32 research outputs found

    Improvement of the Results of Finite Element Method in Plate Analysis Using Mesh Sizing Modifying Function

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    In the finite element methods (FEM), the mesh dimension, and the number of elements can affect the responses of structures. In this paper, a procedure is proposed to modify the stiffness matric of the plate element based on the mesh geometry and mesh size for reducing the central deflection error. For this purpose, the modifying coefficients are defined for the bending and shear stiffness matrices. The sensitivity of coefficients is investigated when the thickness of the plate element, the mesh dimension, and also the type of supports vary. The analysis results prove that the values of the bending coefficient have more effect in comparison to the shear coefficient. Finally, a function is proposed to determine the bending and shear matric coefficients based on the values of the exact displacements. Various numerical studies indicate that the modifying function has significantly improved the performance of the plate element, especially for the plates with irregular and large mesh dimensions

    A comparative study between mathematical models and the ANN data mining technique in draft force prediction of disk plow implement in clay loam soil

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    This paper communicates the prediction of required draft force of disk plow implement during tillage operations. The well-known mathematical model proposed by American Society of Agricultural and Biological Engineers (ASABE), multiple linear regression (MLR) and data mining model, based on artificial neural network (ANN), were employed for this purpose. The input variables of the models were considered as forward speed of 2-6 (km/h) and plowing depth of 10-30 (cm). The development details of the models are documented in the paper. On account of statistical performance criteria, the best ANN model with coefficient of determination of 0.971, root mean square error of 0.762 (kN), mean absolute percentage error of 1.886 (%) and mean value of absolute prediction residual errors of 0.968 (kN) was better performed than ASABE and MLR models for prediction of required draft force. The ANN modeling results also showed that the simultaneous or individual increment of forward speed and plowing depth caused nonlinear increment of draft force. The well-developed ANN model is considered operational to predict draft force as an essential step toward proper selection of combination of tractor and disk plow implement

    Scrutinization of overall energy efficiency of machinery in plowing process

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    This work was dedicated to describe overall energy efficiency of machinery in plowing process as affected by some operational variables of plowing depth (10-30 cm) and forward speed (2-6 km/h). To achieve this aim, field trials in clay loam soil in southern region of Iran were performed by means of disk plow implement and front wheel assist tractor. The effects of the operational variables on the efficiency were examined. General two-variable linear and quadratic equations were fitted to obtained field data in order to model the efficiency with respect to plowing depth and forward speed. The results demonstrated that the individual effect of plowing depth on the efficiency was more dominant (1.2 times) than that of forward speed. Meanwhile, the compounded effect of plowing depth and forward speed on the efficiency was prevailed (4 and 3.2 times) than that of the individual effect of forward speed and plowing depth, respectively. The satisfactory results drawn from fitness of the quadratic equation on data rather than the linear equation manifested nonlinear increasing variations of overall energy efficiency as influenced by augmentation of plowing depth and forward speed. The condensed analytical information in conjunction with modeling results disseminate knowledge in usable and useful form to farmers, associated policy division, and stakeholders

    A Case of Reactive Cervical Lymphadenopathy with Fat Necrosis Impinging on Adjacent Vascular Structures.

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    A tender neck mass in adults can be a diagnostic challenge due to a wide differential diagnosis, which ranges from reactive lymphadenopathy to malignancy. In this report, we describe a case of a young female with an unusually large and tender reactive lymph node with fat necrosis. The diagnostic imaging findings alone mimicked that of scrofula and malignancy, which prompted a complete workup. Additionally, the enlarged lymph node was compressing the internal jugular vein in the setting of oral contraceptive use by the patient, raising concern for Lemierre's syndrome or internal jugular vein thrombosis. This report shows how, in the appropriate clinical context, and especially with the involvement of adjacent respiratory or neurovascular structures, aggressive diagnostic testing can be indicated

    Supplemental irrigation management of rainfed grapevines under drought conditions using the CropSyst model

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    Aim of study: To determine how much water should be used and when it should be applied in rain-fed grapevine using a cropping system simulation model (CropSyst), and also the economic analysis of supplemental irrigation for rainfed grapevine.Area of study: This study was conducted at the School of Agriculture, Shiraz University, Shiraz, Iran, in 2012, 2013 and 2014.Material and methods: The CropSyst model was calibrated to predict the rainfed yields of ‘Askari’ and ‘Yaghooti’ grapevines in different climates using four amounts of SI: 250 L (I1), 500 L (I2), 1000 L (I3) and 0 (I4), five SI times: single in March (T1), single in April (T2), single in March + single in April (T3), single in May (T4) and single in June (T5).Main results: Treatment T3 increased the average simulated yield of ‘Askari’ by 15% to 40% at regions with P/ETo>0.6, 17% to 61% at 0.2<P/ETO<0.6, and 26% to 61% at P/ETO<0.2, while in ‘Yaghooti’ it increased about 2% to 41% at regions with P/ETo>0.6, 4% to 36% at 0.2<P/ETO<0.6 and 2% to 26% at P/ETO<0.2. By increasing the water price by 30% and 50%, net benefits for the ‘Askari’ decreased by about 31% and 54%, while 6% and 18%, for ‘Yaghooti’ respectively.Research highlights: The CropSyst model can successfully predict soil water content and grapevine yields. Application of SI in May increased significantly the grapevine yield as compared to other SI times

    Metabolic and endocrinologic complications in beta-thalassemia major: a multicenter study in Tehran

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    BACKGROUND: The combination of transfusion and chelation therapy has dramatically extended the life expectancy of thalassemic patients. The main objective of this study is to determine the prevalence of prominent thalassemia complications. METHODS: Two hundred twenty patients entered the study. Physicians collected demographic and anthropometric data and the history of therapies as well as menstrual histories. Patients have been examined to determine their pubertal status. Serum levels of 25(OH) D, calcium, phosphate, iPTH were measured. Thyroid function was assessed by T3, T4 and TSH. Zinc and copper in serum were determined by flame atomic absorption spectrophotometry. Bone mineral density (BMD) measurements at lumbar and femoral regions have been done using dual x-ray absorptiometry. The dietary calcium, zinc and copper intakes were estimated by food-frequency questionnaires. RESULTS: Short stature was seen in 39.3% of our patients. Hypogonadism was seen in 22.9% of boys and 12.2% of girls. Hypoparathyroidism and primary hypothyroidism was present in 7.6% and 7.7% of the patients. About 13 % of patients had more than one endocrine complication with mean serum ferritin of 1678 ± 955 micrograms/lit. Prevalence of lumbar osteoporosis and osteopenia were 50.7% and 39.4%. Femoral osteoporosis and osteopenia were present in 10.8% and 36.9% of the patients. Lumbar BMD abnormalities were associated with duration of chelation therapy. Low serum zinc and copper was observed in 79.6% and 68% of the study population respectively. Serum zinc showed significant association with lumbar but not femoral BMD. In 37.2% of patients serum levels of 25(OH) D below 23 nmol/l were detected. CONCLUSION: High prevalence of complications among our thalassemics signifies the importance of more detailed studies along with therapeutic interventions

    Third national surveillance of risk factors of non-communicable diseases (SuRFNCD-2007) in Iran: methods and results on prevalence of diabetes, hypertension, obesity, central obesity, and dyslipidemia

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    <p>Abstract</p> <p>Background</p> <p>The burden of non-communicable diseases is rising globally. This trend seems to be faster in developing countries of the Middle East. In this study, we presented the latest prevalence rates of a number of important non-communicable diseases and their risk factors in the Iranian population.</p> <p>Methods</p> <p>The results of this study are extracted from the third national Surveillance of Risk Factors of Non-Communicable Diseases (SuRFNCD-2007), conducted in 2007. A total of 5,287 Iranian citizens, aged 15–64 years, were included in this survey. Interviewer-administered questionnaires were applied to collect the data of participants including the demographics, diet, physical activity, smoking, history of hypertension, and history of diabetes. Anthropometric characteristics were measured and serum biochemistry profiles were determined on venous blood samples. Diabetes (fasting plasma glucose ≥ 126 mg/dl), hypertension (systolic blood pressure ≥ 140 mmHg, diastolic blood pressure ≥ 90 mmHg, or use of anti-hypertensive drugs), dyslipidemia (hypertriglyceridemia: triglycerides ≥ 150 mg/dl, hypercholesterolemia: total cholesterol ≥ 200 mg/dl), obesity (body mass index ≥ 30 kg/m<sup>2</sup>), and central obesity (waist circumference ≥ 80 cm in females and ≥ 94 cm in males) were identified and the national prevalence rates were estimated.</p> <p>Results</p> <p>The prevalence of diabetes, hypertension, obesity, and central obesity was 8.7% (95%CI = 7.4–10.2%), 26.6% (95%CI = 24.4–28.9%), 22.3% (95%CI = 20.2–24.5%), and 53.6% (95%CI = 50.4–56.8%), respectively. The prevalence of hypertriglyceridemia and hypercholesterolemia was 36.4% (95%CI = 34.1–38.9%) and 42.9% (95%CI = 40.4–45.4%), respectively. All of the mentioned prevalence rates were higher among females (except hypertriglyceridemia) and urban residents.</p> <p>Conclusion</p> <p>We documented a strikingly high prevalence of a number of chronic non-communicable diseases and their risk factors among Iranian adults. Urgent preventive interventions should be implemented to combat the growing public health problems in Iran.</p
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