精细结构常数α发生改变的唯象分析

最近实验显示精细结构常数α＝ｅ２/ｃ是可变的,ｅ,,ｃ ３个量中哪一个改变而导致α改变是当前难题之一.在电子取静质量的情况下,由Dirac大数D、Planck质量mPl和Planck大数A算得α≈１/１３７．３１３,与惯用值α≈１/１３７．０３６符合很好.在动态情况下,电子的电量e将随电子质量的增加而增加,则精细结构常数α是可变的.据轻子结构的亚夸克动态模型,轻子将出现“反常质量”、“反常电荷”、“反常磁矩”等效应,计算得到的与“反常电荷”相关的“反常磁矩”和实验值相符,可以认为电子电荷改变是由电子的“反常电荷”引起的.     

究竟是谁在变--由精细结构常数变化引发的问题与挑战

一、精细结构常数在自然科学中的重要地位20世纪上半期 ,电子的量子理论建立起来。设电子质量为m ,电荷为( -e) ,真空中光速为c ,则可算出e2/mc2=2.8×10 -13cm ,其值约为电子的经典半径。另一方面 ,令h为Planck常数 ,h/mc为电子的Compton波长。如取两者之比 ,则得一无量纲常数 :α= e2c=2πe2hc 1137 (1)它表征基本电荷相互作用的强弱 ;后来发现 ,为描写基本粒子与电磁场相互作用的大小必须用α ,故又称为精细结构常数(finestructureconstant,FSC)。我们知道 ,氢原子的超精细结构裂距是指该原子两状态的能量差 ,状态一为轨道电子自旋与…     

含有变光速的宇宙学模型

最近的观测表明在早期宇宙精细结构常数α＝e^2／(4πhc)是变化的．精细结构常数α的改变可以从不同的方面理解，可能是由于电荷的改变，也可能是光速的改变，或两同时改变引起的．本从含有变光速的度规出发考虑了宇宙的演化并给出了修正的弗里德曼方程．     

具有常数间断点的等电荷阶梯波电流模型

以电荷等效算法为基础,给出常数间断点定理的四个前提条件,提出并证明了常数间断点定理,建立了具有常数间断点的等电荷阶梯波电流(ＣＥＣＳＣ)模型·构造了两相混合式步进电机控制系统,将二阶、四阶ＣＥＣＳＣ模型应用于两相混合式步进电机控制系统,实现了用ＣＥＣＳＣ模型控制电力传动系统·二阶、四阶ＣＥＣＳＣ模型控制的实际电流波形表明,理论分析和实际结果是一致的,实际电流波形随阶梯波电流阶数的增加而逼近于正弦波·     

Lorentz变换的四元数表示

本文研究Lorentz变换的四元数表示.在四元数矩阵表示及其乘法有条件交换性的基础上,导出了Lorentz变换的矩阵表示和四元数表示之间的关系;讨论了正常Lorentz变换分解和两个纯Lorentz变换的合成问题.     

CaF2晶体中四角对称的Yb3+- F-中心的电子顺磁共振参量的理论研究

作者用考虑了二阶微扰贡献的理论公式和由光谱获得的晶场参量，计算了CaF2晶体中四角对称的Yb^3 -F^-中心的电子顺磁共振参量(g因子和超精细结构常数Ai)，计算结果与实验结果符合较好。     

运动体上“时缓”的计算

应用狭义相对论运动系中给出的“时缓”公式和瞬时惯性系统理论 ,从四维不变量出发 ,对实际高速运动系统中的进行了研究 ,导出了较为普遍的“时缓”表达式 ,并借助计算机应用软件“Mathematica” ,通过实例计算并证明了“时缓”的确定性 ,这说明了“时缓”不仅是理论 ,而且在实际情况中同样具有确定性     

量子霍尔电阻的精密测量

1980年冯·克里青教授利用MOSEFT在低温强磁场中发现量子霍尔效应,其量子霍尔电阻(QHR)为:R_H=h/(ne~2),(1)式中,e为电子电荷;h为普朗克常数;n为整数.上式表明,量子霍尔电阻只与基本物理常数h/e~2有关,与材质和样品的几何尺寸无关.因此,可利用它来建立电阻的自然基准和测量精细结构常数.为了用它建立电阻自然基准,许多国家的实验室都进行了量子霍尔电阻的精密测量,最高测量不确定度已达1×10~(-8).1988年第18届国际计量大会(CGPM)及第77届国际计量委员会(CIPM)作出决议:“自1990年1月1日起,国际上将同时正式启用以约瑟夫逊常数和冯·克里青常数的国际公认值为基础的电学计量新基准复现电压单位和电阻单位.作为量子霍尔电阻的公认值——冯·克里青常数     

Maxwell方程组Lorentz表述四维张量形式的讨论

在经典Maxwell方程组的基础上，利用四维空间矢量和四维电磁场张量的变化规律，将Maxwell方程组Lorentz表述的场方程组变换成四维张量形式，证明了Lorentz表述四维张量形式的特点，验证了Maxwell方程组的协变性以及Lorentz表述的四维张量形式的对称性，从而更好地解释了电磁场的运动规律。通过列举实际算例验证了本文算法的实用性和有效性，简化了运动介质相关的问题，体现了在解决运动介质方面问题的优越性，为运动问题的解决提供了一定的帮助。     

量子色动力学(QCD)求和定则在密物质的结果

讨论量子色动力学求和定则解决在真空及核物质中强子性质的方法。核物质情况下,关于谱函数的形式和确定的四夸克凝聚的值,初始的限制缺少可靠的唯象信息;这个方法给出了支持强吸引的Lorentz标量和推斥的Lorentz矢量光学势的Dirac唯象图像的适当证据。对介质中减少的矢量介子质量,这个方法提供了弱证据。     

GaAs压电物性的研究

较详细地讨论了GaAs压电效应的起源。有3种不同的机制对压电效应有贡献.这些机制是离子电荷的内部位移、电子电荷的内部位移和由于应变引起的离子性的变化.推导出了任意晶体取向压电常数张量的表达式,证明了,对正应力而言,GaAs〈111〉方向有最强压电效应发生,且Ga原子呈负电性,而As原子则呈正电性.     

Bipolar supercurrent in graphene

Graphene--a recently discovered form of graphite only one atomic layer thick--constitutes a new model system in condensed matter physics, because it is the first material in which charge carriers behave as massless chiral relativistic particles. The anomalous quantization of the Hall conductance, which is now understood theoretically, is one of the experimental signatures of the peculiar transport properties of relativistic electrons in graphene. Other unusual phenomena, like the finite conductivity of order 4e(2)/h (where e is the electron charge and h is Planck's constant) at the charge neutrality (or Dirac) point, have come as a surprise and remain to be explained. Here we experimentally study the Josephson effect in mesoscopic junctions consisting of a graphene layer contacted by two closely spaced superconducting electrodes. The charge density in the graphene layer can be controlled by means of a gate electrode. We observe a supercurrent that, depending on the gate voltage, is carried by either electrons in the conduction band or by holes in the valence band. More importantly, we find that not only the normal state conductance of graphene is finite, but also a finite supercurrent can flow at zero charge density. Our observations shed light on the special role of time reversal symmetry in graphene, and demonstrate phase coherent electronic transport at the Dirac point.     

Room-temperature electronic phase transitions in the continuous phase diagrams of perovskite manganites

Highly correlated electronic systems--such as transition-metal oxides that are doped Mott insulators--are complex systems which exhibit puzzling phenomena, including high-temperature superconductivity and colossal magnetoresistivity. Recent studies suggest that in such systems collective electronic phenomena are important, arising from long-range Coulomb interactions and magnetic effects. The qualitative behaviour of these systems is strongly dependent on charge filling (the level of doping) and the lattice constant. Here we report a time-efficient and systematic experimental approach for studying the phase diagrams of condensed-matter systems. It involves the continuous mapping of the physical properties of epitaxial thin films of perovskite manganites (a class of doped Mott insulator) as their composition is varied. We discover evidence that suggests the presence of phase boundaries of electronic origin at room temperature.     

一种高稳定高精度单片锂电池充电芯片设计

锂电池是便携式电子设备电源的首选,但是存在充电精度以及充电环路的稳定性问题。论文对一种具有高稳定性,充电电压高精度以及单片集成的锂电池充电芯片进行设计。提出了改进折叠式运放结构作为恒流充电电路和新颖的恒压充电电路,经过这些改进提高了充电环路速度和稳定性,并且利用两级运放的高增益来提高充电环路精度;提出了电流模温度热调整电路;最后基于CSMC0.5um混合CMOS工艺,得到芯片的物理版图,后仿真结果表明充电环路具备很好的稳定性,充电精度达到0.5%以下。     

有效核电荷及其应用

有效核电荷（z）是元素最重要参数之一．通过有效核电荷可计算出电子能量、电离势和电负性等原子结构参数，从而进一步理解和掌握元素的性质．本文注重探讨有效核电荷及其应用等问题．     

Crystallization of charge holes in the spin ladder of Sr14Cu24O41

Determining the nature of the electronic phases that compete with superconductivity in high-transition-temperature (high-T(c)) superconductors is one of the deepest problems in condensed matter physics. One candidate is the 'stripe' phase, in which the charge carriers (holes) condense into rivers of charge that separate regions of antiferromagnetism. A related but lesser known system is the 'spin ladder', which consists of two coupled chains of magnetic ions forming an array of rungs. A doped ladder can be thought of as a high-T(c) material with lower dimensionality, and has been predicted to exhibit both superconductivity and an insulating 'hole crystal' phase in which the carriers are localized through many-body interactions. The competition between the two resembles that believed to operate between stripes and superconductivity in high-T(c) materials. Here we report the existence of a hole crystal in the doped spin ladder of Sr14Cu24O41 using a resonant X-ray scattering technique. This phase exists without a detectable distortion in the structural lattice, indicating that it arises from many-body electronic effects. Our measurements confirm theoretical predictions, and support the picture that proximity to charge ordered states is a general property of superconductivity in copper oxides.     

甲氧基在苯甲醚亲电取代反应的定位作用

从理论上研究了苯甲醚的电子结构,结果表明,苯甲醚的甲氧基在空间的位置影响苯甲醚的原子电荷分布和能量,从而影响苯甲醚的亲电取代反应。苯甲醚的O—Ph键旋转,形成不同构象之间的最大与最小体系能量值之差ΔE仅ΔE=0.006 31 a.u。当C1-O8—C7与苯环垂直时,体系能量[E（90）=E（270）=-344.429 48 a.u]最低,为稳定的优势构象。苯甲醚中甲氧基虽然表现为吸电基,但它的作用使邻、对位碳原子的负电荷比苯环碳原子多,成为亲电取代反应中心,在邻、对位碳原子上较容易被亲电试剂进攻,甲氧基为邻、对位定位基。亲电试剂Me＋与苯甲醚反应形成的各种碳正离子中间体的稳定性差异不大,电子效应是影响亲电取代反应的重要因素。     

电子电量的测量

根据新的实验原理公式对电子电量进行了测量，并且给出了电子电量的加权平均值和不确定度的评定结果。     

相对论效应对巯基金团簇电荷分布的影响

在巯基金团簇中尤其是部分巯基包裹的金核簇,Au原子和S原子的电荷分布是决定金核簇静电势的重要因素.Au是有强相对论效应的重元素,相对论效应对裸露的和有机分子保护的金团簇的几何结构和电子结构有不可忽略的影响.基于密度泛函理论,运用第一性原理研究了环状Au4(SCH3)4簇的电子结构.结果表明相对论效应对电荷分布有重要影响.根据Hirshfeld和Mulliken这两种方法对电子数进行分析,发现当考虑相对论效应时几乎没有电荷从Au转移到S,而不考虑相对论效应时有大量电荷从Au转移到S.     

Non-quantized penetration of magnetic field in the vortex state of superconductors

As first pointed out by Bardeen and Ginzburg in the early sixties, the amount of magnetic flux carried by vortices in superconducting materials depends on their distance from the sample edge, and can be smaller than one flux quantum, phi0 = h/2e (where h is Planck's constant and e is the electronic charge). In bulk superconductors, this reduction of flux becomes negligible at submicrometre distances from the edge, but in thin films the effect may survive much farther into the material. But the effect has not been observed experimentally, and it is often assumed that magnetic field enters type II superconductors in units of phi0. Here we measure the amount of flux introduced by individual vortices in a superconducting film, finding that the flux always differs substantially from phi0. We have observed vortices that carry as little as 0.001phi0, as well as 'negative vortices', whose penetration leads to the expulsion of magnetic field. We distinguish two phenomena responsible for non-quantized flux penetration: the finite-size effect and a nonlinear screening of the magnetic field due to the presence of a surface barrier. The latter effect has not been considered previously, but is likely to cause non-quantized penetration in most cases.