EK系列天然气体积修正仪的检定

文章以EK260体积修正仪为例,从检定过程中遇到的困扰出发,讨论了EK系列天然气体积修正仪的检定方法和注意点,给出了简要的检定实例。     

气体检测报警器检定中需注意的几个问题

本文介绍了气体检测报警器的检定方法,以及在检定过程中需注意的问题。     

硫化氢气体检定装置示值误差测量不确定度评定

本文结合实际检定工作、硫化氢气体检测仪检定规程及不确定度评定方法的步骤,分析与阐述了硫化氢气体检定装置示值误差测量不确定度评定。     

对可燃气体报警器所用检定介质的探讨

由于可燃性气体并非由单一气体构成，因此，对于检定可燃气体报警器用何种标准气体作为检定介质，是我们需要探讨的问题。JJG693—2004《可燃气体检测报警器》计量检定规程规定，检定可燃气体报警器使用的标准气体是异丁烷和丙烷，但使用这两种气体对可燃气体报警器进行检定，会给一些生产企业带来不便。在此，我们拟通过可燃性气体的等热值特性，解决选择多种标准气体作为可燃气体报警器检定介质的难题。     

湿度对容积法检定钟罩式气体流量标准装置影响研究

分析了湿度对容积法检定油封钟罩式气体流量标准装置的影响,建立了湿度对标准体积影响的数学模型。提出了容积法检定方法的改进措施,并评定了改进方法的测量不确定度。验证了水温、环境湿度、大气压力对检定结果的影响,表明容积法检定必须严格控制检定条件和对湿度进行修正。建议采用尺寸法检定油封钟罩。     

气体浮子流量计检定数据处理方法

对标准状态气体浮子流量计检定数据的数据处理方法做了简单介绍,重点介绍了对非标准刻度的气体浮子流量计检定数据的处理方法。通过对非标准刻度气体浮子流量计检定数据的分析,指出了对浮子流量计压力、密度修正的重要性。     

有关气体分析仪(报警器)检定规程中一些问题的探讨

我们在日常的气体报警器和分析仪的检定过程中 ,发现目前现行的一些气体报警器和分析仪的检定规程存在着一些问题 ,主要有以下几点 :1　对于检测同一种类气体的仪器 ,检定规程太多如对于检测氧气的仪器就有ＪＪＧ662 -1990热磁式氧分析器检定规程、ＪＪＧ3 65 -1998电化学电极气体氧分析器检定规程、ＪＪＧ5 3 5 -1988氧化锆氧分析器检定规程等三种 ,当然对于这三种用不同的检测原理的氧分析器检定规程而言有其特殊性 ,但是绝大多数的技术指标及检定用设备都是相同的。是否可以考虑将三者合而为一。相同的还有用于检定可燃气体报警器的规程…     

可燃气体报警器计量检定的意义和现状

本文分析了可燃气体报警器检定的必要性和现有行业主要使用的检测方法和实施检定的现状。     

《氧化锆氧分柝器》计量检定规程的修订势在必行

氧化锆氧分析器计量检定规程的制定至今已为期14年,其检定指标、检定方法等诸条款已严重滞后,对原规程的修订已势在必行.     

动态稀释法配制标准气体在气体分析仪器及气体检测报警器检定中的应用

目前,各种气体分析仪检定规程都规定使用至少3种气体对仪器进行检定。但是,由于气体检测仪种类较多,如果要开展较多种类仪器的检定工作,就需要多瓶气体标准物质,甚至许多腐蚀性的低浓度标准气体,但其瓶装不稳不准,工作极不方便。因此,采用动态稀释法配制标准气体的方法是一种较为理想的方法。过去由于没有进行过详细的分析,     

钟罩式气体流量标准装置内部容积的测量方法

基于尺寸测量法,测量了1000L钟罩内部的分阶容积。2个接触式长度计和旋转测量臂构成弦长测量机构。将罩体沿轴向划分为若干等间距截面,以15°采样间隔测量长度计与罩体内壁的接触点到测量臂旋转中心的距离,由接触点空间坐标确定各截面的轮廓。提出一种新的面积扫描法计算各层截面面积。经与圆度误差法的测量数据对比,当采样间隔密集时(5°或15°)2种方法的测量结果比较吻合。由各层截面面积及其轴向间距,计算得到分阶容积数据表作为罩体内部容积的标定结果。     

电子级多晶硅的生产工艺

就建设1000t电子级多晶硅厂的技术进行了探讨。对三氯氢硅法、四氯化硅法、二氯二氢硅法和硅烷法生产的多晶硅质量、安全性、运输和存贮的可行性、有用沉积比、沉积速率、一次转换率、生长温度、电耗和价格进行了对比;对还原或热分解使用的反应器即钟罩式反应器、流床反应器和自由空间反应器也进行了比较。介绍了用三氯氢硅钟罩式反应器法生产多晶硅三代流程。第三代多晶硅流程适于1000t/a级的电子级多晶硅生产。     

Bell prover — calibration and monitoring of time stability

This paper is focused on the calibration and measurement of the geometric parameters of a bell prover that serves as a standard of volume of gas flow. It also includes methods for monitoring the time stability of the bell prover: intra- and inter-laboratory comparison measurements, Shewhart analysis and planned evaluation of recalibration intervals.     

DX桩桩周土应力场分布的模型试验研究

通过室内小比尺的模型试验,可以进一步为确定DX桩沉降计算公式提供必要的依据。在小型模型试验箱中,通过采用杠杆加砝码的装置对22 mm桩径的DX桩在砂土中进行研究,测定单桩的桩顶荷载-桩顶位移曲线,确定承载力,并与相同情况下的直孔桩进行对比;同时,利用微型土压力盒测定土中应力变化,研究荷载在土中的传递规律。试验结果表明,DX桩的承载力及沉降特性明显优于直孔桩;承力盘在上部和下部时,DX桩尽管承载力相差不大,但是盘在下部时会增大桩端附近土体的应力;两个承力盘的DX桩,两盘受力比较一致,且盘受力的影响范围,在竖     

Control of vortex rings for manoeuvrability

Manoeuvrability is critical to the success of many species. Selective forces acting over millions of years have resulted in a range of capabilities currently unmatched by machines. Thus, understanding animal control of fluids for manoeuvring has both biological and engineering applications. Within inertial fluid regimes, propulsion involves the formation and interaction of vortices to generate thrust. We use both volumetric and planar imaging techniques to quantify how jellyfish (Aurelia aurita) modulate vortex rings during turning behaviour. Our results show that these animals distort individual vortex rings during turns to alter the force balance across the animal, primarily through kinematic modulation of the bell margin. We find that only a portion of the vortex ring separates from the body during turns, which may increase torque. Using a fluorescent actin staining method, we demonstrate the presence of radial muscle fibres lining the bell along the margin. The presence of radial muscles provides a mechanistic explanation for the ability of scyphomedusae to alter their bell kinematics to generate non-symmetric thrust for manoeuvring. These results illustrate the advantage of combining imaging methods and provide new insights into the modulation and control of vorticity for low-speed animal manoeuvring.     

Zur Konstruktion einer berühmten Glocke

The large swinging bell Gloriosa, cast in 1497 for Erfurt Cathedral by Gherardus de Wou, ranks as an outstanding masterpiece of Gothic bell-founding art. Its musical quality and formal aesthetics became an object of emulation for generations of succeeeding bell founders and there have been repeated attempts to discover the hidden deisgn of the bell's profile. An early drawing is based on measurements made in 1865 by Sorge and consistent or modified reproductions of it were subsequently published by several authors. Since 1985, a new admeasure of the bell's profile has been available. From these data a shape-fitting reconstruction was obtained by means of computer aided design (CAD) but following the traditional principles of bell design. With the aid of the finite element method (FEM) the frequencies of the partials of a bell can be calculated from its material and its profile. They make up the inner harmony as an important part of euphony, namely the purity of sound. Calculated values for the most important partials are given in terms of deviation from ideal harmonic intervals and are compared with acoustically ascertained values and modern standards. A further part of euphony, i.e. reverberation and sonority, is related to the bell metal, makingGloriosa highly resonant. As a piece of luck with a singular coincidence of perfect profile and excellent material.Gloriosa will remain the undefeatable prototype of western bells.     

中国古式大钟发声特性研究

根据钟振动发声的理论,从振动模态出发研究了中国古式大钟的发声特性,从理论上找到了与中国古式大钟发声特性密切相关的物理量.进行了中国古式大钟——龙魂大钟的撞击实验,测量了大钟的发声频谱和声衰减．并结合大钟物理参数进行了理论推算。实验测量结果与理论推算结果吻合良好,验证了理论的正确性,从而确认了与中国古式大钟发声特性密切相关的物理量,对中国古式大钟的实际铸造提出了指导性的意见。     

Failure Analysis of Cast Iron Trunk Main in Cleveland, Ohio

This article describes the failure analyses of a 30??-diameter cast iron main that failed suddenly at the bell?Cspigot joint in Cleveland, Ohio in March 2008. The main had been operating largely without problems since its installation in 1880. The failure was analyzed using three models developed previously, each of which considered a specific failure mechanism candidate, namely (a) operational load or static analysis, (b) joint failure due to ground movement (settlement), and (c) fatigue failure. Operational load analysis clearly showed that while the factor of safety was significantly reduced in the presence of a concrete vault installed in 2002 just above the pipe, the margin of safety was still sufficient for the main to have performed safely. Ground movement analysis of the jointed pipe showed that the construction of the concrete vault above the joint of the 30??-cast iron main subjected the joint to rotation, which might have ultimately cracked the bell leading to failure. Under this circumstance, two failure scenarios are possible: namely, (a) additional rotation was large enough to cause the bell to split, or (b) additional rotation was sufficient to induce a minor crack in the bell but fatigue (repeated) loading caused the crack to grow over time until the combination of crack length and loading was sufficient to cause the bell to eventually split. The color differences along the fracture surfaces indicated that the fracture occurred in two distinct stages. This observation suggests that the second scenario is more plausible than the first.     

钟罩装置标准容积的数学模型研究与建立

在钟罩装置标准容积实测数据的基础上,通过描点图定性分析了钟罩罩体高度和半径的关系特性,提出采用傅里叶级数建立数学模型,借助Matlab获得理想的函数方程,并分析了其拟合标准差。实际应用中采用光栅尺测量钟罩下降的高度,运用定积分原理对函数进行积分获得钟罩下降任意高度时排出的气体容积值,在瞬时流量下限标准容积的相对扩展不确定度达到4×10^-4(k=2),相对以半径平均值为估计值的方法,降低了66.7%,同时可实现钟罩在检测过程中任意点的启停。     

Dynamic behavior of a masonry civic belfry under operational conditions

Slender structures, such as towers, are characterized by a high sensitivity to dynamic excitation. As a consequence, meaningful information about their behavior under operational conditions can be obtained by monitoring their response to ambient vibrations. Furthermore, significant stresses could be induced to the ancient masonry walls when the dynamic forces due to the swinging of a bell are acting. To assess the structural conditions of a case study representative of such type of structures and to plan an adequate retrofit, numerical analyses are carried out on a model whose modal parameters are calibrated based on the elaboration of the results from the ambient vibrations tests. In particular, full time histories analyses are performed using as input either the signal recorded while the bell was hit by a hammer, or the numerically calculated dynamic forces that would be produced by the actual swinging of the bell. The first set of analyses aims to investigate the capability of an equivalent linear elastic model to capture the actual dynamic response of the structure. The second set of analyses provides an evaluation of the tower response when dynamic loads of higher intensity and likely occurrence are considered.