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Volume 5 Issue 12
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Original Articles
R-PHASE AND ICOSAHEDRAL PHASE IN AL-FE-CU ALLOY
CHENG Yifan, HUI Mengjun, WU Xiaojing, YANG Dayu, CHEN Xishen, LI Fanghua+
Chin. Phys. Lett. 1988, 5 (12): 529-532 .  
Abstract   PDF(pc) (55KB) ( 449 )
In this letter we report of A165Fe15Cu20 alloy by means of electron and X-ray diffractometry. A new crystalline phase of body-center-cubic structure with a lattice parameter a°=1.407nm was observed together with the icosahedral phase in the same sample. The new phase is supposed to be an isomorph of Mg32(A1, Zn)49 (R phase) on the basis of structure factor calculation.
SOUND POWER DETERMINATION IN REVERBERATION CHAMBERS
MAA Dah-You (MA Dayou)
Chin. Phys. Lett. 1988, 5 (12): 533-536 .  
Abstract   PDF(pc) (47KB) ( 365 )
The determination of sound power in a reverberation chamber is discussed in the light of normal mode theory. It is shown that the sound pressure is proportional to the average contribution of the product of the normal functions at the source and the receiver. Methods of determination of the sound power emitted by a source at a particular point are devised. It is also shown that the sound power determined in reverberation chambers by the standard method is always less than the free-field power, explaining the earlier experiments. A statistical formula is developed to this end.
NUCLEATION AND COARSENING OF Co-RICH α-PHASE IN THE COPPER-COBALT SYSTEM
LIU Zhiguo, SHEN Guangjun+, CHEN Yong, FENG Duan
Chin. Phys. Lett. 1988, 5 (12): 537-541 .  
Abstract   PDF(pc) (98KB) ( 362 )
The kinesics of the early stages of the decomposition reaction in a Cu-1.75at.% Co solid solution aged at 853K were investigated with APFIM (Atom Probe Field Ior Microscopy) and TEM (Transmission Electron Microscopy). The radius of the critical nucleus of α-phase was revealed to be about 0.8nm. The Co-concentration in the fine precipitates was determined to be (95±2)at.%. The results were interpreted in terms of Kampmann-Wagner numerical model for the kinetics of nucleation and growth decomposition in solids.
LEVEL STATISTICS OF DOUBLET SPECTRUM OF SINAIS BILLIARD
JIANG Yimin
Chin. Phys. Lett. 1988, 5 (12): 541-544 .  
Abstract   PDF(pc) (54KB) ( 455 )
The significance of multiplicity of an energy spectrum for the level statistics of a quantum system is considered whose associated classical system exhibits deterministic chaos. The doublet spectrum of the Sinai's billiard on a torus is calculated via the Korringa-Kohn-Rostoker method in order to study its level fluctuation properties. It is found that the level spacing distribution is in full agreement with the prediction of random matrix theory, indicating that the level statistics is independent of the multiplicity of spectrum.
CURRENT DRIVE OF ELECTRON CYCLOTRON WAVES IN THE PRESENCE OF MAGNETIC PUMPING WAVES
CHEN Ji
Chin. Phys. Lett. 1988, 5 (12): 545-548 .  
Abstract   PDF(pc) (47KB) ( 365 )
The scheme of combined current drive by electron cyclotron waves and magnetic pumping waves is proposed. The current density and the efficiency are given in terms of analytically approximate calculation and numerical solution of quasi-linear Fokker-Planck equation, respectively. Both results show consistently that the efficiency of current drive by this scheme is one order of magnitude larger than the theoretical result by Fisch-Boozer mechanism.
SELFCONSISTENT SEMICLASSICAL APPROACH TO NUCLEUS-NUCLEUS OPTICAL POTENTIAL
LI Guoqiang, XU Gongou
Chin. Phys. Lett. 1988, 5 (12): 549-552 .  
Abstract   PDF(pc) (46KB) ( 373 )
The nucleus-nucleus optical potentials of several pairs of spherical nucleus 40Ca, 60Ni, 90Zr and 120Sn are calculated in sudden approximation, with nucleon density ρq(r) determined by means of a selfconsistent semiclassical (SCSC) calculation. Exchange effect is taken into consideration in an approximate way. The spin-orbit contribution is also included.
MARTENSITIC TRANSFORMATION, THERMOMAGNETIC PROPERTIES AND ELECTRONIC RESISTIVITY OF AMORPHOUS ALLOYS (Fe1-xNix)84B16 AFTER CRYSTALLIZATION
GUO Huiqun, ZHAO Jiangao, SHEN Baogen, ZHAN Wenshan, LI Xiaogang, YANG Linyuan
Chin. Phys. Lett. 1988, 5 (12): 553-556 .  
Abstract   PDF(pc) (49KB) ( 725 )
In the reduced curves of electronic resistivity and thermomagnetic measurement of the amorphous alloys, (Fe1-xNix)84B16 with 0.02< x <0.08, preheated to a temperature higher than that of crystallization, an anomalous abruption at about 150°C was observed. The results of differential thermal analysis (DTA) and of X-ray diffraction show that after crystallization of the amorphous alloys (Fe1-xNix)84B16 the anomalous abruption can be attributed to the martensitic transformation of γFe(Ni) to αFe(Ni).


VACANCY FORMATION ENERGY IN MOLECULAR SOLID CH4
WANG Shaojie (S.J.Wang), Y . C . Jean*
Chin. Phys. Lett. 1988, 5 (12): 557-560 .  
Abstract   PDF(pc) (45KB) ( 376 )
The Doppler broadening energy spectra have been measured on high-purity condensed CH4 in temperature range from 30K to 105K. In solid phase and below the melting point, the variations of S-parameter with temperature were interpreted as o-Ps trapped in the thermally activated vacancy-type defects. A vacancy formation energy of 0.10±0.02eV was derived by positronium trapping model.
COULD SUPERCONDUCTING PROPERTIES OF 90K OXIDE YBa2 Cu3O7 BE ELUCIDATED IN THE FRAMEWORK OF BCS-ELIASHBERG THEORY?
WU Hangsheng, YE Xiaoguang, ZHOU Zifang
Chin. Phys. Lett. 1988, 5 (12): 561-563 .  
Abstract   PDF(pc) (0KB) ( 292 )
The analysis by the authors shows that the superconducting properties of the 90K oxide YBa2 Cu3O7 cannot be understood in the framework of the BCS-Eliashberg theory.
RESISTIVITY ANOMALY IN THE HIGH-TEMPERATURE SUPERCONDUCTOR Bi-Sr-Ca-Cu-O
YUAN Songliu+, WANG Wei, ZHENG Guoguang, RAN Qize,
Chin. Phys. Lett. 1988, 5 (12): 564-566 .  
Abstract   PDF(pc) (33KB) ( 450 )
An anomalous resistance drop was observed near 190K in the R-T measurement on a sample in Bi-Sr-Ca-Cu-O system and the transition completed at 80K. After keeping the sample at room temperature for 10h, the temperature dependence of the resistance changed from semiconducting to metallic behavior, while the ending of the transition remained at 80K. This might be an evidence of the existence of a metastable superconducting phase in Bi-Sr-Ca-Cu-O system with Tc as high as 190K.
ANOMALOUS PHONONS IN YBa2Cu3O7-δ SUPERCONDUCTOR
ZHANG Guizhong, LI Zengfa, ZHANG Guangyin, MEN Zhenyu, YAN Jie*, YANG Xiaoning*, SONG Deying*
Chin. Phys. Lett. 1988, 5 (12): 567-569 .  
Abstract   PDF(pc) (43KB) ( 595 )
The anomalous phonon properties in YBa2Cu3O7-δ superconductor quenched from different temperatures were obtained by means of IR refiection spectroscopy. The analyses of the data suggest that polarons exist in the system, and this may provide a cruicial clue to the mechanism study.
BRIEF REPORTS PHASE SEPARATION OF THE METALLIC GLASS Pd77.5Ni6Si16.5
YUE Lanping, SHEN Hui
Chin. Phys. Lett. 1988, 5 (12): 570-571 .  
Abstract   PDF(pc) (46KB) ( 394 )

12 articles