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        • KCI등재
        • KCI등재SCOPUS

          Evaluation of Energy Efficiency of Thermoelectric Generator with Two-Phase Thermo-Syphon Heat Pipes and Nano-Particle Fluids

          Tahsin,Atalay,Yavuz,Köysal,Ali,Ekber,Özdemir,Engin,Özbaş 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.5 No.1

          This paper investigates the effects of heat pipes filled with water and nanoparticles (MgO) on electricity generation. The experimental setup comprises of two-phase thermo-syphon heat pipes filled with water or MgO nanoparticle-water suspension, thermoelectric generator (TEG) modules and heat sinks that use passive and active cooling systems. Concentrated solar radiation with heat pipes was used as a heat source for heating. Specially constructed heat sinks with coolant tunnels were used for cooling. Heating and cooling processes are needed to create a temperature difference to generate electrical energy. The constructed model represents the influence of basic parameters such as the tilt angle of heat pipes, working fluids, cooling process, etc. on the maximum power generated. Systems in the constructed setup were arranged with a specific angle to the incident angle of solar radiation. The experiment was carried out on August 5th, 2015, in the northern coast of Turkey, city of Samsun with latitude of 41o14' N. The results obtained show that the presented experimental setup can be used to evaluate thermoelectric energy potential of local areas or to investigate optimum cooling or heating processes.

        • KCI등재SCOPUS

          Enhanced thermoelectric properties of the SrTiO3 by Zr-doping with different doping level

          Tamal,Tahsin,Khan,김일호,어순철 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.4

          The enhancement of the thermoelctric properties of the SrTiO3 by doping with Zr were investigated in our study. The ZrdopedSrTiO3 with different doping level were synthesized by the conventional solid-state reaction method. The formation ofsingle phase cubic perovskite structure and the changing behavior of the average grain size confirmed that the Zr-dopedSrTiO3 were prepared to control doping level. The thermoelctric properties including Seebeck coefficient, electricalconductivity, and thermal conductivity has been investigated in a moderate temperature regime from 300 K to 1000 K. Theabsolute value of Seebeck coefficient decreased and the electrical conductivity increased monotonically with increasing dopinglevel. The thermal conductivity decreased with increasing doping level. The power factor increased with increasing dopinglevel-up to x = 0.03 mole and the dimensionless figure of merit ZT, increased up to x = 0.03 mole of Zr. The maximum ZT valuewas observed for SrTi0.97Zr0.03O3 at 873 K.

        • KCI등재SCIESCOPUS

          Thermoelectric Properties of the Yttrium-Doped Ceramic Oxide SrTiO3

          Tamal,Tahsin,Khan,어순철 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.1

          The doping dependence of the thermoelectric figure of merit, ZT, of the ceramic oxide SrTiO3 at high temperature has been studied. In this study, yttrium was used as the doping element. A conventional solid-state reaction method was used for the preparation of Y-doped SrTiO3. The doping level in SrTiO3 was controlled to be in the doping range of 2 - 10 mole%. Almost all the yttrium atoms incorporated into the SrTiO3 provided charge carriers, as was observed by using X-ray diffraction pattern. The relative densities of all the samples varied from 98.53% to 99.45%. The thermoelectric properties, including the electrical conductivity σ, Seebeck coefficient S, thermal conductivity k, and the figure of merit, ZT, were investigated at medium temperatures. The ZT value showed an obvious doping level dependence, in which a value as high as 0.18 is realized at 773 K for a doping of 8 mole%.

        • KCI등재

          Detection of bone marrow involvement with FDG PET/CT in patients with newly diagnosed lymphoma

          H.,Tahsin,Özpolat,Ebru,Yilmaz,Hasan,Sami,Goksoy,Sahre,Özpolat,Öner,Dogan,Seher,Nilgun,Unal,Meliha,Nalcaci 대한혈액학회 2018 Blood Research Vol.53 No.4

          BackgroundBone marrow involvement (BMI) affects the lymphoma stage, survival, and treatment. Bone marrow biopsy (BMB) and fluorodeoxyglucose (FDG) positron emission tomog-raphy-computed tomography (PET/CT) are useful techniques to detect BMI. Both have advantages and disadvantages. We aimed to identify factors that could be used to predict BMI with positive and negative results on PET/CT compare them with BMB in newly diag-nosed patients with lymphoma.MethodsWe included 22 non-Hodgkin and 16 Hodgkin lymphoma patients in this single center study. All patients had PET/CT examination and BMB before treatment. BMI in BMB was reported as negative or positive. Bone marrow was classified into 3 types by FDG uptake on PT/CT; diffuse involvement, focal involvement, and normal bone marrow. ResultsPET/CT and BMB results were concordant (7 positive, 15 negative) in 22 patients (57%). We evaluated concordant and discordant patient characteristics and risk-stratified pa-tients for BMI. Our findings suggest that patients with diffuse FDG uptake on PET/CT, especially patients with advanced age and low platelet and white blood cell counts, are likely to have BMI and could potentially forego BMB. Patients with negative PET/CT find-ings and no significant laboratory abnormalities are very unlikely to have BMI.ConclusionOur results suggest that BMI should not be decided solely based PET/CT or BMB findings. It is reasonable to use both diagnostic assays along with clinical and laboratory findings. PET/CT result, clinical and laboratory findings could be useful for predicting BMI in patient for whom BMB is contraindicated.

        • KCI등재SCOPUS

          Optimum cost design of RC columns using artificial bee colony algorithm

          Hasan,Tahsin,Ozturk,Ahmet,Durmus 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.5

          Optimum cost design of columns subjected to axial force and uniaxial bending moment is presented in this paper. In the formulation of the optimum design problem, the height and width of the column, diameter and number of reinforcement bars are treated as design variables. The design constraints are implemented according to ACI 318-08 and studies in the literature. The objective function is taken as the cost of unit length of the column consisting the cost of concrete, steel, and shuttering. The solution of the design problem is obtained using the artificial bee colony algorithm which is one of the recent additions to metaheuristic techniques. The Artificial Bee Colony Algorithm is imitated the foraging behaviors of bee swarms. In application of this algorithm to the constraint problem, Deb's constraint handling method is used. Obtained results showed that the optimum value of numerical example is nearly same with the existing values in the literature.

        • KCI등재SCIESCOPUS

          Optimum design of RC shallow tunnels in earthquake zones using artificial bee colony and genetic algorithms

          Hasan,Tahsin,Öztürk,Erdem,Turkeli,Ahmet,Durmus 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.17 No.4

          The main purpose of this study is to perform optimum cost design of cut and cover RC shallow tunnels using Artificial bee colony and genetic algorithms. For this purpose, mathematical expressions of objective function, design variables and constraints for the design of cut and cover RC shallow tunnels were determined. By using these expressions, optimum cost design of the Trabzon Kalekapısı junction underpass tunnel was carried out by using the cited algorithms. The results obtained from the algorithms were compared with the results obtained from traditional design and remarkable saving from the cost of the tunnel was achieved.

        • SCOPUSKCI등재

          Synthesis and Thermoelectric Properties of the B-Site Substituted SrTiO<sub>3</sub> with Vanadium

          Khan,,Tamal,Tahsin,Mahmud,,Iqbal,Ur,,Soon-Chul Materials Research Society of Korea 2017 한국재료학회지 Vol.27 No.8

          V-substituted $SrTiO_3$ thermoelectric oxide materials were fabricated by the conventional solid state reaction method. From X-ray diffraction pattern analysis, it can be clearly seen that almost every vanadium atom incorporated into the $SrTiO_3$ provided charge carriers. The electrical conductivity ${\sigma}$, Seebeck coefficient S, and thermal conductivity k were investigated in a high temperature regime above 1000 K. The addition of vanadium significantly reduced the thermal conductivity and enhanced the Seebeck coefficient, as well as the electrical conductivity, thus enhancing the ZT value. A maximum ZT value of 0.084 at 673 K was observed for the sample with 1.0 mole% of vanadium substitution. In this study, the reason for the enhanced thermoelectric properties via vanadium addition was also investigated.

        • SCIESCOPUSKCI등재후보

          Optimum cost design of RC columns using artificial bee colony algorithm

          Ozturk,,Hasan,Tahsin,Durmus,,Ahmet Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.5

          Optimum cost design of columns subjected to axial force and uniaxial bending moment is presented in this paper. In the formulation of the optimum design problem, the height and width of the column, diameter and number of reinforcement bars are treated as design variables. The design constraints are implemented according to ACI 318-08 and studies in the literature. The objective function is taken as the cost of unit length of the column consisting the cost of concrete, steel, and shuttering. The solution of the design problem is obtained using the artificial bee colony algorithm which is one of the recent additions to metaheuristic techniques. The Artificial Bee Colony Algorithm is imitated the foraging behaviors of bee swarms. In application of this algorithm to the constraint problem, Deb's constraint handling method is used. Obtained results showed that the optimum value of numerical example is nearly same with the existing values in the literature.

        • KCI등재SCOPUS

          Investigation of wear properties of CaO, MgO added stabilized zirconia ceramics produced by different pressing methods

          Ahmet,Akkus,Tahsin,Boyraz 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.3

          Stabilized zirconia has superior high temperature properties such as high tolerance for thermal shock, low thermalconductivity, mechanical properties, elevated melting point, good phase stability and excellent oxidation resisNtance. Thepresent paper describes the fabrication and wear behaviour of 8 mole% CaO, 4 mole % CaO-4 mole% MgO and 8 mole%MgO - stabilized zirconia (ZrO2) based composites fabricated by the conventional ceramic production process. CaO/MgOadded stabilized zirconia ceramics were fabricated by using a combined method of ball milling, cold press-cold isostaticpressing and sintering. The powder blends containing different amounts of % 8 mole CaO/MgO were wet-milled for 1 hr ina vibratory ball-mill using zirconia vial and balls. After drying, powders were compacted to cylindrical preforms with adiameter of 12.7 mm by uniaxial pressing at 300 MPa and by cold isostatic pressing at 300 MPa. The green compacts weresintered at 1600 oC for 3 hrs under air. Phase and microstructural characterizations of the sintered materials were carried outby using X-ray diffraction technique (XRD) and scanning electron microscope (SEM). The Micro Vickers hardness testing wasperformed using the Shimadzu HMV-MIII hardness tester. Plint brand abrasion tester was used for the abrasion tests ofceramics. As a result, it has been observed that the hardness is increased by increasing the amount of MgO and the ceramicsproduced by cold isostatic pressing are harder.

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