Browsing by Author "Gür, M"

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    Machine Learning for Pedestrian-Level Wind Comfort Analysis
    Gür, M; Karadag, I
    (1) Background: Artificial intelligence (AI) and machine learning (ML) techniques are being more widely employed in the field of wind engineering. Nevertheless, there is a scarcity of research on the comfort of pedestrians in terms of wind conditions with respect to building design, particularly in historic sites. (2) Objectives: This research aims to evaluate ML- and computational fluid dynamics (CFD)-based pedestrian wind comfort (PWC) analysis outputs using a novel method that relies on the sophisticated handling of image data. The goal is to propose a novel assessment method to enhance the efficiency of AI models over different urban scenarios. (3) Methodology: The stages include the analysis of climate data, CFD analysis with OpenFOAM, ML analysis using Autodesk Forma, and comparisons of the CFD and ML results using a novel image similarity assessment method based on the SSIM, MSE, and PSNR metrics. (4) Conclusions: This study effectively demonstrates the considerable potential of utilizing ML as a supplementary tool for evaluating PWC. It maintains a high degree of accuracy and precision, allowing for rapid and effective assessments. The methodology for precise comparison of two visual outputs in the absence of numerical data allows for more objective and pertinent comparisons, as it eliminates any potential distortions. (5) Recommendations: Additional research can explore the integration of ML models with climate data and different case studies, thus expanding the scope of wind comfort studies.
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    Effect of valproic acid treatment on penile structure in prepubertal rats
    Kutlu, Ö; Cansu, A; Karagüzel, E; Gürgen, SG; Koç, Ö; Gür, M; Özgür, GK
    Introduction: The aim of this study was to determine the histological effects of valproic acid (VPA) on the penis in prepubertal rats. Methods: Twelve male Wistar rats (21-24 days old) were divided equally into 2 experimental groups, and given tap water (control group) or 300 mg/kg/day VPA via gavage for 30 days. After the penes had been harvested, the antiangiogenic and antifibrogenic properties of VPA were evaluated immunohistochemically using vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), transforming growth factor-beta 1 (TGF-beta 1) and Masson's trichrome staining. Apoptosis was determined by caspase-3 and caspase-9 immunoreactions. Results were expressed as histochemical score (HSCORE), a semi-quantitative analysis for the intensity of immunohistochemical reactivity. Results: Immunohistochemical HSCORE decreased for VEGF and TGF-beta 1 staining and increased for iNOS staining in rats treated with VPA compared with the control group. Intensities of caspase-3 and caspase-9 labeling were also significantly increased by administration of VPA. Masson's trichrome staining exhibited a fairly diminished level of collagen in the corpus cavernosum of rats treated with VPA. Conclusion: In the light of these results, the administration of VPA from prepuberty to adulthood led to increased apoptosis and deterioration of the smooth muscle/collagen ratio in rat's corpus cavernosum. (C) 2011 Elsevier B.V. All rights reserved.
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    Effects of Inclined Plate in a Channel to Control Melting of PCM in a Body Inserted on the Bottom Wall
    Öztop, HF; Bakir, E; Selimefendigil, F; Gür, M; Cosanay, H
    A two-dimensional time-dependent computational analysis was carried out to examine the effects of inclined plate on melting time of Phase Change Material (PCM) filled square block on the bottom wall of a channel. Solution of the governing equations are performed by using finite volume method. The RT25HC material is chosen as PCM. The study is done for different parameters of inclination angle of the plate and Reynolds number. It is observed that the inclined plate can be used to control of melting time of PCM in a block as well as flow field and temperature distribution in the channel. Using of acceleration angle as theta=110 degrees accelerates the melting time of PCM inside the block. Thus, mass fraction rate increases 4 times with application of inclined thin plate.
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    Analysis of solar underfloor heating system assisted with nano enhanced phase change material for nearly zero energy buildings approach
    Gür, M; Öztop, HF; Selimefendigil, F
    This study focuses on the design of a solar-assisted underfloor heating system specifically tailored for nearly zeroenergy buildings. The system incorporates a Photovoltaic/Thermal (PV/T) collector as the primary heat source. The analysis takes into account the geographical coordinates of Elazig province in Turkey, and the boundary conditions are carefully chosen as the inlet parameters in the program. To enhance the system's performance, Nano-enhanced Phase Change Material (PCM) is utilized by filling pockets around the underfloor heating pipe with varying thicknesses. Cu nanoparticles of 1% solid volume fraction is considered. The fundamental objective of this approach is to achieve room temperature without any additional energy consumption during nighttime periods when solar radiation is unavailable. To investigate the impact of the system, copper nanoparticles are introduced to the PCM, and their effects on room temperature are numerically analyzed using the finite volume method under turbulent flow conditions. Realistic building conditions are considered, and a container is selected as the scenario building for simulations. The results reveal that the best room temperature conditions are obtained with pure PCM of width k (Case 1), pure PCM of width k/2 (Case 3), PCM with nanoparticle added of width k/2 (Case 3), and no PCM (Case 4), respectively. The highest temperature difference of 4 K is obtained between the configurations of Case 1 and Case 4 which shows the favorable impacts of using PCM. However, between the cases of using nano-PCM and PCM, room temperature difference of 0.1 K is obtained which indicates the very slight improvement of using nano-powders in PCM for this energy system. These findings provide valuable insights into the design and optimization of solar-assisted underfloor heating systems for nearly zeroenergy buildings, offering the potential to improve energy efficiency and thermal comfort.
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    Impacts of inclined plate on melting time for phase change material filled blocks: Experimental and numerical analysis
    Öztop, HF; Gür, M; Selimefendigil, F; Cosanay, H
    This study investigates the impact of inclined plates on the melting time of phase change material (PCM)-filled blocks in a channel under turbulent airflow, considering different velocities. The primary objective is to analyse how inclined plates influence the melting process and the time required for complete melting of PCM blocks. Both experimental and numerical approaches are employed using the finite volume method to solve two dimensional time-dependent governing equations. The Reynolds numbers are varied at 40000, 50000, and 60000, while the inclination angle of the plate ranges from alpha = 110 degrees to 130 degrees. RT25HC is selected as the PCM. The findings reveal that inclined plates effectively regulate PCM cube melting times within a block, influencing the flow field and temperature distribution in the channel. Notably, both experimental and numerical results consistently highlight the alpha = 110 degrees inclination angle as the most effective among the considered angles.
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    Analysis of melting of phase change material inserted a block via impinging turbulent slot jet
    Oztop, HF; Gür, M; Selimefendigil, F; Cosanay, H
    PurposeThe purpose of this study is to do a numerical analysis of the jet to a body filled with phase change material (PCM). The melting of the PCM filled body was investigated by the hot jet flow. Four different values of the Reynolds number were taken, ranging from 5 x 103 = Re = 12.5 103. Water, Al2O3 1%, Al2O3 2% and hybrid nanofluid (HNF; Al2O3-Ag mixture) were used as fluid types and the effects of fluid type on melting were investigated. At 60 & DEG;C, the jet stream was impinged on the PCM filled body at different Reynolds numbers. Design/methodology/approachTwo-dimensional analysis of melting of PCM inserted A block via impinging turbulent slot jet is numerically studied. Governing equations for turbulent flow are solved by using the finite element method via analysis and system fluent R2020. FindingsThe obtained results showed that the best melting occurred when the Reynolds number increased and the HNF was used. However, the impacts of using alumina-water nanofluid were slight. At Re = 12,500, phase completion time was reduced by about 13.77% when HNF was used while this was only 3.93% with water + alumina nanofluid as compared to using only water at Re = 5,000. In future studies, HNF concentrations will change the type of nanoenhanced PCMs. In addition, the geometry and jet parameters of the PCM-filled cube can be changed. Originality/valueEffects of impinging jet onto PCM filled block and control of melting via impinging hot jet of PCM. Thus, novelty of the work is to control of melting in a block by impinging hot jet and nanoparticles.