排序方式: 共有26条查询结果,搜索用时 15 毫秒
1.
Hui-Rong Ji Qi-Jun Pu Yi-Hua Yan Yu-Ying Liu Zhi-Jun Chen Cheng-Ming Tan Cong-Ling Cheng De-Bang Lao Shu-Ke Li Zhi-Qiang Wang Min-Hong Yu Jian-Nong Liu Li-Kang Zhang Ji-Yong Gao National Astronomical Observatories Chinese Academy of Sciences Beijing Hebei Semiconductor Research Institute Shijiazhuang 《中国天文和天体物理学报》2005,5(4):433-441
An improved Solar Radio Spectrometer working at 1.10-2.06 GHz with much improved spectral and temporal resolution, has been accomplished by the National Astronomical Observatories and Hebei Semiconductor Research Institute, based on an old spectrometer at 1-2 GHz. The new spectrometer has a spectral resolution of 4 MHz and a temporal resolution of 5ms, with an instantaneous detectable range from 0.02 to 10 times of the quiet Sun flux. It can measure both left and right circular polarization with an accuracy of 10% in degree of polarization. Some results of preliminary observations that could not be recorded by the old spectrometer at 1-2 GHz are presented. 相似文献
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多效唑对2种海洋微藻生长和抗氧化酶活性的影响 总被引:1,自引:0,他引:1
运用实验生态学和生物化学的方法,研究了多效唑对青岛大扁藻(Platymonas helgolandica)和绿色巴夫藻(Pavlova viridis)生长和抗氧化酶活性的影响.结果表明:低浓度(≤5 mg/L)多效唑能促进绿色巴夫藻的生长,与对照组相比,多效唑处理组的干重、叶绿素a、可溶性糖和蛋白质含量均有所增加(p<0.05),而低浓度(≤5 mg/L)多效唑对青岛大扁藻的生长无明显影响;高浓度(≥15 mg/L)多效唑可显著抑制青岛大扁藻和绿色巴夫藻的生长,多效唑处理组的干重、叶绿素a、可溶性糖和蛋白质含量均低于对照组(p<0.05).多效唑对青岛大扁藻和绿色巴夫藻的96 h-EC50值分别是28.6 mg/L和24.9 mg/L. 2种微藻经不同浓度多效唑处理后,细胞内抗氧化防御系统的关键性酶超氧化物歧化酶(superoxide dismutase, SOD)和过氧化物酶(peroxidase, POD)均表现为低浓度(≤5 mg/L)的诱导作用和高浓度(≥15 mg/L)时的抑制作用;不同浓度多效唑处理后,2种微藻细胞内过氧化氢酶(catalase, CAT)活性均降低. 相似文献
3.
古气候模拟比较计划(PMIP)是古气候数值模拟领域一项重大的国际合作研究计划,其主旨是为古气候模拟和模拟结果评估提供一个协调机制,理解过去气候变化的物理机制和气候反馈的重要作用,为未来气候预估提供科学依据。同时,通过对比分析验证模式的模拟性能,探索其不确定性,促进耦合气候系统模式的发展。PMIP目前进行到第四阶段(PMIP4)。PMIP4进一步加强了与第六次国际耦合模式比较计划(CMIP6)的协作,选取了5组共同关注的PMIP4-CMIP6古气候模拟试验(中全新世、末次盛冰期、过去千年、末次间冰期和上新世暖期),考察气候系统对不同气候背景的综合响应。除此以外,PMIP4还设计了众多敏感性试验研究不同外强迫因子的影响。PMIP4模拟试验不仅为古气候研究提供大量的模拟数据,还将服务于CMIP6及其他众多模式比较计划。 相似文献
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Li-Hong Geng Cheng-Ming Tan Yi-Hua Yan Bao-Lin Tan Dong-Hao Liu Jin-Ping Dun 《天文和天体物理学研究(英文版)》2021,(6):219-228
This work analyzes the annual fluctuation of the observation data of the Mingantu Solar radio Telescope(MST) in S, C and X bands. It is found that the data vary with local air temperature as the logarithmic attenuation of equipment increases with temperature and frequency. A simplified and effective calibration method is proposed, which is used to calibrate the MST data in 2018–2020, while the correction coefficients are calculated from data in 2018–2019. For S, C and X bands, the root mean square errors of one polarization are 2.7, 5.7 and 20 sfu, and the relative errors are 4%, 6% and 8% respectively. The calibration of MUSER and SBRS spectra is also performed. The relative errors of MUSER at 1700 MHz,SBRS at 2800 MHz, 3050 MHz and 3350 MHz are 8%, 8%, 11% and 10% respectively. We found that several factors may affect the calibration accuracy, especially at X-band. The method is expected to work for other radio telescopes with similar design. 相似文献
5.
Rui-Xiang Xie Min Wang Yi-Hua YanNational Astronomical Observatories Yunnan Observatory Chinese Academy of Sciences Kunming National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2005,(1)
A rare Type I-like noise storm was observed with the solar radio spectrometers (1.0-2.0 GHz and 2.60-3.8 GHz) at National Astronomical Observatories of China (NAOC) on September 23, 1998. We concentrate on checking the Type I-like noise storm occurred in the decay phase of a Type Ⅳ radio burst. This noise storm consists of many Type I bursts and isolated Type Ⅲ or Type Ⅲ pair bursts. It has a bandwidth of ≤0.5 GHz. The duration of each Type I burst is of the order of 100-300 ms. The total duration is greater than 11 minutes. The circular polarization 相似文献
6.
Lin-Jie Chen Yi-Hua Yan Qiu-Xiang Fan Li-Hong Geng Susanta Kumar Bisoi 《天文和天体物理学研究(英文版)》2021,(4):61-70
The very low frequency(VLF) regime below 30 MHz in the electromagnetic spectrum has presently been drawing global attention in radio astronomical research due to its potentially significant science outcomes exploring many unknown extragalactic sources,transients,and so on.However,the nontransparency of the Earth's ionosphere,ionospheric distortion and artificial radio frequency interference(RFI) have made it difficult to detect the VLF celestial radio emission with ground-based instruments.A straightforward solution to overcome these problems is a space-based VLF radio telescope,just like the VLF radio instruments onboard the Chang'E-4 spacecraft.But building such a space telescope would be inevitably costly and technically challenging.The alternative approach would be then a ground-based VLF radio telescope.Particularly,in the period of post 2020 when the solar and terrestrial ionospheric activities are expected to be in a 'calm' state,it will provide us a good chance to perform VLF ground-based radio observations.Anticipating such an opportunity,we built an agile VLF radio spectrum explorer co-located with the currently operational Mingantu Spectra Radio Heliograph(MUSER).The instrument includes four antennas operating in the VLF frequency range 1-70 MHz.Along with them,we employ an eight-channel analog and digital receivers to amplify,digitize and process the radio signals received by the antennas.We present in the paper this VLF radio spectrum explorer and the instrument will be useful for celestial studies of VLF radio emissions. 相似文献
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Min Wang Rui-Xiang Xie Chun Xu Shuo-Biao Shi Yi-Hua Yan National Astronomical Observatories Yunnan Observatory Chinese Academy of Sciences Kunming National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2005,5(5):508-518
We present a, large complex radio burst and its associated fast tune structures observed on 2001 April 10 in the frequency range of 0.65-7.6 GHz. The NoRH radio image observation shows very complex radio source structures which include preexisting, newly emerging, submerging/cancelling polarities and a bipolar, a tripolar (a 'bipolar + remote unipolar'), and a quadrupolar structure. This suggests that the radio burst is generated from a very complicated loop structure. According to the spectral and image observations, we assume that the beginning of this flare was caused by a single bipolar loop configuration with a 'Y-type' re-connection structure. A composite of radio continuum and fast time structures is contained in this flare. The various fast radio emission phenomena include normal and reverse drifting type III bursts, and slowly drifting and no-drift structures. The tripolar configurations may form a double-loop with a 'three-legged' structure, which is an important source of the various types of fast time structures. The two-loop reconnection model can lead simultaneously to electron acceleration and corona heating. We have also analyzed the behaviors of coronal magnetic polarities and the emission processes of different types radio emission qualitatively. Interactions of a bipolar or multi-polar loop are consistent with our observational results. Our observations favor the magnetic reconnection configurations of the 'inverted Y-type' (bipolar) and the 'three-legged' structures (tripolar or quadrupolar). 相似文献
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Natural Hazards - This study aims to develop a probabilistic rainfall threshold estimation model for shallow landslides (PRTE_LS) in order to quantify its reliability while being affected by... 相似文献
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利用国家天文台云南天文台“分米波(700—1500MHz)射电频谱仪”和“四波段太阳射电高时间分辨率同步观测系统”分别于2001年6月24日和1990年7月30日观测到了两个稀少事件,前者是一个小射电爆发,其上升相伴随有短周期(约29、40和100毫秒)的脉动,后者是一个射电大爆发,在2840MHz上产生了周期约30毫秒的射电脉动,还着重讨论其甚短周期(如29—40毫秒)的脉动现象,甚短周期脉动可能是归因于起源在日冕深处不稳定区域的哨声波束周期链对射电辐射的调制,或沉降电子束驱动的静电高混杂波,经由波-波非线性相互作用导致甚短周期的射电脉动。 相似文献