基于errors-in-variables的预测模型及其应用

预测是统计学实际应用的一个主要方面,多元线性回归预测是一种很好的方法,广泛地应用在各种实际领域,但其局限性及不足也是明显的。本文以一种新的观点认识数据,即认为变量的观测里均含有误差,同时认为不应删除经慎重选择进来的解释变量。为此,本文提出了一种新的多元预测方法———多元线性EIV预测。本文还考虑了新预测模型的一个实例应用,并从相对偏差上与多元回归预测进行了比较,从而揭示了多元线性EIV预测的先进性及较好的预测精度。     

标准化风险度量与投资决策的双目标优化

标准化风险度量(SRM)作为投资中的一种新的风险度量，其较传统风险度量的优点及在投资项目比较中特有的优良性质已被证明，本文导出SRM在概率意义下的一种重要的等价形式，并以此为基础建立以标准化风险(SR)为目标或约束的投资决策优化方法，该方法的核心是将以SRM为风险度量的优化问题转化为线性规划问题的优化技术，此技术结合利用统计抽样数据，可优化含有大量金融工具的投资组合，本文在考虑交易成本的情形下建立了最小化投资的标准化风险的同时最大化其期望有效回报(EER)的双目标优化模型，最后，具体考虑了上证30指数股票组合的优化以说明所建议的方法及模型的应用并实证它们的可行、合理及优良性，其中统计抽样基于近期历史数据。     

Alternative CHCA-based matrices for the analysis of low molecular weight compounds by UV-MALDI-tandem mass spectrometry

Analysis of low molecular weight compounds (LMWC) in complex matrices by vacuum matrix-assisted laser desorption/ionization (MALDI) often suffers from matrix interferences, which can severely degrade limits of quantitation. It is, therefore, useful to have available a range of suitable matrices, which exhibit complementary regions of interference. Two newly synthesized α-cyanocinnamic acid derivatives are reported here; (E)-2-cyano-3-(naphthalen-2-yl)acrylic acid (NpCCA) and (2E)-3-(anthracen-9-yl)-2-cyanoprop-2enoic acid (AnCCA). Along with the commonly used α-cyano-4-hydroxycinnamic acid (CHCA), and the recently developed 4-chloro-α-cyanocinnamic acid (Cl-CCA) matrices, these constitute a chemically similar series of matrices covering a range of molecular weights, and with correspondingly differing ranges of spectral interference. Their performance was compared by measuring the signal-to-noise ratios (S/N) of 47 analytes, mostly pharmaceuticals, with the different matrices using the selected reaction monitoring (SRM) mode on a triple quadrupole instrument equipped with a vacuum MALDI source. AnCCA, NpCCA and Cl-CCA were found to offer better signal-to-noise ratios in SRM mode than CHCA, but Cl-CCA yielded the best results for 60% of the compounds tested. To better understand the relative performance of this matrix series, the proton affinities (PAs) were measured using the kinetic method. Their relative values were: AnCCA > CHCA > NpCCA > Cl-CCA. This ordering is consistent with the performance data. The synthesis of the new matrices is straightforward and they provide (1) tunability of matrix background interfering ions and (2) enhanced analyte response for certain classes of compounds.     

Introducing wet aerosols into the static high sensitivity ICP (SHIP)

A demountable design of the static high sensitivity ICP (SHIP) for optical emission spectrometry is presented, and its use as an excitation source with the introduction of wet aerosols was investigated. Aerosols were produced by standard pneumatic sample introduction systems, namely a cross flow nebulizer, Meinhard nebulizer and PFA low flow nebulizer, which have been applied in conjunction with a double pass and a cyclonic spray chamber. The analytical capabilities of these sample introduction systems in combination with the SHIP system were evaluated with respect to the achieved sensitivity. It was found that a nebulizer tailored for low argon flow rates (0.3–0.5 L min⁻¹) is best suited for the low flow plasma (SHIP). An optimization of all gas flow rates of the SHIP system with the PFA low flow nebulizer was carried out in a two-dimensional way with the signal to background ratio (SBR) and the robustness as optimization target parameters. Optimum conditions for a torch model with 1-mm injector tube were 0.25 and 0.36 L min⁻¹ for the plasma gas and the nebulizer gas, respectively. A torch model with a 2-mm injector tube was optimized to 0.4 L min⁻¹ for the plasma gas and 0.44 L min⁻¹ for the nebulizer gas. In both cases the SHIP system saves approximately 95% of the argon consumed by conventional inductively coupled plasma systems. The limits of detection were found to be in the low microgram per litre range and below for many elements, which was quite comparable to those of the conventional setup. Furthermore, the short-term stability and the wash out behaviour of the SHIP were investigated. Direct comparison with the conventional setup indicated that no remarkable memory effects were caused by the closed design of the torch. The analysis of a NIST SRM 1643e (Trace Elements in Water) with the SHIP yielded recoveries of 97–103% for 13 elements, measured simultaneously. Photo of the SHIP-III during operation     

On the certification of cadmium at trace and ultratrace levels in standard reference materials using ID ICP-MS

Analytical methods used for the isotope dilution inductively coupled plasma mass spectrometric (ID-ICP-MS) measurement of Cd at μg kg⁻¹ and sub-μg kg⁻¹ levels are described and applied to the certification of new dietary supplement, blood, and serum Standard Reference Materials (SRMs). The materials are: SRM 3240 Ephedra sinica Stapf Aerial Parts, SRM 3241 Ephedra sinica Stapf Native Extract, SRM 3243 Ephedra-Containing Solid Oral Dosage Form, SRM 3244 Ephedra-Containing Protein Powder, SRM 966 Toxic Metals in Bovine Blood, Level 1 (L1) and Level 2 (L2), and SRM 1598a Animal Serum. The concentration of Cd in the materials ranges from 120 μg kg⁻¹ down to 0.03 μg kg⁻¹. At these levels, the factors that most influence the accuracy of the ICP-MS data are the procedure blank and spectral and nonspectral interferences. Nonspectral interference, caused by the high concentration of dissolved solids in the matrices investigated, resulted in signal suppression. Matrix separation was used to enhance signal intensity and to reduce spectral interference for the accurate determination of Cd in SRM 1598a and SRM 3244. Chromatographic separation procedures using Chelex for SRM 1598a and anion exchange for SRM 3244 were optimized to achieve the desired separation characteristics without substantially increasing the procedure blank. Sensitivity for the determination of Cd in serum was additionally enhanced through the use of desolvation nebulization. We determined that separations were not required for the accurate ICP-MS determination of Cd in SRM 3240, SRM 3241, SRM 3243, and SRM 966 L2 under optimized analysis conditions. These samples were diluted to a minimum volume and introduced to the ICP-MS via low flow (40–100 μL/min) microconcentric nebulizers. SRM 966 L1 was also analyzed directly, but results were highly variable. The ID-ICP-MS sample preparation and ratio measurement protocols described here resulted in total expanded uncertainties of less than 1% for the determination of 90.85 μg kg⁻¹ Cd in SRM 3240, and less than 10% total expanded uncertainty for the determination of 0.0468 μg kg⁻¹ Cd in SRM 1598a.     

CuO-ZnO-ZrO_2催化甲醇水蒸汽重整反应机理和中间态

应用质谱在线技术,对CuO-ZnO-ZrO2催化甲醇水蒸汽重整(SRM)反应进行程序升温脱附(TPD)和程序升温表面反应(TPSR)研究.结果表明:在反应态催化剂表面,甲醇以分子吸附态形式存在,甲醇水蒸汽重整反应经历甲酸根中间物种.分别用CuO、CuO-ZnO、CuO-ZnO-ZrO2作催化剂,甲醇在气流中的摩尔分数分别高于5.4%、0.37%和0.17%时,甲酸根中间态的分解产物为CO2和H2;而甲醇在气流中的摩尔分数分别低于5.4%、0.37%和0.17%时,甲酸根中间态的分解产物为CO、CO2和H2.     

Validation of a nanoliquid chromatography–tandem mass spectrometry method for the identification and the accurate quantification by isotopic dilution of glutathionylated and cysteinylated precursors of 3-mercaptohexan-1-ol and 4-mercapto-4-methylpentan-2-one in white grape juices

A rapid nanoLC–MS/MS method was developed and validated for the simultaneous determination of glutathionylated and cysteinylated precursors of 3-mercapto-hexan-1-ol (3MH) and 4-methyl-4-mercaptopentan-2-one in grape juice using stable isotope dilution assay (SIDA). The analytes were extracted from must using a cation exchange resin and purified on C18 cartridges. They were chromatographically separated on a reverse phase column and finally analyzed by tandem mass spectrometry in selected reaction monitoring mode (SRM) using deuterated analogues as standards except for glutathionylated conjugate of 4MMP which was analyzed by external calibration. The method was validated according to the International Conference on Harmonization recommendations by determining linearity, accuracy, precision, recovery, matrix effect, repeatability, intermediate reproducibility, LODs and LOQs.     

FTTx用户割接至IMS自动工单化的实现

阐述了自动工单化实现机制原理,即FTTx割接以节点为单位,利用SRM系统发起割接批次,通过PF、ISAP、电子工单系统和OLT设备网管系统自动执行工单命令,实现FTTx用户割接工单化,提高生产效率。     

Characterization of Standard Reference Material 2943, Cu-ion-doped glass, spectral correction standard for blue fluorescence

Standard Reference Material (SRM) 2943 is a cuvette-shaped, Cu-ion-doped glass, recommended for use for relative spectral correction of emission and day-to-day performance verification of steady-state fluorescence spectrometers. Properties of this standard that influence its effective use or contribute to the uncertainty in its certified emission spectrum were explored here. These properties include its photostability, absorbance, dissolution rate in water, anisotropy and temperature coefficient of fluorescence intensity. The expanded uncertainties in the certified spectrum are about 5% around the peak maximum at 446 nm, using an excitation wavelength of 330 nm. SRM 2943 can replace SRM 936a quinine sulfate dihydrate, which is no longer sold by NIST, for many applications, as it covers the same spectral range. SRM 2943 is significantly more photostable than organic dyes, but unlike the other fluorescent glass SRMs in this series, it does photodegrade gradually under lamp-based excitation.     

虎跳峡龙蟠右岸土石混合体粒度分形特征研究

应用分维理论对虎跳峡龙蟠右岸分布的土石混合体粒度分布的分维规律进行了研究分析,建立了平均粒径与相应的分维数之间的定量关系模型。通过研究表明,土石混合体具有良好的统计自相似性,由于其本身为级配不良土,在分维曲线上表现为双重分形分布,这种特殊的分维分布与土石混合体的成因及形成过程有关。