Sever, Hayri
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Prof. Dr.
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sever@cankaya.edu.tr
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Bilgisayar Mühendisliği
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Scholarly Output
27
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26
Citation Count
103
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0
27 results
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Now showing 1 - 10 of 27
Conference Object Citation - WoS: 6Citation - Scopus: 7Blocked-DWT Based Vector Image Watermarking(Ieee, 2015) Senol, Ahmet; Sever, Hayri; Dincer, Kivanc; Sever, Hayri; Elbasi, Ersin; Bilgisayar MühendisliğiImage watermarking is in use for proving ownership for a fairly long time. For most of the study on this area, a pseudo random number sequence PRSN or a binary image logo is embedded as watermark. Nowadays the owner's face or sound is also embedded as biometric watermark. Image is transferred to discrete wavelet transform domain, watermark is embedded to DWT values, then DWT values are retransformed to spatial domain to obtain watermarked image. Embedding a vector image logo as watermark was not tried in previous works. In this work, non-blind robust watermarking is applied using a vector image as watermark. Various attacks are applied to watermarked images and for each of these attacks vector image watermark is obtained equal or almost equal to the original. Embedding vector image as watermark will bring a new discipline for image watermarking and a new development will arise in this perspective.Publication Production and retrieval off rough classes in multi relations(IEEE Computer Soc, 2007) Sever, Hayri; Görür, Abdül Kadir; Görür, Abdül Kadir; 11916; 107251; Bilgisayar MühendisliğiOrganizational memory in today's business world forms basis for organizational learning, which is the ability of an organization to gain insight and understanding from experience through experimentation, observation, analysis, and a willingness to examine both successes and failures. This basically requires consideration of different aspects of knowledge that may reside on top of a conventional information management system. Of them, representation, retrieval and production issues of meta patterns constitute to the main theme of this article. Particularly we are interested in a formal approach to handle rough concepts. We utilize rough classifiers to propose a preliminary framework based on minimal term sets with p-norms to extract meta patterns. We describe a relational rule induction approach, which is called rila. Experimental results are provided on the mutagenesis, and the KDD Cup 2001 genes data sets.Article Otomatik Konuşma Tanımaya Genel Bakış, Yaklaşımlar ve Zorluklar: Türkçe Konuşma Tanımanın Gelecekteki Yolu(2019) Sever, Hayri; Oyucu, Saadin; Polat, Huseyin; Sever, Hayri; 11916; Bilgisayar Mühendisliğiİnsanlar arasındaki en önemli iletişim yöntemi olan konuşmanın, bilgisayarlar tarafından tanınması önemli bir çalışma alanıdır. Bu araştırma alanında farklı diller temel alınarak birçok çalışma gerçekleştirilmiştir. Literatürdeki çalışmalar konuşma tanıma teknolojilerinin başarımının artmasında önemli rol oynamıştır. Bu çalışmada konuşma tanıma ile ilgili bir literatür taraması yapılmış ve detaylı olarak sunulmuştur. Ayrıca farklı dillerde bu araştırma alanında kaydedilen ilerlemeler tartışılmıştır. Konuşma tanıma sistemlerinde kullanılan veri setleri, özellik çıkarma yaklaşımları, konuşma tanıma yöntemleri ve performans değerlendirme ölçütleri incelenerek konuşma tanımanın gelişimi ve bu alandaki zorluklara odaklanılmıştır. Konuşma tanıma alanında son zamanlarda yapılan çalışmaların olumsuz koşullara (çevre gürültüsü, konuşmacıda ve dilde değişkenlik) karşı çok daha güçlü yöntemler geliştirmeye odaklandığı izlenmiştir. Bu nedenle araştırma alanı olarak genişleyen olumsuz koşullardaki konuşma tanıma ile ilgili yakın geçmişteki gelişmelere yönelik genel bir bakış açısı sunulmuştur. Böylelikle olumsuz koşullar altında gerçekleştirilen konuşma tanımadaki tıkanıklık ve zorlukları aşabilmek için kullanılabilecek yöntemleri seçmede yardımcı olunması amaçlanmıştır. Ayrıca Türkçe konuşma tanımada kullanılan ve iyi bilinen yöntemler karşılaştırılmıştır. Türkçe konuşma tanımanın zorluğu ve bu zorlukların üstesinden gelebilmek için kullanılabilecek uygun yöntemler irdelenmiştir. Buna bağlı olarak Türkçe konuşma tanımanın gelecekteki rotasına ilişkin bir değerlendirme ortaya konulmuştur.Article Citation - WoS: 20Citation - Scopus: 28Creating consensus group using online learning based reputation in blockchain networks(Elsevier, 2019) Bugday, Ahmet; Sever, Hayri; Ozsoy, Adnan; Oztaner, Serdar Murat; Sever, Hayri; 11916; Bilgisayar MühendisliğiOne of the biggest challenges to blockchain technology is the scalability problem. The choice of consensus algorithm is critical to the practical solution of the scalability problem. To increase scalability, Byzantine Fault Tolerance (BFT) based methods have been most widely applied. This study proposes a new model instead of Proof of Work (PoW) for forming the consensus group that allows the use of BFT based methods in the public blockchain network. The proposed model uses the adaptive hedge method, which is a decision-theoretic online learning algorithm (Qi et al., 2016). The reputation value is calculated for the nodes that want to participate in the consensus committee, and nodes with high reputation values are selected for the consensus committee to reduce the chances of the nodes in the consensus committee being harmful. Since the study focuses on the formation of the consensus group, a simulated blockchain network is used to test the proposed model more effectively. Test results indicate that the proposed model, which is a new approach in the literature making use of machine learning for the construction of consensus committee, successfully selects the node with the higher reputation for the consensus group. (C) 2019 Elsevier B.V. All rights reserved.Article Citation - WoS: 7Citation - Scopus: 10Extending a sentiment lexicon with synonym-antonym datasets: SWNetTR plus(Tubitak Scientific & Technological Research Council Turkey, 2019) Saglam, Fatih; Sever, Hayri; Genc, Burkay; Sever, Hayri; 11916; Bilgisayar MühendisliğiIn our previous studies on developing a general-purpose Turkish sentiment lexicon, we constructed SWNetTR-PLUS, a sentiment lexicon of 37K words. In this paper, we show how to use Turkish synonym and antonym word pairs to extend SWNetTR-PLUS by almost 33% to obtain SWNetTR++, a Turkish sentiment lexicon of 49K words. The extension was done by transferring the problem into the graph domain, where nodes are words, and edges are synonym- antonym relations between words, and propagating the existing tone and polarity scores to the newly added words using an algorithm we have developed. We tested the existing and new lexicons using a manually labeled Turkish news media corpus of 500 news texts. The results show that our method yielded a significantly more accurate lexicon than SWNetTR-PLUS, resulting in an accuracy increase from 72.2% to 80.4%. At this level, we have now maximized the accuracy rates of translation-based sentiment analysis approaches, which first translate a Turkish text to English and then do the analysis using English sentiment lexicons.Conference Object Citation - WoS: 2Citation - Scopus: 2Clinical Decision Support Systems: From the Perspective of Small and Imbalanced Data Set(Ios Press, 2019) Par, Oznur Esra; Sever, Hayri; Akcapinar Sezer, Ebru; Sever, Hayri; 11916; Bilgisayar MühendisliğiClinical decision support systems are data analysis software that supports health professionals' decision - making the process to reach their ultimate outcome, taking into account patient information. However, the need for decision support systems cannot be denied because of most activities in the field of health care within the decision-making process. Decision support systems used for diagnosis are designed based on disease due to the complexity of diseases, symptoms, and disease-symptoms relationships. In the design and implementation of clinical decision support systems, mathematical modeling, pattern recognition and statistical analysis techniques of large databases and data mining techniques such as classification are also widely used. Classification of data is difficult in case of the small and / or imbalanced data set and this problem directly affects the classification performance. Small and/or imbalance dataset has become a major problem in data mining because classification algorithms are developed based on the assumption that the data sets are balanced and large enough. Most of the algorithms ignore or misclassify examples of the minority class, focus on the majority class. Most health data are small and imbalanced by nature. Learning from imbalanced and small data sets is an important and unsettled problem. Within the scope of the study, the publicly accessible data set, hepatitis was oversampled by distance-based data generation methods. The oversampled data sets were classified by using four different machine learning algorithms. Considering the classification scores of four different machine learning algorithms (Artificial Neural Networks, Support Vector Machines, Naive Bayes and Decision Tree), optimal synthetic data generation rate is recommended.Article Citation - WoS: 2Citation - Scopus: 2Binary background model with geometric mean for author-independent authorship verification(Sage Publications Ltd, 2023) Canbay, Pelin; Sever, Hayri; Sezer, Ebru A.; Sever, Hayri; 11916; Bilgisayar MühendisliğiAuthorship verification (AV) is one of the main problems of authorship analysis and digital text forensics. The classical AV problem is to decide whether or not a particular author wrote the document in question. However, if there is one and relatively short document as the author's known document, the verification problem becomes more difficult than the classical AV and needs a generalised solution. Regarding to decide AV of the given two unlabeled documents (2D-AV), we proposed a system that provides an author-independent solution with the help of a Binary Background Model (BBM). The BBM is a supervised model that provides an informative background to distinguish document pairs written by the same or different authors. To evaluate the document pairs in one representation, we also proposed a new, simple and efficient document combination method based on the geometric mean of the stylometric features. We tested the performance of the proposed system for both author-dependent and author-independent AV cases. In addition, we introduced a new, well-defined, manually labelled Turkish blog corpus to be used in subsequent studies about authorship analysis. Using a publicly available English blog corpus for generating the BBM, the proposed system demonstrated an accuracy of over 90% from both trained and unseen authors' test sets. Furthermore, the proposed combination method and the system using the BBM with the English blog corpus were also evaluated with other genres, which were used in the international PAN AV competitions, and achieved promising results.Article Citation - WoS: 3Citation - Scopus: 6A shallow 3D convolutional neural network for violence detection in videos(Cairo Univ, Fac Computers & information, 2024) Dündar, Naz; Dundar, Naz; Keceli, Ali Seydi; Sever, Hayri; Kaya, Aydin; Sever, Hayri; 366608; 11916; Yazılım Mühendisliği; Bilgisayar MühendisliğiWith the recent worldwide statistical rise in the amount of public violence, automated violence detection in surveillance cameras has become a matter of high importance. This work introduces an end-to-end, trainable 3D Convolutional Neural Network (3D CNN) for detecting violence in video footage. The proposed network is inherently capable of processing both spatial and temporal information, thereby obviating the need for additional models that would introduce higher computational requirements and complexity. This work has two main contributions: 1) developing a lightweight 3D CNN suitable for inference on edge devices as mobile systems, and 2) a comprehensive explanation of all components comprising a CNN model, thereby enhances model interpretability. Experiments were conducted to assess the performance of the proposed model using a consolidated dataset combining four benchmark datasets. The results of the experiments support the asserted contributions, which are discussed in detail.Conference Object Citation - WoS: 1Modeling the symptom-disease relationship by using rough set theory and formal concept analysis(World Acad Sci, Eng & Tech-waset, 2007) Bal, Mert; Sever, Hayri; Sever, Hayri; Kalipsiz, Oya; 11916; Bilgisayar MühendisliğiMedical Decision Support Systems (MDSSs) are sophisticated, intelligent systems that can provide inference due to lack of information and uncertainty. In such systems, to model the uncertainty various soft computing methods such as Bayesian networks, rough sets, artificial neural networks, fuzzy logic, inductive logic programming and genetic algorithms and hybrid methods that formed from the combination of the few mentioned methods are used. In this study, symptom-disease relationships are presented by a framework which is modeled with a formal concept analysis and theory, as diseases, objects and attributes of symptoms. After a concept lattice is formed, Bayes theorem can be used to determine the relationships between attributes and objects. A discernibility relation that forms the base of the rough sets can be applied to attribute data sets in order to reduce attributes and decrease the complexity of computation.Article Sessizliğin Kaldırılması ve Konuşmanın Parçalara Ayrılması İşleminin Türkçe Otomatik Konuşma Tanıma Üzerindeki Etkisi(2020) Sever, Hayri; Sever, Hayri; Polat, Huseyin; Oyucu, Saadin; 11916; Bilgisayar MühendisliğiOtomatik Konuşma Tanıma sistemleri temel olarak akustik bilgiden faydalanılarak geliştirilmektedir. Akustikbilgiden fonem bilgisinin elde edilmesi için eşleştirilmiş konuşma ve metin verileri kullanılmaktadır. Bu verilerile eğitilen akustik modeller gerçek hayattaki bütün akustik bilgiyi modelleyememektedir. Bu nedenle belirli önişlemlerin yapılması ve otomatik konuşma tanıma sistemlerinin başarımını düşürecek akustik bilgilerin ortadankaldırılması gerekmektedir. Bu çalışmada konuşma içerisinde geçen sessizliklerin kaldırılması için bir yöntemönerilmiştir. Önerilen yöntemin amacı sessizlik bilgisinin ortadan kaldırılması ve akustik bilgide uzunbağımlılıklar sağlayan konuşmaların parçalara ayrılmasıdır. Geliştirilen yöntemin sonunda elde edilen sessizlikiçermeyen ve parçalara ayrılan konuşma bilgisi bir Türkçe Otomatik Konuşma Tanıma sistemine girdi olarakverilmiştir. Otomatik Konuşma Tanıma sisteminin çıkışında sisteme giriş olarak verilen konuşma parçalarınakarşılık gelen metinler birleştirilerek sunulmuştur. Gerçekleştirilen deneylerde sessizliğin kaldırılması vekonuşmanın parçalara ayrılması işleminin Otomatik Konuşma Tanıma sistemlerinin başarımını artırdığıgörülmüştür.
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