Mühendislik Fakültesi

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Citation - WoS: 1
Citation - Scopus: 1
Application of the Method of Transition Boundary To the Half-Planes With Mixed Boundary Conditions
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
The scattering problems of waves by soft-hard and hard-soft half-planes are investigated by the method of transition boundary. The functional values at the transition boundaries are found to be identical to the ones for the soft and hard half-screens. It is shown that the factorization process should be applied by also taking into account the boundary conditions besides the principle of reciprocity. The exact diffracted field expressions are obtained for both of the half-planes.
Low Latency Hybrid Structures Involving Convolutional Product Like Codes and Space Time Codes
(Springer, 2017) Al-Kattan, Ahmed A. S.; Gazi, Orhan
In this paper, we propose new joint serially concatenated communication structures constructed from convolutional product codes and space time codes. The proposed structures are suitable for parallel processing operations and they have very low decoding latencies compared to their classical counterparts. Use of multi-antennas increases the spectral efficiency of the joint structures.
Citation - WoS: 135
Citation - Scopus: 148
M²-factor of Coherent and Partially Coherent Dark Hollow Beams Propagating in Turbulent Atmosphere
(Optical Soc Amer, 2009) Yuan, Yangsheng; Cai, Yangjian; Qu, Jun; Eyyuboglu, Halil T.; Bayka, Yahya; Korotkova, Olga
Analytical formula is derived for the M-2-factor of coherent and partially coherent dark hollow beams (DHB) in turbulent atmosphere based on the extended Huygens-Fresnel integral and the second-order moments of the Wigner distribution function. Our numerical results show that the M-2-factor of a DHB in turbulent atmosphere increases on propagation, which is much different from its invariant properties in free-space, and is mainly determined by the parameters of the beam and the atmosphere. The relative M-2-factor of a DHB increases slower than that of Gaussian and flat-topped beams on propagation, which means a DHB is less affected by the atmospheric turbulence than Gaussian and flat-topped beams. Furthermore, the relative M-2-factor of a DHB with lower coherence, longer wavelength and larger dark size is less affected by the atmospheric turbulence. Our results will be useful in long-distance free-space optical communications. (C) 2009 Optical Society of America
A Data Fusion Approach in Protein Homology Detection
(2008) Sever, H.; Polatkan, A.C.; Oǧul, H.
The discriminative framework for protein remote homology detection based on support vector machines (SVMs) is reconstructed by the fusion of sequence based features. In this respect, n-peptide compositions are partitioned and fed into separate SVMs. The SVM outputs are evaluated with different techniques and tested to discern their ability for SCOP protein super family classification on a common benchmarking set. It reveals that the fusion approach leads to an improvement in prediction accuracy with a remarkable gain on computer memory usage. © 2008 IEEE.
Citation - WoS: 2
Investigation on the Influence of Parameter Uncertainties in the Position Tracking of Robot Manipulators
(Univ North, 2019) Ghanbarpour Asl, Habib; Han, Kerim Youde
This paper presents a novel trajectory tracking method for robot arms with uncertainties in parameters. The new controller applies the robust output feedback linearization method and is designed so that it is robust to the variation of parameters. Robustness of the algorithm is evaluated when the parameters of the system are floating over 10 percent up and down. An Unscented Kalman Filter (UKF) is applied for state and parameter estimation purposes. As the considered system has 8 unknown parameters while only 5 of them are independent parameters, UKF is applied only to the augmented system with independent parameters. Three types of simulations are applied depending on sensor groups - first with both position and joint sensors, second with only position sensors and third with only joint sensors. The observation of parameters in these groups is discussed. Simulation results show that when both position sensors and joint sensors are used, all the parameters and states are observable and good tracking performances are obtained. When only position sensors are used, the accuracy of the estimated parameters is reduced, and low tracking performances are revealed. Finally, when only joint sensors are applied, the lengths of robot arms are unobservable, but other parameters related to the dynamic system are observable, and poor tracking performances are given.
Citation - WoS: 23
Citation - Scopus: 33
A New Algorithm for U-Shaped Two-Sided Assembly Line Balancing
(Canadian Science Publishing, 2010) Agpak, Kursad; Yavuz, Mustafa; Yegul, Mustafa Fatih
This study introduces a new hybrid design for a specific case-of assembly lines, and proposes a multi-pass random assignment algorithm to find the minimum number of stations required. The algorithm also finds the sequence and the schedule of the tasks assigned. The new design is a combination of two-sided lines and U-shaped lines, which benefits from the advantages of both designs at the same time. One side of the line is arranged in U-shape allowing stations with crossovers, and the other side of the line is balanced like a traditional straight flow. Depending on product direction, either Left or Right side of the line can be designed in U-shape. Small and large-sized two-sided assembly line test-bed problems were solved using the algorithm. Optimal results are achieved for all small-sized problems. Due to the novelty Of the design, results of large-sized problems are compared to findings of studies on simple two-sided balancing. Algorithm produced better results in most of the cases.
Citation - WoS: 12
Citation - Scopus: 12
Scattering of Waves by a Perfectly Conducting Wedge Residing at the Interface Between Two Isorefractive Media
(Ieee-inst Electrical Electronics Engineers inc, 2016) Basdemir, Husnu Deniz
Scattered field by a wedge that is surrounded by isorefractive media is analyzed. A series-based method is introduced and applied to the wedge problem with soft boundary condition. The fields are examined numerically. The numerical results show that the proposed method is suitable for analysis of these kinds of problems.
MD study of energetics, melting and isomerization of aluminum microclusters
(Springer, 2006) Böyükata, Mustafa; Güvenç, Ziya B.
Voter and Chen version of an Embedded Atom Model has been applied to study the locally stable structures, energies, melting, isomerization and growth patterns of small aluminum clusters, Al(n), in the size range of n = 2 - 13. Using molecular dynamics and thermal quenching simulations, the global minima and the other locally stable structures have been distinguished from those stationary structures that correspond to saddle points of the potential energy surface. A large number (10000) of independent initial configurations generated at high temperatures has been used to obtain the stable isomers, and the probabilities of sampling different basins of attractions, for each size of the clusters. Their energy spectra have been determined and melting, and isomerization dynamics are investigated.
Beam wander of J 0- and i 0-Bessel Gaussian beams propagating in turbulent atmosphere
(2010) Çil, C.Z.; Eyyuboğlu, H.T.; Baykal, Y.; Korotkova, O.; Cai, Y.
Root mean square (rms) beam wander of J 0-Bessel Gaussian and I 0-Bessel Gaussian beams, normalized by the rms beam wander of the fundamental Gaussian beam, is evaluated in atmospheric turbulence. Our formulation is based on the first and the second statistical moments obtained from the Rytov series. It is found that after propagating in atmospheric turbulence, the collimated J 0-Bessel Gaussian and the I 0-Bessel Gaussian beams have smaller rms beam wander than that of the Gaussian beam, regardless of the choice of Bessel width parameter. However, the extent of such an advantage depends on the chosen width parameter, Gaussian source size, propagation distance and the wavelength. Focusing at finite distances of the considered beams causes the rms beam wander to decrease sharply at the propagation distances equal to the focusing parameter.
Citation - WoS: 30
Citation - Scopus: 31
Estimation of Aperture Averaged Scintillations in Weak Turbulence Regime for Annular, Sinusoidal and Hyperbolic Gaussian Beams Using Random Phase Screen
(Elsevier Sci Ltd, 2013) Eyyuboglu, Halil T.
Using the random phase screen method, aperture averaged scintillations for annular, sinusoidal and hyperbolic Gaussian beams are estimated. Prior to this estimation, the designed random phase screen setup is tested against the known results of the existing literature from the aspects of receiver intensity distribution, point-like scintillation index and aperture averaged scintillation of spherical and Gaussian beam waves. Having obtained satisfactory results, we then proceed to estimate aperture averaged scintillations for annular, sinusoidal and hyperbolic Gaussian beams. Our findings indicate that at a fixed aperture radius of 5 cm, sine Gaussian beam exhibits the highest scintillation, annular Gaussian beam has on the other hand has the lowest scintillations. When examined against varying aperture sizes, the scintillation ordering of beams does not change. Furthermore, although larger aperture sizes achieve substantial scintillation reductions, the rate of reductions gradually become smaller. (C) 2013 Elsevier Ltd. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 6
Understanding Personality Differences in Software Organisations Using Keirsey Temperament Sorter
(inst Engineering Technology-iet, 2015) O'Connor, Rory V.; Yilmaz, Murat
In recent years, there has been an increasing interest in exploring personality differences to improve work experience in software organisations. This study presents a personality assessment process conducted on 382 software practitioners using the Keirsey temperament sorter II. The primary goal of this assessment is to explore the personality temperaments of software practitioners working in different types of software development organisations. In addition, a novel visualisation approach is proposed for arranging temperaments using a periodic table-like structure. The results suggest that the authors approach provides an effective means to investigate an organisation's personality profile while assessing personality types.
Guis With Haptic Interfaces
(Springer Verlag, 2015) Ozcelik, E.; Tuner, E.; Sahin, H.; Tokdemir, G.; Arda Aydin, M.; Cagiltay, N.E.
While there are many studies regarding utilization of Haptic feedback to enhance desktop GUIs and utilizing Haptic devices as additional interfaces to improve performance in current interaction techniques, there are not many studies that uses Haptic device as a primary input device. In this study, we present an experimentation conducted with 30 students, comparing performance of a Haptic device with mouse to use a GUI elements commonly used with mouse gestures. This study is inspired by a system that utilizes both mouse and a Haptic device, thus also taking task switching into consideration. We conclude that it is possible to achieve an acceptable performance with a Haptic device in a desktop-like GUI but further study and experimentation is necessary. © Springer International Publishing Switzerland 2015.
Citation - WoS: 25
Citation - Scopus: 27
Crystallization Kinetics and Phase Transformation Mechanisms in Cu56zr44 Glassy Alloy
(Springer, 2015) Kramer, Matthew J.; Napolitano, Ralph E.; Kalay, Ilkay
The kinetics and phase selection mechanisms involved in the crystallization of an amorphous Cu-Zr alloy of eutectic composition (Cu56Zr44) were investigated using in situ high-energy X-ray diffraction (HEXRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) under isothermal and constant heating rate conditions. In situ HEXRD results for 10 K/min (10 A degrees C/min) heating indicate that the amorphous alloy devitrifies into CuZr2 and mainly Cu10Zr7 at the crystallization temperature of 725 K (452 A degrees C). The sequence continues with the precipitation of CuZr (B2) at 1004 K (731 A degrees C), where these three phases coexist until the decomposition of CuZr2 is observed at 1030 K (757 A degrees C). The two equilibrium phases Cu10Zr7 and CuZr (B2) remain present on further heating until melting at the eutectic temperature for the Cu56Zr44 alloy. TEM investigation of the isothermal [705 K (432 A degrees C)] crystallization sequence reveals primary nucleation and growth of the Cu10Zr7 phase, where growth of the Cu10Zr7 crystals is initially planar with a transition to a cellular morphology, associated with partitioning of Zr at the growth front. Related cellular structures and composition profiles are quantified. (C) The Minerals, Metals & Materials Society and ASM International 2015
Content-based lecture video retrieval
(2023) Şahin, Yiğit
Günümüzde e-öğrenme veya çevrimiçi öğrenme olarak sıklıkla karşımıza çıkan uzaktan eğitim, eğitim-öğretim sırasında eğitmen ile öğrencinin fiziksel olarak yan yana olmadığı ve öğrenci-eğitmen iletişimini kolaylaştırmak için çeşitli teknolojilerin kullanıldığı yeni nesil bir eğitim yaklaşımıdır. Bu yaklaşım koronavirüs pandemisi (COVID-19) ile dünya çapındaki ağda (www) özellikle ders-eğitim içerikli videolar ile daha yaygın ve kullanılabilir hale gelmiştir. Ancak internet ortamında bulunan video sayılarındaki yüksek artış hızı, belirli bir içeriğe sahip videoya ulaşmak isteyen kullanıcıların video içeriklerine erişimini oldukça zorlaştırmıştır. Bahsedilen bu zorluklara bir öneri geliştirmek bağlamında bu araştırmada kullanıcıların belirli eğitim içerikleri ile ilgili videolara erişimini amaçlayan içerik tabanlı erişim yöntemi ele alınmıştır. Kullanıcıların aradıkları video içeriklerine daha kolay ulaşması için videoların doğru sınıflandırılması gerekmektedir. Teknik açıdan sınıflandırılmanın yapılabilmesi için ise öncelikle videoların metin bilgilerine ulaşılmalıdır. Bu çerçevede araştırmada videoların metin bilgilerini çıkarmak için optik karakter tanıma (OCR) ve otomatik konuşma tanıma (ASR) isimli iki farklı indeksleme yöntemi kullanılmıştır. Bu iki yöntem ve bu iki yöntemin birlikte kullanıldığı bir analiz, bu tezde belirli bir veri kümesi üzerinden ele alınmıştır. Veri kümesi olarak ise 110 videolu bir eğitim koleksiyonu kullanılmıştır. Bu kapsamda aynı veriyi kullanarak OCR ile analiz yapmış bir tez referans alınarak, bu kez de ASR yöntemi ile aynı metrik analizler yapılmıştır. Son olarak ise, hem OCR hem de ASR yöntemi kullanılarak çeşitli metrik değerler hesaplanmıştır. Verilerin sınıflandırma analizi için 3 farklı geleneksel makine öğrenme yöntemi kullanılmıştır. Kullanılan geleneksel makine öğrenme yöntemleri Support Vector Machine (SVM), Naïve Bayes ve Random Forest yöntemleridir. Bu doğrultuda farklı makine öğrenme yöntemleri ve farklı indeksleme yöntemlerinin aynı veri kümesi üzerinde metrik analizleri karşılaştırılmıştır. Yapılan analizler sonucunda ders videolarının içerik tabanlı erişimde kullanılabilmesi için günümüzde mümkün olan geleneksel makine öğrenme yöntemleri ile indeksleme yöntemlerinin güçlü ve zayıf yönlerinin açıklaması yapılmıştır. Bununla birlikte aynı konuda yapılacak gelecek çalışmalar için yöntemin geliştirilebilecek yönleri vurgulanmış ve bu konudaki öneriler sunulmuştur. Bu tez, yapılan karşılaştırmalı araştırmanın hem eğitim hem de yazılım sektörünü nasıl etkileyebileceği tartışması ile noktalanmaktadır.
Citation - WoS: 9
Citation - Scopus: 19
An Analysis on the Relationship Between Safety Awareness and Safety Behaviors of Healthcare Professionals, Ankara/Turkey
(Oxford Univ Press, 2020) Uzuntarla, Fatma; Kucukali, Serhat; Uzuntarla, Yasin
Objectives: This descriptive study aims to examine the relationship between the safety awareness of healthcare professional and their safety behaviors. Methods: The study was carried out on 418 healthcare professionals working in a training and research hospital in Ankara/Turkey. The survey method was used as data collection tool. The questionnaire consisted of 3 sections and 18 questions. First section consisted of questions on sociodemographic characteristics and, second section consisted of the awareness scale and third section consisted of safety behaviors scale. Results: The safety awareness and safety behaviors are scored on a scale from 1 (completely disagree) to 5 (completely agree). The safety awareness and safety behaviors has an average score of 3.85 +/- 0.81 and 3.56 +/- 0.82, respectively. The safety awareness and safety behavior levels of healthcare professionals were found to be high. Conclusion: A significant positive correlation was found between safety awareness and safety behaviors and it was concluded that the increase in safety awareness led to an increase in safety behavior.
Citation - Scopus: 33
A Collaborative and Content Based Event Recommendation System Integrated With Data Collection Scrapers and Services at a Social Networking Site
(IEEE Computer Society, 2009) Kayaalp, M.; Ozyer, T.; Ozyer, S.T.
There are many activities that people prefer/opt out attending and these events are announced for attracting people. An intelligent recommendation system can be used in a social networking site in order to recommend people according to content and collaboration assessment. This study is an effort to recommend events to users within a social networking site. It can be any networking environment. We have used social environment that has been designed as a facebook1 application. Our application has also been integrated with several web sites. System collects event data from several related web sites either by using web services or web scraping. It also permits users rating events they have attended or planned. Given the social network between people, system tries to recommend upcoming events to users. For this purpose a combination of content based and collaborative filtering has been used. We have also taken geographical location info and social concept of an event. © 2009 IEEE.
Citation - WoS: 22
Citation - Scopus: 26
A Dispassionate View of Seismic-Hazard Assessment
(Seismological Soc Amer, 2013) Gulkan, Polat
Citation - WoS: 3
Citation - Scopus: 3
A Hybrid Maliuzhinets/Po Method for Diffraction Problems by Impedance Wedges
(Elsevier Science Bv, 2011) Umul, Yusuf Ziya
The solution of Maliuzhinets of the diffraction problem of waves by an impedance wedge is transformed into a physical optics integral. The resultant expression is suitable for the investigation of various diffraction problems having impedance wedges. The method is applied to the scattering of waves by an impedance spherical reflector with wedge structure at its discontinuity. The results are examined numerically. (C) 2011 Elsevier B.V. All rights reserved.
Citation - WoS: 127
Citation - Scopus: 135
Average Intensity and Spreading of Cosh-Gaussian Laser Beams in the Turbulent Atmosphere
(Optical Soc Amer, 2005) Eyyuboglu, HT; Baykal, Y
The average intensity and spreading of cosh-Gaussian laser beams in the turbulent atmosphere are examined. Our research is based principally on formulating the average-intensity profile at the receiver plane for cosh-Gaussian excitation. The limiting cases of our formulation for the average intensity are found to reduce correctly to the existing Gaussian beam wave result in turbulence and the cosh-Gaussian beam result in free space (in the absence of turbulence). The average intensity and the broadening of the cosh-Gaussian beam wave after it propagates in the turbulent atmosphere are numerically evaluated versus source size, beam displacement, link length, structure constant, and two wavelengths of 0.85 and 1.55 mum, which are most widely used in currently employed free-space-optical links. Results indicate that in turbulence the beam is widened beyond its free-space diffraction values. At the receiver plane, analogous to the case of free space, this diffraction eventually leads to transformation of the cosh-Gaussian beam into an oscillatory average-intensity profile with a Gaussian envelope. (C) 2005 Optical Society of America.
Throughput maximisation of different signal shapes working on 802.16e mobile multihop network using novel cognitive methods
(Springer-Verlag Berlin, 2010) Preveze, Barbaros; Şafak, Aysel
This study proposes cognitive methods for managing the multimedia packet traffic of 802.16e system providing the dynamic spectrum sharing by TDM & OFDMA under heavy traffic conditions. The cognitive techniques are used in order to maximize the throughput of a system having different signal shapes such as video, voice or data packets. All real time voice and video packets transmissions have been provided with full success where the loss rate of data packets has been minimized using the cognitive methods. By these methods buffers are managed successfully for the given parameters, optimum buffer sizes have been formulized and it's shown that we brought the throughput up to its calculated theoretical limits for multi-hop mobile wimax (802.16e).

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