Transient dynamic response of fluid-saturated soil under a moving cyclic loading

Based on the Theory of Porous Media (TPM), a mathematical model of a two-dimensional incompressible fluid-saturated elastic soil is established, and the periodic boundary conditions are presented to analyze the transient dynamic response of this soil under a moving cyclic loading. The differential quadrature method (DQM) and the second-order backward difference scheme are applied to discretize the governing equations on the spatial and temporal domains, respectively. As application, a typical two-dimensional wave-induced transient problem with a seabed of finite thickness is analyzed, and the numerical results are compared with the analytical results presented in the present work. In addition, a transient dynamic response of fluid-saturated soil under limit moving vehicle loadings is studied. The effects of the velocity of vehicle and the volume fraction on the settlement and the pore water pressure are studied.     

Ab Initio Prediction of 29Si-NMR Chemical Shifts

The ability of several ab initio models to predict experimental 29Si-NMR chemical shift is examined. The shielding values of trimethylsilyl chloride (A), t-butyldimethylsilyl chloride (B) and allyltrimethylsilane (C) are calculated by GIAO, CSGT and IGAIM methods, using HF/6-31G*, B3LYP/6-31G*, HF/6-311+G**, B3LYP/6-311+G** and MPWlPW91/6-311+G** models respectively. The 29Si chemical shifts calculated by GIAO method using HF/6-311+G**model are highly in agreement with those obtained experimentally. All of the models above reproduce the trends of chemical shifts in all cases studied, suggesting that the models are of practical value.     

Canonical Floquet theory

Classical Floquet theory is reviewed with careful attention to the case of repeated eigenvalues common in Hamiltonian systems. Floquet theory generates a canonical transformation to modal variables if the periodic matrix can be made symplectic at the initial time. It is shown that this symplectic normalization can always be carried out, again with careful attention to the degenerate case. The periodic modal vectors and canonical modal variables can always be chosen to be purely real. It is possible to introduce real valued action-angle variables for all modes. Physical interpretation of the canonical degenerate normal modal variables are offered. Finally, it is shown that this transformation enables canonical perturbation theory to be carried out using Floquet modal variables.     

Energy Composition of the Universe: Time-Independent Internal Symmetry

The energy composition of the Universe, as emerged from the Type Ia supernova observations and the WMAP data, looks preposterously complex, – but only at the first glance. In fact, its structure proves to be simple and regular. An analysis in terms of the Friedmann integral enables to recognize a remarkably simple time-independent covariant robust recipe of the cosmic mix: the numerical values of the Friedmann integral for vacuum, dark matter, baryons and radiation are approximately identical. The identity may be treated as a symmetry relation that unifies cosmic energies into a regular set, a quartet, with the Friedmann integral as its common genuine time-independent physical parameter. Such cosmic internal (non-geometrical) symmetry exists whenever cosmic energies themselves exist in nature. It is most natural for a finite Universe suggested by the WMAP data. A link to fundamental theory may be found under the assumption about a special significance of the electroweak energy scale in both particle physics and cosmology. A freeze-out model developed on this basis demonstrates that the physical nature of new symmetry might be due to the interplay between electroweak physics and gravity at the cosmic age of a few picoseconds. The big ‘hierarchy number’ of particle physics represents the interplay in the model. This number quantifies the Friedmann integral and gives also a measure to some other basic cosmological figures and phenomena associated with new symmetry. In this way, cosmic internal symmetry provides a common ground for better understanding of old and recent problems that otherwise seem unrelated; the coincidence of the observed cosmic densities, the flatness of the co-moving space, the initial perturbations and their amplitude, the cosmic entropy are among them.     

用小波变换原理检测原子钟环境温度的变化

根据小演变换的奇异性检测原理，分析了环境温度变化对原子钟特性的影响；基于小坡变换的信号重建原理，将温度变化引起原子钟相位－时间起伏进行时域一频域分析；用小演变换理论分析了由于昼夜温度变化引起原子钟周期性波动的原因，结合传统的谱分析方法，认证了原子钟相位－时间起伏的周期性。结果表明：在有环境温度调节的环境中，氢原子钟的相位－时间起伏标准差为41ns左右；在一般环境中，铯原子钟的相位－时间起伏标准基为21ns左右，改善环境条件可以提高原子钟的频率稳定度。     

波普尔科学哲学理论简介

波普尔是当今伟大的哲学家,他发明了科学增长的四段图式:P1→TT→EE→P2,其中P1代表问题,TT表示试探性理论,EE表示试探性排除错误,P2代表新的问题。波普尔对科学哲学有很多贡献,如他否定了培根的归纳法,主张证伪的方法而反对证实的方法。他颠覆了关于真理的概念,反对将理论与真理联系起来,即使是相对真理。他认为,人不能认识真理,只能探索真理,接近真理,并提出"逼真性"与"逼真度"两个概念,从而否定了相对真理与绝对真理这一对矛盾的关系。他提出,科学理论的发展不是一个量变递增的过程,而是新理论取代旧理论的质变过程,是新范式战胜旧范式的科学革命。他认为,可证伪性、可错性是科学的本质特征,同时也是区分科学与非科学的根本标准。传统的认识论将宇宙划分为物质的与精神的两个世界,波普尔认为宇宙是多元的,多层次进化的,其性质是多样的,可分为三个层次或三个世界。波普尔的三个世界理论,用最简洁的语言表述即:物理世界(世界1)、精神世界(世界2)和客观知识世界(世界3)。世界3是人类智力活动的产物,是人造的;另一方面,它同时也是超人类的,即超越了自己的创造者。波普尔石破天惊地提出了科学哲学的许多惊世骇俗的理论,将科学哲学推到了一个崭新的高度,打破了科学界传统的认识论和方法论。他的哲学理论的核心是证伪主义,证伪就是试错,反驳,批判。只有经过证伪的理论(猜测,假说)才能称之为理论。中国科学需要波普尔理论,中国科学上不去,与我们没有证伪思想有很大的关系。我们必须拨乱反正,改弦易辙,采取批判的态度,反驳的方法,敢于试错,这样,中国科学才有希望。     

新时代城市地质工作战略思考

中国共产党“十九大”提出了满足人民美好生活、人与自然和谐共生的目标,而现有城市地质工作体系不论从理论技术还是理念上,都难以满足服务“绿色、低碳、循环、安全、集约、智慧”城市发展需求,需要建立适应城市发展要求的新时代城市地质工作体系。我国现有城市地质工作经历了2003年以前单要素调查、2003以来多专业综合地质调查两个阶段,虽然在一定程度上服务了城市建设,但尚不能满足新时代城市国土空间立体可持续开发的需要。本文在全面分析国内外城市地质工作现状和存在问题的基础上,对新时代城市地质工作进行战略思考,提出建立以地球系统理论为指导,以多场扰动再平衡、全空间资源与环境评价以及空间资源协同规划等理论为基础的城市地质学理论体系;建立包括1项调查、3项评价、1套监测系统、1套信息系统的“1311”城市地质工作体系;提出新时代城市地质工作新机制。     

科里奥利力效应及对强余震预报方法的研究(一)─预报方法的原理、思路

科里奥利力（Corioli）是一个在旋转系统中运动的物体必然伴随的力,地震是在地球这一旋转系统中相对两断层盘的突然运动过程,因而断层的运动必然要伴随科里奥利力。由于断层错动旋性不同（左旋、右旋等）,因而科里奥利力就会表现出使断层错动时两盘压紧或拉张的效应,压紧则主震释放能量不彻底,随后的余震就强,反之余震弱,这样就可从断层错动方向预报余震强度。     

Magnetic Helicity in fast dynamos

The behaviour of magnetic helicity in kinematic dynamos at large magnetic Reynolds number is considered. Hughes, et al . [ Phys. Lett. A 223 , 167-172 (1996)] observe that the relative helicity tends to zero in the limit of large magnetic Reynolds number. This paper gives upper bounds on the helicity, by relating the helicity spectrum to the energy spectrum. These bounds are confirmed by numerical simulation and the distribution of helicity over scales is considered. Although it is found that the total helicity becomes small in the limit of high conductivity, there can remain significant, but cancelling, helicity at large and small scales of the field. This is illustrated by considering the evolution of helicity in the stretch-twist-fold dynamo picture.     

Modeling scenic quality of wetland landscape resources in South Dongting Lake, China

This study introduces a method to quantify the scenic value of wetland landscapes and provides the guidance on the allocation of efforts for the purpose of preserving the most important environments.Dongting Lake,a traditional tourist location,is one of the five largest freshwater lakes in China and a Grade 5A National Scenic Region. This study objectively analyzes the scenic resources of South Dongting Lake,and presents a model based on Quantification TheoryⅠto assess wetland scenic landscapes.Employing a multilinear regression relationship between land-scape factors and their associated scenic value,we built up the Wetland Landscape Quantification Model(WLQM), which was used to classify 221 landscapes into five grades.Finally,some suggestions are proposed regarding quantitative assessment and its use for the sustainable development of wetland environments.