摘要：
TiAl3 and TiN composite nanoparticles were continuously synthesized from Ti–48Al master alloy by hydrogen plasma-metal reaction in a N2, H2 and Ar atmosphere. The phase, morphology, and size of the nanoparticles were studied by X-ray diffraction (XRD) and transmission electronic microscopy (TEM). X-ray photoelectron spectroscopy (XPS) and evolved gas analysis (EGA) were used to analyze the surface phase constitution and oxygen content of the nanoparticles. The as-synthesized nanopowders were mainly composed of nearly spherical TiAl3 and tetragonal TiN phases, with a mean diameter of ~42 nm and mass fractions of 49.1% and 24.3%, respectively. Passivation in the atmosphere of Ar and O2 for 24 h at room temperature led to the formation of amorphous Al2O3 shells on the TiAl3 particle surface, with a mean thickness of ~5.0 nm and a mass fraction of ~23.5%, as well as TiO2 with a mass fraction of ~3.2%.
作者机构：
[Gartner, Hunter; Almenar, Eva] Michigan State Univ, Sch Packaging, E Lansing, MI 48824 USA.;[Li, Yana] Wuhan Polytech Univ, Mech Engn Coll, Wuhan, Peoples R China.;[Almenar, Eva] Michigan State Univ, 448 Wilson Rd,Room 130,Packaging Bldg, E Lansing, MI 48824 USA.
通讯机构：
[Almenar, Eva] M;Michigan State Univ, 448 Wilson Rd,Room 130,Packaging Bldg, E Lansing, MI 48824 USA.
摘要：
A new approach for the partial eigenvalue and eigenstructure assignment of undamped vibrating systems is developed. This approach deals with the constant output feedback control with the collocated actuator and sensor configuration, and the output matrix is also considered as a design parameter. It only needs those few eigenpairs to be assigned as well as mass and stiffness matrices of the open-loop vibration system and is easy to implement. In addition, this approach preserves symmetry of the systems. Numerical example demonstrates the effectiveness and accuracy of the proposed approach.
摘要：
Considering the requirements of climbing obstacle and stairs for Explosive Ordnance Disposal (EOD) robot, a method about step feature extraction based on two-dimensional (2D) laser radar is in great demand. In this paper, we research the three-dimensional (3D) environment feature extraction (EFE) method including the 3D point clouds map construction, the line feature extraction and the plane feature extraction. The EFE method can be applied to feature extraction of the step vertical plane. Based on the method, we construct a 3D feature recognition system (FRS) using 2D laser radar. FRS can help us extract quickly the step vertical planes from 3D laser radar line map, thus can provide necessary environment information for the decision and action of EOD robot. We demonstrate the ability of FRS by applying it to some typical step environment.
关键词：
acceleration and velocity feedback;partial quadratic eigenvalue assignment;vibrating system;minimum norm;70J50;65F18;93B52
摘要：
The partial quadratic eigenvalue assignment problem (PQEVAP) is to shift a few undesired eigenvalues of a damped vibrating system to suitably chosen locations, while leaving the remaining eigenvalues and corresponding eigenvectors unchanged. In this paper, an algorithm for solving PQEVAPs and the minimum norm PQEVAP (MNPQEVAP) using acceleration and velocity feedback is proposed. It is shown that solving the PQEVAP here is transformed into solving an eigenvalue assignment of a linear system of a much lower order. Furthermore, the MNPQEVAP here can be efficiently solved by a gradient-based unconstrained optimization method with the derived gradient formula. This algorithm works directly on the second-order system model, and requires the knowledge of only the open-loop eigenvalues to be replaced and their corresponding eigenvectors. Lastly, through two numerical examples, the results of solving the MNPQEVAP under two different combined feedback signals, velocity and displacement signals, and acceleration and velocity signals, are compared from two points of view, i.e. the F-norms of their feedback matrices and the active control energy required from the actuators.
摘要：
A new method for partial eigenstructure assignment using acceleration and displacement feedback for undamped vibration systems is presented in this paper. Firstly, a necessary and sufficient condition is proposed for the incremental mass and stiffness matrices that modify some eigenpairs while keeping other eigenpairs unchanged. Secondly, based on this condition, an algorithm for determining the required control gain matrices of acceleration and displacement feedback, which assign the desired eigenstructure, is developed. This algorithm is easy to implement, and works directly on the dsecond-order system model. More importantly, the algorithm allows the control matrix to be specified beforehand and also leads naturally to a small norm solution of the feedback gain matrices. Finally, some numerical examples are given to demonstrate the effectiveness and accuracy of the proposed algorithm. (C) 2013 Elsevier Ltd. All rights reserved.
摘要：
In this work, TiC coating on a copper alloy electrode, which is prepared by a special electron-spark deposition process (ESD), was modified by friction stir processing (FSP). The microstructure evolution of the coating was investigated, while the mechanical properties of the coating and interface were measured. The results show that FSP eliminates the cracks within TiC coating and improves the interface bonding between the TiC coating and substrate. The hardness of the FSPed TiC coating is increased about 800 HV by decreasing cracks. The elimination of the cracks within the coating is ascribed to the thermal-mechanical effect on the coating during the FSP. The increase in hardness is attributed to the decreasing number of cracks and the disappearance of columnar Cu grains, which are modified by FSP.
期刊：
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing,2014年607:6-9 ISSN：0921-5093
通讯作者：
Mei, Q. S.
作者机构：
[Li, J. Y.] Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430023, Peoples R China.;[Mei, Q. S.] Wuhan Univ, Sch Power & Mech Engn, Dept Mat Engn, Wuhan 430072, Peoples R China.;[Cui, Y. Y.; Yang, R.] Chinese Acad Sci, Inst Met Res, Shenyang 110016, Peoples R China.
通讯机构：
[Mei, Q. S.] W;Wuhan Univ, Sch Power & Mech Engn, Dept Mat Engn, Wuhan 430072, Peoples R China.
关键词：
High temperature property;Composite;Mechanical characterization;Ceramic;Hot pressing;Microstructure
摘要：
Al2O3–Ti2AlN composite with a high volume fraction (~40%) of Al2O3 was successfully fabricated by in situ solid reaction of nanoparticles produced by co-evaporation. The composite, characterized by small Al2O3 particles dispersed homogenously in a fine-grained Ti2AlN matrix, showed a novel combination of high temperature mechanical properties and oxidation resistance.
摘要：
Model parameters of a nonlinear mechanical system are identifiable if a unique relationship exists between its input-output behavior and the parameter values. The identifiability analysis of the parameters is one of the most important steps in the parametric model identification of nonlinear mechanical systems. The concept and two numerical approaches of analyzing the identifiability are presented in this paper. We propose that, via case studies, one had better check of the local identifiability of a parametric model at the identified parameter point using the numerical approach, when the parameter identification procedure has been finished. [DOI: 10.1115/1.4004062]
会议论文集名称：
Lecture Notes in Control and Information Sciences
摘要：
The ability to detect a new fault class can be a useful feature for an intelligent fault classification and diagnosis system. In this paper, we adopt two novelty detection methods, the support vector data description (SVDD) and the Parzen density estimation, to represent known fault class samples, and to detect new fault class samples. The experiments on real multi-class bearing fault data show that the SVDD can give both high identification rates for the prescribed ‘unknown’ fault samples and the known fault samples, which shows an advantage over the Parzen density estimation method in our experiments, via choosing the appropriate SVDD algorithm parameters.
摘要：
Through the differentiating and integrating process, a mathematical model for tempering time effect on quenched steel was derived based on the attribute of state function and the general equation of Hollomon parameter, which correlates the tempering hardness with the tempering time at different tempering temperature. Using the established model, the linear relationship between the tempering hardness and the tempering time in logarithm was proved theoretically, and the tempering hardness for various tempering time was reduced to the measurement and calculation of a hardness experiment tempered for 1 h at different tempering temperatures. Moreover, the hardness of steel 42CrMo and T8Mn tempered for various times at 200 similar to 600 similar to C was calculated using this method. The predicted results are in good agreement with those of the available experiments.
