Yazarlar
- Can, Erol(29)
- Kumbasaroglu, Atila(17)
- Yalciner, Hakan(17)
- Bayata, Halim Ferit(14)
- Ting, Naim Suleyman(14)
- Katipoğlu, Okan Mert(13)
- Bayrak, Osman Ünsal(12)
- Sahin, Yakup(12)
- Turan, Ahmet İhsan(9)
- Baş, Fatih İrfan(8)
- Destek, Mehmet Akif(8)
- Manga, Müge(8)
- Çolak, Muhammed Ali(8)
- Bulut, H. Alperen(6)
- Manga, Muge(6)
- Tastimur, Canan(6)
- Akin, Erhan(5)
- Akoğuz, Harun(5)
- Akın, Fatih(5)
- Balli, Esra(5)
- Dede, Tayfun(5)
- Sarıgöl, Metin(5)
- Sarıçiçek, İnci(5)
- Aka, Salih(4)
- Ayasun, Saffet(4)
- Ayaz, Yaşar(4)
- Celik, Alper(4)
- Demirci, Oğuz Kürşat(4)
- Demirel, Soner(4)
- Kalkan, Orhan(4)
- Keleş, Ömer Faruk(4)
- Tortum, Ahmet(4)
- Tuysuz, Suat(4)
- Yavuz, Selahattin(4)
- Yazici, Ahmet(4)
- Yazıcı, Ahmet(4)
- Yesilyurt, Huseyin(4)
- Yılmaz, Mehmet(4)
- Çabuk, Umut Can(4)
- Özkan, Kemal(4)
Yayınlar
- Conference ObjectYalnız künye2019Vibration Signal Processing Based Bearing Defect Diagnosis with Transfer Learning
Tastimur, Canan; Karakose, Mehmet; Akin, Erhan; Varol, A.; Yazici, A.; Yazici, M.A.; Varol, C.; Aygunes, G.S.; Cotur, A.
It is very important to diagnose the fault condition of the bearing machines in order to make the machine run healthier. There are many successful studies in the detection of failures in the bearing machine made by conventional machine learning methods. However, these studies produce successful results in cases where the machines operate under the same condition and feature space is the same. Therefore, a deep learning-based diagnostic has been proposed for changing machine operating conditions. In the scope of our study, Keras and Tensorflow libraries, CNN network from scratch, VGG16 model and VGG19 deep learning models have been used for the classification of vibration images. Freeze the weights for transfer learning and remove the last fully connected layer to update the network in a problem-specific manner. The number of iterations and batch size has been determined by experimental studies. In this study, four faulty conditions have been successfully classified. While the accuracy rate of CNN network from scratch is 25%, the accuracy rate obtained by the VGG16 transfer learning method is 93% and the loss rate is 0.17% and the accuracy rate obtained by the VGG19 transfer learning method is 95% and the loss rate is 0.13%.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019The design and experimentation of the new cascaded DC-DC boost converter for renewable energy
Can, Erol
After renewable energy generated, a direct current value is converted to a direct current value at another level for a power electronics and power system application that is often considered. In this article, the design and application of a new generation multi-time cascaded DC-DC converter are discussed. The dc-to-dc converter is three-levels, and the switches for each step have a working time and a non-working time. Mathematical models are established depending on the relationship between current and voltage according to the operating and non-operating states of the switches at each stage. After these mathematical models are creating, the new generation multi-timed DC-DC converter is run in Matlab Simulink and simulation results are validated in experimentation. The output voltage and inductor current are observed with a scope. Then, the results from the proposed converter are compared with the results of the traditional converters. The results show the effectiveness of the proposed dc-dc converter.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2019Comparison of different regression models to estimate fault location on hybrid power systems
Ekici, Sami; Unal, Fatih; Ozleyen, Umit
Various pattern recognition methods have been suggested for estimating high-voltage alternating current transmission line fault location. However, insufficient studies have been conducted on the transmission lines connected to hybrid power generation systems such as wind and solar plants. In this study, the performance of different regression methods was investigated on a hybrid power system. Different faults with random distances on the transmission line were simulated and a fault database created by recording the current and voltage signals of these faults. After normalising this data in the preprocessing phase, it was passed to the digital signal processing stage. By repeating the experiments, 497 different faults were created. Fault types, fault resistances, and fault inception angles were changed randomly in order to obtain similar fault occurrence conditions as in real life by writing a Matlab code. In order to obtain distinctive features, the discrete wavelet transform was used. For training and validation of the dataset, Matlab Regression Learner App (RLA) was employed and the obtained results compared to select the best model. After significant fault simulation, Matern 5/2, a type of Gaussian progress regression model, showed more promising results compared to other RLA models.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2019Prediction of seismic performance levels of corroded reinforced concrete columns as a function of crack width
Yalciner, Hakan; Kumbasaroglu, Atila; Karimi, Aqludin
An experimental study was conducted for the prediction of the seismic performance levels of corroded reinforced concrete (RC) columns as a function of the initial corrosion crack widths. A full-scale accelerated-corrosion pool was used to corrode 25 full-scale RC columns. The initial crack widths at different levels of corrosion were measured for three different concrete strength levels: 9, 27, and 37 MPa. The seismic performance levels of corroded RC columns under combined cyclic lateral-displacement excursions at two different axial-load ratios (0.20 and 0.40) were measured. The corrosion levels obtained for the initially measured corrosion crack widths were used for establishing a correlation with the lateral-displacement capacities of the RC columns according to an energy-based method. Three empirical models were developed. The first was for predicting the cross-sectional area reduction of reinforcement bars according to the initial corrosion crack widths. The second model was for predicting the percentage of energy capacity of RC columns as a function of the drift ratio and corrosion levels. The third model was for predicting the seismic performance levels of RC columns as a function of the initial corrosion crack widths and was used for an in situ structural assessment. The experimental test results showed that above a 2% drift ratio, all uncorroded RC columns (regardless of the concrete strength levels) exhibited a sudden reduction in energy capacity, and their total energy capacity was consumed. In the case of corrosion, the energy capacity of concrete with high strength levels was prematurely exhausted above a 1.4% drift ratio because of the effects of the corrosion products under the high strength levels of the concrete.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2019An experimental analysis of minimum cut size in wireless sensor networks
Cabuk, Umut Can; Akram, Vahid Khalilpour; Dagdeviren, Orhan
Wireless sensor networks (WSN) and their applications become more and more common as the technology advances. The emerging concepts of Internet of Things and the Industry 4.0 boost their popularity, too. But there are still dominant bottlenecks including battery lifetime, transmission range, routing issues and others. These limitations may cause permanent faults on nodes, and thus, cause exclusion of the nodes from the network, which eventually may disconnect the network. Minimum cut size, a metric regarding the edge-connectivity of a graph, can be used to measure the reliability of a WSN. This work discusses that role of the minimum cut size; and more importantly, presents the results of a fundamental simulation showing the correlations between the total node count, the transmission range, and the achieved minimum cut size as an indicator of the maximum flow, in a randomly generated WSN topology. Our simulation results showed that at least 100 nodes with a transmission range of 140 m are required to create a random connected network on a field of 1000× 1000 m area. If the ranges of the nodes be 80 m, then at least 200 nodes should be distributed on the field to expect a reliable connected network.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019Design and implementation of an IBC reduced voltage across output capacitor
Ting, Naim Suleyman; Sahin, Yakup; Yetgin, Halil
Interleaved boost converter (IBC) is equal to two-boost converter operating in parallel. IBCs are more advantageous than conventional boost converters. Input current of the interleaved converter is less fluctuated compared to that of the boost converter. In this paper, a new IBC structure is introduced unlike the conventional IBC structure. In the presented converter, the place of output filter capacitor is changed unlike the conventional IBC and thus, the voltage across the output filter capacitor is reduced about Vi. The proposed IBC performs similar experimental results compared to that of the conventional IBC. Besides, the proposed IBC enables the utilization of an output filter capacitor even with lower voltage, and thus the cost of IBC is reduced. The analysis of operating stages of the presented converter is conducted for D < 50% and D > 50% modes. Finally, an experimental setup of the presented converter is realized along with the parameters of 640 W and 20 kHz.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Yeni Yapılması Planlanan bir Kavşağın Mikro-Simülasyon ile Değerlendirilmesi
Bayata, Halim Ferit; Bayrak, Osman Ünsal
Erzurum’da trafiğe kayıtlı araç sayısı 2017 yılı (TUİK) verilerine göre, 114.044’tür. Erzurum, Doğu AnadoluBölgesinin en büyük şehirlerinden biridir. Aynı zamanda, bölgenin cazibe merkezlerinden biri olduğu için, araçsayısındaki mevsimsel artış% 17.61'dir. Bu sayı her yıl ortalama %2,8 artmasına rağmen, mevcut yollarınkapasiteleri sabit kalmaktadır. Bu sonuç, yolların yetersiz kalmasına neden olmakta, trafik yoğunluğununartmasıyla birlikte, seyahat süresi, gecikme ve egzoz emisyonlarının artmasını da beraberinde getirmektedir.Buna ek olarak, yapılan araştırmalar, Türkiye’de şehir merkezlerinde meydana gelen trafik kazalarının yaklaşık%52’sinin kavşaklarda meydana geldiğini göstermektedir. Bu çalışmada, Karayolları 12. Bölge Müdürlüğütarafından yapılması planlanan bir kavşağın çevre ve bölge trafiğine etkisi araştırılmıştır. Yapılması düşünülenkavşak, Erzurum-Bingöl devlet yolu üzerinde ve Atatürk Üniversitesi Kampüsünü bu yola bağlayan noktaüzerindedir. Mevcut ve yeni durum, VISSIM mikro-simülasyon programı ile modellenmiş ve seyahat süresi,gecikme, kuyruk uzunlukları ile CO, NOx, VOC ve yakıt tüketimleri karşılaştırılmıştır. Mikro-simülasyonanaliz sonuçlarına göre, seyahat süresi ve gecikmelerde %35, kuyruk uzunluklarında %83, egzozemisyonlarında ise yaklaşık %23’e varan oranlarda azalma gözlenmiştir.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Demiryolları Yolcularının Tutum ve Davranışlarının Farklı İstatistiksel Yöntemler ile Modellenmesi
Bayata, Halim Ferit; Sağlamyürek, Hacer Nur; Bayrak, Osman Ünsal
Ülkemizde son yıllarda gelişim gösteren en önemli sektörlerden biri de ulaşım sistemleri olmuştur. Diğerulaşım sistemlerine göre daha fazla olan yük ve yolcu kapasiteleri, demiryollarının önümüzdeki yüzyılda stratejikönemini artıracaktır. Tarihi İpek Yolu’nun (Pekin-Londra) tekrar hayata geçerek Bakü-Tiflis-Kars demiryolununaçılmış olması, bu ulaşım sınıfının ülkemizde ve uluslararası platformdaki jeopolitik önemini artırmıştır. Buçalışmada, demiryolu bağlantı yollarının kesiştiği sekiz farklı ilde (Erzincan, Elazığ, Erzurum, Eskişehir, Kocaeli,İstanbul, Ankara, Sivas) 515 yolcu anketi yapılmıştır. Bu anketler, Türkiye Cumhuriyeti Devlet Demiryollarını(TCDD) kullanan yolcuların demiryolu hizmetlerinden faydalanırken beklentilerinin ve memnuniyet derecelerinintespiti için yapılmıştır. Bunun tespit edilmesi amacıyla çok kriterli karar verme yöntemlerinden biri olanAnalitik Hiyerarşik Proses (AHP) yöntemi kullanılmıştır. Çalışmanın ikinci kısmında ise yolcuların tercih,tutum ve memnuniyet derecelerine göre demiryolu seyahat sıklığı talep modellemesi Yapay Sinir Ağları (YSA),Çok Değişkenli Regresyon (ÇDR) ve Bulanık Mantık (Fuzzy Logic-BM) yöntemleri yardımıyla modellenmiş,karşılaştırılmış ve yorumlanmıştır. AHP ile yapılan değerlendirmeler neticesinde, TCDD hizmetlerini kullananyolcular için hizmetlerin genellikle yeterli olduğu, hizmet düzeyinin iyileştirmeden ziyade stabil olarak kalmasınınuygun olacağı belirlenmiştir. YSA ve ÇDR ile modellemelere göre istatistiksel olarak YSA’nın daha başarılı biryöntem olduğu belirlenmiştir. BM ile yapılan modellemede ise yolcuların üç ayda bir seyahat ettikleri anlaşılmışolup, tercih, önem ve memnuniyet tutumları değiştikçe seyahat sıklığının değiştiği görülmüştür.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Enerji tüketimi ve ekonomik büyüme arasındaki ilişki: bdt ülkeleri örneği
Manga, Müge; Balli, Esra; Güney, Çıler Sıgeze
Enerji tüketimi ile ekonomik büyüme arasındaki ilişkinin incelenmesi ekonomik büyüme üzerinde enerjitüketiminin rolü hakkında bilgi vermesi ve politika yapıcılarının enerji politikaları oluşturabilmeleri açısındanoldukça büyük öneme sahiptir. Bu çalışmada, Ermenistan, Azerbaycan, Gürcistan, Kazakistan, Kırgızistan,Moldova, Beyaz Rusya, Rusya, Türkmenistan, Tacikistan, Ukrayna ve Özbekistan’dan oluşan Bağımsız DevletlerTopluluğu (BDT)’ndaki enerji tüketimi ile ekonomik büyüme arasındaki ilişki 1992-2013 yılları esas alınarakpanel Düzeltilmiş En Küçük Kareler Yöntemi (FMOLS) ve Dumitrescu-Hurlin (2012) panel nedensellik testi ileanaliz edilmiştir. Elde edilen sonuçlar, mevcut yıllarda BDT ülkelerinde enerji tüketimi ile ekonomik büyümearasında çift yönlü nedensellik ilişkisinin olduğunu göstermektedir. Bunun yanında BDT’ye üye ülkelerin doğalkaynak zenginlikleri önemli ölçüde farklılık göstermektedir. Bu doğrultuda, politika yapıcılarının etkinekonomik ve çevresel politikalar oluşturabilmeleri için ekonomik büyüme ile enerji tüketimi arasındaki ilişkininboyutu hakkında bilgi edinmeleri önem kazanmaktadır.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Gömülü Sistemler İçin Android Tabanlı Bir Mikroişlemci Programlama Yazılımı
Yiğit, Yasin; Süvari, Metin; Çabuk, Umut Can; Dağdeviren, Orhan
Gömülü sistemler belirli görevleri yerine getirmek amacıyla tasarlanıp beyaz eşya, trafik ışıkları, akıllıfabrikalar, ofis cihazları ve nesnelerin interneti gibi alanlarda kullanılır. Farklı gömülü sistemlerinin programlanmasıiçin farklı elektronik kartlar ve bilgisayar desteği gerekebilir. Böyle durumda bazı üreticilerin gömülü sistemlereyazılım yükleme işini dış sağlayıcılardan alınan hazır programlama cihazları ile yaptıkları görülmüştür. Bu cihazlardaparalel programlama imkânı olmadığından yazılım yükleme işi ancak sırayla yapılabilmektedir. Bu cihazlara firmaiçinde birçok birim aynı anda ihtiyaç duyabilir. Tüm bunlar maliyeti yükseltmekte ve performansı düşürmektedir. Diğeryandan, birçok durumda teknik servis ekipleri müşterilere giderken operasyonel nedenlerle bilgisayar taşımamaktadır.Dolayısıyla, bilgisayar kullanılmadan, tablet veya cep telefonu üzerinden gömülü sistem kartlarına yazılım yüklemeişleminin yapılması uygun bir strateji olabilir. Android işletim sistemi günümüzde akıllı telefon ve tabletlerin ötesindeyaygın bir kullanım alanına sahip olmuştur. Öyle ki, gömülü sistemler ve bunları programlamaya yarayan cihazlardadahi Android kullanılabilmektedir. Tablet ve cep telefonlarının maliyet, kullanım kolaylığı ve taşınabilirlikavantajlarından dolayı kişisel bilgisayarlara göre daha fazla kullanım alanı bulunmaktadır. Bu çalışmada Vestel BeyazEşya AŞ için, farklı ürünlere özgü farklı konsept işlemcileri destekleyen, paralel programla yapabilen ve üretimortamına-koşullarına uygun bir programlama cihazı tasarlanmış ve gerçeklenmiştir. Ayrıca, cihazın kontrol edilmesinisağlayan Windows ve Android uygulamaları da yazılmıştır. Üzerinde çalışılan gömülü sistem beyaz eşya odaklıolmasına karşın, tasarlanan sistem farklı gömülü sistemlerde de etkin olarak kullanılabilir.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018THE MODELING AND ANALYSIS OF A POWER TRANSMISSION LINE SUPPLIED BY A SOLAR POWER PLANT
Can, Erol
This article deals with the energy transmission line system which feeds from solar energy at the MATLAB Simulink. So, direct voltage is considered to be converted as an alternating voltage by a 35-level inverter after the solar power plant which has the power of 110 MW produce 360 kV of direct voltage. A line which covers 240 km of distance is preferred to transmit electrical power from the A1 point to an A2 point. Due to this, the required mathematical equations are calculated with a circuit analyzing method for the line modeling in the simulation. Experiments on the model are carried out at the MATLAB Simulink after the creation of an energy transmission line. After that, when measurements are made taking into consideration the A2 node; the capacitor voltage, the transformer current, the A2 node current, and the fault current, values are given according to the converted voltage at the frequencies of 100 Hz, 80 Hz, and 50 Hz. The obtained results demonstrate the success of the proposed line system, while power is distributed with eliminated fault at a long distance at different frequencies.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018Effects of Geo-grid and Conventional Stirrups on Reinforced Concrete Beams With Polypropylene Fibers
Yalciner, Hakan; Kumbasaroglu, Atila; Ergun, Ugurcan
The aim of the present study was to investigate the effects of different confinement techniques (i.e., conventional shear reinforcement bars and confinement provided by a geo-grid) on flexural strength of full scaled reinforced concrete beams with and without the use of polypropylene fibers. Few studies have been performed using the geo-grids as shear reinforcement bars, and these were limited by flexural strength tests with scaled structural members. Meanwhile, no study has been performed that elucidates the contribution of geo-grids on bond-slip relationships. This is the subject of the present study. Fifteen reinforced concrete beams were tested under static bending tests for different scenarios. The effects of plastic fibers were examined for flexural strength, energy absorption capacities, bond-slip, and moment-curvature relationships for two different confinement techniques. The test results indicated that the use of geo-grids as a shear reinforcement in the available literature does not show good agreement in terms of performance provided by conventional stirrups. The performance of geo-grids as a shear reinforcement was limited with the use of a greater amount of plastic fibers.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018Confinement Effect of Geo-grid and Conventional Shear Reinforcement Bars Subjected to Corrosion
Yalciner, Hakan; Kumbasaroglu, Atila; Ertuc, İbrahim; Turan, Ahmet İhsan
An experimental study was performed to examine the effects of polyester geo-grid as a shear reinforcement bar for corroded and uncorroded reinforced concrete beams. The main aim of this study was to investigate the effect of geo-grids on flexural strength, moment-curvature, bond–slip and crack patterns for uncorroded and corroded reinforced concrete beams. For each parameter, a geo-grid confinement technique was compared with conventional reinforced concrete beams as a function of corrosion level. The experimental program consisted of testing ten reinforced concrete beams for two different configurations of shear reinforcement bars at six different corrosion levels (0% and approximately 2, 3, 5, 6, and 9%). Test specimens were subjected to an accelerated corrosion method to corrode the reinforcement bars using a full-scale corrosion pool. Actual corrosion levels were obtained from fully extracted reinforcement bars by breaking the concrete. At the same overall corrosion levels which were differed at longitudinal and transverse reinforcement bars at the same applied corrosion current time for different RC beams. Obtained actual corrosion levels with the aid of fully extracted reinforcement bars from concrete provided to examine the effect of corrosion levels by considering the type of reinforcement bars. The results indicated that the performance of the polyester geo-grid was very poor compared to conventional steel stirrups, even at this stage of corrosion. It was found that the utility of a geo-grid as shear reinforcement bars in reinforced concrete beams is not proper.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018A GIS-based interval type-2 fuzzy set for public bread factory site selection
Deveci, Muhammet; Akyurt, Ibrahim Zeki; Yavuz, Selahattin
Purpose: The purpose of this paper is to present a new public bread factory location selection for Istanbul Metropolitan Municipality (IMM). Design/methodology/approach: A two-stage methodology is proposed to determine the location for the public bread factory facility. This framework is based on both geographic information systems (GIS) and multi-criteria decision-making (MCDM) techniques. The first stage of the methodology aims to decrease the number of possible alternative locations to simplify the selection activity by applying GIS; the second stage utilises interval type-2 fuzzy MCDM approach to exactly determine the public bread factory site location. Findings: In this study, the authors present weighted normalised-based interval type-2 hesitant fuzzy and interval type-2 hesitant fuzzy sets (IT2HFSs)-based compressed proportional assessment (COPRAS) methods to overcome facility location selection problem for a fourth public bread factory in Istanbul. Practical implications: The results show that the proposed approach is practical and can be employed by the bakery industry. Originality/value: In this study, the authors present a two-stage methodology for public bread factory site selection. In the first stage, the number of alternatives is reduced by the GIS. In the second stage, an interval type-2 fuzzy set is implemented for the evaluation of public bakery factory site alternatives. A new integrated approach based on COPRAS method and weighted normalised with IT2HFSs is proposed.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Analysis and performance with vertical divided multilevel voltage on phase of induction engine
Can, Erol
In this study, the quality of the transformed energy form is analysed after comparing the single-phase induction motor operated by the SPWM inverter to the 15-level LPWM inverter. Firstly, multilevel inverter and pulse width modulation are designed. The multi-level inverter has sixteen IGBT switches because inverter circuit is constructed with high multilevel inverter topology. Linear pulse width modulation (LPWM) is designed for operation of sixteen switches in the inverter circuit. Secondly, equations of the induction motor are calculated according to d-q axis with creating 15-level alternating voltage. After described equations, 15-level inverter running single phase induction motor is formed at the Matlab Simulink. The obtained results are analyzed according to motor performance and harmonic distortion of the created alternating energy after the proposed model is simulated. Finally, Simulation results of the proposed system are compared with simulation results of SPWM inverter controlling the single-phase induction motor.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018A novel SSPWM controlling inverter running nonlinear device
Can, Erol; Sayan, H. Hüseyin
In the paper, Step sinus pulse width modulation (SSPWM) three phase inverter is tested on a nonlinear device which can produce harmonics. There are 12 switches on active and passive cases. On the inverter, operations of switches are provided by arranged SSPWM which can be calculated with similarity rules of triangles. A mathematical model of inverter is obtained with operating characteristics of the switches determined. SSPWM technique is used to control non-linear devices as thyristor and rectifiers which are widely used in electronic systems. So, single phase alternating voltage is converted to direct voltage with rectifier circuit to provide input voltage of inverter. After that, Six switches of common three phase inverter model are connected to six thyristors controlling inputs and outputs of three phase loads so that performance of SSPWM can be investigated on high level harmonic of loads. The inverter load of resistive (R) and inductive (L) are performed at the MATLAB Simulink so that SSPWM technique could be showed the reducing effect of the harmonic on loads. So, SSPWM and SPWM controlling inverter are performed on frequencies. Then, performances of common SPWM and SSPWM running nonlinear loads are compared with results.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018A soft switching with reduced voltage stress ZVT-PWM full-bridge converter
Sahin, Yakup; Ting, Naim Suleyman; Acar, Fatih
This paper introduces a novel active snubber cell for soft switching pulse width modulation DC-DC converters. In the proposed converter, the main switch is turned on under zero voltage transition and turned off under zero voltage switching (ZVS). The auxiliary switch is turned on under zero current switching (ZCS) and turned off under zero current transition. The main diode is turned on under ZVS and turned off under ZCS. All of the other semiconductors in the converter are turned on and off with soft switching. There is no extra voltage stress on the semiconductor devices. Besides, the proposed converter has simple structure and ease of control due to common ground. The detailed theoretical analysis of the proposed converter is presented and also verified with both simulation and experimental study at 100 kHz switching frequency and 600 W output power. Furthermore, the efficiency of the proposed converter is 95.7% at nominal power.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2017Experimental Study on the Bond Strength of Different Geometries of Corroded and Uncorroded Reinforcement Bars
Yalciner, Hakan; Marar, Khaled
This study develops empirical models for the prediction of the bond strength of uncorroded and corroded reinforcement bars. The effects of hooked reinforcement on the bar's development length when covered fully and partially are examined. An accelerated corrosion method is used to corrode the reinforcement bars embedded in concrete specimens. Pull-out tests are performed to investigate the ultimate bond strength of the concrete specimens. The effects of two different geometries of reinforcement bars are discussed by considering two different concrete strength levels and concrete cover depths. It is found that partly covered hooked reinforcement bars increase the radial stress on the concrete surface and reduce the bond strength. Increases in the bond strength due to the increased roughness of the steel bar caused by the confined corrosion products are less for hooked bars. The results reveal that the developed models show good relationships with the experimentally computed test results.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2017Providing key diversity for symmetric encryption in Ad-Hoc wireless networks
Polat, Çaǧri; Yildiz, Kadir; Çabuk, Umut Can; Dalkiliç, Gökhan; Adali, E
The revolutionary network that totally changed how the humankind life, the Internet, is now evolving into the Internet of things; which is being achieved by fetching the network connectivity to legacy industrial or commercial devices, as well as everyday objects. This connectivity may be an Internet connection, where the Internet protocol and related technologies are in use. But, there are also many constrained devices, like sensors, actuators, radio frequency identification (RFID) tags and smart cards etc., which cannot handle the full-stack. These devices usually form ad-hoc networks, in which the internal data communication is made via lighter protocols, while the Internet connection is provided by anchor/gateway nodes. This structure brings ease of use, saves power and allows development of new technologies. However, privacy and security are under severe threats, much more than ever. In this paper, we propose a key diversification method, inspired from RFID smart cards, to be used in symmetric encryption within these ad-hoc networks. Thus, lightweight devices will be able to communicate securely, without exhausting their processors and wasting energy.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2017An analysis of the positioning accuracy of iBeacon technology in indoor environments
Dalkiliç, Feriştah; Ankan, Emine; Çabuk, Umut Can; Gürkan, Aslihan; Adali, E
Positioning and location tracking are two major needs of the modern era; in which logistics, industry automation, smart buildings/cities and the Internet of Things concepts are trending topics and are constantly evolving. Introduction of the Global Positioning System (GPS) solved the issue well for outdoor scenarios, however, it is not a reliable solution for indoors, where satellite communication (line-of-sight in general) cannot be maintained. Additionally, there are usually many obstructions (i.e. walls), which block or distort the signals or many signal sources causing interference and noise. Thus, indoor positioning requires different and smarter approaches. iBeacon, is new device-to-device communication technology that relies on Bluetooth Low Energy. In this work, we tested accuracy of a known method used to estimate the distance between two devices communicating through the iBeacon technology. Moreover; effects of the output power, placement of the devices, existence of walls and the possible radio interference, on the accuracy of that distance estimation are investigated.
RDL Kalıcı Kaydıİncele
