Abstract:Basing on the introduction of working principle and structure of sphere cam engine, the variation of cylinder volume was studied. Furthermore, the theoretical thermodynamic model of engine was established to analyze the combustion process of sphere cam engine. Then the theory result was compared with the simulation result in FLUENT. The oil spray process was studied in detail. Results show that the calculated pressure curve and temperature curve in cylinder are similar to the simulation results, which validates the validity of theory model. However, the vortex of sprayed oil observed in FLUENT can lead to the rich oil phenomena, which may decrease the combustion efficiency. 

Abstract:In order to achieve the best repairing effect of carbon fiber/bismaleimides composite materials, carbon fiber/epoxy composite materials and epoxy film adhesive were used as the repair materials to repair carbon fiber/bismaleimides composites with the pre-drilled hole of Φ15 mm and Φ5 mm, respectively. Single-lap repair, double-lap repair and step-lap repair were adopted to repair the carbon fiber/bismaleimides composite structures with pre-drilled hole. The effects of the patch numbers, patch lengths and patch stacking sequences on repairing performance were discussed. The failure model of the repaired plates was analyzed through the experimental method, and the patch-repairing parameters were optimized. The results show that the stress concentration and through-thickness tensile stress along the edges of the patch are the key reasons for the fracture of the repaired plate. The tensile strength of the double-lap repaired specimen can recover up to 90% of the strength of undrilled specimen and the strength of the specimen repaired by the single-lap repair and step-lap repair can also recover up to 80% of the undrilled specimen.

Abstract:The designed new type stitched sandwich structure of composite materials can avoid the disadvantages of fiber cross caused by the traditional angled stitch. The integrated stitched sandwich composite were prepared by VIMP (Vacuum Infusion Molding Process). The flatwise compression test and the three-point bending test were employed to study the effects of stitching structure, stitching mode and stitching yarn on compression properties and bending properties. Results show that the integrated stitched sandwich composites have excellent compression mechanical properties. Compared with the vertical structure, the flexure failure load is increased by 94.4%. Compared with the unpenetrate stitched mode, the compressive strength and the bending load of penetrating stitched mode are improved significantly. The compression properties and the flexure properties of stitched sandwich composite are improved with the increase of stitching yarn.

Abstract:Composite laminates are riveted to the metal frame when applied on aircrafts, hence the boundary condition of composite laminates is four-edge clamped. Based on the real application, the differences of quasi-static indentation damage of the composite laminates with the four edges clamped simply supported were systemically compared from four aspects: delamination propagation mode, contact force, dent depth and damage width. The experimental results show that all these four aspects are different when composite laminates are loaded under different boundary conditions. Also the results can provide experimental data for investigating the quasi-static indentation damage of composite laminates on the basis of real application.

Abstract:The modified C/C composite was quickly prepared by the approach of liquid impregnation combined with reactive melt infiltration. The microstructure was studied and the ablation behavior exposed under oxyacetylene flame and highfrequency plasma wind tunnel atmosphere was assessed. Results show that many high melting point refractory compounds such as HfC, ZrC, TaC are introduced into the modified C/C composite, the density and open porosity of which are 3.83 g/cm³ and 4.71%, respectively. A compact oxide film generates upon the modified C/C composite after oxyacetylene flame ablated 360 s, which is mainly composed of HfO₂, ZrO₂ and Ta₂O₅. The linear ablation rate of modified C/C composite is 0.005 18 mm/s. The ablation resistance of modified C/C composite bulb model is assessed by high-frequency plasma wind tunnel, the heat flux is 3.53 MW/m², the stagnation temperature is 2293 ℃, and the test duration is 180s. After ablation, a dense oxide protective layer forms on the surface of the model, the shape and the dimension of the model are changed insignificantly, and the linear ablation rate is 0.001 72 mm/s after removing the oxide layer.

Abstract:The viscosity and curing characteristics of bisphenol-E cyanate ester resin were studied through experiments to reveal the influence of catalyst on the curing mechanism of the cyanate ester resin. Quartz fiber/bisphenol-E cyanate ester composites were fabricated by RTM (Resin Transfer Molding) and VIMP (Vacuum Infusion Molding Process) processes to investigate its mechanical properties. Results show that the viscosity of the resin system is less than 300 mPa?s and its gel time is more than 10 h from room temperature to 90 ℃. The temperatures of initial curing, curing and final curing of the resin system are 186±5 ℃, 235±5 ℃ and 286±5 ℃ respectively. And the curing characteristic temperature decreases with the increasing content of the catalyst until the catalyst saturates with the range from 0.02% to 0.03%, which can cause the curing temperature of the resin system decreased by nearly 60 ℃. Therefore, it is very important to avoid implosion and to fabricate the quartz fiber/cyanate ester composites by liquid composite molding successfully. The mechanical properties of VIMP manufactured sample is obviously higher than that of RTM fabricated sample.

Abstract:Different interphases between the carbon nanotubes and the epoxy resin were constructed through the organic functionalization of carbon nanotubes. Effects of different functionalized carbon nanotubes on the glass transition temperature of the epoxy resin composites were investigated by using the dynamic mechanical analysis method; the roughness of epoxy resin composites was studied in the pendulum impact test. Results show that: the glass transition temperature of the composites with amination carbon nanotube is the highest, while that of the composites with carboxylation carbon nanotube is lower than that of the pure epoxy resin; toughness of the composites with embedded carbon nanotubes is doubled. These variation laws in the properties are attributed to the different interphases formed between the functionalized carbon nanotubes and epoxy resin matrixes.

Abstract:Fiber reinforced composites have been widely used in aerospace and aircraft structures because of their excellent mechanical properties and light weight. Glass fiber reinforced epoxy composite truss with square cross section under three-point bending exhibites nonlinear behavior according to finite element analysis. On the Isight platform, a multi-parameter optimization method was conducted to obtain five key geometric parameters of the optimal composite truss, which met the demands of structural stiffness, load bearing and light weight. Nonlinear structural responses of the optimal composite truss were obtained. The results showed that the use of Isight platform has high efficiency and reliability for multi-parameter optimization of truss structure.

Abstract:The molybdenum coating was successfully deposited on the surface of silicon carbide by the magnetron sputtering method and the crystallized heat treatment process, and its surface morphology and chemical composition were analyzed. The SiC_p/Cu composite was prepared by vacuum hot-pressing sintering, and the effects of the interfacial layer thickness on the thermal conductivity property were studied in detail. Results are as follows: molybdenum coating can be successfully deposited on the surface of silicon carbide by magnetron sputtering method, the roughness and the thickness of the film are enhanced with the sputter time postponed, and the molybdenum on the surface is in amorphous state. After the crystallized heat treatment, the molybdenum coating is in densification crystalline state. The sputtering time affects the thickness of the Mo coating and the thermal conductivity of SiC_p/Cu obviously. With the time postponed, the thickness of the Mo coating is increased. And the thermal conductivity increases firstly and then decreases as the sputtering time increases. The thermal conductivity of the SiC_p/Cu composite in 800 ℃crystallized heat treatment fabricated by the 9 h Mo coated SiC powders in 850 ℃ hot pressing can reach 274.056 W/(m·K) when the volume fraction of SiC is about 50%.

Abstract:There are problems, such as thermal residual stress and second bonding layers, in radome which is prepared by metal FSSs (frequency selective surfaces). To avoid these disadvantages, carbon fiber fabric/epoxy composite which has good compatibility with radome wall structure of polymer composite was adopted to prepare FSSs; the free space method was carried out to evaluate the electromagnetic transmission characteristics of the composite FSS specimens; the numerical analysis model was employed to analyze the electromagnetic transmission mechanism and influencing factors of FSS. Results show that: the composite FSS with carbon fiber can realize the function of frequency selection, while the transmission loss at the position of resonance frequency is great; the electromagnetic transmission performance of composite FSS can be adjusted by changing the aperture-to-cell ratio, thickness, conductivity and dielectric constant. 

Abstract:A finite element model of the composite T-joints under bending load was established. The Tsai-Wu failure criterion and a cohesive zone model were used to simulate and analyze the failure mechanisms and carrying capacities of the composite T-joints under bending load. By static bending experiments, four failure modes have been investigated during bending failure processes of the composite T-joints. The maximum bending load of the T-joint calculated by finite element model methods was consistent well with experimental results.

Abstract:The impact of ISRJ (Interrupted-Sampling Repeater Jamming) on radar constant false alarm rate detection and the generation principle of false target using ISRJ were analyzed, and then generation methods of false targets jamming were given. On this basis, the detection cost caused by the false alarm and false dismissal in a search period of radar was chosen as the criteria of detection performance. The detection costs of CA-CFAR, OS-CFAR, CMLD-CFAR detectors for active decoy using IRSJ were analyzed, especially the influence of key factors of ISRJ on detection costs. Simulation result shows that the detection costs will increase remarkably for the active decoy from IRSJ and it is sensitive to the jammer power and duty ratios, but have little relationship to the repeating frequency. Among the three detectors, the detection costs of radar CMLDCFAR detectors are higher than those of the OS-CFAR and the CA-CFAR.

Abstract:A large divide will be formed in the output signal of correlator after rejecting narrow-band interface. The traditional anti-interference method based on the time of arrival will be locked on the side-lobes of real signals. To solve this problem, a new delay-waiting detection method based on local maximum value was presented. Under the prerequisite that the side-lobes do not superpose the spoofing signals, the method first searched the local maximum in three chips of main lobes to prevent the capture module from locking side-lobes. Then the earliest code-phase point from those local maximum was chosen to remove repeater spoofing jamming. Compare with the traditional anti-interference method based on the time of arrival, performance of the proposed method is similar in the absence of narrow-band interface, but it is significantly better in the narrow-band interface condition. The numerical simulation results validate the effectiveness of the method.

Abstract:Traditional estimate method has limited capacity when the scan rate of radar antenna varies with time. Thus a state space model for estimating beam azimuth was established, and the particle filter was introduced to estimate the state variables. Particle filter is a powerful method for state estimation in non-linear and non-Gauss case， the radar beam′s azimuth estimating algorithm based on particle filter has better performance, and it can adapt to the case where the scan rate of radar antenna varies with time. The simulation results show that the applicability and the efficiency of the proposed algorithm are desired. 

Abstract:In order to reduce the hardware cost of embryonics system on the promise of ensuring system reliability, a novel genome memory structure—partial-DNA cyclic memory was presented, and only part of the system’s DNA was stored. The embryonics array’s functional differentiation and self repairing were achieved through the gene cyclic and non-cyclic shift in the cell and between cells, and the genes stored in memory were updated during the self repairing process. In this memory structure, the gene backups were set according to actual demand of system reliability and hardware cost, which were independent from the number of idle resources in embryonics array. Theoretical analysis and simulation results show that the new genome memory structure can not only achieve embryonics array’s functional differentiation and self-repair, but also can ensure system reliability and reduce hardware cost, and it has a high practical engineering value.

Abstract:To achieve the goal of high performance and flexibility, a parameterized multi-standard adaptive radix-4 Viterbi decoder based on the field-programmable gate array was presented. This decoder adopts constraint lengths ranging from 3 to 9, code rates of 1/2 or 1/3 and supports error-correcting decoding of arbitrary truncation lengths. The unsigned quantization, add-compare-select unit optimization and normalization judgment logic separation strategies were used to optimize the design of critical path, so that it can improve system throughput. Experiment results show that: the decoder can change the structures according to the parameters set by users and achieve dynamic switching in multiple communication standards; the throughput can reach up to 541 Mbps, apparently superior to the related works; the decoder achieves low bit error ratio in multiple standards such as GPRS, WiMax, LTE, CDMA and 3G and satisfies the decoding requirements of multiple communication standards. 

Abstract:Aimed at an exascale supercomputer, an FPDC (failure prediction data collection framework) was introduced to fully collect the data related to the state of compute nodes’ health. An adaptive multi-layer data aggregation method was presented for data aggregation with less overhead. Extensive experiments, by implementing FPDC on TH-1A，indicate that the FPDC has the advantage of high efficiency and good scalability.

Abstract:The satellite data transmission system is faced with various threats such as single event upset in semiconductor devices, the transmission noise and so on. The key component of the design and implementation of high-capacity SSR (Solid State Recorder) of the transmission system was introduced, and based on the SSR, a fault tolerance mechanism was proposed to protect management information, data bit stream, satellite-to-ground link and file delivery. The mechanism improved the fault tolerance ability of the management information of SSR, the data in store and the transmission channel with the hamming code, the RS code and the LDPC (Low Density Parity Check Code) encoding. Advanced research of one automatic repeat request method with CFDP (CCSDS File Delivery Protocol) was also proposed based on the SSR of one actual space mission to improve the transmission reliability in file-level. The SSR used 4-pipeline writing and bus expansion techniques to achieve the throughput rate of almost 900Mbps theoretically and the capacity of 256Gb.

Abstract:Aiming at the problems of infrared quantitative detection of thermal barrier coating structures, the LM recognition algorithm based on pulse phase was put forward. The transient thermal model of thermal barrier coating structures was established in an axisymmetric cylindrical coordinate in view of the research problem. The surface temperature field of the research model was calculated by the finite volume method. Then the phase distribution of the inspection surface was obtained through a fast Fourier transform. The impacts of parameters to be detected on the phase difference of the inspection surface were analyzed. Taking the phase as identification condition, the quantitative identification of coating thickness and material inner defects was conducted by using LM inversion algorithm. The effectiveness of LM identification method on the basis of phase detection was evidenced by the numerical experiment results.

Abstract:Aimed at the demand of spare parts changes dynamically as the mission phases change, and considering the influence of the scrap probability owing to the finite carrying repair capacity of combat units, by the introduction of the scrap factor, the evaluation model of time-varying operation availability for two echelon support system was developed, in which, the failure parts can be scrapped and there is no exterior supply. And then, a simulation is realized based on the ExtendSim software and the availability results was received. According to the results, the parameter fitting was carried into execution and the approximate analytical formula of scrap factor in the availability model was obtained. In a given example, the scrap factor can adapt to different reliability and maintainability parameters, and the adaptability is validated. The evaluation model is a complementary for conventional models which is developed based on the spare parts balance in support system and can help equipment personals to make appropriate spare parts programs. 

Abstract:In recent years, the network dependency and interdependent networks have become a research hotspot in the field of complex network, but literature about the overview of related research progress is still very rare. Based on the systematic research of domestic and overseas literatures, the percolation theory of the interdependent networks was briefly introduced, and the cascading failure process of the interdependent networks was described. Then the related progress was summarized from three aspects that can affect the robustness of interdependent networks: characteristics of sub network, type of dependency edge, the combination of sub networks. Finally, the future development direction of interdependent networks was prospected in both theoretical and practical aspects.

Abstract:Sequential approximate optimization method has shortcomings in several respects, such as surrogate model establishing and infill strategy at present. Basing on local density of sampling points, the influence volume concept which is inversely proportional to local density was introduced and then the optimal kernel width of radial basis function was obtained by means of total influence volume optimization, thus, the function approximation needs in sequential approximate optimization process under the conditions of different scales and heterogeneous samples were satisfied. Potential feasible region infill strategy was proposed and potential optimal strategy was applied together, both exploration and exploitation capacity of the algorithm were satisfied. Three-step convergence criterion was set up. The algorithm flow process of sequential approximate optimization was constructed. For Golinski reducer optimization problem,the global optimal solution was solved after calculating original model 42 times, which embodied the good global optimization capacity and searching efficiency of the algorithm. Shape optimization mathematical model was established for TH-II rocket, global optimal shape was gained after 165 times of original model calling using the proposed method. The design efficiency was increased greatly and TH-II rocket aerodynamic shape was proved reliable by flight testing.

Abstract:With the goal of solar sail mission to near interstellar space (200AU) in 20 years, a global optimization problem of solar sail gravity assist and solar photonic assist trajectory for interstellar mission was studied. A mathematical model for solar sail time-optimal trajectory was established. By taking the constrains of solar sail gravity assist and solar photonic assist into the object function, the four-point boundary value problem of orbit optimization can be converted to multi-variable optimization problem of no constraint. With choosing appropriate constrain proportions, the problem was solved by using genetic algorithm and sequential quadratic programming method. Optimization result shows that plenty of time can be saved by adding Jupiter gravity assist, though solar sail gains a large velocity with solar photonic assist. The proposed global optimization algorithm will provide a reference for the preliminary design of solar system escape orbit.

Abstract:In order to formulate tactical indicators and mission plan，the footprint for multiple-pulse missile was investigated. The footprint optimization problem can be transformed into an optimal control problem by introducing the cost function which is formulated as a weighted combination of down-range and cross-range. A multiple constraints and phases trajectory optimization model of double optimization design variables that are composed by the angle of attack and slip angle was established，and using the hp-adaptive pseudo-spectral method to solve it. Moreover, the effects of multiple-pulse motor parameters and terminal constraints on the footprint were emphatically analyzed. Simulation results show the efficiency of the proposed method in solving the footprint optimization design problem with multiple constraints and phases. The smaller interval time of multiple-pulse missile motor，the greater of thrust radio and the smaller mass radio of the pulse motor are corresponded to a bigger footprint. Compared with the terminal velocity, the impact angle affects the footprint to a lesser degree．

Abstract:In order to establish an integrated estimation system for quality of information in WSN (wireless sensor network), a flexible tailorable framework was proposed to dynamically estimate information accuracy and information timeliness in different WSN applications. The framework aggregates all information of the sensor nodes at the sink node on the basis of information fusion theory and timescale marking technique. Through approximating the fusion result to ground truth, the accuracy of measurement data and decision information was quantified by utilizing the numerical/nominal difference between the observed information and the fusion result, respectively. According to application deadline and delay sensitivity of information acquisition, timeliness was classified as three categories for characterization and representation, and quantified through the lightweight measurement of the information acquisition time. The estimation results along the time are dynamically updated by adopting a sliding window mechanism and an incremental calculation algorithm. The effectiveness of the framework was validated by simulations, including timeliness estimation in three target surveillance application scenarios and accuracy estimation in two environmental monitoring application scenarios. Simulation results match with the reference criteria, which demonstrates that the framework can be flexibly tailored to estimate information accuracy and information timeliness in different WSN applications.

Abstract:The V-notch asymptotic displacement field was derived through an approach based on the Williams’ series expansion and linear algebraic transforms. By incorporating the displacement expressions to the common isoparametric elements, the enriched and transition element displacement model were obtained, and then the enriched finite element equation was derived consequently. The enriched finite element model for a V-notched bi-material three-point bending beam and an orthogonal bonded materials interface end plane problem were constructed. The stress intensity factors can be solved directly from the finite element equation. Comparisons between the results and the published data computed with other algorithm indicate that the present method is correct and can be used to analyze the fracture property of the Vnotched bimaterial structure.

Abstract:As a complex system combined with optics, electronics and mechanics, the RLG (ring laser gyroscope) can measure the angle rate with high accuracy. In order to meet the requirement of longer-time and higher precision in inertial navigation system, the characteristics between the RLG drift error and different signals from various sensors were studied. Based on the traditional RLG drift error compensation model, the compound signals from thermometers, photodiodes and piezoelectric ceramics attached on the dithered mechanism were introduced into the model. Moreover, by utilizing the support vector machine algorithm which has good nonlinear fitting capacity, the model was optimized by the correlation features between the mechanically dithered RLG drift error and the compound signals. The experimental results show that the precision of the mechanically dithered RLG drift error compensation model is higher than the traditional one.

Abstract:Operation conditions usually change when rotating machinery works. The changing operational conditions and machine fault can make the mechanical vibration characteristics change and cause diagnosis errors, so a new method for the health monitoring of bearings under changing operational conditions was proposed. In this method, the RVMs (Relevance Vector Machines) were used for obtaining the continuous function relationships between the adaptive parameters of the threshold model and the characteristic statistics of vibration features. Based on the characteristic statistic in different operation conditions, the adaptive threshold model was constructed. This method was used for bearings health monitoring at different revolving speed. Monitoring results show that this method is effective only when the rotational speed is higher than a relative small value.

Abstract:The key technology of making human auricular scaffold by using medical silicon was researched. CT scan and reversed modeling were used to obtain the digital auricular model. And the 3D printing technology was utilized to manufacture the mold of auricular scaffold. The medical silicon MED 4735 was used as the material of the scaffold. Animal experiments were then implemented to examine the biocompatibility of the scaffold. The scaffold made by these technologies highly imitates a normal auricle, with high accuracy, short manufacturing cycle, and no immune rejection, which provides the basis for further clinical human experiments.

Abstract:In order to improve the reliability of the levitation sensor in maglev train, the mechanism of the surge under the circumstances of thunder strike and power supply interference were analyzed, and the details of the surge experiment were confirmed. In view of current flow capacity, feasibility of the existing circuit design to suppress surge was explained, and the insufficiency of the reliability at high temperature was pointed out. From the analysis in the aspects of voltage reducing and current shunting, the impact of the surge to the sensitive components is reduced by a large-capacity capacitance shunted in front of the original circuit, and the capability of the sensor power to suppress surge is promoted.