Showing papers by "University of Science and Technology of China published in 1994"
TL;DR: The problem of scale is dealt with, so that the system can locate unknown human faces spanning a wide range of sizes in a complex black-and-white picture.
655 citations
TL;DR: The existence of excess Ar in phengites from coesite-bearing ultrahigh-pressure eclogites of the Dabie Mountains and SuLu terrain, China, has been confirmed by dating of minerals using SmNd, RbSr and 40Ar39Ar methods as mentioned in this paper.
249 citations
TL;DR: In this paper, a generalization of the split Hopkinson bar technique by using polymeric bars is proposed to study the high strain-rate mechanical behavior of materials having lower wave impedance, and a method based on the Zhu-Wang-Tang viscoelastic constitutive equation and the characteristics theory of wave propagation is developed and discussed in detail.
144 citations
TL;DR: In this article, the microstructure of the sol-gel material SnO 2, prepared by the solgel method, was studied by scanning electron microscopy and x-ray diffraction.
Abstract: The microstructure of ${\mathrm{SnO}}_{2}$, prepared by the sol-gel method, was studied by scanning electron microscopy, transmission electron microscopy, high-resolution electron microscopy, and x-ray diffraction. A nanosponge structure was observed. There is much surface and interface structure. The interfaces vary in type from amorphous to crystalline. The high density of defects greatly influences the physical and chemical properties of this material.
124 citations
TL;DR: In this paper, the integrability, commutativity and Lax representation for these FDIHSs are deduced from the adjoint representations of the auxiliary linear problems for the Kaup-Newell hierarchy.
105 citations
TL;DR: In this paper, the authors used the HST observations of the eclipsing dwarf nova OY Car in its quiescent state to isolate the ultraviolet spectrum of the white dwarf, the accretion disk, and the bright spot.
Abstract: Hubble Space Telescope (HST) observations of the eclipsing dwarf nova OY Car in its quiescent state are used to isolate the ultraviolet spectrum (1150-2500 A at 9.2 A Full Width at Half Maximum (FWHM) resolution) of the white dwarf, the accretion disk, and the bright spot. The white dwarf spectrum has a Stark-broadened photospheric L(alpha) absorption, but is veiled by a forest of blended Fe II features that we attribute to absorption by intervening disk material. A fit gives T(sub w) approx. = 16.5 x 10(exp 3) K for the white dwarf with a solar-abundance, log g = 8 model atmosphere, and T approx. = 10(exp 4) K, n(sub e) approx. = 10(exp 13)/cu cm, N(sub H) approx. = 10(exp 22) sq cm, and velocity dispersion delta V approx. = 60 km/s for the veil of homogeneous solar-abundance local thermodynamic equilibrium (LTE) gas. The veil parameters probably measure characteristic physical conditions in the quiescent accretion disk or its chromosphere. The large velocity dispersion is essential for a good fit; it lowers (chi square)/778 from 22 to 4. Keplerian shear can produce the velocity dispersion if the veiling gas is located at R approx. = 5 R(sub W) with (delta R)/R approx. = 0.3, but this model leaves an unobscured view to the upper hemisphere of the white dwarf, incompatible with absorptions that are up to 80% deep. The veiling gas may be in the upper atmosphere of the disk near its outer rim, but we then require supersonic (Mach approx. = 6) but sub-Keplerian (delta V/V(sub Kep) approx. = 0.07) velocity disturbances in this region to produce both the observed radial velocity dispersion and vertical motions sufficient to elevate the gas to z/R = cos i = 0.12. Such motions might be driven by the gas stream, since it may take several Kepler periods to reestablish the disk's vertical hydrostatic equilibrium. The temperature and column density of the gas we see as Fe II absorption in the ultraviolet are similar to what is required to produce the strong Balmer jump and line emissions seen in optical spectra of OY Car and similar quiescent dwarf novae. The outer accretion disk is detected at mid-eclipse with a spectrum that rises from 0.05 to 0.3 mJy between 2000 and 2500 A, consistent with combinations of cool blackbodies, blended Fe II emission lines, and Balmer continuum emission. The total disk flux density is 0.5 mJy at 2500 A, and this shallow disk eclipse implies a roughly flat surface brightness distribution. The bright spot, somewhat bluer than the disk, has a flux density rising from 0.05 to 0.15 mJy between 1600 and 2500 A. The C IV emission line has a broad shallow eclipse, but the radial velocity variations observed during the eclipse do not clearly distinguish between a disk or wind origin. The only possible indications of boundary layer emission are fast UV flares that appear to arise from near the central object -- not from the bright spot.
97 citations
TL;DR: An energy difference is identified which may be used as the criterion for the existence of multiple magnetic solutions in local-spin-density-functional calculations.
Abstract: The structural, electronic, and magnetic properties of small Rh-N clusters (N = 2-8,10,12,13, and 19) are studied using the discrete-variational local-spin-density-functional method. The groundstate structures of Rh-2, Rh-3, and Rh-4 are obtained and found to exhibit a tendency toward higherdimensional geometries with longer bond lengths and more nearest-neighbor bonds. The equilibrium bond lengths in the chosen geometry for the Rh-5-Rh-8, Rh-10, Rh-12, and Rh-13 clusters are determined and show 4-6% bond length contractions compared with the bulk interatomic spacing. A. complex size dependence of the magnetic properties of the Rhry clusters is found to be consistent with a recent experiment. The average magnetic moment per atom of the Rh-N clusters varies from 0 mu(B) to 2 mu(B). The clusters with magnetic ground states have ferromagnetic interactions, while-the local moments of the 5s and 5p often align antiferromagnetically with that of the 4d. The calculated magnetic moments of the Rh-10, Rh-12, Rh-13, and Rh-19 clusters are compared and discussed with the experimental ones. Icosahedral growth is suggested for Rh clusters. The reactivity of the Rh-N clusters toward H-2, N-2, and CO molecules is predicted. The densities of states, exchange splittings, valence band widths, and ground-state electronic configurations are presented for all the clusters. Finally an energy difference is identified which may be used as the criterion for the existence of multiple magnetic solutions in local-spin-density-functional calculations.
96 citations
TL;DR: Based on rigorous kinematical analysis, a unified representation of displacement variation through the thickness of laminated shells is derived in the present paper, and then an approximate theory of laminate shells accounting for continuity of displacements and transverse shear stresses at layer interfaces is established.
89 citations
TL;DR: In this article, the crystallization characteristics of polypropylene and low ethylene content poly-propylene copolymers with and without nucleating agents were studied by differential scanning calorimetry (DSC) and polarized light microscopy (PLM) in order to determine the nonisothermal crystallization rate of these materials.
Abstract: In this paper, the crystallization characteristics of polypropylene and low ethylene content polypropylene copolymers with and without nucleating agents were studied by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). In order to determine the nonisothermal crystallization rate of these materials, a new estimation method was introduced. Comparing with the crystallization rate coefficient (CRC), which was proposed by Khanna, we found the new approach is more reasonable. From the analysis of results of DSC and PLM, it can be concluded that nucleating agent is more efficient than it is in PP homopolymer. © 1994 John Wiley & Sons, Inc.
82 citations
TL;DR: In this article, Fourier transform infra-red spectroscopy provided strong evidence that there is a specific interaction between the epoxy resins and poly(ethylene oxide) molecules.
79 citations
TL;DR: A series of KMoO3γ-Al2O3 catalysts were prepared by varying the K/Mo atomic ratios between 0 and 1.5, maintaining molybdenum content as constant as discussed by the authors.
TL;DR: In this paper, the γ-radiation method has been used to prepare nanocrystalline powders of cuprous oxide from cupric sulfate aqueous solution in the presence of CH 3 COOH CH 3 COONa buffer pair.
TL;DR: In this paper, the Darboux transformations for a class of completely integrable systems in the spacetimeRn + 1, which are much more general than the systems inLett Math Phys26, 199-209 (1989), are considered.
Abstract: The Darboux transformations for a class of completely integrable systems in the spacetimeRn + 1, which are much more general than the systems inLett Math Phys26, 199–209 (1989), are considered The structure of the nonlinear evolution equations with space constraints is elucidated It is pointed out that the inverse scattering method can be used to solve the Cauchy problem with initial data given on a noncharacteristic line
TL;DR: In this article, magnetite particles were obtained through a hydrothermal process at 130°-150°C from a solution of iron chloride and iron powder in the presence of urea.
TL;DR: In this article, the Yang-Mills gauge boson condensate described by the renormalization-group improvement (RGI) effective action is investigated in the Robertson-Walker (R-W) spacetime.
TL;DR: In this paper, the authors present a study of the inclusive production of π0, η, Ks0 and Λ based on 929,000 hadronic Z decays recorded with the L3 detector at LEP.
TL;DR: In this article, statistical models of the strain-rate dependence of the strength of fibres and fiber bundles are established and their stress/strain equations are deduced, and an experimental method of determining mechanical parameters in the stress and strain equations by means of tensile impact loading of the fibre bundles is set up.
TL;DR: Although factors beyond narrowness of spatial-frequency tuning must exist to account for the much stronger orientation and direction preferences of cells in area 17 when compared to LGNd cells, the evidence suggests that the orientational biases present in the afferents to the visual cortex may contribute to the orientation and Direction selectivities found in cortical cells.
Abstract: The cortical contribution to the orientation and direction sensitivity of LGNd relay cells was investigated by recording the responses of relay cells to drifting sinusoidal gratings of varying spatial frequencies, moving bars, and moving spots in cats in which the visual cortex (areas 17, 18, 19, and LS) was ablated. For comparison, the spatial-frequency dependence of orientation and direction tuning of striate cortical cells was investigated employing the same quantitative techniques used to test LGNd cells. There are no significant differences in the orientation and direction tuning to relay cells in the LGNd of normal and decorticate cats. The orientation and direction sensitivities of cortical cells are dependent on stimulus parameters in a fashion qualitatively similar to that of LGNd cells. The differences in the spatial-frequency bandwidths of LGNd cells and cortical cells may explain many of their differences in orientation and direction tuning. Although factors beyond narrowness of spatial-frequency tuning must exist to account for the much stronger orientation and direction preferences of cells in area 17 when compared to LGNd cells, the evidence suggests that the orientation and direction biases present in the afferents to the visual cortex may contribute to the orientation and direction selectivities found in cortical cells.
TL;DR: In this article, the crystal structure of a new monoclinic VUV NLO crystal, sodium beryllium borate fluoride, NaBe2BO3F2 (NBBF), is reported.
TL;DR: In this article, the leptonic and hadronic cross sections were measured with the L3 detector at LEP and the results of these measurements were used to determine the electroweak parameters.
Abstract: We report on the measurement of the leptonic and hadronic cross sections and leptonic forward-backward asymmetries at theZ peak with the L3 detector at LEP. The total luminosity of 40.8 pb−1 collected in the years 1990, 1991 and 1992 corresponds to 1.09·106 hadronic and 0.98·105 leptonicZ decays observed. These data allow us to determine the electroweak parameters. From the cross sections we derive the properties of theZ boson:
$$\begin{gathered} M_Z = 91195 \pm 9MeV\Gamma _{\rm Z} = 2494 \pm 10MeV \hfill \\ \Gamma _{had} = 1748 \pm 10MeV\Gamma _\ell = 83.49 \pm 0.46MeV \hfill \\ \end{gathered} $$
assuming lepton universality. We obtain an invisible width of Γinv=496.5±7.9 MeV which, in the Standard Model, corresponds to a number of light neutrino species ofN
v=2.981±0.050. Using also the three leptonic forward-backward asymmetries and the average tau polarization, we determine the effective vector and axial-vector coupling constants of the neutral weak current to charged leptons to be:
$$\bar g^\ell v = - 0.0378_{ - 0.0042}^{ + 0.0045} \bar g^\ell _A = - 0.4998 \pm 0.0014.$$
Within the framework of the Standard Model, and including our measurements of the
$$Z \to b\bar b$$
forward-backward asymmetry and partial decay width, we derive an effective electroweak mixing angle of
$$sin^2 \bar \theta _W = 0.2326 \pm 0.0012$$
. We obtain an estimate for the strong coupling constant, αS=0.142 ± 0.013 and for the top-quark mass,m
t
=158
−40
+32
±19(Higgs) GeV, where the second error arises due to the uncertainty in the Higgs-boson mass.
TL;DR: An anomalous symmetry dependence of the cluster magnetism is found: the total magnetic moment of the icosahedral Rh cluster is smaller than that of the other two lower-symmetry clusters in a wide range of interatomic spacings.
Abstract: Electronic structures of 13-atom Rh clusters with three possible high-symmetry geometries are studied using the discrete variational local-spin-density-functional method. An anomalous symmetry dependence of the cluster magnetism is found: the total magnetic moment of the icosahedral ${\mathrm{Rh}}_{13}$ cluster is smaller than that of the other two lower-symmetry clusters in a wide range of interatomic spacings. An energy difference is identified to explain this anomalous relationship, which is found to be also useful for judging whether some techniques can or must be used in the local-spin-density-functional calculations. The calculated results are compared and discussed with those of previous theory and a recent experiment. The real geometry of the ${\mathrm{Rh}}_{13}$ cluster is suggested to be a distorted icosahedron.
TL;DR: A short proof of the conditions for nonnegativity of quadratic Bezier triangular patches presented in (Nadler, 1992) is given.
TL;DR: In this paper, an image of a minute crystal of the high-T c superconductor Bi 2 Sr 2 Cacu 2 O x is averaged and then transformed to an image with the average structure by a deconvolution technique based on the principle of maximum entropy.
TL;DR: In this paper, a new theory of multi-input multi-output (MIMO) modal parameters identification technique is developed from the view of system theory, which can serve as a unifying approach, as many well known identifying methods, such as the direct parameter model, polyreference, time domain method and Eigensystem realisation algorithm can be derived as special forms.
TL;DR: In this article, a new method for the bending analysis of anisotropic elastic plates is developed, which is an extension of the Stroh formalism used in generalized plane problems.
Abstract: A new method for the bending analysis of anisotropic elastic plates is developed. It is an extension of Stroh formalism used in generalized plane problems. Some relations concerning the method are discussed. As an application of the method, an anisotropic plate with polygonal holes under uniform bending extension coupling is studied.
TL;DR: In this article, the spectra Dq of the Henon map were calculated and analyzed using the extended G-P method, and the key problems (such as the scaling range determination, data sample selection and the calculation method) were discussed.
01 Dec 1994
TL;DR: In this paper, a single-mode spin linear birefringence (SHB) fiber is investigated as a periodic structure and the modal fields and the propagation coefficients of the two eigenmodes in this fiber are given theoretically for the first time.
Abstract: A single-mode spun linear birefringence fibre is investigated as a periodic structure. By using coupled-mode theory, the modal fields and the propagation coefficients of the two eigenmodes in this fibre are given theoretically for the first time. A spun highly linear birefringence (SHB) fibre is capable of acting as a sensing coil of relatively high sensitivity and temperature stability in current sensors. The mechanism of compensation and the sensitivities of current with SHB fibres and temperature compensation are studied extensively with the above eigenmode theory. The relations of sensitivity and temperature stability to parameters of SHB fibres and light sources are derived. The averaging effect caused by the broadband spectrum of the light source, which effectively eliminate the temperature instability, is investigated quantitatively with the partial-coherent-light theory.
TL;DR: In this article, a study of increasing the flexibility and lowering the internal stress of the cured epoxy resin was carried out by using polysiloxanes capped with functional groups and premaking poly-siloxane particles with d= 1.1 μm and narrow distribution.
Abstract: A study of increasing the flexibility and lowering the internal stress of the cured epoxy resin was carried out by using polysiloxanes capped with functional groups and premaking polysiloxane particles with d= 1.1 μm and narrow distribution. Polysiloxanes capped with functional groups were prepared by the reaction of X-22-163B with bisphenol-A, hexanedioic acid, and decanedioic acid. Poly(dimethylsiloxane-b-arylester was synthesized by the reaction of poly(dimethylsiloxane) (X-22-162C) woth arylester oligomers
TL;DR: The presence of significant numbers of direction-sensitive LGNd cells raises the possibility that subcortical direction specificity is important for the generation of this property in the visual cortex.
Abstract: Drifting sinusoidal gratings, moving bars, and moving spots were employed to study the direction sensitivity of 425 neurons in the A laminae of the cat's LGNd. Thirty-two percent of X- and Y-type LGNd relay cells exhibit significant direction sensitivity when tested with drifting sinusoidal gratings. X and Y cells exhibit the same degree of direction sensitivity. Moving spots and bars elicit direction specific responses from LGNd cells that are consistent with those elicited when drifting sinusoidal gratings are employed. For cells that are both orientation and direction sensitive, the preferred direction tends to be orthogonal to the preferred orientation. In general, direction sensitivity is strongest at relatively low spatial frequencies, well below the spatial-frequency cutoff for the cell. The presence of significant numbers of direction-sensitive LGNd cells raises the possibility that subcortical direction specificity is important for the generation of this property in the visual cortex.