新型黏弹性阻尼器足尺性能试验研究

黏弹性阻尼器是一种典型的被动控制装置,它可以通过黏弹性材料的剪切滞回耗能起到提高结构阻尼和减小结构地震或风振响应的作用.自主研发了损失系数不小于0.5的黏弹性材料,并基于此材料研发了新型国产黏弹性阻尼器.通过对黏弹性阻尼器足尺试件进行不同应变幅值、加载频率工况下的基本力学性能试验、以及低周疲劳性能试验,研究了不同工况下...     

长距离GPS/BDS双系统网络RTK方法

基于区域参考站网的网络实时动态定位(real-time kinematic,RTK)方法是实现全球定位系统(global positioning system,GPS)、北斗卫星导航系统(BeiDou satellite navigation system,BDS)高精度定位的主要手段.研究了一种长距离GPS/BDS双...     

The conservation patterns of grassland ecosystem in response to the forage-livestock balance in North China

Being a key ecological security barrier and production base for grassland animal husbandry in China,the balance between grassland forage supply and livestock-carrying pressure in North China directly affects grassland degradation and restoration,thereby impacting grassland ecosystem services.This paper analyzes the spatiotemporal variation in grassland vegetation coverage,forage supply,and the balance between grassland forage supply and livestock-carrying pressure from 2000 to 2015 in North China.We then discuss the spatial pattern of grassland ecological conservation under the impacts of grassland degradation and restoration,and livestock-carrying pressure.Over the last 16 years,the total grassland area in North China decreased by about 16,000 km2,with vegetation coverage degraded by 6.7％ of the grasslands but significantly restored by another 5.4％ of grasslands.The provisioning of forage by natural grassland mainly increased over time,with an annual growth rate of approximately 0.3 kg/ha,but livestock-carrying pressure also increased continuously.The livestock-carrying pressure index without any supplementary feeding reached as high as 3.8.Apart from the potential livestock-carrying capacity in northeastern Inner Mongolia and the central Tibetan Plateau,most regions in North China are currently overloaded.Considering the actual supplementary feeding during the cold season,the livestock-carrying pressure index is about 3.1,with the livestock-carrying pressure mitigated in central and eastern Inner Mongolia.Assuming full supplementary feeding in the cold season,livestock-carrying pressure index will fall to 1.9,with the livestock-carrying pressure alleviated significantly in Inner Mongolia and on the Tibetan Plateau.Finally,we propose different conservation and development strategies to balance grassland ecological conservation and animal husbandry production in different regions of protected areas,pastoral areas,farming-pastoral ecotone,and farming areas,according to the grassland ecological protection patterns.     

DRY-SEASON VARIABILITY IN SUSPENDED SEDIMENT CONCENTRATIONS IN THE SOUTH PASSAGE OF THE CHANGJIANG ESTUARY

This paper reports the results of continuous monitoring of turbidity, water depth, salinity (using an Optical Backscatter Sensor (OBS)), and current velocity (using a Current meter (SLC9-2)) in the South Passage of the Changjiang Estuary over a spring–neap period in February 2003 (dry season). The turbidity measured via OBS was closely correlated with the suspended sediment concentration (SSC), which was highly variable. Over the study period, the SSC in the middle layer ranged from 110 to 1400 mg/l. The minimum SSC occurred during a late ebb tide, and the maximum SSC occurred during a late flood tide. On average, the SSC was 1.5 times higher during flood tide than during ebb tide. Vertically within the water column, SSC increased downward, with the ratio of SSC measured near the bed to that measured at the surface ranging from 1.90 to 18.3. The temporal variability in SSC is jointly governed by tides and wind-induced waves, whereas the vertical variability in SSC is attributed to the effect of gravity and vertical water circulation.     

向海湿地自然保护区鸟类多样性评价方法的比较研究

鸟类多样性是评价湿地生态环境质量极其敏感的指标。向海湿地自然保护区地处半干旱区,受气候和人为影响,生态环境变化极为剧烈,因此,寻求一种行之有效且简单易行的鸟类多样性评价手段,对于及时了解湿地生态环境质量的动态变化信息,提出湿地和鸟类多样性的管理和保护对策至关重要。稀疏标准化法是一种建立在物种-面积关系上的生物多样性评价方法,主要用于区域尺度上的生物多样性评估。运用改进的稀疏标准化程序,利用多年调查和收集的鸟类数据,来评价和分析向海自然保护区鸟类多样性及其变化,结合香农-威纳多样性指数和均匀度指数,分析了两种方法获取结果的相关性。评估结果表明:稀疏标准化法获取的鸟类多样性和均匀度信息与传统的香农-威纳多样性指数和Pielou均匀度指数间具有显著的相关关系,可以用于鸟类的多样性和均匀度评价,且具有科学、直观、运算简捷、快速等优势。     

东海内陆架泥质体远端表层沉积物孢粉分布规律及其环境意义

东海内陆架泥质沉积区是全新世高海平面时期以来形成的重要地貌单元,其包含了高分辨率沉积环境与气候变化信息,对该地区现代沉积环境及其影响条件的分析,将有助于长时间尺度古记录识别与反演.孢粉是研究植被和气候环境的重要代用指标,通过对东海内陆架泥质沉积区远端海域150个表层沉积物样品的孢粉分析,揭示了孢粉特征的分布规律,并探讨...     

使用MODIS陆地产品LST和NDVI监测中国中、西部干旱

利用中分辨率成像光谱仪AQUA-MODIS卫星资料反演的地表温度LST和归一化差值植被指数NDVI,在中国中、西部地区应用植被温度混合状态指数VTCI方法,遥感监测干旱的空间分布状况。同时结合该地区有代表性的气象站逐月降水资料与VTCI指数进行相关分析,来验证此方法的适用性。结果表明,VTCI指数不仅与当月的降水量,也与其前期2至6个月的累积降水量有较好的线性相关性,显示VTCI方法不仅是较为有效的近实时大范围干旱监测方法,对于干旱的缓慢发展过程也有一定指示作用。     

贵州从江及毗邻地区岩浆岩形成时代探讨

贵州从江及其毗邻地区的岩浆岩较发育,其岩类较多,有基性岩、超基性侵入岩、酸性侵入岩及基性火山岩。笔者通过收集最新的区域地质调查和同位素年龄测定结果等,对其形成时代进行了探讨,认为岩浆岩活动的高峰期为Ca.825Ma左右,即新元古代早期。     

潜孔锤偏心跟管钻进法在卵砾石地层岩土工程勘察中的应用

卵砾石地层是钻探工程中常见的一种典型的难钻进不稳定地层。通过采用潜孔锤偏心跟管钻进法,从根本上解决了卵砾石地层难以钻进的难题,结合都匀市区岩土工程勘察实例,笔者认为潜孔锤偏心跟管钻进法是在卵砾石地层钻进中行之有效的一种钻进法。     

黔西南地区土壤中镉的地球化学分级和污染修复建议

本文利用区域化探扫面成果资料,从地球化学角度对黔西南地区土壤进行分级,经研究表明,在黔西南地区地表覆盖物(土壤)中镉的含量超标,造成土壤污染,多为二级和三级土壤地球化学评价标准。局部达到一级土壤地球化学评价标准。