High-reflectance 193 nm Al2O3/MgF2 mirrors

Thin-film single layers of Al2O3 and MgF2 were deposited upon super polished fused-silica by electron-beam evaporation. The subsequent optical constants n and k were reported for the spectral range of 180-230 nm. High-reflectance dense multilayer coatings for 193 nm were designed on the basis of the evaluated optical constants and produced. The spectra of the reflectance of HR coatings were compared to the theoretical calculations. HR mirrors of 27 layers with a reflectance of more than 98% were reported. (c) 2004 Elsevier B.V. All rights reserved.

高寒草甸小气候考察研究

文章介绍了海北高寒草甸试验区的野外考察现场和考察情况，并对青海海北高寒草甸矮嵩矮嵩草草甸试验区的小气候考察结果进行了讨论，结果表明：高寒草甸地区具有明显高寒大陆性气候特征，日较差大，日照时间长，地表强度具明显的周期变化，太阳辐射强烈，全年总辐射量5.866～6.704*10~6KJ/m~2，但较湿润，可为研究高寒草甸小气候特点、局地生态环境和指导生产实践提供科学依据。

Vertically forced surface wave in weakly viscous fluids bounded in a circular cylindrical vessel

Two-time scale perturbation expansions were developed in weakly viscous fluids to investigate surface wave motions by linearizing the Navier-Stokes equation in a circular cylindrical vessel which is subject to a vertical oscillation. The fluid field was divided into an outer potential flow region and an inner boundary layer region. A linear amplitude equation of slowly varying complex amplitude, which incorporates a damping term and external excitation, was derived for the weakly viscid fluids. The condition for the appearance of stable surface waves was obtained and the critical curve was determined. In addition, an analytical expression for the damping coefficient was determined and the relationship between damping and other related parameters (such as viscosity, forced amplitude, forced frequency and the depth of fluid, etc.) was presented. Finally, the influence both of the surface tension and the weak viscosity on the mode formation was described by comparing theoretical and experimental results. The results show that when the forcing frequency is low, the viscosity of the fluid is prominent for the mode selection. However, when the forcing frequency is high, the surface tension of the fluid is prominent.

Effects of physical parameter range on dimensionless variable sensitivity in water flooding reservoirs

The similarity criterion for water flooding reservoir flows is concerned with in the present paper. When finding out all the dimensionless variables governing this kind of flow, their physical meanings are subsequently elucidated. Then, a numerical approach of sensitivity analysis is adopted to quantify their corresponding dominance degree among the similarity parameters. In this way, we may finally identify major scaling law in different parameter range and demonstrate the respective effects of viscosity, permeability and injection rate.

高温下CF_4在H_2中解离的反应动力学研究

用单脉冲激波管研究了有少量ＣＦ３Ｃｌ参予下的ＣＦ４与Ｈ２的混合物在高温下的反应动力学，发现主要产物为Ｃ２Ｆ４和ＣＦ３Ｈ．对实验结果的分析表明，反应过程为一个双中心链反应。始发反应为ＣＦ３Ｃｌ的Ｃ—Ｃｌ键的断裂，继之以由Ｈ２和ＣＦ４为媒介的双中心链传递，最后测得温度由１０００至１０８０Ｋ，压力为０．１ＭＰａ下的ＣＦ４表观分解速率常数为Ｋｅｆｆ＝１０１３．７ｅｘｐ（－５５０００／ＲＴ）１１／２ｍｏｌ－１ｓ－１对这一结果进行分析，得到以下相关的反应速度常数ｋ（ＣＦ３Ｃｌ→ＣＦ３＋Ｃｌ?）＝１０１５ｅｘｐ（－８１０００／ＲＴ）ｓ－１ｋ（ＣＦ３＋Ｈ２→ＣＦ３Ｈ＋Ｈ?）＝１０８．６ｅｘｐ（－８８００／ＲＴ）１?ｍｏｌ－１?ｓ－１ｋ（ＣＦ４＋Ｈ?→ＣＦ３?＋ＨＦ）＝１０１１．４ｅｘｐ（Ｇ２００００／ＲＴ）１?ｍｏｌ－１?ｓ－１ｋ（ＣＦ３?＋Ｈ?→ＣＦ３Ｈ）＝１０８．０１?ｍｏｌ－１?ｓ－１

秦岭山脉对冷空气屏障的理论研究

利用二维大气中尺度数值模式，以１９７７年１月２０日－２２日的冷空气侵袭秦岭山区为例，从观测资料与数值计算两方面分析了由秦岭山脉的屏障作用而引起南北温差的主要原因。结果表明：这种屏障作用不仅体现在秦岭山脉对冷空气的阻挡作用上，而且还与秦岭南坡上的下坡风引起的绝热下沉增温有关。秦岭山脉对冷空气阻挡的动力原因除与秦岭山脉本身的拔海高度较高有关外，还与它的地形形状有关，尤其是位于秦岭北部的渭河河谷，它抑制冷空气入侵谷内，进而阻挡冷空气翻越秦岭山脉。

含裂纹板壳及三维裂纹体断裂问题研究进展

<正> Ⅰ.前言 由于灾难性工程断裂事故时有发生,工程结构安全性评定引起人们的极大关注。1982年美国Battelle实验室在关于断裂损失的首次综合考察中提出,材料的断裂以及为防止这类破坏所作的努力,使美国工业每年耗费达1190亿美元,相当于国家总产值的4％。但在不增加断裂危险情况下,加强检查、维护和修理,约有29％的断裂耗费可以避免。利用断裂力学的研究成果改进材料制造工艺和加强焊接过程的质量控制,可使每年耗费再减少24％。因

分层介质中快磁声波的传播

<正> 分层介质中阿尔文波的传播特征已有研究,我们讨论分层介质中的快磁声波,对于一维问题,假设基态为在直角坐标系中列出磁流体力学方程组为

平面应力的弹塑性断裂模型及其有限元分析

本文根据文献对薄钢板试样的实验分析,提出一个平面应力的弹塑性断裂模型——带状颈缩区模型.将Dugdale模型推广到弹塑性变形场情形.用弹塑性全量理论和增量理论的有限元法,分别计算了具有中心裂纹的薄宽板受均匀拉仲情形的裂纹张开位移、应力应变场.结果表明Burdekin设计曲线在一定条件下才是安全的,本文计算的裂纹张开位移与一些实验测量结果符合良好.

关于充液腔体旋转运动稳定问题的变分原理及其应用

对于任意形状、充满粘性液体的腔体绕惯性主轴整体旋转的一般情形,导得小扰动运动的一组线性微分一积分方程组.在稳定理论基础上发展的一系列方法都处理不了这个问题.本文应用文献[1]中的方法导得这个问题变分原理的一般形式,并得到一系列稳定判据,以前不少作者的结果均是本文的特例~([3-6])。本文的变分方法在充液腔体运动稳定性问题中具有较广泛的应用,对于线性非自伴本征值问题原则上都能应用。

考虑剪应变的弹性薄壁杆件的振动理论

<正> 对于开口截面彈性薄壁杆件的振动問題,符拉索夫在1940年提出的理論,是基于下列两个基本假設:(1)截面具有剛硬不可变形的周綫;(2)中曲面无剪应变。其后,有些学者也曾提出过相同的理論(例如.R.海里格).由于忽略了中曲面的剪应变,我們可以估計得到,符拉索夫的理論只适用于研究低频率的固有振动和強迫振动,而不适用于研究高频瘁的振动。由于行动載荷和冲击载荷必然引起各个固有频率的振动,因此符拉索夫的理論也不适用于研究这些載荷作用下的振动問題。为了要更好地研究这些問題,必須要考慮剪应变的影响。

物理力学介绍

<正> 一引言物理力学是一个新的力学分枝,具体地提出这个名词还只不过四五年;所以我们必需解释一下物理力学是什么、是为什么的。先说物理力学是为什么的:物理力学的目的是想通过对物质的微观分析,把有关物质宏现性质的实验数据总结和整理,找出其中规律。然后再进一步利用这些规律去予见新物质新材料的宏观

Numerical modeling of 3-D turbulent two-phase flow and coal combustion in a pulverized-coal combustor

In the present paper, a multifluid model of two-phase flows with pulverized-coal combustion, based on a continuum-trajectory model with reacting particle phase, is developed and employed to simulate the 3-D turbulent two-phase hows and combustion in a new type of pulverized-coal combustor with one primary-air jet placed along the wall of the combustor. The results show that: (1) this continuum-trajectory model with reacting particle phase can be used in practical engineering to qualitatively predict the flame stability, concentrations of gas species, possibilities of slag formation and soot deposition, etc.; (2) large recirculation zones can be created in the combustor, which is favorable to the ignition and flame stabilization.

Internal resonance of an L-shaped beam with a limit stop .1. Free vibration

Real-life structures often possess piecewise stiffness because of clearances or interference between subassemblies. Such an aspect can alter a system's fundamental free vibration response and leads to complex mode interaction. The free vibration behaviour of an L-shaped beam with a limit stop is analyzed by using the frequency response function and the incremental harmonic balance method. The presence of multiple internal resonances, which involve interactions among the first five modes and are extremely complex, have been discovered by including higher harmonics in the analysis. The results show that mode interaction may occur if the higher harmonics of a vibration mode are close to the natural frequency of a higher mode. The conditions for the existence of internal resonance are explored, and it is shown that a prerequisite is the presence of bifurcation points in the form of intersecting backbone curves. A method to compute such intersections by using only one harmonic in the free vibration solution is proposed. (C) 1996 Academic Press Limited