Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/20.500.11779/1926

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1441. Quantification of the Flow Noise in Household Refrigerators
(JVE INTERNATIONAL LTD., 2014) Körük, Hasan; Arısoy, Ahmet; Bilgin, Necati
The flow noise in household refrigerators is quantified in this study. First, the sound pressure measurements in a quiet room using typical household refrigerators are conducted and the noise characteristics of the refrigerators are presented. Then, the flow noise in household refrigerators is quantified using the results of the overall analysis and Fourier transform of the measured sound pressure data. After that, the flow noise in household refrigerators is quantified using the sound pressure measurements conducted using a specially designed test rig. The frequency characteristics of the flow noise in household refrigerators are also explored and the contribution of the flow noise is identified.
A 32-Society Investigation of the Influence of Perceived Economic Inequality on Social Class Stereotyping
(Wiley, 2022) Ashokkumar, Ashwini; Billet, Matthew; Becker, Maja; Peters, Kim; Jetten, Joland; Barry, Oumar; Tanjitpiyanond, Porntida; Peker, Müjde
There is a growing body of work suggesting that social class stereotypes are amplified when people perceive higher levels of economic inequality—that is, the wealthy are perceived as more competent and assertive and the poor as more incompetent and unassertive. The present study tested this prediction in 32 societies and also examines the role of wealth-based categorization in explaining this relationship. We found that people who perceived higher economic inequality were indeed more likely to consider wealth as a meaningful basis for categorization. Unexpectedly, however, higher levels of perceived inequality were associated with perceiving the wealthy as less competent and assertive and the poor as more competent and assertive. Unpacking this further, exploratory analyses showed that the observed tendency to stereotype the wealthy negatively only emerged in societies with lower social mobility and democracy and higher corruption. This points to the importance of understanding how socio-structural features that co-occur with economic inequality may shape perceptions of the wealthy and the poor. © 2022 The Authors. European Journal of Social Psychology published by John Wiley & Sons Ltd.
Acoustic Cavitation Model Based on a Novel Reduced Order Gas Pressure Law
(2021) Pasinlioğlu, Şenay; Delale, Can Fuad
The thermal behavior of a spherical gas bubble in a liquid excited by an acoustic pressure signal is investigated by constructing an iterative solution of the energy balance equations between the gas bubble and the surrounding liquid in the uniform pressure approximation. This iterative solution leads to hierarchy equations for the radial partial derivatives of the temperature at the bubble wall, which control the temporal rate of change of the gas pressure and gas temperature within the bubble. In particular, a closure relation for the hierarchy equations is introduced based on the ansatz that approximates the rapid change of state during the collapse of the bubble from almost isothermal to almost adiabatic behavior by time averaging the complex dynamics of change of state over a relatively short characteristic time. This, in turn, leads to the desired reduced order gas pressure law exhibiting power law dependence on the bubble wall temperature and on the bubble radius, with the polytropic index depending on the isentropic exponent of the gas and on a parameter that is a function of the Péclet number and a characteristic time scale. Results of the linear theory for gas bubbles are recovered by identifying this parameter as a function of the Péclet number based on the Minnaert frequency. The novel gas pressure law is then validated against the near-isothermal solution and against the results of the numerical simulations of the original energy balance equations for large amplitude oscillations using spectral methods. Consequently, an acoustic cavitation model that accounts for phase change but that neglects mass diffusion is constructed by employing the reduced order gas pressure law together with the Plesset–Zwick solution for the bubble wall temperature and the Keller–Miksis equation for spherical bubble dynamics. Results obtained using variable interface properties for acoustically driven cavitation bubbles in water show that the time variations of the bubble radius and the bubble wall temperature lie between those obtained by the isothermal and adiabatic laws depending on the value of the Péclet number and the characteristic time scale.
Acoustic Particle Palpation for Measuring Tissue Elasticity
(American Institute of Physics, 2015) El Ghamrawy, Ahmed; Körük, Hasan; Choi, James J; Pouliopoulos, Antonios N
We propose acoustic particle palpation—the use of sound to press a population of acoustic particles against an interface—as a method for measuring the qualitative and quantitative mechanical properties of materials. We tested the feasibility of this method by emitting ultrasound pulses across a tunnel of an elastic material filled with microbubbles. Ultrasound stimulated the microbubble cloud to move in the direction of wave propagation, press against the distal surface, and cause deformations relevant for elasticity measurements. Shear waves propagated away from the palpation site with a velocity that was used to estimate the material’s Young’s modulus.
Acoustic Streaming in a Soft Tissue Microenvironment
(Elsevier, 2019) El Ghamrawy, Ahmed; Mohammed, Ali; Jones, Julian R; Körük, Hasan; Choi, James J; de Comtes, Florentina
We demonstrated that sound can push fluid through a tissue-mimicking material. Although acousticstreaming in tissue has been proposed as a mechanism for biomedical ultrasound applications, such as neuromodu-lation and enhanced drug penetration, streaming in tissue or acoustic phantoms has not been directly observed. Wedeveloped a material that mimics the porous structure of tissue and used a dye and a video camera to track fluidmovement. When applied above an acoustic intensity threshold, a continuous focused ultrasound beam (spatialpeak time average intensity: 238 W/cm2, centre frequency: 5 MHz) was found to push the dye axially, that is, in thedirection of wave propagation and in the radial direction. Dye clearance increased with ultrasound intensity andwas modelled using an adapted version of Eckart’s acoustic streaming velocity equation. No microstructuralchanges were observed in the sonicated region when assessed using scanning electron microscopy. Our study indi-cates that acoustic streaming can occur in soft porous materials and provides a mechanistic basis for future use ofstreaming for therapeutic or diagnostic purposes.
Adaptive Reuse of High-Rise Buildings for Housing: a Study of Istanbul Central Business District
(Cogitatio Press, 2024) Aydemir, Ayşe Zeynep; Akın, Tomris
The abrupt shift to remote work due to the Covid-19 pandemic increased vacant office spaces globally, especially in high -rent central business districts (CBDs). These vacant office spaces offer the potential for conversion into housing, addressing the shortage of affordable housing in central areas. Additionally, this topic presents a unique experimental ground for architecture students. This study focuses on the Istanbul CBD as a case study, examining the historical developments that led to a rise in office vacancy rates and housing inequality, and exploring the potential for adaptive reuse of these vacant office buildings. A key focus of this study is to underline the pedagogical value of adaptive reuse, highlighting how such projects can inspire more diverse and equitable housing models, fostering experimental and sustainable design approaches. It systematically evaluates the outcomes of a 4th -year architectural design studio that focuses on the adaptive reuse of the Tat Towers in the Istanbul CBD, a structurally vacant high-rise office building, and asks: How does the context of adaptive reuse enable a different design approach, and, potentially, new spatial norms and standards to emerge, and how might this hold a pedagogical value for architecture education? Following these questions, the article discusses how norms and standards are not only culturally but also typologically contextual, and how the students have explored how norms and standards might change, outlining new design approaches to adaptive reuse.
Adoption and Use of Learning Management Systems in Education: the Role of Playfulness and Self-Management
(MDPI [Commercial Publisher], 2021) Akküçük, Ulaş; Balkaya, Selen
This article investigates the factors affecting primary and secondary education teachers' behavioral intention to adopt learning management systems (LMSs). Information technology (IT) innovations have the power to change the way we work, educate, learn, and basically the way we live. The effect of IT innovations on education makes it critical to understand the current usage situation of LMSs and the factors affecting their adoption by teachers. The unified theory of acceptance and use of technology (UTAUT) was extended with factors from education and game-based learning literature. In order to see the effect of individual- and organizational-level characteristics, multi-group structural equation modeling (SEM) analysis was conducted and discrepancies in relationships were reported. Evaluation of users and non-users and teachers of different fields were also compared to each other. The findings of this study not only contribute to theory through the development and testing of a thorough model relating technology features and individual characteristics to behavioral intention to use, but also offer strong implications for practitioners who would like to increase LMS usage and create a more effective learning environment.
Advancements in Distributed Ledger Technology for Internet of Things
(Elsevier, 2020) Jurdak, Raja; Arslan, Şuayb Şefik; Krishnamachari, Bhaskar; Jelitto, Jens
Internet 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.
The Age of Anxiety? It Depends Where You Look: Changes in Stai Trait Anxiety, 1970-2010
(Springer, 2016) Booth, Robert William; Leader, Tirza I.; Sharma, Dinkar
Purpose : Population-level surveys suggest that anxiety has been increasing in several nations, including the USA and UK. We sought to verify the apparent anxiety increases by looking for systematic changes in mean anxiety questionnaire scores from research publications. Methods : We analyzed all available mean State–Trait Anxiety Inventory scores published between 1970 and 2010. We collected 1703 samples, representing more than 205,000 participants from 57 nations. Results : Results showed a significant anxiety increase worldwide, but the pattern was less clear in many individual nations. Our analyses suggest that any increase in anxiety in the USA and Canada may be limited to students, anxiety has decreased in the UK, and has remained stable in Australia. Conclusions : Although anxiety may have increased worldwide, it might not be increasing as dramatically as previously thought, except in specific populations, such as North American students. Our results seem to contradict survey results from the USA and UK in particular. We do not claim that our results are more reliable than those of large population surveys. However, we do suggest that mental health surveys and other governmental sources of disorder prevalence data may be partially biased by changing attitudes toward mental health: if respondents are more aware and less ashamed of their anxiety, they are more likely to report it to survey takers. Analyses such as ours provide a useful means of double-checking apparent trends in large population surveys.
Aggression Begets Aggression: Psychological Dating Aggression Perpetration in Young Adults From the Perspective of Intergenerational Transmission of Violence
(Springer, 2021) Toplu-Demirtaş, Ezgi; Hatipoğlu-Sümer, Zeynep
The 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.
Application of Ultrasonic Vibrations for Minimization of the Accumulation of Limescale in Steam Irons
(Elsevier, 2018) Körük, Hasan; Şanlıtürk, Kenan Yüce; Serenli, Muzaffer
The 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.
Approximate Closed-Form Solutions for Vibration of Nano-Beams of Local/Non-local Mixture
(Springer, 2022) Ruta, Giuseppe; Eroğlu, Uğurcan
This paper presents an approach to natural vibration of nano-beams by a linear elastic constitutive law based on a mixture of local and non-local contributions, the latter based on Eringen's model. A perturbation in terms of an evolution parameter lets incremental field equations be derived; another perturbation in terms of the non-local volume fraction yields the variation of the natural angular frequencies and modes with the 'small' amount of non-locality. The latter perturbation does not need to comply with the so-called constitutive boundary conditions, the physical interpretation of which is still debated. The possibility to find closed-form solutions is highlighted following a thorough discussion on the compatibility conditions needed to solve the steps of the perturbation hierarchy; some paradigmatic examples are presented and duly commented.
Assessing Mathematical Higher-Order Thinking Skills: an Analysis of Turkish University Entrance Examinations
(Routledge, 2023) Aydın, Utkun; Birgili, Bengi
Internationally, mathematics education reform has been directed toward characterizing educational goals that go beyond topic/content/skill descriptions and develop students’ problem solving. The Revised Bloom’s Taxonomy and MATH (Mathematical Assessment Task Hierarchy) Taxonomy characterize such goals. University entrance examinations have been seen as one way of accomplishing these goals and influence learning, teaching, and assessment in mathematics. The present study analyzed mathematics items (N = 1077) in Turkish university entrance examinations in 1998-2013 and objectives (N = 621) in mathematics curricula in 2005, 2011, and 2013 to determine the extent to which they represent the dimensions/categories of these taxonomies and the degree to which items are aligned with objectives in terms of reflecting the dimensions/categories of these taxonomies. The findings reveal that the items demand, to a large extent, automated computational skills; this is also evident in the relevant mathematics curricula. Implications for practice are discussed and could play a role in reforming assessment. © 2023 The Author(s). Published with license by Taylor & Francis Group, LLC.
Assessment of the Disaster Recovery Progress Through Mathematical Modelling
(TMMOB İnşaat Mühendisleri Odası, 2020) Dikmen, Seyyit Ümit; Sönmez, Murat; Akbıyıklı, Rıfat
Natural disasters, especially major earthquakes, cause widespread devastation in the built environment. Hence, the major component of the recovery in its aftermath constitutes a chain of projects starting at different times, having different costs and durations. In this study, the post disaster recovery curve modelled through a mathematical approach taking into account these properties of the projects. The approach followed is based on the project S-curve concept that provides the opportunity to simulate the progress by outlining the project spending. Well-known mathematical functions are adapted to model the project spending and the handover processes. Monte Carlo simulation is performed to evaluate the general behavior of the recovery curve using the model developed. Weibull distribution is used to generate the model’s parameters. Results of the Monte Carlo simulation demonstrate that the recovery process exhibits an S-shape, the duration of initial portion and the slope of the bulk portion being significantly governed by the level of preparedness of the community.
Assessment of the Measurement and Prediction Methods for the Acoustic Properties of Natural Fiber Samples and Evaluation of Their Properties
(Taylor & Francis, 2021) Körük, Hasan
Although some studies have been conducted to show how natural fibers canreplace synthetic materials, the use of many natural fibers is still limited. Onthe other hand, the use of natural fibers can become very common in manyapplications once their performance is fully understood. This paper aims topresent a critical assessment of the acoustic properties of natural fibersamples. First, the methods commonly used for the measurement and prediction of the acoustic properties of natural fiber samples are determined.Second, the common techniques for measuring sound absorption coefficients (SACs) and sound transmission losses (STLs) are presented, and theiradvantages and limitations are evaluated. After that, the models commonlyused for the prediction of acoustic properties are presented. Then, the SACsof many natural fiber samples are presented along with the thickness, bulkdensity and flow resistivity of the samples. Furthermore, the SACs of thesamples are normalized using sample thickness and bulk density, and thesound absorption performance of the fiber samples is evaluated. Based onthe results of many natural fiber samples, an empirical model for estimatingthe SACs of natural fiber samples is presented. Finally, the STLs of someporous natural fiber samples are presented.
An Assessment of the Performance of Impedance Tube Method
(Institute of Noise Control Engineering, 2014) Hasan Körük
The impedance tube method is widely used for measuring sound absorption (or reflection) coefficients of acoustic materials as a function of frequency. However, the sound absorption coefficients obtained using the impedance tube method may have some variations due to the dimensions (limits) of an impedance tube, sample preparation and sample mounting. This paper assesses the performance of the two-microphone impedance tube method as a function of frequency for different tube dimensions and materials and presents suggestions for increasing the reliability and repeatability of impedance tube measurements. First, after summarizing a systematic way for measuring acoustic transfer functions, sound absorption coefficients of a variety of materials ranging from conventional absorbing acoustic materials to samples with thin films are measured using two tubes with different tube diameter and microphone spacing. Uncertainty of sound absorption coefficients for various materials is discussed, and the frequency limits of impedance tubes are assessed. Then, a method for minimizing uncertainty due to sample mounting is proposed and the main findings are discussed.
Asymmetric Effects of Eu Cohesion Policy on Eu Regional Growth: the Role of Macroeconomic Uncertainty
(Elsevier B.V., 2024) Pınar, Mehmet; Karahasan, Burhan Can
Cohesion policy and the EU funds have been key elements for territorial integration in Europe. Evidence shows that EU funds support the growth performance of regions. However, less has been discussed about the potential impact of macroeconomic uncertainty on the effectiveness of EU funds. Our analyses confirm that EU funds are important in understanding regional economic growth differences. However, the extent of macroeconomic uncertainty decreases the effectiveness of the EU funds. Our results are robust in including local controls, non-linearity of the EU funds’ effect, different EU fund categories, and regional heterogeneity in the EU. © 2024 The Authors
Asymptotically Mds Array Bp-Xor Codes
(2018) Arslan, Şuayb Şefik
Belief propagation (BP) on binary erasure channels (BEC) is a low complexity decoding algorithm that allows the recovery of message symbols based on bipartite graph pruning process. Recently, array XOR codes have attracted attention for storage systems due to their burst error recovery performance and easy arithmetic based on Exclusive OR (XOR)-only logic operations. Array BP-XOR codes are a subclass of array XOR codes that can be decoded using BP under BEC. Requiring the capability of BP-decodability in addition to Maximum Distance Separability (MDS) constraint on the code construction process is observed to put an upper bound on the achievable code block-length, which leads to the code construction process to become a hard problem. In this study, we introduce asymptotically MDS array BP-XOR codes that are alternative to exact MDS array BP-XOR codes to allow for easier code constructions while keeping the decoding complexity low with an asymptotically vanishing coding overhead. We finally provide a code construction method that is based on discrete geometry to fulfill the requirements of the class of asymptotically MDS array BP-XOR codes.
Barriers in Participative Water Governance: a Critical Analysis of Community Development Approaches
(MDPI, 2022) Shunglu, Raghav; Withanachchi, Chandana Rohana; Kibaroǧlu, Ayşegül; Köpke, Sören; Kanoi, Lav; Nissanka, Thushantha S.; Gamage, Deepika U.
Participatory approaches within development programs involving common-pool resources are intended to revive a community’s role in managing these resources. Certainly, to ensure the successful and equitable use of such resources, community participation is essential. However, in many cases, attempts at applying a participatory approach often fail to genuinely engage all subgroups within a community due to assumptions of homogeneity and a lack of understanding of the deep socio-political divisions between people. As a result, development programs can be plagued by these pre-existing power relations, potentially resulting in tokenistic community participation and the continuation of elite capture of natural resources to the same extent or worse than before a development program has begun. This in turn can negatively impact good governance and the fair distribution of a common pool resource. This paper explores the use of participatory approaches in water projects, assessing to what degree power relationships impact water management programs. Using a qualitative approach, the paper identifies key challenges of participatory water governance through case studies from Turkey, India, and Sri Lanka, exploring: lack of social trust, elite capture of participatory processes, power heterogeneity and imbalances at the micro-level, and a lack of inclusive participation in decision-making. Based on the analysis of these case studies, this paper argues that it is essential for participatory development interventions to understand socio-political power relations within a community—an inherently complex and contested space. The so-called “exit strategy” of a community project play a key role to decide the project sustainability that grants the “community ownership” of the project. Such an understanding can bring about greater success in development interventions attempting to address water-related issues.
Base Station-Assisted Cooperative Network Coding for Cellular Systems With Link Constraints
(IEEE, 2022) Arslan, Suayb S.; Pourmandi, Massoud; Haytaoglu, Elif
We consider a novel distributed data storage/caching scenario in a cellular network, where multiple nodes may fail/depart simultaneously To meet reliability, we allow cooperative regeneration of lost nodes with the help of base stations allocated in a set of hierarchical layers1. Due to this layered structure, a symbol download from each base station has a different cost, while the link capacities between the nodes of the cellular system and the base stations are also constrained. Under such a setting, we formulate the fundamental trade-off with closed form expressions between repair bandwidth cost and the storage space per node. Particularly, the minimum storage as well as bandwidth cost points are formulated. Finally, we provide an explicit optimal code construction for the minimum storage regeneration point for a special set of system parameters.

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