A Note on the Mixing Length Theory and Massive Star Evolution

1 INTRODUCTIONThe mixing length theory (MLT) for stellar convection originally developed by Vitense(1953, 1958) has been the most popularly used local convection theory in the studies of stellarstructure and evolution. The theory was later modified and revised by many investigators,who suggested some different expressions. In fact, MLT is not a real hydrodynamic theory,rather, it is a simple "ballistic" theory which traces the motion of imaginary convective elements. In reality j stell…     

Tectono-thermal modeling of the Yinggehai Basin,South China Sea

Based on the observed data, the average value of surface heat flow in the Yinggehai Basin is calculated and it turns out to be 84.1 mW/m². The thermal evolution of the basin since the Cenozoic era has been attempted by tectono-thermal modeling. Three-phase extension made the basin become hotter and hotter, reaching its climax in paleo-temperature history since 5.2 Ma. And nowadays, the basin is in the heat flow decreasing period. During the Cenozoic era, the basement heat flow remained at 50–70 mW/m² all the time. This is related to the degree of each extension phase, stretching rate mode and also the limited basin scale. Modeling results also show that, the surface heat flow is controlled mainly by the basement heat flow, and less than 20% comes from radiogenic heat production in the sediments of the basin     

大跨预应力混凝土空间框架结构的地震振动台试验研究

利用地震振动台对大跨预应力混凝土井式梁空间框架结构的抗震性能进行了实验研究。两个模型的实验结果表明：(1)大跨预应力井式梁空间框架结构可以提供大的楼层平面内刚度；(2)对称大跨预应力井式梁空间框架结构，可以不考虑耦合地震反应；(3)大跨预应力井式梁空间框架结构的竖向地震反应中心大而周边小；(4)在相同加速度但不同的地震波作用下，结构的竖向地震反应不同。     

湖南走马坪多金属成矿区矿化特征及成因探讨

湖南走马坪矿区是以钨、锡、铅、锌、银矿化为主的多金属成矿区，文章对其矿化特征作了总结，在此基础上分析其成因，并提出了找矿方向。     

枣庄岩溶塌陷形成条件及主要影响因素

近年来枣庄市岩溶塌陷频繁发生。通过野外地质调查、现场采样和室内试验相结合的综合手段,对该区的岩溶塌陷覆盖层进行系统地取样并进行深入细致的实验及分析,论述了覆盖层特征对该区岩溶塌陷的影响;运用宏观调查、细观测量和微观分析相结合的研究方法详细论述了地质构造对岩溶塌陷的影响;结合历年水文动态资料、地下水开采量等论述了地下水活动对岩溶塌陷影响。综合认为,地层岩性、覆盖层性质、构造因素是枣庄岩溶塌陷频繁发生的内因,而超量开采地下水则是外部诱发因素。     

X-ray diffraction investigation of native Si-Fe alloy minerals from Luobusha, Tibet

The origin of native Si-Fe alloy mineral is thought to be related with mantle and aerolite. The native Si-Fe alloy minerals from podiform chromites of the Luobusha ophiolite in the Yarlong Zangbo suture zone were examined by a new method for powder-like diffractograms of small single crystals, using an SMART APEX-CCD area-detector X-ray diffractometer. The powder diffraction pattern shows that the minerals are composed of FeSi, FeSi₂, β-FeSi₂ and native silicon. The association of these minerals suggests that the crystallization order of the mineral may be from early to late FeSi→FeSi₂→native silicon, accompanied by gradually increasing deoxidization. Translated from Acta Petrologica et Mineralogica, 2005, 24(5): 453–456 [译自: 岩石矿物学杂志]     

水盐梯度下黄河三角洲湿地植被空间分异规律的定量分析

三角洲湿地植被的形成和分布同时受水深、土壤含盐量两个环境因子的作用。采用模糊数学排序方法分析了黄河三角洲湿地植被在水深、土壤含盐量两个环境梯度下的空间分异规律。结果表明,由TWINSPAN划分而得到的8个植被类型在模糊数学排序图中有各自的分布范围,界线明显。以穗状狐尾藻(Myriophyllum spica-tum)等水生植物为优势种的群落分布在排序图的左上部,为黄河三角洲湿地高水深、低盐分地区;以柽柳(Tam-arix chinensis)、翅碱蓬(Suaeda heteroptera)等典型盐生植物为优势种的群落分布在排序图的右下部,为黄河三角洲的低水深、高盐分地区;其他以芦苇(Phragmites australis)、荻(Triarrhena sacchariflora)、旱柳(Salix matsudana)等为优势种的群落分布在排序图的中部。利用Gini-Simpson指数,在模糊数学排序图中分析了植物物种多样性随水深、土壤含盐量梯度的空间变化,结果表明,高水深、低盐分和低水深、高盐分地区植物物种多样性均较低,而二者过渡区域植物物种多样性较高。     

Comprehensive Multi-Level Exploration of Buried Active Faults： an Example of the Yinchuan Buried Active Fault

The paper introduces the steps and methods of multi-approach,multi-level exploration of buried faults in thick Quaternary sediment regions by taking the test exploration of the Yinchuan active fault as example.Based on the comprehensive analyses of previous data,we choose the Xinqushao Village of Xingqing District of Yinchuan City as the test site for the comprehensive exploration.Firstly,we adopted shallow seismic investigation with group intervals of 10m,5m and 1m to gradually trace layer by layer the master fault of the Yinchuan buried fault from a deep depth to a shallow depth where drilling could be used.Then,with composite geological profile drilling,we determined the precise location and dip angle of the fault.The drilling show the buried depth of the upper offset point is 8.3m.Finally,large-scale trenching revealed that the actual buried depth of the upper offset point of the fault is 1.5m from the ground surface and there are paleoearthquake events of 5 stages.Combined with the preliminary result of corresponding sample age,we conclude the Yinchuan buried fault is a mid to late Holocene active fault.     

Characteristics and method of synthesis seismic wave based on wavelet reconstruction

A novel method of synthesizing seismic wave using wavelet reconstruction is proposed and compared with the traditional method of using theory of Fourier transform. By adjusting the frequency band energy and taking it as criterion, the formula of synthesizing seismic wave is deduced. Using the design parameters specified in Chinese Seismic Design Code for buildings, seismic waves are synthesized. Moreover, the method of selecting wavelet bases in synthesizing seismic wave and the influence of the damping ratio on synthesizing results are analyzed. The results show that the synthesis seismic waves using wavelet bases can represent the characteristics of the seismic wave as well as the ground characteristic period, and have good time-frequency non-stationary.     

90年代长江中游异常多雨的气候变化背景分析

利用小波变换技术, 对与长江中游地区夏季降水密切相关的赤道东太平洋海温、西太平洋副高、南海夏季风等物理因子进行时间变化的尺度分离.通过对年代际变化和长期趋势等不同尺度变化的分析, 揭示出90年代长江中游异常多雨和频繁洪涝产生的气候变化背景.