A method to interpret fracture aperture of rock slope using adaptive shape and unmanned aerial vehicle multi-angle nap-of-the-object photogrammetry

The aperture of natural rock fractures significantly affects the deformation and strength properties of rock masses,as well as the hydrodynamic properties of fractured rock masses.The conventional measurement methods are inadequate for collecting data on high-steep rock slopes in complex mountainous regions.This study establishes a high-resolution three-dimensional model of a rock slope using unmanned aerial vehicle(UAV)multi-angle nap-of-the-object photogrammetry to obtain edge feature points of fractures.Fracture opening morphology is characterized using coordinate projection and transformation.Fracture central axis is determined using vertical measuring lines,allowing for the interpretation of aperture of adaptive fracture shape.The feasibility and reliability of the new method are verified at a construction site of a railway in southeast Tibet,China.The study shows that the fracture aperture has a significant interval effect and size effect.The optimal sampling length for fractures is approximately 0.5e1 m,and the optimal aperture interpretation results can be achieved when the measuring line spacing is 1%of the sampling length.Tensile fractures in the study area generally have larger apertures than shear fractures,and their tendency to increase with slope height is also greater than that of shear fractures.The aperture of tensile fractures is generally positively correlated with their trace length,while the correlation between the aperture of shear fractures and their trace length appears to be weak.Fractures of different orientations exhibit certain differences in their distribution of aperture,but generally follow the forms of normal,log-normal,and gamma distributions.This study provides essential data support for rock and slope stability evaluation,which is of significant practical importance.

Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Main quadrupole magnets are critical for the Circular Electron and Positron Collider(CEPC)and are specifically designed as dual aperture quadrupole(DAQ)magnets.However,the field crosstalk between the two apertures presents challenges.As the CEPC will work at four beam energies of Z,W,Higgs and ttbar mode,the DAQ magnets will operate at four field gradients spanning from 3.18 to 12.63 T/m.The first short quadrupole magnet prototype with the bore diameter of 76 mm and magnetic length of 1.0 m revealed the problems of large magnetic field harmonics and a magnetic center shift within the beam energy range.Accordingly,a compensation method was proposed in this work to solve the field crosstalk effect.By adjusting the gap height at the middle of the two apertures,the field harmonics and magnetic center shift are significantly reduced.After optimization,the short prototype was modified using a new scheme.The field simulations are validated from the magnetic measurement results.Further,the multipole field meets the requirements of the four beam energies.The detailed magnetic field optimization,field harmonics adjustment,and measurement results are presented herein.

高功率微波大口径相控阵天线拍波辐射方法研究

相控阵天线是未来高功率微波辐射系统的重要形式之一,是当前研究的热点。为了获得超高等效全向辐射功率,高功率微波天线均为大口径形式。而大口径相控阵天线在辐射高功率微波拍波过程中,存在波束分裂、增益下降问题。针对该问题,本文提出了一种大口径相控阵天线拍波辐射结构,采用“子阵-面阵”两级馈电形式,解决了拍波辐射过程中波束分裂问题,有效提高了高功率微波系统的综合性能。该方法极大地节约了移相器数量,节省了系统成本,降低了系统复杂度,有利于实现高功率微波系统的小型化,提高系统的可靠性。

基于柔性铰链结构的大口径压电快摆镜

为了解决压电作动器驱动的快速反射镜因压电作动器伸长量较小,导致快速反射镜偏转角过小的问题,该文提出了一款新型快速反射镜设计方案。采用三级杠杆式柔性铰链放大机构实现压电作动器位移的放大,采用柔性轴承作为快摆镜的运动关节实现快摆镜的大角度定轴偏转。通过理论推导和有限元仿真对快摆镜的最大偏转角度、等效应力、谐振频率以及振型进行分析。实验结果表明,所设计的快摆镜可以实现大于2 mrad的镜面偏转,满足大范围、高精度的光束定位要求。

考虑速度聚束效应的SAR海浪成像仿真方法

针对合成孔径雷达(SAR)海浪成像仿真技术对于速度聚束效应的考虑不充分,仿真数据无法准确反映实际SAR数据的问题,建立一种充分考虑速度聚束效应的SAR海浪成像仿真方法并进行了实验验证。计算了SAR图像强度的概率密度分布的仿真结果与理论结果之间的均方误差(MSE),在风速分别为5、10和15 m/s时,考虑速度聚束效应前、后比对结果的MSE分别为0.1012、0.1576、0.0556与0.0179、0.0314、0.0088。仿真结果表明,所提SAR海浪成像仿真方法有效提高了仿真数据的准确性,对SAR海浪成像的应用具有一定实用价值。

太阳辐照度测量中孔径光阑衍射效应

针对当前在辐照度测量中对孔径光阑衍射效应的评估仍停留在理论计算层面,无法评估衍射修正结果不确定度的现状,研究了光阑衍射效应实验检测方法,以校正孔径光阑的衍射效应并提升太阳总辐照度的测量精度。基于暗场成像技术和夫琅和费远场衍射理论,设计孔径光阑的衍射效应检测方法,开展检测实验,通过研究探测器线性度标定、背景信号校正、衍射图像数据分析等,建立数据修正处理流程,获取孔径光阑在前结构的太阳绝对辐射计衍射效应值,并对实验结果进行不确定度分析。测试结果显示:衍射效应测量值为8.81×10^(-4),合成不确定度为6.49%。研究成果将为我国下一代风云气象卫星太阳辐射监测仪衍射效应的精确校正及实现高精度太阳总辐照度的测量奠定关键技术基础。

核电磁脉冲对计算机机箱的时频域电场耦合特性研究

为研究计算机机箱对核电磁脉冲的时域和频域耦合特性,采用基于时域有限积分法的电磁仿真软件,对计算机机箱采取不同孔缝形状、孔缝布局和机箱内不同位置的电场耦合规律进行了数值仿真。结果表明:机箱的电场屏蔽效能随频率的增加而下降,在谐振频率处达到最小值;同样孔缝面积时,机箱采用圆形孔缝、多圆孔阵列的瞬时电场屏蔽效能和各频点电场屏蔽效能均最优;机箱内的瞬时电场屏蔽效能和各频点屏蔽效能随着与孔缝距离的增大而提升,电场极化方向上的电场屏蔽效能提升缓慢,非极化方向上的电场屏蔽效能提升较快。对提升计算机机箱的屏蔽效能,优化内部电子器件与线路的合理布局提供参考。

星载InSAR方位向逐行的顺轨有效基线计算方法

本文开展了星载干涉合成孔径雷达(Interferometric synthetic aperture radar,InSAR)顺轨有效基线计算方法的改进研究。首先利用多项式拟合卫星轨道方程,使用相干系数法计算待配准图像对的像元偏移量,通过建立顺轨有效基线与方位向行号的函数关系式获得逐行有效基线,解决了在整幅图像使用固定有效基线带来的误差问题。通过TanDEM-X/TerraSAR-X实测干涉数据对本文的改进方法进行了应用和检验,同时针对所使用干涉图像对的特殊线性关系建立了快捷实用的线性方程。通过在整幅图像上精细化使用顺轨有效基线会对诸如海流反演方面有效提高反演精度。

一种宽带大孔径相控阵波控优化设计

针对用于电子对抗系统的大孔径相控阵列天线在瞬时带宽和实施成本间的矛盾,提出了一种波束控制网络优化设计。该设计在现有子阵级模拟延迟波控网络的基础上,采用剩余法和虚位技术,通过末端的小步进移相器波束控制器件,补偿前一级时延器件步进量引入的相位跳变,同时将时延网络分级处理,采用前级小步进时延器件补偿后级大步进时延器件的相位跳变,拟合形成与理论移相需求高吻合度的相位分布。在波束大角度扫描时兼有高指向精度、大瞬时带宽、低损耗、低成本等优点。

孔缝对电子设备机箱屏蔽效能影响的分析

电子设备机箱由于散热及外接其他设备等原因需要开有各种孔缝,从而导致其电磁屏蔽效能降低。采用时域有限差分(Finite Difference Time Domain,FDTD)算法仿真分析了不同开孔形状、开孔尺寸、开孔数量及开孔间距的孔缝对电子设备机箱屏蔽效能的影响,为电子设备机箱提高屏蔽效能工程设计提供依据,同时也为散热结构设计提供电磁兼容方面的参考。

单孔胸腔镜治疗支气管扩张症的效果研究

目的 研究单孔胸腔镜治疗支气管扩张症的效果。方法 选取2022年1月—2023年6月青岛市胶州中心医院胸外科收治的56例支气管扩张症患者为研究对象,遵照掷骰子法平均分为两组,各28例。对比组选用传统开胸手术治疗,治疗组选用单孔胸腔镜治疗。比较两组肺功能指标、症状评分、时间指标、治疗有效性、并发症发生率。结果 治疗后,治疗组各项肺功能指标高于对比组,差异有统计学意义(P均<0.05)。治疗组各项症状评分低于对比组,差异有统计学意义(P均<0.05)。治疗组各项时间指标短于对比组,差异有统计学意义(P均<0.05)。治疗组的治疗有效性为96.43%,高于对比组的75.00%,差异有统计学意义(χ^(2)=5.250,P<0.05)。治疗组的并发症发生率低于对比组,差异有统计学意义(P<0.05)。结论 执行单孔胸腔镜治疗,可以使支气管扩张症患者的肺功能得到改善,缓解咳嗽症状,同时,还可提高治疗有效性,减少并发症情况,缩短住院时间。

Angular extent effect of micromotion target in SAR image by polar format algorithm

Target micromotion not only plays an important role in target recognition but also leads to esoteric characteristics in synthetic aperture radar （SAR） imaging. This paper finds out an interesting phenomenon, i.e. the angular extent effect, in micro-motion target images formulated by the polar format algorithm. A micromotion target takes on multiple pairs of paired echoes （PEs） around the true point, and each PE extends for an angle which is exactly equal to the angular extent of the synthetic aperture, regardless of the micromotion frequency. The effect is derived and interpreted by using the characteristics of Bessel functions. Then it is demonstrated by simulation experiments of a target with different micromotion frequencies. The revelation and interpretation of the effect is highly beneficial to micromotion-target SAR image understanding as wel as target recognition.

Detection, Estimation and Compensation of Ionospheric Effect on SAR Interferogram Using Azimuth Shift

An increasing interest in the use of low frequency Synthetic Aperture Radar(SAR)systems,e.g.,L-and P-bands,makes the research of the ionospheric effects on SAR interferograms become urgent and significant.As the most pronounced signature in interferograms,the ionosphere-induced azimuth streak was thoroughly investigated in this study through processing of the 19 L-band Advanced Land-Observing Satellite(ALOS)Phased Array type L-band Synthetic Aperture Radar(PALSAR)images over the Chongqing City,China.The investigations show that the visible ionosphere-induced stripe-shape azimuth shifts with the invariable direction of 26°E,113°N are observed in some interferometric pairs.Relating these anomalous azimuth shifts to the International GNSS Service(IGS)final ionospheric products shows that the detected ionosphere-contaminated SAR images display the relatively large ionospheric variation with time during SAR satellite travelled through the study area,indicating a somewhat correlation between them.After detecting the ionosphere-contaminated interferograms,we estimated the Ionospheric Phase Streak(IPS)based on an approximate linear relationship between IPS and azimuth shift,and then removed them from the original interferograms.The corrected results show that ionospheric phase patterns are largely removed from the ionosphere-contaminated interferograms.The investigation indicates that the direction of the IPS keeps approximately constant in space and time,which provides the potential chance to develop methods to correct the ionospheric effect.Furthermore,this study once more proves that the ionospheric effect on SAR interferogram can be detected,estimated and corrected from azimuth shifts.

Beam-beam effects and mitigation in a future proton-proton collider

The beam-beam effects in a hadron collider with an unprecedented energy scale were studied.These effects are strongly related to the attainable luminosity of the collider.Long-range interactions were identified as the major factor limiting the dynamic aperture,which is strongly dependent on the crossing angle,β*,and bunch population.Different mitigation methods of the beam-beam effects were addressed,with a focus on the compensation of long-range interactions by electric curren wires.The CEPC-SPPC project is a two-stage large circular collider,with a first-stage circular electron-positron collider(CEPC)and a second-stage super proton-proton collider(SPPC).The design of the SPPC aims to achieve a center-of-mass energy of 75 TeV and peak luminosity of approximately 1×10^(35) cm^(-2)s^(-1).We studied the beam-beam effects in the SPPC and tested the effectiveness of the mitigation methods.We found that with compensation using electric current wires,the dynamic aperture is at an acceptable level.Moreover,considering the significant emittance damping in this future proton-proton collider the beam-beam effects and compensation are more complicated and are studied using long-term tracking.It was found that with a smaller emittance,the head-on interactions with a crossing angle become more prominent in reducing the beam stability,and combined head-on and long-range compensation is needed to improve the beam quality.When the reduction in population owing to burnoff was included,it was found that the coupling between the transverse and longitudinal planes at smaller emittance is the main driving source of the instabilities.Thus,crab cavities and emittance control are also necessary than just the compensation of the long-range interactions to improve the beam stability.This study serves as an example for studying the beam-beam effects in future proton-proton colliders.

WLS filter for reducing atmospheric effects in spaceborne SAR tomography

A new approach was presented to eliminate the atmosphere-induced phase error utilizing only the single look complex(SLC) synthetic aperture radar(SAR) image set. This method exploited the space-invariance characteristic of phase error components contained in image pixels and estimates the phase error using the weighted least-squares(WLS) filter. Actually, this sort of method can be classified as autofocus algorithm which was generally applied in airborne SAR 2-D imaging to compensate the phase error introduced by airplane's nonideal motion. Real data processing, which is relevant to Honda center and Angel stadium of Anaheim test-sites and acquired by Envisat-ASAR during the period from June 2004 to October 2007, was carried out to evaluate this WLS estimation algorithm. Experimental results show that the phase error estimated from WLS filter is very accurate and the focusing quality along NSR dimension is improved prominently via phase correction, which verifies the practicability of this new method.

变开度岩体裂隙多相渗流实验与有效渗透率模型

岩体裂隙的有效渗透率是描述岩体非饱和或多相渗流的关键参数,而裂隙开度是影响有效渗透率的重要因素.通过自主研发的粗糙裂隙多相渗流可视化实验平台,针对天然岩体裂隙复制而成的裂隙模型开展变开度条件下的多相渗流可视化实验,研究开度变化对多相渗流流动结构以及有效渗透率的影响.研究表明:非湿润相流体运动通道,在低流量比条件下呈现出气泡流流动结构,而在高流量比条件下呈现较为稳定的通道流流动结构.随着开度的增加,非湿润相流动通道的分支变少、等效宽度增加,两相流体的有效渗透率均增大,流动结构趋于稳定.可视化结果还阐明了柱塞流流动结构下,两相流体交替占据裂隙空间的竞争机制:当非湿润相流体通道由连续转变为不连续时,裂隙进出口压差显著增加;反之,当该通道由不连续转变为连续时,压差显著减小.最后,基于分形理论以及渗透率统计建模方法,建立了考虑开度效应的岩体裂隙多相渗流有效渗透率理论模型,并通过实验测定的有效渗透率数据验证了该模型的正确性与有效性.

单孔胸腔镜行肺叶切除术在非小细胞肺癌治疗中的临床效果

目的探讨单孔胸腔镜行肺叶切除术在非小细胞肺癌治疗中的临床效果。方法随机选取2018年1月—2021年12月三明市第二医院收治的50例非小细胞肺癌开展单孔胸腔镜行肺叶切除术治疗的患者为观察组,45例非小细胞肺癌以常规三孔胸腔镜行肺叶切除术治疗的患者为对照组。比较两组患者围术期指标、术后不同时间段疼痛评分及术后并发症发生率。结果观察组切口长度、术后引流管留置时间短于对照组,差异有统计学意义(P<0.05)。两组手术时间、术中出血量、淋巴结清扫个数及住院时间相比,差异无统计学意义(P>0.05)。观察组患者术后不同时间段疼痛评分低于对照组,差异有统计学意义(P<0.05)。观察组术后并发症发生率低于对照组,差异有统计学意义(χ^(2)=11.034,P<0.05)。结论非小细胞肺癌患者以单孔胸腔镜行肺叶切除术的治疗相对于传统手术方式,在缩短切口长度、术后引流管留置时间方面更具有优势,同时并不增加手术时间及术中出血量,且不良反应更少。

孔阵腔体屏蔽效能BLT方程修正与拓展分析

以中心位置携带孔缝的机载电子设备屏蔽腔体为研究对象,建立能够计算平面波辐照下腔体屏蔽效能的BLT(Baum-Liu-Tesche)方程。针对Robinson孔阵阻抗计算误差较大这一问题,引入偏心系数C mk修正孔阵阻抗,修正后BLT方程能准确计算开有任意位置孔阵腔体的屏蔽效能。通过对电磁波电场进行矢量分解,实现了任意极化角度下屏蔽腔体屏蔽效能的计算。结果表明,屏蔽腔体屏蔽效能随孔缝数量的增加而升高,极化角度的增大会增强屏蔽腔体电磁屏蔽能力。将BLT方程计算结果与Robinson法结果、CST仿真结果进行对比,证明BLT方程具有准确性,为计算机载电子设备屏蔽腔体屏蔽效能提供了一种有效方法。

电磁屏蔽方舱孔口结构设计及工艺控制

孔口由于存在孔缝产生电磁场泄漏,是影响方舱电磁屏蔽效能的薄弱环节。孔口的结构设计以及安装工艺控制是保证方舱电磁屏蔽效能的关键环节。通过分析孔口的主体结构以及屏蔽效能影响因素,研究总结了电磁屏蔽方舱孔口的设计原则,介绍了门、窗、通风孔口以及空调、暖风机孔口结构设计和工艺控制的相关工程经验,尤其是保证各连接处电连接性的设计形式和工艺控制措施。其中重点对窗和通风孔口的结构设计进行了详细说明。最后对要求屏蔽效能等级为Ⅰ级的电磁屏蔽方舱的孔口采用了上述结构设计和工艺控制措施,并按照标准GJB 6785—2009进行屏蔽效能测试验证,各孔口对应位置的屏蔽效能均满足要求,可为同类型电磁屏蔽方舱的设计与应用提供一定的借鉴。