This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined d...This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined directly on an aluminum plate(180 mm×120 mm×3 mm) covered by a transparent plate.The working fluid employed is ethanol.As a result,various flow patterns and their transitions are observed and found to be related to the fluid fill ratio,input heat load and the device orientation.Also the operational characteristics and working mechanism are discussed.展开更多
In this paper,the dynamic evolution for a dualarm space robot capturing a spacecraft is studied,the impact effect and the coordinated stabilization control problem for postimpact closed chain system are discussed.At f...In this paper,the dynamic evolution for a dualarm space robot capturing a spacecraft is studied,the impact effect and the coordinated stabilization control problem for postimpact closed chain system are discussed.At first,the pre-impact dynamic equations of open chain dual-arm space robot are established by Lagrangian approach,and the dynamic equations of a spacecraft are obtained by Newton-Euler method.Based on the results,with the process of integral and simplify,the response of the dual-arm space robot impacted by the spacecraft is analyzed by momentum conservation law and force transfer law.The closed chain system is formed in the post-impact phase.Closed chain constraint equations are obtained by the constraints of closed-loop geometry and kinematics.With the closed chain constraint equations,the composite system dynamic equations are derived.Secondly,the recurrent fuzzy neural network control scheme is designed for calm motion of unstable closed chain system with uncertain system parameter.In order to overcome the effects of uncertain system inertial parameters,the recurrent fuzzy neural network is used to approximate the unknown part,the control method with H∞tracking characteristic.According to the Lyapunov theory,the global stability is demonstrated.Meanwhile,the weighted minimum-norm theory is introduced to distribute torques guarantee that cooperative operation between manipulators.At last,numerical examples simulate the response of the collision,and the efficiency of the control scheme is verified by the simulation results.展开更多
Microcellular combustible objects for application of combustible case,caseless ammunition or combustible detonator-holding tubes are fabricated through one-step foaming process,in which supercritical CO_2 is used as f...Microcellular combustible objects for application of combustible case,caseless ammunition or combustible detonator-holding tubes are fabricated through one-step foaming process,in which supercritical CO_2 is used as foaming agent.The formulations consist of inert polymer binder and ultra fine RDX.For the inner porous structures of microcellular combustible objects,the cell sizes present a unimodal or bimodal distribution by adjusting the foaming conditions.Closed bomb test is to investigate the influence of both porous structure style and RDX content on burning behavior.The sample with bimodal distribution of cell sizes burns faster than that with unimodal distribution,and the concentration of RDX can influence the burning characteristics in a positive manner.In addition,the translation of laminar burning to convective burning is determined by burning rate versus pressure curves of samples at two different loading densities,and the resulting transition pressure is 30 MPa.Moreover,the samples with bigger sample size present higher burning rate,resulting in providing deeper convective depth.Dynamic vivacity of samples is also studied.The results show that the vivacity increases with RDX content and varies with inner structure.展开更多
Traditional magneto-electric vibration sensors and servo accelerometers have severe shortcomings when used to measure vibration where low frequency components predominate.A low frequency characteristic extension for v...Traditional magneto-electric vibration sensors and servo accelerometers have severe shortcomings when used to measure vibration where low frequency components predominate.A low frequency characteristic extension for velocity vibration sensors is presented in this paper.The passive circuit technology,active compensation technology and the closed- cycle pole compensation technology are used to extend the measurable range and to improve low frequency characteristics of sensors.Thses three types of low frequency velocity vibration sensors have been developed and widely adopted in China.展开更多
基金the Ger man National Science Foundation (GR-412/33-2)Shanghai Leading Academic Discipline Project (No.B604)
文摘This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined directly on an aluminum plate(180 mm×120 mm×3 mm) covered by a transparent plate.The working fluid employed is ethanol.As a result,various flow patterns and their transitions are observed and found to be related to the fluid fill ratio,input heat load and the device orientation.Also the operational characteristics and working mechanism are discussed.
基金supported by the National Natural Science Foundation of China(11372073,11072061)。
文摘In this paper,the dynamic evolution for a dualarm space robot capturing a spacecraft is studied,the impact effect and the coordinated stabilization control problem for postimpact closed chain system are discussed.At first,the pre-impact dynamic equations of open chain dual-arm space robot are established by Lagrangian approach,and the dynamic equations of a spacecraft are obtained by Newton-Euler method.Based on the results,with the process of integral and simplify,the response of the dual-arm space robot impacted by the spacecraft is analyzed by momentum conservation law and force transfer law.The closed chain system is formed in the post-impact phase.Closed chain constraint equations are obtained by the constraints of closed-loop geometry and kinematics.With the closed chain constraint equations,the composite system dynamic equations are derived.Secondly,the recurrent fuzzy neural network control scheme is designed for calm motion of unstable closed chain system with uncertain system parameter.In order to overcome the effects of uncertain system inertial parameters,the recurrent fuzzy neural network is used to approximate the unknown part,the control method with H∞tracking characteristic.According to the Lyapunov theory,the global stability is demonstrated.Meanwhile,the weighted minimum-norm theory is introduced to distribute torques guarantee that cooperative operation between manipulators.At last,numerical examples simulate the response of the collision,and the efficiency of the control scheme is verified by the simulation results.
基金funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Microcellular combustible objects for application of combustible case,caseless ammunition or combustible detonator-holding tubes are fabricated through one-step foaming process,in which supercritical CO_2 is used as foaming agent.The formulations consist of inert polymer binder and ultra fine RDX.For the inner porous structures of microcellular combustible objects,the cell sizes present a unimodal or bimodal distribution by adjusting the foaming conditions.Closed bomb test is to investigate the influence of both porous structure style and RDX content on burning behavior.The sample with bimodal distribution of cell sizes burns faster than that with unimodal distribution,and the concentration of RDX can influence the burning characteristics in a positive manner.In addition,the translation of laminar burning to convective burning is determined by burning rate versus pressure curves of samples at two different loading densities,and the resulting transition pressure is 30 MPa.Moreover,the samples with bigger sample size present higher burning rate,resulting in providing deeper convective depth.Dynamic vivacity of samples is also studied.The results show that the vivacity increases with RDX content and varies with inner structure.
基金The Ministry of Science and Technology Special Foundation Grant No.217Harbin Important Science Technology Foundation Grant No.0014211044
文摘Traditional magneto-electric vibration sensors and servo accelerometers have severe shortcomings when used to measure vibration where low frequency components predominate.A low frequency characteristic extension for velocity vibration sensors is presented in this paper.The passive circuit technology,active compensation technology and the closed- cycle pole compensation technology are used to extend the measurable range and to improve low frequency characteristics of sensors.Thses three types of low frequency velocity vibration sensors have been developed and widely adopted in China.
