TR-Dizin İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8652
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Article W-Band RCS Prediction of Small Objects: Comparing Two Widely Used Methods with Experimental Validation(Gazi Univ, 2025) Kara, Ali; Aydın, Elif; Yardım, Funda Ergün; Sezgin, Deniz; Ergun Yardim, FundaThis paper compares the accuracy of Shooting and Bouncing Rays and Electric Field Integral Equation methods for Radar Cross Section prediction of small objects at 77-81 GHz band. Existing studies on RCS prediction methods often lack comprehensive comparisons between computational and experimental results, particularly for small objects measured with a 77 GHz radar. This study addresses this gap by presenting an in-depth analysis of both simulation and measurement data. In this work, three targets with varying geometries and materials were measured with a frequency modulated continuous wave radar and simulated using Ansys HFSS and CST Studio Suite. The measurements were performed with a commercial off-the-shelf (COTS) frequency modulated continuous wave radar operating at 77-81 GHz. This study aims to emphasize the importance of considering both efficiency and accuracy when opting for an RCS prediction method. Overall, the outcomes of both methods have largely demonstrated good alignment. It has been noted that, while Shooting and Bouncing Rays method offers promising time-saving advantages, Electric Field Integral Equation method remains a valuable tool for complex geometries where precise results are crucial.Article Integrating the Seljuk Cultural Layer Into Contemporary Life: The Case of Niğde Historic City Center(Istanbul Univ, Research Inst Turkology, Dept Art History, 2025) Yavaşcan, Emel Efe; Urak, Zehra GedizGünümüz tarihî kent merkezleri, yer altı ve yer üstündeki tarihî izleriyle, kültürel zenginlikleri ve özgün kimlikle8 rinin yanı sıra, “yerin ruhu”nu yansıtan kentsel hafıza alanlarıdır. Çok katmanlı bu tarihî kent merkezleri, kültür varlıklarının fiziksel ve işlevsel eskimesi, sosyo8kültürel ve ekonomik doku bozulmaları, koruma problemleri vb. sorunlarla giderek çöküntü yerleri hâline gelmektedir. Bu sorunları barındıran Niğde kentinde yapılmış koruma uygulamalarında, kentin yer altında ve yer üstünde bulunan katmanlarının dikkate alınmamış olması çalışmada problem olarak belirlenmiştir. Kentli tarafından tepe olarak algılanan çalışma alanı uzun zamandır çöküntü alanı niteliğindedir. Çalışmanın amacı, Niğde Tarihî Kent Merkezi’nin Selçuklu Dönemi’ne ait tarihî katmanını analiz etmek, haritalan8 dırmak ve bu katmanı çağdaş koruma uygulamalarına entegre etmeye yönelik öneriler geliştirmektir. Araştırma verileri, kentin tarihî gelişiminde en belirleyici dönemin Selçuklu Dönemi olduğunu göstermektedir. Bu sebeple çalışma kapsamında bu katman odak alınmıştır. Ayrıca, diğer tarihî katmanların da korunarak günlük yaşama kazandırılmasına katkı sağlamak, bu çalışmanın bir diğer hedefidir. Bu bağlamda, Selçuklu Dönemi’ne ait yer üstü ve yer altı değerlerinin sürdürülebilir korunmasına yönelik öneriler geliştirilmiştir.Article Contextual, Formal and Correlational Examination of Article Titles Published in International Indexed Journals in the Field of Educational Sciences(Turkish Education Assoc, 2025) Goktas, Yuksel; İskender, Mülkiye Ezgi; Gürbüz, Nihal Elif; Cagiltay, Nergiz Ercil; Topaloglu, Mulkiye Ezgi IskenderBir makalenin yayımlanması ve atıf alması açısından doğru başlık yazımı önemli bir değişkendir. Bu bağlamda bu araştırmada eğitim bilimleri alanında yayımlanan uluslararası indeksli makalelerin başlıkları içerik ve biçim açısından incelenmiştir. Doküman analizi, Web of Science veri tabanında yer alan 800 makale ve başlığın araştırmacılar tarafından literatüre dayalı olarak belirlenen kriterlere göre incelenmesiyle gerçekleştirilmiştir. İçerik-başlık uyumu konusunda elde edilen verilere SPSS 27.0 programından faydalanılarak istatistiksel analizler yapılmıştır. Bulgular, makalelerin cümle yapılarının yayımlandıkları dergilerin menşei ülkelerine göre farklılaştığını göstermiştir. Ayrıca, etki faktörü yüksek olan dergilerin başlıklarının metodolojik eğilimlerini daha net verdiği tespit edilmiştir. Etki faktörünün, potansiyel başlık standartlarına ulaşma ve kelime sayısı ile doğrusal ve orta düzeyde ilişkili olduğu bulunmuştur. Dergilerin Q değerlerine göre yapılan analizde, potansiyel içerik standartlarının Q1 dergilerin lehine anlamlı bir şekilde farklılaştığı görülmüştür. Dergiler için yapılan fark analizine göre başlık potansiyel standartları açısından dört dergi arasında istatistiksel olarak anlamlı farklılık bulunmuştur. Ortalamalara göre Review of Educational Research (Q1), Eğitim ve Bilim (Q4), Educational Researcher (Q1) ve Pedagogy (Q4) şeklinde bir sıralama ortaya çıkmıştır. Elde edilen sonuçlar kapsamında araştırmacılara bilimsel çalışmalar için başlık oluşturmada yol gösterecek bazı önerilerde bulunulmuştur.Article Statistical Models for Porous Asphalt Mixtures Containing Pulverized Surface Dressed Pavement Material/Low-density Polyethylene Waste(MIM RESEARCH GROUP, 2025) Oner, Julide; Almusawı, Alı; Abdulrahman, Hassan Shuaibu; Ahmed, Nasiru IbrahimPorous asphalt (PA) mixtures typically contain a high proportion of coarse aggregates with minimal fine aggregates, along with a binder that creates ample space for water drainage. Since road construction consumes large quantities of aggregates, recycling and reusing materials have become common practices. This study focuses on developing PA by partially replacing traditional aggregates with pulverized surface-dressed pavement material (PSM) and modifying bitumen with low-density polyethylene (LDPE). The mixtures were produced using 60/70 penetration grade bitumen modified with 2%, 4%, and 6% LDPE waste and 20%, 40%, 60%, and 80% PSM. Adding LDPE waste to the bitumen altered key properties, such as the softening point, penetration, flashpoint, and ductility, resulting in a stiffer binder. Replacing aggregates with PSM reduced both stability and flow, leading to a lower Marshall quotient. Flow values for all trial mixes did not meet AAPA (2004) standards, while stability values slightly decreased as LDPE content increased from 2% to 6%. Despite this, all samples met the AAPA (2004) stability standard. The sample containing 2% LDPE and no PSM exhibited the highest Marshall quotient. Linear regression models were developed from experimental data to highlight the relationships between the measured responses and the variables. These polynomial equations demonstrated a strong correlation, indicated by high coefficients of determination. The study introduces an innovative approach by incorporating PSM and LDPE, largely unexplored in PA production, especially in Nigeria. The major societal benefits include reducing environmental pollution through plastic waste reuse, conserving natural aggregates, and promoting cost-effective construction practices. By advancing the use of recycled materials, this research supports sustainable infrastructure development while maintaining compliance with industry standards. © 2025 MIM Research Group. All rights reserved.Article Citation - Scopus: 25On the Geometric and Physical Properties of Conformable Derivative(Murat TOSUN, 2024) Has, A.; Yılmaz, B.; Baleanu, D.In this article, we explore the advantages geometric and physical implications of the conformable derivative. One of the key benefits of the conformable derivative is its ability to approximate the tangent at points where the classical tangent is not readily available. By employing conformable derivatives, alternative tangents can be created to overcome this limitation. Thanks to these alternative (conformable) tangents, physical interpretation can be made with alternative velocity vectors. Furthermore, the conformable derivative proves to be valuable in situations where the tangent plane cannot be defined. It enables the creation of alternative tangent planes, offering a solution in cases where the traditional approach falls short. Geometrically speaking, the conformable derivative carries significant meaning. It provides insights into the local behavior of a function and its relationship with nearby points. By understanding the conformable derivative, we gain a deeper understanding of how a function evolves and changes within its domain. A several examples are presented in the article to better understand the article and visualize the concepts discussed. These examples are accompanied by visual representations generated using the Mathematica program, aiding in a clearer understanding of the proposed ideas. By combining theoretical explanations, practical examples, and visualizations, this article aims to provide a comprehensive exploration of the advantages and geometric and physical implications of the conformable derivative. © MSAEN.Article Citation - WoS: 3Citation - Scopus: 3Exploring Fire Safety Conditions of Double Skin Facades(Gazi Univ, Fac Engineering Architecture, 2024) Aslar, Eylem Ezgi; Harputlugil, Gulsu UlukavakHuman health, comfort and safety are of primary importance in the built environment. Among the security measures, the most important risk is the risk of fire. For this reason, the issue of fire risk, spread and safety is considered as one of the criteria that should be considered from the building design stage. Within the scope of this study, building models with the same floor height, different plan and facade types, designed in 3D, were analyzed in the fire simulation program called PyroSim. Based on the data obtained as a result of the analyzes, the results of the temperature, smoke and flame spread at the time of fire according to the facade and plan types are presented in tables. As a result of the data obtained, it was determined that box-type systems in double-layer facades are the most problematic facade type in terms of evacuation of living creatures. In terms of smoke spread, it has been revealed that the systems that continue uninterruptedly along the facade pose a problem when the access and spread to other floors are taken into account. It is necessary to consider fire safety as a design problem. It is considered that more detailed studies should be carried out in our country on this subject, that the project should be designed by considering the simulations from the decision stage to the implementation stage of the building, and that the regulations should be developed in order to be a good guide in both the design and implementation stages.Article Citation - WoS: 2Citation - Scopus: 3Economic Sentiment and Foreign Portfolio Flows: Evidence From Türkiye(Central Bank Republic Turkey, 2024) Ozkan, Ibrahim; Erden, Lutfi; Gunes, DidemThe notable surge in capital flows in recent years has emerged as a key factor shaping the dynamics of international financial markets and influencing economic performance of emerging economies. Even though macroeconomic fundamentals of an economy can explain some of the patterns in international capital flows, behavioral factors also seem to be essential for positioning capital flows across countries. In this study, we aim to examine whether overall economic sentiment towards Turkish economy plays a significant role on net portfolio flows to Turkiye. To this end, we first construct a novel text-based sentiment index called "Turkish Economic Sentiment Index (TESI)", to capture the behavioral tendencies of international investors and media towards Turkiye. Our subsequent step integrates TESI into autoregressive distributed lag models (ARDL) alongside major pull-push determinants to assess whether market sentiment holds discernible influence on capital influx into Turkey. The results reveal that the TESI and VIX stand out as pivotal determinants influencing international portfolio flows. The TESI has a positive impact on portfolio flow dynamics, whereas the degree of global risk aversion inversely affects these flows. These findings align with the contention that a favorable sentiment can boost portfolio inflows to emerging markets. Conversely, heightened volatility expectations in global markets can prompt outflows from these economies.Article Citation - WoS: 2Citation - Scopus: 1A Simple Selection Method of PV Systems for University Campuses(Gazi Univ, 2023) Harputlugil, Gülsu Ulukavak; Bara, Marıam; Ulukavak Harputlugil, GulsuThis paper briefly outlines part of the research work being carried out on the application of the photovoltaic systems to cover universities’ electrical energy needs, with due consideration to the technical, architectural, economic, social. and legal aspects and impacts of this application. The paper considers optimizing the PV system selection objectives and methodology with a case study application. at a university campus in Ankara, Turkey. The main objective here is to develop a practical simple method of selecting an optimum PV system that gives the maximum energy yield possible in a certain period of one year, with the minimum specific energy cost per kWh, where a multiple-variable multi-criteria decision-making making method is applied, to help designers and system engineers in selecting the optimum system. The developed method is demonstrated in the example of the typical case, where the recommended PV system was turned out to be at an Azmuth angle of 0 degrees, the PV technology was monocrystelline Silicon, the annual electrical energy yield per 100 m2 of PV modules surface area 22.4 MWH/Year, the specific electrical energy cost was 0.15 Euos/Kwh, as a first merit option, making a difference of around 13% of saving compared with the 10th last option. The work concludes that a viable PV application is feasible, encouraging its application in various campuses provided that comprehensive planning and careful considerations are given to the related aspects.Article Citation - Scopus: 3Numerical Simulation and Experimental Investigation: Metal Spinning Process of Stepped Thin-Walled Cylindrical Workpiece(Murat Yakar, 2022) Seyedzavvar, M.; Akar, S.; Abbasi, H.Many equipment and devices utilized in the aerospace industry are formed as symmetric parts through high plastic deformation of high strength sheet metal alloys with low thickness. Considering the inherent advantages of the spinning process of simple tooling and concentrated deformation loading, this process can be considered as one of the main options in producing these thin-sectioned lightweight parts. In this study, a Finite Element (FE) model has been developed to simulate the formation of a stepped thin-walled cylindrical workpiece of AISI 316 stainless steel alloy by spinning process. The FE simulation results were employed to investigate the effects of process parameters, including feed rate of the roller and rotational velocity of the mandrel on the distribution of stress and strain in the sheet metal, wrinkling failure, and thinning of the sheet metal during deformation. Experiments were carried out using selective input parameters based on the results of FE simulations. The comparison between FE simulations and experiments revealed that the developed model could predict the thinning of the sheet metals with over 93 % accuracy. Additionally, a good agreement between the experimentally deformed sheet configurations with those resulting from finite element simulations has been observed. © Author(s) 2022.Article Citation - WoS: 1Citation - Scopus: 1Sustainable Management of a Renewable Fishery Resource With Depensation Dynamics From a Control Systems Perspective(Gazi Univ, 2022) Cıfdaloz, OguzhanHuman societies are exploiting natural renewable sources such as fisheries, forests, groundwater basins, rivers, and soil at an increasing intensity. Around the world, these resources are being managed by various institutions or governments. One of the challenges faced by institutions is to develop strategies and policies to effectively manage these renewable resources under social and ecological uncertainties, disturbances, policy implementation difficulties, and measurement errors. In this paper, a fishery is considered as an example and the problem of managing a fishery is approached from a control systems perspective. The justification behind this approach is due to the observation that the problem of managing a renewable resource can be posed as a control systems problem and that the discipline of control systems possesses tools and methods to deal with model uncertainties, external disturbances, measurement errors and implementation issues. For the fishery, a depensation type population dynamics model is considered. Depensatory models are used in social/ecological systems in order to model dynamics of certain species of fish populations. An optimal control strategy based on Pontryagin’s Maximum Principle is derived and its sustainability and robustness properties with respect to parametric uncertainties, measurement errors and disturbances are examined. Finally, a sub-optimal but more robust control strategy is proposed and its robustness properties are provided. The main objective of the paper is to show that a control systems engineering approach can be applied to a social-ecological problem and it can provide easy to implement management strategies, insight, and guidance into the management of renewable resources.
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