Abstract:A robust parametric design method for spacecraft autonomous rendezvous in elliptical orbit without orbit information is developed. Lawden equation with time-varying parameters is used to describe the relative motion of the chaser and the target. With the assumption that the time-varying parameters are unavailable,all the variable parameters in the equation are classified and the elliptical rendezvous model with uncertainties is given,then the eigenstructure assignment approach and the model reference theory based on the robust parameterized method are employed to design robust control law for autonomous rendezvous of spacecrafts on elliptical orbit. To simplify the autonomous rendezvous control system,a constant feedback controller,which stabilizes the system and does not vary with the time-varying,is proposed. Simulation results indicate that the proposed control law can realize autonomous rendezvous in the elliptical orbit.

Abstract:To obtain damage behaviors in hard borosilicate glass,proton-induced ionizing and nonionizing energy loss were calculated by using the SRIM Monte Carlo program. The result shows that for protons with the energy range of 40-200 keV,the main damage is limited to the surface of borosilicate glass,and the ionizing energy loss,with the peak position of 80keV,is the main type of energy loss. The nonionizing energy loss increases with the decreasing of energy and induces the vacancy production of O,Si and B etc. Both vacancy distribution and phonon distribution,similar to the proton deposition,follow the property of Bragg-type curve. Both the ionizing energy loss and nonionizing energy loss by protons with the energy range of 40-200 keV can change the microstructure of hard borosilicate glass.

Abstract:To understand the thermal fracture behavior deeply,the crack-tip characteristics for a functionally graded material ( FGM) plate with arbitrary thermomechanical properties under thermal load were studied. The temperature and thermal stress fields were derived by analytical method,and the loading on the crack faces was determined from the thermal stress distributions by using the superposition method. A finite element method based on nonhomogeneous elements was used to calculate the crack-tip fields of the FGM plate. Considering different distribution forms of the thermomechanical properties,the thermal stress intensity factors ( TSIFs) of the crack-tip were analyzed. It is found that the distribution forms can affect the crack-tip TSIFs greatly, which indicates that the actual situations may not be considered adequately if the material properties of practical FGMs are assumed to be one certain type of functions.

Abstract:Aluminum foam is a new type of material for shield of spacecrafts which bears fine characteristics when subjected to hypervelocity impact of space debris. A microstructure model of geometry for metallic foams was set up based on their manufacturing process and hypervelocity impact numerical simulations were conducted by self-programmed Smooth Particle Hydrodynamics. Six types of Al-foam stuffed shields were calculated and their ballistic limits were compared with each other. The results indicated that shield performance of Al-foam stuffed shield was better than that of solid Al-plate stuffed shield with the same areal density if the Al-foam was stuffed at appropriate position. The analyses of characteristic parameters of debris cloud of different shields indicated that Al-foam had better shield performance on small-size debris. The microstructure of Al-foam could effectively spread the perpendicular momentum of debris cloud and significantly increase the proportion of material liquefaction and gasification in debris cloud through multi-shock.

Abstract:Influence of plastic deformation on magnetic memory effect was investigated by testing magnetic signal of demagnetized smooth and notched specimens under different tensile deformation levels. The magnetic field distribution curve of the smooth specimen is close to linear in elastic and uniform plastic flow stages,and exhibits pronounced abnormal wave in stress concentration zone only when necking occurs,while that of the notched specimen shows distortion characteristic after the specimen yields. The possible reasons underlying the wave height increment are discussed based on dislocation theory. The horizontal curves of the magnetic memory signals can be used to determine the damaging development trend in the stress concentration zone,and the power function relationship between peak-peak value and strain is fitted to evaluate the degree of plastic deformation. Although the fracture mechanisms of smooth and notched specimens are different,the abnormal waves with crest and trough both appear in the localized damage zone,which is useful for identifying stress concentration early.

Abstract:To solve the attitude control problem of a staring-imaging satellite,a new robust controller is proposed in this paper. The robust controller which consists of a PD part and an additional term is very simple and is globally convergent in the presence of parameter uncertainty and external disturbances. The convergence is proven by lyapunov method. Simulation results show that the controller is qualified with excellent robustness and satisfactory control effect.

Abstract:To improve the lateral guidance performance,a new lateral guidance approach based on the dynamic heading error corridor is proposed. The bank reversal is determined by the dynamic heading error threshold which is on-line adjusted according to the reference heading error corridor and the estimated actual lift-to-drag ratio. Near the end of the trajectory,the bank reversal is determined by the terminal heading error predictor which demands the derivative of heading error respect to the velocity and current velocity. The proposed method effectively improves the terminal guidance precision in the presence of aerodynamic model uncertainty,and prevents unnecessary bank reversals. Simulation results validate the effectiveness of the method.

Abstract:Under the constraints of transmission power of the cognitive users,the optimization process of cognitive users’utility was analyzed with Rayleigh Fading model,and then an algorithm based on water-level continually adjustment was proposed to solve the problem of power allocation and communication utility computation. This algorithm was also applied to spectrum allocation,so that a cognitive radio spectrum allocation mechanism based on channel bisection was proposed too. From this,the users’utility under different optimization models could be obtained. Simulation results show that the model based on proportional fairness not only provide fair spectrum allocation,but also has a higher total utility.

Abstract:To suppress the effect that differences of channel in different indoor environment bring to mitigation of ISI for UWB receiver,an adjustable observation window length-fractionally spaced linear equalization ( AOWL-FSLE) equalization receiver is proposed in this paper. The receiver can adaptively select the observation window length according to difference of channel. Simulation results show that when channel changed, compared with fixed observation window length-fractionally spaced linear equalization (FOWL-FSLE) equalization receiver,the AOWL-FSLE equalization receiver can achieve better BER performance,because it can suppress the effect of ISI more effectively.

Abstract:For describing the topology information in the reconfiguration process of self-reconfigurable robot, an UBot self-reconfigurable robot topology description method based on incidence matrix is proposed. At first, a joint state table during the reconfiguration process is built up based on the analysis of the module motion characteristic of UBot self-reconfigurable robot system; and then a binary number representation is developed by analyzing the linkage and position relation that may exist among modules; finally,taking worm configuration as example,the corresponding topology description matrix is obtained,which can describe not only the information of module address,module connection status and position relation,but also the joint angle status information of each module exactly. This topology description method is helpful to the research of configuration matching and reconfiguration algorithm of reconfigurable robot.

Abstract:To overcome the shortcomings of the traditional artificial potential field method in mobile robot path planning,an improved method was proposed,in which potential field intensity was used instead of force vector to plan the path for the mobile robot. By addition of coefficient item to repulsion potential field of obstacles, the destination unreachable problem caused by the closely distance between destination and obstacles was solved. Considering the speed-effect of mobile obstacles and mobile robot,the velocity information was introduced into potential field function and an"added potential field"was also introduced to guide the robot to be out of local minimum points. Based on the new method,all the potential field intensity was added by algebraic sum style,then the genetic trust region algorithm was used to search the minimum sum point of potential field intensity within the movement scope which the robot can arrive at during a sampling period,and the global optimization path was composed of all the minimum points. Experiment results show that better path planning for mobile robot in dynamic environment can be achieved by this new method.

Abstract:Aiming at the difficulties of applying highly coupled integrated model for wheel-soil interaction mechanics,a closed-form decoupled analytical model is derived by linearizing stress distribution and ignoring the coupled term with small proportion. Six kinds of wheels with different dimensions and wheel lugs were used to do experiments with wheel-soil interaction testbed. The soil parameter identification method is researched based on the decoupled model to estimate the eight unknown wheel-soil interaction parameters,and the method is verified by the experimental data. Due to the compensation role of identified parameters,the decoupled analytical model can predict the drawbar pull,resistance moment of driving,wheel sinkage and slip ratio with high precision,which makes it reasonable to be applied to dynamics simulation and control algorithm design of lunar rover.

Abstract:For researching the flow distribution of squids jetting process,and providing theoretic basis for biomimetic robot,the numerical simulations of this process were studied by CFD. A simplified body of squids was modeled,and the mantle motion during escape-jet locomotion was explicitly included into the simulations by using a deforming mesh. By solving the 2D-axisymmetric,incompressible,laminar,unsteady Navier-Stokes equations,different vortex evolution behavior was observed depending on different mantle contraction rate and jet diameter,and the exiting condition of the critical vortex ring,the formation number L/D = 4,was verified. The calculations of corresponding instantaneous forces during the ejecting have also been carried out. The results show that this model is suitable to simulate jet process of squids and the numerical results are in satisfactory agreements with the experiment data.

Abstract:Two kinds of aerostatic bearing: two-row cylindrical bearings and closed-hole planar thrust bearing in the precision swing angle milling head spindle system were studied. To get the best film thickness and the corresponding maximum stiffness of the bearings in different throttling ways and under different Orifice diameter,the law of the bearing stiffness impacted by different structure parameters was obtained by using engineering design and calculation methods and the numerical simulation of the aerostatic bearing flow was carried out by FLUENT,which indicated that the change of the bearing stiffness and carrying capacity was caused by the change of eccentricity. Meanwhile the structural parameters of the aerostatic bearing were optimized. Results show that when the bearings are working under a small eccentricity ( ε < 0. 3 μm) ,its stiffness is a constant, and the carrying capacity increases with the increasing of eccentricity.

Abstract:The tribological and dynamic characteristics of the head/disk and lift-tap/ramp interfaces during load/unload ( L/UL) process for hard disk drives were modeled. The equation of motion for the L/UL system was proposed,in which the air bearing force at the ultra-thin film lubrication was solved by using a PDE-based method. The contacts between the slider and suspension,as well as the lift-tab/ramp interface,were simulated to analyze the effect of the stiffness of lift-tab,the stiffness at the lift-tab/ramp interface,and the ramp angle on the stability of the suspension slider. It is indicated that PDE-based method has enough accuracy for the description of the air bearing force. The stability of the slider is determined by the suspension stiffness,contact stiffness at the interfaces and the ramp angle. These results are beneficial to improvement of the slider/disk interface and further application of L/UL technology.

Abstract:Geometry parameters and lengths of legs often have close relations with the singularity of a Gough-Stewart platform. When these parameters are improperly selected,the platform may have hunt singularities. The relations among the geometrical parameters and the leg lengths when in hunt singularity for 3-3、6-3、 6-6 Gough-Stewart are derived according to their geometrical constrains. The obtained relations can be used as a geometrical criterions,for a Gough-Stewart platform with given geometrical parameters,to determine if the mechanism may have or close to Hunt singularity in its workspace. Two experiments are performed,which validates the hunt singularity criterions.

Abstract:To evaluate the reliability of Multiagent system accurately,a synthetic evaluation approach considering communication reliability,unit reliability and system topology is proposed. Multiagent system structures are summarized; the influence of communication reliability and unit reliability to the reliability of centralized, distributed and federated Multiagent system is analyzed based on Markov process; and system reliability models are given. The simulation results show that this method can simplify the problem of complex system reliability, for the entire system reliability can be obtained after the reliability of every part is achieved.

Abstract:For solving the problem that the current clone and related bug detection tools can not analyze largescale code and detect modified code clones,a model of clone and identifier inconsistency bugs detection based on the improved model of clone detection via sequential pattern mining is proposed. This model improves the existing submodel of identifier forgotten renaming bug detection,and introduces a new submodel of identifier mistaken renaming bug detection. Identifier renaming inconsistency bugs are detected by computing identifier unchanged ratio ( UnchangedRatio) . Experiment results indicate that this model can detect clone related bugs on the basis of code clone detection,reduce false-negative rate and false-positive rate,and is effective in detecting two kinds of identifier inconsistency bugs.

Abstract:To improve the prediction of transition,the γ-Reθ turbulence model involved with empirical correlations for transition prediction is used to analyze two typical hypersonic flow fields of the blunt cone and the flat plat shock wave/boundary layer interaction,and the computational results agree well with the experimental results,which show that the turbulence transition model adopted in this paper has a higher credibility than traditional turbulence models. Furthermore,two supersonic inlets with triple-compression angle and isentropic compression profile are designed and simulated,respectively. The results show that the isentropic compression profile has better throat flow capability and higher total pressure recovery performance and the aerodynamic performances at the rear part of the throat section are almost the same for the two cases.

Abstract:To save the calculating time and improve the precision of results,Dittus-Boelter criteria formula and Gnielinski criteria formula are adopted in the calculation of conjugate heat transfer analysis for the NASA-MarkII high pressure air-cooled gas turbine. Considering of the geometry and work conditions of inner-cooling channels,and by correcting the temperature difference coefficient and the entry effect coefficient,the commercial software CFX11. 0 is used to simulate NASA-MarkII high pressure air-cooled gas turbine by different turbulence models. The simulation results agree well with the experimental ones. In addition,because of the application of heat transfer coefficient criteria formulas,the calculation of inner-cooling channel fluid domain, the conjugate errors of inner-cooling channel fluid domain and the solid blade domain with different turbulence models and the calculation errors of uncertain inner-cooling channel turbulence characteristic boundary conditions,are all avoided.

Abstract:Four different coals have been used to study the effects of oxygen concentration on coal combustion characteristics under different oxygen volume concentration ( 21% 、30% 、40% 、70% 、100% ) by thermo-gravimetric analysis experiments. The results show: with the oxygen concentration increases,the ignition and burnout temperatures of coal decrease and the burn-out temperature decreases faster; The ignition time brings forward,the combustion time shortens and the maximum weight-loss rate increases; The combustion of pulverized coals complies with the rule of one-rank reaction; The apparent activation energy and frequency factors of coals increase,and from brown coal to anthracite,the magnitude of apparent activation energy increases faster.

Abstract:To improve the economical efficiency,reliability and miniaturization of engine,the cooling effects of water,TiO2 nanofluid,Al2O3 nanofluid and CuO nanofluid are investigated by simulation,and the distributions of heat transfer coefficiency and pressure of the cooling system are obtained. The results show that,compared to water,by using TiO2,Al2O3 and CuO nanofluid,the average surface heat transfer coefficient is increased by 10. 82% ,8. 43% and 11. 24% ,and correspondingly the pump power is increased only by 1. 06% ,1. 30% and 1. 98% ,respectively. It is clear that the heat transfer coefficient increases significantly at a tiny loss of pump power with nanofluid as coolant,which is beneficial to the heat exchange of cooling system.

Abstract:To better understand the heat-transfer character and flow of liquid gallium,a natural convection flow of liquid gallium was numerically simulated by using single phase method on the heat transfer of liquid gallium in a two dimensional enclosure. The effects of boundary condition and Grashof number on the flow and the convective heat transfer behavior are investigated. The numerical results which include temperature and velocity graph are compared with the experimental data and reasonable agreement is achieved. In a case that thermal conductivity takes a leading part,when Grashof number goes up,convection will gradually play a more important role.

Abstract:To solve the problem of data drift and asymmetric misclassification costs in customer segmentation, a cost sensitive learning method integrated with two-step cluster is proposed. This method firstly applied kmeans cluster by the posterior probability distribution of give region to group similar regions together,and then used cost-sensitive support vector machine to find customer segmentation for each region-group. The results show that the cluster based on similarity of customer segmentation structure can improve the total accuracy and the proposed cost-sensitive support vector machine is an effective method to distinguish high value customers compared to the original support vector machine.

Abstract:To reduce the pedestrian injury in accidents,the protection efficacy of sandwich material hood made of steel panel with PVC foam material inside was studied. The sandwich material was treated as anisotropic material by using the Eshelby’s principle and MoriTanaka’s method,and then its mechanical properties was calculated. The simulation of head impacting process was carried out by Ls-Dyna,and the results showed that,when some suitable parameters of the sandwich material were selected,the injury value of pedestrian head could be effectively reduced.

Abstract:A study about the influence factors on effective thrust of pulse detonation engine ( PDE) is carried out to obtain effective thrust. The continuous detonation combustion of air-breathing/gasoline-air PDE is achieved by using the cyclone-type aero-valves in a detonation tube with diameter of 60 mm. The effects of the filling speed of detonation tube and the stamping flow speed on the drag of PDE are analyzed based on the cold-state experiments,while the pressure p3 of the aero-valve is studied in the thermal-state experiments. The results of calculation for the thrust and drag in a period show that PDE can output effective thrust at the frequency of 10 Hz,but this effective thrust is difficult to be measured under actual working conditions. The research on the continuous effective thrust for PDE indicates that the operating frequency,detonation intensity, internal and external drag are the decision factors,while reducing the spoiler drag is the key to obtain the effective thrust.

Abstract:To improve the phase noise immunity of Chinese Digital Terrestrial/Television Multimedia Broad-casting ( DTMB) system,a time domain CPE ( Common Phase Error) correction scheme utilizing PN sequence which was filled in the guard interval of DTMB signal frame,and a decision aided ICI ( Inter-Carrier Interference) eliminating scheme which used Transmission Parameters Signaling ( TPS) in DTMB signal frame,were proposed. Simulation results showed that the proposed schemes can eliminate the ICI and CPE,which were caused by phase noise of receiver local oscillator,and improve the symbol error rate. In addition,the time domain CPE correction scheme exhibits excellent performance in strong noise and interference environment.

Abstract:To improve the mixing of homogenous air-fuel in cylinder,a new fuel supply system for gasoline direct injection engine,compound fuel supply system was presented. With the three-dimensional numerical simulation method,the optimum design of low-pressure fuel injector position was investigated,and the influence of compound fuel supply system on the air-fuel mixture formation in cylinder under the cold-start condition of GDI engine was analyzed. The results showed that the air-fuel mixing process in intake manifolds and the concentration of mixture entered into the cylinder during the intake stroke were greatly influenced by the low-pressure fuel injector position. The compound fuel supply system can improve the mixing of air-fuel and the distribution of air-fuel ratio in cylinder under the cold-start condition,and reduce the HC emission.

Abstract:To solve the problem of optimization of vehicle suspension kinematics,a new method to describe the kinematics constraint conditions by mathematics and to optimize the kinematics parameters by Newton iteration method is presented. With it,the proper variable of the suspension and the optimum solution can be found quickly,so that it is suitable to the optimization of suspension kinematics with multi-variable and multi-objective function. Taking a off-road vehicle’s problem in toe angle and camber angle as an example,the optimization results of hard-points coordinates show that the desired characteristics of the suspension kinematics can be achieved in two step iterations.