Abstract:Ritz method was adopted to study the natural frequency of nonlocal elastic bar. Nonlocal elastic theory, different from classic elastic theory, was presented that the stress of a point is related to the strain of the area around the point, and such a relationship is illustrated by kernel function. Based on Eingen's nonlocal elastic model, a dynamics analysis of nonlocal elastic bar was created by Ritz method with three different kernel functions and the natural frequencies of the bar with two different boundary conditions were supplied. Compared with other methods, this one can deal with different kernel functions. Moreover, its numerical precision is controllable and programming is very convenient.

Abstract:Based on the combination of a tangential impulse maneuver and a constant continuous radial thrust maneuver, a new strategy for space V-bar rendezvous was presented. The absolute and relative motions of the chaser in combined maneuvers were investigated when it maintains its initial circular orbit. Then the guidance rules of space rendezvous V-bar approach and final translation were derived respectively. For V-bar approach, the chaser makes straight line motion at constant velocity while no constraints need to be considered in the transfer duration and line of sight, resulting in a flexible transfer in time. For V-bar final translation, the chaser's straight line motion is switched from a higher constant speed to a smaller docking velocity at the given position. The process is easy to guide and control, satisfying the requirement of the chaser's transfer to be straight and safe.

Abstract:Precise determination of formation states provides the foundation for Formation Constellation to carry out its function. In this paper, the state determination problem of double-satellite formation constellation for earth-observation purpose was discussed. On the basis of GPS, a ‘GPS-like’ ranging technology was introduced to improve the state results. Two mathematical models combining ‘GPS-like’ Ranging technology with GPS were built. In this way, a synchronous initialization method for single differential GPS inter-satellite integer ambiguity and single differential ‘GPS-like’ intra-satellite integer ambiguity were also developed. Finally, these models above were simulated and analyzed. The results indicate that, ‘GPS-like’ observation data, especially the single differential ‘GPS-like’ intra-satellite carrier phase data, significantly improved the states results, and the accuracies of absolute attitudes, relative position and relative clock bias respectively reached rad, m and s. The simulation proves that these methods are correct and model II is more accurate than model I.

Abstract:The soft release mechanism in a controlled hold-down and release system proposed recently was discussed in this paper and a finite element and rigid-body mixed model was put forward to analyze its release characteristic during launch vehicle liftoff. The rigid-body model was used to describe the movement of the launch vehicle and the finite element method was employed to analyze the finite deformation elastic-plastic contact of the soft release mechanism. The interface compatibility condition was enforced between the launch vehicle and the soft release mechanism. The mixed model was solved with an increment algorithm, which can be used to analyze the influences of the material property of the pin, the shape and size of the soft release mechanism, friction between the die and pin on the entire release time, the launch vehicle velocity and the consumed energy during liftoff.

Abstract:In the progress of the trial run of liquid rocket engine, the situation of zero-failure data may happen. For zero-failure data, the reliability of the liquid rocket engine was assessed by the least square method with the classical estimation and the Bayes estimation based on the analysis of the life distributing. An analysis of the estimate result was also given. The computational results indicate that the least square method combined with the Bayes estimation is suitable for the reliability analysis of liquid rocket engine in the case of zero-failure data.

Abstract:The methods of precipitation and blending to adjust the molecular weight and distribution of polycarbosilane (PCS) synthesized at high temperature under high pressure were investigated in the paper. The results show that, the high molecular weight PCS can be precipitated by adding certain amount of precipitator (such as acetone) into the PCS solution of favorable solvent (such as xylene). The higher the molecular weight of PCS, the earlier it precipitates when acetone is added to a degree above the critical value. The softening point, molecular weight and polydispersity index of PCS are therefore decreased. The molecular weight distribution of PCS is thus controlled. Blending of PCSs with different molecular weights and distributions is another method to adjust the molecular weight and distribution. The results show that, the softening point, weight average molecular weight and content of high, middle and low molecular weight of the obtained PCS are accorded with the rule of mixture (ROM) when two different molecular weight PCSs are blended together. Therefore, PCS with required softening point, molecular weight and distribution can be designed in advance according to ROM.

Abstract:Carbon fiber cloth reinforced silicon oxycarbide (2D C_f/Si-O-C) composites were fabricated with cheap polysiloxane (PSO) and divinylbenzene (DVB) as precursors and carbon fiber cloth as reinforcements. The mechanical properties of 2D C_f/Si-O-C composites with polysiloxane as precursors were investigated and the difference of properties and cost between them and 2D C_f/SiC composites were also studied in the paper. The results show that the mechanical properties of 2D C_f/Si-O-C are decreased and the cost of them reduced greatly. The flexural strength, fracture toughness and shear strength reach 157.9MPa, 8.4MPa?m^1/2 and 23.4MPa respectively. Such mechanical properties can be reserved up to 1400℃.

Abstract:A VMN-based MIPv4 fast handoff method based on the basic MIP/AAA model was presented for satisfying the users' demands of security and low latency in MIP services and making up the existing insufficiency in the current MIPv4 handoff method. The method strengthens the basic MIP/AAA model, and sets up a novel data structure in the mobile agents. Through establishing a new bidirectional tunnel between NFA and OFA, it fast transforms the data packets of VMN between them, and realizes the fast low latency handoff under no data packets losing. Through distributing the new temporary security association and the authentication ticket, it enhances the security in the MIP's registration and handoff process, and effectively reduces the network loads between AAAH and the AAAF. The secure analysis and the simulation experiment for the presented method indicates that the method is more secure and effective.

Abstract:Mirroring is a popular technique for enhancing data availability. Based on this technique, this paper proposes a high-availability data objects placement algorithm with mirroring, which groups objects into redundancy sets by using RAID at the algorithm level. The redundancy allows us to reconstruct any corruption or failure of the data objects and storage nodes, thus efficiently ensuring the high availability of storage system. We quantify the availability of storage system by using Markov reward model, and the computing results indicate that the algorithm is efficient.

Abstract:The study was made to research into the effect of the network delay upon the AQM mechanism and to analyze the properties of several typical AQM algorithms in delay networks, which was put forward recently. With a discussion of the advantage and disadvantage of the DC-AQM, this paper, according to the Ziegler-Nichols approach, in which PID controller may compensate for the time delay, proposed an AQM algorithm using Ziegler-Nichols Method that can reduce the negative impact caused by the large delay. Finally, the performance of AQM with Ziegler-Nichols Delay Compensation is evaluated through NS simulations. Results from the simulation reached the objective expected.

Abstract:Contraposing the shortcoming of “flooding schedule” in the standard LDPC(low-density parity-check) decoding algorithm, this paper presents a serial decoding schedule， which shuffles the massage passing schedule of standard LDPC decoding algorithm. The new schedule processes and propagates messages according to a serial update order of bit nodes. Each bit node receives check messages and sends bit messages in the same iteration so that the updated messages could join iterative process immediately. As a result, the convergence property is improved. Simulation results show that, under the same decoding complexity, the proposed version is optimal in the sense of MAP decoding and converges faster than the flooding schedule. Meanwhile, it keeps the appropriate decoding complexity, so it is a good method that can offer better trade-offs between performance and complexity.

Abstract:A new method for modeling and simulation of coherent k-distributed clutter is presented. Compared with ZMNL and SIRP, this method can generate coherent clutter with arbitrary complex ACF, and it doesn't need resolving non-liner equation and matrix inverse. As a result the speed of simulation is improved markedly. The results from simulation prove the validity of this scheme.

Abstract:As one of the key techniques in inverse synthetic radar (ISAR), autofocus is to eliminate the phase errors caused by the target radial motion. The maximum likelihood (ML) estimation of phase errors was derived form the ISAR signal model, and an autofocus algorithm based on the ML estimation was proposed. In the algorithm, the phase gradient algorithm (PGA) was performed, and the signals of multiple scatters on a few range bins were utilized. Hence, the scatters might not be well isolated, and the troublesome phase unwrapping was avoided. Moreover, the algorithm also eliminated the accumulation errors in the phase error estimation. The imaging results based on the measured ISAR data demonstrate a good performance of the autofocus algorithm.

Abstract:To investigate the problem of the congestion control over high-speed long distance networks, this paper presents a new AIMD congestion control algorithm, I-TCP, which is based on a model of network of synchronous AIMD sources competing for a shared bandwidth under drop-tail queuing. With a reasonable design of a high-speed mode, a low-speed mode and the mode switch rule, I-TCP is suitable for deployment in the high-speed long distance networks as well as the traditional low speed networks. Simulation experiments show that the AIMD algorithm of I-TCP performs better than current TCP implementations in terms of efficiency, fairness and network responsiveness over high-speed long distance networks.

Abstract:A new incremental clustering algorithm is proposed in this paper based on the relativity principle, which means that the similarities of objects in the same cluster is higher than those among different clusters. This approach not only inherits the advantages of absolute density based algorithms which can discover arbitrary shape clusters and are insensitive to noises^［1］, but also efficiently solves the following common problems: clustering results are very sensitive to the user-defined parameters, reasonable parameters are hard to be determined, and high density clusters are contained fully in coterminous low density clusters. With this approach, incremental clustering can also be supported effectively by defining the affected sets and seed sets of the updating objects in this approach.

Abstract:Change information of linear objects can be detected based on linear feature in multi-temporal remote sensing images. A new linear feature change detection approach is proposed. In this paper, the changed edge points from multi-temporal remote sensing images are grouped into line support regions based on the difference of gradient information. Then, the regions are fitted based on least square and the changed lines are generated. This approach of linear features change detection uses the gradient information of multi-temporal images as the change detection element instead of match the line information, so it decrease the complexity of the change detection. The experimental results in multi-temporal remote sensing show the effective of the proposed approach.

Abstract:A structure of TLB for low power is introduced. The idea of the proposed TLB is based on the spatial locality, which is the result of combining with the block buffering technology and adjustment of the CAM structure. All of these make the TLB for low power. With Simple Scalar 3.0, a simulation of the proposed TLB and some traditional TLB structures were made to observe the miss ratio. The simulation results from the modified CACTI3 show that the proposed TLB structure can reduce power*delay about 85%, 80%, 66%, and 66%, compared with a FA-TLB, a micro-TLB, a victim-TLB, and a bank-TLB. Therefore the proposed TLB can achieve low power.

Abstract:As the signal-to-noise ratio measurement of each correlation channel fixed in a small area is correlated for multipath signal, the paper proposed a method to reject multi-path by filtering the parameter of multi-path through EKF based on current statistical model. The effect of multi-path to SNR was an alyzed. State formula and measure formula WERE built. The proposed method is proved to be effective in reducing range measurement error and phase measurement error through simulation.

Abstract:This paper researches into the design of the full-scale hybrid magnet in EMS Maglev train. The hybrid magnet was made by combining electromagnet with permanent magnet (PM). Considering the different effects of the positions that PM fixed on, the structure scheme of the hybrid magnet was presented. The analysis result of the hybrid force shows that hybrid magnet can reduce the suspending power as far as the PM has a bigger coercive force. According to the design requirements, the paper also calculated the restriction on the height of the coil's window with its width treated as a constant under the following three typical conditions: rising up at full load, suspending steadily at rated load, and attracting together at zero load. The optimized parameters of the hybrid magnet were thus attained. Finally, based on the FEA (Finite Element Analysis) software, Ansoft Maxwell, the patching up effect of the NdFeB was simulated, and the revised design results were presented.

Abstract:To address the bulk and inflexibility of traditional analog dither system, a new digital dither control method for ring laser gyroscope (RLG) was designed by using single chip processor. The dither mathematical model was built and dither characteristics were investigated for square/sine wave driving signals respectively. By comparing the driving effect, it is found that the square wave driving has different variation rate of dither magnitude and nonlinear random noise infusion method. Simulations and experiments illustrate that the new method can control the RLG dither well and assure the performance.

Abstract:To build a feasible and robust setting model in lunar rover path-planning, MCWM, a novel method of setting modeling, was proposed. The terrain traversability, system uncertainty, human-machine cooperation and movement smoothness were taken into account. Then, for the creation of MCWM model, a synthetic cost map for path-planning was created. Simulation results show that MCWM can improve the safety and performability of the path, thus the feasibility and validity of the modeling is confirmed.

Abstract:The route prediction for multiple unmanned aerial vehicles (UAVs) task allocation in dynamic battlefield is a complicated path planning problem characterized by multiple paths and real time demands. Probabilistic Road Maps (PRM) method wais used to plan combinatorial predictive routes for multiple UAVs and multiple tasks in this paper. The route predicting process was split into two phases: the off-line learning phase and the on-line query phase. The paper presented Cost transform based PRM (CTPRM) algorithm, which transforms the influence of enemy threats to the risk cost of the route segments among roadmaps. When battlefield situation was changed, without reconstructing roadmaps, CTPRM could plan new predictive routes rapidly by updating the risk cost of some route segments. According to different planning condition, relevant sampling strategy could be set flexibly, so that the planning time and route quality could be coordinated to achieve tactical goal. Simulation results demonstrate the feasibility of the approach.

Abstract:Accurate estimation of moving target's postion is a very important research area of optical measurement since it has to be performed in many applications. Under the condition that there are no range information of target and known points on the target, such an assumption is made that the target obeys a movement rule is made which adds extra information for target positioning. For moving target positioning under the condition of monocular camera, a new method, collinear equation method, is proposed. The correctness and feasibility of the method are proven by simulation data.

Abstract:The spectral method and FFT algorithm were applied to the numerical solution of Fokker-Planck-Landau equation of charged particles transported in plasma, the evolution of the distribution function of charged particles in 3-d velocity space was simulated numerically in homogeneous coordinate space. Computational results show that the conservations of mass, momentum and energy are maintained accurately by the adopted numerical scheme, and the computation cost is reduced considerably.

Abstract:For uniform linear motion and uniform rotation blurred images, settling the blur function is the key point in image restoration. The motion direction and blur extent are the important parameters determining the blur function. For the pixels in blurred images have high correlation with the neighbors, the blur extent can be estimated by derivation and correlation methods. The simulation results demonstrate that the algorithm is right, effective and efficient.

Abstract:Mission planning and scheduling of satellite, which is to support task plan making of satellite scientifically, is a main content of space resource management. One of the most important characteristics of satellite mission scheduling is that it is subject to time windows constraint, which means that tasks can only be completed within the given time windows. The scheduling model is formulated based on reasonable assumptions and constraint programming method. The model is solved with Variable Neighborhood Tabu Search (VNTS) algorithm. On the basis of a limited experiment, we observe that the algorithm is very effective in obtaining near-optimal solutions.

Abstract:C⁴ISR architecture framework defines the products which are used to describe system architecture. It follows that the design of products is an important process of building architecture. Based on C⁴ISR architecture framework, the core products which include Operational Node Connectivity Description, Activity Model, System Interface Description and the like are described normatively. Furthermore, the relationships of products are analyzed, and the methods to validate the design of product are presented.