Abstract
An attempt has been made to assess the efficiency of image data compression by wavelet transform encoding using National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) images. Raw and derived images were compressed to various levels and a number of parameters in the decompressed images compared with those obtained using raw data as a yardstick against which to measure the loss of information due to compression. Unsupervised classification, Normalized Difference Vegetation Index (NDVI) values and brightness temperatures appeared to suffer little degradation and only for fractal dimensions was there significant loss of integrity at compression rates of up to a factor of 32. The general conclusion from a visual inspection of the effect of such compressions on artificially generated geometrical imagettes confirms the effectiveness of this method of compression.

Abstract

Abstract
The potential of different fiber Bragg grating pairs for simultaneous sensing of strain and temperature is analyzed. We demonstrate that interferometric interrogation of a fiber grating written in bow-tie fiber enables strain and temperature to be simultaneously determined. This is achieved by independent measurement of the shift in the wavelengths of the reflected light from the grating components along the fast and the slow axes of the hi-bi fiber. A detailed theoretical analysis is presented that includes the basic sensing principle, sensor design and demodulation scheme. The performance of the proposed technique in simultaneous measurement of temperature and strain is experimentally demonstrated and resolutions of +/-2.5 degrees C/root Hz and +/-26 mu epsilon/root Hz are obtained for a fiber with birefringence of B = 5.5 x 10(-4). (C) 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)00808-4].

Abstract
Communications in high-speed wireless mobile networks have to deal with large varying transmission and service requirement conditions, often needing complex radio modulatians and concatenated error control functions. For the latter, it is usual to implement Forward Error Correction and Automatic Repeat reQuest (ARQ) mechanisms in, respectively, the Physical (PHY) and the Data Link Control (DLC) layers. Even so, the communication requirements of medium/high quality real-time services may be hard to meet under hostile transmission conditions. In this paper an analysis on some improvements over current ARQ error control schemes is presented, envisaging more efficient communications in high-speed wireless LANs. It will be shown that high performance ARQ schemes can be used at the DLC layer of wireless LANs by carrying critical control information in more robust physical modes. performance comparisons for current and proposed ARQ schemes, and some protocol implementation aspects, are the main focuses of analysis.

Abstract

Abstract
This paper describes a new method for dealing with multiple regression problems. This method integrates a clustering technique with regression trees, leading to what we have named as clustered regression trees. We use the clustering method to form sub-samples of the given data that are similar in terms of the predictor variables. By proceeding this way we aim at facilitating the subsequent regression modeling process based on the assumption of a certain smoothness of the regression surface. For each of the found clusters we obtain a different regression tree. These clustered regression trees can be used to predict the response value for a query case by an averaging process based on the cluster membership probabilities of the case. We have carried out a series of experimental comparisons of our proposal that have shown a significant predictive accuracy advantage over the use of a single regression tree.