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141.
Xue Xi Tie Guy Brasseur Xing Lin Pierre Friedlingstein Claire Granier Philip Rasch 《Journal of Atmospheric Chemistry》1994,18(2):103-128
The paper discusses the potential effects on the ozone layer of gases released by the engines of proposed high altitude supersonic aircraft. The major problem arises from the emissions of nitrogen oxides which have the potential to destroy significant quantities of ozone in the stratosphere. The magnitude of the perturbation is highly dependent on the cruise altitude of the aircraft. Furthermore, the depletion of ozone is substantially reduced when heterogeneous conversion of nitrogen oxides into nitric acid on sulfate aerosol particles is taken into account in the calculation. The sensitivity of the aerosol load on stratospheric ozone is investigated. First, the model indicates that the aerosol load induced by the SO2 released by aircraft is increased by about 10–20% above the background aerosols at mid-high latitude of the Northern Hemisphere at 15 km for the NASA emission scenario A (the NASA emission scenarios are explained in Tables I to III). This increase in aerosol has small effects on stratospheric ozone. Second, when the aerosol load is increased following a volcanic eruption similar to the eruption of El Chichon (Mexico, April 1982), the ozone column in spring increases by as much as 9% in response to the injection of NO
x
from the aircraft with the NASA emission scenario A. Finally, the modeled suggests that significant ozone depletion could result from the formation of additional polar stratospheric clouds produced by the injection of H2O and HNO3 by the aircraft engines. 相似文献
142.
本文意在通过对磁共振成像和波谱学在各方面的发展及应用现状的评述,提出建议:在中国开展适当的高场磁共振成像和波谱学的研究规划。 相似文献
143.
本文在时域、频域范围内,对直记式QZY型(中国)、SMA—1型(美国)、SMAC—B2型(日本)强震加速度仪的动态特性进行了分析,给出了评价系统跟踪和复现地震加速度信号的快速性、平稳性和准确性的动态性能指标.在此基础上,分析和讨论了直记式加速度仪的高频误差,给出了系统幅频,相频相对畸变误差公式和系统参数设置的误差估计方法,计算了加速度仪系统的高频误差分布.最后,讨论了高频误差的校正方法. 相似文献
144.
145.
高边坡的岩体结构和稳定性研究是工程地质研究的一个重要课题。本次探测使用高分辨率数字地震仪和反射地震CT方法,对金川露天矿高边坡的岩体结构进行了深入细致的探测与研究,清楚地揭示了边坡岩体中优势结构面的产状和组合关系,以及边坡表层松动带厚度分布,未发现顺坡软弱岩层。 相似文献
146.
固体传压高温高压岩石三轴实验中,固体传压介质是影响实验结果的重要因素,NaCl介质以它流动性好,围压均匀等特点,八十年代以来越来越受到人们青睐。本文用NaCl介质在〈3GPa固体传压三轴流变仪〉上进行了高温高压岩石流变特性的实验研究,并达到了较高的压力(〉2GPa)和温度(〉1200℃);本文同时利用NaCl介质对样品装样方式及温度、压力等相关测定方面进行了研究。 相似文献
147.
对华北地区韧性剪切带几种代表上、中、下地壳深度的糜棱岩及其围岩在高温高压条件下进行纵波速度测定及各向异性研究.对实验样品的纵波速度测定得到以下结果:1.沿糜棱岩面理方向的纵波速度大于与面理垂直方向的纵波速度,差值为0.15-0.30km/s,各向异性为3%-5%;2.糜棱岩的纵波速度低于其围岩的纵波速度,差值为0.10-0.45km/s;3.中地壳角闪岩相糜棱岩的纵波速度各向异性高于上地壳绿片岩相糜棱岩和下地壳麻粒岩相糜棱岩的各向异性;4.地震波速各向异性与糜棱岩矿物优选定向有关. 相似文献
148.
The analysis and interpretation of coda waves have received increasing attention since the early seventies. In the past few years interest in this subject has spread worldwide, and the study of high-frequency seismic coda waves has become a very important seismological topic. As a conclusion of the studies accomplished in this time, coda waves are considered the result of scattering processes caused by heterogeneities acting on seismic waves.P andS waves play a particularly important role in this interaction. The process introduces an attenuation which, added to the intrinsic absorption, gives the observed apparent attenuation. Therefore, coda waves constitute a thumbprint left by the heterogeneities on the seismograms. Coda waves offer decisive information about the mechanism of how scattering and attenuation take place. This review describes coda waves in detail, and summarizes the work done in this subject to 1986. The relation between coda waves and attenuation in the context of research on seismic scattering problems is stressed. Particular attention has been given to the application of coda waves to estimate source and medium parameters. The state-of-the-art of the temporal variations of coda wave shape, and the possible use of these variations as an earthquake precursor also are presented. Care has been taken to introduce the statistical models used to deal with the heterogeneities responsible for scattering. 相似文献
149.
150.
Significant advances in flood inundation modelling have been made in the last decade through the use of a new generation of 2D hydraulic numerical models. These offer the potential to predict the local pattern and timing of flood depth and velocity, enabling informed flood risk zoning and improved emergency planning. With the availability of high resolution DEMs derived from airborne lidar, these models can theoretically now be routinely parameterized to represent considerable topographic complexity, even in urban areas where the potential exists to represent flows at the scale of individual buildings. Currently, however, computational constraints on conventional finite element and volume codes typically require model discretization at scales well below those achievable with lidar and are thus unable to make optimal use of this emerging data stream.In this paper we review two strategies that attempt to address this mismatch between model and data resolution in an effort to improve urban flood forecasts. The first of these strives for a solution by simplifying the mathematical formulation of the numerical model by using a computationally efficient 2D raster storage cell approach coupled to a 1D channel model. This parsimonious model structure enables simulations over large model domains offering the opportunity to employ a topographic discretization strategy which explicitly represents the built environment. The second approach seeks to further reduce the computational overhead of this raster method by employing a subgrid parameterization to represent the effect of buildings and micro-relief on flow pathways and floodplain storage. This multi-scale methodology enables highly efficient model applications at coarse spatial resolutions while retaining information about the complex geometry of the built environment.These two strategies are evaluated through numerical experiments designed to reconstruct a flood in the small town of Linton in southern England, which occurred in response to a 1 in 250 year rainfall event in October 2001. Results from both approaches are encouraging, with the spatial pattern of inundation and flood wave propagation matching observations well. Both show significant advantages over a coarse resolution model without subgrid parameterisation, particularly in terms of their ability to reproduce both hydrograph and inundation depth measurements simultaneously, without need for recalibration. The subgrid parameterization is shown to achieve this without contributing significant computational complexity and reduces model run-times by an order of magnitude. 相似文献