Vol. 50, No. 6 (2001)
2001, 50 (6): 1001-1005. doi: 10.7498/aps.50.1001
The conservation laws of relativistic variable mass systems were studied. The d'Alembert-Lagrange principle of relativistic variable mass system are given. By using invariant condition of the d'Alembert-Lagrange principle under infinitesimal transformations, the conditions and forms under which the conserved quantities of the system do exist were obtained. An example is given to illustrate the application of the result.
2001, 50 (6): 1006-1010. doi: 10.7498/aps.50.1006
A lattice Boltzmann equation model of D2Q13 form in two-dimensional space is developed according to the conservative criteria of mass, momentum and energy. The equations of fluid dynamics can be derived from the D2Q13 model, and the momentum equation is obviously improved in the viscosity transport term by comparison with Navier-Stokes equation . The shock wave reflection phenomena on the bevel edge and edge angle have been simulated by using the model so that the results and the numerical stability are very good. It is shown that the model is valid both in theory and in numerical experiment.
2001, 50 (6): 1011-1014. doi: 10.7498/aps.50.1011
Quantization of RLC circuit is given and described by a double-wave function. A comparison between classical limit result and those of classical theory is made.
2001, 50 (6): 1015-1018. doi: 10.7498/aps.50.1015
Based on the Klein-Gordon equations on the background of the Reisser-Nordstrom spacetime, we calculate the free energy and entropy of a scalar field near a black hole by improved brick-wall methodmembrane model. It is obtained that the entropy of the scalar field consists of two parts. As the entropy is an extensive quantity, we obtain that the black hole entropy comes from two thermodynamical systems. And the new Bekenstein-Smarr formula is given. It is shown that the entropy expressed by two thermodynamical subsystems approaches zero when the radiation temperature of the black hole approaches absolute zero. This obeys Nernst theorem. It can be taken as Planck absolute entropy of a black hole.
2001, 50 (6): 1019-1023. doi: 10.7498/aps.50.1019
The problem of signal extraction from received data contaminated with strong chaotic interference has been investigated and a novel approach to this problem is proposed based on the geometry of chaotic interference. According to this approach, chaotic attractor is first reconstructed from the received data, then in the way of projecting chaotic interference and harmonic signals into the local tangent space and its transverse space of the manifold in which the attractor lies, the two signals are successfully separated. Excellent results were achieved from the computer simulation experiments, which verify the effectiveness of the approach.
CONTROLLING CHAOTIC BEHAVIOUR IN ERBIUM-DOPED FIBER DUAL-RING LASER WITH LINEAR TIME-DELAYED FEEDBACK
2001, 50 (6): 1024-1027. doi: 10.7498/aps.50.1024
A method of chaos control with linear time-delayed feedback based on the scheme of linear feedback is presented in this paper. By using the method, we propose a scheme of controlling chaotic behavior in erbium-doped fiber dual-ring laser with one polarized mode. The results of the computer simulation show that controlling the chaos into the stable states could be realized by adjusting the feedback coefficient and delay time.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
In this paper we present an improved double Q2 rescaling model.Based on this condition of the nuclear momentum conservation,we have found a Q2 rescaling parameters' formula of the model,where we have established the connection between the Q2 rescaling parameter ξi(i=v,s,g) and the mean binding energy in nucleus.By using this model,we coned explain the experimental data of the EMC effect in the whole x region,the nuclear Drell-Yan process and J/Ψ photoproduction process.
2001, 50 (6): 1035-1039. doi: 10.7498/aps.50.1035
The energy levels of the odd-odd nucleus 84Y are calculated by using the axially symmetric rotor plus quasiparticles model.The two standard statistical tests of Random-Matrix Theory such as the distribution function p(s) of the nearest-neighbor level spacings (NNS) and the spectral rigidity Δ3 are used to explore the statistical properties of the energy levels.By analyzing the properties of p(s) and Δ3 under various conditions, we find that the quasiparticle features mainly affect the statistical properties of the odd-odd nucleus 84Y through the recoil term and the Coriolis force in this theoretical mode, and that the chaotic degree of the energy levels decreases with the decrease of the Fermi energy and the energy-gap parameters.The effect of the recoil term is small while the Coriolis force plays a major role in the spectral structure of 84 Y.
2001, 50 (6): 1040-1045. doi: 10.7498/aps.50.1040
Within the framework of isospin-dependent quantum molecular dynamics model,isotopic distributions in the reactions of 112Sn+112Sn and 124Sn+124 Sn at 40 and 100 MeV/u are investigated.It is found that the isotopic distribution has a significant isospin effect at 40 MeV/u,but the isospin effect disppears at 100 MeV/u.By investigating mechanical and chemical instabilities at different energies,we find that the energy dependence of isospin effects on isotopic distributions results from the competition between mechanical instabilities and chemical instabilities at different energies.
CLASSICAL AREA OF PHENOMENOLOGY
2001, 50 (6): 1046-1051. doi: 10.7498/aps.50.1046
From three respects such as mathematical principle,geometric stratification and numerical calculation,we have studied the convergence of rigorous coupled-wave approach (RCWA) in solving the grating diffraction problems.The approaches which can be applied to improve the convergence of RCWA are proposed.It is found that,for different cases of grating,the major factors affecting the convergence of RCWA are different.Therefore,the improving methods should be practically chosen for concrete case of grating.
2001, 50 (6): 1052-1057. doi: 10.7498/aps.50.1052
In this paper,the theory and numerical method for the propagation of a pulse wave through a strong turbulence medium are presented.According to the variousy wave structure function,we have computed the two-frequency cross correlation function,shown the numerical value of the pulse broadening and the scintillation index in the screen and extended medium respectively,and made some comparison with the observation data.
2001, 50 (6): 1058-1063. doi: 10.7498/aps.50.1058
The second-,fourth-and sixth-order fluctuations have been discussed by making use of- SU-(2)Lie algebra.On the basis of higher-order uncertainty relation,the definition of higher-order squeezing for the fluctuations of angular momentum has been put forward.In particular,the second-,fourth-and sixth-order squeezing in atomic coherent states are investigated.These methods and definition can be used for studying much higher-order squeezing.The higher-order squeezing can be generalized to the fluctuations of atomic variances thereby.
2001, 50 (6): 1064-1069. doi: 10.7498/aps.50.1064
The dynamical properties of two coupled-atoms Raman-interacting with a single-mode squeezed vacuum field are studied by means of quantum theory.Using the numerical method,the relation between the quantum properties of the atoms and the coupling parameter and initial state of the system is discussed.
A set of laser oscillations of four strontium atom spectral lines simultaneity have been obtained, through high-repetition-frequency pulsed discharge in mixed gases of strontium vapor and helium buffer gas. The corresponding wavelengths with the transitions from compound three-energy levels 4d·3D3,2,1 to 5p·3P02,1,0 are 2.92μm, 3.01μm, 2.69μm and 2.60μm respectively,their ratios of intensities are 5∶4∶4∶1 and the total average laser power is 10mW.As far as we know,the laser spectral lines have never been reported except 3.01μm.On the basis of analyzing characteristics of corresponding energy levels and experimental phenomena,the action mechanism is discussed primarily.We suggest the classification of the spectral lines to be named as M-M transition laser.
2001, 50 (6): 1075-1079. doi: 10.7498/aps.50.1075
Factors are analyzed theoretically which influence gain saturation and output pulse shape in “SHENGGUANG II” main amplifier.Using a set of eigenvalues,we discuss the differences among the factors' influences upon the output pulse shape.A scheme is proposed to control output pulse shape,which could adjust the output energy continuously in some range at the same time.
2001, 50 (6): 1080-1086. doi: 10.7498/aps.50.1080
Using the ray-tracing method,we demonstrate that a grating-telescope stretcher is the conjugation of a grating pair compressor.We present an analytical formula for calculating the phase dispersions of the grating-telescope stretcher.The computer simulation with the formula demonstrates that there exists an optimal material dispersion for an amplification system,with which we can achieve the largest dispersion-free bandwidth.
Brief introduction to χ(2) cascading nonlinearities is presented.The enhancement mechanisms for optical Kerr effect and the photorefractive effect as χ(2) cascading process are discussed.Mutual inductance between quadric and cubic nonlinearities opens possibilities for engineering optical nonlinearities.
2001, 50 (6): 1092-1096. doi: 10.7498/aps.50.1092
A new theory of wide bandwidth optical harmonic generation based on frequency mixing is presented.We point out that the wide bandwidth optical harmonic generation is a process of frequency mixing rather than only frequency doubling if there are phase match among different wavelengths.The sum frequency between different wavelengths can play a leading role in wide bandwidth optical harmonic generation,which can increase the acceptance bandwidth dramatically.This theory is not limited by the acceptance bandwidth of frequency doubling and not only suit for second harmonic generation but also for third harmonic generation.
2001, 50 (6): 1097-1102. doi: 10.7498/aps.50.1097
It is observed that the Sommerfeld's formula for a progressive spherical wave is not covariant with respectro the rotation of the coordinate system.It contains complex partial waves that are not physical.The standing wave representation of the same formula is shown to be covariant and physical.It is applied to solve the boundary value problem of fiber optics.The radiation modes as well as the guided normal modes are obtained in closed forms.The intensity distribution in various modes is obtained.It is remarked that the mode of critical refraction is missing.
A FAST ALGORITHM FOR VISUALIZING MULTIPLE THREE-DIMENSIONAL OBJECTS USING NEAR-FIELD ACOUSTIC MEASUREMENTS
2001, 50 (6): 1103-1109. doi: 10.7498/aps.50.1103
A simple fast algorithm is proposed for visualizing multiple three-dimensional (3D) obstacles from the knowledge of the near-field measurements of the scattered field for point source field.The proposed algorithm is achieved by using the 3D contour plot of the solution of a linear system as a visualization of the scattering object.An attractive feature of this algorithm is that it avoids the use of the iteration technique and does not need any priori knowledge about the geometry and physical properties of scatterers.In addition,the algorithm only requires the knowledge of the near-field measurements of the scattered field at a finite number of incident and observation points distributed over some limited area.Some numerical examples based on synthetic near-field data are given to show the practicality and efficiency of the inversion approach.
2001, 50 (6): 1110-1114. doi: 10.7498/aps.50.1110
Considering the second nearest-neighbor interaction and cubic,quartic anharmonic interactions simultaneously, we employ the multiple scales method combined with a quasidiscreteness approximation to calculate the lattice vibration.It is shown that the kind of nonlinear chain exhibits envelope soliton,envelope kink and envelope antikink soliton.These results can also be used to explain the experimental phenomena that the kink amplitude of the self-localized structure is determined only by the intrinsic properties of its lattices.
SIMULATION TO POISEUILLE FLOW OF ER FLUIDS BY CONSIDERING SHORT-RANGE INTERACTION OF MULTI-PARTICLES
2001, 50 (6): 1115-1120. doi: 10.7498/aps.50.1115
Considering the short-range interaction of multi-particles,we conduct a molecular dynamic simulation to Poiseuille flow of electric rheology (ER) fluids based upon the equivalent conduction model.We discover that the period to form the plug zone is greatly shortened and the velocity peak-value of the “respiring” transition increases markedly, compared with the simulation results using dipole model.The formation of the transition zone are clearly explained and we first obtain the three-dimensional evolving graphs of the velocity profile of particles.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
2001, 50 (6): 1121-1127. doi: 10.7498/aps.50.1121
The interaction of atomic clusters with high-intensity lasers has been investigated based on the hydrodynamic model developed by Ditmire et al.By solving Maxwell equations,an effective plasma dielectric constant is found to replace the quasistatic plasma dielectric constant ε derived from the Drude model.In the vicinity of resonance absorption,the electron density and temperature undergo such a rapid change that the quasistatic plasma dielectric constant ε is no longer appropriate to demonstrate the behavior of resonance absorption.Employing this model,the interaction of atomic clusters with high-intensity lasers at different frequencies has also been studied.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
2001, 50 (6): 1128-1131. doi: 10.7498/aps.50.1128
The average thickness of the interface layer wrapped about sols usually is determined by fitting the Porod curve that shows a negative deviation from Porod's law.In this paper we show that it could also be determined by a new method that includes the following steps:(1)determining the average radius R1 of the sol particles including interface layer from the small angle X-ray scattering data in which shows negative deviation from Porod's law;(2) determining the average radius R2 of the sol particles not including the interface layer from the scattering data in which has been corrected the negative deviation from Porod's law;(3) the difference ΔR between R1 and R2,i.e. ΔR=R1-R2,is just the average thickness of the interface layer wrapped about sols.By using the above method,the average thickness of the interface layer wrapped about SiO2 sols prepared under different conditions were determined.
2001, 50 (6): 1132-1138. doi: 10.7498/aps.50.1132
The X-ray diffraction whole pattern (XDWP) data of semicrystalline poly (ethylene terephthalate)PET2 sample were collected in the symmetric reflection geometry on a diffractometer, employing a copper target(Kα wavelength=0.15418nm).The XDWP was fitted by combining the Rietveld method and Fourier filtering technique,Rietveld structure refinement for PET2 crystalline phase was done,the unit-cell parameters obtained being a=0.445,b=0.592,c=1.072 nm,α=99.6,β=116.9,γ=111.9(°),and the density of the sample being dc=1.495(g/cm3).Meanwhile, the XDWP was separated into two parts,CR2 crystalline region and AM2 non-crystalline region in PET2.The reduced radial distribution function G2(r) was calculated from AM2, finding three main peaks,G21(r)=0.150,G22(r)=0.254,G23(r)=0.460 nm, which characterize the structure of the non-crystalline phase in PET2.We suggest that the amorphous curve is best taken as the sum of several non-crystalline scattering peaks.Reliability and reasonableness of the structural parameters of the crystalline phase and the non-crystalline phase are discussed.In conclusion,it is a very effective method that the combination based on the Fourier filtering technique and the full-pattern diffraction least-squares refinement (Rietveld method) and the radial distribution function analyses to study the two-phase structure in semi-crystalline polymers.
2001, 50 (6): 1139-1144. doi: 10.7498/aps.50.1139
Four arithmetic non-equivalent metric tensor matrices,-have been derived in this paper according to a crystallographic general equation TN=T.T1,T3 and T4 are geometric equivalent ones,therefore,only T1 and T2 are geometric non-equivalent ones.Substituting T1 and T2 into NTN=T,two maximal finite groups can be derived, which have 48 and 24 elements respectively and belong to two crystallographic point groups.The other 30 point groups can be derived according to group-subgroup relationship.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
2001, 50 (6): 1145-1149. doi: 10.7498/aps.50.1145
Based on a plane-wave pseudopotential method,the electronic structure calculations of NaNO2 from first principles are perforined.The linear refractive indices and the static second-harmonic generation (SHG) coefficients are also calculated by the SHG formula improved by us.The calculated values are in good agreement with the experimental values.A real-space atom-cutting method is adopted to analyze the respective contributions of the cation and anionic groups to optical response.The results show that the contribution of the (NO2)- anionic group to the birefringence and the SHG coefficients is dominated in NaNO2 crystal,which is in agreement with the result obtained by the anionic group model.
2001, 50 (6): 1150-1156. doi: 10.7498/aps.50.1150
Based on the tight-binding model of π electrons for a graphite sheet, the electronic structure of the chiral toroidal carbon nanotubes(TCNTs) has been derived.The quantum properties and magnetic pattern of TCNTs have been investigated in detail in this paper. A magnetic field can induce a metal-semiconductor transition for typeⅠ and Ⅱ TCNTs.The computation and analysis also show: when- T=0K, the magnetism of typeⅠand Ⅱ TCNTs are a linearly function of the magnetic flux Φ, with a period Φ0(h/e),which is sensitive to chiral angle θ,toroidal width r and temperture T, independent of toroidal radius R. The magnetism of chiral TCNTs is much stronger than that of the armchair or zigzag TCNTs. The magnetism of type Ⅲ TCNTs is very weak,without regularity.
PROPERTIES OF CONDUCTING POLYMER DONOR-ACCEPTOR COMPOSITE FILMS AND PHOTOVOLTAIC CHARACTERISTICS OF JUNCTION DEVICES
2001, 50 (6): 1157-1162. doi: 10.7498/aps.50.1157
To realize an efficient photovoltaic device,one of the methods of creating a large interfacial area at which the effective dissociation of excitons occurs is to mix an electron donor material with an electron acceptor material.The new soluble conducting polymer-dye ROPPV(poly(2,5-dialkoxy-p-phenylene vinylene)/ N,N'-diphenyl glyoxaline-3,4,9,10-perylene tetracarboxylic acid diacidamide (PV) composite was prepared.Electrical and optical properties of soluble conducting polymer composite films,and current-voltage(I－V) characteristics and photocurrent spectra of photovoltaic cells are discussed.Our results show that the soluble conducting polymer-dye composite represents a new class of organic semiconducting materials that can be used to manufacture photovoltaic cells.
2001, 50 (6): 1163-1166. doi: 10.7498/aps.50.1163
In this paper,we discussed the variation of the quantum state when there is pulse put into the mesoscopic- LC- circuit,and arrived at the coclusion that the quantum state of the system is stable when the width of the pulse is equal to the integral times of the minimum fixed value,and that the minimum value is related to the circuit parameters.
2001, 50 (6): 1167-1171. doi: 10.7498/aps.50.1167
CdSe/Cd0.8Zn0.2 Se quantum wells were grown by means of molecular beam epitaxy on substrate GaAs. The emission peak from excition-exciton scattering is observed in CdSe/CdMnSe quantum wells. When weaker excitation is used, radiative recombination decay time of the exciton is reduced as the excitation intensity is decreased. The results indicate that the dominant mechanism may be quenching of exciton emission by impurities and defects.
2001, 50 (6): 1172-1177. doi: 10.7498/aps.50.1172
Breakdown character of thin SiO2 is investigated by using substrate hot-carrier injection techniques. Hot-carrier induced thin gate oxide damaged shows different breakdown character compared with the case of conventional F-N tunneling experiments.Good correlation between the calculated electron energy in the oxide and the electric field in the silicon substrate suggests that the difference between hot-electron injection and the F-N tunneling can be explained in terms of the average electron energy in the oxide.Hot holes injection experiments reveal that the life of oxide breakdown is not simply determined by the total number of injected holes.New hot-carrier-induced TDDB (Time-dependent dielectric breakdown)models of thin gate oxide are reported in this paper.
PROPAGATION PROPERTIES OF MAGNETIC SURFACE WAVES ON THE INTERFACE BETWEEN TWO NONLINEAR ANTIFERROMAGNETS
2001, 50 (6): 1178-1184. doi: 10.7498/aps.50.1178
The nonlinear behavior of surface waves on the interface between two uni-axis antiferromagnets is studied.The theoretical analysis and the numerical simulation show that there exist two thresholds:frequency threshold and power threshold.All the incident waves satisfying the two thresholds can steadily propagate in this new guiding structure.It is indicated that the peak field will jump from one antiferromagnet into another when the power increases. It is also revealed that the magnetic field amplitude on the interface is not power-dependent but frequency-dependent.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
2001, 50 (6): 1185-1188. doi: 10.7498/aps.50.1185
The ethylene(C2H4)adsorbed on Ru(0001)surface has been studied by using thermal desorption spectroscopy(TDS).The results show that ethylene(C2H4)absorbs in molecular state on Ru(0001)surface stably below 200 K.The dehydrogenation of ethylene occurs at 200 K.The main product of the dehydrogenation of the absorbed ethylene(C2H4)is acetylene(C2H2).There are two adsorption states of ethylene on the clean Ru(0001)surface.Their desorption temperature is 275 K and 360 K respectively.The desorption temperature of acetylene is 350 K.The desorption temperature of both acetylene and ethylene rises with increasing Cs coverage.
2001, 50 (6): 1189-1192. doi: 10.7498/aps.50.1189
The ethylene (C2H4)and acetylene (C2H2)co-adsorbed with K on Ru(1010)surface has been studied by using ultraviolet spectroscopy(UPS).The results show that ethylene (C2H4) is absorbed in molecular state on Ru(1010)surface stably below 200 K.The dehydrogenated of ethylene occurs at 200 K.The main product of the dehydrogenation of the absorbed ethylene (C2H4)is the acetylene (C2H2).After the dehydrogenation of the absorbed ethylene(C2H4),the binding energies of σCC and σCH bonds have an increase of 0.2 eV and 0.5 eV respectively.The acetylene is absorbed in molecular state on Ru(1010)surface stably at room temperature.On a K pre-covered surface,the σCC peak disappears at room temperature.The element K promotes the dissociation of acetylene on Ru(1010)surface.
2001, 50 (6): 1193-1196. doi: 10.7498/aps.50.1193
We report a first-principles local density approximation band structure calculation on the electronic structure of high-TC superconductor MgB2.It is revealed that the band structure of magnesium diboride is of metallic type with a wide valence band.The density of states of electrons at Fermi energy is only about 0.72 (states/eV).We conclude that the present calculation excludes the possibility of BCS mechanism in MgB2.
2001, 50 (6): 1197-1200. doi: 10.7498/aps.50.1197
The temperature-dependent thermopower and resistivity of MgB2 were measured.In the range of 100—300K, the thermopower presents positive nearly linear temperature dependence,indicating that the charge carrier is hole and it is consistent with the energy band pattern.In contrast,the resistivity follows T2 relationship in the same temperature range.Below 100K,thermopower and resistivity change their temperature dependence.The thermopower presents a hump between the superconducting transition temperature Tc (zero resistance,36.6K) and 100K.It has the characteristic of the phonon drag,indicating the strong electron-phonon interaction.Some important parameters are estimated according to experimental results,such as Fermi energy EF and energy band width.