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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only An analytical model based on G/M/1 with self-similar input to provide end-to-end QoS in 3G networks(Association for Computing Machinery (ACM), 2006) Iftikhar, M.; Landfeldt, B.; Department of Mathematics; Çağlar, Mine; Faculty Member; Department of Mathematics; College of Sciences; 105131The dramatic increase in demand for wireless Internet access has lead to the introduction of new wireless architectures and systems including 3G, Wi-Fi and WiMAX. 3G systems such as UMTS and CDMA2000 are leaning towards an all-IP architecture for transporting IP multimedia services, mainly due to its scalability and promising capability of inter-working heterogeneous wireless access networks. During the last ten years, substantial work has been done to understand the nature of wired IP traffic and it has been proven that IP traffic exhibits self-similar properties and burstiness over a large range of time scales. Recently, because of the large deployment of new wireless architectures, researchers have focused their attention towards understanding the nature of traffic carried by different wireless architecture and early studies have shown that wireless data traffic also exhibits strong long-range dependency. Thus, the classical tele-traffic theory based on a simple Markovian process cannot be used to evaluate the performance of wireless networks. Unfortunately, the area of understanding and modeling of different kinds of wireless traffic is still immature which constitutes a problem since it is crucial to guarantee tight bound QoS parameters to heterogeneous end users of the mobile Internet. In this paper, we make several contributions to the accurate modeling of wireless IP traffic by presenting a novel analytical model that takes into account four different classes of self-similar traffic. The model consists of four queues and is based on a G/M/1 queueing system. We analyze it on the basis of priority with no preemption and find exact packet delays. To date, no closed form expressions have been presented for G/M/1 with priority.Publication Metadata only Physics of spectral singularities(Trends in Mathematics, 2015) N/A; Department of Mathematics; Mostafazadeh, Ali; Faculty Member; Department of Mathematics; College of Sciences; 4231Spectral singularities are certain points of the continuous spectrum of generic complex scattering potentials. We review the recent developments leading to the discovery of their physical meaning, consequences, and generalizations. In particular, we give a simple definition of spectral singularities, provide a general introduction to spectral consequences of ��-symmetry (clarifying some of the controversies surrounding this subject), outline the main ideas and constructions used in the pseudo-Hermitian representation of quantum mechanics, and discuss how spectral singularities entered in the physics literature as obstructions to these constructions. We then review the transfer matrix formulation of scattering theory and the application of complex scattering potentials in optics. These allow us to elucidate the physical content of spectral singularities and describe their optical realizations. Finally, we survey some of the most important results obtained in the subject, drawing special attention to the remarkable fact that the condition of the existence of linear and nonlinear optical spectral singularities yield simple mathematical derivations of some of the basic results of laser physics, namely the laser threshold condition and the linear dependence of the laser output intensity on the gain coefficient.Publication Metadata only Code notes: designing a low-cost tangible coding tool for/with children(Association for Computing Machinery (ACM), 2018) N/A; Department of Psychology; N/A; Department of Psychology; Sabuncuoğlu, Alpay; Erkaya, Merve; Buruk, Oğuz Turan; Göksun, Tilbe; PhD Student; Undergraduate Student; PhD Student; Faculty Member; Department of Psychology; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Graduate School of Sciences and Engineering; College of Social Sciences and Humanities; Graduate School of Social Sciences and Humanities; College of Social Sciences and Humanities; N/A; N/A; N/A; 47278Programming has become an essential subject for today's education curriculum and as a result, the importance of creating the right environments to teach is increasing. For such environments, featuring tangible tools enhances creativity and collaboration. However, due to their high prices, current tangible tools are not reachable by most of the students. We developed Code Notes as a low-cost, attainable and tangible tool aimed to motivate children to support programming education. Code Notes is comprised of an Android app and code-cardboards to teach the basic concepts in programming. We continue to develop the platform with insights gained from children. This paper shares the design phases of Code Notes and observations from our two-month programming project. We also presented some future concepts of Code Notes that offer an active and embodied interaction with the teaching material.Publication Metadata only Constructing and embedding mutually orthogonal Latin squares: reviewing both new and existing results(Charles University Faculty of Mathematics and Physics, 2020) Donovan, Diane M.; Grannell, Mike; Department of Mathematics; Yazıcı, Emine Şule; Faculty Member; Department of Mathematics; College of Sciences; 27432We review results for the embedding of orthogonal partial Latin squares in orthogonal Latin squares, comparing and contrasting these with results for embedding partial Latin squares in Latin squares. We also present a new construction that uses the existence of a set of t mutually orthogonal Latin squares of order n to construct a set of 2t mutually orthogonal Latin squares of order n(t).Publication Metadata only Statistical analysis of morphometric measures based on labeled cortical distance maps(IEEE, 2007) Hosakere M.; Nishino T.; Alexopoulos J.; Todd R.D.; Botteron K.N.; Miller M.I.; Ratnanather J.T.; Department of Mathematics; Ceyhan, Elvan; Faculty Member; Department of Mathematics; College of Sciences; N/AShape differences in cortical structures in the brain can be associated with various neuropsychiatric and neuro-developmental diseases or disorders. Labeled Cortical Distance Map (LCDM) can be a powerful tool to quantize such differences in shapes derived from magnetic resonance images (MRI). This article investigates some aspects of LCDM distances in relation to morphometry. Simple morphometric measures based on LCDM indicate some aspect of the shape or size of the tissue in question. The length of the LCDM distance vector provides the number of voxels and thus volume of the tissue. The median, mode, range, and variance of LCDM distances and volume of the tissue are all suggestive of size, thickness, and shape differences. Statistical tests are employed to detect left-right asymmetry, group differences, and stochastic ordering (cdf differences) of these LCDM-based variables. We perform LCDM analysis of gray matter in ventral medial prefrontal cortices (VMPFCs) obtained from a neuro-imaging study of major depressive disorder (MDD), high risk, and control twin subjects. We find significant evidence that VMPFCs with MDD exhibit significant morphometric left-right asymmetry compared to those in high risk and control subjects. The method is also valid for analysis of morphometric measures of other organs or tissues and distances similar to LCDM distances.Publication Metadata only The full metamorphosis of λ-fold block designs with block size four into λ-fold triple systems(Charles Babbage Research Centre, 2012) Lindner, Curt; Department of Mathematics; Department of Mathematics; Yazıcı, Emine Şule; Küçükçifçi, Selda; Faculty Member; Faculty Member; Department of Mathematics; College of Sciences; College of Sciences; 27432; 105252Let (X, B) be a λ-fold block design with block size 4. If a star is removed from each block of B the resulting collection of triangles T is a partial λ-fold triple system (X, T). If the edges belonging to the deleted stars can be arranged into a collection of triangles S, then (X,T ∪ S) is a λ-fold triple system, called a metamorphosis of the A-fold block design (X, B) into a λ-fold triple system. Label the elements of each block b with b 1,b 2,b 3, and b 4 (in any manner). For each i = 1,2,3,4 define a set of triangles T iand a set of stars S i as follows: for each block b = [b 1,b 2,b 3,b 4] belonging to B, partition b into a triangle and a star centered at b i, and place the triangle in T i and the star in S i. Then (X, T i) is a partial λ-fold triple system. Now if the edges belonging to the stars in S i can be arranged into a collection of triangles S i, then (X, T i ∪ S i) is a λ-fold triple system and we say that M i = (X, T i∪S i) is the ith metamorphosis of (X, B). The full metamorphosis of (X, B) is the set of four metamorphoses {M 1, M 2, M 3, M 4}. The purpose of this work is to give a complete solution of the following problem: For which n and λ does there exist a λ-fold block design with block size 4 having a full metamorphosis into λ-fold triple systems? Copyright © 2012, Charles Babbage Research Centre All rights reserved.Publication Metadata only Laser beam propagation in a thermally loaded absorber(Optica Publishing Group, 1996) Department of Physics; Department of Mathematics; Department of Mathematics; Sennaroğlu, Alphan; Aşkar, Attila; Atay, Fatihcan; Faculty Member; Faculty Member; Faculty Member; Department of Physics; Department of Mathematics; College of Sciences; College of Sciences; College of Sciences; 23851; 178822; 253074Beam propagation in a thermally loaded absorber is analyzed by a novel method. The formulation identifies a dimensionless parameter controlling the strength of thermal effects.Publication Metadata only P-adic variation in arithmetic geometry: a survey(Springer, 2017) Department of Mathematics; Büyükboduk, Kazım; Faculty Member; Department of Mathematics; College of SciencesThe main goal of this survey is to provide a general overview of the theme of p-adic variation, both from a historical and technical view point. We start off with Kummer’s work and Iwasawa’s treatment of cyclotomic fields, which eventually paved the way to the modern p-adic variational techniques. These methods have proved extremely powerful and enabled us to gain access to some of the most important problems in mathematics, such as the Bloch-Kato conjectures and Langlands’ Programme. We will point at a variety of concrete applications in this vein.Publication Metadata only 3D shape correspondence by isometry-driven greedy optimization(IEEE Computer Soc, 2010) N/A; Department of Computer Engineering; Sahillioğlu, Yusuf; Yemez, Yücel; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; 215195; 107907We present an automatic method that establishes 3D correspondence between isometric shapes. Our goal is to find an optimal correspondence between two given (nearly) isometric shapes, that minimizes the amount of deviation from isometry. We cast the problem as a complete surface correspondence problem. Our method first divides the given shapes to be matched into surface patches of equal area and then seeks for a mapping between the patch centers which we refer to as base vertices. Hence the correspondence is established in a fast and robust manner at a relatively coarse level as imposed by the patch radius. We optimize the isometry cost in two steps. in the first step, the base vertices are transformed into spectral domain based on geodesic affinity, where the isometry errors are minimized in polynomial time by complete bipartite graph matching. the resulting correspondence serves as a good initialization for the second step of optimization in which we explicitly minimize the isometry cost via an iterative greedy algorithm in the original 3D Euclidean space. We demonstrate the performance of our method on various isometric (or nearly isometric) pairs of shapes for some of which the ground-truth correspondence is available.Publication Metadata only Examining online practices of an autism parent community in Turkey: goals, needs, and opportunities(assoc Computing Machinery, 2019) N/A; N/A; Department of Media and Visual Arts; Department of Media and Visual Arts; N/A; Yıldız, Zeynep; Gatos, Doğa Çorlu; Subaşı, Özge; Yantaç, Asım Evren; Kuşçu, Kemal; PhD Student; PhD Student; Faculty Member; Faculty Member; Other; Department of Media and Visual Arts; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Graduate School of Social Sciences and Humanities; Graduate School of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Social Sciences and Humanities; School of Medicine; N/A; N/A; 240920; 52621; N/AAutism is a complex, life-long condition that manifests itself in unique ways in each person. Due to the complexity of the condition along with not having efficient and immediate social support, parents with autistic children often seek for and rely upon the information generated by the community (parents, caregivers, autistics and experts) on online platforms. We look into what parents of autistic individuals discuss on an online platform in Turkey, how they practice autism online and why those practices are important or relevant. Our findings show how parents cope with understanding and defining autism, and how they seek for empowering each other, and managing the everyday collectively under a dominant medical discourse around autism in Turkish context. Based on our findings, we extend the existing knowledge on collective and alternative ways of re-defining autism as lived experience and introduce recommendations on how those strategies can be integrated to design.