基于无人机正射影像的玉龙雪山白水河1号冰川末端冰裂隙提取

冰川是冰冻圈的重要部分,对局地乃至全球气候变化响应敏感。冰裂隙作为冰川表面上显著的特征,对于认识冰川的状态、稳定性以及内部应力有着重要的作用。针对冰川冰裂隙高精度快速识别提取问题,本文以玉龙雪山白水河1号冰川为研究对象,使用无人机航拍获取的0.12 m分辨率的正射影像,应用U-Net深度学习网络开展白水河1号冰川的冰裂隙的智能提取研究。使用U-Net网络提取冰裂隙的精度高于传统的Canny算子以及SVM算法,总体精度可高达93%,且U-Net网络泛化能力强。提取结果表明,白水河1号冰川冰裂隙主要为横向裂隙,伸展裂隙以及雁行裂隙,呈现随海拔降低,冰裂隙逐渐由横向裂隙变化为伸展裂隙的趋势,通过不同时期提取结果对比,发现冰裂隙数量和平均长度均有增加。基于无人机影像和深度学习方法的冰裂隙智能提取研究,可为监测冰川变化及其与气候变化的关系提供技术支撑。

GPR Surveying in the kernel area of Grove Mountains,Antarctica

The Grove Mountains, located between the Zhongshan Station and Dome A, are a very important area in inland Antarctic research. China has organized ifve investigations of the Grove Mountains, encompassing the geological structure, ancient climate, meteorites, ice-movement monitoring, basic mapping, meteorological observations, and other multi-disciplinary observational studies. During the 26th Chinese National Antarctic Research Expedition in 2010, the Grove Mountains investigation team applied specialized ground-penetrating radar （GPR） to survey subglacial topography in the eastern kernel area of the Grove Mountains. In this paper, we processed GPS and GPR data gathered in the ifeld and drew, for the ifrst time, two subglacial topographic maps of the Grove Mountains kernel area using professional graphics software. The preliminary results reveal the mystery of the nunatak landform of this area, give an exploratory sense of the real bedrock landforms, and indicate a possible sedimentary basin under the Pliocene epoch fossil ice in the Grove Mountains area. Additionally, it has been proven from cross-sectional analysis between Mount Harding and the Zakharoff ridge that the box-valley shape between two nunataks has already matured.

Ice thickness distribution and volume estimation of Burqin Glacier No.18 in the Chinese Altay Mountains

Information on the thickness distribution and volume of glacier ice is highly important for glaciological applications;however,detailed measurements of the ice thickness of many glaciers in the Chinese Altay Mountains remain lacking.Burqin Glacier No.18 is a northeast-orientated cirque glacier located on the southern side of the Altay Mountains.This study used PulseEKKO®PRO 100A enhancement ground-penetrating radar(GPR)to survey the ice thickness and volume of Burqin Glacier No.18 in summer 2018.Together with GPR surveying,spatial distributed profiles of the GPR measurements were concurrently surveyed using the real-time kinematic(RTK)global navigation satellite system(GNSS,Unistrong E650).Besides,we used QuickBird,WorldView-2,and Landsat TM to delineate accurate boundary of the glacier for undertaking estimation of glacier ice volume.GPR measurements revealed that the basal topography of profile B1-B2 was flat,the basal topography of profile C1-C2 presented a V-type form,and the basal topography of profile D1-D2 had a typical U-type topographic feature because the bedrock near the central elevation of the glacier was relatively flat.The longitudinal profile A1-A2 showed a ladder-like distribution.Glacier ice was thin at the terminus and its thickness increased gradually from the elevation of approximately 2620 m a.s.l.along the main axis of the glacier tongue with an average value of 80(±1)m.The average ice thickness of the glacier was determined as 27(±2)m and its total ice volume was estimated at 0.031(±0.002)km3.Interpretation of remote sensing images indicated that during 1989–2016,the glacier area reduced from 1.30 to 1.17 km2(reduction of 0.37%/a)and the glacier terminus retreated at the rate of 8.48 m/a.The mean ice thickness of Burqin Glacier No.18 was less than that of the majority of other observed glaciers in China,especially those in the Qilian Mountains and Central Chinese Tianshan Mountains;this is probably attributable to differences in glacier type and climatic setting.

基于GIS栅格操作方法模拟山地冰川长期变化

地理信息系统(Geographical Information System,GIS)具有强大的空间分析功能。GIS方法建立的模型,可以模拟北极多温冰川Austre Lovénbreen的长时间序列变化。研究发现,GIS方法可以快速有效地获取冰川的冰厚、主流线长度、冰川表面积和冰川体积,其中冰川体积的变化符合高次常函数变化规律;通过对比GIS方法与Elmer/Ice动力学方法模拟的结果,GIS方法对冰川体积的模拟,在十年至几十年的尺度上可行。GIS方法模拟冰川变化,可以快速定量分析冰川未来一定年限内的厚度、面积、体积、主流线长度等几何参数,简化了冰川变化分析研究的过程。

基于3D打印的骨盆肿瘤“三位一体”个性化治疗模式专家共识

骨盆邻近区域解剖复杂,有消化、泌尿、生殖等脏器及重要血管和神经,因此,骨盆肿瘤精准切除及切除后骨缺损精准重建极为困难。医学3D打印技术的发展为骨盆肿瘤的精准切除和个性化重建提供了新思路。3D打印个性化病变模型、截骨导板和重建假体"三位一体"在骨盆肿瘤切除与保肢重建中的应用,取得了良好的临床效果。但目前缺乏针对3D打印个性化骨盆肿瘤模型、截骨导板和重建假体设计、制备流程及应用的规范性指导标准,制约了其推广应用。本共识的制定旨在为基于3D打印的"三位一体"个性化治疗模式在骨盆肿瘤保肢重建中的应用提供规范性指导。

极地雷达冰川学:前沿技术与方法

雷达冰川学是通过冰雷达(也称无线电回波、探冰雷达、穿冰雷达等)探测,测绘极地冰盖冰厚、冰下地形、冰盖内部冰层(等时层)分布及其扰动等,进而研究冰盖底部环境和过程、冰层年代、冰流运动和冰盖动力学的一门年轻的学科,能够用于推断冰盖演化和气候变化,评估冰盖稳定性、物质平衡和对海平面上升的影响。20世纪50年代,无线电回波在冰内的强穿透性被首次发现,直接推动了冰雷达探测技术的发展。此后,冰雷达被广泛用于南北极冰盖的观测和研究。1983年,Bogorodsky等人出版了名为《Radioglaciology》的专著,系统阐释了雷达冰川学的概念、原理和观测研究进展。2014年和2019年,国际冰川学会(IGS)以Radioglaciology为主题,分别在美国堪萨斯大学和斯坦福大学组织了两次大型的雷达冰川学学术研讨会,进一步推动了雷达冰川学学科的发展。

东南极达尔克冰川现场定位观测误差分析

中国南极考察队从2007年开始对达尔克冰川进行现场监测工作,在冰面上投设监测花杆并用前方交会的方法持续对花杆进行精确定位,用于冰川运动监测。2007-2012年,中国南极考察队员在东南极达尔克冰川上共计开展了18个批次的现场测量工作,经分析得到了67个高精度的空间交会点坐标,分属于10个独立的观测标志。为精化计算模型必须对实测数据仔细甄别,因此,同时考虑了仪器的归零差、地球曲率误差、大气折光误差等交会定位的主要误差来源,比较了3种因素对精确定位的影响,结果表明:地球曲率对精确定位的影响最大,其次是归零差,最后是大气折光引起的误差。对交会定位中各种误差的分析有利于改进同类工作中计算模型的选择,为冰川运动监测提供高精度的数据支撑。

北斗三号系统在环南极地区的信号质量与基本定位服务性能分析

随着北斗三号卫星定位系统(BDS-3)的逐步建成,北斗系统的服务范围已从亚太地区扩展到全球,而极地具有重要的科研、航运等价值,因此北斗三号在环南极地区的定位性能需要进行全面评估。利用在中山站、长城站以及环南极航行的"雪龙"号上采集的2018—2020年的北斗三号数据,本文从可见卫星数及位置精度因子、多径值与信噪比、伪距单点定位精度等方面,分析了BDS在环南极地区的信号质量和定位性能。结果表明:BDS在环南极地区可见卫星数均介于4~20颗之间,其卫星可见性及位置精度因子优于GPS;BDS的中轨道地球卫星(MEO)多径值与GPS卫星相当,而BDS的地球同步轨道卫星(GEO)和倾斜地球同步轨道卫星(IGSO)由于在极区的高度角较低,多径值较大;在定位精度方面,环南极地区的BDS伪距单点定位精度在7 m以内,满足北斗系统的设计要求。尽管北斗三号系统还在逐步完善之中,但已经解决了高纬度地区卫星可见数较少的问题,明显提升了定位精度,其中长城站2020年初的定位精度相对于2019年初已经提升50%。

基于RTK-GPS的北极Austre Lovénbreen冰川表面高程变化研究

基于多期RTK-GPS(Real Time Kinematic-Global Position System)高精度测量数据,通过冰面高程变化开展北极Austre Lovénbreen冰川物质变化研究。首先基于冰面GPS测点开展多种空间插值方法的比对,兼顾冰面DEM(Digital Elevation Model)的平滑特性以及插值结果的准确性,优选自然邻域法作为冰面地形的插值算法;继而利用2013—2015年3期RTK-GPS数据,通过冰面地形内插和测线交叉点比对两种方式开展了Austre Lovénbreen冰川表面高程变化的分析,结果表明交叉点方法的精度更高,而地形内插法在测线之间的空白区域存在较大误差。最后通过冰雪密度估计将高程变化转化为水当量,计算相应时段的冰川物质平衡:积累区密度取500 kg·m^-3,消融区密度取900 kg·m^-3,得到2013—2014年和2014—2015年的物质平衡分别为–0.277m w.e.和0.065m w.e.。该物质平衡结果相较于传统的冰面物质平衡而言存在一定的差异,主要源于测量时段的不一致,以及可能存在的冰川内部物质变化。此外,将RTK-GPS交叉点高程的年际变化与所在高程进行联合分析,发现冰川物质变化与冰川高程分布既有较强的相关性,部分区域也存在一些差异。总体而言,冰川物质年变化的海拔梯度为2.67‰,在海拔越低的区域冰川消融得越快,随海拔上升消融减慢,在高海拔或冰川边缘区域还存在少量物质积累。

中国极地冰盖数值模拟研究进展

冰盖数值模拟是一种基于多源观测数据,通过构建并求解冰流动力学方程组,理解冰流运动物理机制以及诊断和预估其演化过程的方法,目前已被广泛应用于冰盖变化研究。本文简要介绍了极地冰盖数值模拟方法,归纳综述了近十余年我国学者在极地冰盖数值模拟方面的研究进展,厘清我国在冰盖数值模拟领域遇到的瓶颈和关键问题。阐述了如何与我国的极地冰盖科考优势区域深度结合,协同多源强化观测和数值模拟,研发和改进冰盖模式,提高冰盖模拟能力,对定量估算极地冰盖的物质平衡及其对未来海平面上升的影响做出实质贡献。通过逐步发展冰盖模式的研究能力,有望将来在冰盖关键动力过程和机制的科学认识上有所突破。

基于REMA数据的东南极达尔克冰川表面塌陷研究

全球气候变暖严重影响冰川的稳定性,南极多条冰川表面发生塌陷。由于缺少高空间和高时间分辨率的南极地表高程模型DEM(Digital Elevation Model),目前单支冰川表面时空变化的研究不充分。利用2011年—2016年11期南极参考高程模型REMA(The Reference Elevation Model of Antarctica)数据,开展东南极达尔克冰川表面塌陷区域的高程变化监测,并利用Landsat 7/8和Worldview-2光学影像等数据分析塌陷过程和原因。结果表明,达尔克冰川在2013年发生了一起严重的塌陷事件,塌陷深度最大约45.29 m,造成了约26.29×10^(6)m^(3)的水体损失;塌陷发生后,该区表面高程不断增加,于2016年恢复至塌陷前的高程。塌陷区具有明显的整体性沉降特征,并存在融水聚集,推测塌陷和达尔克冰川冰下湖的排水过程存在密切的联系。本研究证明达尔克冰川存在较大的不稳定性,同时验证了REMA数据监测冰川表面塌陷的可行性,为未来精细化监测南极冰盖/冰架响应气候变化提供技术参考。

我国东南沿海风暴潮灾害时空分布规律及可视化研究

中国是风暴潮灾害发生频率最高、损失最严重的国家之一,多年来,风暴潮灾害给我国东南沿海造成了巨大的经济损失和严重的人员伤亡。本研究整理了我国东南沿海1989—2018年的风暴潮灾害数据,对风暴潮灾害的时空分布规律进行了研究和分析。我国东海、南海沿岸受台风风暴潮灾害侵袭频次最高,渤海、黄海沿岸温带风暴潮灾害较为频繁,浙江、福建、广东三省受灾最严重。随着年代变化,在灾害频次总体上升的情况下,大灾减少,小灾增多,灾害损失整体上有所减少。研究结果表明,近年来我国风暴潮减灾防灾成效明显,目前的灾害时空分布格局可以进一步从宏观层面指导风暴潮灾害应对工作。

中国历次极地考察航线及破冰船航行特征分析(1984-2019)

1984-2019年,中国共有7艘考察船38次远赴南北两极开展科学考察活动,其中南极29航次,北极9航次,累计航程160万km。重点分析了"雪龙"号破冰船的航行特征参数,并结合GPS、机舱、罗经等多源数据,建立了破冰船航行状态分类识别模型,进而研发了破冰船的经停港口和停靠极地站点的识别模型。运用该模型对以往极地考察航次中考察船的经停港口和停靠极地站点进行识别和统计,累计经停了14个国家的32个港口,累计停靠了11个国家的18个极地考察站。探究了考察航线的空间分布规律和考察船的往返路线选择情况,并总结了南极考察船穿越西风带的航迹规律。最后利用分析结果,总结出中国南极科考4个阶段的特征,为未来南极科考提供参考建议。

旋髂浅动脉穿支皮瓣修复颊-咽-腭缺损的临床应用

目的 探讨旋髂浅动脉穿支皮瓣修复磨牙后区咽旁鳞状细胞癌根治术后颊部-咽旁-腭部复合性缺损的临床效果.方法 2014年1月至2017年1月,应用旋髂浅动脉穿支皮瓣修复8例咽旁鳞状细胞癌根治术后颊部-咽旁-腭部复合性缺损,所有患者术前均进行CT血管造影及彩色多普勒超声检查.根据受区缺损大小,以影像学定位的穿支血管为中心,仔细制备皮瓣并转移至颊部-咽旁-腭部复合性缺损处,显微镜下成功吻合动静脉后严密缝合受区及供区,术后观察皮瓣的存活及功能恢复情况.结果 旋髂浅动脉穿支皮瓣面积5 cm×6 cm -7 cm×9 cm,动脉平均管径0.65 mm,静脉平均管径1.2 mm,动静脉血管蒂平均长度分别为7.1 cm和8.1 cm,8例皮瓣全部成活,术后颊部-咽旁-腭部形态良好,张口度正常.结论 旋髂浅动脉穿支皮瓣质地柔软,穿支血管蒂较长,供区瘢痕隐蔽,是修复磨牙后区咽旁鳞癌术后缺损的良好选择.

基于Argo浮标数据的水文特征三维可视化分析——以南大洋印度洋扇区为例

利用南大洋2009—2020年的Argo浮标温盐剖面数据,通过绘制温度和盐度空间分布图的定性分析以及三维聚类可视化分析等方法,揭示了南大洋印度洋扇区的多水团空间分布特征。结果表明,在60°S~67°S,60°E~80°E之间的海域,海水温度在-1.9~2.5℃之间,盐度在32~34.75 psu之间。整个研究区域海水温度随深度分布均呈现明显的跃层结构,在高纬度区域冷水团厚度较大,随着纬度降低,冷水团的厚度逐渐减小。在100 m层,63°S~65°S的纬度带存在明显的温度锋面,区域内海水温度比南北两侧温度高。在100 m、200 m和500 m层,63°S~65°S的纬度带存在盐度锋面,在该锋面海水盐度达到极大值。根据位于南大洋印度洋扇区普里兹湾区域附近的水团的划分方法,在研究区域内0~2000 m的深度存在南极夏季表层水、冬季水、绕极深层水等水团。根据聚类结果,在63°S以北的表层水区域以下还存在一个盐度和温度较高的水团。

无症状人群与发育性髋关节发育不良人群髋臼三维朝向的半自动测量与对比分析

目的比较分析无症状人群与发育性髋关节发育不良(developmental dysplasia of the hip,DDH)人群的髋臼三维朝向,为髋部疾病的鉴别诊断、手术规划、植入器械设计及术后评估等提供数据参考。方法回顾性收集符合选择标准的无症状人群骨盆CT 84例(无症状组)和DDH患者骨盆CT 47例(DDH组)。两组人群性别构成及年龄(包括男女亚组年龄)比较差异均无统计学意义(P>0.05)。使用半自动测量软件MaxTHA测量3种定义下的前倾角和外展角,包括手术学外展角(operative inclination,OI)、影像学外展角(radiographic inclination,RI)、解剖学外展角(anatomic inclination,AI)、手术学前倾角(operative anteversion,OA)、影像学前倾角(radiographic anteversion,RA)和解剖学前倾角(anatomic anteversion,AA),并进行两人群间、不同Crowe分型亚组间、各性别亚组间及左右侧间的比较。结果无症状组与DDH组健、患侧间比较显示,无症状组与DDH组健侧的髋臼朝向各角度参数差异均无统计学意义(P>0.05);DDH组患侧的OI、RI、AI显著大于健侧和无症状组,AA显著小于健侧和无症状组,差异有统计学意义(P<0.05)。正常髋臼与DDH组不同Crowe分型组间比较显示,CroweⅠ型组与正常组髋臼朝向各角度参数比较差异均无统计学意义(P>0.05);CroweⅡ、Ⅲ、Ⅳ型组OI、RI、AI显著大于正常组,CroweⅢ型组的OI、Ⅳ型组的RI和AI显著大于Ⅰ型组,Ⅳ型组的AI显著大于Ⅱ型组(P<0.05);CroweⅢ型组OA、RA、AA显著小于除Ⅰ型组外的各组(P<0.05)。无症状组女性的OA、RA、AA以及DDH组女性的OA、AI显著大于对应组男性,差异有统计学意义(P<0.05)。无症状组男性右侧髋臼的OI、RI、AI、OA以及女性右侧髋臼的RI、AI均显著大于左侧,差异有统计学意义(P<0.05)。结论髋臼朝向在无症状人群和DDH人群间存在人群差异,在不同Crowe分型亚组间存在组间差异,在各人群亚组内存在性别间差异,在无症状人群中存在双侧差异。

Mass change study on Arctic glacier Pedersenbreen, during 1936-1990-2009

Pedersenbreen is a small polythermal valley glacier, located in Svalbard, which has been one of the two glaciers monitored by Chinese Arctic expedition members since 2004. This study estimates its area and volume and analyzes its change during 1936-1990-2009, using field collected GPS/GPR data in 2009 and historical topographic maps published by the Norwegian Polar Institute. We have found that Pedersenbreen is just like many other valley glaciers in Svalbard, having experienced a significant recession since the end of Little Ice Age in the early 20th century. The glacier tongue has retreated more than 0.6 km, while ice volume has decreased by approximately 13%. The overall thinning rate of Pedersenbreen has shown acceleration during the recent decades. Further analysis shows that the ice tongue in the downstream area of Pedersenbreen is melting at the highest rate, while a simultaneous accumulation occurred in the upstream. However, as global temperatures increase, the accumulation area is reducing year by year.

Sea ice concentration over the Antarctic Ocean from satellite pulse altimetry

Sea ice concentration (SIC) is an important parameter in characterizing sea ice. Limited by the environment and the spatial extent of observation, it is difficult for field work to meet the needs of a large-scale SIC study. However, with its many advantages, such as the ability to make large-scale, high-resolution and long-duration observations, the altimeter can be used to determine SIC on a large scale. Using the correspondence between the satellite pulse altimeter waveform and reflector property, waveform classification is employed. Moreover, this paper develops an algorithm to obtain the SIC from altimeter waveforms. In an actual computation, Pyrz Bay in the Antarctic is taken as an experimental region, and one-year and seasonal SICs are derived from ERS-1/GM waveforms over this study area. Furthermore, altimetric SICs are compared with those of SSMR SSM/I. The results show that the spatial distribution and the regions of maximum SIC determined employing these two methods are consistent. This demonstrates that altimeter data can be used to monitor sea ice.

3D-Printed Porous Titanium Augments for Reconstruction of Massive Bone Defect in Complex Revision Total Knee Arthroplasty:Implant Design and Surgical Technique

Reconstruction of severe bone defects in revision total knee arthroplasty(TKA)remains a challenge for orthopaedists.The progression of medical imaging and additive manufacturing technology has enabled the rapid manufacture of custom-made implants,and 3D-printed augments with interconnected pore structures have become an alternative approach for the reconstruction of bone defects in revision TKA,especially in patients with complex bone defects.The size and location of the bone defect were determined by thin-layer computed tomography(CT;layer thickness is 1 mm)after reduction of artifacts.The 3D reconstruction models of the host bone were obtained based on thin-layer CT imaging.The custom-made augmentation was designed according to the 3D reconstruction bone model.The augmentation had an interconnected porous structure on the bone-implant interface to achieve biological fixation.After the design was complete,the 3D model of augment was exported in STL format,and augments were fabricated with Ti6Al4V powder using electron beam melting.Thin-layer CT and 3D reconstruction bone models are accurate methods for evaluating periprosthetic bone loss after artifact reduction.The 3D-printed augments perfectly match the bone defects during surgery.3D-printed augmentation is an effective approach for the reconstruction of bone defects in revision TKA.Thus,surgeons and engineers should carefully evaluate the bone defect during augment design to avoid a mismatch between the augment and host bone.

Review on Corrosion Characteristics of Porous Titanium Alloys Fabricated by Additive Manufacturing

Porous titanium and its alloys have been considered as promising implants owing to their low elastic modulus and capability to provide channels for bone growth.Currently,additive manufacturing(3D printing)techniques have been successfully applied to produce porous titanium alloys owing to the advantages of controllable and precise fabrication.Considering the safety aspect,an understanding of corrosion in porous titanium alloys and the corresponding mechanisms is important for their long-term application in the human body.In this paper,the recent progress in improving the corrosion properties of porous titanium alloys fabricated via 3D printing techniques is reviewed.The effects of pore type,porosity,electrolyte,and modification of the material on the corrosion properties of porous titanium alloys are introduced and discussed.In addition,the limitations of traditional methods for measuring the corrosion performance of porous titanium alloys were analysed.Perspectives for evaluating and improving the corrosion performance of porous titanium alloys using new methods are provided.