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RISS 인기검색어
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- 저자 : Azeemuddin, (검색결과 2 건)
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A wellbore stability model for formations with anisotropic rock strengths
Lee, H.,Ong, S.H.,Azeemuddin, M.,Goodman, H. Elsevier 2012 Journal of petroleum science & engineering Vol.96 No.-
Shale formations, due to the presence of laminations and weak planes, exhibit directional strength characteristics. In most conventional wellbore stability analyses, rock formations are typically assumed to have isotropic strength. This may cause erroneous results in anisotropic formations such as shales which show strength variations with changing loading directions with respect to the plane of weakness. Therefore a more complex wellbore stability model is required. We have developed such a model in which the anisotropic rock strength characteristic is incorporated. Applying this model to two case studies shows that shear failures occur either along or across the bedding planes depending on the relative orientation between the wellbore trajectories and the bedding planes. Additionally, the extent of failure region around the wellbore and the safe mud weights are significantly affected by the wellbore orientation with respect to the directions of bedding plane and in-situ stress field.
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Alam, Tariq,Khattak, Yasir Jamil,Beg, Madiha,Raouf, Abdul,Azeemuddin, Muhammad,Khan, Asif Alam Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.22
Background: In Pakistan thyroid cancer is responsible for 1.2% cases of all malignant tumors. Ultrasonography (US) is helpful in detecting cancerous thyroid nodules on basis of different features like echogenicity, margins, microcalcifications, size, shape and abnormal neck lymph nodes. We therefore aimed to calculate diagnostic accuracy of ultrasound in detection of carcinoma in thyroid nodules taking fine needle aspiration cytology as the reference standard. Materials and Methods: A cross-sectional analytical study was designed to prospectively collect data from December 2010 till December 2012 from the Department of Radiology in Aga Khan University Hospital, Karachi, Pakistan. A total of 100 patients of both genders were enrolled after informed consent via applying non-probability consecutive sampling technique. Patients referred to Radiology department of Aga Khan University to perform thyroid ultrasound followed by fine-needle aspiration cytology of thyroid nodules were included. They were excluded if proven for thyroid malignancy or if their US or FNAC was conducted outside our institution. Results: The subjects comprised 76 (76%) females and 24 males. Mean age was $41.8{\pm}SD$ 12.3 years. Sensitivity and specificity with 95%CI of ultrasound in differentiating malignant thyroid nodule from benign thyroid nodule calculated to be 91.7% (95%CI, 0.72-0.98) and 78.94% (0.68-0.87) respectively. Reported positive predictive value and negative PV were 57.9% (0.41-0.73) and 96.8% (0.88-0.99) and overall accuracy was 82%. Likelihood ratio (LR) positive was computed to be 4.3 and LR negative was 0.1. Conclusions: Ultrasonography has a high diagnostic accuracy in detecting malignancy in thyroid nodules on the basis of features like echogenicity, margins, micro calcifications and shape.
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