Bedforms and bed material transport pathways in the Changjiang (Yangtze) Estuary

Bed features were mapped using a thermal depth recorder and a side-scan sonar in the Changjiang (Yangtze) Estuary, and flows were observed and bed surface materials were sampled to investigate bed material transport pathways. Distinct scales and dimensions of dunes were observed in terms of the classification scheme of Ashley [Ashley, G.M., 1990. Classification of large-scale sub-aqueous bedforms: A new look at an old problem. Journal of Sedimentary Research, 61, 160–172], forming a dune set in the flood season. Large dunes occurred predominately in the surveyed area of the estuarine zone, and two-dimensional dunes predominated in the dry season while three-dimensional dunes prevailed in the flood season. Sharp lee sides of dunes have low angles, indicating a significant suspended-load transport for the bedform migration, and the majority of them face down-estuary reflecting the controlling process by the ebb current. The bed material migrations in terms of relative maximum gross transport show a satisfactory agreement with the sonar mapping in the dry season. The relative maximum gross transport as an independent estimator of migration direction, can be used to effectively determine the bed material transport directions in the Changjiang Estuary.     

水下砂土层非线性动力反应的直接差分法

应用多孔介质动力学进行了水下的砂土地层的动力反应分析,水下砂层可以看作是多相介质,孔隙水是可压缩的,土壤采用了非线性本构,考虑了砂土的刚度退化和剪胀性及土水相对运动等因素,并研究了多孔介质波动模拟的边界条件,建立了水体下地层平面动力非线性动力反应的直接差分法,直接求解水体的压力和饱和土层的动孔隙压力,可以进一步分析水下砂土地震液化问题。     

一种真空预压区地下水位计算方法

根据抽真空时加固区内真空渗流场的形成机制和变化特点,把真空渗流场的形成过程分为非稳定渗流和稳定渗流两个阶段。利用渗流量计算公式,计算加固区内渗流量随时间变化过程曲线。结合两个阶段加固区地下渗流场的变化特性,分别利用Theis和Dupuit计算模型计算不同时刻的地下水位,并用实测进行验证。     

The S(c) spectrum machine to visualize the motion in galaxies

The behavior of the orbits in a galaxy model composed of an harmonic core and a strong bar potential is studied. Numerical calculations show that a large number of orbits display chaotic motion. These orbits are low angular momentun orbits. The percentage of chaotic orbits increases as the angular velocity of the system increases or the strength of the harmonic term decreases. A new dynamical parameter, the S(c) spectrum, is introduced and used to detect the island motion and the evolution of the sticky regions. Comparison to previously obtained results reveals the leading role of the new spectrum. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical investigation of the orbit of Interball‐1

We investigated the motion of the Earth's artificial satellite Interball‐1 by using a method suitable for the computation of large eccentricity orbits. Though the measured and the computed orbital elements differ from each other within the measured error bound, we found a slight tendency for secular decreasing in the semi‐major axis, caused probably by electromagnetic drag. We analysed the dominant role of the Moon in the variations of the orbital eccentricity, leading to zero perigee height and the end of the lifetime of the satellite. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

空孔直眼掏槽成腔模型理论与实践分析

空孔直眼掏槽是隧道或井巷掘进的主要方法之一。基于典型空孔掏槽炮眼布置,分析了掏槽眼爆破形成空腔的物理力学过程;建立了空腔形成的物理和力学模型;研究了腔内碎石在高压爆生气体作用下的抛射过程;得出了空腔尺寸的理论计算方法。槽腔岩石介质破碎和外端部漏斗形成取决于掏槽眼装药爆炸动作用;碎石的抛出率与炸药性质、岩石性质和爆破参数有关。理论分析与在某矿进行的48次试验结果有较好的吻合性。     

新疆三工河绿洲土地利用变化系统动力学仿真

从小区域(乡域)尺度出发,综合考虑人口、经济、技术、市场等主要人文因素对绿洲土地利用变化的驱动作用,建立系统动力学（SD）模型,并以天山北麓三工河流域为例,用1978—1998年的实际数据验证了模型的适用性和可靠性,在此基础上,模拟和分析了三种发展模式下本区域1998—2050年土地利用变化过程,结果表明：SD方法对于乡域尺度的土地利用变化研究是适宜的;三种模式下土地利用变化规律表现出明显的差异性,人口、经济、技术、市场等因素对本区域土地利用变化具有显著驱动作用。     

The Gyldén‐type problem revisited: More refined analytical solutions

We resume and consistently extend our previous researches concerning the Gyldén‐type problem (a two‐body problem with time‐dependent equivalent gravitational parameter). To approach most of the concrete astronomical situations to be modelled in this way, we consider a periodic small perturbation. For the nonresonant case, we present a second‐order analytical solution. For the resonant case, we adopt the most realistic astronomical situation: only one dominant term of the Hamiltonian. In this case we point out a fundamental model of resonance, common to every resonant situation, and, moreover, identical to the first fundamental model of resonance . Considering the simplest model of periodic change of the equivalent gravitational parameter, we .nd that all possible resonances are con.ned to the first fundamental model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

基于物态本构模型的路基动力反应分析

以动力固结理论和瞬态动力学理论为基础,将有效应力物态动本构关系引入到以动力反应与动力固结相耦合、静应力与动应力变化相耦合、孔压的产生、扩散和消散相耦合的动力三维瞬态动力学基本方程组中,形成了饱和土体有效应力物态地震反应分析的完整理论体系。利用有限元法对饱和路基进行了瞬态地震反应分析,较好地反映了土体在震动过程中剪 胀、剪缩的实际性态,比以往引进孔压模型和静-动交替分析计算更为合理。     

4A沸石分子筛对KNO3和NH4NO3的吸持作用

实验研究了4A沸石分子筛经熔融盐处理后对KNO₃和NH₄NO₃的吸持作用。结果表明：在实验条件下,KNO₃处理后的4A沸石中含钾(以K₂O计)15.01%,含NO^-₃ 9.23%;NH₄NO₃处理后的4A沸石中含NO^-₃ 10.78%,含NH⁺₄ 0.94%。熔融盐处理后的样品X射线衍射峰相对强度发生了变化,红外光谱中1 640 cm^-1附近水的吸收带强度减弱,1 390 cm^-1附近出现的NO^-₃离子的强吸收带及825 cm^-1附近出现的NO^-₃离子的弱吸收带,以及热重-差热曲线中KNO₃和NH₄NO₃的热失重和分解热效应均证明沸石中吸持盐的存在。处理后4A沸石分子筛的基本骨架结构没有被破坏,吸持盐的4A沸石对营养盐的储备大大提高,是潜在的缓释肥料。