Vol. 37, No. 3 (1988)
AN INTERNAL FRICTION STUDY OF INTERFACE DYNAMICS IN THE PROCESS OF PHASE TRANSFORMATIONS OF NiTi ALLOY
1988, 37 (3): 353-362. doi: 10.7498/aps.37.353
The Martensitic (MP) and incommensurate/commensurate (I/C) phase transformations during the athermal process of NiTi alloy were studied by the measurements of internal friction, elastic modulus and electric resistance simultaneously. The IF behaviour in the processes of MP and I/C phase transformations are nearly the same and is associated with the motion of phase interface under the action of phase transformation driving force. Starting with the interface dynamics model, the interface dynamic behaviour of MP and I/C transformations were . studied. An explicit functional relationship of the interface dynamics in the process of marten-sitic transformation was obtained as V = V* exp(-△G*/△G - △GR) and the expression for IF during the process of phase transformation as Q-1 = (n2/2)×(μ△G*/(△G-△GR)2) dF/dT·T/ω. The transformation resistance froce △GR is the order of 10 cal/mol. The "soft mode effect" during the transformation process was discussed, and it was shown that the softfening of pho-non mode and the modulus defect associated with interface motion coexist in the processes of martensitic and I/G phase transformations.
1988, 37 (3): 363-372. doi: 10.7498/aps.37.363
The internal friction (IF) Q-1, modulus f2, electrical resistance R and stress s of superelastic Ni51Ti49 alloy in the process of stress induced incommensurate/commensurate (I/C) transition was measured as a function of strain e by a middle torsion pendulum on a tensile testing machihe modified with a four-terminal potential equipment.The effects of number of stress cycles and strain rate e (in the range of 7×10-7/s to 1×10-4/s) were studied. An IF peak and a minimum of modulus were observed respectively in the Q-1-εand f2-εcurves. The IF peak height Qp-1 and modulus defect △M/M increase with an increasing of ε/ω, where ω is angular frequency of measuring. By utilizing an expression obtained from phase interface dynamics and experimental data of Qp-1 (as a function of ε/ω and amount of phase transition F), an explicit functional relationship of average I/C phase interface velocity V and effective phase transition driving force △G′= △G - △GR (where △GR is resistance) was derived as V =V*(△G - △CR)m, where V* and m are dynamic parameters an △GR is a resistance force exerting on the moving interface, which has the order of 1 cal/mol for stress-induced I/C transition of superelastisity NiTi alloy. The relationship between Q-1 and modulus defect △M/M and soft modulus effect are disussed.
1988, 37 (3): 373-378. doi: 10.7498/aps.37.373
ESCA analysis identifies that the different functional groups of nitrogen compounds have been conbined on the PET surfaces, when modified by the air plasma and the argon plasma. In particular, the double N15 peaks occur on the PET surface after 5 minutes treatment by the low temperature argon plasma. The second peak-N15 is considered as the contribution of nitrogen oxides. The double peaks PET-N15 structure does not result by bombardment with low energy nitrogen ions and argon ions, which indicates that the effect can not be attributed to the action of low energy ion alone.
1988, 37 (3): 379-387. doi: 10.7498/aps.37.379
In this paper, the Bragg diffraction of SAW on acoustic grating is investigated by incorporating the anisotropy of the substrates. In the analysis, the difference between the incident wave, the fundamental wave and spatial harmonic wave in grating region and the diffraction waves in transmission region is phenomenologically described by using their different corresponding velocities. The experimental results for the diffraction of SAW on acoustic grating which is fabricated on Y-cut LiNbO3 are presented. The comparison of the experimental results with the analyzed results obtained on isotropy approximation shows that the discrepancy is significant. The "extraordinary Bragg diffraction" equations are obtained by using the coupled-waves method which takes the anisotropy of the substrates into consideration. It is shown that the calculated results based on "extraordinary Bragg diffraction" equations are coincident with the experimental results fairly well.
FOCUSING BEHAVIOURS OF THE DIFFRACTED BEAM OF SURFACE ACOUSTIC WAVE ON CHIRPED GRATING IN BRAGG REGIME
1988, 37 (3): 388-395. doi: 10.7498/aps.37.388
The acoustic field distribution of the deflected wave beam in transmission region from a chirped acoustic grating is described by using Fresnel-Kirchhoff diffraction integral expression. The transmission function of the SAW beam which is diffracted by a linearly chirped grating in Bragg regime is obtained by using quasi-periodicity approximation and this function is considered as the field distribution function in the aperture of the exit plane. It is shown from the analysis that in Fresnel region there is a Fraunhofer plane where the field distribution is the Fourier transformation of the field along the aperture. It is demonstrated that the role played by the grating is two fold i.e. a deflector and a lens. The most important point we found is that the focusing axis of the focused wave beam will translate parallelly when the frequency of the input signal is changed. This scanning configuration is quite different from the traditional deflection scanning. The theoretical predictions are verified by experimental observations and measurements.
THE FORMAL SOLUTIONS FOR FOKKER-PLANCK EQUATION WITH ZERO OR NEGATIVE DIFFUSION COEFFICIENTS AND THEIR APPLICATIONS TO QUANTUM OPTICS
1988, 37 (3): 396-407. doi: 10.7498/aps.37.396
In this paper, the formal solutions for Fokker-Planck equation with zero or negative diffusion coefficients in quantum optics are given. Their applications to the generation of squeezed states via degenerate parametric amplification or degenerate four wave mixing and other problems are discussed.
1988, 37 (3): 408-415. doi: 10.7498/aps.37.408
Degenerate four wave mixing is treated using the quantum theory of fradiation. Starting from the energy conservation and momentum conservation laws and using the transition rate-formula for quantum states, the equation of motion for photon number densities of four beams is derived and exact solutions are obtained. With these solutions, change of nonlinear reflectivity with the pump waves and the probe wave, and saturation, and parameter oscillation arc-described. Besides, comparisons are made between our theory and classical theory as well as Bloom's large signal experiment. It is shown that our theory is more accurate and reasonable.
1988, 37 (3): 416-423. doi: 10.7498/aps.37.416
We have developed a several-millisecond pulsewidth pulsed Nd:YAG laser with output power of 200 watts in average and 5000 watts in peak. The performance of the long-pulse-width pulsed Nd:YAG laser is investigated. The theoretical analysis agrees with the experiments quite will.
HIGH POWER CONTINUOUSLY TUNABLE FAR INFRARED RAMAN NH3 LASER PUMPED USING A HIGH PRESSURE TE CO2 LASER
1988, 37 (3): 424-429. doi: 10.7498/aps.37.424
A tunable far-infrared Raman transition NH3 laser with output energies up to 4 mJ (～80kW) is reported. The tuning range covered more than 70% of the emission spectrum from 90 to 93 μm, and the continuous tuning range associated with individual K-level transitions is about 30 GHz. Typical experimental results are described and discussed.
EXAFS, IR AND RAMAN SPECTRA STUDIES ON THE NONCRYSTALLINE COPPER IONIC CONDUCTORS IN P2O5-CuI-CuCl SYSTEM
1988, 37 (3): 430-438. doi: 10.7498/aps.37.430
Microstructures of the noncrystalline copper ionic conductors with the network former of P2O5 were studied by means of transverse EXAFS, IR and Raman spectra. From the results, it is derived that in these noncrystalline network structure, there are skeleton structure elements such as [PO4]3-, [CuO4]-6, [CuO3I]5-, [PO31]2- etc., and there are two different distributions for Cu+ ions in voids of the network. The second-order phase transition of the materials at about 50℃ and conduction properties of Cu+ ions are discussed.
A METHOD FOR CALCULATING DC CONDUCTIVITIES OF THE POROUS MEDIUM AND COMPOSITE (Ⅰ)——AN APPROACH TO THE POROUS MEDIUM WITH PERIODIC STRUTURE
1988, 37 (3): 439-446. doi: 10.7498/aps.37.439
A first-principle approach to the calculation of dc conductivities of the porous medium and composite is developed. In this paper, the case of the porous medium with periodic structure is discussed in detail. The effective conductivities for many two dimensional porous systems are calculated by polynomial approximation, Fourier expansion using elimination procedure and iterative approach of Fourier expansion Critical exponents for the dc conductivity of Sierpinski carpets are also calculated by an improved iterative approach. All the theoretical results agree fairly with recent experimental measurements.
1988, 37 (3): 447-451. doi: 10.7498/aps.37.447
Experimental measurements of electron thermal condouctivity coefficient on the CT-6B device are reported here. With the help of MHD internal disruption, which specifies the temperature sawtooth perturbation, analysing the amplitudes, cycles and phases of the perturbation signals of soft x-ray detectors, we have calculated the average electron thermal coefficients in different radiuses. Experiment results are an order of magnitude larger than that predicted by neoclassical theory, showing that electron heat conductivity in the CT-6B plasma is an anomalous one. It is shown that MHD internal disruption can make the energy transport increases obviously. Electron heat conductivity increases with the amplitude of MHD perturbo-tion.
1988, 37 (3): 452-459. doi: 10.7498/aps.37.452
An experiment in which a rotating magnetic field was used to generate and maintain a FRC is described. The FRC life time appeared to be limited by the duration of the rotating field pulse (40 ms), there was no evidence of gross instabities.
1988, 37 (3): 460-462. doi: 10.7498/aps.37.460
This paper gives an "equivalent circle" model which modifies the bow-shaped area model in papers  and  .
1988, 37 (3): 470-474. doi: 10.7498/aps.37.470
The parent ions (H2CO+) and the descendent ions (CO+) from higher energy dissociation channel, generated by 2+1 and 2+2 photon resonant excited processes respectively, have been found in the multiphoton ionization investigation on formaldehyde with XeCl excimer laser. No HCO+ ions from lower energy dissociation channel (which are dominant in both electron impact and single-photon ionization mass spectra) appear as a result of state-selective excitation.
1988, 37 (3): 475-480. doi: 10.7498/aps.37.475
It was well known that the interaction of solid surface with low energy ion beam results in the phenomena of sputtering and implantation. The characteristics of thin film Si3N6 formed by implanting ions N2+ at energy 1350 eV into single crystal Si are studied in this paper.We consider that it is necessary to introduce the concept of effective dose for ion beam which depends on the thickness of damage layer and the etching rate of as-implanted silicon nitrides.
1988, 37 (3): 481-484. doi: 10.7498/aps.37.481
The high conductivity a-Si:H:Y alloy films prepared by rf sputtering have been obtained. The room temperature d.c. conductivity is about 2×101 Ω-1·cm-1 as Y doping concentration reaches 20 at %. Measurements showed that the alloy films are of n-type. The plots of In a versus 1/T over temperature range investigated can be fitted by two straight lines with a kink occurring at a temperature which is ～70℃, ～75℃ and ～90℃, respectively, for samples deposited at substrate temperature T2 = 260℃, 290℃ and 330℃. Present results may be explained on the assumption that there are two parallel transport paths, one above kink temperature takes place in the conduction band and another below kink temperature in the Y-rela-ted donor impurity band, Moreover, we estimated that the center of the impurity band lies about 0.06-0.07 eV below the conduction band EC.
KINETICS OF THE CAPTURING FROM THE FREE MAJORITY CARRIER TAIL REGION AND MEASUREMENT OF THE MAJORITY CARRIER CAPTURE CROSS SECTION
1988, 37 (3): 485-489. doi: 10.7498/aps.37.485
We have discussed the kinetics of the capturing of freemajority tail by deep centres in semeconductors. We pointout that, the DLTS' signal is dicrectly proportional to the pulse width, if the DLTS' response region is restricted in the end of free-carrier tail vegion.This phenomenon may be used to measure the majority carrier capture cross section, in which the net shallow impurity concentration and the majority carrier capture cross section are both relatively wigh.
1988, 37 (3): 490-496. doi: 10.7498/aps.37.490
New methods for obtaining the scattering wave functions of an aperiodic potential are developed. The analysis of amplitude and phase of scattering wave functions demonstrates the efficiency of these methods.
1988, 37 (3): 497-501. doi: 10.7498/aps.37.497
The correlation between the superconducting Tc and the atom mass (M) for amorphous superconductors has been studied. It is found that the superconducting Tc is inversely proportional to the cubic root of the atom mass, i.e. Tc∞1/M1/3 for the elements of the same group in which they have the same number of valence electrons. The Tc of crystalline superconductors are discussed too, including the superionductivity of high Tc oxide superconductors.
1988, 37 (3): 502-506. doi: 10.7498/aps.37.502
The lattice vibrations of polaron in one-dimensional electronlattice coupled system are investigated. Two new localized vibrational modes g6 and g′6 are found, they can exist in some ranges of coupling constant λ. Furthermore, the dependences of frequencies and configurations of various localized modes on λ have been figured out.
1988, 37 (3): 507-510. doi: 10.7498/aps.37.507
We have studied the energy spectra of polaron in SSH model by using a selfconsistent ap-proach. Four new localized electronic state are discovered. They form four discrete levels outside the conduction and valence bands: one locates near the battom of the conduction band and one near the top of conduction bunt, another two are symmetrically near the valence band. Those at the bottom of conduction band and top of valence band only exist in the limited range of coupling constant λ.
1988, 37 (3): 511-514. doi: 10.7498/aps.37.511
The charge density of the local charge neutrality two dimensional electron system has been obtained for 1/3 Landan filling factor by the self consistent iteration method. We find a characteristic density distribution for the downward cusps of the ground state energies.
1988, 37 (3): 515-519. doi: 10.7498/aps.37.515
Application of exact renormalisation transformation, to Ising model via equiscale transformation in the same universality class, yields a four-branch critical surface and four fixed points. In the case of the ferromagnetic and antiferromagnetic phase transitions, the results are in agreement with the known exact and the best approximate ones very satifatorily. For the supperantiferromagnetic phase transition, we propose the critical surface equation as follows —ch(h) = sh(2Kx)sh(2Ky).
1988, 37 (3): 520-523. doi: 10.7498/aps.37.520
Through changing lattice action, the Monte Carlo "observation window" is shifted into g24 lattice. The scaling behaviour and M= (3.9±1.0)σ1/2 are found in this region.
1988, 37 (3): 524-528. doi: 10.7498/aps.37.524
The success of the Big Bang model strongly suggests that the universe may be created, but whether the universe is created from nothing or from vacuum is a problem of controversy. In this paper, we put forth a possible proposal for the creation of universe from vacuum fluctuation. We note that the primordial inflationary universe-primordial de Sitter Universe, could be created from the vacuum fluctuation in one-loop approximation, wherce the SO11, SU14 or E8×E8 symmetry hold. By way of the asymptotic freedom of the gauge coupling g and Higgs self coupling λ, the primordial GUT breaks down and the latent heat releases during the first order phase transition. The released heat will heat the 'cold' universe to Planck temperature, so the created inflationary universe will pass into the standard model dominated by radiation. Thereafter, for example, the SU5 GUT holds and the well known second inflation will appear at 10-35 seconds after the creation.