China Academy of science

Guiyang, China

China Academy of science

Guiyang, China
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An F.X.,China Academy of science | An F.X.,University of Chinese Academy of Sciences | Zheng X.Z.,China Academy of science | Hao C.-N.,Tianjin Normal University | And 2 more authors.
Astrophysical Journal | Year: 2017

The Lyα escape fraction is a key measure to constrain the neutral state of the intergalactic medium and then to understand how the universe was fully reionized. We combine deep narrowband imaging data from the custom-made filter NB393 and the filter centered at 2.14 μm to examine the Lyα emitters and Hα emitters at the same redshift z = 2.24. The combination of these two populations allows us to determine the Lyα escape fraction at z = 2.24. Over an area of 383 arcmin2 in the Extended Chandra Deep Field South (ECDFS), 124 Lyα emitters are detected down to NB393 = 26.4 mag at the 5σ level, and 56 Hα emitters come from An et al. Of these, four have both Lyα and Hα emissions (LAHAEs). We also collect the Lyα emitters and Hα emitters at z = 2.24 in the COSMOS field from the literature, and increase the number of LAHAEs to 15 in total. About one-third of them are AGNs. We measure the individual/volumetric Lyα escape fraction by comparing the observed Lyα luminosity/luminosity density to the extinction-corrected Hα luminosity/luminosity density. We revisit the extinction correction for Hα emitters using the Galactic extinction law with color excess for nebular emission. We also adopt the Calzetti extinction law together with an identical color excess for stellar and nebular regions to explore how the uncertainties in extinction correction affect the estimate of individual and global Lyα escape fractions. In both cases, an anti-correlation between the Lyα escape fraction and dust attenuation is found among the LAHAEs, suggesting that dust absorption is responsible for the suppression of the escaping Lyα photons. However, the estimated Lyα escape fraction of individual LAHAEs varies by up to ∼3 percentage points between the two methods of extinction correction. We find the global Lyα escape fraction at z = 2.24 to be (3.7 1.4)% in the ECDFS. The variation in the color excess of the extinction causes a discrepancy of ∼1 percentage point in the global Lyα escape fraction. © 2017. The American Astronomical Society. All rights reserved.

Sprafke A.,Martin Luther University of Halle Wittenberg | Behrendt A.,University of Hohenheim | Liu J.,China Academy of science | Spencer L.,University of Lethbridge | Tang J.,Soochow University of China
Optics Express | Year: 2017

This feature issue highlights contributions from authors who presented their research at the OSA Light, Energy and the Environment Congress, held in Leipzig, Germany from November 14 to 17, 2016. © 2017 Optical Society of America.

Zhang L.,University of Jinan | Yin J.-Q.,Beijing University of Posts and Telecommunications | Yin J.-Q.,China Academy of Science | Lin J.-B.,China Academy of Science | And 2 more authors.
Solar Physics | Year: 2017

Coronal Mass Ejections (CMEs) release tremendous amounts of energy in the solar system, which has an impact on satellites, power facilities and wireless transmission. To effectively detect a CME in Large Angle Spectrometric Coronagraph (LASCO) C2 images, we propose a novel algorithm to locate the suspected CME regions, using the Extreme Learning Machine (ELM) method and taking into account the features of the grayscale and the texture. Furthermore, space–time continuity is used in the detection algorithm to exclude the false CME regions. The algorithm includes three steps: i) define the feature vector which contains textural and grayscale features of a running difference image; ii) design the detection algorithm based on the ELM method according to the feature vector; iii) improve the detection accuracy rate by using the decision rule of the space–time continuum. Experimental results show the efficiency and the superiority of the proposed algorithm in the detection of CMEs compared with other traditional methods. In addition, our algorithm is insensitive to most noise. © 2017, Springer Science+Business Media Dordrecht.

Han Y.,China Academy of science
Zhonghua yi shi za zhi (Beijing, China : 1980) | Year: 2010

Tai ping sheng hui fang, the first medical formulary of the Song Dynasty, compiled from the 3(rd) year of Taiping-xingguo reign to the 3(rd) year of Chunhua reign (978 ∼ 992), under the edict of the Taizong Emperor, was popularly applied and extensively circulated and called "the first formulary of the Dynasty". It is extremely significant in the medical history of the Song Dynasty due to its theory of prescription art, practical prescriptions and clinical practice. During the process of its circulation, different versions appeared, including the Guozijian Orthodox Version, Guozijian Small-character Version, Chongwen Hall Abridged Version, Newly Carved Version of Zhuanyunsi, and the Local Abridged Version, thus adapting to the demands of various walks of life in the society. Its unique role in the development of the Song society was founded by its introduction, application and popularization by the emperors, local officials, medical scholars, diplomatic envoys, and intellectuals. The "kind administration" of the authority and the government was further greatly facilitated by the involvement of the government and the introduction of printing. Its practical prescriptions became forceful tools to prevent and treat diseases, to conquer witchcraft, to protect local social security, and to pronounce the merits of officials and physicians at all levels.

Wang R.,China Academy of Science | Wang R.,U.S. National Radio Astronomy Observatory | Wang R.,Peking University | Carilli C.L.,U.S. National Radio Astronomy Observatory | And 10 more authors.
Astrophysical Journal | Year: 2010

We report our new observations of redshifted carbon monoxide emission from six z ∼ 6 quasars, using the IRAM Plateau de Bure Interferometer. CO (6-5) or (5-4) line emission was detected in all six sources. Together with two other previous CO detections, these observations provide unique constraints on the molecular gas emission properties in these quasar systems close to the end of the cosmic re-ionization. Complementary results are also presented for low-J CO lines observed at the Green Bank Telescope and the Very Large Array, and dust continuum from five of these sources with the SHARC-II bolometer camera at the Caltech Submillimeter Observatory. We then present a study of the molecular gas properties in our combined sample of eight CO-detected quasars at z 6. The detections of high-order CO line emission in these objects indicates the presence of highly excited molecular gas, with estimated masses on the order of 1010 M ⊙ within the quasar host galaxies. No significant difference is found in the gas mass and CO line width distributions between our z ∼ 6 quasars and samples of CO-detected 1.4 ≤ z ≤ 5 quasars and submillimeter galaxies. Most of the CO-detected quasars at z ∼ 6 follow the far-infrared-CO luminosity relationship defined by actively star-forming galaxies at low and high redshifts. This suggests that ongoing star formation in their hosts contributes significantly to the dust heating at FIR wavelengths. The result is consistent with the picture of galaxy formation co-eval with supermassive black hole (SMBH) accretion in the earliest quasar-host systems. We investigate the black hole-bulge relationships of our quasar sample, using the CO dynamics as a tracer for the dynamical mass of the quasar host. The median estimated black hole-bulge mass ratio is about 15 times higher than the present-day value of 0.0014. This places important constraints on the formation and evolution of the most massive SMBH-spheroidal host systems at the highest redshift. © 2010. The American Astronomical Society. All rights reserved.

Huang K.,China Academy of Science | Huang K.,Anhui University of Science and Technology | Shi P.,Anhui University of Science and Technology | Cao G.W.,Anhui University of Science and Technology | And 4 more authors.
Optics Letters | Year: 2011

We demonstrate that the amplitude of vector-vortex beams has a Bessel-Gauss (BG) distribution through a rigorous vector electromagnetic analysis. We also investigate the intensity profiles in the focal plane of vector-vortex beams that are focused by a high numerical-aperture lens obeying the Helmholtz condition. Although the intensity of a vector-vortex BG beam with a topological charge n = 1 is nonzero along the axis in the focal plane, the beams with n ≠ 1 show discrete multiple spots which can be useful for optical trapping. © 2011 Optical Society of America.

Shi P.,China Academy of Science | Shi P.,Anhui University of Science and Technology | Huang K.,China Academy of Science | Kang X.-L.,China Academy of Science | And 2 more authors.
Optics Express | Year: 2010

A two-dimensional anisotropic annular photonic crystal slab structure composed of circular air holes and dielectric rods with finite thickness in a triangular lattice is presented to achieve an absolute photonic band gap. Positive uniaxial crystal Tellurium is introduced to the structure with the extraordinary axis parallel to the extension direction of rods. The role of each geometric parameter is investigated by employing the conjugate-gradient method. A large mid-gap ratio is realized by the parameter optimization. A flat band called as anomalous group velocity within two large gaps is discovered and can be widely applied in many fields. A hybrid structure with GaAs slab and Te rods is designed to achieve a large gap and demonstrates that the annular structure can improve the gap effectively. © 2010 Optical Society of America.

Yang J.,Peking University | Quan J.,Georgia Institute of Technology | Yan B.,China Academy of Science | He C.,Peking University
Transportation Research Part A: Policy and Practice | Year: 2016

As a response to severe urban congestion, megacities in China have sped up investment in urban rail transit. How effective urban rail investment and relevant planning activities can attract development in China's megacities has rarely been studied. Using eight years' land transaction data in Beijing (2004-2011), this research finds that the market environment in general supports higher density development around transit stations. However, relevant land market regulations and planning practices may prevent the development outcome from reaching its market potential. City governments should adjust existing planning and policy efforts, including more transparent and open process for station location selection, a better articulated investment program that improves transit service, social service and infrastructure quality in suburbs, a shift toward transaction modes of more competition, and a development guidance that grants density bonus to projects closer to metro stations. © 2016 Elsevier Ltd.

Yu J.,China Academy of science | Di Y.,China Academy of science | Dong K.,China Academy of science | Nan K.,China Academy of science
Huazhong Keji Daxue Xuebao (Ziran Kexue Ban)/Journal of Huazhong University of Science and Technology (Natural Science Edition) | Year: 2011

The concept of Internet collaborative environment and cloud computing were introduced, and the evolution of service mode for Internet collaborative environment when adopting the cloud computing technology was analyzed. Then a cloud service oriented Internet collaborative environment was constructed based on grid computing and cloud computing named as ResearchOnline. ResearchOnline aimes to provide collaborative virtual machine using virtualization technology, heterogeneous resource integration using grid computing, and extensibility using multiple portal configuration techonolgy. ResearchOnline helps researchers to create a collaborative platform only with simple steps, which would simplify the collaborative application and enhance the transparent of the system. Several excellent applications were illustrated to prove that ResearchOnline is useful for scientists in CAS (Chinese Academy of Sciences).

Yang J.,Georgia Institute of Technology | Fang C.,China Academy of science | Ross C.,Georgia Institute of Technology | Song G.,Georgia Institute of Technology
Transportation Research Record | Year: 2011

Improved mobility and accessibility for passengers and goods provide competitive advantages for megaregions. This article describes the trends in mobility in China's top three megaregions-the Capital Economic Zone, the Yangtze River Delta, and the Pearl River Delta-and how megaregional planning has led to solutions to the challenges of mobility. China's experience is compared with trends in megaregions in the United States and the European Union. This comparative context confirms that existing trends in China's regional mobility carry severe energy and environmental challenges and that China's movement toward rail, particularly high-speed rail, provides a better chance to mitigate congestion and pollution problems.

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