This paper advances a three-dimensional space interpolation method of grey / depth image sequence, which breaks free from the limit of original practical photographing route. Pictures can cruise at will in space. By u...This paper advances a three-dimensional space interpolation method of grey / depth image sequence, which breaks free from the limit of original practical photographing route. Pictures can cruise at will in space. By using space sparse sampling, great memorial capacity can be saved and reproduced scenes can be controlled. To solve time consuming and complex computations in three-dimensional interpolation algorithm, we have studied a fast and practical algorithm of scattered space lattice and that of 'Warp' algorithm with proper depth. By several simple aspects of three dimensional space interpolation, we succeed in developing some simple and practical algorithms. Some results of simulated experiments with computers have shown that the new method is absolutely feasible.展开更多
Space monitoring of aerosol optical depth (AOD) trends over megacities can serve as a potential space indicator of global anthropogenic air-pollution changes. Three space aerosol sensors, MODIS-Terra, MODIS-Aqua and M...Space monitoring of aerosol optical depth (AOD) trends over megacities can serve as a potential space indicator of global anthropogenic air-pollution changes. Three space aerosol sensors, MODIS-Terra, MODIS-Aqua and MISR, were used in order to study recent decadal trends of AOD over megacities around the world. Space monitoring of AOD trends has the advantage of global coverage and applies the same approach to detecting AOD trends over different sites. In spite of instrumental and time differences among the three sensors investigated, their global pictures of AOD trends over the 189 largest cities in the world are quite similar. The increasing AOD trends over the largest cities in the Indian subcontinent, the Middle East, and North China can be clearly seen. By contrast, megacities in Europe, the north-east of US, and South-East Asia show mainly declining AOD trends. In the cases where all three sensors show similar signs of AOD trends, the results can be considered as reliable. This is supported by the observed trends in surface solar radiation, obtained by using network pyranometer measurements in North and South China, India, and Europe. In the cases where the three sensors show differing signs of AOD trends (e.g. South America), additional research is required in order to verify the obtained AOD trends.展开更多
The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influenc...The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.展开更多
交通标志检测是自动驾驶系统、辅助驾驶系统(DAS)的重要组成部分,对行车安全具有重要意义。针对小目标交通标志检测时受光照、恶劣天气等因素影响而导致的检测精度低、漏检率高等问题,提出一种基于改进YOLOv5的小目标交通标志检测算法...交通标志检测是自动驾驶系统、辅助驾驶系统(DAS)的重要组成部分,对行车安全具有重要意义。针对小目标交通标志检测时受光照、恶劣天气等因素影响而导致的检测精度低、漏检率高等问题,提出一种基于改进YOLOv5的小目标交通标志检测算法。首先,引入空间到深度卷积(SPD-Conv)对特征图进行下采样,有效避免小目标信息丢失,提高小目标敏感度。其次,基于加权双向特征金字塔网络(BiFPN)改进颈部网络,添加跨层连接以融合多尺度特征。之后,增加小目标检测层,增强小目标检测能力。最后,采用SIoU(Shape-aware Intersection over Union)损失函数,关注真实框与预测框的角度信息。实验结果表明,改进后的算法在中国交通标志检测数据集(CCTSDB2021)上的平均精度均值(mAP)达到83.5%,相较于原YOLOv5提升了7.2个百分点,检测速度满足实时性要求。展开更多
煤矿井下弥漫着粉尘和雾气且多数区域为狭长巷道,仅依赖矿灯照明会导致视频监控图像出现细节模糊、局部过曝及目标尺寸多变等问题。这些因素增加了井下安全帽目标检测的难度,现有目标检测算法直接应用于煤矿井下场景时,通常面临精度不...煤矿井下弥漫着粉尘和雾气且多数区域为狭长巷道,仅依赖矿灯照明会导致视频监控图像出现细节模糊、局部过曝及目标尺寸多变等问题。这些因素增加了井下安全帽目标检测的难度,现有目标检测算法直接应用于煤矿井下场景时,通常面临精度不足的挑战。针对这些问题,研究提出一种基于YOLOv8n(You Only Look Once version 8n)的煤矿井下安全帽检测算法。首先,采用空间到深度机制将YOLOv8n主干网络中的Conv模块重新构建为空间到深度卷积(Space-to-Depth Convolutional,SPDConv)模块,以便从特征图中充分提取浅层细节信息,提高模型对细节模糊图像中小目标安全帽的检测精度;其次,引入基于注意力机制的尺度内特征交互模块,减少局部过曝对安全帽特征提取的干扰,增强模型对目标区域的关注能力;最后,借鉴高层次筛选特征融合金字塔对YOLOv8n的颈部网络进行重设计,改善模型对不同尺寸安全帽的检测能力,进一步提升检测精度。试验结果显示,该算法在CUMT-Helme T数据集上的平均精度均值达91.7%,相较于YOLOv8n提升了3.2百分点,同时模型参数量减少了1.9×10^(5)。与单次多边框检测(Single Shot MultiBox Detector,SSD)、快速区域卷积神经网络(Region-based Convolutional Neural Networks,Faster RCNN)、YOLOv5s、YOLOv6n、YOLOv7及YOLOv7-tiny等当前主流目标检测算法相比,该算法的平均精度均值最高,且参数量和浮点运算量较低,在实现较高检测精度的同时还具备一定的轻量化特性。展开更多
In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading level...In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading levels of serviceability state.The effects of the depth of normal section beams on the crack spacing and crack width were analyzed,and the modified model is proposed for calculating the average crack spacing by thinking about the depth of normal section,the reinforcement arrangement and the effective reinforcement ratio.The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied.By theoretical and statistical analysis,a method is proposed to calculate the ratios of crack widths between any position and the reinforcement level on the side surface of large depth reinforced concrete beams.展开更多
文摘This paper advances a three-dimensional space interpolation method of grey / depth image sequence, which breaks free from the limit of original practical photographing route. Pictures can cruise at will in space. By using space sparse sampling, great memorial capacity can be saved and reproduced scenes can be controlled. To solve time consuming and complex computations in three-dimensional interpolation algorithm, we have studied a fast and practical algorithm of scattered space lattice and that of 'Warp' algorithm with proper depth. By several simple aspects of three dimensional space interpolation, we succeed in developing some simple and practical algorithms. Some results of simulated experiments with computers have shown that the new method is absolutely feasible.
文摘Space monitoring of aerosol optical depth (AOD) trends over megacities can serve as a potential space indicator of global anthropogenic air-pollution changes. Three space aerosol sensors, MODIS-Terra, MODIS-Aqua and MISR, were used in order to study recent decadal trends of AOD over megacities around the world. Space monitoring of AOD trends has the advantage of global coverage and applies the same approach to detecting AOD trends over different sites. In spite of instrumental and time differences among the three sensors investigated, their global pictures of AOD trends over the 189 largest cities in the world are quite similar. The increasing AOD trends over the largest cities in the Indian subcontinent, the Middle East, and North China can be clearly seen. By contrast, megacities in Europe, the north-east of US, and South-East Asia show mainly declining AOD trends. In the cases where all three sensors show similar signs of AOD trends, the results can be considered as reliable. This is supported by the observed trends in surface solar radiation, obtained by using network pyranometer measurements in North and South China, India, and Europe. In the cases where the three sensors show differing signs of AOD trends (e.g. South America), additional research is required in order to verify the obtained AOD trends.
基金Project supported by National Basic Research Program of China （973 Program） （2014 CB239501, 2011CB209400）, National Natural Science Foundation of China （NSFC 50877040）.
文摘The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.
文摘交通标志检测是自动驾驶系统、辅助驾驶系统(DAS)的重要组成部分,对行车安全具有重要意义。针对小目标交通标志检测时受光照、恶劣天气等因素影响而导致的检测精度低、漏检率高等问题,提出一种基于改进YOLOv5的小目标交通标志检测算法。首先,引入空间到深度卷积(SPD-Conv)对特征图进行下采样,有效避免小目标信息丢失,提高小目标敏感度。其次,基于加权双向特征金字塔网络(BiFPN)改进颈部网络,添加跨层连接以融合多尺度特征。之后,增加小目标检测层,增强小目标检测能力。最后,采用SIoU(Shape-aware Intersection over Union)损失函数,关注真实框与预测框的角度信息。实验结果表明,改进后的算法在中国交通标志检测数据集(CCTSDB2021)上的平均精度均值(mAP)达到83.5%,相较于原YOLOv5提升了7.2个百分点,检测速度满足实时性要求。
文摘煤矿井下弥漫着粉尘和雾气且多数区域为狭长巷道,仅依赖矿灯照明会导致视频监控图像出现细节模糊、局部过曝及目标尺寸多变等问题。这些因素增加了井下安全帽目标检测的难度,现有目标检测算法直接应用于煤矿井下场景时,通常面临精度不足的挑战。针对这些问题,研究提出一种基于YOLOv8n(You Only Look Once version 8n)的煤矿井下安全帽检测算法。首先,采用空间到深度机制将YOLOv8n主干网络中的Conv模块重新构建为空间到深度卷积(Space-to-Depth Convolutional,SPDConv)模块,以便从特征图中充分提取浅层细节信息,提高模型对细节模糊图像中小目标安全帽的检测精度;其次,引入基于注意力机制的尺度内特征交互模块,减少局部过曝对安全帽特征提取的干扰,增强模型对目标区域的关注能力;最后,借鉴高层次筛选特征融合金字塔对YOLOv8n的颈部网络进行重设计,改善模型对不同尺寸安全帽的检测能力,进一步提升检测精度。试验结果显示,该算法在CUMT-Helme T数据集上的平均精度均值达91.7%,相较于YOLOv8n提升了3.2百分点,同时模型参数量减少了1.9×10^(5)。与单次多边框检测(Single Shot MultiBox Detector,SSD)、快速区域卷积神经网络(Region-based Convolutional Neural Networks,Faster RCNN)、YOLOv5s、YOLOv6n、YOLOv7及YOLOv7-tiny等当前主流目标检测算法相比,该算法的平均精度均值最高,且参数量和浮点运算量较低,在实现较高检测精度的同时还具备一定的轻量化特性。
基金Sponsored by the Outstanding Youth Scientific Fund of Henan Province(Grant No.04120002300)Program for Innovation in University of Henan Province(Grant No.[2004]294)
文摘In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading levels of serviceability state.The effects of the depth of normal section beams on the crack spacing and crack width were analyzed,and the modified model is proposed for calculating the average crack spacing by thinking about the depth of normal section,the reinforcement arrangement and the effective reinforcement ratio.The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied.By theoretical and statistical analysis,a method is proposed to calculate the ratios of crack widths between any position and the reinforcement level on the side surface of large depth reinforced concrete beams.
