利用挤压光纤双折射效应的自适应偏振控制器

报导了利用光纤应力双折射效应研制的1．55μm波长的自适应偏振控制 器,该控制器具有自动搜索、跟踪和精确控制光纤输出偏振态的功能。经初步检测,当偏振态变化3π/s时,输出偏振光强度为给定偏振方向分量总光强的92％,平均偏差小于2％。     

小型机载偏振成像系统研制及应用研究

机载偏振成像是未来遥感探测领域的重要研究方向之一。首先基于液晶双折射率效应完成了高精度液晶偏振控制器研制,并对其偏振调制精度进行标定;然后利用液晶偏振控制器搭建了高精度小型机载偏振成像系统,并基于小型固定翼无人机完成了系统的搭载飞行测试和目标识别探测试验。试验结果表明,液晶偏振控制器的Stokes偏振参数调制精度优于98%,利用液晶偏振控制器搭建的小型机载偏振成像系统可有效抑制背景干扰,提高低对比度目标的轮廓提取能力和目标识别能力。研究成果为偏振成像技术在目标侦察、环境监测、农作物普查等方面的应用提供了一种有效的技术途径。     

一种简单实用低插损的PMD模拟器

采用偏振控制器级联保偏光纤的方案，数值模拟了偏振模色散模拟器的统计分布。通过一种优化算法，采用特定长度的10段高双折射率光纤，使级联而成PMD模拟器的偏振模色散统计分布接近于麦克斯韦分布。实验测量结果表明，这种模拟器插损低，可控性好，变化迅速，DGD分布符合麦克斯韦分布。     

三轴直角结构光电导引平台的捷联控制

结合三轴直角框架结构的光电导引系统消除视线扰动的问题,给出了弹体扰动角速率和框架电机角速率转换到视线坐标系的转换公式,同时采用三轴直接补偿方式消除弹体扰动的影响,构成内回路角速率稳定控制器.进而导出了基于非线性逆动力学和PID控制器组合的外回路角速率跟踪控制器,使得光电导引系统在消除扰动的同时跟踪输入指令角速率信号.最后采用Matlab对稳定回路和跟踪回路进行了仿真,仿真结果表明,系统角速率稳定的解耦精度为1%,角速率跟踪的响应调节时间小于0.1s.     

偏振控制器特征参数与测试方法探究

正随着宽带网络信息运载量日益增长的需求以及密集波分复用技术的发展,在高速光纤通信系统的测试中,偏振现象带来的影响越发显著,因此需要使用性能优良的偏振仪器设备对光路中的偏振效应进行测试分析。一、偏振控制器简介偏振控制器利用晶体的双折射效应,引起一光线相对另一光线产生相位推迟,从而控制光的偏振态。根据相位推迟的形成原理,可分为玻片型、光纤环形等类型偏振控制器,其性能比较如表1所示。     

单模光纤偏振状态在线控制器

研制了一种单模光纤偏振状态在线控制器,通过线性双折射和圆形双折射改变单模光纤中光的偏振状态,实验结果与理论分析一致     

基于DOP监测的PMD补偿的实现与性能分析

针对偏振模色散(PMD)限制光纤通信系统向高速率和长距离发展的问题,本文提出了基于偏振度(DOP)监测的PMD动态自适应补偿系统的设计方案.该方法根据DOP与差分群时延(DGD)之间的关系,通过控制算法实现DOP最佳值的搜索和跟踪,由DOP的变化反映PMD的大小及其补偿效果,采用调节偏振控制器波片的角度和可变时延线,调整两基本偏振态,不断优化DOP使其趋于最佳值,构建了闭环补偿系统.实验结构表明,发生裂化的信号波形得到了有效恢复,眼图张开度得到明显改善.实验中,系统的补偿响应时间约为110 ms,补偿后信号的误码率为3.59e-16,达到了系统对传输误码率的要求.     

飞秒锁模光纤激光器及倍频程超连续谱试验研究

介绍了一种可应用于星载光学频率梳的自锁定全光纤飞秒激光器.该激光器采用非线性偏振旋转(NPR)方式,利用电控偏振控制器(EPC)实现自动锁模.当泵浦功率为420 mW时,通过电控偏振控制器的自动调节来改变腔内偏振态,从而达到稳定的锁模状态.在稳定锁模状态下,激光器输出脉冲的中心波长为1560 nm,输出功率为30 mW...     

可控磁路式永磁悬浮系统的串级控制

可控磁路式永磁悬浮系统具有强非线性、控制难度大等特点。根据该永磁悬浮系统的特点,设计了一种由角度环和位置环组成的串级控制器。利用该控制器对永磁悬浮系统进行位移外扰仿真和实验。实验结果表明应用该串级控制器,系统具有良好的鲁棒稳定性,当给系统一较小阶跃外扰时,系统可以在短时间内跟踪输入位移信号,达到新的稳定悬浮状态。     

欠驱动搬运机器人轨迹跟踪控制

目的为了解决欠驱动搬运机器人的中心和质心不重合的轨迹跟踪问题。方法建立非完整性约束的欠驱动机器人的运动学和动力学的模型,基于反步法控制策略生成新的虚拟反馈量,设计跟踪控制器,同时,利用自适应技术对具有不确定跟踪控制器的参数进行校正,通过Lyapunov理论验证控制器的稳定性。结果仿真实验结果表明,欠驱动搬运机器人的实际轨迹可以快速地跟踪期望轨迹,验证了基于反步法设计的跟踪控制器的可行性和有效性。结论设计的控制器能够使搬运移动机器人达到良好的轨迹跟踪效果,并且保证了控制器的自适应性。     

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