结构地震弹塑性反应谱——损伤谱

首先,本文基于各国广泛使用的由Park和Ang提出的双参数损伤模型,研究基于损伤性能的弹塑性反应谱（损伤谱）的分析方法。其次,文中考虑结构极限状态设计,并通过自编DBDS程序,研究得到了损伤反应谱（简称“RD谱”）,尺。谱综合考虑了结构最大弹塑性位移和结构累积滞回耗能的耦合影响,更加合理地反映结构在罕遇地震作用下的弹塑性行为。第三,通过大量时程分析和拟合得到回归公式及其相关系数,研究成果可供抗震性能评估使用。最后,由本文提倡的RD谱和已有研究的Rμ谱做了定性比较分析,说明了考虑地震动持时的必要性和重要性。     

Estimation Of The Lagrangian Structure Function Constant C0 From Surface-Layer Wind Data

Eulerian turbulence observations, madein the surface layer under unstable conditions (z/L > 0),by a sonic anemometer were used to estimatethe Lagrangian structure function constant _O. Twomethods were considered. The first one makes use of arelationship, widely used in the Lagrangian stochasticdispersion models, relating _O to the turbulent kineticenergy dissipation rate , wind velocity variance andLagrangian decorrelation time. The second one employsa novel equation, connecting _O to the constant of thesecond-order Eulerian structure function. Beforeestimating _O, the measurements were processed in orderto discard non-stationary cases at least to a firstapproximation and cases in which local isotropy couldnot be assumed. The dissipation was estimated eitherfrom the best fit of the energy spectrum in theinertial subrange or from the best fit of the third-orderlongitudinal Eulerian structure function. Thefirst method was preferred and applied to the subsequentpart of the analysis. Both methods predict thepartitioning of _O in different spatial components as aconsequence of the directional dependence of theEulerian correlation functions due to the isotropy.The _O values computed by both methods are presented anddiscussed. In conclusion, both methods providerealistic estimates of _O that compare well withprevious estimations reported in the literature, evenif a preference is to be attributed to the second method.     

地基曙暮光光谱观测反演平流层O3和NO2柱含量

用差分光学吸收光谱(DOAS)方法,从曙暮光天顶散射可见光光谱资料反演了北京上空的O3和NO2柱含量,并对反演结果进行了验证和误差分析.斜柱含量的反演采用了线性和非线性最小二乘拟合方法,拟合时考虑了O3、NO2和H2O的吸收、Ring效应和散射的影响;斜柱含量除以空气质量因子转换成垂直柱含量.空气质量因子的计算使用伪球面DISORT辐射传输模式.O3和NO2总量的检验分别用北京的Dobson O3资料和卫星SAGE Ⅱ的NO2廓线资料.反演的O3总量与Dobson O3总量相比偏差小于10%;NO2总量与SAGE Ⅱ的偏差约20%.     

CHARACTERISTICS OF TURBULENCE SPECTRA IN DIFFERENT WEATHER PROCESSES UNDER UNSTABLE CONDITIONS

In this paper,the data chosen from measurements by supersonic anemometers in Tongxian County of Beijing in1990 are used to study characteristics of turbulence spectra in precipitation weather.Some turbulence parameters such asturbulence intensity,heat and momentum fluxes,friction velocity,M-O length and stability parameter are calculatedand their dependence on turbulence spectra in different stability conditions are analyzed.Some encouraging results areobtained and compared with others' results.     

TURBULENCE CHARACTERISTICS OF THE ATMOSPHERIC SURFACE LAYER OVER AN OPEN GRASSLAND*

Described in this paper is an experiment on atmosphere-surface turbulent exchange and boundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin,China.The characteristics of the turbulent spectrum,and the relationships of the standard deviation of the turbulent velocity components and sensible heat flux with the atmospheric stability are studied using data from a sonic anemometer and a fast-response platinum resistance thermometer mounted on a 100 m tower.The results show that in the surface layer over a flat,uniform and open grassland,for a broad stability range(-22.12≤Z_iL≤17.98),the velocity spectra obey the-2/3 power law in the inertial subrange,and 1 power law at low frequencies.Under near neutral stratification,σ_u/u_*=1.20,σ_v/u_*=1.23 and σ_w/u_*=1.02.For Z_i/L≤-0.2,the standard deviations of the turbulent velocity components follow a 1/3 power law.For Z_i/L≤-0.1,the standard deviation of the temperature fluctuations follows a-1/3 power law,and as Z_i/L≤-0.08,it exhibits nonlinear behavior.Sensible heat flux is well correlated to the stability parameter.     

On the scavenging of SO2 by cloud and raindrops: I. A theoretical study of SO2 absorption and desorption for water drops in air

An extention of our previous theory for trace gas absorption into freely-falling cloud and raindrops is presented. This theory describes the convective diffusion of a trace gas through air and into a water drop with internal circulation, the drop falling at its terminal velocity. Using flow fields for the circulating water inside and for the moving air outside the drop, obtained by numerical solutions to the Navier—Stokes equation of motion, we numerically solved the convective diffusion equation to determine the uptake of SO₂ by water drops of various sizes, time exposure to the gas phase, and concentration of SO₂ in the gas phase. It was found that for drops of radius larger than 1 mm and relatively low gas concentrations (10 ppb (v)), resistance to gas diffusion lies mainly in the gas phase; while for drops of radius less than 500 m and gas concentrations larger than those found in the atmosphere (1% (v)), the resistance to diffusion lies primarily in the liquid phase. With drop sizes and gas concentrations between these limits, the rate of SO₂ uptake is controlled by a coupled resistance to diffusion inside and outside the drop. In addition to our general model, a simplified version was formulated which allows considerable savings in computer time for evaluation and improved ease of handling without significant loss of accuracy. A comparison between our simplified model and that of Barrie (1978) shows that the boundary-layer approach of Barrie may be a useful alternate approach to estimating trace gas absorption by water drops, provided appropriate values are chosen for the thickness of the boundary layers involved.     

Two-Dimensional Scalar Spectra in the Deeper Layers of a Dense and Uniform Model Canopy

The turbulent flow inside dense canopies is characterized by wake production and short-circuiting of the energy cascade. How these processes affect passive scalar concentration variability in general and their spectral properties in particular remains a vexing problem. Progress on this problem is frustrated by the shortage of high resolution spatial concentration measurements, and by the lack of simplified analytical models that connect spectral modulations in the turbulent kinetic energy (TKE) cascade to scalar spectra. Here, we report the first planar two-dimensional scalar concentration spectra (ϕ _cc ) inside tall canopies derived from flow visualization experiments. These experiments were conducted within the deeper layers of a model canopy composed of densely arrayed cylinders welded to the bottom of a large recirculating water channel. We found that in the spectral region experiencing wake production, the ϕ _cc exhibits directional scaling power laws. In the longitudinal direction (x), or the direction experiencing the largest drag force, the ϕ _cc (k _x ) was steeper than and followed an approximate at wavenumbers larger than the injection scale of wake energy, where k _x is the longitudinal wavenumber. In the lateral direction (y), the spectra scaled as up to the injection scale, and then decayed at an approximate power law. This departure from the classical inertial subrange scaling (i.e., k ^−5/3) was reproduced using a newly proposed analytical solution to a simplified scalar spectral budget equation. Near the velocity viscous dissipation range, the scalar spectra appear to approach an approximate k ⁻³, a tantalizing result consistent with dimensional analysis used in the inertial-diffusive range. Implications to subgrid modelling for large-eddy simulations (LES) inside canopies are briefly discussed.     

Correlation study between suspended particulate matter and DOAS data

Continuous data of aerosol optical thickness monitored using differential optical absorption spectroscopy (DOAS) are correlated with the concentration of ground-measured suspended particulate matter (SPM). A high correlation is found between the DOAS and the ground SPM data, making it possible to calculate the mass extinction efficiency of the aerosols in the atmosphere. It is found that the value of mean mass extinction efficiency (MEE) varies over a range of 2.6–13.7m2 g?1, with smaller and larger values occurring for size distributions dominated by coarse and fine particles, respectively.     

利用多模传输理论求解块状云的辐射特征

实际云层在水平与垂直方向都是不均匀的,但为了便于计算,绝大多数关于云辐射的理论模式,都采用平面平行模式.到目前为止,解决三维空间辐射传输问题的方法仍然不多.一般采用统计方法和二流近似法,但这两种方法分别在计算机时和计算精度上受到限制.作者在三维多模传输理论与辐射传输计算程序软件包--DISORT的基础上,发展出计算三维孤立云块多次散射过程的一套程序(MM-DISORT),并由此初步探讨了云块的三维立体结构对云的短波吸收的影响.     

上甸子秋冬季雾霾期间气溶胶光学特性

通过对2004年秋冬季(9—12月)4次雾霾天气过程在京、津背景地区——北京上甸子大气本底污染监测站观测的大气气溶胶光学特性的分析,发现该地区气溶胶光学特性受天气过程的影响很大。4次雾霾影响时段,平均气溶胶散射系数σ_(sca)、吸收系数σ_(abs)和单次散射反照率ω都远高于雾霾过后清洁时段的数值,其中气溶胶ω在雾霾影响时段为0.94～0.97,雾霾后为0.84～0.86,平均减小了0.1左右,表明雾霾天气有利于气溶胶的累积和生成。相比于光吸收性气溶胶,雾霾天气对光散射性气溶胶的增加更为有利,反映了二次气溶胶的产生及其对消光的贡献可能有较大增加。