Crack initiation under generalized plane strain conditions
Shum, D.K.M.; Merkle, J.G.
1991-01-01
A method for estimating the decrease in crack-initiation toughness, from a reference plane strain value, due to positive straining along the crack front of a circumferential flaw in a reactor pressure vessel is presented in this study. This method relates crack initiation under generalized plane strain conditions with material failure at points within a distance of a few crack-tip-opening displacements ahead of a crack front, and involves the formulation of a micromechanical crack-initiation model. While this study is intended to address concerns regarding the effects of positive out-of- plane straining on ductile crack initiation, the approach adopted in this work can be extended in a straightforward fashion to examine conditions of macroscopic cleavage crack initiation. Provided single- parameter dominance of near-tip fields exists in the flawed structure, results from this study could be used to examine the appropriateness of applying plane strain fracture toughness to the evaluation of circumferential flaws, in particular to those in ring-forged vessels which have no longitudinal welds. In addition, results from this study could also be applied toward the analysis of the effects of thermal streaming on the fracture resistance of circumferentially oriented flaws in a pressure vessel. 37 refs., 8 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Cherukuri, Harish P.; Ulysse, Patrick; Smelser, Ronald E.; Subramanian, Kannan; Kotaru, Deepti
2010-06-01
Rapid quenching of aluminum extrusions often results in residual stresses and distortion. The out-of-plane normal component of the residual stress is typically very large and results in undesirable bending (bowing) of the extruded shape. Three-dimensional models to predict the residual stresses and bending of extruded thin-walled shapes are difficult to implement since the wall-thicknesses are often very small compared with the axial dimensions. In this paper, a generalized plane-strain model is presented to predict the residual stresses and distortion. For illusrative purposes of the model, a Z-shaped extrusion is chosen. The model predicts the bowing of the extruded shape along with the in-plane and out-of-plane stress components. An internal state-variable model is used for the constitutive description. The residual stresses and distortion are studied for cold and warm water quenching and three different cases of spray quenching. The numerical results indicate that cold water quenching and the two spray quenching cases with the higher discharge rates lead to significantly larger residual stresses compared to the remaining two cases. For each case, the out-of-plane bows of the extruded shapes are also shown to be significant.
NASA Astrophysics Data System (ADS)
Begley, Matthew R.; Creton, Costantino; McMeeking, Robert M.
2015-11-01
A general asymptotic plane strain crack tip stress field is constructed for linear versions of neo-Hookean materials, which spans a wide variety of special cases including incompressible Mooney elastomers, the compressible Blatz-Ko elastomer, several cases of the Ogden constitutive law and a new result for a compressible linear neo-Hookean material. The nominal stress field has dominant terms that have a square root singularity with respect to the distance of material points from the crack tip in the undeformed reference configuration. At second order, there is a uniform tension parallel to the crack. The associated displacement field in plane strain at leading order has dependence proportional to the square root of the same coordinate. The relationship between the amplitude of the crack tip singularity (a stress intensity factor) and the plane strain energy release rate is outlined for the general linear material, with simplified relationships presented for notable special cases.
NASA Technical Reports Server (NTRS)
Buczek, M. B.; Gregory, M. A.; Herakovich, C. T.
1983-01-01
CLFE2D is a two dimensional generalized plane strain finite element code, using a linear, four node, general quadrilateral, isoparametric element. The program is developed to calculate the displacements, strains, stresses, and strain energy densities in a finite width composite laminate. CLFE2D offers any combination of the following load types: nodal displacements, nodal forces, uniform normal strain, or hygrothermal. The program allows the user to input one set of three dimensional orthotropic material properties. The user can then specify the angle of material principal orientation for each element in the mesh. Output includes displacements, stresses, strains and strain densities at points selected by the user. An option is also available to plot the underformed and deformed finite element meshes.
Turbulent Plane Wakes Subjected to Successive Strains
NASA Technical Reports Server (NTRS)
Rogers, Michael M.
2003-01-01
Six direct numerical simulations of turbulent time-evolving strained plane wakes have been examined to investigate the response of a wake to successive irrotational plane strains of opposite sign. The orientation of the applied strain field has been selected so that the flow is the time-developing analogue of a spatially developing wake evolving in the presence of either a favourable or an adverse streamwise pressure gradient. The magnitude of the applied strain rate a is constant in time t until the total strain e(sup at) reaches about four. At this point, a new simulation is begun with the sign of the applied strain being reversed (the original simulation is continued as well). When the total strain is reduced back to its original value of one, yet another simulation is begun with the sign of the strain being reversed again back to its original sign. This process is done for both initially "favourable" and initially "adverse" strains, providing simulations for each of these strain types from three different initial conditions. The evolution of the wake mean velocity deficit and width is found to be very similar for all the adversely strained cases, with both measures rapidly achieving exponential growth at the rate associated with the cross-stream expansive strain e(sup at). In the "favourably" strained cases, the wake widths approach a constant and the velocity deficits ultimately decay rapidly as e(sup -2at). Although all three of these cases do exhibit the same asymptotic exponential behaviour, the time required to achieve this is longer for the cases that have been previously adversely strained (by at approx. equals 1). These simulations confirm the generality of the conclusions drawn in Rogers (2002) regarding the response of plane wakes to strain. The evolution of strained wakes is not consistent with the predictions of classical self-similar analysis; a more general equilibrium similarity solution is required to describe the results. At least for the cases
The Evolution of Plane Wakes Subjected to Irrotational Strains
NASA Technical Reports Server (NTRS)
Rogers, M. R.; Rai, Man Mohan (Technical Monitor)
1995-01-01
Three direct numerical simulations of time-evolving turbulent plane wakes developing in the presence of various irrotational plane strains have been generated. A pseudospectral numerical method with up to 26 million modes is used to solve the equations in a reference frame moving with the irrotational strain. The initial condition for each simulation is taken from a previous turbulent self-similar plane wake direct numerical simulation at a velocity deficit Reynolds number, Re, of about 2000. Three different plane strains (of the same magnitude) are imposed. In the first two simulations the strain is in a plane normal to the streamwise wake direction (the two cases having strain of opposite sign); in the third the wake is compressed in the streamwise direction and stretched in the inhomogeneous cross-stream direction. The two flows that are stretched in the cross-stream direction experience an exponential increase of Re; flow visualization indicates many small-scale vortices with little or no organized large-scale structure. In the flow that is compressed in the cross-stream direction Re decays exponentially and the layer appears to be relaminarizing. The evolution of several turbulence statistics in each of these flows is examined.
Analysis of crack closure under plane strain conditions
NASA Technical Reports Server (NTRS)
Fleck, Norman A.; Newman, James C., Jr.
1988-01-01
The phenomenon of plasticity-induced crack closure is associated with the development of residual material on the flanks of an advancing fatigue crack. While it is easy to see that this residual material can come from the side faces of a specimen under plane stress conditions, it is difficult to discover the origin of this extra volume of material on the crack flanks when it is assumed that plane deformations occur and plastic flow is incompressible. The purpose of this paper is to determine whether plasticity-induced fatigue crack closure occurs in an elastic-perfectly plastic body under plane strain conditions.
Analysis of crack closure under plane strain conditions
NASA Technical Reports Server (NTRS)
Fleck, N. A.; Newman, J. C.
1986-01-01
The phenomenon of plasticity-induced crack closure is associated with the development of residual material on the flanks of an advancing fatigue crack. While it is easy to see that this residual material can come from the side faces of a specimen under plane stress conditions, it is difficult to discover the origin of this extra volume of material on the crack flanks when it is assumed that plane deformations occur and plastic flow is incompressible. The purpose of this paper is to determine whether plasticity-induced fatigue crack closure occurs in an elastic-perfectly plastic body under plane strain conditions.
Ultrafast vascular strain compounding using plane wave transmission.
Hansen, H H G; Saris, A E C M; Vaka, N R; Nillesen, M M; de Korte, C L
2014-03-01
Deformations of the atherosclerotic vascular wall induced by the pulsating blood can be estimated using ultrasound strain imaging. Because these deformations indirectly provide information on mechanical plaque composition, strain imaging is a promising technique for differentiating between stable and vulnerable atherosclerotic plaques. This paper first explains 1-D radial strain estimation as applied intravascularly in coronary arteries. Next, recent methods for noninvasive vascular strain estimation in a transverse imaging plane are discussed. Finally, a compounding technique that our group recently developed is explained. This technique combines motion estimates of subsequently acquired focused ultrasound images obtained at various insonification angles. However, because the artery moves and deforms during the multi-angle acquisition, errors are introduced when compounding. Recent advances in computational power have enabled plane wave ultrasound acquisition, which allows 100 times faster image acquisition and thus might resolve the motion artifacts. In this paper the performance of strain imaging using plane wave compounding is investigated using simulations of an artery with a vulnerable plaque and experimental data of a two-layered vessel phantom. The results show that plane wave compounding outperforms 0° focused strain imaging. For the simulations, the root mean squared error reduced by 66% and 50% for radial and circumferential strain, respectively. For the experiments, the elastographic signal-to-noise and contrast-to-noise ratio (SNR(e) and CNR(e)) increased with 2.1 dB and 3.7 dB radially, and 5.6 dB and 16.2dB circumferentially. Because of the high frame rate, the plane wave compounding technique can even be further optimized and extended to 3D in future. PMID:24484646
The plane strain tests in the PROMETRA program
NASA Astrophysics Data System (ADS)
Cazalis, B.; Desquines, J.; Carassou, S.; Le Jolu, T.; Bernaudat, C.
2016-04-01
A fuel cladding mechanical test, performed under conditions of plane strain deformation in the transverse direction of tube axis, was originally developed at Pennsylvania State University. It was decided to implement this original test within the PROMETRA program using the same experimental procedure and its optimization for a ring mechanical testing on plane strain conditions (PST tests) in hot cells laboratory. This paper presents a detailed description and an interpretation of the Plane Strain Tensile (PST) tests performed in the framework of the PROMETRA program on fresh and irradiated claddings. At first, the context of the PST tests is situated and the specificities of these tests implemented at CEA are justified. Indeed, a significant adjustment of the original experimental procedure is carried out in order to test the irradiated fuel cladding in the best possible conditions. Then, the tests results on fresh Zircaloy-4 and on irradiated Zircaloy-4, M5™ and ZIRLO® specimens are gathered. The main analyses in support of these tests, such as metallographies, fractographic examinations and finite element simulations are detailed. Finally, a synthesis of the interpretation of the tests is proposed. The PST test seems only representative of plane strain fracture conditions when the test material is very ductile (fresh or high temperature or low hydride material like M5TM). However, it provides a relevant representation of the RIA rupture initiation which is observed in irradiated cladding resulting from hydride rim damage due to the strong irradiation of a fuel rod.
The influence of strain rate and hydrogen on the plane-strain ductility of Zircaloy cladding
Link, T.M.; Motta, A.T.; Koss, D.A.
1998-03-01
The authors studied the ductility of unirradiated Zircaloy-4 cladding under loading conditions prototypical of those found in reactivity-initiated accidents (RIA), i.e.: near plane-strain deformation in the hoop direction (transverse to the cladding axis) at room temperature and 300 C and high strain rates. To conduct these studies, they developed a specimen configuration in which near plane-strain deformation is achieved in the gage section, and a testing methodology that allows one to determine both the limit strain at the onset of localized necking and the fracture strain. The experiments indicate that there is little effect of strain rate (10{sup {minus}3} to 10{sup 2} s{sup {minus}1}) on the ductility of unhydrided Zircaloy tubing deformed under near plane-strain conditions at either room temperature or 300 C. Preliminary experiments on cladding containing 190 ppm hydrogen show only a small loss of fracture strain but no clear effect on limit strain. The experiments also indicate that there is a significant loss of Zircaloy ductility when surface flaws are present in the form of thickness imperfections.
Shear Band Formation in Plane Strain Experiments of Sand
NASA Technical Reports Server (NTRS)
Alshibli, Khalid A.; Sture, Stein
2000-01-01
A series of biaxial (plane strain) experiments were conducted on three sands under low (15 kPa) and high (100 kPa) confining pressure conditions to investigate the effects of specimen density, confining pressure, and sand grain size and shape on the constitutive and stability behavior of granular materials. The three sands used in the experiments were fine-, medium-, and coarse-grained uniform silica sands with rounded, subangular, and angular grains, respectively. Specimen deformation was readily monitored and analyzed with the help of a grid pattern imprinted on the latex membrane. The overall stress-strain behavior is strongly dependent on the specimen density, confining pressure, sand grain texture, and the resulting failure mode(s). That became evident in different degrees of softening responses at various axial strains. The relationship between the constitutive behavior and the specimens' modes of instability is presented. The failure in all specimens was characterized by two distinct and opposite shear bands. It was found that the measured dilatancy angles increase as the sand grains' angularities and sizes increase. The measured shear band inclination angles are also presented and compared with classical Coulomb and Roscoe solutions.
Nobrega, B.N.
1984-01-01
The segmented expanding mandrel test (SEMT) method is generally regarded as a good laboratory simulator of pellet-cladding interactions (PCI) in LWR fuel rods. Yet it does not reproduce the low strain failures in Zircaloy cladding typical of PCI-failed fuel elements and commonly observed in other types of laboratory specimens. This investigation addressed this apparent inconsistency. Iodine-stress corrosion cracking (I-SCC) of cold worked, unirradiated Zircaloy-2 cladding was induced in three different types of tubing specimens (known as regular, thin-wall, and chamfered) in a modified SEMT apparatus designed to test mechanical conditions that could lead to slow strain failures. Only the chamfered sample, which has been shown to be subjected to more nearly plane strain conditions than either of the other two specimen types, failed consistently at low (0.8%) total diametral strains in good agreement with in-reactor failure data. Such conditions were numerically and experimentally quantified by means of finite element calculational models and local strain measurements. The numerical analyses and strain measurements provide valuable insight into the PCI simulating power of the segmented expanding mandrel test and its experimental limitations. Failure-strain results for chamfered barrier claddings were obtained and compared with available literature data. The improved I-SCC resistance of this type of cladding was confirmed but the failure strains were significantly lower than reported for regular barrier tubes.
Strained layer superlattice focal plane array having a planar structure
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.
The plane strain shear fracture of the advanced high strength steels
Sun, Li
2013-12-16
The “shear fracture” which occurs at the high-curvature die radii in the sheet metal forming has been reported to remarkably limit the application of the advanced high strength steels (AHSS) in the automobile industry. However, this unusual fracture behavior generally cannot be predicted by the traditional forming limit diagram (FLD). In this research, a new experimental system was developed in order to simulate the shear fracture, especially at the plane strain state which is the most common state in the auto-industry and difficult to achieve in the lab due to sample size. Furthermore, the system has the capability to operate in a strain rate range from quasi-static state to the industrial forming state. One kinds of AHSS, Quenching-Partitioning (QP) steels have been performed in this test and the results show that the limiting fracture strain is related to the bending ratio and strain rate. The experimental data support that deformation-induced heating is an important cause of “shear fracture” phenomena for AHSS: a deformation-induced quasi-heating caused by smaller bending ratio and high strain rate produce a smaller limiting plane strain and lead a “shear fracture” in the component.
Stress-Strain Behaviour of a Micacious Sand in Plane Strain Condition
NASA Astrophysics Data System (ADS)
Yasin, S. J. M.; Tatsuoka, F.
Unusual failures of river banks and river training structures have been reported during construction and shortly after commissioning of several structures along Jamuna river in Bangladesh that raised widespread questions regarding the design principles and parameters used. The natural sand deposit along the Jamuna river contain relatively larger amount of mica than most other natural soils. Jamuna sand needs to be studied under wide range of loading conditions (such as triaxial, plane strain, simple shear etc.), drainage and density conditions (i.e. drained / undrained, dry / saturated, dense/loose state etc.) to reveal the extent of variation of its strength and deformation characteristics in order to facilitate understanding of the mechanism of past failures of structures and suggest rational design parameters. A series of plane strain compression tests were performed on Jamuna sand. It is observed that Jamuna sand is highly contractive under shear and more anisotropic than other non-mica sands.
Generalized Uncertainty Relations in the Non-commutative Plane
NASA Astrophysics Data System (ADS)
Chung, Won Sang
2015-09-01
In this paper we study two-dimensional noncommutative quantum mechanics (NCQM) with the generalized uncertainty relations . We find the new NCQM algebra from the generalized uncertainty relations. We construct a operator commuting with and discuss two possibilities; One is the case that also commutes with and another is the case that does not commute with . For both case we consider a motion of a charged particle in a magnetic field with a harmonic oscillator potential in the noncommutative plane.
A numerical method for determining the strain rate intensity factor under plane strain conditions
NASA Astrophysics Data System (ADS)
Alexandrov, S.; Kuo, C.-Y.; Jeng, Y.-R.
2016-07-01
Using the classical model of rigid perfectly plastic solids, the strain rate intensity factor has been previously introduced as the coefficient of the leading singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. Since then, many strain rate intensity factors have been determined by means of analytical and semi-analytical solutions. However, no attempt has been made to develop a numerical method for calculating the strain rate intensity factor. This paper presents such a method for planar flow. The method is based on the theory of characteristics. First, the strain rate intensity factor is derived in characteristic coordinates. Then, a standard numerical slip-line technique is supplemented with a procedure to calculate the strain rate intensity factor. The distribution of the strain rate intensity factor along the friction surface in compression of a layer between two parallel plates is determined. A high accuracy of this numerical solution for the strain rate intensity factor is confirmed by comparison with an analytic solution. It is shown that the distribution of the strain rate intensity factor is in general discontinuous.
Comparison of experiment and theory for elastic-plastic plane strain crack growth
Hermann, L; Rice, J R
1980-02-01
Recent theoretical results on elastic-plastic plane strain crack growth, and experimental results for crack growth in a 4140 steel in terms of the theoretical concepts are reviewed. The theory is based on a recent asymptotic analysis of crack surface opening and strain distributions at a quasi-statically advancing crack tip in an ideally-plastic solid. The analysis is incomplete in that some of the parameters which appear in it are known only approximately, especially at large scale yielding. Nevertheless, it suffices to derive a relation between the imposed loading and amount of crack growth, prior to general yielding, based on the assumption that a geometrically similar near-tip crack profile is maintained during growth. The resulting predictions for the variation of J with crack growth are found to fit well to the experimental results obtained on deeply cracked compact specimens.
NASA Astrophysics Data System (ADS)
Thongnum, Anusit; Pinsook, Udomsilp
2015-03-01
Anisotropic transport properties of a two-dimensional electron gas in nonpolar m-plane AlN/GaN heterostructures with the interface roughness coupled anisotropic in-plane strain scattering were investigated theoretically using a path-integral framework. The scattering potential was composed of the interface roughness and the effective field from the electron charge and the net piezoelectric polarization. We showed that the anisotropic biaxial strains generate only the net piezoelectric polarization along the [0 0 0 1]-direction and cause anisotropy in electron mobility with a magnitude lower than the ≤ft[11\\bar{2}0\\right] -direction. We also showed that the anisotropy in electron mobility reduced with increasing electron density. Moreover, the anisotropic electron mobility disappeared when the anisotropic in-plane strain scattering was removed, and the relation for pure interface roughness scattering was reestablished. This formulation with existing roughness parameters gave a good description for the experimental results of polar c-plane AlN/GaN heterostructures.
A semi-implicit finite strain shell algorithm using in-plane strains based on least-squares
NASA Astrophysics Data System (ADS)
Areias, P.; Rabczuk, T.; de Sá, J. César; Natal Jorge, R.
2015-04-01
The use of a semi-implicit algorithm at the constitutive level allows a robust and concise implementation of low-order effective shell elements. We perform a semi-implicit integration in the stress update algorithm for finite strain plasticity: rotation terms (highly nonlinear trigonometric functions) are integrated explicitly and correspond to a change in the (in this case evolving) reference configuration and relative Green-Lagrange strains (quadratic) are used to account for change in the equilibrium configuration implicitly. We parametrize both reference and equilibrium configurations, in contrast with the so-called objective stress integration algorithms which use a common configuration. A finite strain quadrilateral element with least-squares assumed in-plane shear strains (in curvilinear coordinates) and classical transverse shear assumed strains is introduced. It is an alternative to enhanced-assumed-strain (EAS) formulations and, contrary to this, produces an element satisfying ab-initio the Patch test. No additional degrees-of-freedom are present, contrasting with EAS. Least-squares fit allows the derivation of invariant finite strain elements which are both in-plane and out-of-plane shear-locking free and amenable to standardization in commercial codes. Two thickness parameters per node are adopted to reproduce the Poisson effect in bending. Metric components are fully deduced and exact linearization of the shell element is performed. Both isotropic and anisotropic behavior is presented in elasto-plastic and hyperelastic examples.
Texture development and hardening characteristics of steel sheets under plane-strain compression
Friedman, P.A.; Liao, K.C.; Pan, J.; Barlat, F.
1999-04-01
Crystallographic texture development and hardening characteristics of a hot-rolled, low-carbon steel sheet due to cold rolling were investigated by idealizing the cold rolling process as plane-strain compression. The starting anisotropy of the test material was characterized by examination of the grain structure by optical microscopy and the preferred crystal orientation distribution by x-ray diffraction. Various heat treatments were used in an effort to remove the initial deformation texture resulting from hot rolling. The plastic anisotropy of the starting material was investigated with tensile tests on samples with the tensile axis parallel, 45{degree}, and perpendicular to the rolling direction. The grain structure after plane-strain compression was studied by optical microscopy, and the new deformation texture was characterized by x-ray diffraction pole figures. These figures are compared with the theoretical pole figures produced from a Taylor-like polycrystal model based on a pencil-glide slip system. The uniaxial tensile stress-strain curve and the plane-strain, compressive stress-strain curve of the sheet were used to calibrate the material parameters in the model. The experimental pole figures were consistent with the findings in the theoretical study. The experimental and theoretical results suggest that the initial texture due to hot rolling was insignificant as compared with the texture induced by large strains under plane-strain compression.
Strain-mediated control of orbital ordering planes in heteroepitaxial lanthanum manganite thin films
NASA Astrophysics Data System (ADS)
Kim, Yong-Jin; Lee, Jin Hong; Koo, Tae Yeong; Yang, Chan-Ho
Strain engineering which controls the misfit strain of heteroepitaxial thin films leads to distinctive physical properties in contrast to the intrinsic properties of unstrained bulk materials Perovskite LaMnO3 (LMO) has attracted considerable attention due to strong coupling among the lattice, charge, spin and orbital degrees of freedom. Bulk LMO is known to be an A-type antiferromagnetic (TN~140 K) Mott insulator, and its orbital ordering plane is established due to cooperative Jahn-Teller distortion below ~750 K. Previous studies have focused on the orbital ordering planes of the bulk LMO but not researched on correlation between orbital planes and misfit stain. To figure out the strain dependence of orbital ordering planes, we have grown LMO thin films on four different substrates, i . e . , DyScO3(110), GaScO3(110), SrTiO3(001), and LSAT(001), using the pulsed laser deposition technique. The films have been characterized by atomic force microscopy and x-ray diffraction. We have performed resonant x-ray scattering to identify orbital ordering plane on each film. We have found that orbital ordering planes can be modulated depending on the misfit strain.
NASA Astrophysics Data System (ADS)
Zhang, Siyuan; Cui, Ying; Griffiths, James T.; Fu, Wai Y.; Freysoldt, Christoph; Neugebauer, Jörg; Humphreys, Colin J.; Oliver, Rachel A.
2015-12-01
I nxG a1 -xN structures epitaxially grown on a -plane or m -plane GaN exhibit in-plane optical polarization. Linear elasticity theory treats the two planes equivalently and is hence unable to explain the experimentally observed higher degree of linear polarization for m -plane than a -plane I nxG a1 -xN . Using density functional theory, we study the response of I nxG a1 -xN random alloys to finite biaxial strains on both nonpolar planes. The calculated m -plane I nxG a1 -xN valence band splitting is larger than that of the a plane, due to a greater degree of structural relaxation in a -plane I nxG a1 -xN . We provide a parametrization of the valence band splitting of I nxG a1 -xN strained to a -plane and m -plane GaN for In compositions between 0 and 0.5, which agrees with experimental measurements and qualitatively explains the experimentally observed difference between a -plane and m -plane polarization.
Tunable biaxial in-plane compressive strain in a Si nanomembrane transferred on a polyimide film
Kim, Munho; Mi, Hongyi; Cho, Minkyu; Seo, Jung-Hun; Ma, Zhenqiang; Zhou, Weidong; Gong, Shaoqin
2015-05-25
A method of creating tunable and programmable biaxial compressive strain in silicon nanomembranes (Si NMs) transferred onto a Kapton{sup ®} HN polyimide film has been demonstrated. The programmable biaxial compressive strain (up to 0.54%) was generated utilizing a unique thermal property exhibited by the Kapton HN film, namely, it shrinks from its original size when exposed to elevated temperatures. The correlation between the strain and the annealing temperature was carefully investigated using Raman spectroscopy and high resolution X-ray diffraction. It was found that various amounts of compressive strains can be obtained by controlling the thermal annealing temperatures. In addition, a numerical model was used to evaluate the strain distribution in the Si NM. This technique provides a viable approach to forming in-plane compressive strain in NMs and offers a practical platform for further studies in strain engineering.
Tunable biaxial in-plane compressive strain in a Si nanomembrane transferred on a polyimide film
NASA Astrophysics Data System (ADS)
Kim, Munho; Mi, Hongyi; Cho, Minkyu; Seo, Jung-Hun; Zhou, Weidong; Gong, Shaoqin; Ma, Zhenqiang
2015-05-01
A method of creating tunable and programmable biaxial compressive strain in silicon nanomembranes (Si NMs) transferred onto a Kapton® HN polyimide film has been demonstrated. The programmable biaxial compressive strain (up to 0.54%) was generated utilizing a unique thermal property exhibited by the Kapton HN film, namely, it shrinks from its original size when exposed to elevated temperatures. The correlation between the strain and the annealing temperature was carefully investigated using Raman spectroscopy and high resolution X-ray diffraction. It was found that various amounts of compressive strains can be obtained by controlling the thermal annealing temperatures. In addition, a numerical model was used to evaluate the strain distribution in the Si NM. This technique provides a viable approach to forming in-plane compressive strain in NMs and offers a practical platform for further studies in strain engineering.
A New Look at Self-Similarity in Strained Plane Wakes. 1.3
NASA Technical Reports Server (NTRS)
Rogers, Michael M.; Mansour, Nagi N. (Technical Monitor)
2001-01-01
In early experiments, A. J. Reynolds and J. F. Keffer sought to determine whether plane wakes of circular cylinders, when strained by a wind tunnel of varying cross-section, evolved in accordance with an analytically derived self-similar solution. As pointed out by Reynolds, for the strain geometry considered this self-similar solution indicated exponential growth of the viscous term in the mean momentum equation, a result which he interpreted as suggesting that such wakes would eventually relaminarize. The experimental results were found not to agree with the similarity theory and recent direct numerical simulations confirm this. However, a more general self-similar analysis of the kind suggested by W. K. George is found to lead to families of possible similarity solutions, some of which do indeed describe the observed flaw behavior. These equilibrium similarity solutions result from creating a balance in the governing equations by grouping certain terms. For these solutions the viscous terms can be retained in the analysis.
NASA Astrophysics Data System (ADS)
Avitzur, Boaz
1993-04-01
There is a long-standing interest in developing a capability to predict the distribution of retained stresses in thick-walled pressure vessels after the removal of an internal pressure--post autofrettage. The key to such a prediction is in the capacity to compute the stress distribution in a vessel while under externally imposed stress sufficient enough to cause at least partial plastic deformation. A good approximation of the stress distribution was developed by Mises in his 1913 plane-stress solution. The fact that such vessels are not representative of the plane-stress condition not withstanding, Mises recognized that his solution was mathematically restricted to a limited range of vessels' wall ratios. More recently, Avitzur offered a solution similar to that of Mises, but for a plane-strain condition. Depending on the material's Poisson's factor, Avitzur's solution is also mathematically applicable for a limited range of vessels' wall ratios only. The wall ratio, beyond which Avitzur's solution in plane-strain is not applicable, is a few times larger than that which limits Mises' solution in plane-stress. This work introduces a modification to Avitzur's solution in plane-strain, which makes its applicability unlimited.
Skigin, Diana C; Depine, Ricardo A
2008-05-01
We show that the problem of scattering of an obliquely incident plane wave by a general-shaped groove engraved on a perfectly conducting plane, which was recently studied by Basha et al. [J. Opt. Soc. Am. A24, 1647 (2007)], was solved 11 years ago using the same formulation. This method was further extended to deal with a finite number of grooves and also with complex apertures including several nonlossy and lossy dielectrics, as well as real metals. PMID:18451923
Matsui, Hiroaki Tabata, Hitoshi; Hasuike, Noriyuki; Harima, Hiroshi
2014-09-21
In-plane anisotropic strains in A-plane layers on the electronic band structure of ZnO were investigated from the viewpoint of optical polarization anisotropy. Investigations utilizing k·p perturbation theory revealed that energy transitions and associated oscillation strengths were dependent on in-plane strains. The theoretical correlation between optical polarizations and in-plane strains was experimentally demonstrated using A-plane ZnO layers with different in-plane strains. Finally, optical polarization anisotropy and its implications for in-plane optical properties are discussed in relation to the energy shift between two orthogonal directions. Higher polarization rotations were obtained in an A-plane ZnO layer with in-plane biaxially compressive strains as compared to strain-free ZnO. This study provides detailed information concerning the role played by in-plane strains in optically polarized applications based on nonpolar ZnO in the ultra-violet region.
Shimada, T; Okuno, J; Ishii, Y; Kitamura, T
2012-03-01
We investigated a nanometer-sharp magnetic domain wall (DW) structure in a free-standing Fe(110) monolayer and studied the crucial role of in-plane strain using fully unconstrained noncollinear ab initio spin-density-functional theory calculations within the generalized gradient approximation. The DW width is calculated to be 0.86 nm. A precise vector-field description of the magnetization density revealed that a noncollinear character in the DW was spatially confined between atoms, whereas a collinear and high magnetization density was localized around each atom. In the rapid rotation of magnetic moments in the DW, we found an electron rearrangement from the d(zx) and d(x(2)-y(2)) states to the d(xy), d(yz) and d(z(2)) states due to a shift of band structures. Applied tensile and compressive in-plane strains both bring about narrower DWs in the monolayer except when the strain is small. The strain dependence of the DW width is discussed in terms of both exchange interaction and magnetocrystalline anisotropy. PMID:22322862
NASA Astrophysics Data System (ADS)
Bhadauria, S. S.; Pathak, K. K.; Hora, M. S.
2012-09-01
It is widely accepted that failure due to plastic deformation in metals greatly depends on the stress triaxiality factor (TF). This article investigates the variation of stress triaxiality along the yield locus of ductile materials. Von Mises yield criteria and triaxiality factor have been used to determine the critical limits of stress triaxiality for the materials under plane strain condition. A generalized mathematical model for triaxiality factor has been formulated and a constrained optimization has been carried out using genetic algorithm. Finite element analysis of a two dimensional square plate has been carried out to verify the results obtained by the mathematical model. It is found that the set of values of the first and the second principal stresses on the yield locus, which results in maximum stress triaxiality, can be used to determine the location at which crack initiation may occur. Thus, the results indicate that while designing a certain component, such combination of stresses which leads the stress triaxiality to its critical value, should be avoided.
Super switching and control of in-plane ferroelectric nanodomains in strained thin films
NASA Astrophysics Data System (ADS)
Matzen, S.; Nesterov, O.; Rispens, G.; Heuver, J. A.; Biegalski, M.; Christen, H. M.; Noheda, B.
2014-07-01
With shrinking device sizes, controlling domain formation in nanoferroelectrics becomes crucial. Periodic nanodomains that self-organize into so-called ‘superdomains’ have been recently observed, mainly at crystal edges or in laterally confined nanoobjects. Here we show that in extended, strain-engineered thin films, superdomains with purely in-plane polarization form to mimic the single-domain ground state, a new insight that allows a priori design of these hierarchical domain architectures. Importantly, superdomains behave like strain-neutral entities whose resultant polarization can be reversibly switched by 90°, offering promising perspectives for novel device geometries.
NASA Astrophysics Data System (ADS)
Miao, Yu; Chen, L.; Sammynaiken, R.; Lin, Y.; Zhang, W. J.
2011-12-01
The use of carbon nanotubes (CNT) for the application in in-plane strain detection is promising. In recent years, in-plane strain sensors constructed from CNT networks have been developed; however, few studied optimization of these sensors. In this paper, a study of the optimization of pure CNT networks in terms of piezoresistive response is reported. The so-called pure CNT networks are CNT networks free of surfactants. The performances of piezoresistive response are gauge factor (GF) and linearity. The variables are the number of layers of networks, concentration of CNT solution, and length of sonication time. As a result, the study concluded an optimal pure CNT networks sensor (GF: 2.59, linearity 0.98) with ten layers of networks, 0.8 mg/ml concentration, and 2 h of sonication time.
Tests and analyses for fully plastic fracture mechanics of plane strain mode I crack growth
McClintock, F.A.; Parks, D.M.; Kim, Y.J.
1995-12-31
Under monotonic loading, structures should ideally be ductile enough to provide continued resistance during crack growth. For fully plastic crack growth in low strength alloys, existing asymptotic solutions for elastic-plastic growing cracks are not applicable because they reach the fracture strain only in regions small compared to the inhomogeneities of the actual fracture process. For the limiting case of non-hardening fully-plastic plane strain crack growth, in a number of geometries and loadings the near-tip fields are characterized in terms of three parameters: an effective angle 2{theta}{sub s} between a pair of slip planes, and the normal stress {sigma}{sub s} and the increment of displacement {delta}u{sub s} across the planes. This three-parameter characterization is in contrast to the one- or two-parameter (K or J and T or Q) characterization in linear or non-linear elastic fracture mechanics. These {theta}{sub s}, {sigma}{sub s}, and {delta}u{sub s} parameters are found form the far-field geometries and loadings through slip line fields or least upper bound analyses based on circular arcs. The resulting crack growth, in terms of the crack tip opening angle (CTOA), is a function of {theta}{sub s}, {sigma}{sub s}, and the material. The geometry of the crack growing between two moving slip planes emanating from its tip reduces this function to the critical fracture shear strain left behind the slip planes, {gamma}f, as a function of {sigma}{sub s}. {gamma}f({sigma}{sub s}) is found theoretically from a hole initiation and growth model. It is also found from preliminary fully plastic crack growth experiments on unequally grooved specimens with fixed-grip extension or 4-point bending of a 1018 CF steel.
The unique effect of in-plane anisotropic strain in the magnetization control by electric field
NASA Astrophysics Data System (ADS)
Zhao, Y. Y.; Wang, J.; Hu, F. X.; Liu, Y.; Kuang, H.; Wu, R. R.; Sun, J. R.; Shen, B. G.
2016-05-01
The electric field control of magnetization in both (100)- and (011)-Pr0.7Sr0.3MnO3/Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PSMO/PMN-PT) heterostructures were investigated. It was found that the in-plane isotropic strain induced by electric field only slightly reduces the magnetization at low temperature in (100)-PSMO/PMN-PT film. On the other hand, for (011)-PSMO/PMN-PT film, the in-plane anisotropic strain results in in-plane anisotropic, nonvolatile change of magnetization at low-temperature. The magnetization, remanence and coercivity along in-plane [100] direction are suppressed by the electric field while the ones along [01-1] direction are enhanced, which is ascribed to the extra effective magnetic anisotropy induced by the electric field via anisotropic piezostrains. More interestingly, such anisotropic modulation behaviors are nonvolatile, demonstrating a memory effect.
Real-time measurement system for in-plane displacement and strain based on vision
NASA Astrophysics Data System (ADS)
Luo, Tao; Jin, Yi; Zhu, Ye; Zhai, Chao
2013-08-01
In this paper, combining optical measurement with conventional material testing machine, a real-time in-plane displacement and strain measurement system is built, which is applied to the material testing machine. This system can realize displacement and strain measurement of a large deformation sample moreover it can observe the sample crack on line. The change of displacement field is obtained through the change of center coordinate of each point of a grid lattice in the surface of the testing sample, according to two-dimensional sort coding for the grid in the traditional automated grid method, in this paper, an improved one-dimensional code method is adopted which make calculating speed much faster and the algorithm more adaptable. The measurement of the stability and precision of this system are made using the calibration board whose position precision is about 1.5 micron. The results show that the short-time stability of this system is about 0.5micron. At last, this system is used for strain measurement in a sample tension test, and the result shows that the system can acquire in-plane displacement and strain measurement results accurately and real-time, the velocity of image processing can reach 10 frame per second; or it can observe sample crack on line and storage the test process, the max velocity of observation and storage is 100 frame per second.
Dislocation microstructures and strain-gradient plasticity with one active slip plane
NASA Astrophysics Data System (ADS)
Conti, Sergio; Garroni, Adriana; Müller, Stefan
2016-08-01
We study dislocation networks in the plane using the vectorial phase-field model introduced by Ortiz and coworkers, in the limit of small lattice spacing. We show that, in a scaling regime where the total length of the dislocations is large, the phase field model reduces to a simpler model of the strain-gradient type. The limiting model contains a term describing the three-dimensional elastic energy and a strain-gradient term describing the energy of the geometrically necessary dislocations, characterized by the tangential gradient of the slip. The energy density appearing in the strain-gradient term is determined by the solution of a cell problem, which depends on the line tension energy of dislocations. In the case of cubic crystals with isotropic elasticity our model shows that complex microstructures may form in which dislocations with different Burgers vector and orientation react with each other to reduce the total self-energy.
Analysis of plane-plastic stress problems with axial symmetry in strain-hardening range
NASA Technical Reports Server (NTRS)
Wu, M H Lee
1951-01-01
A simple method is developed for solving plane-plastic-stress problems with axial symmetry in the strain-hardening range which is based on the deformation theory of plasticity employing the finite-strain concept. The equations defining the problems are first reduced to two simultaneous nonlinear differential equations involving two dependent variables: (a) the octahedral shear strain, and (b) a parameter indicating the ratio of principal stresses. By multiplying the load and dividing the radius by an arbitrary constant, it is possible to solve these problems without iteration for any value of the modified load. The constant is determined by the boundary condition. This method is applied to a circular membrane under pressure, a rotating disk without and with a central hole, and an infinite plate with a circular hole. Two materials, inconel x and 16-25-6, the octahedral shear stress-strain relations of which do not follow the power law, are used. Distributions of octahedral shear strain, as well as of principal stresses and strains, are obtained. These results are compared with the results of the same problems in the elastic range.
Simultaneous Generalizations of the Theorems of Ceva and Menelaus for Field Planes
ERIC Educational Resources Information Center
Houston, Kelly B.; Powers, Robert C.
2009-01-01
In 1992, Klamkin and Liu proved a very general result in the Extended Euclidean Plane that contains the theorems of Ceva and Menelaus as special cases. In this article, we extend the Klamkin and Liu result to projective planes "PG"(2, F) where F is a field. (Contains 2 figures.)
General Nth order integrals of motion in the Euclidean plane
NASA Astrophysics Data System (ADS)
Post, S.; Winternitz, P.
2015-10-01
The general form of an integral of motion that is a polynomial of order N in the momenta is presented for a Hamiltonian system in two-dimensional Euclidean space. The classical and the quantum cases are treated separately, emphasizing both the similarities and the differences between the two. The main application will be to study Nth order superintegrable systems that allow separation of variables in the Hamilton-Jacobi and Schrödinger equations, respectively.
In-plane displacement and strain measurements using a camera phone and digital image correlation
NASA Astrophysics Data System (ADS)
Yu, Liping; Pan, Bing
2014-05-01
In-plane displacement and strain measurements of planar objects by processing the digital images captured by a camera phone using digital image correlation (DIC) are performed in this paper. As a convenient communication tool for everyday use, the principal advantages of a camera phone are its low cost, easy accessibility, and compactness. However, when used as a two-dimensional DIC system for mechanical metrology, the assumed imaging model of a camera phone may be slightly altered during the measurement process due to camera misalignment, imperfect loading, sample deformation, and temperature variations of the camera phone, which can produce appreciable errors in the measured displacements. In order to obtain accurate DIC measurements using a camera phone, the virtual displacements caused by these issues are first identified using an unstrained compensating specimen and then corrected by means of a parametric model. The proposed technique is first verified using in-plane translation and out-of-plane translation tests. Then, it is validated through a determination of the tensile strains and elastic properties of an aluminum specimen. Results of the present study show that accurate DIC measurements can be conducted using a common camera phone provided that an adequate correction is employed.
Dependence of electronic properties of germanium on the in-plane biaxial tensile strains
NASA Astrophysics Data System (ADS)
Yang, C. H.; Yu, Z. Y.; Liu, Y. M.; Lu, P. F.; Gao, T.; Li, M.; Manzoor, S.
2013-10-01
The hybrid HSE06 functional with the spin-orbit coupling effects is used to calculate the habituation of the electronic properties of Ge on the (0 0 1), (1 1 1), (1 0 1) in-plane biaxial tensile strains (IPBTSs). Our motivation is to explore the nature of electronic properties of tensile-strained Ge on different substrate orientations. The calculated results demonstrate that one of the most effective and practical approaches for transforming Ge into a direct transition semiconductor is to introduce (0 0 1) IPBTS to Ge. At 2.3% (0 0 1) IPBTS, Ge becomes a direct bandgap semiconductor with 0.53 eV band gap, in good agreement with the previous theoretical and experimental results. We find that the (1 1 1) and (1 0 1) IPBTSs are not efficient since the shear strain and inner displacement of atoms introduced by them quickly decrease the indirect gap of Ge. By investigating the dependence of valence band spin-orbit splitting on strain, we prove that the dependency relationship and the coupled ways between the valence-band states of tensile-strained Ge are closely related to the symmetry of strain tensor, i.e., the symmetry of the substrate orientation. The first- and second-order coefficients describing the dependence of indirect gap, direct gap, the valence band spin-orbit coupling splitting, and heavy-hole-light-hole splitting of Ge on IPBTSs have been obtained by the least squares polynomial fitting. These coefficients are significant to quantitatively modulate the electronic properties of Ge by tensile strain and design tensile-strained Ge devices by semiconductor epitaxial technique.
Analytical solutions to general anti-plane shear problems in finite elasticity
NASA Astrophysics Data System (ADS)
Gao, David Yang
2016-03-01
This paper presents a pure complementary energy variational method for solving a general anti-plane shear problem in finite elasticity. Based on the canonical duality-triality theory developed by the author, the nonlinear/nonconvex partial differential equations for the large deformation problem are converted into an algebraic equation in dual space, which can, in principle, be solved to obtain a complete set of stress solutions. Therefore, a general analytical solution form of the deformation is obtained subjected to a compatibility condition. Applications are illustrated by examples with both convex and nonconvex stored strain energies governed by quadratic-exponential and power-law material models, respectively. Results show that the nonconvex variational problem could have multiple solutions at each material point, the complementary gap function and the triality theory can be used to identify both global and local extremal solutions, while the popular convexity conditions (including rank-one condition) provide mainly local minimal criteria and the Legendre-Hadamard condition (i.e., the so-called strong ellipticity condition) does not guarantee uniqueness of solutions. This paper demonstrates again that the pure complementary energy principle and the triality theory play important roles in finite deformation theory and nonconvex analysis.
An Accurate Upper Bound Solution for Plane Strain Extrusion through a Wedge-Shaped Die
Mustafa, Yusof; Lyamina, Elena
2014-01-01
An upper bound method for the process of plane strain extrusion through a wedge-shaped die is derived. A technique for constructing a kinematically admissible velocity field satisfying the exact asymptotic singular behavior of real velocity fields in the vicinity of maximum friction surfaces (the friction stress at sliding is equal to the shear yield stress on such surfaces) is described. Two specific upper bound solutions are found using the method derived. The solutions are compared to an accurate slip-line solution and it is shown that the accuracy of the new method is very high. PMID:25101311
NASA Astrophysics Data System (ADS)
Sun, Y. W.; Holec, D.; Dunstan, D. J.
2015-09-01
Stacking graphene sheets forms graphite. Two in-plane vibrational modes of graphite, E1 u and E2g (2 ), are derived from the graphene E2 g mode, the shifts of which under compression are considered as results of the in-plane bond shortening. Values of the Grüneisen parameter have been reported to quantify such a relation. However, the reason why the shift rates of these three modes with pressure differ is unclear. In this work, we introduce new parameters γE2g'=-0.0131 and γE1u'=0.0585 to quantify the contribution of out-of-plane strain to the shift of the in-plane vibrational frequencies, suggesting that the compression of the π - electrons plays a non-negligible part in both graphite and graphene under high pressure.
NASA Technical Reports Server (NTRS)
Shbeeb, N.; Binienda, W. K.; Kreider, K.
1999-01-01
The driving forces for a generally oriented crack embedded in a Functionally Graded strip sandwiched between two half planes are analyzed using singular integral equations with Cauchy kernels, and integrated using Lobatto-Chebyshev collocation. Mixed-mode Stress Intensity Factors (SIF) and Strain Energy Release Rates (SERR) are calculated. The Stress Intensity Factors are compared for accuracy with previously published results. Parametric studies are conducted for various nonhomogeneity ratios, crack lengths. crack orientation and thickness of the strip. It is shown that the SERR is more complete and should be used for crack propagation analysis.
The impact of strain, bedding plane friction and overburden pressure on joint spacing
NASA Astrophysics Data System (ADS)
Arslan, Arzu; Schöpfer, Martin P. J.; Walsh, John J.; Childs, Conrad
2010-05-01
In layered sequences, rock joints usually best develop within the more brittle layers and commonly display a regular spacing that scales with layer thickness. A variety of conceptual and mechanical models have been advanced to explain this relationship. A limitation of previous approaches, however, is that fracture initiation and associated bedding-parallel slip are not explicitly simulated; instead, fractures were predefined and interfaces were welded. To surmount this problem, we have modelled the formation and growth of joints in layered sequences by using the two-dimensional Distinct Element Method (DEM) as implemented in the Particle Flow Code (PFC-2D). In PFC-2D, rock is represented by an assemblage of circular particles that are bonded at particle-particle contacts, with failure occurring when either the tensile or shear strength of a bond is exceeded. Model materials with different rheological properties can be generated by calibrating the results of synthetic mechanical test procedures with those of real rocks. Our simple models of jointing comprise a central brittle layer with high Young's modulus, which is embedded in a low Young's modulus matrix. The interfaces between the layers (i.e. bedding planes) are defined by ‘smooth joint' contacts, a modelling feature that eliminates interparticle bumpiness and associated interlocking friction. Consequently, this feature allows the user to assign macroscopic properties such as friction along layer interfaces in a controlled manner. Layer parallel extension is applied by assigning a velocity to particles at the lateral boundaries of the model while maintaining a constant vertical confining pressure. Models were extended until joint saturation was reached in the central layer. We thereby explored the impact of strain, bedding plane friction and overburden pressure on joint spacing. The modelling revealed that joint spacing decreases as strain, bedding plane friction and overburden pressure are increased
NASA Astrophysics Data System (ADS)
Kim, K.; Okayasu, K.; Fukutomi, H.
2015-04-01
The formation behavior of basal texture during high temperature deformation of AZ80 magnesium alloys in single phase was investigated by plane strain compression deformation. Three kinds of specimens with different initial textures were machined out from an extruded bar having a <101¯0> texture. Plane strain compression tests were conducted at temperatures of 623K and 723K and a strain rate of 5.0×10-2s-1, with a strain range of between - 0.4 and -1.0. After deformation, the specimens were immediately quenched in oil. Texture measurement was carried out on the compression planes by the Schulz reflection method using nickel filtered Cu Kα radiation. Electron backscatter diffraction (EBSD) measurements were also conducted in order to examine the spatial distribution of orientations. Three kinds of specimens named A, B and C were prepared from the same extruded bar. In the specimens A, B and C, {0001} was distributed preferentially parallel to ND, TD, and RD, respectively. After deformation, texture evaluation was conducted on the mid-plane section. At the plane strain compression deformation, peaks appeared in the true stress-true strain curves irrespective of the kinds of specimen used. It was found that the main components and the pole densities of the textures vary depending on deformation condition and initial texture. Six kinds of texture components were observed after deformation. The (0001)<101¯0> has formed regardless of the initial texture. There are two types of texture components; one exists before the deformation, and the other does not. Either types are considered to have stable orientations for plane strain compression. Also, the basal texture is composed of two crystal orientation components - (0001)<101¯0> and (0001)<112¯0>. When (0001) existed before deformation, an extremely sharp (0001) (compression plane) texture is formed.
Assessment of Constitutive and Stability Behavior of Sands Under Plane Strain Condition
NASA Technical Reports Server (NTRS)
Alshibli, Khalid A.; Sture, Stein
2000-01-01
A series of biaxial (plane strain) experiments were conducted on three sands under low (15 kPa) and high (100 kPa) confining pressure conditions to investigate the effects of specimen density, confining pressure, and sand grains size and shape on the constitutive and stability behavior of granular materials. The three sands used in the experiments were fine, medium, and coarse-grained uniform silica sands with rounded, sub-angular, and angular grains, respectively. Specimen deformation was readily monitored and analyzed with the help of a grid pattern imprinted on the latex membrane. The overall stress-strain behavior is strongly dependent on the specimen density, confining pressure, sand grain texture, and the resulting failure mode(s). That became evident in different degrees of softening responses at various axial strains. The relationship between the constitutive behavior and the specimens' modes of instability is presented. The failure in all specimens was characterized by two distinct and opposite shear bands. It was found that the measured dilatancy angles increase as the sand grains' angularity and size increase. The measured shear band inclination angles are also presented and compared with classical Coulomb and Roscoe solutions.
Development of a new model for plane strain bending and springback analysis
Zhang, Z.T.; Lee, D.
1995-06-01
A new mathematical model is presented for plane strain bending and springback analysis in sheet metal forming. This model combines effects associated with bending and stretching, considers stress and strain distributions and different thickness variations in the thickness direction, and takes force equilibrium into account. An elastic-plastic material model and Hill`s nonquadratic yield function are incorporated in the model. The model is used to obtain force, bending moment, and springback curvature. A typical two-dimensional draw bending part is divided into five regions along the strip, and the forces and moments acting on each region and the deformation history of each region are examined. Three different methods are applied to the two-dimensional draw bending problems: the first using the new model, the second using the new model but also including a kinematic directional hardening material model to consider the bending and unbending deformation in the wall, and the third using membrane theory plus bending strain. Results from these methods, including those from the recent benchmark program, are compared.
Uniqueness of the interior plane strain time-harmonic viscoelastic inverse problem
NASA Astrophysics Data System (ADS)
Zhang, Yixiao; Barbone, Paul E.; Harari, Isaac; Oberai, Assad A.
2016-07-01
Elasticity imaging has emerged as a promising medical imaging technique with applications in the detection, diagnosis and treatment monitoring of several types of disease. In elasticity imaging measured displacement fields are used to generate images of elastic parameters of tissue by solving an inverse problem. When the tissue excitation, and the resulting tissue motion is time-harmonic, elasticity imaging can be extended to image the viscoelastic properties of the tissue. This leads to an inverse problem for the complex-valued shear modulus at a given frequency. In this manuscript we have considered the uniqueness of this inverse problem for an incompressible, isotropic linear viscoelastic solid in a state of plane strain. For a single measured displacement field we conclude that the solution is infinite dimensional, and the data required to render it unique is determined by the measured strain field. In contrast, for two independent displacement fields such that the principal directions of the resulting strain fields are different, the space of possible solutions is eight dimensional, and given additional data, like the value of the shear modulus at four locations, or over a calibration region, we may determine the shear modulus everywhere. We have also considered simple analytical examples that verify these results and offer additional insights. The results derived in this paper may be used as guidelines by the practitioners of elasticity imaging in designing more robust and accurate imaging protocols.
NASA Astrophysics Data System (ADS)
Ridzuan, M. J. M.; Hafis, S. M.; Saifullah, K. N.; Syahrullail, S.
2012-06-01
Large quantities of lubricant are being widely used in the metal forming industry and this high consumption is negatively affecting the environment. Finding an alternative to this current situation is getting more serious and urgent in response to environmental and operational cost pressures. This paper deals with an experimental investigation to obtain the minimum quantity of lubricant (MQL) of RBD palm stearin, which is used as lubricant between the contact sliding surfaces of the taper die and billet via plane-strain-extrusion apparatus. The symmetrical workpieces are designed as combined billets made from pure aluminium A1100. The dies of the apparatus are made of SKD 11 steel. The extrusion ratio of the processes is 3 and the workpieces are extruded by hydraulic press machine. Four conditions of the quantity selected are 0.1 mg, 1 mg, 5 mg, and 20 mg. The analysis of the result shows that the conditions of the quantity are in the load reducing order from 0.1 mg, 1mg and 5 mg. The highest distribution of surface roughness is at 0.1 mg, whereby for others, the conditions are quite similar. However, the distribution of velocity and effective strain are lowest at 5 mg. The minimum quantity of lubricant (MQL) of the RBD palm stearin as lubricant on the contact sliding surfaces in planestrain-extrusion is determined based on the results of load, surface roughness, velocity and effective strain.
Plane strain finite element analysis of sheet forming operations including bending effects
NASA Astrophysics Data System (ADS)
Cho, Uk Youn
1993-01-01
An improved finite element method suitable for the plane-strain analysis of sheet metal forming operations is presented. The method incorporates a computationally efficient shell model and a consistent frictional contact algorithm through an implicit updated Lagrangian formulation. The workpiece material model is rigid-viscoplastic with a choice of power law hardening and plastic normal anisotropy and is capable of modeling a wide variety of sheet metals. A simplified nonlinear incremental shell theory is employed along with an optional reduced integration through the thickness for computational efficiency, while retaining the advantages of the kinematic model containing the bending effects. Complex tool geometry can be handled by discrete data points, by primitives (lines and arcs), or by analytical functions. The capabilities of the method are demonstrated through verification problems and comparisons with experimental data, benchmark results, and published data for several practical problems of the sheet metal forming industry. The problems include stretching and/or deep drawing operations, simulation of automobile panel section, and brake bending operation. As an independent investigation from the first portion of the dissertation, measured data from a set of simple bending experiments of two types of aluminum are presented and analyzed. Generated data from the experiments include strain histories (loading and unloading), spring back information (spring back angle and strains), and friction coefficients. As a by-product, a simple way of estimating the friction coefficient (Coulomb's law) during a bending operation is proposed and demonstrated.
Strained-layer superlattice focal plane array having a planar structure
Kim, Jin K.; Carroll, Malcolm S.; Gin, Aaron; Marsh, Phillip F.; Young, Erik W.; Cich, Michael J.
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.
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.
Gender, General Strain Theory, Negative Emotions, and Disordered Eating
ERIC Educational Resources Information Center
Piquero, Nicole Leeper; Fox, Kristan; Piquero, Alex R.; Capowich, George; Mazerolle, Paul
2010-01-01
Much of the prior work on General Strain Theory (GST) has focused on how strain and negative emotions interrelate to produce criminal--especially violent--activity. Very little research has extended GST to examine other types of non-criminal, negative behavior, such as self-harming behaviors associated with disordered eating, a traditionally…
Infrared focal plane arrays based on dots in a well and strained layer superlattices
NASA Astrophysics Data System (ADS)
Krishna, Sanjay
2009-01-01
In this paper, we will review some of the recent progress that we have made on developing single pixel detectors and focal plane arrays based on dots-in-a-well (DWELL) heterostructure and Type II strained layer superlattice (SLS). The DWELL detector consists of an active region composed of InAs quantum dots embedded in InGaAs/GaAs quantum wells. By varying the thickness of the InGaAs well, the DWELL heterostructure allows for the manipulation of the operating wavelength and the nature of the transitions (bound-to-bound, bound-to-quasibound and bound-to-continuum) of the detector. Based on these principles, DWELL samples were grown using molecular beam epitaxy and fabricated into 320 x 256 focal plane arrays (FPAs) with Indium bumps using standard lithography at the University of New Mexico. The FPA evaluated was hybridized to an Indigo 9705 readout integrated circuit (ROIC). From this evaluation, we have reported the first two-color, co-located quantum dot based imaging system that can be used to take multicolor images using a single FPA. We have also been investigating the use of miniband transitions in Type II SLS to develop infrared detectors using PIN and nBn based designs.
Andrews, D.J.
1985-01-01
A numerical boundary integral method, relating slip and traction on a plane in an elastic medium by convolution with a discretized Green function, can be linked to a slip-dependent friction law on the fault plane. Such a method is developed here in two-dimensional plane-strain geometry. Spontaneous plane-strain shear ruptures can make a transition from sub-Rayleigh to near-P propagation velocity. Results from the boundary integral method agree with earlier results from a finite difference method on the location of this transition in parameter space. The methods differ in their prediction of rupture velocity following the transition. The trailing edge of the cohesive zone propagates at the P-wave velocity after the transition in the boundary integral calculations. Refs.
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.
NASA Astrophysics Data System (ADS)
Benito, L.; Ballesteros, C.; Ward, R. C. C.
2014-04-01
We report on the magnetic and structural characterization of high lattice-mismatched [Dy2nm/SctSc] superlattices, with variable Sc thickness tSc= 2-6 nm. We find that the characteristic in-plane effective hexagonal magnetic anisotropy K66,ef reverses sign and undergoes a dramatic reduction, attaining values of ≈13-24 kJm-3, when compared to K66=-0.76 MJm-3 in bulk Dy. As a result, the basal plane magnetic anisotropy is dominated by a uniaxial magnetic anisotropy (UMA) unfound in bulk Dy, which amounts to ≈175-142 kJm-3. We attribute the large downsizing in K66,ef to the compression epitaxial strain, which generates a competing sixfold magnetoelastic (MEL) contribution to the magnetocrystalline (strain-free) magnetic anisotropy. Our study proves that the in-plane UMA is caused by the coupling between a giant symmetry-breaking MEL constant Mγ ,22≈1 GPa and a morphic orthorhombiclike strain ɛγ ,1≈10-4, whose origin resides on the arising of an in-plane anisotropic strain relaxation process of the pseudoepitaxial registry between the nonmagnetic bottom layers in the superstructure. This investigation shows a broader perspective on the crucial role played by epitaxial strains at engineering the magnetic anisotropy in multilayers.
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.
Oliveira, M. C.; Baptista, A. J.; Menezes, L. F.; Alves, J. L.; Green, D. E.; Ghaei, A.
2007-05-17
The main purpose of the 'Numisheet'05 Benchmark no. 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.
A general view on the reactivity of the oxygen-functionalized graphene basal plane.
Dobrota, Ana S; Pašti, Igor A; Mentus, Slavko V; Skorodumova, Natalia V
2016-03-01
In this contribution we inspect the adsorption of H, OH, Cl and Pt on oxidized graphene using DFT calculations. The introduction of epoxy and hydroxyl groups on the graphene basal plane significantly alters its chemisorption properties, which can be attributed to the deformation of the basal plane and the type and distribution of these groups. We show that a general scaling relation exists between the hydrogen binding energies and the binding energies of other investigated adsorbates, which allows for a simple probing of the reactivity of oxidized graphene with only one adsorbate. The electronic states of carbon atoms located within the 2 eV interval below the Fermi level are found to be responsible for the interaction of the basal plane with the chosen adsorbates. The number of electronic states situated in this energy interval is shown to correlate with hydrogen binding energies. PMID:26866995
Well-posedness and generalized plane waves simulations of a 2D mode conversion model
NASA Astrophysics Data System (ADS)
Imbert-Gérard, Lise-Marie
2015-12-01
Certain types of electro-magnetic waves propagating in a plasma can undergo a mode conversion process. In magnetic confinement fusion, this phenomenon is very useful to heat the plasma, since it permits to transfer the heat at or near the plasma center. This work focuses on a mathematical model of wave propagation around the mode conversion region, from both theoretical and numerical points of view. It aims at developing, for a well-posed equation, specific basis functions to study a wave mode conversion process. These basis functions, called generalized plane waves, are intrinsically based on variable coefficients. As such, they are particularly adapted to the mode conversion problem. The design of generalized plane waves for the proposed model is described in detail. Their implementation within a discontinuous Galerkin method then provides numerical simulations of the process. These first 2D simulations for this model agree with qualitative aspects studied in previous works.
NASA Astrophysics Data System (ADS)
Li, Hong; Tsai, Charlie; Koh, Ai Leen; Cai, Lili; Contryman, Alex W.; Fragapane, Alex H.; Zhao, Jiheng; Han, Hyun Soon; Manoharan, Hari C.; Abild-Pedersen, Frank; Nørskov, Jens K.; Zheng, Xiaolin
2016-01-01
As a promising non-precious catalyst for the hydrogen evolution reaction (HER; refs ,,,,), molybdenum disulphide (MoS2) is known to contain active edge sites and an inert basal plane. Activating the MoS2 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-MoS2 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 bind directly to exposed Mo atoms. The hydrogen adsorption free energy (ΔGH) can be further manipulated by straining the surface with S-vacancies, which fine-tunes the catalytic activity. Proper combinations of S-vacancy and strain yield the optimal ΔGH = 0 eV, which allows us to achieve the highest intrinsic HER activity among molybdenum-sulphide-based catalysts.
Gendered Responses to Serious Strain: The Argument for a General Strain Theory of Deviance
Kaufman, Joanne M.
2010-01-01
This paper expands and builds on newer avenues in research on gender and general strain theory (GST). I accomplish this by focusing on serious strains that are relevant for males and females, including externalizing and internalizing forms of negative emotions, and including multiple gendered deviant outcomes. Using the Add Health dataset, I find strong support for the impact of serious strains on both types of negative emotions and different forms of deviance for males and females. However, the experience of serious strain, emotionally and behaviorally, is gendered. Depressive symptoms are particularly important for all types of deviance by females. Including multiple types of deviant outcomes offers a fuller understanding of both similarities and differences by gender. These results support the utility of GST as a theory of deviance in general and support greater connections between GST, feminist theorizing, and the sociology of mental health. PMID:20625472
General Strain Theory, Peer Rejection, and Delinquency/Crime
ERIC Educational Resources Information Center
Higgins, George E.; Piquero, Nicole L.; Piquero, Alex R.
2011-01-01
The development of general strain theory (GST) has led to a renewed focus on the influence of negative life experiences on antisocial behavior. Although a number of studies have generated an impressive array of support for the theory, several avenues remain open for research. In this article, we examine how a specific noxious stimuli, peer…
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.
General Strain Theory and Substance Use among American Indian Adolescents.
Eitle, Tamela McNulty; Eitle, David; Johnson-Jennings, Michelle
2013-01-01
Despite the well-established finding that American Indian adolescents are at a greater risk of illicit substance use and abuse than the general population, few generalist explanations of deviance have been extended to American Indian substance use. Using a popular generalist explanation of deviance, General Strain Theory, we explore the predictive utility of this model with a subsample of American Indian adolescents from waves one and two of the National Longitudinal Study of Adolescent Health (Add-Health). Overall, we find mixed support for the utility of General Strain Theory to account for American Indian adolescent substance use. While exposure to recent life events, a common measure of stress exposure, was found to be a robust indicator of substance use, we found mixed support for the thesis that negative affect plays a key role in mediating the link between strain and substance use. However, we did find evidence that personal and social resources serve to condition the link between stress exposure and substance use, with parental control, self-restraint, religiosity, and exposure to substance using peers each serving to moderate the association between strain and substance use, albeit in more complex ways than expected. PMID:23826511
NASA Astrophysics Data System (ADS)
Garcia, V.; Sidis, Y.; Marangolo, M.; Vidal, F.; Eddrief, M.; Bourges, P.; Maccherozzi, F.; Ott, F.; Panaccione, G.; Etgens, V. H.
2007-09-01
The α-β magnetostructural phase transition in MnAs/GaAs(111) epilayers is investigated by elastic neutron scattering. The in-plane parameter of MnAs remains almost constant with temperature from 100 to 420 K, following the thermal evolution of the GaAs substrate. This induces a temperature dependent biaxial strain that is responsible for an α-β phase coexistence and, more importantly, for the stabilization of the ferromagnetic α phase at a higher temperature than in the bulk. We explain the premature appearance of the β phase at 275 K and the persistence of the ferromagnetic α phase up to 350 K with thermodynamical arguments based on the MnAs phase diagram. It results that the biaxial strain in the hexagonal plane is the key parameter to extend the ferromagnetic phase well over room temperature.
Garcia, V; Sidis, Y; Marangolo, M; Vidal, F; Eddrief, M; Bourges, P; Maccherozzi, F; Ott, F; Panaccione, G; Etgens, V H
2007-09-14
The alpha-beta magnetostructural phase transition in MnAs/GaAs(111) epilayers is investigated by elastic neutron scattering. The in-plane parameter of MnAs remains almost constant with temperature from 100 to 420 K, following the thermal evolution of the GaAs substrate. This induces a temperature dependent biaxial strain that is responsible for an alpha-beta phase coexistence and, more importantly, for the stabilization of the ferromagnetic alpha phase at a higher temperature than in the bulk. We explain the premature appearance of the beta phase at 275 K and the persistence of the ferromagnetic alpha phase up to 350 K with thermodynamical arguments based on the MnAs phase diagram. It results that the biaxial strain in the hexagonal plane is the key parameter to extend the ferromagnetic phase well over room temperature. PMID:17930469
NASA Astrophysics Data System (ADS)
Peeters, Michael; Panajotov, Krassimir P.; Verschaffelt, Guy; Nagler, Bob; Albert, Jan; Thienpont, Hugo; Veretennicoff, Irina P.; Danckaert, Jan
2002-06-01
It is well known that vertical-cavity surface-emitting lasers (VCSELs) can abruptly switch between two orthogonal linear polarization states if the current is changed. The impact of externally induced in-plane anisotropic strain on this switching was experimentally demonstrated in proton-implanted devices. In this contribution we present a further and thorough experimental investigation of the polarization behavior of different types of VCSELs (proton-implanted, air-post and oxide-confined), under varying strain conditions. We first measure the influence of the strain on the orientation of the axes of the linear polarization states. These axes can be rotated from the crystallographic direction [110] over [100] to [110]. At the same time, we monitor the exact birefringence. From the combination of these two measurements the amount of residual strain in these devices is deduced. Applying strain not only changes the frequency splitting between the two modes (due to birefringence) and their orientation, but also lifts the degeneracy in the gain of the polarization modes. We therefore also measure the gain difference (dichroism) as a function of the applied strain, via the mode suppression ratio and the optical spectrum. Due to the effect on both the birefringence and the dichroism, strain also changes the position of the polarization switching point as a function of current and can lead to the observation of double (consecutive) polarization switching. All this experimental evidence will help to build up a better understanding of the physics of polarization switching in VCSELs.
Gender, General Strain Theory, negative emotions, and disordered eating.
Piquero, Nicole Leeper; Fox, Kristan; Piquero, Alex R; Capowich, George; Mazerolle, Paul
2010-04-01
Much of the prior work on General Strain Theory (GST) has focused on how strain and negative emotions interrelate to produce criminal-especially violent-activity. Very little research has extended GST to examine other types of non-criminal, negative behavior, such as self-harming behaviors associated with disordered eating, a traditionally female-specific self-directed outcome. Using a sample of 338 young adults (54% female, 95% white), this article applies GST to disordered eating by examining how strain and negative emotions relate to this particular outcome across gender. Findings indicate that two types of strain measures predict depressive symptoms among males and females, that inequitable strainful experiences relate to disordered eating among females but not males, that depressive symptoms but not anger increase disordered eating for both males and females, and that membership in Greek organizations (sororities or fraternities) is associated with disordered eating but only for males. Implications for theory and directions for future research are highlighted. PMID:19882239
NASA Astrophysics Data System (ADS)
Bijarnia, R.; Singh, B.
2016-05-01
The paper is concerned with the propagation of plane waves in a transversely isotropic two temperature generalized thermoelastic solid half-space with voids and rotation. The governing equations are modified in the context of Lord and Shulman theory of generalized thermoelasticity and solved to show the existence of four plane waves in the x - z plane. Reflection of these plane waves from thermally insulated stress free surface is also studied to obtain a system of four non-homogeneous equations. For numerical computations of speed and reflection coefficients, a particular material is modelled as transversely isotropic generalized thermoelastic solid half-space. The speeds of plane waves are computed against the angle of propagation to observe the effects of two temperature and rotation. Reflection coefficients of various reflected waves are also computed against the angle of incidence to observe the effects of various parameters.
Generalization of the subsonic kernel function in the s-plane, with applications to flutter analysis
NASA Technical Reports Server (NTRS)
Cunningham, H. J.; Desmarais, R. N.
1984-01-01
A generalized subsonic unsteady aerodynamic kernel function, valid for both growing and decaying oscillatory motions, is developed and applied in a modified flutter analysis computer program to solve the boundaries of constant damping ratio as well as the flutter boundary. Rates of change of damping ratios with respect to dynamic pressure near flutter are substantially lower from the generalized-kernel-function calculations than from the conventional velocity-damping (V-g) calculation. A rational function approximation for aerodynamic forces used in control theory for s-plane analysis gave rather good agreement with kernel-function results, except for strongly damped motion at combinations of high (subsonic) Mach number and reduced frequency.
Kirkwood, Jonah; Ghetler, Andrew; Sedman, Jacqueline; Leclair, Daniel; Pagotto, Franco; Austin, John W; Ismail, Ashraf A
2006-10-01
A method was developed for whole-organism fingerprinting of Clostridium botulinum isolates by focal plane array Fourier transform infrared (FPA-FTIR) spectroscopy. A database of 150,000 infrared spectra of 44 strains of C. botulinum was acquired using a FPA-FTIR imaging spectrometer equipped with a 16 x 16 array detector to evaluate the ability of FTIR spectroscopy to differentiate the 44 strains. The database contained strains from C. botulinum groups I and II producing botulinum neurotoxin of serotypes A, B, E, and F. All strains were grown on each of three agar media (brain heart infusion, McClung Toabe agar base, and universal) prior to spectral acquisition. Given the dependence of the infrared spectra of microorganisms on the composition of the growth medium, the spectra were initially separated into three subsets corresponding to the three growth media employed. However, the replicate spectra of all strains, regardless of growth medium, were properly clustered by hierarchical cluster analysis based on differences in their infrared spectral profiles in three narrow spectral regions (1,428 to 1,412, 1,296 to 1,284, and 1,112 to 1,100 cm(-1)). The dendrogram generated from the FTIR data revealed complete separation between group I and group II strains. The spectral differences between group I and group II strains allowed accurate classification of C. botulinum strains at the group level in two blind validation studies (n = 40). These results demonstrate that FPA-FTIR spectroscopy has the potential for rapid discrimination of group I and group II C. botulinum strains in less than 3 min per sample. PMID:17066916
Full in-plane strain tensor analysis using the microscale ring-core FIB milling and DIC approach
NASA Astrophysics Data System (ADS)
Lunt, Alexander J. G.; Salvati, Enrico; Ma, Lifeng; Dolbyna, Igor P.; Neo, Tee K.; Korsunsky, Alexander M.
2016-09-01
Microscale Full In-plane Strain Tensor (FIST) analysis is crucial for improving understanding of residual stress and mechanical failure in many applications. This study outlines the first Focused Ion Beam (FIB) milling and Digital Image Correlation (DIC) based technique capable of performing precise, reliable and rapid quantification of this behaviour. The nature of semi-destructive FIB milling overcomes the main limitations of X-Ray Diffraction (XRD) strain tensor quantification: unstrained lattice parameter estimates are not required, analysis is performed in within a precisely defined 3D microscale volume, both amorphous and crystalline materials can be studied and access to X-ray/neutron facilities is not required. The FIST FIB milling and DIC experimental technique is based on extending the ring-core milling geometry to quantify the strain variation with angle and therefore benefits from the excellent precision and simple analytical approach associated with this method. In this study in-plane strain analysis was performed on sample of commercial interest: a porcelain veneered Yttria Partially Stabilised Zirconia (YPSZ) dental prosthesis, and was compared with the results of XRD. The two methods sample different gauge volumes and mechanical states: approximately plane stress for ring-core milling, and a through-thickness average for XRD. We demonstrate using complex analysis methods and Finite Element (FE) modelling that valid comparisons can be drawn between these two stress states. Excellent agreement was obtained between principal stress orientation and magnitudes, leading to realistic residual stress estimates that agree well with the literature (σAv ≈ 460 MPa) . As a measure of validity of the matching approach we report the upper and lower bounds on the (101) interplanar spacing of YPSZ that are found to correspond to the range 2.9586 - 2.9596 Å , closely matching published values.
Plane Wave Imaging for ultrasonic non-destructive testing: Generalization to multimodal imaging.
Le Jeune, Léonard; Robert, Sébastien; Lopez Villaverde, Eduardo; Prada, Claire
2016-01-01
This paper describes a new ultrasonic array imaging method for Non-Destructive Testing (NDT) which is derived from the medical Plane Wave Imaging (PWI) technique. The objective is to perform fast ultrasound imaging with high image quality. The approach is to transmit plane waves at several angles and to record the back-scattered signals with all the array elements. Focusing in receive is then achieved by coherent summations of the signals in every point of a region of interest. The medical PWI is generalized to immersion setups where water acts as a coupling medium and to multimodal (direct, half-skip modes) imaging in order to detect different types of defects (inclusions, porosities, cracks). This method is compared to the Total Focusing Method (TFM) which is the reference imaging technique in NDT. First, the two post-processing algorithms are described. Then experimental results with the array probe either in contact or in immersion are presented. A good agreement between the TFM and the PWI is observed, with three to ten times less transmissions required for the PWI. PMID:26323547
How General is General Strain Theory? Assessing Determinacy and Indeterminacy across Life Domains
ERIC Educational Resources Information Center
De Coster, Stacy; Kort-Butler, Lisa
2006-01-01
This article explores how assumptions of determinacy and indeterminacy apply to general strain theory. Theories assuming determinacy assert that motivational conditions determine specific forms of deviant adaptations, whereas those assuming indeterminacy propose that a given social circumstance can predispose a person toward many forms of…
Albocher, U.; Barbone, P.E.; Richards, M.S.; Oberai, A.A.; Harari, I.
2014-01-01
We apply the adjoint weighted equation method (AWE) to the direct solution of inverse problems of incompressible plane strain elasticity. We show that based on untreated noisy displacements, the reconstruction of the shear modulus can be very poor. We link this poor performance to loss of coercivity of the weak form when treating problems with discontinuous coefficients. We demonstrate that by smoothing the displacements and appending a regularization term to the AWE formulation, a dramatic improvement in the reconstruction can be achieved. With these improvements, the advantages of the AWE method as a direct solution approach can be extended to a wider range of problems. PMID:25383085
NASA Technical Reports Server (NTRS)
Fisher, D. M.; Buzzard, R. J.
1979-01-01
Standard round specimen fracture test results compared satisfactorily with results from standard rectangular compact specimens machined from the same material. The location of the loading pin holes was found to provide adequate strength in the load bearing region for plane strain fracture toughness testing. Excellent agreement was found between the stress intensity coefficient values obtained from compliance measurements and the analytic solution proposed for inclusion in the standard test method. Load displacement measurements were made using long armed displacement gages and hollow loading cylinders. Gage points registered on the loading hole surfaces through small holes in the walls of the loading cylinders.
GENERAL STRAIN THEORY, PERSISTENCE, AND DESISTANCE AMONG YOUNG ADULT MALES
Eitle, David
2010-01-01
Purpose Despite the surge in scholarly activity investigating the criminal career, relatively less attention has been devoted to the issue of criminal desistance versus persistence (until recently). The present study contributed to our understanding of this process by exploring the suitability of General Strain Theory (GST) for predicting changes in criminal activity across time. Methods Data from a longitudinal study of males in South Florida are examined using robust regression analyses. Results The core GST relationship, that changes in strain should predict changes in criminal activity, was supported, even after controlling for important adult social roles such as marriage, labor force participation, and education. While no support for the proposition that changes in self-esteem and social support moderate the strain-criminal desistance association was evinced, evidence was found that angry disposition, a measure of negative emotionality, moderated the association between change in chronic stressors and change in criminal activity. Conclusions While exploratory in nature, these findings demonstrate the utility of employing GST principles in studies of criminal desistance. PMID:21499526
Two-Temperature Effects on Plane Waves in Generalized Thermo-Microstretch Elastic Solid
NASA Astrophysics Data System (ADS)
Atwa, Sarhan. Y.; Jahangir, A.
2014-01-01
In this article, the effect of two temperatures on plane waves propagating through a generalized-thermo-microstretch elastic half-space solid has been investigated. The surface of the medium is subjected to a mode-I crack, and the axis is pointing vertically into the medium. Two fascinating theories of generalized thermo-elasticity presented by Green and Naghdi and named as without energy dissipation (GN-II) and with energy dissipation (GN-III) have been used. Governing equations for each particular case are also derived, and a solution is obtained. An analytical technique of normal mode analysis is used to obtain the exact expressions for the displacement components, force stresses, the temperature, and the couple stresses distribution. The variations of the considered variables against the vertical distance are illustrated graphically. Comparisons are made with the results between type II and III in generalized-thermo-microstretch and in a particular case (without microstretch constants). Numerical work is also performed for a suitable material with the aim of illustrating the results. It is found that the maximum amplitude is obtained for the maximum value of the two temperature parametric constant.
ERIC Educational Resources Information Center
Bao, Wan-Ning; Haas, Ain; Chen, Xiaojin; Pi, Yijun
2014-01-01
In Agnew's general strain theory, repeated strains can generate crime and delinquency by reducing social control and fostering social learning of crime. Using a sample of 615 middle-and high-school students in China, this study examines how social control and social learning variables mediate the effect of repeated strains in school and at…
ERIC Educational Resources Information Center
Moon, Byongook; Morash, Merry; McCluskey, Cynthia Perez; Hwang, Hye-Won
2009-01-01
Using longitudinal data on South Korean youth, the authors addressed limitations of previous tests of general strain theory (GST), focusing on the relationships among key strains, situational- and trait-based negative emotions, conditioning factors, and delinquency. Eight types of strain previously shown most likely to result in delinquency,…
NASA Astrophysics Data System (ADS)
Dai, Ming; Schiavone, Peter; Gao, Cun-Fa
2016-06-01
We re-examine the conclusion established earlier in the literature that in the presence of a homogeneously imperfect interface, the circular inhomogeneity is the only shape of inhomogeneity which can achieve a uniform internal strain field in an isotropic or anisotropic material subjected to anti-plane shear. We show that under certain conditions, it is indeed possible to design such non-circular inhomogeneities despite the limitation of a homogeneously imperfect interface. Our method proceeds by prescribing a uniform strain field inside a non-circular inhomogeneity via perturbations of the uniform strain field inside the analogous circular inhomogeneity and then subsequently identifying the corresponding (non-circular) shape via the use of a conformal mapping whose unknown coefficients are determined from a system of nonlinear equations. We illustrate our results with several examples. We note also that, for a given size of inhomogeneity, the minimum value of the interface parameter required to guarantee the desired uniform internal strain increases as the elastic constants of the inclusion approach those of the matrix. Finally, we discuss in detail the relationship between the curvature of the interface and the displacement jump across the interface in the design of such inhomogeneities.
Supersonic crack growth in a solid of upturn stress?strain relation under anti-plane shear
NASA Astrophysics Data System (ADS)
Guo, Gaofeng; Yang, Wei; Huang, Y.
2003-11-01
This paper examines, from the prospect of continuum analysis, the possibility for a supersonic crack growth in a solid with an upturn stress-strain relation. The stress has a linear-upturn power-law relation with the strain, resulting in an elastic modulus, and consequently a wave speed, that increase with the strain. Though appearing to be "supersonic", the local wave speed in the crack tip vicinity of the solid with a sufficient upturn stress-strain relation exceeds the crack extension speed. A pre-request for such a supersonic crack growth is the storage of sufficient deformation energy within the solid to nurse the energy flux drawn to the crack tip that extends at an "apparent supersonic" speed. The idea is demonstrated for the simplest case, the anti-plane shear. We examine the steady-state supersonic crack growth in a hyperelastic material. The governing equation is elliptical in the crack tip vicinity but hyperbolic elsewhere. The boundary between two regions is determined with a certain extent. An asymptotic solution is constructed within the super-hardening zone. The solution connects to the hyperbolic radiation strips by weak discontinuity boundaries and to the pre-stressed frontal field by a strong discontinuity boundary.
NASA Astrophysics Data System (ADS)
Skafte, Anders; Aenlle, Manuel L.; Brincker, Rune
2016-02-01
Measurement systems are being installed in more and more civil structures with the purpose of monitoring the general dynamic behavior of the structure. The instrumentation is typically done with accelerometers, where experimental frequencies and mode shapes can be identified using modal analysis and used in health monitoring algorithms. But the use of accelerometers is not suitable for all structures. Structures like wind turbine blades and wings on airplanes can be exposed to lightning, which can cause the measurement systems to fail. Structures like these are often equipped with fiber sensors measuring the in-plane deformation. This paper proposes a method in which the displacement mode shapes and responses can be predicted using only strain measurements. The method relies on the newly discovered principle of local correspondence, which states that each experimental mode can be expressed as a unique subset of finite element modes. In this paper the technique is further developed to predict the mode shapes in different states of the structure. Once an estimate of the modes is found, responses can be predicted using the superposition of the modal coordinates weighted by the mode shapes. The method is validated with experimental tests on a scaled model of a two-span bridge installed with strain gauges. Random load was applied to simulate a civil structure under operating condition, and strain mode shapes were identified using operational modal analysis.
Insight into the band structure engineering of single-layer SnS2 with in-plane biaxial strain.
Zhou, Wei; Umezawa, Naoto
2016-03-21
The effects of in-plane biaxial strain on the electronic structure of a photofunctional material, single-layer SnS2, were systematically investigated using hybrid density functional calculations. The bonding diagram for the band gap was firstly proposed based on the crystal orbital overlap population analysis. The conduction band-edge of single-layer SnS2 is determined by the anti-bonding interaction between Sn-5s and S-3p orbitals, while the valence band-edge comes from the anti-bonding between the neighboring S atoms. It is found that the compressive strain not only decreases the indirect band gap of single-layer SnS2, but also effectively promotes the band-edges of the conduction band to realize the overall water splitting. Besides, the dispersion of the valence band of single-layer SnS2 becomes weaker with increasing tensile strain which is beneficial for the photo-excitation through direct transitions. PMID:26912413
NASA Astrophysics Data System (ADS)
Harikumar, M.; Sankar, N.; Chandrakaran, S.
2015-09-01
Since 1969, when the concept of earth reinforcing was brought about by Henry Vidal, a large variety of materials such as steel bars, tire shreds, polypropylene, polyester, glass fibres, coir and jute fibres etc. have been widely added to soil mass randomly or in a regular, oriented manner. The conventional reinforcements in use were two dimensional or planar, in the form of strips with negligible widths or in the form of sheets. In this investigation, a novel concept of multi oriented plastic reinforcement (hexa-pods) is discussed. Direct shear tests were conducted on unreinforced and reinforced dry fine, medium and coarse sands. Detailed parametric studies with respect to the effective grain size of soil (d10), normal stress (σ) and the volume ratio of hexa-pods (Vr) were performed. It was noticed that addition of hexa-pods resulted in increase in the shear strength parameters viz. peak deviatoric stresses and increased angle of internal friction. The hexa-pods also changed the brittle behaviour of unreinforced sand samples to ductile ones. Although the peak shear stress did not show a considerable improvement, the angle of internal friction improved noticeably. Addition of a single layer of reinforcement along the shear plane also reduced the post peak loss of strength and changed the soil behavior from brittle to a ductile one.
Development of a Plane Strain Tensile Geometry to Assess Shear Fracture in Dual Phase Steels
NASA Astrophysics Data System (ADS)
Taylor, M. D.; Matlock, D. K.; De Moor, E.; Speer, J. G.
2014-10-01
A geometrically modified sample capable of generating a triaxial stress state when tested on a standard uniaxial tensile frame was developed to replicate shear fractures observed during stretch bend tests and industrial sheet stamping operations. Seven commercially produced dual phase (DP) steels were tested using the geometrically modified sample, and the modified sample successfully produced shear fractures on a unique shear plane for all steels. For each steel, void densities were determined, based on metallographic analyses, as a function of imposed displacement. Microstructural properties of ferrite and martensite grain size, martensite volume fraction (MVF), retained austenite content, Vickers hardness, average nanoindentation hardness, average ferrite and martensite constituent hardness, and tensile properties were obtained in order to evaluate potential correlations with void data. A linear correlation was observed between Vickers hardness and the average nanoindentation hardness, verifying the ability of nanoindentation to produce data consistent with more traditional hardness measurement techniques. A linear relationship was observed between the number of voids present at 90% failure displacement and the martensite/ferrite hardness ratio, indicating that a decrease in relative hardness difference in a microstructure can suppress void formation, and potentially extend formability limits. The void population appeared independent of MVF, grain size, and tensile properties suggesting that constituent hardness may be a dominant parameter when considering suppression of void nucleation in DP steels.
NASA Astrophysics Data System (ADS)
Qiu, J. H.; Jiang, Q.
2007-10-01
A phenomenological Landau Devonshire thermodynamic theory is used to describe the effects of anisotropic in-plane misfit strains on equilibrium polarization states and dielectric properties of single domain epitaxial Pb(Zr1-xTix)O3 thin films grown on dissimilar orthorhombic substrates. Compared with the “isotropic in-plane misfit strains-temperature” phase diagrams, the characteristic features of “misfit strain-misfit strain” and “misfit strain-temperature” phase diagrams under the circumstance of strain anisotropy are the presence of four different phases (a, a, ac, and ac) and the direct 90° polarization switching between c phase and a phase (or a phase), between a phase and a phase. The misfit strain dependence of polarization components, the small-signal dielectric responses and the tunabilities at room temperature are also calculated. We find that the phase diagrams and dielectric properties largely depend on anisotropic in-plane misfit strains as well. Moreover, the strain anisotropy will lead to the polarization and dielectric anisotropy.
Generalized power-law stiffness model for nonlinear dynamics of in-plane cable networks
NASA Astrophysics Data System (ADS)
Giaccu, Gian Felice; Caracoglia, Luca
2013-04-01
Cross-ties are used for mitigating stay-cable vibration, induced by wind and wind-rain on cable-stayed bridges. In-plane cable networks are obtained by connecting the stays by transverse cross-ties. While taut-cable theory has been traditionally employed for simulating the dynamics of cable networks, the use of a nonlinear restoring-force discrete element in each cross-tie has been recently proposed to more realistically replicate the network vibration when snapping or slackening of the restrainer may be anticipated. The solution to the free-vibration dynamics can be determined by "equivalent linearization method". In an exploratory study by the authors a cubic-stiffness spring element, in parallel with a linear one, was used to analyze the restoring-force effect in a cross-tie on the nonlinear dynamics of two simplified systems. This preliminary investigation is generalized in this paper by considering a power-law stiffness model with a generic integer exponent and applied to a prototype network installed on an existing bridge. The study is restricted to the fundamental mode and some of the higher ones. A time-domain lumped-mass algorithm is used for validating the equivalent linearization method. For the prototype network with quadratic-stiffness spring and a positive stiffness coefficient, a stiffening effect is observed, with a ten percent increment in the equivalent frequency for the fundamental mode. Results also show dependency on vibration amplitude. For higher modes the equivalent nonlinear effects can be responsible for an alteration of the linear mode shapes and a transition from a "localized mode" to a "global mode".
Lai, Chih-Ming; Huang, Yu-En; Feng, Shih-Wei; Kou, Kuang-Yang; Chen, Chien-Hsun; Tu, Li-Wei
2015-07-13
Anisotropic strain relaxation and the resulting degree of polarization of photoluminescence (PL) in nonpolar a-plane textured ZnO are experimentally and theoretically studied. A thicker nonpolar a-plane textured ZnO film enhances the anisotropic in-plane strain relaxation, resulting in a larger degree of polarization of PL and better sample quality. Anisotropic in-plane strains, sample quality, and degree of polarization of PL in nonpolar a-plane ZnO are consequences of the degree of anisotropic in-plane strain relaxation. By the k·p perturbation approach, simulation results of the variation of the degree of polarization for the electronic transition upon anisotropic in-plane strain relaxation agree with experimental results.
ERIC Educational Resources Information Center
Moon, Byongook; Blurton, David; McCluskey, John D.
2008-01-01
The study examines the effects of recent, older, and chronic strains and of perceived injustice of strain on delinquency, sampling 777 Korean youth. Seven key strains most likely leading to delinquency, some of which were often overlooked in previous research, were included, and these are family conflict, parental punishment, teachers' punishment,…
The Relativistic Transformation for an Electromagnetic Plane Wave with General Time Dependence
ERIC Educational Resources Information Center
Smith, Glenn S.
2012-01-01
In special relativity, the transformation between inertial frames for an electromagnetic plane wave is usually derived for the time-harmonic case (the field is a sinusoid of infinite duration), even though all practical waves are of finite duration and may not even contain a dominant sinusoid. This paper presents an alternative derivation in which…
Wu, Huaping; Chai, Guozhong; Zhou, Ting; Zhang, Zheng; Kitamura, Takayuki; Zhou, Haomiao
2014-03-21
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 among 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.
Goulet, T.; Keszei, E.; Jay-Gerin, J.
1988-03-15
We present a three-dimensional probabilistic model of particle transport in a medium where the particles suffer quasielastic collisions. The model accounts for bulk and surface scattering, as well as partial reflections at the boundaries of the medium. We give analytical and numerical methods for the evaluation of the particle transmission probability in the case of a medium with a plane-parallel geometry. The influence of the various parameters of the model on this probability is also discussed.
Støylen, Asbjørn; Ingul, Charlotte B; Torp, Hans
2003-01-01
Background We describe a method for 3-/4D reconstruction of tissue Doppler data from three standard apical planes, post processing to derived data of strain rate / strain and parametric colour imaging of the data. The data can be displayed as M-mode arrays from all six walls, Bull's eye projection and a 3D surface figure that can be scrolled and rotated. Numerical data and waveforms can be re-extracted. Methods Feasibility was tested by Strain Rate Imaging in 6 normal subjects and 6 patients with acute myocardial infarction. Reverberation artefacts and dyssynergy was identified by colour images. End systolic strain, peak systolic and mid systolic strain rate were measured. Results Infarcts were visualised in all patients by colour imaging of mid systolic strain rate, end systolic strain and post systolic shortening by strain rate. Reverberation artefacts were visible in 3 of 6 normals, and 2 of 6 patients, and were identified both on bull's eye and M-mode display, but influenced quantitative measurement. Peak systolic strain rate was in controls minimum -1.11, maximum -0.89 and in patients minimum -1.66, maximum 0.02 (p = 0.04). Mid systolic strain rate and end systolic strain did not separate the groups significantly. Conclusion 3-/4D reconstruction and colour display is feasible, allowing quick visual identification of infarcts and artefacts, as well as extension of area of post systolic shortening. Strain rate is better suited to colour parametric display than strain. PMID:12956886
NASA Astrophysics Data System (ADS)
Strine, Matthew; Wojtal, Steven F.
2004-10-01
We report quartz c-axis patterns, grain-shape fabrics, and microstructures for 11 mylonitic quartzites and quartz-phyllosilicate schists from a transect across the Moine thrust at Loch Srath nan Aisinnin, North-West Scotland. In the footwall samples collected more than 42 m normal distance from the thrust surface, quartz c-axis textures indicate a general flattening strain (i.e. 0< k<1). Samples within 19 m normal distance of the thrust are completely recrystallized and exhibit asymmetric c-axis patterns. Recrystallized hanging wall fault rocks exhibit random c-axis patterns on the scale of a standard thin section. Relict footwall grains provide the closest approximation of finite strain; they have octahedral shear strains ( ɛs) between 1.10 and 1.47 and exhibit general flattening k-values (0.0524-0.659). The long axis of the mean relict grain shape trends parallel to the regional transport direction and plunges gently to the ESE. In contrast, recrystallized footwall grains have a mean grain shape with the longest axis oriented nearly perpendicular to the transport direction. Furthermore, these samples have grain shape k-value ranges from 0.157 to 0.295. Recrystallized hanging wall grain shapes exhibit the lowest octahedral shear 'strains' ( ɛs=0.532-0.733) and largest mean k-values (0.351-0.961) of this sample set. The long axes of the mean recrystallized hanging wall grain shapes are parallel to transport, similar to that of relict footwall grains. Unrecrystallized quartz overgrowths about opaque mineral grains suggest concurrent elongation in all directions within the mylonitic foliation and support the inference of general flattening deformation. The mylonitic foliation and penetrative lineation are consistent with a WNW shearing direction; however, both were folded during later deformation increments. Recrystallized grains in footwall quartzites suggest a 305-320° azimuth for the shearing direction. The best-fit π-axis of the poles to the foliation is 18
NASA Astrophysics Data System (ADS)
Hu, Lun-Hui; Xu, Dong-Hui; Zhang, Fu-Chun; Zhou, Yi
2016-08-01
Motivated by the recent discovery of quantized spin Hall effect in InAs/GaSb quantum wells [Du, Knez, Sullivan, and Du, Phys. Rev. Lett. 114, 096802 (2015), 10.1103/PhysRevLett.114.096802], we theoretically study the effects of in-plane magnetic field and strain effect to the quantization of charge conductance by using Landauer-B ütikker formalism. Our theory predicts a robustness of the conductance quantization against the in-plane magnetic field up to a very high field of 20 T. We use a disordered hopping term to model the strain and show that the strain may help the quantization of the conductance. Relevance to the experiments will be discussed.
Generalizing the Fermi velocity of strained graphene from uniform to nonuniform strain
NASA Astrophysics Data System (ADS)
Oliva-Leyva, M.; Naumis, Gerardo G.
2015-10-01
The relevance of the strain-induced Dirac point shift to obtain the appropriate anisotropic Fermi velocity of strained graphene is demonstrated. Then a critical revision of the available effective Dirac Hamiltonians is made by studying in detail the limiting case of a uniform strain. An effective Dirac Hamiltonian for nonuniform strain is thus reported, which takes into account all strain-induced effects: changes in the nearest-neighbor hopping parameters, the reciprocal lattice deformation and the true shift of the Dirac point. Pseudomagnetic fields are thus explained by means of position-dependent Dirac cones, whereas complex gauge fields appear as a consequence of a position-dependent Fermi velocity. Also, position-dependent Fermi velocity effects on the spinor wavefunction are considered for interesting cases of deformations such as flexural modes.
General scaling limitations of ground-plane and isolated-object cloaks
Hashemi, Hila; Johnson, Steven G.; Oskooi, A.; Joannopoulos, J. D.
2011-08-15
We prove that, for arbitrary three-dimensional transformation-based invisibility cloaking of an object above a ground plane or of isolated objects, there are practical constraints that increase with the object size. In particular, we show that the cloak thickness must scale proportionally to the thickness of the object being cloaked, assuming bounded refractive indices, and that absorption discrepancies and other imperfections must scale inversely with the object thickness. For isolated objects, we also show that bounded refractive indices imply a lower bound on the effective cross section.
Scattering of a plane electromagnetic wave by a generalized Luneburg sphere-Part 1: Ray scattering
NASA Astrophysics Data System (ADS)
Lock, James A.; Laven, Philip; Adam, John A.
2015-09-01
We calculated scattering of an electromagnetic plane wave by both a radially-inhomogeneous particle and bubble, the square of whose refractive index profile is parabolic as a function of radius. Depending on the value of the two adjustable parameters of the parabola, the particle or bubble can have either a refractive index discontinuity at its surface, or the refractive index can smoothly merge into that of the exterior medium. Scattering was analyzed in ray theory, and various novel features of the scattering, including the details of the curved ray paths, transmission rainbows, and near-critical-angle scattering were apparent and were contrasted with their behavior for scattering by a homogeneous sphere.
NASA Astrophysics Data System (ADS)
Kim, Ji Hoon; Park, Jung Ho; Hwang, Sung-Min; Baik, Kwang Hyeon
2012-05-01
We studied the growth and the characteristics of nonpolar Si-doped a-plane GaN grown on r-plane sapphire substrates with different off-cut angles which were changed in the range of -0.2° ˜ +0.4°. Samples grown by using -0.2° and +0.2° off-cut angles showed triangular pit-free and smooth surfaces, which resulted from enhanced lateral growth owing to the epitaxial films having a Ga face. On the other hand, the sample grown by using +0.4° off-cut angles revealed a high density of pits and low crystalline quality due to a high density of dislocations. The strain determined by using calculations with the lattice parameters also showed a dependence on the off-cut angles. We expect r-plane sapphire with off-cut angles in the range of -0.2° ˜ +0.2° to be very effective for improving the crystalline quality and the surface morphology of a-plane GaN.
ERIC Educational Resources Information Center
Ellwanger, Steven J.
2007-01-01
This article enhances our knowledge of general strain theory (GST) by applying it to the context of traffic delinquency. It does so by first describing and confirming the development of a social-psychological measure allowing for a test of GST. Structural regression analysis is subsequently employed to test the theory within this context across a…
Frenkel, A.L.; Indireshkumar, K.
1999-10-01
Wavy film flow of incompressible Newtonian fluid down an inclined plane is considered. The question is posed as to the parametric conditions under which the description of evolution can be approximately reduced for all time to a single evolution equation for the film thickness. An unconventional perturbation approach yields the most general evolution equation and least restrictive conditions on its validity. The advantages of this equation for analytical and numerical studies of three-dimensional waves in inclined films are pointed out. {copyright} {ital 1999} {ital The American Physical Society}
NASA Astrophysics Data System (ADS)
Kumar, Rajneesh; Singh, Manjeet
2009-07-01
The present investigation is concerned with the propagation of plane waves at an imperfectly bonded interface of two orthotropic generalized thermoelastic rotating half-spaces with different elastic and thermal properties. The thermoelastic theory with one relaxation time developed by Lord and Shulman [A generalized dynamical theory of thermoelasticity, J. Mech. Phys. Solids 15 (1967) 299-309] is used to study the problem. The reflection and transmission coefficients of Quasi Longitudinal (QL-) wave, Quasi Thermal (T-mode) wave and Quasi Transverse (QT-) wave have been derived. The effect of rotation has been studied on the velocities of different waves. Some special cases of boundaries i.e. normal stiffness, transverse stiffness, thermal contact conductance, slip boundary and welded contact boundary have been deduced from an imperfect one. Impact of different boundaries has been studied graphically. It is observed that thermal properties, rotation and imperfect boundary have significant effect on the propagation of waves.
Strain analysis from objects with a random distribution: A generalized center-to-center method
NASA Astrophysics Data System (ADS)
Shan, Yehua; Liang, Xinquan
2014-03-01
Existing methods of strain analysis such as the center-to-center method and the Fry method estimate strain from the spatial relationship between point objects in the deformed state. They assume a truncated Poisson distribution of point objects in the pre-deformed state. Significant deviations occur in nature and diffuse the central vacancy in a Fry plot, limiting the its effectiveness as a strain gauge. Therefore, a generalized center-to-center method is proposed to deal with point objects with the more general Poisson distribution, where the method outcomes do not depend on an analysis of a graphical central vacancy. This new method relies upon the probability mass function for the Poisson distribution, and adopts the maximum likelihood function method to solve for strain. The feasibility of the method is demonstrated by applying it to artificial data sets generated for known strains. Further analysis of these sets by use of the bootstrap method shows that the accuracy of the strain estimate has a strong tendency to increase either with point number or with the inclusion of more pre-deformation nearest neighbors. A poorly sorted, well packed, deformed conglomerate is analyzed, yielding strain estimate similar to the vector mean of the major axis directions of pebbles and the harmonic mean of their axial ratios from a shape-based strain determination method. These outcomes support the applicability of the new method to the analysis of deformed rocks with appropriate strain markers.
Relation between psychological strain and carotid atherosclerosis in a general population
Wolff, B; Grabe, H J; Völzke, H; Lüdemann, J; Kessler, C; Dahm, J B; Freyberger, H J; John, U; Felix, S B
2005-01-01
Objective: To investigate the hypothesis that psychological strain is related to carotid atherosclerosis in a large general population sample. Methods: Intima–media thickness and the prevalence of atherosclerotic plaques in the carotid arteries were quantitatively assessed by high resolution ultrasound among 2164 participants (1112 women and 1052 men, aged 45 to 75 years) of the SHIP (study of health in Pomerania), an epidemiological survey of a random sample of the population of north eastern Germany. Psychological strain was measured by 13 items reflecting typical psychological complaints. Each item was graded by the study participants on a four point scale (from 0, absent, to 3, severe) and a psychological strain score was generated by summing these 13 items. Results: Mean psychological strain score was 10.8 (7.0) (median score 10) among women and 8.5 (6.2) (median score 8) among men. Psychological strain did not predict carotid intima–media thickness among either men or women. However, after adjustment for covariates, high psychological strain and carotid plaques were independently and linearly related, with plaque prevalence odds of 1.03 (95% confidence interval (CI) 1.01 to 1.05, p = 0.009) per increment of the psychological strain score among women and 1.04 (95% CI 1.01 to 1.07, p = 0.003) among men. Conclusions: This study identified a relation between general psychological strain and carotid atherosclerosis. PMID:15772199
NASA Astrophysics Data System (ADS)
Feng, Shih-Wei; Chen, Yu-Yu; Lai, Chih-Ming; Tu, Li-Wei; Han, Jung
2013-12-01
Anisotropic strain relaxation and the resulting degree of polarization of the electronic transition in nonpolar a-plane GaN using one- and two-step growth are studied. By using two-step growth, a slower coalescence and a longer roughening-recovery process lead to larger anisotropic strain relaxation, a less striated surface, and lower densities of basal stacking fault (BSF) and prismatic stacking fault (PSF). It is suggested that anisotropic in-plane strains, surface striation, and BSF and PSF densities in nonpolar a-GaN are consequences of the rate of coalescence, the period of roughening-recovery process, and the degree of anisotropic strain relaxation. In addition, the two-step growth mode can enhance the degree of polarization of the electronic transition. The simulation results of the kṡp perturbation approach show that the oscillator strength and degree of polarization of the electronic transition strongly depend on the in-plane strains upon anisotropic in-plane strain relaxation. The research results provide important information for optimized growth of nonpolar III-nitrides. By using two-step growth and by fabricating the devices on the high-quality nonpolar free-standing GaN substrates, high-efficiency nonpolar a-plane InGaN LEDs can be realized. Nonpolar a-plane InGaN/GaN LEDs can exhibit a strongly polarized light to improve the contrast, glare, eye discomfort and eye strain, and efficiency in display application.
Feng, Shih-Wei Chen, Yu-Yu; Lai, Chih-Ming; Tu, Li-Wei; Han, Jung
2013-12-21
Anisotropic strain relaxation and the resulting degree of polarization of the electronic transition in nonpolar a-plane GaN using one- and two-step growth are studied. By using two-step growth, a slower coalescence and a longer roughening-recovery process lead to larger anisotropic strain relaxation, a less striated surface, and lower densities of basal stacking fault (BSF) and prismatic stacking fault (PSF). It is suggested that anisotropic in-plane strains, surface striation, and BSF and PSF densities in nonpolar a-GaN are consequences of the rate of coalescence, the period of roughening-recovery process, and the degree of anisotropic strain relaxation. In addition, the two-step growth mode can enhance the degree of polarization of the electronic transition. The simulation results of the k⋅p perturbation approach show that the oscillator strength and degree of polarization of the electronic transition strongly depend on the in-plane strains upon anisotropic in-plane strain relaxation. The research results provide important information for optimized growth of nonpolar III-nitrides. By using two-step growth and by fabricating the devices on the high-quality nonpolar free-standing GaN substrates, high-efficiency nonpolar a-plane InGaN LEDs can be realized. Nonpolar a-plane InGaN/GaN LEDs can exhibit a strongly polarized light to improve the contrast, glare, eye discomfort and eye strain, and efficiency in display application.
Structure and switching of in-plane ferroelectric nano-domains in strained PbxSr1-xTiO3 thin films
Matzen, Sylivia; Nesterov, Okeksiy; Rispens, Gregory; Heuver, J. A.; Bark, C; Biegalski, Michael D; Christen, Hans M; Noheda, Beatriz
2014-01-01
Nanoscale ferroelectrics, the active elements of a variety of nanoelectronic devices, develop denser and richer domain structures than the bulk counterparts. With shrinking device sizes understanding and controlling domain formation in nanoferroelectrics is being intensely studied. Here we show that a precise control of the epitaxy and the strain allows stabilizing a hierarchical domain architecture in PbxSr1-xTiO3 thin films, showing periodic, purely in-plane polarized, ferroelectric nano-domains that can be switched by a scanning probe.
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.
Marquez, J. Pablo; Genin, Guy M.; Zahalak, George I.; Elson, Elliot L.
2005-01-01
Constitutive models are needed to relate the active and passive mechanical properties of cells to the overall mechanical response of bio-artificial tissues. The Zahalak model attempts to explicitly describe this link for a class of bio-artificial tissues. A fundamental assumption made by Zahalak is that cells stretch in perfect registry with a tissue. We show this assumption to be valid only for special cases, and we correct the Zahalak model accordingly. We focus on short-term and very long-term behavior, and therefore consider tissue constituents that are linear in their loading response (although not necessarily linear in unloading). In such cases, the average strain in a cell is related to the macroscopic tissue strain by a scalar we call the “strain factor”. We incorporate a model predicting the strain factor into the Zahalak model, and then reinterpret experiments reported by Zahalak and co-workers to determine the in situ stiffness of cells in a tissue construct. We find that, without the modification in this article, the Zahalak model can underpredict cell stiffness by an order of magnitude. PMID:15596492
NASA Astrophysics Data System (ADS)
Seereeram, D.; McVay, M. C.; Linton, P. F.
1985-06-01
An analytical and experimental investigation into the influences of material anisotropy and principal plane rotation on the stress-strain and strength behavior of granular soil (Reid-Bedford Sand) is conducted. The laboratory investigation entailed the performance of approximately fifteen triaxial tests under conventional compression and extension loading, and five through initial shear, followed by hydrostatic compression. The initial tests with an additional fifteen experiments were used in characterizing the influence of inherent anisotropy and principal plane rotations on material response. The latter were employed to delineate the effects of stress-induced anisotropy. A review of existing elasto-plastic theory as related to soil mechanics showed only a few models of a phenomenological nature which of the multi-surface isotropic/kinematic hardening characterizations, Prevost's pressure sensitive model, was used in the prediction of the hollow cylinder tests. Although the model reasonably reproduced the response along its calibration path, it did not quantitatively or qualitatively predict the laboratory results along other stress paths which involved principal plane and the need for improved analytical representation.
NASA Astrophysics Data System (ADS)
Cakmak, M.; Hassan, M.; Unsal, E.; Martins, C.
2012-12-01
An instrumented and highly integrated biaxial stretching system was designed and constructed to obtain true stress, true strain, and optical behavior of polymeric films during biaxial stretching. With programmable drive motors, any form of temporally varying biaxial deformation profiles, including linear, exponential, logarithmic as well as cyclic, can be applied to a square-shaped films. This machine allows the investigation of mechano-optical behavior of films under profiles captured in industrial processes. To overcome the edge effects, the samples are painted with a dot pattern that is imaged using a high speed video capture system. This system accurately determines the locations of the each dot matrix in subsequent images acquired and calculates the true strains in both directions. The in-plane optical retardation is determined using spectral birefringence method that uses polarized white light and optical spectrometer in the optical train. This is carried out automatically at less than 10 nm in retardation resolution with the light beam passing through the symmetry center of the sample. Out of plane retardation is measured with an identical optical train tilted 45° to the plane of the film with its light beam going through the same spot on the sample as 0° beam. The true stress and birefringences are calculated with the determined instantaneous thickness of the film. With this system, the stress optical behavior of PET's is determined up to very large deformation levels at moderate to high deformation rates. Beyond the initial linear stress optical behavior, these films exhibit sudden positive deviation from linearity and this start of nonlinearity was directly associated with the stress induced crystallization.
General Strain Theory as a Basis for the Design of School Interventions
ERIC Educational Resources Information Center
Moon, Byongook; Morash, Merry
2013-01-01
The research described in this article applies general strain theory to identify possible points of intervention for reducing delinquency of students in two middle schools. Data were collected from 296 youths, and separate negative binomial regression analyses were used to identify predictors of violent, property, and status delinquency. Emotional…
Batra, R.C.; Peng, Z.
1995-12-31
The authors study the initiation and growth of shear bands in prismatic bodies of rectangular cross-section made of either depleted uranium or tungsten and deformed in plane strain compression at a nominal strain-rate of 5000/s. It is found that, in the deformed configuration, shear bands in depleted uranium blocks are inclined at approximately 42.5 deg counterclockwise from the horizontal axis, those in tungsten are inclined at nearly l35 deg. When shear bands initiate, the total compressive force required to deform the body drops sharply for the uranium blocks but gradually for the tungsten blocks. After a shear band has developed, dead zones form in both uranium and tungsten blocks; the size of the dead zone in the tungsten block is more than that in the uranium block. When the shear modulus for the tungsten is artificially changed so as to equal that for the uranium, the angle of inclination for the shear bands in tungsten blocks changes to that found for the uranium blocks. This suggests that the value of the shear modulus plays a noticeable role in the development of shear bands.
ERIC Educational Resources Information Center
Mazerolle, Paul; Piquero, Alex R.; Capowich, George E.
2003-01-01
Explored whether relationships between strain, anger, and deviant outcomes varied when using trait- or situational-based measures of anger, noting whether people with higher trait anger had increased likelihood of experiencing strain, becoming angry from strain, and responding deviantly. Relying on trait-based static indicators of anger was…
NASA Astrophysics Data System (ADS)
Sainath, Kamalesh; Teixeira, Fernando L.; Donderici, Burkay
2014-07-01
We propose the complex-plane generalization of a powerful algebraic sequence acceleration algorithm, the method of weighted averages (MWA), to guarantee exponential-cum-algebraic convergence of Fourier and Fourier-Hankel (F-H) integral transforms. This “complex-plane” MWA, effected via a linear-path detour in the complex plane, results in rapid, absolute convergence of field and potential solutions in multi-layered environments regardless of the source-observer geometry and anisotropy/loss of the media present. In this work, we first introduce a new integration path used to evaluate the field contribution arising from the radiation spectra. Subsequently, we (1) exhibit the foundational relations behind the complex-plane extension to a general Levin-type sequence convergence accelerator, (2) specialize this analysis to one member of the Levin transform family (the MWA), (3) address and circumvent restrictions, arising for two-dimensional integrals associated with wave dynamics problems, through minimal complex-plane detour restrictions and a novel partition of the integration domain, (4) develop and compare two formulations based on standard/real-axis MWA variants, and (5) present validation results and convergence characteristics for one of these two formulations.
Sainath, Kamalesh; Teixeira, Fernando L.; Donderici, Burkay
2014-07-15
We propose the complex-plane generalization of a powerful algebraic sequence acceleration algorithm, the method of weighted averages (MWA), to guarantee exponential-cum-algebraic convergence of Fourier and Fourier–Hankel (F–H) integral transforms. This “complex-plane” MWA, effected via a linear-path detour in the complex plane, results in rapid, absolute convergence of field and potential solutions in multi-layered environments regardless of the source-observer geometry and anisotropy/loss of the media present. In this work, we first introduce a new integration path used to evaluate the field contribution arising from the radiation spectra. Subsequently, we (1) exhibit the foundational relations behind the complex-plane extension to a general Levin-type sequence convergence accelerator, (2) specialize this analysis to one member of the Levin transform family (the MWA), (3) address and circumvent restrictions, arising for two-dimensional integrals associated with wave dynamics problems, through minimal complex-plane detour restrictions and a novel partition of the integration domain, (4) develop and compare two formulations based on standard/real-axis MWA variants, and (5) present validation results and convergence characteristics for one of these two formulations.
NASA Technical Reports Server (NTRS)
Zamula, G. N.; Ierusalimsky, K. M.; Kalmykova, G. S.; Fomin, V. P.
1998-01-01
The present paper is a final technical report within the NCCW-1-233 research program (dated June 1, 1997) accomplished as a part of co-operation between United States' NASA and Russia's Goskomoboronprom in aeronautics, and continues similar NCCW-73 and NCC-1-233 programs accomplished in 1996 and 1997, respectively. The report concludes studies in two domains, "Analyzing the effect of skin postbuckling on general stresses and strains in a composite structure" and "Evaluating the effect of skin postbuckling behavior on general stability of a composite structure"; the work was fulfilled in compliance with NCC-1-233 requirements (as of June 1, 1997). Also, the present studies may be regarded as a partial generalization of efforts in [1, 2] conducted within the above programs in what concerns postbuckling behavior of composite structures.
van Kessel, Marco; Seaton, David; Chan, Jonathan; Yamada, Akira; Kermeen, Fiona; Butler, Thomas; Sabapathy, Surendran; Morris, Norman
2016-06-01
Pulmonary hypertension (PH) is a progressively fatal disease having a significant impact on right ventricular (RV) function, a major determinant of long-term outcome in PH patients. In our clinic we frequently noticed the combination of PH and reduced RV function, but with discordant Tricuspid Annular Plane Systolic Excursion (TAPSE) values. The present study focuses on whether RV free wall strain measured using 2-dimensional speckle-tracking echocardiography is able to predict mortality in this subgroup of PH patients. 57 patients with PH and RV dysfunction (visual echocardiographic assessment of ≥2) and pseudo-normalized TAPSE values (defined as ≥16 mm) were retrospectively evaluated. Patients were divided by RV free -20 % as cut-off value. Follow-up data on all-cause mortality were registered after a median follow-up time of 27.9 ± 1.7 months. RV free of ≥-20 % was predictive of all-cause mortality after a median follow-up time of 27.9 ± 1.7 months (HR 3.76, 95 % CI 1.02-13.92, p = 0.05). RV free ≥-20 % remained a significant predictor of all-cause mortality (HR 4.30, 95 % CI 1.11-16.61, p = 0.04) after adjusting for PH-specific treatment. On the contrary, TAPSE was not a significant predictor of all-cause mortality. RV free wall strain provides prognostic information in patients with PH and RV dysfunction, but with normal TAPSE values. Future studies with larger cohorts, longer follow-up periods and inclusion of more echocardiographic parameters measuring LV and RV function could confirm the strength of RV free ≥-20 % as a predictor of mortality for this subgroup of patients with PH. PMID:26931558
Lin, Wen-Hsu; Cochran, John K; Mieczkowski, Thomas
2011-01-01
Using a national probability sample of adolescents (12–17), this study applies general strain theory to how violent victimization, vicarious violent victimization, and dual violent victimization affect juvenile violent/property crime and drug use. In addition, the mediating effect and moderating effect of depression, low social control, and delinquent peer association on the victimization–delinquency relationship is also examined. Based on SEM analyses and contingency tables, the results indicate that all three types of violent victimization have significant and positive direct effects on violent/property crime and drug use. In addition, the expected mediating effects and moderating effects are also found. Limitations and future directions are discussed. PMID:21858930
NASA Astrophysics Data System (ADS)
Padmanabhan, R.; Oliveira, M. C.; Baptista, A. J.; Alves, J. L.; Menezes, L. F.
2007-05-01
Springback phenomenon associated with the elastic properties of sheet metals makes the design of forming dies a complex task. Thus, to develop consistent algorithms for springback compensation an accurate prediction of the amount of springback is mandatory. The numerical simulation using the finite element method is consensually the only feasible method to predict springback. However, springback prediction is a very complicated task and highly sensitive to various numerical parameters of finite elements (FE), such as: type, order, integration scheme, shape and size, as well the time integration formulae and the unloading strategy. All these numerical parameters make numerical simulation of springback more sensitive to numerical tolerances than the forming operation. In case of an unconstrained cylindrical bending, the in-plane to thickness FE size ratio is more relevant than the number of FE layers through-thickness, for the numerical prediction of final stress and strain states, variables of paramount importance for an accurate springback prediction. The aim of the present work is to evaluate the influence of the refinement of a 3-D FE mesh, namely the in-plane mesh refinement and the number of through-thickness FE layers, in springback prediction. The selected example corresponds to the first stage of the "Numisheet'05 Benchmark♯3", which consists basically in the sheet forming of a channel section in an industrial-scale channel draw die. The physical drawbeads are accurately taken into account in the numerical model in order to accurately reproduce its influence during the forming process simulation. FEM simulations were carried out with the in-house code DD3IMP. Solid finite elements were used. They are recommended for accuracy in FE springback simulation when the ratio between the tool radius and blank thickness is lower than 5-6. In the selected example the drawbead radius is 4.0 mm. The influence of the FE mesh refinement in springback prediction is
Bertacca, Daniele; Maartens, Roy; Raccanelli, Alvise; Clarkson, Chris E-mail: Roy.Maartens@port.ac.uk E-mail: Clarkson@maths.uct.ac.za
2012-10-01
We extend previous analyses of wide-angle correlations in the galaxy power spectrum in redshift space to include all general relativistic effects. These general relativistic corrections to the standard approach become important on large scales and at high redshifts, and they lead to new terms in the wide-angle correlations. We show that in principle the new terms can produce corrections of nearly 10% on Gpc scales over the usual Newtonian approximation. General relativistic corrections will be important for future large-volume surveys such as SKA and Euclid, although the problem of cosmic variance will present a challenge in observing this.
Jana, Biman; Onuchic, José N.
2016-01-01
A structure-based model of myosin motor is built in the same spirit of our early work for kinesin-1 and Ncd towards physical understanding of its mechanochemical cycle. We find a structural adaptation of the motor head domain in post-powerstroke state that signals faster ADP release from it compared to the same from the motor head in the pre-powerstroke state. For dimeric myosin, an additional forward strain on the trailing head, originating from the postponed powerstroke state of the leading head in the waiting state of myosin, further increases the rate of ADP release. This coordination between the two heads is the essence of the processivity of the cycle. Our model provides a structural description of the powerstroke step of the cycle as an allosteric transition of the converter domain in response to the Pi release. Additionally, the variation in structural elements peripheral to catalytic motor domain is the deciding factor behind diverse directionalities of myosin motors (myosin V & VI). Finally, we observe that there are general rules for functional molecular motors across the different families. Allosteric structural adaptation of the catalytic motor head in different nucleotide states is crucial for mechanochemistry. Strain-mediated coordination between motor heads is essential for processivity and the variation of peripheral structural elements is essential for their diverse functionalities. PMID:27494025
Jana, Biman; Onuchic, José N
2016-08-01
A structure-based model of myosin motor is built in the same spirit of our early work for kinesin-1 and Ncd towards physical understanding of its mechanochemical cycle. We find a structural adaptation of the motor head domain in post-powerstroke state that signals faster ADP release from it compared to the same from the motor head in the pre-powerstroke state. For dimeric myosin, an additional forward strain on the trailing head, originating from the postponed powerstroke state of the leading head in the waiting state of myosin, further increases the rate of ADP release. This coordination between the two heads is the essence of the processivity of the cycle. Our model provides a structural description of the powerstroke step of the cycle as an allosteric transition of the converter domain in response to the Pi release. Additionally, the variation in structural elements peripheral to catalytic motor domain is the deciding factor behind diverse directionalities of myosin motors (myosin V & VI). Finally, we observe that there are general rules for functional molecular motors across the different families. Allosteric structural adaptation of the catalytic motor head in different nucleotide states is crucial for mechanochemistry. Strain-mediated coordination between motor heads is essential for processivity and the variation of peripheral structural elements is essential for their diverse functionalities. PMID:27494025
A General Bayesian Approach to Analyzing Diallel Crosses of Inbred Strains
Lenarcic, Alan B.; Svenson, Karen L.; Churchill, Gary A.; Valdar, William
2012-01-01
The classic diallel takes a set of parents and produces offspring from all possible mating pairs. Phenotype values among the offspring can then be related back to their respective parentage. When the parents are diploid, sexed, and inbred, the diallel can characterize aggregate effects of genetic background on a phenotype, revealing effects of strain dosage, heterosis, parent of origin, epistasis, and sex-specific versions thereof. However, its analysis is traditionally intricate, unforgiving of unplanned missing information, and highly sensitive to imbalance, making the diallel unapproachable to many geneticists. Nonetheless, imbalanced and incomplete diallels arise frequently, albeit unintentionally, as by-products of larger-scale experiments that collect F1 data, for example, pilot studies or multiparent breeding efforts such as the Collaborative Cross or the Arabidopsis MAGIC lines. We present a general Bayesian model for analyzing diallel data on dioecious diploid inbred strains that cleanly decomposes the observed patterns of variation into biologically intuitive components, simultaneously models and accommodates outliers, and provides shrinkage estimates of effects that automatically incorporate uncertainty due to imbalance, missing data, and small sample size. We further present a model selection procedure for weighing evidence for or against the inclusion of those components in a predictive model. We evaluate our method through simulation and apply it to incomplete diallel data on the founders and F1's of the Collaborative Cross, robustly characterizing the genetic architecture of 48 phenotypes. PMID:22345610
Childhood abuse and criminal behavior: testing a general strain theory model.
Watts, Stephen J; McNulty, Thomas L
2013-10-01
This article draws on general strain theory (GST) to develop and test a model of the childhood abuse-crime relationship. Using data from the National Longitudinal Study of Adolescent Health (Add Health),(1) we find that early childhood physical and sexual abuse are robust predictors of offending in adolescence, for the full sample and in equations disaggregated by gender. GST is partially supported in that the effects of childhood physical abuse on offending for both females and males are mediated by an index of depression symptoms, whereas the effect of sexual abuse among females appears to be mediated largely by closeness to mother. The effect of childhood sexual abuse among males, however, is more robust than among females and it persists despite controls for low self-control, ties to delinquent peers, school attachment, and closeness to mother. Theoretical implications of the findings are discussed. PMID:23787294
NASA Astrophysics Data System (ADS)
Laven, Philip; Lock, James A.; Adam, John A.
2015-09-01
We calculated scattering of an electromagnetic plane wave by a radially inhomogeneous particle and a radially inhomogeneous bubble when the square of the refractive index profile is parabolic as a function of radius. Such a particle or bubble is called a generalized Luneburg lens. A wide variety of scattering phenomena can occur, depending on the value of the two adjustable parameters of the parabola. These phenomena, including transmission rainbows, the weak caustic for near-critical-angle scattering by a bubble, surface orbiting, the interior orbiting paths of morphology-dependent resonances, and the separation of diffraction are studied here using wave theory and time domain scattering. These phenomena are also compared with their appearance or absence for scattering by a homogeneous sphere.
Borcherdt, R.D.
1988-01-01
Dilatational earth strain, associated with the radiation fields for several hundred local, regional, and teleseismic earthquakes, has been recorded over an extended bandwidth and dynamic range at four borehole sites near the San Andreas fault, CA. The general theory of linear viscoelasticity is applied to account for anelasticity of the near-surface materials and to provide a mathematical basis for interpretation of seismic radiation fields as detected simultaneously by co-located volumetric strain meters and seismometers. The general theory is applied to describe volumetric strain and displacement for general (homogeneous or inhomogeneous) P and S waves in an anelastic whole space. Solutions to the free-surface reflection problems for incident general P and S-I waves are used to evaluate the effect of the free surface on observations from co-located sensors. Corresponding expressions are derived for a Rayleigh-type surface wave on a linear viscoelastic half-space. The theory predicts a number of anelastic wave field characteristics that can be inferred from observation of volumetric strains and displacement fields as detected by co-located sensors that cannot be inferred from either sensor alone. -from Author
NASA Astrophysics Data System (ADS)
Betka, P. M.; Seeber, L.; Steckler, M. S.
2015-12-01
The Indo-Burma fold-thrust belt (FTB) in northeast India and Myanmar records shortening of a forearc prism resulting from ongoing collision of the Burma microplate and the Ganges-Brahmaputra Delta. A >5 km thick succession of deep water, deltaic and tidal as well as fluvial deposits that span the Oligocene to present were deformed to form a ~400 km wide FTB between 91.5-96°E longitude. India-Eurasia convergence across the Indo-Burma region trends northeast and is highly oblique to the northerly structural trend of the FTB. According to geodetic data, 21 mm/yr of dextral shear and 18 mm/yr of approximately east-west shortening must be accommodated within the FTB between the active thrust front in Bangladesh (90.5°E) and the Sagaing Fault in Myanmar (96°E). This paper presents new surface geologic data collected along a ~250 km transect that crosses 15 anticline-syncline pairs between the cities of Argatala (~91.2°E) and Champhai (93.3°E), the part of FTB exposing syn-Himalayan sediment, to determine the degree of noncoaxial shear that is accommodated internally within the belt. Results indicate that the majority of the folds are upright or asymmetric horizontal folds that are either concentric or have a narrow hinge (chevron folds) and form open—closed interlimb angles which generally tighten from the foreland toward the hinterland. A cylindrical best fit describes the data well and shows dominantly east-west shortening with a horizontal north-trending regional fold axis (005/01 ± 2°). Shortening was partly accommodated by flexural slip. Flexural slip-lineations (n=32) are subperpendicular to the regional fold axis. In some locations the limbs of folds are breached by thrust faults that dip either east or west and strike north. Incremental strain axes calculated from the flexural-slip surfaces and thrust faults (n=61) indicate horizontal west-trending shortening (279/03 ± 8°) and vertical extension that is kinematically compatible with folding. Altogether
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.
NASA Astrophysics Data System (ADS)
Le Page, Yvon; Saxe, Paul
2002-03-01
A symmetry-general approach for the least-squares, therefore precise, extraction of elastic coefficients for strained materials is reported. It analyzes stresses calculated ab initio for properly selected strains. The problem, its implementation, and its solution strategy all differ radically from a previous energy-strain approach that we published last year, but the normal equations turn out to be amenable to the same constrainment scheme that makes both approaches symmetry general. The symmetry considerations governing the automated selection of appropriately strained models and their Cartesian systems are detailed. The extension to materials under general stress is discussed and implemented. VASP was used for ab initio calculation of stresses. A comprehensive range of examples includes a triclinic material (kyanite) and simple materials with a range of symmetries at zero pressure, MgO under hydrostatic pressure, Ti4As3 under [001] uniaxial strain, and Si under [001] uniaxial stress. The MgO case agrees with recent experimental work including elastic coefficients as well as their first and second derivatives. The curves of elastic coefficients for Si show a gradual increase in the 33 compliance coefficient, leading to a collapse of the material at -11.7 GPa, compared with -12.0 GPa experimentally. Interpretation of results for Be using two approximations [local density (LDA), generalized gradient (GGA)], two approaches (stress strain and energy strain), two potential types (projector augmented wave and ultrasoft), and two quantum engines (VASP and ORESTES) expose the utmost importance of the cell data used for the elastic calculations and the lesser importance of the other factors. For stiffness at relaxed cell data, differences are shown to originate mostly in the considerable overestimation of the residual compressive stresses at x-ray cell data by LDA, resulting in a smaller relaxed cell, thus larger values for diagonal stiffness coefficients. The symmetry
NASA Technical Reports Server (NTRS)
Jones, M. H.; Bubsey, R. T.; Brown, W. F., Jr.; Bucci, R. J.; Collis, S. F.; Kohm, R. F.; Kaufman, J. G.
1977-01-01
A description is presented of studies which have been conducted to establish an improved technology base for a use of the sharply notched cylindrical specimen in quality assurance tests of aluminum alloy products. The results are presented of an investigation of fundamental variables associated with specimen preparation and testing, taking into account the influence of the notch root radius, the eccentricity of loading, the specimen diameter, and the notch depth on the sharp notch strength. Attention is given to the statistical procedures which are necessary to establish correlations between the sharp notch strength and the plane-strain fracture toughness for high-strength aluminum alloys.
ERIC Educational Resources Information Center
Newcomb, Michael D.; Abbott, Robert D.; Catalano, Richard F.; Hawkins, J. David; Battin-Pearson, Sara; Hill, Karl
2002-01-01
Understanding and preventing high school failure is a national priority. Structural strain and general deviance theories attempt to explain late high school failure. The authors tested the hypotheses that general (vs. specific) deviance and academic competence mediate the relationships between structural strain factors (gender, ethnicity, and…
Bullying Victimization and Adolescent Self-Harm: Testing Hypotheses from General Strain Theory
ERIC Educational Resources Information Center
Hay, Carter; Meldrum, Ryan
2010-01-01
Self-harm is widely recognized as a significant adolescent social problem, and recent research has begun to explore its etiology. Drawing from Agnew's (1992) social psychological strain theory of deviance, this study considers this issue by testing three hypotheses about the effects of traditional and cyber bullying victimization on deliberate…
The Laplace Planes of Uranus and Pluto
NASA Technical Reports Server (NTRS)
Dobrovolskis, Anthony R.
1993-01-01
Satellite orbits close to an oblate planet precess about its equatorial plane, while distant satellites precess around the plane of the planet's heliocentric orbit. In between, satellites in nearly circular orbits precess about a warped intermediate surface called the Laplace 'plane.' Herein we derive general formulas for locating the Laplace plane. Because Uranus and Pluto have high obliquities, their Laplace planes are severely warped. We present maps of these Laplace planes, of interest in telescopic searches for new satellites. The Laplace plane of the Solar System as a whole is similarly distorted, but comets in the inner Oort cloud precess too slowly to sense the Laplace plane.
ERIC Educational Resources Information Center
Drapela, Laurie A.
2006-01-01
General Strain Theory (GST) argues that drug use is one way adolescents mitigate negative emotions brought on by aversive environmental stimuli. To date, many of the empirical tests of the strain-drug use relationship have neglected to include measures of negative emotion, despite its prominence in GST's etiology of deviant behavior. The following…
NASA Astrophysics Data System (ADS)
Singh, Jagadish; Omale, Achonu Joseph
2016-02-01
This article examines the effects of the zonal harmonics on the out-of-plane equilibrium points of Robe's circular restricted three-body problem when the hydrostatic equilibrium shape of the first primary is an oblate spheroid, the shape of the second primary is an oblate spheroid with oblateness coefficients up to the second zonal harmonic, and the full buoyancy of the fluid is considered. It is observed that the size of the oblateness and the zonal harmonics affect the positions of the out-of-plane equilibrium points L6 and L7. It is also observed that these points within the possible region of motion are unstable.
Bullying victimization and adolescent self-harm: testing hypotheses from general strain theory.
Hay, Carter; Meldrum, Ryan
2010-05-01
Self-harm is widely recognized as a significant adolescent social problem, and recent research has begun to explore its etiology. Drawing from Agnew's (1992) social psychological strain theory of deviance, this study considers this issue by testing three hypotheses about the effects of traditional and cyber bullying victimization on deliberate self-harm and suicidal ideation. The data come from a school-based survey of adolescents in a rural county of a southeastern state (n = 426); 50% of subjects are female, their mean age was 15 years, and non-Hispanic whites represent 66% of the sample. The analysis revealed that both types of bullying are positively related to self-harm and suicidal ideation, net of controls. Moreover, those relationships are partially mediated by the negative emotions experienced by those who are bullied and partially moderated by features of the adolescent's social environment and self. Regarding the latter, exposure to authoritative parenting and high self-control diminished the harmful effects of bullying victimization on self-harm and suicidal ideation. The article concludes by discussing the implications of these conclusions for future research and for policy efforts designed to reduce self-harm. PMID:20072852
Binder, Stephan; Siedler, Solvej; Marienhagen, Jan; Bott, Michael; Eggeling, Lothar
2013-07-01
Recombineering in bacteria is a powerful technique for genome reconstruction, but until now, it was not generally applicable for development of small-molecule producers because of the inconspicuous phenotype of most compounds of biotechnological relevance. Here, we establish recombineering for Corynebacterium glutamicum using RecT of prophage Rac and combine this with our recently developed nanosensor technology, which enables the detection and isolation of productive mutants at the single-cell level via fluorescence-activated cell sorting (FACS). We call this new technology RecFACS, which we use for genomic site-directed saturation mutagenesis without relying on pre-constructed libraries to directly isolate L-lysine-producing cells. A mixture of 19 different oligonucleotides was used targeting codon 81 in murE of the wild-type, at a locus where one single mutation is known to cause L-lysine production. Using RecFACS, productive mutants were screened and isolated. Sequencing revealed 12 different amino acid exchanges in the targeted murE codon, which caused different L-lysine production titers. Apart from introducing a rapid genome construction technology for C. glutamicum, the present work demonstrates that RecFACS is suitable to simply create producers as well as genetic diversity in one single step, thus establishing a new general concept in synthetic biology. PMID:23630315
NASA Astrophysics Data System (ADS)
Mallick, Ritam; Bhattacharyya, Abhijit; Ghosh, Sanjay K.; Raha, Sibaji
2013-02-01
The estimate of the energy deposition rate (EDR) for neutrino pair annihilation has been carried out. The EDR for the neutrinos coming from the equatorial plane of a rotating neutron star is calculated along the rotation axis using the Cook-Shapiro-Teukolsky metric. The neutrino trajectories and hence the neutrinos emitted from the disk are affected by the redshift due to disk rotation and gravitation. The EDR is very sensitive to the value of the temperature and its variation along the disk. The rotation of the star has a negative effect on the EDR; it decreases with increase in rotational velocity.
NASA Technical Reports Server (NTRS)
Freed, Alan D.
1995-01-01
The purpose of this paper is to present a consistent and thorough development of the strain and strain-rate measures affiliated with Hencky. Natural measures for strain and strain-rate, as I refer to them, are first expressed in terms of of the fundamental body-metric tensors of Lodge. These strain and strain-rate measures are mixed tensor fields. They are mapped from the body to space in both the Eulerian and Lagrangian configurations, and then transformed from general to Cartesian fields. There they are compared with the various strain and strain-rate measures found in the literature. A simple Cartesian description for Hencky strain-rate in the Lagrangian state is obtained.
NASA Technical Reports Server (NTRS)
Grosveld, F.; Lameris, J.; Dunn, D.
1979-01-01
Experiments and a theoretical analysis were conducted to predict the noise reduction of inclined and curved panels. These predictions are compared to the experimental results with reasonable agreement between theory and experiment for panels under an oblique angle of sound incidence. Theoretical as well as experimental results indicate a big increase in noise reduction when a flat test panel is curved. Further curving the panel slightly decreases the noise reduction. Riveted flat panels are shown to give a higher noise reduction in the stiffness-controlled frequency region, while bonded panels are superior in this region when the test panel is curved. Experimentally measured noise reduction characteristics of flat aluminum panels with uniaxial in-plane stresses are presented and discussed. These test results indicate an important improvement in the noise reduction of these panels in the frequency range below the fundamental panel/cavity frequency.
Wu, Yuan; Zhou, Haijian; Wang, Jing; Li, Lianqing; Li, Wenge; Cui, Zhigang; Chen, Xia; Cen, Ruiqi; Lu, Jinxing; Cheng, Ying
2012-01-01
Multilocus sequence typing (MLST) based on six loci was used to analyze the relationship of 58 Candida tropicalis isolates from individual patients in a general hospital in Beijing, China. A total of 52 diploid sequence types (DSTs) were generated by the MLST, all of which were new to the central database. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) dendrograms were constructed, which showed that the 58 isolates were distributed robustly and 6 main groups were clustered regardless of the specimen source and medical department. The minimum spanning tree (MST) of the 58 isolates (52 DSTs) and all 401 isolates (268 DSTs) in the C. tropicalis central database (http://pubmlst.org/ctropicalis/) indicated that the isolates in this study clustered in three relative pure clonal complexes, and 2 clustered with isolates from Taiwan, Belgium, Brazil, and the US. This study presents the first MLST analysis of C. tropicalis isolates from Mainland China, which may be useful for further studies on the similarity, genetic relationship, and molecular epidemiology of C. tropicalis strains worldwide. PMID:23152759
Rekadwad, Bhagwan N; Khobragade, Chandrahasya N
2016-06-01
A total of 13 short DNA sequences of quality control strains (MCC 2052, MCC 2077, MCC 2078, MCC 2080, MCC 2309, MCC 2322, MCC 2408, MCC 2409, MCC 2412, MCC 2413, MCC 2415, MCC 2483 and MCC 2515) were retrieved from NCBI BioSample database and generated quick response (QR) codes for sequences. 16S rRNA was used for creation of Chaose Game representation (CGR), Chaose Game Representation of Frequencies (FCGR) and measurement of GC percentage. Digital data in the form of QR codes, CGR, FCGR and GC plot would be useful for identification, visual comparison and evaluation of newly isolated strains with quality control strains. The digital data of QR codes, CGR, FCGR and GC content all the quality control strains are made available to users through this paper. This generated digital data helps to evaluate and compare newly isolated strains, less laborious and avoid misinterpretation of newly isolated species. PMID:27222847
Rekadwad, Bhagwan N.; Khobragade, Chandrahasya N.
2016-01-01
A total of 13 short DNA sequences of quality control strains (MCC 2052, MCC 2077, MCC 2078, MCC 2080, MCC 2309, MCC 2322, MCC 2408, MCC 2409, MCC 2412, MCC 2413, MCC 2415, MCC 2483 and MCC 2515) were retrieved from NCBI BioSample database and generated quick response (QR) codes for sequences. 16S rRNA was used for creation of Chaose Game representation (CGR), Chaose Game Representation of Frequencies (FCGR) and measurement of GC percentage. Digital data in the form of QR codes, CGR, FCGR and GC plot would be useful for identification, visual comparison and evaluation of newly isolated strains with quality control strains. The digital data of QR codes, CGR, FCGR and GC content all the quality control strains are made available to users through this paper. This generated digital data helps to evaluate and compare newly isolated strains, less laborious and avoid misinterpretation of newly isolated species. PMID:27222847
Tunaligil, Verda; Dokucu, Ali Ihsan; Erdogan, Mehmet Sarper
2016-07-01
This study investigated the impact of working for public versus private ambulance services in Turkey and elaborated on predictors of mental, physical, and emotional well-being in emergency medical technicians (EMT-Bs). In this observational cross-sectional study, an 81-question self-report survey was used to gather data about employee demographics, socioeconomic status, educational background, working conditions, and occupational health and workplace safety (OHS), followed by the 12-item General Health Questionnaire (GHQ-12), the Work-Related Strain Inventory (WRSI), and the Maslach Burnout Inventory (MBI) with three subscales: Emotional Exhaustion (MBI-EE), Depersonalization (MBI-DP), and Diminished Personal Accomplishment (MBI-PA). In 2011, 1,038 EMT-Bs worked for publicly operated and 483 EMT-Bs worked for privately owned ambulance services in Istanbul, Turkey, of which 606 (58.4%) and 236 (48.9%) participated in the study (overall participation rate = 55.4%), respectively. On all scales, differences between total mean scores in both sectors were statistically insignificant (p > .05). In the public sector, work locations, false accusations, occupational injuries and diseases, work-related permanent disabilities, and organizational support were found to significantly influence self-reported perceptions of well-being (p < .05). In the private sector, commute time to and from work (p < .05), false accusations (p < .05), vocational training and education (p < .05), informed career choices (p < .05), and work-related permanent disabilities (p < .05) were found to significantly influence self-reported perceptions of well-being. EMT-Bs were asked about aspects of their working lives that need improvement; priority expectations in the public and private sectors were higher earnings (17.5%; 16.7%) and better social opportunities (17.4%; 16.8%). Working conditions, vocational training, and OHS emerged as topics that merit priority attention. PMID:27034407
Broken chiral symmetry on a null plane
Beane, Silas R.
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-plane 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.
Poudel, Pramod; Tashiro, Yukihiro; Sakai, Kenji
2016-01-01
Members of the genus Bacillus are considered to be both, among the best studied and most commonly used bacteria as well as the most still unexplored and the most wide-applicable potent bacteria because novel Bacillus strains are continuously being isolated and used in various areas. Production of optically pure l-lactic acid (l-LA), a feedstock for bioplastic synthesis, from renewable resources has recently attracted attention as a valuable application of Bacillus strains. l-LA fermentation by other producers, including lactic acid bacteria and Rhizopus strains (fungi) has already been addressed in several reviews. However, despite the advantages of l-LA fermentation by Bacillus strains, including its high growth rate, utilization of various carbon sources, tolerance to high temperature, and growth in simple nutritional conditions, it has not been reviewed. This review article discusses new findings on LA-producing Bacillus strains and compares them to other producers. The future prospects for LA-producing Bacillus strains are also discussed. PMID:26565947
NASA Astrophysics Data System (ADS)
Menzies, John
2012-09-01
A kinematic model of strain pathways for till formation is developed. This model is linked to microstructures found within tills indicative of multiple styles of deformational regimes and polyrheological conditions during formation. Tills are subdivided into three types. Type A tills are found under high strain rates and a pervasive deformation regime and may be regarded as lodgement tills and are relatively rare. Type B tills are the dominant group formed under variable strain deformation conditions of pervasive and non-pervasive deformation containing evidence of brittle and ductile failure and can be classified as tectomicts (or glacial mélange). Type C tills are found under limited to zero deformation regimes and are melt-out tills of limited preservation potential. Examples of till forming under various strain pathways conditions are presented with photomicrographs of thin sections of such tills. A new till classification scheme is offered that accounts for the deformation regimes till undergo under varying strain pathways. This new model should help to place microstructures obtained from micromorphological analyses within the context of till genesis and subsequent development. This kinematic model is a first attempt to integrate the fields of glacial micromorphology, structural geology and glacial sedimentology into a coherent 'blueprint' for till development leading to deposition and/or emplacement.
Strain effect on coercive field of epitaxial barium titanate thin films
NASA Astrophysics Data System (ADS)
Choudhury, S.; Li, Y. L.; Chen, L. Q.; Jia, Q. X.
2008-04-01
Strain is generally known to increase the coercive field of a ferroelectric thin film as compared to a stress-free single crystal or a strain-relaxed film. We studied the coercive fields and remanent polarizations of (001)-oriented epitaxial barium titanate thin films using the phase-field approach. It is demonstrated, while the remanent polarization decreases as in-plane strain changes from being compressive to tensile, the variation of coercive field with strain is complicated. We noted more than two times drop in coercive field with a reduction of compressive strain of only ˜0.05%, which we attribute to the existence of multiple ferroelectric phases.
The solar system's invariable plane
NASA Astrophysics Data System (ADS)
Souami, D.; Souchay, J.
2012-07-01
Context. The dynamics of solar system objects, such as dwarf planets and asteroids, has become a well-established field of celestial mechanics in the past thirty years, owing to the improvements that have been made in observational techniques and numerical studies. In general, the ecliptic is taken as the reference plane in these studies, although there is no dynamical reason for doing so. In contrast, the invariable plane as originally defined by Laplace, seems to be a far more natural choice. In this context, the latest study of this plane dates back to Burkhardt. Aims: We define and determine the orientation of the invariable plane of the solar system with respect to both the ICRF and the equinox-ecliptic of J2000.0, and evaluate the accuracy of our determination. Methods: Using the long-term numerical ephemerides DE405, DE406, and INPOP10a over their entire available time span, we computed the total angular momentum of the solar system, as well as the individual contribution to it made by each of the planets, the dwarf planets Pluto and Ceres, and the two asteroids Pallas and Vesta. We then deduced the orientation of the invariable plane from these ephemerides. Results: We update the previous results on the determination of the orientation of the invariable plane with more accurate data, and a more complete analysis of the problem, taking into account the effect of the dwarf planet (1) Ceres as well as two of the biggest asteroids, (4) Vesta and (2) Pallas. We show that the inclusion of these last three bodies significantly improves the accuracy of determination of the invariable plane, whose orientation over a 100 y interval does not vary more than 0.1 mas in inclination, and 0.3 mas in longitude of the ascending node. Moreover, we determine the individual contributions of each body to the total angular momentum of the solar system, as well as the inclination and longitude of the node with respect to this latter plane. Conclusions: Owing to the high accuracy
Slipping and Rolling on an Inclined Plane
ERIC Educational Resources Information Center
Aghamohammadi, Cina; Aghamohammadi, Amir
2011-01-01
In the first part of the paper, using a direct calculation two-dimensional motion of a particle sliding on an inclined plane is investigated for general values of friction coefficient ([mu]). A parametric equation for the trajectory of the particle is also obtained. In the second part of the paper, the motion of a sphere on the inclined plane is…
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.
Strain engineering of electronic properties of transition metal dichalcogenide monolayers
NASA Astrophysics Data System (ADS)
Maniadaki, Aristea E.; Kopidakis, Georgios; Remediakis, Ioannis N.
2016-02-01
We present Density Functional Theory (DFT) results for the electronic and dielectric properties of single-layer (2D) semiconducting transition metal dichalcogenides MX2 (M=Mo, W; X=S, Se, Te) under isotropic, uniaxial (along the zigzag and armchair directions), and shear strain. Electronic band gaps decrease while dielectric constants increase for heavier chalcogens X. The direct gaps of equilibrium structures often become indirect under certain types of strain, depending on the material. The effects of strain and of broken symmetry on the band structure are discussed. Gaps reach maximum values at small compressive strains or in equilibrium, and decrease with larger strains. In-plane dielectric constants generally increase with strain, reaching a minimum value at small compressive strains. The out-of-plane constants exhibit a similar behavior under shear strain but under isotropic and uniaxial strain they increase with compression and decrease with tension, thus exhibiting a monotonic behavior. These DFT results are theoretically explained using only structural parameters and equilibrium dielectric constants. Our findings are consistent with available experimental data.
Experiments with Planing Surfaces
NASA Technical Reports Server (NTRS)
Sottorf, W
1934-01-01
A previous report discusses the experimental program of a systematic exploration of all questions connected with the planing problem as well as the first fundamental results of the investigation of a flat planing surface. The present report is limited to the conversion of the model test data to full scale.
Do foliation refraction patterns around buckle folds represent finite strain?
NASA Astrophysics Data System (ADS)
Frehner, M.; Exner, U.
2012-04-01
leads to the conclusion that the geometry of the divergent fan does not reflect the orientation of the long axes of the finite strain ellipses, but can reflect anything from finite to infinitesimal strain. However, the convergent fan in the mechanically strong folded layer takes very different shapes for the different strain measures. The convergent fan is well developed in the case of the finite strain and the passive marker lines, but it is strongly influenced by the migration of the neutral line through the fold in the case of the incremental and the infinitesimal strain. We compare the described strain orientations with foliation refraction patterns in outcrop-scale folds near the village Luarca (Asturias, NW Spain). Generally we observe that the foliation is much better developed in the mechanically weak layers than in the strong folded layers. In the latter, the foliation often has the appearance of fractures and exhibits a nice convergent fan. Therefore, we conclude that the foliation roughly reflects the long axis of the finite strain ellipse or even corresponds to initially layer-orthogonal lines, which rotated passively during folding. This could be explained by a very early formation of the foliation. The foliation in the weak layers, which exhibits divergent fans, may also have developed later in the folding history. In one particular fold, we observe a strong orientation change of the foliation along the axial plane trace. In the numerical models, we observe a similar orientation pattern of the long axis if the incremental strain is used. We conclude that such patterns can be explained by the superposition of two or more generations of axial plane foliation, which developed at different stages of the folding process.
Fourier plane imaging microscopy
Dominguez, Daniel Peralta, Luis Grave de; Alharbi, Nouf; Alhusain, Mdhaoui; Bernussi, Ayrton A.
2014-09-14
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 photonic crystals.
Eight plane IPND mechanical testing.
Zhao, A.; Guarino, V.; Wood, K.; Nephew, T.; Ayres, D.; Lee, A.; High Energy Physics; FNAL
2008-03-18
A mechanical test of an 8 plane IPND mechanical prototype, which was constructed using extrusions from the testing/tryout of the 16 cell prototype extrusion die in Argonne National Laboratory, was conducted. There were 4 vertical and 4 horizontal planes in this 8 plane IPND prototype. Each vertical plane had four 16 cell extrusions, while each horizontal plane had six 16 cell extrusions. Each plane was glued together using the formulation of Devcon adhesive, Devcon 60. The vertical extrusions used in the vertical planes shares the same dimensions as the horizontal extrusions in the horizontal planes with the average web thickness of 2.1 mm and the average wall thickness of 3.1 mm. This mechanical prototype was constructed with end-seals on the both ends of the vertical extrusions. The gaps were filled with epoxy between extrusions and end-seals. The overall dimension of IPND is 154.8 by 103.1 by 21.7 inches with the weight of approximately 1200 kg, as shown in a figure. Two similar mechanical tests of 3 layer and 11 layer prototypes have been done in order to evaluate the strength of the adhesive joint between extrusions in the NOvA detector. The test showed that the IPND prototype was able to sustain under the loading of weight of itself and scintillator. Two FEA models were built to verify the measurement data from the test. The prediction from FEA slice model seems correlated reasonably well to the test result, even under a 'rough' estimated condition for the wall thickness (from an untuned die) and an unknown property of 'garage type' extrusion. A full size of FEA 3-D model also agrees very well with the test data from strain gage readings. It is worthy to point out that the stress distribution of the structure is predominantly determined by the internal pressure, while the buckling stability relies more on the loading weight from the extrusions themselves and scintillate. Results of conducted internal pressure tests, including 3- cell, 11-cell and the IPND
2. VIEW SOUTH, INCLINE PLANE CAR, INCLINE PLANE TRACK, UPPER ...
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
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.
High temperature strain gage apparent strain compensation
NASA Technical Reports Server (NTRS)
Holmes, Harlan K.; Moore, T. C., Sr.
1992-01-01
Once an installed strain gage is connected to a strain indicating device and the instrument is balanced, a subsequent change in temperature of the gage installation will generally produce a resistance change in the gage. This purely temperature-induced resistance will be registered by the indicating device as a strain and is referred to as 'apparent strain' to distinguish it from strain due to applied stress. One desirable technique for apparent strain compensation is to employ two identical gages with identical mounting procedures which are connected with a 'half bridge' configuration where gages see the same thermal environment but only one experiences a mechanical strain input. Their connection in adjacent arms of the bridge will then balance the thermally induced apparent strains and, in principle, only the mechanical strain remains. Two approaches that implement this technique are discussed.
Lampton, Michael L.; Kim, A.; Akerlof, C.W.; Aldering, G.; Amanullah, R.; Astier, P.; Barrelet, E.; Bebek, C.; Bergstrom, L.; Berkovitz, J.; Bernstein, G.; Bester, M.; Bonissent, A.; Bower, C.; Carithers Jr., W.C.; Commins, E.D.; Day, C.; Deustua, S.E.; DiGennaro,R.; Ealet, A.; Ellis, R.S.; Eriksson, M.; Fruchter, A.; Genat, J.-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Harris, S.E.; Harvey, P.R.; Heetderks, H.D.; Holland, S.E.; Huterer, D.; Karcher, A.; Kolbe, W.; Krieger, B.; Lafever, R.; Lamoureux, J.; Levi, M.E.; Levin, D.S.; Linder,E.V.; Loken, S.C.; Malina, R.; Massey, R.; McKay, T.; McKee, S.P.; Miquel, R.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Pratt, R.; Prieto, E.; Refregier, A.; Rhodes, J.; Robinson, K.; Roe, N.; Sholl, M.; Schubnell, M.; Smadja, G.; Smoot, G.; Spadafora, A.; Tarle, G.; Tomasch,A.; von der Lippe, H.; Vincent, R.; Walder, J.-P.; Wang, G.
2002-07-29
The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square-degree field sensitive in the visible and near-infrared wavelength regime. We describe the requirements for the instrument suite and the evolution of the focal plane design to the present concept in which all the instrumentation--visible and near-infrared imagers, spectrograph, and star guiders--share one common focal plane.
Out of plane analysis for composite structures
NASA Technical Reports Server (NTRS)
Paul, P. C.; Saff, C. R.; Sanger, Kenneth B.; Mahler, M. A.; Kan, Han Pin; Kautz, Edward F.
1990-01-01
Simple two dimensional analysis techniques were developed to aid in the design of strong joints for integrally stiffened/bonded composite structures subjected to out of plane loads. It was found that most out of plane failures were due to induced stresses arising from rapid changes in load path direction or geometry, induced stresses due to changes in geometry caused by buckling, or direct stresses produced by fuel pressure or bearing loads. While the analysis techniques were developed to address a great variety of out of plane loading conditions, they were primarily derived to address the conditions described above. The methods were developed and verified using existing element test data. The methods were demonstrated using the data from a test failure of a high strain wingbox that was designed, built, and tested under a previous program. Subsequently, a set of design guidelines were assembled to assist in the design of safe, strong integral composite structures using the analysis techniques developed.
Optical strain measuring techniques for high temperature tensile testing
NASA Technical Reports Server (NTRS)
Gyekenyesi, John Z.; Hemann, John H.
1987-01-01
A number of optical techniques used for the analysis of in-plane displacements or strains are reviewed. The application would be for the high temperature, approximately 1430 C (2600 F), tensile testing of ceramic composites in an oxidizing atmosphere. General descriptions of the various techniques and specifics such as gauge lengths and sensitivities are noted. Also, possible problems with the use of each method in the given application are discussed.
Beamlet focal plane diagnostic
Caird, J.A.; Nielsen, N.D.; Patton, H.G.; Seppala, L.G.; Thompson, C.E.; Wegner, P.J.
1996-12-01
This paper describes the major optical and mechanical design features of the Beamlet Focal Plane Diagnostic system as well as measurements of the system performance, and typical data obtained to date. We also discuss the NIF requirements on the focal spot that we are interested in measuring, and some of our plans for future work using this system.
NASA Technical Reports Server (NTRS)
Munk, Max M
1923-01-01
This report deals with the calculation of the equilibrium, statistical stability, and damping of the tail plane. The author has simplified the present theory of longitudinal stability for the particular purpose of obtaining one definite coefficient characteristics of the effect of the tail plane. This coefficient is obtained by substituting certain aerodynamic characteristics and some dimensions of the airplane in a comparatively simple mathematical expression. Care has been taken to confine all aerodynamical information necessary for the calculation of the coefficient to the well-known curves representing the qualities of the wing section. This is done by making use of the present results of modern aerodynamics. All formulas and relations necessary for the calculation are contained in the paper. They give in some cases only an approximation of the real values. An example of calculation is added in order to illustrate the application of the method. The coefficient indicates not only whether the effect of the tail plane is great enough, but also whether it is not too great. It appears that the designer has to avoid a certain critical length of the fuselage, which inevitably gives rise to periodical oscillations of the airplane. The discussion also shows the way and in what direction to carry out experimental work.
A plane stress finite element model for elastic-plastic mode I/II crack growth
NASA Astrophysics Data System (ADS)
James, Mark Anthony
A finite element program has been developed to perform quasi-static, elastic-plastic crack growth simulations. The model provides a general framework for mixed-mode I/II elastic-plastic fracture analysis using small strain assumptions and plane stress, plane strain, and axisymmetric finite elements. Cracks are modeled explicitly in the mesh. As the cracks propagate, automatic remeshing algorithms delete the mesh local to the crack tip, extend the crack, and build a new mesh around the new tip. State variable mapping algorithms transfer stresses and displacements from the old mesh to the new mesh. The von Mises material model is implemented in the context of a non-linear Newton solution scheme. The fracture criterion is the critical crack tip opening displacement, and crack direction is predicted by the maximum tensile stress criterion at the crack tip. The implementation can accommodate multiple curving and interacting cracks. An additional fracture algorithm based on nodal release can be used to simulate fracture along a horizontal plane of symmetry. A core of plane strain elements can be used with the nodal release algorithm to simulate the triaxial state of stress near the crack tip. Verification and validation studies compare analysis results with experimental data and published three-dimensional analysis results. Fracture predictions using nodal release for compact tension, middle-crack tension, and multi-site damage test specimens produced accurate results for residual strength and link-up loads. Curving crack predictions using remeshing/mapping were compared with experimental data for an Arcan mixed-mode specimen. Loading angles from 0 degrees to 90 degrees were analyzed. The maximum tensile stress criterion was able to predict the crack direction and path for all loading angles in which the material failed in tension. Residual strength was also accurately predicted for these cases.
Thin-film light-intensity measurement strain-analysis technique.
NASA Technical Reports Server (NTRS)
Williams, J. G.
1972-01-01
The optical response to loading of a thin metallic film deposited on a low-modulus structural substrate is studied theoretically and experimentally. Two types of optical properties called total and central-image transmittance (or reflectance) are shown to be related to the mechanical state of the substrate. Empirical optical-mechanical relationships are proposed between these optical properties and the substrate strain field of a general plane-stress problem. A technique based on wrinkle and microfracture patterns is described for determining principal directions of strain. Experimental results for uniaxially loaded specimens show that it is possible to obtain a nearly linear relationship between transmittance and strain for certain materials combinations.
Valley degeneracy in biaxially strained aluminum arsenide quantum wells
NASA Astrophysics Data System (ADS)
Prabhu-Gaunkar, S.; Birner, S.; Dasgupta, S.; Knaak, C.; Grayson, M.
2011-09-01
This paper describes a complete analytical formalism for calculating electron subband energy and degeneracy in strained multivalley quantum wells grown along any orientation with explicit results for AlAs quantum wells (QWs). In analogy to the spin index, the valley degree of freedom is justified as a pseudospin index due to the vanishing intervalley exchange integral. A standardized coordinate transformation matrix is defined to transform between the conventional-cubic-cell basis and the QW transport basis whereby effective mass tensors, valley vectors, strain matrices, anisotropic strain ratios, piezoelectric fields, and scattering vectors are all defined in their respective bases. The specific cases of (001)-, (110)-, and (111)-oriented aluminum arsenide (AlAs) QWs are examined, as is the unconventional (411) facet, which is of particular importance in AlAs literature. Calculations of electron confinement and strain for the (001), (110), and (411) facets determine the critical well width for crossover from double- to single-valley degeneracy in each system. The biaxial Poisson ratio is calculated for the high-symmetry lower Miller index (001)-, (110)-, and (111)-oriented QWs. An additional shear-strain component arises in the higher Miller index (411)-oriented QWs and we define and solve for a shear-to-biaxial strain ratio. The notation is generalized to address non-Miller-indexed planes so that miscut substrates can also be treated, and the treatment can be adapted to other multivalley biaxially strained systems. To help classify anisotropic intervalley scattering, a valley scattering primitive unit cell is defined in momentum space, which allows one to distinguish purely in-plane momentum scattering events from those that require an out-of-plane momentum component.
Bradburne, Christopher E.; Verhoeven, Anne B.; Manyam, Ganiraju C.; Chaudhry, Saira A.; Chang, Eddie L.; Thach, Dzung C.; Bailey, Charles L.; van Hoek, Monique L.
2013-01-01
Pneumonic tularemia is caused by inhalation of Francisella tularensis, one of the most infectious microbes known. We wanted to study the kinetics of the initial and early interactions between bacterium and host cells in the lung. To do this, we examined the infection of A549 airway epithelial cells with the live vaccine strain (LVS) of F. tularensis. A549 cells were infected and analyzed for global transcriptional response at multiple time points up to 16 h following infection. At 15 min and 2 h, a strong transcriptional response was observed including cytoskeletal rearrangement, intracellular transport, and interferon signaling. However, at later time points (6 and 16 h), very little differential gene expression was observed, indicating a general suppression of the host response consistent with other reported cell lines and murine tissues. Genes for macropinocytosis and actin/cytoskeleton rearrangement were highly up-regulated and common to the 15 min and 2 h time points, suggesting the use of this method for bacterial entry into cells. We demonstrate macropinocytosis through the uptake of FITC-dextran and amiloride inhibition of Francisella LVS uptake. Our results suggest that macropinocytosis is a potential mechanism of intracellular entry by LVS and that the host cell response is suppressed during the first 2–6 h of infection. These results suggest that the attenuated Francisella LVS induces significant host cell signaling at very early time points after the bacteria's interaction with the cell. PMID:23322778
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.
Hackel, Lloyd A.; Hermann, Mark R.; Dane, C. Brent; Tiszauer, Detlev H.
1995-01-01
A solid state laser is frequency tripled to 0.3 .mu.m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only .about.1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power.
Hackel, L.A.; Hermann, M.R.; Dane, C.B.; Tiszauer, D.H.
1995-12-12
A solid state laser is frequency tripled to 0.3 {micro}m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only about 1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power. 1 fig.
Mosaic Focal Plane Development
NASA Astrophysics Data System (ADS)
Mason, David L.; Horner, Scott D.; Aamodt, Earl K.
2002-12-01
Advances in systems engineering, applied sciences, and manufacturing technologies have enabled the development of large ground based and spaced based astronomical instruments having a large Field of View (FOV) to capture a large portion of the universe in a single image. A larger FOV can be accomplished using light weighted optical elements, improved support structures, and the development of mosaic Focal Plane Assemblies (mFPA). A mFPA designed for astronomy can use multiple Charged Coupled Devices (CCD) mounted onto a single camera baseplate integrated at the instrument plane of focus. Examples of current, or proposed, missions utilizing mFPA technology include FAME, GEST, Kepler, GAIA, LSST, and SNAP. The development of a mFPA mandates tighter control on the design trades, component development, CCD characterization, component integration, and performance verification testing. This paper addresses the capability Lockheed Martin Space Systems Company's (LMSSC) Advanced Technology Center (ATC) has developed to perform CCD characterization, mFPA assembly and alignment, and mFPA system level testing.
Mosaic Focal Plane Development
NASA Astrophysics Data System (ADS)
Mason, D.; Horner, S.; Aamodt, E.
Advances in manufacturing and applied sciences have enabled the development of large ground and spaced based astronomical instruments having a Field of View (FOV) large enough to capture a large portion of the universe in a single image. A large FOV can be accomplished using light weighted optics, improved structures, and the development of mosaic Focal Plane Assemblies (mFPAs). A mFPA comprises multiple Charged Coupled Devices (CCD) mounted onto a single baseplate integrated at the focus plane of the instrument. Examples of current, or proposed, missions utilizing mFPA technology include FAME, GEST, Kepler, GAIA, LSST, and SNAP. The development of a mFPA mandates tight control on the design trades of component development, CCD definition and characterization, component integration, and performance verification testing. This paper addresses the results of the Lockheed Martin Space Systems Company (LMSSC), Advanced Technology Center (ATC) developed mFPA. The design trades and performance characterization are services provided by the LMSSC ATC but not detailed in this paper.
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…
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%.
NASA Technical Reports Server (NTRS)
1999-01-01
Excerpt from the NASA Connect show 'Plane Weather' This clip explains how our weather occurs, and why Solar radiation is responsible. Weather affects our daily lives. The elements of weather: rain, wind, fog, ice and snow affect the operation and flight of an airplane. In this program, NASA and FAA researchers will introduce students to math, science, and weather; demonstrate how these elements influence flight; and show how NASA and FAA research is used to limit the effects of these elements on flight. Students will examine: the tools, techniques, and technologies used by engineers and scientists to detect these and other climatological factors affecting aircraft in flight. The lesson and classroom experiment will involve students in the scientific process and emphasizing problem solving, measurement, and reasoning skills.
NASA Technical Reports Server (NTRS)
1999-01-01
Excerpt from the NASA Connect show 'Plane Weather' This clip explains what high and low pressure weather systems are, and how they form. Weather affects our daily lives. The elements of weather: rain, wind, fog, ice and snow affect the operation and flight of an airplane. In this program, NASA and FAA researchers will introduce students to math, science, and weather; demonstrate how these elements influence flight; and show how NASA and FAA research is used to limit the effects of these elements on flight. Students will examine: the tools, techniques, and technologies used by engineers and scientists to detect these and other climatological factors affecting aircraft in flight. The lesson and classroom experiment will involve students in the scientific process and emphasizing problem solving, measurement, and reasoning skills.
NASA Technical Reports Server (NTRS)
1999-01-01
Excerpt from the NASA Connect show 'Plane Weather' This clip explains what high and low pressure weather systems are, and how these affect weather patterns. Weather affects our daily lives. The elements of weather: rain, wind, fog, ice and snow affect the operation and flight of an airplane. In this program, NASA and FAA researchers will introduce students to math, science, and weather; demonstrate how these elements influence flight; and show how NASA and FAA research is used to limit the effects of these elements on flight. Students will examine: the tools, techniques, and technologies used by engineers and scientists to detect these and other climatological factors affecting aircraft in flight. The lesson and classroom experiment will involve students in the scientific process and emphasizing problem solving, measurement, and reasoning skills.
Plane gravitational waves in real connection variables
Hinterleitner, Franz; Major, Seth
2011-02-15
We investigate using plane-fronted gravitational wave space-times as model systems to study loop quantization techniques and dispersion relations. In this classical analysis we start with planar symmetric space-times in the real connection formulation. We reduce via Dirac constraint analysis to a final form with one canonical pair and one constraint, equivalent to the metric and Einstein equations of plane-fronted-with-parallel-rays waves. Because of the symmetries and use of special coordinates, general covariance is broken. However, this allows us to simply express the constraints of the consistent system. A recursive construction of Dirac brackets results in nonlocal brackets, analogous to those of self-dual fields, for the triad variables. Not surprisingly, this classical analysis produces no evidence for dispersion, i.e. a variable propagation speed of gravitational plane-fronted-with-parallel-rays waves.
Cleveland, Michael J.; Hecht, Michael L.
2013-01-01
Latent growth curve modeling was used to test four hypotheses. First, this study hypothesized that acculturation-related variables (e.g., Mexican-heritage youth’s country of origin, time spent in the U.S., and language preference with family and friends) would be associated with initial levels of perceived discrimination. Guided by general strain theory (GST), this study then posed a second hypothesis: Initial levels of perceived discrimination would be indirectly related to initial levels of substance use through initial levels of acculturation stress. Third, this study hypothesized that changes in perceived discrimination would be indirectly related to changes in substance use through changes in acculturation stress. As a fourth hypothesis, it was postulated that initial levels of perceived discrimination would be indirectly related to changes in substance use through changes in acculturation stress. Mexican-heritage youth (N=1,106) from 29 schools in Phoenix, AZ completed surveys at six waves from 5th through 8th grades. In partial support of the first hypothesis, more time spent in the U.S. and speaking English with friends were associated with lower levels of perceived discrimination. The second hypothesis was not supported. Initial levels of perceived discrimination were positively associated with initial levels of acculturation stress; however, this association was not found between initial levels of acculturation stress and substance use. The third and fourth hypotheses were supported, which buttressed predictions derived from GST. Both initial levels and increases in perceived discrimination were indirectly related to increases in substance use through increases in acculturation stress. PMID:20490921
Focal Plane Metrology for the LSST Camera
A Rasmussen, Andrew P.; Hale, Layton; Kim, Peter; Lee, Eric; Perl, Martin; Schindler, Rafe; Takacs, Peter; Thurston, Timothy; /SLAC
2007-01-10
Meeting the science goals for the Large Synoptic Survey Telescope (LSST) translates into a demanding set of imaging performance requirements for the optical system over a wide (3.5{sup o}) field of view. In turn, meeting those imaging requirements necessitates maintaining precise control of the focal plane surface (10 {micro}m P-V) over the entire field of view (640 mm diameter) at the operating temperature (T {approx} -100 C) and over the operational elevation angle range. We briefly describe the hierarchical design approach for the LSST Camera focal plane and the baseline design for assembling the flat focal plane at room temperature. Preliminary results of gravity load and thermal distortion calculations are provided, and early metrological verification of candidate materials under cold thermal conditions are presented. A detailed, generalized method for stitching together sparse metrology data originating from differential, non-contact metrological data acquisition spanning multiple (non-continuous) sensor surfaces making up the focal plane, is described and demonstrated. Finally, we describe some in situ alignment verification alternatives, some of which may be integrated into the camera's focal plane.
Plane impact response of PBX 9501 below 2 GPA
Dick, J.J.; Martinez, A.R.; Hixson, R.S.
1998-12-31
The plane impact response of PBX 9501 was measured below 2 GPa using a light-gas gun facility. Time-resolved wave profiles were obtained in a state of uniaxial strain for impact stresses between 0.3 to 1.2 GPa. The dynamic strength of PBX 9501 was measured at high strain rates in both compression and tension. The Hugoniot equation of state was measured.
Axial strain redistribution resulting from off-axis ply cracking in polymer composites
NASA Astrophysics Data System (ADS)
Katerelos, Dionisis G.; Galiotis, Costas
2004-10-01
The initial mode of damage in multidirectional composites is the accumulation of matrix cracks in the off-axis plies. Remote laser Raman spectroscopy, using aramid (Kevlar 49®) fibers as Raman strain sensors, has been employed to monitor the local strains in cracked crossply composites. The strain magnification in the 0° ply caused by 90° matrix cracking are measured at different levels of loading. A relationship between the values of strain magnification and the distance between the position of the fibers sensors vis-à-vis the crack front has been established. The effect of damage progression within the 0° plies on the remaining/surviving glass fibers is modeled satisfactorily and verified against predictions on the basis of a generalized plane strain model by assuming that the 90° ply "expands" in relative size against the 0° ply thickness.
Li, Lin; Sun, Guoqing; Zhong, Ping; Han, Jingwan; Li, Tianyi; Jia, Dijing; Liu, Yongjian; Sun, Changrong; Wang, Zhe; Li, Hanping; Wang, Xiaolin; Li, Jingyun
2016-04-01
Henan, China is characterized by the outbreak of HIV epidemic of Thai B strain in former plasma donors in 1990s. After the forbidden of paid blood donation, whether Thai B strain will spread out of former plasma donors into sexual transmitted population is unknown. To answer the question, phylogenetic analysis was used to explore relationships of HIV strains circulating in those two populations in the study. HIV-1 sero-positive drug-naïve patients infected through sexual contact were enrolled into the study. Full length gag and pol genes were amplified with nested RT-PCR followed by sequencing and phylogenetic analysis. The genotypes of anti-HIV drug resistance were also analyzed with available pol genes. HIV subtypes were determined in 249 individuals from 288 participants. Subtype B was dominant (202/249, 81.1%), followed by CRF01_AE (25/249, 10.0%), CRF07_BC (14/249, 5.6%), C (4/249, 1.6%), URF (3/249, 1.2%), and CRF08_BC (1/249, 0.4%). Most of subtype B strains belong to Thailand B lineage. All of Thai B strains identified in sexual transmitted population intermixed with those from former blood donors in phylogenetic tree, suggesting close phylogenetic relationship between strains epidemic in those two populations. TDR was identified in 9.9% individuals. Thai B strain has spread out of former blood donors in Henan province. The finding will contribute to understanding the distribution and evolution of HIV-1 in Henan province and also provide clue to behavior change intervention. PMID:26381060
The Principle and Applications of Multi-Plane Separation for Balancing Machines
NASA Astrophysics Data System (ADS)
Kang, Y.; Sheen, G.-J.; Tang, P.-H.
1997-11-01
Two-plane separation is a conventional technique of balancing machines for rigid rotors such that each sensor measures the separated effects of equivalent imbalances in two planes. However, some complex rigid rotors such as multicylinder crankshafts need to be balanced by multi-plane correction for reducing mass concentration at two planes. This study verifies the principle of plane separation by using an exact-point influence coefficient approach. From the analysis a generalized algorithm of multiplane separation can be developed. Thus, an unlimited technique of plane separation is provided to improve balancing machines for complex rotors which have several planes in need of correction.
The relationship between strain geometry and geometrically necessary dislocations
NASA Astrophysics Data System (ADS)
Hansen, Lars; Wallis, David
2016-04-01
The kinematics of past deformations are often a primary goal in structural analyses of strained rocks. Details of the strain geometry, in particular, can help distinguish hypotheses about large-scale tectonic phenomena. Microstructural indicators of strain geometry have been heavily utilized to investigate large-scale kinematics. However, many of the existing techniques require structures for which the initial morphology is known, and those structures must undergo the same deformation as imposed macroscopically. Many deformed rocks do not exhibit such convenient features, and therefore the strain geometry is often difficult (if not impossible) to ascertain. Alternatively, crystallographic textures contain information about the strain geometry, but the influence of strain geometry can be difficult to separate from other environmental factors that might affect slip system activity and therefore the textural evolution. Here we explore the ability for geometrically necessary dislocations to record information about the deformation geometry. It is well known that crystallographic slip due to the motion of dislocations yields macroscopic plastic strain, and the mathematics are established to relate dislocation glide on multiple slip systems to the strain tensor of a crystal. This theoretical description generally assumes that dislocations propagate across the entire crystal. However, at any point during the deformation, dislocations are present that have not fully transected the crystal, existing either as free dislocations or as dislocations organized into substructures like subgrain boundaries. These dislocations can remain in the lattice after deformation if the crystal is quenched sufficiently fast, and we hypothesize that this residual dislocation population can be linked to the plastic strain geometry in a quantitative manner. To test this hypothesis, we use high-resolution electron backscatter diffraction to measure lattice curvatures in experimentally deformed
NASA Astrophysics Data System (ADS)
Barkin, Yu. V.; Ferrandiz, J. M.
2009-04-01
theory of Mercury librations in longitude by using three characteristics of Mercury rotation determined in the paper [3]. Two from these parameters are values of angle of librations in longitude and angular velocity in moment of passage of perihelion of Mercury orbit on 17 April 2002: (^g)0 = 0007 ± 0001, (^?? )0 = (2.10± 0.06)? ars/d. Third parameter determined in [3] is a dynamical coefficient: K = (B -A)(4Cm ) = (5.08± 0.30) × 10-5. B > A are principal moment of inertia, corresponding to equatorial axes of inertia; Cm is a polar moment of inertia of the mantle of Mercury. 1 Analytical theory of plane Mercury librations. This theory describes forced and free librations of Mercury in longitude in the frame of plane problem about resonant librations of Mercury considered or as non-spherical rigid body, or as system of rigid non-spherical mantle and liquid ellipsoidal core. Saving the main terms for the perturbations of angle of librations ^g and angular velocity ^? in both mentioned cases we will have formulae [6]: ^g = K(E sin M + E sin2M + E sin 3M + E sin4M + E sin5M ) 1 2 3 4 5+K0 sin(E KM- - φ) (A)
In-plane and out-of-plane motions of the human tympanic membrane.
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
NASA Technical Reports Server (NTRS)
Houseman, G.; England, P.
1986-01-01
The present investigation has the objective to perform numerical experiments on a rheologically simple continuum model for the continental lithosphere. It is attempted to obtain a better understanding of the dynamics of continental deformation. Calculations are presented of crustal thickness distributions, stress, strain, strain rate fields, latitudinal displacements, and finite rotations, taking into account as basis a model for continental collision which treats the litoshphere as a thin viscous layer subject to indenting boundary conditions. The results of this paper support the conclusions of England and McKenzie (1982) regarding the role of gravity in governing the deformation of a thin viscous layer subject to indenting boundary conditions. The results of the experiments are compared with observations of topography, stress and strain rate fields, and palaeomagnetic latitudinal displacements in Asia.
Reflections on the Hyperbolic Plane
NASA Astrophysics Data System (ADS)
Lecian, Orchidea Maria
2013-12-01
The most general solution to the Einstein equations in 4 = 3 + 1 dimensions in the asymptotic limit close to the cosmological singularity under the BKL (Belinskii-Khalatnikov-Lifshitz) hypothesis can be visualized by the behavior of a billiard ball in a triangular domain on the Upper Poincaré Half Plane (UPHP). The billiard system (named "big billiard") can be schematized by dividing the successions of trajectories according to Poincaré return map on the sides of the billiard table, according to the paradigms implemented by the BKL investigation and by the CB-LKSKS (Chernoff-Barrow-Lifshitz-Khalatnikov-Sinai-Khanin-Shchur) one. Different maps are obtained, according to different symmetry-quotienting mechanisms used to analyze the dynamics. In the inhomogeneous case, new structures have been uncovered, such that, in this framework, the billiard table (named "small billiard") consists of 1/6 of the previous one. The connections between the symmetry-quotienting mechanisms are further investigated on the UPHP. The relation between the complete billiard and the small billiard are also further explained according to the role of Weyl reflections. The quantum properties of the system are sketched as well, and the physical interpretation of the wave function is further developed. In particular, a physical interpretation for the symmetry-quotienting maps is proposed.
2013-01-01
Background Xanthomonads are plant-associated bacteria responsible for diseases on economically important crops. Xanthomonas fuscans subsp. fuscans (Xff) is one of the causal agents of common bacterial blight of bean. In this study, the complete genome sequence of strain Xff 4834-R was determined and compared to other Xanthomonas genome sequences. Results Comparative genomics analyses revealed core characteristics shared between Xff 4834-R and other xanthomonads including chemotaxis elements, two-component systems, TonB-dependent transporters, secretion systems (from T1SS to T6SS) and multiple effectors. For instance a repertoire of 29 Type 3 Effectors (T3Es) with two Transcription Activator-Like Effectors was predicted. Mobile elements were associated with major modifications in the genome structure and gene content in comparison to other Xanthomonas genomes. Notably, a deletion of 33 kbp affects flagellum biosynthesis in Xff 4834-R. The presence of a complete flagellar cluster was assessed in a collection of more than 300 strains representing different species and pathovars of Xanthomonas. Five percent of the tested strains presented a deletion in the flagellar cluster and were non-motile. Moreover, half of the Xff strains isolated from the same epidemic than 4834-R was non-motile and this ratio was conserved in the strains colonizing the next bean seed generations. Conclusions This work describes the first genome of a Xanthomonas strain pathogenic on bean and reports the existence of non-motile xanthomonads belonging to different species and pathovars. Isolation of such Xff variants from a natural epidemic may suggest that flagellar motility is not a key function for in planta fitness. PMID:24195767
Rasmussen-Barr, E; Grooten, W J A; Hallqvist, J; Holm, L W; Skillgate, E
2014-01-01
Objective To study whether job strain, that is, psychological job demands and decision latitude, and sleep disturbances among persons with occasional neck/shoulder/arm pain (NSAP) are prognostic factors for having experienced at least one episode of troublesome NSAP, and to determine whether sleep disturbances modify the association between job strain and troublesome NSAP. Design Prospective cohort study. Setting Stockholm, Sweden. Participants A population-based cohort of individuals with occasional NSAP (n=6979) who answered surveys in 2006 and 2010. Outcome measures Report of at least one episode of troublesome NSAP in 2010. Results The ORs for troublesome NSAP at follow-up were in individuals exposed to passive jobs 1.2 (95% CI 0.9 to 1.4); to active jobs 1.3 (95% CI 1.1 to 1.5); to high strain 1.5 (95% CI 1.0 to 2.4); to mild sleep disturbances 1.4 (95% CI 1.3 to 1.6) and to severe sleep disturbances 2.2 (95% CI 1.6 to 3.0). High strain and active jobs were associated with having experienced at least one episode of troublesome NSAP during the previous 6 months in persons with sleep disturbances, but not in individuals without sleep disturbances. Conclusions Our results indicate that high strain, active jobs and sleep disturbances are prognostic factors that should be taken into account when implementing preventive measures to minimise the risk of troublesome NSAP among people of working age. We suggest that sleep disturbances may modify the association between high strain and troublesome NSAP. PMID:25005596
Models for elastic shells with incompatible strains
Lewicka, Marta; Mahadevan, L.; Pakzad, Mohammad Reza
2014-01-01
The three-dimensional shapes of thin lamina, such as leaves, flowers, feathers, wings, etc., are driven by the differential strain induced by the relative growth. The growth takes place through variations in the Riemannian metric given on the thin sheet as a function of location in the central plane and also across its thickness. The shape is then a consequence of elastic energy minimization on the frustrated geometrical object. Here, we provide a rigorous derivation of the asymptotic theories for shapes of residually strained thin lamina with non-trivial curvatures, i.e. growing elastic shells in both the weakly and strongly curved regimes, generalizing earlier results for the growth of nominally flat plates. The different theories are distinguished by the scaling of the mid-surface curvature relative to the inverse thickness and growth strain, and also allow us to generalize the classical Föppl–von Kármán energy to theories of prestrained shallow shells. PMID:24808750
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.
NASA Technical Reports Server (NTRS)
Freed, Alan D.
1997-01-01
Logarithmic strain is the preferred measure of strain used by materials scientists, who typically refer to it as the "true strain." It was Nadai who gave it the name "natural strain," which seems more appropriate. This strain measure was proposed by Ludwik for the one-dimensional extension of a rod with length l. It was defined via the integral of dl/l to which Ludwik gave the name "effective specific strain." Today, it is after Hencky, who extended Ludwik's measure to three-dimensional analysis by defining logarithmic strains for the three principal directions.
Auditory spatial resolution in horizontal, vertical, and diagonal planes
NASA Astrophysics Data System (ADS)
Grantham, D. Wesley; Hornsby, Benjamin W. Y.; Erpenbeck, Eric A.
2003-08-01
Minimum audible angle (MAA) and minimum audible movement angle (MAMA) thresholds were measured for stimuli in horizontal, vertical, and diagonal (60°) planes. A pseudovirtual technique was employed in which signals were recorded through KEMAR's ears and played back to subjects through insert earphones. Thresholds were obtained for wideband, high-pass, and low-pass noises. Only 6 of 20 subjects obtained wideband vertical-plane MAAs less than 10°, and only these 6 subjects were retained for the complete study. For all three filter conditions thresholds were lowest in the horizontal plane, slightly (but significantly) higher in the diagonal plane, and highest for the vertical plane. These results were similar in magnitude and pattern to those reported by Perrott and Saberi [J. Acoust. Soc. Am. 87, 1728-1731 (1990)] and Saberi and Perrott [J. Acoust. Soc. Am. 88, 2639-2644 (1990)], except that these investigators generally found that thresholds for diagonal planes were as good as those for the horizontal plane. The present results are consistent with the hypothesis that diagonal-plane performance is based on independent contributions from a horizontal-plane system (sensitive to interaural differences) and a vertical-plane system (sensitive to pinna-based spectral changes). Measurements of the stimuli recorded through KEMAR indicated that sources presented from diagonal planes can produce larger interaural level differences (ILDs) in certain frequency regions than would be expected based on the horizontal projection of the trajectory. Such frequency-specific ILD cues may underlie the very good performance reported in previous studies for diagonal spatial resolution. Subjects in the present study could apparently not take advantage of these cues in the diagonal-plane condition, possibly because they did not externalize the images to their appropriate positions in space or possibly because of the absence of a patterned visual field.
Hamiltonian maps in the complex plane
Greene, J.M.; Percival, I.C.
1981-01-01
Following Arnol'd's proof of the KAM theorem, an analogy with the vertical pendulum, and some general arguments concerning maps in the complex plane, detailed calculations are presented and illustrated graphically for the standard map at the golden mean frequency. The functional dependence of the coordinate q on the canonical angle variable theta is analytically continued into the complex theta-plane, where natural boundaries are found at constant absolute values of Im theta. The boundaries represent the appearance of chaotic motion in the complex plane. Two independent numerical methods based on Fourier analysis in the angle variable were used, one based on a variation-annihilation method and the other on a double expansion. The results were further checked by direct solution of the complex equations of motion. The numerically simpler, but intrinsically complex, semipendulum and semistandard map are also studied. We conjecture that natural boundaries appear in the analogous analytic continuation of the invariant tori or KAM surfaces of general nonintegrable systems.
Computational strain gradient crystal plasticity
NASA Astrophysics Data System (ADS)
Niordson, Christian F.; Kysar, Jeffrey W.
2014-01-01
A numerical method for viscous strain gradient crystal plasticity theory is presented, which incorporates both energetic and dissipative gradient effects. The underlying minimum principles are discussed as well as convergence properties of the proposed finite element procedure. Three problems of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically oriented face centered cubic crystals are developed in terms of the crystallographic slip parameters. The effect on geometrically necessary dislocation structures introduced by plastic deformation is investigated as a function of the ratio of void radius to plasticity length scale.
NASA Technical Reports Server (NTRS)
1997-01-01
multi-phase research program for tailplane icing (TIP II) to develop test methodologies and tailplane performance and handling qualities evaluation tools. The main objectives of this new NASA/Industry/Academia collaborative research programs were: (1) define and evaluate a sub-scale wind tunnel test methodology for determining tailplane performance degradation due to icing. (2) develop an experimental database of tailplane aerodynamic performance with and without ice contamination for a range of tailplane configurations. Wind tunnel tests were planned with representative general aviation aircraft, i.e., the Learjet 45, and a twin engine low speed aircraft. This report summarizes the research performed during the first year of the study, and outlines the work tasks for the second year.
Surface anatomy and anatomical planes in the adult turkish population.
Uzun, C; Atman, E D; Ustuner, E; Mirjalili, S A; Oztuna, D; Esmer, T S
2016-03-01
Surface anatomy and anatomical planes are widely used in education and clinical practice. The planes are largely derived from cadaveric studies and their projections on the skin show discrepancies between and within anatomical reference textbooks. In this study, we reassessed the accuracy of common thoracic and abdominopelvic anatomical planes using computed tomography (CT) imaging in the live adult Turkish population. After patients with distorting pathologies had been excluded, CT images of 150 supine patients at the end tidal inspiration were analyzed. Sternal angle, transpyloric, subcostal, supracristal and pubic crest planes and their relationships to anatomical structures were established by dual consensus. The tracheal bifurcation, azygos vein/superior vena cava (SVC) junction and pulmonary bifurcation were usually below the sternal angle while the concavity of the aortic arch was generally within the plane. The tip of the tenth rib, the superior mesenteric artery and the portal vein were usually within the transpyloric plane while the renal hila and the fundus of the gallbladder were below it. The inferior mesenteric artery was below the subcostal plane and the aortic bifurcation was below the supracristal plane in most adults. Projectional surface anatomy is fundamental to medical education and clinical practice. Modern cross-sectional imaging techniques allow large groups of live patients to be examined. Classic textbook information regarding anatomy needs to be reviewed and updated using the data gathered from these recent studies, taking ethnic differences into consideration. Clin. Anat. 29:183-190, 2016. © 2015 Wiley Periodicals, Inc. PMID:26403267
Characterization of the KATRIN Focal Plane Detector
NASA Astrophysics Data System (ADS)
Bodine, Laura; Leber, Michelle; Myers, Allan; Tolich, Kazumi; Vandevender, Brent; Wall, Brandon
2008-10-01
The Karlsruhe Tritium Neutrino (KATRIN) Experiment is a next generation tritium beta decay experiment designed to measure directly the electron neutrino mass with a sensitivity of 0.2 eV. In the experiment, electrons from tritium decay of a gaseous source are magnetically guided through analyzing solenoidal retarding electrostatic spectrometers and detected via a focal plane detector. The focal plane detector is a 90mm diameter, 500 micron thick monolithic silicon pin-diode array with 148 pixels. The diode contacts have a titanium nitride overlayer and are connected to preamplifiers via an array of spring-loaded pogo pins. This novel connection scheme minimizes backgrounds from radioactive materials near the detector, facilitates characterization and replacement of the detector wafer, but requires a unique mounting design. The force of the pins strains the silicon, possibly altering the detector properties and performance. Results on the mechanical, thermal and electrical performance of a prototype detector under stress from pogo pin readouts will be presented.
Marsh, Stanley P.
1988-01-01
An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive.
Marsh, S.P.
1988-03-08
An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 4 figs.
Marsh, S.P.
1987-03-12
An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 3 figs., 3 tabs.
NASA Astrophysics Data System (ADS)
Forgács, Péter; Lukács, Árpád; Romańczukiewicz, Tomasz
2013-12-01
It is shown that in a large class of systems, plane waves act as tractor beams: i.e., an incident plane wave can exert a pulling force on the scatterer. The underlying physical mechanism for the pulling force is due to the sufficiently strong scattering of the incoming wave into another mode carrying more momentum, in which case excess momentum is created behind the scatterer. This tractor beam or negative radiation pressure (NRP) effect, is found to be generic in systems with multiple scattering channels. In a birefringent medium, electromagnetic plane waves incident on a thin plate exert NRP of the same order of magnitude as optical radiation pressure, while in artificial dielectrics (metamaterials), the magnitude of NRP can even be macroscopic. In two dimensions, we study various scattering situations on vortices, and NRP is shown to occur by the scattering of heavy baryons into light leptons off cosmic strings, and by neutron scattering off vortices in the XY model.
Plane waves in noncommutative fluids
NASA Astrophysics Data System (ADS)
Abdalla, M. C. B.; Holender, L.; Santos, M. A.; Vancea, I. V.
2013-08-01
We study the dynamics of the noncommutative fluid in the Snyder space perturbatively at the first order in powers of the noncommutative parameter. The linearized noncommutative fluid dynamics is described by a system of coupled linear partial differential equations in which the variables are the fluid density and the fluid potentials. We show that these equations admit a set of solutions that are monochromatic plane waves for the fluid density and two of the potentials and a linear function for the third potential. The energy-momentum tensor of the plane waves is calculated.
Space-Plane Spreadsheet Program
NASA Technical Reports Server (NTRS)
Mackall, Dale
1993-01-01
Basic Hypersonic Data and Equations (HYPERDATA) spreadsheet computer program provides data gained from three analyses of performance of space plane. Equations used to perform analyses derived from Newton's second law of physics, derivation included. First analysis is parametric study of some basic factors affecting ability of space plane to reach orbit. Second includes calculation of thickness of spherical fuel tank. Third produces ratio between volume of fuel and total mass for each of various aircraft. HYPERDATA intended for use on Macintosh(R) series computers running Microsoft Excel 3.0.
Blass, J.J.
1982-01-01
An improved multiaxial fatigue failure criterion was developed based on the results of combined axial-torsional strain cycling tests of AISI 304 and 2-1/4 Cr-1 Mo steel conducted at 538/sup 0/C (1000/sup 0/F). The formulation of this criterion involves the shear and normal components of inelastic strain range on the planes of maximum inelastic shear strain range. Optimum values of certain parameters contained in the formulation were obtained for each material by the method of least squares. The ability of this criterion to correlate the test results was compared with that of the usual (Mises) equivalent inelastic strain range criterion. An improved definition of equivalent inelastic strain range resulting from these considerations was used to generalize the theory of Strain Range Partitioning to multiaxial stress-strain conditions and was also applied to the linear summation of creep and fatigue damage.
Affine Contractions on the Plane
ERIC Educational Resources Information Center
Celik, D.; Ozdemir, Y.; Ureyen, M.
2007-01-01
Contractions play a considerable role in the theory of fractals. However, it is not easy to find contractions which are not similitudes. In this study, it is shown by counter examples that an affine transformation of the plane carrying a given triangle onto another triangle may not be a contraction even if it contracts edges, heights or medians.…
Planes of satellite galaxies and the cosmic web
NASA Astrophysics Data System (ADS)
Libeskind, Noam I.; Hoffman, Yehuda; Tully, R. Brent; Courtois, Helene M.; Pomarède, Daniel; Gottlöber, Stefan; Steinmetz, Matthias
2015-09-01
Recent observational studies have demonstrated that the majority of satellite galaxies tend to orbit their hosts on highly flattened, vast, possibly corotating planes. Two nearly parallel planes of satellites have been confirmed around the M31 galaxy and around the Centaurus A galaxy, while the Milky Way also sports a plane of satellites. It has been argued that such an alignment of satellites on vast planes is unexpected in the standard Λ cold dark matter (ΛCDM) model of cosmology if not even in contradiction to its generic predictions. Guided by ΛCDM numerical simulations, which suggest that satellites are channelled towards hosts along the axis of the slowest collapse as dictated by the ambient velocity shear tensor, we re-examine the planes of local satellites systems within the framework of the local shear tensor derived from the Cosmicflows-2 data set. The analysis reveals that the Local Group and Centaurus A reside in a filament stretched by the Virgo cluster and compressed by the expansion of the Local Void. Four out of five thin planes of satellite galaxies are indeed closely aligned with the axis of compression induced by the Local Void. Being the less massive system, the moderate misalignment of the Milky Way's satellite plane can likely be ascribed to its greater susceptibility to tidal torques, as suggested by numerical simulations. The alignment of satellite systems in the local Universe with the ambient shear field is thus in general agreement with predictions of the ΛCDM model.
Straining Graphene Using Thin Film Shrinkage Methods
2014-01-01
Theoretical works suggest the possibility and usefulness of strain engineering of graphene by predicting remarkable properties, such as Dirac cone merging, bandgap opening and pseudo magnetic field generation. However, most of these predictions have not yet been confirmed because it is experimentally difficult to control the magnitude and type (e.g., uniaxial, biaxial, and so forth) of strain in graphene devices. Here we report two novel methods to apply strain without bending the substrate. We employ thin films of evaporated metal and organic insulator deposited on graphene, which shrink after electron beam irradiation or heat application. These methods make it possible to apply both biaxial strain and in-plane isotropic compressive strain in a well-controlled manner. Raman spectroscopy measurements show a clear splitting of the degenerate states of the G-band in the case of biaxial strain, and G-band blue shift without splitting in the case of in-plane isotropic compressive strain. In the case of biaxial strain application, we find out the ratio of the strain component perpendicular to the stretching direction is at least three times larger than what was previously observed, indicating that shrinkage of the metal or organic insulator deposited on graphene induces both tensile and compressive strain in this atomically thin material. Our studies present for the first time a viable way to apply strain to graphene without the need to bend the substrate. PMID:24490629
Straining graphene using thin film shrinkage methods.
Shioya, Hiroki; Craciun, Monica F; Russo, Saverio; Yamamoto, Michihisa; Tarucha, Seigo
2014-03-12
Theoretical works suggest the possibility and usefulness of strain engineering of graphene by predicting remarkable properties, such as Dirac cone merging, bandgap opening and pseudo magnetic field generation. However, most of these predictions have not yet been confirmed because it is experimentally difficult to control the magnitude and type (e.g., uniaxial, biaxial, and so forth) of strain in graphene devices. Here we report two novel methods to apply strain without bending the substrate. We employ thin films of evaporated metal and organic insulator deposited on graphene, which shrink after electron beam irradiation or heat application. These methods make it possible to apply both biaxial strain and in-plane isotropic compressive strain in a well-controlled manner. Raman spectroscopy measurements show a clear splitting of the degenerate states of the G-band in the case of biaxial strain, and G-band blue shift without splitting in the case of in-plane isotropic compressive strain. In the case of biaxial strain application, we find out the ratio of the strain component perpendicular to the stretching direction is at least three times larger than what was previously observed, indicating that shrinkage of the metal or organic insulator deposited on graphene induces both tensile and compressive strain in this atomically thin material. Our studies present for the first time a viable way to apply strain to graphene without the need to bend the substrate. PMID:24490629
Optimization of starshades: focal plane versus pupil plane
NASA Astrophysics Data System (ADS)
Flamary, R.; Aime, C.
2014-09-01
We search for the best possible transmission for an external occulter coronagraph that is dedicated to the direct observation of terrestrial exoplanets. We show that better observation conditions are obtained when the flux in the focal plane is minimized in the zone in which the exoplanet is observed, instead of for the total flux received by the telescope. We describe the transmission of the occulter as a sum of basis functions. For each element of the basis, we numerically computed the Fresnel diffraction at the aperture of the telescope and the complex amplitude at its focus. The basis functions are circular disks that are linearly apodized over a few centimeters (truncated cones). We complemented the numerical calculation of the Fresnel diffraction for these functions by a comparison with pure circular disks (cylinder) for which an analytical expression, based on a decomposition in Lommel series, is available. The technique of deriving the optimal transmission for a given spectral bandwidth is a classical regularized quadratic minimization of intensities, but linear optimizations can be used as well. Minimizing the integrated intensity on the aperture of the telescope or for selected regions of the focal plane leads to slightly different transmissions for the occulter. For the focal plane optimization, the resulting residual intensity is concentrated behind the geometrical image of the occulter, in a blind region for the observation of an exoplanet, and the level of background residual starlight becomes very low outside this image. Finally, we provide a tolerance analysis for the alignment of the occulter to the telescope, which also favors the focal plane optimization. This means that telescope offsets of a few decimeters do not strongly reduce the efficiency of the occulter.
Thermophoretic Motion of a Sphere Parallel to an Insulated Plane.
Chen
2000-04-01
An analytical study is presented for the thermophoresis of a sphere in a constant applied temperature gradient parallel to an adiabatic plane. The Knudsen number is assumed to be small so that the fluid flow can be described by a continuum model with a thermal creep and a hydrodynamic slip at the particle surface. A method of reflections is used to obtain the asymptotic formulas for the temperature and velocity fields in the quasisteady situation. The thermal insulated plane may be a solid wall (no-slip) and/or a free surface (perfect-slip). The boundary effect on the thermophoretic motion is found to be weaker than that on the axisymmetric thermophoresis of a sphere normal to a plane with constant temperature. In comparison with the motion driven by gravitational force, the interaction between the particle and the boundary is less significant under thermophoresis. Even so, the interaction between the plane and the particle can be very strong when the gap thickness approaches zero. For the thermophoretic motion of a particle parallel to a solid plane, the effect of the plane surface is to reduce the translational velocity of the particle. In the case of particle migration parallel to a free surface due to thermophoresis, the translating velocity of a particle can be either greater or smaller than that which would exist in the absence of the plane surface, depending on the relative thermal conductivity and the surface properties of the particle and its relative distance from the plane. Not only the translational velocity but also the rotational velocity of the thermophoretic sphere near the plane boundary is formulated analytically. The rotating direction of the particle is strongly dominated by its surface properties and the internal-to-external thermal conductivity. Besides the particle motion, the thickness of the thermophoretic boundary layer is evaluated by considering the thermophoretic mobility. Generally speaking, a free surface exerts less influence on the
NASA Technical Reports Server (NTRS)
1995-01-01
HITEC Corporation developed a strain gage application for DanteII, a mobile robot developed for NASA. The gage measured bending forces on the robot's legs and warned human controllers when acceptable forces were exceeded. HITEC further developed the technology for strain gage services in creating transducers out of "Indy" racing car suspension pushrods, NASCAR suspension components and components used in motion control.
Plane Wave and Coulomb Asymptotics
NASA Astrophysics Data System (ADS)
Mulligan, P. G.; Crothers, D. S. F.
2004-01-01
A simple plane wave solution of the Schrödinger Helmholtz equation is a quantum eigenfunction obeying both energy and linear momentum correspondence principles. Inclusion of the outgoing wave with scattering amplitude f obeys unitarity and the optical theorem. By closely considering the standard asymptotic development of the plane wave, we show that there is a problem with angular momentum when we consider forward scattering at the point of closest approach and at large impact parameter given semiclassically by (l + 1/2)/k where l is the azimuthal quantum number and may be large (J Leech et al, Phys. Rev. Lett. 88 257901 (2002)). The problem is resolved via non-uniform, non-standard analysis involving the Heaviside step function, unifying classical, semiclassical and quantum mechanics, and the treatment is extended to the case of pure Coulomb scattering.
Imafuku, Muneyuki; Suzuki, Hiroshi; Sueyoshi, Kazuyuki; Akita, Koichi; Ohya, Shin-ichi
2008-06-09
Generalized formula of the x-ray stress analysis for a single crystal with unknown stress-free lattice parameter was proposed. This method enables us to evaluate the plane stress states with any combination of diffraction planes. We can choose and combine the appropriate x-ray sources and diffraction plane families, depending on the sample orientation and the apparatus, whenever diffraction condition is satisfied. The analysis of plane stress distributions in an iron single crystal was demonstrated combining with the diffraction data for Fe{l_brace}211{r_brace} and Fe{l_brace}310{r_brace} plane families.
Material mechanical characterization method for multiple strains and strain rates
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.
Orbital Space Plane (OSP) Program
NASA Technical Reports Server (NTRS)
McKenzie, Patrick M.
2003-01-01
Lockheed Martin has been an active participant in NASA's Space Launch Initiative (SLI) programs over the past several years. SLI, part of NASA's Integrated Space Transportation Plan (ISTP), was restructured in November of 2002 to focus the overall theme of safer, more afford-able space transportation along two paths - the Orbital Space Plane Program and the Next Generation Launch Technology programs. The Orbital Space Plane Program has the goal of providing rescue capability from the International Space Station by 2008 and transfer capability for crew (and limited cargo) by 2012. The Next Generation Launch Technology program is combining research and development efforts from the 2nd Generation Reusable Launch Vehicle (2GRLV) program with cutting-edge, advanced space transportation programs (previously designated 3rd Generation) into one program aimed at enabling safe, reliable, cost-effective reusable launch systems by the middle of the next decade. Lockheed Martin is one of three prime contractors working to bring Orbital Space Plane system concepts to a system definition level of maturity by December of 2003. This paper and presentation will update the international community on the progress of the' OSP program, from an industry perspective, and provide insights into Lockheed Martin's role in enabling the vision of a safer, more affordable means of taking people to and from space.
Symmetry in finite phase plane
NASA Astrophysics Data System (ADS)
Zak, J.
2010-03-01
The known symmetries in one-dimensional systems are inversion and translations. These symmetries persist in finite phase plane, but a novel symmetry arises in view of the discrete nature of the coordinate xi and the momentum pi : xi and pi can undergo permutations. Thus, if xi assumes M discrete values, i = 0, 1,2,..., M - 1, a permutation will change the order of the set x0,x1,..., xM-1 into a new ordered set. Such a symmetry element does not exist for a continuous x-coordinate in an infinite phase plane. Thus, in a finite phase plane, translations can be replaced by permutations. This is also true for the inversion operator. The new permutation symmetry has been used for the construction of conjugate representations and for the splitting of the M-dimensional vector space into independent subspaces. This splitting is exhaustive in the sense that if M = iMi with Mi being prime numbers, the M-dimensional space splits into M1,M2,...Mn-dimensional independent subspaces. It is shown that following this splitting one can design new potentials with appropriate constants of motion. A related problem is the Weyl-Heisenberg group in the M-dimensional space which turns into a direct product of its subgroups in the Mi-dimensional subspaces. As an example we consider the case of M = 8.
Tuning the Schottky contacts in the phosphorene and graphene heterostructure by applying strain.
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. PMID:27398801
Electronic structure and optic absorption of phosphorene under strain
NASA Astrophysics Data System (ADS)
Duan, Houjian; Yang, Mou; Wang, Ruiqiang
2016-07-01
We studied the electronic structure and optic absorption of phosphorene (monolayer of black phosphorus) under strain. Strain was found to be a powerful tool for the band structure engineering. The in-plane strain in armchair or zigzag direction changes the effective mass components along both directions, while the vertical strain only has significant effect on the effective mass in the armchair direction. The band gap is narrowed by compressive in-plane strain and tensile vertical strain. Under certain strain configurations, the gap is closed and the energy band evolves to the semi-Dirac type: the dispersion is linear in the armchair direction and is gapless quadratic in the zigzag direction. The band-edge optic absorption is completely polarized along the armchair direction, and the polarization rate is reduced when the photon energy increases. Strain not only changes the absorption edge (the smallest photon energy for electron transition), but also the absorption polarization.
NASA Technical Reports Server (NTRS)
Piland, William M.
1987-01-01
An account is given of the technology development management objectives thus far planned for the DOD/NASA National Aero-Space Plane (NASP). The technology required by NASP will first be developed in ground-based facilities and then integrated during the design and construction of the X-30 experimental aircraft. Five airframe and three powerplant manufacturers are currently engaged in an 18-month effort encompassing design studies and tradeoff analyses. The first flight of the X-30 is scheduled for early 1993.
SNAP Satellite Focal Plane Development
Bebek, C.; Akerlof, C.; Aldering, G.; Amanullah, R.; Astier, P.; Baltay, C.; Barrelet, E.; Basa, S.; Bercovitz, J.; Bergstrom, L.; Berstein, G.P.; Bester, M.; Bohlin, R.; Bonissent, A.; Bower, C.; Campbell, M.; Carithers, W.; Commins, E.; Day, C.; Deustua, S.; DiGennaro, R.; Ealet, A.; Ellis, R.; Emmett, W.; Eriksson, M.; Fouchez,D.; Fruchter, A.; Genat, J-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Heetderks, H.; Holland, S.; Huterer, D.; Johnson, W.; Kadel, R.; Karcher,A.; Kim, A.; Kolbe, W.; Lafever, R.; Lamoureaux, J.; Lampton, M.; Lefevre, O.; Levi, M.; Levin, D.; Linder, E.; Loken, S.; Malina, R.; Mazure, A.; McKay, T.; McKee, S.; Miquel, R.; Morgan, N.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Roe, N.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Prieto, E.; Rabinowitz,D.; Refregier, A.; Rhodes, J.; Schubnell, M.; Sholl, M.; Smadja, G.; Smith, R.; Smoot, G.; Snyder, J.; Spadafora, A.; Szymkowiak, A.; Tarle,G.; Taylor, K.; Tilquin, A.; Tomasch, A.; Vincent, D.; von der Lippe, H.; Walder, J-P.; Wang, G.
2003-07-07
The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.
NASA Astrophysics Data System (ADS)
Liang, Canbin; Tian, Guihua
1994-11-01
Electromagnetic fields yielding plane symmetric metrics in higher-dimensional spacetimes are exhausted and classified. It is shown that these EM fields must fall into one of the following two cases: (i)F it =F iz =0,i=1,...,n; (ii)Ftz=0. We give the general solution to the Einstein-Maxwell equations in higher dimensions corresponding to electromagnetic fields of case (ii) withF it =F iz , which covers all even-dimensional spacetimes as well as a subcase of odd-dimensional spacetimes.
Polarization of almost-plane waves.
Sheppard, C J
2000-02-01
The general polarization behavior of almost-plane waves, in which the electric field varies slowly over a circular pupil, is considered, on the basis of an axial Hertz potential treatment and expansion in Zernike polynomials. The resultant modes of a circular aperture are compared with the well-known waveguide (or optical fiber) modes and Gaussian beam modes. The wave can be decomposed into partial waves of electric and magnetic types. The modes for a square pupil are also considered. The particular application of the effect on polarization of focusing the waves is discussed. Another application discussed is the Fresnel reflection from a dielectric interface, it being shown that the Fresnel reflection alters the relative strength of the electric and magnetic components. PMID:10680636
Optics in a nonlinear gravitational plane wave
NASA Astrophysics Data System (ADS)
Harte, Abraham I.
2015-09-01
Gravitational waves can act like gravitational lenses, affecting the observed positions, brightnesses, and redshifts of distant objects. Exact expressions for such effects are derived here in general relativity, allowing for arbitrarily-moving sources and observers in the presence of plane-symmetric gravitational waves. At least for freely falling sources and observers, it is shown that the commonly-used predictions of linear perturbation theory can be generically overshadowed by nonlinear effects; even for very weak gravitational waves, higher-order perturbative corrections involve secularly-growing terms which cannot necessarily be neglected when considering observations of sufficiently distant sources. Even on more moderate scales where linear effects remain at least marginally dominant, nonlinear corrections are qualitatively different from their linear counterparts. There is a sense in which they can, for example, mimic the existence of a third type of gravitational wave polarization.
NASA Astrophysics Data System (ADS)
Chen, Feng; Euaruksakul, Chanan; Liu, Zheng; Himpsel, F. J.; Liu, Feng; Lagally, Max G.
2011-08-01
Strain changes the band structure of semiconductors. We use x-ray absorption spectroscopy to study the change in the density of conduction band (CB) states when silicon is uniaxially strained along the [1 0 0] and [1 1 0] directions. High stress can be applied to silicon nanomembranes, because their thinness allows high levels of strain without fracture. Strain-induced changes in both the sixfold degenerate Δ valleys and the eightfold degenerate L valleys are determined quantitatively. The uniaxial deformation potentials of both Δ and L valleys are directly extracted using a strain tensor appropriate to the boundary conditions, i.e., confinement in the plane in the direction orthogonal to the straining direction, which correspond to those of strained CMOS in commercial applications. The experimentally determined deformation potentials match the theoretical predictions well. We predict electron mobility enhancement created by strain-induced CB modifications.
Eta Carinae: Orientation of The Orbital Plane
NASA Technical Reports Server (NTRS)
Gull, T. R.; Nielsen, K. E.; Ivarsson, S.; Corcoran, M. F.; Verner, E.; Hillier, J. D.
2006-01-01
Evidence continues to build that Eta Carinae is a massive binary system with a hidden hot companion in a highly elliptical orbit. We present imaging and spectroscopic evidence that provide clues to the orientation of the orbital plane. The circumstellar ejecta, known as the Homunculus and Little Homunculus, are hourglass-shaped structures, one encapsulated within the other, tilted at about 45 degrees from the sky plane. A disk region lies between the bipolar lobes. Based upon their velocities and proper motions, Weigelt blobs B, C and D, very bright emission clumps 0.1 to 0.3" Northwest from Eta Carinae, lie in the disk. UV flux from the hot companion, Eta Car B, photoexcites the Weigelt blobs. Other clumps form a complete chain around the star, but are not significantly photoexcited. The strontium filament, a 'neutral' emission structure, lies in the same general direction as the Weigelt blobs and exhibits peculiar properties indicative that much mid-UV, but no hydrogen-ionizing radiation impinges on this structure. It is shielded by singly-ionized iron. P Cygni absorptions in Fe I I lines, seen directly in line of sight from Eta Carinae, are absent in the stellar light scattered by the Weigelt blobs. Rather than a strong absorption extending to -600 km/s, a low velocity absorption feature extends from -40 to -150 km/s. No absorbing Fe II exists between Eta Carinae and Weigelt D, but the outer reaches of the wind are intercepted in line of sight from Weigelt D to the observer. This indicates that the UV radiation is constrained by the dominating wind of Eta Car A to a small cavity carved out by the weaker wind of Eta Car B. Since the high excitation nebular lines are seen in the Weigelt blobs at most phases, the cavity, and hence the major axis of the highly elliptical orbit, must lie in the general direction of the Weigelt blobs. The evidence is compelling that the orbital major axis of Eta Carinae is projected at -45 degrees position angle on the sky. Moreover
The Bolocam Galactic Plane Survey
NASA Technical Reports Server (NTRS)
Glenn, Jason; Aguirre, James; Bally, John; Battersby, Cara; Bradley, Eric Todd; Cyganowski, Claudia; Dowell, Darren; Drosback, Meredith; Dunham, Miranda K.; Evans, Neal J., II; Ginsburg, Adam; Harvey, Paul; Rosolowsky, Erik; Schlingman, Wayne; Shirley, Yancy L.; Stringfellow, Guy S.; Walawender, Josh; Williams, Jonathan
2009-01-01
The Bolocam Galactic Plane Survey (BGPS) is a 1.1 millimeter continuum survey of the northern Galactic Plane made with Bolocam and the Caltech Submillimeter Observatory. The coverage totals 170 square degrees, comprised of a contiguous range from -10.5 deg is less than or equal to 90.5 deg, 0.5 deg is less than or equal to b is less than or equal to 0.5 deg, with extended coverage in b in selected regions, and four targeted regions in the outer Galaxy, including: IC1396, toward the Perseus arm at l is approximately 111 deg, W3/4/5, and Gem OB1. Depths of the maps range from 30 to 60 mJy beam (sup 1). Approximately 8,400 sources were detected and the maps and source catalog have been made publicly available. Millimeter-wave thermal dust emission reveals dense regions within molecular clouds, thus the BGPS serves as a database for studies of the dense interstellar medium and star formation within the Milky Way.
Image plane sweep volume illumination.
Sundén, Erik; Ynnerman, Anders; Ropinski, Timo
2011-12-01
In recent years, many volumetric illumination models have been proposed, which have the potential to simulate advanced lighting effects and thus support improved image comprehension. Although volume ray-casting is widely accepted as the volume rendering technique which achieves the highest image quality, so far no volumetric illumination algorithm has been designed to be directly incorporated into the ray-casting process. In this paper we propose image plane sweep volume illumination (IPSVI), which allows the integration of advanced illumination effects into a GPU-based volume ray-caster by exploiting the plane sweep paradigm. Thus, we are able to reduce the problem complexity and achieve interactive frame rates, while supporting scattering as well as shadowing. Since all illumination computations are performed directly within a single rendering pass, IPSVI does not require any preprocessing nor does it need to store intermediate results within an illumination volume. It therefore has a significantly lower memory footprint than other techniques. This makes IPSVI directly applicable to large data sets. Furthermore, the integration into a GPU-based ray-caster allows for high image quality as well as improved rendering performance by exploiting early ray termination. This paper discusses the theory behind IPSVI, describes its implementation, demonstrates its visual results and provides performance measurements. PMID:22034331
Rewritable photochromic focal plane masks
NASA Astrophysics Data System (ADS)
Molinari, Emilio; Bertarelli, Chiara; Bianco, Andrea; Bortoletto, Fabio; Conconi, Paolo; Crimi, Giuseppe; Gallazzi, Maria C.; Giro, Enrico; Lucotti, Andrea; Pernechele, Claudio; Zerbi, Filippo M.; Zerbi, Giuseppe
2003-02-01
The application of organic photochromic materials in astronomy is opening new possibilities which we are investigating in order to design innovative devices for future instrumentation. The photochromic property of transparent/opaque transition (although in a limited wavelength range) and the changes in intrinsic refractive index have led our studies to application in astronomic spectrographs, both as focal plane mask (for MOS application) and as dispersive elements (volume phase holographic gratings, VPHG), respectively. In both cases the possibility to write and erase devices with suitable irradiation has revealed a new perspective for non-disposable and fully customizable items for spectroscopy. Pursuing this goal we have synthesized a series of novel photochromic materials belonging to the diarylethenes. They fulfill the requirements of thermal stability and fatigue resistance necessary to build functional devices. Prototypes of high contrast focal plane mask working in the H-alpha spectral region have been manufactured and characterized both in laboratory and with the AFOSC camera at Asiago telescope (1.8 m). A custom writing robot (ARATRO) which, taking imaging frames and with the aid of interactive mask design software and ad hoc control electronics, is able to write MOS masks, has been constructed. The design of the MOS masks allow the fitting in the AFOSC slit wheel. The overall set-up is ready for the sky tests.
Growth and properties of m-plane GaN on m-plane sapphire by metalorganic chemical vapor deposition
NASA Astrophysics Data System (ADS)
Paduano, Qing S.; Weyburne, David W.; Tomich, David H.
2013-03-01
A characterization study of heteroepitaxial grown m-plane GaN on m-plane sapphire substrates by MOCVD was undertaken. Using X-ray diffraction and photoluminescence, the growth characteristics and epi-layer properties of m-GaN layers were investigated with special emphasis on the role of AlN buffer layers in preventing unintentional nitridation prior to GaN deposition. Substrate nitridation was found to lead to undesirable crystallographic orientations. In-plane lattice parameters of m-GaN obtained from X-ray reciprocal space mapping indicate anisotropic residual strain is present in these layers even under optimized growth conditions. Compressive and tensile strains were observed along either [0001] or [112¯0] directions, depending on AlN buffer layer conditions and the presence of extended structural defects. In addition, extended structural defects commonly observed in GaN showed a significant effect on stacking fault related luminescence in m-GaN.
StrainModeler: A MATHEMATICA™-based program for 3D analysis of finite and progressive strain
NASA Astrophysics Data System (ADS)
Bobillo-Ares, Nilo C.; Aller, Jesús; Bastida, Fernando; Menéndez, Omar; Lisle, Richard J.
2015-05-01
StrainModeler is a program constructed in the MATHEMATICA™ environment that performs 3D progressive strain calculations for lines and planes undergoing any sequence of homogeneous deformations. The main inputs to the system define the initial line or plane to be deformed and the deformation sequence to be applied, including combinations of simple shear, pure shear and volume change. For the deformation of lines, the output of the program is the change of attitude of the initial line, which can be represented by graphics or plotted in an equal-area projection. For the deformation of planes, the program has several outputs: (i) change of attitude of the initial plane; (ii) magnitudes and ratio of the semi-axes of the strain ellipse on the deformed plane; (iii) orientation of the major and minor axes of the strain ellipse on the deformed plane; (iv) orientations of the axial planes of the folds formed on the deformed plane, and (v) area change on the deformed plane. The variation of any of these parameters can be shown against a linear parameter only linked to the number of steps involved in the deformation, as a kind of "time" line, or it can be shown against the variation of a parameter of the strain ellipsoid (e. g.: major axis/minor axis ratio). A sequence of directions can be also visualized as a curve in an equal-area plot. Three applications of the program are presented. In the first, the deformation by simple shear of a plane with any orientation is analyzed. In the second, we explore the formation of recumbent folds in layers with different initial orientations for simple shear and pure shear deformations. In the third, we use StrainModeler to analyze the deformation of a set of folds located in a ductile shear zone in the Variscan Belt of NW Spain.
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.
Optimal focal-plane restoration
NASA Technical Reports Server (NTRS)
Reichenbach, Stephen E.; Park, Stephen K.
1989-01-01
Image restoration can be implemented efficiently by calculating the convolution of the digital image and a small kernel during image acquisition. Processing the image in the focal-plane in this way requires less computation than traditional Fourier-transform-based techniques such as the Wiener filter and constrained least-squares filter. Here, the values of the convolution kernel that yield the restoration with minimum expected mean-square error are determined using a frequency analysis of the end-to-end imaging system. This development accounts for constraints on the size and shape of the spatial kernel and all the components of the imaging system. Simulation results indicate the technique is effective and efficient.
CLAES focal plane array. [Cryogenic Limb Array Etalon Spectrometer
NASA Technical Reports Server (NTRS)
Roche, A. E.; Sterritt, L. W.; Kumer, J. B.; Callary, P. C.; Nielsen, R. L.
1989-01-01
The Cryogenic Limb Array Etalon Spectrometer for the NASA Upper Atmospheric Research Satellite uses solid-state focal plane arrays to detect emission from the earth's atmosphere over the IR wavelength range 3.5 to 13 microns. This paper discusses the design of the focal plane detector assembly and compares calculated performance with measurements. Measurements were made of focal plane noise and responsivity as functions of frequency (2 to 500 Hz) and temperature (12 to 19 K), pixel-to-pixel and across-array crosstalk, and linearity over a dynamic range of 100,000. The measurements demonstrate that the arrays satisfy the science requirements, and that, in general, there is reasonable agreement between the measurements and the analytical model.
NASA Astrophysics Data System (ADS)
Jönen, H.; Rossow, U.; Langer, T.; Dräger, A.; Hoffmann, L.; Bremers, H.; Hangleiter, A.; Bertram, F.; Metzner, S.; Christen, J.
2008-11-01
GaN/GaN quantum well (QW) structures grown on c-plane and m-plane surfaces have been investigated intended for long wavelength light emitters. On c-plane GaN QWs reached indium concentrations of xIn⩾35% with good optical and structural quality. For QW thicknesses dQW⩽2 nm a fully strained layer structure is observed and the indium concentration is quite homogenous. Under the same growth conditions of the QW region we find similar or even slightly larger indium concentrations on m-plane surfaces. QWs of such high indium concentrations, however, are very sensitive to the growth conditions of the subsequent layers and we observe degradation such as indium outdiffusion or partial relaxation for high growth temperatures.
Phase-field simulation of strain-induced domain switching in magnetic thin films
NASA Astrophysics Data System (ADS)
Hu, Jia-Mian; Sheng, G.; Zhang, J. X.; Nan, C. W.; Chen, L. Q.
2011-03-01
The strain-induced magnetic domain switching in epitaxial CoFe2O4 (CFO) thin films was studied using phase-field method. In particular, we investigated the domain switching from an initial in-plane direction to out-of-plane under the action of in-plane elastic strains. An abrupt switching feature is observed for a single-domain film while the switching of a multidomain CFO thin film is gradual. Typical magnetic domain structures as a result of the biaxial isotropic in-plane strains are presented.
Determining the pivotal plane of fluid lipid membranes in simulations.
Wang, Xin; Deserno, Markus
2015-10-28
Each leaflet of a curved lipid membrane contains a surface at which the area strain vanishes, the so-called pivotal plane. Its distance z0 from the bilayer's midplane arises in numerous contexts, for instance the connection between monolayer and bilayer moduli, stress-profile moments, or area-difference elasticity theories. Here, we propose two precise methods for determining the location of the pivotal plane in computer simulations, both of which rely on monitoring the lipid imbalance across a curved bilayer. The first method considers the ratio of lipid number between the two leaflets of cylindrical or spherical vesicles; it hence requires lipid flip-flop for equilibration. The second method looks at the leaflet difference across local sections cut out from a buckled membrane; this observable equilibrates even in the absence of flip-flop. We apply our methods to two different coarse-grained lipid models, the generic three-bead solvent-free Cooke model and a ten-bead representation of dimyristoylphosphocholine with the explicit solvent MARTINI model. The Cooke model is amenable to both methods and gives results that agree at the percent level. Using it, we also show that the pivotal plane moves outward as lipid curvature becomes more positive. The MARTINI model can only be analyzed with the buckling method; the obtained value z0 = 0.850(11) nm lies about 0.4 nm inwards of the glycerol backbone and is hence unexpectedly small. We attribute this to limitations of the coarse-grained description, suggesting that the location of the pivotal plane might be a good indicator for how well lipid models capture the microscopic origins of curvature elasticity. Finally, we also show that the pivotal plane position itself moves as the membrane is bent. The leading correction is linear in curvature, dependent on the Poisson ratio, and can matter when analyzing experimental results obtained from highly curved inverse hexagonal phases. PMID:26520500
Determining the pivotal plane of fluid lipid membranes in simulations
NASA Astrophysics Data System (ADS)
Wang, Xin; Deserno, Markus
2015-10-01
Each leaflet of a curved lipid membrane contains a surface at which the area strain vanishes, the so-called pivotal plane. Its distance z0 from the bilayer's midplane arises in numerous contexts, for instance the connection between monolayer and bilayer moduli, stress-profile moments, or area-difference elasticity theories. Here, we propose two precise methods for determining the location of the pivotal plane in computer simulations, both of which rely on monitoring the lipid imbalance across a curved bilayer. The first method considers the ratio of lipid number between the two leaflets of cylindrical or spherical vesicles; it hence requires lipid flip-flop for equilibration. The second method looks at the leaflet difference across local sections cut out from a buckled membrane; this observable equilibrates even in the absence of flip-flop. We apply our methods to two different coarse-grained lipid models, the generic three-bead solvent-free Cooke model and a ten-bead representation of dimyristoylphosphocholine with the explicit solvent MARTINI model. The Cooke model is amenable to both methods and gives results that agree at the percent level. Using it, we also show that the pivotal plane moves outward as lipid curvature becomes more positive. The MARTINI model can only be analyzed with the buckling method; the obtained value z0 = 0.850(11) nm lies about 0.4 nm inwards of the glycerol backbone and is hence unexpectedly small. We attribute this to limitations of the coarse-grained description, suggesting that the location of the pivotal plane might be a good indicator for how well lipid models capture the microscopic origins of curvature elasticity. Finally, we also show that the pivotal plane position itself moves as the membrane is bent. The leading correction is linear in curvature, dependent on the Poisson ratio, and can matter when analyzing experimental results obtained from highly curved inverse hexagonal phases.
Strain Engineering of the Electronic Properties in -doped Oxide Superlattices
You, Jeong Ho; Lee, Jun Hee; Okamoto, Satoshi; Cooper, Valentino R; Lee, Ho Nyung
2015-01-01
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% // 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 frommore » 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.« less