Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/11727/4809
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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 Understanding the Effect of Assignment of Importance Scores of Evaluation Criteria Randomly in the Application of DOE-TOPSIS in Decision Making(2019) Ic, Yusuf Tansel; Yurdakul, Mustafa; 0000-0001-9274-7467; AGE-3003-2022In conventional applications of hybrid DoE-TOPSIS technique in decision making problems, full factorial design layouts are generally used because of their ability to measure the effects of all possible combinations for evaluation factors. In a typical application, for a design layout, a number of replications are generated by assigning different sets of relative importance scores for evaluation factors. A TOPSIS score is then obtained for each experiment and replication pair. Regression analysis is finally applied to obtain a relationship with inputs (values of evaluation factors) and outputs (alternatives' TOPSIS meta-model scores). The key in conventional application of hybrid DoE-TOPSIS technique is generation of relative importance scores. Each set of scores can be assigned by a decision maker or generated randomly. This paper aims to determine whether using either of the two methods in determination of relative importance scores makes any difference in the ranking orders of alternatives.Item Gold nanocomposites for biomedical applications(2019) Akturk, Omer; Erdemli, Ozge; Tunali, Beste Cagdas; 0000-0001-8606-8863; AAF-4496-2019; AAG-3927-2019Item 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 T1 Mapping by Cardiac Magnetic Resonance and Multidimensional Speckle-Tracking Strain by Echocardiography for the Detection of Acute Cellular Rejection in Cardiac Allograft Recipients(2019) Sade, Leyla Elif; Hazirolan, Tuncay; Kozan, Hatice; Ozdemir, Handan; Hayran, Mutlu; Eroglu, Serpil; Pirat, Bahar; Sezgin, Atilla; Muderrisoglu, Haldun; 29680337; X-8540-2019OBJECTIVES The aim of this study was to test the hypothesis that echocardiographic strain imaging, by tracking subtle alterations in myocardial function, and cardiac magnetic resonance T1 mapping, by quantifying tissue properties, are useful and complement each other to detect acute cellular rejection in heart transplant recipients. BACKGROUND Noninvasive alternatives to endomyocardial biopsy are highly desirable to monitor acute cellular rejection. METHODS Surveillance endomyocardial biopsies, catheterizations, and echocardiograms performed serially according to institutional protocol since transplantation were retrospectively reviewed. Sixteen-segment global longitudinal strain (GLS) and circumferential strain were measured before, during, and after the first rejection and at 2 time points for patients without rejection using Velocity Vector Imaging for the first part of the study. The second part, with cardiac magnetic resonance added to the protocol, served to validate previously derived strain cutoffs, examine the progression of strain over time, and to determine the accuracy of strain and T1 measurements to define acute cellular rejection. All tests were performed within 48 h. RESULTS Median time to first rejection (16 grade 1 rejection, 15 grade >= 2 rejection) was 3 months (interquartile range: 3 to 36 months) in 49 patients. GLS and global circumferential strain worsened significantly during grade 1 rejection and >= 2 rejection and were independent predictors of any rejection. In the second part of the study, T1 time >= 1,090 ms, extracellutar volume GLS >= 32%, GLS >-14%, and global circumferential strain >=-24% had 100% sensitivity and 100% negative predictive value to define grade >= 2 rejection with 70%, 63%, 55%, and 35% positive predictive values, respectively. The combination of GLS > 16% and T1 time >= 1,060 ms defined grade 1 rejection with 91% sensitivity and 92% negative predictive value. After successful treatment, T1 times decreased significantly. CONCLUSIONS T1 mapping and echocardiographic GLS can serve to guide endomyocardial biopsy selectively. (C) 2019 by the American College of Cardiology Foundation.Item Computational intelligence models for PIV based particle (cuttings) direction and velocity estimation in multi-phase flows(2019) Tombul, Hatice; Ozbayoglu, A. Murat; Ozbayoglu, M. EvrenIn multi-phase flow, the gas phase, the liquid phase and the particles (cuttings) within the liquid have different flow behaviors. Particle velocity and particle direction are two of the important aspects for determining the drilling particle behavior in multi-phase flows. There exists a lack of information about particle behavior inside a drilling annular wellbore. This paper presents an approach for particle velocity and direction estimation based on data obtained through Particle Image Velocimetry (PIV) techniques fed into computational intelligence models, in particular Artificial Neural Networks (ANNs) and Support Vector Machines (SVM). In this work, feed forward neural networks, support vector machines, support vector regression, linear regression and nonlinear regression models are used for estimating both particle velocity and particle direction. The proposed system was trained and tested using the experimental data obtained from an eccentric pipe configuration. Experiments have been conducted at the Cuttings Transport and Multi-phase Flow Laboratory of the Department of Petroleum and Natural Gas Engineering at Middle East Technical University. A high speed digital camera was used for recording the flow at the laboratory. Collected experimental data set consisted of 1080 and 1235 data points for 15 degrees inclined wellbores, 1087 and 1552 data points for 30 degrees inclined wellbores and 885 and 1119 data points for horizontal (0 degrees), wellbores respectively to use in estimation and classification problems. Results obtained from computational intelligence models are compared with each other through some performance metrics. The results showed that the SVM model was the best estimator for direction estimation, meanwhile the SVR model was the best estimator for velocity estimation. The direction and speed of the particles were estimated with a reasonable accuracy; hence the proposed model can be used in eccentric pipes in the field.Item Acute effects of exercise on choroidal thickness and ocular pulse amplitude(2019) Dervisogulları, Mehmet Serdar; Totan, Yuksel; Kulak, Ali Ender; Guler, Emre; 0000-0003-2006-2906; G-7851-2015Aim: To explore ocular changes in healthy people after exercise. Material and Method: Twenty participants underwent exercise for 15 minutes on a treadmill. Measurements of choroidal thickness, intraocular pressure (IOP), ocular pulse amplitude (OPA), and blood pressure were taken before and after exercise. Enhanced Depth, Imaging optical coherence tomography (EDI-OCT) was used to measure choroidal thickness at the fovea and at the areas 1500 mu m nasal and 1500 mu m temporal to the fovea; IOP and OPA were measured by the dynamic contour tonometer (DCT; Swiss Micro technology AG, Port, Switzerland). Blood pressure was measured concurrently with the acquisition of the scans. Results: Twenty participants (20 eyes) with a mean age of 22.65 +/- 0.98 years were measured. There was a significant increase in systolic and diastolic pressure after exercise (p<0.05). There was a significant decrease in IOP and OPA after exercise (p<0.05). There was no significant difference in the subfoveal, nasal or temporal choroidal thickness measurements after exercise (p>0.05). Discussion: In our study, there was no significant change in the thickness of the choroid after exercise. IOP and OPA significantly decreased, and systolic and diastolic blood pressure significantly increased, after exercise. This indicates an adaptation of vascular resistance due to vasoconstriction. The IOP and OPA decreases do not seem to be related with the changes in choroid thickness.Item Classification of acoustic signals with new feature: Fibonacci space (FSp)(2019) Ankishan, Haydar; 0000-0002-6240-2545; AAH-4421-2019In this study, a new feature and feature space (FSp) are introduced by using the approach of Fibonacci series formation. The results are presented as two experimental studies. The nine groups of acoustic signals and pathological human voices are investigated in the first and second experiments, respectively. Convolutional Neural Network (CNN) and Multi-Class Support Vector Machines (M-SVMs) are used to figure out the effect of the proposed feature and its FSp on the classification accuracy. It is observed that the proposed feature and its formed space yield significant results for the discrimination of those signals. Experimental studies show that the classification accuracy of test data is increased by 5.3% when the proposed feature is used with CNN and M-SVMs. In addition, each acoustic group is significantly discriminated in both experimental studies. It is concluded that the proposed feature and its space can be used as a temporal feature for different purposes such as automatic speech recognition, pattern recognition, and emotional voice discrimination etc. (C) 2018 Elsevier Ltd. All rights reserved.