Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://gcris.khas.edu.tr/handle/20.500.12469/1248

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Citation Count: 1
Active and Reactive Power Load Profiling Using Dimensionality Reduction Techniques and Clustering
(Institute of Electrical and Electronics Engineers Inc., 2019) Yetkin, E. Fatih; Ceylan, Oğuzhan; Papadopoulos, Theofilos A.; Kazaki, Anastasia G.; Barzegkar-Ntovom, Georgios A.
This paper proposes a methodology to characterize active and reactive power load profiles. Specifically, the approach makes use of fast Fourier Transform for conversion into frequency domain, principle component analysis to reduce the dimension and K-means++ to determine the representative load profiles. The data set consists of five-year measurements taken from the Democritus University of Thrace Campus. Test days were also classified as working and non-working. From the results it is observed that the proposed methodology determines representative load profiles effectively both regarding active and reactive power.
Citation Count: 3
Activist Communication Design on Social Media: the Case of Online Solidarity Against Forced Islamic Lifestyle
(Sage Publications, 2021) Arda Güney, Talat Balca; Akdemir, Ayşegül
This article explores the relationship between connective and collective group identity through the example of “You Won’t Walk Alone,” a social media platform of solidarity for women suffering from the pressures of Islamic dress code in Turkey. While Turkey has a long history of conservative women’s initiatives against secular institutional code and of secular women against Islamic and misogynist social reactions, the social media platform You Won’t Walk Alone (Yalnız Yürümeyeceksin) illustrates a striking self-reflexivity of women mobilizing against their very own conservative communities. The research is based on multimodal content analysis of the posts including both images and texts in order to grasp to what extent social media offers a genuine public space for anonymous participants of the online platform as opposed to digitally networked movements which primarily reflect personalized agency. We analyze how connective and collective group identity can be correlated in this case in which online participants build solidarity by sharing content anonymously. Hence, this article questions the ways in which activist design of communication affects and shapes activism through this case study.
Citation Count: 5
Analysis of Mixed-Element Structures Formed With Shunt Capacitors Separated by Transmission Lines
(IEEE-Inst Electrical Electronics Engineers Inc, 2019) Şengül, Metin Y.; Çakmak, Gökhan
In this brief, the analysis of mixed-element structures formed with shunt capacitors separated by commensurate transmission lines is performed first time in the literature. First, a low-pass lumped-element ladder network is considered. Then the series inductors are replaced with commensurate transmission lines. As a result, a practically important mixed-element structure is obtained. Then the description of the structure by means of two frequency variables (one for shunt capacitors and one for transmission lines) is detailed: Explicit expressions for the coefficients of the descriptive two-variable polynomials in terms of the coefficients of the single variable boundary polynomials are derived for various numbers of elements, which are obtained first time in the literature. Finally, a mixed-element broadband matching network is designed to illustrate the usage of the obtained expressions. If it is preferred not to have shunt capacitors, they can be replaced with open-ended stubs via Richard's transformation. So the resultant circuit is extremely suitable for microstrip fabrication.
Citation Count: 7
Antifungal Screening and in Silico Mechanistic Studies of an In-House Azole Library
(2019) Sarı, Suat; Kart, Didem; Sabuncuoğlu, Suna; Doğan, İnci Selin; Özdemir, Zeynep; Bozbey, İrem; Gencel, Melis; Eşsiz, Şebnem; Reynisson, Jóhannes; Karakurt, Arzu; Saraç, Selma; Dalkara, Sevim
Systemic Candida infections pose a serious public health problem with high morbidity and mortality. C. albicans is the major pathogen identified in candidiasis; however, non-albicans Candida spp. with antifungal resistance are now more prevalent. Azoles are first-choice antifungal drugs for candidiasis; however, they are ineffective for certain infections caused by the resistant strains. Azoles block ergosterol synthesis by inhibiting fungal CYP51, which leads to disruption of fungal membrane permeability. In this study, we screened for antifungal activity of an in-house azole library of 65 compounds to identify hit matter followed by a molecular modeling study for their CYP51 inhibition mechanism. Antifungal susceptibility tests against standard Candida spp. including C. albicans revealed derivatives 12 and 13 as highly active. Furthermore, they showed potent antibiofilm activity as well as neglectable cytotoxicity in a mouse fibroblast assay. According to molecular docking studies, 12 and 13 have the necessary binding characteristics for effective inhibition of CYP51. Finally, molecular dynamics simulations of the C. albicans CYP51 (CACYP51) homology model's catalytic site complexed with 13 were stable demonstrating excellent binding.
Citation Count: 1
An Approach To Evaluate Cam Software Alternatives
(TAYLOR & FRANCIS LTD, 2020) Ayağ, Zeki
The selection process for the best computer-aided manufacturing (CAM) software among a set of potential number of alternatives in market has been critical issue for most companies that aim to make their design/manufacturing-related activities automated. Because this selection process is very vital for companies because a wrong decision might put them into a difficult position in terms of economical, market share and time spent. Therefore, today's companies have used different multiple-criteria decision making (MCDM) methods for the evaluation study of CAM software alternatives to make this complex process easily applicable and not time-consuming. Among the MCDM methods in literature, the analytic hierarchy process (AHP) method has been widely used for various MCDM problems in both academic researches and industrial practices. However, in some cases, because of the vagueness and uncertainty on the judgments of decision maker(s), the crisp pair wise comparison in the conventional AHP seems to be insufficient and imprecise to capture the right judgments of decision maker(s). Therefore, a fuzzy logic method is integrated in the pair wise comparison of AHP to make up for this deficiency in the conventional AHP, called as fuzzy AHP. Moreover, the proposed approach is also realized on a case study.
Citation Count: 5
Assortment Optimization With Log-Linear Demand: Application at a Turkish Grocery Store
(Elsevier, 2019) Hekimoğlu, Mustafa; Sevim, İsmail; Aksezer, Çağlar Sezgin; Durmuş, İpek
In retail sector product variety increases faster than shelf spaces of retail stores where goods are presented to consumers. Hence assortment planning is an important task for sustained financial success of a retailer in a competitive business environment. In this study we consider the assortment planning problem of a retailer in Turkey. Using empirical point-of-sale data a demand model is developed and utilized in the optimization model. Due to nonlinear nature of the model and integrality constraint we find that it is difficult to obtain a solution even for moderately large product sets. We propose a greedy heuristic approach that generates better results than the mixed integer nonlinear programming in a reasonably shorter period of time for medium and large problem sizes. We also proved that our method has a worst-case time complexity of O(n 2 )while other two well-known heuristics’ complexities are O(n 3 )and O(n 4 ). Also numerical experiments reveal that our method has a better performance than the worst-case as it generates better results in a much shorter run-times compared to other methods. © 2019 Elsevier Ltd
Citation Count: 0
Audience Tracking and Cheering Content Control in Sports Events
(IEEE, 2020) Yeşilyurt, Gözdenur; Dursun, Sefa; Kumas, Osman; Çakir, Nagehan; Arsan, Taner
Swearing cheers encountered in sports competitions do not comply with sports ethics and morals. Even if this kind of cheering is a group, the entire tribune block is penalized in accordance with the current rules. This method is not preventive and individual punishment should be used. The aim of this study is to determine the individuals who cheer with swearing content. In this study, the person detection is made with the multi-task cascaded convolutional neural network. Moreover, facial landmarks representing the facial regions and the regions related to them are determined as a result of this process. The mouth region is also determined by means of these important points removed, and finally the mouth is determined according to the equation. The face recognition is carried out because the person would be in a state of yelling if the mouth opening ratio exceeds the threshold value by determining the rate of opening. Landmarks extracted from the facial regions for the face recognition are transformed into feature vectors by FaceNet, and the model is created by classifying these vectors with classifiers to use in recognition process. When evaluated in terms of industry, face recognition and detection systems find a wide field of study.
Citation Count: 22
Bottom-Up Nationalism and Discrimination on Social Media: an Analysis of the Citizenship Debate About Refugees in Turkey
(Sage Publications Ltd, 2020) Bozdağ Bucak, Çiğdem
This study analyzes social media representations of refugees in Turkey and discusses their role in shaping public opinion. The influx of millions of Syrian refugees in Turkey has created heated debates about their presence and future in the country. One of these debates was triggered by President Erdogan's statement that Turkey would issue citizenship rights to Syrians in July 2016. Due to a lack of critical voices about refugee issues in Turkey's mass media sphere, social media has become a key platform for citizens to voice their opinions. Through a discourse analysis of tweets about the issue of refugees' citizenship, I will map different perceptions of refugees in Turkey. I argue that despite contesting discourses about Syrians, the debate on social media reinforces nationalism and an ethnocentric understanding of citizenship in Turkey. As the number of refugees and migrants increases rapidly worldwide, they become the new 'others' of national imagined communities. Social media becomes a key communication space where the nation is discursively constructed in a bottom-up manner through manifestations of 'us' and 'them'. The analysis shows that social media contributes to trivialization and normalization of discrimination and hatred against Syrian refugees through disseminating overt discourses of 'Othering'. Social media also enables more covert forms of discrimination through 'rationalized' arguments that are used to justify discrimination through the basis of false/non-verified information. Thus, Twitter becomes a space for critical, bottom-up, yet nationalistic and discriminatory statements about refugees.
Citation Count: 12
Cognitive Styles and Religion
(Elsevier B.V., 2021) Yılmaz, Onurcan
I discuss recent research suggesting that individual differences in cognitive style give rise to and explain religious and related supernatural and paranormal beliefs. To do so, I illustrate intuitive cognitive biases (e.g., anthropomorphism) underlying these beliefs and then review the accumulated evidence indicating that non-believers are more open-minded, reflective, and less susceptible to holding epistemically suspect beliefs (e.g., conspiracy theories) on average than those who believe in supernatural events or paranormal experiences such as astrology or magic. However, seeing religion as a search for truth positively predicts reasoning performance. Although these findings are robust across diverse measures, evidence for a causal relationship remains mixed. Stronger and more precise manipulations and cross-cultural investigations are needed.
Citation Count: 3
The Collector's World
(Routledge Journals, Taylor & Francıs Ltd, 2020) Diken, Bülent; Laustsen, Carsten Bagge
The article discusses the figure of the collector. We start with positioning the collector in relation to a lack, emphasizing that collecting is not about aesthetic beauty, pleasure or even perfectness, but primarily about filling a gap. The collection itself is merely a by-product of the desire to collect. Discussing how this desire is socially mediated, we move on to contextualizing the collector in relation to the distinction between the useful and the useless. We stress, in this context, that collecting is an inoperative praxis. This is followed by a discussion of the collector's psychopathology in terms of affects and interpassivity. Finally, we turn to the history of the collector and to collecting as a field in sociological terms, and end with articulating a typology of the collector.
Citation Count: 0
A Comparative Study of Energy Models for Turkish Electricity Market Using Leap
(IEEE Computer Society, 2019) Massaga, Daniel Julius; Kirkil, Gökhan; Çelebi, Emre
Fossil fuel thermal power plants constitute a large part of the Turkish electricity generation capacity. Turkish government has been developing several energy policy documents to evaluate how various renewable energy sources of the country can be utilized optimally in the generation of electricity within the next 30 years. This study considers three scenarios in the transition to renewable energy for Turkey; the business as usual (BAU), energy conservation (EC) and renewable energy (REN) scenarios. EC scenario considers the use of energy-efficient appliances and imposing a carbon tax, whereas REN scenario considers increasing the share of the renewable energy sources as much as possible in the power generation mix. These scenarios were evaluated in terms of cost and environmental impact. The LEAP (Long-range Energy Alternatives Planning Model) was used in the research. The REN scenario has been shown to be the optimal energy policy option for Turkey in terms of cost and environmental impact.
Citation Count: 1
A Comparative Study of Surrogate Based Learning Methods in Solving Power Flow Problem
(IEEE, 2020) Ceylan, Oğuzhan; Taşkın, Gülsen; Paudyal, Sumit
Due to increasing volume of measurements in smart grids, surrogate based learning approaches for modeling the power grids are becoming popular. This paper uses regression based models to find the unknown state variables on power systems. Generally, to determine these states, nonlinear systems of power flow equations are solved iteratively. This study considers that the power flow problem can be modeled as an data driven type of a model. Then, the state variables, i.e., voltage magnitudes and phase angles are obtained using machine learning based approaches, namely, Extreme Learning Machine (ELM), Gaussian Process Regression (GPR), and Support Vector Regression (SVR). Several simulations are performed on the IEEE 14 and 30-Bus test systems to validate surrogate based learning based models. Moreover, input data was modified with noise to simulate measurement errors. Numerical results showed that all three models can find state variables reasonably well even with measurement noise.
Citation Count: 11
Competition and Monopoly in the U.s. Economy: What Do the Industrial Concentration Data Show?
(Sage Publications, 2021) Davis, Leila; Orhangazi, Özgür
A recent series of academic studies, think-tank reports, and news articles shows widespread attention to rising industrial concentration and market power in the U.S. economy. In this paper, we focus on concentration in the U.S. nonfinancial corporate sector to make three contributions to the literature. First, we use examples from the debate on industrial concentration to show that there are often-divergent predictions in the theoretical literature surrounding the expected consequences of concentration and monopolization for nonfinancial firms. Second, we use industry-level concentration data to describe recent trends in average concentration. We show that, while concentration increases across the majority of industries after the late 1990s, the retail and information-services sectors are particularly key for understanding recent trends in average industrial concentration. Third, we link our industry-level analysis with firm-level data to describe the relationship between industrial concentration and nonfinancial corporations' profitability, markups, and investment. Consistent with the ambiguities in the theoretical literature, we find that these relationships are not uniform: while some highly concentrated industries confirm standard expectations with high markups, high profitability, and low investment rates, other highly concentrated industries earn lower-than-average markups and profits, suggesting that - in some industries - increased concentration and intensified competition may go hand in hand.
Citation Count: 5
A Competitive Intelligence Practices Typology in an Airline Company in Turkey
(Springer, 2020) Şahin, Murat; Bisson, Christophe
Oil prices, political instabilities, travel legislations, and many other competitive factors make it essential for any international airline with the instinct to survive to be on constant watch in such a fiercely competitive environment. To meet this need, it is vital for international airline companies to integrate competitive intelligence (CI) into their strategy building process. In this study, we create for the first time a typology of competitive intelligence practices of an international airline company (in Turkey), based on the model developed by (Wright et al.Journal of Strategic Marketing, 20(1), 19-33,2012), and it is one of the very first to investigate Competitive intelligence in this sector. Furthermore, we made a two-step cluster analysis to uncover hidden clusters that change the way of thinking within the company. Our findings show where the company would need to make improvements on the 6 strands of the model which are attitude, gathering, use, location, technological support, and IT support. Yet, that could lead towards stronger business performance. It might also inspire other companies of the airline sector and beyond.
Citation Count: 6
Contemporary Art on the Current Refugee Crisis: the Problematic of Aesthetics Versus Ethics
(British Journal of Middle Eastern Studies, 2019) Arda Güney, Talat Balca
This article focuses on contemporary artworks outlining the current refugee flow from the Middle East to the West namely to European countries together with the US and Canada. Drawing primarily on Jacques Ranciere's conceptualization of ethical art versus aesthetics I explore how various journeys of refugees in its many forms have been represented in the contemporary art scene. My aim is to concretize the theoretical debate surrounding the 'political' engagement of critical art on the issue of refugee representation through various prominent artworks and art practices starting with the well-known image of Alan Kurdi's and Ai Weiwei's replication of this image in his artwork. I will analyse when and in which configurations aesthetics and ethics can be found in contemporary art on the issue of the 'refugee crisis'. I argue that art on refugees can be grouped into two primary categories that I define as 'human condition assessment' and 'agency empowerment'. As such I demonstrate in practice how contemporary art on the current refugee crisis both employs and moves beyond the ethical subject matters by challenging abject victimhood as well as the ideal of egalitarian art for the underrepresented and thus assumingly voiceless depoliticized refugees.
Citation Count: 14
Crystallographic Structure Versus Homology Model: a Case Study of Molecular Dynamics Simulation of Human and Zebrafish Histone Deacetylase 10
(Taylor & Francis, 2020) Uba, Abdullahi İbrahim; Yelekçi, Kemal
Histone deacetylase (HDAC) 10 has been implicated in the pathology of various cancers and neurodegenerative disorders, making the discovery of novel inhibitors of the isoform an important endeavor. However, the unavailability of crystallographic structure of human HDAC10 (hHDAC10) hinders structure-based drug design effort. Previously, we reported the homology modeled structure of human HDAC10 built using the crystallographic structure of Danio rerio (zebrafish) HDAC10 (zHDAC10) (Protein Data Bank (PDB) ID; 5TD7, released on 24 May 2017) as a template. Here, in continuation with our study, both hHDAC10 and zHDAC10, and their respective complexes with trichostatin A (TSA), quisinostat, and the native ligand (in 5TD7), 7-[(3-aminopropyl)amino]-1,1,1-trifluoroheptane-2,2-diol (PDB ID; FKS) were submitted to 100 ns-long unrestrained molecular dynamics (MD) simulations. Comparative analyses of the MD trajectories revealed that zHDAC10 and its complexes displayed higher stability than hHDAC10 and its corresponding complexes over time. Nonetheless, docking of active and inactive set molecules revealed that more reliable conformations of hHDAC10 could be obtained at an extended time period. This study may shed more light on the reliability of hHDAC10 modeled structure for use in selective inhibitor design.Communicated by Ramaswamy H. Sarma.
Citation Count: 7
Daily and Intraday Herding Within Different Types of Investors in Borsa Istanbul
(Routledge Journals, Taylor & Francis Ltd, 2019) Dalgıç, Nihan; Ekinci, Cumhur; Ersan, Oğuz
This paper aims to explore the daily and intraday herd behavior of various investor groups trading in an emerging equity market, Borsa Istanbul (BIST). We analyze a one-year tick-by-tick order and trade data of BIST 100 Index stocks and document differences in herding behavior of investor groups considering market capitalization, market conditions, and announcements as well as daily and intraday periodicities. We find that nonprofessional investors (brokerage houses and domestic funds) tend to herd on large (small) stocks; their herding behavior mostly exhibits a U shape (an inverse U shape) during the day. All types of investors tend to herd in down markets on a daily basis while this behavior disappears, even inverts intraday.
Citation Count: 0
Design of Phase Shifters With Ladder Stubs Via Real Frequency Technique
(World Scientific, 2020) Şengül, Metin Y.
Generally at high frequencies, lumped-elements are not preferred because of their limited range of values. Therefore, in this work, a kind of phase shifter formed with ladder stubs is studied and a new approach to design phase shifter's low pass and high pass sections which are composed of series or shunt connected open-ended or short-ended stubs is proposed. In the approach, since the main focus is to form low pass and high pass two-port sections, switching process is not considered. First, the designer selects the section type and the total number of stubs in the sections; it is not necessary to fix the two-port section topologies and not necessary to derive the characteristic impedance and delay expressions for the stubs. In the example, 5-stub two-port sections of a 180∘ phase shifter are designed by means of the proposed approach.
Citation Count: 9
Determinants of Investment in Turkey: a Firm-Level Investigation
(Routledge Journals Taylor & Francis Ltd, 2019) Gezici, Armağan; Orhangazi, Özgür; Yalçın, Cihan
In this article we analyze the financing constraints-investment link for the case of Turkey between 1996 and 2013. As different from the existing studies on Turkey we use a more comprehensive data set that includes both publicly-traded and privately-owned firms and analyze the differences in constraints across small- and medium-sized firms and large firms. In addition to the commonly used cash-flow sensitivities we use alternative measures of constraints build from multiple firm specific variables. We find that small- and medium-sized manufacturing firms in Turkey are subject to financing constraints regardless of the measure used.
Citation Count: 8
Determining Matchdays in Sports League Schedules To Minimize Rest Differences
(ELSEVIER, 2020) Çavdaroğlu, Burak; Atan, Tankut
Many sports leagues first announce the games to be played in each round and then determine their matchdays as the season progresses. This study focuses on the fairness criterion of minimizing the total rest difference among opposing teams to find the matchdays for an announced schedule. We show that the problem is decomposable into optimizing the rounds separately. We also provide a polynomial-time exact algorithm for canonical schedules.

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