A bi-objective optimization problem for flapping airfoils is solved to maximize the time-averaged thrust coefficient and the propulsive efficiency. Design variables include the plunging amplitude, the pitching amplitu...A bi-objective optimization problem for flapping airfoils is solved to maximize the time-averaged thrust coefficient and the propulsive efficiency. Design variables include the plunging amplitude, the pitching amplitude and the phase shift angle. A well defined Kriging model is used to substitute the time-consuming high fidelity model, and a multi-objective genetic algorithm is employed as the search algorithm. The optimization results show that the propulsive efficiency can be improved by reducing the plunging amplitude and the phase shift angle in a proper way. The results of global sensitivity analysis using the Sobol’s method show that both of the time-averaged thrust coefficient and the propulsive efficiency are most sensitive to the plunging amplitude, and second most sensitive to the pitching amplitude. It is also observed that the phase shift angle has an un-negligible influence on the propulsive efficiency, and has little effect on the time-averaged thrust coefficient.展开更多
HAISHEN is a long-ranged and highly maneuverable AUV which has two operating modes： glider mode and flapping-foil propulsion mode. As part of the vehicle development, a three-dimensional mathematical model of the con...HAISHEN is a long-ranged and highly maneuverable AUV which has two operating modes： glider mode and flapping-foil propulsion mode. As part of the vehicle development, a three-dimensional mathematical model of the conceptual vehicle was developed on the assumption that HAISHEN has a rigid body with two independently controlled oscillating hydrofoils. A flapping-foil model was developed based on the work done by Georgiades et al. （2009）. Effect of controllable hydrofoils on the vehicle stable motion performance was studied theoretically. Finally, a dynamics simulation of the vehicle in both operating modes is created in this paper. The simulation demonstrates that： （1） in the glider mode, owing to the independent control of the pitch angle of each hydrofoil, HAISHEN travels faster and more efficiently and has a smaller turning radius than conventional fix-winged gliders; （2） in the flapping-foil propulsion mode, HAISHEN has a high maneuverability with a turning radius smaller than 15 m and a forward motion velocity about 1.8 m/s; （3） the vehicle is stable under all expected operating conditions.展开更多
Linked tetra shaft and double cantilever flat flap gate is a new type of structure in water conservancy projects,but the traditional method is now adopted in its design.In order to the application and dissemination ...Linked tetra shaft and double cantilever flat flap gate is a new type of structure in water conservancy projects,but the traditional method is now adopted in its design.In order to the application and dissemination of the type of sluice,this paper researches the difficult points of design advance,through researching the motion locus & stress coundition of linked tetra shaft system.The writer will build up the mathmatical model and handle it with the computer.Thus,we can achieve the modern desing on the basis of the software of linked tetra shaft system development.展开更多
A theoretical modeling approach as well as an unsteady analytical method is used to study aerodynamic characteristics of wing flapping with asymmetric stroke-cycles in connection with an oblique stroke plane during in...A theoretical modeling approach as well as an unsteady analytical method is used to study aerodynamic characteristics of wing flapping with asymmetric stroke-cycles in connection with an oblique stroke plane during insect forward flight. It is revealed that the aerodynamic asymmetry between the downstroke and the upstroke due to stroke-asymmetrical flapping is a key to understand the flow physics of generation and modulation of the lift and the thrust. Predicted results for examples of given kinematics validate more specifically some viewpoints that the wing lift is more easily produced when the forward speed is higher and the thrust is harder, and the lift and the thrust are generated mainly during downstroke and upstroke, respectively. The effects of three controlling parameters, i.e. the angles of tilted stroke plane, the different downstroke duration ratios, and the different angles of attack in both down- and up-stroke, are further discussed. It is found that larger oblique angles of stroke planes generate larger thrust but smaller lift; larger downstroke duration ratios lead to larger thrust, while making little change in lift and input aerodynamic power; and again, a small increase of the angle of attack in downstroke or upstroke may cause remarkable changes in aerodynamic performance in the relevant stroke.展开更多
Objectives:?The early healing of the periodontal wound in oral cavity may be critical to the treatment outcome. Thus, we made a novel ointment based on natural constituents that our recent investigation suggested a po...Objectives:?The early healing of the periodontal wound in oral cavity may be critical to the treatment outcome. Thus, we made a novel ointment based on natural constituents that our recent investigation suggested a positive therapeutic effects on gingival wounds. The present study was conducted to evaluate the role of this novel biomaterial on periodontal wound healing including soft as well as hard tissue. Materials and Methods: Experimental periodontitis was induced by wire tied around the cement-enamel junction of I2, P1, P3?and M1?in six adult, healthy beagle dogs. After 3 months, mucoperiostal flap elevated and root surfaced was thoroughly scaled and planed. Randomly, three materials including our ointment with two different ratios including materials A and B and hyluronic acid were applied topically and then the flaps were repositioned and sutured. Three dogs at day 7 and the three remaining ones two weeks post-surgery were sacrificed and histological changes were monitored. Results: The result of this study showed that the local applications of this novel ointment promoted the healing process particularly fibroblast proliferation and collagen density remarkably in comparison with hyaluronic acid and control group. Besides, histological finding of our material revealed that in general terms had all the hallmarks of complete healing two weeks post operatively. Conclusion: Our novel material appeared to have outstanding effect on periodontal wound healing which can improve the periodontal healing consequences and provide better strength of periodontal wound flap. From a clinical standpoint, it could play an important role for better repair in diabetic patients who frequently present difficulties in mucosal and cutanous wound healing.展开更多
基金Supported by the National Science Foundation for Post-doctoral Scientists of China (20090460216 )the National Defense Fundamental Research Foundation of China(B222006060)
文摘A bi-objective optimization problem for flapping airfoils is solved to maximize the time-averaged thrust coefficient and the propulsive efficiency. Design variables include the plunging amplitude, the pitching amplitude and the phase shift angle. A well defined Kriging model is used to substitute the time-consuming high fidelity model, and a multi-objective genetic algorithm is employed as the search algorithm. The optimization results show that the propulsive efficiency can be improved by reducing the plunging amplitude and the phase shift angle in a proper way. The results of global sensitivity analysis using the Sobol’s method show that both of the time-averaged thrust coefficient and the propulsive efficiency are most sensitive to the plunging amplitude, and second most sensitive to the pitching amplitude. It is also observed that the phase shift angle has an un-negligible influence on the propulsive efficiency, and has little effect on the time-averaged thrust coefficient.
文摘HAISHEN is a long-ranged and highly maneuverable AUV which has two operating modes： glider mode and flapping-foil propulsion mode. As part of the vehicle development, a three-dimensional mathematical model of the conceptual vehicle was developed on the assumption that HAISHEN has a rigid body with two independently controlled oscillating hydrofoils. A flapping-foil model was developed based on the work done by Georgiades et al. （2009）. Effect of controllable hydrofoils on the vehicle stable motion performance was studied theoretically. Finally, a dynamics simulation of the vehicle in both operating modes is created in this paper. The simulation demonstrates that： （1） in the glider mode, owing to the independent control of the pitch angle of each hydrofoil, HAISHEN travels faster and more efficiently and has a smaller turning radius than conventional fix-winged gliders; （2） in the flapping-foil propulsion mode, HAISHEN has a high maneuverability with a turning radius smaller than 15 m and a forward motion velocity about 1.8 m/s; （3） the vehicle is stable under all expected operating conditions.
文摘Linked tetra shaft and double cantilever flat flap gate is a new type of structure in water conservancy projects,but the traditional method is now adopted in its design.In order to the application and dissemination of the type of sluice,this paper researches the difficult points of design advance,through researching the motion locus & stress coundition of linked tetra shaft system.The writer will build up the mathmatical model and handle it with the computer.Thus,we can achieve the modern desing on the basis of the software of linked tetra shaft system development.
基金The project supported by the National Natural Science Foundation of China(10072066,90305009) the Chinese Academy of Sciences(KJCX-SW-L04,KJCX2-SW-L2)
文摘A theoretical modeling approach as well as an unsteady analytical method is used to study aerodynamic characteristics of wing flapping with asymmetric stroke-cycles in connection with an oblique stroke plane during insect forward flight. It is revealed that the aerodynamic asymmetry between the downstroke and the upstroke due to stroke-asymmetrical flapping is a key to understand the flow physics of generation and modulation of the lift and the thrust. Predicted results for examples of given kinematics validate more specifically some viewpoints that the wing lift is more easily produced when the forward speed is higher and the thrust is harder, and the lift and the thrust are generated mainly during downstroke and upstroke, respectively. The effects of three controlling parameters, i.e. the angles of tilted stroke plane, the different downstroke duration ratios, and the different angles of attack in both down- and up-stroke, are further discussed. It is found that larger oblique angles of stroke planes generate larger thrust but smaller lift; larger downstroke duration ratios lead to larger thrust, while making little change in lift and input aerodynamic power; and again, a small increase of the angle of attack in downstroke or upstroke may cause remarkable changes in aerodynamic performance in the relevant stroke.
文摘Objectives:?The early healing of the periodontal wound in oral cavity may be critical to the treatment outcome. Thus, we made a novel ointment based on natural constituents that our recent investigation suggested a positive therapeutic effects on gingival wounds. The present study was conducted to evaluate the role of this novel biomaterial on periodontal wound healing including soft as well as hard tissue. Materials and Methods: Experimental periodontitis was induced by wire tied around the cement-enamel junction of I2, P1, P3?and M1?in six adult, healthy beagle dogs. After 3 months, mucoperiostal flap elevated and root surfaced was thoroughly scaled and planed. Randomly, three materials including our ointment with two different ratios including materials A and B and hyluronic acid were applied topically and then the flaps were repositioned and sutured. Three dogs at day 7 and the three remaining ones two weeks post-surgery were sacrificed and histological changes were monitored. Results: The result of this study showed that the local applications of this novel ointment promoted the healing process particularly fibroblast proliferation and collagen density remarkably in comparison with hyaluronic acid and control group. Besides, histological finding of our material revealed that in general terms had all the hallmarks of complete healing two weeks post operatively. Conclusion: Our novel material appeared to have outstanding effect on periodontal wound healing which can improve the periodontal healing consequences and provide better strength of periodontal wound flap. From a clinical standpoint, it could play an important role for better repair in diabetic patients who frequently present difficulties in mucosal and cutanous wound healing.
