双光束光电二极管阵列检测器的设计

由于普通光电二极管阵列检测器无法克服光源波动造成的影响,故设计开发了一种双光束光电二极管阵列检测器。该检测器采用光导纤维束将光源发出的光分成两束,在斩光器的调制下分时射入样品吸收池和参比吸收池。透射出的光信号通过光导纤维束射到狭缝上,被凹面光栅分光成像于光电二极管阵列上。在斩光器和后续电路的配合下,实现了在同一个光电二极管阵列上信号光光谱、参考光光谱和暗电流的分时测量。由于采用参考光光谱和光电二极管阵列暗电流对信号光谱进行实时补偿,可以使基线短期噪声降低为1×10-5AU,漂移降低为1×10-4AU/h。     

10GHz主动锁模光纤激光器研究取得新进展

清华大学电子工程系研制出10GHz主动锁模光纤激光器,其输出光脉冲宽度为9.1pS,光谱宽度0.4nm,时间带宽积为0.48,接近变换极限,调谐范围35nm(1529～1564nm).     

二氧化氮差分吸收激光雷达拉曼激光源的优化研究

Nd:YAG三倍频激光(355nm)抽运高压CH4,获得其第一级斯托克斯光S1(395.60nm),作为NO2差分吸收激光雷达(NO2-DIAL)的激光源λon.通过增大激光脉冲宽度、改变拉曼池耦合透镜的焦距和气体压强等条件,获得了满足实际使用要求的转化效率高、稳定性好的395.60nm波长拉曼激光输出.该实验结果已应用于差分吸收激光雷达的NO2探测.     

Mach-Zehnder电光调制器产生多波长光源的实验研究

随着对光纤通信容量需求的不断增长,DWDM系统和L波段光器件成为当今研究的热点,多波长光源作为重要的有源器件倍受青睐。本文研究了基于Mach-Zehnder结构的电光强度调制器的理论模型,利用公式仿真得到在一定微波功率调制下强度调制器输出的扩频光谱。实验研究了M-Z结构的集成电光波导强度调制器光波长1550nm处10GHz、15GHz、20GHz扩频的实现,对理论分析所得的输出光谱与实际系统的输出光谱进行比较,发现谱线情况较一致。在调制频率10GHz,调制深度C=1.39,V=2.98V时,输出光谱中可清楚观察到正负三阶等频率间隔的边波带,尤其是一阶边波带与中心波长峰值功率几乎相等,可实现三路光源等功率输出。     

8英寸MCP型光电倍增管的实验研究

研制了一套单光电子谱测试仪。对8英寸微通道板型光电倍增管(MCP-PMT)的性能指标进行了标定,包括单光电子谱的增益和峰谷比、光电阴极的均匀性。单光电子谱测试仪采用高精度QDC采集电荷谱。VME数据获取系统积分电荷谱得到单光电子谱。采用LABVIEW的电流采样系统获得光电阴极某确定位置上光电流的I-V坪曲线。单光电子谱测试仪测得MCP-PMT在高压为2100 V、脉冲发生器的设置为脉冲宽度10 ns、采样频率1 k Hz、驱动电压1.735 V驱动LED光源时,单光电子谱的增益为2.5233×107、峰谷比值为2.78,光电阴极的非均匀性小于10%。实验测得的性能指标均满足中微子探测等实验要求。同时为20英寸MCP-PMT的成功研制奠定了理论设计及测试基础。     

非对称光纤反射镜的可调谐光纤激光器

提出一种非对称窄带光纤环形反射镜结构的可调谐掺铒光纤激光器。980nm泵浦光对掺铒有源光纤进行抽运,高双折射光纤、偏振控制器（PC）和光纤耦合器构成窄带光纤反射镜,窄带光纤反射镜和普通光纤反射镜组成激光谐振腔,利用窄带光纤反射镜工作带宽纳米量级的特性得到单纵模激光。调整偏振控制器改变反射镜对不同波长的反射率,实现可变波长的激光输出。实验表明,该激光器的工作带宽为8nm,120mW泵浦光条件下最大输出功率为4mW,3dB带宽（脉冲的半高宽度）小于0．2nm,边模抑制比为20dB以上,在1527nm～1535nm的波长范围内观察到稳定激光输出。     

光谱吸收式光纤甲烷气体传感器及其信号处理方法

基于气体在其特征吸收波长下光的吸收随浓度变化的机理,通过对甲烷气体吸收光谱的分析,提出了一种光谱吸收式全光纤甲烷气体传感器及其系统。该系统以1300nm波段的DFBLD作为光源,波长响应范围为1100~1900nm的高灵敏度、低噪声的InGaAsPIN作为光电探测器,利用锁相放大器对传输信号进行相敏检波,采用一次谐波反馈光源注入电流、二次谐波与一次谐波的比值作为系统输出的谐波检测技术对微弱信号进行处理,使得系统达到很高的灵敏度。研究表明,该传感器的灵敏度达到10ppm,精确度和稳定性等性能指标均可满足甲烷气体检测要求。     

Cr3+:LiNbO3晶体生长和光谱特性的研究

采用提拉法从近化学计量比的熔体中生长出尺寸为φ20mm×60mm的优质LiNbO3Cr(CLN)晶体,其光学均匀度为7.05E-005.进行了吸收和荧光光谱的测定研究.吸收谱测试表明Cr3+离子在晶体中有两个宽且强的吸收带及两个微弱的吸收线,两宽带中心波长分别为481和657nm,对应于4A2→4T1和4A2→4T2两个具有相同的总自旋能级之间的跃迁,在4A2→4T2吸收宽带的长波边缘处有个很小的吸收峰,其波长为727nm,对应于4A2→2E(R线)的跃迁.荧光测试表明当激发波长为660nm时,CLN晶体荧光宽带和一个较弱的荧光线峰并存,宽带范围为800～982nm,峰值波长为870nm,对应于4T2→2E,4A2的联合能级跃迁,荧光线峰波长约为752nm,其强度较弱,相应于2E→4A2(零声子线)能级跃迁.计算了晶场强度和Racah参数,其Dq,B,G大小分别为1522.1、542.5和3218.7cm-1,Dq/B=2.81,晶体属于强场介质.研究表明,CLN晶体具备可调谐激光晶体的基本光谱要求,且有良好的物化性能,可以实现宽频带可调谐激光输出.又具有较大的倍频系数,有望实现410nm附近紫外的自倍频激光输出.     

基于FPGA高速信号采集的多角度动态光散射法纳米粒径测量

根据动态光散射装置测量纳米粒径原理,开发了一套基于现场可编程门阵列(FPGA)的纳米粒径测量系统。该系统通过光电倍增管(PMT)输出光子脉冲信号,利用FPGA实现高速脉冲采集及自相关运算,采用双脉冲计数器实现高精度可控的连续计数,并实现DDR3异步存储以及USB通信交互等接口功能。自研板卡既可实现自相关函数实时采集运算,又可无丢失地保存海量原始数据信号。采用该系统对200nm聚苯乙烯颗粒进行了测量,分析了不同采样时间及延迟时间等参数对粒径测量结果的影响。实验结果表明:自研FPGA采集板卡测量重复性为1.2%,具有很好的稳定性和重复性。     

SANOA长光程差分吸收光谱仪故障维修1例

SANOA长光程差分吸收光谱仪用于空气污染地面自动监测子站的二氧化硫，一氧化氮，氮氧化物，甲醛，氨，臭氧等的测量。它的工作原理是用差分吸收原理，测量从紫外线光源发出的透过大气的光，根据每种气体成分对紫外光的特征吸收谱线，计算大气中该气体的浓度。SANOA由一个固定光源(150W紫外灯)，接收器，数据处理系统组成。紫外灯发射一光束，穿过一定距离的空气后到达接收器，经分光后，由512象素的光电二极管阵列接收(每个象素对应一个波长)，经14位A／D转换器送人CPU进行分析计算。     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...