Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Comparative Analysis of Modulation Shapes on Laser Diode Performance with a High-Efficiency LLC Resonant Converter Driver(Wiley, 2026-02-06) Yigit, Hayri; Rifat boynuegri, Ali; Tekgun, Burak; Rifat Boynuegri, AliHigh-power laser diodes (LDs) are key components in laser-based wireless power transfer (WPT) systems, where end-to-end efficiency is one of the most critical performance metrics. This study investigates the driving performance of an LD powered by a high-efficiency LLC resonant converter under three distinct excitation waveforms-sinusoidal, triangular, and rectified-sine-using a MATLAB/SIMULINK model and an experimental setup designed to reproduce real-world operating conditions. Each waveform is synthesized through frequency modulation of a full-bridge inverter stage and filtered at the output. The analysis examines the impact of modulation shape on output current ripple, converter efficiency, and overall LD efficiency. Experimental validation confirms the simulation trends, underscoring the trade-offs between waveform smoothness, implementation complexity, and efficiency. Beyond confirming that constant-current operation yields the highest LD efficiency, this study explicitly quantifies how low-frequency current ripple induced by different modulation waveforms propagates through the LLC resonant converter, alters RMS current stress, and translates into measurable efficiency degradation at both the driver and LD levels. By experimentally correlating waveform symmetry, ripple magnitude, and loss mechanisms, the work establishes practical design boundaries for waveform-modulated laser drivers in WPT systems.Article Citation - WoS: 1Citation - Scopus: 1A Comprehensive Review on the Extraction and Recovery of Lithium from Primary and Secondary Sources: Advances Toward Battery-Grade Materials(Wiley, 2025-10-20) Top, Soner; Kursunoglu, Sait; Altiner, MahmutLithium-ion battery (LIB) technologies have become indispensable to modern energy systems, driving global demand for high-purity lithium compounds. This review focuses on lithium recovery and purification strategies for battery-grade lithium carbonate (Li2CO3) and lithium hydroxide (LiOH), addressing both primary sources (brines and minerals) and secondary sources (waste materials). Industrially established processes, such as evaporation-based brine treatment and conventional metallurgical methods, are discussed alongside emerging techniques, including membrane separation, solvent extraction, and CO2-assisted precipitation. Particular attention is given to lithium precipitation mechanisms, the behaviour of co-existing ions during extraction, and the specific quality requirements for cathode material synthesis. By evaluating process scalability, environmental impact, and product purity, this review provides a comprehensive understanding of current practices and future directions. Additionally, it highlights the growing importance of lithium in the context of accelerating electric vehicle (EV) adoption, underscoring the bright and expanding future of the lithium industry.Article Citation - WoS: 1Citation - Scopus: 1Unhappiness Among the Unemployed: The Roles of Descriptive Norms, Injunctive Norms and Personal Beliefs(Wiley, 2025-05-19) Ugur, Zeynep B.; Durak, AysenurThis study explores the influence of social norms and individual beliefs on the well-being of unemployed individuals in Turkey, a context marked by both chronic unemployment and a high societal valuation of employment. Using province-level representative data from the 2013 Life Satisfaction Survey, encompassing 196,203 observations, we analyse how descriptive norms (prevalence of unemployment) and injunctive norms (social pressures due to unemployment) at the province level affect the happiness of the unemployed. We utilized people's perception of employment for being respected in social life and personally feeling social pressure as a measure of individual beliefs. Multilevel regression results reveal that descriptive norms can modestly alleviate the adverse impact of unemployment, particularly for the short-term unemployed, while injunctive norms slightly intensify the unhappiness of being unemployed, especially in the short term. The unemployed's personal beliefs about the value of employment matter for their happiness. These findings underscore the theoretical implications of social norms in shaping the well-being of the unemployed and highlight the importance of individual beliefs in moderating these effects.Article Citation - WoS: 6Citation - Scopus: 6The Different Impacts of g-C3N4 Nanosheets on PVDF and PSF Ultrafiltration Membranes for Remazol Black 5 Dye Rejection(Wiley, 2023-08-02) Senol-Arslan, Dilek; Gul, Ayse; Dizge, Nadir; Ocakoglu, Kasim; Uzal, NigmetMembranes combined with nanoparticles are an excellent combination capable of successfully removing various contaminants, such as dyes from wastewater while using very little energy and decreasing pollution. The present study reports an efficient approach for Remazol Black 5 (RB5) dye removal using composite graphitic carbon nitride nanosheets (g-C3N4), polysulfone (PSF), and polyvinylidene fluoride (PVDF) membranes. The membranes were prepared using the phase inversion method, with varying quantities of g-C3N4 nanosheets ranging from 0.1%, 0.2% to 0.3%. The prepared g-C3N4 nanosheets were characterized by FTIR, SEM analyses, and zeta potential measurements. FTIR and SEM studies, contact angle, water permeability, COD, and dye rejection measurements were used to characterize the g-C3N4 nanosheets embedded in PSF and PVDF membranes. After the addition of 0.3 wt% g-C3N4, the water flux of the 0.3 wt% g-C3N4 embedded PSF membrane was the highest, whereas the water flux of the 0.3 wt% g-C3N4 embedded PVDF membrane was the lowest. The ultrafiltration (UF) membrane's performance with g-C3N4 embedded showed an RB5 rejection rate of more than 80% and a COD removal efficiency of more than 45%. The results of the experimental filtration showed that RB5 rejection reached maximum values of 91.3% for 0.1 wt% g-C3N4/PSF, and 85.6% for 0.3 wt% g-C3N4/PVDF.Article Citation - WoS: 28Citation - Scopus: 35Tactile Sensitivity and Capability of Soft-Solid Texture Discrimination(Wiley, 2015-08-09) Aktar, Tugba; Chen, Jianshe; Ettelaie, Rammile; Holmes, MelvinThe sensation and perception of food texture is regulated by tactile-dominated mechanisms and therefore, it is believed that one's capability in discriminating food textural properties could be related to one's tactile sensitivity. However, evidence to support this hypothesis is currently not available. This work aims to test this hypothesis by examining tactile sensitivity of individuals' (touch detection threshold and two-point discrimination threshold) and texture discrimination capability. A range of soft-solid food samples with controlled firmness and elastic moduli were designed for textural discrimination tests. A total of 32 healthy subjects threshold of touch detection was found to be 0.028 g for the fingertip and 0.013 g for the tongue. Similarly, the mean threshold of two-point discrimination was 1.42 mm and 0.62 mm for the fingertip and tongue, respectively. Threshold for firmness discrimination (compressing until yielding) of the gel samples was 13.3% for the fingertip and 11.1% for the tongue. However, the elasticity discrimination threshold (by gentle pressing) of the population was found to be much smaller at 2.3% and 1.2% for the fingertip and the tongue respectively. Results show that tongue is slightly more sensitive than the fingertip in discriminating food texture (P < 0.05). An expected correlation between individual's capability of texture discrimination and their tactile sensitivity was not observed. PRACTICAL APPLICATIONS Texture discrimination capability is a significant factor for food texture preference and appreciation. In order to understand texture perception, it is essential to identify the relevant factors and define characteristics that govern the processes involved. Having a meaningful and reliable texture discrimination indicator is critically important for the food industry in the development and optimization of new food products, and in particular for specific food design for individuals' with special needs, e.g., elderly, dysphagic patients, etc. With this study, we illustrate the differential threshold for soft-solid texture (firmness and elasticity) and also investigate the capabilities of tactile sensation (touch detection and two-point discrimination) and evaluate potential correlations. The results and correlations may provide information about texture sensitivity and also might provide useful information to R&D researchers. Methodologies could also be applied in general food sensory studies and also investigating relationships between sensory psychology and sensory physiology.Article Citation - WoS: 1Citation - Scopus: 4QoS-Aware MAC Protocols Utilizing Sectored Antenna for Wireless Sensor Networks-Based Smart Grid Applications(Wiley, 2016-07-25) Yigit, Melike; Incel, Ozlem Durmaz; Baktir, Selcuk; Gungor, V. Cagri; Durmaz Incel, OzlemWireless sensor networks (WSNs) are the most commonly deployed technology in smart grid environments owing to their advantages including low cost and successful adoption in various harsh smart grid environments. However, providing the quality of service (QoS) requirements of smart grid applications with WSNs is difficult because of the power constraints of sensor nodes and unreliable wireless links. In order to meet the QoS requirements of smart grid applications usingWSNs, in this paper, we first propose a QoS-aware omnidirectional antenna-based medium access control (QODA-MAC). Then, in order to investigate the impact of using sectored antennas on meeting QoS requirements, we also propose another QoS-aware four-sectored antenna-based MAC protocol (QFSA-MAC). The aim of the proposed approaches is to increase channel utilization with efficient service differentiation considering traffic flows with different requirements as well as providing reliable and fast delivery of data. We measure the performance of QODA-MAC and QFSA-MAC by making extensive simulations and compare them with each other. The results show that QFSA-MAC outperforms the QODA-MAC protocol and satisfies QoS requirements of smart grid applications by achieving significant improvement in terms of latency, energy consumption and data delivery. Copyright (C) 2016 John Wiley & Sons, Ltd.Article Citation - WoS: 8Citation - Scopus: 16QoS-Aware LTE-A Downlink Scheduling Algorithm: A Case Study on Edge Users(Wiley, 2019-07-31) Uyan, Osman Gokhan; Gungor, Vehbi Cagri4G/LTE-A (Long-Term Evolution-Advanced) is the state of the art wireless mobile broadband technology. It allows users to take advantage of high Internet speeds. It makes use of the OFDM technology to offer high speed and provides the system resources both in time and frequency domain. A scheduling algorithm running on the base station holds the allocation of these resources. In this paper, we investigate the performance of existing downlink scheduling algorithms in two ways. First, we look at the performance of the algorithms in terms of throughput and fairness metrics. Second, we suggest a new QoS-aware fairness criterion, which accepts that the system is fair if it can provide the users with the network traffic speeds that they demand and evaluate the performance of the algorithms according to this metric. We also propose a new QoS-aware downlink scheduling algorithm (QuAS) according to these two metrics, which increases the QoS-fairness and overall throughput of the edge users without causing a significant degradation in overall system throughput when compared with other schedulers in the literature.Article Citation - WoS: 7Citation - Scopus: 8Prokube: Proactive Kubernetes Orchestrator for Inference in Heterogeneous Edge Computing(Wiley, 2024-08-18) Ali, Babar; Golec, Muhammed; Gill, Sukhpal Singh; Cuadrado, Felix; Uhlig, Steve; Singh Gill, SukhpalDeep neural network (DNN) and machine learning (ML) models/ inferences produce highly accurate results demanding enormous computational resources. The limited capacity of end-user smart gadgets drives companies to exploit computational resources in an edge-to-cloud continuum and host applications at user-facing locations with users requiring fast responses. Kubernetes hosted inferences with poor resource request estimation results in service level agreement (SLA) violation in terms of latency and below par performance with higher end-to-end (E2E) delays. Lifetime static resource provisioning either hurts user experience for under-resource provisioning or incurs cost with over-provisioning. Dynamic scaling offers to remedy delay by upscaling leading to additional cost whereas a simple migration to another location offering latency in SLA bounds can reduce delay and minimize cost. To address this cost and delay challenges for ML inferences in the inherent heterogeneous, resource-constrained, and distributed edge environment, we propose ProKube, which is a proactive container scaling and migration orchestrator to dynamically adjust the resources and container locations with a fair balance between cost and delay. ProKube is developed in conjunction with Google Kubernetes Engine (GKE) enabling cross-cluster migration and/ or dynamic scaling. It further supports the regular addition of freshly collected logs into scheduling decisions to handle unpredictable network behavior. Experiments conducted in heterogeneous edge settings show the efficacy of ProKube to its counterparts cost greedy (CG), latency greedy (LG), and GeKube (GK). ProKube offers 68%, 7%, and 64% SLA violation reduction to CG, LG, and GK, respectively, and it improves cost by 4.77 cores to LG and offers more cost of 3.94 to CG and GK. ProKube is a proactive container scaling and migration orchestrator to dynamically adjust the resources and container locations with a fair balance between cost and delay for ML inferences in the inherent heterogeneous, resource-constrained, and distributed edge environments. imageArticle Citation - WoS: 4Citation - Scopus: 5Predicting Potential of Pressure Retarded Osmosis Power for Different Estuaries in Turkey(Wiley, 2018-11-29) Saki, Seda; Uzal, Nigmet; Gokcek, Murat; Ates, NurayPressure retarded osmosis (PRO) is an alternative renewable energy source recovered from the salinity gradient between the fresh water (feed solution) and salty water (draw solution). In order to implement osmotic power, the site-specific characteristics including the river and sea salinity, annual flow rates, ecological restrictions were taken into account. This study revealed a comprehensive analysis for a theoretical potential of PRO process for different estuaries in Turkey. In this study, the power potential prediction of PRO process for the Ceyhan, Sakarya, and Meric Rivers were analyzed via Gibbs free energy calculations. The net annual energy production is projected to be 167, 164, and 208 GWh/y for Ceyhan, Sakarya, and Meric Rivers, respectively. Meric River has the highest energy production of 208 GWh/yr with 186 m(3)/s mean flow rate and 245 mg/L salinity. These results clearly show that Turkey's rivers having high salinity and flow rate are feasible and applicable for making the osmotic power plant economically. Thereby, it is providing essential direction to the improvement of its design, installation, and operation. The developed methodology for the evaluation of the osmotic power potential of other rivers can be considered as a basis to assess the whole potential on a worldwide level. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38:e13085, 2019Article Citation - WoS: 25Citation - Scopus: 25Microwave-Assisted Green Approach for Graft Copolymerization of L-Lactic Acid Onto Starch(Wiley, 2015-10-15) Salimi, Kouroush; Topuzogullari, Murat; Dincer, Sevil; Aydin, Halil Murat; Piskin, ErhanPoly l-lactic acid grafted starch (St-g-PLA) copolymers were directly synthesized under microwave irradiation by using sodium hydroxide (NaOH) and stannous 2-ethyl hexanoate acting as a catalyst, without the use of toxic solvents. The product were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (C-13 CP/MAS NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA-DTG). SEM analysis indicated that microwave heating had a considerable effect on the interfacial adhesion between PLA and starch. Thermogravimetric analysis (TGA-DTG) revealed that copolymers exhibited better thermal stability. Maximum PLA grafting was achieved with the following reaction conditions: 450W microwave power, monomer ratio of 1:5 and 0.4M of NaOH. This study demonstrates that it is possible to obtain St-g-PLA copolymers with better processing characteristics and smaller sizes via microwave-assisted synthesis. The applied procedure is an interesting green synthesis method for the production of biodegradable materials used in a diverse range of applications. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42937.
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