Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 7Citation - Scopus: 7Unveiling the Multifaceted Properties of a 3D Covalent-Organic Framework: Pressure-Induced Phase Transition, Negative Linear Compressibility and Auxeticity(Elsevier, 2023-08) Erkartal, MustafaHigh-pressure behavior and mechanical properties of a three-dimensional covalent-organic framework (NPN-1) were investigated by using different types of first principles molecular simulations. An irreversible pressureinduced first-order isosymmetric phase transition was predicted at 0.14 GPa. The subunit of NPN-1 retains its rigidity under pressure thanks to the strong covalent bonds. However, compression leads to significant tilting of the nitrophenyl groups. The mechanical properties of frameworks are highly anisotropic. Remarkably, both phases exhibit not only negative linear compressibility along the c-axis but also negative Poisson's ratio in certain directions. Detailed structural analysis revealed that the origin of the phase transition and anomalous mechanical properties of both phases are the wine-rack motif and strut-hinge mechanism. To the best of our knowledge, this study is the first report of such behavior in COFs, opening up new avenues for the exploration of COFs as materials for many promising applications.Article Citation - WoS: 11Citation - Scopus: 17The Impact of Error Control Schemes on Lifetime of Energy Harvesting Wireless Sensor Networks in Industrial Environments(Elsevier, 2020-06) Tekin, Nazli; Gungor, Vehbi CagriDue to the harsh channel conditions of the industrial environments, the data transmission over the wireless channel suffers from erroneous packets. The energy consumption of error control schemes is of great importance for battery-limited Wireless Sensor Networks (WSNs) in industrial environments. In this paper, the lifetime analysis of error control schemes, i.e., Automatic Repeat Request (ARQ), Forward Error Correction (FEC) and Hybrid ARQ (HARQ), is presented under different industrial environment channel conditions. Furthermore, the impact of energy harvesting methods on the network lifetime is investigated. A novel Mixed Integer Programming (MIP) framework is developed to maximize the network lifetime while meeting application reliability. Performance results show that utilizing HARQ-II error control scheme for Mica2 and BCH(31,21,5) for Telos improves the network lifetime while meeting the desired application reliability rate.Article The Ground State Properties of Two Dimensional Fermi Gas System Confined in a Potential Composed of Harmonic and a Gaussian Terms(Elsevier, 2019-01) Gulveren, Berna; Sahin, Mehmet; Atav, UlfetIn this work, the ground state properties of two dimensional Fermi gas system interacting in a potential con- sisting of harmonic and Gaussian terms are investigated in the frame of Thomas-Fermi approximation. The depth and the curvature of the potential are changed by varying confinement parameters and the influence of the constraining conditions on the system properties like the density profile, the kinetic and the potential energy of the fermionic system is analyzed comprehensively. The deviations of the results due to the Gaussian potential are also determined by comparing the results with those obtained for pure harmonic potential. Calculations are also performed analytically for non-interacting case for comparative purposes. The results show that the confinement parameters play crucial role on the ground state properties of confined system.Article Citation - WoS: 80Citation - Scopus: 90Properties of Fly Ash-Based Lightweight Geopolymer Concrete Prepared Using Pumice and Expanded Perlite as Aggregates(Elsevier, 2020-02) Top, Soner; Vapur, Huseyin; Altiner, Mahmut; Kaya, Dogan; Ekicibil, AhmetThe present paper aims to utilize the fly ash wastes with lightweight aggregates for geopolymer concrete production process in which sodium hydroxide (NaOH) and sodium metasilicate (Na2SiO3) were used as alkali activators, respectively. The designed experiments were examined by the Yates Analyses and so the productions of geopolymer concrete were investigated depending on curing temperature, solid/liquid rate and concentration of alkali activators. The curing temperature and alkali activator concentration were revealed as effective parameters in geopolymerization. The effects of expanded perlite (EP) and acidic pumice (AP) aggregates were discovered for the production of lightweight geopolymer concretes. The microstructural properties of each produced geopolymer concrete were characterized using SEM, EDS and laser particle size analyses. The specifications of the concrete were evaluated based on their uniaxial compressive strength (UCS), point load strength (PLS), sonic speed (SS), Mohs hardness (MH), and water absorption (WAR) ratio results. In addition, the effects of pre-wetting of EP aggregates, which have hydrophilic nature, were examined. To the best of our knowledge, this is the first time that pre-wetted lightweight EP aggregates were used to produce lightweight GP concretes. As a result of pre-wetting, chemical usage decreased by 32.5%. The UCSs of the lightweight geopolymer concretes were in a range of 10-50MPa and their unit weights changed between 1250 and 1700 kg/m(3). Lighter concretes were obtained by the addition of EP aggregates rather than AP ones. (C) 2019 Elsevier B.V. All rights reserved.Article Citation - WoS: 14Citation - Scopus: 13Production of Mixed Rare Earth Oxide Powder From a Thorium Containing Complex Bastnasite Ore(Elsevier, 2021-02) Kursunoglu, Sait; Hussaini, Shokrullah; Top, Soner; Ichlas, Zela Tanlega; Gokcen, Hasan Serkan; Ozsarac, Safak; Kaya, MuammerThe production of mixed rare earth oxide powder from a thorium containing bastnasite ore by sulfuric acid bake water leaching followed by precipitation with oxalic acid and thermal decomposition of the oxalates was investigated. The sulfuric acid baking was performed at 250 degrees C and the optimum baking time was found to be 3 h. Using deionized water as lixiviant, 92.6% La, 86.8% Ce, 86.9% Pr, 82.3% Nd, 95.4% Th and 31% Y were dissolved from the baked ore at 25 degrees C after 30 min of leaching. The effect of solid-to-liquid ratio on the dissolution of the rare earth elements and thorium shows that when the solid ratio in the water increased from 1:10 to 1:3, the dissolution percentage decreased. The final mixed rare earth oxide powder contained 88.54% REO and 6% ThO20 together with small amounts of other impurities. The SEM mapping results revealed that the produced REO has an irregular crystal shape. Based on the experimental results obtained from the current study, a flowsheet was proposed for the production of mixed rare earth oxide powder from a specific complex bastnasite ore. (C) 2020 Elsevier B.V. All rights reserved.Article Citation - WoS: 8Citation - Scopus: 9On the Performance of LTE Downlink Scheduling Algorithms: A Case Study on Edge Throughput(Elsevier, 2018-08) Deniz, Coskun; Uyan, O. Gokhan; Gungor, Vehbi CagriRadio resource allocation is a crucial task in the LTE networks. To increase the overall user experience, an efficient radio resource allocation algorithm should be utilized. In this work, a new scheduling algorithm has been proposed to increase the edge throughput without sacrificing system throughput. Comparative performance results indicate that the proposed scheduler increases the edge throughput and fairness while limiting degradation in the cell throughput between 0 to 2 percent with respect to the other schedulers.Article Citation - WoS: 45Citation - Scopus: 55Oil Recovery in Rosehip Seeds From Food Plant Waste Products Using Supercritical CO2 Extraction(Elsevier, 2016-12) Salgin, Ugur; Salgin, Sema; Ekici, Derya Dincyurek; Uludag, GamzeValuable oils in rosehip seeds produced as the solid waste during the process of marmalade production using seed-containing fruits were recovered by supercritical CO2 extraction method. The influence of the particle size (125 <= Dp > 1000 mu m), volumetric flow rate of supercritical solvent (0.75-3.5 mL/min), pressure (20-40 MPa), temperature (40-60 degrees C) and entrainer concentration (2.5-7.5%vol. ethanol) on the extraction yield in the recovery process was examined. The highest extraction yield determined as 16.5 g oil/100 g dry solid was reached in approximately 150 min by using supercritical CO2 extraction (30 MPa, 40 degrees C, 0.75 mL/min, 355 < Dp < 500 mu m) and in the case where 5%vol. ethanol is used as entrainer, it was reached in about 90 min. In similar oil profiles obtained through Soxhlet and supercritical fluid extractions, the ratio of unsaturated fatty acids to saturated fatty acids is about 17. Significant changes were determined in morphological structures of waste seeds compared to unprocessed seeds in marmalade production, by using scanning electron microscope. Apparent solubility values of rosehip oil in supercritical CO2 did exhibit a significant consistency with Chrastil, del Valle-Aguilera, Adachi-Lu and Sparks solubility models. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 5Novel Insights Into Bacillus Thuringiensis: Beyond Its Role as a Bioinsecticide(Elsevier, 2025-03) Jouzani, Gholamreza Salehi; Sharafi, Reza; Argentel-Martinez, Leandris; Penuelas-Rubio, Ofelda; Ozkan, Ceyda; Incegul, Bengisu; Azizoglu, Ugur; Salehi Jouzani, GholamrezaThis review explores the diverse applications of Bacillus thuringiensis (Bt) beyond its traditional role as a bioinsecticide. Bt produces a variety of compounds with distinct chemical structures and biological activities. These include antimicrobial agents effective against plant pathogens and bioactive compounds that promote plant growth through the production of siderophores, hormones, and enzymes. Additionally, Bt's industrial potential is highlighted, encompassing biofuel production, bioplastics, nanoparticle synthesis, food preservation, anticancer therapies, and heavy metal bioremediation. This critical analysis emphasizes recent advancements and applications, providing insights into Bt's role in sustainable agriculture, biotechnology, and environmental management.Article Citation - WoS: 8Citation - Scopus: 11Network Cost Allocation Methods for Pay-As Peer-to-Peer Energy Trading: A Comparison(Elsevier, 2022-11) Noorfatima, N.; Choi, Y.; Onen, A.; Jung, J.In pay-as-bid peer-to-peer (P2P) energy trading, various types of prosumers and consumers can participate, regardless of their offers. Thus, various types of participants impact the network differently. However, very few pay-as-bid P2P energy trading studies have specifically discussed appropriate compensation for network usage, although the market is implemented in existing utility-owned grids. Therefore, to improve the performance of pay-as-bid P2P energy trading, it is important to determine the appropriate compensation to utilities for network usage. This study aims to obtain an appropriate network cost allocation method for pay-as-bid P2P energy trading. Hence, the authors present a review of pay-as-bid P2P market mechanisms and various network cost allocation (NCA) methods. Additionally, a comprehensive evaluation framework is proposed to determine the most appropriate NCA method for the pay-as-bid P2P energy trading system. A comparison was made between various NCA methods to investigate the outcomes of the implementation of different NCA methods to various market conditions. The study constructs a case study based on the operator-oriented P2P model to represent the pay-as-bid P2P energy trading system. The simulation of pay-as-bid P2P energy trading with large participant number is applied in the IEEE 69-bus distribution system. The study concluded that applying the appropriate NCA method would improve the performance of pay-as-bid P2P energy trading operation.Article Citation - WoS: 20Citation - Scopus: 28Leisure Mobility Changes During the COVID-19 Pandemic- An Analysis of Survey and Mobile Phone Data in Sweden(Elsevier, 2023-06) Osth, John; Toger, Marina; Turk, Umut; Kourtit, Karima; Nijkamp, PeterThe COVID-19 pandemic affected travelling in general, and the leisure mobility and the spatial distribution of travellers in particular. In most parts of the world, both domestic and international travel has been replaced by restrictive policies and recommendations on mobility. A modal shift from public transport towards private cars and micro-mobility was also observed. This study seeks to trace the implications of the COVID-19 pandemic for leisure mobility. We use a unique Swedish database containing daily mobility patterns of pseudonymised mobile phone users, combined with a survey on vacation transport behaviour. By contrasting mobility patterns for selected holiday days during the unaffected summer of 2019 with corresponding dates in 2020 and 2021, we are able to model and detect the pandemic effects on tourism and recreational mobility. Moreover, by identifying the general mobility patterns, we analyse whether and how the transport mode has changed. Using data on the spatial distribution of recreational amenities, we identify locations that were favoured during the pandemic. In Sweden, even though the pandemic decreased in spread and severity during the summers, most travel restrictions were still enforced, international vacations uncommon, and larger vacation spots, such as amusement parks and cultural institutions, were closed down. Swedish vacation homes in remote or rural areas were quickly booked. This change in recreational behaviour, where less populated areas, open air and nature recreation were favoured over indoor or crowded urban cultural activities, was more substantial in 2021 than in 2020. This result shows how policies can effectively be developed, so that Swedes respond properly to recommendations and adjust their vacation plans.