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Basic performance and future developments of Beidou global navigation satellite system

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Satellite Navigation 2020年第1期1卷 1-8页

作者： Yuanxi Yang Yue mao Bijiao Sun State Key Laboratory of Geo-Information Engineering Xi’an 710054China

The core performance elements of global navigation satellite system include availability,continuity,integrity and accuracy,all of which are particularly important for the developing Beidou global navigation satellite system(BdS-3).This paper describes the basic performance of BdS-3 and suggests some methods to improve the positioning,navigation and timing(PNT)*** precision of the BdS-3 post-processing orbit can reach centimeter level,the average satellite clock offset uncertainty of 18 medium circular orbit satellites is 1.55 ns and the average signal-in-space ranging error is approximately 0.474 *** future possible improvements for the Beidou navigation system are also *** is suggested to increase the orbital inclination of the inclined geostationary orbit(IGSO)satellites to improve the PNT service in the Arctic *** IGSO satellite can perform part of the geostationary orbit(GEO)satellite’s functions to solve the southern occlusion problem of the GEO satellite service in the northern hemisphere(namely the“south wall effect”).The space-borne inertial navigation system could be used to realize continuous orbit determination during satellite *** addition,high-accuracy space-borne hydrogen clock or cesium clock can be used to maintain the time system in the autonomous navigation mode,and stability of spatial ***,the ionospheric delay correction model of BdS-3 for all signals should be unified to avoid user confusion and improve positioning ***,to overcome the vulnerability of satellite navigation system,the comprehensive and resilient PNT infrastructures are proposed for the future seamless PNT services.

关键词： BdS-3 PNT Performance Constellation Ionospheric delay

BOM-BASEd dESIGN KNOWLEdGE REPRESENTATION ANd REASONING FOR COLLABORATIVE PROdUCT dEVELOPMENT

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Journal of Systems Science and Systems Engineering 2016年第2期25卷 159-176页

作者： Gongzhuang Peng Huachao mao Hongwei Wang Heming Zhang National CIMSEngineeringResearch Center Tsinghua University Beijing 100084 China School of Engineering University of Portsmouth Anglesea Read Portsmouth PO1 3D J UK

Modem product development becomes increasingly collaborative and integrated, which raises the need for effectively and efficiently sharing and re-using design knowledge in a distributed and collaborative environment. To address this need, a framework is developed in this research to support design knowledge representation, retrieval, reasoning and fusion, which takes account of structural, functional and behavioral data, various design attributes and knowledge reasoning cases. Specifically, a multi-level knowledge representation based on the Base Object Model （BOM） is proposed to enable knowledge sharing using Web services technologies. On this basis, a multi-level knowledge reuse method is developed to support the retrieval, matching and assembly of knowledge records. due to the tree structure of BOM, both depth-first and breadth-first searching strategies are employed in the retrieval algorithm while a novel measure is proposed to evaluate similarity. Moreover, a method based on the d-S evidence theory is developed to enable knowledge fusion and thus support effective decision-making. The framework has been implemented and integrated into an HLA-based simulation platform on which the development of a missile simulation example is conducted. It is demonstrated in the case study that the proposed framework and methods are useful and effective for design knowledge representation and reuse.

关键词： Complex product development multi-level knowledge reuse knowledge fusion Base Object Model d-S evidence theory

Risk preferences and the low-carbon agricultural technology adoption:Evidence from rice production in China

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Journal of Integrative Agriculture 2023年第8期22卷 2577-2590页

作者： mao Hui QUAN Yu-rong FU Yong Northwest Institute of Historical Environment and Socio-Economic development Shaanxi Normal UniversityXi'an 710119P.R.China College of Economics and Management Nanjing Agricultural UniversityNanjing 210095P.R.China

Climate change which is mainly caused by carbon emissions is a global problem affecting the economic development and well-being of human ***-carbon agriculture is of particular significance in slowing down global warming and reaching the goal of“carbon peak and carbon neutrality”.Therefore,taking straw incorporation as an example,this paper aims to investigate the impact of risk preferences on farmers’low-carbon agricultural technology(LCAT)*** on a two-phase micro-survey data of 1038 rice farmers in Jiangsu,Jiangxi,and Hunan provinces,this paper uses experimental economics methods to measure farmers’risk aversion and loss aversion to obtain the real risk preferences information of the *** also explore the data to examine the actual LCAT adoption behavior of *** results revealed that both risk aversion and loss aversion significantly inhibit farmers’LCAT adoption:more risk-averse or more loss-averse farmers are less likely to adopt *** is further found that crop insurance,farm scale and governmental regulations can alleviate the negative impact of risk aversion and loss aversion on farmers’LCAT ***,we propose that local governments need to promote low-carbon agricultural development by propagating the benefits of LCAT,extending crop insurance,promoting appropriate scale operations,and strengthening governmental regulations to promote farmers’LCAT adoption.

关键词： risk preferences crop insurance farm scale governmental regulations low-carbon agricultural technology

Lanthanide Inorganic Solids Based on Main Group Borates and Oxyanions of Lone Pair Cations

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Chinese Journal of Chemistry 2018年第1期36卷 63-72页

作者： Fang Kong Yunxiang Ma Jianggao mao State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou Fujian 350002 China College of Chemistry Fuzhou University Fuzhou Fujian 350116 China

Lanthanide borates containing post transition metal main group elements, including Ga（Ⅲ）, Ge（Ⅳ）, Sb（Ⅴ） and Te（Ⅵ）, as well as lanthanide salts of the oxyanions of lone pair cations, such as I（Ⅴ）, Se（Ⅳ） and Te（Ⅳ）, were reviewed. The post transition metal main group elements in lanthanide borates adopt octahedral or tetrahedral geometry only. In the structure of lanthanide galloborates, only octahedral GaO6 was found while both octahedral GeO6 and tetrahedral GeO4 appeared in borogermanates. The fifth period elements Sb（Ⅴ） and Te（VI） prefer octahedral coordination geometry in lanthanide borates system. The second groups introduced to lanthanide oxyanions of lone pairs are mainly focused on do TM units, such as WO4 tetrahedron, VO5 square pyramid or MoO6 octahedron, and rigid tetrahedral groups like sulfate SO4, silica SiO4 or selenate SeO4 units. divalent cations like Pb（Ⅱ） and magnetic ions of Cu（Ⅱ） or Mn（Ⅱ） were also included. The structure chemistry of lanthanide ions in these systems is rich. Coordination numbers from six to ten are discovered, yielding a wide range of coordination geometries including the pentagonal bipyramid, square antiprism, metabidiminished icosahedron, tricapped trigonal prism, capped triangular cupola, etc. The connectivity modes between the Ln polyhedra are miscellaneous, from 3d network, to 2d layer, 1d chain, tetramer, trimer, dimer and finally monomer. A number of compounds display NCS structures and strong SHG response, and many lanthanide compounds exhibit good luminescent properties in visible and IR region.

关键词： lanthanide inorganic solid borate iodate selenite tellurite

The Galois Correspondence in Field Algebra of G-spin Model

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Acta Mathematica Sinica,English Series 2005年第4期21卷 673-680页

作者： Li Ning JIANG mao Zheng GUO department of Mathematics Beijing Institute of Technology Beijing 100081. P. R. China LMAM Department of Mathematics Peking University. Beijing 100871. P. R. China

Suppose that G is a finite group and d（G） the double algebra of G. For a given subgroup H of G, there is a sub-Hopf algebra d（G; H） of d（G）. This paper gives the concrete construction of a d（G; H）-invariant su... 详细信息

关键词： G-spin model double algebra Observable algebra Galois closed

Experimental study by online measurement of the precipitation of nickel hydroxide: Effects of operating conditions

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Chinese Journal of Chemical Engineering 2015年第5期23卷 860-867页

作者： Weiwei E Jingcai Cheng Chao Yang Zaisha mao Key Laboratory of Green Process and Engineering Institute of Process Engineering Chinese Academy of Sciences Jiangsu Marine Resources development Research Institute

The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter ofd = 240mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution （PSd） were investigated, d43 and PSd were measured online using a Malvern Insitec Liquid Pro- cess Sizer every 20 s. It was found that d43 varied between 13 kwh and 26 lain under different operating conditions, and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of d/2 under lower impeller speeds, d43 was significantly smaller than that at d/3. PSds were slightly influenced by operating conditions.

关键词： Nickel hydroxide Precipitation Particle size distribution Online measurement Stirred tank Mixing

Single-phase Computational Fluid dynamics Applicability for the Study of Three-dimensional Flow in 5×5 Rod Bundles with Spacer Grids

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Chinese Journal of Mechanical Engineering 2012年第4期25卷 738-744页

作者： TIAN Ruifeng mao Xiaohui GAO Puzhen HUANG Yanping College of Nuclear Science and Technology Harbin Engineering University Harbin 150001 China National defense Key discipline Laboratory of Nuclear Safety and Simulation Technology Harbin Engineering University Harbin 150001 China National Key Laboratory of Bubble Physics and Nature Circulation Nuclear Power Institute of China Chengdu 610041 China

Spacer grids play an important role in pressurized water reactor（PWR） fuel assembly in that they have significant influence on the thermal-hydraulic characteristics of the reactor *** so far,the numerical studies are performed without regarding dimple and spring of spacer grids,just considering mixing ***,these studies use k-ε turbulence model without considering the suitability of the other turbulence models upon the different spacer grids flow.A study is carried out to understand the 3-d single-phase flow in AFA-2G 5×5 rod bundles with spacer grids based on numerical *** order to investigate the suitability of different turbulence models,k-ε model and k-ω model,the influence of different parts of spacer grid on the fluid flow is also *** using second-order upwind scheme,hybrid grids technique,and improved SIMPLEC algorithm,the Reynolds averaged mass conservation and momentum conservation equations are solved,and the pressure and velocity field of flow are *** numerical simulation results are compared with experiment results and the agreement is *** simulation results show the influences of the spring,dimple and mixing vane,and the different characteristics of the k-ε model and k-ω *** with the experiment results,the simulation results suggest that the k-ω model is suitable for the simulation of the rod bundle flow with spacer grids;the spring and dimple are the main causes of the pressure loss in the spacer grid *** friction coefficient of the channel with spring and dimple is 1.5 times the coefficient of the channel with the *** results are beneficial to enhance the simulation ability of spacer grids flow and optimization design ability of spaces grid.

关键词： rod bundles spacer grids turbulence model SIMPLEC algorithm

Simulation of RFI Cancellation Using Subspace Projection Algorithm for PAF Receiver

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Research in Astronomy and Astrophysics 2024年第1期24卷 237-244页

作者： Peng Wu Jian Li mao-Zheng Chen Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China University of Chinese Academy of Sciences Beijing 100049China Xinjiang Key Laboratory of Microwave Technology Urumqi 830011China

The simulation of radio frequency interference(RFI) cancellation by applying a spatial filtering technique for phased array feed(PAF) is presented. In order to better reflect the characteristics of PAF, a new signal model is to add the coupling coefficient among elements of PAF to the conventional array signal model. Then the subspace projection(SP) algorithm is used to cancel RFI from the correlation matrix of the signal, and finally, the 2d power image is drawn. The power variation of signal-of-interest direction and RFI direction before and after using the SP algorithm is analyzed. The new signal model and simulation strategy can be used to test and verify the beamformer.

关键词： methods:analytical techniques:radar astronomy telescopes

Microstructural formation of semi-solid AZ91d alloy stirred by electromagnetic field

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Journal of University of Science and Technology Beijing 2005年第4期12卷 329-334页

作者： Weimin mao Zisheng Zhen Hongtao Chen Xueyou Zhong Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

With the help of an electromagnetic stirring device, alloy melt quenching and EBSd （electron back scatter diffraction） analysis technology, the microstructure of the semi-solid AZ91d magnesium alloy slurry stirred by rotational electromagnetic field under different stirring power conditions has been studied. The results show that the size of primary α-Mg phase is reduced obviously when the solidifying alloy melt is stirred by rotational electromagnetic field, moreover, the primary α-Mg grains are changed to fine rosette grains or spherical grains which are proved to belong to the different grains in three-dimension by the EBSd analysis technology. The results also show that the stirring power is an important processing parameter in the preparation of the semi-solid AZ91d magnesium alloy slurry. The larger the stirring power, the finer the primary α-Mg grains, the less the rosette primary α-Mg grains, and the more the spherical primary α-Mg grains. Theoretical analysis indicates that a stronger flow motion leads to a more even temperature field and solute field and a stronger man-made temperature fluctuation in the alloy melt so that the specially fine rosette and/or spherical primary α-Mg grains are formed in the semi-solid AZ91d magnesium alloy slurry.

关键词： AZ91d magnesium alloy electromagnetic stirring microstructure semi-solid