On the Type Species of Chusenella     

Y. C. HSU  GENUS Chusenella LEE 《地质学报》1942,(Z2):175-176

正 DIAGNOSIS: Test fusiform, slightly rounded at the ends; about 11.2 mm. long, 3.7 mm. wide, giving an axial ratio of about 1:3; whorl 9 to 10, the first three or four volutions closely coiled thence gradually evolute; spiral wall increases in thickness as the test grows, being 0.016 mm. in the firs  相似文献   

Changes in Surface Energy Partitioning in China over the Past Three Decades     

Yitian QIAN  Pang-Chi HSU  Chi-Han CHENG 《大气科学进展》2017,34(5):635-649

Surface energy balance and the partitioning of sensible heat flux(SHF) and latent heat flux(LHF) play key roles in land–atmosphere feedback. However,the lack of long-term observations of surface energy fluxes,not to mention spatially extensive ones,limits our understanding of how the surface energy distribution has responded to a warming climate over recent decades(1979–2009) at the national scale in China. Using four state-of-the-art reanalysis products with long-term surface energy outputs,we identified robust changes in surface energy partitioning,defined by the Bowen ratio(BR = SHF/LHF),over different climate regimes in China. Over the past three decades,the net radiation showed an increasing trend over almost the whole of China. The increase in available radiative energy flux,however,was balanced by differential partitioning of surface turbulent fluxes,determined by local hydrological conditions. In semi-arid areas,such as Northeast China,the radiative energy was transferred largely into SHF. A severe deficiency in near-surface and soil moistures led to a significant decreasing trend in LHF. The combined effect of increased SHF and decreased LHF resulted in significant upward trends in the BR and surface warming over Northeast China. In contrast,in the wet monsoon regions,such as southern China,increased downward net radiation favored a rise in LHF rather than in SHF,leading to a significant decreasing trend in the BR. Meanwhile,the increased LHF partly cancelled out the surface warming. The warming trend in southern China was smaller than that in Northeast China. In addition to impacts on heat-related events,the changes in the BR also reflected recent cases of extreme drought in China. Our results indicate that information regarding the BR may be valuable for drought monitoring,especially in regions prone to such conditions.  相似文献   

A Simple Eddy Viscosity Model of Rough Turbulent Wave Boundary Layer     

Hsu Tai-Wen  Lin Hwung-Yui Associate Professor 《中国海洋工程》1996,(3)

- A one-layer time-invariant eddy viscosity model is specified to develop a mathematical model for describing the essential features of the turbulent wave boundary layer over a rough bed. The functional form of the eddy viscosity is evaluated based on computational results from a two-equation turbulence model in which the eddy viscosity varies with time and space. The present eddy viscosity model simplifies much of the mathematical complexity in many existing models. Predictions from the present model have been compared with a wide range of experimental data. It is found that the eddy viscosity model adopted in the present study is physically reasonable.  相似文献   

蒙古-贝加尔裂谷区地壳应变场及其地球动力学涵义   总被引：1，自引：0，他引：1       下载免费PDF全文

刁法启  熊熊  郑勇  许厚泽 《地球物理学进展》2009,24(4):1243-1251

蒙古-贝加尔地区是现今构造最活跃的大陆地区之一,其地壳构造运动及变形对我们理解大陆动力学问题具有重要的科学意义.基于融合的这一区域的GPS速度场,本文计算了该区应变率场和应变能变化率场.结果显示,蒙古褶皱带以南区域表现为NNE-SSW方向的压缩状态,主压应变率约为-2.0×10^-9/a,剪应变及面膨胀均较弱,表明蒙古褶皱带比较稳定.贝加尔裂谷整体处于拉张状态且伴有较强的剪应变和面膨胀,暗示可能有多种机制控制裂谷的张裂过程.蒙古高原西部有两条高应变率的构造带,结合深部存在地幔热柱等证据,我们认为这两条构造带及所围限的区域共同构成Amurian板块的西部边界—一条弥散变形的边界带.蒙古-贝加尔地区剪应变分布与0~40 km的地震活动性基本一致,表明该地区形变在地壳尺度耦合程度较高.地幔对流拖曳力场与主应变轴方向及应变率场的一致性表明,地幔对流可能是蒙古—贝加尔地区区域构造动力学过程主要控制因素之一.  相似文献   

地幔岩石圈热结构差异与中国大陆岩石圈均衡分析   总被引：1，自引：1，他引：0       下载免费PDF全文

单斌  熊熊  郑勇  许厚泽 《地球物理学报》2008,51(4):1058-1065

观测表明,大陆地区存在很多传统均衡模型无法解释的现象,其根本原因在于传统均衡理论中没有考虑地幔岩石圈部分由于热结构差异导致密度差异的影响.本文基于岩石圈尺度的质量平衡模型研究了中国大陆20个构造单元地壳及地幔岩石圈对地形海拔的贡献,以及各块体的均衡状态.计算结果表明,在一些地区,如塔里木盆地、北山和柴达木盆地,尽管岩石圈均衡模型和Airy模型得到了一致的海拔值,但岩石圈均衡模型更能体现均衡过程的物理本质;除青藏高原造山带外的多数块体,岩石圈均衡模型的计算结果更接近观测海拔和地表垂直运动状态;总体上,考虑地幔岩石圈热结构影响后,中国大陆各地区的均衡结果普遍优于传统的均衡模型.通过对均衡状态分析,我们得到以下主要结论：(1)构造稳定地区均衡程度较高;(2) 青藏高原及周边造山带现今地壳运动主要为区域构造过程及深部动力学过程所控制,均衡调整过程不是主要控制因素;(3) 现今地壳垂直运动比较明显的块体处于均衡调整阶段,地表垂直运动的大小反映了该区所受的均衡力作用的程度;(4) 构造稳定地区基于岩石层均衡的理论计算海拔与观测海拔之差值和现今地壳垂直运动速率有较好的相关性,据此我们可以通过均衡分析研究构造块体的运动趋势和动力学性质;(5) 地幔热结构对现今地形、海拔及地壳垂直运动有显著影响,在处理均衡问题时,地幔岩石圈热结构是我们必须考虑的重要因素.  相似文献   

利用超导重力仪观测资料检测地球近周日共振   总被引：15，自引：1，他引：14       下载免费PDF全文

徐建桥  许厚泽  孙和平  罗少聪 《地球物理学报》1999,42(5):599-608

简要介绍了地球近周日摆动（ＮＤＦＷ）及其在周日重力潮汐中共振的理论背景,利用武汉和Ｂｒｕｓｓｅｌｓ两台站超导重力仪的潮汐观测结果,采用造积方法（Ｓｔａｃｋｉｎｇｍｅｔｈｏｄ）检测ＮＤＦＷ,根据ＮＤＦＷ在４个周日潮波的共振,得到近周日摆动的本征频率和品质因子．考虑ＮＤＦＷ,可精化地球模型,更客观的理解和分析固体潮观测值和其它一些地球物理现象．  相似文献   

基于残余星间速度法精确和快速反演下一代GRACE Follow-On地球重力场          下载免费PDF全文

郑伟  许厚泽  钟敏  刘成恕  员美娟 《地球物理学报》2014,57(1):31-41

基于新型残余星间速度法（RIRM）反演了120阶GRACE Follow-On地球重力场. 第一,由于GPS定轨精度相对较低,通过将激光干涉测距仪的高精度残余星间速度（测量精度10^-7 m·s^-1）引入残余轨道速度差分矢量的视线分量构建了新型RIRM观测方程. 第二,基于2点、4点、6点和8点RIRM公式对比论证了最优的插值点数. 如果相关系数和采样间隔一定,随着插值点数的增加,卫星观测值的信号量被有效加强,而卫星观测值的误差量也同时增加. 因此,6点RIRM公式是提高下一代地球重力场精度的较优选择. 第三,相关系数对地球重力场精度的影响在不同频段表现为不同特性. 随着相关系数的逐渐增大,地球长波重力场精度逐渐降低,而地球中长波重力场精度逐渐升高. 第四,基于6点RIRM公式,通过30天观测数据和采样间隔5 s,分别利用星间速度和残余星间速度观测值,在120阶次处反演下一代GRACE Follow-On累计大地水准面精度为1.638×10^-3 m和1.396×10^-3 m. 研究结果表明：（1）残余星间速度观测量较星间速度对地球重力场反演精度更敏感;（2）GRACE Follow-On地球重力场精度较GRACE至少高10倍.  相似文献   

Impact melting of lunar meteorite Dhofar 458: Evidence from polycrystalline texture and decomposition of zircon     

Ai‐Cheng ZHANG  Wei‐Biao HSU  Xian‐Hua LI  Hou‐Li MING  Qiu‐Li LI  Yu LIU  Guo‐Qiang TANG 《Meteoritics & planetary science》2011,46(1):103-115

Abstract– Dhofar 458 is a lunar meteorite consisting mainly of olivine‐plagioclase intergrowths, pyroxene‐plagioclase intergrowths, and plagioclase fragments. Pyroxene‐plagioclase globules are also common. In this study, we report the discovery of a polycrystalline zircon in this lunar meteorite. The polycrystalline zircon contains small vesicles and rounded baddeleyite grains at its margin. The polycrystalline and porous texture of the zircon indicates high‐pressure shock‐induced melting and degassing. Baddeleyite grains are derived from decomposition of zircon under high postshock temperature. The shock features in zircon indicates that the shock pressure in Dhofar 458 was greater than approximately 60 GPa and the postshock temperature greater than approximately 1700 °C. The polycrystalline and degassing texture and decomposition zircon also strongly indicates that Dhofar 458 is a clast‐rich impact melt rock. During this shock event, most components were melted and grains of mafic minerals are interstitial to lath‐like plagioclase grains. Large fragments of olivine and chromite also formed polycrystalline texture at margins and chemically reequilibrated with surrounding melts. We suggest that pyroxene‐plagioclase globules could be remains of melted target clasts, whereas vesicles may form during shock‐induced degassing of the rock. The U‐Pb isotopic data plot on a well‐defined discordant line, yielding the age of the zircon of 3434 ± 15 Ma (2σ). This age is interpreted as the time of the impact event that melted Dhofar 458 and caused decomposition and recrystallization of this zircon in Dhofar 458, which reset this zircon’s U‐Pb age.  相似文献   

Al‐Mg systematics of hibonite‐bearing Ca,Al‐rich inclusions from Ningqiang     

Weibiao HSU  Yunbin GUAN  Ying WANG 《Meteoritics & planetary science》2011,46(5):719-728

Abstract– Hibonite‐bearing Ca,Al‐rich inclusions (CAIs) usually occur in CM and CH chondrites and possess petrographic and isotopic characteristics distinctive from other typical CAIs. Despite their highly refractory nature, most hibonite‐bearing CAIs have little or no ²⁶Mg excess (the decay product of ²⁶Al), but do show wide variations of Ca and Ti isotopic anomalies. A few spinel‐hibonite spherules preserve evidence of live ²⁶Al with an inferred ²⁶Al/²⁷Al close to the canonical value. The bimodal distribution of ²⁶Al abundances in hibonite‐bearing CAIs has inspired several interpretations regarding the origin of short‐lived nuclides and the evolution of the solar nebula. Herein we show that hibonite‐bearing CAIs from Ningqiang, an ungrouped carbonaceous chondrite, also provide evidence for a bimodal distribution of ²⁶Al. Two hibonite aggregates and two hibonite‐pyroxene spherules show no ²⁶Mg excesses, corresponding to inferred ²⁶Al/²⁷Al < 8 × 10^?6. Two hibonite‐melilite spherules are indistinguishable from each other in terms of chemistry and mineralogy but have different Mg isotopic compositions. Hibonite and melilite in one of them display positive ²⁶Mg excesses (up to 25‰) that are correlated with Al/Mg with an inferred ²⁶Al/²⁷Al of (5.5 ± 0.6) × 10^?5. The other one contains normal Mg isotopes with an inferred ²⁶Al/²⁷Al < 3.4 × 10^?6. Hibonite in a hibonite‐spinel fragment displays large ²⁶Mg excesses (up to 38‰) that correlate with Al/Mg, with an inferred ²⁶Al/²⁷Al of (4.5 ± 0.8) × 10^?5. Prolonged formation duration and thermal alteration of hibonite‐bearing CAIs seem to be inconsistent with petrological and isotopic observations of Ningqiang. Our results support the theory of formation of ²⁶Al‐free/poor hibonite‐bearing CAIs prior to the injection of ²⁶Al into the solar nebula from a nearby stellar source.  相似文献   

基于下一代四星转轮式编队系统精确和快速反演FSCF地球重力场   总被引：4，自引：1，他引：3       下载免费PDF全文

郑伟  许厚泽  钟敏  刘成恕  员美娟 《地球物理学报》2013,56(9):2928-2935

第一,由于重力卫星编队轨道的稳定性设计是建立下一代高精度和高空间分辨率地球重力场模型的关键,因此为保证下一代四星转轮式编队系统的稳定性,轨道根数的最优设计如下:(1)轨道半长轴a、轨道偏心率e、轨道倾角i和升交点赤经Ω保持不变;(2)每对卫星的近地点幅角ω和平近点角M分别相差180°;(3)初始近地点辐角ω设置于赤道处,初始平近点角M设计于极点处;(4)卫星编队系统椭圆轨道的半长轴和半短轴之比为2:1. 第二,基于下一代四星转轮式编队系统,利用星间速度插值法,通过相关系数(激光干涉测量系统的星间速度0.85、GPS接收机的轨道位置和轨道速度0.95、星载加速度计的非保守力0.90)、观测时间30天和采样间隔10 s,反演了120阶FSCF-1/2/3/4(Four-Satellite Cartwheel Formation)地球重力场,在120阶处累计大地水准面精度为1.162×10^-4 m,较目前GRACE地球重力场精度至少提高一个数量级. 第三,下一代四星转轮式编队系统具有低轨道高度、高精度测量、全张量观测、弱混频效应和强时变信号的优点.  相似文献