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Article Citation - WoS: 11Citation - Scopus: 12Structural and Temperature-Tuned Bandgap Characteristics of Thermally Evaporated β-in2< Thin Films(Springer, 2021) Surucu, O.; Isik, M.; Terlemezoglu, M.; Gasanly, N. M.; Parlak, M.In2S3 is one of the attractive compounds taking remarkable interest in optoelectronic device applications. The present study reports the structural and optical characteristics of thermally evaporated beta-In2S3 thin films. The crystalline structure of the thin films was found as cubic taking into account the observed diffraction peaks in the X-ray diffraction pattern. The atomic compositional ratio of constituent elements was obtained as consistent with chemical formula of In2S3. Three peaks around 275, 309 and 369 cm(-1) were observed in the Raman spectrum. Temperature-tuned bandgap energy characteristics of the In2S3 thin films were revealed from the investigation of transmittance spectra obtained at various temperatures between 10 and 300 K. The analyses of the transmittance spectra indicated that direct bandgap energy of the In2S3 thin films decreases from 2.40 eV (at 10 K) to 2.37 eV (at 300 K) with the increase of measurement temperature. The bandgap energy vs. temperature relation was investigated by means of Varshni optical model. The fitting of the experimental data under the light of theoretical expression revealed the absolute zero bandgap energy, the rate of change of bandgap energy and Debye temperature.Article Citation - WoS: 1Citation - Scopus: 2Controlling Heterogeneous Structure of Smooth Breaks in Panel Unit Root and Cointegration Testing(Springer, 2023) Omay, Tolga; Iren, PerihanThis study aims to show the consequences of a restrictive homogeneity assumption of frequency in heterogeneous panel unit root and cointegration testing with Flexible Fourier Form. For this purpose, we use a simple panel unit root and residual based cointegration test with Flexible Fourier Form in a heterogeneous frequency setting using a bootstrap algorithm. The power of the test statistics and empirical analysis results indicate that failing to take into account a heterogeneous frequency may lead to misleading inferences, thereby leading to misspecified tests and erroneous conclusions concerning the stochastic behavior of the data in the panel sample.Article Citation - WoS: 6Citation - Scopus: 5The Effect of Zn Concentration on the Structural and Optical Properties of Cd1-xznx< Nanostructured Thin Films(Springer, 2021) Isik, M.; Terlemezoglu, M.; Isik, S.; Erturk, K.; Gasanly, N. M.The structural and optical properties of electrodeposited Cd1-xZnxS nanostructured thin films were investigated in the present paper for compositions of x = 0, 0.03, 0.06 and 0.09. X-ray diffraction patterns of the deposited thin films consisted of diffraction peaks related to cubic crystal lattice. The atomic compositional ratios were determined by performing energy dispersive spectroscopy measurements. Scanning electron microscopy images indicated that deposited thin films have nanostructured forms. Raman spectra of the Cd1-xZnxS thin films exhibited two vibrational modes associated with longitudinal optical mode and its first overtone. Transmission measurements were performed on the deposited thin films to get their band gap energies. It was seen from the analyses of absorption coefficient that band gap energy of Cd1-xZnxS thin films increases almost linearly from 2.40 to 2.51 eV as the composition was increased from x = 0 to x = 0.09.Article Citation - WoS: 8Citation - Scopus: 11Proposing a novel mixed-reality framework for basic design and its hybrid evaluation using linkography and interviews(Springer, 2022) Cindioglu, Hasane Ceren; Gursel Dino, Ipek; Surer, ElifImmersive Virtual Environments (IVEs), particularly Mixed-Reality (MR) technologies, continue to have an increasing impact on design processes and design education. This study focuses on MR's potentials in Basic Design (BD) education and its influence on novice designers' design thinking abilities. In this study, through a newly developed MR-based design framework, DesignMR, a comparative analysis between design processes in MR and the physical environment is presented. A hybrid evaluation methodology is used in the context of three-dimensional (3D) BD tasks through two sets of protocol studies: Linkography and exit interviews. Linkography is a method to analyze the design process based on detecting design moves and their links with each other. In this study, linkographic analyses point to an increase in critical moves and link index values in MR as compared to the physical environment for all participants. This indicates that MR can trigger improved creativity, design productivity, and design exploration by idea generation. Exit interviews highlighted the positive impact of DesignMR on the motivation, work efficiency, and 3D perception of the participants. Further research will be pursued for improved hand gestures to increase the effectiveness of object interaction.Article Citation - WoS: 1Citation - Scopus: 2Predictors of E-Democracy Applicability in Turkish K-12 Schools(Springer, 2022) Sendag, Serkan; Toker, Sacip; Uredi, Lutfi; Islim, Omer FarukToday, the COVID-19 pandemic has paved the way for a more democratic climate in K-12 schools. Administrators and teachers have had to seek out new ways through which to interact. This raises two questions; "What about the quality of interaction and participation in decision-making?" and "Which factors affect the level of participation in decision-making?" The aim of the current research is to determine the factors that predict the applicability level of e-democracy (i.e., "reporting and declaring opinions" and "decision-making") in K-12 schools. An associational research design was used in order to attain the main goal of the study, with Discriminant Function Analysis (DFA) technique used to analyze the factors predicting the applicability level of e-democracy. Data were collected from a total of 765 inservice K-12 teachers through a questionnaire developed by the researchers. DFA results showed "motivation to participate," "the level of participatory democracy in the country," and higher levels of the "use of Twitter" as the significant determinants of different levels of e-democracy application. Moreover, the results also indicated that those participants with the belief of e-democracy's applicability at the decision-making level found the "motivation level of stakeholders" to be the most critical. Their level of Twitter use was higher. They also believed that the level of participatory democracy in the country was at a higher level. Another result of the DFA pointed to "security and ethical issues," and lower levels of the "use of Twitter" as factors differentiating the group believing that e-democracy can be applicable with reporting and the declaration of opinions to administrators from the other groups. The discussions highlighted the critical role of participation level in e-democracy within K-12 schools.Article Citation - WoS: 5Citation - Scopus: 3Investigation of Λ (1405)as a molecular pentaquark state(Springer, 2024) Azizi, K.; Sarac, Y.; Sundu, H.Lambda ( 1405 ) is one of the interesting particles with its unclear structure and distinct properties. It has a light mass compared to its non-strange counterpart, despite the strange quark it carries. This situation puts the investigation of this resonance among the hot topics in hadron physics and collects attention to clarify its properties. In this study, we focus on the calculation of the mass and residue of the Lambda ( 1405 ) resonance within the framework of QCD sum rules. We assign a structure in the form of a molecular pentaquark composed from admixture of K - meson-neutron. Using an interpolating current in this form, the masses and the current coupling constant are attained as m = 1406 +/- 128 MeV and lambda = ( 3.35 +/- 0.35 ) x 10( - 5) GeV 6 for q and m = 1402 +/- 141 MeV and lambda = ( 4.08 +/- 1.08 ) x 10( - 5) GeV 6 for I Lorentz structures entering the calculations, respectively. The obtained mass values agree well with the experimental data supporting the plausibility of the considered structure.Article Entropy Based Streaming Big-Data Reduction With Adjustable Compression Ratio(Springer, 2023) Gokcay, ErhanThe Internet of Things is a novel concept in which numerous physical devices are linked to the internet to collect, generate, and distribute data for processing. Data storage and processing become more challenging as the number of devices increases. One solution to the problem is to reduce the amount of stored data in such a way that processing accuracy does not suffer significantly. The reduction can be lossy or lossless, depending on the type of data. The article presents a novel lossy algorithm for reducing the amount of data stored in the system. The reduction process aims to reduce the volume of data while maintaining classification accuracy and properly adjusting the reduction ratio. A nonlinear cluster distance measure is used to create subgroups so that samples can be assigned to the correct clusters even though the cluster shape is nonlinear. Each sample is assumed to arrive one at a time during the reduction. As a result of this approach, the algorithm is suitable for streaming data. The user can adjust the degree of reduction, and the reduction algorithm strives to minimize classification error. The algorithm is not dependent on any particular classification technique. Subclusters are formed and readjusted after each sample during the calculation. To summarize the data from the subclusters, representative points are calculated. The data summary that is created can be saved and used for future processing. The accuracy difference between regular and reduced datasets is used to measure the effectiveness of the proposed method. Different classifiers are used to measure the accuracy difference. The results show that the nonlinear information-theoretic cluster distance measure improves the reduction rates with higher accuracy values compared to existing studies. At the same time, the reduction rate can be adjusted as desired, which is a lacking feature in the current methods. The characteristics are discussed, and the results are compared to previously published algorithms.Article Citation - WoS: 2Citation - Scopus: 2Optimal Limit Order Book Trading Strategies With Stochastic Volatility in the Underlying Asset(Springer, 2023) Aydogan, Burcu; Ugur, Omur; Aksoy, UmitIn quantitative finance, there have been numerous new aspects and developments related with the stochastic control and optimization problems which handle the controlled variables of performing the behavior of a dynamical system to achieve certain objectives. In this paper, we address the optimal trading strategies via price impact models using Heston stochastic volatility framework including jump processes either in price or in volatility of the price dynamics with the aim of maximizing expected return of the trader by controlling the inventories. Two types of utility functions are considered: quadratic and exponential. In both cases, the remaining inventories of the market maker are charged with a liquidation cost. In order to achieve the optimal quotes, we control the inventory risk and follow the influence of each parameter in the model to the best bid and ask prices. We show that the risk metrics including profit and loss distribution (PnL), standard deviation and Sharpe ratio play important roles for the trader to make decisions on the strategies. We apply finite differences and linear interpolation as well as extrapolation techniques to obtain a solution of the nonlinear Hamilton-Jacobi-Bellman (HJB) equation. Moreover, we consider different cases on the modeling to carry out the numerical simulations.Article Citation - WoS: 1Citation - Scopus: 3Optical constants and critical point energies of (AgInSe2)0.75-(In2Se3)0.25 single crystals(Springer, 2020) Isik, M.; Nasser, H.; Guseinov, A.; Gasanly, N. M.AgInSe2 and In2Se3 are two attractive semiconducting materials for various technological applications especially for photovoltaic applications. In the present study, structural and optical properties of (AgInSe2)(x)-(In2Se3)(1-x) crystals for composition of x = 0.75 corresponding to chemical formula of Ag3In5Se9 were characterized by X-ray diffraction, energy-dispersive spectroscopy, room temperature transmission, and ellipsometry experiments. The transmittance spectrum was analyzed to reveal energy band gap. The derivative spectrophotometry analysis resulted in band gap energy of 1.22 eV. The spectra of complex dielectric function, refractive index and extinction coefficient were presented between 1.6 and 6.2 eV from the outcomes of ellipsometry analyses. Critical point energies have been determined using the derivative analyses of dielectric function. Five critical points at 2.70, 3.30, 4.05, 4.73, and 5.42 eV were revealed from the analyses. Crystal structure and atomic composition in semiconducting compound were also reported in the present work. The obtained results were compared with those reported for constituent compounds.Article Citation - WoS: 31Citation - Scopus: 35Fractional Unit-Root Tests Allowing for a Fractional Frequency Flexible Fourier Form Trend: Predictability of Covid-19(Springer, 2021) Omay, Tolga; Baleanu, DumitruIn this study we propose a fractional frequency flexible Fourier form fractionally integrated ADF unit-root test, which combines the fractional integration and nonlinear trend as a form of the Fourier function. We provide the asymptotics of the newly proposed test and investigate its small-sample properties. Moreover, we show the best estimators for both fractional frequency and fractional difference operator for our newly proposed test. Finally, an empirical study demonstrates that not considering the structural break and fractional integration simultaneously in the testing process may lead to misleading results about the stochastic behavior of the Covid-19 pandemic.
