Scopus İndeksli Açık & Kapalı Erişimli Yayınlar

Permanent URI for this communityhttps://hdl.handle.net/11727/10752

Browse

Now showing 1 - 20 of 1286

Aintshop Production Line Optimization Using Response Surface Methodology
(2007) Dengiz, Berna; Belgin, Onder; 0000-0001-6702-2608; K-1080-2019
This paper deals with the problem of determining the optimum number of workstations to be used in parallel and workers at some stations using simulation optimization approach in a paint shop line of an automotive factory in Ankara, Turkey. In the optimization stage of the study Response Surface Methodology (RSM) is used to find the optimum levels of considered factors. Simulation model and optimization stage integration is used both to analyse the performance of the current paint shop line and determine the optimum working conditions, respectively, with reduced cost, time and effort.
A hybrid ant colony optimization approach for the design of reliable networks
(2007) Dengiz, B.; Altiparmak, F.; Belgin, O.; 0000-0003-1730-4214; 0000-0001-6702-2608; AAF-7020-2021; K-1080-2019
This paper presents a new solution approach, which is a hybridization of ant colony optimization (ACO) and simulated annealing (SA), called (h_ACO) to design of communication networks. The design problem is to find the optimal network topology where total cost is minimum and all-terminal reliability is not less-than a given level of reliability. The effectiveness of the h_ACO is investigated comparing its results with those obtained by SA and ACO, which are basic forms of the h_ACO, and also GAs given in the literature for the design problem. Computational results show that the h_ACO is an effective heuristic approach to design of reliable networks.
An International Facility Design Project
(2008) Lacksonen, Thomas; Dengiz, Berna
This paper describes an international facilities design project for Manufacturing and Industrial Engineering students. American and Turkish engineering students collaborated to create and implement the re-design of a Turkish wheelchair manufacturing facility. The company needed engineering assistance to improve the efficiency and increase the capacity of their existing factory. Turkish Industrial Engineering students went on-site to collect data and draw the existing facility layout. American Manufacturing Engineering students analyzed the data and developed new layout designs. Four American students traveled to Turkey between semesters to implement the initial phases of their design. In the second semester, the Turkish students simulated the new layout to see the performance improvements, completing their project. Student learning outcomes were positive for both groups of students. The paper explains critical steps in identifying projects and partners. Lessons are shown about successes and shortcomings in planning, operating, and communicating with design teams across cultures.
A Hybrid Simulated Annealing For A Multi-Objective Stochastic Assembly Line Balancing Problem
(2008) Cakir, Burcin; Dengiz, Berna; Altiparmak, Fulya; Xia, GP; Deng, XQ; 0000-0003-1730-4214; AAF-7020-2021
Asssembly line balancing is the problem of assigning tasks to the workstations, while optimizing one or more objectives without violating restrictions imposed on the line. In practice, task times may be random due to the worker fatigue, low skill levels, job dissatisfaction, poorly maintained equipment, defects in raw material, etc. When stochastic task times are taken consideration in assembly lines, balancing procedure is more complex due to the probability of incompleteness of stations times in a given cycle time. In this study, a multi-objective simulated annealing algorithm (m_SAA) is proposed for single-model, stochastic assembly line balancing problem with the aim of minimizing of smoothness index and total design cost. To obtain Pareto-optimal solutions, m_SAA implements tabu list and a multinomial probability mass function approach. The effectiveness of the proposed m_SAA is comparatively investigated using another SA using weight-sum approach on the test problems. Computational results show that m_SAA with multinomial probability mass function approach is more effective than SA with weight-sum approach in terms of quality of Pareto-optimal solutions.
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-2318-2021
This 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.
A Local Search Heuristic with Self-tuning Parameter for Permutation Flow-Shop Scheduling Problem
(2009) Dengiz, Berna; Alabas-Uslu, Cigdem; Sabuncuoglu, Ihsan
In this paper, a new local search metaheuristic is proposed for the permutation flow-shop scheduling problem. In general, metaheuristics are widely used to solve this problem due to its NP-completeness. Although these heuristics are quite effective to solve the problem, they suffer from the need to optimize parameters. The proposed heuristic, named STLS, has a single self-tuning parameter which is calculated and updated dynamically based on both the response surface information of the problem field and the performance measure of the method throughout the search process. Especially, application simplicity of the algorithm is attractive for the users. Results of the experimental study show that STLS generates high quality solutions and outperforms the basic tabu search, simulated annealing, and record-to-record travel algorithms which are well-known local search based metaheuristics.
A cross entropy approach to design of reliable networks
(2009) Dengiz, Berna; Altiparmak, Fulya; 0000-0003-1730-4214; AAF-7020-2021
One 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.
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.
A Self-adaptive Local Search Algorithm for the Classical Vehicle Routing Problem
(2011) Alabas-Uslu, Cigdem; Dengiz, Berna
The 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.
Early Postoperative Pulmonary Complications Following Heart Transplantation
(2015) Pirat, Aras; Firat, A. Camkiran; Komurcu, O.; Zeyneoglu, P.; Turker, M.; Sezgin, A.
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; 26574641
Heart 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.
A Self-tuning Heuristic for the Design of Communication Networks
(2015) Dengiz, Berna; Alabas-Uslu, Cigdem
This 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.
Early Postoperative Acute Kidney Injury Among Pediatric Liver Transplant Recipients
(2018) Sahinturk, Helin; Kundakci, Aycan; Zeyneloglu, Pinar; Gedik, Ender; Pirat, Arash; Haberal, Mehmet; 0000-0003-0159-4771; 0000-0002-7175-207X; 0000-0002-3462-7632; AAJ-1419-2021; AAH-7003-2019; ABI-2971-2020; AAJ-8097-2021
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-3224-2021
It 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.
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-3003-2022
In 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.
Gold nanocomposites for biomedical applications
(2019) Akturk, Omer; Erdemli, Ozge; Tunali, Beste Cagdas; 0000-0001-8606-8863; AAF-4496-2019; AAG-3927-2019
Is ingroup favoritism contingent on the expectation of reciprocity from ingroup members?: The case of reputation manipulation
(2019) Kologlugil, Serhat; Tekes, Burcu
We 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.
Predicting Pulmonary Complications Following Upper and Lower Abdominal Surgery: ASA vs. ARISCAT Risk Index
(2020) Kara, Sibel; Kupeli, Elif; Yilmaz, Hatice Eylul Bozkurt; Yabanoglu, Hakan; 0000-0002-5826-1997; 0000-0002-1161-3369; 0000-0003-0268-8999; 32259139; AAB-5345-2021; AAJ-7865-2021; AAI-8069-2021; AAK-2011-2021
Objective: Postoperative pulmonary complications (POPC) account for a substantial proportion of risk related to surgery and anaesthesia. The American Society of Anesthesiologists (ASA) classification and the Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) risk index correlate Well with POPC. Here, we compared their accuracy in predicting pulmonary complications following upper and lower abdominal surgery. Methods: We retrospectively reviewed the medical records of patients undergoing upper and lower abdominal surgery. We collected patients' demographic data, comorbidities, preoperative pulmonary risk score, laboratory results, surgical data, respiratory tract infection history within one month before surges); surgical urgency, ASA scores and pulmonary complications within one month after the surgery. Results: We evaluated 241 patients [upper abdominal surgery n=121; lower abdominal surgery (UAS) n=120; mean age 55.7 +/- 3.1 years]. In the UAS. 55.13% of the patients were male. In LAS, all patients were fitmale. In both groups, the most common POPC was pleural elfin:ion with compressive atelectasis (CA). Regarding risk score, in both groups, patients with high-risk developed a higher rate of pulmonary complications [JAS (50%), LAS 140%)]. In patients with low-risk scores, the rate of pulmonary complications was significantly lower than the intermediate and high-risk groups (p<0.001). A positive correlation was observed between preoperative risk score and complications (UAS r=0.34; LAS r=0.35 LAS p<0.05). No association was observed between the ASA scores and POPC (p=0.3). Conclusion: The ASA classification was found to be a weaker modality than ARISCAT risk index to predict pulmonary complications after the upper and lower abdominal surgeries.
A structural equation model to evaluate students' learning and satisfaction
(2020) Erenler, Hale H. Turhangil; 0000-0001-6292-109X; L-3563-2019
Due to the shift from traditional face-to-face to online learning, challenges in learning environments are on the rise. The aim of this study was to assess students' satisfaction with a service course conducted online at a funded university in Europe using a structural equation model. The construction and validation of five scales for measuring students' learning and satisfaction is also presented. One thousand one hundred and sixteen students were given an online questionnaire in January, 2019. The scales were found to be sufficiently valid and reliable. The interaction, instructor behaviors, advantages/flexibility, and perceived learning/course quality were influential in students' satisfaction. Success in e-learning can be achieved with the help of these findings via improving e-learning strategies. Further studies can be conducted on students' learning and satisfaction while participating in other online courses using the same scales.
Airfoil-slat arrangement model design for wind turbines in fuzzy environment
(2020) Atalay, Kumru Didem; Dengiz, Berna; Yavuz, Tahir; Koc, Emre; Ic, Yusuf Tansel
In this study, a multi-element wind turbine blade that consists of NACA 6411 and NACA 4412 leading-edge slat design is investigated computationally. Optimum design parameters of the slatted wind turbine blade leading to maximum value of C-L/C-D related to the turbine power are obtained. In the optimization process, a new fuzzy logic linear programming methodology integrating with fuzzy linear regression and 2D CFD analysis is proposed. The aerodynamic characteristics of the slatted blade are computed by using Incompressible Navier-Stokes equations and k-omega turbulence modeling. Results are compared with the results of linear programming method and direct search optimization method. The computational results reveal that the proposed methodology for performance optimization is more effective than other methods to obtain high-performance value of the C-L/C-D. The maximum value of the C-L/C-D is obtained as 25.1 leading the maximum efficiency of 0.52.