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A structure for ultra long span unrepeatered optical transmission systems

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Chinese Optics Letters 2010年第6期8卷 564-568页

作者：阮浩甘朝钦 key lab of Specialty Fiber Optics and optical Access Network Shanghai University

A novel structure for ultra long span optical transmission systems is *** the scheme,the inverse fast Fourier trans form（IFFT） is used as a way of inverse multiplexing.A 40-Gb/s（total effective capacity） system based on the proposed scheme is simulated to evaluate its performance without consideration for dispersion *** results indicate that the proposed system can tolerate distortion caused by chromatic dispersion effectively after long distance transmission.

关键词： Electromagnetic dispersion

Photometric redshift estimation for quasars by integration of KNN and SVM

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Research in astronomy and Astrophysics 2016年第5期16卷 31-40页

作者： Bo Han Hong-Peng Ding Yan-Xia Zhang Yong-Heng Zhao International School of Software Wuhan University key laboratory of optical astronomy National Astronomical Observatories Chinese Academy of Sciences

The massive photometric data collected from multiple large-scale sky surveys offer significant opportunities for measuring distances of celestial objects by photometric redshifts. However, catastrophic failure is an unsolved problem with a long history and it still exists in the current photometric redshift estimation approaches （such as the k-nearest neighbor （KNN） algorithm）. In this paper, we propose a novel two-stage approach by integration of KNN and support vector machine （SVM） methods together. In the first stage, we apply the KNN algorithm to photometric data and estimate their corresponding Zphot. Our analysis has found two dense regions with catastrophic failure, one in the range of Zphot E [0.3, 1.2] and the other in the range of Zphot E [1.2, 2.1]. In the second stage, we map the photometric input pattern of points falling into the two ranges from their original attribute space into a high dimensional feature space by using a Gaussian kernel function from an SVM. In the high dimensional feature space, many outliers resulting from catastrophic failure by simple Euclidean distance computation in KNN can be identified by a classification hyperplane of SVM and can be further corrected. Experimental results based on the Sloan Digital Sky Survey （SDSS） quasar data show that the two-stage fusion approach can significantly mitigate catastrophic failure and improve the estimation accuracy of photometric redshifts of quasars. The percents in different /△z/ ranges and root mean square （rms） error by the integrated method are 83.47%, 89.83%, 90.90% and 0.192, respectively, compared to the results by KNN （71.96%, 83.78%, 89.73% and 0.204）.

关键词： catalogs -- galaxies: distances and redshifts -- methods: statistical -- quasars: general --surveys -- techniques: photometric

A SVM-kNN method for quasar-star classification

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Science China(Physics,Mechanics & astronomy) 2013年第6期56卷 1227-1234页

作者： PENG NanBo ZHANG YanXia ZHAO YongHeng key laboratory of optical astronomy National Astronomical ObservatoriesChinese Academy of Sciences Graduate University of Chinese Academy of Sciences

We integrate k-Nearest Neighbors(kNN) into Support Vector Machine(SVM) and create a new method called ***-kNN strengthens the generalization ability of SVM and apply kNN to correct some forecast errors of SVM and improve the forecast *** addition,it can give the prediction probability of any quasar candidate through counting the nearest neighbors of that candidate which is produced by *** photometric data of stars and quasars with spectral classification from SDSS DR7 and considering limiting magnitude error is less than 0.1,SVM-kNN and SVM reach much higher performance that all the classification metrics of quasar selection are above 97.0%.Apparently,the performance of SVM-kNN has slighter improvement than that of *** SVM-kNN is such a competitive and promising approach that can be used to construct the targeting catalogue of quasar candidates for large sky surveys.

关键词： classification stars/quasars algorithm:SVM kNN data analysis

Moon night sky brightness simulation for the Xinglong station

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Research in astronomy and Astrophysics 2013年第10期13卷 1255-1268页

作者： Song Yao Hao-Tong Zhang Hai-Long Yuan Yong-Heng Zhao Yi-Qiao Dong Zhong-Rui Bai Li-Cai Deng Ya-Juan Lei key laboratory of optical astronomy National Astronomical Observatories Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

Using a sky brightness monitor at the Xinglong station of National Astronomical Observatories,Chinese Academy of Sciences,we collected data from22 dark clear nights and 90 moon *** first measured the sky brightness variation with time for dark nights and found a clear correlation between sky brightness and human *** with a modified sky brightness model of moon nights and data from these nights,we derived the typical value for several important parameters in the *** these results,we calculated the sky brightness distribution under a given moon condition for the Xinglong ***,we simulated the sky brightness distribution of a moon night for a telescope with a 5 field of view（such as LAMOST）.These simulations will be helpful for determining the limiting magnitude and exposure time,as well as planning the survey for LAMOST during moon nights.

关键词： Moon scattering site testing telescopes

Astronomical data fusion tool based on PostgreSQL

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Research in astronomy and Astrophysics 2016年第11期16卷 105-112页

作者： Bo Han Yan-Xia Zhang Shou-Bo Zhong Yong-Heng Zhao International School of Software Wuhan University key laboratory of optical astronomy National Astronomical ObservatoriesChinese Academy of Sciences

With the application of advanced astronomical technologies, equipments and methods all over the world, astronomical observations cover the range from radio, infrared, visible light, ultraviolet, X-ray and gamma-ray bands, and enter into the era of full wavelength astronomy. How to effectively integrate data from different ground- and space-based observation equipments, different observers, different bands and different observation times, requires data fusion technology. In this paper we introduce a cross-match tool that is developed in the Python language, is based on the PostgreSQL database and uses Q3C as the core index, facilitating the cross-match work of massive astronomical data. It provides four different cross- match functions, namely：（I） cross-match of the custom error range; （II） cross-match of catalog errors; （III） cross-match based on the elliptic error range; （IV） cross-match of the nearest neighbor algorithm. The resulting cross-matched set provides a good foundation for subsequent data mining and statistics based on multiwavelength data. The most advantageous aspect of this tool is a user-oriented tool applied locally by users. By means of this tool, users can easily create their own databases, manage their own data and cross- match databases according to their requirements. In addition, this tool is also able to transfer data from one database into another database. More importantly, it is easy to get started with the tool and it can be used by astronomers without writing any code.

关键词： astronomical databases: miscellaneous - catalogs - surveys

An Encryption-Decryption Method Using XOR Gate Based on the XPM between O-Band and C-Band Light Waves

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Chinese Physics Letters 2009年第7期26卷 181-183页

作者：王亚平吴重庆王智王拥军杨双收 Institute of optical Information Key Lab of Luminescence and Optical Information Technology (Ministry of education) Beijing Jiaotong University Beijing 100044

An all-optical encryption-decryption method using an exclusive-or gate based on the cross-phase modulation between O-band and C-band light waves is proposed. The feasibility of the encryptionecryption technique is verified by handling binary signals at 2.5 Gbps, with less than 3dB penalty of extinction ratio and i dB polarization dependent loss.

关键词： sea surface nonliear interaction numerical method

Principal State Analysis for a Compact in-Line Fiber Polarization Controller

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Chinese Physics Letters 2013年第1期30卷 91-94页

作者： LI Zheng-Yong WU Chong-Qing WANG Zhi-Hao QIN Tao WANG Yi-Xu key lab of Education Ministry on Luminescence and optical Information Technology and Institute of optical Information Beijing Jiaotong UniversityBeijing 100044

A compact in-line fiber-based polarization controller(FPC)made of a rotatable fiber squeezer is investigated in detail with the Mueller matrix model established based on the generalized principal state of polarization(PSP).The PSP caused by the fiber squeezing is in the equator plane,which turns around S3 axis on the Poincarésphere when rotating the ***,a programmable polarization control method is proposed to realize the polarization conversion between arbitrary polarization states,in which only two parameters of phase shift and rotation angle need to be *** type of FPC,which has a highly compact structure,lower insertion loss,and can be directly embedded into any fiber devices without any extra delay,will be an ideal PC for high-speed optical communication and all-optical signal processing.

关键词： Poincaré Polarization rotating

Cascaded optical Buffer Based on Nonlinear Polarization Rotation in Semiconductor optical Amplifiers

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Chinese Physics Letters 2008年第11期25卷 4026-4029页

作者：程木吴重庆刘华 Institute of optical Information Key Lab of Luminescence and Optical Information Technology (Ministry of Education) Beijing Jiaotong University Beijing 100044

A cascaded buffer based on nonlinear polarization rotation in semiconductor optical amplifiers is proposed, which is suitable for fast reconfiguration of buffering time at picoseconds. With the proposed buffer, sixty ... 详细信息

关键词： the power-law exponents precipitation durative abrupt precipitation change

Galactic halo age estimated from LAMOST DR4 and Gaia DR1

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Research in astronomy and Astrophysics 2019年第1期19卷 87-94页

作者： Jin-Cheng Guo Hua-Wei Zhang Yang Huang Xiao-Wei Liu Ji-Feng Liu Mao-Sheng Xiang Bing-Qiu Chen Hai-Bo Yuan Zhi-Jia Tian Zhi-Ying Huo Chun Wang Department of astronomy Peking University Kavli Institute for astronomy and Astrophysics Peking University key laboratory of optical astronomy National Astronomical ObservatoriesChinese Academy of Sciences South-Western Institute for astronomy Research Yunnan University Department of astronomy Beijing Normal University

The stellar halo is one of the major components in the Milky Way. Research on its age can provide critical constraints on the origin of the stellar halo and further on the formation of our *** far, different approaches and samples have been used to estimate the age of the Galactic halo. In our previous paper, we carefully selected 63 field halo turn-off stars within 1 kpc from the literature using a kinematic approach, then estimated the age of the halo. In this following work, we not only update the data from LAMOST DR4 and Gaia DR1, but also try a different method to select a clean halo sample by combining the metallicity and orbital parameters. Then we compare this halo turn-off sample with the GARSTEC model in the B-V vs. metallicity plane. After Monte Carlo simulations are performed, the age is estimated to be 10.5±1.4 Gyr, highly consistent with our previous result and other studies. However,due to the limited common sources between LAMOST DR4 and Gaia DR1, the final sample in this paper is still quite small. The estimated age will be more robust with the much larger Gaia DR2.

关键词： galaxies:halos Galaxy:evolution stars:kinematics and dynamics