Indirect spectral hard modeling for the analysis of reactive and interacting mixtures

We present an indirect hard modeling (IHM) approach for the quantitative analysis of reactive multicomponent mixtures with intermolecular interaction. It can be used when it is not possible to obtain calibration data in the composition region of interest. The goal of this work, specifically, is to analyze reactive systems, although the validation of the method is done with nonreactive systems. Compared to conventional hard modeling, the new approach reduces the manual work required for modeling and renders unnecessary the assignment of bands in mixture spectra to individual components. It is based on parametric models of the pure component spectra that are made just flexible enough to fit the spectra of the unknown mixtures, and it only requires small calibration data sets that may lie in different regions of the composition space. The application to infrared (IR) and Raman spectra of multicomponent systems is discussed.     

Convective regimes of mixing in binary systems with the mechanical equilibrium instability of a gas mixture

Experimental data on pressure that correspond to the diffusion-concentration-induced convection are presented. Stability analysis carried out with allowance for the channel geometry realized in the experiment shows the existence of various modes of perturbations, in good agreement with experimental data. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 501–507, May–June, 2008.     

Investigation of the equilibrium composition of a nitrogen-helium mixture

The results of experimental investigations of the equilibrium composition of a nitrogen-helium mixture are discussed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 6, pp. 1082–1086, June, 1971.     

叶片受软体和硬体外物撞击的损伤分析

针对发动机叶片常遭受外物的撞击损伤,不同材料的外物的撞击损伤存在着差别。从能量守恒和基本水动力学的角度分析了软体和硬体撞击叶片时的不同的撞击载荷模型。通过在LS-DYNA中就软体（以明胶为例）和硬体（以砂石为例）外物对叶片的撞击损伤过程进行了数值仿真分析。结果表明：在相同的初始撞击能量、相同的撞击速度及相同的撞击入射角度下,砂石撞击叶片时的撞击接触力幅值较大,但持续时间较明胶撞击时的要短,在撞击瞬间砂石和叶片获得最大的应变能。撞击过程中,由于明胶发生了流变,其对叶片产生的局部损伤比砂石要小。     

Application of endochronic theory of plasticity for modeling nonproportional repetitive-variable hard loading

To evaluate the effectiveness of the previously proposed constitutive equations of the endochronic theory of plasticity, we examine the deformation of thin-walled tubular specimens along square paths in deviatoric strain space with the combined action of axial force and torque. We obtain the resolving system of equations in application to strain-controlled nonproportional cyclic loading. Good agreement of the modeling results with the experimental data is noted.Translated from Problemy Prochnosti, No. 5, pp. 3–10, May, 1994.     

Thermodynamic analysis of a diabatic two-phase flow for a pure refrigerant and a refrigerant/oil mixture under equilibrium conditions

Two different definitions of the vapor quality during a diabatic two-phase flow with and without the presence of oil are presented in this paper: the well-known vapor flow quality and the thermodynamic vapor quality. The vapor flow quality is based on the mass flow rates whereas the thermodynamic vapor quality is based on the mass. Two-phase thermodynamic diagrams for pure R-134a and R-134a/oil mixture are plotted for different slip ratios. It is shown that the iso-flow quality lines are moved to lower enthalpies for larger slip ratios. In addition, the maximum vapor flow quality of a fluid/oil mixture is shown to increase when increasing the slip ratio whereas the maximum thermodynamic vapor quality remains constant. In addition, the correct expression of the elementary derivative of the vapor quality is also proposed, highlighting the role of the heat capacity at constant vapor quality.     

Reliability analysis for multidisciplinary systems with the mixture of epistemic and aleatory uncertainties

Epistemic and aleatory uncertain variables always exist in multidisciplinary system simultaneously and can be modeled by probability and evidence theories, respectively. The propagation of uncertainty through coupled subsystem and the strong nonlinearity of the multidisciplinary system make the reliability analysis difficult and computational cost expensive. In this paper, a novel reliability analysis procedure is proposed for multidisciplinary system with epistemic and aleatory uncertain variables. First, the probability density function of the aleatory variables is assumed piecewise uniform distribution based on Bayes method, and approximate most probability point is solved by equivalent normalization method. Then, important sampling method is used to calculate failure probability and its variance and variation coefficient. The effectiveness of the procedure is demonstrated by two numerical examples. Copyright © 2013 John Wiley & Sons, Ltd.     

Calculation of gas-gas phase equilibrium for the mixture He-Fl2

Equilibrium conditions are determined by use of the Redlich-Kwong equation of state and two different methods for numerical calculation of the mixture phase behavior.Translated from Inzhenerno-Fizicheskii Zhurnal,Vol. 37, No. 6, pp. 1054–1062, December, 1979.     

Thermal analysis of levitation-heated samples: Application to the niobium-germanium system

We present a new method of thermal analysis based on the position change during melting of samples heated in an electromagnetic levitation coil. The temperature is measured with a two-colour pyrometer, subject to appropriate corrections. This method appears to be a useful complement to other investigations such as differential thermal analysis (DTA) or simultaneous stepwise heating. The technique has been applied to the determination of the melting temperatures of alloys in the Nb-rich part of the Nb-Ge system.     

Thermodynamic equilibrium of a gas mixture with a solution in the condensed phase

A thermodynamic analysis is made of the equilibrium of a gas mixture (using a nitrogen-hydrogen mixture as an example) with a solid solution of its components. The processes occurring in the surface layer and interphase exchange are taken into account. The equilibrium characteristics are determined in terms of the equilibrium constants of the intermediate stages of the surface reactions.A. M. Gorkii Ural State University. S. M. Kirov Ural Polytechnical Institute, Ekaterinburg. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 4, pp. 624–628, April, 1992.     

Reliability modeling of a hard real-time system using the path-space approach

A hard real-time system, such as a fly-by-wire system, fails catastrophically (e.g. losing stability) if its control inputs are not updated by its digital controller computer within a certain timing constraint called the hard deadline. To assess and validate those systems’ reliabilities by using a semi-Markov model that explicitly contains the deadline information, we propose a path-space approach deriving the upper and lower bounds of the probability of system failure. These bounds are derived by using only simple parameters, and they are especially suitable for highly reliable systems which should recover quickly. Analytical bounds are derived for both exponential and Weibull failure distributions encountered commonly, which have proven effective through numerical examples, while considering three repair strategies: repair-as-good-as-new, repair-as-good-as-old, and repair-better-than-old.     

Application of finite mixture models for vehicle crash data analysis

Developing sound or reliable statistical models for analyzing motor vehicle crashes is very important in highway safety studies. However, a significant difficulty associated with the model development is related to the fact that crash data often exhibit over-dispersion. Sources of dispersion can be varied and are usually unknown to the transportation analysts. These sources could potentially affect the development of negative binomial (NB) regression models, which are often the model of choice in highway safety. To help in this endeavor, this paper documents an alternative formulation that could be used for capturing heterogeneity in crash count models through the use of finite mixture regression models. The finite mixtures of Poisson or NB regression models are especially useful where count data were drawn from heterogeneous populations. These models can help determine sub-populations or groups in the data among others. To evaluate these models, Poisson and NB mixture models were estimated using data collected in Toronto, Ontario. These models were compared to standard NB regression model estimated using the same data. The results of this study show that the dataset seemed to be generated from two distinct sub-populations, each having different regression coefficients and degrees of over-dispersion. Although over-dispersion in crash data can be dealt with in a variety of ways, the mixture model can help provide the nature of the over-dispersion in the data. It is therefore recommended that transportation safety analysts use this type of model before the traditional NB model, especially when the data are suspected to belong to different groups.     

带钢-辊子-柔性支承混杂系统动力学建模与模态分析

基于广义Hamilton原理建立带钢连续热镀锌生产线镀锌段带钢-辊子-柔性支承混杂系统的数学模型,线性化后利用实模态理论得到系统的频率方程。以某镀锌线为例求解了系统的特征值问题,分析了带钢横截面积和初始张力对系统特征值和特征向量的影响,并考察了系统的耦合振动特性。最后用有限元软件ANSYS对该混杂系统进行了模态分析,有限元计算结果与理论计算结果一致。     

A method for quantitative histomorphometric evaluation of soft tissue reactions to implants

The spatial distribution and concentration of distinct cellular elements, and the width of the reaction zone are of particular interest in the evaluation of the compatibility of implant materials. There is a dilemma in the use of interactive histomorphometric evaluation system, At low magnifications cell differentiation is difficult and at high magnification (x400) correct cell differentiation is possible but the evaluated area adjacent to the implant border is small and therefore not necessarily representative. The solution could be the evaluation of random samples at precise localization under high magnification. A light microscope with a software-controlled motorized stage is connected to a personal computer. The software allows definition of one or more polygonal areas at low magnification. A random generator determines the coordinates of the microscopic fields to be analysed and the motorized stage moves automatically to these coordinates. The number of microscopic fields which it is necessary to evaluate in each sample is calculated by the statistical methods described by Stein which take the heterogeneity of the histological structures into account. A software package ranks the various cells at selectable class intervals off the material-tissue interface (distance histogram). Data are stored in ASCII format, which allows importation into any evaluation software. The use of statistical methods seems to be justified for quantitative biocompatibility testing when the tissue encapsulating the implant is heterogeneous and larger than the suitable optical field of the microscope.     

Application of quantitative neutron activation analysis to the study of the cement-chloride reaction

Instrumental neutron activation analysis using a Ge(Li) detector has been used for the determination of chlorine bound in the hydration of portland cement. Results obtained are in agreement with data published by other investigators.     

Class modeling analysis of heparin 1H NMR spectral data using the soft independent modeling of class analogy and unequal class modeling techniques

To differentiate heparin samples with varying amounts of dermatan sulfate (DS) impurities and oversulfated chondroitin sulfate (OSCS) contaminants, proton NMR spectral data for heparin sodium active pharmaceutical ingredient samples from different manufacturers were analyzed using multivariate chemometric techniques. A total of 168 samples were divided into three groups: (a) Heparin, [DS] ≤ 1.0% and [OSCS] = 0%; (b) DS, [DS] > 1.0% and [OSCS] = 0%; (c) OSCS, [OSCS] > 0% with any content of DS. The chemometric models were constructed and validated using two well-established methods: soft independent modeling of class analogy (SIMCA) and unequal class modeling (UNEQ). While SIMCA modeling was conducted using the entire set of variables extracted from the NMR spectral data, UNEQ modeling was combined with variable reduction using stepwise linear discriminant analysis to comply with the requirement that the number of samples per class exceed the number of variables in the model by at least 3-fold. Comparison of the results from these two modeling approaches revealed that UNEQ had greater sensitivity (fewer false positives) while SIMCA had greater specificity (fewer false negatives). For Heparin, DS, and OSCS, respectively, the sensitivity was 78% (56/72), 74% (37/50), and 85% (39/46) from SIMCA modeling and 88% (63/72), 90% (45/50), and 91% (42/46) from UNEQ modeling. Importantly, the specificity of both the SIMCA and UNEQ models was 100% (46/46) for Heparin with respect to OSCS; no OSCS-containing sample was misclassified as Heparin. The specificity of the SIMCA model (45/50, or 90%) was superior to that of the UNEQ model (27/50, or 54%) for Heparin with respect to DS samples. However, the overall prediction ability of the UNEQ model (85%) was notably better than that of the SIMCA model (76%) for the Heparin vs DS vs OSCS classes. The models were challenged with blends of heparin spiked with nonsulfated, partially sulfated, or fully oversulfated chondroitin sulfate A, dermatan sulfate, or heparan sulfate at the 1.0, 5.0, and 10.0 wt % levels. The results from the present study indicate that the combination of (1)H NMR spectral data and class modeling techniques (viz., SIMCA and UNEQ) represents a promising strategy for assessing the quality of commercial heparin samples with respect to impurities and contaminants. The methodologies show utility for applications beyond heparin to other complex products.     

Self-consistent metabolic mixture analysis by heteronuclear NMR. Application to a human cancer cell line

Elucidation of the chemical composition of biological samples is a main focus of systems biology and metabolomics. In order to comprehensively study these complex mixtures, reliable, efficient, and automatable methods are needed to identify and quantify the underlying metabolites and natural products. Because of its rich information content, nuclear magnetic resonance (NMR) spectroscopy has a unique potential for this task. Here we present a generalization of the recently introduced homonuclear TOCSY-based DemixC method to heteronuclear HSQC-TOCSY NMR spectroscopy. The approach takes advantage of the high resolution afforded along the (13)C dimension due to the narrow (13)C line widths for the identification of spin systems and compounds. The method combines information from both 1D (13)C and (1)H traces by querying them against an NMR spectral database using our COLMAR query web server. The complementarity of (13)C and (1)H spectral information improves the robustness of compound identification. The method is demonstrated for a metabolic model mixture and is then applied to an extract from DU145 human prostate cancer cells.     

X射线荧光分析在区域地球化学勘查样品分析中的应用

详细论述了X-射线荧光光谱分析化探样品中24个元素的测试条件、方法及其精密度和准确度。采用粉末压片法,选用国家一级标准物质GBW07401～GBW07408、GBW07423～GBW07430和GBW07301～GBW07312为基准物质,使用经验系数法和康普顿散射线作内标校正基体效应。实验数据说明分析结果可靠,完全满足区域化探要求。