EVOLUTION OF LIQUID WATER CONTENT IN A SEA FOG CONTROLLED BY A HIGH-PRESSURE PATTERN

On March 16–17, 2008, a sea fog occurred in Dianbai in the west of Guangdong Province and was accompanied by a high-pressure synoptic system. Using comprehensive observation datasets, this study analyzes the evolution of liquid water content during this sea fog and investigates the relationships between liquid water content and the average diameters and count densities of fog droplets, air temperature, wind speed and turbulence exchanges. The main results are presented as follows. (1) The sea fog showed a quasi-periodic oscillation characteristic, i.e., it developed, disappeared and then developed again. (2) During the sea fog, the number of fog droplets changed significantly while the changes in average diameter of the fog droplets were relatively small. The development and disappearance of the sea fog correlated significantly with the fog droplet numbers. (3) The air-cooling mechanism played a significant role in sea fog formation and development. However, the influences of this mechanism were not evident during fog persistence. (4) During sea fog formation, weak turbulence exchanges were helpful for fog formation. During sea fog development and persistence, liquid water content increased when turbulence exchanges weakened, and vice versa. The changes in turbulence exchanges were closely related to the quasi-periodic oscillations observed in sea fog presence.     

Dynamics and design of systems for geological storage of dissolved CO2

The standard approach for geologic storage of CO₂ consists of injecting it as a supercritical CO₂ phase. This approach places stringent requirements on the caprock, which must display: (1) high entry pressure to prevent the buoyancy driven upwards escape of CO₂; (2) low permeability to minimize the upwards flux of brine displaced by the CO₂; and (3) high strength to ensure that pressure build up does not cause caprock failure. We propose an alternative approach for cases when the above requirements are not met. The approach consists of extracting brine from the storage formation and then re-injecting it so that it mixes with CO₂ at depth in the injection well. Mixing at depth reduces the pressure required for brine and CO₂ at the surface. This CO₂-saturated brine will sink to the aquifer bottom because it is denser than resident brine, which eliminates the risk of buoyant escape of CO₂. The method is particularly favorable when the aquifer dips, because CO₂-saturated brine will tend to flow downslope. We perform two- and three-dimensional numerical simulations to study how far upslope the extraction well needs to be located to ensure a very long operation without CO₂ ever breaking through. Several sets of simulations were carried out to evaluate the effect of slope, temperature, pressure and CO₂ concentration, which is significantly reduced if flue gas (i.e., without capture) is mixed with the brine. We analyze energy requirements to find that the system requires high permeability to be viable, but its performance is improved by taking advantage of the thermal energy of the extracted brine.     

A note on the applicability of log-Gumbel and log-logistic probability distributions in hydrological analyses: I. Known pdf

Abstract

Two probability density functions (pdf), popular in hydrological analyses, namely the log-Gumbel (LG) and log-logistic (LL), are discussed with respect to (a) their applicability to hydrological data and (b) the drawbacks resulting from their mathematical properties. This paper—the first in a two-part series—examines a classical problem in which the considered pdf is assumed to be the true distribution. The most significant drawback is the existence of the statistical moments of LG and LL for a very limited range of parameters. For these parameters, a very rapid increase of the skewness coefficient, as a function of the coefficient of variation, is observed (especially for the log-Gumbel distribution), which is seldom observed in the hydrological data. These probability distributions can be applied with confidence only to extreme situations. For other cases, there is an important disagreement between empirical data and theoretical distributions in their tails, which is very important for the characterization of the distribution asymmetry. The limited range of shape parameters in both distributions makes the analyses (such as the method of moments), that make use of the interpretation of moments, inconvenient. It is also shown that the often-used L-moments are not sufficient for the characterization of the location, scale and shape parameters of pdfs, particularly in the case where attention is paid to the tail part of probability distributions. The maximum likelihood method guarantees an asymptotic convergence of the estimators beyond the domain of the existence of the first two moments (or L-moments), but it is not sensitive enough to the upper tails shape.     

应用浅层地震技术勘查岩溶及溶洞

本文结合工程勘查实例，介绍了浅层地震技术（高密度地震映象法和横波法）在解释工程勘查中探岩溶，溶洞问题的应用，分析岩溶，溶洞等在浅层地震勘探中表现的特征和规律，并探讨其应用效果。     

浅部开采地面塌陷对井下危害及防治

全面调查了某矿浅部开采地面塌陷坑的形成条件及存在状态，采用模糊聚类分析方法对地面塌陷坑进行了科学的分类，分析了塌陷特征及其对井下危害程度，提出了消除塌陷坑对井下危害、恢复矿区生态环境的防治目标及具体原则，研制出地面塌陷坑治理的四种方案，即①排除积水，构筑隔水层；②煤矸石充填塌陷坑复垦土地；③利用塌陷坑发展养殖；④因地制宜，综合治理。通过方案的实施，彻底消除了塌陷坑对井下的危害，地面生态环境得以恢复，取得了理想的治理效果和经济社会效益。     

高密度多波列地震影像法其在合流污水管道探测中的应用

文章简要介绍了高密度多波列地震影像的原理及方法技术。并用实例说明了在合流污水管道探测中的应用。     

高密度电法与多波映象法在覆盖型岩溶勘察中的应用

采用高密度电法与多波映象法对深圳市龙岗某住宅区覆盖型岩溶地质体进行了勘察,并与钻探进行对比分析,说明这两种方法能够较好地探测覆盖型岩溶地区岩溶的发育形态,取得了岩溶基岩面埋深的符合率和强岩溶发育区的符合率,减少钻探工作量87 %75 %,节约勘察投资的好效果。30 %20 %     

粉煤灰扰动样现场取样问题初步探讨

本文结合福州电厂粉煤灰室内试验结果分析，探讨粉煤灰扰动样现场取样及试验控制干密度的等问题，该电厂粉煤灰的沉积规律与其它电厂有所不同，灰料颗粒组细分布和距排灰口远近基本无关，取样也不能按以往经验进行。     

Probabilistic critical excitation for MDOF elastic–plastic structures on compliant ground

Earthquake ground motions and their effects on structural responses are very uncertain even with the present knowledge. It is therefore desirable to develop a robust structural design method taking into account these uncertainties. Critical excitation approaches are promising and a new random critical excitation method is proposed for MDOF elastic–plastic shear‐building structures on compliant ground. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. In contrast to linear elastic structures, transfer functions and simple expressions for response evaluation cannot be defined in elastic–plastic structures and difficulties arise in describing the peak responses except by laborious elastic–plastic time‐history response analysis. Statistical equivalent linearization is used to estimate the elastic–plastic stochastic peak responses approximately. The critical excitation responses are obtained for several examples and compared with those of the corresponding recorded earthquake ground motion. Copyright © 2001 John Wiley & Sons, Ltd.