Isik H.,Turkish Military Academy |
Goktas F.,Turkish Military Academy
Applied Thermal Engineering | Year: 2017
Cook-off is an involuntary self-ignition phenomenon of a propellant in a cartridge often encountered in multiple sequential firings. In this study, an efficient approach has been used for cook-off analysis of a propellant by experimental and numerical methods. Various firing tests have been conducted with a 7.62 mm rifle to determine the temperature distribution in a barrel and the cook-off time. The outer surface temperature at the hottest area on the combustion chamber where the cook-off process was assumed to initiate was measured with a thermal imager as an effective method. For numerical analysis the model of the combustion chamber combined with the cartridge was created and analyzed using the ANSYS 14.5 Academic finite element solver and the temperature distribution of the inner/outer surfaces of the combustion chamber was determined. The numerical results for temperature distribution were observed to be quite close to the temperature values measured by the thermal imager. The numerical analysis was also validated by comparing the numerically determined cook-off time with the experimental measurements. At the end, various parametric analyses have been made that affect the cook-off time of a propellant. © 2016 Elsevier Ltd. All rights reserved.
Aplak H.S.,Turkish Academy Of Sciences |
Sogut M.Z.,Turkish Military Academy
Energy Conversion and Management | Year: 2013
Intensive energy consuming industrial sectors are the most important actors on global climate change which natural habitat and the environment faced. In this study, by the scope of energy management, decision-making process of the industry and the environment are evaluated in a game theoretic approach. Industry and environment are considered as two players which have conflicting objectives and try to find optimal strategies in governing energy policy. According to concept of study, while industry tries to maintain the sustainability of production with the strategies of fossil fuel, renewable energies, energy recovery and nuclear energy usage, environment exhibits reactive approach to ensure its sustainability. In the flow of study, players' strategies are analyzed by using Multi-Criteria Decision Making (MCDM) methods and by calculating performance efficiency values of strategies, game payoff matrix is obtained. Finally, optimal strategies are found for both industry and environment in orienting their energy policy and results are evaluated. According to results of the payoff matrix, the equilibrium point is the cell (2, 1) with the values of 0.5324 and 0.5619. This implies that the environment develops protective reflexes for sustainable nature in case of using renewable energy in industry. © 2013 Elsevier Ltd. All rights reserved.
Kabak M.,Turkish Military Academy |
Dagdeviren M.,Gazi University
Energy Conversion and Management | Year: 2014
Developing countries such as Turkey, with their fast growing population and economy, are facing an increasing demand for energy. Turkey does not possess a sufficient quantity of domestic oil and natural gas resources to support this growing demand. On the other hand, the country does have abundant reserves of renewable energy that can be a major component in providing part of the overall energy supply. The country plans to explore its renewable energy (RE) sources and increase the renewable energy share in near future. With this in mind, this paper proposes a hybrid model based on BOCR (Benefits, Opportunities, Costs and Risks) and ANP (Analytic Network Process) to determine Turkey's energy status and prioritize alternative RE sources. BOCR analysis provides a strategic analysis and detailed overview of the country's energy issues. ANP is a practical multi criteria decision making (MCDM) method and offers the advantages of decision making models, based on tangible and intangible factors. 19 criteria are used to evaluate five alternative RE sources (Hydro, Geothermal, Solar, Wind and Biomass). The subsequent results show that the most important strategic criterion is economy; other criteria include security, human wellbeing, technology and global effects. Their weights are 0.485, 0.235, 0.130, 0.097 and 0.053, respectively. In the conclusion of this paper, the authors propose hydro power as the optimal RE source for the country. © 2013 Elsevier Ltd. All rights reserved.
Kaya I.,Yildiz Technical University |
Kaya I.,Turkish Military Academy
Resources, Conservation and Recycling | Year: 2012
Production and use of electrical and electronic equipment (EEE) have been clearly increased over the last years. This has led to huge amounts of waste of electrical and electronic equipment (WEEE). The management of WEEE is a very critical and important not only for waste treatment but also to recover of valuable materials. Waste electrical and electronic equipment (WEEE or E-waste) must be disposed of properly to reduce waste, to protect the environment from hazardous materials and to obtain more useful materials in recycling. The importance of management of WEEE has become clearer in the last years and it is expected that quantities of WEEE will increase. Therefore, the management of WEEE is a critical and important decision. This paper analyzes an outsourcing decision for the management of WEEE by using a fuzzy multicriteria decision making approach. As outsourcing decisions are often based on multi criteria approaches and group decisions, this paper proposes a methodology based on fuzzy group decision making approach to evaluate and to select the appropriate WEEE outsourcing firm in Istanbul, Turkey. The selected firm will control the management of WEEE process that is the collection, transportation, processing, recycling or disposal of electrical and electronic equipment (EEE). © 2011 Elsevier B.V. All rights reserved.
Degirmenci E.,Turkish Military Academy
Fuel | Year: 2015
A conventional bullet or projectile driven by solid fuels accelerates in the barrel and reaches certain muzzle velocity, spin and propulsion energies. Combustion characteristics of solid fuels are the most important factor affecting bullet performance and maximum range. In this work, double base solid propellants of spherical geometry within the ranges of 300-425, 425-500, 500-600, 600-710 and 710-850 μm in diameter and temperatures of -60, -40, -20, 0, 20, 40 and 60 °C, were investigated in terms of the effects of grain size and temperature on burn rate, internal barrel pressure and bullet velocity. Solid fuel properties such as fuel heat of combustion, density, combustion temperature, particle size and mass were measured. In a constant volume chamber, burn rate was measured for each fuel sample at different pressure and temperature. In addition, cartridges of 7.62 mm in diameter were made using sample solid fuels, and shooting tests were carried out with a special test barrel. In the tests, strains along the barrel were determined using strain gauges and the muzzle exit velocity of the bullet was measured with a doppler radar for calibrations. It was seen that the increase of fuel temperature and decrease of particle size increased burn rate, internal barrel pressure and bullet velocity. © 2015 Elsevier Ltd. All rights reserved.
Tuna C.,Turkish Military Academy
ELECO 2015 - 9th International Conference on Electrical and Electronics Engineering | Year: 2015
In this paper, Intersymbol Interference (ISI) which is one of the most significant problems for the 60 GHz communication channel is analyzed. 60 GHz indoor channel model is developed by IEEE802.15.3c Task Group. By using this model, variation of Bit Error Rate (BER) with MMSE (Minimum Mean Square Error) equalizer is investigated. BPSK modulated data sequence is transmitted on different Signal-to-Noise Ratios (SNR) and different bit packet lengths. Performance of MMSE equalizer is analyzed in LOS and NLOS environments. As a result, obtained results are compared with output of Viterbi algorithm that is used for the MLSE (Maximum Likelihood Sequence Estimation) solution. © 2015 Chamber of Electrical Engineers of Turkey.
Kocer H.,Turkish Military Academy
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields | Year: 2013
Infrared (IR) sensors are widely used in thermal imaging and sensor applications. The performance of IR sensor is strongly dependent on the noise currents of the sensor. If characteristics of the noise currents are known prior to the costly and time-consuming sensor production phase, high performance IR sensors could be obtained rapidly and cost effectively. In this study, a p-n long-wave IR mercury cadmium telluride sensor is evaluated at 77 K using a physics-based numerical modeling and simulation approach. Results of the study showed that 1/f noise originating from the trap-assisted tunneling dominates as the cut-off wavelength and the magnitude of the applied reverse bias voltage increase. Copyright © 2013 John Wiley & Sons, Ltd. Copyright © 2013 John Wiley & Sons, Ltd.
Kabak M.,Turkish Military Academy
Journal of Multiple-Valued Logic and Soft Computing | Year: 2013
Personnel selection is the process of choosing among the candidates applying for a defned job in the organization, the ones who have the qualifcations required to perform the job in the best way. The selection process, depending on the organization's targets, the availability of candidates and the individual preferences of the decision makers (DMs), is a highly complex problem. In addition, nature of the personnel selection problem requires both qualitative and quantitative criteria simultaneously. Multi criteria decision making (MCDM) methods and the fuzzy set theory are the best two approaches to cope with the multi-criteria nature of the personnel selection problem and vagueness of DMs' predictions. For this aim, this paper proposes an effective model based on fuzzy DEMATEL (Decision Making Trial and Evaluation Laboratory) and fuzzy ANP (Analytic Network Process) to help organizations that need to evaluate and select applicants for a described job. The model frst applies DEMATEL to cope with the interdependencies between evaluation criteria. Next, it uses the fuzzy ANP to compute weights for each criterion and evaluate applicants. In this paper, a fuzzy DEMATEL-ANP model is proposed for selection of snipers. Every soldier in the team executes different missions and one or two of them are needed to hit with the frst shot. 10 criteria are used to evaluate team members. The best two candidates could be assigned as snipers. © 2013 Old City Publishing, Inc.
Kocer H.,Turkish Military Academy
Journal of Nanophotonics | Year: 2015
Nanostructured thin film absorbers embedded with phase-change thermochromic material can provide a large level of absorption tunability in the near-infrared region. Vanadium dioxide was employed as the phase-change material in the designed structures. The optical absorption properties of the designed structures with respect to the geometric and material parameters were systematically investigated using finite-difference time-domain computations. Absorption level of the resonance wavelength in the near-IR region was tuned from the perfect absorption level to a low level (17%) with a high positive dynamic range of nearinfrared absorption intensity tunability (83%). Due to the phase transition of vanadium dioxide, the resonance at the near-infrared region is being turned on and turned off actively and reversibly under the thermal bias, thereby rendering these nanostructures suitable for infrared camouflage, emitters, and sensors. © 2015 Society of Photo-Optical Instrumentation Engineers.
Kocer H.,Turkish Military Academy
Solid-State Electronics | Year: 2013
Through numerical simulations at 77 K, it is shown that Auger suppression has a twofold effect on the sensitivity of the LWIR p on n HgCdTe sensors by decreasing the dark current and increasing the photocurrent. It has been demonstrated that Auger mechanism behaves in recombination mode along the n-type absorber layer under illumination. On the other hand, Auger behaves as a generation mechanism throughout the device under dark conditions. It is also shown that the reduction in the photocurrent due the presence of the Auger process results from the partial loss in the density of the photogenerated carriers due to Auger recombination. © 2013 Published by Elsevier Ltd.