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Search Results: 1 - 10 of 2774 matches for " Strain "
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Synthesis and Characterization of Ultrafine Grained 304 Stainless Steel through Machining  [PDF]
V. Senthilkumar, K. Lenin
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2011, DOI: 10.4236/jmmce.2011.105034
Abstract: The microstructures of 304 stainless steel chips created by plane strain machining at ambient temperature have been analyzed using scanning electron microscopy (SEM) and the crystallite size of the ultrafine chips were analyzed using X-Ray Diffraction Analysis. The strain imposed in the chips was varied by changing the tool rake angle. An attempt is made in the present investigation to correlate the plastic strain, strain rate with the grain size of the stainless steel.
A Novel Coupling between the Electron Structure and Properties of Perovskite Transition Metal Oxides  [PDF]
Ghous Narejo, Warren F. Perger
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.49178
Abstract:

The ab-initio computational techniques are employed to extract the coupling between the electronic structure and magnetic properties for a wide variety of transition metal oxides. Optimized crystalline structures are computed by employing Hartree Fock (HF) and Density Functional Theory (DFT) techniques. The hydrostatic pressure is employed upon the optimized cubic crystalline structures of BaScO3, BaTiO3, BaVO3, BaCrO3, BaMnO3 and BaFeO3 to extract the coupling between the electronic structures and magnetic properties originating due to electron spin polarizations.

Myocardial Strain and Strain Rate Imaging: Comparison between Doppler Derived Strain Imaging and Speckle Tracking Echocardiography
Anita Sadeghpour
Archives of Cardiovascular Imaging , 2013,
Abstract: Regional myocardial function has been traditionally assessed by visual estimation (1). Echocardiographic strain imaging which is known as deformation imaging, has been emerged as a quantitative technique to accurately estimate regional myocardial function and contractility. Currently, strain imaging has been regarded as a research tool in the most echocardiography laboratories. However, in recent years, strain imaging has gain momentum in daily clinical practice (2). The following two techniques have dominated the research arena of echocardiography: (1) Doppler based tissue velocity measurements, frequently referred to tissue Doppler or myocardial Doppler, and (2) speckle tracking on the basis of displacement measurements (3). Over the past two decades, Tissue Doppler Imaging (TDI) and Doppler –derived strain (S) and strain rate (SR) imaging were introduced to quantify regional myocardial function. However, Doppler–derived strain variables faced criticisms, with regard to the angle dependency, noise interference, and substantial intraobserver and interobserver variability. The angle dependency is the major weakness of Doppler based methodology; however, it has the advantage of online measurements of velocities and time intervals with excellent temporal resolution, which is essential for the assessment of ischemia (4). Speckle-tracking echocardiography (STE) or Non Doppler 2D strain echocardiography is a relatively new, largely angle-independent technique that analyzes motion by tracking natural acoustic reflections and interference patterns within an ultrasonic window. The image-processing algorithm tracks elements with approximately 20 to 40 pixels containing stable patterns and are described as ‘‘speckles’’ or ‘‘fingerprints’’. The speckles seen in grayscale B-mode (2D) images are tracked consecutively frame to frame (5, 6). Assessment of 2D strain by STE is a semiautomatic method that requires definition of the myocardium. Consequently suboptimal tracking of the endocardial border may be a problem with STE. Assessment of 2D strain by STE has been applied to both ventricles and atria. The articles published in this issue of the journal demonstrate the value of Strain and strain rate imaging in detecting the subclinical atrial and ventricular dysfunction, besides reporting the normal value of right atrium deformation indices. In all, first three articles of this journal, measurement of ventricular and atrial deformation indices have been considered as a feasible and reproducible technique. Assessment of atrial deformation profiles using Doppler-derived
An ultrasound elastography method for examining the anterior cruciate ligament  [PDF]
Amy L. Cochran, Yingxin Gao
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.58A2004
Abstract:

We introduce an ultrasound elastography method for examining the ACL. It consisted of imaging the distal ACL while applying a drawer test and analyzing the resulting displacement and strain maps, where a map refers to how a variable is distributed spatially throughout an image. Our method was applied to healthy knees of cadaveric sheep to determine whether 1) our method can consistently generate displacements and strain maps in healthy ACLs; 2) displacement and strain maps are repeatable; and 3) healthy ACLs experience similar maps. We found that our method could consistently provide displacements and strain maps of the distal ACL region. Moreover, these ACLs experienced displacement and strain maps that were positively-correlated between trials, knees, and specimens. This correlation was statistically significant between pairs of trials and between left and right knees (p < 0.05). These results suggest that the maps are indeed repeatable and similar for healthy ACLs.

Current State of Strain in the Central Cascadia Margin Derived from Changes in Distance between GPS Stations  [PDF]
Kenneth M. Cruikshank, Curt D. Peterson
Open Journal of Earthquake Research (OJER) , 2015, DOI: 10.4236/ojer.2015.41003
Abstract: Using continuously operating Global Positioning Stations in the Pacific Northwest of the United States, over 100 station-station baseline length changes were determined along seven West-East transects, two North-South transects and in three localized areas to determine both the average annual strains over the past several years, and the variation in strain over the central Cascadia convergent margin. The North-South transects (composed of multiple baselines) show shortening. Along West-East transects some baselines show shortening and others extension. The direction of the principle strains calculated for two areas 100 km from the deformation front are close to per-pendicular to the deformation front. The North-South strains are 10?8 a?1, which is an order-of-magnitude less than the West-East strains (10?7 a?1). Along several West-East transects, the magnitude of the strain increases away from the deformation front. All West-East transects showed a change in strain 250 km inland from deformation front.
Assessment of the Left Ventricle Wall Motion Using Tagged Magnetic Resonance Imaging Data (tMRI)  [PDF]
Mohammed D. Alenezy
World Journal of Cardiovascular Surgery (WJCS) , 2015, DOI: 10.4236/wjcs.2015.511018
Abstract: In this paper, the Radial Strain (RS) and Strain Rate (SR) was calculated using tagged MRI (tMRI) data. Using tagged magnetic resonance imaging (tMRI), the left ventricle short axis of five healthy adults (three men and two women) and four healthy male rats was imaged during diastolic and systolic phases on the mid-ventricle level. The RS and radial SR of the left ventricle were calculated at the mid-ventricular level of the cardiac cycle. The peak RS for rat and human heart was found to be 46.8 ± 0.68 and 40.7 ± 1.44, respectively, and it occurred at 40% of the cardiac cycle for both human and rat hearts. The peak systolic and diastolic radial SR for human heart was 1.10 ± 0.08 s- 1 and - 1.78 ± 0.02 s- 1, respectively, while it was 4.25 ± 0.02 s- 1 and - 5.16 ± 0.23 s- 1, respectively for rat heart. The results show that tMRI data can be used to characterize the cardiac function during systolic and diastolic phases of the cardiac cycle, and as a result, it can be used to evaluate the cardiac motion by calculating its RS and radial SR at different locations of the cardiac wall during both diastolic and systolic phases. This study also approves the validity of the tagged MRI data to accurately describe the radial cardiac motion.
Late Stage Interseismic Strain Interval, Cascadia Subduction Zone Margin, USA and Canada  [PDF]
Kenneth M. Cruikshank, Curt D. Peterson
Open Journal of Earthquake Research (OJER) , 2017, DOI: 10.4236/ojer.2017.61001
Abstract: Modern horizontal strain (2006-2016) measured along 56 new and 108 previously published GPS station baselines are used to establish the length (800 km) and width (300 - 400 km) of the central Cascadia convergent margin seismogenic structure. Across-margin (west-east) annual rates of shortening range from 109 a1 at the eastern (landward) limit of the central Cascadia seismogenic structure to 107 a1 along the western onshore portion of the interplate zone. Relatively high shortening strain rates (108 a1 to 107 a1) are also measured in western transects from the northern (Explorer plate) and southern (Gorda plate) segments of the convergent margin, demonstrating that the full length of the margin (1300 km length) is currently capable of sustaining and/or initiating a major great earthquake. Vertical GPS velocities are averaged over the last decade at 321 stations to map patterns of uplift (0 - 5 mm yr1) and subsidence (0 - 9 mm yr1) relative to the study area mean. Along-margin belts of relative uplift and subsidence, respectively, are approximately associated with Coast Ranges and the Cascade volcanic arc. However, the vertical velocity data are locally heterogeneous, demonstrating patchy “anomalies” within the larger along-margin belts. A large coastal subsidence anomaly occurs in southwest Washington where the modern short-term trend is reversed from the long-term (~200 yr) tidal marsh record of coastal uplift since the last co-seismic subsidence event (AD1700). The modern vertical displacements represent a late stage of the current inter-seismic interval. If the horizontal strain is considered largely or fully elastic, extrapolating the modern strain rates over the last 100 years show the accumulated strains would be similar in magnitude to the observed co-seismic strains resulting from the Tōhoku, Japan, Mw 9.0 earthquake in 2011. We believe that the central Cascadia seismogenic structure has accumulated
One Dimensional Modeling of the Shape Memory Effect  [PDF]
Belkacem Meddour, Hamma Zedira, Hamid Djebaili
Modeling and Numerical Simulation of Material Science (MNSMS) , 2013, DOI: 10.4236/mnsms.2013.34017
Abstract:

This paper aims to build a constitutive model intended to describe the thermomechanical behavior of shape memory alloys. This behavior presents many facets, among them we have considered the simple way of shape memory, which is one of most important properties of shape memory alloys. Because of numerous stages of this effect, the subject was divided into three independent parts. For each part, we built the corresponding thermodynamic potential and we deduced the constitutive equations. To make this model workable, we have developed an algorithm. The simulation was performed using the NiTi as shape memory alloy.

The Method Exploration for Measuring the Strain of the Intervertebral Disc  [PDF]
Qinghua Xue, Weiqiang Liu, Zhenhua Liao
Modern Instrumentation (MI) , 2013, DOI: 10.4236/mi.2013.22004
Abstract:

Many researches point out that intervertebral pressure and transformation are key parameters for evaluating intervertebral disc degeneration. Aiming at avoiding the damage caused by direct and indirect measuring methods, this research proposes a cylindroid hypothesis and measuring method, which can monitor the strain condition of the intervertebral disc in vivo and real-time without being damaged.

Linear Algebra Provides a Basis for Elasticity without Stress or Strain  [PDF]
H. H. Hardy
Soft (Soft) , 2015, DOI: 10.4236/soft.2015.43003
Abstract: Linear algebra provides insights into the description of elasticity without stress or strain. Classical descriptions of elasticity usually begin with defining stress and strain and the constitutive equations of the material that relate these to each other. Elasticity without stress or strain begins with the positions of the points and the energy of deformation. The energy of deformation as a function of the positions of the points within the material provides the material properties for the model. A discrete or continuous model of the deformation can be constructed by minimizing the total energy of deformation. As presented, this approach is limited to hyper-elastic materials, but is appropriate for infinitesimal and finite deformations, isotropic and anisotropic materials, as well as quasi-static and dynamic responses.
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