Browsing by Author "Kirkil, Gokhan"

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Citation Count: 0
Exploring non-linear relationships between perceived interactivity or interface design and acceptance of collaborative web-based learning
(Springer, 2023) Kirkil, Gökhan; Kirkil, Gokhan
The novelty of this study is in developing a conceptual model for predicting the non-linear relationships between human-computer interaction factors and ease of use and usefulness of collaborative web-based learning or e-learning. Ten models (logarithmic, inverse, quadratic, cubic, compound, power, s-curve, growth, exponential, and logistic) were examined as functions of effects compared to linear relationships to see which was the most appropriate, based on R-2, adjusted R-2 and SEE values. To answer the addressed questions, the researcher surveyed 103 students from Kadir Has University about the perceived interface and interactivity of e-learning. The results show that most of the hypotheses formulated for this purpose have been proven. Our analysis shows that cubic models (the relationship between ease of use and usefulness, visual design, course environment, learner-interface interactivity, and course evaluation system and ease of use), quadratic models (the relationship between visual design, and system quality and usefulness, course structure and content, course environment, and system quality and ease of use), logarithmic model (the relationship between course evaluation system and usefulness), and s-curve models (learner-interface interactivity, navigation, and course structure and content and usefulness) performed better in the description for the correlations.
Citation Count: 0
FLOW STRUCTURE IN A MIXING LAYER DEVELOPING OVER FLAT BED AT HIGH REYNOLDS NUMBERS
(Iahr-int Assoc Hydro-environment Engineering Research, 2015) Kirkil, Gökhan
Results of a high resolution Detached Eddy Simulation (DES) are used to characterize the evolution of a shallow mixing layer developing between two parallel streams in a long open channel with a flat bed at a high Reynolds number (ReD= 160,000). The influence of Reynolds number on the development of the mixing layer as well as the vertical nonuniformity in the mixing layer structure is discussed. The numerical results show that as Reynolds number increases, the mixing layer development ceases earlier. Mixing layer growth rate and its change in the vertical direction at ReD= 160,000 are compared with experiments and a simulation at ReD= 16,000. Passive scalar is introduced at the tip of the splitter plate close to the free surface to estimate the size of the mixing structures based on mass transport. The effect of the Reynolds number on the shift of the centerline of the mixing layer is quantified.
Citation Count: 9
Students' Web-Based Activities Moderate the Effect of Human-Computer-Interaction Factors on Their E-Learning Acceptance and Success During COVID-19 Pandemic
(Taylor & Francis Inc, 2022) Kirkil, Gökhan; Kirkil, Gokhan
The purpose of this study is to investigate if students' activities on systems web-based moderate the effect of human-computer interaction (HCI) factors on ease of use and usefulness of e-learning and their success (SS) at the time of the COVID-19 pandemic. To answer the questions that addressed the relationship between HCI, e-learning acceptance, and SS, the researcher surveyed 103 students from Kadir Has University whose grade and activity logs were accessible. The survey was related to their perceived course webpage design, system and content quality, interactivity, usability and functionality, and self-assessment. The results show that most of the hypotheses of this study have been proven, a comprehensive conceptual model was developed, and the student grades in the online courses improved their GPA. The findings further reveal that students' activities moderate the effects of course environment and content quality on perceived usefulness and the effect of the course evaluation' system on perceived ease of use, where the changes in R-2 ranged between 0.041 and 0.074. That means including logs as a moderator would increase the explanatory power of the effect of HCI factors on e-learning acceptance which together explained 54.9% of the variance in perceived success (SS), where U is the strongest determinant of SS.
Citation Count: 0
Superior Conductivity of Transparent ZnO/MoS₂ Composite Films for Optoelectronic and Solar Cell Applications
(Mdpi, 2023) Kirkil, Gökhan; Kirkil, Gokhan; OEzugur Uysal, Bengue
The use of transparent conductive oxides in optoelectronics created a revolution where new-generation materials with high transmittance, low sheet resistance values, durability, and portability can be achieved without decreasing efficiency or increasing costs. Transparent ZnO/MoS2 sandwich-structured conductive composite films were produced in this study via the sol-gel method, which is considered the most efficient method due to its simple process and low cost. The crystal structure properties of ZnO/MoS2 were characterized via X-ray diffraction (XRD) patterns. The crystal sizes of ZnO films doped with different amounts of MoS2 were determined. A UV-visible absorption spectrometer was used to perform the spectroscopic analysis of the film. The area under the absorption curve and the full width of the half-maxima of absorbance data were calculated. Using these values, the optimum amount of MoS2 was determined for the best additive distribution. In addition, in order to determine the best transparent conductive material, resistance values measured via the four-point probe method were compared for different MoS2 additive amounts. The optical and electrical characterizations of transparent ZnO/MoS2 conductive oxide films were investigated. According to the parameters obtained via UV-vis spectroscopy, XRD, and four-point probe measurements, the most effective dispersion that exhibits a low width ratio and high resonance ratio was found for ZnO/MoS2 with a doping amount of 4 mg, the crystallite size of the films was found to be within the range of 21.5 and 24.6 nm, and these observations demonstrated a figure-of-merit value of more than 4.8 x 10(-2) with respect to these sandwich-structured films. Compared to the values of previous studies on various transparent ZnO-doped conductive oxide materials, it is possible to claim that these new films have a structure that is very similar to the transparent conductivity characteristics of other films, and they may even be superior relative to some MoS2 amounts.