05. Fakülteler
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Article Citation - WoS: 19Citation - Scopus: 23A Capacitated Lot Sizing Problem With Stochastic Setup Times and Overtime(2019) Jabali, Ola; Gendreau, Michel; Jans, Raf; Taş, DuyguIn this paper, we study a Capacitated Lot Sizing Problem with Stochastic Setup Times and Overtime (CLSPSSTO). We describe a mathematical model that considers both regular costs (including production, setup and inventory holding costs) and expected overtime costs (related to the excess usage of capacity). The CLSP-SSTO is formulated as a two-stage stochastic programming problem. A procedure is proposed to exactly compute the expected overtime for a given setup and production plan when the setup times follow a Gamma distribution. A sample average approximation procedure is applied to obtain upper bounds and a statistical lower bound. This is then used to benchmark the performance of two additional heuristics. A first heuristic is based on changing the capacity in the deterministic counterpart, while the second heuristic artificially modifies the setup time. We conduct our computational experiments on well-known problem instances and provide comprehensive analyses to evaluate the performance of each heuristic. (C) 2018 Elsevier B.V. All rights reserved.Conference Object A Comparative Analysis of the Health Care Utilization and Costs of Patients Diagnosed With and Without Liver Cancer in the Us Medicare Population(2017) Ogbomo, A.; Lin, Y.; Keshishian, A; Xie, L; Yuce, H; Başer, Onur...Article Citation - WoS: 5Citation - Scopus: 8A Data-Assisted Reliability Model for Carrier-Assisted Cold Data Storage Systems(Elsevier, 2020) Arslan, Şuayb Şefik; Göker, Turguy; Peng, JamesCold data storage systems are used to allow long term digital preservation for institutions’ archive. The common functionality among cold and warm/hot data storage is that the data is stored on some physical medium for read-back at a later time. However in cold storage, write and read operations are not necessarily done in the same exact geographical location. Hence, a third party assistance is typically utilized to bring together the medium and the drive. On the other hand, the reliability modeling of such a decomposed system poses few challenges that do not necessarily exist in other warm/hot storage alternatives such as fault detection and absence of the carrier, all totaling up to the data unavailability issues. In this paper, we propose a generalized non-homogenous Markov model that encompasses the aging of the carriers in order to address the requirements of today's cold data storage systems in which the data is encoded and spread across multiple nodes for the long-term data retention. We have derived useful lower/upper bounds on the overall system availability. Furthermore, the collected field data is used to estimate parameters of a Weibull distribution to accurately predict the lifetime of the carriers in an example scale-out setting.Article Citation - WoS: 1Citation - Scopus: 3A Meta-Analytic Review of the Association Between Theory of Mind and Aggression(Elsevier, 2023) Imuta, Kana; Selçuk, Bilge; Yavuz-Müren, Melis; Turunç, Gamze; Ekerim-Akbulut, MügeAlthough the association between theory of mind (ToM) and aggression has been theorized, empirical findings have not revealed a clear link between these constructs. In the current meta-analytic review, we integrated findings from 83 studies (141 effect sizes) involving 41,650 participants from 18 countries to elucidate the association between ToM and aggression in typically developing children, adolescents, and adults. We found a significant negative association between ToM and aggression overall (r = −0.15). Moreover, each type and function of aggression were negatively associated with Theory of Mind (ToM). Bullying—a distinct form of aggression—was not associated with ToM. The strength of the association between overall aggression and ToM varied as a function of methodological variables: First, studies that used self-report questionnaires to measure ToM and aggression yielded the strongest effect sizes, compared to those that used task-based assessments or questionnaires completed by others (parents, teachers, peers). Second, there was a difference in the ToM measurement with the measures examining ToM with non-false belief understanding tasks yielding a stronger mean effect than those that focused exclusively on false-belief understanding. Third, the magnitude of the negative association was found to increase with participants' age, though significant negative associations between ToM and aggression held across the lifespan. These results point to the critical link between ToM and aggressive tendencies and suggest the value in implementing interventions to improve mental state understanding across the age range to foster positive social interactions.Article Citation - WoS: 9Citation - Scopus: 12A New Triangular Composite Shell Element With Damping Capability(Elsevier, 2014) Körük, Hasan; Şanlıtürk, Kenan YüceThis paper presents a new triangular composite shell element with damping capability. Formulation of the composite triangular shell element is based on stacking individual homogeneous triangular shell ele- ments on top of each other. The homogeneous shell element is an assembly of a triangular membrane element with drilling degrees of freedoms and a plate element. Damping capability is provided by means of complex element stiffness matrix of individual flat layers of the composite element. These elements with damping capability allow modelling general structures with damping treatments. A few test cases are modelled using triangular finite element developed here and the results of the complex eigenvalue analyses are compared with those of the quadrilateral shell elements proposed recently. The results obtained using the presented triangular and previous quadrilateral composite elements are also com- pared with those based on modal strain energy method and experimental results. Comparisons of the experimental and the theoretical results confirm that the modal properties including modal damping lev- els of structures with damping treatments can be predicted with high accuracy using the proposed finite element.Conference Object Citation - WoS: 1A Randomized Clinical Trial Comparing the Effects of Mindfulness-Based and Cognitive Behavioral Therapy-Based Stress Reduction in Medical Students(Cambridge Univ Press, 2024) Pence, A. Yay; Coldur, M.; Atalay, Z.; Aslan, S.; Beba, B.; Sayin, C. Coskun; Ertek, I. Ekmekci[No Abstract Available]Article Citation - WoS: 6Citation - Scopus: 7A Reliability Model for Dependent and Distributed Mds Disk Array Units(IEEE Transactions on Reliability, 2018) Arslan, Şuayb ŞefikArchiving and systematic backup of large digital data generates a quick demand for multi-petabyte scale storage systems. As drive capacities continue to grow beyond the few terabytes range to address the demands of today’s cloud, the likelihood of having multiple/simultaneous disk failures became a reality. Among the main factors causing catastrophic system failures, correlated disk failures and the network bandwidth are reported to be the two common source of performance degradation. The emerging trend is to use efficient/sophisticated erasure codes (EC) equipped with multiple parities and efficient repairs in order to meet the reliability/bandwidth requirements. It is known that mean time to failure and repair rates reported by the disk manufacturers cannot capture life-cycle patterns of distributed storage systems. In this study, we develop failure models based on generalized Markov chains that can accurately capture correlated performance degradations with multiparity protection schemes based on modern maximum distance separable EC. Furthermore, we use the proposed model in a distributed storage scenario to quantify two example use cases: Primarily, the common sense that adding more parity disks are only meaningful if we have a decent decorrelation between the failure domains of storage systems and the reliability of generic multiple single-dimensional EC protected storage systems.Conference Object Citation - WoS: 9Citation - Scopus: 11A Value-Adding Approach To Reliability Under Preventive Maintenance Costs and Its Applications(2014) Dubey, Rameshwar; Kılıç, Erdem; Ali, Sadia Samar; Weber, Gerhard WilhelmNo equipment (system) can be perfectly reliable in spite of the utmost care and best efforts on the part of the designer, decision-maker and manufacturer. The two sides of maintenance are corrective and preventive maintenance. It is generally assumed that a preventive maintenance action is less costly than a repair maintenance action. We examine this proposition in detail on the basis of a failure-time model that relates conformance quality to reliability. Illustratively, we present reliability in the context of contracts with asymmetric information. The model shows how to overcome information rents through price distortions and quantity rationing. The paper ends with a conclusion and an outlook to future studies.Article Citation - WoS: 18Citation - Scopus: 18Adding Rapid-Acting Insulin or Glp-1 Receptor Agonist To Basal Insulin: Outcomes in a Community Setting(2015) Dalal, Mehul R; DiGenio, Andres; Xie, Lin; Başer, OnurTo evaluate real-world outcomes in patients with type 2 diabetes mellitus (T2DM)receiving basal insulin, who initiate add-on therapy with a rapid-acting insulin (RAI) or aglucagon-like peptide 1 (GLP-1) receptor agonist.Data were extracted retrospectively from a U.S. health claims database. Adults withT2DM on basal insulin who added an RAI (basal+RAI) or GLP-1 receptor agonist (basal+GLP-1) were included. Propensity score matching (1 up to 3 ratio) was used to control for differencesin baseline demographics, clinical characteristics, and health resource utilization. Endpointsincluded prevalence of hypoglycemia, pancreatic events, all-cause and diabetes-relatedresource utilization, and costs at 1 year follow-up. Overall, 6,718 matched patients were included: 5,013 basal+RAI and 1,705basal+GLP1. Patients in both groups experienced a similar proportion of any hypoglycemicevent (P = .4079). Hypoglycemic events leading to hospitalization were higher in the basal+RAIcohort (2.7% vs. 1.8%; P = .0444). The basal+GLP-1 cohort experienced fewer all-cause(13.55% vs. 18.61%; P<.0001) and diabetes-related hospitalizations (11.79% vs. 15.68%;P<.0001). The basal+GLP-1 cohort had lower total all-cause health care costs ($18,413 vs.$20,821; P = .0002), but similar diabetes-related costs ($9,134 vs. $8,985; P<.0001) comparedwith the basal+RAI cohort. Add-on therapy with a GLP-1 receptor agonist in T2DM patients receiving basalinsulin was associated with fewer hospitalizations and lower total all-cause costs compared withadd-on therapy using a RAI, and could be considered an alternative to a RAI in certain patientswith T2DM, who do not achieve effective glycemic control with basal insulin.Article Citation - WoS: 13Citation - Scopus: 21Advancements in Distributed Ledger Technology for Internet of Things(Elsevier, 2020) Jurdak, Raja; Arslan, Şuayb Şefik; Krishnamachari, Bhaskar; Jelitto, JensInternet of Things (IoT) is paving the way for different kinds of devices to be connected and properly communicated at a mass scale. However, conventional mechanisms used to sustain security and privacy cannot be directly applied to IoT whose topology is increasingly becoming decentralized. Distributed Ledger Technologies (DLT) on the other hand comprise varying forms of decentralized data structures that provide immutability through cryptographically linking blocks of data. To be able to build reliable, autonomous and trusted IoT platforms, DLT has the potential to provide security, privacy and decentralized operation while adhering to the limitations of IoT devices. The marriage of IoT and DLT technology is not very recent. In fact many projects have been focusing on this interesting combination to address the challenges of smart cities, smart grids, internet of everything and other decentralized applications, most based on blockchain structures. In this special issue, the focus is on the new and broader technical problems associated with the DLT-based security and backend platform solutions for IoT devices and applications.Article Citation - WoS: 4Citation - Scopus: 6Aggression Begets Aggression: Psychological Dating Aggression Perpetration in Young Adults From the Perspective of Intergenerational Transmission of Violence(Springer, 2021) Toplu-Demirtaş, Ezgi; Hatipoğlu-Sümer, ZeynepThe aim of this study was threefold: (1) to evaluate the factorial validity of the Psychological Aggression (PA) subscale of the Conflict Tactics Scales–Adult Recall version (CTS2-CA), (2) to investigate the prevalence of and gender differences in psychological dating aggression perpetration (PDAP; restrictive engulfment, denigration, hostile withdrawal, and dominance/intimidation), and (3) to explore a proposed path from witnessing interparental psychological aggression perpetration to PDAP via acceptance of psychological aggression as a mediator and gender as a moderator of the mediation. For the first purpose, college students (N = 275) completed father to mother and mother to father forms of the PA subscale of the CTS2-CA. Exploratory factor analyses yielded a single-factor solution for the father to mother (55.86% of the variance) and mother to father (49.12% of the variance) forms. For the second and third purposes, a separate sample of 1015 dating college students (69.6% women) completed the Multidimensional Measure of Emotional Abuse and Abuse subscale of the Intimate Partner Violence Attitude Scale-Revised, along with the PA subscale of the CTS2-CA. Gender differences emerged in the prevalence of restrictive engulfment (85.8% for women and 80.3% for men) and hostile withdrawal (96.3% for women and 91.1% for men). Moderated-mediation analyses revealed that women college students who witnessed more mother to father psychological aggression perpetration tended to hold more accepting attitudes towards psychological aggression and, in turn, perpetrated more psychological aggression against their partners. Common assumptions that boys are more likely to imitate fathers, whereas girls are more likely to imitate mothers and women [but not men] commit verbal aggression may together explain our findings from the perspective of the intergenerational transmission of violence hypothesis. For future research, we suggest investigating the proposed model with the experience of psychological aggression from the parents to the child, which may provide further insights.Article Citation - WoS: 1Citation - Scopus: 4All You Fear Is Love: the Roles of Rejection by Intimate Others(Wiley, 2023) Aracı-İyiaydın, Ayşegül; Toplu-Demirtaş, Ezgi; Rohner, Ronald P. P.; Akçabozan-Kayabol, Nazlı BüşraInterpersonal acceptance-rejection theory (IPARTheory) asserts that recollections of parental rejection in childhood tend to result in psychological maladjustment and intimacy problems in later romantic relationships. Informed by IPARTheory, we investigated the association between maternal & paternal rejection, and fear of intimacy by the mediating role of psychological maladjustment in a Turkish sample with 462 mostly young adults. We further explored the moderator role of gender in Model 1 and the moderating roles of both gender and intimate partner rejection in Model 2. Model 1 revealed that adults who had experienced maternal and paternal rejection in childhood tended to be psychologically maladjusted. Consequently, they also tended to have a fear of intimacy, regardless of gender. Model 2 revealed that women who recall having been rejected in childhood by their mothers tended to be psychologically maladjusted and to have a significant fear of intimacy when they also experienced moderate or more than moderate intimate-partner rejection. However, both women and men who experienced paternal rejection in childhood tended to be psychologically maladjusted and to experience a greater fear of intimacy when they perceived any degree of intimate partner rejection. Implications of the results for theory, research, and practice are discussed.Article Citation - WoS: 26Citation - Scopus: 26An Efficient Linear Programming Based Method for the Influence Maximization Problem in Social Networks(Elsevier, 2019) Güney, EvrenThe influence maximization problem (IMP) aims to determine the most influential individuals within a social network. In this study first we develop a binary integer program that approximates the original problem by Monte Carlo sampling. Next, to solve IMP efficiently, we propose a linear programming relaxation based method with a provable worst case bound that converges to the current state-of-the-art 1-1/e bound asymptotically. Experimental analysis indicate that the new method is superior to the state-of-the-art in terms of solution quality and this is one of the few studies that provides approximate optimal solutions for certain real life social networks.Correction An Efficient Linear Programming Based Method for the Influence Maximization Problem in Social Networks (vol 503, Pg 589, 2019)(Elsevier, 2020) Güney, EvrenThe influence maximization problem (IMP) aims to determine the most influential individuals within a social network. In this study first we develop a binary integer program thatapproximates the original problem by Monte Carlo sampling. Next, to solve IMP efficiently,we propose a linear programming relaxation based method with a provable worst casebound that converges to the current state-of-the-art 1 − 1/e bound asymptotically. Experimental analysis indicate that the new method is superior to the state-of-the-art in termsof solution quality and this is one of the few studies that provides approximate optimalsolutions for certain real life social networks.Article Citation - WoS: 19Citation - Scopus: 28An Evaluation of Recent Neural Sequence Tagging Models in Turkish Named Entity Recognition(Elsevier, 2021) Makaroğlu, Didem; Demir, Şeniz; Aras, Gizem; Çakır, AltanNamed entity recognition (NER) is an extensively studied task that extracts and classifies named entities in a text. NER is crucial not only in downstream language processing applications such as relation extraction and question answering but also in large scale big data operations such as real-time analysis of online digital media content. Recent research efforts on Turkish, a less studied language with morphologically rich nature, have demonstrated the effectiveness of neural architectures on well-formed texts and yielded state-of-the art results by formulating the task as a sequence tagging problem. In this work, we empirically investigate the use of recent neural architectures (Bidirectional long short-term memory (BiLSTM) and Transformer-based networks) proposed for Turkish NER tagging in the same setting. Our results demonstrate that transformer-based networks which can model long-range context overcome the limitations of BiLSTM networks where different input features at the character, subword, and word levels are utilized. We also propose a transformer-based network with a conditional random field (CRF) layer that leads to the state-of-the-art result (95.95% f-measure) on a common dataset. Our study contributes to the literature that quantifies the impact of transfer learning on processing morphologically rich languages.Article Citation - WoS: 27Citation - Scopus: 37An Explanatory Sequential Mixed-Method Research on the Full-Scale Implementation of Flipped Learning in the First Years of the World's First Fully Flipped University: Departmental Differences(Elsevier, 2021) Demir, Ömer; Birgili, BengiThis study evaluates the first years of the full-scale flipped learning implementation process that began with an authority innovation-decision at the world's first fully flipped university in terms of departmental differences. The study employs an explanatory sequential mixed-method research. The primary respondents were 69 freshmen enrolled in the Faculty of Education at a private university in Istanbul, Turkey. In addition to student participants, five faculty members were recruited to the study. The primary data was collected through a Likert-type scale on flipped learning, including components on motivation, course structure, and interaction. Pre and post semi-structured interviews and a structured ranking form were also used to support the quantitative data. The findings of the study reveal that the students felt relatively unmotivated when instructed through flipped learning, although were satisfied with the course structure. In general, the students lacked student-student interaction. Due to the nature of the Guidance and Psychological Counseling department, the students faced some difficulties in engaging in all three types of interaction (student-student, student-educator, and student-content). Lengthy and poor-quality videos and students' lack of preparation for classes emerged as major problems in flipped learning. The faculty members complained about the amount of time required for pre-class preparation (i.e., recording flipped videos). This paper discusses how to foster motivation, collaboration, discussion, and interaction in flipped learning in higher education settings so as to guide prospective practitioners.Article Citation - WoS: 52Citation - Scopus: 66An Investigation of the Neural Correlates of Purchase Behavior Through Fnirs(2018) Cakir, Murat Perit; Yurdakul, Dicle; Girisken, Yener; Çakar, TunaPurpose This study aims to explore the plausibility of the functional near-infrared spectroscopy (fNIRS) methodology for neuromarketing applications and develop a neurophysiologically-informed model of purchasing behavior based on fNIRS measurements. Design/methodology/approach The oxygenation signals extracted from the purchase trials of each subject were temporally averaged to obtain average signals for buy and pass decisions. The obtained data were analyzed via both linear mixed models for each of the 16 optodes to explore their separate role in the purchasing decision process and a discriminant analysis to construct a classifier for buy/pass decisions based on oxygenation measures from multiple optodes. Findings Positive purchasing decisions significantly increase the neural activity through fronto-polar regions, which are closely related to OFC and vmPFC that modulate the computation of subjective values. The results showed that neural activations can be used to decode the buy or pass decisions with 85 per cent accuracy provided that sensitivity to the budget constraint is provided as an additional factor. Research limitations/implications The study shows that the fNIRS measures can provide useful biomarkers for improving the classification accuracy of purchasing tendencies and might be used as a main or complementary method together with traditional research methods in marketing. Future studies might focus on real-time purchasing processes in a more ecologically valid setting such as shopping in supermarkets. Originality/value This paper uses an emerging neuroimaging method in consumer neuroscience, namely, fNIRS. The decoding accuracy of the model is 85 per cent which presents an improvement over the accuracy levels reported in previous studies. The research also contributes to existing knowledge by providing insights in understanding individual differences and heterogeneity in consumer behavior through neural activities.Article Citation - WoS: 5Citation - Scopus: 8An Online Laboratory School Research on Pre-Service Mathematics Teachers’ Experiences and Mathematics Teaching Anxiety(Springer, 2022) Ölmez, İbrahim Burak; Taylan, Rukiye Didem; Pekkan, Tunç ZelhaDuring the COVID-19 pandemic, we founded an Online Laboratory School (OLS) under the roof of a university in Turkey to support students from public schools that were not technologically prepared for an online education and to provide an opportunity for our pre-service teachers (PSTs) to continue their internship by teaching online. The purpose of this research, consisting of two studies, was to examine experiences of 43 PSTs (first-, third- and fourth-years) during the OLS period of 8 weeks and how the OLS affected their mathematics teaching anxiety during Fall 2020. In the first study, we administered a survey to inquire into PSTs’ views on their experiences at the OLS, and in the second study we examined their mathematics teaching anxiety before and after the OLS experience using another survey. One main result was that the OLS experience served as an effective introduction to the profession for first-year PSTs and fourth- and third-year PSTs reported learning in-depth about online teaching in terms of the planning, teaching, and reflecting cycle. Another main result was that PSTs had mathematics teaching anxiety from “a little” to “a moderate amount” before the OLS and their teaching anxiety did not significantly change during the OLS period of 8 weeks. PSTs experienced highest mathematics teaching anxiety when they were observed and evaluated by supervisors during their teaching. The implications of these findings are discussed for teacher education programs.Article Citation - WoS: 49Citation - Scopus: 57An Optimization Model for Carbon Capture & Storage/Utilization Vs. Carbon Trading: a Case Study of Fossil-Fired Power Plants in Turkey(2018) Uctug, Fehmi Görkem; Ağralı, Semra; Türkmen, Burçin AtılganWe consider fossil-fired power plants that operate in an environment where a cap and trade system is in operation. These plants need to choose between carbon capture and storage (CCS), carbon capture and utilization (CCU), or carbon trading in order to obey emissions limits enforced by the government. We develop a mixed-integer programming model that decides on the capacities of carbon capture units, if it is optimal to install them, the transportation network that needs to be built for transporting the carbon captured, and the locations of storage sites, if they are decided to be built. Main restrictions on the system are the minimum and maximum capacities of the different parts of the pipeline network, the amount of carbon that can be sold to companies for utilization, and the capacities on the storage sites. Under these restrictions, the model aims to minimize the net present value of the sum of the costs associated with installation and operation of the carbon capture unit and the transportation of carbon, the storage cost in case of CCS, the cost (or revenue) that results from the emissions trading system, and finally the negative revenue of selling the carbon to other entities for utilization. We implement the model on General Algebraic Modeling System (GAMS) by using data associated with two coal-fired power plants located in different regions of Turkey. We choose enhanced oil recovery (EOR) as the process in which carbon would be utilized. The results show that CCU is preferable to CCS as long as there is sufficient demand in the EOR market. The distance between the location of emission and location of utilization/storage, and the capacity limits on the pipes are an important factor in deciding between carbon capture and carbon trading. At carbon prices over $15/ton, carbon capture becomes preferable to carbon trading. These results show that as far as Turkey is concerned, CCU should be prioritized as a means of reducing nationwide carbon emissions in an environmentally and economically rewarding manner. The model developed in this study is generic, and it can be applied to any industry at any location, as long as the required inputs are available. (C) 2018 Elsevier Ltd. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 4Application of Ultrasonic Vibrations for Minimization of the Accumulation of Limescale in Steam Irons(Elsevier, 2018) Körük, Hasan; Şanlıtürk, Kenan Yüce; Serenli, MuzafferThe accumulation of limescale in steam irons can significantly reduce the ironing efficiency. It is this problem that inspired us to introduce ultrasonic vibrations to irons in order to minimize limescale accumulation. This study describes a methodology for designing, modelling and optimizing an iron fitted with an ultrasonic exciter in an attempt to minimize limescale accumulation. In our methodology, first, an experimental demonstration of the potential benefits of ultrasonic vibrations in steam irons was conducted, using two existing irons, one of which was equipped with an ultrasonic exciter. Having confirmed the benefits, an experimental iron was designed and then optimized to maximise ultrasonic vibrations using finite element analyses within a predefined frequency range. To validate the results of the finite element analyses, a prototype iron base was built, and forced vibrations of this prototype, at ultrasonic frequencies ranging from 35 to 40 kHz, were measured using a laser vibrometer. The results of the theoretical and experimental vibration analyses as well as the physical experiments on the steam irons indicate that it is possible for ultrasonic vibrations to be utilized in irons to minimize the accumulation of limescale.
