WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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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 Citation - WoS: 2Citation - Scopus: 2An Alternative Mean Reversion Test for Interest Rates(Central Bank Republic Turkey, 2018) Ozel, Ozgur; Ilalan, DenizA number of empirical studies assert that interest rates are governed by unit root processes rejecting any form of reversion to a long term mean by resorting to certain tests, among which the Augmented Dickey Fuller (ADF) is the most widely used one. In this study, we propose an alternative testing methodology that can be applied along with ADF test, in the sense that there are times where it can capture stationarity when the other fails to do so. Moreover, our test has more power than ADF test. As an application to real-data, we consider 10-year US and Turkish T-bond rates. (C) 2017 Central Bank of The Republic of Turkey. Production and hosting by Elsevier B.V.Article ISAR Imaging of Drone Swarms at 77 GHz(TÜBİTAK Scientific & Technological Research Council of Turkey, 2025) Coruk, Remziye Busra; Kara, Ali; Aydin, ElifThe proliferation of easily available, internet-purchased drones, coupled with the emergence of coordinated drone swarms, poses a significant security threat for airspace. Detecting these swarms is crucial to prevent potential accidents, criminal misuse, and airspace disruptions. This paper proposes a novel inverse synthetic aperture radar (ISAR) imaging technique for high-resolution reconstruction of drone swarms at 77 GHz millimeter wave (mmWave) frequency, offering a valuable tool for military and defense antidrone systems. The key parameters affecting down-range and cross-range resolution (0.05 m), ultimately enabling the generation of detailed ISAR images are discussed. Here, we create diverse scenarios encompassing various swarm formations, sizes, and payload configurations by employing ANSYS simulations. To enhance image quality, different window functions are evaluated, and the Hamming window is selected due to its highest peak signal-to-noise ratio (PSNR) (16.3645) and structural similarity (SSIM) (0.9067) values, ensuring superior noise reduction and structural preservation. The results demonstrate that the effectiveness of high-resolution ISAR imaging in accurately detecting and characterizing drone swarms pave the way for enhanced airspace security measures.Article An Empirical Survey of Consumer Ethnocentrism in Kazakhstan and the Preference of Consumers on Imported Products(Ahmet Yesevi Univ, 2017) Nakip, Mahir; Gökmen, AytaçKüreselleşme gerçeği uluslararası işletmecilik ve uluslararası ticaret önündeki engelleri azaltmakta ve de tüketici istek ve beklentilerinin dünya çapında karşılanmasını sağlamaktadır. Tüketici istek ve beklentilerinin küresel ölçekte bütünleşmesi ise uluslararası pazarda faaliyette bulunan işletmelerin işlerini kolaylaştırmaktadır. Ancak, bu konu her ülke ve bölgede aynı biçimde gerçekleşmemektedir. Tüketici etnosentrizmi ise millî duygular, gurur, ve ürünlerin geri çevrilmesini içeren, herhangi bir rasyoneli olmayan ve de millî duyguları vurgulayan önemli bir engel olarak uluslararası işletmelerin önüne çıkar. Dolayısı ile, bu çalışmanın amacı Orta Asya Türk Cumhuriyetleri’nden Kazakistan’da tüketici etnosentrizmini incelemektir. Sonuçlar etnosentrik algı ile ürün gereksinimi arasında güçlü bir korelasyon olmadığını göstermektedir. Ayrıca, etnosentrizm alt boyutları ithal ürünler ile ilgili olarak değişik korelasyon seviyelerine sahiptir. Ek olarak, ithal ürünlerdeki sapmayı açıklamada din ve ahlaki değerler etkin faktörler değildirler.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 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 - WoS: 6The Complementary Nabla Bennett-Leindler Type Inequalities(Ankara Univ, Fac Sci, 2022) Kayar, Zeynep; Kaymakcalan, BillurWe aim to find the complements of the Bennett-Leindler type inequalities in nabla time scale calculus by changing the exponent from 0 < zeta < 1 to zeta > 1. Different from the literature, the directions of the new inequalities, where zeta > 1, are the same as that of the previous nabla Bennett-Leindler type inequalities obtained for 0 < zeta < 1. By these settings, we not only complement existing nabla Bennett-Leindler type inequalities but also generalize them by involving more exponents. The dual results for the delta approach and the special cases for the discrete and continuous ones are obtained as well. Some of our results are novel even in the special cases.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.