纸质构件力学性能试验研究

对铅化纸制作的纸杆和纸带进行了力学试验, 分析了其力学性能, 结果表明:纸杆应力应变曲线存在线弹性段, 弹性模量主要集中在200$\sim$400\,MPa, 并具有一定的离散性. 而纸带抗拉曲线呈明显的非线性特征, 极限拉应变主要集中在0.015$\sim 对铅化纸制作的纸杆和纸带进行了力学试验, 分析了其力学性能, 结果表明:纸杆应力应变曲线存在线弹性段, 弹性模量主要集中在200$\sim$400\,MPa, 并具有一定的离散性. 而纸带抗拉曲线呈明显的非线性特征, 极限拉应变主要集中在0.015$\sim 对铅化纸制作的纸杆和纸带进行了力学试验, 分析了其力学性能, 结果表明:纸杆应力应变曲线存在线弹性段, 弹性模量主要集中在200$\sim$400\,MPa, 并具有一定的离散性. 而纸带抗拉曲线呈明显的非线性特征, 极限拉应变主要集中在0.015$\sim 对铅化纸制作的纸杆和纸带进行了力学试验, 分析了其力学性能, 结果表明:纸杆应力应变曲线存在线弹性段, 弹性模量主要集中在200$\sim$400\,MPa, 并具有一定的离散性. 而纸带抗拉曲线呈明显的非线性特征, 极限拉应变主要集中在0.015$\sim对铅化纸制作的纸杆和纸带进行了力学试验,分析了其力学性能,结果表明:纸杆应力应变曲线存在线弹性段,弹性模量主要集中在200～400 MPa,并具有一定的离散性.而纸带抗拉曲线呈明显的非线性特征,极限拉应变主要集中在0.015～0.025之间,纸带的粘结状态对试件的极限拉应变有较大的影响.     

中频磁控溅射制备a-C：H（Al,W）薄膜及其性能研究

采用中频磁控溅射技术,以W、Al复合靶（面积比为1：1）为靶材,在氩气和甲烷混合气体中于n（100）型单晶硅表面沉积了一系列Al、W共掺杂含氢非晶碳[a-C：H（Al,W）]薄膜.分析了不同甲烷流量对薄膜成分、结构和表面形貌的影响,并表征了薄膜的力学性能和摩擦磨损行为.结果表明：随着甲烷流量的增加,薄膜中C含量呈上升趋势,而W和Al含量均呈现递减趋势,过高流量的CH₄会导致金属靶材中毒.薄膜中的sp²C和sp³C含量受W、Al以及H注入效应的共同影响.所制备的薄膜表面均较为平滑,表面粗糙度（RMS）在0.39 ~0.48 nm范围内.薄膜的纳米硬度（H）在9.98~11.37 GPa之间,弹性模量（E）介于71~93.36 GPa之间,弹性恢复系数均在70 %以上.当薄膜中W和Al的原子百分含量分别为3.74 %和2.37 %时,H/E值和H³/E²值分别为0.141和0.198,且此时薄膜在大气环境下表现出较好的减摩抗磨性能.薄膜具有适度的sp³C/sp²C比值、优异的弹性形变性能、摩擦过程中对偶球表面形成连续而致密的转移层等因素是薄膜具有良好摩擦学性能的重要原因.     

The strain energy criterion of mixed-mode brittle fracture

In this paper, we proposed a new cr tenon or mixea-moae brittle fracture, i.e., the strain energy criterion, which can be stated as (K_Ⅰ/K_Ⅰc)² +(K_Ⅰ/K_Ⅰc)²+(K_Ⅱ/K_Ⅱc)²=1. This criterion is shown to be in good agreement with known experimental data.In this paper, an experimental criterion:(K_Ⅰ/K_Ⅰc)^m+(K_Ⅱ/K_Ⅱc)ⁿ=1, 1≤_n^m≤2.is also proposed.     

都江堰——————优美的工程诗篇

介绍都江堰水利工程所采用的分水及排沙方法, 分析其中的原理. 认识李冰治水的先进 理念以及从中可以得到的启迪.     

[0, k i]1 m -Factorizations Orthogonal to a Subgraph

Let G be a graph,k₁,…,k_m be positive integers. If the edges of graph G can be decomposed into some edge disjoint. [0,k₁]-factor. F₁,…,[0,k_m]-factor F_m, then we can say F={F₁,…,F_m, is a [0,k_i]_m¹-factorization of G. If H is a subgraph with m edges in graph G and |E(H)∩E(F_i)|=1 for all 1≤i≤m, then we can call that F is orthogonal to H. It is proved that if G is a..[0,k₁+…+k_m-m+1]-graph, H is a subgraph with m edges in G, then graph G has a. [0,k_i]₁^m-factorization orthogonal to H.     

BASIC EQUATIONS, THEORY AND PRINCIPLE OF COMPUTATIONAL STOCK MARKET (Ⅲ)-BASIC THEORIES

By basic equations, two basic theories are presented: 1. Theory of stock’s value v^*(t)=v^*(0) exp (ar₂^*t);2. Theory of conservation of stock’s energy. Let stock’s energy Φbe defined as a quadratic function of stock’s price v and its derivative v, Φ=Av²+Bv+Cv²+Dv, under the constraint of basic equation, the problem was reduced to a problem of constrained optimization along optimal path. Using Lagrange multiplier and Euler equation of variation method, it can be proved that Φkeeps conservation for any v,v. The application of these equations and theories on judgement and analysis of tendency of stock market are given, and the judgement is checked to be correct by the recorded tendency of Shenzhen and Shanghai stock markets.     

Fixed point theorem of nonexpansive mappings in convex metric spaces

Let X be a convex metric space with the property that every decreasing sequence of nonenply dosed subsets of X with diameters tending to has menemptyintersection. This paper proved that if T is a mapping of a elosed conver nonempty subset K of X into itself satisfying the inequality:d(T_x,T_y)≤ad(x,t)+b{d(x,T_x)+d(y,T_y)}+c{d(x,T_x)+d(y,T_y)}for all x,y in K,where 0≤a<1,b≥0,c≥0,a+c≠0 and a+2b+3c≤1, then T has a unique fixed point in K.     

走进地震预测——————加卸载响应比方法

 概括介绍了加卸载响应比的基本思路、基本概念、物理基础、加卸载 响应比在地震预测中的应用以及取得的一些成果. 加卸载响应比方法物理基础扎实, 只需利 用地球内部的某些实测数据, 为地震预测提供了一条新的途径.     

THE BÄCKLUND TRANSFORMATION AND NONLINEAR SUPERPOSITION FORMULA OF SOLUTIONS FOR THE LIOUVILLE’S EQUATION IN HIGHER DIMENSIONS

In this paper, we show that Backlund transformation derived by Leibbrandt et al. for the Liouville’s equation in three spatial dimensions, ▽²a=expa, ▽²=-∂_x²+∂_y²+∂_z² can be decomposed into several Backlund transformations for the same equation in two spatial dimensions, moreover, the superposition formula which is derived from this transformation is actually invalid, thus the discussions based on that formula is incorrect as well. We also considered some results about the Liouville’s equation in N spatial dimensions.     

On near-wall hot-wire measurements

A specially constructed hot-wire probe was used to obtain very near-wall velocity measurements in both a fully developed turbulent channel flow and flat plate boundary layer flow. The near-wall hot-wire probe, having been calibrated in a specially constructed laminar flow calibration rig, was used to measure the mean streamwise velocity profile, distributions of streamwise and spanwise intensities of turbulence and turbulence kinetic energy k in the viscous sublayer and beyond; these distributions compare very favorably with available DNS results obtained for channel flow. While low Reynolds number effects were clearly evident for the channel flow, these effects are much less distinct for the boundary layer flow. By assuming the dissipating range of eddy sizes to be statistically isotropic and the validity of Taylor's hypothesis, the dissipation rate ɛ _iso in the very near-wall viscous sublayer region and beyond was determined for both the channel and boundary layer flows. It was found that if the convective velocity U _c in Taylor's hypothesis was assumed to be equal to the mean velocity Uˉ at the point of measurement, the value of (ɛ⁺ _iso)₁ thus obtained agrees well with that of (ɛ ⁺)_DNS for y ⁺ ≥ 80 for channel flow; this suggests the validity of assuming U _c=Uˉ and local isotropy for large values of y ⁺. However, if U _c was assumed to be 10.6u _τ , the value of (ɛ⁺ _iso)₂ thus obtained was found to compare reasonably well with the distribution of (ɛ⁺ _iso)_DNS for y ⁺≤ 15. Received: 31 May 1999/Accepted: 20 December 1999     

Bifurcations of relative equilibria of a heavy bead on a rotating parabolic bowl with dry friction

The motion of a heavy bead on the surface of a parabolic bowl rotating at a constant angular velocity about its axis, which coincides with the vertical, is considered. It is assumed that the dry friction force acts between the bead and the bowl. The sets of nonisolated relative equilibria of the bead on the bowl are determined, and their dependence on the problem parameters is studied. The results are illustrated in the form of bifurcation diagrams.     

大学物理《力学》中的自由度分析

对《力学》中的物体自由度进行多方面分析,以深化教学、提高学生正 确分析物理问题的能力.使用实际教学分析的研究方法,在《力学》范围内讨论自由度与坐标、 自由与约束的关系并得以下结论: (1) 同一物体的自由度随其所在的``空间'不同而不同, 不因坐标系的选取不同而 异, 在同类参考系中不因参考系的动静而有别;(2)自由度遵循叠加原理. 讨论了质点系的总自由度及相关计算问题,并指出研究《力学》中自由度的意义.     

Development and design of new methods of measurement of state of strain of structures

The present paper deals with development and design of new methods utilizing Wiedemann's effect for determination of state of strain in building structures. Wiedemann's effect and some features of torsional strain of magnetic field are the basis of new experimental method. Especially the point electromagnetic strain gages using the effect of pure torsion of electromagnetic field to enable universal examination. For strain-gage measurements, almost all physical quantities are used which can be related to the variation in length of the structures. From the electric strain measurements, the most commonly used methods are the measurements by resonance-wire strain gages or by electric-resistance strain gages. In this paper, electromagnetic strain gages are discussed using the Wiedemann effect, and the author describes some new measuring equipment and his own suggestions and methods based on an application of this effect.     

Calculation of aerodynamic characteristics of arrays of profiles of arbitrary shape

It is well known that the problem on nonseparating potential flow of an incompressible fluid about an array of profiles reduces to an integral equation for a certain real function, determined on the contours of the profiles of the array. As such a function one can take, as was done, for instance, in [1–5], the relative velocity of the fluid on the profiles of the array. For arrays of profiles of arbitrary shape it is necessary to solve the corresponding integral equation numerically. In the particular examples of the calculation of aerodynamic arrays that are available [1–3] the numerical methods used were based on the approximate evaluation of contour integrals by rectangle formulas. As investigations showed, sizeable errors arose thereby in the approximate solution obtained, these being especially significant in the case of curved profiles of relatively small bulk. In the present paper a method for the numerical solution of the integral equation obtained in [5] is proposed. The method is based on the replacement of a profile of the array with an inscribed N polygon, the length of whose sides is of the order N^–1 and whose internal angles are close to . Convergence with increasing N of the numerical solution to an exact solution of the integral equations at the reference points is demonstrated. Examples of the calculation are given.Novosibirsk. Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp. 105–112, March–April, 1972.