Showing papers by "University of Science and Technology of China published in 1997"
TL;DR: In this article, a scheme for protecting quantum states from both independent and cooperative decoherence is proposed by pairing each qubit (two-state quantum system) with an ancilla qubit and encoding the states of the qubits into corresponding coherence-preserving states of qubit pairs.
Abstract: A scheme for protecting quantum states from both independent and cooperative decoherence is proposed. The scheme operates by pairing each qubit (two-state quantum system) with an ancilla qubit and by encoding the states of the qubits into corresponding coherence-preserving states of qubit pairs. In this scheme, amplitude damping (loss of energy) as well as phase damping (dephasing) is prevented by a strategy called ``free-Hamiltonian elimination.'' We further extend the scheme to include quantum gate operations and show that loss and decoherence during such operations can also be prevented.
450 citations
TL;DR: In this article, a nanoscale Y2O3:Eu phosphors have been prepared by glycine-nitrate solution combustion synthesis, and the particle size of resultant powders is much related to the combustion flame temperature, which can be controlled by adjusting the glycine tonitrate ratio.
348 citations
TL;DR: In this article, the microstructural changes of nano-SnO2 have been systematically studied using x-ray diffraction and Raman spectroscopy, and two major Raman peaks N-1 and N-2 in accordance with Matossi's force constant model have been found.
Abstract: The microstructural changes of nano-SnO2 have been systematically studied using x-ray diffraction and Raman spectroscopy. The nano-SnO2 grain assemblage possesses some features of the rutile structure, but has a large amount of defects: vacancies of oxygen, vacancy clusters, and local lattice disorder at the interface and interior surface, which lead to a significant lattice distortion and an evident space-symmetry reduction of D-4h(14) and the appearance of a group of new Raman peaks. Two major Raman peaks N-1 and N-2 in accordance with Matossi's force constant model have been found. When the annealing temperature is close to 673 K, the density of vacant lattice sires and local lattice disorders decreased rapidly in the grains, and the lattice distortion and Raman peaks N-1 and N-2 almost disappeared at the same time. It suggests that N-1 and N-2 are closely related to the microstructural change of the nanocluster grains, or in other words, N-1 and N-2 peaks mark an additional characteristic of space symmetry of the grain assemblage of nano-SnO2. The Raman peak N-3 may be related to local SnO2 clusters and vacancy clusters.
255 citations
TL;DR: In this article, two maleated polypropylenes (s-MAPP and m-Mapp) were used as matrices for composite polypropylene composites, and a considerable amount of β-form crystallinity was produced by mixing with bamboo fiber; and all the bamboo fiber-filled samples contained both α- and β-forms.
Abstract: Bamboo fiber-reinforced polypropylene (PP) composites were prepared. PP and two maleated polypropylenes (s-MAPP and m-MAPP) were used as matrices. Crystallization and interfacial morphology were studied by using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and optical microscopy. It has been shown that the addition of bamboo fiber to any of the three polymers causes an increase in the overall crystallization rate. A considerable amount of β-form crystallinity was produced in the PP, s-MAPP, and m-MAPP by mixing with bamboo fiber; and all the bamboo fiber-filled samples contain both the α- and the β-forms. The relative amount of the β-form in the samples was calculated from WAXD data by the K value. There is no β-form observed in the pure PP, s-MAPP, and m-MAPP. Bamboo fiber acted as both a reinforcement and a β-nucleator. The nucleation density of both s-MAPP and m-MAPP at the fiber surface is remarkably higher than that of PP because an improved interfacial adhesion is reached in the case of s-MAPP and m-MAPP as matrices. The transcrystalline growth of s-MAPP and m-MAPP on the bamboo fiber surface was observed under optical microscope with crossed polars. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1267–1273, 1997
169 citations
TL;DR: In this paper, the temperature dependence of the electric conductance of the elements made of nanocrystalline α -Fe 2 O 3 showed that the gas-sensing properties are strongly related to its surface.
Abstract: α -Fe 2 O 3 ultra-fine powder with an average particle size of 6–26nm has been prepared by a sol-gel process. Thermal analysis, X-ray diffraction and transmission electron microscope were used to study its formation process and micro-structure. The temperature dependence of the electric conductance of the elements made of nanocrystalline α -Fe 2 O 3 shows that the gas-sensing properties are strongly related to its surface. The elements exhibited good sensitivity and selectivity to ethyl alcohol, indicating it is a promising alcohol-sensing material.
158 citations
TL;DR: In this paper, a weak in variance principle for strictly stationary negatively associated sequences is proved under some general conditions, and a probability inequality for Sn and some p th moment (p ≥ 2) inequalities for | Sn | and | Sk | are established.
Abstract: A probability inequality for Sn and some p th moment ( p ≥2) inequalities for | Sn | and max 1≤k≤n | Sk | are established. Here Sn is the partial sum of a negatively associated sequence Based on these inequalities, a weak in variance principle for strictly stationary negatively associated sequences is proved under some general conditions
129 citations
TL;DR: In this article, it was shown that PSF is miscible with 4,4′-diaminodiphenylmethane (DDM)-cured epoxy resin (ER) as revealed by the means of differential scanning calorimetry (d.m.s.c.), dynamic mechanical analysis and scanning electron microscopy (SEM).
110 citations
TL;DR: In this article, a series of EOET segmented copolymers with different long soft segments and different hard-segment contents were synthesized, and the thermally stimulated shape-memory behavior was characterized by the maximum recovery (Rf), the recovery temperature (Tr), and the recovery speed (Vr) or the temperature (TM) of the maximum deformation recovery rate against temperature.
Abstract: A series of ethylene oxide—ethylene terephthalate segmented copolymers (EOET) with different long soft segments and different hard-segment contents were synthesized. The thermally stimulated shape-memory behavior of EOET segmented copolymer is characterized by the maximum recovery (Rf), the recovery temperature (Tr), and the recovery speed (Vr) or the temperature (TM) of the maximum deformation recovery rate against temperature and the maximum recovery speed (VM). These parameters show that the features of thermally stimulated shape-memory effects of EOET segmented copolymers are following: The crystallinity of soft segments determines the temperature Tr and TM, and the parameters Rf, Vr, and VM depend on the stability of the physical crosslinks formed by the hard segments, which at the same time are influenced by the length of soft segment. Rf, Vr, and VM decrease with prolongation of the keeping time (tk) and increasing stretching ratio. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2433–2440, 1997
94 citations
TL;DR: In this article, a scheme for the teleportation of an unknown atomic state via the degenerate Raman atom-cavity field interaction was presented for the first time, and the teleportation was successful.
86 citations
TL;DR: In this article, the proton microprobe has been used to determine contents of Ca, Ti, Ni, Mn and Zn in the olivine of 54 spinel lherzolite xenoliths from Australian and Chinese basalts.
Abstract: The proton microprobe has been used to determine contents of Ca, Ti, Ni, Mn and Zn in the olivine of 54 spinel lherzolite xenoliths from Australian and Chinese basalts. These data are compared with proton-probe data for Ni, Mn and Zn in the olivine of 180 garnet peridotite xenoliths from African and Siberian kimberlites. Fe, Mn, Ni and Zn contents are well-correlated; because the spinel lherzolite olivines have higher mean Fe contents than garnet peridotite olivines (average F089.6 vs. Fo90_92 ) they also have lower Ni and higher Mn contents. Zn and Fe are well-correlated in garnet peridotite olivine, but in spinel peridotites this relationship is perturbed by partitioning of Zn into spinel. None of these elements shows significant correlation with temperature. Consistent differences in trace-element contents of olivines in the two suites is interpreted as reflecting the greater degree of depletion of Archean garnet peridotites as compared to Phanerozoic spinel lherzolites. Ca and Ti contents of spinel-peridotite olivine are well correlated with one another, and with temperature as determined by several types of geothermometer. However, Ca contents are poorly correlated with pressure as determined by the Ca-in-olivine barometer of K6hler and Brey (1990). This reflects the strong T-dependence of this barometer: the uncertainty in pressure (calculated by this method) which is produced by the __+ 50 ~ uncertainty expected of any geothermometer is ca _.+ 8 kbar, corresponding to the entire width of the spinel-lherzolite field at 900-1200~
83 citations
TL;DR: The recording of event-related brain potentials associated with ident@ing the global and local levels of nonlinguistic compound stimuli in a selective attention task found that the amplitude of an early posterior P1 component was modulated by attention to the Global precedence levels, being larger to the local target than to the global one.
Abstract: The global precedence hypothesis (Navon, 1977) assumes that the processing of the global level of a hierarchical pattern precedes that of the local level. To explore further the nature of global and local processing of compound stimuli, we recorded the event-related brain potentials (ERPs) associated with [email protected] the global and local levels of nonlinguistic compound stimuli in a selective attention task. Wile subjects' behavioral responses were similar to those observed by Navon (1977), the analyses of ERP data showed that identification of the local level elicited longer N2 and P3 peak latencies with enhanced N2 and decreased P3 amplitudes relative to the identification of the global level. The inconsistency between the global and local levels made N2 and P3 amplitudes more negative with longer peak latencies. This interference effect on N2 and P3 amplitude and P3 latency was stronger on the local level than on the global level. The modulation of N2 by the consistency of the global and local levels observed in this and the previous (Heinze, Muente, et al., 1994) study suggests that the interference effect may be mediated by the early perceptual processing. Moreover, we found that the amplitude of an early posterior P1 component was modulated by attention to the global and local levels, being larger to the local target than to the global one. This PI effect gives no support to the notion that the variation of attentional spotlight determines the global precedence effect.
TL;DR: A novel application of the wavelet transform in retrieving the separate signals from overlapping chromatographic peaks and quantitative determination of the components in the overlapping Chromatograms is described.
Abstract: A novel application of the wavelet transform in retrieving the separate signals from overlapping chromatographic peaks and quantitative determination of the components in the overlapping chromatograms is described. The signals can be very easily separated by decomposing an overlapping chromatographic peak into localized contributions according to their frequency, and quantitative calculation can be done by studying the contributions of higher frequency. Overlapping peaks of two- and three-component mixtures were investigated by the method, and the results show excellent correlations between peak areas of the retrieved signals and the concentrations for all of the components.
TL;DR: In this article, the motion and distribution of charged dust grains under the action of electrostatic and gravitational forces near the boundary of a dusty plasma are investigated, and it is shown that when gravity is negligible, a spatial localization of the dust can occur.
Abstract: The motion and distribution of charged dust grains under the action of electrostatic and gravitational forces near the boundary of a dusty plasma are investigated. It is shown that when gravity is negligible, a spatial localization of the dust can occur. For heavier grains, gravity enhances this localization, and causes a stratification of the dust density. For even heavier grains, the stratification disappears since the grains are pulled to the wall by gravity.
TL;DR: An ESR dating study on teeth collected from layers 3, 6/7 and 10 at Locality 1, Zhoukoudian provides results that are in general agreement with an earlier multi-dating study and confirm an age range of 300-550 ka for the Homo erectus remains in the Peking Man Cave.
TL;DR: In this article, an upper bound for the eigenvalues of the Laplacian matrix of a graph was established for the line graph of a given graph and the largest eigenvalue of the graph reached the upper bound.
TL;DR: In this paper, a new criterion of polymer-polymer miscibility based on the equation of Krigbaum and Wall was proposed, and the parameter Δ b was used to predict polymer polymers miscibility of PS/PBu, PBu/PMMA and some polyblends.
TL;DR: In this paper, the influence of experimental conditions on the preparation of nanocrystalline Fe3O4 powders is discussed, and the average particle size is 16 nm, which is the smallest known particle size in the literature.
TL;DR: In this paper, Cheng and He [Int. J. Engng Sci., 1995, 33, 389] showed that the micropolar Eshelby tensors are size-dependent both for the inside and for the outside of the circular cylinder.
TL;DR: In this paper, surface textures found on the boulder-clay grains were compared with those on grains with known sedimentary histories including glacial, grus, colluvial, and alluvial grains.
TL;DR: The problem addressed is the construction of a perturbating upper bound on uncertain noise covariances so as to guarantee that the deviation of the estimate error performance index remains within the precision prescribed in actual problems.
Abstract: This paper deals with the problem of a robust filter design for discrete-time descriptor systems with uncertain noise. The problem addressed is the construction of a perturbating upper bound on uncertain noise covariances so as to guarantee that the deviation of the estimate error performance index remains within the precision prescribed in actual problems. Furthermore, the worst performance in the uncertain case can be minimized by a minimax robust filter.
TL;DR: In this paper, the experimental results for clamped mild steel beams under impact loading reported by Yu and Jones (Yu, J. L. and Jones, N. A. (1991) are simulated numerically using the finite-element code ABAQUS with plane stress elements.
TL;DR: In this article, the authors presented the best-fitting synthetic spectra of the G140L spectra for the white dwarf in WZ Sge, exposed during quiescence, yielding a rapidly rotating white dwarf with velocity Vrot sin i = 1200+ 300−400 km s-1, white dwarf effective temperature Twd = 14,800 K, the gravity log g = 8.0, and the chemical abundances relative to solar in number (with 3σ error bars) of C, 5.0+ 2.0−2.
Abstract: We present Hubble Space Telescope Goddard High-Resolution Spectrograph G140L spectra of the white dwarf in WZ Sge, exposed during quiescence. Our best-fitting synthetic spectra yield a rapidly rotating white dwarf with velocity Vrot sin i = 1200+ 300−400 km s-1, white dwarf effective temperature Twd = 14,800 K, the gravity log g = 8.0, and the chemical abundances relative to solar in number (with 3σ error bars) of C, 5.0+ 2.0−2.0; N, 3.0+ 1.0−1.0; and Si, <0.1. We also reexamined a previous Hubble Space Telescope Faint Object Spectrograph G130H spectrum reported by Sion and coworkers and obtained consistent values, but lower C and N abundances. We do not detect a measurable systematic shift in our observed spectra, presumably due to the extremely low mass of the companion.
TL;DR: In this article, the authors studied the purely leptonic decays of heavy flavour mesons, D s − → τ − ν τ and B − → γD s −, and showed that the branching fraction for D s− → τ−ν τ decays at 90% CL.
TL;DR: In this paper, a series of Ni-Co-B amorphous catalysts for hydrogenation of benzene have been prepared in a wide composition range by chemical reduction and their structure were studied by EXAFS.
Abstract: A series of Ni-Co-B amorphous catalysts for hydrogenation of benzene have been prepared in a wide composition range by chemical reduction and their structure were studied by EXAFS. It is shown that the catalytic activity of these Ni-Co-B amorphous alloy is affected by both nickel content and the structural disorder of the sample; the latter could be adjusted by cobalt content of the sample. The EXAFS study also showed that the change of the boron content of the sample has a stronger effect on Ni-B coordination than on Co-B coordination and there is a preferential coordination of boron with nickel when the composition ratio B/Ni is high.
01 Jan 1997
TL;DR: In this paper, the first nonzero eigenvalue λ 1 of the Laplacian of a Riemannian manifold acting on functions on a (n + 1)-dimensional Euclidean ball of radius 1 c was shown to be isometric with respect to an (n − 1)-diameter.
Abstract: Let Ω be an (n + 1)-dimensional compact Riemannian manifold with nonnegative Ricci curvature and nonempty boundary M = ∂Ω. Assume that the principal curvatures of M are bounded from below by a positive constant c. In this paper, we prove that the first nonzero eigenvalue λ1 of the Laplacian of M acting on functions on M satisfies λ1 ≥ nc2 with equality holding if and only if Ω is isometric to an (n + 1)-dimensional Euclidean ball of radius 1 c . Some related rigidity theorems for Ω are also proved.
13 Apr 1997
TL;DR: This paper describes a genetic algorithm for the problem of codebook design, which uses fitness inheritance to assign fitness values to most new chromosomes, rather than evaluating them.
Abstract: Data compression techniques recode data into more compact forms. One such technique is vector quantization, which maps groups of input symbols, called vectors, onto a small set of vectors, called the codebook. Each vector in the codebook is a codeword. The indexes of the codewords represent the original vectors, and writing the codewords that the indexes indicate restores a facsimile of the original data. The similarity of the restored data to the original under vector quantization depends on the codebook, and several algorithms have been proposed for designing it from a training set of typical vectors. This paper describes a genetic algorithm for the problem of codebook design. The genetic algorithm's chromosomes represent partitions of the training set; each vector maps to the codeword that is the centroid of its set in the partition. To speed up its operation, the genetic algorithm uses fitness inheritance to assign fitness values to most new chromosomes, rather than evaluating them. Tests using five standard digitized images compare the genetic algorithm to a popular non-genetic algorithm for codebook design. The genetic algorithm is found to be effective, but slow.
TL;DR: The first direct evidence of proton capture-processed material in the atmosphere of a white dwarf was found in the G160M spectra of the white dwarf in VW Hydri, exposed during quiescence as discussed by the authors.
Abstract: We present Hubble Space Telescope Goddard High-Resolution Spectrograph G160M spectra of the white dwarf in VW Hydri, exposed during quiescence, 1 month after the end of a normal dwarf nova outburst. Our spectra, covering the wavelength interval 1236-1272 A, were obtained at orbital phase 0.06-1.60; they reveal strong photospheric Si II λλ1260, 1265 absorption features and a previously unidentified broad feature centered around 1250 A. This feature is due to a blend of phosphorus lines. From line-shift measurements we determine a gravitational redshift of 58 ± 33 km s-1, yielding a white dwarf mass Mwd = 0.86+ 0.18−0.32 M☉ (this is only the second gravitational redshift determined for a cataclysmic variable white dwarf), white dwarf radius Rwd = 6.5+ 3.1−1.5 × 108 cm, and gravity log g = 8.43+ 0.31−0.54. Our best-fitting synthetic spectra yield white dwarf effective temperature Twd = 22,000 K and a rotational velocity Vrot = 400 km s-1. The chemical abundances, in number relative to solar, are, for C, 0.5; N, 5.0; O, 2.0; Fe, 0.5; Si, 0.1; P, 900; and all other metals, 0.3. The abundance of phosphorus being 900 solar, coupled with the elevated aluminum abundance reported by Sion and coworkers, suggest nucleosynthetic production of these odd-numbered nuclei from proton capture on the even-numbered nuclei during a CNO thermonuclear runaway (TNR) on the white dwarf. It is clear that the white dwarf has undergone a runaway sometime in the past, the first such evidence of a TNR in a dwarf nova. A TNR on a slowly accreting 0.86 M☉ white dwarf should produce a classical nova explosion. If our interpretation is correct, then we have found the first direct spectroscopic link between a dwarf nova and a classical nova by using the white dwarf surface chemical abundance. This is also the first direct evidence of proton capture-processed material in the atmosphere of a white dwarf. Nova explosions on more numerous, lower mass C-O white dwarfs may therefore account for some fraction of the short-lived radionuclide 26Al in the Galaxy. This nuclide is observed from its Galactic gamma-ray line emission and is postulated to have an important role in the heating of small bodies in the solar system.
TL;DR: Experiments showed that CBO can be used under high power density without damage to the crystal and the effective nonlinear-optical coefficient of CBO in the ultraviolet range is close to its maximum.
Abstract: We present sum-frequency generation (SFG) characteristics of CsB3O5 crystal (CBO). The effective nonlinear-optical coefficient of CBO in the ultraviolet range is close to its maximum. High-efficiency SFG with a picosecond Nd:YAG laser with output wavelengths of 355 and 266 nm was achieved. Experiments showed that CBO can be used under high power density without damage to the crystal.
TL;DR: In this article, the hydrogen bonding interaction between the two components of the poly(ethylene oxide) (PEO)/oligoester (OER) blends and the PEO/crosslinked unsaturated polyester resin (PER) blends was found to be an important driving force to the miscibility of these polymer blends.
Abstract: Hydrogen-bonding interaction between the two components of the poly(ethylene oxide) (PEO)/oligoester (OER) blends and the PEO/crosslinked unsaturated polyester resin (PER) blends was found to be an important driving force to the miscibility of these polymer blends. Its strength is approximately as strong as the self-association of hydroxyl groups in either the pure OER or the pure PER. The crystallization kinetics and morphology of PEO in PEO/PER blends was remarkably affected by crosslinking. It was found that the overall crystallization rate of PEO in PEO/PER blends is larger than that in PEO/OER blends at the crystallization temperature investigated, which was considered to be the result of nucleation controlling mechanism. With decreasing PEO content, the regular shape of PEO spherulites turns irregular in PEO/ OER blends, whereas in PEO/PER blends, the birefrigent spherulites turns into dendritic structures. Raising the crystallization temperature favors the formation of dendritic textures in PEO/PER blends.