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
A 130 nm CMOS Receiver for Visible Light Communication
(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Baykaş, Tunçer; Yagan, Muhammed Yaser; Uysal, Murat; Pusane, Ali Emre; Baykas, Tuncer; Dundar, Gunhan; Yalcinkaya, Arda Deniz
Visible light communication (VLC) is an emerging technology that has been gaining attention over the last few years. Transmission of data at higher rates in a VLC system is mainly limited by the modulation bandwidth of the employed LED. To alleviate this limitation, equalization is frequently employed. This is usually achieved by either using discrete circuit elements or in digital form. In this paper, we present a power-efficient VLC receiver as a system-on-chip, implemented in 130 nm CMOS technology. The proposed receiver supports LEDs with different bandwidths thanks to the switchable equalizer. We tested the proposed receiver using phosphorescent white LEDs with different bandwidths on an experimental VLC link. For each tested LED, around 20 fold improvement in data rate was achieved compared to the original bandwidth of the LED. For the LED with a modulation bandwidth of 1.6 MHz, data rates of 32 Mbps and 50 Mbps at a BER of 10(-2) were obtained at a distance of 2 meters without and with a blue filter, respectively.
Citation Count: 1
A 2020 vision for the Black Sea region: the Commission on the Black Sea proposes
(Routledge Journals Taylor & Francis Ltd, 2010) Aydın, Mustafa; Triantaphyllou, Dimitrios
The Black Sea region is coming into its own although it is at times a contested and dangerous neighbourhood. Despite heightened interest in the region its real priorities and needs are still being largely ignored by insiders and outsiders alike. What is needed are regional solutions for regional problems. The authors present the key findings and recommendations of the Commission on the Black Sea a civil society initiative comprising a number of current and former policy-makers scholars and practitioners both from within the region and from outside with the purpose of contributing to a joint vision and a common strategy for the Black Sea region by developing new knowledge in areas of key concern.
Citation Count: 8
2D Materials (WS2, MoS2, MoSe2) Enhanced Polyacrylamide Gels for Multifunctional Applications
(Mdpi, 2022) Uysal, Bengu Ozugur; Nayir, Seyma; Acba, Melike; Citir, Betul; Durmaz, Sumeyye; Kocoglu, Sevval; Yildiz, Ekrem
Multifunctional polymer composite gels have attracted attention because of their high thermal stability, conductivity, mechanical properties, and fast optical response. To enable the simultaneous incorporation of all these different functions into composite gels, the best doping material alternatives are two-dimensional (2D) materials, especially transition metal dichalcogenides (TMD), which have been used in so many applications recently, such as energy storage units, opto-electronic devices and catalysis. They have the capacity to regulate optical, electronic and mechanical properties of basic molecular hydrogels when incorporated into them. In this study, 2D materials (WS2, MoS2 and MoSe2)-doped polyacrylamide (PAAm) gels were prepared via the free radical crosslinking copolymerization technique at room temperature. The gelation process and amount of the gels were investigated depending on the optical properties and band gap energies. Band gap energies of composite gels containing different amounts of TMD were calculated and found to be in the range of 2.48-2.84 eV, which is the characteristic band gap energy range of promising semiconductors. Our results revealed that the microgel growth mechanism and gel point of PAAm composite incorporated with 2D materials can be significantly tailored by the amount of 2D materials. Furthermore, tunable band gap energies of these composite gels are crucial for many applications such as biosensors, cartilage repair, drug delivery, tissue regeneration, wound dressing. Therefore, our study will contribute to the understanding of the correlation between the optical and electronic properties of such composite gels and will help to increase the usage areas so as to obtain multifunctional composite gels.
Citation Count: 0
Acceptable 'expats' versus unwanted 'Arabs': Tracing hierarchies through everyday urban practices of skilled migrant women in Istanbul
(Wiley, 2024) Tuncer, Ezgi
This article focuses on ethnic hierarchies found within highly educated migrant women working in Istanbul traced through their everyday urban practices. It introduces the stratified and comparative results of migration and resettlement of those from the Global North and the Global South through a comprehensive analysis on their urban lives, including their social positionings, preferences of neighbourhoods and daily patterns of their use of the city. Contrary to the common conception that skilled migrants are privileged, our research reveals inequalities and discriminatory practices they face that intersect with gender, nationality and ethnicity. Our research, based on qualitative analyses of in-depth interviews along with online subjective mapping representing use of the city, also reveals that regardless of their origin and identity, almost all our participants experience verbal/physical sexual harassment or discrimination in public space in Istanbul, which forces women to produce spatial tactics of everyday life.
Citation Count: 16
Accretion flows in nonmagnetic white dwarf binaries as observed in X-rays By:Balman, S (Balman, Solen)[ 1 ]
(Elsevıer Scı Ltd, 2020) Balman, Şölen
Cataclysmic Variables (CVs) are compact binaries with white dwarf (WD) primaries. CVs and other accreting WD binaries (AWBs) are useful laboratories for studying accretion flows, gas dynamics, outflows, transient outbursts, and explosive nuclear burning under different astrophysical plasma conditions. They have been studied over decades and are important for population studies of galactic X-ray sources. Recent space-and ground-based high resolution spectral and timing studies, along with recent surveys indicate that we still have observational and theoretical complexities yet to answer. I review accretion in nonmagnetic AWBs in the light of X-ray observations. I present X-ray diagnostics of accretion in dwarf novae and the disk outbursts, the nova-like systems, and the state of the research on the disk winds and outflows in the nonmagnetic CVs together with comparisons and relations to classical and recurrent nova systems, AM CVns and Symbiotic systems. I discuss how the advective hot accretion flows (ADAF-like) in the inner regions of accretion disks (merged with boundary layer zones) in nonmagnetic CVs explain most of the discrepancies and complexities that have been encountered in the X-ray observations. I stress how flickering variability studies from optical to X-rays can be probes to determine accretion history and disk structure together with how the temporal and spectral variability of CVs are related to that of LMXBs and AGNs. Finally, I discuss the nature of accretion in nonmagnetic WDs in terms of ADAF-like accretion flows, and elaborate on the solu-tions it brings and its complications, constructing an observational framework to motivate new theoretical calculations that introduce this flow-type in disks, outflow and wind models together with disk-instability models of outbursts and nova outbursts in AWBs and WD physics, in general. (C) 2020 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords
Citation Count: 31
Acculturation Attitudes and Social Adjustment in British South Asian Children: A Longitudinal Study
(Sage Publications Inc, 2013) Baysu, Gülseli; Baysu, Gülseli; Cameron, Lindsey; Nigbur, Dennis; Rutland, Adam; Watters, Charles; Hossain, Rosa; LeTouze, Dominique; Landau, Anick
A 1-year longitudinal study with three testing points was conducted with 215 British Asian children aged 5 to 11 years to test hypotheses from Berry's acculturation framework. Using age-appropriate measures of acculturation attitudes and psychosocial outcomes it was found that (a) children generally favored an integrationist attitude and this was more pronounced among older (8-10 years) than in younger (5-7 years) children and (b) temporal changes in social self-esteem and peer acceptance were associated with different acculturation attitudes held initially as shown by latent growth curve analyses. However a supplementary time-lagged regression analysis revealed that children's earlier integrationist attitudes may be associated with more emotional symptoms (based on teachers' ratings) 6 months later. The implications of these different outcomes of children's acculturation attitudes are discussed.
Citation Count: 1
Achieving Sustainability in Solar Energy Firms in Turkey through Adopting Lean Principles
(Mdpi, 2022) Ayağ, Zeki; Ayag, Zeki
Lean principles and sustainability are considered important terms in business. Solar firms are witnessing great competition to fulfill energy requirements, suffering from a huge amount of waste, negatively affecting the sustainability dimensions. Thus, the aim of the study is to build a framework for solar energy firms to achieve sustainability through adopting lean principles, which will help to fix many problems as waste and costs. The method included reviewing the literature to explore the founding of the relation between the two terms, and using a questionnaire that was directed to the responsible people in Turkish solar energy firms. The results of the survey were analyzed to: (1) Find out what the responsible people think about the two terms lean and sustainability; (2) Measure the probable relationship between lean principles and sustainability dimensions by applying a linear regression test; (3) Use the results of point number two to build the framework. The result showed there was a high level of relative importance about the two terms from the point of view of managers and experts in solar firms. In addition, the study found a relationship between adopting pull and flow principles of lean, and achieving economic and social dimensions of sustainability, this finding is represented in a framework.
Citation Count: 0
The acquisition and use of relative clauses in Turkish-learning children's conversational interactions: a cross-linguistic approach (vol 46, pg 1142, 2019)
(Cambridge Univ Press, 2022) Uzundag, Berna A.; Kuntay, Aylin C.
[Abstract Not Available]
Citation Count: 20
Activating reflective thinking with decision justification and debiasing training
(Society for Judgment and Decision making, 2020) Yılmaz, Onurcan; Doğruyol, Burak; Doğruyol, Burak
Manipulations for activating reflective thinking, although regularly used in the literature, have not previously been systematically compared. There are growing concerns about the effectiveness of these methods as well as increasing demand for them. Here, we study five promising reflection manipulations using an objective performance measure — the Cognitive Reflection Test 2 (CRT-2). In our large-scale preregistered online experiment (N = 1,748), we compared a passive and an active control condition with time delay, memory recall, decision justification, debiasing training, and combination of debiasing training and decision justification. We found no evidence that online versions of the two regularly used reflection conditions — time delay and memory recall — improve cognitive performance. Instead, our study isolated two less familiar methods that can effectively and rapidly activate reflective thinking: (1) a brief debiasing training, designed to avoid common cognitive biases and increase reflection, and (2) simply asking participants to justify their decisions.
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: 4
An Adaptive Affinity Matrix Optimization for Locality Preserving Projection via Heuristic Methods for Hyperspectral Image Analysis
(IEEE-Inst Electrıcal Electronıcs Engıneers Inc, 2019) Ceylan, Oğuzhan; 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 Count: 4
Addressing climate change with behavioral science: A global intervention tournament in 63 countries
(Amer Assoc Advancement Science, 2024) Vlasceanu, Madalina; Doell, Kimberly C.; Bak-Coleman, Joseph B.; Todorova, Boryana; Berkebile-Weinberg, Michael M.; Grayson, Samantha J.; Van Bavel, Jay J.
Effectively reducing climate change requires marked, global behavior change. However, it is unclear which strategies are most likely to motivate people to change their climate beliefs and behaviors. Here, we tested 11 expert-crowdsourced interventions on four climate mitigation outcomes: beliefs, policy support, information sharing intention, and an effortful tree-planting behavioral task. Across 59,440 participants from 63 countries, the interventions' effectiveness was small, largely limited to nonclimate skeptics, and differed across outcomes: Beliefs were strengthened mostly by decreasing psychological distance (by 2.3%), policy support by writing a letter to a future-generation member (2.6%), information sharing by negative emotion induction (12.1%), and no intervention increased the more effortful behavior-several interventions even reduced tree planting. Last, the effects of each intervention differed depending on people's initial climate beliefs. These findings suggest that the impact of behavioral climate interventions varies across audiences and target behaviors.
Citation Count: 1
Admission control for a capacitated supply system with real-time replenishment information
(Elsevier, 2023) Hekimoğlu, Mustafa; Hekimoglu, Mustafa; Dekker, Rommert
Control towers can provide real-time information on logistic processes to support decision making. The question however, is how to make use of it and how much it may save. We consider this issue for a company supplying expensive spare parts and which has limited production capacity. Besides deciding on base stock levels, it can accept or reject customers. The real-time status information is captured by a k-Erlang distributed replenishment lead time. First we model the problem with patient customers as an infinite-horizon Markov decision process and minimize the total expected discounted cost. We prove that the optimal policy can be characterized using two thresholds: a base work storage level that determines when ordering takes place and an acceptance work storage level that determines when demand of customers should be accepted. In a numerical study, we show that using real-time status information on the replenishment item and adopting admission control can lead to significant cost savings. The cost savings are highest when the optimal admission threshold is a work storage level with a replenishment item halfway in process. This finding is different from the literature, where it is stated that the cost increase of ignoring real-time information is negligible under either the lost sales or the backordering case. Next we study the problem where customers are of limited patience. We find that the optimal admission policy is not always of threshold type. This is different from the literature which assumes an exponential production lead time.
Citation Count: 13
Adoption of Mobile Health Apps in Dietetic Practice: Case Study of Diyetkolik
(Jmır Publıcatıons, Inc, 130 Queens Quay E, 2020) Aydın, Mehmet Nafiz; 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 Count: 1
Adults' recollection of the earliest memories: early parental elaboration mediated the link between attachment and remembering
(Springer, 2022) Oener, Sezin; Guelgoez, Sami
Social interactions are a major factor in organizing the earliest experiences in the memory system. In the current study, we tested the role of parental reminiscing on the relationship between parental attachment and recollection of earliest memories. The present study focused mainly on possible mediating properties of parental elaboration between the relationship of attachment and the recall of the earliest memories. We found a full mediation pattern, showing that high parental avoidance was associated with less parental elaboration, which was then linked to the earliest memories coming from a later age and poor recollection of these memories. On the other hand, although parental anxiety was related to the earliest memories coming from a later age and rich recollection of the earliest memories, the degree of parental elaboration was not found as a mediator. Findings are discussed in line with the role of the early relational and communicative input on adults' recollections of early events.
Citation Count: 24
Adventures in data analysis: a systematic review of Deep Learning techniques for pattern recognition in cyber-physical-social systems
(Springer, 2023) Amiri, Zahra; Heidari, Arash; Navimipour, Nima Jafari; Unal, Mehmet; Mousavi, Ali
Machine Learning (ML) and Deep Learning (DL) have achieved high success in many textual, auditory, medical imaging, and visual recognition patterns. Concerning the importance of ML/DL in recognizing patterns due to its high accuracy, many researchers argued for many solutions for improving pattern recognition performance using ML/DL methods. Due to the importance of the required intelligent pattern recognition of machines needed in image processing and the outstanding role of big data in generating state-of-the-art modern and classical approaches to pattern recognition, we conducted a thorough Systematic Literature Review (SLR) about DL approaches for big data pattern recognition. Therefore, we have discussed different research issues and possible paths in which the abovementioned techniques might help materialize the pattern recognition notion. Similarly, we have classified 60 of the most cutting-edge articles put forward pattern recognition issues into ten categories based on the DL/ML method used: Convolutional Neural Network (CNN), Recurrent Neural Network (RNN), Generative Adversarial Network (GAN), Autoencoder (AE), Ensemble Learning (EL), Reinforcement Learning (RL), Random Forest (RF), Multilayer Perception (MLP), Long-Short Term Memory (LSTM), and hybrid methods. SLR method has been used to investigate each one in terms of influential properties such as the main idea, advantages, disadvantages, strategies, simulation environment, datasets, and security issues. The results indicate most of the articles were published in 2021. Moreover, some important parameters such as accuracy, adaptability, fault tolerance, security, scalability, and flexibility were involved in these investigations.
Citation Count: 0
Aesthetic Approach for Critical Sociology of Contemporary Communication Technology
(Sage Publications inc, 2024) Arda, Balca
Critical theory has already marked that technology often threatens civil liberties, personal autonomy, and rights. Heidegger, later Marcuse, emphasized how technology is not value-free in its own revealing power of the surrounding environment, external and inner nature. Throughout this paper, I explore how the aesthetic approach engages with critical theory and contributes to the sociology of media and communication. For this, I will theoretically survey the terms of sociality under the forces of immediate communication, ubiquitous surveillance, and the compression of time and space that Baudrillard and Virilio once problematized through the lens of critical technology theory to adapt it to media and communication studies. I contend that techno-aesthetics that converge with Ranciere's dissensus can provide practical suggestions on an updated vocation of critical sociology. This article discusses the potential of aesthetic and social criticism of media for democratizing technology that Feenberg inserted. It is urgent to acknowledge the changing spatio-temporal aesthetic regimes that affect the societal imagination and limits of sociality and action to determine the next steps for achieving a commons-based society.
Citation Count: 13
After the Crimean crisis: towards a greater Russian maritime power in the Black Sea
(Routledge Journals Taylor & Francis Ltd, 2014) Delanoe, Igor
The modernization of the Black Sea Fleet currently underway is believed to be one of the most ambitious parts of the Russian State Arms Procurement programme 2011-2020. Up to 18 units are being built and are expected to be commissioned in the Russian Black Sea Fleet by 2020 while new infrastructures are being developed. However Russia's annexation of Crimea in March 2014 has overthrown the Black Sea maritime context. It is likely to give substantial impetus to Russian naval plans in the Black Sea and by extension to sustain Moscow's resumption of naval activity in the Mediterranean. Yet whereas Russia's maritime power has been dramatically enhanced due to the takeover of Crimea Moscow's naval power in the Black Sea and in the Mediterranean remains challenged by a set of qualitative factors. Beyond the Ukrainian crisis has demonstrated the inability of the European Union to manage its Black Sea environment as well as it has highlighted the United States waning influence and interests in the region.
Citation Count: 4
Agent-based Optimization to Estimate Nash Equilibrium in Power Markets
(Taylor & Francis Inc, 2013) Yücekaya, Ahmet; Valenzuela, Jorge
In most deregulated power markets firms bid daily into a day-ahead power market. The auction mechanism supply and demand determine the equilibrium at each hour. In this environment firms aim to maximize their revenues by carefully determining their bids. This requires the development of effective computational methods that help them estimate their competitors' behaviors under incomplete information. In this article an agent-based method that uses particle swarm optimization is described to simulate the behavior of market participants. Particle swarm optimization is used in the bidding process and an agent-based model is applied to find a Nash equilibrium. Different stopping conditions are used to determine the equilibrium. Experimental results are presented for two power systems.
Citation Count: 40
Air quality prediction using CNN plus LSTM-based hybrid deep learning architecture
(Springer Heidelberg, 2022) Özmen, Atilla; Ogrenci, Arif Selcuk; Ozmen, Atilla
Air pollution prediction based on variables in environmental monitoring data gains further importance with increasing concerns about climate change and the sustainability of cities. Modeling of the complex relationships between these variables by sophisticated methods in machine learning is a promising field. The objectives of this work are to develop a supervised model for the prediction of air pollution by using real sensor data and to transfer the model between cities. The combination of a convolutional neural network and a long short-term memory deep neural network model was proposed to predict the concentration of air pollutants in multiple locations of a city by using spatial-temporal relationships. Two approaches have been adopted: the univariate model contains the information of one pollutant whereas the multivariate model contains the information of all pollutants and meteorology data for prediction. The study was carried out for different pollutants which are in the publicly available data of the cities of Barcelona, Kocaeli, and Istanbul. The hyperparameters of the model (filter, frame, and batch sizes; number of convolutional/LSTM layers and hidden units; learning rate; and parameters for sample selection, pooling, and validation) were tuned to determine the architecture that achieved the lowest test error. The proposed model improved the prediction performance (measured by the root mean square error) by 11-53% for particulate matter, 20-31% for ozone, 9-47% for nitrogenoxides, and 18-46% for sulfurdioxide with respect to the 1-hidden layer long short-term memory networks utilized in the literature. The multivariate model without using meteorological data revealed the best results. Regarding transfer learning, the network weights were transferred from the source city to the target city. The model has more accurate prediction performance with the transfer of the network from Kocaeli to Istanbul as those neighbor cities have similar air pollution and meteorological characteristics.

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