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Showing papers by "Sun Yat-sen University published in 1989"


Journal ArticleDOI
TL;DR: There is a newly identified phase transition between 60 and 80 K which has been supported by x-ray analysis and according to the specific-heat experimental data, it is suggested that this phase transition is not a first-order transition.
Abstract: From 15 K to room temperature, dielectric and pyroelectric properties have been measured in six ferroelectric niobate single crystals with tungsten-bronze (TB) structure. Dielectric and pyroelectric experiments show that in the three kinds of ferroelectric niobate single crystals ${\mathrm{Sr}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ba}}_{\mathrm{x}}$${\mathrm{Nb}}_{2}$${\mathrm{O}}_{6}$, ${\mathrm{Pb}}_{\mathrm{x}}$${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Nb}}_{2}$${\mathrm{O}}_{6}$, and (${\mathrm{K}}_{\mathrm{x}}$${\mathrm{Na}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${)}_{0.4}$(${\mathrm{Sr}}_{\mathrm{y}}$Ba $_{1\mathrm{\ensuremath{-}}\mathrm{y}}$${)}_{0.8}$${\mathrm{Nb}}_{2}$${\mathrm{O}}_{6}$ with tetragonal TB structure, there is a newly identified phase transition between 60 and 80 K which has been supported by x-ray analysis. The crystal's symmetry changes from point group 4mm to point group m, and the direction of the ferroelectric polar axis tilts away from the c axis in the tetragonal lattice cell to the a axis in the monoclinic lattice cell as temperature decreases. The difference between the high-frequency dielectric constants and the low-frequency dielectric constants indicates that the phase transition is of a diffuse nature. According to the specific-heat experimental data, it is suggested that this phase transition is not a first-order transition. A model of structural change has been suggested to explain this phase transition.

57 citations


Journal ArticleDOI
TL;DR: In this paper, a procedure for calculating the distance between two points on an intrinsic reaction coordinate (IRC) obtained from two separate runs is proposed, which mainly involves the rotation of the geometrical configuration of one point in order to obtain a configuration not rotated relative to the other point.
Abstract: A procedure for calculating the distance between two points on an intrinsic reaction coordinate (IRC) obtained from two separate runs is proposed. The procedure mainly involves the rotation of the geometrical configuration of one point in order to obtain a configuration not rotated relative to the other point.

26 citations


Journal ArticleDOI
TL;DR: In this paper, the typical conditions of Czochralski growth of a new ferroelectric single crystal family of undoped and doped (K 1 - x Na x ) 0.4 (Sr 1 - y Ba y ), 0.8 Nb 2 O 6 (KNSBN) with tungsten-bronze type structure are described.

24 citations


Journal ArticleDOI
TL;DR: In this paper, a very short OPFIR superradiant laser was studied theoretically and experimentally, and the density matrix equations of a three-level quantum system for NH3 gas was solved for the gains of the FIR signal and the IR signal in the very short OFIR system.
Abstract: A very short OPFIR superradiant laser was studied theoretically and experimentally. The density matrix equations of a three-level quantum system for NH3 gas was solved for the gains of the FIR signal and the IR signal in the very short OPFIRL system. The output characteristics of the OPFIR superradiant laser were calculated numercally. A curve showing the relation between the length of the sampe tube of the OFFIRL and the corresponding optimum pressure was obtained. In our experiment, a 10cm OPFIRL and a 5cm OPFIRL were constructed and operated successfully. The output characteristics were meassured and the calculated results were verified.

18 citations


Journal ArticleDOI
TL;DR: Computed tomography scanning in NPC has demonstrated that the lesion most probably spreads to the carotid sheath area directly from the pharyngeal lesion, and the tendency of submucosal spread of NPC is emphasised.

17 citations


Journal ArticleDOI
TL;DR: It appears that hCG may be less antigenic in fish than is commonly suggested, and that factors other than hCG antibodies contribute to ovarian refractoriness in broodstock induced to ovulate repeatedly with hCG.

16 citations


Journal ArticleDOI
Zeke Wang1
TL;DR: In this article, a geometrical interpretation of the without-exception feasibility of PL homotopy methods is presented, based on the lexicographical system, and the method is shown to be feasible without exceptions.
Abstract: PL homotopy methods are effective methods to locate zerces (or fixed points) of highly nonlinear mappings. Due to the lexicographical system, the methods are feasible without exceptions. This paper presents a geometrical interpretation of the without-exception feasibility.

14 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the characteristics of relaxation and phase-like transitions associated with conductor-superconductor transition of BiSrCaCu2Oy when samples were sintered at different temperatures and went through thermocycles.

12 citations


Book ChapterDOI
01 Jan 1989
TL;DR: In this article, an alternative approach to the foundation of Matsuoka's theory, and with the insight thus gained, to attack the corresponding problem for the torus, is presented, which applies to surfaces of higher genus as well.
Abstract: INTRODUCTION Matsuoka studied in [7J, [8J, [9J the periodic solutions to a periodic system of differential equations en the plane. Based on the braiding information of known solutions, he obtained lower bounds for the number of extra periodic solutions, Some very interesting applications to subharmonic solutions of second order differential equations were given in [8J. The core of his method is Proposition 2 in §4 of [7J, which is an elaborate application of the Lefschetz fixed point theorem. This Proposition is in fact more naturally accessible from the Nielsen fixed point theory. The purpose of the present paper is to give (in §2) such an alternative approach to the foundation of Matsuoka's theory, and then, with the insight thus gained, to attack (in §3) the corresponding problem for the torus. For the convenience of the reader, some relevant material in Nielsen theory is reviewed in §1. In principle, our approach applies to surfaces of higher genus as well. We would like to emphasize the approach rather than the best possible estimates in various cases. So, in §2 we confine ourselves to recovering one of Matsuoka's estimates, and in §3 we will not go into the possible refinements of our estimates.

12 citations


Journal ArticleDOI
TL;DR: Evidence is provided that dopamine functions as a gonadotropin-release inhibitory factor in the Chinese loach by blocking spontaneous and GnRH-stimulated GtH release.
Abstract: The effects of dopamine on gonadotropin (GtH) secretion in sexually mature Chinese loach were investigated. Spontaneous secretion of GtH was inhibited within 1 h following an intramuscular injection of dopamine (100 μg/g body wt). Similarly, dopamine (50 and 100 μg/g body wt) caused a significant reduction in serum GtH in fish with elevated GtH levels as a result of pretreatment with gonadotropin-releasing hormone (GnRH) analogs either alone or in combination with the dopamine receptor antagonist domperidone. In summary, the present study provides direct evidence that dopamine functions as a gonadotropin-release inhibitory factor in the Chinese loach by blocking spontaneous and GnRH-stimulated GtH release.

11 citations


Journal ArticleDOI
TL;DR: Theoretical and experimental studies on film potentiometric stripping analysis are reported in this article, where the metal ion is concentrated as the metal on a glassy carbon electrode and then stripped by a suitable oxidant.

Journal ArticleDOI
TL;DR: In this paper, the self-induced ordering process and the superconductivity property of BiSrCaCu 2 Ox and Pb 0.34 Bi 1.72 Sr 2 Ca 1.2 Cu 2.5 Fe 0.22 Oy have been investigated based on internal friction (IF) experiment, x-ray diffraction and thermoanalysis.

Journal ArticleDOI
TL;DR: In this paper, the optimum operating parameters of OPFIRL were studied theoretically and experimentally, and the theoretical results were in pretty good agreement with experimental results except for 1.5cm laser.
Abstract: The optimum operating parameters of miniature OPFIRL was studied theoretically and experimentally. The theoretical results were in pretty good agreement with experimental results except for 1.5cm laser. The transverse feedback effect plays an important role in the miniature OPFIRL. it's worthv to be funther studied.

Proceedings ArticleDOI
17 May 1989
TL;DR: The fluorescent characteristic of cancerous tissue and blood of cancer patients were studied by Raman-Fluoro-Spectroscopy and fluorescence spectrophotometry in the lab.
Abstract: The fluorescent characteristic of cancerous tissue and blood of cancer patients were studied by Raman-Fluoro-Spectroscopy and fluorescence spectrophotometry in our lab. Fifteen kinds of cancer, more than 250 cases were measured.

Journal ArticleDOI
TL;DR: In this article, a nonadiabatic variational procedure is used to diagonalize the Hamiltonian of the helium atom to obtain the /sup 3/S/sup e/ states.
Abstract: A nonadiabatic variational procedure is used to diagonalize the Hamiltonian of the helium atom to obtain the /sup 3/S/sup e/ states. A partial-wave analysis of the wave functions has been made. The one-body densities and the shape densities have been investigated. Detailed information on electron-electron correlation has been obtained. The K-classification scheme has been recovered. The strong radial-angular correlation regions together with the associated twin nodes have been discovered.

Journal ArticleDOI
TL;DR: The micronuclei of the ciliated protozoan Pseudourostyla cristata were eliminated by amputation shortly before binary fusion and the amicronucleate cell lines derived from regenerants were maintained for more than a year, displaying a lower viability and reduced vigor in asexual propagation.
Abstract: The micronuclei of the ciliated protozoan Pseudourostyla cristata were eliminated by amputation shortly before binary fusion. The amicronucleate cell lines derived from regenerants were maintained for more than a year. They exhibited a lower viability and reduced vigor in asexual propagation. There was some improvement in the growth of the cell lines 1 mo after operation, but the growth rate remained subnormal even up to 1 yr of culture. The exact cause of the poor growth and survival in the first 3 wk after operation, whether the loss of the micronucleus or operational damage, remains to be determined. It is nevertheless clear that the micronucleus is important for subsequent asexual propagation. The amicronucleate cell lines were permanently crippled in morphogenesis, unlike the situation in Paramecium amicronucleates in which stomatogenesis returned to near-normal during asexual propagation. They always included some cells with a characteristically defective adoral zone of membranelles, reduced number of frontal-ventral-transverse cirri, and reduced body length. They were also reluctant to encyst. It is evident that the micronucleus is important for maintaining normality of the oral apparatus. It is postulated that the permanent stomatogenic crippling of amicronucleates might be related to genomic reduction in the developing macronucleus in sexual reproduction, as exhibited by other hypotrichs. The morphological defects associated with the adoral zone of membranelles may be rationalized as arising from the spreading of a zone of degeneration in the cortex affecting the left edge of the membranelles.

Journal ArticleDOI
TL;DR: In this paper, it was proved that any nonrandomized estimator can be approximated in Lebesgue measure by the more general invariant estimators, and a proof that the best estimator is minimax when the sample size is 1 is given.
Abstract: Consider both the classical and some more general invariant decision problems of estimating a continuous distribution function, with the loss function L(F,a)=f(F(t)- a(t))2h(F(t))dF(t) and a sample of size n from F. It is proved that any nonrandomized estimator can be approximated in Lebesgue measure by the more general invariant esti- mators. Some methods for investigating the finite sample problem are discussed. As an application, a proof that the best invariant estimator is minimax when the sample size is 1 is given.

Journal ArticleDOI
TL;DR: In this article, the conductivity and conductivity-temperature characteristics of the Sr(Fe1−xTixO3−δ) system fired in air are studied by means of Mossbauer spectroscopy at room temperature and at 78 K.
Abstract: The conductivity and conductivity-temperature characteristics of the Sr(Fe1−xTixO3−δ system fired in air are studied by means of Mossbauer spectroscopy at room temperature and at 78 K. On the basis of quantitative analysis of the Fe4+ content in the solid solution, the concentrations of oxygen vacancies are calculated and the relationship between Fe4+ content and conductivity is found. It is also found that the turning points of conductivity and material constant B, as well as Fe4+ and the percentage of oxygen vacancies, occur at x=0.7 on the curve. When x=0.7, Fe3+ (II), which has never been reported before, disappears and the lattice parameters no longer vary with x. Besides Fe4+, Fe3+(II) is also a factor affecting the conductivity of this system.

Journal ArticleDOI
TL;DR: In this paper, the two or multi-mode optically pumped NH3 FIR laser was studied theoretically and the NH3 molecular gas was assumed to be a three-level system and obeyed the timedependent behavior of the density matrix equations.
Abstract: The two or multi-mode optically pumped NH3 FIR laser had been studied theoretically. The NH3 molecular gas was assumed to be a three-level system and obeyed the time-dependent behavior of the density matrix equations. Considering the situation of playing the two or multi-mode optical pumping and the FIR laser field were same polarized. The gain coefficient and the output FIR power of the system could be calculated by using the iteration method.

Journal ArticleDOI
TL;DR: In this paper, an exact method for obtaining the solutions for bending moments, twisting moments and deflections of simply supported rectangular grids subjected to static concentrated loads applied at the nodes is presented by employing the cyclic periodicity in two directions of the equivalent systems of the original grid structure.
Abstract: An exact method for obtaining the solutions for the bending moments, twisting moments and deflections of simply supported rectangular grids subjected to static concentrated loads applied at the nodes is presented in this paper. It is developed by employing the cyclic periodicity in two directions of the equivalent systems of the original grid structure. A simple example is worked out to demonstrate the accuracy of this method which is applicable to orthogonal grids subjected to nodal loads only at this stage but will be further developed to extend its applicability to other types of grids such as diagonal grids subjected to arbitrary loading.

Journal ArticleDOI
TL;DR: In this paper, a hollow circular dielectric waveguide was used for laser transverse mode control and a capillary inserted in a conventional transversely pumped pulse dye laser was shown to effectively promote the fundamental gaussian beam oscillation.

Journal ArticleDOI
TL;DR: In this article, a set of coupled equations is derived and used to analyze transient coherent degenerate four-wave mixing (DFWM) in a two-level system, and the numerical results show that in the case of near-resonance, intense pumping, and short pulses, the properties of DFWM have interesting coherent interaction characteristics, such as quasi-periodicity in the pump pulse area, probe pulse areas, and energy reflectivity, oscillatory behavior of the DFWM pulse.
Abstract: A set of coupled equations is derived and used to analyze transient coherent degenerate four-wave mixing (DFWM) in a two-level system. The numerical results show that in the case of near-resonance, intense pumping, and short pulses, the properties of degenerate four-wave mixing have interesting coherent interaction characteristics, such as quasi-periodicity in the pump pulse area, probe pulse areas, and energy reflectivity, oscillatory behavior of the DFWM pulse, and generation of a DFWM signal in the case of delayed incidence, where the three incident pulses do not overlap in the medium. >

Journal ArticleDOI
TL;DR: In this article, an analytical method for the static analysis of double layer grids consisting of diagonals and top and bottom layers which are plane orthogonal grids is presented, assuming that the double layer grid is simply supported at all nodes located at the boundary of the top layer.
Abstract: An analytical method for the static analysis of double layer grids consisting of diagonals and top and bottom layers which are plane orthogonal grids is presented. It is assumed that the double layer grid is simply supported at all nodes located at the boundary of the top layer. By using the double U-transformation technique, exact solutions for the nodal displacements and axial forces of the bars in the double layer grid can be derived. The validity of the method is demonstrated with a simple example.

Journal ArticleDOI
01 Jan 1989-Vacuum
TL;DR: In this paper, three major characteristic peaks in the IR spectra of SOI structures have been calculated and a new non-destructive method to determine the thickness of buried SiO 2 layers in SOI samples is suggested.

Journal ArticleDOI
TL;DR: In this article, a semi-implicit finite element scheme is proposed for two-dimensional tidal flow computations, where each term of the governing equations, rather than each dependent variable, is expanded in terms of the unknown nodal values and it helps to reduce computer execution time.
Abstract: A semi-implicit finite element scheme is proposed for two-dimensional tidal flow computations. In the scheme, each term of the governing equations, rather than each dependent variable, is expanded in terms of the unknown nodal values and it helps to reduce computer execution time. The friction terms are represented semi-implicitly to improve stability, but this requires no additional computational effort. Test cases where analytic solutions have been obtained for the shallow water equations are employed to test the proposed scheme and the test results show that the scheme is efficient and stable. An numerical experiment is also included to compare the proposed scheme with another finite element scheme employing Serendipity-type Hermitian cubic basis functions. A numerical model of an actual bay is constructed based on the proposed scheme and computed tidal flows bear close resemblance to flows measured in field survey.

Proceedings ArticleDOI
19 May 1989
TL;DR: In this paper, a real-time parallel optical associative memory system implemented with a CeiFesLiNb03 crystal as recording medium and a Fe,LiNbin03 crystal amplifier to provide feedback, threshotding and gain is demonstrated.
Abstract: In this paper we report the measurements of the optical absorption spectrum , diffraction efficiency, recording sensitivity , erasure behavior in the poled single crystals LiNb03 with Pr and with Ce and Fe as new impurities respectively, We show associative holographic analog to the Hopfield neural network model in algorithm and present a real-time parallel optical associative memory system implemented with a CeiFesLiNb03 crystal as recording medium and a Fe,LiNb03 crystal amplifier to provide feedback, threshotding and gain . In our experiment, the retrieval of complete image when only a partial image addresses the system is demonstrated.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the {ital N}=3 series of the {sup 1}S{sup e} helium states by partial-wave analysis and by observing the shape densities.
Abstract: The {ital N}=3 series of the {sup 1}S{sup e} helium states have been investigated by partial-wave analysis and by observing the shape densities. The {ital K}-classification scheme has been recovered. The strong radial-radial correlation region (SRRCR) has been found. The process of energy transfer occurring inside the SRRCR has been inspected in detail and two types of mechanisms, the direct push'' and the head-on collision,'' have been discovered.


Journal ArticleDOI
TL;DR: In this article, a model has been proposed, and bands have been assigned on the basis of normal vibration analysis using the NORVIB program, and the calculated frequencies are in agreement with the experimental values.
Abstract: IR and Raman spectra (100–4000 cm−1) of Eu2(CH3COO)6 · 8H2O have been recorded in the solid state. A model has been proposed, and bands have been assigned on the basis of normal vibration analysis using the NORVIB program. The calculated frequencies are in agreement with the experimental values. We find that the present band assignments are different from the empirical assignments.

Journal ArticleDOI
TL;DR: In this paper, the gain formula for the free-electron laser obtained from the simple pendulum equation by means of the weak field approximation is shown to be incompatible with the experimental condition of the Stanford first free electron laser amplifier.