共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Uhlig J.C. Lemm A. Weiguny 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):343-354
Abstact: Three variants of mean field methods for atomic and nuclear reactions are compared with respect to both conception and applicability:
The time–dependent Hartree–Fock method solves the equation of motion for a Hermitian density operator as initial value problem,
with the colliding fragments in a continuum state of relative motion. With no specification of the final state, the method
is restricted to inclusive reactions. The time–dependent mean field method, as developed by Kerman, Levit and Negele as well
as by Reinhardt, calculates the density for specific transitions and thus applies to exclusive reactions. It uses the Hubbard–Stratonovich
transformation to express the full time-development operator with two–body interactions as functional integral over one–body
densities. In stationary phase approximation and with Slater determinants as initial and final states, it defines non–Hermitian,
time–dependent mean field equations to be solved self–consistently as boundary value problem in time. The time–independent
mean field method of Giraud and Nagarajan is based on a Schwinger–type variational principle for the resolvent. It leads to
a set of inhomogeneous, non-Hermitian equations of Hartree–Fock type to be solved for given total energy. All information
about initial and final channels is contained in the inhomogeneities, hence the method is designed for exclusive reactions.
A direct link is established between the time–dependent and time–independent versions. Their relation is non–trivial due to
the non–linear nature of mean field methods.
Received: 7 January 1998 / Revised version: 20 April 1998 相似文献
2.
A validated simple, rapid, and selective spectrofluorimetric method was developed for the determination of some antihistaminic
H1 receptor antagonist drugs namely ebastine (EBS), cetirizine dihydrochloride (CTZ), and fexofenadine hydrochloride (FXD).
The method is based on the reaction of the cited drugs with some Π acceptors namely p-chloranilic acid (CLA), tetracyanoethylene
(TCNE), and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) to give highly fluorescent derivatives. The fluorescence intensity—concentration plots were rectilinear
over the concentration ranges of 0.2–3.0, 0.2–2.5 and 0.15–2.0 μg/ml for EBS with CLA, DDQ, and TCNE respectively; 0.5–7.0,
0.5–6.0, and 0.2–4.0 μg/ml for CTZ with the previously mentioned reagents, and 0.2–3.5, 0.5–6.0, and 0.2–3.5 μg/ml for FXD.
The factors affecting the formation of the reaction products were carefully studied and optimized. The method was applied
for the determination of the studied drugs in their dosage forms. The results obtained were in good agreement with those obtained
by the comparison methods. Reactions Stoichiometries of the complexes formed between the studied drugs and Π acceptors were
defined by the Job’s method of the continuous variation and found in 1:1 in all cases. 相似文献
3.
A generalization of the Roothaan–Bagus method (Roothaan–Hartree–Fock atomic theory) on atoms with open shells of identical
symmetry is given. Using orbital exponents of Slater-type atomic orbitals optimized with high accuracy by methods for the
minimization of the first and second orders, energy values for atoms with two open s-type shells are calculated within the
limits of the Roothaan–Hartree–Fock atomic theory. 相似文献
4.
In this paper, an extended multiple (G′/G)-expansion method is proposed to seek exact solutions of nonlinear evolution equations. The validity and advantages of the
proposed method is illustrated by its applications to the Sharma–Tasso–Olver equation, the sixth-order Ramani equation, the
generalized shallow water wave equation, the Caudrey–Dodd–Gibbon–Sawada–Kotera equation, the sixth-order Boussinesq equation
and the Hirota–Satsuma equations. As a result, various complexiton solutions consisting of hyperbolic functions, trigonometric
functions, rational functions and their mixture with parameters are obtained. When some parameters are taken as special values,
the known double solitary-like wave solutions are derived from the double hyperbolic function solution. In addition, this
method can also be used to deal with some high-dimensional and variable coefficients’ nonlinear evolution equations. 相似文献
5.
E. Hammarén K.W. Schmid A. Faessler 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):371-377
Abstact: The solution of the Hartree–Fock–Bogoliubov problem with restoration of the broken symmetries before the variation has been
generalized for the use of totally unrestricted quasi–particle determinants. With this method doubly–even, doubly–odd and
odd nuclei can be treated on the same footing. Comparison with the results of complete shell–model diagonalizations shows
that already one–determinant representations yield a very good approximation to the exact solutions even in the middle of
the 1s0d shell. The problem is especially suited for numerical implementation on parallel computers. First tests show a linear
dependence of the inverse CPU time with the number of processors used.
Received: 26 February 1998 / Revised version: 8 May 1998 相似文献
6.
Nonlinear optical properties of photonic crystal heterostructures with embedded n–i–p–i superlattices are investigated. Self-consistent calculations of the transmission and reflection spectra near the defect mode
are performed using the transfer-matrix method and taking into account the gain saturation. Analysis of features and output
characteristics is carried out for one-dimensional photonic crystal heterostructure amplifiers in the GaAs–GaInP system having
at the central part an active “defect” from doubled GaAs n–i–p–i crystal layers. The gain saturation in the active layers in the vicinity of the defect changes the index contrast of the
photonic structure and makes worse the emission at the defect mode. Spectral bistability effect, which can be exhibited in
photonic crystal heterostructure amplifiers, is predicted and the hysteresis loop and other attending phenomena are described.
The bistability behavior and modulation response efficiency demonstrate the potential possibilities of the photonic crystal
heterostructures with n–i–p–i layers as high-speed optical amplifiers and switches.
相似文献
7.
In this paper a new method is described for determining the non-diffractive part of the inelastic proton–proton cross section,
at the LHC centre of mass energy of 14 TeV. The method is based on counting the number of inelastic proton–proton interactions
in the collision regions. According to a preliminary investigation, this measurement will be best suited for the initial low
luminosity phase of the LHC. Knowledge of the proton–proton luminosity is likely to dominate the measurement uncertainty.
PACS 13.85.Hd 相似文献
8.
This paper shows some improvements and new results of calibration of Chinese solar radio spectrometer by analyzing the daily
calibration data recorded in the period of 1997–2007. First, the calibration coefficient is fitted for three bands (1.0–2.0
GHz, 2.6–3.8 GHz, 5.2–7.6 GHz) of the spectrometer by using the moving-average method confined by the property of the daily
calibration data. By this calibration coefficient, the standard deviation of the calibration result was less than 10 sfu for
95% frequencies of 2.6–3.8 GHz band in 2003. This result is better than that calibrated with the constant coefficient. Second,
the calibration coefficient is found in good correlation with local air temperature for most frequencies of 2.6–3.8 GHz band.
Moreover, these results are helpful in the research of the quiet solar radio emission. 相似文献
9.
K. V. Kalinina S. S. Molchanov N. D. Stoyanov A. P. Astakhova Kh. M. Salikhov Yu. P. Yakovlev 《Technical Physics》2010,55(2):258-263
An optical method for measuring the water and oil content using mid-IR (1.6–2.4 μm) LEDs and a wideband photodiode is suggested
for the first time. This method is developed based on the absorption spectra of pure water, dewatered oil, and water—oil emulsions
(cut oil) with different content of water and uses 10 types of LEDs in the spectral range 1.6–2.4 μm. It is shown that pure
water heavily absorbs the LED radiation in the spectral range 1.85–2.05 μm, oil absorbs in the range 1.67–1.87 μm, and the
LED radiation with a maximum at 2.20 μm is equally weakly absorbed by water and oil. An optical cell of the water-and-oil
analyzer is designed on the basis of a three-element diode array with radiation maxima at 1.65 (detection of oil), 1.94 (detection
of water), and 2.2 μm (reference signal) wideband photodiode covering the spectral range 1.3–2.4 μm. A calibration curve is
derived that represents the dependence of the water concentration in oil on the amplitude of the reduced signal obtained by
processing three signals from the LEDs. This optical method of measuring the water content in oil underlies a portable analyzer
making possible online measurements directly in an oil well. 相似文献
10.
M. M. Seleim M. S. Abu-Bakr E. Y. Hashem A. M. El-Zohry 《Journal of Applied Spectroscopy》2009,76(4):554-563
A highly sensitive and selective first-derivative spectrophotometric method has been developed for the determination of aluminum
and iron in mixtures. The method is based on the formation of the binary complexes of aluminum and iron with Alizarin yellow
R (AYR) 5-[4-nitrophenylazo]salicylic acid at pH 2.0 with molar absorptivity of 1.1∙104 l⋅mol–1⋅cm–1. A zero-crossing technique is found suitable for the direct measurement of the first derivative value at the specified wavelength,
so aluminum and iron were thus determined in the ranges 1.3–5.4 μg/ml and 1.1–8.3 μg/ml, respectively, in the presence of
both components. The detection limits were found to be 1.4 ng/ml for aluminum and 2.8 ng/ml for iron. The relative standard
deviations were in all cases less than 1.5%. The proposed method was successfully applied for the simultaneous determination
of aluminum and iron in certified reference aluminum samples. 相似文献
11.
Considering the unfixed background space-time and self-gravitational interaction, we review the Hawking radiation of the Kerr–Newman
black hole by Hamilton–Jacobi method. The result shows the tunneling probability is related to the change of Bekenstein–Hawking
entropy and the radiation spectrum deviates from the precisely thermal one, which is in accordance with Parikh and Wilczek’s
result and gives another method to study the Hawking radiation of the black hole. 相似文献
12.
Quantum mechanics equations for a system of the Bose particles are represented in the form of material field equations. A
nonlinear equation for the macroscopic one-particle wave function is derived. Using the Krylov–Bogolyubov–Mitropol’skii method
for equations in partial derivatives, nonlinear waves in the Bose–Einstein condensate are investigated. In the cubic approximation,
dispersion relations for waves are derived and nonlinear frequency shift is calculated in the first- and third-order approximations
for the interaction radius. 相似文献
13.
T. Hjelt K.W. Schmid E. Hammarén A. Faessler 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):201-208
Total binding energies and yrast energy spectra of three selected 1p0f–nuclei have been calculated using an unrestricted
Hartree–Fock–Bogoliubov approach with symmetry–projection before the variation. The full 1p0f–shell has been used as single–particle
basis and the semi–empirical FPD6 interaction as effective Hamiltonian. The results are compared to those of truncated shell–model
calculations performed with the OXBASH code. In the middle of the 1p0f–shell the variational method yields energy gains up
to 4.5 MeV and thus proves to be far superior than the conventional truncation methods at least if in the latter only up to
about 13000 configurations for each spin–isospin combination are admitted.
Received: 15 September 1999 相似文献
14.
Ansgar Jüngel José Luis López Jesús Montejo–Gámez 《Journal of statistical physics》2011,145(6):1661-1673
A quantum Navier–Stokes system for the particle, momentum, and energy densities is formally derived from the Wigner–Fokker–Planck
equation using a moment method. The viscosity term depends on the particle density with a shear viscosity coefficient which
equals the quantum diffusion coefficient of the Fokker–Planck collision operator. The main idea of the derivation is the use
of a so-called osmotic momentum operator, which is the sum of the phase-space momentum and the gradient operator. In this
way, a Chapman–Enskog expansion of the Wigner function, which typically leads to viscous approximations, is avoided. Moreover,
we show that the osmotic momentum emerges from local gauge theory. 相似文献
15.
Highly precise calculations of analytical Hartree–Fock orbitals and energies have been performed within the limits of the
Roothaan–Hartree–Fock atomic theory (Roothaan–Bagus method) for all open p-shell atoms of the Periodic Table. They were calculated
in an algebraic approach using Slater-type atomic orbitals (AOs) as basis functions. Nonlinear parameters (orbital exponents)
of AOs were optimized with exceptional accuracy by second-order methods. As a result, it was possible to satisfy exactly the
virial relation (10–14–10–17) with calculated atomic term energies being close to the Hartree–Fock limit. 相似文献
16.
N. A. Torkhov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(1):45-58
With the concept of fractal surfaces, the influence of the relief of the interface (roughness) and the heterogeneity of the
potential barrier on the behavior of the current–voltage and capacity–voltage characteristics of the metal–semiconductor electric
contacts with the Schottky barrier has been studied. The necessary and satisfactory conditions for the accurate relative measurements
of the surface relief have been found with the mathematical apparatus of the Hausdorff–Besikovitsch fractional dimensionality
2 D
f3. It is shown that due to the fractal geometry the relative change of the real area of the interface of the metal–semiconductor
contacts with the Schottky barrier is proportional to the ratio of their linear dimensions in the 4-Df power. This is considerably slower than the change of the dimensions of the topological areas of their contact windows. The
method to determine the fractal dimensionality of the real interface of the metal–semiconductor electric contacts with the
Schottky barrier from the current–voltage and capacity–voltage characteristics has been developed. 相似文献
17.
A highly sensitive H-point standard addition method (HPSAM) was investigated for identification of dopamine and ascorbic acid in some synthetic and pharmaceutical samples in an aqueous medium at pH 9.2 using a universal buffer. The most suitable wavelengths for dopamine and ascorbic acid detection are 260:271 nm and 248:270 nm respectively. Recovery values are between 99.0–101 %. Also, the effect of most common interferents was studied. Detection ranges for dopamine and ascorbic acid are 2·10–6–5·10–5 M and 6·10–6–3·10–5 M respectively with an RSD range between 1.3 and 2.0 %. The method was used to determine both reagents in real and synthesized samples. 相似文献
18.
The massive particles’ Hawking radiation from a spherically symmetric static black hole is investigated with Parikh-Wilczek
method, Hamilton–Jacobi method and Damour–Ruffini’s method. When energy conservation is considered, the same result can be
concluded that the radiation spectrum is not precisely thermal. The corrected spectrum is consistent to the underlying unitary
quantum theory, which can be used to explain the information loss paradox possibly.
相似文献
19.
A. M. Liudchik 《Journal of Applied Spectroscopy》2009,76(2):273-279
A theoretical rationale is presented for a variational method for determining the extraterrestrial constant of a solar ultraviolet
spectrophotometer for measuring total column ozone in the atmosphere. We have established the connection between this method
and the familiar Langley method for calibration of extraterrestrial constants of solar spectrophotometers.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 291–297, March–April, 2009. 相似文献
20.
A method is proposed for determining the thickness of thin (0.1–5.0 μm) polymer layers and coatings by means of infrared frustrated
total internal reflection (FTIR) spectroscopy. This method is based on an analytic expression derived for the dependence of
the intensities of absorption bands in IR FTIR spectra on the thickness of a polymer layer. The method is tested on model
samples consisting of a thick film of polyethylene terephthalate with a layer of different thicknesses of polystyrene deposited
on it. The advantage of this method is the ability to determine the thickness of thin polymer layers deposited on bulk or
opaque polymer substrates.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 881–885, November–December, 2008. 相似文献