Abstract:The paper presents an approach to deal with residual stress intensity factors for surface cracks in a thick plate with butt joints by using line-spring model. Based on the Reissner's plate theory along with continuously distributed dislocation thought, the problem of the thick plate with butt joints is treated with a set of Cauchy-type singular equations, which are resolved by Gauss-Chebyshev method. The numerical results of the present method for the surface crack are compared with those of finite element method, and the compared results show good agreement. It is indicated that the line-spring model is not only reasonable and viable for surface cracks analysis in residual stress fields, but simple and convenience for engineering application.

Abstract:To investigate the shock impingement on vertical injection in supersonic flow, shock was produced by a 9mm long, 23° angle wedge. The images of shocks impinged at different position and pressure of gas and liquid injection were achieved by using both a high speed camera and a schlieren system. Results revealed that gas and liquid injection almost have similar phenomena, that is, impinged by the shock, fuel turbulent intensity will increase, fuel distribution area will be larger in supersonic flow, spreading more quickly into the main supersonic flow, and the shock impinged at the foreside affect more than rearward of injection.

Abstract:Aerodynamic characteristics of fore-bodies deduced simply from 2D configurations were studied. To restrain the compressed flow from spilling at side edges of forebodies, shaped waverider was added to the fore-body sides and features of the new fore-body as waverider were proven by CFD analysis. More discussion about volume efficiency of the new shape was made and a concept as usable volume efficiency was presented. Different shapes side edges were designed, usable volume efficiency of each shape was discussed together with aerodynamic characteristics.

Abstract:The shaped charge penetration performance is sensitive to material model parameters of armor plate in virtual experiment. A Bayesian linear calibrated approach was proposed to obtain precise prediction of penetration limit. Statistical relationship between the physical process, the computer model output and experiment observations was formulated, combined with calibration experiment observations, to estimate the unknown model parameter. Analysis of an example demonstrates that the proposed approach is efficient in large calibration problem involving various uncertainties.

Abstract:The 3D N-S equations are numerically solved, while NND2M scheme is used for the discretization of the equations, aimed to simulate the dynamic flow about the process in which booster takes apart from upper stage. The effect that the jet of the counter-thrust rocket motor exerts on the axial force on the base of upper stage body is analyzed. The results of the simulation show a law that counter-thrust rocket jet has a great effect on the upper stage body while the distance between them is short, which produces a big axial force doing harm to the flight stability of upper stage.

Abstract:Hybrid polyborosilazane (H-PBSZ) was synthesized and characterized. Meanwhile, the curing process of H-PBSZ was analyzed, and H-PBSZ was cured through different processes. Furthermore, the effects of curing pressure on the structure, appearance and apparent density of cured product were investigated. The results show that chemical bonds of B-N, Si-N, B-H, N-H, and Si-H exist in the structure of H-PBSZ. With the increase of temperature, bonds of B-H, N-H, and Si-H will be broken. Large amounts of gases emit from the precursor in the curing process. The density of the cured product is determined by the volume and velocity of the bubbles. The high pressure curing process can reduce the volume of bubbles, decrease their climbing velocity, and restrain the breaking of the bonds containing H atoms, decrease the amount of gases emission in the process. Therefore, much denser cured product is obtained.

Abstract:A novel two-dimensional phase unwrapping method is proposed. In this idea, the phase wrapped is propagated through an optical diffraction calculation as an input optical field and transformed into the intensity distribution. Then the phase retrieval algorithm is engaged in order to find the best fitting Zernike polynomials for the unwrapped phase based on the diffraction intensity. Because of the maturity of phase retrieval theory, the uniqueness and accuracy of phase unwrapping can be guaranteed. As a result, the phase noise can be remarkably reduced by intensity filtering. The validity of this algorithm is verified by experiment.

Abstract:The one-dimension mixing model is established from steady state theory, thus the recovery pressures of constant-area mixing model and constant-pressure mixing model are attained. The result implies that the performance of constant-pressure mixing is not always better than that of constant-area mixing, so a criterion is established to estimate the better one of the two mixing models. The consistent conclusion is attained by altering some of the initial parameters in reference.

Abstract:Ballistic experiments of ceramic/mild steel composite target against 7.62mm armor-piercing projectile (APP) were designed and carried out. Limit velocities and the base radiuses of ceramic cone were obtained. The influence of projectiles initial velocity, the thickness of front and rear plate on the base radius of ceramic cone and the impact point to the resistant mechanism of target were analyzed. The results show that the ceramic cone can be separated into fragmentation and smash region, the base radius of which approximates the thickness of front plate plus projectile radius. The ballistic performance of composite target area is in a similar case except for an edge area (5mm to the edge of the target), in which the ballistic performance declines obviously. The edge area has to be discarded from the effective protective area.

Abstract:The process of calibration and 3D reconstruction of the scene are always required in view synthesis from image sequences. To avoid those complicated processes, the reference images are first classified into primary reference image and subordinate reference image according to the distance between the reference viewpoints and the novel viewpoint. Then the global optimization problem of view synthesis is transformed from the depth field to disparity field, using a process of nonlinear rectification and multi-epipolar technology. Finally, the novel view is synthesized from the image sequence without matching and calibration. Experimental results show that the method is effective and has potential in the future.

Abstract:To investigate the blind estimation of the symbol rate of a long code direct sequence spread spectrum (DSSS) signal, an algorithm based on autocorrelation processing is proposed. First, the second order moment of the autocorrelation estimator is used to analyze the long code DSSS signal. Next, the estimator output is further processed to get rid of the peaks at multiples of the pseudo-noise (PN) sequence period. Finally, another autocorrelation estimator and the Fourier transform are used to extract the symbol rate. Theoretical analysis and simulation results show the efficiency of the proposed algorithm.

Abstract:Future digital battlefield is crying for a 3D representation of the radar coverage affected by complex environment such as terrain, ocean and weather. However, recent researches still focuses mainly on 2D representation while the existing 3D methods are always embarrassed by their low computation speed, a new hardware accelerated 3D representation method was put forward in this paper. Based on the constructed 3D data field of EM loss affected by environment, a hardware accelerated algorithm was designed to extract the isosurface for building the 3D radar coverage model. Then the model was represented into digital battlefield. In the experiment on popular PC and for typical Radar, the 3D radar coverage affected by terrain and atmosphere was vividly visualized in time. The result has overcomed the implicity of 2D method and the slowness of 3D method, thus providing excellent decision and sense supporting for users.

Abstract:Access control is an important technique to protect computer files. Aiming at malwares that attack files, the paper proposes a quantified estimation method, and points out that the fragibility of prevalent access control policies lies in authorizing programs to access files what the user can access. The paper novelly proposes an access control policy based-on user's intention, which is able to defend unknown file attacks, and has extraordinarily less risk than prevalent access control policies. Furthermore, the paper proves security properties of the policy presented, and its application is discussed.

Abstract:According to the network-coordinate based network distance estimation problem in an Internet-wide environment, an anycast algorithm named Cocast for cooperative network coordinate estimation is presented. All peers join a structured Peer-to-Peer overlay, and any peer in the overlay, i.e., a requestor, may send a network coordinated anycast message, then the anycast message is forwarded to a set of peers in charge of network coordinate estimation, and each of these peers makes responses from a network coordinate to the requestor, finally the requestor gets a synthetical network coordinate. Based on three novel mechanisms, i.e., an anycast service to select peers for network coordinate estimation, a hierarchical network embedding mechanism to compute the network coordinates, and a coordinate-fusion sensor approach to filter malicious peers' fake-coordinate effects, Cocast owns a fast convergence speed in network coordinate estimation and is more stable. Simulation results confirm that Cocast is scalable, fast-convergent, incrementally accurate and resilient.

Abstract:To improve computation efficiency, an enhanced EM algorithm based on self-training named STEM is proposed. In the E-step of each iteration, the unlabeled sample, whose class can be predicted by the current intermediate classifier with the most confidence, is moved to the labeled set and used in the M-step to train the next intermediate classifier. Therefore the mechanism of self-training by inter-result employing is introduced. Experimentation on text classification indicates that STEM outperforms EM in classification accuracy most of the time and improves the learning efficiency by reducing iterations.

Abstract:The critical link routing algorithm for interference minimizing has made a great success in optimizing the efficiency of network resources usage. Its method of critical links identification, however, is not very accurate in some circumstances, and it does not consider much about load balancing. This paper presents a new level based Δ-critical links routing algorithm for interference minimizing, of which the algorithm can identify critical links more precisely in some circumstances, and can perform load balancing better. Simulation results show that the algorithm proposed performs better in the resource utilization efficiency and load balancing.

Abstract:This paper proposes a pre-estimation based enhanced multidimensional resource allocation model (PE-EMRA) and its algorithm for network resource allocation. The PE-EMRA approach allocates both bandwidth and buffer resource for different traffic classes, balancing and limiting the arrival rate of traffic class and also maximizing the system utilization. The advantage of this approach is that it can maximize the system utilization and provide QoS guarantee while being flexible and easy to realize.

Abstract:Range-Doppler algorithm can be applied to imaging of spaceborne bistatic SAR. Range models used by the algorithm include quadratic model and beeline model. Considering the bistatic character of the system, method of getting precise range model parameters was studied. RD algorithm was deduced using quadratic model. In squint side-looking situation, quadratic model may have inignorable error. The error mainly can influence azimuth compression. In order to suppress azimuth sidelobe, imaging using azimuth compressing function according to beeline model was studied. For preserving image phase, right azimuth compressing function should be used to avoid destruction of the phase.

Abstract:Being complex and special, C⁴ISR requirements are, often comprehended and expressed in various ways. Nowadays the results of C⁴ISR requirements development are unsatisfactory. Therefore, the authors put forward a new approach: modeling C⁴ISR requirements based on ontology. In this paper, the ontology of the basic categories and relationships needed to represent C⁴ISR requirements is present. Ontology model and semantic ontology model are included. In particular, the research focuses on clarifying the domain knowledge about C⁴ISR requirements. After that, a procedure for modeling C⁴ISR requirements based on ontology is supplied. Finally, an illustration is provided to show the feasibility,and effectiveness of the approach, indicating its promising prospect.

Abstract:A novel model is put forward which represents combat behavior and network behavior in an unitary form, the evolving network for the combat on the battlefield F_R,Bis constructed jointly by generating a random network on f_R,Band removing nodes from fighting forces' networks, under the condition that the assumptions of Lanchester Model is generalized, and represented as a triple of networks F_R,B=forces R's network I_R∪ forces B's network I_B∪ engagement space f_R,B.In the model the effectiveness of a networked forces relates not only its size and the weapon performance, but also the structure of network and the battlefield in which it operates. An experiment shows that with the same operational assets a scale-free network is more dominant than a random network for both information effectiveness and killing rate but not always wins, the origin is analyzed that the scale-free network is efficiency，robust yet fragile in the conflict system.

Abstract:A creeping micro-pipe robot is designed, which comprises three DC motors and screw-driven units. The three motors are coordinated to realize the creeping motion. Firstly, the load is analyzed for the case that the robot creeps in a vertical pipe. Meanwhile, the mechanical adjustment characteristic for the claws to adapt to the varying pipe size is also discussed. Then with the help of ADAMS software, kinematical and dynamical simulations are presented, which shows the relationship between the driving force, the moving velocity and structural parameters of the robot. Simulations also demonstrate that the robot is applicable to pipes with diameter ranging from 15 to 20mm. The driving force reaches up to 28N and the moving velocity 6mm/s.

Abstract:A method of the fault detection and diagnosis by combining wavelet correlation filter and Shannon information entropy was proposed. The method was called “wavelet correlation feature scale entropy-fault”. At first, the weak fault information features were picked up from roller bearings fault vibration signals by the way of wavelet transform correlation filter, in order to get high signal to noise scales wavelet coefficients. Then, the defining and computing way of wavelet correlation feature scale entropy was presented, based on the integration of shannon information entropy theory. Wavelet correlation feature scale entropy can quantitatively describe energy distributing of different scales which reflects difference of roller bearings running state, the work states and fault types were estimated by magnitude of the selected wavelet correlation feature scale entropy which can mostly embody fault features. Results and analysis of the diagnosing example reveal that the proposed method can effectively estimate roller bearings fault feature and offer one new way for diagnosing roller bearings.

Abstract:A nonlinear model based on the finite element method is provided to compute the static characteristics of partial porous gas thrust bearing, considering the tangential velocity slip at the bearing-film interface. Good agreement is achieved between theoretical and experimental results on static load capacity, mass flow and static stiffness. The new modified Reynolds equation is proved to be a proper model to investigate the characteristics of externally pressurized partial porous gas thrust bearing. With a change to the feeding parameters of permeability coefficient, height or diameter of partial porous restrictors, the effect of the steady state characteristics, such as mass rate of flow, load capacity and static stiffness are studied, Also the performance comparison among the thrust bearings with orifice restrictors, partial porous restrictors and whole porous restrictors shows that this kind of bearing has promising potential in application.

Abstract:A method for fusing evidence information using Bayesian belief network is introduced for sensor data validation. Uncertainty expression and inference mechanism of sensor states and relations in engine and its components test are defined. The algorithms for automatic generation of the Bayesian belief network files, belief probability calculation and network update are developed. The methodology is demonstrated and validated in a model rocket engine.

Abstract:The failure distribution from traditional reliability methods reflects the “average” characteristics of the same kind of product. In order to get the real time reliability of degradation failure product with history test data, this paper adopts the local updating ideas, uses the on-site measuring data through Bayes method and gets the real time reliability model of the product that timely reflects the on-site data. The result shows that real-time reliability model expresses the specific characters gradually with the increase of fusing on-site data.

Abstract:The problem of satellite data transmission is an optimization problem with multi-time windows and multi-resources constrains. In view of the problem, the paper constructs satellite data transmission request model, task model and scheduling model. In the process of constructing models, the style of frame model is adopted, while all the constrains are put into every data transmission task. This not only reduces the complexity of scheduling model, but also reduces the difficulty of designing scheduling algorithm. In addition, this paper also presents the idea of designing scheduling algorithm, and designs a flexibility based scheduling algorithm. Results from simulation show that the model and algorithm are feasible for solving the satellite data transmission scheduling problem.

Abstract:A new algorithm of mesh generation for 2-D adaptive mesh method is proposed while combining the deformation principle and the idea of mesh iteration by means of directional derivatives to compute the monitor function.The numerical experiments show that this algorithm can well adapt to high spatial activities of the solutions. The main advantage of this algorithm is its simple logicality and it can avoid solving moving mesh partial differential equations and save time for computing mesh to compare the other adaptive algorithms.