对道路交通参与者中的行人、骑行者以及车辆进行检测是实现自动驾驶的核心任务之一。在光照不均、遮挡、密集目标和远距离小目标等复杂场景中往往会存在误检及漏检情况;基于此,提出了一种改进YOLOv8模型的复杂交通场景目标检测算法。基...对道路交通参与者中的行人、骑行者以及车辆进行检测是实现自动驾驶的核心任务之一。在光照不均、遮挡、密集目标和远距离小目标等复杂场景中往往会存在误检及漏检情况;基于此,提出了一种改进YOLOv8模型的复杂交通场景目标检测算法。基于GhostNet轻量化网络结构,对原始YOLOv8模型的主干和颈部网络进行改进,利用幻影卷积(ghost convolution,GhostConv)来替换标准卷积(convolution,Conv),并将幻影瓶颈(ghost bottleneck,G-bneck)结合C3模块代替C2f模块,这样就有效抑制了冗余检测,提升了检测效率;应用混合局部通道注意力机制(mixed local channel attention,MLCA)对多元化信息进行整合,以增强模型的特征提取能力;添加小目标检测层,可保留更多细节特征信息,提高对远距离小目标的检测能力;采用WIoU(wise intersection over union loss)损失函数加速了网络收敛并增强了在复杂工况下的鲁棒性。研究结果表明:改进YOLOv8模型在所构建的复杂交通场景数据集RCCW-Dataset中的平均精度均值为0.872,较原始模型提高了2.1%;模型参数量和大小分别降低了41%和37%,能有效完成对实时复杂交通场景目标任务的检测。展开更多
Multilayer ceramic actuator(MLCA)has been widely employed in actuators due to the large cumulative displacement under the low driving voltage.In this work,the MLCA devices consisting of a lead-free MnCO_(3-)and CuO-do...Multilayer ceramic actuator(MLCA)has been widely employed in actuators due to the large cumulative displacement under the low driving voltage.In this work,the MLCA devices consisting of a lead-free MnCO_(3-)and CuO-doped 0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Ta_(0.04))O_(3)-0.04CaZrO_(3) piezoelectric ceramics and a base nickel(Ni)metal inner electrode were well co-fired by the two-step sintering process in a reducing atmosphere.The ceramic layer/electrode interface is well-integrated and clearly continuous without distinct interdiffusion and chemical reaction,which is beneficial to the electrical reliability of the MLCA.As a result,the MLCA laminated with nine active ceramic layers obtains an ultrahigh piezoelectric coefficient d_(33) of 3157 pC/N,about 9 times than bulk ceramics.The 0.5 mm-thick MLCA composed of a series of~50μm-thick ceramic layers and~3μm-thick Ni electrodes reaches a high 1.8μm displacement under the low applied voltage of 200 V(the same displacement requires a voltage as high as 3700 V for~1 mm-thick bulk ceramics).The excellent electrical performance and low-cost base electrode reveal that the(K,Na)NbO_(3)(KNN)-based MLCAs are promising lead-free candidate for actuator application.展开更多
文摘对道路交通参与者中的行人、骑行者以及车辆进行检测是实现自动驾驶的核心任务之一。在光照不均、遮挡、密集目标和远距离小目标等复杂场景中往往会存在误检及漏检情况;基于此,提出了一种改进YOLOv8模型的复杂交通场景目标检测算法。基于GhostNet轻量化网络结构,对原始YOLOv8模型的主干和颈部网络进行改进,利用幻影卷积(ghost convolution,GhostConv)来替换标准卷积(convolution,Conv),并将幻影瓶颈(ghost bottleneck,G-bneck)结合C3模块代替C2f模块,这样就有效抑制了冗余检测,提升了检测效率;应用混合局部通道注意力机制(mixed local channel attention,MLCA)对多元化信息进行整合,以增强模型的特征提取能力;添加小目标检测层,可保留更多细节特征信息,提高对远距离小目标的检测能力;采用WIoU(wise intersection over union loss)损失函数加速了网络收敛并增强了在复杂工况下的鲁棒性。研究结果表明:改进YOLOv8模型在所构建的复杂交通场景数据集RCCW-Dataset中的平均精度均值为0.872,较原始模型提高了2.1%;模型参数量和大小分别降低了41%和37%,能有效完成对实时复杂交通场景目标任务的检测。
基金supported by the National Natural Science Foundation of China(GrantNos.52072150 and 51972146)Shandong Province Key Fundamental Research Program(Grant No.ZR2022ZD39)+1 种基金State Key Laboratory of New Ceramics and Fine Processing,Tsinghua University(Grant No.KF202002)Open Foundation of Guangdong Key Laboratory of Electronic Functional Materials andDevices(Grant No.EFMD2021002Z).
文摘Multilayer ceramic actuator(MLCA)has been widely employed in actuators due to the large cumulative displacement under the low driving voltage.In this work,the MLCA devices consisting of a lead-free MnCO_(3-)and CuO-doped 0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Ta_(0.04))O_(3)-0.04CaZrO_(3) piezoelectric ceramics and a base nickel(Ni)metal inner electrode were well co-fired by the two-step sintering process in a reducing atmosphere.The ceramic layer/electrode interface is well-integrated and clearly continuous without distinct interdiffusion and chemical reaction,which is beneficial to the electrical reliability of the MLCA.As a result,the MLCA laminated with nine active ceramic layers obtains an ultrahigh piezoelectric coefficient d_(33) of 3157 pC/N,about 9 times than bulk ceramics.The 0.5 mm-thick MLCA composed of a series of~50μm-thick ceramic layers and~3μm-thick Ni electrodes reaches a high 1.8μm displacement under the low applied voltage of 200 V(the same displacement requires a voltage as high as 3700 V for~1 mm-thick bulk ceramics).The excellent electrical performance and low-cost base electrode reveal that the(K,Na)NbO_(3)(KNN)-based MLCAs are promising lead-free candidate for actuator application.
