通过应用ArcGIS软件,对《中国植被图集(1:1000000)》中的黄背草植被数据,进行数字化处理,空间配准和矢量化等操作,并以此为基础计算得到黄背草植被各群系的斑块数量特征以及斑块形状指数,分析与评价黄背草植被群系的地理分布格局与斑块...通过应用ArcGIS软件,对《中国植被图集(1:1000000)》中的黄背草植被数据,进行数字化处理,空间配准和矢量化等操作,并以此为基础计算得到黄背草植被各群系的斑块数量特征以及斑块形状指数,分析与评价黄背草植被群系的地理分布格局与斑块特征。结果表明:黄背草植被在全国多数省份均有分布,主要集中分布于陕西和安徽等地。黄背草植被总面积为14219.39 km2,总共有488个斑块,整体上黄背草植被的斑块面积、个数分布较均衡,各斑块形状均相对不规则,小斑块占比较高,大斑块占比较少,且斑块面积差别较大,斑块破碎化程度较高。基于黄背草植被斑块的情况、黄背草植被的地理分布及其斑块特征、斑块形状的分析,为黄背草植被的退牧还草及可持续发展、防止草场退化和恢复退化草场提供理论参考。By applying ArcGIS software, we digitized, spatially aligned and vectorized the Themeda japonica vegetation data in the “China Vegetation Atlas (1:1000000)”, and calculated the number of patches and the patch shape index of each group of Themeda japonica vegetation on the basis of the data, so as to analyse and evaluate the geographic distribution pattern and the characteristics of the patches of Themeda japonica vegetation groups. The results showed that the Themeda japonica vegetation was distributed in most provinces in China, mainly in Shaanxi and Anhui. The total area of Themeda japonica vegetation is 14219.39 km2, and there are 488 patches in total. On the whole, the patch area and number of Themeda japonica vegetation are more balanced, and the shape of each patch is relatively irregular, with a higher proportion of small patches and a smaller proportion of large patches, and the patch area varies greatly, with a higher degree of patch fragmentation. Based on the situation of Themeda japonica vegetation patches, the geographical distribution of Themeda japonica vegetation and its patch characteristics and the analysis of patch shapes, it provides theoretical references for the retreat of Themeda japonica vegetation to grassland and its sustainable development, the prevention of pasture degradation and the restoration of degraded pastures.展开更多
Lead zirconate titanate piezoelectric ceramics have important applications in space and aerospace technology,but the effect and physical mechanism of charged particle radiation on their performance yet to be clarified...Lead zirconate titanate piezoelectric ceramics have important applications in space and aerospace technology,but the effect and physical mechanism of charged particle radiation on their performance yet to be clarified.In this study,we characterized PbZr_(0.52)Ti_(0.48)O_(3)(PZT)thin films,and changes in the ferroelectric properties of the films before and after electron and proton irradiation were investigated.The natural and heat treatment recoverability of the ferroelectric properties were studied,and the damages and mechanisms of different types of radiation in PZT films were also investigated.The results show that,in addition to ionization damages,electron irradiation causes certain structural damage on the PZT film,and the large structural damage caused by proton irradiation reduces drastically the ferroelectricity of the PZT film.展开更多
文摘通过应用ArcGIS软件,对《中国植被图集(1:1000000)》中的黄背草植被数据,进行数字化处理,空间配准和矢量化等操作,并以此为基础计算得到黄背草植被各群系的斑块数量特征以及斑块形状指数,分析与评价黄背草植被群系的地理分布格局与斑块特征。结果表明:黄背草植被在全国多数省份均有分布,主要集中分布于陕西和安徽等地。黄背草植被总面积为14219.39 km2,总共有488个斑块,整体上黄背草植被的斑块面积、个数分布较均衡,各斑块形状均相对不规则,小斑块占比较高,大斑块占比较少,且斑块面积差别较大,斑块破碎化程度较高。基于黄背草植被斑块的情况、黄背草植被的地理分布及其斑块特征、斑块形状的分析,为黄背草植被的退牧还草及可持续发展、防止草场退化和恢复退化草场提供理论参考。By applying ArcGIS software, we digitized, spatially aligned and vectorized the Themeda japonica vegetation data in the “China Vegetation Atlas (1:1000000)”, and calculated the number of patches and the patch shape index of each group of Themeda japonica vegetation on the basis of the data, so as to analyse and evaluate the geographic distribution pattern and the characteristics of the patches of Themeda japonica vegetation groups. The results showed that the Themeda japonica vegetation was distributed in most provinces in China, mainly in Shaanxi and Anhui. The total area of Themeda japonica vegetation is 14219.39 km2, and there are 488 patches in total. On the whole, the patch area and number of Themeda japonica vegetation are more balanced, and the shape of each patch is relatively irregular, with a higher proportion of small patches and a smaller proportion of large patches, and the patch area varies greatly, with a higher degree of patch fragmentation. Based on the situation of Themeda japonica vegetation patches, the geographical distribution of Themeda japonica vegetation and its patch characteristics and the analysis of patch shapes, it provides theoretical references for the retreat of Themeda japonica vegetation to grassland and its sustainable development, the prevention of pasture degradation and the restoration of degraded pastures.
基金supported by the National Natural Science Foundation of China(Grant No.51802056)the Science Foundation of the National Key Laboratory of Science and Technology on Advanced Composites in Special Environmentsthe Key Laboratory of Micro-systems and Micro-structures Manufacturing(Harbin Institute of Technology),Ministry of Education,China。
文摘Lead zirconate titanate piezoelectric ceramics have important applications in space and aerospace technology,but the effect and physical mechanism of charged particle radiation on their performance yet to be clarified.In this study,we characterized PbZr_(0.52)Ti_(0.48)O_(3)(PZT)thin films,and changes in the ferroelectric properties of the films before and after electron and proton irradiation were investigated.The natural and heat treatment recoverability of the ferroelectric properties were studied,and the damages and mechanisms of different types of radiation in PZT films were also investigated.The results show that,in addition to ionization damages,electron irradiation causes certain structural damage on the PZT film,and the large structural damage caused by proton irradiation reduces drastically the ferroelectricity of the PZT film.
文摘目的探讨高原隧道钢筋工弯腰作业过程中下背部肌肉的表面肌电信号(surface electromyography,sEMG)特征及其与时间负荷和弯腰次数的相关性。方法选择高原某隧道4名男性钢筋作业人员,采用表面肌电仪实时采集其正常作业时左右竖脊肌群的sEMG,对其弯腰动作的时域指标均方根值(root mean square,RMS)和频域指标中位频率(mean frequency,MF)随负荷变化特征及其与时间和弯腰次数的相关性进行分析。结果4名钢筋工左、右竖脊肌的RMS均随时间和弯腰次数增加而上升;左竖脊肌RMS与时间相关系数分别为0.663、0.717、0.771和0.478,除4号钢筋工外均具显著统计学意义(P<0.01);右竖脊肌RMS与时间相关系数分别为0.908、0.488、0.782和0.929,除2号钢筋工外均具显著统计学意义(P<0.01);左竖脊肌RMS与弯腰次数相关系数分别为0.754、0.743、0.788和0.529,除4号钢筋工外均具显著统计学意义(P<0.01);右竖脊肌RMS与弯腰次数相关系数分别为0.796、0.456、0.778和0.877,除2号钢筋工外均具显著统计学意义(P<0.01)。4名钢筋工左、右竖脊肌MF均随时间和弯腰次数增加而下降,左竖脊肌MF与时间相关系数分别为-0.522、-0.904、-0.806和-0.493,除4号钢筋工外均具显著统计学意义(P<0.01);右竖脊肌MF与时间相关系数分别为-0.577、-0.873、-0.524和-0.836,均具显著统计学意义(P<0.01);左竖脊肌MF与弯腰次数相关系数分别为-0.486、-0.819、-0.813和-0.414,除4号钢筋工外均具显著统计学意义(P<0.01);右竖脊肌MF与弯腰次数相关系数分别为-0.516、-0.856、-0.515和-0.801,且均具显著统计学意义(P<0.01)。结论隧道钢筋工在弯腰作业时,左、右竖脊肌时域指标RMS和频域指标MF的变化与时间负荷以及弯腰次数有关,sEMG可以作为评价现场作业人员局部肌肉疲劳的一种客观方法。
