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Calculations of Sobol indices for the Gaussian process metamodel

RELIABILITY ENGINEERING & SYSTEM SAFETY 2009年第3期94卷 742-751页

作者： Marrel, Amandine Iooss, Bertrand Laurent, Beatrice Roustant, Olivier CEA DEN DTN SMTMLMTE F-13108 St Paul Les Durance France CEA DEN DER SESILCFR F-13108 St Paul Les Durance France Univ Toulouse Inst Math UMR 5219 Toulouse France Ecole Natl Super Mines F-42023 St Etienne France

Global sensitivity analysis of complex numerical models can be performed by calculating variance-based importance measures of the input variables, such as the Sobol indices. However, these techniques, requiring a large number of model evaluations, are often unacceptable for time expensive computer codes. A well-known and widely used decision consists in replacing the computer code by a metamodel, predicting the model responses with a negligible computation time and rending straightforward the. estimation of Sobol indices. In this paper, we discuss about the Gaussian process model which gives analytical expressions of Sobol indices. Two approaches are studied to compute the Sobol indices: the first based on the predictor of the Gaussian process model and the second based on the global stochastic process model. Comparisons between the two estimates, made on analytical examples, show the superiority of the second approach in terms of convergence and robustness. Moreover, the second approach allows to integrate the modeling error of the Gaussian process model by directly giving some confidence intervals on the Sobol indices. These techniques are finally applied to a real case of hydrogeological modeling. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： Gaussian process Covariance Metamodel Sensitivity analysis Uncertainty computer code

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Implementation of a robust SQP algorithm

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OPTIMIZATION METHODS & SOFTWARE 2008年第6期23卷 827-846页

作者： Fabien, Brian C. Univ Washington Dept Mech Engn Seattle WA 98195 USA

This paper presents an implementation of a sequential quadratic programming (SQP) algorithm for the solution of nonlinear programming (NLP) problems. In the proposed algorithm, a solution to the NLP problem is found by minimizing the L1 exact penalty function. The search direction for the penalty function minimization is determined by solving a strictly convex quadratic programming (QP) problem. Here, we make the basic SQP algorithm more robust (i) by solving a relaxed, strictly convex, QP problem in cases where the constraints are inconsistent, (ii) by performing a non-monotone line search to improve efficiency, and (iii) by using second-order corrections to avoid the Maratos effect. The robustness of the algorithm is demonstrated via a C language implementation that is applied to numerous parameter optimization and optimal control problems that have appeared in the literature. The results obtained show that both non-monotone line searches and second-order corrections can significantly reduce the amount of work required to solve parameter optimization problems.

关键词： nonlinear programming problem sequential quadratic programming computer code

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Development of an advanced computer simulation technique for the modeling of rubber curing process

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COMPUTATIONAL MATERIALS SCIENCE 2009年第2期47卷 539-547页

作者： Rafei, M. Ghoreishy, M. H. R. Naderi, G. Iran Polymer & Petrochem Inst Tehran Iran

This research work is devoted to the development of an advanced computational technique for the simulation of the rubber curing process. The main novelty of the work is to cover the most important features that have not been addressed in the previous works. These include the use of incompatible meshes, thermal contact between rubber and mold, more accurate models for the description of the variation of rubber thermal properties with temperature and state-of-cure, use of a modified kinetic model and development of more robust auxiliary computer code. The general purpose finite element code ABAQUS has been used in conjunction with an in-house written subroutine (UMATHT) to solve the heat conduction equation and the rubber cure kinetics, simultaneously. It is used to simulate the curing process of a thick rubber article in the mold and the post-cure stage. The results were compared with experimentally measured data (temperature and state-of-cure) which confirmed the accuracy and applicability of the method. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Rubber curing Simulation Finite element method computer code Cure kinetics

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DEVELOPMENT OF MIGRATION PREDICTION SYSTEM (MIGSTEM) FOR CATIONIC SPECIES OF RADIONUCLIDES THROUGH SOIL LAYERS

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JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 1989年第8期26卷 795-804页

作者： OHNUKI, T TAKEBE, S YAMAMOTO, T Department of Environmental Safety Research Japan Atomic Energy Research Institute

The migration prediction system (MIGSTEM) has been developed for estimating the migration of cationic species of radionuclides through soil layers systematically. The MIGSTEM consists of the migration experiments, the one-dimensional fitting code (inverse analysis code) for determining retardation factor and dispersivity (migration factors) and the three-dimensional differential code (prediction code) for estimating the migration of the radionuclides. The migration experiments are carried out for obtaining the concentration profiles of the radionuclides in unsaturated and saturated soil layers. Using the inverse analysis code, the migration factors are obtained at one time by fitting the concentration profiles calculated to those observed. The prediction code can give the contours of concentration and the one-dimensional concentration profiles at selected time, as well as the changing in the concentration at a selected position with time. The validity of the MIGSTEM was obtained by the benchmark test on the pre diction and inverse analysis codes. The MIGSTEM was applied to estimate the migration of Sr2+ through the sandy soil.

关键词： prediction system computer code radionuclide distribution radionuclide migration prediction retardation factor dispersivity shallow land disposal waste management sandy soil

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On the self-shielding factors in neutron activation analysis

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NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2009年第2期610卷 553-565页

作者： Trkov, A. Zerovnik, G. Snoj, L. Ravnik, M. Jozef Stefan Inst SI-1000 Ljubljana Slovenia

Whenever the sample size in neutron activation analysis cannot be made small enough, self-shielding effects need to be taken into account. When several resonance absorbers are present in the sample, resonance interference must also be considered. Estimation of the self-shielding factors by the Monte Carlo technique is too cumbersome for routine application. Various simplified approaches were compared to rigorous Monte Carlo calculations, pointing out their potential limitations. Good results are obtained using self-shielding factors calculated from evaluated nuclear data libraries and tabulated as a function of the dilution cross-section. The dilution cross-section depends on the material composition and the sample dimensions through the equivalence principle, which is well known in reactor physics. Resonance interference is calculated by solving the neutron spectrum slowing-down equation from cross-sections in 640-group representation. The MATSSF code was written for the purpose and is available on request. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Self-shielding Neutron activation analysis computer code Resonance integral Slowing-down equation Mean chord length

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Assessment of the models in RELAP/SCDAPSIM with QUENCH-06 analysis

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JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2015年第11期52卷 1417-1424页

作者： Madokoro, Hiroshi Erkan, Nejdet Okamoto, Koji Univ Tokyo Dept Nucl Engn & Management Bunkyo Ku Tokyo 1138654 Japan Univ Tokyo Nucl Profess Sch Tokai Ibaraki 3191188 Japan

A fundamental principle of accident management in a nuclear power plant is the injection of water to cool the core. In this framework, a series of QUENCH tests have been conducted at Karlsruhe Institute of Technology (formerly Forschungszentrum Karlsruhe). The test results constitute a significant experimental database not only for further understanding of reflooding behavior, but also for code validation and improvement. The RELAP/SCDAPSIM code is a system code that is used to model reactor behavior and is widely used around the world. To date, assessment and validation have been performed with numerous experiments, including QUENCH tests. In the previous studies, the results of QUENCH simulations were referred to be sensitive to two main parameters: the electrical resistance and the thermal conductivity of the shroud insulator, which are subject to relatively large uncertainty. It is important to investigate these two parameters in detail, because this would enable identification of those SCDAP models that require further improvement. In this study, the uncertainty of the electrical resistance was reduced by modification of the code and subsequent validation with experimental data. In addition, modification of the thermal properties of the shroud insulator is suggested with consideration of the argon atmosphere in the facility. Finally, upcoming problems and questions are discussed. A rather good agreement was obtained than those of previous studies. As a result, more accurate modeling of the electrical resistance and the thermal properties of the shroud insulator was conducted and the importance of these parameters was evaluated.

关键词： severe accident RELAP SCDAPSIM QUENCH computer code analysis

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RADAR COVERAGE ASSESSMENT IN NONSTANDARD AND DUCTING CONDITIONS - A GEOMETRICAL-OPTICS APPROACH

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IEE PROCEEDINGS-F RADAR AND SIGNAL PROCESSING 1990年第2期137卷 95-101页

作者： DURAND, JC GRANIER, P Division Systèmes Défense et Contrôle Thomson-CSF Meudon-la-Foret France

The paper sets out to show that geometrical optics (GO) is particularly suitable for the real-time accurate computation of radar coverages in nonstandard atmospheres. A somewhat unusual GO differential system is used for predicting both ray paths and complex propagated fields within regular media. Optimal reductions of that formalism are obtained according to symmetry properties of the atmosphere. Reflections from the earth and refractions through discontinuity layers are shown to admit simple analytical expressions in terms of the former system variables. An exact GO reciprocity property is then stated which enables the ‘two-way’ radar equation to be calculated in terms of existing radiated fields at the target location. Applications of the resulting computer code are presented, highlighting the crucial ducting phenomena. The accuracy of this program is demonstrated through a comparison with previous results from a waveguide-mode scientific code. Computation times comply with shipboard operational requirements.

关键词： tropospheric electromagnetic wave propagation radar theory computer code nonstandard atmospheres geometrical optics Radiowave propagation radar coverage assessment waveguide-mode scientific code discontinuity layer refractions shipboard operational requirements ducting phenomena radiowave propagation Electromagnetic wave propagation and interactions in the lower atmosphere Radar theory

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NEW NUMERICAL-METHOD FOR EQUILIBRIUM CYCLES OF HIGH CONVERSION PEBBLE BED REACTORS

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JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 1991年第10期28卷 947-957页

作者： OBARA, T SEKIMOTO, H Research Laboratory for Nuclear Reactors Tokyo Institute of Technology

A new code PREC2 was developed by modifying the PREC code to solve equilibrium OTTO cycle of the pebble bed reactor. The effective multiplication factor at the equilibrium cycle can be chosen as an input. The PREC2 code can analyze high-coverter (or breeder) reactors, for which the calculations by the SOR-Newton method employed in the PREC code can not be converged.

关键词： NUMERICAL SOLUTION computer code PREC PREC2 PEBBLE BED REACTORS HIGH CONVERTER BREEDER FUEL CYCLE THORIUM OTTO CYCLE EQUILIBRIUM CYCLE SOR-NEWTON METHOD DIFFUSION EQUATION BURN-UP EQUATION EFFECTIVE MULTIPLICATION FACTOR SECANT METHOD

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A Gamification Method for Improving the Onboarding Process of Software Engineers

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IT PROFESSIONAL 2024年第2期26卷 67-75页

作者： Ruiz, Mercedes Orta, Elena Gutierrez, Javier Univ Cadiz Dept Comp Sci & Engn Cadiz 11519 Spain Univ Seville Dept Languages & Comp Syst Seville 41012 Spain

In software engineering, the onboarding process of new software engineers is crucial. The primary goal of this process is to ensure that professionals gain the necessary knowledge and skills to comprehend the company's culture, integrate into the organization, and perform their activities effectively. Enhancing corporate learning processes and addressing human aspects, such as motivation, engagement, and commitment, are among the key factors influencing the success of the onboarding process. Gamification-the use of game elements in nongame contexts-has been widely employed in different contexts to promote positive changes in people's behavior and increase their engagement and performance. We consider the integration of gamification into the onboarding process an interesting field of study and research. In this work, we propose a novel method for gamifying the onboarding process and introduce an application case within an organizational context.

关键词： Games Behavioral Sciences Proposals Software Engineering Knowledge Engineering Best Practices Training Software Technology Use Of Techniques Positive Changes Professional Development New Work User Engagement Processing Field Game Experience Game Elements Organizational Implementation Best Practices Web Of Science Organizational Structure Development Of Tools Enjoyment Assertive Software Development Processing Software Game Mechanics Game Strategy Push Notifications Dynamic Game computer code Software Quality Development Of Methodologies Seamless Integration Resource Acquisition

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Structural reliability software at the University of California, Berkeley

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STRUCTURAL SAFETY 2006年第1-2期28卷 44-67页

作者： Der Kiureghian, A Haukaas, T Fujimura, K Univ Calif Berkeley Dept Civil & Environm Engn Berkeley CA 94720 USA Univ British Columbia Vancouver BC V6T 1Z4 Canada

The paper provides an overview of three software for structural reliability analysis developed at the University of California, Berkeley. These are CalREL, which is a general-purpose structural reliability code written in FORTRAN;FERUM, which is a collection of Matlab (R) files that can be used for structural reliability analysis in conjunction with simple finite element models;and OpenSees, which is an object-oriented code for nonlinear structural response simulation with reliability capabilities. Reliability analysis methods featured by these software include FORM, SORM, Monte Carlo simulation, and various importance sampling methods. In addition, variable importance and sensitivity measures are provided. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： computer code finite element FORM probabilistic methods reliability analysis reliability software sampling sensitivity simulation SORM

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