Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
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Article Citation - WoS: 8Citation - Scopus: 9Diffraction of Waves by an Impedance Half-Plane(Elsevier Science Bv, 2013) Umul, Y. Z.The solution of the diffraction problem of waves by an impedance half-plane that satisfies the impedance boundary condition is obtained for the first time in the literature. A reflection coefficient which is the function of the angular and spatial variables in the polar coordinates is defined and its exact expression is obtained with the aid of the impedance boundary condition. The resultant diffraction field is compared with the solution of Malyuzhinets numerically and their differences are stressed. The structures of the total scattered, geometrical optics and diffracted waves are also investigated. (C) 2013 Elsevier B.V. All rights reserved.Article Citation - WoS: 148Citation - Scopus: 155Cantor-Type Cylindrical-Coordinate Method for Differential Equations With Local Fractional Derivatives(Elsevier Science Bv, 2013) Srivastava, H. M.; He, Ji-Huan; Baleanu, Dumitru; Yang, Xiao-JunIn this Letter, we propose to use the Cantor-type cylindrical-coordinate method in order to investigate a family of local fractional differential operators on Cantor sets. Some testing examples are given to illustrate the capability of the proposed method for the heat-conduction equation on a Cantor set and the damped wave equation in fractal strings. It is seen to be a powerful tool to convert differential equations on Cantor sets from Cantorian-coordinate systems to Cantor-type cylindrical-coordinate systems. (c) 2013 Published by Elsevier B.V.Article Citation - WoS: 32Citation - Scopus: 37Environmental Risk Assessment of Small Hydropower (Shp) Plants: a Case Study for Tefen Shp Plant on Filyos River(Elsevier Science Bv, 2014) Kucukali, SerhatA multi-criteria scoring tool is used to assess the environmental risk level of small hydropower plants on the basis of documented evidence, measured data, and on-site observations. The assessment is based on evaluating compliance with the standards of the European Bank for Reconstruction and Development (EBRD). The following environmental criteria are assessed: environmental flow, water quality, fish passage and protection, watershed protection, threatened and endangered species. I evaluated the Tefen hydropower plant, which has been in operation on the Filyos River in northwestern Turkey since 2011. The assessment showed that the plant failed all of the EBRD criteria. (C) 2013 International Energy Initiative. Published by Elsevier Inc. All rights reserved.Editorial Citation - Scopus: 2Software Process Improvement and Capability Determination Conference 2016(Elsevier Science Bv, 2017) Yilmaz, Murat; Clarke, PaulArticle Citation - WoS: 31Citation - Scopus: 32A Comparative Study on Biodegradation and Mechanical Properties of Pressureless Infiltrated Ti/Ti6al4v-mg Composites(Elsevier Science Bv, 2016) Karakas, M. Serdar; Esen, Ziya; Butev, EzgiThe mechanical response and biodegradation behavior of pressureless Mg-infiltrated Ti-Mg and Ti6Al4V-Mg composites were investigated by compression and simulated body fluid immersion tests, respectively. Prior porous preforms were surrounded uniformly with magnesium as a result of infiltration and the resultant composites were free of secondary phases and intermetallics. Although the composites' compressive strengths were superior compared to bone, both displayed elastic moduli similar to that of cortical bone and had higher ductility with respect to their starting porous forms. However, Ti-Mg composites were unable to preserve their mechanical stabilities during in-vitro tests such that they fractured in multiple locations within 15 days of immersion. The pressure generated by H-2 due to rapid corrosion of magnesium caused failure of the Ti-Mg composites through sintering necks. On the other hand, the galvanic effect seen in Ti6Al4V-Mg was less severe compared to that of Ti-Mg. The degradation rate of magnesium in Ti6Al4V-Mg was slower, and the composites were observed to be mechanically stable and preserved their integrities over the entire 25-day immersion test. Both composites showed bioinert and biodegradable characteristics during immersion tests and magnesium preferentially corroded leaving porosity behind while Ti/Ti6Al4V remained as a permanent scaffold. The porosity created by degradation of magnesium was refilled by new globular agglomerates. Mg(OH)(2) and CaHPO4 phases were encountered during immersion tests while MgCl2 was detected during only the first 5 days. Both composites were classified as bioactive since the precipitation of CaHPO4 phase is known to be precursor of hydroxyapatite formation, an essential requirement for an artificial material to bond to living bone. (C) 2016 Elsevier Ltd. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 5Almost Autonomous Training of Mixtures of Principal Component Analyzers(Elsevier Science Bv, 2004) Musa, MEM; de Ridder, D; Duin, RPW; Atalay, VIn recent years, a number of mixtures of local PCA models have been proposed. Most of these models require the user to set the number of submodels (local models) in the mixture and the dimensionality of the submodels (i.e., number of PC's) as well. To make the model free of these parameters, we propose a greedy expectation-maximization algorithm to find a suboptimal number of submodels. For a given retained variance ratio, the proposed algorithm estimates for each submodel the dimensionality that retains this given variability ratio. We test the proposed method on two different classification problems: handwritten digit recognition and 2-class ionosphere data classification. The results show that the proposed method has a good performance. (C) 2004 Elsevier B.V. All rights reserved.Article Citation - WoS: 15Citation - Scopus: 17Characterization of Ti6al7nb Alloy Foams Surface Treated in Aqueous Naoh and Cacl2 Solutions(Elsevier Science Bv, 2016) Esen, Ziya; Bor, Sakir; Butev, EzgiTi6Al7Nb alloy foams having 53-73% porosity were manufactured via evaporation of magnesium space holders. A bioactive 1 mu m thick sodium hydrogel titanate layer, NaxH2-xTiyO2y+1., formed after 5 M NaOH treatment, was converted to crystalline sodium titanate, Na2TiyO2y+1, as a result of post-heat treatment. On the other hand, subsequent CaCl2 treatment of NaOH treated specimens induced calcium titanate formation. However, heat treatment of NaOH-CaCl2 treated specimens led to the loss of calcium and disappearance of the titanate phase. All of the aforementioned surface treatments reduced yield strengths due to the oxidation of the cell walls of the foams, while elastic moduli remained mostly unchanged. Accordingly, equiaxed dimples seen on the fracture surfaces of as-manufactured foams turned into relatively flat and featureless fracture surfaces after surface treatments. On the other hand, Ca- and Na-rich coating preserved their mechanical stabilities and did not spall during fracture. The relation between mechanical properties of foams and macro-porosity fraction were found to obey a power law. The foams with 63 and 73% porosity met the desired biocompatibility requirements with fully open pore structures and elastic moduli similar to that of bone. In vitro tests conducted in simulated body fluid (SBF) showed that NaOH-heat treated surfaces exhibit the highest bioactivity and allow the formation of Ca-P rich phases having Ca/P ratio of 1.3 to form within 5 days. Although Ca-P rich phases formed only after 15 days on NaOH-CaCl2 treated specimens, the Ca/P ratio was closer to that of apatite found in bone. (C) 2016 Elsevier Ltd. All rights reserved.Article Citation - WoS: 20Citation - Scopus: 29A Multi-Classifier for Grading Knee Osteoarthritis Using Gait Analysis(Elsevier Science Bv, 2010) Sen Koktas, Nigar; Yalabik, Nese; Yavuzer, Guenes; Duin, Robert P. W.This study presents a system for detecting and scoring of a knee disorder, namely, osteoarthritis (OA). Data used for training and recognition is mainly data obtained through computerized gait analysis, which is a numerical representation of the mechanical measurements of human walking patterns. History and clinical characteristics of the subjects such as age, body mass index and pain level are also included in decision-making. Subjects are allocated into four OA-severity categories, formed in accordance with the Kellgren-Lawrence scale: "Normal", "Mild", "Moderate", and "Severe". Different types of classifiers are combined to incorporate the different types of data and to make the best advantages of different classifiers for better accuracy. A decision tree is developed with Multilayer Perceptrons (MLP) at the leaves. This gives an opportunity to use neural networks to extract hidden (i.e. implicit) knowledge in gait measurements and use it back into the explicit form of the decision trees for reasoning. The approach is similar to the Mixture of Experts method. Individual feature selection is applied using the Mahalanobis distance measure and most discriminatory features are used for each expert MLP. The system is tested by a separate set and a success rate of about 80% is achieved on the average. (c) 2010 Elsevier B.V. All rights reserved.Article Citation - WoS: 12Citation - Scopus: 11Dualisation of the Symmetric Space Sigma Model With Couplings(Elsevier Science Bv, 2005) Dereli, T; Yilmaz, NTThe first-order formulation of the G/K symmetric space sigma model of the scalar cosets of the supergravity theories is discussed when there is coupling of (m - 1)-form matter fields. The Lie superalgebra which enables the dualized coset formulation is constructed for a general scalar coset G/K with matter coupling where G is a non-compact real form of a semi-simple Lie group and K is its maximal compact subgroup. (C) 2004 Elsevier B.V. All rights reserved.Article Citation - WoS: 51Citation - Scopus: 56Comparative Study of the Continuous Wavelet Transform, Derivative and Partial Least Squares Methods Applied To the Overlapping Spectra for the Simultaneous Quantitative Resolution of Ascorbic Acid and Acetylsalicylic Acid in Effervescent Tablets(Elsevier Science Bv, 2005) Ozdemir, A; Baleanu, D; Dinç, EThe simultaneous spectrophotometric determination of ascorbic acid (AA) and acetylsalicylic acid (ASA) in effervescent tablets in the presence of the overlapping spectra was accomplished by the continuous wavelet transform (CWT), derivative spectrophotometry (DS) and partial least squares (PLS) approaches without using any chemical pre-treatment. CWT and DS calibration equations for AA and ASA were obtained by measuring the CWT and DS amplitudes corresponding to zero-crossing points of spectra obtained by plotting continuous wavelet coefficients and first-derivative absorbance values versus the wavelengths, respectively. The PLS calibration was constructed by using the concentration set and its full absorbance data consisting of 850 points from 220 to 305 urn in the range of 210-310 nun. These three methods were tested by analyzing the synthetic mixtures of the above drugs and they were applied to the real samples containing two commercial pharmaceutical preparations of subjected drugs. A comparative study was carried out by using the experimental results obtained from three analytical methodologies and precise and accurate results were obtained. (c) 2004 Published by Elsevier B.V.