钻孔灌注桩的超声波透射法检测

大直径超长桩的桩身混凝土质量检测一直是困扰工程界的一个难题。本文提出和探讨了大直径超长桩桩身混凝土质量的超声波透射检测方法、技术及可靠程度。工程实践证明采用超声波透射法对大直径超长桩检测 ,其检测精度高 ,结果直观可靠 ,可以较详细查明桩身内部缺陷的性质、深度位置、范围大小及严重程度 ,为控制大直径超长桩桩身混凝土质量提供了一种有效的检测方法。     

北京市某高层建筑高空电磁辐射环境影响分析

选取北京市某代表性高层居民楼顶平台作为高空电磁辐射环境水平监测点进行综合场强和选频监测,评价总体电磁辐射环境水平,并分析监测区域电磁辐射能量的来源。结果表明：该高空监测区域的电磁辐射环境总体水平低于国家规定的公众照射导出限值,但高于地面水平。监测区域主要受30 km 外的中波台影响,其次是9 km 外的中央电视塔。影响最大的是639 kHz频率的中波信号,占100 kHz～300 MHz总场强的95％以上,其次是1．28 MHz频率的中波信号。提出,开展敏感建筑物规划建设时,应考虑中波的传播特性和对环境的影响。     

中波台电磁辐射叠加影响估算及与实测对比分析

以某中波电台为例,对多个不同频率的中波发射台同时运行时复合场强进行理论估算,对电磁辐射叠加影响进行分析,并将理论估算值与该台电磁辐射环境现状监测数据进行比对,得出距离发射塔近,复合场强理论估算值高于实测值,距离较远理论估算值与实测值较接近等结论。     

Canopy Seed Banks as Time Capsules of Biodiversity in Pasture-Remnant Tree Crowns

Abstract: Tropical pastures present multiple barriers to tree regeneration and restoration. Relict trees serve as “regeneration foci” because they ameliorate the soil microclimate and serve as safe spots for dispersers. Here, we describe another mechanism by which remnant trees may facilitate pasture regeneration: the presence of seed banks in the canopy soil that accumulates from decomposing epiphytes within the crowns of mature remnant trees in tropical cloud forest pastures. We compared seed banks of canopy soils (histosols derived from fallen leaves, fruits, flower, and twigs of host trees and epiphytes, dead bryophytes, bark, detritus, dead animals, and microorganisms, and dust that accumulate on trunks and the upper surfaces of large branches) in pastures, canopy soils in primary forest trees, and soil on the forest floor in Monteverde, Costa Rica. There were 5211 epiphytic and terrestrial plant seeds in the three habitats. All habitats were dominated by seeds in a relatively small number of plant families, most of which were primarily woody, animal pollinated, and animal dispersed. The density of seeds on the forest floor was greater than seed density in either pasture‐canopy or forest‐canopy soils; the latter two did not differ. Eight species in 44 families and 61 genera from all of the habitats were tallied. There were 37 species in the pasture‐canopy soil, 33 in the forest‐canopy soil, and 57 on the forest floor. Eleven species were common to all habitats. The mean species richness in the pasture canopy was significantly higher than the forest canopy (F =83.38; p < 0.02). Nonmetric multidimensional scaling ordination revealed that the communities were distinct. Greenhouse experiments verified that many of these seeds were viable, with 29 taxa germinating (23 taxa in pruned mats [mimic of exposed conditions] and 16 taxa in control mats [intact conditions]) within 2 months of observation. Nearly half the species that germinated were characteristic of primary forests (primary forest samples, 19%; pasture samples, 29%). This supports the idea that canopy seed banks of pasture trees can function as time capsules by providing propagules that are removed in both space and time from the primary forest. Their presence may enhance the ability of pastures to regenerate more quickly, reinforcing the importance of trees in agricultural settings.     

USE OF RADAR TO DERWE A STORM INTENSITY-DURATION CURVE1

ABSTRACT: Rainstorms which exceed the design capacity of conveyance systems and cause extensive damage to structures and property, occur frequently in Alberta. After such a severe storm, an early and quick assessment of the storm's location and magnitude and the corresponding frequency for various duration (storm intensity-duration curve) is often required to estimate the damage. The storm intensity-duration curve is produced with information obtained from a sparse network of recording raingages, thus, creating a high degree of uncertainty in the result. Short-duration precipitation is usually quite variable in Alberta; hencea very dense network of recording precipitation stations would be required to provide precise measurements of the storm intensity-duration curve at all locations. Such a dense network does not exist in Alberta; it would be very expensive to install, maintain, and thus difficult to justify financially. One solution for obtaining a large amount of closely spaced in-intensity-duration values is to use weather radar. Using weather radar data, intensity-duration curves could be produced routinely for any set of prespecified locations. The radar data thus have the potential for facilitating the identification of the return period of rainfall events quickly, cheaply, and precisely when the long-term intensity-duration curves are available. As a pilot project to demonstrate the feasibility of the method and the potential of the radar data, computer software was developed to derive from archived radar data, intensity-duration values for up to a 2,500 2 area for a given storm.     

“一一·二四”海难渤海风场的数值模拟

用中尺度数值模式 ＭＭ５对 １９９９年 １１月 ２４日烟台附近发生重大海难事故的渤海风场进行了数值模 拟，探讨了该次冷锋大风的风场特征和影响机制．结果表明：用９０ｋｍ的粗网格可以成功地模拟地面冷高压 与锋面的发展和移动，以及高空环流形势的演变．而通过３０ｋｍ细网格的模拟发现，在冷锋后的行星边界层 中．存在着一条宽度为 ２００ ｋｉｎ的中尺度强风带，最大风速位于 ９２５ｈＰａ，它与高空的极锋急流并不相连；细 网格还模拟出了渤海中尺度低压的发展过程，它使近地面层大风的强度显著加强．模拟还表明，海陆差异对 近地面的风场分布有重要的影响，强风带移入渤海后，在渤海海域形成一个 ２００—３００ ｋｍ的中尺度强风 区．因此，采用具有较高分辨率的中尺度数值模式，对提高渤海大风的预报水平，避兔海难事故的发生更具 有重要意义．     

呼和浩特强对流天气的数值模拟分析

利用三维积云数值模式模拟了呼和浩特地区强对流天气的发展过程，并结合实时雷达回波资料进行了对比分析，指出模式输出的部分物理量与理论值、雷达回波或地面天气及降雹（水）实况符合得较好。从对模式输出的几个物理量的统计分析，得出利用三维积云数值模式预测强冰雹过程的概念模型。结果表明，三维积云数值模式能用于模拟对流云特别是强对流云的发展过程，可在人工影响天气业务工作中应用并不断发展。     

空中交通管制雷达管制训练分类考核方法研究

分析当前我国管制员雷达培训考核环节中存在的问题,提出一种新的雷达管制培训的考核方法——检查单式考核,根据管制过程所涉及的各个环节以及航空器在空中的运行状态,对雷达管制培训实施分类考核。并结合一个进近雷达管制考核表的实例,分析其检查单式考核表的设计思想,详细说明其考核表记录和考核结果量化的步骤和方法。     

天然气钻井井口安全距离研究分析

分析天然气钻井井场可能发生的事故类型及事故的破坏程度,选择适合的事故后果模型,对天然气井井喷失控后可能发生的蒸气云爆炸及硫化氢扩散的后果进行量化分析,根据超压-冲量准则、热剂量准则和硫化氢扩散行为规律,计算出爆炸波、爆炸火球及硫化氢扩散的危害范围。笔者建立了天然气钻井井口安全距离的计算模型,并提出一种确定安全距离的方法。通过计算给出不同无阻流量、不同硫化氢体积含量的20种条件下的天然气钻井井口安全距离,并应用该模型对某含硫气井井口安全距离进行了计算。实例表明,该方法具备实用性,值得在天然气井选址规划中推广和使用。     

A SIMPLE HYDRAULIC SIMULATOR1

ABSTRACT: A simple simulator was constructed, calibrated, programmed and used in management studies of a hydraulic system containing two pumping stations in series, connected by canals and reservoirs. The features of the model, its calibration and use are described, and comparisons between measured and computed hydraulic behavior are presented.