Temperature Evolution During Plane Strain Compression Of Tertiary Oxide Scale On Steel

NASA Astrophysics Data System (ADS)

Suarez, L.; Vanden Eynde, X.; Lamberigts, M.; Houbaert, Y.

2007-04-01

An oxide scale layer always forms at the steel surface during hot rolling. This scale layer separates the work roll from the metal substrate. Understanding the deformation behaviour and mechanical properties of the scale is of great interest because it affects the frictional conditions during hot rolling and the heat-transfer behaviour at the strip-roll interface. A thin wustite scale layer (<20 μm) was created under controlled conditions in an original laboratory device adequately positioned in a compression testing machine to investigate plane strain compression. Oxidation tests were performed on an ULC steel grade. After the oxide growth at 1050°C, plane strain compression (PSC) was performed immediately to simulate the hot rolling process. PSC experiments were performed at a deformation temperature of 1050°C, with reduction ratios from 5 to 70%, and strain rates of 10s-1 under controlled gas atmospheres. Results show that for wustite, ductility is obvious at 1050°C. Even after deformation oxide layers exhibit good adhesion to the substrate and homogeneity over the thickness. The tool/sample temperature difference seems to be the reason for the unexpected ductile behaviour of the scale layer.

Bonded half planes containing an arbitrarily oriented crack

NASA Technical Reports Server (NTRS)

Erdogan, F.; Aksogan, O.

1973-01-01

The plane elastostatic problem for two bonded half planes containing an arbitrarily oriented crack in the neighborhood of the interface is considered. Using Mellin transforms, the problem is formulated as a system of singular integral equations. The equations are solved for various crack orientations, material combinations, and external loads. The numerical results given include the stress intensity factors, tHe strain energy release rates, and tHe probable cleavage angles giving the direction of crack propagation.

Activating and optimizing MoS 2 basal planes for hydrogen evolution through the formation of strained sulphur vacancies

DOE PAGES

Li, Hong; Tsai, Charlie; Koh, Ai Leen; ...

2015-11-09

As a promising non-precious catalyst for the hydrogen evolution reaction, molybdenum disulphide (MoS 2) is known to contain active edge sites and an inert basal plane. Activating the MoS 2 basal plane could further enhance its HER activity but is not often a strategy for doing so. Herein, we report the first activation and optimization of the basal plane of monolayer 2H-MoS 2 for HER by introducing sulphur (S) vacancies and strain. Our theoretical and experimental results show that the S-vacancies are new catalytic sites in the basal plane, where gap states around the Fermi level allow hydrogen to bindmore » directly to exposed Mo atoms. The hydrogen adsorption free energy (ΔG H) can be further manipulated by straining the surface with S-vacancies, which fine-tunes the catalytic activity. Furthermore, proper combinations of S-vacancy and strain yield the optimal ΔG H = 0 eV, which allows us to achieve the highest intrinsic HER activity among molybdenum-sulphide-based catalysts.« less

Steinhaus’ Geometric Location Problem for Random Samples in the Plane.

DTIC Science & Technology

1982-05-11

NAL 411R A1, ’I 7 - I STEINHAUS ’ GEOMETRIC LOCATION PROBLEM FOR RANDOM SAMPLES IN THE PLANE By Dorit Hochbaum and J. Michael Steele TECHNICAL REPORT...DEPARTMENT OF STATISTICS -Dltrib’ytion/ STANFORD UNIVERSITY A-I.abilty Codes STANFORD, CALIFORNIA Dist Spciat ecial Steinhaus ’ Geometric Location Problem for...Random Samples in the Plane By Dorit Hochbaum and J. Michael Steele I. Introduction. The work of H. Steinhaus U wf94 as apparently the first explicit

In-Plane Heterostructures Enable Internal Stress Assisted Strain Engineering in 2D Materials.

PubMed

Liu, Feng; Wang, Tzu-Chiang; Tang, Qiheng

2018-04-01

Conventional methods to induce strain in 2D materials can hardly catch up with the sharp increase in requirements to design specific strain forms, such as the pseudomagnetic field proposed in graphene, funnel effect of excitons in MoS 2 , and also the inverse funnel effect reported in black phosphorus. Therefore, a long-standing challenge in 2D materials strain engineering is to find a feasible scheme that can be used to design given strain forms. In this article, combining the ability of experimentally synthetizing in-plane heterostructures and elegant Eshelby inclusion theory, the possibility of designing strain fields in 2D materials to manipulate physical properties, which is called internal stress assisted strain engineering, is theoretically demonstrated. Particularly, through changing the inclusion's size, the stress or strain gradient can be controlled precisely, which is never achieved. By taking advantage of it, the pseudomagnetic field as well as the funnel effect can be accurately designed, which opens an avenue to practical applications for strain engineering in 2D materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A constitutive framework for modelling thin incompressible viscoelastic materials under plane stress in the finite strain regime

NASA Astrophysics Data System (ADS)

Kroon, M.

2011-11-01

Rubbers and soft biological tissues may undergo large deformations and are also viscoelastic. The formulation of constitutive models for these materials poses special challenges. In several applications, especially in biomechanics, these materials are also relatively thin, implying that in-plane stresses dominate and that plane stress may therefore be assumed. In the present paper, a constitutive model for viscoelastic materials in the finite strain regime and under the assumption of plane stress is proposed. It is assumed that the relaxation behaviour in the direction of plane stress can be treated separately, which makes it possible to formulate evolution laws for the plastic strains on explicit form at the same time as incompressibility is fulfilled. Experimental results from biomechanics (dynamic inflation of dog aorta) and rubber mechanics (biaxial stretching of rubber sheets) were used to assess the proposed model. The assessment clearly indicates that the model is fully able to predict the experimental outcome for these types of material.

Adjustable magnetoelectric effect of self-assembled vertical multiferroic nanocomposite films by the in-plane misfit strain and ferromagnetic volume fraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Huaping, E-mail: wuhuaping@gmail.com; Department of Mechanical Engineering and Science, Kyoto University, Nishikyo-ku, Kyoto 615-8540; Chai, Guozhong

The strain-mediated magnetoelectric (ME) property of self-assembled vertical multiferroic nanocomposite films epitaxially grown on cubic substrates was calculated by a nonlinear thermodynamic theory combined with the elastic theory. The dependent relations of phase state of ferroelectric films with the in-plane misfit strain, out-of-plane misfit strain, temperature, and volume fraction of ferromagnetic phase were confirmed. The effects of in-plane misfit strain and ferromagnetic volume fraction on the polarization and dielectric constant of ferroelectric films at room temperature were elaborately analyzed for the vertical BaTiO{sub 3}-CoFe{sub 2}O{sub 4} and PbTiO{sub 3}-CoFe{sub 2}O{sub 4} nanocomposite films. Our calculated results confirmed the relationship amongmore » ME effect and in-plane misfit strain and ferromagnetic volume fraction in the nanocomposite films. The ME voltage coefficients of vertical BaTiO{sub 3}-CoFe{sub 2}O{sub 4} and PbTiO{sub 3}-CoFe{sub 2}O{sub 4} nanocomposite films displayed various maximums and abrupt points at special phases and phase transition boundaries. The ME voltage coefficients of lead-free BaTiO{sub 3}-CoFe{sub 2}O{sub 4} nanocomposite films epitaxially grown on different substrates could reach a comparative value of ∼2 V·cm{sup −1}·Oe{sup −1} under the controllable in-plane misfit strain induced by substrate clamping. Our results provided an available method for the optimal design of vertical multiferroic nanocomposites with adjustable ME effect by optimizing the ferromagnetic volume fraction and substrate type.« less

Measurement of Heavy Ion Irradiation Induced In-Plane Strain in Patterned Face-Centered-Cubic Metal Films: An in Situ Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, K. Y.; Chen, Y.; Li, J.

Nanocrystalline Ag, Cu, and Ni thin films and their coarse grained counterparts are patterned in this paper using focused ion beam and then irradiated by Kr ions within an electron microscope at room temperature. Irradiation induced in-plane strain of the films is measured by tracking the location of nanosized holes. The magnitude of the strain in all specimens is linearly dose-dependent and the strain rates of nanocrystalline metals are significantly greater as compared to that of the coarse grained metals. Finally, real-time microscopic observation suggests that substantial grain boundary migration and grain rotation are responsible for the significant in-plane strain.

Measurement of Heavy Ion Irradiation Induced In-Plane Strain in Patterned Face-Centered-Cubic Metal Films: An in Situ Study

DOE PAGES

Yu, K. Y.; Chen, Y.; Li, J.; ...

2016-11-28

Nanocrystalline Ag, Cu, and Ni thin films and their coarse grained counterparts are patterned in this paper using focused ion beam and then irradiated by Kr ions within an electron microscope at room temperature. Irradiation induced in-plane strain of the films is measured by tracking the location of nanosized holes. The magnitude of the strain in all specimens is linearly dose-dependent and the strain rates of nanocrystalline metals are significantly greater as compared to that of the coarse grained metals. Finally, real-time microscopic observation suggests that substantial grain boundary migration and grain rotation are responsible for the significant in-plane strain.

The planes of satellite galaxies problem, suggested solutions, and open questions

NASA Astrophysics Data System (ADS)

Pawlowski, Marcel S.

2018-02-01

Satellite galaxies of the Milky Way and of the Andromeda galaxy have been found to preferentially align in significantly flattened planes of satellite galaxies, and available velocity measurements are indicative of a preference of satellites in those structures to co-orbit. There is an increasing evidence that such kinematically correlated satellite planes are also present around more distant hosts. Detailed comparisons show that similarly anisotropic phase-space distributions of sub-halos are exceedingly rare in cosmological simulations based on the ΛCDM paradigm. Analogs to the observed systems have frequencies of ≤ 0.5% in such simulations. In contrast to other small-scale problems, the satellite planes issue is not strongly affected by baryonic processes because the distribution of sub-halos on scales of hundreds of kpc is dominated by gravitational effects. This makes the satellite planes one of the most serious small-scale problems for ΛCDM. This review summarizes the observational evidence for planes of satellite galaxies in the Local Group and beyond, and provides an overview of how they compare to cosmological simulations. It also discusses scenarios which aim at explaining the coherence of satellite positions and orbits, and why they all are currently unable to satisfactorily resolve the issue.

The crack problem for a half plane stiffened by elastic cover plates

NASA Technical Reports Server (NTRS)

Delale, F.; Erdogan, F.

1981-01-01

An elastic half plane containing a crack and stiffened by a cover plate is discussed. The asymptotic nature of the stress state in the half plane around an end point of the stiffener to determine the likely orientation of a possible fracture initiation and growth was studied. The problem is formulated for an arbitrary oriented radial crack in a system of singular integral equations. For an internal crack and for an edge crack, the problem is solved and the stress intensity factors at the crack tips and the interface stress are calculated. A cracked half plane with two symmetrically located cover plates is also considered. It is concluded that the case of two stiffeners appears to be more severe than that of a single stiffener.

Dielectric tunability of vertically aligned ferroelectric-metal oxide nanocomposite films controlled by out-of-plane misfit strain

NASA Astrophysics Data System (ADS)

Wu, Huaping; Ma, Xuefu; Zhang, Zheng; Zhu, Jun; Wang, Jie; Chai, Guozhong

2016-04-01

A nonlinear thermodynamic model based on the vertically aligned nanocomposite (VAN) thin films of ferroelectric-metal oxide system has been developed to investigate the physical properties of the epitaxial Ba0.6Sr0.4TiO3 (BST) films containing vertical Sm2O3 (SmO) nanopillar arrays on the SrTiO3 substrate. The phase diagrams of out-of-plane lattice mismatch vs. volume fraction of SmO are calculated by minimizing the total free energy. It is found that the phase transformation and dielectric response of BST-SmO VAN systems are extremely dependent on the in-plane misfit strain, the out-of-plane lattice mismatch, the volume fraction of SmO phase, and the external electric field applied to the nanocomposite films at room temperature. In particular, the BST-SmO VAN systems exhibit higher dielectric properties than pure BST films. Giant dielectric response and maximum tunability are obtained near the lattice mismatch where the phase transition occurs. Under the in-plane misfit strain of umf=0.3 % and the out-of-plane lattice mismatch of u3=0.002 , the dielectric tunability can be dramatically enhanced to 90% with the increase of SmO volume fraction, which is well consistent with previous experimental results. This work represents an approach to further understand the dependence of physical properties on the lattice mismatch (in-plane and out-of-plane) and volume fraction, and to manipulate or optimize functionalities in the nanocomposite oxide thin films.

Solution of a Plane Hydrofracture Problem with Stress Contrast

NASA Astrophysics Data System (ADS)

Gladkov, I. O.; Linkov, A. M.

2018-03-01

A plane hydrofracture problem for the Khristianovich-Geertsma-de Klerk model is extended and solved in the case where a confining stress closing a fracture is not constant in the direction of its propagation. A method is developed for solving the problem with an arbitrary stress contrast. It is stated that the transition through a contact with positive (negative) contrast occurs with fracture arresting (acceleration), whose intensity is controlled by a dimensionless parameter derived from theoretical considerations and numerical results.

Effects of external magnetic field and out-of-plane strain on magneto-optical Kerr spectra in CrI3 monolayer.

PubMed

Guo, Guanxing; Bi, Gang; Cai, Chunfeng; Wu, Huizhen

2018-07-18

Magnetic semiconductors based on two-dimensional (2D) crystals have attracted attention owing to their intrinsic ferromagnetism and have potential for spintronic devices. Here, full-potential linearized augmented plane wave plus local orbitals method is used to explore the structural, electronic, magnetic, and magneto-optical properties of CrI 3 monolayer. Our first-principles calculations show that CrI 3 monolayer is a ferromagnetic indirect semiconductor with spin-up and spin-down band gaps of 1.23 and 1.90 eV, respectively, and a magnetic moment of 2.93 [Formula: see text] per Cr atom. Based on the macroscopic linear response theory, we systematically study the influences of external magnetic field and out-of-plane strain on the magneto-optical Kerr effect spectra in CrI 3 monolayer. The Kerr rotation of CrI 3 monolayer at 1.96 eV photon energy is [Formula: see text], which is consistent with the recent experiments. We find that the Kerr rotation reaches its maximum when the external magnetic field is perpendicular to CrI 3 plane, while it is almost zero on turning the magnetic field in the plane. This result as well as the sizable magnetocrystalline anisotropy energy (MAE) of 0.79 meV verifies that CrI 3 monolayer has a strong magnetic anisotropy with an out-of-plane easy axis. Further, applying out-of-plane compressive and tensile strain upon CrI 3 monolayer, we observe a redshift of the Kerr rotation spectra with the increase of the strain and the peak values of the Kerr rotation increase correspondingly. The rich electronic and magnetic properties, especially the magneto-optical spectra, render CrI 3 monolayer a promising 2D magnetic material for applications from sensing to data storage.

Direct Three-Dimensional Myocardial Strain Tensor Quantification and Tracking using zHARP★

PubMed Central

Abd-Elmoniem, Khaled Z.; Stuber, Matthias; Prince, Jerry L.

2008-01-01

Images of myocardial strain can be used to diagnose heart disease, plan and monitor treatment, and to learn about cardiac structure and function. Three-dimensional (3-D) strain is typically quantified using many magnetic resonance (MR) images obtained in two or three orthogonal planes. Problems with this approach include long scan times, image misregistration, and through-plane motion. This article presents a novel method for calculating cardiac 3-D strain using a stack of two or more images acquired in only one orientation. The zHARP pulse sequence encodes in-plane motion using MR tagging and out-of-plane motion using phase encoding, and has been previously shown to be capable of computing 3D displacement within a single image plane. Here, data from two adjacent image planes are combined to yield a 3-D strain tensor at each pixel; stacks of zHARP images can be used to derive stacked arrays of 3D strain tensors without imaging multiple orientations and without numerical interpolation. The performance and accuracy of the method is demonstrated in-vitro on a phantom and in-vivo in four healthy adult human subjects. PMID:18511332

The plane elasticity problem for a crack near the curved surface

NASA Astrophysics Data System (ADS)

Lebedeva, M. V.

2018-05-01

The unconventional approach to the plane elasticity problem for a crack near the curved surface is presented. The solution of the problem is considered in the form of the sum of solutions of two auxiliary problems. The first one describes the plane with a crack, whose surfaces are loaded by some unknown self-balanced force p(x). The second problem is dealing with the semi-infinite region with the boundary conditions equal to the difference of boundary conditions of the problem to be sought and the solution of the first problem on the region border. The unknown function p(x) is supposed to be approximated with the sufficient level of accuracy by N order polynomial with complex coefficients. This paper is aimed to determine the critical loads causing the spontaneous growth of cracks. The angles of propagation of the stationary cracks located in the region with a ledge or a cut are found. The influence of length of a crack on the bearing ability of an elastic body with the curved surface is investigated. The effect of a form of the concentrator and orientation of a crack to the fracture load subject to the different combinations of forces acting both on a surface of a crack and at infinity is analysed. The results of this research can be applied for calculation of the durability of thin-walled vessels of pressure, e.g., chemical reactors, in order to ensure their ecological safety.

Strained-layer superlattice focal plane array having a planar structure

DOEpatents

Kim, Jin K [Albuquerque, NM; Carroll, Malcolm S [Albuquerque, NM; Gin, Aaron [Albuquerque, NM; Marsh, Phillip F [Lowell, MA; Young, Erik W [Albuquerque, NM; Cich, Michael J [Albuquerque, NM

2010-07-13

An infrared focal plane array (FPA) is disclosed which utilizes a strained-layer superlattice (SLS) formed of alternating layers of InAs and In.sub.xGa.sub.1-xSb with 0.ltoreq.x.ltoreq.0.5 epitaxially grown on a GaSb substrate. The FPA avoids the use of a mesa structure to isolate each photodetector element and instead uses impurity-doped regions formed in or about each photodetector for electrical isolation. This results in a substantially-planar structure in which the SLS is unbroken across the entire width of a 2-D array of the photodetector elements which are capped with an epitaxially-grown passivation layer to reduce or eliminate surface recombination. The FPA has applications for use in the wavelength range of 3-25 .mu.m.

Strained layer superlattice focal plane array having a planar structure

DOEpatents

Kim, Jin K; Carroll, Malcolm S; Gin, Aaron; Marsh, Phillip F; Young, Erik W; Cich, Michael J

2012-10-23

An infrared focal plane array (FPA) is disclosed which utilizes a strained-layer superlattice (SLS) formed of alternating layers of InAs and In.sub.xGa.sub.1-xSb with 0.ltoreq.x.ltoreq.0.5 epitaxially grown on a GaSb substrate. The FPA avoids the use of a mesa structure to isolate each photodetector element and instead uses impurity-doped regions formed in or about each photodetector for electrical isolation. This results in a substantially-planar structure in which the SLS is unbroken across the entire width of a 2-D array of the photodetector elements which are capped with an epitaxially-grown passivation layer to reduce or eliminate surface recombination. The FPA has applications for use in the wavelength range of 3-25 .mu.m.

Nonsteady Problem for an Elastic Half-Plane with Mixed Boundary Conditions

NASA Astrophysics Data System (ADS)

Kubenko, V. D.

2016-03-01

An approach to studying nonstationary wave processes in an elastic half-plane with mixed boundary conditions of the fourth boundary-value problem of elasticity is proposed. The Laplace and Fourier transforms are used. The sequential inversion of these transforms or the inversion of the joint transform by the Cagniard method allows obtaining the required solution (stresses, displacements) in a closed analytic form. With this approach, the problem can be solved for various types of loads

Investigating Plane Geometry Problem-Solving Strategies of Prospective Mathematics Teachers in Technology and Paper-and-Pencil Environments

ERIC Educational Resources Information Center

Koyuncu, Ilhan; Akyuz, Didem; Cakiroglu, Erdinc

2015-01-01

This study aims to investigate plane geometry problem-solving strategies of prospective mathematics teachers using dynamic geometry software (DGS) and paper-and-pencil (PPB) environments after receiving an instruction with GeoGebra (GGB). Four plane geometry problems were used in a multiple case study design to understand the solution strategies…

Anisotropically biaxial strain in non-polar (112-0) plane In x Ga1-x N/GaN layers investigated by X-ray reciprocal space mapping.

PubMed

Zhao, Guijuan; Li, Huijie; Wang, Lianshan; Meng, Yulin; Ji, Zesheng; Li, Fangzheng; Wei, Hongyuan; Yang, Shaoyan; Wang, Zhanguo

2017-07-03

In this study, the indium composition x as well as the anisotropically biaxial strain in non-polar a-plane In x Ga 1-x N on GaN is studied by X-ray diffraction (XRD) analysis. In accordance with XRD reciprocal lattice space mapping, with increasing indium composition, the maximum of the In x Ga 1-x N reciprocal lattice points progressively shifts from a fully compressive strained to a fully relaxed position, then to reversed tensile strained. To fully understand the strain in the ternary alloy layers, it is helpful to grow high-quality device structures using a-plane nitrides. As the layer thickness increases, the strain of In x Ga 1-x N layer releases through surface roughening and the 3D growth-mode.

Reconstruction of in-plane strain maps using hybrid dense sensor network composed of sensing skin

NASA Astrophysics Data System (ADS)

Downey, Austin; Laflamme, Simon; Ubertini, Filippo

2016-12-01

The authors have recently developed a soft-elastomeric capacitive (SEC)-based thin film sensor for monitoring strain on mesosurfaces. Arranged in a network configuration, the sensing system is analogous to a biological skin, where local strain can be monitored over a global area. Under plane stress conditions, the sensor output contains the additive measurement of the two principal strain components over the monitored surface. In applications where the evaluation of strain maps is useful, in structural health monitoring for instance, such signal must be decomposed into linear strain components along orthogonal directions. Previous work has led to an algorithm that enabled such decomposition by leveraging a dense sensor network configuration with the addition of assumed boundary conditions. Here, we significantly improve the algorithm’s accuracy by leveraging mature off-the-shelf solutions to create a hybrid dense sensor network (HDSN) to improve on the boundary condition assumptions. The system’s boundary conditions are enforced using unidirectional RSGs and assumed virtual sensors. Results from an extensive experimental investigation demonstrate the good performance of the proposed algorithm and its robustness with respect to sensors’ layout. Overall, the proposed algorithm is seen to effectively leverage the advantages of a hybrid dense network for application of the thin film sensor to reconstruct surface strain fields over large surfaces.

Polycrystalline Ba0.6Sr0.4TiO3 thin films on r-plane sapphire: Effect of film thickness on strain and dielectric properties

NASA Astrophysics Data System (ADS)

Fardin, E. A.; Holland, A. S.; Ghorbani, K.; Akdogan, E. K.; Simon, W. K.; Safari, A.; Wang, J. Y.

2006-10-01

Polycrystalline Ba0.6Sr0.4TiO3 (BST) films grown on r-plane sapphire exhibit strong variation of in-plane strain over the thickness range of 25-400nm. At a critical thickness of ˜200nm, the films are strain relieved; in thinner films, the strain is tensile, while compressive strain was observed in the 400nm film. Microwave properties of the films were measured from 1to20GHz by the interdigital capacitor method. A capacitance tunability of 64% was observed in the 200nm film, while thinner films showed improved Q factor. These results demonstrate the possibility of incorporating frequency agile BST-based devices into the silicon on sapphire process.

Topological Insulator State in Thin Bismuth Films Subjected to Plane Tensile Strain

NASA Astrophysics Data System (ADS)

Demidov, E. V.; Grabov, V. M.; Komarov, V. A.; Kablukova, N. S.; Krushel'nitskii, A. N.

2018-03-01

The results of experimental examination of galvanomagnetic properties of thin bismuth films subjected to plane tensile strain resulting from the difference in thermal expansion coefficients of the substrate material and bismuth are presented. The resistivity, the magnetoresistance, and the Hall coefficient were studied at temperatures ranging from 5 to 300 K in magnetic fields as strong as 0.65 T. Carrier densities were calculated. A considerable increase in carrier density in films thinner than 30 nm was observed. This suggests that surface states are more prominent in thin bismuth films on mica substrates, while the films themselves may exhibit the properties of a topological insulator.

A gradient based algorithm to solve inverse plane bimodular problems of identification

NASA Astrophysics Data System (ADS)

Ran, Chunjiang; Yang, Haitian; Zhang, Guoqing

2018-02-01

This paper presents a gradient based algorithm to solve inverse plane bimodular problems of identifying constitutive parameters, including tensile/compressive moduli and tensile/compressive Poisson's ratios. For the forward bimodular problem, a FE tangent stiffness matrix is derived facilitating the implementation of gradient based algorithms, for the inverse bimodular problem of identification, a two-level sensitivity analysis based strategy is proposed. Numerical verification in term of accuracy and efficiency is provided, and the impacts of initial guess, number of measurement points, regional inhomogeneity, and noisy data on the identification are taken into accounts.

Stress-free end problem in layered materials

NASA Technical Reports Server (NTRS)

Erdogan, F.; Bakioglu, M.

1977-01-01

In this paper the plane elastostatic problem for a medium which consists of periodically arranged two sets of bonded dissimilar layers or strips is considered. First it is assumed that one set of strips contains a crack which crosses the bimaterial interfaces. Then, by letting the collinear cracks join, the stress-free end problem is formulated. The singular behavior of the solutions at the point on intersection of the stress-free boundary and the interfaces is examined and appropriate stress intensity factors are defined. The results of some numerical examples are then presented which include the cases of both plane stress and plane strain.

Wiimote Experiments: 3-D Inclined Plane Problem for Reinforcing the Vector Concept

ERIC Educational Resources Information Center

Kawam, Alae; Kouh, Minjoon

2011-01-01

In an introductory physics course where students first learn about vectors, they oftentimes struggle with the concept of vector addition and decomposition. For example, the classic physics problem involving a mass on an inclined plane requires the decomposition of the force of gravity into two directions that are parallel and perpendicular to the…

Wireless Open-Circuit In-Plane Strain and Displacement Sensor Requiring No Electrical Connections

NASA Technical Reports Server (NTRS)

Woodard, Stanley E. (Inventor)

2014-01-01

A wireless in-plane strain and displacement sensor includes an electrical conductor fixedly coupled to a substrate subject to strain conditions. The electrical conductor is shaped between its ends for storage of an electric field and a magnetic field, and remains electrically unconnected to define an unconnected open-circuit having inductance and capacitance. In the presence of a time-varying magnetic field, the electrical conductor so-shaped resonates to generate harmonic electric and magnetic field responses. The sensor also includes at least one electrically unconnected electrode having an end and a free portion extending from the end thereof. The end of each electrode is fixedly coupled to the substrate and the free portion thereof remains unencumbered and spaced apart from a portion of the electrical conductor so-shaped. More specifically, at least some of the free portion is disposed at a location lying within the magnetic field response generated by the electrical conductor. A motion guidance structure is slidingly engaged with each electrode's free portion in order to maintain each free portion parallel to the electrical conductor so-shaped.

An Interactive Artificial Cutting Plane Method for Bicriterion Integer Programming Problems

DTIC Science & Technology

1992-08-01

AUTHOR(S) Diane Breivik Allen, 1st Lt 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER AFIT Student Attending...INTERACTIVE ARTIFICIAL CUTTING PLANE METHOD FOR BICRITERION INTEGER PROGRAMMING PROBLEMS By Diane Breivik Allen A Thesis Submitted to the Faculty of...ITfiSRA&1 DTIC TAB 0 Unannounced 0 Justirication By BY Diane Breivik Allen Distributlon/ Availability CQdes Avail and/or Dist Special Approved: DTI

A solution to the problem of elastic half-plane with a cohesive edge crack

NASA Astrophysics Data System (ADS)

Thanh, Le Thi; Belaya, L. A.; Lavit, I. M.

2018-03-01

This paper considers the problem of extension of an elastic half-plane slackened by a rectilinear edge crack. The opposite edges of the crack are attracted to each other. The intensity of attracting forces – the forces of cohesion – depends on displacements of the edges; this dependence is nonlinear in the general case. External load and cohesive forces are related to each other by the condition of finite stresses at the crack tip. The authors apply Picard’s method of successive approximation. In each iteration, Irwin’s method is used to solve the problem of a half-plane with a crack, the edges of which are subjected to irregularly distributed load. The solution of the resulting integral equation is found by Galerkin’s method. The paper includes examples of calculations and their results. Some of them are compared with the data of previous studies.

Plane elasto-plastic analysis of v-notched plate under bending by boundary integral equation method. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Rzasnicki, W.

1973-01-01

A method of solution is presented, which, when applied to the elasto-plastic analysis of plates having a v-notch on one edge and subjected to pure bending, will produce stress and strain fields in much greater detail than presently available. Application of the boundary integral equation method results in two coupled Fredholm-type integral equations, subject to prescribed boundary conditions. These equations are replaced by a system of simultaneous algebraic equations and solved by a successive approximation method employing Prandtl-Reuss incremental plasticity relations. The method is first applied to number of elasto-static problems and the results compared with available solutions. Good agreement is obtained in all cases. The elasto-plastic analysis provides detailed stress and strain distributions for several cases of plates with various notch angles and notch depths. A strain hardening material is assumed and both plane strain and plane stress conditions are considered.

Derivation of a variational principle for plane strain elastic-plastic silk biopolymers

NASA Astrophysics Data System (ADS)

He, J. H.; Liu, F. J.; Cao, J. H.; Zhang, L.

2014-01-01

Silk biopolymers, such as spider silk and Bombyx mori silk, behave always elastic-plastically. An elastic-plastic model is adopted and a variational principle for the small strain, rate plasticity problem is established by semi-inverse method. A trial Lagrangian is constructed where an unknown function is included which can be identified step by step.

Cutting planes for the multistage stochastic unit commitment problem

DOE PAGES

Jiang, Ruiwei; Guan, Yongpei; Watson, Jean -Paul

2016-04-20

As renewable energy penetration rates continue to increase in power systems worldwide, new challenges arise for system operators in both regulated and deregulated electricity markets to solve the security-constrained coal-fired unit commitment problem with intermittent generation (due to renewables) and uncertain load, in order to ensure system reliability and maintain cost effectiveness. In this paper, we study a security-constrained coal-fired stochastic unit commitment model, which we use to enhance the reliability unit commitment process for day-ahead power system operations. In our approach, we first develop a deterministic equivalent formulation for the problem, which leads to a large-scale mixed-integer linear program.more » Then, we verify that the turn on/off inequalities provide a convex hull representation of the minimum-up/down time polytope under the stochastic setting. Next, we develop several families of strong valid inequalities mainly through lifting schemes. In particular, by exploring sequence independent lifting and subadditive approximation lifting properties for the lifting schemes, we obtain strong valid inequalities for the ramping and general load balance polytopes. Lastly, branch-and-cut algorithms are developed to employ these valid inequalities as cutting planes to solve the problem. Our computational results verify the effectiveness of the proposed approach.« less

Cutting planes for the multistage stochastic unit commitment problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Ruiwei; Guan, Yongpei; Watson, Jean -Paul

As renewable energy penetration rates continue to increase in power systems worldwide, new challenges arise for system operators in both regulated and deregulated electricity markets to solve the security-constrained coal-fired unit commitment problem with intermittent generation (due to renewables) and uncertain load, in order to ensure system reliability and maintain cost effectiveness. In this paper, we study a security-constrained coal-fired stochastic unit commitment model, which we use to enhance the reliability unit commitment process for day-ahead power system operations. In our approach, we first develop a deterministic equivalent formulation for the problem, which leads to a large-scale mixed-integer linear program.more » Then, we verify that the turn on/off inequalities provide a convex hull representation of the minimum-up/down time polytope under the stochastic setting. Next, we develop several families of strong valid inequalities mainly through lifting schemes. In particular, by exploring sequence independent lifting and subadditive approximation lifting properties for the lifting schemes, we obtain strong valid inequalities for the ramping and general load balance polytopes. Lastly, branch-and-cut algorithms are developed to employ these valid inequalities as cutting planes to solve the problem. Our computational results verify the effectiveness of the proposed approach.« less

Hygrothermal wave propagation in viscoelastic graphene under in-plane magnetic field based on nonlocal strain gradient theory

NASA Astrophysics Data System (ADS)

Karami, Behrouz; Shahsavari, Davood; Li, Li

2018-03-01

A size-dependent model is developed for the hygrothermal wave propagation analysis of an embedded viscoelastic single layer graphene sheet (SLGS) under the influence of in-plane magnetic field. The bi-Helmholtz nonlocal strain gradient theory involving three small scale parameters is introduced to account for the size-dependent effects. The size-dependent model is deduced based on Hamilton's principle. The closed-form solution of eigenfrequency relation between wave number and phase velocity is achieved. By studying the size-dependent effects on the flexural wave of SLGS, the dispersion relation predicted by the developed size-dependent model can show a good match with experimental data. The influence of in-plane magnetic field, temperature and moisture of environs, structural damping, damped substrate, lower and higher order nonlocal parameters and the material characteristic parameter on the phase velocity of SLGS is explored.

New insights into classical solutions of the local instability of the sandwich panels problem

NASA Astrophysics Data System (ADS)

Pozorska, Jolanta; Pozorski, Zbigniew

2016-06-01

The paper concerns the problem of local instability of thin facings of a sandwich panel. The classic analytical solutions are compared and examined. The Airy stress function is applied in the case of the state of plane stress and the state of plane strain. Wrinkling stress values are presented. The differences between the results obtained using the differential equations method and energy method are discussed. The relations between core strain energies are presented.

High-order integral equation methods for problems of scattering by bumps and cavities on half-planes.

PubMed

Pérez-Arancibia, Carlos; Bruno, Oscar P

2014-08-01

This paper presents high-order integral equation methods for the evaluation of electromagnetic wave scattering by dielectric bumps and dielectric cavities on perfectly conducting or dielectric half-planes. In detail, the algorithms introduced in this paper apply to eight classical scattering problems, namely, scattering by a dielectric bump on a perfectly conducting or a dielectric half-plane, and scattering by a filled, overfilled, or void dielectric cavity on a perfectly conducting or a dielectric half-plane. In all cases field representations based on single-layer potentials for appropriately chosen Green functions are used. The numerical far fields and near fields exhibit excellent convergence as discretizations are refined-even at and around points where singular fields and infinite currents exist.

Experimental Observations of Localization Phenomena in Sands: Plane Strain Versus Triaxial Compression Conditions

NASA Technical Reports Server (NTRS)

Alshibli, Khalid A.; Batiste, Susan N.; Sture, Stein; Curreri, Peter A. (Technical Monitor)

2002-01-01

A comprehensive experimental investigation was conducted to investigate the effects of loading condition and confining pressure on strength properties and instability phenomena in sands. A uniform sub-rounded to rounded natural silica sand known as F-75 Ottawa sand was used in the investigation. The results of a series on Conventional Triaxial Compression (CTC) experiments tested under very low confining pressures (0.05 - 1.30) kPa tested in a Microgravity environment abroad the NASA Space Shuttle are presented in addition to the results similar specimens tested in terrestrial laboratory to investigate the effect of confining pressure on the constitutive behavior of sands. The behavior of the CTC experiments is compared with the results of Plane Strain (PS) experiments. Computed tomography and other digital imaging techniques were used to study the development and evolution of shear bands.

From Number Lines to Graphs in the Coordinate Plane: Investigating Problem Solving across Mathematical Representations

ERIC Educational Resources Information Center

Earnest, Darrell

2015-01-01

This article reports on students' problem-solving approaches across three representations--number lines, coordinate planes, and function graphs--the axes of which conventional mathematics treats in terms of consistent geometric and numeric coordinations. I consider these representations to be a part of a "hierarchical representational…

Crack growth in bonded elastic half planes

NASA Technical Reports Server (NTRS)

Goree, J. G.

1975-01-01

Two solutions were developed for the two dimensional problem of bonded linearly elastic half-planes. For each solution, numerical results are presented for the stress intensity factors, strain energy release rate, stresses, and displacements. The behavior predicted by the studies was investigated experimentally using polymers for the material pairs. Close agreement was found for the critical stress intensity factor at fracture for the perpendicular crack near the interface. Fracture along the interface proved to be inconclusive due to difficulties in obtaining a brittle bond. Some interesting and predictable behavior regarding the potential for the crack to cross the interface was observed and is discussed.

Transient reaction of an elastic half-plane on a source of a concentrated boundary disturbance

NASA Astrophysics Data System (ADS)

Okonechnikov, A. S.; Tarlakovski, D. V.; Ul'yashina, A. N.; Fedotenkov, G. V.

2016-11-01

One of the key problems in studying the non-stationary processes of solid mechanics is obtaining of influence functions. These functions serve as solutions for the problems of effect of sudden concentrated loads on a body with linear elastic properties. Knowledge of the influence functions allows us to obtain the solutions for the problems with non-mixed boundary and initial conditions in the form of quadrature formulae with the help of superposition principle, as well as get the integral governing equations for the problems with mixed boundary and initial conditions. This paper offers explicit derivations for all nonstationary surface influence functions of an elastic half-plane in a plane strain condition. It is achieved with the help of combined inverse transform of a Fourier-Laplace integral transformation. The external disturbance is both dynamic and kinematic. The derived functions in xτ-domain are studied to find and describe singularities and are supplemented with graphs.

Effects of external mechanical loading on phase diagrams and dielectric properties in epitaxial ferroelectric thin films with anisotropic in-plane misfit strains

NASA Astrophysics Data System (ADS)

Qiu, J. H.; Jiang, Q.

2007-02-01

A phenomenological Landau-Devonshine theory is used to describe the effects of external mechanical loading on equilibrium polarization states and dielectric properties in epitaxial ferroelectric thin films grown on dissimilar orthorhombic substrates which induce anisotropic misfit strains in the film plane. The calculation focuses on single-domain perovskite BaTiO3 and PbTiO3 thin films on the assumption that um1=-um2. Compared with the phase diagrams without external loading, the characteristic features of "misfit strain-misfit strain" phase diagrams at room temperature are the presence of paraelectric phase and the strain-induced ferroelectric to paraelectric phase transition. Due to the external loading, the "misfit strain-stress" and "stress-temperature" phase diagrams also have drastic changes, especially for the vanishing of paraelectric phase in "misfit strain-stress" phase map and the appearance of possible ferroelectric phases. We also investigate the dielectric properties and the tunability of both BaTiO3 and PbTiO3 thin films. We find that the external stress dependence of phase diagrams and dielectric properties largely depends on strain anisotropy as well.

Simultaneous in- and out-of-plane Mitral Valve Annular Force Measurements.

PubMed

Skov, Søren N; Røpcke, Diana M; Telling, Kristine; Ilkjær, Christine; Tjørnild, Marcell J; Nygaard, Hans; Nielsen, Sten L; Jensen, Morten O

2015-06-01

Mitral valve repair with annuloplasty is often favoured over total valve replacement. In order to develop and optimize new annuloplasty ring designs, it is important to study the complex biomechanical behaviour of the valve annulus and the subvalvular apparatus with simultaneous in- and out-of-plane restraining force measurements. A new flat D-shaped mitral valve annular force transducer was developed. The transducer was mounted with strain gauges to measure strain and calibrated to provide simultaneous restraining forces in- and out of the mitral annular plane. The force transducer was implanted and evaluated in an 80 kg porcine experimental model. Accumulation of out-of-plane restraining forces, creating strain in the anterior segment were 0.7 ± 0.0 N (towards apex) and an average force accumulation of 1.5 ± 0.3 N, creating strain in the commissural segments (away from apex). The accumulations of in-plane restraining forces, creating strain on the inner side of the ring were 1.7 ± 0.2 N (away from ring center). A new mitral annular force transducer was successfully developed and evaluated in vivo. The transducer was able to measure forces simultaneously in different planes. Initial indications point towards overall agreement with previous individual force measurements in- and out-of the mitral annular plane. This can provide more detailed insight into the annular force distribution, and could potentially improve the level of evidence based mitral valve repair and support the development of future mitral annuloplasty devices.

Comment on "Out-of-plane equilibrium points in the restricted three-body problem with oblateness (Research Note)"

NASA Astrophysics Data System (ADS)

Wu, Nan; Wang, Xuefeng; Zhou, Li-Yong

2018-06-01

Douskos & Markellos (2006, A&A, 446, 357) first reported the existence of the out-of-plane equilibrium points in restricted three-body problem with oblateness. This result deviates significantly from the intuitive physical point of view that there is no other force that can balance the combined gravitation in Z direction. In fact, the out-of-plane equilibrium in that model is illusory and we prove here that such equilibrium points arise from the improper application of the potential function.

Anti-plane eigenstrain problem of an inclusion of arbitrary shape in an anisotropic bimaterial with a semi-infinite interface crack

NASA Astrophysics Data System (ADS)

Wang, Xu; Schiavone, Peter

2018-02-01

We consider an Eshelby inclusion of arbitrary shape with uniform anti-plane eigenstrains embedded in one of two bonded dissimilar anisotropic half planes containing a semi-infinite interface crack situated along the negative real axis. Using two consecutive conformal mappings, the upper and lower halves of the physical plane are first mapped onto two separate quarters of the image plane. The corresponding boundary value problem is then analyzed in this image plane rather than in the original physical plane. Corresponding analytic functions in all three phases of the composite are derived via the construction of an auxiliary function and repeated application of analytic continuation across the real and imaginary axes in the image plane. As a result, the local stress intensity factor is then obtained explicitly. Perhaps most interestingly, we find that the satisfaction of a particular condition makes the inclusion (stress) invisible to the crack.

Flows in forward deformable roll coating gaps: Comparison between spring and plane-strain models of roll cover

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carvalho, M.S.; Scriven, L.E.

1997-12-01

In this report the flow between rigid and a deformable rotating rolls fully submerged in a liquid pool is studied. The deformation of compliant roll cover is described by two different models (1) independent, radially oriented springs that deform in response to the traction force applied at the extremity of each or one-dimensional model, and (2) a plane-strain deformation of an incompressible Mooney-Rivlin material or non-linear elastic model. Based on the flow rate predictions of both models, an empirical relation between the spring constant of the one dimensional model and the roll cover thickness and elastic modulus is proposed.

Monte-Carlo investigation of in-plane electron transport in tensile strained Si and Si{_{1-y}}C{_y} (y {leq 0.03})

NASA Astrophysics Data System (ADS)

Dollfus, Ph.; Galdin, S.; Hesto, P.

1999-07-01

Electron transport properties in tensile strained Si-based materials are theoretically analyzed using Monte-Carlo calculation. We focus our interest on in-plane transport in Si and Si{1-y}Cy (yleq 0.03), grown respectively on <~ngle 001rangle Si{1-x}Gex pseudo-substrate and Si substrate, with a view to Field-Effect-Transistor application. In comparison with unstrained Si, the tensile strain effect is shown to be very attractive in Si: drift mobilities greater than 3000 cm^2/Vs are obtained at 300 K for a Ge fraction mole of 0.2 in the pseudo-substrate. In the Si{1-y}Cy/Si system, that does not need any pseudo-substrate, the beneficial strain effect on transport is counterbalanced by the alloy scattering whose influence on mobility is studied. If the alloy potential is greater than about 1 eV, the advantage of strain-induced reduction of effective mass is lost in terms of stationary transport performance at 300 K.

Strain effects on oxygen vacancy energetics in KTaO 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xi, Jianqi; Xu, Haixuan; Zhang, Yanwen

Due to lattice mismatch between epitaxial films and substrates, in-plane strain fields are produced in the thin films, with accompanying structural distortions, and ion implantation can be used to controllably engineer the strain throughout the film. Because of the strain profile, local defect energetics are changed. In this study, the effects of in-plane strain fields on the formation and migration of oxygen vacancies in KTaO 3 are investigated using first-principles calculations. In particular, the doubly positive charged oxygen vacancy (V 2+O) is studied, which is considered to be the main charge state of the oxygen vacancy in KTaO 3. Wemore » find that the formation energies for oxygen vacancies are sensitive to in-plane strain and oxygen position. The local atomic configuration is identified, and strong relaxation of local defect structure is mainly responsible for the formation characteristics of these oxygen vacancies. Based on the computational results, formation-dependent site preferences for oxygen vacancies are expected to occur under epitaxial strain, which can result in orders of magnitude differences in equilibrium vacancy concentrations on different oxygen sites. In addition, all possible migration pathways, including intra- and inter-plane diffusions, are considered. In contrast to the strain-enhanced intra-plane diffusion, the diffusion in the direction normal to the strained plane is impeded under the epitaxial strain field. Lastly, these anisotropic diffusion processes can further enhance site preferences.« less

Strain effects on oxygen vacancy energetics in KTaO 3

DOE PAGES

Xi, Jianqi; Xu, Haixuan; Zhang, Yanwen; ...

2017-02-07

Due to lattice mismatch between epitaxial films and substrates, in-plane strain fields are produced in the thin films, with accompanying structural distortions, and ion implantation can be used to controllably engineer the strain throughout the film. Because of the strain profile, local defect energetics are changed. In this study, the effects of in-plane strain fields on the formation and migration of oxygen vacancies in KTaO 3 are investigated using first-principles calculations. In particular, the doubly positive charged oxygen vacancy (V 2+O) is studied, which is considered to be the main charge state of the oxygen vacancy in KTaO 3. Wemore » find that the formation energies for oxygen vacancies are sensitive to in-plane strain and oxygen position. The local atomic configuration is identified, and strong relaxation of local defect structure is mainly responsible for the formation characteristics of these oxygen vacancies. Based on the computational results, formation-dependent site preferences for oxygen vacancies are expected to occur under epitaxial strain, which can result in orders of magnitude differences in equilibrium vacancy concentrations on different oxygen sites. In addition, all possible migration pathways, including intra- and inter-plane diffusions, are considered. In contrast to the strain-enhanced intra-plane diffusion, the diffusion in the direction normal to the strained plane is impeded under the epitaxial strain field. Lastly, these anisotropic diffusion processes can further enhance site preferences.« less

Social strain, couple dynamics and gender differences in gambling problems: evidence from Chinese married couples.

PubMed

Cheung, Nicole W T

2015-02-01

Knowledge of the influence of couple dynamics on gender differences in gambling behavior remains meager. Building on general strain theory from the sociology of deviance and stress crossover theory from social psychology, we argue that the strain encountered by one partner in a social setting may affect his or her spouse. For instance, the wife of a man under more social strain may experience more strain in turn and thus be at a higher risk of developing disordered gambling than the wife of a man under less social strain. Using community survey data of 1620 Chinese married couples, we performed multilevel dyad analyses to address social strain and couple dynamics, in addition to their roles as predictors of gambling behavior in both spouses. This was a community survey of Hong Kong and therefore was not representative of China. Based on the DSM-IV screen, the rates of probable problem gambling and pathological gambling among male partners (12.8% vs. 2.5%) were twice those among female partners (5.2% vs. 0.3%). We also found that the social strain experienced by a male partner significantly predicted both his and his wife's likelihood of developing gambling problems. Although a female partner's exposure to social strain was a significant correlate of her gambling problem, it had no significant association with her husband's gambling behavior. These results suggest that the cross-spouse transference of social strain may be a gendered process. Copyright © 2014 Elsevier Ltd. All rights reserved.

Understanding the anisotropic strain effects on lithium diffusion in graphite anodes: A first-principles study

NASA Astrophysics Data System (ADS)

Ji, Xiang; Wang, Yang; Zhang, Junqian

2018-06-01

The lithium diffusion in graphite anode, which is the most widely used commercial electrode material today, affects the charge/discharge performance of lithium-ion batteries. In this study, the anisotropic strain effects on lithium diffusion in graphite anodes are systematically investigated using first-principles calculations based on density functional theory (DFT) with van der Waals corrections. It is found that the effects of external applied strains along various directions of LixC6 (i.e., perpendicular or parallel to the basal planes of the graphite host) on lithium diffusivity are different. Along the direction perpendicular to the graphite planes, the tensile strain facilitates in-plane Li diffusion by reducing the energy barrier, and the compressive strain hinders in-plane Li diffusion by raising the energy barrier. In contrast, the in-plane biaxial tensile strain (parallel to the graphite planes) hinders in-plane Li diffusion, and the in-plane biaxial compressive strain facilitates in-plane Li diffusion. Furthermore, both in-plane and transverse shear strains slightly influence Li diffusion in graphite anodes. A discussion is presented to explain the anisotropic strain dependence of lithium diffusion. This research provides data for the continuum modelling of the electrodes in the lithium-ion batteries.

Investigation of flaw geometry and loading effects on plane strain fracture in metallic structures

NASA Technical Reports Server (NTRS)

Hall, L. R.; Finger, R. W.

1971-01-01

The effects on fracture and flaw growth of weld-induced residual stresses, combined bending and tension stresses, and stress fields adjacent to circular holes in 2219-T87 aluminum and 5AI-2.5Sn(ELI) titanium alloys were evaluated. Static fracture tests were conducted in liquid nitrogen; fatigue tests were performed in room air, liquid nitrogen, and liquid hydrogen. Evaluation of results was based on linear elastic fracture mechanics concepts and was directed to improving existing methods of estimating minimum fracture strength and fatigue lives for pressurized structure in spacecraft and booster systems. Effects of specimen design in plane-strain fracture toughness testing were investigated. Four different specimen types were tested in room air, liquid nitrogen and liquid hydrogen environments using the aluminum and titanium alloys. Interferometry and holograph were used to measure crack-opening displacements in surface-flawed plexiglass test specimens. Comparisons were made between stress intensities calculated using displacement measurements, and approximate analytical solutions.

Finite element formulation with embedded weak discontinuities for strain localization under dynamic conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Tao; Mourad, Hashem M.; Bronkhorst, Curt A.

Here, we present an explicit finite element formulation designed for the treatment of strain localization under highly dynamic conditions. We also used a material stability analysis to detect the onset of localization behavior. Finite elements with embedded weak discontinuities are employed with the aim of representing subsequent localized deformation accurately. The formulation and its algorithmic implementation are described in detail. Numerical results are presented to illustrate the usefulness of this computational framework in the treatment of strain localization under highly dynamic conditions, and to examine its performance characteristics in the context of two-dimensional plane-strain problems.

Finite element formulation with embedded weak discontinuities for strain localization under dynamic conditions

DOE PAGES

Jin, Tao; Mourad, Hashem M.; Bronkhorst, Curt A.; ...

2017-09-13

Here, we present an explicit finite element formulation designed for the treatment of strain localization under highly dynamic conditions. We also used a material stability analysis to detect the onset of localization behavior. Finite elements with embedded weak discontinuities are employed with the aim of representing subsequent localized deformation accurately. The formulation and its algorithmic implementation are described in detail. Numerical results are presented to illustrate the usefulness of this computational framework in the treatment of strain localization under highly dynamic conditions, and to examine its performance characteristics in the context of two-dimensional plane-strain problems.

Quasi-plane-hypothesis of strain coordination for RC beams seismically strengthened with externally-bonded or near-surface mounted fiber reinforced plastic

NASA Astrophysics Data System (ADS)

Ren, Zhenhua; Zeng, Xiantao; Liu, Hanlong; Zhou, Fengjun

2013-03-01

The application of fiber reinforced plastic (FRP), including carbon FRP and glass FRP, for structural repair and strengthening has grown due to their numerous advantages over conventional materials such as externally bonded reinforcement (EBR) and near-surface mounted (NSM) strengthening techniques. This paper summarizes the results from 21 reinforced concrete beams strengthened with different methods, including externally-bonded and near-surface mounted FRP, to study the strain coordination of the FRP and steel rebar of the RC beam. Since there is relative slipping between the RC beam and the FRP, the strain of the FRP and steel rebar of the RC beam satisfy the quasi-plane-hypothesis; that is, the strain of the longitudinal fiber that parallels the neutral axis of the plated beam within the scope of the effective height ( h 0) of the cross section is in direct proportion to the distance from the fiber to the neutral axis. The strain of the FRP and steel rebar satisfies the equation: ɛ FRP= βɛ steel, and the value of β is equal to 1.1-1.3 according to the test results.

An information-theoretic approach to designing the plane spacing for multifocal plane microscopy

PubMed Central

Tahmasbi, Amir; Ram, Sripad; Chao, Jerry; Abraham, Anish V.; Ward, E. Sally; Ober, Raimund J.

2015-01-01

Multifocal plane microscopy (MUM) is a 3D imaging modality which enables the localization and tracking of single molecules at high spatial and temporal resolution by simultaneously imaging distinct focal planes within the sample. MUM overcomes the depth discrimination problem of conventional microscopy and allows high accuracy localization of a single molecule in 3D along the z-axis. An important question in the design of MUM experiments concerns the appropriate number of focal planes and their spacings to achieve the best possible 3D localization accuracy along the z-axis. Ideally, it is desired to obtain a 3D localization accuracy that is uniform over a large depth and has small numerical values, which guarantee that the single molecule is continuously detectable. Here, we address this concern by developing a plane spacing design strategy based on the Fisher information. In particular, we analyze the Fisher information matrix for the 3D localization problem along the z-axis and propose spacing scenarios termed the strong coupling and the weak coupling spacings, which provide appropriate 3D localization accuracies. Using these spacing scenarios, we investigate the detectability of the single molecule along the z-axis and study the effect of changing the number of focal planes on the 3D localization accuracy. We further review a software module we recently introduced, the MUMDesignTool, that helps to design the plane spacings for a MUM setup. PMID:26113764

Influence of Drawbeads in Deep-Drawing of Plane-Strain Channel Sections: Experimental and FE Analysis

NASA Astrophysics Data System (ADS)

Oliveira, M. C.; Baptista, A. J.; Alves, J. L.; Menezes, L. F.; Green, D. E.; Ghaei, A.

2007-05-01

The main purpose of the "Numisheet'05 Benchmark♯3: Channel Draw/Cylindrical Cup" was to evaluate the forming characteristics of materials in multi-stage processes. The concept was to verify the strain fields achieved during the two stage forming process and also to test the ability of numerical models to predict both strain and stress fields. The first stage consisted of forming channel sections in an industrial-scale channel draw die. The material that flows through the drawbead and over the die radii into the channel sidewalls is prestrained by cyclic bending and unbending. The prestrained channel sidewalls are subsequently cut and subjected to near plane-strain Marciniak-style cup test. This study emphasizes the analysis of the first stage process, the Channel Draw, since accurate numerical results for the first stage forming and springback are essential to guarantee proper initial state variables for the subsequent stage simulation. Four different sheet materials were selected: mild steel AKDQ-HDG, high strength steel HSLA-HDG, dual phase steel DP600-HDG and an aluminium alloy AA6022-T43. The four sheet materials were formed in the same channel draw die, but with drawbead penetrations of 25%, 50% and 100%. This paper describes the testing and measurement procedures for the numerical simulation of these conditions with DD3IMP FE code. A comparison between experimental and numerical simulation results for the first stage is presented. The experimental results indicate that an increase in drawbead penetration is accompanied by a general decrease in springback, with both sidewall radius of curvature and the sidewall angle increasing with increasing drawbead penetration. An exception to this trend occurs at the shallowest bead penetration: the radius of curvature in the sidewall is larger than expected. The sequence of cyclic tension and compression is numerically studied for each drawbead penetration in order to investigate this phenomenon.

Lattice strain effects on the optical properties of MoS2 nanosheets

PubMed Central

Yang, Lei; Cui, Xudong; Zhang, Jingyu; Wang, Kan; Shen, Meng; Zeng, Shuangshuang; Dayeh, Shadi A.; Feng, Liang; Xiang, Bin

2014-01-01

“Strain engineering” in functional materials has been widely explored to tailor the physical properties of electronic materials and improve their electrical and/or optical properties. Here, we exploit both in plane and out of plane uniaxial tensile strains in MoS2 to modulate its band gap and engineer its optical properties. We utilize X-ray diffraction and cross-sectional transmission electron microscopy to quantify the strains in the as-synthesized MoS2 nanosheets and apply measured shifts of Raman-active modes to confirm lattice strain modification of both the out-of-plane and in-plane phonon vibrations of the MoS2 nanosheets. The induced band gap evolution due to in-plane and out-of-plane tensile stresses is validated by photoluminescence (PL) measurements, promising a potential route for unprecedented manipulation of the physical, electrical and optical properties of MoS2. PMID:25008782

Prognostic Value of Right Ventricular Dysfunction in Heart Failure With Reduced Ejection Fraction: Superiority of Longitudinal Strain Over Tricuspid Annular Plane Systolic Excursion.

PubMed

Carluccio, Erberto; Biagioli, Paolo; Alunni, Gianfranco; Murrone, Adriano; Zuchi, Cinzia; Coiro, Stefano; Riccini, Clara; Mengoni, Anna; D'Antonio, Antonella; Ambrosio, Giuseppe

2018-01-01

In heart failure (HF) with reduced ejection fraction, right ventricular (RV) impairment, as defined by reduced tricuspid annular plane systolic excursion, is a predictor of poor outcome. However, peak longitudinal strain of RV free wall (RVFWS) has been recently proposed as a more accurate and sensitive tool to evaluate RV function. Accordingly, we investigated whether RVFWS could help refine prognosis of patients with HF with reduced ejection fraction in whom tricuspid annular plane systolic excursion is still preserved. A total of 200 patients with HF with reduced ejection fraction (age, 66±11 years; ejection fraction, 30±7%) with preserved tricuspid annular plane systolic excursion (>16 mm) underwent RV function assessment using speckle-tracking echocardiography to measure peak RVFWS. After a median follow-up period of 28 months, 62 (31%) patients reached the primary composite end point of all-cause death/HF rehospitalization. Median RVFWS was -19.3% (interquartile range, -23.3% to -15.0%). By lasso-penalized Cox-hazard model, RVFWS was an independent predictor of outcome, along with Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure-HF score, Echo-HF score, and severe mitral regurgitation. The best cutoff value of RVFWS for prediction of outcome was -15.3% (area under the curve, 0.68; P <0.001; sensitivity, 50%; specificity, 80%). In 50 patients (25%), RVFWS was impaired (ie, ≥-15.3%); event rate (per 100 patients per year) was greater in them than in patients with RVFWS <-15.3% (29.5% [95% confidence interval, 20.4-42.7] versus 9.4% [95% confidence interval, 6.7-13.1]; P <0.001). RVFWS yielded a significant net reclassification improvement (0.584 at 3 years; P <0.001), with 68% of nonevents correctly reclassified. In patients with HF with reduced ejection fraction with preserved tricuspid annular plane systolic excursion, RV free-wall strain provides incremental prognostic information and improved risk stratification. © 2018

Influence of growth temperature on laser molecular beam epitaxy and properties of GaN layers grown on c-plane sapphire

NASA Astrophysics Data System (ADS)

Dixit, Ripudaman; Tyagi, Prashant; Kushvaha, Sunil Singh; Chockalingam, Sreekumar; Yadav, Brajesh Singh; Sharma, Nita Dilawar; Kumar, M. Senthil

2017-04-01

We have investigated the influence of growth temperature on the in-plane strain, structural, optical and mechanical properties of heteroepitaxially grown GaN layers on sapphire (0001) substrate by laser molecular beam epitaxy (LMBE) technique in the temperature range 500-700 °C. The GaN epitaxial layers are found to have a large in-plane compressive stress of about 1 GPa for low growth temperatures but the strain drastically reduced in the layer grown at 700 °C. The nature of the in-plane strain has been analyzed using high resolution x-ray diffraction, atomic force microscopy (AFM), Raman spectroscopy and photoluminescence (PL) measurements. From AFM, a change in GaN growth mode from grain to island is observed at the high growth temperature above 600 °C. A blue shift of 20-30 meV in near band edge PL emission line has been noticed for the GaN layers containing the large in-plane strain. These observations indicate that the in-plane strain in the GaN layers is dominated by a biaxial strain. Using nanoindentation, it is found that the indentation hardness and Young's modulus of the GaN layers increases with increasing growth temperature. The results disclose the critical role of growth mode in determining the in-plane strain and mechanical properties of the GaN layers grown by LMBE technique.

National Transonic Facility model and model support vibration problems

NASA Technical Reports Server (NTRS)

Young, Clarence P., Jr.; Popernack, Thomas G., Jr.; Gloss, Blair B.

1990-01-01

Vibrations of models and model support system were encountered during testing in the National Transonic Facility. Model support system yaw plane vibrations have resulted in model strain gage balance design load limits being reached. These high levels of vibrations resulted in limited aerodynamic testing for several wind tunnel models. The yaw vibration problem was the subject of an intensive experimental and analytical investigation which identified the primary source of the yaw excitation and resulted in attenuation of the yaw oscillations to acceptable levels. This paper presents the principal results of analyses and experimental investigation of the yaw plane vibration problems. Also, an overview of plans for development and installation of a permanent model system dynamic and aeroelastic response measurement and monitoring system for the National Transonic Facility is presented.

Strain effects on the electronic properties in δ-doped oxide superlattices

NASA Astrophysics Data System (ADS)

You, Jeong Ho; Lee, Jun Hee; Okamoto, Satoshi; Cooper, Valentino; Lee, Ho Nyung

2015-03-01

Strain effects on the electronic properties of (LaTiO3)1/(SrTiO3)N superlattices were investigated using density functional theory. Under biaxial in-plane strain within the range of -5% ≤ ɛ// ≤ 5%, the dxy orbital electrons are highly localized at the interfaces whereas the dyz and dxz orbital electrons are more distributed in the SrTiO3 (STO) spacer layers. For STO thickness N ≥ 3 unit cells (u.c.), the dxy orbital electrons form two-dimensional (2D) electron gases (2DEGs). The quantized energy levels of the 2DEG are insensitive to the STO spacer thickness, but are strongly dependent on the applied biaxial in-plane strain. As the in-plane strain changes from compressive to tensile, the quantized energy levels of the dxy orbitals decrease thereby creating more states with 2D character. In contrast to the dxy orbital, the dyz and dxz orbitals always have three-dimensional (3D) transport characteristics and their energy levels increase as the strain changes from compressive to tensile. Since the charge densities in the dxy orbital and the dyz and dxz orbitals respond to biaxial in-plane strain in an opposite way, the transport dimensionality of the majority carriers can be controlled between 2D and 3D by applying biaxial in-plane strain.

Numerical modelling of strain in lava tubes

NASA Astrophysics Data System (ADS)

Merle, Olivier

The strain within lava tubes is described in terms of pipe flow. Strain is partitioned into three components: (a) two simple shear components acting from top to bottom and from side to side of a rectangular tube in transverse section; and (b) a pure shear component corresponding to vertical shortening in a deflating flow and horizontal compression in an inflating flow. The sense of shear of the two simple shear components is reversed on either side of a central zone of no shear. Results of numerical simulations of strain within lava tubes reveal a concentric pattern of flattening planes in section normal to the flow direction. The central node is a zone of low strain, which increases toward the lateral borders. Sections parallel to the flow show obliquity of the flattening plane to the flow axis, constituting an imbrication. The strain ellipsoid is generally of plane strain type, but can be of constriction or flattening type if thinning (i.e. deflating flow) or thickening (i.e. inflating flow) is superimposed on the simple shear regime. The strain pattern obtained from numerical simulation is then compared with several patterns recently described in natural lava flows. It is shown that the strain pattern revealed by AMS studies or crystal preferred orientations is remarkably similar to the numerical simulation. However, some departure from the model is found in AMS measurements. This may indicate inherited strain recorded during early stages of the flow or some limitation of the AMS technique.

Large-sized out-of-plane stretchable electrodes based on poly-dimethylsiloxane substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chou, Namsun; Lee, Jongho; Research Institute for Solar and Sustainable Energies

2014-12-15

This paper describes a reliable fabrication method of stretchable electrodes based on poly-dimethylsiloxane (PDMS) substrate. The electrode traces and pads were formed in out-of-plane structures to improve the flexibility and stretchability of the electrode array. The suspended traces and pads were attached to the PDMS substrate via parylene posts that were located nearby the traces and under the pads. As only conventional micro-electro-mechanical systems techniques were used, the out-of-plane electrode arrays were clearly fabricated at wafer level with high yield and reliability. Also, bi-layer out-of-plane electrodes were formed through additional fabrication steps in addition to mono-layer out-of-plane electrodes. The mechanicalmore » characteristics such as the stretchability, flexibility, and foldability of the fabricated electrodes were evaluated, resulting in stable electrical connection of the metal traces with up to 32.4% strain and up to 360° twist angle over 25 mm. The durability in stretched condition was validated by cyclic stretch test with 10% and 20% strain, resulting in electrical disconnection at 8600 cycles when subjected to 20% strain. From these results, it is concluded that the proposed fabrication method produced highly reliable, out-of-plane and stretchable electrodes, which would be used in various flexible and stretchable electronics applications.« less

Dielectric response and structure of in-plane tensile strained BaTiO3 thin films grown on the LaNiO3 buffered Si substrate

NASA Astrophysics Data System (ADS)

Qiao, Liang; Bi, Xiaofang

2008-02-01

Highly (001)-textured BaTiO3 films were grown epitaxially on the LaNiO3 buffered Si substrate. A strong in-plane tensile strain has been revealed by using x-ray diffraction and high resolution transmission electron microscopy. The BaTiO3 film has exhibited a small remnant polarization, indicating the presence of ca1/ca2/ca1/ca2 polydomain state in the film. Temperature dependent dielectric permittivity has demonstrated that two phase transitions occurred at respective temperatures of 170 and 30°C. The result was discussed in detail based on the misfit strain-temperature phase diagrams theory.

A wideband fast multipole boundary element method for half-space/plane-symmetric acoustic wave problems

NASA Astrophysics Data System (ADS)

Zheng, Chang-Jun; Chen, Hai-Bo; Chen, Lei-Lei

2013-04-01

This paper presents a novel wideband fast multipole boundary element approach to 3D half-space/plane-symmetric acoustic wave problems. The half-space fundamental solution is employed in the boundary integral equations so that the tree structure required in the fast multipole algorithm is constructed for the boundary elements in the real domain only. Moreover, a set of symmetric relations between the multipole expansion coefficients of the real and image domains are derived, and the half-space fundamental solution is modified for the purpose of applying such relations to avoid calculating, translating and saving the multipole/local expansion coefficients of the image domain. The wideband adaptive multilevel fast multipole algorithm associated with the iterative solver GMRES is employed so that the present method is accurate and efficient for both lowand high-frequency acoustic wave problems. As for exterior acoustic problems, the Burton-Miller method is adopted to tackle the fictitious eigenfrequency problem involved in the conventional boundary integral equation method. Details on the implementation of the present method are described, and numerical examples are given to demonstrate its accuracy and efficiency.

Lattice strain of osmium diboride under high pressure and nonhydrostatic stress

NASA Astrophysics Data System (ADS)

Kavner, Abby; Weinberger, Michelle B.; Shahar, Anat; Cumberland, Robert W.; Levine, Jonathan B.; Kaner, Richard B.; Tolbert, Sarah H.

2012-07-01

The lattice strain behavior of osmium diboride—a member of a group of third-row transition metal borides associated with hard/superhard behavior—has been studied using radial diffraction in a diamond anvil cell under high pressure and non-hydrostatic stress. We interpret the average values of the measured lattice strains as a lower-bound to the lattice-plane dependent yield strengths using existing estimates for the elastic constants of OsB2, with a yield strength of 11 GPa at 27.5 GPa of hydrostatic pressure. The measured differential lattice strains show significant plane-dependent anisotropy, with the (101) lattice plane showing the largest differential strain and the (001) lattice plane showing the least strain. At the highest pressure, the a-axis develops a larger compressive strain and supports a larger differential strain than either the b or c axes. This causes an increase in the c/a ratio and a decrease in the a/b ratio especially in the maximum stress direction. The large strength anisotropy of this material points to possible ways to modulate directional mechanical properties by taking advantage of the interplay between aggregate polycrystalline texture with directional mechanical properties.

Stress–strain state in an elastoplastic pipe taking into account the temperature and compressibility of the material

NASA Astrophysics Data System (ADS)

Gornostaev, K. K.; Kovalev, A. V.; Malygina, Y. V.

2018-03-01

In the article the authors have considered the problem of determining the stress-strain state of the elastoplastic pipe with the Mises’ condition in case of plane strain for the compressible material taking into account the temperature. The task was solved using the method of the small parameter. The expressions for the fields of stresses and displacements were received as well as the ratio of the radius of the elastoplastic boundary in the zero and first approximations.

Discretization and Numerical Solution of a Plane Problem in the Mechanics of Interfacial Cracks

NASA Astrophysics Data System (ADS)

Khoroshun, L. P.

2017-01-01

The Fourier transform is used to reduce the linear plane problem of the tension of a body with an interfacial crack to a system of dual equations for the transformed stresses and, then, to a system of integro-differential equations for the difference of displacements of the crack faces. After discretization, this latter system transforms into a system of algebraic equations for displacements of the crack faces. The effect of the bielastic constant and the number of discretization points on the half-length of the crack faces and the distribution of stresses at the interface is studied

Bulk Nonlinear Elastic Strain Waves in a Bilayer Coaxial Cylindrical Rod

NASA Astrophysics Data System (ADS)

Gula, I. A.; Samsonov, A. M.

2017-12-01

The problem of the propagation of long nonlinear elastic strain waves in a bilayer coaxial cylindrical rod with an ideal contact between the layers has been considered. Expressions for transverse displacements through longitudinal displacements have been derived. The former satisfies free boundary conditions and continuity conditions for displacements and stresses at the interlayer interface with the desired accuracy. It has been shown how these expressions generalize the well-known plane-section and Love hypotheses for an isotropic homogeneous rod. An equation for the propagation of a nonlinearly elastic strain longitudinal wave has been derived, and its particular solution in the form of a solitary traveling wave has been studied.

Strain mapping in single-layer two-dimensional crystals via Raman activity

NASA Astrophysics Data System (ADS)

Yagmurcukardes, M.; Bacaksiz, C.; Unsal, E.; Akbali, B.; Senger, R. T.; Sahin, H.

2018-03-01

By performing density functional theory-based ab initio calculations, Raman-active phonon modes of single-layer two-dimensional (2D) materials and the effect of in-plane biaxial strain on the peak frequencies and corresponding activities of the Raman-active modes are calculated. Our findings confirm the Raman spectrum of the unstrained 2D crystals and provide expected variations in the Raman-active modes of the crystals under in-plane biaxial strain. The results are summarized as follows: (i) frequencies of the phonon modes soften (harden) under applied tensile (compressive) strains; (ii) the response of the Raman activities to applied strain for the in-plane and out-of-plane vibrational modes have opposite trends, thus, the built-in strains in the materials can be monitored by tracking the relative activities of those modes; (iii) in particular, the A peak in single-layer Si and Ge disappears under a critical tensile strain; (iv) especially in mono- and diatomic single layers, the shift of the peak frequencies is a stronger indication of the strain rather than the change in Raman activities; (v) Raman-active modes of single-layer ReX2 (X =S , Se) are almost irresponsive to the applied strain. Strain-induced modifications in the Raman spectrum of 2D materials in terms of the peak positions and the relative Raman activities of the modes could be a convenient tool for characterization.

A Curved, Elastostatic Boundary Element for Plane Anisotropic Structures

NASA Technical Reports Server (NTRS)

Smeltzer, Stanley S.; Klang, Eric C.

2001-01-01

The plane-stress equations of linear elasticity are used in conjunction with those of the boundary element method to develop a novel curved, quadratic boundary element applicable to structures composed of anisotropic materials in a state of plane stress or plane strain. The curved boundary element is developed to solve two-dimensional, elastostatic problems of arbitrary shape, connectivity, and material type. As a result of the anisotropy, complex variables are employed in the fundamental solution derivations for a concentrated unit-magnitude force in an infinite elastic anisotropic medium. Once known, the fundamental solutions are evaluated numerically by using the known displacement and traction boundary values in an integral formulation with Gaussian quadrature. All the integral equations of the boundary element method are evaluated using one of two methods: either regular Gaussian quadrature or a combination of regular and logarithmic Gaussian quadrature. The regular Gaussian quadrature is used to evaluate most of the integrals along the boundary, and the combined scheme is employed for integrals that are singular. Individual element contributions are assembled into the global matrices of the standard boundary element method, manipulated to form a system of linear equations, and the resulting system is solved. The interior displacements and stresses are found through a separate set of auxiliary equations that are derived using an Airy-type stress function in terms of complex variables. The capabilities and accuracy of this method are demonstrated for a laminated-composite plate with a central, elliptical cutout that is subjected to uniform tension along one of the straight edges of the plate. Comparison of the boundary element results for this problem with corresponding results from an analytical model show a difference of less than 1%.

Altering thermal transport by strained-layer epitaxy

NASA Astrophysics Data System (ADS)

Majdi, Tahereh; Pal, Souvik; Hafreager, Anders; Murad, Sohail; Sahu, Rakesh P.; Puri, Ishwar K.

2018-05-01

Since strain changes the interatomic spacing of matter and alters electron and phonon dispersion, an applied strain can modify the thermal conductivity k of a material. We show how the strain induced by heteroepitaxy is a passive mechanism to change k in a thin film. Molecular dynamics simulations of the deposition and epitaxial growth of ZnTe thin films provide insights into the role of interfacial strain in the conductivity of a deposited film. ZnTe films grow strain-free on lattice-matched ZnTe substrates, but similar thin films grown on a lattice-mismatched CdTe substrate exhibit ˜6% biaxial in-plane tensile strain and ˜7% uniaxial out-of-plane compressive strain. In the T = 700 K-1100 K temperature range, the conductivities of strained ZnTe layers decrease to ˜60% of their unstrained values. The resulting understanding of dk/dT shows that strain engineering can be used to alter the performance of a thermal rectifier and also provides a framework for enhancing thermoelectric devices.

Strain effects on the electronic properties in δ -doped oxide superlattices

DOE PAGES

You, Jeong Ho; Lee, Jun Hee; Okamoto, Satoshi; ...

2015-02-07

We investigated strain effects on the electronic properties of (LaTiO 3) 1/(SrTiO 3)N superlattices using density functional theory. Under biaxial in-plane strain within the range of -5% ≤ ε// ≤ 5%, the d xy orbital electrons are highly localized at the interfaces whereas the d yz and d xz orbital electrons are more distributed in the SrTiO 3 (STO) spacer layers. For STO thickness N ≥ 3 unit cells (u.c.), the d xy orbital electrons form two-dimensional (2D) electron gases (2DEGs). The quantized energy levels of the 2DEG are insensitive to the STO spacer thickness, but are strongly dependent onmore » the applied biaxial in-plane strain. As the in-plane strain changes from compressive to tensile, the quantized energy levels of the dxy orbitals decrease thereby creating more states with 2D character. In contrast to the d xy orbital, the d yz and dxz orbitals always have three-dimensional (3D) transport characteristics and their energy levels increase as the strain changes from compressive to tensile. In conclusion, since the charge densities in the d xy orbital and the d yz and d xz orbitals respond to biaxial in-plane strain in an opposite way, the transport dimensionality of the majority carriers can be controlled between 2D and 3D by applying biaxial in-plane strain.« less

In-plane microwave dielectric properties of paraelectric barium strontium titanate thin films with anisotropic epitaxy

NASA Astrophysics Data System (ADS)

Simon, W. K.; Akdogan, E. K.; Safari, A.; Bellotti, J. A.

2005-08-01

In-plane dielectric properties of ⟨110⟩ oriented epitaxial (Ba0.60Sr0.40)TiO3 thin films in the thickness range from 25-1200nm have been investigated under the influence of anisotropic epitaxial strains from ⟨100⟩ NdGaO3 substrates. The measured dielectric properties show strong residual strain and in-plane directional dependence. Below 150nm film thickness, there appears to be a phase transition due to the anisotropic nature of the misfit strain relaxation. In-plane relative permittivity is found to vary from as much as 500-150 along [11¯0] and [001] respectively, in 600nm thick films, and from 75 to 500 overall. Tunability was found to vary from as much as 54% to 20% in all films and directions, and in a given film the best tunability is observed along the compressed axis in a mixed strain state, 54% along [11¯0] in the 600nm film for example.

Phase formation and strain relaxation of Ga2O3 on c-plane and a-plane sapphire substrates as studied by synchrotron-based x-ray diffraction

NASA Astrophysics Data System (ADS)

Cheng, Zongzhe; Hanke, Michael; Vogt, Patrick; Bierwagen, Oliver; Trampert, Achim

2017-10-01

Heteroepitaxial Ga2O3 was deposited on c-plane and a-plane oriented sapphire by plasma-assisted molecular beam epitaxy and probed by ex-situ and in-situ synchrotron-based x-ray diffraction. The investigation on c-plane sapphire determined a critical thickness of around 33 Å, at which the monoclinic β-phase forms on top of the hexagonal α-phase. A 143 Å thick single phase α-Ga2O3 was observed on a-plane sapphire, much thicker than the α-Ga2O3 on c-plane sapphire. The α-Ga2O3 relaxed very fast in the first 30 Å in both out-of-plane and in-plane directions as measured by the in-situ study.

Material mechanical characterization method for multiple strains and strain rates

DOEpatents

Erdmand, III, Donald L.; Kunc, Vlastimil; Simunovic, Srdjan; Wang, Yanli

2016-01-19

A specimen for measuring a material under multiple strains and strain rates. The specimen including a body having first and second ends and a gage region disposed between the first and second ends, wherein the body has a central, longitudinal axis passing through the first and second ends. The gage region includes a first gage section and a second gage section, wherein the first gage section defines a first cross-sectional area that is defined by a first plane that extends through the first gage section and is perpendicular to the central, longitudinal axis. The second gage section defines a second cross-sectional area that is defined by a second plane that extends through the second gage section and is perpendicular to the central, longitudinal axis and wherein the first cross-sectional area is different in size than the second cross-sectional area.

How Caregivers Make Meaning of Child Mental Health Problems: Toward Understanding Caregiver Strain and Help Seeking.

PubMed

Mayberry, Lindsay S; Heflinger, Craig Anne

Family caregivers' conceptualizations of their child's emotional and behavioral problems (EBP) influence help-seeking for the child and caregiver strain. We analyzed 21 interviews with caregivers to explore their conceptualizations about the cause of their child's EBP, their experiences of strain, and their reported help-seeking behaviors. Caregivers had divergent conceptualizations of their child's EBP: 12 caregivers viewed the EBP as caused by a disorder and described the onset of symptoms as the central stressful event, whereas 9 caregivers described their child's problems as a response to an earlier stressor (e.g. trauma, abuse, divorce). Different patterns of caregiver strain and help-seeking were associated with caregiver conceptualization. All caregivers voiced a need for peer-to-peer support for caregivers and youth with EBP.

Stresses and strains in thick perforated orthotropic plates

Treesearch

A. Alshaya; John Hunt; R. Rowlands

2016-01-01

Stress and strain concentrations and in-plane and out-of-plane stress constraint factors associated with a circular hole in thick, loaded orthotropic composite plates are determined by three-dimensional finite element method. The plate has essentially infinite in-plane geometry but finite thickness. Results for Sitka Spruce wood are emphasized, although some for carbon...

Magnetic domain pattern asymmetry in (Ga, Mn)As/(Ga,In)As with in-plane anisotropy

NASA Astrophysics Data System (ADS)

Herrera Diez, L.; Rapp, C.; Schoch, W.; Limmer, W.; Gourdon, C.; Jeudy, V.; Honolka, J.; Kern, K.

2012-04-01

Appropriate adjustment of the tensile strain in (Ga, Mn)As/(Ga,In)As films allows for the coexistence of in-plane magnetic anisotropy, typical of compressively strained (Ga, Mn)As/GaAs films, and the so-called cross-hatch dislocation pattern seeded at the (Ga,In)As/GaAs interface. Kerr microscopy reveals a close correlation between the in-plane magnetic domain and dislocation patterns, absent in compressively strained materials. Moreover, the magnetic domain pattern presents a strong asymmetry in the size and number of domains for applied fields along the easy [11¯0] and hard [110] directions which is attributed to different domain wall nucleation/propagation energies. This strong influence of the dislocation lines in the domain wall propagation/nucleation provides a lithography-free route to the effective trapping of domain walls in magneto-transport devices based on (Ga, Mn)As with in-plane anisotropy.

Design Guidelines for In-Plane Mechanical Properties of SiC Fiber-Reinforced Melt-Infiltrated SiC Composites

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Pujar, Vijay V.

2008-01-01

In-plane tensile stress-strain, tensile creep, and after-creep retained tensile properties of melt-infiltrated SiC-SiC composites reinforced with different fiber types were evaluated with an emphasis on obtaining simple or first-order microstructural design guidelines for these in-plane mechanical properties. Using the mini-matrix approach to model stress-strain behavior and the results of this study, three basic general design criteria for stress and strain limits are formulated, namely a design stress limit, a design total strain limit, and an after-creep design retained strength limit. It is shown that these criteria can be useful for designing components for high temperature applications.

On a Minimum Problem in Smectic Elastomers

NASA Astrophysics Data System (ADS)

Buonsanti, Michele; Giovine, Pasquale

2008-07-01

Smectic elastomers are layered materials exhibiting a solid-like elastic response along the layer normal and a rubbery one in the plane. Balance equations for smectic elastomers are derived from the general theory of continua with constrained microstructure. In this work we investigate a very simple minimum problem based on multi-well potentials where the microstructure is taken into account. The set of polymeric strains minimizing the elastic energy contains a one-parameter family of simple strain associated with a micro-variation of the degree of freedom. We develop the energy functional through two terms, the first one nematic and the second one considering the tilting phenomenon; after, by developing in the rubber elasticity framework, we minimize over the tilt rotation angle and extract the engineering stress.

Improvement of the 2D/1D Method in MPACT Using the Sub-Plane Scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, Aaron M; Collins, Benjamin S; Downar, Thomas

Oak Ridge National Laboratory and the University of Michigan are jointly developing the MPACTcode to be the primary neutron transport code for the Virtual Environment for Reactor Applications (VERA). To solve the transport equation, MPACT uses the 2D/1D method, which decomposes the problem into a stack of 2D planes that are then coupled with a 1D axial calculation. MPACT uses the Method of Characteristics for the 2D transport calculations and P3 for the 1D axial calculations, then accelerates the solution using the 3D Coarse mesh Finite Dierence (CMFD) method. Increasing the number of 2D MOC planes will increase the accuracymore » of the alculation, but will increase the computational burden of the calculations and can cause slow convergence or instability. To prevent these problems while maintaining accuracy, the sub-plane scheme has been implemented in MPACT. This method sub-divides the MOC planes into sub-planes, refining the 1D P3 and 3D CMFD calculations without increasing the number of 2D MOC planes. To test the sub-plane scheme, three of the VERA Progression Problems were selected: Problem 3, a single assembly problem; Problem 4, a 3x3 assembly problem with control rods and pyrex burnable poisons; and Problem 5, a quarter core problem. These three problems demonstrated that the sub-plane scheme can accurately produce intra-plane axial flux profiles that preserve the accuracy of the fine mesh solution. The eigenvalue dierences are negligibly small, and dierences in 3D power distributions are less than 0.1% for realistic axial meshes. Furthermore, the convergence behavior with the sub-plane scheme compares favorably with the conventional 2D/1D method, and the computational expense is decreased for all calculations due to the reduction in expensive MOC calculations.« less

Coherent field propagation between tilted planes.

PubMed

Stock, Johannes; Worku, Norman Girma; Gross, Herbert

2017-10-01

Propagating electromagnetic light fields between nonparallel planes is of special importance, e.g., within the design of novel computer-generated holograms or the simulation of optical systems. In contrast to the extensively discussed evaluation between parallel planes, the diffraction-based propagation of light onto a tilted plane is more burdensome, since discrete fast Fourier transforms cannot be applied directly. In this work, we propose a quasi-fast algorithm (O(N 3  log N)) that deals with this problem. Based on a proper decomposition into three rotations, the vectorial field distribution is calculated on a tilted plane using the spectrum of plane waves. The algorithm works on equidistant grids, so neither nonuniform Fourier transforms nor an explicit complex interpolation is necessary. The proposed algorithm is discussed in detail and applied to several examples of practical interest.

Microstructure and Optical Properties of Nonpolar m-Plane GaN Films Grown on m-Plane Sapphire by Hydride Vapor Phase Epitaxy

NASA Astrophysics Data System (ADS)

Wei, Tongbo; Duan, Ruifei; Wang, Junxi; Li, Jinmin; Huo, Ziqiang; Yang, Jiankun; Zeng, Yiping

2008-05-01

Thick nonpolar (1010) GaN layers were grown on m-plane sapphire substrates by hydride vapor phase epitaxy (HVPE) using magnetron sputtered ZnO buffers, while semipolar (1013) GaN layers were obtained by the conventional two-step growth method using the same substrate. The in-plane anisotropic structural characteristics and stress distribution of the epilayers were revealed by high resolution X-ray diffraction and polarized Raman scattering measurements. Atomic force microscopy (AFM) images revealed that the striated surface morphologies correlated with the basal plane stacking faults for both (1010) and (1013) GaN films. The m-plane GaN surface showed many triangular-shaped pits aligning uniformly with the tips pointing to the c-axis after etching in boiled KOH, whereas the oblique hillocks appeared on the semipolar epilayers. In addition, the dominant emission at 3.42 eV in m-plane GaN films displayed a red shift with respect to that in semipolar epilayers, maybe owing to the different strain states present in the two epitaxial layers.

Maternal Caregiving Strain as a Mediator in the Relationship between Child and Mother Mental Health Problems

ERIC Educational Resources Information Center

Sales, Esther; Greeno, Catherine; Shear, M. Katherine; Anderson, Carol

2004-01-01

This study examined whether the general stress--caregiver strain--mental health outcome model may be as appropriate for caregivers of minor-age children as it has been for caregivers of adults with chronic illness. The authors examined whether children's behavioral problems are related to mothers' caregiving strains, which then is related to…

Lattice strain measurements of deuteride phase formation in epitaxial niobium on sapphire

NASA Astrophysics Data System (ADS)

Allain, Monica Marie Cortez

Deuteride phase formation in epitaxial niobium on sapphire was investigated for two film thicknesses (200 and 1200A). A palladium cap of approximately 40A facilitated deuterium absorption from the gas phase and each exposure condition ensured that the film passed through the miscibility gap. In situ resistivity and x-ray diffraction (XRD) provided a correlation between the film resistance and each of the phases. This correlation was used during helium-3 nuclear reaction analysis to determine the deuterium concentration at the beginning and end of the miscibility gap providing a closer look at the strain behavior vs. deuterium concentration within the single and two-phase region. Three orthogonal reciprocal lattice points, the out-of-plane (1--10), the in-plane (002), and the in-plane (110), were monitored with XRD during deuterium absorption to saturation. Cycling effects on the 1200A Nb film were analyzed and found not to influence the strain behavior. The strain was anisotropic for both films, giving an enhanced out-of-plane expansion relative to the two in-plane directions. This is consistent with a clamping force inhibiting in-plane expansion. The observed out-of-plane strain can be used to estimate the in-plane clamping stress; the result is approximately 1 and 2 GPa for the 1200 and 200A Nb films respectively. The volumetric expansion determined from in situ XRD measurements demonstrate that the know value of the specific volume of deuterium, Deltanu/O, in bulk Nb (Deltanu/O = 0.174) does not hold for thin-film, epitaxial geometry (Deltanu/O ≈ 1). Further, the behavior of the specific volume shows a discontinuity at the phase boundary that does not exist in bulk. Lattice strain and overall film expansion from simultaneous XRD and x-ray reflectivity (XRR) measurements, respectively, were performed on both films. These results demonstrate a larger out-of-plane film expansion compared to the out-of-plane lattice strain for the 1200A Nb film compared to the 200

Hybrid near-optimal aeroassisted orbit transfer plane change trajectories

NASA Technical Reports Server (NTRS)

Calise, Anthony J.; Duckeman, Gregory A.

1994-01-01

In this paper, a hybrid methodology is used to determine optimal open loop controls for the atmospheric portion of the aeroassisted plane change problem. The method is hybrid in the sense that it combines the features of numerical collocation with the analytically tractable portions of the problem which result when the two-point boundary value problem is cast in the form of a regular perturbation problem. Various levels of approximation are introduced by eliminating particular collocation parameters and their effect upon problem complexity and required number of nodes is discussed. The results include plane changes of 10, 20, and 30 degrees for a given vehicle.

Magnetic anisotropy in (Ga,Mn)As: Influence of epitaxial strain and hole concentration

NASA Astrophysics Data System (ADS)

Glunk, M.; Daeubler, J.; Dreher, L.; Schwaiger, S.; Schoch, W.; Sauer, R.; Limmer, W.; Brandlmaier, A.; Goennenwein, S. T. B.; Bihler, C.; Brandt, M. S.

2009-05-01

We present a systematic study on the influence of epitaxial strain and hole concentration on the magnetic anisotropy in (Ga,Mn)As at 4.2 K. The strain was gradually varied over a wide range from tensile to compressive by growing a series of (Ga,Mn)As layers with 5% Mn on relaxed graded (In,Ga)As/GaAs templates with different In concentration. The hole density, the Curie temperature, and the relaxed lattice constant of the as-grown and annealed (Ga,Mn)As layers turned out to be essentially unaffected by the strain. Angle-dependent magnetotransport measurements performed at different magnetic-field strengths were used to probe the magnetic anisotropy. The measurements reveal a pronounced linear dependence of the uniaxial out-of-plane anisotropy on both strain and hole density. Whereas the uniaxial and cubic in-plane anisotropies are nearly constant, the cubic out-of-plane anisotropy changes sign when the magnetic easy axis flips from in-plane to out-of-plane. The experimental results for the magnetic anisotropy are quantitatively compared with calculations of the free energy based on a mean-field Zener model. Almost perfect agreement between experiment and theory is found for the uniaxial out-of-plane and cubic in-plane anisotropy parameters of the as-grown samples. In addition, magnetostriction constants are derived from the anisotropy data.

Strain-driven electric control of magnetization reversal at multiferroic interfaces

NASA Astrophysics Data System (ADS)

Odkhuu, Dorj; Kioussis, Nicholas

2018-03-01

We predict that biaxial strain of several percent has a colossal effect on the magnetic anisotropy of ultrathin Fe /X TiO3 (X =Sr ,Ba ) bilayers grown epitaxially on appropriate substrates. We demonstrate that under large compressive biaxial strain the Fe film undergoes an in-plane to out-of-plane spin reorientation via ferroelectric polarization switching, where the critical strain depends on the Fe film thickness. The underlying mechanism is the interplay between the strain-enhanced magnetoelectric coupling associated with the enhanced polarization in the ferroelectric substrate and the strain-reduced magnetic anisotropy energy of the Fe overlayer. These findings open interesting prospects for exploiting stain engineering to harvest higher electric field efficiency of magnetic anisotropy for the next generation of magnetoelectric random access memory devices.

An Experimental Study of the Influence of in-Plane Fiber Waviness on Unidirectional Laminates Tensile Properties

NASA Astrophysics Data System (ADS)

Zhao, Cong; Xiao, Jun; Li, Yong; Chu, Qiyi; Xu, Ting; Wang, Bendong

2017-12-01

As one of the most common process induced defects of automated fiber placement, in-plane fiber waviness and its influences on mechanical properties of fiber reinforced composite lack experimental studies. In this paper, a new approach to prepare the test specimen with in-plane fiber waviness is proposed in consideration of the mismatch between the current test standard and actual fiber trajectory. Based on the generation mechanism of in-plane fiber waviness during automated fiber placement, the magnitude of in-plane fiber waviness is characterized by axial compressive strain of prepreg tow. The elastic constants and tensile strength of unidirectional laminates with in-plane fiber waviness are calculated by off-axis and maximum stress theory. Experimental results show that the tensile properties infade dramatically with increasing magnitude of the waviness, in good agreement with theoretical analyses. When prepreg tow compressive strain reaches 1.2%, the longitudinal tensile modulus and strength of unidirectional laminate decreased by 25.5% and 57.7%, respectively.

Simple quasi-analytical holonomic homogenization model for the non-linear analysis of in-plane loaded masonry panels: Part 1, meso-scale

NASA Astrophysics Data System (ADS)

Milani, G.; Bertolesi, E.

2017-07-01

A simple quasi analytical holonomic homogenization approach for the non-linear analysis of masonry walls in-plane loaded is presented. The elementary cell (REV) is discretized with 24 triangular elastic constant stress elements (bricks) and non-linear interfaces (mortar). A holonomic behavior with softening is assumed for mortar. It is shown how the mechanical problem in the unit cell is characterized by very few displacement variables and how homogenized stress-strain behavior can be evaluated semi-analytically.

Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lotsari, A.; Kehagias, Th.; Katsikini, M.

2014-06-07

Heteroepitaxial non-polar III-Nitride layers may exhibit extensive anisotropy in the surface morphology and the epilayer microstructure along distinct in-plane directions. The structural anisotropy, evidenced by the “M”-shape dependence of the (112{sup ¯}0) x-ray rocking curve widths on the beam azimuth angle, was studied by combining transmission electron microscopy observations, Raman spectroscopy, high resolution x-ray diffraction, and atomic force microscopy in a-plane GaN epilayers grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). The structural anisotropic behavior was attributed quantitatively to the high dislocation densities, particularly the Frank-Shockley partial dislocations that delimit the I{sub 1} intrinsic basal stacking faults,more » and to the concomitant plastic strain relaxation. On the other hand, isotropic samples exhibited lower dislocation densities and a biaxial residual stress state. For PAMBE growth, the anisotropy was correlated to N-rich (or Ga-poor) conditions on the surface during growth, that result in formation of asymmetric a-plane GaN grains elongated along the c-axis. Such conditions enhance the anisotropy of gallium diffusion on the surface and reduce the GaN nucleation rate.« less

Strain-assisted current-induced magnetization reversal in magnetic tunnel junctions: A micromagnetic study with phase-field microelasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H. B., E-mail: houbinghuang@gmail.com; Department of Physics, University of Science and Technology Beijing, Beijing 100083; Hu, J. M.

2014-09-22

Effect of substrate misfit strain on current-induced in-plane magnetization reversal in CoFeB-MgO based magnetic tunnel junctions is investigated by combining micromagnetic simulations with phase-field microelasticity theory. It is found that the critical current density for in-plane magnetization reversal decreases dramatically with an increasing substrate strain, since the effective elastic field can drag the magnetization to one of the four in-plane diagonal directions. A potential strain-assisted multilevel bit spin transfer magnetization switching device using substrate misfit strain is also proposed.

Crystallographic tilt and in-plane anisotropies of an a-plane InGaN/GaN layered structure grown by MOCVD on r-plane sapphire using a ZnO buffer

NASA Astrophysics Data System (ADS)

Liu, H. F.; Liu, W.; Guo, S.; Chi, D. Z.

2016-03-01

High-resolution x-ray diffraction (HRXRD) was used to investigate the crystallographic tilts and structural anisotropies in epitaxial nonpolar a-plane InGaN/GaN grown by metal-organic chemical vapor deposition on r-plane sapphire using a ZnO buffer. The substrate had an unintentional miscut of 0.14° towards its [-4 2 2 3] axis. However, HRXRD revealed a tilt of 0.26° (0.20°) between the ZnO (GaN) (11-20) and the Al2O3 (1-102) atomic planes, with the (11-20) axis of ZnO (GaN) tilted towards its c-axis, which has a difference of 163° in azimuth from that of the substrate’s miscut. Excess broadenings in the GaN/ZnO (11-20) rocking curves (RCs) were observed along its c-axis. Specific analyses revealed that partial dislocations and anisotropic in-plane strains, rather than surface-related effects, wafer curvature or stacking faults, are the dominant factors for the structural anisotropy. The orientation of the partial dislocations is most likely affected by the miscut of the substrate, e.g. via tilting of the misfit dislocation gliding planes created during island coalescences. Their Burgers vector components in the growth direction, in turn, gave rise to crystallographic tilts in the same direction as that of the excess RC-broadenings.

In plane oscillation of a bifilar pendulum

NASA Astrophysics Data System (ADS)

Hinrichsen, Peter F.

2016-11-01

The line tensions, the horizontal and vertical accelerations as well as the period of large angle oscillations parallel to the plane of a bifilar suspension are presented and have been experimentally investigated using strain gauges and a smart phone. This system has a number of advantages over the simple pendulum for studying large angle oscillations, and for measuring the acceleration due to gravity.

Out-of-plane three-stable-state ferroelectric switching: Finding the missing middle states

NASA Astrophysics Data System (ADS)

Lee, Jin Hong; Chu, Kanghyun; Kim, Kwang-Eun; Seidel, Jan; Yang, Chan-Ho

2016-03-01

By realizing a nonvolatile third intermediate ferroelectric state through anisotropic misfit strain, we demonstrate electrical switching among three stable out-of-plane polarizations in bismuth ferrite thin films grown on (110) pc-oriented gadolinium scandate substrates (where pc stands for pseudocubic) by the use of an asymmetric external electric field at the step edge of a bottom electrode. We employ phenomenological Landau theory, in conjunction with electrical poling experiments using piezoresponse force microscopy, to understand the role of anisotropic misfit strain and an in-plane electric field in stabilization of multiple ferroelectric states and their competition. Our finding provides a useful insight into multistep ferroelectric switching in rhombohedral ferroelectrics.

Strain engineered barium strontium titanate for tunable thin film resonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khassaf, H.; Khakpash, N.; Sun, F.

2014-05-19

Piezoelectric properties of epitaxial (001) barium strontium titanate (BST) films are computed as functions of composition, misfit strain, and temperature using a non-linear thermodynamic model. Results show that through adjusting in-plane strains, a highly adaptive rhombohedral ferroelectric phase can be stabilized at room temperature with outstanding piezoelectric response exceeding those of lead based piezoceramics. Furthermore, by adjusting the composition and the in-plane misfit, an electrically tunable piezoelectric response can be obtained in the paraelectric state. These findings indicate that strain engineered BST films can be utilized in the development of electrically tunable and switchable surface and bulk acoustic wave resonators.

Serial Back-Plane Technologies in Advanced Avionics Architectures

NASA Technical Reports Server (NTRS)

Varnavas, Kosta

2005-01-01

Current back plane technologies such as VME, and current personal computer back planes such as PCI, are shared bus systems that can exhibit nondeterministic latencies. This means a card can take control of the bus and use resources indefinitely affecting the ability of other cards in the back plane to acquire the bus. This provides a real hit on the reliability of the system. Additionally, these parallel busses only have bandwidths in the 100s of megahertz range and EMI and noise effects get worse the higher the bandwidth goes. To provide scalable, fault-tolerant, advanced computing systems, more applicable to today s connected computing environment and to better meet the needs of future requirements for advanced space instruments and vehicles, serial back-plane technologies should be implemented in advanced avionics architectures. Serial backplane technologies eliminate the problem of one card getting the bus and never relinquishing it, or one minor problem on the backplane bringing the whole system down. Being serial instead of parallel improves the reliability by reducing many of the signal integrity issues associated with parallel back planes and thus significantly improves reliability. The increased speeds associated with a serial backplane are an added bonus.

Applications of FEM and BEM in two-dimensional fracture mechanics problems

NASA Technical Reports Server (NTRS)

Min, J. B.; Steeve, B. E.; Swanson, G. R.

1992-01-01

A comparison of the finite element method (FEM) and boundary element method (BEM) for the solution of two-dimensional plane strain problems in fracture mechanics is presented in this paper. Stress intensity factors (SIF's) were calculated using both methods for elastic plates with either a single-edge crack or an inclined-edge crack. In particular, two currently available programs, ANSYS for finite element analysis and BEASY for boundary element analysis, were used.

Trajectory optimization for the National Aerospace Plane

NASA Technical Reports Server (NTRS)

Lu, Ping

1993-01-01

The objective of this second phase research is to investigate the optimal ascent trajectory for the National Aerospace Plane (NASP) from runway take-off to orbital insertion and address the unique problems associated with the hypersonic flight trajectory optimization. The trajectory optimization problem for an aerospace plane is a highly challenging problem because of the complexity involved. Previous work has been successful in obtaining sub-optimal trajectories by using energy-state approximation and time-scale decomposition techniques. But it is known that the energy-state approximation is not valid in certain portions of the trajectory. This research aims at employing full dynamics of the aerospace plane and emphasizing direct trajectory optimization methods. The major accomplishments of this research include the first-time development of an inverse dynamics approach in trajectory optimization which enables us to generate optimal trajectories for the aerospace plane efficiently and reliably, and general analytical solutions to constrained hypersonic trajectories that has wide application in trajectory optimization as well as in guidance and flight dynamics. Optimal trajectories in abort landing and ascent augmented with rocket propulsion and thrust vectoring control were also investigated. Motivated by this study, a new global trajectory optimization tool using continuous simulated annealing and a nonlinear predictive feedback guidance law have been under investigation and some promising results have been obtained, which may well lead to more significant development and application in the near future.

In Situ Study of Strain-Dependent Ion Conductivity of Stretchable Polyethylene Oxide Electrolyte

PubMed Central

Kelly, Taylor; Ghadi, Bahar Moradi; Berg, Sean; Ardebili, Haleh

2016-01-01

There is a strong need in developing stretchable batteries that can accommodate stretchable or irregularly shaped applications including medical implants, wearable devices and stretchable electronics. Stretchable solid polymer electrolytes are ideal candidates for creating fully stretchable lithium ion batteries mainly due to their mechanical and electrochemical stability, thin-film manufacturability and enhanced safety. However, the characteristics of ion conductivity of polymer electrolytes during tensile deformation are not well understood. Here, we investigate the effects of tensile strain on the ion conductivity of thin-film polyethylene oxide (PEO) through an in situ study. The results of this investigation demonstrate that both in-plane and through-plane ion conductivities of PEO undergo steady and linear growths with respect to the tensile strain. The coefficients of strain-dependent ion conductivity enhancement (CSDICE) for in-plane and through-plane conduction were found to be 28.5 and 27.2, respectively. Tensile stress-strain curves and polarization light microscopy (PLM) of the polymer electrolyte film reveal critical insights on the microstructural transformation of stretched PEO and the potential consequences on ionic conductivity. PMID:26831948

Plane stress analysis of wood members using isoparametric finite elements, a computer program

Treesearch

Gary D. Gerhardt

1983-01-01

A finite element program is presented which computes displacements, strains, and stresses in wood members of arbitrary shape which are subjected to plane strain/stressloading conditions. This report extends a program developed by R. L. Taylor in 1977, by adding both the cubic isoparametric finite element and the capability to analyze nonisotropic materials. The...

Goldstone-like phonon modes in a (111)-strained perovskite

NASA Astrophysics Data System (ADS)

Marthinsen, A.; Griffin, S. M.; Moreau, M.; Grande, T.; Tybell, T.; Selbach, S. M.

2018-01-01

Goldstone modes are massless particles resulting from spontaneous symmetry breaking. Although such modes are found in elementary particle physics as well as in condensed-matter systems like superfluid helium, superconductors, and magnons, structural Goldstone modes are rare. Epitaxial strain in thin films can induce structures and properties not accessible in bulk and has been intensively studied for (001)-oriented perovskite oxides. Here we predict Goldstone-like phonon modes in (111)-strained SrMn O3 by first-principles calculations. Under compressive strain the coupling between two in-plane rotational instabilities gives rise to a Mexican hat-shaped energy surface characteristic of a Goldstone mode. Conversely, large tensile strain induces in-plane polar instabilities with no directional preference, giving rise to a continuous polar ground state. Such phonon modes with U (1) symmetry could emulate structural condensed-matter Higgs modes. The mass of this Higgs boson, given by the shape of the Mexican hat energy surface, can be tuned by strain through proper choice of substrate.

Problems Associated with Attaching Strain Gages to Titanium Alloy Ti-61-4V

NASA Technical Reports Server (NTRS)

Jenkins, J. M.; Lemcoe, M. M.

1977-01-01

Weldable strain gages have shown excellent high temperature characteristics for supersonic cruise aircraft application. The spotwelding attachment method, however, has resulted in serious reductions in the fatigue life of titanium alloy (Ti-6Al-4V) fatigue specimens. The reduction is so severe that the use of weldable strain gages on operational aircraft must be prohibited. The cause of the fatigue problem is thought to be a combination of the microstructure changes in the material caused by spotwelding and the presence of the flange of the stain gage. Brazing, plating, and plasma spraying were investigated as substitutes for spotwelding. The attachment of a flangeless gage by plasma spraying provided the most improvement in the fatigue life of the titanium.

Effect of strain on the electronic structure and optical properties of germanium

NASA Astrophysics Data System (ADS)

Wen, Shumin; Zhao, Chunwang; Li, Jijun; Hou, Qingyu

2018-05-01

The effects of biaxial strain parallel to the (001) plane on the electronic structures and optical properties of Ge are calculated using the first-principles plane-wave pseudopotential method based on density functional theory. The screened-exchange local-density approximation function was used to obtain more reliable band structures, while strain was changed from ‑4% to +4%. The results show that the bandgap of Ge decreases with the increase of strain. Ge becomes a direct-bandgap semiconductor when the tensile strain reaches to 2%, which is in good agreement with the experimental results. The density of electron states of strained Ge becomes more localized. The tensile strain can increase the static dielectric constant distinctly, whereas the compressive strain can decrease the static dielectric constant slightly. The strain makes the absorption band edge move toward low energy. Both the tensile strain and compressive strain can significantly increase the reflectivity in the range from 7 eV to 14 eV. The tensile strain can decrease the optical conductivity, but the compressive strain can increase the optical conductivity significantly.

Large strain cruciform biaxial testing for FLC detection

NASA Astrophysics Data System (ADS)

Güler, Baran; Efe, Mert

2017-10-01

Selection of proper test method, specimen design and analysis method are key issues for studying formability of sheet metals and detection of their forming limit curves (FLC). Materials with complex microstructures may need an additional micro-mechanical investigation and accurate modelling. Cruciform biaxial test stands as an alternative to standard tests as it achieves frictionless, in-plane, multi-axial stress states with a single sample geometry. In this study, we introduce a small-scale (less than 10 cm) cruciform sample allowing micro-mechanical investigation at stress states ranging from plane strain to equibiaxial. With successful specimen design and surface finish, large forming limit strains are obtained at the test region of the sample. The large forming limit strains obtained by experiments are compared to the values obtained from Marciniak-Kuczynski (M-K) local necking model and Cockroft-Latham damage model. This comparison shows that the experimental limiting strains are beyond the theoretical values, approaching to the fracture strain of the two test materials: Al-6061-T6 aluminum alloy and DC-04 high formability steel.

Line spring model and its applications to part-through crack problems in plates and shells

NASA Technical Reports Server (NTRS)

Erdogan, Fazil; Aksel, Bulent

1988-01-01

The line spring model is described and extended to cover the problem of interaction of multiple internal and surface cracks in plates and shells. The shape functions for various related crack geometries obtained from the plane strain solution and the results of some multiple crack problems are presented. The problems considered include coplanar surface cracks on the same or opposite sides of a plate, nonsymmetrically located coplanar internal elliptic cracks, and in a very limited way the surface and corner cracks in a plate of finite width and a surface crack in a cylindrical shell with fixed end.

Line Spring Model and Its Applications to Part-Through Crack Problems in Plates and Shells

NASA Technical Reports Server (NTRS)

Erdogan, F.; Aksel, B.

1986-01-01

The line spring model is described and extended to cover the problem of interaction of multiple internal and surface cracks in plates and shells. The shape functions for various related crack geometries obtained from the plane strain solution and the results of some multiple crack problems are presented. The problems considered include coplanar surface cracks on the same or opposite sides of a plate, nonsymmetrically located coplanar internal elliptic cracks, and in a very limited way the surface and corner cracks in a plate of finite width and a surface crack in a cylindrical shell with fixed end.

Rolling motion of an elastic cylinder induced by elastic strain gradients

NASA Astrophysics Data System (ADS)

Chen, Lei; Chen, Shaohua

2014-10-01

Recent experiment shows that an elastic strain gradient field can be utilized to transport spherical particles on a stretchable substrate by rolling, inspired by which a generalized plane-strain Johnson-Kendall-Roberts model is developed in this paper in order to verify possible rolling of an elastic cylinder adhering on an elastic substrate subject to a strain gradient. With the help of contact mechanics, closed form solutions of interface tractions, stress intensity factors, and corresponding energy release rates in the plane-strain contact model are obtained, based on which a possible rolling motion of an elastic cylinder induced by strain gradients is found and the criterion for the initiation of rolling is established. The theoretical prediction is consistent well with the existing experimental observation. The result should be helpful for understanding biological transport mechanisms through muscle contractions and the design of transport systems with strain gradient.

Wrinkling instability in nanoparticle-supported graphene: implications for strain engineering

NASA Astrophysics Data System (ADS)

Cullen, William; Yamamoto, Mahito; Pierre-Louis, Olivier; Huang, Jia; Fuhrer, Michael; Einstein, Theodore

2013-03-01

We have carried out a systematic study of the wrinkling instability of graphene membranes supported on SiO2 substrates with randomly placed silica nanoparticles. At small nanoparticle density, monolayer graphene adheres to the substrate and is highly conformal over the nanoparticles. With increasing nanoparticle density, and decreasing nanoparticle separation to ~100 nm, graphene's elastic response dominates substrate adhesion, and elastic stretching energy is reduced by the formation of wrinkles which connect protrusions. Above a critical nanoparticle density, the wrinkles form a percolating network through the sample. As the graphene membrane is made thicker, delamination from the substrate is observed. Since the wrinkling instability acts to remove inhomogeneous in-plane elastic strains through out-of-plane buckling, our results can be used to place limits on the possible in-plane strain magnitudes that may be created in graphene to realized strain-engineered electronic structures.[2] Supported by the UMD NSF-MRSEC under Grant No. DMR 05-20471, the US ONR MURI and UMD CNAM.

Twin and habit plane microstructures due to the tetragonal to monoclinic transformation of zirconia

NASA Astrophysics Data System (ADS)

Simha, N. K.

1997-02-01

We first construct Bain strains for the tetragonal to monoclinic ( t → m) transformation of zirconia (ZrO 2), and then examine the resulting twin and habit plane microstructures. The ( t → m) transformation in zirconia occurs via two paths; transformation along path I has two Bain strains that involve shearing of a rectangular face of the tetragonal unit cell, and shearing of the square base corresponds to path II. The monoclinic variants resulting from each of the three Bain strains can form 12 twins, and four of the twins corresponding to path II are neither of type I nor of type II. Habit planes do not exist for the transformation along path I, whereas transformation along path II has: (± 0.8139, ± 0.3898, - 0.4309) t, (± 0.6489, ± 0.6271, - 0.4309) t, (± 0.7804, ± 0.4530, - 0.4309) t. We predict the exact twin planes observed by Bailey [(1964) Phase transformation at high temperatures in hafnia and zirconia. Proc. Roy. Soc.279A, 395-412], Bansal and Heuer [(1972) On a martensitic phase transformation in Zirconia ZrO 2—I. Metallographic evidence. Acta Metall.20, 1281-1289] and Buljan et al. [(1976) Optical and X-ray single crystal studies of the monoclinic ↔ tetragonal transition in ZrO 2. J. Am. Ceram. Soc.59, 351-354]; additional twins and habit planes that we predict have not yet been observed.

Controlled multiple neutral planes by low elastic modulus adhesive for flexible organic photovoltaics.

PubMed

Kim, Wansun; Lee, Inhwa; Yoon Kim, Dong; Yu, Youn-Yeol; Jung, Hae-Yoon; Kwon, Seyeoul; Seo Park, Weon; Kim, Taek-Soo

2017-05-12

To protect brittle layers in organic photovoltaic devices, the mechanical neutral plane strategy can be adopted through placing the brittle functional materials close to the neutral plane where stress and strain are zero during bending. However, previous research has been significantly limited in the location and number of materials to protect through using a single neutral plane. In this study, multiple neutral planes are generated using low elastic modulus adhesives and are controlled through quantitative analyses in order to protect the multiple brittle materials at various locations. Moreover, the protection of multiple brittle layers at various locations under both concave and convex bending directions is demonstrated. Multilayer structures that have soft adhesives are further analyzed using the finite element method analysis in order to propose guidelines for structural design when employing multiple neutral planes.

Strain Measurement System Developed for Biaxially Loaded Cruciform Specimens

NASA Technical Reports Server (NTRS)

Krause, David L.

2000-01-01

A new extensometer system developed at the NASA Glenn Research Center at Lewis Field measures test area strains along two orthogonal axes in flat cruciform specimens. This system incorporates standard axial contact extensometers to provide a cost-effective high-precision instrument. The device was validated for use by extensive testing of a stainless steel specimen, with specimen temperatures ranging from room temperature to 1100 F. In-plane loading conditions included several static biaxial load ratios, plus cyclic loadings of various waveform shapes, frequencies, magnitudes, and durations. The extensometer system measurements were compared with strain gauge data at room temperature and with calculated strain values for elevated-temperature measurements. All testing was performed in house in Glenn's Benchmark Test Facility in-plane biaxial load frame.

In-plane stability analysis of non-uniform cross-sectioned curved beams

NASA Astrophysics Data System (ADS)

Öztürk, Hasan; Yeşilyurt, İsa; Sabuncu, Mustafa

2006-09-01

In this study, in-plane stability analysis of non-uniform cross-sectioned thin curved beams under uniformly distributed dynamic loads is investigated by using the Finite Element Method. The first and second unstable regions are examined for dynamic stability. In-plane vibration and in-plane buckling are also studied. Two different finite element models, representing variations of cross-section, are developed by using simple strain functions in the analysis. The results obtained from this study are compared with the results of other investigators in existing literature for the fundamental natural frequency and critical buckling load. The effects of opening angle, variations of cross-section, static and dynamic load parameters on the stability regions are shown in graphics.

Attitude analysis in Flatland: The plane truth

NASA Technical Reports Server (NTRS)

Shuster, Malcolm D.

1993-01-01

Many results in attitude analysis are still meaningful when the attitude is restricted to rotations about a single axis. Such a picture corresponds to attitude analysis in the Euclidean plane. The present report formalizes the representation of attitude in the plane and applies it to some well-known problems. In particular, we study the connection of the 'additive' and 'multiplicative' formulations of the differential corrector for the quaternion in its two-dimensional setting.

Some space shuttle tile/strain-isolator-pad sinusoidal vibration tests

NASA Technical Reports Server (NTRS)

Miserentino, R.; Pinson, L. D.; Leadbetter, S. A.

1980-01-01

Vibration tests were performed on the tile/strain-isolator-pad system used as thermal protection for the space shuttle orbiter. Experimental data on normal and in-plane vibration response and damping properties are presented. Three test specimens exhibited shear type motion during failures that occurred in the tile near the tile/strain-isolator-pad bond-line. A dynamic instability is described which has large in-plane motion at a frequency one-half that of the nominal driving frequency. Analysis shows that this phenomenon is a parametric response.

Strain-induced optical band gap variation of SnO 2 films

DOE PAGES

Rus, Stefania Florina; Ward, Thomas Zac; Herklotz, Andreas

2016-06-29

In this paper, thickness dependent strain relaxation effects are utilized to study the impact of crystal anisotropy on the optical band gap of epitaxial SnO 2 films grown by pulsed laser deposition on (0001)-oriented sapphire substrates. An X-ray diffraction analysis reveals that all films are under tensile biaxial in-plane strain and that strain relaxation occurs with increasing thickness. Variable angle spectroscopic ellipsometry shows that the optical band gap of the SnO 2 films continuously increases with increasing film thickness. This increase in the band gap is linearly related to the strain state of the films, which indicates that the mainmore » origin of the band gap change is strain relaxation. The experimental observation is in excellent agreement with results from density functional theory for biaxial in-plane strain. Our research demonstrates that strain is an effective way to tune the band gap of SnO 2 films and suggests that strain engineering is an appealing route to tailor the optical properties of oxide semiconductors.« less

Characterization of hot bonding of bi-metal C45/25CrMo4 by plane strain compression test

NASA Astrophysics Data System (ADS)

Enaim, Mohammed; Langlois, Laurent; Zimmer-Chevret, Sandra; Bigot, Régis; Krumpipe, Pierre

2018-05-01

The need to produce multifunctional parts in order to conform to complex specifications becomes crucial in today's industrial context. This is why new processes are under study to develop multi-material parts which can satisfy this kind of requirements. This paper investigates the possibility of producing hot bonding of bi-metal C45/25CrMo4 parts by forging. This manufacturing process is a solid state joining process that involves, simultaneously, the welding and shaping of multi-material part. In this study, the C45/25CrMo4 bimetal was investigated. The forging is conducted at 1100°C and the influence of reduction rate on microstructure and bonding was investigated. The bonding model is inspired from Bay's model. Following this model, two parameters govern the solid-state bonding at the interface between materials: normal contact pressure and surface expansion. The objective is to check the bonding quality under different pressure and surface expansion. To achieve this goal, the plane strain compression test is chosen as the characterization test. Finally, simulations and experiments of this test are compared.

Plane Evanescent Waves and Interface Waves

NASA Astrophysics Data System (ADS)

Luppé, F.; Conoir, J. M.; El Kettani, M. Ech-Cherif; Lenoir, O.; Izbicki, J. L.; Duclos, J.; Poirée, B.

The evanescent plane wave formalism is used to obtain the characteristic equation of the normal vibration modes of a plane elastic solid embedded in a perfect fluid. Simple drawings of the real and imaginary parts of complex wave vectors make quite clear the choice of the Riemann sheets on which the roots of the characteristic equation are to be looked for. The generalized Rayleigh wave and the Scholte - Stoneley wave are then described. The same formalism is used to describe Lamb waves on an elastic plane plate immersed in water. The damping, due to energy leaking in the fluid, is shown to be directly given by the projection of evanescence vectors on the interface. Measured values of the damping coefficient are in good agreement with those derived from calculations. The width of the angular resonances associated to Lamb waves or Rayleigh waves is also directly related to this same evanescence vectors projection, as well as the excitation coefficient of a given Lamb wave excited by a plane incident wave. This study shows clearly the strong correlation between the resonance point of view and the wave one in plane interface problems.

High Temperature Capacitive Strain Gage

NASA Technical Reports Server (NTRS)

Wnuk, Stephen P., Jr.; Wnuk, Stephen P., III; Wnuk, V. P.

1990-01-01

Capacitive strain gages designed for measurements in wind tunnels to 2000 F were built and evaluated. Two design approaches were followed. One approach was based on fixed capacitor plates with a movable ground plane inserted between the plates to effect differential capacitive output with strain. The second approach was based on movable capacitor plates suspended between sapphire bearings, housed in a rugged body, and arranged to operate as a differential capacitor. A sapphire bearing gage (1/4 in. diameter x 1 in. in size) was built with a range of 50,000 and a resolution of 200 microstrain. Apparent strain on Rene' 41 was less than + or - 1000 microstrain from room temperature to 2000 F. Three gage models were built from the Ground Plane Differential concept. The first was 1/4 in. square by 1/32 in. high and useable to 700 F. The second was 1/2 in. square by 1/16 in. high and useable to 1440 F. The third, also 1/2 in. square by 1/16 in. high was expected to operate in the 1600 to 2000 F range, but was not tested because time and funding ended.

High temperature capacitive strain gage

NASA Astrophysics Data System (ADS)

Wnuk, Stephen P., Jr.; Wnuk, Stephen P., III; Wnuk, V. P.

1990-01-01

Capacitive strain gages designed for measurements in wind tunnels to 2000 F were built and evaluated. Two design approaches were followed. One approach was based on fixed capacitor plates with a movable ground plane inserted between the plates to effect differential capacitive output with strain. The second approach was based on movable capacitor plates suspended between sapphire bearings, housed in a rugged body, and arranged to operate as a differential capacitor. A sapphire bearing gage (1/4 in. diameter x 1 in. in size) was built with a range of 50,000 and a resolution of 200 microstrain. Apparent strain on Rene' 41 was less than + or - 1000 microstrain from room temperature to 2000 F. Three gage models were built from the Ground Plane Differential concept. The first was 1/4 in. square by 1/32 in. high and useable to 700 F. The second was 1/2 in. square by 1/16 in. high and useable to 1440 F. The third, also 1/2 in. square by 1/16 in. high was expected to operate in the 1600 to 2000 F range, but was not tested because time and funding ended.

Centre-based restricted nearest feature plane with angle classifier for face recognition

NASA Astrophysics Data System (ADS)

Tang, Linlin; Lu, Huifen; Zhao, Liang; Li, Zuohua

2017-10-01

An improved classifier based on the nearest feature plane (NFP), called the centre-based restricted nearest feature plane with the angle (RNFPA) classifier, is proposed for the face recognition problems here. The famous NFP uses the geometrical information of samples to increase the number of training samples, but it increases the computation complexity and it also has an inaccuracy problem coursed by the extended feature plane. To solve the above problems, RNFPA exploits a centre-based feature plane and utilizes a threshold of angle to restrict extended feature space. By choosing the appropriate angle threshold, RNFPA can improve the performance and decrease computation complexity. Experiments in the AT&T face database, AR face database and FERET face database are used to evaluate the proposed classifier. Compared with the original NFP classifier, the nearest feature line (NFL) classifier, the nearest neighbour (NN) classifier and some other improved NFP classifiers, the proposed one achieves competitive performance.

3D Tendon Strain Estimation Using High-frequency Volumetric Ultrasound Images: A Feasibility Study.

PubMed

Carvalho, Catarina; Slagmolen, Pieter; Bogaerts, Stijn; Scheys, Lennart; D'hooge, Jan; Peers, Koen; Maes, Frederik; Suetens, Paul

2018-03-01

Estimation of strain in tendons for tendinopathy assessment is a hot topic within the sports medicine community. It is believed that, if accurately estimated, existing treatment and rehabilitation protocols can be improved and presymptomatic abnormalities can be detected earlier. State-of-the-art studies present inaccurate and highly variable strain estimates, leaving this problem without solution. Out-of-plane motion, present when acquiring two-dimensional (2D) ultrasound (US) images, is a known problem and may be responsible for such errors. This work investigates the benefit of high-frequency, three-dimensional (3D) US imaging to reduce errors in tendon strain estimation. Volumetric US images were acquired in silico, in vitro, and ex vivo using an innovative acquisition approach that combines the acquisition of 2D high-frequency US images with a mechanical guided system. An affine image registration method was used to estimate global strain. 3D strain estimates were then compared with ground-truth values and with 2D strain estimates. The obtained results for in silico data showed a mean absolute error (MAE) of 0.07%, 0.05%, and 0.27% for 3D estimates along axial, lateral direction, and elevation direction and a respective MAE of 0.21% and 0.29% for 2D strain estimates. Although 3D could outperform 2D, this does not occur in in vitro and ex vivo settings, likely due to 3D acquisition artifacts. Comparison against the state-of-the-art methods showed competitive results. The proposed work shows that 3D strain estimates are more accurate than 2D estimates but acquisition of appropriate 3D US images remains a challenge.

Determination of Dynamic Recrystallization Process by Equivalent Strain

NASA Astrophysics Data System (ADS)

Qin, Xiaomei; Deng, Wei

Based on Tpнoвckiй's displacement field, equivalent strain expression was derived. And according to the dynamic recrystallization (DRX) critical strain, DRX process was determined by equivalent strain. It was found that equivalent strain distribution in deformed specimen is inhomogeneous, and it increases with increasing true strain. Under a certain true strain, equivalent strains at the center, demisemi radius or on tangential plane just below the surface of the specimen are higher than the true strain. Thus, micrographs at those positions can not exactly reflect the true microstructures under the certain true strain. With increasing strain rate, the initial and finish time of DRX decrease. The frozen microstructures of 20Mn23AlV steel with the experimental condition validate the feasibility of predicting DRX process by equivalent strain.

Ferroelectric domain structure of anisotropically strained NaNbO3 epitaxial thin films

NASA Astrophysics Data System (ADS)

Schwarzkopf, J.; Braun, D.; Schmidbauer, M.; Duk, A.; Wördenweber, R.

2014-05-01

NaNbO3 thin films have been grown under anisotropic biaxial strain on several oxide substrates by liquid-delivery spin metalorganic chemical vapor deposition. Compressive lattice strain of different magnitude, induced by the deposition of NaNbO3 films with varying film thickness on NdGaO3 single crystalline substrates, leads to modifications of film orientation and phase symmetry, which are similar to the phase transitions in Pb-containing oxides near the morphotropic phase boundary. Piezoresponse force microscopy measurements exhibit large out-of-plane polarization components, but no distinctive domain structure, while C-V measurements indicate relaxor properties in these films. When tensile strain is provoked by the epitaxial growth on DyScO3, TbScO3, and GdScO3 single crystalline substrates, NaNbO3 films behave rather like a normal ferroelectric. The application of these rare-earth scandate substrates yields well-ordered ferroelectric stripe domains of the type a1/a2 with coherent domain walls aligned along the [001] substrate direction as long as the films are fully strained. With increasing plastic lattice relaxation, initially, a 2D domain pattern with still exclusively in-plane electric polarization, and finally, domains with in-plane and out-of-plane polar components evolve.

Large Strain Behaviour of ZEK100 Magnesium Alloy at Various Strain Rates

NASA Astrophysics Data System (ADS)

Lévesque, Julie; Kurukuri, Srihari; Mishra, Raja; Worswick, Michael; Inal, Kaan

A constitutive framework based on a rate-dependent crystal plasticity theory is employed to simulate large strain deformation in hexagonal closed-packed metals that deform by slip and twinning. The model allows the twinned zones and the parent matrix to rotate independently. ZEK100 magnesium alloy sheets which significant texture weakening compared to AZ31 sheets are investigated using the model. There is considerable in-plane anisotropy and tension compression asymmetry in the flow behavior of ZEK100. Simulations of uniaxial tension in different directions at various strain rates and the accompanying texture evolution are performed and they are in very good agreement with experimental measurements. The effect of strain rate on the activation of the various slip systems and twinning show that differences in the strain rate dependence of yield stress and Rvalues in ZEK100 have their origin in the activation of different deformation mechanisms.

Eshelby's problem of polygonal inclusions with polynomial eigenstrains in an anisotropic magneto-electro-elastic full plane

PubMed Central

Lee, Y.-G.; Zou, W.-N.; Pan, E.

2015-01-01

This paper presents a closed-form solution for the arbitrary polygonal inclusion problem with polynomial eigenstrains of arbitrary order in an anisotropic magneto-electro-elastic full plane. The additional displacements or eigendisplacements, instead of the eigenstrains, are assumed to be a polynomial with general terms of order M+N. By virtue of the extended Stroh formulism, the induced fields are expressed in terms of a group of basic functions which involve boundary integrals of the inclusion domain. For the special case of polygonal inclusions, the boundary integrals are carried out explicitly, and their averages over the inclusion are also obtained. The induced fields under quadratic eigenstrains are mostly analysed in terms of figures and tables, as well as those under the linear and cubic eigenstrains. The connection between the present solution and the solution via the Green's function method is established and numerically verified. The singularity at the vertices of the arbitrary polygon is further analysed via the basic functions. The general solution and the numerical results for the constant, linear, quadratic and cubic eigenstrains presented in this paper enable us to investigate the features of the inclusion and inhomogeneity problem concerning polynomial eigenstrains in semiconductors and advanced composites, while the results can further serve as benchmarks for future analyses of Eshelby's inclusion problem. PMID:26345141

Thermal transport and anharmonic phonons in strained monolayer hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Li, Shasha; Chen, Yue

2017-03-01

Thermal transport and phonon-phonon coupling in monolayer hexagonal boron nitride (h-BN) under equibiaxial strains are investigated from first principles. Phonon spectra at elevated temperatures have been calculated from perturbation theory using the third-order anharmonic force constants. The stiffening of the out-of-plane transverse acoustic mode (ZA) near the Brillouin zone center and the increase of acoustic phonon lifetimes are found to contribute to the dramatic increase of thermal transport in strained h-BN. The transverse optical mode (TO) at the K point, which was predicted to lead to mechanical failure of h-BN, is found to shift to lower frequencies at elevated temperatures under equibiaxial strains. The longitudinal and transverse acoustic modes exhibit broad phonon spectra under large strains in sharp contrast to the ZA mode, indicating strong in-plane phonon-phonon coupling.

Extended linear detection range for optical tweezers using image-plane detection scheme

NASA Astrophysics Data System (ADS)

Hajizadeh, Faegheh; Masoumeh Mousavi, S.; Khaksar, Zeinab S.; Reihani, S. Nader S.

2014-10-01

Ability to measure pico- and femto-Newton range forces using optical tweezers (OT) strongly relies on the sensitivity of its detection system. We show that the commonly used back-focal-plane detection method provides a linear response range which is shorter than that of the restoring force of OT for large beads. This limits measurable force range of OT. We show, both theoretically and experimentally, that utilizing a second laser beam for tracking could solve the problem. We also propose a new detection scheme in which the quadrant photodiode is positioned at the plane optically conjugate to the object plane (image plane). This method solves the problem without need for a second laser beam for the bead sizes that are commonly used in force spectroscopy applications of OT, such as biopolymer stretching.

A uniform GTD analysis of the EM diffraction by a thin dielectric/ferrite half-plane and related configurations

NASA Technical Reports Server (NTRS)

Rojas, Roberto G.

1985-01-01

A uniform geometrical theory of diffraction (UTD) solution is developed for the problem of the diffraction by a thin dielectric/ferrite half plane when it is excited by a plane, cylindrical, or surface wave field. Both transverse electric and transverse magnetic cases are considered. The solution of this problem is synthesized from the solutions to the related problems of EM diffraction by configurations involving perfectly conducting electric and magnetic walls covered by a dielectric/ferrite half-plane of one half the thickness of the original half-plane.

Effects of strain relaxation in Pr 0.67Sr 0.33MnO 3 films probed by polarization dependent X-ray absorption near edge structure

DOE PAGES

zhang, Bangmin; Chen, Jingsheng; Venkatesan, T.; ...

2016-01-28

In this study, the Mn K edge X-ray absorption near edge structure (XANES) of Pr 0.67Sr 0.33MnO 3 films with different thicknesses on (001) LaAlO 3 substrate were measured, and the effects of strain relaxation on film properties were investigated. The films experienced in-plane compressive strain and out-of-plane tensile strain. Strain relaxation evolved with the film thickness. In the polarization dependent XANES measurements, the in-plane (parallel) and out-of-plane (perpendicular) XANES spectrocopies were anisotropic with different absorption energy E r. The resonance energy Er along two directions shifted towards each other with increasing film thickness. Based on the X-ray diffraction results,more » it was suggested that the strain relaxation weakened the difference of the local environment and probability of electronic charge transfer (between Mn 3d and O 2p orbitals) along the in-plane and out-of-plane directions, which was responsible for the change of E r. XANES is a useful tool to probe the electronic structures, of which the effects on magnetic properties with the strain relaxation was also been studied.« less

Variation of Shrinkage Strain within the Depth of Concrete Beams.

PubMed

Jeong, Jong-Hyun; Park, Yeong-Seong; Lee, Yong-Hak

2015-11-16

The variation of shrinkage strain within beam depth was examined through four series of time-dependent laboratory experiments on unreinforced concrete beam specimens. Two types of beam specimens, horizontally cast and vertically cast, were tested; shrinkage variation was observed in the horizontally cast specimens. This indicated that the shrinkage variation within the beam depth was due to water bleeding and tamping during the placement of the fresh concrete. Shrinkage strains were measured within the beam depth by two types of strain gages, surface-attached and embedded. The shrinkage strain distribution within the beam depth showed a consistent tendency for the two types of gages. The test beams were cut into four sections after completion of the test, and the cutting planes were divided into four equal sub-areas to measure the aggregate concentration for each sub-area of the cutting plane. The aggregate concentration increased towards the bottom of the beam. The shrinkage strain distribution was estimated by Hobbs' equation, which accounts for the change of aggregate volume concentration.

Variation of Shrinkage Strain within the Depth of Concrete Beams

PubMed Central

Jeong, Jong-Hyun; Park, Yeong-Seong; Lee, Yong-Hak

2015-01-01

The variation of shrinkage strain within beam depth was examined through four series of time-dependent laboratory experiments on unreinforced concrete beam specimens. Two types of beam specimens, horizontally cast and vertically cast, were tested; shrinkage variation was observed in the horizontally cast specimens. This indicated that the shrinkage variation within the beam depth was due to water bleeding and tamping during the placement of the fresh concrete. Shrinkage strains were measured within the beam depth by two types of strain gages, surface-attached and embedded. The shrinkage strain distribution within the beam depth showed a consistent tendency for the two types of gages. The test beams were cut into four sections after completion of the test, and the cutting planes were divided into four equal sub-areas to measure the aggregate concentration for each sub-area of the cutting plane. The aggregate concentration increased towards the bottom of the beam. The shrinkage strain distribution was estimated by Hobbs’ equation, which accounts for the change of aggregate volume concentration. PMID:28793677

Out-of-plane strain and electric field tunable electronic properties and Schottky contact of graphene/antimonene heterostructure

NASA Astrophysics Data System (ADS)

Phuc, Huynh V.; Hieu, Nguyen N.; Hoi, Bui D.; Phuong, Le T. T.; Hieu, Nguyen V.; Nguyen, Chuong V.

2017-12-01

In this paper, the electronic properties of graphene/monolayer antimonene (G/m-Sb) heterostructure have been studied using the density functional theory (DFT). The effects of out-of-plane strain (interlayer coupling) and electric field on the electronic properties and Schottky contact of the G/m-Sb heterostructure are also investigated. The results show that graphene is bound to m-Sb layer by a weak van-der-Waals interaction with the interlayer distance of 3.50 Å and the binding energy per carbon atom of -39.62 meV. We find that the n-type Schottky contact is formed at the G/m-Sb heterostructure with the Schottky barrier height (SBH) of 0.60 eV. By varying the interlayer distance between graphene and the m-Sb layer we can change the n-type and p-type SBH at the G/m-Sb heterostructure. Especially, we find the transformation from n-type to p-type Schottky contact with decreasing the interlayer distance. Furthermore, the SBH and the Schottky contact could be controlled by applying the perpendicular electric field. With the positive electric field, electrons can easily transfer from m-Sb to graphene layer, leading to the transition from n-type to p-type Schottky contact.

Effect of strain on thermoelectric properties of SrTiO3: First-principles calculations

NASA Astrophysics Data System (ADS)

Zou, Daifeng; Liu, Yunya; Xie, Shuhong; Lin, Jianguo; Li, Jiangyu

2013-10-01

The electronic structures of strained SrTiO3 were investigated by using first-principles calculations, and the anisotropic thermoelectric properties of n-type SrTiO3 under biaxial strain were calculated on the base of the semi-classical Boltzmann transport theory. It was theoretically found that the in-plane and out-of-plane power factors of n-type SrTiO3 can be increased under compressive and tensile strains, respectively, and such dependence can be explained by the strain-induced redistribution of electrons. To further optimize the thermoelectric performance of n-type SrTiO3, the maximum power factors and the corresponding optimal n-type doping levels were evaluated.

Laser speckle strain and deformation sensor using linear array image cross-correlation method for specifically arranged triple-beam triple-camera configuration

NASA Technical Reports Server (NTRS)

Sarrafzadeh-Khoee, Adel K. (Inventor)

2000-01-01

The invention provides a method of triple-beam and triple-sensor in a laser speckle strain/deformation measurement system. The triple-beam/triple-camera configuration combined with sequential timing of laser beam shutters is capable of providing indications of surface strain and structure deformations. The strain and deformation quantities, the four variables of surface strain, in-plane displacement, out-of-plane displacement and tilt, are determined in closed form solutions.

Anisotropic spin-density distribution and magnetic anisotropy of strained La1-xSrxMnO3 thin films: angle-dependent x-ray magnetic circular dichroism

NASA Astrophysics Data System (ADS)

Shibata, Goro; Kitamura, Miho; Minohara, Makoto; Yoshimatsu, Kohei; Kadono, Toshiharu; Ishigami, Keisuke; Harano, Takayuki; Takahashi, Yukio; Sakamoto, Shoya; Nonaka, Yosuke; Ikeda, Keisuke; Chi, Zhendong; Furuse, Mitsuho; Fuchino, Shuichiro; Okano, Makoto; Fujihira, Jun-ichi; Uchida, Akira; Watanabe, Kazunori; Fujihira, Hideyuki; Fujihira, Seiichi; Tanaka, Arata; Kumigashira, Hiroshi; Koide, Tsuneharu; Fujimori, Atsushi

2018-01-01

Magnetic anisotropies of ferromagnetic thin films are induced by epitaxial strain from the substrate via strain-induced anisotropy in the orbital magnetic moment and that in the spatial distribution of spin-polarized electrons. However, the preferential orbital occupation in ferromagnetic metallic La1-xSrxMnO3 (LSMO) thin films studied by x-ray linear dichroism (XLD) has always been found out-of-plane for both tensile and compressive epitaxial strain and hence irrespective of the magnetic anisotropy. In order to resolve this mystery, we directly probed the preferential orbital occupation of spin-polarized electrons in LSMO thin films under strain by angle-dependent x-ray magnetic circular dichroism (XMCD). Anisotropy of the spin-density distribution was found to be in-plane for the tensile strain and out-of-plane for the compressive strain, consistent with the observed magnetic anisotropy. The ubiquitous out-of-plane preferential orbital occupation seen by XLD is attributed to the occupation of both spin-up and spin-down out-of-plane orbitals in the surface magnetic dead layer.

Acceleration of planes segmentation using normals from previous frame

NASA Astrophysics Data System (ADS)

Gritsenko, Pavel; Gritsenko, Igor; Seidakhmet, Askar; Abduraimov, Azizbek

2017-12-01

One of the major problem in integration process of robots is to make them able to function in a human environment. In terms of computer vision, the major feature of human made rooms is the presence of planes [1, 2, 20, 21, 23]. In this article, we will present an algorithm dedicated to increase speed of a plane segmentation. The algorithm uses information about location of a plane and its normal vector to speed up the segmentation process in the next frame. In conjunction with it, we will address such aspects of ICP SLAM as performance and map representation.

Submicron mapping of strained silicon-on-insulator features induced

NASA Astrophysics Data System (ADS)

Murray, Conal E.; Sankarapandian, M.; Polvino, S. M.; Noyan, I. C.; Lai, B.; Cai, Z.

2007-04-01

Real-space maps of strain within silicon-on-insulator (SOI) features induced by adjacent, embedded shallow-trench-isolation (STI) SiO2 regions were obtained using x-ray microbeam diffraction. The quantitative strain mapping indicated that the SOI strain was largest at the SOI/STI interface and decreased as a function of distance from this interface. An out-of-plane residual strain of approximately -31μɛ was observed in the blanket regions of the SOI. A comparison of the depth-averaged strain distributions to the strain profiles calculated from an Eshelby inclusion model indicated an equivalent eigenstrain of -0.55% in the STI regions acting on the SOI features.

Unusual Enhancement in Intrinsic Thermal Conductivity of Multilayer Graphene by Tensile Strains

DOE PAGES

Kuang, Youdi; Lindsay, Lucas R.; Huang, Baoling

2015-01-01

High basal plane thermal conductivity k of multi-layer graphene makes it promising for thermal management applications. Here we examine the effects of tensile strain on thermal transport in this system. Using a first principles Boltzmann-Peierls equation for phonon transport approach, we calculate the room-temperature in-plane lattice k of multi-layer graphene (up to four layers) and graphite under different isotropic tensile strains. The calculated in-plane k of graphite, finite mono-layer graphene and 3-layer graphene agree well with previous experiments. The dimensional transitions of the intrinsic k and the extent of the diffusive transport regime from mono-layer graphene to graphite are presented.more » We find a peak enhancement of intrinsic k for multi-layer graphene and graphite with increasing strain and the largest enhancement amplitude is about 40%. In contrast the calculated intrinsic k with tensile strain decreases for diamond and diverges for graphene, we show that the competition between the decreased mode heat capacities and the increased lifetimes of flexural phonons with increasing strain contribute to this k behavior. Similar k behavior is observed for 2-layer hexagonal boron nitride systems, suggesting that it is an inherent thermal transport property in multi-layer systems assembled of purely two dimensional atomic layers. This study provides insights into engineering k of multi-layer graphene and boron nitride by strain and into the nature of thermal transport in quasi-two-dimensional and highly anisotropic systems.« less

Giant room temperature magnetoelectric response in strain controlled nanocomposites

NASA Astrophysics Data System (ADS)

Rafique, Mohsin; Herklotz, Andreas; Dörr, Kathrin; Manzoor, Sadia

2017-05-01

We report giant magnetoelectric coupling at room temperature in a self-assembled nanocomposite of BiFeO3-CoFe2O4 (BFO-CFO) grown on a BaTiO3 (BTO) crystal. The nanocomposite consisting of CFO nanopillars embedded in a BFO matrix exhibits weak perpendicular magnetic anisotropy due to a small out-of-plane compression (˜0.3%) of the magnetostrictive (CFO) phase, enabling magnetization rotation under moderate in-plane compression. Temperature dependent magnetization measurements demonstrate strong magnetoelastic coupling between the BaTiO3 substrate and the nanocomposite film, which has been exploited to produce a large magnetoelectric response in the sample. The reorientation of ferroelectric domains in the BTO crystal upon the application of an electric field (E) alters the strain state of the nanocomposite film, thus enabling control of its magnetic anisotropy. The strain mediated magnetoelectric coupling coefficient α = μ o d M / d E calculated from remnant magnetization at room temperature is 2.6 × 10-7 s m-1 and 1.5 × 10-7 s m-1 for the out-of-plane and in-plane orientations, respectively.

Enhancement of piezoelectric constants induced by cation-substitution and two-dimensional strain effects on ZnO predicted by density functional perturbation theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, Kaoru, E-mail: n-kaoru@criepi.denken.or.jp; Higuchi, Sadao; Ohnuma, Toshiharu

2016-03-21

Using density functional perturbation theory, we investigated the effect of various substitutional dopant elements and in-plane strain on the piezoelectric properties of ZnO. The piezoelectric stress constant e{sub 33} of doped ZnO was found to depend on the formal charge of the substitutional dopant. By decomposing the piezoelectric stress constant e{sub 33} into the individual atomic contributions, the change in the piezoelectric properties was found to originate from a change in the coupling between the atomic displacement and the strain. Furthermore, we found that in-plane tensile strain along the a axis, which is specific to the thin film, can enhancemore » the piezoelectric constant of ZnO. A phase transition from wurtzite to h-BN-type structure was found to occur with increasing in-plane tensile. The piezoelectric strain constant d{sub 33} was predicted to reach ∼200 pC/N for 2.78 at. % V-substituted ZnO at 5.5% in-plane strain, just before the phase transition. These theoretical results suggest that the piezoelectric constant of ZnO can be enhanced by controlling the in-plane strain via selection of the substrate material and dopant element.« less

Strain localization in <111> single crystals of Hadfield steel under compressive load

NASA Astrophysics Data System (ADS)

Astafurova, E. G.; Zakharova, G. G.; Melnikov, E. V.

2010-07-01

A study of strain localization under compression of <111> Hadfield steel single crystals at room temperature was done by light and transmission electron microscopy. At epsilon<1%, macro shear bands (MSB) form that have non-crystallographic and complex non-linear habit planes and are the results of the interaction of dislocation slip on conjugate slip planes. Mechanical twinning was experimentally found inside the MSB. After the stage of MSBs formation, deformation develops with high strain hardening coefficient and corresponds to interaction of slip and twinning inside as well as outside the MSBs.

Mechanical and electrical strain response of a piezoelectric auxetic PZT lattice structure

NASA Astrophysics Data System (ADS)

Fey, Tobias; Eichhorn, Franziska; Han, Guifang; Ebert, Kathrin; Wegener, Moritz; Roosen, Andreas; Kakimoto, Ken-ichi; Greil, Peter

2016-01-01

A two-dimensional auxetic lattice structure was fabricated from a PZT piezoceramic. Tape casted and sintered sheets with a thickness of 530 μm were laser cut into inverted honeycomb lattice structure with re-entrant cell geometry (θ = -25°) and poling direction oriented perpendicular to the lattice plane. The in-plane strain response upon applying an uniaxial compression load as well as an electric field perpendicular to the lattice plane were analyzed by a 2D image data detection analysis. The auxetic lattice structure exhibits orthotropic deformation behavior with a negative in-plane Poisson’s ratio of -2.05. Compared to PZT bulk material the piezoelectric auxetic lattice revealed a strain amplification by a factor of 30-70. Effective transversal coupling coefficients {{d}al}31 of the PZT lattice exceeding 4 × 103 pm V-1 were determined which result in an effective hydrostatic coefficient {{d}al}h 66 times larger than that of bulk PZT.

Influence of strain on dislocation core in silicon

NASA Astrophysics Data System (ADS)

Pizzagalli, L.; Godet, J.; Brochard, S.

2018-05-01

First principles, density functional-based tight binding and semi-empirical interatomic potentials calculations are performed to analyse the influence of large strains on the structure and stability of a 60? dislocation in silicon. Such strains typically arise during the mechanical testing of nanostructures like nanopillars or nanoparticles. We focus on bi-axial strains in the plane normal to the dislocation line. Our calculations surprisingly reveal that the dislocation core structure largely depends on the applied strain, for strain levels of about 5%. In the particular case of bi-axial compression, the transformation of the dislocation to a locally disordered configuration occurs for similar strain magnitudes. The formation of an opening, however, requires larger strains, of about 7.5%. Furthermore, our results suggest that electronic structure methods should be favoured to model dislocation cores in case of large strains whenever possible.

Type IIB Colliding Plane Waves

NASA Astrophysics Data System (ADS)

Gutperle, M.; Pioline, B.

2003-09-01

Four-dimensional colliding plane wave (CPW) solutions have played an important role in understanding the classical non-linearities of Einstein's equations. In this note, we investigate CPW solutions in 2n+2-dimensional Einstein gravity with a n+1-form flux. By using an isomorphism with the four-dimensional problem, we construct exact solutions analogous to the Szekeres vacuum solution in four dimensions. The higher-dimensional versions of the Khan-Penrose and Bell-Szekeres CPW solutions are studied perturbatively in the vicinity of the light-cone. We find that under small perturbations, a curvature singularity is generically produced, leading to both space-like and time-like singularities. For n = 4, our results pertain to the collision of two ten-dimensional type-IIB Blau-Figueroa o'Farrill-Hull-Papadopoulos plane waves.

Electric-regulated enhanced in-plane uniaxial anisotropy in FeGa/PMN-PT composite using oblique pulsed laser deposition

NASA Astrophysics Data System (ADS)

Zhang, Yi; Huang, Chaojuan; Turghun, Mutellip; Duan, Zhihua; Wang, Feifei; Shi, Wangzhou

2018-04-01

The FeGa film with in-plane uniaxial magnetic anisotropy was fabricated onto different oriented single-crystal lead magnesium niobate-lead titanate using oblique pulsed laser deposition. An enhanced in-plane uniaxial magnetic anisotropy field of FeGa film can be adjusted from 18 Oe to 275 Oe by tuning the oblique angle and polarizing voltage. The competitive relationship of shape anisotropy and strain anisotropy has been discussed, which was induced by oblique angle and polarizing voltage, respectively. The (100)-oriented and (110)-oriented PMN-PT show completely different characters on voltage-dependent magnetic properties, which could be attributed to various anisotropy directions depended on different strain directions.

Precession of a Spinning Ball Rolling down an Inclined Plane

ERIC Educational Resources Information Center

Cross, Rod

2015-01-01

A routine problem in an introductory physics course considers a rectangular block at rest on a plane inclined at angle a to the horizontal. In order for the block not to slide down the incline, the coefficient of sliding friction, µ, must be at least tan a. The situation is similar for the case of a ball rolling down an inclined plane. In order…

Search for and Study of Nearly Periodic Orbits in the Plane Problem of Three Equal-Mass Bodies

NASA Astrophysics Data System (ADS)

Martynova, A. I.; Orlov, V. V.

2005-09-01

We analyze nearly periodic solutions in the plane problem of three equal-mass bodies by numerically simulating the dynamics of triple systems. We identify families of orbits in which all three points are on one straight line (syzygy) at the initial time. In this case, at fixed total energy of a triple system, the set of initial conditions is a bounded region in four-dimensional parameter space. We scan this region and identify sets of trajectories in which the coordinates and velocities of all bodies are close to their initial values at certain times (which are approximately multiples of the period). We classify the nearly periodic orbits by the structure of trajectory loops over one period. We have found the families of orbits generated by von Schubart’s stable periodic orbit revealed in the rectilinear three-body problem. We have also found families of hierarchical, nearly periodic trajectories with prograde and retrograde motions. In the orbits with prograde motions, the trajectory loops of two close bodies form looplike structures. The trajectories with retrograde motions are characterized by leafed structures. Orbits with central and axial symmetries are identified among the families found.

Strain distribution in an Si single crystal measured by interference fringes of X-ray mirage diffraction

PubMed Central

Jongsukswat, Sukswat; Fukamachi, Tomoe; Ju, Dongying; Negishi, Riichirou; Hirano, Keiichi; Kawamura, Takaaki

2013-01-01

In X-ray interference fringes accompanied by mirage diffraction, variations have been observed in the spacing and position of the fringes from a plane-parallel Si single crystal fixed at one end as a function of distance from the incident plane of the X-rays to the free crystal end. The variations can be explained by distortion of the sample crystal due to gravity. From the variations and positions of the fringes, the strain gradient of the crystal has been determined. The distribution of the observed strain agrees with that expected from rod theory except for residual strain. When the distortion is large, the observed strain distribution does not agree with that expected from rod theory. PMID:24068841

Strain Imaging of Nanoscale Semiconductor Heterostructures with X-Ray Bragg Projection Ptychography

NASA Astrophysics Data System (ADS)

Holt, Martin V.; Hruszkewycz, Stephan O.; Murray, Conal E.; Holt, Judson R.; Paskiewicz, Deborah M.; Fuoss, Paul H.

2014-04-01

We report the imaging of nanoscale distributions of lattice strain and rotation in complementary components of lithographically engineered epitaxial thin film semiconductor heterostructures using synchrotron x-ray Bragg projection ptychography (BPP). We introduce a new analysis method that enables lattice rotation and out-of-plane strain to be determined independently from a single BPP phase reconstruction, and we apply it to two laterally adjacent, multiaxially stressed materials in a prototype channel device. These results quantitatively agree with mechanical modeling and demonstrate the ability of BPP to map out-of-plane lattice dilatation, a parameter critical to the performance of electronic materials.

Tuning the magnetic properties of LaCoO3 thin films by epitaxial strain

NASA Astrophysics Data System (ADS)

Fuchs, D.; Arac, E.; Pinta, C.; Schuppler, S.; Schneider, R.; v. Löhneysen, H.

2008-01-01

Ferromagnetic order can be induced in LaCoO3 (LCO) thin films by epitaxial strain. Here, we show that the magnetic properties can be “tuned” by epitaxial strain imposed on LCO thin films by the epitaxial growth on various substrate materials, i.e., (001) oriented SrLaAlO4 , LaAlO3 , SrLaGaO4 , (LaAlO3)0.3(Sr2AlTaO6)0.7 , and SrTiO3 . The lattice mismatch at room temperature of the in-plane lattice parameters between the substrate, as , and bulk LCO, ab , ranges from -1.31% to +2.63% . Single-phase, ⟨001⟩ oriented LCO thin films were grown by pulsed laser deposition on all these substrates. Due to the difference of the thermal-expansion coefficients between LCO and the substrates, the films experience an additional tensile strain of about +0.3% during the cooling process after the deposition at Ts=650°C . The film lattice parameters display an elastic behavior, i.e., an increase of the in-plane film lattice parameter with increasing as . From the ratio between the out-of-plane and in-plane strain, we obtain a Poisson ratio of ν≈1/3 . All films show a ferromagnetic transition as determined from magnetization measurements. The magnetization increases strongly with increasing tensile strain, whereas the transition temperature TC after a rapid initial rise appears to saturate at TC≈85K above a=3.86Å . The effective magnetic moment μeff in the paramagnetic state increases almost linearly as a function of the mean lattice parameter ⟨a⟩ , indicating an enhanced population of higher spin states, i.e., intermediate- or high-spin states. The experimental results are discussed in terms of a decrease of the octahedral-site rotation with increasing tensile strain.

Shear sensing in bonded composites with cantilever beam microsensors and dual-plane digital image correlation

NASA Astrophysics Data System (ADS)

Baur, Jeffery W.; Slinker, Keith; Kondash, Corey

2017-04-01

Understanding the shear strain, viscoelastic response, and onset of damage within bonded composites is critical to their design, processing, and reliability. This presentation will discuss the multidisciplinary research conducted which led to the conception, development, and demonstration of two methods for measuring the shear within a bonded joint - dualplane digital image correlation (DIC) and a micro-cantilever shear sensor. The dual plane DIC method was developed to measure the strain field on opposing sides of a transparent single-lap joint in order to spatially quantify the joint shear strain. The sensor consists of a single glass fiber cantilever beam with a radially-grown forest of carbon nanotubes (CNTs) within a capillary pore. When the fiber is deflected, the internal radial CNT array is compressed against an electrode within the pore and the corresponding decrease in electrical resistance is correlated with the external loading. When this small, simple, and low-cost sensor was integrated within a composite bonded joint and cycled in tension, the onset of damage prior to joint failure was observed. In a second sample configuration, both the dual plane DIC and the hair sensor detected viscoplastic changes in the strain of the sample in response to continued loading.

Solving ethanol production problems with genetically modified yeast strains

PubMed Central

Abreu-Cavalheiro, A.; Monteiro, G.

2013-01-01

The current world demand for bioethanol is increasing as a consequence of low fossil fuel availability and a growing number of ethanol/gasoline flex-fuel cars. In addition, countries in several parts of the world have agreed to reduce carbon dioxide emissions, and the use of ethanol as a fuel (which produces fewer pollutants than petroleum products) has been considered to be a good alternative to petroleum products. The ethanol that is produced in Brazil from the first-generation process is optimized and can be accomplished at low cost. However, because of the large volume of ethanol that is produced and traded each year, any small improvement in the process could represent a savings of billions dollars. Several Brazilian research programs are investing in sugarcane improvement, but little attention has been given to the improvement of yeast strains that participate in the first-generation process at present. The Brazilian ethanol production process uses sugarcane as a carbon source for the yeast Saccharomyces cerevisiae. Yeast is then grown at a high cellular density and high temperatures in large-capacity open tanks with cells recycle. All of these culture conditions compel the yeast to cope with several types of stress. Among the main stressors are high temperatures and high ethanol concentrations inside the fermentation tanks during alcohol production. Moreover, the competition between the desired yeast strains, which are inoculated at the beginning of the process, with contaminants such as wild type yeasts and bacteria, requires acid treatment to successfully recycle the cells. This review is focused on describing the problems and stressors within the Brazilian ethanol production system. It also highlights some genetic modifications that can help to circumvent these difficulties in yeast. PMID:24516432

Solving ethanol production problems with genetically modified yeast strains.

PubMed

Abreu-Cavalheiro, A; Monteiro, G

2013-01-01

The current world demand for bioethanol is increasing as a consequence of low fossil fuel availability and a growing number of ethanol/gasoline flex-fuel cars. In addition, countries in several parts of the world have agreed to reduce carbon dioxide emissions, and the use of ethanol as a fuel (which produces fewer pollutants than petroleum products) has been considered to be a good alternative to petroleum products. The ethanol that is produced in Brazil from the first-generation process is optimized and can be accomplished at low cost. However, because of the large volume of ethanol that is produced and traded each year, any small improvement in the process could represent a savings of billions dollars. Several Brazilian research programs are investing in sugarcane improvement, but little attention has been given to the improvement of yeast strains that participate in the first-generation process at present. The Brazilian ethanol production process uses sugarcane as a carbon source for the yeast Saccharomyces cerevisiae. Yeast is then grown at a high cellular density and high temperatures in large-capacity open tanks with cells recycle. All of these culture conditions compel the yeast to cope with several types of stress. Among the main stressors are high temperatures and high ethanol concentrations inside the fermentation tanks during alcohol production. Moreover, the competition between the desired yeast strains, which are inoculated at the beginning of the process, with contaminants such as wild type yeasts and bacteria, requires acid treatment to successfully recycle the cells. This review is focused on describing the problems and stressors within the Brazilian ethanol production system. It also highlights some genetic modifications that can help to circumvent these difficulties in yeast.

Strained hybrid perovskite thin films and their impact on the intrinsic stability of perovskite solar cells

PubMed Central

Zhao, Jingjing; Deng, Yehao; Wei, Haotong; Zheng, Xiaopeng; Yu, Zhenhua; Shao, Yuchuan; Shield, Jeffrey E.; Huang, Jinsong

2017-01-01

Organic-inorganic hybrid perovskite (OIHP) solar cells have achieved comparable efficiencies to those of commercial solar cells, although their instability hinders their commercialization. Although encapsulation techniques have been developed to protect OIHP solar cells from external stimuli such as moisture, oxygen, and ultraviolet light, understanding of the origin of the intrinsic instability of perovskite films is needed to improve their stability. We show that the OIHP films fabricated by existing methods are strained and that strain is caused by mismatched thermal expansion of perovskite films and substrates during the thermal annealing process. The polycrystalline films have compressive strain in the out-of-plane direction and in-plane tensile strain. The strain accelerates degradation of perovskite films under illumination, which can be explained by increased ion migration in strained OIHP films. This study points out an avenue to enhance the intrinsic stability of perovskite films and solar cells by reducing residual strain in perovskite films. PMID:29159287

Bugs, Planes, and Ferris Wheels: A Problem-Centered Curriculum

ERIC Educational Resources Information Center

Campbell, William E.; Kemp, Joyce C.; Zia, Joan H.

2006-01-01

This article describes a problem-centered curriculum for grades 9-12, using problem sets developed by a mathematics department and designed to take the place of textbooks. The students discover mathematical concepts in the context of the problems and activities in the materials.

Cross-layer shared protection strategy towards data plane in software defined optical networks

NASA Astrophysics Data System (ADS)

Xiong, Yu; Li, Zhiqiang; Zhou, Bin; Dong, Xiancun

2018-04-01

In order to ensure reliable data transmission on the data plane and minimize resource consumption, a novel protection strategy towards data plane is proposed in software defined optical networks (SDON). Firstly, we establish a SDON architecture with hierarchical structure of data plane, which divides the data plane into four layers for getting fine-grained bandwidth resource. Then, we design the cross-layer routing and resource allocation based on this network architecture. Through jointly considering the bandwidth resource on all the layers, the SDN controller could allocate bandwidth resource to working path and backup path in an economical manner. Next, we construct auxiliary graphs and transform the shared protection problem into the graph vertex coloring problem. Therefore, the resource consumption on backup paths can be reduced further. The simulation results demonstrate that the proposed protection strategy can achieve lower protection overhead and higher resource utilization ratio.

Conceptual design and multidisciplinary optimization of in-plane morphing wing structures

NASA Astrophysics Data System (ADS)

Inoyama, Daisaku; Sanders, Brian P.; Joo, James J.

2006-03-01

In this paper, the topology optimization methodology for the synthesis of distributed actuation system with specific applications to the morphing air vehicle is discussed. The main emphasis is placed on the topology optimization problem formulations and the development of computational modeling concepts. For demonstration purposes, the inplane morphing wing model is presented. The analysis model is developed to meet several important criteria: It must allow large rigid-body displacements, as well as variation in planform area, with minimum strain on structural members while retaining acceptable numerical stability for finite element analysis. Preliminary work has indicated that addressed modeling concept meets the criteria and may be suitable for the purpose. Topology optimization is performed on the ground structure based on this modeling concept with design variables that control the system configuration. In other words, states of each element in the model are design variables and they are to be determined through optimization process. In effect, the optimization process assigns morphing members as 'soft' elements, non-morphing load-bearing members as 'stiff' elements, and non-existent members as 'voids.' In addition, the optimization process determines the location and relative force intensities of distributed actuators, which is represented computationally as equal and opposite nodal forces with soft axial stiffness. Several different optimization problem formulations are investigated to understand their potential benefits in solution quality, as well as meaningfulness of formulation itself. Sample in-plane morphing problems are solved to demonstrate the potential capability of the methodology introduced in this paper.

Strain driven sequential magnetic transitions in strained GdTiO3 on compressive substrates: a first-principles study.

PubMed

Yang, Li-Juan; Weng, Ya-Kui; Zhang, Hui-Min; Dong, Shuai

2014-11-26

The compressive strain effect on the magnetic ground state and electronic structure of strained GdTiO3 has been studied using the first-principles method. Unlike the cases of congeneric YTiO3 and LaTiO3, both of which become the A-type antiferromagnetism on the (0 0 1) LaAlO3 substrate despite their contrastive magnetism, the ground state of strained GdTiO3 on the LaAlO3 substrate changes from the original ferromagnetism to a G-type antiferromagnetim, instead of the A-type one although Gd(3+) is between Y(3+) and La(3+). It is only when the in-plane compressive strain is large enough, e.g. on the (0 0 1) YAlO3 substrate, that the ground state finally becomes the A-type. The band structure calculation shows that the compressive strained GdTiO3 remains insulating, although the band gap changes a little in the strained GdTiO3.

Two-dimensional mapping of triaxial strain fields in a multiferroic BiFeO3 thin film using scanning x-ray microdiffraction

NASA Astrophysics Data System (ADS)

Bark, Chung W.; Cho, Kyung C.; Koo, Yang M.; Tamura, Nobumichi; Ryu, Sangwoo; Jang, Hyun M.

2007-03-01

The dramatically enhanced polarizations and saturation magnetizations observed in the epitaxially constrained BiFeO3 (BFO) thin films with their pronounced grain-orientation dependence have attracted much attention and are attributed largely to the constrained in-plane strain. Thus, it is highly desirable to directly obtain information on the two-dimensional (2D) distribution of the in-plane strain and its correlation with the grain orientation of each corresponding microregion. Here the authors report a 2D quantitative mapping of the grain orientation and the local triaxial strain field in a 250nm thick multiferroic BFO film using a synchrotron x-ray microdiffraction technique. This direct scanning measurement demonstrates that the deviatoric component of the in-plane strain tensor is between 5×10-3 and 6×10-3 and that the local triaxial strain is fairly well correlated with the grain orientation in that particular region.

Plane Smoothers for Multiblock Grids: Computational Aspects

NASA Technical Reports Server (NTRS)

Llorente, Ignacio M.; Diskin, Boris; Melson, N. Duane

1999-01-01

Standard multigrid methods are not well suited for problems with anisotropic discrete operators, which can occur, for example, on grids that are stretched in order to resolve a boundary layer. One of the most efficient approaches to yield robust methods is the combination of standard coarsening with alternating-direction plane relaxation in the three dimensions. However, this approach may be difficult to implement in codes with multiblock structured grids because there may be no natural definition of global lines or planes. This inherent obstacle limits the range of an implicit smoother to only the portion of the computational domain in the current block. This report studies in detail, both numerically and analytically, the behavior of blockwise plane smoothers in order to provide guidance to engineers who use block-structured grids. The results obtained so far show alternating-direction plane smoothers to be very robust, even on multiblock grids. In common computational fluid dynamics multiblock simulations, where the number of subdomains crossed by the line of a strong anisotropy is low (up to four), textbook multigrid convergence rates can be obtained with a small overlap of cells between neighboring blocks.

General image method in a plane-layered elastostatic medium

NASA Technical Reports Server (NTRS)

Fares, N.; Li, V. C.

1988-01-01

The general-image method presently used to obtain the elastostatic fields in plane-layered media relies on the use of potentials in order to represent elastic fields. For the case of a single interface, this method yields the displacement field in closed form, and is applicable to antiplane, plane, and three-dimensional problems. In the case of multiplane interfaces, the image method generates the displacement fields in terms of infinite series whose convergences can be accelerated to improve method efficiency.

The effects of orthotic intervention on multisegment foot kinematics and plantar fascia strain in recreational runners.

PubMed

Sinclair, Jonathan; Isherwood, Josh; Taylor, Paul J

2015-02-01

Chronic injuries are a common complaint in recreational runners. Foot orthoses have been shown to be effective for the treatment of running injuries but their mechanical effects are still not well understood. This study aims to examine the influence of orthotic intervention on multisegment foot kinematics and plantar fascia strain during running. Fifteen male participants ran at 4.0 m · s(-1) with and without orthotics. Multisegment foot kinematics and plantar fascia strain were obtained during the stance phase and contrasted using paired t tests. Relative coronal plane range of motion of the midfoot relative to the rearfoot was significantly reduced with orthotics (1.0°) compared to without (2.2°). Similarly, relative transverse plane range of motion was significantly lower with orthotics (1.1°) compared to without (1.8°). Plantar fascia strain did not differ significantly between orthotic (7.1) and nonorthotic (7.1) conditions. This study shows that although orthotics did not serve to reduce plantar fascia strain, they are able to mediate reductions in coronal and transverse plane rotations of the midfoot.

Investigation of the interface characteristics of Y2O3/GaAs under biaxial strain, triaxial strain, and non-strain conditions

NASA Astrophysics Data System (ADS)

Shi, Li-Bin; Liu, Xu-Yang; Dong, Hai-Kuan

2016-09-01

We investigate the interface behaviors of Y2O3/GaAs under biaxial strain, triaxial strain, and non-strain conditions. This study is performed by first principles calculations based on density functional theory (DFT). First of all, the biaxial strain is realized by changing the lattice constants in ab plane. Averaged electrostatic potential (AEP) is aligned by establishing Y2O3 and GaAs (110) surfaces. The band offsets of Y2O3/GaAs interface under biaxial strain are investigated by generalized gradient approximation and Heyd-Scuseria-Ernzerhof (HSE) functionals. The interface under biaxial strain is suitable for the design of metal oxide semiconductor (MOS) devices because the valence band offsets (VBO) and conduction band offsets (CBO) are larger than 1 eV. Second, the triaxial strain is applied to Y2O3/GaAs interface by synchronously changing the lattice constants in a, b, and c axis. The band gaps of Y2O3 and GaAs under triaxial strain are investigated by HSE functional. We compare the VBO and CBO under triaxial strain with those under biaxial strain. Third, in the absence of lattice strain, the formation energies, charge state switching levels, and migration barriers of native defects in Y2O3 are assessed. We investigate how they will affect the MOS device performance. It is found that VO+2 and Oi-2 play a very dangerous role in MOS devices. Finally, a direct tunneling leakage current model is established. The model is used to analyze current and voltage characteristics of the metal/Y2O3/GaAs.

Three-dimensional ultrasound strain imaging of skeletal muscles

NASA Astrophysics Data System (ADS)

Gijsbertse, K.; Sprengers, A. M. J.; Nillesen, M. M.; Hansen, H. H. G.; Lopata, R. G. P.; Verdonschot, N.; de Korte, C. L.

2017-01-01

In this study, a multi-dimensional strain estimation method is presented to assess local relative deformation in three orthogonal directions in 3D space of skeletal muscles during voluntary contractions. A rigid translation and compressive deformation of a block phantom, that mimics muscle contraction, is used as experimental validation of the 3D technique and to compare its performance with respect to a 2D based technique. Axial, lateral and (in case of 3D) elevational displacements are estimated using a cross-correlation based displacement estimation algorithm. After transformation of the displacements to a Cartesian coordinate system, strain is derived using a least-squares strain estimator. The performance of both methods is compared by calculating the root-mean-squared error of the estimated displacements with the calculated theoretical displacements of the phantom experiments. We observe that the 3D technique delivers more accurate displacement estimations compared to the 2D technique, especially in the translation experiment where out-of-plane motion hampers the 2D technique. In vivo application of the 3D technique in the musculus vastus intermedius shows good resemblance between measured strain and the force pattern. Similarity of the strain curves of repetitive measurements indicates the reproducibility of voluntary contractions. These results indicate that 3D ultrasound is a valuable imaging tool to quantify complex tissue motion, especially when there is motion in three directions, which results in out-of-plane errors for 2D techniques.

Multi-scale finite element modeling of strain localization in geomaterials with strong discontinuity

NASA Astrophysics Data System (ADS)

Lai, Timothy Yu

2002-01-01

Geomaterials such as soils and rocks undergo strain localization during various loading conditions. Strain localization manifests itself in the form of a shear band, a narrow zone of intense straining. It is now generally recognized that these localized deformations lead to an accelerated softening response and influence the response of structures at or near failure. In order to accurately predict the behavior of geotechnical structures, the effects of strain localization must be included in any model developed. In this thesis, a multi-scale Finite Element (FE) model has been developed that captures the macro- and micro-field deformation patterns present during strain localization. The FE model uses a strong discontinuity approach where a jump in the displacement field is assumed. The onset of strain localization is detected using bifurcation theory that checks when the governing equations lose ellipticity. Two types of bifurcation, continuous and discontinuous are considered. Precise conditions for plane strain loading conditions are reported for each type of bifurcation. Post-localization behavior is governed by the traction relations on the band. Different plasticity models such as Mohr-Coulomb, Drucker-Prager and a Modified Mohr-Coulomb yield were implemented together with cohesion softening and cutoff for the post-localization behavior. The FE model is implemented into a FORTRAN code SPIN2D-LOC using enhanced constant strain triangular (CST) elements. The model is formulated using standard Galerkin finite element method, applicable to problems under undrained conditions and small deformation theory. A band-tracing algorithm is implemented to track the propagation of the shear band. To validate the model, several simulations are performed from simple compression test of soft rock to simulation of a full-scale geosynthetic reinforced soil wall model undergoing strain localization. Results from both standard and enhanced FE method are included for comparison. The

2. VIEW SOUTH, INCLINE PLANE CAR, INCLINE PLANE TRACK, UPPER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. VIEW SOUTH, INCLINE PLANE CAR, INCLINE PLANE TRACK, UPPER STATION. - Monongahela Incline Plane, Connecting North side of Grandview Avenue at Wyoming Street with West Carson Street near Smithfield Street, Pittsburgh, Allegheny County, PA

Role of grain-size in phyllonitisation: Insights from mineralogy, microstructures, strain analyses and numerical modeling

NASA Astrophysics Data System (ADS)

Bose, Narayan; Dutta, Dripta; Mukherjee, Soumyajit

2018-07-01

Brittle Y- and P-planes exist in an exposure of greywacke in the Garhwal Lesser Himalaya, India. Although, Y-planes are well developed throughout, the P-planes are prominent only in some parts (domain-A), and not elsewhere (domain-B). To investigate why the P-planes developed selectively, the following studies were undertaken: 1. Clay-separated XRD analyses: clinochlore and illite are present in both the domains. 2. Strain analyses by Rf-φ method: it deduces strain magnitudes of ∼1.8 for the ductile deformed quartz grains from both the domains A and B. 3. Grain size analyses of quartz clasts: domain-A is mostly composed of finer grains (area up to 40,000 μm2), whereas domain-B consists of a population of coarser grains (area >45,000 μm2). A 2D finite element modeling of linear elastic material was performed using COMSOL software to investigate the control of grain-size variation on the generation brittle shear planes. The results of numerical modeling corroborate the known fact that an increase in grain-size reduces the elastic strain energy density. A broader grain-size distribution increases the effects of diffusion creep and resists the onset of dislocation creep. Thus, rocks with coarser grain population (domain B) tend to resist the generation of shear fractures, unlike their fine-grained counterpart (domain A).

Determination of plane stress state using terahertz time-domain spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Zhiyong; Kang, Kai; Wang, Shibin; Li, Lin'an; Xu, Ningning; Han, Jiaguang; He, Mingxia; Wu, Liang; Zhang, Weili

2016-11-01

THz wave has been increasingly applied in engineering practice. One of its outstanding advantages is the penetrability through certain optically opaque materials, whose interior properties could be therefore obtained. In this report, we develop an experimental method to determine the plane stress state of optically opaque materials based on the stress-optical law using terahertz time-domain spectroscopy (THz-TDS). In this method, two polarizers are combined into the conventional THz-TDS system to sense and adjust the polarization state of THz waves and a theoretical model is established to describe the relationship between phase delay of the received THz wave and the plane stress applied on the specimen. Three stress parameters that represent the plane stress state are finally determined through an error function of THz wave phase-delay. Experiments were conducted on polytetrafluoroethylene (PTFE) specimen and a reasonably good agreement was found with measurement using traditional strain gauges. The presented results validate the effectiveness of the proposed method. The proposed method could be further used in nondestructive tests for a wide range of optically opaque materials.

Determination of plane stress state using terahertz time-domain spectroscopy

PubMed Central

Wang, Zhiyong; Kang, Kai; Wang, Shibin; Li, Lin'an; Xu, Ningning; Han, Jiaguang; He, Mingxia; Wu, Liang; Zhang, Weili

2016-01-01

THz wave has been increasingly applied in engineering practice. One of its outstanding advantages is the penetrability through certain optically opaque materials, whose interior properties could be therefore obtained. In this report, we develop an experimental method to determine the plane stress state of optically opaque materials based on the stress-optical law using terahertz time-domain spectroscopy (THz-TDS). In this method, two polarizers are combined into the conventional THz-TDS system to sense and adjust the polarization state of THz waves and a theoretical model is established to describe the relationship between phase delay of the received THz wave and the plane stress applied on the specimen. Three stress parameters that represent the plane stress state are finally determined through an error function of THz wave phase-delay. Experiments were conducted on polytetrafluoroethylene (PTFE) specimen and a reasonably good agreement was found with measurement using traditional strain gauges. The presented results validate the effectiveness of the proposed method. The proposed method could be further used in nondestructive tests for a wide range of optically opaque materials. PMID:27824112

Effects of strain and thickness on the electronic and optical behaviors of two-dimensional hexagonal gallium nitride

NASA Astrophysics Data System (ADS)

Behzad, Somayeh

2017-06-01

The full potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory has been used to study effects of strain and thickness on the electronic and optical properties of two-dimensional GaN. The band gap of monolayer and bilayer GaN under compressive in-plane strain change from indirect to direct with bond length shortening. Also, the semiconductor to semimetal transition occurs for monolayer and bilayer GaN under in-plane tensile strain with bond length elongation. It is found that the tensile and compressive strains cause the red and blue shifts in the optical spectra, respectively, for both monolayer and bilayer GaN. Applying the perpendicular strain on the bilayer GaN by decreasing the inter layer distance leads to the shift of valence band maximum towards the Γ point in the band structure and shift of peak positions and variation of peak intensities in ε2(ω) spectrum. The results show that the n-layer GaN has an indirect band gap for n < 16. The results suggest that monolayer and multilayer GaN are good candidates for application in optoelectronics and flexible electronics.

Study on observation planning of LAMOST focal plane positioning system and its simulation

NASA Astrophysics Data System (ADS)

Zhai, Chao; Jin, Yi; Peng, Xiaobo; Xing, Xiaozheng

2006-06-01

Fiber Positioning System of LAMOST focal plane based on subarea thinking, adopts a parallel controllable positioning plan, the structure is designed as a round area and overlapped each other in order to eliminate the un-observation region. But it also makes the observation efficiency of the system become an important problem. In this paper According to the system, the model of LAMOST focal plane Observation Planning including 4000 fiber positioning units is built, Stars are allocated using netflow algorithm and mechanical collisions are diminished through the retreat algorithm, then the simulation of the system's observation efficiency is carried out. The problem of observation efficiency of LAMOST focal plane is analysed systemic and all-sided from the aspect of overlapped region, fiber positioning units, observation radius, collisions and so on. The observation efficiency of the system in theory is describes and the simulation indicates that the system's observation efficiency is acceptable. The analyses play an indicative role on the design of the LAMOST focal plane structure.

Optical properties of a-plane (Al, Ga)N/GaN multiple quantum wells grown on strain engineered Zn1-xMgxO layers by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Xia, Y.; Brault, J.; Nemoz, M.; Teisseire, M.; Vinter, B.; Leroux, M.; Chauveau, J.-M.

2011-12-01

Nonpolar (112¯0) Al0.2Ga0.8N/GaN multiple quantum wells (MQWs) have been grown by molecular beam epitaxy on (112¯0) Zn0.74Mg0.26O templates on r-plane sapphire substrates. The quantum wells exhibit well-resolved photoluminescence peaks in the ultra-violet region, and no sign of quantum confined Stark effect is observed in the complete multiple quantum well series. The results agree well with flat band quantum well calculations. Furthermore, we show that the MQW structures are strongly polarized along the [0001] direction. The origin of the polarization is discussed in terms of the strain anisotropy dependence of the exciton optical oscillator strengths.

Steady-state LPO is not always reached in high-strain shear zones

NASA Astrophysics Data System (ADS)

Kumamoto, K. M.; Warren, J. M.

2017-12-01

Seismic anisotropy in the upper mantle results from the alignment of olivine crystal lattices during flow by dislocation creep. Experiments on the evolution of olivine lattice preferred orientation (LPO) as a function of shear strain have found that high strains (>10) are necessary to achieve a steady-state LPO (i.e., the dominant slip system does not change appreciably with further strain) when a pre-existing LPO is present. At lower strain ( 2), a pseudo-steady-state fabric is reached, in which the [100] axes of olivine reach a steady orientation relative to the deformation kinematics, but the [010] and [001] axes continue to evolve (e.g. Hansen et al., 2014). To constrain LPO evolution at mantle conditions, we looked at the LPO variation across three high temperature mantle shear zones in the Josephine Peridotite of SW Oregon. These shear zones provide a rare opportunity to examine LPO evolution in natural samples as a function of shear strain, due to the presence of a pyroxene foliation that serves as a strain marker. Observations of two of these shear zones are consistent with experimental observations (Warren et al., 2008; Skemer et al., 2010). Shear Zone G reaches a steady-state LPO at a strain of >20. Shear Zone P reaches a pseudo-steady-state LPO, with a consistent [100] axis orientation, at a strain of 3.5. However, a steady-state orientation is not reached in the [010] or [001] axes at the maximum strain of 5.25. The third shear zone, Shear Zone A, does not appear to reach even a pseudo-steady-state LPO, despite reaching strains >20 at its center. Instead, the dominant slip plane switches back and forth between the (010) and (001) planes with increasing strain, while the [100] axis orientations continue to evolve. Unusually, at peak strain, the [100] axes are oriented 40° past the shear plane. In contrast, the other two shear zones, along with other natural and experimental examples, have the [100] axes oriented approximately parallel to the shear

Reverse-mode PSLC multi-plane optical see-through display for AR applications.

PubMed

Liu, Shuxin; Li, Yan; Zhou, Pengcheng; Chen, Quanming; Su, Yikai

2018-02-05

In this paper we propose an optical see-through multi-plane display with reverse-mode polymer-stabilized liquid crystal (PSLC). Our design solves the problem of accommodation-vergence conflict with correct focus cues. In the reverse mode PSLC system, power consumption could be reduced to ~1/(N-1) of that in a normal mode system if N planes are displayed. The PSLC films fabricated in our experiment exhibit a low saturation voltage ~20 V rms , a high transparent-state transmittance (92%), and a fast switching time within 2 ms and polarization insensitivity. A proof-of-concept two-plane color display prototype and a four-plane monocolor display prototype were implemented.

Recognition of isotropic plane target from RCS diagram

NASA Astrophysics Data System (ADS)

Saillard, J.; Chassay, G.

1981-06-01

The use of electromagnetic waves for the recognition of a structure represented by point scatterers is seen as posing a fundamental problem. It is noted that much research has been done on this subject and that the study of aircraft observed in the yaw plane gives interesting results. To apply these methods, however, it is necessary to use many sophisticated acquisition systems. A method is proposed which can be applied to plane structures composed of isotropic scatterers. The method is considered to be of interest because it uses only power measurements and requires only a classical tracking radar.

Application of boundary integral equations to elastoplastic problems

NASA Technical Reports Server (NTRS)

Mendelson, A.; Albers, L. U.

1975-01-01

The application of boundary integral equations to elastoplastic problems is reviewed. Details of the analysis as applied to torsion problems and to plane problems is discussed. Results are presented for the elastoplastic torsion of a square cross section bar and for the plane problem of notched beams. A comparison of different formulations as well as comparisons with experimental results are presented.

Strain rate effects on mechanical properties of fiber composites, part 3

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Liber, T.

1976-01-01

An experimental investigation was conducted to determine the strain rate effects in fiber composites. Unidirectional composite specimens of boron/epoxy, graphite/epoxy, S-glass/epoxy and Kevlar/epoxy were tested to determine longitudinal, transverse and intralaminar (in-plane) shear properties. In the Longitudinal direction the Kevlar/epoxy shows a definite increase in both modulus and strength with strain rate. In the transverse direction, a general trend toward higher strength with strain rate is noticed. The intralaminar shear moduli and strengths of boron/epoxy and graphite/epoxy show a definite rise with strain rate.

Simple Numerical Simulation of Strain Measurement

NASA Technical Reports Server (NTRS)

Tai, H.

2002-01-01

By adopting the basic principle of the reflection (and transmission) of a plane polarized electromagnetic wave incident normal to a stack of films of alternating refractive index, a simple numerical code was written to simulate the maximum reflectivity (transmittivity) of a fiber optic Bragg grating corresponding to various non-uniform strain conditions including photo-elastic effect in certain cases.

Strain effect on the magnetic and transport properties of LaCoO3 thin films

NASA Astrophysics Data System (ADS)

Li, Y.; Peng, S. J.; Wang, D. J.; Wu, K. M.; Wang, S. H.

2018-05-01

LaCoO3 (LCO) has attracted much attention due to the unique magnetic transition and spin transition of Co3+ ions. Epitaxial LCO film exhibits an unexpected ferromagnetism, in contrast to the non-magnetism of bulk LCO. An in-depth study on the property of strained LCO film is of great importance. We have fabricated 30 nm LCO films on various substrates and studied the magnetic and transport properties of films in different strain states (compressed strain for LCO/LaAlO3, tensile strain for LCO/(LaAlO3)0.3(Sr2TaAlO6)0.35, SrTiO3). The in-plane tensiled LCO films exhibit ferromagnetic ground state at 5K and magnetic transition with TC around 85K, while compressed LCO/LaAlO3 film has a negligibly small moment signal. Our results reveal that in-plane tensile strain and tetragonal distortion are much more favorable for stabilizing the FM order in LCO films.

Study of magnetic domain evolution in an auxetic plane of Galfenol using Kerr microscopy

NASA Astrophysics Data System (ADS)

Raghunath, Ganesh; Flatau, Alison B.

2015-05-01

Galfenol (FexGa100-x), a magnetostrictive alloy (3/2λ 110-400 ppm) of Iron and Gallium exhibits an in-plane auxetic response in the ⟨110⟩ crystallographic direction. Negative Poisson's ratios have been observed in response to application of stress fields, where values of as low as -0.7 have been reported for compositions of greater than roughly 20% Ga [Zhang et al., J. Appl. Phys. 108(2), 023513 (2010)] and in response to application of magnetic fields, where values of as low as -2.5 have been reported to be expected for compositions of less than roughly 20% Ga [G. Raghunath and A. B. Flatau, IEEE Trans. Magn. (in press)]. Several models have been proposed to understand these two distinct phenomena. Galfenol samples with less than 20% Ga also exhibit an unusual response to an increasing magnetic field applied along the ⟨110⟩ direction. The longitudinal strain which increases initially with applied field experiences a dip (until ˜10 mT) before increasing again to reach saturation. The transverse strain increases and reaches a maximum value (at the same field of ˜10 mT) and then drops from the maximum by 5%-10% as magnetic saturation is approached [G. Raghunath and A. B. Flatau, IEEE Trans. Magn. (in press)].This work deals with discussing the evolution of magnetic domains in a 16 at. % Ga single crystal Galfenol sample when subjected to magnetic fields in the ⟨110⟩ direction in the (100) plane. The magnetic domains on the surface of mechanically polished Galfenol samples were imaged using Magneto-Optic Kerr Effect microscopy. Simultaneously, the strains along the longitudinal and transverse ⟨110⟩ directions were recorded using a bi-directional strain gauge rosette mounted on the unpolished bottom surface of the planar samples. The energy from the applied magnetic field is expected to grow the ⟨110⟩ oriented domains at the expense of domains oriented along all other directions. But since the plane has an easy ⟨100⟩ axis, we expect the

Complex space monofilar approximation of diffraction currents on a conducting half plane

NASA Technical Reports Server (NTRS)

Lindell, I. V.

1987-01-01

Simple approximation of diffraction surface currents on a conducting half plane, due to an incoming plane wave, is obtained with a line current (monofile) in complex space. When compared to an approximating current at the edge, the diffraction pattern is seen to improve by an order of magnitude for a minimal increase of computation effort. Thus, the inconvient Fresnel integral functions can be avoided for quick calculations of diffracted fields and the accuracy is good in other directions than along the half plane. The method can be applied to general problems involving planar metal edges.

Scattering by a groove in an impedance plane

NASA Technical Reports Server (NTRS)

Bindiganavale, Sunil; Volakis, John L.

1993-01-01

An analysis of two-dimensional scattering from a narrow groove in an impedance plane is presented. The groove is represented by a impedance surface and the problem reduces to that of scattering from an impedance strip in an otherwise uniform impedance plane. On the basis of this model, appropriate integral equations are constructed using a form of the impedance plane Green's functions involving rapidly convergent integrals. The integral equations are solved by introducing a single basis representation of the equivalent current on the narrow impedance insert. Both transverse electric (TE) and transverse magnetic (TM) polarizations are treated. The resulting solution is validated by comparison with results from the standard boundary integral method (BIM) and a high frequency solution. It is found that the presented solution for narrow impedance inserts can be used in conjunction with the high frequency solution for the characterization of impedance inserts of any given width.

Strain driven sequential magnetic transitions in strained GdTiO3 on compressive substrates: a first-principles study

NASA Astrophysics Data System (ADS)

Yang, Li-Juan; Weng, Ya-Kui; Zhang, Hui-Min; Dong, Shuai

2014-11-01

The compressive strain effect on the magnetic ground state and electronic structure of strained GdTiO3 has been studied using the first-principles method. Unlike the cases of congeneric YTiO3 and LaTiO3, both of which become the A-type antiferromagnetism on the (0 0 1) LaAlO3 substrate despite their contrastive magnetism, the ground state of strained GdTiO3 on the LaAlO3 substrate changes from the original ferromagnetism to a G-type antiferromagnetim, instead of the A-type one although Gd3+ is between Y3+ and La3+. It is only when the in-plane compressive strain is large enough, e.g. on the (0 0 1) YAlO3 substrate, that the ground state finally becomes the A-type. The band structure calculation shows that the compressive strained GdTiO3 remains insulating, although the band gap changes a little in the strained GdTiO3.

Strain-Enhanced p Doping in Monolayer MoS2

NASA Astrophysics Data System (ADS)

Choi, Minseok

2018-02-01

Achievement of desired p -type electrical properties in MoS2 remains a challenge. Here, we demonstrate that p doping in monolayer MoS2 can be enhanced in terms of strain manipulation, through first-principles hybrid functional calculations. Biaxial tensile strain and shear strain with smaller in-plane angles induce the dramatic reduction in formation energy of p dopants such as niobium and tantalum, providing the moderate doping contents required for applications. In addition, the formation of sulfur vacancies which are potential compensators of holes released from the dopants is suppressed by the strains. Our calculations pave an alternative strategy to overcome in the realization of p doping in monolayer MoS2 .

Thermal conductance of suspended nanoribbons: interplay between strain and interatomic potential nonlinearity

NASA Astrophysics Data System (ADS)

Barreto, Roberto; Florencia Carusela, M.; Monastra, Alejandro G.

2017-10-01

We investigate the role that nonlinearity in the interatomic potential has on the thermal conductance of a suspended nanoribbon when it is subjected to a longitudinal strain. To focus on the first cubic and quartic nonlinear terms of a general potential, we propose an atomic system based on an α-β Fermi-Pasta-Ulam nearest neighbor interaction. We perform classical molecular dynamics simulations to investigate the contribution of longitudinal, transversal and flexural modes to the thermal conductance as a function of the α-β parameters and the applied strain. We compare the cases where atoms are allowed to vibrate only in plane (2D) with the case of vibrations in and out of plane (3D). We find that the dependence of conductance on α and β relies on a crossover phenomenon between linear/nonlinear delocalized/localized flexural and transversal modes, driven by an on/off switch of the strain.

Gap discrete breathers in strained boron nitride

NASA Astrophysics Data System (ADS)

Barani, Elham; Korznikova, Elena A.; Chetverikov, Alexander P.; Zhou, Kun; Dmitriev, Sergey V.

2017-11-01

Linear and nonlinear dynamics of hexagonal boron nitride (h-BN) lattice is studied by means of molecular dynamics simulations with the use of the Tersoff interatomic potentials. It is found that sufficiently large homogeneous elastic strain along zigzag direction opens a wide gap in the phonon spectrum. Extended vibrational mode with boron and nitrogen sublattices vibrating in-plane as a whole in strained h-BN has frequency within the phonon gap. This fact suggests that a nonlinear spatially localized vibrational mode with frequencies in the phonon gap, called discrete breather (also often termed as intrinsic localized mode), can be excited. Properties of the gap discrete breathers in strained h-BN are contrasted with that for analogous vibrational mode found earlier in strained graphene. It is found that h-BN modeled with the Tersoff potentials does not support transverse discrete breathers.

High contrast imaging through adaptive transmittance control in the focal plane

NASA Astrophysics Data System (ADS)

Dhadwal, Harbans S.; Rastegar, Jahangir; Feng, Dake

2016-05-01

High contrast imaging, in the presence of a bright background, is a challenging problem encountered in diverse applications ranging from the daily chore of driving into a sun-drenched scene to in vivo use of biomedical imaging in various types of keyhole surgeries. Imaging in the presence of bright sources saturates the vision system, resulting in loss of scene fidelity, corresponding to low image contrast and reduced resolution. The problem is exacerbated in retro-reflective imaging systems where the light sources illuminating the object are unavoidably strong, typically masking the object features. This manuscript presents a novel theoretical framework, based on nonlinear analysis and adaptive focal plane transmittance, to selectively remove object domain sources of background light from the image plane, resulting in local and global increases in image contrast. The background signal can either be of a global specular nature, giving rise to parallel illumination from the entire object surface or can be represented by a mosaic of randomly orientated, small specular surfaces. The latter is more representative of real world practical imaging systems. Thus, the background signal comprises of groups of oblique rays corresponding to distributions of the mosaic surfaces. Through the imaging system, light from group of like surfaces, converges to a localized spot in the focal plane of the lens and then diverges to cast a localized bright spot in the image plane. Thus, transmittance of a spatial light modulator, positioned in the focal plane, can be adaptively controlled to block a particular source of background light. Consequently, the image plane intensity is entirely due to the object features. Experimental image data is presented to verify the efficacy of the methodology.

Local atomic and electronic structures of epitaxial strained LaCoO3 thin films

NASA Astrophysics Data System (ADS)

Sterbinsky, G. E.; Ryan, P. J.; Kim, J.-W.; Karapetrova, E.; Ma, J. X.; Shi, J.; Woicik, J. C.

2012-01-01

We have examined the atomic and electronic structures of perovskite lanthanum cobaltite (LaCoO3) thin films using Co K-edge x-ray absorption fine structure (XAFS) spectroscopy. Extended XAFS (EXAFS) demonstrates that a large difference between in-plane and out-of-plane Co-O bond lengths results from tetragonal distortion in highly strained films. The structural distortions are strongly coupled to the hybridization between atomic orbitals of the Co and O atoms, as shown by x-ray absorption near edge spectroscopy (XANES). Our results indicate that increased hybridization is not the cause of ferromagnetism in strained LaCoO3 films. Instead, we suggest that the strain-induced distortions of the oxygen octahedra increase the population of eg electrons and concurrently depopulate t2g electrons beyond a stabilization threshold for ferromagnetic order.

Out-of-plane stretching for simultaneous generation of different morphological wrinkles on a soft matter

NASA Astrophysics Data System (ADS)

Li, Xin; Zhao, Zhi-Jun; Park, Sang-Hu

2016-07-01

This study demonstrates a simple and flexible out-of-plane induced mechanical stretching method for generating labyrinthic, waving, and straight orderly microscale directional wrinkles. Different complex wrinkling patterns were fabricated simultaneously using a UV-curable thin layer of resin NOA-68T that was coated on a soft foundation. Then an out-of-plane pre-straining deformation was applied by a specially designed punch to generate internal elastic instabilities. The surface wrinkling pattern characteristics (shapes and size) changed according to the amount of punch stroke (pre-strain) and the cross-sectional shape of the punch. This study confirms the usefulness of this method for controlling and generating local wrinkling patterns for diverse applications. As an example, the contact angles of a water droplet on a local area of the same pattern were measured to identify the change in wettability with respect to different wrinkling shapes. This method can be utilized in topographical tunable wrinkle fabrication for local surface modification.

The Role of Personal and Job Resources in the Relationship between Psychosocial Job Demands, Mental Strain, and Health Problems

PubMed Central

Mayerl, Hannes; Stolz, Erwin; Waxenegger, Anja; Rásky, Éva; Freidl, Wolfgang

2016-01-01

Recent research highlights the importance of both job resources and personal resources in the job demands-resources model. However, the results of previous studies on how these resources are related to each other and how they operate in relation to the health-impairment process of the job demands-resources model are ambiguous. Thus, the authors tested an alternative model, considering job and personal resources to be domains of the same underlying factor and linking this factor to the health-impairment process. Survey data of two Austrian occupational samples (N1 = 8657 and N2 = 9536) were analyzed using confirmatory factor analysis (CFA) and structural equation modeling (SEM). The results revealed that job and personal resources can be considered as indicators of a single resources factor which was negatively related to psychosocial job demands, mental strain, and health problems. Confirming previous studies, we further found that mental strain mediated the relationship between psychosocial job demands and health problems. Our findings suggest that interventions aimed at maintaining health in the context of work may take action on three levels: (1) the prevention of extensive job demands, (2) the reduction of work-related mental strain, and (3) the strengthening of resources. PMID:27582717

Enhanced carrier mobility and direct tunneling probability of biaxially strained Ge{sub 1−x}Sn{sub x} alloys for field-effect transistors applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Lei; Liang, Renrong, E-mail: liangrr@tsinghua.edu.cn, E-mail: junxu@tsinghua.edu.cn; Wang, Jing

The carrier transport and tunneling capabilities of biaxially strained Ge{sub 1−x}Sn{sub x} alloys with (001), (110), and (111) orientations were comprehensively investigated and compared. The electron band structures of biaxially strained Ge{sub 1−x}Sn{sub x} alloys were calculated by the nonlocal empirical pseudopotential method and the modified virtual crystal approximation was adopted in the calculation. The electron and hole effective masses at the band edges were extracted using a parabolic line fit. It is shown that the applied biaxial strain and the high Sn composition are both helpful for the reduction of carrier effective masses, which leads to the enhanced carriermore » mobility and the boosted direct band-to-band-tunneling probability. Furthermore, the strain induced valance band splitting reduces the hole interband scattering, and the splitting also results in the significantly enhanced direct tunneling rate along the out-of-plane direction compared with that along the in-plane direction. The biaxially strained (111) Ge{sub 1−x}Sn{sub x} alloys exhibit the smallest band gaps compared with (001) and (110) orientations, leading to the highest in-plane and out-of-plane direct tunneling probabilities. The small effective masses on (110) and (111) planes in some strained conditions also contribute to the enhanced carrier mobility and tunneling probability. Therefore, the biaxially strained (110) and (111) Ge{sub 1−x}Sn{sub x} alloys have the potential to outperform the corresponding (001) Ge{sub 1−x}Sn{sub x} devices. It is important to optimize the applied biaxial strain, the Sn composition, and the substrate orientation for the design of high performance Ge{sub 1−x}Sn{sub x} field-effect transistors.« less

High temperature strain measurement with a resistance strain gage

NASA Technical Reports Server (NTRS)

Lei, Jih-Fen; Fichtel, ED; Mcdaniel, Amos

1993-01-01

A PdCr based electrical resistance strain gage was demonstrated in the laboratory to be a viable sensor candidate for static strain measurement at high temperatures. However, difficulties were encountered while transferring the sensor to field applications. This paper is therefore prepared for recognition and resolution of the problems likely to be encountered with PdCr strain gages in field applications. Errors caused by the measurement system, installation technique and lead wire attachment are discussed. The limitations and some considerations related to the temperature compensation technique used for this gage are also addressed.

Characterization of Strain Due to Nitrogen Doping Concentration Variations in Heavy Doped 4H-SiC

NASA Astrophysics Data System (ADS)

Yang, Yu; Guo, Jianqiu; Raghothamachar, Balaji; Chan, Xiaojun; Kim, Taejin; Dudley, Michael

2018-02-01

Highly doped 4H-SiC will show a significant lattice parameter difference with respect to the undoped material. We have applied the recently developed monochromatic contour mapping technique for 4H-SiC crystals to a 4H-SiC wafer crystal characterized by nitrogen doping concentration variation across the whole sample surface using a synchrotron monochromatic x-ray beam. Strain maps of 0008 and - 2203 planes were derived by deconvoluting the lattice parameter variations from the lattice tilt. Analysis reveals markedly different strain values within and out of the basal plane indicating the strain induced by nitrogen doping is anisotropic in the 4H-SiC hexagonal crystal structure. The highest strain calculated along growth direction [0001] and along [1-100] on the closed packed basal plane is up to - 4 × 10-4 and - 2.7 × 10-3, respectively. Using an anisotropic elasticity model by separating the whole bulk crystal into numerous identical rectangular prism units, the measured strain was related to the doping concentration and the calculated highest nitrogen level inside wafer crystal was determined to be 1.5 × 1020 cm-3. This is in agreement with observation of double Shockley stacking faults in the highly doped region that are predicted to nucleate at nitrogen levels above 2 × 1019 cm-3.

A Method for Calculating Strain Energy Release Rates in Preliminary Design of Composite Skin/Stringer Debonding Under Multi-Axial Loading

NASA Technical Reports Server (NTRS)

Krueger, Ronald; Minguet, Pierre J.; OBrien, T. Kevin

1999-01-01

Three simple procedures were developed to determine strain energy release rates, G, in composite skin/stringer specimens for various combinations of unaxial and biaxial (in-plane/out-of-plane) loading conditions. These procedures may be used for parametric design studies in such a way that only a few finite element computations will be necessary for a study of many load combinations. The results were compared with mixed mode strain energy release rates calculated directly from nonlinear two-dimensional plane-strain finite element analyses using the virtual crack closure technique. The first procedure involved solving three unknown parameters needed to determine the energy release rates. Good agreement was obtained when the external loads were used in the expression derived. This superposition technique was only applicable if the structure exhibits a linear load/deflection behavior. Consequently, a second technique was derived which was applicable in the case of nonlinear load/deformation behavior. The technique involved calculating six unknown parameters from a set of six simultaneous linear equations with data from six nonlinear analyses to determine the energy release rates. This procedure was not time efficient, and hence, less appealing. A third procedure was developed to calculate mixed mode energy release rates as a function of delamination lengths. This procedure required only one nonlinear finite element analysis of the specimen with a single delamination length to obtain a reference solution for the energy release rates and the scale factors. The delamination was extended in three separate linear models of the local area in the vicinity of the delamination subjected to unit loads to obtain the distribution of G with delamination lengths. This set of sub-problems was Although additional modeling effort is required to create the sub- models, this local technique is efficient for parametric studies.

Basal-plane dislocations in bilayer graphene - Peculiarities in a quasi-2D material

NASA Astrophysics Data System (ADS)

Butz, Benjamin

2015-03-01

Dislocations represent one of the most fascinating and fundamental concepts in materials science. First and foremost, they are the main carriers of plastic deformation in crystalline materials. Furthermore, they can strongly alter the local electronic or optical properties of semiconductors and ionic crystals. In layered crystals like graphite dislocation movement is restricted to the basal plane. Thus, those basal-plane dislocations cannot escape enabling their confinement in between only two atomic layers of the material. So-called bilayer graphene is the thinnest imaginable quasi-2D crystal to explore the nature and behavior of dislocations under such extreme boundary conditions. Robust graphene membranes derived from epitaxial graphene on SiC provide an ideal platform for their investigation. The presentation will give an insight in the direct observation of basal-plane partial dislocations by transmission electron microscopy and their detailed investigation by diffraction contrast analysis and atomistic simulations. The investigation reveals striking size effects. First, the absence of stacking fault energy, a unique property of bilayer graphene, leads to a characteristic dislocation pattern, which corresponds to an alternating AB <--> BA change of the stacking order. Most importantly, our experiments in combination with atomistic simulations reveal a pronounced buckling of the bilayer graphene membrane, which directly results from accommodation of strain. In fact, the buckling completely changes the strain state of the bilayer graphene and is of key importance for its electronic/spin transport properties. Due to the high degree of disorder in our quasi-2D material it is one of the very few examples for a perfect linear magnetoresistance, i.e. the linear dependency of the in-plane electrical resistance on a magnetic field applied perpendicular to the graphene sheet up to field strengths of more than 60 T. This research is financed by the German Research

The computation of all plane/surface intersections for CAD/CAM applications

NASA Technical Reports Server (NTRS)

Hoitsma, D. H., Jr.; Roche, M.

1984-01-01

The problem of the computation and display of all intersections of a given plane with a rational bicubic surface patch for use on an interactive CAD/CAM system is examined. The general problem of calculating all intersections of a plane and a surface consisting of rational bicubic patches is reduced to the case of a single generic patch by applying a rejection algorithm which excludes all patches that do not intersect the plane. For each pertinent patch the algorithm presented computed the intersection curves by locating an initial point on each curve, and computes successive points on the curve using a tolerance step equation. A single cubic equation solver is used to compute the initial curve points lying on the boundary of a surface patch, and the method of resultants as applied to curve theory is used to determine critical points which, in turn, are used to locate initial points that lie on intersection curves which are in the interior of the patch. Examples are given to illustrate the ability of this algorithm to produce all intersection curves.

Angular-dependent Raman study of a- and s-plane InN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filintoglou, K.; Katsikini, M., E-mail: katsiki@auth.gr; Arvanitidis, J.

2015-02-21

Angular-dependent polarized Raman spectroscopy was utilized to study nonpolar a-plane (11{sup ¯}20) and semipolar s-plane (101{sup ¯}1) InN epilayers. The intensity dependence of the Raman peaks assigned to the vibrational modes A{sub 1}(TO), E{sub 1}(TO), and E{sub 2}{sup h} on the angle ψ that corresponds to rotation around the growth axis, is very well reproduced by using expressions taking into account the corresponding Raman tensors and the experimental geometry, providing thus a reliable technique towards assessing the sample quality. The s- and a-plane InN epilayers grown on nitridated r-plane sapphire (Al{sub 2}O{sub 3}) exhibit good crystalline quality as deduced frommore » the excellent fitting of the experimental angle-dependent peak intensities to the theoretical expressions as well as from the small width of the Raman peaks. On the contrary, in the case of the s-plane epilayer grown on non-nitridated r-plane sapphire, fitting of the angular dependence is much worse and can be modeled only by considering the presence of two structural modifications, rotated so as their c-axes are almost perpendicular to each other. Although the presence of the second variant is verified by transmission electron and atomic force microscopies, angular dependent Raman spectroscopy offers a non-destructive and quick way for its quantification. Rapid thermal annealing of this sample did not affect the angular dependence of the peak intensities. The shift of the E{sub 1}(TO) and E{sub 2}{sup h} Raman peaks was used for the estimation of the strain state of the samples.« less

Combined strain and composition-induced effects in the metal-insulator transition of epitaxial VO2 films

NASA Astrophysics Data System (ADS)

Théry, V.; Boulle, A.; Crunteanu, A.; Orlianges, J. C.

2017-12-01

The role of epitaxial strain, thermal strain, and bulk (strain-free) lattice parameters in the metal-insulator transition (MIT) and the structural phase transition (SPT) of VO2 is investigated for the case of epitaxial films grown on (001)-oriented TiO2 substrates. Temperature-resolved X-ray reciprocal space mapping has been used to determine the absolute state of strain as well as the bulk lattice parameters of VO2 at 100 °C. For the thinnest film (15 nm), the state of strain is dominated by the film/substrate lattice mismatch yielding an in-plane tensile strain which, in turn, shifts both the MIT and the SPT towards lower temperatures. Conversely, for the thickest film (100 nm), the epitaxial strain is relaxed, so that the state of strain is dominated by the VO2/TiO2 thermal expansion mismatch which is responsible for a compressive in-plane strain. In all cases, a swelling of the strain-free VO2 unit-cell is observed which indicates the presence of interfacial oxygen vacancies and/or Ti diffusion into the VO2 films. The presence of oxygen vacancies stabilizes the metallic rutile phase and counterbalances the action of thermal strain on the MIT and the SPT and degrades the electric properties for the thinnest film. For the thickest film, the resistivity ratio is 6.4 × 104.

Versatile strain-tuning of modulated long-period magnetic structures

DOE PAGES

Fobes, D. M.; Luo, Yongkang; León-Brito, N.; ...

2017-05-10

In this paper, we report a detailed small-angle neutron scattering (SANS) study of the skyrmion lattice phase of MnSi under compressive and tensile strain. In particular, we demonstrate that tensile strain applied to the skyrmion lattice plane, perpendicular to the magnetic field, acts to destabilize the skyrmion lattice phase. Finally, this experiment was enabled by our development of a versatile strain cell, unique in its ability to select the application of either tensile or compressive strain in-situ by using two independent helium-actuated copper pressure transducers, whose design has been optimized for magnetic SANS on modulated long-period magnetic structures and vortexmore » lattices, and is compact enough to fit in common sample environments such as cryostats and superconducting magnets.« less

Differences in the Experience of Caregiver Strain between Families Caring for Youth with Substance Use Disorders and Families of Youth with Mental Health Problems

ERIC Educational Resources Information Center

Heflinger, Craig Anne; Brannan, Ana Maria

2006-01-01

This study examined caregiver strain (i.e., burden of care, caregiver burden) among families of adolescents in treatment for substance abuse disorders compared to youth with mental health problems. We used descriptive and regression analyses to compare groups and to examine the youth and family variables associated with caregiver strain across the…

The surface and through crack problems in layered orthotropic plates

NASA Technical Reports Server (NTRS)

Erdogan, Fazil; Wu, Binghua

1991-01-01

An analytical method is developed for a relatively accurate calculation of Stress Intensity Factors in a laminated orthotropic plate containing a through or part-through crack. The laminated plate is assumed to be under bending or membrane loading and the mode 1 problem is considered. First three transverse shear deformation plate theories (Mindlin's displacement based first-order theory, Reissner's stress-based first-order theory, and a simple-higher order theory due to Reddy) are reviewed and examined for homogeneous, laminated and heterogeneous orthotropic plates. Based on a general linear laminated plate theory, a method by which the stress intensity factors can be obtained in orthotropic laminated and heterogeneous plates with a through crack is developed. Examples are given for both symmetrically and unsymmetrically laminated plates and the effects of various material properties on the stress intensity factors are studied. In order to implement the line-spring model which is used later to study the surface crack problem, the corresponding plane elasticity problem of a two-bonded orthotropic plated containing a crack perpendicular to the interface is also considered. Three different crack profiles: an internal crack, an edge crack, and a crack terminating at the interface are considered. The effect of the different material combinations, geometries, and material orthotropy on the stress intensity factors and on the power of stress singularity for a crack terminating at the interface is fully examined. The Line Spring model of Rice and Levy is used for the part-through crack problem. The surface crack is assumed to lie in one of the two-layered laminated orthotropic plates due to the limitation of the available plane strain results. All problems considered are of the mixed boundary value type and are reduced to Cauchy type of singular integral equations which are then solved numerically.

The crack problem in bonded nonhomogeneous materials

NASA Technical Reports Server (NTRS)

Erdogan, Fazil; Kaya, A. C.; Joseph, P. F.

1988-01-01

The plane elasticity problem for two bonded half planes containing a crack perpendicular to the interface was considered. The effect of very steep variations in the material properties near the diffusion plane on the singular behavior of the stresses and stress intensity factors were studied. The two materials were thus, assumed to have the shear moduli mu(o) and mu(o) exp (Beta x), x=0 being the diffusion plane. Of particular interest was the examination of the nature of stress singularity near a crack tip terminating at the interface where the shear modulus has a discontinuous derivative. The results show that, unlike the crack problem in piecewise homogeneous materials for which the singularity is of the form r/alpha, 0 less than alpha less than 1, in this problem the stresses have a standard square-root singularity regardless of the location of the crack tip. The nonhomogeneity constant Beta has, however, considerable influence on the stress intensity factors.

The crack problem in bonded nonhomogeneous materials

NASA Technical Reports Server (NTRS)

Erdogan, F.; Joseph, P. F.; Kaya, A. C.

1991-01-01

The plane elasticity problem for two bonded half planes containing a crack perpendicular to the interface was considered. The effect of very steep variations in the material properties near the diffusion plane on the singular behavior of the stresses and stress intensity factors were studied. The two materials were thus, assumed to have the shear moduli mu(o) and mu(o) exp (Beta x), x=0 being the diffusion plane. Of particular interest was the examination of the nature of stress singularity near a crack tip termination at the interface where the shear modulus has a discontinuous derivative. The results show that, unlike the crack problem in piecewise homogeneous materials for which the singularity is of the form r/alpha, 0 less than alpha less than 1, in this problem the stresses have a standard square-root singularity regardless of the location of the crack tip. The nonhomogeneity constant Beta has, however, considerable influence on the stress intensity factors.

Trajectory optimization for the National Aerospace Plane

NASA Technical Reports Server (NTRS)

Lu, Ping

1992-01-01

The primary objective of this research is to develop an efficient and robust trajectory optimization tool for the optimal ascent problem of the National Aerospace Plane (NASP). This report is organized in the following order to summarize the complete work: Section two states the formulation and models of the trajectory optimization problem. An inverse dynamics approach to the problem is introduced in Section three. Optimal trajectories corresponding to various conditions and performance parameters are presented in Section four. A midcourse nonlinear feedback controller is developed in Section five. Section six demonstrates the performance of the inverse dynamics approach and midcourse controller during disturbances. Section seven discusses rocket assisted ascent which may be beneficial when orbital altitude is high. Finally, Section eight recommends areas of future research.

Application of the Finite Element Method to Reveal the Causes of Loss of Planeness of Hot-Rolled Steel Sheets during Laser Cutting

NASA Astrophysics Data System (ADS)

Garber, E. A.; Bolobanova, N. L.; Trusov, K. A.

2018-01-01

A finite element technique is developed to simulate the stresses and the strains during strip flattening to reveal the causes of the cutting-assisted loss of planeness of hot-rolled steel sheets processed in roller levelers. The loss of planeness is found to be caused by a nonuniform distribution of the flattening-induced longitudinal tensile stresses over the strip thickness and width. The application of tensile forces to a strip in a roller leveler decreases this nonuniformity and prevents loss of planeness in cutting.

Strain engineering of van der Waals heterostructures.

PubMed

Vermeulen, Paul A; Mulder, Jefta; Momand, Jamo; Kooi, Bart J

2018-01-18

Modifying the strain state of solids allows control over a plethora of functional properties. The weak interlayer bonding in van der Waals (vdWaals) materials such as graphene, hBN, MoS 2 , and Bi 2 Te 3 might seem to exclude strain engineering, since strain would immediately relax at the vdWaals interfaces. Here we present direct observations of the contrary by showing growth of vdWaals heterostructures with persistent in-plane strains up to 5% and we show that strain relaxation follows a not yet reported process distinctly different from strain relaxation in three-dimensionally bonded (3D) materials. For this, 2D bonded Bi 2 Te 3 -Sb 2 Te 3 and 2D/3D bonded Bi 2 Te 3 -GeTe multilayered films are grown using Pulsed Laser Deposition (PLD) and their structure is monitored in situ using Reflective High Energy Electron Diffraction (RHEED) and post situ analysis is performed using Transmission Electron Microscopy (TEM). Strain relaxation is modeled and found to solely depend on the layer being grown and its initial strain. This insight demonstrates that strain engineering of 2D bonded heterostructures obeys different rules than hold for epitaxial 3D materials and opens the door to precise tuning of the strain state of the individual layers to optimize functional performance of vdWaals heterostructures.

Nonlinear equations for dynamics of pretwisted beams undergoing small strains and large rotations

NASA Technical Reports Server (NTRS)

Hodges, D. H.

1985-01-01

Nonlinear beam kinematics are developed and applied to the dynamic analysis of a pretwisted, rotating beam element. The common practice of assuming moderate rotations caused by structural deformation in geometric nonlinear analyses of rotating beams was abandoned in the present analysis. The kinematic relations that described the orientation of the cross section during deformation are simplified by systematically ignoring the extensional strain compared to unity in those relations. Open cross section effects such as warping rigidity and dynamics are ignored, but other influences of warp are retained. The beam cross section is not allowed to deform in its own plane. Various means of implementation are discussed, including a finite element formulation. Numerical results obtained for nonlinear static problems show remarkable agreement with experiment.

Tuning the Schottky contacts in the phosphorene and graphene heterostructure by applying strain.

PubMed

Liu, Biao; Wu, Li-Juan; Zhao, Yu-Qing; Wang, Lin-Zhi; Caii, Meng-Qiu

2016-07-20

The structures and electronic properties of the phosphorene and graphene heterostructure are investigated by density functional calculations using the hybrid Heyd-Scuseria-Ernzerhof (HSE) functional. The results show that the intrinsic properties of phosphorene and graphene are preserved due to the weak van der Waals contact. But the electronic properties of the Schottky contacts in the phosphorene and graphene heterostructure can be tuned from p-type to n-type by the in-plane compressive strains from -2% to -4%. After analyzing the total band structure and density of states of P atom orbitals, we find that the Schottky barrier height (SBH) is determined by the P-pz orbitals. What is more, the variation of the work function of the phosphorene monolayer and the graphene electrode and the Fermi level shift are the nature of the transition of Schottky barrier from n-type Schottky contact to p-type Schottky contact in the phosphorene and graphene heterostructure under different in-plane strains. We speculate that these are general results of tuning of the electronic properties of the Schottky contacts in the phosphorene and graphene heterostructure by controlling the in-plane compressive strains to obtain a promising method to design and fabricate a phosphorene-graphene based field effect transistor.

Reversible strain effect on the magnetization of LaCoO3 films

NASA Astrophysics Data System (ADS)

Herklotz, A.; Rata, A. D.; Schultz, L.; Dörr, K.

2009-03-01

The magnetization (M) of a LaCoO3 film grown epitaxially on a piezoelectric substrate has been investigated in dependence on the biaxial in-plane strain. M decreases with the reversible release of tensile strain, with a maximum change of at least 6% per 0.1% of biaxial strain near the Curie temperature (TC) . The biaxial strain response of TC is estimated to be below 5 K/% in the tensile strain state. This is in agreement with results from statically strained films on various substrates. As possible origins of the strain-induced magnetization are considered (i) the strain-dependent Curie temperature, (ii) a strain-dependent magnetically inhomogeneous (phase-separated) state, and (iii) a strain-dependent magnetic moment (spin state) of Co ions. The TC shift is found insufficient to explain the measured strain-induced magnetization change but contributions from mechanism (ii) or (iii) must be involved.

Quantification of local strain distributions in nanoscale strained SiGe FinFET structures

NASA Astrophysics Data System (ADS)

Mochizuki, Shogo; Murray, Conal E.; Madan, Anita; Pinto, Teresa; Wang, Yun-Yu; Li, Juntao; Weng, Weihao; Jagannathan, Hemanth; Imai, Yasuhiko; Kimura, Shigeru; Takeuchi, Shotaro; Sakai, Akira

2017-10-01

Strain within nanoscale strained SiGe FinFET structures has been investigated using a combination of X-ray diffraction and transmission electron microscopy-based nanobeam diffraction (NBD) techniques to reveal the evolution of the stress state within the FinFETs. Reciprocal space maps collected using high-resolution X-ray diffraction exhibited distinct features corresponding to the SiGe fin width, pitch, and lattice deformation and were analyzed to quantify the state of stress within the fins. Although the majority of the SiGe fin volume exhibited a uniaxial stress state due to elastic relaxation of the transverse in-plane stress, NBD measurements confirmed a small interaction region near the SOI interface that is mechanically constrained by the underlying substrate. We have quantitatively characterized the evolution of the fin stress state from biaxial to uniaxial as a function of fin aspect ratio and Ge fraction and confirmed that the fins obey elastic deformation based on a model that depends on the relative difference between the equilibrium Si and SiGe lattice constants and relative fraction of in-plane stress transverse to the SiGe fins. Spatially resolved, nanobeam X-ray diffraction measurements conducted near the SiGe fin edge indicate the presence of additional elastic relaxation from a uniaxial stress state to a fully relaxed state at the fin edge. Mapping of the lattice deformation within 500 nm of this fin edge by NBD revealed large gradients, particularly at the top corner of the fin. The values of the volume averaged lattice deformation obtained by nanoXRD and NBD are qualitatively consistent. Furthermore, the modulation of strain at the fin edge obtained by quantitative analysis of the nanoXRD results agrees with the lattice deformation profile obtained by NBD.

Statistical framework for the utilization of simultaneous pupil plane and focal plane telemetry for exoplanet imaging. I. Accounting for aberrations in multiple planes.

PubMed

Frazin, Richard A

2016-04-01

A new generation of telescopes with mirror diameters of 20 m or more, called extremely large telescopes (ELTs), has the potential to provide unprecedented imaging and spectroscopy of exoplanetary systems, if the difficulties in achieving the extremely high dynamic range required to differentiate the planetary signal from the star can be overcome to a sufficient degree. Fully utilizing the potential of ELTs for exoplanet imaging will likely require simultaneous and self-consistent determination of both the planetary image and the unknown aberrations in multiple planes of the optical system, using statistical inference based on the wavefront sensor and science camera data streams. This approach promises to overcome the most important systematic errors inherent in the various schemes based on differential imaging, such as angular differential imaging and spectral differential imaging. This paper is the first in a series on this subject, in which a formalism is established for the exoplanet imaging problem, setting the stage for the statistical inference methods to follow in the future. Every effort has been made to be rigorous and complete, so that validity of approximations to be made later can be assessed. Here, the polarimetric image is expressed in terms of aberrations in the various planes of a polarizing telescope with an adaptive optics system. Further, it is shown that current methods that utilize focal plane sensing to correct the speckle field, e.g., electric field conjugation, rely on the tacit assumption that aberrations on multiple optical surfaces can be represented as aberration on a single optical surface, ultimately limiting their potential effectiveness for ground-based astronomy.

Ultrasensitive tunability of the direct bandgap of 2D InSe flakes via strain engineering

NASA Astrophysics Data System (ADS)

Li, Yang; Wang, Tianmeng; Wu, Meng; Cao, Ting; Chen, Yanwen; Sankar, Raman; Ulaganathan, Rajesh K.; Chou, Fangcheng; Wetzel, Christian; Xu, Cheng-Yan; Louie, Steven G.; Shi, Su-Fei

2018-04-01

InSe, a member of the layered materials family, is a superior electronic and optical material which retains a direct bandgap feature from the bulk to atomically thin few-layers and high electronic mobility down to a single layer limit. We, for the first time, exploit strain to drastically modify the bandgap of two-dimensional (2D) InSe nanoflakes. We demonstrated that we could decrease the bandgap of a few-layer InSe flake by 160 meV through applying an in-plane uniaxial tensile strain to 1.06% and increase the bandgap by 79 meV through applying an in-plane uniaxial compressive strain to 0.62%, as evidenced by photoluminescence (PL) spectroscopy. The large reversible bandgap change of ~239 meV arises from a large bandgap change rate (bandgap strain coefficient) of few-layer InSe in response to strain, ~154 meV/% for uniaxial tensile strain and ~140 meV/% for uniaxial compressive strain, representing the most pronounced uniaxial strain-induced bandgap strain coefficient experimentally reported in 2D materials. We developed a theoretical understanding of the strain-induced bandgap change through first-principles DFT and GW calculations. We also confirmed the bandgap change by photoconductivity measurements using excitation light with different photon energies. The highly tunable bandgap of InSe in the infrared regime should enable a wide range of applications, including electro-mechanical, piezoelectric and optoelectronic devices.

Rapid near-optimal aerospace plane trajectory generation and guidance

NASA Technical Reports Server (NTRS)

Calise, A. J.; Corban, J. E.; Markopoulos, N.

1991-01-01

Effort was directed toward the problems of the real time trajectory optimization and guidance law development for the National Aerospace Plane (NASP) applications. In particular, singular perturbation methods were used to develop guidance algorithms suitable for onboard, real time implementation. The progress made in this research effort is reported.

A method of plane geometry primitive presentation

NASA Astrophysics Data System (ADS)

Jiao, Anbo; Luo, Haibo; Chang, Zheng; Hui, Bin

2014-11-01

Point feature and line feature are basic elements in object feature sets, and they play an important role in object matching and recognition. On one hand, point feature is sensitive to noise; on the other hand, there are usually a huge number of point features in an image, which makes it complex for matching. Line feature includes straight line segment and curve. One difficulty in straight line segment matching is the uncertainty of endpoint location, the other is straight line segment fracture problem or short straight line segments joined to form long straight line segment. While for the curve, in addition to the above problems, there is another difficulty in how to quantitatively describe the shape difference between curves. Due to the problems of point feature and line feature, the robustness and accuracy of target description will be affected; in this case, a method of plane geometry primitive presentation is proposed to describe the significant structure of an object. Firstly, two types of primitives are constructed, they are intersecting line primitive and blob primitive. Secondly, a line segment detector (LSD) is applied to detect line segment, and then intersecting line primitive is extracted. Finally, robustness and accuracy of the plane geometry primitive presentation method is studied. This method has a good ability to obtain structural information of the object, even if there is rotation or scale change of the object in the image. Experimental results verify the robustness and accuracy of this method.

Motion estimation in the frequency domain using fuzzy c-planes clustering.

PubMed

Erdem, C E; Karabulut, G Z; Yanmaz, E; Anarim, E

2001-01-01

A recent work explicitly models the discontinuous motion estimation problem in the frequency domain where the motion parameters are estimated using a harmonic retrieval approach. The vertical and horizontal components of the motion are independently estimated from the locations of the peaks of respective periodogram analyses and they are paired to obtain the motion vectors using a procedure proposed. In this paper, we present a more efficient method that replaces the motion component pairing task and hence eliminates the problems of the pairing method described. The method described in this paper uses the fuzzy c-planes (FCP) clustering approach to fit planes to three-dimensional (3-D) frequency domain data obtained from the peaks of the periodograms. Experimental results are provided to demonstrate the effectiveness of the proposed method.

Plane Poiseuille Flow of a Rarefied Gas in the Presence of a Strong Gravitation

NASA Astrophysics Data System (ADS)

Doi, Toshiyuki

2010-11-01

Poiseuille flow of a rarefied gas between two horizontal planes in the presence of a strong gravitation is considered, where the gravity is so strong that the path of a molecule is curved considerably as it ascends or descends the distance of the planes. The gas behavior is studied based on the Boltzmann equation. An asymptotic analysis for a slow variation in the longitudinal direction is carried out and the problem is reduced to a spatially one dimensional problem, as was in the Poiseuille flow problem in the absence of the gravitation. The mass flow rate as well as the macroscopic variables is obtained for a wide range of the mean free path of the gas and the gravity. A numerical analysis of a two dimensional problem is also carried out and the result of the asymptotic analysis is verified.

Strain effects on the work function of an organic semiconductor

PubMed Central

Wu, Yanfei; Chew, Annabel R.; Rojas, Geoffrey A.; Sini, Gjergji; Haugstad, Greg; Belianinov, Alex; Kalinin, Sergei V.; Li, Hong; Risko, Chad; Brédas, Jean-Luc; Salleo, Alberto; Frisbie, C. Daniel

2016-01-01

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ∼0.05% tensile strain along the rubrene π-stacking direction. The results provide the first concrete link between mechanical strain and WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder in soft organic electronic materials. PMID:26831362

Strain effects on the work function of an organic semiconductor

NASA Astrophysics Data System (ADS)

Wu, Yanfei; Chew, Annabel R.; Rojas, Geoffrey A.; Sini, Gjergji; Haugstad, Greg; Belianinov, Alex; Kalinin, Sergei V.; Li, Hong; Risko, Chad; Brédas, Jean-Luc; Salleo, Alberto; Frisbie, C. Daniel

2016-02-01

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ~0.05% tensile strain along the rubrene π-stacking direction. The results provide the first concrete link between mechanical strain and WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder in soft organic electronic materials.

Strain effects on the work function of an organic semiconductor.

PubMed

Wu, Yanfei; Chew, Annabel R; Rojas, Geoffrey A; Sini, Gjergji; Haugstad, Greg; Belianinov, Alex; Kalinin, Sergei V; Li, Hong; Risko, Chad; Brédas, Jean-Luc; Salleo, Alberto; Frisbie, C Daniel

2016-02-01

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ∼0.05% tensile strain along the rubrene π-stacking direction. The results provide the first concrete link between mechanical strain and WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder in soft organic electronic materials.

Ultrasound-Guided Out-of-Plane vs. In-Plane Interscalene Catheters: A Randomized, Prospective Study.

PubMed

Schwenk, Eric S; Gandhi, Kishor; Baratta, Jaime L; Torjman, Marc; Epstein, Richard H; Chung, Jaeyoon; Vaghari, Benjamin A; Beausang, David; Bojaxhi, Elird; Grady, Bernadette

2015-12-01

Continuous interscalene blocks provide excellent analgesia after shoulder surgery. Although the safety of the ultrasound-guided in-plane approach has been touted, technical and patient factors can limit this approach. We developed a caudad-to-cephalad out-of-plane approach and hypothesized that it would decrease pain ratings due to better catheter alignment with the brachial plexus compared to the in-plane technique in a randomized, controlled study. To compare an out-of-plane interscalene catheter technique to the in-plane technique in a randomized clinical trial. Eighty-four patients undergoing open shoulder surgery were randomized to either the in-plane or out-of-plane ultrasound-guided continuous interscalene technique. The primary outcome was VAS pain rating at 24 hours. Secondary outcomes included pain ratings in the recovery room and at 48 hours, morphine consumption, the incidence of catheter dislodgments, procedure time, and block difficulty. Procedural data and all pain ratings were collected by blinded observers. There were no differences in the primary outcome of median VAS pain rating at 24 hours between the out-of-plane and in-plane groups (1.50; IQR, [0 - 4.38] vs. 1.25; IQR, [0 - 3.75]; P = 0.57). There were also no differences, respectively, between out-of-plane and in-plane median PACU pain ratings (1.0; IQR, [0 - 3.5] vs. 0.25; IQR, [0 - 2.5]; P = 0.08) and median 48-hour pain ratings (1.25; IQR, [1.25 - 2.63] vs. 0.50; IQR, [0 - 1.88]; P = 0.30). There were no differences in any other secondary endpoint. Our out-of-plane technique did not provide superior analgesia to the in-plane technique. It did not increase the number of complications. Our technique is an acceptable alternative in situations where the in-plane technique is difficult to perform.

Mechanical properties of novel forms of graphyne under strain: A density functional theory study

NASA Astrophysics Data System (ADS)

Majidi, Roya

2017-06-01

The mechanical properties of two forms of graphyne sheets named α-graphyne and α2-graphyne under uniaxial and biaxial strains were studied. In-plane stiffness, bulk modulus, and shear modulus were calculated based on density functional theory. The in-plane stiffness, bulk modulus, and shear modulus of α2-graphyne were found to be larger than that of α-graphyne. The maximum values of supported uniaxial and biaxial strains before failure were determined. The α-graphyne was entered into the plastic region with the higher magnitude of tension in comparison to α2-graphyne. The mechanical properties of α-graphyne family revealed that these forms of graphyne are proper materials for use in nanomechanical applications.

Topological analysis of the motion of an ellipsoid on a smooth plane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivochkin, M Yu

2008-06-30

The problem of the motion of a dynamically and geometrically symmetric heavy ellipsoid on a smooth horizontal plane is investigated. The problem is integrable and can be considered a generalization of the problem of motion of a heavy rigid body with fixed point in the Lagrangian case. The Smale bifurcation diagrams are constructed. Surgeries of tori are investigated using methods developed by Fomenko and his students. Bibliography: 9 titles.

Digital Image Correlation of 2D X-ray Powder Diffraction Data for Lattice Strain Evaluation

PubMed Central

Zhang, Hongjia; Sui, Tan; Daisenberger, Dominik; Fong, Kai Soon

2018-01-01

High energy 2D X-ray powder diffraction experiments are widely used for lattice strain measurement. The 2D to 1D conversion of diffraction patterns is a necessary step used to prepare the data for full pattern refinement, but is inefficient when only peak centre position information is required for lattice strain evaluation. The multi-step conversion process is likely to lead to increased errors associated with the ‘caking’ (radial binning) or fitting procedures. A new method is proposed here that relies on direct Digital Image Correlation analysis of 2D X-ray powder diffraction patterns (XRD-DIC, for short). As an example of using XRD-DIC, residual strain values along the central line in a Mg AZ31B alloy bar after 3-point bending are calculated by using both XRD-DIC and the conventional ‘caking’ with fitting procedures. Comparison of the results for strain values in different azimuthal angles demonstrates excellent agreement between the two methods. The principal strains and directions are calculated using multiple direction strain data, leading to full in-plane strain evaluation. It is therefore concluded that XRD-DIC provides a reliable and robust method for strain evaluation from 2D powder diffraction data. The XRD-DIC approach simplifies the analysis process by skipping 2D to 1D conversion, and opens new possibilities for robust 2D powder diffraction data analysis for full in-plane strain evaluation. PMID:29543728

Cutting solid figures by plane - analytical solution and spreadsheet implementation

NASA Astrophysics Data System (ADS)

Benacka, Jan

2012-07-01

In some secondary mathematics curricula, there is a topic called Stereometry that deals with investigating the position and finding the intersection, angle, and distance of lines and planes defined within a prism or pyramid. Coordinate system is not used. The metric tasks are solved using Pythagoras' theorem, trigonometric functions, and sine and cosine rules. The basic problem is to find the section of the figure by a plane that is defined by three points related to the figure. In this article, a formula is derived that gives the positions of the intersection points of such a plane and the figure edges, that is, the vertices of the section polygon. Spreadsheet implementations of the formula for cuboid and right rectangular pyramids are presented. The user can check his/her graphical solution, or proceed if he/she is not able to complete the section.

Computational strategy for the solution of large strain nonlinear problems using the Wilkins explicit finite-difference approach

NASA Technical Reports Server (NTRS)

Hofmann, R.

1980-01-01

The STEALTH code system, which solves large strain, nonlinear continuum mechanics problems, was rigorously structured in both overall design and programming standards. The design is based on the theoretical elements of analysis while the programming standards attempt to establish a parallelism between physical theory, programming structure, and documentation. These features have made it easy to maintain, modify, and transport the codes. It has also guaranteed users a high level of quality control and quality assurance.

Strain-induced changes of the electronic properties of B -site ordered double-perovskite Sr2CoIrO6 thin films

NASA Astrophysics Data System (ADS)

Esser, S.; Chang, C. F.; Kuo, C.-Y.; Merten, S.; Roddatis, V.; Ha, T. D.; Jesche, A.; Moshnyaga, V.; Lin, H.-J.; Tanaka, A.; Chen, C. T.; Tjeng, L. H.; Gegenwart, P.

2018-05-01

B -site ordered thin films of double perovskite Sr2CoIrO6 were epitaxially grown by a metalorganic aerosol deposition technique on various substrates, actuating different strain states. X-ray diffraction, transmission electron microscopy, and polarized far-field Raman spectroscopy confirm the strained epitaxial growth on all used substrates. Polarization-dependent Co L2 ,3 x-ray absorption spectroscopy reveals a change of the magnetic easy axis of the antiferromagnetically ordered (high-spin) Co3 + sublattice within the strain series. By reversing the applied strain direction from tensile to compressive, the easy axis changes abruptly from in-plane to out-of-plane orientation. The low-temperature magnetoresistance changes its sign respectively and is described by a combination of weak antilocalization and anisotropic magnetoresistance effects.

Optimal Chebyshev polynomials on ellipses in the complex plane

NASA Technical Reports Server (NTRS)

Fischer, Bernd; Freund, Roland

1989-01-01

The design of iterative schemes for sparse matrix computations often leads to constrained polynomial approximation problems on sets in the complex plane. For the case of ellipses, we introduce a new class of complex polynomials which are in general very good approximations to the best polynomials and even optimal in most cases.

Nonlinear finite element modeling of vibration control of plane rod-type structural members with integrated piezoelectric patches

NASA Astrophysics Data System (ADS)

Chróścielewski, Jacek; Schmidt, Rüdiger; Eremeyev, Victor A.

2018-05-01

This paper addresses modeling and finite element analysis of the transient large-amplitude vibration response of thin rod-type structures (e.g., plane curved beams, arches, ring shells) and its control by integrated piezoelectric layers. A geometrically nonlinear finite beam element for the analysis of piezolaminated structures is developed that is based on the Bernoulli hypothesis and the assumptions of small strains and finite rotations of the normal. The finite element model can be applied to static, stability, and transient analysis of smart structures consisting of a master structure and integrated piezoelectric actuator layers or patches attached to the upper and lower surfaces. Two problems are studied extensively: (i) FE analyses of a clamped semicircular ring shell that has been used as a benchmark problem for linear vibration control in several recent papers are critically reviewed and extended to account for the effects of structural nonlinearity and (ii) a smart circular arch subjected to a hydrostatic pressure load is investigated statically and dynamically in order to study the shift of bifurcation and limit points, eigenfrequencies, and eigenvectors, as well as vibration control for loading conditions which may lead to dynamic loss of stability.

Stretchable spiral thin-film battery capable of out-of-plane deformation

NASA Astrophysics Data System (ADS)

Kammoun, Mejdi; Berg, Sean; Ardebili, Haleh

2016-11-01

There is a compelling need for innovative design concepts in energy storage devices such as flexible and stretchable batteries that can simultaneously provide electrochemical and mechanical functions to accommodate nonconventional applications including wearable and implantable devices. In this study, we report on the design and fabrication of a stretchable spiral thin-film lithium ion battery that is capable of large out-of-plane deformation of 1300% while exhibiting simultaneous electrochemical functionality. The spiral battery is fabricated using a flexible solid polymer nanocomposite electrolyte film that offers enhanced safety and stability compared to the conventional organic liquid-based electrolyte. The spiral lithium ion battery exhibits robust mechanical stretchability over 9000 stretching cycles and an energy density of 4.862 mWh/cm3 at ∼650% out-of-plane deformation. Finite element analysis of the spiral battery offers insights about the nature of stresses and strains during battery stretching.

Automatic extraction of the mid-sagittal plane using an ICP variant

NASA Astrophysics Data System (ADS)

Fieten, Lorenz; Eschweiler, Jörg; de la Fuente, Matías; Gravius, Sascha; Radermacher, Klaus

2008-03-01

Precise knowledge of the mid-sagittal plane is important for the assessment and correction of several deformities. Furthermore, the mid-sagittal plane can be used for the definition of standardized coordinate systems such as pelvis or skull coordinate systems. A popular approach for mid-sagittal plane computation is based on the selection of anatomical landmarks located either directly on the plane or symmetrically to it. However, the manual selection of landmarks is a tedious, time-consuming and error-prone task, which requires great care. In order to overcome this drawback, previously it was suggested to use the iterative closest point (ICP) algorithm: After an initial mirroring of the data points on a default mirror plane, the mirrored data points should be registered iteratively to the model points using rigid transforms. Finally, a reflection transform approximating the cumulative transform could be extracted. In this work, we present an ICP variant for the iterative optimization of the reflection parameters. It is based on a closed-form solution to the least-squares problem of matching data points to model points using a reflection. In experiments on CT pelvis and skull datasets our method showed a better ability to match homologous areas.

Effects of tissue mechanical and acoustic anisotropies on the performance of a cross-correlation-based ultrasound strain imaging method.

PubMed

Li, He; Lee, Wei-Ning

2017-02-21

The anisotropic mechanical properties (mechanical anisotropy) and view-dependent ultrasonic backscattering (acoustic anisotropy) of striated muscle due to the underlying myofiber arrangement have been well documented, but whether they impact on ultrasound strain imaging (USI) techniques remains unclear. The aim of this study was therefore to investigate the performance of a cross-correlation-based two-dimensional (2D) USI method in anisotropic media under controlled quasi-static compression in silico and in vitro. First, synthetic pre- and post-deformed 2D radiofrequency images of anisotropic phantoms were simulated in two scenarios to examine the individual effect of the mechanical and acoustic anisotropies on strain estimation. In the first scenario, the phantom was defined to be transversely isotropic with the scatterer amplitudes following a zero-mean Gaussian distribution, while in the second scenario, the phantom was defined to be mechanically isotropic with Gaussian distributed scatterer amplitudes correlated along the principal directions of pre-defined fibers. These two anisotropies were then jointly incorporated into the ultrasound image simulation model with additional depth-dependent attenuation. Three imaging planes-the fiber plane with the fiber direction perpendicular to the ultrasound beam (TIS perp_fb ), the fiber plane with the fiber direction parallel to the beam (TIS para ), and the transverse fiber plane (TIS perp_cfb )-were studied. The absolute relative error (ARE) of the lateral strain estimates in TIS perp_fb (20.99  ±  15.65%) was much higher than that in TIS perp_cfb (4.14  ±  3.17%). The ARE in TIS para was unavailable owing to the large spatial extent of false peaks. The effect of tissue anisotropy on the performance of the 2D USI was further confirmed in an in vitro porcine skeletal muscle phantom. The best in-plane strain quality was again shown in TIS perp_cfb (elastographic signal-to-noise ratio, or SNR e :�

Thermal strain-induced dielectric anisotropy in Ba0.7Sr0.3TiO3 thin films grown on silicon-based substrates

NASA Astrophysics Data System (ADS)

Zhu, X. H.; Guigues, B.; Defaÿ, E.; Dubarry, C.; Aïd, M.

2009-07-01

Dielectric properties of Ba0.7Sr0.3TiO3 (BST) thin films, which were prepared on silicon-based substrates by ion beam sputtering and postdeposition annealing method, were systematically investigated in different electrode configurations of metal-insulator-metal and coplanar interdigital capacitors. It was found that a large dielectric anisotropy exists in the films with better in-plane dielectric properties (higher dielectric permittivity and tunability) than those along the out-of-plane direction. The observed anisotropic dielectric responses are explained qualitatively in terms of a thermal strain effect that is related to dissimilar film strains along the in-plane and out-of-plane directions. Another reason for the dielectric anisotropy is due to different influences of the interfacial low-dielectric layer between the BST film and the substrate (metal electrode).

An experimental study on the manufacture and characterization of in-plane fibre-waviness defects in composites.

PubMed

Christian, W J R; DiazDelaO, F A; Atherton, K; Patterson, E A

2018-05-01

A new method has been developed for creating localized in-plane fibre waviness in composite coupons and used to create a large batch of specimens. This method could be used by manufacturers to experimentally explore the effect of fibre waviness on composite structures both directly and indirectly to develop and validate computational models. The specimens were assessed using ultrasound, digital image correlation and a novel inspection technique capable of measuring residual strain fields. To explore how the defect affects the performance of composite structures, the specimens were then loaded to failure. Predictions of remnant strength were made using a simple ultrasound damage metric and a new residual strain-based damage metric. The predictions made using residual strain measurements were found to be substantially more effective at characterizing ultimate strength than ultrasound measurements. This suggests that residual strains have a significant effect on the failure of laminates containing fibre waviness and that these strains could be incorporated into computational models to improve their ability to simulate the defect.

In-plane and out-of-plane motions of the human tympanic membrane

PubMed Central

Khaleghi, Morteza; Cheng, Jeffrey Tao; Furlong, Cosme; Rosowski, John J.

2016-01-01

Computer-controlled digital holographic techniques are developed and used to measure shape and four-dimensional nano-scale displacements of the surface of the tympanic membrane (TM) in cadaveric human ears in response to tonal sounds. The combination of these measurements (shape and sound-induced motions) allows the calculation of the out-of-plane (perpendicular to the surface) and in-plane (tangential) motion components at over 1 000 000 points on the TM surface with a high-degree of accuracy and sensitivity. A general conclusion is that the in-plane motion components are 10–20 dB smaller than the out-of-plane motions. These conditions are most often compromised with higher-frequency sound stimuli where the overall displacements are smaller, or the spatial density of holographic fringes is higher, both of which increase the uncertainty of the measurements. The results are consistent with the TM acting as a Kirchhoff–Love's thin shell dominated by out-of-plane motion with little in-plane motion, at least with stimulus frequencies up to 8 kHz. PMID:26827009

Strain Gradient Solution for the Eshelby-Type Polyhedral Inclusion Problem

DTIC Science & Technology

2012-01-01

2011 Available online 6 November 2011 Keywords: Eshelby tensor Polyhedral inclusion Size effect Eigenstrain Strain gradient a b s t r a c t The Eshelby...material containing an ellipsoidal inclusion prescribed with a uniform eigenstrain is a milestone in micromechanics. The solution for the dynamic Eshelby...strain to the prescribed uniform eigenstrain , is constant inside the inclusion. However, this property is true only for ellipsoidal inclusions (and when

Strain effect in epitaxial VO2 thin films grown on sapphire substrates using SnO2 buffer layers

NASA Astrophysics Data System (ADS)

Kim, Heungsoo; Bingham, Nicholas S.; Charipar, Nicholas A.; Piqué, Alberto

2017-10-01

Epitaxial VO2/SnO2 thin film heterostructures were deposited on m-cut sapphire substrates via pulsed laser deposition. By adjusting SnO2 (150 nm) growth conditions, we are able to control the interfacial strain between the VO2 film and SnO2 buffer layer such that the semiconductor-to-metal transition temperature (TC) of VO2 films can be tuned without diminishing the magnitude of the transition. It is shown that in-plane tensile strain and out-of-plane compressive strain of the VO2 film leads to a decrease of Tc. Interestingly, VO2 films on SnO2 buffer layers exhibit a structural phase transition from tetragonal-like VO2 to tetragonal-VO2 during the semiconductor-to-metal transition. These results suggest that the strain generated by SnO2 buffer provides an effective way for tuning the TC of VO2 films.

The Development of Electrical Strain Gages

NASA Technical Reports Server (NTRS)

De Forest, A V; Leaderman, H

1940-01-01

The design, construction, and properties of an electrical-resistance strain gage consisting of fine wires molded in a laminated plastic are described. The properties of such gages are discussed and also the problems of molding of wires in plastic materials, temperature compensation, and cementing and removal of the gages. Further work to be carried out on the strain gage, together with instrument problems, is discussed.

Neutron Bragg-edge-imaging for strain mapping under in situ tensile loading

NASA Astrophysics Data System (ADS)

Woracek, R.; Penumadu, D.; Kardjilov, N.; Hilger, A.; Strobl, M.; Wimpory, R. C.; Manke, I.; Banhart, J.

2011-05-01

Wavelength selective neutron radiography at a cold neutron reactor source was used to measure strain and determine (residual) stresses in a steel sample under plane stress conditions. We present a new technique that uses an energy-resolved neutron imaging system based on a double crystal monochromator and is equipped with a specially developed (in situ) biaxial load frame to perform Bragg edge based transmission imaging. The neutron imaging technique provides a viewing area of 7 cm by 7 cm with a spatial resolution on the order of ˜ 100 μm. The stress-induced shifts of the Bragg edge corresponding to the (110) lattice plane were resolved spatially for a ferritic steel alloy A36 (ASTM international) sample. Furthermore it is demonstrated that results agree with comparative data obtained using neutron diffraction and resistance based strain-gauge rosettes.

Edge softening of the Shuttle TPS strain isolation pad. [Thermal Protection System

NASA Technical Reports Server (NTRS)

Ransone, P. O.; Rummler, D. R.

1982-01-01

Tensile tests and an analytical investigation were performed to characterize the edge softening behavior of the strain isolation pad (SIP) between the Orbiter skin and thermal protection system. The tensile tests were carried out with varying sizes of disk-shaped specimens bonded between aluminum disks. The specimens strength and stiffness were determined on the basis of specimen size, and an analytical model of the microstructural stress-strain characteristics was developed. Strength and stiffness were found to decrease near the free edges because through-the-thickness fibers located there were not anchored. No size dependence at maximum load was observed in specimens between 0.75-4.0 in. thick. In-plane and out-of-plane coupling in deformation was detected. The model gave accurate predictions of the tensile behavior of the SIP as a function of distance to a free edge.

Microstrip patch antenna for simultaneous strain and temperature sensing

NASA Astrophysics Data System (ADS)

Mbanya Tchafa, F.; Huang, H.

2018-06-01

A patch antenna, consisting of a radiation patch, a dielectric substrate, and a ground plane, resonates at distinct fundamental frequencies that depend on the substrate dielectric constant and the dimensions of the radiation patch. Since these parameters change with the applied strain and temperature, this study investigates simultaneous strain and temperature sensing using a single antenna that has two fundamental resonant frequencies. The theoretical relationship between the antenna resonant frequency shifts, the temperature, and the applied strain was first established to guide the selection of the dielectric substrate, based on which an antenna sensor with a rectangular radiation patch was designed and fabricated. A tensile test specimen instrumented with the antenna sensor was subjected to thermo-mechanical tests. Experiment results validated the theoretical predictions that the normalized antenna resonant frequency shifts are linearly proportional to the applied strain and temperature changes. An inverse method was developed to determine the strain and temperature changes from the normalized antenna resonant frequency shifts, yielding measurement uncertainty of 0.4 °C and 17.22 μ \\varepsilon for temperature and strain measurement, respectively.

Cleavage strain in the Variscan fold belt, County Cork, Ireland, estimated from stretched arsenopyrite rosettes

USGS Publications Warehouse

Ford, M.; Ferguson, C.C.

1985-01-01

In south-west Ireland, hydrothermally formed arsenopyrite crystals in a Devonian mudstone have responded to Variscan deformation by brittle extension fracture and fragment separation. The interfragment gaps and terminal extension zones of each crystal are infilled with fibrous quartz. Stretches within the cleavage plane have been calculated by the various methods available, most of which can be modified to incorporate terminal extension zones. The Strain Reversal Method is the most accurate currently available but still gives a minimum estimate of the overall strain. The more direct Hossain method, which gives only slightly lower estimates with this data, is more practical for field use. A strain ellipse can be estimated from each crystal rosette composed of three laths (assuming the original interlimb angles were all 60??) and, because actual rather than relative stretches are estimated, this provides a lower bound to the area increase in the plane of cleavage. Based on the average of our calculated strain ellipses this area increase is at least 114% and implies an average shortening across the cleavage of at least 53%. However, several lines of evidence suggest that the cleavage deformation was more intense and more oblate than that calculated, and we argue that a 300% area increase in the cleavage plane and 75% shortening across the cleavage are more realistic estimates of the true strain. Furthermore, the along-strike elongation indicated is at least 80%, which may be regionally significant. Estimates of orogenic contraction derived from balanced section construction should therefore take into account the possibility of a substantial strike elongation, and tectonic models that can accommodate such elongations need to be developed. ?? 1985.

An interferometric strain-displacement measurement system

NASA Technical Reports Server (NTRS)

Sharpe, William N., Jr.

1989-01-01

A system for measuring the relative in-plane displacement over a gage length as short as 100 micrometers is described. Two closely spaced indentations are placed in a reflective specimen surface with a Vickers microhardness tester. Interference fringes are generated when they are illuminated with a He-Ne laser. As the distance between the indentations expands or contracts with applied load, the fringes move. This motion is monitored with a minicomputer-controlled system using linear diode arrays as sensors. Characteristics of the system are: (1) gage length ranging from 50 to 500 micrometers, but 100 micrometers is typical; (2) least-count resolution of approximately 0.0025 micrometer; and (3) sampling rate of 13 points per second. In addition, the measurement technique is non-contacting and non-reinforcing. It is useful for strain measurements over small gage lengths and for crack opening displacement measurements near crack tips. This report is a detailed description of a new system recently installed in the Mechanisms of Materials Branch at the NASA Langley Research Center. The intent is to enable a prospective user to evaluate the applicability of the system to a particular problem and assemble one if needed.

Out-of-plane chiral domain wall spin-structures in ultrathin in-plane magnets

DOE PAGES

Chen, Gong; Kang, Sang Pyo; Ophus, Colin; ...

2017-05-19

Chiral spin textures in ultrathin films, such as skyrmions or chiral domain walls, are believed to offer large performance advantages in the development of novel spintronics technologies. While in-plane magnetized films have been studied extensively as media for current- and field-driven domain wall dynamics with applications in memory or logic devices, the stabilization of chiral spin textures in in-plane magnetized films has remained rare. Here we report a phase of spin structures in an in-plane magnetized ultrathin film system where out-of-plane spin orientations within domain walls are stable. Moreover, while domain walls in in-plane films are generally expected to bemore » non-chiral, we show that right-handed spin rotations are strongly favoured in this system, due to the presence of the interfacial Dzyaloshinskii-Moriya interaction. These results constitute a platform to explore unconventional spin dynamics and topological phenomena that may enable high-performance in-plane spin-orbitronics devices.« less

Comparative analysis of methods for modeling the penetration and plane-parallel motion of conical projectiles in soil

NASA Astrophysics Data System (ADS)

Bazhenov, V. G.; Bragov, A. M.; Konstantinov, A. Yu.; Kotov, V. L.

2015-05-01

This paper presents an analysis of the accuracy of known and new modeling methods using the hypothesis of local and plane sections for solution of problems of the impact and plane-parallel motion of conical bodies at an angle to the free surface of the half-space occupied by elastoplastic soil. The parameters of the local interaction model that is quadratic in velocity are determined by solving the one-dimensional problem of the expansion of a spherical cavity. Axisymmetric problems for each of the meridional section are solved simultaneously neglecting mass and momentum transfer in the circumferential direction and using an approach based on the hypothesis of plane sections. The dynamic and kinematic parameters of oblique penetration obtained using modified models are compared with the results of computer simulation in a three-dimensional formulation. The results obtained with regard to the contact stress distribution along the generator of the pointed cone are in satisfactory agreement.

Making planes plain.

PubMed

O'Rahilly, R

1997-01-01

The major anatomical planes (horizontal, coronal, and sagittal, including the median plane) are discussed from a historical perspective, and their correct usage is clarified. Unofficial and unnecessary terms to be avoided (for reasons explained) include midsagittal, parasagittal, and midline.

Strain effects on the work function of an organic semiconductor

DOE PAGES

Wu, Yanfei; Chew, Annabel R.; Rojas, Geoffrey A.; ...

2016-02-01

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding the electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively withmore » density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ~0.05% tensile strain along the rubrene -stacking direction. The results provide the first concrete link between mechanical strain and the WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder (charge traps) in soft organic electronic materials.« less

Theory and application of equivalent transformation relationships between plane wave and spherical wave

NASA Astrophysics Data System (ADS)

Wang, Yao; Yang, Zailin; Zhang, Jianwei; Yang, Yong

2017-10-01

Based on the governing equations and the equivalent models, we propose an equivalent transformation relationships between a plane wave in a one-dimensional medium and a spherical wave in globular geometry with radially inhomogeneous properties. These equivalent relationships can help us to obtain the analytical solutions of the elastodynamic issues in an inhomogeneous medium. The physical essence of the presented equivalent transformations is the equivalent relationships between the geometry and the material properties. It indicates that the spherical wave problem in globular geometry can be transformed into the plane wave problem in the bar with variable property fields, and its inverse transformation is valid as well. Four different examples of wave motion problems in the inhomogeneous media are solved based on the presented equivalent relationships. We obtain two basic analytical solution forms in Examples I and II, investigate the reflection behavior of inhomogeneous half-space in Example III, and exhibit a special inhomogeneity in Example IV, which can keep the traveling spherical wave in constant amplitude. This study implies that our idea makes solving the associated problem easier.

Structural Affects on the Slamming Pressures of High-Speed Planing Craft

NASA Astrophysics Data System (ADS)

Ikeda, Christine; Taravella, Brandon; Judge, Carolyn

2015-11-01

High-speed planing craft are subjected to repeated slamming events in waves that can be very extreme depending on the wave topography, impact angle of the ship, forward speed of the ship, encounter angle, and height out of the water. The current work examines this fluid-structure interaction problem through the use of wedge drop experiments and a CFD code. In the first set of experiments, a rigid 20-degree deadrise angle wedge was dropped from a range of heights (0 <= H <= 0 . 6 m) and while pressures and accelerations of the slam even were measured. The second set of experiments involved a flexible-bottom 15-degree deadrise angle wedge that was dropped from from the same range of heights. In these second experiments, the pressures, accelerations, and strain field were measured. Both experiments are compared with a non-linear boundary value flat cylinder theory code in order to compare the pressure loading. The code assumes a rigid structure, therefore, the results between the code and the first experiment are in good agreement. The second experiment shows pressure magnitudes that are lower than the predictions due to the energy required to deform the structure. Funding from University of New Orleans Office of Research and Sponsored Programs and the Office of Naval Research.

The lateral plane delivers higher dose than the frontal plane in biplane cardiac catheterization systems.

PubMed

Aldoss, Osamah; Patel, Sonali; Harris, Kyle; Divekar, Abhay

2015-06-01

The objective of the study is to compare radiation dose between the frontal and lateral planes in a biplane cardiac catheterization laboratory. Tube angulation progressively increases patient and operator radiation dose in single-plane cardiac catheterization laboratories. This retrospective study captured biplane radiation dose in a pediatric cardiac catheterization laboratory between April 2010 and January 2014. Raw and time-indexed fluoroscopic, cineangiographic and total (fluoroscopic + cineangiographic) air kerma (AK, mGy) and kerma area product (PKA, µGym(2)/Kg) for each plane were compared. Data for 716 patients were analyzed: 408 (56.98 %) were male, the median age was 4.86 years, and the median weight was 17.35 kg. Although median beam-on time (minutes) was 4.2 times greater in the frontal plane, there was no difference in raw median total PKA between the two planes. However, when indexed to beam-on time, the lateral plane had a higher median-indexed fluoroscopic (0.75 vs. 1.70), cineangiographic (16.03 vs. 24.92), and total (1.43 vs. 5.15) PKA (p < 0.0001). The median time-indexed total PKA in the lateral plane is 3.6 times the frontal plane. This is the first report showing that the lateral plane delivers a higher dose than the frontal plane per unit time. Operators should consciously reduce the lateral plane beam-on time and incorporate this practice in radiation reduction protocols.

Strain doping: Reversible single-axis control of a complex oxide lattice via helium implantation

DOE PAGES

Guo, Hangwen; Dong, Shuai; Rack, Philip D.; ...

2015-06-25

We report on the use of helium ion implantation to independently control the out-of-plane lattice constant in epitaxial La 0.7Sr 0.3MnO 3 thin films without changing the in-plane lattice constants. The process is reversible by a vacuum anneal. Resistance and magnetization measurements show that even a small increase in the out-of-plane lattice constant of less than 1% can shift the metal-insulator transition and Curie temperatures by more than 100 °C. Unlike conventional epitaxy-based strain tuning methods which are constrained not only by the Poisson effect but by the limited set of available substrates, the present study shows that strain canmore » be independently and continuously controlled along a single axis. This permits novel control over orbital populations through Jahn-Teller effects, as shown by Monte Carlo simulations on a double-exchange model. As a result, the ability to reversibly control a single lattice parameter substantially broadens the phase space for experimental exploration of predictive models and leads to new possibilities for control over materials’ functional properties.« less

Parallax handling of image stitching using dominant-plane homography

NASA Astrophysics Data System (ADS)

Pang, Zhaofeng; Li, Cheng; Zhao, Baojun; Tang, Linbo

2015-10-01

In this paper, we present a novel image stitching method to handle parallax in practical application. For images with significant amount of parallax, the more effective approach is to align roughly and globally the overlapping regions and then apply a seam-cutting method to composite naturally stitched images. It is well known that images can be modeled by various planes result from the projective parallax under non-ideal imaging condition. The dominant-plane homography has important advantages of warping an image globally and avoiding some local distortions. The proposed method primarily addresses large parallax problem through two steps: (1) selecting matching point pairs located on the dominant plane, by clustering matching correspondences and then measuring the cost of each cluster; and (2) in order to obtain a plausible seam, edge maps of overlapped area incorporation arithmetic is adopted to modify the standard seam-cutting method. Furthermore, our approach is demonstrated to achieve reliable performance of handling parallax through a mass of experimental comparisons with state-of-the-art methods.

Tight frames of k-plane ridgelets and the problem of representing objects that are smooth away from d-dimensional singularities in Rn

PubMed Central

Donoho, David L.

1999-01-01

For each pair (n, k) with 1 ≤ k < n, we construct a tight frame (ρλ : λ ∈ Λ) for L2 (Rn), which we call a frame of k-plane ridgelets. The intent is to efficiently represent functions that are smooth away from singularities along k-planes in Rn. We also develop tools to help decide whether k-plane ridgelets provide the desired efficient representation. We first construct a wavelet-like tight frame on the X-ray bundle χn,k—the fiber bundle having the Grassman manifold Gn,k of k-planes in Rn for base space, and for fibers the orthocomplements of those planes. This wavelet-like tight frame is the pushout to χn,k, via the smooth local coordinates of Gn,k, of an orthonormal basis of tensor Meyer wavelets on Euclidean space Rk(n−k) × Rn−k. We then use the X-ray isometry [Solmon, D. C. (1976) J. Math. Anal. Appl. 56, 61–83] to map this tight frame isometrically to a tight frame for L2(Rn)—the k-plane ridgelets. This construction makes analysis of a function f ∈ L2(Rn) by k-plane ridgelets identical to the analysis of the k-plane X-ray transform of f by an appropriate wavelet-like system for χn,k. As wavelets are typically effective at representing point singularities, it may be expected that these new systems will be effective at representing objects whose k-plane X-ray transform has a point singularity. Objects with discontinuities across hyperplanes are of this form, for k = n − 1. PMID:10051554

An exact plane-stress solution for a class of problems in orthotropic elasticity

NASA Technical Reports Server (NTRS)

Erb, D. A.; Cooper, P. A.; Weisshaar, T. A.

1982-01-01

An exact solution for the stress field within a rectangular slab of orthotropic material is found using a two dimensional Fourier series formulation. The material is required to be in plane stress, with general stress boundary conditions, and the principle axes of the material must be parallel to the sides of the rectangle. Two load cases similar to those encountered in materials testing are investigated using the solution. The solution method has potential uses in stress analysis of composite structures.

Crack problems for a rectangular plate and an infinite strip

NASA Technical Reports Server (NTRS)

Civelek, M. B.; Erdogan, F.

1980-01-01

The general plane problem for an infinite strip containing multiple cracks perpendicular to its boundaries is considered. The problem is reduced to a system of singular integral equations. Two specific problems of practical interest are then studied in detail. The first problem explores the interaction effect of multiple edge cracks in a plate or beam under tension or bending. The second problem is that of a rectangular plate containing an arbitrarily oriented crack in the plane of symmetry. Particular emphasis is placed on the problem of a plate containing an edge crack and subjected to concentrated forces.

Exact solution for an optimal impermeable parachute problem

NASA Astrophysics Data System (ADS)

Lupu, Mircea; Scheiber, Ernest

2002-10-01

In the paper there are solved direct and inverse boundary problems and analytical solutions are obtained for optimization problems in the case of some nonlinear integral operators. It is modeled the plane potential flow of an inviscid, incompressible and nonlimited fluid jet, witch encounters a symmetrical, curvilinear obstacle--the deflector of maximal drag. There are derived integral singular equations, for direct and inverse problems and the movement in the auxiliary canonical half-plane is obtained. Next, the optimization problem is solved in an analytical manner. The design of the optimal airfoil is performed and finally, numerical computations concerning the drag coefficient and other geometrical and aerodynamical parameters are carried out. This model corresponds to the Helmholtz impermeable parachute problem.

Contact problem on indentation of an elastic half-plane with an inhomogeneous coating by a flat punch in the presence of tangential stresses on a surface

NASA Astrophysics Data System (ADS)

Volkov, Sergei S.; Vasiliev, Andrey S.; Aizikovich, Sergei M.; Sadyrin, Evgeniy V.

2018-05-01

Indentation of an elastic half-space with functionally graded coating by a rigid flat punch is studied. The half-plane is additionally subjected to distributed tangential stresses. Tangential stresses are represented in a form of Fourier series. The problem is reduced to the solution of two dual integral equations over even and odd functions describing distribution of unknown normal contact stresses. The solutions of these dual integral equations are constructed by the bilateral asymptotic method. Approximated analytical expressions for contact normal stresses are provided.

Reduction of Polarization Field Strength in Fully Strained c-Plane InGaN/(In)GaN Multiple Quantum Wells Grown by MOCVD.

PubMed

Zhang, Feng; Ikeda, Masao; Zhang, Shu-Ming; Liu, Jian-Ping; Tian, Ai-Qin; Wen, Peng-Yan; Cheng, Yang; Yang, Hui

2016-12-01

The polarization fields in c-plane InGaN/(In)GaN multiple quantum well (MQW) structures grown on sapphire substrate by metal-organic chemical vapor deposition are investigated in this paper. The indium composition in the quantum wells varies from 14.8 to 26.5% for different samples. The photoluminescence wavelengths are calculated theoretically by fully considering the related effects and compared with the measured wavelengths. It is found that when the indium content is lower than 17.3%, the measured wavelengths agree well with the theoretical values. However, when the indium content is higher than 17.3%, the measured ones are much shorter than the calculation results. This discrepancy is attributed to the reduced polarization field in the MQWs. For the MQWs with lower indium content, 100% theoretical polarization can be maintained, while, when the indium content is higher, the polarization field decreases significantly. The polarization field can be weakened down to 23% of the theoretical value when the indium content is 26.5%. Strain relaxation is excluded as the origin of the polarization reduction because there is no sign of lattice relaxation in the structures, judging by the X-ray diffraction reciprocal space mapping. The possible causes of the polarization reduction are discussed.

What Strains the Anterior Cruciate Ligament During a Pivot Landing?

PubMed Central

Oh, Youkeun K.; Lipps, David B.; Ashton-Miller, James A.; Wojtys, Edward M.

2015-01-01

Background The relative contributions of an axial tibial torque and frontal plane moment to anterior cruciate ligament (ACL) strain during pivot landings are unknown. Hypothesis The peak normalized relative strain in the anteromedial (AM) bundle of the ACL is affected by the direction of the axial tibial torque but not by the direction of the frontal plane moment applied concurrently during a simulated jump landing. Study Design Controlled and descriptive laboratory studies. Methods Fifteen adult male knees with pretensioned knee muscle-tendon unit forces were loaded under a simulated pivot landing test. Compression, flexion moment, internal or external tibial torque, and knee varus or valgus moment were simultaneously applied to the distal tibia while recording the 3D knee loads and tibiofemoral kinematics. The AM-ACL relative strain was measured using a 3-mm differential variable reluctance transducer. The results were analyzed using nonparametric Wilcoxon signed–rank tests. A 3D dynamic biomechanical knee model was developed using ADAMS and validated to help interpret the experimental results. Results The mean (SD) peak AM-ACL relative strain was 192% greater (P <.001) under the internal tibial torque combined with a knee varus or valgus moment (7.0% [3.9%] and 7.0% [4.1%], respectively) than under external tibial torque with the same moments (2.4% [2.5%] and 2.4% [3.2%], respectively). The knee valgus moment augmented the AM-ACL strain due to the slope of the tibial plateau inducing mechanical coupling (ie, internal tibial rotation and knee valgus moment); this augmentation occurred before medial knee joint space opening. Conclusion An internal tibial torque combined with a knee valgus moment is the worst-case ACL loading condition. However, it is the internal tibial torque that primarily causes large ACL strain. Clinical Relevance Limiting the maximum coefficient of friction between the shoe and playing surface should limit the peak internal tibial torque

Strain-assisted magnetization reversal in Co/Ni multilayers with perpendicular magnetic anisotropy

PubMed Central

Gopman, D. B.; Dennis, C. L.; Chen, P. J.; Iunin, Y. L.; Finkel, P.; Staruch, M.; Shull, R. D.

2016-01-01

Multifunctional materials composed of ultrathin magnetic films with perpendicular magnetic anisotropy combined with ferroelectric substrates represent a new approach toward low power, fast, high density spintronics. Here we demonstrate Co/Ni multilayered films with tunable saturation magnetization and perpendicular anisotropy grown directly on ferroelectric PZT [Pb(Zr0.52Ti0.48)O3] substrate plates. Electric fields up to ±2 MV/m expand the PZT by 0.1% and generate at least 0.02% in-plane compression in the Co/Ni multilayered film. Modifying the strain with a voltage can reduce the coercive field by over 30%. We also demonstrate that alternating in-plane tensile and compressive strains (less than 0.01%) can be used to propagate magnetic domain walls. This ability to manipulate high anisotropy magnetic thin films could prove useful for lowering the switching energy for magnetic elements in future voltage-controlled spintronic devices. PMID:27297638

Effects of tissue mechanical and acoustic anisotropies on the performance of a cross-correlation-based ultrasound strain imaging method

NASA Astrophysics Data System (ADS)

Li, He; Lee, Wei-Ning

2017-02-01

The anisotropic mechanical properties (mechanical anisotropy) and view-dependent ultrasonic backscattering (acoustic anisotropy) of striated muscle due to the underlying myofiber arrangement have been well documented, but whether they impact on ultrasound strain imaging (USI) techniques remains unclear. The aim of this study was therefore to investigate the performance of a cross-correlation-based two-dimensional (2D) USI method in anisotropic media under controlled quasi-static compression in silico and in vitro. First, synthetic pre- and post-deformed 2D radiofrequency images of anisotropic phantoms were simulated in two scenarios to examine the individual effect of the mechanical and acoustic anisotropies on strain estimation. In the first scenario, the phantom was defined to be transversely isotropic with the scatterer amplitudes following a zero-mean Gaussian distribution, while in the second scenario, the phantom was defined to be mechanically isotropic with Gaussian distributed scatterer amplitudes correlated along the principal directions of pre-defined fibers. These two anisotropies were then jointly incorporated into the ultrasound image simulation model with additional depth-dependent attenuation. Three imaging planes—the fiber plane with the fiber direction perpendicular to the ultrasound beam (TISperp_fb), the fiber plane with the fiber direction parallel to the beam (TISpara), and the transverse fiber plane (TISperp_cfb)—were studied. The absolute relative error (ARE) of the lateral strain estimates in TISperp_fb (20.99  ±  15.65%) was much higher than that in TISperp_cfb (4.14  ±  3.17%). The ARE in TISpara was unavailable owing to the large spatial extent of false peaks. The effect of tissue anisotropy on the performance of the 2D USI was further confirmed in an in vitro porcine skeletal muscle phantom. The best in-plane strain quality was again shown in TISperp_cfb (elastographic signal-to-noise ratio, or SNRe:  >25 d

Absence of rippling in graphene under biaxial tensile strain

NASA Astrophysics Data System (ADS)

Rakshit, Bipul; Mahadevan, Priya

2010-10-01

Recent experiments [C. H. Lui, L. Liu, K. F. Mak, G. W. Flynn, and T. F. Heinz, Nature (London) 462, 339 (2009)10.1038/nature08569] on graphene grown on ultraflat substrates have found no rippling in graphene when subject to temperature cycling. Unsupported/unstrained films of graphene as well as films grown on various substrates on the other hand have been found to show rippling effects. As graphene grown on a substrate is invariably strained, we examine the behavior of the out-of-plane acoustic-phonon mode with biaxial tensile strain. This mode is generally associated with the rippling of graphene. We find that it can be fit to a relation of the form w2=Ak4+Bk2 , where w and k are the frequency and wave vector, respectively. The coefficient A is found to show a weak dependence on strain while B is found to increase linearly with strain. The strain-induced hardening explains the absence of rippling in graphene subject to biaxial strain. In addition, we find that graphene when subject to a biaxial tensile strain is found to undergo a structural transition with the mode at K going soft at a strain percentage of 15%.

Phase transition induced strain in ZnO under high pressure

DOE PAGES

Yan, Xiaozhi; Dong, Haini; Li, Yanchun; ...

2016-05-13

Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strengthmore » decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. Ultimately, these findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure.« less

Scaling of plane-wave functions in statistically optimized near-field acoustic holography.

PubMed

Hald, Jørgen

2014-11-01

Statistically Optimized Near-field Acoustic Holography (SONAH) is a Patch Holography method, meaning that it can be applied in cases where the measurement area covers only part of the source surface. The method performs projections directly in the spatial domain, avoiding the use of spatial discrete Fourier transforms and the associated errors. First, an inverse problem is solved using regularization. For each calculation point a multiplication must then be performed with two transfer vectors--one to get the sound pressure and the other to get the particle velocity. Considering SONAH based on sound pressure measurements, existing derivations consider only pressure reconstruction when setting up the inverse problem, so the evanescent wave amplification associated with the calculation of particle velocity is not taken into account in the regularized solution of the inverse problem. The present paper introduces a scaling of the applied plane wave functions that takes the amplification into account, and it is shown that the previously published virtual source-plane retraction has almost the same effect. The effectiveness of the different solutions is verified through a set of simulated measurements.

Computer simulation of solutions of polyharmonic equations in plane domain

NASA Astrophysics Data System (ADS)

Kazakova, A. O.

2018-05-01

A systematic study of plane problems of the theory of polyharmonic functions is presented. A method of reducing boundary problems for polyharmonic functions to the system of integral equations on the boundary of the domain is given and a numerical algorithm for simulation of solutions of this system is suggested. Particular attention is paid to the numerical solution of the main tasks when the values of the function and its derivatives are given. Test examples are considered that confirm the effectiveness and accuracy of the suggested algorithm.

Effects of Adiabatic Heating on the High Strain Rate Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Sorini, Chris; Chattopadhyay, Aditi; Goldberg, Robert K.

2017-01-01

Polymer matrix composites (PMCs) are increasingly being used in aerospace structures that are expected to experience complex dynamic loading conditions throughout their lifetime. As such, a detailed understanding of the high strain rate behavior of the constituents, particularly the strain rate, temperature, and pressure dependent polymer matrix, is paramount. In this paper, preliminary efforts in modeling experimentally observed temperature rises due to plastic deformation in PMCs subjected to dynamic loading are presented. To this end, an existing isothermal viscoplastic polymer constitutive formulation is extended to model adiabatic conditions by incorporating temperature dependent elastic properties and modifying the components of the inelastic strain rate tensor to explicitly depend on temperature. It is demonstrated that the modified polymer constitutive model is capable of capturing strain rate and temperature dependent yield as well as thermal softening associated with the conversion of plastic work to heat at high rates of strain. The modified constitutive model is then embedded within a strength of materials based micromechanics framework to investigate the manifestation of matrix thermal softening, due to the conversion of plastic work to heat, on the high strain rate response of a T700Epon 862 (T700E862) unidirectional composite. Adiabatic model predictions for high strain rate composite longitudinal tensile, transverse tensile, and in-plane shear loading are presented. Results show a substantial deviation from isothermal conditions; significant thermal softening is observed for matrix dominated deformation modes (transverse tension and in-plane shear), highlighting the importance of accounting for the conversion of plastic work to heat in the polymer matrix in the high strain rate analysis of PMC structures.

Derivation of the out-of-plane behaviour of an English bond masonry wall through homogenization strategies

NASA Astrophysics Data System (ADS)

Silva, Luís Carlos; Milani, Gabriele; Lourenço, Paulo B.

2017-11-01

Two finite element homogenized-based strategies are presented for the out-of-plane behaviour characterization of an English bond masonry wall. A finite element micro-modelling approach using Cauchy stresses and first order movements are assumed for both strategies. The material nonlinearity is lumped on joints interfaces and bricks are considered elastic. Nevertheless, the first model is based on a Plane-stress assumption, in which the out-of-plane quantities are derived through on-thickness wall integration considering a Kirchhoff-plate theory. The second model is a tridimensional one, in which the homogenized out-of-plane quantities can be directly derived after solving the boundary value problem. The comparison is conducted by assessing the obtained out-of-plane bending- and torsion-curvature diagrams. A good agreement is found for the present study case.

The magnetic transition temperature tuned by strain in YMn0.9Ru0.1O3 thin films

NASA Astrophysics Data System (ADS)

Yang, L. P.; Zhang, A. M.; Wang, K.; Wu, X. S.; Zhai, Z. Y.

2018-05-01

Epitaxial orthorhombic YMn0.9Ru0.1O3 films with different thickness have been grown on (001)-SrTiO3 substrates by pulsed laser deposition (PLD). The crystal structure is well investigated by X-ray Diffraction. It is found that the out-of-plane parameter c slowly increases with decreasing thickness of samples because of the tensile strain between the films and substrates along c axis. The lengths of in-plane Mn-O bonds expand with the enhancement of strains, which is proved by Raman scatting. The magnetic measurements reveal that there exist two magnetic transition temperatures TN1 and TN2. The TN1 is close to that of orthorhombic YMnO3 bulk. With decreasing thickness of the films, TN1 keeps almost constant because of the small stain along c-axis. TN2, however, obviously increases from 117 K to 134 K, which could be related to the expansion of in-plane Mn-O bonds. Results show that the magnetic transition temperature of YMn0.9Ru0.1O3 films can be sensitively manipulated by the strain of the films.

Evolution of strain localization in variable-width three-dimensional unsaturated laboratory-scale cut slopes

USGS Publications Warehouse

Morse, Michael S.; Lu, Ning; Wayllace, Alexandra; Godt, Jonathan W.

2017-01-01

To experimentally validate a recently developed theory for predicting the stability of cut slopes under unsaturated conditions, the authors measured increasing strain localization in unsaturated slope cuts prior to abrupt failure. Cut slope width and moisture content were controlled and varied in a laboratory, and a sliding door that extended the height of the free face of the slope was lowered until the cut slope failed. A particle image velocimetry tool was used to quantify soil displacement in the x-y">x-y (horizontal) and x-z">x-z (vertical) planes, and strain was calculated from the displacement. Areas of maximum strain localization prior to failure were shown to coincide with the location of the eventual failure plane. Experimental failure heights agreed with the recently developed stability theory for unsaturated cut slopes (within 14.3% relative error) for a range of saturation and cut slope widths. A theoretical threshold for sidewall influence on cut slope failures was also proposed to quantify the relationship between normalized sidewall width and critical height. The proposed relationship was consistent with the cut slope experiment results, and is intended for consideration in future geotechnical experiment design. The experimental data of evolution of strain localization presented herein provide a physical basis from which future numerical models of strain localization can be validated.

An experimental study on the manufacture and characterization of in-plane fibre-waviness defects in composites

PubMed Central

DiazDelaO, F. A.; Atherton, K.

2018-01-01

A new method has been developed for creating localized in-plane fibre waviness in composite coupons and used to create a large batch of specimens. This method could be used by manufacturers to experimentally explore the effect of fibre waviness on composite structures both directly and indirectly to develop and validate computational models. The specimens were assessed using ultrasound, digital image correlation and a novel inspection technique capable of measuring residual strain fields. To explore how the defect affects the performance of composite structures, the specimens were then loaded to failure. Predictions of remnant strength were made using a simple ultrasound damage metric and a new residual strain-based damage metric. The predictions made using residual strain measurements were found to be substantially more effective at characterizing ultimate strength than ultrasound measurements. This suggests that residual strains have a significant effect on the failure of laminates containing fibre waviness and that these strains could be incorporated into computational models to improve their ability to simulate the defect. PMID:29892446

A stable numerical solution method in-plane loading of nonlinear viscoelastic laminated orthotropic materials

NASA Technical Reports Server (NTRS)

Gramoll, K. C.; Dillard, D. A.; Brinson, H. F.

1989-01-01

In response to the tremendous growth in the development of advanced materials, such as fiber-reinforced plastic (FRP) composite materials, a new numerical method is developed to analyze and predict the time-dependent properties of these materials. Basic concepts in viscoelasticity, laminated composites, and previous viscoelastic numerical methods are presented. A stable numerical method, called the nonlinear differential equation method (NDEM), is developed to calculate the in-plane stresses and strains over any time period for a general laminate constructed from nonlinear viscoelastic orthotropic plies. The method is implemented in an in-plane stress analysis computer program, called VCAP, to demonstrate its usefulness and to verify its accuracy. A number of actual experimental test results performed on Kevlar/epoxy composite laminates are compared to predictions calculated from the numerical method.

Unique Abnormalities in Right Ventricular Longitudinal Strain in Systemic Sclerosis Patients.

PubMed

Mukherjee, Monica; Chung, Shang-En; Ton, Von Khue; Tedford, Ryan J; Hummers, Laura K; Wigley, Fredrick M; Abraham, Theodore P; Shah, Ami A

2016-06-01

Cardiac involvement in systemic sclerosis (scleroderma [SSc]) adversely affects long-term prognosis, often remaining undetectable despite close clinical examination and 2-dimensional echocardiographic monitoring. Speckle-derived strain of the right ventricle (RV) was utilized to detect occult abnormalities in regional and global contractility in SSc patients. A total of 138 SSc patients with technically adequate echocardiograms was studied and compared with 40 age- and sex-matched healthy non-SSc controls. Standard assessment of RV chamber function included tricuspid annular plane systolic excursion and fractional area change. RV longitudinal systolic speckle-derived strain was assessed in the basal, mid, and apical free wall. Tricuspid annular plane systolic excursion was not different between groups (P=0.307). Although fractional area change was lower in SSc patients than in controls (mean, 48.9 versus 55; P=0.002), the mean fractional area change was still within the normal range (>35). In contrast, RV longitudinal systolic speckle-derived strain measures were significantly different between groups, both globally (-20.4% versus -17.7%; P=0.005) and regionally: they were decreased in the apex (-8.5% versus -17.1%; P<0.0001) and mid segments (-12.4% versus -20.9%; P<0.0001), and increased in the base (-32.2% versus -23.3%; P=0.0001) for the SSc group. The regional difference in the base compared with the apex was significantly greater for SSc than for controls (P<0.0001 for interaction). The differences observed in regional strain between SSc and control were unchanged after adjusting for RV systolic pressure. Speckle-derived strain reveals a heterogenous pattern of regional heart strain in SSc that is not detected by conventional measures of function, suggestive of occult RV myocardial disease. © 2016 American Heart Association, Inc.

Plane wave diffraction by a finite plate with impedance boundary conditions.

PubMed

Nawaz, Rab; Ayub, Muhammad; Javaid, Akmal

2014-01-01

In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in.

Measurement of strain in Al-Cu interconnect lines with x-ray microdiffraction

NASA Astrophysics Data System (ADS)

Solak, H. H.; Vladimirsky, Y.; Cerrina, F.; Lai, B.; Yun, W.; Cai, Z.; Ilinski, P.; Legnini, D.; Rodrigues, W.

1999-07-01

We report measurement of strain in patterned Al-Cu interconnect lines with x-ray microdiffraction technique with a ˜1 μm spatial resolution. Monochromatized x rays from an undulator were focused on the sample using a phase fresnel zone plate and diffracted light was collected by an area detector in a symmetric, angle dispersive x-ray diffraction geometry. Measurements were made before and after the line sample was stressed for electromigration. Results show an increase in inter- and intra-grain strain variation after the testing. Differences in strain behavior of grains with (111) and (200) crystallographic planes parallel to the substrate surface were observed. A position dependent variation of strain after the testing was measured whereas no such dependence was found before the testing.

Learning-based scan plane identification from fetal head ultrasound images

NASA Astrophysics Data System (ADS)

Liu, Xiaoming; Annangi, Pavan; Gupta, Mithun; Yu, Bing; Padfield, Dirk; Banerjee, Jyotirmoy; Krishnan, Kajoli

2012-03-01

Acquisition of a clinically acceptable scan plane is a pre-requisite for ultrasonic measurement of anatomical features from B-mode images. In obstetric ultrasound, measurement of gestational age predictors, such as biparietal diameter and head circumference, is performed at the level of the thalami and cavum septum pelucidi. In an accurate scan plane, the head can be modeled as an ellipse, the thalami looks like a butterfly, the cavum appears like an empty box and the falx is a straight line along the major axis of a symmetric ellipse inclined either parallel to or at small angles to the probe surface. Arriving at the correct probe placement on the mother's belly to obtain an accurate scan plane is a task of considerable challenge especially for a new user of ultrasound. In this work, we present a novel automated learning-based algorithm to identify an acceptable fetal head scan plane. We divide the problem into cranium detection and a template matching to capture the composite "butterfly" structure present inside the head, which mimics the visual cues used by an expert. The algorithm uses the stateof- the-art Active Appearance Models techniques from the image processing and computer vision literature and tie them to presence or absence of the inclusions within the head to automatically compute a score to represent the goodness of a scan plane. This automated technique can be potentially used to train and aid new users of ultrasound.

Left ventricular function quantified by myocardial strain imaging in small-breed dogs with chronic mitral regurgitation.

PubMed

Smith, Danielle N; Bonagura, John D; Culwell, Nicole M; Schober, Karsten E

2012-03-01

The presence of left ventricular (LV) systolic dysfunction may influence prognosis or therapy in dogs with chronic mitral regurgitation (MR). Assessment of LV function in MR by conventional echocardiography is confounded by altered ventricular loading. Myocardial deformation (strain) imaging might offer more sensitive estimates of LV function in this disease. Prospectively measure myocardial strain in dogs with asymptomatic MR compared to a control group. Forty healthy dogs (3.5-11.5 kg): 20 Controls; 20 dogs with MR and LV remodeling (Stage B2), were evaluated in this study. LV size and function were assessed in a short-axis plane. Segmental radial strain and strain rate and global circumferential strain were measured using a 2D echocardiographic speckle-tracking algorithm (GE EchoPAC). Groups were compared using Bonferroni t-tests. Influences of heart rate and body weight were explored with linear regression. The MR group had significantly greater mean values for heart rate, LV size, and LV systolic function. Specifically, LV diastolic diameter, diastole area, shortening fraction, averaged peak systolic and early diastolic radial strain, global circumferential strain, and averaged radial strain rate were significantly greater in the MR group (p < 0.015 to p < 0.001). Strain was unrelated to weight, but weakly correlated with heart rate. Similar to conventional indices, Stage B2 dogs with MR demonstrate hyperdynamic deformation in the short-axis plane. Short-axis strain variables measured by 2D speckle tracking are greater than for controls of similar age and weight. These results imply either preserved LV systolic function or that LV dysfunction is masked by altered ventricular loading. Copyright © 2012 Elsevier B.V. All rights reserved.

The path integral on the Poincaré upper half-plane with a magnetic field and for the Morse potential

NASA Astrophysics Data System (ADS)

Grosche, Christian

1988-10-01

Rigorous path integral treatments on the Poincaré upper half-plane with a magnetic field and for the Morse potential are presented. The calculation starts with the path integral on the Poincaré upper half-plane with a magnetic field. By a Fourier expansion and a non-linear transformation this problem is reformulated in terms of the path integral for the Morse potential. This latter problem can be reduced by an appropriate space-time transformation to the path integral for the harmonic oscillator with generalised angular momentum, a technique which has been developed in recent years. The well-known solution for the last problem enables one to give explicit expressions for the Feynman kernels for the Morse potential and for the Poincaré upper half-plane with magnetic field, respectively. The wavefunctions and the energy spectrum for the bound and scattering states are given, respectively.

Strain-engineered diffusive atomic switching in two-dimensional crystals

PubMed Central

Kalikka, Janne; Zhou, Xilin; Dilcher, Eric; Wall, Simon; Li, Ju; Simpson, Robert E.

2016-01-01

Strain engineering is an emerging route for tuning the bandgap, carrier mobility, chemical reactivity and diffusivity of materials. Here we show how strain can be used to control atomic diffusion in van der Waals heterostructures of two-dimensional (2D) crystals. We use strain to increase the diffusivity of Ge and Te atoms that are confined to 5 Å thick 2D planes within an Sb2Te3–GeTe van der Waals superlattice. The number of quintuple Sb2Te3 2D crystal layers dictates the strain in the GeTe layers and consequently its diffusive atomic disordering. By identifying four critical rules for the superlattice configuration we lay the foundation for a generalizable approach to the design of switchable van der Waals heterostructures. As Sb2Te3–GeTe is a topological insulator, we envision these rules enabling methods to control spin and topological properties of materials in reversible and energy efficient ways. PMID:27329563

Cyclic loading of simulated fault gouge to large strains

NASA Astrophysics Data System (ADS)

Jones, Lucile M.

1980-04-01

As part of a study of the mechanics of simulated fault gouge, deformation of Kayenta Sandstone (24% initial porosity) was observed in triaxial stress tests through several stress cycles. Between 50- and 300-MPa effective pressure the specimens deformed stably without stress drops and with deformation occurring throughout the sample. At 400-MPa effective pressure the specimens underwent strain softening with the deformation occurring along one plane. However, the difference in behavior seems to be due to the density variation at different pressures rather than to the difference in pressure. After peak stress was reached in each cycle, the samples dilated such that the volumetric strain and the linear strain maintained a constant ratio (approximately 0.1) at all pressures. The behavior was independent of the number of stress cycles to linear strains up to 90% and was in general agreement with laws of soil behavior derived from experiments conducted at low pressure (below 5 MPa).

Effect of nano/micro B4C and SiC particles on fracture properties of aluminum 7075 particulate composites under chevron-notch plane strain fracture toughness test

NASA Astrophysics Data System (ADS)

Morovvati, M. R.; Lalehpour, A.; Esmaeilzare, A.

2016-12-01

Reinforcing aluminum with SiC and B4C nano/micro particles can lead to a more efficient material in terms of strength and light weight. The influence of adding these particles to an aluminum 7075 matrix is investigated using chevron-notch fracture toughness test method. The reinforcing factors are type, size (micro/nano), and weight percent of the particles. The fracture parameters are maximum load, notch opening displacement, the work up to fracture and chevron notch plane strain fracture toughness. The findings demonstrate that addition of micro and nano size particles improves the fracture properties; however, increasing the weight percent of the particles leads to increase of fracture properties up to a certain level and after that due to agglomeration of the particles, the improvement does not happen for both particle types and size categories. Agglomeration of particles at higher amounts of reinforcing particles results in improper distribution of particles and reduction in mechanical properties.

Simulation of cemented granular materials. I. Macroscopic stress-strain response and strain localization.

PubMed

Estrada, Nicolas; Lizcano, Arcesio; Taboada, Alfredo

2010-07-01

This is the first of two papers investigating the mechanical response of cemented granular materials by means of contact dynamics simulations. In this paper, a two-dimensional polydisperse sample with high-void ratio is constructed and then sheared in a simple shear numerical device at different confinement levels. We study the macroscopic response of the material in terms of mean and deviatoric stresses and strains. We show that the introduction of a local force scale, i.e., the tensile strength of the cemented bonds, causes the material to behave in a rigid-plastic fashion, so that a yield surface can be easily determined. This yield surface has a concave-down shape in the mean:deviatoric stress plane and it approaches a straight line, i.e., a Coulomb strength envelope, in the limit of a very dense granular material. Beyond yielding, the cemented structure gradually degrades until the material eventually behaves as a cohesionless granular material. Strain localization is also investigated, showing that the strains concentrate in a shear band whose thickness increases with the confining stress. The void ratio inside the shear band at the steady state is shown to be a material property that depends only on contact parameters.

A parallel orbital-updating based plane-wave basis method for electronic structure calculations

NASA Astrophysics Data System (ADS)

Pan, Yan; Dai, Xiaoying; de Gironcoli, Stefano; Gong, Xin-Gao; Rignanese, Gian-Marco; Zhou, Aihui

2017-11-01

Motivated by the recently proposed parallel orbital-updating approach in real space method [1], we propose a parallel orbital-updating based plane-wave basis method for electronic structure calculations, for solving the corresponding eigenvalue problems. In addition, we propose two new modified parallel orbital-updating methods. Compared to the traditional plane-wave methods, our methods allow for two-level parallelization, which is particularly interesting for large scale parallelization. Numerical experiments show that these new methods are more reliable and efficient for large scale calculations on modern supercomputers.

A Critical Plane-energy Model for Multiaxial Fatigue Life Prediction of Homogeneous and Heterogeneous Materials

NASA Astrophysics Data System (ADS)

Wei, Haoyang

A new critical plane-energy model is proposed in this thesis for multiaxial fatigue life prediction of homogeneous and heterogeneous materials. Brief review of existing methods, especially on the critical plane-based and energy-based methods, are given first. Special focus is on one critical plane approach which has been shown to work for both brittle and ductile metals. The key idea is to automatically change the critical plane orientation with respect to different materials and stress states. One potential drawback of the developed model is that it needs an empirical calibration parameter for non-proportional multiaxial loadings since only the strain terms are used and the out-of-phase hardening cannot be considered. The energy-based model using the critical plane concept is proposed with help of the Mroz-Garud hardening rule to explicitly include the effect of non-proportional hardening under fatigue cyclic loadings. Thus, the empirical calibration for non-proportional loading is not needed since the out-of-phase hardening is naturally included in the stress calculation. The model predictions are compared with experimental data from open literature and it is shown the proposed model can work for both proportional and non-proportional loadings without the empirical calibration. Next, the model is extended for the fatigue analysis of heterogeneous materials integrating with finite element method. Fatigue crack initiation of representative volume of heterogeneous materials is analyzed using the developed critical plane-energy model and special focus is on the microstructure effect on the multiaxial fatigue life predictions. Several conclusions and future work is drawn based on the proposed study.

Topologically protected edge states for out-of-plane and in-plane bulk elastic waves.

PubMed

Huo, Shao-Yong; Chen, Jiu-Jiu; Huang, Hong-Bo

2018-04-11

Topological phononic insulators (TPnIs) show promise for application in the manipulation of acoustic waves for the design of low-loss transmission and perfectly integrated communication devices. Since solid phononic crystals exist as a transverse polarization mode and a mixed longitudinal-transverse polarization mode, the realization of topological edge states for both out-of-plane and in-plane bulk elastic waves is desirable to enhance the controllability of the edge waves in solid systems. In this paper, a two-dimensional (2D) solid/solid hexagonal-latticed phononic system that simultaneously supports the topologically protected edge states for out-of-plane and in-plane bulk elastic waves is investigated. Firstly, two pairs of two-fold Dirac cones, respectively corresponding to the out-of-plane and in-plane waves, are obtained at the same frequency by tuning the crystal parameters. Then, a strategy of zone folding is invoked to form double Dirac cones. By shrinking and expanding the steel scatterer, the lattice symmetry is broken, and band inversions induced, giving rise to an intriguing topological phase transition. Finally, the topologically protected edge states for both out-of-plane and in-plane bulk elastic waves, which can be simultaneously located at the frequency range from 1.223 to 1.251 MHz, are numerically observed. Robust pseudospin-dependent elastic edge wave propagation along arbitrary paths is further demonstrated. Our results will significantly broaden its practical application in the engineering field.

Topologically protected edge states for out-of-plane and in-plane bulk elastic waves

NASA Astrophysics Data System (ADS)

Huo, Shao-Yong; Chen, Jiu-Jiu; Huang, Hong-Bo

2018-04-01

Topological phononic insulators (TPnIs) show promise for application in the manipulation of acoustic waves for the design of low-loss transmission and perfectly integrated communication devices. Since solid phononic crystals exist as a transverse polarization mode and a mixed longitudinal-transverse polarization mode, the realization of topological edge states for both out-of-plane and in-plane bulk elastic waves is desirable to enhance the controllability of the edge waves in solid systems. In this paper, a two-dimensional (2D) solid/solid hexagonal-latticed phononic system that simultaneously supports the topologically protected edge states for out-of-plane and in-plane bulk elastic waves is investigated. Firstly, two pairs of two-fold Dirac cones, respectively corresponding to the out-of-plane and in-plane waves, are obtained at the same frequency by tuning the crystal parameters. Then, a strategy of zone folding is invoked to form double Dirac cones. By shrinking and expanding the steel scatterer, the lattice symmetry is broken, and band inversions induced, giving rise to an intriguing topological phase transition. Finally, the topologically protected edge states for both out-of-plane and in-plane bulk elastic waves, which can be simultaneously located at the frequency range from 1.223 to 1.251 MHz, are numerically observed. Robust pseudospin-dependent elastic edge wave propagation along arbitrary paths is further demonstrated. Our results will significantly broaden its practical application in the engineering field.

The Sierpinski Triangle Plane

NASA Astrophysics Data System (ADS)

Ettestad, David; Carbonara, Joaquin

The Sierpinski Triangle (ST) is a fractal which has Haussdorf dimension log23 ≈ 1.585 that has been studied extensively. In this paper, we introduce the Sierpinski Triangle Plane (STP), an infinite extension of the ST that spans the entire real plane but is not a vector subspace or a tiling of the plane with a finite set of STs. STP is shown to be a radial fractal with many interesting and surprising properties.

Geometric reconstruction using tracked ultrasound strain imaging

NASA Astrophysics Data System (ADS)

Pheiffer, Thomas S.; Simpson, Amber L.; Ondrake, Janet E.; Miga, Michael I.

2013-03-01

The accurate identification of tumor margins during neurosurgery is a primary concern for the surgeon in order to maximize resection of malignant tissue while preserving normal function. The use of preoperative imaging for guidance is standard of care, but tumor margins are not always clear even when contrast agents are used, and so margins are often determined intraoperatively by visual and tactile feedback. Ultrasound strain imaging creates a quantitative representation of tissue stiffness which can be used in real-time. The information offered by strain imaging can be placed within a conventional image-guidance workflow by tracking the ultrasound probe and calibrating the image plane, which facilitates interpretation of the data by placing it within a common coordinate space with preoperative imaging. Tumor geometry in strain imaging is then directly comparable to the geometry in preoperative imaging. This paper presents a tracked ultrasound strain imaging system capable of co-registering with preoperative tomograms and also of reconstructing a 3D surface using the border of the strain lesion. In a preliminary study using four phantoms with subsurface tumors, tracked strain imaging was registered to preoperative image volumes and then tumor surfaces were reconstructed using contours extracted from strain image slices. The volumes of the phantom tumors reconstructed from tracked strain imaging were approximately between 1.5 to 2.4 cm3, which was similar to the CT volumes of 1.0 to 2.3 cm3. Future work will be done to robustly characterize the reconstruction accuracy of the system.

Steady sliding frictional contact problem for a 2d elastic half-space with a discontinuous friction coefficient and related stress singularities

NASA Astrophysics Data System (ADS)

Ballard, Patrick

2016-12-01

The steady sliding frictional contact problem between a moving rigid indentor of arbitrary shape and an isotropic homogeneous elastic half-space in plane strain is extensively analysed. The case where the friction coefficient is a step function (with respect to the space variable), that is, where there are jumps in the friction coefficient, is considered. The problem is put under the form of a variational inequality which is proved to always have a solution which, in addition, is unique in some cases. The solutions exhibit different kinds of universal singularities that are explicitly given. In particular, it is shown that the nature of the universal stress singularity at a jump of the friction coefficient is different depending on the sign of the jump.

Acoustic plane wave diffraction from a truncated semi-infinite cone in axial irradiation

NASA Astrophysics Data System (ADS)

Kuryliak, Dozyslav; Lysechko, Victor

2017-11-01

The diffraction problem of the plane acoustic wave on the semi-infinite truncated soft and rigid cones in the case of axial incidence is solved. The problem is formulated as a boundary-value problem in terms of Helmholtz equation, with Dirichlet and Neumann boundary conditions, for scattered velocity potential. The incident field is taken to be the total field of semi-infinite cone, the expression of which is obtained by solving the auxiliary diffraction problem by the use of Kontorovich-Lebedev integral transformation. The diffracted field is sought via the expansion in series of the eigenfunctions for subdomains of the Helmholtz equation taking into account the edge condition. The corresponding diffraction problem is reduced to infinite system of linear algebraic equations (ISLAE) making use of mode matching technique and orthogonality properties of the Legendre functions. The method of analytical regularization is applied in order to extract the singular part in ISLAE, invert it exactly and reduce the problem to ISLAE of the second kind, which is readily amenable to calculation. The numerical solution of this system relies on the reduction method; and its accuracy depends on the truncation order. The case of degeneration of the truncated semi-infinite cone into an aperture in infinite plane is considered. Characteristic features of diffracted field in near and far fields as functions of cone's parameters are examined.

Self-accommodation of B19' martensite in Ti-Ni shape memory alloys - Part II. Characteristic interface structures between habit plane variants

NASA Astrophysics Data System (ADS)

Nishida, M.; Okunishi, E.; Nishiura, T.; Kawano, H.; Inamura, T.; S., Ii; Hara, T.

2012-06-01

Four characteristic interface microstructures between habit plane variants (HPVs) in the self-accommodation morphologies of B19‧ martensite in Ti-Ni alloys have been investigated by scanning transmission electron microscopy (STEM). The straight interface of a ? B19‧ type I twin is present at interface I. The relaxation of the transformation strain at interface II is achieved by a volume reduction of the minor correspondence variants (CVs) in the relevant habit plane variants (HPVs). The relaxation of the transformation strain at interface III is mainly due to the formation of a ? B19‧ type I twin between the two major CVs. Subsequently, local strain around the tips of the minor CVs perpendicular to the interface is released by the formation of micro-twins with the ⟨011⟩B19‧ type II and/or ? B19‧ type I relation. The major and minor CVs in each HPV are alternately connected through fine variants with the ? B19‧ type I twin relation parallel to interface IV. The results are compared with macroscopic observations and the predictions of PTMC analysis.

Finite Strain Analysis of the Wadi Fatima Shear Zone in Western Arabia, Saudi Arabia

NASA Astrophysics Data System (ADS)

Kassem, O. M. K.; Hamimi, Z.

2018-03-01

Neoproterozoic rocks, Oligocene to Neogene sediments and Tertiary Red Sea rift-related volcanics (Harrat) are three dominant major groups exposed in the Jeddah tectonic terrane in Western Arabia. The basement complex comprises amphibolites, schists, and older and younger granites unconformably overlain by a post-amalgamation volcanosedimentary sequence (Fatima Group) exhibiting post-accretionary thrusting and thrust-related structures. The older granites and/or the amphibolites and schists display mylonitization and shearing in some outcrops, and the observed kinematic indicators indicate dextral monoclinic symmetry along the impressive Wadi Fatima Shear Zone. Finite strain analysis of the mylonitized lithologies is used to interpret the deformation history of the Wadi Fatima Shear Zone. The measured finite strain data demonstrate that the amphibolites, schists, and older granites are mildly to moderately deformed, where XZ (axial ratios in XZ direction) vary from 2.76 to 4.22 and from 2.04 to 3.90 for the Rf/φ and Fry method respectively. The shortening axes ( Z) have subvertical attitude and are associated with subhorizontal foliation. The data show oblate strain ellipsoids in the different rocks in the studied area and indication bulk flattening strain. We assume that the different rock types have similar deformation behavior. In the deformed granite, the strain data are identical in magnitude with those obtained in the Fatima Group volcanosedimentary sequence. Finite strain accumulated without any significant volume change contemporaneously with syn-accretionary transpressive structures. It is concluded that a simple-shear deformation with constant-volume plane strain exists, where displacement is strictly parallel to the shear plane. Furthermore, the contacts between various lithological units in the Wadi Fatima Shear Zone were formed under brittle to semi-ductile deformation conditions.

Strain-engineered optoelectronic properties of 2D transition metal dichalcogenide lateral heterostructures

DOE PAGES

Lee, Jaekwang; Huang, Jingsong; Sumpter, Bobby G.; ...

2017-02-17

Compared with their bulk counterparts, 2D materials can sustain much higher elastic strain at which optical quantities such as bandgaps and absorption spectra governing optoelectronic device performance can be modified with relative ease. Using first-principles density functional theory and quasiparticle GW calculations, we demonstrate how uniaxial tensile strain can be utilized to optimize the electronic and optical properties of transition metal dichalcogenide lateral (in-plane) heterostructures such as MoX 2/WX 2 (X = S, Se, Te). We find that these lateral-type heterostructures may facilitate efficient electron–hole separation for light detection/harvesting and preserve their type II characteristic up to 12% of uniaxialmore » strain. Based on the strain-dependent bandgap and band offset, we show that uniaxial tensile strain can significantly increase the power conversion efficiency of these lateral heterostructures. Our results suggest that these strain-engineered lateral heterostructures are promising for optimizing optoelectronic device performance by selectively tuning the energetics of the bandgap.« less

Effect of biaxial strain on the magnetism of Fe16N2: Density-functional investigations

NASA Astrophysics Data System (ADS)

Zhou, Wei; Liu, Lijuan; Wu, Ping

2014-02-01

The effect of biaxial strain on the magnetism of α″-Fe16N2 was investigated by the first principles calculations. The GGA, GGA + U and HSE06 calculations give the same result that the magnetic moments increase with the biaxial strain in the ab plane. All non-equivalent Fe atoms contribute to the increase of magnetic moments, although the variations of inter-atomic distances between non-equivalent Fe and N are different. Additionally, the magnetic anisotropy of Fe16N2 could be controlled by the biaxial strain.

A Constitutive Model for Strain-Controlled Strength Degradation of Rockmasses (SDR)

NASA Astrophysics Data System (ADS)

Kalos, A.; Kavvadas, M.

2017-11-01

The paper describes a continuum, rate-independent, incremental plasticity constitutive model applicable in weak rocks and heavily fractured rockmasses, where mechanical behaviour is controlled by rockmass strength rather than structural features (discontinuities). The model describes rockmass structure by a generalised Hoek-Brown Structure Envelope (SE) in the stress space. Stress paths inside the SE are nonlinear and irreversible to better simulate behaviour at strains up to peak strength and under stress reversals. Stress paths on the SE have user-controlled volume dilatancy (gradually reducing to zero at large shear strains) and can model post-peak strain softening of brittle rockmasses via a structure degradation (damage) mechanism triggered by accumulated plastic shear strains. As the SE may strain harden with plastic strains, ductile behaviour can also be modelled. The model was implemented in the Finite Element Code Simulia ABAQUS and was applied in plane strain (2D) excavation of a cylindrical cavity (tunnel) to predict convergence-confinement curves. It is shown that small-strain nonlinearity, variable volume dilatancy and post-peak hardening/softening strongly affect the predicted curves, resulting in corresponding differences of lining pressures in real tunnel excavations.

Galois groups of Schubert problems via homotopy computation

NASA Astrophysics Data System (ADS)

Leykin, Anton; Sottile, Frank

2009-09-01

Numerical homotopy continuation of solutions to polynomial equations is the foundation for numerical algebraic geometry, whose development has been driven by applications of mathematics. We use numerical homotopy continuation to investigate the problem in pure mathematics of determining Galois groups in the Schubert calculus. For example, we show by direct computation that the Galois group of the Schubert problem of 3-planes in mathbb{C}^8 meeting 15 fixed 5-planes non-trivially is the full symmetric group S_{6006} .

On the role of constant-stress surfaces in the problem of minimizing elastic stress concentration

NASA Technical Reports Server (NTRS)

Wheeler, L.

1976-01-01

Cases involving antiplane shear deformation, axisymmetric torsion, and plane strain theory, with surfaces of constant stress magnitude optimal in terms of minimizing stress, are investigated. Results for the plane theory refer to exterior doubly connected domains. Stresses generated by torsion of an elastic solid lying within a radially convex region of revolution with plane ends, body force absent, and lateral surface traction-free, are examined. The unknown portion of the boundary of such domains may involve a hole, fillet, or notch.

Determining the ice-binding planes of antifreeze proteins by fluorescence-based ice plane affinity.

PubMed

Basu, Koli; Garnham, Christopher P; Nishimiya, Yoshiyuki; Tsuda, Sakae; Braslavsky, Ido; Davies, Peter

2014-01-15

Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal ice growth. AFPs bind to specific planes of ice through their ice-binding surfaces. Fluorescence-based ice plane affinity (FIPA) analysis is a modified technique used to determine the ice planes to which the AFPs bind. FIPA is based on the original ice-etching method for determining AFP-bound ice-planes. It produces clearer images in a shortened experimental time. In FIPA analysis, AFPs are fluorescently labeled with a chimeric tag or a covalent dye then slowly incorporated into a macroscopic single ice crystal, which has been preformed into a hemisphere and oriented to determine the a- and c-axes. The AFP-bound ice hemisphere is imaged under UV light to visualize AFP-bound planes using filters to block out nonspecific light. Fluorescent labeling of the AFPs allows real-time monitoring of AFP adsorption into ice. The labels have been found not to influence the planes to which AFPs bind. FIPA analysis also introduces the option to bind more than one differently tagged AFP on the same single ice crystal to help differentiate their binding planes. These applications of FIPA are helping to advance our understanding of how AFPs bind to ice to halt its growth and why many AFP-producing organisms express multiple AFP isoforms.

Determining the Ice-binding Planes of Antifreeze Proteins by Fluorescence-based Ice Plane Affinity

PubMed Central

Basu, Koli; Garnham, Christopher P.; Nishimiya, Yoshiyuki; Tsuda, Sakae; Braslavsky, Ido; Davies, Peter

2014-01-01

Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal ice growth. AFPs bind to specific planes of ice through their ice-binding surfaces. Fluorescence-based ice plane affinity (FIPA) analysis is a modified technique used to determine the ice planes to which the AFPs bind. FIPA is based on the original ice-etching method for determining AFP-bound ice-planes. It produces clearer images in a shortened experimental time. In FIPA analysis, AFPs are fluorescently labeled with a chimeric tag or a covalent dye then slowly incorporated into a macroscopic single ice crystal, which has been preformed into a hemisphere and oriented to determine the a- and c-axes. The AFP-bound ice hemisphere is imaged under UV light to visualize AFP-bound planes using filters to block out nonspecific light. Fluorescent labeling of the AFPs allows real-time monitoring of AFP adsorption into ice. The labels have been found not to influence the planes to which AFPs bind. FIPA analysis also introduces the option to bind more than one differently tagged AFP on the same single ice crystal to help differentiate their binding planes. These applications of FIPA are helping to advance our understanding of how AFPs bind to ice to halt its growth and why many AFP-producing organisms express multiple AFP isoforms. PMID:24457629

Electrostatic engineering of strained ferroelectric perovskites from first principles

NASA Astrophysics Data System (ADS)

Cazorla, Claudio; Stengel, Massimiliano

2015-12-01

Design of novel artificial materials based on ferroelectric perovskites relies on the basic principles of electrostatic coupling and in-plane lattice matching. These rules state that the out-of-plane component of the electric displacement field and the in-plane components of the strain are preserved across a layered superlattice, provided that certain growth conditions are respected. Intense research is currently directed at optimizing materials functionalities based on these guidelines, often with remarkable success. Such principles, however, are of limited practical use unless one disposes of reliable data on how a given material behaves under arbitrary electrical and mechanical boundary conditions. Here we demonstrate, by focusing on the prototypical ferroelectrics PbTiO3 and BiFeO3 as test cases, how such information can be calculated from first principles in a systematic and efficient way. In particular, we construct a series of two-dimensional maps that describe the behavior of either compound (e.g., concerning the ferroelectric polarization and antiferrodistortive instabilities) at any conceivable choice of the in-plane lattice parameter, a , and out-of-plane electric displacement, D . In addition to being of immediate practical applicability to superlattice design, our results bring new insight into the complex interplay of competing degrees of freedom in perovskite materials and reveal some notable instances where the behavior of these materials depart from what naively is expected.

The Three Planes of Language.

ERIC Educational Resources Information Center

Sampson, Gloria

1999-01-01

Currently, the language sciences place together four different forms of mental activity on one plane of language, which results in confusion. This paper presents arguments from metaphysics, hermeneutics, and semiotics to demonstrate that there are actually three planes of language (a biologically-based information processing plane, a literal…

Splitting of the neutral mechanical plane depends on the length of the multi-layer structure of flexible electronics.

PubMed

Li, Shuang; Su, Yewang; Li, Rui

2016-06-01

Multi-layer structures with soft (compliant) interlayers have been widely used in flexible electronics and photonics as an effective design for reducing interactions among the hard (stiff) layers and thus avoiding the premature failure of an entire device. The analytic model for bending of such a structure has not been well established due to its complex mechanical behaviour. Here, we present a rational analytic model, without any parameter fitting, to study the bending of a multi-layer structure on a cylinder, which is often regarded as an important approach to mechanical reliability testing of flexible electronics and photonics. For the first time, our model quantitatively reveals that, as the key for accurate strain control, the splitting of the neutral mechanical plane depends not only on the relative thickness of the middle layer, but also on the length-to-thickness ratio of the multi-layer structure. The model accurately captures the key quantities, including the axial strains in the top and bottom layers, the shear strain in the middle layer and the locations of the neutral mechanical planes of the top and bottom layers. The effects of the length of the multi-layer and the thickness of the middle layer are elaborated. This work is very useful for the design of multi-layer structure-based flexible electronics and photonics.

Splitting of the neutral mechanical plane depends on the length of the multi-layer structure of flexible electronics

PubMed Central

Li, Shuang; Li, Rui

2016-01-01

Multi-layer structures with soft (compliant) interlayers have been widely used in flexible electronics and photonics as an effective design for reducing interactions among the hard (stiff) layers and thus avoiding the premature failure of an entire device. The analytic model for bending of such a structure has not been well established due to its complex mechanical behaviour. Here, we present a rational analytic model, without any parameter fitting, to study the bending of a multi-layer structure on a cylinder, which is often regarded as an important approach to mechanical reliability testing of flexible electronics and photonics. For the first time, our model quantitatively reveals that, as the key for accurate strain control, the splitting of the neutral mechanical plane depends not only on the relative thickness of the middle layer, but also on the length-to-thickness ratio of the multi-layer structure. The model accurately captures the key quantities, including the axial strains in the top and bottom layers, the shear strain in the middle layer and the locations of the neutral mechanical planes of the top and bottom layers. The effects of the length of the multi-layer and the thickness of the middle layer are elaborated. This work is very useful for the design of multi-layer structure-based flexible electronics and photonics. PMID:27436977

Determination of lattice parameters, strain state and composition in semipolar III-nitrides using high resolution X-ray diffraction

NASA Astrophysics Data System (ADS)

Frentrup, Martin; Hatui, Nirupam; Wernicke, Tim; Stellmach, Joachim; Bhattacharya, Arnab; Kneissl, Michael

2013-12-01

In group-III-nitride heterostructures with semipolar or nonpolar crystal orientation, anisotropic lattice and thermal mismatch with the buffer or substrate lead to a complex distortion of the unit cells, e.g., by shearing of the lattice. This makes an accurate determination of lattice parameters, composition, and strain state under assumption of the hexagonal symmetry impossible. In this work, we present a procedure to accurately determine the lattice constants, strain state, and composition of semipolar heterostructures using high resolution X-ray diffraction. An analysis of the unit cell distortion shows that four independent lattice parameters are sufficient to describe this distortion. Assuming only small deviations from an ideal hexagonal structure, a linear expression for the interplanar distances dhkl is derived. It is used to determine the lattice parameters from high resolution X-ray diffraction 2ϑ-ω-scans of multiple on- and off-axis reflections via a weighted least-square fit. The strain and composition of ternary alloys are then evaluated by transforming the elastic parameters (using Hooke's law) from the natural crystal-fixed coordinate system to a layer-based system, given by the in-plane directions and the growth direction. We illustrate our procedure taking an example of (112¯2) AlκGa1-κN epilayers with Al-contents over the entire composition range. We separately identify the in-plane and out-of-plane strains and discuss origins for the observed anisotropy.

Round-off errors in cutting plane algorithms based on the revised simplex procedure

NASA Technical Reports Server (NTRS)

Moore, J. E.

1973-01-01

This report statistically analyzes computational round-off errors associated with the cutting plane approach to solving linear integer programming problems. Cutting plane methods require that the inverse of a sequence of matrices be computed. The problem basically reduces to one of minimizing round-off errors in the sequence of inverses. Two procedures for minimizing this problem are presented, and their influence on error accumulation is statistically analyzed. One procedure employs a very small tolerance factor to round computed values to zero. The other procedure is a numerical analysis technique for reinverting or improving the approximate inverse of a matrix. The results indicated that round-off accumulation can be effectively minimized by employing a tolerance factor which reflects the number of significant digits carried for each calculation and by applying the reinversion procedure once to each computed inverse. If 18 significant digits plus an exponent are carried for each variable during computations, then a tolerance value of 0.1 x 10 to the minus 12th power is reasonable.

Analysis of heterogeneities in strain and microstructure in aluminum alloy and magnesium processed by high-pressure torsion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panda, Subrata, E-mail: subrata.panda@univ-lorrain

2017-01-15

Two distinct bulk light metals were opted to study the shear strain evolution and associated heterogeneities in texture/microstructure development during torsional straining by high pressure torsion (HPT): a face centered cubic Al alloy (A5086) and a hexagonal commercial purity Mg. Relatively thick disk samples - four times thicker than usually employed in HPT process - were processed to 180° and 270° rotations. With the help of X-ray tomography, the shear strain gradients were examined in the axial direction. The results showed strongly localized shear deformation in the middle plane of the disks in both materials. These gradients involved strong heterogeneitiesmore » in texture, microstructure and associated hardness, in particular through the thickness direction at the periphery of the disk where the interplay between significant strain hardening and possible dynamic recrystallization could occur. - Highlights: •HPT processing was conducted on bulk specimens thicker than the usual thin-disks. •The Al alloy (A5086) and commercial purity magnesium samples were compared. •Distributions of strain and microhardness were evaluated in the radial and axial direction. •Plastic deformation is highly localized in the middle plane at outer edge in both materials. •Different DRX rates governed the differences in microstructure and hardening behavior.« less

Effects of strain on ferroelectric polarization and magnetism in orthorhombic HoMnO3

NASA Astrophysics Data System (ADS)

Iuşan, Diana; Yamauchi, Kunihiko; Barone, Paolo; Sanyal, Biplab; Eriksson, Olle; Profeta, Gianni; Picozzi, Silvia

2013-01-01

We explore how the ferroelectric polarization of antiferromagnetic E-type orthorhombic HoMnO3 can be increased, by investigating the effects of in-plane strain on both the magnetic properties and the ferroelectric polarization, using combined density functional theory calculations and a model Hamiltonian technique. Our results show that the net polarization is strongly enhanced under compressive strain, due to an increase of the elec-tronic contribution to the polarization. In contrast, the ionic contribution is found to decrease. We identify the electron-lattice coupling, due to Jahn-Teller (JT) distortions, and its response to strain, to be responsible for the observed behavior. The JT-induced orbital ordering of occupied Mn-eg1 electrons in alternating 3x2-r23y2-r2 orbital states in the unstrained structure, changes under in-plane compressive strain to a mixture with x2-z2y2-z2 states. The asymmetric hopping of eg electrons between Mn ions along zigzag spin chains (typical of the AFM-E spin configuration) is therefore enhanced under strain, explaining the large value of the polarization. Using a degenerate double-exchange model including electron-phonon interaction, we reproduce the change in the orbital ordering pattern. In this picture, the orbital ordering change is related to a change of the Berry phase of the eg electrons. This causes an increase of the electronic contribution to the polarization.

"A Tale of Two Planes": Deep Versus Superficial Serratus Plane Block for Postmastectomy Pain Syndrome.

PubMed

Piracha, Mohammad M; Thorp, Stephen L; Puttanniah, Vinay; Gulati, Amitabh

Postmastectomy pain syndrome (PMPS) is a significant burden for breast cancer survivors. Although multiple therapies have been described, an evolving field of serratus anterior plane blocks has been described in this population. We describe the addition of the deep serratus anterior plane block (DSPB) for PMPS. Four patients with history of PMPS underwent DSPB for anterior chest wall pain. A retrospective review of these patients' outcomes was obtained through postprocedure interviews. Three of the patients previously had a superficial serratus anterior plane block, which was not as efficacious as the DSPB. The fourth patient had a superficial serratus anterior plane that was difficult to separate with hydrodissection but had improved pain control with a DSPB. We illustrate 4 patients who have benefitted from a DSPB and describe indications that this block may be more efficacious than a superficial serratus plane block. Further study is recommended to understand the intercostal nerve branches within the lateral and anterior muscular chest wall planes.

Optically Active Plasmonic Metasurfaces based on the Hybridization of In-Plane Coupling and Out-of-Plane Coupling.

PubMed

Wu, Dong; Yang, Liu; Liu, Chang; Xu, Zenghui; Liu, Yumin; Yu, Zhongyuan; Yu, Li; Chen, Lei; Ma, Rui; Ye, Han

2018-05-10

Plasmonic metasurfaces have attracted much attention in recent years owing to many promising prospects of applications such as polarization switching, local electric field enhancement (FE), near-perfect absorption, sensing, slow-light devices, and nanoantennas. However, many problems in these applications, like only gigahertz switching speeds of electro-optical switches, low-quality factor (Q) of plasmonic resonances, and relatively low figure of merit (FOM) of sensing, severely limit the further development of plasmonic metasurface. Besides, working as nanoantennas, it is also challenging to realize both local electric FE exceeding 100 and near-perfect absorption above 99%. Here, using finite element method and finite difference time domain methods respectively, we firstly report a novel optically tunable plasmonic metasurface based on the hybridization of in-plane near-field coupling and out-of-plane near-field coupling, which provides a good solution to these serious and urgent problems. A physical phenomenon of electromagnetically induced transparency is obtained by the destructive interference between two plasmon modes. At the same time, ultrasharp perfect absorption peaks with ultra-high Q-factor (221.43) is achieved around 1550 nm, which can lead to an ultra-high FOM (214.29) in sensing application. Particularly, by using indium-doped CdO, this metasurface is also firstly demonstrated to be a femtosecond optical reflective polarizer in near-infrared region, possessing an ultra-high polarization extinction ratio. Meanwhile, operating as nanoantennas, this metasurface achieves simultaneously strong local electric FE(|E loc |/|E 0 | > 100) and a near-perfect absorption above 99.9% for the first time, which will benefit a wide range of applications including photocatalytic water splitting and surface-enhanced infrared absorption.

Optically Active Plasmonic Metasurfaces based on the Hybridization of In-Plane Coupling and Out-of-Plane Coupling

NASA Astrophysics Data System (ADS)

Wu, Dong; Yang, Liu; Liu, Chang; Xu, Zenghui; Liu, Yumin; Yu, Zhongyuan; Yu, Li; Chen, Lei; Ma, Rui; Ye, Han

2018-05-01

Plasmonic metasurfaces have attracted much attention in recent years owing to many promising prospects of applications such as polarization switching, local electric field enhancement (FE), near-perfect absorption, sensing, slow-light devices, and nanoantennas. However, many problems in these applications, like only gigahertz switching speeds of electro-optical switches, low-quality factor (Q) of plasmonic resonances, and relatively low figure of merit (FOM) of sensing, severely limit the further development of plasmonic metasurface. Besides, working as nanoantennas, it is also challenging to realize both local electric FE exceeding 100 and near-perfect absorption above 99%. Here, using finite element method and finite difference time domain methods respectively, we firstly report a novel optically tunable plasmonic metasurface based on the hybridization of in-plane near-field coupling and out-of-plane near-field coupling, which provides a good solution to these serious and urgent problems. A physical phenomenon of electromagnetically induced transparency is obtained by the destructive interference between two plasmon modes. At the same time, ultrasharp perfect absorption peaks with ultra-high Q-factor (221.43) is achieved around 1550 nm, which can lead to an ultra-high FOM (214.29) in sensing application. Particularly, by using indium-doped CdO, this metasurface is also firstly demonstrated to be a femtosecond optical reflective polarizer in near-infrared region, possessing an ultra-high polarization extinction ratio. Meanwhile, operating as nanoantennas, this metasurface achieves simultaneously strong local electric FE(| E loc|/| E 0| > 100) and a near-perfect absorption above 99.9% for the first time, which will benefit a wide range of applications including photocatalytic water splitting and surface-enhanced infrared absorption.

User's guide for analysis of finite elastoplastic deformation: The FIPDEF and FIPAX programs for the CDC 6600

NASA Technical Reports Server (NTRS)

Osias, J. R.

1974-01-01

Computer programs are presented which provide incremental finite-element analysis capability for problems of quasi-static, finite, elastoplastic deformation in two spatial dimensions (plane strain, plane stress, axisymmetric). Monotonic or cyclic loading of isotropic hardening materials is considered. The only restriction on the form of the stress-strain curve is that the rate of work hardening exceed some small positive value. The user's guide assumes familiarity with both finite-element analysis and FORTRAN IV programming for the CDC 6600. Sufficient information is provided to support problem solving ultization of the programs.

Tensile strain effect in ferroelectric perovskite oxide thin films on spinel magnesium aluminum oxide substrate

NASA Astrophysics Data System (ADS)

Zhou, Xiaolan

Ferroelectrics are used in FeRAM (Ferroelectric random-access memory). Currently (Pb,Zr)TiO3 is the most common ferroelectric material. To get lead-free and high performance ferroelectric material, we investigated perovskite ferroelectric oxides (Ba,Sr)TiO3 and BiFeO3 films with strain. Compressive strain has been investigated intensively, but the effects of tensile strain on the perovskite films have yet to be explored. We have deposited (Ba,Sr)TiO3, BiFeO3 and related films by pulsed laser deposition (PLD) and analyzed the films by X-ray diffractometry (XRD), atomic force microscopy (AFM), etc. To obtain inherently fully strained films, the selection of the appropriate substrates is crucial. MgAl2O4 matches best with good quality and size, yet the spinel structure has an intrinsic incompatibility to that of perovskite. We introduced a rock-salt structure material (Ni 1-xAlxO1+delta) as a buffer layer to mediate the structural mismatch for (Ba,Sr)TiO3 films. With buffer layer Ni1-xAlxO1+delta, we show that the BST films have high quality crystallization and are coherently epitaxial. AFM images show that the films have smoother surfaces when including the buffer layer, indicating an inherent compatibility between BST-NAO and NAO-MAO. In-plane Ferroelectricity measurement shows double hysteresis loops, indicating an antiferroelectric-like behavior: pinned ferroelectric domains with antiparallel alignments of polarization. The Curie temperatures of the coherent fully strained BST films are also measured. It is higher than 900°C, at least 800°C higher than that of bulk. The improved Curie temperature makes the use of BST as FeRAM feasible. We found that the special behaviors of ferroelectricity including hysteresis loop and Curie temperature are due to inherent fully tensile strain. This might be a clue of physics inside ferroelectric stain engineering. An out-of-plane ferroelectricity measurement would provide a full whole story of the tensile strain. However, a

Strain accumulation and rotation in the Eastern California Shear Zone

USGS Publications Warehouse

Savage, J.C.; Gan, Weijun; Svarc, J.L.

2001-01-01

Although the Eastern California Shear Zone (ECSZ) (strike ???N25??W) does not quite coincide with a small circle drawn about the Pacific-North America pole of rotation, trilateration and GPS measurements demonstrate that the motion within the zone corresponds to right-lateral simple shear across a vertical plane (strike N33??W??5??) roughly parallel to the tangent to that local small circle (strike ???N40??W). If the simple shear is released by slip on faults subparallel to the shear zone, the accumulated rotation is also released, leaving no secular rotation. South of the Garlock fault the principal faults (e.g., Calico-Blackwater fault) strike ???N40??W, close enough to the strike of the vertical plane across which maximum right-lateral shear accumulates to almost wholly accommodate that accumulation of both strain and rotation by right-lateral slip. North of the Garlock fault dip slip as well as strike slip on the principal faults (strike ???N20??W) is required to accommodate the simple shear accumulation. In both cases the accumulated rotation is released with the shear strain. The Garlock fault, which transects the ECSZ, is not offset by north-northwest striking faults nor, despite geological evidence for long-term left-lateral slip, does it appear at the present time to be accumulating left-lateral simple shear strain across the fault due to slip at depth. Rather the motion is explained by right-lateral simple shear across the orthogonal ECSZ. Left-lateral slip on the Garlock fault will release the shear strain accumulating there but would augment the accumulating rotation, resulting in a secular clockwise rotation rate ???80 nrad yr-1 (4.6?? Myr-1).

Systematic study of Reynolds stress closure models in the computations of plane channel flows

NASA Technical Reports Server (NTRS)

Demuren, A. O.; Sarkar, S.

1992-01-01

The roles of pressure-strain and turbulent diffusion models in the numerical calculation of turbulent plane channel flows with second-moment closure models are investigated. Three turbulent diffusion and five pressure-strain models are utilized in the computations. The main characteristics of the mean flow and the turbulent fields are compared against experimental data. All the features of the mean flow are correctly predicted by all but one of the Reynolds stress closure models. The Reynolds stress anisotropies in the log layer are predicted to varying degrees of accuracy (good to fair) by the models. None of the models could predict correctly the extent of relaxation towards isotropy in the wake region near the center of the channel. Results from the directional numerical simulation are used to further clarify this behavior of the models.

Electronic and phononic modulation of MoS2 under biaxial strain

NASA Astrophysics Data System (ADS)

Moghadasi, A.; Roknabadi, M. R.; Ghorbani, S. R.; Modarresi, M.

2017-12-01

Dichalcogenides of transition metals are attractive material due to its unique properties. In this work, it has been investigated the electronic band structure, phonon spectrum and heat capacity of MoS2 under the applied tensile and compressive biaxial strain using the density functional theory. The Molybdenum disulfide under compressive (tensile) strain up to 6% (10%) has stable atomic structure without any negative frequency in the phonon dispersion curves. The tensile biaxial strain reduces the energy gap in the electronic band structure and the optical-acoustic gap in phonon dispersion curves. The tensile biaxial strain also increases the specific heat capacity. On the other hand, the compressive biaxial strain in this material increases phonon gap and reduces the heat capacity and the electronic band gap. The phonon softening/hardening is reported for tensile/compressive biaxial strain in MoS2. We report phonon hardening for out of plane ZA mode in the presence of both tensile and compressive strains. Results show that the linear variation of specific heat with strain (CV ∝ε) and square dependency of specific heat with the temperature (CV ∝T2) for low temperature regime. The results demonstrate that the applied biaxial strain tunes the electronic energy gap and modifies the phonon spectrum of MoS2.

Lattice strain measurements on sandstones under load using neutron diffraction

NASA Astrophysics Data System (ADS)

Frischbutter, A.; Neov, D.; Scheffzük, Ch.; Vrána, M.; Walther, K.

2000-11-01

Neutron diffraction methods (both time-of-flight- and angle-dispersive diffraction) are applied to intracrystalline strain measurements on geological samples undergoing uniaxial increasing compressional load. The experiments were carried out on Cretaceous sandstones from the Elbezone (East Germany), consisting of >95% quartz which are bedded but without crystallographic preferred orientation of quartz. From the stress-strain relation the Young's modulus for our quartz sample was determined to be (72.2±2.9) GPa using results of the neutron time-of-flight method. The influence of different kinds of bedding in sandstones (laminated and convolute bedding) could be determined. We observed differences of factor 2 (convolute bedding) and 3 (laminated bedding) for the elastic stiffness, determined with angle dispersive neutron diffraction (crystallographic strain) and with strain gauges (mechanical strain). The data indicate which geological conditions may influence the stress-strain behaviour of geological materials. The influence of bedding on the stress-strain behaviour of a laminated bedded sandstone was indicated by direct residual stress measurements using neutron time-of-flight diffraction. The measurements were carried out six days after unloading the sample. Residual strain was measured for three positions from the centre to the periphery and within two radial directions of the cylinder. We observed that residual strain changes from extension to compression in a different manner for two perpendicular directions of the bedding plane.

On the estimation of thermal strains developed during oxide growth

NASA Astrophysics Data System (ADS)

Sabau, Adrian S.; Wright, Ian G.

2009-07-01

This paper presents results for the strains and stresses in oxide scales under the conditions of temperature and pressure expected in typical steam boiler operation. These conditions are radically different from those typically encountered in laboratory testing and include features such as a thermal gradient across the tube wall, significant internal (steam) pressure, and cycling of both steam temperature and pressure. Critical examination of the assumptions of flat-plate geometry, which is usually made in calculating stresses and strains in oxide scales, indicated that only the component of the hoop strain that generates stress must be reported for the cylindrical case, and that the use of simple plane-strain is adequate for the system studied. Calculations were made for alloy T22 with a hypothetical, single-layered oxide with appropriate properties. Typical conditions associated with transition of the boiler from full to partial load involve a decrease in both steam temperature and pressure, and these two sources of stress generation were found to exert opposite effects. The relative magnitudes of the resulting strains were used to explain the trends in strain levels calculated when the effects of thermal expansion, temperature loading, and pressure loading were superimposed.

The emergence of the Activity Reduces Conflict Associated Strain (ARCAS) model: a test of a conditional mediation model of workplace conflict and employee strain.

PubMed

Dijkstra, Maria T M; Beersma, Bianca; Cornelissen, Roosmarijn A W M

2012-07-01

To test and extend the emerging Activity Reduces Conflict-Associated Strain (ARCAS) model, we predicted that the relationship between task conflict and employee strain would be weakened to the extent that people experience high organization-based self-esteem (OBSE). A survey among Dutch employees demonstrated that, consistent with the model, the conflict-employee strain relationship was weaker the higher employees' OBSE and the more they engaged in active problem-solving conflict management. Our data also revealed that higher levels of OBSE were related to more problem-solving conflict management. Moreover, consistent with the ARCAS model, we could confirm a conditional mediation model in which organization-based self-esteem through its relationship with problem-solving conflict management weakened the relationship between task conflict and employee strain. Potential applications of the results are discussed.

Separating strain from composition in unit cell parameter maps obtained from aberration corrected high resolution transmission electron microscopy imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulz, T.; Remmele, T.; Korytov, M.

2014-01-21

Based on the evaluation of lattice parameter maps in aberration corrected high resolution transmission electron microscopy images, we propose a simple method that allows quantifying the composition and disorder of a semiconductor alloy at the unit cell scale with high accuracy. This is realized by considering, next to the out-of-plane, also the in-plane lattice parameter component allowing to separate the chemical composition from the strain field. Considering only the out-of-plane lattice parameter component not only yields large deviations from the true local alloy content but also carries the risk of identifying false ordering phenomena like formations of chains or platelets.more » Our method is demonstrated on image simulations of relaxed supercells, as well as on experimental images of an In{sub 0.20}Ga{sub 0.80}N quantum well. Principally, our approach is applicable to all epitaxially strained compounds in the form of quantum wells, free standing islands, quantum dots, or wires.« less

Mechanical control of the electro-optical properties of monolayer and bilayer BC3 by applying the in-plane biaxial strain

NASA Astrophysics Data System (ADS)

Behzad, Somayeh

2017-11-01

Recently, a new two-dimensional (2D) material, the 2D BC3 crystal, has been synthesized. Here, the mechanical control of the electro-optical properties of monolayer and bilayer BC3 by applying the biaxial strain is investigated. The electronic structure calculations showed that the strain-free monolayer and bilayer BC3 are indirect band-gap semiconductors with band gap of 0.62 and 0.29 eV, respectively, where the conduction band minimum (CBM) is at the M point whereas the valence band maximum (VBM) is at the Γ point. The doubly degenerated bands in the monolayer BC3 are splitted in the bilayer BC3 due to the interlayer interactions. Both monolayer and bilayer BC3 remain indirect gap semiconductor under biaxial tensile strain and their band gaps increases with strain. On the other hand, by increasing the magnitude of tensile strain, the optical spectra shift to the lower energies and the static dielectric constant increases. These findings suggest the potential of strain-engineered 2D BC3 in electronic and optoelectronic device applications.

In-plane optical anisotropy of InAs/GaSb superlattices with alternate interfaces

PubMed Central

2013-01-01

The in-plane optical anisotropy (IPOA) in InAs/GaSb superlattices has been studied by reflectance difference spectroscopy (RDS) at different temperatures ranging from 80 to 300 K. We introduce alternate GaAs- and InSb-like interfaces (IFs), which cause the symmetry reduced from D2d to C2v. IPOA has been observed in the (001) plane along [110] and [11¯0] axes. RDS measurement results show strong anisotropy resonance near critical point (CP) energies of InAs and GaSb. The energy positions show red shift and RDS intensity decreases with the increasing temperature. For the superlattice sample with the thicker InSb-like IFs, energy positions show red shift, and the spectra exhibit stronger IPOA. The excitonic effect is clearly observed by RDS at low temperatures. It demonstrates that biaxial strain results in the shift of the CP energies and IPOA is enhanced by the further localization of the carriers in InSb-like IFs. PMID:23799946

Confinement- and strain-induced enhancement of thermoelectric properties in LaNiO3/LaAlO3(001 ) superlattices

NASA Astrophysics Data System (ADS)

Geisler, Benjamin; Pentcheva, Rossitza

2018-05-01

By combining ab initio simulations including an on-site Coulomb repulsion term and Boltzmann theory, we explore the thermoelectric properties of (LaNiO3)n /(LaAlO3)n (001) superlattices (n =1 ,3 ) and identify a strong dependence on confinement, spacer thickness, and epitaxial strain. While the system with n =3 shows modest values of the Seebeck coefficient and power factor, the simultaneous reduction of the LaNiO3 region and the LaAlO3 spacer thickness to single layers results in a strong enhancement, in particular of the in-plane values. This effect can be further tuned by using epitaxial strain as a control parameter: Under tensile strain corresponding to the lateral lattice constant of SrTiO3 we predict in- and cross-plane Seebeck coefficients of ±600 μ V /K and an in-plane power factor of 11 μ W /K2cm for an estimated relaxation time of τ =4 fs around room temperature. These values are comparable to some of the best performing oxide systems such as La-doped SrTiO3 or layered cobaltates and are associated with the opening of a small gap (0.29 eV) induced by the concomitant effect of octahedral tilting and Ni-site disproportionation. This establishes oxide superlattices at the verge of a metal-to-insulator transition driven by confinement and strain as promising candidates for thermoelectric materials.

Strain System for the Motion Base Shuttle Mission Simulator

NASA Technical Reports Server (NTRS)

Huber, David C.; Van Vossen, Karl G.; Kunkel, Glenn W.; Wells, Larry W.

2010-01-01

The Motion Base Shuttle Mission Simulator (MBSMS) Strain System is an innovative engineering tool used to monitor the stresses applied to the MBSMS motion platform tilt pivot frames during motion simulations in real time. The Strain System comprises hardware and software produced by several different companies. The system utilizes a series of strain gages, accelerometers, orientation sensor, rotational meter, scanners, computer, and software packages working in unison. By monitoring and recording the inputs applied to the simulator, data can be analyzed if weld cracks or other problems are found during routine simulator inspections. This will help engineers diagnose problems as well as aid in repair solutions for both current as well as potential problems.

Misfit strain relaxation in (Ba0.60Sr0.40)TiO3 epitaxial thin films on orthorhombic NdGaO3 substrates

NASA Astrophysics Data System (ADS)

Simon, W. K.; Akdogan, E. K.; Safari, A.

2006-07-01

Strain relaxation in (Ba0.60Sr0.40)TiO3 (BST) thin films on ⟨110⟩ orthorhombic NdGaO3 substrates is investigated by x-ray diffractometry. Pole figure analysis indicates a [010]BST∥[1¯10]NGO and [001]BST∥[001]NGO in-plane and [100]BST∥[100]NGO out-of-plane epitaxial relationship. The residual strains are relaxed at h ˜200nm, and for h >600nm, films are essentially strain free. Two independent dislocations mechanisms operate to relieve the anisotropic misfit strains along the principal directions. The critical thickness for misfit dislocation formation along [001] and [010] are 11 and 15nm, respectively. Stress analysis indicates deviation from linear elasticity for h <200. The films with 10

Thermal conductivity of graphene mediated by strain and size

DOE PAGES

Kuang, Youdi; Shi, Sanqiang; Wang, Xinjiang; ...

2016-06-09

Based on first-principles calculations and full iterative solution of the linearized Boltzmann–Peierls transport equation for phonons, we systematically investigate effects of strain, size and temperature on the thermal conductivity k of suspended graphene. The calculated size-dependent and temperature-dependent k for finite samples agree well with experimental data. The results show that, contrast to the convergent room-temperature k = 5450 W/m-K of unstrained graphene at a sample size ~8 cm, k of strained graphene diverges with increasing the sample size even at high temperature. Out-of-plane acoustic phonons are responsible for the significant size effect in unstrained and strained graphene due tomore » their ultralong mean free path and acoustic phonons with wavelength smaller than 10 nm contribute 80% to the intrinsic room temperature k of unstrained graphene. Tensile strain hardens the flexural modes and increases their lifetimes, causing interesting dependence of k on sample size and strain due to the competition between boundary scattering and intrinsic phonon–phonon scattering. k of graphene can be tuned within a large range by strain for the size larger than 500 μm. These findings shed light on the nature of thermal transport in two-dimensional materials and may guide predicting and engineering k of graphene by varying strain and size.« less

Super-stretchable metallic interconnects on polymer with a linear strain of up to 100%

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arafat, Yeasir; Dutta, Indranath; Panat, Rahul, E-mail: Rahul.panat@wsu.edu

Metal interconnects in flexible and wearable devices are heterogeneous metal-polymer systems that are expected to sustain large deformation without failure. The principal strategy to make strain tolerant interconnect lines on flexible substrates has comprised of creating serpentine structures of metal films with either in-plane or out-of-plane waves, using porous substrates, or using highly ductile materials such as gold. The wavy and helical serpentine patterns preclude high-density packing of interconnect lines on devices, while ductile materials such as Au are cost prohibitive for real world applications. Ductile copper films can be stretched if bonded to the substrate, but show high levelmore » of cracking beyond few tens of % strain. In this paper, we demonstrate a material system consisting of Indium metal film over an elastomer (PDMS) with a discontinuous Cr layer such that the metal interconnect can be stretched to extremely high linear strain (up to 100%) without any visible cracks. Such linear strain in metal interconnects exceeds that reported in literature and is obtained without the use of any geometrical manipulations or porous substrates. Systematic experimentation is carried out to explain the mechanisms that allow the Indium film to sustain the high strain level without failure. The islands forming the discontinuous Cr layer are shown to move apart from each other during stretching without delamination, providing strong adhesion to the Indium film while accommodating the large strain in the system. The Indium film is shown to form surface wrinkles upon release from the large strain, confirming its strong adhesion to PDMS. A model is proposed based upon the observations that can explain the high level of stretch-ability of the Indium metal film over the PDMS substrate.« less

Cardiac biplane strain imaging: initial in vivo experience

NASA Astrophysics Data System (ADS)

Lopata, R. G. P.; Nillesen, M. M.; Verrijp, C. N.; Singh, S. K.; Lammens, M. M. Y.; van der Laak, J. A. W. M.; van Wetten, H. B.; Thijssen, J. M.; Kapusta, L.; de Korte, C. L.

2010-02-01

In this study, first we propose a biplane strain imaging method using a commercial ultrasound system, yielding estimation of the strain in three orthogonal directions. Secondly, an animal model of a child's heart was introduced that is suitable to simulate congenital heart disease and was used to test the method in vivo. The proposed approach can serve as a framework to monitor the development of cardiac hypertrophy and fibrosis. A 2D strain estimation technique using radio frequency (RF) ultrasound data was applied. Biplane image acquisition was performed at a relatively low frame rate (<100 Hz) using a commercial platform with an RF interface. For testing the method in vivo, biplane image sequences of the heart were recorded during the cardiac cycle in four dogs with an aortic stenosis. Initial results reveal the feasibility of measuring large radial, circumferential and longitudinal cumulative strain (up to 70%) at a frame rate of 100 Hz. Mean radial strain curves of a manually segmented region-of-interest in the infero-lateral wall show excellent correlation between the measured strain curves acquired in two perpendicular planes. Furthermore, the results show the feasibility and reproducibility of assessing radial, circumferential and longitudinal strains simultaneously. In this preliminary study, three beagles developed an elevated pressure gradient over the aortic valve (Δp: 100-200 mmHg) and myocardial hypertrophy. One dog did not develop any sign of hypertrophy (Δp = 20 mmHg). Initial strain (rate) results showed that the maximum strain (rate) decreased with increasing valvular stenosis (-50%), which is in accordance with previous studies. Histological findings corroborated these results and showed an increase in fibrotic tissue for the hearts with larger pressure gradients (100, 200 mmHg), as well as lower strain and strain rate values.

Theoretical study on strain induced variations in electronic properties of 2H-MoS{sub 2} bilayer sheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Liang; Dongare, Avinash M., E-mail: dongare@uconn.edu; Namburu, Raju R.

2014-02-03

The strain dependence of the electronic properties of bilayer sheets of 2H-MoS{sub 2} is studied using ab initio simulations based on density functional theory. An indirect band gap for bilayer MoS{sub 2} is observed for all variations of strain along the basal plane. Several transitions for the indirect band gap are observed for various strains for the bilayer structure. The variation of the band gap and the carrier effective masses for the holes and the electrons for the bilayer MoS{sub 2} structure under conditions of uniaxial strain, biaxial strain, as well as uniaxial stress is investigated.

A New Selective Area Lateral Epitaxy Approach for Depositing a-Plane GaN over r-Plane Sapphire

NASA Astrophysics Data System (ADS)

Chen, Changqing; Zhang, Jianping; Yang, Jinwei; Adivarahan, Vinod; Rai, Shiva; Wu, Shuai; Wang, Hongmei; Sun, Wenhong; Su, Ming; Gong, Zheng; Kuokstis, Edmundas; Gaevski, Mikhail; Khan, Muhammad Asif

2003-07-01

We report a new epitaxy procedure for growing extremely low defect density a-plane GaN films over r-plane sapphire. By combining selective area growth through a SiO2 mask opening to produce high height to width aspect ratio a-plane GaN pillars and lateral epitaxy from their c-plane facets, we obtained fully coalesced a-plane GaN films. The excellent structural, optical and electrical characteristics of these selective area lateral epitaxy (SALE) deposited films make them ideal for high efficiency III-N electronic and optoelectronic devices.

Comparative study on hydrostatic strain, stress and dislocation density of Al{sub 0.3}Ga{sub 0.7}N/GaN heterostructure before and after a-Si{sub 3}N{sub 4} passivation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dinara, Syed Mukulika, E-mail: smdinara.iit@gmail.com; Jana, Sanjay Kr.; Mukhopadhyay, Partha

2015-08-28

The hydrostatic strain, stress and dislocation densities were comparatively analyzed before and after passivation of amorphous silicon nitride (a-Si{sub 3}N{sub 4}) layer on Al{sub 0.3}Ga{sub 0.7}N/GaN heterostructure by nondestructive high resolution x-ray diffraction (HRXRD) technique. The crystalline quality, in-plane and out-of plane strain were evaluated from triple-axis (TA) (ω-2θ) diffraction profile across the (002) reflection plane and double-axis (DA) (ω-2θ) glancing incidence (GI) diffraction profile across (105) reflection plane. The hydrostatic strain and stress of Al{sub 0.3}Ga{sub 0.7}N barrier layer were increased significantly after passivation and both are tensile in nature. The dislocation density of GaN was also analyzed andmore » no significant change was observed after passivation of the heterostructure. The crystalline quality was not degraded after passivation on the heterostructure confirmed by the full-width-half-maximum (FWHM) analysis.« less

Electrical tuning of microwave properties via strain-mediated magnetoelectric coupling in multiferroic composites

NASA Astrophysics Data System (ADS)

Phuoc, Nguyen N.; Ong, C. K.

2018-02-01

Electrical field induced electromagnetic properties via strain-mediated magnetoelectric effect were studied in FeCoNi/[Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32 (PMN-PT) multiferroic heterostructures. Both the resonance frequency f FMR and the frequency linewidth Δ f are electrically tunable with f FMR being varied from 3.8 to 8.1 GHz and Δ f from 0.66 to 3.6 GHz. The static magnetic characterization result of the sample before and after poling is also in good agreement with the dynamic magnetic measurement. These results were discussed in details within the framework of the strain-mediated magnetoelectric coupling, which was firmly supported by the electrical field dependence of the in-plane strain measured by a strain gauge.

Point-to-plane and plane-to-plane electrostatic charge injection atomization for insulating liquids

NASA Astrophysics Data System (ADS)

Malkawi, Ghazi

An electrostatic charge injection atomizer was fabricated and used to introduce and study the electrostatic charge injection atomization methods for highly viscous vegetable oils and high conductivity low viscosity aviation fuel, JP8. The total, spray and leakage currents and spray breakup characteristics for these liquids were investigated and compared with Diesel fuel data. Jet breakup and spray atomization mechanism showed differences for vegetable oils and lower viscosity hydrocarbon fuels. For vegetable oils, a bending/spinning instability phenomenon was observed similar to the phenomenon found in liquid jets of high viscosity polymer solutions. The spray tip lengths and cone angles were presented qualitatively and quantitatively and correlated with the appropriate empirical formulas. The different stages of the breakup mechanisms for such oils, as a function of specific charges and flow rates, were discussed. In order to make this method of atomization more suitable for practical use in high flow rate applications, a blunt face electrode (plane-to-plane) was used as the charge emitter in place of a single pointed electrode (point-to-plane). This allowed the use of a multi-orifice emitter that maintained a specific charge with the flow rate increase which could not be achieved with the needle electrode. The effect of the nozzle geometry, liquid physical properties and applied bulk flow on the spray charge, total charge, maximum critical spray specific charge and electrical efficiency compared with the needle point-to-plane atomizer results was presented. Our investigation revealed that the electrical efficiency of the atomizer is dominated by the charge forced convection rate rather than charge transport by ion motilities and liquid motion by the electric field. As a result of the electric coulomb forces between the electrified jets, the multi-orifice atomizer provided a unique means of dispersing the fuel in a hollow cone with wide angles making the new

Effect of misfit strains on fourth and sixth order permittivity in (Ba0.60,Sr0.40)TiO3 films on orthorhombic substrates

NASA Astrophysics Data System (ADS)

Simon, W. K.; Akdogan, E. K.; Safari, A.; Bellotti, J.

2006-03-01

The in-plane dielectric response of [110] oriented Ba0.60Sr0.40TiO3 epitaxial films grown on [100] NdGaO3 is used to determine the field induced polarization at 10GHz. The nonlinear polarization curve is used to determine the linear and nonlinear permittivity terms for the in-plane principal directions, [001] and [1¯10]. Studied films are in the thickness range of 75-1200nm, and clearly show the influences that drive tunability down with increasing residual strain. The variation of the tunability, along the [001] direction, proves to be less sensitive to residual strain then the [1¯10] direction, although [1¯10] is capable of greater tunability at low residual strains.

Strain-compensated infrared photodetector and photodetector array

DOEpatents

Kim, Jin K; Hawkins, Samuel D; Klem, John F; Cich, Michael J

2013-05-28

A photodetector is disclosed for the detection of infrared light with a long cutoff wavelength in the range of about 4.5-10 microns. The photodetector, which can be formed on a semiconductor substrate as an nBn device, has a light absorbing region which includes InAsSb light-absorbing layers and tensile-strained layers interspersed between the InAsSb light-absorbing layers. The tensile-strained layers can be formed from GaAs, InAs, InGaAs or a combination of these III-V compound semiconductor materials. A barrier layer in the photodetector can be formed from AlAsSb or AlGaAsSb; and a contact layer in the photodetector can be formed from InAs, GaSb or InAsSb. The photodetector is useful as an individual device, or to form a focal plane array.

Multiaxial Fatigue Life Prediction Based on Short Crack Propagation Model with Equivalent Strain Parameter

NASA Astrophysics Data System (ADS)

Zhao, Xiang-Feng; Shang, De-Guang; Sun, Yu-Juan; Song, Ming-Liang; Wang, Xiao-Wei

2018-01-01

The maximum shear strain and the normal strain excursion on the critical plane are regarded as the primary parameters of the crack driving force to establish a new short crack model in this paper. An equivalent strain-based intensity factor is proposed to correlate the short crack growth rate under multiaxial loading. According to the short crack model, a new method is proposed for multiaxial fatigue life prediction based on crack growth analysis. It is demonstrated that the method can be used under proportional and non-proportional loadings. The predicted results showed a good agreement with experimental lives in both high-cycle and low-cycle regions.

Excitation of plane Lamb wave in plate-like structures under applied surface loading

NASA Astrophysics Data System (ADS)

Zhou, Kai; Xu, Xinsheng; Zhao, Zhen; Yang, Zhengyan; Zhou, Zhenhuan; Wu, Zhanjun

2018-02-01

Lamb waves play an important role in structure health monitoring (SHM) systems. The excitation of Lamb waves has been discussed for a long time with absorbing results. However, little effort has been made towards the precise characterization of Lamb wave excitation by various transducer models with mathematical foundation. In this paper, the excitation of plane Lamb waves with plane strain assumption in isotropic plate structures under applied surface loading is solved with the Hamiltonian system. The response of the Lamb modes excited by applied loading is expressed analytically. The effect of applied loading is divided into the product of two parts as the effect of direction and the effect of distribution, which can be changed by selecting different types of transducer and the corresponding transducer configurations. The direction of loading determines the corresponding displacement of each mode. The effect of applied loading on the in-plane and normal directions depends on the in-plane and normal displacements at the surface respectively. The effect of the surface loading distribution on the Lamb mode amplitudes is mainly reflected by amplitude versus frequency or wavenumber. The frequencies at which the maxima and minima of the S0 or A0 mode response occur depend on the distribution of surface loading. The numerical results of simulations conducted on an infinite aluminum plate verify the theoretical prediction of not only the direction but also the distribution of applied loading. A pure S0 or A0 mode can be excited by selecting the appropriate direction and distribution at the corresponding frequency.

High-Resolution Strain Analysis of the Human Heart with Fast-DENSE

NASA Astrophysics Data System (ADS)

Aletras, Anthony H.; Balaban, Robert S.; Wen, Han

1999-09-01

Single breath-hold displacement data from the human heart were acquired with fast-DENSE (fast displacement encoding with stimulated echoes) during systolic contraction at 2.5 × 2.5 mm in-plane resolution. Encoding strengths of 0.86-1.60 mm/π were utilized in order to extend the dynamic range of the phase measurements and minimize effects of physiologic and instrument noise. The noise level in strain measurements for both contraction and dilation corresponded to a strain value of 2.8%. In the human heart, strain analysis has sufficient resolution to reveal transmural variation across the left ventricular wall. Data processing required minimal user intervention and provided a rapid quantitative feedback. The intrinsic temporal integration of fast-DENSE achieves high accuracy at the expense of temporal resolution.

Tidal Friction in the Earth-Moon System and Laplace Planes: Darwin Redux

NASA Technical Reports Server (NTRS)

Rubincam, David P.

2015-01-01

The dynamical evolution of the Earth-Moon system due to tidal friction is treated here. George H. Darwin used Laplace planes (also called proper planes) in his study of tidal evolution. The Laplace plane approach is adapted here to the formalisms of W.M. Kaula and P. Goldreich. Like Darwin, the approach assumes a three-body problem: Earth, Moon, and Sun, where the Moon and Sun are point-masses. The tidal potential is written in terms of the Laplace plane angles. The resulting secular equations of motion can be easily integrated numerically assuming the Moon is in a circular orbit about the Earth and the Earth is in a circular orbit about the Sun. For Earth-Moon distances greater than 10 Earth radii, the Earth's approximate tidal response can be characterized with a single parameter, which is a ratio: a Love number times the sine of a lag angle divided by another such product. For low parameter values it can be shown that Darwin's low-viscosity molten Earth, M. Ross's and G. Schubert's model of an Earth near melting, and Goldreich's equal tidal lag angles must all give similar histories. For higher parameter values, as perhaps has been the case at times with the ocean tides, the Earth's obliquity may have decreased slightly instead of increased once the Moon's orbit evolved further than 50 Earth radii from the Earth, with possible implications for climate. This is contrast to the other tidal friction models mentioned, which have the obliquity always increasing with time. As for the Moon, its orbit is presently tilted to its Laplace plane by 5.2deg. The equations do not allow the Moon to evolve out of its Laplace plane by tidal friction alone, so that if it was originally in its Laplace plane, the tilt arose with the addition of other mechanisms, such as resonance passages.

Influence of anisotropic strain on the dielectric and ferroelectric properties of SrTiO3 thin films on DyScO3 substrates

NASA Astrophysics Data System (ADS)

Biegalski, M. D.; Vlahos, E.; Sheng, G.; Li, Y. L.; Bernhagen, M.; Reiche, P.; Uecker, R.; Streiffer, S. K.; Chen, L. Q.; Gopalan, V.; Schlom, D. G.; Trolier-McKinstry, S.

2009-06-01

The in-plane dielectric and ferroelectric properties of coherent anisotropically strained SrTiO3 thin films grown on orthorhombic (101) DyScO3 substrates were examined as a function of the angle between the applied electric field and the principal directions of the substrate. The dielectric permittivity revealed two distinct maxima as a function of temperature along the [100]p and [010]p SrTiO3 pseudocubic directions. These data, in conjunction with optical second-harmonic generation, show that the switchable ferroelectric polarization develops first predominantly along the in-plane axis with the larger tensile strain before developing a polarization component along the perpendicular direction with smaller strain as well, leading to domain twinning at the lower temperature. Finally, weak signatures in the dielectric and second-harmonic generation response were detected at the SrTiO3 tilt transition close to 165 K. These studies indicate that anisotropic biaxial strain can lead to new ferroelectric domain reorientation transitions that are not observed in isotropically strained films.

Fourier plane imaging microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dominguez, Daniel, E-mail: daniel.dominguez@ttu.edu; Peralta, Luis Grave de; Nano Tech Center, Texas Tech University, Lubbock, Texas 79409

We show how the image of an unresolved photonic crystal can be reconstructed using a single Fourier plane (FP) image obtained with a second camera that was added to a traditional compound microscope. We discuss how Fourier plane imaging microscopy is an application of a remarkable property of the obtained FP images: they contain more information about the photonic crystals than the images recorded by the camera commonly placed at the real plane of the microscope. We argue that the experimental results support the hypothesis that surface waves, contributing to enhanced resolution abilities, were optically excited in the studied photonicmore » crystals.« less

Strain-tuned enhancement of ferromagnetic TC to 176 K in Sm-doped BiMnO3 thin films and determination of magnetic phase diagram.

PubMed

Choi, Eun-Mi; Kleibeuker, Josée E; MacManus-Driscoll, Judith L

2017-03-03

BiMnO 3 is a promising multiferroic material but it's ferromagnetic T C is well below room temperature and the magnetic phase diagram is unknown. In this work, the relationship between magnetic transition temperature (T C ) and the substrate induced (pseudo-) tetragonal distortion (ratio of out-of-plane to in-plane lattice parameters, c/a) in BiMnO 3 thin films, lightly doped to optimize lattice dimensions, was determined. For c/a > 0.99, hidden antiferromagnetism was revealed and the magnetisation versus temperature curves showed a tail behaviour, whereas for c/a < 0.99 clear ferromagnetism was observed. A peak T C of up to 176 K, more than 70 K higher than for bulk BiMnO 3 , was achieved through precise strain tuning. The T C was maximised for strong tensile in-plane strain which produced weak octahedral rotations in the out-of-plane direction, an orthorhombic-like structure, and strong ferromagnetic coupling.

Errors Analysis of Students in Mathematics Department to Learn Plane Geometry

NASA Astrophysics Data System (ADS)

Mirna, M.

2018-04-01

This article describes the results of qualitative descriptive research that reveal the locations, types and causes of student error in answering the problem of plane geometry at the problem-solving level. Answers from 59 students on three test items informed that students showed errors ranging from understanding the concepts and principles of geometry itself to the error in applying it to problem solving. Their type of error consists of concept errors, principle errors and operational errors. The results of reflection with four subjects reveal the causes of the error are: 1) student learning motivation is very low, 2) in high school learning experience, geometry has been seen as unimportant, 3) the students' experience using their reasoning in solving the problem is very less, and 4) students' reasoning ability is still very low.

An efficient global energy optimization approach for robust 3D plane segmentation of point clouds

NASA Astrophysics Data System (ADS)

Dong, Zhen; Yang, Bisheng; Hu, Pingbo; Scherer, Sebastian

2018-03-01

Automatic 3D plane segmentation is necessary for many applications including point cloud registration, building information model (BIM) reconstruction, simultaneous localization and mapping (SLAM), and point cloud compression. However, most of the existing 3D plane segmentation methods still suffer from low precision and recall, and inaccurate and incomplete boundaries, especially for low-quality point clouds collected by RGB-D sensors. To overcome these challenges, this paper formulates the plane segmentation problem as a global energy optimization because it is robust to high levels of noise and clutter. First, the proposed method divides the raw point cloud into multiscale supervoxels, and considers planar supervoxels and individual points corresponding to nonplanar supervoxels as basic units. Then, an efficient hybrid region growing algorithm is utilized to generate initial plane set by incrementally merging adjacent basic units with similar features. Next, the initial plane set is further enriched and refined in a mutually reinforcing manner under the framework of global energy optimization. Finally, the performances of the proposed method are evaluated with respect to six metrics (i.e., plane precision, plane recall, under-segmentation rate, over-segmentation rate, boundary precision, and boundary recall) on two benchmark datasets. Comprehensive experiments demonstrate that the proposed method obtained good performances both in high-quality TLS point clouds (i.e., http://SEMANTIC3D.NET)

Measurement and control of in-plane surface chemistry during the oxidation of H-terminated (111) Si

PubMed Central

Gokce, Bilal; Adles, Eric J.; Aspnes, David E.; Gundogdu, Kenan

2010-01-01

In-plane directional control of surface chemistry during interface formation can lead to new opportunities regarding device structures and applications. Control of this type requires techniques that can probe and hence provide feedback on the chemical reactivity of bonds not only in specific directions but also in real time. Here, we demonstrate both control and measurement of the oxidation of H-terminated (111) Si. Control is achieved by externally applying uniaxial strain, and measurement by second-harmonic generation (SHG) together with the anisotropic-bond model of nonlinear optics. In this system anisotropy results because bonds in the strain direction oxidize faster than those perpendicular to it, leading in addition to transient structural changes that can also be detected at the bond level by SHG. PMID:20876145

Perspective - Systematic study of Reynolds stress closure models in the computations of plane channel flows

NASA Technical Reports Server (NTRS)

Demuren, A. O.; Sarkar, S.

1993-01-01

The roles of pressure-strain and turbulent diffusion models in the numerical calculation of turbulent plane channel flows with second-moment closure models are investigated. Three turbulent diffusion and five pressure-strain models are utilized in the computations. The main characteristics of the mean flow and the turbulent fields are compared against experimental data. All the features of the mean flow are correctly predicted by all but one of the Reynolds stress closure models. The Reynolds stress anisotropies in the log layer are predicted to varying degrees of accuracy (good to fair) by the models. None of the models could predict correctly the extent of relaxation towards isotropy in the wake region near the center of the channel. Results from the directional numerical simulation are used to further clarify this behavior of the models.

Effect of Biaxial Strain on the Phase Transitions of Ca (Fe1 -xCox)2As2

NASA Astrophysics Data System (ADS)

Böhmer, A. E.; Sapkota, A.; Kreyssig, A.; Bud'ko, S. L.; Drachuck, G.; Saunders, S. M.; Goldman, A. I.; Canfield, P. C.

2017-03-01

We study the effect of applied strain as a physical control parameter for the phase transitions of Ca (Fe1 -xCox)2As2 using resistivity, magnetization, x-ray diffraction, and Fe 57 Mössbauer spectroscopy. Biaxial strain, namely, compression of the basal plane of the tetragonal unit cell, is created through firm bonding of samples to a rigid substrate via differential thermal expansion. This strain is shown to induce a magnetostructural phase transition in originally paramagnetic samples, and superconductivity in previously nonsuperconducting ones. The magnetostructural transition is gradual as a consequence of using strain instead of pressure or stress as a tuning parameter.

Misfit strain-temperature phase diagrams and domain stability of asymmetric ferroelectric capacitors: Thermodynamic calculation and phase-field simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, W. J.; Zheng, Yue, E-mail: zhengy35@mail.sysu.edu.cn; Wu, C. M.

Thermodynamic calculation and phase-field simulation have been conducted to investigate the misfit strain-temperature phase diagrams, dielectric property, and domain stability of asymmetric ferroelectric capacitors (FCs), with considering the effects of dissimilar screening properties and work function steps at the two interfaces. The distinct features of asymmetric FCs from their symmetric counterparts have been revealed and discussed. Polar states with nonzero out-of-plane polarization in parallel with the built-in field are found preferential to form in asymmetric FCs. Meanwhile, the built-in field breaks the degeneracy of states with out-of-plane polarization in anti-directions. This leads to the necessity of redefining phases according tomore » the bistability of out-of-plane polarization. Moreover, the phase stability as well as the dielectric behavior can be significantly controlled by the properties of electrodes, misfit strain, and temperature. The phase-field simulation result also shows that polydomain instability would happen in asymmetric FCs as the equivalence of domain stability in anti-directions is destroyed.« less

Numerical techniques in radiative heat transfer for general, scattering, plane-parallel media

NASA Technical Reports Server (NTRS)

Sharma, A.; Cogley, A. C.

1982-01-01

The study of radiative heat transfer with scattering usually leads to the solution of singular Fredholm integral equations. The present paper presents an accurate and efficient numerical method to solve certain integral equations that govern radiative equilibrium problems in plane-parallel geometry for both grey and nongrey, anisotropically scattering media. In particular, the nongrey problem is represented by a spectral integral of a system of nonlinear integral equations in space, which has not been solved previously. The numerical technique is constructed to handle this unique nongrey governing equation as well as the difficulties caused by singular kernels. Example problems are solved and the method's accuracy and computational speed are analyzed.

Avalanche atomic switching in strain engineered Sb2Te3-GeTe interfacial phase-change memory cells

NASA Astrophysics Data System (ADS)

Zhou, Xilin; Behera, Jitendra K.; Lv, Shilong; Wu, Liangcai; Song, Zhitang; Simpson, Robert E.

2017-09-01

By confining phase transitions to the nanoscale interface between two different crystals, interfacial phase change memory heterostructures represent the state of the art for energy efficient data storage. We present the effect of strain engineering on the electrical switching performance of the {{Sb}}2{{Te}}3-GeTe superlattice van der Waals devices. Multiple Ge atoms switching through a two-dimensional Te layer reduces the activation barrier for further atoms to switch; an effect that can be enhanced by biaxial strain. The out-of-plane phonon mode of the GeTe crystal remains active in the superlattice heterostructures. The large in-plane biaxial strain imposed by the {{Sb}}2{{Te}}3 layers on the GeTe layers substantially improves the switching speed, reset energy, and cyclability of the superlattice memory devices. Moreover, carefully controlling residual stress in the layers of {{Sb}}2{{Te}}3-GeTe interfacial phase change memories provides a new degree of freedom to design the properties of functional superlattice structures for memory and photonics applications.

RECENT DEVELOPMENTS IN SURGICAL SKIN PLANING

PubMed Central

Ayres, Samuel; Wilson, J. Walter; Luikart, Ralph

1958-01-01

In surgical skin planing steel wire brushes have been largely replaced by the less hazardous diamond chip burs or “fraises” and serrated steel wheels. In addition to acne pits and wrinkling, multiple actinic (senile) keratoses are an important indication for planing. Planing provides a nonscarring method for the treatment of existing keratoses, as well as a prophylaxis against skin cancer by replacing the sun-damaged, precancerous epidermis with new epidermal cells derived from the cutaneous adnexa (pilosebaceous and sweat gland units). There are clinical landmarks indicating the depth of planing which can serve as a guide to the operator and can be correlated with microscopic findings. The results of experiments on the comparative effects of refrigerants on animal and human skin indicate that human facial skin can tolerate considerable freezing with ethyl chloride or dichlorotetrafluoroethane (Freon 114) but that mixtures containing large proportions of the much colder dichlorodifluoromethane (Freon 12) may be undesirable. Refreezing an area of the skin in order to perform a more adequate planing is not considered hazardous. The regeneration of the skin following planing has three components: Epidermal, adnexal and dermal. The cells of the epidermis and the adnexa are equipotential. A knowledge of the anatomy of the acne pit enables the operator to decide which pits can be benefited by planing and which should be excised before planing. The successful treatment of acne pits of the face by planing in patients having keloids elsewhere on the body is reported. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.Figure 7. PMID:13500217

Broken chiral symmetry on a null plane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beane, Silas R., E-mail: silas@physics.unh.edu

2013-10-15

On a null-plane (light-front), all effects of spontaneous chiral symmetry breaking are contained in the three Hamiltonians (dynamical Poincaré generators), while the vacuum state is a chiral invariant. This property is used to give a general proof of Goldstone’s theorem on a null-plane. Focusing on null-plane QCD with N degenerate flavors of light quarks, the chiral-symmetry breaking Hamiltonians are obtained, and the role of vacuum condensates is clarified. In particular, the null-plane Gell-Mann–Oakes–Renner formula is derived, and a general prescription is given for mapping all chiral-symmetry breaking QCD condensates to chiral-symmetry conserving null-plane QCD condensates. The utility of the null-planemore » description lies in the operator algebra that mixes the null-plane Hamiltonians and the chiral symmetry charges. It is demonstrated that in a certain non-trivial limit, the null-plane operator algebra reduces to the symmetry group SU(2N) of the constituent quark model. -- Highlights: •A proof (the first) of Goldstone’s theorem on a null-plane is given. •The puzzle of chiral-symmetry breaking condensates on a null-plane is solved. •The emergence of spin-flavor symmetries in null-plane QCD is demonstrated.« less

Microstructural dependency of optical properties of m-plane InGaN multiple quantum wells grown on 2° misoriented bulk GaN substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Fengzai; Barnard, Jonathan S.; Zhu, Tongtong

A non-polar m-plane structure consisting of five InGaN/GaN quantum wells (QWs) was grown on ammonothermal bulk GaN by metal-organic vapor phase epitaxy. Surface step bunches propagating through the QW stack were found to accommodate the 2° substrate miscut towards the -c direction. Both large steps with heights of a few tens of nanometres and small steps between one and a few atomic layers in height are observed, the former of which exhibit cathodoluminescence at longer wavelengths than the adjacent m-plane terraces. This is attributed to the formation of semi-polar facets at the steps on which the QWs are shown tomore » be thicker and have higher Indium contents than those in the adjacent m-plane regions. Discrete basal-plane stacking faults (BSFs) were occasionally initiated from the QWs on the main m-plane terraces, but groups of BSFs were frequently observed to initiate from those on the large steps, probably related to the increased strain associated with the locally higher indium content and thickness.« less

Focal-plane electric field sensing with pupil-plane holograms

NASA Astrophysics Data System (ADS)

Por, Emiel H.; Keller, Christoph U.

2016-07-01

The direct detection and spectral characterization of exoplanets requires a coronagraph to suppress the diffracted star light. Amplitude and phase aberrations in the optical train fill the dark zone of the coronagraph with quasi-static speckles that limit the achievable contrast. Focal-plane electric field sensing, such as phase diversity introduced by a deformable mirror (DM), is a powerful tool to minimize this residual star light. The residual electric field can be estimated by sequentially applying phase probes on the DM to inject star light with a well-known amplitude and phase into the dark zone and analyzing the resulting intensity images. The DM can then be used to add light with the same amplitude but opposite phase to destructively interfere with this residual star light. Using a static phase-only pupil-plane element we create holographic copies of the point spread function (PSF), each superimposed with a certain pupil-plane phase probe. We therefore obtain all intensity images simultaneously while still retaining a central, unaltered science PSF. The electric field sensing method only makes use of the holographic copies, allowing for correction of the residual electric field while retaining the central PSF for uninterrupted science data collection. In this paper we demonstrate the feasibility of this method with numerical simulations.

Regional differences in prognostic value of cardiac valve plane displacement in systemic light-chain amyloidosis.

PubMed

Ochs, Marco M; Fritz, Thomas; Arenja, Nisha; Riffel, Johannes; Andre, Florian; Mereles, Derliz; Siepen, Fabian Aus dem; Hegenbart, Ute; Schönland, Stefan; Katus, Hugo A; Friedrich, Matthias G W; Buss, Sebastian J

2017-11-09

To compare the prognostic value of cardiac valve plane displacement (CVPD) on various locations in cardiac light chain (AL) amyloidosis. Consecutive patients with biopsy-proven cardiac involvement in AL amyloidosis who had undergone cardiovascular magnetic resonance (CMR) between 2005 and 2014 in our institution, were retrospectively identified and data analyzed. The primary combined endpoint was all-cause mortality or heart transplantation. Systolic CVPD were obtained from standard cine bSSFP in 2-, 3- and 4-chamber views at anterior aortic plane systolic excursion (AAPSE); anterior, anterolateral, inferolateral, inferior, inferoseptal mitral (MAPSE); and lateral tricuspid (TAPSE) annular segments. We identified 68 patients (58 ± 10 years; 59% male). Median follow-up period was 1.2 years (IQR, 0.3-4.1). Significant differences in CVPD between patients who reached a primary endpoint (n = 44) and transplant-free survivors were found only for AAPSE (6.1 mm (IQR, 4.6-9.4) vs. 8.8 mm (IQR, 6.9-10.4); p = 0.02) and MAPSE anterolateral (7.3 mm (IQR, 5.4-11.7) vs. 10.5 mm (IQR, 8.1-13.4); p = 0.03). AAPSE (χ 2  = 15.6; p = 0.0002) provided the best predictive value for transplant-free survival compared to all other valvular plane locations. A high-risk cutoff (AAPSE ≤ 7.6 mm) was calculated by ROC analysis to predict all-cause death or heart transplantation within 6 months from index examination (AUC = 0.80; CI: 0.68 to 0.89; p < 0.0001). AAPSE added incremental prognostic power to an imaging prediction model of late gadolinium enhancement and global longitudinal strain (GLS) (∆χ 2  = 5.8, p = 0.02) as well as to a clinical model including Karnofsky index and NT-proBNP (∆χ 2  = 6.2, p = 0.01). In patients with cardiac involvement in AL amyloidosis, systolic CVPD obtained from standard long axis cine views appear to indicate outcome better, when obtained in the anterior aortic plane (AAPSE) and provide incremental prognostic

Multiview robotic microscope reveals the in-plane kinematics of amphibian neurulation.

PubMed

Veldhuis, Jim H; Brodland, G Wayne; Wiebe, Colin J; Bootsma, Gregory J

2005-06-01

A new robotic microscope system, called the Frogatron 3000, was developed to collect time-lapse images from arbitrary viewing angles over the surface of live embryos. Embryos are mounted at the center of a horizontal, fluid-filled, cylindrical glass chamber around which a camera with special optics traverses. To hold them at the center of the chamber and revolve them about a vertical axis, the embryos are placed on the end of a small vertical glass tube that is rotated under computer control. To demonstrate operation of the system, it was used to capture time-lapse images of developing axolotl (amphibian) embryos from 63 viewing angles during the process of neurulation and the in-plane kinematics of the epithelia visible at the center of each view was calculated. The motions of points on the surface of the embryo were determined by digital tracking of their natural surface texture, and a least-squares algorithm was developed to calculate the deformation-rate tensor from the motions of these surface points. Principal strain rates and directions were extracted from this tensor using decomposition and eigenvector techniques. The highest observed principal true strain rate was 28 +/- 5% per hour, along the midline of the neural plate during developmental stage 14, while the greatest contractile true strain rate was--35 +/- 5% per hour, normal to the embryo midline during stage 15.

An octahedral shear strain-based measure of SNR for 3D MR elastography

NASA Astrophysics Data System (ADS)

McGarry, M. D. J.; Van Houten, E. E. W.; Perriñez, P. R.; Pattison, A. J.; Weaver, J. B.; Paulsen, K. D.

2011-07-01

A signal-to-noise ratio (SNR) measure based on the octahedral shear strain (the maximum shear strain in any plane for a 3D state of strain) is presented for magnetic resonance elastography (MRE), where motion-based SNR measures are commonly used. The shear strain, γ, is directly related to the shear modulus, μ, through the definition of shear stress, τ = μγ. Therefore, noise in the strain is the important factor in determining the quality of motion data, rather than the noise in the motion. Motion and strain SNR measures were found to be correlated for MRE of gelatin phantoms and the human breast. Analysis of the stiffness distributions of phantoms reconstructed from the measured motion data revealed a threshold for both strain and motion SNR where MRE stiffness estimates match independent mechanical testing. MRE of the feline brain showed significantly less correlation between the two SNR measures. The strain SNR measure had a threshold above which the reconstructed stiffness values were consistent between cases, whereas the motion SNR measure did not provide a useful threshold, primarily due to rigid body motion effects.

Application of the wavenumber jump condition to the normal and oblique interaction of a plane acoustic wave and a plane shock

NASA Technical Reports Server (NTRS)

Kleinstein, G. G.; Gunzburger, M. D.

1977-01-01

The kinematics of normal and oblique interactions between a plane acoustic wave and a plane shock wave are investigated separately using an approach whereby the shock is considered as a sharp discontinuity surface separating two half-spaces, so that the dispersion relation on either side of the shock and the wavenumber jump condition across a discontinuity surface completely specify the kinematics of the problem in the whole space independently of the acoustic-field dynamics. The normal interaction is analyzed for a stationary shock, and the spectral change of the incident wave is investigated. The normal interaction is then examined for the case of a shock wave traveling into an ambient region where an acoustic disturbance is propagating in the opposite direction. Detailed attention is given to the consequences of the existence of a critical shock speed above which the frequency of the transmitted wave becomes negative. Finally, the oblique interaction with a fixed shock is considered, and the existence and nature of the transmitted wave is investigated, particularly as a function of the angle of incidence.

Epitaxially grown BaM hexaferrite films having uniaxial axis in the film plane for self-biased devices

PubMed Central

Zhang, Xiaozhi; Meng, Siqin; Song, Dongsheng; Zhang, Yao; Yue, Zhenxing; Harris, Vincent G.

2017-01-01

Barium hexaferrite (BaM) films with in-plane c-axis orientation are promising and technically important materials for self-biased magnetic microwave devices. In this work, highly oriented BaM films with different thickness and an in-plane easy axis (c-axis) of magnetization were grown on a-plane single-crystal sapphire substrates by direct current magnetron sputtering. A procedure involving seed layers, layer-by-layer annealing was adopted to reduce the substrate-induced strains and allow for the growth of thick (~3.44 μm) films. The epitaxial growth of the BaM film on sapphire was revealed by high-resolution transmission electron microscopy with dislocations being observed at the film-substrate interface. The orientation was also verified by X-ray diffraction and more notably, polarized Raman scattering. The magnetic properties and ferromagnetic resonant frequencies were experimentally characterized by a vibrating sample magnetometry and a frequency-swept ferromagnetic resonant flip-chip technique, respectively. The micron-thick BaM films exhibited a large remanence ratio of 0.92 along in-plane easy axis and a small one of 0.09 for the in-plane hard axis loop measurement. The FMR frequency was 50.3 GHz at zero field and reached 57.9 GHz under a magnetic field of 3 kOe, indicating that the epitaxial BaM films with strong self-biased behaviors have good electromagnetic properties in millimeter-wave range. PMID:28276492

Epitaxially grown BaM hexaferrite films having uniaxial axis in the film plane for self-biased devices.

PubMed

Zhang, Xiaozhi; Meng, Siqin; Song, Dongsheng; Zhang, Yao; Yue, Zhenxing; Harris, Vincent G

2017-03-09

Barium hexaferrite (BaM) films with in-plane c-axis orientation are promising and technically important materials for self-biased magnetic microwave devices. In this work, highly oriented BaM films with different thickness and an in-plane easy axis (c-axis) of magnetization were grown on a-plane single-crystal sapphire substrates by direct current magnetron sputtering. A procedure involving seed layers, layer-by-layer annealing was adopted to reduce the substrate-induced strains and allow for the growth of thick (~3.44 μm) films. The epitaxial growth of the BaM film on sapphire was revealed by high-resolution transmission electron microscopy with dislocations being observed at the film-substrate interface. The orientation was also verified by X-ray diffraction and more notably, polarized Raman scattering. The magnetic properties and ferromagnetic resonant frequencies were experimentally characterized by a vibrating sample magnetometry and a frequency-swept ferromagnetic resonant flip-chip technique, respectively. The micron-thick BaM films exhibited a large remanence ratio of 0.92 along in-plane easy axis and a small one of 0.09 for the in-plane hard axis loop measurement. The FMR frequency was 50.3 GHz at zero field and reached 57.9 GHz under a magnetic field of 3 kOe, indicating that the epitaxial BaM films with strong self-biased behaviors have good electromagnetic properties in millimeter-wave range.

Size effects and strain localization in atomic-scale cleavage modeling

NASA Astrophysics Data System (ADS)

Elsner, B. A. M.; Müller, S.

2015-09-01

In this work, we study the adhesion and decohesion of Cu(1 0 0) surfaces using density functional theory (DFT) calculations. An upper stress to surface decohesion is obtained via the universal binding energy relation (UBER), but the model is limited to rigid separation of bulk-terminated surfaces. When structural relaxations are included, an unphysical size effect arises if decohesion is considered to occur as soon as the strain energy equals the energy of the newly formed surfaces. We employ the nudged elastic band (NEB) method to show that this size effect is opposed by a size-dependency of the energy barriers involved in the transition. Further, we find that the transition occurs via a localization of bond strain in the vicinity of the cleavage plane, which resembles the strain localization at the tip of a sharp crack that is predicted by linear elastic fracture mechanics.

Size effects and strain localization in atomic-scale cleavage modeling.

PubMed

Elsner, B A M; Müller, S

2015-09-04

In this work, we study the adhesion and decohesion of Cu(1 0 0) surfaces using density functional theory (DFT) calculations. An upper stress to surface decohesion is obtained via the universal binding energy relation (UBER), but the model is limited to rigid separation of bulk-terminated surfaces. When structural relaxations are included, an unphysical size effect arises if decohesion is considered to occur as soon as the strain energy equals the energy of the newly formed surfaces. We employ the nudged elastic band (NEB) method to show that this size effect is opposed by a size-dependency of the energy barriers involved in the transition. Further, we find that the transition occurs via a localization of bond strain in the vicinity of the cleavage plane, which resembles the strain localization at the tip of a sharp crack that is predicted by linear elastic fracture mechanics.

The position of the occlusal plane in natural and artificial dentitions as related to other craniofacial planes.

PubMed

Al Quran, Firas A M; Hazza'a, Abdalla; Al Nahass, Nabeel

2010-12-01

This study aimed at determining the most reliable ala-tragus line as a guide for the orientation of the occlusal plane in complete denture patients by use of cephalometric landmarks on dentate volunteers. Analysis was made for prosthodontically related craniofacial reference lines and angles of lateral cephalometric radiographs taken for 47 dentate adults. Variables were determined and data were analyzed using SPSS (SPSS, Inc., Chicago, IL). Occlusal plane angle formed between the occlusal plane and Camper's plane had the lowest mean value in the angle formed with Camper's I, which represents the measure taken from the superior border of the tragus of the ear with a score of 2.1°. The highest was measured in the angle formed with Camper's III with a score of 6.1°, while the angle formed with Camper's II was 3.2°. The differences between the three planes in relation to the occlusal plane was significant (p < 0.001). The superior border of the tragus with the inferior border of the ala of the nose was most accurate in orienting the occlusal plane. © 2010 by The American College of Prosthodontists.

Influences of strain rate on yield strength aluminum alloys

NASA Astrophysics Data System (ADS)

Rizal, Samsul; Firdaus, Hamdani Teuku; Thaib, Razali; Homma, Hiroomi

2005-04-01

The simulation of aircraft has often been performing by implementing finite element code on supercomputers. The reliability an accuracy of simulation depends mainly on the material model as well as on structural model used in calculations. Consequently, an accurate knowledge of mechanical behavior of materials under impact loading is essential for safety performance evaluation of structure. Impact tension tests on specimens for aircrafts and automotive structural applications are conduct by means of the split Hopkinson bar apparatus. Small specimens having diameter 4 mm are use in the test. Tensile stress-strain relations at strain rates of 102 s-1 to over 103 s-1 are present and compared with those obtained at quasi-static strain rates. The limitations on the applicability of apparatus are also discusses. The other importance of the reference of strain, while studying void growth in elastic-viscoplastic material, is emphasized. In the present paper, a simplified plane-symmetrical two-dimensional finite element model for a SHPB with a plate specimen made of an elastic material is first established. The used of strain gage mounted at the specimens to be monitored strain during the course of impact test. Comparisons may then be made between the numerical predicted and experimentally observed of load and a specimen strain. This report also describes the apparatus and instrumentation, and also be discusses the advantages and limitations of experimental technique. Fractograph is taken by scanning electron microscope on the center of the specimens for judgment of the fracture mechanism and strain rates influences on the materials.

Covariance of dynamic strain responses for structural damage detection

NASA Astrophysics Data System (ADS)

Li, X. Y.; Wang, L. X.; Law, S. S.; Nie, Z. H.

2017-10-01

A new approach to address the practical problems with condition evaluation/damage detection of structures is proposed based on the distinct features of a new damage index. The covariance of strain response function (CoS) is a function of modal parameters of the structure. A local stiffness reduction in structure would cause monotonous increase in the CoS. Its sensitivity matrix with respect to local damages of structure is negative and narrow-banded. The damage extent can be estimated with an approximation to the sensitivity matrix to decouple the identification equations. The CoS sensitivity can be calibrated in practice from two previous states of measurements to estimate approximately the damage extent of a structure. A seven-storey plane frame structure is numerically studied to illustrate the features of the CoS index and the proposed method. A steel circular arch in the laboratory is tested. Natural frequencies changed due to damage in the arch and the damage occurrence can be judged. However, the proposed CoS method can identify not only damage happening but also location, even damage extent without need of an analytical model. It is promising for structural condition evaluation of selected components.

In-plane and out-of-plane defectivity in thin films of lamellar block copolymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahadevapuram, Nikhila; Mitra, Indranil; Bozhchenko, Alona

2015-10-29

We investigate the ordering of poly(styrene-b-methyl methacrylate) (PS-PMMA) lamellar copolymers (periodicity L 0 = 46 nm) confined between a free surface and brushed poly(styrene-r-methyl methacrylate) silicon substrate. The processing temperature was selected to eliminate wetting layers at the top and bottom interfaces, producing approximately neutral boundaries that stabilize perpendicular domain orientations. The PS-PMMA film thickness (t = 0.5L 0–2.5L 0) and brush grafting density (Σ = 0.2–0.6 nm –2) were systematically varied to examine their impacts on in-plane and out-of-plane ordering. Samples were characterized with a combination of high-resolution microscopy, X-ray reflectivity, and grazing-incidence small-angle X-ray scattering. In-plane order atmore » the top of the film (quantified through calculation of orientational correlation lengths) improved with t n, where the exponent n increased from 0.75 to 1 as Σ decreased from 0.6 to 0.2 nm –2. Out-of-plane defects such as tilted domains were detected in all films, and the distribution of domain tilt angles was nearly independent of t and Σ. These studies demonstrate that defectivity in perpendicular lamellar phases is three-dimensional, comprised of in-plane topological defects and out-of-plane domain tilt, with little or no correlation between these two types of disorder. As a result, strong interactions between the block copolymer and underlying substrate may trap both kinds of thermally generated defects.« less

Physical nature of strain rate sensitivity of metals and alloys at high strain rates

NASA Astrophysics Data System (ADS)

Borodin, E. N.; Gruzdkov, A. A.; Mayer, A. E.; Selyutina, N. S.

2018-04-01

The role of instabilities of plastic flow at plastic deformation of various materials is one of the important cross-disciplinary problems which is equally important in physics, mechanics and material science. The strain rate sensitivities under slow and high strain rate conditions of loading have different physical nature. In the case of low strain rate, the sensitivity arising from the inertness of the defect structures evolution can be expressed by a single parameter characterizing the plasticity mechanism. In our approach, this is the value of the characteristic relaxation time. In the dynamic case, there are additional effects of “high-speed sensitivity” associated with the micro-localization of the plastic flow near the stress concentrators. In the frames of mechanical description, this requires to introduce additional strain rate sensitivity parameters, which is realized in numerous modifications of Johnson–Cook and Zerilli–Armstrong models. The consideration of both these factors is fundamental for an adequate description of the problems of dynamic deformation of highly inhomogeneous metallic materials such as steels and alloys. The measurement of the dispersion of particle velocities on the free surface of a shock-loaded material can be regarded as an experimental expression of the effect of micro-localization. This is also confirmed by our results of numerical simulation of the propagation of shock waves in a two-dimensional formulation and analytical estimations.

High-temperature Strain Sensor and Mounting Development

NASA Technical Reports Server (NTRS)

Williams, W. Dan; Lei, Jih-Fen; Reardon, Lawrence F.; Krake, Keith; Lemcoe, M. M.; Holmes, Harlan K.; Moore, Thomas C., Sr.

1996-01-01

This report describes Government Work Package Task 29 (GWP29), whose purpose was to develop advanced strain gage technology in support of the National Aerospace Plane (NASP) Program. The focus was on advanced resistance strain gages with a temperature range from room temperature to 2000 F (1095 C) and on methods for reliably attaching these gages to the various materials anticipated for use in the NASP program. Because the NASP program required first-cycle data, the installed gages were not prestabilized or heat treated on the test coupons before first-cycle data were recorded. NASA Lewis Research Center, the lead center for GWP29, continued its development of the palladium-chromium gage; NASA Langley Research Center investigated a new concept gage using Kanthal A1; and the NASA Dryden Flight Research Center chose the well-known BCL-3 iron-chromium-aluminum gage. Each center then tested all three gages. The parameters investigated were apparent strain, drift strain, and gage factor as a function of temperature, plus gage size and survival rate over the test period. Although a significant effort was made to minimize the differences in test equipment between the three test sites (e.g., the same hardware and software were used for final data processing), the center employed different data acquisition systems and furnace configurations so that some inherent differences may be evident in the final results.

Robust Notion Vision For A Vehicle Moving On A Plane

NASA Astrophysics Data System (ADS)

Moni, Shankar; Weldon, E. J.

1987-05-01

A vehicle equipped with a cemputer vision system moves on a plane. We show that subject to certain constraints, the system can determine the motion of the vehicle (one rotational and two translational degrees of freedom) and the depth of the scene in front of the vehicle. The constraints include limits on the speed of the vehicle, presence of texture on the plane and absence of pitch and roll in the vehicular motion. It is possible to decouple the problems of finding the vehicle's motion and the depth of the scene in front of the vehicle by using two rigidly connected cameras. One views a field with known depth (i.e. the ground plane) and estimates the motion parameters and the other determines the depth map knowing the motion parameters. The motion is constrained to be planar to increase robustness. We use a least squares method of fitting the vehicle motion to observer brightness gradients. With this method, no correspondence between image points needs to be established and information fran the entire image is used in calculating notion. The algorithm performs very reliably on real image sequences and these results have been included. The results compare favourably to the performance of the algorithm of Negandaripour and Horn [2] where six degrees of freedom are assumed.

Bounded parametric control of plane motions of space tethered system

NASA Astrophysics Data System (ADS)

Bezglasnyi, S. P.; Mukhametzyanova, A. A.

2018-05-01

This paper is focused on the problem of control of plane motions of a space tethered system (STS). The STS is modeled as a heavy rod with two point masses. Point masses are fixed on the rod. A third point mass can move along the rod. The control is realized as a continuous change of the distance from the centre of mass of the tethered system to the movable mass. New limited control laws processes of excitation and damping are built. Diametric reorientation and gravitational stabilization to the local vertical of an STS were obtained. The problem is solved by the method of Lyapunov's functions of the classical theory of stability. The theoretical results are confirmed by numerical calculations.

Strain energy release rate analysis of the end-notched flexure specimen using the finite-element method

NASA Technical Reports Server (NTRS)

Salpekar, S. A.; Raju, I. S.; O'Brien, T. K.

1988-01-01

Two-dimensional finite-element analysis of the end-notched flexure specimen was performed using 8-node isoparametric, parabolic elements to evaluate compliance and mode II strain energy release rates, G sub II. The G sub II values were computed using two different techniques: the virtual crack-closure technique (VCCT) and the rate of change of compliance with crack length (compliance derivative method). The analysis was performed for various crack-length-to-semi-span (a/L) ratios ranging from 0.2 to 0.9. Three material systems representing a wide range of material properties were analyzed. The compliance and strain energy release rates of the specimen calculated with the present finite-element analysis agree very well with beam theory equations including transverse shear. The G sub II values calculated using the compliance derivative method compared extremely well with those calculated using the VCCT. The G sub II values obtained by the compliance derivative method using the top or bottom beam deflections agreed closely with each other. The strain energy release rates from a plane-stress analysis were higher than the plane-strain values by only a small percentage, indicating that either assumption may be used in the analysis. The G sub II values for one material system calculated from the finte-element analysis agreed with one solution in the literature and disagreed with the other solution in the literature.

Strain-energy-release rate analysis of the end-notched flexure specimen using the finite-element method

NASA Technical Reports Server (NTRS)

Salpekar, S. A.; Raju, I. S.; Obrien, T. K.

1987-01-01

Two-dimensional finite-element analysis of the end-notched flexure specimen was performed using 8-node isoparametric, parabolic elements to evaluate compliance and mode II strain energy release rates, G sub II. The G sub II values were computed using two different techniques: the virtural crack-closure technique (VCCT) and the rate of change of compliance with crack length (compliance derivative method). The analysis was performed for various crack-length-to-semi-span (a/L) ratios ranging from 0.2 to 0.9. Three material systems representing a wide range of material properties were analyzed. The compliance and strain energy release rates of the specimen calculated with the present finite-element analysis agree very well with beam theory equations including transverse shear. The G sub II values calculated using the compliance derivative method compared extremely well with those calculated using the VCCT. The G sub II values obtained by the compliance derivative method using the top or bottom beam deflections agreed closely with each other. The strain energy release rates from a plane-stress analysis were higher than the plane-strain values by only a small percentage, indicating that either assumption may be used in the analysis. The G sub II values for one material system calculated from the finite-element analysis agreed with one solution in the literature and disagreed with the other solution in the literature.

Strain-induced oxygen vacancies in ultrathin epitaxial CaMnO3 films

NASA Astrophysics Data System (ADS)

Chandrasena, Ravini; Yang, Weibing; Lei, Qingyu; Delgado-Jaime, Mario; de Groot, Frank; Arenholz, Elke; Kobayashi, Keisuke; Aschauer, Ulrich; Spaldin, Nicola; Xi, Xiaoxing; Gray, Alexander

Dynamic control of strain-induced ionic defects in transition-metal oxides is considered to be an exciting new avenue towards creating materials with novel electronic, magnetic and structural properties. Here we use atomic layer-by-layer laser molecular beam epitaxy to synthesize high-quality ultrathin single-crystalline CaMnO3 films with systematically varying coherent tensile strain. We then utilize a combination of high-resolution soft x-ray absorption spectroscopy and bulk-sensitive hard x-ray photoemission spectroscopy in conjunction with first-principles theory and core-hole multiplet calculations to establish a direct link between the coherent in-plane strain and the oxygen-vacancy content. We show that the oxygen vacancies are highly mobile, which necessitates an in-situ-grown capping layer in order to preserve the original strain-induced oxygen-vacancy content. Our findings open the door for designing and controlling new ionically active properties in strongly-correlated transition-metal oxides.

Matrix basis for plane and modal waves in a Timoshenko beam

PubMed Central

Tolfo, Daniela de Rosso; Tonetto, Leticia

2016-01-01

Plane waves and modal waves of the Timoshenko beam model are characterized in closed form by introducing robust matrix basis that behave according to the nature of frequency and wave or modal numbers. These new characterizations are given in terms of a finite number of coupling matrices and closed form generating scalar functions. Through Liouville’s technique, these latter are well behaved at critical or static situations. Eigenanalysis is formulated for exponential and modal waves. Modal waves are superposition of four plane waves, but there are plane waves that cannot be modal waves. Reflected and transmitted waves at an interface point are formulated in matrix terms, regardless of having a conservative or a dissipative situation. The matrix representation of modal waves is used in a crack problem for determining the reflected and transmitted matrices. Their euclidean norms are seen to be dominated by certain components at low and high frequencies. The matrix basis technique is also used with a non-local Timoshenko model and with the wave interaction with a boundary. The matrix basis allows to characterize reflected and transmitted waves in spectral and non-spectral form. PMID:28018668

Matrix basis for plane and modal waves in a Timoshenko beam.

PubMed

Claeyssen, Julio Cesar Ruiz; Tolfo, Daniela de Rosso; Tonetto, Leticia

2016-11-01

Plane waves and modal waves of the Timoshenko beam model are characterized in closed form by introducing robust matrix basis that behave according to the nature of frequency and wave or modal numbers. These new characterizations are given in terms of a finite number of coupling matrices and closed form generating scalar functions. Through Liouville's technique, these latter are well behaved at critical or static situations. Eigenanalysis is formulated for exponential and modal waves. Modal waves are superposition of four plane waves, but there are plane waves that cannot be modal waves. Reflected and transmitted waves at an interface point are formulated in matrix terms, regardless of having a conservative or a dissipative situation. The matrix representation of modal waves is used in a crack problem for determining the reflected and transmitted matrices. Their euclidean norms are seen to be dominated by certain components at low and high frequencies. The matrix basis technique is also used with a non-local Timoshenko model and with the wave interaction with a boundary. The matrix basis allows to characterize reflected and transmitted waves in spectral and non-spectral form.

Strain-Induced Anisotropic Fermi Contour of 2D Holes and Composite Fermions

NASA Astrophysics Data System (ADS)

Jo, Insun; Rosales, K. A. V.; Mueed, M. A.; Padmanabhan, M.; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Winkler, R.; Shayegan, M.

We present experimental and theoretical results demonstrating strain-induced Fermi contour anisotropy of two-dimensional (2D) holes and composite fermions (CFs) confined to a (001) GaAs quantum well. We apply a tunable uniaxial strain to a thinned (001) GaAs wafer, glued to a piezoelectric actuator. When the 2D holes are subjected to an in-plane uniaxial strain, their band structure and Fermi contour become anisotropic by about 30% even for a minute amount of strain, on the order of 10-4. Via measurements of commensurability oscillations, we determine the Fermi contour anisotropy for holes near zero magnetic field, and for CFs at high magnetic fields, as a function of uniaxial strain. The measured Fermi contour anisotropy of holes is consistent with the calculation results. The observed CF Fermi contour anisotropy also shows a strong dependence on the applied strain, which we compare quantitatively to that of the low-field holes. Supported by the NSF(Grants DMR-1305691, ECCS-1508925, and MRSEC DMR-1420541), the DOE Basic Energy Sciences (DE-FG02-00-ER45841), the Gordon and Betty Moore Foundation (GBMF4420), and the Keck Foundation. R. W. is supported by the NSF (DMR-1310199).

Deformation mode and strain path dependence of martensite phase transformation in a medium manganese TRIP steel

DOE PAGES

Wu, Wei; Wang, Yu-wei; Makrygiannis, Panagiotis; ...

2017-11-06

The martensite phase transformation dependence upon deformation modes and strain paths in a medium manganese (10 wt%) TRIP steel stamped into a T-shape panel was quantified through combination of 3D digital image correlation and synchrotron X-ray diffraction. The T-shape emulates a portion of a common anti-intrusion component. The stamping speed was kept intentionally slow (1 mm/s) so as to avoid excessive heat generation. The steel, which belongs to the third generation advanced high strength steel (3GAHSS) family, was chosen for two reasons: (1) it is two-phase, i.e. austenite and ferrite, with martensite resulting from deformation-induced phase transformation; (2) the 66more » vol.% initial retained austenite volume fraction (RAVF) enabled a thorough examination of the martensite phase transformation at large deformation levels without exhaustion. Strain fields were coupled with measured RAVF values of small specimens extracted from specific locations on a formed T-shape panel. This enabled an exploration of the effects of linear, bilinear, and non-linear strain paths as well as deformation modes such as tension, plane strain, biaxial tension, and equibiaxial tension. Results suggest a significant martensite phase transformation dependence on deformation mode and strain path in the absence of fracture and when martensite phase transformation is unaffected by heat generated during forming. In general, the uniaxial and biaxial tension deformation modes facilitate the martensite phase transformation, while the smallest amount of martensite phase transformation occurs under plane strain. Some discussion as to further application of the experimental methods detailed in this study to other 3GAHSS and the effects of fracture on martensite phase transformation is provided.« less

Deformation mode and strain path dependence of martensite phase transformation in a medium manganese TRIP steel

DOE PAGES

Wu, Wei; Wang, Yu -Wei; Makrygiannis, Panagiotis; ...

2017-11-06

The martensite phase transformation dependence upon deformation modes and strain paths in a medium manganese (10 wt%) TRIP steel stamped into a T-shape panel was quantified through combination of 3D digital image correlation and synchrotron X-ray diffraction. The T-shape emulates a portion of a common anti-intrusion component. The stamping speed was kept intentionally slow (1 mm/s) so as to avoid excessive heat generation. The steel, which belongs to the third generation advanced high strength steel (3GAHSS) family, was chosen for two reasons: (1) it is two-phase, i.e. austenite and ferrite, with martensite resulting from deformation-induced phase transformation; (2) the 66more » vol.% initial retained austenite volume fraction (RAVF) enabled a thorough examination of the martensite phase transformation at large deformation levels without exhaustion. Strain fields were coupled with measured RAVF values of small specimens extracted from specific locations on a formed T-shape panel. This enabled an exploration of the effects of linear, bilinear, and non-linear strain paths as well as deformation modes such as tension, plane strain, biaxial tension, and equibiaxial tension. Results suggest a significant martensite phase transformation dependence on deformation mode and strain path in the absence of fracture and when martensite phase transformation is unaffected by heat generated during forming. In general, the uniaxial and biaxial tension deformation modes facilitate the martensite phase transformation, while the smallest amount of martensite phase transformation occurs under plane strain. In conclusion, some discussion as to further application of the experimental methods detailed in this study to other 3GAHSS and the effects of fracture on martensite phase transformation is provided.« less

Deformation mode and strain path dependence of martensite phase transformation in a medium manganese TRIP steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wei; Wang, Yu -Wei; Makrygiannis, Panagiotis

The martensite phase transformation dependence upon deformation modes and strain paths in a medium manganese (10 wt%) TRIP steel stamped into a T-shape panel was quantified through combination of 3D digital image correlation and synchrotron X-ray diffraction. The T-shape emulates a portion of a common anti-intrusion component. The stamping speed was kept intentionally slow (1 mm/s) so as to avoid excessive heat generation. The steel, which belongs to the third generation advanced high strength steel (3GAHSS) family, was chosen for two reasons: (1) it is two-phase, i.e. austenite and ferrite, with martensite resulting from deformation-induced phase transformation; (2) the 66more » vol.% initial retained austenite volume fraction (RAVF) enabled a thorough examination of the martensite phase transformation at large deformation levels without exhaustion. Strain fields were coupled with measured RAVF values of small specimens extracted from specific locations on a formed T-shape panel. This enabled an exploration of the effects of linear, bilinear, and non-linear strain paths as well as deformation modes such as tension, plane strain, biaxial tension, and equibiaxial tension. Results suggest a significant martensite phase transformation dependence on deformation mode and strain path in the absence of fracture and when martensite phase transformation is unaffected by heat generated during forming. In general, the uniaxial and biaxial tension deformation modes facilitate the martensite phase transformation, while the smallest amount of martensite phase transformation occurs under plane strain. In conclusion, some discussion as to further application of the experimental methods detailed in this study to other 3GAHSS and the effects of fracture on martensite phase transformation is provided.« less

Deformation mode and strain path dependence of martensite phase transformation in a medium manganese TRIP steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wei; Wang, Yu-wei; Makrygiannis, Panagiotis

The martensite phase transformation dependence upon deformation modes and strain paths in a medium manganese (10 wt%) TRIP steel stamped into a T-shape panel was quantified through combination of 3D digital image correlation and synchrotron X-ray diffraction. The T-shape emulates a portion of a common anti-intrusion component. The stamping speed was kept intentionally slow (1 mm/s) so as to avoid excessive heat generation. The steel, which belongs to the third generation advanced high strength steel (3GAHSS) family, was chosen for two reasons: (1) it is two-phase, i.e. austenite and ferrite, with martensite resulting from deformation-induced phase transformation; (2) the 66more » vol.% initial retained austenite volume fraction (RAVF) enabled a thorough examination of the martensite phase transformation at large deformation levels without exhaustion. Strain fields were coupled with measured RAVF values of small specimens extracted from specific locations on a formed T-shape panel. This enabled an exploration of the effects of linear, bilinear, and non-linear strain paths as well as deformation modes such as tension, plane strain, biaxial tension, and equibiaxial tension. Results suggest a significant martensite phase transformation dependence on deformation mode and strain path in the absence of fracture and when martensite phase transformation is unaffected by heat generated during forming. In general, the uniaxial and biaxial tension deformation modes facilitate the martensite phase transformation, while the smallest amount of martensite phase transformation occurs under plane strain. Some discussion as to further application of the experimental methods detailed in this study to other 3GAHSS and the effects of fracture on martensite phase transformation is provided.« less

Predicting grid-size-dependent fracture strains of DP980 with a microstructure-based post-necking model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, G.; Hu, X. H.; Choi, K. S.

Ductile fracture is a local phenomenon, and it is well established that fracture strain levels depend on both stress triaxiality and the resolution (grid size) of strain measurements. Two-dimensional plane strain post-necking models with different representative volume element (RVE) sizes are used to predict the size-dependent fracture strain of a commercial dual-phase steel, DP980. The models are generated from the actual microstructures, and the individual phase flow properties and literature-based individual phase damage parameters for the Johnson-Cook model are used for ferrite and martensite. A monotonic relationship is predicted: the smaller the model size, the higher the fracture strain. Thus,more » a general framework is developed to quantify the size-dependent fracture strains for multiphase materials. In addition to the RVE sizes, the influences of intrinsic microstructure features, i.e., the flow curve and fracture strains of the two constituent phases, on the predicted fracture strains also are examined. Application of the derived fracture strain versus RVE size relationship is demonstrated with large clearance trimming simulations with different element sizes.« less

Enhanced Proton Conductivity in Y-Doped BaZrO3 via Strain Engineering.

PubMed

Fluri, Aline; Marcolongo, Aris; Roddatis, Vladimir; Wokaun, Alexander; Pergolesi, Daniele; Marzari, Nicola; Lippert, Thomas

2017-12-01

The effects of stress-induced lattice distortions (strain) on the conductivity of Y-doped BaZrO 3 , a high-temperature proton conductor with key technological applications for sustainable electrochemical energy conversion, are studied. Highly ordered epitaxial thin films are grown in different strain states while monitoring the stress generation and evolution in situ. Enhanced proton conductivity due to lower activation energies is discovered under controlled conditions of tensile strain. In particular, a twofold increased conductivity is measured at 200 °C along a 0.7% tensile strained lattice. This is at variance with conclusions coming from force-field simulations or the static calculations of diffusion barriers. Here, extensive first-principles molecular dynamic simulations of proton diffusivity in the proton-trapping regime are therefore performed and found to agree with the experiments. The simulations highlight that compressive strain confines protons in planes parallel to the substrate, while tensile strain boosts diffusivity in the perpendicular direction, with the net result that the overall conductivity is enhanced. It is indeed the presence of the dopant and the proton-trapping effect that makes tensile strain favorable for proton conduction.

Normal references of right ventricular strain values by two-dimensional strain echocardiography according to the age and gender.

PubMed

Park, Jae-Hyeong; Choi, Jin-Oh; Park, Seung Woo; Cho, Goo-Yeong; Oh, Jin Kyung; Lee, Jae-Hwan; Seong, In-Whan

2018-02-01

Right ventricular (RV) strain values by 2-dimensional strain echocardiography (STE) can be used as objective markers of RV systolic function. However, there is little data about normal reference RV strain values according to age and gender. We measured normal RV strain values by STE. RV strain values were analyzed from the digitally stored echocardiographic images from NORMAL (Normal echOcardiogRaphic diMensions and functions in KoreAn popuLation) study for the measurement of normal echocardiographic values performed in 23 Korean university hospitals. We enrolled total 1003 healthy persons in the NORMAL study. Of them, we analyzed 2-dimensional RV strain values in 493 subjects (261 females, mean 47 ± 15 years old) only with echocardiographic images by GE machines. Their LV systolic and diastolic functions were normal. RV fractional area change was 48 ± 6% and tricuspid annular plane systolic excursion was 23 ± 3 mm. Total RV global longitudinal peak systolic strain (RVGLS total ) was -21.5 ± 3.2%. Females had higher absolute RVGLS total (-22.3 ± 3.3 vs -20.7 ± 2.9%, p < 0.001) than males. Younger (<50 years old) females had higher absolute RVGLS total (-22.9 ± 3.2 vs -20.5 ± 2.8%, p < 0.001) than age matched males. RVGLS total in females gradually increased according to age (p for trend = 0.002) and becomes almost similar in age ≥50 years. However, this trend was not seen in males (p for trend = 0.287), and younger males had similar RVGLS total value to that of older males (age ≥50 years, -20.5 ± 2.8 vs -20.9 ± 3.1%, p = 0.224). We calculated normal RVGLS values in normal population. Females have higher absolute strain values than males, especially in younger age groups (<50 years old).

Strain memory of 2D and 3D rigid inclusion populations in viscous flows - What is clast SPO telling us?

NASA Astrophysics Data System (ADS)

Stahr, Donald W.; Law, Richard D.

2014-11-01

We model the development of shape preferred orientation (SPO) of a large population of two- and three-dimensional (2D and 3D) rigid clasts suspended in a linear viscous matrix deformed by superposed steady and continuously non-steady plane strain flows to investigate the sensitivity of clasts to changing boundary conditions during a single or superposed deformation events. Resultant clast SPOs are compared to one developed by an identical initial population that experienced a steady flow history of constant kinematic vorticity and reached an identical finite strain state, allowing examination of SPO sensitivity to deformation path. Rotation paths of individual triaxial inclusions are complex, even for steady plane strain flow histories. It has been suggested that the 3D nature of the system renders predictions based on 2D models inadequate for applied clast-based kinematic vorticity gauges. We demonstrate that for a large population of clasts, simplification to a 2D model does provide a good approximation to the SPO predicted by full 3D analysis for steady and non-steady plane strain deformation paths. Predictions of shape fabric development from 2D models are not only qualitatively similar to the more complex 3D analysis, but they display the same limitations of techniques based on clast SPO commonly used as a quantitative kinematic vorticity gauge. Our model results from steady, superposed, and non-steady flow histories with a significant pure shearing component at a wide range of finite strain resemble predictions for an identical initial population that experienced a single steady simple shearing deformation. We conclude that individual 2D and 3D clasts respond instantaneously to changes in boundary conditions, however, in aggregate, the SPO of a population of rigid inclusions does not reflect the late-stage kinematics of deformation, nor is it an indicator of the unique 'mean' kinematic vorticity experienced by a deformed rock volume.

Strain and curvature induced evolution of electronic band structures in twisted graphene bilayer.

PubMed

Yan, Wei; He, Wen-Yu; Chu, Zhao-Dong; Liu, Mengxi; Meng, Lan; Dou, Rui-Fen; Zhang, Yanfeng; Liu, Zhongfan; Nie, Jia-Cai; He, Lin

2013-01-01

It is well established that strain and geometry could affect the band structure of graphene monolayer dramatically. Here we study the evolution of local electronic properties of a twisted graphene bilayer induced by a strain and a high curvature, which are found to strongly affect the local band structures of the twisted graphene bilayer. The energy difference of the two low-energy van Hove singularities decreases with increasing lattice deformation and the states condensed into well-defined pseudo-Landau levels, which mimic the quantization of massive chiral fermions in a magnetic field of about 100 T, along a graphene wrinkle. The joint effect of strain and out-of-plane distortion in the graphene wrinkle also results in a valley polarization with a significant gap. These results suggest that strained graphene bilayer could be an ideal platform to realize the high-temperature zero-field quantum valley Hall effect.

Look down from the Sky: Is It a Bird? Is It Superman? No, It's a Plane

ERIC Educational Resources Information Center

Chick, Helen

2016-01-01

The plane problem is a real-world problem, presented without any suggestion as to how it might be solved. It arose unexpectedly as the author was messing around on the internet, not thinking about maths at all. She did not encounter the problem in a maths lesson, nor as homework in the middle of a unit on a particular topic, and so she had no…

Conjugate gradient determination of optimal plane changes for a class of three-impulse transfers between noncoplanar circular orbits

NASA Technical Reports Server (NTRS)

Burrows, R. R.

1972-01-01

A particular type of three-impulse transfer between two circular orbits is analyzed. The possibility of three plane changes is recognized, and the problem is to optimally distribute these plane changes to minimize the sum of the individual impulses. Numerical difficulties and their solution are discussed. Numerical results obtained from a conjugate gradient technique are presented for both the case where the individual plane changes are unconstrained and for the case where they are constrained. Possibly not unexpectedly, multiple minima are found. The techniques presented could be extended to the finite burn case, but primarily the contents are addressed to preliminary mission design and vehicle sizing.

Implementation of Laminate Theory Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

2000-01-01

A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to impact loads. Previously, strain rate dependent inelastic constitutive equations developed to model the polymer matrix were implemented into a mechanics of materials based micromechanics method. In the current work, the computation of the effective inelastic strain in the micromechanics model was modified to fully incorporate the Poisson effect. The micromechanics equations were also combined with classical laminate theory to enable the analysis of symmetric multilayered laminates subject to in-plane loading. A quasi-incremental trapezoidal integration method was implemented to integrate the constitutive equations within the laminate theory. Verification studies were conducted using an AS4/PEEK composite using a variety of laminate configurations and strain rates. The predicted results compared well with experimentally obtained values.

A comparative evaluation of in-plane shear test methods for laminated graphite-epoxy composites

NASA Technical Reports Server (NTRS)

Morton, John; Ho, Henjen

1992-01-01

The objectives were to evaluate popular shear test methods for various forms of graphite-epoxy composite materials and to determine the shear response of graphite-epoxy composites with various forms of fiber architecture. Numerical and full-field experimental stress analyses were performed on four shear test configurations for unidirectional and bidirectional graphite-epoxy laminates to assess the uniformity and purity of the shear stress (strain) fields produced in the specimen test section and to determine the material in-plane shear modulus and shear response. The test methods were the 10 deg off-axis, the +/- 45 deg tension, the Iosipescu V-notch, and a compact U-notch specimen. Specimens were prepared from AS4/3501-6 graphite-epoxy panels, instrumented with conventional strain gage rosettes and with a cross-line moire grating, and loaded in a convenient testing machine. The shear responses obtained for each test method and the two methods of specimen instrumentation were compared. In a second phase of the program the shear responses obtained from Iosipescu V-notch beam specimens were determined for woven fabric geometries of different weave and fiber architectures. Again the responses of specimens obtained from strain gage rosettes and moire interferometry were compared. Additional experiments were performed on a bidirectional cruciform specimen which was also instrumented with strain gages and a moire grating.

A simple laminate theory using the orthotropic viscoplasticity theory based on overstress. I - In-plane stress-strain relationships for metal matrix composites

NASA Technical Reports Server (NTRS)

Krempl, Erhard; Hong, Bor Zen

1989-01-01

A macromechanics analysis is presented for the in-plane, anisotropic time-dependent behavior of metal matrix laminates. The small deformation, orthotropic viscoplasticity theory based on overstress represents lamina behavior in a modified simple laminate theory. Material functions and constants can be identified in principle from experiments with laminae. Orthotropic invariants can be repositories for tension-compression asymmetry and for linear elasticity in one direction while the other directions behave in a viscoplastic manner. Computer programs are generated and tested for either unidirectional or symmetric laminates under in-plane loading. Correlations with the experimental results on metal matrix composites are presented.

Strain-induced alignment and phase behavior of blue phase liquid crystals confined to thin films.

PubMed

Bukusoglu, Emre; Martinez-Gonzalez, Jose A; Wang, Xiaoguang; Zhou, Ye; de Pablo, Juan J; Abbott, Nicholas L

2017-12-06

We report on the influence of surface confinement on the phase behavior and strain-induced alignment of thin films of blue phase liquid crystals (BPs). Confining surfaces comprised of bare glass, dimethyloctadecyl [3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP)-functionalized glass, or polyvinyl alcohol (PVA)-coated glass were used with or without mechanically rubbing to influence the azimuthal anchoring of the BPs. These experiments reveal that confinement can change the phase behavior of the BP films. For example, in experiments performed with rubbed-PVA surfaces, we measured the elastic strain of the BPs to change the isotropic-BPII phase boundary, suppressing formation of BPII for film thicknesses incommensurate with the BPII lattice. In addition, we observed strain-induced alignment of the BPs to exhibit a complex dependence on both the surface chemistry and azimuthal alignment of the BPs. For example, when using bare glass surfaces causing azimuthally degenerate and planar anchoring, BPI oriented with (110) planes of the unit cell parallel to the contacting surfaces for thicknesses below 3 μm but transitioned to an orientation with (200) planes aligned parallel to the contacting surfaces for thicknesses above 4 μm. In contrast, BPI aligned with (110) planes parallel to confining surfaces for all other thicknesses and surface treatments, including bare glass with uniform azimuthal alignment. Complementary simulations based on minimization of the total free energy (Landau-de Gennes formalism) confirmed a thickness-dependent reorientation due to strain of BPI unit cells within a window of surface anchoring energies and in the absence of uniform azimuthal alignment. In contrast to BPI, BPII did not exhibit thickness-dependent orientations but did exhibit orientations that were dependent on the surface chemistry, a result that was also captured in simulations by varying the anchoring energies. Overall, the results in this paper reveal that the orientations

An inverse dynamics approach to trajectory optimization and guidance for an aerospace plane

NASA Technical Reports Server (NTRS)

Lu, Ping

1992-01-01

The optimal ascent problem for an aerospace planes is formulated as an optimal inverse dynamic problem. Both minimum-fuel and minimax type of performance indices are considered. Some important features of the optimal trajectory and controls are used to construct a nonlinear feedback midcourse controller, which not only greatly simplifies the difficult constrained optimization problem and yields improved solutions, but is also suited for onboard implementation. Robust ascent guidance is obtained by using combination of feedback compensation and onboard generation of control through the inverse dynamics approach. Accurate orbital insertion can be achieved with near-optimal control of the rocket through inverse dynamics even in the presence of disturbances.

Coherent, atomically thin transition-metal dichalcogenide superlattices with engineered strain

NASA Astrophysics Data System (ADS)

Xie, Saien; Tu, Lijie; Han, Yimo; Huang, Lujie; Kang, Kibum; Lao, Ka Un; Poddar, Preeti; Park, Chibeom; Muller, David A.; DiStasio, Robert A.; Park, Jiwoong

2018-03-01

Epitaxy forms the basis of modern electronics and optoelectronics. We report coherent atomically thin superlattices in which different transition metal dichalcogenide monolayers—despite large lattice mismatches—are repeated and laterally integrated without dislocations within the monolayer plane. Grown by an omnidirectional epitaxy, these superlattices display fully matched lattice constants across heterointerfaces while maintaining an isotropic lattice structure and triangular symmetry. This strong epitaxial strain is precisely engineered via the nanoscale supercell dimensions, thereby enabling broad tuning of the optical properties and producing photoluminescence peak shifts as large as 250 millielectron volts. We present theoretical models to explain this coherent growth and the energetic interplay governing the ripple formation in these strained monolayers. Such coherent superlattices provide building blocks with targeted functionalities at the atomically thin limit.

Triggering of the Ms = 5.4 Little Skull Mountain, Nevada, earthquake with dynamic strains

USGS Publications Warehouse

Gomberg, Joan; Bodin, Paul

1994-01-01

We have developed an approach to test the viability of dynamic strains as a triggering mechanism by quantifying the dynamic strain tensor at seismogenic depths. We focus on the dynamic strains at the hypocenter of the Ms = 5.4 Little Skull Mountain (LSM), Nevada, earthquake. This event is noteworthy because it is the largest earthquake demonstrably triggered at remote distances (∼280 km) by the Ms = 7.4 Landers, California, earthquake and because of its ambiguous association with magmatic activity. Our analysis shows that, if dynamic strains initiate remote triggering, the orientation and modes of faulting most favorable for being triggered by a given strain transient change with depth. The geometry of the most probable LSM fault plane was favorably oriented with respect to the geometry of the dynamic strain tensor. We estimate that the magnitude of the peak dynamic strains at the hypocentral depth of the LSM earthquake were ∼4 μstrain (∼.2 MPa) which are ∼50% smaller than those estimated from velocity seismograms recorded at the surface. We suggest that these strains are too small to cause Mohr-Coulomb style failure unless the fault was prestrained to near failure levels, the fault was exceptionally weak, and/or the dynamic strains trigger other processes that lead to failure.

Optimal aeroassisted orbital transfer with plane change using collocation and nonlinear programming

NASA Technical Reports Server (NTRS)

Shi, Yun. Y.; Nelson, R. L.; Young, D. H.

1990-01-01

The fuel optimal control problem arising in the non-planar orbital transfer employing aeroassisted technology is addressed. The mission involves the transfer from high energy orbit (HEO) to low energy orbit (LEO) with orbital plane change. The basic strategy here is to employ a combination of propulsive maneuvers in space and aerodynamic maneuvers in the atmosphere. The basic sequence of events for the aeroassisted HEO to LEO transfer consists of three phases. In the first phase, the orbital transfer begins with a deorbit impulse at HEO which injects the vehicle into an elliptic transfer orbit with perigee inside the atmosphere. In the second phase, the vehicle is optimally controlled by lift and bank angle modulations to perform the desired orbital plane change and to satisfy heating constraints. Because of the energy loss during the turn, an impulse is required to initiate the third phase to boost the vehicle back to the desired LEO orbital altitude. The third impulse is then used to circularize the orbit at LEO. The problem is solved by a direct optimization technique which uses piecewise polynomial representation for the state and control variables and collocation to satisfy the differential equations. This technique converts the optimal control problem into a nonlinear programming problem which is solved numerically. Solutions were obtained for cases with and without heat constraints and for cases of different orbital inclination changes. The method appears to be more powerful and robust than other optimization methods. In addition, the method can handle complex dynamical constraints.

Open Cluster Dynamics via Fundamental Plane

NASA Astrophysics Data System (ADS)

Lin, Chien-Cheng; Pang, Xiao-Ying

2018-04-01

Open clusters (OCs) are important objects for stellar dynamics studies. The short survival timescale of OCs makes them closely related to the formation of Galactic field stars. We motivate to investigate the dynamical evolution of OCs on the aspect of internal effect and the external influence. Firstly, we make use of the known OC catalog to obtain OCs masses, effective radii. Additionally, we estimate OCs kinematics properties by OC members cross-matched with radial velocity and metallicity from SDSSIV/APOGEE2. We then establish the fundamental plane of OCs based on the radial velocity dispersion, the effective radius, and average surface brightness. The deviation of the fundamental plane from the Virial Plane, so called the tilt, and the r.m.s. dispersion of OCs around the average plane are used to indicate the dynamical status of OCs. Parameters of the fitted plane will vary with cluster age and distance.

In-plane g factor of low-density two-dimensional holes in a Ge quantum well.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Tzu-Ming; Harris, Charles Thomas; Huang, Shih-Hsien

High-mobility two-dimensional (2D) holes residing in a Ge quantum well are a new electronic system with potentials in quantum computing and spintronics. Since for any electronic material, the effective mass and the g factor are two fundamental material parameters that determine the material response to electric and magnetic fields, measuring these two parameters in this material system is thus an important task that needs to be completed urgently. Because of the quantum confinement in the crystal growth direction (z), the biaxial strain of epitaxial Ge on SiGe, and the valance band nature, both the effective mass and the g factormore » can show very strong anisotropy. In particular, the in-plane g factor (g ip) can be vanishingly small while the perpendicular g factor (g z) can be much larger than 2. Here we report the measurement of g ip at very low hole densities using in-plane magneto-resistance measurement performed at the NHMFL.« less

Effect of biaxial strain on the phase transitions of Ca ( Fe 1 – x Co x ) 2 As 2

DOE PAGES

Bohmer, A. E.; Sapkota, A.; Kreyssig, A.; ...

2017-03-10

We study the effect of applied strain as a physical control parameter for the phase transitions of Ca(Fe 1–xCo x) 2As 2 using resistivity, magnetization, x-ray diffraction, and 57Fe Mossbauer spectroscopy. Biaxial strain, namely, compression of the basal plane of the tetragonal unit cell, is created through firm bonding of samples to a rigid substrate via differential thermal expansion. This strain is shown to induce a magnetostructural phase transition in originally paramagnetic samples, and superconductivity in previously nonsuperconducting ones. Lastly, the magnetostructural transition is gradual as a consequence of using strain instead of pressure or stress as a tuning parameter.

[Anatomical planes and landmarks of transanal total mesorectal excision for rectal cancer and prophylaxis of intraoperative complications].

PubMed

Shen, Zhanlong; Ye, Yingjiang; Wang, Shan

2017-07-25

Total mesorectal excision (TME) is a mile-stone procedure in the history of rectal cancer surgery, but the exposure of surgical field of distal rectum is usually poor in patients with male, obese and narrow pelvis, which may lead to tumor residue and relative complications. Recently, a new technique called transanal TME (taTME) is considered to solve the above problems, but most medical centers are still in the learning curve of this procedure. Therefore, anatomical planes and landmarks of taTME for rectal cancer and prophylaxis of intraoperative complications are induced in this paper, which includes posterior plane: angle of anus and distal mesorectum and bleeding of mesorectum; rectosacral fascia and presacral bleeding; lateral and posterior-lateral plane: posterior branches of pelvic plexus and damage of anal function; anterior plane: vessel branches of neurovascular bundle and bleeding. Familiarity with the specific anatomical planes and landmarks plays an important role in shortening the learning curve, decreasing the complications, increasing the success rate of operation and standardization of taTME.

Viewing Saturn from the Plane

NASA Image and Video Library

2006-04-19

This view of the ringed planet shows its tilt relative to the plane of its orbit around the Sun. The planet tilts nearly 27 degrees relative to the ecliptic plane giving rise to seasons in which the rings shadow each hemisphere in its respective winter

A direct correlation of x-ray diffraction orientation distributions to the in-plane stiffness of semi-crystalline organic semiconducting films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Bingxiao; Awartani, Omar; O'Connor, Brendan

2016-05-02

Large charge mobilities of semi-crystalline organic semiconducting films could be obtained by mechanically aligning the material phases of the film with the loading axis. A key element is to utilize the inherent stiffness of the material for optimal or desired alignment. However, experimentally determining the moduli of semi-crystalline organic thin films for different loading directions is difficult, if not impossible, due to film thickness and material anisotropy. In this paper, we address these challenges by presenting an approach based on combining a composite mechanics stiffness orientation formulation with a Gaussian statistical distribution to directly estimate the in-plane stiffness (transverse isotropy)more » of aligned semi-crystalline polymer films based on crystalline orientation distributions obtained by X-ray diffraction experimentally at different applied strains. Our predicted results indicate that the in-plane stiffness of an annealing film was initially isotropic, and then it evolved to transverse isotropy with increasing mechanical strains. This study underscores the significance of accounting for the crystalline orientation distributions of the film to obtain an accurate understanding and prediction of the elastic anisotropy of semi-crystalline polymer films.« less

Strain induced novel quantum magnetotransport properties of topological insulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Ning, E-mail: maning@stu.xjtu.edu.cn; Department of Applied Physics, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi’an Jiaotong University, Xi’an 710049; Zhang, Shengli, E-mail: zhangsl@mail.xjtu.edu.cn

Recent theoretical and experimental researches have revealed that the strained bulk HgTe can be regarded as a three-dimensional topological insulator (TI). Motivated by this, we explore the strain effects on the transport properties of the HgTe surface states, which are modulated by a weak 1D in-plane electrostatic periodic potential in the presence of a perpendicular magnetic field. We analytically derive the zero frequency (dc) diffusion conductivity for the case of quasielastic scattering in the Kubo formalism, and find that, in strong magnetic field regime, the Shubnikov–de Haas oscillations are superimposed on top of the Weiss oscillations due to the electricmore » modulation for null and finite strain. Furthermore, the strain is shown to remove the degeneracy in inversion symmetric Dirac cones on the top and bottom surfaces. This accordingly gives rise to the splitting and mixture of Landau levels, and the asymmetric spectrum of the dc conductivity. These phenomena, not known in a conventional 2D electron gas and even in a strainless TI and graphene, are a consequence of the anomalous spectrum of surface states in a fully stained TI. These results should be valuable for electronic and spintronic applications of TIs, and thus we fully expect to see them in the further experiment. - Highlights: • The strain removes the degeneracy in inversion symmetric Dirac cones. • The strain gives rise to the splitting and mixture of the Landau levels. • The strain leads to the asymmetric spectrum of the dc conductivity. • Shubnikov de Haas oscillations are shown to be superimposed on Weiss oscillations. • Interplay between strain and electric field causes different occupancy of TI states.« less

Job strain, job insecurity, and health: rethinking the relationship.

PubMed

Strazdins, Lyndall; D'Souza, Rennie M; Lim, Lynette L-Y; Broom, Dorothy H; Rodgers, Bryan

2004-10-01

Job strain (high demands and low control) is a widely used measure of work stress. The authors introduce a new way of looking at work stress by combining job strain with job insecurity, a combination increasingly prevalent in contemporary economies, using data from a cross-sectional survey (N = 1,188) of mid-aged Australian managers and professionals. Those reporting both strain and insecurity showed markedly higher odds for mental and physical health problems (depression: odds ratio [OR] 13.88, 95% confidence interval [CI] 5.67-34.01; anxiety: OR 12.88, CI 5.12-32.39; physical health problems: OR 3.97, CI 1.72-9.16; and poor self-rated health: OR 7.12, CI 2.81-18.01). Job strain and insecurity showed synergistic associations with health, and employees experiencing both could be at heightened health risk.

An extensometer for global measurement of bone strain suitable for use in vivo in humans

NASA Technical Reports Server (NTRS)

Perusek, G. P.; Davis, B. L.; Sferra, J. J.; Courtney, A. C.; D'Andrea, S. E.

2001-01-01

An axial extensometer able to measure global bone strain magnitudes and rates encountered during physiological activity, and suitable for use in vivo in human subjects, is described. The extensometer uses paired capacitive sensors mounted to intraosseus pins and allows measurement of strain due to bending in the plane of the extensometer as well as uniaxial compression or tension. Data are presented for validation of the device against a surface-mounted strain gage in an acrylic specimen under dynamic four-point bending, with square wave and sinusoidal loading inputs up to 1500 mu epsilon and 20 Hz, representative of physiological strain magnitudes and frequencies. Pearson's correlation coefficient (r) between extensometer and strain gage ranged from 0.960 to 0.999. Mean differences between extensometer and strain gage ranged up to 15.3 mu epsilon. Errors in the extensometer output were directly proportional to the degree of bending that occurs in the specimen, however, these errors were predictable and less than 1 mu epsilon for the loading regime studied. The device is capable of tracking strain rates in excess of 90,000 mu epsilon/s.

Effect of strain and deformation route on grain boundary characteristics and recrystallization behavior of aluminum

NASA Astrophysics Data System (ADS)

Sakai, Tetsuo; Utsunomiya, Hiroshi; Takahashi, Yasuo

2014-08-01

The effect of strain and deformation route on the recrystallization behavior of aluminum sheets has been investigated using well lubricated cold rolling and continuous equal channel angular extrusion. Three different deformation routes in plane strain corresponding to (1) simple shear, (2) compression, and (3) the combination of simple shear and compression were performed on 1100 aluminum sheet. Fixed amounts of the equivalent strain of 1.28 and 1.06 were accumulated in each route. In case of the combined deformation route, the ratio of shear strain to the total equivalent strain was varied. The recrystallized grain size was finer if the combined deformation route was employed instead of the monotonic route under the same amount of equivalent strain at either strain level. The density of high angle grain boundaries that act as nucleation sites for recrystallization was higher in materials deformed by the combined route. The orientation imaging micrographs revealed that the change in deformation route is effective for introducing a larger number of new high angle grain boundaries with relatively low misorientation angle.

Paraxial design of an optical element with variable focal length and fixed position of principal planes.

PubMed

Mikš, Antonín; Novák, Pavel

2018-05-10

In this article, we analyze the problem of the paraxial design of an active optical element with variable focal length, which maintains the positions of its principal planes fixed during the change of its optical power. Such optical elements are important in the process of design of complex optical systems (e.g., zoom systems), where the fixed position of principal planes during the change of optical power is essential for the design process. The proposed solution is based on the generalized membrane tunable-focus fluidic lens with several membrane surfaces.

The Davey-Stewartson Equation on the Half-Plane

NASA Astrophysics Data System (ADS)

Fokas, A. S.

2009-08-01

The Davey-Stewartson (DS) equation is a nonlinear integrable evolution equation in two spatial dimensions. It provides a multidimensional generalisation of the celebrated nonlinear Schrödinger (NLS) equation and it appears in several physical situations. The implementation of the Inverse Scattering Transform (IST) to the solution of the initial-value problem of the NLS was presented in 1972, whereas the analogous problem for the DS equation was solved in 1983. These results are based on the formulation and solution of certain classical problems in complex analysis, namely of a Riemann Hilbert problem (RH) and of either a d-bar or a non-local RH problem respectively. A method for solving the mathematically more complicated but physically more relevant case of boundary-value problems for evolution equations in one spatial dimension, like the NLS, was finally presented in 1997, after interjecting several novel ideas to the panoply of the IST methodology. Here, this method is further extended so that it can be applied to evolution equations in two spatial dimensions, like the DS equation. This novel extension involves several new steps, including the formulation of a d-bar problem for a sectionally non-analytic function, i.e. for a function which has different non-analytic representations in different domains of the complex plane. This, in addition to the computation of a d-bar derivative, also requires the computation of the relevant jumps across the different domains. This latter step has certain similarities (but is more complicated) with the corresponding step for those initial-value problems in two dimensions which can be solved via a non-local RH problem, like KPI.

Strain and in-plane orientation effects on the ferroelectricity of (111)-oriented tetragonal Pb(Zr0.35Ti0.65)O3 thin films prepared by metal organic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kuwabara, Hiroki; Menou, Nicolas; Funakubo, Hiroshi

2007-05-01

The growth and characterization of epitaxial (111)-oriented Pb(Zr0.35Ti0.65)O3 films deposited by metal organic chemical vapor deposition on (100)-oriented silicon substrates [(111)SrRuO3‖(111)Pt ‖(100)yttria-stabilizedzirconia‖(100)Si] are reported. The orientation, microstructure, and electric properties of these films are compared to those of fiber-textured highly (111)-oriented lead zirconate titanate (PZT) films deposited on (111)SrRuO3/(111)Pt/TiOx/SiO2/(100)Si substrates and epitaxial (111)-oriented PZT films deposited on (111)SrRuO3‖(111)SrTiO3 substrates. The ferroelectric properties of these films are not drastically influenced by the in-plane orientation of the film and by the strain state imposed by the underlying substrate. These results support the use of fiber-textured highly (111)-oriented films in highly stable ferroelectric capacitors.

Beneficial defects: exploiting the intrinsic polishing-induced wafer roughness for the catalyst-free growth of Ge in-plane nanowires

PubMed Central

2014-01-01

We outline a metal-free fabrication route of in-plane Ge nanowires on Ge(001) substrates. By positively exploiting the polishing-induced defects of standard-quality commercial Ge(001) wafers, micrometer-length wires are grown by physical vapor deposition in ultra-high-vacuum environment. The shape of the wires can be tailored by the epitaxial strain induced by subsequent Si deposition, determining a progressive transformation of the wires in SiGe faceted quantum dots. This shape transition is described by finite element simulations of continuous elasticity and gives hints on the equilibrium shape of nanocrystals in the presence of tensile epitaxial strain. PACS 81.07.Gf; 68.35.bg; 68.35.bj; 62.23.Eg PMID:25114649

Beneficial defects: exploiting the intrinsic polishing-induced wafer roughness for the catalyst-free growth of Ge in-plane nanowires.

PubMed

Persichetti, Luca; Sgarlata, Anna; Mori, Stefano; Notarianni, Marco; Cherubini, Valeria; Fanfoni, Massimo; Motta, Nunzio; Balzarotti, Adalberto

2014-01-01

We outline a metal-free fabrication route of in-plane Ge nanowires on Ge(001) substrates. By positively exploiting the polishing-induced defects of standard-quality commercial Ge(001) wafers, micrometer-length wires are grown by physical vapor deposition in ultra-high-vacuum environment. The shape of the wires can be tailored by the epitaxial strain induced by subsequent Si deposition, determining a progressive transformation of the wires in SiGe faceted quantum dots. This shape transition is described by finite element simulations of continuous elasticity and gives hints on the equilibrium shape of nanocrystals in the presence of tensile epitaxial strain. 81.07.Gf; 68.35.bg; 68.35.bj; 62.23.Eg.

Near Real-Time Imaging of the Galactic Plane with BATSE

NASA Technical Reports Server (NTRS)

Harmon, B. A.; Zhang, S. N.; Robinson, C. R.; Paciesas, W. S.; Barret, D.; Grindlay, J.; Bloser, P.; Monnelly, C.

1997-01-01

The discovery of new transient or persistent sources in the hard X-ray regime with the BATSE Earth occultation Technique has been limited previously to bright sources of about 200 mCrab or more. While monitoring known source locations is not a problem to a daily limiting sensitivity of about 75 mCrab, the lack of a reliable background model forces us to use more intensive computer techniques to find weak, previously unknown emission from hard X-ray/gamma sources. The combination of Radon transform imaging of the galactic plane in 10 by 10 degree fields and the Harvard/CFA-developed Image Search (CBIS) allows us to straightforwardly search the sky for candidate sources in a +/- 20 degree latitude band along the plane. This procedure has been operating routinely on a weekly basis since spring 1997. We briefly describe the procedure, then concentrate on the performance aspects of the technique and candidate source results from the search.

Transition between free-space Helmholtz equation solutions with plane sources and parabolic wave equation solutions.

PubMed

Mahillo-Isla, R; Gonźalez-Morales, M J; Dehesa-Martínez, C

2011-06-01

The slowly varying envelope approximation is applied to the radiation problems of the Helmholtz equation with a planar single-layer and dipolar sources. The analyses of such problems provide procedures to recover solutions of the Helmholtz equation based on the evaluation of solutions of the parabolic wave equation at a given plane. Furthermore, the conditions that must be fulfilled to apply each procedure are also discussed. The relations to previous work are given as well.

Strain distribution in the lumbar vertebrae under different loading configurations.

PubMed

Cristofolini, Luca; Brandolini, Nicola; Danesi, Valentina; Juszczyk, Mateusz M; Erani, Paolo; Viceconti, Marco

2013-10-01

The stress/strain distribution in the human vertebrae has seldom been measured, and only for a limited number of loading scenarios, at few locations on the bone surface. This in vitro study aimed at measuring how strain varies on the surface of the lumbar vertebral body and how such strain pattern depends on the loading conditions. Eight cadaveric specimens were instrumented with eight triaxial strain gauges each to measure the magnitude and direction of principal strains in the vertebral body. Each vertebra was tested in a three adjacent vertebrae segment fashion. The loading configurations included a compressive force aligned with the vertebral body but also tilted (15°) in each direction in the frontal and sagittal planes, a traction force, and torsion (both directions). Each loading configuration was tested six times on each specimen. The strain magnitude varied significantly between strain measurement locations. The strain distribution varied significantly when different loading conditions were applied (compression vs. torsion vs. traction). The strain distribution when the compressive force was tilted by 15° was also significantly different from the axial compression. Strains were minimal when the compressive force was applied coaxial with the vertebral body, compared with all other loading configurations. Also, strain was significantly more uniform for the axial compression, compared with all other loading configurations. Principal strains were aligned within 19° to the axis of the vertebral body for axial-compression and axial-traction. Conversely, when the applied force was tilted by 15°, the direction of principal strain varied by a much larger angle (15° to 28°). This is the first time, to our knowledge, that the strain distribution in the vertebral body is measured for such a variety of loading configurations and a large number of strain sensors. The present findings suggest that the structure of the vertebral body is optimized to sustain

C1,1 regularity for degenerate elliptic obstacle problems

NASA Astrophysics Data System (ADS)

Daskalopoulos, Panagiota; Feehan, Paul M. N.

2016-03-01

The Heston stochastic volatility process is a degenerate diffusion process where the degeneracy in the diffusion coefficient is proportional to the square root of the distance to the boundary of the half-plane. The generator of this process with killing, called the elliptic Heston operator, is a second-order, degenerate-elliptic partial differential operator, where the degeneracy in the operator symbol is proportional to the distance to the boundary of the half-plane. In mathematical finance, solutions to the obstacle problem for the elliptic Heston operator correspond to value functions for perpetual American-style options on the underlying asset. With the aid of weighted Sobolev spaces and weighted Hölder spaces, we establish the optimal C 1 , 1 regularity (up to the boundary of the half-plane) for solutions to obstacle problems for the elliptic Heston operator when the obstacle functions are sufficiently smooth.

Multiaxial Fatigue Life Prediction Based on Nonlinear Continuum Damage Mechanics and Critical Plane Method

NASA Astrophysics Data System (ADS)

Wu, Z. R.; Li, X.; Fang, L.; Song, Y. D.

2018-04-01

A new multiaxial fatigue life prediction model has been proposed in this paper. The concepts of nonlinear continuum damage mechanics and critical plane criteria were incorporated in the proposed model. The shear strain-based damage control parameter was chosen to account for multiaxial fatigue damage under constant amplitude loading. Fatigue tests were conducted on nickel-based superalloy GH4169 tubular specimens at the temperature of 400 °C under proportional and nonproportional loading. The proposed method was checked against the multiaxial fatigue test data of GH4169. Most of prediction results are within a factor of two scatter band of the test results.

A Collaborative Knowledge Plane for Autonomic Networks

NASA Astrophysics Data System (ADS)

Mbaye, Maïssa; Krief, Francine

Autonomic networking aims to give network components self-managing capabilities. Several autonomic architectures have been proposed. Each of these architectures includes sort of a knowledge plane which is very important to mimic an autonomic behavior. Knowledge plane has a central role for self-functions by providing suitable knowledge to equipment and needs to learn new strategies for more accuracy.However, defining knowledge plane's architecture is still a challenge for researchers. Specially, defining the way cognitive supports interact each other in knowledge plane and implementing them. Decision making process depends on these interactions between reasoning and learning parts of knowledge plane. In this paper we propose a knowledge plane's architecture based on machine learning (inductive logic programming) paradigm and situated view to deal with distributed environment. This architecture is focused on two self-functions that include all other self-functions: self-adaptation and self-organization. Study cases are given and implemented.

A mixed parallel strategy for the solution of coupled multi-scale problems at finite strains