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.
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 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.
Early clinical predictors of intractable epilepsy in childhood
(2014) Saygi, Semra; Erol, Ilknur; Alehan, Fusun
Aim: In this retrospective study, we evaluated the clinical responses to antiepileptic drug (AED) therapy in pediatric epilepsy patients treated at a single center. Materials and methods: We identified 28 children with intractable epilepsy and 213 patients with drug-responsive epilepsy. Results: Univariate analysis showed that age at onset, high (daily) initial seizure frequency, infantile spasm, history of neonatal seizures, abnormal neurodevelopmental status, neurological abnormalities, mental retardation, remote symptomatic etiology, and abnormal brain imaging results were significant risk factors for the development of intractable epilepsy (P < 0.05). Multivariate logistic regression analysis revealed that high (daily) initial seizure frequency and remote symptomatic etiology were significant and independent risk factors for intractable epilepsy (P < 0.05). Conclusion: Our study suggests that the risk of developing intractable epilepsy in childhood may be predicted, to some extent, by the early clinical course. Early identification of patients at high risk of developing intractable epilepsy will guide appropriate therapy and reduce exposure to ineffectual treatments.
Paraaortic Lymph Node Dissection in Endometrial Cancer; Is It Necessary?
(2014) Dizdar, Omer; Oguz, Arzu; Kucukoztas, Nadire; Dursun, Polat; Altundag, Ozden; Ayhan, Ali
Evaluation of choroidal thickness using spectral-domain optical coherence tomography in migraine patients during acute migraine attacks: a comparative study
(2014) Karalezli, A.; Simsek, C.; Celik, G.; Eroglu, F.C.; 25257772
Purpose The purpose of this study was to assess choroidal thickness in migraine patients during acute migraine attacks and compare them with healthy controls, using spectral domain optical coherence tomography (OCT). Patients and methods In this prospective case-control study, choroidal thicknesses of 46 migraine patients during acute migraine attacks and 46 age-and sex-matched healthy subjects were measured using a high-speed, high-resolution frequency domain-OCT device. All patients underwent a complete ophthalmic examination before the measurements. OCT measurements were taken at the same time of day (0900 hours), in order to minimize the effects of diurnal variation. Results There was a statistically significant difference in mean choroidal thickness between the migraine patients during acute migraine attacks (356.3 +/- 21.46 mm) and the controls (302.3 +/- 18.34 mu m; P = 0.000). There were significant differences at all measurement points (P < 0.001 for all). Conclusion The increased choroidal thickness of the migraine patients during acute migraine attacks might be related to the vascular pathology of the disease. Further studies are needed to evaluate the etiopathologic relationship between choroidal thickness and acute migraine attack.
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.
PANCREATIC CYSTIC LYMPHANGIOMA: DIAGNOSTIC APPROACH WITH MDCT AND MR IMAGING
(2014) Macin, G.; Hekimoglu, K.; Uner, H.; Tarhan, C.
Lymphangiomas are rare congenital benign tumors arising from the lymphatic system mostly encountered in the neck and axillary regions of pediatric patients. Pancreatic cystic lymphangiomas very rarely occur in adults. Radio-logically, the lesion may mimic pancreatic carcinoma and should be considered in the differential diagnosis of any patient found to have an abdominal cystic mass. In this article, we present a 50-year-old man who presented with pain in the upper abdomen, nausea, and abdominal swelling. On computed tomography (CT) and magnetic resonance (MR) imaging, a gross septated cystic lesion was detected in the upper abdomen which extended from the pancreatic corpus to the left liver lobe. The patient underwent complete resection of tumor Pathology revealed a cystic lymphangioma.
Use of Mesenchymal Cells to Modulate Immune Suppression and Immune Reconstruction in a Patient with Aplastic Anemia Complicated by Invasive Sino-Orbital Aspergillosis
(2014) Ozdogu, Hakan; Yeral, Mahmut; Boga, Can; Kozanoglu, Ilknur
Cultured human bone marrow mesenchymal cells (MSCs) have immunomodulatory and tissue regenerative properties. This report summarizes the result of post-transplant treatment with MSCs of a 26-year-old patient with aplastic anemia complicated by invasive sino-orbital aspergillosis. The patient was treated with MSCs to benefit from the dual effects of MSCs in immune reconstitution: suppression against alloreactive T cells and facilitation of the re-engraftment process. The patient did not develop acute or chronic graft-versus-host disease. The aspergillus infection healed completely. The engraftment failure was also ended without any complications. During his last visit in his fourth year after transplantation, the patient was in hematological remission. Human bone marrow-derived MSCs seem to have an important role in preventing or overcoming immunological complications in patients who undergo stem cell transplantation.
Efficacy and Safety of First Line Vincristine with Doxorubicin, Bleomycin and Dacarbazine (ABOD) for Hodgkin's Lymphoma: a Single Institute Experience
(2014) Ozdemir, Nuriye; Dogan, Mutlu; Sendur, Mehmet Ali Nahit; Yazici, Ozan; Abali, Huseyin; Yazilitas, Dogan; Akinci, Muhammed Bulent; Aksoy, Sercan; Zengin, Nurullah; 25374196
Background: ABVD (doxorubicin, bleomycin, vinblastine (Vb) and dacarbazine) is the standard regimen in Hodgkin's lymphoma (HL). Vincristine (O) is a mitotic spindle agent like Vb. We aimed to evaluate the efficacy and safety of O as a part of ABOD in HL. Materials and Methods: Patients who had ABOD were enrolled. Stage I-II HL were evaluated for unfavorable risk factors according to NCCN. National Cancer Institute Common Toxicity Criteria was used for toxicity. Results: Seventy-nine HL patients in our center between 2003 and 2007 were evaluated retrospectively. Median follow-up was 54 months. Most of the patients were male in their third decade. Median ABOD cycles were 6 (2-8). Primary refractory disease rate was 17.7% whereas it was 5.1% for early relapse and 5.1% for late relapse disease. Response rates were as 82.3% for complete response, 11.4% for partial response, 5.1% for stable disease and 1.3% for progressive disease. Half of relapsed patients had autologous stem cell transplantation. Estimated 5-year failure-free survival was 71% and significantly longer in early stage patients without risk factors, bulky disease or radiotherapy (RT) (p=0.05, p<0.0001, p=0.02; respectively). Estimated 5-year overall survival was 74% and significantly longer in those who had no RT (p=0.001). Dose modification rate was 5.1% and chemotherapy delay rate was 19%. There were no toxicity-related deaths. Conclusions: ABOD seems to be effective with managable toxicity in HL, even in those with poor prognostic factors.
The Role of Choice-Lock Catheter and Trocar Technique in Percutaneous Ablation of Symptomatic Renal Cysts
(2014) Ozkan, Burak; Harman, Ali; Emiroglu, Baris; Arer, Ilker; Aytekin, Cuneyt; 25035702
Background: The most common benign lesions of the kidney are simple cysts. They are acquired lesions and mostly affect the elderly population. Objectives: To describe the usage of choice-lock catheter and trocar technique in percutaneous renal cyst treatment and determining long-term outcomes. Patients and Methods: This retrospective study was carried out between February 2000 and July 2011 Eighty-eight cysts all of which were Bosniak type-1 cysts were selected in 75 patients. The treatment indications were flank pain, hydronephros is and hypertension. The choice-lock catheter was used for 84 cysts with the trocar technique. Ninety-five percent ethanol was used as the sclerosing agent. Maximum volume of the injected ethanol was 175 ml. The mean follow-up time after the treatment procedure was 23 months. Sixty-four cysts were located in the cortical and 24 cysts were located at the parapelvic region. Results: Fifty-seven cysts had complete regression, while 31 cysts regressed partially After the procedure, pain was relieved in 44 (82%) patients and the pain alleviated in four (8%). Normotension was obtained in five (62.5%) of the eight hypertensive patients and no hydronephrosis was detected in nine patients. There were no relationship between the localization and the regression rate. No major complications occurred. Conclusions: Percutaneous ethanol sclerotheraphy in simple cysts is a safe, cost-effective and minimally invasive method. We consider that this technique may be an alternative solution in the percutaneous cyst treatment.
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.
Thyroid volume in patients with glucose metabolism disorders
(2014) Duran, Ayse Ocak; Anil, Cuneyd; Gursoy, Alptekin; Nar, Asli; Inanc, Mevlude; Bozkurt, Oktay; Tutuncu, Neslihan Bascil; 25465604
Objective: Thyroid volume and the prevalence of thyroid nodules are higher in patients with insulin resistance. A relationship between thyroid volume and glucose metabolism disorders (GMD) has not as yet been clarified. The present retrospective study aimed to investigate the association between GMD and thyroid volume. Subjects and methods: We investigated the data of 2,630 patients who were evaluated for thyroid biopsy in our hospital. The study population included 602 patients with GMD, 554 patients with diabetes mellitus (DM) and 1,474 patients with normal glucose metabolism as a control group. We obtained the levels of serum thyroid stimulating hormone (TSH) and the thyroid volumes of those patients retrospectively. Results: The median ages for the control group, GMD group and DM group were 55 (15-91) years, 60 (27-97) years, and 65 (27-91) years respectively and there was a statistically significant difference between the groups with regard to age and gender (p < 0.001). Levels of TSH were similar in all groups. The median total thyroid volumes for patients with DM and GMD were significantly higher than that of the control group [22.5 (3-202) mL, 20.2 (4-190) mL, and 19.2 (3-168) mL respectively, p <= 0.001 for all parameters]. Also the median total thyroid volume for patients with DM was significantly higher than that of the GMD group (p < 0.001). According to the correlation analysis, thyroid volume was significantly correlated with age (r = 0.92, p < 0.001) and TSH (r = 0.435, p < 0.001). Age, gender, TSH levels, GMD and DM diagnosis were independently correlated with thyroid volume. Conclusion: The thyroid gland is one of the target tissues of metabolic disorders. We reported a positive correlation between GMD/type 2 DM and thyroid volume. Further controlled, prospective, randomized studies on this subject are required to gain more information.