This work deals with the estimation of solar radiation through a solar tracker aimed at evaluating the effect of solar tracking on the solar deposit in Burkina Faso. Using a two-axis solar tracking system, we experime...This work deals with the estimation of solar radiation through a solar tracker aimed at evaluating the effect of solar tracking on the solar deposit in Burkina Faso. Using a two-axis solar tracking system, we experimentally measured solar radiation at our Joseph KI-ZERBO University site and compared it with that obtained by a numerical simulation run using Fortran programming software based on a mathematical model by Brichambaut. The results obtained from the mathematical and experimental studies show that, with a solar tracker, on a clear-sky day, solar irradiation is between 800 W·m−2 and 1000 W·m−2 between about 8 a.m. and 4 p.m., i.e. a duration of 8 hours of insolation. Analysis of the numerical and experimental results shows very good quantitative and qualitative agreement, with an average relative error of 18%.展开更多
In order to satisfy the machining requirements of aero-engine casing in modern aviation industry, this paper investigates three main issues during the design and development process of a five-axis machine tool with hi...In order to satisfy the machining requirements of aero-engine casing in modern aviation industry, this paper investigates three main issues during the design and development process of a five-axis machine tool with high accuracy, stiffness and efficiency, including whole structure design,key components design, and supporting stiffness design. First, an appropriate structure of five-axis machine tool is determined considering the processing characteristics of aero-engine casing. Then, a dual drive swing head and a compact motorized spindle are designed with enough drive capability and stiffness, and related structure, assembly method, cooling technology, and performance simulation are given in detail. Next, a design method of supporting stiffness of guide is proposed through the deformation prediction of the spindle end. Based on above work, a prototype of machine tool is developed, and some experiments are carried out, including performance tests of swing head and motorized spindle, and machining of a simulated workpiece of aero-engine casing. All experimental results show that the machine tool has satisfactory accuracy, stiffness and efficiency, which meets the machining requirements of aero-engine casing. The main work can be used as references for engineers and technicians, which are meaningful in practice.展开更多
Background Dual-axis rotational coronary angiography （DARCA） was developed as an innovative adaptation of rotational angiography （RA）, but it requires a longer coronary injection compared to standard coronary angi...Background Dual-axis rotational coronary angiography （DARCA） was developed as an innovative adaptation of rotational angiography （RA）, but it requires a longer coronary injection compared to standard coronary angiography （SA）. As the body of the average Chinese patient is smaller than that of most western patients, with the same contrast injection time, the risk of complications from the contrast agent is increased in this population. The purpose of this study was to assess the clinical safety and efficacy of DARCA in the diagnosis of coronary artery disease （CAD） in the Chinese population by directly comparing it to SA. Methods Two hundred Chinese patients were randomized to either the SA group （n=100） or DARCA group （n=100）. Contrast utilization, radiation exposure and procedure time were recorded for each modalities. Blood pressure （BP）, heart rate （HR） pre and post injection symptoms and any arrhythmias were recorded. Results Compared to the SA group, there was a 42% reduction in contrast utilization, 55% reduction in radiation exposure and a 31% shorter procedure time in the DARCA group. In both groups, there were slight declines in the systolic BP values in the left coronary artery （LCA） post injection （P 〈0.01）. Moreover, post injection HRs for the LCA were also reduced in the DARCA group （P 〈0.01）. But all of these changes were small, transient and without clinical importance. Only one patient （1%） in the DARCA group had an attack of ventricular tachycardia immediately post injection and it resolved by itself during LCA angiography. No arrhythmias occurred in the SA group. Conclusion DARCA is a safe, efficient, and clinically comparable alternative to SA in the diagnosis of coronary artery disease in the Chinese population with less contrast utilized, which is less radiation exposure and a shorter procedure展开更多
Dual axis laser scanning diameter measuring gauge system(DALSDMGS) with PID controller,which can be used for online non-contact diameter measuring and control on the hose,wire and rod production line,is introduced.The...Dual axis laser scanning diameter measuring gauge system(DALSDMGS) with PID controller,which can be used for online non-contact diameter measuring and control on the hose,wire and rod production line,is introduced.The measure principle and im-plementation of this system are also presented.A PID control module with PID parameters tuning is included in the measuring and control system,which functions as a PID automatic controller of the diameter.展开更多
This paper developed a theoretical model substantially based on the principle that only the normal component of solar radiation is actually converted into electrical energy. This theoretical model helped to predict mi...This paper developed a theoretical model substantially based on the principle that only the normal component of solar radiation is actually converted into electrical energy. This theoretical model helped to predict minimum and maximum daily energy gain (compared to static PV system tilted with certain angle) when using dual axis PV solar tracking systems, at any given location on earth without prior experimental data. Based on equations derived from model, minimum and maximum energy gain </span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> computed and summarized in tables of minimum and maximum. Furthermore</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> the model equations could be used to set up future experimental studies related to the matter.展开更多
文摘This work deals with the estimation of solar radiation through a solar tracker aimed at evaluating the effect of solar tracking on the solar deposit in Burkina Faso. Using a two-axis solar tracking system, we experimentally measured solar radiation at our Joseph KI-ZERBO University site and compared it with that obtained by a numerical simulation run using Fortran programming software based on a mathematical model by Brichambaut. The results obtained from the mathematical and experimental studies show that, with a solar tracker, on a clear-sky day, solar irradiation is between 800 W·m−2 and 1000 W·m−2 between about 8 a.m. and 4 p.m., i.e. a duration of 8 hours of insolation. Analysis of the numerical and experimental results shows very good quantitative and qualitative agreement, with an average relative error of 18%.
基金co-supported by the Natural Science Foundation of Beijing(No.3214043)the Project of State Key Lab of Tribology of Tsinghua University(No.SKLT2021D16)the National Natural Science Foundation of China(No.51975319)。
文摘In order to satisfy the machining requirements of aero-engine casing in modern aviation industry, this paper investigates three main issues during the design and development process of a five-axis machine tool with high accuracy, stiffness and efficiency, including whole structure design,key components design, and supporting stiffness design. First, an appropriate structure of five-axis machine tool is determined considering the processing characteristics of aero-engine casing. Then, a dual drive swing head and a compact motorized spindle are designed with enough drive capability and stiffness, and related structure, assembly method, cooling technology, and performance simulation are given in detail. Next, a design method of supporting stiffness of guide is proposed through the deformation prediction of the spindle end. Based on above work, a prototype of machine tool is developed, and some experiments are carried out, including performance tests of swing head and motorized spindle, and machining of a simulated workpiece of aero-engine casing. All experimental results show that the machine tool has satisfactory accuracy, stiffness and efficiency, which meets the machining requirements of aero-engine casing. The main work can be used as references for engineers and technicians, which are meaningful in practice.
文摘Background Dual-axis rotational coronary angiography （DARCA） was developed as an innovative adaptation of rotational angiography （RA）, but it requires a longer coronary injection compared to standard coronary angiography （SA）. As the body of the average Chinese patient is smaller than that of most western patients, with the same contrast injection time, the risk of complications from the contrast agent is increased in this population. The purpose of this study was to assess the clinical safety and efficacy of DARCA in the diagnosis of coronary artery disease （CAD） in the Chinese population by directly comparing it to SA. Methods Two hundred Chinese patients were randomized to either the SA group （n=100） or DARCA group （n=100）. Contrast utilization, radiation exposure and procedure time were recorded for each modalities. Blood pressure （BP）, heart rate （HR） pre and post injection symptoms and any arrhythmias were recorded. Results Compared to the SA group, there was a 42% reduction in contrast utilization, 55% reduction in radiation exposure and a 31% shorter procedure time in the DARCA group. In both groups, there were slight declines in the systolic BP values in the left coronary artery （LCA） post injection （P 〈0.01）. Moreover, post injection HRs for the LCA were also reduced in the DARCA group （P 〈0.01）. But all of these changes were small, transient and without clinical importance. Only one patient （1%） in the DARCA group had an attack of ventricular tachycardia immediately post injection and it resolved by itself during LCA angiography. No arrhythmias occurred in the SA group. Conclusion DARCA is a safe, efficient, and clinically comparable alternative to SA in the diagnosis of coronary artery disease in the Chinese population with less contrast utilized, which is less radiation exposure and a shorter procedure
文摘Dual axis laser scanning diameter measuring gauge system(DALSDMGS) with PID controller,which can be used for online non-contact diameter measuring and control on the hose,wire and rod production line,is introduced.The measure principle and im-plementation of this system are also presented.A PID control module with PID parameters tuning is included in the measuring and control system,which functions as a PID automatic controller of the diameter.
文摘This paper developed a theoretical model substantially based on the principle that only the normal component of solar radiation is actually converted into electrical energy. This theoretical model helped to predict minimum and maximum daily energy gain (compared to static PV system tilted with certain angle) when using dual axis PV solar tracking systems, at any given location on earth without prior experimental data. Based on equations derived from model, minimum and maximum energy gain </span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> computed and summarized in tables of minimum and maximum. Furthermore</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> the model equations could be used to set up future experimental studies related to the matter.
