Based on the standard k-ε turbulence model and the RANS equations, thefinite volume method and the SIMPLE algorithm were adopted to carry out the three-dimensionalviscous numerical simulation of the internal flow wit...Based on the standard k-ε turbulence model and the RANS equations, thefinite volume method and the SIMPLE algorithm were adopted to carry out the three-dimensionalviscous numerical simulation of the internal flow within a vortex pump in double reference frames.According to the results of numerical simulation, the internal flow in the vortex pump was analyzed,and the calculated results of blade surface pressure of the impeller were compared withexperimental results. The maximum relative error is 6.6% between calculated value and experimentalvalue of the pump head under operation conditions.展开更多
Objective To evaluate the outcome of off-pump coronary artery bypass grafting （OPCABG） using a bilateral internal mammary artery （BIMA） Y configuration graft to achieve total arterial myocardial revascularization....Objective To evaluate the outcome of off-pump coronary artery bypass grafting （OPCABG） using a bilateral internal mammary artery （BIMA） Y configuration graft to achieve total arterial myocardial revascularization. Methods From October 2002 to December 2008, 208 patients （196 males and 12 females） underwent OPCABG using a BIMA Y configuration graft. The average age of the patients was 56.5 ± 11.3 years, with an age range of 33-78 years. A total of 167 （80.2%） cases had triple-vessel disease. Left main stem disease was found in 33 （15.9%） cases, and double-vessel disease was found in 8 （3.9%） cases. The semi-skeletonization technique was used to harvest the two internal mammary arteries （IMAs）, and then the free right internal mammary artery was connected end-to-side to the left internal mammary artery （LIMA） in situ to complete the Y configuration graft. Off-pump and sequential anastomosis methods were used to perform coronary artery bypass surgery in all patients. Graft patency was assessed intm-operatively with the HT311 transit time flowmeter. Results A total of 728 distal anastomoses were performed in 208 patients, with the average being 3.5± 1.3 per person. No one died or experienced recurrent angina within 30 days after the operation. Conclusions OPCABG using the BIMA Y graft was safe and effective to achieve total arterial revascularization. This method avoids surgical operation on the ascending aorta and other incisions.展开更多
Background： Arterial grafts had better mid-term and long-term patency than saphenous vein grafts in coronary artery bypass grafting （CABG）. We summarized our experience with total arterial off-pump coronary artery ...Background： Arterial grafts had better mid-term and long-term patency than saphenous vein grafts in coronary artery bypass grafting （CABG）. We summarized our experience with total arterial off-pump coronary artery bypass grafting （OPCAB） and assessed the early clinical results, surgical complications, and follow-up. Methods： From January 2007 to May 2017,508 coronary artery disease patients undergoing total arterial OPCAB were enrolled. Clinical features, approaches, outcomes of surgical treatments, and follow-up data of these patients were studied retrospectively. A total of 122 patients underwent single left internal mammary artery （IMA）-left anterior descending artery grafts, whereas the other 386 patients underwent multiple vessel grafts. Results： The average distal anastomosis was 2.34 ± 0.97 （range： 1-4）. All the patients were discharged from hospital except one died. A total of 457 （90.32%） patients were followed up. In the 4-, 7-, and 10-year follow-up groups, the rate of death from any cause was 1.19%, 6.47%, and 10.67%; rate of cardiac death was 0.60%, 2.88%, and 3.33%; rate of repeat revascularization was 0.00%, 3.60%. and 8.67%; rate ofischemic symptoms was 1.79%, 7.91%, and 11.33%; and incidence of stroke was 2.38%, 4.32%, and 6.67%, respectively. Poor medication adherence was observed in 9.38% of the follow-up population. Conclusions： Total arterial OPCAB with bilateral IMA, radial artery, and right gastroepiploic artery grafting yielded satisfactory early and midterm outcomes in this patient group, without a significant increase in early mortality or morbidity. Moreover, the long-term outcomes are also positive.展开更多
In this paper, we studied the effects of thermal radiation, Joule heating and viscous dissipation on forced convection flow in a magnetohydrodynamics (namely MHD) pump in rectangular channel with uniform surface tempe...In this paper, we studied the effects of thermal radiation, Joule heating and viscous dissipation on forced convection flow in a magnetohydrodynamics (namely MHD) pump in rectangular channel with uniform surface temperature. Numerical results were obtained by solving the nonlinear governing momentum and energy equations with steady state fully developed assumptions by finite difference method. The Lorentz force in momentum and Joule heating, and viscous dissipation in energy equation with the Rossel and approximation are assumed to increase the knowledge of the details of the temperature and flow field in order to design a MHD pump. The purpose of this study is the parametric study of a Newtonian fluid in a MHD pump. The values of maximum velocity, fully developed Nusselt number for different values of magnetic density flux, Brinkman number, viscous heating and radiation number are obtained. However, the maximum temperature stays almost constant with magnetic field, as current increases, the velocity and the temperature increase too. Besides, the increase of thermal radiation number causes the increase in effective thermal conductivity and decrease in thermal boundary layer and the Nusselt number at wall.展开更多
The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase s...The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.展开更多
文摘Based on the standard k-ε turbulence model and the RANS equations, thefinite volume method and the SIMPLE algorithm were adopted to carry out the three-dimensionalviscous numerical simulation of the internal flow within a vortex pump in double reference frames.According to the results of numerical simulation, the internal flow in the vortex pump was analyzed,and the calculated results of blade surface pressure of the impeller were compared withexperimental results. The maximum relative error is 6.6% between calculated value and experimentalvalue of the pump head under operation conditions.
文摘Objective To evaluate the outcome of off-pump coronary artery bypass grafting （OPCABG） using a bilateral internal mammary artery （BIMA） Y configuration graft to achieve total arterial myocardial revascularization. Methods From October 2002 to December 2008, 208 patients （196 males and 12 females） underwent OPCABG using a BIMA Y configuration graft. The average age of the patients was 56.5 ± 11.3 years, with an age range of 33-78 years. A total of 167 （80.2%） cases had triple-vessel disease. Left main stem disease was found in 33 （15.9%） cases, and double-vessel disease was found in 8 （3.9%） cases. The semi-skeletonization technique was used to harvest the two internal mammary arteries （IMAs）, and then the free right internal mammary artery was connected end-to-side to the left internal mammary artery （LIMA） in situ to complete the Y configuration graft. Off-pump and sequential anastomosis methods were used to perform coronary artery bypass surgery in all patients. Graft patency was assessed intm-operatively with the HT311 transit time flowmeter. Results A total of 728 distal anastomoses were performed in 208 patients, with the average being 3.5± 1.3 per person. No one died or experienced recurrent angina within 30 days after the operation. Conclusions OPCABG using the BIMA Y graft was safe and effective to achieve total arterial revascularization. This method avoids surgical operation on the ascending aorta and other incisions.
基金This study was funded by a grant from the National Natural Science Foundation of China （No. 81370237）.
文摘Background： Arterial grafts had better mid-term and long-term patency than saphenous vein grafts in coronary artery bypass grafting （CABG）. We summarized our experience with total arterial off-pump coronary artery bypass grafting （OPCAB） and assessed the early clinical results, surgical complications, and follow-up. Methods： From January 2007 to May 2017,508 coronary artery disease patients undergoing total arterial OPCAB were enrolled. Clinical features, approaches, outcomes of surgical treatments, and follow-up data of these patients were studied retrospectively. A total of 122 patients underwent single left internal mammary artery （IMA）-left anterior descending artery grafts, whereas the other 386 patients underwent multiple vessel grafts. Results： The average distal anastomosis was 2.34 ± 0.97 （range： 1-4）. All the patients were discharged from hospital except one died. A total of 457 （90.32%） patients were followed up. In the 4-, 7-, and 10-year follow-up groups, the rate of death from any cause was 1.19%, 6.47%, and 10.67%; rate of cardiac death was 0.60%, 2.88%, and 3.33%; rate of repeat revascularization was 0.00%, 3.60%. and 8.67%; rate ofischemic symptoms was 1.79%, 7.91%, and 11.33%; and incidence of stroke was 2.38%, 4.32%, and 6.67%, respectively. Poor medication adherence was observed in 9.38% of the follow-up population. Conclusions： Total arterial OPCAB with bilateral IMA, radial artery, and right gastroepiploic artery grafting yielded satisfactory early and midterm outcomes in this patient group, without a significant increase in early mortality or morbidity. Moreover, the long-term outcomes are also positive.
文摘In this paper, we studied the effects of thermal radiation, Joule heating and viscous dissipation on forced convection flow in a magnetohydrodynamics (namely MHD) pump in rectangular channel with uniform surface temperature. Numerical results were obtained by solving the nonlinear governing momentum and energy equations with steady state fully developed assumptions by finite difference method. The Lorentz force in momentum and Joule heating, and viscous dissipation in energy equation with the Rossel and approximation are assumed to increase the knowledge of the details of the temperature and flow field in order to design a MHD pump. The purpose of this study is the parametric study of a Newtonian fluid in a MHD pump. The values of maximum velocity, fully developed Nusselt number for different values of magnetic density flux, Brinkman number, viscous heating and radiation number are obtained. However, the maximum temperature stays almost constant with magnetic field, as current increases, the velocity and the temperature increase too. Besides, the increase of thermal radiation number causes the increase in effective thermal conductivity and decrease in thermal boundary layer and the Nusselt number at wall.
基金This project is supported by National Natural Science Foundation of China(No.10342003).
文摘The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.
