WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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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.Conference Object Turkish English Teachers' Professional Teacher Self as One of the Possible Selves(Elsevier Science Bv, 2016-10) Demirezen, Mehmet; Ozonder, OzgulThis study reports the results of a study exploring Turkish English teachers' professional self in relation to teacher education. The study also examines the relationship between the participants' educational background, teaching experience and their professional self The study was carried out in Ankara, Turkey. The participants of the study were English language instructors of Hacettepe University, School of Foreign Languages. A total of 43 English instructors (females: 36 and males: 7) voluntarily participated in the study, responding to a questionnaire composed of 40 items regarding teacher professional self. The results of the Professional Self Questionnaire revealed that the rate of Turkish English teachers' professional self was very high (81%, M=4.09). Also, there was a significant difference in participants' professional self depending on their educational background. The results indicated that the participants' professional self did not differ significantly in relation to their teaching experience. (C) 2016 Published by Elsevier Ltd.Conference Object Citation - WoS: 9Citation - Scopus: 10The Relationship of Surface Roughness and Wettability of 316L Stainless Steel Implants With Plastic Deformation Mechanisms(Elsevier Science Bv, 2019) Cicek, S.; Karaca, A.; Torun, I.; Onses, M. S.; Uzer, B.The wettability of the implant plays significant role in successful tissue-implant integration and shows strong dependence on the surface topography of the material. Recent studies showed that the plastic deformation mechanisms can improve cell response, and increase surface roughness and energy. In order to understand the effect of these mechanisms on wettability, 316L stainless steel samples were subjected to tensile test and deformed up to 15% to 35% of strain levels. Atomic force microscopy (AFM) presented approximately 22-fold greater average surface roughness on the 35% deformed sample compared to undeformed one. On the other hand, sessile drop test showed contact angle decrease from 82 degrees to 52 degrees as the deformation increased. This finding is significant since much higher contact angle value at similar surface roughness was presented in the literature. This demonstrates that the plastic deformation mechanisms can play significant role in enhancing the surface wettability without a need for a surface treatment technique. Hence, through the activation of these mechanisms, wettability and surface energy of the implant materials could be further increased which would result with enhanced cell response and lessened post-surgical complications. (C) 2018 Elsevier Ltd. All rights reserved.Conference Object Citation - WoS: 2Student EFL Teachers' Receptive Vocabulary Size(Elsevier Science Bv, 2016-10) Ozonder, OzgulThis study reports the results of a study investigating the receptive vocabulary size of student EFL teachers. The study also examined the relationship between the participants' academic achievement (departmental GPA) and their receptive vocabulary size and the existence of any gender-related difference. The study was carried out in English Language Teaching (ELT) Department of a major state university in Turkey. A total of 104 undergraduate students (females: 76 and males: 28) enrolled in the department voluntarily participated in the study, took the Version 2 of the Vocabulary Levels Tests (Schmitt, Schmitt & Clapham, 2001) and responded to a survey investigating their GPA scores and genders. The results revealed that student EFL teachers have a high level of total receptive vocabulary capacity size in their foreign language (M=103.82). Learners' academic achievement (GPA) is treated as an indicator of their language proficiency level in many studies of English Language Teaching (ELT) field. However, the results of this study revealed that there was not any statistically significant correlation between academic achievement (GPA) and their receptive vocabulary size. Although GPA may be a sign of academic achievement (GPA) and successful studentship, it may not readily one's actual English language proficiency. The results also indicated that there was no significant difference between males and females regarding their receptive vocabulary size. (C) 2016 The Authors. Published by Elsevier Ltd.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: 52Citation - Scopus: 69Spectrum-Aware Bio-Inspired Routing in Cognitive Radio Sensor Networks for Smart Grid Applications(Elsevier Science Bv, 2017-03) Fadel, E.; Faheem, M.; Gungor, V. C.; Nassef, L.; Akkari, N.; Malik, M. G. A.; Akyildiz, I. F.Cognitive radio sensor networks (CRSNs) have been proposed to serve as a reliable, robust, and efficient communications infrastructure that can address both the existing and future energy management requirements of the smart grid. The existing and envisioned applications of CRSN-based smart grid include substation automation, overhead transmission line monitoring, home energy management, advanced metering infrastructure, wide-area situational awareness, demand response, outage management, distribution automation, asset management. To realize these applications, in this paper, honey bee mating optimization-based routing and cooperative channel assignment algorithms have been proposed. The developed framework significantly decreases the probability of packet loss and preserves high link quality among sensor nodes in harsh smart grid spectrum environments. The proposed approach performance has been evaluated in terms of packet delivery ratio, delay, and energy consumption demonstrating that it has successfully addressed the QoS requirements of most of the SG applications presented. (C) 2017 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.Conference Object Citation - WoS: 24Pre-Service Elementary Teachers' Motivations to Become a Teacher and Its Relationship With Teaching Self-Efficacy(Elsevier Science Bv, 2014-10) Bilim, IbrahimThis study investigated 341 pre-service elementary teachers' motives to become a teacher using Factors Influencing Teaching Choice (FIT-Choice) theory as a basis. It then investigated how these motivations change as candidates follow their training and these motivations' relationship with teaching self-efficacy. The results suggests that Altruistic motives (make social contribution, shape future of children and enhance social equity) were the most influential followed by prior teaching and learning experiences, work with children/adolescents, and job security. Intrinsic motives (perceived teaching ability and intrinsic career value) came next. ANOVA results suggest that the motivations for choosing this profession remain stable between Freshman, Sophomore and Junior candidates. Teaching self-efficacy was positively related to intrinsic motives and negatively related to "fallback career" motives of elementary teacher candidates. Implications of the results are further discussed. (C) 2014 The Authors. Published by Elsevier Ltd.