Role of FEA, Closed-Form, and Empirical Models in Certifying Aircraft Composite Structures

2016 ◽  
Author(s):  
Alex S. Selvarathinam ◽  
Carl Rousseau ◽  
Stephen P. Engelstad ◽  
Lori Flansburg
Keyword(s):  
Closed Form ◽  
Composite Structures ◽  
Empirical Models

scholarly journals Taking account of topography when calculating the resistance of the global atmospheric conductor

10.12737/6044 ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 104-108 ◽  
Author(s):  
Валерий Денисенко ◽  
Valery Denisenko ◽  
Олег Якубайлик ◽  
Oleg Yakubailik
Keyword(s):  
Large Scale ◽  
Electric Circuit ◽  
Empirical Models ◽  
Global Electric Circuit ◽  
Local Resistance ◽  
High Mountains ◽  
One Dimensional ◽  
Geodetic Coordinates ◽  
Dimensional Simulation

The role of topography in the formation of the global electric circuit is analyzed. The topography of the Earth’s surface is determined using the GLOBE data-base providing data on height of the Earth’s surface above mean sea level in geodetic coordinates with spatial resolution of 30 angular seconds. The atmosphere is considered as a global conductor between the Earth’s surface and the ionosphere simulated as ideal conductors. Empirical models of air conductivity are used. To simplify the description of large-scale phenomena, the model is reduced to one-dimensional simulation of vertical columns of air. The inclusion of topography is shown to reduce the resistance of the atmosphere by 10 % and to reduce the local resistance above high mountains several times. Note that taking topography into account is also important in more general models of electrical conductivity of the atmosphere.

scholarly journals The nth-Order Comprehensive Adjoint Sensitivity Analysis Methodology for Response-Coupled Forward/Adjoint Linear Systems (nth-CASAM-L): II. Illustrative Application

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8315
Author(s):  
Dan Gabriel Cacuci
Keyword(s):  
Sensitivity Analysis ◽  
Closed Form ◽  
Linear Systems ◽  
Predictive Modeling ◽  
Adjoint Sensitivity Analysis ◽  
Adjoint Sensitivity ◽  
Third Order ◽  
Analysis Methodology ◽  
Illustrative Application

This work illustrates the application of the nth-order comprehensive adjoint sensitivity analysis methodology for response-coupled forward/adjoint linear systems (abbreviated as “nth-CASAM-L”) to a paradigm model that describes the transmission of particles (neutrons and/or photons) through homogenized materials, as encountered in radiation protection and shielding. The first-, second-, and third-order sensitivities of responses that depend on both the forward and adjoint particle fluxes are obtained exactly, in closed-form, underscoring the principles and methodology underlying the nth-CASAM-L. The results presented in this work underscore the fundamentally important role of the nth-CASAM-L in the quest to overcome the “curse of dimensionality” in sensitivity analysis, uncertainty quantification and predictive modeling.

scholarly journals FlhA Undergoes Cyclic Open-close Domain Motions During Flagellar Protein Export in Salmonella

2021 ◽  
Author(s):  
Tohru Minamino ◽  
Yumi Inoue ◽  
Miki Kinoshita ◽  
Akio Kitao ◽  
Keiichi Namba
Keyword(s):  
Closed Form ◽  
Protein Transport ◽  
Building Blocks ◽  
Protein Export ◽  
Side Chain ◽  
Transport Activity ◽  
Flagellar Assembly ◽  
Flagellar Protein ◽  
Domain Motions

Abstract The flagellar type III secretion system (fT3SS) transports flagellar building blocks from the cytoplasm to the distal end of the growing flagellar structure. The C-terminal cytoplasmic domain of FlhA (FlhAC) serves as a docking platform for flagellar chaperones in complex with their cognate substrates and ensures the strict order of protein export for efficient flagellar assembly. FlhAC adopts open and closed conformations, and the chaperones bind to the open form, allowing the fT3SS to transport the substrates to the cell exterior. To clarify the role of the closed form in flagellar protein export, we isolated pseudorevertants from the flhA(G368C/K549C) mutant, in which the closed conformation is stabilized to inhibit the protein transport activity of the fT3SS. Each of M365I, R370S, A446E and P550S substitutions in FlhAC identified in the pseudorevertants affected hydrophobic side-chain interaction networks in the closed FlhAC structure, thereby restoring the protein transport activity to a considerable degree. We propose that a cyclic open-close domain motion of FlhAC is required for rapid and efficient flagellar protein export where a structural transition from the open to the closed form induces the dissociation of empty chaperones from FlhAC.

Stiffness-toughness balance in PP/EPDM/SiO2 ternary blend-nanocomposites: The role of microstructural evolution

2020 ◽  
Vol 55 (2) ◽  
pp. 265-275
Author(s):  
S Hajibabazadeh ◽  
MK Razavi Aghjeh ◽  
M Mehrabi Mazidi
Keyword(s):  
Microstructural Evolution ◽  
Composite Structures ◽  
Ternary Systems ◽  
Ternary Blend ◽  
Dispersed Particles ◽  
Stress Concentration Region ◽  
Dispersion State ◽  
Izod Impact ◽  
Blend Nanocomposites

The effect of microstructural evolution with hydrophilic-nanosilica (SiO2) concentration, ranging from 0 to 5 wt%, on mechanical properties and deformation micromechanisms of PP/EPDM/SiO2 (80/20/x) ternary blend-nanocomposites was investigated. Morphological observations revealed that, SiO2 nanoparticles tend to localize either around the dispersed EPDM particles or at the PP/EPDM interface, promoting the formation of three dimentional network-like EPDM/SiO2 composite structures dispersed in the PP matrix, especially at higher SiO2 loadings. This type of dispersion state was further confirmed by the rheological analysis. Synergistic toughening effect of soft EPDM particles and rigid SiO2 particles under Izod impact test was observed in these ternary systems, so that the materials with a better balance of stiffness/toughness were achieved. The results demonstrated that the extent of impact toughness increase is higher, where a large amount of the SiO2 nanoparticles surrounded the EPDM dispersed particles distributed in the PP matrix. This significant increase was attributed to the change in the size of stress concentration region and evolution of stress distribution throughout the material. The failure mechanisms were studied, and the underlying toughening micromechanisms were proposed.

Reliabilist Approach of Arched Tubes

1998 ◽  
Author(s):  
Hossein Shakourzadeh ◽  
Jean-Claude Djeni ◽  
Vincent Braibant ◽  
Pascal Patou
Keyword(s):  
Experimental Tests ◽  
Empirical Models ◽  
Spring Back ◽  
Second Stage

Abstract Understanding spring back for the arched tubes constitutes a major problem for every tube manufacturer. Even when the allowable fluctuations are limited to tenth of degrees, angular fluctuations of several degrees are usually observed. This indicates the importance of the problem. The aim of this study is to understand the role of materials in determining spring back characteristics of bent tubes. The first stage of the work thus consists in finding analytical, semi-analytical, numerical or even empirical models in order to formulate the spring back. These models are then validated by experimental tests. In second stage, an analysis of sensitivity is carried out in order to determine the influence of various parameters like the geometry, the process or material.

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