环境气体标准样品综述

本文介绍了环境气体标准样品的现状、制备和检测方法,同时简要介绍了环境气体标准样品在环境气态污染物监测分析和管理工作的应用,以及在使用气体标准样品过程中应注意的几点问题。     

Diffusion-controlled reference material for volatile organic compound emissions testing: Pilot inter-laboratory study

To improve the reliability and accuracy of tests used to measure emissions of volatile organic compounds (VOCs) from samples of interior building products, the National Institute of Standards and Technology (NIST) and Virginia Tech (VT) have created a program to develop reference materials with independently predictable emission rates. A diffusive reference material and associated mechanistic model have been developed and are undergoing extensive evaluation. As part of this process, a pilot inter-laboratory study (ILS) was conducted with four laboratories using a polymer material loaded with toluene as the reference source. Results showed the prototype material to be a relatively stable, homogeneous source with consistent emissions both within and between production batches. A comparison of toluene emission rates determined by the laboratories showed relative standard deviations as low as 9%, which are significantly lower than inter-laboratory variations for most previous ILS exercises with VOC sources. At a sample time of 48 h, the mean measured toluene emission rate for all four laboratories was within 1% of the model predicted value. The success of this pilot ILS is a key step toward being able to provide a VOC reference material for independent validation of VOC emission tests conducted in small chambers.     

A 1 V CMOS programmable accurate charge pump with wide output voltage range

A 1 V, programmable, accurate, high speed, single-ended charge pump is proposed, suitable for low voltage PLLs. It is designed in TSMC 90-nm digital CMOS process and it consists of four switches in a current steering configuration, a unity gain rail to rail buffer for the charge sharing effect elimination, one more rail to rail amplifier for minimizing the DC current mismatch, a programmable current bias circuitry and two drivers based on the standard cell XOR gates specific configuration for achieving good synchronization between all charge pump input pulses at the PLL lock state. Replica biasing technique is applied to all charge pump switches. Current glitches and charge mismatch are suppressed by employing a mechanism with additional switches at the output. It exhibits a maximum DC current mismatch of 1% and charge mismatch of 6% over a wide output voltage range of 0.7 V for the entire range of output currents. The wide range of the output voltage remains relatively constant and independent of the selected charge pump current amplitude. This is attained by applying appropriate variation of the W/L ratios of the bias cascode current sources via the employment of additional programmable switches such that their saturation voltages remain relatively constant, something which in turn enables the output currents range to be as wide as it is required.     

三电平STATCOM不平衡条件下指令电流检测方法研究

本文针对三电平STATCOM在三相电网电压不平衡情况下,为了能够准确快速检测出负载电流的基波无功、负序以及谐波分量,提出了一种基于微分环节的改进指令电流检测方法,并对该检测方法在电网电压不平衡条件下的检测效果进行了仿真分析。     

《福建省建筑结构风压规程》编制介绍

本文对《福建省建筑结构风压规程》的主要内容、背景资料和编制过程中考虑的因素作出全面介绍,为该规程的推广使用提供参考资料。     

架空输电线路基本风速的确定方法探讨

本文根据《110～750 kV架空输电线路设计规范》和《建筑结构荷载规范》的要求,提出了架空输电线路基本风速的确定方法,其结果大于设计手册公式和一般软件的计算结果,值得有关人员借鉴与参考.     

Development of a Ag/Ag micro-reference electrode for electrochemical measurements in ionic liquids

We report on a novel miniaturized Ag/Ag⁺ reference electrode (RE) design suitable for electrochemical measurements in room temperature ionic liquids (RTILs). The electrode is based on capillaries with an outer diameter of 365 μm and contains a 10 mmol/l solution of a silver salt in a RTIL. The silver salt bears the same type of anion as the RTIL. While potential shifts of several hundred millivolts have been observed for common platinum or silver pseudo-reference electrodes, our Ag/Ag⁺ micro electrode provides a stable and reliable reference potential over a period of more than two weeks, if protected from light and stored in a nitrogen atmosphere. Due to the small dimensions of the RE, it can be placed close to the working electrode (WE) and it is well-suited for application in electrochemical micro cells as well as for potential-controlled in situ AFM, STM or electrochemical impedance measurements. The electrode characteristics were determined by voltammetric measurements on ferrocene and cobaltocenium hexafluorophosphate dissolved in a RTIL. The highest expected contamination of the sample with Ag⁺ ions was calculated and found to be below 4 ppm.     

短距双站在远距基准点上观测目标的定位精度

在基于时差一方位测量的短距双基站的数百公里之外,选定一个地图基准位置,并以此地图基准位置作为计算分析远距目标位置的几何坐标起始点。先由双站间的时差方程和几何关系解得目标相对于双站的测距式,然后,利用双站测距式以及双站与远距地图基准点之间的几何关系解得目标相对于地图基准点的径向距离和方位。虽然测向误差很大,但误差分析表明只要双站与地图基准点之间的距离足够远,就能在双站距离小于10km的情况下,使目标与地图基准点之间的测距误差满足小于5％R的精度要求。     

基于人类视觉系统的立体图像质量评价方法

随着立体图像的大规模发展,很多应用场合需要能够迅速有效地完成对立体图像的质量评价工作,以便于后续应用,而对其进行主观质量评价在效率上很难满足要求。因此,提出了一种感知质量评价算法,并结合了一些人类视觉系统的特性。首先需要得到视差图,然后通过边界图和显著图来对视差图进行加权调整。接着使用Minkowski融合方法将加权后的视差图整合成感知分数。最后,使用多尺度分析来得到最终的感知质量分数。通过使用EPFL立体质量评价数据库来验证文中的立体图像感知质量评价算法。实验显示算法最后得到的客观分数和EPFL数据库中的主观分数具有高度的一致性和单调性,证明了文中的立体图像感知质量评价算法是有效的。     

Particle size measurement of reference particle candidates and uncertainty region of count and mass based cumulative distribution

In order to confirm reliable particle size measurement technique and to prepare standard reference particles for calibrating particle size measurement devices, uncertainty region of count and mass based size distribution have been theoretically examined. The uncertainty region of count base cumulative size distribution is smaller than that of the mass base cumulative distribution.The uncertainty region of count base cumulative size distribution is nearly constant over wide range of particle diameter and the region is nearly constant for sample size greater than about 20,000.On the other hand, the uncertainty region of mass base cumulative distribution increases with the increase of particle diameter.The reliability of theoretical uncertainty region is confirmed by the experimental data of particle size measurement.