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Showing papers by "University of Science and Technology of China published in 1988"


Journal ArticleDOI
TL;DR: In this paper, a new approach for choosing the stress terms for hybrid stress elements is proposed based on the condition of vanishing of the virtual work along the element boundary due to stress terms higher than constant and the additional incompatible displacements.
Abstract: A new approach for choosing the stress terms for hybrid stress elements is based on the condition of vanishing of the virtual work along the element boundary due to the stress terms higher than constant and the additional incompatible displacements. Examples using 4-node plane stress elements have shown that when the incompatible displacements also satisfy the constant strain patch test the resulting element will provide the most accurate solutions.

145 citations


Journal ArticleDOI
TL;DR: In this paper, the authors compared the slow crack-growth behavior of a high-density polyethylene and an ethylene-hexene copolymer with 4.5 butyl chains per 1000 carbon atoms.
Abstract: The slow crack-growth behaviours of a high-density polyethylene and an ethylene-hexene copolymer with 4.5 butyl chains per 1000 carbon atoms are compared. The slow crack-growth rate in the copolymer is about 102 to 103 times slower than for the homopolymer. The two polymers are compared with respect to their kinetics of slow crack growth, the morphology of the damage zone that grows from a notch, the stress-strain behaviour and the temperature dependence of the rate of damage. The results suggest that the major effect of the butyl branches is to decrease the rate of disentanglement which governs the process of slow crack growth.

62 citations


Journal ArticleDOI
TL;DR: In this paper, the preparation and conductivity study of complex oxides in the systems Bi2O3−Y2O 3−Nb2O5, Bi 2O3 −Y 2 O3−Gd 2 O 3, Bi 2 O O 3−Y 2 OD 3−Sm2 O 3 and Bi O O O 11/3 was carried out.

49 citations


Patent
13 Jun 1988
TL;DR: In this paper, LiB 3 O 5 NLO devices are used in a laser system of high power density and relatively large divergence and possess a character of high SHG conversion efficiency.
Abstract: This invention relates to NLO devices made of LiB 3 O 5 crystals, which can be used in a laser system of high power density and relatively large divergence and possess a character of high SHG conversion efficiency. Moreover the NLO devices (including waveguide devices) of this invention are capable of producing coherent harmonics of wavelength below 2000Å and tolerating larger processing error of crystals.

39 citations


Journal ArticleDOI
TL;DR: In this article, the superconducting properties of a new series Bi 2−x Sb x Sr 2 Ca 2 Cu 3 O y (x = 0.05, 0.1,0.15, 02) have been reported.
Abstract: Superconducting properties of a new series Bi 2−x Sb x Sr 2 Ca 2 Cu 3 O y ( x =0.05, 0.1, 0.15, 0.2) have been reported in this paper. All of these samples have two superconducting transitions. The first superconducting transition is at about 120 K, zero resistance temperature is about 75 K. A new high- T c phase appears because of the substitution of Sb in the Bi-Sr-Ca-Cu-O system

33 citations



Journal ArticleDOI
TL;DR: In this paper, the authors considered a two-dimensional rectangular cavity whose portion of the bottom surface is isothermally heated, the upper surface is cooled at a constant temperature, and all other surfaces are adiabatic.
Abstract: Natural convection flow induced by localized heating from below in a horizontal porous layer is investigated numerically. The geometry considered is a two-dimensional rectangular cavity whose portion of the bottom surface is isothermally heated, the upper surface is cooled at a constant temperature, and all other surfaces are adiabatic. Parameters of the problem are the cavity aspect ratio A, dimensionless length of heat source B, dimensionless position of heat source e with respect to the vertical line of symmetry of the cavity, and Rayleigh number R based on cavity width. Three main convective modes are studied—conduction and single- and double-cell convection—and their features are described in detail. Maximum stream function and global Nussett numbers are presented as functions of the external parameters. Multiplicity of solutions is explored for an aspect ratio of unity. The existence of two steady-state solutions for a given set of the governing parameters is demonstrated.

29 citations


Journal ArticleDOI
TL;DR: In this article, two main phases are found in the Bi2-xPbxCa2Sr2Cu3Oy system, one is 4334 phase, another is a new one with cell parameters a =5.09 A, b = 5.18 A, and c =36.98 A.

26 citations


Journal ArticleDOI
TL;DR: The Pliocene volcanic rocks of the Anhui-Jiangsu region of eastern China are composed of an alkali basaltic suite consisting of alkali basalts, basanites and nephelinites as mentioned in this paper.
Abstract: The Pliocene volcanic rocks of the Anhui-Jiangsu region of eastern China are composed of an alkali basaltic suite consisting of alkali basalts, basanites and nephelinites. The basalts underwent a limited degree of fractional crystallization dominated in the initial stage by olivine and subsequently by clinopyroxene. The magmas were derived from a metasomatized amphibole-bearing garnet peridotite source variously enriched in incompatible trace elements. The metasomatic enrichment of the incompatible trace elements was probably produced by a zone refining process and was superimposed on a depleted upper mantle source compositionally similar to that of mid-ocean ridge basalts.

24 citations


Journal ArticleDOI
TL;DR: The grafted membranes showed improved permeability toward urea and uric acid in comparison with the polypropylene membranes, and the urea permeation coefficient of the grafted membrane was close to that of cuprophan.

23 citations


Journal ArticleDOI
TL;DR: In this paper, the relation between superconductivity and phase structure in YBa2Cu3O7−y doped with Sr and Ca has been studied systematically by the measurements of superconductivities, phase structure and thermal analysis.
Abstract: The relation between superconductivity and phase structure in YBa2Cu3O7−y doped with Sr and Ca has been studied systematically by the measurements of superconductivity, phase structure and thermal analysis. It is found that, for series of YBa2−xCaxCu3O7−y as 0⩽x⩽0.25, the samples are of single phase, and their Tc decrease linearly with content of Ca; for series of YBa2−xSrxCu3O7−y as 0⩽x⩽1.25, the samples are of single phase, but their Tc can change with the content of Sr either monotonously or non-monotonously, depending on the preparation conditions. A strong correlation exists between Tc and the crystal structure of the samples. The results obtained suggest strongly that the intensity of the coupling between Cu-O planes and Cu-O chains is very important to the high-Tc superconductivity of YBa2Cu3O7−y.

Journal ArticleDOI
TL;DR: In this paper, the growth of a new red emission host luminescent single crystal Na5Eu(WO4)4 and its luminescence properties were reported.

Journal ArticleDOI
15 Jun 1988-EPL
TL;DR: By measuring the structure, superconductivity, magnetoresistance of polycrystalline single-phase YBa2Cu3O7-δ samples, the phenomena of negative magnetore-sistance and the hysteresis of the magnetoreresistance have been studied as discussed by the authors.
Abstract: By measuring the structure, superconductivity, magnetoresistance of polycrystalline single-phase YBa2Cu3O7-δ samples, the phenomena of negative magnetoresistance and the hysteresis of the magnetoresistance have been studied. An analysis of the origin of the influence of grain boundaries on the superconductivity and the electronic transport properties are given.

Journal ArticleDOI
TL;DR: In this paper, a 2-(bromomethyl)-5-oxo-tetrahydrofuran with 1,2-epoxyhexane, followed by dehydrobromination, was shown to give a viscous polymer.
Abstract: 2-Butyl-7-methylene-1,4,6-trioxaspiro(4,4)nonane (7) was prepared by the reaction of 2-(bromomethyl)-5-oxo-tetrahydrofuran with 1,2-epoxyhexane, followed by dehydrobromination. Compound 7 could be polymerized by free radical initiators to give a viscous polymer. The IR and NMR spectra of the polymers indicated that the polymer structure contained ester and ketone units in the backbone, and a cyclic acetal side chain. Compound 7 readily copolymerized with acrylonitrile in the presence and absence of radical initiators, but did not copolymerize well with styrene. Ultraviolet spectra suggest that the spontaneous polymerization proceeds via a chargetransfer complex between 7 as an electron donor and AN as an electron acceptor.

Journal ArticleDOI
TL;DR: Li et al. as mentioned in this paper presented a model-based remotely-sensed image interpretation expert system embeded in a knowledge-based geographic information system (K. BIS), which consists of four sub-systems: a pictorial data base system, an image interpretation experts system, a computer-aided planning system and a computer aided cartographic system.
Abstract: We present a model-based remotely-sensed image interpretation expert system embeded in a knowledge-based geographic information system (K. BIS). The KBIS consists of four sub-systems: a pictorial data base system, an image interpretation expert system, a computer-aided planning system and a computer-aided cartographic system. The image interpretation expert system represents ecological knowledge and other expert knowledge by frames. Its reasoning process consists of a forward reasoning based on the Bayes classification of Landsat imagery, a backward reasoning using frame knowledge and reasoning using a spatial consistency model. A forest inventory study was conducted in Shaxian county, in the southern part of China, using this expert system. The results have shown a significant improvement. Building image interpretation expert systems within knowledge-based pictorial systems is very convenient and efficient because there are well-organized data, knowledge and procedures available.

Journal ArticleDOI
TL;DR: In this article, it was shown that the set of y-limit points is either empty or countably infinite, where P denotes the closure of the set P of periodic points, and the period of each periodic point is a power of 2 if and only if every -y-limit point is recurrent.
Abstract: Let / denote a continuous map of a compact interval / to itself. A point x 6 / is called a y-limit point of/ if it is both an w-limit point and an a-limit point of some point ye I. Let T denote the set of y-limit points. In the present paper, we show that (1) P F is either empty or countably infinite, where P denotes the closure of the set P of periodic points, (2) x e / is a y-limit point if and only if there exist yx and y2 in / such that x is an oi-limit point of yx, and y{ is an co-limit point of y2, and if and only if there exists a sequence yx, y2, • • • of points in / such that x is an co-limit point of yx, and yt is an &>-limit point of yi+l for every i > 1, and (3) the period of each periodic point of / is a power of 2 if and only if every -y-limit point is recurrent.

Journal ArticleDOI
TL;DR: In this article, a more appropriate fracture parameter to correlate various load levels, crack lengths, and specimen geometries under small-scale-yielding conditions is the J-integral rather than K.
Abstract: In previous investigations it has been shown that the regime of slow crack growth and the time to failure depend directly on the initial rate of crack-tip opening and damage. In this paper we demonstrate that a more appropriate fracture parameter to correlate various load levels, crack lengths, and specimen geometries under small-scale-yielding conditions is the J-integral rather than K. Since the initial rate of damage depends directly on the J-integral, the phenomenon of long-time failure by slow crack growth should be correlated by the J-integral for linear PE.

Journal ArticleDOI
TL;DR: In this paper, the measurements of X-ray diffraction, dependence of d.c. resistance on temperature and Hall effect have been performed for YBa2Cu3−xZnxOy system.

Journal ArticleDOI
TL;DR: In this article, the crystal structure, electron transport properties in normal state and superconductivity of a series of YBa2Cu3−xNixO7−y samples (0≤×≤0.5) were investigated.

Journal ArticleDOI
TL;DR: A sufficient condition for the convexity of the Bernstein-Bezier polynomials of degree n over triangles is presented and it is shown that the condition is superior to that of Chang and Feng.

Journal ArticleDOI
TL;DR: The positron annihilation technique has been used for studying the high Tc-superconductor YBa2Cu3O7-x as discussed by the authors, and the positron lifetimes of the normal state and of the superconducting state have been measured.
Abstract: The positron annihilation technique has been used for studying the high-Tc-superconductor YBa2Cu3O7-x. The Doppler broadening lineshape parameter as a function of temperature between 75 and 300 K, and the positron lifetimes of the normal state and of the superconducting state have been measured. A sharp negative anomaly in the S-parameter was observed near the superconducting transition temperature. In addition, it was found that the S-parameter and mean lifetime decrease below the transition temperature Tc. These phenomena vanish for the samples annealed in vacuum at 800 degrees C. It is suggested that high-Tc superconductivity in the new oxide is probably accompanied by an adjustment in the positions of the oxygen vacancies and the occurrence of 'valence pairs', i.e. an enhancement of the covalent character of the electrons after the superconducting transition.

Journal ArticleDOI
TL;DR: An overrelaxation projection (ORP) method to restore blurred images is presented and results of restored blurred images by computer simulation are given.
Abstract: Blur mechanisms of TV pictures caused by uniform linear motion are analyzed and a blur model is established. An overrelaxation projection (ORP) method to restore blurred images is presented. Results of restored blurred images by computer simulation are given.

Journal ArticleDOI
TL;DR: An elastic analysis of fiber-reinforced composites subjected to normal or/and shear stress in planes normal to the fiber direction is presented in this article, where the effect of material properties on the stress distribution is studied and a stress concentration factor valid for all the laminae presently used in industry is obtained.
Abstract: An elastic analysis of fiber-reinforced composites subjected to normal or/and shear stress in planes normal to the fiber direction is presented The effect of material properties on the stress distribution is studied and a stress concentration factor valid for all the laminae presently used in industry is obtained It is found that this factor is essentially unaffected by the substantial variation of the ratio of the elastic moduli of the fiber and the epoxy of the various laminae considered herein This result is of theoretical interest and also useful in composites design

Journal ArticleDOI
TL;DR: In this article, two hierarchies of the Benjamin-Ono equation and their Lax pairs are derived by an algebraic approach, and the hierarchies are proved to be the isospectral flows and non-isospector flows and the corresponding time evolutions of the scattering data are obtained, thus the inverse scattering transform can be applied to solve them.

Journal ArticleDOI
TL;DR: In this paper, a model for the formation of fractal-like structures has been proposed, which is the consequences caused by the latent heat released quickly during the crystallization of a-Si and during the void formation.

Journal ArticleDOI
TL;DR: In this paper, a group of random numbers which obey Gaussian distribution was introduced to simulate the fluctuation of period, the thickness ratio of two elements and the average period have been calculated by fitting with the experimental data for two artificial multilayered structures.

Journal ArticleDOI
TL;DR: In this paper, the preliminary application of ESR dating to loess strata was reported, where samples were collected from the 7th palaeosol layer (S7) of the Luochuan section, Shaanxi province in China.

Journal ArticleDOI
01 Jan 1988-Toxicon
TL;DR: NAD glycohydrolase (NADase) from five-pace snake venom was purified to electrophoretic homogeneity through a 4-step isolation procedure, including column chromatography, and showed maximal activity at about 40 degrees C with optimal pH at 7.2.

Journal ArticleDOI
TL;DR: The specific heat anomaly Δ C of Bi 16 Pb 04 Sr 2 Ca 2 Cu 3 O y was observed in the temperature range 80-100 K as discussed by the authors, and it was estimated from Δ C that γ∼15 mJ/mol·K 2 and H c2(T = 0)∼100 T in this sample.
Abstract: The specific heat anomaly Δ C of Bi 16 Pb 04 Sr 2 Ca 2 Cu 3 O y was observed in the temperature range 80–100 K It is estimated from Δ C that γ∼15 mJ/mol·K 2 and H c2( T =0)∼100 T in this sample The specific heat anomaly confirmed the occurrence of bulk superconductivity of the high- T c phase in Bi 16 Pb 04 Sr 2 Ca 2 Cu 3 O y superconductor

Journal ArticleDOI
TL;DR: In this article, the magnetization measurement and the study of the Ic(B) characteristic have been made on a single phase sample in Y1Ba2Cu3O7−δ.