复合材料结构的界面振动能量传递损耗研究

机床在工作过程中会产生振动,严重影响机床的加工精度,需要有一种新型高阻尼材料来代替传统的机床床身材料,为此,对不同骨料厚度的树脂与骨料复合结构的界面振动能量传递损耗进行了研究。首先,结合应力波理论,构建了树脂、骨料以及树脂与骨料复合材料的数学模型和应力波能量计算方法;然后,通过两端自由摆锤冲击实验,测得了应力波输出端试件截面质点的振动位移曲线,基于振动位移曲线拟合得到了模型的参数;最后,利用平面简谐波传播的衰减系数,对输入端截面质点的振动位移曲线进行了指数放大,得到了输入端质点的振动位移曲线;通过应力波输出端和输入端试件截面质点振动位移曲线,计算得到了应力波传播的能量损耗。研究结果表明:随着骨料厚度的增加,复合材料的界面振动能量传递损耗先增大后减小,当骨料含量在25%~50%之间时,复合材料界面振动能量传递损耗较高;因此,在实际制备高阻尼、减振良好的树脂矿物复合材料时,骨料系统占整体的体积含量应该尽可能控制在25%~50%之间。

里兹法在压杆稳定分析中的应用

根据里兹能量方法求出了一端固支、一端自由和两端铰支的两种压杆的临界压力 。

Energy Embodied in Goods in International Trade of China: Calculation and Policy Implications

In recent years, China's energy demand and Greenhouse gas (GHG) emissions have grown very fast, quite an amount of which was exported as energy embodied in goods in international trade rather than consumed domestically. Starting from the concept of embodied energy, based on input-output energy analysis approach, in this paper the energy embodied in goods in international trade of China during the period from 2001 to 2006 is calculated. The results show that although China has become a net importer of petroleum since 1993, China is a net exporter of embodied energy due to international trade in goods. In 2002, the total amount of energy embodied in exported goods was about 410 million tce (ton of coal equivalent, hereinafter referred to as "tce"). Eliminating the amount of energy embodied in imported goods of about 170 million tce, the net export of embodied energy was about 240 million tce, accounting for 16% of the aggregate primary energy consumption of that very year in China, and the net export of embodied emissions was about 150 million tons of carbon. With the rapid growth of China's international trade, assuming no structural input-output changes of among sectors, in 2006 the net export of embodied energy went up to about 630 million tce, an increase of 162 % over 2002. In addition, this paper also analyzes the possible sources of error in calculation, and also discusses the policy implications according to the result of the calculation.

The Maximum Ice Age Glaciation between the Karakorum Main Ridge (K_2) and the Tarim Basin and its Influence on Global Energy Balance

A modern research approach and working techniques in hitherto unexamined areas, produced the following results: 1). The tongues of deca- kilometre long Karakorum glaciers belong to temperate ice-streams with an annual meltwater output. The short Aghil glaciers on the contrary are continental, arid and cold. 2). The present-day oscillations of the Karakorum glaciers are related to their own mass, and are contrary to and independent of the actual climate. Only the short glaciers, with steep tongue fronts, show a present-day positive balance. 3). C- dated Late Glacial moraines indicate14 a 400~800 m thick valley glacier at the former confluence point of the K2-, Sarpo Laggo- and Skamri glaciers. 4). From the evidence of transfluence passes with roches moutonnées, striae and the limits of glacial polishing, as well as moraines and erratics, a High Glacial at least 1200 m thick ice-stream network between the Karakorums and the Kuen Lun north slopes was reconstructed. The Shaksgam and Yarkand valleys were occupied by glaciers coming from west Tibet. The lowest-lying moraines are to be found in the foreland down to 2000 m, indicating a depression of the High Glacial (LGM) snowline (ELA) by 1300 m. 5). The approximately 10,000 measurements of the radiation balance at up to heights of 5500 m on K2 indicate that with incoming energy near the solar constant the reflection from snow- covered ice is up to 70% greater than from rock and rock waste surfaces. 6).These results confirm for the very dry western margins of Tibet an almost complete ice sheet cover in an area with subtropical energy balance, conforming with the Ice Age hypothesis of the author which is based upon the presence of a 2.4 million km2 Tibetan inland ice sheet. This inland ice developed for the first time when Tibet was uplifted over the snowline during the early Pleistocene. As the measured subtropical radiation balance shows, it was able to trigger the Quaternary Ice Ages.

Casimir Effect of Massive Scalar Field with Hybrid Boundary Condition in(1+1)-Dimensional Spacetime

The Casimir energy of massive scalar field with hybrid （Diriehlet-Neumann） boundary condition is calculated. In order to regularize the model, the typical methods named as mode summation method and Green＇s function method are used respectively. It is found that the regularized zero-point energy density depends on the scalar field＇s mass. When the field is massless, the result is consistent with previous literatures.

Experiments on exactly computing non-linear energy transfer rate in MASNUM-WAM

The Webb-Resio-Tracy(WRT) method for exact computation of the non-linear energy transfer rate was implemented in MASNUM-WAM, which is a third-generation wave model solving the discrete spectral balance equation. In this paper, we describe the transformation of the spectral space in the original WRT method. Four numerical procedures were developed in which the acceleration techniques in the original WRT method, such as geometric scaling, pre-calculating, and grid-searching, are all reorganized. A series of numerical experiments including two simulations based on real data were performed. The availability of such implementation in both serial and parallel versions of the wave model was proved, and a comparison of computation times showed that some of the developed procedures provided good effi cacy. With exact computation of non-linear energy transfer, MASNUM-WAM now can be used to perform numerical experiments for research purposes, which augurs well for further developments of the model.

撑竿跳高的机械能分析方法研究

以往撑竿跳的运动生物力学研究仅仅局限在人。近年来撑竿跳高研究已经开始关注人与竿子的相互作用。能量分析就是研究这种相互作用的方法。通过这种方法,我们可以对撑竿跳有一个全新的认识,并且帮助运动员提高成绩。目的在于得出撑竿跳能量分析的计算方法,并使用能量分析法对我国优秀撑竿跳高选手高淑英的技术进行分析。

Effects of hydrogen in a vanadium grain boundary:From site occupancy to mechanical properties

We have investigated site occupancy and mechanical properties of a vanadium (V) Σ 5(310)/[001] grain boundary (GB) with hydrogen (H) using a first-principles method. The segregation energy is calculated to be 0.29 eV for the energetically favora- ble V GB interstitial site, indicating that H energetically prefers to segregate into the V GB. We demonstrate that H can largely affect the mechanical properties of the V GB. The tensile strength and the Griffith fracture energy are reduced by approximately 13% (to 18.42 GPa) and 10% (to 1.74 J/m2) because of H segregation in comparison with that of the clean V GB, respectively. Our total energy calculations show that H acts as an embrittler to the V GB based on the Rice-Wang model. The atomic configurations and charge transfer analysis show that the segregated H weakens the surrounding interfacial V-V bonds, leading to the V GB mechanical properties degradation.