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Impact Experiment (impact + experiment)
Selected AbstractsA COST-EFFECTIVE EDUCATIONAL PENDULUM FOR IMPACT EXPERIMENTSEXPERIMENTAL TECHNIQUES, Issue 2 2002D. Carter No abstract is available for this article. [source] Aerosol Direct Radiative Impact Experiment (ADRIEX) overviewTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue S1 2007E. J. Highwood Abstract The Aerosol Direct Radiative Experiment (ADRIEX) took place over the Adriatic and Black Seas during August and September 2004 with the aim of characterizing anthropogenic aerosol in these regions in terms of its physical and optical properties and establishing its impact on radiative balance. Eight successful flights of the UK BAE-146 Facility for Atmospheric Airborne Measurements were completed together with surface-based lidar and AERONET measurements, in conjunction with satellite overpasses. This paper outlines the motivation for the campaign, the methodology and instruments used, describes the synoptic situation and provides an overview of the key results. ADRIEX successfully measured a range of aerosol conditions across the northern Adriatic, Po Valley and Black Sea. Generally two layers of aerosol were found in the vertical: in the flights over the Black Sea and the Po Valley these showed differences in chemical and microphysical properties, whilst over the Adriatic the layers were often more similar. Nitrate aerosol was found to be important in the Po Valley region. The use of new instruments to measure the aerosol chemistry and mixing state and to use this information in determining optical properties is demonstrated. These results are described in much more detail in the subsequent papers of this special issue. Copyright © 2007 Royal Meteorological Society [source] Analysis of Single Particle Attrition during Impact Experiments,PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 5 2003Ramanan Pitchumani Abstract Particle breakage can be characterised as attrition, chipping, fracture, abrasion and wear. All these types of breakage mechanisms are the effect of the damage caused to these particles. These mechanisms can be differentiated not just on the basis of magnitude and direction of the force but also by the damage caused to the particles. The damage is measured by change in the size distribution and the change in shape of the particles. In the current research, experiments were performed on the newly developed Repeated Impact Test. The unique feature of this test is that about hundred particles can be subjected simultaneously to a monitored number of impacts, without particle-particle interactions at regulated velocities. The preliminary experiments were performed with single crystalline particles of different shapes and sizes. After fixed number of impacts, the images of the particles were taken. The volume and shape of the particles were determined by image analysis. It was observed that the rate of attrition was very high when the particles are irregular. The rate decreased as the particles became more spherical. [source] Combined forecast impact of GRACE-A and CHAMP GPS radio occultation bending angle profilesATMOSPHERIC SCIENCE LETTERS, Issue 2 2007S. B. Healy Abstract Impact experiments assimilating GRACE-A and CHAMP GPS radio occultation (GPSRO) bending angle profiles are presented. The standard deviation of the observation minus background bending angle departures above 35-km is 30% smaller for GRACE-A than CHAMP, indicating that the GRACE-A measurements are more accurate. Assimilating the GPSRO measurements improves stratospheric temperatures in the Southern Hemisphere. The combined impact of GRACE-A and CHAMP is greater than assimilating either instrument individually. Copyright © 2007 Royal Meteorological Society [source] Forecast impact experiment with a constellation of GPS radio occultation receiversATMOSPHERIC SCIENCE LETTERS, Issue 3 2008S. B. Healy Abstract A forecast impact experiment with a constellation of global positioning system radio occultation (GPSRO) receivers is presented. The constellation includes the six COSMIC/FORMO- SAT-3 satellites, combined with the GRACE-A and CHAMP satellites. It is shown that rising and setting occultations measured with the COSMIC satellites have similar bending angle error characteristics. The GPSRO measurements improve the root mean square (rms) geopotential height forecast errors at 500, 200, and 100 hPa in both the Northern and Southern Hemispheres. The forecast fit to radiosonde temperature measurements in the Stratosphere is also improved. Copyright © 2008 Royal Meteorological Society [source] A computational model for impact failure with shear-induced dilatancyINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 14 2003Z. Chen Abstract It has been observed in plate impact experiments that some brittle solids may undergo elastic deformation at the shock wave front, and fail catastrophically at a later time when they are shocked near but below the apparent Hugoniot elastic limit. Because this phenomenon appears to have features different from those of usual inelastic waves, it has been interpreted as the failure wave. To design an effective numerical procedure for simulating impact failure responses, a three-dimensional computational damage model is developed in this paper. The propagation of the failure wave behind the elastic shock wave is described by a non-linear diffusion equation. Macroscopic shear-induced dilatancy is assumed and treated as a one-to-one measure of the mean intensity of microcracking. The damage evolution in time is determined based on the assumption that the deviatoric strain energy in the elastically compressed material (undamaged) is converted, through the damaging process, into the volumetric potential energy in the comminuted and dilated material. For the ease in large-scale simulations, the coupled damage diffusion equation and the stress wave equation are solved via a staggered manner in a single computational domain. Numerical solutions by using both the finite element method and the material point method, i.e. with and without a rigid mesh connectivity, are presented and compared with the experimental data available. It is shown that the model simulations capture the essential features of the failure wave phenomenon observed in shock glasses, and that the numerical solutions for localized failure are not mesh-dependent. Copyright © 2003 John Wiley & Sons, Ltd. [source] Assimilation of Meteosat radiance data within the 4D-Var system at ECMWF: Assimilation experiments and forecast impactTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 601 2004Christina Köpken Abstract The direct assimilation of water vapour (WV) clear-sky radiances (CSRs) from geostationary satellites within the ECMWF four-dimensional variational assimilation (4D-Var) became operational on 9 April 2002 with the assimilation of radiances from Meteosat-7. To extend the coverage provided by geostationary radiances, the derivation of a similar CSR product from the Geostationary Operational Environmental Satellites GOES-W and GOES-E was initiated and since 14 January 2003 these data have been operationally assimilated as well. This paper discusses results from the pre-operational impact experiments using Meteosat-7 and the subsequent operational implementation of the WV radiance assimilation. The pre-operational data monitoring of the CSRs shows contamination of certain time slots caused by intruding solar stray light and a certain degree of cloud influence present in the CSR. Data quality control is introduced to exclude affected data. When assimilated, the Meteosat WV CSRs correct the upper-tropospheric humidity field in areas of known model problems. While the analysis draws well to Meteosat data, the fit to other conventional observations does not degrade, and the fit to other satellite observations is noticeably improved. This is visible in statistics for the assimilated HIRS-12 as well as for passive Advanced Microwave Sounding Unit B (AMSUB) radiances, both in the pre-operational experiments and in the operational assimilation cycle. The impact on forecast quality is slightly positive to neutral for different areas of the globe. In some experiments a positive impact on upper-level wind fields (around 200 hPa) is seen, especially in the tropics. A relatively large sensitivity is noted of the mean increments and also forecast scores to the bias correction. Copyright © 2004 Royal Meteorological Society [source] | |||||||||||||