The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Shizhao Shen - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of solar temperature field under different wind speeds for Shanghai 65 m Radio Telescope
International Journal of Steel Structures, 2016Co-Authors: Hongliang Qian, Feng Fan, Deshen Chen, Ye Liu, Shizhao ShenAbstract:The Shanghai 65 m Radio Telescope is currently the largest full range rotatable Radio Telescope in Asia. Gravity, wind and temperature are the three main factors which may have a bad effect on the reflector’s surface precision. To study the effect of the thermal deformation caused by daily non-uniform temperature fields on the surface precision of the main reflector, both the temperature field and its effect were studied in detail for two typical days (January 15th and July 15th). The method to simulate temperature fields was studied initially, considering heat conduction, solar radiation, shadowing, air convection, sky radiation and ground radiation. Then, an integral parametric thermal finite element model (FEM) of the Telescope was established using the ANSYS thermal analysis module. Finally, the effect of non-uniform temperature fields on the surface precision of the main reflector was estimated in terms of the Root Mean Square (RMS) deformation based on temperature transient analysis. The proposed methods and conclusions drawn can provide valuable information for thermal design, thermal monitoring and thermal control of the Shanghai 65 m Radio Telescope and other similar giant antenna structures.
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Solar cooker effect test and temperature field simulation of Radio Telescope subreflector
Applied Thermal Engineering, 2016Co-Authors: Deshen Chen, Huajie Wang, Hongliang Qian, Gang Zhang, Shizhao ShenAbstract:Abstract The solar cooker effect can cause a local high temperature of the subreflector and can directly affect the working performance of the Radio Telescope. To study the daily temperature field and solar cooker effect of a subreflector, experimental studies are carried out with a 3-m-diameter Radio Telescope model for the first time. Initially, the solar temperature distribution rules, especially the solar cooker effect, are summarized according to the field test results under the most unfavorable conditions. Then, a numerical simulation for the solar temperature field of the subreflector is studied by light beam segmentation and tracking methods. Finally, the validity of the simulation methods is evaluated using the test results. The experimental studies prove that the solar cooker effect really exists and should not be overlooked. In addition, simulation methods for the subreflector temperature field proposed in this paper are effective. The research methods and conclusions can provide valuable references for thermal design, monitoring and control of similar high-precision Radio Telescopes.
Deshen Chen - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of solar temperature field under different wind speeds for Shanghai 65 m Radio Telescope
International Journal of Steel Structures, 2016Co-Authors: Hongliang Qian, Feng Fan, Deshen Chen, Ye Liu, Shizhao ShenAbstract:The Shanghai 65 m Radio Telescope is currently the largest full range rotatable Radio Telescope in Asia. Gravity, wind and temperature are the three main factors which may have a bad effect on the reflector’s surface precision. To study the effect of the thermal deformation caused by daily non-uniform temperature fields on the surface precision of the main reflector, both the temperature field and its effect were studied in detail for two typical days (January 15th and July 15th). The method to simulate temperature fields was studied initially, considering heat conduction, solar radiation, shadowing, air convection, sky radiation and ground radiation. Then, an integral parametric thermal finite element model (FEM) of the Telescope was established using the ANSYS thermal analysis module. Finally, the effect of non-uniform temperature fields on the surface precision of the main reflector was estimated in terms of the Root Mean Square (RMS) deformation based on temperature transient analysis. The proposed methods and conclusions drawn can provide valuable information for thermal design, thermal monitoring and thermal control of the Shanghai 65 m Radio Telescope and other similar giant antenna structures.
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Solar cooker effect test and temperature field simulation of Radio Telescope subreflector
Applied Thermal Engineering, 2016Co-Authors: Deshen Chen, Huajie Wang, Hongliang Qian, Gang Zhang, Shizhao ShenAbstract:Abstract The solar cooker effect can cause a local high temperature of the subreflector and can directly affect the working performance of the Radio Telescope. To study the daily temperature field and solar cooker effect of a subreflector, experimental studies are carried out with a 3-m-diameter Radio Telescope model for the first time. Initially, the solar temperature distribution rules, especially the solar cooker effect, are summarized according to the field test results under the most unfavorable conditions. Then, a numerical simulation for the solar temperature field of the subreflector is studied by light beam segmentation and tracking methods. Finally, the validity of the simulation methods is evaluated using the test results. The experimental studies prove that the solar cooker effect really exists and should not be overlooked. In addition, simulation methods for the subreflector temperature field proposed in this paper are effective. The research methods and conclusions can provide valuable references for thermal design, monitoring and control of similar high-precision Radio Telescopes.
Rendong Nan - One of the best experts on this subject based on the ideXlab platform.
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the five hundred meter aperture spherical Radio Telescope fast project
International Journal of Modern Physics D, 2011Co-Authors: Rendong Nan, Chengjin Jin, Qiming Wang, Lichun Zhu, Wenbai Zhu, Haiyan Zhang, Youling Yue, Lei QianAbstract:Five-hundred-meter Aperture Spherical Radio Telescope (FAST) is a Chinese mega-science project to build the largest single dish Radio Telescope in the world. Its innovative engineering concept and design pave a new road to realize a huge single dish in the most effective way. FAST also represents Chinese contribution in the international efforts to build the square kilometer array (SKA). Being the most sensitive single dish Radio Telescope, FAST will enable astronomers to jump-start many science goals, such as surveying the neutral hydrogen in the Milky Way and other galaxies, detecting faint pulsars, looking for the first shining stars, hearing the possible signals from other civilizations, etc. The idea of sitting a large spherical dish in a karst depression is rooted in Arecibo Telescope. FAST is an Arecibo-type antenna with three outstanding aspects: the karst depression used as the site, which is large to host the 500-meter Telescope and deep to allow a zenith angle of 40 degrees; the active main ref...
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five hundred meter aperture spherical Radio Telescope fast
Science China-physics Mechanics & Astronomy, 2006Co-Authors: Rendong NanAbstract:Five hundred meter aperture spherical Radio Telescope (FAST) will be the largest Radio Telescope in the world. The innovative engineering concept and design pave a new road to realizing a huge single dish in the most effective way. Three outstanding features of the Telescope are the unique karst depressions as the sites, the active main reflector which corrects spherical aberration on the ground to achieve full polarization and a wide band without involving a complex feed system, and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. Being the most sensitive Radio Telescope, FAST will enable astronomers to jumpstart many of the science goals, for example, the neutral hydrogen line surveying in distant galaxies out to very large redshifts, looking for the first shining star, detecting thousands of new pulsars, etc. Extremely interesting and exotic objects may yet await discovery by FAST. As a multi-science platform, the Telescope will provide treasures to astronomers, as well as bring prosperity to other research, e.g. space weather study, deep space exploration and national security. The construction of FAST itself is expected to promote the development in high technology of relevant fields.
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singularity analysis of fine tuning stewart platform for large Radio Telescope using genetic algorithm
Mechatronics, 2003Co-Authors: B Y Duan, B Peng, Rendong NanAbstract:Abstract A new singularity analysis method for general six degree-of-freedom (DOF) Stewart platform using genetic algorithm (GA) is proposed in this paper. The Jacobian matrix of Stewart platform is first deduced, then the square of determinant of the Jacobian matrix is selected as the objective function, and the minimal of this objective function is searched in the workspace of Stewart platform by the GA. The singularity of Stewart platform depends on this minimal objective function: if this value is zero, the singularity of Stewart platform will take place, otherwise, the Stewart platform is singularity-free. The effectiveness of this new genetic singularity analysis method is validated by the singularity analysis of a six-DOF fine-tuning Stewart platform for the next generation large Radio Telescope. The results have shown that the fine-tuning Stewart platform is singularity-free, which has laid a solid base for the requirement of high precision trajectory tracking for the next generation large Radio Telescope.
Roberto Ambrosini - One of the best experts on this subject based on the ideXlab platform.
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The sardinia Radio Telescope: Overview and status
2013 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2013Co-Authors: Roberto Ambrosini, Pietro Bolli, N. D'amico, A. Bocchinu, F. Buffa, M. Buttu, A. Cattani, G. L. Deiana, A. Fara, F. FiocchiAbstract:The Sardinia Radio Telescope is approaching to its official inauguration. Nowadays, the technical staff is accomplishing the last remaining activities to set up and integrate the microwave receivers, the digital processing systems and all the equipment necessary to reach a top level in the international scenario of large Radio Telescopes. Even if the Radio Telescope is still along the technical commissioning, SRT has already performed its first astronomical detection. This early scientific result opens exciting perspectives for the time when SRT will be in the full operational phase.
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Radio frequency self-interference from a data processing centre at a Radio Telescope site
Experimental Astronomy, 2010Co-Authors: Roberto Ambrosini, Pietro Bolli, C Bortolotti, Francesco Gaudiomonte, Filippo Messina, Mauro RomaAbstract:Apart from externally generated Radio Frequency Interference (RFI), the occurrence of self-interference is a major concern at any modern Radio Telescope site. Antenna servo motor controllers, data acquisition processors, and fast computing capabilities operate very close to extremely sensitive and wideband Radio astronomical receivers. In this paper, we present a set of measurements of the RFI level generated by a cluster of computers that will be installed at the site of the Sardinia Radio Telescope (SRT). The measured levels are compared to Recommendation ITU-R RA.769-2, which gives the threshold levels for interference detrimental to Radio astronomy observations. Our analysis shows that, with proper shielding of the noisiest devices, it will be possible to preserve the present excellent RFI conditions of the SRT site.
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status of the sardinia Radio Telescope project
Proceedings of SPIE, 2008Co-Authors: Gianni Tofani, G. Alvito, Roberto Ambrosini, Pietro Bolli, F. Buffa, A. Cattani, C Bortolotti, Loredana Bruca, Gianni Comoretto, A CremoniniAbstract:We present the status of the Sardinia Radio Telescope (SRT) project, a new general purpose, fully steerable 64 m diameter parabolic RadioTelescope capable to operate with high efficiency in the 0.3-116 GHz frequency range. The instrument is the result of a scientific and technical collaboration among three Structures of the Italian National Institute for Astrophysics (INAF): the Institute of Radio Astronomy of Bologna, the Cagliari Astronomy Observatory (in Sardinia,) and the Arcetri Astrophysical Observatory in Florence. Funding agencies are the Italian Ministry of Education and Scientific Research, the Sardinia Regional Government, and the Italian Space Agency (ASI,) that has recently rejoined the project. The Telescope site is about 35 km North of Cagliari. The Radio Telescope has a shaped Gregorian optical configuration with a 7.9 m diameter secondary mirror and supplementary Beam-WaveGuide (BWG) mirrors. With four possible focal positions (primary, Gregorian, and two BWGs), SRT will be able to allocate up to 20 remotely controllable receivers. One of the most advanced technical features of the SRT is the active surface: the primary mirror will be composed by 1008 panels supported by electromechanical actuators digitally controlled to compensate for gravitational deformations. With the completion of the foundation on spring 2006 the SRT project entered its final construction phase. This paper reports on the latest advances on the SRT project.
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Sardinia Radio Telescope: the new Italian project
Ground-based Telescopes, 2004Co-Authors: Gavril Grueff, G. Alvito, Roberto Ambrosini, Pietro Bolli, A. Maccaferri, Giuseppe Maccaferri, M. Morsiani, L. Mureddu, V. Natale, Luca OlmiAbstract:This contribution gives a description of the Sardinia Radio Telescope (SRT), a new general purpose, fully steerable antenna proposed by the Institute of Radio Astronomy (IRA) of the National Institute for Astrophysics. The Radio Telescope is under construction near Cagliari (Sardinia) and it will join the two existing antennas of Medicina (Bologna) and Noto (Siracusa) both operated by the IRA. With its large antenna size (64m diameter) and its active surface, SRT, capable of operations up to about 100GHz, will contribute significantly to VLBI networks and will represent a powerful single-dish Radio Telescope for many science fields. The Radio Telescope has a Gregorian optical configuration with a supplementary beam-waveguide (BWG), which provides additional focal points. The Gregorian surfaces are shaped to minimize the spill-over and the standing wave between secondary mirror and feed. After the start of the contract for the Radio Telescope structural and mechanical fabrication in 2003, in the present year the foundation construction will be completed. The schedule foresees the Radio Telescope inauguration in late 2006.
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The Sardinia Radio Telescope
2004Co-Authors: Gavril Grueff, G. Alvito, Roberto Ambrosini, Pietro Bolli, N. D'amico, A. Maccaferri, Giuseppe Maccaferri, M. Morsiani, L. Mureddu, V. NataleAbstract:We describe the Sardinia Radio Telescope (SRT), a new general purpose, fully steerable antenna of the National Institute for Astrophysics. The Radio Telescope is under construction near Cagliari (Sardinia). With its large aperture (64m diameter) and its active surface, SRT is capable of operations up to ∼100GHz, it will contribute significantly to VLBI networks and will represent a powerful single-dish Radio Telescope for many science fields. The Radio Telescope has a Gregorian optical configuration with a supplementary beam-waveguide (BWG), which provides additional focal points. The Gregorian surfaces are shaped to minimize the spill-over and standing wave. After the start of the contract for the Radio Telescope structural and mechanical fabrication in 2003, in the present year the foundation construction will be completed. The schedule foresees the Radio Telescope inauguration in late 2006.
Hongliang Qian - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of solar temperature field under different wind speeds for Shanghai 65 m Radio Telescope
International Journal of Steel Structures, 2016Co-Authors: Hongliang Qian, Feng Fan, Deshen Chen, Ye Liu, Shizhao ShenAbstract:The Shanghai 65 m Radio Telescope is currently the largest full range rotatable Radio Telescope in Asia. Gravity, wind and temperature are the three main factors which may have a bad effect on the reflector’s surface precision. To study the effect of the thermal deformation caused by daily non-uniform temperature fields on the surface precision of the main reflector, both the temperature field and its effect were studied in detail for two typical days (January 15th and July 15th). The method to simulate temperature fields was studied initially, considering heat conduction, solar radiation, shadowing, air convection, sky radiation and ground radiation. Then, an integral parametric thermal finite element model (FEM) of the Telescope was established using the ANSYS thermal analysis module. Finally, the effect of non-uniform temperature fields on the surface precision of the main reflector was estimated in terms of the Root Mean Square (RMS) deformation based on temperature transient analysis. The proposed methods and conclusions drawn can provide valuable information for thermal design, thermal monitoring and thermal control of the Shanghai 65 m Radio Telescope and other similar giant antenna structures.
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Solar cooker effect test and temperature field simulation of Radio Telescope subreflector
Applied Thermal Engineering, 2016Co-Authors: Deshen Chen, Huajie Wang, Hongliang Qian, Gang Zhang, Shizhao ShenAbstract:Abstract The solar cooker effect can cause a local high temperature of the subreflector and can directly affect the working performance of the Radio Telescope. To study the daily temperature field and solar cooker effect of a subreflector, experimental studies are carried out with a 3-m-diameter Radio Telescope model for the first time. Initially, the solar temperature distribution rules, especially the solar cooker effect, are summarized according to the field test results under the most unfavorable conditions. Then, a numerical simulation for the solar temperature field of the subreflector is studied by light beam segmentation and tracking methods. Finally, the validity of the simulation methods is evaluated using the test results. The experimental studies prove that the solar cooker effect really exists and should not be overlooked. In addition, simulation methods for the subreflector temperature field proposed in this paper are effective. The research methods and conclusions can provide valuable references for thermal design, monitoring and control of similar high-precision Radio Telescopes.
