稀疏卷积在处理激光雷达点云单目标跟踪时的潜力尚未得到充分发掘.目前,绝大多数点云跟踪算法使用基于球邻域的骨干网络,其显存计算资源占用大并且目标感知的关系建模不充分.针对此问题,本文提出一种基于稀疏卷积结构的LiDAR(Lightlaser...稀疏卷积在处理激光雷达点云单目标跟踪时的潜力尚未得到充分发掘.目前,绝大多数点云跟踪算法使用基于球邻域的骨干网络,其显存计算资源占用大并且目标感知的关系建模不充分.针对此问题,本文提出一种基于稀疏卷积结构的LiDAR(Lightlaser Detection And Ranging)点云跟踪算法,并创新性地融合了空间点与体素双通道的关系建模模块,以高效适应稀疏框架下目标判别信息的嵌入.首先,本文采用3D稀疏卷积残差网络来分别提取模板和搜索区域的特征,并利用反卷积来获取逐点特征来保证跟踪任务中对空间位置特性的要求.其次,关系建模模块进一步在模板与搜索区域特征之间计算相似度语义查询表.为了捕捉到模板与搜索区域间细粒度的关联性,该模块一方面在空间点通道中利用近邻算法找出每个搜索区域点的模板近邻点,并根据语义查询表提取对应特征;另一方面,在体素通道中以每个搜索区域点为中心构建局部多尺度体素,并根据落入体素单元的模板点索引计算语义查询表中值的累计和.最后,将双通道的特征融合并送入基于鸟瞰图的候选包围盒生成模块来回归目标包围盒.为了验证所提出方法的优越性,本文在KITTI和NuScenes数据集进行了测试,对比其他使用稀疏卷积的算法,本文方法平均成功率和精确率分别提升了11.0%和12.0%.本文方法在继承了稀疏卷积高效特点的同时还实现了跟踪精度的提高.展开更多
为了研究首都功能核心区新建小型城市森林公园缓解城市热岛效应的能力,以广阳谷城市森林公园为研究对象,基于遥感(remote sensing,RS)和地理信息系统(geographic information system,GIS)完成了2014年、2017年和2019年公园内及周边区域...为了研究首都功能核心区新建小型城市森林公园缓解城市热岛效应的能力,以广阳谷城市森林公园为研究对象,基于遥感(remote sensing,RS)和地理信息系统(geographic information system,GIS)完成了2014年、2017年和2019年公园内及周边区域的地表温度反演,同时结合长期定点监测公园内外空气温湿度,分析城市森林公园内及周边冷岛效应。结果发现:广阳谷城市森林公园建成后,在园外100 m范围内有一定的降温效果。相比建成前,2017年和2019年其100 m缓冲区内热岛区域占比分别减少了4.83%和1.38%,地表平均温度比核心区分别降低了0.72℃和1.15℃,说明公园建成以来,充分发挥了冷岛作用;公园内各测点在10:00—17:00的平均温度低于对照点1.65℃,公园内部的相对湿度比对照点高2.68%;3—8月公园内各点的平均温度比对照点低0.67℃,在3月、4月、6月和7月公园内各点的平均湿度比对照点高1.82%,说明森林公园在此段时间发挥着降温增湿的作用。展开更多
为解决柔性智能制造过程中对密集工件漏检率高的问题,提出一种基于改进SSD(single shot multiBox detector)算法的目标检测模型。首先,在SSD网络中融入RFB(receptive field block,感受野模块),提高网络的特征提取能力;其次,采用激活函数...为解决柔性智能制造过程中对密集工件漏检率高的问题,提出一种基于改进SSD(single shot multiBox detector)算法的目标检测模型。首先,在SSD网络中融入RFB(receptive field block,感受野模块),提高网络的特征提取能力;其次,采用激活函数PReLU(parametric rectified linear unit,参数化修正线性单元)代替传统的ReLU激活函数,避免部分神经元出现“死亡”现象;然后,使用CIoU(complete intersection over union)对损失函数进行优化;同时,使用平滑标签、融入BN层(batch normalization,批量标准化)等优化方法防止过拟合现象。在构建的密集工件数据集进行实验,平均精度均值达到95.24%,较改进之前算法提高4.42%,满足实际工业需求。展开更多
The Beijing-Tianjin Sand Source Control Project(BTSSCP), a national ecological restoration project, was launched to construct an ecological protection system in the Beijing-Tianjin sand source areas to reduce dust haz...The Beijing-Tianjin Sand Source Control Project(BTSSCP), a national ecological restoration project, was launched to construct an ecological protection system in the Beijing-Tianjin sand source areas to reduce dust hazards. The carbon sequestration dynamics can be used to assess the ecological effects of an ecological restoration project. Here, we conducted vegetation and soil study to assess the carbon sequestration in the plantations with 10 years old stands in Beijing-Tianjin sand source areas. The results at the site scales indicated that the average net increase of plantation ecosystem carbon stock was 33.8 Mg C ha^(-1), with an annual increase rate of 3.38 Mg C ha^(-1) yr^(-1). The average net increase of carbon varied among regions, vegetation types, and forest management activities. Soil bulk density in the top soil decreased slightly after 10-year implementation of the project. Coniferous forests and shrubs are suitable plant species for sand source areas.Natural restoration in the plantations is a practical and feasible and promising approach for enhancing ecosystem carbon sequestration potential.展开更多
Dung deposition is an important pathway of nutrient return and redistribution in alpine grasslands of the Qinghai-Tibetan Plateau.To date,information on the greenhouse gas emissions of yak dung on alpine grasslands,es...Dung deposition is an important pathway of nutrient return and redistribution in alpine grasslands of the Qinghai-Tibetan Plateau.To date,information on the greenhouse gas emissions of yak dung on alpine grasslands,especially where there are large amounts of rock fragments,is limited.Our aim,therefore,was to evaluate variations in N_2O,CH_4,and CO_2 emissions from yak dung(CCD),and compare it to dung placed on rock fragments(RCD),alpine steppe soil(CSD),and a soil and rock fragment mixture(RSD) over a 30-day incubation period.The results showed that the total N_2O emissions from treatments without soil were significantly(P < 0.05) lower than those from treatments with soil.The highest total CH_4 emissions were detected in the CSD treatment,while CH_4 losses from treatments without rock fragments were significantly(P < 0.05) greater than those with rock fragments.The total CO_2 emissions from the RSD treatment was 6.30%–12.0% lower than those in the other three treatments.The soil beneath yak dung pats elevated the globalwarming potential(GWP),while the addition of rock fragments to the soil significantly(P < 0.05) decreased the GWP by reducing emissions of the three greenhouse gases.We therefore suggest that interactions between rock fragments and alpine steppe soil are effective in decreasing yak dung greenhouse gas emissions.This finding indicates that rock fragments are an effective medium for reducing greenhouse gas emissions from dung pats,and more attention should therefore be paid to evaluate its ecological impact in future studies.These results should help guide scientific assessments of regional GHG budgets in agricultural ecosystems where the addition of livestock manure to soils with large amounts of rock fragments is common.展开更多
文摘稀疏卷积在处理激光雷达点云单目标跟踪时的潜力尚未得到充分发掘.目前,绝大多数点云跟踪算法使用基于球邻域的骨干网络,其显存计算资源占用大并且目标感知的关系建模不充分.针对此问题,本文提出一种基于稀疏卷积结构的LiDAR(Lightlaser Detection And Ranging)点云跟踪算法,并创新性地融合了空间点与体素双通道的关系建模模块,以高效适应稀疏框架下目标判别信息的嵌入.首先,本文采用3D稀疏卷积残差网络来分别提取模板和搜索区域的特征,并利用反卷积来获取逐点特征来保证跟踪任务中对空间位置特性的要求.其次,关系建模模块进一步在模板与搜索区域特征之间计算相似度语义查询表.为了捕捉到模板与搜索区域间细粒度的关联性,该模块一方面在空间点通道中利用近邻算法找出每个搜索区域点的模板近邻点,并根据语义查询表提取对应特征;另一方面,在体素通道中以每个搜索区域点为中心构建局部多尺度体素,并根据落入体素单元的模板点索引计算语义查询表中值的累计和.最后,将双通道的特征融合并送入基于鸟瞰图的候选包围盒生成模块来回归目标包围盒.为了验证所提出方法的优越性,本文在KITTI和NuScenes数据集进行了测试,对比其他使用稀疏卷积的算法,本文方法平均成功率和精确率分别提升了11.0%和12.0%.本文方法在继承了稀疏卷积高效特点的同时还实现了跟踪精度的提高.
文摘为解决柔性智能制造过程中对密集工件漏检率高的问题,提出一种基于改进SSD(single shot multiBox detector)算法的目标检测模型。首先,在SSD网络中融入RFB(receptive field block,感受野模块),提高网络的特征提取能力;其次,采用激活函数PReLU(parametric rectified linear unit,参数化修正线性单元)代替传统的ReLU激活函数,避免部分神经元出现“死亡”现象;然后,使用CIoU(complete intersection over union)对损失函数进行优化;同时,使用平滑标签、融入BN层(batch normalization,批量标准化)等优化方法防止过拟合现象。在构建的密集工件数据集进行实验,平均精度均值达到95.24%,较改进之前算法提高4.42%,满足实际工业需求。
基金supported by the National Key Research and Development Program of China(2016YFC0500802)the "Strategic Priority Research Program" of the Chinese Academy of Sciences(XDA05060600)+1 种基金Visiting Scholars Program of ported by Chinese Academy of SciencesYouth Innovation Promotion Association,CAS(2014083)
文摘The Beijing-Tianjin Sand Source Control Project(BTSSCP), a national ecological restoration project, was launched to construct an ecological protection system in the Beijing-Tianjin sand source areas to reduce dust hazards. The carbon sequestration dynamics can be used to assess the ecological effects of an ecological restoration project. Here, we conducted vegetation and soil study to assess the carbon sequestration in the plantations with 10 years old stands in Beijing-Tianjin sand source areas. The results at the site scales indicated that the average net increase of plantation ecosystem carbon stock was 33.8 Mg C ha^(-1), with an annual increase rate of 3.38 Mg C ha^(-1) yr^(-1). The average net increase of carbon varied among regions, vegetation types, and forest management activities. Soil bulk density in the top soil decreased slightly after 10-year implementation of the project. Coniferous forests and shrubs are suitable plant species for sand source areas.Natural restoration in the plantations is a practical and feasible and promising approach for enhancing ecosystem carbon sequestration potential.
基金supported by grants from the“Strategic Priority Research Program”of the Chinese Academy of Sciences(Grant No.XDB03030505)the National Natural Science Foundation of China(Grant No.41573070)the Open Fund of the State Key Laboratory of Soiland Sustainable Agriculture,Institute of Soil Science,Chinese Academy of Sciences(Grant No.Y412201403)
文摘Dung deposition is an important pathway of nutrient return and redistribution in alpine grasslands of the Qinghai-Tibetan Plateau.To date,information on the greenhouse gas emissions of yak dung on alpine grasslands,especially where there are large amounts of rock fragments,is limited.Our aim,therefore,was to evaluate variations in N_2O,CH_4,and CO_2 emissions from yak dung(CCD),and compare it to dung placed on rock fragments(RCD),alpine steppe soil(CSD),and a soil and rock fragment mixture(RSD) over a 30-day incubation period.The results showed that the total N_2O emissions from treatments without soil were significantly(P < 0.05) lower than those from treatments with soil.The highest total CH_4 emissions were detected in the CSD treatment,while CH_4 losses from treatments without rock fragments were significantly(P < 0.05) greater than those with rock fragments.The total CO_2 emissions from the RSD treatment was 6.30%–12.0% lower than those in the other three treatments.The soil beneath yak dung pats elevated the globalwarming potential(GWP),while the addition of rock fragments to the soil significantly(P < 0.05) decreased the GWP by reducing emissions of the three greenhouse gases.We therefore suggest that interactions between rock fragments and alpine steppe soil are effective in decreasing yak dung greenhouse gas emissions.This finding indicates that rock fragments are an effective medium for reducing greenhouse gas emissions from dung pats,and more attention should therefore be paid to evaluate its ecological impact in future studies.These results should help guide scientific assessments of regional GHG budgets in agricultural ecosystems where the addition of livestock manure to soils with large amounts of rock fragments is common.
