A Novel Method for Estimating Light-Scattering Properties of Soot Aerosols Using a Modified Single-Particle Soot Photometer

A Single-Particle Soot Photometer (SP2) detects black refractory or elemental carbon (EC) in particles by passing them through an intense laser beam. The laser light heats EC in particles causing them to vaporize in the beam. Detection of wavelength-resolved thermal radiation emissions provides quantitative information on the EC mass of individual particles in the size range of 0.2–1 μm diameter. Non-absorbing particles are sized based on the amount of light they scatter from the laser beam. The time series of the scattering signal of a non-absorbing particle is a Gaussian, because the SP2 laser is in the TEM00 mode. Information on the scattering properties of externally and internally mixed EC particles as detected by the SP2 is lost in general, because each particle changes size, shape, and composition as it passes through the laser beam. Thus, scattered light from a sampled EC particle does not yield a full Gaussian waveform. A method for determining the scattering properties of EC particles using a two-element avalanche photodiode (APD) is described here. In this method, the Gaussian scattering function is constructed from the leading edge of the scattering signal (before the particle is perturbed by the laser), the Gaussian width, and the location of the leading edge in the beam derived from the two-element APD signal. The method allows an SP2 to determine the scattering properties of individual EC particles as well as the EC mass. Detection of polystyrene latex spheres, well-characterized EC particles with and without organic coatings, and Mie scattering calculations are used to validate the method.     

玻璃液高温电阻率的测定

运用模拟仿真测试方法分析高温玻璃液中不同温度下电阻与温度的关系, 并将测试电阻与实测电阻做比较, 探讨影响测试电阻的因素, 为提高仿真测试方法测试电阻率精确度带来有益启示.     

用电阻率法确定混凝土结构形成的发展阶段及结构形成动力学参数

测定和分析了水灰比为0.4和0.5的不同骨料掺量(Va)的混凝土早龄期(24 h)水化期间电阻率发展的特性.根据电阻率微分曲线上的特征峰值点将混凝土分为:溶解和结晶期、诱导和凝结期、硬化加速期、硬化减速期4个结构形成发展阶段.相同水灰比、不同骨料掺量的混凝土电阻率微分曲线上的前2个特征峰值点对应的时间几乎相等,骨料含量高(Va=70％)的混凝土的第3个特征峰值点对应的时间延长,这与其界面过渡区面积较大有关.不同水灰比、相同骨料掺量的混凝土的电阻率微分曲线表明,水灰比为0.4时混凝土的3个特征峰值点对应的时间都提前,这与低水灰比基体材料的结构密实速度较快有关.混凝土电阻率随时间对数的发展在硬化后表现出线性关系,混凝土电阻率时间对数曲线斜率越大,说明单位体积混凝土中的骨料量较多,或者净浆基体的水泥颗粒较多.     

微位移法在物料总质量检测中的应用

为解决某些化工过程中物料总质量测量困难的问题,基于支架系统的载荷与变形线性关系,提出了一种利用微位移来测量的新方法。分别采用有限元分析和试验标定法对支撑鼓泡塔的悬挂系统进行检测,结果表明微位移的测量方法准确、可行。     

Oxygen Potential Measurement of Americium Oxide by Electromotive Force Method

The oxygen potentials of AmO_{2− x} were measured in the x range of 0.01–0.5 and the temperature range of 1000–1333 K by the electromotive force method. The oxygen potentials at 1333 K were −19.83 kJ/mol for x =0.019 and −319.1 kJ/mol for x =0.485, which were higher than those of CeO_{2− x} by approximately 200 kJ/mol for the corresponding x values. From the dependence of the oxygen potentials on x and temperature, a tentative phase diagram of Am–O system was proposed, which suggested the presence of the intermediate phases of Am₇O₁₂ and Am₉O₁₆ in the Am–O system.     

Two-Angle Ratio Scattering (STAR) Method for Real-Time Measurement of Agglomerate Soot Concentration and Size: Theory

The Scattering by Two-Angle Ratio (STAR) light scattering method described in this article is based on a new analysis of a well-established theory in the literature that describes black carbon soot as fractal agglomerates. Previous analyses have shown that the measured scattering signals at two appropriate angles can be used to determine the mean agglomerate particle size and mass concentration. The current work shows that a dimensionless invariant function of the two-angle scattering ratio can be defined (C_m #), for computation of the mass concentration and mean agglomerate size. In addition, the three soot optical properties can be combined into one overall soot property constant, S_p , which, based on literature measurements of each component property, is also near invariant for a variety of fuel and combustor conditions. Research literature on optical parameters has been used (without resorting to arbitrary calibrations) to compute values of the gas phase soot mass concentration. In a companion article (Holve et al. 2011 Holve, D., Chapman, J. and Graze, R. 2011. Two-Angle Ratio Scattering (STAR) Method for Real-Time Measurement of Agglomerate Soot Concentration and Size: Experimental Measurements. Aerosol Sci. Technol., 45: 1400–1407. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]), measurements of diesel and gas turbine engines show that the model for interpreting scattering measurements from STAR is in reasonable agreement with gravimetric measurements.     

基于BP神经网络的流体流量补偿方法

针对流体质量流量测量中密度随温度及压力等参数的变化而变化,在BP算法的基础上,采用BP神经网络补偿方法对液氨的密度进行了补偿,给出了网络训练后误差渐进过程的仿真图和补偿后的仿真结果图,通过函数调用网络训练后非采样点上的温度来得到对应的密度值。可以得到结论:基于BP神经网络的补偿方法弥补了最小二乘法在非线性补偿方面的缺陷,且误差比较小,是一种性能比较优越的补偿方法。     

Two-Angle Ratio Scattering (STAR) Method for Real-Time Measurement of Agglomerate Soot Concentration and Size: Experimental Measurements

The Scattering by Two-Angle Ratio (STAR) light scattering method described in this (and companion) article has been developed and tested on a range of gas turbine and diesel engines. Research literature on optical parameters has been used (without resorting to arbitrary calibrations) to predict values of the gas phase soot mass concentration, which are in good agreement with gravimetric measurements. More than 90 measurements for gas turbine and diesel engines are shown for both in situ and sampling configurations of STAR. Results are obtained for transient concentrations ranging from less than 1 μg/m³ to 100 mg/m³ at data rates up to 10 Hz. Absolute concentration comparisons with gravimetric measurements agree with an R ² correlation of 97% and have a precision of better than ±5%. These experimental results are consistent with the assumption that primary particle soot properties are nearly invariant for a wide range of engine operating conditions.     

定电位电解法测定固定污染源中二氧化硫的不确定度

根据《测量不确定度评定与表示》(JJF 1059-1999),提出适用于依据《固定污染源排气中二氧化硫的测定定电位电解法》(HJ/T57-2000)进行烟气中二氧化硫测定不确定度的评定方法。     

Determination of Mass Transport Mechanism of Rutile by Sinusoidal Profile Decay Method

Amplitude decay of sinusoidal surface profiles on the c surface of TiO₂ single crystals was measured in air over the range 1500 to 1700 K. The rate of decay was proportional to –2.75 powers of the sinusoidal wave length (4.3 to 17.6 μrn), indicating that volume diffusion is the dominant mass-transport mechanism. The effective volume diffusion coefficient, Deff , given agreed with tracer diffusion data for the Ti ion. Hence Deff was assumed to be equal to the self-diffusion coefficient of the Ti ion as oxygen ion transport along the surface was enhanced. No anisotropy was observed for transport on this surface.     

电阻率法测定硅酸盐水泥水化活化能

研究了温度对水泥水化时电阻率的影响情况,建立了用于估算电阻率极大值的双曲线方程,提出根据不同温度时的电阻率可以计算孔隙液相活化能(Eas)和水化反应的活化能(Ear).试验所用水泥浆体试样的水灰比分别为0.30、0.35、0.40、0.45和0.55,养护温度分别为15、20℃和30℃,测试时间均为72h.为消除温度对...     

聚氨酯绝缘材料体积电阻率测量的不确定度评定

对测试绝缘材料体积电阻率的硬件系统进行了简单介绍,探讨了固体绝缘材料体积电阻率测量的不确定度评定方法。基于测量原理,对测量系统中的主要不确定度因素进行了分析。以聚氨酯垫片为例考察每个因素带来的影响,得出测量结果的扩展不确定度,提出了减小测量不确定度的方法。     

基于红外测温的对流换热系数反识别算法研究

The heat transfer coefficient in a multidimensional heat conduction problem is obtained from the solution of the inverse heat conduction problem based on the thermographic temperature measurement. The modified one-dimensional correction method （MODCM）, along with the finite volume method, is employed for both two- and three-dimensional inverse problems. A series of numerical experiments are conducted in order to verify the effectiveness of the method. In addition, the effect of the temperature measurement error, the ending criterion of the iteration, etc. on the result of the inverse problem is investigated. It is proved that the method is a simple, stable and accurate one that can solve successfully the inverse heat conduction problem.     

Determination of Resistivity of Lossy Materials from Dielectric Measurements, Making Use of Interfacial Polarization

It is a well-known fact that the phenomenon of interfacial polarization complicates dielectric measurements at low frequencies. This effect leads to a pseudo-Debye relaxation process in a frequency or temperature spectrum of dielectric constant and loss, with the relaxation time determined by the physical dimensions of the barrier layer and by the resistivity of the bulk material. Use of this effect has been made to determine the resistivity of glass by purposely introducing a barrier of known dimensions, in the form of a thin sheet of mica. Values of resistivity and activation energy obtained by this method agree with values obtained by direct-current measurements.     

基于热重-质谱联用技术测定EVA的方法探究

乙酸乙烯酯-乙烯共聚物乳胶粉(EVA)应用广泛,其检测技术的发展至关重要。本研究利用热重-质谱联用技术(TG-MS),在质量维度上建立了一种对EVA进行定量分析的方法。通过热重-红外-气质联用仪探究了EVA的热解过程,结果表明EVA的热解可分为三个阶段,其中第二阶段脱乙酰化步骤产生大量的乙酸能被清晰识别,同时在此步骤中也有低分子量的(CH)_n碎片和丙酮产生。随着热解温度升高,分子量较大的苯环衍生物和(CH)_n碎片在高温下被检测到。这表明在脱乙酰过程中聚合物主链末端发生了断链反应,随着温度的升高,不饱和烯烃结构热解产生芳香挥发物。通过在线质谱监测等温脱乙酰化反应,确定酮类物质的生成并不会影响脱乙酰化反应的进行,因此使用乙酸对EVA进行定量分析是合理的。通过MS信号与乙酸质量关联,建立了EVA的定量分析方法,为分析样品中EVA的定量检测提供了一种新方案。     

柴油机油烟炱含量测定研究

利用热重分析法ffGA）和红外光谱法（IR）对12个柴油机油的烟炱含量进行了分析,结果表明：在烟炱含量为0．06～2．78％（TGA法）的范围内,精确度高的热重分析法与快速便捷的红外光谱法在烟炱含量测定上有良好的相关性,其线性相关系数R^2=0．9937,因此在油液监测领域可用快速的红外光谱法代替繁琐的热重法对烟炱负荷趋势进行监测。     

液相色谱-串联质谱联用法测定玩具材料中的双酚A

建立了采用高效液相色谱-质谱联用法(LC-MS-MS)测定玩具材料中总量双酚A的检测方法。样品经二氯甲烷萃取,通过旋转蒸发仪进行净化后,采用C18柱,以甲醇-水混合液为流动相,等比例洗脱分离,经串联四级杆质谱仪在负离子模式下以多反应监测模式进行检测。结果表明:该方法在0.01~10 mg/L范围内线性关系良好,线性方程的相关系数r2=0.9993。该方法的检出限为0.005 mg/kg;在20 mg/kg、50 mg/kg和80mg/kg三个添加浓度水平下,玩具材料中双酚A的平均回收率为76.8%~99.0%。相对标准偏差(n=6)均小于10.0%。该方法操作简便,灵敏度高,适用于玩具原材料、玩具及儿童产品部件中双酚A的总含量测定。     

推进剂火焰烟尘对CARS测温精确度的影响

采用透过率(激光透过率、可见光透过率)表征推进剂火焰烟尘的量,以理论计算温度作为CARS(Coherent Anti-Stokes Raman Spectrometry)测温的相对标准温度,并将测得的CARS温度与热电偶温度进行了对比。通过研究CARS温度和理论计算温度的差值与透过率的相关性得到烟尘对CARS测温的影响规律：CARS测温的偏差随着推进剂火焰中烟尘量的增加而增大;推进剂火焰烟尘对CARS测温精度的影响规律基本呈线性关系。     

钠钙玻璃熔体电阻率测量影响因素及边界条件研究

玻璃熔体电阻率是设计玻璃电熔窑或电助熔窑的关键参数之一,研究玻璃熔体电阻率测量的边界条件对获得精确电阻率值极其重要。本文基于欧姆定律,构建玻璃熔体电阻率测量装置,探讨了馈入电压、交流电频率、试样颗粒尺寸和填充率等因素对钠钙玻璃熔体在900~1 450 ℃电阻特性的影响。结果显示,当馈入电压为2~10 V,交流电频率为1 kHz,试样颗粒尺寸为830~1 700 μm,填充率为80%,降温速率为2 ℃/min时,电阻率测量结果的误差在各温度段都小于1。该研究可以为玻璃熔体电阻率测量提供参考,进而支撑玻璃电熔窑及电助熔窑电加热系统的设计,实现难熔及易挥发玻璃的熔化。