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1.
"牛顿由于发现了万有引力定律而创立了科学的天文学,由于进行了光的分解而创立了科学的光学,由于建立了二项式定律和无穷理论而创立了科学的数学,由于认识了力的本性而创立了科学的力学."恩格斯的这段话很好地总结了牛顿的科学业绩.为了纪念牛顿在科学上的伟大建树,许多国家发行了多枚一套的邮票.  相似文献   

2.
冉晓红 《物理通报》2011,40(11):58-59
针对教材中自由落体实验操作的不稳定性,改进了实验,增强了实验操作的稳定性,提高了实验的精确度,减少了实验次数,节省了时间,提高了课堂效率.  相似文献   

3.
章义朋 《物理学进展》2011,1(2):280-303
本文系统地讨论了大统一理论的来龙去脉。回顾了大统一理论的发展历史,讨论了其发展现状及存在问题,指出了进一步发展的方向。本文重点介绍了SU(5)和SO(10)两个模型,讨论了Higgs场、规范等级、渐近自由、重正化等问题。文章进而讨论了一些有趣问题,比如提供了对宇宙重子起源的解释、计算了质子衰变寿命、论述了B-L是否守恒以及讨论了中子和中微子可能有的振荡现象等。  相似文献   

4.
本文系统地讨论了大统一理论的来龙去脉。回顾了大统一理论的发展历史,讨论了其发展现状及存在问题,指出了进一步发展的方向。本文重点介绍了SU(5)和SO(10)两个模型,讨论了Higgs场、规范等级、渐近自由、重正化等问题。文章进而讨论了一些有趣问题,比如提供了对宇宙重子起源的解释、计算了质子衰变寿命、论述了B-L是否守恒以及讨论了中子和中微子可能有的振荡现象等。  相似文献   

5.
物理实验开放式教学初探   总被引:23,自引:3,他引:20  
周岚  朱蜀梅  王伟 《物理实验》2002,22(1):25-28
网上预约实验实现了各校区资源共享、教学内容有弹性满足了不同层次学生的需求,开放式教学增强了教师的责任心,激发了学生学习的主动性和积极性,提高了实验教学质量,充分利用了实验室的资源,取得了较好的效果。  相似文献   

6.
HLS直线加速器调制器系统设计与改造   总被引:1,自引:0,他引:1  
尚雷  罗雪芳  王炜  洪钧  陆业明  张毅  赵枫 《中国物理 C》2003,27(12):1133-1137
介绍了合肥同步辐射光源速调管调制器改造项目.在新的设计中采用了开关型恒流PFN充电电源,计算了充电参数,建立了主放电回路的仿真模型,重点分析了电路中反向电压问题,依据仿真结果及分析设计了反向保护电路.给出了运行中的主要波形.最后介绍了新的调制器控制系统.  相似文献   

7.
光电信息工程专业建设的探索与实践   总被引:1,自引:0,他引:1  
介绍了天津大学光电信息工程专业建设的改革与实践。构建了新的课程体系,强化了教材建设,改革了实验和实践教学环节,加强了师资队伍建设,提高了专业建设水平和人才培养质量。  相似文献   

8.
采用控制环量方法设计了一单级涡轮。该方法打破了传统的设计规律,为验证该方法的可靠性进行了模型试验。在宽广的范围内测定了总特性;在设计点附近作了沿叶高效率分布及动叶进、出口速度三角形的测定。本文给出了主要试验结果并作了简要分析。结果表明基本上达到了设计要求,控制环量设计的主要特征得到了验证,该方法基本可行。  相似文献   

9.
介绍了一种新型小视场、高精度的双波段扫描辐射计。描述了系统的特点,分析了系统的总体方案。介绍了系统的工作原理,对系统的NETD进行了估算,对其探测器的选择、光学系统设计、调制系统设计、扫描机构设计、信号处理等方案进行了详细论述,对系统的标定和测量原理进行了分析,并给出了相应的计算公式。给出了系统的检测结果。  相似文献   

10.
王洪伟阮萍  徐广洲 《光子学报》2014,38(12):3226-3229
介绍了基础激励下机构随机振动响应的理论与分析方法.利用有限元分析软件ANSYS建立了某空间望远镜相关跟踪系统摆镜的有限元模型,并进行了随机振动响应分析.通过分析考察了其承受动力学环境的能力.对计算结果进行了分析.指出了现有结构中的薄弱环节,提出了改进方案,为摆镜的设计提供了重要参考依据.  相似文献   

11.
外电场作用下FO分子的特性研究   总被引:1,自引:1,他引:0  
采用密度泛函的B3P86方法,以6-311+G(3df)为基函数优化得到不同外电场下FO基态分子的稳定几何结构、键长、总能量、HOMO能级、LUMO能级、费米能级、能隙、红外光谱和谐振频率.结果表明,分子结构与外电场有着强烈的依赖关系,且对电场方向的依赖呈现出不对称性;随着正向电场的增大,HOMO能级、LUMO能级和费米能级是减小的,能隙是先增大后减小;红外光谱和谐振频率是增大的,而频率间隔是不断减小的.  相似文献   

12.
理论分析和实验结果都证明:He-Ne激光器的旁侧光谱强度与激光输出功率有着密切的关系.对于3S2能级,有激光输出的粒子数少于无激光输出的粒子数,而对于2P4能级,有激光输出的粒子数多于无激光输出的粒子数.对于3S2和2P4能级都有如下关系:有无激光输出的粒子数差随激光输出功率单调变化,前单调上升,后单调下降;当激光输出功率增大到一定值时,粒子数差变化很小。  相似文献   

13.
We have measured the photoemission spectra both for CO adsorbed on Ni and Pd films and for gas phase CO over a wide photon energy range. The comparison of these two sets of measurements lead to the following interpreation of the two observed electronic energy levels of molecularly adsorbed CO. The lower binding energy CO-induced level corresponds to the 1π gas phase level with some admixture of the 5σ level and the higher binding energy level corresponds to the 4σ gas phase level. The hω-dependence of the photoionization cross section is shown to play a predominant role in determining the surface sensitivity.  相似文献   

14.
There has been much discussion in the literature concerning the definition of a suitable reference level for electron binding energies in solids and adsorbed species. The reference level in molecular photoelectron spectroscopy is the vacuum level at infinity; and, in order to calculate the total energy of the system, it is also the appropriate reference level for electron binding energies in solids. We show that for solids and adsorbates the vacuum level is not a chemically useful reference level. This is because the absolute binding energy is affected by electrostatic potentials which are unrelated to the local chemical bonding. It is concluded that there is no experimental energy level, to which adsorbate binding energies can be referenced, which allows one to make an absolute measurement of binding energy shifts due to surface interaction. Approaches to obtaining chemically meaningful binding energies from the photoelectron spectra of adsorbates are discussed.  相似文献   

15.
V S Ramamurthy  S S Kapoor 《Pramana》1978,10(3):319-327
A method is proposed to deduce the shell correction energy corresponding to the fission transition state shape of nuclei in the mass region around 200, from an analysis of the first chance fission values of the ratio of fission to neutron widths, (Γ f n )1. The method is applied to the typical case of the fissioning nucleus212Po, formed by alpha bombardment of208Pb. For the calculation of the neutron width, the level densities of the daughter nucleus after neutron emission were obtained from a numerical calculation starting from shell model single particle energy level scheme. It is shown that with the use of standard Fermi gas expression for the level densities of the fission transition state nucleus in the calculation of the fission width, an apparent energy dependence of the fission barrier height is required to fit the experimental data. This energy dependence, which arises from the excitation energy dependence of shell effects on level densities, can be used to deduce the shell correction energy at the fission transition state point. It is found that in the case of212Po, the energy of the actual transition state point is higher than the energy of the liquid drop model (LDM) saddle point by (3 ± 1) MeV, implying significant positive shell correction energy at the fission transition state. Further, the liquid drop model value of level density parametera is found to be a few per cent smaller for the saddle point shape as compared to its spherical shape.  相似文献   

16.
A new method for the derivation of the density of final states in the nuclear equilibration process, based on the Darwin-Fowler method of statistical physics, is suggested. This method is generally valid for an arbitrary energy level scheme and includes the Pauli principle. When it is applied to the equidistant-spacing energy level scheme, the results are very close to those derived by Oblo?inský et al.  相似文献   

17.
The density of stationary quasilocal states of the continuous spectrum arising due to the presence of defects in a medium with spatial dispersion is analyzed. The influence of plane and point defects on the specific features of the spectral quasilocal state density is studied. It is demonstrated that the spectral density has a strict maximum caused by the quasilocal energy level arising in the system. For a plane defect, the energy of the quasilocal level is displaced from the resonance energy of total quasi-particle reflection from the defect. The influence of the quasilocal state on the electronic heat capacity in the presence of the point defect is analyzed.  相似文献   

18.
The one-shell SU(3) energies are given and the corresponding level density is calculated approximately by use of a distribution function for the SU(3) quantum numbers. The calculation is extended to include many shells by a renormalization procedure and an effective one-shell interaction. The traditional level density is then obtained from the related mean-field hamiltonian which corresponds to a deformed harmonic oscillator potential. Various rotational enhancement factors are considered. Numerical results, are obtained and comparisons between the SU(3) and the traditional level densities allow the first computation of the energy dependence of the rotational enhancement factor. A transition from axial to spherical level density is found. A simple parametrization is suggested in terms of a deformation-dependent half-value energy and a transition width.  相似文献   

19.
基于密度泛函理论的第一性原理方法,本文旨在探索确定绝缘体-金属转变临界浓度的理论计算方法.以Co重掺杂Si为研究对象,构建并计算了10个Co不同掺杂浓度模型的晶体结构、杂质形成能及其电子性质.发现在Co掺杂Si体系的带隙中形成了杂质能级,杂质能级的位置和宽度随着Co浓度的增加呈线性变化.当Co掺杂浓度较高时杂质形成能逐渐稳定,且杂质能级穿过费米能级使体系表现出金属性.综合杂质形成能的变化趋势,以及杂质能级极小值与费米能级间的距离条件,可预测出发生绝缘体-金属转变的Co掺杂浓度为2.601Wingdings 2MC@10~(20) cm~(-3),与实验结果相一致.上述两条依据应用于S重掺杂Si体系和Se重掺杂Si体系同样成立.  相似文献   

20.
We study the radiative energy level shifts of a two-level atom in dipole coupling to the derivative of a massless scalar quantum field in a spacetime with a perfectly reflecting boundary, and calculate the contributions of vacuum fluctuations and radiation reaction to the level shift. It is found that the energy level shift of the excited state is an oscillating function of the atom's distance from the boundary and it can either be positive or negative, while that of the ground state is always positive. The most remarkable feature is that the energy level shift of the ground state behaves like 1/z^4 when the atom's distance from the boundary, z, is very large as compared to the transition wavelength of the atom, while it behaves like 1/z^3 when z is very small  相似文献   

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