scholarly journals Stiffness Model Reduction for Manipulators with Double Encoders: Algebraic Approach

2021 ◽  
Vol 17 (3) ◽  
pp. 347-360
Author(s):  
S. K. Mikhel ◽  
◽  
A. S. Klimchik ◽  
Keyword(s):  
Model Reduction ◽  
Experimental Method ◽  
Experimental Approach ◽  
Algebraic Approach ◽  
Reduced Model ◽  
Identification Process ◽  
Stiffness Model ◽  
Accuracy Of Measurements

To compare the proposed techniques with the experimental approach, the robot deformation under load is simulated and the tool displacement is estimated. It is shown that both approaches are equivalent in terms of accuracy. While the experimental method is easier to implement, the algebraic approach allows analyzing the contribution of each link in a reduced model of elasticity. Besides, the obtained estimate of the parameters does not depend on the accuracy of measurements and configurations used in the identification process.

How can experiments play a greater role in public policy? Twelve proposals from an economic model of scaling

2020 ◽  
Vol 5 (1) ◽  
pp. 2-49 ◽  
Author(s):  
OMAR AL-UBAYDLI ◽  
MIN SOK LEE ◽  
JOHN A. LIST ◽  
CLAIRE L. MACKEVICIUS ◽  
DANA SUSKIND
Keyword(s):  
Public Policy ◽  
Experimental Method ◽  
Economic Model ◽  
Large Scale ◽  
Experimental Approach ◽  
Scale Up ◽  
Original Research ◽  
Economic Framework ◽  
Scientific Experiments ◽  
Research Findings

AbstractPolicymakers are increasingly turning to insights gained from the experimental method as a means to inform large-scale public policies. Critics view this increased usage as premature, pointing to the fact that many experimentally tested programs fail to deliver their promise at scale. Under this view, the experimental approach drives too much public policy. Yet, if policymakers could be more confident that the original research findings would be delivered at scale, even the staunchest critics would carve out a larger role for experiments to inform policy. Leveraging the economic framework of Al-Ubaydli et al. (2019), we put forward 12 simple proposals, spanning researchers, policymakers, funders and stakeholders, which together tackle the most vexing scalability threats. The framework highlights that only after we deepen our understanding of the scale-up problem will we be on solid ground to argue that scientific experiments should hold a more prominent place in the policymaker's quiver.

Chemical Kinetic Model Reduction and Analysis of Tetrahydrofuran Combustion Using Stochastic Species Elimination

2020 ◽  
Author(s):  
Mazen A. Eldeeb ◽  
Malshana Wadugurunnehalage
Keyword(s):  
Kinetic Model ◽  
Model Reduction ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Laminar Flame ◽  
Chemical Kinetic ◽  
Reduced Model ◽  
Chemical Kinetic Model ◽  
Parameter Modification

Abstract In this work, a chemical kinetic modeling study of the high-temperature ignition and laminar flame behavior of Tetrahydrofuran (THF), a promising second-generation transportation biofuel, is presented. Stochastic Species Elimination (SSE) model reduction approach (Eldeeb and Akih-Kumgeh, Proceedings of ASME Power Conference 2018) is implemented to develop multiple skeletal versions of a detailed chemical kinetic model of THF (Fenard et al., Combustion and Flame, 2018) based on ignition delay time simulations at various pressures and temperature ranges. The detailed THF model contains 467 species and 2390 reactions. The developed skeletal versions are combined into an overall reduced model of THF, consisting of 193 species and 1151 reactions. Ignition delay time simulations are performed using detailed and reduced models, with varying levels of agreement observed at most conditions. Sensitivity analysis is then performed to identify the most important reactions responsible for the observed performance of the reduced model. Reaction rate parameter modification is performed for such reactions in order to improve the agreement of detailed and reduced model predictions with literature experimental ignition data. The work contributes toward improved understanding and modeling of the oxidation kinetics of potential transportation biofuels, especially cyclic ethers.

MODEL REDUCTION WITH GEOMETRIC STIFFENING NONLINEARITIES FOR DYNAMIC SIMULATIONS OF MULTIBODY SYSTEMS

2013 ◽  
Vol 13 (08) ◽  
pp. 1350046 ◽  
Author(s):  
FENGXIA WANG
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Reduction ◽  
Reduction Process ◽  
Flexible Multibody Dynamics ◽  
Element Model ◽  
Reduced Model ◽  
Matrix Operation ◽  
Reduced Models ◽  
Geometric Stiffening

This work investigates the implementation of nonlinear model reduction to flexible multibody dynamics. Linear elastic theory will lead to instability issues with rotating beam-like structures, due to the neglecting of the membrane-bending coupling on the beam cross-section. During the past decade, considerable efforts have been focused on the derivation of geometric nonlinear formulation based on nodal coordinates. In order to reduce the computation cost in flexible multibody dynamics, which is extremely important for complex large system simulations, modal reduction is usually implemented to a rotating flexible structure with geometric nonlinearities retained in the model. In this work, a standard model reduction process based on matrix operation is developed, and the essential geometric stiffening nonlinearities are retained in the reduced model. The time responses of a tip point on a rotating Euler–Bernoulli blade are calculated based on two nonlinear reduced models. The first reduced model is derived by the standard matrix operation from a full finite element model and the second reduced model is obtained via the Galerkin method. The matrix operation model reduction process is validated through the comparison of the simulation results obtained from these two different reduced models. An interesting phenomenon is observed in this work: In the nonlinear model, if only quadratic geometric stiffing term is retained, the two reduced models converge to the full finite element model with only one bending mode and two axial modes. While if both quadratic and cubic geometric stiffing terms are retained in the nonlinear equation, the modal-based reduced model will not converge to the finite element model unless all eigenmodes are retained, that is the reduced model has no degree of freedom reduction at all.

scholarly journals DIFFICULTÉS DU DÉMARCHE EXPÉRIMENTALE EN ÉDUCATION SCIENTIFIQUE / DIFFICULTIES OF THE EXPERIMENTAL PROCESS IN SCIENTIFIC EDUCATION

2021 ◽  
Vol 8 (2) ◽  
Author(s):  
Dimitri Nertivich
Keyword(s):  
Experimental Method ◽  
Experimental Approach ◽  
Scientific Education ◽  
Experimental Process ◽  
Method Approach ◽  
Teaching Situations ◽  
Méthode Expérimentale ◽  
The Way

<p>Cet article présente une série des réflexions et un exemple détaillé sur les difficultés du démarche expérimental dans de l’éducation scientifique. Après une discussion sur les obstacles et les difficultés qui s'opposent à l'appropriation de la démarche de la méthode expérimentale, ce travail touche la question de la démarche expérimentale pour la formation des ombres. Deux exemples typiques de situations d'enseignement sont utilisés et les difficultés tant au niveau conceptuel que procédural sont mises en évidence.</p><p> </p><p>This article presents a series of reflections and a detailed example of the difficulties of the experimental approach in scientific education. After a discussion on the obstacles and difficulties that stand in the way of appropriation of the experimental method approach, this work touches on the question of the experimental approach to the formation of shadows. Two typical examples of teaching situations are used and the difficulties at both the conceptual and procedural levels are highlighted.</p><p> </p><p><strong> Article visualizations:</strong></p><p><img src="/-counters-/edu_01/0720/a.php" alt="Hit counter" /></p>

Intrinsic Gettering of Iron in Czochralski Silicon Crystals

1992 ◽  
Vol 262 ◽  
Author(s):  
M. Aoki ◽  
A. Hara ◽  
A. Ohsawa
Keyword(s):  
Experimental Method ◽  
Annealing Time ◽  
Experimental Approach ◽  
Surface Contamination ◽  
Defect Region ◽  
Czochralski Silicon ◽  
Low Level ◽  
Arrhenius Relationship ◽  
Silicon Crystals ◽  
Fe Impurities

ABSTRACTWe present a new experimental approach to studying the mechanism of intrinsic gettering of Fe in Czochralski silicon crystals. We present our experimental method and results for as-grown and intrinsic gettered wafers with high and low-level Fe surface contamination. We found that when annealing at the Fe supersaturation temperature, Fe concentration decreases faster in intrinsic gettered wafers than in as-grown wafers. Concentration saturated with annealing time for each sample and the saturated Fe concentration followed a simple Arrhenius relationship. Re-emission of Fe from the bulk defect region occurred above the gettering temperature. We conclude that in intrinsic gettering, Fe precipitates preferentially in the bulk defect region when the Fe impurities supersaturate as temperature drops.

Randomized Control Trials in the Field of Development

2020 ◽  
Keyword(s):  
Experimental Method ◽  
Experimental Approach ◽  
Randomized Control Trials ◽  
Global Poverty ◽  
Narrow Scope ◽  
Randomized Control ◽  
To Come ◽  
Coherent Picture

In October 2019, Abhijit Banerjee, Esther Duflo, and Michael Kremer jointly won the 51st Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel "for their experimental approach to alleviating global poverty." But what is the exact scope of their experimental method, known as randomized control trials (RCTs)? Which sorts of questions are RCTs able to address and which do they fail to answer? This book provides answers to these questions, explaining how RCTs work, what they can achieve, why they sometimes fail, how they can be improved and why other methods are both useful and necessary. Chapters contributed by leading specialists in the field present a full and coherent picture of the main strengths and weaknesses of RCTs in the field of development. Looking beyond the epistemological, political, and ethical differences underlying many of the disagreements surrounding RCTs, it explores the implementation of RCTs on the ground, outside of their ideal theoretical conditions and reveals some unsuspected uses and effects, their disruptive potential, but also their political uses. The contributions uncover the implicit worldview that many RCTs draw on and disseminate, and probe the gap between the method's narrow scope and its success, while also proposing improvements and alternatives. This book warns against the potential dangers of their excessive use, arguing that the best use for RCTs is not necessarily that which immediately springs to mind, and offering opportunity to come to an informed and reasoned judgement on RCTs and what they can bring to development.

Experimentation, Innovation, and Economics

2020 ◽  
Vol 110 (7) ◽  
pp. 1974-1994
Author(s):  
Michael Kremer
Keyword(s):  
Experimental Method ◽  
Experimental Approach ◽  
Scientific Understanding ◽  
Causal Relationships ◽  
Rich Sense

The experimental method not only helps identify causal relationships, but also provides economists with a rich sense of context, focuses research on specific practical questions, stimulates collaboration with practitioners and specialists from other fields, and allows for rapid iteration. In this lecture, I present a series of examples illustrating how together these features make the experimental approach a powerful tool for advancing scientific understanding, informing policy, and promoting innovation. I then discuss how institutions can be designed to accelerate innovation and direct it toward the world’s most pressing needs. (JEL B31, C90, I10, O15, O30, O43)

Model reduction technique for mechanical behaviour modelling: Efficiency criteria and validity domain assessment

2008 ◽  
Vol 222 (3) ◽  
pp. 493-505 ◽  
Author(s):  
K Ordaz-Hernandez ◽  
X Fischer ◽  
F Bennis
Keyword(s):  
Neural Network ◽  
Model Reduction ◽  
Linear Model ◽  
Cantilever Beam ◽  
Reduction Technique ◽  
Reduced Model ◽  
Large Displacements ◽  
Large Deflections ◽  
Non Linear ◽  
Model Reduction Technique

The current paper presents the study of a neural network-based technique used to create fast, reduced, non-linear behavioural models. The studied approach is the use of artificial neural networks (ANNs) as a model reduction technique to create more efficient models, mostly in terms of computational speed. The test case is the deformation of a cantilever beam under large deflections (geometrical non-linearity). A reduced model is created by means of a multi-layer feed-forward neural network, a type of ANN reported as ‘universal approximator’ in the literature. Then it is compared with two finite-element models: linear (inaccurate for large deflections but fast) and non-linear (accurate but slow). Under large displacements, the reduced model approximates well the non-linear model while having similar speed to the linear model. Unfortunately, the resulting model presents a shortening of its validity domain, as being incapable of approximating the deformed configuration of the cantilever beam under small displacements. In other words, the ANN-based model provides a very good compromise between accuracy and speed within its validity domain, despite the low fidelity presented: accurate for large displacements but inaccurate for small displacements.

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