The Primary Bilayer Ruga-Phase Diagram II: Irreversibility in Ruga Evolution

2016 ◽  
Vol 83 (9) ◽  
Author(s):  
R. Zhao ◽  
M. Diab ◽  
K.-S. Kim
Keyword(s):  
Phase Diagram ◽  
Large Strain ◽  
Small Strain ◽  
Mode Locking ◽  
Practical Applications ◽  
Underlying Mechanisms ◽  
Mode Transitions ◽  
Film Substrate ◽  
Surface Morphologies ◽  
Strain Mismatch

When an elastic thin-film/substrate bilayer is cyclically compressed with a large plane-strain stroke, various surface morphologies develop either reversibly or irreversibly with cyclic hysteresis. Here, we examine the cyclic morphology evolution with extensive finite-element analyses and present a generic irreversibility map on the primary bilayer Ruga-phase diagram (PB-RPD). The term “PB” refers to a system of a film on a substrate, both of which are incompressible neo-Hookean, while the term “Ruga-phase” refers to the classification of corrugated surface morphologies. Our generic map reveals two configurational irreversibility types of Ruga-phases during a loading and unloading cycle. One, localization irreversibility, is caused by unstable crease localization and the other, modal irreversibility, by unstable mode transitions of wrinkle-Ruga configurations. While the instability of crease localization depends mainly on smoothness of the creasing surface or interface, the instability of Ruga-mode transition is sensitive to film/substrate stiffness ratio, film/substrate strain mismatch (εps), and material viscosity of the bilayer. For small strain mismatches (εps ≲ 0.5), PB Ruga structures are ordered; otherwise, for large strain mismatches, the Ruga structures can evolve to ridge configurations. For evolution of ordered Ruga phases, the configurational irreversibility leads to shake-down or divergence of cyclic hysteresis. Underlying mechanisms of the cyclic hysteresis are found to be the unstable Ruga-phase transitions of mode-period multiplications in the loading cycle, followed by either mode “locking” or primary-period “switching” in the unloading cycle. In addition, we found that the primary-period switching is promoted by the strain mismatch and material viscosity. These results indicate that various Ruga configurations can be excited, and thus, diverse Ruga-phases can coexist, under cyclic loading. Our irreversibility map will be useful in controlling reversibility as well as uniformity of Ruga configurations in many practical applications.

Properties of Yttrium Oxide Thin Films on Silicon (100) Prepared by Evaporation of Yttrium in Atomic Oxygen

1994 ◽  
Vol 341 ◽  
Author(s):  
J. Hudner ◽  
H. Ohlsén ◽  
E. Fredriksson
Keyword(s):  
Atomic Oxygen ◽  
Oxygen Plasma ◽  
Rutherford Backscattering Spectrometry ◽  
Thin Layers ◽  
Force Microscopy ◽  
Intermediate Layers ◽  
Activated Reactive Evaporation ◽  
Film Substrate ◽  
Surface Morphologies ◽  
Substrate Temperatures

AbstractThin layers of Y2O3 have been prepared on silicon (100) by an activated reactive evaporation process involving evaporation of metal Y in an atomic oxygen plasma. The presence of the oxygen plasma was found to be crucial for the formation of homogeneous Y2O3 films on Si. The formation of Y2O3 films on Si (100) at different substrate temperatures was investigated. X-ray diffraction analysis showed that Y2O3 films formed between 300 °C and 650 °C were (111) textured while Y2O3 prepared at lower substrate temperatures (80 °C) exhibited mixed orientations. Rutherford backscattering spectrometry indicated that films were stoichiometric. No pronounced channeling was observed in films grown at 350 °C, suggesting polycrystalline film structures. Atomic force microscopy revealed very smooth surface morphologies with average surface roughness < 20 Å for films 700 Å thick deposited at 350 °C. Secondary ion mass spectroscopy indicated the abundance of intermediate layers in the film-substrate interface.

The Further Exploration of Applying Small-Strain and Large-Strain Formulations to SMA

2012 ◽  
Vol 529 ◽  
pp. 228-235
Author(s):  
Jie Yao ◽  
Yong Hong Zhu
Keyword(s):  
Phase Transformation ◽  
Constitutive Model ◽  
Uniaxial Tension ◽  
Driving Force ◽  
Research Team ◽  
Large Strain ◽  
Small Deformation ◽  
Small Strain ◽  
Proportional Loading ◽  
The Difference

Recently, our research team has been considering to applying shape memory alloys (SMA) constitutive model to analyze the large and small deformation about the SMA materials because of the thermo-dynamics and phase transformation driving force. Accordingly, our team use simulations method to illustrate the characteristics of the model in large strain deformation and small strain deformation when different loading, uniaxial tension, and shear conditions involve in the situations. Furthermore, the simulation result unveils that the difference is nuance concerning the two method based on the uniaxial tension case, while the large deformation and the small deformation results have huge difference based on shear deformation case. This research gives the way to the further research about the constitutive model of SMA, especially in the multitiaxial non-proportional loading aspects.

A Zebrafish Embryo Behaves both as a “Cortical Shell – Liquid Core” Structure and a Homogeneous Solid when Experiencing Mechanical Forces

2014 ◽  
Vol 20 (6) ◽  
pp. 1841-1847 ◽  
Author(s):  
Fei Liu ◽  
Dan Wu ◽  
Ken Chen
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Zebrafish Embryo ◽  
Large Strain ◽  
Liquid Core ◽  
Small Strain ◽  
Core Structure ◽  
Mechanical Forces ◽  
Cortical Shell ◽  
A Cell

AbstractMechanical properties are vital for living cells, and various models have been developed to study the mechanical behavior of cells. However, there is debate regarding whether a cell behaves more similarly to a “cortical shell – liquid core” structure (membrane-like) or a homogeneous solid (cytoskeleton-like) when experiencing stress by mechanical forces. Unlike most experimental methods, which concern the small-strain deformation of a cell, we focused on the mechanical behavior of a cell undergoing small to large strain by conducting microinjection experiments on zebrafish embryo cells. The power law with order of 1.5 between the injection force and the injection distance indicates that the cell behaves as a homogenous solid at small-strain deformation. The linear relation between the rupture force and the microinjector radius suggests that the embryo behaves as membrane-like when subjected to large-strain deformation. We also discuss the possible reasons causing the debate by analyzing the mechanical properties of F-actin filaments.

scholarly journals An Adaptive Operation Strategy for Voltage Stability Enhancement in DMFCs

2018 ◽  
Author(s):  
Qinwen Yang ◽  
Xu-Qu Hu ◽  
Ying Zhu ◽  
Xiu-Cheng Lei ◽  
Xing-Yi Wang
Keyword(s):  
Voltage Stability ◽  
Optimization Method ◽  
Operation Strategy ◽  
Practical Applications ◽  
Operating Current ◽  
Voltage Stability Enhancement ◽  
Voltage Deviation ◽  
Adaptive Operation ◽  
Underlying Mechanisms ◽  
Stability Enhancement

An adaptive operation strategy for on-demand control of DMFC system is proposed as an alternative method to enhance the voltage stability. Based on a single-cell DMFC stack, a newly simplified semi-empirical model is developed from the uniform-designed experimental results to describe the I-V relationship. Integrated with this model, the multi-objective optimization method is utilized to develop an adaptive operation strategy. Although the voltage instability is frequently encountered in unoptimized operations, the voltage deviation is successfully decreased to a required level by adaptive operations with operational adjustments. Moreover, the adaptive operations are also found to be able to extend the range of operating current density or to decrease the voltage deviation according to ones requirements. Numerical simulations are implemented to investigate the underlying mechanisms of the proposed adaptive operation strategy, and experimental adaptive operations are also performed on another DMFC system to validate the adaptive operation strategy. Preliminary experimental study shows a rapid response of DMFC system to the operational adjustment, which further validates the effectiveness and feasibility of the adaptive operation strategy in practical applications. The proposed strategy contributes to a guideline for the better control of output voltage from operating DMFC systems.

scholarly journals Tilt and strain change during the explosion at Minami-dake, Sakurajima, on November 13, 2017

2021 ◽  
Author(s):  
Kohei Hotta ◽  
Masato Iguchi
Keyword(s):  
Ground Deformation ◽  
Large Strain ◽  
Phase 1 ◽  
Small Strain ◽  
Phase 2 ◽  
The North ◽  
Strombolian Eruption ◽  
Strain Change ◽  
Tilt Change

Abstract We herein propose an alternative model for deformation caused by an eruption at Sakurajima, which have been previously interpreted as being due to a Mogi-type spherical point source beneath Minami-dake. On November 13, 2017, a large explosion with a plume height of 4,200 m occurred at Minami-dake. During the three minutes following the onset of the explosion (November 13, 2017, 22:07–22:10 (Japan standard time (UTC+9); the same hereinafter), phase 1, a large strain change was detected at the Arimura observation tunnel (AVOT) located approximately 2.1 km southeast from the Minami-dake crater. After the peak of the explosion (November 13, 2017, 22:10–24:00), phase 2, a large deflation was detected at every monitoring station due to the continuous Strombolian eruption. Subsidence toward Minami-dake was detected at five out of six stations whereas subsidence toward the north of Sakurajima was detected at the newly installed Komen observation tunnel (KMT), located approximately 4.0 km northeast from the Minami-dake crater. The large strain change at AVOT as well as small tilt changes of all stations and small strain changes at HVOT and KMT during phase 1 can be explained by a very shallow deflation source beneath Minami-dake at 0.1 km below sea level (bsl). For phase 2, a deeper deflation source beneath Minami-dake at a depth of 3.3 km bsl was found in addition to the shallow source beneath Minami-dake which turned inflation after the deflation obtained during phase 1. However, this model cannot explain the tilt change of KMT. Adding a spherical deflation source beneath Kita-dake at a depth of 3.2 km bsl can explain the tilt and strain change at KMT and the other stations. The Kita-dake source was also found in a previous study of long-term ground deformation. Not only the deeper Minami-dake source MD but also the Kita-dake source deflated due to the Minami-dake explosion.

scholarly journals Elastic Properties of Magnetorheological Elastomers in a Heterogeneous Uniaxial Magnetic Field

2018 ◽  
Vol 19 (10) ◽  
pp. 3045 ◽  
Author(s):  
Takehito Kikuchi ◽  
Yusuke Kobayashi ◽  
Mika Kawai ◽  
Tetsu Mitsumata
Keyword(s):  
Magnetic Field ◽  
Elastic Properties ◽  
Uniform Magnetic Field ◽  
Large Strain ◽  
Small Strain ◽  
Experimental Results ◽  
The Other ◽  
Magnetorheological Elastomers ◽  
Other Hand ◽  
Strain Model

Magnetorheological elastomers (MREs) are stimulus-responsive soft materials that consist of polymeric matrices and magnetic particles. In this study, large-strain response of MREs with 5 vol % of carbonyl iron (CI) particles is experimentally characterized for two different conditions: (1) shear deformation in a uniform magnetic field; and (2), compression in a heterogeneous uniaxial magnetic field. For condition (1), dynamic viscoelastic measurements were performed using a rheometer with a rotor disc and an electric magnet that generated a uniform magnetic field on disc-like material samples. For condition (2), on the other hand, three permanent magnets with different surface flux densities were used to generate a heterogeneous uniaxial magnetic field under cylindrical material samples. The experimental results were mathematically modeled, and the relationship between them was investigated. We also used finite-element method (FEM) software to estimate the uniaxial distributions of the magnetic field in the analyzed MREs for condition (2), and developed mathematical models to describe these phenomena. By using these practicable techniques, we established a simple macroscale model of the elastic properties of MREs under simple compression. We estimated the elastic properties of MREs in the small-strain regime (neo–Hookean model) and in the large-strain regime (Mooney–Rivlin model). The small-strain model explains the experimental results for strains under 5%. On the other hand, the large-strain model explains the experimental results for strains above 10%.

Investigation of Small- to Large-Strain Moduli Correlations of Rockfill Materials – Application to Romaine-2 Dam

2021 ◽  
Author(s):  
Ibrahim Lashin ◽  
Michael Ghali ◽  
Marc Smith ◽  
Daniel Verret ◽  
Mourad Karray
Keyword(s):  
Large Strain ◽  
Deformation Behaviour ◽  
Numerical Data ◽  
Small Strain ◽  
Hyperbolic Model ◽  
Large Strains ◽  
Initial Modulus ◽  
Rockfill Materials ◽  
Materials Used

Establishment of a relationship between the shear wave velocity (Vs) and other geotechnical parameters of rockfill soils at large strains (oedometer modulus, Moedo, tangent modulus, Et) is considered a significant step towards more precise modelling of earth-structure deformation behaviour. In this study, four samples of different gradations, reconstituted from the rockfill materials used in the construction of the Romaine-2 dam, were experimented to correlate the small strain to large strain moduli. Development of Moedo and Vs with consolidation was measured in the laboratory using the piezoelectric ring-actuator technique (P-RAT) incorporated in a large oedometer. Therefore, a correlation between Moedo and small strain shear modulus Go was proposed. Moreover, numerical simulations were performed based on the Duncan-Chang hyperbolic model to correlate the Vs to Duncan-Chang initial modulus(Ei). Based on the experimental and numerical data, a relation between Ei and Vs of the tested rockfill has been established. Verification studies were also carried out on in-situ measurements during Romaine-2 dam construction, proofing the ability of the proposed relationships to predict Ei related to the minor principal stress (σ3) from in-situ Vs measurement. The proposed correlations could help the geotechnical designers to estimate accurately the deformation of rockfill materials from in-situ Vs measurement.

How to Represent the World

2008 ◽  
pp. 214-257
Author(s):  
Azamat Abdoullaev
Keyword(s):  
Information Exchange ◽  
World Knowledge ◽  
Lexical Resources ◽  
Practical Applications ◽  
The World ◽  
Computer Scientists ◽  
Application Potential ◽  
Global Language ◽  
Underlying Mechanisms ◽  
Machine Readable

As far as human knowledge about the world is commonly given in NL expressions and as far as universal ontology is a general science of the world, the examination of its impact on natural language science and technology is among the central topics of many academic workshops and conferences. Ontologists, knowledge engineers, lexicographers, lexical semanticists, and computer scientists are attempting to integrate top-level entity classes with language knowledge presented in extensive corpora and electronic lexical resources. Such a deep quest is mostly motivated by high application potential of reality-driven models of language for knowledge communication and management, information retrieval and extraction, information exchange in software and dialogue systems, all with an ultimate view to transform the World Wide Web into a machine-readable global language resource of world knowledge, the Onto-Semantic Web. One of the practical applications of integrative ontological framework is to discover the underlying mechanisms of representing and processing language content and meaning by cognitive agents, human and artificial. Specifically, to provide the formalized algorithms or rules, whereby machines could derive or attach significance (or signification) from coded signals, both natural signs obtained by sensors and linguistic symbols.

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