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。     

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.     

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.     

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.     

改进人工蜂群算法优化的LSSVM在混合气体定量分析中的应用

针对在易燃易爆混合气体定量分析中因交叉敏感易产生测量误差以及最小二乘支持向量机（least squares support vector machine,LSSVM）参数难以确定的问题,提出一种改进人工蜂群（improved artificial bee colony,IABC）算法优化的最小二乘支持向量机。首先,在标准人工蜂群（artificial bee colony, ABC）算法中引入自适应递减因子以更新步长,并结合轮盘赌和反向轮盘赌改进待工蜂跟随概率公式,从而提高收敛精度;然后,利用改进后的人工蜂群算法对最小二乘支持向量机的惩罚参数C和核参数σ²进行优化;最后,利用优化后的参数重建最小二乘支持向量机定量分析模型,并与利用常用的混合气体定量分析方法——粒子群优化（particle swarm optimization,PSO）算法优化的最小二乘支持向量机定量分析模型进行对比。实验结果表明,在交叉敏感状态下,采用改进人工蜂群算法优化的最小二乘支持向量机时的建模总时间和各组分气体浓度测量的平均相对误差均低于采用粒子群算法优化的,有效提高了混合气体的浓度测量精度。研究表明,改进人工蜂群算法优化的最小二乘支持向量机可为混合气体定量分析提供理论支撑,具有一定的工程应用价值。     

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.     

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.     

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.     

Adaptive reduced order modeling for nonlinear dynamical systems through a new a posteriori error estimator: Application to uncertainty quantification

Multiquery problems such as uncertainty quantification (UQ), optimization of a dynamical system require solving a differential equation at multiple parameter values. Therefore, for large systems, the computational cost becomes prohibitive. This issue can be addressed by using a cheaper reduced order model (ROM) instead. However, the ROM entails error in the solution due to approximation in a lower dimensional subspace. Moreover, the ROM lacks robustness over a wide range of parameter values. To address these issues, first, an upper bound on the norm of the state transition matrix is derived. This bound, along with the residual in the governing equation, are then used to develop an error estimator for general nonlinear dynamical systems. Furthermore, this error estimator is used in conjunction with the modified greedy search algorithm proposed by Hossain and Ghosh (Int J Numer Methods Eng, 2018;116(12-13): 741-758) to adaptively construct a robust proper orthogonal decomposition-based ROM. This adaptive ROM is subsequently deployed for UQ by invoking it in a statistical simulation. Two numerical studies: (i) viscous Burgers' equation and (ii) beam on nonlinear Winkler foundation, showed an improved accuracy of the error estimator compared to the current literature. A significant computational speed-up in UQ is achieved.     

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.