Araştırma Çıktıları | WoS | Scopus | TR-Dizin | PubMed

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Citation - WoS: 9
Citation - Scopus: 8
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 - WoS: 1
Citation - Scopus: 1
Judgments of Capability and Conformity as Distinct Forms of Social Judgments, and the Way They Interact To Shape Evaluator Decisions
(Wiley, 2020) Topaler, Başak; Küp, Eyuep Tolunay
Objective Social judgments are evaluators' opinions about the social properties of a set of actors. Different types of judgments rendered by the evaluators and potential interactions between them may have major consequences for the actors who are evaluated. In this article, we distinguish between judgments of capability and conformity, and examine their concurrent and interdependent effects on evaluator impressions. Methods We investigate these dynamics in the context of authors competing for the best paper award at the Academy of Management (AoM) conference. Results Findings of our empirical analyses demonstrate interdependent effects of capability and conformity judgments on the committee members' decisions. We demonstrate that evaluators expect greater conformity to their ideal template from more capable actors who have greater potential to contribute to these ideals. Conclusion Our study advances the literature on social judgments by showing that congruence (or incongruence) among distinct types of judgment shape evaluators' decisions, beyond their independent effects.
Classification of Adhd Using Ensemble Algorithms With Deep Learning and Hand Crafted Features
(IEEE, 2019) Çiçek, Gülay; Çevik, Mesut; Akan, Aydın
Attention Deficit Hyperactivity (ADHD) is a common neurodevelopmental disorder that typically appears in early childhood. Methods developed for diagnosing gives different results at different times. This is a major obstacle in the diagnosis of disease. Diagnosis model of ADHD must be unique, objective, and reliable. In this study, comparative evaluations of both manual and deep features for classification of structural magnetic resonance images is presented. For this purpose, datasets of NPIstanbul Neuropsychiatry Hospital and public datasets of ADHD-200 is used. In order to characterize MRI images First Order, Second Order statictical features and the Alexnet architecture is used. Images are classified with the ensemble algorithm. In order to determine classification performance, accuracy, sensitivity, specificity, tp rate, fp rate and F-measure values are taken into consideration. It was observed that the combination of three manually extracted data sets yielded more successful results in characterizing the data.
Graph Optimized Locality Preserving Projection Via Heuristic Optimization Algorithms
(IEEE, 2019) Ceylan, Oğuzhan; Taşkın, Gülşen
Dimensionality reduction has been an active research topic in hyperspectral image analysis due to complexity and non-linearity of the hundreds of the spectral bands. Locality preserving projection (LPP) is a linear extension of the manifold learning and has been very effective in dimensionality reduction compared to linear methods. However, its performance heavily depends on construction of the graph affinity matrix, which has two parameters need to be optimized: k-nearest neighbor parameter and heat kernel parameter. These two parameters might be optimally chosen simply based on a grid search when using only one representative kernel parameter for all the features, but this solution is not feasible when considering a generalized heat kernel in construction the affinity matrix. In this paper, we propose to use heuristic methods, including harmony search (HS) and particle swarm optimization (PSO), in exploring the effects of the heat kernel parameters on embedding quality in terms of classification accuracy. The preliminary results obtained with the experiments on the hyperspectral images showed that HS performs better than PSO, and the heat kernel with multiple parameters achieves better performance than the isotropic kernel with single parameter.
Citation - WoS: 37
Citation - Scopus: 46
Turkey and the Changing Energy Geopolitics of Eurasia
(Elsevier Science, 2019) Ersen, Emre; Çelikpala, Mitat
While Turkeys geographical location is usually viewed as a major advantage in the energy sphere since many countries in its immediate neighbourhood require active Turkish collaboration in order to export or import oil and natural gas via economically feasible pipeline projects the ongoing political economic and military conflicts between the same global and regional actors not only negatively affect the development of the energy transportation routes in Eurasia but also present a major foreign policy challenge for Ankara that has traditionally sought to maintain a careful balance in its relations with the West and Russia. The goal of this article is to elaborate on the influence of such geopolitical factors in evaluating Turkeys role in terms of the oil and natural gas pipelines that are either planned or already under construction to connect the various sub-regions of Eurasia. Employing a traditional geopolitical approach it seeks to understand what kind of geopolitical factors come into play regarding Turkey's role in the changing energy geopolitics of Eurasia and in what ways these geopolitical factors strengthen or weaken Turkeys objective to be perceived as a regional energy hub by other actors.
Irregular Immigration in Southern Europe: Actors, Dynamics and Governance
(TRANSNATIONAL PRESS LONDON, 2020) Oral, Gul
[Abstract Not Available]
Theory of Planned Behavior: Physical Activity Predictors Among Turkish University Students
(Human Kinetics Publ Inc, 2019) Gürleyik, Duygu; Sen, Celia K. Naivar; Baruh, Lemi; Kumkale, Gökçe Tarcan
[Abstract Not Available]
Citation - WoS: 3
Citation - Scopus: 6
Machine Learning Model To Predict an Adult Learner's Decision To Continue Esol Course or Not
(Springer, 2019) Dahman, Mohammed R.; Dağ, Hasan
This study investigated the ability of the demographic and the affective variables to predict the adult learners' decision to continue ESOL courser. 278 adult learners, enrolled on ESOL course at FLS institution in Istanbul, Turkey, participated in the study. The result showed that the continued or dropped out groups, demonstrated statistical differences in the demographic variable (the placement test score) with a magnitude of large effect size (.378). Additionally, the result showed the effect size in the perception of the affective variables (motivation, attitude, and anxiety), accounts for about 50% of the variation between the continuation and dropout groups. Following that, three machine learning models were proposed; all possible subset regression analysis was used to compare the three models. The adequate model, which fitted the demographic variable (the placement test score) and the affective variables (motivation, attitude, and anxiety), correctly predicted 83.3% of the adult learners' decision to continue ESOL course. The model showed about 68% goodness-of-fit. The cultural implications of these findings are discussed, along with suggestions for future research.
Citation - WoS: 3
Citation - Scopus: 3
Does governance affect corporate diversification behaviour in emerging markets?
(Routledge Journals, Taylor & Francıs Ltd, 2020) Sener, Pınar; Akben Selçuk, Elif
This paper investigates the role of firm-level and country-level governance on corporate diversification behaviour in emerging markets. The results show that firms with combined leadership structure are more diversified while firms with more independent directors are less diversified. There is a U-shaped relationship between ownership concentration and diversification. No significant association between country-level shareholder protection and diversification is demonstrated.
Citation - WoS: 1
Citation - Scopus: 3
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 - WoS: 80
Citation - Scopus: 86
Economic Policy Uncertainty and Bank Credit Growth: Evidence From European Banks
(Elsevier B.V., 2020) Danışman, Gamze Öztürk; Ersan, Oğuz; Demir, Ender
Using a sample of 2977 private and listed banks in the EU-5 countries (the United Kingdom, Germany, Spain, Italy, France) for the years 2009–2018, this paper explores the impact of Economic Policy Uncertainty (EPU) on credit growth. Using panel data fixed effects methodology and controlling for endogeneity using two-step difference GMM estimators, our findings indicate that uncertainty in economic policies hampers the credit growth of European banks. Our bank type-based analyses indicate that the effect is mainly valid for cooperative banks. Additional analyses imply that the negative impact of EPU on credit growth is more pronounced in civil law countries, increases with debt maturity, and weakens for banks with a larger number of employees and branches. Furthermore, the unfavorable effects are stronger in well-capitalized banks, banks with foreign subsidiaries, and banks with a higher share of wholesale funding. We also provide several policy implications for different economic actors.
Blending Science and Art: an Educational Perspective
(Iated-Int Assoc Technology Education & Development, 2019) Balkır Kuru, Nur; Şaher, Konca; Mıhçı, Gürkan
rt and design education enable students to find creative and logical solutions to various design problems. The use of materials, constructive analysis, craftmanship, and originality are some key criteria in the process. Size and dimensionality, the proportion analysis, expression integrity, substantiality, and presentability can vary depending on the project and the context. As one of the methods used to provide targeted experience and learning in art and design education, interdisciplinary work presents a right ground for complex design issues. The workshop we carried out together with the Tubitak National Metrology Institution (UME) named "Art's Metrology, Metrology's Art" aimed to transform art, design, and science together into a product. As rational, natural, and appropriate connections can be established between art and science, students were asked to develop a method to meet the objectives and criteria of both around a certain conceptual focus. An important inclusive of the workshop was to have students observe, get informed, and engage in dialogue and ultimately increase their curiosity about a certain mechanism outside of their studies. The group dynamic in the process of creating three-dimensional and displayable works within a scheduled time was supported by a scientist from the metrology department, three art and design instructors, Konca Saher, Nur Balkir, and Gurkan Mihci from Kadir Has University. The finished works were then exhibited in the Tubitak-UME in Gebze compound. This study, which blends science and art, provided students with the opportunity to experiment with a science field, and to develop their predictions about their own disciplines. The paper will present the development and the outcome of the workshop.
Citation - WoS: 6
Citation - Scopus: 8
Does Migration Contribute To Women's Empowerment? Portrait of Urban Turkey and Istanbul
(Routledge Journals Taylor & Francis Ltd, 2019) Eryar, Değer; Tekgüç, Hasan; Toktaş, Şule
This article empirically investigates the impact of internal migration on women's empowerment in urban areas of Turkey. Based on data from a nationally representative household survey we find that migration exerts a positive impact in urban settings through improvements in educational attainment and labor market outcomes. Migration contributes to women's empowerment by raising their education levels and lowering the gap in schooling between men and women. Migration also allows migrants both men and women and particularly those with tertiary education to access jobs and occupations in high wage regions like Istanbul. However unlike in education a gender wage gap persists even after migration.
Citation - WoS: 55
Citation - Scopus: 66
Role Conflict Role Ambiguity and Proactive Behaviors: Does Flexible Role Orientation Moderate the Mediating Impact of Engagement?
(Routledge Journals Taylor & Francis Ltd, 2019) Maden-Eyiusta, Ceyda
This study investigates the relationships between role conflict role ambiguity and proactive behaviors at work (i.e. individual innovation and taking charge) as mediated by work engagement. It also investigates the moderating role of flexible role orientation on the relationships between role conflict and ambiguity work engagement and employee proactivity. Data were collected from 227 employees and their supervisors working in 20 small and medium-sized enterprises in Istanbul Turkey. The findings indicated that role conflict was negatively related to taking charge while role ambiguity was negatively related to individual innovation. Work engagement acted as a full mediator in the relationship between role ambiguity and individual innovation while partially mediating the relationship between role conflict and taking charge. With regard to the moderating role of flexible role orientation the findings indicated that the conditional indirect relationship between (a) role conflict and taking charge and (b) role ambiguity and individual innovation through engagement were stronger when the level of flexible role orientation was low.
Citation - Scopus: 3
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 - WoS: 52
Citation - Scopus: 55
Joint Communication and Computing Resource Allocation in 5g Cloud Radio Access Networks
(IEEE-Inst Electrical Electronics Engineers Inc, 2019) Ferdouse, Lilatul; Anpalagan, Alagan; Erküçük, Serhat
Cloud-radio access network (C-RAN) is regarded as a promising solution to manage heterogeneity and scalability of future wireless networks. The centralized cooperative resource allocation and interference cancellation methods in C-RAN significantly reduce the interference levels to provide high data rates. However, the centralized solution is not scalable due to the dense deployment of small cells with fractional frequency reuse, causing severe inter-tier and inter-cell interference turning the resource allocation and user association into a more challenging problem. In this paper, we investigate joint communication and computing resource allocation along with user association, and baseband unit (BBU) and remote radio head (RRH) mapping in C-RANs. We initially establish a queueing model in C-RAN, followed by formulation of two optimization problems for communication [e.g., resource blocks (RBs) and power] and computing [e.g., virtual machines (VMs)] resources allocation with the aim to minimize mean response time. User association along with the RB allocation, interference, and queueing stability constraints are considered in the communication resource optimization problem. The computing resource optimization problem considers BBU-RRH mapping and VM allocation for small cells, constrained to BBU server capacity and queueing stability. To solve the communication and computing resource optimization problem, we propose a joint resource allocation solution that considers a double-sided auction based distributed resource allocation (DS-ADRA) method, where small cell base stations and users jointly participate using the concept of auction theory. The proposed method is evaluated via simulations by considering the effect of bandwidth utilization percentage, signal-to-interference ratio threshold value and the number of users. The results show that the proposed method can be successfully implemented for 5G C-RANs.
Citation - WoS: 10
Citation - Scopus: 13
Responses To Replica (vs. Genuine) Touristic Experiences
(Pergamon-Elsevier Science, 2020) Gülen, Sarial-Abi; Ezgi, Merdin-Uygur; Gürhan-Canlı, Zeynep
A growing trend in tourism is the use of replica experiences. Yet, consumers' responses to replica (vs. genuine) touristic experiences are mostly overlooked in the literature. In this paper, we propose that consumers' perceptions of authenticity of the replica (vs. genuine) touristic experiences mediate their responses to these experiences. We define three theoretically driven factors that influence the authenticity perceptions of consumers-experience characteristics (restricted experience vs. not restricted experience; within close vs. distant geographical proximity to the genuine) and a consumer characteristic (salient goal: collecting experiences vs. having fun/pleasure), which influence consumers' responses to replica and genuine touristic experiences. We found support for the proposed theory using two field studies from Egypt's Luxor Tutankhamun tomb and three experimental studies.
Citation - WoS: 26
Citation - Scopus: 31
Homology Modeling of Human Histone Deacetylase 10 and Design of Potential Selective Inhibitors
(Taylor & Francis Inc, 2019) Uba, Abdullahi Ibrahim; Yelekçi, Kemal
Histone deacetylases (HDACs) are implicated in the pathology of various cancers, and their pharmacological blockade has proven to be promising in reversing the malignant phenotypes. However, lack of crystal structures of some of the human HDAC isoforms (e.g., HDAC10) hinders the design of the isoform-selective inhibitor. Here, the recently solved X-ray crystal structure of Danio rerio (zebrafish) HDAC10 (Protein Data Bank (PDB) ID; 5TD7, released on 24 May 2017) was retrieved from the PDB and used as a template structure to model the three-dimensional structure of human HDAC10. The overall quality of the best model (M0017) was assessed by computing its z-score-a measure of the deviation of the total energy of the structure with respect to an energy distribution derived from random conformations and by docking of known HDAC10 inhibitors to its catalytic cavity. Furthermore, to identify potential HDAC10-selective inhibitor ligand-based virtual screening was carried out against the ZINC database. The free modeled structure of HDAC10 and its complexes with quisinostat and the highest-ranked compound ZINC19749069 were submitted to molecular dynamics simulation. The comparative analysis of root-mean-squared deviation, root-mean-squared fluctuation, radius of gyration (Rg), and potential energy of these systems showed that HDAC10-ZINC19749069 complex remained the most stable over time. Thus, M0017 could be potentially used for structure-based inhibitor against HDAC10, and ZINC19749069 may provide a scaffold for further optimization. Communicated by Ramaswamy H. Sarma
The American Passport in Turkey: National Citizenship in the Age of Transnationalism
(Routledge Journals, Taylor & Francıs Ltd, 2020) Yanardağoğlu, Eylem
[Abstract Not Available]
Citation - WoS: 21
Citation - Scopus: 21
A Dynamic Game Theory Model for Tourism Supply Chains
(Sage Publications, 2021) Keskin, Kerim; Ucal, Meltem Şengün
This article contributes to the game-theoretic analysis of tourism supply chains. We start with a baseline model including three types of agents: (a) one theme park, (b) multiple accommodation providers, and (c) multiple tour operators. We investigate the strategic dynamics (i.e., collaboration and competition) embedded in a market with two different tourism supply chains, and then we extend our model to an infinite-horizon repeated game arguing that agents would face the same decision problem in each week of every holiday season in each year. We show how agents in a tourism supply chain end up with higher profits in any given period of a repeated game compared with their profits in the static version of the game.

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