烟道流量计量标准装置

为了解决我国烟道流量计的量值溯源问题,中国计量科学研究院建立了烟道流量计量标准装置。装置使用可溯源至标准转盘的激光多普勒测速仪作为原级标准器,采用激光多普勒流速剖面扫描和超声流量计波动修正的方式测量标准流量,经校准的8声道超声流量计为工作级标准表,具备了908~104840m3/h的测量能力,扩展不确定度为0.62%(k=2),可对最大口径为1m的流量计进行校准。装置下游测试段包括圆形管段和矩形管段,能够开展烟道流量计测量性能的研究。     

Virtual Testing Stand for evaluation of car cabin indoor environment

In the paper the authors refer to a new computational tool for the transient prediction of the car cabin environment and heat load during real operating conditions. The aim of the Virtual Testing Stand software is to support an early stage of the HVAC design process to predict demands for the heating and cooling for various operational conditions and types of car. This software was developed in Matlab as a standalone executable application including a parametric generator of car cabin geometry, a heat transfer model and a graphical user interface. The mathematical model is formed by the set of heat balance equations, which takes into account the heat accumulation, and the heat exchange between the car cabin, the outside environment, the HVAC system and the passengers. In this paper the main features of Matlab application are presented together with a selected sensitivity study of two significant parameters in a winter test case.     

High-temperature dilute-acid hydrolysis of olive stones for furfural production

We studied the production of furfural by acid hydrolysis of olive stones, which in Spain are an abundant lignocellulosic residue derived from the production of olive oil. We focused on the hydrolysis in dilute sulfuric acid (0.05 to $\text{0.250}\text{mol}\text{l}{}^{\mathrm{-1}}$), at high temperature (220–240°C), and short reaction times, of a few minutes at the most. The experimental study was performed in a tubing-bomb reactor system that approximately reproduces the temperature profiles obtained in a continuous tubular reactor. We obtained maximum furfural yields ranging from 50% to 65% of the potential depending on acid concentration and temperature.     

基于同轴线相位法的两相流含气率测量研究

为了准确测量气液两相流含气率,提出一种同轴线相位差测量方法。利用同轴线传感器,通过测量电磁波经过在同轴线内分布状况不同的气液混合介质后相位差的变化,得到混合介质的含气率。完成了同轴线测量电路及测量传感器的设计,建立了一种含气率测量模型。以气液两相做了室内静态实验,并对垂直管状态下传感器响应和实验结果进行了误差分析。结果表明:相位差输出与含气率呈线性关系;同时,在不同频率下,预测结果和实验结果的相对误差在±5%范围内,说明预测模型准确度较好。     

Preparation and electromagnetic-wave-absorption properties of a nitrogen-doped carbon–supported iron(II,III) oxide composite

Journal of Materials Science: Materials in Electronics - A single material with dielectric or magnetic loss behavior cannot optimally absorb electromagnetic waves because such waves are composed of...     

移液器容量自动校准系统研究

针对移液器人工校准中存在的按压不稳、温度偏差、数据无法批量处理等缺陷,提出了一种基于模拟人工按压的移液器容量自动校准方法。通过测量移液器按钮2个停止点的压力值,获取近似按压的距离;分析数据并与人工操作进行比对,得出模拟手动按压的最佳按压距离。开发了一套同时校准4支移液器容量的自动化装置,采用机械手和LabVIEW软件智能控制取液、排液、称量、数据处理等工作,实现了自动校准。研究结果表明,与人工操作相比,重复性减小了0.0%~0.9%,相对误差减小了0.1%~0.7%。     

Third-order nonlinear optical properties of new polyfluoroalkylsulfanyl-substituted tetrathiafulvalene derivatives

We investigate the third-order nonlinearities of new polyfluoroalkylsulfanyl-substituted tetrathiafulvalene derivatives using the degenerate four wave mixing method (DFWM). For each compound, the study of the influence of the concentration on DFWM efficiency leads to the choice of an optimum solution for which DFWM efficiency R attains its maximum. From the measurements of R versus the pump intensity, we deduce the values of third-order susceptibilities χ^〈3〉 and the corresponding second-order hyperpolarizabilities γ. The largest γ obtained is 10³ larger than the γ value of CS².     

Installation effects on an ultrasonic flow meter with implications for self diagnostics

A small ultrasonic flow meter for water was exposed to five different test configurations, a reference experiment, a single elbow, a double elbow out of plane, a reduction in pipe diameter and a pulsating flow experiment. All tests were performed in a flow calibration facility ranging over Reynolds number from 25 to 110 000. The experiments with the four installation effects were compared with a reference experiment. The error and the change in standard deviation compared to the reference experiment were calculated. The standard deviation serve as a measure of the noise level of the flow meter. The results show that all disturbances generated errors in the flow measurement. The maximum errors were mainly in the range of 2–4% of flow rate, but at very low flow rates the pulsating flow caused larger errors. In most of the flow range there were no or smaller errors. All installation effects also generated an increase in the noise level. The different pipe configurations increased the standard deviation up to more than 100%. The pulsating flow induced even higher enlargements in the noise level. The errors and the increase in the standard deviation are present in about the same flow ranges. The results demonstrate not only that the installation effects tested introduce errors in the flow measurements but also that these effects can be detected from the noise level in the data. The noise level was determined from the standard deviation. This could be interpreted as that the disturbances amplify the turbulence intensity. Thus the standard deviation can be used as a measure of the turbulence. The presence of a disturbance could be recognised by comparing the magnitude of the noise level in the present data with a reference level valid for the measured flow rate. A procedure like this could possibly be performed by the meter itself in operation.     

The LiyNi0.2Mn0.2Co0.6O2 electrode materials: A structural and magnetic study

Layered LiNi_0.2Mn_0.2Co_0.6O₂ phase, belonging to a solid solution between LiNi_1/2Mn_1/2O₂ and LiCoO₂ most commercialized cathodes, was prepared via the combustion method at 900 °C for a short time (1 h). Structural and magnetic properties of this material during chemical extraction were investigated. The powders adopted the α-NaFeO₂ structure with almost none of the well-known Li/Ni cation disorder. The analysis of the magnetic properties in the paramagnetic domain agrees with the combination of Ni²⁺ (S = 1), Co³⁺ (S = 0) and Mn⁴⁺ (S = 3/2) spin-only values. X-ray analysis of the chemically delithiated Li_yNi_0.2Mn_0.2Co_0.6O₂ reveals no structural transition. The process of lithium extraction from and insertion into LiNi_0.2Mn_0.2Co_0.6O₂ was discussed on the basis of ex situ EPR experiments and magnetic susceptibility. Oxidation of Ni²⁺ (S = 1) to Ni³⁺ (S = 1/2) and to Ni⁴⁺ (S = 0) was observed upon lithium removal.     

Improved numerical integration method for flowrate of ultrasonic flowmeter based on Gauss quadrature for non-ideal flow fields

Multipath ultrasonic flowmeters with large diameter are widely used in industry. And their measurement performances are sensitive to velocity profiles in conduits. Gauss–Jacobi and Optimized Weighted Integration for Circular Sections (OWICS) method are commonly applied in flow measurement of multipath ultrasonic flowmeters, both of which assume ideal flow in pipes. They are not proper for non-ideal flow measurement. Therefore, an improved numerical integration method for flowrate based on Gauss quadrature is proposed. With this method, optimum relative path heights and corresponding weights are determined according to specific disturbed flows. By comparison Gauss–Jacobi, OWICS with the improved method, the validity of the proposed method is verified for typical disturbed flows based on both theoretical analysis and experiments, and measurement performances of ultrasonic flowmeters are improved significantly.