科研成果 by Year: 2009

An experimental investigation on the interaction of an ultraintense femtosecond laser pulse at the intensity of 2×1017 W/cm2 (60 fs, 120 mJ at 800 nm) with clusters in a supersonic jet of deuterated methane gas has shown the generation of energetic deuterons and nuclear fusion events. The deuteron density and the average size of the clusters in the gas jet, as well as the fusion neutron yields under different backing pressures were measured simultaneously as a function of the time delays of the laser pulses with respect to the puffing of the gas jet. The results demonstrate that during the development of the gas jet expanding through a conical nozzle, the clusters grew up with time, and the average size of the clusters reached the maximum when the molecular density in the jet started to drop. The fusion neutron yields were found to increase with the larger average cluster size and the higher deuteron density, in accordance with the theoretical prediction. Experimental data indicate the existence of a ~1 ms steady region in which the fusion neutron yields have reached the maximum of 2.0×105 per shot at the backing pressure of 74 bars. Consequently, an efficiency of 1.6×106 neutrons per joule of incident laser energy was realized. ©2009 American Institute of Physics

Emission inventories of sixty-seven speciated non-methane volatile organic compounds (NMVOC) from on-road vehicles in China were estimated for the period of 1980–2005, using seven NMVOC emission profiles, which were summarized based on local and international measurements from published literatures dealing with specific vehicle categories running under particular modes. Results show an exponential growth trend of China's historical emissions of alkanes, alkenes, alkines, aromatics and carbonyls during the period of 1980–2005, increasing from 63.9, 39.3, 6.9, 36.8 and 24.1 thousand tons, respectively, in 1980 to 2778.2, 1244.5, 178.7, 1351.7 and 406.0 thousand tons, respectively, in 2005, which coincided well with China's economic growth. Emission inventories of alkenes, aromatics and carbonyls were gridded at a high resolution of 40 km×40 km for air quality simulation and health risk evaluation, using the geographic information system (GIS) methodology. Spatial distribution of speciated NMVOC emissions shows a clear difference in emission densities between developed eastern and relatively underdeveloped western and inland China. Besides, the appearance and expansion of high-emission areas was another notable characteristic of spatial distribution of speciated NMVOC emissions during the period. Emission contributions of vehicle categories to speciated NMVOC groups showed annual variation, due to the variance in the provincial emissions and in the relative fractions of the seven emission profiles adopted at the provincial level. Highly reactive and toxic compounds accounted for high proportions of emissions of speciated NMVOC groups. The most abundant compounds were isopentane, pentane and butane from alkanes; ethene, propene, 2-methyl-2-butene and ethyne from alkenes and alkines; benzene, toluene, ethylbenzene, o-xylene, and m,p-xylene (BTEX) and 1,2,4-trimethylbenzene from aromatics and formaldehyde, acetaldehyde, benzaldehyde and acetone from 

In Canada approximately 45% of ammonia (NH(3)) emissions are attributed to dairy and beef cattle industries. The present study focused on NH(3) emissions from a beef feedlot with a one-time capacity of 17,220 head. The aim was to improve the Canadian NH(3) emission inventories and air quality forecasting capabilities. A Cessna 207. equipped with a fast-response NH(3)/NO(y) detector and a quadrupole aerosol mass spectrometer, was flown in a grid pattern covering an area of 8 x 8 km centered on a feedlot (800 x 800 m) at altitudes ranging from 30 to 300 m above ground. Stationary ground measurements of NH(3) concentration and turbulence parameters were made downwind of the feedlot. Three flights were conducted under varying meteorological conditions, ranging from very calm to windy with near-neutral stratification. NH(3) mixing ratios up to 100 ppbv were recorded on the calm day, up to 300 m above ground. An average feedlot NH(3) emission rate of 76 +/- 4 mu g m(-2) s(-1) (equivalent to 10.2 g head(-1) h(-1)) was estimated. Characteristics of the measured NH(3) plume were compared to those predicted by a Lagrangian dispersion model. The spatially integrated pattern of NH(3) concentrations predicted and measured agreed but the measured was often more complex than the predicted spatial distribution. The study suggests that the export of NH(3) through advection accounted for about 90% of the emissions from the feedlot, chemical transformation was insignificant, and dry deposition accounted for the remaining 10%. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.