为使水果采摘机器人在复杂情况下如树叶遮挡、果实目标尺度变化大等情况能准确地检测出水果,提出一种YOLO(you only look once)改进模型与NMS(non-maximum suppression)改进算法的目标检测方法。首先,对传统YOLO深度卷积神经网络架构进...为使水果采摘机器人在复杂情况下如树叶遮挡、果实目标尺度变化大等情况能准确地检测出水果,提出一种YOLO(you only look once)改进模型与NMS(non-maximum suppression)改进算法的目标检测方法。首先,对传统YOLO深度卷积神经网络架构进行改进,设计一种更细化的SPP5(spatial pyramid pooling)特征融合网络模块,强化特征图多重感受野信息的融合,并基于此模块提出一种YOLOv4-SPP2-5模型,在标准YOLOv4网络中跨层添加并改进SPP层,重新分布池化核大小,增强感受野范围,从而降低目标误检率;其次,提出一种Greedy-Confluence的NMS改进算法,通过对高度接近的检测框直接抑制和对重叠检测框综合考虑距离交并比DIOU(distance-intersection over union)和加权接近度WP(weighted proximity)的方法,均衡NMS的计算消耗并减少检测框的错误抑制,从而提高遮挡、重叠物体的检测精度;最后,分别对改进方法进行性能测试,验证方法的可行性,随后制作水果检测数据集并进行格式转换和标签标注,然后采用数据增强技术对训练数据进行扩充,并使用K-means++聚类方法获取先验锚定框,在计算机上进行了水果检测实验。结果表明,基于改进YOLO网络及改进NMS的水果检测方法在准确率方面有显著的提高,平均精度均值(mean average precision,MAP)在YOLOv4上达到了96.65%,较原网络提升1.70%,并且实时性也得到了保证,在测试设备上达到了39.26帧/s。展开更多
The thorium-229 nucleus possesses a uniquely low-energy nuclear transition(-8.4 eV,corresponding to a wavelength of-148 nm),which is the first confirmed nuclear excitation that can be coherently manipulated by narrow-...The thorium-229 nucleus possesses a uniquely low-energy nuclear transition(-8.4 eV,corresponding to a wavelength of-148 nm),which is the first confirmed nuclear excitation that can be coherently manipulated by narrow-linewidth lasers.Consequently,this transition has garnered widespread interest over the past decades.Owing to the small nuclear size and strong resistance to environmental perturbations,a thorium-based nuclear clock is theoretically capable of achieving an unprecedented fractional frequency uncertainty at the 10^(−20) level,offering great promise as a next-generation frequency standard.Among the key ingredients of such a thorium-based nuclear clock,a high-performance 148 nm excitation source is of critical importance.Since the feasibility of directly exciting the transition,as well as the overall clock performance,depends heavily on the availability and quality of such a source,the development of high-quality 148 nm laser sources represents a frontier for scientists worldwide.In this article,we provide a systematic overview of the current development of 148 nm laser sources.First,we briefly introduce the scientific motivation for high-precision spectroscopy of the thorium nuclear transition and the corresponding technical requirements for 148 nm laser sources.Then,we summarize four main types of existing 148 nm source generation schemes and their working principles,along with recent progress in nuclear transition measurements using such sources.Finally,we discuss potential future directions.展开更多
文摘为使水果采摘机器人在复杂情况下如树叶遮挡、果实目标尺度变化大等情况能准确地检测出水果,提出一种YOLO(you only look once)改进模型与NMS(non-maximum suppression)改进算法的目标检测方法。首先,对传统YOLO深度卷积神经网络架构进行改进,设计一种更细化的SPP5(spatial pyramid pooling)特征融合网络模块,强化特征图多重感受野信息的融合,并基于此模块提出一种YOLOv4-SPP2-5模型,在标准YOLOv4网络中跨层添加并改进SPP层,重新分布池化核大小,增强感受野范围,从而降低目标误检率;其次,提出一种Greedy-Confluence的NMS改进算法,通过对高度接近的检测框直接抑制和对重叠检测框综合考虑距离交并比DIOU(distance-intersection over union)和加权接近度WP(weighted proximity)的方法,均衡NMS的计算消耗并减少检测框的错误抑制,从而提高遮挡、重叠物体的检测精度;最后,分别对改进方法进行性能测试,验证方法的可行性,随后制作水果检测数据集并进行格式转换和标签标注,然后采用数据增强技术对训练数据进行扩充,并使用K-means++聚类方法获取先验锚定框,在计算机上进行了水果检测实验。结果表明,基于改进YOLO网络及改进NMS的水果检测方法在准确率方面有显著的提高,平均精度均值(mean average precision,MAP)在YOLOv4上达到了96.65%,较原网络提升1.70%,并且实时性也得到了保证,在测试设备上达到了39.26帧/s。
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0920000)the National Natural Science Foundation of China(Grant Nos.12121004 and U21A20435)+1 种基金the Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YSBR-055)the Science and Technology Department of Hubei Province(Grant No.2025AFA004)。
文摘The thorium-229 nucleus possesses a uniquely low-energy nuclear transition(-8.4 eV,corresponding to a wavelength of-148 nm),which is the first confirmed nuclear excitation that can be coherently manipulated by narrow-linewidth lasers.Consequently,this transition has garnered widespread interest over the past decades.Owing to the small nuclear size and strong resistance to environmental perturbations,a thorium-based nuclear clock is theoretically capable of achieving an unprecedented fractional frequency uncertainty at the 10^(−20) level,offering great promise as a next-generation frequency standard.Among the key ingredients of such a thorium-based nuclear clock,a high-performance 148 nm excitation source is of critical importance.Since the feasibility of directly exciting the transition,as well as the overall clock performance,depends heavily on the availability and quality of such a source,the development of high-quality 148 nm laser sources represents a frontier for scientists worldwide.In this article,we provide a systematic overview of the current development of 148 nm laser sources.First,we briefly introduce the scientific motivation for high-precision spectroscopy of the thorium nuclear transition and the corresponding technical requirements for 148 nm laser sources.Then,we summarize four main types of existing 148 nm source generation schemes and their working principles,along with recent progress in nuclear transition measurements using such sources.Finally,we discuss potential future directions.
