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Article A Wavelet-Based Feature Set for Recognizing Pulse Repetition Interval Modulation Patterns(2016) Gençol, Kenan; At, Nuray; Kara, AlıThis paper presents a new feature set for the problem of recognizing pulse repetition interval (PRI) modulation patterns. The recognition is based upon the features extracted from the multiresolution decomposition of different types of PRI modulated sequences. Special emphasis is placed on the recognition of jittered and stagger type PRI sequences due to the fact that these types of PRI sequences appear predominantly in modern electronic warfare environments for some specific mission requirements and recognition of them is heavily based on histogram features. We test our method with a broad range of PRI modulation parameters. Simulation results show that the proposed feature set is highly robust and separates jittered, stagger, and other modulation patterns very well. Especially for the stagger type of PRI sequences, wavelet-based features outperform conventional histogram-based features. Advantages of the proposed feature set along with its robustness criteria are analyzed in detail.Article ISAR Imaging of Drone Swarms at 77 GHz(Tubitak Scientific & Technological Research Council 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 Citation - WoS: 2Measuring Dependence Between Electricity Consumption and Economic Indicators Via Copulas: Turkish Case(Gazi Univ, 2018) Evkaya, O. Ozan; Yozgatligil, Ceylan; Selcuk-Kestel, A. Sevtap; Kestel, A. Sevtap Selçuk; MathematicsThis paper implements copulas to identify the dependence structure between electricity consumption and its cofounding indicators. To achieve this, Turkish electricity demand, its economic and sectoral indicators are taken into account. As a first step, bivariate copulas are used to identify the best fitting copula and the degree of the dependence. Thereafter, multivariate model is established using vine copulas using highly correlated variables. The empirical results confirm the added value of the proposed approach in determining numerous tail properties. We indicate that the copulas are useful to underline, especially, the tail properties of indicators in the market for decision makers.Article Quality of Service Assessment: a Case Study on Performance Benchmarking of Cellular Network Operators in Turkey(2015) Kadıoğlu, Rana; Dalveren, Yaser; Kara, AliAbstract: This paper presents findings on performance benchmarking of cellular network operators in Turkey. Bench- marking is based on measurements of standard key performance indicators (KPIs) in one of the metropolitan cities of Turkey, Ankara. Performance benchmarking is formulated by incorporating customer perception by conducting surveys on how important KPIs are from the user s point of view. KPIs are measured, with standard test equipment, by drive test method on specified routes. According to the performance benchmarking results, the GSM and UMTS network operators achieving the best performance were determined in Ankara. Speech qualities of network operators, as the most popular service, were also evaluated by several statistical methods including pdf/cdf analysis and chi-square and Fisher s exact tests. The network operator providing the highest speech quality in Ankara was determined with the methods applied. Overall, the results and approaches on benchmarking of cellular networks in Turkey are reported for the first time in this paper. The approaches proposed in this paper could be adapted to wide-scale benchmarking of services in cellular networks.Article On the Success Probabilities of Differential Attacks On Present(2016) Sulak, Fatih; Şeker, OkanAdvanced growth in ubiquitous devices leads to increasing popularity of lightweight cryptography and as a result, various block ciphers are designed. The analysis of these algorithms has become popular and as a result, underlying theory of analysis tools including success probabilities has widely been studied recently. In this work, we focus on Present, a lightweight block cipher introduced by Bogdanov et al. and the analysis of this algorithm. We give a detailed information of differential cryptanalysis and multiple differential cryptanalysis on Present. Also, the underlying theory of statistical cryptanalysis are presented. As an important part of cryptanalysis, success probability is examined and expressed by the formulas given by Selçuk and Blondeau et al. The main aim of this work is to contribute to the theory of statistical cryptanalysis. Therefore, we give a general framework of statistical cryptanalysis and success probabilities. The details of success probabilities are given with experimental results. Also, we apply the sieving phase to decrease the cost of the attacksReview Analysis of Different Methods of Suppressing Generator Noise Reaching Indoor Noise(2022) Öz, Hatice Mehtap; Koçyiğit, Filiz Bal; Köse, Ercan; Buluklu, Hatice MehtapThe noise which occurs during the operation of the auxiliary power units is a disturbing factor, although its level varies depending on the environment. This high level of noise in occupational areas can cause not only health but also accidents risks. While silencers are mostly preferred for active noise control, acoustic foam or textile products are preferred according to passive control methods. In this review, the noises produced by the generators were examined and the studies in the literature on suppressing these noises were evaluated by making comparative analyzes. New recommendations have been developed according to the results of the comparative analysis. In case the sampled natural gas generator is closed with 2 mm thick plywood and a steel framed box covered with an acoustic sponge, the sound pressure level is approximately 30 dB in low frequency diesel + electric generators using a silencer according to active control methods. In measurements; It was observed that it decreased from 93.2 to 88.4 dB. While materials such as an acoustic sponge, which are preferred in passive control methods, are open-celled and porous structures, it is advantageous to have sound absorption capacity, but it can be a disadvantage due to its synthetic content.Article Öz Bağlanım Denklem Tahmini ile Durağanlık Testi: Bir Endüstriyel İşletişim Örneği(2022) Yucesan, Ongun; Ozkil, AltanAR ve ARMA tahminleri, eldeki bir seri için temel bir matematiksel ifadeyi belirlemek açısından iyi bilinen araçlar olmaya devam etmektedir. Matematiksel bir denklem elde edildiğinde, girdi ve çıktı arasında bir transfer fonksiyonu türetmek mümkündür. Bu transfer fonksiyonunun kutupları birim çemberin üzerinde veya dışında yer alıyorsa, üretilen seri durağan olmayacaktır. Önemli sayıda numunenin üretildiği böyle bir seri, bir simülasyon etkinliği için tamsayı taşmalarına neden olacaktır. Çalışma için, Hatalar Arası Ortlama Zaman (HAOZ) gözlem amaçlı doğrulama serisi, bir Endüstriyel Gömülü PC İletişimi Sınama yatağından alınmıştır. Bunlar zaman ve sıklık açısından AR ve ARMA tarafından tahmin edilenlerle karşılaştırılır. AR tahmini, durağan özelliği koruyan 57 derecelik bir polinom durumunda, orijinal gözlemle daha iyi bir eşleşmeye sahiptir.Article Citation - Scopus: 2An Approach for Performance Prediction of Saturated Brushed Permanent Magnet\rdirect Current (dc) Motor From Physical Dimensions(Tubitak Scientific & Technological Research Council Turkey, 2022) Asl, Rasul Tarvirdilu; Zeinali, Reza; Ertan, Hulusi Bulent; Tarvirdilu-Asl, Rasul; Tarvirdilu–Asl, RasulAn analytical approach for performance prediction of saturated brushed permanent magnet direct current\r(DC) motors is proposed in this paper. In case of a heavy saturation in the stator back core of electrical machines, some\rflux completes its path through the surrounding air, and the conventional equivalent circuit cannot be used anymore.\rThis issue has not been addressed in the literature. The importance of considering the effect of the flux penetrating\rthe surrounding air is shown in this paper using finite element simulations and experimental results, and an analytical\rapproach is proposed to consider this effect on magnet operating point determination and performance prediction of\rsaturated brushed permanent magnet DC motors. An analytical method is also presented to determine the boundary\rradius of the surrounding air for obtaining accurate results in finite element (FE) solutions and analytical calculations.\rAn analytical approach based on Carter’s coefficient is also proposed to calculate the effective length of the magnet when\rthe length of the magnet and rotor length are not the same. The accuracy of the proposed analytical model is illustrated\rusing finite element simulations and experimental results. With this accuracy, this analytical model is very suitable to\rbe used for reliable and quick mathematical design optimization.Article Otonom Araç Radarları için 79 GHz Fazlı Mikroşerit Anten Dizisinin Besleme Analizi(2025) Dalveren, Yaser; Kara, Ali; Yılmaz, SelenOtomotiv radarı, güvenilirliği nedeniyle otonom araçlarda umut vadeden bir algılama teknolojisi olarak bilinmektedir. Günümüz otonom araçlarında, 77 – 81 GHz frekans bandı otomotiv radarları için ana çalışma bandıdır. Otomotiv radarlarının verimli çalışabilmesi için radar anteninin son derece hassas olması gerekir. Ancak, yüksek çalışma frekansları, yüksek kazanç, geniş bant genişliği ve düşük yan lob seviyeleri (SLL) gerektiren radar anteni tasarımında zorluklar ortaya çıkarabilmektedir. Bu sorunu ele almak için, bu çalışmada, eş düzlemli boşluk kaynak portu, dikey toprak köprüsü ve dalga portu dahil olmak üzere üç farklı topraklanmış eş düzlemli dalga kılavuzu (GCPW) besleme konfigürasyonu kullanılarak düzlemsel seri beslemeli doğrusal bir anten dizisinin 79 GHz otomotiv radar uygulamalarına uyarlaması amaçlanmaktadır. Antenin besleme yapılandırmalarıyla performansını değerlendirmek için benzetimler yürütülmüştür. Elde edilen sonuçlara göre, dalga portu beslemeli antenin en iyi empedans bant genişliğini (>3 GHz) elde ettiği, eş düzlemli boşluk kaynak portu veya dikey toprak köprüsü konfigürasyonları beslemeli antenin ise daha iyi ana lob faz merkezlemesi ve daha yüksek bir kazanç (>18,4 dBi) sergilediği, yan lob seviyelerinin (SLL) -16,28 dB’nin altında olduğu gösterilmiştir. Bu bulguların, yeni nesil otonom araçlar için yüksek performanslı radar antenlerinin geliştirilmesine katkıda bulunabileceği düşünülmektedir.Article Impact of Operations on a Series Per Reliability Perspective(2025) Yucesan, OngunThe Mean Time Between Failure (MTBF) figures are the average of test durations between failure observations formed into a series. They can be seen to suit classical statistical distributions. An equally possible condition is that they are not stationary as a contradiction to the previous statement. In such worse conditions accepting availability of a concealed statistical property, this paper tries to identify the impact of Bi-sample Differencing and Bi-sample mean manipulations. In other words, operating on reliability observations series to reveal concealed statistical knowledge. Experimentation based on observation over a stationary series as a controlled experiment. As an outcome of experiments, the differencing seems to be alleviating the trend and seasonality to a degree. The bi-sample averaging is observed to be hiding variant conditions.
