目的:研究一种改进的视觉同时定位与地图构建(simultaneous localization and mapping,SLAM)回环检测方法,以提高算法的定位与建图精度。方法:在ORB-SLAM2回环检测算法基础上,增加图像深度信息利用率,通过词袋模型加速匹配当前帧与每一...目的:研究一种改进的视觉同时定位与地图构建(simultaneous localization and mapping,SLAM)回环检测方法,以提高算法的定位与建图精度。方法:在ORB-SLAM2回环检测算法基础上,增加图像深度信息利用率,通过词袋模型加速匹配当前帧与每一个回环候选帧,分别索引当前帧与该回环候选帧地图匹配点的深度信息,将两者的比值与设定的阈值进行比较,满足阈值条件则证明该回环候选帧为相似场景图像帧,将其剔除。通过相似场景布置,使用Kinect1.0相机采集场景图片,制作相似场景数据集,结合TUM RGBD标准数据集中fr1-room序列对ORB-SLAM2算法和改进算法的性能进行测试,使用evo评价工具比较2种算法的定位精度。结果:在相似场景数据集中,改进算法能够有效剔除错误回环,准确率较高的同时还具有很好的召回率。在TUM RGBD数据集中,改进算法相较于ORBSLAM2算法,均方根误差减小了24.1%,最大误差减小了14.0%。结论:提出的改进算法在相似场景中具有较好的鲁棒性,相较于ORB-SLAM2算法具有更高的定位与建图精度,对于提高搜救机器人的自主行动能力和搜救效率具有重要意义。展开更多
We report on a three-colour InAs/InP(100)quantum dot laser under continuous wave mode at an operation temperature of 20℃.Three lasing peaks are observed simultaneously,the high-energy peak undergoes continuous bluesh...We report on a three-colour InAs/InP(100)quantum dot laser under continuous wave mode at an operation temperature of 20℃.Three lasing peaks are observed simultaneously,the high-energy peak undergoes continuous blueshift,while the splitting energy gap between the low-energy peaks is somewhat fixed as the injection current increases.The maximum output power from one facet without coating is more than 34mW with a slope efficiency of 102mW/A just above the threshold current.Three peaks of differential efficiency of output power are observed,just corresponding to each peak in lasing spectra,respectively.At the same time,the far-field distribution shows only a single transverse mode over the full range of injection current.展开更多
Background Bare stent implantation in the treatment for native and recurrent coarctation of the aorta （CoA） has become established as an alternative to surgery and balloon angioplasty. However, this modality still e...Background Bare stent implantation in the treatment for native and recurrent coarctation of the aorta （CoA） has become established as an alternative to surgery and balloon angioplasty. However, this modality still encounters significant complications during the procedure and/or follow-up. The covered Cheatham-Platinum （CP） stent commonly used to be chosen as a rescue treatment in these patients. The purpose of this study was to evaluate the use of covered CP stent as the primary modality in the treatment for native CoA. Methods Twenty-five covered CP stents and 2 bare CP stents were implanted in 25 patients with native CoA. All patients after the intervention were invited for follow-up examinations. Results The peak systolic gradient across the lesion decreased significantly from a median value of 67.5 mmHg （quartile range, 19.3 mmHg） to 2 mmHg （quartile range, 4.0 mmHg） （P 〈0.0001）. Stenotic segment diameter increased from a median value of 5.0 mm （quartile range, 1.5 mm） to 17.9 mm （quartile range, 2.5 mm） （P 〈0.0001）. The median ratio of diameter of the coarctation postprocedure to preprocedure was 4.2 （quartile range, 1.6）. All of the CP stents were placed in the suitable position without any acute complications. During a follow-up period of up to 72 months, no complications were encountered. Most of the patients （21/25） were normotensive, apart from four patients requiring antihypertensive medication during the follow-up. Conclusion The implantation of covered CP stent as the primary modality is safe and effective in the treatment for native CoA in adolescents and adults.展开更多
基金by the Natural Foundation of Guangdong Province under Grant Nos S2011040001330。
文摘We report on a three-colour InAs/InP(100)quantum dot laser under continuous wave mode at an operation temperature of 20℃.Three lasing peaks are observed simultaneously,the high-energy peak undergoes continuous blueshift,while the splitting energy gap between the low-energy peaks is somewhat fixed as the injection current increases.The maximum output power from one facet without coating is more than 34mW with a slope efficiency of 102mW/A just above the threshold current.Three peaks of differential efficiency of output power are observed,just corresponding to each peak in lasing spectra,respectively.At the same time,the far-field distribution shows only a single transverse mode over the full range of injection current.
文摘Background Bare stent implantation in the treatment for native and recurrent coarctation of the aorta （CoA） has become established as an alternative to surgery and balloon angioplasty. However, this modality still encounters significant complications during the procedure and/or follow-up. The covered Cheatham-Platinum （CP） stent commonly used to be chosen as a rescue treatment in these patients. The purpose of this study was to evaluate the use of covered CP stent as the primary modality in the treatment for native CoA. Methods Twenty-five covered CP stents and 2 bare CP stents were implanted in 25 patients with native CoA. All patients after the intervention were invited for follow-up examinations. Results The peak systolic gradient across the lesion decreased significantly from a median value of 67.5 mmHg （quartile range, 19.3 mmHg） to 2 mmHg （quartile range, 4.0 mmHg） （P 〈0.0001）. Stenotic segment diameter increased from a median value of 5.0 mm （quartile range, 1.5 mm） to 17.9 mm （quartile range, 2.5 mm） （P 〈0.0001）. The median ratio of diameter of the coarctation postprocedure to preprocedure was 4.2 （quartile range, 1.6）. All of the CP stents were placed in the suitable position without any acute complications. During a follow-up period of up to 72 months, no complications were encountered. Most of the patients （21/25） were normotensive, apart from four patients requiring antihypertensive medication during the follow-up. Conclusion The implantation of covered CP stent as the primary modality is safe and effective in the treatment for native CoA in adolescents and adults.
