基于二次曝光法的切趾2mm短栅距光纤布拉格光栅制作研究

研究了基于二次曝光法的2 mm短栅距型光纤布拉格光栅(FBG)的制作及切趾函数参数控制.针对所选取的3种切趾函数,在耦合模理论基础上,利用传输矩阵法进行了FBG光学特性仿真分析,给出了最佳切趾参数下的光栅反射谱.FBG制作实验结果表明,所选取的不同切趾型短栅距FBG性能较好满足传感用性能要求,为高反射率、较窄带宽、高边模抑制比的短栅距型FBG的制作研究提供了有益的参考.     

光子晶体光纤光栅反射谱及时延特性研究

利用多极法对包层空气孔为正六边形对称结构光子晶体光纤的模式场进行了分析,计算出不同波长下基模的有效折射率,结合使用模式耦合理论和传输矩阵法对基于光子晶体光纤的布拉格光栅特性进行了计算和仿真,对比了常规单模光纤所成光栅与相同光栅周期的光子晶体光纤布拉格光栅反射谱及时延特性之间的差异.在此基础上,对光纤光栅的切趾特性进行了研究,选择不同的切趾函数,得出最佳切趾函数下光栅传输谱.理论计算和仿真结果表明,随波长增加,基模有效折射率下降,光栅谐振波长出现蓝移,采用啁啾化处理后,10 cm长光子晶体光纤光栅可以提供1 200 ps以上的线性时延.     

高双折射光纤光栅扭转特性分析与应用

通过对高双折射光纤光栅的特性进行分析,提出了一种新型的可埋入工程材料的扭转传感器结构。基于光纤光栅的模耦合理论和高双折射光纤的扭转特性,建立了扭转高双折射光纤光栅传输光波的数学模型,并分析其光谱特性,仿真结果表明扭转高双折射光纤光栅的反射谱不具备方向性,只与扭转角度大小有关。当扭转角度从0变化到360°时,高双折射光纤光栅的2个主峰波长都随之产生漂移,x方向的光向短波长方向移动,y方向的光向长波长方向移动,并且反射谱峰值逐渐减小,通过前向耦合模理论与反向耦合模理论结合分析并仿真,得出x和y方向上波峰值变化量,以及相应的中心波长的变化量,最后通过实验数据对高双折射光纤光栅的变化参数与扭转角度的关系作出验证。     

扩束光纤与宽波导光栅的光耦合特性

为了研究光纤与宽波导光栅的有效耦合,基于高斯光束与波导光栅的光耦合理论,以30μm宽波导光栅为研究对象,利用矩阵光学和高斯光束理论分析和设计了一种扩束光纤,并通过分析其耦合损耗,建立了扩束光纤与波导光栅耦合模型.优化所设计扩束光纤的结构参数后,得到束腰半径为10.8μm的输出光束.最后分析了扩束光纤的结构容差,并讨论了所设计扩束光纤的输出光束、单模光纤的输出光束以及束腰半径为16 μm的自由空间高斯光束各自在光栅表面的位置变化对光栅耦合效率的影响.可知扩束光纤输出的光束与单模光纤输出的光束相比具有较大的位置容差,与束腰半径为16 μm的自由空间高斯光束相比,光耦合效率基本相同.     

基于狭缝整形的低损耗飞秒光纤光栅制备

为了解决飞秒激光逐点法制备的光纤布拉格光栅（Fiber Bragg Gratings, FBG）损耗较高的问题,利用逐面法完成飞秒光纤光栅制备的实验研究。运用高斯光束传播的基本理论,通过狭缝整形技术对聚焦的飞秒激光能量分布进行等高宽整形,突破在光纤横截面内诱导产生圆形折射率调制的难点,最终制备得到低损耗的飞秒光纤光栅。开展不同狭缝宽度制备FBG的光谱特性对比实验,结果表明：利用光斑直径为5.0 mm的飞秒激光光束刻写FBG时,采用宽度为1.7 mm的狭缝制备得到的FBG插入损耗降低至0.15 dB,短波损耗降低至0.5 dB,验证了基于狭缝整形的低损耗飞秒光纤光栅制备方法的有效性。针对狭缝法制备的FBG反射率分散问题,提出控制折射率匹配液填充量以及调整飞秒激光能量的方法,并优化光束聚焦流程,成功降低FBG反射率的分散度。本研究对推动飞秒光纤光栅在大容量、高链路损耗等环境中的实际应用具有重要意义。     

高斯光束到光纤的单透镜耦合

分析了基模高斯激光束到单模和多模光纤的单透镜耦合过程中的各种损耗,把多模光纤的光场用高斯分布近似,采用模场耦合理论计算了基模高斯光束到单模和多模光纤的单透镜耦合效率.模拟计算了当激光-光纤耦合系统的工程参数(光束束宽、光纤数值孔径和光纤的纤芯芯径)一定时,单透镜耦合效率与所选用透镜的焦距之间的关系.并利用532mn激光(M2≤1.05)在几种不同焦距的透镜下对纤芯直径为3.μm的单模光纤和25μm的多模光纤进行了耦合效率的测定实验,得到了与理论计算基本吻合的实验结果.     

基于可饱和吸收稳频技术的光纤激光应变传感特性研究

提出了一种环形光纤激光用于光纤传感的方法,结合光纤可饱和吸收体稳频技术,获得稳定的激光输出,并成功将其应用于应变传感.使用980 nm激光二极管作为泵浦源,长度为2 m的掺铒光纤作为增益介质,通过光环形器引入未泵浦的掺铒光纤作为可饱和吸收体形成窄带滤波器,并选用高反射率光纤光栅作为波长选择元件.可饱和吸收体长度为4 m时获得了稳定的激光输出,输出3 d B带宽小于0.2 nm,边模抑制比大于70 d B,阈值电流为63.3 m A.通过选频光纤光栅对等强度梁应变的感知引起的光纤激光输出调谐,实现0~2 100με应变传感检测,对这种掺铒光纤激光的应变特性进行了实验研究,得到了应变与激光峰值波长的线性关系.实验结果表明:该激光传感器获得了很好的线性度和重复度,线性拟合度高于0.999.     

倾斜光纤光栅温度及溶液浓度传感特性研究

本文通过模拟仿真、理论分析和实验对倾斜光纤光栅（TFBG）的温度及溶液浓度传感特性进行了研究。实验结果表明TFBG的纤芯模和包层模具有相同的温度灵敏度，约为10pm/℃，且线性度良好；在溶液浓度实验中通过求取TFBG纤芯模与包层模的差分波长来消除温度对浓度测量的干扰，解决了TFBG包层模对温度和浓度交叉敏感的难题。溶液...     

FBG光纤的飞秒激光刻蚀特性及传感应用

在布拉格光栅（FBG）光纤的包层中制作微槽,结合敏感材料提高了FBG光纤传感器的灵敏度,拓宽了其传感应用领域。利用飞秒（fs）激光对I型布拉格光栅光纤进行刻蚀,通过调节激光功率和辐照时间,分析光纤折射率变化以及光纤表面和内部结构的刻蚀特性,并探讨fs激光对光纤光栅微沟槽形貌和反射光谱的影响。实验结果表明,微槽表面由于碎屑的凝固而产生许多柱状结构,且随着激光能量的增加,柱状结构不断长大,槽深和形状服从高斯能量分布;随着激光功率和辐照时间的增加,反射率谱永久红移,带宽增加。利用微结构光纤增敏性能,有效提高微结构光纤光栅磁场探头和氢气探头的传感性能。     

基于倾斜光纤光栅的传感解调技术

该文设计了一种基于倾斜光纤光栅（tilted fiber Bragg grating,TFBG）的不受温度影响的光纤布拉格光栅（fiber Brag ggrating,FBG）应变解调系统．将倾斜光纤光栅用作边沿痣波器,当周围环境温度变化时,利用倾斜光纤光栅纤芯模与包层模的温度特性与普通光纤布拉格光栅相同这一特点,无需另加温度补偿,就可以实现FBG应变传感的动态解调,消除温度噪声对应变信号的影响．由实验可知,当温度在25℃到39℃范围变化时,解调系统的性能基本不发生改变,解调范围达到6nm．     

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.     

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...     

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.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

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.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.