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Permanent URI for this collectionhttps://ada.atilim.edu.tr/handle/123456789/19

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Citation Count: 13
[1,2,5]thiadiazolo[3,4-g]quinoxaline acceptor-based donor-acceptor-donor-type polymers: Effect of strength and size of donors on the band gap
(Wiley, 2017) Gokce, Gurcan; Karabay, Baris; Cihaner, Atilla; Ozkut, Merve Icli; Chemical Engineering
Electrochromic polymers based on [1,2,5]thiadiazolo[3,4-g]quinoxaline acceptor and thiophene, 3,4-ethylenedioxythiophene and 3,3-didecyl-3,4-proylenedioxythiophene donors, namely poly(6,7-diphenyl-4,9-di(thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline) (P1), poly(4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-6,7-diphenyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline) (P2), and poly(4-(3,3-didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)-9-(3,3-didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-8-yl)-6,7-diphenyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline) (P3), respectively, were electrochemically and/or chemically synthesized and characterized. Electrochemical and optical properties of the polymers were then investigated. The results, which were obtained electrochemically and optically, indicate that the polymers bearing the same acceptor and different donor units have a band gap range of 0.59-1.24 eV depending on the strength and size of the donor units and band gap determination method. A significant finding in this study was the phenomenon that when the acceptor is physically huge, the general rule that a weak donor would have a high band gap whereas a strong donor would have low band gap can be broken due to the torsional angles/steric hindrances involved with physically large donor molecules. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3483-3493
Citation Count: 102
A 1.6-mm, metal tube ultrasonic motor
(Ieee-inst Electrical Electronics Engineers inc, 2003) Cagatay, S; Koc, B; Uchino, K
A miniaturized metal tube ultrasonic motor, the dimensions of which are 1.6 mm in diameter and 6 rum in length, was developed. Two flattened surfaces with 90-degrees were ground on the outer surface of the stator. Two PZT-based piezoelectric ceramics were bonded onto these flat surfaces. The asymmetrical surface of the stator developed the split of the two degenerated orthogonal bending modes, resulting in a wobble motion. The working frequency of the 1.6-mm motor with 6 mm in length was 130 kHz. A torque of 0.5 mNm was reached at a maximum power of 45 mW with a speed of 45 rad/sec. The maximum efficiency was 16%.
Citation Count: 0
16S Bacterial Metagenomic Analysis of Herby Cheese (Otlu Peynir) Microbiota
(Istanbul Univ-cerrahpasa, 2021) Sudağıdan, Mert; Yurt, Mediha Nur Zafer; Taşbaşı, Behiye Büşra; Acar, Elif Esma; Ömeroğlu, Esra Ersoy; Uçak, Samet; Aydın, Ali
Cheese microbiota may contain various bacterial species due to the use of different types of milk, rennet, and herbs. In this study, the distribution of the dominant bacteria present in the microbiota of herby cheese samples (n = 13) were examined by the next generation sequencing (NGS) technique. DNA was extracted both directly from cheese samples and after pre-enrichment. The metagenomic analysis of the NGS results revealed that Firmicutes were dominant both in DNA directly extracted from herby cheese (KOP), and pre-enriched samples (OP), at the phylum level. At the genus level, Lactobacillus, Lactococcus, and Streptococcus were dominant in the KOP samples, whereas in the OP samples, Enterococcus, Streptococcus, and Bacillus were determined as the dominant bacterial genera. Although Lactococcus raffinolactis and Streptococcus salivarius were dominant in the KOP samples, Enterococcus faecalis and S. salivarius were dominant in the OP samples. The Shannon species diversity index and principal coordinates analysis (PCoA) were used to determine the distribution in KOP and OP samples at the genus level. The PCoA of KOP-10, KOP-11, KOP-2, and KOP-7, KOP-3, and KOP-6 samples showed the wide distribution, whereas KOP-5, KOP-8, KOP-9, and KOP-14 herby cheese samples were closely related. The OP samples, especially OP-7 and OP-14, showed wide distribution in comparison to other OP samples. Finally, the dominant bacterial communities were identified by DNAbased metagenomic analysis, and this is the first report to elucidate the microbiota of herby cheese produced in Turkey using the NGS technique.
Citation Count: 5
2-D digital filter realization without overflow oscillations
(Pergamon-elsevier Science Ltd, 2013) Singh, Vimal; Department of Mechatronics Engineering
A novel criterion for the elimination of overflow oscillations in 2-D state-space digital filters described by the Roesser model employing two's complement overflow arithmetic is presented. The criterion takes the form of linear matrix inequality (LMI) and, hence, is computationally tractable. The criterion is a generalization and improvement over an earlier criterion. An example shows the effectiveness of the new criterion. (C) 2012 Elsevier Ltd. All rights reserved.
Citation Count: 4
2D FE modelling of machining: A comparison of different approaches with experiments
(2005) Bil,H.; Tekkaya,A.E.; Kiliç,S.E.; Manufacturing Engineering
[No abstract available]
Citation Count: 5
3-D Dynamic UAV Base Station Location Problem
(informs, 2021) Cicek, Cihan Tugrul; Shen, Zuo-Jun Max; Gultekin, Hakan; Tavli, Bulent; Industrial Engineering
We address a dynamic covering location problem of an unmanned aerial vehicle base station (UAV-BS), in which the location sequence of a single UAV-BS in a wireless communication network is determined to satisfy data demand arising from ground users. This problem is especially relevant in the context of smart grid and disaster relief. The vertical movement ability of the UAV-BS and nonconvex covering functions in wireless communication restrict utilizing classical planar covering location approaches. Therefore, we develop new formulations to this emerging problem for a finite time horizon to maximize the total coverage. In particular, we develop a mixed-integer nonlinear programming formulation that is nonconvex in nature and propose a Lagrangean decomposition algorithm (LDA) to solve this formulation. Because of the high complexity of the problem, the LDA is still unable to find good local solutions to large-scale problems. Therefore, we develop a continuum approximation (CA) model and show that CA would be a promising approach in terms of both computational time and solution accuracy. Our numerical study also shows that the CA model can be a remedy to build efficient initial solutions for exact solution algorithms. Summary of Contribution: This paper addresses a facet of mixed integer nonlinear programming formulations. Dynamic facility location problems (DFLPs) arise in a wide range of applications. However, classical DFLPs typically focus on the two-dimensional spaces. Emerging technologies in wireless communication and some other promising application areas, such as smart grids, have brought new location problems that cannot be solved with classical approaches. For practical reasons, many research attempts to solve this new problem, especially by researchers whose primary research area is not OR, have seemed far from analyzing the characteristics of the formulations. Rather, solution-oriented greedy heuristics have been proposed. This paper has two main objectives: (i) to close the gap between practical and theoretical sides of this new problem with the help of current knowledge that OR possesses to solve facility location problems and (ii) to support the findings with an exhaustive computational study to show how these findings can be applied to practice.
Citation Count: 0
A 30-year journey of hospitality and tourism research: a comprehensive topic modeling analysis
(Emerald Group Publishing Ltd, 2024) Kurt, Senol; Assefa, Feven Zewdie; Tuzlukaya, Sule Erdem; Karatepe, Osman M.; Business
PurposeThe purpose of this study is to provide an overview of the research conducted on hospitality and tourism articles published in Q1 category journals from 1990 to 2023. This study also aims to measure the topic prevalence in selected journals throughout the years, their change over time and similarities of journals.Design/methodology/approachLatent dirichlet allocation algorithm is used as a topic modeling method to identify and analyze topics in hospitality and tourism research over the past 30 years.FindingsThe results of the study indicate that hospitality and tourism research has recently focused on topics such as employee behavior, customer satisfaction, online reviews, medical tourism and tourist experience. However, the results also indicate a negative trend in topics such as hotel management, sustainability, profession, economic growth and tourist destination.Practical implicationsThis study can be used to examine the evolution of research patterns over time, find hot and cold themes and uncover untapped or understudied areas. This can aid academics in their investigations and practitioners in making sound strategic decisions.Originality/valueThis study contributes to the existing literature by providing a new approach and comprehensive analysis of hospitality and tourism research topics. It delineates an overview of the progression of hospitality and tourism research over the past 30 years, identifies the trending topics and explores the potential impacts that these identified topics may have on future studies.
Citation Count: 4
3D Bioprinting tissue analogs: Current development and translational implications
(Sage Publications inc, 2023) Liu, Suihong; Cheng, Lijia; Liu, Yakui; Zhang, Haiguang; Song, Yongteng; Park, Jeong-Hui; Ramalingam, Murugan
Three-dimensional (3D) bioprinting is a promising and rapidly evolving technology in the field of additive manufacturing. It enables the fabrication of living cellular constructs with complex architectures that are suitable for various biomedical applications, such as tissue engineering, disease modeling, drug screening, and precision regenerative medicine. The ultimate goal of bioprinting is to produce stable, anatomically-shaped, human-scale functional organs or tissue substitutes that can be implanted. Although various bioprinting techniques have emerged to develop customized tissue-engineering substitutes over the past decade, several challenges remain in fabricating volumetric tissue constructs with complex shapes and sizes and translating the printed products into clinical practice. Thus, it is crucial to develop a successful strategy for translating research outputs into clinical practice to address the current organ and tissue crises and improve patients' quality of life. This review article discusses the challenges of the existing bioprinting processes in preparing clinically relevant tissue substitutes. It further reviews various strategies and technical feasibility to overcome the challenges that limit the fabrication of volumetric biological constructs and their translational implications. Additionally, the article highlights exciting technological advances in the 3D bioprinting of anatomically shaped tissue substitutes and suggests future research and development directions. This review aims to provide readers with insight into the state-of-the-art 3D bioprinting techniques as powerful tools in engineering functional tissues and organs.
Citation Count: 0
3D Printing and Bioprinting Technologies in Pharmaceutics: Commercial Perspectives and Market Analytics.
(CRC Press, 2023) Liu,S.; Liu,Y.; Hu,Q.; Zhang,H.; Park,J.-H.; Dashnyam,K.; Ramalingam,M.
Three-dimensional (3D) printing is a fast-emerging applied technology that has had a major impact on healthcare applications, particularly the pharmaceutical field, over the last decades. 3D printing, also known as additive manufacturing (AM), has been used for building a wide range of 3D structures and complex geometries layer by layer through a computer-aided design since the early 1980s [1]. 3D printing widens the manufacturing window, allowing the production of customized medical devices from metals, ceramics, and polymers without the need for molds or machining which was typically used in conventional formative and subtractive manufacturing [1,2]. Since the early 2000s, 3D printing has been successfully applied in pharmaceutics, tissue engineering, and regenerative medicine due to its capability for the fabrication of 3D biological constructs with high shape complexity and fidelity [3,4]. 3D printing involving biological substances is called 3D bioprinting, where bioinks, which comprise a choice of biomaterials, cells, drugs, proteins, or growth factors, play a major role in printing desired constructs or devices [5]. 3D bioprinting could transform the future of medicine, that is, the way drugs and complex living tissues are made. © 2024 selection and editorial matter, Jose Luis Pedraz Muñoz, Laura Saenz del Burgo Martínez, Gustavo Puras Ochoa, Jon Zarate Sesma; individual chapters, the contributors
Citation Count: 2
4-Stage Target Detection Approach in Hyperspectral Images
(IEEE Computer Society, 2018) Ozdil,O.; Gunes,A.; Esin,Y.E.; Ozturk,S.; Demirel,B.; Department of Mechatronics Engineering
Practical target detection systems require an automatic way to detect targets with high accuracy. Detection errors is not tolerable and they should be reduced as much as possible. In classical detection systems, generally single target detection algorithm is performed and the result will be evaluated according to the thresholding techniques. However, in these uncontrolled systems, false alarm rate strongly depends on the thresholding technique success. It is very hard to find a general and constant threshold value for images taken at different conditions and practical detection systems needs reliable threshold value. In this paper, we propose a new multi-stage target detection system which is the combination of different detection algorithms and thresholding technique. This system compose of 4-stages, i.e. namely 1-initial target detection (ACE, GLRT), 2-adaptive Constant False Alarm Rate (CFAR) thresholding, 3-spatially grouping, 4-statistical confidence operation. This system configuration removes the need for interactive user and it automatically implements confirmation and rejection steps. Moreover, this system can be used both for pure pixel and subpixel target detection purposes and it reduces computational processing time considerably with the implementation of consequtive processing stages. © 2018 IEEE.
Citation Count: 2
Ab initio study of structural and electronic properties of single crystal and core/shell II-VI semiconductor nanowires
(Elsevier, 2016) Pekoz, R.; Department of Electrical & Electronics Engineering
Structural and electronic properties of pristine and H-passivated wurtzite type ZnSe, ZnTe nanowires and ZnX/ZnY (X = Se(Te) and Y = Te(Se)) core/shell nanowires oriented along the [0001] direction have been investigated using first-principles calculations. The changes in the electronic structure of the nanowires due to the quantum confinement and morphology have been searched. Quantum confinement increases the band gap energy as the diameters of ZnSe and ZnTe nanowires decrease. Both homostructured and heterostructured nanowires are found to show a semiconducting character with direct band gaps at Gamma-point. Changing the morphology from homostructured nanowires to heterostructured core/shell nanowires has an important impact on the electronic structure. For instance, the charge separation of electrons and holes along the infinite direction of core/shell nanowires shows a strong preference for electron(hole) states localized inside ZnSe(ZnTe) regions. (C) 2016 Elsevier B.V. All rights reserved.
Citation Count: 5
Absorption edge and optical constants of Tl₂Ga₂S₃Se crystals from reflection and transmission, and ellipsometric measurements
(Elsevier, 2012) Isik, M.; Gasanly, N. M.; Department of Electrical & Electronics Engineering
The optical properties of Tl2Ga2S3Se layered crystalline semiconductors were investigated from transmission, reflection and ellipsometric measurements. The experimental results of the room temperature transmission and reflection measurements performed in the wavelength range of 400-1100 nm showed the presence of both indirect and direct transitions in the band structure of the crystals with 2.38 and 2.62 eV band gap energies. Spectroscopic ellipsometry measurements on Tl2Ga2S3Se crystals were carried out on the layer-plane (0 0 1) surfaces with light polarization E perpendicular to c* in the 1.20-4.70 eV spectral range at room temperature. The real and imaginary parts of the dielectric function as well as refractive and absorption indices were found as a result of analysis of ellipsometric data. The Wemple-DiDomenico single-effective-oscillator model was used to study the dispersion of the refractive index in the below band gap energy range. The structures of critical points have been characterized from the second derivative spectra of the dielectric function. The analysis revealed four interband transition structures with 3.14, 3.40, 3.86 and 4.50 eV critical point energies. (C) 2012 Elsevier B.V. All rights reserved.
Citation Count: 4
Abstract conceptual database model approach
(2013) Çaĝiltay,N.E.; Topalli,D.; Aykaç,Y.E.; Tokdemir,G.; Information Systems Engineering; Computer Engineering
One of the main objectives of the software engineers is to provide software related solutions for social problems and to increase the availability of social welfare. In that sense, the quality of the software is directly related to address the users' needs and their level of satisfaction. To reflect user requirements to the software processes, the correct design of the database model provides a critical stage during software development. Database design is a fundamental tool for modeling all the requirements related to users' data. The possible faulty conditions in database design have adverse effects on all of the software development processes. The possible faulty conditions can also cause continuous changes in the software and the desired functionality of the targeted system which may result in user dissatisfaction. In this context, reflecting the user requirements accurately in the database model and understanding of the database model correctly by every person involved in the software development process is the factor that directly affects the success of software systems' development. In this study, a two-stage conceptual data modeling approach is proposed to reduce the level of complexity, to improve the understandability of database models and to improve the quality of the software. This study first describes the proposed two-stage conceptual data modeling. Than the proposed method's impact on software engineers' comprehension is also investigated and the results are compared with the degree of complexity of the related conceptual data models. Results of this study show that, the proposed two-stage conceptual modeling approach improves the understanding levels of software engineers and eliminated possible defects in this stage. © 2013 The Science and Information Organization.
Citation Count: 1
Acceptance of Educational Use of AI Chatbots in the Context of Self-Directed Learning with Technology and ICT Self-Efficacy of Undergraduate Students
(Taylor & Francis inc, 2024) Esiyok, Elif; Gokcearslan, Sahin; Kucukergin, Kemal Gurkan; Tourism Management; Public Relations and Advertising
For long now, the use of Artificial Intelligence (AI) chatbots in higher education to support and engage learners in classroom learning activities has been attracting the attention of researchers. The acceptance of this technology for learning purposes is indicative of learners' intentions and actual use in the future. Hence, this study aims to test the educational use of AI chatbots in the context of self-directed learning with technology (SDLT) along with information and communication technology (ICT) self-efficacy, using the extended Technology Acceptance Model (TAM). The study involved 414 undergraduate students, and the research model was tested by utilizing the Partial Least Square Structural Equation Model (PLS-SEM). The results indicate that ICT self-efficacy affects only the perceived ease of use (PEU), whereas PEU and perceived usefulness have a positive effect on the intention to use AI chatbots. Moreover, SDLT is shown to affect both the intention and the actual use of AI chatbots. As such, it is suggested - among other notes - that universities update their curricula and activities to support SDLT, and also organize activities in order to increase ICT self-efficacy among students.
Citation Count: 28
Accessibility evaluation of top university websites: a comparative study of Kyrgyzstan, Azerbaijan, Kazakhstan and Turkey
(Springer Heidelberg, 2018) Ismailova, Rita; Inal, Yavuz; Information Systems Engineering
It is important that university websites and services offered through their sites are used effectively, efficiently and satisfactorily by the whole target group of the university, including disabled users. However, universities in many countries are still unable to meet the criteria for web accessibility. This study aimed to test the websites of the top universities in Kyrgyzstan, Kazakhstan, Azerbaijan and Turkey using automated assessment tools. The results showed that university websites are more popular in Turkey, and in Turkish universities developers pay more attention to the performance of websites, followed by websites of Azerbaijani, Kyrgyz and Kazakh universities. The majority of the university websites in the study did not meet the WCAG 2.0 accessibility criteria. Only two Kyrgyz and two Kazakh university websites attained conformance level A, and only three, one Kyrgyz and two Kazakh, achieved accessibility conformance level AAA. Based on the results, it was determined that universities included in the present study need to devote more effort to making their websites more accessible for their users.
Citation Count: 33
Accuracy assessment of temperature trends from ERA5 and ERA5-Land
(Elsevier, 2023) Yilmaz, Meric; Civil Engineering
Many environmental processes and ecological systems are being affected by the warming temperatures as a result of climate change. To correctly identify and attribute the uncertainty estimates in these systems, an investigation of tem-perature trend signal existing in the datasets that are used to study such systems is necessary. In this study, the trend of widely used ERA5 and ERA5-Land temperature estimates between 1951 and 2020 were validated using temperature trends from ground station-based observations in Turkey. The investigation included datasets obtained over 540 stations, and the seasonality and spatio-temporal variability of the trend accuracy was also investigated. On average, the trends of observations over all stations were 0.82 degrees C/decade and 0.30 degrees C/decade for the periods 2001-2020 and 1951-2020, respectively, indicating strong evidence of climate change. When the model datasets used spatially and temporally continuous datasets, the trends identified were 0.91 degrees C/decade and 0.21 degrees C/decade over the entire Turkey for the years 2001-2020 and 1951-2020, respectively. The difference in the 70-year trends of the two esti-mates was attributed to the missing datasets in observations. The differences between the trends of model estimates and observations were higher for the first decade than for the last two decades, stressing the impact of improved model estimates over time. All products showed heavy seasonality, suggesting that winter trends (1.3 degrees C/decade on average) are much higher than the summer (0.3 degrees C/decade) between 2001 and 2020. The results indicated a high degree of consistency between the trends of ERA5/ERA5-Land and observations, implying they may be used as a replacement to observations.
Citation Count: 15
An accurate optical gain model using adaptive neurofuzzy inference system
(National Institute of Optoelectronics, 2009) Çelebi,F.V.; Altindag,T.; Computer Engineering
This paper presents a single, simple, new and an accurate optical gain model based on adaptive neuro-fuzzy inference system (ANFIS) which combines the benefits of Artificial Neural Networks (ANNs) and Fuzzy Inference Systems (FISs). The dynamic optical gain model results are in very good agreement with the previously published experimental findings.
Citation Count: 0
ACE-PE: An Automated Code Evaluation Software Tool For Programming Education
(Institute of Electrical and Electronics Engineers Inc., 2023) Alper,B.; Nazlioglu,S.; Kilic,H.; Computer Engineering; Software Engineering
An automated code evaluation tool that combines the usage of software quality metrics and object-oriented programming teaching subjects is designed and developed. The tool (called ACE-PE) gives flexibility to instructors to assess student assignments at the level of precision of specific subjects which reveals the degree of student's understanding of covered subjects, and to observe his/her own effort, as well. Provision of content-aware automated fast feedback to students to improve quality of their products and development efforts is another outcome of the proposed solution. © 2023 IEEE.
Citation Count: 0
ACEMP-OPTIM 2019 Opening Speech
(Institute of Electrical and Electronics Engineers Inc., 2019) Bulent Ertan,H.; Electrical-Electronics Engineering
[No abstract available]
Citation Count: 3
Achieving business benefits from ERP systems
(IGI Global, 2008) Mishra,A.; Software Engineering
Enterprise resource planning (ERP) systems are becoming popular in medium and large-scale organizations all over the world. As companies have to collaborate across borders, languages, cultures, and integrate business processes, ERPs will need to take globalization into account, be based on a global architecture, and support the features required to bring all the worldwide players and processes together. Due to the high cost of implementation for these systems, organizations all over the world are interested in evaluating their benefits in the short and long terms. This chapter discusses various kinds of business benefits in a comprehensive way in order to justify the acquisition and implementation of ERP systems in organizations in the present global context. © 2008, IGI Global.

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