Araştırma Çıktıları | TR-Dizin | WoS | Scopus | PubMed

Permanent URI for this communityhttps://hdl.handle.net/11727/4806

Browse

Now showing 1 - 20 of 4173

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.
Subcutaneous emphysema, pneumo-orbita and pneumomediastinum following a facial trauma caused by a high-pressure car washer
(2014) Yilmaz, Fevzi; Ciftci, Orcun; Ozlem, Miray; Komut, Erdal; Altunbilek, Ertugrul
Pneumomediastinum is air leakage to mediastinal space from various potential sites, including lung, esophagus, trachea, and neck. It is a rare condition that develops either spontaneously with increased intraalveolar or intrabronchial pressure, or due to trauma. Although cases where face or neck trauma with subcutaneous emphysema that extended to mediastinal cavity via anatomical connections in face and neck have been reported, orbital traumas leading to pneumomediastinum are very rare occurrences that have seldom been reported. This paper documents a 17-year-old male who presented with diffuse subcutaneous emphysema involving paraorbital facial areas, which extended to neck and mediastinal cavity.
Evaluation of Coronary Artery-Saphenous Vein Composite Grafts: The Aortic No-Touch Technique
(2014) Coskun, Isa; Colkesen, Yucel; Demirturk, Orhan Saim; Tunel, Huseyin Ali; Turkoz, Riza; Gulcan, Oner; 24512396
We retrospectively compared the results of conventional coronary artery bypass grafting (CABG) performed on patients who showed no preoperative evidence of serious atherosclerosis of the ascending aorta with the results of the aortic no-touch technique (using coronary artery-saphenous vein composite grafts) on CABG patients who did show such evidence. From 2003 through 2012, 3,152 consecutive patients underwent isolated primary CABG at our hospital. We chose 360 for the current study. The study group (n=120) comprised patients who had undergone operation via the aortic no-touch technique. Propensity-score-matching (1: 2) was used to select the control group of 240 patients who had undergone conventional CABG. Early and late survival rates, reintervention-free survival rates, and freedom from cardiac death were compared. Early and late mortality rates were similar in the study and control groups (P=0.19 vs P=0.29, respectively), as were cardiac-related death (2.5% vs 2.1%, respectively; P=0.53) and overall death (8.3% vs 7.9%, respectively; P=0.51). Overall survival rates were 91.7% vs 92.1% and freedom-from-cardiac-death rates were 97.4% vs 97.5% (P=0.71 vs P=0.78, respectively; mean follow-up period, 5.27 +/- 2.51 yr). Reintervention-free survival rates were also similar (96.7% vs 98.8%, respectively; P=0.2). As a result of the similar rates of early and late survival, reintervention-free survival, and freedom from cardiac death, we conclude that the aortic no-touch technique with composite grafts might be a reasonable option in patients who have atherosclerotic ascending aorta that cannot be clamped.
EFFECTS OF REFERENCE PRICE SYSTEM ON MEDICINES WHICH HAVE ANNUAL AVERAGE HIGHEST AMOUNT OF SALES OF BETWEEN YEARS 2008-2013
(2014) Uman, N.; Tolun, C.; Babacan, S.; Dogan, E.; Vural, I.M.; Dasdag, M. M.; Yilmaz, Safak E.; Malhan, S.; Kahveci, R.; Akbulat, A.; Artiran, G; Kerman, S.; 27201003
A Preliminary Investigation on the Presence of Calcifying Nanoparticles in the Breast Tumor
(2014) Ozkal-Baydin, Pinar; Gocmen, Sedef J.; Erdemli, Esra; Tunc, Ibrahim G.; Sener, Hasan B.; Gumuskaya, Berrak; Sunguroglu, Asuman
Calcium phosphate is deposited in many diseases, but the molecular basis of mineralization remains largely unknown. Biomineralizied calcifications that are formed by calcium deposits are also detected in breast mammograms. Some of the detected microcalcifications are thought to be related with malignancy. Taken together, calcifying nanoparticles (CNP) may be thought as a source of malign calcifications in breast cancers. The aim of the study is to research the presence of CNP in breast tumor tissue. With this aim, the presence of CNP was investigated by culturing 16 patients' breast tumor tissue and from 2 pathologic tissues with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Their growth was monitored by optical density (OD) at a wavelength of 650 nm. CNP couldn't be found in the analysed tissues. The presence of CNP in the breast tumor tissue was researched for the first time. We could not find CNP in the breast tumor tissue, but we think this research will open a new field of study for researchers.
Amyloid Goiter Due to Familial Mediterranean Fever in a Patient with Byler Syndrome: A Case Report
(2014) Cigerli, Ozlem; Unal, Asli Dogruk; Parildar, Hulya; Demiralay, Ebru; Tarcin, Ozlem; 25337425
Background: Familial Mediterranean Fever (FMF), also inherited with autosomal recessive trait, is characterized by recurrent episodes of fever, arthritis, and serositis. Congenital Byler Syndrome (Progressive Familial Intrahepatic Cholestasis) inherited with autosomal recessive trait and characterized by defective secretion of bile acids. FMF associated Amyloid A deposition occurs in many tissues and organs, but amyloid goiter is a rare entity that leads to enlargement and dysfunction of the thyroid. Case Report: We present a rare case of 24 year old male patient who had liver and kidney transplantation due to Byler Syndrome and secondary amyloidosis related to FMF, diagnosed as rapidly growing large amyloid goiter. Deposits of extracellular amyloid and dense adipose metaplasia diagnostic for amyloid goiter are determined upon histopathological examination of thyroidectomy material. Conclusion: When goiter was detected in cases with history of systemic amyloidosis and rapidly growing goitre, amyloid goiter should be remembered at first. This case is unique since two autosomal genetic disorders are together in the same patient and important as it emphasizes the consequences of consanguineous marriage, early diagnosis and treatment compliance of FMF and the awareness of amyloid goiter in patients followed by primary care physicians and healthcare professionals.
Amiodarone Induced Epididymitis: A Case Report
(2014) Cicek, Tufan; Demir, Canan Cicek; Coban, Gokcen; Coner, Ali
Introduction: Amiodarone is an effective drug for life-threatening arrhythmias like recurrent ventricular fibrillation and atrial fibrillation. Amiodarone creates rarely genitourinary side effects are seen. These are epididymitis, testicular dysfunction and impotance. Amiodarone aggregates and triggers inflammation in the head of the epididym. Case report: We present the case of a patient who developed epididymitis after 17 months of amiodarone therapy, using a low dose (100 mg per day). Although cessation of medication or dose lowering was not performed, remission of the patient only by analgesics is a distinct case reported in urological literature. Conclusions: This case stresses the importance of considering an adverse effect of amiodarone treatment as a cause when making a differential diagnosis of epididymitis.
Depigmented skin and phantom color measurements for realistic prostheses
(2014) Tanner, Paul; Leachman, Sancy; Boucher, Kenneth; Ozcelik, Tuncer Burak
PurposeThe purpose of this study was to test the hypothesis that regardless of human skin phototype, areas of depigmented skin, as seen in vitiligo, are optically indistinguishable among skin phototypes. The average of the depigmented skin measurements can be used to develop the base color of realistic prostheses. Methods and MaterialsData was analyzed from 20 of 32 recruited vitiligo study participants. Diffuse reflectance spectroscopy measurements were made from depigmented skin and adjacent pigmented skin, then compared with 66 pigmented polydimethylsiloxane phantoms to determine pigment concentrations in turbid media for making realistic facial prostheses. ResultsThe Area Under spectral intensity Curve (AUC) was calculated for average spectroscopy measurements of pigmented sites in relation to skin phototype (P=0.0505) and depigmented skin in relation to skin phototype (P=0.59). No significant relationship exists between skin phototypes and depigmented skin spectroscopy measurements. The average of the depigmented skin measurements (AUC 19,129) was the closest match to phantom 6.4 (AUC 19,162). ConclusionAreas of depigmented skin are visibly indistinguishable per skin phototype, yet spectrometry shows that depigmented skin measurements varied and were unrelated to skin phototype. Possible sources of optical variation of depigmented skin include age, body site, blood flow, quantity/quality of collagen, and other chromophores. The average of all depigmented skin measurements can be used to derive the pigment composition and concentration for realistic facial prostheses.
Primary Extranodal Non-Hodgkin's Lymphoma: Clinicopathological Features, Survival and Treatment Outcome in Two Cancer Centers of Southern Turkey
(2014) Mertsoylu, Huseyin; Muallaoglu, Sadik; Besen, Ayberk Ali; Erdogdu, Suleyman; Sezer, Ahmet; Sedef, Ali Murat; Kose, Fatih; Arican, Ali; Ozyilkan, Ozgur
Background: The aim of this study was to assess the epidemiological and clinicopathological characteristics of primary extranodal non-Hodgkin's lymphoma (pENL) patients, focusing on treatment and survival outcome. Materials and Methods: Between October 2003 and March 2012, 802 patients with non-Hodgkin's lymphoma (NHL) were diagnosed and treated in two different cancer centers of Southern Turkey. Results: pENL, constituted 12.4% (100/802) of all NHL studied during this period. Median age of the patients was 56 years (range 17-87 years) and the male: female distribution was 3:2. Eighty-five of 100 patients (85%) were in stage I/II, 9/100 (9%) in stage III, whereas 6/100 (6%) were in stage IV. Head and neck constituted the most common site (51/100, 51%), followed by gastrointestinal tract (GIL) (37/100, 37%), and cerebrum (CL) (5/100, 5%). Diffuse large B cell lymphoma (DLBCL) was the most common histological type, observed in 53% of patients, followed by marginal zone extranodal lymphoma (13%). Most of patients (76%) received a CHOP containing regimen. Complete remission (CR) were achieved in 71% of patients. The median follow-up duration of all patients was reported as 37.6 months (range, 0.8-165 months). This period was reported as 137.5 months (range, 117.5-1578.6 months) in gastrointestinal lymphoma (GIL) patients, 119.0 months (range, 91.8-146.1 months) in head and neck lymphoma (HNL) patients, and 18.4 months (range, 12.6-24.1 months) in cerebral lymphoma (CL) patients. Conclusions: Head and neck, and the gastrointestinal tract were the two most common extranodal sites observed. Histologically DLBC accounted for the majority of cases. Most patients were on earlier stages, had low-low intermediate IPI scores and had a favorable prognosis.
Simultaneous integrated boost to intraprostatic lesions using different energy levels of intensity-modulated radiotherapy and volumetric-arc therapy
(2014) Onal, C.; Sonmez, S.; Erbay, G.; Guler, O.C.; Arslan, G.
Objective: This study compared the dosimetry of volumetric-arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) with a dynamic multileaf collimator using the Monte Carlo algorithm in the treatment of prostate cancer with and without simultaneous integrated boost (SIB) at different energy levels. Methods: The data of 15 biopsy-proven prostate cancer patients were evaluated. The prescribed dose was 78 Gy to the planning target volume (PTV78) including the prostate and seminal vesicles and 86 Gy (PTV86) in 39 fractions to the intraprostatic lesion, which was delineated by MRI or MR-spectroscopy. Results: PTV dose homogeneity was better for IMRT than VMAT at all energy levels for both PTV78 and PTV86. Lower rectum doses (V-30-V-50) were significantly higher with SIB compared with PTV78 plans in both IMRT and VMAT plans at all energy levels. The bladder doses at high dose level (V-60-V-80) Were significantly higher in IMRT plans with SIB at all energy levels compared with PTV78 plans, but no significant difference was Observed in VMAT plans. VMAT plans resulted in a significant decrease in the mean monitor units (MUs) for 6,10, and 15 MV energy levels both in plans with and those without SIB. Conclusion: Dose escalation to intraprostatic lesions with 86 Gy is safe without causing Serious increase in organs at risk (OARs) doses. VMAT is advantageous in sparing OARs and requiring less MU than IMRT. Advances in knowledge: VMAT with SIB to intraprostatic lesion is a feasible method in treating prostate cancer. Additionally, no dosimetric advantage of higher energy is observed.
CHARACTERISTICS OF THE MEDICINES WHICH HAVE ANNUAL AVERAGE HIGHEST AMOUNT OF SALES OF BETWEEN YEARS 2008-2013
(2014) Akbulat, A.; Dogan, E.; Babacan, S.; Uman, N.; Tolun, C.; Vural, I. M.; Vural, E. H.; Yilmaz, Safak E.; Dasdag, M. M.; Kahveci, R.; Malhan, S.; Artiran, G.; Kerman, S.; 27201011
How Elementary School Principals' Change Tendencies Are Related With Their Opinion About Curriculum Change
(2014) Altun, Sadegul Akbaba; Buyukkurt, Sener
Leadership is important in change process and change management. Turkish educational system is undergoing a constant change. One of those changes was the change of the elementary school curricula, which had been accepted in the 2004-2005 academic year. Therefore, it is important to understand how school principals, as the persons who are in charge of this change, handle this process. In this respect, this study was aimed to determine school principals' tendencies toward change. Furthermore, it will also be explored whether those tendencies show any significant differences on some variables. Finally, having incorporated school principals' views on curriculum, school principals' change tendencies will be interpreted within this change phenomenon. This study was designed with a mixed methodology. In order to understand school principals' tendencies toward change, a change tendency scale, developed by Akbaba-Altun and Buyukozturk (2011), was utilized. In addition, school principals were asked to narrate their opinions regarding the changed curricula and its reflections on practice. The quantitative data were analysed through descriptive and interpretive analysis whereas the qualitative data were analysed through content analysis. A total of 179 elementary school principals joined the quantitative part of this study, whereas 154 of them participated in the qualitative one. It was observed that school principals were generally homogenous in their change tendencies. Within this context, this finding was supported by the qualitative data, as well. (C) 2014 The Authors. Published by Elsevier Ltd.