Non-Stationary Rayleigh-Taylor Instabilities in Pulsar Wind Interaction with a Supernova Shell

The Rayleigh-Taylor instability (RTI) plays an important role in the dynamics of several astronomical objects, in particular, in the supernovae (SN) evolution. In the present paper we examine the dynamics of a shell (representing a type II SN remnant) blown-up by a wind emitted by a central pulsar. The shell is accelerated by the pulsar wind and its inner surface experiences the RTI. We develop an analytical approach by using a specific transformation into the coordinate frame co-moving with the SN ejecta. We first derive a non-stationary spherically symmetric solution describing an expansion of a gas shell under the pressure of a central source (pulsar). Then, we analyze its 3D stability with respect to a small perturbation on the inner shell surface. The dispersion relation is derived in the co-moving reference frame. The growth rate of the perturbation is found and its temporal evolution is discussed. We compare our result with the previous published studies and apply it to the Crab nebula evolution.     

New insights into a late-Pleistocene human occupation in America: The Vale da Pedra Furada complete chronological study

Within the framework of the studies focusing on the Pleistocene peopling of the Americas, our French-Brazilian team has undertaken a pluridisciplinary research on different archaeological sites, inside and in the neighborhood of the Serra da Capivara National Park, in Brazilian Nordeste. The present study regards an archaeological site, Vale da Pedra Furada, situated in the Piauí state in Brazil. The results of technological and functional studies suggest the existence of different successive human occupations during the Pleistocene in this region. Moreover, the geological and geomorphological studies shed new light on our understanding of sedimentary processes and confirm that the levels were not subject to any significant post-depositional processes. This is also confirmed by macro- and micro-analysis of quartz artefact surfaces. The chronological study has recently been completed employing both radiocarbon and luminescence techniques; radiocarbon dates were obtained on charcoal, multi-grain and single-grain OSL ages on sedimentary quartz grains. The results obtained with the different methods are consistent with each other: the most recent archaeological level is dated to around 8 ka and the oldest to 24 ka, indicating the open-air site of Vale da Pedra Furada to be a succession of human occupations beginning from OIS 2. These results are discussed in the context of some archaeological sites studied in the Serra da Capivara National Park of the last few decades.     

A multi-index coupling system of ice slope stability and its application

Based on the Simplified Bishop Method, the minimum safety factor of ice slope both with and without tension cracks is calculated in combination with triaxial compression tests. It is found that there exists a critical depth for each crack. Then, factors influencing ice slope stability such as slope ratio, slope height, ice cohesion, internal friction angle, unit weight and temperature were analyzed. Meanwhile, a regression equation between the aforementioned factors and safety factor is obtained, with which sensitivity analysis is carried out. The performance function is built in combination with random distribution of physical and mechanical parameters to analyze the reliability index. The Advanced First Order Second Moment Method is employed on the solution to the performance function. The one-way coupling system of ice slope stability is therefore formed based on safety factor and reliability index. Finally, an illustrated example of ice slope is provided, which shows that failure probability is relatively high, up to 6.18%, although safety factor is 2.77. Thus, it is objective and reasonable to apply the coupled system method to the slope stability rating.     

南海岩石圈厚度变化特征及其构造意义

地震层析资料表明,南海地区,自红河口向南经南海、苏录海到苏拉威西海,岩石圈速度低,底部横波速度仅4.4km/s,岩石圈厚度在60～80km,为薄岩石圈地区;而软流层的速度也较低,在4.2～4.4km/s,但厚度较大,大于200km。从红河—莺歌海断裂带经南海到苏录海,存在一条北西向宽约200km的上地幔北西向低速带,速度在4.05～4.25km/s(面波速度)。它反映了新生代南海地区上地幔的动力学过程。南海岩石圈厚度变化存在明显差异,南海陆缘,岩石圈厚度在70～80km,而在南海洋盆之下,岩石圈厚度超过100km,岩石圈底部存在高速岩石层,并且洋盆下的岩石圈之厚度比大陆边缘厚,在海盆岩石圈下部的60～80km深度上存在一高速层,纵波速度为8.2～8.3km/s。特别是中央海盆及西北海盆与西南海盆,其下部岩石圈中均存在一高速岩石层,这是非常具有构造意义的。由此笔者提出大陆岩石圈裂离、上地幔因减压而部分熔融所产生的基性岩浆形成南海新生代洋壳的猜想。     

钢锚墩在锦屏一级水电站地下厂房的运用

锦屏一级水电站地下厂房地应力高,分层开挖完成后随着地应力的释放及重新分布,局部岩体出现压碎、层状劈裂破坏,围岩松弛深度及变位不断加深、加大。为了尽快实现锚索锚固支护效应以确保地下厂房洞室群围岩稳定和工程安全,施工时将部分原设计现浇混凝土锚墩调整为钢锚墩进行施工,取得了较好的质量、进度效果。主要介绍了钢锚墩的施工工艺、质量控制要点及其与混凝土锚墩的工效对比分析。     

广东前汛期异常旱涝的大气环流特征

用1957～1999年广东省19个代表站4～6月降水资料和500hPa高度场资料，着重分析和讨论了广东省前汛期异常旱、涝年的同期和前期500hPa合成平均场的主要差异,以及前期关键月、关键区的特点，为广东省前汛期异常旱、涝的预测提供判别依据。     

新疆克孜尔水库F_2断层近期形变特征初探

通过对布设在克孜尔水库大坝及库区一等水准点及 GPS监测网多期观测结果的分析 ,对贯穿大坝的 F2 断层近期形变特征进行了初步研究。结果表明 :F2 断层的活动属于新构造继承性运动 ,其水平形变速率大于垂直形变速率 ,并与地震活动存在着一定相关性     

Discrimination Between Foreshocks and Earthquake Swarm from the Change of First Motion Sign

Based on the data of first motion of 11 earthquake sequences with ML ≥ 3.0 recorded by the Telemetric Seismic Network of Shanxi since the 1980s, the first motion characteristics of each earthquake sequence were studied. It is known that earthquake sequences of different types have different consistency characteristics of focal mechanism. The decrease and increase of the first motion contradictory sign ratios could be taken as an index to judge whether there would still be a larger earthquake to come after the earthquake sequence.     

伊通－舒兰断裂分段及地震危险性探讨

本文用地震活动性参数等地震学方法和用时间域小地震地震图测量震源物理参数及介质Ｑ值等震源参数方法，对伊通－舒兰断裂进行分段及地震危险性探讨。初步研究结果表明该断裂乌拉街－舒兰段（北段）、伊通－双阳段（南段）存在明显差异，北段介质强度大，易积累能量而发生较大地震。     

我国首次发现的多水钼铀矿

多水钼铀矿属铀酰钼酸盐类矿物。我国首次发现的多水钼铀矿产于北方某火山岩型铀钼矿床的氧化带，为非晶质矿物，在显微镜下呈均质性，电子探针分析既含铀又含钼等是其主要特征。