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Article Citation - WoS: 13Citation - Scopus: 18A note on some coupled fixed-point theorems on G-metric spaces(Springeropen, 2012) Ding, Hui-Sheng; Karapinar, Erdal; Karapina, ErdalThe purpose of this paper is to extend some recent coupled fixed-point theorems in the context of G-metric space by essentially different and more natural way. We state some examples to illustrate our results.Article Citation - WoS: 16Citation - Scopus: 16q-bernstein Polynomials of the Cauchy Kernel(Elsevier Science inc, 2008) Ostrovska, SofiyaDue to the fact that in the case q > 1, q-Bernstein polynomials are not positive linear operators on C[0, 1], the study of their approximation properties is essentially more difficult than that for 0 < q < 1. Despite the intensive research conducted in the area lately, the problem of describing the class of functions in C[0, 1] uniformly approximated by their q-Bernstein polynomials (q > 1) is still open. In this paper, the q-Bernstein polynomials B-n,B-q(f(a); z) of the Cauchy kernel f(a) = 1/(z - a), a is an element of C \ [0, 1] are found explicitly and their properties are investigated. In particular, it is proved that if q > 1, then polynomials B-n,B-q(f(a); z) converge to f(a) uniformly on any compact set K subset of {z : vertical bar z vertical bar < vertical bar a vertical bar}. This result is sharp in the following sense: on any set with an accumulation point in {z : vertical bar z vertical bar > vertical bar a vertical bar}, the sequence {B-n,B-q(f(a); z) is not even uniformly bounded. (C) 2007 Elsevier Inc. All rights reserved.Article Citation - WoS: 9Citation - Scopus: 7Pulse Frequency Fluctuations of Persistent Accretion Powered Pulsars(Oxford University Press, 2023) Serim,D.; Serim,M.M.; Baykal,A.In this study, we examine the long-term torque noise fluctuations of persistent X-ray binaries Her X-1, Vela X-1, GX 301-2, Cen X-3, 4U 1538-53, OAO 1657-415, and 4U 1626-67 using the historical pulse frequency measurements provided by CGRO/BATSE and Fermi/GBM. We find that known disc-fed sources exhibit a 1/ω2 red noise component in their power density spectra which is saturated over long time-scales. On the other hand, wind-fed sources form a clear white noise component, and the wind-fed sources with occasional transient disc formation imprint 1/ω type flicker noise. We discuss their long-term timing noise properties based on the models to describe the power density spectrum of pulse frequency derivative fluctuations in terms of monochromatic and coloured noise processes. Furthermore, we investigate the relation between measured timing noise strengths and other independently measured physical parameters. Despite the low number of sample sources, we suggest that the noise strengths of these sources are correlated with their luminosities and uncorrelated with their magnetic field strengths, implying that the dominant noise-generating mechanism is accretion. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Article Citation - WoS: 56Citation - Scopus: 68The h-laplace and q-laplace Transforms(Academic Press inc Elsevier Science, 2010) Bohner, Martin; Guseinov, Gusein Sh.Starting with a general definition of the Laplace transform on arbitrary time scales, we specify the particular concepts of the h-Laplace and q-Laplace transforms. The convolution and inversion problems for these transforms are considered in some detail. (c) 2009 Elsevier Inc. All rights reserved.Article Citation - WoS: 9Citation - Scopus: 10Investigation of the Performance of High-Temperature Electrochemical Hydrogen Purification From Reformate Gases(Wiley, 2022) Durmus, Gizem Nur Bulanik; Durmuş, Gizem Nur Bulanık; Colpan, C. Ozgur; Devrim, Yilser; Devrim, Yılser; Durmuş, Gizem Nur Bulanık; Devrim, Yılser; Mechanical Engineering; Energy Systems Engineering; Mechanical Engineering; Energy Systems EngineeringIn the present work, the purification of hydrogen from a hydrogen/carbon dioxide/carbon monoxide (H-2:CO2:CO) mixture by a high-temperature electrochemical purification (HT-ECHP) system is examined. Electrochemical H-2 purification experiments were carried out in the temperature range of 140-180 degrees C. The effects of the molar ratio of the gases in the mixture (H-2:CO2:CO-75:25:0, H-2:CO2:CO-72:26:2,0 H-2:CO2:CO-75:22:3, H-2:CO2:CO-75:20:5, H-2:CO2:CO-97:0:3, H-2:CO2:CO-95:0:5) and the operating temperature on the electrochemical H-2 separation were investigated. As a result of the electrochemical H-2 purification experiments, it was determined that the operating temperature is the most important parameter affecting the performance. According to the results obtained, H-2 purity of 99.999% was achieved at 160 degrees C with the reformate gas mixture containing 72% H-2, 26% CO2, and 2% CO by volume. According to the polarization curves of the gas mixtures containing CO, high current densities at low voltage were reached at 180 degrees C, and it was observed that the performance increased as the temperature increased, whereas the gas mixture without CO gave the best performance at 160 degrees C.Article Citation - WoS: 15Citation - Scopus: 15The Effect of Sevoflurane and Fullerenol C 60 on the Liver and Kidney in Lower Extremity Ischemia-Reperfusion Injury in Mice With Streptozocin-Induced Diabetes(Dove Medical Press Ltd, 2023) Sengel, Necmiye; Kucuk, Ayseguel; Ozdemir, Cagri; Sezen, Saban Cem; Kip, Gulay; Er, Fatma; Arslan, MustafaObjective: This study aimed to demonstrate whether fullerenol C60, sevoflurane anesthesia, or a combination of both had protective effects on the liver and kidneys in lower extremity ischemia-reperfusion injury (IRI) in mice with streptozocin-induced diabetes. Methods: A total of 46 Swiss albino mice were divided into six groups as follows: control group (group C, n=7), diabetes group (group D, n=7), diabetes-ischemia/reperfusion (group DIR, n=8), diabetes-ischemia/reperfusion-fullerenol C60 (group DIR-FC60, n=8), diabetes-ischemia/reperfusion-sevoflurane (group DIR-S, n=8), and the diabetes-ischemia/reperfusion-fullerenol C60-sevoflurane (group DIR-S-FC60, n=8). Fullerenol C60 (100mg/kg) was administered intraperitoneally 30 min before the ischemia-reperfusion procedure to the fullerenol groups (DIR-FC60 and DIR-S-FC60). In the DIR groups, 2 hours (h) ischemia-2h reperfusion periods were performed. In the sevoflurane groups, sevoflurane was applied during the ischemia-reperfusion period with 100% O2. Liver and kidney tissues were removed at the end of the reperfusion procedure for biochemical and histopathological examinations.Results: In liver tissue, hydropic degeneration, sinusoidal dilatation, pycnotic nuclei, prenecrotic cells, and mononuclear cell infiltration in parenchyma were significantly more frequent in group DIR than in groups D and group C. In terms of the histopathologic criteria examined, more positive results were seen in group DIR-FC60, and when group DIR-FC60 was compared with group DIR, the difference was significant. The best results in AST, ALT, glucose, TBARS levels, and SOD enzyme activities in liver tissue were in group DIR-FC60 compared with group DIR, followed by groups DIR-S-FC60 and DIR-S, respectively. Regarding TBARS levels and SOD enzyme activities in kidney tissue, the best results were in groups DIR-FC60, DIR-S-FC60, and DIR-S, respectively.Conclusion: According to our findings, it is clear that fullerenol C60 administered intraperitoneally 30 min before ischemia, alone or together with sevoflurane, reduces oxidative stress in distant organ damage caused by lower extremity IRI, and reduces liver and kidney tissue damage in histopathologic examinations.Article Citation - WoS: 10Citation - Scopus: 11Is There Convergence in Renewable Energy Deployment? Evidence From a New Panel Unit Root Test With Smooth and Sharp Structural Breaks(Pergamon-elsevier Science Ltd, 2023) Corakci, Aysegul; Omay, TolgaThis study examines whether the contribution of renewable energy to the total primary energy supply converges in a panel of 24 OECD countries over the period 1960-2020. To this end, a new panel unit root test that allows for both sharp and smooth breaks is proposed to test for the stochastic convergence hypothesis. Although renewable energy convergence is not rejected when the newly proposed test is applied to the full panel of OECD countries, it found only moderate support within the members of the panel using a sequential panel selection methodology. In fact, in two high-income OECD countries, the contribution of renewable energy to the primary energy supply shows no sign of convergence: Poland and Iceland. Therefore, the renewable energy shares seem to be converging to a common steady state in only a group of OECD countries over the long run. This uneven pattern of convergence, in turn, suggests that the OECD countries are still far away from developing a common sustainable renewable energy target, calling for urgent international policy cooperation to encourage the divergent econo-mies to seek out the menu of policies that ensure the worldwide success of renewable energy transformation.Article Citation - WoS: 43Citation - Scopus: 60Impact of Physical Ambiance on Communication, Collaboration and Coordination in Agile Software Development: an Empirical Evaluation(Elsevier, 2012) Mishra, Deepti; Mishra, Alok; Ostrovska, SofiyaContext: Communication, collaboration and coordination are key enablers of software development and even more so in agile methods. The physical environment of the workspace plays a significant role in effective communication, collaboration, and coordination among people while developing software. Objective: In this paper, we have studied and further evaluated empirically the effect of different constituents of physical environment on communication, coordination, and collaboration, respectively. The study aims to provide a guideline for prospective agile software developers. Method: A survey was conducted among software developers at a software development organization. To collect data, a survey was carried out along with observations, and interviews. Results: It has been found that half cubicles are 'very effective' for the frequency of communication. Further, half cubicles were discovered 'effective' but not 'very effective' for the quality/effectiveness of communication. It is found that half-height cubicles and status boards are 'very effective' for the coordination among team members according to the survey. Communal/discussion space is found to be 'effective' but not 'very effective' for coordination among team members. Our analysis also reveals that half-height glass barriers are 'very effective' during the individuals problem-solving activities while working together as a team. Infact, such a physically open environment appears to improve communication, coordination, and collaboration. Conclusion: According to this study, an open working environment with only half-height glass barriers and communal space plays a major role in communication among team members. The presence of status boards significantly help in reducing unnecessary communication by providing the required information to individuals and therefore, in turn reduce distractions a team member may confront in their absence. As communication plays a significant role in improving coordination and collaboration, it is not surprising to find the effect of open working environment and status boards in improving coordination and collaboration. An open working environment increases the awareness among software developers e.g. who is doing what, what is on the agenda, what is taking place, etc. That in turn, improves coordination among them. A communal/discussion space helps in collaboration immensely. (C) 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 64Citation - Scopus: 69A Semi-Empirical Approach for Residual Stresses in Electric Discharge Machining (edm)(Elsevier Sci Ltd, 2006) Ekmekci, Bulent; Tekkaya, A. Erman; Erden, AbdulkadirHigh residual stresses are developed on the surfaces of electric discharge machined parts. In this study, layer removal method is used to measure the residual stress profile as a function of depth beneath the surface caused by die sinking type EDM. Cracking and its consequences on residual stresses are also studied on samples machined at long pulse durations. A modified empirical equation is developed for scaling residual stresses in machined surfaces with respect to operating conditions. In this model, a unit amplitude shape function representing change in curvature with respect to removal depth is proposed. The proposed form is found to be a special form of a Gauss Distribution. It is the sum of two Gaussian peaks, with the same amplitude and pulse width but opposite center location. The form can be represented by three constant coefficients. These coefficients depend on the released energy by a power function. (C) 2005 Elsevier Ltd. All rights reserved.Article Citation - WoS: 8Citation - Scopus: 9Contribution of Surface Silanization Process on Mechanical Characteristics of Tpu-Based Composites Involving Feldspar and Quartz Minerals(Wiley, 2023) Bouzmane, Hajar; Tirkes, Suha; Yilmaz, Volkan Murat; Tayfun, Umit; Tirkes, SehaIn this study, quartz and feldspar powders were surface treated using a silane coupling agent to achieve a more compatible mineral surface with the polymer matrix. Details of surface characteristics of minerals were examined by energy-dissipative X-ray spectroscopy, contact angle measurements, and infrared spectroscopy. Thermoplastic polyurethane-TPU was compounded with minerals using the melt-blending technique. Mechanical, thermo-mechanical, melt-flow, and morphological characterizations of TPU and relevant composites were performed by utilizing tensile and Shore hardness tests, dynamic mechanical analysis (DMA), melt flow index (MFI) measurements, and scanning electron microscopy (SEM), respectively. Water repellency of TPU and composites were also evaluated experimentally. Effects of surface treatments were discussed by comparing the results of composites filled with pristine and modified minerals. Results revealed that enrichment of quartz and feldspar surfaces confer mechanical and thermo-mechanical performance of composites. Mineral inclusions caused no drastic changes to the MFI parameter of TPU. The silane layer on the mineral surface displayed a barrier effect to water uptake of composites. Homogeneous dispersion and improved interfacial adhesion of mineral particles to the TPU phase were confirmed with help of SEM observations. Quartz exhibited slightly higher performance thanks to its silica-rich composition. The findings of this research exhibited the considerable influence of the silane layer on the mineral surface on the mechanical performance of TPU-based composites.
