WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Citation - WoS: 37Citation - Scopus: 35Performance Prediction and Adaptation for Database Management System Workload Using Case-Based Reasoning Approach(Pergamon-Elsevier Science Ltd, 2018-07) Raza, Basit; Kumar, Yogan Jaya; Malik, Ahmad Kamran; Anjum, Adeel; Faheem, MuhammadWorkload management in a Database Management System (DBMS) has become difficult and challenging because of workload complexity and heterogeneity. During and after execution of the workload, it is hard to control and handle the workload. Before executing the workload, predicting its performance can help us in workload management. By knowing the type of workload in advance, we can predict its performance in an adaptive way that will enable us to monitor and control the workload, which ultimately leads to performance tuning of the DBMS. This study proposes a predictive and adaptive framework named as the Autonomic Workload Performance Prediction (AWPP) framework. The proposed AWPP framework predicts and adapts the DBMS workload performance on the basis of information available in advance before executing the workload. The Case-Based Reasoning (CBR) approach is used to solve the workload management problem. The proposed CBR approach is compared with other machine learning techniques. To validate the AWPP framework, a number of benchmark workloads of the Decision Support System (DSS) and the Online Transaction Processing (OLTP) are executed on the MySQL DBMS. For preparation of training and testing data, we executed more than 1000 TPC-H and TPC-C like workloads on a standard data set. The results show that our proposed AWPP framework through CBR modeling performs better in predicting and adapting the DBMS workload. DBMSs algorithms can be optimized for this prediction and workload can be controlled and managed in a better way. In the end, the results are validated by performing post-hoc tests. (C) 2018 Elsevier Ltd. All rights reserved.Article Citation - WoS: 15Citation - Scopus: 17Investigation of the Performance and Properties of ZnO/GO Double-Layer Supercapacitor(Pergamon-Elsevier Science Ltd, 2024-08) Buyukkurkcu, Handan; Durmus, Ali; Colak, Hakan; Kurban, Rifat; Sahmetlioglu, Ertugrul; Karakose, ErcanComposite electrode material was formed by mixing reduced graphene oxide (rGO) and zinc oxide (ZnO) compound, using the Hummers and green synthesis methods, respectively. Of rGO powder, 10 g was mixed with 10%, 20% and 30% ZnO, and composite electrodes were obtained by using 10% binder. The energy storage performance and structural characteristics of the supercapacitor were evaluated by analyzing the capacitance values of the synthesized electrodes. The structural characterization of ZnO/rGO composites was performed using X-ray diffraction and field-emission scanning electron microscopy. The electrochemical properties of the ZnO/GO electrodes were analyzed by cyclic voltammetry, electrochemical impedance and galvanostatic charge -discharge tests. The specific capacitance value of electrodes increased as zinc content increased in the ZnO/ rGO composite material used to produce electrodes. The maximum specific capacitance values were measured at 5 mV/s scanning rate as 194.23 (rGO), 366.81 (10% ZnO), 383.18 (20% ZnO) and 410.48 F/g (30% ZnO). In conclusion, the use of composite material formed by the combination of ZnO nanoparticles obtained by green synthesis method from orange peel and graphene oxide increased the electrochemical efficiency of the supercapacitor.Article Citation - WoS: 14Citation - Scopus: 14Experimental Studies on the Physico-Mechanical Properties of Jet-Grout Columns in Sandy and Silty Soils(Pergamon-Elsevier Science Ltd, 2016-04) Akin, Muge K.The term of ground improvement states to the modification of the engineering properties of soils. Jet grouting is one of the grouting methods among various ground improvement techniques. During jet grouting, different textures of columns can be obtained depending on the characteristics of surrounding subsoil as well as the adopted jet-grouting system for each site is variable. In addition to textural properties, strength and index parameters of jet-grout columns are highly affected by the adjacent soil. In this study, the physical and mechanical properties of jet-grout columns constructed at two different sites in silty and sandy soil conditions were determined by laboratory tests. A number of statistical relationships between physical and mechanical properties of soilcrete were established in this study in order to investigate the dependency of numerous variables. The relationship between q(u) and gamma(d) is more reliable for sandy soilcrete than that of silty columns considering the determination coefficients. Positive linear relationships between Vp and gamma(d) with significantly high determination coefficients were obtained for the jet-grout columns in silt and sand. The regression analyses indicate that the P-wave velocity is a very dominant parameter for the estimation of physical and mechanical properties of jet-grout columns and should be involved during the quality control of soilcrete material despite the intensive use of uniaxial compressive strength test. Besides, it is concluded that the dry unit weight of jet-grout column is a good indicator of the efficiency of employed operational parameters during jet-grouting. (C) 2016 Elsevier Ltd. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1Amorphous Zircon at High Pressure(Pergamon-Elsevier Science Ltd, 2021-06) Bolat, Suleyman; Durandurdu, MuratThe high-pressure behavior of a very low-density amorphous zircon model having Zr (Si) coordination of 5.6 (4.02) is explored by ab initio simulations. Two consecutive pressure-induced phase modifications are proposed for this material. The first transition is from a very low-density amorphous state to a dense amorphous state having Zr (Si) coordination of 7.3 (4.5). The second one is from the dense phase to a high-density amorphous structure with Zr and Si coordination numbers of about 8 and 5.5, correspondingly. Both phase changes proceed progressively. The first phase transformation is irreversible whist the second one is reversible. The Voronoi polyhedron analysis reveals the presence of polyhedron of the zircon crystal (<0,4,4,0>), the zirconia baddaliyette phase (<1,3,3,0>) and the zirconia cotunnite state (<0,3,6,0>) around Zr atoms in the amorphous states formed on both compression and decompression, meaning that the amorphous configurations consist of a mixed state of them.Article Citation - WoS: 62Citation - Scopus: 63A Novel Method for the Site Selection of Large-Scale PV Farms by Using AHP and GIS: A Case Study in Izmir, Turkiye(Pergamon-Elsevier Science Ltd, 2023-07) Demir, Abdullah; Dincer, Ali Ersin; Yilmaz, KutayEffective and sustainable climate-friendly policies to reduce carbon dioxide emissions in line with the 2020 European Green Deal are necessary. Accordingly, renewable energies assumed a critical role, rendering the site selection of these systems very crucial. The present study proposes a novel approach to the site selection of large-scale photovoltaic (PV) plants using a combination of analytic hierarchy process (AHP) and geographic infor-mation system (GIS). In the study, the weights of criteria used for selecting solar PV panels are adjusted according to the installed capacity of the PV plant. The land of cost is included as a criterion in the AHP for the first time in PV plant site selection. Besides, a novel method called optimality-based site growing (OBSG) is introduced to further analyze the suitable sites obtained from GIS simulations and to determine the most suitable locations of PV farms. The proposed method is demonstrated with a case study of Turkiye, and the results show that the method effectively determines the most suitable locations for large-scale PV plants.Article Citation - WoS: 37Citation - Scopus: 36Flexible Electrodes Composed of Flower-Like MoS2 and MXene for Supercapacitor Applications(Pergamon-Elsevier Science Ltd, 2024) Hayat, Hilal Pecenek; Dokan, Fatma Kilic; Onses, M. Serdar; Yilmaz, Erkan; Duran, Ali; Sahmetlioglu, ErtugrulFlexible supercapacitors with high charge storage ability are needed for emerging applications in wearable electronics. Here, we introduce a novel flexible supercapacitor electrode by incorporating flower-like MoS2 into MXene via a hydrothermal technique. We mostly focused on the structural design for electrode configuration to enhance the charge storage mechanism. Three different electrodes composed of MoS2, MXene, and MoS2@MXene were fabricated via a versatile drop-casting and drying method. There are unique advantages of incorporating MoS2 with MXene such as the fast electron transfer, hydrophilicity of the interface, and structural stability. The MoS2@MXene // MXene flexible asymmetric supercapacitor device offered a high energy density of 1.21 W h /kg and a power density of 54.45 W /kg. Moreover, the asymmetric device exhibits nearly identical electrochemical behavior following 100 bending cycles at different angles. The high electrochemical activity of MoS2 and MXene and good interaction are ascribed to the superior electrochemical performance of the composite material. Furthermore, this research could guide the development of flexible, high-performance, and low-cost electrodes which will be useful in wearable electronics.