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Acta Mechanica Sinica 2016年第5期32卷 841-853页

作者： reza ansari Jalal Torabi Department of Mechanical Engineering University of Guilan

Based on the nonlocal elasticity theory, the vibration behavior of circular double-layered graphene sheets（DLGSs） resting on the Winkler- and Pasternak-type elastic foundations in a thermal environment is *** governing equation is derived on the basis of Eringen＇s nonlocal elasticity and the classical plate theory（CLPT）.The initial thermal loading is assumed to be due to a uniform temperature rise throughout the thickness direction. Using the generalized differential quadrature（GDQ）method and periodic differential operators in radial and circumferential directions, respectively, the governing equation is discretized. DLGSs with clamped and simply-supported boundary conditions are studied and the influence of van der Waals（vd W） interaction forces is taken into *** the numerical results, the effects of various parameters such as elastic medium coefficients, radius-to-thickness ratio,thermal loading and nonlocal parameter are examined on both in-phase and anti-phase natural frequencies. The results show that the thermal load and elastic foundation respectively decreases and increases the fundamental frequencies of DLGSs.

关键词： Circular DLGS Vibration Nonlocal theory Thermal environment Numerical solution

Size-Dependent Geometrically Nonlinear Free Vibration of First-Order Shear Deformable Piezoelectric-Piezomagnetic Nanobeams Using the Nonlocal Theory

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Advances in Applied Mathematics and Mechanics 2018年第1期10卷 184-208页

作者： Raheb Gholami reza ansari Department of Mechanical Engineering Lahijan BranchIslamic Azad UniversityP.O.Box 1616LahijanIran Department of Mechanical Engineering University of GuilanP.O.Box 3756RashtIran

This article investigates the geometrically nonlinear free vibration of piezoelectric-piezomagnetic nanobeams subjected to magneto-electro-thermal loading taking into account size effect using the nonlocal elasticity *** this end,the sizedependent nonlinear governing equations of motion and corresponding boundary conditions are derived according to the nonlocal elasticity theory and the first-order shear deformation theory with von K´arm´an-type of kinematic *** effects of size-dependence,shear deformations,rotary inertia,piezoelectric-piezomagnetic coupling,thermal environment and geometrical nonlinearity are taken into *** generalized differential quadrature(GDQ)method in conjunction with the numerical Galerkin method,periodic time differential operators and pseudo arclength continuation method is utilized to compute the nonlinear frequency response of piezoelectric-piezomagnetic *** influences of various parameters such as non-dimensional nonlocal parameter,temperature change,initial applied electric voltage,initial applied magnetic potential,length-to-thickness ratio and different boundary conditions on the geometrically nonlinear free vibration characteristics of piezoelectric-piezomagnetic nanobeams are demonstrated by numerical *** is illustrated that the hardening spring effect increases with increasing the non-dimensional nonlocal parameter,positive initial applied voltage,negative initial applied magnetic potential,temperature rise and decreases with increasing the negative initial applied voltage,positive initial applied magnetic potential and length-tothickness ratio.

关键词： Piezoelectric-piezomagnetic nanobeams geometrically nonlinear free vibration nonlocal elasticity theory size effect magneto-electro-thermal loading

Extracting 21 cm signal by frequency and angular filtering

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Research in Astronomy and Astrophysics 2018年第9期18卷 101-112页

作者： Qi-Zhi Huang Feng-Quan Wu reza ansari Xuelei Chen Key Laboratory of Computational Astrophysics National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Universite Paris-Sud LALUMR 8607F-91898 Orsay CedexFrance&CNRS/IN2P3F-91405 OrsayFrance Center for High Energy Physics Peking UniversityBeijing 100871China

Extracting the neutral hydrogen （HI） signal is a great challenge for cosmological 21 cm experiments; both the astrophysical foregrounds and receiver noise are typically several orders of magnitude greater than the 21 cm signal. However, the different properties of the 21 cm signal, foreground and noise can be exploited to separate these components. The foregrounds are generally smooth or correlated over the frequency space along a line of sight （LOS）, while both the 21 cm signal and noise vary stochastically along the same LoS. The foreground can be removed by filtering out the smooth component in frequency space. The receiver noise is basically uncorrelated for observations at different times, hence for surveys it is also uncorrelated in different directions, while the 21 cm signal, which traces the large scale structure, is correlated up to certain scales. In this exercise, we apply Wiener filters in frequency and angular space to extract the 21 cm signals. We found that the method works well. Inaccurate knowl- edge about the beam could degrade the reconstruction, but the overall result is still good, showing that the method is fairly robust.

关键词： methods: data analysis - (cosmology:) dark ages reionization first stars - cosmology:observations

Spatial Reactor Dynamics and Thermo Hydraulic Behavior Simulation of a Large AGR Nuclear Power Reactor in Response to a Reactivity Step Change Disturbance

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Energy and Power Engineering 2011年第3期3卷 366-375页

作者： Mohammad reza ansari reza Marzooghi 不详

In this article, two-dimensional partial differential equations with time representation of nuclear power reactor kinetics are considered for spatial reactor dynamics and thermo hydraulic behavior analysis of a large thermal advanced gas cooled reactor (AGR) type used for nuclear power generation. The equations include the neutron flux equation and delayed neutron precursor concentration, together with taking into account the equations to represent the thermo hydraulic behavior of the fuel, coolant and moderator temperatures. These equations are solved numerically using the finite difference method. For time propagation, an implicit method is applied. The desired initial condition for the reactor to stay at stable critical condition is established by finding the correct value of reactivity. The reactivity disturbance effect in the reactor is studied for different cases and presented for high reactivity values. The model was developed for the analysis of a large AGR with 2000 MWe for future power generation. The results show that the model not only behaves stably but also predicts the results physically for all the various parameters.

关键词： Nuclear Reactor AGR Reactivity Neutron Flux Thermo Hydraulics

Sky reconstruction for the Tianlai cylinder array

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Research in Astronomy and Astrophysics 2016年第10期16卷 71-80页

作者： Jiao Zhang Shi-Fan Zuo reza ansari Xuelei Chen Yi-Chao Li Feng-Quan Wu Jean-Eric Campagne Christophe Magneville Key Laboratory of Computational Astrophysics National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China Universite Paris-Sud LALUMR 8607F-91898 Orsay CedexFrance&CNRS/IN2P3F-91405 OrsayFrance University of Chinese Academy of Sciences Beijing 100049China Center for High Energy Physics Peking UniversityBeijing 100871China CEA DSM/IRFUCentre d'Etudes de SaclayF-91191 Gif-sur-YvetteFrance

We apply our sky map reconstruction method for transit type interferometers to the Tianlai cylin- der array. The method is based on spherical harmonic decomposition, and can be applied to a cylindrical array as well as dish arrays and we can compute the instrument response, synthesized beam, transfer func- tion and noise power spectrum. We consider cylinder arrays with feed spacing larger than half a wavelength and, as expected, we find that the arrays with regular spacing have grating lobes which produce spurious images in the reconstructed maps. We show that this problem can be overcome using arrays with a different feed spacing on each cylinder. We present the reconstructed maps, and study the performance in terms of noise power spectrum, transfer function and beams for both regular and irregular feed spacing configura- tions.

关键词： cosmology: observation -- HI intensity mapping -- method: transit telescope -- map making

The Electromagnetic Characteristics of the Tianlai Cylindrical Pathfinder Array

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Research in Astronomy and Astrophysics 2022年第6期22卷 234-255页

作者： Shijie Sun Jixia Li Fengquan Wu Peter Timbie reza ansari Jingchao Geng Huli Shi Albert Stebbins Yougang Wang Juyong Zhang Xuelei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Department of Physics University of Wisconsin Madison1150 University AveMadison WI 53703united States of America IJC Lab CNRS/IN2P3&UniversitéParis-Saclay15 rue Georges ClemenceauF-91405 OrsayFrance The 54th Research Institute China Electronics Technology Group CorporationShijiazhuangHebei 050051China Fermi National Accelerator Laboratory P.O.Box 500Batavia IL 60510-5011United States of America School of Mechanical Engineering Hangzhou Dianzi UniversityHangzhou 310017China Department of Physics College of SciencesNortheastern UniversityShenyang 110819China Center of High Energy Physics Peking UniversityBeijing 100871China

A great challenge for 21 cm intensity mapping experiments is the strong foreground radiation which is orders of magnitude brighter than the 21 cm *** of the foreground takes advantage of the fact that its frequency spectrum is smooth while the redshifted 21 cm signal spectrum is ***,a complication is the nonsmoothness of the instrument *** paper describes the electromagnetic simulation of the Tianlai cylinder array,a pathfinder for 21 cm intensity mapping *** to the vast scales involved,a direct simulation requires a large amount of computing *** have made the simulation practical by using a combination of methods:first simulate a single feed,then an array of feed units,finally with the feed array and a cylindrical reflector together,obtain the response for a single *** studied its radiation pattern,bandpass response and the effects of mutual coupling between feed units,and compared the results with *** features seen in the measurement result are reproduced well in the simulation,especially the oscillatory features which are associated with the standing waves on the *** mutual coupling between feed units is quantified with Sparameters,which decrease as the distance between the two feeds *** on the simulated S-parameters,we estimate the correlated noise which has been seen in the visibility data,and the results show very good agreement with the data in both magnitude and frequency *** results provide useful insights on the problem of 21 cm signal extraction for real instruments.

关键词： instrumentation interferometers-methods numerical-methods observational-cosmology observations-(cosmology:)dark ages-reionization-first stars-(cosmology:)diffuse radiation

Reflections and standing waves on the Tianlai cylinder array

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Research in Astronomy and Astrophysics 2021年第3期21卷 73-85页

作者： Ji-Xia Li Feng-Quan Wu Shi-Jie Sun Zi-Jie Yu Shi-Fan Zuo Ying-Feng Liu You-Gang Wang Cong Zhang reza ansari Peter Timbie Xuelei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Center for Astrophysics and Department of Astronomy Tsinghua UniversityBeijing 100084China IJC Lab CNRS/IN2P3&Universite Paris-Saclay15 rue Georges Cl´emenceau91405 OrsayFrance´ Department of Physics University of Wisconsin Madison1150 University AveMadison WI 53703USA Center of High Energy Physics Peking UniversityBeijing 100871China

In 21 cm intensity mapping,the spectral smoothness of the foreground is exploited to separate it from the much weaker 21 cm ***,the non-smooth frequency response of the instrument complicates this *** and standing waves generate modulations on the frequency *** we report the analysis of the standing waves in the bandpass of the signal channels of the Tianlai Cylinder *** Fourier transforming the bandpass into the delay time domain,we find various standing waves generated on the telescope.A standing wave with time delay at~142 ns is most clearly identified which is produced in the 15-meter feed *** also identify a strong peak at a shorter delay ofτ<50 ns,which may be a mix of the standing wave between the reflector and feed,and the standing wave on the 4 m intermediate frequency(IF)*** also show that a smoother frequency response could be partially recovered by removing the reflection-inducted ***,the standing wave on the antenna is direction-dependent,which poses a more difficult challenge for high precision calibration.

关键词： techniques:interferometric methods:data analysis

A Fast Radio Burst Backend for the Tianlai Dish Pathfinder Array

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Research in Astronomy and Astrophysics 2022年第12期22卷 211-223页

作者： Zijie Yu Furen Deng Shijie Sun Chenhui Niu Jixia Li Fengquan Wu Wei-Yang Wang Yougang Wang Hui Feng Lin Shu Jie Hao reza ansari Albert Stebbins Xuelei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Department of Astronomy Peking UniversityBeijing 100871China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China Institute of Automation Chinese Academy of SciencesBeijing 100190China Guangdong Institute of Artificial Intelligence and Advanced Computing Guangzhou 510535China UniversitéParis-Saclay CNRS/IN2P3IJCLabF-91405 OrsayFrance Fermi National Accelerator Laboratory P.O.Box 500BataviaIL 60510-5011United States of America Department of Physics College of SciencesNortheastern UniversityShenyang 110819China Center of High Energy Physics Peking UniversityBeijing 100871China

The Tianlai Dish Pathfinder Array is a radio interferometer array consisting of 16 six-meter dish *** original digital backend integration time is at the seconds level,designed for H I intensity mapping experiment.A new digital backend with millisecond response is added to enable it to search for fast radio burst during its *** design and calibration of this backend,and the real time search pipeline for it are described in this *** is capable of forming 16 digital beams for each linear polarization,covering an area of 19.6 square *** search pipeline is capable of searching for,recording and classifying FRBs automatically in real *** commissioning,we succeeded in capturing the signal pulses from the pulsars PSR B0329+54 and B2021+51.

关键词： instrumentation:miscellaneous techniques:interferometric telescopes radio continuum:general (stars:)pulsars:general

The FRB-searching Pipeline of the Tianlai Cylinder Pathfinder Array

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Research in Astronomy and Astrophysics 2024年第8期24卷 113-132页

作者： Zijie Yu Furen Deng Shijie Sun Chenhui Niu Jixia Li Fengquan Wu Wei-Yang Wang Yougang Wang Shifan Zuo Lin Shu Jie Hao Xiaohui Liu reza ansari Ue-Li Pen Albert Stebbins Peter Timbie Xuelei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Radio Astronomy and Technology Chinese Academy of ScienceBeijing 100101China Institute of Astrophysics Central China Normal UniversityWuhan 430079China Institute of Automation Chinese Academy of SciencesBeijing 100190China Guangdong Institute of Artificial Intelligence and Advanced Computing Guangzhou 510535China UniversitéParis-Saclay CNRS/IN2P3IJCLab91405 OrsayFrance Institute of Astronomy and Astrophysics Academia SinicaRoosevelt RoadTaipei 10617TaiwanChina Canadian Institute for Theoretical Astrophysics University of Toronto60 Saint George StreetTorontoON M5S 3H8Canada Department of Physics University of Wisconsin-MadisonMadisonWI 53706USA Fermi National Accelerator Laboratory P.O.Box 500Batavia IL 60510-5011USA Department of Physics College of SciencesNortheastern UniversityShenyang 110819China Center of High Energy Physics Peking UniversityBeijing 100871China

This paper presents the design,calibration,and survey strategy of the Fast Radio Burst(FRB)digital backend and its real-time data processing pipeline employed in the Tianlai Cylinder Pathfinder *** array,consisting of three parallel cylindrical reflectors and equipped with 96 dual-polarization feeds,is a radio interferometer array designed for conducting drift scans of the northern celestial *** FRB digital backend enables the formation of 96 digital beams,effectively covering an area of approximately 40 square degrees with the 3 dB *** pipeline demonstrates the capability to conduct an automatic search of FRBs,detecting at quasi-realtime and classifying FRB candidates *** current FRB searching pipeline has an overall recall rate of88%.During the commissioning phase,we successfully detected signals emitted by four well-known pulsars:PSR B0329+54,B2021+51,B0823+26,and B2020+*** report the first discovery of an FRB by our array,designated as FRB *** also investigate the optimal arrangement for the digitally formed beams to achieve maximum detection rate by numerical simulation.

关键词： instrumentation interferometers-methods data analysis-(stars )pulsars general-telescopes

The Tianlai Cylinder Pathfinder array: System functions and basic performance analysis

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Science China(Physics,Mechanics & Astronomy) 2020年第12期63卷 2-28页

作者： JiXia Li ShiFan Zuo FengQuan Wu YouGang Wang JuYong Zhang ShiJie Sun YiDong Xu ZiJie Yu reza ansari YiChao Li Albert Stebbins Peter Timbie YanPing Cong JingChao Geng Jie Hao QiZhi Huang JianBin Li Rui Li DongHao Liu YingFeng Liu Tao Liu John PMarriner ChenHui Niu Ue-Li Pen Jeffery BPeterson HuLi Shi Lin Shu YaFang Song HaiJun Tian GuiSong Wang QunXiong Wang RongLi Wang WeiXia Wang Xin Wang KaiFeng Yu Jiao Zhang BoQin Zhu JiaLu Zhu XueLei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Center for Astrophysics and Department of Astronomy Tsinghua UniversityBeijing 100084China School of Mechanical Engineering Hangzhou Dianzi UniversityHangzhou 310018China IJC Lab CNRS/IN2P3&UniversitéParis-SaclayOrsay 91405France Department of Physics and Astronomy University of the Western CapeBelville 7535Republic of South Africa Fermi National Accelerator Laboratory Batavia IL 60510-5011USA Department of Physics University of Wisconsin MadisonMadison WI 53703USA The 54th Research Institute China Electronics Technology Group CorporationShijiazhuang 050051China Institute of Automation Chinese Academy of SciencesBeijing 100190China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830001China Canadian Institute for Theoretical Astrophysics University of TorontoToronto M5S 3H8Canada Department of Physics Carnegie Mellon UniversityPittsburgh PA 15213USA Center for Astronomy and Space Sciences China Three Gorges UniversityYichang 443002China School of Physics and Astronomy Sun Yat-sen UniversityGuangzhou 510297China College of Physics and Electronic Engineering Shanxi UniversityTaiyuan 030006China Center of High Energy Physics Peking UniversityBeijing 100871China

The Tianlai Cylinder Pathfinder is a radio interferometer array designed to test techniques for 21 cm intensity mapping in the post-reionization Universe,with the ultimate aim of mapping the large scale structure and measuring cosmological parameters such as the dark energy equation of *** of its three parallel cylinder reflectors is oriented in the north-south direction,and the array has a large field of *** the Earth rotates,the northern sky is observed by drift *** array is located in Hongliuxia,a radio-quiet site in Xinjiang,and saw its first light in September *** this first data analysis paper for the Tianlai cylinder array,we discuss the sub-system qualification tests,and present basic system performance obtained from preliminary analysis of the commissioning observations during *** show typical interferometric visibility data,from which we derive the actual beam profile in the east-west direction and the frequency band-pass *** describe also the calibration process to determine the complex gains for the array elements,either using bright astronomical point sources,or an artificial on site calibrator source,and discuss the instrument response stability,crucial for transit *** on this analysis,we find a system temperature of about 90 K,and we also estimate the sensitivity of the array.

关键词： interferometer radio astronomy neutral hydrogen cosmology dark energy