Digital processing of weather radar signals for rainfall estimation

Abstract

Raw weather radar reflectivities are processed and registered to the ground before radar rainfall measurements are used conjunctively with rain-gauge data to produce areal surface rainfall estimates. However, there are several factors causing errors in the returned power of weather radar signals, as well as other sources of error affecting the accuracy of radar rainfall measurements. In this study, several deterministic corrective techniques are applied to the digital processing stage of raw radar data to consider a number of sources of error, namely non-rainfall echoes, signal attenuation and wind effect. The results indicate that the deterministic techniques are still a necessary step for the ultimate improvement of surface rainfall estimates by the use of weather radar.     

NEUROBAT,A PREDICTIVE AND ADAPTIVE HEATING CONTROL SYSTEM USING ARTIFICIAL NEURAL NETWORKS

The paper describes a predictive and adaptive heating controller, using artificial neural networks to allow the adaptation of the control model to the real conditions (climate, building characteriitics user'viour) The controller algorithm has been developed and tested as a collaborative project between the CSEM (Centre Suisse d'onique et de Microtechnique, Neuchatel, Switzerland, project leader), and the LESO-PB (Solar Energy and Building Physics Laboratory, EPFL, Lausanne, Switzerland). A significant support has been provided by leading Swiss industries in HVAC control systems. The project itself has been funded by the Swiss Federal Office of Energy (SFOE)

The project has allowed the development of an original algorithm, especially suited for water heating systems, and its testing both by simulation and by experimentation on an inhabited building. The experimentation has been done using a PC software implementation. A second phase of the project, currently going on, aims at building an industrial prototype system based on the NEUROBAT algorithm.     

Non‐rigid alignment in electron tomography in materials science

Electron tomography is a key technique that enables the visualization of an object in three dimensions with a resolution of about a nanometre. High‐quality 3D reconstruction is possible thanks to the latest compressed sensing algorithms and/or better alignment and preprocessing of the 2D projections. Rigid alignment of 2D projections is routine in electron tomography. However, it cannot correct misalignments induced by (i) deformations of the sample due to radiation damage or (ii) drifting of the sample during the acquisition of an image in scanning transmission electron microscope mode. In both cases, those misalignments can give rise to artefacts in the reconstruction. We propose a simple‐to‐implement non‐rigid alignment technique to correct those artefacts. This technique is particularly suited for needle‐shaped samples in materials science. It is initiated by a rigid alignment of the projections and it is then followed by several rigid alignments of different parts of the projections. Piecewise linear deformations are applied to each projection to force them to simultaneously satisfy the rigid alignments of the different parts. The efficiency of this technique is demonstrated on three samples, an intermetallic sample with deformation misalignments due to a high electron dose typical to spectroscopic electron tomography, a porous silicon sample with an extremely thin end particularly sensitive to electron beam and another porous silicon sample that was drifting during image acquisitions.     

Corrosion of Lead Glasses in Acid Media: II, Concentration Profile Measurements

Lead concentration profiles were measured in a binary lead silicate glass corroded by acid using ahd a-backscattering technique. These profiles were characteristic of those predicted for an interdiffusion process and revealed a surface layer deficient in lead. Diffusion coefficients for Pb²⁺ were calculated, together with values of the total amount of lead removed at the various experimental temperatures and times. Good agreement was found between these data and those previously obtained experimentally. All diffusion coefficient values were high and, correspondingly, activation energy values were low compared with those predicted by the literature for similar glass compositions. This difference was justified from consideration of the leaching process.     

Enzymatic Browning of Model Solutions and Apple Phenolic Extracts by Apple Polyphenoloxidase

Model solutions containing chlorogenic acid (CG) and (-)-epicatechin (EP), and phenolics from nine apple cv., were oxidized with apple polyphenoloxidase (PPO). Browning was determined by absorbance at 380–700 nm, and transformed into CIE L*, a* and b*. Multilinear correlations were established between initial and degraded amounts of each phenolic. In model solutions of CG and EP, color values and A₄₀₀ correlated strongly with initial and oxidized CG and EP. Both phenolics contributed to decrease in L* and increase in A₄₀₀. Increase ii CG increased a*, but EP had little effect. The imnact of increased EP on b* was two to three times higher than for CG_: In each phenol class (hydroxycinnamic (HD), flavan-3-ol (FA), flavonol (FO) and dihydrochalcone (DC) derivatives), degraded amounts were increased or decreased by increasing amounts of other classes. Besides major phenolics, HD (mainly CG) and FA (mainly EP and procyanidin B2), FO and DC, appeared to affect color development.     

Wettability and Work of Adhesion of Nonreactive Liquid Metals on Silica

Wettability of silica by gold, silicon, and lead has been determined by the sessile-drop method. The contact angle, θ, and the work of adhesion, W , have been found to be 143° and 227 mJ·m⁻² for gold at 1353 K, 87° and 869 mJ·m⁻² for silicon at 1723 K, and 120° and 203 mJ·m⁻² for lead at 1000 K. Thermodynamic adhesion between silica and nonreactive pure metals has been analyzed using models for metal-oxide bonds. Models based on the assumption that only van der Waals interactions and/or metal-oxygen chemical bonds exist at the metal-oxide interface are unsuited for explaining the relative variations in the W values. A valid model can be accomplished by using an empirical equation which takes into account both metal-oxygen and metal-oxide chemical bonds. It appears that chemical bonds exist at the interface even for nonreactive metal-ionocovalent oxide systems.