Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 4Citation - Scopus: 5Dma: Matrix Based Dynamic Itemset Mining Algorithm(IGI Global Publishing, 2013) Oğuz, Damla; Yıldız, Baroş; Ergenç, BelginUpdates on an operational database bring forth the challenge of keeping the frequent itemsets up-to-date without re-running the itemset mining algorithms. Studies on dynamic itemset mining, which is the solution to such an update problem, have to address some challenges as handling i) updates without re-running the base algorithm, ii) changes in the support threshold, iii) new items and iv) additions/deletions in updates. The study in this paper is the extension of the Incremental Matrix Apriori Algorithm which proposes solutions to the first three challenges besides inheriting the advantages of the base algorithm which works without candidate generation. In the authors' current work, the authors have improved a former algorithm as to handle updates that are composed of additions and deletions. The authors have also carried out a detailed performance evaluation study on a real and two benchmark datasets.Article Citation - WoS: 15Citation - Scopus: 17Genetic Algorithm-Based Discharge Estimation at Sites Receiving Lateral Inflows(American Society of Civil Engineers (ASCE), 2009) Tayfur, Gökmen; Barbetta, Silvia; Moramarco, TommasoThe genetic algorithm (GA) technique is applied to obtain optimal parameter values of the standard rating curve model (RCM) for predicting, in real time, event-based flow discharge hydrographs at sites receiving significant lateral inflows. The standard RCM uses the information of discharge and effective cross-sectional flow area at an upstream station and effective cross-sectional flow area wave travel time later at a downstream station to predict the flow rate at this last site. The GA technique obtains the optimal parameter values of the model, here defined as the GA-RCM model, by minimizing the mean absolute error objective function. The GA-RCM model was tested to predict hydrographs at three different stations, located on the Upper Tiber River in central Italy. The wave travel times characterizing the three selected river branches are, on the average, 4, 8, and 12h. For each river reach, seven events were employed, four for the model parameters' calibration and three for model testing. The GA approach, employing 100 chromosomes in the initial gene pool, 75% crossover rate, 5% mutation rate, and 10,000 iterations, made the GA-RCM model successfully simulate the hydrographs observed at each downstream section closely capturing the trend, time to peak, and peak rates with, on the average, less than 5% error. The model performance was also tested against the standard RCM model, which uses, on the contrary to the GA-RCM model, different values for the model parameters and wave travel time for each event, thus, making the application of the standard RCM for real time discharge monitoring inhibited. The comparative results revealed that the RCM model improved its performance by using the GA technique in estimating parameters. The sensitivity analysis results revealed that at most two events would be sufficient for the GA-RCM model to obtain the optimal values of the model parameters. A lower peak hydrograph can also be employed in the calibration to predict a higher peak hydrograph. Similarly, a shorter travel time hydrograph can be used in GA to obtain optimal model parameters that can be used to simulate floods characterized by longer travel time. For its characteristics, the GA-RCM model is suitable for the monitoring of discharge in real time, at river sites where only water levels are observed.Conference Object Citation - WoS: 6Citation - Scopus: 6A Merging Clustering Algorithm for Mobile Ad Hoc Networks(Springer Verlag, 2006) Dağdeviren, Orhan; Erciyeş, Kayhan; Çokuslu, DenizClustering is a widely used approach to ease implementation of various problems such as routing and resource management in mobile ad hoc networks (MANET)s. We propose a new fully distributed algorithm for clustering in MANETs that merges clusters to form higher level clusters by increasing their levels. We show the operation of the algorithm and analyze its time and message complexities and provide results in the simulation environment of ns2. Our results conform that the algorithm proposed is scalable and has a lower time and message complexities than the other algorithmsConference Object Citation - WoS: 8Citation - Scopus: 13A Distributed Backbone Formation Algorithm for Mobile Ad Hoc Networks(Springer Verlag, 2006) Dağdeviren, Orhan; Erciyeş, KayhanConstruction of a backbone architecture is an important issue in mobile ad hoc networks(MANET)s to ease routing and resource management. We propose a new fully distributed algorithm for backbone formation in MANETs that constructs a directed ring architecture. We show the operation of the algorithm, analyze its message complexity and provide results in the simulation environment of ns2. Our results conform that the algorithm is scalable in terms of its running time and roundtrip delay against mobility, surface area, number of nodes and number of clusterheads.Conference Object Citation - WoS: 3Citation - Scopus: 5Serial and Parallel Multilevel Graph Partitioning Using Fixed Centers(Springer Verlag, 2005) Erciyeş, Kayhan; Alp, Ali; Marshall, GeoffreyWe present new serial and parallel algorithms for multilevel graph partitioning. Our algorithm has coarsening, partitioning and uncoarsening phases like other multilevel partitioning methods. However, we choose fixed nodes which are at least a specified distance away from each other and coarsen them with their neighbor nodes in the coarsening phase using various heuristics. Using this algorithm, it is possible to obtain theoretically and experimentally much more balanced partitions with substantially decreased total edge costs between the partitions than other algorithms. We also developed a parallel method for the fixed centered partitioning algorithm. It is shown that parallel fixed centered partitioning obtains significant speedups compared to the serial case.Conference Object Citation - WoS: 1Citation - Scopus: 1Multilevel Static Real-Time Scheduling Algorithms Using Graph Partitioning(Springer Verlag, 2005) Erciyeş, Kayhan; Soysert, ZehraWe propose static task allocation algorithms for the periodic tasks of a distributed real-time system. The cyclic task consists of task threads which may communicate and share resources. A graph partitioning process and a thread sequencing algorithm are applied to these threads to yield local schedules. The exact analysis is then obtained and further refinements are performed if the worst case response time of a task is greater than its deadline.Conference Object Citation - WoS: 4Citation - Scopus: 4Merging Clustering Algorithms in Mobile Ad Hoc Networks(Springer Verlag, 2005) Dağdeviren, Orhan; Erciyeş, Kayhan; Çokuslu, DenizClustering is a widely used approach to ease implementation of various problems such as routing and resource management in mobile ad hoc networks (MANET)s. We first look at minimum spanning tree(MST) based algorithms and then propose a new algorithm for clustering in MANETs. The algorithm we propose merges clusters to form higher level clusters by increasing their levels. We show the operation of the algorithm and analyze its time and message complexities.Conference Object Citation - Scopus: 2Crympix: Cryptographic Multiprecision Library(Springer Verlag, 2005) Koltuksuz, Ahmet; Hışıl, HüseyinThis paper delineates the results gained throughout the development of a cryptographic multiprecision1 integer library, CRYMPIX. To obtain the know-how for cryptographic computation and thus being able to create the high level cryptographic protocols in an in-housefashion are the main reasons of this development. CRYMPIX is mainly designed to supply code readability and portability plus an increased performance over other similar libraries. The whole work is achieved by detailed investigation of current algorithms and multi-precision libraries. The selected algorithms are discussed by means of efficiency and various implementation techniques. The comparative performance measurements of CRYMPIX against other multiprecision libraries show that the overall performance of CRYMPIX is not behind its predecessors if not superior.