On m-ovoids of finite classical polar spaces with an irreducible transitive automorphism group

In this paper, we classify the m-ovoids of finite classical polar spaces that admit a transitive automorphism group acting irreducibly on the ambient vector space. In particular, we obtain several new infinite families of transitive m-ovoids.

Air-Stable Dy(III)-Macrocycle Enantiomers:From Chiral to Polar Space Group

Magnetoelectric(ME)multiferroic materials have unique advantages in low-power and high-density information storage,because they can simultaneously display ferroelectricity and ferromagnetism.However,research on how to construct air-stable highperformance ME single-molecule magnets(SMMs)is nonexistent.Herein,by introducing homochirality while reducing molecular symmetry,two doubledecker Dy(III)enantiomers adopting the polar space group P2_(1) and exhibiting excellent thermal stability were obtained.They displayed zero field SMM behavior with an anisotropy barrier(Ueff)of ca.100 cm^(−1).This work establishes a rational chemical design strategy for crystallizing SMMs in polar space groups and elucidates the direction for future research,that is,engineering small-size high-performance SMMs.

基于KA-SRCN-pSTAP的低空风切变风速估计方法

针对由于独立同分布(IID)样本严重不足,导致极化空时自适应(pSTAP)处理性能下降,进而导致低空风切变风速估计不准确的问题,本文提出了一种基于知识辅助的稀疏表示杂波零陷极化空时自适应(KA-SRCN-pSTAP)的低空风切变风速估计方法。该方法首先利用杂波脊的先验知识辅助构造极化空时稀疏字典,然后利用极化空时稀疏字典,通过SRCN算法挑选原子并对到杂波线性子空间补空间上的投影矩阵进行估计,从而得到pSTAP权矢量,最后构造pSTAP滤波器对地杂波进行抑制,准确估计低空风切变风速。该方法仅使用少量IID样本,将SRCN算法与极化-空时域相结合,完成对风切变风速的有效估计。仿真实验结果证明该方法可以有效实现少样本情况下的风速准确估计。

空间天文紫外偏振探测技术研究进展

新型空间天文探测技术在科学进步和国家发展方面起着至关重要的作用。其高精度的观测提供了独特的机遇,深化了人们对宇宙的理解,同时推动了天体物理学和宇宙学的前沿研究。这些探测不仅为理论模型的验证与发展提供了不可或缺的数据,还在基础物理学领域催生了新理论。在国家层面,拥有先进的空间天文探测技术不仅凸显了国家在科研领域的实力,同时为培养高水平的科研人才提供了重要平台,有助于国家在全球科研舞台上赢得竞争优势。因此,对新型空间天文探测技术的研究和发展显得十分紧迫。天文紫外偏振作为一种创新的空间天文探测手段,相较于传统探测手段,紫外偏振测量技术能够提供多维度的观测数据,进而实现全方位的宇宙感知能力,具备巨大地应用潜力。鉴于目前尚未有关于空间天文紫外偏振探测的系统性综述报告和文章,因此,文中从紫外偏振科学研究的角度出发,总结已有的紫外偏振载荷,挖掘这一领域技术发展的思路和途径,最后对该技术未来发展方向进行展望与总结,为我国在该领域的未来研究提供有益参考。

交替极化阵列对消盲区分析与验证

当干扰信号的空域和极化域特征与目标信号相似时,采用空极化域联合抗干扰技术在消除干扰的同时也会抑制目标信号,导致干扰对消后信干噪比(signal to interference plus noise ratio,SINR)低于雷达系统需求,从而形成干扰对消盲区。针对这一现象,通过在空域、极化域与空极化域分别建立交替极化阵列对消盲区模型,推导了对消盲区位置和大小的数学表达式,从而给出了交替极化阵列对消盲区的数学表征方法。进而分析了交替极化阵列对消盲区的分布规律与影响因素,研究发现阵元间距能够显著影响交替极化阵列对消盲区的分布,在相同条件下交替极化阵列对消盲区大于共点极化阵列对消盲区,结果表明交替极化阵列虽然通过减少天线数目降低了设备成本,但增大了阵列的对消盲区。然后,对消盲区模型进行了数值仿真,仿真结果验证了理论分析。最后,利用信道模拟器搭建了实验平台,信道模拟实验测得的对消盲区与理论值基本一致,再次证明了分析结论的有效性。

TG-2伽玛暴偏振探测仪POLAR

伽玛暴偏振的测量对喷流机制的确定有着至关重要的作用。伽玛暴偏振探测仪POLAR是中欧合作的、专门用于探测伽玛暴偏振的探测仪器,POLAR通过康普顿散射的原理实现对伽玛暴偏振度高灵敏度的测量。介绍了POLAR的整体方案和载荷研制情况,通过蒙卡模拟和地面实验对仪器性能进行验证,结果表明POLAR具有符合设计要求的偏振测量能力。

浅谈极区空间物理学的科学革命

极区空间物理学重要的研究方向之一是剖析南北两极的热层、电离层和磁层的耦合问题。本文简明扼要地描述了极区空间物理学的一场革命——即理论框架的革新。这场科学革命是用磁流体力学理论取代电机工程理论,目前进行得比较缓慢,但将在今后的30~50年彻底改变人们对于热层-电离层-磁层的认知。

基于空间馈电的高功率波束扫描螺旋透射阵列天线设计

传统的透射式空馈阵列存在功率容量低的缺点,不能直接应用于高功率微波领域。现有的高功率空馈阵列布局不够灵活,波束扫描速度较慢,不能充分发挥空馈阵列在系统集成方面的优势。提出并设计了一种新型的采用空间馈电的螺旋辐射单元,并构建了一种透射式空馈螺旋阵列天线,通过控制单个螺旋旋转可以实现二维波束扫描,在设计上更加灵活,可根据实际应用需求调整阵列布局,符合高功率微波天线紧凑化、模块化的发展趋势。仿真设计了包含324个单元的透镜阵列,数值模拟结果表明,单元反射系数S11≤-20 dB,功率容量0.35 MW,阵列口径效率0.68,可在±45°范围内扫描,最大增益下降3 dB。

高压电缆在电压极性反转过程中的空间电荷行为研究

为探明同轴结构交联聚乙烯(XLPE)电缆绝缘在外施电压极性反转过程中的空间电荷注入、迁移、抽出等动态演变规律,分析外施电压极性反转过程中空间电荷导致的反转“滞后效应”,并探究温度梯度协同作用的影响规律,对XLPE电缆进行了不同电场强度、温度梯度场下,外施电压快速极性反转过程中的空间电荷研究,并基于异极性电荷注入、迁移理论,对极性反转过程中电缆绝缘空间电荷的演变规律进行分析。研究结果表明:XLPE电缆在外施电压快速反转过程中,由于电缆绝缘内部残余电荷的影响,电缆两侧电极电荷峰表现出不平衡的反转特性,导致电缆外半导电层电极的电荷峰出现了明显的反转“滞后效应”。

Progress in polar upper atmospheric physics research in China

The Chinese Antarctic Great Wall, Zhongshan, Kunlun and Arctic Yellow River stations have unique geographical locations, well suited to carry out polar upper atmospheric observations. This paper reviews the tremendous history of nearly 30 years of Chinese polar expeditions and major progress in polar upper atmospheric physics research. This includes the polar upper atmospheric physics conjugate observation system at Zhongshan Station in the Antarctic and Yellow River Station in the Arctic, and original research achievements in polar ionospheric fields, aurora and particle precipitation, the polar current system, polar plasma convection, geomagnetic pulsations and space plasma waves, inter-hemispheric comparisons of the space environment, space weather in polar regions, power spectrum of the incoherent scatter radar, ionospheric heating experiments and polar meso- spheric summer echoes, polar ionosphere-magnetosphere numerical simulation and others. Finally, prospects for Chinese polar upper atmospheric physics research are outlined.

SCATTERING OF CIRCULAR CAVITY IN RIGHT-ANGLE PLANAR SPACE TO STEADY SH-WAVE

Complex function method and multi-polar coordinate transformation technology are used here to study scattering of circular cavity in right-angle planar space to SH-wave with out-of-plane loading on the horizontal straight boundary. At first, Green function of right-angle planar space which has no circular cavity is constructed; then the scattering solution which satisfies the free stress conditions of the two right-angle boundaries with the circular cavity existing in the space is formulated. Therefore, the total displacement field can be constructed using overlapping principle. An infinite algebraic equations of unknown coefficients existing in the scattering solution field can be gained using multi-polar coordinate and the free stress condition at the boundary of the circular cavity. It can be solved by using limit items in the infinite series which can give a high computation precision. An example is given to illustrate the variations of the tangential stress at the boundary of the circular cavity due to different dimensionless wave numbers, the location of the circular cavity, the loading center and the distributing range of the out-of-plane loading. The results show the efficiency and effectiveness of the mothod introduced here.

A novel x-ray circularly polarized ranging method

Range measurement has found multiple applications in deep space missions. With more and further deep space ex- ploration activities happening now and in the future, the requirement for range measurement has risen. In view of the future ranging requirement, a novel x-ray polarized ranging method based on the circular polarization modulation is proposed, termed as x-ray circularly polarized ranging （XCPolR）. XCPolR utilizes the circular polarization modulation to process x-ray signals and the ranging information is conveyed by the circular polarization states. As the circular polarization states present good stability in space propagation and x-ray detectors have light weight and low power consumption, XCPolR shows great potential in the long-distance range measurement and provides an option for future deep space ranging. In this paper, we present a detailed illustration of XCPolR. Firstly, the structure of the polarized ranging system is described and the signal models in the ranging process are established mathematically. Then, the main factors that affect the ranging accuracy, including the Doppler effect, the differential demodulation, and the correlation error, are analyzed theoretically. Finally, numerical simulation is carded out to evaluate the performance of XCPolR.

Einstein’s General Relativity and Pure Gravity in a Cosserat and De Sitter-Witten Spacetime Setting as the Explanation of Dark Energy and Cosmic Accelerated Expansion

Ordinary energy and dark energy density are determined using a Cosserat-Cartan and killing-Yano reinterpretation of Einstein’s special and general relativity. Thus starting from a maximally symmetric space with 528 killing vector fields corresponding to Witten’s five Branes model in eleven dimensional M-theory we reason that 504 of the 528 are essentially the components of the relevant killing-Yano tensor. In turn this tensor is related to hidden symmetries and torsional coupled stresses of the Cosserat micro-polar space as well as the Einstein-Cartan connection. Proceeding in this way the dark energy density is found to be that of Einstein’s maximal energy mc2 where m is the mass and c is the speed of light multiplied with a Lorentz factor equal to the ratio of the 504 killing-Yano tensor and the 528 states maximally symmetric space. Thus we have E (dark) = mc2 (504/528) = mc2 (21/22) which is about 95.5% of the total maximal energy density in astounding agreement with COBE, WMAP and Planck cosmological measurements as well as the type 1a supernova analysis. Finally theory and results are validated via a related theory based on the degrees of freedom of pure gravity, the theory of nonlocal elasticity as well as ‘t Hooft-Veltman renormalization method.

Recent progress in Chinese polar upper-atmospheric physics research: review of research advances supported by the Chinese Arctic and Antarctic expeditions

It has been more than 30 years since the first Chinese Antarctic Expedition took place. Polar upper atmospheric observations started at this time. First began at Great Wall Station and then at Zhongshan Station in Antarctica, and later in the Arctic at Yellow River Station, Kjell Henriksen Observatory on Svalbard, and at the China-Iceland Joint Aurora Observatory in Iceland. In this paper, we reviewed the advances in polar upper atmosphere physics （UAP） based on the Chinese national Arctic and Antarctic research over the last five years. These included newly deployed observatories and research instruments in the Arctic and Antarctic; and new research findings, from grotmd-based observations, about polar ionosphere dynamics, aurora and particle precipitation, polar plasma convection, geomagnetic pulsations and space plasma waves, space weather in the polar regions, simulations of the polar ionosphere-magnetosphere. In conclusion, suggestions were made for future polar upper atmosphere physics research in China.

Dynamic Stress and Pore Pressure Around Circular Cavity in Saturated Porous Elastic Half-space Under Harmonic Plane Dilatational Waves

Dynamic stress concentration and pore pressure concentration around an infinitely long cylindrical cavity of circular cross-section subjected to harmonic plane dilatational waves in fluid-saturated porous elastic half-space were obtained by a complex function method based on potential function and multi-polar coordinate. The steady state Biot’s dynamic field equations of porous elastic solid with a viscous liquid were uncoupled into Helmholtz equations via given potential functions. A circular cavity with large radius is used to replace the straight boundary of the saturated porous elastic half-space. The stresses and pore pressures were obtained by using complex functions in multi-polar coordinates with certain boundary conditions of the solid matrix and the fluid matrix. The approximate solutions were compared to existing numerical solutions. Then the variations of the coefficients of dynamic stress concentration and the pore pressures concentration on boundaries of the cavity were discussed with different parameter conditions. The results of the given numerical example indicate that the method used is useful and efficient to the scattering and dynamic stress concentration of plane dilatational waves in saturated porous elastic half-space.

基于三极化单元的平面阵列半空间扫描波束形成与分析

为了实现三极化平面阵列的高性能宽角扫描,提出一种基于三极化单元的平面阵列半空间扫描波束形成方法,并对相控阵扫描特性进行了分析。首先,在假设单元3个极化特性一致的前提下,从期望的合成波束指向出发,将与之正交的极化电场单位矢量沿3个极化方向分解,从而获得3个极化电场分量的相位和幅度,再依据功率与极化电场幅度平方成正比的关系,推导获得4种极化形式下极化合成所需的激励表达式,并通过仿真验证了该激励表达式的正确性。接着采用经典的阵因子控制方法,改变阵元相位差,使阵因子扫描角与单元波束指向一致,从而形成半空间任意方向扫描的阵列波束。最后,在不考虑阵元间互耦的情况下,对4种极化形式下的阵列扫描特性进行仿真分析与对比,结果表明,该阵列具有优越的半空间扫描特性,验证了该波束形成方法的有效性。

不同偏光系统下的岩石薄片图像联合分割

针对传统切换单偏光与正交偏光系统进行镜下岩石薄片分析和含量估计耗时耗力,且准确率较低的问题,在色度亮度空间设计一种岩石薄片图像联合分割方法:先将相同视域下的单偏光图像与正交偏光图像在色度亮度空间中分别进行分解,然后对色度图像进行双边滤波处理,抑制噪声和去除纹理,计算滤波后两个色度图像之间的差值,并依次使用K-Means聚类算法和分水岭分割算法得到最终分割结果。结果表明,使用单偏光岩石薄片图像与正交偏光岩石薄片图像联合分割较大提升了矿物颗粒计数准确率和分割结果的交并比。研究结果可为地质工作者鉴定岩石薄片提供指导。

基于M-W极化模型的低电场极性反转下XLPE/硅橡胶空间电荷与电场分布特性研究

相比于单一介质的电缆绝缘,高压直流电缆附件复合绝缘因介质不连续性更易在界面处积聚空间电荷。在基于电网换相器的高压直流(LCC-HVDC)输电系统中,进行潮流反转调整时需改变电压极性,高压直流电缆附件将会承受极性反转电场,尽管是短时的,但由于空间电荷的累积效应也会在局部产生极高的电场,严重影响绝缘性能。为此,该文利用实验获得交联聚乙烯(XLPE)与硅橡胶(SR)电导率与电场强度的变化关系,基于Maxwell-Wagner(M-W)极化模型仿真研究了低电场极性反转下XLPE/SR双层介质中空间电荷与电场的分布特性。结果表明:室温下,SR的低电场电导率要高于XLPE,且SR电导率受电场强度的影响相对较小而XLPE则较大。由于界面电荷极性变化滞后于电压极性变化,极性反转期间界面处残留的负极性电荷造成SR中出现最大瞬态电场;电压极性反转越快,XLPE/SR界面残留的负极性电荷越多,SR中的最大瞬态电场强度越高;外施电压越高,由于SR与XLPE的电导率比值降低,SR中的最大瞬态电场畸变率越小。

高动态场景下的极化空时零陷展宽算法

在高动态场景下,干扰源相对于抗干扰天线快速运动,传统抗干扰算法会零陷失配,导致抗干扰性能失效。为此,提出一种极化空时多维域联合的协方差矩阵锥化(CMT)算法。基于Laplace分布构造锥化矩阵来模拟干扰运动状态,通过锥化矩阵与原始协方差矩阵重构新的协方差矩阵实现零陷展宽,结合最小方差无失真响应(MVDR)准则求解阵列权矢量。仿真结果从波束方向图、输出性能和卫星捕获结果3个方面证实了所提算法在干扰位置快变情形下的稳健性,即使在干扰信号和导航信号具有相同的方位角和频带时,也能有效抑制干扰。

数字技术创新对劳动力市场极化的影响研究

选取2011—2020年30个省级面板数据,实证检验数字技术创新对劳动力市场极化的作用效果与机制路径。研究结果显示:数字技术创新能够同时加剧高技能劳动力市场极化与低技能劳动力市场极化现象,且这一影响存在显著空间溢出效应;数字技术创新可以通过劳动力流动加剧高技能与低技能劳动力市场极化。基于此,应深挖数字技术创新优势,培育复合型高技能人才;全面开展数字化技能培训,推动中等技能劳动力就业;构建数字化灵活就业平台,畅通低技能劳动力向上流动渠道;健全劳动力流动机制,提升人力资源配置效率,以优化劳动力市场配置。