山西霍山植物群落主要层LAI垂直分布规律

在山西霍山七里峪林场，采用间接的光学测量方法对沿着海拔分布的植物群落主要层叶面积指数（LAI）进行了测量，从不同的角度对LAI的垂直分布规律进行分析。结果表明：1．海拔不同，LAI表现出很大的差异，海拔1750m左右的LAI值大于较高与较低海拔的；对LAI和海拔之间的关系进行回归，得到LAI分布的拟合方程：y=b0＋b1x＋b2x^2＋b3x^3（R=0．712，P〈0．01）。2．同一海拔样带，阴坡LAI均大于阳坡，但对同种种群来说，阴坡树种平均胸径并不一定均大于阳坡。3．植被类型LAI比较表现为：低山针叶林〈低山灌丛〈落叶阔叶林〈落叶针叶林〈常绿针叶林；而主要群系LAI比较表现为：油松林（0．38）〈落叶松林（0．78）〈山杨林及其混交林（1．09）〈白桦林（2．00）〈辽东栎林及其混交林（3．73）。4．典型群落LAI值变化分析和人工林与天然林以，比较表明，LAI值在一定海拔达到最大值，这对于山西霍山人工林栽培和丰产林培育等具有重要意义。     

Retrieval of stratospheric O3 and NO2 vertical profiles using zenith scattered light observations

Daily zenith scattered light intensity observations were carried out in the morning twilight hours using home-made UV-visible spectrometer over the tropical station Pune (18‡31′, 73‡51′) for the years 2000–2003. These observations are obtained in the spectral range 462–498 nm for the solar zenith angles (SZAs) varying from 87‡ to 91.5‡. An algorithm has been developed to retrieve vertical profiles of ozone (O₃) and nitrogen dioxide (NO₂) from ground-based measurements using the Chahine iteration method. This retrieval method has been checked using measured and recalculated slant column densities (SCDs) and they are found to be well matching. O₃ and NO₂ vertical profiles have been retrieved using a set of their air mass factors (AMFs) and SCDs measured over a range of 87–91.5‡ SZA during the morning. The vertical profiles obtained by this method are compared with Umkehr profiles and ozonesondes and they are found to be in good agreement. The bulk of the column density is found near layer 20–25 km. Daily total column densities (TCDs) of O₃ and NO₂ along with their stratospheric and tropospheric counterparts are derived using their vertical profiles for the period 2000–2003. The total column, stratospheric column and tropospheric column amounts of both trace gases are found to be maximum in summer and minimum in the winter season. Increasing trend is found in column density of NO₂ in stratospheric, tropospheric and surface layers, but no trend is observed in O₃ columns for above layers during the period 2000–2003     

深部找铀及湘南-桂北地区深部找铀潜景分析

概述了国内外深部找矿的研究成果,指出深部找矿是当今发展的趋势。国内外重大矿产的成功发掘,其深度均在千米以上,铀矿化垂向分布深度可达4 km以上。综合介绍了国内外勘查深大矿床的特点和条件,认为岩石-构造条件是深部矿化定位的重要因素,复式岩体、成矿系统的垂向变化、构造地球物理-地球化学异常模型是深部找矿的关键依据。综述了中国南方湘南—桂北地区深部找铀的有利地质构造条件和潜力,成矿流体是该区铀矿化的根源,白垩—第三纪重大地质事件是该区深部铀成矿的重要前提,重大地质事件引发的NE-NNE,NW向深大断裂及断陷盆地是铀矿化赋存的重要场所和勘查靶区。在已知铀矿田、成矿带勘查范围基础上,在该区进行深部探索将会获得重大突破。探讨了湘南—桂北地区深部找铀的勘查思路和方法。     

不等电极距情况下高密度电阻率法的反演结果分析

通过高密度电阻率法的模型实验,得出不等电极距情况对直立高阻薄板和低阻球体反演结果的影响:缺失电极对它正下方的ρ_s影响最大,而异常形态主要在水平方向有明显的变化,异常体随电极缺失的位置有趋势变化,电极缺失的数目越多,异常形态变化越大,但是从整体来看反演剖面图基本相似。     

可控深度电法对水平柱体和垂直界面的计算和实验

球状地球体可控深度电法的效应系数可近似地全面表达可控深度电法和各种效应。通过点源二度体的电算模拟实验，证明了该方法在水平柱状体和地下存在电阻率垂直界面的条件下，也是有效的。     

西南某电站右岸倾坡内夹泥裂隙成因探讨

西南某拟建大型水电站的右岸岩体中存在倾向坡内的夹泥裂隙，通过对其的发育情况以及所处的地质环境进行系统的研究和认真剖析，认为该区内的倾坡内夹泥裂隙的成因并非正常卸荷引起，而是在构造的基础上，穹隆挽近期隆起的结果，为右岸坝肩稳定性评价提供了可靠的依据。     

Tests on low‐ductility RC frames under high‐ and low‐frequency excitations

The response of low‐ductility reinforced concrete (RC) frames, designed typically for a non‐seismic region, subjected to two frequencies of base excitations is studied. Five half‐scaled, two‐bay, two‐storey, RC frames, each approximately 5 m wide by 3.3 m high, were subjected to both horizontal and/or vertical base excitations with a frequency of 40 Hz as well as a lower frequency of about 4 Hz (close to the fundamental frequency) using a shake table. The imposed acceleration amplitude ranged from 0.2 to 1.2g. The test results showed that the response characteristics of the structures differed under high‐ and low‐frequency excitations. The frames were able to sustain high‐frequency excitations without damage but were inadequate for low‐frequency excitations, even though the frames exhibited some ductility. Linear‐elastic time‐history analysis can predict reasonably well the structural response under high‐frequency excitations. As the frames were not designed for seismic loads, the reinforcement detailing may not have been adequate, based on the crack pattern observed. The effect of vertical excitation can cause significant additional forces in the columns and moment reversals in the beams. The ‘strong‐column, weak‐beam’ approach for lateral load RC frame design is supported by experimental observations. Copyright © 2001 John Wiley & Sons, Ltd.     

半无限空间中圆形孔洞周围SH波的散射

建立了求解在含有圆形孔洞的弹性半空间中SH波散射与圆形孔洞附近动应力集中问题的解析方法。利用SH波散射的对称性和多极坐标的方法，构造了一个可以预先满足半空间自由表面上应力自由边界条件的圆形孔洞对SH波散射的波函数。利用这一波函数，则可将该问题转化成对一个圆形孔洞散射的求解问题。该问题的解答最终又可归结为对一组无究代数方程组的求解问题，并可利用截断有限项的方法对其进行计算，最后给出了有关圆形也洞附近动应力集中问题的算例和数值结果，并讨论了波数与圆孔至自由边界距离变化对动应力集中的影响。     

Modelling the effects of temperature and food on individual growth and reproduction of Daphnia and their consequences on the population level

Individual based simulations of population dynamics require the availability of growth models with adequate complexity. For this purpose a simple-to-use model (non-linear multiple regression approach) is presented describing somatic growth and reproduction of Daphnia as a function of time, temperature and food quantity. The model showed a good agreement with published observations of somatic growth (r² = 0.954, n = 88) and egg production (r² = 0.898, n = 35). Temperature is the main determinant of initial somatic growth and food concentration is the main determinant of maximal body length and clutch size. An individual based simulation was used to demonstrate the simultaneous effects of food and temperature on the population level. Evidently, both temperature and food supply affected the population growth rate but at food concentrations above approximately 0.4 mg Cl⁻¹ Scenedesmus acutus temperature appeared as the main determinant of population growth.

Four simulation examples are given to show the wide applicability of the model: (1) analysis of the correlation between population birth rate and somatic growth rate, (2) contribution of egg development time and delayed somatic growth to temperature-effects on population growth, (3) comparison of population birth rate in simulations with constant vs. decreasing size at maturity with declining food concentrations and (4) costs of diel vertical migration. Due to its plausible behaviour over a broad range of temperature (2–20 °C) and food conditions (0.1–4 mg Cl⁻¹) the model can be used as a module for more detailed simulations of Daphnia population dynamics under realistic environmental conditions.     

Identification of soil degradation during earthquake excitations by Bayesian inference

A Bayesian inference approach is introduced to identify soil degradation behaviours at four downhole array sites. The approach of inference is based on a parametric time‐varying infinite impulse response filter model. The approach is shown to be adaptive to the changes of filter parameters and noise amplitudes. Four sites, including the Lotung (Taiwan), Chiba (Japan), Garner Valley (California), and Treasure Island (California) sites with downhole seismic arrays are analysed. Our results show two major types of soil degradation behaviour: the well‐known strain‐dependent softening, and reduction in stiffness that is not instantaneously recoverable. It is also found that both types of soil degradation are more pronounced in sandy soils than in clayey soils. The mechanism for the second type of soil degradation is not yet clear to the authors and suggested to be further studied. Copyright © 2003 John Wiley & Sons, Ltd.