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Article Citation - WoS: 20Citation - Scopus: 23A Novel Comfort Temperature Determination Model Based on Psychology of the Participants for Educational Buildings in a Temperate Climate Zone(Elsevier, 2023) Ozbey, Mehmet Furkan; Turhan, CihanMaintaining thermal comfort in the educational buildings is vital due to the impacts on learning effectiveness of students. Therefore, development of a proper comfort temperature in educational buildings is a must. In naturally ventilated and mixed-mode buildings, the adaptive thermal comfort model, which considers additively psychological, and behavioural factors to the Fanger's PMV/PPD model, is commonly applied based on regression analyses. However, the psychological adjustments based on current mood state are very limited in these adaptive thermal comfort models. Therefore, this study focuses on the psychological adjustments in terms of Profile of Mood States in order to predict comfort temperature of students in a case building. The experiments are conducted in a university on a temperate climate zone for a long period-data including both heating and cooling seasons. In this study, the comfort temperatures for each student are determined via Griffith method for the case building. Moreover, the current mood states of students are assessed utilizing the Profile of Mood States survey, which are collected via a developed mobile application. As a conclusion, the relation between the current mood state of the students and comfort temperature are statistically investigated. The results show that a Griffith constant are found as 0.332/K and mean annual comfort temperature is found as 21.32 degrees C in the case building. Additionally, a significant difference is found in the comfort temperatures among the students who have more, or fewer concerns than typically reported. The novelty of the study is to present a comfort temperature determination model which considers human psychology as a starter study in the literature.Article Citation - WoS: 30Citation - Scopus: 30New approach to stability of 2-D discrete systems with state saturation(Elsevier, 2012) Singh, VimalA new criterion for the global asymptotic stability of 2-D discrete systems described by the Roesser model using saturation arithmetic is presented. The criterion is a generalization over an earlier criterion due to Liu and Michel. The generalized criterion has the feature that Lyapunov matrix P is not restricted to be symmetric, i.e., P can be even unsymmetric. A modified form of the criterion is also presented. Two examples showing the effectiveness of the generalized approach to yield new 2-D stability results are provided. To the best of author's knowledge, the use of unsymmetric P to obtain new 2-D stability conditions (i.e., conditions which are outside the scope of symmetric P) is demonstrated, for first time, in this paper. (C) 2011 Elsevier B.V. All rights reserved.Article Citation - WoS: 23Citation - Scopus: 22Wavelength Dependence of the Nonlinear Absorption Performance and Optical Limiting in Bi12tio20 Single Crystal(Elsevier, 2023) Pepe, Yasemin; Isik, Mehmet; Karatay, Ahmet; Gasanly, Nizami; Elmali, AyhanIn this study, the influence of excitation wavelength and input intensity on the nonlinear absorption (NA) mechanism and optical limiting behavior of the Bi12TiO20 (BTO) single crystal were reported. The energy band gap of the BTO single crystal was obtained to be 2.38 eV. Urbach energy revealed that the single crystal has a highly defective structure. Open aperture (OA) Z-scan experiments were conducted at 532 and 1064 nm exci-tation wavelengths at various input intensities. Obtained experimental data were analyzed with a theoretical model considering one photon, two-photon and free carrier absorption contributions to NA. The obtained results revealed that the BTO single crystal possesses NA. The NA coefficient increased with increasing input intensity at 532 nm excitation wavelength, while it decreased with increasing input intensity at 1064 nm excitation wave-length. Due to the intense localized defect states distribution at the energy of 532 nm excitation wavelength within the band gap, increasing contribution to NA came from one photon absorption (OPA), sequential two -photon absorption (TPA) and free carrier absorption (FCA) with increasing input intensity. The filling of the defect states at 1064 excitation wavelength caused a reduction in NA due to increasing saturable absorption with increasing input intensity. TPA coefficients were also found from the fitting ignoring the defect states. As ex-pected, the values of the nonlinear absorption coefficient beta eff are higher than that of the TPA coefficients for both excitation wavelengths. The optical limiting threshold of the BTO single crystal was obtained to be 6.62 mJ/cm2. The results of the present works indicated that BTO single crystal can be used as a potential optical limiter.Article Citation - WoS: 136Citation - Scopus: 148Palladium(0) Nanoparticles Supported on Silica-Coated Cobalt Ferrite: a Highly Active, Magnetically Isolable and Reusable Catalyst for Hydrolytic Dehydrogenation of Ammonia Borane(Elsevier, 2014) Akbayrak, Serdar; Kaya, Murat; Volkan, Murvet; Ozkar, SaimPalladium(0) nanoparticles supported on silica-coated cobalt ferrite (Pd(0)/SiO2-CoFe2O4) were in situ generated during the hydrolysis of ammonia borane, isolated from the reaction solution by using a permanent magnet and characterized by ICP-OES, XRD, TEM, TEM-EDX, XPS and the N-2 adsorption-desorption techniques. All the results reveal that well dispersed palladium(0) nanoparticles were successfully supported on silica coated cobalt ferrite and the resulting Pd(0)/SiO2-CoFe2O4 are highly active, magnetically isolable, and recyclable catalysts in hydrogen generation from the hydrolysis of ammonia borane with an unprecedented turnover frequency (TOF, calculated on the basis of the total amount of Pd) of 254 mol H-2 (mol Pd min)(-1) at 25 +/- 0.1 degrees C. The reusability tests reveal that Pd(0)/SiO2-CoFe2O4 are still active in the subsequent runs of hydrolysis of ammonia borane providing 100% conversion. Pd(0)/SiO2-CoFe2O4 provide the highest catalytic activity with a TOF value of 198 mol H-2 (mol Pd min)(-1) in the 10th use in hydrogen generation from the hydrolysis of ammonia borane as compared to the other palladium catalysts. The work reported here also includes the kinetic studies depending on the temperature to determine the activation energy of the reaction (E-a = 52 +/- 2 kJ/mol) and the effect of catalyst concentration on the rate of hydrolytic dehydrogenation of ammonia borane, respectively. (C) 2013 Elsevier B.V. All rights reserved.Article Citation - WoS: 27Citation - Scopus: 30Effects of Au Nanoslabs on the Performance of Cdo Thin Films Designed for Optoelectronic Applications(Elsevier, 2021) Alharbi, Seham Reef; Qasrawi, A. F.In this work, the effect of 50 nm thick gold nanosheets on the structural, morphological, optical and electrical properties of stacked layers of CdO are investigated. The insertion of Au nanoslabs decreased the lattice parameters of the cubic unit cells of CdO. It also decreased the microstrain, the defect density, the stacking fault percentage and increased the crystallite and grain sizes. Optically, the light absorbability is enhanced, the energy band gap is shrunk and the optical conductivity is increased. The optical conductivity parameters presented by scattering time, plasmon frequency, drift mobility and free carrier density are all engineered via participation of Au nanosheets. On the other hand, electrical measurements in the frequency domain of 0.01-1.80 GHz indicated that the Au nanosheets forced the capacitance spectra to exhibit negative values and increased the electrical conductivity in the studied frequency domain. The terahertz cutoff frequency is tuned in the range of 5.0-22.0 THz indicating the applicability of the CdO/Au/CdO (CAC) films as terahertz filters. The direct current electrical conductivity measurements have shown that while the CC samples exhibit nondegenerate extrinsic nature of conduction, the CAC samples displayed degenerate/nondegenerate transitions at 400 K. With the feature of negative capacitance that can be used for noise reduction and parasitic capacitance cancellation, the CAC films can be regarded as promising structure for multifunctional device applications.Article Citation - WoS: 5Citation - Scopus: 5Molecular/Antigenic Mimicry and Immunological Cross-Reactivity Explains Sars-Cov Autoimmunity(Elsevier, 2025) Adiguzel, Yekbun; Bogdanos, Dimitros P.; Shoenfeld, YehudaCOVID-19 pandemic is over, but its effects on chronic illnesses remain a challenging issue. Understanding the influence of SARS-COV-2-mediated autoimmunity and overt autoimmune disease is of paramount importance, as it can provide a critical mass of information regarding both infection-mediated (and vaccination-induced) autoimmune phenomena in susceptible individuals during the disease course, and short or long-term post-disease sequelae. The high prevalence of organ and non-organ specific autoantibody positivity in patients with COVID-19 led to studies attempting to delineate the origin and the underlying mechanism responsible for their induction nature, identifying novel autoantigens, and the self-epitope sequences which could be the impetus for the initiating autoreactive responses. Herein, we provide a meticulous review of the studies reporting those mimicking sequences that have been experimentally validated, based on the assumption that molecular mimicry and immunological crossreactivity may account for autoantibody development. Most reports are based on bioinformatics approaches, and only a disproportionally small number of studies currently demonstrate immunological crossreactivity. We took the opportunity to further review and searched for the linear human epitope sequences of human, through the epitopes deposited at the Immune Epitope Database. This included an analysis of autoimmune disease as the disease data to comprehensively understand the subject matter. The critical overview of the findings underscore the urgent and immense need for further research to gain a comprehensive understanding of the mechanisms involved and the anticipated appraisal that molecular mimicry and immunological crossreactivity is indeed central to the loss of immunological tolerance during SARS-COV-2 infection.Article Citation - WoS: 21Citation - Scopus: 21The Role of Defects on the Transition From Saturable Absorption To Nonlinear Absorption of Bi12geo20< Single Crystal Under Increasing Laser Excitation(Elsevier, 2022) Pepe, Yasemin; Isik, Mehmet; Karatay, Ahmet; Yildiz, Elif Akhuseyin; Gasanly, Nizami; Elmali, AyhanThis work reports defect and input intensity dependent nonlinear optical behaviors of Bi12GeO20 (BGO) single crystal. Open aperture (OA) Z-scan experiments were performed with 532 nm excitation wavelength under 4 ns and 100 fs pulsed laser irradiation. Obtained data were fitted with a theoretical model considering one-photon, two-photon and free carrier absorption contributions to nonlinear absorption due to longer lifetime of localized defect states than that of used laser pulse durations. At low input intensities, the BGO single crystal showed saturable absorption (SA) behavior and transition to nonlinear absorption (NA) behavior observed with further increase of the input intensities both of pulse durations. At low input intensity, the OPA mechanism is dominant and results in SA by filling of the defect states due to defect state at around one photon energy (2.32 eV). At higher input intensity, multi-photon, two-photon and free carrier absorption become dominant mechanisms, and nonlinear absorption behavior was observed. The lowest saturation threshold was found as 1.36 x 1010 W/cm2 with nanosecond pulses. We have revealed the mechanisms contributing both SA and NA, and determined saturation intensity threshold and effective nonlinear absorption coefficients. Our findings indicate that the tails of defect states overlap in the energy band gaps especially in sufficiently disordered crystal. With this way, the spectral range for saturable absorption and nonlinear absorption can be broadened.Article Citation - WoS: 8Citation - Scopus: 7Structural and Optical Characteristics of Thermally Evaporated Tlgase2 Thin Films(Elsevier, 2022) Isik, M.; Işık, Mehmet; Karatay, A.; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringThe present paper reports the structural and optical properties of thermally evaporated TlGaSe2 thin films. X-ray diffraction pattern of evaporated film presented two diffraction peaks around 24.15 and 36.00 degrees which are associated with planes of monoclinic unit cell. Surface morphology of the TlGaSe2 thin films was investigated by scanning electron and atomic force microscopy techniques. Although there was observed some ignorable amount of clusters of quasi-spherical shape in the scanning electron microscope image, the film surface was observed almost uniform. Raman spectrum exhibited six peaks around 253, 356, 488, 800, 1053 and 1440 cm(-1) associated with possible vibrational mode combinations. Band gap energy of the thin film was determined as 3.01 eV from the analyses of transmission spectrum. Transmission spectrum presented strong Urbach tail and analyses of corresponding region resulted in Urbach energy of 0.66 eV. The structural and optical properties of deposited TlGaSe2 thin films were compared with those of single crystal. This comparison would provide valuable information about influence of thickness on the studied compounds.Article Citation - WoS: 7Citation - Scopus: 7Exploring the Linear and Nonlinear Optical Behavior of (tlins2)0.75(tlinse2)0.25: Insights From Ellipsometry Measurements(Elsevier, 2023) Isik, M.; Guler, I.; Gasanly, N.The search for layered structured new semiconductor materials with remarkable optical properties has become a driving force, especially for materials science. Tl2In2S3Se [(TlInS2)0.75(TlInSe2)0.25], a fascinating compound, holds great promise for advanced photonic and optoelectronic applications. In the present study, the linear and nonlinear optical properties of Tl2In2S3Se layered single crystals were studied by ellipsometry measurements. The variation of refractive index, extinction coefficient, absorption coefficient and skin depth with energy were investigated. Applying the derivative analysis technique to the absorption spectrum, indirect bandgap was found as 2.19 eV. The refractive index data was analyzed considering single-effective-oscillator model. The lattice dielectric constant, plasma frequency, carrier density to the effective mass ratio and zero-frequency refractive index were found. Moreover, the change in optical conductivity with energy yielded to determine the direct bandgap as 2.40 eV. The optical parameters of nonlinear refractive index, first-and third-order nonlinear susceptibilities were also reported.Article Citation - WoS: 14Citation - Scopus: 15Thermoluminescence Characteristics of Bi 12 Sio 20 Single Crystals(Elsevier, 2020) Isik, M.; Sarigul, N.; Gasanly, N. M.[No Abstract Available]
