树轮稳定同位素记录:进展、问题及展望

树轮稳定同位素比率(δ13 C、δ18O 和δD)变化与树木生长季的气候和环境条件密切相关。控制实验表明, 树轮稳定同位素比率变化可较好地记录树木叶片气孔活动、水分来源、水分利用效率等相关信息, 已成为古气候和全球变化生态学研究的重要代用指标和手段之一。树轮稳定同位素记录能够较好地保留低频气候环境变化信息, 与年轮宽度相结合, 可有效地进行区域古气候重建和全球变化生态学方面的研究。文章综述了树轮稳定同位素的分馏机理及其发展, 系统阐述和评价了利用树轮稳定同位素指标进行古气候和古环境的相关研究成果, 并指出树轮稳定同位素研究在中国未来亟须着重发展的方向。     

Implications of diverse sedimentation patterns in Hala Lake, Qinghai Province, China for reconstructing Late Quaternary climate

Hala Lake is located in the Qilian Mountains, Qinghai Province, China, at 4,078?m a.s.l. Its sediments contain an archive of climate and hydrologic changes during the Late Quaternary, as it is located close to the area influenced by the East-Asian summer monsoon and westerly-driven air masses. Sedimentation patterns and depositional conditions within the lake were investigated using eight sediment cores from different water depths, and this information was used to evaluate the feasibility of using a single core to reconstruct past climate and hydrological conditions. Long core H7, from the center of the lake (65?m water depth) and core H8 from a western, near-shore location (20?m water depth), were compared in detail using sediment composition and geochemical data (X-ray fluorescence, loss-on-ignition and CNS analysis). Age models were constructed using 17 AMS radiocarbon dates and indicate negligible reservoir error for sediments from the lake center and?~1,000?year errors for the near-shore sediment core. Cores H1?CH5 and HHLS21-1 revealed a sediment succession from sand and silty clay to laminated clay on the southern side of the lake. Undisturbed, finely laminated sediments were found at water depths???15?m. Core H5 (2.5?m long), from 31?m water depth, yielded abundant green algal mats mixed with clayey lake deposits and was difficult to interpret. Algae occurred between 25 and 32?m water depth and influenced the dissolved oxygen content of the stratified lake. Comparison of cores H7 and H8 yielded prominent mismatches for different time periods, which may, in part, be attributed to internal lacustrine processes, independent of climate influence. We thus conclude that data from a single sediment core may lead to different climate inferences. Common shifts among proxy data, however, showed that major climate shifts, of regional to global significance, can be tracked and allow reconstruction of lake level changes over the last 24,000?years. Results indicate advance of glaciers into the lake basin during the LGM, at which time the lake experienced lowest levels, 25?C50?m below present stage. Stepwise refilling began at ca. 16 kyr BP and reached the ?25?m level during the B?lling/Aller?d warm phase, ca. 13.5 kyr BP. A desiccation episode falls within the Younger Dryas, followed by a substantial lake level rise during the first millennium of the Holocene, a result of climate warming, which promoted glacier melt. By ca. 7.6 kyr BP, the lake reached a stable high stand similar to the present level, which persisted until ca. 6 kyr BP. Disturbed sediments in core H7 indicate a single mass flow that was most likely triggered by a major seismic event?~8.5 kyr BP. Subsequent lake development remains unclear as a consequence of data mismatches, but may indicate a general trend to deteriorating conditions and lake level lowstands at ca. 5.0?C4.2, 2.0 and 0.5 kyr BP.     

巧用CASIO fx-4800P计算器测设线路复合曲线

应用地面点与线路中线相对关系的统一数学模型，使用CASIO fx-4800P程序型计算器编制的适合野外测设线路各种复合曲线(包括直线、缓和曲线、圆曲线的任意组合)的实用程序。     

常州市数字化测绘工程及GIS建库概述

数字化地形图和地籍图是城市规划、建设和管理及国土资源管理的重要基础资料．也是开展数字城市和信息化建设的最基础平台。通过对系统总体结构的设计和应用成果介绍，分析了目前基础地理数据生产、管理和应用的现状，介绍了基于GIS的常州市数字化地形图、地籍图测绘工程总体目标及基础地理信息系统总体设计．并概述了整个数字化测绘工程的实施过程和特点。     

矢量地形图拓扑等问题的研究与实践

对矢量地图生产过程中常见的图形拓扑、数据冗余问题进行分析和研究；在此基础上结合生产实践，提出了相应的解决办法。研制了基于AutoCAD2000平台的相关程序。     

谈遥感和计算机技术在城市消防规划中的应用

介绍了城市消防规划的编制方法,同时分析其规划编制中的缺陷,提出了利用遥感和计算机手段进行城市消防规划的方法,并对遥感技术进行了简要介绍。     

秩亏自由网平差的一种新解法

提出秩亏自由网平差的一种新解法,只亲知道误差方程系数阵中ｔ０个线性无关的列向量,就能很快地得到最小二乘最小范数解,实际计算表明,这种新解法是简单有效的。     

地籍信息系统图形处理的几个问题

对地籍信息系统中地籍图的显示与变换、注记、地籍实体的捕捉等的实现进行了探讨,运用一些有效的算法,取得较好效果。     

互联网时代GIS设计的新观念──以数据为中心的GIS

本文讨论了以数据为中心的GIS设计新概念。指出互联网造就了巨大的信息资源,GIS的数据源从自供自给到从网上获取是一种观念的巨大转变。进而探讨了WebGIS在网上数据服务,网上数据互操作,网上数据采掘和网上数据管理等方面的新进展和面临的新挑战。     

广义球谐函数及其在梯度边值问题中的应用

本文首先指出球谐函数不是球面上唯一的正交函数系,接着证明了体谐函数的一阶、二阶水平导数（称之为广义球函数）也是球面上的正交函数系,最后利用球面上的正交函数系研究了物理大地测量中的一阶、二阶梯度边值问题。