WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collections
Permanent URI for this collectionhttps://hdl.handle.net/20.500.13091/2
Browse
228 results
Search Results
Conference Object Citation - WoS: 1Performance Evaluation of NOMA-Based Cooperative Communications over Cascaded Rician Fading Channels(IEEE, 2019-04-01) Ozdemir, OzgurThe necessity of the retransmissions of the source signal from the relay terminals restricts the spectral efficiency of the wireless cooperative communications systems. It has been shown that cooperative communications systems using non-orthogonal multiple access (NOMA) technique can prevent these capacity decreases and constitutes an ideal physical layer solution for inter-vehicular communication systems which is an important future 5G applications. In this study, the performance of NOMA based cooperative communications is investigated over the cascaded Rician fading channels since theoretical and experimental studies have shown that cascaded channel structure supplies more realistic statistical model for mobile network models such as inter-vehicular communication systems. The achievable average rate provided by cooperative communication systems using NOMA is found by computer simulations. The obtained results for cascaded Rician fading channels have shown that the capacity is decreased as the cascading degree increases.Conference Object Citation - WoS: 2Modelling and Voltage Control of the Solar-Wind Hybrid Micro-Grid with Optimized STATCOM(IEEE, 2019-06-01) Kulaksiz, Ahmet Afsin; Bakir, HaleElectricity generation from the wind and solar photovoltaic (PV) systems are highly dependent upon weather conditions. Their intermittent nature leads to fluctuations in their output. Therefore, the need for rapid compensation for energy transmission and distribution systems is increasingly important. Static Synchronous Compensator (STATCOM) can be adopted for reactive power compensation and for decreasing the voltage fluctuation caused by the system and renewable energy sources. This study presents modelling of a Solar PV-Wind Hybrid Micro-grid and the increase of the stable operating limit of the system in case of the incorporation of STATCOM is examined. The major contribution of this paper is the optimization of gain parameters of four PI controllers in STATCOM based on genetic algorithms (GA) and therefore obtaining better responses and voltage stability in terms of nonlinear nature of solar-wind hybrid micro-grid. The Simulink models of the system architecture include a 2 MW wind turbine model based on a doubly fed induction generator (DFIG), 0.4 MW solar PV power system model and a STATCOM rated at 3 MVAR. It is certified that the voltage fluctuation at the end of the bus bar is reduced by 8 % using conventional PI controller. The results obtained by GA-based optimization of PI controllers are compared with that of the conventional controller and better results attained.Conference Object Citation - WoS: 20Comparison of Traditional Transformations for Data Augmentation in Deep Learning of Medical Thermography(IEEE, 2019) Ornek, Ahmet Haydar; Ceylan, MuratConvolutional neural networks (CNN) models demonstrate high performance in image-based applications such as image classification, segmentation, noise reduction and object recognition. However, balanced and sufficient data are required to effectively train a CNN model but this is not always possible. Since conditions of both hospitals and patients are not always appropriate for collecting data and patients with the same disease are not always available, the problem of collecting balanced and sufficient data are often occurred in medical fields. In this study, comparison of traditional data augmentation methods such as rotating, mirroring, zooming, shearing, histogram equalization, color changing, sharpening, blurring, brightness enhancement and contrast changing were performed by using neonatal thermal images. These images belonged to 19 unhealthy and 19 healthy neonates were obtained from Selcuk University, Faculty of Medicine, Neonatal Intensive Care Unit. A combination of three different augmentation methods were implemented to original images in each one of the 10 different comparisons accomplished and CNN was used to classify the these comparisons in the study. When contrast changing, sharpening and blurring methods were used, increased the sensitivity rate by 23.49%, the specificity rate by 29.09% and the accuracy rate by 26.29%. The obtained results show that simple and low-cost traditional data enhancement methods can improve the performance of classification.Article Citation - WoS: 1Thinking With Universal Design in Historical Environment(Selcuk Univ, 2018-08-31) Tutal, Osman; Topçu, MehmetHistorical environment is a unique and irreplaceable resource which reflects the social, cultural and economic characteristics of the past societies (Donely, 2011). It is an integral part of local, regional and national cultural idendity. The environment especially consists of historical environment and buildings are significant because of their uses as place where people’s daily life activities. Moreover, meeting of social and cultural assets which societies have been figuring from the past with daily life turns into a resource for a sustainable future. However, it is generally impossible that those buildings which have been constructed in their own terms can satisfy the needs of today. In Turkey where the balance of protecting-using is on behalf of the first one, the protection policies and protection regulations exceedingly limit the intervention to the natural environments. Wishing that historical buildings are actualized into daily life on one hand and clamping down on accessing, visiting and using those buildings on the other hand leads to a serious discrepancy. However, the prominent examples which oversee the balance of protecting-using show that historical environments can be intervened through designing which will create or add values without compromising on protection. All sorts of interventions to be conducted consider the potential needs of the users without giving any harms to the originality of the building. Thus, it is expected that everyone can access the buildup area including the historical buildings, products and services and information equally and under equitable conditions. For that reason, making the built-upenvironment accessible, visitable and usable through universal design is one of the fundamental rights for the people who expand their daily living environment through accessibility and universal design. In this study, accessibility, visitability and usability of Bedesten Historical Site in the city of Konya are discussed through the theme of “Thinking through Universal design” and suggestions of designing are given in various scales (urban scale, street scale and building scale).Article Transient Heat Transfer in Pipes With Time Periodically Changing Boundary Condition(Turk Isı Bilimi ve Teknigi Dernegi, 2018) Altun, A.H.; Ateş, A.; Atmaca, Şükrü Ulaş; Koçak, Sedat; Bilir, Şefik; Atmaca, UlasTransient heat transfer in thermal entrance region of pipes with time periodically changing surface temperature is investigated. The problem is handled in a two-regional pipe for laminar, hydrodynamically developed flow by involving fluid axial conduction. The solution is made numerically by a finite-difference method. A parametric study is done to analyse the effects of Peclet number and angular frequency on heat transfer characteristics. The results show that, considerable amount of heat is diffused back towards the upstream region by axial fluid conduction, which causes preheating the fluid prior to the heated downstream region. The heat transfer characteristics, in all axial positions, including the preheated upstream and the fully developed region, are seen to change periodically in time, similar to the periodic change of the surface temperature in the downstream region. ©2018 TIBTD Printed in Turkey.Article Citation - WoS: 123Citation - Scopus: 144Point Cloud Filtering on Uav Based Point Cloud(ELSEVIER SCI LTD, 2019-02-01) Zeybek, Mustafa; Şanlıoğlu, İsmailNowadays, Unmanned Aerial Vehicles (UAVs) have been attracted wide attentions such as a new measurement equipment and mapping, which are capable of the high-resolution point cloud data collection. In addition, a massive point cloud data has brought about the data filtering and irregular data organization for the generation of digital terrain models. Filtering of point clouds contains vegetations and artificial objects play a crucial role for bare earth terrain modelling. Topographical maps rely on the data structures which are built on bare ground terrain points. The bare earth surface extraction is not the only crucial to the topographical maps but also decision-making processes such as natural hazards management, deformation analysis and interpretation. In order to filter a UAV-based 3D raw point cloud data, in this paper, filtering performance of four different algorithms using open source and commercial software's have been investigated, (1) curvature based (Multiscale Curvature Classification-MCC), (2) surface-based filtering (FUSION), (3) progressive TIN based (LasTool-LasGround module-commercial) and (4) physical simulation processing (Cloth Simulation Filtering-CSF). The applied filtering results were validated with the reference data set classified by operator. Although different filtering methodologies implemented on point clouds, these methods demonstrated similar results to extract ground on distinctive terrain feature such as dense vegetated, flat surface, rough and complex landscapes. The filtering algorithms' results revealed that UAV-generated data suitable for extraction of bare earth surface feature on the different type of a terrain. Accuracy of the filtered point cloud reached the 93% true classification on flat surfaces from CSF filtering method. (C) 2018 Elsevier Ltd. All rights reserved.Article Citation - WoS: 28Citation - Scopus: 29Separation of Formic Acid From Aqueous Solutions Onto Anion Exchange Resins: Equilibrium, Kinetic, and Thermodynamic Data(AMER CHEMICAL SOC, 2019-05-29) Zeidan, Hani; Martı, Mustafa EsenWastewaters containing organic compounds such as acids, ketones, phenols, and amines can cause critical environmental problems depending on their concentration and composition. Efficient and low-cost separation of these components may also bring their reuse in industry while cleaning the aqueous streams. Formic acid (FA) is an important raw material in industry and is widely seen in wastewaters. In this study, two different anion exchangers were compared for the separation of FA from aqueous solutions. Effects of process parameters and the mechanism were discussed. Kinetic, equilibrium, and thermodynamic studies were performed, and the data were interpreted using the relevant isotherm and kinetic models. The results showed that Lewatit MP-64 was more efficient than Amberlite IRA-96 in the range of the parameters studied. The maximum adsorption capacity obtained with Lewatit MP-64 (442.75 mg/g) was significantly higher than that were previously reported in the literature for FA separation. The data were well explained by the Langmuir isotherm model. However, relatively high R-2 values were obtained with Temkin and Freundlich isotherms. Therefore, further studies are ongoing to clarify the mechanism.Article Citation - WoS: 5Citation - Scopus: 5Experimental Investigation of Retrofitted Shear Walls Reinforced With Welded Wire Mesh Fabric(TECHNO-PRESS, 2019) Yüksel, S. BahadırThe aim of the present paper is to present the cyclic behavior of strengthened reinforced concrete shear wall test specimen, which was reinforced with cold drawn welded wire mesh fabric. Two reinforced concrete shear wall specimens have been tested in the present study. The walls were tested under reversed cyclic loading with loading applied near the tip of the walls. The control wall is tested in its original state to serve as a baseline for the evaluation of the repair and strengthening techniques. The two test specimens include a control wall and a repaired wall. The control wall test specimen was designed and detailed to simulate non-ductile reinforced concrete shear walls that do not meet the modern seismic provisions. The response of the original wall was associated with the brittle failure. The control shear wall was repaired by addition of the reinforcements and the concrete and then it was reloaded. The effectiveness of the repair technique was investigated. Test results indicate that there can be a near full restoration of the walls' strength. The data from this test, augmenting other data available in the literature, will be useful in calibrating improved analytical methods as they are developed.Article Citation - WoS: 28Citation - Scopus: 25Initiated Chemical Vapor Deposition of Poly(ethylhexyl Acrylate) Films in a Large-Scale Batch Reactor(AMER CHEMICAL SOC, 2019) Yılmaz, Kurtuluş; Şakalak, Hüseyin; Gürsoy, Mehmet; Karaman, MustafaThe present study demonstrates the successful deposition of poly(ethylhexyl acrylate) thin films in a large-scale closed-batch initiated chemical vapor deposition (iCVD) system. A horizontal cylindrical stainless-steel vacuum tank, which is highly utilized in industrial vacuum applications, was used as iCVD reactor. The effects of substrate temperature, precursor ratio, and pressure on the deposition rates were studied, and the results showed that a deposition rate of 315 nm/min can be achieved in a single run at a reactor pressure of 600 mTorr. At a lower chamber pressure of 400 mTorr, deposition rate decreases, whereas film uniformity increases. By carrying out depositions at successive cycles, thicker films could be obtained, without the need for extensive monomer consumption. The yield percentage was found to be 3.5 for the films deposited in closed-batch system at 400 mTorr, which is 35-fold larger than that of the classical iCVD flow system.Article Citation - WoS: 14Citation - Scopus: 20Removal of Methylene Blue Dye From Aqueous Solution by Semi-Interpenetrating Polymer Network Hybrid Hydrogel: Optimization Through Taguchi Method(WILEY, 2019-03-19) Yılmaz, Elif; Kaya Güzel, Gülcihan; Deveci, Hüseyin; Kaya, Gulcihan GuzelIn this study, sodium humate/poly(acrylamide-co-methacrylic acid)/kaolin semi-interpenetrating polymer network hybrid hydrogel was synthesized as an effective adsorbent for the removal of methylene blue. The morphological and structural properties, and swelling behavior in distilled water and various environments of hybrid hydrogel were investigated with different analyses and tests. The equilibrium swelling percent of hybrid hydrogel reached to 37,000% in 240min. The parameters (agitation time, concentration, dose, temperature, and pH) affecting adsorption process for methylene blue were optimized using Taguchi method. The data obtained in optimum conditions were well fitted to Langmuir adsorption isotherm and maximum adsorption capacity was determined as 833. 33mg/g. In the light of the results, the utilization of hybrid hydrogel with high swelling capacity is foreseen as a favored adsorbent in several separation processes. (c) 2019 Wiley Periodicals, Inc.