Publications without Fulltext

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3

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Department: search.filters.department.Department of MathematicsSubject: search.filters.subject.Engineering

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Now showing 1 - 10 of 28
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    Performance evaluation of an exact method for the obstacle neutralization problem
    (IEOM Society, 2016) Alkaya, Ali Fuat; Algin, Ramazan; Oz, Dindar; Aksakalli, Vural; Department of Mathematics; Ceyhan, Elvan; Faculty Member; Department of Mathematics; College of Sciences; N/A
    The Obstacle Neutralization Problem (ONP) is an NP-Hard path planning problem wherein an agent needs to swiftly navigate from a given start location to a target location through an arrangement of disc-shaped obstacles on the plane. The agent has a limited neutralization capability in the sense that it can neutralize an obstacle after which it can safely traverse through. A neutralization can only be performed at a cost, which is added to the overall traversal length. The goal is to find the optimal neutralization sequence that minimizes the agent's total traversal length. In this study, we compare the performance of a recently proposed exact algorithm for ONP against a conventional solution obtained via an integer programming formulation. This exact algorithm consists of two phases. In Phase I, an effective and fast algorithm is used to obtain a suboptimal solution. In the Phase II, a k-th shortest path algorithm is used to close any gaps. The integer programming formulation is solved via the popular SCIP solver. We present computational experiments conducted on synthetic problem instances on a discrete plane with varying resolutions. Our results indicate that the exact algorithm provides an almost 10-fold improvement in execution time when compared against the integer programming approach.
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    Exploratory and inferential methods for spatio-temporal analysis of residential fire clustering in urban areas
    (Elsevier, 2013) Ertugay, Kıvanç; Düzgün, Şebnem; Department of Mathematics; Ceyhan, Elvan; Faculty Member; Department of Mathematics; College of Sciences; N/A
    The spatio-temporal analysis of residential fires could allow decision makers to plan effective resource allocations in fire management according to fire clustering levels in space and time. In this study, we provide guidelines for the use of various methods in detecting the differences in clustering patterns of fire and non-fire (i.e., background residential) locations and how these patterns change over time. As a preliminary analysis step, various exploratory data analysis methods, such as, intensity plots (i.e., kernel density estimates) are used. Moreover, the use of Diggle's-function (a second order analysis technique) is proposed for detecting the clustering of residential fire locations (if any) and whether there is additional clustering (or regularity) in the locations of the fires compared to background residential pattern. A test for trend over time (in years, months, and weeks) of the fire location patterns are provided with a space-time interaction analysis by the spatio-temporal-function. Residential fire data from Cankaya Municipality of Ankara, Turkey is used as an illustrative example. The presented methodology is also applicable to residential fire data from similar urban settings. (C) 2013 Elsevier Ltd. All rights reserved.
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    Topology dependent information dissemination in P2P networks for anti-entropy algorithmS
    (Ieee, 2008) N/A; N/A; Department of Computer Engineering; Department of Mathematics; İskender, Emre; Özkasap, Öznur; Çağlar, Mine; Master Student; Faculty Member; Faculty Member; Department of Computer Engineering; Department of Mathematics; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; N/A; 113507; 105131
    Analyzing the behavior of epidemic spreading in a network is a good way of modeling several network phenomena. There are several studies analyzing the spreading of email viruses. Spreading of epidemics is also a good model for several types of information dissemination in distributed systems. In this study, we examine spreading of epidemics for anti-entropy algorithms in a peer-to-peer network with any given topology. We derive nodes' exact probability distributions of being infected in each epidemic cycle.
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    Interval algebra to deal with pattern loading and structural uncertainties - Closure
    (Asce-Amer Soc Civil Engineers, 1997) Çakmak, Ahmet Ş.; Nielsen, Søren R.K.; Department of Mathematics; Köylüoğlu, Hasan Uğur; Teaching Faculty; Department of Mathematics; College of Sciences; N/A
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    System dynamics and modified cumulant neglect closure schemes
    (Amer Soc Civil Engineers, 1996) Nielsen, Rune Kristian Lundedal; Department of Mathematics; Köylüoğlu, Hasan Uğur; Teaching Faculty; Department of Mathematics; College of Sciences; N/A
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    Faster simulation methods for the non-stationary random vibrations of non-linear mdof systems
    (A A Balkema, 1995) Department of Mathematics; Department of Mathematics; N/A; N/A; Aşkar, Attila; Köylüoğlu, Hasan Uğur; Çakmak, Ayşe Selin; Nielsen, Susanne Ramtung; Faculty Member; Teaching Faculty; Other; Other; Department of Mathematics; College of Sciences; College of Sciences; N/A; N/A; 178822 N/A; N/A; N/A
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    Wireless controller for interactive virtual reality games
    (Ieee, 2017) Yazıcı, Mahmut Sami; Ozmen, Laurence; Ulusoy, Erdem; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Computer Engineering; Department of Mathematics; Department of Electrical and Electronics Engineering; Kazempourradi, Seyedmahdi; Öztürk, Seyfettin Onurhan; Erdemli, Murat Berke; Tuncer, Sidem Işıl; Dağıdır, Can Hakan; Ürey, Hakan; PhD Student; Undergraduate Student; Undergraduate Student; Undergraduate Student; Undergraduate Student; Undergraduate Student; Faculty Member; Department of Computer Engineering; Department of Mathematics; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; College of Engineering; College of Sciences; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 8579
    An array of tiny, low-cost, stand-alone and wireless inertial motion sensor units is designed and fabricated. These sensor units recognise gestures of a user, enabling a comfort control in game applications. Despite the wide usage of motion sensor units in various applications, we utilize an array of detached and low-cost controller units and an Oculus Rift DK2 to develop two VR games, for the first time. In one application, the user can control a spaceship movements by its hand movements. The other game is a first-person shooting game, in which an array of sensors are used for aiming and shooting purpose. This type of control provides the feeling of full immersion inside a VR environment. The developed sensor unit is a promising controller for a broad range of applications in virtual and augmented reality industry.
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    Simulation and characterization of multi-class spatial patterns from stochastic point processes of randomness, clustering and regularity
    (Springer, 2014) Department of Mathematics; Ceyhan, Elvan; Faculty Member; Department of Mathematics; College of Sciences; N/A
    Spatial pattern analysis of data from multiple classes (i.e., multi-class data) has important implications. We investigate the resulting patterns when classes are generated from various spatial point processes. Our null pattern is that the nearest neighbor probabilities being proportional to class frequencies in the multi-class setting. In the two-class case, the deviations are mainly in two opposite directions, namely, segregation and association of the classes. But for three or more classes, the classes might exhibit mixed patterns, in which one pair exhibiting segregation, while another pair exhibiting association or complete spatial randomness independence. To detect deviations from the null case, we employ tests based on nearest neighbor contingency tables (NNCTs), as NNCT methods can provide an omnibus test and post-hoc tests after a significant omnibus test in a multi-class setting. In particular, for analyzing these multi-class patterns (mixed or not), we use an omnibus overall test based on NNCTs. After the overall test, the pairwise interactions are analyzed by the post-hoc cell-specific tests based on NNCTs. We propose various parameterizations of the segregation and association alternatives, list some appealing properties of these patterns, and propose three processes for the two-class association pattern. We also consider various clustering and regularity patterns to determine which one(s) cause segregation from or association with a class from a homogeneous Poisson process and from other processes as well. We perform an extensive Monte Carlo simulation study to investigate the newly proposed association patterns and to understand which stochastic processes might result in segregation or association. The methodology is illustrated on two real life data sets from plant ecology.
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    Multiclass G/M/1 queueing system with self-similar input and non-preemptive priority
    (Elsevier, 2008) Iftikhar, Mohsin; Singh, Tejeshwar; Landfeldt, Bjorn; Department of Mathematics; Çağlar, Mine; Faculty Member; Department of Mathematics; College of Sciences; 105131
    In order to deliver innovative and cost-effective IP multimedia applications over mobile devices, there is a need to develop a unified service platform for the future mobile Internet referred as the Next Generation (NG) all-IP network. It is convincingly demonstrated by numerous recent studies that modern multimedia network traffic exhibits long-range dependence (LRD) and self-similarity. These characteristics pose many novel and challenging problems in traffic engineering and network planning. One of the major concerns is how to allocate network resources efficiently to diverse traffic classes with heterogeneous QoS constraints. However, much of the current understanding of wireless traffic modeling is based on classical Poisson distributed traffic, which can yield misleading results and hence poor network planning. Unlike most existing studies that primarily focus on the analysis of single-queue systems based on the simplest First-Come-First-Serve (FCFS) scheduling policy, in this paper we introduce the first of its kind analytical performance model for multiple-queue systems with self-similar traffic scheduled by priority queueing to support differentiated QoS classes. The proposed model is based on a G/M/1 queueing system that takes into account multiple classes of traffic that exhibit long-range dependence and self-similarity. We analyze the model on the basis of non-preemptive priority and find exact packet delay and packet loss rate of the corresponding classes. We develop a finite queue Markov chain for non-preemptive priority scheduling, extending the previous work on infinite capacity systems. We extract a numerical solution for the proposed analytical framework by formulating and solving the corresponding Markov chain. We further present a comparison of the numerical analysis with comprehensive simulation studies of the same system. We also implement a Cisco-router based test bed, which serves to validate the mathematical, numerical, and simulation results as well as to support in understanding the QoS behaviour of realistic traffic input.
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    Segmentation of arteries in mprage images of the ventral medial prefrontal cortex
    (Elsevier, 2008) Penumetcha, N.; Jedynak, B.; Hosakere, M.; Botteron, K. N.; Ratnanather, J. T.; Department of Mathematics; Ceyhan, Elvan; Faculty Member; Department of Mathematics; College of Sciences; N/A
    A method for removing arteries that appear bright with intensities similar to white matter in Magnetized Prepared Rapid Gradient Echo images of the ventral medial prefrontal cortex is described. The Fast Marching method is used to generate a curve within the artery. Then, the largest connected component is selected to segment the artery which is used to mask the image. The surface reconstructed from the masked image yielded cortical thickness maps similar to those generated by manually pruning the arteries from surfaces reconstructed from the original image. The method may be useful in masking vasculature in other cortical regions. (c) 2007 Elsevier Ltd. All rights reserved.