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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3b T1 Ağırlıklı Mr Görüntülerinde Atlas Tabanlı Hacim Ölçüm Yöntemini Kullanarak Alzheimer Hastalığının Teşhisi
(Gazi Univ, 2022) Öziç, Muhammet Üsame; Ekmekci, Ahmet Hakan; Özşen, Seral; Barstuğan, Mücahid; Yıldoğan, Aydın Talip
Alzheimer Hastalığı yaşlılık ile beraber başlayan bir beyin hastalığıdır. Hastalığın teşhisi, takibi ve ilgili beyin bölgelerinin ölçümleri yüksek çözünürlüklü üç boyutlu yapısal manyetik rezonans görüntüleri ile yapılabilmektedir. Bu çalışmada, OASIS veri tabanından alınan 70 Alzheimer 70 Normal 3B T1 ağırlıklı MR görüntüleri üzerinde 116 subkortikal bölgenin hacimsel ölçümünü yapabilecek atlas tabanlı bir hacim ölçüm ve sınıflandırma modeli tasarlanmıştır. Ölçülen değerler her bir denekte gri madde, parankim, total beyin hacmi ile bölünerek normalizasyon işlemi yapılmıştır. Böylece ham ölçülen değerler dahil olmak üzere 140x116 matris boyutlu 4 farklı veri kümesi elde edilmiştir. Veri kümeleri entropi, t-test, roc, Bhattacharyya, Wilcoxon özellik derecelendirme yöntemleri ile en anlamlı özellikten en anlamsız özelliğe doğru derecelendirilmiştir. Derecelendirilen veriler her döngüde sırasıyla birleştirilmiş, lineer ve rbf kernel kullanan destek vektör makinelerine 10-kat çapraz geçerleme ile verilerek sınıflandırma işlemi yapılmıştır. Tüm senaryolar analiz edilerek, en az özellikle en iyi sonucu veren küme, özellik derecelendirme ve sınıflandırma metodu ortaya konulmuştur. Normalizasyon ve özellik derecelendirme yöntemlerinin sınıflandırma sonucuna etkisi incelenmiştir. Deneysel işlemler sonucunda roc özellik derecelendirme tabanlı lineer destek vektör makinesi, total beyin hacmi normalizasyonlu 107 özellik kullanarak %95.71 hassasiyet, %94.29 özgüllük, %95.00 doğruluk, 0.95 eğri altında kalan alan değerleri ile en yüksek oranları vermektedir.
Citation - WoS: 1
Deep Learning Based Super Resolution Application for a New Data Set Consisting of Thermal Facial Images
(Gazi Univ, 2022) Şenalp, Fatih Mehmet; Ceylan, Murat
Although thermal camera systems can be used in any application that requires the detection of temperature change, thermal imaging systems are highly costly systems and this situation makes difficult the common use of thermal systems. In addition, blurry images of low quality can occur when thermal images are obtained. In this article, super resolution application has been carried out on a data set consisting of thermal face images obtained from two different thermal cameras. The specified data set was created differently from traditional methods, low resolution (LR) thermal images were obtained from a 160x120 thermal resolution camera, while high resolution (reference) images were obtained from a camera with a thermal resolution of 640x480. Later, unnecessary parts of these images were cropped and another study was carried out by focusing only on the face area. A deep learning model based on adversarial generative networks (GAN) has been developed for these applications. The success performance of the results was evaluated by the image quality metrics PSNR (peak signal to noise ratio) and SSIM (structural similarity index). It has been observed that the results of the application performed by focusing only on the facial areas are better than the results of the application with original images. In addition, this study gave positive results in terms of approximating the resolution of the thermal images obtained by the less costly thermal camera to the resolution of the thermal camera, which has a high cost and can obtain high quality images, especially visually.
Design of a Three Degrees of Freedom (3r) Drawing Robot and Optimal Trajectory Control Using the Bees Algorithm
(Gazi Univ, 2022) Çinar, Muhammet Ali; Kalyoncu, Mete; Sen, Muhammed Arif
In this study, the controller design for the position control of the terminal functionary of a three-degree-of-freedom (RRR) planar drawing robot and its optimization were realised with the developed swarm-based The Bees Algorithm (BA) inspired by the intuitive behavior of bees. First of all, the mathematical modeling of the system was obtained and advanced kinematic calculations were made. In addition to analytical calculations, Matlab/Simulink environment was used for multi-mass dynamic modeling and PID controller design of the system over the solid model of the system. Controller gains (Kp-proportional, Ki-integral, Kd-derivative) were determined by optimizing using AA, in order to minimize the orbital error of the terminal operator and to obtain an optimal PID controller. In addition, 8 (eight) and square drawings were plotted by using optimized PID parameters. The error comparison between the plotted drawings and the reference drawing was carried out according to the error values obtained by considering 11 different error criteria. After optimization, the percent accuracies for drawing 8 (eight) and the square drawing increase 2,0233% and 0,1711% in the X-Y plane respectively. The results obtained from the simulation and optimization studies of the system are presented and evaluated.
Examination of the Impact of Contemporary Additions on the Historical Building's Energy Performance
(Gazi Univ, 2024) Sayın, Selçuk; Öztürk, Büşra
Historical buildings are being destroyed over time and energy losses are increasing. Therefore, energy efficient preservation of historical buildings is an important issue. However, the application of contemporary additions has increased in cases such as the revival of building units that have not survived to the present day or when a new post-functional space is required. The aim of this study is to evaluate the impact of contemporary additions on the energy performance of historic buildings through a case study. For this purpose, energy simulation analyzes of the historical Süleyman Pasha Bath in Kocaeli province were performed through Design Builder. Before the simulations applied, information about stone, which is the original material of the building, and glass applied with contemporary materials were entered into the programme. The provinces of Izmir, Konya, Sivas, and Erzurum were selected from five climatic regions for the contemporary additional analysis. In these provinces there are many traditional bathing buildings with similar plan types. According to simulated results, it was concluded that the application of modern additions after the restoration negatively affected the energy performance in all five climate zones. Before applying contemporary additions to historical buildings, factors such as the microclimate, material properties and geometry of the building should be taken into consideration during the design phase and a decision should be made as a result of various analyses. Consequently, when contemporary additions to historic buildings are required, using the most effective construction techniques and materials is important in terms of building sustainability and effectiveness.
Citation - WoS: 2
Impact of Tilt Angle on the Performance of the Photovoltaic Systems for Different Row Spacing
(Gazi Univ, 2023) Aksoy, Muharrem Hilmi; İspir, Murat; Yeşil, Emin
The optimum tilt angle for a photovoltaic (PV) system depends on the row spacing because it affects the amount of shading on the panels. This study modeled PV systems for four different panel row spacings of 2 m, 2.5 m, 3 m, and 4 m in a fixed 3000 m2 area in Konya province, Turkey. For different panel row spacings, the system performances were compared using a constant tilt angle of 35 degrees, expressed as a proper angle for PV installations at the considered location. In addition, the optimum tilt angle is found for four different cases in terms of electricity generation. In systems with 35 degrees tilt angles at electricity were produced annually as 622.77 MWh, 566.49 MWh, 495.36 MWh, and 385.72 MWh, respectively, for panel row spacings of 2 m, 2.5 m, 3 m, and 4 m. In addition, these electricity productions are 6.19%, 4.41%, 2.56%, and 0.92% higher with optimum tilt angles as 1 degrees, 15 degrees, 21 degrees and 27 degrees. Similarly, the Performance Ratio (PR) values obtained with the optimum angles are 20.61%, 8.39%, 4.12%, and 1.44%, higher than the fixed tilt angle cases. According to the economic analysis, systems with a fixed tilt angle for these panel row spacings pay back themselves in 5.13, 4.67, 4.44, and 4.28 years, respectively, while systems at optimum angles pay back themselves in a shorter time by 5.83%, 4.26%, 2.49%, and 0.91%. Furthermore, the highest NPV/INV, IRR, and ROI values were obtained from the system with 3 m panel row spacing with the optimum tilt angle of 21 degrees as 0.915, 20.42%, and 91.57%, respectively, which is techno economically found to be the most feasible case.
Investigation and Efficiency Analysis of Dual-Boost Bridgeless PFC Converter
(Gazi Univ, 2025) Akkaya, Ramazan; Özdentürk, Aybüke
Artan enerji tüketimi ile birlikte elektrik sistemlerinde verimlilik günden güne daha da önemli hale gelmektedir. Bu durum doğrultuculardan kaynaklanan güç kalitesi sorunlarına çözüm sunan Güç Faktörü Düzeltmeli dönüştürücülerde yüksek verim arayışını zorunlu kılmıştır. Bu çalışmada yüksek verim sunan Köprüsüz Boost PFC Dönüştürücüler incelenmiştir. Bu dönüştürücülerin olumlu ve olumsuz özellikleri sunulmuştur. Köprüsüz dönüştürücülerin bir türü olan Dual-Boost Köprüsüz PFC Dönüştürücü tanıtılmış ve dönüştürücünün PSIM ortamında simülasyonu yapılmıştır. Elde edilen giriş akımı harmonik içeriği, güç faktörü ve verimlilik değerleri, daha önceki çalışmalarımızda aynı parametrelerle tasarlanan Klasik Boost PFC Dönüştürücü ile karşılaştırılmıştır. Dual-Boost Köprüsüz PFC Dönüştürücü farklı güç seviyelerinde çalıştırılarak güç faktörünün ve toplam harmonik bozulmanın değişimi grafiksel olarak sunulmuştur. Daha detaylı bir verim analizi için dönüştürücüler farklı iletim dirençlerine sahip MOSFET'ler kullanılarak tekrar çalıştırılmıştır. Sonuç olarak Köprüsüz PFC Dönüştürücülerin verimlilik avantajı kanıtlanmıştır. Ayrıca SiC gibi düşük iletim direncine sahip MOSFET'lerin bu dönüştürücüler için önemi anlaşılmıştır.
Citation - WoS: 1
Investigation of Nonlinear Behavior of the Reinforced Concrete Columns for Different Confined Concrete Models
(Gazi Univ, 2022) Foroughi, Saeid; Yüksel, S. Bahadır
Stress-strain and moment-curvature behavior of the reinforced concrete (RC) square columns have been analytically investigated according to different confined concrete models. The effect of transverse reinforcement diameter, transverse reinforcement spacing and concrete grade on the behavior of RC column models were investigated. For different confined concrete models, the confinement effectiveness coefficient, effective lateral confining stress, confined concrete compressive strength, strain at maximum concrete stress and ultimate concrete compressive strain values were calculated. In the second part, a parametric investigation was carried out for examining the effects of different design parameters on the moment-curvature relationships. Analytical moment-curvature relationships were obtained for RC cross-sections by using the TBEC (2018), Mander model (1988), Saatcioglu and Ravzi (1992) confined concrete models. The effects of the design parameters on the RC square column behavior were evaluated in terms of moment capacity and the curvature of the cross-section. In RC column models, stress-strain and moment-curvature relationships are obtained and compared according to different parameters. Confined concrete strength and the ultimate moment values obtained from the Mander model were higher than the Saatcioglu and Ravzi model when the transverse reinforcement close to the minimum spacing values. The results obtained from the Mander model and TBEC (2018) are close to each other.
Citation - WoS: 4
Moment-Curvature and Effective Section Stiffness of Reinforced Concrete Beams
(Gazi Univ, 2023) Foroughi, Saeid; Yüksel, S. Bahadır
In determining the seismic performance of reinforced concrete (RC) structures in national and international earthquake regulations, it is desired to use effective section stiffness of the cracked section in RC structural elements during the design phase. Although the effective section stiffness of the cracked section is not constant, it depends on parameters such as the concrete strength and reinforcement ratio. In this study, RC beam models with different concrete strength, tensile and compression reinforcement ratios were designed to investigate nonlinear moment-curvature relationships and effective stiffness coefficients. Analytically investigated parameters were calculated from TBEC (2018), ACI318 (2014), ASCE/SEI41 (2017), Eurocode2 (2004) and Eurocode8 (2004, 2005) regulations and moment-curvature relationships. The effective section stiffness coefficient obtained from the analyses were compared with the effective section stiffness coefficient given for RC members in different regulations. The results obtained at the end were examined by comparing them according to different parameters and models. For constant concrete strength and tensile reinforcement ratio in RC beams, with increasing compression reinforcement ratio, effective stiffness coefficient values increase. In RC beams with constant compression and tensile strength ratio, effective stiffness coefficient values increase with increasing concrete strength. The compression reinforcement ratio has been proved to be effective on the maximum moment bearing capacity of the RC beams, effective flexural stiffness and effective stiffness coefficient and ductility of the sections.
Citation - WoS: 2
Multi-Level Competitive Closed Loop Supply Chain Network Design
(Gazi Univ, 2022) Torgul, Belkız; Paksoy, Turan
Limited natural resources and unconscious consumption have led to a substantial increase in the rate of processing waste material instead of raw materials in recent years and changed the dynamics of Supply Chain Management (SCM) by making the industrial environment more competitive. The interest in Closed Loop Supply Chain (CLSC) design and optimization is increased with great care being taken to reverse logistics in order to respond to customer pressures as well as environmental concerns associated with the increasing number of end-of-life products. CLSC has extensive literature and many models have been developed to optimize supply chain costs. Most of the literature deals with single supply chains and ignores existing competing supply chains. However, in today's competitive markets, supply chains are integrated with each other by several competitive companies and work together to gain more market share. In such an environment, there are different forms of competition within and between supply chains. In this context, the paper addresses the problem of design and optimization of distribution networks in multi-level competitive CLSC management consisting of two producers, a collection & recycling center and customers trying to improve sustainable consumption by increasing the willingness to return used products with some incentives for product recovery. In order to reach a consensus solution for decision makers who have a different purpose in CLSC management, four different Interactive Fuzzy Programming (IFP) approaches are used and the results are analyzed.
Nonlinear Behaviour of the Concrete Core of the Diagonally Reinforced Coupling Beams
(Gazi Univ, 2024) Yüksel, Süleyman Bahadır; Foroughi, Saeid
Coupled shear walls with coupling beams are constructed because of openings such as doors, windows, or other installations that are left behind due to functional reasons in shear walls. In coupling beams having a ratio of span-to-depth less than two, shear fracture occurs rather than flexural fracture. In order to meet the shear force and the bending moment formed by the coupling beams, diagonal bundles are used in the coupling beams. Diagonal reinforced coupling beams are generally preferred because diagonal reinforced coupling beams exhibit better behaviour than conventional reinforced coupling beams. The diagonal reinforcement bundles have to be confined by transverse reinforcements prescribed in the codes. Confined concrete in the diagonal reinforcement bundles has stress-strain characteristics that are distinctly different from those of plain concrete. The effects of longitudinal and transverse reinforcement ratios on the stress-strain behaviour of confined concrete inside the diagonal reinforcement bundles were investigated. Fifty-four reinforced concrete coupling beams with different confining parameters of the diagonal reinforcement bundles and different variables were analysed using the program. It was demonstrated that the strength and the maximum strain of the concrete inside the diagonal reinforcement bundles increase with the reinforcement ratio of the confinement reinforcement. The increase in the diameter of the transverse reinforcement and the decrease in the spacing of the transverse reinforcement diagonal bundles, increase the confining effect, strength, and ductility in the concrete sections. The increase in the ratio of transverse and diagonal reinforcement significantly affects the seismic behaviour of the coupling beams.
Citation - WoS: 3
Smart and Sustainable Supplier Selection Using Interval Type-2 Fuzzy Ahp
(Gazi Univ, 2022) Torğul, Belkız; Paksoy, Turan
Government regulations, customers' environmental awareness, quality of life-improving efforts and developments in the information and communication system have almost obliged organizations to consider smart and sustainable factors while evaluating their suppliers. Working with suitable suppliers in terms of technological, environmental and social aspects as well as economic aspects, will be the basis for smart and sustainable supply chains. An effective supplier selection running is also needed to continue the process in harmony. The issue of supplier selection is one of the multi-criteria decision- making problems that requires consideration of many qualitative and/or quantitative factors. In this study, Analytic hierarchy process (AHP) method with interval type-2 fuzzy sets, which are more flexible and successful in reflecting uncertainty for fuzzy decision-making problems with contradictory criteria, was proposed to evaluate the overall performance of suppliers. In order to demonstrate the applicability of the proposed method, an empirical study was conducted on the evaluation of material suppliers for an automotive manufacturer and a comparative scenario analysis was performed to investigate the effect of different criteria under different conditions.

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