WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653

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A First-Order System of Equations on a Compact Star Graph
(Ankara Univ, FAC Sci, 2025) Mutlu, Gokhan; Ugulu, Ekin
This study concerns a boundary value problem generated by a system of first-order differential equations and some symmetric boundary conditions on a compact star graph. Unlike usual quantum graph Hamiltonians, the Hamiltonian considered in this paper acts on vector-valued functions living on the edges. Appropriate vertex conditions are introduced to ensure the corresponding boundary value problem is symmetric. In particular, coupling and separated conditions are imposed at the central and boundary vertices, respectively. Moreover, the general form of the vertex conditions at the central vertex is discussed. Finally, the characteristic function is constructed for the symmetric boundary value problem generated by the first-order system and specific coupling vertex conditions.
A Housing Satisfaction Study in an Area of Urban Transformation: The Case of the Turk-Is Apartment Blocks
(Yildiz Technical Univ, FAC Architecture, 2017) Kahraman, Zerrin Ezgi; Ozdemir, Suna Senem
This study investigated the housing satisfaction and the urban transformation expectations in the Turk-is Blocks, built by a labor cooperative in the Altinpark neighborhood of Altindag, Ankara. The area was declared risky in 2013. A survey and in-depth interviews were conducted to examine the satisfaction of residents with housing and their expectations of urban transformation. The results revealed that a large number of the respondents were satisfied with their houses and living environment. Satisfaction increased with duration of time living in the area and age. Over time, the homogenous and stable population in the area has reorganized their houses according to their needs and established a spatial, social, and emotional connection to their neighborhood. The strengths of the area include its neighborhood identity, close social relations, accessibility, and sufficiency of urban services and green areas. Areas of dissatisfaction included insufficient indoor installations, cultural/sports facilities, and security and parking lot problems. Most residents did not support urban transformation plans; however, those who do support the idea have high expectations of the process. With the condition of maintaining their current spatial rights, many perceived urban transformation as a solution to the problems of the area and indicated that their economic status has improved and that life has become more luxurious and comfortable.
A Meta-Heuristic Stochastic Algorithm for the Numerical Treatment of Cancer Model through the Chemotherapy and Stem Cells
(Elsevier, 2026) Baleanu, Dumitru; Defterli, Ozlem; Sabir, Zulqurnain; Abdelkawy, M. A.
Objective: The aim of current research is to present the numerical performances of the cancer treatment model based on chemotherapy and stem cells using one of the heuristic computing neural network procedures. The cancer treatment model through chemotherapy and stem cells is categorized into stem cells, affected cells, tumor cells, and chemotherapy-based concentration drug. Method: A process of artificial neural network is applied using the hybrid optimization of global and local search schemes, which are taken as genetic algorithm (GA) and an active set (AS). An error-based fitness function is designed by using the differential model and then optimized by the hybridization of both global and local search schemes. GA is applied to exploit the global result and give a primary guess to the AS that further improves the results locally. AS is rooted in the GA, where GA produces new populaces and AS optimizes the fitness function for every individual. The hybridization of these two schemes is used iteratively for purifying the results. Ten numbers of neurons and log-sigmoid activation functions has been used to solve the cancer treatment model based on chemotherapy and stem cells. Results: For the correctness of the stochastic solver, the obtained numerical results have been compared with any traditional scheme. Moreover, the reliability and capability of the scheme are performed through the absolute error around 10-05 to 10-07 along with different statistical approaches for solving the mathematical model. Novelty: The proposed artificial neural network structure along with the hybrid optimization of global and local search schemes has never been implemented before to solve the cancer treatment model based on chemotherapy and stem cells.
A New Classification System for Weathered Weak Rock Masses
(Techno-Press, 2026) Mao, Yimin; Nanehkaran, Yaser A.; Azarafza, Mohammad; Miao, Decheng
This research presents a new empirical rock mass classification system for sedimentary weak rocks, such as marlstones, taking into account the extent of weathering within the rock mass. For this purpose, 45 marlstone samples were systematically collected from the South Pars region in southwest Iran. The study involved measuring the geoengineering characteristics of the marls and assessing the degree of weathering they had undergone. The collected data was used to create variation weathering charts that show changes in rock mass durability and geoengineering properties with different degrees of weathering. These new charts are valuable tools for evaluating the condition of marlstone rock masses, providing a clearer understanding of how weathering affects their stability and durability. The empirical classification system introduced in this study significantly advances the assessment and management of marlstone formations in geotechnical engineering and related fields.
A Soft Sensor-Integrated Cell Stretching Device for Precise and Reproducible Mechanotransduction
(Royal Soc, 2026) Yildiz, Solen Kumbay; Akar, Samet; Ozturk, Emre; Dincer, Pervin; Uyanik, Ismail; Duz, Nilufer
Mechanical stretch is a fundamental regulator of cell fate, yet in vitro replication remains challenging because conventional stretchers deliver non-uniform strain and ignore batch-to-batch variations in substrate stiffness-so the stress actually experienced by cells varies unpredictably. We introduce the first biaxial cell-stretching platform that couples an embedded soft resistive micro-channel sensor with high-frequency closed-loop control. Real-time deformation read-out (60 Hz) drives a 24 kHz actuator loop to compensate for polydimethylsiloxane (PDMS) moduli spanning an order of magnitude, delivering user-defined triangular or square waveforms (5-20% amplitude; 0.5-10 s period) with less than 2% steady-state error. Closed-loop operation maintains strain-invariant membrane stress within +/- 5%, reducing well-to-well variability threefold compared with open-loop actuation. Biological validation using immortalized human myoblasts exposed to 10% cyclic stretch for 4 h produced a significant upregulation of YAP/TAZ target genes (C-MYC, MYL9, DIAPH1, ANKRD1; p < 0.001), confirming mechanotransductive efficacy. The platform's modular architecture accommodates stiffness-tunable hydrogels and live imaging, offering a reproducible tool for mechanobiology, tissue engineering, disease modelling and personalized mechanotherapy.
A Switching Inverse Dynamics Controller for Parallel Manipulators around Drive Singular Configurations
(Tubitak Scientific & Technological Research Council Turkey, 2016) Ider, Sitki Kemal; Ozdemir, Mustafa
Despite many advantages, parallel manipulators are known to possess drive singularities where the control of one or more degrees of freedom is lost. Around these singular configurations, the required actuator forces grow unbounded. Previous efforts in the literature put forward singularity-consistent trajectory planning and singularity robust modification of the dynamic equations as a solution to this problem. However, this previous method is applicable only for the open-loop operation of the manipulator, whereas initial configuration errors, external disturbances, and modeling errors should necessarily be taken into account in a closed-loop sense in real-life applications. With this aim, a switching inverse dynamics controller is proposed in this study for the trajectory tracking control of parallel manipulators as they pass through drive singular configurations. Simulations of the application of the developed controller result in good tracking performance, even in the presence of modeling errors, while the actuator efforts remain bounded and continuous in the neighborhood of the singularity.
Adaptive Decision Fusion Based Framework for Short-Term Wind Speed and Turbulence Intensity Forecasting: Case Study for North West of Turkey
(Tubitak Scientific & Technological Research Council Turkey, 2017) Dinckal, Cigdem; Toreyin, Bechet Ugur; Kucukali, Serhat; Din Çkal, Çigdem
In this paper, an online learning framework called adaptive decision fusion (ADF) is employed for short-term wind speed and turbulence intensity forecasting by use of wind speed data for each season for the city of Izmit, located in the northwest of Turkey. Fixed-weight (FW) linear combination is derived and used for comparison with ADF. Wind speeds and turbulence intensities are predicted from the existing wind speed data and computed turbulence intensities, respectively, using the ADF and FW methods. Simulations are carried out for each season and the results are tested on mean absolute percentage error criterion. It is shown that the proposed model captured the system dynamic behavior and made accurate predictions based on the seasonal wind speed characteristics of the site. The procedure described here can be used to estimate the local velocity and turbulence intensity in a wind power plant during a storm.
AGENT: An Elitism-Guided Evolutionary Framework for Enhanced Task Allocation Performance in Heterogeneous Cloud Systems
(Elsevier, 2026) Osama, Muhammad; Riaz, Muhammad Bilal; Shahid, Muhammad Farrukh; Qadri, Syed Shah Sultan Mohiuddin
Cloud Computing (CC) delivers on-demand services through Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS) models. This study specializes in the approach to IaaS task scheduling in the heterogeneous data centers, where resource allocation is a critical issue to ensure that makespan is minimized. The NP-complete nature of such a scheduling problem requires sophisticated meta-heuristic solutions as the use of cloud workloads increases exponentially. Although Genetic Algorithms (GA) have received extensive use, available adaptive variants usually vary parameters based on aggregate populations statistics without individual solution tracking and elitism is not commonly implemented with adaptive mechanisms in a size-conserving fashion. This paper presents the Adaptive Genetic Algorithm with Elitism and Nonlinear Tuning (AGENT) that combines three new innovations: (1) size-preserving elitism that guarantees a monotonic improvement without growing the population, (2) feedback-based nonlinear parameter adaptation which is controlled by explicit success/failure counters as indicators of evolutionary progress of a population, unlike fitness-proportional or population-statistics-based methods, and (3) a multi-task-per-VM allocation model that captures real cloud elasticity. Experimental validation of CloudSim Plus simulation with Amazon EC2 VM setups showed makespan improvements of 3.14%-28.89% than baseline algorithms (HAGA, AIGA, SGA, Max-Min, Min-Min) with synthetic workloads. Scalability was tested on workloads of various sizes and was found to perform well with near-optimal results. Reduced makespan is associated with shorter VM operating time, which implies that energy efficiency may be improved and therefore, it should be investigated in the future by taking direct measurements.
An Experimental Investigation of the Split-Attention Effect on Endoscopic Surgical Performance
(Wolters Kluwer Medknow Publications, 2025) Ozcelik, Erol; Cagiltay, Nergiz Ercil; Topalli, Damla
Introduction:Surgeons in the operating theatre frequently need to split their attention, such as when switching between the monitor and radiological images during endoscopic surgery. This split attention can lead to cognitive overload, potentially impacting performance. Despite this, limited research has been conducted on how split attention affects surgical outcomes.Patients and Methods:This study examines the impact of split attention on surgical performance in a simulation-based training environment with two conditions: A far-condition (where information sources were spaced farther apart) and a near-condition (where sources were positioned closer together). A total of 53 participants (13 experienced surgical residents and 40 beginners) completed ten trials in each condition.Results:The results indicated that split attention led to diminished performance in beginners but not in residents. These findings suggest that expertise plays a crucial role in managing cognitive load for surgeons.Conclusion:The study highlights the need to develop training curricula that promote the automation of surgical skills through practice, allowing surgeons to allocate more cognitive resources effectively.
An Investigation of Atmospheric Icing Effects on Wind Turbine Blade Aerodynamics and Power Output: A Case Study of the NREL 5 MW Turbine
(MDPI, 2026) Ozturk, Berkay; Kocak, Eyup
This study presents a numerical investigation of the effects of atmospheric icing on the aerodynamic performance and power output of the NREL 5 MW reference wind turbine. In cold climate regions, ice accretion on wind turbine blades significantly alters the airfoil geometry, leading to aerodynamic degradation characterized by increased drag, reduced lift, and substantial power losses. Understanding these effects is therefore essential for reliable performance prediction and efficient turbine operation under icing conditions. To address this problem, numerical simulations were conducted on six representative blade sections using the FENSAP-ICE framework, which integrates flow field calculations, droplet transport, and ice accretion modeling within a unified computational environment. The analyses were performed under different atmospheric icing conditions, considering liquid water content values of 0.22 g/m3 and 0.50 g/m3 and ambient temperatures of -2.5 degrees C and -10 degrees C. The median volumetric diameter was fixed at 20 & micro;m, and the icing duration was set to one hour for all cases, allowing for both glaze and rime ice formations to be systematically examined. The results reveal that ice accretion becomes increasingly pronounced toward the blade tip, mainly due to higher relative velocities and increased collection efficiency in the outer sections. Glaze icing conditions produce irregular horn-shaped ice formations and lead to severe aerodynamic degradation, whereas rime ice forms more compact structures near the leading edge and results in comparatively lower performance losses. The degraded aerodynamic coefficients obtained from the iced airfoils were subsequently incorporated into BEM-based power calculations, indicating that total power losses can reach up to 40% under severe icing conditions, with the outer blade sections contributing most significantly to this reduction. Furthermore, an economic assessment based on annual energy losses highlights the substantial impact of atmospheric icing on wind turbine performance and operational costs.
Analysis of the α-β Transition in Bismuth Titanate as a Function of Pressure and Temperature
(Taylor & Francis Ltd, 2026) Kiraci, A.
The temperature and pressure dependence of the damping constant (half-width) for the soft Raman mode in bismuth titanate, Bi2Ti4O11, was calculated using the pseudospin-phonon coupled (PS) and the energy fluctuation (EF) models in the vicinity of the transition at T-C = 513 K and P-C = 3.7 GPa. The order parameter that is associated with the observed soft Raman mode frequency and also the pressure-temperature phase diagram was used for this calculation of the damping constant. Our calculated values of both the Raman frequency and the damping constant were compared with the observed data from the literature. Finally, the values of the activation energy were deduced using our calculated damping constant via the Arrhenius plots.
Compatibility Assessment of Exterior Finish Coats for Insulated Walls
(Middle East Technical Univ, 2013) Demirci, Sahinde; Duzgunes, Arda; Ors, Kerime; Tavukcuoglu, Ayse
Configurations of a Drop Stuck between Two Parallel Laminae under Zero Gravity
(Springer INT Publ AG, 2026) Kessi, Arezki; Adjabi, Yassine; Jarad, Fahd; Namazov, Atif
In a zero-gravity environment and under static conditions, the interface between a drop and the surrounding fluid forms a surface of constant mean curvature. This concept is based on a general parametric representation proposed by Kenmotsu in 1980 with further developments discussed in 2003. In this article, we focus on studying the resulting axisymmetric surfaces in detail. Additionally, we rigorously characterize various configurations of a drop that is trapped between two parallel plates in the absence of gravity, while maintaining a fixed volume. These configurations depend on the contact angle with the plates (a phenomenological parameter) and the gap between them (a controllable parameter). Special attention is given to the case where the contact angle is equal to pi/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \pi /2 $$\end{document}.
Critical Aspects, Motivators and Barriers of Building-Integrated Vegetation
(Konya Technical Univ, FAC Architecture & Design, 2020) Almuder, Monder M.; Suzer, Ozge
Purpose Green buildings which provide improved user health conditions and environmentally responsible applications have gained significant attention, due to the increasing environmental problems, particularly caused by the construction industry at the global scale. However, vegetation is still not sufficiently integrated into buildings, even though numerous benefits of plants have been proven by many studies in literature. This research aims to find out the opinions of professionals and academicians in architecture-related fields regarding the critical aspects, as well as the motivators and barriers faced in BIV applications, namely; green roofs, green walls and interior gardens. Hence, it strives to help increase their application rates by underlining the significant issues to be considered. Design/methodology/approach As to fulfilling these objectives, a questionnaire survey was conducted on 120 participants with varying professions including architects, landscape designers and civil engineers, from four countries. Findings The results of this study pointed out that, healthcare buildings were given the first priority among the building types for applying BIV. Moreover, among the motivator factors, receiving a certificate was found as an important incentive, besides the environmental, social and economic benefits of BIV. Furthermore, although the highly rated barriers were found as 'the lack of proper regulations' and 'lack of demand by the user/client', the findings showed that the highest responsibility for the implementation of these applications was placed on the architect. Research Limitations/Implications Based on the five major groups of Koppen climate classification system, the case countries were selected as one from each of the four main types, and by neglecting only Polar, as it lacks settlements. By considering diverse levels of development and economic welfare, countries were selected as; Canada (Snow: Humid-Subarctic), Libya (Dry: Desert-arid), Malaysia (Tropical: Tropical-Rain forest) and Turkey (Mild temperate: Mediterranean). Since the study covered four different countries, the survey was conducted by the use of Google Forms software program. This tool enabled the production and distribution of questionnaires, as well as the collection of data based on the responses of the participants. Furthermore, in order to provide consistency among the questionnaires applied in different countries, the survey was conducted in English language, although it was not the native language for a majority of the participants. Moreover, based on studies claiming that participants are more inclined to select the option with the mid-value in a Likert scale, which implies a neutral position, in the questionnaire, these types of questions were constructed with the forced choice method, by keeping the scales with even number of options. Practical Implications It is expected that the results of this study would be beneficial to both the academicians and professionals involved in the green building industry, as well as to the governmental and/or green building authorities. It is expected that this study will help serve as a guide for the stakeholders to increase the application rates of BIV in the construction industry. Social Implications The results of this study were also evaluated based on the findings of four case countries and certain conclusions were derived as to their underlying socio-economic and geographical reasons. Originality/value - Although studies on similar subjects have appeared in the literature, there are none which solely focuses on BIV applications by conducting a survey on the mentioned four case countries and compares its findings with the literature and presents an in-depth analysis on the issue.
Dirac Systems with Regular and Singular Transmission Effects
(Tubitak Scientific & Technological Research Council Turkey, 2017) Ugurlu, Ekin
In this paper, we investigate the spectral properties of singular eigenparameter dependent dissipative problems in Weyl's limit-circle case with finite transmission conditions. In particular, these transmission conditions are assumed to be regular and singular. To analyze these problems we construct suitable Hilbert spaces with special inner products and linear operators associated with these problems. Using the equivalence of the Lax-Phillips scattering function and Sz-Nagy-Foias characteristic functions we prove that all root vectors of these dissipative operators are complete in Hilbert spaces.
Dissipative Operator and Its Cayley Transform
(Tubitak Scientific & Technological Research Council Turkey, 2017) Ugurlu, Ekin; Tas, Kenan
In this paper, we investigate the spectral properties of the maximal dissipative extension of the minimal symmetric differential operator generated by a second order differential expression and dissipative and eigenparameter dependent boundary conditions. For this purpose we use the characteristic function of the maximal dissipative operator and inverse operator. This investigation is done by the characteristic function of the Cayley transform of the maximal dissipative operator, which is a completely nonunitary contraction belonging to the class C-0. Using Solomyak's method we also introduce the self-adjoint dilation of the maximal dissipative operator and incoming/outgoing eigenfunctions of the dilation. Moreover, we investigate other properties of the Cayley transform of the maximal dissipative operator.
Effects of Communication Competency and Self-Esteem on Gaming Addiction Symptoms
(Turkish Green Crescent Soc, 2022) Bulut, Merve Topcu; Salis, Irem
Gaming behavior has become more and more popular, but there has not been any research that considers the relationship between communication competency, self-esteem, and internet gaming addiction symptoms. The main aim of the ongoing study was to assess the associations between internet gaming addiction symptoms, self-esteem, and dimensions of communication competency. For this purpose, data were obtained from 455 individuals (47.7% females and 52.3% males) who reported that they are involved in gaming. In this study, participants were assessed with the following scale set: Sociodemographic Form, Internet Gaming Disorder Scale-Short Form, Communicative Competence Scale, and Rosenberg Self-Esteem Scale. Analyses indicated that the internet gaming disorder total score has a significant and negative correlation with self-esteem and dimensions of communication competency. Besides these results, self-esteem and listening competency of dimensions of communication competency have been found as a significant predictor of internet gaming disorder total score. In the literature, there has been only finite published research analyzing the dimensions of communication competency, self-esteem, and internet gaming disorder.
Effects of Routing Algorithms on Novel Throughput Improvement of Mobile Ad Hoc Networks
(Tubitak Scientific & Technological Research Council Turkey, 2012) Preveze, Barbaros; Safak, Aysel
A cognitive method called most congested access first (MCAF), minimizing the packet loss ratio and improving the throughput of a multihop mobile WiMAX network, is proposed. MCAF combines both the time division multiple access and the orthogonal frequency division multiple access methods. MCAF additionally uses spectral aid and buffer management methods, which air proposed in this paper, to manage both spectrum. access and packets in the buffers. By using these novel methods, real-time video and voice packet transmission is achieved, data packet loss rate is minimized, and the system throughput per node is improved. Effects of fastest path and ant colony routing algorithms on throughput improvement methods are investigated. It is shown that the fastest path routing algorithm, provides higher throughput values than the ant colony routing algorithm.
Energy Intensity in CIS Economies: Insights into Convergence with OECD Benchmarks
(Savez Ekonomista Vojvodine, 2026) Baskaraagac, Nermin Yasar
This study evaluates energy intensity convergence in Commonwealth of Independent States (CIS) economies in comparison to the OECD average from 2000 to 2019, utilising beta-convergence and sigma-convergence analyses based on conventional unit root analysis alongside the KSS stationarity approach, which accounts for data nonlinearities, and the Phillips-Sul club convergence procedure. The results indicate that most CIS countries did not achieve energy intensity convergence during the period under review. Furthermore, while the Phillips-Sul test classifies all studied countries, including the OECD-20, into a single convergence club, it only presents weak evidence of significant convergence. This limited convergence is likely hindered by the continued presence of Soviet-era manufacturing infrastructure in many CIS economies. From a policy perspective, the development of comprehensive economic frameworks that incorporate legal, institutional, technical, and financial reforms, supported by targeted investments in research, cutting-edge technologies, and updated standards, is essential to significantly boost energy efficiency and effectively address challenges on both the supply and demand sides.
Experimental Investigation of Granular Soil and Clay Interfaces with Direct Shear Tests
(MDPI, 2026) Ozturk, Sevki; Ergun, Mehmet Ufuk
This study experimentally investigates the shear strength behavior of interfaces formed between granular soils and clay under drained conditions, with particular emphasis on peak-to-residual strength evolution. Large and small-scale direct shear tests were performed on clay, granular soils (sand and gravel), and their interfaces, and shearing was continued to large displacements to reliably capture residual behavior. Unlike most previous studies that focus on soil mixtures, this study explicitly quantifies interface-specific shear strength parameters and highlights their distinct mechanical response. The results show that while interface cohesion remains comparable to that of clay, the interface friction angle is consistently higher. Specifically, under residual conditions, the friction angle of the clay (12.9 degrees) increased to 16.4 degrees for the sand-clay interface and to 19.8 degrees for the gravel-clay interface. These findings demonstrate that adopting clay residual parameters for granular soil-clay interfaces may be overly conservative and that interface-specific residual friction angles should be considered in stability analyses of slopes and earth structures.

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