A Fuzzy TOPSIS Approach Based on Trapezoidal Numbers to Material Selection Problem

Erkan Celik,Muhammet Gul,Alev Taskin Gumus,Ali Fuat Guneri 한국데이타베이스학회 2012 Journal of information technology applications & m Vol.19 No.3

Material selection is a complex problem in the design and development of products for diverse engineering applications. This paper is aimed to present a fuzzy decision‐making approach to deal with the material selection in engineering design problems. A fuzzy multi criteria decision‐making model is proposed for solving the material selection problem. The proposed model makes use of fuzzy TOPSIS (Technique for Order reference by Similarity to Ideal Solution) with trapezoidal numbers for evaluating the criteria and ranking the alternatives. And result is compared with fuzzy VIKOR (VlseKriterijumska Optimizacija I Kompromisno Resenje in Serbian, means Multi criteria Optimisation and Compromise Solution) which is proposed by Jeya Girubha and Vinodh [2012]. The present paper is aimed to also improve literature of fuzzy decision making for material selection problem.

A Novel Grounded Inductor Realization Using a Minimum Number of Active and Passive Components

Erkan Yuce,Shahram Minaei,Oguzhan Cicekoglu 한국전자통신연구원 2005 ETRI Journal Vol.27 No.4

In this study, we present a new topology for realizing a grounded inductor employing only a single current conveyor, called a negative-type modified inverting second-generation current conveyor (MICCII-), and a minimum number of passive components, two resistors, and one capacitor. The non-ideality effects of the MICCII- on a simulated inductor are investigated. To demonstrate the performance of the presented inductance simulator, we use it to construct a third order Butterworth high-pass filter and a parallel resonant circuit. Simulation results are given to confirm the theoretical analysis.

StellaTUM: current consensus and discussion on pancreatic stellate cell research

Erkan, Mert,Adler, Guido,Apte, Minoti V,Bachem, Max G,Buchholz, Malte,Detlefsen, Sö,nke,Esposito, Irene,Friess, Helmut,Gress, Thomas M,Habisch, Hans-Joerg,Hwang, Rosa F,Jaster, Robert,Kleeff, J&ou BMJ Group 2012 Gut: journal of the British Society of Gastroenter Vol.61 No.2

Experience of the Endoscopists Matters in Endoscopic Retrograde Cholangiopancreatography in Billroth II Gastrectomy Patients

Erkan Caglar,Deniz Atasoy,Mukaddes Tozlu,Engin Altınkaya,Serkan Dogan,Hakan Senturk 대한소화기내시경학회 2020 Clinical Endoscopy Vol.53 No.1

Background/Aims: Altered anatomy is a challenge in endoscopic retrograde cholangiopancreatography (ERCP) for patients withBillroth II anastomosis. In this study, we investigated the overall success and role of endoscopist experience. Methods: Data of patients who underwent ERCP between 2014 and 2018 after a previous Billroth II operation were retrievedretrospectively from 2 tertiary ERCP centers. The procedures were performed by 2 endoscopists with different levels of experience. Clinical success was defined as extraction of the stone, placement of a stent through a malignant stricture, and clinical and laboratoryimprovements in patients. Results: Seventy-five patients were included. The technical success rate was 83% for the experienced endoscopist and 75% for theinexperienced endoscopist (p=0.46). The mean (±standard deviation) procedure time was 23.8±5.7 min for the experienced endoscopistand 40.68±6.07 min for the inexperienced endoscopist (p<0.001). In total, 3 perforations (4%) were found. The rate of afferent loopperforation was 6.25% (1/16) for the inexperienced endoscopist and 0% (0/59) for the experienced endoscopist (p=0.053). Conclusions: ERCP in patients who had undergone Billroth II gastrectomy was time consuming for the inexperienced endoscopistwho should beware of the unique adverse events related to ERCP in patients with altered anatomy.

Self-Expandable Metallic Stent Placement in the Palliative Treatment of Malignant Obstruction of Gastric Outlet and Duodenum

Erkan Çaglar,Ahmet Dobrucali 대한소화기내시경학회 2013 Clinical Endoscopy Vol.46 No.1

Background/Aims: To asses the usefulness of flexible metallic stents in the palliation of malignant obstruction of gastric outlet and duodenum. Methods: Retrospective review was performed between January 2006 and December 2011 in 30 patients. Thirty consecutive patients with obstruction of the gastric outlet underwent palliative treatment with self-expandable flexible metallic stents. Complications and clinical outcomes were assessed. Results: Twenty-four patients had advanced gastric carcinoma at the antrum and/or pylorus, four patients had obstruction at the pylorus due to pancreas tumours and one patient had duodedum and one patient had gall bladder tumour. Symptoms improved in 82.7% of the patients after the procedure. The improvement in ability to eat using the score system was statistically significant (p<0.001). Tumor ingrowth and/or overgrowth were seen in four patients (13.3%), and a second stent was inserted in these patients. The mean stent patency was 100 days (range, 5 to 410). The mean survival was 120.76±38.96 days. Conclusions: Endoscopic placement of self-expendable metallic stents under fluoroscopy is a safe and effective treatment for the palliation of patients with inoperable malignant gastric outlet obstruction caused by stomach or pancreas cancer.

Burr Measurement Method Based on Burr Surface Area

Erkan Bahçe,Burak Özdemir 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4

One of the major issues of drilling operations pertains to the formation of burrs, which greatly influences the accuracy of the manufactured parts, and, thus, the capability to meet the desired performance of the part. To remove or prevent these burrs, their geometry must be measured accurately, even though they are sharp and irregular in shape. The accurate measurement of the geometry of a burr will lead to the development of a proper deburring method. In this work, the authors describe a simple and convenient new measurement technique for drilling burr profiles and a developed drilling burr measurement system based on surface area. The new method presented in this research aims at providing a comparative evaluation of the height, arc length and area of the burr, as well as its geometrical characteristics. When the average height and arc length measurement methods are compared with the area measurement method, large deviations in burr height are detected. In particular, these deviations increase more in non-uniform burrs. In the measurement of burr size, the new developed method is based on area measurement and is carried out using a computer. Therefore, there is no deviation between the measurements. In contrast, the average deviation ranges for the height and arc length measurement methods are found to be 9.94–48.14% and 6.07–18.82%, respectively.

Long-Term Palliative Effect of Stenting in Gastric Outlet Obstruction Due to Transarterial Chemoembolization with Yttrium-90 in a Patient with Metastatic Neuroendocrine Tumor

Erkan Caglar,Gulen Doğusoy,Levent Kabasakal,Ahmet Dobrucali 대한소화기내시경학회 2016 Clinical Endoscopy Vol.49 No.5

Internal radioembolization with yttrium-90 is a promising treatment method, predominantly for liver tumors. However, the shifting of yttrium-90-loaded spherules into the arteries and veins that supply the duodenum and stomach, leading to ulceration, hemorrhage, perforation, and outlet obstruction of these organs, is one of the major undesirable consequences of this technique. We report a case of gastric outlet obstruction (GOO) due to antropyloric stenosis with ulceration, edema, and inflammation following transarterial yttrium-90 treatment for a metastatic neuroendocrine tumor in a 58-year-old man. Stenting was used for palliation in this case. GOO improved after stenting and recovery of oral intake was permanent after stent removal.

Low velocity impact behavior of concrete beam strengthened with CFRP strip

Erkan Kantar,Özgür Anil 국제구조공학회 2012 Steel and Composite Structures, An International J Vol.12 No.3

Nowadays CFRP (Carbon Fiber Reinforced Polymer) became widely used materials for the strengthening and retrofitting of structures. Many experimental and analytical studies are encountered at literature about strengthening beams by using this kind of materials against static loads and cyclic loads such as earthquake or wind loading for investigating their behavior. But authors did not found any study about strengthening of RC beams by using CFRP against low velocity impact and investigating their behavior. For these reasons an experimental study is conducted on totally ten strengthened RC beams. Impact loading is applied on to specimens by using an impact loading system that is designed by authors. Investigated parameters were concrete compression strength and drop height. Two different sets of specimens with different concrete compression strength tested under the impact loading that are applied by dropping constant weight hammer from five different heights. The acceleration arises from the impact loading is measured against time. The change of velocity, displacement and energy are calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. Impact behaviors of beams are positively affected from the strengthening with CFRP. Measured accelerations, the number of drops up to failure and dissipated energy are increased. Finite element analysis that are made by using ABAQUS software is used for the simulation of experiments, and model gave compatible results with experiments.

Solving design optimization problems via hunting search algorithm with Levy flights

Erkan Doğan 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.2

This study presents a hunting search based optimum design algorithm for engineering optimization problems. Hunting search algorithm is an optimum design method inspired by group hunting of animals such as wolves, lions, and dolphins. Each of these hunters employs hunting in a different way. However, they are common in that all of them search for a prey in a group. Hunters encircle the prey and the ring of siege is tightened gradually until it is caught. Hunting search algorithm is employed for the automation of optimum design process, during which the design variables are selected for the minimum objective function value controlled by the design restrictions. Three different examples, namely welded beam, cellular beam and moment resisting steel frame are selected as numerical design problems and solved for the optimum solution. Each example differs in the following ways: Unlike welded beam design problem having continuous design variables, steel frame and cellular beam design problems include discrete design variables. Moreover, while the cellular beam is designed under the provisions of BS 5960, LRFD-AISC (Load and Resistant Factor Design-American Institute of Steel Construction) is considered for the formulation of moment resisting steel frame. Levy Flights is adapted to the simple hunting search algorithm for better search. For comparison, same design examples are also solved by using some other well-known search methods in the literature. Results reveal that hunting search shows good performance in finding optimum solutions for each design problem.

PLM Services 를 이용한 이기종 PDM 시스템의 통합

Erkan Gunpinar,김병철(Byungchul Kim),천상욱(Sanguk Cheon),한순흥(Soonhung Han) (사)한국CDE학회 2006 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2006 No.2