“电路”中最大功率传输定理的教学方法探讨

最大功率传输定理是电路理论中一个重要定理。教学中发现：学生在应用定理解题时，经常出现不注意使用条件，引起定理误用的情况，基于此，本文从如何正确使用定理解题角度出发，从所用教材的一道习题引出问题，对最大功率传输定理的使用条件进行了说明，同时给出了不满足使用条件下的解题对策，并通过例子加以说明，指出在教学中强调使用条件的重要性，旨在提高学生对最大功率传输定理的正确掌握。     

弱化条件的Newton—Leibniz公式

鉴于定积分基本公式要求的条件较强，从定积分基本公式-Newton-Leibniz公式出发，首先在弱化其条件的基础上得到一个预备定理并予以证明。然后将预备定理的条件进一步削弱，得到定理弱化条件的Newton-Leibniz公式并予以证明，同时，对上述预备定理及定理中的情况分别举例说明，从而使得定积分基本公式的适用范围更加广泛。     

使用置换定理应注意其条件

研究了电路理论中有关置换定理的使用条件，强调置换定理必须在一定条件下才能使用，这个条件就是置换前、后的电路必须具有唯一解。当线性非时变电路中含有某种受控源时，可能不存在唯一解，不能使用置换定理求解响应     

牛顿-莱布尼兹定理的注记

在牛顿－莱布尼兹定理中连续这个条件必不可少，然而极易忽略。同时，牛顿－莱布尼兹定理的条件可以改进。     

广义Lienard系统初值解的唯一性

目的是研究广义Lienard系统初值问题解的唯一性，所采用的主要方法是微分方程的比较定理，给出了两个定理，这两个定理改进了篇末文献中的有关结果，其中定理1不要求h单调，定理2不要求F满足局部Lipschitz条件，两个定理都减弱了g(z)应满足的条件。     

关于Brezis-Nirenberg定理的注记

在较为自然的条件下，证明了Ｂｒｅｚｉｓ－Ｎｉｒｅｎｂｅｒｇ定理的条件与原有的环绕定理的条件是等价的     

微分中值定理的逆问题

研究了Lagrange定理和Taylor定理的逆问题，证明了在一定的条件下，Lagrange定理和Taylor定理的逆定理成立，为更好地利用微分中值定理提供了理论根据．     

微分中值定理的不等式形式及其应用

通过弱化中值定理的条件．得到了一个减弱了的结果．即中值定理的不等式形式．它在许多方面有一般中值定理的功效．且用它来证明一些定理时，还减弱了部分条件。     

积分第一中值定理的证明及其推广

在条件完全相同的情况下改进积分第一中值定理，并利用变上限积分函数和拉格郎日中值定理证明该定理，并给出积分第一中值定理的几个推广．     

Poincare-Miranda定理的推广

给出Poincare-Miranda定理的一个推广，给出满足该定理条件的集值映射的零点的单纯同伦算法和定理的构造性证明，并证明此定理与Kakutani不动点定理等价。     

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