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Öğe Analyses of elliptical coplanar coupled waveguides and coplanar coupled waveguides with finite ground width(2006) Duyar M.; Akan V.; Yazgan E.; Bayrak M.In this paper, the quasi-TEM characteristic parameters of elliptical coplanar coupled waveguides and coupled coplanar waveguide with a finite ground width configuration are presented and analyzed. Computer-aided design (CAD)-oriented fast, simple, and accurate analytic formulas are derived by using conformal mapping techniques, which provide satisfactory accuracy at microwave frequencies and lead to closed-form analytical solutions suitable for CAD software packages. The results for the odd- and even-mode characteristic impedance, effective dielectric constant, and coupling coefficient have been computed by these formulas. Good agreement between the present results and published results [1] is observed. For the planar case, simulations have also been undertaken with Sonnet electromagnetic-circuit solver software. The computed results agree well with those of the simulation ones. © 2006 IEEE.Öğe Analytical attenuation calculation of asymmetrical coplanar waveguide with finite-extent ground planes for coplanar waveguide mode(2007) Duyar M.; Akan V.; Yazgan E.; Bayrak M.In this study, fast and new analytical formulations have been presented for correct loss calculations in asymmetrical coplanar waveguides (CPW) with finite-extent ground planes for CPW mode. To generalize loss analysis for CPW mode, not only gaps but also finite ground planes are assumed as asymmetric. Moreover, dielectric thickness and ground plane widths are considered as finite for this transmission line. Another important concept presented in this article is that the proposed expressions are easily applicable for CAD platforms. Through the analyses, conformal mapping techniques (CMT) have been employed. The obtained results in this work have been compared with the results of other similar studies (spectral domain method, mode matching, etc.) available in the literature. These comparisons indicate that the expressions developed in this study are found to be more suitable for accurate calculations of loss as well as the characterization of asymmetrical CPW with finite-extent ground planes. © 2007 Wiley Periodicals, Inc.Öğe Effects of variations in alloy content and machining parameters on the strength of the intermetallic bonding between a diesel piston and a ring carrier [Vpliv sprememb v sestavi zlitine in parametrov obdelave na trdnost intermetalne vezave med dieselskim batom in nosilcem obrocka](2010) Acar A.F.; Ozturk F.; Bayrak M.The intermetallic bonding between an aluminium alloy piston and a cast-iron ring carrier must be able to withstand prolonged exposure to the high-pressure and high-temperature environment of a diesel engine. Weak cohesion may result in the debonding of the ring carrier. Such debonding causes devastating damage to the piston while the engine is in service. Thus, the quality and strength of the intermetallic bonding is very important in piston manufacturing. In the present study, the effects of variations in the alloy content and the machining parameters on the overall strength of the intermetallic bonding are investigated. The defects are determined by ultrasonic inspection. The results indicate that the variation in the alloy content and graphite flakes affects the bond quality adversely. It was determined that the graphite size is a very important parameter. If the graphite size gets smaller, then stronger intermetallic bonding is observed. The graphite accumulation can be resolved by choosing the right amount of alloying elements. The machining process parameters were found to be ineffective for the formation of defects on the intermetallic bonding.Öğe Energy and exergy analyses of sugar production stages(2003) Bayrak M.; Midilli A.; Nurveren K.This paper presents the energy and exergy analyses of sugar production stages by using the operational data from Bor Sugar Plant, Turkey. For these purposes, all stages of sugar production, considered as a steady-state open thermodynamic system, were analysed by employing the first and second law of thermodynamics. In this regard, the first and second law efficiencies, the magnitude and place of exergy losses in these production stages were estimated and discussed in detail. It was concluded that the exergy loses took place mostly during the sherbet production process (?I.sp = 96.8% ?II.sp = 49.3%) because of the irreversibility in the sub-operation stages, which are vapour production, circulation sherbet mixing and bagasse compression. Therefore, it is generally suggested that the irreversibility, mostly stem from the finite temperature differences at the production stages, should be reduced to conduct more productively the sugar production process. © 2003 John Wiley and Sons, Ltd.Öğe New accurate analytical analyses of shielded planar transmission lines(2006) Duyar M.; Akan V.; Yazgan E.; Bayrak M.In order to calculate the quasi-static TEM parameters of shielded coupled coplanar waveguides (SC CPWs) and shielded broad-side-coupled coplanar waveguides (SBC CPWs), closed-form analytical formulas are obtained and presented using conformal-mapping techniques. The variation of electrical parameters with respect to different physical dimensions is observed for each type of transmission lines under investigation. The obtained results are also confirmed by comparison with the results in the literature. Further verification has been realized via Sonnet electromagnetic-circuit solver software. The proposed method in this study is thus well proved by these compared results. © 2006 Wiley Periodicals, Inc.Öğe Quasi-static solutions of elliptical, cylindrical-coupled parallel coplanar waveguide, and coupled parallel coplanar waveguide with finite ground planes(2007) Duyar M.; Akan V.; Yazgan E.; Bayrak M.This article presents the quasi-static analyses of elliptical-coupled parallel coplanar waveguide (ECP CPW), cylindrical-coupled parallel coplanar waveguide (CCP CPW), and coupled parallel coplanar waveguide (CP CPW) with finite ground planes. Conformal-mapping techniques have been used through the analyses. The obtained results show good agreement with IE3D electromagnetic-circuit solver software's simulations for the planar case. In addition, the results have been compared with others available in the literature. © 2007 Wiley Periodicals, Inc.Öğe Single phase flow of nanofluid including graphite and water in a microchannel(Springer Verlag, 2019) Yıldız O.; Açıkgöz Ö.; Yıldız G.; Bayrak M.; Dalkılıç A.S.; Wongwises S.In this study, convective heat transfer performance of a nanofluids containing graphite is studied in an industrial microchannel. In the experiments, initially, to prepare nanofluids at the volume fraction values of 0.5, 1, 1.5, 2%, distilled water has been employed as the base liquid. To provide sedimentation and stabilization of nanofluids in distilled water, Cetyltrimethylammonium bromide (CTAB) is utilized as surfactant. Thermophysical properties of nanofluids such as thermal conductivity, dynamic viscosity, and specific heat are determined experimentally. Furthermore, by building an experimental setup, in the temperature range of 20–30 °C and with temperature intervals of 2 °C, performance experiments are carried out in a microchannel of which hydraulic diameter is 1.6 × 10-3 m. Additionally, experiments have been conducted using nanofluids at different volumetric rates from 1 to 7 l min-1, heat fluxes from 100 to 1100 W, and volume fractions from 0.5 to 2%. Measuring heat flux, temperature, and flow rate, outcomes such as convective heat transfer coefficient, Reynolds number, and Nusselt number are calculated. The validation process of the experimental results has been performed by plotting the figures of Nusselt numbers vs Reynolds ones, and heat transfer coefficient vs supplied heat considering distilled water and nanofluids having various volumetric proportions. Regarding with the performance of nanofluids against distilled water under similar operating conditions, some proportional positive increase are acquired. Using outcomes attained from experiments, new correlations for Nusselt number have been derived with the R2 values around 0.96, and afterward by means of those correlations experimental data have been compared with those in the literature. A large number of measured and calculated data are given in the paper for other researchers to validate their theoretical models. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.Öğe Two novel transmission lines with vertical conductors added to ground planes(2007) Duyar M.; Akan V.; Yazgan E.; Bayrak M.In this article, two different novel Coplanar Waveguides (CPW) structures have been proposed and analyzed. The CPW structures proposed provide flexibility for practical applications. For the analyses, conformal mapping techniques were employed. The closed form analytical expressions are generally suitable for usage in CAD-oriented microwave circuit design. Both the structures have been simulated for quasi-TEM mode in a 3D commercially available software. In addition, the results obtained in this work have been compared with the others available in the literature. Simulations and comparisons give support to the validity of the obtained analytical expressions in this study. © 2007 Wiley Periodicals, Inc.
