Challenges in preparing water-matrix reference materials for PAHs and pesticides: examples from SWIFT-WFD proficiency-testing schemes

In accordance with Article 8 of the European Union (EU) Water Framework Directive (WFD), EU Member States are required to establish monitoring programs for the quality of the surface water and the groundwater within each river-basin district. As such data are the basis for regulatory decisions and measures required to achieve WFD environmental objectives, appropriate analytical quality-assurance and quality-control tools have to be implemented by the monitoring laboratories. In this respect, reference materials (RMs) play a key role. Within the framework of the SWIFT-WFD project (Screening methods for Water data InFormation in support of the WFD), several approaches to the preparation of matrix RMs for the analysis of polycyclic aromatic hydrocarbons and pesticides in water have been used in wide-scale proficiency-testing (PT) schemes. We present the different strategies employed in preparing water-matrix RMs for organic analytes. By reviewing the results from the SWIFT-WFD PT schemes, we reflect on the applicability and the suitability of the different approaches.     

基于ARH的太阳能发电控制系统的设计与实现

设计了基于ARM LPC2131的驱动系统,自动跟踪太阳光直射方向来提高光伏电池的效率,并采用了改进的步进式扰动观察算法来寻找太阳电池阵列的最大功率点,使系统在任何温度和日照条件下都能获得太阳电池的最大功率.实践证明,该系统精确地跟踪了各种情况下的太阳光变化,并将光伏电池的实际转换率提高到30%以上.     

QC活动增强企业核心竞争力

本文介绍富士通持续开展QC活动的实践,说明企业核心竞争力的源泉来自于品质改善.     

经营分析系统数据质量保障体系综述

经营分析系统数据质量的高低决定了企业精确管理和科学决策的精度。从经营分析系统的数据质量存在问题的原因入手,提出了数据质量评价的五大指标,论述了相关管理制度和流程的保障体系,提出了收敛数据源、元数据管理、编码管理、审核校验、数据交互QC机制等技术保障方法。     

用Gaussian 98程序计算钪和钛原子价层电子组态能量

用Gaussian98程序计算了钪和钛原子的价电子组态能量。计算表明,Hartree-Fock(HF)迭代应采用可靠性较高的QC标准方法,所得的波函数要进行稳定性分析,根据布居分析调整电子的初始占据轨道,以便最终得到所需要的原子组态,在全组态相互作用CASSCF计算中,需要用关键词GUESS=ALTER选择适当的活动组态空间,计算结果说明,随着计算从基态转向激发态,从原子序数小的钪转向原子序数大的钛,需要考虑的因素明显加多,根据HF,QCISD（T）和PM4SDTQ计算得到Sc:3d^254s(^4F)与Sc:3d4s^2(^2D)的能量差分别是96.80,152.92和149.10KJ/mol,与实验值138.75KJ/mol相一致,根据HF,QCISD（T）和CASSCF（4,5）计算得到Ti:3d^34s(^5F)和Ti:3d^24s^2(^3F)的能量差分别为57.85,91.74和82.06KJ/mol,与实验值80.88KJ/mol相一致。     

APON系统保护倒换策略的探讨

由于用户对宽带业务的需求逐步增长,传统的模拟接入网正在向数字化的高速宽带网络过渡,其中基于ＡＴＭ的无源光网络（ＡＰＯＮ）又是接入网研究中的热点。本文先介绍ＡＰＯＮ的基本概念和特点,然后在此基础上对ＡＰＯＮ系统应采取的保护倒换方式进行分析,并给出了几种保护倒换结构的配置形式。     

A Note on the Maximal Functions on Weighted Harmonic AN Groups

In this paper, the authors point out that the methods used by Li (2004, 2005, 2007) can be applied to study maximal functions on weighted harmonic AN groups.     

1-(Bromoacetyl)pyrene,a novel photoinitiator for the copolymerization of styrene and acrylonitrile

A comparative study on photoinitiated solution copolymerization of Styrene (Sty), with acrylonitrile (AN) using pyrene, 1-acetylpyrene, and 1-(bromoacetyl)pyrene (BrPy) as initiators, showed that the introduction of a chromophoric moiety, bromoacetyl (–COCH₂Br), significantly increased the photoinitiating ability of pyrene. The kinetics and mechanism of copolymerization of Sty with AN (Sty–co–AN) using BrPy as photoinitiator has been studied in detail. The kinetic data, inhibiting effect of benzoquinone, and electron spin resonance (ESR) studies suggest that the polymerization proceeds via a free radical mechanism. The system followed non-ideal kinetics (R _p α[BrPy]^0.7[Sty]^1.09[AN]^1.01) and degradative solvent transfer reasonably explained these kinetic non-idealities. The co-monomer reactivity ratios calculated by using the Finemann–Ross and Kelen–Tudos models were r ₁ (Sty) = 0.39 and r ₂ (AN) = 0.05. The reactivity ratios strongly indicate that the two monomers enter in almost alternating arrangement along the copolymer chain.     

A New Type of High Pressure System for a Tian-Calvet Calorimeter

A Tian-Calvet heat flux calorimeter has been modified for use with high pressures in measurements of thermal hazards of materials. The system comprising a specially designed high pressure vessel and an associated manifold is described. With this system, comparative measurements using both standard and high pressure vessels can be made, different materials and/or liners can be used for the high pressure vessel and an assessment of the influence of the gaseous environment on thermal behaviour can be made. Calibration was carried out in the range 25 to 300°C at different pressures and heating rates, using sapphire and the calibration results were verified with benzoic acid, both reference grade materials. With the new vessel, pressures up to about 70 MPa can be used or recorded during the thermal decomposition of energetic materials. The reproducibility of the baseline, as illustrated by standard error results, was about 0.02% compared with 0.13% for the standard vessel, over the entire temperature range. The corresponding results for the baseline of the pressure vessel at 5.5 MPa (in air and Ar) and in a calibration experiment with sapphire were 0.08%. Experimental data obtained for ammonium nitrate and 2,3-dimethyl-2,3-dinitrobutane in the standard and pressure vessels are compared and discussed. The effect of pressure and the nature of the gaseous environment (inert or oxidizing) on the results for these two materials will be described. This revised version was published online in July 2006 with corrections to the Cover Date.     

An advanced solventless column test for capillary GC columns

Manufacturing skills for capillary GC columns have improved to a point where the commonly used tests no longer distinguish between "adequate" and "excellent" columns. A more stringent test mixture, coupled with a more exacting procedure, was proposed for testing capillary columns in 2004. The solutes were less sterically hindered and less retained, permitting the test to be run isothermally at lower temperatures where sorptive forces are stronger. To avoid masking active sites by solvent flooding, the test used a higher boiling solvent that eluted last. This test mixture, used under the prescribed conditions, differentiated adequate from excellent columns, but removal of the late-eluting solvent prolonged run times to as long as 1 h. The new test uses the same probes proposed in 2004, but entirely eliminates the solvent. Injections utilize a plunger-in-needle microvolume syringe, and the "gas saver" feature of a contemporary gas chromatograph. The latter serves as a dynamic diluter to deliver nanogram quantities of undiluted solutes to the column. The test can be conducted isothermally at a lower temperature in less than 15 min for most of the columns. This paper summarizes the analytical approach used, and presents method performance data and test results obtained on contemporary capillary columns from leading manufacturers.