Considerations about antenna pattern measurements of 2-D aperture synthesis radiometers

Accurate measurement of the antenna voltage patterns of large-aperture synthesis radiometers is critical in order to achieve good radiometric accuracy, and a very time consuming and expensive task. Measurement requirements and a tradeoff study relating radiometric accuracy degradation and number of elements to be measured are presented.     

A Frequency Matching Method: Solving Inverse Problems by Use of Geologically Realistic Prior Information

The frequency matching method defines a closed form expression for a complex prior that quantifies the higher order statistics of a proposed solution model to an inverse problem. While existing solution methods to inverse problems are capable of sampling the solution space while taking into account arbitrarily complex a priori information defined by sample algorithms, it is not possible to directly compute the maximum a posteriori model, as the prior probability of a solution model cannot be expressed. We demonstrate how the frequency matching method enables us to compute the maximum a posteriori solution model to an inverse problem by using a priori information based on multiple point statistics learned from training images. We demonstrate the applicability of the suggested method on a synthetic tomographic crosshole inverse problem.     

Vikings and virtues: a decade of CO2 taxation

Abstract

Experience with implementation of CO² taxes spans almost a decade in the Nordic countries, and time is ripe for an evaluation of their performance. In contrast to ex-ante forecasts, empirical research can show the extent to which such taxes deliver on the assumptions of economic theory. A survey of the existing literature shows that there are currently 20 ex-post studies of the full or partial effects of CO² taxes. Evaluations are complicated by frequent changes in tax rates, widespread exemptions and the ‘too many variables’ problem. Attempts have been made to deal with these problems by using a variety of approaches and research techniques, some more advanced than others. On balance the studies appear to show that emissions have been curbed when compared to businessas-usual forecasts, while absolute CO² reduction remains the exception. Among the Nordic countries, Denmark's scheme, which combines taxes with subsidies for energy efficiency, seems to have attained the most marked results, although the achieved reductions also reflect the higher carbon content of the Danish energy sector. The evaluations differ considerably in scope, approach and methodology. Methodological issues connected with expost evaluation are considered. An adequate evaluation of the impact of the CO² taxes, in both environmental and economic terms, will require the establishment of comprehensive panel databases of energy consumers.     

Microwave signatures of the sea ice in the east Greenland current

Airborne microwave radiometer measurements at 5, 17, and 34 GHz have been carried out over the East Greenland Current. Sea ice signatures have been established for some of the basic ice types like first-year ice and multiyear ice. Other signatures have been experienced like that of presumably very old arctic ice and signatures associated more with the snow cover on the ice than with the ice itself. During MIZEX-83 measurements of total ice concentration were carried out.     

Smart Interpretation – automatic geological interpretations based on supervised statistical models

A method that infers a statistical model, which describes a relation between the knowledge of a geologist (quantified by geological interpretations) and the available information (such as geophysical data, well log data, etc.) that a geologist uses when he/she interprets is proposed and tested. The statistical model is then used to perform automatic geological interpretations wherever the same kinds of information, as used for the initial interpretations, are available. This methodology is named Smart Interpretation (SI). In this study, we look at two different approaches to infer such a model, and we demonstrate the applicability of the model to predict the depth to a low resistivity subsurface layer, based on interpretations from a geological expert, using a 19-layered resistivity model obtained from inversion of airborne electromagnetic (AEM) data. This study shows that SI is capable of making predictions with great accuracy. The method is fast and is able to handle large amounts of data of different origin, which suggest that the method may become a very useful approach to assist in geological modeling based on increasingly large amounts of data of different nature.