A review of: “Principles of Geodynamics, 3rd edition. By Adrian E. Scheiddeger. Springer-Verlag,Berlin-Heidelberg-New York,xvii + 395pp. DM165, U.S. $73.30 (ISBN 3-540-11323-1). 1982.”

Abstract

Edited by J.-P. Zhan and J. Zinn-Justin, Elsevier, 1993. XXIV+ 615 pp., US$248.50, hardbound (ISBN-0-444-81797-2).     

Towards establishing practical multi-hazard bridge design limit states

In the U.S.,the current Load and Resistance Factor Design(LRFD) Specifications for highway bridges is a reliability-based formulation that considers failure probabilities of bridge components due to the actions of typical dead load and frequent vehicular loads.Various extreme load effects,such as earthquake and vessel collision,are not considered on the same reliability-based platform.Since these extreme loads are time variables,combining them with frequent,nonextreme loads is a significant challenge.The number of design limit state equations based on these failure probabilities can be unrealistically large and unnecessary from the view point of practical applications.Based on the opinion of AASHTO State Bridge Engineers,many load combinations are insignificant in their states.This paper describes the formulation of a criterion to include only the necessary load combinations to establish the design limit states.This criterion is established by examining the total failure probabilities for all possible time-invariant and time varying load combinations and breaking them down into partial terms.Then,important load combinations can be readily determined quantitatively.     

Born序列频散方程和Born-Kirchhoff传播算子

传统的Kirchhoff传播算子结构简洁,适用于描述横向均匀介质中波的传播.Ray-Kirchhoff传播算子较为精确地描述了波在非均匀介质中传播的运动学特征,其理论上的先天不足依赖于介质的复杂性.本文通过Born序列逼近波在非均匀介质中传播的大角度波分量,提出一种Born-Kirchhoff传播算子,将传统Kirchhoff传播算子的适用范围扩展至非均匀介质,同时描述波的运动学和动力学特征,其精度取决于Born序列逼近的阶数.利用Born序列频散方程,可以精确分析各阶Born-Kirchhoff传播算子对波长、传播角和非均质性的尺度依赖特征,其中,一阶Born-Kirchhoff传播算子的精度高于传统的相屏传播算子.波数域的Born-Kirchhoff传播算子对于高波数波是奇异的,导致波数域数值计算发散,但其空间域版本是非奇异的,无条件数值稳定,可通过Kirchhoff求和数值实施.本文给出各阶Born-Kirchhoff传播算子及其频散方程,可用于不同程度非均匀介质中的波传播模拟,复杂构造地震成像和速度估计.本文利用零阶和一阶Born-Kirchhoff传播算子计算简单二维模型的合成地震图,并与边界元法进行了比较.     

Factors and mechanism driving the land-use conversion in Jiangxi Province

This article explores the factors and mechanism driving the land-use conversion at regional level by developing and using an econometric approach which is called the simultaneous equations model (SEM). A case study in Jiangxi Province of China is conducted by establishing the SEM, which consists of three equations including agricultural production, land conversion of cultivated land to built-up area and land conversion of cultivated land to forest cover/grassland from 1988 to 2005. And then this paper employs the method of piecewise estimation to represent the influences of the factors such as population, society, economy, location and geophysical conditions on the process of land-use conversion in Jiangxi Province. Estimation results show that population is a predominant factor driving the land-use conversion at counties, while social and economic factors are determinant factors in the short term for the entire Jiangxi Province. Specifically, the size of agricultural population and the magnitude of agricultural input determine the agricultural production to a large extent; population size, plain area proportion at counties and land management policies together affect the direction and magnitude of conversion between cultivated land and built-up area; agricultural population proportion, terrain slope, grain production and non-agricultural industry promote the conversion of cultivated land to forest cover/grassland. Furthermore, the explored mechanism also reveals the underlying causes of the land use changes driven by a series of factors in Jiangxi Province. Finally, this paper concludes that factors proven to play an important role in driving the land-use conversion need to be considered when the land management agencies make out the land use planning to optimize the land use, expand the agricultural production, and conserve the cultivated land.     

Preliminary empirical scaling of pseudo relative velocity spectra in Serbia from the Vrancea earthquakes

First frequency-dependent empirical scaling equations of pseudo-relative velocity spectral amplitudes (PSV) of strong earthquake ground motions in the former Yugoslavia were introduced in the mid-1990s by Lee and Trifunac (1990) [15]. This followed the development of the Fourier spectral amplitudes (FS) scaling equations by Lee and Trifunac (1993) [17] in terms of earthquake source parameters, and the region-specific frequency dependent attenuation function given by Lee and Trifunac (1992) [16]. More recently, a new frequency-dependent attenuation function was developed for central and eastern Serbia for earthquakes of intermediate and large magnitudes and for large epicentral distances—exceeding 300 km—suggested by Lee et al. (2016) [19] that occur in the Vrancea source region in Romania. In this paper we use this frequency-dependent attenuation function to develop empirical scaling equations for PSV spectral amplitudes in Serbia. These scaling equations will form a basis for macro- and micro-zoning earthquake hazard studies in Serbia.     

一种快速准确校正手持式GPS的方法

目前,手持式GPS已成为地质工作人员必不可少的工具之一,正确使用和校正GPS是每个技术人员必须掌握的。在工作实践中,笔者总结出GPS的显示坐标X,Y变化量与校正参数DX,DY,DZ的变化量的比值(即变化率)在某一地区是一定值(即线性关系),不同地区该定值不同。通过变化量的此种线性关系用解方程法可快速准确地确定DX,DY,DZ参数,且只要满足该方程解的不同组合的DX,DY,DZ均可作为该地区正确的校正参数,从而可准确校正GPS。     

修正的Benjamin-Bona-Mahoney方程的精确解

基于齐次平衡法的思想,利用高效的G′G展开法,求解了修正的Benjamin-Bona-Mahoney(BBM)方程。修正的BBM方程是一个同时含有耗散和色散的非线性偏微分方程,求解难度大。利用对方程解的合理假设和G′G展开法可以将其约化为一个复杂的非线性代数方程组,借助数学软件Maple符号运算功能的帮助成功地求解了该非线性代数方程组,从而求得修正的BBM方程的精确解。这些解中包含3组更具有一般性质的精确解,它们分别是双曲函数解、三角函数周期解、有理数解。这些解对于研究方程的物理性质及物理现象有很重要的意义。为了能够更直观地理解这几组行波解,给出了相应的解的数值模拟图。     

Application of headed studs in steel fiber reinforced cementitious composite slab of steel beam-column connection

Steel fiber reinforced cementitous composites(SFRCC)is a promising material with high strength in both compression and tension compared with normal concrete.The ductility is also greatly improved because of 6%volume portion of straight steel fibers.A steel beam-column connection with Steel fiber reinforced cementitous composites(SFRCC) slab diaphragms is proposed to overcome the damage caused by the weld.The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs.The failure mechanism of the grouped arrangement is further discussed based on a series of parametric analysis.In the proposed connection,the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face.The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams.The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test.Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab.     

基于最小二乘法的边坡稳定性分析

利用经典土压力理论设定合理土条推力线范围,根据静力平衡及力矩平衡条件建立以条块界面安全系数 为变量的线性超定方程组,应用MATLAB软件基于最小二乘方法对此方程组求解,依据极大值原理及合理性条件： ,最终获得边坡整体安全系数 。经算例验证得出如下结论：当条块界面与条块整体安全系数相等时,边坡抗剪能力发挥最大;安全系数随推力线位置的升高而减小,但影响并不大;由于考虑了极大值原理,该法求得的安全系数略微偏大于其他方法。     

Integration rules from the equivalent differential equation method applied to equations of motion

The numerical integration of equations of motion necessarily implies the presence of errors that depend on initial conditions as well as the different physical parameters under consideration. More particularly, dumping or dissipative terms can appear and it is especially interesting to determine its causes. The equivalent differential equation method may allow the errors from a certain numerical scheme to be analyzed and, together with other considerations, can help us to eliminate or reduce them.