Scopus İndeksli Açık & Kapalı Erişimli Yayınlar

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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.
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.
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 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 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 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 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.
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.
Early Postoperative Pulmonary Complications Following Heart Transplantation
(2015) Pirat, Aras; Firat, A. Camkiran; Komurcu, O.; Zeyneoglu, P.; Turker, M.; Sezgin, A.
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.
Children with Iron Deficiency Anemia Have a Tendency to Hypercoagulation: An Evaluation by Thromboelastography
(2020) Kilci, Ceren; Olcay, Lale; Ozdemir, Beril; Fettah, Ali; Colak, Meric Yavuz; 0000-0002-5684-0581; 0000-0002-0294-6874; 31852173; AAK-3548-2021; AAA-4360-2021
CAN CHOLECYSTECTOMY BE PERFORMED AS SAFELY IN ELDERLY PATIENTS AS IT IS IN YOUNG PATIENTS?
(2020) Arslan, Baha; Yilmaz, Tugbahan; Erol, Varlik; Tuncali, Bahattin; Gulay, Huseyin; 0000-0002-9590-0276; 0000-0002-7898-2943; 0000-0002-0442-6178; 0000-0003-4461-4904; AAJ-6354-2021; AAJ-7840-2021; AAJ-6407-2021; AAD-6127-2021
Introduction: In this study, we aimed to compare the surgical outcomes between elderly and young patients undergoing surgery for gallstone disease and determine variations in patient characteristics, if any. Materials and Method: Data of patients who underwent surgery for gallstone disease at a single center between 2010 and 2018 were analyzed retrospectively. Two patient groups were evaluated: patients <65 years and >= 65 years. Patient characteristics, preoperative outpatient clinic data, surgical data, and postoperative data were collected. Results: In total, 1,198 patients with a mean age of 54.77 +/- 15.03 (15-91) years were assessed. Comorbid conditions, including cardiovascular disease, pulmonary disease, renal disease, and diabetes mellitus were significantly more common in elderly patients (p<0.001). Acute cholecystitis in the preoperative period was noted in 15.36% of young patients and in 30.4% of elderly patients (p<0.001). Need for emergency surgery was higher in elderly patients than in young patients [13.86% (47) and 9.31% (80), respectively] (p=0.021). Laparoscopic cholecystectomy and open cholecystectomy were performed in 98.37% and 1.04% of young patients, respectively, and in 92.62% and 3.53% of elderly patients, respectively (p<0.001). Among factors affecting the length of hospital stay in elderly patients, the duration of hospitalization was significantly longer in elderly patients who underwent emergency surgery, open surgery, needed additional surgery, and who had high American Society of Anesthesiologists scores (p<0.001, p<0.001, p=0.013, p<0.001, respectively). Conclusion: Complications rates associated with cholecystectomy are similar between young and elderly patients when appropriate surgical preparations are performed. Surgery for gallstone disease can be performed safely in elderly patients with low morbidity and mortality rates.
Spinal Metastatic Disease Survival Analysis of 146 Patients and Evaluation of 4 Different Preoperative Scoring Systems
(2020) Derincek, Alihan; Guler, Umit O.; Uysal, Mustafa; Ozalay, Metin; 0000-0002-5375-635X; 31393277; AAJ-4844-2021; O-7590-2017
Study Design: This was a retrospective analysis. Objective: The objective of this study was to evaluate the predictive value of the 4 different scoring systems Tomita, Bauer modified, Tokuhashi revised, and Van der Linden and some parameters that are used in these scoring systems. Summary and Background Data: Prediction of the survival period before treatment for spinal metastasis is extremely important. A lot of scoring systems have been described to predict the survival periods and to select the ideal treatment modality in the literature. Materials and Methods: Retrospectively 146 patients with spinal metastasis were investigated between 2002 and 2011. The following parameters were analyzed: age, pathologic vertebra fracture, neurological deficit, visceral metastasis, diagnosis of primary tumor and its spinal metastasis interval, other skeletal metastasis, involved region of vertebra, and undergone spinal surgery. Patients were also scored by the 4 different scoring systems. The survival period was calculated from date of diagnosis of the spinal metastasis to the date of death or last follow-up (minimum: 12 mo). Cox regression, Kaplan-Meier survival test, and Cronbach alpha tests were performed for statistical analysis. Results: Median overall survival for all patients was 13 months (range: 1-68 mo). The primary tumor (P=0.015), existence of visceral metastasis (P=0.017), presence of pathologic vertebra fracture (P=0.009), and undergone spinal surgery (P=0.047) showed significant influence on survival. Each scoring system was reliable and concordant with the other scoring systems (Cronbach alpha=80%); however, after 2 years, Modified Bauer score appeared to be the most reliable system for predicting survival (Cronbach alpha=25%). Conclusions: According to this analysis, lung cancer, visceral metastasis, pathologic vertebra fracture, and undergone spinal surgery have shown a negative effect on survival. All 4 scoring systems were reliable for predicting survival of patients with spinal metastatic disease. However, modified Bauer scoring system seems to be more predictive after 2 years.