检索结果-南通市图书馆

From polarimetry to helicity: Studies of solar magnetic fields at the Huairou Solar Observing Station

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2019年第9期62卷 16-33页

作者： hongqi zhang Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences

In this paper, we briefly introduce the basic questions in the measurements of solar magnetic fields and the possible error sources due to the approximation of the theory of radiation transfer of spectral lines in the solar atmosphere. We introduce some basic research progress in magnetic field measurement at Huairou Solar Observing Station of National Astronomical Observatories,Chinese Academy of Sciences, especially concerning the non-potentiality in solar active regions, such as the magnetic shear,current and helicity. We also discuss some basic questions for the measurements of the magnetic fields and corresponding challenges for the future studies.

关键词： solar spectrum polarization-stokes parameters magnetic fields-current and helicity

A model for integrated spatial land use characteristics linking to surface nutrient concentration

在线全文

学校读者我要写书评

暂无评论

International Journal of Digital Earth 2018年第10期11卷 1064-1084页

作者： Erqi Xu hongqi zhang Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijingPeople’s Republic of China

Quantifying land use heterogeneity helps better understand how it influences biophysical *** use area proportions have been used conventionally to predict water quality *** an insight into the combined effect of various spatial characteristics could lead to the statistical bias and confused understanding in previous *** this study,using spatial techniques and mathematical models,a diagnostic model was developed and applied for quantifying and incorporating three spatial components,namely,slope,distance to sampling spots,and *** upper catchment of Miyun Reservoir was studied as the test *** nitrogen,total phosphorus,and chemical oxygen demand of water samples from field measurements were used to characterize the surface water quality in 52 *** parameter calibrations and determinations,combined spatial characteristics were explored and *** land use proportions were calculated by spatial weights of discriminating the relative contribution of each location to water quality and used to build the integrated *** with traditional methods only using area proportions,our model increased the explanatory power of land use and quantified the effects of spatial information on water *** can guide the optimization of land use configuration to control water eutrophication.

关键词： Spatial distance spatial arrangement land use water eutrophication

Terahertz Band: Lighting up Next-Generation Wireless Communications

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China Communications 2021年第5期18卷 153-174页

作者： hongqi zhang Lu zhang Xianbin Yu College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China Zhejiang Lab Hangzhou 310000China

With the explosion of wireless data rates,the terahertz(THz)band(0.1–10 THz)is envisioned as a promising candidate to break the existing bandwidth bottleneck and satisfy the ever-increasing capacity *** THz wireless communications feature a number of attractive properties,such as potential terabit-per-second capacity and high energy *** this paper,an overview on the state-of-the-art THz communications is studied,with a special focus on key technologies of THz transceivers and THz communication *** recent progress on both electronic and photonic THz transmitters are presented,and then the THz receivers operating in direct-and heterodyne reception modes are individually *** on the THz transceiver schemes,three kinds of THz wireless communication systems are reviewed,including solid-state electronic systems,photonics-assisted systems and all-photonics *** prospective key enabling technologies,corresponding challenges and research directions for lighting up high-speed THz communication systems are discussed as well.

关键词： terahertz communication 6th-generation terahertz photonics terahertz transceivers terahertz waves

Progress in Space Solar Telescope

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1655-1659页

作者： DENG YuanYong zhang hongqi Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China

In this paper we will summarize the progress in the development of the Chinese Space Solar Telescope (SST) during the past few years. The main scientific objective of SST is to observe the fundamental structure of solar magnetic field with its 1-m optical telescope. The success of 1-m Swedish Solar Telescope and Hinode underscores the importance of this 1-m space telescope. In addition, some key technical problems have been solved.

关键词： the Sun magnetic field high resolution high sensitivity Space Solar Telescope

Agricultural Land Use Optimal Allocation System in Developing Area:Application to Yili Watershed, Xinjiang Region

在线全文

学校读者我要写书评

暂无评论

Chinese Geographical Science 2012年第2期22卷 232-244页

作者： zhang Ying zhang hongqi NI Dongying SONG Wei Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beij＇ing 100101 China Graduate University of Chinese Academy of Sciences Beo＇ing 100049 China Beijing Forestry University Beijing 100083 China

In developing countries, land productivity involves little market, where the agricultural land use is mainly determined by the food demands as well as the land suitability. The land use pattern will not ensure everywhere enough land for certain cropping if spatial allocation just according to land use suitability. To solve this problem, a subzone and a pre-allocation for each land use are added in spatial allocation module, and land use suitability and area optimi- zation module are incorporated to constitute a whole agricultural land use optimal allocation （ALUOA） system. The system is developed on the platform .Net 2005 using ArcGIS Engine （version 9.2） and C# language, and is tested and validated in Yili watershed of Xinjiang Region on the newly reclaimed area. In the case study, with the help of soil data obtained from 69 points sampled in the fieldwork in 2008, main river data supplied by the Department of Water Resources of Xinjiang Uygur Autonomous Region in China, and temperature data provided by Data Center for Resources and Environmental Sciences, Chinese Academy of Sciences, land use suitability on eight common crops are evaluated one by one using linear weighted summation method in the land use suitability model. The linear pro- gramming （LP） model in area optimization model succeeds to give out land area target of each crop under three scenarios. At last, the land use targets are allotted in space both with a six subzone file and without a subzone file. The resuits show that the land use maps with a subzone not only ensure every part has enough land for every crop, but also gives a more fragmental land use pattern, with about 87.99% and 135.92% more patches than the one without, while at the expense of loss between 15.30% and 19.53% in the overall suitability at the same time.

关键词： developing country agricultural land subzone optimal allocation Yili watershed

A comparison of co-temporal magnetograms obtained with the Huairou magnetograph and the Spectro-Polarimeter on board Hinode

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1707-1712页

作者： WANG Dong zhang Mei LI Hui zhang hongqi Key Laboratory of Solar Activity National Astronomical ObservatoryChinese Academy of SciencesBeijing 100012China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China

We have compared a set of co-temporal magnetograms obtained with the Solar Magnetic Field Tele-scope (SMFT) of the Huairou Solar Observing Station (HSOS) and with the Spectro-Polarimeter of the Solar Optical Telescope (SP/SOT) on board Hinode to check the linear calibrations of SMFT vector magnetograms. The comparison shows that the currently used calibration coefficients of the SMFT have under-estimated the flux density and that a center-to-limb variation of the calibration coefficients was not taken into account by previous calibrations.

关键词： atmosphere magnetic fields magnetic fields

Quantum Key Distribution Network： Optimal Secret- Key- Aware Routing Method for Trust Relaying

在线全文

学校读者我要写书评

暂无评论

China Communications 2018年第2期15卷 33-45页

作者： Chao Yang hongqi zhang Jinhai Su Science and Technology Information Research Institute Zhengzhou Henan China

Since the QKD network can overcome the distance limitation and expand the point-to-point QKD system to a multi-user key distribution system, some testing QKD networks have been built. However, all of this previous research seldom focused on the routing mechanism of QKD network in detail. Therefore, this paper focuses on the routing issue in trust relaying QKD network, builds a model of the trust relaying QKD network and proposes a secret-key-aware routing method. In our method, a dynamic model for the residual local key is proposed to forecast the residual local key quantity of each QKD link more accurately, and the cost of QKD link and relaying path are defined by multiple affecting factors, e.g. the generation, consumption rate and the local key depletion index. The proposed method is implemented and evaluated in a simulation environment. The simulation results show that our routing method can increase the success rate of key exchange, make all the QKD links participate key exchange with almost equal opportunity to achieve load balance, and trade off the local key generation and consumption of each QKD link. Therefore, our proposed method can contribute to effectively improve the holistic performance of the trust relaying QKD network.

关键词： quantum key distribution QKDnetwork routing algorithm

Some basic questions on helicity inferred from vector magnetograms

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1749-1753页

作者： XU HaiQing GAO Yu zhang hongqi Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China

This paper summarizes current helicity measurements in the solar active regions (ARs). There is a basic agreement with the "hemispheric sign rule (HSR)" of the current helicity among different vector magnetographs through two solar cycles, but there is a large dispersion of the fraction of ARs following the HSR. In our sample, there are 50%-78% ARs in solar cycle 22 and 44%-79% ARs in cycle 23 following the HSR. A variation is also found in the fraction of the ARs following the HSR between different instruments even when the same ARs are selected. The difference also exists for the same instrument when the selected ARs are different. There are some differences in the variation of HSR with solar cycle for the individual helicity parameter inferred from different instruments. Factors which influence the correlation of different data sets are analyzed.

关键词： photosphere magnetic field helicity solar dynamo

Observational cross helicity on the solar surface

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2014年第3期57卷 589-596页

作者： ZHAO MingYu WANG XiaoFan zhang hongqi Key Laboratory of Solar Activity National Astronomical ObservatoryChinese Academy of Sciences

We analyzed the correlation of the solar magnetograms and Dopplergrams from SOHO/MDI and SDO/HMI respectively. It is found that the full disk correlation coefficient of Dopplergrams is more than 0.80 between SOHO/MDI and SDO/HMI. The full disk correlation coefficient of magnetograms is about 0.73 and is more than 0.95 for active regions only. We also analyzed the distribution of the cross helicity （velocity-magnetic-field correlation） on the solar surface. It is found that the latitude distributions of the cross helicity based on SOHO/MDI data and SDO/HMI data have similar tendencies, and in the analysis of solar active regions the amplitude of the horizontal component of the mean cross helicity is about two times the line-of-sight one.

关键词： cross helicity photosphere magnetic fields solar activity