激光气体分析仪在钢铁行业的应用

本文论述了基于半导体激光吸收光谱测量技术的激光气体分析仪的分析原理、仪器结构和主要性能特点,并介绍了它在钢铁行业在线气体检测中的应用.     

基于TDLAS技术的激光氧分析仪在线标定方法研究

基于可调谐半导体激光吸收光谱(TDLAS)技术的激光氧分析仪,可以实现原位测量方式对样气中的氧气含量进行快速检测。但是随着仪器长时间的使用,由于激光器、光电检测器及硬件电路等方面的原因造成仪器测量结果出现漂移,此时需要对仪器进行标定。目前,激光氧分析仪标定方式采用离线标定方式,较费时费力。通过波长扫描技术同时扫描到谱线不重合且距离较近的被测气体16 O2和参比气体18 O2的吸收谱线,对氧气同位素18 O2信号在线检测,从而实现对被测气体16 O2的在线标定。通过测试表明该在线标定方法准确度可以达到≤±0.5%F.S,能够满足实际应用。     

气溶胶在线质谱仪及其在汽车尾气中的应用

汽车排放的颗粒气溶胶和有害气体严重影响着大气环境和人们的健康。我们研制了一台能够在线监测气溶胶粒径分布和气体组成成分的气溶胶在线质谱仪。此仪器具有响应时间快,性能稳定,自动化程度高和移动性好等特点。仪器采用了软电离方式,避免了碎片离子峰的形成,便于对污染环境中挥发性有机物的解析。实验结果表明仪器对挥发性有机物的检测下限为25ppb量级,并能实时测量尾气中气溶胶的浓度,在工厂废气以及污染场所气溶胶的测定方面有广阔的应用前景。     

基于相关原理的CO浓度测量仪器的研制

基于气体相关原理的红外光谱测量方法具有精度高、选择性好、在线性强的优点。本文阐述了一种新型CO浓度测量仪器的设计原理及其基本结构,介绍了在设计研制其机械系统、信号处理系统和系统软件过程中遇到的技术难点及相应的解决方法。该种仪器可广泛应用于对城市焚烧炉、工业燃烧炉烟道以及机动车辆尾气中的有害气体CO浓度的精确快速在线测量。收稿日期:2002-09-09     

海水重金属元素现场分析仪器的硬件设计

描述了用于海水中痕量重金属在线分析的检测仪器的硬件实现。仪器集成了1个多通道高精度开路电压测量系统和用于溶出伏安法测量的多路恒电位计,仪器内嵌软件可控制仪器自动完成全部测量过程,为全自动在线测量提供完善解决方案。仪器具有精度高、全自动测量、可扩展性好及可靠性高等特点。对完成的样机进行了性能测试,仪器指标达到了要求。     

内孔珩磨在线气动测量系统量程影响的仿真研究

气动测量具有精度高、测量力小、能够自洁、可以在比较恶劣的加工环境中使用的特点,因而被广泛应用于珩磨加工中。珩磨加工中的在线测量通常采用气动在线测量方法,但是,气动式测量的量程较小,制约着其在加工尺寸变化范围大的场合的使用。针对此种不足,基于FLUENT以气体介质参数为研究对象,并以差压型气动测量公式为基础,推导了气体粘度对测量量程的影响规律,进行了仿真研究。结果表明,气体介质的粘性影响了气动测量的范围和分辨率,正确选择不同种类的气体介质可以满足不同的在线测量要求。     

烟气连续排放监测系统 (3 测量气体浓度和烟气流速的在线监测系统)

由于抽取式监测系统存在不少问题 ,导致直接在烟道测量源水平气体浓度在线监测系统的发展。所谓在线系统即在没有改变烟气的组成并在颗粒物存在的条件下直接测量气体浓度的系统。在线监测系统要求能经受烟道环境条件的考验 ,结构简单 ,比抽取式监测系统的子系统要少。最初设计的在线监测系统 ,只能测量燃烧源排放烟气中污染物浓度在 5 0 0ＰＰｍ和以上的气体。业已证明 ,只要按适合的质量保证措施进行维护 ,在线监测系统就能够顺利地、连续地运行。由于气体控制装置的出现 ,使排气中污染物的浓度降低。一些在线监测器要满足测量低浓度的污染…     

关节轴承球面尺寸检测仪的误差修正方法

针对关节轴承球面尺寸检测仪专用于测量不同尺寸系列工件的特点,提出了关节轴承球面尺寸检测仪误差在线辨识与修正法。该方法通过在线测量系列工件和分析实测结果,可以准确地辨识并修正仪器系统误差,具有无须借助标准件、可低成本大幅度提高测量精度的优点。实验结果表明,使用该方法,仪器的测量值与高精度仪器测量值的偏差在10μm以内,最大测量误差由修正前的0.110mm减小到0.004mm,仪器测量精度明显提高,满足了企业提出的测量精度要求。     

污水COD在线快速检测仪的研制及其性能分析

本论介绍基于虚拟仪器平台构建的污水COD在线检测仪的测量原理,硬、软件设计及性能参数。仪器实现COD的在线快速连续自动测量。     

一种新型氨氮在线监测仪的研制

本在线监测仪器采用通气低温蒸馏吹脱、精确滴定、HSL颜色传感器精准指示滴定终点等方法,使其仪器结构简单、使用方便、稳定性高.解决了同类仪器测量下限低、使用成本高等缺点,使其满足各类水质中氨氮的在线测量要求.     

Operation survivability of civil aircraft

The fulfillment of the standard requirements for fatigue and damage tolerance of aircraft structures is the basis for ensuring their safe operation. The paper analyzes the rules formulated in the U.S. FAA Standards and Recommendation Circulars, Soviet Airworthiness Standards, and Russian Aviation Rules. The main requirements for ensuring the damage safety, damage tolerance, and preventing widespread fatigue damages in operating aircraft structures are stated. The results of studying the multiple site damages of full-scale aircraft structures are presented. The principle of the staged increase in the service life limit of Russian aircraft is considered. The rules of Russia are noted to be harmonized with the rules of the United States and Europe. The values of design service lives, scales of fatigue tests of full-scale structures and flight times in operation of different aircraft types are presented. The required values of the statistical and cyclical fracture resistance of structural materials are substantiated, and the achieved values of these characteristics in modern aluminum alloys are presented.     

叶轮机械内部流动研究进展

以叶轮机械内部流动研究方法为线索,分别从理论分析、试验测试和数值计算三个方面对国内外叶轮机械内部流动的研究进展和现状进行综述.首先概述叶轮机械内部流动损失的分类、定义和研究现状.然后分别从分离流动理论、涡动力学和叶轮机械流型三个层次介绍叶轮机械内部流动理论的发展;从平面叶栅、环形叶栅、动态试验和试验技术等方面回顾叶轮机械试验研究进展;从控制方程、数值方法、网格生成等方面综述叶轮机械数值计算研究方法、研究内容及成果等,并概括改善叶轮机械气动性能的方法和现状.最后对叶轮机械内部流动研究进行展望.结果表明,叶轮机械内部流动研究取得了巨大进展,有些研究成果已经应用到了设计工作中,但仍需对叶轮机械内部流动进行更深入的研究.     

A scanning and transmission electron microscopy study of the parabronchial unit in quail (Coturnix coturnix) and town pigeons (Columba livia).

A combined scanning electron (SEM) and transmission electron microscopy (TEM) investigation was undertaken to gain insight into the complex structural pattern of the atrial compartment and the gas exchange tissue of parabronchial units in quail and town pigeons. The aim was also to depict the changes taking place in the parabronchial unit in the late prehatching and early posthatching periods in quail. The standard SEM and TEM investigation was carried out in 13 mature quail and 8 town pigeons. The developmental study involved embryonic quail (Days 15, 16, 17), newly hatched quail, quail 24 h after hatching, and quail aged 2, 10, 19, and 25 days (3 individuals per group). The luminal relief of the parabronchus is formed by anastomosing interatrial septa delineating the atrial pits, which are thinner and shallower in pigeons. The atrial bottom opens in mature individuals into 3-6 infundibula. The extracellular material represented by trilaminar substance, which does not appear until hatching, veils the surface relief of the parabronchial epithelium, which is consequently hardly accessible to three-dimensional visualization. Only in town pigeons with fewer discontinuous layers of extracellular material was it possible to visualize the surface of the atrial epithelium, that is, of the granular and squamous atrial cells. The SEM analysis has convincingly shown the intricate spatial organization of atria, infundibula, and air and blood capillaries of the gas exchange tissue. The retinacula, that is, parallelly arranged processes of squamous respiratory cells bridging the air-capillary lumina, were evidenced by SEM and TEM. The complex structure of the avian parabronchus has been successfully demonstrated in the present SEM and TEM study.     

MODELING APPROACHES AND SOFTWARE FOR PREDICTING THE PERFORMANCE OF MILLING OPERATIONS AT MAL-UBC

The author has been conducting research in the area of metal cutting mechanics, metal cutting dynamics, machine tool vibrations, precision machining and machine tool control in his Manufacturing Automation Laboratory, at The University of British Columbia, Canada since 1986. This article summarizes the research conducted in mechanics and dynamics of metal cutting in our laboratory. Modeling of mechanics of metal cutting is summarized first. The models include orthogonal to oblique cutting transformation, mechanistic modeling of cutting coefficients, slip line field and Finite Element modeling. The author mostly focused on milling. The kinematics of milling with and without structural vibrations is modeled. The geometric model of end mills and inserted cutters with arbitrary geometry are modeled. The prediction of forces, torque, power and dimensional surface finish is explained for milling operations. The chatter stability for milling operations is presented. The metal cutting knowledge is transferred to manufacturing industry by combining all the models in shop friendly software.     

A computational analysis of the airflow in a twin-track subway tunnel with a sliding-curtain to improve ventilation performance

A computational model of an actual Seoul subway tunnel was analyzed in this study. The computational model was comprised of one natural ventilation shaft, two mechanical ventilation shafts, one mechanical air supply, a twin-track tunnel and a train. The natural ventilation shaft discharges and supplies air due to the train’s movement. The mechanical ventilation shaft and the mechanical air supply discharges and supplies, respectively, the airflow from the axial flow fans in the middle of the ducts of the shafts. A sliding-curtain was installed in the tunnel. The objective of this study was to numerically investigate train-induced airflow in the twin-track subway tunnel with natural and mechanical ventilation shafts and an installed curtain. The numerical analysis characterized the aerodynamic behavior and performance of the ventilation system by solving three-dimensional turbulent Reynolds-averaged Navier-Stokes equations. ANSYS CFX software was used for the computations. The airflow velocity from the computational results was validated by experimental results. Understanding the flow pattern of the train-induced airflow in the tunnel is necessary to improve ventilation performance. The ventilation and aerodynamic characteristics in the tunnel, including train-induced airflow, were investigated by analyzing the volume flowrate at the exits of the ventilation shafts and the velocity in the tunnel. The computational results were compared to cases with and without a curtain installed in the twin-track tunnel. As the train passed the mechanical ventilation shafts, the quantity of discharged-air in the ventilation shafts decreased rapidly. The flowrate at the exits of the ventilation shafts was gradually recovered with time, after the train passed the ventilation shafts. The airflow at the natural shaft and mechanical ventilation shaft 2, which was closest to the curtain, was increased. The computational results showed that the installed curtain can improve ventilation performance in the tunnel.     

Investigation on ball end milling of P20 die steel with cutter orientation

The generation mechanism of machining-induced residual stresses is a complex nonlinear and thermal–mechanical coupling problem. The cutting forces and cutting temperature produced in machining process must be considered simultaneously. The influence of cutter orientation and feed per tooth on the cutting speed, cutting forces, cutting temperature, and residual stresses is discussed in the present study. Effective cutting speed in accordance with the inclination angle in feed direction is analyzed. The cutting forces are gained by milling experiment, and the cutting temperature is obtained by finite element method. Moreover, the influence of the effective cutting speed on the cutting forces and cutting temperature is stated, and the relationship among the cutting forces, cutting temperature, and residual stresses is discussed. The experimental and numerical methods are both adopted in this study to give a better understanding of the milling process. After analysis of the phenomenon, several conclusions are made. The inclination angle in feed direction affects the effective cutting speed, and then the cutting forces, cutting temperature, and residual stresses are affected. Priority selection of inclination angle in feed direction is suggested from 5° to 30° in order to reduce the cutting forces. The overall trend of the workpiece temperature presents the parabolic shape, while the chip temperature increases with the increasing inclination angle in feed direction. Residual stress in feed direction almost increases with the increasing feed per tooth, which is not obvious in the general scope of the feed rate. The inclination angle of 5° and 15° is the priority in order to produce residual compressive stresses in cross feed direction.     

Morphology and histology of P. argentinus (Crustacea, Decapoda, Caridea) digestive tract.

This work describes the morphology and histology of the P. argentinus digestive tract. The foregut comprises the mouth, oesophagus, and stomach and is lined by a simple cylindrical epithelium overlain by cuticle. There are tegumental glands in the oral region and in the first portion of the oesophagus and of the hindgut. The cardiac stomach is an oval dorsal sac in the cephalothorax and has no calcified structures. The pyloric stomach comprises an upper chamber and a lower gland filter. The filter consists of an outer row of elongated setae and an inner row of dorsally curved setae forming longitudinal channels 16-18 microm wide. The midgut runs from the dorsal chamber of the pyloric stomach to the sixth abdominal somite without caeca. The hindgut runs from the sixth abdominal somite to the ventral anus. The mid-gut epithelium comprises dominant cylindrical cells and small undifferentiated cells in the first portion. The hindgut wall presents longitudinal folds, conspicuous muscular bundles, and a folded cuticle. The digestive tract of P. argentinus is basically similar to that of most of decapods. The absence of calcified structures in the stomach and the width of the longitudinal channels in the filter are related to the predominantly detritivorous diet.     

特殊钢锭翻转装置的结构设计与应用

对特殊超大钢锭翻转装置的功能、用途以及钢锭的上线上料方式中存在的问题进行了说明;并对翻转装置的结构、原理、使用方式进行了说明;该翻转装置在江阴兴澄特钢4300mm宽厚板轧钢工程中得到应用,表明翻转装置运行平稳、操作方便、控制可靠,翻转周期可调,达到预期目的。     

利用激光技术测量直升机旋翼共锥度的系统

旋翼共锥度测量是直升机生产、维护中的重要的检查项目,目前对旋翼共锥度的测量有CCD技术方法和激光技术方法,激光技术测量方法简单、快速且精度高.本文讨论了利用激光技术对直升机旋翼共锥度进行非接触测量的原理与方法,介绍了一种应用系统,该系统由激光器、硅光探测器、信号放大处理器、定时器、计算机和数据输出接口组成,具体给出了测量系统的组成结构和计算方法,并进行了精度分析,分析结果表明测量精度可保证在1 mm内.     

一种基于案例与规则推理的集成故障诊断技术

提出一种基于案例与基于规则推理的集成故障诊断技术,在基于案例推理与基于规则推理的诊断技术特点的基础上,论述了这种集成故障诊断系统的总体结构和系统协调问题,给出了系统的功能模型和案例检索流程,系统较好地解决了推理方法选择的技术问题,避免了案例与规则间的相互转换和冲突,接口简单、协调性好、实用性强、效率高,已获得实际应用验证.