İşletme Fakültesi

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Citation - WoS: 6
Citation - Scopus: 10
An Adaptive Affinity Matrix Optimization for Locality Preserving Projection Via Heuristic Methods for Hyperspectral Image Analysis
(IEEE-Inst Electrıcal Electronıcs Engıneers Inc, 2019) Taşkın, Gülşen; Ceylan, Oğuzhan
Locality preserving projection (LPP) has been often used as a dimensionality reduction tool for hyperspectral image analysis especially in the context of classification since it provides a projection matrix for embedding test samples to low dimensional space. However, the performance of LPP heavily depends on the optimization of two parameters of the graph affinity matrix: k-nearest neighbor and heat kernel width, when one considers an isotropic kernel. These two parameters might be optimally chosen simply based on a grid search. In case of using a generalized heat kernel where each feature is separately weighted by a kernel width, the number of parameters that need to be optimized is related to the number of features of the dataset, which might not be very easy to tune. Therefore, in this article, we propose to use heuristic methods, including genetic algorithm (GA), harmony search (HS), and particle swarm optimization (PSO), to explore the effects of the heat kernel parameters aiming to analyze the embedding quality of LPP's projection in terms of various aspects, including 1-NN classification accuracy, locality preserving power, and quality of the graph affinity matrix. The results obtained with the experiments on three hyperspectral datasets show that HS performs better than GA and PSO in optimizing the parameters of the affinity matrix, and the generalized heat kernel achieves better performance than the isotropic kernel. Additionally, a feature selection application is performed by using the kernel width of the generalized heat kernel for each heuristic method. The results show that very promising results are obtained in comparison with the state-of-the-art feature selection methods.
Citation - WoS: 21
Citation - Scopus: 31
Adoption of Mobile Health Apps in Dietetic Practice: Case Study of Diyetkolik
(Jmır Publıcatıons, Inc, 130 Queens Quay E, 2020) Akdur, Görkem; Aydın, Mehmet Nafiz; Akdur, Gizdem
Background: Dietetics mobile health apps provide lifestyle tracking and support on demand. Mobile health has become a new trend for health service providers through which they have been shifting their services from clinical consultations to online apps. These apps usually offer basic features at no cost and charge a premium for advanced features. Although diet apps are now more common and have a larger user base, in general, there is a gap in literature addressing why users intend to use diet apps. We used Diyetkolik, Turkey's most widely used online dietetics platform for 7 years, as a case study to understand the behavioral intentions of users. Objective: The aim of this study was to investigate the factors that influence the behavioral intentions of users to adopt and use mobile health apps. We used the Technology Acceptance Model and extended it by exploring other factors such as price-value, perceived risk, and trust factors in order to assess the technology acceptance of users. Methods: We conducted quantitative research on the Diyetkolik app users by using random sampling. Valid data samples gathered from 658 app users were analyzed statistically by applying structural equation modeling. Results: Statistical findings suggested that perceived usefulness (P<.001), perceived ease of use (P<.001), trust (P<.001), and price-value (P<.001) had significant relationships with behavioral intention to use. However, no relationship between perceived risk and behavioral intention was found (P=.99). Additionally, there was no statistical significance for age (P=.09), gender (P=.98), or previous app use experience (P=.14) on the intention to use the app. Conclusions: This research is an invaluable addition to Technology Acceptance Model literature. The results indicated that 2 external factors (trust and price-value) in addition to Technology Acceptance Model factors showed statistical relevance with behavioral intention to use and improved our understanding of user acceptance of a mobile health app. The third external factor (perceived risk) did not show any statistical relevance regarding behavioral intention to use. Most users of the Diyetkolik dietetics app were hesitant in purchasing dietitian services online. Users should be frequently reassured about the security of the platform and the authenticity of the platform's dietitians to ensure that users' interactions with the dietitians are based on trust for the platform and the brand.
Citation - WoS: 6
Citation - Scopus: 6
Alone but Together Autonomous but Related: Self-Construal Effects on Happiness in Social Experiences
(Wiley, 2018) Merdin-Uygur, Ezgi; Hesapci, Ozlem
Communal tables and open workspaces have become popular servicescapes that is contemporary spaces for experiencing dining or working alone but together. Previous research demonstrates that experiencing with close others (e.g. with friends or family) increases happiness and satisfaction but experiences shared with strangers in contexts such as communal tables or workshops have not yet been thoroughly analyzed. Addressing this research gap from a social-psychological perspective we suggest that even though individuals are generally happier when they share experiences with loved ones self-construal plays a moderating role in the relationship. Individuals with high autonomy and high relatedness do not anticipate greater happiness from experiences shared with friends than with those shared with strangers. Three experimental studies (two online and one field) demonstrate this effect using different operationalizations of autonomy relatedness. Managerial implications are discussed and suggestions are made for future research.
Citation - WoS: 33
Citation - Scopus: 37
Antecedents and Performance Outcomes of Value-Based Selling in Sales Teams: a Multilevel, Systems Theory of Motivation Perspective
(Springer, 2020) Mullins, Ryan; Mengüç, Bülent; Panagopoulos, Nikolaos G.
Firms are increasingly deploying a value-based selling (VBS) approach in their sales organizations to drive growth for new offerings. However, VBS adoption remains challenging, signaling that leaders need guidance to motivate VBS. Drawing from the systems theory of motivation, we examine motivational mechanisms at two levels-salesperson and sales team-to understand how to motivate, and benefit from, VBS. Using multisource data (i.e., salespeople, managers, archival performance) from 70 sales teams in a U.S.-based manufacturing and services provider, our findings illustrate drivers and outcomes of VBS. Specifically, we uncover a framework of salesperson, leader, customer, and team factors that help explain salesperson motivation for VBS. Importantly, we link VBS to customers' adoption of new products to support VBS's role for selling new products. Critical for sales team strategy, our model also integrates a team-level motivational mechanism to provide a comprehensive framework for salesperson and sales team motivations and outcomes.
Citation - WoS: 2
Citation - Scopus: 2
Babbling Through Social Media: a Cross-Country Study Mapping Out Social Networks Using Ewom Intentions
(Springer, 2023) Zülal, İşler; Kıygı-Çallı, Meltem; El Oraiby, Maryam
This research aims to determine the factors affecting the users’ electronic word-of-mouth (eWOM) seeking and sharing intentions and to reveal the interactions among and within clusters using social network analysis (SNA). This study includes three hierarchical sub-studies conducted in two countries, Turkey and Poland. First, we develop a segmentation for social networking site (SNS) users based on the frequency of sharing product-related information on SNSs. Second, we investigate the impact of several factors that affect eWOM seeking and sharing intentions using regression analysis. In the second sub-study, we also include the identified segments developed in the first sub-study as another factor that may have differentiated eWOM intentions. Third, to understand the degree of interaction among SNS users, we apply an SNA using the forecasted eWOM intentions scores from the second sub-study, which gives us hypothetical social networks. The results of SNA present strong interactions inter- and intra-clusters in both countries. Some key findings include the identification of three SNS user segments, including “Middlers,” that may be of particular interest to brands. We also find that in terms of eWOM intentions, users in Turkey are more active than in Poland. Although some predictors of eWOM seeking and sharing intentions differ between the two countries, users intend to be more active in eWOM seeking than in eWOM sharing. The comparative study provides valuable insights for decision-makers to engage different market segments via SNSs with various proposed features using suggested information contents for selected product categories.
Citation - WoS: 42
Citation - Scopus: 44
Bank Credit in Uncertain Times: Islamic Vs. Conventional Banks
(Elsevier Ltd, 2020) Bilgin, Mehmet Hüseyin; Danışman, Gamze Öztürk; Demir, Ender; Tarazi, Amine
This paper explores whether the impact of economic uncertainty on credit growth differs for Islamic vs. conventional banks. Using a sample of 416 banks (58 Islamic and 358 conventional) in 12 countries, the findings indicate that an increase in economic uncertainty significantly decreases the credit growth of conventional banks but does not have any significant impact on Islamic banks’ credit growth. Our results are robust to alternative specifications and addressing endogeneity concerns using GMM estimators. We further observe that our findings are stronger for the following countries: (1) countries with explicit deposit insurance protection system for Islamic banks, (2) lower foreign dominance, and (3) countries with a higher share of deposits and assets in Islamic banks.
Citation - WoS: 15
Citation - Scopus: 17
Behavioral Biases of Finance Professionals: Turkish Evidence
(Elsevier Science Bv, 2016) Kiymaz, Halil; Öztürkkal, Belma; Akkemik, K. Ali
This study extends the existing literature on the determinants of behavioral biases of Turkish finance sector professionals. It examines the impact of various personal and objective attributes of finance sector professionals on their risk choices derived from their portfolio allocation and personal wealth data. Utilizing survey data from 206 professionals we find that these professionals take higher risk in the form of investment in equities when investing in home country firms (geographic bias) and investing in firms headquartered in their home towns (home bias). Those relying on their own predictions when making investment decisions and those with emotional biases invest less in equities. Findings further show that younger professionals professional with less education with lower risk aversion and with single broker accounts are more likely to invest in equities. We also find that those with higher expected returns invest more in equities showing overconfidence. Subsample analysis results for finance professionals suggest that portfolio managers and brokerage company professionals display differing risk taking behavior. (C) 2016 Elsevier B.V. All rights reserved.
Citation - WoS: 11
Citation - Scopus: 11
Bivariate Pseudo-Gompertz Distribution and Concomitants of Its Order Statistics
(Elsevier Science Bv, 2013) Yorubulut, Serap; Gebizlioğlu, Ömer Lütfi
This paper presents a new bivariate Pseudo-Gompertz distribution that sprouts from the classical Gompertz distribution and possesses the features of pseudo-distribution functions. In addition to some standard properties of the proposed distribution distributions of order statistics and their concomitants for samples drawn from the new distribution are obtained. The survival and hazard functions of the concomitants are shown and their values are tabled. Interpretations of the results are given in connection with risk events and risk management. (C) 2013 Elsevier B.V. All rights reserved.
Capital Markets Trade Openness and Productivity in Emerging Economies Introduction
(M.E Sharpe Inc., 2011) Bilgin, Mehmet Hüseyin; Danis, Hakan
[Abstract Not Available]
Citation - WoS: 5
Citation - Scopus: 6
Computing Finite Time Non-Ruin Probability and Some Joint Distributions in Discrete Time Risk Model With Exchangeable Claim Occurrences
(Elsevier Science, 2017) Eryilmaz, Serkan; Gebizlioğlu, Ömer Lütfi
In this paper we study a discrete time risk model based on exchangeable dependent claim occurrences. In particular we obtain expressions for the finite time non-ruin probability and the joint distribution of the time to ruin the surplus immediately before ruin and the deficit at ruin. An illustration of the results is given and some implications of the results are provided. Comparisons are made with the corresponding results for the classical compound binomial model of independent and identically distributed claim occurrences. (C) 2016 Elsevier E.V. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 2
Continuous Dependence on Data for a Solution of the Quasilinear Parabolic Equation With a Periodic Boundary Condition
(Springer International Publishing Ag, 2013) Kanca, Fatma; Baglan, Irem Sakinc; Kanca, Fatma
In this paper we consider a parabolic equation with a periodic boundary condition and we prove the stability of a solution on the data. We give a numerical example for the stability of the solution on the data.
Citation - WoS: 134
Citation - Scopus: 174
Coordinated Electric Vehicle Charging With Reactive Power Support To Distribution Grids
(IEEE, 2019) Wang, Jingyuan; Bharati, Guna R.; Paudyal, Sumit; Ceylan, Oğuzhan; Bhattarai, Bishnu P.; Myers, Kurt S.
We develop hierarchical coordination frameworks to optimally manage active and reactive power dispatch of number of spatially distributed electric vehicles (EVs) incorporating distribution grid level constraints. The frameworks consist of detailed mathematical models which can benefit the operation of both entities involved i.e. the grid operations and EV charging. The first model comprises of a comprehensive optimal power flow model at the distribution grid level while the second model represents detailed optimal EV charging with reactive power support to the grid. We demonstrate benefits of coordinated dispatch of active and reactive power from EVs using a 33-node distribution feeder with large number of EVs (more than 5000). Case studies demonstrate that in constrained distribution grids coordinated charging reduces the average cost of EV charging if the charging takes place at nonunity power factor mode compared to unity power factor. Similarly the results also demonstrate that distribution grids can accommodate charging of increased number of EVs if EV charging takes place at nonunity power factor mode compared to unity power factor.
Citation - WoS: 12
Citation - Scopus: 17
Corporate Diversification and Firm Value: Evidence From Emerging Markets
(Emerald Group Publishing Limited, 2015) Akben Selçuk, Elif
Purpose - The purpose of this paper is to investigate the impact of corporate diversification on firm value in a sample of nine emerging markets including Brazil Chile Indonesia Malaysia Philippines Poland South Africa Thailand and Turkey. For the purpose of this study a company is classified as diversified when it is operating in two or more lines of business defined by the two-digit SIC codes. Design/methodology/approach - Employing panel data from 1568 companies for the period 2005-2010 this paper estimates both a fixed effects model and a dynamic generalized method of moments model. Data are collected both at company level and segment level within each firm. Findings - Overall analysis results suggest that for the period from 2005 to 2010 diversified firms in emerging markets are valued more compared to single-segment firms operating in similar industries providing support for diversification premium. Originality/value - The effect of diversification on company value in emerging markets is an important managerial and public policy concern. Although the literature on developed country diversified firms is rich only a few studies have examined diversification-value relationship in the context of developing countries. Furthermore most previous research on the value effects of corporate diversification in emerging markets has taken the form of case studies within countries and concentrated on the 1990s. This paper tries to fill these gaps by using a larger sample and more recent data and methodology.
Citation - WoS: 26
Citation - Scopus: 31
Customer Participation Variation and Its Impact on Customer Service Performance: Underlying Process and Boundary Condition
(Sage Publications, 2020) Mengüç, Bülent; Auh, Seigyoung; Wang, Fatima
Drawing on the customer participation (CP) literature, this research proposes that CP variation is the degree to which employees perceive variability across customers with regard to customers sharing information, time, and effort and making suggestions to enhance the service delivery process and outcome. Drawing on the job demands-resources model, this research explicates the mediating process by which CP variation affects customer service performance and its boundary conditions. Study 1 uses data from a field study in the banking industry to show that CP variation negatively influences customer service performance through greater customer-related burnout. The authors show that this mediation process is moderated by contingencies that mitigate or exacerbate the indirect relationship. Study 2 further validates the CP variation construct by testing for discriminant validity against similar and related constructs, such as CP quality, in more diverse service industries (insurance, legal consulting, travel and tourism, health care, and physical fitness). Finally, an examination of the moderating role of CP quality provides a more nuanced picture of the intricacies between CP variation and CP quality. This article concludes with a discussion of the theoretical and practical implications for CP variation research.
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: 5
Citation - Scopus: 5
Designing of Multi-Targeted Molecules Using Combination of Molecular Screening and in Silico Drug Cardiotoxicity Prediction Approaches
(Elsevier Science Inc, 2014) Buturak, Birce; Durdagi, Serdar; Noskov, Sergei Y.; Ildeniz, A. Tugba Ozal
We have previously investigated and reported a set of phenol- and indole-based derivatives at the binding pockets of carbonic anhydrase isoenzymes using in silico and in vitro analyses. In this study we extended our analysis to explore multi-targeted molecules from this set of compounds. Thus 26 ligands are screened at the binding sites of 229 proteins from 5 main enzyme family classes using molecular docking algorithms. Derived docking scores are compared with reported results of ligands at carbonic anhydrase I and II isoenzymes. Results showed potency of multi-targeted drugs of a few compounds from investigated ligand set. These promising ligands are then tested in silico for their cardiotoxicity risks. Results of this work can be used to improve the desired effects of these compounds by molecular engineering studies. In addition these results may lead to further investigation of studied molecules by medicinal chemists to explore different therapeutic aims. (C) 2014 Elsevier Inc. All rights reserved.
Citation - WoS: 16
Citation - Scopus: 22
Determinants of Saving-Borrowing Decisions and Financial Inclusion in a High Middle Income Country: the Turkish Case
(Routledge Journals Taylor & Francis Ltd, 2016) Davutyan, Nurhan; Öztürkkal, Belma
We use a representative survey of the Turkish household sector and investigate factors impinging on saving-borrowing behavior. We run four probit regressions to elucidate (i) the saving decision (ii) asset choice or portfolio composition for those who save (iii) the bank loan decision and lastly (iv) the formal versus informal borrowing decision. We find income education marital status and region within country strongly correlate with those decisions. We offer some insights regarding the influence of variables like rural to urban migrant status and religious belief on saving and borrowing decisions. We discuss the long-term implications of our findings on the Turkish household savings performance.
Citation - WoS: 7
Citation - Scopus: 7
Dissidents With an Innovation Cause? Non-Institutionalized Actors' Online Social Knowledge Sharing Solution-Finding Tensions and Technology Management Innovation
(Emerald Group Publishing Limited, 2015) De Kervenoael, Ronan; Bisson, Christophe; Palmer, Mark
Purpose - Traditionally most studies focus on institutionalized management-driven actors to understand technology management innovation. The purpose of this paper is to argue that there is a need for research to study the nature and role of dissident non-institutionalized actors' (i.e. outsourced web designers and rapid application software developers). The authors propose that through online social knowledge sharing non-institutionalized actors' solution-finding tensions enable technology management innovation. Design/methodology/approach - A synthesis of the literature and an analysis of the data (21 interviews) provided insights in three areas of solution-finding tensions enabling management innovation. The authors frame the analysis on the peripherally deviant work and the nature of the ways that dissident non-institutionalized actors deviate from their clients (understood as the firm) original contracted objectives. Findings - The findings provide insights into the productive role of solution-finding tensions in enabling opportunities for management service innovation. Furthermore deviant practices that leverage non-institutionalized actors' online social knowledge to fulfill customers' requirements are not interpreted negatively but as a positive willingness to proactively explore alternative paths. Research limitations/implications - The findings demonstrate the importance of dissident non-institutionalized actors in technology management innovation. However this work is based on a single country (USA) and additional research is needed to validate and generalize the findings in other cultural and institutional settings. Originality/value - This paper provides new insights into the perceptions of dissident non-institutionalized actors in the practice of IT managerial decision making. The work departs from but also extends the previous literature demonstrating that peripherally deviant work in solution-finding practice creates tensions enabling management innovation between IT providers and users.
Citation - WoS: 8
Citation - Scopus: 11
Does mood affect institutional herding?
(Elsevier, 2020) Gavriilidis, Konstantinos; Kallinterakis, Vasileios; Öztürkkal, Belma
Drawing on a unique data set of daily portfolio holdings for Turkish mutual funds we investigate the relationship between mood and institutional herding on the premises of various established mood proxies (weekend effect; holiday effect; Ramadan; sunshine). Results indicate that fund managers in Turkey herd significantly, with their herding growing in magnitude as the number of active funds per stock rises and appearing stronger on the buy-than the sell-side. Although the relationship of mood with institutional herding occasionally assumes the correct sign as per theoretical expectations, institutional herding is found to be insignificantly different across various mood states, thus denoting that mood does not impact the propensity of fund managers to herd. (C) 2020 Elsevier B.V. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 2
Double Branch Outage Modeling and Simulation: Bounded Network Approach
(Elsevier Science, 2015) Ceylan, Oğuzhan; Özdemir, Aydoğan; Dağ, Hasan
Energy management system operators perform regular outage simulations in order to ensure secure operation of power systems. AC power flow based outage simulations are not preferred because of insufficient computational speed. Hence several outage models and computational methods providing acceptable accuracy have been developed. On the other hand double branch outages are critical rare events which can result in cascading outages and system collapse. This paper presents a double branch outage model and formulation of the phenomena as a constrained optimization problem. Optimization problem is then solved by using differential evolution method and particle swarm optimization algorithm. The proposed algorithm is applied to IEEE test systems. Computational accuracies of differential evolution based solutions and particle swarm optimization based solutions are discussed for IEEE 30 Bus Test System and IEEE 118 Bus Test System applications. IEEE 14 Bus Test System IEEE 30 Bus Test System IEEE 57 Bus Test System IEEE 118 Bus Test System and IEEE 300 Bus Test System simulation results are compared to AC load flows in terms of computational speed. Finally the performance of the proposed method is analyzed for different outage configurations. (C) 2015 Elsevier Ltd. All rights reserved.

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