首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
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。  相似文献   

2.
Recent commissioning of the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou enabled us to conduct high-precision mass measurements at the Institute of Modern Physics in Lanzhou (IMP). In the past few years, mass measurements were performed using the CSRe-based isochronous mass spectrometry employing the fragmentation of the energetic beams of 58Ni, 78Kr, 86Kr, and 112Sn projectiles. Masses of short-lived nuclides on both sides of the stability valley were addressed. Relative mass precision of down to 10−6 ~ 10−7 is routinely achieved. The mass values were used as an input for dedicated nuclear structure and astrophysics studies, providing for instance new insights into the rp-process of nucleosynthesis in X-ray bursts. In this contribution, we briefly review the so far conducted experiments and the main achieved results, as well as outline the plans for future experiments.  相似文献   

3.
In this paper,a new approach is devoted to find novel analytical and approximate solutions to the damped quadratic nonlinear Helmholtz equation(HE)in terms of the Weiersrtrass elliptic function.The exact solution for undamped HE(integrable case)and approximate/semi-analytical solution to the damped HE(non-integrable case)are given for any arbitrary initial conditions.As a special case,the necessary and sufficient condition for the integrability of the damped HE using an elementary approach is reported.In general,a new ansatz is suggested to find a semi-analytical solution to the non-integrable case in the form of Weierstrass elliptic function.In addition,the relation between the Weierstrass and Jacobian elliptic functions solutions to the integrable case will be derived in details.Also,we will make a comparison between the semi-analytical solution and the approximate numerical solutions via using Runge-Kutta fourth-order method,finite difference method,and homotopy perturbation method for the first-two approximations.Furthermore,the maximum distance errors between the approximate/semi-analytical solution and the approximate numerical solutions will be estimated.As real applications,the obtained solutions will be devoted to describe the characteristics behavior of the oscillations in RLC series circuits and in various plasma models such as electronegative complex plasma model.  相似文献   

4.
季小玲  蒲政才 《中国物理 B》2010,19(2):29201-029201
Based on a recently formulated unified theory of coherence and polarization, a method is described to study turbulence-induced changes in the polarization, the coherence and the spectrum of partially coherent electromagnetic beams on propagation. The electromagnetic Gaussian Schell-model beam is taken as a typical example of partially coherent electromagnetic beams, and the closed-form expressions for the degree of polarization, the degree of coherence and the spectrum of electromagnetic Gaussian Schell-model beams propagating through atmospheric turbulence are derived in the quadratic approximation of Rytov’s phase structure function. Some interesting results are obtained, which are illustrated by numerical examples and are explained in physics.  相似文献   

5.
郭培荣  徐伟  刘迪 《中国物理 B》2010,19(3):30520-030520
A stochastic dynamical system with double singularities driven by non-Gaussian noise is investigated.The Fokker-Plank equation of the system is obtained through the path-integral approach and the method of transformation.Based on the definition of Shannon’s information entropy and the Schwartz inequality principle,the upper bound for the time derivative of entropy is calculated both in the absence and in the presence of non-equilibrium constraint.The present calculations can be used to interpret the effects of the system dissipative parameter,the system singularity strength parameter,the noise correlation time and the noise deviation parameter on the upper bound.  相似文献   

6.
吕翠红  范洪义  姜年权 《中国物理 B》2010,19(12):120303-120303
We newly construct two mutually-conjugate tripartite entangled state representations,based on which we propose the formulation of three-mode entangled fractional Fourier transformation(EFFT) and derive the transformation kernel.The EFFT’s additivity property is proved and the eigenmode of EFFT is derived.As an application,we calculate the EFFT of the three-mode squeezed vacuum state.  相似文献   

7.
<正>With the development of the compressive sensing theory,the image reconstruction from the projections viewed in limited angles is one of the hot problems in the research of computed tomography technology.This paper develops an iterative algorithm for image reconstruction,which can fit most cases.This method gives an image reconstruction flow with the difference image vector,which is based on the concept that the difference image vector between the reconstructed and the reference image is sparse enough.Then the l_2-norm minimization method is used to reconstruct the difference vector to recover the image for flat subjects in limited angles.The algorithm has been tested with a thin planar phantom and a real object in limited-view projection data.Moreover,all the studies showed the satisfactory results in accuracy at a rather high reconstruction speed.  相似文献   

8.
In 1949, Tolman found the relation between the surface tension and Tolman length, which determines the dimensional effect of the surface tension. Tolman length is the difference between the equimolar surface and the surface of tension. In recent years, the magnitude, expression, and sign of the Tolman length remain an open question. An incompressible and homogeneous liquid droplet model is proposed and the approximate expression and sign for Tolman length are derived in this paper. We obtain the relation between Tolman length and the radius of the surface of tension(Rs) and found that they increase with the Rs decreasing. The Tolman length of plane surface tends to zero. Taking argon for example, molecular dynamics simulation is carried out by using the Lennard–Jones(LJ) potential between atoms at a temperature of 90 K. Five simulated systems are used, with numbers of argon atoms being 10140, 10935, 11760, 13500, and 15360, respectively. By methods of theoretical study and molecular dynamics simulation, we find that the calculated value of Tolman length is more than zero, and it decreases as the size is increased among the whole size range. The value of surface tension increases with the radius of the surface of tension increasing, which is consistent with Tolman’s theory. These conclusions are significant for studying the size dependence of the surface tension.  相似文献   

9.
Counter-rotating-wave terms(CRWTs)are traditionally viewed to be crucial in open small quantum systems with strong system–bath dissipation.Here by exemplifying in a nonequilibrium qubit–phonon hybrid model,we show that CRWTs can play the significant role in quantum heat transfer even with weak system–bath dissipation.By using extended coherent phonon states,we obtain the quantum master equation with heat exchange rates contributed by rotating-waveterms(RWTs)and CRWTs,respectively.We find that including only RWTs,the steady state heat current and current fluctuations will be significantly suppressed at large temperature bias,whereas they are strongly enhanced by considering CRWTs in addition.Furthermore,for the phonon statistics,the average phonon number and two-phonon correlation are nearly insensitive to strong qubit–phonon hybridization with only RWTs,whereas they will be dramatically cooled down via the cooperative transitions based on CRWTs in addition.Therefore,CRWTs in quantum heat transfer system should be treated carefully.  相似文献   

10.
罗质华  曹锡金  余超凡 《中国物理 B》2011,20(6):67103-067103
Based on the Holstein model Hamiltonian of one-dimensional molecular crystals, by making use of the expansion approach of the correlated squeezed-coherent states of phonon instead of the two-phonon coherent state expansion scheme, the properties of the ground state and the anomalous quantum fluctuations are investigated in a strongly coupled electron-phonon system with special consideration of the electron-two-phonon interaction. The effective renormalization (αi) of the displacement of the squeezed phonons with the effect of the squeezed-coherent states of phonon and both the electron-displaced phonon and the polaron-squeezed phonon correlations have been combined to obtain the anomalous quantum fluctuations for the corrections of the coherent state. Due to these non-adiabatic correlations, the effective displacement parameter αi is larger than the ordinary parameter α (0) i . In comparison with the electron-one-phonon interaction (g) corrected as αig, we have found the electron-two-phonon interaction (g1) corrected as αi2 g1 is enhanced significantly. For this reason, the ground state energy (E(2) 0 ) contributed by the electron-two-phonon interaction is more negative than the single-phonon case (E(1) 0 ) and the soliton solution is more stable. At the same time, the effects of the electron-two-phonon interaction greatly increase the polaron energy and the quantum fluctuations. Furthermore, in a deeper level, we have considered the effect of the polaron-squeezed phonon correlation (f-correlation). Since this correlation parameter f > 1, this effect will strengthen the electron-one and two-phonon interactions by fαig and f2αi2 g1, respectively. The final results show that the ground state energy and the polaron energy will appear more negative further and the quantum fluctuations will gain further improvement.  相似文献   

11.
刘振兴 《物理》1999,28(10):585-592
我国磁层物理是在赵九章倡导下从1959年开始发展起来的,40多年来,我国磁层物理有了很大进展。文章对我国磁层物理研究的主要成果作了概述,主要内容包括:磁层顶边界层的瞬时重联研究,磁层顶的不稳定性和反常输产业暴过程研究,磁尾动力学过程研究,极光加速区非线性波和粒子加速研究,行星磁了后是磁层物理发展趋势的展望。  相似文献   

12.
This article is an overview of our investigations of polymorphism in isotactic polypropylene. We suggest the reason for the formation of different forms is perturbations in the mobility of the chains during crystallization. In this work, we try to prove this hypothesis considering the influence of the presence of small organic compounds or external forces, like an electric field, on the process of crystallization. We also analyzed the formation of the polymorphic forms in polypropylene blends and in composites with natural fibers. It was found that in the composites with natural fibers the hexagonal form arises when the fibers are in motion in relation to the polymeric matrix.  相似文献   

13.
早期波谱学在北京大学   总被引:2,自引:0,他引:2  
郑乐民 《波谱学杂志》1995,12(5):557-559
简单回顾了1954-1966年北京大学波谱学的活动。  相似文献   

14.
文章讨论了在间接测量中当各直接测量量是独立量和非独立量时,间接测量的误差计算。  相似文献   

15.
矩形通道内横流喷雾掺混流场的实验研究   总被引:2,自引:0,他引:2  
应用PIV系统对矩形通道内横流-喷雾掺混过程中液滴沿横流方向的流场进行了实验测量.分别获得了单喷嘴和双喷嘴下横流掺混中的流场结构,以及液滴的水平速度分布.横流作用下,液滴的最大水平速度为横流速度的两倍左右;反旋涡对降低了液滴的水平速度,提高了液滴在横流中的停留时间.双喷嘴条件下,横流截面上的液滴密集区域呈狭长的三角形,...  相似文献   

16.
超小金属微粒超导电性的能级统计   总被引:9,自引:0,他引:9       下载免费PDF全文
用平均场理论的自洽方程计算了随机矩阵理论中三种系综(Gauss Orthogonal Ensemble;Gauss Unitary Ensemble;Gauss Symplectic Ensemble)所对应的电子能级的奇/偶电子数分布对临界电子能级间距的影响,得到了在不同的自旋-轨道耦合和磁场中奇/偶电子数分布的临界电子能级间距的定量关系以及奇电子数的Δ((0)随平均能间距o>的变化. 关键词:  相似文献   

17.
忽满利  李育林 《光子学报》1998,27(7):607-610
通常光折变全息存储中用原记录时的参考光再现时,透过光折变晶体的散射光会降低再现图象的质量.我们在实验中对这种影响进行了研究,发现信噪比低的再现象是由信号-嗓音混合栅产生的相位畸变波.我们用参考光的相位共轭光作为再现光,有效地降低了再现象中的噪音,获得了高信噪比的再现图象.基于光折变波耦合理论,我们得到了和实验结果相符合的理论结果.  相似文献   

18.
张宗燧 《物理学报》1958,14(4):308-316
这篇短文的内容是:(i)对於量子场论中的i(δψ[σ])/(δσ(x))=V(x,σ)ψ[σ] 如何由寻常的“曲面上的薛定谔方程”导出,作一个较严格的讨论,以及 (ii)讨论上式中的V(x,σ)在什么条件下不包含有σ。我们证明了所需的条件是 (?LI)/(?φμ) (?LI)/(?φν)=(?2L)/(?φμν)F(φ,φρ),式中L,LI代表总拉格朗日及作用拉格朗日,φ代表场量,φμ代表φ/xμ,F(φ,φρ)代表φ及φμ的一个任意函数。  相似文献   

19.
Bolometric detectors used in radio-astronomical instruments such as the ESA Planck Surveyor, operate as incoherent receivers of electromagnetic radiation. Meanwhile, the optical (quasi-optical) parts of the instruments (feed horns, telescope mirrors) are conventionally designed in transmitting mode when a coherent source of radiation (supposedly, equivalent to the bolometric detector) replaces the detector and radiates the electromagnetic waves through the optical system to the sky. The rules of reciprocity in such a replacement of a detector by an “equivalent transmitter” located in a lossy (open) structure (a bolometric cavity coupled via the feed horn with the outer space) are not obvious and usually ignored. A conventional simplistic approach used in this problem may cause errors in the design of such systems. By considering simple, analytically solvable models that simulate bolometric detectors surrounded by some structures, we find the rules of reciprocity providing the necessary equivalence in replacing the receiver by an appropriate transmitter as needed for the rigorous simulations of infrared and submillimetre-wave bolometric systems.  相似文献   

20.
固体微/纳米尺度传热理论研究进展   总被引:3,自引:0,他引:3  
随着半导体技术的飞速发展,器件的尺寸已进入到微/纳米尺度。由于量子效应、表面及界面效应,使得微尺度下的热物性与宏观尺度下有了明显的区别。人们针对微观传热领域的特点,发展了声子玻尔兹曼传输方程、分子动力学等方法,取得了一定的成果,但仍存在不少问题。一些基础概念问题,特别是非平衡态下的局域温度的定义,有待澄清。本文主要回顾近年来微/纳米尺度传热在理论和数值模拟方面的进展,以及目前所面临的挑战和问题。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号