Abstract:Waverider is an important designing reference in the design of hypersonic high L/D vehicle. L/D, volumetric efficiency and volumetric are factors to be considered in the designing process. A parameter design model of cone derived waverider was established in this paper and an improved multi-object Genetic Algorithm was chosen as the optimized algorithm. Lift to Drag ratio, volumetric and volumetric efficiency were chosen as optimized objective functions in the multi-object optimization of the cone derived waverider. The optimized model was designed and experiments of attack state's wind tunnel at KD-01 hypersonic gun wind tunnel were conducted. The experiment results were compared with those of CFD. It shows that the model has good L/D performance and can maintain high L/D at certain angle of attack's scope. The CFD results and experiment results are almost identical. The research result is helpful for the hypersonic glide aircraft's aerodynamic design.

Abstract:Structural integrity is one criterion of vital importance for solid motor. It is shown that the optimization of grain shapes and material properties can greatly improve the structural integrity. Owing to particularity of shape optimization, the Basis Vector which guides the optimization procedure is introduced. The auxiliary model which is used to help generate basis vectors is also designed. Based on the characteristics of solid motor and its loads conditions, the plain-strain model of the star is built. Several sensitivity factors of the shape parameters are studied, and the optimal schemes are discussed later. The results obtained will offer guidance to the structural integrity analysis and optimization design for solid motor. The methods and conclusions are beneficial to the designers and manufacturing of solid motor.

Abstract:Mathematical model and characteristic analysis of return trajectory for lunar probe were studied. Firstly, mathematical model of return trajectory was established in 3D space; then some important characteristics were obtained from simulation analysis, especially those characteristics of trajectory escapes from lunar sphere of influence on longitude 80°E costing the least energy; at last an example with a preliminary trajectory and a precise trajectory was proposed, which proves that this analytical method is able to provide initial value for precise design，and the characteristics can guide the actual design.

Abstract:The controlled equations based on thermo-chemical non-equilibrium model under the condition of three temperatures were solved numerically by finite difference NND scheme. The inverse bremsstrahlung absorption and plasma resonance absorption were considered when laser transmitted in air plasma. Plasma initiation process was simulated in coupling computation. The mechanism of formation and development of plasma absorbing wave were investigated under different incident laser intensity, while viscidity and diffuseness effects were considered. The results show that the minimum laser intensity needed to form LSD wave based on ZND model is 5.0×10⁶ W/cm² at the initialized temperature 300K and the pressure is 1atm.

Abstract:In the manned spacecraft rescue at low altitude, the initial conditions of recovery system at parachute-opening point affect obviously cabin safety landing, such as its velocity, altitude and trajectory angle. Similar to the normal return rescue, the process of recovery system rescue at low altitude also has the stages of deployment, inflation, and full-inflation of multilevel parachute. Through applying the recovery system landing dynamic model, and analyzing contrastively the results from simulation, it can be known that the initial altitude from ground of recovery system at parachute-opening point is the first effect factor on the cabin safety landing in rescue at low altitude. In the end, the deceleration process of parachute-opening of multilevel parachute in recovery system is analyzed in detail.

Abstract:A numerical simulation of dynamical model for some key dynamics problems of terminal correction submunition is built, using Kane's method which can solve the problem of the Multi-Rigid-body system. Numerical results were validated in the experimentation of airdrop in Airship-towed system. This dynamical model also can be used to solve the problem of Tether dynamics in other fields.

Abstract:The perforation mechanism of the high-strength armor by Armor Piercing Bullet (AP) was investigated by experiments. A theoretical model for the ballistic limit of the armor and residual velocity of the bullet including the effects of the strain rate and the thermal softening of the material was presented. The results show that the theoretical values have fine agreement with those of the experiments. The impact of failure criterion on the results was analyzed and the temperature rising of the shear band and the change rules of energy-dissipating of the target with the input velocities were discussed.

Abstract:Alumina aerogel thermal insulation composites were prepared by sol-gel and supercritical drying process, using aluminum sec-butoxide as precursor, and ceramic fiber as reinforcement. The microstructures were characterized by nitrogen adsorption experiments and scanning electron microscope (SEM), and the thermal insulation property was tested by hot plate method. The mechanism of thermal insulation of alumina aerogel composites was analyzed. The results show that, compared with silica aerogel, alumina aerogel can withstand even 1000℃ calcinations but still keeps the porous network. When alumina aerogel is introduced into the ceramic fiber, due to the excellent thermal resistance property of alumina aerogel, the thermal insulation property of composites is evidently improved, and the thermal conductivity of composites is 0.685 W/m·K at 1000℃.

Abstract:To analyze the thermal stress problem of thin conical shells, the basic thermoelastic differential equations of thin conical shells are established; the displacement and thermal stress in conical shells under temperature field are analyzed, using the distributed transfer function method. The calculation results show that the solution obtained by the distributed transfer function method matches well with the solution of the finite element method. The proposed method is able to analyze the thermal stress in thin conical shells with arbitrary boundary conditions and other loads; besides it can be further extended to the case of revolution shells with curvilinear generatrix.

Abstract:To solve the imaging scheduling problem of an optical satellite, which is characterized by multiple complex constraints, including skip, memory, energy and the data transmission, an action sequence for the small number of participant tasks is designed. A graph model with both edge and node having weight and the algorithm based on the label-setting shortest path algorithm is proposed to generate the imaging tasks sequence. For the generation of data transmission sequence, the knapsack model and the greedy heuristic with looking back are proposed. The experiment results show that the approaches proposed are feasible and effective.

Abstract:With the growing increase in software/hardware system scale and function, the further development and application of model checking has been greatly limited by state space explosion, which has been the bottleneck of verifying large industrial designs. Based on the Murphi, an explicit state model checking tool, the problem of organization of reachable state space of model checking was studied, and a novel organization method of reachable state space based on integer pointer and Fibonacci hash was presented. In the approach, an efficient model checking system was suggested. The new approach can effectively shorten verification cycle, and give counter example when the system specification is unsatisfiable. All this greatly helped rapid error location. The analysis and experiment results prove the effectiveness of our method.

Abstract:Aimed for the copyright protection and integrality authentication, a space significant watermarking algorithm of color images controlled by chaotic binary keys which mainly use the Least Significant Bit (LSB) substitution operations and regard the lightness data of RGB layers as cover messages has been proposed in this paper. The experimental result shows that the algorithm is easy to implement and has good transparence, high security and conformity. The algorithm can also realize blind detection, copyright protection, sophistication detection and localization efficiently. At the same time, it has good robustness for hostility attacks such as pepper-salt noise wiping off, cutting and bit-plane deleting. So it is a good half-fragile watermarking algorithm.

Abstract:Based on the affine geometry theory, a new method for image invariant construction is proposed under the global affine transformation condition. At first, the image feature points are obtained by affine region cutting. Secondly, the convex hull of feature points is established, and then the vertices of the convex hull are well proportionally combined into some feature regions. At last, we use these feature regions to construct affine invariants, based on affine geometry invariant property. In order to validate the image invariant's stability and high time efficiency, experiments were performed and the proposed method was analyzed in comparison with the existent methods.

Abstract:According to the characteristics of Bi-satellite formation SAR system, the peculiarity and superiority of differential interferometry were discussed, valid components of baseline for differential interferometry were obtained by decomposing the solid baseline, and then the model of differential interferometry for Bi-satellite formation SAR was established, and a method based on data fusion was used to compensate the measurement noises that were very hard to be avoided. Finally, a computer simulation results confirmed the feasibility and precision of the proposed model and method.

Abstract:Based on an overview of the distributed spaceborne SAR/ATI, this paper describes the principle of SAR/ATI and the impact of clutter and noise to the SAR/ATI performance, and proposes a new SAR/ATI method based on a priori information. Based on the multifunctional spaceborne radar simulator, simulation experiment and performance analysis are carried out to verify the effectiveness of the method.

Abstract:To solve the performance problem in Regular Expression matching of Protocol Identification, this paper introduces a Multi-pattern FSM (MPFSM), which can use one FSM to match several Regular Expressions. Based on Thompson algorithm, an Epsilon Compressed NFA Construction Algorithm is also put forward and implemented. This algorithm enhances the performance of conversion from NFA to DFA by decreasing the epsilon edges and the corresponding states. A One-pass Multiple-pattern protocol identification system is also implemented using the Multi-pattern FSM and corresponding algorithms. Experiments based on actual traffic are employed to show that the compile speed would be 7 times faster than the usual transfer process, and the Matching speed would be 20 times faster than the L7-Filter.

Abstract:To satisfy the real-time need of JPEG2000 satellite remote image compression system, a no-time spending data moving strategy based on parallel mechanism is proposed in this paper. It is implemented by splitting the EBC algorithm and adapting EDMA transport method, which parallels the operations of the algorithm and data moving. With the new data moving strategy, the coding efficiency can achieve one hundred percent and the total time for EBC algorithm implementation has been decreased by 46%. The new data moving strategy has been applied to satellite on-board JPEG2000 image real-time compression system successfully.

Abstract:A refinement-based triangular meshing algorithm is proposed to generate finite element meshes of arbitrary two-dimensional domains. The boundary is triangulated by the ear-removal method, constructing an initial mesh with coarse elements. To meet the pre-specified sizing requirement by refining the initial mesh, a novel mesh refinement method, Delaunay-optimized bisection, is presented. By combining global-longest-edge bisection with Delaunay edge swapping, well-shaped triangular elements are constructed. Meshing examples are presented along with mesh statistics, showing that the presented algorithm is capable of generating quality finite element meshes for arbitrary 2D domains.

Abstract:The hybrid locomotion system is a hotspot in mobile robot research. This paper firstly gives a brief review of the achievements accomplished in wheel-leg hybrid mobile platform, and the structural characters. Based on the spherical gear mechanism, a new mobile platform with wheel-leg hybrid mechanism is put forward. The wheel-leg mechanism has a novel character, that is, the wheel mode and the leg mode can be fused not only in structure but also in their function. As a result, the mobile platform has three mobile modes: independent wheel mode, independent leg mode and wheel-leg-fusion mode. The mobile platform can realize several mobile poses such as straight moving, sloping moving, turning in a smaller radius and even turning-in-place. The current design was testified by the results of simulation using virtual prototype technology and experiments based on the wheel-leg-system and the mobile platform physical prototype.

Abstract:To increase the validity of real-time fault detection of turbopump in Liquid-propellant rocket engine, a new signal processing method called modified Time Encoded Signal Processing and Recognition (TESPR) was presented to extract the features of vibration signal in real time. To extend the application of TESPR, the constraint about the duration of signal waveform components was abolished and a new encoding method was advanced. By the test of vibration data from normal as well as abnormal turbopump, the stability of this method and its affectivity for fault detection were verified. It shows that this signal processing method can be applied to turbopump fault detection.

Abstract:In this paper, the measurement matrix optimization approach is presented when the linear system's cycle index is 1, which is the case frequently occurring in the engineering application. The measurement matrix can be found when it can make the system observable by transferring the system matrix to Jordan canonical form. By this method, the best measurement setup to achieve the minimum cost can be obtained simply and with much intuition while the system keeps observable. An example shows that this algorithm can be easily applied in engineering.

Abstract:The qualitative analysis and comparison of commonly-used autonomous control architectures of Distributed Satellite Systems (DSS) are discussed. Based on it, a hybrid systematic hierarchical architectures model with two levels is put forward to fulfill autonomous cooperation demands of DSS under the dynamic and complicated uncertain circumstances. Furthmore, a novel agent model on satellite control architecture is outlined, and the components, functions and relationships of agents in the architecture are analyzed. It is designed for multi-satellites cooperation and satellite self-government, thus it has generality to a certain extent.

Abstract:Difficulties in the measurement of the couple coefficient for a compact Tesla transformer is solved using the method proposed by I. D. Smith. The couple coefficient was experimentally measured to be about 0.9, a little lower than the figure designed. The reasons for the decrease in the couple coefficient were presented. Electrical parameters of the Tesla transformer's circuits were estimated by experimental voltage waveforms, which is in good agreement with that from theoretical calculation. The Tesla transformer can meet the requirements of high-voltage charge to the forming line (FL).

Abstract:In this paper, the mechanical model of the stepped piston vibrator is constructed and the generating mechanism of impact signal produced by the vibrator is studied firstly. Then based on experiments, the exciting signals produced by two common kinds of stepped piston vibrators are emulated under different pressure values. Finally the low frequency energies of exciting signals are taken as the performance indexes of vibrators and two kinds of vibrators are evaluated. The results of this paper show that big vibrators are superior to small ones under different pressure values.

Abstract:One of the most important model in image processing based on partial difference equations is the mean curvature motion model, which has a geometric property. An accurate calculation method to the degenerating diffusion term in this model is proposed, adopting two new orientation estimation methods-one based on the Hessian matrix and one based on tensor-and then making a comparison between the two. The results of the experiments prove that these measurements are effective.

Abstract:The existence of the periodic solution for neural networks of two neurons with McCulloch-Pitts type signal functions and oscillatory initial value was proposed. By using the resultant techniques and method of analysis, resultant conditions which ensure the existence of periodic solution of the system with sign change of initial value were established. Furthermore, the stability of the periodic solution of the system with zero threshold was shown by example.

Abstract:In this paper, the vector stochastic integrals are considered with respect to semimartingales. It establishes a result which can be easily applied to the problem derived from the different predictable process in the decomposition of semimartingales in the sense of vector stochastic integrals. As its applications, a straightforward proof of theorem 4.2 and theorem 4.6 in ref. is provided, and by using this idea, an important property of the vector stochastic integrals with respect to semimartingales is presented.