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Article Citation - WoS: 12Citation - Scopus: 13Performance of the Au/Mgo Photovoltaic Devices(Elsevier Sci Ltd, 2015) Khanfar, H. K.; Qasrawi, A. F.A 100 mu m thick MgO film is used to design a metal semiconductor metal device. The device is characterized by means of current voltage characteristics in the dark and under various light energies in the photon energy range of 3.70-2.15 eV. A photovoltaic effect presented by an open circuit voltage of 0.12-0.47 V. short circuit current density of 3.9-10.5 mu A/cm(2), quantum efficiency of 0.662-0.052, and responsivity of 0.179-0.024 A/W under photoexcitation optical power of 2.2-28.2 mu W is observed. The device was also tested as a UV optical communication component. The test revealed a wide range of tunability and sensitivity for microwave resonant frequencies of 0.5 and 2.9 GHz. The differential resistance of the device exhibited different values at each applied ac signal frequency. When the frequency is fixed, the illuminated to the dark current ratio remained constant for all signal powers in the range of 0.00-20.0 dBm. (C) 2014 Elsevier Ltd. All rights reserved.Article Citation - WoS: 31Citation - Scopus: 37Effect of Initial Water Content and Calcination Temperature on Photocatalytic Properties of Tio2 Nanopowders Synthesized by the Sol-Gel Process(Elsevier Sci Ltd, 2015) Agartan, Lutfi; Kapusuz, Derya; Park, Jongee; Ozturk, AbdullahThe effects of initial water content and calcination temperature on sol gel synthesized TiO2 powders were studied. Mother solutions had water/Ti-precursor mole ratios (R ratio) of 1, 5, 10, and 50. Dried aerogels were calcined for 3 h at temperatures of 300, 400, and 500 degrees C to obtain crystallized TiO2 nanopowders in the range of 15-30 nm. PE-scanning electron microscopy and X-ray diffraction techniques were employed to investigate the morphological and structural properties of the nanopowders synthesized. Profound effect of gel viscosity was observed on the formation mechanism and extent of crystallinity in the powders. Methylene blue degradation test results suggest, photocatalytic performance is enhanced as initial water content and calcination temperature increased. Band-gap energy of the powders ranged from 3.09 to 3.27 eV. Overall, this study shows that initial water content and calcination regime have a profound effect on the phase assembly, crystallite size, band-gap energy, and photocatalytic performance of sol gel synthesized TiO2 nanopowders. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Article Citation - WoS: 58Citation - Scopus: 66Experimental Investigation of a Natural Zeolite-Water Adsorption Cooling Unit(Elsevier Sci Ltd, 2011) Solmus, Ismail; Kaftanoglu, Bilgin; Yamali, Cemil; Baker, DerekIn this study, a thermally driven adsorption cooling unit using natural zeolite-water as the adsorbent-refrigerant pair has been built and its performance investigated experimentally at various evaporator temperatures. The primary components of the cooling unit are a shell and tube adsorbent bed, an evaporator, a condenser, heating and cooling baths, measurement instruments and supplementary system components. The adsorbent bed is considered to enhance the bed's heat and mass transfer characteristics; the bed consists of an inner vacuum tube filled with zeolite (zeolite tube) inserted into a larger tubular shell. Under the experimental conditions of 45 degrees C adsorption, 150 degrees C desorption, 30 degrees C condenser and 22.5 degrees C, 15 degrees C and 10 degrees C evaporator temperatures, the COP of the adsorption cooling unit is approximately 0.25 and the maximum average volumetric cooling power density (SCR,) and mass specific cooling power density per kg adsorbent (SCP) of the cooling unit are 5.2 kW/m(3) and 7 W/kg, respectively. (C) 2011 Elsevier Ltd. All rights reserved.Article Citation - WoS: 77Citation - Scopus: 80Reliability and Optimal Replacement Policy for an Extreme Shock Model With a Change Point(Elsevier Sci Ltd, 2019) Eryilmaz, Serkan; Kan, CihangirAn extreme shock model when there is a change in the distribution of the magnitudes of shocks is defined and studied. Such a model is useful in practice since a sudden change in environmental conditions may cause a larger shock. In particular, the reliability and mean time to failure of the system is obtained by assuming that the times between arrivals of shocks follow phase-type distribution. The optimal replacement policy that is based on a control limit is also proposed. The results are illustrated when the number of shocks until the change point follows geometric distribution.Article Citation - WoS: 10Citation - Scopus: 12Anomaly Detection With Low Magnetic Flux: a Fluxgate Sensor Network Application(Elsevier Sci Ltd, 2016) Ege, Yavuz; Coramik, Mustafa; Kabadayi, Murat; Citak, Hakan; Kalender, Osman; Yuruklu, Emrah; Nazlibilek, SedatRecent studies on remote detection methods were mostly for improving variables like sensing distance, sensitivity and power consumption. Especially using anisotropic magneto-resistive sensors with low power consumption and high sensitivity for detecting subsurface magnetic materials became very popular in last decades. In our study, for detecting subsurface materials, we have used fluxgate sensor network for having even higher sensitivity and also minimizing the power consumption by detecting the changing rates of horizontal component of earth's magnetic flux which is assumed to be very low. We have constituted a magnetic measurement system which comprises a detector system, which has a mechanism enables sensors to move in 3-D space, a data acquisition module for processing and sending all sensor information, and a computer for running the magnetic flux data evaluation and recording software. Using this system, tests are carried out to detect anomalies on horizontal component of earth's magnetic flux which is created by different subsurface materials with known magnetic, chemical and geometric properties. The harmonics of horizontal component of earth's magnetic flux in scanned area are analyzed by the help of DSP Lock-In amplifier and the amplitudes of high variation harmonics are shown as computer graphics. Using the graphic information, the upside surface geometry of subsurface material is defined. For identifying the magnetic anomalies, we have used the scale-invariant feature transform (SIFT)-binary robust invariant scalable keypoints (BRISKs) as keypoint and descriptor. We used an algorithm for matching the newly scanned image to the closest image in database which is constituted of mines and possible other metal objects like cans, etc. Results show that, if the proposed detection system is used instead of metal detectors which cannot distinguish mines from other metal materials and alert for every type of metal with different geometries, it can be said that miss alarm count, work force and time can be decreased dramatically. In this paper, mostly the setup of the system is described and in Appendix A some experimental outputs of the system for different geometries of metal samples are given. And also for comparing the results of the proposed system, additional experiments are carried out with a different type of sensor chip, namely KMZ51, and also given in Appendix A. (C) 2015 Elsevier Ltd. All rights reserved.Article Citation - WoS: 8Citation - Scopus: 8Improvement of Optical Properties and Redox Stability of Poly(3,4-Ethylenedioxythiophene)(Elsevier Sci Ltd, 2018) Ertan, Salih; Cihaner, AtillaIn order to improve the optical properties and redox stability of poly(3,4-ethylenedioxythiophene) (PEDOT) without changing its electrochemical and electrochromic behaviour, it was supported with alkyl-substituted polyhedral oligomeric silsesquioxane (POSS) cage. The corresponding copolymers were obtained electrochemically via potentiostatic or potentiodynamic methods and compared to the parent homopolymers. Electrochemical polymerization of EDOT and POSS containing EDOT called EDOT-POSS in various monomer feed ratios was performed in an electrolyte solution of 0.1 M TBAPF(6) dissolved in a mixture of dichloromethane and acetonitrile (1/3: v/v). Just as PEDOT, the copolymers represented the similar band gap (1.61 eV), redox and electrochromic behaviors. On the other hand, when compared to the parent PEDOT, the presence of POSS cages in the copolymer backbone improved the redox stability and optical properties of PEDOT such as higher percent transmittance change (65% at 621 nm), higher transparency at oxidized state, lower switching time (similar to 1.0 s) and higher coloration efficiency (463 cm(2)/C for 95% switching) as well as higher electrochemical stability (86% of its electroactivity retains after 1750 cycles under ambient conditions).Article Citation - WoS: 5Citation - Scopus: 6Gd and Tb Doping Effects on the Physical Properties of Nd2sn2<(Elsevier Sci Ltd, 2018) Saleh, Adli A.; Hamamera, Hanan Z.; Khanfar, Hazem K.; Qasrawi, A. F.; Yumusak, G.In the current study, we report the light doping effects of the gadolinium and the terbium on the structural, morphological, optical and electrical properties of Nd2Sn2O7 pyrochlore ceramics. The pyrochlore which is prepared by the conventional solid state reaction technique is analyzed by means of scanning electron microscopy, energy dispersive X-ray analyzer, X-ray diffraction, ultraviolet- visible light spectrophotometry and temperature dependent current -voltage characteristics techniques. It is found that even though the doping content of both metals is low (2%), they significantly alter the physical properties of the pyrochlore. Particularly, it is observed that, these two doping agents increases the lattice parameter and strain and reduces the crystallite size and dislocation density. Optically, the effect of Gd doping on shrinking the energy band gap value of the Nd(2)Sn(2)O(7 )pyrochlore ceramic is more pronounced than that of Tb. On the other hand, the electrical investigations have shown that while the Gd make the pyrochlore exhibit p-type conductivity through forming shallow acceptor levels, the Tb forces n-type conductivity by forming deep donor levels below the conduction band edge. Such acceptor and donor impurity levels increases the electrical conductivity of the Nd(2)Sn(2)O(7 )pyrochlore ceramics by 390 and 58 times, respectively.Article Citation - WoS: 150Citation - Scopus: 183Effects of Elevated Temperature on Compressive Strength and Weight Loss of the Light-Weight Concrete With Silica Fume and Superplasticizer(Elsevier Sci Ltd, 2008) Sancak, Emre; Sari, Y. Dursun; Simsek, OsmanIn this study, structural light-weight concretes produced by Pumice (LWC) and concretes with normal-weight aggregate (NWC) were investigated. Compressive strength and weight loss of the concretes were determined after being exposed to high temperatures (20, 100, 400, 800, 1000 degrees C). To achieve these objectives, 12 different types of concrete mixtures were produced. In producing the mixtures, silica fume (SF) was used to replace the Portland cement in the ratios of 0%, 5% and 10% by weight. Half of the mixtures were obtained by adding superplasticizers (SP) to the above mixtures in the ratio of 2% by weight. In conclusion; unit weight of LWC was 23% lower than that of NWC. The LWC containing 2% SP could retain 38% of the initial compressive strength. Rate of deterioration was higher in NWC when compared to LWC. The loss of compressive strengths increased depending on the ratio of using SF at about 800 degrees C and over. (C) 2008 Elsevier Ltd. All rights reserved.Article Citation - WoS: 11Citation - Scopus: 11Electrochemical and Optical Properties of Substituted Phthalimide Based Monomers and Electrochemical Polymerization of 3,4-Ethylenedioxythiophene Oligomeric Silsesquioxane (poss) Analogue(Elsevier Sci Ltd, 2019) Cakal, Deniz; Ertan, Salih; Cihaner, Atilla; Onal, Ahmet M.A new series of donor-acceptor-donor type trimeric monomers bearing substituted phthalimide units as acceptor units and thiophene and 3,4-ethylenedioxythiophene (EDOT) as donor units was synthesized and characterized. The strength of acceptor units and intramolecular charge transfer between donor and acceptor units were investigated by using electrochemical and optical methods. The main advantage of phthalimide unit over other acceptor units is the ease of its functionalizability. Thus, utilizing this property, a phthalimide derivative (E2P-POSS) bearing polyhedral oligomeric silsesquioxane (POSS) cage was introduced successfully with EDOT and polymerized electrochemically. The corresponding electroactive polymer, PE2P-POSS, has a band gap of 1.72 eV and is an electrochromic polymer: gray when neutralized and eggplant purple when oxidized.Article Citation - WoS: 46Citation - Scopus: 56Marginal and Joint Reliability Importance Based on Survival Signature(Elsevier Sci Ltd, 2018) Eryilmaz, Serkan; Coolen, Frank P. A.; Coolen-Maturi, TahaniMarginal and joint reliability importance measures have been found to be useful in optimal system design. Various importance measures have been defined and studied for a variety of system models. The results in the literature are mostly based on the assumption that the components within the system are independent or identical. The present paper is concerned with computation of marginal and joint reliability importance for a coherent system that consists of multiple types of dependent components. In particular, by utilizing the concept of survival signature, expressions for marginal and joint reliability importance measures are presented. We also introduce reliability importance for a system of which only the survival signature is known, which therefore can be regarded to be a black box system. (C) 2017 Elsevier Ltd. All rights reserved.
