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针对气压大于133Pa的气体放电时等离子体鞘层及粒子碰撞对微波共振探针密度测量的影响变大的问题,对微波共振探针模型进行了改进,推导了鞘层修正因子和碰撞修正因子,探讨了微波共振探针尺寸对测量等离子体密度的影响。结果表明,针丝半径选择0.2mm,并且选用较大宽度的探针有利于减小测量误差。     

Fermions Tunneling and Entropy Correction of Black Hole in Gravity’s Rainbow Space Time

Based on the fermions tunneling method, correction to Bekenstein-Hawking entropy of black hole in gravity’s rainbow space time is discussed. We consider not only the quantum corrections in the single particle action revealing that these are proportional to the usual semiclassical contribution but also the quantum effects of space time arising from the change of energy of probe particles moving in it. The result shows that as the high order terms with respect to ℏ of the action is considered, the first and second corrections, namely the logarithmic term and the inverse area term respectively, are produced. This result is consistent with that of loop quantum gravity and other entropy correction theories.     

发光二极管光谱测量中的杂散光与带宽校正

光谱仪的杂散光和带宽是LED光谱测量中比较重要的两个误差影响因素,为了得到更精确的测量结果,必须对杂散光和带宽影响进行校正.用He-Ne激光测出光谱仪的线扩展函数,在假设光谱仪是线性波长不变系统的前提下,构建杂散光分布函数矩阵,转化为杂散光校正矩阵,从而对所测信号进行杂散光校正;在三个波段内分别由光谱仪带宽函数计算带宽校正系数,将被测波长点及其邻近带宽波长点上的测量结果进行加权平均,从而得到带宽校正结果.将两种校正方法应用在一台多通道快速光谱仪上,测量各种颜色的LED,实验结果表明能有效地校正杂散光和带宽影响,色品坐标最大校正了(-0.003,0.007).且该方法降低了应用成本,在保证精度的情况下简化了计算量,使得校正更易于实施.     

Optimized partial semicoarsening multigrid algorithm for heat diffusion problems and anisotropic grids

The purpose of this work is to reduce the CPU time necessary to solve three two-dimensional linear diffusive problems governed by Laplace and Poisson equations, discretized with anisotropic grids. The Finite Difference Method is used to discretizate the differential equations with central differencing scheme. The systems of equations are solved with the lexicographic and red–black Gauss–Seidel methods associated to the geometric multigrid with correction scheme and V-cycle. The anisotropic grids considered have aspect ratios varying from 1/1024 up to 16,384. Four algorithms are compared: full coarsening, semicoarsening, full coarsening followed by semicoarsening and partial semicoarsening. Three new restriction schemes for anisotropic grids are proposed: geometric half weighting, geometric full weighting and partial weighting. Comparisons are made among these three new schemes and some restriction schemes presented in literature: injection, half weighting and full weighting. The prolongation process used is the bilinear interpolation. It is also investigated the effects on the CPU time caused by: the number of inner iterations of the smoother, the number of grids and the number of grid elements. It was verified that the partial semicoarsening algorithm is the fastest. This work also provides the optimum values of the multigrid components for this algorithm.     

Decent flow methods for inverse Sturm–Liouville problem

In this paper, we propose three numerical methods for the inverse Sturm–Liouville operator in impedance form. We use a finite difference method to discretize the Sturm–Liouville operator and expand the impedance function with some basis functions. The correction technique is discussed. By solving an un-weighted least squares problem, we find an approximation to the impedance function. Numerical experiments are presented to show the accuracy and stability of the numerical methods.     

Effect of insignificant bias and its uncertainty on the coverage probability of uncertainty intervals Part 1. Evaluation for a given value of the true bias

This paper investigates the coverage probability of the uncertainty intervals determined in compliance with the GUM and EURACHEM Guide, which are defined by expanded uncertainty U about the results uncorrected with the insignificant biases and corrected with the significant biases. This coverage probability can significantly fall below the chosen level of confidence in some cases as Maroto et al. discovered by using the Monte Carlo method. Their numerical results obtained provided that only the β errors have occurred in the test significance and findings that the coverage reduction depends on the mutual proportions of the magnitudes of the systematic error, overall uncertainty and bias uncertainty are confirmed in this paper by using probability calculus and numerical integration. This problem is also studied when all possible experimental biases, both significant and insignificant, are considered. From this point of view, the reduction of the coverage probability turns out to be less severe than from the previous one. The coverage probability is also investigated for some uncertainty intervals computed in different ways than the above mentioned documents recommend. The intervals defined by U about the results corrected with both significant and insignificant bias give always the same coverage probability equalling the chosen level of confidence. The intervals with some uncertainties modified or enlarged with the insignificant biases remove or moderate the coverage reduction.     

Arsenic and its speciation in water samples by high performance liquid chromatography inductively coupled plasma mass spectrometry--last decade review

Arsenic composes a danger for human health all over the world as it is responsible for water resources contamination. The toxicity of arsenic depends on its chemical form. However, occurrence of particular arsenic species is dependent on processes occurring in water. Nowadays, more arsenic species is detected and analyzed in different kind of water (mineral, tap, waste), mainly owing to great possibilities resulting from coupling high performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). This review mainly describes arsenic speciation analysis by HPLC-ICP-MS technique on the basis of articles that have been published since 2000. Arsenic chemistry, occurrence in different kind of water, total arsenic determination with interferences elimination and its validation and analytical performance are also reviewed.     

Photooxidation of PVC

Pure and peroxided PVC films were irradiated under monochromatic ultraviolet light between 300 and 400 nm. The degradation state of PVC is measured by means of carbonyl absorption in the infrared spectra and polyene content by UV spectroscopy. The initial rate of carbonyl formation depends on the wavelengths and oxidized impurities content. Peroxided PVC is oxidized faster than pure PVC with wavelengths above 320 nm. Two hazardous ranges of wavelengths have been detected: 300–320 and 350–370 nm. Good protection of PVC against UV radiation can be assured by the exclusion of wavelengths under 380 nm.     

石墨炉原子吸收光谱法测定土壤和底泥中的铅、镉

利用自吸效应背景校正，以磷酸氢二铵为基体改进剂，石墨炉原子吸收法测定土壤和底泥中的铅、镉。铅和镉的相对标准偏差(n=11)分别为4．2％和3．5％，加标回收率分别为94％-106％和92％-105％。     

Evaluation of matrix effect in isotope dilution mass spectrometry based on quantitative analysis of chloramphenicol residues in milk powder

In the present study, we developed a comprehensive strategy to evaluate matrix effect (ME) and its impact on the results of isotope dilution mass spectrometry (IDMS) in analysis of chloramphenicol (CAP) residues in milk powder. Stable isotope-labeled internal standards do not always compensate ME, which brings the variation of the ratio (the peak area of analyte/the peak area of isotope). In our investigation, impact factors of this variation were studied in the extraction solution of milk powder using three mass spectrometers coupled with different ion source designs, and deuterium-labeled chloramphenicol (D5-CAP) was used as the internal standard. ME from mobile phases, sample solvents, pre-treatment methods, sample origins and instruments was evaluated, and its impact on the results of IDMS was assessed using the IDMS correction factor (θ). Our data showed that the impact of ME of mobile phase on the correction factor was significantly greater than that of sample solvent. Significant ion suppression and enhancement effects were observed in different pre-treated sample solutions. The IDMS correction factor in liquid–liquid extraction (LLE) and molecular imprinted polymer (MIP) extract with different instruments was greater or less 1.0, and the IDMS correction factor in hydrophilic lipophilic balance (HLB) and mix-mode cation exchange (MCX) extract with different instruments was all close to 1.0. To the instrument coupled with different ion source design, the impact of ME on IDMS quantitative results was significantly different, exhibiting a large deviation of 11.5%. Taken together, appropriate chromatographic conditions, pre-treatment methods and instruments were crucial to overcome ME and obtain reliable results, when IDMS methods were used in the quantitative analysis of trace target in complex sample matrix.