新经济形势下汇率波动会我国出口的影响——基于面板数据的实证检验

我国在2005年汇率改革后,进一步放开了汇率波动幅度.2007年爆发的全球金融危机更是加剧了汇率震荡.选取2001年-2008年间中国与12个主要贸易出口国或地区的面板数据,分为两个对称时段,运用经典引力模型实证检验了新经济形势下汇率波动对于出口的影响.研究发现,在2001年到2004年时段,汇率波动对出口的影响并不显著,但从2005年到2008年的新经济状况下,汇率波动的增加明显抑制了出口.因此,建议在金融危机新背景下,政府应加强汇率管制以求稳定,增强本国出口商的信心,暂时不宜进一步放开汇率.     

基于互相关函数的分形城市引力模型--对Reilly-Converse引力模型的修正与发展

引入时间函数Ｑ＝ｆ（ｔ）和时滞参数τ,借助互相关函数Ｒ（τ）＝∫ｆｉ（ｔ）ｆｊ（ｔ＋τ）ｄｔ,将城市引力模型Ｉｉｊ＝ＧＱｉＱｊｒ－ｂ由瞬间关系推广到相关过程,化为具有分形特征的引力模型Ｆｉｊ（ｒ,τ）＝ＧＲｉｊ（τ）ｒ－Ｄｉｊ,其中Ｇ被定义为城市间的最大相关系数,Ｄ（由ｂ推广而来）具有广义的分形维数性质。     

运移距离对CO2混相驱重力超覆的影响规律及表征分析

CO2驱油技术具有提高原油采收率和资源化利用与封存的双重目的,已在低渗-致密油藏得到广泛应用。为明确运移距离对CO2混相驱油过程中密度差引起的重力超覆程度的影响规律,分别采用室内物理模型和数值模型开展研究。实验结果表明,混相条件下,由于岩心长度减小,重力超覆的扩展空间受限,但油气混相程度的降低,导致重力超覆程度降低幅度较小;当岩心长度继续减小时,混相程度降低对重力超覆的影响大于岩心长度对重力超覆扩展空间限制的影响,从而使重力超覆程度加剧。数模结果表明,随着运移距离的减小,重力超覆程度减弱,混相驱采收率提高。因此,结合油田现场情况,为减缓重力超覆,应适当减小井距,缩短CO2气体运移距离,从而提高CO2驱的波及效率。研究结果对于CO2驱油现场试验方案设计和参数优化具有一定的指导意义。     

The transcendental method from Newton to Kant

Kant’s transcendental method, as applied to natural philosophy, considers the laws of physics as conditions of the possibility of experience. A more modest transcendental project is to show how the laws of motion explicate the concepts of motion, force, and causal interaction, as conditions of the possibility of an objective account of nature. This paper argues that such a project is central to the natural philosophy of Newton, and explains some central aspects of the development of his thinking as he wrote the Principia. One guiding scientific aim was the dynamical analysis of any system of interacting bodies, and in particular our solar system; the transcendental question was, what are the conceptual prerequisites for such an analysis? More specifically, what are the conditions for determining “true motions” within such a system—for posing the question of “the frame of the system of the world” as an empirical question? A study of the development of Newton’s approach to these questions reveals surprising connections with his developing conceptions of force, causality, and the relativity of motion. It also illuminates the comparison between his use of the transcendental method and that of Euler and Kant.     

Holography and emergence

In this paper, I discuss one form of the idea that spacetime and gravity might ‘emerge’ from quantum theory, i.e. via a holographic duality, and in particular via AdS/CFT duality. I begin by giving a survey of the general notion of duality, as well as its connection to emergence. I then review the AdS/CFT duality and proceed to discuss emergence in this context. We will see that it is difficult to find compelling arguments for the emergence of full quantum gravity from gauge theory via AdS/CFT, i.e. for the boundary theory's being metaphysically more fundamental than the bulk theory.     

Gravity’s cause and substance counting: contextualizing the problems

This paper considers Newton’s position on gravity’s cause, both conceptually and historically. With respect to the historical question, I argue that while Newton entertained various hypotheses about gravity’s cause, he never endorsed any of them, and in particular, his lack of confidence in the hypothesis of robust and unmediated distant action by matter is explained by an inclination toward certain metaphysical principles. The conceptual problem about gravity’s cause, which I identified earlier along with a deeper problem about individuating substances, is that a decisive conclusion is impossible unless certain speculative aspects of his empiricism are abandoned. In this paper, I situate those conceptual problems in Newton’s natural philosophy. They arise from ideas that push empiricism to potentially self-defeating limits, revealing the danger of allowing immaterial spirits any place in natural philosophy, especially spatially extended spirits supposed capable of co-occupying place with material bodies. Yet because their source ideas are speculative, Newton’s method ensures that these problems pose no threat to his rational mechanics or the profitable core of his empiricism. They are easily avoided by avoiding their source ideas, and when science emerges from natural philosophy, it does so with an ontology unencumbered by immaterial spirits.     

基于基本变量集的仿人机器人在线运动规划

仿人机器人在线规划方法对于其走向实际应用具有重要作用.通过对仿人机器人运动规划方法的调研以及实时性需求分析,提出了一种基于基本变量集的仿人机器人在线规划方法.该方法将运动规划问题转化为反映机器人运动状态的基本变量集的规划问题,通过对基本变量的规划和计算,得到基于关节空间的运动状态序列.该基本变量集包含零力矩点、仿人机器人重心(CoG)、髋部中心(CoC)、脚掌位置及相关关键姿态关系,所提方法结合仿人机器人动力学约束和物理约束,给出了关键变量集的规划和计算方法.最后,通过仿真实验,对规划结果的可行性进行了验证,实现了仿人机器人的稳定行走.     

波数域重力异常正演计算精度分析

重力异常正演计算是反演计算的关键环节,其精度对波数域反演有着重要影响。介绍了基于Parker公式的波数域重力异常正演计算的原理与算法过程,通过与空间域的高斯求积法进行比较,探讨了波数域算法正演重力异常的精度问题。结果发现波数域parker方法正演重力异常的精度较高,与空间域高斯求积法所求结果一致,两者之间差异微小,差值最大最小值出现在界面起伏较大处。     

模拟退火算法及其在多层密度界面反演中的应用

模拟退火算法是以固体退火过程为物理背景的全局优化算法,具有全局寻优的能力,是一种有效的非线性组合优化算法。模拟退火反演算法实质是利用了地球物理反演问题求解过程与熔化固体退火过程的相似性,模拟其达到最低能量状态为系统目标函数的最优解。本文概要地介绍了模拟退火法的基本原理,解的接受准则,模拟退火法的实现方法、特点及其局限性。总结了近年来对模拟退火方法进行的改进,并给出了模拟退火法在多层密度界面反演中的实例。     

应力强度因子的边界配置法程序及工程应用

从断裂力学的观点出发，在水压和自重的作用下应用边界配置法，求解重力坝坝踵区的应力强度因子，据此分析重力坝的开裂和稳定性，突破了传统的重力坝关于强度和稳定性的设计方法，其工程效益显而易见。