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Publication Metadata only Cognitive Backgrounds of Problem Solving: A Comparison of Open-ended vs. Closed Mathematics Problems(MODESTUM LTD, 2015) Bahar, Abdulkadir; Maker, C. June; Bahcesehir University; University of ArizonaProblem solving has been a core theme in education for several decades. Educators and policy makers agree on the importance of the role of problem solving skills for school and real life success. A primary purpose of this study was to investigate the influence of cognitive abilities on mathematical problem solving performance of elementary students. The author investigated this relationship by separating performance in open-ended and closed situations. Findings of the study indicated that the cognitive abilities explained 32.3% (open-ended) and 48.2% (closed) of the variance in mathematical problem solving performance as a whole. Mathematical knowledge and general intelligence were found to be the only variables that contributed significant variance to closed problem solving performance. General creativity and verbal ability were found to be the only variables that contributed significant variance to open-ended problem solving performance.Publication Open Access A note on the numerical approach for the reaction-diffusion problem with a free boundary condition(2010) Özuğurlu, Ersin; Ozugurlu, Ersin, Department of Mathematics and Computer Science, Bahçeşehir Üniversitesi, Istanbul, TurkeyThe equation modelling the evolution of a foam (a complex porous medium consisting of a set of gas bubbles surrounded by liquid films) is solved numerically. This model is described by the reaction-diffusion differential equation with a free boundary. Two numerical methods, namely the fixed-point and the averaging in time and forward differences in space (the Crank-Nicolson scheme), both in combination with Newtons method, are proposed for solving the governing equations. The solution of Burgers equation is considered as a special case. We present the Crank-Nicolson scheme combined with Newtons method for the reaction-diffusion differential equation appearing in a foam breaking phenomenon. Copyright © Australian Mathematical Society 2010. © 2011 Elsevier B.V., All rights reserved.Publication Open Access Full analytical model for obtaining surface plasmon resonance modes of metal nanoparticle structures embedded in layered media(Optical Society of American (OSA) info@osa.org, 2010) Şimşek, Ergün; Ŝimŝek, Ergün, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, TurkeyThis work addresses the need for a fully-retarded theoretical model for surface plasmons on metal nanoparticle chains and arrays embedded in a multilayered medium. The proposed method uses dyadic layered medium Green's functions not only to obtain the electric field created by an oscillating electric dipole but also to modify the polarizability of nanoparticles in a multilayered medium appropriately. Theoretically calculated resonance frequencies show a very good agreement with the experimental results found in the literature. Theoretical results suggest that surface plasmon propagation lengths of 1 μm are possible using silver or gold nanoparticles embedded in a multilayered medium. © 2010 Optical Society of America. © 2014 Elsevier B.V., All rights reserved.Publication Open Access Evaluation of e-learning web sites using fuzzy axiomatic design based approach(2010) Büyüközkan, Gülҫin; Arsenyan, Jbid; Ertek, Gürdal; Büyüközkan, Gülҫin, Department of Industrial Engineering, Galatasaray Üniversitesi, Istanbul, Turkey; Arsenyan, Jbid, Department of Industrial Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Ertek, Gürdal, Faculty of Engineering and Natural Sciences, Sabancı Üniversitesi, Tuzla, TurkeyHigh quality web site has been generally recognized as a critical enabler to conduct online business. Numerous studies exist in the literature to measure the business performance in relation to web site quality. In this paper, an axiomatic design based approach for fuzzy group decision making is adopted to evaluate the quality of e-learning web sites. Another multi-criteria decision making technique, namely fuzzy TOPSIS, is applied in order to validate the outcome. The methodology proposed in this paper has the advantage of incorporating requirements and enabling reductions in the problem size, as compared to fuzzy TOPSIS. A case study focusing on Turkish e-learning websites is presented, and based on the empirical findings, managerial implications and recommendations for future research are offered. © 2010 Elsevier B.V., All rights reserved.Publication Open Access Oscillation of second-order mixed-nonlinear delay dynamic equations(2010) Ünal, Mehmet; Ağacık, Zafer A.; Ünal, Mehmet, Department of Software Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Zafer, Agacik A., Department of Mathematics, Middle East Technical University (METU), Ankara, TurkeyNew oscillation criteria are established for second-order mixed-nonlinear delay dynamic equations on time scales by utilizing an interval averaging technique. No restriction is imposed on the coefficient functions and the forcing term to be nonnegative. Copyright © 2010 M. Ünal and A. Zafer. © 2010 Elsevier B.V., All rights reserved.Publication Open Access An occlusion insensitive adaptive focus measurement method(Optical Society of American (OSA) info@osa.org, 2010) Aydın, Tarkan; Akgül, Yusuf Sinan; Aydin, Tarkan, Department of Computer Engineering, Gebze Teknik Üniversitesi, Gebze, Turkey, Department of Mathematics and Computer Science, Bahçeşehir Üniversitesi, Istanbul, Turkey; Akgül, Yusuf Sinan, Department of Computer Engineering, Gebze Teknik Üniversitesi, Gebze, TurkeyThis paper proposes a new focus measurement method for Depth From Focus to recover depth of scenes. The method employs an all-focused image of the scene to address the focus measure ambiguity problem of the existing focus measures in the presence of occlusions. Depth discontinuities are handled effectively by using adaptively shaped and weighted support windows. The size of the support window can be increased conveniently for more robust depth estimation without introducing any window size related Depth From Focus problems. The experiments on the real and synthetically refocused images show that the introduced focus measurement method works effectively and efficiently in real world applications. © 2010 Optical Society of America. © 2014 Elsevier B.V., All rights reserved.Publication Open Access A robust image watermarking in the joint time-frequency domain(2010) Özturk, Mahmut; Akan, Aydın I.; Çekiç, Yalçın; Ozturk, Mahmut, Department of Electrical and Electronic Engineering, Istanbul Üniversitesi, Istanbul, Turkey; Akan, Aydin I., Department of Electrical and Electronic Engineering, Istanbul Üniversitesi, Istanbul, Turkey; Cekic, Yalcin, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, TurkeyWith the rapid development of computers and internet applications, copyright protection of multimedia data has become an important problem. Watermarking techniques are proposed as a solution to copyright protection of digital media files. In this paper, a new, robust, and high-capacity watermarking method that is based on spatiofrequency (SF) representation is presented. We use the discrete evolutionary transform (DET) calculated by the Gabor expansion to represent an image in the joint SF domain. The watermark is embedded onto selected coefficients in the joint SF domain. Hence, by combining the advantages of spatial and spectral domain watermarking methods, a robust, invisible, secure, and high-capacity watermarking method is presented. A correlation-based detector is also proposed to detect and extract any possible watermarks on an image. The proposed watermarking method was tested on some commonly used test images under different signal processing attacks like additive noise, Wiener and Median filtering, JPEG compression, rotation, and cropping. Simulation results show that our method is robust against all of the attacks. © 2010 Mahmut Öztürk et al. © 2010 Elsevier B.V., All rights reserved.Publication Open Access Obtaining better quality final clustering by merging a collection of clusterings(2010) Mimaroglu, Selim N.; Erdil, Ertunç; Mimaroglu, Selim N., Department of Computer Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Erdil, Ertunç, Department of Computer Engineering, Bahçeşehir Üniversitesi, Istanbul, TurkeyMotivation: Clustering methods including k-means, SOM, UPGMA, DAA, CLICK, GENECLUSTER, CAST, DHC, PMETIS and KMETIS have been widely used in biological studies for gene expression, protein localization, sequence recognition and more. All these clustering methods have some benefits and drawbacks. We propose a novel graph-based clustering software called COMUSA for combining the benefits of a collection of clusterings into a final clustering having better overall quality. Results: COMUSA implementation is compared with PMETIS, KMETIS and k-means. Experimental results on artificial, real and biological datasets demonstrate the effectiveness of our method. COMUSA produces very good quality clusters in a short amount of time. © The Author 2010. Published by Oxford University Press. All rights reserved. © 2011 Elsevier B.V., All rights reserved.Publication Open Access Whole-exome sequencing identifies recessive WDR62 mutations in severe brain malformations(2010) Bilgüvar, Kaya; Öztürk, Ali Kemal; Louvi, Angeliki; Kwan, Kenneth Y.; Choi, Murim; Tatlí, Burak; Yalnizoǧlu, Dilek; Tüysüz, Beyhan; Caglayan, Ahmet Okay; Gökben, Sarenur; Bilgüvar, Kaya, Department of Neurosurgery, Yale School of Medicine, New Haven, United States, Department of Neurobiology, Yale School of Medicine, New Haven, United States, Department of Genetics, Yale School of Medicine, New Haven, United States; Öztürk, Ali Kemal, Department of Neurosurgery, Yale School of Medicine, New Haven, United States, Department of Neurobiology, Yale School of Medicine, New Haven, United States, Department of Genetics, Yale School of Medicine, New Haven, United States; Louvi, Angeliki, Department of Neurosurgery, Yale School of Medicine, New Haven, United States, Department of Neurobiology, Yale School of Medicine, New Haven, United States, Department of Genetics, Yale School of Medicine, New Haven, United States; Kwan, Kenneth Y., Department of Neurobiology, Yale School of Medicine, New Haven, United States, Kavli Institute for Neuroscience, Yale School of Medicine, New Haven, United States; Choi, Murim, Department of Genetics, Yale School of Medicine, New Haven, United States; Tatlí, Burak, Department of Pediatrics, İstanbul Tıp Fakültesi, Istanbul, Turkey; Yalnizoǧlu, Dilek, Department of Pediatrics, Hacettepe Üniversitesi, Ankara, Turkey; Tüysüz, Beyhan, Department of Pediatrics, İstanbul University-Cerrahpaşa Cerrahpaşa Faculty of Medicine, Istanbul, Turkey; Caglayan, Ahmet Okay,; Gökben, Sarenur, Department of Pediatrics, Ege University Medical School, Izmir, TurkeyThe development of the human cerebral cortex is an orchestrated process involving the generation of neural progenitors in the periventricular germinal zones, cell proliferation characterized by symmetric and asymmetric mitoses, followed by migration of post-mitotic neurons to their final destinations in six highly ordered, functionally specialized layers1,2. An understanding of the molecular mechanisms guiding these intricate processes is in its infancy, substantially driven by the discovery of rare mutations that cause malformations of cortical development3-6. Mapping of disease loci in putative Mendelian forms of malformations of cortical development has been hindered by marked locus heterogeneity, small kindred sizes and diagnostic classifications that may not reflect molecular pathogenesis. Here we demonstrate the use of whole-exome sequencing to overcome these obstacles by identifying recessive mutations in WD repeat domain 62 (WDR62) as the cause of a wide spectrum of severe cerebral cortical malformations including microcephaly, pachygyria with cortical thickening as well as hypoplasia of the corpus callosum. Some patients with mutations in WDR62 had evidence of additional abnormalities including lissencephaly, schizencephaly, polymicrogyria and, in one instance, cerebellar hypoplasia, all traits traditionally regarded as distinct entities. In mice and humans, WDR62 transcripts and protein are enriched in neural progenitors within the ventricular and subventricular zones. Expression of WDR62 in the neocortex is transient, spanning the period of embryonic neurogenesis. Unlike other known microcephaly genes, WDR62 does not apparently associate with centrosomes and is predominantly nuclear in localization. These findings unify previously disparate aspects of cerebral cortical development and highlight the use of whole-exome sequencing to identify disease loci in settings in which traditional methods have proved challenging. © 2010 Macmillan Publishers Limited. All rights reserved. © 2012 Elsevier B.V., All rights reserved., MEDLINE® is the source for the MeSH terms of this document.Publication Open Access On numerical optimization theory of infinite kernel learning(2010) Akyüz, Süreyya; Weber, Gerhard Wilhelm; Akyüz, Süreyya, Department of Mathematics and Computer Science, Bahçeşehir Üniversitesi, Istanbul, Turkey; Weber, Gerhard Wilhelm, Institute of Applied Mathematics, Middle East Technical University (METU), Ankara, Turkey, Faculty of Economics, Business and Law, Universität Siegen, Siegen, GermanyIn Machine Learning algorithms, one of the crucial issues is the representation of the data. As the given data source become heterogeneous and the data are large-scale, multiple kernel methods help to classify nonlinear data. Nevertheless, the finite combinations of kernels are limited up to a finite choice. In order to overcome this discrepancy, a novel method of infinite kernel combinations is proposed with the help of infinite and semi-infinite programming regarding all elements in kernel space. Looking at all infinitesimally fine convex combinations of the kernels from the infinite kernel set, the margin is maximized subject to an infinite number of constraints with a compact index set and an additional (Riemann-Stieltjes) integral constraint due to the combinations. After a parametrization in the space of probability measures, it becomes semi-infinite. We adapt well-known numerical methods to our infinite kernel learning model and analyze the existence of solutions and convergence for the given algorithms. We implement our new algorithm called infinite kernel learning (IKL) on heterogenous data sets by using exchange method and conceptual reduction method, which are well known numerical techniques from solve semi-infinite programming. The results show that our IKL approach improves the classifaction accuracy efficiently on heterogeneous data compared to classical one-kernel approaches. © 2009 Springer Science+Business Media, LLC. © 2010 Elsevier B.V., All rights reserved.