Computer Engineering / Bilgisayar Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/10

Browse

Filters

2001 - 200945

Settings

End date: 2009Publication Index: search.filters.publicationIndex.WoS

Search Results

Now showing 1 - 10 of 45
  • Conference Object
    Citation - WoS: 1
    On Defining Security Metrics for Information Systems
    (Brill Academic Publishers, 2005) Koltuksuz, Ahmet
    [No abstract available]
  • Conference Object
    Citation - WoS: 37
    Graph Theoretic Clustering Algorithms in Mobile Ad Hoc Networks and Wireless Sensor Networks (survey)
    (Azerbaijan National Academy of Sciences, 2007) Erciyeş, Kayhan; Dağdeviren, Orhan; Çokuslu, Deniz; Özsoyeller, Deniz
    Clustering in mobile ad hoc networks (MANETs) and wireless sensor networks (WSNs) is an important method to ease topology management and routing in such networks. Once the clusters are formed, the leaders (coordinators) of the clusters may be used to form a backbone for efficient routing and communication purposes. A set of clusters may also provide the underlying physical structure for multicast communication for a higher level group communication module which may effectively be used for fault tolerance and key management for security purposes. We survey graph theoretic approaches for clustering in MANETs and WSNS and show that although there is a wide range of such algorithms, each may be suitable for a different cross-layer design objective.
  • Conference Object
    Duyarga Ağları için Bir Γ Eşuyumcusu Tasarım ve Uygulaması
    (IEEE, 2008) Özsoyeller, Deniz; Erciyeş, Kayhan; Dağdeviren, Orhan
    Implementation of synchronous algorithms in distributed systems in general is less troublesome than the implementation of asynchronous algorithms. Synchronizers provide synchronous execution of an asynchronous algorithm in distributed systems. In this study, we propose a gamma synchronizer for Wireless Sensor Networks (WSNs). This synchronizer consists of a and beta synchronizers. In our work, the WSN is first divided into clusters and then these clusters are connected using a ring protocol. Synchronization is provided using the beta synchronizer in the cluster and a synchronizer among the clusters. We describe the clustering algorithm and the ring formation algorithm for the WSNs and give the results obtained so far.
  • Conference Object
    Citation - Scopus: 15
    Gezgin Tasarsız Ağlar için Taşırma Tabanlı Yönlendirme Yordamı
    (IEEE, 2008) Çokuslu, Deniz; Erciyeş, Kayhan
    Mobile Ad Hoc Networks (MANETs) are videly in use in rescue, military operations, scientific and business areas. Many studies are addressed in MANETs because of their need to long lasting liveness, fault tolerance, dynamic addressing, collusion prevention, mobility management and security. Especially, self clustering, backbone construction and routing are the most interesting academic and industrial research areas in MANETs. A wide range of studies addressed the routing problem in MANETs. Many previous studies address the clustering and routing problems as seperate subjects. However, rowing approaches which are specific to the clustering methodologies may have many advantages in terms of efficiency and availability. In this study, a flooding based routing algorithm is proposed. First, a detailed description of the algorithm is explained, then the analysis and test results using the ns2 simulator are given which show that the designed algorithm is scalable and has favorable performance.
  • Conference Object
    Citation - WoS: 1
    Automatic Enforcement of Location Aware User Based Network Access Control Policies
    (World Scientific and Engineering Academy and Society, 2008) Tuğlular, Tuğkan
    Multiple interconnected network segments distributed across various locations, such as corporate networks, where users or employees constantly travel among segments and require to access servers, need to have network access control mechanisms that are able to adapt to these location changes. The idea of a firewall changing or adapting its rules depending on the location of users is presented by an architecture in this paper. This architecture proposes deployment of a policy server at the management level and policy agents at the firewall level, so that policy-driven network security management is enabled by specifying location aware user based network access control policies at the network security management and enforcing them at the managed firewalls. The architecture presented in this paper utilizes user VPN connection event triggers for dynamic policy configuration and automated policy deployment to firewalls. Location aware user based network access control policies, which are management level policies, are implemented using XACML. A network level policy is usually a configuration, or policy, file local to the firewall. The policy agent incorporated into the firewall performs the mapping from management level policy to firewall policy.
  • Conference Object
    Citation - Scopus: 2
    Telsiz Duyarga Ağlarında Hızlı Hareket Eden Hedefler için Küme Tabanlı Hedef İzleme Algoritması
    (Institute of Electrical and Electronics Engineers Inc., 2009) Alaybeyoğlu, Ayşegül; Dağdeviren, Orhan; Kantarcı, Aylin; Erciyes, Kayhan
    Kablosuz iletişim teknolojilerindeki ilerlemelerle birlikte telsiz duyarga ağları (TDA) birçok sivil ve askeri uygulamalarda özellikle de hareketli hedefin takibi gibi konularda yaygın olarak kullanılmaya başlanmıştır. Bu çalışmada da TDA’da hızlı hareket eden nesneler için küme tabanlı bir hedef izleme algoritması önerilmiştir. Literatürde bulunan mevcut çalışmalarda lider düğüm, hedefin sadece t+1 anında yaklaşacağı konumu tahminleyerek bu konuma en yakın düğümü uyandırır. Hedefin çok hızlı hareket etmesi durumunda ise hedefin kısa süre içerisinde bir grup düğümün yakınlarından algılanmadan geçip gitmesi söz konusudur. Önermiş olduğumuz algoritma ile hedefin hızına bağlı olarak, hedefin tahmini gideceği yöndeki düğümler önceden uyandırılarak, kümeler önceden oluşturulmaktadır. Böylece hedefin ani hızlanması durumunda, önceden oluşturmuş olduğumuz kümeler sayesinde hedefin kaybolma riskini azaltmış bulunmaktayız.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 5
    Query optimization: Mobile agents versus accuracy of the cost estimation
    (CRL Publishing, 2005) Özakar, Belgin; Morvan, F.; Hameurlaint, A.
    Since an increasing number of diverse sources of data and information become available through World Wide Web, the field of distributed heterogeneous query processing attracts attention of the researchers. One of the main concerns is to reduce the amount of communication and the volume of data transferred in terms of query optimization where it is a real challenge to have the statistics of the resources predictable and up-to-date. Autonomy, proactivity and mobility features of mobile agents seem promising under some conditions. In this paper we are interested in the study of the efficiency of the mobile agents in relation with the approach of the cost model used during the optimization process. We present an execution model based on mobile agents. Performance evaluation shows the efficiency intervals of the execution model according to the estimation errors and the current state of the system. The major contribution of this paper is to point out the effective use of an execution model based on mobile agents in relation with the approach of the cost model and with the query type. © 2005 CRL Publishing Ltd.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 26
    Mobile Join Operators for Restricted Sources
    (Hindawi Publishing Corporation, 2005) Özakar, Belgin; Morvan, Franck; Hameurlain, Abdelkader
    We consider the problem of query execution when there is limited access to the relations, i.e. when binding patterns require values to be specified in order to get data from the relation. This problem is common in virtual data integration systems where there are heterogeneous sources with various restricted access patterns and query capabilities. Another problem is the lack of the statistical information about the sources and occurrence of unpredictable events. We introduce two mobile join operators, MDJoin and SMDJoin which are designed for restricted sources and implemented using ‘mobile agents’ in order to benefit from their autonomous and reactive characteristics. Mobile operators of restricted sources are capable to deal with restricted sources and react to the variations between the compile-time estimations and run-time computations of data during query execution. The difference between the two new query operators lies in their level of adaptation ability to the execution environment. Performance results show that mobile agent-based approach at operator level can lead to a significant reduction in response time with restricted sources.
  • Conference Object
    Citation - WoS: 11
    Citation - Scopus: 20
    Learning Styles Diagnosis Based on Learner Behaviors in Web Based Learning
    (Springer Verlag, 2009) Atman, Nilüfer; İnceoğlu, Mustafa Murat; Aslan, Burak Galip
    Individuals have different backgrounds, motivation and preferences in their own learning processes. Web-based systems that ignore these differences have difficulty in meeting learners' needs effectively. One of these individual differences is the learning style. For providing adaptively incorporated learning styles, firstly learning styles of learners have to be identified. There are many different learning models in literature. This study is based on Felder and Silverman's Learning Styles Model and investigates only active/reflective and visual/verbal dimensions of this model. Instead of filling out a questionnaire, learner behaviors are analyzed with the help of literature-based approaches so that learning styles of learners can be detected.
  • Conference Object
    Citation - WoS: 1
    Feedback Control Static Scheduling for Real-Time Distributed Embedded Systems
    (Institute of Electrical and Electronics Engineers Inc., 2005) Ayav, Tolga; Sorel, Yves
    This paper presents an implementation of feedback control strategy on distributed static scheduling. The static schedule is created taking into account the average execution times of the tasks. Feedback control algorithm handles the unestimated dynamic behaviors in the system and keeps the performance at a desired level. The approach of feedback control supporting static scheduling yields more flexible scheduling, low scheduling overhead and better resource utilization while preserving the realtime constraints.