反射波法地震勘探在工程勘察中的应用

对于地下复杂的地质构造，地震反射波法比折射波法能够提供更多更详细的地下信息。多次覆盖反射波法观测系统可以增加同一反射点的重复观测次数，从而起到压制干扰，提高有效波信号的作用。其次选取合适的地震参数能有效地拓宽有效波频带范围，对地震勘探分辨率的提高起到非常重要的作用。     

Surface vibration due to a sequence of high speed moving harmonic rectangular loads

The transmission of vibrations over the surface of the ground, due to high-speed moving, vertical harmonic rectangular loads, is investigated theoretically. The problem is three-dimensional and the interior of the ground is modelled as an elastic half-space or a multilayered ground. The transformed solutions are obtained using the Fourier transform on the space variable. A new damping model in the spatial wavenumber domain, presented in Lefeuve-Mesgouez et al. [J. Sound. Vibr. 231 (2000) 1289] is used. Numerical results for the displacements on the surface are presented for loads moving with speeds up to and beyond the Rayleigh wave speed of the half-space.     

Composite analytical solutions for a soil vapour extraction system

Soil vapour extraction (SVE) is a common remediation technique for cleaning up unsaturated soils contaminated by volatile organic compounds (VOCs). Analytical solutions, which result from simple mathematical models, can allow the fast approximation of the time‐dependent effluent concentration and the gaining of insight into the processes that take place during soil remediation. Deriving the analytical solutions to advection–dispersion equations that simultaneously take into account the mechanical dispersion and molecular diffusion is very difficult because of the variable dependence of governing equations' coefficients. In this study, we first present two simplified analytical solutions that only consider mechanical dispersion or molecular diffusion. The two developed analytical solutions are compared with the numerical solution that simultaneously considers both mechanical dispersion and molecular diffusion to examine the applicability of the two simplified analytical solutions and distinguishes the individual contribution of the mechanical dispersion and molecular diffusion to total VOCs transport in an SVE system. Results show that dispersion plays an important role during SVE decontamination and neither the diffusion‐dominated solution nor the dispersion‐dominated solution can agree well with the numerical solution when both mechanical dispersion and molecular diffusion have significant contributions to the total VOCs transport flux. A composite analytical solution that linearly couples the diffusion‐ and dispersion‐dominated analytical solutions, which is proposed herein to eliminate the discrepancy between the analytical solutions and the numerical solution. Results indicate that the proposed composite analytical solution agrees well with the numerical solution and is an effective tool for quickly and accurately evaluating the time‐dependent effluent concentration for parameters of the different ranges of interest in an SVE remedial system. Copyright © 2006 John Wiley & Sons, Ltd.     

天津武清地区云凝结核变化特征

利用2009年11—12月在天津武清气象局测量的云凝结核(CCN:Cloud Condensation Nuclei)浓度资料以及气溶胶数谱分布的观测资料,分析了武清地区在不同过饱和度(0.1%～1.0%)下云凝结核浓度及活化率的变化特征。结果表明:武清地区冬季CCN数浓度变化范围很大,过饱和度1%时,浓度变化范围为4000～32000cm-3,且浓度受风速影响明显,风速2级以下CCN数浓度很高,过饱和度1%时,其平均浓度可达16000cm-3,但对于4级风速以上CCN平均浓度为4000cm-3左右;在过饱和度0.1%～0.4%间CCN浓度变化较大,过饱和度每增加0.1%,CCN浓度增加值平均约为过饱和度0.4%～1.0%间浓度增量的5倍。低过饱和度(0.1%、0.2%)下,活化率受风速影响明显,1级风速下的CCN活化率约为4级风速下的3倍,但在过饱和度1%时活化率则相差不大。CCN浓度的日变化呈双峰型,峰值时刻为北京时间08:00和18:00左右,活化率的日变化则呈双谷型,这主要是受局地排放影响的结果。利用指数函数拟合各风速下CCN浓度过饱和度谱,表明该地谱型为典型的大陆型。     

The population structural transition effect on rising per capita CO2 emissions: evidence from China

ABSTRACT

The per capita CO₂ emissions (PCCE) of many developing countries like China have been rising faster than total CO₂ emissions, and display spatial divergence. Such temporal growth and spatial divergence will have a significant influence on efforts to mitigate CO₂ emissions. Given the research gap on the impact of the structural transition in population on PCCE, we constructed an econometric model using the dynamic panel method. The results reveal that the population structural transition has a significant nonlinear impact on PCCE, as the rate of population growth in China decelerates. Both demographic ageing and urban-rural migration have a stronger impact on PCCE than other factors. This effect, however, decreases beyond a certain threshold. An increase in the number of households due to urbanization and family downsizing has resulted in a positive effect on PCCE, without a threshold turning point. The research also finds that an increased share of the service sector in employment can reduce PCCE only if the sector employs more than 31.56% of the total employed population. Overall, these findings indicate that policymakers should pay attention to the prominence of the demographic structural transition for effective climate policy.

Key policy insights

• Policymakers should address rising per capita carbon emissions (PCCE) and their spatial divergence in future climate policies, not just total CO₂ emissions.

• The transitioning demographics of ageing and urbanization in China show a nonlinear, inverted U-shaped effect on PCCE instead of a continuously positive effect.

• Based on the nonlinear effect of employment structure on PCCE, policymakers should focus on the relationship between the structural transition of the economy and PCCE in future climate mitigation policies.

     

统一上海工程地质分层编号的讨论

地层的工程地质统一划分和编号是一项标准化工作。和所有的标准化工作一样,应具有科学性、通用性和严肃性,应体现地区工程地质勘察水平。上海的工作应以已完成的上海地区第四纪地层分层研究成果为基础,直观地反映各组地层的工程地质性质的差异。应注意各地段地质结构的差别。并避免由於各地地层的差异性和地层编号上人为的多层编码所产生的混乱。     

A Finite Volume Scheme for the Transport of Radionucleides in Porous Media

The COUPLEX1 Test case (Bourgeat et al., 2003) is devoted to the comparison of numerical schemes on a convection–diffusion–reaction problem. We first show that the results of the simulation can be mainly predicted by a simple analysis of the data. A finite volume scheme, with three different treatments of the convective term, is then shown to deliver accurate and stable results under a low computational cost.     

洪湖网簖数量调查和渔获物分析

利用卫星遥感定点技术,估算洪湖１９９３年初约有１１０００部网簖,洪湖网簖可分为“稀阵”,“密阵”两种。１９８６年稀阵渔获物中,乌鳢,鲤、鲇,草鱼等大中型鱼类的比例达４７．６％,１９９２￣１９９４年这些鱼类的比例不到７％,１９８６年鲫,红鳍三各小型鱼类的比例为５１．０％,１９９２￣１９９４年达８７．６％。九十年代洪湖主要经济鱼类的捕捞规格进一步下降,为此应地网簖渔业实施管理。     

低轨卫星增强北斗三号导航星座性能分析

针对低轨卫星星座有待合理化设计的问题,深入研究了低轨卫星星座增强北斗三号系统定位性能。分析轨道高度、轨道倾角、星座构型对星座覆盖性能的影响,仿真北斗三号、GPS和3种不同类型的低轨星座,研究各低轨星座与北斗三号、GPS的组合系统在所选7个测站以及全球范围内的可见卫星数和PDOP值分布。结果表明低轨卫星对北斗三号的增强效果主要与低轨卫星数目有关,且不同轨道倾角的组合低轨星座有利于均衡系统在全球范围内的可见卫星数与PDOP值分布。低轨卫星有望通过改善卫星观测几何构型提高北斗三号系统的定位性能,且增强效果与低轨星座构型密切相关。