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Öğe Investigation of electrical conductivity of PAN nanofibers containing silica nanoparticles produced by electrospinning method(ELSEVIER, 2019) Mpukuta, Olivier Mukongo.; Dincer, Kevser.; Erdal, Mehmet Okan.This paper sheds new light on how an amount of silica nanoparticles (1, 3 and 5 wt. %) acts on the morphology, the hydrophobicity and on the electrical conductivity of polyacrylonitrile (PAN) nanofibers. In this study, electrospinning technique was used to fabricate nanofibers composites consisting of PAN, dimethylformamide (DMF) and silica at two different applied voltages (15 kV and 20 kV). The scanning electron microscopy (SEM), X-ray diffraction technique (XRD), contact angle technique and the four-point probe technique were respectively used to investigate the morphology and diameter range, the crystalline structure, the hydrophobicity and the electrical conductivity of the obtained nanofibers. At the end, different results of the investigation were compared each other and discussed. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Heating and cooling vehicle seat via air conditioner coils(E D P SCIENCES, 2019) Ates, Ali.; Canli, Eyub.A real vehicle seat was modified in order to locate evaporator coils extended from a vehicle air conditioner system just beneath the back and cushion surfaces. The seat back and cushion surface temperatures were measured by several thermocouples. Air conditioner system was operated in heat pump and cooling modes for different compressor speeds. After steady operation of the air conditioner was attained, a live manikin sat to the seat and remained in sitting position for five minutes. The temperatures were recorded during the existence of the manikin and they were recorded for an additional five minutes after the manikin left the seat. The coils embedded under the seat surfaces were made of flexible hoses for the sake of usage due to the shape changing seat surfaces under the load of the manikin weight. Coils were in parallel configuration by the help of a distributer and collector. The temperatures of the seat surfaces were evaluated in respect of the thermal comfort and feasibility of the application. Air conditioner system was also monitored in respect of the COP and energy consumption values. At the instance of sitting, the transient response of the system is very significant due to the weight of the live manikin. However it settles quickly. Cooling was observed to be more realizable while heating seat surfaces had problems due to flow blockage. There were no significant discomfort issues due to the seat surface temperatures and the existence of the coils. The surface temperatures of the seat back exhibited differences from the seat cushion although the formations were same. The orientation of the coils and the weight of the passenger were concluded to be the reason for that. COP was found to be changing between 3 and 3.56 for cooling mode while the highest amount was found for 600 rev/min compressor speed in cooling operation. Heat pump operation had relatively higher COP values ranging between 3.31-3.64. 700 rev/min compressor speed gave the 3.64 COP value for heat pump operation. The difference between COP values of the working modes was concluded to be due to the seat coils and their effect on the additional pumping work. The potential of the application and possible field of studies were evaluated according to the conducted tests and the survey about the topic.Öğe Experimental investigation of 11x11 cm(2) membrane microbial fuel cell performance(ELSEVIER, 2019) Hayder, Mustafa Akram Hayder.; Dincer, Kevser.Microbial fuel cells (MFC's) are systems that can convert chemical energy into electricity directly from biochemically commutable substances (organic substances) by using microorganisms as a catalyst in an oxygen-free environment. Electrode-growing microorganisms in the anode chamber converts water organics into hydrogen ions and electrons. In this study, performance of 11x11 cm(2) membrane microbial fuel cell have been experimentally investigated. In the experimental studies, activated sludge sample have been used. In this study, current density (= I/V), power density (= P / V) values have been calculated by measuring current (I) and voltage (V) values. The performance of 11x11 cm(2) Nafion 117 membrane activated sludge microbial fuel cell (#ASMFC) have been determined. The maximum values of voltage, current density and power density values from the (#ASMFC) are represented subsequently (0.616 V, 0.463 A/m(3) and 75.64 W/m(3)). (C) 2019 Elsevier Ltd. All rights reserved.Öğe Axisymmetric Smooth Contact for an Elastic Isotropic Infinite Hollow Cylinder Compressed by an Outer Rigid Ring With Circular Profile(Springer Heidelberg, 2006) Avcı, A.; Bulu, A.; Yapıcı, A.A contact problem for an infinitely long hollow cylinder is considered. The cylinder is compressed by an outer rigid ring with a circular profile. The material of the cylinder is linearly elastic and isotropic. The extent of the contact region and the pressure distribution are sought. Governing equations of the elasticity theory for the axisymmetric problem in cylindrical coordinates are solved by Fourier transforms and general expressions for the displacements are obtained. Using the boundary conditions, the formulation is reduced to a singular integral equation. This equation is solved by using the Gaussian quadrature. Then the pressure distribution on the contact region is determined. Numerical results for the contact pressure and the distance characterizing the contact area are given in graphical form.Öğe Torsional Vibrations of Camshafts(PERGAMON-ELSEVIER SCIENCE LTD, 1992) Şaka, Ziya; Yılmaz, YükselThis study deals with the torsional vibrations on the camshafts in force closed cam mechanisms. On the cam mechanisms with reciprocating followers, the variable torque which is produced by force exerted to the cam from the follower, will create torsional vibrations on the camshaft. A dynamic model of the camshaft was established and some nondimensional parameters which can be used to characterize dynamic behaviour of a camshaft were obtained. Torsional vibrations of camshafts are parametric and self-induced vibrations. The governing nonlinear differential equations were solved numerically. Vibrations of camshafts with a flat-faced follower differ from ones with a roller follower because of the friction between cam and follower. Vibrations on the camshaft affect the follower motion and contact force.
