Vol. 32, No. 9 (1983)
1983, 32 (9): 1109-1117. doi: 10.7498/aps.32.1109
In this paper, an experimental and theoretical investigation on finite-amplitude reflection sound wave of circular piston sources is presented. The reflected field of harmonic waves from the boundary surface have been calculated. Thinking of them as the waves which radiate from the image of the piston source and treating them as the waves that seem to be generated by a new source on the vibrating boundary surface, by means of weak-shock theory, the reflection of the finite-amplitude waves can be predicated.By making use of the boundary wall of a pool, some experiments on second harmonic reflection have been done. It is shown that the average attenuation of the harmonic pressure with distance is consistent with the theory. However, along the longitudinal distance and in the cross sections perpendicular to it there are obvious interference of the harmonic waves, and longitudinal interference lengths have an order of magnitude greater than the traverse ones. According to the theoretical evaluation, it seems to be that the reflection results from the pool wall that has a thickness, a small angle between its two boundary surfaces and a fixed beam width of the primary wave. The theoretical evaluation and the experiments are in agreement with each other.
1983, 32 (9): 1118-1126. doi: 10.7498/aps.32.1118
In this paper, the magnetic field distribution around a coil is worked out by solving the Maxwell equations for both the cases before and after inserting a "concentrating body" into the winding coil. The solution shows that, if we keep the current in the winding coil constant before and after then inserting, then the magnetic field in the hollow region will not change; but if we keep the supplied energy unchanged before and after the inserting (i.e. C, V fixed), then the ratio of magnitude of the field inthe two cases Will be B/B0∝(R0)1/2. The latter effect results, however, completely from redistribution of the field. The total flux in the hollow region is reduced after the inserting, the fluix is not costant, there is not any flux concentrating effect. Hence the expectation of using such an effect to produce pulsed intense magnetic field is misleading in principle.We have also analysed why it is wrong to regard the flux concentrator as a pulse transformer. The theoretical calculation further shows that the increasing of magnetic field obtained by using devices with truncated cone shaped endings is due to the effect of construction.
1983, 32 (9): 1127-1138. doi: 10.7498/aps.32.1127
The generating functional approach to Green's functions in the thermal equilibrium is applied to explore the geometrical origin of the temperatures of the quantum fields in the Rindler spacetime and black hole spacetimes. It is shown that under the transformation from Minkowski space to the Rindler space the path integral representation for the Euclidean generating functionals of Green's functions at zero temperature would transform into the corresponding ones of the quantum fields at a certain finite temperature, and the Minkowski vacuum state would have the same properties as that of the quantum mixed state at that temperature. All thermal Green's functions for the mixed state are given. Similar results would be obtained for the Schwarzschild, the Reissner-Nordstrom and the Kerr black holes and whereupon the Hawking temperature for the black holes would have geometrical origin as well as that in the Eindler spacetime. The various density operators of the mixed states at the Hawking temperature for the black hole spacetimes are specified.
We show numerically that in the model of trimolecular reaction under external periodic force (the forced Brusselator) there exists the intermittent route to chaos. The time development of intermittent chaos and the method to distinquish intermittency from transients are studied. The large region of period 3 in the parameter space, discovered previously in the forced Brusselator, as well as smaller regions of periods 4, 5, 6 … etc., correspond to tangent bifurcations in one-dimensional mappings. Intermittency appears just before the start of every tangent bifurcation. Therefore, the period-doubling and the intermittent routes to chase are "twin" phenomena and they should be observable in many other systems described by nonlinear differential equations.
1983, 32 (9): 1149-1158. doi: 10.7498/aps.32.1149
In this paper we give a simple method by which all the Gelfand states can be obtained from the action of a generator on a Gelfand state. Combining with the method of calculating segment values, we suggest an approach to calculate the matrix elements of unitary group generator products.
THE CRYSTALLIZATION PROCESS OF METGLASS (Fe0.1Co0.55Ni0.35)78Si8B14 AND THE EFFECT OF HIGH PRESSURE (I)——THE PHASE PRECIPITATION PROCESS
1983, 32 (9): 1159-1169. doi: 10.7498/aps.32.1159
The crystallization process, precipitation sequence and structure of precipitated phases during heating metglass (Fe0.1Co0.55Ni0.35)78Si8B14 at normal and 20 kbar high pressures were examined by means of X-ray diffraction method. It was determined that both at normal and 20 kbar high pressures the crystallization will proceed in two stages corresponding to the primary and eutectic crystallization respectively. At normal pressure, fee-Co was observed on primary crystallization, while Ni31Si12 and (FeCoNi)3(SiB) compounds appeared in eutectic transition. With increasing temperature or prolonging of tempering, the (FeCoNi)3(SiB) compound transforms into the (FeCoNi)23B6 phase gradually. On the other hand, on heating the metglass at 20 kbar, in addition to the increasing in crystallization temperature, another compound Co2B appears. Besides, it has been found that high pressure will restrain the formation of (FeCoNi)23B6 phase.The influence of high pressure on the crystallization of metglass is discussed from point of view of thermodynamics and kinetics.
NEW LITHIUM IONIC CONDUCTORS IN PSEUDOBINARY SYSTEM Li4SiO4-Li3VO4 AND PSEUDOTERNARY SYSTEM Li4GeO4-Li4SiO4-Li3VO4
1983, 32 (9): 1170-1176. doi: 10.7498/aps.32.1170
The ionic conduction in the systems of Li4SiO4-Li3VO4 and Li4GeO4-Li4SiO4-Li3VO4 has been studied in the temperature range from room temperature to 300℃. It is found that the γII-phase solid solution Li3+xV1-xSixO4, are good ionic conductors. Among the compositions studied Li3.3V0.7Si0.3O4 is the highest ionic conductivity which reaches 1×10-5Ω-1·cm-1 at room temperature with activation energy 0.36eV in the temperature range 42°-192℃. It's electronic conductivity is negligible, therefore it is one of the best lithium ionic conductors discovered so far. The high conductivity domains in system Li4GeO4-Li4SiO4-Li3VO4 have been roughly determined. It is found that the substitution Si for Ge in Li3.5V0.5Ge0.5O4 can cause the ionic conductivity increase. The ionic conductivity of Li3.5V0.5Ge0.4Si0.1O4 at room temperature is 1.3×10-5Ω-1·cm-1 with an activation energy 0.4eV.
1983, 32 (9): 1177-1182. doi: 10.7498/aps.32.1177
The temperature dependence of ionic conductivity, especially the ion transport property during pre-crystallization process in amorphous ionic conductor Li2B2O4 has been studied. When the temperature is lower than Tk(≈310℃), the ionic conduction obeys Arrhenius relation. Above the crystallization temperature Tc(≈411℃), the ion transport behaviour is dominated by the process in crystalline state. In the range Tkc, the ionic conductivity deviates from thermal excitation mechanism and is enhanced anomalously. This process is now called pre-crystallization process. It is found that the free volume model could be used to describe the ion transport properties. In pre-crystallization process there are two distinguishable steps. Below Tp(≈380℃) the ionic conductivity increase is due to the redistribution of free volume. While above Tp considerable enhancement of the ionic conductivity is caused by the in-terfacial effect between the crystallites and amorphous matrix because small amount of crystallites (less than 5%) were emerged. The pre-crystallization status of the amorphous could be remained at ambient condition by quenching the specimen to room temperature. Therefore it is possible to prepare material with higher ionic conductivity than that of pure amorphous.
1983, 32 (9): 1183-1186. doi: 10.7498/aps.32.1183
Having considered the anisotropic property of the interaction between grain-boundaries and flux line lattice, we point out that the shearing flow of FLL along grain-boundaries is accompained by the depinning of FLS from weak pinning centers on GB, and this may be responsible for the "tail" of Fp at the vicinity of Hc2.
1983, 32 (9): 1187-1190. doi: 10.7498/aps.32.1187
The phonon spectra of C-15 phase (Hf0.5Zr0.5V2)Hx with five different composition was measured with the Beryllium Filter Detector spectrometer. It was observed that their phonon spectra vary with their hydrogen content. The result shows that the change of Tc of (Hf0.5Zr0.5V2)Hx system with x is related to the softening of their acoustic branches. The softening of acoustic branches seems favourable to the rise of Tc, while the softening of optical branches may restrain its superconductivity transition.
1983, 32 (9): 1191-1195. doi: 10.7498/aps.32.1191
We have studied the phase transition and superconductivity of InSb films condensed on substrate at low temperatures and obtained the following new experimental results: (a) First jump of conductance is spontaneous and independent of temperature in the temperature region in which InSb films were condensed, (b) After second jump of the conductance appears and reaches a peak, the conductance drops quickly and is accompanied by the formation of crystalline semiconductor phase as annealing temperature is increased further. But experimental results show that it is a metastable crystalline phase and third jump of the conductance takes place as annealing temperature is raised further. The phase formed after third jump of the conductance is a metallic one, but it does not become superconductive until 1.5 K. (c) Superconducting transition temperature of the phase formed after first jump of the conductance is different along with different temperatures of the substrate.
1983, 32 (9): 1196-1199. doi: 10.7498/aps.32.1196
The structure of KLiSO4 at room temp erature was determined (C66) in 1925 by Bradley. The position of Li atom at the void on a triad was inferred but not measured. This result is in contradiction with the general theory of chemical bonding, so, recently, Meng and Cao presented a view disagreeing with it.We have redetermined the structure of KLiSO4, in particular the position of Li atom. New result shows that Li atom is located at x=1/3, y=2/3, z=0.1797(16) instead of x=1/3, y=2/3, z=0.3488 as described by Bradley. The former is roughly the same as that predicted by steric considerations in ref. . Four nearest O atoms around Li atom form a tetrahedroid.
The Raman spectrum of Gd3Ga5O12 single crystals grown by both flux and pulling methods are measured. The different Raman phonons, are identified. Comparing with ref. , we get more complete results. The Raman spectrum of the two kinds of crystals grown by different methods are also compared, the phonon modes are in agreement with each other. The observed different lines are interpreted as fluorescence of contaminating rare earth ions introduced possibly during the sample preparation.
1983, 32 (9): 1204-1210. doi: 10.7498/aps.32.1204
High resolution polarized absorption spectra in visible and ultra-violet spectral region have been examined sysmatically. We have mainly determined the stark sublevels and their irreducible representations for the higher energy levels. We find that the groups of their absorption lines are corresponding to those of Br3+ in CaWOLiYF4 and in LaFLiYF3, but there exist sysmatically shifts between the centers of gravity of energy levels in these three different crystals.
1983, 32 (9): 1211-1214. doi: 10.7498/aps.32.1211
In this work, we have studied the forward Raman scattering of circularly polarized KrF excimer laser beam in hydrogen gas. The conversion efficiency of the first Stokes line has reached about 44%.
1983, 32 (9): 1215-1219. doi: 10.7498/aps.32.1215
In this paper, we report a new design of a rectangular uncorrelated double-beam tunable flashlamp pumped dye laser. The output of this laser can give simultaneously two laser beams with different frequencies by using two different dyes. The frequency difference of these two beams can be large, and they are easy to synchronize and do not have mode competition. Structure design and typical experimental results are presenied. A brief discussion is also given.
1983, 32 (9): 1220-1226. doi: 10.7498/aps.32.1220
By means of MOS-DLTS method, two electron traps in LPE n-type In0.75Ga0.25As0.58P0.42 material have been observed. Their depths are 0.20 eV and 0.48 eV below conduction band, and capture cross sections of electrons are about 14×10-16cm2 and 3.8×10-12cm2, respectively.Some discussion on the method applied to studying DLTS of multilayer composition semiconductor materials are also given.
POSSIBILITY OF GASEOUS SUPERFLUID AND ITS ACOUSTICAL PROPERTIES IN SPIN POLARIZED HYDROGEN ATOMS (H↓)
1983, 32 (9): 1227-1232. doi: 10.7498/aps.32.1227
The spin polarized hydrogen atoms (H↓) are treated as a weak interacting Bose-Einstein system. On the basis of Isihara's finite temperature theory and hard-sphere approximation, the possibility of gaseous superfluid and two modes of sound have been discussed. The importance of acoustical measurement technique in study on H↓ system is emphasized.
1983, 32 (9): 1233-1236. doi: 10.7498/aps.32.1233
In this paper, it is proved that the crossing of the positive and negative energy levels must occur, and the. nonthermal radiations also must be generated near a horizon irrespective of the detailed form of the metric when there exists static electromagnetic field or "dragging movement" of the space by the gravitational field near the horizon.