Wyniki wyszukiwania - BazTech

1

Regional recovery of gravity anomaly from the inversion of diagonal components of GOCE gravitational tensor: A case study in Ethiopia

Eshagh Mehdi, Gedamu Andenet A., Bedada Tulu B.

Artificial Satellites : Journal of Planetary Geodesy

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2018

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Vol. 53, No. 2

55--74

EN

The tensor of gravitation is traceless as the gravitational field of the Earth is harmonic outside the Earth’s surface. Therefore, summation of the 2nd-order horizontal derivatives on its diagonal components should be equal to the radial one but with the opposite sign. The gravity field can be recovered locally from either of them, or even their combination. Here, we use the in-orbit diagonal components of the gravitational tensor measured by the gravity field and steady state ocean circulation explorer (GOCE) mission for recovering gravity anomaly with a resolution of 1°×1° at sea level in Ethiopia. In order to solve the system of equations, derived after discretisation of integral equations, the Tikhonov regularisation is applied and the bias of this regularisation is estimated and removed from the estimated gravity anomalies. The errors of the anomalies are estimated and their significance of recovery from these diagonal components is investigated. Statistically, the difference between the recovered anomalies from each scenario is not significant comparing to their errors. However, their joint inversion of the diagonal components improved the solution by about 1 mGal. Furthermore, the inversion processes are better stabilised when using errors of the input data compared with its exclusion, but at the penalty of degradation in accuracy of the estimates.

2

Comparison of five SVD-based algorithms for calibration of spectrophotometric analyzers

Wagner J., Morawski R. Z., Miękina A.

Metrology and Measurement Systems

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2014

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Vol. 21, nr 2

191--204

EN

Spectrophotometry is an analytical technique of increasing importance for the food industry, applied i.a. in the quantitative assessment of the composition of mixtures. Since the absorbance data acquired by means of a spectrophotometer are highly correlated, the problem of calibration of a spectrophotometric analyzer is, as a rule, numerically ill-conditioned, and advanced data-processing methods must be frequently applied to attain an acceptable level of measurement uncertainty. This paper contains a description of four algorithms for calibration of spectrophotometric analyzers, based on the singular value decomposition (SVD) of matrices, as well as the results of their comparison - in terms of measurement uncertainty and computational complexity - with a reference algorithm based on the estimator of ordinary least squares. The comparison is carried out using an extensive collection of semi-synthetic data representative of trinary mixtures of edible oils. The results of that comparison show the superiority of an algorithm of calibration based on the truncated SVD combined with a signal-to-noise ratio used as a criterion for the selection of regularisation parameters - with respect to other SVD-based algorithms of calibration.

3

Regularising Ill-posed Discrete Optimisation: Quests with P Systems

Nicolescu R., Gimel’farb G., Morris J., Delmas P., Gong R.

Fundamenta Informaticae

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2014

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Vol. 131, nr 3-4

465--483

EN

We propose a novel approach to justify and guide regularisation of an ill-posed one-dimensional global optimisation with multiple solutions using a massively parallel (P system) model of the solution space. Classical optimisation assumes a well-posed problem with a stable unique solution. Most of important practical problems are ill posed due to an unstable or non-unique global optimum and are regularised to get a unique best-suited solution. Whilst regularisation theory exists largely for unstable unique solutions, its recommendations are often routinely applied to inverse optical problems with essentially non-unique solutions, e.g. computer stereo vision or image segmentation, typically formulated in terms of global energy minimisation. In these cases the recommended regularisation becomes purely heuristic and does not guarantee a unique solution. As a result, classical optimisation algorithms: dynamic programming (DP) and belief propagation (BP) – meet with difficulties. Our recent concurrent propagation (CP), leaning upon the P systems paradigm, extends DP and BP to always detect whether the problem is ill posed or not and store in the ill-posed case an entire space of solutions that yield the same global optimum. This suggests a radically new path to proper regularisation: select the best-suited unique solution by exploring statistical and structural features of this space. We propose a P systems based implementation of CP and set out as a case study an application of CP to the image matching problem in stereo vision.

4

Fourier transform computation algorithm with regularization

Emets V., Rogowski J.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 1

175-177

EN

Regularization theory for calculation of the Fourier transformations of continuous functions that vanish at infinity is considered. Procedure is based on using of the Gauss means. The regularization parameter is simple connected with error level of input data.

PL

W artykule przedstawiono teorię obliczania transformaty Fouriera funkcji ciągłych i zanikających w nieskończoności. Procedura jest oparta o wykorzystanie średnich Gaussa. Parametr regularyzacji jest połączony w prosty sposób z poziomem błędu danych wejściowych.

5

O regularyzacji rozwiązań niejednoznacznych w grze przeciwko naturze

Laskowski S.

Telekomunikacja i Techniki Informacyjne

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2007

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nr 3-4

30-46

PL

Zaprezentowano kilka znanych z literatury kryteriów wyboru strategii w grach przeciwko naturze i wykazano użyteczność lub nieużyteczność określonych regularyzacji.

EN

Certain common know criteria of choosing strategy in games against nature were presented, and usefulness and lack of it in some kinds of regularization were proved.

6

The application of regularisation methods to analysis of structure dynamics

Iwaniec J.

Diagnostyka

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2004

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Vol. 30, T. 1

199--203

EN

In the paper there are discussed issues concerning ill-posed problems. Mathematical definition and a method of detecting ill-posed problems as well as a method of improving such problems conditioning by the use of the Tikhonov regularisation are presented. The results of transfer function noise reduction by the use of the Tikhonov regularisation method are shown.

PL

W pracy omówiono zagadnienia dotyczące zagadnień źle zdefiniowanych. Przedstawiono definicję matematyczną, metodę wykrywania zagadnień źle zdefiniowanych oraz metodę poprawiania uwarunkowania tych zagadnień przy użyciu regularyzacji Tikhonova. Zaprezentowano również możliwość zastosowania metody regularyzacji Tikhonova do redukcji szumów widmowych funkcji przejścia.