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81.
简析"静止液体内部压强公式验证"实验的设计策略 总被引:1,自引:1,他引:0
“静止液体内部压强公式验证”在现行教材中有两种实验方法。通过分析实验的设计策略,说明其作用、效果及操作上的困难,指出合理的与不合理诸因素,从而提出改进实验的方法,化难为易,提高实验教学效果。 相似文献
82.
Electronic properties of model quantum-dot structures in zero and finite magnetic fields 总被引:1,自引:0,他引:1
H. Saarikoski E. Räsänen S. Siljamäki A. Harju M.J. Puska R.M. Nieminen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):241-252
We have computed electronic structures and total energies of circularly confined two-dimensional quantum dots and their lateral
dimers in zero and finite uniform external magnetic fields using different theoretical schemes: the spin-density-functional
theory (SDFT), the current-and-spin-density-functional theory (CSDFT), and the variational quantum Monte Carlo (VMC) method.
The SDFT and CSDFT calculations employ a recently-developed, symmetry-unrestricted real-space algorithm allowing solutions
which break the spin symmetry. Results obtained for a six-electron dot in the weak confinement limit and in zero magnetic
field as well as in a moderate confinement and in finite magnetic fields enable us to draw conclusions about the reliability
of the more approximative SDFT and CSDFT schemes in comparison with the VMC method. The same is true for results obtained
for the two-electron quantum dot dimer as a function of inter-dot distance. The structure and role of the symmetry-breaking
solutions appearing in the SDFT and CSDFT calculations for the above systems are discussed.
Received 16 October 2001 and Received in final form 17 January 2002 相似文献
83.
84.
Based on the theory of calculus of variation, some suffcient conditions are given for some Euler-Lagrangcequations to be equivalently represented by finite or even infinite many Hamiltonian canonical equations. Meanwhile,some further applications for equations such as the KdV equation, MKdV equation, the general linear Euler Lagrangeequation and the cylindric shell equations are given. 相似文献
85.
We study the propagation of the light mesons σ,ω,ρ, and a0(980) in dense hadronic matter in an extended derivative scalar coupling model. Within the scheme proposed it is possible
to unambiguously define effective density-dependent couplings at the Lagrangian level. We first apply the model to study asymmetric
nuclear matter with fixed isospin asymmetry, and then we pay particular attention to hypermatter in β-equilibrium. The equation
of state and the potential contribution to the symmetry coefficient arising from the mean-field approximation are investigated.
Received: 16 October 2001 / Accepted: 10 January 2002 相似文献
86.
S. Zschocke G. Plunien G. Soff 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):147-156
The renormalization method of Bogoljubov-Parasiuk-Hepp-Zimmermann (BPHZ) is used in order to derive the renormalized energy
shift due to the gauge invariant K?llén-Sabry diagram of the two-photon vacuum polarization (VPVP) as well as the self energy
vacuum polarization S(VP)E beyond the Uehling approximation. It is outlined, that no outer renormalization is required for
the two-photon vacuum polarization and that only the inner renormalization has to be accomplished. It is shown that the so-called
nongauge invariant spurious term is absent for a wide class of vacuum polarization (VP) diagrams if one applies the widely
used spherical expansion of bound and free-electron propagator. This simplifies significantly calculations in bound state
quantum electrodynamics. As one result of our paper the use of the BPHZ-approach in bound state QED is established.
Received 28 September 2001 相似文献
87.
A. Shaporenko A. Terfort M. Grunze M. Zharnikov 《Journal of Electron Spectroscopy and Related Phenomena》2006
Analysis of photoemission spectra of complex thioaromatic self-assembled monolayers (SAMs) requires the knowledge and understanding of such spectra for the basic systems. Keeping this goal in mind, synchrotron-based high-resolution X-ray photoelectron spectroscopy was used to characterize SAMs formed from the simplest thioaromatic compounds, namely thiophenol, 1,1′-biphenyl-4-thiol and 1,1′;4′,1″-terphenyl-4-thiol on evaporated Au(1 1 1) and Ag(1 1 1) substrates. The acquired S 2p and C 1s spectra were analyzed in terms of fine structure and initial and final state effects in the photoemission process. The assignment of the individual spectral features was considered in detail. Conclusions on quality and chemical and structural homogeneity of the investigated SAMs were derived. 相似文献
88.
A new sample business survey for agriculture, the REA survey, and a project of integration with the FADN network (RICA in
Italy) have significantly changed the production of statistical information nowadays available with reference to the agricultural
sector. On the basis of this relevant information, new economic analyses are being developed on farms’ performance, agricultural
households’ income and the Common Agricultural Policy (CAP). In this paper the authors estimate the relationship between the
levels of variables of interest and their sampling errors using models in order to improve the accessibility of the information
on estimates accuracy to the final users (agricultural analysts, policy makers).
The paper is the result of a joint research of the three authors. Sections 1–3 and 6 by Pizzoli, Sects. 4 and 5 by Rondinelli,
Sect. 7 by Filiberti, conclusions joint to the three authors. 相似文献
89.
90.
Maria Mamalui Chien-Yueh Huang 《Physica E: Low-dimensional Systems and Nanostructures》2004,22(4):912-920
We present the theoretical study of the effect of external random field characterized by a Gaussian probability distribution function on the continuous phonon spectrum of one-dimensional (1D) chain, based on the Jacobian matrix method. The cumulative effect of the random field and simple isotopic defect is studied analytically and numerically. The Gaussian random field removes a square-root divergence appearing in the phonon spectrum of ideal 1D chain. The impurity phonon DOS shows strong dependence on the variance and the mean of the random field and exhibits very different behavior from the non-random case: the continuous spectrum is expanded and the δ-peak, describing discrete impurity vibrations in the non-random chain with the impurity, falls into a continuous zone. 相似文献