Ensemble of models

In terms of the generalized parameter matrices, the Jacobian is given as product of a simple matrix multiplication. Using explicit kinetic parameters, the estimation of the Jacobian can be tedious and computationally demanding, prohibiting the analysis of large ensembles of models. 

Figure 43. Measuring the importance of parameters. A The distribution of the saturation parameter 0pga (saturation of TPT with respect to PGA) for the full ensemble of models, chosen randomly from the unit interval. B The distribution of the saturation parameter 0pga after restricting the ensemble to stable states only. Within the ensemble of stable models, instances with 0pga close to the linear regime are overrepresented.

Figure 45. The distribution of the real parts of the eigenvalues sampled from the parametric model of the human erythrocyte. (A) The ensemble of models with Creg and without regulation Cnoreg- ( ) Comparing the distributions associated with two metabolic states normal conditions (Cyivo) and increased energy drain (Catp). The data are adapted from Ref. 296.

A great amount of real particles (for instance, liquid droplets) is modeled by an ensemble of model particles (their number is of the order of thousands). Each model particle is characterized by a vector of values, representing its location, velocity, mass, and other properties. The following vector, determined for each model particle, is introduced ... 

The Atmospheric Chemistry Transport modelling system used is based on the off-line coupled CAMx and HIRLAM models has been developed to simulate particulate and gas-phase air pollution on different scales. It has been used to simulate short and longterm releases of different chemical species and air pollution episodes. At present it is run in a pre-operational mode 4 times per day based on 3D meteorological fields produced by the HIRLAM NWP model. Currently this modelling system is setup to perform chemical weather forecasts for a series of chemical species (such as O3, NO, NO2, CO and SO2) and forecasted 2D fields at surface are available for each model as well as an ensemble of models (based on 12 European regional air quality models). The simulated output is publicly available and it is placed at the ECMWF website (http //gems.ecmwf.int/d/products/raq/forecasts/) of the EC FP6 GEMS project. 

Lately, consensus modeling has come into play as a useful tool for obtaining robust models with good predictive ability. By using this approach the weakness of one particular model is compensated by the other models thus obtaining a much more robust behavior for the ensemble of models. 

The meta-modelling approach can automate the surveying of model space and partition local models. An ensemble of models can be more stable and reliably predictive. Since a key element of the QSAR practitioner s expertise is the selection of the appropriate method, meto-modelling can lead to more reliable automation of model discovery, as is often required in the context of large and continuously operated screening campaigns. 

In stacking, an ensemble of models is built, using different methods, and a model of the models is created, which weights the predictions from the different models. 

Support Vector regression, Gaussian process, random forest N= 110 literature compounds and N = 550 in house compounds. 3 fold cross validation RMSE 0.6 in cross validation. ChemAxon, MOE, VolSurf descriptors. Ensemble of models. 44... 

Baraldi R, Cammi A., Mangili R, Zio E., 2010, Local fusion of an ensemble of models for the reconstruction of faulty signals", IEEE Transactions on Nuclear Science, Vol. 57, No. 2 part 2, pp. 793-806. 

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