大底盘多塔楼结构的混合隔震控制

结合某实际工程,针对大底盘多塔楼结构提出混合隔震的控制策略,即对大底盘上的一栋或多栋塔楼采用隔震技术,并在隔震层附设一定数量的被动、主动或半主动的减震控制装置。建立了这种大底盘多塔楼结构混合隔震控制体系的运动方程,方程中各塔楼与下部结构及隔震层之间的刚度解耦,并考虑了隔震层的非线性。研究中比较了被动非线性粘滞阻尼器,半主动变孔隙阻尼器与理想主动控制时的减震控制效果。结果表明,这种混合隔震体系可以有效地减小上部塔楼与下部结构的地震反应,提高大底盘多塔楼结构的抗震安全性,取得明显的经济和社会效益。半主动变孔隙阻尼器可以极好地追踪理想主动控制力,取得与理想主动控制相近的减震控制效果。被动非线性粘滞阻尼器也能取得较好的减震效果,且易于维护,经济性较好,从工程应用的角度来看更为现实可行,具有较好的应用推广价值。     

陕西马元地区铅锌矿地质特征及找矿远景

陕西马元地区铅锌矿位于扬子地台北缘碑坝隆起东南缘一带。矿化带长大于60km,宽10～200m,可分为南、东、北3个铅锌矿化带,已圈出了40多条铅锌矿体。其中南矿化带长大于20km,宽20～120m,已圈出了40多条铅锌矿体;东矿化带长大于30km,宽20～200m,地表已发现7条铅锌矿体;北矿化带长大于10km,宽10～100m。矿体一般长100～2560m,厚0.80～10.01m,锌品位1.05%～10.82%,铅品位0.55%～7.54%。主矿体长2560m,厚1.46～32.53m,平均厚约7.60m,最厚28.40m,锌品位1.45%～11.42%,平均4.47%。矿化带主体由震旦系灯影组白云岩组成,产于灯影组的砾状白云质角砾岩带中。矿化主要受地层和构造的控制。经预测,马元地区铅锌矿有较好的找矿远景,具有形成超大型铅锌矿的潜力。     

连续降雨作用下非饱和土边坡的稳定性分析

在边坡稳定性研究中,吸力的影响经常被忽略。基于非饱和土的渗流理论,利用数值分析方法研究了一个由于连续降雨导致的非饱和土边坡失稳的工程实例。研究结果表明:非饱和土的吸力对于维持边坡稳定具有重要影响,而吸力与降雨频率、降雨量、降雨时间、蒸发量等密切相关。对于工程实践而言,吸力的监测对于维持土坡稳定具有重要意义。     

Peatland development at the arctic tree line (Québec, Canada) influenced by flooding and permafrost

In this study, we documented the Holocene history of a peat plateau at the arctic tree line in northern Québec using stratigraphic and macrofossil analyses to highlight the effects of geomorphic setting in peatland development. Paludification of the site began about 6800 cal yr BP. From 6390 to 4120 cal yr BP, the peatland experienced a series of flooding events. The location of the peatland in a depression bounded by two small lakes likely explains its sensitivity to runoff. The proximity of a large hill bordering the peatland to the south possibly favored the inflow of mineral-laden water. The onset of permafrost aggradation in several parts of the peatland occurred after 3670 cal yr BP. Uplifting of the peatland surface caused by permafrost stopped the flooding. According to radiocarbon dating of the uppermost peat layers, permafrost distribution progressed from the east to the west of the peatland, indicating differential timing for the initiation of permafrost throughout the peatland. Most of the peatland was affected by permafrost growth during the Little Ice Age. Picea mariana macroremains at 6450 cal yr BP indicate that the species was present during the early stages of peatland development, which occurred soon after the sea regression.     

基于高光谱遥感数据提取森林结构参数的研究

以位于三峡库区的龙门河森林自然保护区为研究区,综合利用线性光谱混合模型和几何光学模型,基于高光谱遥感数据提取森林结构参数是本文研究的重点。在研究区地面调查数据的基础上,通过高光谱数据和混合光谱分解法,获得反演几何光学模型所需的四分量参数,根据背景光照分量与森林植被冠层各参数间的关系,反演得到森林冠层郁闭度及平均冠幅的定量分布图,并利用37个野外实测样本进行结果验证。     

气象条件对大气波导的影响

在介绍大气折射基本类型及其对电磁波影响的基础上,概述了三种类型大气波导的形成机制,分析了不同天气系统、气象要素和天气现象对大气波导的影响,总结了易于出现大气波导现象的天气条件。研究气象条件对大气波导的影响,对于研究和预测电磁波在大气中的传播特性以及在军事上的应用都具有十分重要的意义。     

教育测量数据的多元自建模模型分析

将关于形状不变的自建模回归模型推广到多元自变量,解决了计算问题,并结合教育测量数据给出了实例。该模型既可以反映多条曲线走势的共性,又可以反映每条曲线之间的相互关系及其个性。     

Point Cumulative Semivariogram for Identification of Heterogeneities in Regional Seismicity of Turkey

Geological events are neither isotropic nor homogeneous in their occurrences. These two properties present difficulties for spatial modeling of regionalized variables. This paper presents a point cumulative semivariogram (PCSV) technique for quantifying the heterogeneity characteristics of the phenomenon concerned. The basis of the methodology is to obtain experimental PCSVs for each measurement point which led to estimation of radius of influence around each site. In addition, the experimental PCSVs provide basic information about the heterogeneity of the geological variable in the region, and furthermore many useful interpretations can be made concerning the regional variability of the variable. It provides the measure of cumulative similarity of a regional variable around any measurement site. Because PCSV is a means of measuring total similarity, maps at fixed similarity levels are provided in order to document the regional heterogeneity. Identification of heterogeneities depends on the comparison of fixed PCSV values at a multitude of irregularly scattered sites. The PCSV methodology has been applied to the regional seismic data of Turkey.     

Damage distribution during the 1994 Northridge, California, earthquake relative to generalized categories of surficial geology

The spatial distributions of severely damaged buildings (red-tagged) and of breaks in the water distribution system following the 1994 Northridge, California, earthquake (M_L = 6·4) are investigated relative to the local characteristics of surficial geology. The pipe breaks are used as an indicator of nonlinear soil response, and the red-tagged buildings as indicator of severe shaking. The surficial geology is described by several generalized categories based on age, textural character and thickness of the near surface layer. Two regions are studied: the San Fernando Valley and Los Angeles-Santa Monica. The analysis shows that there is no simple correlation between damage patterns and surficial geology. Single family wood-frame buildings were damaged less when built on fine silt and clay (0–3 m thick) from the late Holocene.     

Estimating open boundary conditions from coastal tidal observations by adjoint approach

A numerical study for estimating the tidal open boundary conditions of a shelf current modrl from tb coastal tidal observations is presented. The method is based on the optimal control/adjoint method. A lrast square fitting of the model state to simulated data is used. Two ideal domains and coastlines are considered. Using the IAP shallow. water model and its adjoint model, some identical twin experiments are carried out to test efficiency and lirnilsd of the method. The results show that the adjoint method can efficiently estimate the open boundary conditions well for gulf/bay like domains. The adjoint method seems to have great potential to improve the accuracy of tide and shelf current modeling in coastal regions. Project supported hy the National Natural Science Fuundation of China (Grant No. 49376256)