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Chin. Phys. B  
  Chin. Phys. B--1997, Vol.6, No.8
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GENERAL

(2+1)-DIMENSIONAL DERIVATIVE NONLINEAR SCHRODINGER EQUATION

LOU SEN-YUE
Chin. Phys. B 1997, 6 (8): 0561;  doi: 10.1088/1004-423X/6/8/001
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A(2+1)-dimensional multi-component derivative nonlinear Schr?dinger (DNLS) equation is obtained from the symmetry constraint of the modified Kadomtsev-Petviashvili equation, The model is proved to be inte- grable under the meaning that it possesses the Paitdevé property and the infinitely many generalized symmetries which constitute a generalized W algebra, An integrable DNLS hierarchy is obtained from the flow equation of infinitely many symntetries of the DNLS equation.
CLASSICAL AREAS OF PHENOMENOLOGY

A DESCRIPTION OF THE THERMO-ELASTIC RESPONSE OF LAYERED MEDIA BY A MATRIX FORMALISM

A.V.FOKIN
Chin. Phys. B 1997, 6 (8): 0574;  doi: 10.1088/1004-423X/6/8/002
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A matrix formalism is introduced here for the analytical calculation of the thermo-elastic response of one-dimensional optically inhomogeneous layered structures exposed to the periodic laser heating. The multilayer structure consists of thermally and mechanically homogeneous solid layers which can be interleaved by liquid ot galore interlayers. The method enables the modelling of photoacoustic and photothermal measurements in a variety of engineering applications.

A STATISTICAL THEORY OF CREEP FRACTURE

XU HUI-YING, XING XIU-SAN
Chin. Phys. B 1997, 6 (8): 0578;  doi: 10.1088/1004-423X/6/8/003
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A theory of creep fracture has been constructed by means of the concept and the method of nonequilibrium statistical physics. In this paper, the cavity evolution equation is given; the cavity distribution function, the cavity distribution probability, the creep fracture life of materials and the famous Monkman-Grant empirical relation are derived on the basis of the two mechanisms of the constrained cavity growth and the unconstrained cavity growth, respectively.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

ELECTRONIC SPECTRAL PROPERTIES OF ONE-DIMENSIONAL NANOSTRUCTURED SYSTEMS

YAN XIAO-HONG, ZHANG LI-DE, DUAN ZHU-PING, ZHOU YI-CHUN
Chin. Phys. B 1997, 6 (8): 0589;  doi: 10.1088/1004-423X/6/8/004
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Introducing a model nanostructured chain, we study the electronic properties of one-dimensional ordered nanostructured solids in terms of an exact Green's function renormalization-group approach, It is found that two kinds of electronic state, namely localized state and extended statess exist in certain energy regions. As the grain size decreases, the energy regions corresponding to the extended quantity, as well as the gaps, become wider, while the number of the isolated peaks decreases. Furthermore, the appearances of isolated peaks are mainly, due to the modulations of the interface sites.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

ELECTRONIC AND OPTICAL PROPERTIES OF WURTZITE GaN:——A THEORETICAL APPROACH

YANG ZHONG-QIN, XU ZHI-ZHONG
Chin. Phys. B 1997, 6 (8): 0597;  doi: 10.1088/1004-423X/6/8/005
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The band structures of wurtzite GaN(α-GaN) are studied using the nearest and second-nearest neighbour semi-empirical tight-hinding method in sp3 s* model. The calculated direct fundamental gap of α-GaN is 3.45 eV, which is in good agreement with the experimental data. The density of states and the imaginary pert of dielectric function (ε2 (ω)) are evaluated to he in the regions - 10.0 - 12 eV and (1.0 - 10.0 eV, respectively. There are mainly three peaks at 6,4, 7,5, 8.4 eV, dominating the ε2(ω) spectrum. The two components of the ε2(ω) (i. e. ε2xy(ω) and ε2z(ω) ) are also calculated; and the real prat of dielectric function, reflectivity, absorption coefficient, and refractive index are all studied.

ELECTRONIC AND OPTICAL PROPERTIES OF STRAINED WURTZITE GaN

YANG ZHONG-QIN, XU ZHI-ZHONG
Chin. Phys. B 1997, 6 (8): 0606;  doi: 10.1088/1004-423X/6/8/006
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Band structures of wurtzite GaN (α-GaN) under strains in the region -5%—5% are calculated in a tight-binding framework. The empirical scaling rule has been used for considering the effects of hydroatatic strains. The scaling indexes are determined by fitting the deformation-potential constants with other theoretical values. The band gap at Γ point increases with the absolute value of strains. GaN turns to be of indirect band gap when strains reach 5 %. The density of states and the imaginary part of dialectic function (ε2(ω)) are studied. Both the shape and energy position of the highest peak in the ε2(ω) spectrum successively change with the strains. The real part of dielectric/unction, refractive index and the effects of the strains on them are also shown.

EFFECT OF THERMAL TREATMENTS ON THE SUPERCONDUCTIVITY OF UNDOPED AND WO3 DOPED Y-Ba-Cu-O SYSTEM

SHI LEI, FENG YONG, PANG WEN-HUA, DU SHE-JUN, ZHOU LIAN, LI XIAO-GUANG, ZHOU GUI-EN, ZHANG YU-HENG
Chin. Phys. B 1997, 6 (8): 0614;  doi: 10.1088/1004-423X/6/8/007
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Undoped and WO3-doped Y-Ba-Cu-O ceramics have been slowly cooled in flowing oxygen or quenched in air from 900℃ to room temperature, after sintering at 900℃ for 3Oh in flowing oxygen. The ac susceptibility measurements show that the Tc of the quenched WO3-doped Y-Ba-Gu-O superconductor can reach 88K, while the undoped Y-Ba-Cu-O ceramic quenched in air is a non-superconductor. X-ray diffraction data show that WO3 does not enter into the YBa2Cu3O7-x lattice but forms all impurity phase. The WO3-doped YBCO specimens quenched in air consist of orthorhombic YBa2Cu3O7-x phase and an impurity phase which increases with increasing WO3 content. Raman spectra chow that oxygen contents are different for undoped and WO3-doped samples. It la suggested that suitable doping with WO3 can change the oxygen content and reduce the effect of thermal treatments on the superconductivity of Y-Ba-Cu-O system.

FORMATION OF MULTI-BRANCHED DOMAINS IN GARNET BUBBLE FILMS BY LOW-BIAS-PULSE METHOD

HAN BAO-SHAN, MENG GUANG-QING, GUO GE-XIN
Chin. Phys. B 1997, 6 (8): 0619;  doi: 10.1088/1004-423X/6/8/008
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The formation of multi-branched domains( MBDs) at low static bias field was first studied. With multiple branches, MBDs contain more or less same-signed vertical-Bloch-lines (VBLs) in their walls, Experiments. on four samples have shown that under certain conditions, the amount and hardness of the MBDs formed can be easily controlled, and so-called "low-bias-field method" is another effective way to form VBL chains. It was found that MBDs are formed due to the expansion of domain segments after compressed by a rectangular bias pulse. The number of VBLs nucleated in domain walls is affected by the space where the domains expand rapidly.

STIMULATED EMISSION AND GAIN MEASUREMENTS IN InAsP/InP STRAINED-MULTIPLE-QUANTUM WELLS

ZHAO YI-GUANG, HUANG XIAN-LING
Chin. Phys. B 1997, 6 (8): 0624;  doi: 10.1088/1004-423X/6/8/009
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We have studied the stimulated emission from InAsP/InP strained-multiple-quantum wells at room temperature. The stimulated emission spectra weave seen with three lobes, which are E1H and E1L transitions, and a tran-sitions from heavy hole initial states to localized interface states. The E1H transitions exhibited different gain value from that of the transitions between the heavy hole and the interface states. With increasing excitation intensity, the gain of the interface peak appears to be saturated at lower excitation intensity. A method for identifying the inter face peak in the photoluminescene spectrum has been proposed.
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