230,073 research outputs found
A new approach to the assessment of stochastic errors of radio source position catalogues
Assessing the external stochastic errors of radio source position catalogues
derived from VLBI observations is important for tasks such as estimating the
quality of the catalogues and their weighting during combination. One of the
widely used methods to estimate these errors is the three-cornered-hat
technique, which can be extended to the N-cornered-hat technique. A critical
point of this method is how to properly account for the correlations between
the compared catalogues. We present a new approach to solving this problem that
is suitable for simultaneous investigations of several catalogues. To compute
the correlation between two catalogues and , the differences between
these catalogues and a third arbitrary catalogue are computed. Then the
correlation between these differences is considered as an estimate of the
correlation between catalogues and . The average value of these
estimates over all catalogues is taken as a final estimate of the target
correlation. In this way, an exhaustive search of all possible combinations
allows one to compute the paired correlations between all catalogues. As an
additional refinement of the method, we introduce the concept of weighted
correlation coefficient. This technique was applied to nine recently published
radio source position catalogues. We found large systematic differences between
catalogues, that significantly impact determination of their stochastic errors.
Finally, we estimated the stochastic errors of the nine catalogues
Towards a new evolutionary subsampling technique for heuristic optimisation of load disaggregators
In this paper we present some preliminary work towards the development of a new evolutionary subsampling technique for solving the non-intrusive load monitoring (NILM) problem. The NILM problem concerns using predictive algorithms to analyse whole-house energy usage measurements, so that individual appliance energy usages can be disaggregated. The motivation is to educate home owners about their energy usage. However, by their very nature, the datasets used in this research are massively imbalanced in their target value distributions. Consequently standard machine learning techniques, which often rely on optimising for root mean squared error (RMSE), typically fail. We therefore propose the target-weighted RMSE (TW-RMSE) metric as an alternative fitness function for optimising load disaggregators, and show in a simple initial study in which random search is utilised that TW-RMSE is a metric that can be optimised, and therefore has the potential to be included in a larger evolutionary subsampling-based solution to this problem
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