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1

An iterative method based on 1D subspace for projective reconstruction

Liu S., Peng Y., Zeng Z., Han C.

Opto-Electronics Review

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2011

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Vol. 19, No. 1

89-94

EN

Heyden et al. introduced an iterative factorization method for projective reconstruction from image sequences. In their formulation, the projective structure and motion are computed by using an iterative factorization based on 4D subspace. In this paper, the problem is reformulated based on fact that the x, y, and z coordinates of each feature in projective space are known from their projection. The projective reconstruction, i.e., the relative depths w and the 3D motion, is obtained by a simple iterative factorization based on 1D subspace. This allows the use of very fast algorithms even when using a large number of features and large number of frames. The experiments with both simulate and real data show that the method presented in the paper is efficient and has good convergency.

2

The application of the self-adaptive tracking method to the sinusoidal phase modulating interferometry

He G., Lu Y., Liao C., Zeng Z.

Optica Applicata

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2009

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Vol. 39, nr 1

109--122

EN

In this paper, we analyze theoretically the accuracy of the surface profile measurement in a sinusoidal phase modulating interferometer, derive the relative error formula, and investigate the influence of spectral leakage on the measurement accuracy. The theoretical results show that when the offset of sampling frequency from its theoretical ideal is outside the range of - 0.188% to +0.075%, the spectrum leakage results in an relative error greater than ?/320 nm, and thus the spectral leakage is not negligible. In order to eliminate the influence of the spectral leakage, a self-adaptive tracking method is proposed. The tracking method can adjust automatically the sampling signal frequency in such a way that the sampling signal frequency is an integer multiple of the modulating signal frequency. The simulation and experimental results show that the problem of the spectrum leakage can be solved with the proposed technique, and therefore the measurement accuracy and reliability of the SPM interferometer are enhanced.

3

Reduced magnetic vector potential and electric scalar potential formulation for eddy current modeling

Zeng Z., Liu X., Deng Y., Udpa L., Udpa S.

Przegląd Elektrotechniczny

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2007

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R. 83, nr 6

35-37

EN

A finite element formulation using the reduced magnetic vector potential and the electric scalar potential is proposed for modeling eddy current nondestructive testing problems in which the probe coil scans across the sample. Excitation coil is not meshed and the remeshing is avoided during the motion of the coil. The mesh and system matrix remain unchanged with different coil positions. The incomplete factorization of the system matrix as preconditioner is performed only once during the entire scan, which results in a significant reduction of computation time.

PL

Zaproponowano sformułowanie metody elementów skończonych, wykorzystujące zredukowany wektorowy potencjał magnetyczny i skalarny potencjał elektryczny, do modelowania wiroprądowych badań nieniszczących, w których cewka jest przesuwana nad próbką. Cewka wzbudzająca nie jest dyskretyzowana na elementy skończone. Siatka i macierz układu pozostają niezmienione przy różnych położeniach cewki. Niepełna faktoryzacja macierzy jest wykonywana tylko raz podczas całego skanowania, co prowadzi do skrócenia czasu obliczeń.