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101.
102.
The laser cladding of Fe-based alloys on a medium carbon steel substrate was performed using a CO2 laser and Ar shielding gas that was blown into a molten pool. The microstructure and cracking susceptibility of the laser-clad layers were studied in terms of carbon additions. Results show that the small change of the carbon content in the alloy powders can obviously change the microstructure and properties of the layers. When the carbon content is in the range of 0.3–0.4 wt.%, the decrease of the carbon content in alloy powders will increase the hardness and toughness of the layers simultaneously under the same process parameters. As a result, crack-free coatings with high hardness can be obtained. As the carbon content increases from 0.2 wt.% to 0.4 wt.%, the segregation ratio of chromium increases, while the segregation ratios of nickel, manganese, and silicon first decrease and then increase. At the same time, a new designing principle concerning the composition and microstructure has been put forward, and the principal mechanisms of strengthening and toughening of the layers are fine-grain strengthening and low carbon martensitic phase transformation strengthening. 相似文献
103.
本文综合应用因素空间、信息系统和重于关系的方法,讨论了概念的内涵表示及其他有关问题。特别是,对在描述概念问题中不同于内涵和外延的第三种方法,即典型示范表示做了进一步的分析。 相似文献
104.
Lenglart不等式与特殊半鞅的收敛集 总被引:3,自引:1,他引:2
本文讨论局部鞅和特殊半鞅的收敛集。我们给出Lenglart不等式的一个推广形式,利用这一不等式对一些定理给出了简单证明,对一些结果作了改进和推广。 相似文献
105.
该文通过构造特殊形式的有效集来逼近KKT点处的有效集,给出了一个任意初始点下的序列线性方程组新算法,并证明了该算法在没有严格互补松驰条件的情况下具有全局收敛性和一步超线性收敛性。
相似文献
106.
We prove that the quasi continuous version of a functional in Epr is continuous along the sample paths of the Dirichlet process provided that p>2, 0<r?1 and pr>2, without assuming the Meyer equivalence. Parallel results for multi-parameter processes are also obtained. Moreover, for 1<p<2, we prove that a n parameter Dirichlet process does not touch a set of (p,2n)-zero capacity. As an example, we also study the quasi-everywhere existence of the local times of martingales on path space. 相似文献
107.
Navier-Stokes方程带Backtracking技巧的两重网格算法 总被引:3,自引:1,他引:2
1 引 言考虑二维不可压 Navier-Stokes方程: 相似文献
108.
In this article, the linear and nonlinear shear rheological behaviors of polylactide (PLA)/clay (organophilic‐montmorillonite) nanocomposites (PLACNs) were investigated by an Advanced Rheology Expanded System rheometer. The nanocomposites were prepared by master batch method using a twin‐screw extruder with poly(ε‐caprolactone) (PCL) as a compatibilizer. The presence of org‐MMT leads to obvious pseudo‐solid‐like behaviors of nanocomposite melts. The behaviors caused by the formation of a “percolating network” derived from the reciprocity among the strong related sheet particles. Therefore, the storage moduli, loss moduli, and dynamic viscosities of PLACNs show a monotonic increase with MMT content. Nonterminal behaviors exists in PLACNs nanocomposites. Besides the PLACNs melts show a greater shear thinning tendency than pure PLA melt because of the preferential orientation of the MMT layers. Therefore, PLACNs have higher moduli but better processibility compared with pure PLA. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3189–3196, 2007 相似文献
109.
Qi Sheng Liu Lian Dong Liu Jing Min Shi 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(1):m58-m60
In the title centrosymmetric binuclear complex, [Cd2(C17H11N3O)4(H2O)2](ClO4)4, the CdII ion assumes a distorted octahedral geometry. There are π–π stacking interactions between the pyridine and 1,10‐phenanthroline ring systems of adjacent ligands at the same CdII centre. Intermolecular hydrogen bonds between the coordinated aqua ligand and the O atom of a keto group connect adjacent complex cations into extended chains. Hydrogen bonds also exist between the complex cations and the perchlorate anions. Compared with the fluorescence spectrum of the organic ligand, the complex displays strong fluorescent emission and an ipsochromic shift of the emission peaks, which may be attributed to the structural character. 相似文献
110.
In this paper, a projection method is presented for solving the flow problems in domains with moving boundaries. In order to track the movement of the domain boundaries, arbitrary‐Lagrangian–Eulerian (ALE) co‐ordinates are used. The unsteady incompressible Navier–Stokes equations on the ALE co‐ordinates are solved by using a projection method developed in this paper. This projection method is based on the Bell's Godunov‐projection method. However, substantial changes are made so that this algorithm is capable of solving the ALE form of incompressible Navier–Stokes equations. Multi‐block structured grids are used to discretize the flow domains. The grid velocity is not explicitly computed; instead the volume change is used to account for the effect of grid movement. A new method is also proposed to compute the freestream capturing metrics so that the geometric conservation law (GCL) can be satisfied exactly in this algorithm. This projection method is also parallelized so that the state of the art high performance computers can be used to match the computation cost associated with the moving grid calculations. Several test cases are solved to verify the performance of this moving‐grid projection method. Copyright © 2004 John Wiley Sons, Ltd. 相似文献