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Lagrangian simulation of multi-step and rate-limited chemical reactions in multi-dimensional porous media

Water Science and Engineering 2018年第2期11卷 101-113页

作者： Bing-qing Lu Yong Zhang Hong-guang Sun Chun-miao Zheng Department of Geological Sciences University of Alabama College of Mechanics and Materials Hohai University School of Environmental Science and Engineering Southern University of Science and Technology

Management of groundwater resources and remediation of groundwater pollution require reliable quantification of contaminant dynamics in natural aquifers, which can involve complex chemical dynamics and challenge traditional modeling approaches. The kinetics of chemical reactions in groundwater are well known to be controlled by medium heterogeneity and reactant mixing, motivating the development of particle-based Lagrangian approaches. Previous Lagrangian solvers have been limited to fundamental bimolecular reactions in typically one-dimensional porous media. In contrast to other existing studies, this study developed a fully Lagrangian framework, which was used to simulate diffusion-controlled, multi-step reactions in one-, two-, and three-dimensional porous media. The interaction radius of a reactant molecule, which controls the probability of reaction, was derived by the agent-based approach for both irreversible and reversible reactions. A flexible particle tracking scheme was then developed to build trajectories for particles undergoing mixing-limited, multi-step reactions. The simulated particle dynamics were checked against the kinetics for diffusion-controlled reactions and thermodynamic wellmixed reactions in one-and two-dimensional domains. Applicability of the novel simulator was further tested by(1) simulating precipitation of calcium carbonate minerals in a two-dimensional medium, and(2) quantifying multi-step chemical reactions observed in the laboratory. The flexibility of the Lagrangian simulator allows further refinement to capture complex transport affecting chemical mixing and hence reactions.

关键词： Lagrangian framework Chemical reaction Diffusion-limited process multi-step reactions Interaction radius

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Strategies for multi-step-ahead available parking spaces forecasting based on wavelet transform

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Journal of Central South University 2017年第6期24卷 1503-1512页

作者：季彦婕高良鹏陈晓实郭卫红 School of Transportation Southeast UniversityNanjing 210096China Fujian Communications Planning&Design Institute Fuzhou 350000China Transport Operations Research Group School of Civil Engineering&GeosciencesNewcastle UniversityUK

A new methodology for multi-step-ahead forecasting was proposed herein which combined the wavelet transform(WT), artificial neural network(ANN) and forecasting strategies based on the changing characteristics of available parking spaces(APS). First, several APS time series were decomposed and reconstituted by the wavelet transform. Then, using an artificial neural network, the following five strategies for multi-step-ahead time series forecasting were used to forecast the reconstructed time series: recursive strategy, direct strategy, multi-input multi-output(MIMO) strategy, DIRMO strategy(a combination of the direct and MIMO strategies), and newly proposed recursive multi-input multi-output(RECMO) strategy which is a combination of the recursive and MIMO strategies. Finally, integrating the predicted results with the reconstructed time series produced the final forecasted available parking spaces. Three findings appear to be consistently supported by the experimental results. First, applying the wavelet transform to multi-step ahead available parking spaces forecasting can effectively improve the forecasting accuracy. Second, the forecasting resulted from the DIRMO and RECMO strategies is more accurate than that of the other strategies. Finally, the RECMO strategy requires less model training time than the DIRMO strategy and consumes the least amount of training time among five forecasting strategies.

关键词： available parking spaces multi-step ahead time series forecasting wavelet transform forecasting strategies recursive multi-input multi-output strategy

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Influence of a multi-step process on the thickness reduction error of sheet metal in a flexible rolling process

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International Journal of Minerals,Metallurgy and Materials 2019年第1期26卷 76-85页

作者： Yi Li Ming-zhe Li Kai Liu Dieless Forming Technology Center Roll Forging Institute Jilin University College of Materials Science and Engineering Jilin University

Flexible rolling is a forming process based on thickness reduction, and the precision of thickness reduction is the key factor affecting bending deformation. The major purpose of the present work is to solve the problem of bending deformation error caused by insufficient thickness reduction. Under the condition of different rolling reductions with the same sheet thickness and the same thickness reduction with different sheet thicknesses, the thickness reduction error of sheet metal is analyzed. In addition, the bending deformation of sheet metal under the same conditions is discussed and the influence of the multi-step forming process on the thickness reduction error is studied. The results show that, under the condition of the same sheet thickness, the thickness reduction error increases with increasing rolling reduction because of an increase in work hardening. As rolling reduction increases, the longitudinal bending deformation decreases because of the decrease of the maximum thickness difference. Under the condition with the same thickness reduction, the thickness reduction error increases because of the decrease of the rolling force with increasing sheet thickness. As the sheet thickness increases, the longitudinal bending deformation increases because of the increase in the maximum thickness difference. A larger bending deformation is divided into a number of small bending deformations in a multi-step forming process, avoiding a sharp increase in the degree of work hardening; the thickness reduction error is effectively reduced in the multi-step forming process. Numerical simulation results agree with the results of the forming experiments.

关键词： flexible rolling convex surface numerical simulation thickness reduction error multi-step forming process

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LOW SIDELOBE APERTURE DISTRIBUTION OF multi-step AMPLITUDE QUANTIZATION WITH PEDESTAL

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Journal of Electronics(China) 1995年第3期12卷 228-234页

作者：高铁郭燕昌 Nanjing Research Institute of Electronic Technology Nanjing 210013Nanjing Research Institute of Electronic Technology Nanjing 210013

A low sidelobe aperture design method of multi-step amplitude quantization with pedestal is proposed, and general analysis and formulas are described. The computation results compared with our previous method "multi-step Amplitude Quantization(MSAQ)" on peak side-lobe level, aperture efficiency, normalized input power and sidelobe degradation with tolerance are given. It is shown that, under the same conditions, the method presented in this paper is better than the MSAQ.

关键词： Low sidelobe Aperture distribution multi-step amplitude quantization with pedestal Aperture efficiency Sidelobe degradation Tolerance

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DESIGN AND ANALYSIS OF multi-step AMPLITUDE QUANTIZATION WEIGHTED 2-D SOLID-STATE ACTIVE PHASED ARRAY ANTENNAS

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Journal of Electronics(China) 1994年第1期11卷 71-78页

作者：高铁李建新郭燕昌 Nanjing Research Institute of Electronic Technology Nanjing 210013Nanjing Research Institute of Electronic Technology Nanjing 210013Nanjing Research Institute of Electronic Technology Nanjing 210013

An aperture design technique using multi-step amplitude quantization for two-dimensional solid-state active phased arrays to achieve low sidelobe is described. It can be applied to antennas with arbitrary complex aperture. Also, the gain drop and sidelobe degradation due to random amplitude and phase errors and element (or T/R module) failures are investigated.

关键词： Solid-state active phased array antenna multi-step amplitude quantization Low sidelobe Amplitude and phase errors Gain loss Failure

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Application of multi-step Differential Transform Method on Flow of a Second-Grade Fluid over a Stretching or Shrinking Sheet

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American Journal of Computational Mathematics 2011年第2期1卷 119-128页

作者： M.M Rashidi Ali J. Chamkha M Keimanesh 不详

In this study, a reliable algorithm to develop approximate solutions for the problem of fluid flow over a stretching or shrinking sheet is proposed. It is depicted that the differential transform method (DTM) solutions are only valid for small values of the independent variable. The DTM solutions diverge for some differential equations that extremely have nonlinear behaviors or have boundary-conditions at infinity. For this reason the governing boundary-layer equations are solved by the multi-step Differential Transform Method (MDTM). The main advantage of this method is that it can be applied directly to nonlinear differential equations without requiring linearization, discretization, or perturbation. It is a semi analytical-numerical technique that formulizes Taylor series in a very different manner. By applying the MDTM the interval of convergence for the series solution is increased. The MDTM is treated as an algorithm in a sequence of intervals for finding accurate approximate solutions for systems of differential equations. It is predicted that the MDTM can be applied to a wide range of engineering applications.

关键词： Non-Newtonian Fluid Stretching Surface Shrinking Sheet multi-step Differential Transform Method (MDTM)

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A variable importance criterion for variable selection in near-infrared spectral analysis

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Science China Chemistry 2019年第2期62卷 271-279页

作者： Jin Zhang Xiaoyu Cui Wensheng Cai Xueguang Shao Research Center for Analytical Sciences College of Chemistry Nankai University Tianjin Key Laboratory of Biosensing and Molecular Recognition State Key Laboratory of Medicinal Chemical Biology Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Xinjiang Laboratory of Native Medicinal and Edible Plant Resources Chemistry College of Chemistry and Environmental ScienceKashgar University

Variable selection is a universal problem in building multivariate calibration models, such as quantitative structure-activity relationship(QSAR) and quantitative relationships between quantity or property and spectral data. Significant improvement in the prediction ability of the models can be achieved by reducing the bias induced by the uninformative variables. A new criterion,named as C, is proposed in this study to evaluate the importance of the variables in a model. The value of C is defined as the average contribution of a variable to the model, which is calculated by the statistics of the models built with different combinations of the variables. In the calculation, a large number of partial least squares(PLS) models are built using a subset of variables selected by randomly re-sampling. Then, a vector of the prediction errors, in terms of root mean squared error of cross validation(RMSECV), and a matrix composed of 1 and 0 indicating the selected and unselected variables can be obtained. If multiple linear regression(MLR) is employed to model the relationship between the RMSECVs and the matrix, the coefficients of the MLR model can be used as a criterion to evaluate the contribution of a variable to the RMSECV. To enhance the efficiency of the method, a multi-step shrinkage strategy was used. Comparison with Monte Carlo-uninformative variables elimination(MC-UVE), randomization test(RT) and competitive adaptive reweighted sampling(CARS) was conducted using three NIR benchmark datasets. The results show that the proposed criterion is effective for selecting the informative variables from the spectra to improve the prediction ability of models.

关键词： near-infrared spectroscopy variable selection multivariate calibration multi-step strategy

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THE SIMULATION AND OPTIMIZATION OF GRADIENT ELUTION HPLC

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Science China Chemistry 1992年第9期35卷 1056-1066页

作者：林炳承刘文烨卢佩章 D.L.MASSART M.DE.SMET B.KOPPENHOEFER Dalian Institute of Chemical Physics Academia Sinica Dalian 116012PRC Free University of Brussels Belgium University of Tuebingen Germany

The movement of a particular component along an HPLC column is studied on the ba-sis of equilibrium equations. Numerical simulation of multi--step gradient elution HPLC isperformed by means o? a personal computer program. The location x, as a fraction of thecolumn length, for a given time t o? each compound is calculated, the velocity and corre-sponding acceleration are given as well. Diagrams for x,dx/dt and d^2x/dt^2 versus t display themovement process of the different components along the HPLC column during gradient elu-tion. The prediction of the retention time and peak width, and the optimization for the multi-step gradient elution HPLC are all based on such simulation and the molecular structure ofthe. components is separated as well.

关键词： HPLC multi-step gradient elution simulation in HPLC column optimization separation of chiral drugs

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Study on Short-term multi-step Wind Speed Forecast based on the multi-scale Predictability

Study on Short-term Multi-step Wind Speed Forecast based on ...

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智能化电站技术发展研讨暨电站自动化2013年会

作者： Wan Jie Liu Jinfu Yu Daren Harbin Institute of Technology

Giving a high precise Short-term wind speed multi-step forecast for wind farms,which can effectively relieves disadvantageous impact of wind power plants on power systems,enhances the competitive ability of wind power in electricity market.This work proposes to analyze the available horizon of the multi-step wind speed forecasting and improve the forecasting accuracy in this specific horizon.The final horizon is determined through analyzing the ACF of each sub-series decomposed by wavelet transform.Each sub-series’NN model has different horizons and then a multiresolution ensemble strategy is ensured.

关键词： Wind Speed Forecast Short-term multi-step multi-scale ensemble strategy

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NANOPARTICLE DESIGN AND HANDLING-CHALLENGES FOR ENGINEERS AND PARTICLE TECHNOLOGISTS

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China Particuology 2005年第1期3卷 99-104页

作者： F. Einar Kruis Rakesh K. Joshi Faculty of Engineering Sciences University of Duisburg-Essen Campus Duisburg Bismarckstraβe 81 47057 Duisburg Germany

In this paper, the opportunities and challenges which future applications based on nanoparticles offer to engineers are described. New high-added value products induce us to rethink ways to control nanoparticle design and handling. Several challenges are described and typical solutions are given: (1) finding relevant engineering tasks outside traditional process industry; (2) the importance of mixing reactants; (3) obtaining monodisperse particles; (4) gaining efficient control via electric forces and (5) developing multi-step processes which allow more control over particle properties.

关键词： nanoparticle challenges mixing electric forces multi-step gas sensing

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