SAR regional all-azimuth observation orbit design for target 3D reconstruction

Three-dimensional(3D) synthetic aperture radar(SAR)extends the conventional 2D images into 3D features by several acquisitions in different aspects. Compared with 3D techniques via multiple observations in elevation, e.g. SAR interferometry(InSAR) and SAR tomography(TomoSAR), holographic SAR can retrieve 3D structure by observations in azimuth. This paper focuses on designing a novel type of orbit to achieve SAR regional all-azimuth observation(AAO) for embedded targets detection and holographic 3D reconstruction. The ground tracks of the AAO orbit separate the earth surface into grids. Target in these grids can be accessed with an azimuth angle span of360°, which is similar to the flight path of airborne circular SAR(CSAR). Inspired from the successive coverage orbits of optical sensors, several optimizations are made in the proposed method to ensure favorable grazing angles, the performance of 3D reconstruction, and long-term supervision for SAR sensors. Simulation experiments show the regional AAO can be completed within five hours. In addition, a second AAO of the same area can be duplicated in two days. Finally, an airborne SAR data process result is presented to illustrate the significance of AAO in 3D reconstruction.

眼眶爆裂性骨折修复手术模拟的眼眶3D打印模型和外科种植体模型的研究

目的设计并制作可用于眼眶爆裂性骨折修复手术临床与教学的3D眼眶模型。方法选取2016年11月至2017年2月在山东文登整骨医院眼科确诊的10例(10眼)眼眶下壁爆裂性骨折患者眼眶CT检查DICOM格式的原始CT数据。使用Mimics软件对二维CT图像依次进行阈值选取、区域增长、处理模具、多层编辑修饰等过程,最终获得完整的眼眶爆裂性骨折3D模型,通过3D打印机打印出患者的3D眼眶模型,测量各模型的具体大小,分别将模型与患者的眼眶解剖标志测量数据进行配对t检验。由高年资眼眶外科医师对打印的眼眶爆裂性骨折模型和外科种植体模型进行模拟手术操作。结果共有10例眼眶下壁爆裂性骨折患者,其中男5例(5眼)、女5例(5眼)。3D模型和外科种植体模型成功设计并打印。全部男性组和女性组眼眶爆裂性骨折3D打印模型与CT测量的眼眶数据基本相吻合,差异均无统计学意义(均为P>0.05)。由高年资眼眶外科医师在模拟手术室手术环境下向住院医师示范眼眶骨折修复术手术操作,3D打印的眼眶爆裂性骨折模型可成功用于模拟手术操作和教学示范。结论 3D打印的眼眶爆裂性骨折模型能够真实还原患者眼眶损伤情况和眼眶解剖细节,为医师提供了立体直观的术前设计的模型,对了解眼眶爆裂性骨折的波及范围和手术教学模拟具有积极意义。

NMR and NQR studies on transition-metal arsenide superconductors LaRu2As2,KCa2Fe4As4F2,and A2Cr3As3

We report 75As-nuclear magnetic resonance(NMR)and nuclear quadrupole resonance(NQR)measurements on transition-metal arsenides LaRu2As2,KCa2Fe4As4F2,and A2Cr3As3.In the superconducting state of LaRu2As2,a Hebel–Slichter coherence peak is found in the temperature dependence of the spin-lattice relaxation rate 1/T1 just below Tc,which indicates that LaRu2As2 is a full-gap superperconducor.For KCa2Fe4As4F2,antiferromagnetic spin fluctuations are observed in the normal state.We further find that the anisotropy rate RAF=Tc 1/Tab 1 is small and temperature independent,implying that the low energy spin fluctuations are isotropic in spin space.Our results indicate that KCa2Fe4As4F2 is a moderately overdoped iron-arsenide high-temperature superconductor with a stoichiometric composition.For A2Cr3As3(A=Na,K,Rb,Cs),we calculate the electric field gradient by first-principle method and assign the 75As-NQR peaks to two crystallographically different As sites,paving the way for further NMR investigation.

Pressure Effects on Spectra of Tunable Laser Crystal GSGG:Cr3+ III: Pressure-Induced Shift of R1 Line at 70 K

By means of both a theory for pressure-induced shifts (PS) of energy spectra and a theory for shifts of energy spectra due to electron-phonon interaction (EPI), the 'pure electronic' PS and the PS due to EPI of R1 line of GSGG:Cr3+ at 70 K have been calculated, respectively. Their physical origins have been revealed. It is found that the admixture of and base-wavefunctions in the wavefunctions of R1 level of GSGG:Cr3+ at 70 K is remarkable under the normal pressure, and the degree of the admixture rapidly decreases with increasing pressure. The change of the degree of the admixture with the pressure plays a key role for not only the pure electronic PS of R1 line but also the PS of R1 line due to EPI. The detailed calculations and analyses show that the pressure-dependent behaviors of the pure electronic PS of R1 line and the PS of R1 line due to EPI are quite different. It is the combined effect of them that gives rise to the total PS of R1 line, which has satisfactorily explained the experimental data (including a reversal of PS of R1 line). In contributions to PS of R1 line due to EPI at 70 K, the temperature-independent contribution is much larger than the temperature-dependent contribution. The former results from the interaction between the zero-point vibration of the lattice and localized electronic state.

Pressure Effects on Spectra of Tunable Laser Crystal GSGG： Cr^3＋ IV： Pressure—Induced Shifts of R1 Line, R2 Line, and U Band at 300 K

By means of both a theory for pressure-induced shifts (PS) of energy spectra and a theory for shifts of energy spectra due to electron-phonon interaction (EPI), the 'pure electronic' PS and the PS due to EPI of R1 line, R2 line, and U band of GSGG:Cr3+ at 300 K have been calculated, respectively. The calculated results are in good agreement with all the experimental data. Their physical origins have also been explained. It is found that the mixing-degree of and base-wavefunctions in the wavefunctions of R1 level of GSGG:Cr3+ at 300 K is remarkable under normal pressure, and the mixing-degree rapidly decreases with increasing pressure. The change of the mixing-degree with pressure plays a key role not only for the 'pure electronic' PS of R1 line and R2 line but also the PS of R1 line and R2 line due to EPI. The pressure-dependent behaviors of the 'pure electronic' PS of R1 line (or R2 line) and the PS of R1 line (or R2 line) due to EPI are quite different. It is the combined effect of them that gives rise to the total PS of R1 line (or R2 line). In the range of about 15 kbar ~ 45 kbar, the mergence and/or order-reversal between levels and levels take place, which cause the fluctuation of the rate of PS for with pressure. At 300 K, both the temperature-dependent contribution to R1 line (or R2 line or U band) from EPI and the temperature-independent one are important.

Mathcad在物理中的应用

对Mathcad软件的特点和主要功能作了简单介绍,并通过几个实例探讨了Mathcad在物理教学中的应用.

The design and artificial realization of a controller of pulse coupling feedback

In this paper a controller of pulse coupling feedback （PCF） is designed to control chaotic systems. Control principles and the technique to select the feedback coefficients are introduced. This controller is theoretically studied with a three dimensional （3D） chaotic system. The artificial simulation results show that the chaotic system can be stabilized to different periodic orbits by using the PCF method, and the number of the periodic orbits are 2^n×3^m p （n and m are integers）. Therefore, this control method is effective and practical.

THE INFLUENCE OF THE 3d ORBITS OF SULFUR ATOMS ON THE ELECTRONIC PROPERTIES OF POLYACETYLENE SULFIDE

Ⅰ. INTRODUCTIONA problem needing urgent resolution in the world at present is the study of the polyacetylene (PA) conductive material which is stable in the air. We produce the polyacetylene-like sulfide (SLPA) which is stable in the air from polyvinyl chloride, and characterize its structure and property, and make studies on the influence of sulfidation on PA’s electronic property by means of the quantum method.

Biomechanical analysis of an absorbable material for treating fractures of the inferior orbital wall

AIM:To investigate the biomechanical properties and practical application of absorbable materials in orbital fracture repair.METHODS:The three-dimensional(3D)model of orbital blowout fractures was reconstructed using Mimics21.0 software.The repair guide plate model for inferior orbital wall fracture was designed using 3-matic13.0 and Geomagic wrap 21.0 software.The finite element model of orbital blowout fracture and absorbable repair plate was established using 3-matic13.0 and ANSYS Workbench 21.0 software.The mechanical response of absorbable plates,with thicknesses of 0.6 and 1.2 mm,was modeled after their placement in the orbit.Two patients with inferior orbital wall fractures volunteered to receive single-layer and double-layer absorbable plates combined with 3D printing technology to facilitate surgical treatment of orbital wall fractures.RESULTS:The finite element models of orbital blowout fracture and absorbable plate were successfully established.Finite element analysis(FEA)showed that when the Young’s modulus of the absorbable plate decreases to 3.15 MPa,the repair material with a thickness of 0.6 mm was influenced by the gravitational forces of the orbital contents,resulting in a maximum total deformation of approximately 3.3 mm.Conversely,when the absorbable plate was 1.2 mm thick,the overall maximum total deformation was around 0.4 mm.The half-year follow-up results of the clinical cases confirmed that the absorbable plate with a thickness of 1.2 mm had smaller maximum total deformation and better clinical efficacy.CONCLUSION:The biomechanical analysis observations in this study are largely consistent with the clinical situation.The use of double-layer absorbable plates in conjunction with 3D printing technology is recommended to support surgical treatment of infraorbital wall blowout fractures.

Precise orbit determination of Haiyang‑2D using onboard BDS‑3 B1C/B2a observations with ambiguity resolution

The Haiyang-2D altimetry mission of China is one of the first Low Earth Orbit(LEO)satellites that can receive new B1C/B2a signals from the BeiDou-3 Navigation Satellite System(BDS-3)for Precise Orbit Determination(POD).In this work,the achievable accuracy of the single-receiver ambiguity resolution for onboard LEO satellites is studied based on the real measurements of new BDS-3 frequencies.Under normal conditions,six BDS-3 satellites on average are visible.However,the multipath of the B1C/B2a code observations presents some patchy patterns that cause near-field variations with an amplitude of approximately 40 cm and deteriorate the ambiguity-fixed rate.By modeling those errors,for the B2a code,a remarkable reduction of 53%in the Root Mean Square(RMS)is achieved at high elevations,along with an increase of 8%in the ambiguity-fixed rates.Additionally,an analysis of the onboard antenna’s phase center offsets reveals that when compared to the solutions with float ambiguities,the estimated values in the antenna’s Z direction in the solutions with fixed ambiguities are notably smaller.The independent validation of the resulting POD using satellite laser ranging at 16 selected high-performance stations shows that the residuals are reduced by a minimum of 15.4%for ambiguity-fixed solutions with an RMS consistency of approximately 2.2 cm.Furthermore,when compared to the DORIS-derived orbits,a 4.3 cm 3D RMS consistency is achieved for the BDS-3-derived orbits,and the along-track bias is reduced from 2.9 to 0.4 cm using ambiguity fixing.

Accelerating water dissociation kinetics of Ni3N by tuning interfacial orbital coupling

The high unoccupied d band energy of Ni_(3)N basically results in weak orbital coupling with water molecule,consequently leading to slow water dissociation kinetics.Herein,we demonstrate Cr doping can downshift the unoccupied d orbitals and strengthen the interfacial orbital coupling to boost the water dissociation kinetics.The prepared Cr-Ni_(3)N/Ni displays an impressive overpotential of 37 mV at 10 mA·cmgeo-2,close to the benchmark Pt/C in 1.0 M KOH solution.Refined structural analysis reveals the Cr dopant exists as the Cr-N_(6)states and the average d band energy of Ni_(3)N is also lowered.Density functional theory calculation further confirms the downshifted d band energy can strengthen the orbital coupling between the unpaired electrons in O 2p and the unoccupied state of Ni 3d,which thus facilitates the water adsorption and dissociation.The work provides a new concept to achieve on-demand functions for hydrogen evolution catalysis and beyond,by regulating the interfacial orbital coupling.

Theoretical model of pediatric orbital trapdoor fractures and provisional personalized 3D printing-assisted surgical solution

Pediatric orbital trapdoor fractures are common in children and adolescents and usually require emergency surgical intervention.Herein,a personalized 3D printing-assisted approach to surgical treatment is proposed,serving to accurately and effectively repair pediatric orbital trapdoor fractures.We first investigated stress distribution in external force-induced orbital blowout fractures via numerical simulation,determining that maximum stresses on inferior and medial walls exceed those on superior and lateral walls and thus confer higher probability of fracture.We also examined 36 pediatric patients treated for orbital trapdoor fractures between 2014 and 2019 to verify our theoretical construct.Using 3D printing technique,we then created orbital models based on computed tomography(CT)studies of these patients.Absorbable implants were tailor-made,replicating those of 3D-printed models during surgical repairs of fractured orbital bones.As follow-up,we compared CT images and clinical parameters(extraocular movements,diplopia,enophthalmos)before and 12 months after operative procedures.There were only two patients with diplopia and six with enophthalmos>2 mm at 12 months,attesting to the efficacy of our novel 3D printing-assisted strategy.

应用3D打印机制作个体化眼眶模型的研究

目的探索根据骨折患者的cT数据应用3D打印机制作个体化眼眶模型的方法。方法将患者眼眶CT的医学数字成像和通信格式（digital imaging and communications in medicine，DICOM）影像数据通过交互式医学图像控制系统（materialise’s interactive medical image control system，mimics）软件三维重建，生成3D模型文件格式（STL）文件，通过开源三维打印程序（ReplicatorG）软件将STL文件转化成X3g文件，最后X3g文件通过3D打印机（Maker Bot Replicator2）等比例打印出三维立体眼眶模型。结果根据每个眼眶骨折患者的CT影像DICOM数据成功打印出个体化等比例眼眶骨折的三维实体模型。结论基于mimics软件、ReplicatorG软件及3D打印机制作的等比例眼眶实体三维模型，使临床医生能够更加充分地了解骨折的形态、面积及其与周围骨骼的三维结构关系。

The role of 3d orbitals in the bonding of phosphorus compounds

Ab initio LCAO-MO-SCF calculations for several typical molecules containing phosphorus have been undertaken to study the role of phosphorus 3d orbitals in the bonding.It is emphasized that the discussion about the 3d orbital participation in bonding should be based on a reasonable choice of basis sets and it seems suitable to choose the atomic orbitals in proper molecular environment as the basis set.As an approximation,the optimized minimal STO-NG basis sets have been adopted in the present paper.The results obtained well exhibit the model of 3d orbital participation in bonding. It is shown that under the influence of highly electronegative ligands the phosphorus 3d orbitals con- tract greatly,their energy levels drop considerably,and thus they can effectively participate in bond- ing.The presence of highly electronegative ligands seems necessary.The contribution of 3d orbitals to bonding is achieved mainly through the concertedformation of σ bonds and p-d backbonds,though the contribution to σ bonding is minor.The three-center,four-electron bond modelis only approxi- mately correct.The results of the present paper demonstrate that the model of 3d orbital participation in bonding favoured by experimental chemists is reasonable and possesses sound ground.

The role of the sulfur 3d orbitals in bond formation in sulfur-containing compounds

The role of the sulfur 3d orbitals in bond formation is discussed by taking into account the influence of the environment on the orbitals of the sulfur atom in the molecules. The ca cula- tion results of a series of prototype molecules containing sulfur such as SF_2, SF_4, NSF_3, SF_1, H_2S are reported. It is convincingly shown that in highly electronegative environment the energy levels of the sulfur 3d orbitals are reduced to the vicinity of those of the ligand valence orbitals and their spatial distributions are contracted to the bonding area, and therefore they can participate in bond formation to a certain extent, which is enhanced by the formation of the d-p π back bonds. It seems that the result reported in this paper is helpful for the solution of the long-standing debate about the sulfur 3d orbital participation in bond formation.

Monitoring and analysis of mining 3D deformation by multiplatform SAR images with the probability integral method

Only one-dimensional (1D)deformation along the radar line of sight (LOS)can be obtained using differential interferometry synthetic aperture radar (D-InSAR),and D-InSAR observation is insensitive to deformation in the north direction.This study inferred three-dimensional (3D)deformation of a mining subsidence basin by combining the north-south deformation predicted by a probability integral method with the LOS deformation obtained by D-InSAR.The 15235 working face in Fengfeng mining area (Hebei Province,China)was used as the object of study.The north-south horizontal movement was predicted by the probability integral method according to the site's geological and mining conditions.Then,the vertical and east-west deformation fields were solved by merging ascend-orbit RadarSAT-2, descend-orbit TerraSAR,and predicted north-south deformation based on a least squares method.Comparing with the leveling data,the results show that the vertical deformation accuracy of the experimental method is better than the inversed vertical deformation neglecting the horizontal deformation.Finally,the impact of the relationship between the azimuth of the working face and the SAR imaging geometry on the monitoring of the mining subsidence basin was analyzed.The results can be utilized in monitoring mining subsidence basins by single SAR image sources.

眶部种植模板在CT影像分析中的应用

目的了解热压成型模板在眶部种植术前应用计算机体层摄影(CT)扫描及图像分析中的指导效果。方法利用热压成型机对薄塑胶板加热、真空加压,按时钟方式制作成带标记孔的CT模板。将该模板佩戴入12具干颅标本和4例眶部缺失的患者,通过常规眶部CT扫描和CT工作站AdvancedWorkstation(AW)4.0图像分析,观察眶部受植区骨量和骨解剖结构。结果带标记点的放射模板准确地定位了眶部受植区的骨结构,能够方便的测量受植区的骨量。结论热压成型CT模板可以精确分析眶部受植区骨量和骨结构,在眶部种植术前分析受植区骨量时值得推广应用。

地球同步轨道圆迹SAR研究

该文介绍了地球同步轨道圆迹合成孔径雷达(Geosynchronous Circular SAR,Geo-CSAR)的概念,通过设计同步轨道的轨道参数,可以形成近圆的卫星相对地球轨迹,使SAR载荷的凝视成像模式成为可能,实现对地的大面积定点连续观测以及真3维信息获取;研究分析了Geo-CSAR的成像能力,指出其在瞬时覆盖度、连续观测范围及3维精确定位方面,具有现有低轨星载SAR无法比拟的优势,是实现全球不间断覆盖的有效途径之一,在军事侦察、灾害监测方面具有重要的应用前景。

三维重建单侧眼眶部缺损的面部数字化模型

目的:建立活体单侧眼眶部缺损的面部三维数字化模型,探讨颜面部缺损三维数据快速精确采集的新方法。方法:采用位相测量轮廓技术对患者面部进行活体测量,获得三维点云数据,运用CloudForm反求工程软件对点云数据进行处理后,转化为相应的数字化文件格式,在Geomagic实体构造软件中重建缺损面部三维数字化模型。结果:实现了单侧眼眶部缺损面部组织的活体三维重建,取得的面部模型数据清晰可靠。结论:应用位相测量轮廓术可快速安全的重建缺损面部的真实三维形态,为眼眶部缺损的计算机辅助设计奠定了基础。

螺旋CT扫描立体成像对眼眶爆裂骨折的诊断价值

目的 分析眼眶爆裂骨折螺旋CT(SCT)容积扫描的表现 ,旨在对本病作出早期诊断。资料与方法 回顾性分析 80例眼眶爆裂骨折的SCT轴位扫描图像以及多平面重建 (MPR)和三维 (3D)重建立体图像的CT表现。并根据CT征象将其分为 3型 :(1)单眶壁爆裂骨折 ;(2 )双眶壁爆裂骨折 ;(3)混合型骨折 (并发其他面部直接骨折的爆裂骨折 )。结果 眼眶爆裂骨折的直接SCT征象为眶壁骨质连续性中断、粉碎、凹陷及曲度失常 ;上颌窦和筛窦内“泪滴征”是诊断眼眶下壁和内侧壁爆裂骨折的特异性间接征象。由于骨折局部往往伴有软组织增厚及眼外肌的改变 ,所以对早期诊断、选择治疗方法、估计预后及法医学鉴定可提供更多的信息。