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For the purpose of track maintenance in a cluttered environment with some false alarms, false dismissals and measurement disturbances, this paper presents a new multi-object tracking procedure with uncertainty of the source of the measurement data returned from multi-sensor. The tracking method is a thrice deeply-fusion approach constructed by a primary fusion based on an improved probabilistic data association filter (IPDAF), a secondary fusion with historical motion trajectories, and a thrice fusion with road-markings. It incorporates the existence probabilities of the individual tracks and the variable number of objects based on the Bayesian estimation theory, which can improve the tracking performances effectively in an environment with high clutter density. A binary 2-D assignment is adopted for the optimal data association, which is established as a nonlinear optimization problem. In the motion modeling, it introduces multiple measurement models for different sensors into the method. Then, the estimation could be performed with greater reliability. The computational efficiency is satisfying and it can be used for real-time application, which is verified by two real test scenarios.

The solidification microstructure of Al−Si alloy was observed in the experiment, the second dendrite arm spacing (SDAS) was measured, and the effect of temperature on the microstructure was analyzed. Phase-field (PF) model incorporating natural convection caused by gravity was employed to simulate the microstructure evolution of Al−Si alloy under the experimental conditions. Good agreements between the experimental and simulation results verified the reliability of the simulation approach proposed in this study. Based on the proposed model, a series of simulation cases (2D and 3D) were performed to investigate the evolution of columnar and equiaxed dendritic structures. It was found that the solute content of the alloy had little impact on the microstructure evolution, while the solute expansion coefficient had obvious effect on the dendrite tip velocities. Significant improvement of computational efficiency was achieved via novel algorithms, making it possible to perform massive simulation for studying the evolution of solidification microstructures, which is hard to be directly observed in experiments via synchrotron radiation for Al−Si alloy.

Three types of three-dimensional stitched carbon fiber reinforced silicon carbide composites (3DS C/SiCs) with 4, 9 and 16 Z-yarn/cm2 were fabricated by chemical vapor infiltration, respectively. Both iosipescu specimens without enough representative volume elements (RVEs) and ±45° tension specimens containing enough RVEs were tested to attain the in-plane shear properties of 3DS C/SiCs. The results showed that these two methods produced similar results. This demonstrated that the dimensions of iosipescu specimens were not necessary to cover enough RVEs for 3DS ceramic matrix composite in-plane shear testing. With respect to the shear modulus, both two methods would be regarded as the effective methods. However, in terms of the in-plane shear strength, iosipescu method would be a more reliable method.

The TPA method has gradually developed into a mature approach to solve the internal noise problem of vehicles in recent years. Among the excitation transfer path from excitation to the noise at the target point, the noise transfer function is an important path. The noise transfer function is an inherent property of the commercial vehicle cab like the modes. When noise transfer function is low; the noise caused by the vibration transformed from the suspension is relatively low, which will be great help for the comfort of the cab. A vibro-acoustic model of some commercial vehicle cab has been built in this research, and the low frequency region noise transfer function from the mount points to the driver's ears has been simulated. From the comparison of the numerical result and the relevant test result, the accuracy of the simulation model has been proved. For the sensitive frequencies, the vibro-acoustic modes have larger vibration on some thin plates, which has been proved to be the reason for the peak for the noise transfer function. In order to reduce the noise transfer function, damping materials were applied to the sensitive thin plates, the modification effect proved to be content in the real working condition.

Si3N4/SiBCN composite ceramics were prepared by infiltrating and pyrolyzing liquid polyborosilazane in porous Si3N4 ceramics. To increase their wave-absorbing ability, SiC nanoparticles and SiC film obtained by chemical vapor infiltration were separately introduced into the composite ceramics. The surface morphology, element and phase composition of ceramics were analyzed by means of scanning electron microscopy, energy dispersive spectrometer and X-ray diffraction. Dielectric and electromagnetic wave absorbing property researches show that the permittivity and dielectric loss of the ceramics were effectively improved and the electromagnetic reflection coefficient was visibly decreased when SiC was loaded. It is indicated that SiC is an effective dielectric lossy absorbent, and the Si3N4/SiBCN composite ceramics containing SiC possess the great potential in the application of wave-absorbing material.

Boron nitride (BN) coatings were deposited on carbon substrates by low pressure chemical vapor deposition (LPCVD) in a large temperature range of 650~1200 °C, employing BCl3-NH3-H2 reaction system. The effects of depositing temperature on the yield, control step of deposition progress (deposition mechanism), microstructure, and crystallization degree of BN coating were investigated. Results show that BN deposition rate first increases and then decreases as the rising temperature and the maximum deposition rate occurs at 900~1000 °C. By the determination of the Arrenius relationship, there are three temperature regions with different active energies and controlled by different deposition mechanisms, i.e. chemical reaction, mass transport and depletion of reactants. Through the surface morphology observation by scanning electron microscopy (SEM), chemical composition analyses by energy dispersion spectroscopy (EDS) and crystallization degree and grain size comparison by Raman spectroscopy, it can be drawn that interphase-used BN is suitable to be deposited at 1000 °C.

The deposition rate(r) of pyrocarbon deposited from propylene pyrolysis has been explored as a function of residence time (tr=0.2-5s) and deposition temperature (T=1173-1333K) at a constant pressure of 6 kPa. The main feature of r vs. curves was that the deposition rate, firstly increase and then decrease with the residence time. A qualitative chemical model was developed and the kinetic domains were defined for the formation of pyrocarbon. The model could explain the change of deposition rates and kinetic transition due to the occurrence of two different families of ultimate carbon precursor.

The initial pathways in the CVD process of preparing silicon carbides with CH3SiCl3-H2 precursors was searched theoretically, which involves 21 well-defined transition states. The geometries of the species were optimized by employing the B3PW91/6-311G(d,p) method. The energy barriers and the reaction energies were evaluated with the accurate model chemistry method at G3(MP2) level after a non-dynamical electronic correlation detection. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K and 1200 K for all the possible elementary reactions, including both direct decomposition and the radical attacking dissociations for MTS were reported. The energies at any temperature could be derived classically by using the analytical heat capacities. It was found that the free radical reactions have clearly kinetic ascendency to be the most efficient decomposition pathway.

ZrC coatings were prepared by CVD using ZrCl4, C3H6, and H2 as the precursors. The mechanisms responsible for the effects of deposition temperature, H2 flow rate and inlet C/Zr ratio on the ZrC coatings were studied based on the deposition mechanism of ZrC. The results indicate that the ZrC morphologies change from a loose spherical structure to a cauliflower structure, then to a glassy structure as the deposition temperature increases from 1050oC to 1150oC, then to 1250oC. The carbon content in the ZrC coatings increases with increasing the deposition temperature. Higher inlet C/Zr ratio can lead to rough surfaces and higher carbon content. Reasonable H2 concentration can inhibit carbon deposition, and lead to a cauliflower structure.

The 3D needled C/SiC composites were fabricated by chemical vapor infiltration combined with liquid melt infiltration. The microstructure and compressive behavior of 3D needled C/SiC composites were investigated. The results indicated that the 3D needled C/SiC composites were composed of the layers of 0 ° non-woven fiber cloth, short fiber web, 90 ° non-woven fiber cloth, and needle fibers. The materials were composed of carbon fiber, PyC, Si, and SiC. SiC and Si were mostly distributed in the short fiber web layers. Local C/C units (local carbon fiber reinforced PyC) were formed in the fiber bundles of non-woven fiber cloth. A great deal of pores and cracks existed in the 3D needled C/SiC composites. The pores less than 10 μm were generally located in the non-woven cloth layers, while the big pores were in the short fiber web layers. The cracks were regularly presented in the Si and SiC region of the composites and were normal to the axial direction of the fiber bundles. The compressive strengths perpendicular and parallel to the non-woven fiber cloth were about 118±18 MPa and 260±41 MPa, respectively. The compressive fractography revealed stepwise fracture along fiber layers direction.

Two composites of 2D C/SiC-C and 2D C/SiC were fabricated by isothermal-isobaric chemical vapor infiltration (ICVI). The microstructures and mechanical behaviors at room temperature were characterized and investigated, respectively. In the 2D C/SiC-C composite, the PyC matrix layers are homogeneous and continuous. Moreover, the matrix layers of SiC and PyC bond well and almost no microcracks are found in the multilayered matrix. Compared with the 2D C/SiC composite, the 2D C/SiC-C composite exihibits improved mechanical properties.The successive extraction of matrix layers and multiple deflections of cracks in the SiC/PyC multilayered matrix contribute to the improvement of mechanical properties.

Thermal barrier coatings (TBCs) were deposited by an Air Plasma Spraying (APS) technique. The TBC coating comprised of 92 wt.% ZrO2 and 8 wt.% Y2O3 (YSZ), CoNiCrAlY bond coat, and MarM247 nickel base super alloy. After APS of YSZ two batches of TBC specimens were tested, one batch of which was pre-oxidised in air for 10h at 1080 oC. Both types of the specimens were directly pushed into a combustion gas at 1150 oC for 25 min and then out to the natural air for quenching. The combustion gas was produced by burning jet fuel with high speed air in a high temperature wind tunnel, which simulates the real service conditions in an aeroengine. Results show that TBCs prepared by the APS had good thermal shock resistance in the combustion gas. The pre-oxidation treatment of the TBC had a significant effect on its thermal shock life. The as-oxidised TBCs always had worse thermal shock resistance than the as-sprayed ones after thermal shock cycles.

Materials characterization is a crucial issue in the development and application of new materials. Materials characterization aims to mine and acquire characteristic information and their evolution in the materials. It mainly includes three important topics which are microstructural characterization, properties characterization, and environmental degradation. In this paper, characterization techniques about these topics were discussed for C/SiC composites and a characterization system was preliminarily established. All these characterization research and their results further the better understanding of the relationship between microstructure and properties and of the failure mechanisms in the C/SiC composites.

Carbon fiber reinforced silicon carbide matrix composites (C/SiC) are promising candidate materials for high-temperature structural applications. However, in oxidizing environments the two main constituents, that is, carbon fiber and pyrolytic carbon interphase which bears and transfers loads respectively are susceptible to deplete rapidly for oxidation. In this paper, the oxidation behavior of carbon fiber and pyrolytic carbon were investigated by simulating environmental experiments and scanning electron microscopy. The reactivity discrepancy in the carbonaceous constituents and in the different zone of carbon fiber was discerned. After oxidation, the morphology of carbon phase broken before oxidation were compared with that of those broken after oxidation. Based on the microstructural model, the contrast results of morphology were well interpreted from the reactive preference and selectivity.

A highly branched polycarbosilane bearing allyl groups has been prepared by a one-pot synthesis with chloromethyltrichlorosilane, chloromethylmethyldichlorosilane and allyl chloride as the starting materials. The resultant polymer, with the approximate formula [SiH1.2(CH3)0.71(CH2CHCH2)0.09CH2]n, has been characterized by 1H, 13C, and 29Si NMR, GPC, TG and elemental analysis. It could be cross-linked thermally at 170°C in the absence of oxygen. Pyrolysis of the polymer gave a ceramic with a yield of about 70%.

Three-dimensional (3D) carbon fiber reinforced silicon carbide matrix composites (C/SiC) were prepared by a low-pressure chemical vapor infiltration method. The thermal shock behaviors of the composites in different environments were researched using an advanced acoustic emission (AE) system. Damage initiation and propagation were easily detected and evaluated by AE. The thermal shock damage to C/SiC composites mainly occurred at the process of cooling and was limited at argon but unlimited at wet oxygen atmosphere. Also correlations have been established between the different damage mechanisms and the characteristics of acoustic emission signals obtained during thermal shock tests. In this way, the paper contributes to the development of the acoustic emission technique for monitoring of damage development in ceramic-matrix composites.

Internal friction of 2D C/SiC composites fabricated by chemical vapor infiltration (CVI) method was measured by dynamical mechanical analysis (DMA) at different frequencies from room temperature (RT) to 400°C in air atmosphere. Internal friction of 2D C/SiC composites increased gradually with increasing temperature and then decreased after damping peak appeared in the temperature range of 250°C to 300°C. Damping capacity and peak value decreased gradually with increasing frequency, accompanied with a shift of damping peak towards lower temperatures. Moreover, the effect of interphase thickness on damping behavior of 2D C/SiC composites was investigated. The results showed that damping peak of the composites increased gradually and the temperature of the peak shifted to the lower temperature with increasing PyC interphase thickness, when the interphase thickness is in the range of 90~296nm. The influence of interphase thickness on interfacial bonding strength, sliding resistance and the microstructure of SiC matrix was discussed, which was considered to be responsible for the results.

Nano-yttria powder can be synthesized by yttrium citrate-urea precursor, combusted at 600ºC in air. The CVD SiC coated on graphite (CVD SiC/Graphite) infiltrated by the yttrium citrate-urea precursor, combusted at of 600ºC, and then sintered at 1450ºC, the thin yttria film can be achieved. The SEM morphology and EDS result of the thin yttria film show a mass of needle-shaped pining into the CVD SiC layer, which improves the combination of CVD SiC layer and wash yttria coating. Therefore, it is an effective transition layer between CVD SiC coating and wash yttria layer.

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Directional solidification of LaB6-ZrB2, by use of an electron beam heating technique, yielded oriented ZrB2fibers in a LaB6matrix. The average diameter of the ZrB2fibers was ?0.2-1.2 µm, with fiber lengths up to 100 µm. Primary platelike LaB6dendrites formed upon the solidification of an ingot with a composition of LaB6-18 wt ZrB2. LaB6was the first phase to nucleate when eutectic growth occurred, and ZrB2showed nonfaceted growth. For the ingot solidified with planar growth the orientation relations of the phases were as follows: growth direction, 001LaB600.1ZrB2; interfacial plane, 11.0LaB6(11.0)ZrB2.

The conventional ultimate performance test by applying a component in its true application (i.e., in an engine) is often very expensive and impractical when dealing with developmental materials. Simpler, less expensive, and more practical test methods must be utilized. The present work aims toward the applications of an innovative methodology for testing environmental performance of advanced Ceramic Matrix Composites (CMCs) in the presence of combined mechanical, thermal, and environmental applied conditions. To obtain a comprehensive understanding of how a composite might perform in certain application environments, a newly developed environmental performance testing system, which is able to provide the fundamental damage information of the composites in simulating service environments including variables such as temperature, mechanical and thermal stresses, flowing oxidizing gases and high gas pressure, is proposed. The system comprises of two subsystems: (1) equivalent experimental simulating subsystem, and (2) wind tunnel experimental simulating subsystem. The evolution mechanisms of the composites properties and microstructures can be achieved by the former, and then be validated and modified by the latter. Various loading (e.g. fatigue, creep), various atmospheres (e.g. argon, oxygen, water vapor, wet oxygen and molten salt vapor) and various temperature conditions (e.g. constant or cyclic temperatures) can be conducted on the system. Some typical experimental results are presented in this paper. Large quantities of tests have demonstrated the extraordinary stability and reliability of the system.