孟公界花岗岩型脉状铀矿床成矿构造研究及找矿预测

笔者运用大陆构造体系分析方法，详细研究了桂北苗儿山矿田孟公界花岗岩型铀矿床的成矿构造特征，初步查明了北北西向矿脉的形成是受区域性北北东向左旋剪切的次级剪应力场控制，成矿前形成的韧性剪切带既是矿液运移的通道，也是矿体赋存的有利空间；剪切作用造成矿脉、脉体在空间上呈雁行排列并向北北西方向侧伏。根据成矿构造预测，该矿床在1号矿脉的深部有较好的找矿前景，2～6号脉矿化地段由西向东逐渐加深，盲矿体应埋藏在较深部位。     

植株冠层几何形状对草地反射率的影响

本研究建立了一个反映植被辐射传输和几何光学特性的混合模型,以模拟半干旱地区天然草地的多波段反射率值。该模型引入一个几何相似性参数,用以描述植株冠层的几何形状对叶/枝角分布、阴影地面比例、冠层和地面各光学分量、冠层反射率和总反射率的影响。模型模拟值与研究区3个不同退化程度羊草草地的实测值较为吻合,而且退化程度越轻的草地,模拟效果也越好。对于中度退化草地,在高度与冠幅之比（chw）不变的情况下,当45°≤太阳天顶角sza≤75°时,不同几何形状植株的总反射率之间无显著差异;当0°≤sza〈45°或75°〈sza≤90°时，锥体与球体和柱体植株的总反射率之间有较显著差异；而球体和柱体植株的总反射率之间始终无显著差异。当chw由小到大变化时，以上结论基本不变。     

Seismic behaviour of self‐centring braced frame buildings with reusable hysteretic damping brace

This paper presents the seismic behaviour of a concentrically braced frame system with self‐centring capability, in which a special type of bracing element termed reusable hysteretic damping brace (RHDB) is used. The RHDB is a passive energy dissipation device with its core energy‐dissipating component made of superelastic Nitinol wires. Compared with conventional bracing in steel structures, RHDB has a few prominent performance characteristics: damage free under frequent and design basis earthquakes in earthquake prone areas; minimal residual drifts due to the self‐centring capability of RHDB frame; and ability to survive several strong earthquakes without the need for repair or replacement. This paper also includes a brief discussion of the RHDB's mechanical configuration and analytical model for RHDB. The seismic performance study of RHDB frame was carried out through a non‐linear time history analysis of 3‐storey and 6‐storey RHDB frame buildings subjected to two suites of 20 earthquake ground motions. The analysis results were compared with buckling‐restrained brace (BRB) frames. This study shows that RHDB frame has a potential to outperform BRB frames by eliminating the residual drift problem. Copyright © 2007 John Wiley & Sons, Ltd.     

Particle size distribution analysis of sand-sized particles by laser diffraction: an experimental investigation of instrument sensitivity and the effects of particle shape

Laser diffraction is now widely used for particle size distribution analysis of sediments and soils. The technique can be very precise, and offers advantages of speed and cost over many other methods when used to analyse mixtures of sand, silt and clay. This study presents the results of an experimental investigation that examined the sensitivity of the Beckman-Coulter LS230 instrument to mixtures of different grain populations and differences in particle shape. The instrument was found to have high sensitivity to coarse particles in a finer matrix (detection threshold 1–2%), but much lower sensitivity to finer particles in a coarser mixture (detection threshold 12–17%). Experiments using near-spherical ballotini showed that laser analysis provides very similar values to dry sieving for the mean, median and mode, but for a range of natural sand samples values for the mean, median and mode were offset by 8–21%, with an average of ca 15%, compared with sieving. Analysis using a Beckman-Coulter RapidVUE instrument, which provides both size and shape information, provided support for the hypothesis that the differences between laser analysis and sieving are partly attributable to the effects of particle shape. However, an additional factor is the way in which the laser software interprets the optical diffraction data. The software predicts a high degree of log-normality in the size distribution, such that highly skewed, truncated or bimodal samples are poorly represented. Experiments using sieved fractions of ballotini indicated that, even with near-perfectly spherical particles, the particle size distribution predicted by the laser software includes a relatively large percentage of particles outside the sieve class limits.     

近景摄影测量限差的特殊性

在近景摄影测量的全过程中 ,包括摄影机检校、实地控制测量以及摄影测量处理各阶段 ,其操作限差存在特殊的理论 ,系统说明这些理论并详尽推导了一系列相应的关系式。     

非规则采矿工作面积分区间确定方法

针对工作面形状多种多样的特点,本文采用二次曲线描述工作面水平投影边界,并且利用分段积分的方法处理更加复杂的工作面形状,合理地解决了非规则采矿工作面积分区间的划分问题;同时,给出了工作面形状系数的计算公式,整个计算过程利用计算机技术实现自动解算,避免了对任意曲边形工作面采用矩形分割的近似处理方法,提高了地面沉陷预计精度。最后,用实例说明了本文提供的对非规则采矿工作面的处理方法比现行处理方法具有更高的     

掺气减蚀设施体型优化研究

建立了计算掺气设施水力特性的数学模型和挑坎掺气槽坎高的优化目标函数,对原型掺气槽的体型优化进行了研究.研究表明,掺气设施的优化坎高主要与来流Fr数有关,来流Fr数愈大,所需坎高愈小;来流Fr数愈小,所需坎高愈大.     

New high resolution observations of the solar diameter from space and ground with the microsatellite program PICARD

The PICARD microsatellite mission will provide 2 to 6 years simultaneous measurements of the solar diameter, differential rotation and solar constant to investigate the nature of their relations and variabilities. The 100 kg satellite has a 40 kg payload consisting of 3 instruments which will provide an absolute measure (better than 10 milliarcsec) of the diameter and the solar shape, a measure of total solar irradiance, and UV and visible flux in selected wavelength bands. Now in Phase B, PICARD is expected to be launched before mid-2003. The engineering model of the diameter telescope will be used on ground simultaneously with the satellite to investigate the atmospheric bias and state on the possible accuracy of the ground measurements carried up to now. We review the scientific goals linked to the diameter measurement, present the payload, and give a brief overview of the program aspects.     

利用稳态坡形类比法预测基岩岸坡的库岸再造

水库库岸再造是水利水电工程中经常遇到的工程地质问题之一.依据库岸地质结构和岩性组合, 划分出工程地质条件相近的库岸段, 与工程地质条件相类似的稳态坡形进行类比, 确定出再造后的稳态坡形的坡角大小, 从而进行库岸再造预测.利用稳态坡形类比法对三峡库区迁建新址的基岩库岸进行了再造预测, 定量预测出三峡水利枢纽工程建成蓄水后, 巫山县城新址基岩库岸最终再造带宽度在40166m之间, 预测结果可以用来指导新城的规划与建设.      

藏东南泥石流沟纵剖面演化的最小功模式

西藏东南地区的泥石流可分为雨水、冰雪融水和冰湖溃决等3种成因类型,其沟谷纵剖面演化均遵循最小功原理,即通过调整坡降使流速增大,表现为单位流体的全程流速平均值ū与纵剖面形态指数N正相关:ū∝f(N),对雨水型泥石流沟,流速函数f(N)={1/3-2/[(N+1)(N+2)(N+3)]}^1/2;对融水型泥石流沟,f(N)={2/3-2/[(N+1)(N+3)]}^1/2;对溃决型泥石流沟,f(N)=[NP(N+1)]^2/3。在泥石流沟谷演化进程中,与ū值由小变大相应,N值由小变大,沟谷纵剖面从上凸抛物线形变为下凹抛物线形,泥石流沟谷地貌演化阶段按泥石流孕育阶段、发展阶段、旺盛阶段、衰减阶段的顺序演替。以藏东南典型泥石流沟作为实例,检验了上述沟谷地貌演化的模式与规律。