Maxwell理论电磁对偶性的费米子表述

通过引入复量场F=E-iB,给出了无源Maxwell方程组的电磁对偶对称性的费米子表述形式.接着给出了有源情况下Maxwell方程的费米子表述形式.在有源情况下必须引入Dirac磁单极而且这一描述形式具有洛伦兹协变性和电磁对偶性.     

三种度规下Maxwell方程的双矢势对偶理论

介绍了电磁场双四维矢势的概念，讨论了三种度规下引入双矢势后电磁场张量的特性，给出了具有电磁对偶性的Maxwell方程。在有源情况下引入磁单极，利用电磁场的双矢势表述可以避开Dirac奇异弦得到具有电磁对偶性的电磁场方程。最后给出了有磁单极存在时具有S0(2)对称性的d'A1emben方程及推迟解。     

电偶极和磁偶极辐射的SO(2)对偶理论

在引入Drac磁单极(即磁荷)的情况下，首先介绍了Maxwell方程双矢势下的电磁对偶性．接着给出了有磁荷存在的d‘Alembert方程，利用这个方程推迟解求出了带磁荷粒子和双荷粒子的电磁辐射的表达式,最后讨论了电偶极和磁偶极辐射在双矢势下的表达式。     

电四极和磁四极辐射的SO(2)对偶理论

在Dirac磁单极存在的情况下,考虑保持Maxwell方程双矢势下的电磁对偶性.利用有磁荷存在的d’Alembert方程推迟解,求出了带磁荷粒子和双荷拉子的电磁辐射的表达式。最后得到了电四极和磁四极辐射双矢势下表达式,并对电多极和磁多极辐射问题进行了讨论。     

基于矩量法的三维介质目标电磁散射特性研究

想要具体地分析三维介质目标的电磁散射问题,需要知道未知电磁流系数.首先介绍三维介质目标的体积分方程,接着将体积分方程变为矩阵方程,在此过程中利用了矩量法进行了转化,根据矩阵方程对电磁流系数进行了计算,从而得出三维介质目标的雷达散射截面,最后对具体的三维介质目标：介质球、介质立方体的RCS进行了计算.实验结果表明：基于矩量法的三维介质目标的电磁散射特性分析是准确有效的.     

电磁波的能量传播速度

电磁波作为一种电磁信号的传递形式,其速度的标志应是电磁能量的传递速度。我们通常所表示的V=1/((ε_0μ_0)~(1/2))是平面电磁波在真空中的传播速度。那么电磁波在介质中其能量传播速度如何?在不同介质中结论是不同的。 一、各向同性线性介质 设在B=μH,D=qE的各向同性线性介质的自由空间传播的电磁波满足波动方程     

现代通讯鼻祖——麦克斯韦

麦克斯韦(J.C.Maxwell,公元1831～1879年)是一位杰出的物理学家。他的一生,是在不断探索中度过的。麦克斯韦的功绩是在法拉第工作的基础上,总结了电磁现象,建立了麦克斯韦方程,导出了电磁场的波动方程,预言了电磁波的存在,从而推断出光是一种电磁波,为电磁理论的创立奠定了基础。     

一类具源漏的自由边界问题的局部正解

引言本文讨论由两种不可溶混的可压缩流体在一维有源漏多孔介质中渗流所引起的一类自由边值问题。它的实际背景是多孔介质中一种流体对另一种流体的驱替，例如石油开采中的水驱油。在多孔介质和流体不可压的情况下，Muskat在三十年代建立了相应的数学模型，即Mu－skat问题；在流体可压缩的一线情形，Cannon在1978年给出了数学模型（见文[1]P16），它是一类自由边值问题，其方程为（其中只为压强，为自山边界），当方程是线性时，已被L．C．Ev。us等人解决了（见文[2]、[3]），当流体可压缩并具有源漏时，得到的方程是拟线性的、形式上可…     

随机介质中光激发理论的数值方法

根据Jiang提出的随机介质模型,从Maxwell方程出发,结合速率方程和极化方程,并应用FDTD方法对方程组进行求解,着重讨论了求解的方法.     

从十个基本方程看电磁场理论

本文用麦克斯韦方程组、介质边界关系、电荷守恒定律及洛伦兹力公式概述了电磁作用的一般规律，提出了电磁场基本理论统一在十个方程上的思想。文中首先对一般情况的电磁场相互作用规律作阐述，谈了十个公式是怎样揭示电磁现象的实质。其次着重介绍了静电场稳恒电流磁场及电磁波的传播和辐射三部分的主要内容，从中我们可以看出，求解电磁场问题实质就是求解麦克斯韦方程组的问题，针对不同情况引入了不同的物理量，使问题简单化。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.