Rebuilding of metal components with laser cladding forming

Laser cladding forming (LCF) is a novel powerful tool for the repairing of metal components. Rebuilding of V-grooves on medium carbon steel substrates has been carried out with laser cladding forming technique using stainless steel powder as the cladding material. Microstructure of the deposited layers has been characterized using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDAX), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Mechanical properties of the rebuilt V-groove samples have been evaluated by tensile and impacting tests and microhardness measurement. Experimental results show that good fusion bonding between the rebuilt layers and the substrate has been formed, and the microstructure of the cladding layers is mainly composed of fine, dense and defect-free epitaxial columnar dendrites. Due to the effect of grain size refinement, the tensile strength, impacting toughness, elongation and microhardness of the rebuilt samples have been greatly enhanced compared to those of the substrate. Microhardness is also very uniform throughout the rebuilt regions. With the growth of the deposited layers, the microhardness increases gradually. The good ductility of the deposited regions is verified by the SEM fracture analysis.     

一类求解奇异延迟微分方程的两步连续Runge-Kutta方法的收敛性

本文给出了一类求解延迟落在当前积分步内延迟微分方程的两步连续Runge-Kutta方法。在一定条件下我们证明了方法收敛性,数值试验表明方法是有效的。     

A simplified dispersion limit formula for IM/DD systems and itscomparison with experimental results

A simplified formula for the dispersion limit of single-mode-fiber intensity modulation/direct detection (IM/DD) systems is derived for arbitrary given normalized pulse width U, eye opening penalty X and source linewidth enhancement factor α. From the comparison with published theoretical analyses, computer simulation and experimental data, its validity and the limits of existing formulae are shown. Using this simple and general formula, one can easily obtain the dispersion limit of various fiber types under different working conditions in IM/DD systems     

Semilinear Differential Inclusions in Separable Banach Spaces

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Vertical bridgman techniques to homogenize zinc composition of CdZnTe substrates

In order to improve the Zn homogeneity along the axial direction of CdZnTe boule, we have employed a modified Bridgman technique using a (Cd, Zn) alloy source in communication with the melt, whose temperature has been gradually changed from 800 to 840°C during growth. Electron probe microanalysis (EPMA) measurements of Zn composition in the boule shows an excellent homogeneity of Zn along the axis of the CdZnTe boule compared with results in a boule grown by using a fixed source temperature. We have performed a numerical simulation to obtain the approximate temperatures of additional heating and cooling needed to improve the radial Zn homogeneity. CdZnTe boule has been grown by seeded vertical Bridgman furnace with two zones of heater and cooler. Ultraviolet/visible spectroscopic measurements of Zn composition over the length of the boule indicate that the radial distribution of Zn composition is very homogeneous in the body region of the boule, where the radial variation of Zn composition is ±0.0005.     

受激布里渊散射相位共轭现象的二维数值模拟

 使用P.H.Hu等人[3，4]提出的计算途径，数值解了A.Flusberg等人[2]提出的零级方程。计算了布里渊池内随位置而变化的斯托克斯光强度、泵浦光强度和保真度，得到了布里渊池内几个位置上的斯托克斯光相位和强度的横向分布，并计算了泵浦光入口处的反射率和保真度。     

一类多维的非线性Schrdinger方程组的初边值问题

本文考虑一类具有耗散与磁场效应的多维非线性Schrdinger型方程组的初边值问题。使用积分估计(包括L~p—L~q估计)证明了整体解的存在性。     

High-performance InP/InGaAs heterojunction bipolar transistors with highly carbon-doped base grown by chemical beam epitaxy

InP/In/sub 0.53/Ga/sub 0.47/As heterojunction bipolar transistors (HBTs) using a highly carbon-doped base are reported. High carbon doping has been achieved by chemical beam epitaxy (CBE). The resulting hole concentration in the carbon-doped base is as high as 7*10/sup 19//cm/sup 3/. To the authors' knowledge, this is the highest doping level reported using carbon. HBTs with a 20 AA spacer layer exhibited nearly ideal I-V characteristics with collector and base current ideality factor of 1.018 and 1.037, respectively. Current gain and breakdown voltage BV/sub CEO/ were 7 and 6 V, respectively.<>     

Invasiveness of LiTaO/sub 3/ and GaAs probes in external E-O sampling

Disturbances of signals on a coplanar waveguide (CPW) induced by the presence of LiTaO/sub 3/ and GaAs electrooptic probes in external electrooptic (EO) sampling have been simulated and compared quantitatively. The finite-difference-time-domain method is used to simulate the full wave field around a coplanar waveguide on a GaAs substrate in an external EO sampling configuration. The results indicate that the induced signal disturbance, or invasiveness, of a LiTaO/sub 3/ probe is almost ten times that of a GaAs probe in terms of the magnitude of S/sub 11/, but that LiTaO/sub 3/ yields about two times the EO response for a given S/sub 11/ and optical probing wavelength. The transparency of LiTaO/sub 3/ to shorter wavelengths, however, allows an even higher sensitivity for this material relative to GaAs. The results suggest that these probes do not exhibit significant invasiveness (magnitude of S/sub 11/ smaller than -40 dB), if they are removed from contact by the distance of CPWs center conductor width.<>