Wyniki wyszukiwania - Biblioteka Nauki

1

Parameter estimation of non-stationary random media driven by partially stacked seismic data

100%

Lin Y. , Zhang G. , Chen S. , Huang M. , Wang B.

Acta Geophysica

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2022

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tom Vol. 70, no 5

2119--2133

EN

The estimation of non-stationary random medium parameters is the key to the application of random medium theory in fine seismic exploration. We propose a method for estimating non-stationary random medium parameters from partially stacked seismic data. To begin with, the relationship between seismic data and random medium p-wave velocity, s-wave velocity, density model in random medium is described, and the principle and method of estimating the parameters of autocorrelation function of random medium are introduced in this paper. Subsequently, the specific steps of applying the power spectrum method for non-stationary random media parameter estimation are also presented. The feasibility and correctness of the method are verified through the estimation test of the two-dimensional theoretical model. Eventually, the estimation test of non-stationary random medium parameters is carried out by field seismic data. The results show that the non-stationary random medium parameters can better describe the elastic parameter information of the subsurface media and provide a reference for the initial model construction of the elastic parameters, reflecting that the method has good application prospects. Compared with previous studies, this method extends the random medium parameter estimation from stationary to non-stationary and from single wave impedance random medium parameter to multi-elastic parameter random medium parameters. It provides a basis for the in-depth application of random media theory in field data. Meanwhile, this estimation method based on the power spectrum method has the advantage of being intuitive and easy to interpret. However, there are also problems in smoothing effect, which needs further improvement and refinement.

2

Estimation of lateral correlation length from deep seismic refection profle based on stochastic model

100%

Yong F. , Lu Q. , Feng J. , Zhang J. , Luo S.

Acta Geophysica

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2021

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tom Vol. 69, no. 4

1297--1312

EN

The fractal nature of crustal seismic velocity heterogeneity makes the interpretation of deep seismic refection data difcult by conventional methods developed in oil and gas exploration. Thus, several statistical approaches have been introduced as promising tools for interpreting the complex refection patterns of deep seismic data. Because stochastic models have been successfully used to describe the heterogeneity of crustal rocks, stochastic parameter estimation has become a potentially powerful tool for recovering information on geometric geological variations. However, there are many factors that infuence parameter estimation, with limited data being a profound one. We present a novel algorithm to estimate the lateral correlation length, an important stochastic parameter, from deep seismic refection data. First, an autoregressive power spectrum-based method was introduced to calculate the autocorrelation function from limited data. Second, the average multi-trace 1D autocorrelation function was used to replace the 2D autocorrelation function to improve the computation efciency, accuracy, and stability. Compared with other algorithms, a velocity model test showed that our method exhibited signifcantly better performance for a small dataset. Then, an appropriately sized sliding window of synthetic seismic data was applied to map the relative variations of lateral stochastic parameters. The results indicated that our method could distinguish the lateral variations in stochastic parameters as well as vertical changes. Finally, the geological meaning of diferent seismic refection patterns was discussed after applying our methods to deep seismic refection feld data. The results demonstrated that lateral correlation can clearly identify Moho discontinuity, crustal refections, and some sedimentary structures.

3

Large-scale parameter estimation for three-phase distillation based on a nonequilibrium model

100%

Chen L. , Repke J. , Wozny G.

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tom R. 105, z. 5-M

37-44

EN

Mathematical NEQ modeling of three-phase distillation is a fundamental and difficult task, since no reliable correlations available to calculate the inter-phase mass and heat transfer coefficients. Parameter estimation based on a rigorous NEQ model rather than short-cut methods is needed to generate a robust and accurate model. In this paper, parameter estimation is carried out based on a large-scale optimization strategy. The transfer parameters are estimated based on multi-set experiment data. The NEQ model is updated with substantial improvement on the model predictive capability.

PL

Zasadniczym celem artykułu jest matematyczne modelowanie NEQ destylacji trójfazowej. Podstawową trudnością jest brak dostępnych korelacji służących do obliczania współczynników przenikania masy i ciepła w fazie przejściowej. Stworzenie stabilnego i dokładnego modelu wymaga szacowania parametru opartego na rygorystycznym modelu NEQ, a nie na metodach uproszczonych. W niniejszej pracy zaprezentowano szacowanie parametru na podstawie ogólnej strategii optymalizacji. Parametry transportowe zostały oszacowane na bazie multizbioru danych eksperymentalnych. Model NEQ został uaktualniony z uwzględnieniem istotnej poprawy zdolności prognozowania modelu.

4

Parameter identifiability for nonlinear LPV models

84%

Srinivasarengan K. , Ragot J. , Aubrun C. , Maquin D.

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2022

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tom Vol. 32, no. 2

255--269

EN

Linear parameter varying (LPV) models are being increasingly used as a bridge between linear and nonlinear models. From a mathematical point of view, a large class of nonlinear models can be rewritten in LPV or quasi-LPV forms easing their analysis. From a practical point of view, that kind of model can be used for introducing varying model parameters representing, for example, nonconstant characteristics of a component or an equipment degradation. This approach is frequently employed in several model-based system maintenance methods. The identifiability of these parameters is then a key issue for estimating their values based on which a decision can be made. However, the problem of identifiability of these models is still at a nascent stage. In this paper, we propose an approach to verify the identifiability of unknown parameters for LPV or quasi-LPV state-space models. It makes use of a parity-space like formulation to eliminate the states of the model. The resulting input-output-parameter equation is analyzed to verify the identifiability of the original model or a subset of unknown parameters. This approach provides a framework for both continuous-time and discrete-time models and is illustrated through various examples.

5

Użyteczność deterministycznych metod optymalizacji globalnej do szacowania parametrów w zagadnieniach hydrologicznych

84%

Grządziel M. , Jełowicki J.

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2011

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tom T. 11, z. 1

61-74

PL

Numeryczne metody optymalizacji, powszechnie stosowane w zagadnieniach hydrologicznych, nie gwarantują wyznaczenia minimum globalnego funkcji celu. Ich popularność wiąże się z tym, że mogą one być stosowane w zagadnieniach, w których liczba zmiennych decyzyjnych jest stosunkowo duża. W pracy dokonano przeglądu metod deterministycznych, które umożliwiają znalezienie optimum globalnego w przypadku, gdy funkcja celu ma więcej niż jedno minimum lokalne. Metody te mogą być podzielone na dwie kategorie: asymptotycznie kompletne oraz kompletne. Podczas gdy algorytmy należące do obu klas są w stanie generować ciąg rozwiązań przybliżonych zbieżny do rozwiązania zagadnienia optymalizacji globalnej, to tylko dla algorytmów należących do drugiej z wymienionych kategorii są dostępne nieheurystyczne kryteria stopu. Przykłady przedstawione w pracy ilustrują możliwości zastosowania metod asymptotycznie kompletnych do szacowania parametrów w modelach procesów hydrologicznych, takich jak: modele różniczkowe przepływu wód gruntowych, modele hydrauliczne wchodzące w skład modeli hydrodynamicznych wykorzystywanych do modelowania zasobów wód powierzchniowych, modele typu opad-odpływ czy też integralne modele zlewni.

EN

Most numerical optimization methods that are widely used in hydrology don't guarantee reaching the global minimum of the goal function. They became popular mainly due to their ability of handling relatively multi-dimensional problems. The paper reviews the deterministic methods capable of finding the global optimum in the presence of local optima. They can be divided into two categories: asymptotically complete methods and complete methods. While algorithms from both classes can generate a sequence converging to a solution of the global optimization problem, only for the algorithms from the latter class non-heuristic stopping criteria are available. The examples presented in the paper illustrate the applicability of asymptotically complete methods to parameter estimation in modelling hydrological processes, such as differential models of groundwater flow, hydraulic models embedded into hydrodynamic models of river systems, the precipitation–outflow models or integral catchment models.

6

Application of model-based failure detection and identification to industrial production

84%

Schubert U. , Arellano-Garcia H. , Wozny G.

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tom R. 105, z. 5-M

261-274

EN

In this work, new prospects for current process control in the chemical process industry with application of model based predictive methods are presented. The data from a research cooperation work with the Evonik Degussa GmbH at Hanau-Wolfang, Germany let authors work out the models for failure detection and identification besides the basic regulatory control. The data derived from existing controllers, which make use of the predictive functional control method, is an attempt to define lower limits for model quality that is necessary to fulfill the secondary task satisfactory.

PL

W artykule przedstawiono nowe perspektywy bieżącego sterowania procesami w przemyśle chemicznym z zastosowaniem prognozowania opartego o rozwój precyzyjnych modeli. Wykorzystano dane z instalacji Evonik Degussa GmbH at Hanau-Wolfang, Germany, które pozwoliły, poza usprawnieniem sterowania, na wprowadzenie systemów identyfikacji i wykrywania awarii. Wykorzystując informacje z istniejących czujników sterowania predykcyjnego opracowano precyzyjny model jakościowy.

7

Modelowanie przepływu wód gruntowych w ujęciu obszarowym

84%

Zaradny H.

Biuletyn Państwowego Instytutu Geologicznego

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2008

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tom nr 431, Hydrogeologia

275--286

PL

W pracy omówiono metody postępowania przy modelowaniu filtracji w ujęciu obszarowym, z podkreśleniem szczególnej roli szacowania wartości parametrów, kalibracji i analizy wrażliwości przy tworzeniu modeli prognostycznych. Ponadto przedstawiono przykładowe wyniki symulacji otrzymane za pomocą programu HZPLASKI, opracowanego przez autora. Program ten umożliwia rozwiązywanie zagadnień filtracji obszarowej dla stanów ustalonych, przy wykorzystaniu metody elementów skończonych.

EN

The paper presents a modelling approach to the two-dimensional groundwater flow in a horizontal plane. Particular attention is paid to the parameter estimation procedure, model calibration and sensitivity analysis. Examples of numerical simulations, performed with the HZPLASKI code developed by the author, are presented. The code was developed in order to solve steady-state groundwater flow in a horizontal plane, using the finite element method.

8

Ligament-based spine-segment mechanisms

84%

Ciszkiewicz A. , Milewski G.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2018

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tom Vol. 66, nr 5

705--712

EN

Nowadays, a growing interest in spine-segment mechanisms for humanoid robots can be observed. The ones currently available are mostly inspired by an intervertebral joint but rarely use its structure and behaviour as input data. The aim of this study was to propose and verify an approach to spine-segment mechanisms synthesis, in which the mechanisms were obtained directly from a ligament system of the intervertebral joint through numerical optimization. The approach consists of two independent optimization procedures performed with genetic algorithm. The first one searches for the optimal structure, while the second estimates its geometrical and stiffness parameters. The mechanisms are rated by their ability to reproduce the static behaviour of the joint in selected aspects. Both procedures use the lumbar L4-L5 intervertebral joint reference data. The approach was tested in two numerical scenarios. It was possible to obtain a mechanism with 7 flexible linear legs that accurately emulated the elastostatic behaviour of the intervertebral joint under moment loads. The results prove that the proposed method is feasible and worth exploring. It may be employed in design of bioinspired joints for use in humanoid robots and can also serve as an initial step in the design of prosthetic and orthotic devices for a human spine.