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Yayın Calculating the VC-dimension of decision trees(IEEE, 2009) Aslan, Özlem; Yıldız, Olcay Taner; Alpaydın, Ahmet İbrahim EthemWe propose an exhaustive search algorithm that calculates the VC-dimension of univariate decision trees with binary features. The VC-dimension of the univariate decision tree with binary features depends on (i) the VC-dimension values of the left and right subtrees, (ii) the number of inputs, and (iii) the number of nodes in the tree. From a training set of example trees whose VC-dimensions are calculated by exhaustive search, we fit a general regressor to estimate the VC-dimension of any binary tree. These VC-dimension estimates are then used to get VC-generalization bounds for complexity control using SRM in decision trees, i.e., pruning. Our simulation results shows that SRM-pruning using the estimated VC-dimensions finds trees that are as accurate as those pruned using cross-validation.Yayın Univariate margin tree(Springer, 2010) Yıldız, Olcay TanerIn many pattern recognition applications, first decision trees are used due to their simplicity and easily interpretable nature. In this paper, we propose a new decision tree learning algorithm called univariate margin tree, where for each continuous attribute, the best split is found using convex optimization. Our simulation results on 47 datasets show that the novel margin tree classifier performs at least as good as C4.5 and LDT with a similar time complexity. For two class datasets it generates smaller trees than C4.5 and LDT without sacrificing from accuracy, and generates significantly more accurate trees than C4.5 and LDT for multiclass datasets with one-vs-rest methodology.Yayın Numerical integration methods for simulation of mass-spring-damper systems(Springer-Verlag, 2012) Özgüz, Mete; Eskil, Mustafa TanerThe dynamics of a face are often implemented as a system of connected particles with various forces acting upon them. Animation of such a system requires the approximation of velocity and position of each particle through numerical integration. There are many numerical integrators that are commonly used in the literature. We conducted experiments to determine the suitability of numerical integration methods in approximating the particular dynamics of mass-spring-damper systems. Among Euler, semi-implicit Euler, Runge-Kutta and Leapfrog, we found that simulation with Leapfrog numerical integration characterizes a mass-spring-damper system best in terms of the energy loss of the overall system.Yayın Design of real-time VBR traffic shaping schemes by considering the impact of both buffer overflows and deadline violations(Int Inst Informatics & Systemics, 2005) Dağ, Tamer; Stavrakakis, IoannisWhile smoothing the traffic of time sensitive applications at the user premises can reduce the losses due to buffer overflows within the network, it may have an adverse effect on the losses due to the deadline violations due to the delay introduced by the smoothing process. In this paper, these loss factors are investigated and some simple metrics that capture the potential for buffer overflow and deadline violation losses under a traffic shaping scheme are introduced. Such metrics can be useful for the design of effective traffic shaping schemes that balance the adverse effects of buff-er overflow and deadline violation losses. An example of a more effective traffic shaping scheme is presented and its performance is compared to that of some more traditional schemes.Yayın Palmprint verification using SIFT majority voting(Springer-Verlag, 2012) Abeysundera, Hasith Pasindu; Eskil, Mustafa TanerIn this paper we illustrate the implementation of a robust, real-time biometric system for identity verification based on palmprint images. The palmprint images are preprocessed to align the major axes of hand shapes and to extract the palm region. We extract features using Scale Invariant Feature Transform (SIFT). Classification of individual SIFT features is done through KNN. The class of the hand image is decided by a majority based voting among its classified SIFT features. We demonstrate on the CASIA and PolyU datasets that the proposed system achieves authentication accuracy comparable to other state of the art algorithms.Yayın Dilemma of the HR manager: An optimization for training and development budgets using integer programming a case study from an international firm(Int Inst Informatics & Systemics, 2005) Yanık, Serhat; Yazıcı, Selim; Şenel, İlhan KeremThis paper is about a dilemma of an HR manager of an international company. The major problem of HR managers is to minimize their training and development budgets. Making a training budget is not so complex; but the important, yet often neglected, part of budgeting is the costs of absence of employees. In every kind of training, whether traditional or e-learning, there is a cost for the time being spent away from work. Some of the managers think that this is an idle time for company, plus the employee is paid during this period. This paper focuses on the costs of the absence and their effect on training budgets. Some scenarios were developed with the help of an HR manager of an international firm. The feasibility of these scenarios was studied by using integer programming.Yayın Regularizing soft decision trees(Springer, 2013) Yıldız, Olcay Taner; Alpaydın, Ahmet İbrahim EthemRecently, we have proposed a new decision tree family called soft decision trees where a node chooses both its left and right children with different probabilities as given by a gating function, different from a hard decision node which chooses one of the two. In this paper, we extend the original algorithm by introducing local dimension reduction via L-1 and L-2 regularization for feature selection and smoother fitting. We compare our novel approach with the standard decision tree algorithms over 27 classification data sets. We see that both regularized versions have similar generalization ability with less complexity in terms of number of nodes, where L-2 seems to work slightly better than L-1.Yayın Türkçe kelime ağı KeNet için arayüz(Institute of Electrical and Electronics Engineers Inc., 2019-04) Özçelik, Rıza; Uludoğan, Gökçe; Parlar, Selen; Bakay, Özge; Ergelen, Özlem; Yıldız, Olcay TanerKelime ağları, bir dildeki kelimeler arasındaki bağlantıları, eş anlam kümeleri oluşturarak ve bu kümeleri birbirine çeşitli anlamsal bağıntılar ile bağlayarak temsil eden bir çizge veri yapısıdır. Doğal dil işleme alanındaki en yaygın bilinen kelime ağı WordNet 1990 yılında İngilizce için oluşturulmuşken, Türkçe için en kapsamlı ağ, 2018 yılında oluşturulan KeNet’tir. Bildiğimiz kadarıyla, içinde 80000 eş anlam kümesi ve 25 farklı anlamsal bağlantı bulunan KeNet için şu ana kadar geliştirilen bir kullanıcı arayüzü yoktur. Bu çalışmada, KeNet çizgesinde, anlamsal bağlantıları kullanarak eş anlam kümeleri arasında çevrimiçi olarak gezinmeyi sağlayan bir arayüz sunuyoruz. Bu arayüz sayesinde, bir söz öbeği KeNet’te aranabilir ve eş anlam kümeleri arasındaki üst/alt anlam, parça-bütün ilişkileri gibi ilişkiler kullanılarak KeNet üzerinde gezilebilir. Ayrıca, herhangi bir eş anlam kümesinin, varsa, İngilizce karşılığının kimliği de görüntülenebilir ve bu kümeye WordNet’e ait internet sayfasından erişilebilir.Yayın Power control in the cognitive cooperative multiple access channel(IEEE, 2012) Kaya, Onur; İşleyen, MuratWe extend several encoding and decoding techniques from cooperative communications framework, to a cognitive radio system consisting of a primary user (PU) and a secondary user (SU), sending their messages to a common receiver. Assuming that the transmitters and the receiver have full channel state information (CSI) collected and distributed by the common receiver, and that the SU knows the PU's codebook, the cooperation is obtained by block Markov superposition coding, and backwards decoding, which yield a causal overlay scenario. We formulate two rate optimization problems with the aim of, (i) maximizing the sum rate of the system, and (ii) maximizing the rate of the secondary user. We obtain the optimal power allocations for both cases, and the resulting rate regions. The power controlled cooperation turns out to be especially useful when maximizing the sum rate of the system, as it gives the PU significant rate rewards for allowing the cognitive transmitter to access its resources.Yayın A robust localization framework to handle noisy measurements in wireless sensor networks(IEEE, 2009-09-14) Erten, Cesim; Karataş, ÖmerWe construct a robust localization framework to handle noisy measurements in wireless sensor networks. Traditionally many approaches employ the distance information gathered from ranging devices of the sensor nodes to achieve localization. However the measurements of these devices may contain noise both as hardware noise and as environmental noise due to the employment conditions of the network. It Is necessary to provide a general framework that handles such a noise in data and yet still be applicable within several localization algorithms. In order to handle noise in distance measurements, our framework utilizes convex constraints and confidence intervals of a random variable. At the end of the localization process nodes are assigned to a set of feasible regions with corresponding probabilities. The accuracy of the localization can be adjusted and the framework can easily be embedded to work within previously suggested localization algorithms.
