云南天文台的非太阳天体物理观测研究

简要总结了自１９７９年以来云南天文台在宇宙学、星系物理、行星和彗星物理方面的主要进展。也对相关仪器的研制和选址工作进行了评述。

活动星系核中黑洞质量和吸积率分布研究

红移、中心黑洞质量和吸积率是活动星系核演化的重要参数.利用反响映射法计算了172个类星体和Seyfert星系样本的中心黑洞质量,并分析了中心黑洞的质量、红移、爱丁顿吸积率的分布,进而验证了从类星体过渡到Seyfert星系的演化.

活跃星系核的模型研究

活跃星系核是中央核区活动性很强的一种银河系外星系核心。活跃星系核是20世纪90年代至今天文学界最活跃和最热门的研究领域之一，因此，对于这种天体现象有很多东西已被科学家们达成了共识，也有很多未知的东西并没有被科学家们搞清楚。所以，这是一门十分前沿却比较困难的学科。本文的目的是为了以较容易于理解的方式来帮助天体物理学初学者以及天体爱好者来初步认识活跃星系核这一前沿的天体现象。本文简要概述了几种较为常见的活跃星系核模型，并介绍了活跃星系核的标准模型、统一模型以及活跃星系核中最重要的黑洞。

Stochastic Dynamic Modeling of Rain Attenuation: A Survey

Satellite communication systems(SCS) operating on frequency bands above 10 GHz are sensitive to atmosphere physical phenomena, especially rain attenuation. To evaluate impairments in satellite performance, stochastic dynamic modeling(SDM) is considered as an effective way to predict real-time satellite channel fading caused by rain. This article carries out a survey of SDM using stochastic differential equations(SDEs) currently in the literature. Special attention is given to the different input characteristics of each model to satisfy specific local conditions. Future research directions in SDM are also suggested in this paper.

A Multi-parameter Model for Radio Dichotomy of Active Galactic Nuclei and Jets

Based on the coexistence of the Blandford-Znajek and magnetic coupling processes in black hole （BH） accretion disc, a multi-parameter model for jet powers and radio loudnees of active galactic nuclei （AGNs） is studied. It turns out that radio-loudnees of AGNs couM be governed by five parameters： （i） the BH spin, （ii） a power-law index of the variation of the magnetic field on the disc; （iii） a parameter determining the position of the inner edge of the disc, （iv） the ratio of the pressure of the magnetic field on the horizon to the ram pressure of the innermost parts of an accretion flow, and （v） the ratio of the angular velocity of the open field lines to that of the horizon. The observed dichotomy between radio-loud and radio-quiet AGNs is well interpreted by the effects of the above parameters. Furthermore, we discuss the derivative of radio loudness of AGNs with respect to each parameter separately. In addition, the effect of the screw instability on radio loudness of AGNs is discussed.

MP-WFRFT and Constellation Scrambling Based Physical Layer Security System

In this paper, a multiple parameters weighted fractional Fourier transform(MPWFRFT) and constellation scrambling(CS) method based physical layer(PHY) security system is proposed. The proposed scheme is executed by two steps. In the first step, MPWFRFT, implemented as the constellation beguiling(CB) method, is applied to change the signal's identity. In the second step the additional pseudo random phase information, regarded as the encryption key, is attached to the original signal to enhance the security. Typically, the pseudo random phase information can be removed effectively by the legitimate receiver. In contrast to the cryptography based encryption algorithms and the conventional PHY secrecy techniques, the main contribution of the proposed scheme is concentrated on the variation in signal's characteristics. Simulation results show that the proposed scheme can prevent the exchanging signal from eavesdroppers' classifi cation or inception. Moreover, the proposed scheme can guarantee the BER performance at a tolerate increasing in computational complexity for the legitimate receivers.

Initial results of China's GNSS-R airborne campaign: soil moisture retrievals

The global navigation satellite system reflectometry （GNSS-R） technique has been proven to be a powerful tool for retrieving geophysical parameters of ocean and land/hydrology processes. The ultimate goal for such GNSS-R applications is to achieve large-scale, all- weather, and full-time mapping using spaceborne platforms. In order to ensure both GNSS-R receiver and algorithm meet the requirements of spaceborne observations, airborne experimental campaigns need to be first carried out for early testing and validation purposes. This paper presents a first comprehensive overview of China＇s airborne GNSS-R campaign conducted on May 30, 2014. There were two objectives for this campaign： （l） to examine the capability of the GNSS-R receiver developed by the National Space Science Center, Chinese Academy of Sciences, for airborne observations and （2） to study algo-rithms for soil moisture and altimetry retrievals. In this paper, initial results of soil moisture retrievals are pre- sented. The left-hand circularly polarized-predominant satellite information was successfully used to retrieval soil moisture over the cropland. The right-hand circularly polarized components of the reflected signals were also received and examined. The GPS-derived soil moisture results, on the one hand, correctly represented the spatial variations of the soil moisture along the tracking of the flight; on the other hand, the results underestimated the ground-truth. Errors from the retrieval model and from the positioning and effects from the vegetation layer and from the atmospheric water vapor were the primary causes of the uncertainties in soil moisture retrievals using the airborne GNSS-R data. This airborne experimental campaign firstly investigate that China has the capability to perform airborne GNSS-R observation using the self-developed receiver, although the receiver developed by the NSSC needs to be further examined for its capability for spaceborne observation. The early findings of this study will provide illustrations for planned future airborne campaigns.

Discovery of two broad absorption line quasars at redshift about 4.75 using the Lijiang 2.4 m telescope

The ultraviolet broad absorption lines have been seen in the spectra of quasars at high redshift, and are generally considered to be caused by outflows with velocities from thousands kilometers per second to one tenth of the speed of light. They provide crucial implications for the cosmological structures and physical evolutions related to the feedback of active galactic nuclei(AGNs).Recently, through a dedicated program of optically spectroscopic identifications of selected quasar candidates at redshift 5 by using the Lijiang 2.4 m telescope, we discovered two luminous broad absorption line quasars(BALQSOs) at redshift about 4.75. One of them may even have the potentially highest absorption Balnicity Index(BI) ever found to date, which is remarkably characterized by its deep, broad absorption lines and sub-relativistic outflows. Further physical properties, including the metal abundances,variabilities, evolutions of the supermassive black holes(SMBH) and accretion disks associated with the feedback process, can be investigated with multi-wavelength follow-up observations in the future.

A first comprehensive evaluation of China's GNSS-R airborne campaign:part Ⅱ—river remote sensing

The Global Navigation Satellite System Reflectometry(GNSS-R) has been proven to be a powerful technique for retrieving geophysical parameters of ocean and land. Airborne GNSS-R is an important experimental platform, because it is not only needed as validation for spaceborne application, but also possesses the advantages to be capable of remote sensing of small and medium scale targets, such as rivers and lakes. This paper presents an overview of China's airborne GNSS-R campaign conducted on May 30, 2014, in Henan. The campaign has two objectives, i.e.:(1) to examine the capability of a GNSS-R payload developed by National Space Science Center,Chinese Academy of Sciences(NSSC, CAS) for airborneobservations and(2) to study the algorithms for soil moisture and river remote sensing, including altimetry and flow velocity measurement. A previous paper has presented results of soil moisture retrieval as part I, and in this paper,initial results of the Yellow River remote sensing are presented as part II. This paper presents the river altimetry results and explores a new potential application of GNSS-R technology, which is used to detect the flow velocity of the river. The river surface height results observed by code delay altimetry method were consistent with the height results of GPS dual-frequency differential positioning altimetry. The GNSS-R altimetry results showed that decimeter level heights were achieved in 1-min sliding average. Comparing with in situ measurements, the GNSSR flow velocity result was reasonable; the error was about0.027 m/s, which indicated the validity and feasibility of using GNSS-R technique to detect river flow velocity.

On the non-synchronous rotation of binary systems

During the evolution of the binary system, many physical processes occur, which can influence the orbital angular velocity and the spin angular velocities of the two components, and influence the non-synchronous or synchronous rotation of the system. These processes include the transfer of masses and angular momentums between the component stars, the loss of mass and angular momentum via stellar winds, and the deformation of the structure of component stars. A study of these processes indicates that they are closely related to the combined effects of tide and rotation. This means, to study the synchronous or non-synchronous rotation of binary systems, one has to consider the contributions of different physical processes simultaneously, instead of the tidal effect alone. A way to know whether the rotation of a binary system is synchronous or non-synchronous is to calculate the orbital angular velocity and the spin angular velocities of the component stars. If all of these angular velocities are equal, the rotation of the system is synchronous. If not, the rotation of the system is non-synchronous. For this aim, a series of equations are developed to calculate the orbital and spin angular velocities. The evolutionary calculation of a binary system with masses of 10M~ ＋ 6Me shows that the transfer of masses and angular momentums between the two components, and the deformation of the components structure in the semidetached or in the contact phase can change the rotation of the system from synchronous into non-synchronous rotation.