汉江城固段防洪河堤渗透机理与防治方案研究

根据汉江城固段堤防工程土料室内试验资料与河堤、堤基土料分布,运用渗流理论和有限元法,通过多方案计算分析,研究了该段粉沙土河堤发生渗透破坏的机理,分析了1998年"8·20"洪水造成河堤背水坡脚和附近农田内发生渗透破坏的主要原因,提出了防治渗透破坏的工程措施。     

柔性吊桥设计理论及其应用研究Ⅰ.福建省简易柔性悬索桥分析研究

在收集有关资料和调查研究的基础上 ,根据我国桥梁规范 ,对典型的简易柔性悬索桥主要技术参数及构造进行分析和评价。简述近年在简易柔性悬索桥理论设计和工程实践方面的成果 ,并结合省情展望其发展趋势     

Predicting the humidity control capacity of material based on a linear excitation-response relationship

The Cb value is a useful parameter for estimating the humidity control capacity of materials. It is defined as the ratio of the range of variation of relative humidity in a steel box lined with the material of interest to that in an empty steel box, when sinusoidal temperature variation is applied. However, because it takes a long time to obtain the Cb values for materials at each temperature variation period, we developed an easier method based on a linear excitation-response theory to obtain the Cb values without measuring at each period. Japanese cedar was the material used in this study. The temperature excitation, a jump from a constant temperature to another constant temperature, was used to obtain the absolute humidity response. Under the assumption that the temperature excitation-humidity response relationship is linear, we were able to predict humidity variation to sinusoidal temperature variation at any period, and we obtained the Cb value for each temperature variation period. Predicted values agreed well with the experimental values. From this, it was found that the Cb value could be predicted without measuring the Cb value at each period over a long time. In addition, the peak time difference, which is closely related to the Cb value, could also be predicted in a similar manner.     

Young’s modulus obtained by flexural vibration test of a wooden beam with inhomogeneity of density

The object of this study was to investigate the inhomogeneity of density within a beam from a relationship between the dynamic Young’s moduli from the Euler-Bernoulli elementary theory of bending (E _n) and resonance mode numbers (n), which is plotted as the “E-n” diagram in this article. Rectangular beams with dimensions of 300 (L) × 25 (R) × 5mm (T) of Sakhalin spruce (Picea glehnii Mast.), Sitka spruce (Picea sitchensis Carr.), Japanese red pine (Pinus densiflora Zieb. et Zucc.) and white oak (Cyclobalanopsis myrsinaefolia Oerst.) were used for specimens. Small parts of beams were replaced with a small portion of another species to examine the influence of the inhomogeneity of density on E _n. A free-free flexural vibration test was undertaken and E _n was calculated by the Euler-Bernoulli theory. The resonance frequency of a specimen with inhomogeneity of density was simulated by modal analysis. The density distribution in the longitudinal direction of the specimen for which E _n did not decrease monotonically with n was obtained. From the modal analysis, the inhomogeneity of density was equivalent to a concentrated mass attached to a uniform beam. The pattern of the E-n diagram was changed by replacing a part of the specimen with another species. Specimens for which E _n did not decrease monotonically with n had a high density part because of indented rings, knots, or resin.     

Postbuckling of thin wood-based sandwich panels due to hygroexpansion under high humidity

This study was carried out to investigate the postbuckling behavior of thin wood-based sandwich panels under high humidity. Using the Rayleigh-Ritz method based on the von Karman nonlinear theory for the panel, the solutions for both the approximate and the closed form for postbuckling of orthotropic panels were derived to evaluate the deflection for the boundary condition of all clamped edges. The results suggested that the edge movement be considered for evaluation of a critical moisture content and deflection of thin wood-based panels fixed on the core with an adhesive. The numerical solution obtained from the derived model showed some discrepancy with the experimental results. The predicted results overestimated the center deflection of the panels because creep and plastic deformation might be caused by considerable in-plane stress on panels.Appendix: Abbreviations and symbols total potential energy of panel - A _ij ,D _ij extensional and bending stiffness, respectively - _x , _y midplane strains inx andy directions, respectively - _xy midplane shear strain inxy plane - N _x ^M , N _y ^M hygroscopic forces inx andy directions, respectively - h panel thickness - a, b panel length inx andy directions, respectively - x, y, z coordinate system - u, v, w displacement inx, y, andz directions, respectively - MC moisture content change - a _x ,a _y coefficient of linear expansion inx andy directions, respectively - LE linear expansion (MC) - s arc length - R radius of curvature - N _x ,N _y resultant in-plane forces per unit length inx andy directions, respectively - N _n nondimensional loadN _x ^M b ²/E ₂ h ³ - N _cr nondimensional critical load,N _x,cr ^M b ²/E ₂ h ³ - ratio of the core to the total width,a _c /a + a _c - E _c effective core MOE,E +E (i.e., the summation of MOE parallel to the grain and perpendicular to the grain) - h _c core thickness     

20MuSi螺纹钢强度与晶粒度间的关系

对不同规格螺纹钢的晶粒度和强度进行了测定，并运用回归分析方法对晶粒度与强度的关系进行了分析．结果表明：螺纹钢的直径影响着晶粒度和强度，并且该钢强度与晶粒度成中度正相关．     

网络理论在热处理炉温度测量上的应用

热处理炉的温度测定,是保证工件质量的重要手段,而在温度测量中,普遍存在着换热误差。本文应用热力学与传热学原理,分析了换热误差产生的原因及其影响因素,建立了换热误差计算公式。并应用Oppemheim的辐射换热网络理论,画出了多物质辐射换热的网络图,列出了换热方程组。同时,对减小换热误差的途径与措施,进行了分析和讨论。为提高热处理炉的温度测定精度,给出了一种科学的方法。     

长白落叶松工业人工林密度控制技术的研究

以马尔柯夫过程理论为基础对长白落叶松工业人工林进行了模拟密度控制，提出了合理的培育密度和相应的抚育间伐对象。结果表明：马尔柯夫过程理论确能反映长白落叶松工业人工林的直径转移过程，这对于定量分析长白落叶松工业人工林直径分布的动态规律，从而拟定合理的密度控制措施非常有益；长白落叶松工业人工林成林后的密度控制间伐无论从培育森林方面，还是从取得木材、加大林分收益方面考虑，都应该以间伐小径阶的林木为主；２０－２５龄长白落叶松工业人工林的经营密度以０．７为最佳。     

Division of afforestation site type in the watershed of Wangjiagou, West Shanxi through GIS

Using quantification theory I, an analysis of the relation of soil water and qualitative factors, such as, slope degree, slope aspect, slope position, and soil in Wangjiagou watershed area has been done. The study aims to quantify the factors influencing soil water, the descending order of the factors being the slope aspect, soil, slope degree, and slope position, thereby scientifically facilitating division of afforestation site types and afforestation site products digitally on geographical information system (GIS). __________ Translated from Journal of Northwest Forestry University, 2006, 21(3): 184–188 [译自: 西北林学院学报, 2006, 21(3): 184–188]