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Öğe Taming the late Quaternary phylogeography of the Eurasiatic wild ass through ancient and modern DNA(PLoS One, 2017-04-19) Gündem, Can Yumni; Bennett, E Andrew; Champlot, Sophie; Peters, Joris; Arbuckle, Benjamin S; Guimaraes, Silvia; Pruvos, Mlanie; David, Shirli Bar; Davis, Simon J M; Gautier, Mathieu; Kaczensky, Petra; Kuehn, Ralph; Mashkour, Marjan; Morales, Arturo; Muiz, Morales; Pucher, Erich; Tournepiche, Jean François; Uerpmann, HansPeter; Blşescu, Adrian; Germonpr, Mietje; Moull, Pierre Elie; Ötzan, Aliye; Walzer, Chris; Grange, Thierry; Geigl, Eva MariaTaxonomic over-splitting of extinct or endangered taxa, due to an incomplete knowledge of both skeletal morphological variability and the geographical ranges of past populations, continues to confuse the link between isolated extant populations and their ancestors. This is particularly problematic with the genus Equus. To more reliably determine the evolution and phylogeographic history of the endangered Asiatic wild ass, we studied the genetic diversity and inter-relationships of both extinct and extant populations over the last 100,000 years, including samples throughout its previous range from Western Europe to Southwest and East Asia. Using 229 bp of the mitochondrial hypervariable region, an approach which allowed the inclusion of information from extremely poorly preserved ancient samples, we classify all non-African wild asses into eleven clades that show a clear phylogeographic structure revealing their phylogenetic history. This study places the extinct European wild ass, E. hydruntinus, the phylogeny of which has been debated since the end of the 19th century, into its phylogenetic context within the Asiatic wild asses and reveals recent mitochondrial introgression between populations currently regarded as separate species. The phylogeographic organization of clades resulting from these efforts can be used not only to improve future taxonomic determination of a poorly characterized group of equids, but also to identify historic ranges, interbreeding events between various populations, and the impact of ancient climatic changes. In addition, appropriately placing extant relict populations into a broader phylogeographic and genetic context can better inform ongoing conservation strategies for this highly-endangered species.Öğe Temperature dependent electrical transport in Al/Poly(4-vinyl phenol)/ p -GaAs metal-oxide-semiconductor by sol-gel spin coating method(Hindawi, 2016-03-10) Özden, Şadan; Tozlu, Cem; Pakma, OsmanDeposition of poly(4-vinyl phenol) insulator layer is carried out by applying the spin coating technique onto p-type GaAs substrate so as to create Al/poly(4-vinyl phenol)/p-GaAs metal-oxide-semiconductor (MOS) structure. Temperature was set to 80-320 K while the current-voltage (I-V) characteristics of the structure were examined in the study. Ideality factor (n) and barrier height (φ b) values found in the experiment ranged from 3.13 and 0.616 eV (320 K) to 11.56 and 0.147 eV (80 K). Comparing the thermionic field emission theory and thermionic emission theory, the temperature dependent ideality factor behavior displayed that thermionic field emission theory is more valid than the latter. The calculated tunneling energy was 96 meV.Öğe Investigation of the effects of butanol addition on safflower biodiesel usage as fuel in a generator diesel engine(Elsevier, 2018-06-15) Aydın, Hüseyin; Çelebi, YahyaAs our world demands more and more energy and fossil fuel resources are running out, searches onfindingalternative fuels in internal combustion engines are increasing. Alcohols and biofuels obtained from oils can beused as alternative diesel fuels. The present work investigated the effects ofn-butanol addition to safflowerbiodiesel usage in a diesel engine used for driving an electrical power generator. Safflower biodiesel was ob-tained by using transesterification method. Binary blends of butanol-biodiesel and ternary blends of ultra-lowsulfur diesel-biodiesel–butanol were contained 5%, 10%, and 20% butanol in volume basis. The tests werecarried out on a four-cylinder, four-strokes, and direct-injection diesel engine at half load operation with stableengine speed of 1500 rpm. Experimental test results on combustion characteristics, emission and performance ofthe fuels were investigated. According to test results, formation of heat release rates and in-cylinder pressurecurves were considerably similar and total heat transfer, average gas temperature and mass fraction burned wereslightly changed. The ternary blends showed lower emission and increased brake thermal efficiency up to 1.5%.Besides, average mass fuel consumption was increased up to 5% and brake specific fuel consumption up to 6%.For the other fuels, emission and brake thermal efficiency were deteriorated.Öğe First boundary value problem for cordes-type semilinear parabolic equation with discontinuous coefficients(Hindawi, 2020-06-19) Harman, Aziz; Harman, EzgiFor a class of semilinear parabolic equations with discontinuous coefficients, the strong solvability of the Dirichlet problem is studied in this paper. The problem ∑i,j=1naijt,xuxixj-ut+gt,x,u=ft,x,uΓQT=0, in QT=Ω×0,T is the subject of our study, where Ω is bounded C2 or a convex subdomain of En+1,ΓQT=∂QT\∖t=T. The function gx,u is assumed to be a Caratheodory function satisfying the growth condition gt,x,u≤b0uq, for b0>0,q∈0,n+1/n-1,n≥2, and leading coefficients satisfy Cordes condition b0>0,q∈0,n+1/n-1,n≥2.Öğe Evaluation of combustion, performance and emission indicators of canola oil-kerosene blends in a power generator diesel engine(Elsevier, 2017-03-05) Aydın, Hüseyin; Işık, Mehmet Zerrakki; Bayındır, HasanDirect use of vegetable oils as fuel in diesel engines leads to some important engine operational problems that need to be solved in order to make their usability possible. Canola oil was blended with kerosene by percentages of 90% canola oil-10% kerosene (C90&K10), 75% canola oil-25% kerosene (C75&K25) and 50% canola oil-50% kerosene (C50&K50). These blend fuels were initially analyzed by means of physicochemical fuel properties and comparisons were made with standard diesel fuel. Blend fuels and standard diesel fuel (D2) were than tested in a diesel power generator with 4 cylinders in order to investigate the combustion, performance and emission characteristics of the blend fuels and compare them with the petroleum based diesel fuel (D2). All experiments were carried out at specified output power values of 3.6, 7.2 and 10.8 kW and 1500 rpm constants speed. The combustion characteristics of canola oil kerosene blends have found be quite similar to those of D2. Mass fuel consumption and brake specific fuel consumption (bsfc) were slightly increased for blend fuels. Nitrogen oxide (NOx) emissions and exhaust smoke opacities were considerably reduced for blends while carbon monoxides (CO) and unburned hydrocarbon (HC) emissions were a bit increased. It can be concluded that kerosene blended vegetable oils can be used as fuel with improved combustion and performance characteristics compared to those of pure vegetable oils.Öğe Current mechanism in HfO 2-gated metal-oxide-semiconductor devices(Hindawi, 2012-06-19) Pakma, OsmanThe present study aimed to examine the current density-voltage (J-V) characteristics of Al/HfO2/p-Si (MOS) structure at temperatures ranging between 100 and 320 K and to determine the structure’s current transport mechanism. The HfO2 film was coated on a single side of the p-Si (111) crystal using the spin coating method. The J-V measurements of the obtained structure at the temperatures between 100 and 320 K revealed that the current transport mechanism in the structure was compatible with the Schottky emission theory. The Schottky emission theory was also used to calculate the structure’s Schottky barrier heights (φB), dielectric constants (εr) and refractive index values of the thin films at each temperature value. The dielectric constant and refractive index values were observed to decrease at decreasing temperatures. The capacitance-voltage (C-V) and conductancevoltage (G/ω-V) characteristics of Al/HfO2/p-Si (MOS) structure was measured in the temperature range of 100–320 K. The values of measured C and G/ω decrease in accumulation and depletion regions with decreasing temperature due to localized Nss at Si/HfO2 interface.Öğe Improved kidney-inspired algorithm approach for tuning of PID controller in AVR system(IEEE, 2019-03-22) Ekinci, Serdar; Hekimoğu, BaranThis paper proposes a novel tuning design of proportional integral derivative (PID) controller via an improved kidney-inspired algorithm (IKA) with a new objective function. The main objective of the proposed approach is to optimize the transient response of the AVR system by minimizing the maximum overshoot, settling time, rise time and peak time values of the terminal voltage, and eliminating the steady state error. After obtaining the optimal values of the three gains of the PID controller (K P , K I , and K D ) with the proposed approach, the transient response analysis was performed and compared with some of the current heuristic algorithms-based approaches in literature to show the superiority of the optimized PID controller. In order to evaluate the stability of the automatic voltage regulator (AVR) system tuned by IKA method, the pole/zero map analysis and Bode analysis are performed. Finally, the robustness analysis of the proposed approach has been carried out with variations in the parameters of the AVR system. The numerical simulation results demonstrated that the proposed IKA tuned PID controller has better control performances compared to the other existing approaches. The essence of the presented study points out that the proposed approach may successfully be applied for the AVR system.Öğe Improved combustion of asphaltite coals in a rotating head combustor with various air supply arrangements(ACS Publications, 2014-04-16) Altun, Şehmus; Öner, CengizWhen burned in conventional stokers, coals with high swelling properties such as asphaltites make coke blocks (coking). The plastic layer formed on them prevents air from diffusing into coal; hence, the air provided for swollen coal to burn becomes insufficient. This problem can partially be resolved by shaking the flame bed automatically or by mixing the burning coals manually in order to provide continuous air for the surface of the unburned coal. Therefore, in this study, a coal combustion system with the rotating head was manufactured for burning effectively Turkish coking coals characterized by high sulfur and ash content in agitation conditions with air supply arrangements. This type of coals known as asphaltite, abundantly found in southeastern Anatolia coal basin in Turkey, were burned in the rotating head combustor in order to investigate the effect of operating parameters, such as excess air ratio, coal particle size and feeding speed, air delivery type, addition of flange, bed slope, and rotation speed on the combustion efficiency and temperature distribution on the head. Experimental results showed that both the rotating of combustion chamber and additional air supply, which was blown out with pressure from the air delivery holes, reduced the negative impact of ash on the combustion efficiency, mainly due to the coal getting in touch with air better. It was possible to increase the peak combustion efficiency over 80% by both improving the air supply and agitation of coalbed preventing coking during combustion. As a result, this system could be highly recommended to burn the coals with high swelling properties like asphaltite at a high efficiency.Öğe Microstructure and mechanical properties of AA7075/AA5182 jointed by FSW(Journals & Books, 2019-06) Çelik, Yahya Hışman; Çetkin, Edip; Temiz, ŞemsettinIn this study, AA7075 and AA5182 aluminium alloys were joined using different rotation speeds (980, 1325 and 1800 rpm), feed rates (108 and 233 mm/min) and stirred pins having two different geometries (conical helical and triangular). Microstructures of welding joints were examined by an optical microscope and a scanning electron microscope (SEM). Vickers hardness measurements were performed in the welding zone of samples removed from each welded plate. Tensile and fatigue tests were also applied to the test specimens taken from the welded plates. After the tensile tests, the surface fractures and possible welding defects were scanned via SEM. The best mechanical properties were obtained when conical helical shape stirrer pins were used. The values were 265 MPa for tensile test and 159 MPa for fatigue test. The hardness value was very close to each other and varied depending on the rotation speed. The highest hardness value was determined as 87 HV in the weld center at 1325-rpm rotation speed.Öğe Investigation of the effect of use of Nano-Al2O3, Nano-TiO2 and Nano-SiO2 powders on strength of single lap joints bonded with epoxy adhesive(Elsevier, 2019-06) Adin, Hamit; Temiz, Şemsettin; Saraç, İsmailIn this study, single lap joints were formed by adding nano-Al2O3, nano-TiO2and nano-Al2O3powders in variousproportions to the epoxy adhesive and using the additive-free epoxy adhesive; and also the mechanical prop-erties of the connections were experimentally investigated at 20, 25, 30, 50 and 70 mm overlap lengths undershear load. In the experimental work, DP460 epoxy adhesive was used as adhesive and AISI 304 stainless steelplate as adherent material. When the results obtained from the experiments were examined, it was revealed thatthe average damage load in connection with the use of nanoparticle-added adhesives increased considerably ingeneral. As a result of the experiments, the most effective nanoparticle in increasing the failure strength of theadhesive joints with nano-Al2O3particles and the maximum failure strength increase rate was 20 mm in overlaplength and 97% in 4 wt% nano-Al2O3reinforced specimens. It was also found that the nanoparticle strain was animportant parameter in the tensile strength of the adhesive joints. In addition, it has been found that the additionof nanoparticles into the adhesive increases the elongation of the joints. When the adhesion surfaces of thesamples were examined as in the case of plain adhesives, damage was observed as adhesion separation whilenanoparticle reinforcement was observed as a mixture of adhesion and cohesion.
