scholarly journals Parameter Dependences Arising from Calibration of a Riverine Diatom Model - Representation in Terms of Posterior Conditional Distributions

2021 ◽  
Author(s):  
Ulrich Callies ◽  
Christopher G. Albert ◽  
Udo von Toussaint
Keyword(s):  
Loss Rate ◽  
Likelihood Function ◽  
Monte Carlo Sampling ◽  
Model Parameters ◽  
Quality Model ◽  
Temperature Dependent ◽  
Management Options ◽  
Elbe River ◽  
The Elbe River ◽  
Joint Posterior Distribution

Abstract We address the analysis and proper representation of posterior dependence among parameters obtained from model calibration. A simple water quality model for the Elbe River (Germany) is referred to as an example. The joint posterior distribution of six model parameters is estimated by Markov Chain Monte Carlo sampling based on a quadratic likelihood function. The estimated distribution shows to which extent model parameters are controlled by observations, highlighting issues that cannot be settled unless more information becomes available. In our example, some vagueness occurs due to problems in distinguishing between the effects of either growth limitation by lack of silica or a temperature dependent algal loss rate. Knowing such indefiniteness of the model structure is crucial when the model is to be used in support of management options. Bayesian network technology can be employed to convey this information in a transparent way.

scholarly journals Surrogate-Enhanced Parameter Inference for Function-Valued Models

2021 ◽  
Vol 3 (1) ◽  
pp. 11
Author(s):  
Christopher G. Albert ◽  
Ulrich Callies ◽  
Udo von Toussaint
Keyword(s):  
Time Series ◽  
Continuous Time ◽  
Time Series Data ◽  
Gaussian Process Regression ◽  
Optimization Methods ◽  
Series Data ◽  
Model Parameters ◽  
Elbe River ◽  
Linear Dimensionality Reduction ◽  
The Elbe River

We present an approach to enhance the performance and flexibility of the Bayesian inference of model parameters based on observations of the measured data. Going beyond the usual surrogate-enhanced Monte-Carlo or optimization methods that focus on a scalar loss, we place emphasis on a function-valued output of a formally infinite dimension. For this purpose, the surrogate models are built on a combination of linear dimensionality reduction in an adaptive basis of principal components and Gaussian process regression for the map between reduced feature spaces. Since the decoded surrogate provides the full model output rather than only the loss, it is re-usable for multiple calibration measurements as well as different loss metrics and, consequently, allows for flexible marginalization over such quantities and applications to Bayesian hierarchical models. We evaluate the method’s performance based on a case study of a toy model and a simple riverine diatom model for the Elbe river. As input data, this model uses six tunable scalar parameters as well as silica concentrations in the upper reach of the river together with the continuous time-series of temperature, radiation, and river discharge over a specific year. The output consists of continuous time-series data that are calibrated against corresponding measurements from the Geesthacht Weir station at the Elbe river. For this study, only two scalar inputs were considered together with a function-valued output and compared to an existing model calibration using direct simulation runs without a surrogate.

scholarly journals A General Temperature-Dependent Stress–Strain Constitutive Model for Polymer-Bonded Composite Materials

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1393
Author(s):  
Xiaochang Duan ◽  
Hongwei Yuan ◽  
Wei Tang ◽  
Jingjing He ◽  
Xuefei Guan
Keyword(s):  
Composite Materials ◽  
Constitutive Model ◽  
Model Parameters ◽  
Temperature Dependent ◽  
Stress Strain ◽  
Proposed Model ◽  
Single Temperature ◽  
Testing Data ◽  
Bonded Composite ◽  
Tension And Compression

This study develops a general temperature-dependent stress–strain constitutive model for polymer-bonded composite materials, allowing for the prediction of deformation behaviors under tension and compression in the testing temperature range. Laboratory testing of the material specimens in uniaxial tension and compression at multiple temperatures ranging from −40 ∘C to 75 ∘C is performed. The testing data reveal that the stress–strain response can be divided into two general regimes, namely, a short elastic part followed by the plastic part; therefore, the Ramberg–Osgood relationship is proposed to build the stress–strain constitutive model at a single temperature. By correlating the model parameters with the corresponding temperature using a response surface, a general temperature-dependent stress–strain constitutive model is established. The effectiveness and accuracy of the proposed model are validated using several independent sets of testing data and third-party data. The performance of the proposed model is compared with an existing reference model. The validation and comparison results show that the proposed model has a lower number of parameters and yields smaller relative errors. The proposed constitutive model is further implemented as a user material routine in a finite element package. A simple structural example using the developed user material is presented and its accuracy is verified.

The occurrence of xenoestrogens in the Elbe river and the North Sea

Chemosphere ◽  
2001 ◽  
Vol 45 (3) ◽  
pp. 245-259 ◽  
Author(s):  
O.P Heemken ◽  
H Reincke ◽  
B Stachel ◽  
N Theobald
Keyword(s):  
North Sea ◽  
Elbe River ◽  
The North ◽  
The North Sea ◽  
The Elbe River

scholarly journals Regional Airports Influence Economic Development of the Region

2018 ◽  
Vol 236 ◽  
pp. 02004
Author(s):  
Václav Cempírek ◽  
Iveta Dočkalíková
Keyword(s):  
Economic Development ◽  
Water Transport ◽  
Freight Transport ◽  
Elbe River ◽  
Inland Water ◽  
The Elbe River ◽  
Regional Airports ◽  
Inland Water Transport ◽  
Technical Terms

The paper deals with the importance of regional airport for economic development of the particular region with the possibility to cover also freight transport. In technical terms it is called the logistics centre or Freight Village. The special emphasis is given to the Pardubice airport and to creation of logistics centre on the Elbe river. The logistics centre would link four types of transport – railway, road, air and inland water transport. Terminal of the combined transport, which lacks in long term in the region, is also a part of the logistics centre.

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