On the interaction of the responses at the resonance frequencies of a nonlinear two degrees-of-freedom system

This paper describes the dynamic behaviour of a coupled system which includes a nonlinear hardening system driven harmonically by a shaker. The shaker is modelled as a linear single degree-of-freedom system and the nonlinear system under test is modelled as a hardening Duffing oscillator. The mass of the nonlinear system is much less than the moving mass of the shaker and thus the nonlinear system has little effect on the shaker dynamics. The nonlinearity is due to the geometric configuration consisting of a mass suspended on four springs, which incline as they are extended. Following experimental validation, the model is used to explore the dynamic behaviour of the system under a range of different conditions. Of particular interest is the situation when the linear natural frequency of the nonlinear system is less than the natural frequency of the shaker such that the frequency response curve of the nonlinear system bends to higher frequencies and thus interacts with the resonance frequency of the shaker. It is found that for some values of the system parameters a complicated frequency response curve for the nonlinear system can occur; closed detached curves can appear as a part of the overall amplitude-frequency response. These detached curves can lie outside or inside the main resonance curve, and a physical explanation for their occurrence is given.     

基于Ackermann模型的全轮转向电动汽车的随动跟踪控制策略研究

本文提出了一种新型的基于Ackermann模型的全轮转向电动汽车的随动跟踪控制系统,该随动跟踪控制的思想是：当四轮中出现有车轮运动受阻使得车轮转向和驱动的转速徒降,此时其它的车轮将不执行整车控制系统的运动指令,转而去跟随受阻车轮的运动状态,直到受阻车轮脱离困境后,四个车轮再各自执行整车控制系统的运动指令。该控制系统是由转向控制、驱动控制和CAN总线网络系统组成的复杂的电气系统。该控制系统的优势在于：不仅能实现四轮独立转向四轮独立驱动控制的功能,而且在不平路面上车轮失步情况下,各轮转向角能自动随动同步协调,有效地防止磨胎现象。实验结果表明,该动力随动控制系统控制实时同步性好,响应速度快,能使四个轮子在转向和差速过程中达到和机械连接一样的刚度要求。     

Impacts of the transformation of the German energy system on the transmission grid

The German Energiewende, the transformation of the energy system, has deep impacts on all parts of the system. This paper presents an approach that has been developed to simultaneously analyse impacts on the energy system as a whole and on the electricity system in particular. In the analysis, special emphasis is placed on the transmission grid and the efficiency of recommended grid extensions according to the German Network Development Plan. The analysis reveals that the measures in the concept are basically suitable for integrating the assumed high share of renewables in the future electricity system. Whereas a high feed-in from PV will not cause problems in the transmission grid in 2022, congestion may occur in situations with a high proportion of wind feed-in. Moreover, future bottlenecks in the grid are located in the same regions as today.     

回热对跨临界CO2热泵系统性能影响的实验研究

本文实验研究了回热器的回热率对跨临界CO2热泵系统性能的影响。结果表明:在一定压缩机频率下,随着排气压力的升高,系统制热量和COPh都存在最大值,并分别存在对应最大制热量和最大COPh的最优排气压力;在25Hz压缩机频率下,系统在低排气压力下运行时,引入回热器才能提高系统COPh,且引入回热器可在较低排气压力下,获得更高的系统COPh;在一定压缩机频率下,系统分别存在最大制热量、最高出水温度和最大COPh对应的最优回热率.在本实验条件下,如果以系统获得最大COPh为设计目标,系统回热率取15%左右为宜;如果以系统获得最高出水温度为设计目标,系统回热率取5%左右为宜。     

Lorenz系统的可预报性

定义一个动态窗口，以Lorenz模型为预报方程，通过对落入动态窗口中的粒子数和平均预报X分量随积分时间演化规律的分析，从另一个角度初步研究了Lorenz系统的可预报性问题，并讨论了高斯白噪声对系统可预报性的影响.结果表明，落入动态窗口中的粒子数在一定程度上反映了系统的可预报性，处于不同区域的初值集合预报时限各不相同，且不同区域内的初值对于小扰动的敏感程度不一样；对于不同区域内的初值集合，高斯白噪声对系统的可预报时限的影响各不相同. 关键词： 可预报性 Lorenz 动态窗口     

气溶胶前向散射大气能见度测量系统传递系数的标定及校准方法

分析了气溶胶的前向角散射特性,利用标准的大气透射仪标定前向散射大气能见度测量系统的传递系数。当系统结构发生变化时,传递系数也随之改变,为保证系统测量的准确性和简化系统传递系数的标定过程,提出了一种利用标准漫透射板校准系统传递系数的方法。该方法使用了两块具有相同透射系数的漫透射板,使气溶胶粒子团在前向半球上产生漫散射,此时探测器的测量值即为包含了仪器常数的定值。当系统结构改变时,这个测量值相对于原测量值的变化率作为比例系数代入系统传递系数的计算,实现校准。     

嵌入单量子点Aharonov-Bohm环中的近藤效应

使用单杂质的Ansderson模型, 从理论上研究了一个嵌入单量子点Aharonov-Bohm环系统处在 近藤区时的基态性质, 并用slave-boson平均场方法求解了该模型.结果表明：在零温, 当介 观环内电子平均能级间隔大于近藤关联能时, 系统内仍然存在一个被减弱了的近藤效应；系 统的基态性质依赖于系统的宇称和环的大小；而尺寸效应和近藤屏蔽效应的共存导致了系统 丰富的物理性质.同时, 可以通过测量介观环中的持续电流和杂质磁化率, 达到探测近藤屏 蔽云的目的. 关键词： 持续电流 杂质磁化率 宇称效应 近藤效应 近藤屏蔽云     

On the interbasis expansion for the Kaluza-Klein monopole system

We study the interbasis expansion of the wave-functions of the Kaluza-Klein monopole system in the parabolic coordinate system with respect to the spherical coordinate system, and vice versa. We show that the coefficients of the expansion are proportional to Clebsch-Gordan coefficients. We analyse the discrete and continuous spectrum as well, briefly discuss the feature that the (reduced) Kaluza-Klein monopole system is separable in three coordinate systems, and the fact that there are five functionally independent integrals of motion, respectively observables, a property which characterizes this system as super-integrable.     

Optimizing a refinery using the pinch technology and the mind method

The Pinch Technology and the MIND method are combined in the analysis of a Swedish refinery. The heat exchanger network of the crude distillation system is analysed using the Pinch Technology. The results show that the steam demand from the boiler units in the energy supply part of the system can be reduced by 20% in the optimized heat exchanger network and by 21% when a heat pump is added to the system. A multi-period cost optimization of the operating strategy is performed using the MIND method. The results from the Pinch analysis are then input to the MIND optimization. The system cost of the total energy system of the refinery is optimized with regard to flexibility in the process system as well as changes of energy costs and the operating conditions of the cogeneration unit. The combination of methods shows that significant capital savings can be achieved when the energy saving potential of the process system is integrated in the overall operating strategy of the energy system. It is, in this case, possible to compare investments in energy saving measures to investments in increased steam production capacity.     

A study of the asymmetric Malkus waterwheel: the biased Lorenz equations

In this work, the asymmetric case of the Malkus waterwheel is studied, where the water inflow to the system is biasing the system toward stable motion in one direction, like a Pelton wheel. The governing equations of this system, when expressed in Fourier space and decoupled to form a closed set, can be mapped into a four-dimensional space where they form a quasi-Lorenz system. This set of equations is analyzed in light of analogues of the Rayleigh Bernard convection and conclusions are drawn. The properties and behavior of the equations are studied and correlated to the physical model. Phase space behavior and linear stability analysis are used for this. Spectral analysis is used as a qualitative measure of chaos. Chaotic behavior is quantified through the calculation of the Lyapunov exponents and these are further correlated to the bifurcation diagrams for a conclusive analysis of the dynamical behavior of the system.     

On the relationship between the temperature and the geometry of the two-dimensional superconducting system

A set of vortices in the superconducting system being a two-dimensional region with a boundary has been considered. Here the system under study is described by the model of the Ginzburg-Landau potential in the dual point. This model predicts that in the bounded superconducting system non-interacting vortices appear. These vortices make the absolute minima of this potential. It turned out that in the thermodynamic equilibrium for the fixed number of vortices, the temperature of the system and the geometry of the boundary are related to each other. The simultaneous change of the temperature of the system and of the geometry of the boundary has been investigated under the assumption that the number of vortices is fixed. In the case of the flat disc the explicit form of the temperature vs. area relation has been obtained for two different boundary conditions.Received: 29 April 2004, Published online: 31 August 2004PACS: 74.25.Bt Thermodynamic properties - 74.25.Dw Superconductivity phase diagrams     

大尺度环流与中尺度对流的作用研究

气候系统是一个复杂的、开放的非线性系统，具有层次结构. 高层次系统控制着低层次系统的行为，并决定了气候变化的基本形态. 一般地，观测资料或器测资料往往直接记录的是低层次系统的输出结果，它包含了各层次相互作用的信息. 如何从观测资料中提取与分离高层次系统的尺度信息已成为观测资料的非线性时空分布理论和方法的研究热点之一. 目前对气候系统的具体的形式还没有统一的定论. 为了分析问题的方便，引用了一个由Logistic模型与Lorenz模型构建的两层系统模型，在不同的控制参数下，分别应用功率谱分析和小波变换对低层次系统的输出结果进行了分析，进而提取与分离高层次系统的尺度变化信息.     

On the generalized principle of reversibility in the optics of thin films

A system of thin films can be regarded as a relatively isolated system with two inputs and two outputs. In order to obtain the identities between the amplitude coefficients we use the theorem of duality of a prospective and retrospective relatively isolated system. Apart fromT transformation, this theorem also requires the exchange of the inputs and outputs of the system.     

基于中阶梯光栅光谱仪的激光诱导等离子体分析系统研究

为了满足激光诱导等离子体分析系统(LIPS)对分光系统的分辨率,光谱范围,体积等多方面要求。本文研制了一台中阶梯光栅光谱仪,该光谱仪能同时获得所有谱段范围内的光谱信息,令LIPS系统可实现快速在线实时分析。并且,该光谱仪采用可调节延迟时间的ICCD作为后端探测器,令整个系统可根据实际实验情况选择最优延迟时间接收光谱,提高了整个系统的信噪比。最后,搭建了一套激光诱导等离子体分析系统,对研制的中阶梯光栅光谱仪在系统中的可用性进行验证。通过对合金样品测试,整个系统的分辨率达0.02 nm,光谱范围覆盖190～600 nm。并且研制的LIPS系统光谱重复性较好,特征元素波长提取误差不超过0.01 nm,可较准确的对样品成分进行分析。     

光学相干层析系统相干传递函数研究

在弱物体近似下从成像系统角度对光学相干层析测量技术进行了理论研究。分析了该技术测量样品纵深结构时图像的形成机理。结果表明它相当于一复振幅线性平移不变系统，从而可用相干传递函数描述系统性能，所得相干传递函数表明系统具有低通特性，半峰值带宽△ｋ＝２△λ／λ＾２。由于物体频谱整体平移了１／λ，测量的是纵向结构的高频信息。本文的工作为定量分析光学相干层析对未知结构的测量结果及进一步提高空间分辨率提供了理论     

离心机动态失准角测量方法的研究

针对精密离心机动态失准角测量中存在的问题,提出以双轴光电自准直仪为核心测量仪器的失准角测量方法,在测量系统中采用真空光路屏蔽技术,减少了由于测量环境空气扰动带来的误差。对组成测量系统的各环节进行了误差分析与设计,理论分析与实验表明系统测量不确定度可达到0 2″。     

Inclusion of the causality principle in the dynamical description of nonequilibrium systems

In the nonequilibrium-statistical-operator (NSO) method a correction to the Hamiltonian of a system is found, corresponding to a source in the Liouville equation, which destroys the invariance of this equation with respect to time reversal. Analysis of this correction enables one to conclude that the forces leading to the irreversible behavior of a system are of an essentially nonpotential nature. Inclusion of the causality principle in the Hamiltonian of a system also makes it possible to give a new representation of the NSO.     

Brownian Motion of the Quantum Dissipation in the RWA

A microscopic approach treating the quantum dissipation process presented by Sun and Yu (Phys. Rev. A49 (1994) 592; A51 (1995) 1845) is invoked to construct the wavefunction of the composite system——the model for a harmonic oscillator interacting with a many-oscillator bath under the rotating wave approximation. It shows the back-action of the system on the bath. In particular, the dynamic evolution of the wavefunction for the composite system maintains a factorized form in its wavefunction. In the limited temperature, the reduced density matrix for the system is also calculated to clarify the influence of Brownian motion on the system.     

Meaning of the Density Matrix

Protective measurement, which was proposed as a method of observing the wavefunction of a single system, is extended to the observation of the density matrix of a single system. This provides a new meaning to the density matrix as having the same ontological status as the wave function describing a pure state. This also enables quantum entropy to be associated with a single system.     

The covariant form of the Klein-Kramers equation and the associated moment equations

We provide a covariant, coordinate-free formulation of the many-dimensional Klein-Kramers equation for the phase space distribution of a Brownian particle. We construct a complete set of eigenfunctions of the collision operator adapted to the coordinate system, which involve covariant tensorial Hermite polynomials. The Klein-Kramers equation can then be reformulated as a system of coupled equations for the expansion coefficients with respect to this system. Truncation of this system of moment equations and application of a subsidiary condition yields a covariant generalization of Grad's thirteen-moment equations. As an application we give the explicit form of these equations for spherically symmetric, stationary solutions in spherical coordinates. We briefly comment on possible extensions of our treatment to slightly more complicated cases.