人工神经网络在岩体质量分级中的应用

结合四川省金沙江某水电站工程实例，应用BP人工神经网络方法建立3层BP网络模型，选取岩石单轴抗压强度等6个影响因素为输入变量，对坝基复杂岩体进行质量分级。通过机算机Visual C 语言编程实现神经网络模型，进行网络的学习和运算。以神经网络合理结构分析方法选取合理结构，确定合理隐层单元的数量，提高网络测试的精度。对测试结果的分析发现，经过优化的BP网络模型经多次学习后，测试精度提高，结果可靠，取得较好的实际应用效果。     

南秦岭十里坪锑矿床成矿时代及成因的初步研究

十里坪锑矿床受赵川陆缘隆_滑构造的主滑脱拆离带的控制。矿体呈脉状赋存于韧_脆性主滑脱带上部的脆性次级断层_节理中,矿石类型主要为萤石石英辉锑矿型。围岩为太古宙_元古宙变质岩系,围岩蚀变弱。成矿流体属H2O_CO2_NaCl体系,流体包裹体盐度w(NaCleq)为3.6%～11.3%,均一温度为109～232℃,形成压力大致为800×105Pa。硫、铅同位素研究表明,矿质主要来源于变火山岩围岩;氢、氧同位素显示,成矿流体以大气降水为主,初步将该矿床定为变质岩源就地式大气降水热液矿床。矿石中萤石Sm_Nd等时线年龄为(392±24)Ma,与南秦岭北部晚古生代拗陷区热水喷流_沉积成矿时代相一致,它们都形成于秦岭微板块泥盆纪非造山裂解阶段。     

长江三角洲主要城市产业结构转换的综合评价

文章在对地区产业结构转换影响因素系统分析的基础上，采用定量分析方法，对长江三角洲15个主要城市的产业结构转换能力、产业转换速度、产业转换方向以及它们之间的关系进行探讨。研究表明：长江三角洲主要城市产业结构转换能力的区域差异明显，产业结构转换能力与区域经济发展所处阶段有很大的关系；产业结构转换能力、速度与经济发展水平呈正相关。     

近1800年以来内蒙古达里湖浮游植物群落演变及驱动因素

湖泊是地质历史上区域生态环境演变的重要载体,其沉积物中包含了丰富的环境演变信息。达里湖是典型的草原内陆封闭型湖泊,位于东亚夏季风的北部边缘,地理位置关键。本研究基于在达里湖采集的约238 cm沉积物岩芯 (GDL-1),通过²¹⁰Pb和¹³⁷Cs (岩芯上部20 cm)、AMS¹⁴C测年,以及沉积物样品中甾醇等生物标志物含量分析,重建了近1800年以来达里湖硅藻、蓝藻等典型藻类含量的演化历史,并结合总氮(TN)、总磷(TP)、盐度(Sr/Ba)和温度(T)等环境代用指标,分析藻类群落的主要影响因素。结果显示达里湖典型藻类总量平均为2.03 ng/g(最高6.69 ng/g,最小0.53 ng/g),其中蓝藻占比平均为60%,绿藻和硅藻占比平均为20%;环境因子对硅藻、蓝藻和典型藻类生物量的解释率分别为47.7%、55.20%和48.10%,T、TN和Sr/Ba是影响浮游植物群落的主要影响因素;硅藻占比与温度呈显著负相关,小冰期硅藻占比最高,中世纪暖期占比最低;在达里湖的高盐环境下,湖泊营养盐浓度对藻类的影响受到限制,成为藻类等生长的限制因素;Sr/Ba小于0.9时,硅藻含量与典型藻类总量随着Sr/Ba值的升高而增加,Sr/Ba大于0.9时,典型藻类总量与Sr/Ba值呈负相关关系,而硅藻则表现出对盐度具有一定的耐受性;整体上,近1800年以来,区域或全球性气候事件通过改变达里湖盐度、营养元素浓度和温度来影响典型藻类群落结构。在暖期阶段,蒸发作用增强等导致的湖泊盐度增加成为达里湖典型藻类群落结构演变的主要影响因素;在冷期,营养元素浓度和温度的降低成为湖泊水体浮游植物生物量的主要影响因素。     

涡北河网区三维地震采集技术

涡北勘探区属于河网地带,难以进行正常的地震施工。为此,本文提出了一种以规则束状观测为基础和特殊观测系统相结合的数据采集方法。该方法适应了这种复杂的地表条件,获得了"空白区"的地震资料,为今后类似地表条件地区的三维地震勘探提供了经验。      

Vertical structures of PM10 and PM 2.5 and their dynamical character in low atmosphere in Beijing urban areas

The vertical structures and their dynamical character of PM2.5 and PM10 over Beijing urban areas are revealed using the 1 min mean continuous mass concentration data of PM2.5 and PM10 at 8, 100, and 320 m heights of the meteorological observation tower of 325 m at Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP CAS tower hereafter) on 10―26 August, 2003, as well as the daily mean mass concentration data of PM2.5 and PM10 and the continuous data of CO and NO2 at 8, 100 (low layer), 200 (middle layer), and 320 m (high layer) heights, in combination with the same period meteorological field observation data of the meteorological tower. The vertical distributions of aerosols observed on IAP CAS tower in Beijing can be roughly divided into two patterns: gradually and rapidly decreasing patterns, I.e. The vertical distribution of aerosols in calm weather or on pollution day belongs to the gradually decreasing pattern, while one on clean day or weak cold air day belongs to the rapidly decreasing pattern. The vertical distributive characters of aerosols were closely related with the dynamical/thermal structure and turbulence character of the atmosphere boundary layer. On the clean day, the low layer PM2.5 and PM10 concentrations were close to those at 8 m height, while the concentrations rapidly decreased at the high layer, and their values were only one half of those at 8 m, especially, the concentration of PM2.5 dropped even more. On the clean day, there existed stronger turbulence below 150 m, aerosols were well mixed, but blocked by the more stronger inversion layer aloft, and meanwhile, at various heights, especially in the high layer, the horizontal wind speed was larger, resulting in the rapid decrease of aerosol concentration, I.e. Resulting in the obvious vertical difference of aerosol concentrations between the low and high layers. On the pollution day, the concentrations of PM2.5 and PM10 at the low, middle, and high layers dropped successively by, on average, about 10% for each layer in comparison with those at 8 m height. On pollution days, in company with the low wind speed, there existed two shallow inversion layers in the boundary layer, but aerosols might be, to some extent, mixed below the inversion layer, therefore, on the pollution day the concentrations of PM2.5 and PM10 dropped with height slowly; and the observational results also show that the concentrations at 320 m height were obviously high under SW and SE winds, but at other heights, the concentrations were not correlated with wind directions. The computational results of footprint analysis suggest that this was due to the fact that the 320 m height was impacted by the pollutants transfer of southerly flow from the southern peripheral heavier polluted areas, such as Baoding, and Shijiazhuang of Hebei Province, Tianjin, and Shandong Province, etc., while the low layer was only affected by Beijing's local pollution source. The computational results of power spectra and periods preliminarily reveal that under the condition of calm weather, the periods of PM10 concentration at various heights of the tower were on the order of minutes, while in cases of larger wind speed, the concentrations of PM2.5 and PM10 at 320 m height not only had the short periods of minute-order, but also the longer periods of hour order. Consistent with the conclusion previously drawn by Ding et al., that air pollutants at different heights and at different sites in Beijing had the character of "in-phase" variation, was also observed for the diurnal variation and mean diurnal variation of PM2.5 and PM10 at various heights of the tower in this experiment, again confirming the "in-phase" temporal/spatial distributive character of air pollutants in the urban canopy of Beijing. The gentle double-peak character of the mean diurnal variation of PM2.5 and PM10 was closely related with the evident/similar diurnal variation of turbulent momentum fluxes, sensible heat fluxes, and turbulent kinetic energy at various heights in the urban canopy. Besides, under the condition of calm weather, the concentration of PM2.5 and PM10 declined with height slowly, it was 90% of 8 m concentration at the low layer, a little lesser than 90% at the middle layer, and 80% at the high layer, respectively. Under the condition of weak cold air weather, the concentration remarkably dropped with height, it was 70% of 8 m concentration at the low layer, and 20%―30% at the middle and high layers, especially the concentration of PM2.5 was even lower.     

1) I. A. H. S. / A. I. H. S.

Abstract

A simple method is used to study the response of runoff in the Sahel to climate change. The statistical characteristics of rainfall are calculated over the western part of the Sahel for the period 1961–1990, using the BADOPLU network. Daily rainfall is simulated using a Markov process with Weibull distribution for rainfall depths. Runoff is modelled using a conceptual SCS model and the curve numbers are calculated for West Africa. Climate change is provided by simulations using the Arpège GCM (Scenario A1B), and a perturbation method is used on the parameters which describe the rainfall. Changes in rainfall are assumed to occur through increases in frequency, not intensity. Using Arpège, runoff is mainly found to increase, in depth and in number of events, by the end of the 21st century. Changes in evaporation and land use are not included in the analysis. The impact of this 21st century potential climate change (rainfall) on the runoff is found to be of the same magnitude as the impact of changes in land use.     

Axial kinematic response of end‐bearing piles to P waves

Kinematic pile–soil interaction under vertically impinging seismic P waves is revisited through a novel continuum elastodynamic solution of the Tajimi type. The proposed model simulates the steady‐state kinematic response of a cylindrical end‐bearing pile embedded in a homogeneous viscoelastic soil stratum over a rigid base, subjected to vertically propagating harmonic compressional waves. Closed‐form solutions are obtained for the following: (i) the displacement field in the soil and along the pile; (ii) the kinematic Winkler moduli (i.e., distributed springs and dashpots) along the pile; (iii) equivalent, depth‐independent, Winkler moduli to match the motion at the pile head. The solution for displacements is expressed in terms of dimensionless transfer functions relating the motion of the pile head to the free‐field surface motion and the rock motion. It is shown that (i) a pile foundation may significantly alter (possibly amplify) the vertical seismic excitation transmitted to the base of a structure and (ii) Winkler moduli pertaining to kinematic loading differ from those for inertial loading. Simple approximate expressions for kinematic Winkler moduli are derived for use in applications. Copyright © 2013 John Wiley & Sons, Ltd.