TR Dizin İndeksli Yayınlar Koleksiyonu / TR Dizin Indexed Publications Collections
Permanent URI for this collectionhttps://hdl.handle.net/20.500.13091/4
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Browsing TR Dizin İndeksli Yayınlar Koleksiyonu / TR Dizin Indexed Publications Collections by Publisher "Gazi Universitesi"
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Article Citation - WoS: 3Citation - Scopus: 4A Comparison of Rans-Based Turbulence Modeling and Piv Experiments for Flow Over a Simplified Road Vehicle(Gazi Universitesi, 2023) Aksoy, M.H.; Okbaz, A.; Yaǧmur, S.; Doǧan, S.The aerodynamic forces on road vehicles and flow structures around them result from complex interactions between fluid and structure. Ahmed body is a simplified car model created to demonstrate and simplify the flow around real-size ground vehicles. In this study, the flow structure on the wake region of Ahmed body with different slant angles (Θ=15°, 25°, and 35°) was investigated. Experimental studies were conducted in a water channel by Particle Image Velocimetry (PIV). The freestream velocity was set to 0.2 m/s, and the Reynolds number defined by the characteristic length of the Ahmed body was 4.16×104 for Computational Fluid Dynamics (CFD) and PIV experiments. CFD simulations were performed using three different turbulence models: realizable k-ϵ, RNG k-ϵ, and SST k-ω, and the results were compared to experiments. The results are presented with different flow features such as time-averaged velocity vectors and velocity contours, streamline topology, vorticity, and Turbulence Kinetic Energy. The closest results to the experiments were obtained by the SST k-ω turbulence model for all slant angles of the Ahmed body. In addition, the drag coefficient is found to be 0.37 for all slant angles analyzed by SST k-ω turbulence models, which are also close to the results in the literature. © 2023 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Article Citation - Scopus: 2Effect of Pyrolysis Char Produced From Co-Pyrolysis of Waste Sycamore Leaves and Plastic Cups on Bitumen Viscosity and High Temperature Performance Grade(Gazi Universitesi, 2021) Atasağun, NeslihanIn this study, the effects of pyrolysis char produced from co-pyrolysis of waste sycamore leaves and plastic cups on bitumen viscosity and high temperature performance grade were investigated. For this purpose, 50/70 penetration bitumen was modified with pyrolysis char produced by weight of 6% and 12% ratios in bitumen. Softening point test, penetration test, dynamic shear rheometer (DSR) test and rotational viscosity (RV) test were applied on pure bitumen and modified bitumens, also temperature susceptibility of bituminous binders were evaluated by determining the PI values. As a result, it was detected that pyrolysis char used as additive by weight of 6% and 12% ratios in bitumen increased the viscosity of pure bitumen approximately 33% and 83% ratios at 135?, increased the rutting resistance of pure bitumen 46% and 24% ratios at 70? respectively and increased the high temperature PG of pure bitumen. © 2021 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Article Gelişimsel Kalça Displazisi Ultrason Görüntülerinin İki Aşamalı Derin Öğrenme Yaklaşımı ile Kullanabilirlik Analizinin Yapılması(Gazi Universitesi, 2025) Ceylan, Murat; Aydin, Bahattin Kerem; Çiftci, Sadettin; Özdemir, CihadGelişimsel kalça displazisini tespit etmek için ana standart ultrasonik görüntülemedir. Ancak bu teknik operatöre ve dış faktörlere bağlıdır. Bu çalışmada değişkenliği ortadan kaldırmak ve hataları en aza indirmek için yapay zekâ tabanlı bir sistem geliştirilmiştir. Derin öğrenme modeli ilk olarak 3 temel anatomik yapının bulunduğu alanı segmentlere ayırır, daha sonra segmente edilen alanı özelliklerine göre sınıflandırarak 2 aşamalı bir derin öğrenme modeli oluşturur. 3 temel anatomik yapı segmente edildikten sonra ultrason görüntüsünün analiz edilebilirliği kontrol edilir. Ultrason görüntüsünün analiz edilebilirliğinin kontrolü için önce 3 temel anatomik yapının tespit edilip edilmediği kontrol edilmektedir. 3 temel anatomik yapı tespit edilmişse, iliak kemiğin taban çizgisine paralelliği kontrol edilerek US görüntüsünün analiz edilebilirliği kontrol edilmektedir. Geliştirilen sistemde toplam 840 görüntü kullanılmıştır. Sistem US görüntülerinin kullanılabilirliğini %96 doğrulukla karar verdiği gözlemlenmiştir. Geliştirilen sistemin gelişimsel kalça displazisi tanısında doğruluk ve hız açısından doktorlara yardımcı olacağı düşünülmektedir.Article Citation - WoS: 1Citation - Scopus: 1İnsan Aktivite Tanıması için Yeni Bir Veri Kümesi ve Derin Öğrenme Modelleri ile Sınıflandırılması(Gazi Universitesi, 2025) Kıran, Mustafa Servet; Vurgun, YasinMobil sensörler ile insan aktivite tanıma, giyilebilir ve mobil sensörlerin artması nedeniyle son yıllarda ilgi çekici bir araştırma alanı haline gelmiştir. Müslüman hayatında Namaz, müminlerin günde beş vakit kılmak zorunda oldukları bir aktivitedir. Bu çalışmada insan aktivitesi tanımada kullanılmak üzere namaz kılmayı da içeren yeni bir veri kümesi sunulmaktadır. HAR-P (Human Activity Recognition for Praying) adını verdiğimiz veri setinde yürüme, koşma, yazı yazma, merdiven inme, merdiven çıkma, oturma, ayakta durma ve namaz kılma gibi 8 aktivite için doğrusal hızlanma, ivme, manyetik alan ve jiroskop sensör verileri yer almaktadır. HAR-P veri seti için akıllı saat ile 15-60 yaş arası 50 erkek gönüllüden veri toplanmıştır. HAR-P veri kümesinde LSTM, ConvLSTM ve CNN-LSTM modellerinin sınıflandırma başarısı karşılaştırılmıştır. Ortalama en yüksek başarı oranı olan %91’e doğrusal hızlanma sensörü ile LSTM yöntemi ve ivme sensörü ile ConvLSTM modelinde ulaşılırken, en düşük ortalama başarı oranı olan %83,6’a jiroskop sensörü ve ConvLSTM yöntemi ile ulaşılmıştır.Article Citation - Scopus: 2Mathematical Programming Based Heuristic Approach for Two-Echelon Vehicle Routing Problem With Simultaneous Pickup and Delivery(Gazi Universitesi, 2021) Belgin, Ö.; Karaoğlan, İ.; Altıparmak, F.In this study, the two-echelon vehicle routing problem with simultaneous pickup and delivery (2E-VRPSPD) is considered. A two-index node-based mixed integer programming (MIP) formulation is developed for the problem and then valid inequalities are used to strengthen the formulation. Moreover, several variants of the 2E-VRPSPD are introduced and the MIP formulation is adapted for these variants. To solve the problem and its variants, a matheuristic algorithm based on variable neighborhood descent algorithm with local search and mathematical programming is proposed. The performance of the proposed matheuristic is analyzed on 2E-VRPSPD and each variant of the problem using test problems derived from the literature. The experimental studies indicate that 390 out of 564 test instances up to 10 depots and 100 customers are solved to optimality for the base problem 2E-VRPSPD. Similar satisfactory results are also obtained for the other variants of the problem using same data sets. © 2021 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Optimization of Anaerobic Co-Digestion of Sewage Sludge With Fruit and Vegetable Wastes (fvw): Methane Production Potential, Process Performance and Stabilized Sludge Quality(Gazi Universitesi, 2022) Sarıkaya, Fatmanur; Erdirençelebi, DilekAnaerobic co-digestion performance and stabilized sludge quality were investigated with fruit and vegetable wastes in semi-continuous lab-scale reactors for primary (PS), secondary (SS) and mixed sludge (MS) fractions at organic loading rates (OLRs) of 1.65, 0.40 and 1.0 kg VS/m3.day, respectively, at 35°. Fruit waste (FW), vegetable waste (VW) or fruit+vegetable waste (FVW) fractions were added as co-substrates at different OLR combinations. Optimum OLR values were 0.84, 0.33-0.44 and 1.18 g VS/L.day at %51, 209 and 84% (w:w) respectively for FW, VW and FVW, resulting in increases at 50-75, 250-300 ve 44-66% in daily methane production. Increase in OLRs led to decrease in methane yield and hydrolysis degree in the FW receiving digester whereas a toxic effect took place in VW feeding, especially on methanation with an irreversible pattern in PS co-digestion. VW exhibited a higher biodegradegradability than FW with a higher methane yield while pH was lowered in FW co-digestion.The results showed that co-digestion at low OLRs was beneficial in obtaining higher methane recovery while stabilized sludge worsened in dewatering ability. Stabilized SS gained a suitable level of electrical conductivity and nutrient content for soil application through higher conversion to microbial biomass. © 2022 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.
