Combining high precision numerical analysis methods with optimization algorithms to make a systematic exploration of a design space has become an important topic in the modern design methods. During the design process...Combining high precision numerical analysis methods with optimization algorithms to make a systematic exploration of a design space has become an important topic in the modern design methods. During the design process of an underwater glider＇s flying-wing structure, a surrogate model is introduced to decrease the computation time for a high precision analysis. By these means, the contradiction between precision and efficiency is solved effectively. Based on the parametric geometry modeling, mesh generation and computational fluid dynamics analysis, a surrogate model is constructed by adopting the design of experiment （DOE） theory to solve the multi-objects design optimization problem of the underwater glider. The procedure of a surrogate model construction is presented, and the Gaussian kernel function is specifically discussed. The Particle Swarm Optimization （PSO） algorithm is applied to hydrodynamic design optimization. The hydrodynamic performance of the optimized flying-wing structure underwater glider increases by 9.1%.展开更多
Sail is the core part of autonomous sailboat and wing sail is a new type of sail. Wing sail generates not only propulsion but also lateral force and heeling moment. The latter two will affect the navigation status and...Sail is the core part of autonomous sailboat and wing sail is a new type of sail. Wing sail generates not only propulsion but also lateral force and heeling moment. The latter two will affect the navigation status and bring resistance. Double sail can effectively reduce the center of wind pressure and heeling moment. In order to study the effect of distance between two sails, airfoil and attack angle on the total lift coefficient of double sail propulsion system, pressure coefficient distribution and lift coefficient calculation model have been established based on vortex panel method. By using the basic finite solution, the fluid dynamic forces on the two-dimensional sails are computed.The results show that, the distance in the range of 0 to 1 time chord length, when using the same airfoil in the fore and aft sail, the total lift coefficient of the double sail increases with the increase of distance, finally reaches a stable value in the range of one to three times chord length. Lift coefficients of thicker airfoils are more sensitive to the change of distance. The thicker the airfoil, the longer distance is required of the total lift coefficient toward stable.When different airfoils are adopted in fore and aft sail, the total lift coefficient increases with the increase of the thickness of aft sail. The smaller the thickness difference is, the more sensitive to the distance change the lift coefficient is. The thinner the fore sail is, the lower the influence will be on the lift coefficient of aft sail.展开更多
This paper presents autonomous docking of an inhouse built resident Remotely Operated Vehicle(ROV),called Rover ROV,through acoustic guided techniques.A novel cage-type docking station has been developed.The docking s...This paper presents autonomous docking of an inhouse built resident Remotely Operated Vehicle(ROV),called Rover ROV,through acoustic guided techniques.A novel cage-type docking station has been developed.The docking station can be placed on a deep-sea lander,taking the Rover ROV to the seafloor.Instead of using vision-based pose estimation techniques and expensive navigation sensors,the Rover ROV docking adopts an ultra-short baseline(USBL)and low-cost inertial sensors to build an adaptive fault-tolerant integrated navigation system.To solve the problem of sonar-based failure positioning,the measurement residuals are exploited to detect measurement faults.Then,an adaptation scheme for estimating the statistical characteristics of noise in real-time is proposed,which can provide robust and smooth positioning results.It is more suitable for a compact and low-cost deep-sea resident ROV.Field experiments have been conducted successfully in the Qiandao Lake and the South China Sea area with a depth of 3000 m,respectively.The experimental results show that the functionality of autonomous docking has been achieved.Under the guidance of the navigation system,the Rover ROV can autonomously and efficiently return to the docking station within a range of 100 m even when the amounts of outliers exist in the acoustic positioning data.These achievements can be applied to current ROVs by an easy retrofit.展开更多
Background Hepatectomy is a standard hepatic surgica line with improvements in surgical techniques. This study with hepatectomy. technique. The safety of hepatectomy has been improved in analyzed the operative and per...Background Hepatectomy is a standard hepatic surgica line with improvements in surgical techniques. This study with hepatectomy. technique. The safety of hepatectomy has been improved in analyzed the operative and perioperative factors associated Methods A total of 2008 patients who underwent consecutive hepatectomies between January 1986 and December 2005 were investigated retrospectively. Diagnoses were made based on pathological findings. Results Malignant and benign liver diseases accounted for 58.5% and 41.2%, respectively, of the conditions requiring resections. Primary liver cancers accounted for 76.1% of the malignant tumors, while hilar cholangiocarcinomas accounted for 6.7%. Hemangiomas （41.7%） and hepatolithiasis （29.6%） were the most common of the benign conditions. Microwave in-line coagulation was used in 236 of our liver resection cases. The overall postoperative complication rate was 14.44%, of which 12.54% of resections were performed for primary liver cancer, 16.40% for secondary liver cancer, and 16.32% for hepatolithiasis. The overall hospital mortality was 0.55%, and that for malignant liver disease was 0.51%. A high mortality （2.53%） was associated with extensive liver resections for hilar cholangiocarcinomas （two deaths in 79 cases）. Microwave in-line pre-coagulation resection, Child-Pugh grading, operating time, postoperative length of stay, and preoperative serum albumin level were independent predictors of morbidity. Blood loss, Child-Pugh grading, operating time and preoperative serum albumin level were independent predictors of mortality. Conclusions Hepatectomy can be performed safely with low morbidity and mortality, provided that it is carried out with optimal perioperative management and innovative surgical techniques.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.61233013)
文摘Combining high precision numerical analysis methods with optimization algorithms to make a systematic exploration of a design space has become an important topic in the modern design methods. During the design process of an underwater glider＇s flying-wing structure, a surrogate model is introduced to decrease the computation time for a high precision analysis. By these means, the contradiction between precision and efficiency is solved effectively. Based on the parametric geometry modeling, mesh generation and computational fluid dynamics analysis, a surrogate model is constructed by adopting the design of experiment （DOE） theory to solve the multi-objects design optimization problem of the underwater glider. The procedure of a surrogate model construction is presented, and the Gaussian kernel function is specifically discussed. The Particle Swarm Optimization （PSO） algorithm is applied to hydrodynamic design optimization. The hydrodynamic performance of the optimized flying-wing structure underwater glider increases by 9.1%.
基金financially supported by the JIANG Xinsong Innovation Fund(Grant No.Y8F7010701)
文摘Sail is the core part of autonomous sailboat and wing sail is a new type of sail. Wing sail generates not only propulsion but also lateral force and heeling moment. The latter two will affect the navigation status and bring resistance. Double sail can effectively reduce the center of wind pressure and heeling moment. In order to study the effect of distance between two sails, airfoil and attack angle on the total lift coefficient of double sail propulsion system, pressure coefficient distribution and lift coefficient calculation model have been established based on vortex panel method. By using the basic finite solution, the fluid dynamic forces on the two-dimensional sails are computed.The results show that, the distance in the range of 0 to 1 time chord length, when using the same airfoil in the fore and aft sail, the total lift coefficient of the double sail increases with the increase of distance, finally reaches a stable value in the range of one to three times chord length. Lift coefficients of thicker airfoils are more sensitive to the change of distance. The thicker the airfoil, the longer distance is required of the total lift coefficient toward stable.When different airfoils are adopted in fore and aft sail, the total lift coefficient increases with the increase of the thickness of aft sail. The smaller the thickness difference is, the more sensitive to the distance change the lift coefficient is. The thinner the fore sail is, the lower the influence will be on the lift coefficient of aft sail.
基金financially supported by the National Key R&D Program of China (Grant No. 2017YFC0306402)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA22040102)
文摘This paper presents autonomous docking of an inhouse built resident Remotely Operated Vehicle(ROV),called Rover ROV,through acoustic guided techniques.A novel cage-type docking station has been developed.The docking station can be placed on a deep-sea lander,taking the Rover ROV to the seafloor.Instead of using vision-based pose estimation techniques and expensive navigation sensors,the Rover ROV docking adopts an ultra-short baseline(USBL)and low-cost inertial sensors to build an adaptive fault-tolerant integrated navigation system.To solve the problem of sonar-based failure positioning,the measurement residuals are exploited to detect measurement faults.Then,an adaptation scheme for estimating the statistical characteristics of noise in real-time is proposed,which can provide robust and smooth positioning results.It is more suitable for a compact and low-cost deep-sea resident ROV.Field experiments have been conducted successfully in the Qiandao Lake and the South China Sea area with a depth of 3000 m,respectively.The experimental results show that the functionality of autonomous docking has been achieved.Under the guidance of the navigation system,the Rover ROV can autonomously and efficiently return to the docking station within a range of 100 m even when the amounts of outliers exist in the acoustic positioning data.These achievements can be applied to current ROVs by an easy retrofit.
文摘Background Hepatectomy is a standard hepatic surgica line with improvements in surgical techniques. This study with hepatectomy. technique. The safety of hepatectomy has been improved in analyzed the operative and perioperative factors associated Methods A total of 2008 patients who underwent consecutive hepatectomies between January 1986 and December 2005 were investigated retrospectively. Diagnoses were made based on pathological findings. Results Malignant and benign liver diseases accounted for 58.5% and 41.2%, respectively, of the conditions requiring resections. Primary liver cancers accounted for 76.1% of the malignant tumors, while hilar cholangiocarcinomas accounted for 6.7%. Hemangiomas （41.7%） and hepatolithiasis （29.6%） were the most common of the benign conditions. Microwave in-line coagulation was used in 236 of our liver resection cases. The overall postoperative complication rate was 14.44%, of which 12.54% of resections were performed for primary liver cancer, 16.40% for secondary liver cancer, and 16.32% for hepatolithiasis. The overall hospital mortality was 0.55%, and that for malignant liver disease was 0.51%. A high mortality （2.53%） was associated with extensive liver resections for hilar cholangiocarcinomas （two deaths in 79 cases）. Microwave in-line pre-coagulation resection, Child-Pugh grading, operating time, postoperative length of stay, and preoperative serum albumin level were independent predictors of morbidity. Blood loss, Child-Pugh grading, operating time and preoperative serum albumin level were independent predictors of mortality. Conclusions Hepatectomy can be performed safely with low morbidity and mortality, provided that it is carried out with optimal perioperative management and innovative surgical techniques.
