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Citation - WoS: 16
Citation - Scopus: 21
A Decision Theoretic Framework for Reliability-Based Optimal Wind Turbine Selection
(Elsevier Sci Ltd, 2022) Eryilmaz, Serkan; Navarro, Jorge
The problem of choosing the optimal wind turbine for a specific site is of special importance in the design process of wind farm. Manifestly, the selection of the optimal wind turbine should depend on a certain criteria. In this paper, optimal wind turbine selection is studied in terms of the capacity factor of wind turbine generator and the Expected Energy not Supplied which is one of the most commonly used reliability indices for power systems. The latter one considers the load profile of the system and is suitable to compare different wind farm compositions while the former one completely ignores the load profile of the system. This paper presents general theoretical results that are helpful to compare performance of wind turbines and wind farms without data collection and further numerical assessment. In particular, the conditions on wind turbine characteristics and availability values of wind turbines are determined to compare wind turbines and wind farms in terms of the capacity factor and Expected Energy not Supplied.
Citation - WoS: 8
Citation - Scopus: 10
Structural, Electrical and Dielectric Properties of Bi_1.5zn_{0.92< Pyrochlore Ceramics}
(Elsevier Sci Ltd, 2012) Qasrawi, A. F.; Mergen, A.
The micro-structural, compositional, temperature dependent dielectric and electrical properties of the Bi1.5Zn0.92Nb1.5-xTaxO6.92 solid solution has been investigated. The increasing Ta content from 0.2 to 1.5 caused; single phase formation, a pronounced grain size reduction from similar to 7.0 to 2.5 mu m, sharp decrease in the dielectric constant from 198 to 88 and an increase in the electrical conductivity from 3.16 x 10(-10) to 5.0 x 10(-9) (Omega cm)(-1), respectively. The temperature dependent dielectric constant which is found to be frequency invariant in the frequency range of (0.0-2.0 MHz) exhibited a sharp change in the temperature coefficient of dielectric constant at a (doping independent) critical temperature of 395 K. The analysis of the measured data reflects a promising future for this type of pyrochlore to be used in high voltage passive device applications. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Citation - WoS: 35
Citation - Scopus: 43
Reliability Analysis of Multi-State System With Three-State Components and Its Application To Wind Energy
(Elsevier Sci Ltd, 2018) Eryilmaz, Serkan
In most real life situations, the system's components contribute differently in different performance levels. Such a situation can be modeled by systems with multi-state components having more than one working status, e.g. perfect functioning, and partial working. In this paper, a multi-state system that consists of two types of three-state components is defined and studied. An explicit formula for the probability that the performance of the system is at least a given level is obtained for the most general case when the components are statistically dependent. The model is applied to evaluate the wind power system that consists of two wind plants in different regions. An optimization problem is formulated to find the optimal number of wind turbines that must be installed in the wind plants by minimizing the total cost under specific power production. (C) 2017 Elsevier Ltd. All rights reserved.
Citation - WoS: 10
Citation - Scopus: 10
Determination of Mechanical Properties of Bi₁₂tio_{20< Crystals by Nanoindentation}
(Elsevier Sci Ltd, 2022) Isik, M.; Gasanly, N. M.; Rustamov, F. A.
Bi12TiO20 (BTO) single crystal was grown by Czochralski method and investigated mechanically by nano-indentation measurements. X-ray diffraction pattern of the crystal presented one intensive peak around 37.95 degrees associated with (330) plane of cubic crystalline structure. Nanoindentation experiments were performed at various loads between 5 and 100 mN. Hardness and Young's modulus of the crystal were determined by Oliver-Pharr method. The hardness-load dependency exhibited behavior of indentation size effect. True hardness value of BTO crystal was revealed as 4.4 GPa. Young's modulus decreased with increase of load and load-independent Young's modulus was found around 93 GPa at high loads. The load-dependent elastic and plastic deformation components were calculated and it was observed that the dominant component in BTO single crystal is plastic deformation at the applied loads. The present paper reports for the first time the mechanical characteristics of the BTO single crystal by carrying out nanoindentation experiments.
Citation - WoS: 43
Citation - Scopus: 45
Enhancing Machining Efficiency of Ti-6al Through Multi-Axial Ultrasonic Vibration-Assisted Machining and Hybrid Nanofluid Minimum Quantity Lubrication
(Elsevier Sci Ltd, 2024) Namlu, Ramazan Hakki; Lotfi, Bahram; Kilic, S. Engin
Ti-6Al-4V offers a balance of good strength with lightweight properties. Yet, Ti-6Al-4V poses machining challenges, including low thermal conductivity, chemical adhesion to cutting tools, and chip removal difficulties. To improve machining efficiency, Ultrasonic Vibration-Assisted Machining (UVAM) has emerged as a promising approach. UVAM has demonstrated reduced tool wear, cutting forces, and improved surface quality compared to Conventional Machining (CM). Additionally, Minimum Quantity Lubrication (MQL) methods offer sustainable coolant alternatives, with recent research focusing on Nanofluid-MQL (NMQL) and Hybrid Nanofluid-MQL (HNMQL) for enhanced performance. Although there exists a body of literature showcasing the promising effects of UVAM and MQL methods individually, comprehensive investigations into the synergistic effects of these methodologies remain limited. This study addresses these critical research gaps by conducting a systematic examination of combined application of multi-axial UVAM and HNMQL. Specifically, it delves into the comparison of different vibration directions within UVAM, evaluates the effectiveness of UVAM when combined with cutting fluids incorporating Al2O3 and CuO nanoparticles in NMQLs and HNMQLs, and contrasts these novel approaches with conventional machining methods. The study unfolds in three distinct stages. The first stage examines the ultrasonic cutting mechanism and its combined application with the MQL technique. In the second stage, the study investigates the physical properties of the cutting fluids, including contact angle and surface tension. The final stage encompasses slot milling operations, where an array of parameters such as cutting forces, surface roughness, surface topography, surface texture, and the occurrence of burr formations are rigorously analyzed. The results demonstrate that the combination of multi-axial UVAM with HNMQL yields substantial advantages over traditional machining methods. Notably, it leads to a remarkable reduction in cutting forces (up to 37.6 %) and surface roughness (up to 37.4 %). Additionally, this combination engenders the production of highly homogeneous and uniform surface textures, characterized by minimal surface defects and a significantly diminished occurrence of burr formations. These findings underscore the potential of multi-axial UVAM combined with HNMQL as a promising approach in enhancing the machining of Ti-6Al-4V, thus offering a pathway to enhance the efficiency and precision of aerospace component manufacturing processes.
Citation - WoS: 1
Citation - Scopus: 1
Culinary Acculturation Assessment Inventory (caai): Construction and Validation in First Generation Immigrant Consumers in Turkey
(Elsevier Sci Ltd, 2021) Kalyoncu, Z. Begum; Demir, Ahmet U.; Ayaz, Aylin
The effect of immigration upon immigrants' choice of food should be captured not only with dietary intake, but also through assessing culturally-based culinary exposures. This approach would advance dietary acculturation research towards culinary acculturation. For this purpose, Culinary Acculturation Assessment Inventory (CAAI) is developed, using visual items. Validity and reliability of CAAI relating to the Turkish Cuisine were determined in a group of first-generation immigrants. Recommended scale development methods were employed. The initial version, including 40 items across two domains of dietary intake and culinary exposures was administered to 256 participants (162 immigrants from 53 countries, 94 Turkish participants). Exploratory factor analyses were performed to identify dietary and culinary practice patterns. Final version of CAAI included 37 items, comprising five factors in dietary domain as basic, meat-heavy, starch-heavy, and accessory foods patterns (Cronbach's alpha: 0.834), and one factor in cuisine-related practices domain (Cronbach's alpha: 0.732). Construct validity was investigated by Multiple Analysis of Covariance (MANCOVA) comparing CAAI factor scores between the immigrant and Turkish participants. Among immigrants, comparisons were made according to acculturation proxies, while accounting for potential covariates. Factor scores that differed significantly between the immigrants and Turkish people (basic and cuisine-related practices patterns) also differed significantly among immigrants with high vs. low fluency in Turkish. In conclusion, CAAI is a reliable and valid measure of culinary acculturation of immigrant population. This novel instrument and its short version can be adapted and used in other countries to capture the culinary acculturation of their immigrants.
Citation - WoS: 17
Citation - Scopus: 19
Synthesis and Characterization of Bi_1.5zn_{0.92< Pyrochlore Ceramics}
(Elsevier Sci Ltd, 2012) Qasrawi, A. F.; Kmail, Bayan H.; Mergen, A.
The morphological, compositional, structural, dielectric and electrical properties of Bi1.5Zn0.92Nb1.5-xSnxO6.92-x/2 ceramics have been investigated by means of scanning electron microscopy (SEM), X-ray energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), temperature and frequency dependent dielectric constant and temperature dependent conductivity measurements for Sn-contents in the range of 0.00 <= x <= 0.60. It was shown that single phase of the pyrochlore ceramics can only be obtained for x <= 0.25. Above this value a ZnO phase appeared in the XRD patterns and SEM micrographs as well. An increase in the lattice constant and in the temperature coefficient of dielectric constant and a decrease in the dielectric constant values with increasing Sn content was observed for the ceramics which exhibited a single phase formation. A temperature dependent but frequency invariant dielectric constant was observed for this type of ceramics. The lowest electrical conductivity and highest dielectric constant was observed for the sample which contains 0.06 Sn. The Bi1.5Zn0.92Nb1.5-xSnxO6.92-x/2 pyrochlore ceramic conductivities are thermally active above 395 K. For temperatures greater than 395 K, the conductivity activation energy which was found to be 0.415 eV for the pure sample increased to 1.371 eV when sample was doped with 0.06 Sn. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Citation - WoS: 61
Citation - Scopus: 73
Mechanical Properties of B₄c-sic Composites Fabricated by Hot-Press Sintering
(Elsevier Sci Ltd, 2020) So, Sung Min; Choi, Woo Hyuk; Kim, Kyoung Hun; Park, Joo Seok; Kim, Min Suk; Park, Jongee; Kim, Hyung Sun
We fabricated boron carbide-silicon carbide (B4C-SiC) composites by hot-press sintering without additives and evaluated the crystal phase, relative density, microstructure, and mechanical properties of the sintered body. When B4C and SiC were uniformly dispersed in the composite, crystal growth was inhibited, and a sintered body with a fine and uniform microstructure, with improved mechanical properties, was fabricated. The relative density of B4C-SiC composites sintered at temperatures lower than 2000 degrees C and 40 MPa of pressure exceeded 99.8%, and the bending strength and Vickers hardness at B4C 50 wt% were 645 MPa and 30.6 GPa, respectively.
Citation - WoS: 7
Citation - Scopus: 10
Optimizing the Performance of Single-Mode Laser Diode System Using Genetic Algorithm
(Elsevier Sci Ltd, 2004) Aydin, E; Aydın, Elif; Yildirim, R; Aydın, Elif; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
In this correspondence, micro-genetic algorithm (MGA) application results for optimizing the performance of electronic feedback of a laser diode are presented. The goal of optimization is to find the maximum bandwidth of the laser diode with electronic feedback used in fiber optic digital communication. A numerical analysis of the system theory of the single-mode laser diode to obtain numerical results of the gain, the Pulse response, and the harmonic distortion for electronic feedback is also presented. The dependence of the system gain on the feedback gain and delay is examined. The Pulse response is studied and it is shown that a transmission rate over 1 Gbyte/s can be achieved. (C) 2003 Elsevier Ltd. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 6
Laser Induced Breakdown Spectroscopy Based Diffusion Modelling in Cheese Matrix
(Elsevier Sci Ltd, 2019) Sezer, Banu; Bilge, Gonca; Eseller, Kemal Efe; Berberoglu, Halil; Boyaci, Ismail Hakki
In the cheese industry, mass transfer of small solutes like salt during brining and ripening is extremely important for the quality of final products. In general, effective diffusion coefficient values have been reported in the studies using destructive concentration profile methods. This study aims to monitor NaCl diffusion in cheese by using laser induced breakdown spectroscopy (LIBS) as a nondestructive method to fulfill the requirement of measuring mass transfer properties of solutes in microscopic size complex heterogeneous structures. To this end, spherical shaped white cheese samples were brined in 16% salt solution for 5-210 min and overnight, and Na emission lines were monitored by scanning the cross-section of each sample at 30 points on the radial axis. As was expected, increasing brining time decreased the concentration difference between the center and edge of the cheese samples. Experimental results were fitted to Fick's Diffusion Equation. It was observed that NaCl distribution became uniform and equal at different locations of the cheese sample after 13.8 h. All these results have demonstrated that LIBS can be utilized for optimization of the brining conditions of cheese. Although the use of LIBS in this study was limited to parameter optimization, it can also be applied for real time monitoring of food processes due to its rapid and continuous measurement mode.

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