Transient electromagnetic response due to a pair of horizontal conducting sheets in a loop field

The transient electromagnetic response due to a pair of horizontal conducting sheets induced by a loop field is obtained. The response characteristics in the three different regions (above the upper sheet, between the two sheets and below the lower sheet) are briefly discussed. In the first and second regions the composite response is characterised by an overburden response asymptote during early times and a target response asymptote during late times. The transition zones are characterised by shoulder-like bends. In the third region, the composite response increases in direct proportion to the induction number, eventually merging with the target response for large values of the induction number.     

西藏碧土地区怒江缝合带基本特征与演化

碧土地区怒江缝合带由二叠纪—早三叠世蛇绿混杂岩和志留纪─晚三叠世不同类型沉积岩构成的蛇绿─构造混杂带所组成。带中零星出现的蓝闪石、３Ｔ型多硅白云母等组合表明为中高压变质带,以逆冲断裂、褶皱构造构成的双向背冲叠瓦构造为变形特征。该带经历了６个阶段的演化,最终将冈底斯─念青唐古拉陆块和亲扬子的昌都陆块缝合在一起,形成了现今两弧夹一带之构造格局。     

再论盐源模范村喜马拉雅期斑岩铜矿床地质特征及找矿前景

该矿床具有典型斑岩铜矿特征,成岩的多期次构成复式岩体,断裂构造控制的隐爆碎裂岩筒为成矿提供了通道和沉积场所.多期次成矿,特别是次生富集作用形成达中型规模的Ⅰ号矿体,影响次生富集带发育的F7断裂带起了重要作用.总结出适合本区斑岩群特点的找矿标志和提出的找矿靶区,对开展新一轮普查找矿具有现实意义.     

Surf zone dynamics simulated by a Boussinesq type model. Part I. Model description and cross-shore motion of regular waves

This is the first of three papers on the modelling of various types of surf zone phenomena. In this first paper, part I, the model is presented and its basic features are studied for the case of regular waves. The model is based on two-dimensional equations of the Boussinesq type and it features improved linear dispersion characteristics, possibility of wave breaking, and a moving boundary at the shoreline. The moving shoreline is treated numerically by replacing the solid beach by a permeable beach characterized by an extremely small porosity. Run-up of nonbreaking waves is verified against the analytical solution for nonlinear shallow water waves. The inclusion of wave breaking is based on the surface roller concept for spilling breakers using a geometrical determination of the instantaneous roller thickness at each point and modelling the effect of wave breaking by an additional convective momentum term. This is a function of the local wave celerity, which is determined interactively. The model is applied to cross-shore motions of regular waves including various types of breaking on plane sloping beaches and over submerged bars. Model results comprise time series of surface elevations and the spatial variation of phase-averaged quantities such as the wave height, the crest and trough elevations, the mean water level, and the depth-averaged undertow. Comparisons with physical experiments are presented. The phaseaveraged balance of the individual terms in the momentum and energy equation is determined by time-integration and quantities such as the cross-sectional roller area, the radiation stress, the energy flux and the energy dissipation are studied and discussed with reference to conventional phase-averaged wave models. The companion papers present cross-shore motions of breaking irregular waves, swash oscillations and surf beats (part II) and nearshore circulations induced by breaking of unidirectional and multidirectional waves (part III).     

Prevalence and distribution of fecal indicator organisms in South Florida beach sand and preliminary assessment of health effects associated with beach sand exposure

Fecal indicator levels in nearshore waters of South Florida are routinely monitored to assess microbial contamination at recreational beaches. However, samples of sand from the surf zone and upper beach are not monitored which is surprising since sand may accumulate and harbor fecal-derived organisms. This study examined the prevalence of fecal indicator organisms in tidally-affected beach sand and in upper beach sand and compared these counts to levels in the water. Since indicator organisms were statistically elevated in sand relative to water, the study also considered the potential health risks associated with beach use and exposure to sand. Fecal coliforms, Escherichia coli, enterococci, somatic coliphages, and F(+)-specific coliphages were enumerated from sand and water at three South Florida beaches (Ft. Lauderdale Beach, Hollywood Beach, and Hobie Beach) over a 2-year period. Bacteria were consistently more concentrated in 100g samples of beach sand (2-23 fold in wet sand and 30-460 fold in dry sand) compared to 100ml samples of water. Somatic coliphages were commonly recovered from both sand and water while F(+)-specific coliphages were less commonly detected. Seeding experiments revealed that a single specimen of gull feces significantly influenced enterococci levels in some 3.1m(2) of beach sand. Examination of beach sand on a micro-spatial scale demonstrated that the variation in enterococci density over short distances was considerable. Results of multiple linear regression analysis showed that the physical and chemical parameters monitored in this study could only minimally account for the variation observed in indicator densities. A pilot epidemiological study was conducted to examine whether the length of exposure to beach water and sand could be correlated with health risk. Logistic regression analysis results provided preliminary evidence that time spent in the wet sand and time spent in the water were associated with a dose-dependent increase in gastrointestinal illness.     

“门”地貌单元的能量耗散和过程机制

基岩岛屿组成的"门"地貌单元是珠江河口区别于世界其他河口的重要地貌特征之一。文章基于重整化群k-ε湍流模型(RNG k-ε)的FLOW3D流体计算模型研究了"门"地貌单元的时均动力结构及湍流能耗特性。"门"地形致动力结构伴随不同类型能耗区。根据能耗空间分布特性可分为核心区(A1区)、混合区(A2区)、上游区(A3区)、下游区(A4区)。"门"地形作用下,不同分区的动力结构、湍流特性、能量转化、能量耗散特征及其驱动机制不同。     

论工业企业防震减灾

本文论述了我国工业企业防震减灾现状，提出工业企业防震减灾的目标和指导原则，以及部分工业企业的防震减灾措施和对策。     

Urbanised beaches of the Ligurian coastal area (NW Mediterranean): A classification based on organic-matter characteristics and hydrolytic enzymatic activities

The beaches of Liguria have been intensively affected by human activities for over a century, transforming nearly the entire coastline from natural to urbanised and significantly upsetting beach ecological properties. The present study aims to investigate 9 Ligurian beaches characterised by different degree of urbanisation, to test if and to what extent the organic-matter (OM) recycling processes can be linked to the human activity. Swash zone sediment, sampled during the spring–summer–autumn period, when the anthropogenic influence is at its maximum due to tourism, was analysed for OM features and recycling processes. Multivariate statistical analyses showed that huge amounts of detrital OM accumulated in the more urbanised sites, where the anthropogenic influence was at its peak, deriving from higher inhabitant number and density, from the presence of crowded roads very near to the swash zone and sewage treatment plants. The presence of torrent outlets on the beaches provided further OM accumulation. Lipids, carbohydrates and degraded autotrophic pigments were the OM fractions mainly responsible of the differentiation, and rather constant, high labile phosphorus contents were found in the more urbanised sites. The high activity values of the hydrolytic enzymes indicate the response of the microbial system to the OM accumulation in the urban sites. However, a decoupling of the trends of some enzymatic activities (namely glucosidase and lipase) and their target OM was observed in the highly urbanised conditions.