微分方程的电路模型与图形解

利用信号与系统的有关概念建立了模拟微分方程的电路模型。通过Ｘ－Ｙ方向的压缩与扩展变换，可以直接在ＣＲＴ的荧光屏上看到方程的图形解。     

二阶微分方程组的SPICE2模型

以模拟二阶微分方程组的方法为例，讨论了应用ＳＰＩＣＥ２（集成电路通用模拟程序）模拟微分方程组的几种方法。本文应用ＳＰＩＣＥ程序的多项式受控源功能，结合电容、电感、受控源构成的积分器、微分器子电路，产生由微分方程组数学模型转换的等效电路模型，得出了与微分方程变化一致的ＳＰＩＣＥ瞬态分析响应曲线，阐述了积分器、微分器子电路的构成方法，模拟电路结构图的建立过程及求解以空间变量为自变量的微分方程的参数法．该方法还可推广到求解高阶微分方程组。     

两类基于MATLAB的非线性微分方程数值解的算法研究

通过对工程动态控制及计算机仿真中有重要应用的两类非线性微分方程数值解的数学算法分析,建立四阶定步长Runge-Kutta及Lorenz模型数值解的MATLAB算法结构,讨论了变步长情形下的误差控制,绘制了基于MATLAB的Lorenz系统数值解在二维和三维空间下的图形,提出了在可接受误差限内的数值解检验的基本思路.     

利用相平面上的稳定性分析法求微分方程的解

微分方程方法是建立动态模型的行之有效的方法之一．如果建立的模型是自治方程（组）,有时求解微分方程会比较困难．此时,可以转移到相平面上,通过分析方程解的稳定性和发展趋势,进而求得微分方程的解．     

分析电路的各种变换方法之综述

分析电路的各种变换方法之综述李彩萍（陕西电大榆林分校）求解动态电路问题，从数学上讲是一个求线性非齐次常系数微分方程解的问题，可分两步进行：一是依照两类的约束列出电路的微分方程，二是根据电路的初始条件解微分方程。齐次方程的解与输入无关，它反映电路的固有...     

证券投资者群体行为的系统描述

利用分布参数系统模型研究了证券市场中投资者的群体行为．引入了投资者关于其自身因素的分布函数，把投资者行为定义为n维因素空间中的轨线，建立了投资者群体行为分布函数满足的偏微分方程，描述了投资者群体行为的变化规律，并证明了该方程的重要性质．在一定假设条件下，建立了不同资金禀赋的投资者行为分布函数满足的偏微分方程，并给出了解析解．     

一类具比例时滞的脉冲微分方程解的振动性

建立一类具比例时滞和正负系数脉冲微分方程解振动的充分条件．所得结果揭示：脉冲微分方程解的振动性可以仅由脉冲条件所引起;在一定脉冲条件下,非脉冲微分方程解的振动性可以被脉冲微分方程所继承．最后举例予以说明．     

物体在粗糙斜面上的运动─—一个非线性微分方程问题

本文就物体在粗糙斜面上的运动建立了非线性微分方程，并且在适当条件下求出了非线性微分方程以参数表示的解．     

路面不平度影响下的汽车驱动桥动载荷

在考虑阻尼和刚度的前提下,建立了路面不平度影响下的汽车驱动桥振动系统模型及微分方程表达式·通过Laplace变换和线性系统理论给出了求系统固有频率的方法并得出了微分方程的解析解·运用微分方程特解与通解内在关系的理论,给出了微分方程的数值解·解析解偏重于控制方面的研究,数值解偏重于对结果的重视,在编程及仿真模拟时采用数值方法求解效果较好,推荐采用Newton Raphson算法·这两种解完善了驱动桥所受动载荷的表达式,为驱动桥的有限元动态分析与设计提供了载荷方面的准备·     

猫追老鼠的Simulink动画仿真

对于数学建模中经典的猫追老鼠问题,建立了该问题的微分方程模型,在此基础上构建了相应的Simulink模型,然后在Matlab软件的Simulink环境下进行仿真,给出了微分方程的数值解.在仿真过程中,通过编写S函数的方式,用动画模拟了猫追老鼠的全过程.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the