由58Fe 和209Bi 熔合后的相关衰变过程得到的109号元素的证据

本文报导了合成109号元素的实验。用能量为4.95,5.05和5.15MeV/u 的~(58)Fe 束轰击~(209)Bi 靶,研究了全熔合产物衰变模式的特性。总辐照剂量为7×10~(17)粒子。所用的实验方法是:用静电场速度过滤器在飞行过程中分离向前方向成峰的反应产物,经过飞行时间装置后注入到位置灵敏固态探测器中,测量其动能,估算出质量、入射的时间和位置。以所有的出射粒子的能量和时间来记录很有限的反应产物发生级联α粒子和(或)自发裂变的继发衰变。在5.15 MeV/u 时的一个特别的衰变过程是:在5ms 和22ms 先分别发射两个α粒子,最后,在13s 后发生自发裂变。第一个α粒子的动能为11.10±0.04MeV。对各种可能的解释进行了详细的分析,例如纯属偶然的信号相关,转移反应产物的衰变和从能量上看允许的余核蒸发等。最后表明质量数为266的109号元素的同位素、即全熔合后的单中子蒸发道、从统计的观点看是最好的指定。本文同时也讨论了合成新元素的前景。     

Unifying the theory of integration within normal-, Weyl- and antinormal-ordering of operators and the s-ordered operator expansion formula of density operators

By introducing the s-parameterized generalized Wigner operator into phase-space quantum mechanics we invent the technique of integration within s-ordered product of operators(which considers normally ordered,antinormally ordered and Weyl ordered product of operators as its special cases).The s-ordered operator expansion(denoted by...) formula of density operators is derived,which is ρ = 2 1 s ∫ d2βπβ|ρ |β exp { 2 s 1(s|β|2 β a + βa a a) }.The s-parameterized quantization scheme is thus completely established.     

物理学咬文嚼字之十心有千千结,都付画图中

图像可以帮助表述难以言传之意,所以它一直是物理学以及其他众多学科之重要表现工具.英文物理学文献中常遇到的与图像有关的词汇包括chart,map(mapping),histogram,scratch, sketch,image,plot,inset, painting,drawing,illustration,depict, delineation,profile,graphics,figure, picture,diagram(schematic diagram), graph, photograph, micrograph, cartoon,portrait,以及最近也可以作为稿件部分的film,flash,video,等等.研究者要善于选择最有效的图形表现工具,并要明了这些不同方式间的细微差别.然而,对物理学渐进境界之理解却又要求研究者心中不能着相.此中微义,愿读者诸公参详.     

2008年全国高考理综卷(Ⅰ)物理试卷评析

2008年全国高考理科综合能力测试卷(Ⅰ)物理试卷供湖北、湖南、河北、河南、浙江、江西、广西、陕西、山西、安徽、福建、辽宁等省使用,全卷无超纲题、偏题、怪题,绝大部分试题及评分标准,表述科学、严谨、规范.     

Strain effect on the orientation-dependent harmonic spectrum of monolayer aluminum nitride

In this study, we theoretically investigate the strain effect on the orientation-dependent high-order harmonic generation(HHG) of monolayer aluminum nitride(Al N) by solving the multiband semiconductor Bloch equations in strong laser fields. Our simulations denote that the efficiency of the orientation-dependent HHG is considerably enhanced when a 15% biaxial tensile strain is applied to Al N, which is attributed to the downshifting energy level of the conduction band. Furthermore, the odd-even feature in the orientation-dependent high harmonic spectra owing to the strain is considerably different when compared with that in the case without strain. The enhanced quantum interference between different energy bands in strained Al N around the Γ-M direction is responsible for the observed odd-even distributions of the orientation-dependent HHG. This study helps to better understand the HHG in solids by tuning their electronic structures.     

Weak deflection angle of extended uncertainty principle black holes

We discuss the effects of quantum fluctuations spewed by a black hole on its deflection angle.The GaussBonnet theorem(GBT)is exploited with quantum corrections through the extended uncertainty principle(EUP),and the corresponding deflection angle is obtained.Moreover,we have attempted to broaden the scope of our work by subsuming the effects of plasma medium on the deflection angle.To demonstrate the degree of difference,the acquired results are compared with the prevailing findings.     

The forward and inverse problem of cardiac magnetic fields based on concentric ellipsoid torso-heart model

<正>This paper constructs a concentric ellipsoid torso-heart model by boundary element method and investigates the impacts of model structures on the cardiac magnetic fields generated by both equivalent primary source—a current dipole and volume currents.Then by using the simulated magnetic fields based on the torso-heart model as input,the cardiac current sources—an array of current dipoles by optimal constrained linear inverse method are constructed.Next, the current dipole array reconstruction considering boundaries are compared with that in an unbounded homogeneous medium.Furthermore,the influence of random noise on reconstruction is also considered and the reconstructing effect is judged by several reconstructing parameters.     

A new complex variable meshless method for transient heat conduction problems

<正>In this paper,based on the improved complex variable moving least-square(ICVMLS) approximation,a new complex variable meshless method(CVMM) for two-dimensional(2D) transient heat conduction problems is presented. The variational method is employed to obtain the discrete equations,and the essential boundary conditions are imposed by the penalty method.As the transient heat conduction problems are related to time,the Crank-Nicolson difference scheme for two-point boundary value problems is selected for the time discretization.Then the corresponding formulae of the CVMM for 2D heat conduction problems are obtained.In order to demonstrate the applicability of the proposed method,numerical examples are given to show the high convergence rate,good accuracy,and high efficiency of the CVMM presented in this paper.     

Novel travelling wave structures: few-cycle-pulse solitons and soliton molecules

We discuss a fifth order KdV(FOKdV)equation via a novel travelling wave method by introducing a background term.Results show that the background term plays an essential role in finding new abundant travelling wave structures,such as the soliton induced by negative background,the periodic travelling wave excited by the positive background,the few-cycle-pulse(FCP)solitons with and without background,the soliton molecules excited by the background.The FCP solitons are first obuained for the FOKdV equation.     

吴大猷先生大陆行

1992年5月17日,吴大猷先生在时隔46年后第一次重返祖国大陆,他在李政道教授及其夫人秦惠莙女士陪同下,从台北转道香港来北京.他虽是以个人身份,但当时是海峡对岸来访者中现职最高的人,他那时已87岁高龄了,而且有病在身.我们都感到压力很大,生怕有闪失.我在机场迎接他时,见他虽然坐在轮椅上,但精神很好.除李政道教授夫妇外,只有一位学者谢云生教授作为秘书陪同,并无前呼后拥的随从.那天在北京机场,有很多两岸的记者.他对记者们的提问,谈笑自如.