Mühendislik Fakültesi

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Citation - Scopus: 1
Adaptive Embedded Zero Tree for Scalable Video Coding
(int Assoc Engineers-iaeng, 2011) Choupanı, Roya; Choupani, Roya; Tolun, Mehmet Reşit; Wong, Stephan; Tolun, Mehmet R.; Bilgisayar Mühendisliği; Yazılım Mühendisliği
Video streaming over the Internet has gained popularity during recent years mainly due to the revival of video-conferencing and video-telephony applications and the proliferation of (video) content providers. However, the heterogeneous, dynamic, and best-effort nature of the Internet cannot always guarantee a certain bandwidth for an application utilizing the Internet. Scalability has been introduced to deal with such issues (up to a certain point) by adapting the video quality with the available bandwidth. In addition, wavelet based scalability combined with representation methods such as embedded zero trees (EZWs) provides the possibility of reconstructing the video even when only the initial part of the streams have been received. EZW prioritizes the wavelet coefficients based on their energy content. Our experiments however, indicate that giving more priority to low frequency content improves the video quality at a specific bit rate. In this paper, we propose a method to improve on the compression rate of the EZW by prioritizing the coefficients by combining each frequency sub-band with its energy content. Initial experimental show that the first two layers of the generated EZW are about 22.6% more concise.
Citation - WoS: 2
Adopting Augmented Reality for the Purpose of Software Development Process Training and Improvement: an Exploration
(Springer international Publishing Ag, 2018) Oge, Irem; Orkun, Bora; Yilmaz, Murat; Tuzun, Eray; Clarke, Paul; O'Connor, Rory V.; Ohri, Ipek
Augmented reality (AR) is a technological field of study that bridges the physical and digital world together with a view to improving user experience. AR holds great potential to change the delivery of software services or software process improvement by utilizing a specific set of components. The purpose of this exploratory study is to propose an integration framework to support AR for improving the onboarding process, notably in introducing new hires to the development process while performing their daily tasks. In addition, it also aims to enhance the software development workflow process using AR. Similar to a GPS device that can guide you from point A to point B, our goal is to create software artifacts like navigation components where software teams may benefit from digitally enhanced working conditions provided using AR. After conducting a review in the literature, we confirmed that there is lack of studies about the combination of augmented reality with software engineering disciplines for onboarding. In this paper, we formalized our approach based on the benefits of AR. Ultimately; we propose an AR-based preliminary model for improving the software development process.
Alternative Enhancement of Associativity Based Routing (Aeabr) for Mobile Networks
(Springer, 2010) Preveze, Barbaros; Safak, Aysel
This study proposes an alternative enhancement for the Enhanced Associativity Based Routing (EABR) method which is a derivation of ABR (Associativity Based Routing) by relative speed and relative distance estimation using the received power strength (RPS) of the nodes. In this study, it is shown that EABR outperforms some other well known protocols. The performance of EABR is improved in terms of number of route reconstructions (RRC) and connected status percentage (CSP). Message overhead and bandwidth utilization is also investigated.
Analog and Digital Filter Design
(Springer Science and Business Media B.V., 2018) Gazi, O.
In this chapter, we will study analog and digital filter design techniques. A filter is nothing but a linear time invariant (LTI) system. Any LTI system can be described using its impulse response. If the impulse response of a LTI system is known, then for any arbitrary input the system output can be calculated by taking the convolution of the impulse response and arbitrary input. This also means that filtering operation is nothing but a convolution operation. And filter design is nothing but finding the impulse response of a linear time invariant system. For this purpose, we can work either in time domain or frequency domain. © Springer Nature Singapore Pte Ltd. 2018.
Citation - WoS: 2
Citation - Scopus: 2
Analysis of Heat Transfer Enhancement in Tubes With Capsule Dimpled Surfaces and Al2o3-Water Nanofluid
(Turkish Soc thermal Sciences Technology, 2022) Ibrahim, Mahmoud Awni A. Haj; Turkoglu, Hasmet; Yapici, Ekin Ozgirgin
This study aims to numerically investigate and evaluate the enhancement of heat transfer by new capsule dimples on tube surfaces for flow of water and Al2O3-water nanofluid with different concentrations, under uniform surface heat flux. The originality of this work lies in combining two passive heat transfer enhancement methods such as geometrical improvements and nanofluids together. Capsule dimples with different depths were considered. Al2O3- water nanofluid was modeled as a single-phase flow based on the mixture properties. The effects of dimple depth and nanoparticle concentrations on Nusselt number, friction factor and performance evaluation criteria (PEC) were studied. Numerical computations were performed using ANSYS Fluent commercial software for 2000-14000 Reynolds number range. It was found that when laminar, transient and fully developed turbulent flow cases are considered, increase in the dimple depth increases the Nusselt number and friction factor for both pure water and Al2O3-water nanofluids cases. Also, the friction factor increases as dimple depth increases. Results show that increase in PEC is more pronounced in the laminar region than in the transition region, it starts to decrease for turbulent flows. For nanofluid, PEC values are considerably higher than pure water cases. The variation of PEC for capsule dimpled tubes are dependent on flow regimes and dimple depths. Increasing the nano particle volume concentration and dimple depth in laminar flows increase the PEC significantly.
Citation - Scopus: 1
Analysis of Parallel Decodable Turbo Codes
(Ieice-inst Electronics information Communications Eng, 2012) Gazi, Orhan
Turbo codes suffer from high decoding latency which hinders their utilization in many communication systems. Parallel decodable turbo codes (PDTCs) are suitable for parallel decoding and hence have low latency. In this article, we analyze the worst case minimum distance of parallel decodable turbo codes with both S-random interleaver and memory collision free Row-Column S-random interleaver. The effect of minimum distance on code performance is determined through computer simulations.
Citation - WoS: 5
Citation - Scopus: 5
Ann and Anfis Performance Prediction Models for Francis Type Turbines
(Turkish Soc thermal Sciences Technology, 2020) Aylı, Ülkü Ece; Ayli, Ece; Ulucak, Oguzhan; Makine Mühendisliği
Turbines can be operated under partial loading conditions due to the seasonal precipitation fluctuations and due to the needed electrical demand over time. According to this partial working need, designers generate hill chart diagrams to observe the system behavior under different flow rates and head values. In order to generate a hill chart, several numerical or experimental studies have been performed at different guide vane openings and head values which are very time consuming and expensive. In this study, the efficiency prediction of Francis turbines has been performed with ANN and ANFIS methods under different operating conditions and compared with simulation results. The obtained results indicate that it is possible to obtain a hill chart using ANFIS method instead of a costly experimental or numerical tests. ANN and ANFIS parameters which effect the output, have been optimized with trying 100 different cases. 75% of the numerical data set is used for training and 25 % is used for validation as testing data. To asses and compare the performance of multiple ANN and ANFIS models several statistical indicators have been used. Insight to the performance evaluation, it is seen that ANFIS can predict the efficiency distribution with higher accuracy than the ANN model. The developed ANFIS model predicts the efficiency with 1.41% mean average percentage error and 0.999 R-2 value. To the best of the author's knowledge, this is the first study in the literature that ANN and ANFIS are used in order to predict the efficiency distribution of the turbines at different loading conditions.
Citation - WoS: 8
Citation - Scopus: 16
Applying Blockchain To Improve the Integrity of the Software Development Process
(Springer international Publishing Ag, 2019) Tuzun, Eray; Gulec, Ulas; O'Connor, Rory V.; Clarke, Paul M.; Yilmaz, Murat; Tasel, Serdar
Software development is a complex endeavor that encompasses application and implementation layers with functional (refers to what is done) and non-functional (how is done) aspects. The efforts to scale agile software development practices are not wholly able to address issues such as integrity, which is a crucial non-functional aspect of the software development process. However, if we consider most software failures are Byzantine failures (i.e., where components may fail and there is imperfect information on which a component has failed.) that might impair the operation but do not completely disable the production line. In this paper, we assume software practitioners who cause defects as Byzantine participants and claim that most software failures can be mitigated by viewing software development as the Byzantine Generals Problem. Consequently, we propose a test-driven incentive mechanism based on a blockchain concept to orchestrate the software development process where production is controlled by a similar infrastructure based on the working principles of blockchain. We discuss the model that integrates blockchain with the software development process, and provide some recommendations for future work to address the issues while orchestrating software production.
Augmented Reality Based Continuous Onboarding Framework
(CEUR-WS, 2018) Yılmaz, Murat; Ohri, İ.; Öge, İ.; Orkun, B.; Yılmaz, M.; Tüzün, E.; Yazılım Mühendisliği
Having an efficient and effective onboarding process for a newcoing employee is a very important factor for the following work performance. For this reason, the orientation process is a process that should be well assessed both in terms of company and employees. Based on the fact that using virtual objects in the real environment enhances the efficiency in learning new things, in this project, the onboarding process is managed by augmented reality (AR) technology. One of the main objectives of the project is guiding the software engineers effectively with the help of augmented reality by providing them interactive communication between their colleagues and the projects.
Citation - WoS: 1
Citation - Scopus: 4
Automatic Detection of Mitochondria From Electron Microscope Tomography Images: a Curve Fitting Approach
(Spie-int Soc Optical Engineering, 2014) Mumcuoglu, Erkan U.; Perkins, Guy; Martone, Maryann; Tasel, Serdar F.; Hassanpour, Reza
Mitochondria are sub-cellular components which are mainly responsible for synthesis of adenosine tri-phosphate (ATP) and involved in the regulation of several cellular activities such as apoptosis. The relation between some common diseases of aging and morphological structure of mitochondria is gaining strength by an increasing number of studies. Electron microscope tomography (EMT) provides high-resolution images of the 3D structure and internal arrangement of mitochondria. Studies that aim to reveal the correlation between mitochondrial structure and its function require the aid of special software tools for manual segmentation of mitochondria from EMT images. Automated detection and segmentation of mitochondria is a challenging problem due to the variety of mitochondrial structures, the presence of noise, artifacts and other sub-cellular structures. Segmentation methods reported in the literature require human interaction to initialize the algorithms. In our previous study, we focused on 2D detection and segmentation of mitochondria using an ellipse detection method. In this study, we propose a new approach for automatic detection of mitochondria from EMT images. First, a preprocessing step was applied in order to reduce the effect of non-mitochondrial sub-cellular structures. Then, a curve fitting approach was presented using a Hessian-based ridge detector to extract membrane-like structures and a curve-growing scheme Finally, an automatic algorithm was employed to detect mitochondria which are represented by a subset of the detected curves. The results show that the proposed method is more robust in detection of mitochondria in consecutive EMT slices as compared with our previous automatic method.
Citation - WoS: 1
Average Received Intensity for Optical Beam of Arbitrary Field Profile After Propagation in Turbulent Atmosphere
(Spie-int Soc Optical Engineering, 2009) Arpali, Caglar; Baykal, Yahya
Employing our previously obtained formulation of the average received intensity for arbitrary optical beam in turbulent atmosphere, intensity patterns of already known and new source profiles are obtained. Arbitrary beam is defined as an incidence having arbitrary source field distribution which is produced by decomposing the source into pixels and assigning the related field to each pixel. For each source field originating from each pixel, incremental received field is found and the total received field is obtained by superposing the contributions from all the incremental received fields. Using the mentioned formula governing the arbitrary beam excitation in turbulence, average received intensity patterns for various types of beams such as cos-Gaussian, cosh-Gaussian, higher-order annular, flat-topped, general type and arbitrary beams are obtained. Our results can be applied in atmospheric optics communication links, reflection from rough surfaces, optical cryptography, optical imaging systems and propagation of partially coherent light.
Citation - WoS: 1
Citation - Scopus: 7
Beam Wander Characteristics of Flat-Topped, Dark Hollow, Cos and Cosh-Gaussian, J0- and I0- Bessel Gaussian Beams Propagating in Turbulent Atmosphere: a Review
(Spie-int Soc Optical Engineering, 2010) Eyyuboglu, Halil T.; Baykal, Yahya; Cil, Celal Z.; Korotkova, Olga; Cai, Yangjian
In this paper we review our work done in the evaluations of the root mean square (rms) beam wander characteristics of the flat-topped, dark hollow, cos-and cosh Gaussian, J(0)-Bessel Gaussian and the I-0-Bessel Gaussian beams in atmospheric turbulence. Our formulation is based on the wave-treatment approach, where not only the beam sizes but the source beam profiles are taken into account as well. In this approach the first and the second statistical moments are obtained from the Rytov series under weak atmospheric turbulence conditions and the beam size are determined as a function of the propagation distance. It is found that after propagating in atmospheric turbulence, under certain conditions, the collimated flat-topped, dark hollow, cos-and cosh Gaussian, J(0)-Bessel Gaussian and the I-0-Bessel Gaussian beams have smaller rms beam wander compared to that of the Gaussian beam. The beam wander of these beams are analyzed against the propagation distance, source spot sizes, and against specific beam parameters related to the individual beam such as the relative amplitude factors of the constituent beams, the flatness parameters, the beam orders, the displacement parameters, the width parameters, and are compared against the corresponding Gaussian beam.
Citation - WoS: 5
Citation - Scopus: 10
Beams With Arbitrary Field Profiles in Turbulence - Art. No. 652209
(Spie-int Soc Optical Engineering, 2006) Baykal, Yahya
Characteristics of optical beam incidences that have arbitrary field profiles are examined when they propagate in the turbulent atmosphere. Arbitrary source field profile is introduced by decomposing the source into incremental areas and the received field in the presence of turbulence is expressed as the summation of the fields originating from each incremental area. Intensity moments such as average intensity and the scintillation index in turbulence are formulated under such excitation. Our results correctly reduce to the well established Gaussian beam wave solutions when the arbitrary source beam is taken as the Gaussian field profile. Naturally, all the beam structures such as the higher-order single-mode, multimode, off-axis Hermite-Gaussian, Hermite-sinusoidal-Gaussian, higher-order annular, flat-topped-Gaussian beams form the special cases of our derivation. Numerical results that cover the scintillations in turbulence for various types of arbitrary beam profiles are presented. Our results for the arbitrary source field profiles can be applied in atmospheric optics telecommunication links where combination of several known beams are employed as incidence in an effort to reduce the degrading effects of turbulence. Also in the problems of reflection from rough surfaces, propagation of spatially partially coherent optical beams or double passage imaging in turbulence, our formulation can be utilized.
Bilgisayar Mühendisligi Bitirme Projeleri için Düsünülmüş Bir Süreç Yönetim Modeli
(CEUR-WS, 2016) Yilmaz, M.; Güleç, Ulaş; Taşel, S.; Yılmaz, Murat; Güleç, U.; Sopaoǧlu, U.; Bilgisayar Mühendisliği; Yazılım Mühendisliği
Citation - WoS: 1
Citation - Scopus: 1
Calculation of the Spin-Lattice Relaxation Time and the Activation Energy Near the Iv-Iii Phase Transition in Pyridinium Fluorosulfonate (C5nh6)fso3
(Taylor & Francis Ltd, 2022) Kara, N.; Kiraci, A.; Yurtseven, Hamit
The spin-lattice relaxation time T-1(H) for protons nuclei is calculated in term of the pseudospin-phonon (PS) coupled and the energy fluctuation (EF) models close to the IV-III solid-solid phase transition of T-C = 235 K in (C5NH6)FSO3. This calculation was performed by associating the observed second moment of the H-1 as the order parameter below k and the disorder parameter above T-C. Values of the activation energy for the cation reorientation in this crystal are also deduced by using both models. In addition, the observed dielectric permittivity of this crystal is analyzed within the framework of the Landau theory and values of the spontaneous polarization (P-s) are determined as a function of temperature. The normalized values of P-s are used in the PS and EF models to extract the activation energy for the reorientation of the dipole moment of this compound arising from cation-anion interaction. Our results show that the PS and EF models can describe the observed behavior of the spin-lattice relaxation time adequately for the IV-III solid-solid transition in (C5NH6)FSO3.
Citation - WoS: 14
Citation - Scopus: 20
Cavitation in Hydraulic Turbines
(Edizioni Ets, 2019) Ayli, Ece
Hydroenergy is one of the richest and most useful renewable energy sources in the world. Hydropower is a vital source as it is the clean energy source, sustainable and last but not least it is also cost-effective. One of the most important parameters that affect the performance of the hydraulic machines is the cavitation phenomenon, which is defined as the formation of the vapor bubbles in the liquid through any hydraulic turbine. In this paper, hydraulic machines, cavitation, types of cavitation are briefly described. After theoretical studies, analytical and numerical researches about cavitation in hydraulic machinery are discussed extensively. With those studies which are summarized in this paper covers a lot of ground about cavitation on the other hand further studies are needed about cavitation in hydro turbines. Numerical methods provide sufficient predictions for cavitation. However, numerical results should be verified by experimental measurements and detection methods to decide what intensity and which shape of cavitation is hazardous and vital, where the local pressure is lower than the vapor pressure and at which static pressure cavities start to grow and collapse.
Citation - WoS: 13
Citation - Scopus: 16
Cengo: a Web-Based Serious Game To Increase the Programming Knowledge Levels of Computer Engineering Students
(Springer international Publishing Ag, 2019) Yalcin, Alihan Dogus; O'Connor, Rory V.; Clarke, Paul M.; Gulec, Ulas; Yilmaz, Murat
In recent years there has been an increased use of serious games to help increase the level of knowledge and experience of individuals working in different domains. In particular serious games for educational purposes have been used in many domains including software engineering and computer science [1]. Hence, this study proposes a quantitative research approach to increase the programming knowledge levels of the first-year undergraduate students at computer engineering departments. For this aim, a responsive web platform was developed to teach the syntax and logic of the C programming language by using game elements. This environment provided students with an ability to independently investigate the C programming language continuously since the platform is always accessible. To better understand the effectiveness of the designed environment, 10 first-year computer engineering students were selected as a pilot experimental group. According to the results obtained from the user tests, this game can be used as an educational tool, which supports the traditional training methods, to increase the knowledge levels of students about the syntax and logic of the C programming language.
Channel Coding Theorem
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.
In this chapter, we will discuss the channel coding theorem in details. Channel coding theorem can be accepted as a milestone in electronic communication field. For this reason, it is very critical for a communication engineer to comprehend the channel coding theorem very well. In many information theory books, or in many lecture notes delivered in classes about information theory, channel coding theorem is very briefly summarized, for this reason, many readers fail to comprehend the details behind the theorem. © 2018, Springer Nature Singapore Pte Ltd.
Citation - WoS: 2
Citation - Scopus: 2
Clinical Decision Support Systems: From the Perspective of Small and Imbalanced Data Set
(Ios Press, 2019) Akcapinar Sezer, Ebru; Sever, Hayri; Par, Oznur Esra
Clinical decision support systems are data analysis software that supports health professionals' decision - making the process to reach their ultimate outcome, taking into account patient information. However, the need for decision support systems cannot be denied because of most activities in the field of health care within the decision-making process. Decision support systems used for diagnosis are designed based on disease due to the complexity of diseases, symptoms, and disease-symptoms relationships. In the design and implementation of clinical decision support systems, mathematical modeling, pattern recognition and statistical analysis techniques of large databases and data mining techniques such as classification are also widely used. Classification of data is difficult in case of the small and / or imbalanced data set and this problem directly affects the classification performance. Small and/or imbalance dataset has become a major problem in data mining because classification algorithms are developed based on the assumption that the data sets are balanced and large enough. Most of the algorithms ignore or misclassify examples of the minority class, focus on the majority class. Most health data are small and imbalanced by nature. Learning from imbalanced and small data sets is an important and unsettled problem. Within the scope of the study, the publicly accessible data set, hepatitis was oversampled by distance-based data generation methods. The oversampled data sets were classified by using four different machine learning algorithms. Considering the classification scores of four different machine learning algorithms (Artificial Neural Networks, Support Vector Machines, Naive Bayes and Decision Tree), optimal synthetic data generation rate is recommended.
Citation - Scopus: 31
Cloud Computing Investigation for Cloud Computer Networks Using Cloudanalyst
(Little Lion Scientific, 2018) Mezaal, Y.S.; Madhi, H.H.; Abd, T.; Khaleel, S.K.
In this paper, the performances of load balancing algorithms; Round Robin, Equally Spread Current Execution, and Throttled, in two workload cases, normal and burst are investigated using CloudAnalyst simulator tool. The main objective is to examine the effect of three experiments for regular and irregular normal workloads on the performance of different load balancing algorithms as well as for bursty workload. Each test has two different configurations for parametric investigations. These parametric studies can be used to analyze any electronic service provided by cloud technology vendors in any institutions, especially those offer self-reporting details for every day. © 2005 – ongoing JATIT & LLS.

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