Fast and accurate nonlinear hyper‐elastic deformation with a posteriori numerical verification of the convergence of solution: Application to the simulation of liver deformation

2021 ◽  
Author(s):  
Farah Saidi ◽  
Abed Malti
Keyword(s):  
Elastic Deformation ◽  
Numerical Verification ◽  
A Posteriori ◽  
Hyper Elastic ◽  
Convergence Of Solution

Practical Correction of Three Fold Astigmatism in the Philips CM TEM

1996 ◽  
Vol 54 ◽  
pp. 418-419
Author(s):  
Arno J. Bleeker ◽  
Mark H.F. Overwijk ◽  
Max T. Otten
Keyword(s):  
Optical Properties ◽  
Phase Contrast ◽  
The Other ◽  
Objective Lens ◽  
Symmetric Part ◽  
A Posteriori ◽  
Contrast Transfer Function ◽  
High Brightness ◽  
Rotationally Symmetric ◽  
Brightness Field

With the improvement of the optical properties of the modern TEM objective lenses the point resolution is pushed beyond 0.2 nm. The objective lens of the CM300 UltraTwin combines a Cs of 0. 65 mm with a Cc of 1.4 mm. At 300 kV this results in a point resolution of 0.17 nm. Together with a high-brightness field-emission gun with an energy spread of 0.8 eV the information limit is pushed down to 0.1 nm. The rotationally symmetric part of the phase contrast transfer function (pctf), whose first zero at Scherzer focus determines the point resolution, is mainly determined by the Cs and defocus. Apart from the rotationally symmetric part there is also the non-rotationally symmetric part of the pctf. Here the main contributors are not only two-fold astigmatism and beam tilt but also three-fold astigmatism. The two-fold astigmatism together with the beam tilt can be corrected in a straight-forward way using the coma-free alignment and the objective stigmator. However, this only works well when the coefficient of three-fold astigmatism is negligible compared to the other aberration coefficients. Unfortunately this is not generally the case with the modern high-resolution objective lenses. Measurements done at a CM300 SuperTwin FEG showed a three fold-astigmatism of 1100 nm which is consistent with measurements done by others. A three-fold astigmatism of 1000 nm already sinificantly influences the image at a spatial frequency corresponding to 0.2 nm which is even above the point resolution of the objective lens. In principle it is possible to correct for the three-fold astigmatism a posteriori when through-focus series are taken or when off-axis holography is employed. This is, however not possible for single images. The only possibility is then to correct for the three-fold astigmatism in the microscope by the addition of a hexapole corrector near the objective lens.

Expected A Posteriori Estimation of Multiple Latent Traits

2005 ◽  
Author(s):  
Damon U. Bryant ◽  
Ashley K. Smith ◽  
Sandra G. Alexander ◽  
Kathlea Vaughn ◽  
Kristophor G. Canali
Keyword(s):  
A Posteriori ◽  
Latent Traits ◽  
Posteriori Estimation

Tire Rolling Kinematics Model for an Intelligent Tire Based on an Accelerometer

2020 ◽  
Vol 48 (4) ◽  
pp. 287-314
Author(s):  
Yan Wang ◽  
Zhe Liu ◽  
Michael Kaliske ◽  
Yintao Wei
Keyword(s):  
Elastic Deformation ◽  
Estimation Algorithm ◽  
Force Sensor ◽  
Euler Method ◽  
Rolling Contact ◽  
Body Motion ◽  
Identification Algorithm ◽  
Active Perception ◽  
Kinematics Model ◽  
Ring Model

ABSTRACT The idea of intelligent tires is to develop a tire into an active perception component or a force sensor with an embedded microsensor, such as an accelerometer. A tire rolling kinematics model is necessary to link the acceleration measured with the tire body elastic deformation, based on which the tire forces can be identified. Although intelligent tires have attracted wide interest in recent years, a theoretical model for the rolling kinematics of acceleration fields is still lacking. Therefore, this paper focuses on an explicit formulation for the tire rolling kinematics of acceleration, thereby providing a foundation for the force identification algorithms for an accelerometer-based intelligent tire. The Lagrange–Euler method is used to describe the acceleration field and contact deformation of rolling contact structures. Then, the three-axis acceleration vectors can be expressed by coupling rigid body motion and elastic deformation. To obtain an analytical expression of the full tire deformation, a three-dimensional tire ring model is solved with the tire–road deformation as boundary conditions. After parameterizing the ring model for a radial tire, the developed method is applied and validated by comparing the calculated three-axis accelerations with those measured by the accelerometer. Based on the features of acceleration, especially the distinct peak values corresponding to the tire leading and trailing edges, an intelligent tire identification algorithm is established to predict the tire–road contact length and tire vertical load. A simulation and experiments are conducted to verify the accuracy of the estimation algorithm, the results of which demonstrate good agreement. The proposed model provides a solid theoretical foundation for an acceleration-based intelligent tire.

Características Psicométricas de uma Avaliação de Matemática

2020 ◽  
Vol 7 (3) ◽  
pp. 1-27
Author(s):  
Denilson Junio Marques Soares ◽  
Paulo César Emiliano ◽  
Talita Emidio Andrade Soares
Keyword(s):  
A Posteriori

O Departamento de Matemática da Universidade Federal de Viçosa tem realizado algumas medidas de prevenção à reprovação dos estudantes na disciplina de Cálculo, cujos índices têm assustado os professores. Uma dessas medidas está na elaboração de avaliações de matemática básica que objetivam identificar estudantes propensos à reprovação, a fim de proporcionar uma intervenção pedagógica capaz de reverter esta situação. Tendo em vista a importância desta avaliação como parte integrante dos processos de ensino e aprendizagem da disciplina, o presente artigo tem como objetivo oferecer uma análise estatística, pautada nas duas vertentes da Psicometria moderna: a Teoria Clássica dos Testes (TCT) e a Teoria de Resposta ao Item (TRI), e uma análise pedagógica dos descritores e distratores de alguns itens-chave que compõem uma dessas avaliações, escolhida para um estudo de caso. Os resultados apontaram para uma avaliação composta por itens com variados índices de dificuldade e, no geral, com bom poder discriminativo tanto pela análise via TCT, quanto pela TRI, cujos resultados foram obtidos através da estimação, pelo método da média a posteriori, de um modelo logístico de dois parâmetros. A consistência interna da avaliação como instrumento de mensuração de habilidades foi verificada pelo coeficiente alpha de Cronbach, assegurando a qualidade e confiabilidade dos resultados deste estudo. Espera-se que este trabalho sirva como um instrumento de difusão das teorias psicométricas na análise da estrutura de avaliações e aponte para a necessidade de uma maior discussão pedagógica acerca das possíveis lacunas existentes na aprendizagem de matemática básica dos estudantes do ensino superior.

The study of the elastic deformation of a flexible wheel by a cam wave generator

2020 ◽  
Vol 65 (1) ◽  
pp. 51-58
Author(s):  
Sava Ianici
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Finite Element ◽  
Elastic Deformation ◽  
Theoretical Study ◽  
Elastic Field ◽  
The Finite Element Method ◽  
Elastic Deformations ◽  
Wave Generator ◽  
Two Stages

The paper presents the results of research on the study of the elastic deformation of a flexible wheel from a double harmonic transmission, under the action of a cam wave generator. Knowing exactly how the flexible wheel is deformed is important in correctly establishing the geometric parameters of the wheels teeth, allowing a better understanding and appreciation of the specific conditions of harmonic gearings in the two stages of the transmission. The veracity of the results of this theoretical study on the calculation of elastic deformations and displacements of points located on the average fiber of the flexible wheel was subsequently verified and confirmed by numerical simulation of the flexible wheel, in the elastic field, using the finite element method from SolidWorks Simulation.

Sign in / Sign up

Export Citation Format

Share Document