Scopus İndeksli Açık & Kapalı Erişimli Yayınlar
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Item A Tabu Search Algorithm for the Training of Neural Networks(2009) Dengiz, B.; Alabas-Uslu, C.; Dengiz, O.The most widely used training algorithm of neural networks (NNs) is back propagation ( BP), a gradient-based technique that requires significant computational effort. Metaheuristic search techniques such as genetic algorithms, tabu search (TS) and simulated annealing have been recently used to cope with major shortcomings of BP such as the tendency to converge to a local optimal and a slow convergence rate. In this paper, an efficient TS algorithm employing different strategies to provide a balance between intensification and diversification is proposed for the training of NNs. The proposed algorithm is compared with other metaheuristic techniques found in literature using published test problems, and found to outperform them in the majority of the test cases.Item A Self-tuning Heuristic for the Design of Communication Networks(2015) Dengiz, Berna; Alabas-Uslu, CigdemThis paper addresses the design of communication networks that has a large application area. The problem is to design a minimum cost network subject to a given reliability level. Complexity of the problem is twofold: (1) finding a minimum-cost network topology that every pair of nodes can communicate with each other and (2) computing overall reliability to provide the reliability constraint. Over the last two decades, metahemistic algorithms have been widely applied to solve this problem due to its NP-hardness. In this study, a self-tuning heuristic (STH), which is a new approach free from parameter tuning, is applied to the design of communication networks. Extensive computational results confirm that STH generates superior solutions to the problem in comparison to some well-known local search metaheuristics, and also more sophisticated metaheuristics proposed in the literature. The practical advantage of STH lies in both its effectiveness and simplicity in application to the design problem.Item A Self-adaptive Local Search Algorithm for the Classical Vehicle Routing Problem(2011) Alabas-Uslu, Cigdem; Dengiz, BernaThe purpose of this study is introduction of a local search heuristic free from parameter tuning to solve classical vehicle routing problem (VRP). The VRP can be described as the problem of designing optimal delivery of routes from one depot to a number of customers under the limitations of side constraints to minimize the total traveling cost. The importance of this problem comes from practical as well as theoretical point of view. The proposed heuristic, self-adaptive local search (SALS), has one generic parameter which is learnt throughout the search process. Computational experiments confirm that SALS gives high qualified solutions to the VRP and ensures at least an average performance, in terms of efficiency and effectiveness, on the problem when compared with the recent and sophisticated approaches from the literature. The most important advantage of the proposed heuristic is the application convenience for the end-users. SALS also is flexible that can be easily applied to variations of VRP. (C) 2011 Elsevier Ltd. All rights reserved.Item A General Neural Network Model for Estimating Telecommunications Network Reliability(2009) Altiparmak, Fulya; Dengiz, Berna; Smith, Alice E.; 0000-0003-1730-4214; 0000-0001-8808-0663; AAF-7020-2021; AAK-2318-2021This paper puts forth a new encoding method for using neural network models to estimate the reliability of telecommunications networks with identical link reliabilities. Neural estimation is computationally speedy, and can be used during network design optimization by an iterative algorithm such as tabu search, or simulated annealing. Two significant drawbacks of previous approaches to using neural networks to model system reliability are the long vector length of the inputs required to represent the network link architecture, and the specificity of the neural network model to a certain system size. Our encoding method overcomes both of these drawbacks with a compact, general set of inputs that adequately describe the likely network reliability. We computationally demonstrate both the precision of the neural network estimate of reliability, and the ability of the neural network model to generalize to a variety of network sizes, including application to three actual large scale communications networks.Item A cross entropy approach to design of reliable networks(2009) Dengiz, Berna; Altiparmak, Fulya; 0000-0003-1730-4214; AAF-7020-2021One of the most important parameters determining the performance of communication networks is network reliability. The network reliability strongly depends on not only topological layout of the communication networks but also reliability and availability of the communication facilities. The selection of optimal network topology is an NP-hard problem so that computation time of enumeration-based methods grows exponentially with network size. This paper presents a new solution approach based on cross-entropy method, called NCE, to design of communication networks. The design problem is to find a network topology with minimum cost such that all-terminal reliability is not less than a given level of reliability. To investigate the effectiveness of the proposed NCE, comparisons with other heuristic approaches given in the literature for the design problem are carried out in a three-stage experimental study. Computational results show that NCE is an effective heuristic approach to design of reliable networks. (C) 2008 Elsevier B.V. All rights reserved.Item A METHOD SUGGESTION TO MEASURE THE EFFECTIVENESS OF INFORMED CONSENT DURING TREATMENT PROCESS A Study on University Students(2019) Buken, Erhan; Yasar, Zehtiye Fusun; Zengin, Hatice Yagmur; Buken, Bora; 0000-0002-4779-0623; 0000-0002-9855-2449; AAL-6847-2021; ABA-3224-2021It is difficult and subjective to evaluate how much of the treatment information given has been understood by the patient during the informing process. Various court decisions show that courts expect a hundred percent success in the informing process. This research was conducted to observe the effectiveness of written and verbal information given under ideal conditions. A coronary angiography consent form was standardized to measure readability and understandability. Two different labyrinth tests were performed from the text. Tests were performed on the Baskent University students in Turkey. The labyrinth test's subjects responded to the test after verbal information, had an absolute rate of 32.5% while the labyrinth test's subjects, responded to prior verbal information had an absolute success rate of 15%. 87.7% of those who achieved absolute success, in the second labyrinth test, also received verbal information. In the verbally informed group, those who achieved absolute success in the first test were 8.5%, while this rate increased to 28.5% after verbal information. There was no difference between the groups, in terms of the number of correct answers and response time, in the first test. Significant differences between the groups' tests arose in the test administered after being informed. This paper argues that the difference of total correct answers between the groups, in the post-test, stems from the effects of verbal informing. This study observed that verbally informing is more effective than written informing. It concludes that the success of the informing process can be measured by developing standardized methods, though it is unlikely to achieve 100% success.Item Is ingroup favoritism contingent on the expectation of reciprocity from ingroup members?: The case of reputation manipulation(2019) Kologlugil, Serhat; Tekes, BurcuWe use a game of cooperation with minimal groups to test whether ingroup favoritism can be explained by the expectation of reciprocity from ingroup members. To do this, we first manipulate participants' level expected cooperation from ingroup and outgroup partners by letting them play the game with different partners having different (high or low) cooperative reputations. We then analyze how these expectations affect ingroup bias in the game across different reputation conditions. We find that even if subjects expect the same level of cooperation from ingroup and outgroup partners withhigh reputation, they still cooperate more with the former than the latter. This contradicts the reciprocity hypothesis in the literature which explains intergroup discrimination solely in reference to differential reciprocal expectations. But, against ingroup and outgroup partners withlow cooperative reputation, subjects' level of cooperation almost exactly parallel their reciprocal expectations. This result is in line with the reciprocity hypothesis. We explain these findings by arguing that both reciprocal expectations and social identity play their parts in the emergence of ingroup favoritism, but that their relative strengths may depend on the interaction with other contextual factors. We also argue in favor of further experimental research as to how reciprocity and social identity interact with such third factors as partner's reputation in different games of social exchange.Item Practical approaches for the treatment of chronic heart failure: Frequently asked questions, overlooked points and controversial issues in current clinical practice(2015) Cavusoglu, Yuksel; Altay, Hakan; Ekmekci, Ahmet; Eren, Mehmet; Kucukoglu, Mehmet Serdar; Nalbantgil, Sanem; San, Ibrahim; Selcuk, Timur; Temizhan, Ahmet; Ural, Dilek; 26574641Heart failure (HF) is a progressive disorder associated with impaired quality of life, high morbidity, mortality and frequent hospitalization and affects millions of people from all around the world. Despite further improvements in HF therapy, mortality and morbidity remains to be very high. The life-long treatment, frequent hospitalization, and sophisticated and very expensive device therapies for HF also leads a substantial economic burden on the health care system. Therefore, implementation of evidence-based guideline-recommended therapy is very important to overcome its worse clinical outcomes. However, HF therapy is a long process that has many drawbacks and sometimes HF guidelines cannot answers to every question which rises in everyday clinical practice. In this paper, commonly encountered questions, overlooked points, controversial issues, management strategies in grey zone and problems arising during follow up of a HF patient in real life clinical practice have been addressed in the form of expert opinions based on the available data in the literature.