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利用21CMA射电低频阵聆听来自轴子暗物质的回响（英文）

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Science Bulletin 2024年第19期69卷 2971-2973页

作者： Ariel Arza 郭铨武雷杨峤立杨小龙袁强祝斌 Department of Physics and Institute of Theoretical Physics Nanjing Normal University Shanghai Astronomical observatory Chinese Academy Sciences College of Physics and Optoelectronic Engineering Department of PhysicsJinan University Shanghai Key Laboratory of Space Navigation and Positioning Techniques Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of Sciences School of Astronomy and Space Science University of Science and Technology of China Department of Physics Yantai University

The axion is nowadays one of the leading candidates to compose the dark matter of the universe.A great experimental effort has been performed by the so-called axion haloscopes experiments among others (for complete reviews on updated axion phenomenology,see Ref.[1]).In this paper,we take the new axion dark matter echo idea proposed in Ref.[2].This technique aims to send out of space a powerful beam of electromagnetic radiation in the radio/microwave frequency range and search for the electromagnetic echo produced by stimulated decay of ambient axion dark matter.

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Dispersion Equation of Low-Frequency Waves Driven by Temperature Anisotropy

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Plasma Science and Technology 2012年第10期14卷 880-885页

作者：陈玲吴德金 purple mountain observatory Chinese Academy of Sciences

The plasma temperature （or the kinetic pressure） anisotropy is an intrinsic characteristic of a collisionless magnetized plasma. In this paper, based on the two-fluid model, a dispersion equation of low-frequency （ω〈〈ωci, ωci the ion gyrofrequency） waves, including the plasma temperature anisotropy effect, is presented. We investigate the properties of low-frequency waves when the parallel temperature exceeds the perpendicular temperature, and especially their dependence on the propagation angle, pressure anisotropy, and energy closures. The results show that both the instable Alfven and slow modes are purely growing. The growth rate of the Alfven wave is not affected by the propagation angle or energy closures, while that of the slow wave depends sensitively on the propagation angle and energy closures as well as pressure anisotropy. The fast wave is always stable. We also show how to elaborate the symbolic calculation of the dispersion equation performed using Mathematica Notebook.

关键词： dispersion equation low-frequency waves temperature anisotropy

Surface shape detection methods for large radio telescopes

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Astronomical Techniques and Instruments 2024年第5期1卷 275-283页

作者： Zhengxiong Sun Jinqing Wang Linfeng Yu Yongchen Jiang Zheng Lou Yongbin Jiang Rongbin Zhao Qian Ye Qinghui Liu Guangli Wang Shanghai Astronomical observatory Chinese Academy of SciencesShanghai 200030China Key Laboratory of Radio Astronomy Chinese Academy of SciencesNanjing 210023China Shanghai Key Laboratory of Space Navigation and Positioning Techniques Shanghai 200030China University of Chinese Academy of Sciences Beijing 100049China purple mountain observatory Chinese Academy of SciencesNanjing 210023China

The surface accuracy of a radio telescope is directly related to its operational efficiency and detection *** is crucial under high-frequency observation conditions,where surface shape errors need to be controlled to within 1/16 of the working *** addition,the primary reflector of large radio telescopes is subject to dynamic deformation,caused by factors such as gravity and thermal *** paper presents a method for detecting the surface shape of radio telescopes using radio interferometry techniques combined with active reflector adjustment *** enables accurate assessment and correction of surface errors,ensuring the electrical performance of the radio *** study investigates the practical applications of high-precision measurement techniques,such as microwave holography,out-of-focus holography,and wavefront distortion methods at the Tianma 65 m radio telescope(TMRT).Furthermore,the study presents the construction method of gravity models at different elevation angles and demonstrates the efficacy of the active reflector *** results of the measurements indicate that the application of these methods to the TMRT has led to a notable enhancement of the accuracy of the primary reflector and a substantial improvement in efficiency in the *** a process of iterative measurements and adjustments,the surface shape error is ultimately reduced to 0.28 mm root mean square(RMS).

关键词： Radio telescope Holographic measurements Surface shape measurements Antenna efficiency

面向波束自动跟踪双向无线通信的CMOS反向阵芯片（英文）

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Engineering 2024年第6期 196-207页

作者：郭嘉诚沈一竹董国庆韩壮胡三明 State Key Laboratory of Millimeter Waves School of Information Science and Engineering Southeast University purple mountain Laboratories

This article proposes and demonstrates a retrodirective array（RDA） for two-way wireless communication with automatic beam tracking. The proposed RDA is enabled by specifically designed chips made using a domestic complementary metal-oxide semiconductor（CMOS） process. The highly integrated CMOS chip includes a receiving（Rx） chain, a transmitting（Tx） chain, and a unique tracking phaselocked loop（PLL） for the crucial conjugated phase recovery in the RDA. This article also proposes a method to reduce the beam pointing error（BPE） in a conventional RDA. To validate the above ideas simply yet without loss of generality, a 2.4 GHz RDA is demonstrated through two-way communication links between the Rx and Tx chains, and an on-chip quadrature coupler is designed to achieve a nonretrodirective signal suppression of 23 d Bc. The experimental results demonstrate that the proposed RDA, which incorporates domestically manufactured low-cost 0.18 μm CMOS chips, is capable of automatically tracking beams covering ±40° with a reduced BPE. Each CMOS chip in the RDA has a compact size of 4.62 mm2and a low power consumption of 0.15 W. To the best of the authors' knowledge, this is the first research to demonstrate an RDA with a fully customized CMOS chip for wireless communication with automatic beam tracking.

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Analysis of the applicability of collision probability algorithms for nonlinear relative motion

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Science China(Physics,Mechanics & Astronomy) 2013年第5期56卷 1041-1046页

作者： XU XiaoLi XIONG YongQing purple mountain observatory Chinese Academy of Sciences Key Laboratory of Space Object and Debris observatory Purple Mountain ObservatoryChinese Academy of Sciences

In the calculation of the collision probability between space objects, the assumption of linear relative motion is generally adopted to simplify the problem because most encounters are at high relative velocity. Nevertheless, the assumption is no longer valid for encounters at extremely low velocities, and a new algorithm is urgently needed for computing collision probability for space objects having nonlinear relative motion. In this particular case, the direction associated with relative velocity is reintroduced for integration. The different integral limits would lead to the variations of probability and integral time. Moreover, the application scope of this new algorithm is also presented. Since the nonlinear effect is only significant in some certain situations, the new algorithm needs to be considered only in such certain situations. More specifically, when space objects in circular orbits encounter with a tiny inclined angle (the extreme situation), the new algorithm can derive much more accurate collision probability than the linear method, that is to say, the linearity assumption involved in general collision probability formulation is not adequate anymore. In addition, the deviation of the probability derived by the linear method (linear collision probability) from that derived by the nonlinear method (nonlinear collision probability) also weakly depends on the relative distance and combined covariance, and essentially depends on their ratio.

关键词： space debris collision probability nonlinear relative motion integral limits

The investigation of the Neupert effect in two solar flares

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Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1686-1690页

作者： NING ZongJun purple mountain observatory, Nanjing 210008, China purple mountain observatory Nanjing China

The Neupert effect suggests a flare model in which the nonthermal emissions are produced by energetic electrons which heat lower corona and chromosphere to produce the thermal emissions. Based on this concept, we investigate the Neupert effect to test the correlation between the hard X-ray spectral index and the time rate of the UV flare area at 1600 or 171 . Using the T RACE and RHESSI observations, we explore these quantities for two solar flares, one on March 14, 2002 and the other on November 1, 2003. The negative dependence between the spectral index and the time rate of the UV flare area is found, especially during the hard X-ray sub-peaks. This finding indicates that the electron-beam-driven heating plays a prominent role in the UV emission of these two flares.

关键词： solar flares UV radiation X-rays

The total column densities and fractional abundances of CH_3CN,CH_3OH,HCOOCH_3 and^(13)CS in W51 cores

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Science China(Physics,Mechanics & Astronomy) 2005年第2期48卷 158-167页

作者： PEI Chunchuan MA Hongjun ZENG Qin LI Bo purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

We present interferometric observations of the W51 region at 2.7 mm and 3.3 mm with the Berkeley-Illinois-Maryland Association Array. The lines of CH3CN (J = 6 – 5, K = 0,1,2,3,4), CH3OH (15-2 ?151 E), HCOOCH3-A (71,6 – 61,5), HCOOCH3 -E (71,6 – 61,5) and 13CS (2-1) as well as the 2.7 mm continuum toward W51 have been observed. The derived total beam-averaged column densities NT and fractional abundances of CH3CN, CH3OH, HCOOCH3 and 13CS in W51 cores have been obtained.

关键词： massive star formation, interstellar molecular lines, column density, fractional abundance.

The structure of molecular cloud W51 and dense cores——CO(J=1-0)and HCO^+(J=1-0)spectral line mapping

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Science China(Physics,Mechanics & Astronomy) 2005年第2期48卷 168-177页

作者： MA Hongjun PEI Chunchuan ZENG Qin purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

We present a large scale map of about 15′×15′of CO(J=1-0) toward W51 giant molecular cloud (GMC), which covers the most active star-forming region of W51 GMC, and an interferometry HCO+(J=1-0) map of a high spatial resolution (i.e. 8″.7× 6″.1) with a field of view (2′×2′) centered at W51IRS1. A structure model of W51GMC is obtained according to the results of the observations and analyses. The observations demonstrate that some small molecular cores generated by the collision between the W51GMC and the 60—73 km·s-1 foreground cloud are collapsing toward their own centers. In addition, 16 new molecular cores are discovered from the HCO+(J=1-0) map.

关键词： molecular core, continuum source, star formation.

A method of autonomous orbit determination for satellite using star sensor

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Science China(Physics,Mechanics & Astronomy) 2005年第3期48卷 268-281页

作者： MA Jianbo XU Jin CAO Zhibin purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

In this paper a method of autonomous orbit determination using star sensor is studied. By building relatively consummate dynamical models which simulate attitude motion of satellite and observation from satellite to background stars, the simulant computation of this method is executed, and it is shown that the method of autonomous orbit determination is feasible. Academic and calculation analyses have been done for the relation between the direction of star sensor with respect to satellite-body coordinate system and the accuracy of autonomous orbit determination.

关键词： autonomous orbit determination of satellite, star sensor, attitude of satellite.