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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 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 Multivariate padé approximation for solving partial differential equations (PDE)(Wiley-Blackwell, 2011-07-30) Turut, Veyis; Çelik, Ercan; Yiğider, MuhammedIn this paper, numerical solution of partial differential equations (PDEs) is considered by multivariate padé approximations. We applied these method to two examples. First, PDE has been converted to power series by two-dimensional differential transformation, Then the numerical solution of equation was put into multivariate padé series form. Thus, we obtained numerical solution of PDE.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 Calculating molding parameters in plastic injection molds with ANN and developing software(Taylor & Francis, 2012-02) Çelik, Yahya Hışman; Özek, CebeliIn recent years, plastic injection molds are widely used for producing products in various areas, such as aerospace, automotive, medical, electronics, and toys. The quality of these products depends on correctly chosen molding parameters. In this study, a new package program (NPP)-Software that calculates various injection molding parameters was developed to mold plastic products obtained by plastic injection molding techniques using the model of artificial neural network (ANN). The Delphi programming language was used in the develop the (NPP)-Software. The developed (NPP)-Software was trained and tested using the Levenberg–Marquardt (LM) algorithm, the ANN. One-thousand three-hunderd pieces of data were collected, out of which 250 were used to train the network. The ANN is employed to find optimum molding parameters that enable minimum defects in the injection-molded part, such as volumetric shrinkage, injection time, and cooling time. The three parameters predicted, using the (NPP)-Software, were compared using experimental results.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 Buried with turtles: the symbolic role of the Euphrates soft-shelled turtle (Rafetus euphraticus) in Mesopotamia(Antiquity, 2016-02) Kozbe, Gülriz; Mashkour, Marjan; Berthon, Rémi; Erdal, Yılmaz SelimExcavations at Kavuşan Höyük (south-eastern Turkey) have revealed evidence of the use of turtles, tortoises and terrapins in post-Assyrian funerary practices. Of particular significance are the remains of the Euphrates soft-shelled turtle (Rafetus euphraticus), distinguished from other species of turtle by their quantity and treatment in the burial pit under investigation here. The unique finds from Kavuşan Höyük, coupled with archaeological and textual records, underline the economic and symbolic significance of these animals for communities in prehistoric and early historical Mesopotamia.Öğe Effects of isopropanol-butanol-ethanol (IBE) on combustion characteristics of a RCCI engine fueled by biodiesel fuel(Journals & Books, 2021-10) Altun, Şehmus; Okcu, Mutlu; Varol, Yasin; Fırat, MüjdatThe reactivity controlled compression ignition (RCCI) strategy using fuels with different reactivity’s has attracted attention due to its high thermal efficiency as well as very low NOx and PM emissions in comparison to conventional combustion. As previous studies have shown that the type and amount of low reactivity fuel have a significant contribution to the in-cylinder reactivity, thus RCCI combustion, in this study, Iso-Propanol-Butanol-Ethanol (IBE), which has comparable characteristics to n-butanol and ethanol, is employed as low reactivity fuel (LRF) in a RCCI engine fueled by petroleum based EN590 fuel and commercial biodiesel. The IBE mixture was in volumetric ratios of 3:6:1 as in the fermentation process of butanol, that is to say; 30% Iso-Propanol, 60% Butanol and 10% Ethanol. In each experimental condition, keeping the total energy of the fuel supplied to the engine in conventional combustion mode for each cycle as constant, the premixed ratio (Rp) in case RCCI combustion was applied as 0%, 15%, 30%, 45% and 60% (the amount of LRF in energy basis) over this energy amount. The effect of premixed ratio of IBE on combustion characteristics were investigated in a single-cylinder RCCI engine under different loads with using both petroleum diesel and biodiesel as high-reactivity fuels (HRF), respectively. According to experimental results, a higher in-cylinder pressure was measured by using diesel in both conventional and RCCI mode compared to the use of biodiesel. Considering the peak in-cylinder pressure and rate of heat release, the premixed ratio (Rp) of up to 45% was found as optimum for all loads while it was up to 30%Rp for the NOx emissions. In addition, the biodiesel-fueled RCCI engine produced the lowest smoke opacity in all loads and it gradually decreased by up to 97% with the application of the RCCI strategy. Furthermore, the results showed that a simultaneous reduction in NOx and smoke opacity could be obtained under 60% load and up to 30% Rp with a marginal increase in unburned HC emissions.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.
