导航星座自主导航技术研究

导航星座自主导航日益成为新一代卫星导航系统的主要研究方向。在系统地论述导航星座自主导航的信息处理流程的基础上，重点提出了导航星座自主导航的关键技术，包括卫星星历与时钟参数的长期预报技术、星间测距与通信链路的建立和维持技术、星座卫星自主时间同步技术、星座卫星自主星历更新技术、自主导航信息处理的鲁棒滤波技术、星座整体旋转建模技术，以及地球自转及极移参数的长期预报技术。详细分析了关键技术实施途径，论证了相关数学模型。最后，对星座卫星自主时间同步与星历更新算法进行了系统仿真，结果表明：通过星载滤波器处理星间双向测     

卫星星座自主时间同步算法的研究

主要研究了空间卫星间时间同步的方法.在分析了卫星星座的特点和空间时间同步的要求后,提出了一种新的卡尔曼滤波方法来实现星座内卫星间的时间同步,并得到整个星座的系统时间.该方法通过伪距测量得到各卫星间的伪距,用卡尔曼滤波器得到卫星间的钟差和频率差,再对这些钟差和频率差进行加权统计平均,得到星座的系统时间,并以此结果修正卡尔曼滤波器参数,循环渐进优化预测结果,使整个星座内的卫星钟同步于星座的系统时间.对该方法进行仿真后,结果表明具有良好的收敛性和准确的预测值.     

卫星导航接收机时延测定技术研究

利用卫星导航接收机进行高精度授时同步是一种简单有效的授时同步手段。导航接收系统时延的精确测量是进行高精度授时的前提,其输出秒脉冲信号的时延更是影响远距离授时、时间同步的关键。围绕卫星导航接收系统时延的测定,通过分析卫星导航接收机的时延构成及特点,建立了卫星导航接收机的时延构成模型,制定了便于操作的卫星导航接收机时延测定的方法,搭建了一套完整的卫星导航接收机时延测定系统,并对系统进行了标定和实验验证。     

航天器高精度GPS导航定位技术研究

将GPS测量定位技术、求解卫星轨道摄动运动的Encke方法和广义Kalman滤波技术有机地结合在一起，提出了利用GPS实现低轨道航天器高精度自主导航定位的新方法——载波相位-伪距综合动态定轨技术，解决了GPS载波相位应用中动态解模糊和跳周修复的难题。以此为基础，提出了两个航天器之间的载波相位-伪距综合差分动态相对导航技术。数值仿真分析和半物理仿真实验结果表明，所提出的动态定轨技术是可行的，对提高GPS导航定位精度的效果是显著的，并且其模型、算法和软件具有工程实用性。     

基于激光链路的星间信息传输与仿真研究

星间链路是导航卫星实现精密定轨和自主导航的关键技术之一.导航卫星通过星间链路完成伪距测量和数据交换,维持系统稳定运行的时空基准,保证系统持续提供精准导航服务.本文根据全球导航卫星系统的建设情况和发展趋势,首先对星间观测和信息传输频段进行了介绍,然后从天线特征,多址控制方式和网络拓扑结构等角度分析了常见星间链路的工作体制...     

PNT体系视角下卫星导航与不依赖卫星导航技术融合发展研究

卫星导航自问世以来以其全天候、全天时、低成本的优势，成为广泛使用的导航定位授时（PNT）方式；但在应用层面，为了规避对卫星导航单一手段的过度依赖，“不依赖卫星导航技术”概念被提出并受到重视，如何准确把握两者之间的关系成为现实而迫切的问题。本文概述了卫星导航技术特征与体系定位，进而基于PNT体系视角，对比分析了惯性导航、匹配导航、无线电导航（除卫星导航外）等典型不依赖卫星导航技术的性能、成本、应用场景；辨析了卫星导航与不依赖卫星导航的关系，明晰了卫星导航作为最大共性需求满足者、体系核心与基石的总体定位，量化分析了卫星导航与不依赖卫星导航技术融合的效能。我国PNT体系的科学发展，需要创新突破不依赖卫星导航技术，促进卫星导航和不依赖卫星导航技术深度融合，同时加快低轨导航系统建设，提升卫星导航性能并最大化体系贡献率。     

北斗导航剑指天 警务应用箭在弦

金秋送爽,又是一年国庆时。距北斗卫星导航系统首星"北斗一号"发射已经11年之久,伴随着一颗颗卫星的成功升空,导航技术的不断进步,我国的卫星导航事业正进入飞速发展的轨道。2011年7月27日第九颗北斗导航卫星送入太空预定转移轨道,这是北斗导航系统组网的第四颗倾斜地球同步轨道卫星。它标志着     

GPS伪距单点定位

给出GPS伪距动态单点定位、相关改正的计算模型以及精度评定方法即精度因子的计算方法。通过实例计算,得到伪距单点定位坐标精度优于10米的结论,并分析平差值与已知值的差值与卫星个数之间的关系、模型的误差以及精度因子与卫星个数之间分布。     

伽利略导航系统若干关键技术分析

分析了目前最新的卫星导航定位系统——伽利略系统所采用的若干关键技术．从卫星轨道布置方式、信号与频率设计方法、伪卫星技术及信号服务等几个方面与GPS进行了对比研究．研究结果表明，Galileo系统具有定位精度高、兼容性好、功能全等优点，在新一代导航系统中具有重要地位．     

中国卫星导航建设现代化管理研究

卫星导航建设风险链条长、关联行业多、涉及主体广、牵涉利益多，加之国内国际特征存在差异性，在管理上具有较强的系统性、较高的复杂性；在推进国家治理体系与治理能力现代化的背景下，积极探索现代化管理体制与发展模式是提高卫星导航现代化管理质效、确保卫星导航事业持续稳定发展的必然要求。本文立足历史与现实、理论与实践等多个层面，梳理和总结了中国卫星导航系统在“三步走”发展战略实践中形成的管理经验，剖析了在新发展阶段卫星导航系统建设管理所面临的挑战，论证提出了中国卫星导航建设现代化管理的发展目标以及需统筹处理的要素关系。研究建议，从卫星导航领导体制、管理体制、法治体系、应用产业体系、科技创新体系、战略人才培养、国际化发展机制等方面同步发力，切实提升卫星导航建设现代化管理水平，为中国卫星导航系统高质量发展提供有力支撑。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to