Abstract
SrBi2Ta2O9 (SBT) is a bismuth-layered perovskite that finds application as thin film for nonvolatile random-access memories and as high temperature ceramic transducer. The synthesis of SBT by the solid-state reaction requires high temperatures (Tsimilar to1000degreesC), at which bismuth losses are significant, leading to non-stoichiometric compositions with decreased properties. To overcome this drawback, lower temperature reactions of organic precursors have been reported for the production of this oxide. This work describes a novel method to obtain SBT powders that uses Ta2O5 as starting reagent. The thermal behaviour of the SBT precursor gel obtained by this new method is compared to other SBT precursors: those produced by a sol-gel method starting from alkoxides reagents and those related to conventional solid-state reaction. The new method combines the advantage of using reagents that are less toxic and less expensive than alkoxides with the possibility of producing SBT at lower temperatures than those required by the conventional route.

Abstract
Polar orbital satellites with low spatial resolution sensors, such as the AVHRR, provide global coverage with a short repetition period. The data is directly transmitted to ground stations, and can be distributed immediately after data acquisition. Near real time applications can be implemented if the adequate processing tools are available. One task usually needed is the geometric correction of image data. Automatic methods, based on satellite orbital parameters, can in some cases provide satisfactory results. However, the identification of Ground Control Points (GCPs) is generally required in order to achieve registration errors below the pixel size. A fully automatic method for the geometric registration of AVHRR data is proposed here. The method comprises four stages: (i) an initial image transformation based on orbital parameters, (ii) image segmentation of this image into 3 main classes (land, water, cloud) and 9 additional classes of mixed water and land at various levels, (iii) automatic GCP collection by image matching, (iv) final image production combining both orbital and GCP information. The method was tested on ten images of the Iberian Peninsula, and proved effective in accurately geo-referencing sub-sections of an AVHRR scene of medium dimension in a few minutes.

Abstract
This paper describes a method designed for data mining applications where the main goal is to predict extreme and rare values of a continuous target variable, as well as to understand under which conditions these values occur. Our objective is to induce models that are accurate at predicting these outliers but are also interpretable from the user perspective. We describe a new splitting criterion for regression trees that enables the induction of trees achieving these goals. We evaluate our proposal on several real world problems and contrast the obtained models with standard regression trees. The results of this evaluation show the clear advantage of our proposal in terms of the evaluation statistics that are relevant for these applications.

Abstract
In several applications the main interest resides in predicting rare and extreme values. This is the case of the prediction of harmful algae blooms. Though it's rare, the occurrence of these blooms has a strong impact in river life forms and water quality and turns out to be a serious ecological problem. In this paper, we describe a data mining method whose main goal is to predict accurately this kind of rare extreme values. We propose a new splitting criterion for regression trees that enables the induction of trees achieving these goals. We carry out an analysis of the results obtained with our method on this application domain and compare them to those obtained with standard regression trees. We conclude that this new method achieves better results in terms of the evaluation statistics that are relevant for this kind of applications.

Abstract
We compare the thermal tuning capabilities of two type I gratings written in unloaded and in hydrogen-loaded germanium-doped silica fibers, and a type IIa grating written in unloaded fiber. The hydrogen-loaded grating is annealed after writing, to remove any unreacted hydrogen. We further study the gratings' response stability with temperature, an important property when these devices are used as optical filters in wavelength division multiplexing systems. Experimental results show that the worst option is the type I grating in unloaded fiber, which presents the highest bandwidth and group delay variations with temperature, so that it is the least suitable as a thermotunable optical filter in wavelength-multiplexed systems. For the other two options, the bandwidth and group delay variations are much smaller, the lowest values being obtained with the hydrogen-loaded type I grating, and the best thermal tuning efficiency with the type IIa grating. (C) 2003 Society of Photo-Optical Instrumentation Engineers.

Abstract