Use of a “least square” optimization procedure to estimate enzyme characteristics and substrate affinities in the denitrification reactions in soil

1995 ◽  
Vol 27 (10) ◽  
pp. 1261-1270 ◽  
Author(s):  
L. Dendooven ◽  
J.M. Anderson
Keyword(s):  
Optimization Procedure ◽  
Least Square ◽  
Substrate Affinities

scholarly journals Two view NURBS reconstruction based on GACO model

2021 ◽  
Author(s):  
Deepika Saini ◽  
Sanoj Kumar ◽  
Manoj K. Singh ◽  
Musrrat Ali
Keyword(s):  
Optimization Algorithms ◽  
Three Dimensional ◽  
Optimization Procedure ◽  
Least Square ◽  
Ant Colony ◽  
Free Form ◽  
Reconstruction Process ◽  
Nurbs Curve ◽  
Data Points ◽  
Ant Colony Optimization Algorithms

AbstractThe key job here in the presented work is to investigate the performance of Generalized Ant Colony Optimizer (GACO) model in order to evolve the shape of three dimensional free-form Non Uniform Rational B-Spline (NURBS) curve using stereo (two) views. GACO model is a blend of two well known meta-heuristic optimization algorithms known as Simple Ant Colony and Global Ant Colony Optimization algorithms. Basically, the work talks about the solution of NURBS-fitting based reconstruction process. Therefore, GACO model is used to optimize the NURBS parameters (control points and weights) by minimizing the weighted least-square errors between the data points and the fitted NURBS curve. The algorithm is applied by first assuming some pre-fixed values of NURBS parameters. The experiments clearly show that the optimization procedure is a better option in a case where good initial locations of parameters are selected. A detailed experimental analysis is given in support of our algorithm. The implemented error analysis shows that the proposed methodology perform better as compared to the conventional methods.

THE CONSTRAINED LEAST-SQUARE OPTIMIZATION OF SPHERICAL FOUR-BAR LINKAGES FOR RIGID-BODY GUIDANCE

1992 ◽  
Vol 16 (1) ◽  
pp. 47-60 ◽  
Author(s):  
Zheng Liu ◽  
J. Angeles
Keyword(s):  
Rigid Body ◽  
Numerical Procedure ◽  
Optimization Procedure ◽  
Least Square ◽  
Optimization Scheme ◽  
Loop Optimization ◽  
Linkage Error ◽  
General Basis ◽  
Set Up ◽  
Guidance Problem

The synthesis of spherical four-bar linkages for rigid-body guidance consists of the computation of the relevant dimensions of this type of linkage so that it can guide its coupler link to attain a set of prescribed orientations, Generalized coupler curves are used to describe the specified orientations and to evaluate the linkage error, defined as the sum of the errors between the corresponding computed and prescribed orientations. A two-loop optimization procedure is set up to minimize this error, results being obtained resorting to the orthogonal decomposition algorithm, an iterative numerical scheme introduced elsewhere. Continuation and damping techniques are used in the numerical procedure to enhance the convergence likelihood and its rate. The optimization scheme is developed on a general basis and can handle the spherical rigid-body guidance problem for any number of prescribed orientations. A numerical example is included in the paper.

Parameter Identification for Multibody Dynamic Systems

1997 ◽  
Author(s):  
Radu Serban ◽  
Jeffrey S. Freeman ◽  
Dan Negrut
Keyword(s):  
Sensitivity Analysis ◽  
Parameter Identification ◽  
Dynamic Systems ◽  
Time History ◽  
Optimization Procedure ◽  
Optimal Choice ◽  
Least Square ◽  
Unknown Parameters ◽  
Multibody Dynamic ◽  
Dynamic Sensitivity Analysis

Abstract This paper presents a parameter identification technique for multibody dynamic systems, based on a nonlinear least-square optimization procedure. The procedure identifies unknown parameters in the differential-algebraic multibody system model by matching the acceleration time history of a point of interest with given data. Derivative information for the optimization process is obtained through dynamic sensitivity analysis. Direct differentiation methods are used to perform the sensitivity analysis. Examples of the procedure are presented, applying the technique both to perfect data; i.e. data produced by the assumed model with the optimal choice of parameters, and to experimental data; i.e. data measured on the real system and thus subject to noise and modelling imperfections.

scholarly journals The application of Chaboche model in uniaxial ratcheting simulations

2020 ◽  
Vol 44 (2) ◽  
pp. 57-61
Author(s):  
Marta Wójcik ◽  
Andrzej Skrzat
Keyword(s):  
Kinematic Hardening ◽  
Strain Curve ◽  
Optimization Procedure ◽  
Least Square Method ◽  
Least Square ◽  
Compression Tests ◽  
Loading Test ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Chaboche Model

AbstractThis article presents the application of Chaboche nonlinear kinematic hardening model in simulations of uniaxial ratcheting. First, the symmetrical strain-controlled cyclic tension/compression tests for PA6 aluminum samples were done. Using the experimental stress–strain curve, initial material hardening parameters were determined by the ABAQUS software. The experimental curve was compared with the numerical one. For better fitting of both curves, the optimization procedure based on the least-square method was applied. Using the determined hardening parameters, numerical simulations of the ratcheting were done by the finite element analysis software. Numerical results were then compared with the experimental data obtained in the stress-controlled cyclic loading test.

scholarly journals Ethylene Polymerization via Zirconocene Catalysts and Organoboron Activators: an Experimental and Kinetic Modeling Study

2020 ◽  
Author(s):  
Luis Valencia ◽  
Francisco Enríquez-Medrano ◽  
Ricardo López-González ◽  
Priscila Quiñonez-Angulo ◽  
Enrique Saldívar-Guerra ◽  
...  
Keyword(s):  
Active Sites ◽  
Optimization Procedure ◽  
Kinetic Mechanism ◽  
Least Square ◽  
Coordination Polymerization ◽  
Solvent Phase ◽  
Vapor Equilibrium ◽  
Kinetic Rate Constants ◽  
Rate Of Polymerization ◽  
Polymerization Behavior

After 40 years of the discovery of metallocene catalysts, there are still several aspects that remain unresolved, especially when the “conventional” alkylaluminum activators are not used. Herein, we systematically investigate the synthesis of PE via three different zirconocene catalysts, with different alkyl substituents, activated via different organoboron compounds. The polymerization behavior, as well as the properties of the materials, are evaluated. The results demonstrate that the highest catalytic activity is shown by Bis(cyclopentadienyl)dimethylzirconium activated by trityl tetra(pentafluorophenyl)borate. Also finding that toluene is the optimum solvent for these systems and at these reaction conditions. Moreover, to validate our experimental results, a comprehensive mathematical model is developed on the basis of thermodynamic and kinetic principles. The concentration of ethylene transferred to the solvent phase (toluene) in a liquid-vapor equilibrium (LVE) system is estimated based on the Duhem’s theorem. Arrhenius expressions for the kinetic rate constants of a proposed kinetic mechanism are estimated by a kinetic model, in which the rate of polymerization is fitted by a least-square optimization procedure and the molecular weight averages by the method of moments. The simulations of the coordination polymerization suggest the presence of two types of active sites, principally at low temperatures, and the reactivation of the deactivated sites via a boron-based activator. However, the effect of the temperature on the reactivation step is no clear; a deeper understanding via designed experiments is required.

The Global Least-Square Optimization of Function-Generating Linkages

1987 ◽  
Vol 109 (2) ◽  
pp. 204-209 ◽  
Author(s):  
J. Angeles ◽  
A. Bernier
Keyword(s):  
Optimization Procedure ◽  
Least Square ◽  
Decision Variable ◽  
Single Variable ◽  
Performance Indices ◽  
Design Error ◽  
Global Properties ◽  
Transmission Quality ◽  
Maximum Transmission

As shown elsewhere, the approximate least-square synthesis of function-generating linkages can be formulated in terms of one single decision variable. Hence, functions representing global properties of linkages such as accuracy and transmission quality, which are terms precisely defined in this paper, as well as mobility type, are all functions of one single variable. The optimization procedure presented here is aimed at the synthesis of function-generating linkages with a minimum least-square design error and a maximum transmission quality, while meeting conditions prescribed on the type of mobility (crank or rocker) of its input and/or output links. Alternative performance indices and/or constraints can be treated likewise.

scholarly journals Ensemble-Based Electrical Resistivity Tomography with Data and Model Space Compression

2021 ◽  
Author(s):  
Mattia Aleardi ◽  
Alessandro Vinciguerra ◽  
Azadeh Hojat
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Electrical Resistivity Tomography ◽  
Synthetic Data ◽  
Optimization Procedure ◽  
Model Space ◽  
Least Square ◽  
Resistivity Tomography ◽  
Initial Ensemble ◽  
The Difference

AbstractInversion of electrical resistivity tomography (ERT) data is an ill-posed problem that is usually solved through deterministic gradient-based methods. These methods guarantee a fast convergence but hinder accurate assessments of model uncertainties. On the contrary, Markov Chain Monte Carlo (MCMC) algorithms can be employed for accurate uncertainty appraisals, but they remain a formidable computational task due to the many forward model evaluations needed to converge. We present an alternative approach to ERT that not only provides a best-fitting resistivity model but also gives an estimate of the uncertainties affecting the inverse solution. More specifically, the implemented method aims to provide multiple realizations of the resistivity values in the subsurface by iteratively updating an initial ensemble of models based on the difference between the predicted and measured apparent resistivity pseudosections. The initial ensemble is generated using a geostatistical method under the assumption of log-Gaussian distributed resistivity values and a Gaussian variogram model. A finite-element code constitutes the forward operator that maps the resistivity values onto the associated apparent resistivity pseudosection. The optimization procedure is driven by the ensemble smoother with multiple data assimilation, an iterative ensemble-based algorithm that performs a Bayesian updating step at each iteration. The main advantages of the proposed approach are that it can be applied to nonlinear inverse problems, while also providing an ensemble of models from which the uncertainty on the recovered solution can be inferred. The ill-conditioning of the inversion procedure is decreased through a discrete cosine transform reparameterization of both data and model spaces. The implemented method is first validated on synthetic data and then applied to field data. We also compare the proposed method with a deterministic least-square inversion, and with an MCMC algorithm. We show that the ensemble-based inversion estimates resistivity models and associated uncertainties comparable to those yielded by a much more computationally intensive MCMC sampling.

scholarly journals Quantitative High Resolution Electron Microscopy of Grain Boundaries

1996 ◽  
Vol 466 ◽  
Author(s):  
Geoffrey H. Campbell ◽  
Wayne E. King ◽  
Dov Cohen ◽  
Barry Carter
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Simulation Optimization ◽  
Image Data ◽  
Optimization Procedure ◽  
High Resolution Electron Microscopy ◽  
Perfect Crystal ◽  
Least Square ◽  
Image Simulation ◽  
Resolution Electron

ABSTRACTThe Σ11 (113)/[110] symmetric tilt grain boundary has been characterized by high resolution transmission electron microscopy. The method by which the images are prepared for analysis is described. The statistics of the image data have been found to follow a normal distribution. The electron-optical imaging parameters used to acquire the image have been determined by non-linear least-square image simulation optimization within the perfect crystal region of the micrograph. A similar image simulation optimization procedure is used to determine the atom positions which provide the best match between the experimental image and the image simulation.

scholarly journals Ethylene Polymerization via Zirconocene Catalysts and Organoboron Activators: An Experimental and Kinetic Modeling Study

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 162
Author(s):  
Luis Valencia ◽  
Francisco Enríquez-Medrano ◽  
Ricardo López-González ◽  
Priscila Quiñonez-Ángulo ◽  
Enrique Saldívar-Guerra ◽  
...  
Keyword(s):  
Active Sites ◽  
Optimization Procedure ◽  
Kinetic Mechanism ◽  
Least Square ◽  
Coordination Polymerization ◽  
Solvent Phase ◽  
Vapor Equilibrium ◽  
Kinetic Rate Constants ◽  
Rate Of Polymerization ◽  
Polymerization Behavior

Forty years after the discovery of metallocene catalysts, there are still several aspects that remain unresolved, especially when the “conventional” alkylaluminum activators are not used. Herein, we systematically investigated the synthesis of polyethylene (PE) via three different zirconocene catalysts, with different alkyl substituents, activated via different organoboron compounds. The polymerization behavior, as well as the properties of the materials, were evaluated. The results demonstrate that the highest catalytic activity is shown by bis(cyclopentadienyl)dimethylzirconium activated by trityl tetra(pentafluorophenyl)borate. Additionally, it was found that toluene is the optimum solvent for these systems and at these reaction conditions. Moreover, to validate our experimental results, a comprehensive mathematical model was developed on the basis of thermodynamic and kinetic principles. The concentration of ethylene transferred to the solvent phase (toluene) in a liquid–vapor equilibrium (LVE) system was estimated based on Duhem’s theorem. Arrhenius expressions for the kinetic rate constants of a proposed kinetic mechanism were estimated by a kinetic model, in which the rate of polymerization was fitted by a least-square optimization procedure and the molecular weight averages by the method of moments. The simulations of the coordination polymerization suggest the presence of two types of active sites, principally at low temperatures, and the reactivation of the deactivated sites via a boron-based activator. However, the effect of the temperature on the reactivation step was not clear; a deeper understanding via designed experiments is required.

Least-square refinement of structure parameters from CBED integrated intensities: application to determination of temperature factors in Y BA2CU3O7

1992 ◽  
Vol 50 (2) ◽  
pp. 1456-1457
Author(s):  
Kjersti Gjønnes ◽  
Jon Gjønnes
Keyword(s):  
Least Square ◽  
Measured Intensity ◽  
Structure Information ◽  
Accurate Temperature ◽  
Least Square Fit ◽  
Case Application ◽  
Integrated Intensities ◽  
Temperature Factors ◽  
Narrow Bands

Electron diffraction intensities can be obtained at large scattering angles (sinθ/λ ≥ 2.0), and thus structure information can be collected in regions of reciprocal space that are not accessable with other diffraction methods. LACBED intensities in this range can be utilized for determination of accurate temperature factors or for refinement of coordinates. Such high index reflections can usually be treated kinematically or as a pertubed two-beam case. Application to Y Ba2Cu3O7 shows that a least square refinememt based on integrated intensities can determine temperature factors or coordinates.LACBED patterns taken in the (00l) systematic row show an easily recognisable pattern of narrow bands from reflections in the range 15 < l < 40 (figure 1). Integrated intensities obtained from measured intensity profiles after subtraction of inelastic background (figure 2) were used in the least square fit for determination of temperature factors and refinement of z-coordinates for the Ba- and Cu-atoms.

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