低压供电系统接地制式的分类          下载免费PDF全文

吴明柱 《山西气象》2003,(1):40-42,46

我国制定的建筑物内电气装置安全性能标准已经与国际电工委员会(1EC)制定的标准相一致，简要介绍了IEC标准中关于供电系统的接地形式和分类。正确理解低压供电系统接地形式的分类和规定的相关术语，对山西省以后大规模的防雷检测和防雷工程施工有极大的帮助。  相似文献   

Power law olivine crystal size distributions in lithospheric mantle xenoliths     

P. Armienti  S. Tarquini 《Lithos》2002,65(3-4):273-285

Olivine crystal size distributions (CSDs) have been measured in three suites of spinel- and garnet-bearing harzburgites and lherzolites found as xenoliths in alkaline basalts from Canary Islands, Africa; Victoria Land, Antarctica; and Pali Aike, South America. The xenoliths derive from lithospheric mantle, from depths ranging from 80 to 20 km. Their textures vary from coarse to porphyroclastic and mosaic–porphyroclastic up to cataclastic. Data have been collected by processing digital images acquired optically from standard petrographic thin sections. The acquisition method is based on a high-resolution colour scanner that allows image capturing of a whole thin section. Image processing was performed using the VISILOG 5.2 package, resolving crystals larger than about 150 μm and applying stereological corrections based on the Schwartz–Saltykov algorithm. Taking account of truncation effects due to resolution limits and thin section size, all samples show scale invariance of crystal size distributions over almost three orders of magnitude (0.2–25 mm). Power law relations show fractal dimensions varying between 2.4 and 3.8, a range of values observed for distributions of fragment sizes in a variety of other geological contexts.

A fragmentation model can reproduce the fractal dimensions around 2.6, which correspond to well-equilibrated granoblastic textures. Fractal dimensions >3 are typical of porphyroclastic and cataclastic samples. Slight bends in some linear arrays suggest selective tectonic crushing of crystals with size larger than 1 mm. The scale invariance shown by lithospheric mantle xenoliths in a variety of tectonic settings forms distant geographic regions, which indicate that this is a common characteristic of the upper mantle and should be taken into account in rheological models and evaluation of metasomatic models.  相似文献   

The influence of matrix rheology and vorticity on fabric development of populations of rigid objects during plane strain deformation     

Sandra Piazolo  P. D. Bons  C. W. Passchier   《Tectonophysics》2002,351(4)

The influence of vorticity and rheology of matrix material on the development of shape-preferred orientation (SPO) of populations of rigid objects was experimentally studied. Experiments in plane strain monoclinic flow were performed to model the fabric development of two populations of rectangular rigid objects with object aspect ratios (R_ob) 2 and 3. The density of the rigid object populations was 14% of the total area. Objects were dispersed in a Newtonian and a non-Newtonian, power law matrix material with a power law exponent n of 1.2. The kinematic vorticity number (W_n) of the plane strain monoclinic flow was 1, 0.8 and 0.6 with finite simple shear strain of 4.6, 3.0 and 0.9, respectively. In experiments with R_ob=3, the SPO is strongly influenced by W_n and the material properties of the matrix. Deformation of a power law matrix material and low W_n resulted in a stronger SPO than deformation of a linear viscous matrix and high W_n. Strain localization coupled with particle interaction plays a significant role in the development of a shape-preferred orientation. High strain simple shear zones separate trains of rigid objects that are surrounded by low strain zones with W_n lower than the bulk W_n. In fabrics involving populations of objects with R_ob=2, rheology of the matrix materials does not systematically influence the intensity of the SPO.  相似文献   

山洞电源、信号线路改造与接地网建设相关技术探讨     

张荣挺  于沈平 《东北地震研究》2002,18(3):35-38

本文对铁岭地震台在山洞电源，信号线路改造与接地网建设中遇到的问题及解决的办法做简要介绍，依据洞室固有条件，结合《规范》要求，探讨了监测环境建设施工经验。  相似文献   

A stochastic approach to site-response component in seismic ground motion coherency model     

S. Liao  J. Li 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):813-820

In order to account for the site-response part of the seismic ground motion coherency for sites of interest, an analytical stochastic methodology is proposed in this paper. By combining the pseudo-excitation method with wave motion finite element simulation techniques, a numerical approach for the computation of the coherency function between observation points is developed firstly. Then the orthogonal expansion method is introduced into this approach to study the effect of the uncertainty in soil properties on the coherency function. Finally some numerical examples are given to show the applicability of the methodology. The computational results demonstrate that the lagged coherency values tend to decrease in the vicinity of the resonant frequencies of the site.  相似文献   

土工织物在广州抽水蓄能电站边坡中的应用     

梁成平  李俊  方丽芳 《岩土力学》2002,23(1):116-119

广州抽水蓄能电站（下称广蓄电站）进／出水口边坡高，水位变动大，骤降变幅大。经试验选用规格为500g/m^2的纯涤纶无纺土工织布和规格为100g/m^2的聚丙烯防滑编织布，组成护坡的土工织物反滤层，护坡面板采用现浇20cm厚的混凝土，并采取了一些加固措施。电站从1993年投产至今已安全运行8年多，实践表明，土工织物在广州抽水蓄能电站上、加进、出水口边坡中的应用是成功的。  相似文献   

最大值函数对建筑物沉降的回归分析     

乔月 《现代测绘》2008,31(4)

为有效地对建筑物的沉降进行回归分析,本文以新城花园酒店为例,用幂级数和最大值函数两种回归函数对观测数据进行分析,通过显著性检验值和均方差的大小来推测建筑沉降的规律,并根据分析预测结果来评价两种回归函数的性能,理论分析和实验表明:采用最大值函数和幂级数对LS5的观测数据进行回归分析都能够达到建筑物沉降变形的精度要求,但最大值函数的性能优于幂级数。  相似文献   

中国地区价格指数测度与空间分异     

闫梅  李国平  黄金川 《地理研究》2019,38(6):1451-1463

地区价格指数是不同地区购买一篮子相同商品和服务的价格之比,表征同一时期、不同地区的物价综合水平。借鉴购买力平价理论,构建适用于中国地区价格指数测算的指标体系和计算方法,测度了100个典型城市的地区价格指数并进行差异分析。研究结果表明：不同地区商品和服务的价格差异显著,地区价格指数界于0.849~1.662之间,最高值为最低值的1.95倍;住房价格的地区差异最大,教育、医疗次之,是影响居民实际生活水平的三大主要因素;食品、交通、教育和医疗价格的空间集聚程度较高,通信、住房、文娱价格的空间集聚程度较低;地区价格指数在全国呈“东高西低、南高北低”的空间分异格局,东南沿海地区物价水平较高、黄河中游地区物价水平较低。通过对地区价格指数的研究,能够为关注民生时代的区域协调发展政策制定提供科学依据。  相似文献   

Alternative approach for dynamic-positioning thrust allocation using linear pseudo-inverse model     

《Applied Ocean Research》2019

Application of ship Dynamic-Positioning systems strongly depends on physical ability of actuators (Thrusters) in providing commanded loads. This will consequently introduce some constraints and limitations to Thrust Allocation problem in design and control of such systems. However, there is a special case in which a simple explicit solution could be found by fixing orientation of azimuth thruster relative to vessel regarded as linear model. In this paper, three new alternative approaches based on linear model are introduced. Case study is a time domain simulation of Station-Keeping (instant Point-Tracking) operation for a supply vessel called Northern Clipper in North Sea with Beaufort number 6. As is evident by results, these approaches improve maneuvering performance and power consumption efficiency compared to the conventional linear model. Results show improved robustness of yaw control in Point-Tracking operation and decreased overall consumption of power compared to linear model. Furthermore, it is apparent from the results that these approaches are particularly efficient in tunnel thrusters compared to linear counterpart.  相似文献   

Tigers, trees and Tharu: An analysis of community forestry in the buffer zone of the Royal Chitwan National Park, Nepal   总被引：1，自引：0，他引：1  

Samantha Jones 《Geoforum》2007,38(3):558-575

In the buffer zone of the Royal Chitwan National Park (RCNP), community forests represent a key land use to meet the objectives of the buffer zone concept. This article examines three diverse community forests surrounding the national park and explores how national policy has been mediated by emerging community forestry institutions to create different levels of resource access and benefit distribution both within and between local user groups. Mindful of recent critiques of community-based conservation, the analysis gives considerable attention to the dynamics of power relations and inequality. The extent to which property rights have been transferred to the local level is evaluated and to whom power has been devolved in the process is assessed. The distribution of benefits arising from community forestry is critically examined. It seems that the current system for community forestry creates sufficient incentives for local cooperation due to the potential for increased access to important resources and a high perception of ownership of community forests among the communities. However, emerging institutions vary in the extent to which they reproduce favourable resource access conditions for elites and benefit distribution does seem to be skewed in favour of the wealthy and higher castes, even where management practices on the surface appear fair. National policy creates sufficient but not necessary conditions for achieving downward accountability, transparency and fairness. Greater attention to these issues is needed for buffer zone community forestry to better serve the poor and marginalised populations within user groups.  相似文献