Research Progress of Atmospheric Carbon Monoxide

Nowadays, researchers pay more attention to the atmospheric CO, which are including the chemical characteristics of atmospheric CO and its indirect effects on the climate, environment pollution monitoring, the source and sink, the distribution characteristics and change rules of its concentration and so on. In order to understand the research status well, we carried out a preliminary summary about the research methods of atmospheric CO based on the former research. The purpose of this study is to give some reasonable suggestions to improve the observation of the Polar Regions and the atmospheric chemical models.     

基于抛物线拟合的椭球面区域面积计算方法

在对高斯投影面积变形的性质及量级进行全面分析的基础上,顾及地球曲率,提出抛物线拟合面积修正法,用以计算椭球面区域的面积。该方法根据区域的横坐标平均值,可直接将高斯平面面积转化为椭球面面积,不仅计算简便、精度高,而且稳定性好。     

A compact representation of spatio-temporal slip distribution on a rupturing fault

We propose a mathematical representation to qualitatively describe the spatio-temporal slip evolution during earthquake rupture in an efficient and easy-to-use manner for numerical simulations of strong ground motion. It is based on three basis functions and associated expansion coefficients. It is an extension of the approach of Ide and Takeo, (J Geophys Res, 102:27379–27391, 1997). We compare our approach and theirs using simple kinematic source models to illustrate differences between the two approaches, and show that our approach more accurately represents the spatio-temporal slip evolution. We also propose a technique based on our representation for extracting a spatio-temporal slip velocity function from a kinematic source model obtained by the conventional source inversion. We then demonstrate the feasibility of our procedure with application to an inverted source model of the 26 March 1997 Northwestern Kagoshima, Japan, earthquake (M _W6.1). In the simulations for actual earthquakes, source models obtained from kinematic source inversions are commonly employed. Our scheme could be used as an interpolation method of slip time functions from relatively coarse finite-source models obtained by conventional kinematic source inversions.     

Quantitative microbial risk assessment: uncertainty and measures of central tendency for skewed distributions

In the past, arithmetic and geometric means have both been used to characterise pathogen densities in samples used for microbial risk assessment models. The calculation of total (annual) risk is based on cumulative independent (daily) exposures and the use of an exponential dose–response model, such as that used for exposure to Giardia or Cryptosporidium. Mathematical analysis suggests that the arithmetic mean is the appropriate measure of central tendency for microbial concentration with respect to repeated samples of daily exposure in risk assessment. This is despite frequent characterisation of microbial density by the geometric mean, since the microbial distributions may be Log normal or skewed in nature. Mathematical derivation supporting the use of the arithmetic mean has been based on deterministic analysis, prior assumptions and definitions, the use of point-estimates of probability, and has not included from the outset the influence of an actual distribution for microbial densities. We address these issues by experiments using two real-world pathogen datasets, together with Monte Carlo simulation, and it is revealed that the arithmetic mean also holds in the case of a daily dose with a finite distribution in microbial density, even when the distribution is very highly-skewed, as often occurs in environmental samples. Further, for simplicity, in many risk assessment models, the daily infection risk is assumed to be the same for each day of the year and is represented by a single value, which is then used in the calculation of p _Σ, which is a numerical estimate of annual risk, P _Σ, and we highlight the fact that is simply a function of the geometric mean of the daily complementary risk probabilities (although it is sometimes approximated by the arithmetic mean of daily risk in the low dose case). Finally, the risk estimate is an imprecise probability with no indication of error and we investigate and clarify the distinction between risk and uncertainty assessment with respect to the predictive model used for total risk assessment.     

Behaviour of the geomagnetic field during the Matuyama–Brunhes polarity transition

The ability to derive Gauss coefficients, up to and including degree 3, and their variation through a geomagnetic polarity transition is studied using simulated palaeomagnetic data. It is concluded that for a specified distribution of palaeomagnetic sites reasonable estimates of the behaviour of the coefficients can be derived even when uncertainties in the data, and in the compilation of contemporaneous records, are considered. Published palaeomagnetic records of the Matuyama–Brunhes transition are then used as basis for deriving the variation of the Gauss coefficients over a 32 kyear period encompassing the reversal. Individual records are interpolated to uniform time intervals of 0.5 kyear and put on to a common time scale by correlating between sites the variation in the latitude of VGP's through the reversal. Relative palaeointensity data are scaled by the geocentric axial dipole field intensity for 2000 at each site, and the Gauss coefficients derived by a matrix inversion employing singular value decomposition. The derived variation with time of the Gauss coefficients suggests that, over the time span of the data, the dipole and non-dipole fields have approximately equal intensities. Plots of the variation of the surface vertical magnetic field through the reversal suggest that immediately prior to the reversal a large patch of reverse flux appears in the southern hemisphere. This may subsequently have been responsible for the weakening of the vertical field leading into the reversal. A similar patch of reverse flux is observed some 20–15 kyear prior to the actual reversal and may be associated with an observed excursion in VGPs at several sites.     

川西及邻近地区地震活动性模拟和断层间相互作用研究

本研究采用基于库仑破裂准则的地震活动性准静态模型,模拟计算了川西地区长达10000年的理论地震目录,通过对理论地震目录的分析发现川西地区M_s≥7.0强震在时间上表现出很强的随机性,与平均地震发生率为1/22.0年^－1（≈0.0454年^－1）的Poisson过程很相近, Poisson模型可能是川西地区开展长期（数10年）地震危险性计算中较为合适的模型.而单一断层M_s≥7.0强震的时间间隔分布与Poisson过程存在很大的差异,用Poisson模型估计单一构造上长期地震危险性可能是不合适的.通过分析模拟产生的长时间理论地震目录,逐一给出了川西地区主要断层的M_s≥7.0强震的时间间隔分布与平均M_s≥7.0强震的复现时间,并讨论了主要断层间强震活动的相互关联,计算出了强震在各断层间的转移概率.定量计算了研究区一断层的破裂产生的库仑应力在研究区其他断层面上的投影.从而为研究断层间的相互作用,研究一断层发生强震对其他断层发生强震危险性的影响提供了依据.本文为开展区域地震危险性分析研究提出了新的思想和途径.     

气象条件对烟囱污染物影响的模拟研究

利用ISC3模型模拟了某电厂不同高度烟囱在不同风速、不同稳定度情况下SO2的最大落地浓度和落地距离。结果表明:在烟囱高度不变的情况下,稳定度不变,如果风速逐渐加大,则SO2最大落地浓度变小,且最大落地距离亦变小;烟囱高度不变且风速不变情况下,稳定度由稳定趋向于不稳定,则SO2最大浓度变小且最大落地距离变小;在风速和稳定度不变的条件下,随着烟囱高度的减小,SO2最大浓度变大且最大落地距离不变;在建烟囱最高高度不宜超过300 m。     

Approaches to modelling coupled flow and reaction in a 2D cementation experiment

Porosity evolution at reactive interfaces is a key process that governs the evolution and performances of many engineered systems that have important applications in earth and environmental sciences. This is the case, for example, at the interface between cement structures and clays in deep geological nuclear waste disposals. Although in a different transport regime, similar questions arise for permeable reactive barriers used for biogeochemical remediation in surface environments.The COMEDIE project aims at investigating the coupling between transport, hydrodynamics and chemistry when significant variations of porosity occur. The present work focuses on a numerical benchmark used as a design exercise for the future COMEDIE-2D experiment. The use of reactive transport simulation tools like Hytec and Crunch provides predictions of the physico-chemical evolutions that are expected during the future experiments in laboratory. Focus is given in this paper on the evolution during the simulated experiment of precipitate, permeability and porosity fields.A first case is considered in which the porosity is constant. Results obtained with Crunch and Hytec are in relatively good agreement. Differences are attributable to the models of reactive surface area taken into account for dissolution/precipitation processes. Crunch and Hytec simulations taking into account porosity variations are then presented and compared. Results given by the two codes are in qualitative agreement, with differences attributable in part to the models of reactive surface area for dissolution/precipitation processes. As a consequence, the localization of secondary precipitates predicted by Crunch leads to lower local porosities than for predictions obtained by Hytec and thus to a stronger coupling between flow and chemistry. This benchmark highlights the importance of the surface area model employed to describe systems in which strong porosity variations occur as a result of dissolution/precipitation. The simulation of highly non-linear reactive transport systems is also shown to be partly dependent on specific numerical approaches.     

Approximate solution of normal equations by eigenvalue decomposition

Geodetic adjustment problems frequently require the solution of large systems of linear equations. An approximation method is presented based on the decomposition of the estimated covariance matrix of the observation matrix, calculated in a pre-processing step, into a system of eigenvalues and eigenvectors. Neglecting the non-dominant eigenvalues and the assigned eigenvectors, the matrix of the residuals is approximated applying the synthesis formula of principal-component analysis. Although the number of observation vectors in the multivariate Gauss–Markoff model is drastically reduced, all unknown parameters are estimated approximately. The described method is tested using a numerical example of satellite altimetry. Received: 6 January 1997 / Accepted: 16 November 1998     

伸展边界方向对伸展盆地正断层走向的影响——来自平面砂箱实验的启示

五种不同边界几何条件的平面砂箱实验模型表明,一个方向的伸展变形可因伸展边界方向的变化形成不同走向的正断层,伸展裂陷盆地中不同走向的正断层并非一定代表不同方向区域构造应力作用、或多期构造变形的结果。伸展裂陷盆地正断层走向受伸展边界走向和构造伸展的方向共同控制,伸展边界的控制力随距离增大而逐渐衰减。伸展边界附近的断层走向主要受伸展边界方向控制,大致反映伸展边界方向。盆地内部断层走向主要受构造伸展方向控制(趋向于垂直构造伸展方向),主要反映构造伸展方向。盆地伸展边界方向的变化可以引起伸展裂陷盆地内部断层走向的转向。因铲式正断层上盘滚动变形产生的正断层,其走向平行于铲式边界断层的走向。