مقالههای Ahmad khosravi
توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقالههای نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده میشوند.
۱Optimization of a Gas turbine model (KWU V94.2) Siemens by using PSO and GA for reducing CO2 and NOx emission based on exergy and economic analysis
اطلاعات انتشار: سومین کنفرانس بین المللی رویکردهای نوین در نگهداشت انرژی، سال ۱۳۹۲
تعداد صفحات: ۱۰
Carbon dioxide and oxides of nitrogen as greenhouse gases play a vital role in global warming. A significant contribution to CO2 and NOx emitted to the atmosphere is attributed to fossil fuel combustion. Optimally tuning design parameters of gas turbine power plants from an exergoeconomic perspective and economic analysis is a challenging optimization problem to reduce CO2 and NOx emission. This study first develops a cost function based on key parameters of the plant which include air compressor pressure ratio, gas turbine inlet temperature, gas turbine isentropic efficiency and compressor isentropic efficiency. The integration of gas turbines then leads to a reduction in the operating costs due to fuel savings, and it also provides flexibility for importing and exporting power. Evolutionary algorithms such genetic algorithm (GA) and particle swarm optimization (PSO) are applied to minimize the cost function and optimally adjusting four design parameters. Also environmental impact is considered to reduce CO2 and NOx with respect to the base case. The proposed methods and algorithms are implemented for a gas turbine power plant made by Siemens (model V94.2). Gas turbine model SGT5–2000E (KWU V94.2) is one of the most known that uses in a lot of power plants in Iran. The results exhibit that the GA is more performance PSO.<\div>
۲Reliability and Validity of the Persian Version of the World Health Organization–Five Well–Being Index
نویسنده(ها): Ahmad khosravi، SeyedAbass Mousavi، Reza Chaman، Mahdi Sepidar Kish، Elham Ashrafi، Malahat Khalili، Marziye Ghofrani، mohammad amiri، Kourosh Holakouie Naieni
اطلاعات انتشار: International Journal of Health Studies، اول،شماره۱، ۲۰۱۵، سال ۰
تعداد صفحات: ۳
Introduction: A multidimensional approach to health which addresses the psychological features of health justifies the necessity of designing or validation of brief instruments for screening in general population. This study aims to evaluate the reliability and validity of the Persian version of the WHO–5–P as a brief scale of well–being.Methods: In this study 451 individuals, i.e., over–15–year old subjects completed the WHO–5–P and GHQ–28 questionnaires. Crombach’s alpha and factor analysis were used for internal consistency evaluation. For predictive validity we compared WHO–5–P with GHQ–28 scores using receiver operating characteristic (ROC) analysis.Results: The mean age, score of WHO–5–P and GHQ–28 were 32.3±11.5, 13.4±6.5, and 25.4±13.4 respectively. The WHO–5–P had an acceptable internal consistency (α= 0.94), and it showed adequate convergent validity with the GHQ–28 (r= –0.66; P0.001). The optimal cut–off score of the WHO–5–P was 13 (12.13) with a sensitivity of 0.68 and a specificity of 0.85. The area under curve in this study was 0.82. Confirmatory factor analysis revealed one factor structure.Conclusion: WHO–5–P is a valid and reliable instrument for screening psychological state.
اطلاعات انتشار: Caspian Journal of Reproductive Medicine، اول،شماره۲، ۲۰۱۵، سال ۰
تعداد صفحات: ۷
Background: Many observational studies were published concerning the mean age at menarche and suggested those which may be a decreasing age at menarche in Iranian girls. The aim of this systematic review and meta–analysis was to estimate the overall mean age at menarche in Iranian girls. Methods: We searched using online databases through December 2014 using and examined the reference lists of pertinent paper. Finally, 28 cross–sectional studies were selected for this meta–analysis. Cochran and tau–two tests were used for the detection of homogeneity of samples. The common average was calculated by random effect using RevMan 5 and Stata software. The cumulative meta–analysis and meta–regression were used to review the factors affecting heterogeneity. Results: The mean age at menarche was13.9 years before 2000 and after 2000 was 12.6 years. The overall mean (95% CI) age at menarche was calculated 12.872 (95% CI: 12.874, 12.870) years based on stochastic models. Conclusion: These findings indicated that the mean age at menarche in Iranian girls was less than that of the region and developing countries therefore performing a systematic review and meta–analysis to evaluate related factors that influence age at menarche in Iranian girls could be beneficial.
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