Nanometer thick elastic graphene engine.
Lee, Jong Hak; Tan, Jun You; Toh, Chee-Tat; Koenig, Steven P; Fedorov, V E; Castro Neto, Antonio H; Ozyilmaz, Barbaros
2014-05-14
Significant progress has been made in the construction and theoretical understanding of molecular motors because of their potential use. Here, we have demonstrated fabrication of a simple but powerful 1 nm thick graphene engine. The engine comprises a high elastic membrane-piston made of graphene and weakly chemisorbed ClF3 molecules as the high power volume changeable actuator, while a 532 nm LASER acts as the ignition plug. Rapid volume expansion of the ClF3 molecules leads to graphene blisters. The size of the blister is controllable by changing the ignition parameters. The estimated internal pressure per expansion cycle of the engine is about ∼10(6) Pa. The graphene engine presented here shows exceptional reliability, showing no degradation after 10,000 cycles. PMID:24773247
Martian lithospheric thickness from elastic flexure theory
NASA Technical Reports Server (NTRS)
Thurber, C. H.; Toksoz, M. N.
1978-01-01
The thickness of the elastic lithosphere in the Tharsis region of Mars is estimated from effects due to the surface load of Olympus Mons. Deformation (vertical displacement) and stress are calculated using elastic flexure theory for a range of possible lithospheric thicknesses (T), modeling the lithosphere as a thin elastic shell and the interior as a Newtonian fluid. For T below 150 km, displacement and stress rise rapidly with decreasing thickness. For T near 100 km, deformation of the region surrounding the volcano would be clearly visible in the topography, and resulting tensional stresses exceeding 5 kbar should produce observable fracturing at the surface. In contrast, for T near 200 km deformation is minimal and the tensional stress, being less than a kilobar, would not result in extensive fracturing. Since significant deformation and fracturing are not observed, it is concluded that the Martian elastic lithosphere is at least 150 km in thickness. Seismic, tectonic, and gravity observations all suggest a thick Martian lithosphere as well.
Tensile Instability in a Thick Elastic Body
NASA Astrophysics Data System (ADS)
Overvelde, Johannes T. B.; Dykstra, David M. J.; de Rooij, Rijk; Weaver, James; Bertoldi, Katia
2016-08-01
A range of instabilities can occur in soft bodies that undergo large deformation. While most of them arise under compressive forces, it has previously been shown analytically that a tensile instability can occur in an elastic block subjected to equitriaxial tension. Guided by this result, we conducted centimeter-scale experiments on thick elastomeric samples under generalized plane strain conditions and observed for the first time this elastic tensile instability. We found that equibiaxial stretching leads to the formation of a wavy pattern, as regions of the sample alternatively flatten and extend in the out-of-plane direction. Our work uncovers a new type of instability that can be triggered in elastic bodies, enlarging the design space for smart structures that harness instabilities to enhance their functionality.
Tensile Instability in a Thick Elastic Body.
Overvelde, Johannes T B; Dykstra, David M J; de Rooij, Rijk; Weaver, James; Bertoldi, Katia
2016-08-26
A range of instabilities can occur in soft bodies that undergo large deformation. While most of them arise under compressive forces, it has previously been shown analytically that a tensile instability can occur in an elastic block subjected to equitriaxial tension. Guided by this result, we conducted centimeter-scale experiments on thick elastomeric samples under generalized plane strain conditions and observed for the first time this elastic tensile instability. We found that equibiaxial stretching leads to the formation of a wavy pattern, as regions of the sample alternatively flatten and extend in the out-of-plane direction. Our work uncovers a new type of instability that can be triggered in elastic bodies, enlarging the design space for smart structures that harness instabilities to enhance their functionality. PMID:27610857
Coal Thickness Gauging Using Elastic Waves
NASA Technical Reports Server (NTRS)
Nazarian, Soheil; Bar-Cohen, Yoseph
1999-01-01
The efforts of a mining crew can be optimized, if the thickness of the coal layers to be excavated is known before excavation. Wave propagation techniques can be used to estimate the thickness of the layer based on the contrast in the wave velocity between coal and rock beyond it. Another advantage of repeated wave measurement is that the state of the stress within the mine can be estimated. The state of the stress can be used in many safety-related decisions made during the operation of the mine. Given these two advantages, a study was carried out to determine the feasibility of the methodology. The results are presented herein.
Poudjom Djomani, Y.H.; Nnange, J.M.; Ebinger, C.J.
1995-11-10
This report uses coherence function analysis of 32,000 gravity and topography points from Cameroon west Africa to determine the relationship between the plate tectonic and flexural rigidity of the lithosphere in terms of the crusts effective elastic thickness.
Furrow Topography and the Elastic Thickness of Ganymede's Dark Terrain Lithosphere
NASA Technical Reports Server (NTRS)
Pappalardo, Robert T.; Nimmo, Francis; Giese, Bernd; Bader, Christina E.; DeRemer, Lindsay C.; Prockter, Louise M.
2003-01-01
The effective elastic thickness of Ganymede's lithosphere tell of the satellite's thermal evolution through time. Generally it has been inferred that dark terrain, which is less tectonically deformed than grooved terrain, represents regions of cooler and thicker lithosphere [1]. The ancient dark terrain is cut by furrows, tectonic troughs about 5 to 20 km in width, which may have formed in response to large ancient impacts [1, 2]. We have applied the methods of [3] to estimate effective elastic thickness based on topographic profiles across tectonic furrows, extracted from a stereo-derived digital elevation model (DEM) of dark terrain in Galileo Regio [4]. Asymmetry in furrow topography and inferred flexure suggests asymmetric furrow fault geometry. We find effective elastic thicknesses 0.4 km, similar to analyzed areas alongside bright grooved terrain. Data and Analysis: A broken-plate elastic model.
Wang, Ji; Yang, Jiashi; Li, Jiangyu
2007-03-01
Energy trapping has important applications in the design of thickness-shear resonators. Considerable efforts have been made for the effective utilization and improvement of energy trapping with variations of plate configurations, such as adding electrodes and contouring. As a new approach in seeking improved energy trapping feature, we analyze thickness-shear vibrations in an elastic plate with functionally graded material (FGM) of in-plane variation of mechanical properties, such as elastic constants and density. A simple and general equation governing the thickness-shear modes is derived from a variational analysis. A plate with piecewise constant material properties is analyzed as an example. It is shown that such a plate can support thickness-shear vibration modes with obvious energy trapping. Bechmann's number for the existence of only one trapped mode also can be determined accordingly.
The elastic thickness of the lithosphere in the Pacific Ocean
NASA Astrophysics Data System (ADS)
Calmant, Stephane
1987-09-01
The effective elastic thickness T(e) of the oceanic lithosphere along the Hawaiian-Emperor, the Marquesas, the Pitcairn-Mururoa-Gloucester (PMG) chains, the Tuamotu archipelago, and the Samoa islands was determined by computing the deflection of a continuous elastic plate under the load of volcanoes and was constrained by the geoid heights over the oceans provided by Seasat. The prediction by Watts (1978) according to which the value of the T(e) should increase with the square root of crustal age of the lithosphere at the time of volcano emplacement was not confirmed; while the T(e) estimate of the Hawaiian-Emperor chain and an isolated estimate in the Samoan group agree with the empirical trend found by Watts, the Marquesas and the PMG chains, as well as the previously analyzed Cook-Austral and Society chains, present anomalously low values which increase only slightly with age.
Qiang, Bo; Greenleaf, James; Oyen, Michelle; Zhang, Xiaoming
2011-07-01
A two-step viscoelastic spherical indentation method is proposed to compensate for 1) material relaxation and 2) sample thickness. In the first step, the indenter is moved at a constant speed and the reaction force is measured. In the second step, the indenter is held at a constant position and the relaxation response of the material is measured. Then the relaxation response is fit with a multi-exponential function which corresponds to a three-branch general Maxwell model. The relaxation modulus is derived by correcting the finite ramp time introduced in the first step. The proposed model takes into account the sample thickness, which is important for applications in which the sample thickness is less than ten times the indenter radius. The model is validated numerically by finite element simulations. Experiments are carried out on a 10% gelatin phantom and a chicken breast sample with the proposed method. The results for both the gelatin phantom and the chicken breast sample agree with the results obtained from a surface wave method. Both the finite element simulations and experimental results show improved elasticity estimations by incorporating the sample thickness into the model. The measured shear elasticities of the 10% gelatin sample are 6.79 and 6.93 kPa by the proposed finite indentation method at sample thickness of 40 and 20 mm, respectively. The elasticity of the same sample is estimated to be 6.53 kPa by the surface wave method. For the chicken breast sample, the shear elasticity is measured to be 4.51 and 5.17 kPa by the proposed indentation method at sample thickness of 40 and 20 mm, respectively. Its elasticity is measured by the surface wave method to be 4.14 kPa.
Vibration of visco-elastic rectangular plate with linearly thickness variations in both directions
NASA Astrophysics Data System (ADS)
Gupta, A. K.; Khanna, A.
2007-04-01
The analysis presented here is to study the effect of linear thickness variations in both directions on vibration of visco-elastic rectangular plate having clamped boundary conditions on all the four edges. Using the separation of variables method, the governing differential equation has been solved for vibration of visco-elastic rectangular plate. An approximate but quite convenient frequency equation is derived by using Rayleigh-Ritz technique with a two-term deflection function. Logarithmic decrement, time period and deflection at different points for the first two modes of vibration are calculated for various values of taper constants and aspect ratio.
Estimates of the Elastic Thickness of Antarctica from GOCE Gravity Models
NASA Astrophysics Data System (ADS)
McKenzie, Dan; Yi, Weiyong; Rummel, Reiner
2015-03-01
The most recent GOCE models, such as DIR5 are sufficiently accurate at wavelengths as short as 200 km to provide estimates of the elastic thickness Te. The topographic load of Hawaii on the elastic Pacific plate was chosen as test case. It is a region, where independently of GOCE there exist good gravity and bathymetry/topography data. The derived elastic thickness is about 20 km. The same approach was applied to Antarctica, where GOCE is the only gravity data source of sufficient spatial resolution and accuracy. A certain weakness of any GOCE model results from the 6.7 degree data gap around the poles. Bedmap-2 is a new topographic data set with bedrock topography and ice thickness data. From the comparison of gravity and equivalent rock topography a Te of about 20 km resulted for East Antarctica, while the value for West Antarctica is only 6 km. This great difference results from the enormous difference in lithospheric thickness between Antarctica’s West and East.
Lithospheric structure of Africa: insights from its effective elastic thickness variations.
NASA Astrophysics Data System (ADS)
Pérez-Gussinyé, M.; Metois, M.; Fernández, M.; Vergés, J.; Fullea, J.
2009-04-01
Detailed images of lithospheric structure can help understand how surface deformation is related to Earth's deep structure. A proxy for lithospheric structure is its effective elastic thickness, Te, which mainly depends on its thermal state and composition. We present a new effective elastic thickness, Te, map of the African lithosphere estimated using the coherence function between topography and Bouguer anomaly. The Bouguer anomaly used in this study derives from the EGM 2008 model, which constitutes the highest resolution gravity database over Africa, allowing a significant improvement on lateral resolution in Te. Our map shows that Te is high > 100 km, in the West African, Congo, Kalahari and Tanzania cratons. Of these, the Kalahari presents the thinnest elastic thicknesses and, based on additional seismic and mineral physics studies, we suggest this may reflect modification of the lithosphere by anomalously hot mantle beneath the lithosphere. The effective elastic thickness is lowest beneath the Afar and Main Ethiopian rifts, where the maximum extension and thinnest lithosphere of Africa occur. The Tanzania craton appears as two rigid blocks separated by a relatively low Te area located southwest of lake Victoria. This coincides with the centre of seismic radial anisotropy beneath the craton, suggested to be the Victoria plume head by Weertrane et al. [2003]. Along the eastern branch of the East African rift Te is low and increases abruptly at 2 to 3 degrees South, coinciding with a deepening of earthquake depocenter and a change from narrow to wide rifting. These and other considerations suggest that the southern part of the eastern branch is underlain by thick, rigid cratonic lithosphere. Finally, the northern part of Africa is characterised by low Te on the Darfur, Tibesti, Hoggar and Cameroon line volcanic provinces, suggesting that the underlying lithospheric mantle has been thermally thinned. Corridors of low Te connect these volcanic provinces
Estimates of the Effective Elastic Thickness: Any signs of agreement?
NASA Astrophysics Data System (ADS)
McKenzie, Dan
2016-04-01
There is little controversy about the value of Te estimated from oceanic measurements of gravity and bathymetry. Its value is often obtained from the relationship between the free air gravity and bathymetry in the spectral domain. Estimates of Te from those few regions where there is good 2D bathymetric coverage give values which vary from 2-4 km for spreading ridges to ˜ 20 km for old lithosphere like that beneath Hawaii. There is a general belief that the elastic thickness is controlled by the depth of an isotherm whose value is ˜ 450°C, and that Te < T_s, the seismogenic thickness, which closely follows the 600°C isotherm. In contrast, there is no agreement between different estimates of Te from continents, most of which are based on Forsyth's method using the coherence between Bouguer gravity and topography. In regions of rough topography his approach gives estimates of Te that are similar to, though generally about double, those obtained from the free air gravity using the same approach as in the oceans. However, in regions with little topography, which includes most shields, the ratio between the two estimates often exceeds a factor of 5, with estimates of Te from Forsyth's method often exceeding 100 km, corresponding to a limiting isotherm of 1000°C or more. Laboratory experiments at such temperatures show that elastic stresses are relaxed in hours. This problem has generated a long running controversy. It is straightforward to show that estimates of Te from Bouguer gravity depend only on the ratio of the power spectra of free air gravity to topography when the two are incoherent (McK, 2015), and are independent of the actual value of T_e. In many shield regions the topography is indeed incoherent with the topography. No valid estimates of Te can then be obtained. However, it is nonetheless often possible to use the spectral ratio to estimate an upper bound on the value of T_e, which is generally < 30 km. Accurate maps of topography and gravity are now
Global model for the lithospheric strength and effective elastic thickness
NASA Astrophysics Data System (ADS)
Tesauro, Magdala; Kaban, Mikhail K.; Cloetingh, Sierd A. P. L.
2013-08-01
Global distribution of the strength and effective elastic thickness (Te) of the lithosphere are estimated using physical parameters from recent crustal and lithospheric models. For the Te estimation we apply a new approach, which provides a possibility to take into account variations of Young modulus (E) within the lithosphere. In view of the large uncertainties affecting strength estimates, we evaluate global strength and Te distributions for possible end-member 'hard' (HRM) and a 'soft' (SRM) rheology models of the continental crust. Temperature within the lithosphere has been estimated using a recent tomography model of Ritsema et al. (2011), which has much higher horizontal resolution than previous global models. Most of the strength is localized in the crust for the HRM and in the mantle for the SRM. These results contribute to the long debates on applicability of the "crème brulée" or "jelly-sandwich" model for the lithosphere structure. Changing from the SRM to HRM turns most of the continental areas from the totally decoupled mode to the fully coupled mode of the lithospheric layers. However, in the areas characterized by a high thermal regime and thick crust, the layers remain decoupled even for the HRM. At the same time, for the inner part of the cratons the lithospheric layers are coupled in both models. Therefore, rheological variations lead to large changes in the integrated strength and Te distribution in the regions characterized by intermediate thermal conditions. In these areas temperature uncertainties have a greater effect, since this parameter principally determines rheological behavior. Comparison of the Te estimates for both models with those determined from the flexural loading and spectral analysis shows that the 'hard' rheology is likely applicable for cratonic areas, whereas the 'soft' rheology is more representative for young orogens.
Elastic Thickness Estimates for Coronae Associated with Chasmata on Venus
NASA Technical Reports Server (NTRS)
Hoogenboom, T.; Martin, P.; Housean, G. A.
2005-01-01
Coronae are large-scale circular tectonic features surrounded by annular ridges. They are generally considered unique to Venus and may offer insights into the differences in lithospheric structure or mantle convective pattern between Venus and Earth. 68% of all coronae are associated with chasmata or fracture belts. The remaining 32% are located at volcanic rises or in the plains. Chasmata are linear to arcuate troughs, with trough parallel fractures and faults which extend for 1000 s of kilometers. Estimates of the elastic thickness of the lithosphere (T(sub e)) have been calculated in a number of gravity/topography studies of Venus and for coronae specifically. None of these studies, however, have explored the dependence of T(sub e) on the tectonic history of the region, as implied from the interpretation of relative timing relationships between coronae and surrounding features. We examine the relationship between the local T(sub e) and the relative ages of coronae and chasmata with the aim of further constraining the origin and evolution of coronae and chasmata systems.
Forced in-plane vibration of a thick ring on a unilateral elastic foundation
NASA Astrophysics Data System (ADS)
Wang, Chunjian; Ayalew, Beshah; Rhyne, Timothy; Cron, Steve; Dailliez, Benoit
2016-10-01
Most existing studies of a deformable ring on elastic foundation rely on the assumption of a linear foundation. These assumptions are insufficient in cases where the foundation may have a unilateral stiffness that vanishes in compression or tension such as in non-pneumatic tires and bushing bearings. This paper analyzes the in-plane dynamics of such a thick ring on a unilateral elastic foundation, specifically, on a two-parameter unilateral elastic foundation, where the stiffness of the foundation is treated as linear in the circumferential direction but unilateral (i.e. collapsible or tensionless) in the radial direction. The thick ring is modeled as an orthotropic and extensible circular Timoshenko beam. An arbitrarily distributed time-varying in-plane force is considered as the excitation. The Equations of Motion are explicitly derived and a solution method is proposed that uses an implicit Newmark scheme for the time domain solution and an iterative compensation approach to determine the unilateral zone of the foundation at each time step. The dynamic axle force transmission is also analyzed. Illustrative forced vibration responses obtained from the proposed model and solution method are compared with those obtained from a finite element model.
Elastic bending modulus of single-layer molybdenum disulfide (MoS2): finite thickness effect.
Jiang, Jin-Wu; Qi, Zenan; Park, Harold S; Rabczuk, Timon
2013-11-01
We derive, from an empirical interaction potential, an analytic formula for the elastic bending modulus of single-layer MoS2 (SLMoS2). By using this approach, we do not need to define or estimate a thickness value for SLMoS2, which is important due to the substantial controversy in defining this value for two-dimensional or ultrathin nanostructures such as graphene and nanotubes. The obtained elastic bending modulus of 9.61 eV in SLMoS2 is significantly higher than the bending modulus of 1.4 eV in graphene, and is found to be within the range of values that are obtained using thin shell theory with experimentally obtained values for the elastic constants of SLMoS2. This increase in bending modulus as compared to monolayer graphene is attributed, through our analytic expression, to the finite thickness of SLMoS2. Specifically, while each monolayer of S atoms contributes 1.75 eV to the bending modulus, which is similar to the 1.4 eV bending modulus of monolayer graphene, the additional pairwise and angular interactions between out of plane Mo and S atoms contribute 5.84 eV to the bending modulus of SLMoS2. PMID:24084656
Estimates of elastic plate thicknesses beneath large volcanos on Venus
NASA Technical Reports Server (NTRS)
Mcgovern, Patrick J.; Solomon, Sean C.
1992-01-01
Megellan radar imaging and topography data are now available for a number of volcanos on Venus greater than 100 km in radius. These data can be examined to reveal evidence of the flexural response of the lithosphere to the volcanic load. On Earth, flexure beneath large hotspot volcanos results in an annual topographic moat that is partially to completely filled in by sedimentation and mass wasting from the volcano's flanks. On Venus, erosion and sediment deposition are considered to be negligible at the resolution of Magellan images. Thus, it may be possible to observe evidence of flexure by the ponding of recent volcanic flows in the moat. We also might expect to find topographic signals from unfilled moats surrounding large volcanos on Venus, although these signals may be partially obscured by regional topography. Also, in the absence of sedimentation, tectonic evidence of deformation around large volcanos should be evident except where buried by very young flows. We use analytic solutions in axisymmetric geometry for deflections and stresses resulting from loading of a plate overlying an inviscid fluid. Solutions for a set of disk loads are superimposed to obtain a solution for a conical volcano. The deflection of the lithosphere produces an annular depression or moat, the extent of which can be estimated by measuring the distance from the volcano's edge to the first zero crossing or to the peak of the flexural arch. Magellan altimetry data records (ARCDRs) from data cycle 1 are processed using the GMT mapping and graphics software to produce topographic contour maps of the volcanos. We then take topographic profiles that cut across the annular and ponded flows seen on the radar images. By comparing the locations of these flows to the predicted moat locations from a range of models, we estimate the elastic plate thickness that best fits the observations, together with the uncertainty in that estimate.
Elastic thickness and heat flux estimates for the uranian satellite Ariel
NASA Astrophysics Data System (ADS)
Peterson, G.; Nimmo, F.; Schenk, P.
2015-04-01
The surface of Ariel, an icy satellite orbiting Uranus, shows extensional tectonic features suggesting an episode of endogenic heating in the satellite's past. Using topography derived from stereo-photoclinometry, we identified flexural uplift at a rift zone suggesting elastic thickness values in the range 3.8-4.4 km. We estimate the temperature at the base of the lithosphere to be in the range 99-146 K, depending on the strain rate assumed, with corresponding heat fluxes of 28-92 mW/m2. Neither tidal heating, assuming Ariel's current eccentricity, nor radiogenic heat production from the silicate core are enough to cause the inferred heat fluxes. None of three proposed ancient mean-motion resonances produce equilibrium tidal heating values in excess of 4.3 mW/m2. Thus, the origin of the inferred high heat fluxes is currently mysterious.
Definition and application of longitudinal stability derivatives for elastic airplanes
NASA Technical Reports Server (NTRS)
Kemp, W. B., Jr.
1972-01-01
A set of longitudinal stability derivatives for elastic airplanes is defined from fundamental principles allowing perturbations in forward speed. Application of these derivatives to longitudinal stability analysis by use of approximate expressions for static stability and control parameters as well as the dynamic equations of motion is illustrated. One commonly used alternative formulation for elastic airplanes is shown to yield significant inaccuracies because of inappropriate interpretation of inertial effects.
Topological derivatives for fundamental frequencies of elastic bodies
NASA Astrophysics Data System (ADS)
Kobelev, Vladimir
2016-01-01
In this article a new method for topological optimization of fundamental frequencies of elastic bodies, which could be considered as an improvement on the bubble method, is introduced. The method is based on generalized topological derivatives. For a body with different types of inclusion the vector genus is introduced. The dimension of the genus is the number of different elastic properties of the inclusions being introduced. The disturbances of stress and strain fields in an elastic matrix due to a newly inserted elastic inhomogeneity are given explicitly in terms of the stresses and strains in the initial body. The iterative positioning of inclusions is carried out by determination of the preferable position of the new inhomogeneity at the extreme points of the characteristic function. The characteristic function was derived using Eshelby's method. The expressions for optimal ratios of the semi-axes of the ellipse and angular orientation of newly inserted infinitesimally small inclusions of elliptical form are derived in closed analytical form.
Elastic thickness and heat flux estimates for the Uranian satellite Ariel
NASA Astrophysics Data System (ADS)
Peterson, G.; Nimmo, F.; Schenk, P.
2013-12-01
The exterior of Ariel, an icy satellite orbiting Uranus, shows tectonic features suggesting an episode of endogenic heating in the satellite's past [1]. Using topography derived from stereo images, we identified flexural uplift at two different rift zones. The elastic thickness is estimated using the wavelength of the deformation [2], yielding elastic thickness values of 2-4 km for the first region and 5-8 km for the second region. Using creep parameters for ice [3] and the approach of [4], we estimate the temperature at the base of the lithosphere to be in the range 110 to 140 K, depending on the strain rate assumed. The corresponding heat fluxes are 40-120 mW/m^2 and 20-50 mW/m^2, respectively. Neither tidal heating assuming Ariel's current eccentricity nor radiogenic heat production from the silicate core are enough to cause the inferred heat flux. Unstable resonant configurations of the Uranian satellites may have occurred in the past [5], including a 2:1 mean-motion resonance between Ariel and Umbriel. This resonance would have generated a higher eccentricity, possibly explaining the endogenic heat source. However, the maximum equilibrium heating rate in Ariel due to this resonance [1] is 2.9 GW (0.6 mW/m2), inadequate to cause the inferred heat flux. The origin of the inferred high heat fluxes is thus currently mysterious. [1] Peale 1999 [2] Turcotte and Schubert 2002 [3] Goldsby and Kohlstedt 2001 [4] Nimmo et al. 2002 [5] Dermott et al. 1988
Determination of the Elastic Thickness of the Crust using GOES and LIDAR images
NASA Astrophysics Data System (ADS)
Taghavi, Farahnaz; Ghalenoiee, Samira; Ebrahim-zadeh Ardestani, Vahid
2016-07-01
In this study, to identify the elastic thickness (Te) of the crust, the local variations of the coherence between Bouguer gravity and topography in the three area included Canadian Shield region, Appalachian region, and Basin and Range region are determined. We use a coherence method based on Windowed Fourier Transform (WFT) under the assumption of an isotropic lithosphere. Data sources are selected from GOES and LIDAR images for Bouguer gravity and topography, respectively. First, the coherence distribution is calculated and then, the characteristic wavelengths are obtained where the coherence is 0.5. Results show that values of the elastic thickness of the lithosphere are 110km in the Canadian Shield region, 49km in the Appalachian region and 3.5km in the Basin and Range region. The results are in good agreement with the existing values calculated from other spectral methods. Key words: Effective elastic thickness, Coherence method, Bouguer gravity anomaly, topography, satellite images.
NASA Astrophysics Data System (ADS)
Karami, Keyhan; Abedi, Majid; Zamani Nejad, Mohammad; Lotfian, Mohammad Hassan
2012-12-01
On the basis of plane elasticity theory (PET), the displacement and stress components in a thick-walled spherical pressure vessels made of heterogeneous materials subjected to internal and external pressure is developed. The mechanical properties except the Poisson's ratio are assumed to obey the parabolic variations throughout the thickness. Effect of material inhomogeneity on the elastic deformations and stresses is investigated. The analytical solutions and the solutions carried out through the FEM have a good agreement. The values used in this study are arbitrary chosen to demonstrate the effect of inhomogeneity on displacements, and stresses distributions.
Zhu, Jun; Chen, Weiqiu; Yang, Jiashi
2014-09-01
We study the propagation of thickness-twist (TT) waves in a crystal plate of AT-cut quartz with periodically varying, piecewise constant thickness. The scalar differential equation by Tiersten and Smythe is employed. The problem is found to be mathematically equivalent to the motion of an electron in a periodic potential field governed by Schrodinger's equation. An analytical solution is obtained. Numerical results show that the eigenvalue (frequency) spectrum of the waves has a band structure with allowed and forbidden bands. Therefore, for TT waves, plates with periodically varying thickness can be considered as phononic crystals. The effects of various parameters on the frequency spectrum are examined. PMID:24924785
Spatial variations of effective elastic thickness of the Lithosphere in the Southeast Asia regions
NASA Astrophysics Data System (ADS)
Shi, Xiaobin; Kirby, Jon; Yu, Chuanhai; Swain, Chris; Zhao, Junfeng
2016-04-01
The effective elastic thickness Te corresponds to the thickness of an idealized elastic beam that would bend similarly to the actual lithosphere under the same applied loads, and could provide important insight into rheology and state of stress. Thus, it is helpful to improve our understanding of the relationship between tectonic styles, distribution of earthquakes and lithospheric rheology in various tectonic settings. The Southeast Asia, located in the southeastern part of the Eurasian Plate, comprises a complex collage of continental fragments, volcanic arcs, and suture zones and marginal oceanic basins, and is surrounded by tectonically active margins which exhibit intense seismicity and volcanism. The Cenozoic southeastward extrusion of the rigid Indochina Block due to the Indo-Asian collision resulted in the drastic surface deformation in the western area. Therefore, a high resolution spatial variation map of Te might be a useful tool for the complex Southeast Asia area to examine the relationships between surface deformation, earthquakes, lithospheric structure and mantle dynamics. In this study, we present a high-resolution map of spatial variations of Te in the Southeast Asia area using the wavelet method, which convolves a range of scaled wavelets with the two data sets of Bouguer gravity anomaly and topography. The topography and bathymetry grid data was extracted from the GEBCO_08 Grid of GEBCO digital atlas. The pattern of Te variations agrees well with the tectonic provinces in the study area. On the whole, low lithosphere strength characterizes the oceanic basins, such as the South China Sea, the Banda sea area, the Celebes Sea, the Sulu Sea and the Andaman Sea. Unlike the oceanic basins, the continental fragments show a complex pattern of Te variations. The Khorat plateau and its adjacent area show strong lithosphere characteristics with a Te range of 20-50 km, suggesting that the Khorat plateau is the strong core of the Indochina Block. The West
Zamani Nejad, Mohammad; Jabbari, Mehdi; Ghannad, Mehdi
2014-01-01
Using disk form multilayers, a semi-analytical solution has been derived for determination of displacements and stresses in a rotating cylindrical shell with variable thickness under uniform pressure. The thick cylinder is divided into disk form layers form with their thickness corresponding to the thickness of the cylinder. Due to the existence of shear stress in the thick cylindrical shell with variable thickness, the equations governing disk layers are obtained based on first-order shear deformation theory (FSDT). These equations are in the form of a set of general differential equations. Given that the cylinder is divided into n disks, n sets of differential equations are obtained. The solution of this set of equations, applying the boundary conditions and continuity conditions between the layers, yields displacements and stresses. A numerical solution using finite element method (FEM) is also presented and good agreement was found.
Endothelium-derived nitric oxide regulates arterial elasticity in human arteries in vivo.
Kinlay, S; Creager, M A; Fukumoto, M; Hikita, H; Fang, J C; Selwyn, A P; Ganz, P
2001-11-01
Arterial elasticity is determined by structural characteristics of the artery wall and by vascular smooth muscle tone. The identity of endogenous vasoactive substances that regulate elasticity has not been defined in humans. We hypothesized that NO, a vasodilator released constitutively by the endothelium, augments arterial elasticity. Seven healthy young men were studied. A 20-MHz intravascular ultrasound catheter was introduced through an arterial sheath to measure brachial artery cross-sectional area, wall thickness, and intra-arterial pressure. After control was established, indices of elasticity (pressure-area relationship, instantaneous compliance, and stress-strain, pressure-incremental elastic modulus (E(inc)), and pressure-pulse wave velocity relationships) were examined over 0 to 100 mm Hg transmural pressure obtained by inflation of an external cuff. Thereafter, the basal production of endothelium-derived NO was inhibited by N(G)-monomethyl-L-arginine (L-NMMA) (4 and 8 mg/min). Finally, nitroglycerin (2.5 and 12.5 microgram/min), an exogenous donor of NO, was given to relax the vascular smooth muscle. Elasticity was measured under all of these conditions. L-NMMA (8 mg/min) decreased brachial artery area (P=0.016) and compliance (P<0.0001) and increased E(inc) (P<0.01) and pulse wave velocity (P<0.0001). Nitroglycerin (12.5 microgram/min) increased brachial artery area (P<0.001) and compliance (P<0.001) and decreased pulse wave velocity (P=0.02). NO, an endothelium-derived vasodilator, augments arterial elasticity in the human brachial artery. Loss of constitutively released NO associated with cardiovascular risk factors may adversely affect arterial elasticity in humans.
NASA Astrophysics Data System (ADS)
Ratheesh Kumar, R. T.; Windley, B. F.; Rajesh, V. J.; Santosh, M.
2013-12-01
We use the Bouguer coherence (Morlet isostatic response function) technique to compute the spatial variation of effective elastic thickness (Te) of the Andaman subduction zone. The recovered Te map resolves regional-scale features that correlate well with known surface structures of the subducting Indian plate and the overriding Burma plate. The major structure on the India plate, the Ninetyeast Ridge (NER), exhibits a weak mechanical strength, which is consistent with the expected signature of an oceanic ridge of hotspot origin. However, a markedly low strength (0 < Te < 3 km) in that region, where the NER is close to the Andaman trench (north of 10°N), receives our main attention in this study. The subduction geometry derived from the Bouguer gravity forward modeling suggests that the NER has indented beneath the Andaman arc. We infer that the bending stresses of the viscous plate, which were reinforced within the subducting oceanic plate as a result of the partial subduction of the NER buoyant load, have reduced the lithospheric strength. The correlation, Te < Ts (seismogenic thickness) reveals that the upper crust is actively deforming beneath the frontal arc Andaman region. The occurrence of normal-fault earthquakes in the frontal arc, low Te zone, is indicative of structural heterogeneities within the subducting plate. The fact that the NER along with its buoyant root is subducting under the Andaman region is inhibiting the subduction processes, as suggested by the changes in trench line, interrupted back-arc volcanism, variation in seismicity mechanism, slow subduction, etc. The low Te and thinned crustal structure of the Andaman back-arc basin are attributed to a thermomechanically weakened lithosphere. The present study reveals that the ongoing back-arc spreading and strike-slip motion along the West Andaman Fault coupled with the ridge subduction exerts an important control on the frequency and magnitude of seismicity in the Andaman region.
Dutta, Parikshit; Urban, Matthew W.; Le Maître, Olivier P.; Greenleaf, James F.; Aquino, Wilkins
2015-01-01
The elastic and geometric properties of arteries have been long recognized as important predictors of cardiovascular disease. This work presents a robust technique for the noninvasive characterization of anisotropic elastic properties as well as thickness and diameter in arterial vessels. In our approach, guided waves are excited along arteries using the radiation force of ultrasound. Group velocity is used as the quantity of interest to reconstruct elastic and geometric features of the vessels. One of the main contributions of this work is a systematic approach based on sparse-grid collocation interpolation to construct surrogate models of arteries. These surrogate models are in turn used with direct-search optimization techniques to produce fast and accurate estimates of elastic properties, diameter, and thickness. One of the attractive features of the proposed approach is that once a surrogate model is built, it can be used for near real-time identification across many different types of arteries. We demonstrate the feasibility of the method using simulated and in vitro laboratory experiments on a silicon rubber tube and a porcine carotid artery. Our results show that using our proposed method, we can reliably identify the longitudinal modulus, thickness, and diameter of arteries. The circumferential modulus was found to have little influence in the group velocity, which renders the former quantity unidentifiable using the current experimental setting. Future work will consider the measurement of circumferential waves with the objective of improving the identifiability of the circumferential modulus. PMID:26109582
Fisher, K A
2007-01-26
In this letter, a low frequency ultrasonic resonance technique that operates in the (20 - 80 kHz) regime is presented that demonstrates detection of thickness changes on the order of +/- 10{micro}m. This measurement capability is a result of the direct correlation between the electrical impedance of an electro-acoustic transducer and the mechanical loading it experiences when placed in contact with a layered elastic structure. The relative frequency shifts of the resonances peaks can be estimated through a simple one-dimensional transmission model. Separate experimental measurements confirm this technique to be sensitive to subtle changes in the underlying layered elastic structure.
Temperature- and thickness-dependent elastic moduli of polymer thin films
2011-01-01
The mechanical properties of polymer ultrathin films are usually different from those of their counterparts in bulk. Understanding the effect of thickness on the mechanical properties of these films is crucial for their applications. However, it is a great challenge to measure their elastic modulus experimentally with in situ heating. In this study, a thermodynamic model for temperature- (T) and thickness (h)-dependent elastic moduli of polymer thin films Ef(T,h) is developed with verification by the reported experimental data on polystyrene (PS) thin films. For the PS thin films on a passivated substrate, Ef(T,h) decreases with the decreasing film thickness, when h is less than 60 nm at ambient temperature. However, the onset thickness (h*), at which thickness Ef(T,h) deviates from the bulk value, can be modulated by T. h* becomes larger at higher T because of the depression of the quenching depth, which determines the thickness of the surface layer δ. PMID:21711747
Implications of Large Elastic Thicknesses for the Composition and Current Thermal State of Mars
NASA Astrophysics Data System (ADS)
Grott, M.; Breuer, D.
2008-12-01
The elastic lithosphere thickness at the Martian north polar cap has recently been constrained using radar sounding data obtained by SHARAD, the shallow radar onboard the Mars Reconnaissance Orbiter. Analysis of the SHARAD radargrams showed that the amount of deflection caused by ice loading at the polar caps is negligible - less than 100 m. Quantitative analysis yielded a lower bound on the elastic lithosphere thickness Te of 300 km, a value twice as large as previous estimates from theoretical considerations and flexure studies. Such large elastic thicknesses are only compatible with the planet's thermal evolution if the planetary interior is relatively cold and this could have direct bearing on the admissible amount of radioactive elements in the Martian interior. On the other hand, if the concentration of heat producing elements in the Martian interior is indeed reduced, the resulting low interior temperatures could possibly inhibit partial mantle melting and magmatism. However, geological evidence suggests that Mars has been volcanically active in the recent past. We have investigated the Martian thermal evolution and identified models which are consistent with a present day elastic thickness in excess of 300 km. We find that a wet mantle rheology is best compatible with the observed elastic thicknesses, but in this case the bulk concentration of heat producing elements in the silicate fraction cannot exceed 50 % of the chondritic concentration if 50 % of the radioacitve elements are concentrated in the crust. Furthermore, due to the efficient cooling of the planet for a wet mantle rheology, recent volcanism can only be explained by hydrous mantle melting. This requires the mantle water content to exceed 1500 ppm and although this is within the range reported for the shergottite parent magmas, it is certainly on the boundary of the plausible parameter range. If a dry mantle rheology is assumed, bulk Mars does not need to be sub-chondritic, but at least 70 % of
Elastic Properties of 4-6 nm-thick Glassy Carbon Thin Films
NASA Astrophysics Data System (ADS)
Manoharan, M. P.; Lee, H.; Rajagopalan, R.; Foley, H. C.; Haque, M. A.
2010-01-01
Glassy carbon is a disordered, nanoporous form of carbon with superior thermal and chemical stability in extreme environments. Freestanding glassy carbon specimens with 4-6 nm thickness and 0.5 nm average pore size were synthesized and fabricated from polyfurfuryl alcohol precursors. Elastic properties of the specimens were measured in situ inside a scanning electron microscope using a custom-built micro-electro-mechanical system. The Young’s modulus, fracture stress and strain values were measured to be about 62 GPa, 870 MPa and 1.3%, respectively; showing strong size effects compared to a modulus value of 30 GPa at the bulk scale. This size effect is explained on the basis of the increased significance of surface elastic properties at the nanometer length-scale.
Yildirim, Ali; Kosger, Pelin; Ozdemir, Gokmen; Sahin, Fezan Mutlu; Ucar, Birsen; Kilic, Zubeyir
2015-09-01
A significant correlation between hypertension history and high blood pressure has been observed with regard to age, race and gender. Investigating carotid intima-media thickness and aortic stiffness prior to the development of hypertension in children of hypertensive parents enabled us to evaluate these patients for subclinical atherosclerosis. We compared carotid intima-media thickness, aortic strain, distensibility, stiffness indices and elastic modulus in 67 normotensive children whose parents had a diagnosis of essential hypertension and 39 normotensive children with no parental history of hypertension. Although there were no significant differences between the two groups in terms of systolic blood pressure, diastolic blood pressure, average blood pressure and pulse pressure (P>0.05), systolic blood pressures were higher among patients 15 years and older in the study group. No significant differences were noted between the control and study groups regarding interventricular septal thickness, left-ventricular posterior wall thickness, left-ventricular systolic and diastolic diameter and aortic annulus diameter (P>0.05). The left atrium diameter was larger in the study group compared with that in the control group, mainly because of the values of the 15-year-old and older children (P=0.01). The mean, maximum and minimum values of carotid intima-media thickness were significantly different in the study group compared with the control group among all age groups (P<0.001, P<0.001, P=0.006, respectively). Aortic systolic and diastolic diameters were larger in normotensive children of hypertensive parents compared with the control group (P=0.014, P=0.001, respectively). Although there were no differences between the study and control groups regarding aortic strain, aortic distensibility, elastic modulus and stiffness indices (P>0.05), aortic distensibility was lower, and aortic stiffness indices were higher among children 15 years and older in the study group. An
The elasticity problem for a thick-walled cylinder containing a circumferential crack
NASA Technical Reports Server (NTRS)
Nied, H. F.; Erdogan, F.
1982-01-01
The elasticity problem for a long hollow circular cylinder containing an axisymmetric circumferential crack subjected to general nonaxisymmetric external loads is considered. The problem is formulated in terms of a system of singular integral equations with the Fourier coefficients of the derivative of the crack surface displacement as density functions. The stress intensity factors and the crack opening displacement are calculated for a cylinder under uniform tension, bending by end couples, and self-equilibrating residual stresses.
Lithospheric strength and its relationship to the elastic and seismogenic layer thickness
NASA Astrophysics Data System (ADS)
Watts, A. B.; Burov, E. B.
2003-08-01
Plate flexure is a phenomenon that describes how the lithosphere responds to long-term (>105 yr) geological loads. By comparing the flexure in the vicinity of ice, volcano, and sediment loads to predictions based on simple plate models it has been possible to estimate the effective elastic thickness of the lithosphere, Te. In the oceans, Te is the range 2-50 km and is determined mainly by plate and load age. The continents, in contrast, are characterised by Te values of up to 80 km and greater. Rheological considerations based on data from experimental rock mechanics suggest that Te reflects the integrated brittle, elastic and ductile strength of the lithosphere. Te differs, therefore, from the seismogenic layer thickness, Ts, which is indicative of the depth to which anelastic deformation occurs as unstable frictional sliding. Despite differences in their time scales, Te and Ts are similar in the oceans where loading reduces the initial mechanical thickness to values that generally coincide with the thickness of the brittle layer. They differ, however, in continents, which, unlike oceans, are characterised by a multi-layer rheology. As a result, Te≫Ts in cratons, many convergent zones, and some rifts. Most rifts, however, are characterised by a low Te that has been variously attributed to a young thermal age of the rifted lithosphere, thinning and heating at the time of rifting, and yielding due to post-rift sediment loading. Irrespective of their origin, the Wilson cycle makes it possible for low values to be inherited by foreland basins which, in turn, helps explain why similarities between Te and Ts extend beyond rifts into other tectonic regions such as orogenic belts and, occasionally, the cratons themselves.
Elastic thickness control of lateral dyke intrusion at mid-ocean ridges
NASA Astrophysics Data System (ADS)
Grandin, Raphaël; Socquet, Anne; Doubre, Cécile; Jacques, Eric; King, Geoffrey C. P.
2012-02-01
Magmatic accretion at slow-spreading mid-ocean ridges exhibits specific features. Although magma supply is focused at the centre of second-order segments, melts are episodically distributed along the rift toward segment ends by lateral dyke intrusions. It has been previously suggested that an along-axis downward topographic slope away from the magma source is sufficient to explain lateral dyke propagation. However, this cannot account for the poor correlation between dyke opening and surface elevation in the 2005-2010 series of 14 dyke intrusions of Afar (Ethiopia). Using mechanical arguments, constrained by both geodetic and seismological observations, we propose that the large dykes that initiate near the mid-segment magma source are attracted toward segment ends as a result of a thickening of the elastic-brittle lithosphere in the along-rift direction. This attraction arises from the difference of elastic resistance between the segment centre where the lithosphere is thermally weakened by long-term focusing of melts, and comparatively "colder", hence stronger segment ends. The axial topographic gradient in magmatic rifts may be more likely explained as an incidental consequence of these variations of along-axis elastic-brittle thickness, rather than the primary cause of lateral dyke injections.
N13+p elastic resonance scattering via a thick-target method
NASA Astrophysics Data System (ADS)
Wang, Y. B.; Wang, B. X.; Qin, X.; Bai, X. X.; Guo, B.; Jiang, C.; Li, Y. J.; Li, Z. H.; Lian, G.; Su, J.; Zeng, S.; Liu, W. P.
2008-04-01
The N13+p elastic resonance scattering has been studied in inverse kinematics via a thick-target method. A N13 secondary beam of 47.8±1.5 MeV produced by the H2(C12,N13)n reaction was used to bombard a 9.33 mg/cm2 (CH2)n target. The recoil protons were detected by a ΔE-E silicon counter telescope at θlab=15°. The performance of the setup was checked by C12+p elastic resonance scattering with the same (CH2)n target. The excitation function for the N13(p,p) elastic scattering was obtained in the energy interval of Ec.m.~0.5-3.2 MeV and was analyzed by using a multilevel R-matrix code MULTI7. Several low-lying excited states in O14 were surveyed. Our results confirm a very recent 2- assignment to the 6.8 MeV level and agree with the observation of a new 0- level at 5.7 MeV with a width of 400(45) keV.
NASA Technical Reports Server (NTRS)
Moresi, Louis
1993-01-01
Both the Earth and Venus have a convecting mantle at the top of which is a relatively strong, mechanical boundary layer. The surface topography and gravity signals which result from the convection within the viscous mantle are modified by the elastic properties of this lithospheric boundary layer. In particular the ability of the lithosphere to support loads and transmit stresses from below is a function of the wavelength of the load--the lithosphere is strong to loading at shorter wavelengths. As a consequence it is usual to expect that long wavelength topography cannot be supported by the mechanical strength of the lithosphere and must be compensated--isostatically or dynamically--within the uppermost mantle or the crust. The flexural rigidity of the lithosphere can therefore be determined by estimating the greatest wavelength at which uncompensated surface topography can be supported, usually by measuring the admittance as a function of wavelength. In fact this procedure for determining the elastic thickness relies upon being able to distinguish topography with underlying support from that supported by the brittle lithosphere on the basis of their each having a characteristic value of the admittance. However, in the presence of lateral viscosity variations in the mantle, it is possible for topography to be generated which is NOT compensated by density anomalies in the underlying mantle at the same wavelength. Although this effect is not likely to be important for the Earth, on Venus, where the high surface temperatures would be expected to give a weaker lithosphere, lateral viscosity variations in the mantle can give a misleadingly large apparent elastic thickness for the lithosphere.
The long-wavelength admittance and effective elastic thickness of the Canadian Shield
NASA Astrophysics Data System (ADS)
Kirby, J. F.; Swain, C. J.
2014-06-01
The strength of the cratonic lithosphere has been controversial. On the one hand, many estimates of effective elastic thickness (Te) greatly exceed the crustal thickness, but on the other the great majority of cratonic earthquakes occur in the upper crust. This implies that the seismogenic thickness of cratons is much smaller than Te, whereas in the ocean basins they are approximately the same, leading to suspicions about the large Te estimates. One region where such estimates have been questioned is the Canadian Shield, where glacial isostatic adjustment (GIA) and mantle convection are thought to contribute to the long-wavelength undulations of the topography and gravity. To date these have not been included in models used to estimate Te from topography and gravity which conventionally are based only on loading and flexure. Here we devise a theoretical expression for the free-air (gravity/topography) admittance that includes the effects of GIA and convection as well as flexure and use it to estimate Te over the Canadian Shield. We use wavelet transforms for estimating the observed admittances, after showing that multitaper estimates, which have hitherto been popular for Te studies, have poor resolution at the long wavelengths where GIA and convection predominate, compared to wavelets. Our results suggest that Te over most of the shield exceeds 80 km, with a higher-Te core near the southwest shore of Hudson Bay. This means that the lack of mantle earthquakes in this craton is simply due to its high strength compared to the applied stresses.
NASA Astrophysics Data System (ADS)
Li, Li; Wei, P. J.
2015-03-01
The propagation behaviour of Love wave in an initially stressed functionally graded magnetic-electric-elastic half-space carrying a homogeneous layer is investigated. The material parameters in the substrate are assumed to vary exponentially along the thickness direction only. The velocity equations of Love wave are derived on the electrically or magnetically open circuit and short circuit boundary conditions, based on the equations of motion of the graded magnetic-electric-elastic mate- rial with the initial stresses and the free traction boundary conditions of surface and the continuous boundary conditions of interface. The dispersive curves are obtained numerically and the influences of the initial stresses and the material gradient index on the dispersive curves are dis- cussed. The investigation provides a basis for the development of new functionally graded magneto-electro-elastic surface wave devices.
Effect of curvature and thickness on elastic wave velocity in cornea-like structures by FEM and OCE
NASA Astrophysics Data System (ADS)
Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Vantipalli, Srilatha; Aglyamov, Salavat R.; Wu, Chen; Liu, Chih-hao; Twa, Michael D.; Larin, Kirill V.
2016-03-01
Wave models, which have been utilized in the past to reconstruct corneal biomechanical properties based on the propagation of an elastic wave, were often developed assuming a thin-plate geometry. However, the curvature and thickness of the cornea are not considered when utilizing these models. In this work, optical coherence elastography (OCE) experiments were conducted on tissue-mimicking agar phantoms and contact lenses along with finite element (FE) modeling of four kinds of cornea-like structures to understand the effects of curvature and thickness on the group velocity of an elastic wave. As the radius of curvature increased from 19.1 to 47.7 mm, the group velocity of the elastic wave obtained by both FE and OCE from a spherical shell section model decreased from ~2.8 m/s to ~2.2 m/s. When the thickness of the agar phantom increased from 1.9 mm to 5.6 mm, the elastic wave velocity increased from ~3.0 m/s to ~4.1 m/s. Both the FE and OCE results show that the group velocity of the elastic wave decreased with radius of curvature but increased with thickness. Therefore, the curvature and thickness must be considered when developing accurate wave models for quantifying biomechanical properties of the cornea.
Three-dimensional admittance analysis of lithospheric elastic thickness over the Louisville Ridge
NASA Astrophysics Data System (ADS)
Hu, Minzhang; Li, Hui; Shen, Chongyang; Xing, Lelin; Hao, Hongtao
2016-04-01
Using bathymetry and altimetric gravity anomalies, a 1° × 1° lithospheric effective elastic thickness ( T e) model over the Louisville Ridge and its adjacent regions is calculated using the moving window admittance technique. For comparison, three bathymetry models are used: general bathymetric charts of the oceans, SIO V15.1, and BAT_VGG. The results show that BAT_VGG is more suitable for calculating T e than the other two models. T e along the Louisville Ridge was re-evaluated. The southeast of the ridge has a medium T e of 10-20 km, while T e increases dramatically seaward of the Tonga-Kermadec trench as a result of the collision of the Pacific and Indo-Australian plates.
On the Opening of Thick Walled Elastic Tubes: A Fluid-Structure Model for Acid Reflux
NASA Astrophysics Data System (ADS)
Ghosh, Sudip; Kahrilas, Peter
2005-11-01
A coupled fluid-structure mathematical model was developed to quantify rapid opening of thick-walled elastic tubes, a phenomenon underlying biological flows such as gastroesophageal reflux disease (GERD). The wall was modeled using non-linear finite deformation theory to predict space-time radial distention of an axisymmetric tube with luminal fluid flow. Anisotropic azimuthal and longitudinal muscle-induced stresses were incorporated, and interstitial material properties were assumed isotropic and linearly elastic. Fluid flow was modeled using lubrication theory with inertial correction. Opening and flow were driven by a specified inflow pressure and zero pressure gradient was specified at outflow. No-slip and surface force balance were applied at the fluid-wall interface. Viscoelasticity was modeled with ad hoc damping and the evolution of the tube geometry was predicted at mid-layer. A potentially important discovery was made when applied to studies of initiation of opening with GERD: while material stiffness is of minor consequence, small changes in resting lumen distension (˜2 mm diameter) may be a sensitive distinguishing feature of the disease.
NASA Astrophysics Data System (ADS)
Daly, E.; Brown, C.; Stark, C. P.; Ebinger, C. J.
2004-11-01
There have been some inconsistencies in estimates of the effective elastic thickness of the continental lithosphere Te based upon admittance or coherence relationships between gravity and topography. This paper compares multitaper and wavelet methods to analyse the coherence between Bouguer gravity and bathymetric data over the Irish Atlantic margin. The analyses show that similar lateral Te variations can be recovered from the data, but demonstrate that the size of the data window can give rise to a significant downward bias in Te estimates. A seismically constrained 3-D gravity inversion over the Rockall basin shows the presence of surface and subsurface loads whose ratio is loosely correlated with load ratio variations generated from the wavelet coherence method. The Te and load ratio, f variations can be plausibly related to major geological structures on the margin. If the load ratio variations can be interpreted geologically, it implies that spectral based methods to estimate effective elastic thickness must incorporate subsurface loads within the underlying theoretical model. On the Irish Atlantic margin, Te is generally low (6-18 km) and is associated with a NE-SW Caledonian trend. The weakest lithosphere is in the southern Rockall basin, Porcupine bank and Porcupine basin and the strongest lithosphere is along the Rockall-Hatton region. The low Te values are consistent with results from other passive margins. The reasons for such low Te values on the Irish Atlantic margin remain unclear, but may be the consequence of Te being frozen into the lithosphere when loads were emplaced during continental breakup and temperature gradients were high. The process of sedimentation and the presence of fluids may be contributory factors. There is an indication of a geological and rheological divide between the Rockall-Hatton region and the Rockall basin, possibly associated with the Caledonian orogenic front.
Elastic thickness of the lithosphere and tectonic evolution: implications for GIA models
NASA Astrophysics Data System (ADS)
Amantov, Aleksey; Fjeldskaar, Willy
2015-04-01
Rheological properties used in GIA models require independent verifications and possible modifications. To estimate the flexural rigidity of the lithosphere in simple platform areas we use peneplain distortion, which enable us to compute isostatic response from sediment load and compare the results with observed changes in geometry. This was done for several different platform regions: - Baltic (Fennoscandian) Shield, including structural elements of the Russian Platform - Barents Sea platform areas - Kara and Western Siberian domain - Eastern Siberian Platform In the East European and East Siberian old cratons we modeled isostatic distortion of Neoproterozoic Ediacaran peneplain and some other relevant surfaces. For the Arctic we used Mid-Late Jurassic surface (JP) as a distinct unconformity and well-traced (by seismic and well data) surface in the Arctic region. The isostatic distortion of peneplains under sediment load / erosion for the old Archean - Proterozoic cratons in general confirms earlier rheology model with the flexural rigidity of the lithosphere around 5x10**23 Nm (effective elastic thickness of 30-40 km), but could be slightly lower in the Barents basins. Deviations are generally relatively small and could be explained by e.g. by averaging over fault-zones, tectonic events, compaction structures and density variations. However, the situation for the Kara-Western Siberian domain is very different, with large deviations between observations and calculations. With a slight reduction of the effective elastic thickness in the Kara Sea to 10-20 km the fit is much better. Based on the results we suggest two different major types of lithosphere rigidity in the area. This seems reasonable because they typify domains with different crustal age. Western Siberian platform, with Kara continuation has much younger basement, in addition to significant magmatic activity and Early Mesosoic extension. The lithosphere rigidity is a function of age and temperature; as
NASA Astrophysics Data System (ADS)
Kalnins, L. M.; Watts, A. B.
2010-05-01
We have developed a moving window admittance technique to determine the relationship between free-air gravity anomaly and bathymetry as a function of wavelength over the world's ocean basins and their margins. Preliminary results from the western Pacific Ocean show that the technique resolves the effective elastic thickness of the oceanic lithosphere, Te, to better than ±5 km for Te < 30 km over horizontal distances of a few tens of km. In this paper, we investigate the robustness of our results using different tapering schemes (e.g. single versus multitaper) and synthetic tests that illustrate our ability to recover Te in the region of long wavelength features such as trench outer rises, mid-plate swells and mid-ocean ridges. By investigating observed admittances in the Pacific, Indian, and Atlantic Oceans, we have found that there is a 'critical wavelength' that separates the relatively short wavelength contributions of lithospheric flexure to the gravity field from longer wavelength effects such as those associated with mantle dynamics. We examine here this 'critical wavelength' and its implications for swell compensation depths, plate cooling models, and mantle convection.
Measurement of relevant elastic and damping material properties in sandwich thick plates
NASA Astrophysics Data System (ADS)
Rébillat, Marc; Boutillon, Xavier
2011-12-01
An easy-to-implement method to measure relevant elastic and damping properties of the constituents of a sandwich structure, possibly with a heterogeneous core, is proposed. The method makes use of a one-point dynamical measurement on a thick-plate. The hysteretic model for each (possibly orthotropic) constituent is written generically as " E(1+jη)" for all mechanical parameters. The estimation method of the parameters relies on a mixed experimental/numerical procedure. The frequencies and dampings of the natural modes of the plate are obtained from experimental impulse responses by means of a high-resolution modal analysis technique. This allows for considerably more experimental data to be used. Numerical modes (frequencies, dampings, and modal shapes) are computed by means of an extended Rayleigh-Ritz procedure under the "light damping" hypothesis, for given values of the mechanical parameters. Minimising the differences between the modal characteristics yields an estimation of the values of the mechanical parameters describing the hysteretic behaviour. A sensitivity analysis assesses the reliability of the method for each parameter. Validations of the method are proposed by (a) applying it to virtual plates on which a finite-element model replaces the experimental modal analysis, (b) some comparisons with results obtained by static mechanical measurements, and (c) by comparing the results on different plates made of the same sandwich material.
Variations of the lithospheric strength and elastic thickness in North America
NASA Astrophysics Data System (ADS)
Tesauro, Magdala; Kaban, Mikhail K.; Mooney, Walter D.
2015-07-01
We evaluate the effect of temperature variations on strength and effective elastic thickness (Te) of the lithosphere of the North American (NA) continent. To this purpose, we use two thermal models that are corrected for compositional variations and anelasticity effects in the upper mantle. These thermal models are obtained from a joint inversion of gravity data and two recent seismic tomography models (NA07 and SL2013sv). The crustal rheology was defined using NACr14, the most recent NA crustal model. This model specifies seismic velocities and thickness for a three-layer model of the crystalline crust. Strength in the lithosphere and in the crust has similar distributions, indicating that local geotherms play a dominant role in determining strength rather than crustal composition. A pronounced contrast is present in strength between cratonic and off-cratonic regions. Lithospheric strength in the off-cratonic regions is prevalently localized within the crust and Te shows low values (<20 km), while the inner part of the cratons is characterized by a strong lithosphere with large Te (>150 km). In contrast to previous results, our models indicate that Phanerozoic regions located close to the edge of the cratons, as the Appalachians, are characterized by low strength. We also find that locally weak zones exist within the cratons (e.g., beneath the intracratonic Illinois Basin and Midcontinent rift). Seismic tomography models NA07 and SL2013sv differ mainly in some peripheral parts of the cratons, as the Proterozoic Canadian Platform, the Grenville, and the western part of the Yavapai-Mazatzal province, where the integrated strength for the model NA07 is 10 times larger than in model SL2013sv due to a temperature difference (>200°C) in the uppermost mantle. The differences in Te between the two models are less pronounced. In both models, Proterozoic regions reactivated by Meso-Cenozoic tectonics (e.g., Rocky Mountains and the Mississippi Embayment) are characterized
Indentation-derived elastic modulus of multilayer thin films: Effect of unloading induced plasticity
Jamison, Ryan Dale; Shen, Yu -Lin
2015-08-13
Nanoindentation is useful for evaluating the mechanical properties, such as elastic modulus, of multilayer thin film materials. A fundamental assumption in the derivation of the elastic modulus from nanoindentation is that the unloading process is purely elastic. In this work, the validity of elastic assumption as it applies to multilayer thin films is studied using the finite element method. The elastic modulus and hardness from the model system are compared to experimental results to show validity of the model. Plastic strain is shown to increase in the multilayer system during the unloading process. Additionally, the indentation-derived modulus of a monolayer material shows no dependence on unloading plasticity while the modulus of the multilayer system is dependent on unloading-induced plasticity. Lastly, the cyclic behavior of the multilayer thin film is studied in relation to the influence of unloading-induced plasticity. Furthermore, it is found that several cycles are required to minimize unloading-induced plasticity.
Linear elastic properties derivation from microstructures representative of transport parameters.
Hoang, Minh Tan; Bonnet, Guy; Tuan Luu, Hoang; Perrot, Camille
2014-06-01
It is shown that three-dimensional periodic unit cells (3D PUC) representative of transport parameters involved in the description of long wavelength acoustic wave propagation and dissipation through real foam samples may also be used as a standpoint to estimate their macroscopic linear elastic properties. Application of the model yields quantitative agreement between numerical homogenization results, available literature data, and experiments. Key contributions of this work include recognizing the importance of membranes and properties of the base material for the physics of elasticity. The results of this paper demonstrate that a 3D PUC may be used to understand and predict not only the sound absorbing properties of porous materials but also their transmission loss, which is critical for sound insulation problems. PMID:24907783
Out-of-Plane Bending of Beam-Wall Joints Based on Elastic Medium Thick Plate Theory
NASA Astrophysics Data System (ADS)
Zhifei, Shi; Shuling, Yang
2011-01-01
The out-of-plane response of beam-wall joints is studied in the present paper. The governing equations of shear walls obtained by using the orthotropic elastic medium thick plate theory are solved. Additionally, different reinforcing ratios for shear walls in different directions are considered. It is also found that reinforced shear walls can be simplified as isotropic walls no matter whether the reinforcing ratio in both directions is the same or not for most engineering structures. In view of this, the out-of-plane response of beam-wall joints is investigated based on the isotropic medium thick plate theory and the effects of geometrical parameters of the joints on the responses of the shear walls are discussed in detail. For further simplification, the equivalent frame model is introduced and a very simple formula to determine the equivalent width is suggested for practical applications.
NASA Astrophysics Data System (ADS)
Vestyak, V. A.; Tarlakovskii, D. V.
2015-11-01
This paper considers a homogeneous isotropic elastic body bounded by concentric spheres and acted upon by axisymmetric unsteady volume forces. Displacement fields are determined using series expansions in Legendre and Gegenbauer polynomials, Laplace transforms in time, and integral representations with kernels in the form of Green's functions. Explicit formulas for the Green's functions are constructed that allow accurate determination of the originals. Examples of the calculations are presented.
NASA Astrophysics Data System (ADS)
Pérez-Gussinyé, M.; Metois, M.; Fernández, M.; Vergés, J.; Fullea, J.; Lowry, A. R.
2009-09-01
Detailed information on lateral variations in lithospheric properties can aid in understanding how surface deformation relates to deep Earth processes. The effective elastic thickness, Te, of the lithosphere is a proxy for lithospheric strength. Here, we present a new Te map of the African lithosphere estimated from coherence analysis of topography and Bouguer anomaly data. The latter data set derives from the EGM 2008 model, the highest resolution gravity database over Africa, enabling a significant improvement in lateral resolution of Te. The methodology used for Te estimation improves upon earlier approaches by optimally combining estimates from several different window sizes and correcting for an estimation bias term. Our analysis finds that Te is high, ~ 100 km, in the West African, Congo, Kalahari and Tanzania cratons. Of these, the Kalahari exhibits the lowest Te. Based in part on published seismic and mineral physics constraints, we suggest this may reflect modification of Kalahari lithosphere by anomalously hot asthenospheric mantle. Similarly, the Tanzania craton exhibits relatively lower Te east of Lake Victoria, where a centre of seismic radial anisotropy beneath the craton has been located and identified with a plume head, thus suggesting that here too, low Te reflects modification of cratonic lithosphere by an underlying hot mantle. The lowest Te in Africa occurs in the Afar and Main Ethiopian rifts, where lithospheric extension is maximum. In the western Ethiopian plateau a local Te minimum coincides with published images of a low P and S seismic velocity anomaly extending to ~ 400 km depth. Finally, the Darfur, Tibesti, Hoggar and Cameroon line volcanic provinces are characterised by low Te and no deep-seated seismic anomalies in the mantle. Corridors of relatively low Te connect these volcanic provinces to the local Te minima within the western Ethiopian plateau. We interpret the low Te to indicate thinner lithosphere within the corridors than in
NASA Astrophysics Data System (ADS)
Perez-Gussinye, M.; Metois, M.; Fernandez, M.; Verges, J.; Fullea, J.; Lowry, A. R.
2009-12-01
Detailed information on lateral variations in lithospheric properties can aid in understanding how surface deformation relates to deep Earth processes. The effective elastic thickness, Te, of the lithosphere is a proxy for lithospheric strength. Here, we present a new Te map of the African lithosphere estimated from coherence analysis of topography and Bouguer anomaly data. The latter data set derives from the EGM 2008 model, the highest resolution gravity database over Africa, enabling a significant improvement in lateral resolution of Te. The methodology used for Te estimation improves upon earlier approaches by optimally combining estimates from several different window sizes and correcting for an estimation bias term. Our analysis finds that Te is high, ~ 100 km, in the West African, Congo, Kalahari and Tanzania cratons. Of these, the Kalahari exhibits the lowest Te. Based in part on published seismic and mineral physics constraints, we suggest this may reflect modification of Kalahari lithosphere by anomalously hot asthenospheric mantle. Similarly, the Tanzania craton exhibits relatively lower Te east of Lake Victoria, where a centre of seismic radial anisotropy beneath the craton has been located and identified with a plume head, thus suggesting that here too, low Te reflects modification of cratonic lithosphere by an underlying hot mantle. The lowest Te in Africa occurs in the Afar and Main Ethiopian rifts, where lithospheric extension is maximum. In the western Ethiopian plateau a local Te minimum coincides with published images of a low P and S seismic velocity anomaly extending to ~400 km depth. Finally, the Darfur, Tibesti, Hoggar and Cameroon line vo provinces lcanic are characterised by low Te and no deep-seated seismic anomalies in the mantle. Corridors of relatively low Te connect these volcanic provinces to the local Te minima within the western Ethiopian plateau. We interpret the low Te to indicate thinner lithosphere within the corridors than in
Lavrentyev, A I; Rokhlin, S I
2001-04-01
An ultrasonic method proposed by us for determination of the complete set of acoustical and geometrical properties of a thin isotropic layer between semispaces (J. Acoust. Soc. Am. 102 (1997) 3467) is extended to determination of the properties of a coating on a thin plate. The method allows simultaneous determination of the coating thickness, density, elastic moduli and attenuation (longitudinal and shear) from normal and oblique incidence reflection (transmission) frequency spectra. Reflection (transmission) from the coated plate is represented as a function of six nondimensional parameters of the coating which are determined from two experimentally measured spectra: one at normal and one at oblique incidence. The introduction of the set of nondimensional parameters allows one to transform the reconstruction process from one search in a six-dimensional space to two searches in three-dimensional spaces (one search for normal incidence and one for oblique). Thickness, density, and longitudinal and shear elastic moduli of the coating are calculated from the nondimensional parameters determined. The sensitivity of the method to individual properties and its stability against experimental noise are studied and the inversion algorithm is accordingly optimized. An example of the method and experimental measurement for comparison is given for a polypropylene coating on a steel foil.
NASA Technical Reports Server (NTRS)
Bar-Cohen, Yoseph; Lih, Shyh-Shiuh; El-Azab, A.; Mal, Ajit K.
1996-01-01
Electroactive thin-film polymers are candidate sensors and actuators materials. They are also finding significant potential in muscle mechanisms and microelectromechanical systems (MEMS). In these applications, polymer thin films of thickness varying between 20 and 300 micrometers are utilized. The authors are currently studying the potential use of platewave dispersion curve measurements as an effective gauging tool for electroactive thin-film polymers.
Indentation-derived elastic modulus of multilayer thin films: Effect of unloading induced plasticity
Jamison, Ryan Dale; Shen, Yu -Lin
2015-08-13
Nanoindentation is useful for evaluating the mechanical properties, such as elastic modulus, of multilayer thin film materials. A fundamental assumption in the derivation of the elastic modulus from nanoindentation is that the unloading process is purely elastic. In this work, the validity of elastic assumption as it applies to multilayer thin films is studied using the finite element method. The elastic modulus and hardness from the model system are compared to experimental results to show validity of the model. Plastic strain is shown to increase in the multilayer system during the unloading process. Additionally, the indentation-derived modulus of a monolayermore » material shows no dependence on unloading plasticity while the modulus of the multilayer system is dependent on unloading-induced plasticity. Lastly, the cyclic behavior of the multilayer thin film is studied in relation to the influence of unloading-induced plasticity. Furthermore, it is found that several cycles are required to minimize unloading-induced plasticity.« less
NASA Astrophysics Data System (ADS)
Tandon, K.; Lorenzo, J. M.; O'Brien, G. W.
2000-12-01
Pliocene-Recent continent-island arc collision of the northern Australian continental lithosphere across the Banda orogen from Roti to the Kai Plateau (˜121-137°E longitude) has formed an underfilled foreland basin within the Timor-Tanimbar-Aru Trough. Continental collision on northern Australian lithosphere is most advanced near central Timor Island in terms of shortening and absorbing the forearc basin (Savu Basin) within the accretionary prism. Australian continental lithosphere north of area around central Timor Island is believed to be detached from the oceanic lithosphere. Effective Elastic Thickness (EET) of the northern Australian continental lithosphere from Roti to the Kai Plateau are derived using an elastic half-beam model. Modeled deflection is matched to the seafloor bathymetry and the marine complete 3D Bouguer gravity anomalies. The EET varies from 27 to 75 km across the northern Australian continental lithosphere from Roti to Kai Plateau when the thickness of the elastic half-beam is kept constant. The highest EET values lies near central Timor. From the shelf to beneath the Banda orogen, the EET of the northern Australian continental lithosphere is reduced from ˜90 to ˜30 km when the thickness of the elastic half-beam is allowed to vary down dip. Elastic half-beam modeling approximates the Banda orogen as a triangular load and hidden subsurface loads as end-point loads. Wider triangular loads modeling the load contribution from Banda orogen need higher values of EET. Such an observation highlights the role of high EET in thin-skinned collisional tectonics by promoting the support of wider accretionary prisms by parts of foreland basins with higher EET. Variations in EET may result from inelastic yielding in the northern Australian continental lithosphere. Oroclinal bending of the Australian continental lithosphere in the east, from Tanimbar to the Kai Plateau, may create additional yielding and further decrease the EET. Change in EET occurred
Kozlovsky, Pavel; Rosenfeld, Moshe; Jaffa, Ariel J; Elad, David
2015-06-25
The physical mechanism that drives blood flow in the valveless tubular embryonic heart is still debatable whether it is peristaltic flow or valveless dynamic suction. Previous studies of valveless pumping were concerned with either the role of the excitation parameters or the mechanisms that generate the unidirectional outflow. In this study, a dimensionless one-dimensional (1D) analysis of the valveless pumping due to local excitation at an asymmetric longitudinal location was performed for non-uniform thick-wall elastic tubes, including tubes with local bulging and tapering. A general tube law that accounts for wall thicknesses was implemented for describing the physically realistic dynamics of the tube and the two-step MacCormack algorithm was utilized for the numerical analysis. A comprehensive analysis was conducted to explore the affecting roles of the system (e.g., tube geometry) and the working (e.g., Strouhal number and flow friction parameter) parameters on the net outflow of the pump. The maximal positive net outflow in all the tested cases always occurred when the natural Strouhal number was about π. Flow reversals were observed only for relatively low friction parameters. A local bulging at the site of excitation and thick walls contributed to larger outflows, while tube tapering reduced the net outflow.
NASA Astrophysics Data System (ADS)
Kirby, Jon F.
2014-09-01
The effective elastic thickness (Te) is a geometric measure of the flexural rigidity of the lithosphere, which describes the resistance to bending under the application of applied, vertical loads. As such, it is likely that its magnitude has a major role in governing the tectonic evolution of both continental and oceanic plates. Of the several ways to estimate Te, one has gained popularity in the 40 years since its development because it only requires gravity and topography data, both of which are now readily available and provide excellent coverage over the Earth and even the rocky planets and moons of the solar system. This method, the ‘inverse spectral method’, develops measures of the relationship between observed gravity and topography data in the spatial frequency (wavenumber) domain, namely the admittance and coherence. The observed measures are subsequently inverted against the predictions of thin, elastic plate models, giving estimates of Te and other lithospheric parameters. This article provides a review of inverse spectral methodology and the studies that have used it. It is not, however, concerned with the geological or geodynamic significance or interpretation of Te, nor does it discuss and compare Te results from different methods in different provinces. Since the three main aspects of the subject are thin elastic plate flexure, spectral analysis, and inversion methods, the article broadly follows developments in these. The review also covers synthetic plate modelling, and concludes with a summary of the controversy currently surrounding inverse spectral methods, whether or not the large Te values returned in cratonic regions are artefacts of the method, or genuine observations.
NASA Astrophysics Data System (ADS)
Hall, Richard; Miyachi, Kouichi; Newton, David; Takezoe, Hideo; Fukuda, Atsuo
1992-02-01
The effects of the finite scattering volume on the values of elastic constant ratios determined have been studied by computer simulation. The errors in the simulated values of K1/K2 and K3/K2 are dependent on the position of the starting angle of the scan. The error is greatest for thinner cells (≈7 μm) and in the angular regions where the geometrical factor Gm introduced by de Gennes, or a component of the scattering vector q becomes zero, i.e. for external scattering angles approximately less than 10° and those between approximately 20° and 60°, depending on the scattering geometry used. The approximation introduced by van der Meulen and Zijlstra in defining the orthogonal base system (\\hat{\\mbi{e}}1, \\hat{\\mbi{e}}2, \\hat{\\mbi{e}}3) has also been discussed; it is inappropriate in thin cells to use the scattering vector q instead of the wave vector \\mbi{k}l of the director fluctuations when determining K1/K2.
Mizuno, Mitsuru; Kobayashi, Shinji; Takebe, Takanori; Kan, Hiroomi; Yabuki, Yuichiro; Matsuzaki, Takahisa; Yoshikawa, Hiroshi Y; Nakabayashi, Seiichiro; Ik, Lee Jeong; Maegawa, Jiro; Taniguchi, Hideki
2014-03-01
In healthy joints, hyaline cartilage covering the joint surfaces of bones provides cushioning due to its unique mechanical properties. However, because of its limited regenerative capacity, age- and sports-related injuries to this tissue may lead to degenerative arthropathies, prompting researchers to investigate a variety of cell sources. We recently succeeded in isolating human cartilage progenitor cells from ear elastic cartilage. Human cartilage progenitor cells have high chondrogenic and proliferative potential to form elastic cartilage with long-term tissue maintenance. However, it is unknown whether ear-derived cartilage progenitor cells can be used to reconstruct hyaline cartilage, which has different mechanical and histological properties from elastic cartilage. In our efforts to develop foundational technologies for joint hyaline cartilage repair and reconstruction, we conducted this study to obtain an answer to this question. We created an experimental canine model of knee joint cartilage damage, transplanted ear-derived autologous cartilage progenitor cells. The reconstructed cartilage was rich in proteoglycans and showed unique histological characteristics similar to joint hyaline cartilage. In addition, mechanical properties of the reconstructed tissues were higher than those of ear cartilage and equal to those of joint hyaline cartilage. This study suggested that joint hyaline cartilage was reconstructed from ear-derived cartilage progenitor cells. It also demonstrated that ear-derived cartilage progenitor cells, which can be harvested by a minimally invasive method, would be useful for reconstructing joint hyaline cartilage in patients with degenerative arthropathies.
Porcine cholecyst–derived scaffold promotes full-thickness wound healing in rabbit
Revi, Deepa; Vineetha, Vadavanath Prabhakaran; Muhamed, Jaseer; Rajan, Akhila
2013-01-01
Graft-assisted healing is an important strategy for treating full-thickness skin wounds. This study evaluated the properties of porcine cholecyst–derived scaffold and its use for treating full-thickness skin wound in rabbit. The physical properties of cholecyst-derived scaffold were congenial for skin-graft application. Compared to a commercially available skin-graft substitute made of porcine small intestinal submucosa, the cholecyst-derived scaffold was rich in natural biomolecules like elastin and glycosaminoglycans. When used as a xenograft, it promoted healing with excess cell proliferation at early phases and acceptable collagen deposition in the later remodelling phases. PMID:24555014
Stachiv, I.; Zapomel, J.; Chen, Y.-L.
2014-03-28
Thin films are widely used in microelectronics, optics, filters, and various sensing devices. We propose a method to simultaneously determine the elastic modulus and density or thickness of ultrathin films deposited on various substrate materials. This methodology utilizes measurement of the resonant frequencies of the micro-/nanoresonator under intentionally applied axial tension and, consequently, the beam to string transition. Elastic modulus and density/thickness of thin film are obtained from the ratio between the resonant frequencies of the nanoresonator with and without applied axial force.
Water Permeability of Aquaporin-4 Channel Depends on Bilayer Composition, Thickness, and Elasticity
Tong, Jihong; Briggs, Margaret M.; McIntosh, Thomas J.
2012-01-01
Aquaporin-4 (AQP4) is the primary water channel in the mammalian brain, particularly abundant in astrocytes, whose plasma membranes normally contain high concentrations of cholesterol. Here we test the hypothesis that the water permeabilities of two naturally occurring isoforms (AQP4-M1 and AQP4-M23) depend on bilayer mechanical/structural properties modulated by cholesterol and phospholipid composition. Osmotic stress measurements were performed with proteoliposomes containing AQP4 and three different lipid mixtures: 1), phosphatidylcholine (PC) and phosphatidylglycerol (PG); 2), PC, PG, with 40 mol % cholesterol; and 3), sphingomyelin (SM), PG, with 40 mol % cholesterol. The unit permeabilities of AQP4-M1 were 3.3 ± 0.4 × 10−13 cm3/s (mean ± SE), 1.2 ± 0.1 × 10−13 cm3/s, and 0.4 ± 0.1 × 10−13 cm3/s in PC:PG, PC:PG:cholesterol, and SM:PG:cholesterol, respectively. The unit permeabilities of AQP4-M23 were 2.1 ± 0.2 × 10−13 cm3/s, 0.8 ± 0.1 × 10−13 cm3/s, and 0.3 ± 0.1 × 10−13 cm3/s in PC:PG, PC:PG:cholesterol, and SM:PG:cholesterol, respectively. Thus, for each isoform the unit permeabilities strongly depended on bilayer composition and systematically decreased with increasing bilayer compressibility modulus and bilayer thickness. These observations suggest that altering lipid environment provides a means of regulating water channel permeability. Such permeability changes could have physiological consequences, because AQP4 water permeability would be reduced by its sequestration into SM:cholesterol-enriched raft microdomains. Conversely, under ischemic conditions astrocyte membrane cholesterol content decreases, which could increase AQP4 permeability. PMID:23199918
Pressure derivatives of elastic moduli of fused quartz to 10 kb
Peselnick, L.; Meister, R.; Wilson, W.H.
1967-01-01
Measurements of the longitudinal and shear moduli were made on fused quartz to 10 kb at 24??5??C. The anomalous behavior of the bulk modulus K at low pressure, ???K ???P 0, at higher pressures. The pressure derivative of the rigidity modulus ???G ???P remains constant and negative for the pressure range covered. A 15-kb hydrostatic pressure vessel is described for use with ultrasonic pulse instrumentation for precise measurements of elastic moduli and density changes with pressure. The placing of the transducer outside the pressure medium, and the use of C-ring pressure seals result in ease of operation and simplicity of design. ?? 1967.
NASA Astrophysics Data System (ADS)
Kalnins, L. M.; Watts, A. B.
2009-08-01
We have used free-air gravity anomaly and bathymetric data, together with a moving window admittance technique, to determine the spatial variation in oceanic elastic thickness, Te, in the Western Pacific ocean. Synthetic tests using representative seamounts show that Te can be recovered to an accuracy of ± 5 km for plates up to 30 km thick, with increased accuracy of ± 3 km for Te ≤ 20 km. The Western Pacific has a T e range of 0-50 km, with a mean of 9.4 km and a standard deviation of 6.8 km. The T e structure of the region is dominated by relatively high Te over the Hawaiian-Emperor Seamount Chain, intermediate values over the Marshall Islands, Gilbert Ridge, and Marcus-Wake Guyots, and low values over the Line Islands, Mid-Pacific Mountains, Caroline Islands, Shatsky Rise, Hess Rise, and Musician Seamounts. Plots of Te at sites with radiometric ages suggest that Te is to first order controlled by the age of the lithosphere at the time of loading. In areas that backtrack into the South Pacific Isotopic and Thermal Anomaly (SOPITA), Te may be as low as the depth to the 180 ± 120 °C isotherm at least locally. In the northern part of the study area including the Hawaiian-Emperor Seamount Chain, Te correlates with the depth to 310 ± 120 °C. These best-fitting isotherms imply peak rates of volcanism during 100-120 Ma (Early Cretaceous) and 140-150 Ma (Late Jurassic). The corresponding addition of 8 × 10 6 km 3 and 4 × 10 6 km 3 of volcanic material to the surface of the oceanic crust would result in long-term sea-level rises of 20 m and 10 m respectively. The Late Jurassic volcanic event, like the later Early Cretaceous event, appears to have influenced the tectonic evolution of the Pacific plate convergent boundaries, resulting in increased volcanism and orogenesis.
Baseline Maritime Aerosol: Methodology to Derive the Optical Thickness and Scattering Properties
NASA Technical Reports Server (NTRS)
Kaufman, Yoram J.; Smirnov, Alexander; Holben, Brent N.; Dubovik, Oleg; Einaudi, Franco (Technical Monitor)
2001-01-01
Satellite Measurements of the global distribution of aerosol and their effect on climate should be viewed in respect to a baseline aerosol. In this concept, concentration of fine mode aerosol particles is elevated above the baseline by man-made activities (smoke or urban pollution), while coarse mode by natural processes (e.g. dust or sea-spray). Using 1-3 years of measurements in 10 stations of the Aerosol Robotic network (ACRONET we develop a methodology and derive the optical thickness and properties of this baseline aerosol for the Pacific and Atlantic Oceans. Defined as the median for periods of stable optical thickness (standard deviation < 0.02) during 2-6 days, the median baseline aerosol optical thickness over the Pacific Ocean is 0.052 at 500 am with Angstrom exponent of 0.77, and 0.071 and 1.1 respectively, over the Atlantic Ocean.
Improvements to the Two-Thickness Method for Deriving Acoustic Properties of Materials
NASA Technical Reports Server (NTRS)
Palumbo, Daniel L.; Jones, Michael G.; Klos, Jacob; Park, Junhong
2004-01-01
The characteristic impedance and other derivative acoustic properties of a material can be derived from impedance tube data using the specific impedance measured from samples with two different thicknesses. In practice, samples are chosen so that their respective thicknesses differ by a factor of 2. This simplifies the solution of the equations relating the properties of the two samples so that the computation of the characteristic impedance is straightforward. This approach has at least two drawbacks. One is that it is often difficult to acquire or produce samples with precisely a factor of 2 difference in thickness. A second drawback is that the phase information contained in the imaginary part of the propagation constant must be unwrapped before subsequent computations are performed. For well-behaved samples, this is not a problem. For ill behaved samples of unknown properties, the phase unwrapping process can be tedious and difficult to automate. Two alternative approaches have been evaluated which remove the factor-of-2 sample thickness requirement and directly compute unwrapped phase angles. One uses a Newton-Raphson approach to solve for the roots of the samples' simultaneous equations. The other produces a wave number space diagram in which the roots are clearly discernable and easily extracted. Results are presented which illustrate the flexibility of analysis provided by the new approaches and how this can be used to better understand the limitations of the impedance tube data.
NASA Astrophysics Data System (ADS)
Ma, Yanling; Zhang, Shu Yan; Goodway, Chris; Done, Robert; Evans, Beth; Kirichek, Oleg; Bowden, Zoë
2012-09-01
Positions of elastic plastic interfaces play a vital role in safe design and safe use of high pressure vessels. The ENGIN-X neutron diffractometer at the ISIS facility was used to measure the residual strain profiles in a series of aluminium vessels which had been subjected to different pressure levels. The positions of elastic plastic interfaces of the autofrettaged pressure vessels were identified. The results revealed that the residual strain magnitude and the depth of the plastic region will increase with increasing autofrettage pressure level. When autofrettage pressure produces an elastic-plastic boundary at a greater depth than the geometric mean position of the vessel wall, reverse yielding will occur, hence the loss of the vessels' elastic ability to its subsequent loading. The neutron experimental results agreed well with both the suggestions from existing literatures and the results from FE simulations.
Choi, Ji Suk; Kim, Jae Dong; Yoon, Hyun Soo; Cho, Yong Woo
2013-02-01
The human placenta, a complex organ, which facilitates exchange between the fetus and the mother, contains abundant extracellular matrix (ECM) components and well-preserved endogenous growth factors. In this study, we designed a new dermal substitute from human placentas for full-thickness wound healing. Highly porous, decellularized ECM sheets were fabricated from human placentas via homogenization, centrifugation, chemical and enzymatic treatments, molding, and freeze-drying. The physical structure and biological composition of human placenta-derived ECM sheets dramatically supported the regeneration of full-thickness wound in vivo. At the early stage, the ECM sheet efficiently absorbed wound exudates and tightly attached to the wound surface. Four weeks after implantation, the wound was completely closed, epidermic cells were well arranged and the bilayer structure of the epidermis and dermis was restored. Moreover, hair follicles and microvessels were newly formed in the ECM sheet-implanted wounds. Overall, the ECM sheet produced a dermal substitute with similar cellular organization to that of normal skin. These results suggest that human placenta-derived ECM sheets provide a microenvironment favorable to the growth and differentiation of cells, and positive modulate the healing of full-thickness wounds.
Shakya, Poonam; Sharma, A. K.; Kumar, Naveen; Vellachi, Remya; Mathew, Dayamon D.; Dubey, Prasoon; Singh, Kiranjeet; Shrivastava, Sonal; Shrivastava, Sameer; Maiti, S. K.; Hasan, Anwarul; Singh, K. P.
2016-01-01
An acellular cholecyst derived extracellular matrix (b-CEM) of bubaline origin was prepared using anionic biological detergent. Healing potential of b-CEM was compared with commercially available collagen sheet (b-CS) and open wound (C) in full thickness skin wounds in rats. Thirty-six clinically healthy adult Sprague Dawley rats of either sex were randomly divided into three equal groups. Under general anesthesia, a full thickness skin wound (20 × 20 mm2) was created on the dorsum of each rat. The defect in group I was kept as open wound and was taken as control. In group II, the defect was repaired with commercially available collagen sheet (b-CS). In group III, the defect was repaired with cholecyst derived extracellular matrix of bovine origin (b-CEM). Planimetry, wound contracture, and immunological and histological observations were carried out to evaluate healing process. Significantly (P < 0.05) increased wound contraction was observed in b-CEM (III) as compared to control (I) and b-CS (II) on day 21. Histologically, improved epithelization, neovascularization, fibroplasia, and best arranged collagen fibers were observed in b-CEM (III) as early as on postimplantation day 21. These findings indicate that b-CEM have potential for biomedical applications for full thickness skin wound repair in rats. PMID:27127678
Na, Kyoung-Sae; Won, Eunsoo; Kang, June; Chang, Hun Soo; Yoon, Ho-Kyoung; Tae, Woo Suk; Kim, Yong-Ku; Lee, Min-Soo; Joe, Sook-Haeng; Kim, Hyun; Ham, Byung-Joo
2016-01-01
Recent studies have reported that methylation of the brain-derived neurotrophic factor (BDNF) gene promoter is associated with major depressive disorder (MDD). This study aimed to investigate the association between cortical thickness and methylation of BDNF promoters as well as serum BDNF levels in MDD. The participants consisted of 65 patients with recurrent MDD and 65 age- and gender-matched healthy controls. Methylation of BDNF promoters and cortical thickness were compared between the groups. The right medial orbitofrontal, right lingual, right lateral occipital, left lateral orbitofrontal, left pars triangularis, and left lingual cortices were thinner in patients with MDD than in healthy controls. Among the MDD group, right pericalcarine, right medical orbitofrontal, right rostral middle frontal, right postcentral, right inferior temporal, right cuneus, right precuneus, left frontal pole, left superior frontal, left superior temporal, left rostral middle frontal and left lingual cortices had inverse correlations with methylation of BDNF promoters. Higher levels of BDNF promoter methylation may be closely associated with the reduced cortical thickness among patients with MDD. Serum BDNF levels were significantly lower in MDD, and showed an inverse relationship with BDNF methylation only in healthy controls. Particularly the prefrontal and occipital cortices seem to indicate key regions in which BDNF methylation has a significant effect on structure. PMID:26876488
Derive Arctic Sea-ice Freeboard and Thickness from NASA's LVIS Observations
NASA Astrophysics Data System (ADS)
Yi, D.; Hofton, M. A.; Harbeck, J.; Cornejo, H.; Kurtz, N. T.
2015-12-01
The sea-ice freeboard and thickness are derived from the six sea-ice flights of NASA's IceBridge Land, Vegetation, and Ice Sensor (LVIS) over the Arctic from 2009 to 2013. The LVIS is an airborne scanning laser altimeter. It can operate at an altitude up to 10 km above the ground and produce a data swath up to 2 km wide with 20-m wide footprints. The laser output wavelength is 1064 nm and pulse repetition rate is 1000 Hz. The LVIS L2 geolocated surface elevation product and Level-1b waveform product (http://nsidc.org/data/ilvis2.html and http://nsidc.org/data/ilvis1b.html) at National Snow and Ice Data Center, USA (NSIDC) are used in this study. The elevations are referenced to a geoid with tides and dynamic atmospheric corrections applied. The LVIS waveforms were fitted with Gaussian curves to calculate pulse width, peak location, pulse amplitude, and signal baseline. For each waveform, the centroid, skewness, kurtosis, and pulse area were also calculated. The waveform parameters were calibrated based on laser off pointing angle and laser channels. Calibrated LVIS waveform parameters show a coherent response to variations in surface features along their ground tracks. These parameters, combined with elevation, can be used to identify leads, enabling the derivation of sea-ice freeboard and thickness without relying upon visual images. Preliminary results show that the elevations in some of the LVIS campaigns may vary with laser incident angle; this can introduce an elevation bias if not corrected. Further analysis of the LVIS data shown that the laser incident angle related elevation bias can be removed empirically. The sea-ice freeboard and thickness results from LVIS are compared with NASA's Airborne Topographic Mapper (ATM) for an April 20, 2010 flight, when both LVIS and ATM sensors were on the same aircraft and made coincidental measurements along repeat ground tracks.
Cochrane, Alexander P.; Merrett, Craig G.; Hilton, Harry H.
2014-12-10
The advent of new structural concepts employing composites in primary load carrying aerospace structures in UAVs, MAVs, Boeing 787s, Airbus A380s, etc., necessitates the inclusion of flexibility as well as viscoelasticity in static structural and aero-viscoelastic analyses. Differences and similarities between aeroelasticity and aero-viscoelasticity have been investigated in [2]. An investigation is undertaken as to the dependence and sensitivity of aerodynamic and stability derivatives to elastic and viscoelastic structural flexibility and as to time dependent flight and maneuver velocities. Longitudinal, lateral and directional stabilities are investigated. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [5]. Such elastic analyses are extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings one of the critical static parameters is the velocity at which control reversal takes place (V{sub REV}{sup E}). Since elastic formulations constitute viscoelastic initial conditions, viscoelastic reversal may occur at speeds V{sub REV<}{sup ≧}V{sub REV}{sup E}, but furthermore does so in time at 0 < t{sub REV} ≤ ∞. The influence of the twin effects of viscoelastic and elastic materials and of variable flight velocities on longitudinal, lateral, directional and spin stabilities are also investigated. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [5]. Such elastic analyses are here extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings the critical parameter is the velocity at
NASA Astrophysics Data System (ADS)
Cochrane, Alexander P.; Merrett, Craig G.; Hilton, Harry H.
2014-12-01
The advent of new structural concepts employing composites in primary load carrying aerospace structures in UAVs, MAVs, Boeing 787s, Airbus A380s, etc., necessitates the inclusion of flexibility as well as viscoelasticity in static structural and aero-viscoelastic analyses. Differences and similarities between aeroelasticity and aero-viscoelasticity have been investigated in [2]. An investigation is undertaken as to the dependence and sensitivity of aerodynamic and stability derivatives to elastic and viscoelastic structural flexibility and as to time dependent flight and maneuver velocities. Longitudinal, lateral and directional stabilities are investigated. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [5]. Such elastic analyses are extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings one of the critical static parameters is the velocity at which control reversal takes place (VREVE). Since elastic formulations constitute viscoelastic initial conditions, viscoelastic reversal may occur at speeds VREV<≧VREVE, but furthermore does so in time at 0 < tREV ≤ ∞. The influence of the twin effects of viscoelastic and elastic materials and of variable flight velocities on longitudinal, lateral, directional and spin stabilities are also investigated. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [5]. Such elastic analyses are here extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings the critical parameter is the velocity at which control reversal takes place (VREVE
NASA Astrophysics Data System (ADS)
Whitman, Dean
1994-08-01
The seismically constrained shape of the Moho beneath the eastern margin of the northwest Argentine Andes (24 deg S) is interpreted in the context of regional isostasy to constrain the flexural rigidity of the lithosphere in this actively deforming orogen. Seismic travel time residuals from regional intermediate depth earthquakes are inverted for three-dimensional variations in the Moho depth beneath a portable seismic network spanning the eatern margin of the Punic plateau and the Santa Barbara foreland system. Beneath the easternmost Santa Barbara ranges, the Moho is relatively flat and lies at 40-45 km depth. Farther west, beneath the eastern margin of the Puna, the Moho dips 10-15 deg to the west before flatening out at a depth of 60-65 km beneath the plateau. The Moho inversion model and coincident gravity data constrain the flexural rigidity of the foreland lithosphere to be between 10(exp 21) and 10(exp 22) N m. The corresponding effective elastic thickness of 6-12 km is a factor of 2 to 4 less than that estimated in previous published studies for the Bolivian Altiplano and Subandean ranges farther to the north. These results indicate that in contrast to the Bolivian Andes, the foreland lithosphere in northwest Argentina does not provide significant flexural support to the plateau margin, and the eastern margin of the Andes is nearly in a state of local isostatic compensation. The north to south decrease in the elastic thickness of the Andean lithosphere supports published seismic wave attenuation which indicate that south of 23 deg S the lithospheric thickness decreases beneath the plateau and foreland.
Rachik, Mohamed; Barthes-Biesel, Dominique; Carin, Muriel; Edwards-Levy, Florence
2006-09-01
The mechanical properties of a capsule membrane are evaluated by means of a compression experiment between two parallel plates. Since large deformations of the membrane are involved, the choice of the wall material constitutive law is essential. In this paper, we explore different classical laws to describe the behavior of the membrane and evaluate also the limit of application of the thin shell approximation. A numerical study of the compression process is performed using Abaqus software and an inverse method is used to identify the material constants of the constitutive laws. The comparison between the model predictions and experimental measurements on capsules with serum albumin-alginate membranes, indicates that the thin shell approximation is valid only for thickness to radius ratios up to 5% and that thick membranes obey non linear elastomer type constitutive laws. The Young modulus of the membrane material is found to increase non-linearly with membrane thickness, thus indicating that fabrication of thicker serum albumin-alginate walls results in capsules stiffer than expected.
CARMELLO, Juliana Cabrini; FAIS, Laiza Maria Grassi; RIBEIRO, Lígia Nunes de Moraes; CLARO NETO, Salvador; GUAGLIANONI, Dalton Geraldo; PINELLI, Lígia Antunes Pereira
2012-01-01
The need to develop new dental luting agents in order to improve the success of treatments has greatly motivated research. Objective The aim of this study was to evaluate the diametral tensile strength (DTS) and film thickness (FT) of an experimental dental luting agent derived from castor oil (COP) with or without addition of different quantities of filler (calcium carbonate - CaCO3). Material and Methods Eighty specimens were manufactured (DTS N=40; FT N=40) and divided into 4 groups: Pure COP; COP 10%; COP 50% and zinc phosphate (control). The cements were mixed according to the manufacturers' recommendations and submitted to the tests. The DTS test was performed in the MTS 810 testing machine (10 KN, 0.5 mm/min). For FT test, the cements were sandwiched between two glass plates (2 cm2) and a load of 15 kg was applied vertically on the top of the specimen for 10 min. The data were analyzed by means of one-way ANOVA and Tukey's test (α=0.05). Results The values of DTS (MPa) were: Pure COP- 10.94±1.30; COP 10%- 30.06±0.64; COP 50%- 29.87±0.27; zinc phosphate- 4.88±0.96. The values of FT (µm) were: Pure COP- 31.09±3.16; COP 10%- 17.05±4.83; COP 50%- 13.03±4.83; Zinc Phosphate- 20.00±0.12. One-way ANOVA showed statistically significant differences among the groups (DTS - p=1.01E-40; FT - p=2.4E-10). Conclusion The experimental dental luting agent with 50% of filler showed the best diametral tensile strength and film thickness. PMID:22437672
NASA Astrophysics Data System (ADS)
Fleischmann, J. A.; Drugan, W. J.; Plesha, M. E.
2013-07-01
We derive the macroscopic elastic moduli of a statistically isotropic particulate aggregate material via the homogenization methods of Voigt (1928) (kinematic hypothesis), Reuss (1929) (static hypothesis), and Hershey (1954) and Kröner (1958) (self-consistent hypothesis), originally developed to treat crystalline materials, from the directionally averaged elastic moduli of three regular cubic packings of uniform spheres. We determine analytical expressions for these macroscopic elastic moduli in terms of the (linearized) elastic inter-particle contact stiffnesses on the microscale under the three homogenization assumptions for the three cubic packings (simple, body-centered, and face-centered), assuming no particle rotation. To test these results and those in the literature, we perform numerical simulations using the discrete element method (DEM) to measure the overall elastic moduli of large samples of randomly packed uniform spheres with constant normal and tangential contact stiffnesses (linear spring model). The beauty of DEM is that simulations can be run with particle rotation either prohibited or unrestrained. In this first part of our two-part series of papers, we perform DEM simulations with particle rotation prohibited, and we compare these results with our theoretical results that assumed no particle rotation. We show that the self-consistent homogenization assumption applied to the locally body-centered cubic (BCC) packing most accurately predicts the measured values of the overall elastic moduli obtained from the DEM simulations, in particular Poisson's ratio. Our new analytical self-consistent results lead to significantly better predictions of Poisson's ratio than all prior published theoretical results. Moreover, our results are based on a direct micromechanics analysis of specific geometrical packings of uniform spheres, in contrast to all prior theoretical analyses, which were based on difficult-to-verify hypotheses involving overall inter
NASA Astrophysics Data System (ADS)
Tahouneh, Vahid; Naei, Mohammad Hasan
2016-03-01
The main purpose of this paper is to investigate the effect of bidirectional continuously graded nanocomposite materials on free vibration of thick shell panels rested on elastic foundations. The elastic foundation is considered as a Pasternak model after adding a shear layer to the Winkler model. The panels reinforced by randomly oriented straight single-walled carbon nanotubes are considered. The volume fractions of SWCNTs are assumed to be graded not only in the radial direction, but also in axial direction of the curved panel. This study presents a 2-D six-parameter power-law distribution for CNTs volume fraction of 2-D continuously graded nanocomposite that gives designers a powerful tool for flexible designing of structures under multi-functional requirements. The benefit of using generalized power-law distribution is to illustrate and present useful results arising from symmetric, asymmetric and classic profiles. The material properties are determined in terms of local volume fractions and material properties by Mori-Tanaka scheme. The 2-D differential quadrature method as an efficient numerical tool is used to discretize governing equations and to implement boundary conditions. The fast rate of convergence of the method is shown and results are compared against existing results in literature. Some new results for natural frequencies of the shell are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The interesting results indicate that a graded nanocomposite volume fraction in two directions has a higher capability to reduce the natural frequency than conventional 1-D functionally graded nanocomposite materials.
NASA Astrophysics Data System (ADS)
Kirby, J. F.; Swain, C. J.
2013-12-01
The flexural rigidity of the Earth's cratonic regions is a topic of much controversy. While many studies have suggested that cratons possess high elastic strength, others maintain that the continental lithosphere is everywhere weak. In this study we focus on the Canadian shield, and show that perceived evidence for weak cratonic lithosphere is compromised by shortcomings of the spectral analysis technique. Here we compare estimates of the admittance between free-air gravity and topography in the spectral domain from wavelet and multitaper methods. We apply particular attention to their long wavelength values, since it is here that the signals from mantle convection, glacial isostatic adjustment (GIA) and flexure are often present together. Our results show that, when used with certain parameter values, the multitaper method has a comparatively poor resolution at long wavelengths, and hence is not always able to distinguish between the harmonics due to convection and flexural processes. This renders it unreliable for estimating the flexural rigidity. We then show that the wavelet method does have the requisite properties to make this distinction, since it is able to correctly resolve a low-admittance dip at long wavelengths in both synthetic and real data. When the observed wavelet admittance of the Canadian shield is inverted against the predictions of a combined flexural, convection and GIA model, we find that the shield possesses a core of high effective elastic thickness (Te), greater than 118 km to 95% confidence, located to the immediate south-west of Hudson Bay.
Doster, W.; Nakagawa, H.; Appavou, M. S.
2013-07-28
Numerous neutron scattering studies of bio-molecular dynamics employ a qualitative analysis of elastic scattering data and atomic mean square displacements. We provide a new quantitative approach showing that the intensity at zero energy exchange can be a rich source of information of bio-structural fluctuations on a pico- to nano-second time scale. Elastic intensity scans performed either as a function of the temperature (back-scattering) and/or by varying the instrumental resolution (time of flight spectroscopy) yield the activation parameters of molecular motions and the approximate structural correlation function in the time domain. The two methods are unified by a scaling function, which depends on the ratio of correlation time and instrumental resolution time. The elastic scattering concept is illustrated with a dynamic characterization of alanine-dipeptide, protein hydration water, and water-coupled protein motions of lysozyme, per-deuterated c-phycocyanin (CPC) and hydrated myoglobin. The complete elastic scattering function versus temperature, momentum exchange, and instrumental resolution is analyzed instead of focusing on a single cross-over temperature of mean square displacements at the apparent onset temperature of an-harmonic motions. Our method predicts the protein dynamical transition (PDT) at T{sub d} from the collective (α) structural relaxation rates of the solvation shell as input. By contrast, the secondary (β) relaxation enhances the amplitude of fast local motions in the vicinity of the glass temperature T{sub g}. The PDT is specified by step function in the elastic intensity leading from elastic to viscoelastic dynamic behavior at a transition temperature T{sub d}.
NASA Astrophysics Data System (ADS)
Doster, W.; Nakagawa, H.; Appavou, M. S.
2013-07-01
Numerous neutron scattering studies of bio-molecular dynamics employ a qualitative analysis of elastic scattering data and atomic mean square displacements. We provide a new quantitative approach showing that the intensity at zero energy exchange can be a rich source of information of bio-structural fluctuations on a pico- to nano-second time scale. Elastic intensity scans performed either as a function of the temperature (back-scattering) and/or by varying the instrumental resolution (time of flight spectroscopy) yield the activation parameters of molecular motions and the approximate structural correlation function in the time domain. The two methods are unified by a scaling function, which depends on the ratio of correlation time and instrumental resolution time. The elastic scattering concept is illustrated with a dynamic characterization of alanine-dipeptide, protein hydration water, and water-coupled protein motions of lysozyme, per-deuterated c-phycocyanin (CPC) and hydrated myoglobin. The complete elastic scattering function versus temperature, momentum exchange, and instrumental resolution is analyzed instead of focusing on a single cross-over temperature of mean square displacements at the apparent onset temperature of an-harmonic motions. Our method predicts the protein dynamical transition (PDT) at Td from the collective (α) structural relaxation rates of the solvation shell as input. By contrast, the secondary (β) relaxation enhances the amplitude of fast local motions in the vicinity of the glass temperature Tg. The PDT is specified by step function in the elastic intensity leading from elastic to viscoelastic dynamic behavior at a transition temperature Td.
Static versus dynamic gerbil tympanic membrane elasticity: derivation of the complex modulus.
Aernouts, Jef; Dirckx, Joris J J
2012-07-01
An accurate estimation of tympanic membrane stiffness is important for realistic modelling of middle ear mechanics. Tympanic membrane stiffness has been investigated extensively under either quasi-static or dynamic loading conditions. It is known that biological tissues are sensitive to strain rate. Therefore, in this work, the mechanical behaviour of the tympanic membrane was studied under both quasi-static and dynamic loading conditions. Experiments were performed on the pars tensa of four gerbil tympanic membranes. A custom-built indentation apparatus was used to perform in situ tissue indentations and testing was done applying both quasi-static and dynamic sinusoidal indentations up to 8.2 Hz. The unloaded shape of the tympanic membrane was measured and used to create specimen-specific finite element models to simulate the experiments. The frequency dependent Young's modulus of each specimen was then estimated by an inverse analysis in which the error between experimental and simulated indentation data was optimised for each indentation frequency separately. Using an 8 μm central region thickness, we found Young's moduli between 71 and 106 MPa (n = 4) at 0.2 Hz indentation frequency. A standard linear viscoelastic model and a viscoelastic model with a continuous relaxation spectrum were used to derive a complex modulus in the frequency domain. Due to experimental limitations, the indentation frequency upper limit was 8.2 Hz. The average relative modulus increase in this domain was 14% and the increase was the strongest below 6 Hz.
Du, Ping; Suhaeri, Muhammad; Subbiah, Ramesh; Van, Se Young; Park, Jimin; Kim, Sang Heon; Park, Kwideok; Lee, Kangwon
2016-03-01
Biophysical properties of the microenvironment, including matrix elasticity and topography, are known to affect various cell behaviors; however, the specific role of each factor is unclear. In this study, fibroblast-derived matrix (FDM) was used as cell culture substrate and physically modified to investigate the influence of its biophysical property changes on human umbilical vein endothelial cells (HUVECs) and human mesenchymal stem cells (hMSCs) behavior in vitro. These FDMs were physically modified by simply storing them at different temperatures: the one stored at 4°C, maintained its original properties, was considered natural FDM, whereas the ones stored at -20°C or -80°C, exhibited a distinct surface morphology, were considered physically modified FDM. Physical modification induced matrix fiber rearrangement in FDM, forming different microstructures on the surface as characterized by focused ion beam (FIB)-cryoSEM. A significant increase of matrix elasticity was found with physically modified FDMs as determined by atomic force microscopy. HUVEC and hMSC behaviors on these natural and physically modified FDMs were observed and compared with each other and with gelatin-coated coverslips. HUVECs showed a similar adhesion level on these substrates at 3 h, but exhibited different proliferation rates and morphologies at 24 h; HUVECs on natural FDM proliferated relatively slower and assembled to capillary-like structures (CLSs). It is observed that HUVECs assembled to CLSs on natural FDMs are independent on the exogenous growth factors and yet dependent on nonmuscle myosin II activity. This result indicates the important role of matrix mechanical properties in regulating HUVECs vascular morphogenesis. As for hMSCs multilineage differentiation, adipogenesis is improved on natural FDM that with lower matrix elasticity, while osteogenesis is accelerated on physically modified FDMs that with higher matrix elasticity, these results further confirm the crucial
NASA Astrophysics Data System (ADS)
Oh, Ju-Won; Alkhalifah, Tariq
2016-07-01
Multi-parameter full waveform inversion (FWI) applied to an elastic orthorhombic model description of the subsurface requires in theory a nine-parameter representation of each pixel of the model. Even with optimal acquisition on the Earth surface that includes large offsets, full azimuth, and multi component sensors, the potential for tradeoff between the elastic orthorhombic parameters are large. The first step to understanding such trade-off is analysing the scattering potential of each parameter, and specifically, its scattering radiation patterns. We investigate such radiation patterns for diffraction and for scattering from a horizontal reflector considering a background isotropic model. The radiation patterns show considerable potential for trade-off between the parameters and the potentially limited resolution in their recovery. The radiation patterns of C11, C22 and C33 are well separated so that we expect to recover these parameters with limited trade-offs. However, the resolution of their recovery represented by recovered range of model wavenumbers varies between these parameters. We can only invert for the short wavelength components (reflection) of C33 while we can mainly invert for the long wavelength components (transmission) of the elastic coefficients C11 and C22 if we have large enough offsets. The elastic coefficients C13, C23 and C12 suffer from strong trade-offs with C55, C44 and C66, respectively. The trade-offs between C13 and C55, as well as C23 and C44, can be partially mitigated if we acquire P-SV and SV-SV waves. However, to reduce the trade-offs between C12 and C66, we require credible SH-SH waves. The analytical radiation patterns of the elastic constants are supported by numerical gradients of these parameters.
NASA Astrophysics Data System (ADS)
Oh, Ju-Won; Alkhalifah, Tariq
2016-09-01
Multiparameter full waveform inversion (FWI) applied to an elastic orthorhombic model description of the subsurface requires in theory a nine-parameter representation of each pixel of the model. Even with optimal acquisition on the Earth surface that includes large offsets, full azimuth, and multicomponent sensors, the potential for trade-off between the elastic orthorhombic parameters are large. The first step to understanding such trade-off is analysing the scattering potential of each parameter, and specifically, its scattering radiation patterns. We investigate such radiation patterns for diffraction and for scattering from a horizontal reflector considering a background isotropic model. The radiation patterns show considerable potential for trade-off between the parameters and the potentially limited resolution in their recovery. The radiation patterns of C11, C22, and C33 are well separated so that we expect to recover these parameters with limited trade-offs. However, the resolution of their recovery represented by recovered range of model wavenumbers varies between these parameters. We can only invert for the short wavelength components (reflection) of C33 while we can mainly invert for the long wavelength components (transmission) of the elastic coefficients C11 and C22 if we have large enough offsets. The elastic coefficients C13, C23, and C12 suffer from strong trade-offs with C55, C44, and C66, respectively. The trade-offs between C13 and C55, as well as C23 and C44, can be partially mitigated if we acquire P-SV and SV-SV waves. However, to reduce the trade-offs between C12 and C66, we require credible SH-SH waves. The analytical radiation patterns of the elastic constants are supported by numerical gradients of these parameters.
NASA Astrophysics Data System (ADS)
Ampuero, Jean Paul; Mao, Xiaolin
2016-04-01
The interaction between earthquakes, fault network geometry and fault zone structure is a key question motivating the integration of dynamic rupture and long-term crustal deformation modeling. Here, we address the scaling between fault structural properties from the perspective of dynamic and quasi-static processes involved in fault system evolution. Faults are surrounded by materials damaged through quasi-static and dynamic processes, forming damaged zones whose thickness and damage intensity may vary as a function of fault maturity and length. In the vicinity (typically less than a few hundred meters) of their principal slip surface, faults develop an "inner damage zone", usually characterized by micro-fracture observations. At a larger scale, faults develop an "outer damage zone" of secondary macroscopic fault branches at their tips, which organize into fans of splay faults. Inner damage zones can significantly affect earthquake ruptures, enhance near-field ground motions and facilitate fluid transport in the crust. Fault zone trapped waves can generate pulse-like rupture and oscillatory rupture speed, facilitate supershear rupture transition and allow for steady rupture propagation at speeds that are unstable or inadmissible in homogeneous media. The effects of a fault damage zone crucially depend on its thickness. Field observations of inner damage zone thickness as a function of cumulated slip show linear scaling at small slip but saturation at large slip, with maximum damage zone thickness of a few hundred meters. We previously developed fracture mechanics theoretical arguments and dynamic rupture simulations with off-fault inelastic deformation that predict saturation of the thickness of co-seismic damage zone controlled by the depth extent of the seismogenic zone. In essence, the stress intensity factor at the front of a rupture, which controls the distance reached by the large off-fault stresses that cause damage, scales with the shortest characteristic
NASA Astrophysics Data System (ADS)
Lin, J.; Zhu, J.
2012-12-01
We present a new global model of oceanic crustal thickness based on inversion of global oceanic gravity anomaly with constrains from seismic crustal thickness profiles. We first removed from the observed marine free-air gravity anomaly all gravitational effects that can be estimated and removed using independent constraints, including the effects of seafloor topography, marine sediment thickness, and the age-dependent thermal structure of the oceanic lithosphere. We then calculated models of gravity-derived crustal thickness through inversion of the residual mantle Bouguer anomaly using best-fitting gravity-modeling parameters obtained from comparison with seismically determined crustal thickness profiles. Modeling results show that about 5% of the global crustal volume (or 9% of the global oceanic surface area) is associated with model crustal thickness <5.2 km (designated as "thin" crust), while 56% of the crustal volume (or 65% of the surface area) is associated with crustal thickness of 5.2-8.6 km thick (designated as "normal" crust). The remaining 39% of the crustal volume (or 26% of the surface area) is associated with crustal thickness >8.6 km and is interpreted to have been affected by excess magmatism. The percentage of oceanic crustal volume that is associated with thick crustal thickness (>8.6 km) varies greatly among tectonic plates: Pacific (33%), Africa (50%), Antarctic (33%), Australia (30%), South America (34%), Nazca (23%), North America (47%), India (74%), Eurasia (68%), Cocos (20%), Philippine (26%), Scotia (41%), Caribbean (89%), Arabian (82%), and Juan de Fuca (21%). We also found that distribution of thickened oceanic crust (>8.6 km) seems to depend on spreading rate and lithospheric age: (1) On ocean basins younger than 5 Ma, regions of thickened crust are predominantly associated with slow and ultraslow spreading ridges. The relatively strong lithospheric plate at slow and ultraslow ridges might facilitate the loading of large magmatic
The Effect of Adipose-Derived Stem Cells on Full-Thickness Skin Grafts.
Wang, Juan; Hao, Haojie; Huang, Hong; Chen, Deyun; Han, Yan; Han, Weidong
2016-01-01
Background. The purpose of this study was to evaluate the effects of ASCs on full-thickness skin grafts. Specifically, we investigated the anti-inflammatory effects of ASCs that are mediated via regulation of the phenotypes of activated macrophages. Methods. ASCs were isolated, cultured, and injected under full-thickness skin grafts in 15 rats (ASC group). An additional 15 rats served as controls (PBS group). Skin graft survival assessment and vascularization detection were assessed with H&E staining and laser Doppler blood flowmetry (LDF). The effects of ASCs on angiogenesis, anti-inflammation, collagen accumulation-promoting, and antiscarring were assessed. Results. We found that the skin graft survival rate was significantly increased in the ASC group. The neovascularization, collagen deposition, collagen type I to type III ratio, and levels of VEGF and TGF-β3 in the ASC group were markedly higher than those in the PBS group at day 14. Additionally, in the ASC group, the levels of iNOS, IL-1β, and TNF-α were remarkably decreased, whereas the levels of IL-10 and Arg-1 were substantially increased. Conclusions. Our results confirm that ASCs transplantation can effectively improve full-thickness skin graft survival. Additionally, the anti-inflammatory role of ASCs may indirectly contribute to skin graft survival via its effect on macrophage polarization. PMID:27413735
The Effect of Adipose-Derived Stem Cells on Full-Thickness Skin Grafts
Hao, Haojie; Huang, Hong; Chen, Deyun; Han, Yan; Han, Weidong
2016-01-01
Background. The purpose of this study was to evaluate the effects of ASCs on full-thickness skin grafts. Specifically, we investigated the anti-inflammatory effects of ASCs that are mediated via regulation of the phenotypes of activated macrophages. Methods. ASCs were isolated, cultured, and injected under full-thickness skin grafts in 15 rats (ASC group). An additional 15 rats served as controls (PBS group). Skin graft survival assessment and vascularization detection were assessed with H&E staining and laser Doppler blood flowmetry (LDF). The effects of ASCs on angiogenesis, anti-inflammation, collagen accumulation-promoting, and antiscarring were assessed. Results. We found that the skin graft survival rate was significantly increased in the ASC group. The neovascularization, collagen deposition, collagen type I to type III ratio, and levels of VEGF and TGF-β3 in the ASC group were markedly higher than those in the PBS group at day 14. Additionally, in the ASC group, the levels of iNOS, IL-1β, and TNF-α were remarkably decreased, whereas the levels of IL-10 and Arg-1 were substantially increased. Conclusions. Our results confirm that ASCs transplantation can effectively improve full-thickness skin graft survival. Additionally, the anti-inflammatory role of ASCs may indirectly contribute to skin graft survival via its effect on macrophage polarization. PMID:27413735
Use of Fish Scale-Derived BioCornea to Seal Full-Thickness Corneal Perforations in Pig Models
Lin, Han-Tse; Huang, Min-Chang; Lin, Chien-Chen; Chou, Cheng-Hung; Hjortdal, Jesper
2015-01-01
The aim of this study was to test the use of BioCornea, a fish scale-derived collagen matrix for sealing full-thickness corneal perforations in mini-pigs. Two series of experiments were carried out in 8 Lan-Yu and 3 Göttingen mini-pigs, respectively. A 2mm central full thickness corneal perforation was made with surgical scissors and 2mm trephines. The perforations were sealed immediately by suturing BioCornea to the wounded cornea. The conditions of each patched cornea were followed-up daily for 3 or 4 days. Status of operated eyes was assessed with slit lamp examination or optical coherence tomography (OCT). Animals were sacrificed after the study period and the corneas operated were fixated for histological examination. Both OCT imaging and handheld slit lamp observations indicated that a stable ocular integrity of the perforated corneas was maintained, showing no leakage of aqueous humor, normal depth of anterior chamber and only mild swelling of the wounded cornea. Hematoxylin and eosin staining of the patched cornea showed no epithelial ingrowths to the perforated wounds and no severe leucocyte infiltration of the stroma. The fish scale-derived BioCornea is capable to seal full-thickness corneal perforation and stabilize the integrity of ocular anterior chamber in pre-clinic mini-pig models. BioCornea seems to be a safe and effective alternative for emergency treatment of corneal perforations. PMID:26599018
NASA Astrophysics Data System (ADS)
de Tullio, M. D.; Pascazio, G.
2016-11-01
A versatile numerical method is presented to predict the fluid-structure interaction of bodies with arbitrary thickness immersed in an incompressible fluid, with the aim of simulating different biological engineering applications. A direct-forcing immersed boundary method is adopted, based on a moving-least-squares approach to reconstruct the solution in the vicinity of the immersed surface. A simple spring-network model is considered for describing the dynamics of deformable structures, so as to easily model and simulate different biological systems that not always may be described by simple continuum models, without affecting the computational time and simplicity of the overall method. The fluid and structures are coupled in a strong way, in order to avoid instabilities related to large accelerations of the bodies. The effectiveness of the method is validated by means of several test cases involving: rigid bodies, either falling in a quiescent fluid, fluttering or tumbling, or transported by a shear flow; infinitely thin elastic structures with mass, such as a two-dimensional flexible filament and, concerning three-dimensional cases, a flapping flag and an inverted flag in a free stream; finally, a three-dimensional model of a bio-prosthetic aortic valve opening and closing under a pulsatile flowrate. A very good agreement is obtained in all the cases, comparing with available experimental data and numerical results obtained by different methods. In particular, the method is shown to be second-order accurate by means of a mesh-refinement study. Moreover, it is able to provide results comparable with those of sharp direct-forcing approaches, and can manage high pressure differences across the surface, still obtaining very smooth hydrodynamic forces.
NASA Astrophysics Data System (ADS)
Grzibovskis, Raitis; Vembris, Aivars; Pudzs, Kaspars
2016-08-01
Nowadays most organic devices consist of thin (below 100 nm) layers. Information about the morphology and energy levels of thin films at such thickness is essential for the high efficiency devices. In this work we have investigated thin films of 2-(4-[N,N-dimethylamino]-benzylidene)-indene-1,3-dione (DMABI) and 2-(4-(bis(2-(trityloxy)ethyl)amino)benzylidene)-2H-indene-1,3-dione (DMABI-6Ph). DMABI-6Ph is the same DMABI molecule with attached bulky groups which assist formation of amorphous films from solutions. Polycrystalline structure was obtained for the DMABI thin films prepared by thermal evaporation in vacuum and amorphous structure for the DMABI-6Ph films prepared by spin-coating method. Images taken by SEM showed separate crystals or islands at the thickness of the samples below 100 nm. The ionization energy of the studied compounds was determined using photoemission yield spectroscopy. A vacuum level shift of 0.40 eV was observed when ITO electrode was covered with the thin film of the organic compound. Despite of the same active part of the investigated molecules the ITO/DMABI interface is blocking electrons while ITO/DMABI-6Ph interface is blocking holes.
Global features of ionospheric slab thickness derived from JPL TEC and COSMIC observations
NASA Astrophysics Data System (ADS)
Huang, He; Liu, Libo
2016-04-01
The ionospheric equivalent slab thickness (EST) is the ratio of total electron content (TEC) to F2-layer peak electron density (NmF2), describing the thickness of the ionospheric profile. In this study, we retrieve EST from Jet Propulsion Laboratory (JPL) TEC data and NmF2 retrieved from Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) ionospheric radio occultation data. The diurnal, seasonal and solar activity variations of global EST are analyzed as the excellent spatial coverage of JPL TEC and COSMIC data. During solstices, daytime EST in the summer hemisphere is larger than that in the winter hemisphere, except in some high-latitude regions; and the reverse is true for the nighttime EST. The peaks of EST often appear at 0400 local time. The pre-sunrise enhancement in EST appears in all seasons, while the post-sunset enhancement in EST is not readily observed in equinox. The dependence of EST on solar activity is very complicated. Furthermore, an interesting phenomenon is found that EST is enhanced from 0° to 120° E in longitude and 30° to 75° S in latitude during nighttime, just to the east of Weddell Sea Anomaly, during equinox and southern hemisphere summer.
NASA Astrophysics Data System (ADS)
Meng, Fei; Shi, Tongguang
2016-04-01
Two-year records of Visible Infrared Imaging Radiometer Suite (VIIRS) Intermediate Product (IP) data on the aerosol optical thickness (AOT) at 550 nm were evaluated by comparing them with sun-sky radiometer measurements from the Chinese sun hazemeter network (CSHNET) and the aerosol robotic network (AERONET). The monthly and seasonal variations in the aerosol optical properties over eastern China were then investigated using collocated VIIRS IP data and CSHNET and AERONET measurements.Results show that the performances of the current VIIRS IP AOT retrievals at the provisional stage were consistent with ground measurements. Similar characteristics of seasonal and monthly variations were found among the measurements, though the observational methodologies were different, showing maxima in the summer and spring and minima in the winter and autumn.
Derivation of total filtration thickness for diagnostic x-ray source assembly
NASA Astrophysics Data System (ADS)
Sekimoto, Michiharu; Katoh, Yoh
2016-08-01
The method defined by the IEC 60522 for determining the inherent filtration of an x-ray source device is applicable only for a limited range of tube voltage. Because the users cannot legally remove the x-ray movable diaphragm of the x-ray source device, total filtration, which is the sum of the additional filtration diaphragm movable for specific filtration and x-ray, cannot be measured. We develop a method for simply obtaining the total filtration for different tube voltage values. Total filtration can be estimated from a ratio R‧ of the air kerma Kx+T\\prime , which is measured with an Al plate with thickness T, and Kx\\prime measured without an Al plate. The conditions of the target material of the x-ray source device are then entered into the Report 78 Spectrum Processor to calculate the air kerma K x and K x+T for Al thicknesses x and (x + T), respectively, to obtain R. The minimum value of x, which is the difference between the R and R‧, is the total filtration of the x-ray source device. The total filtration calculated using the industrial x-ray source device was within ±1% in the 40–120 kV range. This method can calculate the total filtration using air kerma measurements with and without the Al plate. Therefore, the load on the x-ray tube can be reduced, and preparation of multiple Al plates is not necessary. Furthermore, for the 40–120 kV tube voltage range, the user can easily measure the total filtration.
Derivation of total filtration thickness for diagnostic x-ray source assembly.
Sekimoto, Michiharu; Katoh, Yoh
2016-08-21
The method defined by the IEC 60522 for determining the inherent filtration of an x-ray source device is applicable only for a limited range of tube voltage. Because the users cannot legally remove the x-ray movable diaphragm of the x-ray source device, total filtration, which is the sum of the additional filtration diaphragm movable for specific filtration and x-ray, cannot be measured. We develop a method for simply obtaining the total filtration for different tube voltage values. Total filtration can be estimated from a ratio R' of the air kerma [Formula: see text], which is measured with an Al plate with thickness T, and [Formula: see text] measured without an Al plate. The conditions of the target material of the x-ray source device are then entered into the Report 78 Spectrum Processor to calculate the air kerma K x and K x+T for Al thicknesses x and (x + T), respectively, to obtain R. The minimum value of x, which is the difference between the R and R', is the total filtration of the x-ray source device. The total filtration calculated using the industrial x-ray source device was within ±1% in the 40-120 kV range. This method can calculate the total filtration using air kerma measurements with and without the Al plate. Therefore, the load on the x-ray tube can be reduced, and preparation of multiple Al plates is not necessary. Furthermore, for the 40-120 kV tube voltage range, the user can easily measure the total filtration.
NASA Astrophysics Data System (ADS)
Huang, He; Liu, Libo; Chen, Yiding; Le, Huijun; Wan, Weixing
2016-01-01
The ionospheric equivalent slab thickness (EST), defined as the ratio of total electron content (TEC) to F2 layer peak electron density (NmF2), describes the thickness of the ionospheric profile. In this study, we retrieve EST from TEC data obtained from Global Ionospheric Map (GIM) and NmF2 retrieved from Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) ionospheric radio occultation data. The diurnal, seasonal, and solar activity variations of global EST are analyzed as the excellent spatial coverage of GIM and COSMIC data. During solstices, daytime EST in the summer hemisphere is larger than that in the winter hemisphere, except in some high-latitude regions, and the reverse is true for the nighttime EST. The peaks of EST often appear at 0400 local time. The presunrise enhancement in EST appears in all seasons, while the postsunset enhancement in EST is not readily observed in equinox. Both enhancements are attributed to the more remarkable electron density decay of NmF2 compared to that of TEC. The dependence of EST on solar activity is related to the inconsistent solar activity dependences of electron density at different altitudes. Furthermore, it is interesting that EST is enhanced from 0° to 120°E in longitude and 30° to 75°S in latitude during nighttime, just to the east of Weddell Sea Anomaly, during equinox and the Southern Hemisphere summer. This phenomenon is supposed to be related to the effects of geomagnetic declination-related plasma vertical drifts.
NASA Astrophysics Data System (ADS)
Cheng, S. J.; Steiner, A. L.; Hollinger, D. Y.; Bohrer, G.; Nadelhoffer, K. J.
2016-07-01
Clouds scatter direct solar radiation, generating diffuse radiation and altering the ratio of direct to diffuse light. If diffuse light increases plant canopy CO2 uptake, clouds may indirectly influence climate by altering the terrestrial carbon cycle. However, past research primarily uses proxies or qualitative categories of clouds to connect the effect of diffuse light on CO2 uptake to sky conditions. We mechanistically link and quantify effects of cloud optical thickness (τc) to surface light and plant canopy CO2 uptake by comparing satellite retrievals of τc to ground-based measurements of diffuse and total photosynthetically active radiation (PAR; 400-700 nm) and gross primary production (GPP) in forests and croplands. Overall, total PAR decreased with τc, while diffuse PAR increased until an average τc of 6.8 and decreased with larger τc. When diffuse PAR increased with τc, 7-24% of variation in diffuse PAR was explained by τc. Light-use efficiency (LUE) in this range increased 0.001-0.002 per unit increase in τc. Although τc explained 10-20% of the variation in LUE, there was no significant relationship between τc and GPP (p > 0.05) when diffuse PAR increased. We conclude that diffuse PAR increases under a narrow range of optically thin clouds and the dominant effect of clouds is to reduce total plant-available PAR. This decrease in total PAR offsets the increase in LUE under increasing diffuse PAR, providing evidence that changes within this range of low cloud optical thickness are unlikely to alter the magnitude of terrestrial CO2 fluxes.
NASA Astrophysics Data System (ADS)
Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.
2010-01-01
A cloud frequency of occurrence matrix is generated using merged cloud vertical profiles derived from the satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and cloud profiling radar. The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical profiles can be related by a cloud overlap matrix when the correlation length of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches random overlap with increasing distance separating cloud layers and that the probability of deviating from random overlap decreases exponentially with distance. One month of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat data (July 2006) support these assumptions, although the correlation length sometimes increases with separation distance when the cloud top height is large. The data also show that the correlation length depends on cloud top hight and the maximum occurs when the cloud top height is 8 to 10 km. The cloud correlation length is equivalent to the decorrelation distance introduced by Hogan and Illingworth (2000) when cloud fractions of both layers in a two-cloud layer system are the same. The simple relationships derived in this study can be used to estimate the top-of-atmosphere irradiance difference caused by cloud fraction, uppermost cloud top, and cloud thickness vertical profile differences.
NASA Astrophysics Data System (ADS)
Lewis, M. J.; Parra, J.; Weissling, B.; Ackley, S. F.; Maksym, T. L.; Wilkinson, J.; Wagner, T.
2011-12-01
Sea ice is a critical component of the Earth's climate system and is a highly complex media. The physical characteristics are important in interpretation of remote sensing data. Sea ice characteristics such as snow surface topography, snow depth and ice thickness were derived from in situ measurements obtained during the J.C. Ross (ICEBell) and Oden Southern Ocean (OSO) expeditions during the austral summer of 2010-11. Select areas of sea ice floes in the Bellingshausen, Weddell and Amundsen Seas were measured using terrestrial scanning LiDAR (TSL) and also by conventional gridded and transect surveys. Snow depths were obtained at 2-5 meter sampling intervals and ice thickness was estimated by both electromagnetic induction (EMI) and auger drilling at 2-5 meter intervals. The LiDAR data is gridded to a 10cm rasterized data set. The field data from multiple floes in different regions provide a unique three dimensional perspective of sea ice elevation, snow depth and derived freeboard. These floes are visualized in both space and spectral domains and analyzed using classic statistical and geostatistical methods to assess surface roughness, snow depth, and the effects of differing scales on data resolution. The correlation lengths needed for isostatic equilibrium of freeboard were determined. These relationships are useful in assessing radar and laser altimetry data from airborne and satellite sources.
Yang, Yun Jung; Kim, Chang Sup; Choi, Bong-Hyuk; Cha, Hyung Joon
2015-12-14
As biodegradable scaffolds, protein hydrogels have considerable potential, particularly for bioartificial organs and three-dimensional space-filling materials. However, their low strength and stiffness have been considered to be limitations for enduring physiological stimuli. Therefore, protein hydrogels have been commonly utilized as delivery vehicles rather than as supporting materials. In this work, sea anemone tentacle-derived recombinant silk-like protein (aneroin) was evaluated as a potential material for a mechanically durable protein hydrogel. Inspired by the natural hardening mechanism, photoinitiated dityrosine cross-linking was employed to fabricate an aneroin hydrogel. It was determined that the fabricated aneroin hydrogel was approximately 10-fold stiffer than mammalian cardiac or skeletal muscle. The aneroin hydrogel provided not only structural support but also an adequate environment for cells. It exhibited an adequate swelling ability and microstructure, which are beneficial for facilitating mass transport and cell proliferation. Based on its mechanical and biological properties, this aneroin hydrogel could be used in various biomedical applications, such as cell-containing patches, biomolecule carriers, and artificial extracellular matrices. PMID:26539814
Chaudhury, Manoj K; Finlay, John A; Chung, Jun Young; Callow, Maureen E; Callow, James A
2005-01-01
The effect of modulus and film thickness on the release of adhered spores and sporelings (young plants) of the green fouling alga Ulva (syn. Enteromorpha) was investigated. PDMS elastomers of constant thickness (100 microm) but different elastic moduli were prepared by varying cross-link density with functional silicone oligomers with degrees of polymerization ranging from 18-830. This provided a 50-fold range of modulus values between 0.2 and 9.4 MPa. Three PDMS coatings of different thicknesses were tested at constant elastic modulus (0.8 MPa). The data revealed no significant increase in percentage spore removal except at the lowest modulus of 0.2 MPa although sporelings released more readily at all but the highest modulus. The influence of coating thickness was also greater for the release of sporelings compared to spores. The release data are discussed in the light of fracture mechanics models that have been applied to hard fouling. New concepts appertaining to the release of soft fouling organisms are proposed, which take into account the deformation in the adhesive base of the adherand and deformation of the PDMS film.
2016-01-01
The construction of regularization operators presented in this work is based on the introduction of strain or damage micromorphic degrees of freedom in addition to the displacement vector and of their gradients into the Helmholtz free energy function of the constitutive material model. The combination of a new balance equation for generalized stresses and of the micromorphic constitutive equations generates the regularization operator. Within the small strain framework, the choice of a quadratic potential w.r.t. the gradient term provides the widely used Helmholtz operator whose regularization properties are well known: smoothing of discontinuities at interfaces and boundary layers in hardening materials, and finite width localization bands in softening materials. The objective is to review and propose nonlinear extensions of micromorphic and strain/damage gradient models along two lines: the first one introducing nonlinear relations between generalized stresses and strains; the second one envisaging several classes of finite deformation model formulations. The generic approach is applicable to a large class of elastoviscoplastic and damage models including anisothermal and multiphysics coupling. Two standard procedures of extension of classical constitutive laws to large strains are combined with the micromorphic approach: additive split of some Lagrangian strain measure or choice of a local objective rotating frame. Three distinct operators are finally derived using the multiplicative decomposition of the deformation gradient. A new feature is that a free energy function depending solely on variables defined in the intermediate isoclinic configuration leads to the existence of additional kinematic hardening induced by the gradient of a scalar micromorphic variable. PMID:27274684
Revi, Deepa; Geetha, C; Thekkuveettil, Anoopkumar; Anilkumar, Thapasimuthu V
2016-02-01
Graft-assisted healing is often proposed for clinical management of large-sized third-degree cutaneous burn wounds. Skin-graft substitutes prepared by loading appropriate cell types on suitable scaffolds have been found successful. We have previously shown that cholecyst-derived scaffold prepared by a non-detergent/enzymatic method can be used as skin-graft substitute for promoting healing of full thickness excision wounds in rabbit. This article examines the use of this scaffold for preparing bio-artificial grafts by loading homologous fibroblasts. The healing potential was evaluated in a rabbit model of full thickness skin-burn wound. The healing process was evaluated by gross morphology evaluation and histomorphology evaluation at 7, 14 and 28 days of healing. Ex vivo imaging of the wounded tissue was performed and it was found that the loaded fibroblasts remained viable at least for 14 days in the healing wound. By the first week, re-epithelialisation was evident in all animals treated with the cell-loaded graft. Histomorphological wound healing parameters such as the quickness of re-epithelialisation, the nature of collagen deposition and the extent of neo-vascularisation indicated that cell-loaded grafts promoted faster healing of the wounds. Results of immunohistochemistry indicated a parallel change in the number of proliferating cells and myofibroblast in the healing tissue. Although the pathophysiology of the healing reaction was not established, the observations suggested that homologus fibroblast-loaded cholecyst-derived scaffold promoted faster healing of third-degree wounds in rabbit model by modulating myofibroblast response. It was concluded that cholecyst-derived scaffold prepared by the non-detergent/enzymatic method is a potential scaffold for fabricating bioartificial skin grafts. PMID:26589297
Swaminathan, Ganesh; Sivaraman, Balakrishnan; Moore, Lee; Zborowski, Maciej; Ramamurthi, Anand
2016-04-01
Abdominal aortic aneurysms (AAA) represent abnormal aortal expansions that result from chronic proteolytic breakdown of elastin and collagen fibers by matrix metalloproteases. Poor elastogenesis by adult vascular smooth muscle cells (SMCs) limits regenerative repair of elastic fibers, critical for AAA growth arrest. Toward overcoming these limitations, we recently demonstrated significant elastogenesis by bone marrow mesenchymal stem cell-derived SMCs (BM-SMCs) and their proelastogenesis and antiproteolytic effects on rat aneurysmal SMCs (EaRASMCs). We currently investigate the effects of super paramagnetic iron oxide nanoparticle (SPION) labeling of BM-SMCs, necessary to magnetically guide them to the AAA wall, on their functional benefits. Our results indicate that SPION-labeling is noncytotoxic and does not adversely impact the phenotype and elastogenesis by BM-SMCs. In addition, SPION-BM-SMCs showed no changes in the ability of the BM-SMCs to stimulate elastin regeneration and attenuate proteolytic activity by EaRASMCs. Together, our results are promising toward the utility of SPIONs for magnetic targeting of BM-SMCs for in situ AAA regenerative repair. PMID:26830683
Abe, Takashi; Fujita, Eiji; Thiebaud, Robert S; Loenneke, Jeremy P; Akamine, Takuya
2016-09-01
To test the validity of published equations, anterior forearm muscle thickness (MT-ulna) of 158 Japanese older adults (72 men and 86 women) aged 50-79 y was measured with ultrasound. Appendicular lean soft tissue mass (aLM) was estimated from MT-ulna using two equations (body height without [eqn 1] and with [eqn 2]) previously published in the literature. Appendicular lean mass was measured using dual-energy X-ray absorption (DXA), and this method served as the reference criterion. There was a strong correlation between DXA-derived and ultrasound-estimated aLM in both equations (r = 0.882 and r = 0.944). Total error was 2.60 kg for eqn (1) and 1.38 kg for eqn (2). A Bland-Altman plot revealed that there was no systematic bias between DXA-derived and ultrasound-estimated aLM; however, eqn (1) overestimated aLM compared with DXA-derived aLM. Our results suggest that an ultrasound MT-ulna equation that includes body height is appropriate and useful for estimating aLM in Japanese adults. PMID:27321173
Machula, Hans; Ensley, Burt; Kellar, Robert
2014-01-01
Objective: To evaluate the physiological effects of electrospun tropoelastin scaffolds as therapeutic adipose-derived stem cell (ADSC) delivery vehicles for the treatment of full-thickness dermal wounds. Approach: Using the process of electrospinning, several prototype microfiber scaffolds were created with tropoelastin. Initial testing of scaffold biocompatibility was performed in vitro through ADSC culture, followed by scanning electron microscopy (SEM) for assessment of ADSC attachment, morphology, and new extracellular matrix (ECM) deposition. The wound healing effects of ADSC-seeded scaffolds were then evaluated in a murine dermal excisional wound model. Results: For the in vitro study, SEM revealed exceptional biocompatibility of electrospun tropoelastin for ADSCs. In the wound-healing study, ADSC-treated groups demonstrated significantly enhanced wound closure and epithelial thickness compared to controls. Innovation: This is the first report on the use of tropoelastin-based biomaterials as delivery vehicles for therapeutic ADSCs. Conclusion: We have demonstrated that tropoelastin-based ADSC delivery vehicles significantly accelerate wound healing compared to controls that represent the current clinical standard of care. Furthermore, the unique mechanical and biochemical characteristics of tropoelastin may favor its use over other biological or synthetic scaffolds for the treatment of certain pathologies due to its unique intrinsic mechanical properties. PMID:24804156
Liu, Yanchun; Skardal, Aleksander; Shu, Xiao Zheng; Prestwich, Glenn D
2008-04-01
Peritendinous adhesions are an important complication of flexor tendon injury. Three hyaluronan (HA)-derived biomaterials were evaluated for the reduction of peritendinous adhesions following partial-thickness tendon injury in rabbits. Rabbits (n = 24) were divided into three groups (n = 8 per group), which were used for gross evaluation, histologic assessment, or biomechanical testing. The fourth and third toes from both hindpaws of each rabbit were randomly assigned to one of four treatments: (i) untreated control, (ii) Seprafilm, (iii) Carbylan-SX in situ crosslinked hydrogel, and (iv) preformed Carbylan-SX film. Rabbits were sacrificed at 3 weeks postsurgery and evaluated anatomically, histologically, and mechanically. All materials used reduced adhesions relative to untreated controls for all three evaluations. Both the gross anatomic and histologic results revealed that Carbylan-SX film was statistically superior to Seprafilm and Carbylan-SX gel in preventing tendon adhesion formation. In biomechanical tests, the Carbylan-SX film-treated hindpaws required the least force to pull the tendon from the sheath. This force was statistically indistinguishable from that required to extrude an unoperated tendon (n = 8). Carbylan-SX gel was less effective than Carbylan-SX film but superior to Seprafilm for all evaluations. A crosslinked HA-derived film promoted healing of a flexor tendon injury without the formation of fibrosis at 3 weeks postoperatively.
Adolph, Elizabeth J.; Pollins, Alonda C.; Cardwell, Nancy L.; Davidson, Jeffrey M.; Guelcher, Scott A.; Nanney, Lillian B.
2014-01-01
Lysine-derived polyurethane scaffolds (LTI-PUR) support cutaneous wound healing in loose-skinned small animal models. Due to the physiological and anatomical similarities of human and pig skin we investigated the capacity of LTI-PUR scaffolds to support wound healing in a porcine excisional wound model. Modifications to scaffold design included the addition of carboxymethylcellulose (CMC) as a porogen to increase interconnectivity and an additional plasma treatment (Plasma) to decrease surface hydrophobicity. All LTI-PUR scaffold and formulations supported cellular infiltration and were biodegradable. At 15 days, CMC and Plasma scaffolds simulated increased macrophages more so than LTI PUR or no treatment. This response was consistent with macrophage-mediated oxidative degradation of the lysine component of the scaffolds. Cell proliferation was similar in control and scaffold treated wounds at 8 and 15 days. Neither apoptosis nor blood vessel area density showed significant differences in the presence of any of the scaffold variations compared to untreated wounds, providing further evidence that these synthetic biomaterials had no adverse effects on those pivotal wound healing processes. During the critical phase of granulation tissue formation in full thickness porcine excisional wounds, LTI-PUR scaffolds supported tissue infiltration, while undergoing biodegradation. Modifications to scaffold fabrication modify the reparative process. This study emphasizes the biocompatibility and favorable cellular responses of PUR scaffolding formulations in a clinically relevant animal model. PMID:25290884
NASA Technical Reports Server (NTRS)
Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.
2009-01-01
A cloud frequency of occurrence matrix is generated using merged cloud vertical profile derived from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR). The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical pro les can be related by a set of equations when the correlation distance of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches the random overlap with increasing distance separating cloud layers and that the probability of deviating from the random overlap decreases exponentially with distance. One month of CALIPSO and CloudSat data support these assumptions. However, the correlation distance sometimes becomes large, which might be an indication of precipitation. The cloud correlation distance is equivalent to the de-correlation distance introduced by Hogan and Illingworth [2000] when cloud fractions of both layers in a two-cloud layer system are the same.
NASA Astrophysics Data System (ADS)
Kondragunta, S.
2012-12-01
Suomi National Polar-orbiting Partnership (NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) instrument was launched on October 28, 2011. The VIIRS instrument provides Aerosol Optical Thickness (AOT) at two different spatial resolutions: a pixel level (~750 m at nadir) product called the Intermediate Product (IP) and an aggregated (~6 km at nadir) product called the Environmental Data Record (EDR). The air quality and public health community has been using the 10-km Aqua and Terra MODIS (Moderate resolution Imaging Spectroradiometer) AOT products as a proxy to monitor surface PM2.5 (particulate mass for particles smaller than 2.5 μm in median diameter). The United States Environmental Protection Agency (USEPA) monitors surface PM2.5 because high concentrations have adverse human health impacts. The monitoring stations are not dense, especially in the rural regions, requiring the EPA and scientific community to use satellite-derived AOT as a proxy to derive surface PM2.5. VIIRS AOT will provide continuity to the use of MODIS AOT and its two different spatial resolutions provide an opportunity to test the impact of spatial resolution on the AOT-PM2.5 relationship. A preliminary comparison of VIIRS best quality aerosol products with in situ L1.5 AERONET data using nearest neighbor matchup criteria for one month (May 2012) shows that the IP and EDR AOT bias is 0.204 and 0.153 respectively, and the precision of IP and EDR AOT is 0.319 and 0.235 respectively. A comparison to Aqua MODIS for the same time period also shows that VIIRS AOT is biased high over land but the magnitudes of bias and precision are lower. Given that this evaluation places the VIIRS aerosol products at the beta maturity level (product is minimally validated, may contain significant errors, and not appropriate for quantitative applications) and algorithm refinements are forthcoming, this study compares the collocated satellite-derived AOT and surface PM2.5 relationship for summer 2012 using
NASA Astrophysics Data System (ADS)
Steinberger, Bernhard
2016-04-01
Large-scale topography may be due to several causes, including (1) variations in crustal thickness and density structure, (2) oceanic lithosphere age differences, (3) subcrustal density variations in the continental lithosphere and (4) convective flow in the mantle beneath the lithosphere. The last contribution in particular may change with time and be responsible for continental inundations; distinguishing between these contributions is therefore important for linking Earth's history to its observed geological record. As a step towards this goal, this paper aims at such distinction for the present-day topography: the approach taken is deriving a `model' topography due to contributions (3) and (4), along with a model geoid, using a geodynamic mantle flow model. Both lithosphere thickness and density anomalies beneath the lithosphere are inferred from seismic tomography. Density anomalies within the continental lithosphere are uncertain, because they are probably due to variations in composition and temperature, making a simple scaling from seismic to density anomalies inappropriate. Therefore, we test a number of different assumptions regarding these. As a reality check, model topography is compared, in terms of both correlation and amplitude ratio, to `residual' topography, which follows from observed topography after subtracting contributions (1) and (2). The model geoid is compared to observations as well. Comparatively good agreement is found if there is either an excess density of ≈0.2 per cent in the lithosphere above ≈150 km depth, with anomalies below as inferred from tomography, or if the excess density is ≈0.4 per cent in the entire lithosphere. Further, a good fit is found for viscosity ≈1020 Pa s in the asthenosphere, increasing to ≈1023 Pa s in the lower mantle above D'. Results are quite dependent on which tomography models they are based on; for some recent ones, topography correlation is ≈0.6, many smaller scale features are matched
Meinhold, Lars; Clement, David; Tehei, M; Daniel, R. M.; Finney, J.L.; Smith, Jeremy C
2008-11-01
The temperature dependence of the dynamics of mesophilic and thermophilic dihydrofolate reductase is examined using elastic incoherent neutron scattering. It is demonstrated that the distribution of atomic displacement amplitudes can be derived from the elastic scattering data by assuming a (Weibull) functional form that resembles distributions seen in molecular dynamics simulations. The thermophilic enzyme has a significantly broader distribution than its mesophilic counterpart. Furthermore, although the rate of increase with temperature of the atomic mean-square displacements extracted from the dynamic structure factor is found to be comparable for both enzymes, the amplitudes are found to be slightly larger for the thermophilic enzyme. Therefore, these results imply that the thermophilic enzyme is the more flexible of the two.
NASA Astrophysics Data System (ADS)
Yoon, J.; von Hoyningen-Huene, W.; Kokhanovsky, A. A.; Vountas, M.; Burrows, J. P.
2012-06-01
Regular aerosol observations based on well-calibrated instruments have led to a better understanding of the aerosol radiative budget on Earth. In recent years, these instruments have played an important role in the determination of the increase of anthropogenic aerosols by means of long-term studies. Only few investigations regarding long-term trends of aerosol optical characteristics (e.g. aerosol optical thickness (AOT) and Ångström exponent (ÅE)) have been derived from ground-based observations. This paper aims to derive and discuss linear trends of AOT (440, 675, 870, and 1020 nm) and ÅE (440-870 nm) using AErosol RObotic NETwork (AERONET) level 2.0 spectral observations. Additionally, temporal trends of coarse- and fine-mode dominant AOTs (CdAOT and FdAOT) have been estimated by applying an aerosol classification based on accurate ÅE and Ångström exponent difference (ÅED). In order to take into account the fact that cloud disturbance is having a significant influence on the trend analysis of aerosols, we introduce a weighted least squares regression depending on two weights: (1) monthly standard deviation (σt) and (2) number of observations per month (nt). Temporal increase of FdAOTs (440 nm) prevails over newly industrializing countries in East Asia (weighted trends; +6.23% yr-1 at Beijing) and active agricultural burning regions in South Africa (+1.89% yr-1 at Mongu). On the other hand, insignificant or negative trends for FdAOTs are detected over Western Europe (+0.25% yr-1 at Avignon and -2.29% yr-1 at Ispra) and North America (-0.52% yr-1 for GSFC and -0.01% yr-1 at MD_Science_Center). Over desert regions, both increase and decrease of CdAOTs (+3.37% yr-1 at Solar_Village and -1.18% yr-1 at Ouagadougou) are observed depending on meteorological conditions.
NASA Astrophysics Data System (ADS)
Faraoni, Valerio; Vokey, Marshall W.
2015-09-01
Basic formulae and results of glacier physics appearing in glaciology textbooks can be derived from first principles introduced in algebra-based first year physics courses. We discuss the maximum thickness of alpine glaciers and ice sheets and the relation between maximum thickness and length of an ice sheet. Knowledge of ordinary differential equations allows one to derive also the local ice thickness.
Abd-Allah, Somia H; El-Shal, Amal S; Shalaby, Sally M; Abd-Elbary, Eman; Mazen, Nehad F; Abdel Kader, Rania R
2015-09-01
We examined the effect of placenta-derived MSCs (PDMSCs) injection intraregionally and intraperitoneally on healing of induced full thickness mice skin wounds; moreover, the mechanisms by which MSCs exert their effects were also studied. Sixty female mice were divided into three groups after induction of full thickness skin wound; untreated group, wounded mice were injected with MSCs derived from human placenta intraperitoneally or intraregionally. Skin biopsies were obtained 7 and 12 days after wound incision for histological examinations, detection of vascular endothelial growth factor (VEGF) by ELISA, and estimation of expression of mouse ICAM-1, Integrin β1, Integrin β3 genes and human albumin and GAPDH genes by reverse transcription polymerase chain reaction. Human placenta derived-MSCs treated groups showed accelerated wound healing than non-treated group. VEGF, Integrin β1, and Integrin β3 levels were significantly increased in the intraregionally and intraperitoneally treated mice as compared to non-treated group at day 7 after wound induction. ICAM-1 showed significant decrease in its expression in treated groups compared with non-treated group. Interestingly, the intraperitoneal MSCs injections showed better results than intraregional one. PDMSCs accelerate full thickness skin wound healing and the intraperitoneal MSCs injections are more effective than intraregional one. MSCs promote wound healing through release of proangiogenic factors as VEGF, increase healing promoting factors as integrin β1 and β3, and decrease proinflammatory cytokines as ICAM-1.
NASA Technical Reports Server (NTRS)
Roskam, J.; Lan, C.; Mehrotra, S.
1972-01-01
The computer program used to determine the rigid and elastic stability derivatives presented in the summary report is listed in this appendix along with instructions for its use, sample input data and answers. This program represents the airplane at subsonic and supersonic speeds as (a) thin surface(s) (without dihedral) composed of discrete panels of constant pressure according to the method of Woodward for the aerodynamic effects and slender beam(s) for the structural effects. Given a set of input data, the computer program calculates an aerodynamic influence coefficient matrix and a structural influence coefficient matrix.
NASA Astrophysics Data System (ADS)
Annapureddy, Venkateswarlu; Choi, Jong-Jin; Kim, Jong-Woo; Hahn, Byung-Dong; Ahn, Cheol-Woo; Ryu, Jungho
2016-06-01
The effects of crystalline orientation on the ferroelectric properties of lead zirconate titanate (PZT) thick films deposited on (111)-oriented Pt/Ti/SiO2/Si substrates by using a modified spincoating method have been studied. The texture and the microstructure of the thick films were characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, respectively. The XRD results implied that the texture of the PZT films was sensitive to the pyrolysis conditions after spin-coating, but less dependent on the film's thickness. The texture had mainly a (111)-orientation for pyrolysis temperatures from 330 to 400 °C, and changes in the (100)- orientation occurred for pyrolysis temperatures at or above 450 °C after annealing at 650 °C for 5 min. The formation of a preferred texture could be explained by using the intermetallic phases and the internal stress energies between the substrate and the film. The ferroelectric properties of the PZT films fabricated by using this method have been found to be enhanced as compared to those of the PZT films fabricated by using the conventional spin-coating method and to be correlated to the microstructure of the film.
Micromechanics of intraply hybrid composites: Elastic and thermal properties
NASA Technical Reports Server (NTRS)
Chamis, C. C.; Sinclair, J. H.
1979-01-01
Composite micromechanics are used to derive equations for predicting the elastic and thermal properties of unidirectional intraply hybrid composites. The results predicted using these equations are compared with those predicted using approximate equations based on the rule of mixtures, linear laminate theory, finite element analysis and limited experimental data. The comparisons for three different intraply hybrids indicate that all four methods predict approximately the same elastic properties and are in good agreement with measured data. The micromechanics equations and linear laminate theory predict about the same values for thermal expansion coefficients. The micromechanics equations predict through-the-thickness properties which are in good agreement with the finite element results.
NASA Astrophysics Data System (ADS)
Wiendartun, Syarif, Dani Gustaman
2010-10-01
Fabrication of CuFe2O4 thick film ceramics utilizing Fe2O3 derived from yarosite using screen printing technique for NTC thermistor has been carried out. Effect of thickness variation due to different size of screen (screen 225; 300 and 375 mesh) has been studied. X-ray diffraction analyses (XRD) was done to know crystal structure and phases formation. SEM analyses was carried out to know microstructure of the films. Electrical properties characterization was done through measurement of electrical resistance at various temperatures (room temperature to 100° C). The XRD data showed that the films crystalize in tetragonal spinel. The SEM images showed that the screen with the smaller of the hole size, made the grain size was bigger. Electrical data showed that the larger the screen different size thickness variation (mesh), the larger the resistance, thermistor constant and sensitivity. From the electrical characteristics data, it was known that the electrical characteristics of the CuFe2O4 thick film ceramics followed the NTC characteristic. The value of B and RRT of the produced CuFe2O4 ceramics namely B = 3241-3484 K and RRT = 25.6-87.0 M Ohm, fitted market requirement.
Thick plate flexure. [for lithospheric models of Mars and earth
NASA Technical Reports Server (NTRS)
Comer, R. P.
1983-01-01
Analytical expressions are derived for the displacements and stresses due to loading of a floating, uniform, elastic plate of arbitrary thickness by a plane or axisymmetric harmonic load. The solution is exact except for assumptions of small strains and linear boundary conditions, and gravitation within the plate is neglected. For typical earth parameters its predictions are comparable to those of the usual thin plate theory frequently assumed in studies of lithospheric flexure, gravity and regional isostasy. Even for a very thick lithosphere, which may exist in some regions of Mars, the thin plate theory is a better approximation to the thick plate solution than the elastic half-space limit, except for short-wavelength loads.
Elastic properties of nanowires
NASA Astrophysics Data System (ADS)
da Fonseca, Alexandre F.; Malta, C. P.; Galva~O, Douglas S.
2006-05-01
We present a model to study Young's modulus and Poisson's ratio of the composite material of amorphous nanowires. It is an extension of the model derived by two of us [da Fonseca and Galva~o, Phys. Rev. Lett. 92, 175502 (2004)] to study the elastic properties of amorphous nanosprings. The model is based on twisting and tensioning a straight nanowire and we propose an experimental setup to obtain the elastic parameters of the nanowire. We used the Kirchhoff rod model to obtain the expressions for the elastic constants of the nanowire.
Bergmann, Juri; Hackl, Florian; Koyama, Taro; Aflaki, Pejman; Smith, Charlotte A.; Robson, Martin C.; Eriksson, Elof
2009-01-01
Objective: The purpose of this study was to determine whether amnion-derived cellular cytokine solution (ACCS) could improve the quality of epithelialization and accelerate closure of dermatome-created partial-thickness wounds in normal and streptozotocin-induced diabetic pigs. Methods: Dermatome-created partial-thickness wounds were sealed with wound chambers in healthy and diabetic pigs and were injected with ACCS. Wound fluid was exchanged daily for total protein concentration, and biopsies were taken on days 6, 8, 10, and 12. Epithelialization, thickness of epidermis, number of epidermal cell layers, and rete ridges were evaluated. Results: The macroscopic appearance of the wounds and speed of healing was similar in all groups at each time point. All wounds were healed by day 6. The epidermis was thicker in the ACCS-treated diabetic wounds than in the controls (140.6 μm vs 82.7 μm on day 12 in diabetic pigs). There were more cell layers (13 vs 7.7) in ACCS-treated diabetic pigs on day 12. The number of rete ridges per 2.5 mm was greater on day 12 in the ACCS-treated diabetic wounds (13 vs 8). There was also a significant increase in the number of rete ridges in ACCS-treated nondiabetic pigs but no difference in epidermal thickness or number of cell layers. Conclusion: In diabetic pigs, we found a significantly thicker epidermis and more cell layers and rete ridges in the ACCS-treated wounds. Healthy pigs showed more rete ridges but no difference in thickness of epidermis or number of cell layers on day 12. PMID:19936023
NASA Astrophysics Data System (ADS)
Nagalski, T.
2012-12-01
It is known that the estimates of the Earth's gravity field produced by the Gravity Recovery and Climate Experiment (GRACE) satellite mission can be used to infer changes in equivalent water thickness (EWT). However, inadequately smoothed GRACE satellite mission EWT data contain significant striping and thus ought to be filtered to improve signal to noise ratio. We used Stokes coefficients data from GFZ (GeoForschungsZentrum), JPL (Jet Propulsion Laboratory) and CSR (Center for Space Research), filtered by decorrelation anisotropic filters: DDK3, DDK2 and DDK1 (Kusche et al., 2009) and made available in the ICGEM (International Center for Global Earth Models). To determine gravimetric excitation function of polar motion for the entire globe or selected areas, we convert gravity coefficients into Equivalent Water Thickness fields. To eliminate stripes from the maps of the EWT, one uses anisotropic filters (Kusche et al., 2009) that are smoothing the EWT data. In this study we investigate the influence of decorrelation anisotropic DDK filters used to process the GRACE EWT fields on the determined polar motion gravimetric excitation functions. We investigate the effect of these filters for four regions: 1) entire Earth, 2) ocean area, 3) land area and 4) Tibetan Plateau area (a rectangle bounded by 4 points A(37.N,78.E), B(37.N,102.E), C(28.N,78.E), D(28.N,102.E). Stokes coefficients are made available on the ICGEM web site. The data contain spherical harmonic coefficients delivered by three research centers: CSR, GFZ, JPL. The time span of the data is 2002 - 2010. The time resolution is 30 days. The ICGEM delivers either the raw Stokes coefficients or filtered Stokes coefficients after application of the anisotropic filters. Computation were based on the following equations
NASA Astrophysics Data System (ADS)
Deming, J. W.; Ewert, M.; Bowman, J. S.
2013-12-01
The brines of polar winter sea ice are inhabited by significant densities of microbes (Bacteria and Archaea) that experience a range of extreme conditions depending on location in, and age of, the ice. Newly formed sea ice in winter expels microbes (and organic exudates) onto the surface of the ice, where they can be wicked into frost flowers or into freshly deposited snow, resulting in populations at the ice-air and air-snow interfaces characterized by even more extreme conditions. The influence of snow thickness over the ice on the fate of these microbes, and their potential for dispersal or mediation of exchanges with other components of the ice-snow system, is not well known. Examination of in situ temperature data from the Mass Balance Observatory (MBO) offshore of Barrow, Alaska, during the winter of 2011 allowed recognition of an hierarchy of fluctuation regimes in temperature and (by calculation) brine salinity, where the most stable conditions were encountered within the sea ice and the least stable highest in the snow cover, where temperature fluctuations were significantly more energetic as determined by an analysis of power spectral density. A prior analysis of snow thickness near the MBO had already revealed significant ablation events, potentially associated with bacterial mortality, that would have exposed the saline (microbe-rich) snow layer to wind-based dispersal. To better understand the survival of marine bacteria under these dynamic and extreme conditions, we conducted laboratory experiments with Arctic bacterial isolates, subjecting them to simulations of the freezing regimes documented at the MBS. The impact of the fluctuation regime was shown to be species-specific, with the organism of narrower temperature and salinity growth ranges suffering 30-50% mortality (which could be partially relieved by providing protection against salt-shock). This isolate, the psychrophilic marine bacterium Colwellia psychrerythraea strain 34H (temperature range
NASA Astrophysics Data System (ADS)
Rohan, Eduard; Naili, Salah; Lemaire, Thibault
2016-09-01
We propose a model of complex poroelastic media with periodic or locally periodic structures observed at microscopic and mesoscopic scales. Using a two-level homogenization procedure, we derive a model coherent with the Biot continuum, describing effective properties of such a hierarchically structured poroelastic medium. The effective material coefficients can be computed using characteristic responses of the micro- and mesostructures which are solutions of local problems imposed in representative volume elements describing the poroelastic medium at the two levels of heterogeneity. In the paper, we discus various combinations of the interface between the micro- and mesoscopic porosities, influence of the fluid compressibility, or solid incompressibility. Gradient of porosity is accounted for when dealing with locally periodic structures. Derived formulae for computing the poroelastic material coefficients characterize not only the steady-state responses with static fluid, but are relevant also for quasistatic problems. The model is applicable in geology, or in tissue biomechanics, in particular for modeling canalicular-lacunar porosity of bone which can be characterized at several levels.
NASA Astrophysics Data System (ADS)
Rohan, Eduard; Naili, Salah; Lemaire, Thibault
2015-09-01
We propose a model of complex poroelastic media with periodic or locally periodic structures observed at microscopic and mesoscopic scales. Using a two-level homogenization procedure, we derive a model coherent with the Biot continuum, describing effective properties of such a hierarchically structured poroelastic medium. The effective material coefficients can be computed using characteristic responses of the micro- and mesostructures which are solutions of local problems imposed in representative volume elements describing the poroelastic medium at the two levels of heterogeneity. In the paper, we discus various combinations of the interface between the micro- and mesoscopic porosities, influence of the fluid compressibility, or solid incompressibility. Gradient of porosity is accounted for when dealing with locally periodic structures. Derived formulae for computing the poroelastic material coefficients characterize not only the steady-state responses with static fluid, but are relevant also for quasistatic problems. The model is applicable in geology, or in tissue biomechanics, in particular for modeling canalicular-lacunar porosity of bone which can be characterized at several levels.
NASA Astrophysics Data System (ADS)
Tátrai, Erika; Ranganathan, Sudarshan; Ferencz, Mária; Debuc, Delia Cabrera; Somfai, Gábor Márk
2011-05-01
Purpose: To compare thickness measurements between Fourier-domain optical coherence tomography (FD-OCT) and time-domain OCT images analyzed with a custom-built OCT retinal image analysis software (OCTRIMA). Methods: Macular mapping (MM) by StratusOCT and MM5 and MM6 scanning protocols by an RTVue-100 FD-OCT device are performed on 11 subjects with no retinal pathology. Retinal thickness (RT) and the thickness of the ganglion cell complex (GCC) obtained with the MM6 protocol are compared for each early treatment diabetic retinopathy study (ETDRS)-like region with corresponding results obtained with OCTRIMA. RT results are compared by analysis of variance with Dunnett post hoc test, while GCC results are compared by paired t-test. Results: A high correlation is obtained for the RT between OCTRIMA and MM5 and MM6 protocols. In all regions, the StratusOCT provide the lowest RT values (mean difference 43 +/- 8 μm compared to OCTRIMA, and 42 +/- 14 μm compared to RTVue MM6). All RTVue GCC measurements were significantly thicker (mean difference between 6 and 12 μm) than the GCC measurements of OCTRIMA. Conclusion: High correspondence of RT measurements is obtained not only for RT but also for the segmentation of intraretinal layers between FD-OCT and StratusOCT-derived OCTRIMA analysis. However, a correction factor is required to compensate for OCT-specific differences to make measurements more comparable to any available OCT device.
Frequency dependent elastic impedance inversion for interstratified dispersive elastic parameters
NASA Astrophysics Data System (ADS)
Zong, Zhaoyun; Yin, Xingyao; Wu, Guochen
2016-08-01
The elastic impedance equation is extended to frequency dependent elastic impedance equation by taking partial derivative to frequency. With this equation as the forward solver, a practical frequency dependent elastic impedance inversion approach is presented to implement the estimation of the interstratified dispersive elastic parameters which makes full use of the frequency information of elastic impedances. Three main steps are included in this approach. Firstly, the elastic Bayesian inversion is implemented for the estimation of elastic impedances from different incident angle. Secondly, with those estimated elastic impedances, their variations are used to estimate P-wave velocity and S-wave velocity. Finally, with the prior elastic impedance and P-wave and S-wave velocity information, the frequency dependent elastic variation with incident angle inversion is presented for the estimation of the interstratified elastic parameters. With this approach, the interstratified elastic parameters rather than the interface information can be estimated, making easier the interpretation of frequency dependent seismic attributes. The model examples illustrate the feasibility and stability of the proposed method in P-wave velocity dispersion and S-wave velocity dispersion estimation. The field data example validates the possibility and efficiency in hydrocarbon indication of the estimated P-wave velocity dispersion and S-wave velocity dispersion.
Malkov, Serghei; Cawthon, Peggy M; Peters, Kathy Wilt; Cauley, Jane A; Murphy, Rachel A; Visser, Marjolein; Wilson, Joseph P; Harris, Tamara; Satterfield, Suzanne; Cummings, Steve; Shepherd, John A
2015-08-01
Mid-thigh cross-sectional muscle area (CSA), muscle attenuation, and greater trochanter soft tissue thickness have been shown to be independent risk factors of hip fracture. Our aim was to determine whether muscle and adipose tissue measures derived from dual-energy X-ray absorptiometry (DXA) scans would have a similar risk association as those measured using other imaging methods. Using a case-cohort study design, we identified 169 incident hip fracture cases over an average of 13.5 years among participants from the Health ABC Study, a prospective study of 3075 individuals initially aged 70 to 79 years. We modeled the thigh 3D geometry and compared DXA and computed tomography (CT) measures. DXA-derived thigh CSA, muscle attenuation, and subcutaneous fat thickness were found to be highly correlated to their CT counterparts (Pearson's r = 0.82, 0.45, and 0.91, respectively; p < 0.05). The fracture risk of men and women were calculated separately. We found that decreased subcutaneous fat, CT thigh muscle attenuation, and appendicular lean mass by height squared (ALM/Ht(2)) were associated with fracture risk in men; hazard ratios (HR) = 1.44 (1.02, 2.02), 1.40 (1.05, 1.85), and 0.58 (0.36, 0.91), respectively, after adjusting for age, race, clinical site, body mass index (BMI), chronic disease, hip bone mineral density (BMD), self-reported health, alcohol use, smoking status, education, physical activity, and cognitive function. In a similar model for women, only decreases in subcutaneous fat and DXA CSA were associated with hip fracture risk; HR = 1.39 (1.07, 1.82) and 0.78 (0.62, 0.97), respectively. Men with a high ALM/Ht(2) and low subcutaneous fat thickness had greater than 8 times higher risk for hip fracture compared with those with low ALM/Ht(2) and high subcutaneous fat. In women, ALM/Ht(2) did not improve the model when subcutaneous fat was included. We conclude that the DXA-derived subcutaneous fat thickness is a strong marker for hip fracture
Stamping and wrinkling of elastic plates.
Hure, Jérémy; Roman, Benoît; Bico, José
2012-08-01
We study the peculiar wrinkling pattern of an elastic plate stamped into a spherical mold. We show that the wavelength of the wrinkles decreases with their amplitude, but reaches a minimum when the amplitude is of the order of the thickness of the plate. The force required for compressing the wrinkled plate presents a maximum independent of the thickness. A model is derived and verified experimentally for a simple one-dimensional case. This model is extended to the initial situation through an effective Young modulus representing the mechanical behavior of the wrinkled state. The theoretical predictions are shown to be in good agreement with the experiments. This approach provides a complement to the "tension field theory" developed for wrinkles with unconstrained amplitude.
McCloskey, Kate; Burgner, David; Carlin, John B; Skilton, Michael R; Cheung, Michael; Dwyer, Terence; Vuillermin, Peter; Ponsonby, Anne-Louise
2016-03-01
Infant body composition and postnatal weight gain have been implicated in the development of adult obesity and cardiovascular disease, but there are limited prospective data regarding the association between infant adiposity, postnatal growth and early cardiovascular parameters. Increased aortic intima-media thickness (aortic IMT) is an intermediate phenotype of early atherosclerosis. The aim of the present study was to investigate the relationship between weight and adiposity at birth, postnatal growth and aortic IMT. The Barwon Infant Study (n=1074 mother-infant pairs) is a population-derived birth cohort. Infant weight and other anthropometry were measured at birth and 6 weeks of age. Aortic IMT was measured by trans-abdominal ultrasound at 6 weeks of age (n=835). After adjustment for aortic size and other factors, markers of adiposity including increased birth weight (β=19.9 μm/kg, 95%CI 11.1, 28.6; P<0.001) and birth skinfold thickness (β=6.9 μm/mm, 95%CI 3.3, 10.5; P<0.001) were associated with aortic IMT at 6 weeks. The association between birth skinfold thickness and aortic IMT was independent of birth weight. In addition, greater postnatal weight gain was associated with increased aortic IMT, independent of birth weight and age at time of scan (β=11.3 μm/kg increase, 95%CI 2.2, 20.3; P=0.01). Increased infant weight and adiposity at birth, as well as increased early weight gain, were positively associated with aortic IMT. Excessive accumulation of adiposity during gestation and early infancy may have adverse effects on cardiovascular risk.
McCloskey, Kate; Burgner, David; Carlin, John B; Skilton, Michael R; Cheung, Michael; Dwyer, Terence; Vuillermin, Peter; Ponsonby, Anne-Louise
2016-03-01
Infant body composition and postnatal weight gain have been implicated in the development of adult obesity and cardiovascular disease, but there are limited prospective data regarding the association between infant adiposity, postnatal growth and early cardiovascular parameters. Increased aortic intima-media thickness (aortic IMT) is an intermediate phenotype of early atherosclerosis. The aim of the present study was to investigate the relationship between weight and adiposity at birth, postnatal growth and aortic IMT. The Barwon Infant Study (n=1074 mother-infant pairs) is a population-derived birth cohort. Infant weight and other anthropometry were measured at birth and 6 weeks of age. Aortic IMT was measured by trans-abdominal ultrasound at 6 weeks of age (n=835). After adjustment for aortic size and other factors, markers of adiposity including increased birth weight (β=19.9 μm/kg, 95%CI 11.1, 28.6; P<0.001) and birth skinfold thickness (β=6.9 μm/mm, 95%CI 3.3, 10.5; P<0.001) were associated with aortic IMT at 6 weeks. The association between birth skinfold thickness and aortic IMT was independent of birth weight. In addition, greater postnatal weight gain was associated with increased aortic IMT, independent of birth weight and age at time of scan (β=11.3 μm/kg increase, 95%CI 2.2, 20.3; P=0.01). Increased infant weight and adiposity at birth, as well as increased early weight gain, were positively associated with aortic IMT. Excessive accumulation of adiposity during gestation and early infancy may have adverse effects on cardiovascular risk. PMID:26666445
Minjuan, Wu; Jun, Xiong; Shiyun, Shao; Sha, Xu; Haitao, Ni
2016-01-01
Early repair of skin injury and maximal restoration of the function and appearance have become important targets of clinical treatment. In the present study, we observed the healing process of skin defects in nude mice and structural characteristics of the new skin after transplantation of isolated and cultured adipose derived mesenchymal stem cells (ADMSCs) onto the human acellular amniotic membrane (AAM). The result showed that ADMSCs were closely attached to the surface of AAM and grew well 24 h after seeding. Comparison of the wound healing rate at days 7, 14, and 28 after transplantation showed that ADMSCs seeded on AAM facilitated the healing of full-thickness skin wounds more effectively as compared with either hAM or AAM alone, indicating that ADMSCs participated in skin regeneration. More importantly, we noticed a phenomenon of hair follicle development during the process of skin repair. Composite ADMSCs and AAM not only promoted the healing of the mouse full-thickness defects but also facilitated generation of the appendages of the affected skin, thus promoting restoration of the skin function. Our results provide a new possible therapy idea for the treatment of skin wounds with respect to both anatomical regeneration and functional restoration. PMID:27597871
Minjuan, Wu; Jun, Xiong; Shiyun, Shao; Sha, Xu; Haitao, Ni
2016-01-01
Early repair of skin injury and maximal restoration of the function and appearance have become important targets of clinical treatment. In the present study, we observed the healing process of skin defects in nude mice and structural characteristics of the new skin after transplantation of isolated and cultured adipose derived mesenchymal stem cells (ADMSCs) onto the human acellular amniotic membrane (AAM). The result showed that ADMSCs were closely attached to the surface of AAM and grew well 24 h after seeding. Comparison of the wound healing rate at days 7, 14, and 28 after transplantation showed that ADMSCs seeded on AAM facilitated the healing of full-thickness skin wounds more effectively as compared with either hAM or AAM alone, indicating that ADMSCs participated in skin regeneration. More importantly, we noticed a phenomenon of hair follicle development during the process of skin repair. Composite ADMSCs and AAM not only promoted the healing of the mouse full-thickness defects but also facilitated generation of the appendages of the affected skin, thus promoting restoration of the skin function. Our results provide a new possible therapy idea for the treatment of skin wounds with respect to both anatomical regeneration and functional restoration.
Minjuan, Wu; Jun, Xiong; Shiyun, Shao; Sha, Xu; Haitao, Ni; Yue, Wang; Kaihong, Ji
2016-01-01
Early repair of skin injury and maximal restoration of the function and appearance have become important targets of clinical treatment. In the present study, we observed the healing process of skin defects in nude mice and structural characteristics of the new skin after transplantation of isolated and cultured adipose derived mesenchymal stem cells (ADMSCs) onto the human acellular amniotic membrane (AAM). The result showed that ADMSCs were closely attached to the surface of AAM and grew well 24 h after seeding. Comparison of the wound healing rate at days 7, 14, and 28 after transplantation showed that ADMSCs seeded on AAM facilitated the healing of full-thickness skin wounds more effectively as compared with either hAM or AAM alone, indicating that ADMSCs participated in skin regeneration. More importantly, we noticed a phenomenon of hair follicle development during the process of skin repair. Composite ADMSCs and AAM not only promoted the healing of the mouse full-thickness defects but also facilitated generation of the appendages of the affected skin, thus promoting restoration of the skin function. Our results provide a new possible therapy idea for the treatment of skin wounds with respect to both anatomical regeneration and functional restoration. PMID:27597871
NASA Astrophysics Data System (ADS)
Yoon, J.; von Hoyningen-Huene, W.; Kokhanovsky, A. A.; Vountas, M.; Burrows, J. P.
2011-08-01
Regular aerosol observations based on well-calibrated instruments have led to a better understanding of the aerosol radiative budget on Earth. In recent years, these instruments have played an important role in the determination of the increase of anthropogenic aerosols by means of long-term studies. Only few investigations regarding long-term trends of aerosol optical characteristics (e.g. Aerosol Optical Thickness (AOT) and Ångström Exponent (ÅE)) have been derived from ground-based observations. This paper aims to derive and discuss linear trends of AOT (440, 675, 870, and 1020 nm) and ÅE (440-870 nm) using AErosol RObotic NETwork (AERONET) spectral observations. Additionally, temporal trends of Coarse- and Fine-mode dominant AOTs (CAOT and FAOT) have been estimated by applying an aerosol classification based on accurate ÅE and Ångström Exponent Difference (ÅED). In order to take into account the fact that cloud disturbance is having a significant influence on the trend analysis of aerosols, we introduce a weighted least squares regression depending on two weights: (1) monthly standard deviation and (2) Number of Observations (NO) per month. Temporal increase of FAOTs prevails over regions dominated by emerging economy or slash-burn agriculture in East Asia and South Africa. On the other hand, insignificant or negative trends for FAOTs are detected over Western Europe and North America. Over desert regions, both increase and decrease of CAOTs are observed depending on meteorological conditions.
Costa, A; Naranjo, J D; Turner, N J; Swinehart, I T; Kolich, B D; Shaffiey, S A; Londono, R; Keane, T J; Reing, J E; Johnson, S A; Badylak, S F
2016-11-01
The use of synthetic surgical mesh materials has been shown to decrease the incidence of hernia recurrence, but can be associated with undesirable effects such as infection, chronic discomfort, and adhesion to viscera. Surgical meshes composed of extracellular matrix (i.e., biologically-derived mesh) are an alternative to synthetic meshes and can reduce some of these undesirable effects but are less frequently used due to greater cost and perceived inadequate strength as the mesh material degrades and is replaced by host tissue. The present study assessed the temporal association between mechanical properties and degradation of biologic mesh composed of urinary bladder matrix (UBM) in a rodent model of full thickness abdominal wall defect. Mesh degradation was evaluated for non-chemically crosslinked scaffolds with the use of (14)C-radiolabeled UBM. UBM biologic mesh was 50% degraded by 26 days and was completely degraded by 90 days. The mechanical properties of the UBM biologic mesh showed a rapid initial decrease in strength and modulus that was not proportionately associated with its degradation as measured by (14)C. The loss of strength and modulus was followed by a gradual increase in these values that was associated with the deposition of new, host derived connective tissue. The strength and modulus values were comparable to or greater than those of the native abdominal wall at all time points. PMID:27619242
NASA Astrophysics Data System (ADS)
Lebedeva-Ivanova, Nina; Gaina, Carmen; Minakov, Alexander; Kashubin, Sergey
2016-04-01
We derived Moho depth and crustal thickness for the High Arctic region by 3D forward and inverse gravity modelling method in the spectral domain (Minakov et al. 2012) using lithosphere thermal gravity anomaly correction (Alvey et al., 2008); a vertical density variation for the sedimentary layer and lateral crustal variation density. Recently updated grids of bathymetry (Jakobsson et al., 2012), gravity anomaly (Gaina et al, 2011) and dynamic topography (Spasojevic & Gurnis, 2012) were used as input data for the algorithm. TeMAr sedimentary thickness grid (Petrov et al., 2013) was modified according to the most recently published seismic data, and was re-gridded and utilized as input data. Other input parameters for the algorithm were calibrated using seismic crustal scale profiles. The results are numerically compared with publically available grids of the Moho depth and crustal thickness for the High Arctic region (CRUST 1 and GEMMA global grids; the deep Arctic Ocean grids by Glebovsky et al., 2013) and seismic crustal scale profiles. The global grids provide coarser resolution of 0.5-1.0 geographic degrees and not focused on the High Arctic region. Our grids better capture all main features of the region and show smaller error in relation to the seismic crustal profiles compare to CRUST 1 and GEMMA grids. Results of 3D gravity modelling by Glebovsky et al. (2013) with separated geostructures approach show also good fit with seismic profiles; however these grids cover the deep part of the Arctic Ocean only. Alvey A, Gaina C, Kusznir NJ, Torsvik TH (2008). Integrated crustal thickness mapping and plate recon-structions for the high Arctic. Earth Planet Sci Lett 274:310-321. Gaina C, Werner SC, Saltus R, Maus S (2011). Circum-Arctic mapping project: new magnetic and gravity anomaly maps of the Arctic. Geol Soc Lond Mem 35, 39-48. Glebovsky V.Yu., Astafurova E.G., Chernykh A.A., Korneva M.A., Kaminsky V.D., Poselov V.A. (2013). Thickness of the Earth's crust in the
Elastic Solution of a Constrained FG Short Cylinder Under Axially Variable Pressure
NASA Astrophysics Data System (ADS)
Arefi, Mohammad; Mohammad-Rezaei Bidgoli, Elyas
2016-06-01
Elastic analysis of a functionally graded thick cylinder under longitudinally variable mechanical loadings is studied in the present paper. The modulus of elasticity is graded along the thickness direction based on the power law function. The cylinder is subjected to variable pressure along the longitudinal direction. First order shear deformation theory is employed for description of a two dimensional displacement field. This is due to fully constrained boundary conditions of the cylinder. An analytical approach was proposed for solution of non homogenous system of differential equations and derivation of homogenous and particular solutions. This approach has capability to model different types of loading (constant, linear and other types) along the longitudinal direction. The effect of different constant and variable loads is considered on the elastic results of FG cylinder.
Sewell, T. D.; Bedrov, D.; Menikoff, Ralph; Smith, G. D.
2001-01-01
Atomistic molecular dynamics simulations have been used to calculate isothermal elastic properties for {beta}-, {alpha}-, and {delta}-HMX. The complete elastic tensor for each polymorph was determined at room temperature and pressure via analysis of microscopic strain fluctuations using formalism due to Rahman and Parrinello [J. Chem. Phys. 76,2662 (1982)]. Additionally, the isothermal compression curve was computed for {beta}-HMX for 0 {le} p {le} 10.6 GPa; the bulk modulus K and its pressure derivative K{prime} were obtained from two fitting forms employed previously in experimental studies of the {beta}-HMX equation of state. Overall, the results indicate good agreement between the bulk modulus predicted from the measured and calculated compression curves. The bulk modulus determined directly from the elastic tensor of {beta}-HMX is in significant disagreement with the compression curve-based results. The explanation for this discrepancy is an area of current research.
Singular layers for transmission problems in thin shallow shell theory: Elastic junction case
NASA Astrophysics Data System (ADS)
Merabet, Ismail; Chacha, D. A.; Nicaise, Serge
2010-05-01
In this Note we study two-dimensional transmission problems for the linear Koiter's model of an elastic multi-structure composed of two thin shallow shells with the same thickness ɛ≪1, in the elastic junction case. We suppose that the loading is singular, that the elastic coefficients are of different order on each part ( O(ɛ) and O(1) respectively) and that the elastic stiffness coefficient of the hinge is k=O(ɛ). The formal limit problem fails to give a solution satisfying all boundary and transmission conditions; it gives only the outer solution. We derive the inner limit problem which allows us to describe the transmission layer.
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
Fulcher, G R; Farrer, M; Walker, M; Rodham, D; Clayton, B; Alberti, K M
1991-05-01
The measurement of body composition is an important part of metabolic and epidemiological research, but most currently available methods are complex and expensive. We have, therefore, compared measurements of fat mass (FM) and lean body mass (LBM), obtained using a commercially available bioelectrical impedance monitor (The Holtain Body Composition Monitor) (IMP), and by measuring skinfold thickness (SFT), with values obtained by measuring total body potassium (TBK). Twenty subjects, 10 with a body mass index (BMI) less than 30 (kg m-2), (non-obese) and 10 with BMI greater than or equal to 30 (obese) took part in the study. There was a strongly significant linear relationship between LBM calculated from TBK and that calculated from impedance (IMP), in both non-obese and obese groups analysed separately (non-obese: r = 0.92; p less than 0.001 and obese: r = 0.92; p less than 0.001) and together (all: r = 0.89; p less than 0.001). LBM calculated from TBK was strongly linearly correlated with values derived from SFT for non-obese (r = 0.91; p less than 0.001) but not for obese subjects. Mean values of LBM of non-obese subjects derived by each method were not significantly different (TBK: 51.3 +/- 10.40 kg; IMP: 53.18 +/- 10.37 kg; SFT: 48.87 +/- 9.48 kg), but significant differences existed when the subjects were obese (TBK: 51.86 +/- 9.65 kg; IMP: 58.69 +/- 8.55 kg; SFT: 67.61 +/- 8.14 kg; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
NASA Astrophysics Data System (ADS)
Chao, B. F.
2016-09-01
The equivalent water thickness (EWT, including mascon) solutions derived from the GRACE time-variable gravity (TVG) data are gaining recognition. We examine the physics of this practice from first principle in light of the non-uniqueness of 3-D gravitational inversion. We raise caveats on the indiscriminate utilization of the EWT solutions, because a surface EWT solution cannot represent an internal process in a physically meaningful way. In practice, EWT is often a good-enough representation of the reality as the predominant TVG signals do originate from surficial processes such as the water cycle, but it should be recognized that all internal geophysical processes leave signatures to different extent in the TVG observations. Treating all TVG as EWT will render physical quantities in general not directly resolvable by gravity to be misinterpreted. As the TVG observations span longer and improve in precision, the gravity itself, rather than EWT, should still be the quantity of choice. This is not just a problem of model uncertainties or numerical errors, but one in the understanding and treatment in the interest of the rigor of physics.
Brinkman, K
2009-01-08
Mixed conductive oxides are a topic of interest for applications in oxygen separation membranes as well as use in producing hydrogen fuel through the partial oxidation of methane. The oxygen flux through the membrane is governed both by the oxygen ionic conductivity as well as the material's electronic conductivity; composite membranes like Ce{sub 0.8}Gd{sub 0.2}O{sub 2-{delta}} (CGO)-CoFe{sub 2}O{sub 4} (CFO) use gadolinium doped ceria oxides as the ionic conducting material combined with cobalt iron spinel which serves as the electronic conductor. In this study we employ {approx} 50 nm sputtered CeO{sub 2} layers on the surface of porous CGO ceramic substrates which serve as solution 'blocking' layers during the thin film fabrication process facilitating the control of film thickness. Films with thickness of {approx} 2 and 4 microns were prepared by depositing 40 and 95 separate sol-gel layers respectively. Oxygen flux measurements indicated that the permeation increased with decreasing membrane thickness; thin film membrane with thickness on the micron level showed flux values an order of magnitude greater (0.03 {micro}mol/cm{sup 2} s) at 800 C as compared to 1mm thick bulk ceramic membranes (0.003 {micro}mol/cm{sup 2}).
Biodegradable stents with elastic memory.
Venkatraman, Subbu S; Tan, Lay Poh; Joso, Joe Ferry D; Boey, Yin Chiang Freddy; Wang, Xintong
2006-03-01
This work reports, for the first time, the development of a fully biodegradable polymeric stent that can self-expand at body temperatures (approximately 37 degrees C), using the concept of elastic memory. This self-expansion is necessary in fully polymeric stents, to overcome the problem of elastic recoil following balloon expansion in a body vessel. Bi-layered biodegradable stent prototypes were produced from poly-L-lactic acid (PLLA) and poly glycolic acid (PLGA) polymers. Elastic memory was imparted to the stents by temperature conditioning. The thickness and composition of each layer in the stents are critical parameters that affect the rate of self-expansion at 37 degrees C, as well as the collapse strengths of the stents. The rate of self-expansion of the stents, as measured at 37 degrees C, exhibits a maximum with layer thickness. The Tg of the outer layer is another significant parameter that affects the overall rate of expansion.
Ido, Ayumi; Nakayama, Yuki; Ishii, Kojiro; Iemitsu, Motoyuki; Sato, Koji; Fujimoto, Masahiro; Kurihara, Toshiyuki; Hamaoka, Takafumi; Satoh-Asahara, Noriko; Sanada, Kiyoshi
2015-01-01
Sarcopenia has never been diagnosed based on site-specific muscle loss, and little is known about the relationship between site-specific muscle loss and metabolic syndrome (MetS) risk factors. To this end, this cross-sectional study aimed to investigate the relationship between site-specific muscle size and MetS risk factors. Subjects were 38 obese men and women aged 40-82 years. Total body fat and lean body mass were assessed by whole-body dual-energy X-ray absorptiometry (DXA) scan. Muscle thickness (MTH) was measured using B-mode ultrasound scanning in six body regions. Subjects were classified into general obesity (GO) and sarcopenic obesity (SO) groups using the threshold values of one standard deviation below the sex-specific means of either MTH or skeletal muscle index (SMI) measured by DXA. MetS risk score was acquired by standardizing and summing the following continuously distributed variables: visceral fat area, mean blood pressure, HbA1c, and serum triglyceride / high density lipoprotein cholesterol, to obtain the Z-score. Multiple regression analysis revealed that the MetS risk score was independently associated with abdominal MTH in all subjects, but not with MTH in other muscle regions, including the thigh. Although HbA1c and the number of MetS risk factors in the SO group were significantly higher than those in the GO group, there were no significant differences between GO and SO groups as defined by SMI. Ultrasound-derived abdominal MTH would allow a better assessment of sarcopenia in obese patients and can be used as an alternative to the conventionally-used SMI measured by DXA. PMID:26700167
Casal, Carmen; Alvarez, Julio; Bezos, Javier; Quick, Harrison; Díez-Guerrier, Alberto; Romero, Beatriz; Saez, Jose L; Liandris, Emmanouil; Navarro, Alejandro; Perez, Andrés; Domínguez, Lucas; de Juan, Lucía
2015-09-01
The official technique for diagnosis of bovine tuberculosis (bTB) worldwide is the tuberculin skin test, based on the evaluation of the skin thickness increase after the intradermal inoculation of a purified protein derivative (PPD) in cattle. A number of studies performed on experimentally infected or sensitized cattle have suggested that the relative sensitivity of the cervical test (performed in the neck) may vary depending on the exact location in which the PPD is injected. However, quantitative evidence on the variation of the test accuracy associated to changes in the site of inoculation in naturally infected animals (the population in which performance of the test is most critical for disease eradication) is lacking. Here, the probability of obtaining a positive reaction (>2 or 4 millimeters and/or presence of local clinical signs) after multiple inoculations of bovine PPD in different cervical and scapular locations was assessed in animals from five bTB-infected herds (818 cattle receiving eight inoculations) using a hierarchical Bayesian logistic regression model and adjusting for the potential effect of age and sex. The effect of the inoculation site was also assessed qualitatively in animals from four officially tuberculosis free (OTF) herds (two inoculations in 210 animals and eight inoculations in 38 cattle). Although no differences in the qualitative outcome of the test were observed in cattle from OTF herds, a statistically important association between the test outcome and the inoculation site in animals from infected herds was observed, with higher probabilities of positive results when the test was performed in the neck anterior area. Our results suggest that test sensitivity may be maximized by considering the area of the neck in which the test is applied, although lack of effect of the inoculation site in the specificity of the test should be confirmed in a larger sample.
NASA Astrophysics Data System (ADS)
Zeng, S.; Cornet, C.; Parol, F.; Riedi, J.; Thieuleux, F.
2012-05-01
Cloud optical thickness (COT) is one of the most important parameter for the characterization of cloud in the Earth radiative budget. Its retrieval strongly depends on instrument characteristics and on many cloud and environment factors. Using coincident observations from POLDER/PARASOL and MODIS/AQUA in the A-train constellation, geographical distributions and seasonal changes of COT are presented, in good agreement with general cloud climatology characteristics. Retrieval uncertainties mainly associated to sensor spatial resolution, cloud inhomogeneity and microphysical assumptions are also discussed. Comparisons of COT derived from POLDER and MODIS illustrate that as the primary factor, the sensor spatial resolution impacts COT retrievals and statistics through both cloud detection and sub-pixel cloud inhomogeneity sensitivity. The uncertainties associated to cloud microphysics assumptions, namely cloud phase, particle size and shape, also impact significantly COT retrievals. For clouds with unambiguous cloud phase, strong correlations exist between the two COTs, with MODIS values comparable to POLDER ones for liquid clouds and MODIS values larger than POLDER ones for ice clouds. The large differences observed in ice phase cases are due to the use of different microphysical models in the two retrieval schemes. In cases when the two sensors disagree on cloud phase decision, COT retrieved assuming liquid phase are systematically larger. The angular biases related to specific observation geometries are also quantified and discussed in particular based on POLDER observations. Those exhibit a clear increase of COT with decreasing sun elevation and a decrease of COT in forward scattering directions due to sub-pixel inhomogeneities and shadowing effects, this especially for lower sun. It also demonstrates unrealistic COT variations in the rainbow and backward directions due to inappropriate cloud optical properties representation and an important increase of COT in the
NASA Astrophysics Data System (ADS)
Chakraborty, Abhisek; Sharma, Rashmi; Kumar, Raj; Basu, Sujit
2015-10-01
Sea surface salinity (SSS) from Aquarius mission and sea surface temperature (SST) from Advanced Very High Resolution Radiometer (AVHRR) for the years 2012-2014 are assimilated into the global Massachusetts Institute of Technology General Circulation Model (MITGCM). Investigation of the impact of assimilation of these two data sets on simulated mixed layer depth (MLD) and barrier layer thickness (BLT) forms the core of our study. The method of assimilation is the Singular Evolutive Extended Kalman (SEEK) filter. Several assimilation runs are performed. Single-parameter assimilation, as well as joint assimilation, is conducted. To begin with, the model simulated SST and SSS are compared with independent Argo observations of these two parameters. Use of latitudinally varying error variances, which is a novel feature of our study, gives rise to the significant improvement in the simulation of SSS and SST. The best result occurs when joint assimilation is performed. Afterward, simulated MLD and BLT are compared with the same parameters derived from Argo observations forming an independent validation data set. Comparisons are performed both in temporal and spatial domains. Significant positive impact of assimilation is found in all the cases studied, and joint assimilation is found to outperform single-parameter assimilation in each of the cases considered. It is found that simulations of MLD and BLT improve up to 24% and 29%, respectively, when a joint assimilation of SSS and SST is carried out.
Calcification of medial elastic fibers and aortic elasticity.
Niederhoffer, N; Lartaud-Idjouadiene, I; Giummelly, P; Duvivier, C; Peslin, R; Atkinson, J
1997-04-01
We tested the hypothesis that a simple change in wall composition (medial calcium overload of elastic fibers) can decrease aortic elasticity. Calcium overload was produced by hypervitaminosis D plus nicotine (VDN) in the young rat. Two months later, measurement of central aortic mean blood pressure in the unanesthetized, unrestrained rat showed that the VDN rat suffered from isolated systolic hypertension but that mean blood pressure was normal. Wall thickness and internal diameter determined after in situ pressurized fixation were unchanged, as was calculated wall stress. Wall stiffness was estimated from (1) elastic modulus (determined with the Moens-Korteweg equation and values for aortic pulse wave velocity in the unanesthetized, unrestrained rat and arterial dimensions) and (2) isobaric elasticity (= slope relating pulse wave velocity to mean intraluminal pressure in the phenylephrine-infused, pithed rat preparation). Both increased after VDN, and both were significantly correlated to the wall content of calcium and the elastin-specific amino acids desmosine and isodesmosine. Left ventricular hypertrophy occurred in the VDN model, and left ventricular mass was related to isobaric elasticity. In conclusion, elastocalcinosis induces destruction of elastic fibers, which leads to arterial stiffness, and the latter may be involved in the development of left ventricular hypertrophy in a normotensive model.
Constraining the Mean Crustal Thickness on Mercury
NASA Technical Reports Server (NTRS)
Nimmo, F.
2001-01-01
The topography of Mercury is poorly known, with only limited radar and stereo coverage available. However, radar profiles reveal topographic contrasts of several kilometers over wavelengths of approximately 1000 km. The bulk of Mercury's geologic activity took place within the first 1 Ga of the planet's history), and it is therefore likely that these topographic features derive from this period. On Earth, long wavelength topographic features are supported either convectively, or through some combination of isostasy and flexure. Photographic images show no evidence for plume-like features, nor for plate tectonics; I therefore assume that neither convective support nor Pratt isostasy are operating. The composition and structure of the crust of Mercury are almost unknown. The reflectance spectrum of the surface of Mercury is similar to that of the lunar highlands, which are predominantly plagioclase. Anderson et al. used the observed center-of-mass center-of-figure offset together with an assumption of Airy isostasy to infer a crustal thickness of 100-300 km. Based on tidal despinning arguments, the early elastic thickness (T(sub e)) of the (unfractured) lithosphere was approximately equal to or less than 100 km. Thrust faults with lengths of up to 500 km and ages of about 4 Ga B.P. are known to exist on Mercury. Assuming a semicircular slip distribution and a typical thrust fault angle of 10 degrees, the likely vertical depth to the base of these faults is about 45 km. More sophisticated modelling gives similar or slightly smaller answers. The depth to the base of faulting and the elastic layer are usually similar on Earth, and both are thought to be thermally controlled. Assuming that the characteristic temperature is about 750 K, the observed fault depth implies that the heat flux at 4 Ga B.P. is unlikely to be less than 20 mW m(exp -2) for a linear temperature gradient. For an elastic thickness of 45 km, topography at 1000 km wavelength is likely to be about 60
Impact of Hydration Media on Ex Vivo Corneal Elasticity Measurements
Dias, Janice; Ziebarth, Noël M.
2014-01-01
Objectives To determine the effect of hydration media on ex vivo corneal elasticity. Methods Experiments were conducted on forty porcine eyes retrieved from an abattoir (10 eyes each for PBS, BSS, Optisol, 15% Dextran). The epithelium was removed and the cornea was excised with an intact scleral rim and placed in 20% Dextran overnight to restore its physiological thickness. For each hydration media, corneas were evenly divided into two groups: one with an intact scleral rim and the other without. Corneas were mounted onto a custom chamber and immersed in a hydration medium for elasticity testing. While in each medium, corneal elasticity measurements were performed for 2 hours: at 5-minute intervals for the first 30 minutes and then 15-minute intervals for the remaining 90 minutes. Elasticity testing was performed using nanoindentation with spherical indenters and Young’s modulus was calculated using the Hertz model. Thickness measurements were taken before and after elasticity testing. Results The percentage change in corneal thickness and elasticity was calculated for each hydration media group. BSS, PBS, and Optisol showed an increase in thickness and Young’s moduli for corneas with and without an intact scleral rim. 15% Dextran exhibited a dehydrating effect on corneal thickness and provided stable maintenance of corneal elasticity for both groups. Conclusions Hydration media affects the stability of corneal thickness and elasticity measurements over time. 15% Dextran was most effective in maintaining corneal hydration and elasticity, followed by Optisol. PMID:25603443
Elastic properties of spherically anisotropic piezoelectric composites
NASA Astrophysics Data System (ADS)
Wei, En-Bo; Gu, Guo-Qing; Poon, Ying-Ming
2010-09-01
Effective elastic properties of spherically anisotropic piezoelectric composites, whose spherically anisotropic piezoelectric inclusions are embedded in an infinite non-piezoelectric matrix, are theoretically investigated. Analytical solutions for the elastic displacements and the electric potentials under a uniform external strain are derived exactly. Taking into account of the coupling effects of elasticity, permittivity and piezoelectricity, the formula is derived for estimating the effective elastic properties based on the average field theory in the dilute limit. An elastic response mechanism is revealed, in which the effective elastic properties increase as inclusion piezoelectric properties increase and inclusion dielectric properties decrease. Moreover, a piezoelectric response mechanism, of which the effective piezoelectric response vanishes due to the symmetry of spherically anisotropic composite, is also disclosed.
Elastic Properties of Mantle Minerals
NASA Astrophysics Data System (ADS)
Duffy, T. S.; Stan, C. V.
2012-12-01
clearly needed. We also show how the combination of single-crystal elasticity data and volume compression data for diopside can be used to constrain the pressure derivative of the bulk modulus -- an important parameter for modeling seismic velocities in mantle assemblages. More broadly, the mineral elasticity data set can provide insights into the systematic variation of elastic properties that are of great importance in mineral physics and geophysics. We will examine the role of anisotropy, Vp/Vs variations, pressure derivatives of elastic moduli, and auxetic behavior to name a few properties of interest. The pioneering work on mineral elasticity carried out by Bob Liebermann has made an immense contribution to this important database, as well as providing strong scientific motivation for this work.
Surface sensitivity of elastic peak electron spectroscopy
NASA Astrophysics Data System (ADS)
Jablonski, A.
2016-08-01
New theoretical model describing the sampling depth of elastic peak electron spectroscopy (EPES) has been proposed. Surface sensitivity of this technique can be generally identified with the maximum depth reached by trajectories of elastically backscattered electrons. A parameter called the penetration depth distribution function (PDDF) has been proposed for this description. Two further parameters are descendant from this definition: the mean penetration depth (MPD) and the information depth (ID). From the proposed theory, relatively simple analytical expressions describing the above parameters can be derived. Although the Monte Carlo simulations can be effectively used to estimate the sampling depth of EPES, this approach may require a considerable amount of computations. In contrast, the analytical model proposed here (AN) is very fast and provides the parameters PDDF, MPD and ID that very well compare with results of MC simulations. As follows from detailed comparisons performed for four elements (Al, Ni, Pd and Au), the AN model practically reproduced complicated emission angle dependences of the MPDs and the IDs, correctly indicating numerous maximum and minimum positions. In the energy range from 200 eV to 5 keV, the averaged percentage differences between MPDs obtained from the MC and the AN models were close to 4%. An important conclusion resulting from the present studies refers to the procedure of determination of the inelastic mean free path (IMFP) from EPES. Frequently, the analyzed sample is deposited as a thin overlayer on a smooth substrate. From an analysis of the presently obtained IDs, is follows that 99% of trajectories in analyzed experimental configurations reaches depth not exceeding 2.39 in units of IMFP. Thus, one can postulate that a safe minimum thickness of an overlayer should be larger than about 3 IMFPs. For example, the minimum thickness of an Al overlayer shoud be about 8 nm at 5000 eV.
Vibrational analysis of rectangular sandwich plates resting on some elastic point supports
Ichinomiya, Osamu; Maruyama, Koichi; Sekine, Kouji
1995-11-01
An approximate solution of forced-vibration for rectangular sandwich plate resting on some elastic point supports is presented. The sandwich plate has thin, anisotropic composite laminated faces and a thick orthotropic core. The simplified sandwich plate model is used in the analysis. The governing equation of elastically point supported rectangular sandwich plate is obtained by using the Lagrange equation. The steady state response solution to a sinusoidally varying point force is also derived. The response curves of rectangular sandwich plates having CFRP laminated faces and aluminum honeycomb core is calculated. Application examples illustrate the effects of laminate lay-up of face sheets, core material properties and core thickness ratio on the vibration characteristics of rectangular sandwich plate.
AFM Investigation of Liquid-Filled Polymer Microcapsules Elasticity.
Sarrazin, Baptiste; Tsapis, Nicolas; Mousnier, Ludivine; Taulier, Nicolas; Urbach, Wladimir; Guenoun, Patrick
2016-05-10
Elasticity of polymer microcapsules (MCs) filled with a liquid fluorinated core is studied by atomic force microscopy (AFM). Accurately characterized spherical tips are employed to obtain the Young's moduli of MCs having four different shell thicknesses. We show that those moduli are effective ones because the samples are composites. The strong decrease of the effective MC elasticity (from 3.0 to 0.1 GPa) as the shell thickness decreases (from 200 to 10 nm) is analyzed using a novel numerical approach. This model describes the evolution of the elasticity of a coated half-space according to the contact radius, the thickness of the film, and the elastic moduli of bulk materials. This numerical model is consistent with the experimental data and allows simulating the elastic behavior of MCs at high frequencies (5 MHz). While the quasi-static elasticity of the MCs is found to be very dependent on the shell thickness, the high frequency (5 MHz) elastic behavior of the core leads to a stable behavior of the MCs (from 2.5 to 3 GPa according to the shell thickness). Finally, the effect of thermal annealing on the MCs elasticity is investigated. The Young's modulus is found to decrease because of the reduction of the shell thickness due to the loss of the polymer. PMID:27058449
Loewenthal, M.; Loseke, K.; Dow, T.A.; Scattergood, R.O.
1988-12-01
Elastic emission polishing, also called elastic emission machining (EEM), is a process where a stream of abrasive slurry is used to remove material from a substrate and produce damage free surfaces with controlled surface form. It is a noncontacting method utilizing a thick elasto-hydrodynamic film formed between a soft rotating ball and the workpiece to control the flow of the abrasive. An apparatus was built in the Center, which consists of a stationary spindle, a two-axis table for the workpiece, and a pump to circulate the working fluid. The process is controlled by a programmable computer numerical controller (CNC), which presently can operate the spindle speed and movement of the workpiece in one axis only. This apparatus has been used to determine material removal rates on different material samples as a function of time, utilizing zirconium oxide (ZrO{sub 2}) particles suspended in distilled water as the working fluid. By continuing a study of removal rates the process should become predictable, and thus create a new, effective, yet simple tool for ultra-precision mechanical machining of surfaces.
NASA Astrophysics Data System (ADS)
Wang, Wenjun; Li, Peng; Jin, Feng
2016-09-01
A novel two-dimensional linear elastic theory of magneto-electro-elastic (MEE) plates, considering both surface and nonlocal effects, is established for the first time based on Hamilton’s principle and the Lee plate theory. The equations derived are more general, suitable for static and dynamic analyses, and can also be reduced to the piezoelectric, piezomagnetic, and elastic cases. As a specific application example, the influences of the surface and nonlocal effects, poling directions, piezoelectric phase materials, volume fraction, damping, and applied magnetic field (i.e., constant applied magnetic field and time-harmonic applied magnetic field) on the magnetoelectric (ME) coupling effects are first investigated based on the established two-dimensional plate theory. The results show that the ME coupling coefficient has an obvious size-dependent characteristic owing to the surface effects, and the surface effects increase the ME coupling effects significantly when the plate thickness decreases to its critical thickness. Below this critical thickness, the size-dependent effect is obvious and must be considered. In addition, the output power density of a magnetic energy nanoharvester is also evaluated using the two-dimensional plate theory obtained, with the results showing that a relatively larger output power density can be achieved at the nanoscale. This study provides a mathematical tool which can be used to analyze the mechanical properties of nanostructures theoretically and numerically, as well as evaluating the size effect qualitatively and quantitatively.
On the elastic properties of arteries.
Stephanis, C G; Mourmouras, D E; Tsagadopoulos, D G
2003-11-01
A new coefficient of elasticity is proposed that relates to the elastic state of the blood vessels. This measure is proposed as a result of the realization, from personal experience as well as from the international literature, of the difficulty in measuring the thickness of the blood vessels in vivo with acceptable precision. The measurement of E being dependent on the measurement of the thickness of the vessels becomes a highly unreliable proposition. Its relation to E (Young modulus) and to the pulse wave velocity (PWV) is established. We give three examples showing how the proposed coefficient can be measured.
NASA Astrophysics Data System (ADS)
Wang, Ying; Hao, Xihong; Yang, Jichun; Xu, Jinbao; Zhao, Diyi
2012-08-01
In this work, Pb0.97La0.02(Zr0.98Ti0.02)O3 (PLZT 2/98/2) antiferroelectric (AFE) thick films were successfully deposited on LaNiO3/Si(100) substrates by polyvinylpyrrolidone (PVP)-modified chemical solution. Each wet layer was first dried at 300 °C and then pyrolyzed at higher temperature B of 600, 650, or 700 °C, respectively. The effects of the pyrolyzed temperature B on the microstructure and the energy-storage performance of the AFE films were investigated in detail. As the increasing of the pyrolyzed temperature, the crystallized PLZT 2/98/2 films displayed a more uniform and dense surface microstructure. As a result, the dielectric properties, AFE characterization, and energy-storage performance were remarkably improved for the AFE thick films pyrolyzed at higher temperature. The maximum energy-storage density of 58.1 J/cm3 and the corresponding energy-storage efficiency of 37.3% were obtained in the PLZT 2/98/2 films pyrolyzed at 700 °C for every layer.
Variations in lithospheric thickness on Venus
NASA Technical Reports Server (NTRS)
Johnson, C. L.; Sandwell, David T.
1992-01-01
Recent analyses of Magellan data have indicated many regions exhibiting topograhic flexure. On Venus, flexure is associated predominantly with coronae and the chasmata with Aphrodite Terra. Modeling of these flexural signatures allows the elastic and mechanical thickness of the lithosphere to be estimated. In areas where the lithosphere is flexed beyond its elastic limit the saturation moment provides information on the strength of the lithosphere. Modeling of 12 flexural features on Venus has indicated lithospheric thicknesses comparable with terrestrial values. This has important implications for the venusian heat budget. Flexure of a thin elastic plate due simultaneously to a line load on a continuous plate and a bending moment applied to the end of a broken plate is considered. The mean radius and regional topographic gradient are also included in the model. Features with a large radius of curvature were selected so that a two-dimensional approximation could be used. Comparisons with an axisymmetric model were made for some features to check the validity of the two-dimensional assumption. The best-fit elastic thickness was found for each profile crossing a given flexural feature. In addition, the surface stress and bending moment at the first zero crossing of each profile were also calculated. Flexural amplitudes and elastic thicknesses obtained for 12 features vary significantly. Three examples of the model fitting procedures are discussed.
Application of nonlocal models to nano beams. Part II: Thickness length scale effect.
Kim, Jun-Sik
2014-10-01
Applicability of nonlocal models to nano-beams is discussed in terms of the Eringen's nonlocal Euler-Bernoulli (EB) beam model. In literature, most work has taken the axial coordinate derivative in the Laplacian operator presented in nonlocal elasticity. This causes that the non-locality always makes the beam soften as compared to the local counterpart. In this paper, the thickness scale effect is solely considered to investigate if the nonlocal model can simulate stiffening effect. Taking the thickness derivative in the Laplacian operator leads to the presence of a surface stress state. The governing equation derived is compared to that of the EB model with the surface stress. The results obtained reveal that the nonlocality tends to decrease the bending moment stiffness whereas to increase the bending rigidity in the governing equation. This tendency also depends on the surface conditions. PMID:25942832
Li, Xue; Xu, Chang-peng; Cui, Zhuang; Jiang, Nan; Jia, Jun-jie; Yu, Bin
2014-01-01
Objective Current medical practice for the treatment of articular cartilage lesions remains a clinical challenge due to the limited self-repair ability of articular cartilage. Both experimental and clinical researches show that moderate exercise can improve articular cartilage repair process. However, optimal timing of moderate exercise is unclear. We aimed to evaluate the effect of timing of moderate treadmill exercise on repair of full-thickness defects of articular cartilage. Design Full-thickness cartilage defects were drilled in the patellar groove of bilateral femoral condyles in a total of 40 male SD rats before they were randomly assigned into four even groups. In sedentary control (SED) group, no exercise was given; in 2-week (2W), 4-week (4W) and 8-week groups, moderate treadmill exercise was initiated respectively two, four and eight weeks after operation. Half of the animals were sacrificed at week 10 after operation and half at week 14 after operation. Femoral condyles were harvested for gross observation and histochemical measurement by O'Driscoll scoring system. Collagen type II was detected by immunohistochemistry and mRNA expressions of aggrecan and collagen type II cartilage by RT-PCR. Results Both 10 and 14 weeks post-operation, the best results were observed in 4W group and the worst results appeared in 2W group. The histochemistry scores and the expressions of collagen type II and aggrecan were significantly higher in 4W group than that in other three groups (P<0.05). Conclusions Moderate exercise at a selected timing (approximately 4 weeks) after injury can significantly promote the healing of cartilage defects but may hamper the repair process if performed too early while delayed intervention by moderate exercise may reduce its benefits in repair of the defects. PMID:24595327
Applications of film thickness equations
NASA Technical Reports Server (NTRS)
Hamrock, B. J.; Dowson, D.
1983-01-01
A number of applications of elastohydrodynamic film thickness expressions were considered. The motion of a steel ball over steel surfaces presenting varying degrees of conformity was examined. The equation for minimum film thickness in elliptical conjunctions under elastohydrodynamic conditions was applied to roller and ball bearings. An involute gear was also introduced, it was again found that the elliptical conjunction expression yielded a conservative estimate of the minimum film thickness. Continuously variable-speed drives like the Perbury gear, which present truly elliptical elastohydrodynamic conjunctions, are favored increasingly in mobile and static machinery. A representative elastohydrodynamic condition for this class of machinery is considered for power transmission equipment. The possibility of elastohydrodynamic films of water or oil forming between locomotive wheels and rails is examined. The important subject of traction on the railways is attracting considerable attention in various countries at the present time. The final example of a synovial joint introduced the equation developed for isoviscous-elastic regimes of lubrication.
NASA Astrophysics Data System (ADS)
Ansari, Reza; Torabi, Jalal
2016-06-01
Based on the nonlocal elasticity theory, the vibration behavior of circular double-layered graphene sheets (DLGSs) resting on the Winkler- and Pasternak-type elastic foundations in a thermal environment is investigated. The governing equation is derived on the basis of Eringen's nonlocal elasticity and the classical plate theory (CLPT). The initial thermal loading is assumed to be due to a uniform temperature rise throughout the thickness direction. Using the generalized differential quadrature (GDQ) method and periodic differential operators in radial and circumferential directions, respectively, the governing equation is discretized. DLGSs with clamped and simply-supported boundary conditions are studied and the influence of van der Waals (vdW) interaction forces is taken into account. In the numerical results, the effects of various parameters such as elastic medium coefficients, radius-to-thickness ratio, thermal loading and nonlocal parameter are examined on both in-phase and anti-phase natural frequencies. The results show that the thermal load and elastic foundation respectively decreases and increases the fundamental frequencies of DLGSs.
Kahl, W.K.
1997-03-01
The paper describes a study which attempted to extrapolate meaningful elastic-plastic fracture toughness data from flexure tests of a chemical vapor-infiltrated SiC/Nicalon fiber-reinforced ceramic matrix composite. Fibers in the fabricated composites were pre-coated with pyrolytic carbon to varying thicknesses. In the tests, crack length was not measured and the study employed an estimate procedure, previously used successfully for ductile metals, to derive J-R curve information. Results are presented in normalized load vs. normalized displacements and comparative J{sub Ic} behavior as a function of fiber precoating thickness.
Figueroa-Vega, Nicté; Moreno-Frías, Carmen; Malacara, Juan Manuel
2015-01-01
Menopause, the cessation of menses, occurs with estrogens decline, low-grade inflammation, and impaired endothelial function, contributing to atherosclerotic risk. Intima-media thickness (IMT) is an early subclinical biomarker of atherosclerosis. Inflammation may have a role on symptoms: hot flashes, anxiety, and depressive mood, which also are related to endothelial dysfunction, increased IMT and cardiovascular risk. In this study we compared several inflammatory markers in early vs. late postmenopausal women and studied the association of IMT and symptoms with these markers in the full sample. In a cross-sectional design including 60 women (53.1±4.4 years old) at early and late postmenopause, we evaluated the expression of CD62L, ICAM-1, PSGL-1, CD11b, CD11c, and IL-8R on PBMC by flow cytometry. Serum soluble ICAM-1, sVCAM-1, sCD62E, sCD62P, CXCL8, IL-1β, IL-6, and TNF-α levels were quantified by ELISA. Plasma levels of microparticles (MPs) were determined by FACS. Finally, carotid intima-media thickness (IMT) was measured by ultrasound. We observed that ICAM-1 expression by lymphocytes and serum sVCAM-1 levels were augmented at late postmenopause. Late postmenopause women with severe hot flashes had increased expression of CD62L and IL-8R on neutrophils. By multivariate analysis, the carotid IMT was strongly associated with membrane-bound TNF-α, CD11b expression, Annexin V+ CD3+ MPs, LPS-induced NO production, HDL-cholesterol and age. Depressive mood was associated negatively with PSGL-1 and positively with LPS-induced NO. Finally, Log(AMH) levels were associated with carotid IMT, IL-8R expression and time since menopause. IMT and depressive mood were the main clinical features related to vascular inflammation. Aging, hormonal changes and obesity were also related to endothelial dysfunction. These findings provide further evidence for a link between estrogen deficiency and low-grade inflammation in endothelial impairment in mature women. PMID:25993480
Figueroa-Vega, Nicté; Moreno-Frías, Carmen; Malacara, Juan Manuel
2015-01-01
Menopause, the cessation of menses, occurs with estrogens decline, low-grade inflammation, and impaired endothelial function, contributing to atherosclerotic risk. Intima-media thickness (IMT) is an early subclinical biomarker of atherosclerosis. Inflammation may have a role on symptoms: hot flashes, anxiety, and depressive mood, which also are related to endothelial dysfunction, increased IMT and cardiovascular risk. In this study we compared several inflammatory markers in early vs. late postmenopausal women and studied the association of IMT and symptoms with these markers in the full sample. In a cross-sectional design including 60 women (53.1 ± 4.4 years old) at early and late postmenopause, we evaluated the expression of CD62L, ICAM-1, PSGL-1, CD11b, CD11c, and IL-8R on PBMC by flow cytometry. Serum soluble ICAM-1, sVCAM-1, sCD62E, sCD62P, CXCL8, IL-1β, IL-6, and TNF-α levels were quantified by ELISA. Plasma levels of microparticles (MPs) were determined by FACS. Finally, carotid intima-media thickness (IMT) was measured by ultrasound. We observed that ICAM-1 expression by lymphocytes and serum sVCAM-1 levels were augmented at late postmenopause. Late postmenopause women with severe hot flashes had increased expression of CD62L and IL-8R on neutrophils. By multivariate analysis, the carotid IMT was strongly associated with membrane-bound TNF-α, CD11b expression, Annexin V(+) CD3(+) MPs, LPS-induced NO production, HDL-cholesterol and age. Depressive mood was associated negatively with PSGL-1 and positively with LPS-induced NO. Finally, Log(AMH) levels were associated with carotid IMT, IL-8R expression and time since menopause. IMT and depressive mood were the main clinical features related to vascular inflammation. Aging, hormonal changes and obesity were also related to endothelial dysfunction. These findings provide further evidence for a link between estrogen deficiency and low-grade inflammation in endothelial impairment in mature women.
Edge wrinkling in elastically supported pre-stressed incompressible isotropic plates
NASA Astrophysics Data System (ADS)
Destrade, Michel; Fu, Yibin; Nobili, Andrea
2016-09-01
The equations governing the appearance of flexural static perturbations at the edge of a semi-infinite thin elastic isotropic plate, subjected to a state of homogeneous bi-axial pre-stress, are derived and solved. The plate is incompressible and supported by a Winkler elastic foundation with, possibly, wavenumber dependence. Small perturbations superposed onto the homogeneous state of pre-stress, within the three-dimensional elasticity theory, are considered. A series expansion of the plate kinematics in the plate thickness provides a consistent expression for the second variation of the potential energy, whose minimization gives the plate governing equations. Consistency considerations supplement a constraint on the scaling of the pre-stress so that the classical Kirchhoff-Love linear theory of pre-stretched elastic plates is retrieved. Moreover, a scaling constraint for the foundation stiffness is also introduced. Edge wrinkling is investigated and compared with body wrinkling. We find that the former always precedes the latter in a state of uni-axial pre-stretch, regardless of the foundation stiffness. By contrast, a general bi-axial pre-stretch state may favour body wrinkling for moderate foundation stiffness. Wavenumber dependence significantly alters the predicted behaviour. The results may be especially relevant to modelling soft biological materials, such as skin or tissues, or stretchable organic thin-films, embedded in a compliant elastic matrix.
Elastic properties of external cortical bone in the craniofacial skeleton of the rhesus monkey.
Wang, Qian; Dechow, Paul C
2006-11-01
Knowledge of elastic properties and of their variation in the cortical bone of the craniofacial skeleton is indispensable for creating accurate finite-element models to explore the biomechanics and adaptation of the skull in primates. In this study, we measured elastic properties of the external cortex of the rhesus monkey craniofacial skeleton, using an ultrasonic technique. Twenty-eight cylindrical cortical specimens were removed from each of six craniofacial skeletons of adult Macaca mulatta. Thickness, density, and a set of longitudinal and transverse ultrasonic velocities were measured on each specimen to allow calculation of the elastic properties in three dimensions, according to equations derived from Newton's second law and Hooke's law. The axes of maximum stiffness were determined by fitting longitudinal velocities measured along the perimeter of each cortical specimen to a sinusoidal function. Results showed significant differences in elastic properties between different functional areas of the rhesus cranium, and that many sites have a consistent orientation of maximum stiffness among specimens. Overall, the cortical bones of the rhesus monkey skull can be modeled as orthotropic in many regions, and as transversely isotropic in some regions, e.g., the supraorbital region. There are differences from human crania, suggesting that structural differences in skeletal form relate to differences in cortical material properties across species. These differences also suggest that we require more comparative data on elastic properties in primate craniofacial skeletons to explore effectively the functional significance of these differences, especially when these differences are elucidated through modeling approaches, such as finite-element modeling.
Inexpensive Measurements of the Elastic Constants of Steel
ERIC Educational Resources Information Center
Scott, Bernard
1977-01-01
Describes experiments that utilize unsophisticated equipment to measure the elastic constants of thin flexible strips of material. The attainable accuracy is limited by the measurement of the material's thickness. (MLH)
Cohen, Shahar; Leshansky, Lucy; Zussman, Eyal; Burman, Michael; Srouji, Samer; Livne, Erella; Abramov, Natalie; Itskovitz-Eldor, Joseph
2010-10-01
The use of stem cells for tissue engineering (TE) encourages scientists to design new platforms in the field of regenerative and reconstructive medicine. Human embryonic stem cells (hESC) have been proposed to be an important cell source for cell-based TE applications as well as an exciting tool for investigating the fundamentals of human development. Here, we describe the efficient derivation of connective tissue progenitors (CTPs) from hESC lines and fetal tissues. The CTPs were significantly expanded and induced to generate tendon tissues in vitro, with ultrastructural characteristics and biomechanical properties typical of mature tendons. We describe a simple method for engineering tendon grafts that can successfully repair injured Achilles tendons and restore the ankle joint extension movement in mice. We also show the CTP's ability to differentiate into bone, cartilage, and fat both in vitro and in vivo. This study offers evidence for the possibility of using stem cell-derived engineered grafts to replace missing tissues, and sets a basic platform for future cell-based TE applications in the fields of orthopedics and reconstructive surgery.
NASA Astrophysics Data System (ADS)
Rejith, Pullanhiyodan Puthiyaveedu; Vidya, Sukumariamma; Thomas, Jijimon Kumbukkattu
2015-12-01
Enhancement in critical current density (Jc) and flux pinning force (Fp) in superconducting thick films of YBa2Cu3O7-δ (YBCO) added with small quantities of nanopowders of HfO2, BaHfO3 and YBa2HfO5.5, coated on YBa2ZrO5.5 substrate by dip-coating technique is reported. Critical current density measurements were done over an applied magnetic field using standard four probe technique and the results are compared with that of pure YBCO. High critical current density (Jc) of ∼4.84 MA/cm2 at 77 K in self-field was obtained for 2 wt% of YBa2HfO5.5 added YBCO. A systematic increase in Jc observed in YBCO films prepared by the addition of nano HfO2, BaHfO3 and YBa2HfO5.5, attributed to the formation of a non-reacting 'derived secondary phase' YBa2HfO5.5 (YBHO) in the YBCO matrix. YBCO-YBa2HfO5.5 composite thick films have showed eightfold increases in Jc (3.29 MA/cm2) at 77 K and 0.4 T compared to pure YBa2Cu3O7-δ film (0.37 MA/cm2), while maintaining a high transition temperature (Tc). The development of effective pinning centers in nano particle added YBCO thick film have enhanced the flux pinning force from 1.8 GN/m3 for pure YBCO to a maximum value of 13.15 GN/m3 for YBCO-YBa2HfO5.5. X-ray diffraction and energy dispersive spectroscopic analysis confirmed the presence of secondary phase, derived in the matrix.
Ohashi, Satoru; Ohnishi, Isao; Matsumoto, Takuya; Bessho, Masahiko; Matsuyama, Juntaro; Tobita, Kenji; Kaneko, Masako; Nakamura, Kozo
2012-03-01
The present study aimed to develop a method to measure three-dimensional (3-D) thickness of cartilage (Tc) at the femoral condyle using B-mode ultrasonography (US) and to clarify the feasibility of US in clinical evaluations of articular cartilage by comparing the results with 3-D measurement values using magnetic resonance imaging (MRI) and assessing repeatability. The medial surface of the right knees of two healthy male volunteers (age, 37 and 59 years) and the knees on affected side of three male patients with osteoarthritis (OA) (age, 73, 81 and 83 years) were scanned using B-mode US with the knee flexed at 120°. The range of the angle of probe rotation for the arm was 0-80° and B-mode images (total, 101 images) were acquired every 0.8°. MRI of the knees was also performed using the double echo steady-state sequence. Both US and MRI images were used to create 3-D models of medial femoral condyle articular cartilage. Tc was determined at points 1 mm apart from one another in the US model (Tc-US) and MRI model (Tc-MRI). Tc-US was compared with Tc-MRI and the repeatability of Tc-US was assessed by mean Tc in the specific region of interest of the femoral condyle. Tc-US correlated significantly with Tc-MRI both in volunteers and in OA patients (p < 0.0001 each) and coefficients of correlation were 0.976 and 0.964 for volunteers and OA patients, respectively. The coefficient of variance for mean Tc-US was 4.90%. Our results show that 3-D US measurements of femoral cartilage are reproducible and correlate strongly with MRI measurements.
Elastic waves in ice-covered ocean
NASA Astrophysics Data System (ADS)
Presnov, Dmitriy; Zhostkow, Ruslan; Gusev, Vladimir; Shurup, Andrey; Sobisevich, Alex
2014-05-01
The problem of propagation of acoustic waves in a shallow ice-covered sea is considered in frames of the mathematical model of the layered medium: ice sheet over a liquid layer (shallow sea) positioned on an elastic half-space (seabed). As the result of analytical solution the simplified dispersion equation has been derived and used for further analytical and numerical analysis. It has been shown that there are five types of waves subject to propagate in the layered model medium: flexural waves of ice-cover, Rayleigh-type wave on the boundary between elastic half-space and the liquid layer, normal modes in ice (as in waveguide), hydro-acoustic normal modes and quasi-longitudinal wave in ice plate. Variations initial conditions as well as source parameters allow obtaining solution for acoustical pressure. Field experiments with geophones, hydrophones and microphones were carried out on the Ladoga Lake (Leningrad Oblast in northwestern Russia) using small controllable explosions as source signals. The experiment has shown satisfactory agreement with theoretical results. Analysis of the dispersion equation for various parameters of the model provides an opportunity to estimate geophysical characteristics of the geophysical medium, based on the experimentally registered wave's velocities. It has been shown, that it is possible to extract valuable information from flexural and Rayleigh-type waves in the low-frequency domain of the recorded data via spatial-temporal analysis. Separate study of those waves allows measuring ice thickness (which is important because of ice melting and ecological situation in Arctic) and velocity of transverse waves in seabed (that can help to determine type of material and can be useful in mineral deposit prospecting).
Kelp, G; Tätte, T; Pikker, S; Mändar, H; Rozhin, A G; Rauwel, P; Vanetsev, A S; Gerst, A; Merisalu, M; Mäeorg, U; Natali, M; Persson, I; Kessler, V G
2016-04-01
Tin oxide is considered to be one of the most promising semiconductor oxide materials for use as a gas sensor. However, a simple route for the controllable build-up of nanostructured, sufficiently pure and hierarchical SnO2 structures for gas sensor applications is still a challenge. In the current work, an aqueous SnO2 nanoparticulate precursor sol, which is free of organic contaminants and sorbed ions and is fully stable over time, was prepared in a highly reproducible manner from an alkoxide Sn(OR)4 just by mixing it with a large excess of pure neutral water. The precursor is formed as a separate liquid phase. The structure and purity of the precursor is revealed using XRD, SAXS, EXAFS, HRTEM imaging, FTIR, and XRF analysis. An unconventional approach for the estimation of the particle size based on the quantification of the Sn-Sn contacts in the structure was developed using EXAFS spectroscopy and verified using HRTEM. To construct sensors with a hierarchical 3D structure, we employed an unusual emulsification technique not involving any additives or surfactants, using simply the extraction of the liquid phase, water, with the help of dry butanol under ambient conditions. The originally generated crystalline but yet highly reactive nanoparticles form relatively uniform spheres through self-assembly and solidify instantly. The spheres floating in butanol were left to deposit on the surface of quartz plates bearing sputtered gold electrodes, producing ready-for-use gas sensors in the form of ca. 50 μm thick sphere-based-films. The films were dried for 24 h and calcined at 300 °C in air before use. The gas sensitivity of the structures was tested in the temperature range of 150-400 °C. The materials showed a very quickly emerging and reversible (20-30 times) increase in electrical conductivity as a response to exposure to air containing 100 ppm of H2 or CO and short (10 s) recovery times when the gas flow was stopped. PMID:26960813
NASA Astrophysics Data System (ADS)
Kelp, G.; Tätte, T.; Pikker, S.; Mändar, H.; Rozhin, A. G.; Rauwel, P.; Vanetsev, A. S.; Gerst, A.; Merisalu, M.; Mäeorg, U.; Natali, M.; Persson, I.; Kessler, V. G.
2016-03-01
Tin oxide is considered to be one of the most promising semiconductor oxide materials for use as a gas sensor. However, a simple route for the controllable build-up of nanostructured, sufficiently pure and hierarchical SnO2 structures for gas sensor applications is still a challenge. In the current work, an aqueous SnO2 nanoparticulate precursor sol, which is free of organic contaminants and sorbed ions and is fully stable over time, was prepared in a highly reproducible manner from an alkoxide Sn(OR)4 just by mixing it with a large excess of pure neutral water. The precursor is formed as a separate liquid phase. The structure and purity of the precursor is revealed using XRD, SAXS, EXAFS, HRTEM imaging, FTIR, and XRF analysis. An unconventional approach for the estimation of the particle size based on the quantification of the Sn-Sn contacts in the structure was developed using EXAFS spectroscopy and verified using HRTEM. To construct sensors with a hierarchical 3D structure, we employed an unusual emulsification technique not involving any additives or surfactants, using simply the extraction of the liquid phase, water, with the help of dry butanol under ambient conditions. The originally generated crystalline but yet highly reactive nanoparticles form relatively uniform spheres through self-assembly and solidify instantly. The spheres floating in butanol were left to deposit on the surface of quartz plates bearing sputtered gold electrodes, producing ready-for-use gas sensors in the form of ca. 50 μm thick sphere-based-films. The films were dried for 24 h and calcined at 300 °C in air before use. The gas sensitivity of the structures was tested in the temperature range of 150-400 °C. The materials showed a very quickly emerging and reversible (20-30 times) increase in electrical conductivity as a response to exposure to air containing 100 ppm of H2 or CO and short (10 s) recovery times when the gas flow was stopped.Tin oxide is considered to be one of the
Acoustic Radiation Force Elasticity Imaging in Diagnostic Ultrasound
Doherty, Joshua R.; Trahey, Gregg E.; Nightingale, Kathryn R.; Palmeri, Mark L.
2013-01-01
The development of ultrasound-based elasticity imaging methods has been the focus of intense research activity since the mid-1990s. In characterizing the mechanical properties of soft tissues, these techniques image an entirely new subset of tissue properties that cannot be derived with conventional ultrasound techniques. Clinically, tissue elasticity is known to be associated with pathological condition and with the ability to image these features in vivo, elasticity imaging methods may prove to be invaluable tools for the diagnosis and/or monitoring of disease. This review focuses on ultrasound-based elasticity imaging methods that generate an acoustic radiation force to induce tissue displacements. These methods can be performed non-invasively during routine exams to provide either qualitative or quantitative metrics of tissue elasticity. A brief overview of soft tissue mechanics relevant to elasticity imaging is provided, including a derivation of acoustic radiation force, and an overview of the various acoustic radiation force elasticity imaging methods. PMID:23549529
Bending and Forced Vibration Response of a Clamped Orthotropic Thick Plate and Sandwich Panel
NASA Astrophysics Data System (ADS)
LOK, T. S.; CHENG, Q. H.
2001-08-01
A closed-form solution for the forced response of an orthotropic thick plate and sandwich panel has been developed and is presented in this paper. The paper outlines the methodology and develops the formulation to enable the solution to be derived. A novel truss-core sandwich panel is introduced and a method is outlined in which the panel is represented as an equivalent homogeneous orthotropic thick plate continuum. The 3-D dynamic finite element method is one of the most versatile developments of the 20th century. However, the software is not as accessible or as user-friendly for engineers who are not trained in such analytical tools. Therefore, alternative methods of analysis must be found, especially in the dynamic assessment of thin-walled truss-core sandwich panels. One way is to transform the sandwich structure into an equivalent homogeneous orthotropic thick plate continuum and to conduct the analysis on the equivalent model. The authors have derived the necessary elastic constants to hasten this transformation. In this paper, the derived elastic constants are used with closed-form solution to determine the bending and forced vibration response of a clamped truss-core sandwich panel, represented as a homogeneous orthotropic thick plate continuum. The Rayleigh-Ritz method is employed for the closed-form solution and the forced response is determined using Duhamel's integral. Admissible functions are taken as a series of products of beam mode-shape functions in the two orthogonal directions. The beam function in either direction is derived from the corresponding beam eigenvalue problem. Numerical examples, which include the influence of transverse shear on the response, show that the closed-form solution agrees with analytical and numerical data available in the literature and also with 3-D finite element results.
NASA Astrophysics Data System (ADS)
Spagnolie, Saverio E.; Lauga, Eric
2010-03-01
Motile eukaryotic cells propel themselves in viscous fluids by passing waves of bending deformation down their flagella. An infinitely long flagellum achieves a hydrodynamically optimal low-Reynolds number locomotion when the angle between its local tangent and the swimming direction remains constant along its length. Optimal flagella therefore adopt the shape of a helix in three dimensions (smooth) and that of a sawtooth in two dimensions (nonsmooth). Physically, biological organisms (or engineered microswimmers) must expend internal energy in order to produce the waves of deformation responsible for the motion. Here we propose a physically motivated derivation of the optimal flagellum shape. We determine analytically and numerically the shape of the flagellar wave which leads to the fastest swimming for a given appropriately defined energetic expenditure. Our novel approach is to define an energy which includes not only the work against the surrounding fluid, but also (1) the energy stored elastically in the bending of the flagellum, (2) the energy stored elastically in the internal sliding of the polymeric filaments which are responsible for the generation of the bending waves (microtubules), and (3) the viscous dissipation due to the presence of an internal fluid. This approach regularizes the optimal sawtooth shape for two-dimensional deformation at the expense of a small loss in hydrodynamic efficiency. The optimal waveforms of finite-size flagella are shown to depend on a competition between rotational motions and bending costs, and we observe a surprising bias toward half-integer wave numbers. Their final hydrodynamic efficiencies are above 6%, significantly larger than those of swimming cells, therefore indicating available room for further biological tuning.
Ji, Hongfen; Ren, Wei; Wang, Lingyan; Shi, Peng; Chen, Xiaofeng; Wu, Xiaoqing; Yao, Xi; Lau, Sien-Ting; Zhou, Qifa; Shung, K. Kirk
2011-01-01
Lead-free Na0.5Bi0.5TiO3 (NBT) ferroelectric thick films were prepared by a poly(vinylpyrrolidone) (PVP) modified sol-gel method. The NBT thick films annealed from 500°C to 750°C exhibit a perovskite structure. The relationship between annealing temperature, thickness, and electrical properties of the thick films has been investigated. The dielectric constants and remnant polarizations of the thick films increase with annealing temperature. The electrical properties of the NBT films show strong thickness dependence. As thickness increases from 1.0 to 4.8 μm, the dielectric constant of the NBT films increases from 620 to 848, whereas the dielectric loss is nearly independent of the thickness. The remnant polarization of the NBT thick films also increases with increasing thickness. The leakage current density first decreases and then increases with film thickness. PMID:21989868
Sabatelli, Lorenzo
2016-01-01
Income and price elasticity of demand quantify the responsiveness of markets to changes in income and in prices, respectively. Under the assumptions of utility maximization and preference independence (additive preferences), mathematical relationships between income elasticity values and the uncompensated own and cross price elasticity of demand are here derived using the differential approach to demand analysis. Key parameters are: the elasticity of the marginal utility of income, and the average budget share. The proposed method can be used to forecast the direct and indirect impact of price changes and of financial instruments of policy using available estimates of the income elasticity of demand. PMID:26999511
Sabatelli, Lorenzo
2016-01-01
Income and price elasticity of demand quantify the responsiveness of markets to changes in income and in prices, respectively. Under the assumptions of utility maximization and preference independence (additive preferences), mathematical relationships between income elasticity values and the uncompensated own and cross price elasticity of demand are here derived using the differential approach to demand analysis. Key parameters are: the elasticity of the marginal utility of income, and the average budget share. The proposed method can be used to forecast the direct and indirect impact of price changes and of financial instruments of policy using available estimates of the income elasticity of demand. PMID:26999511
Elasticity of a soap film junction
NASA Astrophysics Data System (ADS)
Elias, F.; Janiaud, E.; Bacri, J.-C.; Andreotti, B.
2014-03-01
We investigate the elasticity of an isolated, threefold junction of soap films (Plateau border), which displays static undulations when liquid rapidly flows into it. By analyzing the shape of the Plateau border (thickness R and transverse displacement) as a function of the liquid flow rate Q, we show experimentally and theoretically that the elasticity of the Plateau border is dominated by the bending of the soap films pulling on the Plateau border. In this asymptotic regime, the undulation wavelength obeys the scaling law ˜Q2 R-2 and the decay length ˜Q2 R-4.
Holographic measurements of fresh dry bone elasticity
NASA Astrophysics Data System (ADS)
Silvennoinen, Raimo; Nygren, Kaarlo; Karna, Markku; Karna, Kari
1992-08-01
To compare the elasticity of bones covered with soft tissue and the elasticity of defleshed and dried bones, we used sampling screws to make the surface movements of the bones visible through the soft tissue. We compared fresh and dry European moose skulls before and after skinning. External forces were focused on the skull bones through the pedicles. A high correlation in fringe orientation was observed in the case of thick bone structures with rigid interdigited sutures. We also compared compression dynamics of fresh and dry moose antler cubes.
Danilenko, D. M.; Ring, B. D.; Tarpley, J. E.; Morris, B.; Van, G. Y.; Morawiecki, A.; Callahan, W.; Goldenberg, M.; Hershenson, S.; Pierce, G. F.
1995-01-01
The topical application of recombinant growth factors such as epidermal growth factor, platelet-derived growth factor-BB homodimer (rPDGF-BB), keratinocyte growth factor (rKGF), and neu differentiation factor has resulted in significant acceleration of healing in several animal models of wound repair. In this study, we established highly reproducible and quantifiable full and deep partial thickness porcine burn models in which burns were escharectomized 4 or 5 days postburn and covered with an occlusive dressing to replicate the standard treatment in human burn patients. We then applied these growth factors to assess their efficacy on several parameters of wound repair: extracellular matrix and granulation tissue production, percent reepithelialization, and new epithelial area. In full thickness burns, only rPDGF-BB and the combination of rPDGF-BB and rKGF induced significant changes in burn repair. rPDGF-BB induced marked extracellular matrix and granulation tissue production (P = 0.013) such that the burn defect was filled within several days of escharectomy, but had no effect on new epithelial area or reepithelialization. The combination of rPDGF-BB and rKGF in full thickness burns resulted in a highly significant increase in extracellular matrix and granulation tissue area (P = 0.0009) and a significant increase in new epithelial area (P = 0.007), but had no effect on reepithelialization. In deep partial thickness burns, rKGF induced the most consistent changes. Daily application of rKGF induced a highly significant increase in new epithelial area (P < 0.0001) but induced only a modest increase in reepithelialization (83.7% rKGF-treated versus 70.2% control; P = 0.016) 12 days postburn. rKGF also doubled the number of fully reepithelialized burns (P = 0.02) at 13 days postburn, at least partially because of marked stimulation of both epidermal and follicular proliferation as assessed by proliferating cell nuclear antigen expression. In situ hybridization for
Elastic modulus of viral nanotubes
NASA Astrophysics Data System (ADS)
Zhao, Yue; Ge, Zhibin; Fang, Jiyu
2008-09-01
We report an experimental and theoretical study of the radial elasticity of tobacco mosaic virus (TMV) nanotubes. An atomic force microscope tip is used to apply small radial indentations to deform TMV nanotubes. The initial elastic response of TMV nanotubes can be described by finite-element analysis in 5nm indentation depths and Hertz theory in 1.5nm indentation depths. The derived radial Young’s modulus of TMV nanotubes is 0.92±0.15GPa from finite-element analysis and 1.0±0.2GPa from the Hertz model, which are comparable with the reported axial Young’s modulus of 1.1GPa [Falvo , Biophys. J. 72, 1396 (1997)].
NASA Technical Reports Server (NTRS)
Tessler, A.; Annett, M. S.; Gendron, G.
2001-01-01
A {1,2}-order theory for laminated composite and sandwich plates is extended to include thermoelastic effects. The theory incorporates all three-dimensional strains and stresses. Mixed-field assumptions are introduced which include linear in-plane displacements, parabolic transverse displacement and shear strains, and a cubic distribution of the transverse normal stress. Least squares strain compatibility conditions and exact traction boundary conditions are enforced to yield higher polynomial degree distributions for the transverse shear strains and transverse normal stress through the plate thickness. The principle of virtual work is used to derive a 10th-order system of equilibrium equations and associated Poisson boundary conditions. The predictive capability of the theory is demonstrated using a closed-form analytic solution for a simply-supported rectangular plate subjected to a linearly varying temperature field across the thickness. Several thin and moderately thick laminated composite and sandwich plates are analyzed. Numerical comparisons are made with corresponding solutions of the first-order shear deformation theory and three-dimensional elasticity theory. These results, which closely approximate the three-dimensional elasticity solutions, demonstrate that through - the - thickness deformations even in relatively thin and, especially in thick. composite and sandwich laminates can be significant under severe thermal gradients. The {1,2}-order kinematic assumptions insure an overall accurate theory that is in general superior and, in some cases, equivalent to the first-order theory.
Elastically Decoupling Dark Matter.
Kuflik, Eric; Perelstein, Maxim; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai
2016-06-01
We present a novel dark matter candidate, an elastically decoupling relic, which is a cold thermal relic whose present abundance is determined by the cross section of its elastic scattering on standard model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross section with electrons, photons and/or neutrinos in the 10^{-3}-1 fb range. PMID:27314712
Elastically Decoupling Dark Matter.
Kuflik, Eric; Perelstein, Maxim; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai
2016-06-01
We present a novel dark matter candidate, an elastically decoupling relic, which is a cold thermal relic whose present abundance is determined by the cross section of its elastic scattering on standard model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross section with electrons, photons and/or neutrinos in the 10^{-3}-1 fb range.
Study on the AFM Force Spectroscopy method for elastic modulus measurement of living cells
NASA Astrophysics Data System (ADS)
Demichelis, A.; Pavarelli, S.; Mortati, L.; Sassi, G.; Sassi, M.
2013-09-01
The cell elasticity gives information about its pathological state and metastatic potential. The aim of this paper is to study the AFM Force Spectroscopy technique with the future goal of realizing a reference method for accurate elastic modulus measurement in the elasticity range of living cells. This biological range has not been yet explored with a metrological approach. Practical hints are given for the realization of a Sylgard elasticity scale. Systematic effects given by the sample curing thickness and nanoindenter geometry have been found with regards of the measured elastic modulus. AFM measurement reproducibility better than 20% is obtained in the entire investigated elastic modulus scale of 101 - 104 kPa.
Irrigation water demand: A meta-analysis of price elasticities
NASA Astrophysics Data System (ADS)
Scheierling, Susanne M.; Loomis, John B.; Young, Robert A.
2006-01-01
Metaregression models are estimated to investigate sources of variation in empirical estimates of the price elasticity of irrigation water demand. Elasticity estimates are drawn from 24 studies reported in the United States since 1963, including mathematical programming, field experiments, and econometric studies. The mean price elasticity is 0.48. Long-run elasticities, those that are most useful for policy purposes, are likely larger than the mean estimate. Empirical results suggest that estimates may be more elastic if they are derived from mathematical programming or econometric studies and calculated at a higher irrigation water price. Less elastic estimates are found to be derived from models based on field experiments and in the presence of high-valued crops.
Peng, Qing; De, Suvranu
2014-10-21
Silicane is a fully hydrogenated silicene-a counterpart of graphene-having promising applications in hydrogen storage with capacities larger than 6 wt%. Knowledge of its elastic limit is critical in its applications as well as tailoring its electronic properties by strain. Here we investigate the mechanical response of silicane to various strains using first-principles calculations based on density functional theory. We illustrate that non-linear elastic behavior is prominent in two-dimensional nanomaterials as opposed to bulk materials. The elastic limits defined by ultimate tensile strains are 0.22, 0.28, and 0.25 along armchair, zigzag, and biaxial directions, respectively, an increase of 29%, 33%, and 24% respectively in reference to silicene. The in-plane stiffness and Poisson ratio are reduced by a factor of 16% and 26%, respectively. However, hydrogenation/dehydrogenation has little effect on its ultimate tensile strengths. We obtained high order elastic constants for a rigorous continuum description of the nonlinear elastic response. The limitation of second, third, fourth, and fifth order elastic constants are in the strain range of 0.02, 0.08, and 0.13, and 0.21, respectively. The pressure effect on the second order elastic constants and Poisson's ratio were predicted from the third order elastic constants. Our results could provide a safe guide for promising applications and strain-engineering the functions and properties of silicane monolayers. PMID:25190587
Elastic properties of minerals
Aleksandrov, K.S.; Prodaivoda, G.T.
1993-09-01
Investigations of the elastic properties of the main rock-forming minerals were begun by T.V. Ryzhova and K.S. Aleksandrov over 30 years ago on the initiative of B.P. Belikov. At the time, information on the elasticity of single crystals in general, and especially of minerals, was very scanty. In the surveys of that time there was information on the elasticity of 20 or 30 minerals. These, as a rule, did not include the main rock-forming minerals; silicates were represented only by garnets, quartz, topaz, tourmaline, zircon, beryl, and staurolite, which are often found in nature in the form of large and fairly high-quality crystals. Then and even much later it was still necessary to prove a supposition which now seems obvious: The elastic properties of rocks, and hence the velocities of elastic (seismic) waves in the earth`s crust, are primarily determined by the elastic characteristics of the minerals composing these rocks. Proof of this assertion, with rare exceptions of mono-mineralic rocks (marble, quartzite, etc.) cannot be obtained without information on the elasticities of a sufficiently large number of minerals, primarily framework, layer, and chain silicates which constitute the basis of most rocks. This also served as the starting point and main problem of the undertakings of Aleksandrov, Ryzhova, and Belikov - systematic investigations of the elastic properties of minerals and then of various rocks. 108 refs., 7 tabs.
NASA Astrophysics Data System (ADS)
Davis, R. O.; Selvadurai, A. P. S.
1996-04-01
This book concisely examines the use of elasticity in solving geotechnical engineering problems. In a highly illustrated and user-friendly format, it provides a thorough grounding in the linear theory of elasticity and an understanding of the applications. The first two chapters present a basic framework of the theory of elasticity and describe test procedures for the determination of elastic parameters for soils. Chapters 3 and 4 present the fundamental solutions of Boussinesque, Kelvin, and Mindlin, and use these to formulate solutions to problems of practical interest in geotechnical engineering. The book concludes with a sequence of appendices designed to provide the interested student with details of elasticity theory that are peripheral to the main text. Each chapter concludes with a set of questions for the student to answer. The book is appropriate for upper level students in civil engineering and engineering geology.
Foiret, Josquin; Minonzio, Jean-Gabriel; Chappard, Christine; Talmant, Maryline; Laugier, Pascal
2014-09-01
This paper reports for the first time on inverse estimation of several bone properties from guided-wave measurements in human bone samples. Previously, related approaches have focused on ultrasonic estimation of a single bone property at a time. The method is based on two steps: the multi-Lamb mode response is analyzed using the singular value decomposition signal processing method recently introduced in the field, then an identification procedure is run to find thickness and anisotropic elastic properties of the considered specimen. Prior to the measurements on bone, the method is validated on cortical bone-mimicking phantoms. The repeatability and the trueness of the estimated parameters on bone-mimicking phantoms were found around a few percent. Estimation of cortical thickness on bone samples was in good agreement with cortical thickness derived from high-resolution peripheral quantitative computed tomography data analysis of the samples.
Transparent material thickness measurements by Raman scattering.
Pershin, Sergey M; Lednev, Vasily N; Yulmetov, Renat N; Klinkov, Vladimir K; Bunkin, Alexey F
2015-07-01
An efficient and simple and convenient technique for transparent samples thickness measurements by Raman spectroscopy is suggested. The elastic scattering can be effectively used for sample border indication if the refractive index changes more than 3%, while it fails to detect an ice-to-water border of floating ice. The alternative is to use Raman spectroscopy to detect the interface between different layers of transparent materials. The difference between the Raman spectra of poly methyl methacrylate (PMMA) and water, and between ice and liquid water were employed to locate the PMMA-water and ice-water interfaces, while elastic scattering was used for air-solid surface detection. This approach yields an error of 2%-5% indicating that it is promising to express a remote and noninvasive thickness measurement technique in field experiments. PMID:26193136
Elastic Gauge Fields in Weyl Semimetals
NASA Astrophysics Data System (ADS)
Cortijo, Alberto; Ferreiros, Yago; Landsteiner, Karl; Hernandez Vozmediano, Maria Angeles
We show that, as it happens in graphene, elastic deformations couple to the electronic degrees of freedom as pseudo gauge fields in Weyl semimetals. We derive the form of the elastic gauge fields in a tight-binding model hosting Weyl nodes and see that this vector electron-phonon coupling is chiral, providing an example of axial gauge fields in three dimensions. As an example of the new response functions that arise associated to these elastic gauge fields, we derive a non-zero phonon Hall viscosity for the neutral system at zero temperature. The axial nature of the fields provides a test of the chiral anomaly in high energy with three axial vector couplings. European Union structural funds and the Comunidad de Madrid MAD2D-CM Program (S2013/MIT-3007).
Proton Nucleus Elastic Scattering Data.
1993-08-18
Version 00 The Proton Nucleus Elastic Scattering Data file PNESD contains the numerical data and the related bibliography for the differential elastic cross sections, polarization and integral nonelastic cross sections for elastic proton-nucleus scattering.
An improved plate theory of order (1,2) for thick composite laminates
NASA Technical Reports Server (NTRS)
Tessler, A.
1992-01-01
A new (1,2)-order theory is proposed for the linear elasto-static analysis of laminated composite plates. The basic assumptions are those concerning the distribution through the laminate thickness of the displacements, transverse shear strains and the transverse normal stress, with these quantities regarded as some weighted averages of their exact elasticity theory representations. The displacement expansions are linear for the inplane components and quadratic for the transverse component, whereas the transverse shear strains and transverse normal stress are respectively quadratic and cubic through the thickness. The main distinguishing feature of the theory is that all strain and stress components are expressed in terms of the assumed displacements prior to the application of a variational principle. This is accomplished by an a priori least-square compatibility requirement for the transverse strains and by requiring exact stress boundary conditions at the top and bottom plate surfaces. Equations of equilibrium and associated Poisson boundary conditions are derived from the virtual work principle. It is shown that the theory is particularly suited for finite element discretization as it requires simple C(sup 0)- and C(sup -1)-continuous displacement interpolation fields. Analytic solutions for the problem of cylindrical bending are derived and compared with the exact elasticity solutions and those of our earlier (1,2)-order theory based on the assumed displacements and transverse strains.
Sun, Qicheng; Jin, Feng; Wang, Guangqian; Song, Shixiong; Zhang, Guohua
2015-01-01
Mesoscopic structures form in dense granular materials due to the self-organisation of the constituent particles. These structures have internal structural degrees of freedom in addition to the translational degree of freedom. The resultant granular elasticity, which exhibits intrinsic variations and inevitable relaxation, is a key quantity that accounts for macroscopic solid- or fluid-like properties and the transitions between them. In this work, we propose a potential energy landscape (PEL) with local stable basins and low elastic energy barriers to analyse the nature of granular elasticity. A function for the elastic energy density is proposed for stable states and is further calibrated with ultrasonic measurements. Fluctuations in the elastic energy due to the evolution of internal structures are proposed to describe a so-called configuration temperature Tc as a counterpart of the classical kinetic granular temperature Tk that is attributed to the translational degrees of freedom. The two granular temperatures are chosen as the state variables, and a fundamental equation is established to develop non-equilibrium thermodynamics for granular materials. Due to the relatively low elastic energy barrier in the PEL, granular elasticity relaxes more under common mechanical loadings, and a simple model based on mean-field theory is developed to account for this behaviour. PMID:25951049
Modeling and characterization of through-the-thickness properties of 3D woven composites
NASA Technical Reports Server (NTRS)
Hartranft, Dru; Pravizi-Majidi, Azar; Chou, Tsu-Wei
1995-01-01
The through-the-thickness properties of three-dimensionally (3D) woven carbon/epoxy composites have been studied. The investigation aimed at the evaluation and development of test methodologies for the property characterization in the thickness direction, and the establishment of fiber architectures were studied: layer-to-layer Angle Interlock, through-the-thickness Orthogonal woven preform with surface pile was also designed and manufactured for the fabrication of tensile test coupons with integrated grips. All the preforms were infiltrated by the resin transfer molding technique. The microstructures of the composites were characterized along the warp and fill (weft) directions to determine the degree of yarn undulations, yarn cross-sectional shapes, and microstructural dimensions. These parameters were correlated to the fiber architecture. Specimens were designed and tested for the direct measurement of the through-the-thickness tensile, compressive and shear properties of the composites. Design optimization was conducted through the analysis of the stress fields within the specimen coupled with experimental verification. The experimentally-derived elastic properties in the thickness direction compared well with analytical predictions obtained from a volume averaging model.
Localizing gravity on exotic thick 3-branes
Castillo-Felisola, Oscar; Melfo, Alejandra; Pantoja, Nelson; Ramirez, Alba
2004-11-15
We consider localization of gravity on thick branes with a nontrivial structure. Double walls that generalize the thick Randall-Sundrum solution, and asymmetric walls that arise from a Z{sub 2} symmetric scalar potential, are considered. We present a new asymmetric solution: a thick brane interpolating between two AdS{sub 5} spacetimes with different cosmological constants, which can be derived from a 'fake supergravity' superpotential, and show that it is possible to confine gravity on such branes.
Elastic membranes in confinement
NASA Astrophysics Data System (ADS)
Bostwick, Joshua; Miksis, Michael; Davis, Stephen
2014-11-01
An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and DNA, have finer internal structure in which a membrane (or elastic member) is geometrically ``confined'' by another object. We study the shape stability of elastic membranes in a ``confining'' box and introduce repulsive van der Waals forces to prevent the membrane from intersecting the wall. We aim to define the parameter space associated with mitochondria-like deformations. We compare the confined to `unconfined' solutions and show how the structure and stability of the membrane shapes changes with the system parameters.
TOPICAL REVIEW: Inverse problems in elasticity
NASA Astrophysics Data System (ADS)
Bonnet, Marc; Constantinescu, Andrei
2005-04-01
This review is devoted to some inverse problems arising in the context of linear elasticity, namely the identification of distributions of elastic moduli, model parameters or buried objects such as cracks. These inverse problems are considered mainly for three-dimensional elastic media under equilibrium or dynamical conditions, and also for thin elastic plates. The main goal is to overview some recent results, in an effort to bridge the gap between studies of a mathematical nature and problems defined from engineering practice. Accordingly, emphasis is given to formulations and solution techniques which are well suited to general-purpose numerical methods for solving elasticity problems on complex configurations, in particular the finite element method and the boundary element method. An underlying thread of the discussion is the fact that useful tools for the formulation, analysis and solution of inverse problems arising in linear elasticity, namely the reciprocity gap and the error in constitutive equation, stem from variational and virtual work principles, i.e., fundamental principles governing the mechanics of deformable solid continua. In addition, the virtual work principle is shown to be instrumental for establishing computationally efficient formulae for parameter or geometrical sensitivity, based on the adjoint solution method. Sensitivity formulae are presented for various situations, especially in connection with contact mechanics, cavity and crack shape perturbations, thus enriching the already extensive known repertoire of such results. Finally, the concept of topological derivative and its implementation for the identification of cavities or inclusions are expounded.
Mimicking the effect of gravity using an elastic membrane
NASA Astrophysics Data System (ADS)
Wu, Yecun; Zhu, Changqing; Wang, Yijun; Shi, Qingfan
2014-05-01
Comparing astrospace with an elastic membrane is an interesting analogy but it lacks a theoretical basis and experimental support. We develop a theoretical model that brings to light the relationship between the conceptual model of a gravity well and an elastic deformation equation of a membrane supporting a heavy ball, and further derive the ‘gravitational constant’ for such a small ‘elastic space’. The experimental data obtained are consistent with the prediction of our model, in mimicking the revolution of a small planet. Teaching practice shows that using an elastic membrane is a simple, intuitive and reliable method to enhance the quality of learning about the effect of gravity.
Mechanism of Resilin Elasticity
Qin, Guokui; Hu, Xiao; Cebe, Peggy; Kaplan, David L.
2012-01-01
Resilin is critical in the flight and jumping systems of insects as a polymeric rubber-like protein with outstanding elasticity. However, insight into the underlying molecular mechanisms responsible for resilin elasticity remains undefined. Here we report the structure and function of resilin from Drosophila CG15920. A reversible beta-turn transition was identified in the peptide encoded by exon III and for full length resilin during energy input and release, features that correlate to the rapid deformation of resilin during functions in vivo. Micellar structures and nano-porous patterns formed after beta-turn structures were present via changes in either the thermal or mechanical inputs. A model is proposed to explain the super elasticity and energy conversion mechanisms of resilin, providing important insight into structure-function relationships for this protein. Further, this model offers a view of elastomeric proteins in general where beta-turn related structures serve as fundamental units of the structure and elasticity. PMID:22893127
NASA Astrophysics Data System (ADS)
Quilliet, Catherine; Quemeneur, François; Marmottant, Philippe; Imhof, Arnout; Pépin-Donat, Brigitte; van Blaaderen, Alfons
2010-03-01
The deflation of elastic spherical surfaces has been numerically investigated, and show very different types of deformations according the range of elastic parameters, some of them being quantitatively explained through simple calculations. This allows to retrieve various shapes observed on hollow shells (from colloidal to centimeter scale), on lipid vesicles, or on some biological objects. The extension of this process to other geometries allows to modelize vegetal objects such as the ultrafast trap of carnivorous plants.
Stress distribution in continuously heterogeneous thick laminated pressure vessels
Verijenko, V.E.; Adali, S.; Tabakov, P.Y.
1995-11-01
Stress analysis of multilayered pressure vessels possessing cylindrical anisotropy and under internal, external and interlaminar pressure is given. The special case when the axis of anisotropy coincides with the axis of symmetry Oz and the stresses do not vary long the generator is investigated. In this case there exists a plane of elastic symmetry normal to this axis at every point of the cylinder so that each layer may be considered s orthotropic. However, elastic properties can vary through the thickness of a layer. Exact elasticity solutions are obtained for both open-ended and closed-ended cylinders using a stress function approach. The method of solution allows the forces on the layer interfaces to be taken into account with relative ease. Numerical results are presented for thick cylinders with isotropic and orthotropic layers, and stress distributions across the thickness are given.
Elastic Collisions and Gravity
NASA Astrophysics Data System (ADS)
Ball, Steven
2009-04-01
Elastic collisions are fascinating demonstrations of conservation principles. The mediating force must be conservative in an elastic collision. Truly elastic collisions take place only when the objects in collision do not touch, e.g. magnetic bumpers on low friction carts. This requires that we define a collision as a momentum transfer. Elastic collisions in 1-D can be solved in general and the implications are quite remarkable. For example, a heavy object moving initially towards a light object followed by an elastic collision results in a final velocity of the light object greater than either initial velocity. This is easily demonstrated with low friction carts. Gravitational elastic collisions involving a light spacecraft and an extremely massive body like a moon or planet can be approximated as 1-D collisions, such as the ``free return'' trajectory of Apollo 13 around the moon. The most fascinating gravitational collisions involve the gravitational slingshot effect used to boost spacecraft velocities. The maximum gravitational slingshot effect occurs when approaching a nearly 1-D collision, revealing that the spacecraft can be boosted to greater than twice the planet velocity, enabling the spacecraft to travel much further away from the Sun.
Elasticity of plagioclase feldspars
NASA Astrophysics Data System (ADS)
Brown, J. Michael; Angel, Ross J.; Ross, Nancy L.
2016-02-01
Elastic properties are reported for eight plagioclase feldspars that span compositions from albite (NaSi3AlO8) to anorthite (CaSi2Al2O8). Surface acoustic wave velocities measured using Impulsive Stimulated Light Scattering and compliance sums from high-pressure X-ray compression studies accurately determine all 21 components of the elasticity tensor for these triclinic minerals. The overall pattern of elasticity and the changes in individual elastic components with composition can be rationalized on the basis of the evolution of crystal structures and chemistry across this solid-solution join. All plagioclase feldspars have high elastic anisotropy; a* (the direction perpendicular to the b and c axes) is the softest direction by a factor of 3 in albite. From albite to anorthite the stiffness of this direction undergoes the greatest change, increasing twofold. Small discontinuities in the elastic components, inferred to occur between the three plagioclase phases with distinct symmetry (C1>¯, I1>¯, and P1>¯), appear consistent with the nature of the underlying conformation of the framework-linked tetrahedra and the associated structural changes. Measured body wave velocities of plagioclase-rich rocks, reported over the last five decades, are consistent with calculated Hill-averaged velocities using the current moduli. This confirms long-standing speculation that previously reported elastic moduli for plagioclase feldspars are systematically in error. The current results provide greater assurance that the seismic structure of the middle and lower crusts can be accurately estimated on the basis of specified mineral modes, chemistry, and fabric.
Donaldson, F E; Pankaj, P; Cooper, D M L; Thomas, C D L; Clement, J G; Simpson, A H R W
2011-06-01
Homogenized elastic properties are often assumed for macro-finite element (FE) models used in orthopaedic biomechanics. The accuracy of material property assignments may have a strong effect on the ability of these models to make accurate predictions. For cortical bone, most macro-scale FE models assume isotropic elastic material behaviour and do not include variation of material properties due to bone micro-architecture. The first aim of the present study was to evaluate the variation of apparent-level (homogenized) orthotropic elastic constants of cortical bone with age and indices of bone micro-architecture. Considerable age-dependent differences in porosity were noted across the cortical thickness in previous research. The second aim of the study was to quantify the resulting differences in elastic constants between the periosteum and endosteum. Specimens were taken from the anterior femoral midshaft of 27 female donors (age 53.4 +/- 23.6 years) and micro-FE (gFE) analysis was used to derive orthotropic elastic constants. The variation of orthotropic elastic constants (Young's moduli, shear moduli, and Poisson's ratios) with various cortical bone micro-architectural indices was investigated. The ratio of canal volume to tissue volume, Ca.V/TV, analogous to porosity, was found to be the strongest predictor (r2(ave) = 0.958) of the elastic constants. Age was less predictive (r2(ave) = 0.385) than Ca.V/TV. Elastic anisotropy increased with increasing Ca.V/TV, leading to lower elastic moduli in the transverse, typically less frequently loaded, directions. Increased Ca.V/TV led to a more substantial reduction in elastic constants at the endosteal aspect than at the periosteal aspect. The results are expected to be most applicable in similar midshaft locations of long bones; specific analysis of other sites would be necessary to evaluate elastic properties elsewhere. It was concluded that Ca.V/TV was the most predictive of cortical bone elastic constants and that
Elastic constants of Transversely Isotropically Porous (TIP) materials
Tuchinskii, L.I.; Kalimova, N.L.
1994-11-01
The authors derive formulas describing the dependence of the elastic characteristics of multicapillary materials on the capillary porosity. The investigated materials are classified as transversely isotropic, and the anisotropy in their properties is the result of the directionality of the capillary pores. Analysis of the dependences obtained has shown that the elasticity moduli of these materials may be calculated using formulas suggested for reinforced materials, in which the elastic constants of the fibers are assumed to be equal to zero. The authors derive a relation between the Poisson`s ratios and the capillary porosity.
Collis, Jon M; Frank, Scott D; Metzler, Adam M; Preston, Kimberly S
2016-05-01
Sound propagation predictions for ice-covered ocean acoustic environments do not match observational data: received levels in nature are less than expected, suggesting that the effects of the ice are substantial. Effects due to elasticity in overlying ice can be significant enough that low-shear approximations, such as effective complex density treatments, may not be appropriate. Building on recent elastic seafloor modeling developments, a range-dependent parabolic equation solution that treats the ice as an elastic medium is presented. The solution is benchmarked against a derived elastic normal mode solution for range-independent underwater acoustic propagation. Results from both solutions accurately predict plate flexural modes that propagate in the ice layer, as well as Scholte interface waves that propagate at the boundary between the water and the seafloor. The parabolic equation solution is used to model a scenario with range-dependent ice thickness and a water sound speed profile similar to those observed during the 2009 Ice Exercise (ICEX) in the Beaufort Sea. PMID:27250161
Collis, Jon M; Frank, Scott D; Metzler, Adam M; Preston, Kimberly S
2016-05-01
Sound propagation predictions for ice-covered ocean acoustic environments do not match observational data: received levels in nature are less than expected, suggesting that the effects of the ice are substantial. Effects due to elasticity in overlying ice can be significant enough that low-shear approximations, such as effective complex density treatments, may not be appropriate. Building on recent elastic seafloor modeling developments, a range-dependent parabolic equation solution that treats the ice as an elastic medium is presented. The solution is benchmarked against a derived elastic normal mode solution for range-independent underwater acoustic propagation. Results from both solutions accurately predict plate flexural modes that propagate in the ice layer, as well as Scholte interface waves that propagate at the boundary between the water and the seafloor. The parabolic equation solution is used to model a scenario with range-dependent ice thickness and a water sound speed profile similar to those observed during the 2009 Ice Exercise (ICEX) in the Beaufort Sea.
Elastic fiber-mediated enthesis in the human middle ear.
Kawase, Tetsuaki; Shibata, Shunichi; Katori, Yukio; Ohtsuka, Aiji; Murakami, Gen; Fujimiya, Mineko
2012-10-01
Adaptation to constant vibration (acoustic oscillation) is likely to confer a specific morphology at the bone-tendon and bone-ligament interfaces at the ear ossicles, which therefore represent an exciting target of enthesis research. We histologically examined (i) the bone attachments of the tensor tympani and stapedius muscles and (ii) the annular ligament of the incudostapedial joint obtained from seven elderly donated cadavers. Notably, both aldehyde-fuchsin and elastic-Masson staining demonstrated that the major fibrous component of the entheses was not collagen fibers but mature elastic fibers. The positive controls for elastic fiber staining were the arterial wall elastic laminae included in the temporal bone materials. The elastic fibers were inserted deeply into the type II collagen-poor fibrocartilage covering the ear ossicles. The muscle tendons were composed of an outer thin layer of collagen fibers and an inner thick core of elastic fibers near the malleus or stapes. In the unique elastic fiber-mediated entheses, hyaluronan, versican and fibronectin were expressed strongly along the elastic fibers. The hyaluronan seemed to act as a friction-reducing lubricant for the elastic fibers. Aggrecan was labeled strongly in a disk- or plica-like fibrous mass on the inner side of the elastic fiber-rich ligament, possibly due to compression stress from the ligament. Tenascin-c was not evident in the entheses. The elastic fiber-mediated entheses appeared resistant to tissue destruction in an environment exposed to constant vibration. The morphology was unlikely to be the result of age-related degeneration.
Elastic membranes in confinement.
Bostwick, J B; Miksis, M J; Davis, S H
2016-07-01
An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and coiled DNA, have fine internal structure in which a membrane (or elastic member) is geometrically 'confined' by another object. Here, the two-dimensional shape of an elastic membrane in a 'confining' box is studied by introducing a repulsive confinement pressure that prevents the membrane from intersecting the wall. The stage is set by contrasting confined and unconfined solutions. Continuation methods are then used to compute response diagrams, from which we identify the particular membrane mechanics that generate mitochondria-like shapes. Large confinement pressures yield complex response diagrams with secondary bifurcations and multiple turning points where modal identities may change. Regions in parameter space where such behaviour occurs are then mapped. PMID:27440257
Elastic anisotropy of crystals
NASA Astrophysics Data System (ADS)
Kube, Christopher M.
2016-09-01
An anisotropy index seeks to quantify how directionally dependent the properties of a system are. In this article, the focus is on quantifying the elastic anisotropy of crystalline materials. Previous elastic anisotropy indices are reviewed and their shortcomings discussed. A new scalar log-Euclidean anisotropy measure AL is proposed, which overcomes these deficiencies. It is based on a distance measure in a log-Euclidean space applied to fourth-rank elastic tensors. AL is an absolute measure of anisotropy where the limiting case of perfect isotropy yields zero. It is a universal measure of anisotropy applicable to all crystalline materials. Specific examples of strong anisotropy are highlighted. A supplementary material (ftp://ftp.aip.org/epaps/aip_advances/E-AAIDBI-6-041609) provides an anisotropy table giving the values of AL for 2,176 crystallite compounds.
NASA Astrophysics Data System (ADS)
Yu, Betty; Kang, Soo-Young; Akthakul, Ariya; Ramadurai, Nithin; Pilkenton, Morgan; Patel, Alpesh; Nashat, Amir; Anderson, Daniel G.; Sakamoto, Fernanda H.; Gilchrest, Barbara A.; Anderson, R. Rox; Langer, Robert
2016-08-01
We report the synthesis and application of an elastic, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific elasticity, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low strain (<40%), and that withstands elongations exceeding 250%, elastically recoiling with minimal strain-energy loss on repeated deformation. The application of XPL to the herniated lower eyelid fat pads of 12 subjects resulted in an average 2-grade decrease in herniation appearance in a 5-point severity scale. The XPL platform may offer advanced solutions to compromised skin barrier function, pharmaceutical delivery and wound dressings.
Zacharias, Mario; Paul, Indranil; Garst, Markus
2015-07-10
We discuss elastic instabilities of the atomic crystal lattice at zero temperature. Because of long-range shear forces of the solid, at such transitions the phonon velocities vanish, if at all, only along certain crystallographic directions, and, consequently, the critical phonon fluctuations are suppressed to a lower dimensional manifold and governed by a Gaussian fixed point. In the case of symmetry-breaking elastic transitions, a characteristic critical phonon thermodynamics arises that is found, e.g., to violate Debye's T(3) law for the specific heat. We point out that quantum critical elasticity is triggered whenever a critical soft mode couples linearly to the strain tensor. In particular, this is relevant for the electronic Ising-nematic quantum phase transition in a tetragonal crystal as discussed in the context of certain cuprates, ruthenates, and iron-based superconductors. PMID:26207483
Norris, Andrew N.
2014-01-01
We consider a periodic lattice structure in d=2 or 3 dimensions with unit cell comprising Z thin elastic members emanating from a similarly situated central node. A general theoretical approach provides an algebraic formula for the effective elasticity of such frameworks. The method yields the effective cubic elastic constants for three-dimensional space-filling lattices with Z=4, 6, 8, 12 and 14, the last being the ‘stiffest’ lattice proposed by Gurtner & Durand (Gurtner & Durand 2014 Proc. R. Soc. A 470, 20130611. (doi:10.1098/rspa.2013.0611)). The analytical expressions provide explicit formulae for the effective properties of pentamode materials, both isotropic and anisotropic, obtained from the general formulation in the stretch-dominated limit for Z=d+1. PMID:25484608
Yu, Betty; Kang, Soo-Young; Akthakul, Ariya; Ramadurai, Nithin; Pilkenton, Morgan; Patel, Alpesh; Nashat, Amir; Anderson, Daniel G; Sakamoto, Fernanda H; Gilchrest, Barbara A; Anderson, R Rox; Langer, Robert
2016-08-01
We report the synthesis and application of an elastic, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific elasticity, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low strain (<40%), and that withstands elongations exceeding 250%, elastically recoiling with minimal strain-energy loss on repeated deformation. The application of XPL to the herniated lower eyelid fat pads of 12 subjects resulted in an average 2-grade decrease in herniation appearance in a 5-point severity scale. The XPL platform may offer advanced solutions to compromised skin barrier function, pharmaceutical delivery and wound dressings. PMID:27159017
Peselnick, L.; Robie, R.A.
1962-01-01
The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.
Mechanics of elastic networks.
Norris, Andrew N
2014-12-01
We consider a periodic lattice structure in d=2 or 3 dimensions with unit cell comprising Z thin elastic members emanating from a similarly situated central node. A general theoretical approach provides an algebraic formula for the effective elasticity of such frameworks. The method yields the effective cubic elastic constants for three-dimensional space-filling lattices with Z=4, 6, 8, 12 and 14, the last being the 'stiffest' lattice proposed by Gurtner & Durand (Gurtner & Durand 2014 Proc. R. Soc. A470, 20130611. (doi:10.1098/rspa.2013.0611)). The analytical expressions provide explicit formulae for the effective properties of pentamode materials, both isotropic and anisotropic, obtained from the general formulation in the stretch-dominated limit for Z=d+1.
Three-dimensional elasticity solution of layered plates with viscoelastic interlayers
NASA Astrophysics Data System (ADS)
Wu, Peng; Zhou, Ding; Liu, Weiqing; Lu, Weidong; Wan, Li
2016-10-01
An analytical solution for simply supported layered plates with viscoelastic interlayers under a transverse load is proposed. The deformation of each plate layer is described by the exact three-dimensional elasticity equations. The viscoelastic property of interlayer is simulated by the generalized Maxwell model. The constitutive relation of the interlayer is simplified by the quasi-elastic approximation, which significantly simplifies the analytical process. The solution of stress and displacement fields with undetermined coefficients is derived by solving a group of ordinary differential equations. The undetermined coefficients can be efficiently deduced by using the recursive matrix technique for the plate with any number of layers. The practical convergence is observed during numerical tests. The comparison analysis indicates that the present solution has a close agreement with the finite element solution. However, the solution based on the Mindlin-Reissner hypothesis is significantly different from the present solution for thick plates. Finally, the effect of interlayer thickness on stress and displacement distributions of a five-layer plate is discussed in detail.
NASA Astrophysics Data System (ADS)
Gangodagamage, C.; Rowland, J. C.; Hubbard, S. S.; Brumby, S. P.; Liljedahl, A.; Wainwright, H. M.; Sloan, V. L.; Altmann, G.; Skurikhin, A. N.; Shelef, E.; Wilson, C. J.; Dafflon, B.; Peterson, J.; Ulrich, C.; Gibbs, A.; Tweedie, C. E.; Painter, S. L.; Wullschleger, S. D.
2014-12-01
Landscape attributes that vary with micro-topography, such as active layer thickness (ALT) in ice-wedge polygon ground, are labor-intensive to document in the field at large spatial extents, necessitating remotely sensed methods. Robust techniques to estimate ALT over large areas would improve understanding of coupled dynamics between permafrost, hydrology and landsurface processes, and improve simulations of the rate and timing of release of soil carbon from permafrost settings. In particular, it would provide critically needed data to parameterize and initialize soil property information in permafrost models and evaluate model predictions for large, complex domains. In this work, we demonstrate a new data fusion approach using high-resolution remotely sensed data for estimating cm scale ALT in a 5 km2 area of ice-wedge polygon terrain in Barrow, Alaska. We used topographic (directed distance, slope, wavelet-curvature) and spectral (NDVI) metrics derived from multisensor data obtained from LiDAR and WorldView-2 platforms to develop a simple data fusion algorithm using statistical machine learning. This algorithm was used to estimate ALT (2 m spatial resolution) across the study area. A comparison of the estimates with ground-based measurements documented the accuracy (±4.4 cm, r2=0.76) of the approach. Our findings suggest that the broad climatic variability associated with warming air temperature will govern the regional averages of ALT, but the smaller-scale variability could be controlled by local eco-hydro-geomorphic variables. This work demonstrates a path forward for mapping subsurface properties over large areas from readily available remote sensing data. Methodology of Mapping and Characterization Polygons:We convolve LiDAR elevations with multiscale wavelets and objectively chose appropriate scales to map interconnected troughs of high- and low-centered polygons. For the ice wedges where LiDAR surface expressions (troughs) are not well developed, we used
Corneal thickness in glaucoma.
De Cevallos, E; Dohlman, C H; Reinhart, W J
1976-02-01
The central corneal stromal thickness of patients with open angle glaucoma, secondary glaucoma (the majority aphakic), or a history of unilateral acute angle closure glaucoma were measured and compared with the stromal thickness of a group of normal patients. In open angle glaucoma, there was a small but significant increase in the average stromal thickness. This thickness increase was, in all likelihood, due to an abnormal function of the endothelium in this disease since the level of the intraocular pressure did not seem to be a factor. There was no correlation between stromal thickness and duration of the glaucoma or type of anti-glaucomatous medication. Most cases of secondary glaucome, controlled medically or not, had markedly increased corneal thickness, again, most likely, due to endothelial damage rather than to level of intraocular pressure. After an angle closure attack, permanent damage to the cornea was found to be rare. PMID:1247273
Relativistic elasticity of stationary fluid branes
NASA Astrophysics Data System (ADS)
Armas, Jay; Obers, Niels A.
2013-02-01
Fluid mechanics can be formulated on dynamical surfaces of arbitrary codimension embedded in a background space-time. This has been the main object of study of the blackfold approach in which the emphasis has primarily been on stationary fluid configurations. Motivated by this approach we show under certain conditions that a given stationary fluid configuration living on a dynamical surface of vanishing thickness and satisfying locally the first law of thermodynamics will behave like an elastic brane when the surface is subject to small deformations. These results, which are independent of the number of space-time dimensions and of the fluid arising from a gravitational dual, reveal the (electro)elastic character of (charged) black branes when considering extrinsic perturbations.
Acquired disorders of elastic tissue: Part II. decreased elastic tissue.
Lewis, Kevan G; Bercovitch, Lionel; Dill, Sara W; Robinson-Bostom, Leslie
2004-08-01
Elastic fibers in the extracellular matrix are integral components of dermal connective tissue. The resilience and elasticity required for normal structure and function of the skin are attributable to the network of elastic tissue. Advances in our understanding of elastic tissue physiology provide a foundation for studying the pathogenesis of elastic tissue disorders. Many acquired disorders are nevertheless poorly understood owing to the paucity of reported cases. Several acquired disorders in which loss of dermal elastic tissue produces prominent clinical and histopathologic features have recently been described, including middermal elastolysis, papular elastorrhexis, and pseudoxanthoma-like papillary dermal elastolysis, which must be differentiated from more well-known disorders such as anetoderma, acquired cutis laxa, and acrokeratoelastoidosis. Learning objective At the conclusion of this learning activity, participants should have an understanding of the similarities and differences between acquired disorders of elastic tissue that are characterized by a loss of elastic tissue.
Rucinski, R.; /Fermilab
1998-02-16
The preshower lead thickness applied to the outside of D-Zero's superconducting solenoid vacuum shell was measured at the time of application. This engineering documents those thickness measurements. The lead was ordered in sheets 0.09375-inch and 0.0625-inch thick. The tolerance on thickness was specified to be +/- 0.003-inch. The sheets all were within that thickness tolerance. The nomenclature for each sheet was designated 1T, 1B, 2T, 2B where the numeral designates it's location in the wrap and 'T' or 'B' is short for 'top' or 'bottom' half of the solenoid. Micrometer measurements were taken at six locations around the perimeter of each sheet. The width,length, and weight of each piece was then measured. Using an assumed pure lead density of 0.40974 lb/in{sup 3}, an average sheet thickness was calculated and compared to the perimeter thickness measurements. In every case, the calculated average thickness was a few mils thinner than the perimeter measurements. The ratio was constant, 0.98. This discrepancy is likely due to the assumed pure lead density. It is not felt that the perimeter is thicker than the center regions. The data suggests that the physical thickness of the sheets is uniform to +/- 0.0015-inch.
ERIC Educational Resources Information Center
Gordon, Warren B.
2006-01-01
This paper examines the elasticity of demand, and shows that geometrically, it may be interpreted as the ratio of two simple distances along the tangent line: the distance from the point on the curve to the x-intercept to the distance from the point on the curve to the y-intercept. It also shows that total revenue is maximized at the transition…
Elastic and Inelastic Collisions
ERIC Educational Resources Information Center
Gluck, Paul
2010-01-01
There have been two articles in this journal that described a pair of collision carts used to demonstrate vividly the difference between elastic and inelastic collisions. One cart had a series of washers that were mounted rigidly on a rigid wooden framework, the other had washers mounted on rubber bands stretched across a framework. The rigidly…
ERIC Educational Resources Information Center
Cocco, Alberto; Masin, Sergio Cesare
2010-01-01
Participants estimated the imagined elongation of a spring while they were imagining that a load was stretching the spring. This elongation turned out to be a multiplicative function of spring length and load weight--a cognitive law analogous to Hooke's law of elasticity. Participants also estimated the total imagined elongation of springs joined…
Hydrodynamic Elastic Magneto Plastic
1985-02-01
The HEMP code solves the conservation equations of two-dimensional elastic-plastic flow, in plane x-y coordinates or in cylindrical symmetry around the x-axis. Provisions for calculation of fixed boundaries, free surfaces, pistons, and boundary slide planes have been included, along with other special conditions.
Elastomer modulus and dielectric strength scaling with sample thickness
NASA Astrophysics Data System (ADS)
Larson, Kent
2015-04-01
Material characteristics such as adhesion and dielectric strength have well recognized dependencies on material thickness. There is disagreement, however, on the scale: the long held dictum that dielectric strength is inversely proportional to the square root of sample thickness has been shown to not always hold true for all materials, nor for all possible thickness regions. In D-EAP applications some studies have postulated a "critical thickness" below which properties show significantly less thickness dependency. While a great deal of data is available for dielectric strength, other properties are not nearly as well documented as samples get thinner. In particular, elastic modulus has been found to increase and elongation to decrease as sample thickness is lowered. This trend can be observed experimentally, but has been rarely reported and certainly does not appear in typical suppliers' product data sheets. Both published and newly generated data were used to study properties such as elastic modulus and dielectric strength vs sample thickness in silicone elastomers. Several theories are examined to explain such behavior, such as the impact of defect size and of common (but not well reported) concentration gradients that occur during elastomer curing that create micron-sized layers at the upper and lower interfaces with divergent properties to the bulk material. As Dielectric Electro-Active Polymer applications strive to lower and lower material thickness, changing mechanical properties must be recognized and taken into consideration for accurate electro-mechanical predictions of performance.
Structures and Elastic Moduli of Polymer Nanocomposite Thin Films
NASA Astrophysics Data System (ADS)
Yuan, Hongyi; Karim, Alamgir; University of Akron Team
2014-03-01
Polymeric thin films generally possess unique mechanical and thermal properties due to confinement. In this study we investigated structures and elastic moduli of polymer nanocomposite thin films, which can potentially find wide applications in diverse areas such as in coating, permeation and separation. Conventional thermoplastics (PS, PMMA) and biopolymers (PLA, PCL) were chosen as polymer matrices. Various types of nanoparticles were used including nanoclay, fullerene and functionalized inorganic particles. Samples were prepared by solvent-mixing followed by spin-coating or flow-coating. Film structures were characterized using X-ray scattering and transmission electron microscopy. Elastic moduli were measured by strain-induced elastic buckling instability for mechanical measurements (SIEBIMM), and a strengthening effect was found in certain systems due to strong interaction between polymers and nanoparticles. The effects of polymer structure, nanoparticle addition and film thickness on elastic modulus will be discussed and compared with bulk materials.
Structure and elastic properties of smectic liquid crystalline elastomer films.
Stannarius, R; Köhler, R; Dietrich, U; Lösche, M; Tolksdorf, C; Zentel, R
2002-04-01
Mechanical measurements, x-ray investigations, and optical microscopy are employed to characterize the interplay of chemical composition, network topology, and elastic response of smectic liquid crystalline elastomers (LCEs) in various mesophases. Macroscopically ordered elastomer films of submicrometer thicknesses were prepared by cross linking freely suspended smectic polymer films. The cross-linked material preserves the mesomorphism and phase transitions of the precursor polymer. The elastic response of the smectic LCE is entropic, and the corresponding elastic moduli are of the order of MPa. In the tilted ferroelectric smectic-C* phase, the network structure plays an important role. Due to the coupling of elastic network deformations to the orientation of the mesogenic groups in interlayer cross-linked materials (mesogenic cross-linker units), the stress-strain characteristics is found to differ qualitatively from that in the other phases.
Hoffheins, Barbara S.; Lauf, Robert J.
1995-01-01
A thick film hydrogen sensor element includes an essentially inert, electrically-insulating substrate having deposited thereon a thick film metallization forming at least two resistors. The metallization is a sintered composition of Pd and a sinterable binder such as glass frit. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors.
Hoffheins, B.S.; Lauf, R.J.
1995-09-19
A thick film hydrogen sensor element includes an essentially inert, electrically-insulating substrate having deposited thereon a thick film metallization forming at least two resistors. The metallization is a sintered composition of Pd and a sinterable binder such as glass frit. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors. 8 figs.
Education and "Thick" Epistemology
ERIC Educational Resources Information Center
Kotzee, Ben
2011-01-01
In this essay Ben Kotzee addresses the implications of Bernard Williams's distinction between "thick" and "thin" concepts in ethics for epistemology and for education. Kotzee holds that, as in the case of ethics, one may distinguish between "thick" and "thin" concepts of epistemology and, further, that this distinction points to the importance of…
Elastic buckling of tapered circular plates
NASA Astrophysics Data System (ADS)
Wang, C. M.; Hong, G. M.; Tan, T. J.
1995-06-01
This paper is concerned with the elastic buckling of tapered circular plates. The study is prompted by the fact that results hitherto available are restricted to a narrow range of taper parameters and are somewhat different from each other. For the buckling analysis, a simple and yet accurate numerical method is presented. It is based on the shooting method and the Rayleigh-Ritz approach. Comprehensive generic buckling results of circular plates with linearly and parabolically varying thicknesses are generated. Comparison studies of the buckling results showed that some of the existing results were erroneous. Optimal values of taper parameters for such tapered plates are also given.
On contact problems of elasticity theory
NASA Technical Reports Server (NTRS)
Kalandiya, A. I.
1986-01-01
Certain contact problems are reviewed in the two-dimensional theory of elasticity when round bodies touch without friction along most of the boundary and, therefore, Herz' hypothesis on the smallness of the contact area cannot be used. Fundamental equations were derived coinciding externally with the equation in the theory of a finite-span wing with unkown parameter. These equations are solved using Multhopp's well-known technique, and numerical calculations are performed in specific examples.
Multidimensional Contact Moduli of Elastically Anisotropic Solids
Gao, Yanfei; Pharr, George Mathews
2007-01-01
Effective moduli of elastically anisotropic solids under normal and tangential contacts are derived using the Stroh formalism and the two dimensional Fourier transform. Each Fourier component corresponds to a plane field in the plane spanned by the surface normal and a wavevector, the solution of which only involves an algebraic eigenvalue problem. Exact solutions are obtained for indenters described by parabolae of revolution, which are found to be a good approximation for arbitrary axisymmetric indenters.
Rolling Wrinkles on Elastic Substrates
NASA Astrophysics Data System (ADS)
Imburgia, Michael; Crosby, Alfred
The mechanics of rolling contact between an elastomer layer and a thin film present unique opportunities for taking advantage of elastic instabilities, such as surface wrinkling, to create patterned surfaces. Here we present a plate-to-roll(P2R) geometry to laminate a thin film onto an elastomer layer in order to induce surface wrinkling. First, a poly(dimethylsiloxane)(PDMS) layer is draped around a roller and pressed into contact with a poly(styrene)(PS) film supported on a plate. Once rolling begins, the PS film preferentially laminates onto the PDMS layer. During this process, the deformation of the PDMS layer can induce wrinkling when the contact load exceeds a critical value. Wrinkle feature size consists of amplitudes of 0 . 2 - 4 μm and wavelengths of 15 - 20 μm . Wrinkle amplitude can be controlled by contact load and roller curvature, as well as the mechanical properties and thickness of the film and elastomer. We develop semi-empirical equations to describe the effect of contact load and roller curvature on the wrinkle aspect ratio. Finite-element modeling of an elastomer layer in rolling contact with a rigid plate is used to support experimental results. Using these models, wrinkle-based technologies such as optoelectronics and enhanced adhesives can be envisioned.
Elastohydrodynamics of elliptical contacts for materials of low elastic modulus
NASA Technical Reports Server (NTRS)
Hamrock, B. J.; Dowson, D.
1983-01-01
The influence of the ellipticity parameter k and the dimensionless speed U, load W, and materials G parameters on minimum film thickness for materials of low elastic modulus was investigated. The ellipticity parameter was varied from 1 (a ball-on-plane configuration) to 12 (a configuration approaching a line contact); U and W were each varied by one order of magnitude. Seventeen cases were used to generate the minimum- and central-film-thickness relations. The influence of lubricant starvation on minimum film thickness in starved elliptical, elastohydrodynamic configurations was also investigated for materials of low elastic modulus. Lubricant starvation was studied simply by moving the inlet boundary closer to the center of the conjunction in the numerical solutions. Contour plots of pressure and film thickness in and around the contact were presented for both fully flooded and starved lubrication conditions. It is evident from these figures that the inlet pressure contours become less circular and closer to the edge of the Hertzian contact zone and that the film thickness decreases substantially as the serverity of starvation increases. The results presented reveal the essential features of both fully flooded and starved, elliptical, elastohydrodynamic conjunctions for materials of low elastic modulus.
Yong, Ee Hou; Nelson, David R; Mahadevan, L
2013-10-25
On microscopic scales, the crystallinity of flexible tethered or cross-linked membranes determines their mechanical response. We show that by controlling the type, number, and distribution of defects on a spherical elastic shell, it is possible to direct the morphology of these structures. Our numerical simulations show that by deflating a crystalline shell with defects, we can create elastic shell analogs of the classical platonic solids. These morphologies arise via a sharp buckling transition from the sphere which is strongly hysteretic in loading or unloading. We construct a minimal Landau theory for the transition using quadratic and cubic invariants of the spherical harmonic modes. Our approach suggests methods to engineer shape into soft spherical shells using a frozen defect topology.
Introduction to physical properties and elasticity models: Chapter 20
Dvorkin, Jack; Helgerud, Michael B.; Waite, William F.; Kirby, Stephen H.; Nur, Amos
2003-01-01
Estimating the in situ methane hydrate volume from seismic surveys requires knowledge of the rock physics relations between wave speeds and elastic moduli in hydrate/sediment mixtures. The elastic moduli of hydrate/sediment mixtures depend on the elastic properties of the individual sedimentary particles and the manner in which they are arranged. In this chapter, we present some rock physics data currently available from literature. The unreferenced values in Table I were not measured directly, but were derived from other values in Tables I and II using standard relationships between elastic properties for homogeneous, isotropic material. These derivations allow us to extend the list of physical property estimates, but at the expense of introducing uncertainties due to combining property values measured under different physical conditions. This is most apparent in the case of structure II (sII) hydrate for which very few physical properties have been measured under identical conditions.
Three-dimensional collapse and steady flow in thick-walled flexible tubes
NASA Astrophysics Data System (ADS)
Marzo, A.; Luo, X. Y.; Bertram, C. D.
2005-08-01
Three-dimensional collapse of and steady flow through finite-length elastic tubes are studied numerically. The Navier-Stokes equations coupled with large, nonlinear deformation of the elastic wall are solved by using the finite-element software, FIDAP. Three-dimensional solid elements are used for the elastic wall, allowing us to specify any wall thickness required. Plane-strain results for the cross-sectional shape of thinner-walled tubes are validated by comparison with published numerical data. Three-dimensional results for flow through finite-thickness tubes are in excellent agreement with published numerical results based on thin-shell elements, and are used to show the effects of varying wall thickness. Finally, the computational predictions are compared with experimental pressure area relationships for thick-walled tubes. The simulations confirm a previously neglected experimental finding, that the Young wavespeed can be lower between buckling and osculation for thick tubes than for thinner ones.
Asare-Asher, Samuel; Connor, Jason N; Sedev, Rossen
2015-07-01
Liquid marbles are liquid droplets covered densely with small particles. They exhibit hydrophobic properties even on hydrophilic surfaces and this behaviour is closely related to the Cassie wetting state and the phenomenon of superhydrophobicity. Typical liquid marbles are of millimetre size but their properties are analogous to smaller capsules and droplets of Pickering emulsions. We study water marbles covered with an uneven multilayer of polyethylene particles. Their elastic properties were assessed under quasi-static conditions. The liquid marbles are highly elastic and can sustain a reversible deformation of up to 30%. The spring constant is of the same order of magnitude as that for bare water droplets. Therefore the elasticity of the liquid marble is provided mainly by the liquid menisci between the particles. Upon further compression, the spring constant increases up to the point of breakage. This increase may be due to capillary attraction acting across the emerging cracks in the particle coating. The stress-strain curve for liquid marbles is similar to that obtained with liquid-filled microcapsules. A mechanical scaling description proposed for capsules is qualitatively applicable for liquid marbles. The exact mechanical role of the multilayer particle network remains elusive.
NASA Astrophysics Data System (ADS)
Dremin, I. M.
2013-01-01
Colliding high-energy hadrons either produce new particles or scatter elastically with their quantum numbers conserved and no other particles produced. We consider the latter case here. Although inelastic processes dominate at high energies, elastic scattering contributes considerably (18-25%) to the total cross section. Its share first decreases and then increases at higher energies. Small-angle scattering prevails at all energies. Some characteristic features can be seen that provide information on the geometrical structure of the colliding particles and the relevant dynamical mechanisms. The steep Gaussian peak at small angles is followed by the exponential (Orear) regime with some shoulders and dips, and then by a power-law decrease. Results from various theoretical approaches are compared with experimental data. Phenomenological models claiming to describe this process are reviewed. The unitarity condition predicts an exponential fall for the differential cross section with an additional substructure to occur exactly between the low momentum transfer diffraction cone and a power-law, hard parton scattering regime under high momentum transfer. Data on the interference of the Coulomb and nuclear parts of amplitudes at extremely small angles provide the value of the real part of the forward scattering amplitude. The real part of the elastic scattering amplitude and the contribution of inelastic processes to the imaginary part of this amplitude (the so-called overlap function) are also discussed. Problems related to the scaling behavior of the differential cross section are considered. The power-law regime at highest momentum transfer is briefly described.
NASA Astrophysics Data System (ADS)
Chen, Yan; Peng, Rui; You, Zhong
2015-07-01
Origami patterns, including the rigid origami patterns in which flat inflexible sheets are joined by creases, are primarily created for zero-thickness sheets. In order to apply them to fold structures such as roofs, solar panels, and space mirrors, for which thickness cannot be disregarded, various methods have been suggested. However, they generally involve adding materials to or offsetting panels away from the idealized sheet without altering the kinematic model used to simulate folding. We develop a comprehensive kinematic synthesis for rigid origami of thick panels that differs from the existing kinematic model but is capable of reproducing motions identical to that of zero-thickness origami. The approach, proven to be effective for typical origami, can be readily applied to fold real engineering structures.
Importance of Corneal Thickness
... News About Us Donate In This Section The Importance of Corneal Thickness email Send this article to ... is important because it can mask an accurate reading of eye pressure, causing doctors to treat you ...
Modal analysis of Lamb wave generation in elastic plates by liquid wedge transducers
Jia, X.
1997-02-01
A modal analysis is presented to describe the excitation of Lamb waves in an elastic plate using a liquid wedge transducer. Analytical expression for the displacement of a given mode is derived for the excitation by a uniform bounded beam. In contrast to previous studies, the contribution of the reflected wave is included in the input exciting forces using a perturbation theory. The conversion efficiency, defined as the ratio of the guided mode power to the incident power, is related to a single parameter which depends on the rate of attenuation due to leakage from the guided wave into the liquid wedge. Numerical results relevant to the fundamental Lamb modes are obtained as a function of frequency for various incident beam widths and plate thickness. Using optical interferometric detection, direct measurements of the Lamb modes displacements have been carried out in aluminium plates to verify the theoretical analysis. {copyright} {ital 1997 Acoustical Society of America.}
Behaviour study of thick laminated composites: Experimentation and finite element analyses
NASA Astrophysics Data System (ADS)
Duchaine, Francois
In today's industries, it is common practice to utilize composite materials in very large and thick structures like bridge decks, high pressure vessels, wind turbine blades and aircraft parts to mention a few. Composite materials are highly favoured due to their physical characteristics: low weight, low cost, adaptable mechanical properties, high specific strength and stiffness. The use of composite materials for large structures has however raised several concerns in the prediction of the behaviour of thick laminated composite parts. A lack of knowledge and experience in the use of composite materials during the design, sizing and manufacturing of thick composite parts can lead to catastrophic events. In this thesis, it was supposed that the elastic material properties may vary with the laminate thickness. In order to measure the influence of the thickness on nine orthotropic elastic material properties (E1, E2, E3, nu12, nu 13, nu23, G12, G13 and G23), three categories of thickness have been defined using a comparison between the classical lamination theory (CLT), different beam theories and a numerical 3D solid finite element analysis (FEA) model. The defined categories are: thin laminates for thicknesses below 6 mm (0.236"), moderately thick laminates for thicknesses up to 16 mm (0.630") and thick laminates for thicknesses above 16 mm (0.630"). For three different thicknesses (thin -- 1.5 mm, moderately thick -- 10 mm and thick -- 20 mm), the influence of the thickness on the orthotropic elastic material properties of unidirectional (UD) fibreglass/epoxy laminates has been measured. A torsion test on rectangular bar is also proposed to measure the influence of the thickness on G13 and G23. The nine elastic material properties, in function of the thickness, have been used in CLT and 3D solid FEA model in order to predict the axial Young's modulus and Poisson's ratios of cross-ply and quasi-isotropic laminates. Experimental results have also been obtained for
Dynamic Visco-elastic Buckling Analysis for Airway Model
NASA Astrophysics Data System (ADS)
Bando, Kiyoshi; Ohba, Kenkichi; Yamanoi, Yuta
In order to clarify the mechanism by which the lung airway narrows during an asthma attack, dynamic buckling analysis of the wall was conducted. The wall was modeled using a visco-elastic thin-walled circular cylinder of the Voigt model for the planestress state. A governing equation for dynamic buckling was derived, and in the equation, the contraction of smooth muscle was replaced by uniform inward transmural pressure. The non-dimensional parameters for the buckling wave number n were nondimensional retardation time τ, non-dimensional increasing velocity of inward transmural pressure β, thickness radius ratio α2, radius length ratio η, density ratio ζ, and Poisson's ratio ν. The validity of the theoretical model was confirmed by comparing the calculated wave number with that obtained from the experiment, in which a silicone rubber tube blended with silicone potting gel was used as the in vitro airway model. In addition, the wave number n increased with β. It was necessary to consider the damping effect of the tube model or the airway wall, and n increased by 1.5 to 2 due to the additional mass effect of surrounding tissues of the basement membrane in the airway wall.
Elastic properties of hollow colloidal particles
NASA Astrophysics Data System (ADS)
Zoldesi, C. I.; Ivanovska, I. L.; Quilliet, C.; Wuite, G. J. L.; Imhof, A.
2008-11-01
The elastic properties of micrometer-sized hollow colloidal particles obtained by emulsion templating are probed by nanoindentation measurements in which point forces are applied to solvent-filled particles supported on a flat substrate. We show that the shells respond linearly up to forces of 7-21nN , where the indentation becomes of the order of the shell thickness (20-40nm) . In the linear region, the particle deformation is reversible. The measured Young’s modulus (˜200MPa) is comparable to values for stiff rubbers or soft polymers. At larger applied force, we observe a crossover into a nonlinear regime, where the shells assume a buckled shape. Here, the force increases approximately as the square root of the indentation, in agreement with the theory of elasticity of thin shells. We also observe permanent deformation of the shells after probing them repetitively beyond the linear regime. Finally, the measured elastic properties of the shells nicely explain their spontaneous buckling in solution and due to drying.
Nonlinear elastic model for faceting of vesicles with soft grain boundaries
NASA Astrophysics Data System (ADS)
Sknepnek, Rastko; Olvera de la Cruz, Monica
2012-05-01
We use an elastic model to explore faceting of solid-wall vesicles with elastic heterogeneities. We show that faceting occurs in regions where the vesicle wall is softer, such as areas of reduced wall thicknesses or concentrated in crystalline defects. The elastic heterogeneities are modeled as a second component with reduced elastic parameters. Using simulated annealing Monte Carlo simulations we obtain the vesicle shape by optimizing the distributions of facets and boundaries. Our model allows us to reduce the effects of the residual stress generated by crystalline defects, and reveals a robust faceting mechanism into polyhedra other than the icosahedron.
Elastic coupling between layers in two-dimensional materials
NASA Astrophysics Data System (ADS)
Gao, Yang; Kim, Suenne; Zhou, Si; Chiu, Hsiang-Chih; Nélias, Daniel; Berger, Claire; de Heer, Walt; Polloni, Laura; Sordan, Roman; Bongiorno, Angelo; Riedo, Elisa
2015-07-01
Two-dimensional materials, such as graphene and MoS2, are films of a few atomic layers in thickness with strong in-plane bonds and weak interactions between the layers. The in-plane elasticity has been widely studied in bending experiments where a suspended film is deformed substantially; however, little is known about the films’ elastic modulus perpendicular to the planes, as the measurement of the out-of-plane elasticity of supported 2D films requires indentation depths smaller than the films’ interlayer distance. Here, we report on sub-ångström-resolution indentation measurements of the perpendicular-to-the-plane elasticity of 2D materials. Our indentation data, combined with semi-analytical models and density functional theory, are then used to study the perpendicular elasticity of few-layer-thick graphene and graphene oxide films. We find that the perpendicular Young’s modulus of graphene oxide films reaches a maximum when one complete water layer is intercalated between the graphitic planes. This non-destructive methodology can map interlayer coupling and intercalation in 2D films.
Ovtchinnikov, Evgueni E.; Xanthis, Leonidas S.
2000-01-01
We present a methodology for the efficient numerical solution of eigenvalue problems of full three-dimensional elasticity for thin elastic structures, such as shells, plates and rods of arbitrary geometry, discretized by the finite element method. Such problems are solved by iterative methods, which, however, are known to suffer from slow convergence or even convergence failure, when the thickness is small. In this paper we show an effective way of resolving this difficulty by invoking a special preconditioning technique associated with the effective dimensional reduction algorithm (EDRA). As an example, we present an algorithm for computing the minimal eigenvalue of a thin elastic plate and we show both theoretically and numerically that it is robust with respect to both the thickness and discretization parameters, i.e. the convergence does not deteriorate with diminishing thickness or mesh refinement. This robustness is sine qua non for the efficient computation of large-scale eigenvalue problems for thin elastic structures. PMID:10655469
Rifting Thick Lithosphere - Canning Basin, Western Australia
NASA Astrophysics Data System (ADS)
Czarnota, Karol; White, Nicky
2016-04-01
The subsidence histories and architecture of most, but not all, rift basins are elegantly explained by extension of ~120 km thick lithosphere followed by thermal re-thickening of the lithospheric mantle to its pre-rift thickness. Although this well-established model underpins most basin analysis, it is unclear whether the model explains the subsidence of rift basins developed over substantially thick lithosphere (as imaged by seismic tomography beneath substantial portions of the continents). The Canning Basin of Western Australia is an example where a rift basin putatively overlies lithosphere ≥180 km thick, imaged using shear wave tomography. Subsidence modelling in this study shows that the entire subsidence history of the <300 km wide and <6 km thick western Canning Basin is adequately explained by mild Ordovician extension (β≈1.2) of ~120 km thick lithosphere followed by post-rift thermal subsidence. This is consistent with the established model, described above, albeit with perturbations due to transient dynamic topography support which are expressed as basin-wide unconformities. In contrast the <150 km wide and ~15 km thick Fitzroy Trough of the eastern Canning Basin reveals an almost continuous period of normal faulting between the Ordovician and Carboniferous (β<2.0) followed by negligible post-rift thermal subsidence. These features cannot be readily explained by the established model of rift basin development. We attribute the difference in basin architecture between the western and eastern Canning Basin to rifting of thick lithosphere beneath the eastern part, verified by the presence of ~20 Ma diamond-bearing lamproites intruded into the basin depocentre. In order to account for the observed subsidence, at standard crustal densities, the lithospheric mantle is required to be depleted in density by 50-70 kg m-3, which is in line with estimates derived from modelling rare-earth element concentrations of the ~20 Ma lamproites and global isostatic
JKR adhesive contact for a transversely isotropic layer of finite thickness
NASA Astrophysics Data System (ADS)
Argatov, I. I.; Borodich, F. M.; Popov, V. L.
2016-02-01
A frictionless contact interaction with a circular area of contact between an arbitrary axisymmetric rigid probe and a transversely isotopic elastic layer deposited on a substrate is studied in the framework of the JKR (Johnson, Kendall, and Roberts) adhesion theory. Under the assumption that the diameter of the contact area is less than the thickness of the elastic layer, the forth-order asymptotic model is explicitly written out. The effect of the layer thickness and the material anisotropy is taken into account via the asymptotic coefficients, which are integral characteristics of the elastic layer and also depend on the boundary conditions at the layer/substrate interface. A special case of an isotropic elastic layer bonded to an isotropic elastic half-space is considered in detail.
Film thickness for different regimes of fluid-film lubrication. [elliptical contacts
NASA Technical Reports Server (NTRS)
Hamrock, B. J.; Dowson, D.
1983-01-01
Mathematical formulas are presented which express the dimensionless minimum film thickness for the four lubrication regimes found in elliptical contacts: isoviscous-rigid regime; piezoviscous-rigid regime; isoviscous-elastic regime; and piezoviscous-elastic regime. The relative importance of pressure on elastic distortion and lubricant viscosity is the factor that distinguishes these regimes for a given conjunction geometry. In addition, these equations were used to develop maps of the lubrication regimes by plotting film thickness contours on a log-log grid of the dimensionless viscosity and elasticity parameters for three values of the ellipticity parameter. These results present a complete theoretical film thickness parameter solution for elliptical constants in the four lubrication regimes. The results are particularly useful in initial investigations of many practical lubrication problems involving elliptical conjunctions.
Stress Formulation in Three-Dimensional Elasticity
NASA Technical Reports Server (NTRS)
Patnaik, Surya N.; Hopkins, Dale A.
2001-01-01
The theory of elasticity evolved over centuries through the contributions of eminent scientists like Cauchy, Navier, Hooke Saint Venant, and others. It was deemed complete when Saint Venant provided the strain formulation in 1860. However, unlike Cauchy, who addressed equilibrium in the field and on the boundary, the strain formulation was confined only to the field. Saint Venant overlooked the compatibility on the boundary. Because of this deficiency, a direct stress formulation could not be developed. Stress with traditional methods must be recovered by backcalculation: differentiating either the displacement or the stress function. We have addressed the compatibility on the boundary. Augmentation of these conditions has completed the stress formulation in elasticity, opening up a way for a direct determination of stress without the intermediate step of calculating the displacement or the stress function. This Completed Beltrami-Michell Formulation (CBMF) can be specialized to derive the traditional methods, but the reverse is not possible. Elasticity solutions must be verified for the compliance of the new equation because the boundary compatibility conditions expressed in terms of displacement are not trivially satisfied. This paper presents the variational derivation of the stress formulation, illustrates the method, examines attributes and benefits, and outlines the future course of research.
Elastic response and wrinkling onset of curved elastic membranes subjected to indentation test.
Bernal, R; Tassius, Ch; Melo, F; Géminard, J-Ch
2011-02-01
Starting from a polymeric-fluid droplet, by vulcanization of the fluid free surface, curved elastic membranes, several nanometers thick and a few millimeters in diameter, which enclose a constant fluid volume, are produced. In an indentation-type test, carried out by pushing the membrane along its normal by means of a micro-needle, under some conditions, wrinkles are likely to appear around the contact region. Interestingly, we observe that the instability does not significantly alter the force-displacement relation: the relation between the force and the displacement remains linear and the associated stiffness is simply proportional to the tension of the membrane. In addition, we determine that the wrinkles develop when the stretching modulus of the membrane compares with its tension, which provides a useful method to estimate the elastic constant. PMID:21337016
Holographic measurements of fresh- and dry-bone elasticity
NASA Astrophysics Data System (ADS)
Silvennoinen, Raimo V. J.; Nygren, Kaarlo; Karna, Markku; Karna, Kari
1992-08-01
To compare the elasticity of bones covered with soft tissue and the elasticity of defleshed and dried bones we used sampling screws to make the surface movements of the bones visible through the soft tissue. We compared fresh and dry European moose skulls with antlers before and after skinning. External forces were focused on the skull bones through the antlers and on the metatarsal bones through the distal epiphysis. A high correlation in fringe orientation was observed in the case of thick skull bone structures with rigid interdigited sutures. We also compared compression dynamics of fresh and dry moose antler cubes.
NASA Astrophysics Data System (ADS)
Wisdom, Jack; Meyer, Jennifer
2016-04-01
This is an exploration of dynamic tides on elastic bodies. The body is thought of as a dynamical system described by its modes of oscillation. The dynamics of these modes are governed by differential equations that depend on the rheology. The modes are damped by dissipation. Tidal friction occurs as exterior bodies excite the modes and the modes act back on the tide raising body. The whole process is governed by a closed set of differential equations. Standard results from tidal theory are recovered in a two-timescale approximation to the solution of these differential equations.
NASA Astrophysics Data System (ADS)
Wisdom, Jack; Meyer, Jennifer
2016-11-01
This is an exploration of dynamic tides on elastic bodies. The body is thought of as a dynamical system described by its modes of oscillation. The dynamics of these modes are governed by differential equations that depend on the rheology. The modes are damped by dissipation. Tidal friction occurs as exterior bodies excite the modes and the modes act back on the tide raising body. The whole process is governed by a closed set of differential equations. Standard results from tidal theory are recovered in a two-timescale approximation to the solution of these differential equations.
D. Day
2007-03-01
The nucleon form factors are still the subject of active investigation even after an experimental effort spanning 50 years. This is because they are of critical importance to our understanding of the electromagnetic properties of nuclei and provide a unique testing ground for QCD motivated models of nucleon structure. Progress in polarized beams, polarized targets and recoil polarimetry have allowed an important and precise set of data to be collected over the last decade. I will review the experimental status of elastic electron scattering from the nucleon along with an outlook for future progress.
Elastic constants of the human lens capsule.
Fisher, R F
1969-03-01
1. A technique is described whereby the elasticity of the human lens capsule has been determined at birth and throughout life. This technique requires three separate determinations: (a) thickness; (b) stress and strain; (c) Poisson's ratio; (a) the capsule was clamped between accurately perforated ground glass plates and its thickness determined by noting the change in depth of focus between Latex spherules adhering to its upper and lower surfaces; (b) the undisturbed capsule was then placed in a specially designed glass distension apparatus and the relationship between volume and pressure recorded when it was distended with isotonic saline. The permeability of the capsule was also measured; (c) in some cases Poisson's ratio was determined by measuring the change of thickness of the capsule and the height to which it rose when distended with isotonic saline at different pressures. An apparatus was designed for this purpose.2. The average thickness of the anterior capsule increases from birth until about the 60th year but thereafter it decreases slightly.3. Poisson's ratio was about 0.47 for both cat and human capsule, and no significant variations with age in human capsule could be detected.4. Corrected volume pressure curves obeyed Hook's law almost to the point of capsule rupture.5. In childhood Young's Modulus of elasticity is about 6 x 10(7) dyn/cm(2) and decreases to 3 x 10(7) dyn/cm(2) at 60 and 1.5 x 10(7) dyn/cm(2) in extreme old age.6. The ultimate tensile stress was 2.3 x 10(7) dyn/cm(2) in young capsules and 0.7 x 10(7) dyn/cm(2) in old ones. The maximum percentage elongation was 29 per cent and independent of age.7. The implications of these findings are discussed in relation to(a) the mechanical properties of the lens capsule;(b) the ageing of the lens capsule and basement membranes; and(c) the decrease in elasticity of the lens capsule as a cause of presbyopia.
The Propagation of a Liquid Bolus Through an Elastic Tube and Airway Reopening
NASA Technical Reports Server (NTRS)
Howell, Peter D.; Grotberg, James B.
1996-01-01
We use lubrication theory and matched asymptotic expansions to model the quasi-steady propagation of a liquid bridge through an elastic tube. In the limit of small capillary number, asymptotic expressions are found for the pressure drop across the bridge and the thickness of the liquid film left behind, as functions of the capillary number, the thickness of the liquid lining ahead of the bridge and the elastic characteristics of the tube wall. For a given precursor thickness, we find a critical propagation speed, and hence a critical imposed pressure drop, above which the bridge will eventually burst, and hence the tube will reopen.
Hypo-Elastic Model for Lung Parenchyma
Freed, Alan D.; Einstein, Daniel R.
2012-03-01
A simple elastic isotropic constitutive model for the spongy tissue in lung is derived from the theory of hypoelasticity. The model is shown to exhibit a pressure dependent behavior that has been interpreted by some as indicating extensional anisotropy. In contrast, we show that this behavior arises natural from an analysis of isotropic hypoelastic invariants, and is a likely result of non-linearity, not anisotropy. The response of the model is determined analytically for several boundary value problems used for material characterization. These responses give insight into both the material behavior as well as admissible bounds on parameters. The model is characterized against published experimental data for dog lung. Future work includes non-elastic model behavior.
Squeeze elastic deformation and contact area of a rubber adhesive
NASA Astrophysics Data System (ADS)
Tordjeman, P.; Papon, E.; Villenave, J.-J.
2000-12-01
New experimental results show that the tack energy of a nonstringing rubber adhesive is proportional to the square function of the contact area. However, this area seems only to be controlled by the contact force and the thickness of the adhesive. A study of how the contact area depends on physical parameters is of great interest for the modeling of the tack properties of pressure-sensitive adhesives (PSAs). With this objective, we give a mechanical analysis of the tack test in the framework of elasticity. This analysis leads to an analytical expression of force versus thickness of material that is in agreement with the experimental data. Based on this mechanical analysis, a model is proposed to take into account the dependence of the contact area with the contact force and the adhesive thickness. This model is based on the idea that, in confined geometry, the adhesive behaves like an elastic solid and the contact area is a function of the elastic squeeze deformation close to the probe surface. The confrontation with experimental results is good and shows the relevance of this approach. Finally, the model underlines the importance of the roughness, the thickness and the Young's modulus of the adhesive according to the experimental results.
Polysoaps: Configurations and Elasticity
NASA Astrophysics Data System (ADS)
Halperin, A.
1997-03-01
Simple polymers are very long, flexible, linear molecules. Amphiphiles, soaps, are small molecules comprising of a part that prefers water over oil and a part that prefers oil over water. By combining the two we arrive at an interesting, little explored, class of materials: Polysoaps. These comprise of a water soluble backbone incorporating, at intervals, covalently bound amphiphilic monomers. In water, the polymerised amphiphiles aggregate into self assembled units known as micelles. This induces a dramatic modification of the spatial configurations of the polymers. What were featureless random coils now exhibit intramolecular, hierachial self organisation. Due to this self organisation it is necessary to modify the paradigms describing the large scale behaviour of these polymers: Their configurations, dimensions and elasticity. Understanding the behaviour of these polymers is of practical interest because of their wide range of industrial applications, ranging from cosmetics to paper coating. It is of fundamental interest because polysoaps are characterised by a rugged free energy landscape that is reminiscent of complex systems such as proteins and glasses. The talk concerns theoretical arguments regarding the following issues: (i) The design parameters that govern the spatial configurations of the polysoaps, (ii) The interaction between polysoaps and free amphiphiles, (iii) The effect of the intramolecular self organisation on the elasticity of the chains.
Design guidance for elastic followup
Naugle, F.V.
1983-01-01
The basic mechanism of elastic followup is discussed in relation to piping design. It is shown how mechanistic insight gained from solutions for a two-bar problem can be used to identify dominant design parameters and to determine appropriate modifications where elastic followup is a potential problem. It is generally recognized that quantitative criteria are needed for elastic followup in the creep range where badly unbalanced lines can pose potential problems. Approaches for criteria development are discussed.
Mathematical Models for Elastic Structures
NASA Astrophysics Data System (ADS)
Villaggio, Piero
1997-10-01
During the seventeenth century, several useful theories of elastic structures emerged, with applications to civil and mechanical engineering problems. Recent and improved mathematical tools have extended applications into new areas such as mathematical physics, geomechanics, and biomechanics. This book offers a critically filtered collection of the most significant theories dealing with elastic slender bodies. It includes mathematical models involving elastic structures that are used to solve practical problems with particular emphasis on nonlinear problems.
Predicting gravity and sediment thickness in Afghanistan
NASA Astrophysics Data System (ADS)
Jung, W.; Brozena, J.; Peters, M.
2013-02-01
wavelength 132 km which is approximately equivalent to the reported safe degree and order 250 of GOCO02S at 34º N) combined airborne free-air anomalies. The rms difference between the two data sets was 12.4 mGal. The observed admittance in the western Afghanistan mountains appears to be best fit to a theoretical elastic plate compensation model (with an effective elastic thickness of 5 km and crustal thickness of 22 km) where the ratio between surface load and subsurface load is equal.
ERIC Educational Resources Information Center
Hoffman, Saul D.
2009-01-01
The third Marshall-Hicks-Allen rule of elasticity of derived demand purports to show that labor demand is less elastic when labor is a smaller share of total costs. As Hicks, Allen, and then Bronfenbrenner showed, this rule is not quite correct, and actually is complicated by an unexpected negative relationship involving labor's share of total…
Eneh, Chibuzor T M; Liukkonen, Jukka; Malo, Markus K H; Jurvelin, Jukka S; Töyräs, Juha
2015-12-01
Knowledge about simultaneous contributions of tissue microstructure and elastic properties on ultrasound speed in cortical bone is limited. In a previous study, porosities and elastic coefficients of cortical bone in human femurs were shown to change with age. In the present study, influences of inter-individual and site-dependent variation in cortical bone microstructure and elastic properties on radial speed of sound (SOS; at 4, 6, and 8 MHz) were investigated using three-dimensional (3D) finite difference time domain modeling. Models with fixed (nominal model) and sample-specific (sample-specific model) values of radial elastic coefficients were compared. Elastic coefficients and microstructure for samples (n = 24) of human femoral shafts (n = 6) were derived using scanning acoustic microscopy and micro-computed tomography images, respectively. Porosity-related SOS varied more extensively in nominal models than in sample-specific models. Linear correlation between pore separation and SOS was similar (R = 0.8, p < 0.01, for 4 MHz) for both models. The determination coefficient (R(2)= 0.75, p < 0.05) between porosity and radial SOS, especially at 4 MHz, was highest in the posterior quadrant. The determination coefficient was lower for models with sample-specific values of radial elastic coefficient implemented (R(2) < 0.33, p < 0.05), than for nominal models (0.48 < R(2)< 0.63, p < 0.05). This information could be useful in in vivo pulse-echo cortical thickness measurements applying constant SOS. PMID:26723306
Avian eggshell thickness: Variability and sampling
Klaas, E.E.; Ohlendorf, H.M.; Heath, R.G.
1974-01-01
Measurements of shell thickness of the eggs of five species were subjected to nested analyses of variance. The analyses separated variation into two or three levels for which variances and percentages of the total variation were derived. The results show that differences among measurements of the same egg contribute little to the sample variance whereas differences among eggs within clutches contribute nearly as much as differences among clutches. It is more efficient and less costly to collect entire clutches of eggs in most studies of shell thickness. Using entire clutches, sample sizes needed to detect differences of 10 percent in shell thickness (at given significance levels and power) were estimated to be eight to 11 clutches for the species studied. For differences of five percent, 26 to 38 clutches are required. Guidelines are presented which may assist other workers in evaluating the efficiency of their sampling designs, and in estimating sample sizes for detecting differences in eggshell thickness in wild birds.
Singular path-independent energy integrals for elastic bodies with thin elastic inclusions
NASA Astrophysics Data System (ADS)
Shcherbakov, V. V.
2016-06-01
An equilibrium problem for a two-dimensional homogeneous linear elastic body containing a thin elastic inclusion and an interfacial crack is considered. The thin inclusion is modeled within the framework of Euler-Bernoulli beam theory. An explicit formula for the first derivative of the energy functional with respect to the crack perturbation along the interface is presented. It is shown that the formulas for the derivative associated with translation and self-similar expansion of the crack are represented as path-independent integrals along smooth contour surrounding one or both crack tips. These path-independent integrals consist of regular and singular terms and are analogs of the well-known Eshelby-Cherepanov-Rice J-integral and Knowles-Sternberg M-integral.
Imaging of the elastic properties of tissue--a review.
Gao, L; Parker, K J; Lerner, R M; Levinson, S F
1996-01-01
Recently, a number of methods have been developed that make it possible to image the elastic properties of soft tissues. Because certain types of tissues such as malignant lesions, for example, have elastic properties that are markedly different from surrounding tissues, elasticity imaging could provide a significant adjunct to current diagnostic ultrasonic methods. Further, elasticity imaging techniques could be used to augment the study of tissues that change their elastic properties, such as skeletal and cardiac muscle. In this paper, we survey some of the previous work done in the related field of biomechanics, and we review measurement techniques from the 1950s to the 1980s. Different approaches to elastic imaging and signal processing are then discussed and a lexicography for elastic imaging is introduced. It is hoped that this nomenclature will provide a meaningful categorization of various approaches and will make evident the inherent parameters displayed and conditions applied in deriving the resulting images. Key assumptions and signal processing approaches are also reviewed. Finally, directions for future work are suggested.
Matched Interface and Boundary Method for Elasticity Interface Problems
Wang, Bao; Xia, Kelin; Wei, Guo-Wei
2015-01-01
Elasticity theory is an important component of continuum mechanics and has had widely spread applications in science and engineering. Material interfaces are ubiquity in nature and man-made devices, and often give rise to discontinuous coefficients in the governing elasticity equations. In this work, the matched interface and boundary (MIB) method is developed to address elasticity interface problems. Linear elasticity theory for both isotropic homogeneous and inhomogeneous media is employed. In our approach, Lamé’s parameters can have jumps across the interface and are allowed to be position dependent in modeling isotropic inhomogeneous material. Both strong discontinuity, i.e., discontinuous solution, and weak discontinuity, namely, discontinuous derivatives of the solution, are considered in the present study. In the proposed method, fictitious values are utilized so that the standard central finite different schemes can be employed regardless of the interface. Interface jump conditions are enforced on the interface, which in turn, accurately determines fictitious values. We design new MIB schemes to account for complex interface geometries. In particular, the cross derivatives in the elasticity equations are difficult to handle for complex interface geometries. We propose secondary fictitious values and construct geometry based interpolation schemes to overcome this difficulty. Numerous analytical examples are used to validate the accuracy, convergence and robustness of the present MIB method for elasticity interface problems with both small and large curvatures, strong and weak discontinuities, and constant and variable coefficients. Numerical tests indicate second order accuracy in both L∞ and L2 norms. PMID:25914439
Application of gradient elasticity to benchmark problems of beam vibrations
NASA Astrophysics Data System (ADS)
Kateb, K. M.; Almitani, K. H.; Alnefaie, K. A.; Abu-Hamdeh, N. H.; Papadopoulos, P.; Askes, H.; Aifantis, E. C.
2016-04-01
The gradient approach, specifically gradient elasticity theory, is adopted to revisit certain typical configurations on mechanical vibrations. New results on size effects and scale-dependent behavior not captured by classical elasticity are derived, aiming at illustrating the usefulness of this approach to applications in advanced technologies. In particular, elastic prismatic straight beams in bending are discussed using two different governing equations: the gradient elasticity bending moment equation (fourth order) and the gradient elasticity deflection equation (sixth order). Different boundary/support conditions are examined. One problem considers the free vibrations of a cantilever beam loaded by an end force. A second problem is concerned with a simply supported beam disturbed by a concentrated force in the middle of the beam. Both problems are solved analytically. Exact free vibration frequencies and mode shapes are derived and presented. The difference between the gradient elasticity solution and its classical counterpart is revealed. The size ratio c/L (c denotes internal length and L is the length of the beam) induces significant effects on vibration frequencies. For both beam configurations, it turns out that as the ratio c/L increases, the vibration frequencies decrease, a fact which implies lower beam stiffness. Numerical examples show this behavior explicitly and recover the classical vibration behavior for vanishing size ratio c/L.
ERIC Educational Resources Information Center
Trefil, James
1983-01-01
Discusses why interference effects cannot be seen with a thick film, starting with a review of the origin of interference patterns in thin films. Considers properties of materials in films, properties of the light source, and the nature of light. (JN)
NASA Technical Reports Server (NTRS)
Brunelle, Eugene J.
1994-01-01
The first few viewgraphs describe the general solution properties of linear elasticity theory which are given by the following two statements: (1) for stress B.C. on S(sub sigma) and zero displacement B.C. on S(sub u) the altered displacements u(sub i)(*) and the actual stresses tau(sub ij) are elastically dependent on Poisson's ratio nu alone: thus the actual displacements are given by u(sub i) = mu(exp -1)u(sub i)(*); and (2) for zero stress B.C. on S(sub sigma) and displacement B.C. on S(sub u) the actual displacements u(sub i) and the altered stresses tau(sub ij)(*) are elastically dependent on Poisson's ratio nu alone: thus the actual stresses are given by tau(sub ij) = E tau(sub ij)(*). The remaining viewgraphs describe the minimum parameter formulation of the general classical laminate theory plate problem as follows: The general CLT plate problem is expressed as a 3 x 3 system of differential equations in the displacements u, v, and w. The eighteen (six each) A(sub ij), B(sub ij), and D(sub ij) system coefficients are ply-weighted sums of the transformed reduced stiffnesses (bar-Q(sub ij))(sub k); the (bar-Q(sub ij))(sub k) in turn depend on six reduced stiffnesses (Q(sub ij))(sub k) and the material and geometry properties of the k(sup th) layer. This paper develops a method for redefining the system coefficients, the displacement components (u,v,w), and the position components (x,y) such that a minimum parameter formulation is possible. The pivotal steps in this method are (1) the reduction of (bar-Q(sub ij))(sub k) dependencies to just two constants Q(*) = (Q(12) + 2Q(66))/(Q(11)Q(22))(exp 1/2) and F(*) - (Q(22)/Q(11))(exp 1/2) in terms of ply-independent reference values Q(sub ij); (2) the reduction of the remaining portions of the A, B, and D coefficients to nondimensional ply-weighted sums (with 0 to 1 ranges) that are independent of Q(*) and F(*); and (3) the introduction of simple coordinate stretchings for u, v, w and x,y such that the process is
Effects of Auger electron elastic scattering in quantitative AES
NASA Astrophysics Data System (ADS)
Jablonski, Aleksander
1987-09-01
The Monte Carlo algorithm was developed for simulating the trajectories of electrons elastically scattered in the solid. The distribution of scattering angles was determined using the partial wave expansion method. This algorithm was used to establish the influence of Auger electron elastic collisions on the results of quantitative AES analysis. The calculations were performed for the most pronounced KLL, L 3 MM and M 5NN Auger transitions. It turned out that due to the elastic collisions the Auger electron signal is decreased by up to 10%. The corresponding decreased of the escape depth of Auger electrons reaches 30% as compared with the value derived from the inelastic mean free path. The values of the inelastic mean free path resulting from the overalyer method may be strongly affected by elastic scattering of Auger electrons.
NASA Astrophysics Data System (ADS)
Kannajosyula, Haraprasad; Nino, Giovanni F.
2015-03-01
Elastic helical guided wave propagation in pipes that has recently gained importance in applications related to tomography and structural health monitoring is analyzed using an alternate formalism. Closed form exponential function based solutions for the Helmholtz vector equation in cylindrical polar coordinates are derived. Relationship of these alternate solutions for the Helmholtz vector equation with the traditional integer order Bessel function based formulation - that has been established for the corresponding solutions of Helmholtz scalar equation in prior literature - is presented. The solutions are single valued at every point in the physical space, and therefore, unlike traditional non-integer order Bessel function based methods, the formulation presented herein preserves the physical uniqueness of the field quantities involved in the wave propagation. The alternate solutions, when applied to the boundary value problem of an isotropic elastic pipe with stress free boundaries, yield a formulation for helical guided wave propagation. A class of helical guided wave modes that have a constant helix angle across the wall thickness of the pipe is predicted. Dispersion characteristics for guided wave propagation such as phase velocity curves; displacement profiles for some points of interest on the phase velocity curves, for select helical angles are presented. The results are compared against traditional notions about helical guided wave propagation.
NASA Astrophysics Data System (ADS)
Farin, Maxime; Mangeney, Anne; Rosny, Julien de; Toussaint, Renaud; Sainte-Marie, Jacques; Shapiro, Nikolaï M.
2016-02-01
Estimating the energy lost in elastic waves during an impact is an important problem in seismology and in industry. We propose three complementary methods to estimate the elastic energy radiated by bead impacts on thin plates and thick blocks from the generated vibration. The first two methods are based on the direct wave front and are shown to be equivalent. The third method makes use of the diffuse regime. These methods are tested for laboratory experiments of impacts and are shown to give the same results, with error bars of 40 percent and 300 percent for impacts on a smooth plate and on a rough block, respectively. We show that these methods are relevant to establish the energy budget of an impact. On plates of glass and PMMA, the radiated elastic energy increases from 2 percent to almost 100 percent of the total energy lost as the bead diameter approaches the plate thickness. The rest of the lost energy is dissipated by viscoelasticity. For beads larger than the plate thickness, plastic deformation occurs and reduces the amount of energy radiated in the form of elastic waves. On a concrete block, the energy dissipation during the impact is principally inelastic because only 0.2-2 percent of the energy lost by the bead is transported by elastic waves. The radiated elastic energy estimated with the presented methods is quantitatively validated by Hertz's model of elastic impact.
Two parabolic equations for propagation in layered poro-elastic media.
Metzler, Adam M; Siegmann, William L; Collins, Michael D; Collis, Jon M
2013-07-01
Parabolic equation methods for fluid and elastic media are extended to layered poro-elastic media, including some shallow-water sediments. A previous parabolic equation solution for one model of range-independent poro-elastic media [Collins et al., J. Acoust. Soc. Am. 98, 1645-1656 (1995)] does not produce accurate solutions for environments with multiple poro-elastic layers. First, a dependent-variable formulation for parabolic equations used with elastic media is generalized to layered poro-elastic media. An improvement in accuracy is obtained using a second dependent-variable formulation that conserves dependent variables across interfaces between horizontally stratified layers. Furthermore, this formulation expresses conditions at interfaces using no depth derivatives higher than first order. This feature should aid in treating range dependence because convenient matching across interfaces is possible with discretized derivatives of first order in contrast to second order.
Elasticity of ``Fuzzy'' Biomembranes
NASA Astrophysics Data System (ADS)
Evans, E.; Rawicz, W.
1997-09-01
Sensitive micropipet methods have been used to measure the elastic stretch modulus and bending rigidity of biomembranes studded with water-soluble polymers. The fully extended lengths of the chemically grafted chains ranged from 10-50× the length of the embedding membrane lipid. Concentrations of the polymer were varied from 1-10× the surface density needed for isolated chains to touch, nominally satisfying the scaling theory requirement for semidilute brushes. Over this range, the membrane stretch modulus was unchanged by the polymer layers, but the bending rigidity increased by as much as 10kBT. Surprisingly, the increase in rigidity deviated significantly from scaling theory predictions, revealing a large marginal brush regime between dilute mushrooms and a semidilute brush.
NASA Astrophysics Data System (ADS)
Bik, W. M. A.; Habraken, F. H. P. M.
1993-07-01
In elastic recoil detection (ERD) one determines the yield and energy of particles ejected out of the surface region of samples under MeV ion bombardment. By application of this surface and thin film analysis technique one can obtain quantitative information concerning the depth distribution of light elements in a sample to be analysed. The quantitativity and the depth resolving power are based on knowledge of the recoil cross section and the stopping power of high-energy ions in matter. This paper reviews the fundamentals of this technique and the various experimental methods for recoil identification. Furthermore, important features for material analysis, such as detection limits, depth resolution and elemental range are discussed. Some emphasis is put on the conversion of the spectral contribution of the elements to atomic concentrations in the films for several representative cases. Throughout the review numerous examples are given to illustrate the features of ERD and to demonstrate empirically the accuracy of the quantification method.
The crustal thickness of Australia
Clitheroe, G.; Gudmundsson, O.; Kennett, B.L.N.
2000-01-01
We investigate the crustal structure of the Australian continent using the temporary broadband stations of the Skippy and Kimba projects and permanent broadband stations. We isolate near-receiver information, in the form of crustal P-to-S conversions, using the receiver function technique. Stacked receiver functions are inverted for S velocity structure using a Genetic Algorithm approach to Receiver Function Inversion (GARFI). From the resulting velocity models we are able to determine the Moho depth and to classify the width of the crust-mantle transition for 65 broadband stations. Using these results and 51 independent estimates of crustal thickness from refraction and reflection profiles, we present a new, improved, map of Moho depth for the Australian continent. The thinnest crust (25 km) occurs in the Archean Yilgarn Craton in Western Australia; the thickest crust (61 km) occurs in Proterozoic central Australia. The average crustal thickness is 38.8 km (standard deviation 6.2 km). Interpolation error estimates are made using kriging and fall into the range 2.5-7.0 km. We find generally good agreement between the depth to the seismologically defined Moho and xenolith-derived estimates of crustal thickness beneath northeastern Australia. However, beneath the Lachlan Fold Belt the estimates are not in agreement, and it is possible that the two techniques are mapping differing parts of a broad Moho transition zone. The Archean cratons of Western Australia appear to have remained largely stable since cratonization, reflected in only slight variation of Moho depth. The largely Proterozoic center of Australia shows relatively thicker crust overall as well as major Moho offsets. We see evidence of the margin of the contact between the Precambrian craton and the Tasman Orogen, referred to as the Tasman Line. Copyright 2000 by the American Geophysical Union.
Capillary-induced giant elastic dipoles in thin nematic films
Jeridi, Haifa; Gharbi, Mohamed A.; Othman, Tahar; Blanc, Christophe
2015-01-01
Directed and true self-assembly mechanisms in nematic liquid crystal colloids rely on specific interactions between microparticles and the topological defects of the matrix. Most ordered structures formed in thin nematic cells are thus based on elastic multipoles consisting of a particle and nearby defects. Here, we report, for the first time to our knowledge, the existence of giant elastic dipoles arising from particles dispersed in free nematic liquid crystal films. We discuss the role of capillarity and film thickness on the dimensions of the dipoles and explain their main features with a simple 2D model. Coupling of capillarity with nematic elasticity could offer ways to tune finely the spatial organization of complex colloidal systems. PMID:26554001
Determination of the elastic modulus of snow via acoustic measurements
NASA Astrophysics Data System (ADS)
Gerling, Bastian; van Herwijnen, Alec; Löwe, Henning
2016-04-01
The elastic modulus of snow is a key quantity from the viewpoint of avalanche research and forecasting, snow engineering or materials science in general. Since it is a fundamental property, many measurements have been reported in the literature. Due to differences in measurement methods, there is a lot of variation in the reported values. Especially values derived via computer tomography (CT) based numerical calculations using finite element methods are not corresponding to the results of other methods. The central issue is that CT based moduli are purely elastic whereas other methods may include viscoelastic deformation. In order to avoid this discrepancy we derived the elastic modulus of snow via wave propagation measurements and compared our results with CT based calculations. We measured the arrival times of acoustic pulses propagating through the snow samples to determine the P-wave velocity and in turn derive the elastic modulus along the direction of wave propagation. We performed a series of laboratory experiments to derive the P-wave modulus of snow in relation to density. The P-wave modulus ranged from 10 to 280 MPa for a snow density between 150 and 370 kg/m^3;. The moduli derived from the acoustic measurements correlated well with the CT-based values and both exhibited a power law trend over the entire density range. Encouraged by these results we used the acoustic method to investigate the temporal evolution of the elastic modulus. The rate of increase was very close to values mentioned in literature on the sintering rate of snow. Overall, our results are a first but important step towards a new measurement method to attain the elastic properties of snow.
Larkin, A. I.; Khmelnitskii, D. E.
2013-09-15
Friction of elastic bodies is connected with the passing through the metastable states that arise at the contact of surfaces rubbing against each other. Three models are considered that give rise to the metastable states. Friction forces and their dependence on the pressure are calculated. In Appendix A, the contact problem of elasticity theory is solved with adhesion taken into account.
ERIC Educational Resources Information Center
Girill, T. R.
1972-01-01
The Boyle-Mariotte gas law was formulated in terms of pneumatic springs," subsumed by Hooke under his own stress-strain relation, and generally regarded as a law of elasticity. The subsequent development of Boyle's principle and elasticity provide thought-provoking test cases for Kuhn's notations of paradigm and puzzle solving in physics.…
Support Of The Lunar Fossil Figure By The Elastic Lithosphere
NASA Astrophysics Data System (ADS)
Matsuyama, Isamu
2010-10-01
The figure of the Moon is triaxial, with three different principal moments of inertia, as expected. However, the moment differences are significantly larger than those predicted assuming hydrostatic equilibrium. This has been explained as due to a fossil bulge that retains a figure for prior rotational and tidal deformation, at a time when the Moon was closer to Earth (Jeffeys, 1915; Lambeck & Pullan, 1980; Garrick-Bethell et al.,2006). Garrick-Bethell et al. (2006) illustrated that a fossil figure can entirely account for the moment differences if it is established at a time when the orbital eccentricity was high. They approximate the Moon as a strengthless homogeneous body; however, a strengthless Moon cannot support a fossil figure over billions of years. We extend the analysis of Garrick-Bethell et al. (2006) by taking into the presence of an elastic lithosphere capable of supporting a fossil figure. The fossil figure is established when the elastic lithosphere forms. For a 50 km thick elastic lithosphere, the moment differences can be explained by a lunar orbit with an initial semimajor axis a=17.1 Earth radii and eccentricity e=0.49 if the Moon remains locked in synchronous rotation. If the fossil figure is established during a 3:2 spin-orbit resonance, a=18.1 Earth radii and e=0.16, or a=20.0 Earth radii and e=0.60. The initial semimajor axis decreases with decreasing elastic lithospheric thickness, as expected. The initial orbital eccentricity is not sensitive to the elastic lithospheric thickness. As Lambeck & Pullan (1980) noted, it is unlikely that the moment differences are due to a fossil figure alone. Therefore, we also consider the effect of including other contributions to the moment differences. This work is supported by the Miller Institute for Basic Research.
Support of the lunar fossil figure by the elastic lithosphere
NASA Astrophysics Data System (ADS)
Matsuyama, I.
2010-12-01
The figure of the Moon is triaxial, with three different principal moments of inertia, as expected. However, the moment differences are significantly larger than those predicted assuming hydrostatic equilibrium. This has been explained as due to a fossil bulge that retains a figure for prior rotational and tidal deformation, at a time when the Moon was closer to Earth (Jeffeys, 1915; Lambeck & Pullan, 1980; Garrick-Bethell et al.,2006). Garrick-Bethell et al. (2006) illustrated that a fossil figure can entirely account for the moment differences if it is established at a time when the orbital eccentricity was high. They approximate the Moon as a strengthless homogeneous body; however, a strengthless Moon cannot support a fossil figure over billions of years. We extend the analysis of Garrick-Bethell et al. (2006) by taking into the presence of an elastic lithosphere capable of supporting a fossil figure. The fossil figure is established when the elastic lithosphere forms. For a 50 km thick elastic lithosphere, the moment differences can be explained by a lunar orbit with an initial semimajor axis a=17.1 Earth radii and eccentricity e=0.49 if the Moon remains locked in synchronous rotation. If the fossil figure is established during a 3:2 spin-orbit resonance, a=18.1 Earth radii and e=0.16, or a=20.0 Earth radii and e=0.60. The initial semimajor axis decreases with decreasing elastic lithospheric thickness, as expected. The initial orbital eccentricity is not sensitive to the elastic lithospheric thickness. As Lambeck & Pullan (1980) noted, it is unlikely that the moment differences are due to a fossil figure alone. Therefore, we also consider the effect of including other contributions to the moment differences. This work is supported by the Miller Institute for Basic Research.
Optimization of multilayered composite pressure vessels using exact elasticity solution
Adali, S.; Verijenko, V.E.; Tabakov, P.Y.; Walker, M.
1995-11-01
An approach for the optimal design of thick laminated cylindrical pressure vessels is given. The maximum burst pressure is computed using an exact elasticity solution and subject to the Tsai-Wu failure criterion. The design method is based on an accurate 3-D stress analysis. Exact elasticity solutions are obtained using the stress function approach where the radial, circumferential and shear stresses are determined taking the closed ends of the cylindrical shell into account. Design optimization of multilayered composite pressure vessels are based on the use of robust multidimensional methods which give fast convergence. Two methods are used to determine the optimum ply angles, namely, iterative and gradient methods. Numerical results are given for optimum fiber orientation of each layer for thick and thin-walled multilayered pressure vessels.
Preferred orientation and elastic anisotropy in shales.
Lonardelli, I.; Wenk, H.-R.; Ren, Y.; Univ. of California at Berkeley
2007-03-01
Anisotropy in shales is becoming an important issue in exploration and reservoir geophysics. In this study, the crystallographic preferred orientation of clay platelets that contributes to elastic anisotropy was determined quantitatively by hard monochromatic X-ray synchrotron diffraction in two different shales from drillholes off the coast of Nigeria. To analyze complicated diffraction images with five different phases (illite/smectite, kaolinite, quartz, siderite, feldspar) and many overlapping peaks, we applied a methodology based on the crystallographic Rietveld method. The goal was to describe the intrinsic physical properties of the sample (phase composition, crystallographic preferred orientation, crystal structure, and microstructure) and compute macroscopic elastic properties by averaging single crystal properties over the orientation distribution for each phase. Our results show that elastic anisotropy resulting from crystallographic preferred orientation of the clay particles can be determined quantitatively. This provides a possible way to compare measured seismic anisotropy and texture-derived anisotropy and to estimate the contribution of the low-aspect ratio pores aligned with bedding.
Nonlinear elasticity of semiflexible filament networks.
Meng, Fanlong; Terentjev, Eugene M
2016-08-10
We develop a continuum theory for equilibrium elasticity of a network of crosslinked semiflexible filaments, spanning the full range between flexible entropy-driven chains to stiff athermal rods. We choose the 3-chain constitutive model of network elasticity over several plausible candidates, and derive analytical expressions for the elastic energy at arbitrary strain, with the corresponding stress-strain relationship. The theory fits well to a wide range of experimental data on simple shear in different filament networks, quantitatively matching the differential shear modulus variation with stress, with only two adjustable parameters (which represent the filament stiffness and the pre-tension in the network, respectively). The general theory accurately describes the crossover between the positive and negative Poynting effect (normal stress on imposed shear) on increasing the stiffness of filaments forming the network. We discuss the network stability (the point of marginal rigidity) and the phenomenon of tensegrity, showing that filament pre-tension on crosslinking into the network determines the magnitude of linear modulus G0. PMID:27444846
Nonlinear elasticity of semiflexible filament networks.
Meng, Fanlong; Terentjev, Eugene M
2016-08-10
We develop a continuum theory for equilibrium elasticity of a network of crosslinked semiflexible filaments, spanning the full range between flexible entropy-driven chains to stiff athermal rods. We choose the 3-chain constitutive model of network elasticity over several plausible candidates, and derive analytical expressions for the elastic energy at arbitrary strain, with the corresponding stress-strain relationship. The theory fits well to a wide range of experimental data on simple shear in different filament networks, quantitatively matching the differential shear modulus variation with stress, with only two adjustable parameters (which represent the filament stiffness and the pre-tension in the network, respectively). The general theory accurately describes the crossover between the positive and negative Poynting effect (normal stress on imposed shear) on increasing the stiffness of filaments forming the network. We discuss the network stability (the point of marginal rigidity) and the phenomenon of tensegrity, showing that filament pre-tension on crosslinking into the network determines the magnitude of linear modulus G0.
Bilayer-thickness-mediated interactions between integral membrane proteins.
Kahraman, Osman; Koch, Peter D; Klug, William S; Haselwandter, Christoph A
2016-04-01
Hydrophobic thickness mismatch between integral membrane proteins and the surrounding lipid bilayer can produce lipid bilayer thickness deformations. Experiment and theory have shown that protein-induced lipid bilayer thickness deformations can yield energetically favorable bilayer-mediated interactions between integral membrane proteins, and large-scale organization of integral membrane proteins into protein clusters in cell membranes. Within the continuum elasticity theory of membranes, the energy cost of protein-induced bilayer thickness deformations can be captured by considering compression and expansion of the bilayer hydrophobic core, membrane tension, and bilayer bending, resulting in biharmonic equilibrium equations describing the shape of lipid bilayers for a given set of bilayer-protein boundary conditions. Here we develop a combined analytic and numerical methodology for the solution of the equilibrium elastic equations associated with protein-induced lipid bilayer deformations. Our methodology allows accurate prediction of thickness-mediated protein interactions for arbitrary protein symmetries at arbitrary protein separations and relative orientations. We provide exact analytic solutions for cylindrical integral membrane proteins with constant and varying hydrophobic thickness, and develop perturbative analytic solutions for noncylindrical protein shapes. We complement these analytic solutions, and assess their accuracy, by developing both finite element and finite difference numerical solution schemes. We provide error estimates of our numerical solution schemes and systematically assess their convergence properties. Taken together, the work presented here puts into place an analytic and numerical framework which allows calculation of bilayer-mediated elastic interactions between integral membrane proteins for the complicated protein shapes suggested by structural biology and at the small protein separations most relevant for the crowded membrane
Continuum elastic modeling of graphene resonators.
Atalaya, Juan; Isacsson, Andreas; Kinaret, Jari M
2008-12-01
Starting from an atomistic approach, we have derived a hierarchy of successively more simplified continuum elasticity descriptions for modeling the mechanical properties of suspended graphene sheets. We find that already for deflections of the order of 0.5 A a theory that correctly accounts for nonlinearities is necessary and that for many purposes a set of coupled Duffing-type equations may be used to accurately describe the dynamics of graphene membranes. The descriptions are validated by applying them to square graphene-based resonators with clamped edges and studying numerically their mechanical responses. Both static and dynamic responses are treated, and we find good agreement with recent experimental findings. PMID:19367927
Elastic Response of Crimped Collagen Fibrils
NASA Technical Reports Server (NTRS)
Freed, Alan D.; Doehring, Todd C.
2005-01-01
A physiologic constitutive expression is presented in algorithmic format for the elastic response of wavy collagen fibrils found in soft connective tissues. The model is based on the observation that crimped fibrils have a three-dimensional structure at the micrometer scale that we approximate as a helical spring. The symmetry of this waveform allows the force/displacement relationship derived from Castigliano's theorem to be solved in closed form. Model predictions are in good agreement with experimental observations for mitral-valve chordae tendineae
Elastic model for crimped collagen fibrils
NASA Technical Reports Server (NTRS)
Freed, Alan D.; Doehring, Todd C.
2005-01-01
A physiologic constitutive expression is presented in algorithmic format for the nonlinear elastic response of wavy collagen fibrils found in soft connective tissues. The model is based on the observation that crimped fibrils in a fascicle have a three-dimensional structure at the micron scale that we approximate as a helical spring. The symmetry of this wave form allows the force/displacement relationship derived from Castigliano's theorem to be solved in closed form: all integrals become analytic. Model predictions are in good agreement with experimental observations for mitral-valve chordae tendinece.
Enamel thickness trends in Plio-Pleistocene hominin mandibular molars.
Skinner, Matthew M; Alemseged, Zeresenay; Gaunitz, Charleen; Hublin, Jean-Jacques
2015-08-01
Enamel thickness continues to be an important morphological character in hominin systematics and is frequently invoked in dietary reconstructions of Plio-Pleistocene hominin taxa. However, to date, the majority of published data on molar enamel thickness of Pliocene and early Pleistocene hominins derive from naturally fractured random surfaces of a small number of specimens. In this study we systematically analyze enamel thickness in a large sample of Plio-Pleistocene fossil hominins (n = 99), extant hominoids (n = 57), and modern humans (n = 30). Based on analysis of 2D mesial planes of section derived from microtomography, we examine both average and relative enamel thickness, and the distribution of enamel across buccal, occlusal, and lingual components of mandibular molars. Our results confirm the trend of increasing enamel thickness during the Pliocene that culminates in the thick enamel of the robust Australopithecus species, and then decreases from early Homo to recent modern humans. All hominin taxa share a regional average enamel thickness pattern of thick occlusal enamel and greater buccal than lingual enamel thickness. Pan is unique in exhibiting the thinnest average enamel thickness in the occlusal basin. Statistical analysis indicates that among Pliocene hominins enamel thickness is a weak taxonomic discriminator. The data underlying these results are included in a table in the Supplementary Online Material. PMID:26024565
Elasticity theory of smectic and canonic mesophases
Stallinga, S.; Vertogen, G. )
1995-01-01
The general theory of elasticity for smectic and canonic mesophases is formulated, starting from the assumption that the equilibrium state is spatially periodic. The various surface terms appearing in the deformation free energy density are considered as well. The effective description of the elastic behavior of a general nonchiral smectic mesophase involves one positional elastic constant, 16 bulk orientational elastic constants, and six surface orientational elastic constants. One additional bulk orientational elastic constant is required for the description of a general chiral smectic mesophase. The effective description of the elastic behavior of a general nonchiral canonic mesophase involves six positional elastic constants and three bulk orientational elastic constants. In this case the property of chirality does not introduce additional orientational elastic constants. The elastic constants for some relevant smectic and canonic mesophases are given, including the elastic constants for the antiferroelectric Sm-[ital C][sub [ital A
Coat thickness dependent adsorption of hydrophobic molecules at polymer brushes
NASA Astrophysics Data System (ADS)
Smiatek, Jens; Heuer, Andreas; Wagner, Hendrik; Studer, Armido; Hentschel, Carsten; Chi, Lifeng
2013-01-01
We study the adsorption properties of hydrophobic test particles at polymer brushes with different coat thicknesses via mesoscopic dissipative particle dynamics simulations. Our findings indicate stronger free energies of adsorption at thin polymer brushes. The reason for this difference is mainly given by entropic contributions due to different elastic deformations of the coatings. The numerical findings are supported by analytical calculations and are in good qualitative agreement to experimental fluorescence intensity results.
Crosslinked Polymer Lamellae with Tunable Elasticity & Stability
NASA Astrophysics Data System (ADS)
Discher, Dennis; Bermudez, Harry; Hammer, Daniel; Bates, Frank; Discher, Bohdana
2001-03-01
Polymerization of self-assembled block copolymers has long been viewed as an effective means of locking in nanostructure but very little information exists on end-point properties. To address this issue, amphiphilic diblocks were used to make micron-size vesicles in water with subsequent crosslinking within the membrane. Massive crosslinking of polyethyleneoxide-polybutadiene (EO26-BD46) leads to surface wrinkles and other solid-like elastic characteristics in a membrane with a core that is less than 10 nm thick. Vesicles prove stable in chloroform, retaining their contents, and can also be dehydrated and rehydrated without membrane permeation, implying a defect-free surface many microns squared in area. Mechanically, the extensively crosslinked membranes exhibit elastic moduli consistent with crosslinking between close-packed neighbors and can also withstand lateral stresses of 1000 Atm orders of magnitude higher than any natural lipid membrane. However, bond dilution by tunable addition of the non-crosslinkable analog polyethyleneoxide-polyethylethylene (EO40-EE37) destabilizes the membrane in a manner consistent with rigidity percolation through a novel multi-layer stack of two-dimensional lattices.
Thick Photoresist Original Master:
NASA Astrophysics Data System (ADS)
Mizuno, Hirotaka; Sugihara, Okihiro; Kaino, Toshikuni; Ohe, Yuka; Okamoto, Naomichi; Hoshino, Masahito
A simple and low-cost fabrication method of polymeric optical waveguides with large core sizes for plastic optical fibers is presented. The waveguides are fabricated by hot embossing with a rectangular ridge ultraviolet (UV)-cured epoxy resin stamper. The stamper is fabricated by replication of a rectangular groove mold that is made from silicone rubber replicated from a rectangular ridge original master made from thick photoresist (SU-8). A rectangular ridge shape of the original photoresist master of 1 mm size was realized by using a flattening process, which involves hot embossing before the exposure process and using a UV-cut filter during the exposure process.
Elasticity of methane hydrate phases at high pressure.
Beam, Jennifer; Yang, Jing; Liu, Jin; Liu, Chujie; Lin, Jung-Fu
2016-04-21
Determination of the full elastic constants (cij) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases' compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment. PMID:27389226
Elasticity of interfacial rafts of hard particles with soft shells.
Knoche, Sebastian; Kierfeld, Jan
2015-05-19
We study an elasticity model for compressed protein monolayers or particle rafts at a liquid interface. Based on the microscopic view of hard-core particles with soft shells, a bead-spring model is formulated and analyzed in terms of continuum elasticity theory. The theory can be applied, for example, to hydrophobin-coated air-water interfaces or, more generally, to liquid interfaces coated with an adsorbed monolayer of interacting hard-core particles. We derive constitutive relations for such particle rafts and describe the buckling of compressed planar liquid interfaces as well as their apparent Poisson ratio. We also use the constitutive relations to obtain shape equations for pendant or buoyant capsules attached to a capillary, and to compute deflated shapes of such capsules. A comparison with capsules obeying the usual Hookean elasticity (without hard cores) reveals that the hard cores trigger capsule wrinkling. Furthermore, it is shown that a shape analysis of deflated capsules with hard-core/soft-shell elasticity gives apparent elastic moduli which can be much higher than the original values if Hookean elasticity is assumed.
Elasticity of methane hydrate phases at high pressure
NASA Astrophysics Data System (ADS)
Beam, Jennifer; Yang, Jing; Liu, Jin; Liu, Chujie; Lin, Jung-Fu
2016-04-01
Determination of the full elastic constants (cij) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases' compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment.
Elasticity of interfacial rafts of hard particles with soft shells.
Knoche, Sebastian; Kierfeld, Jan
2015-05-19
We study an elasticity model for compressed protein monolayers or particle rafts at a liquid interface. Based on the microscopic view of hard-core particles with soft shells, a bead-spring model is formulated and analyzed in terms of continuum elasticity theory. The theory can be applied, for example, to hydrophobin-coated air-water interfaces or, more generally, to liquid interfaces coated with an adsorbed monolayer of interacting hard-core particles. We derive constitutive relations for such particle rafts and describe the buckling of compressed planar liquid interfaces as well as their apparent Poisson ratio. We also use the constitutive relations to obtain shape equations for pendant or buoyant capsules attached to a capillary, and to compute deflated shapes of such capsules. A comparison with capsules obeying the usual Hookean elasticity (without hard cores) reveals that the hard cores trigger capsule wrinkling. Furthermore, it is shown that a shape analysis of deflated capsules with hard-core/soft-shell elasticity gives apparent elastic moduli which can be much higher than the original values if Hookean elasticity is assumed. PMID:25901364
Structural and elastic determinants of axial transmission ultrasonic velocity in the human radius
NASA Astrophysics Data System (ADS)
Raum, Kay; Leguerney, Ingrid; Chandelier, Florent; Talmant, Maryline; Saied, Amena; Laugier, Pascal; Peyrin, Françoise
2004-10-01
Accurate clinical interpretation of the sound velocity derived from axial transmission devices requires a detailed understanding of the propa-gation phenomena involved and of the bone factors that have an impact on measurements. In the low-megahertz range, ultrasonic propagation in cortical bone depends on anisotropic elastic tissue properties, porosity, and the spatial dimensions, e.g., cortical thickness. A subset of ten human radius samples from a previous biaxial transmission investigation was inspected using 50-MHz scanning acoustic microscopy (SAM) and synchrotron radiation computed tomography (SR-CT). Low-frequency axial transmission sound speed at 1 and 2 MHz was related to structural properties (cortical thickness C.Th, porosity POR, Haversian cavity density CDH) and tissue parameters (acoustic impedance Z, mineral density MD) on site-matched cross sections. Significant linear multivariate regression models (1 MHz: R=0.84, p<1E-4, 2 MHz: R=0.65, p<1E-4) were found for the combination of C.Th with POR and Z (measured in the external cortical quarter). A modified model accounting for the nonlinear dispersion relation with C.Th was also highly significant (R=0.75, p<1E-4, rmse=49.22 m/s) and explained (after adjustment for dispersion) 55.6% of the variance of the sound velocity by variations of porosity (15.6%) and impedance (40%).
An elastic-plastic analysis of short-leg shear wall structures during earthquakes
NASA Astrophysics Data System (ADS)
Ding, Jianguo; Zhu, Ying
2012-12-01
Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. To analyze the elastic-plastic response of a short-leg shear wall structure during an earthquake, this study modified the multiple-vertical-rod element model of the shear wall, considered the shear lag effect and proposed a multiple-vertical-rod element coupling beam model with a new local stiffness domain. Based on the principle of minimum potential energy and the variational principle, the stiffness matrixes of a short-leg shear wall and a coupling beam are derived in this study. Furthermore, the bending shear correlation for the analysis of different parameters to describe the structure, such as the beam height to span ratio, short-leg shear wall height to thickness ratio, and steel ratio are introduced. The results show that the height to span ratio directly affects the structural integrity; and the short-leg shear wall height to thickness ratio should be limited to a range of approximately 6.0 to 7.0. The design of short-leg shear walls should be in accordance with the "strong wall and weak beam" principle.
Theory of the Sea Ice Thickness Distribution
NASA Astrophysics Data System (ADS)
Toppaladoddi, Srikanth; Wettlaufer, J. S.
2015-10-01
We use concepts from statistical physics to transform the original evolution equation for the sea ice thickness distribution g (h ) from Thorndike et al. into a Fokker-Planck-like conservation law. The steady solution is g (h )=N (q )hqe-h /H, where q and H are expressible in terms of moments over the transition probabilities between thickness categories. The solution exhibits the functional form used in observational fits and shows that for h ≪1 , g (h ) is controlled by both thermodynamics and mechanics, whereas for h ≫1 only mechanics controls g (h ). Finally, we derive the underlying Langevin equation governing the dynamics of the ice thickness h , from which we predict the observed g (h ). The genericity of our approach provides a framework for studying the geophysical-scale structure of the ice pack using methods of broad relevance in statistical mechanics.
Theory of the Sea Ice Thickness Distribution.
Toppaladoddi, Srikanth; Wettlaufer, J S
2015-10-01
We use concepts from statistical physics to transform the original evolution equation for the sea ice thickness distribution g(h) from Thorndike et al. into a Fokker-Planck-like conservation law. The steady solution is g(h)=N(q)h(q)e(-h/H), where q and H are expressible in terms of moments over the transition probabilities between thickness categories. The solution exhibits the functional form used in observational fits and shows that for h≪1, g(h) is controlled by both thermodynamics and mechanics, whereas for h≫1 only mechanics controls g(h). Finally, we derive the underlying Langevin equation governing the dynamics of the ice thickness h, from which we predict the observed g(h). The genericity of our approach provides a framework for studying the geophysical-scale structure of the ice pack using methods of broad relevance in statistical mechanics. PMID:26551827
Radial thickness variations of Orientale basin ejecta
NASA Technical Reports Server (NTRS)
Cordell, B. M.
1978-01-01
Moore et al. (1974) measure the thickness of Orientale basin ejecta on the basis of filling of individual prebasin craters and a depth-diameter relation for fresh lunar craters. In the reported investigation the concept of filling of preexisting craters with basin ejecta is utilized somewhat differently to ascertain Orientale basin ejecta thicknesses and volume from the Cordillera ring with a radius of 450 km out to almost 2 radii. Briefly, the approach is to assume a reasonable geometric model for the form of Orientale ejecta, calculate how many pre-Orientale craters would be destroyed by the deposition of the ejecta, and match the model to Orientale crater statistics. The results of the investigation show that a radial ejecta thickness function can be derived from crater statistics.
Elasticity of hcp cobalt at high pressure and temperature: a quasi-harmonic case
Antonangeli, D; Krisch, M; Farber, D L; Ruddle, D G; Fiquet, G
2007-11-30
We performed high-resolution inelastic x-ray scattering measurements on a single crystal of hcp cobalt at simultaneous high pressure and high temperature, deriving 4 of the 5 independent elements of the elastic tensor. Our experiments indicate that the elasticity of hcp-Co is well described within the frame of a quasi-harmonic approximation and that anharmonic high-temperature effects on the elastic moduli, sound velocities and elastic anisotropy are minimal at constant density. These results support the validity of the Birch's law and represent an important benchmark for ab initio thermal lattice dynamics and molecular-dynamics simulations.
Coherency in neutrino-nucleus elastic scattering
NASA Astrophysics Data System (ADS)
Kerman, S.; Sharma, V.; Deniz, M.; Wong, H. T.; Chen, J.-W.; Li, H. B.; Lin, S. T.; Liu, C.-P.; Yue, Q.; Texono Collaboration
2016-06-01
Neutrino-nucleus elastic scattering provides a unique laboratory to study the quantum mechanical coherency effects in electroweak interactions, towards which several experimental programs are being actively pursued. We report results of our quantitative studies on the transitions towards decoherency. A parameter (α ) is identified to describe the degree of coherency, and its variations with incoming neutrino energy, detector threshold, and target nucleus are studied. The ranges of α that can be probed with realistic neutrino experiments are derived, indicating complementarity between projects with different sources and targets. Uncertainties in nuclear physics and in α would constrain sensitivities in probing physics beyond the standard model. The maximum neutrino energies corresponding to α >0.95 are derived.
Inverse obstacle scattering for elastic waves
NASA Astrophysics Data System (ADS)
Li, Peijun; Wang, Yuliang; Wang, Zewen; Zhao, Yue
2016-11-01
Consider the scattering of a time-harmonic plane wave by a rigid obstacle which is embedded in an open space filled with a homogeneous and isotropic elastic medium. An exact transparent boundary condition is introduced to reduce the scattering problem into a boundary value problem in a bounded domain. Given the incident field, the direct problem is to determine the displacement of the wave field from the known obstacle; the inverse problem is to determine the obstacle’s surface from the measurement of the displacement on an artificial boundary enclosing the obstacle. In this paper, we consider both the direct and inverse problems. The direct problem is shown to have a unique weak solution by examining its variational formulation. The domain derivative is derived for the displacement with respect to the variation of the surface. A continuation method with respect to the frequency is developed for the inverse problem. Numerical experiments are presented to demonstrate the effectiveness of the proposed method.
A Membrane Model from Implicit Elasticity Theory
Freed, A. D.; Liao, J.; Einstein, D. R.
2014-01-01
A Fungean solid is derived for membranous materials as a body defined by isotropic response functions whose mathematical structure is that of a Hookean solid where the elastic constants are replaced by functions of state derived from an implicit, thermodynamic, internal-energy function. The theory utilizes Biot’s (1939) definitions for stress and strain that, in 1-dimension, are the stress/strain measures adopted by Fung (1967) when he postulated what is now known as Fung’s law. Our Fungean membrane model is parameterized against a biaxial data set acquired from a porcine pleural membrane subjected to three, sequential, proportional, planar extensions. These data support an isotropic/deviatoric split in the stress and strain-rate hypothesized by our theory. These data also demonstrate that the material response is highly non-linear but, otherwise, mechanically isotropic. These data are described reasonably well by our otherwise simple, four-parameter, material model. PMID:24282079
Elastic energy release in great earthquakes and eruptions
NASA Astrophysics Data System (ADS)
Gudmundsson, Agust
2014-05-01
The sizes of earthquakes are measured using well-defined, measurable quantities such as seismic moment and released (transformed) elastic energy. No similar measures exist for the sizes of volcanic eruptions, making it difficult to compare the energies released in earthquakes and eruptions. Here I provide a new measure of the elastic energy (the potential mechanical energy) associated with magma chamber rupture and contraction (shrinkage) during an eruption. For earthquakes and eruptions, elastic energy derives from two sources: (1) the strain energy stored in the volcano/fault zone before rupture, and (2) the external applied load (force, pressure, stress, displacement) on the volcano/fault zone. From thermodynamic considerations it follows that the elastic energy released or transformed (dU) during an eruption is directly proportional to the excess pressure (pe) in the magma chamber at the time of rupture multiplied by the volume decrease (-dVc) of the chamber, so that . This formula can be used as a basis for a new eruption magnitude scale, based on elastic energy released, which can be related to the moment-magnitude scale for earthquakes. For very large eruptions (>100 km3), the volume of the feeder-dike is negligible, so that the decrease in chamber volume during an eruption corresponds roughly to the associated volume of erupted materials , so that the elastic energy is . Using a typical excess pressures of 5 MPa, it is shown that the largest known eruptions on Earth, such as the explosive La Garita Caldera eruption (27-28 million years ago) and largest single (effusive) Colombia River basalt lava flows (15-16 million years ago), both of which have estimated volumes of about 5000 km3, released elastic energy of the order of 10EJ. For comparison, the seismic moment of the largest earthquake ever recorded, the M9.5 1960 Chile earthquake, is estimated at 100 ZJ and the associated elastic energy release at 10EJ.
Flame resistant elastic elastomeric fibers
NASA Technical Reports Server (NTRS)
Howarth, J. T.; Massucco, A. A.
1972-01-01
Development of materials to improve flame resistance of elastic elastomeric fibers is discussed. Two approaches, synthesis of polyether based urethanes and modification of synthesized urethanes with flame ratardant additives, are described. Specific applications of both techniques are presented.
Measuring How Elastic Arteries Function.
ERIC Educational Resources Information Center
DeMont, M. Edwin; MacGillivray, Patrick S.; Davison, Ian G.; McConnell, Colin J.
1997-01-01
Describes a procedure used to measure force and pressure in elastic arteries. Discusses the physics of the procedure and recommends the use of bovine arteries. Explains the preparation of the arteries for the procedure. (DDR)
Elasticity of crystalline molecular explosives
Hooks, Daniel E.; Ramos, Kyle J.; Bolme, C. A.; Cawkwell, Marc J.
2015-04-14
Crystalline molecular explosives are key components of engineered explosive formulations. In precision applications a high degree of consistency and predictability is desired under a range of conditions to a variety of stimuli. Prediction of behaviors from mechanical response and failure to detonation initiation and detonation performance of the material is linked to accurate knowledge of the material structure and first stage of deformation: elasticity. The elastic response of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), and cyclotetramethylene tetranitramine (HMX), including aspects of material and measurement variability, and computational methods are described in detail. Experimental determinations of elastic tensors are compared, and an evaluation of sources of error is presented. Furthermore, computed elastic constants are also compared for these materials and for triaminotrinitrobenzene (TATB), for which there are no measurements.
Elasticity of crystalline molecular explosives
Hooks, Daniel E.; Ramos, Kyle J.; Bolme, C. A.; Cawkwell, Marc J.
2015-04-14
Crystalline molecular explosives are key components of engineered explosive formulations. In precision applications a high degree of consistency and predictability is desired under a range of conditions to a variety of stimuli. Prediction of behaviors from mechanical response and failure to detonation initiation and detonation performance of the material is linked to accurate knowledge of the material structure and first stage of deformation: elasticity. The elastic response of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), and cyclotetramethylene tetranitramine (HMX), including aspects of material and measurement variability, and computational methods are described in detail. Experimental determinations of elastic tensors are compared, andmore » an evaluation of sources of error is presented. Furthermore, computed elastic constants are also compared for these materials and for triaminotrinitrobenzene (TATB), for which there are no measurements.« less
Elastic protectors for ultrasound injection
Barkhatov, V.A.; Nesterova, L.A.
1995-07-01
A new material has been developed for elastic protectors on ultrasonic probes: sonar rubber. This combines low ultrasonic absorption, high strength, and wear resistance, and so the rubber can be used in sensor designs.
Hsiao, Chao-Tsung; Chahine, Georges L.
2013-01-01
A simplified three-dimensional (3-D) zero-thickness shell model was developed to recover the non-spherical response of thick-shelled encapsulated microbubbles subjected to ultrasound excitation. The model was validated by comparison with previously developed models and was then used to study the mechanism of bubble break-up during non-spherical deformations resulting from the presence of a nearby rigid boundary. The effects of the shell thickness and the bubble standoff distance from the solid wall on the bubble break-up were studied parametrically for a fixed insonification frequency and amplitude. A diagram of bubble shapes versus the normalized shell thickness and wall standoff was derived, and the potential bubble shapes at break-up from reentrant jets were categorized resulting in four distinct zones. PMID:23556560
Ultrasonic Inspection Of Thick Sections
NASA Technical Reports Server (NTRS)
Friant, C. L.; Djordjevic, B. B.; O'Keefe, C. V.; Ferrell, W.; Klutz, T.
1993-01-01
Ultrasonics used to inspect large, relatively thick vessels for hidden defects. Report based on experiments in through-the-thickness transmission of ultrasonic waves in both steel and filament-wound composite cases of solid-fuel rocket motors.
Kanamori, H; Press, F
1970-04-25
A rapid decrease in shear velocity in the suboceanic mantle is used to infer the thickness of the lithosphere. It is proposed that new and highly precise group velocity data constrain the solutions and imply a thickness near 70 km.
Levesque, Daniel; Moreau, Andre; Dubois, Marc; Monchalin, Jean-Pierre; Bussiere, Jean; Lord, Martin; Padioleau, Christian
2000-01-01
Apparatus and method for detecting shear resonances includes structure and steps for applying a radiation pulse from a pulsed source of radiation to an object to generate elastic waves therein, optically detecting the elastic waves generated in the object, and analyzing the elastic waves optically detected in the object. These shear resonances, alone or in combination with other information, may be used in the present invention to improve thickness measurement accuracy and to determine geometrical, microstructural, and physical properties of the object. At least one shear resonance in the object is detected with the elastic waves optically detected in the object. Preferably, laser-ultrasound spectroscopy is utilized to detect the shear resonances.
Bauer-Gogonea, S.; Camacho-Gonzalez, F.; Schwoediauer, R.; Ploss, B.; Bauer, S.
2007-09-17
Nonlinearities in ferroelectret polymer foam capacitors arise from voltage-dependent thickness changes. Such thickness changes are caused by the converse piezoelectric and electrostrictive effects in these soft materials. The authors show that the higher harmonics of the current response during application of a sinusoidal voltage to ferroelectret capacitors provide information on the elastic and electromechanical properties of the foam. The authors demonstrate the potential of this versatile measurement technique by investigating the temperature dependence of the piezoelectric response and by monitoring the changes in the elastic and electromechanical properties during inflation of cellular polypropylene.
NASA Astrophysics Data System (ADS)
Bauer-Gogonea, S.; Camacho-Gonzalez, F.; Schwödiauer, R.; Ploss, B.; Bauer, S.
2007-09-01
Nonlinearities in ferroelectret polymer foam capacitors arise from voltage-dependent thickness changes. Such thickness changes are caused by the converse piezoelectric and electrostrictive effects in these soft materials. The authors show that the higher harmonics of the current response during application of a sinusoidal voltage to ferroelectret capacitors provide information on the elastic and electromechanical properties of the foam. The authors demonstrate the potential of this versatile measurement technique by investigating the temperature dependence of the piezoelectric response and by monitoring the changes in the elastic and electromechanical properties during inflation of cellular polypropylene.
Cosserat elasticity of negative Poisson’s ratio foam: experiment
NASA Astrophysics Data System (ADS)
Rueger, Zach; Lakes, Roderic S.
2016-05-01
Negative Poisson’s ratio polymer foams derived from reticulated open cell foams exhibit large size effects in torsion and bending. Effective moduli increase as diameter decreases in contrast to the prediction of classical elasticity. Size effects of this sort are predicted by Cosserat (micropolar) elasticity in which points can rotate as well as translate and distributed moments are incorporated. The Cosserat coupling number N was about twice as large as that of as-received foam, leading to strong effects. The torsion characteristic length {{\\ell }}{{t}} was similar. Cosserat effects are known to enhance toughness and immunity from stress concentration.
Distinct Transport Regimes for Two Elastically Coupled Molecular Motors
NASA Astrophysics Data System (ADS)
Berger, Florian; Keller, Corina; Klumpp, Stefan; Lipowsky, Reinhard
2012-05-01
Cooperative cargo transport by two molecular motors involves an elastic motor-motor coupling, which can reduce the motors’ velocity and/or enhance their unbinding from the filament. We show theoretically that these interference effects lead, in general, to four distinct transport regimes. In addition to a weak coupling regime, kinesin and dynein motors are found to exhibit a strong coupling and an enhanced unbinding regime, whereas myosin motors are predicted to attain a reduced velocity regime. All of these regimes, which we derive by explicit calculations and general time scale arguments, can be explored experimentally by varying the elastic coupling strength.
Simulation study of the elastic mechanical properties of HMX
Sewell, T. D.
2002-01-01
Results of calculations of the elastic mechanical response of crystalline HMX polymorphs are summarized. The work is based on atomistic molecular dynamics and Monte Carlo simulations. Principal achievements are: (1) prediction of room temperature and pressure elastic tensors for {beta}-, {alpha}- and {delta}-HMX; (2) calculation of room temperature isotherms for each polymorph; (3) extraction of initial bulk modulus and pressure derivative from the isotherm; and (4) 'discovery' of a pressure induced phase transition in {alpha}-HMX (preliminary result). Details of the work, and implications, will be discussed.
Converging shocks in elastic-plastic solids.
Ortega, A López; Lombardini, M; Hill, D J
2011-11-01
We present an approximate description of the behavior of an elastic-plastic material processed by a cylindrically or spherically symmetric converging shock, following Whitham's shock dynamics theory. Originally applied with success to various gas dynamics problems, this theory is presently derived for solid media, in both elastic and plastic regimes. The exact solutions of the shock dynamics equations obtained reproduce well the results obtained by high-resolution numerical simulations. The examined constitutive laws share a compressible neo-Hookean structure for the internal energy e=e(s)(I(1))+e(h)(ρ,ς), where e(s) accounts for shear through the first invariant of the Cauchy-Green tensor, and e(h) represents the hydrostatic contribution as a function of the density ρ and entropy ς. In the strong-shock limit, reached as the shock approaches the axis or origin r=0, we show that compression effects are dominant over shear deformations. For an isothermal constitutive law, i.e., e(h)=e(h)(ρ), with a power-law dependence e(h) is proportional to ρ(α), shock dynamics predicts that for a converging shock located at r=R(t) at time t, the Mach number increases as M is proportional to [log(1/R)](α), independently of the space index s, where s=2 in cylindrical geometry and 3 in spherical geometry. An alternative isothermal constitutive law with p(ρ) of the arctanh type, which enforces a finite density in the strong-shock limit, leads to M is proportional to R(-(s-1)) for strong shocks. A nonisothermal constitutive law, whose hydrostatic part e(h) is that of an ideal gas, is also tested, recovering the strong-shock limit M is proportional to R(-(s-1)/n(γ)) originally derived by Whitham for perfect gases, where γ is inherently related to the maximum compression ratio that the material can reach, (γ+1)/(γ-1). From these strong-shock limits, we also estimate analytically the density, radial velocity, pressure, and sound speed immediately behind the shock. While the
NASA Astrophysics Data System (ADS)
Masterlark, T.; Lu, Z.; Rykhus, R.
2003-12-01
We construct finite element models (FEMs) of a pyroclastic flow deposit (PFD) emplaced during the 1986 eruption of Augustine volcano, Alaska. Interferometric synthetic aperture radar (InSAR) imagery documents the consistent contraction of the PFD during 1992-2000. Three-dimensional problem domains of the FEMs include an elastic substrate overlain by a thermoelastic material representing the PFD. The geometry of the substrate is determined from a digital elevation model (DEM) and bathymetry data. The thickness of the PFD is initially determined from the difference between post- and pre-eruptive DEMs. Systematic prediction errors suggest the PFD thickness distribution, estimated from the DEM difference, is inaccurate. We combine InSAR images, FEMs, and an adaptive mesh algorithm to re-estimate the geometry of the PFD and optimize the thickness distribution for the PFD. Prediction errors from the FEM that includes an optimized PFD geometry are reduced by 20% with respect to those from an FEM that includes a PFD geometry derived from the DEM difference.
Accurate stress resultants equations for laminated composite deep thick shells
Qatu, M.S.
1995-11-01
This paper derives accurate equations for the normal and shear force as well as bending and twisting moment resultants for laminated composite deep, thick shells. The stress resultant equations for laminated composite thick shells are shown to be different from those of plates. This is due to the fact the stresses over the thickness of the shell have to be integrated on a trapezoidal-like shell element to obtain the stress resultants. Numerical results are obtained and showed that accurate stress resultants are needed for laminated composite deep thick shells, especially if the curvature is not spherical.
Biometric estimation of chest wall thickness of females
Berger, C.D.; Lane, B.H.
1985-09-01
Optimal use of whole-body counting data to estimate pulmonary deposition of many of the actinides is dependent upon accurate measurement of the thickness of the chest wall because of severe attenuation of low-energy x rays and photons associated with the decay of these radionuclides. An algorithm for estimation of female chest wall thicknesses, verified by real-time ultrasonic measurements, has been derived based on the correlation of measured chest wall thickness and other common biometric quantities. Use of this algorithm will reduce the error generally associated with estimation of internal actinide deposition previously resulting from assuming an average chest wall thickness for all female subjects.
Elastic-plastic analysis of crack in ductile adhesive joint
Ikeda, Toru; Miyazaki, Noriyuki; Yamashita, Akira; Munakata, Tsuyoshi
1995-11-01
The fracture of a crack in adhesive is important to the structural integrity of adhesive structures and composite materials. Though the fracture toughness of a material should be constant according to fracture mechanics, it is said that the fracture toughness of a crack in an adhesive joint depends on the bond thickness. In the present study, the elastic-plastic stress analyses of a crack in a thin adhesive layer are performed by the combination of the boundary element method and the finite element method. The effect of adhesive thickness on the J-integral, the Q`-factor which is a modified version of the Q-factor, and the crack tip opening displacement (CTOD) are investigated. It is found from the analyses that the CTOD begins to decrease at very thin bond thickness, the Q`-factor being almost constant. The decrease of the fracture toughness at very thin adhesive layer is expected by the present analysis.
Waterway Ice Thickness Measurements
NASA Technical Reports Server (NTRS)
1978-01-01
The ship on the opposite page is a U. S. Steel Corporation tanker cruising through the ice-covered waters of the Great Lakes in the dead of winter. The ship's crew is able to navigate safely by plotting courses through open water or thin ice, a technique made possible by a multi-agency technology demonstration program in which NASA is a leading participant. Traditionally, the Great Lakes-St. Lawrence Seaway System is closed to shipping for more than three months of winter season because of ice blockage, particularly fluctuations in the thickness and location of ice cover due to storms, wind, currents and variable temperatures. Shippers have long sought a system of navigation that would allow year-round operation on the Lakes and produce enormous economic and fuel conservation benefits. Interrupted operations require that industrial firms stockpile materials to carry them through the impassable months, which is costly. Alternatively, they must haul cargos by more expensive overland transportation. Studies estimate the economic benefits of year-round Great Lakes shipping in the hundreds of millions of dollars annually and fuel consumption savings in the tens of millions of gallons. Under Project Icewarn, NASA, the U.S. Coast Guard and the National Oceanic Atmospheric Administration collaborated in development and demonstration of a system that permits safe year-round operations. It employs airborne radars, satellite communications relay and facsimile transmission to provide shippers and ships' masters up-to-date ice charts. Lewis Research Center contributed an accurate methods of measuring ice thickness by means of a special "short-pulse" type of radar. In a three-year demonstration program, Coast Guard aircraft equipped with Side-Looking Airborne Radar (SLAR) flew over the Great Lakes three or four times a week. The SLAR, which can penetrate clouds, provided large area readings of the type and distribution of ice cover. The information was supplemented by short
Buckling modes of elastic thin films on elastic substrates
NASA Astrophysics Data System (ADS)
Mei, Haixia; Huang, Rui; Chung, Jun Young; Stafford, Christopher M.; Yu, Hong-Hui
2007-04-01
Two buckling modes have been observed in thin films: buckle delamination and wrinkling. This letter identifies the conditions for selecting the favored buckling modes for elastic films on elastic substrates. Transition from one buckling mode to another is predicted as the stiffness ratio between the substrate and the film or is predicted for variation of the stiffness ratio between the substrate and the film or variation of theinterfacial defect size. The theoretical results are demonstrated experimentally by observing the coexistence of both buckling modes and mode transition in one film-substrate system.
Contact instabilities of anisotropic and inhomogeneous soft elastic films
NASA Astrophysics Data System (ADS)
Tomar, Gaurav; Sharma, Ashutosh
2012-02-01
Anisotropy plays important roles in various biological phenomena such as adhesion of geckos and grasshoppers enabled by the attachment pods having hierarchical structures like thin longitudinal setae connected with threads mimicked by anisotropic films. We study the contact instability of a transversely isotropic thin elastic film when it comes in contact proximity of another surface. In the present study we investigate the contact stability of a thin incompressible transversely isotropic film by performing linear stability analysis. Based on the linear stability analysis, we show that an approaching contactor renders the film unstable. The critical wavelength of the instability is a function of the total film thickness and the ratio of the Young's modulus in the longitudinal direction and the shear modulus in the plane containing the longitudinal axis. We also analyze the stability of a thin gradient film that is elastically inhomogeneous across its thickness. Compared to a homogeneous elastic film, it becomes unstable with a longer wavelength when the film becomes softer in going from the surface to the substrate.
Weak Elastic Anisotropy in a Cracked Rock
NASA Astrophysics Data System (ADS)
Zhu, W.; Wong, T.
2006-12-01
Crack and textural fabrics have significant control over the development of mechanical anisotropy in a rock. Bedding in sedimentary rocks, cleavage in slates, preferred orientation of anisotropic minerals and anisotropic distribution of microcracks can all contribute to elastic anisotropy. Using Kachanov's (1992, 1993) formulation we analyzed the effects of an axisymmetric system of microcracks on seismic anisotropy. The elastic behavior of such a cracked rock is transversely isotropic, and its seismic properties can be characterized by the three Thomsen parameters. In this study we calculated the parameters ɛ, δ and γ under dry and saturated conditions. We derived analytic expressions for the model proposed by Sayers & Kachanov (1995), which assumes that the contribution from the fourth rank crack density tensor is negligible. This model predicts that the elliptic anisotropy condition ɛ=δ is obeyed in a dry rock. Guided by microstructural observations we adopted a two-parameter axisymmetric distribution to characterize the crack density, which predicts that δ and γ in a fluid saturated rock are related to ɛ in a nonlinear manner. All three Thomsen parameters are sensitively dependent on the crack density difference. While our model shows basic agreement with some of the laboratory data on seismic anisotropy in saturated shale, there are discrepancies which suggest that the petrofabric associated with preferred orientation of clay minerals and elastic anisotropy of the rock matrix may have considerable influence which should not be neglected in model. Preliminary comparison with borehole log data suggests rock physics tests which may be useful for interpreting the shear wave anisotropy observations.
Substrate-dependent cell elasticity measured by optical tweezers indentation
NASA Astrophysics Data System (ADS)
Yousafzai, Muhammad S.; Ndoye, Fatou; Coceano, Giovanna; Niemela, Joseph; Bonin, Serena; Scoles, Giacinto; Cojoc, Dan
2016-01-01
In the last decade, cell elasticity has been widely investigated as a potential label free indicator for cellular alteration in different diseases, cancer included. Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. In this paper, we propose a simple approach to perform cell indentation at pN forces by axially moving the cell against a trapped microbead. The elastic modulus is calculated using the Hertz-model. Besides the axial component, the setup also allows us to examine the lateral cell-bead interaction. This technique has been applied to measure the local elasticity of HBL-100 cells, an immortalized human cell line, originally derived from the milk of a woman with no evidence of breast cancer lesions. In addition, we have studied the influence of substrate stiffness on cell elasticity by performing experiments on cells cultured on two substrates, bare and collagen-coated, having different stiffness. The mean value of the cell elastic modulus measured during indentation was 26±9 Pa for the bare substrate, while for the collagen-coated substrate it diminished to 19±7 Pa. The same trend was obtained for the elastic modulus measured during the retraction of the cell: 23±10 Pa and 13±7 Pa, respectively. These results show the cells adapt their stiffness to that of the substrate and demonstrate the potential of this setup for low-force probing of modifications to cell mechanics induced by the surrounding environment (e.g. extracellular matrix or other cells).
Shakedown analysis of thick cylinders with multiple radial openings
NASA Astrophysics Data System (ADS)
Singh, A. K.; Khan, I. A.; Sharma, K.; Sen, R. N.; Vyas, K. N.
2016-09-01
Shakedown and ratcheting behaviour of thick cylinder with multiple radial crossholes is investigated in this paper by inelastic finite element analysis. Effect of opening radius (ri/Ri), thickness of the vessel i.e. thickness ratios (R0/Ri) and availability of ligament between two openings (L/1) is studied. In order to normalise the applied pressure, limit load for thick cylindrical vessel without any opening was considered and it was found to be highly conservative. Later, interaction diagram normalised with respect to the limit load for thick cylinder taking into account the effects of opening was plotted. In order to distinguish between plastic shakedown and ratcheting, thickness advantage is taken into consideration. A more practical assessment technique is also discussed where the maximum range of thermal stress is computed through finite element analysis and the results were found to be in accordance with the Bree diagram. However the elastic-plastic shakedown boundary was found to be affected significantly with the incorporation of discontinuities and with changes in the parameters.
Mapping Elasticity at the Nanoscale
NASA Astrophysics Data System (ADS)
Stan, Gheorghe; Price, William
2006-03-01
In the last few years Atomic Force Acoustic Microscopy has been developed to investigate the elastic response of materials at the nanoscale ^[1],[2]. We have extended this technique to the real-time mapping of nanomechanical properties of material surfaces. This mapping allows us to investigate the local variation of elastic properties with nanometer resolution and to reduce the uncertainties that arise from single measurements. Quantitative measurements are acquired by first performing an accurate calibration of the elastic properties of the Atomic Force Microscope’s probes with respect to single crystal reference materials. A wide variety of surfaces with different mechanical properties have been investigated to illustrate the applicability of this technique. ^[1] U. Rabe et al., Surf. Interface Anal. 33 , 65 (2002)^[2] D.C. Hurley et al., J. Appl. Phys. 94, 2347 (2003)
Elastic properties of nematoid arrangements formed by amoeboid cells
NASA Astrophysics Data System (ADS)
Kemkemer, R.; Kling, D.; Kaufmann, D.; Gruler, H.
2000-02-01
In culture migrating and interacting amoeboid cells can form nematoid arrangements in analogy to a nematic liquid crystal phase. A nematoid arrangement is formed if the interaction has an apolar symmetry. Different cell types like human melanocytes (=pigment cells of the skin), human fibroblasts (=connective tissue cells), human osteoblasts (=bone cells), human adipocytes (=fat cells) etc., form a nematoid structure. Our hypothesis is that elastic properties of these nematoid structures can be described in analogy to that of classical nematic liquid crystals. The orientational elastic energy is derived and the orientational defects (disclination) of nematoid arrangements are investigated. The existence of half-numbered disclinations shows that the nematoid structure has an apolar symmetry. The density- and order parameter dependence of the orientational elastic constants and their absolute values are estimated. From the defect structure, one finds that the splay elastic constant is smaller than the bend elastic constant (melanocytes). The core of a disclination is either a cell free space or occupied by non oriented cells (isotropic state), by a cell with a different symmetry, or by another cell type.
Elastic Waves Green Functions For Stratified Medium
NASA Astrophysics Data System (ADS)
Albuquerque, E. L.; Ferreira, E. C.; Mauriz, P. W.
Multiple scattering analysis of elastic waves propagating in a stratified medium is a powerful method to model seismic reflection signals, widely used in the exploration for oil and gas reservoirs. Reflection imaging and inversion method derive their exis- tence from the presence of singularities in the Earth's material properties that support the waves. Considering a Green's function formalism based on the {it frequency distri- bution} of the elastic wave spectra, we study their propagation within a model in which the Earth is treated as a stratified medium. The calculations are based on the linear response function approach, which is very convenient to deal with this kind of prob- lem. Both the displacement ({it space}) and the wavevector ({it space-time}) Green's functions are determined. A damping term gamma is included in a phenomenolog- ical way into the wavevector expression. In order to examine the waves' excitation, we also determine, by using the fluctuation-dissipation theorem, their power spectra, which have many interesting properties.
Folding and faulting of an elastic continuum
Gourgiotis, Panos A.
2016-01-01
Folding is a process in which bending is localized at sharp edges separated by almost undeformed elements. This process is rarely encountered in Nature, although some exceptions can be found in unusual layered rock formations (called ‘chevrons’) and seashell patterns (for instance Lopha cristagalli). In mechanics, the bending of a three-dimensional elastic solid is common (for example, in bulk wave propagation), but folding is usually not achieved. In this article, the route leading to folding is shown for an elastic solid obeying the couple-stress theory with an extreme anisotropy. This result is obtained with a perturbation technique, which involves the derivation of new two-dimensional Green's functions for applied concentrated force and moment. While the former perturbation reveals folding, the latter shows that a material in an extreme anisotropic state is also prone to a faulting instability, in which a displacement step of finite size emerges. Another failure mechanism, namely the formation of dilation/compaction bands, is also highlighted. Finally, a geophysical application to the mechanics of chevron formation shows how the proposed approach may explain the formation of natural structures. PMID:27118925
Design of controlled elastic and inelastic structures
NASA Astrophysics Data System (ADS)
Reinhorn, A. M.; Lavan, O.; Cimellaro, G. P.
2009-12-01
One of the founders of structural control theory and its application in civil engineering, Professor Emeritus Tsu T. Soong, envisioned the development of the integral design of structures protected by active control devices. Most of his disciples and colleagues continuously attempted to develop procedures to achieve such integral control. In his recent papers published jointly with some of the authors of this paper, Professor Soong developed design procedures for the entire structure using a design — redesign procedure applied to elastic systems. Such a procedure was developed as an extension of other work by his disciples. This paper summarizes some recent techniques that use traditional active control algorithms to derive the most suitable (optimal, stable) control force, which could then be implemented with a combination of active, passive and semi-active devices through a simple match or more sophisticated optimal procedures. Alternative design can address the behavior of structures using Liapunov stability criteria. This paper shows a unified procedure which can be applied to both elastic and inelastic structures. Although the implementation does not always preserve the optimal criteria, it is shown that the solutions are effective and practical for design of supplemental damping, stiffness enhancement or softening, and strengthening or weakening.
NASA Astrophysics Data System (ADS)
Nakamura, Nozomu; Yamasaki, Kazuhito
2016-08-01
We consider the relationship between the magnetic field and the non-elastic displacement field including defects, from the viewpoints of non-commutativity of the positions and non-commutativity of the derivatives. The former non-commutativity is related to the magnetic field by Feynman's proof (1948), and the latter is related to the defect fields by the continuum theory of defects. We introduce the concept of differential geometry to the non-elastic displacement field and derive an extended relation that includes basic equations, such as Gauss's law for magnetism and the conservation law for dislocation density. The relation derived in this paper also extends the first Bianchi identity in linear approximation to include the effect of magnetism. These findings suggest that Feynman's approach with a non-elastic displacement field is useful for understanding the relationship between magnetism and non-elastic mechanics.
Price and Income Elasticities of Iranian Exports
NASA Astrophysics Data System (ADS)
Atrkar Roshan, Sedigheh
This study investigates the export demand elasticities at the aggregate and disaggregated levels over the period 1977 to 2001 for Iran. By utilizing an export demand model and using time series techniques that account for the nonstationarity in the data, the price and income elasticities of demand are estimated by commodity class. As the elasticities of demand for various categories of exports are different, while they are crucial for policy determination. Based upon the estimated results, price and income elasticities are almost similar to those obtained in earlier studies in the case of developing countries. The main findings of this paper demonstrate that, price elasticities are smaller than -1 for all exports categories, whereas the income elasticities are found to be greater than one. The results also suggested, the income elasticities of industrial goods are higher compared to other export categories, while the lower elasticities are found in primary exports. The price and income elasticity estimates have also good statistical properties.
Thermal fluctuations and rubber elasticity.
Xing, Xiangjun; Goldbart, Paul M; Radzihovsky, Leo
2007-02-16
The effects of thermal elastic fluctuations in rubbery materials are examined. It is shown that, due to their interplay with the incompressibility constraint, these fluctuations qualitatively modify the large-deformation stress-strain relation, compared to that of classical rubber elasticity. To leading order, this mechanism provides a simple and generic explanation for the peak structure of Mooney-Rivlin stress-strain relation and shows good agreement with experiments. It also leads to the prediction of a phonon correlation function that depends on the external deformation. PMID:17359034
Thermal Fluctuations and Rubber Elasticity
NASA Astrophysics Data System (ADS)
Xing, Xiangjun; Goldbart, Paul M.; Radzihovsky, Leo
2007-02-01
The effects of thermal elastic fluctuations in rubbery materials are examined. It is shown that, due to their interplay with the incompressibility constraint, these fluctuations qualitatively modify the large-deformation stress-strain relation, compared to that of classical rubber elasticity. To leading order, this mechanism provides a simple and generic explanation for the peak structure of Mooney-Rivlin stress-strain relation and shows good agreement with experiments. It also leads to the prediction of a phonon correlation function that depends on the external deformation.
Cellular Uptake of Elastic Nanoparticles
NASA Astrophysics Data System (ADS)
Yi, Xin; Shi, Xinghua; Gao, Huajian
2011-08-01
A fundamental understanding of cell-nanomaterial interaction is of essential importance to nanomedicine and safe applications of nanotechnology. Here we investigate the adhesive wrapping of a soft elastic vesicle by a lipid membrane. We show that there exist a maximum of five distinct wrapping phases based on the stability of full wrapping, partial wrapping, and no wrapping states. The wrapping phases depend on the vesicle size, adhesion energy, surface tension of membrane, and bending rigidity ratio between vesicle and membrane. These results are of immediate interest to the study of vesicular transport and endocytosis or phagocytosis of elastic particles into cells.
NASA Astrophysics Data System (ADS)
Czechowski, Grzegorz; Zywucki, B.; Jadzyn, Jan
1993-10-01
The Frederiks transitions for the n-octyloxycyanobiphenyl (8-OCB) placed in the external magnetic and electric field as a function of the temperature have been studied. On the basis of threshold values Bc and Uc, the elastic constants for splay, bend and twist modes are determined. The magnetic anisotropy of 8-OCB as a function of temperature has been determined. The K11 and K33 elastic constants show the pretransitional nematic- smectic A effect. The values of critical exponents obtained from the temperature dependence of K11 and K33 in the vicinity of N-SA phase transition are discussed.
Intelligent processing for thick composites
NASA Astrophysics Data System (ADS)
Shin, Daniel Dong-Ok
2000-10-01
Manufacturing thick composite parts are associated with adverse curing conditions such as large in-plane temperature gradient and exotherms. The condition is further aggravated because the manufacturer's cycle and the existing cure control systems do not adequately counter such affects. In response, the forecast-based thermal control system is developed to have better cure control for thick composites. Accurate cure kinetic model is crucial for correctly identifying the amount of heat generated for composite process simulation. A new technique for identifying cure parameters for Hercules AS4/3502 prepreg is presented by normalizing the DSC data. The cure kinetics is based on an autocatalytic model for the proposed method, which uses dynamic and isothermal DSC data to determine its parameters. Existing models are also used to determine kinetic parameters but rendered inadequate because of the material's temperature dependent final degree of cure. The model predictions determined from the new technique showed good agreement to both isothermal and dynamic DSC data. The final degree of cure was also in good agreement with experimental data. A realistic cure simulation model including bleeder ply analysis and compaction is validated with Hercules AS4/3501-6 based laminates. The nonsymmetrical temperature distribution resulting from the presence of bleeder plies agreed well to the model prediction. Some of the discrepancies in the predicted compaction behavior were attributed to inaccurate viscosity and permeability models. The temperature prediction was quite good for the 3cm laminate. The validated process simulation model along with cure kinetics model for AS4/3502 prepreg were integrated into the thermal control system. The 3cm Hercules AS4/3501-6 and AS4/3502 laminate were fabricated. The resulting cure cycles satisfied all imposed requirements by minimizing exotherms and temperature gradient. Although the duration of the cure cycles increased, such phenomena was
NASA Astrophysics Data System (ADS)
Wu, Ru-Shan
1994-01-01
In this paper a system of equations for wide-angle one-way elastic wave propagation in arbitrarily heterogeneous media is formulated in both the space and wavenumber domains using elastic Rayleigh integrals and local elastic Born scattering theory. The wavenumber domain formulation leads to compact solutions to one-way propagation and scattering problems. It is shown that wide-angle scattering in heterogeneous elastic media cannot be formulated as passage through regular phase-screens, since the interaction between the incident wavefield and the heterogeneities is not local in both the space domain and the wavenumber domain. Our more generally valid formulation is called the 'thin-slap; formulation. After applying the small-angle approximation, the thin slab effect degenerates to that of an elastic complex-screen (or generalized phase-screen). For the complex-screen method the cross-coupling term is neglected because it is higher order small quantity for small-angle scattering. Relative to prior derivations of vector phase-screen method, our method can correctly treat the conversion between P and S waves and the cross-coupling between differently polarized S waves. A comparison with solutions from three-dimensional finite difference and exact solutions using eigenfunctions expansion is made for two special cases. One is for a solid sphere with only P velocity pertubation; the other is with only S velocity perturbation. The Elastic complex-screen method generally agrees well with the three-dimensional finite difference method and the exact solutions. In the limiting case of scalar waves, the derivation in this paper leads to a move generally valid new method, namely, a scaler thin-slab method. When making the small-angle approximation to the interaction term while keeping the propagation term unchanged, the thin-slab method approaches the currently available scalar wide-angle phase screen method.
NASA Astrophysics Data System (ADS)
Ansari, R.; Shahabodini, A.; Faghih Shojaei, M.
2016-02-01
In the present work, a three-dimensional (3D) elastic plate model capturing the small scale effects is developed for the free vibration of functionally graded (FG) nanoplates resting on elastic foundations. The theoretical model is formulated employing the nonlocal differential constitutive relations of Eringen in conjunction with the 3D equations of motion of elasticity.The material properties are assumed to vary continuously along the thickness of the nanoplate in accordance with the power law formulation. Through extending the generalized differential quadrature (GDQ) method to the three-dimensional case, the governing equations are simultaneously discretized in every three coordinate directions and are then recast to the standard form of an eigen value problem. Solving the acquired problem, the natural frequencies of the nanoplates with different boundary conditions are calculated. The convergence behavior of the numerical results is checked out and comparison studies are conducted to make sure of the accuracy and reliability of the present model. Finally, the dependence of the vibration behavior of the nanoplate on edge conditions, elastic coefficients of the foundation, scale coefficient, mode number, material and geometric parameters are discussed.
On geoid heights derived from GEOS 3 altimeter data along the Hawaiian-Emperor seamount chain
NASA Technical Reports Server (NTRS)
Watts, A. B.
1979-01-01
The geoid heights derived from preliminary GEOS 3 satellite radar altimeter data over the Hawaiian-Emperor seamount chain are examined. Two objectives are pursued: (1) to evaluate the contribution of the topography of the seamount chain and its compensation to the marine geoid; and (2) to determine whether geoid heights derived from GEOS 3 altimeter data can be used to provide information on isostasy at geological features such as the Hawaiian-Emperor seamount chain which formed as relatively young loads on the oceanic lithosphere. Short-wavelength geoid highs of 5-12 m over the crest of the seamount chain and geoid lows over flanking regions are observed. The geological undulations can be explained by a simple model in which the seamount-chain load is supported by a strong rigid lithospheric plate. The elastic thickness estimates agree with values based on surface ship gravity and bathymetry observations, and provide further support to the hypothesis that the elastic thickness acquired at a surface load depends on the temperature gradient of the lithosphere at the time of loading.
Effect of chain length and unsaturation on elasticity of lipid bilayers.
Rawicz, W; Olbrich, K C; McIntosh, T; Needham, D; Evans, E
2000-01-01
Micropipette pressurization of giant bilayer vesicles was used to measure both elastic bending k(c) and area stretch K(A) moduli of fluid-phase phosphatidylcholine (PC) membranes. Twelve diacyl PCs were chosen: eight with two 18 carbon chains and degrees of unsaturation from one double bond (C18:1/0, C18:0/1) to six double bonds per lipid (diC18:3), two with short saturated carbon chains (diC13:0, diC14:0), and two with long unsaturated carbon chains (diC20:4, diC22:1). Bending moduli were derived from measurements of apparent expansion in vesicle surface area under very low tensions (0.001-0.5 mN/m), which is dominated by smoothing of thermal bending undulations. Area stretch moduli were obtained from measurements of vesicle surface expansion under high tensions (>0.5 mN/m), which involve an increase in area per molecule and a small-but important-contribution from smoothing of residual thermal undulations. The direct stretch moduli varied little (< +/-10%) with either chain unsaturation or length about a mean of 243 mN/m. On the other hand, the bending moduli of saturated/monounsaturated chain PCs increased progressively with chain length from 0.56 x 10(-19) J for diC13:0 to 1.2 x 10(-19) J for diC22:1. However, quite unexpectedly for longer chains, the bending moduli dropped precipitously to approximately 0.4 x 10(-19) J when two or more cis double bonds were present in a chain (C18:0/2, diC18:2, diC18:3, diC20:4). Given nearly constant area stretch moduli, the variations in bending rigidity with chain length and polyunsaturation implied significant variations in thickness. To test this hypothesis, peak-to-peak headgroup thicknesses h(pp) of bilayers were obtained from x-ray diffraction of multibilayer arrays at controlled relative humidities. For saturated/monounsaturated chain bilayers, the distances h(pp) increased smoothly from diC13:0 to diC22:1 as expected. Moreover, the distances and elastic properties correlated well with a polymer brush model of the
Wave propagation in elastic medium with heterogeneous quadratic nonlinearity
Tang Guangxin; Jacobs, Laurence J.; Qu Jianmin
2011-06-23
This paper studies the one-dimensional wave propagation in an elastic medium with spatially non-uniform quadratic nonlinearity. Two problems are solved analytically. One is for a time-harmonic wave propagating in a half-space where the displacement is prescribed on the surface of the half-space. It is found that spatial non-uniformity of the material nonlinearity causes backscattering of the second order harmonic, which when combined with the forward propagating waves generates a standing wave in steady-state wave motion. The second problem solved is the reflection from and transmission through a layer of finite thickness embedded in an otherwise linearly elastic medium of infinite extent, where it is assumed that the layer has a spatially non-uniform quadratic nonlinearity. The results show that the transmission coefficient for the second order harmonic is proportional to the spatial average of the nonlinearity across the thickness of the layer, independent of the spatial distribution of the nonlinearity. On the other hand, the coefficient of reflection is proportional to a weighted average of the nonlinearity across the layer thickness. The weight function in this weighted average is related to the propagating phase, thus making the coefficient of reflection dependent on the spatial distribution of the nonlinearity. Finally, the paper concludes with some discussions on how to use the reflected and transmitted second harmonic waves to evaluate the variance and autocorrelation length of nonlinear parameter {beta} when the nonlinearity distribution in the layer is a stochastic process.
Nonlinear Elasticity in a Deforming Ambient Space
NASA Astrophysics Data System (ADS)
Yavari, Arash; Ozakin, Arkadas; Sadik, Souhayl
2016-07-01
In this paper, we formulate a nonlinear elasticity theory in which the ambient space is evolving. For a continuum moving in an evolving ambient space, we model time dependency of the metric by a time-dependent embedding of the ambient space in a larger manifold with a fixed background metric. We derive both the tangential and the normal governing equations. We then reduce the standard energy balance written in the larger ambient space to that in the evolving ambient space. We consider quasi-static deformations of the ambient space and show that a quasi-static deformation of the ambient space results in stresses, in general. We linearize the nonlinear theory about a reference motion and show that variation of the spatial metric corresponds to an effective field of body forces.
Elasticity of smectic-A elastomers
Adams, J.M.; Warner, M.
2005-02-01
We present a fully nonlinear model of the elasticity smectic-A elastomers, and compare our results with a wide range of experimental observations: extreme Poisson ratios, the in-plane modulus, the modulus before and after threshold to layer rotation in response to stretches along the layer normal, the threshold strain, the characteristic, and singular rotation of layers after the threshold. We calculate the x-ray scattering from rotating layers and compare with available data. The model is derived in two ways: from geometrical constraints imposed by layers on a nematic elastomer, and from application of statistical mechanics to a microscopic model of the effect of crosslink points confined in a corrugated potential.
Computation of elastic properties of 3D digital cores from the Longmaxi shale
NASA Astrophysics Data System (ADS)
Zhang, Wen-Hui; Fu, Li-Yun; Zhang, Yan; Jin, Wei-Jun
2016-06-01
The dependence of elastic moduli of shales on the mineralogy and microstructure of shales is important for the prediction of sweet spots and shale gas production. Based on 3D digital images of the microstructure of Longmaxi black shale samples using X-ray CT, we built detailed 3D digital images of cores with porosity properties and mineral contents. Next, we used finite-element (FE) methods to derive the elastic properties of the samples. The FE method can accurately model the shale mineralogy. Particular attention is paid to the derived elastic properties and their dependence on porosity and kerogen. The elastic moduli generally decrease with increasing porosity and kerogen, and there is a critical porosity (0.75) and kerogen content (ca. ≤3%) over which the elastic moduli decrease rapidly and slowly, respectively. The derived elastic moduli of gas- and oil-saturated digital cores differ little probably because of the low porosity (4.5%) of the Longmaxi black shale. Clearly, the numerical experiments demonstrated the feasibility of combining microstructure images of shale samples with elastic moduli calculations to predict shale properties.
Three-dimensional analysis of pore effect on composite elasticity by means of finite element method
NASA Astrophysics Data System (ADS)
Yoneda, A.
2015-12-01
A three-dimensional buffer-layer finite element method (FEM) model was developed to investigate the porosity effect on macroscopic elasticity. Using the three-dimensional model, the effect of pores on bulk effective elastic properties were systematically analyzed by changing the degree of porosity, the aspect ratio of the ellipsoidal pore, and the elasticity of the material. The present results in 3D space was compared with the previous ones in 2D space. Derivatives of normalized elastic stiffness constants with respect to needle-type porosity are integers, if the Poisson ratio of a matrix material is zero; those derivatives of normalized stiffness elastic constants for C33, C44, C11, and C66 converge to -1, -2, -3, and -4, respectively, at the corresponding condition. We proposed a criterion of R <~1/3, where the mutual interaction between pores becomes negligible for macroscopic composite elasticity. These derivatives are nearly constant below 5% porosity in the case of spherical pore, suggesting that the interaction between neighboring pores is insignificant if the representative size of the pore is less than one-third of the mean distance between neighboring pores. The relations we obtained in this work were successfully applied to invert bulk modulus and rigidity of Cmcm-CaIrO3 as a case study; the performance of the inverting scheme was confirmed through this assessment. Thus the present scheme is applicable to predict macroscopic elasticity of porous object as well.
Theory of sequence-dependent DNA elasticity
NASA Astrophysics Data System (ADS)
Coleman, Bernard D.; Olson, Wilma K.; Swigon, David
2003-04-01
The elastic properties of a molecule of duplex DNA are strongly dependent on nucleotide sequence. In the theory developed here the contribution ψn of the nth base-pair step to the elastic energy is assumed to be given by a function ψ˜n of six kinematical variables, called tilt, roll, twist, shift, slide, and rise, that describe the relative orientation and displacement of the nth and (n+1)th base pairs. The sequence dependence of elastic properties is determined when one specifies the way ψ˜n depends on the nucleotides of the two base pairs of the nth step. Among the items discussed are the symmetry relations imposed on ψ˜n by the complementarity of bases, i.e., of A to T and C to G, the antiparallel nature of the DNA sugar-phosphate chains, and the requirement that ψ˜n be independent of the choice of the direction of increasing n. Variational equations of mechanical equilibrium are here derived without special assumptions about the form of the functions ψ˜n, and numerical solutions of those equations are shown for illustrative cases in which ψ˜n is, for each n, a quadratic form and the DNA forms a closed, 150 base-pair, minicircle that can be called a DNA o-ring because it has a nearly circular stress-free configuration. Examples are given of noncircular equilibrium configurations of naked DNA o-rings and of cases in which the interaction with ligands induces changes in configuration that are markedly different from those undergone by a minicircle of intrinsically straight DNA. When a minicircle of intrinsically straight DNA interacts with an intercalating agent that upon binding to DNA causes a local reduction of intrinsic twist, the configuration that minimizes elastic energy depends on the number of intercalated molecules, but is independent of the spatial distribution of those molecules along the minicircle. In contrast, it is shown here that the configuration and elastic energy of a DNA o-ring can depend strongly on the spatial distribution of
Elastic modes and their computation
Hedstrom, G.W.
1995-04-01
In this note we summarize the theory of modes in stratified elastic media, and we discuss some of the considerations necessary to achieve reliable numerical computations. We also point out the consequences of the fact that the corresponding eigenvalue problem is not selfadjoint. 14 refs.
Elastic forward scattering of gluons
NASA Astrophysics Data System (ADS)
Ermolaev, B. I.
1995-06-01
The colour octet and singlet parts of the elastic gg→ gg-scattering amplitude are evaluated in the Regge kinematical region s≫- t in the LLA, with iπ-terms taken into account, by constructing and solving a set of the infrared evolution equations.
Pilot Study of Debt Elasticity
ERIC Educational Resources Information Center
Greiner, Keith; Girardi, Tony
2006-01-01
This report examines the relationship between student loan debt and the manner in which that debt is described. It focuses on three forms of description: (1) monthly payments, (2) total debt, and (3) income after graduation. The authors used the term elasticity to describe the relationship between consumers' college choices and the retention…
HEMP. Hydrodynamic Elastic Magneto Plastic
Wilkins, M.L.; Levatin, J.A.
1985-02-01
The HEMP code solves the conservation equations of two-dimensional elastic-plastic flow, in plane x-y coordinates or in cylindrical symmetry around the x-axis. Provisions for calculation of fixed boundaries, free surfaces, pistons, and boundary slide planes have been included, along with other special conditions.
Duration of an Elastic Collision
ERIC Educational Resources Information Center
de Izarra, Charles
2012-01-01
With a pedagogical goal, this paper deals with a study of the duration of an elastic collision of an inflatable spherical ball on a planar surface suitable for undergraduate studies. First, the force generated by the deformed spherical ball is obtained under assumptions that are discussed. The study of the motion of the spherical ball colliding…
Analysis of transverse shear strains in pre-twisted thick beams using variational asymptotic method
Ameen, Maqsood M.; Harursampath, Dineshkumar E-mail: dinesh@aero.iisc.ernet.in
2015-03-10
The cross-sectional stiffness matrix is derived for a pre-twisted, moderately thick beam made of transversely isotropic materials and having rectangular cross sections. An asymptotically-exact methodology is used to model the anisotropic beam from 3-D elasticity, without any further assumptions. The beam is allowed to have large displacements and rotations, but small strain is assumed. The strain energy is computed making use of the beam constitutive law and kinematical relations derived with the inclusion of geometrical nonlinearities and an initial twist. The energy functional is minimized making use of the Variational Asymptotic Method (VAM), thereby reducing the cross section to a point on the beam reference line with appropriate properties, forming a 1-D constitutive law. VAM is a mathematical technique employed in the current problem to rigorously split the 3-D analysis of beams into two: a 2-D analysis over the beam cross-sectional domain, which provides a compact semi-analytical form of the properties of the cross sections, and a nonlinear 1-D analysis of the beam ref-erence curve. In this method, as applied herein, the cross-sectional analysis is performed asymptotically by taking advantage of a material small parameter and two geometric small parameters. 3-D strain components are derived using kinematics and arranged in orders of the small parameters. Closed-form expressions are derived for the 3-D non-linear warping and stress fields. Warping functions are obtained by the minimization of strain energy subject to certain set of constraints that render the 1-D strain measures well-defined. The zeroth-order 3-D warping field thus yielded is then used to integrate the 3-D strain energy density over the cross section, resulting in the 1-D strain energy density, which in turn helps identify the corresponding cross-sectional stiffness matrix. The model is capable of predicting interlaminar and transverse shear stresses accurately up to first order.
Tectonic determinations of lithospheric thickness on Ganymede and Callisto
NASA Technical Reports Server (NTRS)
Croft, S. K.
1985-01-01
The concept of the Maxwell time of a viscoelastic material (4.5) is used in conjunction with calculated thermal profiles to evaluate the significance of tectonic estimates of lithospheric thickness. Thermal lithospheric thicknesses provide fundamental constraints on planetary thermal histories that complement the constraints provided by dateable surface deposits of endogenic origin. Lithospheric constraints are of particular value on the icy satellites where our understanding of both rheology and surface ages is considerably poorer than it is for the terrestrial planets. Certain extensional tectonic features can and have been used to estimate lithospheric thicknesses on Ganymede and Callisto. These estimates, however, refer to the depth of the elastic lithosphere defined by the zone of brittle failure. The relation between the elastic lithosphere and the thermal lithosphere (generally defined by the zone of conductive heat transport) is not straightforward, because the depth of brittle failure depends not only on the thermal profile, but also on rheology and strain rate (or the characteristic time over which stresses build towards failure). Characteristic time considerations are not trivial in this context because stresses generating brittle failure on the icy satellites may be produced by impacts, with characteristic times of seconds to days, or by geologic processes with time scales of hundreds of millions of years.
Fabry-Perot Laser Ultrasonic Elastic Anisotropy Measurements on a Moving Paper Web
Walter, John Bradley; Telschow, Kenneth Louis; Gerhardstein, J. P.; Pufahl, B. M.; Habeger, C. C; Lafond, E. M.; Brodeur, P. H.
1999-07-01
On-line measurement of material properties is a goal of many manufacturers to improve production and quality. The elastic stiffness of paper is important for the paper industry. Currently, the elastic constants of paper are measured offline with contact ultrasonic methods [1-4]. Piezoelectric transducers are placed in contact with the paper surface to generate and detect plate wave modes, known as Lamb wave modes [5-7]. At low frequencies, where the wavelength of the elastic wave is larger than the paper thickness, two wave modes dominate in the paper, an anti-symmetric or flexural mode and a symmetric or thickness mode. Measurements of the phase velocities of these modes along both the machine direction (MD) and the perpendicular cross direction (CD) of the paper web provide an important parameter revealing the increased stiffness in the paper along the MD direction.
Visual perception of thick transparent materials.
Fleming, Roland W; Jäkel, Frank; Maloney, Laurence T
2011-06-01
Under typical viewing conditions, human observers readily distinguish between materials such as silk, marmalade, or granite, an achievement of the visual system that is poorly understood. Recognizing transparent materials is especially challenging. Previous work on the perception of transparency has focused on objects composed of flat, infinitely thin filters. In the experiments reported here, we considered thick transparent objects, such as ice cubes, which are irregular in shape and can vary in refractive index. An important part of the visual evidence signaling the presence of such objects is distortions in the perceived shape of other objects in the scene. We propose a new class of visual cues derived from the distortion field induced by thick transparent objects, and we provide experimental evidence that cues arising from the distortion field predict both the successes and the failures of human perception in judging refractive indices.
Visual perception of thick transparent materials.
Fleming, Roland W; Jäkel, Frank; Maloney, Laurence T
2011-06-01
Under typical viewing conditions, human observers readily distinguish between materials such as silk, marmalade, or granite, an achievement of the visual system that is poorly understood. Recognizing transparent materials is especially challenging. Previous work on the perception of transparency has focused on objects composed of flat, infinitely thin filters. In the experiments reported here, we considered thick transparent objects, such as ice cubes, which are irregular in shape and can vary in refractive index. An important part of the visual evidence signaling the presence of such objects is distortions in the perceived shape of other objects in the scene. We propose a new class of visual cues derived from the distortion field induced by thick transparent objects, and we provide experimental evidence that cues arising from the distortion field predict both the successes and the failures of human perception in judging refractive indices. PMID:21597102
Topological rubber elasticity theory. II. SCL networks
NASA Astrophysics Data System (ADS)
Iwata, Kazuyoshi
1982-06-01
The theory presented in part I [Iwata, J. Chem. Phys. 76, 6363 (1982)] is applied to networks having a simple-cubic-lattice (SCL) regular connection pattern, for which the projection matrix Γ* is computed easily. Derivatives of elastic free energies in regard to parameter λ for macroscopic deformation ∂F˜e/∂λ are computed numerically for isotropic deformations (swelling or deswelling) and for simple deformations (extension or contraction under swelling by α times). The initial arrangement of junction points r0 is assumed to be exactly SCL, and δ = d0/√νb is chosen as one of parameters in the calculation, where d0 is an end-to-end distance of the strands at the time of network formation, ν is a degree of polymerization in regard to the strands, and b is a statistical length per monomer. A repeating cell is chosen as a cube composed of 3×3×3 ( = 27) junction points and 3×27 ( = 81) strands. The following are found in this work. (1) Among four terms ∂F0,ph/∂λ, ∂F˜0,top/∂λ, ∂F˜1/∂λ, and ∂F˜2/∂λ of the derivative of the elastic free energy, the principal term is ∂F˜0,top/∂λ, which comes from the topological interaction among the strands; the phantom network term ∂F0,ph/∂λ is only a small correction to the net stress. (2) In isotropic deformations, the elastic free energy takes a minimum at λ0, a little below λ = 1; for compression below λ0, a strong postitive inner pressure, which comes from the topological repulsive forces among the strands, arises. (3) In simple deformations, the Mooney-Rivlin term appears for unswollen systems and it disappears as swelling of the network proceeds. Experimental plans are proposed which will reveal the existence of the topological repulsive interactions in the networks.
A de Sitter tachyon thick braneworld
Germán, Gabriel; Herrera-Aguilar, Alfredo; Malagón-Morejón, Dagoberto; Mora-Luna, Refugio Rigel; Rocha, Roldão da E-mail: aha@fis.unam.mx E-mail: rigel@ifm.umich.mx
2013-02-01
Among the multiple 5D thick braneworld models that have been proposed in the last years, in order to address several open problems in modern physics, there is a specific one involving a tachyonic bulk scalar field. Delving into this framework, a thick braneworld with a cosmological background induced on the brane is here investigated. The respective field equations — derived from the model with a warped 5D geometry — are highly non-linear equations, admitting a non-trivial solution for the warp factor and the tachyon scalar field as well, in a de Sitter 4D cosmological background. Moreover, the non-linear tachyonic scalar field, that generates the brane in complicity with warped gravity, has the form of a kink-like configuration. Notwithstanding, the non-linear field equations restricting character does not allow one to easily find thick brane solutions with a decaying warp factor which leads to the localization of 4D gravity and other matter fields. We derive such a thick brane configuration altogether in this tachyon-gravity setup. When analyzing the spectrum of gravity fluctuations in the transverse traceless sector, the 4D gravity is shown to be localized due to the presence of a single zero mode bound state, separated by a continuum of massive Kaluza-Klein (KK) modes by a mass gap. It contrasts with previous results, where there is a KK massive bound excitation providing no clear physical interpretation. The mass gap is determined by the scale of the metric parameter H. Finally, the corrections to Newton's law in this model are computed and shown to decay exponentially. It is in full compliance to corrections reported in previous results (up to a constant factor) within similar braneworlds with induced 4D de Sitter metric, despite the fact that the warp factor and the massive modes have a different form.
Elastic And Plastic Deformations In Butt Welds
NASA Technical Reports Server (NTRS)
Verderaime, V.
1992-01-01
Report presents study of mathematical modeling of stresses and strains, reaching beyond limits of elasticity, in bars and plates. Study oriented toward development of capability to predict stresses and resulting elastic and plastic strains in butt welds.
Durand, Letícia Brandão; Guimarães, Jackeline Coutinho; Monteiro Junior, Sylvio; Baratieri, Luiz Narciso
2015-01-01
The purpose of this study was to determine the effect of cavity depth, ceramic thickness, and resin bases with different elastic modulus on von Mises stress patterns of ceramic inlays. Tridimensional geometric models were developed with SolidWorks image software. The differences between the models were: depth of pulpal wall, ceramic thickness, and presence of composite bases with different thickness and elastic modulus. The geometric models were constrained at the proximal surfaces and base of maxillary bone. A load of 100 N was applied. The stress distribution pattern was analyzed with von Mises stress diagrams. The maximum von Mises stress values ranged from 176 MPa to 263 MPa and varied among the 3D-models. The highest von Mises stress value was found on models with 1-mm-thick composite resin base and 1-mm-thick ceramic inlay. Intermediate values (249-250 MPa) occurred on models with 2-mm-thick composite resin base and 1-mm-thick ceramic inlay and 1-mm-thick composite resin base and 2-mm-thick ceramic inlay. The lowest values were observed on models restored exclusively with ceramic inlay (176 MPa to 182 MPa). It was found that thicker inlays distribute stress more favorably and bases with low elastic modulus increase stress concentrations on the internal surface of the ceramic inlay. The increase of ceramic thickness tends to present more favorable stress distribution, especially when bonded directly onto the cavity without the use of supporting materials. When the use of a composite base is required, composite resin with high elastic modulus and reduced thickness should be preferred. PMID:25831105
Durand, Letícia Brandão; Guimarães, Jackeline Coutinho; Monteiro Junior, Sylvio; Baratieri, Luiz Narciso
2015-01-01
The purpose of this study was to determine the effect of cavity depth, ceramic thickness, and resin bases with different elastic modulus on von Mises stress patterns of ceramic inlays. Tridimensional geometric models were developed with SolidWorks image software. The differences between the models were: depth of pulpal wall, ceramic thickness, and presence of composite bases with different thickness and elastic modulus. The geometric models were constrained at the proximal surfaces and base of maxillary bone. A load of 100 N was applied. The stress distribution pattern was analyzed with von Mises stress diagrams. The maximum von Mises stress values ranged from 176 MPa to 263 MPa and varied among the 3D-models. The highest von Mises stress value was found on models with 1-mm-thick composite resin base and 1-mm-thick ceramic inlay. Intermediate values (249-250 MPa) occurred on models with 2-mm-thick composite resin base and 1-mm-thick ceramic inlay and 1-mm-thick composite resin base and 2-mm-thick ceramic inlay. The lowest values were observed on models restored exclusively with ceramic inlay (176 MPa to 182 MPa). It was found that thicker inlays distribute stress more favorably and bases with low elastic modulus increase stress concentrations on the internal surface of the ceramic inlay. The increase of ceramic thickness tends to present more favorable stress distribution, especially when bonded directly onto the cavity without the use of supporting materials. When the use of a composite base is required, composite resin with high elastic modulus and reduced thickness should be preferred.
Elastic constants for superplastically formed/diffusion-bonded sandwich structures
NASA Technical Reports Server (NTRS)
Ko, W. L.
1979-01-01
Formulae and the associated graphs are presented for contrasting the effective elastic constants for a superplastically formed/diffusion-bonded (SPF/DB) corrugated sandwich core and a honeycomb sandwich core. The results used in the comparison of the structural properties of the two types of sandwich cores are under conditions of equal sandwich density. It was found that the stiffness in the thickness direction of the optimum SPF/DB corrugated core (i.e., triangular truss core) was lower than that of the honeycomb core, and that the former had higher transverse shear stiffness than the latter.
Tissue thickness calculation in ocular optical coherence tomography
Alonso-Caneiro, David; Read, Scott A.; Vincent, Stephen J.; Collins, Michael J.; Wojtkowski, Maciej
2016-01-01
Thickness measurements derived from optical coherence tomography (OCT) images of the eye are a fundamental clinical and research metric, since they provide valuable information regarding the eye’s anatomical and physiological characteristics, and can assist in the diagnosis and monitoring of numerous ocular conditions. Despite the importance of these measurements, limited attention has been given to the methods used to estimate thickness in OCT images of the eye. Most current studies employing OCT use an axial thickness metric, but there is evidence that axial thickness measures may be biased by tilt and curvature of the image. In this paper, standard axial thickness calculations are compared with a variety of alternative metrics for estimating tissue thickness. These methods were tested on a data set of wide-field chorio-retinal OCT scans (field of view (FOV) 60° x 25°) to examine their performance across a wide region of interest and to demonstrate the potential effect of curvature of the posterior segment of the eye on the thickness estimates. Similarly, the effect of image tilt was systematically examined with the same range of proposed metrics. The results demonstrate that image tilt and curvature of the posterior segment can affect axial tissue thickness calculations, while alternative metrics, which are not biased by these effects, should be considered. This study demonstrates the need to consider alternative methods to calculate tissue thickness in order to avoid measurement error due to image tilt and curvature. PMID:26977367
NASA Astrophysics Data System (ADS)
Shiina, Tsuyoshi; Maki, Tomonori; Yamakawa, Makoto; Mitake, Tsuyoshi; Kudo, Masatoshi; Fujimoto, Kenji
2012-07-01
Precise evaluation of the stage of chronic hepatitis C with respect to fibrosis has become an important issue to prevent the occurrence of cirrhosis and to initiate appropriate therapeutic intervention such as viral eradication using interferon. Ultrasound tissue elasticity imaging, i.e., elastography can visualize tissue hardness/softness, and its clinical usefulness has been studied to detect and evaluate tumors. We have recently reported that the texture of elasticity image changes as fibrosis progresses. To evaluate fibrosis progression quantitatively on the basis of ultrasound tissue elasticity imaging, we introduced a mechanical model of fibrosis progression and simulated the process by which hepatic fibrosis affects elasticity images and compared the results with those clinical data analysis. As a result, it was confirmed that even in diffuse diseases like chronic hepatitis, the patterns of elasticity images are related to fibrous structural changes caused by hepatic disease and can be used to derive features for quantitative evaluation of fibrosis stage.
Defect Dependent Elasticity: Nanoindentation as a Probe of Stress-State
JARAUSCH,K.F.; KIELY,J.D.; HOUSTON,JACK E.; RUSSELL,P.E.
2000-01-18
Nanoindentation studies reveal that the measured elastic properties of materials can be strongly dependent upon their stress-state and defect structure. Using an interfacial force microscope (IFM), the measured elastic response of 100 nm thick Au films was found to be strongly correlated with the films' stress state and thermal history. Indentation elasticity was also found to vary in close proximity to grain boundaries in thin films and near surface steps on single crystal surfaces. Molecular dynamics simulations suggest that these results cannot be explained by elasticity due only to bond stretching. Instead, the measured elastic properties appear to be a combination of bond and defect compliance representing a composite modulus. We propose that stress concentration arising from the structure of grains, voids and grain boundaries is the source of an additional compliance which is sensitive to the stress state and thermal history of a material. The elastic properties of thin metallic films appear to reflect the collective elastic response of the grains, voids and grain boundaries. These results demonstrate that nanoindentation can be useful as a highly localized probe of stress-state and defect structures.
Nonlinear elastic properties of particulate composites
NASA Astrophysics Data System (ADS)
Chen, Yi-Chao; Jiang, Xiaohu
1993-07-01
A METHOD of computing effective elastic moduli of isotropic nonlinear composites is developed by using a perturbation scheme. It is demonstrated that only solutions from linear elasticity are needed in computing higher order moduli. As an application of the method, particulate composites of nonlinear elastic materials are analysed.
The vertical structure and thickness of Saturn's rings
NASA Technical Reports Server (NTRS)
Cuzzi, J. N.; Durisen, R. H.; Burns, J. A.; Hamill, P.
1979-01-01
The steady state thickness and vertical structure of Saturn's rings are discussed with regard to whether a collapse to a monolayer due to particle collisions may be prevented by various mechanisms. The differences between thick rings and wavy monolayers are outlined and used to show that such coherent perturbations to the rings as satellite and solar gravitational effects would produce a wavy monolayer while such dispersive mechanisms as meteoroid impact, radiation pressure, Kepler shear and radial spreading, which would produce the random particle motions necessary to maintain a thick layer, are probably insignificant. Given a typical power law distribution of particle sizes, it is found that gravitational scattering of small particles by large ones would maintain a ring thickness of several times the radius of the largest particles. A steady state ring thickness of 20 to 50 meters, derived from energy considerations, would imply a maximum particle size of a few meters.
Neutron density distribution and neutron skin thickness of Pb208
NASA Astrophysics Data System (ADS)
Meucci, Andrea; Vorabbi, Matteo; Giusti, Carlotta; Finelli, Paolo
2014-08-01
We present and discuss numerical predictions for the neutron density distribution of Pb208 using various nonrelativistic and relativistic mean-field models for the nuclear structure. Our results are compared with the very recent pion photoproduction data from Mainz. The parity-violating asymmetry parameter for elastic electron scattering at the kinematics of the PREX experiment at JLab and the neutron skin thickness are compared with the available data. We consider also the dependence between the neutron skin and the parameters of the expansion of the symmetry energy.
Comparison of mechanical and ultrasound elastic modulus of ovine tibial cortical bone.
Grant, Caroline A; Wilson, Lance J; Langton, Christian; Epari, Devakar
2014-07-01
Finite element models of bones can be created by deriving geometry from an X-ray CT scan. Material properties such as the elastic modulus can then be applied using either a single or set of homogeneous values, or individual elements can have local values mapped onto them. Values for the elastic modulus can be derived from the CT density values using an elasticity versus density relationship. Many elasticity-density relationships have been reported in the literature for human bone. However, while ovine in vivo models are common in orthopaedic research, no work has been done to date on creating FE models of ovine bones. To create these models and apply relevant material properties, an ovine elasticity-density relationship needs to be determined. Using fresh frozen ovine tibias the apparent density of regions of interest was determined from a clinical CT scan. The bones were the sectioned into cuboid samples of cortical bone from the regions of interest. Ultrasound was used to determine the elastic modulus in each of three directions - longitudinally, radially and tangentially. Samples then underwent traditional compression testing in each direction. The relationships between apparent density and both ultrasound, and compression modulus in each direction were determined. Ultrasound testing was found to be a highly repeatable non-destructive method of calculating the elastic modulus, particularly suited to samples of this size. The elasticity-density relationships determined in the longitudinal direction were very similar between the compression and ultrasound data over the density range examined. A clear difference was seen in the elastic modulus between the longitudinal and transverse directions of the bone samples, and a transverse elasticity-density relationship is also reported.
Second order Method for Solving 3D Elasticity Equations with Complex Interfaces
Wang, Bao; Xia, Kelin; Wei, Guo-Wei
2015-01-01
Elastic materials are ubiquitous in nature and indispensable components in man-made devices and equipments. When a device or equipment involves composite or multiple elastic materials, elasticity interface problems come into play. The solution of three dimensional (3D) elasticity interface problems is significantly more difficult than that of elliptic counterparts due to the coupled vector components and cross derivatives in the governing elasticity equation. This work introduces the matched interface and boundary (MIB) method for solving 3D elasticity interface problems. The proposed MIB elasticity interface scheme utilizes fictitious values on irregular grid points near the material interface to replace function values in the discretization so that the elasticity equation can be discretized using the standard finite difference schemes as if there were no material interface. The interface jump conditions are rigorously enforced on the intersecting points between the interface and the mesh lines. Such an enforcement determines the fictitious values. A number of new techniques has been developed to construct efficient MIB elasticity interface schemes for dealing with cross derivative in coupled governing equations. The proposed method is extensively validated over both weak and strong discontinuity of the solution, both piecewise constant and position-dependent material parameters, both smooth and nonsmooth interface geometries, and both small and large contrasts in the Poisson’s ratio and shear modulus across the interface. Numerical experiments indicate that the present MIB method is of second order convergence in both L∞ and L2 error norms for handling arbitrarily complex interfaces, including biomolecular surfaces. To our best knowledge, this is the first elasticity interface method that is able to deliver the second convergence for the molecular surfaces of proteins.. PMID:25914422
Coupling between the nematic/isotropic transition and a thickness transition: A theoretical approach
NASA Astrophysics Data System (ADS)
van Effenterre, D.; Valignat, M. P.; Roux, D.
2003-05-01
In this letter, we develop a theoretical model of the effect of a free surface on the nematic-to-isotropic phase transition in a confined geometry. Simply by coupling a bulk first-order phase transition with a thickness-dependent elastic distortion field in a Landau-like description, the model predicts a coexistence at equilibrium between the isotropic and the nematic phases at two different thicknesses. A phase diagram is constructed in the temperature-thickness plane and a comparison is given with experimental results obtained on thin films (van Effenterre D., Ober R., Valignat M. P. and Cazabat A. M., Phys. Rev. Lett. 87(2001) 125701).
Anchoring energy and orientational elasticity of a ferroelectric liquid crystal
Kaznacheev, A. V.; Pozhidaev, E. P.
2012-06-15
The dielectric susceptibility of a helix-free ferroelectric liquid crystal layer has been experimentally and theoretically studied as a function of the layer thickness. The investigation has been performed on the inner branch of the polarization hysteresis loop, in the region of a linear dependence of the polarization on the electric field. The experimental results are explained using the notion of effective layer thickness, which involves the characteristic distance {xi} over which the orienting effect of interfaces is operative. Comparison of the experimental data and theoretical results made it possible to estimate this distance as {xi} = 41 {mu}m and evaluate the anchoring energy (W = 2.8 Multiplication-Sign 10{sup -3}-1.1 Multiplication-Sign 10{sup -2} J/m{sup 2}) and the intralayer elastic constant (K Double-Prime Almost-Equal-To 1 Multiplication-Sign 10{sup -8}-3 Multiplication-Sign 10{sup -7} N).
Modeling of thermal stresses in elastic multilayer coating systems
NASA Astrophysics Data System (ADS)
Gao, Chunxue; Zhao, Zhiwei; Li, Xuehua
2015-02-01
The performance and reliability of multilayer coating systems are strongly influenced by thermal stresses. The present study develops an alternative analytical model to predict the thermal stresses in elastic multilayer coating systems. An exact closed-form solution is obtained which is independent of the number of coating layers. In addition, with the definition of the coordinate system, the closed-form solution is concisely formulated. Specific results are calculated for thermal stresses in HfO2/SiO2 multilayer optical coatings, and a finite element analysis is performed to confirm the analytical results. The two results agree fairly well with each other. Also, when the thicknesses of the coating layers are much less than the substrate thickness, the approximate solution is obtained based on the exact closed-form solution, and its accuracy is examined.
Linear elastic fracture mechanics primer
NASA Technical Reports Server (NTRS)
Wilson, Christopher D.
1992-01-01
This primer is intended to remove the blackbox perception of fracture mechanics computer software by structural engineers. The fundamental concepts of linear elastic fracture mechanics are presented with emphasis on the practical application of fracture mechanics to real problems. Numerous rules of thumb are provided. Recommended texts for additional reading, and a discussion of the significance of fracture mechanics in structural design are given. Griffith's criterion for crack extension, Irwin's elastic stress field near the crack tip, and the influence of small-scale plasticity are discussed. Common stress intensities factor solutions and methods for determining them are included. Fracture toughness and subcritical crack growth are discussed. The application of fracture mechanics to damage tolerance and fracture control is discussed. Several example problems and a practice set of problems are given.
Elastic scattering in geometrical model
NASA Astrophysics Data System (ADS)
Plebaniak, Zbigniew; Wibig, Tadeusz
2016-10-01
The experimental data on proton-proton elastic and inelastic scattering emerging from the measurements at the Large Hadron Collider, calls for an efficient model to fit the data. We have examined the optical, geometrical picture and we have found the simplest, linear dependence of this model parameters on the logarithm of the interaction energy with the significant change of the respective slopes at one point corresponding to the energy of about 300 GeV. The logarithmic dependence observed at high energies allows one to extrapolate the proton-proton elastic, total (and inelastic) cross sections to ultra high energies seen in cosmic rays events which makes a solid justification of the extrapolation to very high energy domain of cosmic rays and could help us to interpret the data from an astrophysical and a high energy physics point of view.
Elastic cone for Chinese calligraphy
NASA Astrophysics Data System (ADS)
Cai, Fenglei; Li, Haisheng
2014-01-01
The brush plays an important role in creating Chinese calligraphy. We regard a single bristle of a writing brush as an elastic rod and the brush tuft absorbing ink as an elastic cone, which naturally deforms according to the force exerted on it when painting on a paper, and the brush footprint is formed by the intersection region between the deformed tuft and the paper plane. To efficiently generate brush strokes, this paper introduces interpolation and texture mapping approach between two adjacent footprints, and automatically applies bristle-splitting texture to the stroke after long-time painting. Experimental results demonstrate that our method is effective and reliable. Users can create realistic calligraphy in real time.
Laser detection of material thickness
Early, James W.
2002-01-01
There is provided a method for measuring material thickness comprising: (a) contacting a surface of a material to be measured with a high intensity short duration laser pulse at a light wavelength which heats the area of contact with the material, thereby creating an acoustical pulse within the material: (b) timing the intervals between deflections in the contacted surface caused by the reverberation of acoustical pulses between the contacted surface and the opposite surface of the material: and (c) determining the thickness of the material by calculating the proportion of the thickness of the material to the measured time intervals between deflections of the contacted surface.
Bulk solitary waves in elastic solids
NASA Astrophysics Data System (ADS)
Samsonov, A. M.; Dreiden, G. V.; Semenova, I. V.; Shvartz, A. G.
2015-10-01
A short and object oriented conspectus of bulk solitary wave theory, numerical simulations and real experiments in condensed matter is given. Upon a brief description of the soliton history and development we focus on bulk solitary waves of strain, also known as waves of density and, sometimes, as elastic and/or acoustic solitons. We consider the problem of nonlinear bulk wave generation and detection in basic structural elements, rods, plates and shells, that are exhaustively studied and widely used in physics and engineering. However, it is mostly valid for linear elasticity, whereas dynamic nonlinear theory of these elements is still far from being completed. In order to show how the nonlinear waves can be used in various applications, we studied the solitary elastic wave propagation along lengthy wave guides, and remarkably small attenuation of elastic solitons was proven in physical experiments. Both theory and generation for strain soliton in a shell, however, remained unsolved problems until recently, and we consider in more details the nonlinear bulk wave propagation in a shell. We studied an axially symmetric deformation of an infinite nonlinearly elastic cylindrical shell without torsion. The problem for bulk longitudinal waves is shown to be reducible to the one equation, if a relation between transversal displacement and the longitudinal strain is found. It is found that both the 1+1D and even the 1+2D problems for long travelling waves in nonlinear solids can be reduced to the Weierstrass equation for elliptic functions, which provide the solitary wave solutions as appropriate limits. We show that the accuracy in the boundary conditions on free lateral surfaces is of crucial importance for solution, derive the only equation for longitudinal nonlinear strain wave and show, that the equation has, amongst others, a bidirectional solitary wave solution, which lead us to successful physical experiments. We observed first the compression solitary wave in the
Model-based cartilage thickness measurement in the submillimeter range
Streekstra, G. J.; Strackee, S. D.; Maas, M.; Wee, R. ter; Venema, H. W.
2007-09-15
Current methods of image-based thickness measurement in thin sheet structures utilize second derivative zero crossings to locate the layer boundaries. It is generally acknowledged that the nonzero width of the point spread function (PSF) limits the accuracy of this measurement procedure. We propose a model-based method that strongly reduces PSF-induced bias by incorporating the PSF into the thickness estimation method. We estimated the bias in thickness measurements in simulated thin sheet images as obtained from second derivative zero crossings. To gain insight into the range of sheet thickness where our method is expected to yield improved results, sheet thickness was varied between 0.15 and 1.2 mm with an assumed PSF as present in the high-resolution modes of current computed tomography (CT) scanners [full width at half maximum (FWHM) 0.5-0.8 mm]. Our model-based method was evaluated in practice by measuring layer thickness from CT images of a phantom mimicking two parallel cartilage layers in an arthrography procedure. CT arthrography images of cadaver wrists were also evaluated, and thickness estimates were compared to those obtained from high-resolution anatomical sections that served as a reference. The thickness estimates from the simulated images reveal that the method based on second derivative zero crossings shows considerable bias for layers in the submillimeter range. This bias is negligible for sheet thickness larger than 1 mm, where the size of the sheet is more than twice the FWHM of the PSF but can be as large as 0.2 mm for a 0.5 mm sheet. The results of the phantom experiments show that the bias is effectively reduced by our method. The deviations from the true thickness, due to random fluctuations induced by quantum noise in the CT images, are of the order of 3% for a standard wrist imaging protocol. In the wrist the submillimeter thickness estimates from the CT arthrography images correspond within 10% to those estimated from the anatomical
Improved Indentation Test for Measuring Nonlinear Elasticity
NASA Technical Reports Server (NTRS)
Eldridge, Jeffrey I.
2004-01-01
A cylindrical-punch indentation technique has been developed as a means of measuring the nonlinear elastic responses of materials -- more specifically, for measuring the moduli of elasticity of materials in cases in which these moduli vary with applied loads. This technique offers no advantage for characterizing materials that exhibit purely linear elastic responses (constant moduli of elasticity, independent of applied loads). However, the technique offers a significant advantage for characterizing such important materials as plasma-sprayed thermal-barrier coatings, which, in cyclic loading, exhibit nonlinear elasticity with hysteresis related to compaction and sliding within their microstructures.
NASA Astrophysics Data System (ADS)
Ansari, R.; Ashrafi, M. A.; Pourashraf, T.; Sahmani, S.
2015-04-01
The buckling and vibration responses of nanoplates made of functionally graded materials (FGMs) subjected to thermal loading are studied in prebuckling domain with considering the effect of surface stress. To accomplish this purpose, Gurtin-Murdoch elasticity theory is incorporated into the classical plate theory to develop a non-classical plate model including the surface effects. The material properties of FGM nanoplate are considered to be graded in the thickness direction on the basis of the power law function. Hamilton's principle is utilized to derive size-dependent governing differential equations of motion and associated boundary conditions. Selected numerical results are presented to indicate the importance of surface stress effect. It is revealed that in the presence of surface stress effect, the influence of material property gradient index on the critical thermal buckling load is more prominent for FGM nanoplates with lower length-to-thickness ratios. Also, by increasing the natural frequency of FGM nanoplate, the role of surface stress effect in the value of critical thermal buckling load is more prominent.
Shi, P; Chen, C Q; Zou, W N
2015-01-01
Coupled shear (SH) elastic and electromagnetic (EM) waves propagating oblique to a one dimensional periodic piezoelectric and piezomagnetic composite are investigated using the transfer matrix method. Closed-form expression of the dispersion relations is derived. We find that the band structures of the periodic composite show simultaneously the features of phononic and photonic crystals. Strong interaction between the elastic and EM waves near the center of the Brillouin zone (i.e., phonon-polariton) is revealed. It is shown the elastic branch of the band structures is more sensitive to the piezoelectric effect while the phonon-polariton is more sensitive to the piezomagnetic effect of the composite.
Serum factors from pseudoxanthoma elasticum patients alter elastic fiber formation in vitro.
Le Saux, Olivier; Bunda, Severa; VanWart, Christopher M; Douet, Vanessa; Got, Laurence; Martin, Ludovic; Hinek, Aleksander
2006-07-01
Pseudoxanthoma elasticum (PXE) is a heritable disorder mainly characterized by calcified elastic fibers in cutaneous, ocular, and vascular tissues. PXE is caused by mutations in ABCC6, a gene encoding an ABC transporter predominantly expressed in liver and kidneys. The functional relationship between ABCC6 and elastic fiber calcification is unknown. We speculated that ABCC6 deficiency in PXE patients induces a persistent imbalance in circulating metabolite(s), which may impair the synthetic abilities of normal elastoblasts or specifically alter elastic fiber assembly. Therefore, we compared the deposition of elastic fiber proteins in cultures of fibroblasts derived from PXE and unaffected individuals. PXE fibroblasts cultured with normal human serum expressed and deposited increased amounts of proteins, but structurally normal elastic fibers. Interestingly, normal and PXE fibroblasts as well as normal smooth muscle cells deposited abnormal aggregates of elastic fibers when maintained in the presence of serum from PXE patients. The expression of tropoelastin and other elastic fiber-associated genes was not significantly modulated by the presence of PXE serum. These results indicated that certain metabolites present in PXE sera interfered with the normal assembly of elastic fibers in vitro and suggested that PXE is a primary metabolic disorder with secondary connective tissue manifestations.
Elastic scattering and total reaction cross section of {sup 6}He+{sup 120}Sn
Faria, P. N. de; Lichtenthaeler, R.; Pires, K. C. C.; Lepine-Szily, A.; Guimaraes, V.; Mendes, D. R. Jr.; Barioni, A.; Morcelle, V.; Morais, M. C.; Camargo, O. Jr.; Alcantara Nunez, J.; Moro, A. M.; Arazi, A.; Rodriguez-Gallardo, M.; Assuncao, M.
2010-04-15
The elastic scattering of {sup 6}He on {sup 120}Sn has been measured at four energies above the Coulomb barrier using the {sup 6}He beam produced at the RIBRAS (Radioactive Ion Beams in Brasil) facility. The elastic angular distributions have been analyzed with the optical model and three- and four-body continuum-discretized coupled-channels calculations. The total reaction cross sections have been derived and compared with other systems of similar masses.
Ab-initio study of electronic structure and elastic properties of ZrC
NASA Astrophysics Data System (ADS)
Mund, H. S.; Ahuja, B. L.
2016-05-01
The electronic and elastic properties of ZrC have been investigated using the linear combination of atomic orbitals method within the framework of density functional theory. Different exchange-correlation functionals are taken into account within generalized gradient approximation. We have computed energy bands, density of states, elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, lattice parameters and pressure derivative of the bulk modulus by calculating ground state energy of the rock salt structure type ZrC.
Mars - Thickness of the lithosphere from the tectonic response to volcanic loads
NASA Astrophysics Data System (ADS)
Comer, R. P.; Solomon, S. C.; Head, J. W.
1985-02-01
The response to loading of the elastic lithosphere of Mars by seven large volcanic features is estimated based on the hypothesis of a flexural origin for a definable set of load-concentric graben. From the locations of such graben, or from their absence, the lithospheric thickness and flexural rigidity are inferred. For the Tharsis montes, Alba Patera, and Elysium Mons, elastic lithospheric thicknesses at the time of loading range from 20 to 50 km, assuming a Young's modulus of a trillion dyn/sq cm. The thickness exceeded 120 km beneath Olympus Mons and Isidis Planitia. The corresponding ranges in flexural rigidity are approximately 10 to the 30th to 31st dyn cm and greater than 10 to the 32nd dyn cm, respectively. These results indicate a local thinning of the lithosphere beneath portions of the central regions of the Tharsis and Elysium volcanic provinces at the time of loading-induced fracturing.
Elastic fibres in health and disease.
Kielty, Cay M
2006-08-08
Elastic fibres are a major class of extracellular matrix fibres that are abundant in dynamic connective tissues such as arteries, lungs, skin and ligaments. Their structural role is to endow tissues with elastic recoil and resilience. They also act as an important adhesion template for cells, and they regulate growth factor availability. Mutations in major structural components of elastic fibres, especially elastin, fibrillins and fibulin-5, cause severe, often life-threatening, heritable connective tissue diseases such as Marfan syndrome, supravalvular aortic stenosis and cutis laxa. Elastic-fibre function is also frequently compromised in damaged or aged elastic tissues. The ability to regenerate or engineer elastic fibres and tissues remains a significant challenge, requiring improved understanding of the molecular and cellular basis of elastic-fibre biology and pathology, and ability to regulate the spatiotemporal expression and assembly of its molecular components.
Elastic fibres in health and disease.
Baldwin, Andrew K; Simpson, Andreja; Steer, Ruth; Cain, Stuart A; Kielty, Cay M
2013-08-20
Elastic fibres are insoluble components of the extracellular matrix of dynamic connective tissues such as skin, arteries, lungs and ligaments. They are laid down during development, and comprise a cross-linked elastin core within a template of fibrillin-based microfibrils. Their function is to endow tissues with the property of elastic recoil, and they also regulate the bioavailability of transforming growth factor β. Severe heritable elastic fibre diseases are caused by mutations in elastic fibre components; for example, mutations in elastin cause supravalvular aortic stenosis and autosomal dominant cutis laxa, mutations in fibrillin-1 cause Marfan syndrome and Weill-Marchesani syndrome, and mutations in fibulins-4 and -5 cause autosomal recessive cutis laxa. Acquired elastic fibre defects include dermal elastosis, whereas inflammatory damage to fibres contributes to pathologies such as pulmonary emphysema and vascular disease. This review outlines the latest understanding of the composition and assembly of elastic fibres, and describes elastic fibre diseases and current therapeutic approaches.
Improved Coal-Thickness Measurement
NASA Technical Reports Server (NTRS)
Barr, T. A.
1984-01-01
Summed signals and dielectric-filled antenna improve measurement. Improved FM radar for measuring thickness of coal seam eliminates spectrum splitting and reduces magnitude of echo from front coal surface.
NASA Astrophysics Data System (ADS)
Kasparova, A.; Katkov, I.; Chilingarian, I.; Silchenko, O.; Moiseev, A.; Borisov, S.
2016-06-01
Although thick stellar discs are detected in nearly all edge-on disc galaxies, their formation scenarios still remain a matter of debate. Due to observational difﬁculties, there is a lack of information about their stellar populations. Using the Russian 6-m telescope BTA we collected deep spectra of thick discs in three edge-on early-type disc galaxies located in different environments: NGC4111 in a dense group, NGC4710 in the Virgo cluster, and NGC5422 in a sparse group. We see intermediate age (4 ‑ 5 Gyr) metal rich ([Fe/H] ~ ‑0.2 ‑ 0.0 dex) stellar populations in NGC4111 and NGC4710. On the other hand, NGC5422 does not harbour young stars, its only disc is thick and old (10 Gyr) and its α-element abundance suggests a long formation epoch implying its formation at high redshift. Our results prove the diversity of thick disc formation scenarios.
Avalanche dynamics of elastic interfaces.
Le Doussal, Pierre; Wiese, Kay Jörg
2013-08-01
Slowly driven elastic interfaces, such as domain walls in dirty magnets, contact lines wetting a nonhomogeneous substrate, or cracks in brittle disordered material proceed via intermittent motion, called avalanches. Here we develop a field-theoretic treatment to calculate, from first principles, the space-time statistics of instantaneous velocities within an avalanche. For elastic interfaces at (or above) their (internal) upper critical dimension d≥d(uc) (d(uc)=2,4 respectively for long-ranged and short-ranged elasticity) we show that the field theory for the center of mass reduces to the motion of a point particle in a random-force landscape, which is itself a random walk [Alessandro, Beatrice, Bertotti, and Montorsi (ABBM) model]. Furthermore, the full spatial dependence of the velocity correlations is described by the Brownian-force model (BFM) where each point of the interface sees an independent Brownian-force landscape. Both ABBM and BFM can be solved exactly in any dimension d (for monotonous driving) by summing tree graphs, equivalent to solving a (nonlinear) instanton equation. We focus on the limit of slow uniform driving. This tree approximation is the mean-field theory (MFT) for realistic interfaces in short-ranged disorder, up to the renormalization of two parameters at d=d(uc). We calculate a number of observables of direct experimental interest: Both for the center of mass, and for a given Fourier mode q, we obtain various correlations and probability distribution functions (PDF's) of the velocity inside an avalanche, as well as the avalanche shape and its fluctuations (second shape). Within MFT we find that velocity correlations at nonzero q are asymmetric under time reversal. Next we calculate, beyond MFT, i.e., including loop corrections, the one-time PDF of the center-of-mass velocity u[over ·] for dimension d
Christensen, T; Neubauer, B
1988-01-01
By means of ultrasonography, arterial wall stiffness, arterial wall thickness, and the elastic modulus of the common femoral artery were estimated in a group of 19 young insulin-dependent diabetics. The ultrasound technique for determination of these parameters is described as well as the echo-anatomy of the arterial wall. In accordance with a previous investigation a significant rise in arterial wall stiffness was found. Furthermore, there was a highly significant correlation between the stiffness and the thickness of the arterial wall. The elastic modulus also correlated to the stiffness. It is concluded that the diabetic macroangiopathy is characterized by an increased stiffness of the arterial wall caused by increased thickness as well as by progressive alterations of the elastic characteristics of the wall tissue. Possible pathogenetic reasons are discussed.
Dynamic elastic moduli during isotropic densification of initially granular media
NASA Astrophysics Data System (ADS)
Vasseur, Jérémie; Wadsworth, Fabian B.; Lavallée, Yan; Dingwell, Donald B.
2016-03-01
The elastic properties of homogeneous, isotropic materials are well constrained. However, in heterogeneous and evolving materials, these essential properties are less well-explored. During sintering of volcanic ash particles by viscous processes as well as during compaction and cementation of sediments, microstructure and porosity undergo changes that affect bulk dynamic elastic properties. Here using a model system of glass particles as an analogue for initially granular rock-forming materials, we have determined porosity and P-wave velocity during densification. Using these results, we test models for the kinetics of densification and the resultant evolution of the elastic properties to derive a quantitative description of the coupling between the kinetics of isotropic densification and the evolving dynamic elastic moduli. We demonstrate the power of the resultant model on a wide range of data for non-coherent sediments as well as sedimentary and volcanic rocks. We propose that such constraints be viewed as an essential ingredient of time-dependent models for the deformation of evolving materials in volcanoes and sedimentary basins.
Implementation of a Combined Elastic-Viscous-Plastic and Collisional Sea Ice Rheology
NASA Astrophysics Data System (ADS)
Rynders, Stefanie; Aksenov, Yevgeny; Feltham, Daniel
2015-04-01
The Marginal Ice Zone (MIZ) is a transitional area between the open ocean and pack ice. The MIZ is present in the Arctic and Southern Ocean and measures up to several hundred kilometers across. It is characterized by high surface ocean waves and consists of severely fragmented sea ice with ice floes less than 100m in diameter. With declining summer Arctic sea ice cover and increased wave heights in the Arctic Ocean, in the Arctic the MIZ widened by about 40 percent during the last three decades. The changes in sea ice and growing economic activity in the Polar Oceans necessitate new climate and forecasting models that can simulate the MIZ. Current models are not fit for the purpose since they do not model the surface ocean waves, which determine the MIZ width, or the sea ice rheology that represents MIZ ice dynamics. This study presents an implementation of collisional ice rheology that takes into account jostling of ice floes and also includes the effects of the ice floe distribution on internal ice stresses. The collisional contribution is derived from the magnitude of velocity fluctuations of ice floes. These are calculated from a kinetic energy evolution equation for the ice floes. Properties taken from a coupled wave-in-ice module determine the maximum floe size. This information is taken form a coupled wave-in-ice module. The rheology is derived in the framework of the Elastic-Viscous-Plastic rheology. This allows combination with the Elastic-Viscous-Plastic rheology and thus formulation of a unified sea ice rheology suitable for both the central pack ice and MIZ. The combined ice rheology is implemented in the Los Alamos CICE model and tested in the 2-degree resolution global NEMO Ocean General Circulation model. The 10-year run is forced by CORE2 climatological forcing. Prelimary results show that in the Arctic the new rheology decreases ice thicknesses near the coasts where ice is stationary. Overall, the change in the basin-scale Arctic ice thickness is
Supersonic flow past oscillating airfoils including nonlinear thickness effects
NASA Technical Reports Server (NTRS)
Van Dyke, Milton D
1954-01-01
A solution to second order in thickness is derived for harmonically oscillating two-dimensional airfoils in supersonic flow. For slow oscillations of an arbitrary profile, the result is found as a series including the third power of frequency. For arbitrary frequencies, the method of solution for any specific profile is indicated, and the explicit solution derived for a single wedge. Nonlinear thickness effects are found generally to reduce the torsional damping, and so enlarge the range of Mach numbers within which torsional instability is possible.
Tuning the period of elastic MnAs/GaAs(001) {alpha}-{beta} pattern by Fe deposition
Vidal, F.; Marangolo, M.; Eddrief, M.; Etgens, V. H.; Spezzani, C.; Breitwieser, R.; Sacchi, M.
2010-12-20
The {alpha}-{beta} elastic striped pattern of MnAs/GaAs(001) is shown to be perturbed by Fe overlayer growth. After nanometric Fe thin film deposition, the elastic pattern is still present in the 10-45 deg. C temperature range, but the period of the pattern increases by up to 40% for MnAs epilayers 70 to 400 nm thick. This observation can be interpreted within a simple model calculation of the pattern elastic energy, providing quantitative agreement with the experimental results.
Elastic modulus of tree frog adhesive toe pads.
Barnes, W Jon P; Goodwyn, Pablo J Perez; Nokhbatolfoghahai, Mohsen; Gorb, Stanislav N
2011-10-01
Previous work using an atomic force microscope in nanoindenter mode indicated that the outer, 10- to 15-μm thick, keratinised layer of tree frog toe pads has a modulus of elasticity equivalent to silicone rubber (5-15 MPa) (Scholz et al. 2009), but gave no information on the physical properties of deeper structures. In this study, micro-indentation is used to measure the stiffness of whole toe pads of the tree frog, Litoria caerulea. We show here that tree frog toe pads are amongst the softest of biological structures (effective elastic modulus 4-25 kPa), and that they exhibit a gradient of stiffness, being stiffest on the outside. This stiffness gradient results from the presence of a dense network of capillaries lying beneath the pad epidermis, which probably has a shock absorbing function. Additionally, we compare the physical properties (elastic modulus, work of adhesion, pull-off force) of the toe pads of immature and adult frogs. PMID:21667266
Elastic properties of liquid and solid argon in nanopores.
Schappert, Klaus; Pelster, Rolf
2013-10-16
We have measured sorption isotherms and determined the intrinsic longitudinal elastic modulus β(Ar,ads) of nanoconfined material via ultrasonic measurements combined with a special effective medium analysis. In the liquid regime the adsorbate only contributes to the measured effective properties when the pores are completely filled and the modulus is bulklike. At partial fillings its contribution is cancelled out by the high compressibility of the vapour phase. In contrast, at lower temperatures frozen argon as well as underlying liquid surface layers cause a linear increase of the effective longitudinal modulus upon filling. During sorption the contribution of the liquid surface layers near the pore wall β(Ar,surf) increases with the thickness of the solid layers reaching the bulk value β(Ar,liquid) only in the limit of complete pore filling. We interpret this effect as due to the gradual stiffening of the solid argon membrane. The measurements and their analysis show that longitudinal ultrasonic waves are well suited to the study of the elastic properties and liquid-solid phase transitions in porous systems. This method should also help to detect the influence of nanoconfinement on elastic properties in further research.
NASA Astrophysics Data System (ADS)
Ebrahimi, Farzad; Barati, Mohammad Reza
2016-10-01
In this article, a nonlocal four-variable refined plate theory is developed to examine the buckling behavior of nanoplates made of magneto-electro-elastic functionally graded (MEE-FG) materials resting on Winkler-Pasternak foundation. Material properties of nanoplate change in spatial coordinate based on power-law distribution. The nonlocal governing equations are deduced by employing the Hamilton principle. For various boundary conditions, the analytical solutions of nonlocal MEE-FG plates for buckling problem will be obtained based on an exact solution approach. Finally, dependency of buckling response of MEE-FG nanoplate on elastic foundation parameters, magnetic potential, external electric voltage, various boundary conditions, small scale parameter, power-law index, plate side-to-thickness ratio and aspect ratio will be figure out. These results can be advantageous for the mechanical analysis and design of intelligent nanoscale structures constructed from magneto-electro-thermo-elastic functionally graded materials.
Effects of geometric confinement on the adhesive debonding of soft elastic solids.
Webber, Rebecca E; Shull, Kenneth R; Roos, Alexandra; Creton, Costantino
2003-08-01
The effect of increasing confinement on soft elastic gel layers has been investigated and a means of analyzing the behavior of such systems has been developed. A probe tack test was used to study the behavior of thin elastic layers during interfacial debonding from a cylindrical glass indenter. For this gel-indenter system, confinement is defined as the ratio of a(0), the radius of the indenter, to h, the thickness of the elastic layer. In order to investigate geometric effects, the adhesion energy of the gel was kept constant while the thickness and modulus of the gels were varied. A fracture mechanics approach, based on the compliance of the layer, has been employed in analyzing the experimental data. It is shown that a fracture mechanics analysis is appropriate for these systems, allowing quantitative results to be obtained, despite very irregular contacts. It has also been shown that the interfacial instabilities observed during debonding maximize the compliance of the elastic layer. Additionally, four dimensionless parameters that dictate the behavior of confined systems have been defined, offering a general guide to understanding and characterizing the mechanical behavior of thin elastic layers.
Wang, Qian; Ashley, Dennis W.; Dechow, Paul C.
2010-01-01
Understanding the mechanical features of cortical bone and their changes with growth and adaptation to function plays an important role in our ability to interpret the morphology and evolution of craniofacial skeletons. We assessed the elastic properties of cortical bone of juvenile and adult baboon mandibles using ultrasonic techniques. Results showed that, overall, cortical bone from baboon mandibles could be modeled as an orthotropic elastic solid. There were significant differences in the directions of maximum stiffness, thickness, density, and elastic stiffness among different functional areas, indicating regional adaptations. After maturity, the cortical bone becomes thicker, denser, and stiffer, but less anisotropic. There were differences in elastic properties of the corpus and ramus between male and female mandibles which are not observed in human mandibles. There were correlations between cortical thicknesses and densities, between bone elastic properties and microstructural configuration, and between the directions of maximum stiffness and bone anatomical axes in some areas. The relationships between bone extrinsic and intrinsic properties bring us insights into the integration of form and function in craniofacial skeletons and suggest that we need to consider both macroscopic form, microstructural variation, and the material properties of bone matrix when studying the functional properties and adaptive nature of the craniofacial skeleton in primates. The differences between baboon and human mandibles is at variance to the pattern of differences in crania, suggesting differences in bone adaption to varying skeletal geometries and loading regimes at both phylogenetic and ontogenetic levels. PMID:19927280
Composite elastic magnet films with hard magnetic feature
NASA Astrophysics Data System (ADS)
Wang, Weisong; Yao, Zhongmei; Chen, Jackie C.; Fang, Ji
2004-10-01
Hard magnetic materials with high remnant magnetic moment, Mr, have unique advantages that can achieve bi-directional (push-pull) movement in an external magnetic field. This paper presents the results on the fabrication and testing of novel composite elastic permanent magnet films. The microsize hard barium ferrite powder, NdFeB powder, and different silicone elastomers have been used to fabricate various large elongation hard magnetic films. Three different fabrication methods, screen-coating processing, moulding processing and squeegee-coating processing, have been investigated, and the squeegee-coating process was proven to be the most successful method. The uniform composite elastic permanent magnet films range from 40 µm to 216 µm in thickness have been successfully fabricated. These films were then magnetized in the thickness direction after fabrication. They exhibited permanent magnet behaviour; for instance, the film (0.640 mm3 in volume) made of polydimethyl siloxane (PDMS) and hard barium ferrite powders is measured to give a coercive force, Hc, of 3.24 × 105 A m-1 and Mr of 1.023 × 10-5 A m2, and the film (0.504 mm3 in volume) made of PDMS and NdFeB powders gives 1.55 × 105 A m-1 Hc and 8.081 × 10-5 A m2 Mr. These composite elastic permanent magnet films' mechanical properties, like Young's modulus and deflection force, have been evaluated. To validate the films' Young's modulus, a finite-element computer simulation (ANSYS®) is used and one film is chosen whose Young's modulus (16.60 MPa) is confirmed by the simulation results with ANSYS®. The large elongation composite elastic permanent magnet film provides an excellent diaphragm material, which plays an important role in the micropump or valve. The movement of the 126 µm thick film with 4.5 mm diameter made of PDMS and NdFeB powders has been tested in a 0.21 Tesla external magnetic field. It was proven to have large deflection of 125 µm.
Factors influencing elastic stresses in double cantilever beam specimens
NASA Technical Reports Server (NTRS)
Crews, J. H., Jr.; Shivakumar, K. N.; Raju, I. S.
1986-01-01
An elastic stress analysis was conducted for a double cantilever beam (DCB) specimen using finite-element methods. The purpose of this study was to identify the important parameters that influence stresses ahead of the delamination front. The study focused on an aluminum DCB specimen, typical of adhesively-bonded joints, and on a graphite/epoxy specimen representing a cocured composite. Opening mode sigma sub y stresses ahead of the crack tip were calculated and compared with those for a monolithic reference specimen. Beyond the singularity-dominated region very near the crack tip, the sigma sub y distribution was elevated compared to the monolithic case. Both the adhesive thickness and the adherend transverse (thickness-direction) stiffness were found to influence the elevation of sigma sub y. In contrast, adherend thickness and longitudinal stiffness has very little effect on this stress distribution. Estimates for adhesive yielding beyond the aluminum DCB crack tip showed that both the area and height of the plastic zone increased to a peak value for increasing adhesive thicknesses. Results from this study would provide insight for comparing data from different DCB specimens and for designing new DCB specimens.
Factors influencing elastic stresses in double cantilever beam specimens
NASA Technical Reports Server (NTRS)
Crews, J. H., Jr.; Shivakumar, K. N.; Raju, I. S.
1988-01-01
An elastic stress analysis was conducted for a double cantilever beam (DCB) specimen using finite-element methods. The purpose of this study was to identify the important parameters that influence stresses ahead of the delamination front. The study focused on an aluminum DCB specimen, typical of adhesively-bonded joints, and on a graphite/epoxy specimen representing a cocured composite. Opening mode sigma sub y stresses ahead of the crack tip were calculated and compared with those for a monolithic reference specimen. Beyond the singularity-dominated region very near the crack tip, the sigma sub y distribution was elevated compared to the monolithic case. Both the adhesive thickness and the adherend transverse (thickness-direction) stiffness were found to influence the elevation of sigma sub y. In contrast, adherend thickness and longitudinal stiffness has very little effect on this stress distribution. Estimates for adhesive yielding beyond the aluminum DCB crack tip showed that both the area and height of the plastic zone increased to a peak value for increasing adhesive thicknesses. Results from this study would provide insight for comparing data from different DCB specimens and for designing new DCB specimens.
Prediction of elastic properties for polymer-particle nanocomposites exhibiting an interphase.
Deng, Fei; Van Vliet, Krystyn J
2011-04-22
Particle-polymer nanocomposites often exhibit mechanical properties described poorly by micromechanical models that include only the particle and matrix phases. Existence of an interfacial region between the particle and matrix, or interphase, has been posited and indirectly demonstrated to account for this effect. Here, we present a straightforward analytical approach to estimate effective elastic properties of composites comprising particles encapsulated by an interphase of finite thickness and distinct elastic properties. This explicit solution can treat nanocomposites that comprise either physically isolated nanoparticles or agglomerates of such nanoparticles; the same framework can also treat physically isolated nanoparticle aggregates or agglomerates of such aggregates. We find that the predicted elastic moduli agree with experiments for three types of particle-polymer nanocomposites, and that the predicted interphase thickness and stiffness of carbon black-rubber nanocomposites are consistent with measured values. Finally, we discuss the relative influence of the particle-polymer interphase thickness and stiffness to identify maximum possible changes in the macroscale elastic properties of such materials. PMID:21393814
Dynamic Response of a Pulse-Heated, Thick-Walled, Hollow Sphere: Validation of Code Numerics
Canaan, R.E.
2000-01-19
Volumetric pulse heating of a thick-walled hollow sphere is numerically investigated. The primary objective is to validate a variety of LLNL 30 hydrocodes for modeling the dynamic behavior of fissile/fissionable metals subject to rapid ''fission-heating'' transients. The 30 codes tested include both DYNA3D and NIKE3D, as well as the ''ASCI'' code, ALE3D. The codes are compared ''head-to-head'' and are benchmarked against a 1D finite difference solution to the problem that is derived from basic principles. Three pulse-heating transients are examined with full-width-half-maximum pulse durations of 41{micro}s, 85{micro}s, and 140{micro}s, respectively. These three transients produce a significant range of dynamic responses in the thermo-elastic regime. We present results for dynamic radial displacements and stresses for each pulse, and also discuss which code features/options worked best for these types of calculations. In general, the code results are in excellent agreement for the simple system considered. Validation of code numerics in simple systems is a key first step toward future application of the codes in more complicated geometries (U).
Admittance Survey of Type 1 Coronae on Venus: Implications for Elastic Thickness
NASA Technical Reports Server (NTRS)
Hoogenboom, T.; Smrekar, S. E.; Anderson, F. S.; Houseman, G.
2003-01-01
Coronae are volcano-tectonic features on Venus which range from 60km to 2600km and are defined by their nearly circular patterns of fractures. Type 1 (regular) coronae are classified as having >50% complete fracture annuli. Previous work has examined the factors controlling the morphology, size, and fracture pattern of coronae, using lithospheric properties, loading signature and geologic characteristics. However, these studies have been limited to Type 2 (topographic) coronae (e.g. coronaes with <50% fracture annuli), and the factors controlling the formation of Type 1 coronae remain poorly understood. In this study, we apply the methodology of to survey the admittance signature for Type 1 coronae to determine the controlling parameters which govern Type 1 coronae formation.
NASA Technical Reports Server (NTRS)
El-Azab, A.; Mal, A. K.; Bar-Cohen, Y.; Lih, S.
1996-01-01
Electroactive thin-film polymers are candidate sensors and actuators materials [1,2]. They are also finding a significant potential for applications in muscle mechanisms and micro-electro-mechanical systems (MEMS).
Global map of lithosphere thermal thickness on a 1 deg x 1 deg grid - digitally available
NASA Astrophysics Data System (ADS)
Artemieva, Irina
2014-05-01
This presentation reports a 1 deg ×1 deg global thermal model for the continental lithosphere (TC1). The model is digitally available from the author's web-site: www.lithosphere.info. Geotherms for continental terranes of different ages (early Archean to present) are constrained by reliable data on borehole heat flow measurements (Artemieva and Mooney, 2001), checked with the original publications for data quality, and corrected for paleo-temperature effects where needed. These data are supplemented by cratonic geotherms based on xenolith data. Since heat flow measurements cover not more than half of the continents, the remaining areas (ca. 60% of the continents) are filled by the statistical numbers derived from the thermal model constrained by borehole data. Continental geotherms are statistically analyzed as a function of age and are used to estimate lithospheric temperatures in continental regions with no or low quality heat flow data. This analysis requires knowledge of lithosphere age globally. A compilation of tectono-thermal ages of lithospheric terranes on a 1 deg × 1 deg grid forms the basis for the statistical analysis. It shows that, statistically, lithospheric thermal thickness z (in km) depends on tectono-thermal age t (in Ma) as: z=0.04t+93.6. This relationship formed the basis for a global thermal model of the continental lithosphere (TC1). Statistical analysis of continental geotherms also reveals that this relationship holds for the Archean cratons in general, but not in detail. Particularly, thick (more than 250 km) lithosphere is restricted solely to young Archean terranes (3.0-2.6 Ga), while in old Archean cratons (3.6-3.0 Ga) lithospheric roots do not extend deeper than 200-220 km. The TC1 model is presented by a set of maps, which show significant thermal heterogeneity within continental upper mantle. The strongest lateral temperature variations (as large as 800 deg C) are typical of the shallow mantle (depth less than 100 km). A map of the
Influence of thickness and undercut of thermoplastic resin clasps on retentive force.
Osada, Hidekazu; Shimpo, Hidemasa; Hayakawa, Tohru; Ohkubo, Chikahiro
2013-01-01
Thermoplastic resin clasps have been used for esthetic denture rehabilitation. However, details of the design of the clasps have never been thoroughly clarified. This study investigated the retentive forces of thermoplastic resin clasps for non-metal clasp dentures. The retentive forces of all thermoplastic resin clasps depended on the elastic modulus of each resin, undercuts, thickness, and widths of the tested. A clasp with more than 0.5 mm undercut and 1.0 mm thickness is needed for Valplast. Similarly, more than 0.25 mm undercut and 1.0 mm thickness and 0.5 mm undercut and 0.5 mm thickness are required for Estheshot and Reigning, respectively; thus, the recommended clasp arm thickness is 1.0 mm to 1.5 mm for Valplast and Estheshot and 0.5 mm to 1.0 mm for Reigning when the width of the retentive arm is 5.0 mm. PMID:23718997
Energy distribution of elastically scattered electrons from double layer samples
NASA Astrophysics Data System (ADS)
Tőkési, K.; Varga, D.
2016-02-01
We present a theoretical description of the spectra of electrons elastically scattered from thin double layered Au-C samples. The analysis is based on the Monte Carlo simulation of the recoil and Doppler effects in reflection and transmission geometries of the scattering at a fixed angle of 44.3 ° and a primary energy of 40 keV. The relativistic correction is taken into account. Besides the experimentally measurable energy distributions the simulations give many partial distributions separately, depending on the number of elastic scatterings (single, and multiple scatterings of different types). Furthermore, we present detailed analytical calculations for the main parameters of the single scattering, taking into account both the ideal scattering geometry, i.e. infinitesimally small angular range, and the effect of the real, finite angular range used in the measurements. We show our results for intensity ratios, peak shifts and broadenings for four cases of measurement geometries and layer thicknesses. While in the peak intensity ratios of gold and carbon for transmission geometries were found to be in good agreement with the results of the single scattering model, especially large deviations were obtained in reflection geometries. The separation of the peaks, depending on the geometry and the thickness, generally smaller, and the peak width generally larger than it can be expected from the nominal values of the primary energy, scattering angle, and mean kinetic energy of the atoms. We also show that the peaks are asymmetric even for the case of the single scattering due to the finite solid angle. Finally, we present a qualitative comparison with the experimental data. We find our resulting energy distribution of elastically scattered electrons to be in good agreement with recent measurements.
NASA Astrophysics Data System (ADS)
Whitlow, H. J.; Zhang, Y.; Wang, Y.; Winzell, T.; Simic, N.; Ahlberg, E.; Limbäck, M.; Wikmark, G.
2000-03-01
The trend towards increased fuel burn-up and higher operating temperatures in order to achieve more economic operation of nuclear power plants places demands on a better understanding of oxidative corrosion of Zircaloy (Zry) fuel rod cladding. As part of a programme to study these processes we have applied time-of-flight-energy elastic recoil detection (ToF-E ERD), electrochemical impedance measurements and scanning electron microscopy to quantitatively characterise thin-oxide films corresponding to the pre-transition oxidation regime. Oxide films of different nominal thickness in the 9-300 nm range were grown on a series of rolled Zr and Zry-2 plates by anodisation in dilute H 2SO 4 with applied voltages. The dielectric thickness of the oxide layer was determined from the electrochemical impedance measurements and the surface topography characterised by scanning electron microscopy. ToF-E ERD with a 60 MeV 127I 11+ ion beam was used to determine the oxygen content and chemical composition of the oxide layer. In the Zr samples, the oxygen content (O atom cm -2) that was determined by ERD was closely similar to the O content derived from impedance measurements from the dielectric film. The absolute agreement was well within the uncertainty associated with the stopping powers. Moreover, the measured composition of the thick oxide layers corresponded to ZrO 2 for the films thicker than 65 nm where the oxide layer was resolved in the ERD depth profile. Zry-2 samples exhibited a similar behaviour for small thickness ( ⩽130 nm) but had an enhanced O content at larger thicknesses that could be associated either with enhanced rough surface topography or porous oxide formation that was correlated with the presence of Second Phase Particles (SPP) in Zry-2. The concentration of SPP elements (Fe, Cr, Ni) in relation to Zr was the same in the outer 9×10 17 atom cm -2 of oxide as in the same thickness of metal. The results also revealed the presence of about 1 at.% 32S in the
The Foucault pendulum with an ideal elastic suspension string
NASA Astrophysics Data System (ADS)
Stanovnik, A.
2006-03-01
It is interesting and instructive to compare the precession of a Foucault pendulum, which has an inextensible suspension string, to the precession of an ideal elastic pendulum, for which the string force is proportional to string length (a harmonic oscillator). For the latter case, a simple derivation is presented of the bob trajectories as seen by the local observer on the rotating earth. It is shown that the initial precession rate is equal to the precession rate of the Foucault pendulum, and that the precession period is equal to the rotation period of the earth. The different precession period of the Foucault pendulum may therefore be seen as a cumulative effect of its inextensible suspension string, which constrains the motion of the bob. It is also shown that the initial angular acceleration of the oscillation plane of the ideal elastic pendulum is opposite for opposite initial azimuth angles. If any such difference were observed for a real Foucault pendulum, it might indicate the presence of effects due to elasticity of the suspension string. Another interesting application of the present derivation would be to the precession of the spring-mass oscillator.
Shear elastic modulus estimation from indentation and SDUV on gelatin phantoms
Amador, Carolina; Urban, Matthew W.; Chen, Shigao; Chen, Qingshan; An, Kai-Nan; Greenleaf, James F.
2011-01-01
Tissue mechanical properties such as elasticity are linked to tissue pathology state. Several groups have proposed shear wave propagation speed to quantify tissue mechanical properties. It is well known that biological tissues are viscoelastic materials; therefore velocity dispersion resulting from material viscoelasticity is expected. A method called Shearwave Dispersion Ultrasound Vibrometry (SDUV) can be used to quantify tissue viscoelasticity by measuring dispersion of shear wave propagation speed. However, there is not a gold standard method for validation. In this study we present an independent validation method of shear elastic modulus estimation by SDUV in 3 gelatin phantoms of differing stiffness. In addition, the indentation measurements are compared to estimates of elasticity derived from shear wave group velocities. The shear elastic moduli from indentation were 1.16, 3.40 and 5.6 kPa for a 7, 10 and 15% gelatin phantom respectively. SDUV measurements were 1.61, 3.57 and 5.37 kPa for the gelatin phantoms respectively. Shear elastic moduli derived from shear wave group velocities were 1.78, 5.2 and 7.18 kPa for the gelatin phantoms respectively. The shear elastic modulus estimated from the SDUV, matched the elastic modulus measured by indentation. On the other hand, shear elastic modulus estimated by group velocity did not agree with indentation test estimations. These results suggest that shear elastic modulus estimation by group velocity will be bias when the medium being investigated is dispersive. Therefore a rheological model should be used in order to estimate mechanical properties of viscoelastic materials. PMID:21317078
Elasticity Imaging of Polymeric Media
Sridhar, Mallika; Liu, Jie; Insana, Michael F.
2009-01-01
Viscoelastic properties of soft tissues and hydropolymers depend on the strength of molecular bonding forces connecting the polymer matrix and surrounding fluids. The basis for diagnostic imaging is that disease processes alter molecular-scale bonding in ways that vary the measurable stiffness and viscosity of the tissues. This paper reviews linear viscoelastic theory as applied to gelatin hydrogels for the purpose of formulating approaches to molecular-scale interpretation of elasticity imaging in soft biological tissues. Comparing measurements acquired under different geometries, we investigate the limitations of viscoelastic parameters acquired under various imaging conditions. Quasistatic (step-and-hold and low-frequency harmonic) stimuli applied to gels during creep and stress relaxation experiments in confined and unconfined geometries reveal continuous, bimodal distributions of respondance times. Within the linear range of responses, gelatin will behave more like a solid or fluid depending on the stimulus magnitude. Gelatin can be described statistically from a few parameters of low-order rheological models that form the basis of viscoelastic imaging. Unbiased estimates of imaging parameters are obtained only if creep data are acquired for greater than twice the highest retardance time constant and any steady-state viscous response has been eliminated. Elastic strain and retardance time images are found to provide the best combination of contrast and signal strength in gelatin. Retardance times indicate average behavior of fast (1–10 s) fluid flows and slow (50–400 s) matrix restructuring in response to the mechanical stimulus. Insofar as gelatin mimics other polymers, such as soft biological tissues, elasticity imaging can provide unique insights into complex structural and biochemical features of connectives tissues affected by disease. PMID:17408331
Elastic mismatch enhances cell motility
NASA Astrophysics Data System (ADS)
Bresler, Yony; Palmieri, Benoit; Grant, Martin
In recent years, the study of physics phenomena in cancer has drawn considerable attention. In cancer metastasis, a soft cancer cell leaves the tumor, and must pass through the endothelium before reaching the bloodstream. Using a phase-field model we have shown that the elasticity mismatch between cells alone is sufficient to enhance the motility of thesofter cancer cell by means of bursty migration, in agreement with experiment. We will present further characterization of these behaviour, as well as new possible applications for this model.
Variable Joint Elasticities in Running
NASA Astrophysics Data System (ADS)
Peter, Stephan; Grimmer, Sten; Lipfert, Susanne W.; Seyfarth, Andre
In this paper we investigate how spring-like leg behavior in human running is represented at joint level. We assume linear torsion springs in the joints and between the knee and the ankle joint. Using experimental data of the leg dynamics we compute how the spring parameters (stiffness and rest angles) change during gait cycle. We found that during contact the joints reveal elasticity with strongly changing parameters and compare the changes of different parameters for different spring arrangements. The results may help to design and improve biologically inspired spring mechanisms with adjustable parameters.
NASA Astrophysics Data System (ADS)
Favache, Audrey; Ryelandt, Sophie; Melchior, Maxime; Zeb, Gul; Carbonnelle, Pierre; Raskin, Jean-Pierre; Pardoen, Thomas
2016-01-01
Accurate measurement of the mechanical properties of ultra-thin films with thicknesses typically below 100 nm is a challenging issue with an interest in many fields involving coating technologies, microelectronics, and MEMS. A bilayer curvature based method is developed for the simultaneous determination of the elastic mismatch strain and Young's modulus of ultra-thin films. The idea is to deposit the film or coating on very thin cantilevers in order to amplify the curvature compared to a traditional "Stoney" wafer curvature test, hence the terminology "micro-Stoney." The data reduction is based on the comparison of the curvatures obtained for different supporting layer thicknesses. The elastic mismatch strain and Young's modulus are obtained from curvature measurements of cantilevers before and after the film deposition. The data reduction scheme relies on both analytical and finite element calculations, depending on the magnitude of the curvature. The experimental validation has been performed on ultra-thin low pressure chemical vapor deposited silicon nitride films with thickness ranging between 54 and 133 nm deposited on silicon cantilevers. The technique is sensitive to the cantilever geometry, in particular, to the thickness ratio and width/thickness ratio. Therefore, the precision in the determination of the latter quantities determines the accuracy on the extracted elastic mismatch strain and elastic modulus. The method can be potentially applied to films as thin as a few nanometers.
Favache, Audrey; Ryelandt, Sophie; Melchior, Maxime; Zeb, Gul; Carbonnelle, Pierre; Raskin, Jean-Pierre; Pardoen, Thomas
2016-01-01
Accurate measurement of the mechanical properties of ultra-thin films with thicknesses typically below 100 nm is a challenging issue with an interest in many fields involving coating technologies, microelectronics, and MEMS. A bilayer curvature based method is developed for the simultaneous determination of the elastic mismatch strain and Young's modulus of ultra-thin films. The idea is to deposit the film or coating on very thin cantilevers in order to amplify the curvature compared to a traditional "Stoney" wafer curvature test, hence the terminology "micro-Stoney." The data reduction is based on the comparison of the curvatures obtained for different supporting layer thicknesses. The elastic mismatch strain and Young's modulus are obtained from curvature measurements of cantilevers before and after the film deposition. The data reduction scheme relies on both analytical and finite element calculations, depending on the magnitude of the curvature. The experimental validation has been performed on ultra-thin low pressure chemical vapor deposited silicon nitride films with thickness ranging between 54 and 133 nm deposited on silicon cantilevers. The technique is sensitive to the cantilever geometry, in particular, to the thickness ratio and width/thickness ratio. Therefore, the precision in the determination of the latter quantities determines the accuracy on the extracted elastic mismatch strain and elastic modulus. The method can be potentially applied to films as thin as a few nanometers. PMID:26827345
System for measuring film thickness
Batishko, Charles R.; Kirihara, Leslie J.; Peters, Timothy J.; Rasmussen, Donald E.
1990-01-01
A system for determining the thicknesses of thin films of materials exhibiting fluorescence in response to exposure to excitation energy from a suitable source of such energy. A section of film is illuminated with a fixed level of excitation energy from a source such as an argon ion laser emitting blue-green light. The amount of fluorescent light produced by the film over a limited area within the section so illuminated is then measured using a detector such as a photomultiplier tube. Since the amount of fluorescent light produced is a function of the thicknesses of thin films, the thickness of a specific film can be determined by comparing the intensity of fluorescent light produced by this film with the intensity of light produced by similar films of known thicknesses in response to the same amount of excitation energy. The preferred embodiment of the invention uses fiber optic probes in measuring the thicknesses of oil films on the operational components of machinery which are ordinarily obscured from view.
Tube wall thickness measurement apparatus
Lagasse, Paul R.
1987-01-01
An apparatus for measuring the thickness of a tube's wall for the tube's entire length and circumference by determining the deviation of the tube wall thickness from the known thickness of a selected standard item. The apparatus comprises a base and a first support member having first and second ends. The first end is connected to the base and the second end is connected to a spherical element. A second support member is connected to the base and spaced apart from the first support member. A positioning element is connected to and movable relative to the second support member. An indicator is connected to the positioning element and is movable to a location proximate the spherical element. The indicator includes a contact ball for first contacting the selected standard item and holding it against the spherical element. The contact ball then contacts the tube when the tube is disposed about the spherical element. The indicator includes a dial having a rotatable needle for indicating the deviation of the tube wall thickness from the thickness of the selected standard item.
Tube wall thickness measurement apparatus
Lagasse, P.R.
1985-06-21
An apparatus for measuring the thickness of a tube's wall for the tube's entire length and radius by determining the deviation of the tube wall thickness from the known thickness of a selected standard item. The apparatus comprises a base and a first support member having first and second ends. The first end is connected to the base and the second end is connected to a spherical element. A second support member is connected to the base and spaced apart from the first support member. A positioning element is connected to and movable relative to the second support member. An indicator is connected to the positioning element and is movable to a location proximate the spherical element. The indicator includes a contact ball for first contacting the selected standard item and holding it against the spherical element. The contact ball then contacts the tube when the tube is disposed about the spherical element. The indicator includes a dial having a rotatable needle for indicating the deviation of the tube wall thickness from the thickness of the selected standard item.
D Multicomponent Time Domain Elastic Full Waveform Inversion
NASA Astrophysics Data System (ADS)
Silva, R. U.; De Basabe, J. D.; Gallardo, L. A.
2015-12-01
The search of hydrocarbon reservoirs between the finest stratigraphic and structural traps relies on the detailed surveying and interpretation of multicomponent seismic waves. This need makes Full Waveform Inversion (FWI) one of the most active topics in seismic exploration research and there are a limited number of FWI algorithms that undertake the elastic approach required to model these multicomponent data. We developed an iterative Gauss-Newton 2D time-domain elastic FWI scheme that reproduces the vertical and horizontal particle velocity as measured by common seismic surveys and obtains simultaneously the distribution of three elastic parameters of our subsurface model (density ρ and the Lame parameters λ and μ). The elastic wave is propagated in a heterogeneous elastic media using a time domain 2D velocity-stress staggered grid finite difference method. Our code observes the necessary stability conditions and includes absorbing boundary conditions and basic multi-thread parallelization. The same forward modeling code is also used to calculate the Frechet's derivatives with respect to the three parameters of our model following the sensitivity equation approach and perturbation theory. We regularized our FWI algorithm applying two different criteria: (1) First order Tikhonov regularization (maximum smoothness) and (2) Minimum Gradient Support (MGS) that adopts an approximate zero-norm of the several property gradients. We applied our algorithm to various test models and demonstrated that their structural information resemble closely those of the original three synthetic model parameters (λ, µ and ρ). Finally, we compared the role of both regularization criteria in terms of data fit, model stability and structural resemblance.
Joint inversion of AVA data for elastic parameters by bootstrapping
NASA Astrophysics Data System (ADS)
Kurt, Hülya
2007-03-01
A joint inversion method is developed to estimate the elastic constants of two elastic, homogeneous, isotropic media separated by a flat horizontal boundary. The method jointly uses P and S-converted wave reflection amplitude-versus-angle (AVA) data and seeks the Poisson's ratios of each layer, ratios of the densities and bulk modulus of the layers. The generalized linear inversion (GLI) method is used as a mathematical tool and the Zoeppritz equations defining the seismic energy partitioning at a boundary are used as the physical model. The P and S-converted wave velocity terms in the Zoeppritz equations were replaced by the bulk modulus (k1,k2), Poisson's ratios (σ1,σ2), and densities (ρ1,ρ2) of each layer. After expressing the equations in these six elastic constants, reflection coefficients of P and S-converted waves (Rpp,Rps) are obtained as functions of ratios of bulk modulus and densities of the lower layer to those of the upper layer ( k2/k1 and ρ2/ρ1) and Poisson's ratios of the upper and lower layers ( σ1 and σ2). Using the ratios of bulk modulus and densities, the number of unknown parameters is reduced from 6 to 4 and this improves the success of inversion. The other contribution is that the calculation of Rpp and Rps and their derivatives with respect to elastic constants and their ratios in the inversion are calculated analytically and coded in the Fortran programming language. In this way, the approach has an important advantage among the other AVA inversion methods, which are mostly based on numerical solutions or approximations to the Zoeppritz equations. A bootstrapping method of statistical analysis is combined with the GLI method to find the most likely elastic parameters and their confidence limits for repeated inversions for a large number of times by rearranging the noise distribution of the AVA data.
NASA Astrophysics Data System (ADS)
Penta, Raimondo; Gerisch, Alf
2016-08-01
The classical asymptotic homogenization approach for linear elastic composites with discontinuous material properties is considered as a starting point. The sharp length scale separation between the fine periodic structure and the whole material formally leads to anisotropic elastic-type balance equations on the coarse scale, where the arising fourth rank operator is to be computed solving single periodic cell problems on the fine scale. After revisiting the derivation of the problem, which here explicitly points out how the discontinuity in the individual constituents' elastic coefficients translates into stress jump interface conditions for the cell problems, we prove that the gradient of the cell problem solution is minor symmetric and that its cell average is zero. This property holds for perfect interfaces only (i.e., when the elastic displacement is continuous across the composite's interface) and can be used to assess the accuracy of the computed numerical solutions. These facts are further exploited, together with the individual constituents' elastic coefficients and the specific form of the cell problems, to prove a theorem that characterizes the fourth rank operator appearing in the coarse-scale elastic-type balance equations as a composite material effective elasticity tensor. We both recover known facts, such as minor and major symmetries and positive definiteness, and establish new facts concerning the Voigt and Reuss bounds. The latter are shown for the first time without assuming any equivalence between coarse and fine-scale energies (Hill's condition), which, in contrast to the case of representative volume elements, does not identically hold in the context of asymptotic homogenization. We conclude with instructive three-dimensional numerical simulations of a soft elastic matrix with an embedded cubic stiffer inclusion to show the profile of the physically relevant elastic moduli (Young's and shear moduli) and Poisson's ratio at increasing (up to
Mixed finite element methods for linear elasticity with weakly imposed symmetry
NASA Astrophysics Data System (ADS)
Arnold, Douglas N.; Falk, Richard S.; Winther, Ragnar
2007-12-01
In this paper, we construct new finite element methods for the approximation of the equations of linear elasticity in three space dimensions that produce direct approximations to both stresses and displacements. The methods are based on a modified form of the Hellinger-Reissner variational principle that only weakly imposes the symmetry condition on the stresses. Although this approach has been previously used by a number of authors, a key new ingredient here is a constructive derivation of the elasticity complex starting from the de Rham complex. By mimicking this construction in the discrete case, we derive new mixed finite elements for elasticity in a systematic manner from known discretizations of the de Rham complex. These elements appear to be simpler than the ones previously derived. For example, we construct stable discretizations which use only piecewise linear elements to approximate the stress field and piecewise constant functions to approximate the displacement field.
Human enamel thickness and ENAM polymorphism
Daubert, Diane M; Kelley, Joanna L; Udod, Yuriy G; Habor, Carolina; Kleist, Chris G; Furman, Ilona K; Tikonov, Igor N; Swanson, Willie J; Roberts, Frank A
2016-01-01
The tooth enamel development gene, enamelin (ENAM), showed evidence of positive selection during a genome-wide scan of human and primate DNA for signs of adaptive evolution. The current study examined the hypothesis that a single-nucleotide polymorphism (SNP) C14625T (rs7671281) in the ENAM gene identified in the genome-wide scan is associated with a change in enamel phenotype. African Americans were selected as the target population, as they have been reported to have a target SNP frequency of approximately 50%, whereas non-Africans are predicted to have a 96% SNP frequency. Digital radiographs and DNA samples from 244 teeth in 133 subjects were analysed, and enamel thickness was assessed in relation to SNP status, controlling for age, sex, tooth number and crown length. Crown length was found to increase with molar number, and females were found to have thicker enamel. Teeth with larger crowns also had thicker enamel, and older subjects had thinner enamel. Linear regression and generalized estimating equations were used to investigate the relationship between enamel thickness of the mandibular molars and ENAM SNP status; enamel in subjects with the derived allele was significantly thinner (P=0.040) when the results were controlled for sex, age, tooth number and crown length. The derived allele demonstrated a recessive effect on the phenotype. The data indicate that thinner dental enamel is associated with the derived ENAM genotype. This is the first direct evidence of a dental gene implicated in human adaptive evolution as having a phenotypic effect on an oral structure. PMID:27357321
Elastic response of a grounded ice sheet coupled to a floating ice shelf.
Sayag, Roiy; Worster, M Grae
2011-09-01
An ice sheet that spreads into an ocean is forced to bend owing to its buoyancy and detaches from the bedrock to form a floating ice shelf. The location of the transition between the grounded sheet and the floating shelf, defined as the grounding line, behaves as a free boundary. We develop a model of an elastic grounded sheet resting on a deformable elastic bed and coupled to an elastic floating shelf. We find that the grounding-line position is determined by the geometry of the bed and the bending-buoyancy length scale of the system. These two contributions depend on the reaction modulus of the bed in opposite ways. We show that the structure of the floating shelf depends on the bending-buoyancy length scale only, allowing us to calculate the bending stiffness of the elastic sheet independently of the properties of the bed. Relations between the structure of the floating shelf and the grounding-line position are also developed. Our theoretical predictions agree with laboratory experiments made using thick elastic sheets and a dense salt solution. Our findings may provide new insights into the dynamics near grounding lines, as well as methods to infer the bending stiffness of ice sheets and the grounding-line position from satellite altimetery that can be applied to elastic sheets in general.
Fermion localization on thick branes
Melfo, Alejandra; Pantoja, Nelson; Tempo, Jose David
2006-02-15
We consider chiral fermion confinement in scalar thick branes, which are known to localize gravity, coupled through a Yukawa term. The conditions for the confinement and their behavior in the thin-wall limit are found for various different BPS branes, including double walls and branes interpolating between different AdS{sub 5} spacetimes. We show that only one massless chiral mode is localized in all these walls, whenever the wall thickness is keep finite. We also show that, independently of wall's thickness, chiral fermionic modes cannot be localized in dS{sub 4} walls embedded in a M{sub 5} spacetime. Finally, massive fermions in double wall spacetimes are also investigated. We find that, besides the massless chiral mode localization, these double walls support quasilocalized massive modes of both chiralities.
LTCC Thick Film Process Characterization
Girardi, M. A.; Peterson, K. A.; Vianco, P. T.
2016-05-01
Low temperature cofired ceramic (LTCC) technology has proven itself in military/space electronics, wireless communication, microsystems, medical and automotive electronics, and sensors. The use of LTCC for high frequency applications is appealing due to its low losses, design flexibility and packaging and integration capability. Moreover, we summarize the LTCC thick film process including some unconventional process steps such as feature machining in the unfired state and thin film definition of outer layer conductors. The LTCC thick film process was characterized to optimize process yields by focusing on these factors: 1) Print location, 2) Print thickness, 3) Drying of tapes and panels,more » 4) Shrinkage upon firing, and 5) Via topography. Statistical methods were used to analyze critical process and product characteristics in the determination towards that optimization goal.« less
Elastic positron-cadmium scattering at low energies
Bromley, M. W. J.; Mitroy, J.
2010-05-15
The elastic and annihilation cross sections for positron-cadmium scattering are reported up to the positronium-formation threshold (at 2.2 eV). The low-energy phase shifts for the elastic scattering of positrons from cadmium were derived from the bound and pseudostate energies of a very large basis configuration-interaction calculation of the e{sup +}-Cd system. The s-wave binding energy is estimated to be 126{+-}42 meV, with a scattering length of A{sub scat}=(14.2{+-}2.1)a{sub 0}, while the threshold annihilation parameter, Z{sub eff}, was 93.9{+-}26.5. The p-wave phase shift exhibits a weak shape resonance that results in a peak Z{sub eff} of 91{+-}17 at a collision energy of about 490{+-}50 meV.
Half-oxidized phosphorene: band gap and elastic properties modulation.
Drissi, L B; Sadki, S; Sadki, K
2016-04-13
Based on a first principles approach, we study structural, electronic and elastic properties, as well as stabilities of all possible half-oxidized phosphorene conformers. Stability analysis reveals that oxygen chemisorption is an exothermic process in the six configurations despite the formation of interstitial oxygen bridges in three of them. Electronic structure calculations show that oxidation induces a band gap modulation ranging between 0.54 and 1.57 eV in the generalized gradient approximation corrected to 1.19 and 2.88 eV using GW. The mechanical response of the conformers is sensitively dependent on direction and indicates that the new derivatives are incompressible materials and one configuration has an auxetic behavior. The present results provide a basis for tailoring the electronic and elastic properties of phosphorene via half oxidation. PMID:26964522
Half-oxidized phosphorene: band gap and elastic properties modulation
NASA Astrophysics Data System (ADS)
Drissi, L. B.; Sadki, S.; Sadki, K.
2016-04-01
Based on a first principles approach, we study structural, electronic and elastic properties, as well as stabilities of all possible half-oxidized phosphorene conformers. Stability analysis reveals that oxygen chemisorption is an exothermic process in the six configurations despite the formation of interstitial oxygen bridges in three of them. Electronic structure calculations show that oxidation induces a band gap modulation ranging between 0.54 and 1.57 eV in the generalized gradient approximation corrected to 1.19 and 2.88 eV using GW. The mechanical response of the conformers is sensitively dependent on direction and indicates that the new derivatives are incompressible materials and one configuration has an auxetic behavior. The present results provide a basis for tailoring the electronic and elastic properties of phosphorene via half oxidation.
Vibration and wave propagation characteristics of multisegmented elastic beams
NASA Technical Reports Server (NTRS)
Nayfeh, Adnan H.; Hawwa, Muhammad A.
1990-01-01
Closed form analytical solutions are derived for the vibration and wave propagation of multisegmented elastic beams. Each segment is modeled as a Timoshenko beam with possible inclusion of material viscosity, elastic foundation and axial forces. Solutions are obtained by using transfer matrix methods. According to these methods formal solutions are first constructed which relate the deflection, slope, moment and shear force of one end of the individual segment to those of the other. By satisfying appropriate continuity conditions at segment junctions, a global 4x4 matrix results which relates the deflection, slope, moment and shear force of one end of the beam to those of the other. If any boundary conditions are subsequently invoked on the ends of the beam one gets the appropriate characteristic equation for the natural frequencies. Furthermore, by invoking appropriate periodicity conditions the dispersion relation for a periodic system is obtained. A variety of numerical examples are included.
On gradient field theories: gradient magnetostatics and gradient elasticity
NASA Astrophysics Data System (ADS)
Lazar, Markus
2014-09-01
In this work, the fundamentals of gradient field theories are presented and reviewed. In particular, the theories of gradient magnetostatics and gradient elasticity are investigated and compared. For gradient magnetostatics, non-singular expressions for the magnetic vector gauge potential, the Biot-Savart law, the Lorentz force and the mutual interaction energy of two electric current loops are derived and discussed. For gradient elasticity, non-singular forms of all dislocation key formulas (Burgers equation, Mura equation, Peach-Koehler stress equation, Peach-Koehler force equation, and mutual interaction energy of two dislocation loops) are presented. In addition, similarities between an electric current loop and a dislocation loop are pointed out. The obtained fields for both gradient theories are non-singular due to a straightforward and self-consistent regularization.
Elastic wave velocities of Apollo 14, 15, and 16 rocks
NASA Technical Reports Server (NTRS)
Mizutani, H.; Newbigging, D. F.
1973-01-01
Elastic wave velocities of two Apollo 14 rocks, 14053 and 14321, three Apollo 15 rocks, 15058, 15415, and 15545, and one Apollo 16 rock 60315 have been determined at pressures up to 10 kb. For sample 14321, the variation of the compressional wave velocities with temperature has been measured over the temperature range from 27 to 200 C. Overall elastic properties of these samples except sample 15415 are very similar to those of Apollo 11, 12, and 14 rocks and are concordant with Toksoz et al.'s (1972) interpretation that lunar upper crust is of basaltic composition. Temperature derivative of the P wave velocity for sample 14321 is a half to one order of magnitude larger than that for single crystalline minerals. This suggests that the seismic velocity in the lunar crust may be affected significantly by the temperature distribution.
Elastic, Conductive, Polymeric Hydrogels and Sponges
Lu, Yun; He, Weina; Cao, Tai; Guo, Haitao; Zhang, Yongyi; Li, Qingwen; Shao, Ziqiang; Cui, Yulin; Zhang, Xuetong
2014-01-01
As a result of inherent rigidity of the conjugated macromolecular chains resulted from the delocalized π-electron system along the polymer backbone, it has been a huge challenge to make conducting polymer hydrogels elastic by far. Herein elastic and conductive polypyrrole hydrogels with only conducting polymer as the continuous phase have been simply synthesized in the indispensable conditions of 1) mixed solvent, 2) deficient oxidant, and 3) monthly secondary growth. The elastic mechanism and oxidative polymerization mechanism on the resulting PPy hydrogels have been discussed. The resulting hydrogels show some novel properties, e.g., shape memory elasticity, fast functionalization with various guest objects, and fast removal of organic infectants from aqueous solutions, all of which cannot be observed from traditional non-elastic conducting polymer counterparts. What's more, light-weight, elastic, and conductive organic sponges with excellent stress-sensing behavior have been successfully achieved via using the resulting polypyrrole hydrogels as precursors. PMID:25052015
Simulation of water-table aquifers using specified saturated thickness
Sheets, Rodney A.; Hill, Mary C.; Haitjema, Henk M.; Provost, Alden M.; Masterson, John P.
2014-01-01
Simulating groundwater flow in a water-table (unconfined) aquifer can be difficult because the saturated thickness available for flow depends on model-calculated hydraulic heads. It is often possible to realize substantial time savings and still obtain accurate head and flow solutions by specifying an approximate saturated thickness a priori, thus linearizing this aspect of the model. This specified-thickness approximation often relies on the use of the “confined” option in numerical models, which has led to confusion and criticism of the method. This article reviews the theoretical basis for the specified-thickness approximation, derives an error analysis for relatively ideal problems, and illustrates the utility of the approximation with a complex test problem. In the transient version of our complex test problem, the specified-thickness approximation produced maximum errors in computed drawdown of about 4% of initial aquifer saturated thickness even when maximum drawdowns were nearly 20% of initial saturated thickness. In the final steady-state version, the approximation produced maximum errors in computed drawdown of about 20% of initial aquifer saturated thickness (mean errors of about 5%) when maximum drawdowns were about 35% of initial saturated thickness. In early phases of model development, such as during initial model calibration efforts, the specified-thickness approximation can be a very effective tool to facilitate convergence. The reduced execution time and increased stability obtained through the approximation can be especially useful when many model runs are required, such as during inverse model calibration, sensitivity and uncertainty analyses, multimodel analysis, and development of optimal resource management scenarios.
NASA Astrophysics Data System (ADS)
Chang, Nien-An
Theory and experiments on speckle generated from a thick diffuser are presented in this thesis. An overview of speckle from a diffuser in a 4F optical processor gives a basic understanding of the speckle formation and properties. The speckle size depends on the F number of the system, while the interior properties of a diffuser are evident in the wavelength dependence of speckle. We then move on to analyzing speckle from a thick diffuser, which is composed of particles embedded in a host medium. Emphasis on the theory is placed on solving for the wavelength decorrelation of speckle in a thick diffuser. A brief overview of the scattering theory for a particle using the Lorenz-Mie theory is included. Then we present a careful analysis of the speckle created by propagation through a thick diffuser. In the analysis we use an angular spectrum approach that is valid in the non-paraxial case together with a decomposition of the thick diffuser into a cascade of many screens. This calculation is well-suited to numerical analysis and an original computer software program has been provided as an Appendix in this thesis. By adding the scattered field from the randomly-located particles on any screen and propagating through a free space between each screen, one can generate a speckled field after going through the whole cascade. The theoretical predictions are summarized and later compared with experimental results on a series of opal milk glass diffusers. In many practical applications it is particularly advantageous to have mild thick diffusers of controllable diffusivity. We have extensively studied a new diffuser series fabricated using polystyrene spheres of various diameters embedded in gelatin. Theory and experiments are in good agreement.
Elastic multipoles in the field of the nematic director distortions.
Pergamenshchik, V M
2014-12-01
Theory of the interaction between all types of elastic dipoles and quadrupoles and distortions of the nematic director is presented. If a particle is small relative to the characteristic distortion length, the interaction is determined by the director derivatives at the particle location. We consider a spherical particle since, even under the standard assumptions of the multipole theory (weak deformations, one constant approximation), the problem can be solved analytically only in this case. Different dipoles interact with different distortion modes (e.g., isotropic dipole interacts with the splay, chiral dipole with the twist, and so on). In the main order, the interaction of a dipole is linear in the director derivatives, and the interaction of a quadrupole is linear in the second-order director derivatives. The theory goes beyond the main-order terms and predicts an effective distortion-induced dipolar component on a particle. This effect is described by the free energy term quadratic in the director derivatives and has contributions both of a bulk and surface origin. The bulk effect takes place even if the director at the particle surface is fixed, whereas the surface effect appears if the surface director is perturbed by the distortions due to a weak surface anchoring. The theory is illustrated by simple examples of the interaction of elastic dipoles with a disclination line, with cholesteric spiral, and with the director distortions in a hybrid cell.
Hummingbird tongues are elastic micropumps
Rico-Guevara, Alejandro; Fan, Tai-Hsi; Rubega, Margaret A.
2015-01-01
Pumping is a vital natural process, imitated by humans for thousands of years. We demonstrate that a hitherto undocumented mechanism of fluid transport pumps nectar onto the hummingbird tongue. Using high-speed cameras, we filmed the tongue–fluid interaction in 18 hummingbird species, from seven of the nine main hummingbird clades. During the offloading of the nectar inside the bill, hummingbirds compress their tongues upon extrusion; the compressed tongue remains flattened until it contacts the nectar. After contact with the nectar surface, the tongue reshapes filling entirely with nectar; we did not observe the formation of menisci required for the operation of capillarity during this process. We show that the tongue works as an elastic micropump; fluid at the tip is driven into the tongue's grooves by forces resulting from re-expansion of a collapsed section. This work falsifies the long-standing idea that capillarity is an important force filling hummingbird tongue grooves during nectar feeding. The expansive filling mechanism we report in this paper recruits elastic recovery properties of the groove walls to load nectar into the tongue an order of magnitude faster than capillarity could. Such fast filling allows hummingbirds to extract nectar at higher rates than predicted by capillarity-based foraging models, in agreement with their fast licking rates. PMID:26290074
Hummingbird tongues are elastic micropumps.
Rico-Guevara, Alejandro; Fan, Tai-Hsi; Rubega, Margaret A
2015-08-22
Pumping is a vital natural process, imitated by humans for thousands of years. We demonstrate that a hitherto undocumented mechanism of fluid transport pumps nectar onto the hummingbird tongue. Using high-speed cameras, we filmed the tongue-fluid interaction in 18 hummingbird species, from seven of the nine main hummingbird clades. During the offloading of the nectar inside the bill, hummingbirds compress their tongues upon extrusion; the compressed tongue remains flattened until it contacts the nectar. After contact with the nectar surface, the tongue reshapes filling entirely with nectar; we did not observe the formation of menisci required for the operation of capillarity during this process. We show that the tongue works as an elastic micropump; fluid at the tip is driven into the tongue's grooves by forces resulting from re-expansion of a collapsed section. This work falsifies the long-standing idea that capillarity is an important force filling hummingbird tongue grooves during nectar feeding. The expansive filling mechanism we report in this paper recruits elastic recovery properties of the groove walls to load nectar into the tongue an order of magnitude faster than capillarity could. Such fast filling allows hummingbirds to extract nectar at higher rates than predicted by capillarity-based foraging models, in agreement with their fast licking rates. PMID:26290074
Eulerian formulation of elastic rods
NASA Astrophysics Data System (ADS)
Huynen, Alexandre; Detournay, Emmanuel; Denoël, Vincent
2016-06-01
In numerous biological, medical and engineering applications, elastic rods are constrained to deform inside or around tube-like surfaces. To solve efficiently this class of problems, the equations governing the deflection of elastic rods are reformulated within the Eulerian framework of this generic tubular constraint defined as a perfectly stiff normal ringed surface. This reformulation hinges on describing the rod-deformed configuration by means of its relative position with respect to a reference curve, defined as the axis or spine curve of the constraint, and on restating the rod local equilibrium in terms of the curvilinear coordinate parametrizing this curve. Associated with a segmentation strategy, which partitions the global problem into a sequence of rod segments either in continuous contact with the constraint or free of contact (except for their extremities), this re-parametrization not only trivializes the detection of new contacts but also transforms these free boundary problems into classic two-points boundary-value problems and suppresses the isoperimetric constraints resulting from the imposition of the rod position at the extremities of each rod segment.
Inversion of elastic impedance for unconsolidated sediments
Lee, Myung W.
2006-01-01
Elastic properties of gas-hydrate-bearing sediments are important for quantifying gas hydrate amounts as well as discriminating the gas hydrate effect on velocity from free gas or pore pressure. This paper presents an elastic inversion method for estimating elastic properties of gas-hydrate-bearing sediments from angle stacks using sequential inversion of P-wave impedance from the zero-offset stack and S-wave impedance from the far-offset stack without assuming velocity ratio.
Effective elastic constants of polycrystalline aggregates
NASA Astrophysics Data System (ADS)
Bonilla, Luis L.
A METHOD is presented for the determination of the effective elastic constants of a transversely isotropic aggregate of weakly anisotropic crystallites with cubic symmetry. The results obtained generalize those given in the literature for the second and third order elastic constants. In addition, the second moments and the binary angular correlations of the second order stiffnesses are obtained. It is also explained how these moments can be used to find the two-point correlations of the elastic constants.
Multi-spectral photoacoustic elasticity tomography
Liu, Yubin; Yuan, Zhen
2016-01-01
The goal of this work was to develop and validate a spectrally resolved photoacoustic imaging method, namely multi-spectral photoacoustic elasticity tomography (PAET) for quantifying the physiological parameters and elastic modulus of biological tissues. We theoretically and experimentally examined the PAET imaging method using simulations and in vitro experimental tests. Our simulation and in vitro experimental results indicated that the reconstructions were quantitatively accurate in terms of sizes, the physiological and elastic properties of the targets. PMID:27699101
Multi-spectral photoacoustic elasticity tomography
Liu, Yubin; Yuan, Zhen
2016-01-01
The goal of this work was to develop and validate a spectrally resolved photoacoustic imaging method, namely multi-spectral photoacoustic elasticity tomography (PAET) for quantifying the physiological parameters and elastic modulus of biological tissues. We theoretically and experimentally examined the PAET imaging method using simulations and in vitro experimental tests. Our simulation and in vitro experimental results indicated that the reconstructions were quantitatively accurate in terms of sizes, the physiological and elastic properties of the targets.
NASA Astrophysics Data System (ADS)
Zhang, J. L.; Liu, X.; Yuan, Y.; Mang, H. A.
2015-01-01
A multiscale model of fiber-reinforced fine concrete is developed, with special emphasis on the interfacial transition zone (ITZ). It does not only allow the prediction of the modulus of elasticity but also permits the determination of the strain and stress field. The model is based on the mathematical homogenization method and implemented in the frame of the finite element method. A comparison of model predictions with experimental results taken from the literature validates the model's effectiveness for prediction of the elasticity modulus. The effect of the thickness and of the elasticity modulus of the ITZ on the elasticity modulus of the homogenized material as well as the influence of the strength of the ITZ on the elastic limit of the homogenized material, are investigated numerically. Furthermore, a sensitivity analysis is carried out to evaluate the influence of fine-scale factors on the elasticity modulus of ultra-high performance concrete.
Faraday wave lattice as an elastic metamaterial.
Domino, L; Tarpin, M; Patinet, S; Eddi, A
2016-05-01
Metamaterials enable the emergence of novel physical properties due to the existence of an underlying subwavelength structure. Here, we use the Faraday instability to shape the fluid-air interface with a regular pattern. This pattern undergoes an oscillating secondary instability and exhibits spontaneous vibrations that are analogous to transverse elastic waves. By locally forcing these waves, we fully characterize their dispersion relation and show that a Faraday pattern presents an effective shear elasticity. We propose a physical mechanism combining surface tension with the Faraday structured interface that quantitatively predicts the elastic wave phase speed, revealing that the liquid interface behaves as an elastic metamaterial. PMID:27300815
Elastic properties of solids at high pressure
NASA Astrophysics Data System (ADS)
Vekilov, Yu Kh; Krasilnikov, O. M.; Lugovskoy, A. V.
2015-11-01
This review examines the elastic response of solids under load. The definitions of isothermal and adiabatic elastic constants of ( n≥2) for a loaded crystal are given. For the case of hydrostatic pressure, two techniques are proposed for calculating the second-, third-, and fourth-order elastic constants from the energy-strain and stress-strain relations. As an example, using the proposed approach within the framework of the density functional theory, the second- to fourth-order elastic constants of bcc tungsten are calculated for the pressure range of 0-600 GPa.
Elastic moduli of pyrope rich garnets
NASA Astrophysics Data System (ADS)
Pandey, B. K.; Pandey, A. K.; Singh, C. K.
2013-06-01
The elastic properties of minerals depend on its composition, crystal structure, temperature and level of defects. The elastic parameters are important for the interpretation of the structure and composition of the garnet rich family. In present work we have calculated the elastic moduli such as isothermal bulk modulus, Young's modulus and Shear modulus over a wide range of temperature from 300 K to 1000 K by using Birch EOS and Poirrier Tarantola equation of state. The obtained results are compared with the experimental results obtained by measuring the elastic moduli of single crystal. The calculated results show that the logarithmic isothermal EOS does not cooperate well with experimental results.
Universal Elasticity and Fluctuations of Nematic Gels
NASA Astrophysics Data System (ADS)
Xing, Xiangjun; Radzihovsky, Leo
2003-04-01
We study elasticity of spontaneously orientationally ordered amorphous solids, characterized by a vanishing transverse shear modulus, as realized by nematic elastomers and gels. We show that local heterogeneities and elastic nonlinearities conspire to lead to anomalous nonlocal universal elasticity controlled by a nontrivial infrared fixed point. Namely, such solids are characterized by universal shear and bending moduli that, respectively, vanish and diverge at long scales, are universally incompressible, and exhibit a universal negative Poisson ratio and a non-Hookean elasticity down to arbitrarily low strains. Based on expansion about five dimensions, we argue that the nematic order is stable to thermal fluctuation and local heterogeneities down to dlc<3.
Accounting for elastic bodies in multibody loops
NASA Astrophysics Data System (ADS)
Hiller, Manfred; Sokol, Peter
A technique for modeling multibody systems with closed kinematic loops containing elastic bodies is developed analytically. The elastic body is treated as a beam element, and its linear-elastic deformation is discretized using ansatz functions. The free elastic body is then integrated into the multibody loop with the help of coupling equations, as described by Woernle (1988), and the equations of motion are obtained in minimal form via the principle of D'Alembert. The applicability of the present approach to problems in large space structures and robotics is indicated.
Thickness network features for prognostic applications in dementia.
Raamana, Pradeep Reddy; Weiner, Michael W; Wang, Lei; Beg, Mirza Faisal
2015-01-01
Regional analysis of cortical thickness has been studied extensively in building imaging biomarkers for early detection of Alzheimer's disease but not its interregional covariation of thickness. We present novel features based on the inter-regional covariation of cortical thickness. Initially, the cortical labels of each subject are partitioned into small patches (graph nodes) by spatial k-means clustering. A graph is then constructed by establishing a link between 2 nodes if the difference in thickness between the nodes is below a certain threshold. From this binary graph, a thickness network is computed using nodal degree, betweenness, and clustering coefficient measures. Fusing them with multiple kernel learning, it is observed that thickness network features discriminate mild cognitive impairment (MCI) converters from controls (CN) with an area under curve (AUC) of 0.83, 74% sensitivity and 76% specificity on a large subset obtained from the Alzheimer's Disease Neuroimaging Initiative data set. A comparison of predictive utility in Alzheimer's disease and/or CN classification (AUC of 0.92, 80% sensitivity [SENS] and 90% specificity [SPEC]), in discriminating CN from MCI (converters and nonconverters combined; AUC of 0.75, SENS and SPEC of 64% and 73%, respectively) and in discriminating between MCI nonconverters and MCI converters (AUC of 0.68, SENS and SPEC of 65% and 64%) is also presented. ThickNet features as defined here are novel, can be derived from a single magnetic resonance imaging scan, and demonstrate the potential for the computer-aided prognostic applications.
Worldwide dataset of glacier thickness observations compiled by literature review
NASA Astrophysics Data System (ADS)
Naegeli, Kathrin; Gärtner-Roer, Isabelle; Hagg, Wilfried; Huss, Matthias; Machguth, Horst; Zemp, Michael
2013-04-01
The volume of glaciers and ice caps is still poorly known, although it is expected to contribute significantly to changes in the hydrological cycle and global sea level rise over the next decades. Studies presenting worldwide estimations are mostly based on modelling and scaling approaches and are usually calibrated with only few measurements. Direct investigations of glacier thickness, a crucial parameter for ice volume calculations, are rather sparse but nevertheless available from all around the globe. This study presents a worldwide compilation of glacier thickness observation data. Literature review revealed mean and/or maximum thickness values from 442 glaciers and ice caps, elevation band information and point measurements for 10 and 14 glaciers, respectively. Resulting in a dataset containing glaciers and ice caps with areas ranging from smaller than 0.1 km2 (e.g. Pizolgletscher, Switzerland) to larger than 10'000 km2 (e.g. Agassiz Ice Cap, Canada), mean ice thicknesses between 4 m (Blaueis, Germany) and 550 m (Aletschgletscher, Switzerland) and 64 values for ice masses with entries from different years. Thickness values are derived from various observation methods and cover a survey period between 1923 and 2011. A major advantage of the database is the included metadata, giving information about specific fields, such as the mean thickness value of Aletschgletscher, which is only valid for the investigation area Konkordiaplatz and not over the entire glacier. The relatively small collection of records in the two more detailed database levels reflects the poor availability of such data. For modelling purposes, where ice thicknesses are implemented to derive ice volumes, this database provides essential information about glacier and ice cap characteristics and enables the comparison between various approaches. However, the dataset offers a great variety of locations, thicknesses and surface areas of glaciers and ice caps and can therefore help to compare
Elastic fields due to centers of dilatation and thermal inhomogeneities in plane-layered solids
NASA Astrophysics Data System (ADS)
Yu, H. Y.; Sanday, S. C.
1993-02-01
A N IMAGE METHOD for obtaining the solution for a center of dilatation in a three-layer elastic solid with planar interfaces is presented. The three-layered elastic solid consists of an elastic slab sandwiched between two semi-infinite elastic solids. The three elastic solids are perfectly bonded together at the two planar interfaces. The solution is given in terms of Galerkin vectors which are in terms of an infinite series of the Newtonian potential function of a mass point at the center of dilatation, its mirror images and their derivatives. As an application, the solution for the center of dilatation is used to obtain the elastic solution due to thermal inhomogeneities. The thermoelastic solution is obtained by a method which is based on the integration of properly weighted centers of dilatation over the volume occupied by the inhomogeneity. The potential functions for the problem solved are the harmonic potential functions of attracting matter filling the volume of the thermal inhomogeneity and its mirror images. The solution for the thermal elastic stresses due to an expanding (or contracting) thermal inhomogeneity (inclusion) of any shape embedded in one of the solids is given as an example. Numerical results for a spherical inclusion with pure dilatation eigenstrain are also presented and discussed.
NASA Astrophysics Data System (ADS)
Liu, B.; Arsenlis, A.; Aubry, S.
2016-06-01
Driven by the growing interest in numerical simulations of dislocation–interface interactions in general crystalline materials with elastic anisotropy, we develop algorithms for the integration of interface tractions needed to couple dislocation dynamics with a finite element or boundary element solver. The dislocation stress fields in elastically anisotropic media are made analytically accessible through the spherical harmonics expansion of the derivative of Green’s function, and analytical expressions for the forces on interface elements are derived by analytically integrating the spherical harmonics series recursively. Compared with numerical integration by Gaussian quadrature, the newly developed analytical algorithm for interface traction integration is highly beneficial in terms of both computation precision and speed.
Formulas for the elastic constants of plates with integral waffle-like stiffening
NASA Technical Reports Server (NTRS)
Dow, Norris R; Libove, Charles; Hubka, Ralph E
1954-01-01
Formulas are derived for the fifteen elastic constants associated with bending, stretching, twisting, and shearing of plates with closely spaced integral ribbing in a variety of configurations and proportions. In the derivation the plates are considered, conceptually, as more uniform orthotropic plates somewhat on the order of plywood. The constants, which include the effectiveness of the ribs for resisting deformations other than bending and stretching in their longitudinal directions, are defined in terms of four coefficients, and theoretical and experimental methods for the evaluation of these coefficients are discussed. Four of the more important elastic constants are predicted by these formulas and are compared with test results. Good correlation is obtained. (author)
Eddy current thickness measurement apparatus
Rosen, Gary J.; Sinclair, Frank; Soskov, Alexander; Buff, James S.
2015-06-16
A sheet of a material is disposed in a melt of the material. The sheet is formed using a cooling plate in one instance. An exciting coil and sensing coil are positioned downstream of the cooling plate. The exciting coil and sensing coil use eddy currents to determine a thickness of the solid sheet on top of the melt.
Equilibrium theory for braided elastic filaments
NASA Astrophysics Data System (ADS)
van der Heijden, Gert
Motivated by supercoiling of DNA and other filamentous structures, we formulate a theory for equilibria of 2-braids, i.e., structures formed by two elastic rods winding around each other in continuous contact and subject to a local interstrand interaction. Unlike in previous work no assumption is made on the shape of the contact curve. Rather, this shape is found as part of the solution. The theory is developed in terms of a moving frame of directors attached to one of the strands with one of the directors pointing to the position of the other strand. The constant-distance constraint is automatically satisfied by the introduction of what we call braid strains. The price we pay is that the potential energy involves arclength derivatives of these strains, thus giving rise to a second-order variational problem. The Euler-Lagrange equations for this problem give balance equations for the overall braid force and moment referred to the moving frame as well as differential equations that can be interpreted as effective constitutive relations encoding the effect that the second strand has on the first as the braid deforms under the action of end loads. Simple analytical cases are discussed first and used as starting solutions in parameter continuation studies to compute classes of both open and closed (linked or knotted) braid solutions.
NASA Astrophysics Data System (ADS)
Gelis, C.; Virieux, J.; Grandjean, G.; Operto, S.
2005-12-01
The superficial weathered zone, few hundreds meters thick, presents highly variable and complex near-surface structures. Energetic seismic surface waves, often called ground roll, may hide information coming from deeper areas. Moreover near-surface anomalies (cavities, overthrusts) are quite important and, therefore, detecting heterogeneities in near-surface areas and quantifying their physical properties is still a challenge for seismic imaging. Since heterogeneities are located in near-surface areas, both surface and body waves induce complex footprints in seismic data. The propagation of 2D P-SV is performed in a frequency domain modeling. This frequency formulation takes into account attenuating behavior and efficiently takes benefit of multisource and multireceiver configurations. A new finite-difference stencil of second order using rotated derivatives axes (Saenger et al., 2000) simulates surface waves precisely and remains stable nearby the free surface and/or rapidly-varying zones. It will be the forward problem kernel of our approach. We follow the matrix formalism of Pratt et al. (1998) and perform a linearized inversion in the least-square sense, since heterogeneities of reasonable amplitudes towards the surrounding medium are considered. We use the gradient method to perform the full waveform inversion for elastic waves. In this formulation we take only the Hessian diagonal part and use a parabolic approximation to find the stepping in the gradient direction. To compute Fréchet derivatives, we resort to the Born and the Rytov approximations and evaluate their performances in transmission and reflection acquisitions geometries. We test as well the influence of the inverted parameters choice. Moreover we highlight the influence of data preconditioning that must be particularly efficient to deal with both body and surface waves. We apply this elastic full waveform inversion to near-surface data, containing strong surface waves and acquired just above a
The elastic constants of the human lens.
Fisher, R F
1971-01-01
1. When the lens is spun around its antero-posterior polar axis in an apparatus designed for the purpose, high speed photography can be used to record its changing profile. By this method a variable radial centrifugal force can be applied to the lens which mimics the pull of the zonule.2. If the lens is not stressed at its centre beyond 100 Nm(-2) it behaves as a truly elastic body. When stressed beyond this limit visco-elastic strain is produced at its poles.3. The human lens has isotropic elastic properties at the extremes of life, but at the other times Young's Modulus of Elasticity varies with the direction in which it is measured.4. Young's Modulus of Elasticity of the lens varies with age, polar elasticity and equatorial elasticity, at birth being 0.75 x 10(3) and 0.85 x 10(3) Nm(-2) respectively, while at 63 years of age both are equal to 3 x 10(3) Nm(-2).5. A comparison of Young's Modulus of the young human lens with that of the rabbit and cat shows that the polar elasticity of the lenses of these animals was 5 times greater in the young rabbit, and 21 times greater in the adult cat. Equatorial elasticities of the rabbit and human lens were equal, while in the cat the equatorial elasticity was four times greater.6. A mathematical model showing the lens substance possessing a nucleus of lower isotropic elasticity than that of the isotropic elastic cortex surrounding it, accounts for the difference between polar and equatorial elasticity of the intact adult lens.7. The implications of these findings are discussed in relation to:(i) accommodation and the rheological properties of the lens;(ii) possible differences in the physical state of the lenticular proteins in the cortex and nucleus which may account for the senile variations in Young's Modulus of Elasticity in these regions of the lens;(iii) the loss of accommodation due solely to an increase in Young's Modulus of Elasticity of the lens between the ages of 15 and 60. This would amount to 44% of the total
The elastic constants of the human lens
Fisher, R. F.
1971-01-01
1. When the lens is spun around its antero-posterior polar axis in an apparatus designed for the purpose, high speed photography can be used to record its changing profile. By this method a variable radial centrifugal force can be applied to the lens which mimics the pull of the zonule. 2. If the lens is not stressed at its centre beyond 100 Nm-2 it behaves as a truly elastic body. When stressed beyond this limit visco-elastic strain is produced at its poles. 3. The human lens has isotropic elastic properties at the extremes of life, but at the other times Young's Modulus of Elasticity varies with the direction in which it is measured. 4. Young's Modulus of Elasticity of the lens varies with age, polar elasticity and equatorial elasticity, at birth being 0·75 × 103 and 0·85 × 103 Nm-2 respectively, while at 63 years of age both are equal to 3 × 103 Nm-2. 5. A comparison of Young's Modulus of the young human lens with that of the rabbit and cat shows that the polar elasticity of the lenses of these animals was 5 times greater in the young rabbit, and 21 times greater in the adult cat. Equatorial elasticities of the rabbit and human lens were equal, while in the cat the equatorial elasticity was four times greater. 6. A mathematical model showing the lens substance possessing a nucleus of lower isotropic elasticity than that of the isotropic elastic cortex surrounding it, accounts for the difference between polar and equatorial elasticity of the intact adult lens. 7. The implications of these findings are discussed in relation to: (i) accommodation and the rheological properties of the lens; (ii) possible differences in the physical state of the lenticular proteins in the cortex and nucleus which may account for the senile variations in Young's Modulus of Elasticity in these regions of the lens; (iii) the loss of accommodation due solely to an increase in Young's Modulus of Elasticity of the lens between the ages of 15 and 60. This would amount to 44% of the
Coupled channel effect in elastic scattering and fusion for 6,7Li+28Si
NASA Astrophysics Data System (ADS)
Sinha, Mandira; Roy, Subinit; Basu, P.; Majumdar, H.; Santra, S.; Parkar, V. V.; Golda, K. S.; Kailas, S.
2011-10-01
The fusion excitation and elastic angular distribution were measured for 6,7Li+28Si from below to above Coulomb barrier (≤ 3Vb) energies. The barrier distribution derived from the fusion data was found to be broad and asymmetric at the sub-barrier region, compared to 1D BPM estimation. Effect of rotational coupling on fusion was found to be not so dominant. Phenomenological optical potential parameters, with surface and volume type imaginary potentials, were obtained from f tting of elastic scattering data and energy dependence of real and imaginary surface strengths were investigated around the barrier. CDCC calculations considering only breakup of projectile were performed for 6,7Li+28Si with the elastic scattering data, using the code FRESCO. The effects of breakup of projectile on elastic cross section do not agree with the energy dependence of real and imaginary strength with volume type imaginary potential around the barrier.
Quantum diffraction grating: A possible new description of nuclear elastic scattering
NASA Astrophysics Data System (ADS)
Wojciechowski, H.
2016-02-01
The problem of discontinuous functions and their representations in the form of Legendre polynomial series in quantum nuclear scattering theory is presented briefly. The problem is quite old yet not adequately explained in numerous Quantum Theory textbooks and sometimes not correctly understood by physicists. Introduction of the generalized functions into the quantum scattering theory clarifies the problem and allows to propose new interpretations of nuclear elastic scattering phenomenon. The derived new forms of the full elastic scattering amplitudes and possibility of splitting them suggest existence of dynamical quantum diffraction grating around the nuclei. Particularly important fact is that this grating existing in the space around the nucleus makes considerable contribution to the experimental elastic differential cross-section. All these might be quite important in analyses of nuclear elastic scattering data and so require to be stated in a more detailed and clear way.