In this article, electromagnetic control of turbulent boundary layer on a ship hull is numerically investigated. This study is conducted on the geometry of tanker model hull. For this purpose, a combination of electri...In this article, electromagnetic control of turbulent boundary layer on a ship hull is numerically investigated. This study is conducted on the geometry of tanker model hull. For this purpose, a combination of electric and magnetic fields is applied to a region of boundary layer on stern so that produce wall parallel Lorentz forces in streamwise direction as body forces in stern flow. The governing equations including RANS equations with SST k-ω?turbulent model coupled with electric potential equation are numerically solved by using Ansys Fluent codes. Accuracy of this turbulent model of Fluent in predicting Turbulent flow around a ship is also tested by comparing with available experimental results that it shows a good agreement with experimental data. The results obtained for ship flow show that by applying streamwise Lorentz forces that are large enough, flow is accelerated. The results are caused to delay or avoid the flow separation in stern, increase the propeller inlet velocity, create uniform flow distribution behind the ship’s hull in order to improve the propeller performance, and finally decrease the pressure resistance and total resistance.展开更多
The purpose of this study was to investigate the dimensions and conditions caused by shifts in nurses who worked in constant shifts in non-governmental selective hospitals in Tehran in 2014. In this cross-sectional an...The purpose of this study was to investigate the dimensions and conditions caused by shifts in nurses who worked in constant shifts in non-governmental selective hospitals in Tehran in 2014. In this cross-sectional and applied research, the shifts standard questionnaire was used. After confirming the validity and reliability (Cronbach’s alpha 0.73), the questionnaires were distributed among 305 nurses of 6 non-governmental selective hospitals in Tehran, based on stratified random sampling. In the research, the data analysis was conducted in two levels of descriptive and inferential statistics. The response rate was 0.91. 74.4% of the participant nurses were female and 25.6% were male. The results showed that there was a significant relationship between age and physical health (P = 0.008), gender and physical health (P = 0.015), education and health (P = 0.014), gender and physical-cognitive anxiety (P = 0.006), age and social-familial status (P = 0.001), Marital status and social-familial status (P = 0.001), having a second job and social-familial status (P = 0.001), education and sleep-fatigue (P = 0.002). Planning with respect to standards of nurses’ working hours and avoiding overtime, especially nurses who have more experience, can prevent severe complications of shifts and improve health level and ultimately the quality of care.展开更多
文摘In this article, electromagnetic control of turbulent boundary layer on a ship hull is numerically investigated. This study is conducted on the geometry of tanker model hull. For this purpose, a combination of electric and magnetic fields is applied to a region of boundary layer on stern so that produce wall parallel Lorentz forces in streamwise direction as body forces in stern flow. The governing equations including RANS equations with SST k-ω?turbulent model coupled with electric potential equation are numerically solved by using Ansys Fluent codes. Accuracy of this turbulent model of Fluent in predicting Turbulent flow around a ship is also tested by comparing with available experimental results that it shows a good agreement with experimental data. The results obtained for ship flow show that by applying streamwise Lorentz forces that are large enough, flow is accelerated. The results are caused to delay or avoid the flow separation in stern, increase the propeller inlet velocity, create uniform flow distribution behind the ship’s hull in order to improve the propeller performance, and finally decrease the pressure resistance and total resistance.
文摘The purpose of this study was to investigate the dimensions and conditions caused by shifts in nurses who worked in constant shifts in non-governmental selective hospitals in Tehran in 2014. In this cross-sectional and applied research, the shifts standard questionnaire was used. After confirming the validity and reliability (Cronbach’s alpha 0.73), the questionnaires were distributed among 305 nurses of 6 non-governmental selective hospitals in Tehran, based on stratified random sampling. In the research, the data analysis was conducted in two levels of descriptive and inferential statistics. The response rate was 0.91. 74.4% of the participant nurses were female and 25.6% were male. The results showed that there was a significant relationship between age and physical health (P = 0.008), gender and physical health (P = 0.015), education and health (P = 0.014), gender and physical-cognitive anxiety (P = 0.006), age and social-familial status (P = 0.001), Marital status and social-familial status (P = 0.001), having a second job and social-familial status (P = 0.001), education and sleep-fatigue (P = 0.002). Planning with respect to standards of nurses’ working hours and avoiding overtime, especially nurses who have more experience, can prevent severe complications of shifts and improve health level and ultimately the quality of care.
