六盘山植物区系基本特征的初步分析

六盘山位于陕甘宁交接地区,属于半湿润气候向半干旱气候的过渡带,是黄土高原生物多样性最丰富的地区之一,有维管植物836种,隶属于93科,359属。本区属于泛北极植物区、中国-日本森林植物亚区、华北植物地区的黄土高原亚地区。全部种子植物可分为13个分布区类型和12个变型,以北温带分布类型为主,与其他植物区系联系广泛,但特有属较贫乏。六盘山与小陇山、太白山和中条山的属相似性系数较高,均达60%以上,表明几座山体处于相似的生物气候背景之下,地理隔离性不明显。与贺兰山的属相似性系数低于60%,因为贺兰山位于干旱的荒漠与半荒漠区,可能有地理隔离作用。     

顾及字符特征的中文地名词典查询方法

地名词典查询是地名校正、地名匹配等地名服务应用的重要基础,但是地名数量的快速增长使得词典查询性能面临严峻挑战。针对大规模数据环境中传统词典查询方法准确率不高且效率较低等问题,提出了一种顾及字符特征的中文地名词典查询方法（CGQM）。首先,查询具有相同字符特征的地名形成候选地名集合,同时构建单字索引提升查询效率;其次,依据字符数量特征比较查询地名与候选地名的差异,进一步过滤候选地名集合;最后,基于字符位置特征优化查询结果排序策略,使得结果排序更为合理。实验以全国地名词典为例,构建5组测试集进行CGQM方法与Lucene检索方法的对比分析。研究结果表明,CGQM方法对于增强地名词典查询功能、提升查询效率具有实际意义。     

呼图壁地区震源机制解及构造应力场特征分析

基于新疆测震台网记录的数字地震波形,运用CAP方法测定呼图壁地区2010-01-15~2017-01-02共50次MS≥3.0地震的震源机制解,同时结合早期23次MS≥3.0地震的震源机制解数据,应用MSATSI软件反演研究区时空应力场。结果表明,研究区应力结构类型表现为逆断型,整个区域主压应力P轴近NNE向且倾角较小,说明整个呼图壁地区应力场以NNE向水平挤压作用为主要特征。从空间上看,东部的水平挤压作用更为显著;从时间上看,2010~2016年受到更为显著的NNE向应力场控制,反映了研究区在不同时段应力场的调整变化,但没有改变该区域最大主压应力轴呈NNE向的总体特征,说明整个呼图壁地区可能主要受一种较稳定的NNE向应力场控制。     

实验研究岩石圈深部流体及相关科学问题

实验研究地球岩石圈深部流体和对地球深部流体的观测发现,水溶液在跨越临界态时有许多特殊性质。使用水热金刚石压钻在200～800MPa,300～700℃条件下,可观测到：NaCl-H2O溶液两相不混溶相区的结构和近临界态现象。测量高温高压下NaCl溶液的电导率,在近临界和跨越临界态时发现最大电导率值。在对大洋中脊热水观测中可发现大多数喷口是在2200m深。喷口正在近临界态条件下喷出含矿流体。这些临界态研究对于重新分析岩石圈的地球物理测量结果和对认识大陆岩石圈内流体性质有很大意义。     

酸溶法测定硫铁矿中的全硫

在野外地质队实验室仪器少的条件下,用酸溶的方法分析硫铁矿中全硫,简单、快速、易操作,取得良好的结果。     

Lateral dynamic response of a pipe pile in saturated soil layer

This paper presents an analytical solution for the lateral dynamic response of a pipe pile in a saturated soil layer. The wave propagations in the saturated soil and the pipe pile are simulated by Biot's three‐dimensional poroelastic theory and one‐dimensional elastic theory, respectively. The governing equations of soil are solved directly without introducing potential functions. The displacement response and dynamic impedances of the pipe pile are obtained based on the continuous conditions between the pipe pile and both the outer and inner soil. A comparison with an existing solution is performed to verify the proposed solution. Selected numerical results for the lateral dynamic responses and impedances of the pipe pile are presented to reveal the lateral vibration characteristics of the pile‐soil system. Copyright © 2015 John Wiley & Sons, Ltd.     

Bearing capacity of strip foundations reinforced with geogrid sheets by using upper bound finite‐element limit analysis

By using the upper bound finite‐elements limit analysis, with an inclusion of single and two horizontal layers of reinforcements, the ultimate bearing capacity has been computed for a rigid strip footing placed over (i) fully granular, (ii) cohesive‐frictional, and (iii) fully cohesive soils. It is assumed that (i) the reinforcements are structurally strong so that no axial tension failure can occur, (ii) the reinforcement sheets have negligible resistance to bending, and (iii) the shear failure can take place between the reinforcement and soil mass. It is expected that the different approximations on which the analysis has been based would generally remain applicable for reinforcements in the form of geogrid sheets. A method has been proposed to incorporate the effect of the reinforcement in the analysis. The efficiency factors, η_c and η_γ, to be multiplied with N_c and N_γ , for finding the bearing capacity of reinforced foundations, have been established. The results have been obtained (i) for different values of ? in case of fully granular and cohesive‐frictional soils, and (ii) for different rates at which the cohesion increases with depth for a fully cohesive soil. The optimum positions of the reinforcements' layers have also been determined. The effect of the reinforcements' length on the results has also been analyzed. As compared to cohesive soils, the granular soils, especially with higher values of ?, cause a much greater increase in the bearing capacity. The results compare reasonably well with the available theoretical and experimental data from literature. Copyright © 2013 John Wiley & Sons, Ltd.     

One‐dimensional consolidation with a threshold gradient: a Stefan problem with rate‐dependent latent heat

During the process of one‐dimensional consolidation with a threshold gradient, the seepage front moves downward gradually, and the problem is indicated as a Stefan problem. The novel feature in this Stefan problem is a latent heat that varies inversely with the rate of the moving boundary. An exact solution for the external load that increases in proportion to the square root of time is constructed using the similarity transformation technique. Computational examples concerning the effect of different parameters on the motion of the seepage front are presented. The exact solution provides a worthwhile benchmark for verifying the accuracy of numerical and approximate methods. Copyright © 2013 John Wiley & Sons, Ltd.     

Analytical solutions for Euler–Bernoulli beam on visco‐elastic foundation subjected to moving load

Analytical solutions for the steady‐state response of an infinite beam resting on a visco‐elastic foundation and subjected to a concentrated load moving with a constant velocity are developed in this paper. The beam responses investigated are deflection, bending moment, shear force and contact pressure. The mechanical resistance of the foundation is modeled using two parameters k_s and t_s — k_s accounts for soil resistance due to compressive strains in the soil and t_s accounts for the resistance due to shear strains. Since this model represents the ground behavior more accurately than the Winkler spring model, the developed solutions produce beam responses that are closer to reality than those obtained using the existing solutions for Winkler model. The dynamic beam responses depend on the damping present in the system and on the velocity of the moving load. Based on the study, dynamic amplification curves are developed for beam deflection. Such amplification curves for deflection, bending moment, shear force and contact pressure can be developed for any beam‐foundation system and can be used in design. Copyright © 2012 John Wiley & Sons, Ltd.     

大气降水热液成矿——西秦岭某硅、灰、泥岩型铀矿床成矿模式探讨

西秦岭某硅、灰、泥岩型层控铀矿床是在矿源层(中志留统)的基础上,由地下水热液渗滤改造而成。铀的工业富集发生在矿源层褶皱成陆之后,成矿高峰则发生在中、新生代交替时期。成矿溶液是受大气降水补给的地下水热液;成矿物质主要来自矿源层本身。矿源层长期遭受地下水热液作用,溶液中大量的铀酰离子形成稳定的碳酸铀酰络合物,并被运移至岩性和构造的圈闭部位,通过吸附和共沉淀等作用富集,或通过还原、水解和过饱和沉淀等作用形成沥青铀矿或再生铀黑。该层控铀矿床的整个成矿过程具有典型的逐级增量特点,属于塔式累积成矿的基本模式,后生富集是成矿的关键。