超薄SiO2层的热生长

隧道小孔中超薄ＳｉＯ２的生长是ＥＥＰＲＯＭ电路制造的关键工艺之一。采用ＳＵＰＲＥＭ－Ⅲ工艺模拟程序对超薄ＳｉＯ２的热生长进行了工艺模拟，经过大量的工艺实验及优化，确定了超薄ＳｉＯ２的最佳生长条件，生长出的ＳｉＯ２性能良好，完全可满足ＥＥＰＲＯＭ研制的要求。     

LiNbO_3晶体的力学参数与晶面取向间的关系

本实验采用 LiNbO_3 单晶,取四种不同晶面指向的样品进行了力学参数,如断裂强度σ_f、断裂功γ_f、断裂韧性 K_(Ic)和弹性模量 E 的测量。在三点弯曲试验条件下,对 LiNbO_3 单晶不同取向时的声发射特征也作了研究。实验发现,σ_f、γ_f 和 E 与晶面间距、晶面上的离子排列关系较为明显,声发射信号随单晶的取向不同而变化,这是其各向异性结构所致。     

Effects of ternary additions on the thermoelastic martensitic transformation of NiAl

Nickel-rich β-NiAl alloys, which are potential materials for high-temperature shape-memory alloys, show a thermoelastic martensitic transformation, which produces their shape memory effect. However, the transformation to Ni₅Al₃ phase during heating of NiAl martensite can interrupt the reversible martensitic transformation; consequently, the shape memory effect in NiAl martensite might not appear after heating. The phase transformation process in binary Ni-(34 to 37)Al martensite was investigated by differential thermal analysis (DTA) method, and we found that the condition of reversible martensitic transformation was not the β → Ni₅Al₃ transformation, but rather the M → Ni₅Al₃ transformation occurring at 250 °C to 300 °C. Therefore, the transformation temperature of M → Ni₅Al₃ determined the highest operating temperature for the shape memory effect. For verifying the critical temperature, the phase transformation process was investigated for eight ternary Ni-33Al-X alloys (X=Cu, Co, Fe, Mn, Cr, Ti, Si, and Nb). Only Ti, Si, and Nb additions were found to be effective in dropping the M _s temperature, and they facilitated the shape memory effect in Ni-33Al-X alloys. In particular, the addition of Si and Nb raised the transformation temperature of M → Ni₅Al₃, a potentially beneficial effect for shape memory at higher temperatures. This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee on Mechanical Behavior of Materials.     

无线光接入技术

无线光通信系统以其高带宽、低成本和安装迅捷等优势成为非常有竞争力的光接入新技术。对无线光通信系统的关键技术、主要优势和存在的问题及国内外相关产品的发展状况和主要特点进行了论述和介绍。     

An efficient implementation of surface impedance boundaryconditions for the finite-difference time-domain method

An efficient way to implement the surface impedance boundary conditions (SIBC) for the finite-difference time-domain (FDTD) method is presented in this paper. Surface impedance boundary conditions are first formulated for a lossy dielectric half-space in the frequency domain. The impedance function of a lossy medium is approximated with a series of first-order rational functions. Then, the resulting time-domain convolution integrals are computed using recursive formulas which are obtained by assuming that the fields are piecewise linear in time. Thus, the recursive formulas derived here are second-order accurate. Unlike a previously published method [7] which requires preprocessing to compute the exponential approximation prior to the FDTD simulation, the preprocessing time is eliminated by performing a rational approximation on the normalized frequency-domain impedance. This approximation is independent of material properties, and the results are tabulated for reference. The implementation of the SIBC for a PEC-backed lossy dielectric shell is also introduced     

Synthesis of ultrafine LiCoO2 powders by the sol-gel method

Ultrafine high-temperature (HT) LiCoO₂ powders were synthesized by the sol-gel method using polyacrylic acid (PAA) as a chelating agent. The decomposition process of the gel precursor was examined to determine the crystallization temperature and the dependence of the physicochemical properties of HT-LiCoO₂ powders on the PAA quantity was extensively investigated. Polycrystalline HT-LiCoO₂ powders, composed of very uniformly sized ultrafine particulates with an average particle size of 30–50 nm and a specific surface area of 2.3–17 m²g^–1, could be obtained at the lower calcination temperature of 550 °C and the shorter calcination time of 1 h compared to the solid-state reaction.     

IP over Optical网络联合流量工程研究

对IPoverOptical网络的流量工程进行了深入的研究。问题,给出了两种流量工程体系结构,重叠流量工程和联合流量工程,然后对这两种流量工程体系进行了比较,并给出了联合流量工程的实现框图以及需要解决的关键问题。     

A new Thermo-viscoplastic Material Model for Finite-Element-Analysis of the Chip Formation Process

A new material model for describing the thermo-viscoplastic flow behavior of workpiece material in metal cutting is presented. In order to express the complex flow behavior which depends on the local strain, strain rate and temperature, a new methodology for sequential formulation is proposed. The material parameters which are achieved by using the flow stress data available at low strain rates are enhanced by matching the results of the experimental investigations and finite element simulations of the orthogonal cutting process. As a result, a material model which has a wide validity range of strain, strain rate and temperature is established.     

苯部分加氢催化剂失活原因的研究

探讨了环己醇装置苯部分加氢催化剂失活的原因，分析了失活机理，并结合实例——母液置换法解决催化剂的氮化物中毒。