Showing papers by "University of Science and Technology of China published in 1984"

A new approach to removing cloud cover from satellite imagery

Abstract: A new approach is proposed for removing cloud clover from satellite imagery, based on O. R. Mitchell's model (O. R. Mitchell, B. J. Delp, and P. L. Chen, IEEE Trans. Geosci. Electron. GE-15, 1977, 137–141). It is useful in the case where clouds have relatively low spatial-frequency content compared to the ground reflectance. Results from a computer simulation are shown.

A new structure for narrow transition band, lowpass digital filter design

Abstract: In this paper, a new class of lowpass linear phase FIR filters is introduced. It is shown that lowpass filters with narrow transition bands can be realized efficiently by a structured form composed mainly of a few small FIR filters. The modular structure is suited for an implementation by a fast short convolution algorithm or a few single-chip filter IC's. A design procedure is considered in some detail and illustrated by an example. The properties and performance of the filter are discussed by analysis as well as design results. A brief discussion on its implementations concludes the paper.

Charge density wave depinning in TaS3

Abstract: Two polytypes of TaS3 have been synthesized, one with a monoclinic unit cell, the other with an orthorhombic unit cell. Monoclinic TaS3 has a structure similar to that of NbSe3 and undergoes two independent Peierls transitions at T 1 = 240 K and T 2 = 160 K. A unique Peierls transition occurs in orthorhomic TaS3 at T 0 = 215 K, with a slightly incommensurate periodic lattice distortion which locks to a commensurability of four lattice parameters along the chain direction at T'0 ∼ 130 K. Both TaS3 varieties show nonlinear transport properties associated with the motion of the charge density wave produced by applying an electric field with an amplitude higher than a threshold value. Measurements are reported of the threshold field and of the a.c. frequency measured by Fourier anaysis of the noise as a function of the temperature. Monoclinic TaS3 behaves similarly to NbSe3, with a higher threshold field for the upper temperature Peierls transition than for the lower one. For orthorhombic TaS3 it is ...

Large deplection of corrugated circular plate with a plane central region under the action of concentrated loads at the center

Abstract: This paper solves the problem of large deflections for corrugated circular plates with a plane central region under the action of concentrated loads at the center by means of the non-linear bending theory for anisotropic circular plates. Using the modified iteration method, the characteristic relation of the plate is obtained. This formula may be applied directly to design of elastic elements of measuring instruments.

On the cost of computing roots of polynomials

Abstract: Recently Smale has obtained probabilistic estimates of the cost of computing a zero of a polynomial using a global version of Newton's method. Roughly speaking, his result says that, with the exception of a set of polynomials where the method fails or is very slow, the cost grows as a polynomial in the degree. He also asked whether similar results hold for PL homotopy methods. This paper gives such a result for a special algorithm of the PL homotopy type devised by Kuhn. Its main result asserts that the cost of computing some zero of a polynomial of degreen to an accuracy of e (measured by the number of evaluations of the polynomial) grows no faster than O(n 3 log2(n/e)). This is a worst case analysis and holds for all polynomials without exception.

Bernstein Polynomials Via the Shifting Operator

Abstract: (1984). Bernstein Polynomials Via the Shifting Operator. The American Mathematical Monthly: Vol. 91, No. 10, pp. 634-638.

The fission of spectrum line of monochoromatic elastic wave

Abstract: On the basis of the anology with quantum electrodynamics, Dirac equation of elastic wave-phonon is developed and the fission of spectrum line of monochoromatic elastic wave under the action of an external field is studied in this paper.

The solution of deflection of elastic thin plate by the joint action of dynamical lateral pressure, force in central surface and external field on the elastic base

Abstract: In this paper the Euler equation of the deflection of clastic thin plate is reduced to the equation with schrodinger form by the principle of quantum electro-dynamics. Then we can obtain the general solution of deflection of eleastic thin bending plate by the joint action of dynamical lateral pressure, force in central surface and external field on the elastic base.

Effects of diagonal and off-diagonal disorder on the Anderson-model densities of states in two and three dimensions

Abstract: Calculations of the densities of states of the Anderson-model Hamiltonian are reported for cases with diagonal and off-diagonal disorder and for the following lattices: in two dimensions, (i) simple square, (ii) honeycomb, and (iii) triangular; and in three dimensions, simple cubic. In all cases diagonal disorder destroys the van Hove singularity peaks. With strong off-diagonal disorder, the density of states for a square lattice exhibits a band-center peak, at $E=0$, where the ordered lattice had a van Hove singularity; no such peak is found for a triangular lattice. These results correlate with the conclusion of Soukoulis et al. for off-diagonal disorder that the $E=0$ state of the triangular lattice is exponentially localized, but that of the square lattice is not. However, zero-energy peaks are found for both the honeycomb two-dimensional lattice and the cubic three-dimensional lattice, demonstrating that the band-center peak is not derived from a van Hove singularity of the ordered Hamiltonian. The implications are discussed.

Comments on "On sequential estimation of state noise variance"

Abstract: It is shown that the algorithm given by J. F. Leathrum in the paper for estimating state noise variance can be considerably simplified.

Origin of Graphite in Early Precambrian Banded Iron Formation in Anshan, China

Abstract: Graphite which occurs in the early Precambrian banded iron formation (BIF) (31x109yr) at Gongchangling, Anshan, China, can be divided into two genetic types on the basis of its modes of occurrence: biogenic and inorganic; the former occurs in garnet-mica-quartz schist and the latter in rich magnetite ore

Singular Integrals in Several Complex Variables

Abstract: Let Ω be a smooth, bounded, strictly pseudo-convex domain in (ℂn. Let H(w, z) be the Henkin-Ramirez kernel and E(w,z)+C(w,z) be the Stein-Kerzman kernel. Since both H(w,z) dσz and E(w,z) dσz are Cauchy-Fantappie forms, they may be written as

Measurement of the Dijet Cross Section in 400-GeV pp Collisions

Abstract: The invariant cross section for production of jet pairs in 400-GeV/c pp interactions has been measured as a function of p{tau} in the p{tau} range 4 to 9 GeV/c The results are in good agreement with predictions of perturbative QCD models 20 refs, 3 figs, 1 tab

Absorption cross sections of a Schwarzschild black hole

Abstract: An explicit expression for the cross section of absorption of non-relativistic particles by a mini Schwarzschild black hole is obtained in a quantum mechanical scheme.

Metric spaces which cannot be isometrically embedded in Hilbert space

Abstract: Let A1A2A3A4, be a planar convex quadrangle with diagonals A1A3 and A2A4. Is there a quadrangle B1B2B3B4 in Euclidean space such that A1A3 BiBj for other edges?The answer is “no”. It seems to be obvious but the proof is more difficult. In this paper we shall solve similar more complicated problems by using a higher dimensional geometric inequality which is a generalisation of the well-known Pedoe inequality (Proc. Cambridge Philos. Soc.38 (1942), 397–398) and an interesting result by L.M. Blumenthal and B.E. Gillam (Amer. Math. Monthly50 (1943), 181–185).

Spatial instability of a swirling flow

Abstract: The instability of a swirling flow of an inviscidand incompressible fluid is studied on the assumption that the wavenumberk=k,+ik i , of the disturbance is complex while its frequency ω is real. This implies that the disturbance grows with distance along the axis of the swirling flow, but it does not grow with time. The occurrence of such disturbance is called spatial instability, in contrast to the temporal instability, in whichk is a real number and ω=ωr+iωi is a complex one. The results show that spatial instability analysis is a useful tool for the comprehensive understanding of the instability behaviours of a swirling flow.

Large deformation solution of stiffened plates by a mixed finite element method

Abstract: In the present paper, a finite element mixed variational functional and the iterative equations of the eccentric orthogonal stiffened plates are developed in accordance with nonlinear elasticity. By using an important technique the coupling coefficients of the two-dimensional coupling matrix are resolved into the known input data in the programming which is a three-dimensional coefficient matrix. The nonlinear equations are transformed into the instantaneous linear equations; and by using the conjugate gradient method the linear equations are solved. As a result, therefore, the calculation is enormously simplified, the precision manifested, and a satisfactory result obtained.