Accuracy of screw placement in the apical region of Lenke 1 adolescent idiopathic scoliosis surgery using a calibration technique for the intraoperative navigation error

Objective:To study the position and the grade of screw perforation in the apical region of adolescent idiopathic scoliosis(AIS)surgery using a calibration technique for the intraoperative navigation error,and to analyze the related factors of navigation deviation and the clinical significance of the calibration technique.Methods:From 2017 to 2020,a total of 60 Lenke 1 AIS surgical cases were enrolled in this research.The 30 cases received surgery using the intraoperative navigation system(Navigation group)and another 30 cases were assisted with intraoperative navigation system with calibration technique(Calibration group)for the intraoperative navigation error.The basic information and radiological data of the both groups were all recorded.According to the Fu Chang-feng’s pedicle channel classification system,the pedicle on the apical region of the two groups was classified.And then the accuracy of screw placement of the two groups was evaluated according to the Rao’s classification.Results:A total of 600 screws were placed in the two groups.The 297 and 303 pedicle screws were implanted in the navigation group and the calibration group,respectively.In the apical region of the calibration group,the rates of the grade 0 screw placement in type A,B and C pedicle were 95.7%,86.7%and 68.9%respectively.It was a statistically significant difference from the 73.9%,66.9%and 30.0%in the navigation group respectively(P<0.05).In the calibration group,the rates of the medial cortical perforation in the type A,B,C and D pedicle were 0%,1.6%,1.6%and 0%,respectively.The corresponding rates were 16.3%,16.9%,30.0%and 47.6%in the navigation group,respectively.Moreover,in the concave side of the apical region of the calibration group,the rates of the medial cortical perforation in the type A,B,C and D pedicle were 0%,3.6%,2.6%and 0%,respectively.Compared with the calibration group,the corresponding rates were higher in the navigation group(34.4%,25.9%,37.2%and 60.0%,respectively).No serious complications such as spinal cord or neurovascular injury occurred for the two groups.Conclusion:Compared with the intraoperative navigation system,the calibration technique for the intraoperative navigation error could provide the higher accuracy of pedicle screw placement in the apical region of the major curve,the lower medial cortical perforation rate,the less screws misplacement rate on the concave side and the less complication rate of the severe Lenke 1 AIS patients.

BeiDou Regional Navigation Satellite System Completed

As the 16th BeiDou navigation satellite was successfully launched into space at 23:33 Beijing Time from the Xichang Satellite Launch Center (XSLC) on October 25, 2012, China completed the construction of the BeiDou Regional Navigation Satellite System that starts to officially provide services for most parts of the Asia-Pacific region from December 27. The 16th BeiDou navigation satellite, the last one for the regional BeiDou system, was developed by China Academy of Space Technology under CASC.

Combined proportional navigation law for interception of high-speed targets

A new proportional navigation(PN) guidance law,called combined proportional navigation(CPN),is proposed.The guidance law is designed to intercept high-speed targets,which is a common case for ballistic targets.The range of target-to-interceptor speed ratio during target interception is derived when guidance laws are applied in high-speed targets interception,and the effectiveness of negative navigation ratio in the PN-based guidance law is proven analytically in some lemmas.Based on the lemmas,the lateral acceleration command of CPN is defined,and the solution to the appearance of singularity in time-varying navigation ratio is given.The simulation results show that CPN can determine headon engagement(as PN) or tail-chase engagement(as RPN) through initial path angle compared with PN and retro proportional navigation(RPN),and can adjust the value of navigation ratio for head-on engagement or tail-chase engagement.Therefore,the capture region of CPN is larger than that of other guidance laws using PN-based methods.

Biased retro-proportional navigation law for interception of high-speed targets with angular constraint

A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target interception. BRPN guidance law is defined, and the exact time-varying bias for a required impact angle is derived. Furthermore, the simulation results(trajectory, variation of navigation ratio, capture region, etc) are compared with those of biased proportional navigation(BPN), proportional navigation and retro-proportional navigation. The results show that,at the cost of a higher intercept time, BRPN demands lower terminal lateral acceleration and has larger capture region compared to BPN.

Plane extraction for navigation of humanoid robot

In order to make the humanoid robot walk freely in complicated circumstance,the reliable capabilities for obtaining plane information from its surroundings are demanded.A system for extracting planes from data taken by stereo vision was presented.After the depth image was obtained,the pixels of each line were scanned and split into straight line segments.The neighbouring relation of line segments was kept in link structure.The groups of three line segments were selected as seed regions.A queue was maintained for storing seed regions,and then the plane region was expanded around the seed region.The process of region growing continued until the queue of seed regions was empty.After trimming,the edges of the planes became smooth.In the end,extracted planes were obtained.In the experiment,two models were used:pipe and stairs.Two planes in pipe model and six planes in stairs model were extracted exactly.The speed and precision of algorithm can satisfy the demands of humanoid robot's navigation.

虚拟环境中大尺度空间定向能力的地域差异

基于空间参照系理论,本文采用虚拟现实技术探讨了大尺度空间定向能力的地域差异及其原因。实验1采用基于两种空间参照系且生态效度更高的路线重走与回溯任务以考察空间定向能力的地域差异;实验2进一步采用基于空间参照转换灵活性的定向接近任务以澄清该差异产生的原因;实验3通过在任务前激活环境中心参照,提高转换灵活性以改善南方被试大尺度空间定向能力。结果发现,大尺度空间定向能力存在地域差异,北方被试更擅长环境中心参照的任务,南方被试的自我中心参照在任务中有更大优势作用;说明该地域差异除与个体空间参照使用偏好有关之外,还与其空间参照转换灵活性有关;而当南方被试环境中心参照被激活,任务绩效显著提升。

智能航保体系构架与关键技术研究

智能航保作为智能航运五大要素之一,是航运数字化转型的重要环节,需构建标准化航海保障基础设施和信息服务体系,以适应智能化水上交通动态管控需求。对国内外智能航保发展现状进行分析,从数据中心、服务平台和场景应用等方面提出智能航保体系架构;对智能航保建设关键技术进行探讨,包括6个基础技术和3大前瞻技术;以智能海事监管和智能港口服务作为案例分析智能航保的典型服务模式与作用。结果表明:智能航保是一个以应用需求为导向、以数据为基础的航海保障数字化、智能化转型的发展体系。该研究能为我国智能航保建设提供技术支持。

基于马氏距离的极区容错联邦滤波算法

针对舰船组合导航系统受极区极端恶劣环境影响发生外部量测故障从而降低系统精度的问题,提出基于马氏距离的极区容错联邦滤波算法。通过引入真实量测与预测量测之间的马氏距离来衡量各个子滤波器的量测质量,并通过马氏距离来构建各个子滤波器在主滤波器最优融合中对应的融合系数,降低故障子滤波器在最优融合中的比例,减少故障子滤波器对全局估计的不良影响。实验仿真表明,该算法相较于传统的联邦滤波算法,尤其在子滤波器量测故障情况下,具有更好的容错性和可靠性。

不同术式治疗基底节区高血压脑出血的近期疗效观察

目的探讨不同术式对基底节区高血压脑出血(HICH)患者围术期指标、血清神经特异性烯醇化酶(NSE)、前白蛋白(PA)水平、神经功能及术后并发症的影响。方法纳入南京市溧水区人民医院2021年1月至2023年1月收治入院并接受手术治疗的83例基底节区HICH患者资料,其中43例患者接受导航辅助神经内镜硬通道微创治疗(内镜组),余40例接受小骨窗开颅血肿清除术治疗(开颅组)。对两组围术期指标、手术前后的血清NSE、PA水平、美国国立卫生院卒中量表(NIHSS)评分及术后并发症进行统计分析。结果与开颅组相比,内镜组手术时间较长,出血量较少,血肿清除率较高,ICU入住时间较短,差异有统计学意义(t=8.504、8.332、10.222、9.180,P<0.05)。与术前相比,两组术后7 d血清NSE、NIHSS评分明显降低(t=28.137、19.333、30.472、16.683,P<0.05),且内镜组术后7 d的血清NSE及NIHSS评分明显低于对照组,差异有统计学意义(t=3.775、10.113,P<0.05)。与术前相比,两组术后7 d血清PA明显升高(t=-13.077、-9.189,P<0.05),且内镜组术后7 d的血清PA明显高于开颅组,差异有统计学意义(t=3.541,P<0.05)。内镜组术后并发症总发生率为9.30%,较开颅组的30.00%更低,差异有统计学意义(χ^(2)=5.705,P<0.05)。结论导航辅助神经内镜硬通道微创血肿清除术治疗基底节区HICH具有微创、高效、术后神经功能恢复好、并发症少特点,相比小骨窗开颅血肿清除术更具有优势。

New Regional Satellite Positioning Constellation Scheme Discussion

The characteristics of present “Beidou” satellite positioning system are analyzed. In order to perfect our country regional satellite positioning system, the idea of “Beidou” geosychronous earth orbit （GEO） satellites combined with some middle earth orbit （MEO） satellites constellation is put forward. The details of general satellite constellation optimized method are described, using this method the multiple positioning constellation design results are gained. And those results belong to two type of sehems, one is 2 GEO plus some MEO satellites and the other is 3 GEO plus some MEO satellites. Through simulation and comparison, among those multiple design results, final optimized regional positioning constellation is given. In order to check the chosen constellation cover performance, the position dilution of preeision（PDOP） is calculated, and with ,satellite constellation simulation software Satlab many coverage performances of the chosen constellation substellar point track, elevation, azimuth and visible satellites number changing situation are also simulated.

基于二阶SiamRPN多重交并比回归的无人机视觉导航

针对无人机视觉导航中实时图像目标物体尺寸小、干扰物多、存在运动模糊,导致识别与定位性能差的问题,提出了一种基于二阶SiamRPN多重交并比(Multiple Intersection over Union, MIoU)回归网络的一阶段算法。在孪生卷积神经网络(Convolutional Neural Network, CNN)框架中引入归一化协方差增加二阶信息,提升网络对边缘的特征提取;使用区域建议模块对匹配位置进行分类和锚定,并在网络优化过程中提出MIoU损失函数,从而精确地实现端到端的特征提取与匹配过程。在旋翼型无人机搭建平台进行实验验证,结果表明该算法可以稳健地进行目标定位。

极地船舶冰区航行中冰激结构疲劳的累积损伤分析

极地船舶在冰区航行中经常与各种类型的海冰发生不同程度的碰撞,充足的疲劳强度储备至关重要。本文提出了基于实测冰载荷的极地船舶结构冰激疲劳的累积损伤分析方法。以“雪龙”号极地考察船为研究对象,通过对我国第8次北极科学考察中的冰厚和航速等现场测量数据进行统计分析,在冰厚0.5~2.5 m、航速2~12 kn范围内构造冰激疲劳工况,并将二者的联合概率分布作为疲劳工况的发生概率;基于支持向量机方法反演识别出典型工况下的冰载荷时程,通过动力学分析确定关键位置及相应的热点应力,并采用雨流计数法统计应力循环次数;最后通过S-N曲线和Miner线性累积损伤理论进一步计算该航次内的疲劳损伤度,验证了“雪龙”号在冰区航行的安全性。本文对极地船舶结构的抗冰设计和安全评估具有一定的参考意义。

终端区进场航空器管制效率量化分析

终端区航空器的飞行密度和复杂度较高,此管制区域的处理能力是制约航空体系效率的瓶颈,对进场航空器管制效率进行量化研究,有助于提高管制工作处理能力和质量。首先,提出以区域导航(RNAV,regional area navigation)标准仪表进场程序的标称里程为计算基准量化进场管制效率,通过随机搜索聚类算法的结果得到航空器使用的RNAV标准仪表进场程序,选用在北京首都国际机场着陆的航空器为分析对象,计算航空器的进场管制效率,结合航迹讨论不同RNAV标准仪表进场程序下航空器的运行方式及特点。其次,对进场管制效率的影响因素进行分析,并采用灰色关联分析法量化各影响因素的影响程度与权重,结果显示:雷达引导度和航行三要素改变次数对进场管制效率具有显著影响,飞行流量和RNAV标准仪表进场程序的标称里程对进场管制效率的影响相对较小。继而,从影响因素角度出发评估整体进场管制效率,得到更为全面客观的整体进场管制效率。最后,尝试从RNAV进场程序路径以及优良管制行为模式两方面寻求进场管制效率的提升途径和方法。

机载无线电导航技术发展趋势简述

以新航行系统(CNS/ATM系统)规划发展需求牵引,阐述了机载无线电导航技术区域导航、所需导航性能、基于性能的导航等技术发展趋势,并以基于卫星导航的精密进近为例阐释机载无线电导航领域当前关键技术专题,以此为相关机载导航系统的研制提供借鉴。

基于区域生长顺序聚类-RANSAC的水稻苗带中心线检测

为提高水稻苗带中心线检测的适应性和实时性,满足巡田机器人导航的低成本、轻量级计算、高实时性需求,针对水稻苗带中心线检测结果容易受到光照变化和机器震动等原因产生图像噪声影响的问题,该研究以返青期和分蘖初期水稻秧苗为研究对象,提出基于区域生长顺序聚类-随机抽样一致性算法(random sample consensus,RANSAC)的水稻苗带中心线检测方法。首先,对采集的水稻秧苗图像运用归一化超绿特征法(excess green,ExG)和最大类间方差法(Otsu)分割水田背景和秧苗区域,应用先腐蚀后开运算的形态学方法去除秧苗图像噪声点;然后,采用基于水平带的秧苗轮廓质心检测方法提取秧苗特征点,利用区域生长顺序聚类方法将同一秧苗行的特征点聚成一类;最后,通过RANSAC算法拟合苗带中心线,从而得到巡田机器人视觉导航基准线。试验结果表明:该方法对返青期和分蘖初期水稻苗带中心线检测率均在97%以上,比已有YOLOv3算法提高6.12个百分点,比基于区域生长均值漂移聚类算法降低2.41个百分点;平均误差角度为2.34°,比已有YOLOv3算法高1.37°,比基于区域生长均值漂移聚类算法低0.12°,平均每帧图像检测时间为15.53 ms,比已有YOLOv3算法缩短81.19%,比基于区域生长均值漂移聚类算法缩短82.74%,本文方法在保证检测精度的基础上,大幅提升了检测速度,具有良好的适应性和实时性。研究结果可为巡田机器人视觉导航提供参考。

术中导航漂移校准技术对Lenke 1型青少年特发性脊柱侧凸顶椎区置钉精度的影响

目的:研究Lenke 1型青少年特发性脊柱侧凸(Adolescent idiopathic scoliosis,AIS)顶椎区在术中导航漂移校准技术辅助下置钉的精确性及偏出方向,并分析影响导航置钉偏移的相关因素及导航漂移校准技术的临床意义。方法:分析2017年~2020年行三维矫形术的Lenke 1型AIS患者60例,其中导航辅助置钉30例(导航组),术中导航漂移校准技术辅助置钉30例(导航校准组)。收集两组患者的基本信息和影像学资料,根据付长峰椎弓根分型系统对两组患者顶椎区椎弓根分型,并依据Rao分型评估两组间置钉的精确性。结果:两组间共置入600枚螺钉,导航组297枚,导航校准组303枚。导航校准组A、B、C型椎弓根0级椎弓根螺钉置钉率分别为95.7%、86.7%与68.9%,显著高于导航组的73.9%、66.9%与30.0%,两组间差异均具有统计学意义(P<0.05)。此外,导航校准组A、B、C、D型椎弓根螺钉穿破内侧皮质率分别为0%、1.6%、1.6%与0%,低于导航组的16.3%、16.9%、30.0%与47.6%。同时,在顶椎区凹侧导航校准组A、B、C、D型椎弓根置入螺钉穿破内侧皮质率为0%、3.6%、2.6%与0%,显著低于导航组的34.4%、25.9%、37.2%与60%,两组间差异具有统计学意义(P<0.05)。两组间均未发生脊髓、神经血管损伤等严重并发症。结论:与单纯导航相比,术中导航漂移校准技术可提高重度Lenke 1型AIS顶椎区置钉精度,降低内侧皮质穿破率,减少凹侧椎弓根误置率,增加重度AIS患者顶椎区置钉安全性。

基于北斗三号区域短报文通信的滑坡灾害监测数据传输方案设计

稳定的有线/无线通信链路是北斗/GNSS-RTK技术应用于滑坡灾害监测的必要条件,当监测区域地面通信基础设施缺失或突发险情引起通信链路中断时,滑坡监测工作难以开展。针对于此,研究并分析了北斗三号区域短报文通信(regional short message communication,RSMC)技术应用于滑坡灾害监测的可行性。首先设计了一种基于北斗三号RSMC的GNSS观测数据编码方法,在此基础上分析了基准站与流动站观测数据的不同传输方案对滑坡灾害监测的影响。最后对其中两种可行性较高方案的通信指标与定位效果进行了评估,结果表明,基准站采用4G、监测站采用北斗三号RSMC的第一种传输方案,平均解算时延优于1.1 s,传输成功率可达98.46%,实时监测序列精度在水平方向优于1cm,高程方向可达厘米级水平。该方案保持了监测序列的高频率高精度实时获取,同时提升了地面通信受限时监测信息的可用性。

不同GNSS在高纬度地区时间传递性能分析

全球卫星导航系统(GNSS)载波相位时间传递技术是高精度时间传递领域的主要研究方法之一,但目前关于该部分的研究主要集中在中低纬度地区,在高纬度地区并不多见。不同GNSS由于星座设计不同,在高纬度地区结构差异较大,因此需要对不同GNSS在高纬度地区的时间传递性能进行分析。实验结果表明,在高纬度地区时间传递中,Galileo稳定度最高,GPS和BDS次之,GLONASS最差。同时因在高纬度地区卫星的高度角普遍偏低,为合理平衡低高度角时可视卫星多和多路径误差大的矛盾,对不同截止高度角下获取的链路时间传递性能进行了分析。结果表明,在5°截止高度角下,高纬度地区的时间传递链路稳定性最好。

不同模式下BDS动态PPP精度分析

针对接收机可能存在解码差异,导致北斗卫星导航(区域)系统(BDS-2)与北斗三号全球卫星导航系统(BDS-3)间存在系统偏差(ISB)的问题,分析不同模式下北斗卫星导航系统(BDS)动态精密单点定位(PPP)精度:通过2种组合4种ISB处理场景下的BDS动态PPP实验,给出分析结果。结果表明,B1I/B3I信号可见卫星数和位置精度因子(PDOP)均最优,B1C/B2a和L1/L2信号可见卫星数和PDOP均相当;在无电离层组合模式下,大多数测站采用白噪声ISB估计更易加速收敛,与不估计ISB相比,在东(E)、北(N)、天(U)方向的收敛时间分别提升了-0.47%、3.18%和0.94%,收敛精度分别为1.90、1.70、5.44 cm;与无电离层组合模式相比,非差非组合受不同ISB估计的影响差异更大,因此,在使用非差非组合时,一定要选择合适的ISB估计策略;B1C/B2a组合在BDS-2服务范围外,表现出更好的动态PPP定位性能。

Novel method for the visual navigation path detection of jujube harvester autopilot based on image processing

To realize automatic harvesting of the jujube,the jujube harvester was designed and manufactured.For achieving the jujube harvester autopilot,a novel algorithm for visual navigation path detection was proposed.The centerline of tree row lines was taken as the navigation path.The method included four main parts:image preprocessing,image segmentation,tree row lines access,and navigation path access.The methods of threshold segmentation,noise removal,and border smoothing were utilized on the image in Lab color space for the image segmentation.The least square method was employed to fit the tree row lines,and the centerline was obtained as the navigation path.Experimental results indicated that the average false detection rate was 3.98%,and the average detection speed was 41 fps.The algorithm meets the requirements of the jujube harvester autopilot in terms of accuracy and speed.It also can lay the foundation for accomplishing the jujube harvester vision-based autopilot.