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Acta Physica Sinica  
  Acta Physica Sinica--1984, 33 (9)   Published: 15 September 1984
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BRIEF REPORT

EFFECT OF PRESSURE ON THE TRANSITIONS OF NH4IO3 AND ITS SOLID SOLUTIONS

YAO YU-SHU, CHEN HONG, LI YONG-JIN
Acta Physica Sinica. 1984, 33 (9): 01278 doi: 10.7498/aps.33.1278
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The effects of hydrostatic pressure on the transition temperatures Tc of NH4IO3 and its solid solutions Kx(NH4)1-xIO3 have been investigated by means of differential thermal analysis (DTA) up to 10 kbar. The experimental results of Kx(NH4)1-xIO3 solid solutions indicates that the dTc/dP values are independent of the concentration of K+, although Tc decreased with increasing concentration. This appears to imply that the IO3- ions elongation under pressure will play a more important role in the pressure effect on the rising of Tc.

STUDY OF ACOUSTICAL NONLINEARITY B/A IN BIOLOGICAL MEDIUM

FENG RUO, GONG XIU-FEN, ZHU ZHENG-YA, SHI TAO
Acta Physica Sinica. 1984, 33 (9): 01282 doi: 10.7498/aps.33.1282
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By using insert substitution method, the acoustical parameter of nonlinearity B/A have been determined for a series of liquid biological samples: porcine whole blood, bovine whole blood, milk and aqueous solutions of polyethylene glycol of various molecular weight. The values of B/A for solutions of PEG increase linearly with solute concentration and exhibit no evident dependence on solute molecular weight.

A NEW METHOD FOR OBTAINING LARGE-ANGLE CONVERGENT-BEAM ELECTRON DIFFRACTION

FENG GUO-GUANG
Acta Physica Sinica. 1984, 33 (9): 01287 doi: 10.7498/aps.33.1287
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The symmetry of CBBD patterns provides a powerful means for determ'ning the crystal point groups and space groups. To obtain a useful CBED pattern, the angle of convergence of the electron beam must be large enough, but the diffraction discs must not overlap. A new method for obtaining non-overlapping large-angle CBED is proposed here. The principle of this method is equivalent to that proposed by Tanaka et al. Instead of shifting the specimen, the electron beam is defocused, thus retaining the eccentric height of the specimen. Hence the area of interest will not be lost when the specimen is tilted. Large-angle CBED patterns generated by a large electron probe (>2μm) may besdistorted, but they are useful.

THE MICROWAVE-RADIO FREQUENCY WAVE MULTI-QUANTUM TRANSITION IN OPTICAL PUMPING EXPERIMENT

LIU SHU-QIN, DONG TAI-QIAN
Acta Physica Sinica. 1984, 33 (9): 01291 doi: 10.7498/aps.33.1291
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In the optical pumping experiment for 87Rb gas cell, when the microwave and radio frequency wave are applied simultaneously, the optically detected resonance signals of microwave-radio frequency wave multi-quantum transition are observed.

ON CONVECTIVE EFFECTS IN GAS LASERES

GAO ZHI
Acta Physica Sinica. 1984, 33 (9): 01294 doi: 10.7498/aps.33.1294
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The convection of the gain medium is a decisive factor for large increase in power output of gas lasers. The present analysis shows that both the saturation intensity and the laser power density (or the small-signal gain coefficient) by which CW laser is characterized increase nonlinearly with the flow speed and tend to the respective limiting values. It is also shown that the increment of the saturation intensity does not go beyond about 10 times, and a large increase in power density is caused by the accumulation of excited energy in the flowing gas. These results are not the same as those of the currently accepted theory which predicts that the saturation intensity increase linearly and unlimitedly with flow speed, and a large increase in power density is due to a large increase in the saturation intensity. The present quantitative results of the variation of the saturation intensity with the gas flow transient time are consistent with the experimental data of the flowing CO2 gas lasers, where the gas flow transient time denotes the time required for the flowing gas to move across the gas gain region, or the probing-beam section.

OPTICAL CHARACTERISTICS OF RAMSDELLITE CRYSTAL Li2Ti3O7

HU BO-QING, CHEN HUI
Acta Physica Sinica. 1984, 33 (9): 01301 doi: 10.7498/aps.33.1301
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Absorption, refractive indices and direction of principle indices of metastable ra-msdellite single crystal Li2Ti3O7 have been determined. Its substructure and ceramic-like transform of R-phase single crystal have been observed. Finally, a brief discussion is given.

ABNORMAL SENSIBILITY OF REFLECTION STRUCTURES FOR WEAK VIBRATIONS ON THE SHORT-WAVE SIDE OF RESTSTRAHLEN BAND OF CRYSTALS

ZHANG GUANG-YIN, WANG BAO-MING
Acta Physica Sinica. 1984, 33 (9): 01306 doi: 10.7498/aps.33.1306
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Using the classical theory of vibration and n-k relation curve and n-k half-circle graph of reflectivity for vibrators, the abnormal sensibility of reflection structure for weak-vibrations on the short-wave side of reststrahlen band of crystals is explained, also the forms and characteristics of the reflection structure are given. By this abnormal sensibility, it is possible to study various types of weak vibrations in crystals.

SPECIFIC CONTACT RESISTANCE OF METAL-BULK SEMI-CONDUCTOR——FOUR-POINT CONFIGURATION MODEL

CHEN CUN-LI
Acta Physica Sinica. 1984, 33 (9): 01314 doi: 10.7498/aps.33.1314
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In this paper, a method to measure the specific contact resistance ρc of M-S bulk sample-the four-point configuration model-is presented. The location of. four circular metal electrodes is arbitrary and the equations for specific contact resistance ρc have been derived. It is shown that if the sample is not semi-infinite but has a definite thickness, the equation must be modified with some correction factors. According to this model, we carried out some measurements and calculations, the results are in good agreement with that of reference [7].

TRANSITION FROM QUASIPERIODIC REGIME TO CHAOS IN THE FORCED BRUSSELATOR

WANG GUANG-RUI, HAO BAI-LIN
Acta Physica Sinica. 1984, 33 (9): 01321 doi: 10.7498/aps.33.1321
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We have observed transitions from quasiperiodic regime to chaos in the periodically forced Brusselator. It takes place via kinking and folding of the originally smooth Poincare map which may be more generic as compared to the transition in circle mapping, where the quasiperiodic orbit looses smoothness globally. Now all the well-known "routes" to chaos have been shown to coexist in this mathematical model in different part of the parameter space. This is in agreement with experimental observations in some hydrodynamical systems where different routes to turbulence have been found in one and the same system under slightly different conditions.

THEORY OF THE CRITICAL TEMPERATURE FOR SUPERCONDUCTORS WITH SMALLλ (Ⅱ)

WENG ZHENG-YU, WU HANG-SHENG
Acta Physica Sinica. 1984, 33 (9): 01326 doi: 10.7498/aps.33.1326
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A Tc formula valid for the region of small λ and arbitrary effective phonon spectrum is derived from the Eliashberg equation by the method used in the previouspapers[1,2].
CONTENT

ELECTRICAL PROPERTIES OF IONIC CONDUCTOR AgI CONTAINING DSPP

ZHAO ZONG-YUAN, WANG CHAO-YING, CHEN LI-QUAN
Acta Physica Sinica. 1984, 33 (9): 01205 doi: 10.7498/aps.33.1205
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Electrical conductivities of pure AgI and AgI containing DSPP (η-Al203, 0.05 and γ-Fe2O3, 0.6) have been measured as a fuctions of composition and temperature. The conductivity in β-phase was increased by the addition of DSPP. The maximum increment which appears at about 40-50 mol% DSPP is two or three orders of magnitude at room temperature. The conductivities in α-AgI contain DSPP decreases and activation energy increases. Both conductivity measurement and DTA experiment show that DSPP influences the phase transition, especialy α-phase to β-phase trasition. For instance, the α- to β-phase transition temperature of AgI (Al2O3 50mol%) is 17℃ lower than that of pure AgI. The dc polarization experiment carried out for AgI (γ-Fe2O3 50mol%) system, indicated the AgI (γ-Fe2O3) is a n-type conductor and the electronic conductivity is negligible compared with the total conductivity.

ACOUSTIC PROPERTIES OF GLASSES IN Li2O-(LiCl)2-B2O3-A12O3 SYSTEM

HUANG PENG-NIAN, HUANG XI-HUAI
Acta Physica Sinica. 1984, 33 (9): 01213 doi: 10.7498/aps.33.1213
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The densities and supersonic velocities were measured and the adiabatic compressibilities were calculated for several series of glasses in Li2O-(LiCl)2-B2O3-Al2O3 system. The changes of structures of glass networks with compositions were analyzed according to their acoustic properties. These provided a method and basis of analysis for our study of the ionic conduction of glasses.

ON CALCULATION AND APPLICATION OF PARTIAL STRUCTURE FACTORS FOR MODELS OF AMORPHOUS BINARY ALLOYS

WU GUO-AN
Acta Physica Sinica. 1984, 33 (9): 01219 doi: 10.7498/aps.33.1219
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The equation of calculating Faber-Ziman partial structure factors for models of binary alloys is derived from Debye equation. The SFeB(Q) and SNiB(Q) of models for Fe83B17 and Ni64B36 metallic glasses are calculated, and compared with the experimental results and the partial scattering intensities IFeB(Q) and INiB(Q) The partial structure factors of model for Hg2Na liquid alloy are also calculated, and extrapolated to the long wavelength limit. Finally, the behavior of the total structure factors near the long wavelength limit for alloys, which have chemical short range order, is discussed.

SCATTERING OF ELECTRONS BY SCREW DISLOCATIONS IN SILICON CRYSTALS

HUANG HENG-JI, YASUNARI ZEMPO
Acta Physica Sinica. 1984, 33 (9): 01227 doi: 10.7498/aps.33.1227
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In this paper, the scattering of electrons by 〈110〉-screw dislocations insilicon crystals is discussed. We use the tight-binding approximation, only electrons in the s and p state are taken into account. With the long wave length approximation, only scattering of electrons near Г in the first BZ is considered. A scattering theoretical approach yields an integral equation of Kirchh off-Huygens type. The scatlering equation has been solved by means of gauge transformation and Green's function. It is confirmed that, as in the ease of single band in the case of many bands the shadow, which is the region that can not be affected by electron flux, appears in the down stream side of dislocations as well.

A STEEP CHANGE IN THE TEMPERATURE DEPENDENCE OF THE STICKING COEFFICIENT OF In ATOMS ON THE Si(111)4×1-In SURFACE

ZHOU JUN-MING, HUANG YI, LIN ZHANG-DA
Acta Physica Sinica. 1984, 33 (9): 01240 doi: 10.7498/aps.33.1240
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AES and RHEED techniques have been applied to a study of temperature dependence of the sticking coefficient of In atoms on the Si(lll)4×1-In surface. At temperatures below 110℃, the sticking coefficient for In atoms is close to zero due to saturation of valence bonds resulting from the arrangement of In atoms in the 4×1-In overlayer. The steep change of the sticking coefficient in the temperature range 110-120℃ may be explained by a model of the order-disorder transition arisen from the surface melting. At temperatures above 120℃, the sticking coefficient of In atoms is always close to unity.

KOLMOGOROV CAPACITY AND LYAPUNOV DIMENSION OF STRANGE ATTRACTORS OF FORCED BRUSSELATOR

WANG GUANG-RUI, CHEN SHI-GANG, HAO BAI-LIN
Acta Physica Sinica. 1984, 33 (9): 01246 doi: 10.7498/aps.33.1246
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In this paper, by using stroboscopic sampling method which reduces the dimension of attractors, the Kolmogorov Capacity dC and Lyapunov dimension dL of some typical attractors of forced Brusselator are computed. The results show that the conjectures of ref. [6, 16] about the relations between dC and dL are correct. We spell out these conjectures as that if the maximal Lyapunov exponent λ1>0, then dC=dL; if λ1=0, then there exist examples that do not satisfy dC=dL. The reasons for noncon-vergence of dC for the forced Brusselator Caculated by using the Runge-Kutta difference equations and the way to improve it are pointed out and tested numerically. We conjecture further that by the same reason of using difference equations to approach differential equations, the capacity caculated from time series of a single observable may not be convergent.

AN INVERSE CHERENKOV FOCUSING LASER ACCELERATOR

ZHUANG JIE-JIA
Acta Physica Sinica. 1984, 33 (9): 01255 doi: 10.7498/aps.33.1255
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The principle of the inverse cherenkov focusing laser accelerator is presented. It is readily shown, by studying the dynamics of the charged particles, that the particles are accelerated steadily and continuously when the condition of the cherenkov radiation is satisfied, and need no additional focusing systems since the laser field on the focusing axis is just the accelerating field, so that the intensity of the latter may be higher than that in the previously proposed inverse cherenkov laser accelerator. The limitations of this accelerating mechanism are also discussed.

NONPERTURBATION THEORY OF TIME-RESOLVED DEGENE-RATE FOUR-WAVE MIXING IN TWO-LEVEL SYSTEM

FU PAN-MING, YE PEI-XIAN
Acta Physica Sinica. 1984, 33 (9): 01261 doi: 10.7498/aps.33.1261
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In this paper, the time-resolved degenerate four-wave mixing in two-level system is treated rigorously with the density-matrix method. The phenomena related to the saturation effect are discussed. The physical origin of these phenomena is analysed.

THE STABILITY OF 2-DIMENSIONAL ELECTRON GAS AT HIGH DENSITY

XIE HAN-KUN, ZHOU SHI-XUN, SUN XIN
Acta Physica Sinica. 1984, 33 (9): 01269 doi: 10.7498/aps.33.1269
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The edge energy of the 2-dimensional electron gas with high density is calculated, here the edge energy implies the energy which is needed to form a unit length of new edge when a 2-dimensional infinite homogeneous electron system is cleft into two pieces of semi-infinite electron systems. It is found that, for rss(c)≈0.415, the edge energy becomes negative, indicating that at high enough density the ground state of the 2-dimensional electron gas can be unstable. The stability of the ground state of the bound and unbound 2-dimensional electron gas is discussed and a criterion for the ground-state stability of the bound 2-dimensional electron gas is obtained for a simplified model.
LETTERS

A STUDY ON KINETICS OF STRAIN-INDUCED MAGNETIC ANISOTROPY IN A METALLIC GLASS

CHEN DU-XING
Acta Physica Sinica. 1984, 33 (9): 01332 doi: 10.7498/aps.33.1332
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The kinetics of development of strain-induced magnetic anisotropy Kus has been studied in a zero-magnetostriction metallic glass Co65.2Fe4.2Ni3Nb1Al2Si9.8B14.8. The variations of Kus with annealing time ta involve the effect of a wide distribution of relaxation times. It was found that △E = 180-290kJ/mol and τ0=10-14-10-22s for 155 MPa isothermal annealing at 280-320℃ after 244MPa annealing at 440℃.

THE IMAGE FORCE ON THE DISLOCATION NEAR A CRACK TIP

LONG QI-WEI, WANG LI
Acta Physica Sinica. 1984, 33 (9): 01337 doi: 10.7498/aps.33.1337
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The image force on the dislocation near an elliptical hole is calculated by confor-mal mapping technique. Allowing one axis of the ellipse to dwindle to zero, the crack limit solution is obtained.
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