The DS(directional solidification) polycrystalline silicon ingot is the most important photovoltaic material today,and the conversion efficiency of solar cells is affected by the morphology and organization of the cry...The DS(directional solidification) polycrystalline silicon ingot is the most important photovoltaic material today,and the conversion efficiency of solar cells is affected by the morphology and organization of the crystal.Uniform grains with larger size are conducive to get high-quality wafer,so improving the cell conversion efficiency.However,grains sizes that are less than 1 mm2 can be observed frequently in the central district of mc-Si ingots,which bring negative effect to the quality of the mc-Si ingot and decrease the electrical performance of wafer.In this paper,we make an attempt to explain the formation mechanism and influence factors of microcrystal in mc-Si ingot with computer simulation technology and theory of component supercooling.It was found that:to avoid production of microcrystal,it's better to increase the value of G/V(V is the growth rate and G is the near-interface temperature gradient),strengthen the melt convection front in the solidification interface and keep a fairly flat solid/melt interface in producing mc-Si ingot.展开更多
A comparative study and management has been conducted in (KTHDV). For some patients who attend the out patients clinic concern on treatment of the vitiligo with a new formula (Oxabet) alone VS Oxabet (oxpsolaren plus ...A comparative study and management has been conducted in (KTHDV). For some patients who attend the out patients clinic concern on treatment of the vitiligo with a new formula (Oxabet) alone VS Oxabet (oxpsolaren plus betamethasone) formula plus NB. UVB311 is during a period from (Jan 2011-Jan 2013). The study sample includes different age groups of both sexes. The study revealed that the formula alone gives good results. The localized vitiligo has a good response to the formula than generalized one. The early lesions have good responses than the old ones. The continuations of applying the treatment and the follow up of the patients enhance the efficacy of the treatment.展开更多
在气候变化和人类活动的综合影响下,青海省生态环境发生了明显变化。在此背景下,以GIMMS NDVI 3g.v1为数据源,采用Sen+Mann-Kendal方法研究青海省1982-2015年植被覆盖区域NDVI时空变化,将趋势分析和R/S(rescaled range analysis)分析叠...在气候变化和人类活动的综合影响下,青海省生态环境发生了明显变化。在此背景下,以GIMMS NDVI 3g.v1为数据源,采用Sen+Mann-Kendal方法研究青海省1982-2015年植被覆盖区域NDVI时空变化,将趋势分析和R/S(rescaled range analysis)分析叠加,研究植被生长季NDVI变化的持续性特征,并揭示植被对气候变化及人类活动的响应规律。结果表明:1)近34年青海省植被NDVI整体呈从西北到东南的增加趋势;且变异系数显示,波动性较大地区集中在柴达木盆地周边和青南牧区西北部等植被NDVI较低的区域,波动性较小地区集中在祁连山东部、东部农业区和青南牧区东南部等植被NDVI较高的区域。2)近34年青海省植被NDVI整体呈增加趋势,增长率为0.38%·10a^(-1);且NDVI变化具有明显的阶段性,存在1994年和2000年两个突变点。3)近34年青海省植被改善区域(75.4%)远大于退化区域(24.6%),其中显著改善面积占植被覆盖区域面积的40.9%,退化区随时间变化在空间上表现出明显的转移现象。4)Hurst指数表明,青海省植被变化反持续性较强,趋势分析与Hurst指数叠加得出,由退化转为改善的区域占植被覆盖区面积的13.7%,由改善转为退化的区域占植被覆盖区面积的44.3%,另41.5%的区域无法确定未来变化趋势。5)青海省植被生长季NDVI受气候变化和人类活动的双重影响,且不同植被类型对气候变化的响应存在较大差异。展开更多
Vegetation is the main component of the terrestrial ecosystem and plays a key role in global climate change. Remotely sensed vegetation indices are widely used to detect vegetation trends at large scales. To understan...Vegetation is the main component of the terrestrial ecosystem and plays a key role in global climate change. Remotely sensed vegetation indices are widely used to detect vegetation trends at large scales. To understand the trends of vegetation cover, this research examined the spatial-temporal trends of global vegetation by employing the normalized difference vegetation index(NDVI) from the Advanced Very High Resolution Radiometer(AVHRR) Global Inventory Modeling and Mapping Studies(GIMMS) time series(1982–2015). Ten samples were selected to test the temporal trend of NDVI, and the results show that in arid and semi-arid regions, NDVI showed a deceasing trend, while it showed a growing trend in other regions. Mann-Kendal(MK) trend test results indicate that 83.37% of NDVI pixels exhibited positive trends and that only 16.63% showed negative trends(P < 0.05) during the period from 1982 to 2015. The increasing NDVI trends primarily occurred in tree-covered regions because of forest growth and re-growth and also because of vegetation succession after a forest disturbance. The increasing trend of the NDVI in cropland regions was primarily because of the increasing cropland area and the improvement in planting techniques. This research describes the spatial vegetation trends at a global scale over the past 30+ years, especially for different land cover types.展开更多
蜂窝车联网(cellular vehicle to everything,C-V2X)是智能交通系统的关键技术之一,车辆通过与周围的信息实体实时交换信息以实现保障城市交通安全、提高城市交通效率等目的,实现V2X通信的基本需求。在NR-V2X定义的场景中,它还将支持自...蜂窝车联网(cellular vehicle to everything,C-V2X)是智能交通系统的关键技术之一,车辆通过与周围的信息实体实时交换信息以实现保障城市交通安全、提高城市交通效率等目的,实现V2X通信的基本需求。在NR-V2X定义的场景中,它还将支持自动驾驶、远程驾驶、车辆编队、扩展传感四大类先进V2X服务。通过OPNET搭建5G-V2X系统级仿真平台,针对基于PC5接口和Uu接口的车联网通信两大通信模式对5G蜂窝车联网的系统性能进行分析研究,给出相应的性能分析和评估结果,并提出改进建议,对5G蜂窝车联网的研究方向和实际系统部署都具有重要的指导作用。展开更多
5G技术发展使用户能够通过车联网和V2X(vehicle to everything)技术快速获取周围物理环境的信息。车辆、电网运营商等也能根据路网信息进行更好的资源分配与调度,从而促进现代化智慧交通、智慧城市等发展战略的实现。考虑到现代化城市...5G技术发展使用户能够通过车联网和V2X(vehicle to everything)技术快速获取周围物理环境的信息。车辆、电网运营商等也能根据路网信息进行更好的资源分配与调度,从而促进现代化智慧交通、智慧城市等发展战略的实现。考虑到现代化城市不同区域承担着不同功能,在车辆停靠、电网容量、土地约束、成本价格等方面具有不同特征,为优化充电站部署,建立了V2X辅助下城市区域特征差异充电站模型。考虑实际情况,引入M/M/S/K排队模型和用户充电决策模型对用户行为进行刻画。进一步建立优化模型,在用地面积、电网容量以及服务需求的约束下,通过充电站点选择和充电桩部署,最大化运营商收益。为求解该问题,设计了一种基于站点容量和用户充电行为的充电站网络规划方法,首先求解给定站点的最优充电桩部署数目,然后对候选站点进行筛选聚合实现充电站网络优化。仿真验证了所提优化方法的有效性,所提充电站网络优化方法能够有效提高站点内充电桩利用率,减少运营商建设成本,提升运营商整体盈利。展开更多
基金supported by the Natural Science Foundation of Jiangsu Province of China (Grant No BK2008548)
文摘The DS(directional solidification) polycrystalline silicon ingot is the most important photovoltaic material today,and the conversion efficiency of solar cells is affected by the morphology and organization of the crystal.Uniform grains with larger size are conducive to get high-quality wafer,so improving the cell conversion efficiency.However,grains sizes that are less than 1 mm2 can be observed frequently in the central district of mc-Si ingots,which bring negative effect to the quality of the mc-Si ingot and decrease the electrical performance of wafer.In this paper,we make an attempt to explain the formation mechanism and influence factors of microcrystal in mc-Si ingot with computer simulation technology and theory of component supercooling.It was found that:to avoid production of microcrystal,it's better to increase the value of G/V(V is the growth rate and G is the near-interface temperature gradient),strengthen the melt convection front in the solidification interface and keep a fairly flat solid/melt interface in producing mc-Si ingot.
文摘A comparative study and management has been conducted in (KTHDV). For some patients who attend the out patients clinic concern on treatment of the vitiligo with a new formula (Oxabet) alone VS Oxabet (oxpsolaren plus betamethasone) formula plus NB. UVB311 is during a period from (Jan 2011-Jan 2013). The study sample includes different age groups of both sexes. The study revealed that the formula alone gives good results. The localized vitiligo has a good response to the formula than generalized one. The early lesions have good responses than the old ones. The continuations of applying the treatment and the follow up of the patients enhance the efficacy of the treatment.
文摘在气候变化和人类活动的综合影响下,青海省生态环境发生了明显变化。在此背景下,以GIMMS NDVI 3g.v1为数据源,采用Sen+Mann-Kendal方法研究青海省1982-2015年植被覆盖区域NDVI时空变化,将趋势分析和R/S(rescaled range analysis)分析叠加,研究植被生长季NDVI变化的持续性特征,并揭示植被对气候变化及人类活动的响应规律。结果表明:1)近34年青海省植被NDVI整体呈从西北到东南的增加趋势;且变异系数显示,波动性较大地区集中在柴达木盆地周边和青南牧区西北部等植被NDVI较低的区域,波动性较小地区集中在祁连山东部、东部农业区和青南牧区东南部等植被NDVI较高的区域。2)近34年青海省植被NDVI整体呈增加趋势,增长率为0.38%·10a^(-1);且NDVI变化具有明显的阶段性,存在1994年和2000年两个突变点。3)近34年青海省植被改善区域(75.4%)远大于退化区域(24.6%),其中显著改善面积占植被覆盖区域面积的40.9%,退化区随时间变化在空间上表现出明显的转移现象。4)Hurst指数表明,青海省植被变化反持续性较强,趋势分析与Hurst指数叠加得出,由退化转为改善的区域占植被覆盖区面积的13.7%,由改善转为退化的区域占植被覆盖区面积的44.3%,另41.5%的区域无法确定未来变化趋势。5)青海省植被生长季NDVI受气候变化和人类活动的双重影响,且不同植被类型对气候变化的响应存在较大差异。
基金Under the auspices of National Natural Science Foundation of China(No.41771179,41871103,41771138)the National Key Research and Development Project(No.2016YFA0602301)
文摘Vegetation is the main component of the terrestrial ecosystem and plays a key role in global climate change. Remotely sensed vegetation indices are widely used to detect vegetation trends at large scales. To understand the trends of vegetation cover, this research examined the spatial-temporal trends of global vegetation by employing the normalized difference vegetation index(NDVI) from the Advanced Very High Resolution Radiometer(AVHRR) Global Inventory Modeling and Mapping Studies(GIMMS) time series(1982–2015). Ten samples were selected to test the temporal trend of NDVI, and the results show that in arid and semi-arid regions, NDVI showed a deceasing trend, while it showed a growing trend in other regions. Mann-Kendal(MK) trend test results indicate that 83.37% of NDVI pixels exhibited positive trends and that only 16.63% showed negative trends(P < 0.05) during the period from 1982 to 2015. The increasing NDVI trends primarily occurred in tree-covered regions because of forest growth and re-growth and also because of vegetation succession after a forest disturbance. The increasing trend of the NDVI in cropland regions was primarily because of the increasing cropland area and the improvement in planting techniques. This research describes the spatial vegetation trends at a global scale over the past 30+ years, especially for different land cover types.
文摘蜂窝车联网(cellular vehicle to everything,C-V2X)是智能交通系统的关键技术之一,车辆通过与周围的信息实体实时交换信息以实现保障城市交通安全、提高城市交通效率等目的,实现V2X通信的基本需求。在NR-V2X定义的场景中,它还将支持自动驾驶、远程驾驶、车辆编队、扩展传感四大类先进V2X服务。通过OPNET搭建5G-V2X系统级仿真平台,针对基于PC5接口和Uu接口的车联网通信两大通信模式对5G蜂窝车联网的系统性能进行分析研究,给出相应的性能分析和评估结果,并提出改进建议,对5G蜂窝车联网的研究方向和实际系统部署都具有重要的指导作用。
文摘5G技术发展使用户能够通过车联网和V2X(vehicle to everything)技术快速获取周围物理环境的信息。车辆、电网运营商等也能根据路网信息进行更好的资源分配与调度,从而促进现代化智慧交通、智慧城市等发展战略的实现。考虑到现代化城市不同区域承担着不同功能,在车辆停靠、电网容量、土地约束、成本价格等方面具有不同特征,为优化充电站部署,建立了V2X辅助下城市区域特征差异充电站模型。考虑实际情况,引入M/M/S/K排队模型和用户充电决策模型对用户行为进行刻画。进一步建立优化模型,在用地面积、电网容量以及服务需求的约束下,通过充电站点选择和充电桩部署,最大化运营商收益。为求解该问题,设计了一种基于站点容量和用户充电行为的充电站网络规划方法,首先求解给定站点的最优充电桩部署数目,然后对候选站点进行筛选聚合实现充电站网络优化。仿真验证了所提优化方法的有效性,所提充电站网络优化方法能够有效提高站点内充电桩利用率,减少运营商建设成本,提升运营商整体盈利。
