Primal—Dual Constraint Aggregation with Application to Stochastic Programming

The special constraint structure and large dimension are characteristic for multistage stochastic optimization. This results from modeling future uncertainty via branching process or scenario tree. Most efficient algorithms for solving this type of problems use certain decomposition schemes, and often only a part of the whole set of scenarios is taken into account in order to make the problem tractable.We propose a primal–dual method based on constraint aggregation, which constructs a sequence of iterates converging to a solution of the initial problem. At each iteration, however, only a reduced sub-problem with smaller number of aggregate constraints has to be solved. Number of aggregates and their composition are determined by the user, and the procedure for calculating aggregates can be parallelized. The method provides a posteriori estimates of the quality of the current solution approximation in terms of the objective function value and the residual.Results of numerical tests for a portfolio allocation problem with quadratic utility function are presented.     

Specific UV photodissociation of tyrosyl-containing peptides in multistage mass spectrometry

UV photodissociation (UVPD) at 262 nm has been carried out on protonated tyrosyl-containing peptides formed by trypsin digestion of apo-transferrin. Under UVPD, the main event is the fragmentation of the C(alpha)-C(beta) bond of the tyrosyl residues leading to a radical ion 107 Da below the precursor ion. The dissociation rate of this specific cleavage appears to be strongly dependent on the peptide sequence and is more prominent on the singly protonated species than on the doubly protonated state. The fragmentation spectra resulting from collisional activation of the protonated even-electron native peptides and of the odd-electron radical species prepared by UVPD are dominated by y-type backbone cleavages. A comparison of their respective y-ion pattern shows complementarities since the combination of both increases the sequence coverage of the peptide sequence. The specific detection of the neutral loss of 107 Da from peptides witnesses the content of at least one tyrosyl residue and, though preliminary, is proposed as a potential new filtering strategy during protein database searching.     

LDI and ESI MS as well as low energy CID of a self-assembling nanorod-forming fullerene derivative

An amphiphatic fullerene derivative (8-(N-Methyl-Fullero-Pyrrolidinium-1-yl-chloride)-3,6-Dioxaoctan-1-Ammonium Chloride (MFPDAC)), which is of great interest in nanotechnology due to the fact that it forms self-assembling fullerenic nanorods, has been structurally characterized with emphasis to its purity and thermal treatment of a formed nanorod film (on a LDI target) by means of laser desorption/ionization (LDI) coupled with high-resolution curved field reflectron time-of-flight (TOF) mass spectrometry, and by low energy MS/MS as well as in-source fragmentation experiments applying an quadrupole ion trap (QIT) combined with a two-stage reflectron TOF analyzer. The interpretation of LDI results has been supplemented by ESI QIT MS(n) (n = 1-3), as well as high-resolution ESI reflectron TOF mass spectrometric experiments. Based on the experimental data obtained by both desorption/ionization techniques, various types of analyzers and sample treatments, we could completely characterize MFPDAC and further found out that the investigated sample was not entirely free of impurities. Furthermore, the envisaged loss of the derivative sidechain upon the heat treatment in vacuum of the self-assembled nanorod sample film on a metallic substrate could be successfully monitored by LDI MS.     

行波管中多级降压收集极效率评估的研究

在行波管中,多级降压收集极(MDC)效率由于其与总效率的关系密切而显得非常重要. 而在设计MDC之前对其效率和行波管的总效率进行准确的评估可以把握管子的整体性能, 并为相关软件的开发提供理论指导,因而对MDC的优化和行波管总效率的提高具有十分重要的意义. 虽然Kosmahl在1980年就给出了MDC的效率评估公式,但其预测值比实测值偏高较多, 因而需要更为准确的评估公式.本文首先引入耗散公差的概念, 然后建立作用完电子注等差三角能量分布模型推导了MDC效率评估的公式,与Kosmahl给出的预测相比, 新公式的估计结果更接近实测值.最后根据MDC效率最高和各个电极上耗散能量最低这两个极值条件, 给出了MDC最佳电极级数的选取公式,其预测结果合理而且准确.     

基于PLSR的多级制造过程关键质量特性识别方法

为解决多级制造过程关键质量特性识别中多质量特性之间的相关性问题,将偏最小二乘回归方法(Partial Least Squares Regression, PLSR)引入模型构建与分析中。首先应用状态空间方法建立多级制造过程关键质量特性识别模型,进而利用PLSR方法解决质量特性间的多重共线性问题并进行模型分析,识别关键质量特性,最后以卷烟生产过程为例介绍了该方法的应用。实例表明,该方法不仅可以有效识别多级制造过程关键质量特性,而且能够建立各级过程的输出质量对最终产品质量的影响及其质量特性之间相互关系的模型,反映多级生产过程的结构特征和各级过程质量特性之间的因果关系,为多级制造过程质量分析与控制提供依据。     

Determination of the Alternaria mycotoxin tenuazonic acid in cereals by high-performance liquid chromatography–electrospray ionization ion-trap multistage mass spectrometry after derivatization with 2,4-dinitrophenylhydrazine

Tenuazonic acid (TA) is a major Alternaria mycotoxin. In the present work a novel approach for the detection of TA in cereals by liquid chromatography–ion-trap multistage mass spectrometry after derivatization with 2,4-dinitrophenylhydrazine is described. The product of the derivatization reaction and its major MS² fragments were characterised by Fourier transform-ion cyclotron resonance tandem mass spectrometry. Without preconcentration, the established method features a limit of detection of 10 μg/kg using 2 g of sample in a rapid workup procedure. Accuracy, precision and linearity were evaluated in the working range of 50–5000 μg/kg. TA was detected in 13 and quantified in 3 out of 27 cereal samples obtained from a local supermarket, the average content being 49 μg/kg (highest incidence: 851 ± 41 μg/kg).     

多级混沌映射变参数伪随机序列产生方法研究

针对单混沌系统因计算机有限精度效应产生的混沌退化问题,提出了一种多级混沌映射变参数伪随机序列产生方法,基于该方法构建的混沌系统较单混沌系统具有伪随机序列周期大,密钥数量多,密钥空间大等优势,所产生的密码具有更高的安全性能.仿真结果表明,该方法在低复杂度条件下可以生成大量具有良好自相关和互相关特性的混沌序列,在安全领域具有良好的应用前景.     

Electrospray multistage mass spectrometry in the negative ion mode for the unambiguous molecular and structural characterization of acidic hydrolysates from 4‐O‐methylglucuronoxylan generated by endoxylanases

A rapid analytical methodology is proposed to answer the two questions about the molecular and structural features of the acidic xylo‐oligosaccharides (XOSs) formed upon the enzymatic hydrolysis of 4‐O‐methylglucuronoxylan. The shortest acidic XOSs carrying a methylglucuronic acid moiety and the possible distribution of larger products (molecular feature) are instantly found by electrospray ionization mass spectrometry (ESI‐MS) in the negative ion mode, which filters the unwanted neutral XOS. The acidic moiety is then unambiguously localized along the xylose backbone (structural feature) by ESI‐MSⁿ in the negative ion mode via the selection/activation/dissociation of the product ions formed upon the one‐way and stepwise glycosidic bond cleavage at the reducing end. Using the shortest acidic XOS with a known shape generated by glycoside hydrolase family (GH) 10 and GH11 xylanases as a proof of principle, pairs of diagnostic ions are proposed to instantly interpret the MSⁿ fingerprints and localize the acidic moiety along the xylose chain of the activated ion. The original structure of the acidic XOS is then reconstructed by adding as many xylose units at the reducing end as MSⁿ steps. Relying on pairs of ions, the methodology is robust enough to highlight the presence of isomeric products. Mass spectra reported in the present article will be conveniently used as reference data for the forthcoming analysis of acidic XOS generated by new classes of enzymes using this multistage mass spectrometry methodology.     

基于CVaR衍生的多期多面风险度量下的投资组合研究

为了解决多期投资组合的决策问题,本文将由CVaR衍生的多期多面风险度量作为风险控制目标,建立了一个在收益约束条件下最小化风险的多阶段投资组合模型。为求解模型,设计了多期投资组合优化流程,它将非参数抽样方法、基于聚类算法的多阶段情景树生成方法和多期多面风险度量组合在一起。该流程基于计算、容易实现、直观合理。根据我国金融市场数据进行的实证研究结果表明,这一流程具有较好的实用性。     

基于DEM-CFD耦合的泵内颗粒流动特性研究

随着我国加快深海、深地资源的开发力度,对此类应用环境下的液体提升泵的可靠性提出了更高的要求。而泵内固体颗粒引起的磨损破坏是其中一个严重问题。本文基于DEM-CFD耦合方法,针对自开发的两级混流泵研究了颗粒在泵内部与流体相互作用下的流动特性和对泵的磨损规律,并基于该泵分析了不同颗粒形状、颗粒浓度下的运动特性和泵磨损分布,发现颗粒主要沿着叶轮工作面以及导叶凹面运动,且随着浓度增加,磨损速率会逐渐达到一个饱和值。本文分析探讨了颗粒在泵内的流动特性、颗粒与叶轮导叶发生碰撞的形式及磨损严重区域,对设计抗磨损多级混流泵提供了理论支撑。