信号流图求解部分分式展开

含有多重极点的有理真分式展开为部分分式，不需要计算低阶导数。列出被求函数的各阶导数的关系式，画出各阶导数作为节点的信号流图。该图无环路，既直观表现出各高阶导数的相互关系及影响的单向性，也使求节点增益的梅森公式特别简便。该方法将求高阶导数问题简化为代数运算，特别适合于编制成计算机程序     

从《徐霞客游记》看明末南方的社会经济生活——纪念徐霞客逝世350周年

本文以《徐霞客游记》为依据,对明末南方的社会经济生活状况进行了初步归纳和分析,以揭示徐霞客对我国人文地理学的突出贡献。     

超新星遗迹X射线研究

在此介绍我们基于ＡＳＣＡ 和ＲＯＳＡＴ 等Ｘ 射线天文卫星,对３Ｃ３９７ 、Ｇ３２７ ．１１ ．１ 、Ｇ２１ ．５０ ．９ 和ＲＸＪ１７１３ ．７３９４６ 等超新星遗迹的物理特性进行的分析,简要地讨论了３Ｃ３９７ 的非平衡电离双热分量和双极泡结构以及Ｇ３２７ ．１１ ．１ 和Ｇ２１ ．５０ ．９ 中隐匿脉冲星的性质,并提出ＲＸＪ１７１３ ．７３９４６ 和ＡＤ３９３ 客星之间可能的关系。     

Paleomagnetic Excursions Recorded in the Yanchi Playa in Middle Hexi Corridor, NW China Since the Last Interglacial

Paleomagnetic determinations on lithologieal profiles of two paralleled long drillin gcores covering the past 130 kyr B.P., GT40 and GT60,from the Yanchi Playa in the arid Northwestern China indicate that a series of pronounced paleomagnetic excursions have been documented. By correlating our results with published regional and worldwide reports 4 excursion events out of 10 apparent reversal signals (labeled from GT-1 to GT-10) were identified as excursion events coeval with the Mono Lake Event (28.4 kyr-25.8 kyr), Laschamp Event (43.3 kyr-40.5kyr), Gaotai Event (82.8 kyr-72.4 kyr) and the Blake Event (127.4 kyr-113.3 kyr), respectively. GT-9 correlates with the above-mentioned Gaotai Event,GT-7 and GT-6 correspond to two stages of the Laschamp Event and GT-5 to the Mono Lake Event. It is noteworthy that the so-called Gaotai Event has not been reported as a pronounced paleomagnetic excursion in the Northwestern China. Every magnetic excursion event corresponds to paleointensity minima, anteceding those established abrupt paleoclimatic change events, such as the Younger Drays and the Heinrich Events (H1-H6). Here, we tentatively propose that these geomagnetic excursions/reversals can be viewed as precursors to climate abruptness. During the transitional stages when the earth‘s magnetic field shifted between a temporal normal and a negative period, the earth‘s magnetic paleointensity fell correspondingly to a pair of minima. Although more precise chronology and more convincing rock magnetic parameter determinations are essentially required for further interpretation of their intricate coupling mechanism, these results may have revealed, to some extent, that the earth‘s incessantly changing magnetic field exerts an strong influence on the onset of saw-tooth shaped abrupt climate oscillations through certain feedback chains in arid Central Asia or even North Hemispheric high latitude regions.     

贺兰山群变质杂岩中的变余动力变质岩

贺兰山群变质杂岩形成于晚太古代,遭受过多期变质和变形的改造,其中发育了不同期次和层次的动力变质岩。变余韧性剪切带内发育了条带状片麻岩和变粒岩,相伴有变余鞘褶皱和构造透镜体,变余韧性剪切带的变形发生在较低的温度、压力条件下,地壳加厚作用的初期。变余糜棱岩貌似条带状片麻岩,但在青石中保留了早期石英拔丝构造和加粗的动态重结晶长石集合体。糜棱岩化作用的温度在550℃以上,变形后沿面理形成了饼状或椭圆状青石,变晶时温度近600℃,压力近300MPa。     

Spatial distribution of snow depth based on geographically weighted regression kriging in the Bayanbulak Basin of the Tianshan Mountains,China

Snow depth is a general input variable in many models of agriculture,hydrology,climate and ecology.This study makes use of observational data of snow depth and explanatory variables to compare the accuracy and effect of geographically weighted regression kriging(GWRK)and regression kriging(RK)in a spatial interpolation of regional snow depth.The auxiliary variables are analyzed using correlation coefficients and the variance inflation factor(VIF).Three variables,Height,topographic ruggedness index(TRI),and land surface temperature(LST),are used as explanatory variables to establish a regression model for snow depth.The estimated spatial distribution of snow depth in the Bayanbulak Basin of the Tianshan Mountains in China with a spatial resolution of 1 km is obtained.The results indicate that 1)the result of GWRK's accuracy is slightly higher than that of RK(R~2=0.55 vs.R~2=0.50,RMSE(root mean square error)=0.102 m vs.RMSE=0.077 m);2)for the subareas,GWRK and RK exhibit similar estimation results of snow depth.Areas in the Bayanbulak Basin with a snow depth greater than 0.15m are mainly distributed in an elevation range of 2632.00–3269.00 m and the snow in this area comprises 45.00–46.00% of the total amount of snow in this basin.However,the GWRK resulted in more detailed information on snow depth distribution than the RK.The final conclusion is that GWRK is better suited for estimating regional snow depth distribution.     

中蒙地块的水平运动及应变特征

GPS观测结果显示中蒙块体的位移速率较小,块体各部分的位移方向存在差别,说明块体有差异活动但不显著。连续应变场的应变率参量值在10-8/a以下;主压应力轴方向为NE74.6°,与该区内的浅源强震震源机制解的P轴方向基本一致。由应变产生的贝加尔湖裂谷的裂开速率为4.71mm/a,最大主应变率为34.34×10-9/a,张应变主轴方向NW310.49°,垂直于裂谷走向;嫩江断裂带和萝北-营口断裂带为走滑兼挤压或拉张活动断裂,位移速率和应变率都较小,活动性不显著。2003年8月16日巴林左旗5.9级地震和2004年3月24日东乌珠沁旗6.4级地震均发生在由1999~2003年GPS资料得出的多种应变速率参量的相对高值带和应变率高梯度带上。     

多层弹性平面问题解的精确刚度矩阵法

从平面弹性力学的基本方程出发,利用Fourier积分变换等数学手段,推导出了单层平面问题的刚度矩阵,然后按有限元法组成总体刚度矩阵。通过求解由总体刚度矩阵所构成的代数方程和Fourier积分逆变换,得到在任意静荷载作用下多层弹性平面问题的精确解。由于刚度矩阵不含有正指数项,计算时不会出现溢出现象,从而克服了传递矩阵法的缺点。推导过程中摒弃了应力函数的选择,使得问题的求解更加合理化,同时也为进一步研究此类问题如温度场、动力学等奠定了理论基础。计算实例证明了推导结果的准确性。