Scopus İndeksli Yayınlar Koleksiyonu

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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.
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 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.
Effect of HLA on Hepatitis C Virus Clearance and Persistence in Anti-HCV-positive End-stage Renal Disease Patients
(2014) Ocal, Serkan; Selcuk, Haldun; Korkmaz, Murat; Altun, Reskan; Yildirim, Abdullah E.; Akbas, Enver; 24976281
Background/Aims: The efficacy of immune response against hepatitis C virus (HCV) is determined by human leukocyte antigen (HLA) molecules of the host which present HCV antigens to CD4+ and CD8+ Tlymphocytes. In this study, we aimed to investigate the possible relationship between the frequencies of certain HLA class I-II alleles and the natural history of HCV in patients with end-stage renal disease (ESRD). Settings and Design: This is a retrospective cohort study conducted in a university hospital. Patients and Methods: The present study comprised 189 ESRD patients (candidates for renal transplantation) who had positive anti-HCV antibody test. The results concerning HCV and HLA status were gathered from patients files. The viral persistence was compared between the groups that were determined by HLA sub-typing. Statistical Analysis: Statistical evaluation was performed using Mann-Whitney U-test, Chi-square test, and Fisher's exact test. Level of error was set at 0.05 for all statistical evaluations, and P values < 0.05 were considered statistically significant. Results: We found possible association between the course of HCV infection and specific HLA alleles. HLA class I Cw*6 and HLA class II DRB*10 alleles were observed more frequently in the viral clearance group (P < 0.05). The HLA class I B*38 allele group was more prone to develop chronic hepatitis C (P < 0.01). Conclusions: These findings suggest that HLA class I Cw*6 and HLA class II DRB*10 alleles may be associated with immunological elimination of HCV in Turkish patients on hemodialysis. HLA sub-typing could help predict the prognosis of HCV infection.
Can serial monitoring of serum Vascular Endothelial Growth Factor (VEGF), Nitric Oxide (NO), and Angiotensin II (ANGII) levels have predictive role during Bevacizumab treatment?
(2014) Sumbul, Ahmet Taner; Disel, Umut; Sezgin, Nurzen; Sezer, Ahmet; Kose, Fatih; Besen, Ali Ayberk; Sumbul, Zehra; Abali, Huseyin; Ozyilkan, Ozgur
Background: Standard treatment of colorectal cancer includes both cytostatic chemotherapy and targeted therapies. Bevacizumab, targeting the VEGF receptor, is one of the primary targeted therapies that achieve better response rate and survival rate as compared to combination chemotherapy. To the best of our knowledge, there is no established single marker that can be used as a predictive marker in bevacizumab therapy. Material/Methods: We enrolled 24 patients with the diagnosis of metastatic colorectal cancer in our study. During the study, 2 blood samples were drawn from patients before the first cycle and after the sixth cycle of bevacizumab therapy. Serum levels of VEGF, ANG II, and NO were recorded. Results: While the change across VEGF levels was found to be a statistically significant decreasing trend (p=0.009), this decrease was not found to be correlated with treatment response and hypertension development. Additionally, no statistically significant difference was found in terms of NO and ANG II levels. Conclusions: This study showed a significant decrease in serum VEGF, but failed to show a significant change in NO and ANG II levels during bevacizumab treatment. Although no significant correlation was found between the presence of hypertension and markers, most patients (83%) had an increase in their blood pressure. Our results suggest that dynamic monitoring of NO and ANG II, along with VEGF, may not be useful as predictive markers for bevacizumab treatment in colorectal cancer.
Analysis and injury paterns of walnut tree falls in central anatolia of turkey
(2014) Ersoy, Suleyman; Sonmez, Bedriye Muge; Yilmaz, Fevzi; Kavalci, Cemil; Ozturk, Derya; Altinbilek, Ertugrul; Alagoz, Fatih; Cesur, Fatma; Yildirim, Ali Erdem; Uckun, Ozhan Merzuk; Akin, Tezcan
Introduction: Falls are the second most common cause of injury-associated mortality worldwide. This study aimed to analysis the injuries caused by falls from walnut tree and assess their mortality and morbidity risk. Methods: This is a retrospective hospital-based study of patients presenting to emergency department (ED) of Ahi Evran Univercity between September and October 2012. For each casualty, we computed the ISS (defined as the sum of the squares of the highest Abbreviated Injury Scale (AIS) score in each of the three most severely injured body regions). Severe injury was defined as ISS >= 16. The duration of hospital stay and final outcome were recorded. Statistical comparisons were carried out with Chi-Square test for categorical data and non-parametric spearman correlation tests were used to test the association between variables. A p value less than 0.05 was considered to be statistically significant. Results: Fifty-four patients admitted to our emergency department with fall from walnut tree. Fifty (92.6%) patients were male. The mean age was 48 +/- 14 years. Spinal region (44.4%) and particularly lumbar area (25.9%) sustained the most of the injuries among all body parts. Wedge compression fractures ranked first among all spinal injuries. Extremities injuries were the second most common injury. None of the patients died. Morbidity rate was 9.25%. Conclussion: Falls from walnut trees are a significant health problem. Preventive measures including education of farmers and agricultural workers and using mechanized methods for harvesting walnut will lead to a dramatic decrease in mortality and morbidity caused by falls from walnut trees.
Endovascular treatment of an iliac artery rupture caused by invasive Salmonella spondylodiscitis
(2014) Kursun, Ebru; Turunc, Tuba; Ozkan, Ugur; Demiroglu, Yusuf Ziya; 25230272
The rate of non-typhoid Salmonella infections has increased remarkably in recent years. Endovascular system infection is one of the most serious forms of extraintestinal Salmonella infection. The abdominal aorta is frequently involved, while bone and joint involvement are rarely seen. We present a rare case of successful endovascular treatment of a left iliac artery rupture and pseudoaneurysm both occurring due to the direct invasion of lumbar spondylodiscitis caused by Salmonella typhimurium.
Timing of noninvasive ventilation failure: causes, risk factors, and potential remedies
(2014) Ozyilmaz, Ezgi; Ugurlu, Aylin Ozsancak; Nava, Stefano
Background: Identifying the predictors of noninvasive ventilation (NIV) failure has attracted significant interest because of the strong link between failure and poor outcomes. However, very little attention has been paid to the timing of the failure. This narrative review focuses on the causes of NIV failure and risk factors and potential remedies for NIV failure, based on the timing factor. Results: The possible causes of immediate failure (within minutes to <1 h) are a weak cough reflex, excessive secretions, hypercapnic encephalopathy, intolerance, agitation, and patient-ventilator asynchrony. The major potential interventions include chest physiotherapeutic techniques, early fiberoptic bronchoscopy, changing ventilator settings, and judicious sedation. The risk factors for early failure (within 1 to 48 h) may differ for hypercapnic and hypoxemic respiratory failure. However, most cases of early failure are due to poor arterial blood gas (ABGs) and an inability to promptly correct them, increased severity of illness, and the persistence of a high respiratory rate. Despite a satisfactory initial response, late failure (48 h after NIV) can occur and may be related to sleep disturbance. Conclusions: Every clinician dealing with NIV should be aware of these risk factors and the predicted parameters of NIV failure that may change during the application of NIV. Close monitoring is required to detect early and late signs of deterioration, thereby preventing unavoidable delays in intubation.
Therapeutic Potential of Apigenin, a Plant Flavonoid, for Imatinib-Sensitive and Resistant Chronic Myeloid Leukemia Cells
(2014) Solmaz, Soner; Gokbulut, Aysun Adan; Cincin, Birsu; Ozdogu, Hakan; Boga, Can; Cakmakoglu, Bedia; Kozanoglu, Ilknur; Baran, Yusuf
Despite the presence of many therapeutic regimens like imatinib and other tyrosine kinase inhibitors, the development of resistance, intolerance, and side effects makes chronic myeloid leukemia (CML) therapy challenging. Thus, there is a need to discover novel drugs for CML patients. In this study, we attempted to assess apigenin, a common plant dietary flavonoid, in terms of its cytotoxic, apoptotic, and cytostatic effects on imatinib-sensitive and resistant Philadelphia-positive CML cells. We analyzed apigenin's effects on cell proliferation, apoptosis, caspase-3 activity, loss of mitochondrial membrane potential, and cell cycle progression in K562 and K562/IMA3 cells. Furthermore, we described genes and gene networks that are modulated in CML in response to apigenin. Results of our study revealed that apigenin has cytotoxic and apoptotic effects on both cell types. We also displayed that apigenin induced G2/M arrest in K562 cells while arresting K562/IMA3 cells in S phase especially at the highest apigenin concentration. The expression analysis identified a set of genes that were regulated by apigenin in K652 and K562/IMA3 cells. Association of modulated genes with biological functional groups identified several networks affected by apigenin including cell survival, proliferation, cell death, cell cycle, and cell signalling pathways.
Gastrointestinal endoscopy in pregnancy
(2014) Savas, Nurten; 25386072
Gastrointestinal endoscopy has a major diagnostic and therapeutic role in most gastrointestinal disorders; however, limited information is available about clinical efficacy and safety in pregnant patients. The major risks of endoscopy during pregnancy include potential harm to the fetus because of hypoxia, premature labor, trauma and teratogenesis. In some cases, endoscopic procedures may be postponed until after delivery. When emergency or urgent indications are present, endoscopic procedures may be considered with some precautions. United States Food and Drug Administration category B drugs may be used in low doses. Endoscopic procedures during pregnancy may include upper gastrointestinal endoscopy, percutaneous endoscopic gastrostomy, sigmoidoscopy, colonoscopy, enteroscopy of the small bowel or video capsule endoscopy, endoscopic retrograde cholangiopancreatography and endoscopic ultrasonography. All gastrointestinal endoscopic procedures in pregnant patients should be performed in hospitals by expert endoscopists and an obstetrician should be informed about all endoscopic procedures. The endoscopy and flexible sigmoidoscopy may be safe for the fetus and pregnant patient, and may be performed during pregnancy when strong indications are present. Colonoscopy for pregnant patients may be considered for strong indications during the second trimester. Although therapeutic endoscopic retrograde cholangiopancreatography may be considered during pregnancy, this procedure should be performed only for strong indications and attempts should be made to minimize radiation exposure. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.
The Effect of Haematological Parameters on Overall Survival in Advanced Stage Non Small Cell Lung Cancer
(2014) Oguz, Arzu; Colak, Dilsen; Ersoy, Ugur; Imamoglu, Inanc G.; Altinbas, Mustafa; Unal, Dilek; Zararsiz, Gokmen
In this study, we aimed to evaluate the prognostic value of pretreatment blood count values, particularly WBC counts, in patients with advanced non-small cell lung cancer (NSCLC). The records of 186 patients with advanced stage (stage IIIB and IV) NSCLC were assessed retrospectively. Patients were divided into 3 subgroups according to WBC levels; <= 0000 /mm(3) as Group 1, >10000 and <= 15000/mm(3) as Group 2 and >15000/mm(3) as Group 3. Patient and tumor characteristics as well as outcomes in terms of overall survival (OS) were evaluated. Median OS was 13.3 months in the whole population, 25.7 months in stage IIIB and 8.9 months in stage IV patients. According to the pretreatment leukocyte values, median OS was 17.9 months in Group 1, 11.2 months in Group 2 and 8.4 months in Group 3 (p= 0.003). Median OS values in WBC groups according to stages IIIB and IV were significantly different (p< 0.001). In multivariate analyses, ECOG-PS 2 or 3, stage IV disease, anemia and high WBC levels were associated with poorer OS. In this study, higher pretreatment WBC levels were associated with poorer OS in patients with advanced stage NSCLC. Pretreatment WBC counts may represent a simple prognostic factor and may aid in tailoring treatment in patients with advanced NSCLC.
Triggering drug use in patients with psoriasis: an investigative report from Turkey
(2014) Ogretmen, Zerrin; Askin, Ulku; Hiz, Meliha Merve; Cevizci, Sibel; 25395925
Introduction: The patients clinically diagnosed with psoriasis were investigated for drug use that may trigger psoriasis. Aim: To minimize the triggering drug use and help the medical treatment of psoriasis patients. Material and methods: The study involved 289 psoriatic patients who attended our clinic in 2010-2012 and were asked to bring their drug lists of the last year, which they obtained from the pharmacy's record system. They were advised not to use the drugs that may trigger psoriasis. Data analyses were performed using SPSS program version 19.0. Results: A total of 289 patients were included in the study. Two hundred and twenty-one patients were using non-steroidal anti-inflammatory drugs; 133 patients were using anti-reflux drugs; 35 patients were using antidiabetic drugs; 31 patients were using calcium-channel blockers and 24 patients were using beta-blockers. In our study group, there was no significantly difference between median PASI scores of the patients using a triggering drug and those of who are not using a triggering drug. However, there was a positive low correlation between PASI rates and numbers of drugs used (r = 0.180, p = 0.013). Conclusions: Many other factors may trigger psoriasis, therefore the effect of stopping or minimizing the drug use on disease remission is not known. Because of the high triggering drug use rate, it is important to enlighten psoriasis patients about triggering drugs.
Pneumorrhachis and Pneumocephalus with Severe Chest Pain Symptom: A Rare Complication of Epidural Steroid Injection
(2014) Ergenoglu, Pinar; Bali, Cagla; Akin, Sule; Ozyilkan, Nesrin B.; Aribogan, Anis
Plasma fetuin-A levels are reduced in patients with hypothyroidism
(2014) Bakiner, Okan; Bozkirli, Emre; Ertugrul, Derun; Sezgin, Nurzen; Ertorer, Eda
Objective: To determine plasma fetuin-A levels in hypothyroid patients before and after treatment with L-thyroxine (T-4) and to determine the relation between plasma fetuin-A levels with cardiovascular risk factors. Design: A prospective, controlled, single-blind study. Methods: Forty-four treatment-naive female patients diagnosed with hypothyroidism and 39 age-and sex-matched control subjects were enrolled. Anthropometric measurements, blood pressure, plasma TSH, fetuin-A, free T-4, LDL-cholesterol, triglyceride, C-reactive protein, fibrinogen levels, and brachial artery flow-mediated dilatation were measured. All measurements were repeated after 3 months in the control group and 3 months after the attainment of euthyroidism with (L)-T4 replacement in the hypothyroid group. Baseline data were compared between the two groups. Posttreatment plasma fetuin-A levels of hypothyroid patients were compared with baseline levels of both groups. The relationship between plasma fetuin-A, TSH levels, and other cardiovascular risk factors was evaluated. Results: Plasma fetuin-A levels were similar to 20% lower in hypothyroid female patients compared with the controls (P=0.0001). Fetuin-A levels increased by similar to 20% in hypothyroid patients after achievement of euthyroidism (P=0.0001) and were no longer different compared with controls (P=0.38). There was a negative correlation between plasma TSH and fetuin-A levels (r=-0.79; P=0.001). There was no significant correlation between plasma fetuin-A levels and cardiovascular risk factors within or between groups. The fetuin-A levels were normalized with thyroid hormone treatment. Conclusion: Plasma fetuin-A levels are reduced in female patients with hypothyroidism, which are restored to normal during restoration of euthyroidism. There was no relation with cardiovascular risk factors.