Subjects: Astronomy submitted time 2024-04-12 Cooperative journals: 《天文学报》
WEN Zhi-gang
WANG Na
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WANG Hong-guang
CHEN Jian-ling
YUAN Jian-ping
YUEN Rai
YAN Wen-ming
TOKTONUR Ergesh
CUI Si-ran
LI Jian
LYU Cheng-bing
Abstract： We study the waiting time distribution of giant pulses from the Crab pulsar observed with the Nanshan 26-m radio telescope at a center frequency of 1556\;MHz with 512 MHz bandwidth. The observations were performed over a duration of 12.6 hours with 32\;$\upmu$s sampling interval. Our analysis has led to the detection of 2097 giant pulses above a threshold of 10 $\sigma$, with flux density $>$ 100\;Jy. The occurrence rate of giant pulses is characterized by a highly intermittent giant pulse productivity in short clusters with high rates, separated by relatively long quiescent intervals with low occurrence rates, especially for the giant pulses associated with the interpulse emission. The distribution of waiting times between two subsequent giant pulses displays a power-law tail and can be modeled with a non-stationary Poisson process, which indicates that giant pulses are independent and random events. Distinct waiting time distributions between giant pulses in the main pulse and interpulse phases are presented, which implies that the giant pulse emission mechanisms maybe different in the opposite magnetic poles. The ramification for our understanding of the radio emission mechanisms is discussed.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-12-06 Cooperative journals: 《天文研究与技术》
Abstract： Multi band correlation analysis is of great significance to the study of the physical model and radiation mechanism of Blazars. In order to study the physical model of TeV Blazars, we search and sort out their γ-ray band data and optical band data according to the names and coordinates of their counterparts of 78 TeV Blazars in the 4FGL-DR3 catalogue, and find that there are 56 TeV Blazars with both optical band and γ-ray band data. The Discrete Correlation Function (DCF) is used to calculate the correlation between the optics and γ-ray of each Blazar. The calculation results show that 20 sources show weak γ-ray-optical correlation, 30 sources show strong γ-ray-optical correlation, and 6 sources show no γ-ray-optical correlation. Among sources that exhibit strong correlation. there is also varying degrees of time delay between the optical and γ-ray bands. These results support that the high-energy photons of TeV Blazar mainly come from synchronous self Compton radiation of lepton model. However, we also find that there are some “orphan flares” in both the optical and γ-ray bands, which may indicate that the source of low energy photons is not unique.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-12-06 Cooperative journals: 《天文研究与技术》
Abstract： We study the characteristics of radio galaxy (RDG) and Narrow line Seyfert 1 (NLSY1) in the fourth Fermi LAT catalogue, the distribution characteristics of γ-ray flux and the RMS-Flux linear relationship. Based on these two types of active galactic nuclei in the data processing of γ-ray flux, the Gaussian function and log-normal distribution function are used to fit the flux distribution. By K-S test, S-W test, and reduced chi square χ2. It is found that the distributions of RDG and NLSY1 are more consistent with the log-normal distribution than the Gaussian distribution, which indicates that their light variability may have nonlinear and multiplicative properties. In addition, linear fitting is also performed on two different groups of RMS-Flux for these two types of sources, and it is found that RMS-Flux has a strong linear correlation and its slopes are both positive.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-20 Cooperative journals: 《天文研究与技术》
Abstract： The variability is an important observational feature of Blazars. In order to study the multiband optical variability of Blazar, we collected the light curves of PKS 1424-41 of the gamma-ray band (0.1-100GeV), optical R band, near infrared K band, X band and radio band, released by Fermi LAT, SMARTS, SWIFT (XRT) and Submillimeter Array (SMA). Discrete correlation function is used to analyze the correlation between the light curves. The results show that the gamma-ray band, X-band, optical R-band, near-infrared K-band and radio band are strongly correlated with each other, and there is a time delay between the bands. This result supports the “single region” lepton radiation model. The LSP (Lomb-Scargle Periodogram) method is used to analyze the Quasi-periodic Oscillations (QPO) of PKS 1424-41 for the γ band Light Curve in a flare period (MJD56100-MJD56500). It is found that there are two QPOs in this period: ~75 days and ~50 days, with a ratio of 3∶2. The helical structure of the jet itself and the radiation of high-energy plasma matter moving within it may be the origin of this monthly QPO.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-12 Cooperative journals: 《天文研究与技术》
Abstract： Optimizing the wind environment at the site is important to improve the effective observation time of large-aperture and high-precision radio telescopes in the middle and high frequency bands. Through wind barrier regulating wind flow that can effectively reduce the impact of wind load on the telescope, the layout design of wind barriers is not only related to the height, porosity and other parameters of wind barriers, but also consider the impact of the terrain on wind shield. However, there are few researches on this area. Taking the QiTai radio Telescope (QTT) site as the research object, the influence of different terrains on regulating wind flow is carried out based on numerical simulation. The simulation result shows that the wind speed at the telescope location without wind barriers is mainly related to the highest elevation of the upstream and downstream boundary terrain. Under the condition with wind barriers, if the telescope is located in horizontal terrain, the magnitude of reducing wind speed in the shelter area is related to the wind attack angle of the upstream incoming wind and the elevation of the downstream terrain. The actual slope terrain of the site increases the complexity of the wind flow, and when doing wind flow simulation for wind barriers, the upstream boundary should be extended to the outside of the relatively high mountain as far as possible. The simulation result of different boundary terrains show that the difference of reducing wind speed coefficient at telescope position reaches a maximum of 6%. This study can provide a reliable reference for terrain modeling of regulating wind flow simulation.
Subjects: Astronomy >> Astrophysical processes submitted time 2021-03-04 Cooperative journals: 《天文研究与技术》
Abstract： 控制系统能衔接、集成和管理射电望远镜的软硬件系统。控制系统中的序列化工具可将射电望远镜中不同设备、操作系统、编程语言和网络之间传输的信息进行编码和解码，增强系统之间数据的传输效率。本文分析和比较了三款二进制序列化工具Msgpack、Protobuf和Flatbuffers的编码原理及特性，并通过一个实例测试了它们的序列化数据大小、序列化时间和CPU利用率。结果表明，Msgpack的综合性能优于Protobuf和Flatbuffers，适用于周期长、需求易变的射电望远镜系统之间传输信息的编码和解码。
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Basic Disciplines of Agriculture submitted time 2017-11-06 Cooperative journals: 《中国生态农业学报》
Abstract：利用农业气象试验站作物资料及土壤资料, 评价APSIM-Wheat 模型在西南地区的适应性, 应用该模 型分析该地区1961—2010 年冬小麦潜在和雨养产量的时空变化特征, 通过逐步回归分析揭示小麦生长季主要气象因子对潜在产量和雨养产量的影响及相对贡献率。研究结果表明: APSIM 模型对该区5 个常用小麦品种的模拟效果较好, 模拟与实测生育期的均方根误差(RMSE)在7.0 d 以内, 地上部分生物量和产量模拟值与实测值的归一化均方根误差(NRMSE)均低于25%, 模型在西南地区具有较好的适应性。1961—2010 年研究区域36%的站点冬小麦生长季总辐射显著降低, 其中北部、东南部和南部中区最显著; 68%的站点生长季≥0 ℃有效积温显著增加, 西部增温显著; 30%的站点生长季平均气温日较差显著减小, 南部中区最显著; 全区生长季总降水大面积减少但不显著, 减少区主要位于最南端和东南部。模拟的冬小麦潜在产量在65%的站点呈显著减产趋势, 南部中区和北部变化最明显; 雨养产量在25%的站点显著降低, 北部地区较明显, 全区减产趋势较弱。减产显著的站点中, 生长季辐射降低、温度升高、气温日较差减小对潜在产量降低的贡献率分别为45%、36%和2%, 对雨养产量降低的贡献率分别为36%、39%和-8%, 而降水减少对雨养产量降低的贡献率为7%。西南冬小麦生长季辐射降低、温度升高及降水减少共同导致了冬小麦潜在和雨养产量的显著下降, 而气温日较差的降低对冬小麦潜在和雨养产量的影响分别表现为负作用和正作用, 整体上辐射和温度的影响程度最大。
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