Wos 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 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.
Could Plasma Asymmetric Dimethylarginine Level Be A Novel Predictor Beyond The Classic Predictors of Stent Restenosis?
(2014) Bal, Ugur Abbas; Yildirir, Aylin; Aydinalp, Alp; Kaynar, Gamze; Kanyilmaz, Suleyman; Murat, Koza; Muderrisoglu, Ibrahim Haldun; https://orcid.org/0000-0002-9446-2518; https://orcid.org/0000-0001-8750-5287; https://orcid.org/0000-0002-3761-8782; 25233494; AAK-4322-2021; A-4947-2018; AAD-5841-2021
Objective: The aim of this study was to investigate the factors associated with coronary stent restenosis and if there is an association between plasma asymmetric dimethylarginine (ADMA) levels and stent restenosis. Methods: Ninety-one patients, who had a history of coronary bare metal stent implantation due to any cause in the last one year period, were admitted to this observational cross-sectional study. Coronary angiography was performed to all patients and quantitative angiography was used to determine the presence of stent restenosis. Laboratory parameters and angiographic features that contribute to stent restenosis were evaluated. Plasma ADMA levels were measured by using high performance liquid chromatography. Logistic regression analysis was used to determine the independent factors of stent restenosis. Results: Angiographic restenosis was found in 35 patients (38.5%). Stent diameter (p=0.038) and left ventricular ejection fraction (p=0.023) were lower and stent implantation history due to acute coronary syndrome (p=0.029), plasma ADMA level (5.0 +/- 1.8x10(-4) mmol/L vs. 3.9 +/- 1.0x10(-4) mmol/L, p=0.001), C-reactive protein concentration (p=0.016), white blood cell count (p=0.044) and stent length (p=0.005) were higher in patients with restenosis. Plasma ADMA level (beta=0.536; OR: 1.710; CI: 1.022-2.861; p=0.041), C-reactive protein concentration (beta=0.062; OR: 1.064; CI: 1.003-1.129; p=0.041), stent diameter (beta=-3.047; OR: 0.048; CI: 0.007-0.313; p=0.002) and length (beta=0.165; OR: 1.179; CI: 1.036-1.343; p=0.013) were found to be the independent predictors of stent restenosis in logistic regression analysis. Conclusion: We conclude that plasma ADMA levels may be used as a novel marker for stent restenosis beyond the classic stent restenosis markers.
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.
De Novo Malignant Neoplasms in Renal Transplant Patients
(2016) Akcay, Eda Yilmaz; Tepeoglu, Merih; Ozdemir, Binnaz Handan; Deniz, Ebru; Borcek, Pelin; Haberal, Mehmet; 0000-0002-3462-7632; 0000-0002-9894-8005; 0000-0002-7528-3557; 0000-0001-6831-9585; 27805524; AAJ-8097-2021; AAK-5222-2021; X-8540-2019; AAK-1960-2021
Objectives: The aim of this study was to evaluate the incidence of posttransplant malignancy in kidney transplant patients and investigate the clinical and histopathologic features of these patients. Materials and Methods: We retrospectively reviewed information on donor and recipient characteristics, patient and graft survival, and cancer incidence after transplant for 867 kidney transplant patients. Patients with neoplasms prior to transplant were excluded. A follow-up study estimated cancer incidence after transplant. Results: Neoplasms were diagnosed in 59 patients (6.8%), 41 men and 18 women; 22 (37.3%) had skin tumors, 19 (32.2%) had solid tumors, 10 (16.9%) had posttransplant lymphoproliferative disorders, and 8 (13.6%) had Kaposi sarcoma. The mean age at the time of malignant tumor diagnosis was 42.7 +/- 13.6 years, and statistically significant differences were found between tumor groups (P < .01). The average latency period between transplant and diagnosis of malignant tumors was 99.8 +/- 56.9 months for solid tumors, 78.4 +/- 52 months for skin tumors, 64.5 +/- 48.8 months for posttransplant lymphoproliferative disorders, and 13.5 +/- 8.8 months for Kaposi sarcoma, with significant difference found between tumor groups (P < .01). Ten patients (16.9%) had more than 1 malignant tumor. Eighteen patients died, with a mean time to death of 31.5 +/- 22.8 months after tumor diagnosis. A significant positive association was found between survival and the number of tumors (P = .001); 5-year survival after tumor diagnosis was 81% and 40% for patients with 1 malignant tumor and patients with more than 1 malignant tumor, respectively. Conclusions: Malignancy is a common cause of death after renal transplant. Early detection and treatment of posttransplant malignancies is an important challenge. Screening these patients for malignancies posttransplant is crucial, and efforts should be directed to define effective immunosuppressive protocols that are associated with a lower incidence of malignancy.
The Effect of Three Different Crown Heights and Two Different Bone Types on Implants Placed in the Posterior Maxilla: Three-Dimensional Finite Element Analysis
(2016) Cinar, Duygu; Imirzalioglu, Pervin; 27004295
Purose: The purpose of this study was to determine the amount and localization of functional stresses in implants placed in two different bone types (type 3 and type 4) with three different crown heights in the atrophic posterior maxilla using finite element analysis. Materials and Methods: A three-dimensional finite element model of the posterior maxilla was created from a computerized tomography image by using the Marc 2005 (MSC Software) program. Three different crown/implant ratios (1/1, 1.5/1, 2/1) in the first molar tooth zone were modeled. Type 3 and type 4 bone quality according to the classiication system of Lekholm and Zarb was created. The total oblique force of 300 N with a 30-degree angle was applied from the locations of the mesiobuccal cusp (150 N) and the distobuccal cusp (150 N) of first molar teeth. Results: For the implants, the highest stresses were observed around the implant neck at the crown/implant ratio of 2/1 (430.57 MPa). As the crown/implant ratio increased two times, the von Mises stresses increased at a rate of 47%. The highest tensile values exceeded the ultimate tensile strength of the cortical bone for all the designs. Also, the highest compressive values exceeded the ultimate compressive strength of the cortical bone in the 2/1 design for type 3 bone, and in the 1.5/1 and 2/1 designs for type 4 bone. As the crown/implant ratio increased from 1/1 to 2/1, the highest tensile value and the highest compressive value increased 13%. For the spongious bone, as the crown/implant ratio increased, the highest tensile value increased 42% and 85%, respectively. Tensile stresses increased at a rate of 26% in the 1/1 ratio, 30% in the 1.5/1 ratio, and 32% in the 2/1 ratio when the density of spongious bone decreased. Compression-related values also increased 34% in the 1/1 ratio, 35% in the 1.5/1 ratio, and 36% in the 2/1 ratio when the density of spongious bone decreased. Conclusion: Compressive and tensile stresses formed mostly at the alveolar bone around the implant neck that was cortical bone. Thus, it had to be preserved during the surgical procedures. Deformation due to the stresses had great importance for the type IV spongious bone due to the increase caused by the higher crown height levels.
Wegener Granulomatosis Complicated by Brain Abscess Caused by Nocardia spp.
(2016) Sahin, Sevgi; Balcan, Baran; Kiziltas, Safak; Aydin, Mehtap; Y-1366-2018; A-4721-2018
Wegener granulomatosis is a multisystemic disease associated with high mortality rate and characterized by necrotizing granulomatous vasculitis predominantly in the respiratory tract and kidneys. Presence of kidney failure at the time of diagnosis describes a poor prognostic marker. We presented a Wegener granulomatosis case complicated with brain abscess caused by Nocardia.
A Framework for Computational Thinking Based on a Systematic Research Review
(2016) Kalelioglu, Filiz; Gulbahar, Yasemin; Kukul, Volkan
Computational Thinking (CT) has become popular in recent years and has been recognised as an essential skill for all, as members of the digital age. Many researchers have tried to define CT and have conducted studies about this topic. However, CT literature is at an early stage of maturity, and is far from either explaining what CT is, or how to teach and assess this skill. In the light of this state of affairs, the purpose of this study is to examine the purpose, target population, theoretical basis, definition, scope, type and employed research design of selected papers in the literature that have focused on computational thinking, and to provide a framework about the notion, scope and elements of CT. In order to reveal the literature and create the framework for computational thinking, an inductive qualitative content analysis was conducted on 125 papers about CT, selected according to pre-defined criteria from six different databases and digital libraries. According to the results, the main topics covered in the papers composed of activities (computerised or unplugged) that promote CT in the curriculum. The targeted population of the papers was mainly K-12. Gamed-based learning and constructivism were the main theories covered as the basis for CT papers. Most of the papers were written for academic conferences and mainly composed of personal views about CT. The study also identified the most commonly used words in the definitions and scope of CT, which in turn formed the framework of CT. The findings obtained in this study may not only be useful in the exploration of research topics in CT and the identification of CT in the literature, but also support those who need guidance for developing tasks or programs about computational thinking and informatics.
Multiple Systems Metastasis Bladder Cancer with Imaging Findings
(2016) Tok, Sermin; Altinkaya, Naime; Nursal, Gul Nihal; 0000-0002-5302-4386; 0000-0003-1348-8167; R-3735-2016; AAM-5169-2021
Effect of L-arginine on Hemodynamic, Biochemical, and Histopathological Outcomes in a New Zealand Rabbit Model of Renal Ischemia-Reperfusion Injury
(2016) Ozulku, Mehmet; Aygun, Fatih
Objective: In this study, we investigated the effect of L-arginine on hemodynamic, biochemical, and histopathological changes in a rabbit model with renal ischemia. Methods: Forty white New Zealand rabbits were used. The rabbits were divided into two groups as the control group (n=20) and L-arginine group (n=20). They were monitored by cannulating the auricular and femoral arteries. An aortic occlusion catheter was inserted through the contralateral femoral artery and was extended to the distal aspect of the left subclavian artery; it was then inflated, and occlusion was performed for 30 min. All rabbits received 4 mL/kg/h of NaCl infusion during the course of occlusion and within the first 60 min of reperfusion. In the L-arginine group, L-arginine was infused at a dosage of 3 mg/kg/h through the auricular vein during the first 60 min of occlusion and perfusion. Blood samples for biochemical parameters [glucose, lactate, hematocrit, blood urea nitrogen (BUN), and serum creatinine] were obtained in the peri-ischemic period, in the 20th minute of reperfusion, and just before sacrificing (48th hour). A histopathological examination was performed in both renal tissues. Histopathological scoring was performed by taking tubular epithelial cell flattening, brush border loss, cytoplasmic vacuolization, cell necrosis, and tubular lumen obstruction into consideration. All animals were sacrificed 48 h after the procedure. Results: A significant difference was found between the L-arginine and control groups in terms of the hemodynamic outcomes and 48th hour BUN and serum creatinine levels (p<0.05). The histopathological examination revealed a mean score of 3.2 +/- 0.89 in the control group and 2.60 +/- 0.68 in the L-arginine group (p<0.05) (p=0.022). Conclusion: It can be suggested that L-arginine reduces renal ischemia-reperfusion injury and in particular, the histopathological effects.
The relation of presenting symptoms with staging, grading, and postoperative 3-year mortality in patients with stage I-III non-metastatic colon cancer
(2016) Bedir, Osman; Kiziltas, Safak; Kostek, Osman; Ozkanli, Seyma; 27210779
Background/Aims: To evaluate the association of presenting symptoms with staging, grading, and postoperative 3-year mortality in patients with colon cancer. Materials and Methods: A total of 132 patients-with a mean (standard deviation; SD) age of 63.0 (10.0) years and of whom 56.0% were males-with non-metastatic stage I-III colon cancer were included. Symptoms prior to diagnosis were evaluated with respect to tumor localization, tumor node metastasis (TNM) stage, histological grade, and postoperative 3-year mortality. Results: Constipation and abdominal pain were the two most common symptoms appearing first (29.5% and 16.7%, respectively) and remained most predominant (25.0% and 20.0%, respectively) up to diagnosis. The frequency of admission symptoms significantly differed with respect to tumor location, TNM stage and histological grade. The postoperative 3-year survival rate was 61.4%. Multivariate logistic regression revealed that melena and rectal bleeding increased the likelihood of 3-year mortality by 13.6-fold (p=0.001) and 4.08-fold (p=0.011), respectively. Conclusion: Our findings revealed differences in presenting symptom profiles with respect to the time of manifestation and predominance as well as to the TNM stage, histological grade, and tumor location. Given that melena and rectal bleeding increased the 3-year mortality risk by 13.6-fold and 4.08-fold, respectively, our findings indicate the association of admission symptoms with outcome among patients with colon cancer.
After a Workshop on the Novel Antivirals for Treatment of Hepatitis C Virus Infection (4-6 December 2015, Istanbul)
(2016) Tekin, Suda; Aygen, Bilgehan; Aydin, Mehtap; Simsek, Funda
Effects of Radial Extracorporeal Shock Wave Therapy on Pain, Grip Strength, and Functionality in Patients with Lateral Epicondylitis: A Randomized Controlled Study
(2016) Yuruk, Zeliha Ozlem; Kirdi, Nuray; Simsek, Nihal
Objective: In this study, the effects of radial extracorporeal shock wave therapy (RESWT) on pain, grip strength, and functionality were investigated in patients with lateral epicondylitis. Methods: The study included 30 patients who were divided into two groups: RESWT and exercise and placebo RESWT and exercise. In the RESWT and exercise group, RESWT was applied at 2000 pulses, once a week, for a total of three sessions, and in the placebo RESWT and exercise group, RESWT was applied at 20 pulses, once a week, for a total of three sessions. Patients in all groups underwent stretching and eccentric strengthening exercises. Patients were evaluated before and after undergoing the treatment and at 6 and 12 weeks after undergoing the treatment using a visual analog scale (VAS) for pain intensity during palpation and gripping, dynamometer for grip strength, and patient-rated tennis elbow evaluation (PRTEE) for functionality. Results: There were statistically significant differences between groups with respect to all parameters, except VAS during palpation (p<0.05). With time, there were more significant changes in VAS during palpation and gripping, grip strength, and PRTEE in the RESWT and exercise group compared with those in the placebo RESWT and exercise group (p<0.05). Conclusion: We concluded that using RESWT combined with other conservative treatments, mostly exercise, could be more effective.
Is there any association between colonic polyps and gastric intestinal metaplasia?
(2016) Unler, Gulhan Kanat; Ozgur, Gulsum Teke; Gokturk, Huseyin Savas; Korkmaz, Huseyin; Erinanc, Ozgur Hilal; 27210777
Background/Aims: Chronic gastritis progression is a multistep process of atrophy, intestinal metaplasia (IM), and dysplasia, which may lead to invasive carcinoma. In this study, we identified an association of colonic polyps with gastric IM in patients undergoing colonoscopy. Materials and Methods: This retrospective case-control, cross-sectional study was conducted in a tertiary-care institution in Turkey. Pathology and endoscopy reports were reviewed. The study group comprised 400 patients with colonic adenomatous polyps, and the control group comprised 360 patients without colonic adenomatous polyps on colonoscopy. Results: The risk of gastric IM was 1.42-fold higher in the study group (p<0.05). The risk of IM in patients aged >= 50 years with colonic polyps was 3.35-fold higher than in those aged <50 years (p<0.05). The risk of Helicobacter pylori infection in the study group was 1.07-folder higher than that in the control group (p<0.05). H. pylori infection prevalence was higher only in patients with high-grade colonic polyp dysplasia (p<0.05). There were no statistically significant differences in the proportion of incomplete IM between the groups (p<0.05). Conclusion: This study observed increased rates of gastric IM with colonic polyps. An increased risk of gastric IM was associated with higher grades of polyp dysplasia.