A new rule of vibration sampling for predicting acoustical radiation from rectangular plates

Structural surface velocity distribution is often used to predict structural borne sound radiation. However the sampling interval of velocity should be chosen carefully to increase the prediction accuracy and to reduce the system cost. In this paper, several factors affecting the sampling interval are theoretically analyzed and discussed for a vibrating baffled rectangular plate. A new rule for the determination of the sampling interval is formulated. Using this rule, the results from both numerical simulations and experiments may be explained well.     

Atomic distributions in acetylene-air flame using hydraulic high-pressure nebulization with direct (100%) introduction of solutions Applications to speciation analysis

One of the fundamental factors of the performance of atomic spectrometric methods is the efficiency of sample introduction into flame or plasma. By utilization of the formerly developed hydraulic high-pressure nebulizer, a nebulizer/burner system with solution uptake efficiency of 100% have been worked out. Optimizing operation parameters of nebulizer/burner system, an improvement of 2-12 times was achieved for the signal-to-noise ratio in the flame emission and flame atomic absorption spectrometry, depending on sample flow rate. This nebulizer is especially suitable for development of liquid chromatography-AAS/FES coupled technique for speciation analytical tasks.     

A highly selective solid phase extraction sorbent for pre-concentration of sameridine made by molecular imprinting

Summary A novel approach to solid phase extraction, based on the use of a highly selective molecularly imprinted polymer, is presented. The versatility of this type of sorbent for solid phase extraction was demonstrated in a model batch-wise pre-concentration of sameridine prior to gas chromatography. Problems associated with leakage of remaining imprint molecules during the desorption phase could be eliminated by the use of a close structural analogue of sameridine as the imprint species. It was found that a major benefit of the imprinted polymer was its specificity, which lead to distinctly cleaner chromatographic traces and ability to improve sensitivity by extracting sameridine from larger sample volumes.     

Membrane introduction mass spectrometry

An overview of membrane introduction mass spectrometry (MIMS) is presented and comparisons are made with other direct sample introduction techniques. Special attention is given to the unique advantages and the limitations of newer variants on the MIMS technique, including affinity MIMS, reverse-phase and trap MIMS. The salient features of the interfaces used in MIMS are summarized and the various membrane materials commonly used are delineated. The applicability of MIMS is illustrated via discussion of

1. (i) bioreactor monitoring (represented by yeast fermentation),

2. (ii) environmental monitoring (illustrated by analysis of contaminated ground water samples) and

3. (iii) on-line chemical reaction monitoring (exemplified by the photolysis of aryl esters).

The applicability of MIMS to the analysis of environmental samples, including complex mixtures in water, air and soil, is noted.     

甚高频等离子体增强化学气相沉积法沉积μc-Si∶H薄膜中氧污染的初步研究

对不同的本底真空条件下,采用甚高频等离子体增强化学气相沉积技术沉积的氢化微晶硅（μc_Si∶H）薄膜中的氧污染问题进行了比较研究.对不同氧污染条件下制备的薄膜样品的x射线光电子能谱与傅里叶变换红外吸收光谱测量结果表明：μc_Si∶H薄膜中,氧以Si—O，O—O和O—H三种不同的键合模式存在,不同的键合模式源自不同的物理机理.μc_Si∶H薄膜的Raman光谱、电导率与激活能的测量结果进一步显示：沉积过程中氧污染程度的不同,对μc_Si∶H薄膜的结构特性与电学特性产生显著影响；而不同氧污染对μc_Si∶H薄膜电学特性的影响不同于氢化非晶硅（a_Si:H）薄膜. 关键词： 氢化微晶硅薄膜 甚高频等离子体增强化学气相沉积 氧污染     

New methodologies in trace analysis of volatile organic compounds

Two methods for sampling and concentration of volatile organic compounds are reported. In the first method, traps coated with a very thick film (ca. 100 μm) of cross-linked silicone stationary phase are employed. Such thick films can be prepared with a modified dynamic coating procedure, which is briefly described. The low phase ratio traps can be utilized for enrichment of volatiles from gaseous as well as aqueous matrices. The second technique is based on chromatographic evaporation of a solvent in a capillary tube, where the process is sustained by a repeated sample injection and a cyclic flow reversal. In this way, large solvent volumes can be handled by a small volume system. Under optimal conditions, when using a solvent barrier, quantitative recovery is possible even for compounds of comparatively high volatility. Another important application of the technique is extraction of trace components from gases such as headspace samples, polluted air, etc.     

Imaging of wood tissue by ToF-SIMS: Critical evaluation and development of sample preparation techniques

Tissue of Norway spruce wood was investigated by time-of-flight secondary-ion mass spectrometry (ToF-SIMS) and field-emission scanning electron microscopy (FE-SEM). Different sample preparation techniques (including sectioning and drying) traditionally used for SEM analysis were compared and critically evaluated. A high contamination of wood surfaces by polytetrafluoroethylene (PTFE) introduced onto the sample during sectioning was detected by ToF-SIMS. A new protocol was developed and images of wood sections dried in different ways were compared. Main location of Mg, Na, K and Ca, but no lignin in membranes of bordered pits in spruce section surfaces was detected by ToF-SIMS imaging if critical point drying (CPD) or acetone extraction followed by drying under nitrogen flow (AEND) was applied. No specific locations of wood components as well as low signals from metal ions (Mg and Na) were observed on the wood surfaces of freeze-dried (FD) or air-dried (AD) sections. It was found that extractive substances, presenting on surfaces of FD and AD wood section, were evenly distributed on the surfaces and interfered with ToF-SIMS analysis. Our results indicated that ToF-SIMS imaging was critically sensitive to the sample preparation technique and a strict protocol for characterization of metals, lignin and polysaccharides in wood was suggested.     

电热蒸发进样微波等离子体炬原子发射光谱法中共存元素的影响

本文考察了以微波等离子体炬（MPT）为光源，电热钽丝环进样时，溶液中共存元素对发射信号的影响。     

傅里叶变换红外光谱固体制样技术

通过对溴化钾与纳米固体超强酸样品的比例进行了探讨 ,得出制样时溴化钾与样品比例范围为1∶ 0 .0 0 1— 1∶ 0 .0 2 9,其最佳比例范围为 1∶ 0 .0 0 98— 1∶ 0 .0 1 5 ,并且应用于其他固体样品的测定 ,结果基本一致。同时得出 ,固体样品的最少检测量为 2 .0× 1 0 -5g     

Hair dye distribution in human hair by ToF-SIMS

A single hair sample preparation protocol modified from reported method was developed and used to prepare longitudinally sectioned hair for ToF-SIMS analysis. Preliminary results demonstrate that ToF-SIMS is capable of providing molecular distribution of fragment ions from intrinsic constituents as well as external chemicals like the hair dye ingredients used in this study. The observation of pPDA and H₂PO₄⁻ penetrating into the internal region of hair might initiate a renewed interest in exposure study.