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Effect of FGM coating thickness on apparent fracture toughness of a thick-walled cylinder
Afsar, A.M.,Song, J.I. Elsevier 2010 Engineering fracture mechanics Vol.77 No.14
<P><B>Abstract</B></P><P>This study describes the effect of FGM coating thickness on apparent fracture toughness (AFT) of a thick-walled cylinder containing two diametrically-opposed edge cracks emanating from the inner surface of the cylinder. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion because of cooling from sintering temperature is taken into account. Based on a generalized method of evaluating stress intensity factor (SIF) addressed in a previous study, an approach is developed to calculate AFT. Some numerical results of AFT are presented for a TiC/Al<SUB>2</SUB>O<SUB>3</SUB> FGM coating at the inner surface of an Al<SUB>2</SUB>O<SUB>3</SUB> thick-walled cylinder.</P>
Afsar, A.M.,Ahmed, S.R. Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.21 No.1
This study analyzes stress intensity factors for a number of periodic edge cracks in a semiinfinite medium subjected to a far field uniform applied load along with a distribution of eigenstrain. The eigenstrain is considered to be distributed arbitrarily over a region of finite depth extending from the free surface. The cracks are represented by a continuous distribution of edge dislocations. Using the complex potential functions of the edge dislocations, a simple as well as effective method is developed to calculate the stress intensity factor for the edge cracks. The method is employed to obtain the numerical results of the stress intensity factor for different distributions of eigenstrain. Moreover, the effect of crack spacing and the intensity of the normalized eigenstress on the stress intensity factor are investigated in details. The results of the present study reveal that the stress intensity factor of the periodic edge cracks is significantly influenced by the magnitude as well as distribution of the eigenstrain within the finite depth. The eigenstrains that induce compressive stresses at and near the free surface of the semi-infinite medium reduce the stress intensity factor that, in turn, contributes to the toughening of the material.
Afsar, Cigdem Usul,Gunaldi, Meral,Kum, Pinar,Sahin, Berksoy,Erkisi, Melek,Kara, Ismail Oguz,Paydas, Semra,Duman, Berna Bozkurt,Ercolak, Vehbi,Karaca, Feryal,Uyeturk, Ummugul,Guner, Sebnem Izmir Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.21
Background: The aim of this study was to investigate the general characteristics of patients with deep vein thrombosis (DVT) and pancreatic cancer as well as evaluate the relationship between mean platelet volume (MPV), DVT and survival. Materials and Methods: Seventy-seven patients with pancreatic cancer, who were admitted to Cukurova University Medical Faculty, Department of Medical Oncology, were enrolled in the study Results: The mean age was $59{\pm}20$. Forty-nine (63.6%) were men and 28 women (36.4%). Sixty-eight (88.3%) patients had adenocarcinoma and 9 (11.7%) had a malignant epithelial tumor. Thirty-six (46.7%) had liver metastasis at diagnosis. Twenty-six (33.8%) patients were alive, 20 (26%) were dead and in 31 (40.2%) the status was unknown. Only 14 (18.1%) patients had DVT. In 42 (54.5%) patients MPV values were normal, in 28 (36.4%) patients they were above normal, and in 7 (9.1%) patients they were below normal. There was no statistically significant difference between gender, tumour localization, chemotherapy and survival rates (p:0.56, p:0.11, p:0.21). There was no significant difference between DVT, gender, localisation, histological subtype, the presence of metastasis, stage and if the patient had been treated with chemotherapy (p:0.5, p:0.6, p:0.2, p:0.32, p:0.1, p:0.84). There was also no significant difference between MPV and DVT (p:0.57) but there was a significant difference between liver metastasis and DVT (p:0.02). Age, stage, the presence of metastasis and DVT were prognostic in pancreatic cancer patients. Conclusions: Cases of pancreatic cancer with liver metastasis should be studied more carefully as thrombosis is more common in these patients.
Mohammad Afsar Uddin,김태효,염승집,최효성,황승구,김진영,우한영 한국물리학회 2015 Current Applied Physics Vol.15 No.5
Three kinds of donoreacceptor (DeA) type photovoltaic polymers were synthesized based on 2,7- carbazole and thieno[3,4-c]pyrrole-4,6-dione (TPD). The conjugation of weakly electron (e)-donating 2,7-carbazole and strongly e-accepting TPD moieties yielded a deep highest occupied molecular orbital (HOMO) and its energy level was fine-controlled to be -5.72, -5.67 and -5.57 eV through the incorporation of thiophene (T), thieno[3,2-b]thiophene (TT) and bithiophene (BT) as a π-bridge. Polymer:[ 6,6]-phenyl-C71 butyric acid methyl ester (PC71BM) based bulk heterojunction solar cells exhibited a high open-circuit voltage (VOC) in the range, 0.86e0.94 V, suggesting good agreement with the measured HOMO levels. Despite the high VOC, the thiophene (or thienothiophene)-containing PCTTPD (or PCTTTPD) showed poor power conversion efficiency (PCE, 1.14 and 1.25%) because of the very low short-circuit current density (JSC). The voltage-dependent photocurrent and photoluminescence quenching measurements suggested that hole transfer from PC71BM to polymer depends strongly on the HOMO level of the polymer. The PCTTPD and PCTTTPD devices suffered from electronehole recombination at the polymer/PC71BM interfaces because of the insufficient energy offset between the HOMOs of the polymer and PC71BM. The PCBTTPD:PC71BM device showed the best PCE of 3.42% with a VOC and JSC of 0.86 V and 7.79 mA cm-2, respectively. These results show that photovoltaic polymers should be designed carefully to have a deep HOMO level for a high VOC and sufficient energy offset for ensuring efficient hole transfer from PC71BM to the polymer.
Baris Afsar 대한내분비학회 2013 Endocrinology and metabolism Vol.28 No.3
Background: Many studies have aimed to determine whether body mass index (BMI), waist circumference (WC), or waist to hip ratio (WHR) best predicts hypertension in diabetic patients, with conflicting results. However, no study has examined the specific relationship between these anthropometric parameters with sustained normotension (SNT), white coat hypertension (WCHT),masked hypertension (MHT), and sustained hypertension (SHT) based on office and ambulatory blood pressure (BP) measurements in these patients.Methods: Patients with newly diagnosed type 2 diabetes underwent the following procedures: history taking, measurements of anthropometric parameters, office and ambulatory BP measurements, physical examination, laboratory analysis, and random and 24-hour urine analysis.Results: In total, there were 65 dippers and 37 nondipper patients. None of the anthropometric parameters were different between the dippers and the nondippers. There were 25 patients with SNT, 32 with WCHT, seven with MHT, and 38 with SHT. A comparison of anthropometric parameters between these four groups of patients showed that WC (P=0.016) and WHR (P=0.015) were different among all groups. According to regression analysis, only BMI was independently related with MHT (odds ratio [OR],1.373, P=0.022), whereas only WC has been associated with SHT (OR, 1.321, P=0.041).Conclusion: Among anthropometric parameters, only WC and WHR were different in SNT, WCHT, MHT, and SHT in newly diagnosed patients with type 2 diabetes.
( Mohammad Afsar Uddin ),우한영 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
The molecular weight of a conjugated polymer is one of the key factors for electronics device properties. In this study, a series of semi-crystalline PTTBT and PPDT2FBT polymers with different number-average molecular weights (Mn) were synthesized and their photovoltaic properties as electron donors for Polymer-PCBM and all-polymer solar cells (all- PSCs) were studied respectively. Tuning the Mn induced dramatic effects on the aggregation behaviors of the polymers and their bulk heterojunction (BHJ) morphology, which was thoroughly examined by GIWAX, Ro-SoXS, AFM etc. High Mn PPDT2FBT promoted a strong “face-on” geometry in the blend film, suppressed the formation of an excessively large crystalline domain, and facilitated molecularly-intermixed phases with acceptor material leading to high power conversion efficiency.