全新世东亚季风活动在印度尼西亚多岛海的表现

印度尼西亚多岛海位于印度洋东部 ,北印度洋和西太平洋交界处 ,由至少 8个盆地通过相对较浅的海槛相连而成 ,海盆水深一般能达 45 0 0ｍ以上。它属于表层水温大于2 8℃的西太平洋暖池范围 ,并受强烈的季风活动影响。由于风场模式差异 ,太平洋海平面较印度洋海平面有一个显著高差 ,致使海水自太平洋向印度洋流动产生印度尼西亚穿越流。 2 0 0 0ｍ深的帝汶海和位于巴厘岛和龙目岛之间的龙目海峡是印度尼西亚穿越流两个最主要的传输通道。南半球冬季 (8月 )澳大利亚上空的高压系统与亚洲上空的低压系统之间的相互作用 ,在印尼海区形成东南方向…     

爱琴爱—安纳托利亚相互作用的地震学和GPS证据

将地震学资料和GPS数据用于检验东地中海地区的地震构造格局和板块运动，主要目的是重新评价最近提出的一种观点，即认为安纳托利亚－爱琴海微板块围绕着位于北非的一个欧拉轴存在刚体转动。两种数据显示出了更为复杂的格局。在北人利托利民层（NAF）的南部，安纳托利亚相对于欧洲的板块运动可被恰当的描述为简单的刚体转动，其主要分量为东西分量，平均速度约为22mm/a，然而，两种数据均显示出爱琴海区域形变速率的明显增加（30－50mm/a），并且显示出一个比刚体旋转所预期的大得多的南北分最（达20mm/a），这一形变图象与将爱琴海区域作一个分离的微型板块的模型更为一致。     

基本物理常数

科学技术数据委员会(CODATA)作为国际科学理事会(ICSU，前国际科学联合会理事会)的跨学科委员会。成立于1966年。之后不久，即1969年，科学技术数据委员会成立了基本常数工作组，定期为科学技术团体提供自相一致的基本常数及物     

Damage localization under ambient vibration using changes in flexibility

In recent years, Structural Health Monitoring (SHM) has emerged as a new research area in civil engineering. Most existing health monitoring methodologies require direct measurement of input excitation for implementation. However, in many cases, there is no easy way to measure these inputs - or alternatively to externally excite the structure. Therefore, SHM methods based on ambient vibration have become important in civil engineering. In this paper, an approach is proposed based on the Damage Location Vector (DLV) method to handle the ambient vibration case. Here, this flexibility-matrix-based damage localization method is combined with a modal expansion technique to eliminate the need to measure the input excitation. As a by-product of this approach, in addition to determining the location of the damage, an estimate of the damage extent also can be determined. Finally, a numerical example analyzing a truss structure with limited sensors and noisy measurement is provided to verify the efficacy of the proposed approach. Sponsored by: Notional Science Foundation Grant CMS 99-00234     

河套地区新生代湖泊演化与“吉兰泰-河套”古大湖形成机制的初步研究

研究发现,河套地区在距今5～6万年前存在一个统一的"吉兰泰-河套"古大湖,覆盖吉兰泰和河套盆地的大部分地区。本研究试图依据钻孔资料和湖泊沉积物的测年结果,讨论新生代以来河套盆地的湖泊演化和古大湖的形成机制。结果表明,新生代以来,特别是早更新世以来吉兰泰盆地和河套平原的3个坳陷盆地就已经处于湖泊环境,但没有证据显示存在统一的湖泊。湖泊沉积及其OSL测年显示,"吉兰泰-河套"古大湖大约在距今10万年前后开始发育,至距今5～6万年之前湖面达到海拔1080m上下,随后湖泊衰退。我们认为,鄂尔多斯高原东北边缘距今12万年前后开始的快速构造隆升,可能导致了晋陕峡谷黄河外流受阻,最终在河套盆地积水形成统一湖泊,末次冰期中期(深海氧同位素3阶段)相对湿润的气候环境进一步促进了"吉兰泰-河套"古大湖的发育。     

Variation of Small Scale Magnetic Fields Over a Century using Ca-K Images as Proxy

A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory, Mount Wilson Observatory and Mauna Loa Solar Observatory was used to identify and study the Ca-K small-scale features and their solar cycle variations over a century. The small scale features are classified into three distinct categories:enhanced network, active network and quiet network. All these features show that their areas vary according to the11 yr solar cycle. The relative amplitude of the Ca-K networ...     

Deadly oasis:Recurrent annihilation of Cretaceous desert bryophyte colonies;the role of solar,climate and lithospheric forcing

Many oases(wet interdunes)are sedimentary systems characterized by high-frequency water-level oscillations,marked changes in salinity and intense biological activity at their margins.They are considered to be one of the most challenging environments on Earth for ecosystem development.These dynamic,depositional settings are usually unfavourable for fossilization and subsequent preservation of vegetal remains.This paper describes bryophyte(liverwort)assemblages occurring in three successive horizons interpreted to represent(i)recurrent early successional phases of biological soil crust colonization of wet interdune margins or(ii)exceptional preservation of floating or riparian liverworts in oasis pond waters associated with a progressive fall of the interdune water level.The record of in situ colonization surfaces characterized by delicate(e.g.lignin-free)three-dimensional structures represents an exceptional type of preservation herein associated with a rapid variation in phreatic interdune water level and the subsequent establishment of anoxic and reducing conditions.The occurrence of exceptionally preserved liverwort colonies coincides with the sedimentary record of,at least,three seismite levels in the oasis.Data gathered from the site suggests that the water table of the oasis was controlled by a combination of(i)a positive creation of accommodation space due to subsidence associated with movement on syn-sedimentary extensional faults,and(ii)the rise and fall of the oasis water table controlled by the oscillations of the groundwater system due to orbital changes which appear to drive the variability of the climate system.Rising groundwater levels flooded the oasis soil crusts and lead to the exceptional recurrent preservation of liverwort colonies at the oasis margins.Alternatively,considering the hypothesis of floating or riparian liverworts in the oasis pond waters,the fall in the level of the oasis water table placed the floating liverworts in contact with the oasis bottom sediments.This fall in the level of the oasis water table could indicate a cessation of accommodation space by syn-sedimentary extensional faults and/or a regional lowering of the groundwater system level associated with drought periods.Preliminary results indicate that oasis lamination between liverwort colonies records decadal and sub-decadal cyclicity,related with 11-year Schwabe sunspot and sub-decadal NAO cyclicities,conferring for every sedimentary cycle between liverwort colonies a duration of approximately 200 years,that otherwise matches the expected recurrence period for the De Vries cycle of solar activity.