scholarly journals Mixing Hetero- and Homogeneous Models in Weighted Ensembles

2019 ◽  
pp. 129-136
Author(s):  
James Large ◽  
Anthony Bagnall
Keyword(s):  
Homogeneous Models

An homogeneous growth model of gallium arsenide epitaxial layers from the gas phase

1989 ◽  
Vol 54 (11) ◽  
pp. 2933-2950
Author(s):  
Emerich Erdös ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma
Keyword(s):  
Experimental Data ◽  
Gallium Arsenide ◽  
Kinetic Study ◽  
Gas Phase ◽  
Growth Model ◽  
Epitaxial Layers ◽  
Inhomogeneous Model ◽  
Homogeneous Models ◽  
Active Centres

This paper represents a continuation and ending of the kinetic study of the gallium arsenide formation, where a so-called inhomogeneous model is proposed and quantitatively formulated in five variants, in which two kinds of active centres appear. This model is compared both with the experimental data and with the previous sequence of homogeneous models.

Dynamics of fracture. Homogeneous models

2014 ◽  
pp. 205-231
Author(s):  
Agustin Udias ◽  
Raul Madariaga ◽  
Elisa Buforn
Keyword(s):  
Homogeneous Models

scholarly journals Real-time simulation of large-scale HTS systems: multi-scale and homogeneous models using the T–A formulation

2019 ◽  
Vol 32 (6) ◽  
pp. 065003 ◽  
Author(s):  
Edgar Berrospe-Juarez ◽  
Víctor M R Zermeño ◽  
Frederic Trillaud ◽  
Francesco Grilli
Keyword(s):  
Real Time ◽  
Large Scale ◽  
Real Time Simulation ◽  
Multi Scale ◽  
Time Simulation ◽  
Homogeneous Models

scholarly journals Intima heterogeneity in stress assessment of atherosclerotic plaques

2017 ◽  
Vol 8 (1) ◽  
pp. 20170008 ◽  
Author(s):  
Ali C. Akyildiz ◽  
Lambert Speelman ◽  
Bas van Velzen ◽  
Raoul R. F. Stevens ◽  
Antonius F. W. van der Steen ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Plaque Rupture ◽  
Homogeneous Model ◽  
Sensitivity Analyses ◽  
Homogeneous Material ◽  
Sensitivity Index ◽  
Stress Assessment ◽  
Heterogeneous Models ◽  
Homogeneous Models ◽  
Accuracy Stress

Atherosclerotic plaque rupture is recognized as the primary cause of cardiac and cerebral ischaemic events. High structural plaque stresses have been shown to strongly correlate with plaque rupture. Plaque stresses can be computed with finite-element (FE) models. Current FE models employ homogeneous material properties for the heterogeneous atherosclerotic intima. This study aimed to evaluate the influence of intima heterogeneity on plaque stress computations. Two-dimensional FE models with homogeneous and heterogeneous intima were constructed from histological images of atherosclerotic human coronaries ( n = 12). For homogeneous models, a single stiffness value was employed for the entire intima. For heterogeneous models, the intima was subdivided into four clusters based on the histological information and different stiffness values were assigned to the clusters. To cover the reported local intima stiffness range, 100 cluster stiffness combinations were simulated. Peak cap stresses (PCSs) from the homogeneous and heterogeneous models were analysed and compared. By using a global variance-based sensitivity analysis, the influence of the cluster stiffnesses on the PCS variation in the heterogeneous intima models was determined. Per plaque, the median PCS values of the heterogeneous models ranged from 27 to 160 kPa, and the PCS range varied between 43 and 218 kPa. On average, the homogeneous model PCS values differed from the median PCS values of heterogeneous models by 14%. A positive correlation ( R 2 = 0.72) was found between the homogeneous model PCS and the PCS range of the heterogeneous models. Sensitivity analysis showed that the highest main sensitivity index per plaque ranged from 0.26 to 0.83, and the average was 0.47. Intima heterogeneity resulted in substantial changes in PCS, warranting stress analyses with heterogeneous intima properties for plaque-specific, high accuracy stress assessment. Yet, computations with homogeneous intima assumption are still valuable to perform sensitivity analyses or parametric studies for testing the effect of plaque geometry on PCS. Moreover, homogeneous intima models can help identify low PCS, stable type plaques with thick caps. Yet, for thin cap plaques, accurate stiffness measurements of the clusters in the cap and stress analysis with heterogeneous cap properties are required to characterize the plaque stability.

scholarly journals The Geometry of Marked Contact Engel Structures

2020 ◽  
Author(s):  
Gianni Manno ◽  
Paweł Nurowski ◽  
Katja Sagerschnig
Keyword(s):  
Local Geometry ◽  
Dimensional Manifold ◽  
Twisted Cubic ◽  
Homogeneous Models ◽  
Local Invariants ◽  
Twisted Cubics ◽  
Cubic Structure ◽  
Contact Distribution ◽  
Engel Structures ◽  
Engel Structure

AbstractA contact twisted cubic structure$$({\mathcal M},\mathcal {C},{\varvec{\upgamma }})$$ ( M , C , γ ) is a 5-dimensional manifold $${\mathcal M}$$ M together with a contact distribution $$\mathcal {C}$$ C and a bundle of twisted cubics $${\varvec{\upgamma }}\subset \mathbb {P}(\mathcal {C})$$ γ ⊂ P ( C ) compatible with the conformal symplectic form on $$\mathcal {C}$$ C . The simplest contact twisted cubic structure is referred to as the contact Engel structure; its symmetry group is the exceptional group $$\mathrm {G}_2$$ G 2 . In the present paper we equip the contact Engel structure with a smooth section $$\sigma : {\mathcal M}\rightarrow {\varvec{\upgamma }}$$ σ : M → γ , which “marks” a point in each fibre $${\varvec{\upgamma }}_x$$ γ x . We study the local geometry of the resulting structures $$({\mathcal M},\mathcal {C},{\varvec{\upgamma }}, \sigma )$$ ( M , C , γ , σ ) , which we call marked contact Engel structures. Equivalently, our study can be viewed as a study of foliations of $${\mathcal M}$$ M by curves whose tangent directions are everywhere contained in $${\varvec{\upgamma }}$$ γ . We provide a complete set of local invariants of marked contact Engel structures, we classify all homogeneous models with symmetry groups of dimension $$\ge 6$$ ≥ 6 up to local equivalence, and we prove an analogue of the classical Kerr theorem from Relativity.

An Assessment of Computational Fluid Dynamics Cavitation Models Using Bubble Growth Theory and Bubble Transport Modeling

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Michael P. Kinzel ◽  
Jules W. Lindau ◽  
Robert F. Kunz
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Analytic Solutions ◽  
Cfd Modeling ◽  
Computational Time ◽  
Cavitation Model ◽  
Modeling Framework ◽  
Homogeneous Models ◽  
Bubble Transport ◽  
Computational Fluid Dynamics Cfd

This effort investigates advancing cavitation modeling relevant to computational fluid dynamics (CFD) through two strategies. The first aims to reformulate the cavitation models and the second explores adding liquid–vapor slippage effects. The first aspect of the paper revisits cavitation model formulations with respect to the Rayleigh–Plesset equation (RPE). The present approach reformulates the cavitation model using analytic solutions to the RPE. The benefit of this reformulation is displayed by maintaining model sensitivities similar to RPE, whereas the standard models fail these tests. In addition, the model approach is extended beyond standard homogeneous models, to a two-fluid modeling framework that explicitly models the slippage between cavitation bubbles and the liquid. The results indicate a significant impact of slip on the predicted cavitation solution, suggesting that the inclusion of such modeling can potentially improve CFD cavitation models. Overall, the results of this effort point to various aspects that may be considered in future CFD-modeling efforts with the goal of improving the model accuracy and reducing computational time.

scholarly journals Homogeneous models and almost decidability

1989 ◽  
Vol 46 (3) ◽  
pp. 343-355 ◽  
Author(s):  
Terry Millar
Keyword(s):  
Elementary Theory ◽  
Homogeneous Model ◽  
Point Of View ◽  
Type Spectrum ◽  
Homogeneous Models ◽  
Theoretic Point

AbstractCountable homogeneous models are ‘simple’ objects from a model theoretic point of view. From a recursion theoretic point of view they can be complex. For instance the elementary theory of such a model might be undecidable, or the set of complete types might be recursively complex. Unfortunately even if neither of these conditions holds, such a model still can be undecidable. This paper investigates countable homogeneous models with respect to a weaker notion of decidability called almost decidable. It is shown that for theories that have only countably many type spectra, any countable homogeneous model of such a theory that has a Σ2 type spectrum is almost decidable.

scholarly journals Influence of the Stellar Winds on the Evolution of the Planetary Nebula Nuclei

1993 ◽  
Vol 155 ◽  
pp. 483-483
Author(s):  
S.K. Górny
Keyword(s):  
Mass Loss ◽  
Planetary Nebula ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Stellar Winds ◽  
Hydrogen Burning ◽  
Wind Theory ◽  
Homogeneous Models ◽  
Image Position ◽  
Zero Points

A grid of homogeneous models of evolution of hydrogen burning planetary nebulae nuclei, assuming different stellar winds and the zero points for the post-AGB evolution, have been constructed from original Schönberners tracks. Following a simplified line-driven wind theory the mass loss rate has been adopted to be

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