In this paper, we present a study on the spatial confinement effect of laser-induced plasma with a cylindrical cavity in laser-induced breakdown spectroscopy （LIBS）. The emission intensity with the spatial confineme...In this paper, we present a study on the spatial confinement effect of laser-induced plasma with a cylindrical cavity in laser-induced breakdown spectroscopy （LIBS）. The emission intensity with the spatial confinement is dependent on the height of the confinement cavity. It is found that, by selecting the appropriate height of cylindrical cavity, the signal enhancement can be significantly increased. At the cylindrical cavity （diameter = 2 mm） with a height of 6 mm, the enhancement ratio has the maximum value （approximately 8.3）, and the value of the relative standard deviation （RSD） （7.6%） is at a minimum, the repeatability of LIBS signal is best. The results indicate that the height of confinement cavity is very important for LIBS technique to reduce the limit of detection and improve the precision.展开更多
The temporal and spatial variations in the wind and wave fields in the Pacific Ocean between 2002 and 2011 are analyzed using a third-generation wave model（WAVEWATCH III）. The model performance for a significant wav...The temporal and spatial variations in the wind and wave fields in the Pacific Ocean between 2002 and 2011 are analyzed using a third-generation wave model（WAVEWATCH III）. The model performance for a significant wave height is validated using in situ buoy data. The results show that the wave model effectively hindcasts the significant wave height in the Pacific Ocean, but the errors are relatively large in the mid- and low-latitude regions. The spatial distributions and temporal variations in a wind speed and the significant wave height in the Pacific Ocean are then considered after dividing the Pacific Ocean into five regions, which show meridional differences and seasonal cycles. Regional mean values are used to give yearly average time series for each separate zone. The high latitude region in the Southern Hemisphere had a stronger significant wave height trend in the model results than regions at other latitudes. The sources and sinks of wave energy are then investigated. Their regional mean values are used to quantify variations in surface waves. Finally, the spectral analyses of the daily mean wind speeds and the significant wave heights are obtained. The significant wave height and the wind speed spectra are found to be connected in some ways but also show certain differences.展开更多
为了迅速获取森林资源调查的树高因子,以南宁树木园坛里管理区为研究对象,基于无人机影像数据,结合实地调查,采用PostFlight Terra 3D软件处理得到研究区的DOM、DEM和DSM,利用ArcGIS空间分析技术估测树高;比较分析实测样木树高与估测树...为了迅速获取森林资源调查的树高因子,以南宁树木园坛里管理区为研究对象,基于无人机影像数据,结合实地调查,采用PostFlight Terra 3D软件处理得到研究区的DOM、DEM和DSM,利用ArcGIS空间分析技术估测树高;比较分析实测样木树高与估测树高精度,建立实测样木树高与估测树高相关模型并估测林分平均高。结果表明:通过无人机影像提取的树高与实测树高比较,总体平均精度达90.9%;提取树高与实测树高存在较强相关性,模型树高的平均精度达93.2%;估测林分平均高准确率达97.2%。该树高参数自动化提取方法,能够达到相关实践要求,可以在一定程度上替代人工实测,在人工林中具有广阔的应用前景。展开更多
利用ERA40、NCEPI(NCEP/NCAR version I)再分析资料以及高原地区的探空资料和1979年青藏高原地区第1次气象科学试验资料,详细的比较了高原地区位势高度的特征。结果表明,两套再分析资料在高原地区具有一定的相似性,但仍存在着明显的差...利用ERA40、NCEPI(NCEP/NCAR version I)再分析资料以及高原地区的探空资料和1979年青藏高原地区第1次气象科学试验资料,详细的比较了高原地区位势高度的特征。结果表明,两套再分析资料在高原地区具有一定的相似性,但仍存在着明显的差别。相比较而言,高原北部地区ERA40再分析资料除1980—1990年在200hPa高层优于NCEPI再分析资料外,NCEPI再分析资料在年际变化上更接近探空资料;高原中部和南部地区NCEPI再分析资料除1980—1990年在200 hPa高层优于ERA40再分析资料外,ERA40再分析资料在年际变化上更接近探空资料。与1979年青藏高原地区第1次气象科学试验资料空间相关关系的比较显示,ERA40再分析资料在空间上与试验资料更相似。展开更多
基金the support from the Fundamental Research Project of Chinese State Key Laboratory of Laser Interaction with Matter(Grant No.SKLLIM 1502)the National Natural Science Foundation of China(Grant Nos.11674128,11474129 and 11504129)the China Postdoctoral Science Foundation(Grant No.2014M551169)
文摘In this paper, we present a study on the spatial confinement effect of laser-induced plasma with a cylindrical cavity in laser-induced breakdown spectroscopy （LIBS）. The emission intensity with the spatial confinement is dependent on the height of the confinement cavity. It is found that, by selecting the appropriate height of cylindrical cavity, the signal enhancement can be significantly increased. At the cylindrical cavity （diameter = 2 mm） with a height of 6 mm, the enhancement ratio has the maximum value （approximately 8.3）, and the value of the relative standard deviation （RSD） （7.6%） is at a minimum, the repeatability of LIBS signal is best. The results indicate that the height of confinement cavity is very important for LIBS technique to reduce the limit of detection and improve the precision.
基金The National High Technology Research and Development Program(863 Program)of China under contract No.2013AA122803the National Natural Science Foundation of China under contract Nos 41506033,41576013 and 41476021
文摘The temporal and spatial variations in the wind and wave fields in the Pacific Ocean between 2002 and 2011 are analyzed using a third-generation wave model（WAVEWATCH III）. The model performance for a significant wave height is validated using in situ buoy data. The results show that the wave model effectively hindcasts the significant wave height in the Pacific Ocean, but the errors are relatively large in the mid- and low-latitude regions. The spatial distributions and temporal variations in a wind speed and the significant wave height in the Pacific Ocean are then considered after dividing the Pacific Ocean into five regions, which show meridional differences and seasonal cycles. Regional mean values are used to give yearly average time series for each separate zone. The high latitude region in the Southern Hemisphere had a stronger significant wave height trend in the model results than regions at other latitudes. The sources and sinks of wave energy are then investigated. Their regional mean values are used to quantify variations in surface waves. Finally, the spectral analyses of the daily mean wind speeds and the significant wave heights are obtained. The significant wave height and the wind speed spectra are found to be connected in some ways but also show certain differences.
文摘为了迅速获取森林资源调查的树高因子,以南宁树木园坛里管理区为研究对象,基于无人机影像数据,结合实地调查,采用PostFlight Terra 3D软件处理得到研究区的DOM、DEM和DSM,利用ArcGIS空间分析技术估测树高;比较分析实测样木树高与估测树高精度,建立实测样木树高与估测树高相关模型并估测林分平均高。结果表明:通过无人机影像提取的树高与实测树高比较,总体平均精度达90.9%;提取树高与实测树高存在较强相关性,模型树高的平均精度达93.2%;估测林分平均高准确率达97.2%。该树高参数自动化提取方法,能够达到相关实践要求,可以在一定程度上替代人工实测,在人工林中具有广阔的应用前景。
文摘利用ERA40、NCEPI(NCEP/NCAR version I)再分析资料以及高原地区的探空资料和1979年青藏高原地区第1次气象科学试验资料,详细的比较了高原地区位势高度的特征。结果表明,两套再分析资料在高原地区具有一定的相似性,但仍存在着明显的差别。相比较而言,高原北部地区ERA40再分析资料除1980—1990年在200hPa高层优于NCEPI再分析资料外,NCEPI再分析资料在年际变化上更接近探空资料;高原中部和南部地区NCEPI再分析资料除1980—1990年在200 hPa高层优于ERA40再分析资料外,ERA40再分析资料在年际变化上更接近探空资料。与1979年青藏高原地区第1次气象科学试验资料空间相关关系的比较显示,ERA40再分析资料在空间上与试验资料更相似。
