The East Asian Very Long Baseline Interferometry(VLBI) Network(EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China,Japan and Korea.EAVN aims at forming a joi...The East Asian Very Long Baseline Interferometry(VLBI) Network(EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China,Japan and Korea.EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions.After the combination of the Korean VLBI Network(KVN) and the VLBI Exploration of Radio Astrometry(VERA) into Ka VA,further expansion with the joint array in East Asia is actively promoted.Here we report the first imaging results(at 22 and 43 GHz) of bright radio sources obtained with Ka VA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China.To test the EAVN imaging performance for different sources,we observed four active galactic nuclei(AGN) having different brightness and morphology.As a result,we confirmed that the Tianma 65-m Radio Telescope(TMRT) significantly enhances the overall array sensitivity,a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of Ka VA only.The addition of the Nanshan 26-m Radio Telescope(NSRT) further doubled the east-west angular resolution.With the resulting high-dynamic-range,high-resolution images with EAVN(Ka VA+TMRT+NSRT),various fine-scale structures in our targets,such as the counter-jet in M87,a kink-like morphology of the 3 C 273 jet and the weak emission in other sources are successfully detected.This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general.Ongoing expansion of EAVN will further enhance the angular resolution,detection sensitivity and frequency coverage of the network.展开更多
The surface accuracy of a large parabolic antenna is an important indicator to evaluate the quality of the antenna.It not only directly affects the antenna’s aperture efficiency,thereby determining the shortest wavel...The surface accuracy of a large parabolic antenna is an important indicator to evaluate the quality of the antenna.It not only directly affects the antenna’s aperture efficiency,thereby determining the shortest wavelength that the antenna can work,but also affects the main lobe width and side lobe structure of the antenna pattern.Microwave holography is an important method for parabolic antenna profile detection.In this article we adopt a new algorithm to adjust the panels for the large radio telescope with an active main reflector through the TM65 m antenna’s aperture phase profile.The panels of the TM65 m radio telescope is in a radial pattern with 14 rings.Each corner of the panel is fixed on the screw of the actuator to move up and down,and the adjacent corners of the four panels share an actuator.We use the method of plane fitting to calculate the adjustment value of every panel’s corner.But one actuator,which simultaneously controls the common corner of the adjacent panels,will have different adjustment values according to the different plane fitting equation based on adjacent panels.In this paper,the adjustment value of the adjacent panels’crosspoints are constrained to be equal to the constraint condition to calculate each actuator’s adjustment value of the TM65 m radio telescope.Through multiple adjustments and application of the new algorithms,the accuracy of the TM65 m antenna reflector profile has been improved from the original 0.28 mm to the current 0.19 mm.展开更多
This paper proposes an active sub-reflector suitable for large radio telescopes,which can compensate both of the deformation of the main reflector and sub-reflector position offsets.The mathematical formula of the mai...This paper proposes an active sub-reflector suitable for large radio telescopes,which can compensate both of the deformation of the main reflector and sub-reflector position offsets.The mathematical formula of the main reflector deformation compensated by the sub-reflector is deduced based on Cassegrain and Gregory antenna structures.The position of the sub-reflector is adjustable to compensate for defocusing errors on high and low elevations,which are mainly caused by the deformation of the sub-reflector supporting legs.In this paper,the method of obtaining the optimum position of the sub-reflector from the aperture phase by the interferometric method is introduced.The actual measurement is verified on the Tianma 65 m radio telescope,which provides a new way to diagnose the position error of the sub-reflector.展开更多
Taking the Tianma Radio Telescope(TMRT)as an object,this paper focuses on the determination of temperature gradients and thermal deformations of the backup structure(BUS)with the finite element method.To this end,a mo...Taking the Tianma Radio Telescope(TMRT)as an object,this paper focuses on the determination of temperature gradients and thermal deformations of the backup structure(BUS)with the finite element method.To this end,a modeling and analysis method,which consists of a simplified FEM and a four-component simulation process,is proposed.In the development,only solar radiation is considered and thermal convection is neglected.Based on the thermal time constant of the BUS,the simulations of temperature gradients are simplified as static analysis.The superposed temperature gradients agree well with the ones measured by thermometers with a 0.57℃ root mean square(rms)error.In addition,the illuminated-weighted rms errors of the primary reflector surface calculated by the simulation and measured by the extended out-of-focus holography are in good agreement.The rms error increases approximately 170μm when the Sun persistently illuminated the BUS for 3 hr.The optimized initial temperature of the antenna structure is 20℃ by comparing the results between the finite element analysis and the e-OOF measurement.The thermal deformation database can support the real-time compensation of the active surface system if the traces of the radio telescope are known in advance.展开更多
The design of novel devices with specific technical interests through modulating structural properties and bonding characteristics promotes the vigorous development of materials informatics.Boron arsenide and boron ni...The design of novel devices with specific technical interests through modulating structural properties and bonding characteristics promotes the vigorous development of materials informatics.Boron arsenide and boron nitride,as remarkably high thermal conductivity(κ)materials,are unfavorable for thermal insulation applications as well as thermoelectric devices.In this study,based on first-principles calculations,we identify a group of novel borides with ultra-lowκ,i.e.,g-B_(3)X_(5)(X=N,P,and As).Theκof g-B_(3)N_(5),g-B_(3)P_(5),and g-B_(3)As_(5)are 21.08,2.50,and 1.85 W·m^(-1)·K^(-1),respectively,which are boron nitride and boron arsenide systems with the lowestκreported so far.The ultra-lowκis attributed to the synergy effect of electronics(lone-pair electrons)and geometry(buckling structures)on thermal transport.The discovery of the ultralowκof boron nitride and boron arsenide systems can well fill the gaps in applications of thermal insulation and thermoelectric devices.展开更多
Trying to achieve the best surface accuracy control with the fewest actuators, this article mainly studies the distribution of actuators and the method of panel design. The influence of the number of faulty actuators ...Trying to achieve the best surface accuracy control with the fewest actuators, this article mainly studies the distribution of actuators and the method of panel design. The influence of the number of faulty actuators on the accuracy of the surface shape is demonstrated. In addition, the method incorporating a triangular panel, node index and the fitting solution method of a single panel is also given. This method provides a reference for the design and realization of an active surface or a deformable sub-reflector for high performance large aperture radio telescopes.展开更多
A Q-band two-beam cryogenic receiver for the Tianma Radio Telescope（TMRT）has been developed,and it uses the independently-developed key microwave and millimeter-wave components operating from 35 to 50 GHz with a fra...A Q-band two-beam cryogenic receiver for the Tianma Radio Telescope（TMRT）has been developed,and it uses the independently-developed key microwave and millimeter-wave components operating from 35 to 50 GHz with a fractional bandwidth of 35%.The Q-band receiver consists of three parts：optics,cold unit assembly and warm unit assembly,and it can receive simultaneously the lefthanded and right-handed circularly polarized waves.The cold unit assembly of each beam is composed of a feed horn,a noise injection coupler,a differential phase shifter,an orthomode transducer and two low-noise amplifiers,and it works at a temperature range near 20 K to greatly improve the detection sensitivity of the receiving system.The warm unit assembly includes four radio-frequency amplifiers,four radio-frequency high-pass filters,four waveguide biased mixers,four 4–12 GHz intermediate-frequency amplifiers and one 31–38 GHz frequency synthesizer.The measured Q-band four-channel receiver noise temperatures are roughly 30–40 K.In addition,the single-dish spectral line and international very long baseline interferometry（VLBI）observations between the TMRT and East Asia VLBI Network at the Q-band have been successfully carried out,demonstrating the advantages of the TMRT equipped with the state-of-the-art Q-band receiver.展开更多
基金supported by The Graduate University for Advanced Studies (SOKENDAI)supported by the Japanese Government (MEXT) Scholarship+18 种基金supported by JSPS KAKENHI Grant Numbers JP18K03656 (M.K.),JP18H03721 (K.N.,K.H.and M.K.),JP19H01943 (K.H.,F.T.and Y.H.) and JP18KK0090 (K.H.and F.T.)supported by the Mitsubishi Foundation (grant number 201911019)supported by an EACOA Fellowship awarded by the East Asia Core Observatories Association,which consists of the Academia Sinica Institute of Astronomy and Astrophysics,the National Astronomical Observatory of Japan,the Center for Astronomical Mega-Science,the Chinese Academy of Sciencesthe Korea Astronomy and Space Science Institutethe financial support from the National Research Foundation (NRF) of Korea via Global Ph.D.Fellowship Grant 2014H1A2A1018695 and 2015H1A2A1033752,respectivelysupport from the NRF via Grant 2019R1F1A1059721supported by the Major Program of the National Natural Science Foundation of China (NSFC,Grant Nos.11590780 and 11590784)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No.KJCX1-YW-18)the Scientific Program of Shanghai Municipality (08DZ1160100)Key Laboratory for Radio Astronomy,CASsupport from NSFC (Grant No.11803071)supported by the National Key R&D Program of China (Grant No.2018YFA0404602)the CAS ‘Light of West China’ Program (Grant No.2018-XBQNXZ-B021)the NSFC (Grant Nos.U2031212 and 61931002)the Youth Innovation Promotion Association of the CAS (Grant No.2017084)support from Fundamental Research Grant Scheme (FRGS) FRGS/1/2019/STG02/UM/02/6supported by the Max Planck Partner Group of the MPG and the CASthe support by the Key Program of the NSFC (Grant No.11933007)the Research Program of Fundamental and Frontier Sciences,CAS (Grant No.ZDBS-LY-SLH011)。
文摘The East Asian Very Long Baseline Interferometry(VLBI) Network(EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China,Japan and Korea.EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions.After the combination of the Korean VLBI Network(KVN) and the VLBI Exploration of Radio Astrometry(VERA) into Ka VA,further expansion with the joint array in East Asia is actively promoted.Here we report the first imaging results(at 22 and 43 GHz) of bright radio sources obtained with Ka VA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China.To test the EAVN imaging performance for different sources,we observed four active galactic nuclei(AGN) having different brightness and morphology.As a result,we confirmed that the Tianma 65-m Radio Telescope(TMRT) significantly enhances the overall array sensitivity,a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of Ka VA only.The addition of the Nanshan 26-m Radio Telescope(NSRT) further doubled the east-west angular resolution.With the resulting high-dynamic-range,high-resolution images with EAVN(Ka VA+TMRT+NSRT),various fine-scale structures in our targets,such as the counter-jet in M87,a kink-like morphology of the 3 C 273 jet and the weak emission in other sources are successfully detected.This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general.Ongoing expansion of EAVN will further enhance the angular resolution,detection sensitivity and frequency coverage of the network.
文摘The surface accuracy of a large parabolic antenna is an important indicator to evaluate the quality of the antenna.It not only directly affects the antenna’s aperture efficiency,thereby determining the shortest wavelength that the antenna can work,but also affects the main lobe width and side lobe structure of the antenna pattern.Microwave holography is an important method for parabolic antenna profile detection.In this article we adopt a new algorithm to adjust the panels for the large radio telescope with an active main reflector through the TM65 m antenna’s aperture phase profile.The panels of the TM65 m radio telescope is in a radial pattern with 14 rings.Each corner of the panel is fixed on the screw of the actuator to move up and down,and the adjacent corners of the four panels share an actuator.We use the method of plane fitting to calculate the adjustment value of every panel’s corner.But one actuator,which simultaneously controls the common corner of the adjacent panels,will have different adjustment values according to the different plane fitting equation based on adjacent panels.In this paper,the adjustment value of the adjacent panels’crosspoints are constrained to be equal to the constraint condition to calculate each actuator’s adjustment value of the TM65 m radio telescope.Through multiple adjustments and application of the new algorithms,the accuracy of the TM65 m antenna reflector profile has been improved from the original 0.28 mm to the current 0.19 mm.
基金supported by the National Key R&D Program of China(No.2018YFA0404702)the National Natural Science Foundation of China(Grant Nos.A030802 and U1631114)CAS Key Technology Talent Program
文摘This paper proposes an active sub-reflector suitable for large radio telescopes,which can compensate both of the deformation of the main reflector and sub-reflector position offsets.The mathematical formula of the main reflector deformation compensated by the sub-reflector is deduced based on Cassegrain and Gregory antenna structures.The position of the sub-reflector is adjustable to compensate for defocusing errors on high and low elevations,which are mainly caused by the deformation of the sub-reflector supporting legs.In this paper,the method of obtaining the optimum position of the sub-reflector from the aperture phase by the interferometric method is introduced.The actual measurement is verified on the Tianma 65 m radio telescope,which provides a new way to diagnose the position error of the sub-reflector.
文摘Taking the Tianma Radio Telescope(TMRT)as an object,this paper focuses on the determination of temperature gradients and thermal deformations of the backup structure(BUS)with the finite element method.To this end,a modeling and analysis method,which consists of a simplified FEM and a four-component simulation process,is proposed.In the development,only solar radiation is considered and thermal convection is neglected.Based on the thermal time constant of the BUS,the simulations of temperature gradients are simplified as static analysis.The superposed temperature gradients agree well with the ones measured by thermometers with a 0.57℃ root mean square(rms)error.In addition,the illuminated-weighted rms errors of the primary reflector surface calculated by the simulation and measured by the extended out-of-focus holography are in good agreement.The rms error increases approximately 170μm when the Sun persistently illuminated the BUS for 3 hr.The optimized initial temperature of the antenna structure is 20℃ by comparing the results between the finite element analysis and the e-OOF measurement.The thermal deformation database can support the real-time compensation of the active surface system if the traces of the radio telescope are known in advance.
基金financially supported by the National Natural Science Foundation of China(Nos.52006057,52006059 and 51906097)the Fundamental Research Funds for the Central Universities(Nos.531119200237 and 541109010001531118010490)+1 种基金the State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body at Hunan University(No.52175011)RWTH Aachen University under project bund0011。
文摘The design of novel devices with specific technical interests through modulating structural properties and bonding characteristics promotes the vigorous development of materials informatics.Boron arsenide and boron nitride,as remarkably high thermal conductivity(κ)materials,are unfavorable for thermal insulation applications as well as thermoelectric devices.In this study,based on first-principles calculations,we identify a group of novel borides with ultra-lowκ,i.e.,g-B_(3)X_(5)(X=N,P,and As).Theκof g-B_(3)N_(5),g-B_(3)P_(5),and g-B_(3)As_(5)are 21.08,2.50,and 1.85 W·m^(-1)·K^(-1),respectively,which are boron nitride and boron arsenide systems with the lowestκreported so far.The ultra-lowκis attributed to the synergy effect of electronics(lone-pair electrons)and geometry(buckling structures)on thermal transport.The discovery of the ultralowκof boron nitride and boron arsenide systems can well fill the gaps in applications of thermal insulation and thermoelectric devices.
文摘Trying to achieve the best surface accuracy control with the fewest actuators, this article mainly studies the distribution of actuators and the method of panel design. The influence of the number of faulty actuators on the accuracy of the surface shape is demonstrated. In addition, the method incorporating a triangular panel, node index and the fitting solution method of a single panel is also given. This method provides a reference for the design and realization of an active surface or a deformable sub-reflector for high performance large aperture radio telescopes.
基金supported by the Special Fund for Astronomy from the Ministry of Finance, the National Natural Science Foundation of China (Nos. 11403080, 11590780 and 11590783)the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KJCX1-YW-18)+1 种基金the Scientific Program of Shanghai Municipality (No. 08DZ1160100)the Youth Innovation Promotion Association of Chinese Academy of Sciences (No. 2017315)
文摘A Q-band two-beam cryogenic receiver for the Tianma Radio Telescope（TMRT）has been developed,and it uses the independently-developed key microwave and millimeter-wave components operating from 35 to 50 GHz with a fractional bandwidth of 35%.The Q-band receiver consists of three parts：optics,cold unit assembly and warm unit assembly,and it can receive simultaneously the lefthanded and right-handed circularly polarized waves.The cold unit assembly of each beam is composed of a feed horn,a noise injection coupler,a differential phase shifter,an orthomode transducer and two low-noise amplifiers,and it works at a temperature range near 20 K to greatly improve the detection sensitivity of the receiving system.The warm unit assembly includes four radio-frequency amplifiers,four radio-frequency high-pass filters,four waveguide biased mixers,four 4–12 GHz intermediate-frequency amplifiers and one 31–38 GHz frequency synthesizer.The measured Q-band four-channel receiver noise temperatures are roughly 30–40 K.In addition,the single-dish spectral line and international very long baseline interferometry（VLBI）observations between the TMRT and East Asia VLBI Network at the Q-band have been successfully carried out,demonstrating the advantages of the TMRT equipped with the state-of-the-art Q-band receiver.
