Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
Browse
16 results
Search Results
Article Citation - WoS: 4Citation - Scopus: 4Very Low Density Amorphous Phase of Zircon(Elsevier Science Bv, 2019-06) Bolat, Suleyman; Durandurdu, MuratUsing a reliable ab initio molecular dynamics method, we investigate the rapid solidification of the zircon melt. Accompanied by amorphization, a drastic volume expansion of 27% is perceived. This value is fairly larger than 18% observed in the metamict zircon. Such a large volume swelling leads to a significant decrease in the mean coordination number of Zr atoms, which is about 5.66 and the lowest one reported so far. On the other hand, the volume expansion is found to have almost no impact on the average coordination number of Si atoms i.e., they maintain their tetragonal coordination. As suggested by earlier investigations, the polymerization of SiO4 units is witnessed but our model shows the highest polymerization with respect to the previous simulations. Based on our findings, we propose that our model does not represent the metamict zircon but a very low density amorphous phase of zircon.Article Citation - WoS: 58Citation - Scopus: 68Structure Health Monitoring Using Wireless Sensor Networks on Structural Elements(Elsevier Science Bv, 2019-01) Ayyildiz, Cem; Erdem, H. Emre; Dirikgil, Tamer; Dugenci, Oguz; Kocak, Taskin; Altun, Fatih; Gungor, V. CagriThis paper presents a system that monitors the health of structural elements in Reinforced Concrete (RC), concrete elements and/or masonry buildings and warn the authorities in case of physical damage formation. Such rapid and reliable detection of impairments enables the development of better risk management strategies to prevent casualties in case of earthquake and floods. Piezoelectric (PZT) sensors with lead zirconate titanate material are the preferred sensor type for fracture detection. The developed sensor mote hardware triggers the PZT sensors and collects the responses they gather from the structural elements. It also sends the collected data to a data center for further processing and analysis in an energy-efficient manner utilizing low-power wireless communication technologies. The access and the analysis of the collected data can be remotely performed via a web interface. Performance results show that the fractures serious enough to cause structural problems can be successfully detected with the developed system. (C) 2018 Elsevier B.V. All rights reserved.Article Citation - WoS: 62Citation - Scopus: 68Solvent Extraction Process for the Recovery of Nickel and Cobalt From Caldag Laterite Leach Solution: The First Bench Scale Study(Elsevier Science Bv, 2017-05) Kursunoglu, Sait; Ichlas, Zela Tanlega; Kaya, MuammerA solvent extraction application consisting of two-sequential solvent extraction circuits to separate the nickel and cobalt from a synthetic sulphate leach solution which simulates a typical Caldag lateritic leach solution was conceived and experimentally explored. The first circuit allowed the simultaneous extraction of most of the nickel (98%), cobalt (98%) and manganese (94%) with 20% neodecanoic acid (Versatic 10) and 5% tri-n-butyl phosphate (TBP) in ShellSol 2046 at pH 72 together with substantial amounts of calcium (65%) and magnesium (12%). Three stages of scrubbing at pH 5.6 using diluted sulphuric acid solution allowed the removal of most of the magnesium (90%) and substantial amount of calcium (16%). Complete stripping of nickel, cobalt, manganese, magnesium and calcium was achieved at pH 0.75. This loaded strip solution was the feed for the second circuit. The use 15% bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) and 5% TBP in ShellSol 2046 allowed the extraction of most of the cobalt (94%) and manganese (98%) at pH 5.0 but with substantial co-extraction of magnesium (41%) and calcium (40%) and a minor amount of nickel (3%). A two-stage scrubbing of this loaded organic with cobalt (20 g L-1) solution was performed. Magnesium, calcium and nickel were completely displaced with cobalt. Most of the manganese (93%) was removed from the organic. Complete stripping of the cobalt and manganese in the scrubbed organic phase was achieved at pH 1.0. Therefore, nickel (94%) and cobalt (91%) were totally separated from the feed solution. In addition, slope analyses were carried out to determine the nature of the extracted complexes of the nickel and cobalt with each extractant. Based on the experimental results, a flowsheet for the separation process is presented. (C) 2017 Elsevier B.V. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1Solute Aggregation in Ca72Zn28 Metallic Glass(Elsevier Science Bv, 2018-11) Tahaoglu, Duygu; Durandurdu, MuratSolidification of the Ca72Zn28 melt is achieved by using both the thermal quenching and rapid pressurizing techniques in ab initio molecular dynamics simulations within a generalized gradient approximation. A chemical segregation process is perceived in the Ca72Zn28 system and hence the resulting configurations show nanosized glassy domains with different compositions. The structural and mechanical properties of both Ca72Zn28 metallic glasses have been probed by using various analyzing methods. Although the mean coordination number of the both models is found to be fairly close to each other, a careful investigation exposes that they have a different short-range order around Zn atoms. It appears that pressurizing significantly affects the environment of Zn atom, suppresses the occurrence of Zn-centered ideal icosahedral polyhedrons and retains the Zn centered tri-capped trigonal prism like configurations. On the other hand, the impact of pressure on the environment of Ca atoms is found to be not too drastic. The computer-generated models represent slightly different mechanical properties. The model obtained using the rapid pressurizing technique is stiffer than the one produced using the thermal quenching technique.Article Citation - WoS: 1Citation - Scopus: 1Pressure-Induced Phase Transformations in Amorphous Arsenic(Elsevier Science Bv, 2016-04) Durandurdu, MuratThe atomic structure of amorphous arsenic and its response to high pressure are explored using a constant pressure ab initio molecular dynamics technique. Different analyzing techniques reveal that amorphous arsenic has a local structure close to that of the crystalline phase. The model also presents some twofold and fourfold coordination defects. The existence of a possible amorphous to amorphous phase transition for arsenic is proposed on the bases of the observation of a gradual coordination increase with the application of pressure. Further compression of the amorphous state yields a transformation into a simple cubic crystal. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 285Citation - Scopus: 318Potential Ion Exchange Membranes and System Performance in Reverse Electrodialysis for Power Generation: A Review(Elsevier Science Bv, 2015-07) Hong, Jin Gi; Zhang, Bopeng; Glabman, Shira; Uzal, Nigmet; Dou, Xiaomin; Zhang, Hongguo; Chen, YongshengReverse electrodialysis (RED) is an emerging membrane based energy conversion process used to extract electricity by mixing two water streams of different salinities. This technique utilizes transport of cations and anions during controlled mixing of saltwater and freshwater through selective ion exchange membranes. The development of ion exchange membranes and optimization of system performance are crucial for sustainable energy capture from salinity gradients using RED. Recently, increased attention has been given to the preparation of ion exchange membranes and to understanding the factors that determine the RED power performance. This review evaluates potential ion exchange membrane materials, currently available state-of-the-art RED membranes, and their key properties. Discussion will focus on the electrochemical and physical properties of these membranes (e.g., resistance, permselectivity, and swelling) because of their significant role in RED performance throughout the system, Although an interconnected relationship exists between membrane properties, RED requires high quality membranes that are uniquely tailored to have a low resistance and high permselectivity. Moreover, harnessing this potential technology demands not only carefully optimized components but also a novel RED stack design and system optimization. The key findings and advancements needed to assure proper stack design and optimization are also described. This review paper's goal is to elucidate effective energy conversion from salinity gradients and expedite implementation of RED as the next promising renewable source of power for large-scale energy generation. (C) 2015 Elsevier B.V. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 4Permanent Densification of Amorphous Zinc Oxide Under Pressure: A First Principles Study(Elsevier Science Bv, 2018-02) Tahaoglu, Duygu; Durandurdu, MuratAb initio simulations within a generalized gradient approximation are carried out to investigate the densification mechanism of amorphous zinc oxide (a-ZnO) under hydrostatic pressure. In contrast to the crystalline ZnO, the densification of a-ZnO is found to proceed gradually and is associated with a structural modification from a low density amorphous state to a high density amorphous state. Accompanied by the phase transformation, the mean coordination number increases from similar to 4.0 to similar to 5.5. The high-density amorphous form of ZnO has a local structure, partially comparable with that of the rocksalt type ZnO crystal and presents a semiconducting behavior. The phase change is irreversible because upon pressure release, an amorphous model largely consisting of fivefold coordination is recovered. The decompressed model can be, therefore, classified as an intermediate phase between the wurtzite-like and the rocksalt-like amorphous configurations.Article Citation - WoS: 52Citation - Scopus: 62MGRP: Mobile Sinks-Based QoS-Aware Data Gathering Protocol for Wireless Sensor Networks-Based Smart Grid Applications in the Context of Industry 4.0-Based on Internet of Things(Elsevier Science Bv, 2018-05) Faheem, Muhammad; Gungor, V. C.The recent advances in internet of things (IoT) and industrial wireless sensor networks (IWSNs) paradigm provide a promising opportunity for upgrading todays elderly electricity industrial systems and even allow the fourth stage of the industrial revolution, referred to as smart grid industry (SGI) 4.0. In SGI 4.0 paradigm, the WSNs are considered as promising solutions due to their advantages, such as cable replacement, ease of deployment, flexibility, and cost reduction. However, harsh and complex smart grid (SG) environments pose great challenges to guarantee reliable communication for WSNs-based SG applications due to equipment noise, electromagnetic interference, multipath effects and fading in SG environments. This results in deteriorating the quality-of-service (QoS) requirements as well as the network lifetime of multi-hop communication-based WSNs for SG applications. Thus, for SGI 4.0 paradigm to come true, a WSN-based highly reliable communication infrastructure is crucial that will wirelessly connect and integrate power system components for more efficient, reliable, and intelligent operations of the next-generation electricity power grids. To address these challenges, in this paper a novel multi-mobile sinks-based QoS-aware data gathering protocol (called MQRP) for WSNs-based SG applications has been proposed to empower SGI 4.0. The extensive simulations study is carried through a network simulation tool called EstiNet9.0. The obtained experimental facts show that the proposed scheme has not only improved the QoS performance metrics, such as packet delivery ratio, memory utilization, control message overhead, residual energy, network lifetime, and throughput, but also reduced packet error rate and end-to-end delay compared to existing data collection schemes. (C) 2017 Elsevier B.V. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 2Local Structure of As2O3 Glass From First Principles Simulations(Elsevier Science Bv, 2016-03) Durandurdu, MuratWe model As2O3 glass from the liquid state using ab initio molecular dynamics simulations and probe its atomic structure using various analyzing techniques. The model is almost free from coordination and chemical defects and has an average coordination number of 238. The AsO3 pyramids are randomly connected via corner sharing to form the glass state. The glass network presents six membered hexagonal-like rings similar to those formed in the As4O6 molecules but isolated or complete As4O6 molecules do not exist. The glass state mainly consists of layer-like and incomplete As4O6-like structures. (C) 2016 Elsevier B.V. All rights reserved.Editorial Citation - WoS: 1Citation - Scopus: 1Human-Oriented Approaches for Assistive and Rehabilitation Robotics - Engineering Methods, Technical Implementation, and Treatment(Elsevier Science Bv, 2017-10) Beckerle, P.; Salvietti, G.; Unal, R.; Mastrogiovanni, F.