wind energy has emerged as the most dominant participants. Site selection of solar power plants is a complex spatial decision problem for decision makers. The purpose of this study was to determine suitable site selection for solar power plant by using Geographical Information System (GIS) and Analytic Hierarchy Process (AHP) that one of the multi-criteria decision making (MCDM) methods in the Çumra/Konya. According to the results, 1.5% of the study area has high suitable, 26% has moderate suitable and 11% has low suitable for solar power plant sites.

In this paper, wind energy potential of Sakarya University was evaluated. In the study of wind energy potential assessment for Sakarya University, topography, obstacles, roughness data of the region with wind data obtained from Esentepe wind measurement station were used. Calculations were made by using WAsP (Wind Atlas Analysis and Application Program) software and other wind energy analysis software. Some advices were given to possible wind energy investors by evaluating the results obtained for different heights.

Petroleum production generates an immense amount of oily polluted water which may have harmful effects on environment. At the same time, produced water is the biggest waste stream produced in the petroleum industry. In the past decades produced water treatment was the point of attention. However, the processes of treatment to separating water and oil have been enhanced gradually. This study used a two-dimensional computational fluid dynamics (CFD) model to investigate the effect of space between coalescing plates, orifice diameter and mixture inlet velocity on separation efficiency. Spacing values of 8, 12, 16, 20, 24 mm between plates, orifice diameters of 10, 15, 20 mm with different cross sections (e.g., cylindrical, rectangular, ellipse, and triangle) along with four different mixture inlet velocities of 0.02, 0.03, 0.04, 0.05 m/s were utilized to discover the effect of each parameter on the separation efficiency. The investigation revealed that the increase in the distance between plates was inversely proportional to the separation efficiency and the increase in the velocity of the mixture or mass flow rate inlet was inversely proportional to the separation efficiency. It was also found that the highest separation efficiency was obtained for the cylindrical shape with a hole diameter of 15 mm. It was also observed that the separation efficiency varied between 25% and 99.25% depending on the values of mixture inlet velocities and distance between plates.

In this study, the optimization conditions for the design of an ejector cooling system are investigated theoretically and experimentally. First law of thermodynamics analysis in accordance with the ejector theory is made with water which is the preferred working fluid in the ejector cooling system. Thermodynamic properties such as enthalpy, temperature, mass flow rate and velocity are calculated at each point of the system. The intersection of Rayleigh and Fanno curves, which enables the theoretical acquisition of the shock phenomenon in the throat region of the ejector, is obtained by iteration. In this section, the dimensioning of the ejector is carried out by obtaining optimum value. Cooling coefficient of performance (COP) and entrainment ratio (G) of the ejector cooling system is calculated at different operating conditions. The effect on the coefficient of performance and entrainment ratio of the system parameters are investigated. The obtained numerical results are presented in tables and graphics. The generator temperature is determined as three different values (80, 85 and 90 °C) and the results are obtained. It is determined that the cooling performance coefficient (COP) is 0.15-0.42 and the flow entrainment ratio (G) is 0.15-0.45 at different temperatures and pressures. In this study, all theoretical and experimental analyses of cooling systems are carried out. As a result, in the theoretical and experimental analyzes of the ejector system, experimental results are found to be similar to theoretically calculated results.

In the present numerical study, effects of the shape of the cross-section and their surface roughness on the pipe hydrodynamic entry length have been investigated for various Reynolds (Re) numbers. Standard
k- turbulence model has been adopted to analyze the turbulent flows in circular, square and equilateral triangle cross-sectional pipes. Analyses indicate that the rough surfaces have the shorter entry lengths than that of the smooth surfaces and increasing surface roughness reduces the entry length regardless of the cross-section of the pipes. The equilateral triangle pipes have the longest while circular cross-sectional pipe has the shortest entry lengths. Re number has the significant effect on the entry length and it is seen that the higher the Re number the longer the entry length.

In this paper, effectiveness of heated tube with conical baffles was studied experimentally as a function of various inclination angles. By using inclined conical baffles vortex of the flow was increased thereby giving rise to heat transfer and the best inclination angle was determined. Experiments were performed for three different inclination angles (45°, 60° ve 80°). Water as hot fluid and air as cold fluid were used as working fluids in the experiments. Water temperature was fixed as 65 °C. Air flow velocities were taken at 8 distinct levels between 2-20 m/s. The results indicated that for NTU>1, 45° and 80° were more effective compared to 60°. In addition for NTU<1, all three angles were found to be similarly effective.

In this study, effects of surface roughness on the load carrying capacity of the rotor-bearing system supported by externally pressurized air bearing are theoretically investigated. Air flow between rotor and bearing surfaces, is modeled using Reynold's equation. In this model, film thickness function which is defined gap between rotor and bearing, is described with surface roughness. In order to obtained pressure distribution between rotor and bearing surface, Reynold's equation is solved with Differential Transform & Finite Difference hybrid numerical solution method and load carrying capacities is calculated. In order to analyze effect of the surface roughness on the load carrying capacity of rotor-bearing system supported by externally pressurized air bearing, an algorithm is developed in Matlab environment and it is simulated for different bearing geometric parameters and rotor angular velocities.

In this study, for the turning of AISI 1040 steel that has cylindrical shape and hardened up to 46 HRc, Taguchi L16 experimental design was created according to the parameters of cutting speed, feed rate and cutting depth which consist from four levels. Formed in result of turning, the total surface roughness (Rt) were measured. Regression models have been built. Taguchi analyzes were carried out utilizing by MINITAB 14 Program for measured values of Rt. The closest results of the test results, generated for the Rt regression model, were obtained with 99.8% specify coefficients in order second degrees regression model. Signal/Noise (S/N) ratios were determined in design of the Taguchi. In ANOVA analysis, it was obtained as an effect of the 95% confidence level on Rt values in order feed rate, cutting depth and cutting speed. The result of the regression model and Taguchi analysis was determined as feed rate to be the optimum parameter for Rt values.

In this study, the effect of artificial aging on hardness and the corrosion properties of 6063 Al alloy was investigated. Time and temperature play a very important role in the precipitation hardening process of the Al-alloy. The results show that the variation in time and temperature have changed the hardness of aluminum alloy. Corrosion test revealed that the corrosion resistance of the alloy strongly depended on artificial aging times. The highest corrosion resistance for all artificial aging temperatures was observed at obtained the highest hardness value.

In this study, cuts between 2 and 5 cm formed on Aluminum 2024 T-3 plate for damage detection and structural health monitoring were examined with Lamb waves and the symmetric and asymmetric modes of Lamb waves were compared. The envelopes of the acquired surface frequency responses are obtained by Hilbert transform and the amount of attenuation of each damage is shown as a percentage. The results show that both Lamb wave modes can be used to investigate the cut dimensions created in the Aluminum 2024 T-3 plate.

In this study, ceramic coatings were deposited on 7075 Al alloy using a plasma electrolytic oxidation (PEO) technique. Effects of current density and electrolyte content on microstructure, thickness, surface roughness and wear behavior of PEO coatings were studied. The microstructure and phase composition of the coatings were investigated by SEM and XRD analyses. Dry sliding wear tests, micro hardness and surface roughness measurements were also performed. It was found that the thickness, microhardness, surface roughness and wear resistance of the coatings increased with an increase of current density during plasma electrolytic oxidation.

In this study, Inconel 625 Ni-based superalloy, widely used in industrial application, was borided with three different boriding powders. The boriding powders used were as follows: the first one consists of 90% elemental nanoboron and 10% NaBF4, (NB), the second one consisting of 90% nano hexagonal boron nitride and 10% NaBF4 (h-NBN), and the third one being commercial EKabor 2 powder. Boriding is conducted at 1000 °C for 180 minutes. Then the borided samples were investigated with optical microscopy, microhardness test and X-Ray Diffraction (XRD) analysis. In these investigations, the effect of boriding powders with different chemical content on the properties of the coating layer and the phase formation was examined. As a result of these examinations it was observed that boride, silicide and nitride coating layers were obtained depending on the chemical content of boriding powder. The fact that the boron phases with higher boron contents were obtained with nano boron powder indicate that the degree of purity of boron powder has an effect on the type of phases to be formed. In this study, undesirable silicide layer formation encountered in Ni-based super alloys was prevented by changing the chemical composition of boriding powders. Furthermore, nano boron and hexagonal boron nitride powders, have been developed as alternative boron powders to commercial EKabor-Ni boriding powder as well as thicker coating layers have been obtained by using these newly developed boriding powders than commercial boron powders (Ekabor 2, Ekabor-Ni and B4C).

The ferromagnetic particle, are used in many areas due to their magnetic field sensitivity. Composite MRE materials which obtained from the combination of the matrix material with these particles are classified as a kind of smart materials. In this study, it is aimed that the compressive mechanical properties of MRE materials produced by adding four different magnetic particles in RTV (room temperature vulcanizing) silicone elastomer are investigated. As a matrix material Vario 40 silicone rubber were used, which is common in engineering application. The particle rate inside MRE materials was kept at 30% by volume. In addition, to investigate the influence of orientation of particles inside MRE materials, some samples were subjected to external magnetic field during production. These samples are named as anisotropic MRE materials while the others are described as isotropic ones. The tests showed that anisotropic samples have much more strength values according to isotropic samples. Of all, the MRE samples including BASF CN particles reveal the biggest strength values. Also, the samples were evaluated in terms of MR effect and the largest MR effect with an increase value of 201% was found for anisotropic samples including SQ-I particles with regard to the corresponding isotropic one. As a result, this study determined that the mechanical and MR properties of MRE materials seriously depend on ferromagnetic particle kind and its magnetic characteristic.

Pipes exposed to internal pressure are damaged due to the change in temperature and pressure. In the repair of these damaged pipes, adhesively bonded joints, which have been widely used in almost all kinds of fields in recent years, are used. Materials to be bonded in adhesively bonded joints may be of different types or the same type. Material choice has great importance in the repair of damaged pipe with adhesive because adhesives may exhibit different strength values in different materials. In this study, three different patching materials including composite, aluminum and steel were selected for the repair of damaged galvanized steel pipes, and how they would exhibit a mechanical behavior on the adhesive was investigated. Damages that had occurred in pipe installations exposed to internal pressure were bonded with a uniform adhesive and investigated numerically and experimentally. Therefore, cracks were formed in the galvanized pipes, and flat braided carbon fiber composite, aluminum and steel patches consisting of 7 (2 mm), 9 (2.6 mm) and 11 (3.2 mm) layers were bonded with two-component acrylic adhesives (DP810). Internal pressure was exerted to the repaired pipes, and the effects on the adhesive of patch material depending on the patch thickness, overlapping angles and overlapping length were investigated.

Delamination factor is an important parameter for evaluating the surface damage in the drilling of compact laminate composites (CLC). In this study, delamination occurred in the hole exit region was studied and the effects of control factors on delamination factor were investigated in the drilling of pre-drilled CLC materials with new (T1) and worn (T2) tungsten carbide flat end mill cutting tools. CLC workpieces are drilled on CNC machine at three different cutting speed (178, 250 and 350 m/min), three different feed rate (0.07, 0.111 and 0.156 mm/rev) and two different drilling type (linear drilling and peck drilling). An experimental study has been performed according to L18 (21x32) orthogonal array using Taguchi method and the optimum levels of control factors are determined. In addition, predictive equations were developed showing the effects of drilling parameters on delamination factor. Delamination factor calculated with an average of 1.036 in drilling T1 tools while delamination factor was measured with an average of 1.473 in drilling T2 tools. Analysis of variance (ANOVA) was applied to determine the effects of control factor on the delamination factor. The most influential parameters on delamination factor in drilling with T1 tools has been the cutting speed (65.30%), type of drilling (11.63%) and feed rate (8.16%) when the cutting speed (58.79%), drilling type (18.38%) and feed rate (3.43%) has been the most influential parameters on delamination factor in drilling with T2 tools, respectively. As a result; higher maximum deformed diameter was obtained in the drilling CLC material with worn tools.

Uncontrolled increasing population, unplanned urbanization and enhancement in private vehicles number have revealed the of congestion traffic problem in urban area. These conditions have led to increase the need to remodeling the transportation plans. For this reason, a huge number of intensive studies were carried out in order to insure more efficiency to the public transport system by their different modes. One of these studies concerns the monorail service in Ankara, one of the most safe, fast and comfortable transport modes. Indeed, we made selection from several transport projects in Ankara Metropolitan Municipality using Analytic Hierarchy Process (AHP) and 0-1 Goal Programming methods.

This paper proposes a large neighbourhood search (LNS) algorithm for type-II simple assembly line balancing problem (SALBP-II). The LNS algorithm was initially developed for solving vehicle routing problem and its later implementations were used to solve scheduling problems. The reported results about these two problems indicate that LNS algorithm is a powerful method. Vehicle routing problem has the main objective to find the optimal match between a certain number of routes and a certain number of customers, while SALBP-II is trying to find the optimal match between a certain number of workstations and a certain number of assembly operations. To our point of view, LNS algorithm would also be a powerful method for solving SALBP-II due to the structural similarity between these two problems. Within this context, a LNS algorithm is developed to tackle SALBP-II and the performance of the proposed algorithm is tested on a set of benchmark instances. Computational results indicate the satisfactory performance of LNS algorithm in solving SALBP-II.

This paper addresses the problem of a retailer who buys a certain amount of inventory at the start of a selling season. Holding inventory is costly and the demand is dependent on the current price and the reference price. The reference price is developed by customers and acts as a benchmark against the current price. The aim of the retailer is to maximize its discounted profit. The problem is modeled as an optimal control problem to determine the optimal pricing policy. For general demand models, the marginal cost due to an increase in the inventory and the marginal gain due to an increase in the reference price are provided analytically. For the linear demand models, the optimal pricing strategy is given explicitly and shown to be characterized by three stages: After a penetration or a skimming pricing strategy at the initial stage, the optimal price increases with time and the season ends with a discount. By introducing the reduced price which is the premium over the cost of the products, it is shown that the existence of procurement and holding cost is the driver for the increase in the price during the intermediary stage. The sensitivity of the optimal price to demand and cost parameters is also provided with a numerical study.

Lean principles have been followed by many organizations in recent years due to the increase of tough competition in the market. These principles focus on improving the efficiency of operations by eliminating and reducing wastes. Different techniques and methods have been applied in order to become lean. One of them is the Value Stream Mapping (VSM) which can be easily applied in a variety of industries. However, VSM is a static tool which only shows the current state of the organization. To deal with this shortcoming, simulation is widely used as a complimentary technique in which the assessment of the impact of proposed improvements can be easily analyzed. This paper presents an industrial case example combining VSM and simulation in furniture industry in which there are a lot of wastes to deal with. Both current and future state maps for a particular product family are described by VSM following the suggestions for improvement. A simulation model is also developed to show the “before” and “after” scenarios in detail.

Mean-variance portfolio optimization model, introduced by Markowitz, provides a fundamental answer to the problem of portfolio management. This model seeks an efficient frontier with the best trade-offs between two conflicting objectives of maximizing return and minimizing risk. The problem of determining an efficient frontier is known to be NP-hard. Due to the complexity of the problem, genetic algorithms have been widely employed by a growing number of researchers to solve this problem. In this study, a literature review of genetic algorithms implementations on mean-variance portfolio optimization is examined from the recent published literature. Main specifications of the problems studied and the specifications of suggested genetic algorithms have been summarized.

Supply chain is a value chain management, which consists of all activities beginning from purchasing of the raw materials until delivering the goods to consumers. It is an indispensable strategic management model since it offers controlling materials, information and money according to customer satisfaction. The concept of sustainable supply chain has emerged with increasing public awareness on exhaustion of the natural resources. According to this phenomenon, companies maintain their existence with ongoing supply chain operations under economic, environmental and social dimensions. In this study, a supplier selection problem in a healthcare company is analyzed with utilizing Decision Making Trial and Evaluation Laboratory (DEMATEL) approach under sustainable supply chain management concept in order to measure suppliers’ sustainability performances. By the help of this multi criteria decision-making method, the most efficient performance criterion is selected among the criteria in order to improve sustainable supply chain performance.