A number of effective procedures for improving the distorted Born iterative method are proposed, including the accurate and efficient solution of the direct problem, second-difference regularization, weighted least-squares solution, estimation of the initial guess by using a priori information and multiple-frequency scheme.

The compensation coefficient R is the function of time sampling interval (△t), spatial sampling interval (△x), depth step (△τ), interval velocity (V), frequency (f), dip (φ) and approximate second-difference coefficient (B).

The energy of the charges comes from interactions with an electrostatic potential, which is the solution of a symmetric second-difference Poisson equation on the lattice.

For example, a wavelet that is a second-difference operator can provide no information on the linear trend in a turbulence signal.

In this paper a method of the speech feature extraction for the ship-bridge speech recognition experiment system is described. The original character matrix is obtained from a 1/3 octave spectrum analyser. Using various different ways such as the first difference in the frequency domain; the second difference in the frequency domain; the first difference in the time domain and the Laplacian, we can obtain some different character marries from the original character matrix. Then we binarize each element of these...

In this paper a method of the speech feature extraction for the ship-bridge speech recognition experiment system is described. The original character matrix is obtained from a 1/3 octave spectrum analyser. Using various different ways such as the first difference in the frequency domain; the second difference in the frequency domain; the first difference in the time domain and the Laplacian, we can obtain some different character marries from the original character matrix. Then we binarize each element of these matries. In nonlinear time normalization we emphasize varing spectral section by two different weights. Thereby we can obtain various feature matries. On the basis of the experiments two feature marries are selected for the ship-bridge speech recognition experiment system.

DEM, resently has been widely used in different fields, especially in photogrammetry for topographic map production. One of the problems of DEM is how to collect data accurately, efficiently and comprehensively. Prgressive samling conceived by Makarovic is considered a more promising approach for DEM data acquisition.The basic principle of progressive sampling is progressive grid densification starting with sampling in a coarse homogenous grid and proceeding to a finer sampling in partial grids. Data collection...

DEM, resently has been widely used in different fields, especially in photogrammetry for topographic map production. One of the problems of DEM is how to collect data accurately, efficiently and comprehensively. Prgressive samling conceived by Makarovic is considered a more promising approach for DEM data acquisition.The basic principle of progressive sampling is progressive grid densification starting with sampling in a coarse homogenous grid and proceeding to a finer sampling in partial grids. Data collection and analysis are performed interactively. The result is a square grid in variable density, locally adapted to the roughness of terrain relief. Progressive sampling allows for semi-automatic operation, i. e. , computer controlled Ⅹ. Y-positioning of the measuring device of a photogrammetric stereaplotter and manual height setting (Z-positioning) by the operator. Progressive sampling can be done either on an analytical plotter or on an analogue stereoplotter interfaced with a computer by a feedback loop. Progrssive sampling has the potential of meeting the requirements on sampling, i.e., to collect terrain relief data accurately,comprehenslvely and store them in a favourable structure for later efficient process.Based on the principle of method, corresponding parameters of progressive sampling are experimetally investigated in this paper. Through the analysis of testing results, the influences of the sampling parameters on the accuracy of DEMs and the accuracy of contour lines derived from DEM, and the interrelationship between different parameters are proved. According to this, some conclusions are drawn with respect to the experiments performed in the paper, and a tentitive procedure is proposed in which the values of sampling parameters are determined by considering the accuracy specifications of topographic map and the measuring error of height, that is: under the assumption of accuracy specification for derived contour lines requiring that the standard error of checked contour points should not be larger than 1/3 of the contour interval, a proper minimum grid spacing of progrossive sampling can firstly be defined by analyzing the comprehensiveness of equispaced sampling for different regular spacings yielding a standard error of DEM of 1/5 of the contour interval. A threshold value of second difference equal to the contour interval can be chosen if the contour interval is not smaller than 5 times the standard error of measuremnet.

In the paper the autor gives a medium-term and a long term prediction of cereal output in Hubei Province using GM(1,1) model of grey systems, auto correlation regression model of second difference, exponential moving average of a cubic, exponential regression and prediction of cycle ratio models.