Vol. 53, No. 10 (2004)
2004-05-20
GENERAL
2004, 53 (10): 3245-3247.
doi: 10.7498/aps.53.3245
Abstract +
A delayed oscillator of El NiňoSouthern Oscillation (ENSO) models are conside red. Using the method of homotopic mapping, the approximation of the solution for ENSO models is obtained.
2004, 53 (10): 3248-3251.
doi: 10.7498/aps.53.3248
Abstract +
The linearized form of (2+1)dimensional Broer-Kaup equations is established b y using the improved homogeneous balance method. Starting from the B?cklund tra nsformation, a variableseparation solution with the entrance of some arbitrary function is obtained. By using Jacobian elliptic functions, new fractal structu res are obtained.
2004, 53 (10): 3252-3257.
doi: 10.7498/aps.53.3252
Abstract +
The dependence of proper temperature on cylindrical coordinatesT0（ρ）in thermal equilibrium of a fluid system on Einstein turntable is solved by special and general relativity separately. The results show that the contraction of motiontemperature depends only on the speed instead of on the acceleration of subsystems. According to uniformity in space and constancy in time of the coordinate temperature of an equilibrium system, the space-time duality between Einstein turntable and early universe directly presents that the proper temperature of a medium of the early universe is inversely proportional to the spatial scale-factor R(t).
2004, 53 (10): 3258-3264.
doi: 10.7498/aps.53.3258
Abstract +
By solving convectiondiffusion equation, we have studied the influence of d if ferent difference schemes on the rumerical solutions under the condition of stoc h astic disturbance of the border or parameter, which provides a reliable differen ce scheme for solving the convectiondiffusion equation, and we have drawn a co nclusion that the influence for the stochastic disturbance on the border or para meter could be controlled by increasing the number of the grid point in numerica l calculation.
2004, 53 (10): 3265-3269.
doi: 10.7498/aps.53.3265
Abstract +
We generalized the Jacobi elliptic function expansion method and obtained some new exact periodic solutions, thus replenished the known results of a number of nonlinear wave equations by using this method.
2004, 53 (10): 3270-3273.
doi: 10.7498/aps.53.3270
Abstract +
Using the new equation for density of states due to the generalized uncertainty relation, the entropy of Schwarzchildde Sitter spacetime is discussed. By use of the new equation for density of states, it overcomes the shortcoming that on eliminating divergence the calculation of black hole entropy with brickwall pattern needs a cut off. Thus, it gets the result of the direct proportion betwee n black hole entropy and its horizon area, brings to light the relationship between Schwarzchildde Sitter and its cosmos event horizon and makes clear that the black hole entropy is the entropy of quantum state near the event horizon.
2004, 53 (10): 3274-3279.
doi: 10.7498/aps.53.3274
Abstract +
The definition of partial variables inverse sequence feedback controller of a chaotic system is proposed. We studied this kind of controller with Chen's chaotic system and get the existing condition of the controller，and extended the conclusion of the related article, so get various controllers of the chaotic system. Numerical simulations are presented to show that chaotic system control based on partial variables feedback is simple and effective.
2004, 53 (10): 3280-3286.
doi: 10.7498/aps.53.3280
Abstract +
In this paper, the stable control of spatiotemporal chaos in coupled map lattices is realized by state feedback method. The feedback mode can be either delayed or without delay. The control mode can be either continuous or pulsate. The numerical simulation results demonstrate that this method is an effective one.
2004, 53 (10): 3287-3292.
doi: 10.7498/aps.53.3287
Abstract +
Synchronizations in coupled limitcycle systems are studied. The order parameter does not change monotonically with increasing coupling. Phase synchronization among oscillators shows a treelike bifurcation, and a number of clustered states are experienced. At the onset of synchronization, simultaneous phase slips of all oscillators and quantized phase shifts are observed. The phase synchronization bifurcation is accompanied by a bifurcation process of the amplitudes of oscillators, that is, the synchronization of phases corresponds to an inhomogeneou sprocess of amplitudes.
2004, 53 (10): 3293-3297.
doi: 10.7498/aps.53.3293
Abstract +
For dynamic systems with complex, illconditioned, or nonlinear characteristics, the fuzzy model based on fuzzy sets is very useful to describe the properties of the dynamic systems using fuzzy inference rules. Modeling and prediction of nonlinear systems using fuzzy modeling is discussed in this paper. First, the fuzzy space of input variables is partitioned by means of online fuzzy competitive learning. Further, the parameters of fuzzy model are estimated by means of Kalman filtering algorithm. To illustrate the performance of the proposed method, simulations on the chaotic MackeyGlass time series prediction are performed. Combining either offline or online learning with the proposed method, we can show that the chaotic MackeyGlass time series are accurately predicted, and demonstrate the effectiveness.
2004, 53 (10): 3298-3302.
doi: 10.7498/aps.53.3298
Abstract +
An adaptive H∞ synchronization approach for continuoustime chaotic syst ems is proposed. An adaptive controller is designed such that the global asympto tic synchronization between the drive and response systems can be accomplished w ithout noise, and the influence of noises in the response system on the synchron ization error is less than the expected level. Finally, the simulation results v ia Chua's circuit verify the theoretical results.
2004, 53 (10): 3311-3315.
doi: 10.7498/aps.53.3311
Abstract +
Three-dimensionally ordered macroporous polystyrene was successfully synthesized through using silica sphere colloid crystals as template and in-situ polymeriza tion of styrene inside the template. The silica spheres with a diameter of 330 n m and 2.75% relative standard deviation were prepared by seeding method. For th e purpose of improving the wetting ability between the silica particles and styr ene, the hydrophilic surface of silica particles was switched to hydrophobic by 3-Aminopropyl-triethoxysilan (APS). Three-dimensionally ordered colloidal crystal was prepared by assembling the modified particles through a vertical depositio n technique at 30℃ for 48h. Styrene monomer was filled into the void of the tem plate and the polymerization of the styrene was carried out at 60℃ for 6h, being used (put the initiator in here) as initiator. The three-dimensionally ordered macroporous polystyrene was thus obtained by removing the silica template from polystyrene materials with 04% HF. The macroporous polystyrene shows a beautif ul iridescence in reflected light, which resulted from Bragg diffraction. SEM im ages indicated that the pores with a diameter of about 210nm were arrayed period ically and connected with each other.
NUCLEAR PHYSICS
2004, 53 (10): 3316-3320.
doi: 10.7498/aps.53.3316
Abstract +
Based on the isospindependent quantum molecular dynamics model, we have invest igated the dependences of isospin fractionation degree (N/Z)n/(N/Z)fragon the mass and the beam energy of colliding system. The (N/Z)n a nd (N/Z)frag are the neutron proton ratio of the nucleon emission (gas-phase) and that of the fragment emission (liquid phase) respectively. The isosp in fractionation degree is a sensitive func tion to the mass and beam energy of the colliding system. The (N/Z)n/(N/Z)frag reduces with increasing mass of the colliding system when the beam energy and n eutron proton ratio of the colliding system are fixed. This is due to the larg er compr ession, small heating energy and larger critical temperature of the gasliquid phase transition for the heavy colliding system, compared to those of the light colliding system. We also found that (N/Z)n/(N/Z)frag enhances wit h increasing beam energy due to the increase of excitation energy of the collidi ng system which leads to larger nucleon transport and isospin fractionation. But the isospin frac tionation only occurr in the energy region for producing the liquidgas phase t r ansition. In this case, we propose that (N/Z)n/(N/Z)frag can be directly compa red with the experimental data to get the information about symmetry potential.
2004, 53 (10): 3321-3325.
doi: 10.7498/aps.53.3321
Abstract +
The new type of pulse neutron detector consists of two PIN detectors. The respon se for the rays was studied with the pulse gamma sources. The neutron respons e was studied using the DT neutron sources and compared with the scintillator de tector. Results show that the detector is insensitive to gamma radiation, and th e neutron sensitivity was determined by the neutron radiator. It is a new pulse neutron detector in the neutron and gamma mixed radiation fields.
ATOMIC AND MOLECULAR PHYSICS
Theoretical predictions on the low-lying excitation structure of super-heavy element bohrium (Z=107)
2004, 53 (10): 3326-3329.
doi: 10.7498/aps.53.3326
Abstract +
The success of theoretical and experimental study of fermium (Z=100) enlightened us to perform further investigation of heavy elements. We studied so me lowlying absorption spectroscopy and the resonant absorption probability of bohrium (Z=107) by using MCDF method which included the correlation effects and relativistic effects systematically. We hope our results will be useful for the further experiments.
2004, 53 (10): 3330-3335.
doi: 10.7498/aps.53.3330
Abstract +
Based on the relativistic multiconfiguration DiracFock theory, the level energies and level degeneration of ions from Au48+ to Au52+have been calculated using the Generalpurpose Relativistic Atomic Structure Progra m with quantum electrodynamics effect and Breit correction. The partition functi on of each ion is derived using statistical thermodynamics. The equilibrium dist ribution of Au48+to Au52+in Au plasma is obtained from the theory of simultaneous reactions.
2004, 53 (10): 3336-3340.
doi: 10.7498/aps.53.3336
Abstract +
We propose a new theory of ultra-narrow bandwidth optical filter which consists of two-dimensional photonic crystal of an anomalous dispersion material. Based on our investigation of the anomalous dispersion of 6P1/2←6S1/2 tran sition of the cesium atom, we designed a photonic crystal anomalous dispersion o ptical filter (PCADOF) by use of the plane wave expansion method. The calculated result shows that the bandwidth of the filter can be less than 0.002nm.
2004, 53 (10): 3341-3346.
doi: 10.7498/aps.53.3341
Abstract +
The measurement of light spectrum of NiⅠand NiⅡwith wavelengths from 200 to 1 000nm emitted from the solid surface of Ni, which is excited by slow highly char ged ions 126Xe30+，is reported. The result shows that the chara cteristic spectral lines from transitions between complex configurations of atom s and ions can be effectively excited by the impact of highly charged ions on a solid surface even though the ionic beam is very weak. The result shows especia lly that the characteristic spectral lines from forbidden transition (M1and E2) of NiⅠand NiⅡcan be effectively excited.
2004, 53 (10): 3347-3352.
doi: 10.7498/aps.53.3347
Abstract +
The bond breaking at high excitation of the HCN molecule with various couplings is studied along with Morse oscillator by the coset (phase) space method of Lie algebra. It is demonstrated that the couplings of higher orders, are prone to bo nd dissociation. We also note that couplings reduce the dissociation energy.
CLASSICAL AREA OF PHENOMENOLOGY
2004, 53 (10): 3353-3357.
doi: 10.7498/aps.53.3353
Abstract +
The interaction between two optical vortices in a linear medium is investigated numerically. An instability resembling the symmetrybreaking instability occurs when the vortices carry opposite topological charges. The screw dislocations wi ll evolve into another type of dislocationedge dislocation with the propagatin g of optical field. The sum of the topological charges conserves in the whole pr ocess.
2004, 53 (10): 3358-3362.
doi: 10.7498/aps.53.3358
Abstract +
By means of the expression of twomode squeezed vacuum in electron paramagnetic resonance (EPR) entangled state representation, we study the teleportation of a ny form of singlemode and twomode quantum states by using twomode squeezed vacuum as quantum channels.
2004, 53 (10): 3363-3368.
doi: 10.7498/aps.53.3363
Abstract +
Using the linear approximation method, the normalized intensity fluctuation(NIF) for bias signal modulation is calculated in a gainnoise model of a singlemo de laser driven by colored correlated noises, in which each is colored; and the influences of the strength of bias signal modulation, the frequency of period si gnal, the correlation strength and correlation time of noises on NIF is studied in detail. We observed that a minimum appears in the NIF versus pump noise inten sity curve and quantum noise intensity curve; the normalized intensity fluctuati ons of a singlemodel laser for bias signalmodulation and direct signal modul ation are compared.
2004, 53 (10): 3369-3374.
doi: 10.7498/aps.53.3369
Abstract +
To our knowledge, we first deduced the analytic expression of the indexchanged istribution in LiNbO3:Fe crystal induced by a Gaussian sheet beam considering th e photorefractive onecenter model and the photovoltaic charge carriers transp or tmechanism. A planar waveguide structure was fabricated by sheet beam illuminat ion employing the sandwich method in LiNbO3:Fe crystal. The index distribu tion i n the waveguide region was measured by using interferometric technique and the g uiding test was also performed. The rationality of the deduced analytic expression was demonstrated by the fitting results of the measured data point. Based on the ray equation, the guiding properties of the light-induced waveguide were analyzed by using numerical simulation. The results show that the interferom etric technique is valid for measuring the index distribution of waveguide with large width, and the guiding properties of the lightinduced waveguide structures depend on the waveguide width strongly. Using sheet beam with small width, planar waveguide structure with high quality can be fabricated in LiNbO3:Fe cryst al . And the analytic expression of the indexchangedistribution can be employed to predict the guiding properties of the lightinduced waveguide.
2004, 53 (10): 3375-3378.
doi: 10.7498/aps.53.3375
Abstract +
A Ti: sapphire oscillator emitting an octavespanning spectrum that ra nges from 460nm to 1000nm is demonstrated. To our knowledge, it is the first tim e that a supercontinuum extending beyond 500nm in the blue end is generated from a femtosecond oscillator. The selfQswitched and selfmodelocked Ti: sapphi re oscillator uses chirped mirrors and a prism pair for dispersion compensation. Th ese results will make the measurement of carrierenvelope offset frequency simp ler and improve the stability of optical frequency metrology at the same time.
2004, 53 (10): 3379-3383.
doi: 10.7498/aps.53.3379
Abstract +
The defect effect in the two_dimensional (2D) negative permeability material, co nsisting of copper hexagon split ring resonators (SRRs), is investigated. The pr inted circuit boards with SRRs on one side are fabricated using a shadow mask/et ching technique. We use a rectangular waveguide system to measure the X_band tra nsmission in 2D negative permeability materials with different dot and line defe cts. The measured data shows that there is only one resonance frequency and high quality factor \%Q\% for a 2D negative permeability material without defects. T he main resonance frequency has a shift and the resonant peak value decreases wh en the defect SRRs are introduced into the samples. We consider that the defect SRRs break the periodic structure of the samples, which results in the shift of the main resonance frequency and the resonant intensity. The investigation of th e defect effects is important not only for the understanding of the characterisf ics of the negative permeability material, but also for the realization of the l eft_handed metamaterials in the infrared and visible region.
2004, 53 (10): 3384-3388.
doi: 10.7498/aps.53.3384
Abstract +
With each unit cell replaced by finite cascaded massspring oscillators, 1D pho nonic crystals (PCs) can be simplified to an infinite periodic massspring chai n. Therefore, the elastic wave band structures of the 1D PCs can be calculated w ith a straightforward approach which we call lumpedmass method (LM). For compa rison, the band structures of the same 1D PC calculated with this method and the wellknown plane wave expansion method are both presented in this paper. The r esults of the two methods are in good agreement while the computation costs of L M method are much lower than that of PWE method.
2004, 53 (10): 3389-3393.
doi: 10.7498/aps.53.3389
Abstract +
We have investigated experimentally the twodimensional flow of stainless steel balls through a smooth inclined plane and between two parallel plates so that the side walls are rough and the inclination is adjustable. It is shown that th e dynamical behavior of the dilute granular flow is different from the Newtonian fluids because of the energy dissipation. Compared to the viscous fluids, the velocity profiles of the granular flow are more blunted than the parabolic form and the density profiles are nonuniform. Near the side walls, the density is hig her than the center of the channel. The distribution of the density is influence d by increasing inclination and the width of the channel. The transverse d istribution of the granules in the channel is affected chiefly by the density di stribution.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
2004, 53 (10): 3394-3397.
doi: 10.7498/aps.53.3394
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The characteristics in low-pressure inductively coupled CF4 plasma have been-inv estigated using a Langmuir probe method. Results for the CF4 gas have shown that there are two electron populations: one with low temperature and high densit y and the second w ith higher temperature and lower density, in this region. Fast electron temperat ure The, slow electron temperature Tceand mean electron tem perature Te decrease , while their densities nhe,nce, ne increase with in creasing r.f. input pow er. Our findings suggest that the dependence of two-electron-temperature on r. f.input power can be explained by the thermodynamic equilibrium of the collision between electrons and particles.
2004, 53 (10): 3398-3403.
doi: 10.7498/aps.53.3398
Abstract +
Thorough numerical studies of the characters of maserinstability driven by a b eam of weak relativistic electrons are performed on the basis of the theoretical model of Chen et al due to its important applicatio n in the solar radio emission. It enriches the f undamental content of the plasma instabilities. And it is expected to be applica ble widely in the study of solar and celestial emission mechanism.
2004, 53 (10): 3404-3408.
doi: 10.7498/aps.53.3404
Abstract +
The time evolution of plasma channel produced by ultrashort and ultra high power laser pulses in the air has been investigated. The theoretical model considers the recombinati on of free electrons, positive and negative ions, as well as the attachment and detachment of electrons on neutral molecules in the air under the interaction with the successive coming laser's pulses. The analytical solution of rate equations of the charged particles in the plasma channel has been found when the detachment laser intensity is constant. Calculations show that the lifetime of the plasma channel with an electron density higher than 1012—1013cm-3 can be extended to microseconds by using a detachment laser to suppress the attachment between el ectrons and neutral moleculars. In the case of same wavelength and average power, the detachment efficiency of a short pulse sequence with a high repetiti on rate is higher than that of a continuous detachment laser.
2004, 53 (10): 3409-3412.
doi: 10.7498/aps.53.3409
Abstract +
The structure of the plasma sheath in an oblique magnetic field was investigated with the fluid method. In various different magnitude and directions of the ma g netic field, the electron and ion density distribution, ion flow velocity, elect ron potential and Bohm's criterion have been calculated. It is shown that the magnetic field has obvious effect on the plasma sheath. Under the action of electrostatic and Lorentz forces, the ion flow makes a helical movement, and the ion densi ty distribution fluctuates.
2004, 53 (10): 3413-3418.
doi: 10.7498/aps.53.3413
Abstract +
Supersonic radiation transport, where the ratio of the radiation wave front velocity to the material sound speed was more than 10, has been investigated experimentally in the low-density foam. Four beams of 0.35μm laser with pulse d uration of 1ns and 2kJ of total energy entered into a hohlraum to create intense x-ray radiation that heated C66H12
2004, 53 (10): 3419-3423.
doi: 10.7498/aps.53.3419
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This paper describes the diagnostic techniques and experimental methods used for investigating the properties of implosion compression in direct drive . Several diagnostic techniques with fine time, space and spectrum resolution are employed to obtain the information concerning implosion, such as radiation un iformity on the capsule, compression symmetry, volume compression ratio, implosi on time, implosion velocity and average electron temperature of the capsule shell. Some of the typical results measured in the experiments are presented and as imple discussion is also given.
2004, 53 (10): 3424-3428.
doi: 10.7498/aps.53.3424
Abstract +
A high Z cylindrical hohlraum was used to produce xray radiation flux, whic h was used to drive shock waves in an Al step sample. The radiation temperature i s 15 5eV. Experiments were carried ont on `Shenguang II' laser facility, with eight 2 50J, 0.35μm wavelength, 1ns Gaussian laser pulses. The planar and preheatfre e s ho ck wave was generated and a clear image of shock and preheat wave was obtained . The shock wave velocity and pressure was 31.2km/s and 17.5×1011Pa, respectively.The radiation temperature measured by streaked pyrometer, was consistent with th at measured with a soft x-ray spectrometer which views through the laser entran ce hole.
2004, 53 (10): 3429-3434.
doi: 10.7498/aps.53.3429
Abstract +
A twodimensional,radiation magnetohydrodynamics model is applied to the simu lation of Zpinch plasma sausage instability.Different implosion mechanisms in the cases of the existence and the nonexistence of instability are analyzed,an d the effects of various initial density perturbation levels on the x-ray power and energy are investigated.Numerical results show that x-ray energy output is not susceptive to sausage instabilities in a certain extent but x-ray power ve rsus time is evidently dependent on the instabilities.In addition,this paper als o studies the effects of numerical treatment of extreme low density in Zpinch simulations on numerical results.
2004, 53 (10): 3435-3439.
doi: 10.7498/aps.53.3435
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This paper is involved in generation, explosion of cathode plasma of electron va cuum diode under four-pulse mode. Diode breakdown caused by cathode explosion is observed in experiment. On the assumption that the diode beams are space charge limited beams and according to the experimental data, the explosion velocity of cat hode plasma is 0.5—4cm/μs and is different from each other in differe nt pulse process. The effects of explosion of cathode plasma on diode voltage, dio de impendence and multi-pulse beams are analyzed too.
2004, 53 (10): 3440-3446.
doi: 10.7498/aps.53.3440
Abstract +
A microhollow cathode discharge (MHCD) was investigated by means of a fluid mode l. A highpressure He gas discharge for a cylindrical cathode was used in the model. The distribution of the electric field, electrons, ions and electron e nerg y has been calculated. The results show that there exists a hollow cathode disch arge ef fect in the discharge process. There existed electrons with high energy, and the electric field was mainly a radial field close to the cathode in the discharge area. The influ ences of gas pressure and dimension of the cathode on discharge characteristics were also investigated. We found that reducing the dimension of the cathode can enhance the hollow cathode effect, and increasing pressure will shorten the catho de fall.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
2004, 53 (10): 3447-3452.
doi: 10.7498/aps.53.3447
Abstract +
Novel properties of surfaces with heteronanostructures are of considerable interest in recent years. Although glycine can only be physisorbed on pure sil ver surfaces, our recent results show that monolayersilver islands deposited o n copper surfaces, with the help from the nearby nude copper surface areas, have the ability of chemisorption of glycine. In the present study we find that, on the other way round, copper islands deposited on the Ag(111) surface can also ma ke glycine being chemisorbed on the nude silver areas, although in the latter ca se the surface of a silver bulk is involved. This result demonstrates that it is the nanocoexistance of Cu and Ag on the surface, rather than any specific str ucture of the coexistance, that gives rise to the novel chemical property of the silver surfaces. Furthermore, we also find that all deposited copper islands will gradually be covered by a monolayer of Ag atoms, even at the room temperature , and thus lose the ability of helping the silver surface to gain the novel chem ical property. This indicates that in order to take advantage of the novel prope rties of heteronanostructures, we have to consider their longterm stabilit y and very often it is possible to choose the stable ones.
2004, 53 (10): 3453-3456.
doi: 10.7498/aps.53.3453
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Amorphous Fe78 Si9 B13alloys have been treated by pulsed magnetic field with lowe r frequency. The macrostructural change of amorphous specimens after treatment were observed by mssbauer spectroscopy and TEM etc.This investigation show that nanocrystallization of amorpous Fe78 Si9 B13occurs under the con ditions: pulsed fiel d 16—32kA/m,pulse frequency 20—25 Hz,acting time ≤2min. The grain size of nano crystalline phase Fe(Si) is about 10nm. And, the temperature rise of specimens during the course of the application of pulsed magnetic field is very low(ΔΤ≤20℃).
2004, 53 (10): 3457-3461.
doi: 10.7498/aps.53.3457
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In this paper, we study the electrical resistance of nonmagnetic amorphous alloy Cu60Zr20Hf10Ti10 and amorphous ferromagnet Fe61Co7Zr10Mo5W2B15. We fit the c urve in the light of special models, and analyze the origination of the minima which occurs in both of the samples. The contributions both from the disorder structure and magnetic status are discussed.
2004, 53 (10): 3462-3466.
doi: 10.7498/aps.53.3462
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The humidity sensitive properties of multiwalled carbon nanotubes(MWNTs) films h ave been studied.Multiwalled carbon nanotubes were synthesized by hot filament chemical vapor deposition.Carboxyl modified and non_modified MWNTs film's tempera ture effect and humidity sensitive behavior were investigated separately.The res ults showed that carboxyl modified MWNTs films were very sensitive to temperatur e and humidity,response and restored time were much faster than that of non_modi fied MWNTs films.The origin of humidity sensitivity of MWNTs films were also discussed,and the theoretical formula was given.
2004, 53 (10): 3467-3471.
doi: 10.7498/aps.53.3467
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Structural phase transformation from multiwalled carbon nanotubes to nanocr ystalline diamond by hydrogen plasma posttreatment was carried out. Ultrahigh equivalent diamond nucleation density above 1011 nuclei/cm2 was easily obtained . The diamond formation and growth mechanism was proposed to be the consequence of the formation of sp3 bonded amorphous carbon clusters. The hydrogen chemi so rption on curved graphite network and the energy deposited on the carbon nanotu bes by continuous impingement of activated molecular or atomic hydrogen are resp onsible for the formation of amorphous carbon matrix. The diamond nucleates and grows in the way similar to that of diamond CVD processes on amorphous carbon films. The present method of hydrogen treatment provides a controllable way for the CVD of high quality diamond films.
2004, 53 (10): 3472-3476.
doi: 10.7498/aps.53.3472
Abstract +
Taken into account the curvature effects，we build a singleπ orbital tight-bi ndi ng model for armchair toroidal carbon nanotubes, from which the interaction matr i x elements have been derived by means of the wavefunction decomposition method. The electronic structures of armchair toroidal carbon nanotubes are studied, whi ch are dependent on both the torus radius and the tube radius. The energy spectr al transition is observed from the discrete to continuous ones, as the t orus radius and the tube radius are varied.
2004, 53 (10): 3477-3481.
doi: 10.7498/aps.53.3477
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In order to reflect the characteristic of sharp interface during the d endritic growth process, cellular automaton method is used to simulate the dendr ite evolution. In this method the different physical properties in both solid an d liquid phases are adopted to reflect the different heat_transfer rate. The simulated results show that there is solute micro-segregation between the two p rimary dendritic arms. In addition，the solute concentration gradient and temper ature ahead of the solid/liquid interface decrease gradually with increasing solidification time. Comparing the simulated radius of the dendritic tip with the theore tical radius, we obtain that the simulated results fit the theoretical radius well, and the deviation is less than 1μm.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
2004, 53 (10): 3482-3486.
doi: 10.7498/aps.53.3482
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The model of liquidphase of ZA27 cast alloy was set up in terms of the molecul ar dynamics simulation. The atomic structural models of the α phaseliquid int erf ace and the grain boundary of α phase with the coincidencesite lattice were c on structed by computer programming. The environmentsensitive embedding energy (E S E) of rare earth (or iron) atom in grain, on grain boundary and on α phaseliq uid interface was calculated by Recursion method. The bond order integrals (BOI) be tween Fe, RE atom and Al were also computed. The results show that RE and iron e lements are more stable on the α phaseliquid interface than in grain, which e xpl ains the fact of very small solid solubility of RE and iron elements in α phase , and the enrichment of RE and iron elements in the solid-liquid growth front whe n solidifying. This leads to the segregation of RE and iron atoms on the grain b oundaries and the formation of the complicated REcompounds.
2004, 53 (10): 3487-3492.
doi: 10.7498/aps.53.3487
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There is considerable interest in the study of self_assembled quantum dots as on e of the new optoelectronic materials in the field of physics. It is interest ing in theory, and also applications. In this article, we consider the InAs isla nds buried in GaAs, because of large lattice mismatch (≈-0.067), which makes s t rain effect to be the main factor in the formation of quantum dots. Most methods for calculations of strain distribution are based on the numerical solution of qu antum dots structures, which need heavy calculations work. We present a detailed process to derive an analytical formula for the strain distribution in some f am iliar shapes of quantum dots with Green function method, and discuss their influ ence on the strain distribution in quantum dots by taking into account the anisotr opy of elastic properties and shape. The results showed that the strain distribu t ions in the major part of the quantum dot structure are very similar for differe nt shapes and that the characteristic value of the hydrostatic strain component depends o nly weakly on variation of the shape of quantum dots.
2004, 53 (10): 3493-3497.
doi: 10.7498/aps.53.3493
Abstract +
Nonacomposites of NiSe2was successfully synthesized by EDTAassisted hydrothe rm al method, adding NiSe2 with MX2 structure as seed. X_ray diffraction pa tterns indicate that the products are single phase FeS2(pyrite) with the average grain size of about 48nm. FeS2thin films were prepared by screen_printing method and annealed at high temperature. It has been shown that they have an increased direct bandgap. With increasing amount of seed, the absorbance edges in the ultraviolet_visible range show a red shift; the resistance goes up; Hall mobility rises and the carrier c oncentration decreases. The FeS2thin film shows an n_type semiconductor chara cteristic. The mechanism of the formation of FeS2(pyrite) nanocrystalline was discussed in terms of the growth process.
2004, 53 (10): 3498-3503.
doi: 10.7498/aps.53.3498
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An acoustoelectric current is induced by a surface acoustic wave (SAW) launched along the quasionedimensional electron channel defined in a GaAs/Al x Ga1-x As heterostructure by split gates. Using the WKB approxima tion, the acoust oelectric current is calculated when only one electron is captured in the quantu m well. We discussed the effect on acoustoeletric current caused by SAW power, S AW frequency, gate voltage and sourcedrain bias.
2004, 53 (10): 3504-3509.
doi: 10.7498/aps.53.3504
Abstract +
An acoustoelectric current is induced by a surface acoustic wave (SAW) launched along the quasionedimensional electron channel defined in a GaAs/Al x Ga1-x As heterostructure by split gates. Using the WKB approxima tion, the acoust oelectric current is calculated when only one electron is captured in the quantu m well. We discussed the effect on acoustoeletric current caused by SAW power, S AW frequency, gate voltage and sourcedrain bias.
2004, 53 (10): 3515-3520.
doi: 10.7498/aps.53.3515
Abstract +
We have studied the optical properties of the interface of Al and GaAs surface q uant um well by insitu photoreflectance (PR) spectroscopy in a molecular beam e pitax y (MBE) system. The intermixing of Al and GaAs surface quantum wells forms an AlxGa1-xAs barrier layer on GaAs, which would shift the inte r_band transition peaks of the GaAs quantum well. Based on the calculation using effective mass approximate method, we fi nd that the intermixing length is 0.5nm, which is an important parameter in sem iconductor technology.
2004, 53 (10): 3521-3524.
doi: 10.7498/aps.53.3521
Abstract +
We have studied the optical properties of the interface of Al and GaAs surface q uant um well by insitu photoreflectance (PR) spectroscopy in a molecular beam e pitax y (MBE) system. The intermixing of Al and GaAs surface quantum wells forms an AlxGa1-xAs barrier layer on GaAs, which would shift the inte r_band transition peaks of the GaAs quantum well. Based on the calculation using effective mass approximate method, we fi nd that the intermixing length is 0.5nm, which is an important parameter in sem iconductor technology.
2004, 53 (10): 3525-3529.
doi: 10.7498/aps.53.3525
Abstract +
Highquality Tl2Ba2CaCu2Oy(Tl2212) thin films were prepared on s ingle crystal(001) lanthanum aluminate (LaAlO3) substrates by a twostep method. Tlfree amor phous precursor films were first deposited by a pulsed laser deposition techniqu e and then the thalliation, crystallization and oriented growth of the films wer e obtained in the process of annealing treatment in a sealed high-temperature st eel capsule at temperature of 720—850℃ . Xray diffraction reflections reveal th e existence of only Tl2212 phase with nearly perfect caxis orientation. The fu ll width at half maximum of ω scan of (0012) peak was 072°. Scanning electro n m icrographs of the thin films show that the surfaces of the films are smooth. The zeroresistance transition temperature TC0 is 1062K.
2004, 53 (10): 3530-3534.
doi: 10.7498/aps.53.3530
Abstract +
We have proposed a novel method for designing the second_order planar gradiomete rs and even high_order gradiometers.The gradiometer consists of two parts,one is the superconducting quantum interference device(SQUID),the other is the pickup loop which is directly coupled with the SQUID.The pickup loop consists of two p arallel_connected loops,each loop consists of several opening loops which are co nnected with minimal channels between them.By adjusting the site,size and shape of these opening loops,we can realize that the current in the common line betwee n the two loops is proportioned by the high_order gradient of the magnetic field .Because the line is coupled with SQUID,so we can measure the high_order gradien t of the magnetic field.We have got the relations between the site and the size of loops by calculation, and prove it can work.For high_order gradiometers,the baseline is important.Our design can use flip_chip configration to lengthen the baseline.Another method to get longer baseline is to design two_dimensional gradiometers which are easy to design using our method.
2004, 53 (10): 3535-3539.
doi: 10.7498/aps.53.3535
Abstract +
Based on the theory developed by Safonov and Yamazaki in nonlinear radiation damping of parametrically excited spin waves (J. MMM. [STHZ]161[STBZ] (1996) 27 5), we calculate the effect of microwave cavity Q_value on the threshold of instab ility and autooscilations of microwave absorption, considering both processes of nonlinear magnon_magnon interaction and magnon_photon interaction. The resu lt is basically consistent with experimental data.
2004, 53 (10): 3540-3544.
doi: 10.7498/aps.53.3540
Abstract +
Within the t_J model, the spin dynamics of the underdoped spatially ani sotropic triangular antiferromagnets is studied based on the fermion_spin theory . It is shown that the pattern of the neutron scattering peaks depends on both a nisotropic parameter and doping. Although the positions of the neutron scatterin g peaks are energy independent, the weight of these peaks decreases with increas ing energy.
2004, 53 (10): 3545-3549.
doi: 10.7498/aps.53.3545
Abstract +
The effects of interstitial Mn (MnI) atoms on the electronic and magnet ic properties of (Ga,Mn) As are studied within the pseudopotential plane_wave f rame work based on the density functional theory. Numerical results show that MnI atoms are donors in GaAs. The Mn atoms that substitute for Ga sublattices (MnGa) and MnI are antiferromagnetically coupled. The static electrical interaction makes the MnGaand MnI atoms tend to form MnGa_MnI pairs. The MnI atoms not only compensate the holes, and reduce the hole density of (Ga,Mn)As, but also deactivate MnGaatoms. The existence of MnI atoms are very disadvantageous for obtaining (Ga,Mn)As samp les having high Curie temperatures.
2004, 53 (10): 3555-3559.
doi: 10.7498/aps.53.3555
Abstract +
In this paper, charge storage and its dynamics in positively corona char ged polytetrafluoroethylene（PTFE） film electrets have been studied. It is foun d that from room temperature to 100℃ and from about 150℃, especially from 180 ℃ to higher temperatures, slow retrapping controls the transport of detrapped c h arge; however, from about 100℃ to 150℃ the fast retrapping plays a dominant ro le. The increase of the initial surface potential will lead to a significant decay of charge density, so by means of properly controlling the charging parameter an d the heat treatment process we can get positively and negatively charged PTFE f ilm electrets with the same charge density, which not only have a similar charge storage life but also an outstanding charge storage stability.
2004, 53 (10): 3560-3564.
doi: 10.7498/aps.53.3560
Abstract +
In this paper, charge storage and its dynamics in positively corona char ged polytetrafluoroethylene（PTFE） film electrets have been studied. It is foun d that from room temperature to 100℃ and from about 150℃, especially from 180 ℃ to higher temperatures, slow retrapping controls the transport of detrapped c h arge; however, from about 100℃ to 150℃ the fast retrapping plays a dominant ro le. The increase of the initial surface potential will lead to a significant decay of charge density, so by means of properly controlling the charging parameter an d the heat treatment process we can get positively and negatively charged PTFE f ilm electrets with the same charge density, which not only have a similar charge storage life but also an outstanding charge storage stability.
2004, 53 (10): 3565-3570.
doi: 10.7498/aps.53.3565
Abstract +
In this paper, the interaction between the optical activity and electr o_optic effect has been studied, and its influence on the electro_optic Q s witcher made of the optically active crystal has also been studied.
2004, 53 (10): 3571-3576.
doi: 10.7498/aps.53.3571
Abstract +
Because of the localization of light, the magneto_optical (MO) photonic crystal, composed of magnetic and dielectric films periodically or quasi_periodically, can be used to manufacture the MO isolator. A transfer matrix method, suitable for computing the propagation of polarized l ight in anisotropic media, is described in detail in this paper. Using this met hod, we discuss the MO properties of a new type of MO isolator with multi_defect , and find that the spectra are broadened with increasing number of defects. A reflection_mode MO isolator without extra reflected layers is proposed when th e number of defects is large enough.
2004, 53 (10): 3577-3582.
doi: 10.7498/aps.53.3577
Abstract +
We report the experimental results on the effect of pulse width on transient thermally induced optical nonlinearities in the nanosecond r egime. We have obtained the Z_scan curves of the CS2 solutions of nigrosin e for different pulse widths, and analyzed the co_existence of third_order and transie n t thermally induced optical nonlinearities. The process of changing from transi ent state to steady_state thermal_induced optical nonlinearities was observed. M eanwhile, we have obtained the results of numerical simulation by solving simult aneously acoustic and electromagnetic wave equations, which agree well with the experimental results.
2004, 53 (10): 3583-3586.
doi: 10.7498/aps.53.3583
Abstract +
Two_dimensional air_cylinder photonic crystals were fabricated based on silicon by using the multiplex inductively coupled plasma system supplied by STS company . Photonic band gap was theoretically calculated by using the finite different t ime domain (FDTD) method, and the reflection spectrum was measured experimentall y using the microscope infrared spectrometer instrument. We find that the reflec tion measurements are in good agreement with the theoretically expected behaviour.
2004, 53 (10): 3587-3590.
doi: 10.7498/aps.53.3587
Abstract +
Effect of Mg doping on the properties of AlGaN layers gro wn on sapphire substrates by metal_organic chemical vapor deposition were studie d using x_ray diffraction and Raman scattering. When the doping of Mg was low, the E2 mode shifted to lower frequency and the full width half at maximum of the rocking curve and A1(LO) mode decreased. However, as the flow rate of CP2Mg increased ti ll the AlGaN was doped with a dose as high as 4×102/sup>cm-3, the quali ty of film de creased gradually and the E2mode shifted to higher frequency, indicat ing a compressive stress in the films. Finally, the relation between the Raman s hift and the stress alteration was described by Δσ＝-0298+0562ΔE.
2004, 53 (10): 3591-3595.
doi: 10.7498/aps.53.3591
Abstract +
Z_scan experiments are performed on the azobenzene polymer (DR_13_PMMA) films with He_Ne laser. It is found that the relation between the cha nge of refractive index of the sample and the light intensity behaves like a sat u rable effect, whose relative parameters are alterable with light intensity. It i s also found that the change of refractive index induced by linearly polarized l ight is distinctly greater than that induced by circularly polarized light. The phenomena are explained by using the theory based on the effect of angular hole burning of photoisomerization.
Z-scan measurements on photoisomerization of azobenzene polymer and their theoretical interpretation
2004, 53 (10): 3596-3600.
doi: 10.7498/aps.53.3596
Abstract +
Z_scan experiments are performed on the azobenzene polymer (DR_13_PMMA) films with He_Ne laser. It is found that the relation between the cha nge of refractive index of the sample and the light intensity behaves like a sat u rable effect, whose relative parameters are alterable with light intensity. It i s also found that the change of refractive index induced by linearly polarized l ight is distinctly greater than that induced by circularly polarized light. The phenomena are explained by using the theory based on the effect of angular hole burning of photoisomerization.
2004, 53 (10): 3601-3608.
doi: 10.7498/aps.53.3601
Abstract +
The evolution of microstructural parameters (mean size and volume fracti on) of precipitates in three types of Al_Zn_Mg_Cu alloys during ageing has been studied by synchrotron_radiation small angle x_ray scattering (SAXS). The influe nce of Zn content on the precipitation has been analyzed. The results show that the precipitates are in nanometer scale for the three types alloys (A, B, C) . Th e maxima of the precipitate volume fractions forA, Band Cincrease wi th Zn content and are about 0.023—0.028, 0.052—0.054 and 0.04 respectively The evolution of volume fra ction at a certain temperature is consistent with the kinetic process of precipi tate nucleation, growth and Ostwald ripening.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
2004, 53 (10): 3609-3613.
doi: 10.7498/aps.53.3609
Abstract +
An optimum composition range （29％≤x≤31%） of 〈001〉 oriented (1_x)P b(Mg1/3Nb2/3)O3_xPbTiO3(PMNT) crystals was ascertain ed for multilayer actuator applications, which exhibited high_strain and low_hyster esis behavior. A nearby -2kV/cm negative E_field can be applied to PMNT ferr oele ctric samples with low hysteresis. Forty_layer PMNT strain actuators with indiv idua l element sizes of 7mm×7mm×0.7mm were fabricated from their optimum composit ions, with displacements of 38.1μm at E_fields from -1.5 to 10 kV/cm. Wh en a 4 kg load was added to the PMNT multiplayer actuators, the displacements we re decreased to 34 μm.
2004, 53 (10): 3614-3618.
doi: 10.7498/aps.53.3614
Abstract +
Fe_Si_B_Nb_Cu alloy thin films were deposited by radio frequenc y (rf) magnetro_sputtering. Their microstructures have been analysed by x_ray di ffraction (XRD) and Mssbauer spectrum. The results show that the thin films, p repared by low rf power, are amorphous. With the increase of rf power, the depo sited thin films were turned to be a mixted structure composed of nano_crystals and amorphous matrix. The nano_crystals contain α_Fe(Si) and α_Fe(B) solid solutio ns, which are in nanometer size, their relative volume fractions, atomic assembly features , magnetic moment orientations and macro_magnetic properties are changed under d ifferent rf powers.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
2004, 53 (10): 3619-3626.
doi: 10.7498/aps.53.3619
Abstract +
A new tortoise coordinate transformation is defined. With the thin film model , we calculate again the temperature and the entropy of non_stationary black holes. The problem of indetermination of the cut_off factor in calculating the entr opy of non_stationary black holes is solved. We study and understand again the t emperature and the entropy of non_stationary black holes by way of the Vaidya b lack hole and the rectilinearly accelerating black hole.
