Recent Progress in Atmospheric Observation Research in China

Recent progress in atmospheric observation techniques, observational systems and their application in China are reviewed. According to different observational platforms, the review is presented in three sections, i.e., satellite remote sensing （SRS）, ground-based observation technologies and applications, and aircraft/balloon measurements. The section ＂satellite remote sensing＂ presents advances in SRS techniques, SRS of clouds and aerosols, and SRS of trace gases and temperature/moisture profiles. The section ＂groundbased observation technologies and applications＂ focuses on research such as lidar systems and applications, sun/sky radiometer and broadband radiation observations, weather radar and wind profilers, GPS measurements, and some new concept systems. The section ＂aircraft/balloon measurements＂ presents some newly developed aircraft- and balloon-based sounding techniques.

Atmospheric extinction coefficients and night sky brightness at the Xuyi Observation Station

We present measurements of the optical broadband atmospheric extinction coefficients and the night sky brightness at the Xuyi Observation Station of Purple Mountain Observatory. The measurements are based on CCD imaging data taken in the Sloan Digital Sky Survey＇s g, r and i bands with the Xuyi 1.04/1.20m Schmidt Telescope for the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticenter （XSTPS-GAC）, the photometric part of the Digital Sky Survey of the Galactic Anti-center （DSS-GAC）. The data were collected during more than 140 winter nights from 2009 to 2011. We find that the atmospheric extinction coefficients for the g, r and i bands are 0.69, 0.55 and 0.38 mag/airmass, respectively, based on observations taken on several photometric nights. The night sky brightness determined from images with good quality has median values of 21.7, 20.8 and 20.0 mag arcsec-2 and reaches 22.1, 21.2 and 20.4mag arcsec-2 under the best observing conditions for the g, r and i bands, respectively. The relatively large extinction coefficients compared with other good astronomical observing sites are mainly due to the relatively low elevation （i.e. 180 m） and high humidity at the station.

How to co-add images? I. A new iterative method for image reconstruction of dithered observations

By employing the previous Voronoi approach and replacing its nearest neighbor approx- imation with Drizzle in iterative signal extraction, we develop a fast iterative Drizzle algorithm, namedfiDrizzle, to reconstruct the underlying band-limited image from undersampled dithered frames. Compared with the existing iDrizzle, the new algorithm improves rate of convergence and accelerates the computational speed. Moreover, under the same conditions （e.g. the same number of dithers and iterations）, fiDrizzle can make a better quality reconstruction than iDrizzle, due to the newly discov- ered High Sampling caused Decelerating Convergence （HSDC） effect in the iterative signal extraction process.fiDrizzle demonstrates its powerful ability to perform image deconvolution from undersampled dithers.

Fabrication of a model specimen for understanding micro-galvanic corrosion at the boundary ofα-Mg andβ-Mg17Al12

A model specimen with a single boundary of theα/βphase simulating Mg-Al alloys was successfully fabricated by spark plasma sintering.A small electrode area ofαphase orβphase was prepared using the model specimen,and the OCPs(open-circuit potentials)of each phase and a small electrode area containing theα/βphase boundary in 0.1 M NaCl at pH 8.0 were compared:theβphase exhibited a higher potential,and theαphase showed a lower potential.The OCP of the small area containing theα/βphase boundary was the intermediate value of these phases.In a small area containingα/βphase boundary,discoloration and gas bubbles were observed on theαphase,but no bubble generation was detected on theβphase.The gas bubbles were initially generated on theαphase near theβphase,but as the discoloration(corrosion)of theαphase approached theβphase,the bubbles were generated on theβphase.In micro-galvanic corrosion of theαandβphases,theβphase did not always function as the preferred cathode.Theαphase partially corroded(or discolored)and became the anodes,so that the surrounding areas were most likely to be the cathodes.When corroded areas(anodes)in theαphase approached theβphase,theβphase would become cathodes.In addition to the micro-galvanic corrosion mechanism,the role of Al in corrosion resistance at theα/βphase boundary was determined by surface analysis.

Geodesy Discipline: Progress and Perspective

The geodesy discipline has been evolving and constantly intersecting and merging with other disciplines in the last 50 years,due to the continuous progress of geodetic observation techniques and expansion of application fields.This paper first introduces the development and roles of geodesy and its formation.Secondly,the development status of geodesy discipline is analyzed from the progress of observation techniques and cross-discipline formation is analyzed from the expansion of application fields.Furthermore,the development trend of geodesy is stated from the perspective of national requirements and scientific developments.Finally,the sub-disciplines for geodesy are suggested at the present stage,based on the requirements of the National Natural Science Foundation of China and development status of geodesy itself,which can provide references for topic selection and fund application of geodetic scientific research.

Distributed Robust Containment Control of Linear Heterogeneous Multi-Agent Systems:An Output Regulation Approach

In this paper,we consider the robust output containment problem of linear heterogeneous multi-agent systems under fixed directed networks.A distributed dynamic observer based on the leaders’measurable output was designed to estimate a convex combination of the leaders’states.First,for the case of followers with identical state dimensions,distributed dynamic state and output feedback control laws were designed based on the state-coupled item and the internal model compensator to drive the uncertain followers into the leaders’convex hull within the output regulation framework.Subsequently,we extended theoretical results to the case where followers have nonidentical state dimensions.By establishing virtual errors between the dynamic observer and followers,a new distributed dynamic output feedback control law was constructed using only the states of the compensator to solve the robust output containment problem.Finally,two numerical simulations verified the effectiveness of the designed schemes.

The radio environment of the 21 Centimeter Array:RFI detection and mitigation

Detection and mitigation of radio frequency interference （RFI） is the first and also the key step for data processing in radio observations, especially for ongoing low frequency radio experiments towards the detection of the cosmic dawn and epoch of reionization （EoR）. In this paper we demonstrate the tech- nique and efficiency of RFI identification and mitigation for the 21 Centimeter Array （21CMA）, a radio interferometer dedicated to the statistical measurement of EoR. For terrestrial, man-made RFI, we concen- trate mainly on a statistical approach by identifying and then excising non-Gaussian signatures, in the sense that the extremely weak cosmic signal is actually buried under thermal and therefore Gaussian noise. We also introduce the so-called visibility correlation coefficient instead of conventional visibility, which allows a further suppression of rapidly time-varying RFI. Finally, we briefly discuss removals of the sky RFI, the leakage of sidelobes from off-field strong radio sources with time-invariant power and a featureless spec- trum. It turns out that state of the art technique should allow us to detect and mitigate RFI to a satisfactory level in present low frequency interferometer observations such as those acquired with the 21CMA, and the accuracy and efficiency can be greatly improved with the employment of low-cost, high-speed computing facilities for data acquisition and processing.

Particle swarm optimization based space debris surveillance network scheduling

The increasing number of space debris has created an orbital debris environment that poses increasing impact risks to existing space systems and human space flights. For the safety of in-orbit spacecrafts, we should optimally schedule surveillance tasks for the existing facilities to allocate re- sources in a manner that most significantly improves the ability to predict and detect events involving affected spacecrafts. This paper analyzes two criteria that mainly affect the performance of a scheduling scheme and introduces an artificial intelligence algorithm into the scheduling of tasks of the space debris surveillance network. A new scheduling algorithm based on the particle swarm optimization algorithm is proposed, which can be implemented in two different ways： individual optimization and joint optimiza- tion. Numerical experiments with multiple facilities and objects are conducted based on the proposed algorithm, and simulation results have demonstrated the effectiveness of the proposed algorithm.

A new multi-wavelength solar telescope: Optical and Near-infrared Solar Eruption Tracer (ONSET)

A new multi-wavelength solar telescope, the Optical and Near-infrared Solar Eruption Tracer （ONSET） of Nanjing University, has been constructed. It was fabricated at the Nanjing Institute of Astronomical Optics ＆ Technology, and the oper- ation is jointly administered with Yunnan Astronomical Observatory. ONSET is able to observe the Sun in three wavelength windows： He I 10830 A, Ha and white-light at 3600 A and 4250 A, which are selected in order to simultaneously record the dynam- ics of the corona, chromosphere and photosphere respectively. Full-disk or partial-disk solar images with a field of 10~ at three wavelengths can be obtained nearly simultane- ously. It is designed to trace solar eruptions with high spatial and temporal resolutions. This telescope was installed at a new solar observing site near Fuxian Lake in Yunnan Province, southwest China. The site is located at E102N24, with an altitude of 1722 m. The seeing is stable and has high quality. We give a brief description of the scientific objectives and the basic structure of ONSET. Some preliminary results are also pre- sented.

Research on scheduling of robotic transient survey for Antarctic Survey Telescopes(AST3)

Antarctic Survey Telescopes（AST3） are designed to be fully robotic telescopes at Dome A,Antarctica,which aim for highly efficient time-domain sky surveys as well as rapid response to special transient events（e.g.,gamma-ray bursts,near-Earth asteroids,supernovae,etc.）.Unlike traditional observations,a well-designed real-time survey scheduler is needed in order to implement an automatic survey in a very efficient,reliable and flexible way for the unattended telescopes.We present a study of the survey strategy for AST3 and implementation of its survey scheduler,which is also useful for other survey projects.

Photometric studies of two W UMa type variables in the field of distant open cluster NGC 6866

We present photometric analysis of the two W UMa type binaries identified in the field of distant open star cluster NGC 6866. Although these systems, namely ID487 and ID494, were reported by Joshi et al., a detailed study of these stars has not been carried out before. The orbital periods of these stars are found to be 0.415110±0.000001 day and 0.366709±0.000004 day, respectively. Based on the photometric and infrared colors, we find their respective spectral types to be K0 and K3. The photometric light vari- ations of both stars show the O＇Connell effect which can be explained by employing a dark spot on the secondary components. The V and I band light curves are analyzed using the Wilson-Devinney （WD） code and relations given by Gazeas which yield radii and masses for the binary components of star ID487 of R1 = 1.24 ± 0.01R,R2 = 1.11 4- 0.02Re, and M1 = 1.24 ± 0.02Me, M2 = 0.96 ±0.05Me and for star ID494 of R1 = 1.22 ± 0.02Re, R2 = 0.81 4- 0.01 Re, and M1 = 1.20 4- 0.06 Me, M2 = 0.47 4- 0.01 Me.

Long-term photometric study of a faint W UMa binary in the direction of M31

We carry out a re-analysis of the photometric data in Rclc bands which were taken during the Nainital Microlensing Survey from 1998 to 2002 with the aim to detect gravitational microlensing events in the direction of M31. Here, we do photometric analysis of a faint W UMa binary CSS_JO04259.3＋410629 identified in the target field. The orbital period of this star is found to be 0.266402±0.000018 d. The photometric mass ratio, q, is found to be 0.28±0.01. The photometric light curves are investigated using the Wilson-Devinney （WD） code and absolute parameters are determined using empirical relations which provide masses and radii of the binary as M1 = 1.19±0.09M⊙, M2 = 0.33±0.02M⊙ and R1 = 1.02±0.04R⊙, R2 = 0.58±0.08Re respectively based on Rc band data. Quite similar values are found by analyzing/c band data. From the photometric light curve examination, the star is understood to be a low mass-ratio overcontact binary of A-subtype with a high fill-out factor of about 47%. The binary system is found to be located approximately at a distance of 2.64±0.03 kpc having a separation of 2.01 ±0.05 Re between the two components.

South Galactic Cap u-band Sky Survey(SCUSS):Project Overview

The South Galactic Cap u-band Sky Survey （SCUSS） was established in 2009 in order to provide a photometric input catalog for target selection of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope （LAMOST） project. SCUSS is an international cooperative project between National Astronomical Observatories, Chinese Academy of Sciences, and Steward Observatory at the University of Arizona, using the 90 inch （2.3 m） Bok telescope on Kitt Peak. The telescope is equipped with a prime focus camera that is composed of a mosaic of four 4096 × 4096 CCDs and has a field of view of about 1 deg2. From 2009 to 2013, SCUSS performed a sky survey of an approximately 5000 deg2 field of the South Galactic Cap in u band, including the Galactic anticenter area and the SDSS-IV extended imaging area. The limiting magnitude of SCUSS is deeper than 23 mag （at a signal-to-noise ratio of 5）. In this paper, we briefly describe the goals of this project, method of observations and data reduction, and we also introduce current and potential scientific activities related to the SCUSS project.

Manifestations of bright points observed in G-band and CaⅡH by Hinode/SOT

An algorithm was developed for identifying and tracking a magnetic bright point, or bright point （BP） for short, observed in both the photosphere （G-band） and chromosphere （Ca II H）, as well as for pairing a photospheric BP （PBP） with its conjugate chromospheric BP （CBP）. Two sets of data observed by Hinode/SOT in the quiet Sun near the disk center were analyzed. About 278 PBP-CBP pairs were identified and tracked. Lifetimes of both the PBPs and CBPs follow an exponential distribution with average lifetimes of 174 s and 163 s, respectively. We found that the differences in appearance time, in disappearance time and in lifetime of the two kinds of BPs all follow Gaussian distributions,which may indicate that the mechanisms of PBP and CBP formation/disintegration are different. However, the lifetimes of PBPs and CBPs are positively correlated with one another, with a correlation coefficient of 0.8. Furthermore, we calculated the horizontal displacement between the PBP and its conjugate CBP, which follows a Gaussian function with an average and standard deviation of （67.7 ± 38.5）km. We also calculated the amplitude of the flux tube shape change which might be caused by MHD waves propagating along the flux tube, and found that it follows an exponential distribution very well.

Frequency drift rate of solar decameter"drift pair"bursts

This paper deals with the detailed analysis of frequency drift rates of solar ＂drift pair＂ （DP） bursts observed from 2015 July 10 to 12 during a type III burst storm. The observations were conducted by the UTR-2 radio telescope at 9-33 MHz with high frequency and time resolution. DPs were recorded drifting from higher to lower frequencies （forward DPs） as well as from lower to higher ones （reverse DPs）. Patterns on their dynamic spectrum had various inclines and occupied different bandwidths. The frequency drift rate versus frequency dependence of these bursts has been studied. The fitting model to describe the peak evolution of these bursts in the frequency-time plane is presented. The relationship between DPs and type III solar bursts is discussed.

The Coudé Echelle Spectrograph for the Xinglong 2.16m Telescope

A brief description of the NAO coude echelle spectrograph mounted on the 2.16 m telescope at Xinglong station is given. This echelle spectrograph is located at the coudé focus with a prism cross disperser. The echelle image covers the spectral region from 330 to 1100 nm displayed in 80 spectral orders in one exposure through two light beams. With a slit height of 2mm, spectral orders are separated by 15 to 23 pixels in blue region and by 7 to 19 pixels in red region. Alternatively, two additional resolution modes corresponding to different focal length cameras with resolving power R 16000, 170 000 in the blue beam and R = 13000, 170 000 in the red beam could be provided by this spectrograph. The bias, dark, wavelength calibration, flat field and science exposure are described in details. The limiting magnitude for 1 hour exposure with an S/N ratio of 100 scales to V = 9.5 in the red path and to V = 7.2 in the blue path.

Design of a P-&-O algorithm based MPPT charge controller for a stand-alone 200W PV system

Solar cells convert sun light into electricity,but have the major drawbacks of high initial cost,low photo-conversion efficiency and intermittency.The current-voltage characteristics of the solar cells depend on solar insolation level and temperature,which lead to the variation of the maximum power point(MPP).Herein,to improve photovoltaic(PV)system efficiency,and increase the lifetime of the battery,a microcontroller-based battery charge controller with maximum power point tracker(MPPT)is designed for harvesting the maximum power available from the PV system under given insolation and temperature conditions.Among different MPPT techniques,perturb and observe(P&O)technique gives excellent results and thus is used.This work involves the design of MPPT charge controller using DC/DC buck converter and microcontroller.A prototype MPPT charge controller is tested with a 200 W PV panel and lead acid battery.The results show that the designed MPPT controller improves the efficiency of the PV panel when compared to conventional charge controllers.

Observer-based adaptive sliding mode backstepping output-feedback DSC for spin-stabilized canard-controlled projectiles

This article presents a complete nonlinear controller design for a class of spin-stabilized canard-controlled projectiles.Uniformly ultimate boundedness and tracking are achieved,exploiting a heavily coupled,bounded uncertain and highly nonlinear model of longitudinal and lateral dynamics.In order to estimate unmeasurable states,an observer is proposed for an augmented multiple-input-multiple-output（MIMO） nonlinear system with an adaptive sliding mode term against the disturbances.Under the frame of a backstepping design,an adaptive sliding mode output-feedback dynamic surface control（DSC） approach is derived recursively by virtue of the estimated states.The DSC technique is adopted to overcome the problem of ‘‘explosion of complexity＂ and relieve the stress of the guidance loop.It is proven that all signals of the MIMO closed-loop system,including the observer and controller,are uniformly ultimately bounded,and the tracking errors converge to an arbitrarily small neighborhood of the origin.Simulation results for the observer and controller are provided to illustrate the feasibility and effectiveness of the proposed approach.

The Change of Orientation Relationships Between Austenite and α'-Martensite During Deformation in High Manganese TRIP Steel

In situ observation of electron backscattering diffraction technique was used to evaluate the orientation relationships between austenite and α′-martensite（α′-M） for high manganese transformation-induced plasticity steel.It was noted that different from the thermal martensite,which well obeyed K-S relationship with austenite,the orientation relationship between deformation-induced α′-M with austenite changed during deformation,namely K-S and N-W relations coexisted.No clear differences existed between α′-M variants with two kinds of relationships in terms of martensitic orientation,shape and the misorientation between α′-M variants.And this phenomenon happened in almost all austenitic grains with different orientations investigated in this study.An atom displacement mechanism through conjugate complex slips of partial dislocations in the distorted fcc lattice was applied in this article to interpret the coexistence of K-S and N-W relationships.