Energy Technology Data Exchange (ETDEWEB)
Suzuki, H.; Yoshida, K. [The University of Tokyo, Tokyo (Japan)
1996-12-31
A policy of improving a very large floating body was planned based on its dynamic characteristics, and a proposal was made thereon. Furthermore, discussions were given on stability that considers effect of elastic deformation required when a structure is mounted on a floating body. With respect to a structural design of a very large floating body in which elastic response is governing, and upon modeling the very large floating body into an aeolotropic plate on an elastic supporting floor, it was shown that the existing range of natural vibration speed in the elastic response is in higher range than the natural vibration speed of heave. It was also indicated that the peak height of response to waves in resonance is inversely proportional to wave frequency, and furthermore, degree of flowing in of vibration energy during the resonance is determined by an inner product of spatial vibration patterns of wave force and the excited mode shape. A proposal was made on a floating body improved of excessive response in the floating body edges by changing the characteristics of the floating body edges. In addition, discussions were given on stability that considers elastic deformation of a floating body that becomes necessary when a structure, such as a building, is built on a very large floating body. 9 refs., 9 figs., 3 tabs.
Energy Technology Data Exchange (ETDEWEB)
Ota, M.; Ikegami, H.; Yamaguchi, Y. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)
1997-10-01
The elastic response of VLFS of 1200m long in wave was studied experimentally using a water tank and integral elastic model of 1/80 scale. As offshore airport, a ultra- thin box type floating structure of 5km long, 1km wide and several meter thick is used, and the effect of elasticity is not negligible for such a structure. The experiment used a water tank of 160m long, 30m wide and 3.1m deep. Supposing a water depth of 20m for real VLFSs, the experiment was carried out mainly in a local shallow water area prepared with a temporary bottom together with that in a deep water area. A simple mooring equipment with a linear spring equivalent to real VLFSs was used. The integral floating model was prepared by not mechanical but welded junction to obtain uniform elasticity. The response in wave showed a complicated 3-D behavior, offering useful data for verification of a behavior estimation method. The response was nearly equal between shallow and deep water areas at the same wave length, and the response amplitude in regular waves was equivalent to the significant amplitude in long and short crested irregular waves. 7 refs., 8 figs., 3 tabs.
Energy Technology Data Exchange (ETDEWEB)
Yasuzawa, Y.; Kagawa, K.; Kitabayashi, K. [Kyushu University, Fukuoka (Japan); Kawano, D. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)
1997-08-01
The theory and formulation for the numerical response analysis of a large floating structure in regular waves were given. This paper also reports the comparison between the experiment in the Shipping Research Institute in the Minitry of Transport and the result calculated using numerical analytic codes in this study. The effect of the bending rigidity of a floating structure and the wave direction on the dynamic response of a structure was examined by numerical calculation. When the ratio of structure length and incident wavelength (L/{lambda}) is lower, the response amplitude on the transmission side becomes higher in a wave-based response. The hydrodynamic elasticity exerts a dominant influence when L/{lambda} becomes higher. For incident oblique waves, the maximum response does not necessarily appear on the incidence side. Moreover, the response distribution is also complicated. For example, the portion where any flexible amplitude hardly appears exists. A long structure response can be predicted from a short structure response to some degree. They differ in response properties when the ridigity based on the similarity rule largely differs, irrespective of the same L/{lambda}. For higher L/{lambda}, the wave response can be easily predicted when the diffrection force is replaced by the concentrated exciting force on the incidence side. 13 refs., 14 figs., 3 tabs.
Energy Technology Data Exchange (ETDEWEB)
Fujikubo, M.; Yao, T.; Oida, H. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering
1996-12-31
Formulation was made on a one-dimensional beam finite element which is effective in analyzing structural response of very large floating structures by modeling them on beams on an elastic foundation. This element allows strict solution of vibration response in the beams on the elastic foundation to be calculated efficiently for a case where mass and rigidity change in the longitudinal direction. This analysis method was used to analyze structural response of a large pontoon-type floating structure to investigate mass in the end part for the structural response and the effect of decay while passing the structure. With a pontoon-type floating structure, reduction in bends and bending stress in the end part of the floating structure is important in designing the structure. Reducing the mass in the end part is effective as a means to avoid resonance in these responses and reduce the responses. Increase in rigidity of a floating structure shifts the peak in quasi-static response to lower frequency side, and reduces response in resonance, hence it is advantageous for improving the response. Since incident waves decay while passing through the floating structure, response in the lower wave side decreases. The peak frequency in the quasi-static response also decreases at the end part of the structure in the upper wave side due to decay in wave force. 7 refs., 11 figs., 1 tab.
Energy Technology Data Exchange (ETDEWEB)
Ma, N.; Hirayama, T.; Sato, N. [Yokohama National University, Yokohama (Japan). Faculty of Engineering
1996-12-31
A semisubmersible very large floating structure is compared with an equivalent pontoon type in vertical displacement and longitudinal bending moment in waves. The theoretical calculation is based on the mode synthesis method, and fluid force is analyzed by the three-dimensional singularity method for the symmetric structure, in which the effects of elastic deformation are taken into account. The semisubmersible and pontoon types are not much different from each other in eigenfrequency and mode shape in the dry mode. In the wet mode, on the other hand, the pontoon type is characterized by the synthetic mode in which torsional and bending modes overlap each other, each mode having a similar eigenfrequency. These types are different in elastic response, the pontoon type having several tens times higher coefficient of attenuation than the semisubmersible type. The pontoon type is generally lower in response, but its torsional mode is excited in transverse waves, making it higher than the semisubmersible type at near eigenfrequency of this mode. 15 refs., 17 figs., 2 tabs.
Investor response to consumer elasticity
International Nuclear Information System (INIS)
Grenaa Jensen, Stine; Meibom, Peter; Ravn, H.F.; Straarup, Sarah
2004-01-01
In the Nordic electricity system there is considerable uncertainty with respect to the long-term development in production capacity. The process towards liberalisation of the electricity sector started in a situation with a large reserve margin, but this margin is gradually vanishing. Since the potential investors in new production capacity are unaccustomed with investments under the new regime it is unknown if and when investments will take place. The electricity price is the key market signal to potential investors. The price is settled as a balance between supply and demand, and it is generally assumed that the demand side has an important role in this, and increasingly so. However, since consumers have not earlier had the incentive to respond to electricity prices, no reliable estimate of demand elasticity is known. The purpose of the present study is to analyse the role of electricity demand elasticity for investments in new electricity production capacity. Electricity price scenarios generated with a partial equilibrium model (Balmorel) are combined with a model of investment decisions. In this, various scenarios concerning the development in the demand elasticity are used. The simulated investment decisions are taken in a stochastic, dynamic setting, where a key point is the timing of the investment decision in relation to the gathering of new information relative to the stochastic elements. Based on this, the consequences of the development in consumer price elasticity for investments in a base load and a peak load plant are investigated. The main result of the analysis is that peak load investments can be made unprofitable by the development in consumer price elasticity, such that an investor will tend to wait with his peak load investment, until the development in consumer price elasticity has been revealed. (au)
Elastic response of graphene nanodomes.
Koch, Sascha; Stradi, Daniele; Gnecco, Enrico; Barja, Sara; Kawai, Shigeki; Díaz, Cristina; Alcamí, Manuel; Martín, Fernando; Vázquez de Parga, Amadeo Lopez; Miranda, Rodolfo; Glatzel, Thilo; Meyer, Ernst
2013-04-23
The mechanical behavior of a periodically buckled graphene membrane has been investigated by noncontact atomic force microscopy in ultrahigh vacuum. When a graphene monolayer is grown on Ru(0001), a regular arrangement of 0.075 nm high nanodomes forming a honeycomb lattice with 3 nm periodicity forms spontaneously. This structure responds in a perfectly reversible way to relative normal displacements up to 0.12 nm. Indeed, the elasticity of the nanodomes is proven by realistic DFT calculations, with an estimated normal stiffness k∼40 N/m. Our observations extend previous results on macroscopic graphene samples and confirm that the elastic behavior of this material is maintained down to nanometer length scales, which is important for the development of new high-frequency (terahertz) electromechanical devices.
Energy Technology Data Exchange (ETDEWEB)
Maeda, H.; Miyajima, S. [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science; Masuda, K.; Ikoma, T. [Nihon University, Tokyo (Japan). College of Science and Technology
1996-12-31
Steady-state drift force in regular waves is theoretically analyzed. It is also studied under combined external force experimentally using a two-dimensional water tank. The fluid forces are analyzed by the pressure distribution method based on the potential theory, in which the effects of water depth are taken into account to discuss the effects of elastic deformation of the floating structure on the drift characteristics of steady-state waves. The tests were carried out using a wave-making circulating water tank equipped with a wind duct to create wind, waves and tidal flow. Drift force under a combined external force by wind, wave and/or tidal flow cannot be accurately predicted by arithmetically adding these components. For predicting drift force by tidal flow, it is necessary to take into account drag force in current at the floating structure bottom as well as that in wind at the front face. Drift force by tidal flow is affected by shallowness of water, which should be taken into account for drag forces. The floating structure will be deformed along the wave face as its stiffness decreases, basically decreasing steady-state drift force. 9 refs., 14 figs.
Extremal Overall Elastic Response of Polycrystalline Materials
DEFF Research Database (Denmark)
Bendsøe, Martin P; Lipton, Robert
1996-01-01
Polycrystalline materials comprised of grains obtained froma single anisotropic material are considered in the frameworkof linear elasticity. No assumptions on the symmetry of thepolycrystal are made. We subject the material to independentexternal strain and stress fields with prescribed mean val...
Extremal Overall Elastic Response of Polycrystalline Materials
DEFF Research Database (Denmark)
Bendsøe, Martin P; Lipton, Robert
1997-01-01
Polycrystalline materials comprised of grains obtained from a single anisotropic material are considered in the framework of linear elasticity. No assumptions on the symmetry of the polycrystal are made. We subject the material to independent external strain and stress fields with prescribed mean...
Instantaneous stiffness and hysteresis of dynamic elastic response prosthetic feet.
Webber, Christina M; Kaufman, Kenton
2017-10-01
Dynamic elastic response prosthetic feet are designed to mimic the functional characteristics of the native foot/ankle joint. Numerous designs of dynamic elastic response feet exist which make the prescription process difficult, especially because of the lack of empirical evidence describing the objective performance characteristics of the feet. To quantify the mechanical properties of available dynamic elastic response prosthetic feet, specifically the stiffness and hysteresis. Mechanical testing of dynamic elastic response prosthetic feet. Static Proof Testing in accordance with ISO 10328 was conducted on seven dynamic elastic response prosthetic feet. Load-displacement data were used to calculate the instantaneous stiffness in both the heel and forefoot regions, as well as hysteresis associated with each foot. Heel stiffness was greater than forefoot stiffness for all feet. The heel of the glass composite prosthetic foot was stiffer than the carbon fiber feet and it exhibited less hysteresis. Two different carbon fiber feet had the stiffest forefoot regions. Mechanical testing is a reproducible method that can be used to provide objective evidence about dynamic elastic response prosthetic foot performance and aid in the prescription process. Clinical relevance The quantitative stiffness and hysteresis data from this study can be used by prosthetists to aid the prescription process and make it more objective.
Elastic limit and microplastic response of hardened steels
Energy Technology Data Exchange (ETDEWEB)
Zaccone, M.A. (McDonnell Douglas Aerospace Co., St. Louis, MO (United States)); Krauss, G. (Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering)
1993-10-01
Tempered martensite-retained austenite microstructures were produced by direct quenching a series of 41XX medium carbon steels, direct quenching and reheating a series of five 0.8C-Cr-Ni-Mo steels and intercritically austenitizing at various temperatures, and quenching a SAE 52100 steel. All specimens were tempered either at 150 C or at 200 C. Specimens were subjected to compression and tension testing in the microstrain regime to determine the elastic limits and microplastic response of the microstructures. The retained austenite and matrix carbon content of the intercritically austenized specimens were measured by X-ray diffraction and Mossbauer spectroscopy. The elastic limit of the microstructures decreases with increasing amounts of retained austenite. Refining of the austenite distribution increases the elastic limit. Low elastic limits are mainly due to low flow stresses in the austenite and not internal stresses. The elastic limit correlates with the largest austenite free-mean path by a Hall-Petch type equation. The elastic limit increases with decreasing intercritical austenitizing temperature in the SAE 52100 due to a lower carbon content in the matrix reducing the retained austenite levels and retained carbides that refine grain size and, therefore, the austenite distribution in quenched specimens. In the microplastic region, the strain is accommodated by successively smaller austenite regions until the flow strength matches that of the martensite. Reheating and quenching refines the microstructure and renders the austenite unstable in the microplastic regime, causing transformation of the austenite to martensite by a strain-induced mechanism. The transformation of austenite to martensite occurs by a stress-assisted mechanism in medium carbon steels. The low elastic limits in medium carbon steels were due to the inability of the strain from the stress-assisted transformation to balance the plastic strain accumulated in the austenite.
Quenching of the elastic magnetic response function of 49Ti
International Nuclear Information System (INIS)
Selig, A.M.; Suzuki, T.; Lapikas, L.; Witt Huberts, P.K.A. de; Platchkov, S.K.; Frois, B.; Mooy, R.B.M.; Zybert, L.; Glaudemans, P.W.M.
1985-01-01
Cross sections for elastic magnetic electron scattering from 49 Ti have been obtained in the momentum transfer range 0.75 -1 . Apart from the M1 and M7 moments the observed quenching of the response function cannot be described by the present large space shell-model calculations. Core-polarization calculations including the effect of meson-exchange currents yield a considerably better description of the present data. (orig.)
International Nuclear Information System (INIS)
Elsner, B.A.M.; Müller, S.; Bargmann, S.; Weissmüller, J.
2017-01-01
Predicting the influence of the surface on the effective elastic properties of nanoscale structures and nanomaterials remains a challenge, which we here address on both levels, continuum and atomic. Density Functional Theory (DFT) computation at the atomic level yields the first reliable surface excess elastic parameters for the (111) and (001) surfaces of gold. At the continuum level, we derive closed-form expressions for the effective elastic behavior that can be combined with the DFT-derived excess elastic parameters to obtain the effective axial, torsion, and bending stiffness of circular nanowires with surface excess elasticity. The two approaches use different reference frames, and we emphasize the need for consistent stress definitions and for conversion between the separate stress measures when transferring results between the approaches. We present excess elastic parameters separately for Cauchy and 2 nd Piola-Kirchhoff stresses, demonstrating that the conversion substantially modifies their numerical value and may even invert their sign. The results afford an assessment of the contribution of the surface excess elastic parameters to the effective elastic response of nanoscale beams or wires. This assessment sheds doubt on earlier suggestions relating experimental observations of an effective stiffening or softening at small size to the excess elasticity of clean surfaces.
Elastic Properties and Enhanced Piezoelectric Response at Morphotropic Phase Boundaries
Cordero, Francesco
2015-01-01
The search for improved piezoelectric materials is based on the morphotropic phase boundaries (MPB) between ferroelectric phases with different crystal symmetry and available directions for the spontaneous polarization. Such regions of the composition x−T phase diagrams provide the conditions for minimal anisotropy with respect to the direction of the polarization, so that the polarization can easily rotate maintaining a substantial magnitude, while the near verticality of the TMPBx boundary extends the temperature range of the resulting enhanced piezoelectricity. Another consequence of the quasi-isotropy of the free energy is a reduction of the domain walls energies, with consequent formation of domain structures down to nanoscale. Disentangling the extrinsic and intrinsic contributions to the piezoelectricity in such conditions requires a high level of sophistication from the techniques and analyses for studying the structural, ferroelectric and dielectric properties. The elastic characterization is extremely useful in clarifying the phenomenology and mechanisms related to ferroelectric MPBs. The relationship between dielectric, elastic and piezoelectric responses is introduced in terms of relaxation of defects with electric dipole and elastic quadrupole, and extended to the response near phase transitions in the framework of the Landau theory. An account is provided of the anelastic experiments, from torsional pendulum to Brillouin scattering, that provided new important information on ferroelectric MPBs, including PZT, PMN-PT, NBT-BT, BCTZ, and KNN-based systems. PMID:28793707
Elastic Properties and Enhanced Piezoelectric Response at Morphotropic Phase Boundaries
Directory of Open Access Journals (Sweden)
Francesco Cordero
2015-12-01
Full Text Available The search for improved piezoelectric materials is based on the morphotropic phase boundaries (MPB between ferroelectric phases with different crystal symmetry and available directions for the spontaneous polarization. Such regions of the composition x − T phase diagrams provide the conditions for minimal anisotropy with respect to the direction of the polarization, so that the polarization can easily rotate maintaining a substantial magnitude, while the near verticality of the TMPB(x boundary extends the temperature range of the resulting enhanced piezoelectricity. Another consequence of the quasi-isotropy of the free energy is a reduction of the domain walls energies, with consequent formation of domain structures down to nanoscale. Disentangling the extrinsic and intrinsic contributions to the piezoelectricity in such conditions requires a high level of sophistication from the techniques and analyses for studying the structural, ferroelectric and dielectric properties. The elastic characterization is extremely useful in clarifying the phenomenology and mechanisms related to ferroelectric MPBs. The relationship between dielectric, elastic and piezoelectric responses is introduced in terms of relaxation of defects with electric dipole and elastic quadrupole, and extended to the response near phase transitions in the framework of the Landau theory. An account is provided of the anelastic experiments, from torsional pendulum to Brillouin scattering, that provided new important information on ferroelectric MPBs, including PZT, PMN-PT, NBT-BT, BCTZ, and KNN-based systems.
On elastic response of disordered triangular lattice during dynamic loading
Directory of Open Access Journals (Sweden)
Mastilović Sreten
2008-01-01
Full Text Available The present investigation focuses on an observation regarding the initial elastic response of a triangular geometrically and structurally disordered lattice during medium-to-high strain rate loading. Namely: a transition from the short-time modulus of elasticity to the long-time one, which is not accompanied by the corresponding change of the stiffness tensor. It is demonstrated that the difference between the two moduli is, in the case of the homogeneous biaxial test simulations performed herein, a consequence of the geometrical and structural disorder "quenched" within the lattice. The investigation is performed on the triangular lattice with the first-neighbor central interactions under practically identical in-plane conditions over eight decades of strain rate.
Influence of Vertical Loadings on Elastic System Response
Slavchev, Y.
2010-10-01
A model of a simply supported Euler-Bernoulli beam with suspended oscillators in series, which is a common technique for analyzing the dynamic response of bridge and gantry cranes, reloader bridges, etc., is employed here to study the influence of vertical loadings on the elastic system. The dynamic response of the model includes the beam partial differential equation that is solved through an effective numerical-analytic approach, based on the method of separation of variables and modal analysis. It is shown that the model is suitable for investigating the dynamic response for various vertical loadings which in the case of bridge cranes are due to the operation cycles of different hoisting and load handling mechanisms. Separate computer simulations of a real-world crane structure are carried out by the proposed numerical-analytic approach and by the finite element method. Results from both solutions are compared.
Electrical resistivity response due to elastic-plastic deformations
International Nuclear Information System (INIS)
Stout, R.B.
1987-01-01
The electrical resistivity of many materials is sensitive to changes in the electronic band configurations surrounding the atoms, changes in the electron-phonon interaction cross-sections, and changes in the density of intrinsic defect structures. These changes are most directly dependent on interatomic measures of relative deformation. For this reason, a model for resistivity response is developed in terms of interatomic measures of relative deformation. The relative deformation consists of two terms, a continuous function to describe the recoverable displacement between two atoms in the atomic lattice structure and a functional to describe the nonrecoverable displacement between two atoms as a result of interatomic discontinuities from dislocation kinetics. This model for resistivity extends the classical piezoresistance representation and relates electric resistance change directly to physical mechanisms. An analysis for the resistivity change of a thin foil ideally embedded in a material that undergoes elastic-plastic deformation is presented. For the case of elastic deformations, stress information in the material surrounding the thin foil is inferred for the cases of pure strain coupling boundary conditions, pure stress coupling boundary conditions, and a combination of stress-strain coupling boundary conditions. 42 refs., 4 figs
Weakly interacting massive particle-nucleus elastic scattering response
Anand, Nikhil; Fitzpatrick, A. Liam; Haxton, W. C.
2014-06-01
Background: A model-independent formulation of weakly interacting massive particle (WIMP)-nucleon scattering was recently developed in Galilean-invariant effective field theory. Purpose: Here we complete the embedding of this effective interaction in the nucleus, constructing the most general elastic nuclear cross section as a factorized product of WIMP and nuclear response functions. This form explicitly defines what can and cannot be learned about the low-energy constants of the effective theory—and consequently about candidate ultraviolet theories of dark matter—from elastic scattering experiments. Results: We identify those interactions that cannot be reliably treated in a spin-independent/spin-dependent (SI/SD) formulation: For derivative- or velocity-dependent couplings, the SI/SD formulation generally mischaracterizes the relevant nuclear operator and its multipolarity (e.g., scalar or vector) and greatly underestimates experimental sensitivities. This can lead to apparent conflicts between experiments when, in fact, none may exist. The new nuclear responses appearing in the factorized cross section are related to familiar electroweak nuclear operators such as angular momentum l⃗(i) and the spin-orbit coupling σ⃗(i).l⃗(i). Conclusions: To unambiguously interpret experiments and to extract all of the available information on the particle physics of dark matter, experimentalists will need to (1) do a sufficient number of experiments with nuclear targets having the requisite sensitivities to the various operators and (2) analyze the results in a formalism that does not arbitrarily limit the candidate operators. In an appendix we describe a code that is available to help interested readers implement such an analysis.
Characteristics of Jerk Response Spectra for Elastic and Inelastic Systems
Directory of Open Access Journals (Sweden)
Haoxiang He
2015-01-01
Full Text Available Jerk is the time rate of acceleration and mainly represents the nonstationary component in high frequency band of the earthquake wave. The study on jerk and its response spectra can enhance the recognition of the nonstationary ground motion. The mechanical meaning and research value of jerk are described. Jerk is recommended to be solved by establishing state-space equations and Runge-Kutta method. The solution method of elastic and inelastic jerk response spectra under ground motion is established, and the accurate jerk spectrum should be calculated directly according to numerical computing instead of pseudo-acceleration spectrum. The characteristics of jerk response spectra are studied according to the influencing factors, such as site condition, amplification factor, ductility factor, and reduction factor. The concept of impact reduction factor is presented. The statistical results show that the jerk spectrum has similar rules as the acceleration spectrum, and the amplitude is relative to the predominant period, especially for structures with short or medium period. If the ductility is improved, the effective jerk will reduce obviously, and the impact reduction factor will be enhanced. Different from the strength reduction factor, the impact reduction factor is nearly not relevant to the period.
Response of orthotropic micropolar elastic medium due to time ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
Yet, the eigen-value approach has not been applied in micropolar orthotropic medium. Mahalanabis & Manna (1989) applied eigen-value approach to linear micropolar elasticity by arranging basic equations of linear micropolar elasticity in the form of matrix differential equation. Mahalanabis & Manna (1997) discussed the ...
Invester Response to Consumer Elasticity, Nordic Energy Research
DEFF Research Database (Denmark)
Jensen, Stine Grenaa; Meibom, Peter; Ravn, Hans V.
2004-01-01
, and it is generally assumed that the demand side has an important role in this, and increasingly so. However, since consumers have not earlier had the incentive to respond to electricity prices, no reliable estimate of demand elasticity is known. The purpose of the present study is to analyse the role of electricity...... demand elasticity for investments in new electricity production capacity. Electricity price scenarios generated with a partial equilibrium model (Balmorel) are combined with a model of investment decisions. In this, various scenarios concerning the development in the demand elasticity are used...... the potential investors in new production capacity are unaccustomed with investments under the new regime, it is unknown if and when investments will take place. The electricity price is the key market signal to potential investors. The price is settled as a balance between supply and demand...
Response of multiphase magneto-electro-elastic sensors under ...
African Journals Online (AJOL)
The finite element formulation for coupled magneto-electro-elastic sensor bonded to a mild steel beam with plane stress assumption is presented in this paper. The beam is subjected to harmonic excitation with a point load at tip and a uniformly distributed load along the bottom surface of the mild steel beam. Numerical ...
Response of orthotropic micropolar elastic medium due to time ...
Indian Academy of Sciences (India)
The present paper is concerned with the plane strain problem in homogeneous micropolar orthotropic elastic solids. The disturbance due to time harmonic concentrated source is investigated by employing eigen-value approach. The integral transforms have been inverted by using a numerical technique to obtain the ...
Dynamic Response Analysis of Microflow Electrochemical Sensors with Two Types of Elastic Membrane
Directory of Open Access Journals (Sweden)
Qiuzhan Zhou
2016-05-01
Full Text Available The Molecular Electric Transducer (MET, widely applied for vibration measurement, has excellent sensitivity and dynamic response at low frequencies. The elastic membrane in the MET is a significant factor with an obvious effect on the performance of the MET in the low frequency domain and is the focus of this paper. In simulation experiments, the elastic membrane and the reaction cavity of the MET were analysed in a model based on the multiphysics finite element method. Meanwhile, the effects caused by the elastic membrane elements are verified in this paper. With the numerical simulation and practical experiments, a suitable elastic membrane can be designed for different cavity structures. Thus, the MET can exhibit the best dynamic response characteristics to measure the vibration signals. With the new method presented in this paper, it is possible to develop and optimize the characteristics of the MET effectively, and the dynamic characteristics of the MET can be improved in a thorough and systematic manner.
Role of architecture in the elastic response of semiflexible polymer and fiber networks
Heussinger, Claus; Frey, Erwin
2007-01-01
We study the elasticity of cross-linked networks of thermally fluctuating stiff polymers. As compared to their purely mechanical counterparts, it is shown that these thermal networks have a qualitatively different elastic response. By accounting for the entropic origin of the single-polymer elasticity, the networks acquire a strong susceptibility to polydispersity and structural randomness that is completely absent in athermal models. In extensive numerical studies we systematically vary the architecture of the networks and identify a wealth of phenomena that clearly show the strong dependence of the emergent macroscopic moduli on the underlying mesoscopic network structure. In particular, we highlight the importance of the polymer length, which to a large extent controls the elastic response of the network, surprisingly, even in parameter regions where it does not enter the macroscopic moduli explicitly. Understanding these subtle effects is only possible by going beyond the conventional approach that considers the response of typical polymer segments only. Instead, we propose to describe the elasticity in terms of a typical polymer filament and the spatial distribution of cross-links along its backbone. We provide theoretical scaling arguments to relate the observed macroscopic elasticity to the physical mechanisms on the microscopic and mesoscopic scales.
Energy Technology Data Exchange (ETDEWEB)
Johnson, P.A.; McCall, K.R.; Meegan, G.D. Jr. [Los Alamos National Lab., NM (United States)
1993-11-01
Experiments in rock show a large nonlinear elastic wave response, far greater than that of gases, liquids and most other solids. The large response is attributed to structural defects in rock including microcracks and grain boundaries. In the earth, a large nonlinear response may be responsible for significant spectral alteration at amplitudes and distances currently considered to be well within the linear elastic regime.
Comparison of elastic and inelastic seismic response of high temperature piping systems
International Nuclear Information System (INIS)
Thomas, F.M.; McCabe, S.L.; Liu, Y.
1994-01-01
A study of high temperature power piping systems is presented. The response of the piping systems is determined when subjected to seismic disturbances. Two piping systems are presented, a main steam line, and a cold reheat line. Each of the piping systems are modeled using the ANSYS computer program and two analyses are performed on each piping system. First, each piping system is subjected to a seismic disturbance and the pipe material is assumed to remain linear and elastic. Next the analysis is repeated for each piping system when the pipe material is modeled as having elastic-plastic behavior. The results of the linear elastic analysis and elastic-plastic analysis are compared for each of the two pipe models. The pipe stresses, strains, and displacements, are compared. These comparisons are made so that the effect of the material yielding can be determined and to access what error is made when a linear analysis is performed on a system that yields
Forced Response of Polar Orthotropic Tapered Circular Plates Resting on Elastic Foundation
Directory of Open Access Journals (Sweden)
A. H. Ansari
2016-01-01
Full Text Available Forced axisymmetric response of polar orthotropic circular plates of linearly varying thickness resting on Winkler type of elastic foundation has been studied on the basis of classical plate theory. An approximate solution of problem has been obtained by Rayleigh Ritz method, which employs functions based upon the static deflection of polar orthotropic circular plates. The effect of transverse loadings has been studied for orthotropic circular plate resting on elastic foundation. The transverse deflections and bending moments are presented for various values of taper parameter, rigidity ratio, foundation parameter, and flexibility parameter under different types of loadings. A comparison of results with those available in literature shows an excellent agreement.
Extracting Earth's Elastic Wave Response from Noise Measurements
Snieder, Roel; Larose, Eric
2013-05-01
Recent research has shown that noise can be turned from a nuisance into a useful seismic source. In seismology and other fields in science and engineering, the estimation of the system response from noise measurements has proven to be a powerful technique. To convey the essence of the method, we first treat the simplest case of a homogeneous medium to show how noise measurements can be used to estimate waves that propagate between sensors. We provide an overview of physics research—dating back more than 100 years—showing that random field fluctuations contain information about the system response. This principle has found extensive use in surface-wave seismology but can also be applied to the estimation of body waves. Because noise provides continuous illumination of the subsurface, the extracted response is ideally suited for time-lapse monitoring. We present examples of time-lapse monitoring as applied to the softening of soil after the 2011 Tohoku-oki earthquake, the detection of a precursor to a landslide, and temporal changes in the lunar soil.
Geometrically Nonlinear Transient Response of Laminated Plates with Nonlinear Elastic Restraints
Directory of Open Access Journals (Sweden)
Shaochong Yang
2017-01-01
Full Text Available To investigate the dynamic behavior of laminated plates with nonlinear elastic restraints, a varied constraint force model and a systematic numerical procedure are presented in this work. Several kinds of typical relationships of force-displacement for spring are established to simulate the nonlinear elastic restraints. In addition, considering the restraining moments of flexible pads, the pads are modeled by translational and rotational springs. The displacement- dependent constraint forces are added to the right-hand side of equations of motion and treated as additional applied loads. These loads can be explicitly defined, via an independent set of nonlinear load functions. The time histories of transverse displacements at typical points of the laminated plate are obtained through the transient analysis. Numerical examples show that the present method can effectively treat the geometrically nonlinear transient response of plates with nonlinear elastic restraints.
Desmin modulates lung elastic recoil and airway responsiveness.
Shardonofsky, Felix R; Capetanaki, Yassemi; Boriek, Aladin M
2006-05-01
Desmin is a structural protein that is expressed in smooth muscle cells of both airways and alveolar ducts. Therefore, desmin could be well situated to participate in passive and contractile force transmission in the lung. We hypothesized that desmin modulates lung compliance, lung recoil pressure, and airway contractile response. To test this hypothesis, respiratory system complex impedance (Zin,rs) at different positive end-expiratory pressure (PEEP) levels and quasi-static pressure-volume data were obtained in desmin-null and wild-type mice at baseline and during methacholine administration. Airways and lung tissue properties were partitioned by fitting Zin,rs to a constant-phase model. Relative to controls, desmin-null mice showed 1) lower values for lung stiffness and recoil pressure at baseline and induced airway constriction, 2) greater negative PEEP dependence of H and airway resistance under baseline conditions and cholinergic stimulation, and 3) airway hyporesponsiveness. These results demonstrate that desmin is a load-bearing protein that stiffens the airways and consequently the lung and modulates airway contractile response.
Dynamic response of a linear elastic/linear strain-hardening thin ring
International Nuclear Information System (INIS)
Carey, J.J.
1974-03-01
In studying the dynamic response of fluid filled cylindrical shells to large internal pressure pulses, it would be advantageous to have a rapid method of computing the final deformed shape of the shell. In treating the dynamic response of liquid metal heat transport system to pressures generated by large sodium/water reactions, determinations of the structural response of various components is only a fraction of the information required to describe the entire event. The problem treated in this report is an initial investigation of the value of correlation parameters for removing the effect of pulse shape on predicted plastic deformation. It is an attempt to extend previous studies by inclusion of elastic/plastic response rather than limiting the model to a rigid/plastic description. Since many of the pressure pulses of interest in piping system analysis do not involve pressures that produce large plastic deformation, it is necessary to include the effect of elastic response. A simple bilinear elastic/strain hardening model was thus chosen for this study. The dynamic response of a bilinear thin ring to various spacially uniform pressure pulses is analyzed. Solutions have been obtained for rectangular and for linear and exponentially decaying pulses. Numerical procedures have been employed to obtain maximum inelastic displacement as a function of material and pulse parameters
On the Geometrically Nonlinear Elastic Response of Class θ = 1 Tensegrity Prisms
Directory of Open Access Journals (Sweden)
Ida Mascolo
2018-03-01
Full Text Available The present work studies the geometrically nonlinear response of class θ = 1 tensegrity prisms modeled as a collection of elastic springs reacting in tension (strings or cables or compression (bars, under uniform uniaxial loading. The incremental equilibrium equations of the structure are numerically solved through a path-following procedure, with the aim of modeling the mechanical behavior of the structure in the large displacement regime. Several numerical results are presented with reference to a variety of physical models, which use two different materials for the cables and the bars, and show different aspect ratios associated with either “standard” or “expanded” configurations. An experimental validation of the predicted constitutive response is conducted with reference to a “thick” and a “slender” model, observing rather good theory vs. experiment matching. The given numerical and experimental results highlight that the elastic response of the examined structures may switch from stiffening to softening, depending on the geometry of the system, the magnitude of the external load, and the applied prestress. The outcomes of the current study confirm previous literature results on the elastic response of minimal tensegrity prisms, and pave the way to the use of tensegrity systems as nonlinear spring units forming tunable mechanical metamaterials.
Modeling of demand response in electricity markets : effects of price elasticity
International Nuclear Information System (INIS)
Banda, E.C.; Tuan, L.A.
2007-01-01
A design mechanism for the optimal participation of customer load in electricity markets was presented. In particular, this paper presented a modified market model for the optimal procurement of interruptible loads participating in day-ahead electricity markets. The proposed model considers the effect of price elasticity and demand-response functions. The objective was to determine the role that price elasticity plays in electricity markets. The simulation model can help the Independent System Operator (ISO) identify customers offering the lowest price of interruptible loads and load flow patterns that avoid problems associated with transmission congestion and transmission losses. Various issues associated with procurement of demand-response offerings such as advance notification, locational aspect of load, and power factor of the loads, were considered. It was shown that demand response can mitigate price volatility by allowing the ISO to maintain operating reserves during peak load periods. It was noted that the potential benefits of the demand response program would be reduced when price elasticity of demand is taken into account. This would most likely occur in actual developed open electricity markets, such as Nordpool. This study was based on the CIGRE 32-bus system, which represents the Swedish high voltage power system. It was modified for this study to include a broad range of customer characteristics. 18 refs., 2 tabs., 14 figs
The role of beneficial bacteria wall elasticity in regulating innate immune response
?okrozub, Viktoria V.; Lazarenko, Liudmyla M.; Sichel, Liubov M.; Babenko, Lidia P.; Lytvyn, Petro M.; Demchenko, Olga M.; Melnichenko, Yulia O.; Boyko, Nadiya V.; Biavati, Bruno; DiGioia, Diana; Bubnov, Rostyslav V.; Spivak, Mykola Ya
2015-01-01
Background Probiotics have great potential to contribute to development of healthy dietary regimes, preventive care, and an integrated approach to immunity-related disease management. The bacterial wall is a dynamic entity, depending on many components and playing an essential role in modulating immune response. The impact of cell wall elasticity on the beneficial effects of probiotic strains has not been sufficiently studied. The aim was to investigate the effect of lactic acid bacteria (LAB...
Polymorphism and Elastic Response of Molecular Materials from First Principles: How Hard Can it Be?
Reilly, Anthony; Tkatchenko, Alexandre
2014-03-01
Molecular materials are of great fundamental and applied importance in science and industry, with numerous applications in pharmaceuticals, electronics, sensing, and catalysis. A key challenge for theory has been the prediction of their stability, polymorphism and response to perturbations. While pairwise models of van der Waals (vdW) interactions have improved the ability of density functional theory (DFT) to model these systems, substantial quantitative and even qualitative failures remain. In this contribution we show how a many-body description of vdW interactions can dramatically improve the accuracy of DFT for molecular materials, yielding quantitative description of stabilities and polymorphism for these challenging systems. Moreover, the role of many-body vdW interactions goes beyond stabilities to response properties. In particular, we have studied the elastic properties of a series of molecular crystals, finding that many-body vdW interactions can account for up to 30% of the elastic response, leading to quantitative and qualitative changes in elastic behavior. We will illustrate these crucial effects with the challenging case of the polymorphs of aspirin, leading to a better understanding of the conflicting experimental and theoretical studies of this system.
Directory of Open Access Journals (Sweden)
Shengchun Yang
2016-01-01
Full Text Available Demand response (DR programs provide an effective approach for dealing with the challenge of wind power output fluctuations. Given that uncertain DR, such as price elastic load (PEL, plays an important role, the uncertainty of demand response behavior must be studied. In this paper, a multi-objective stochastic optimization problem of PEL is proposed on the basis of the analysis of the relationship between price elasticity and probabilistic characteristic, which is about stochastic demand models for consumer loads. The analysis aims to improve the capability of accommodating wind output uncertainty. In our approach, the relationship between the amount of demand response and interaction efficiency is developed by actively participating in power grid interaction. The probabilistic representation and uncertainty range of the PEL demand response amount are formulated differently compared with those of previous research. Based on the aforementioned findings, a stochastic optimization model with the combined uncertainties from the wind power output and the demand response scenario is proposed. The proposed model analyzes the demand response behavior of PEL by maximizing the electricity consumption satisfaction and interaction benefit satisfaction of PEL. Finally, a case simulation on the provincial power grid with a 151-bus system verifies the effectiveness and feasibility of the proposed mechanism and models.
Price elasticity matrix of demand in power system considering demand response programs
Qu, Xinyao; Hui, Hongxun; Yang, Shengchun; Li, Yaping; Ding, Yi
2018-02-01
The increasing renewable energy power generations have brought more intermittency and volatility to the electric power system. Demand-side resources can improve the consumption of renewable energy by demand response (DR), which becomes one of the important means to improve the reliability of power system. In price-based DR, the sensitivity analysis of customer’s power demand to the changing electricity prices is pivotal for setting reasonable prices and forecasting loads of power system. This paper studies the price elasticity matrix of demand (PEMD). An improved PEMD model is proposed based on elasticity effect weight, which can unify the rigid loads and flexible loads. Moreover, the structure of PEMD, which is decided by price policies and load types, and the calculation method of PEMD are also proposed. Several cases are studied to prove the effectiveness of this method.
Harmonic Response of Magneto-electro-elastic Sensors Bonded to Cylindrical Shells
Directory of Open Access Journals (Sweden)
B. Biju
2010-05-01
Full Text Available This paper deals with semi analytical finite element formulation for coupled magneto-electro-elastic sensor bonded to a mild steel cylindrical shell. The cylinder is subjected to harmonically varying internal pressure with clamped free and clamped-clamped boundary condition. Numerical results are presented for the first three axial modes associated with the axisymmetric mode of the shell with different sensor locations. The sensor response is controlled mainly by its radial displacement in all the modes. The third mode response becomes significant when the sensor is placed at the free end of the mild steel cylinder for clamped free boundary condition.
The role of beneficial bacteria wall elasticity in regulating innate immune response.
Мokrozub, Viktoria V; Lazarenko, Liudmyla M; Sichel, Liubov M; Babenko, Lidia P; Lytvyn, Petro M; Demchenko, Olga M; Melnichenko, Yulia O; Boyko, Nadiya V; Biavati, Bruno; DiGioia, Diana; Bubnov, Rostyslav V; Spivak, Mykola Ya
2015-01-01
Probiotics have great potential to contribute to development of healthy dietary regimes, preventive care, and an integrated approach to immunity-related disease management. The bacterial wall is a dynamic entity, depending on many components and playing an essential role in modulating immune response. The impact of cell wall elasticity on the beneficial effects of probiotic strains has not been sufficiently studied. The aim was to investigate the effect of lactic acid bacteria (LAB) and bifidobacteria strains on phagocytic system cells (macrophages) as related to bacterial wall elasticity, estimated using atomic force microscopy (AFM). We conducted studies on Balb/c line mice 18-20 g in weight using lyophilized strains of LAB-Lactobacillus acidophilus IMV B-7279, Lactobacillus casei IMV B-7280, Lactobacillus delbrueckii subsp. bulgaricus IMV B-7281, and bifidobacteria-Bifidobacterium animalis VKL and Bifidobacterium animalis VKB. We cultivated the macrophages obtained from the peritoneal cavity of mice individually with the strains of LAB and bifidobacteria and evaluated their effect on macrophages, oxygen-dependent bactericidal activity, nitric oxide production, and immunoregulatory cytokines. We used AFM scanning to estimate bacterial cell wall elasticity. All strains had a stimulating effect on the functional activity of macrophages and ability to produce NO/NO2 in vitro. Lactobacilli strains increased the production of IL-12 and IFN-γ in vitro. The AFM demonstrated different cell wall elasticity levels in various strains of LAB and bifidobacteria. The rigidity of the cell walls among lactobacilli was distributed as follows: Lactobacillus acidophilus IMV B-7279 > Lactobacillus casei IMV B-7280 > Lactobacillus delbrueckii subsp. bulgaricus IMV B-7281; among the strains of bifidobacteria: B. animalis VKB > B. animalis VKL. Probiotic strain survival in the macrophages depended on the bacterial cell wall elasticity and on the time of their joint cultivation. LAB
An analytical approach to activating demand elasticity with a demand response mechanism
International Nuclear Information System (INIS)
Clastres, Cedric; Khalfallah, Haikel
2015-01-01
The aim of this work is to demonstrate analytically the conditions under which activating the elasticity of consumer demand could benefit social welfare. We have developed an analytical equilibrium model to quantify the effect of deploying demand response on social welfare and energy trade. The novelty of this research is that it demonstrates the existence of an optimal area for the price signal in which demand response enhances social welfare. This optimal area is negatively correlated to the degree of competitiveness of generation technologies and the market size of the system. In particular, it should be noted that the value of un-served energy or energy reduction which the producers could lose from such a demand response scheme would limit its effectiveness. This constraint is even greater if energy trade between countries is limited. Finally, we have demonstrated scope for more aggressive demand response, when only considering the impact in terms of consumer surplus. (authors)
Czech Academy of Sciences Publication Activity Database
Eck, Ch.; Jarušek, Jiří; Sofonea, M.
2010-01-01
Roč. 21, č. 3 (2010), s. 229-251 ISSN 0956-7925 R&D Projects: GA AV ČR IAA100750802 Institutional research plan: CEZ:AV0Z10190503 Keywords : elastic-vosco plastic material * dynamic contact problem * normal damped response * unilateral constraint * Coulomb friction * weak solution * penalitazion * smoothing Subject RIV: BA - General Mathematics Impact factor: 1.480, year: 2010 http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7675484&fileId=S0956792510000045
Jelinska, N.; Kalnins, M.; Kovalovs, A.; Chate, A.
2015-11-01
By the surface response method, a regression equation is constructed, and the tensile elastic modulus of films made from polyvinyl alcohol/polyvinyl acetate (PVA/PVAc) blends filled with montmorillonite clay and microcrystalline cellulose nanoparticles is investigated. It is established that the introduction of the nanoparticles improves the mechanical properties of the blends in tension considerably: their strength and elastic modulus increase with content of the particles. Using the regression equation, the optimum composition of nanoparticlefilled PVA/PVAc blends with the highest value of elastic modulus is found.
Yasukuni, Ryohei; Fukushima, Ryosuke; Iino, Takanori; Hosokawa, Yoichiroh
2017-11-01
A femtosecond-laser-induced impulsive force was applied to microsized calcium alginate (CaAlg) gel spheres as an external force to excite elastic waves. To evaluate elasticity, atomic force microscopy (AFM) was applied to detect vibration propagation. The sphere size dependence of the vibration was well reproduced by finite element method (FEM) simulation for pressure waves and surface acoustic waves. The obtained results indicate that the pulsed-laser-activated impulse response encoder (PLAIRE) enables the sensitive detection of elasticities, not only on inside but also on the surface.
Full Scale Measurements of the Hydro-Elastic Response of Large Container Ships for Decision Support
DEFF Research Database (Denmark)
Andersen, Ingrid Marie Vincent
The overall topic of this thesis is decision support for operation of ships and several aspects are covered herein. However, the main focus is on the wave-induced hydro-elastic response of large container ships and its implications on the structural response. The analyses are based mainly on full...... scale measurements from four container ships of 4,400 TEU, 8,600 TEU, 9,400 TEU and 14,000 TEU Primarily, strains measured near the deck amidships are used. Furthermore, measurements of motions and the encountered sea state are available for one of the ships. The smallest ship is in operation...... on the North Atlantic, while the three largest ships are operated on the Europe - Asia route. In the design rules of the classification societies for container ships the minimum design sagging bending moment amidships is larger than the hogging bending moment. Due to their design (full midship section...
Inferring bread doneness with air-pulse/ultrasonic ranging measurements of the loaf elastic response
Faeth, Loren Elbert
This research marks the discovery of a method by which bread doneness may be determined based on the elastic properties of the loaf as it bakes. The purpose of the study was to determine if changes in bread characteristics could be determined by non-contact methods during baking, as the basis for improved control of the baking process. Current control of the baking process is based on temperature and dwell time, which are determined by experience to produce a produce which is approximately ``done.'' There is no direct measurement of the property of interest, doneness. An ultrasonic measurement system was developed to measure the response of the loaf to an external stimulus. ``Doneness,'' as reflected in the internal elastic consistency of the bakery product, is assessed in less than 1/2 second, and requires no closer approach to the moving bakery product than about 2 inches. The system is designed to be compatible with strapped bread pans in a standard traveling-tray commercial oven.
Kim, Dae-Hyeong; Song, Jizhou; Choi, Won Mook; Kim, Hoon-Sik; Kim, Rak-Hwan; Liu, Zhuangjian; Huang, Yonggang Y; Hwang, Keh-Chih; Zhang, Yong-wei; Rogers, John A
2008-12-02
Electronic systems that offer elastic mechanical responses to high-strain deformations are of growing interest because of their ability to enable new biomedical devices and other applications whose requirements are impossible to satisfy with conventional wafer-based technologies or even with those that offer simple bendability. This article introduces materials and mechanical design strategies for classes of electronic circuits that offer extremely high stretchability, enabling them to accommodate even demanding configurations such as corkscrew twists with tight pitch (e.g., 90 degrees in approximately 1 cm) and linear stretching to "rubber-band" levels of strain (e.g., up to approximately 140%). The use of single crystalline silicon nanomaterials for the semiconductor provides performance in stretchable complementary metal-oxide-semiconductor (CMOS) integrated circuits approaching that of conventional devices with comparable feature sizes formed on silicon wafers. Comprehensive theoretical studies of the mechanics reveal the way in which the structural designs enable these extreme mechanical properties without fracturing the intrinsically brittle active materials or even inducing significant changes in their electrical properties. The results, as demonstrated through electrical measurements of arrays of transistors, CMOS inverters, ring oscillators, and differential amplifiers, suggest a valuable route to high-performance stretchable electronics.
Kim, Dae-Hyeong; Song, Jizhou; Choi, Won Mook; Kim, Hoon-Sik; Kim, Rak-Hwan; Liu, Zhuangjian; Huang, Yonggang Y.; Hwang, Keh-Chih; Zhang, Yong-wei; Rogers, John A.
2008-01-01
Electronic systems that offer elastic mechanical responses to high-strain deformations are of growing interest because of their ability to enable new biomedical devices and other applications whose requirements are impossible to satisfy with conventional wafer-based technologies or even with those that offer simple bendability. This article introduces materials and mechanical design strategies for classes of electronic circuits that offer extremely high stretchability, enabling them to accommodate even demanding configurations such as corkscrew twists with tight pitch (e.g., 90° in ≈1 cm) and linear stretching to “rubber-band” levels of strain (e.g., up to ≈140%). The use of single crystalline silicon nanomaterials for the semiconductor provides performance in stretchable complementary metal-oxide-semiconductor (CMOS) integrated circuits approaching that of conventional devices with comparable feature sizes formed on silicon wafers. Comprehensive theoretical studies of the mechanics reveal the way in which the structural designs enable these extreme mechanical properties without fracturing the intrinsically brittle active materials or even inducing significant changes in their electrical properties. The results, as demonstrated through electrical measurements of arrays of transistors, CMOS inverters, ring oscillators, and differential amplifiers, suggest a valuable route to high-performance stretchable electronics. PMID:19015528
Directory of Open Access Journals (Sweden)
Zhenxing He
2016-01-01
Full Text Available Based on vehicle-track coupled dynamic theory, a three-dimensional asymmetric vehicle-track coupling vibration model is developed to investigate the effect of voided elastic two-block sleepers on vehicle and track system dynamic responses. For the vehicle system, one car body, two frames, and four wheel sets are assumed to be rigid, with 35 degrees of freedom (DOF. For the track system, the rails and the concrete two-block sleepers are the main vibration components. The rails are modelled as Timoshenko beams, and the concrete two-block sleepers are assumed to be rigid mass with vertical and lateral movement. The pads under the rails and the rubber boots under the sleepers provide greater vertical and lateral elasticity for the track. The Hertz nonlinear elastic contact theory is used to calculate the normal wheel/rail force. The wheel/rail tangent creep force is first calculated using Kalker’s linear creep theory and then modified by the Shen-Hedrick-Elkins theory. The results show that the asymmetric voided elastic two-block sleepers have greater effects on the dynamic responses for fasteners and sleepers than on the car body and the wheel/rail forces under measured geometric irregularity and random irregularity. Two or more voided sleepers will greatly affect the vehicle running safety.
Gallezot, M.; Treyssède, F.; Laguerre, L.
2018-03-01
This paper investigates the computation of the forced response of elastic open waveguides with a numerical modal approach based on perfectly matched layers (PML). With a PML of infinite thickness, the solution can theoretically be expanded as a discrete sum of trapped modes, a discrete sum of leaky modes and a continuous sum of radiation modes related to the PML branch cuts. Yet with numerical methods (e.g. finite elements), the waveguide cross-section is discretized and the PML must be truncated to a finite thickness. This truncation transforms the continuous sum into a discrete set of PML modes. To guarantee the uniqueness of the numerical solution of the forced response problem, an orthogonality relationship is proposed. This relationship is applicable to any type of modes (trapped, leaky and PML modes) and hence allows the numerical solution to be expanded on a discrete sum in a convenient manner. This also leads to an expression for the modal excitability valid for leaky modes. The physical relevance of each type of mode for the solution is clarified through two numerical test cases, a homogeneous medium and a circular bar waveguide example, excited by a point source. The former is favourably compared to a transient analytical solution, showing that PML modes reassemble the bulk wave contribution in a homogeneous medium. The latter shows that the PML mode contribution yields the long-term diffraction phenomenon whereas the leaky mode contribution prevails closer to the source. The leaky mode contribution is shown to remain accurate even with a relatively small PML thickness, hence reducing the computational cost. This is of particular interest for solving three-dimensional waveguide problems, involving two-dimensional cross-sections of arbitrary shapes. Such a problem is handled in a third numerical example by considering a buried square bar.
Analysis of the Thermo-Elastic Response of Space Reflectors to Simulated Space Environment
Allegri, G.; Ivagnes, M. M.; Marchetti, M.; Poscente, F.
2002-01-01
high pressure Xenon lamps to simulate the direct solar irradiation and a cryogenic heat exchanger to reproduce the earth shadowing of sunlight. The temperature of the thermal cycles ranges from -80°C up to 100°C: the thermo-elastic response of the antenna has been surveyed by employing strain gauges place on the structures at several different locations. The structure has been subjected to 100 thermal cycles, each of which lasting two hours: the total duration of the exposition to the vacuum environment has been equal to 300 hours. Finally the antenna has been disassembled and its elements have been examined to evaluate the effects of the simulated exposition on each of them: the total mass loss and the final thermo-mechanical properties of the polymeric based materials which constitute the structural core of the antenna have been surveyed. The experimental results have been compared to numerical simulation performed by the NASTRAN code: the basic FEM model, developed for the unexposed antenna, has been updated to take into account the thermo-mechanical degradation of the structural elements and materials. This has allowed to obtain, by extrapolation, a FEM based prevision of the antenna thermo-elastic response for long-term operative conditions. References. [1] D. Hastings, H. Garret "Spacecraft environment interactions", Cambridge University Press, Atmospheric Series, Cambridge, 1996. [2] IAF-01-I.6.05 "On the Reliability of Honeycomb Core Bonding Joint in Sandwich Composite Materials for Space Applications" G. Allegri, U. Lecci, M. Marchetti, F. Poscente, 52° IAF Congress, 2001. [3] Meguro A. and alii, "Technology status of the 13 m aperture deployment antenna reflectors for Engineering Test Satellite VIII", Acta Astronautica, Volume: 47, Issue: 2-9, July - November, 2000, pp. 147-152. [4] Novikov L. S. "Contemporary state of spacecraft/environment interaction research" Radiation Measurements, Volume: 30, Issue: 5, October, 1999, pp. 661-667. [5] IAF-01-I.1
Toro-Mendoza, Jhoan; Rodriguez-Lopez, Gieberth; Paredes-Altuve, Oscar
2017-03-29
Here, the effect of the elastic response of the surface on the translational diffusion coefficient of a partly submerged-in-water spherical Brownian particle is considered. The elastic nature of the surface, mediated by the surface tension, generates an additional dissipative mechanism. Therefore, the collisions at the surface contribute to the diffusion as the source of the driving force and the dissipation results from the combined action of both elastic reaction of the surface and viscous dissipation. However, it can be estimated that the surface elastic mechanism is several orders of magnitude greater than the viscous one. This simple yet physically plausible approach leads us to assume that the diffusion on the surface is proportional to a power of the number of collisions and, consequently, the dissipative mechanisms are proportional to an inverse power of it. The lowering in dimensionality from 3 (bulk) to 2 (surface) also contributes to the decrease of diffusion. This model allows the reproduction of the reported experimental values of the surface/bulk dissipative force ratio. Additionally, we also compared the traditional viscous approach with other theoretical hydrodynamic treatments of the problem, which drastically failed to explain the experiments.
On the Effect of Unit-Cell Parameters in Predicting the Elastic Response of Wood-Plastic Composites
Directory of Open Access Journals (Sweden)
Fatemeh Alavi
2013-01-01
Full Text Available This paper presents a study on the effect of unit-cell geometrical parameters in predicting elastic properties of a typical wood plastic composite (WPC. The ultimate goal was obtaining the optimal values of representative volume element (RVE parameters to accurately predict the mechanical behavior of the WPC. For each unit cell, defined by a given combination of the above geometrical parameters, finite element simulation in ABAQUS was carried out, and the corresponding stress-strain curve was obtained. A uniaxial test according to ASTM D638-02a type V was performed on the composite specimen. Modulus of elasticity was determined using hyperbolic tangent function, and the results were compared to the sets of finite element analyses. Main effects of RVE parameters and their interactions were demonstrated and discussed, specially regarding the inclusion of two adjacent wood particles within one unit cell of the material. Regression analysis was performed to mathematically model the RVE parameter effects and their interactions over the modulus of elasticity response. The model was finally employed in an optimization analysis to arrive at an optimal set of RVE parameters that minimizes the difference between the predicted and experimental moduli of elasticity.
Chetty, Raj; Friedman, John N.; Olsen, Tore; Pistaferri, Luigi
2011-01-01
We show that the effects of taxes on labor supply are shaped by interactions between adjustment costs for workers and hours constraints set by firms. We develop a model in which firms post job offers characterized by an hours requirement and workers pay search costs to find jobs. We present evidence supporting three predictions of this model by analyzing bunching at kinks using Danish tax records. First, larger kinks generate larger taxable income elasticities. Second, kinks that apply to a larger group of workers generate larger elasticities. Third, the distribution of job offers is tailored to match workers' aggregate tax preferences in equilibrium. Our results suggest that macro elasticities may be substantially larger than the estimates obtained using standard microeconometric methods. PMID:21836746
Knight, Norman F., Jr.; Warren, Jerry E.; Elliott, Kenny B.; Song, Kyongchan; Raju, Ivatury S.
2012-01-01
Elastic-plastic, large-deflection nonlinear thermo-mechanical stress analyses are performed for the Space Shuttle external tank s intertank stringers. Detailed threedimensional finite element models are developed and used to investigate the stringer s elastic-plastic response for different thermal and mechanical loading events from assembly through flight. Assembly strains caused by initial installation on an intertank panel are accounted for in the analyses. Thermal loading due to tanking was determined to be the bounding loading event. The cryogenic shrinkage caused by tanking resulted in a rotation of the intertank chord flange towards the center of the intertank, which in turn loaded the intertank stringer feet. The analyses suggest that the strain levels near the first three fasteners remain sufficiently high that a failure may occur. The analyses also confirmed that the installation of radius blocks on the stringer feet ends results in an increase in the stringer capability.
Directory of Open Access Journals (Sweden)
Daniel Pelaez
2016-12-01
Full Text Available The processes of cellular differentiation and phenotypic maintenance can be influenced by stimuli from a variety of different factors. One commonly overlooked factor is the mechanical properties of the growth substrate in which stem cells are maintained or differentiated down various lineages. Here we explored the effect that growth on an elastic silicone substrate had on the myogenic expression and cytoskeletal morphology of periodontal ligament derived stem cells. Cells were grown on either collagen I coated tissue culture polystyrene plates or collagen I coated elastic silicone membranes for a period of 4 days without further induction from soluble factors in the culture media. Following the 4-day growth, gene expression and immunohistochemical analysis for key cardiomyogenic markers was performed along with a morphological assessment of cytoskeletal organization. Results show that cells grown on the elastic substrate significantly upregulate key markers associated with contractile activity in muscle tissues. Namely, the myosin light chain polypeptides 2 and 7, as well as the myosin heavy chain polypeptide 7 genes underwent a statistically significant upregulation in the cells grown on elastic silicone membranes. Similarly, the cells on the softer elastic substrate stained positive for both sarcomeric actin and cardiac troponin t proteins following just 4 days of growth on the softer material. Cytoskeletal analysis showed that substrate stiffness had a marked effect on the organization and distribution of filamentous actin fibers within the cell body. Growth on silicone membranes produced flatter and shorter cellular morphologies with filamentous actin fibers projecting anisotropically throughout the cell body. These results demonstrate how crucial the mechanical properties of the growth substrate of cells can be on the ultimate cellular phenotype. These observations highlight the need to further optimize differentiation protocols to enhance
Energy Technology Data Exchange (ETDEWEB)
ML Renauld; H Lien
2004-12-13
The evolution of global and local stress/strain conditions in test fasteners under test conditions is investigated using elastic-plastic, time-dependent finite element analyses (FEA). For elastic-plastic response, tensile data from multiple specimens, material heats and test temperatures are integrated into a single, normalized flow curve from which temperature dependency is extracted. A primary creep model is calibrated with specimen- and fastener-based thermal relaxation data generated under a range of times, temperatures, stress levels and environments. These material inputs are used in analytical simulations of experimental test conditions for several types of fasteners. These fastener models are constructed with automated routines and contact conditions prescribed at all potentially mating surfaces. Thermal or mechanical room temperature pre-loading, as appropriate for a given fastener, is followed by a temperature ramp and a dwell time at constant temperature. While the amount of thermal stress relaxation is limited for the conditions modeled, local stress states are highly dependent upon geometry (thread root radius, for example), pre-loading history and thermal expansion differences between the test fastener and test fixture. Benefits of this FE approach over an elastic methodology for stress calculation will be illustrated with correlations of Stress Corrosion Cracking (SCC) initiation time and crack orientations in stress concentrations.
Sivaraman, Balakrishnan; Swaminathan, Ganesh; Moore, Lee; Fox, Jonathan; Seshadri, Dhruv; Dahal, Shataakshi; Stoilov, Ivan; Zborowski, Maciej; Mecham, Robert; Ramamurthi, Anand
2017-04-01
Arresting or regressing growth of abdominal aortic aneurysms (AAAs), localized expansions of the abdominal aorta are contingent on inhibiting chronically overexpressed matrix metalloproteases (MMPs)-2 and -9 that disrupt elastic matrix within the aortic wall, concurrent with providing a stimulus to augmenting inherently poor auto-regeneration of these matrix structures. In a recent study we demonstrated that localized, controlled and sustained delivery of doxycycline (DOX; a tetracycline-based antibiotic) from poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs), enhances elastic matrix deposition and MMP-inhibition at a fraction of the therapeutically effective oral dose. The surface functionalization of these NPs with cationic amphiphiles, which enhances their arterial uptake, was also shown to have pro-matrix regenerative and anti-MMP effects independent of the DOX. Based on the hypothesis that the incorporation of superparamagnetic iron oxide NPs (SPIONs) within these PLGA NPs would enhance their targetability to the AAA site under an applied external magnetic field, we sought to evaluate the functional effects of NPs co-encapsulating DOX and SPIONs (DOX-SPION NPs) on elastic matrix regeneration and MMP synthesis/activity in vitro within aneurysmal smooth muscle cell (EaRASMC) cultures. The DOX-SPION NPs were mobile under an applied external magnetic field, while enhancing elastic matrix deposition 1.5-2-fold and significantly inhibiting MMP-2 synthesis and MMP-2 and -9 activities, compared to NP-untreated control cultures. These results illustrate that the multifunctional benefits of NPs are maintained following SPION co-incorporation. Additionally, preliminary studies carried out demonstrated enhanced targetability of SPION-loaded NPs within proteolytically-disrupted porcine carotid arteries ex vivo, under the influence of an applied external magnetic field. Thus, this dual-agent loaded NP system proffers a potential non-surgical option for treating small
Coupled Thermo-Electro-Magneto-Elastic Response of Smart Stiffened Panels
Bednarcyk, Brett A.; Yarrington, Phillip W.
2009-01-01
This report documents the procedures developed for incorporating smart laminate and panel analysis capabilities within the HyperSizer aerospace structural sizing software package. HyperSizer analyzes stiffened panels composed of arbitrary composite laminates through stiffener homogenization, or "smearing " techniques. The result is an effective constitutive equation for the stiffened panel that is suitable for use in a full vehicle-scale finite element analysis via MSC/NASTRAN. The existing thermo-elastic capabilities of HyperSizer have herein been extended to include coupled thermo-electro-magneto-elastic analysis capabilities. This represents a significant step toward realization of design tools capable of guiding the development of the next generation of smart aerospace structures. Verification results are presented that compare the developed smart HyperSizer capability with an ABAQUS piezoelectric finite element solution for a facesheet-flange combination. These results show good agreement between HyperSizer and ABAQUS, but highlight a limitation of the HyperSizer formulation in that constant electric field components are assumed.
Energy Technology Data Exchange (ETDEWEB)
Zenkour, Ashraf M., E-mail: zenkour@hotmail.com [Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516 (Egypt); Abbas, Ibrahim A. [Department of Mathematics, Faculty of Science and Arts-Khulais, King Abdulaziz University, Jeddah (Saudi Arabia); Department of Mathematics, Faculty of Science, Sohag University, Sohag (Egypt)
2015-12-01
The electro-magneto-thermo-elastic analysis problem of an infinite functionally graded (FG) hollow cylinder is studied in the context of Green–Naghdi's (G–N) generalized thermoelasticity theory (without energy dissipation). Material properties are assumed to be graded in the radial direction according to a novel power-law distribution in terms of the volume fractions of the metal and ceramic constituents. The inner surface of the FG cylinder is pure metal whereas the outer surface is pure ceramic. The equations of motion and the heat-conduction equation are used to derive the governing second-order differential equations. A finite element scheme is presented for the numerical purpose. The system of differential equations is solved numerically and some plots for displacement, radial and electromagnetic stresses, and temperature are presented. The radial displacement, mechanical stresses and temperature as well as the electromagnetic stress are all investigated along the radial direction of the infinite cylinder. - Highlights: • The electro-magneto-thermo-elastic analysis problem of a FG cylinder is studied. • A finite element scheme is presented for the numerical purpose. • The results are investigated along the radial direction of the infinite cylinder. • It provides interesting information for all researchers working on this subject.
International Nuclear Information System (INIS)
Zenkour, Ashraf M.; Abbas, Ibrahim A.
2015-01-01
The electro-magneto-thermo-elastic analysis problem of an infinite functionally graded (FG) hollow cylinder is studied in the context of Green–Naghdi's (G–N) generalized thermoelasticity theory (without energy dissipation). Material properties are assumed to be graded in the radial direction according to a novel power-law distribution in terms of the volume fractions of the metal and ceramic constituents. The inner surface of the FG cylinder is pure metal whereas the outer surface is pure ceramic. The equations of motion and the heat-conduction equation are used to derive the governing second-order differential equations. A finite element scheme is presented for the numerical purpose. The system of differential equations is solved numerically and some plots for displacement, radial and electromagnetic stresses, and temperature are presented. The radial displacement, mechanical stresses and temperature as well as the electromagnetic stress are all investigated along the radial direction of the infinite cylinder. - Highlights: • The electro-magneto-thermo-elastic analysis problem of a FG cylinder is studied. • A finite element scheme is presented for the numerical purpose. • The results are investigated along the radial direction of the infinite cylinder. • It provides interesting information for all researchers working on this subject
Vibration responses analysis of an elastic-support cantilever beam with crack and offset boundary
Zhang, Wensheng; Ma, Hui; Zeng, Jin; Wu, Shuang; Wen, Bangchun
2017-10-01
In this study, a finite element model of an elastic-support cantilever beam with crack and offset boundary is established by using mixed elements in ANSYS software. In the proposed model, different contact elements are adopted to describe the breathing effect of crack and offset boundary, and spring elements are used to simulate the elastic support, and the model is also validated by comparing the natural frequencies with those in published literatures. Based on the developed model, the combined effects of the crack and offset boundary on the system dynamic characteristics are studied. The results indicate that the amplitude of double frequency component (2fe) firstly decreases and then increases with the offset values when the crack position is on the opposite side of offset boundary. 2fe may disappear when the crack and the offset boundary locate at a certain position. In addition, the more distant the offset boundary is, the more intense the system nonlinearity becomes. The amplitude of 2fe increases with the offset values when the crack position is on the same side of offset boundary under a constant crack depth and location. Moreover, it also shows some complicated frequency components due to the gradually strengthened nonlinearity of the system with the increasing offset values, and the obvious distortion phenomenon in the phase plane portraits can be observed near the super-harmonic resonance region. This study can provide some basis for the diagnosis of beam-like structures with crack.
Dynamic elastic-plastic response of a 2-DOF mass-spring system.
Energy Technology Data Exchange (ETDEWEB)
Corona, Edmundo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2018-02-01
The objective of the work presented here arose from abnormal, drop scenarios and specifically the question of how the accelerations and accumulation of plastic strains of internal components could be a ected by the material properties of the external structure. In some scenarios, the impact loads can induce cyclic motion of the internal components. Therefore, a second objective was to explore di erences that could be expected when simulations are conducted using isotropic hardening vs. kinematic hardening plasticity models. The simplest model that can be used to investigate the objectives above is a two-degree-offreedom mass/spring model where the springs exhibit elastic-plastic behavior. The purpose of this memo is to develop such model and present a few results that address the objectives.
Gellaerts, Jules; Pirard, Maxime; Muzic, Jessie; Peseux, Maxime; Ménétrier, Arnaud
2017-10-01
The aim of this study was to establish whether maximalist shoes engender fewer muscular oscillations than minimalist shoes and determine to what extent these shoes, when combined with elastic compression (EC), help reduce muscle oscillations. For that purpose, we tested the effects of various levels of compression on the muscular oscillations in maximalist and minimalist footwear. Eleven volunteers executed 16 one-minute passages on a flat treadmill in a randomized order: maximalists or minimalists, walking (6 km/h) or running (10 km/h), without EC (control condition [CON]) or with EC applying different pressures (9.6 mmHg, 14.5 mmHg and 20.4 mmHg). The muscular oscillations were measured on both thighs, on the rectus femoris and on the vastus medialis with tri-axial accelerometers. Muscular oscillations are lower in maximalist shoes than in minimalist shoes, for both walking to 6 km/h and running to 10 km/h (Pshoes reduces muscular oscillations as much as maximalist shoes, when combined with lower compression.
Dynamic Response of a Circular Tunnel in an Elastic Half Space
Directory of Open Access Journals (Sweden)
İrfan Coşkun
2017-01-01
Full Text Available The vibration of a circular tunnel in an elastic half space subjected to uniformly distributed dynamic pressure at the inner boundary is studied in this paper. For comparison purposes, two different ground materials (soft and hard soil are considered for the half space. Under the assumption of plane strain, the equations of motion for the tunnel and the surrounding medium are reduced to two wave equations in polar coordinates using Helmholtz potentials. The method of wave expansion is used to construct the displacement fields in terms of displacement potentials. The boundary conditions associated with the problem are satisfied exactly at the inner surface of the tunnel and at the interface between the tunnel and surrounding medium, and they are satisfied approximately at the free surface of the half space. A least-squares technique is used for satisfying the stress-free boundary conditions at the half space. It is shown by comparison that the stresses and displacements are significantly influenced by the properties of the surrounding soil, wave number (i.e., the frequency, depth of embedment, and thickness of the tunnel wall.
Shalimova, I. A.; Sabelfeld, K. K.
2010-11-01
The response of an elastic half-space to random excitations of displacements on the boundary under the condition of no shearing forces is studied. We analyze the white noise excitations and general random fluctuations of displacements prescribed on the boundary. We consider the case of partially ordered defects on the boundary whose positions are governed by an exponential-cosine-type correlation function. The analysis is based on a Poisson-type integral formula which we derive here for the case of zero shearing forces on the boundary. We obtain exact representations for the displacement correlation tensor and the Karhunen-Loève expansion for the solution of the Lamé equation itself, and analyze some features of the correlation structure of the displacements. The Monte Carlo technique developed can be applied to a wide class of differential equations with random boundary conditions.
Energy Technology Data Exchange (ETDEWEB)
MACKEY TC; ABATT FG; JOHNSON KI
2009-01-16
The purpose of this study was to determine the sensitivity of the dynamic response of the Hanford double-shell tanks (DSTs) to the assumptions regarding the constitutive properties of the contained waste. In all cases, the waste was modeled as a uniform linearly elastic material. The focus of the study was on the changes in the modal response of the tank and waste system as the extensional modulus (elastic modulus in tension and compression) and shear modulus of the waste were varied through six orders of magnitude. Time-history analyses were also performed for selected cases and peak horizontal reaction forces and axial stresses at the bottom of the primary tank were evaluated. Because the analysis focused on the differences in the responses between solid-filled and liquid-filled tanks, it is a comparative analysis rather than an analysis of record for a specific tank or set of tanks. The shear modulus was varied between 4 x 10{sup 3} Pa and 4.135 x 10{sup 9} Pa. The lowest value of shear modulus was sufficient to simulate the modal response of a liquid-containing tank, while the higher values are several orders of magnitude greater than the upper limit of expected properties for tank contents. The range of elastic properties used was sufficient to show liquid-like response at the lower values, followed by a transition range of semi-solid-like response to a clearly identifiable solid-like response. It was assumed that the mechanical properties of the tank contents were spatially uniform. Because sludge-like materials are expected only to exist in the lower part of the tanks, this assumption leads to an exaggeration of the effects of sludge-like materials in the tanks. The results of the study show that up to a waste shear modulus of at least 40,000 Pa, the modal properties of the tank and waste system are very nearly the same as for the equivalent liquid-containing tank. This suggests that the differences in critical tank responses between liquid-containing tanks
Lytra, A.; Pelekasis, N.
2018-03-01
The static response of coated microbubbles is investigated with a novel approach employed for modeling contact between a microbubble and the cantilever of an atomic force microscope. Elastic tensions and moments are described via appropriate constitutive laws. The encapsulated gas is assumed to undergo isothermal variations. Due to the hydrophilic nature of the cantilever, an ultrathin aqueous film is formed, which transfers the force onto the shell. An interaction potential describes the local pressure applied on the shell. The problem is solved in axisymmetric form with the finite element method. The response is governed by the dimensionless bending, k^ b=kb/(χ R02 ), pressure, P^ A=(PAR0 )/χ , and interaction potential, W ^ =w0/χ . Hard polymeric shells have negligible resistance to gas compression, while for the softer lipid shells gas compressibility is comparable with shell elasticity. As the external force increases, numerical simulations reveal that the force versus deformation (f vs d) curve of polymeric shells exhibits a transition from the linear O(d) (Reissner) regime, marked by flattened shapes around the contact region, to a non-linear O(d1/2) (Pogorelov) regime dominated by shapes exhibiting crater formation due to buckling. When lipid shells are tested, buckling is bypassed as the external force increases and flattened shapes prevail in an initially linear f vs d curve. Transition to a curved upwards regime is observed as the force increases, where gas compression and area dilatation form the dominant balance providing a nonlinear regime with an O(d3) dependence. Asymptotic analysis recovers the above patterns and facilitates estimation of the shell mechanical properties.
International Nuclear Information System (INIS)
Ledbetter, H.M.
1983-01-01
This chapter investigates the following five aspects of engineering-material solid-state elastic constants: general properties, interrelationships, relationships to other physical properties, changes during cooling from ambient to near-zero temperature, and near-zero-temperature behavior. Topics considered include compressibility, bulk modulus, Young's modulus, shear modulus, Poisson's ratio, Hooke's law, elastic-constant measuring methods, thermodynamic potentials, higher-order energy terms, specific heat, thermal expansivity, magnetic materials, structural phase transitions, polymers, composites, textured aggregates, and other-phenomena correlations. Some of the conclusions concerning polycrystalline elastic properties and their temperature dependence are: elastic constants are physical, not mechanical, properties which relate thermodynamically to other physical properties such as specific heat and thermal expansivity; elastic constants at low temperatures are nearly temperature independent, as required by the third law of thermodynamics; and elastic constants can be used to study directional properties of materials, such as textured aggregates and composites
Viesca, R. C.
2015-12-01
Subsurface fluid injection is often followed by observations of an enlarging cloud of microseismicity. The cloud's diffusive growth is thought to be a direct response to the diffusion of elevated pore fluid pressure reaching pre-stressed faults, triggering small instabilities; the observed high rates of this growth are interpreted to reflect a relatively high permeability of a fractured subsurface [e.g., Shapiro, GJI 1997]. We investigate an alternative mechanism for growing a microseismic cloud: the elastic transfer of stress due to slow, aseismic slip on a subset of the pre-existing faults in this damaged subsurface. We show that the growth of the slipping region of the fault may be self-similar in a diffusive manner. While this slip is driven by fluid injection, we show that, for critically stressed faults, the apparent diffusion of this slow slip may quickly exceed the poroelastically driven diffusion of the elevated pore fluid pressure. Under these conditions, microseismicity can be first triggered by the off-fault stress perturbation due to the expanding region of slip on principal faults. This provides an alternative interpretation of diffusive growth rates in terms of the subsurface stress state rather than an enhanced hydraulic diffusivity. That such aseismic slip may occur, outpace fluid diffusion, and in turn trigger microseismic events, is also suggested by on- and near-fault observations in past and recently reported fluid injection experiments [e.g., Cornet et al., PAGEOPH 1997; Guglielmi et al., Science 2015]. The model of injection-induced slip assumes elastic off-fault behavior and a fault strength determined by the product of a constant friction coefficient and the local effective normal stress. The sliding region is enlarged by the pore pressure increase resolved on the fault plane. Remarkably, the rate of self-similar expansion may be determined by a single parameter reflecting both the initial stress state and the magnitude of the pore pressure
Improved modeling accuracy of the elastic object response by inclusion of higher order scattering
Nijhoff, M.J.J.
2014-01-01
Current methods of automatic target detection and classification using low- to mid- frequency sonar are based on correlating the measured Target In the Environment Response (TIER) of potential targets with the TIERs in a database of known objects. Obtaining experimental TIER measurements of proud,
International Nuclear Information System (INIS)
Rashidifar, Mohammed Amin; Rashidifar, Ali Amin
2014-01-01
Conventional model-based control strategies are very complex and difficult to synthesize due to high complexity of the dynamics of robots manipulator considering joint elasticity. This paper presents investigations into the development of hybrid control schemes for trajectory tracking and vibration control of a flexible joint manipulator. To study the effectiveness of the controllers, initially a collocated proportional-derivative (P D)-type Fuzzy Logic Controller (FLC) is developed for tip angular position control of a flexible joint manipulator. This is then extended to incorporate a non-collocated Fuzzy Logic Controller and input shaping scheme for vibration reduction of the flexible joint system. The positive zero-vibration-derivative-derivative (ZVDD) shaper is designed based on the properties of the system. Simulation results of the response of the flexible joint manipulator with the controllers are presented in time and frequency domains. The performances of the hybrid control schemes are examined in terms of input tracking capability, level of vibration reduction and time response specifications. Finally, a comparative assessment of the control techniques is presented and discussed. (Author)
Matsu: An Elastic Cloud Connected to a SensorWeb for Disaster Response
Mandl, Daniel
2011-01-01
This slide presentation reviews the use of cloud computing combined with the SensorWeb in aiding disaster response planning. Included is an overview of the architecture of the SensorWeb, and overviews of the phase 1 of the EO-1 system and the steps to improve it to transform it to an On-demand product cloud as part of the Open Cloud Consortium (OCC). The effectiveness of this system is demonstrated in the SensorWeb for the Namibia flood in 2010, using information blended from MODIS, TRMM, River Gauge data, and the Google Earth version of Namibia the system enabled river surge predictions and could enable planning for future disaster responses.
Goldberg, Robert K.; Bonacuse, Peter J.; Mital, Subodh K.
2012-01-01
To develop methods for quantifying the effects of the microstructural variations of woven ceramic matrix composites on the effective properties and response of the material, a research program has been undertaken which is described in this paper. In order to characterize and quantify the variations in the microstructure of a five harness satin weave, CVI SiC/SiC, composite material, specimens were serially sectioned and polished to capture images that detailed the fiber tows, matrix, and porosity. Open source quantitative image analysis tools were then used to isolate the constituents and collect relevant statistics such as within ply tow spacing. This information was then used to build two dimensional finite element models that approximated the observed section geometry. With the aid of geometrical models generated by the microstructural characterization process, finite element models were generated and analyses were performed to quantify the effects of the microstructure and its variation on the effective stiffness and areas of stress concentration of the material. The results indicated that the geometry and distribution of the porosity appear to have significant effects on the through-thickness modulus. Similarly, stress concentrations on the outer surface of the composite appear to correlate to regions where the transverse tows are separated by a critical amount.
Hilburger, Mark W.; Nemeth, Michael P.; Riddick, Jaret C.; Thornburgh, Robert P.
2004-01-01
A parametric study of the effects of test-fixture-induced initial prestress and elastic edge restraints on the prebuckling and buckling responses of a compression-loaded, quasi-isotropic curved panel is presented. The numerical results were obtained by using a geometrically nonlinear finite element analysis code with high-fidelity models. The results presented show that a wide range of prebuckling and buckling behavior can be obtained by varying parameters that represent circumferential loaded-edge restraint and rotational unloaded-edge restraint provided by a test fixture and that represent the mismatch in specimen and test-fixture radii of curvature. For a certain range of parameters, the panels exhibit substantial nonlinear prebuckling deformations that yield buckling loads nearly twice the corresponding buckling load predicted by a traditional linear bifurcation buckling analysis for shallow curved panels. In contrast, the results show another range of parameters exist for which the nonlinear prebuckling deformations either do not exist or are relatively benign, and the panels exhibit buckling loads that are nearly equal to the corresponding linear bifurcation buckling load. Overall, the results should also be of particular interest to scientists, engineers, and designers involved in simulating flight-hardware boundary conditions in structural verification and certification tests, involved in validating structural analysis tools, and interested in tailoring buckling performance.
Rezaeian, Sanaz; Bozorgnia, Yousef; Idriss, I.M.; Abrahamson, Norman; Campbell, Kenneth; Silva, Walter
2014-01-01
Ground motion prediction equations (GMPEs) for elastic response spectra are typically developed at a 5% viscous damping ratio. In reality, however, structural and nonstructural systems can have other damping ratios. This paper develops a new model for a damping scaling factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE for damping ratios between 0.5% to 30%. The model is developed based on empirical data from worldwide shallow crustal earthquakes in active tectonic regions. Dependencies of the DSF on potential predictor variables, such as the damping ratio, spectral period, ground motion duration, moment magnitude, source-to-site distance, and site conditions, are examined. The strong influence of duration is captured by the inclusion of both magnitude and distance in the DSF model. Site conditions show weak influence on the DSF. The proposed damping scaling model provides functional forms for the median and logarithmic standard deviation of DSF, and is developed for both RotD50 and GMRotI50 horizontal components. A follow-up paper develops a DSF model for vertical ground motion.
Chubelaschwili, David; Pinkall, Ulrich
2010-01-01
Motivated by the problem of finding an explicit description of a developable narrow Moebius strip of minimal bending energy, which was first formulated by M. Sadowsky in 1930, we will develop the theory of elastic strips. Recently E.L. Starostin and G.H.M. van der Heijden found a numerical description for an elastic Moebius strip, but did not give an integrable solution. We derive two conservation laws, which describe the equilibrium equations of elastic strips. In applying these laws we find...
Directory of Open Access Journals (Sweden)
Afed U. Khan
2017-11-01
Full Text Available Investigating water–land–climate interactions is critical for urban development and watershed management. This study examined this nexus by elasticity and statistical approaches through the lens of three watersheds: The Yukon, Mekong and Murray. Here, this study reports the fundamental characteristics, explanations and ecological and management implications of terrestrial determinant influence on the response of water quality to climate drivers. The stability of the response, measured by climate elasticity of water quality (CEWQ, is highly dependent on terrestrial determinants, with strong impacts from anthropogenic biomes and low impacts from surficial geology. Compared to temperature elasticity, precipitation elasticity of water quality is more unstable due to its possible linkages with many terrestrial determinants. Correlation and linear models were developed for the interaction system, which uncovered many interesting scenarios. The results implied that watersheds with a higher ratio of rangeland biomes have a lower risk of instability as compared to watersheds with a higher proportion of dense settlement, cropland and forested biomes. This study discusses some of the most essential pathways where instability might adversely affect CEWQ parameters and recommends suggestions for policy makers to alleviate the instability impacts to bring sustainability to the water environment.
Energy Technology Data Exchange (ETDEWEB)
Wang, Chenju [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics; Gu, Jianbing [Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics; Sichuan Univ., Chengdu (China). College of Physical Science and Technology; Kuang, Xiaoyu [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Xiang, Shikai [Institute of Fluid Physics, Sichuan (China). National Key Laboratory of Shock Wave and Detonation Physics
2015-10-01
Nonlinear elastic properties of diamond-cubic silicon and germanium have not been investigated sufficiently to date. Knowledge of these properties not only can help us to understand nonlinear mechanical effects but also can assist us to have an insight into the related anharmonic properties, so we investigate the nonlinear elastic behaviour of single silicon and germanium by calculating their second- and third-order elastic constants. All the results of the elastic constants show good agreement with the available experimental data and other theoretical calculations. Such a phenomenon indicates that the present values of the elastic constants are accurate and can be used to further study the related anharmonic properties. Subsequently, the anharmonic properties such as the pressure derivatives of the second-order elastic constants, Grueneisen constants of long-wavelength acoustic modes, and ultrasonic nonlinear parameters are explored. All the anharmonic properties of silicon calculated in the present work also show good agreement with the existing experimental results; this consistency not only reveals that the calculation method of the anharmonic properties is feasible but also illuminates that the anharmonic properties obtained in the present work are reliable. For the anharmonic properties of germanium, since there are no experimental result and other theoretical data till now, we hope that the anharmonic properties of germanium first offered in this work would serve as a reference for future studies.
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. © 2016 The Author(s).
Vliet, Jurg; Wel, Steven; Dowd, Dara
2011-01-01
While it's always been possible to run Java applications on Amazon EC2, Amazon's Elastic Beanstalk makes the process easier-especially if you understand how it works beneath the surface. This concise, hands-on book not only walks you through Beanstalk for deploying and managing web applications in the cloud, you'll also learn how to use this AWS tool in other phases of development. Ideal if you're a developer familiar with Java applications or AWS, Elastic Beanstalk provides step-by-step instructions and numerous code samples for building cloud applications on Beanstalk that can handle lots
Form finding in elastic gridshells
Baek, Changyeob; Sageman-Furnas, Andrew O.; Jawed, Mohammad K.; Reis, Pedro M.
2018-01-01
Elastic gridshells comprise an initially planar network of elastic rods that are actuated into a shell-like structure by loading their extremities. The resulting actuated form derives from the elastic buckling of the rods subjected to inextensibility. We study elastic gridshells with a focus on the rational design of the final shapes. Our precision desktop experiments exhibit complex geometries, even from seemingly simple initial configurations and actuation processes. The numerical simulations capture this nonintuitive behavior with excellent quantitative agreement, allowing for an exploration of parameter space that reveals multistable states. We then turn to the theory of smooth Chebyshev nets to address the inverse design of hemispherical elastic gridshells. The results suggest that rod inextensibility, not elastic response, dictates the zeroth-order shape of an actuated elastic gridshell. As it turns out, this is the shape of a common household strainer. Therefore, the geometry of Chebyshev nets can be further used to understand elastic gridshells. In particular, we introduce a way to quantify the intrinsic shape of the empty, but enclosed regions, which we then use to rationalize the nonlocal deformation of elastic gridshells to point loading. This justifies the observed difficulty in form finding. Nevertheless, we close with an exploration of concatenating multiple elastic gridshell building blocks.
Liu, Lu; Kamm, Paul; García-Moreno, Francisco; Banhart, John; Pasini, Damiano
2017-10-01
This paper examines three-dimensional metallic lattices with regular octet and rhombicuboctahedron units fabricated with geometric imperfections via Selective Laser Sintering. We use X-ray computed tomography to capture morphology, location, and distribution of process-induced defects with the aim of studying their role in the elastic response, damage initiation, and failure evolution under quasi-static compression. Testing results from in-situ compression tomography show that each lattice exhibits a distinct failure mechanism that is governed not only by cell topology but also by geometric defects induced by additive manufacturing. Extracted from X-ray tomography images, the statistical distributions of three sets of defects, namely strut waviness, strut thickness variation, and strut oversizing, are used to develop numerical models of statistically representative lattices with imperfect geometry. Elastic and failure responses are predicted within 10% agreement from the experimental data. In addition, a computational study is presented to shed light into the relationship between the amplitude of selected defects and the reduction of elastic properties compared to their nominal values. The evolution of failure mechanisms is also explained with respect to strut oversizing, a parameter that can critically cause failure mode transitions that are not visible in defect-free lattices.
CSIR Research Space (South Africa)
Maina, JW
2007-08-01
Full Text Available that simulate pavement layer interface slip and introduced into the multi-layered elastic analysis freeware known as GAMES are presented in this paper. The GAMES software is capable of analyzing effects of five different types of airport pavement surface loading...
Vassiliev, Dmitri
2017-04-01
We consider an infinite three-dimensional elastic continuum whose material points experience no displacements, only rotations. This framework is a special case of the Cosserat theory of elasticity. Rotations of material points are described mathematically by attaching to each geometric point an orthonormal basis that gives a field of orthonormal bases called the coframe. As the dynamical variables (unknowns) of our theory, we choose the coframe and a density. We write down the general dynamic variational functional for our rotational theory of elasticity, assuming our material to be physically linear but the kinematic model geometrically nonlinear. Allowing geometric nonlinearity is natural when dealing with rotations because rotations in dimension three are inherently nonlinear (rotations about different axes do not commute) and because there is no reason to exclude from our study large rotations such as full turns. The main result of the talk is an explicit construction of a class of time-dependent solutions that we call plane wave solutions; these are travelling waves of rotations. The existence of such explicit closed-form solutions is a non-trivial fact given that our system of Euler-Lagrange equations is highly nonlinear. We also consider a special case of our rotational theory of elasticity which in the stationary setting (harmonic time dependence and arbitrary dependence on spatial coordinates) turns out to be equivalent to a pair of massless Dirac equations. The talk is based on the paper [1]. [1] C.G.Boehmer, R.J.Downes and D.Vassiliev, Rotational elasticity, Quarterly Journal of Mechanics and Applied Mathematics, 2011, vol. 64, p. 415-439. The paper is a heavily revised version of preprint https://arxiv.org/abs/1008.3833
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 (pharmaceutical delivery and wound dressings.
Energy Technology Data Exchange (ETDEWEB)
Murai, M.; Kagemoto, H.; Fujino, M. [The University of Tokyo, Tokyo (Japan)
1997-08-01
On the hydroelastic behaviors of a huge floating structure, a mutual interaction theory based on the area division method is used for the analysis of a fluid problem and a mode analysis method is used for the analysis of deformation. On the continuous deformation of a floating structure, the structure is considered as a set of partial structures obtained when the plane shape was divided into squares and discretely handled as a series of rigid motions in the small partial structures obtained by dividing the partial structures more finely. The experimental result in a water tank and the distribution method at a singular point were compared on the deformation of the elastic floating structure estimated by calculation based on this formulation. The result showed that the estimation method on the hydroelastic problem proposed in this paper is valid. On the prediction of hydroelastic behaviors of a huge floating structure, various calculation examples indicate that the hydroelastic behavior is not only the relation between the structure length and wavelength, but also that the bending rigidity of a structure is a very important factor. For a huge floating structure in the 5,000 m class, up to shorter wavelength of about {lambda}/L = 1/100 must be investigated. 6 refs., 14 figs., 5 tabs.
Transient Response of a Fluid-Filled, Thick-Walled Spherical Shell Embedded in an Elastic Medium
Directory of Open Access Journals (Sweden)
Bahari Ako
2016-01-01
Full Text Available The paper addresses the problem of transient elastodynamics analysis of a thick-walled, fluid-filled spherical shell embedded in an elastic medium with an analytical approach. This configuration is investigated at first step for a full-space case. Different constitutive relations for the elastic medium, shell material and filling fluid can be considered, as well as different excitation sources (including S/P wave or plane/spherical incident wave at different locations. With mapmaking visualisation, the wave propagation phenomena can be described and better understood. The methodology is going to be applied to analysis of the tunnels or other shell like structures under the effect of nearby underground explosion.
Ou, Dayi; Mak, Cheuk Ming
2011-08-01
The transient vibration and sound radiation (TVSR) of plate-like structures with general elastic boundary conditions was investigated using the time-domain finite element method (TDFEM) and time-domain boundary element method (TDBEM). In this model, the structure can have arbitrary elastic boundary conditions and hence the effects of the boundary conditions on the TVSR can be effectively studied. The predicted results agreed well with existing experimental data using two classical boundary conditions: simply supported at all edges and clamped-free-free-free. The TVSR of a single panel with a more general boundary condition in two connected chambers was also measured. The predicted results agreed well with these experimental results. The prediction method was subsequently applied to evaluate the effects of elastic boundary supports on the TVSR of a window caused by a sonic boom. Loudness, non-audible acoustic perception, and tactile vibration thresholds were analyzed for different boundary conditions (varying between clamped and simply supported). The possibility of improving the transient vibration and noise isolation performance by selecting an appropriate boundary condition was thereby demonstrated.
The Price Elasticity of Residential Energy Use,
household energy- consumption behavior : The difference between the own-price elasticity of total consumption and that of saturation is a measure of the responsiveness of ’conservation’ to price....estimates of the own-price elasticities of total consumption but almost surely will produce erroneous estimates of the cross-price elasticities. As regards
Cordero, F.
2018-03-01
A method is proposed for evaluating the potential piezoelectric response, that a ferroelectric material would exhibit after full poling, from elastic and dielectric measurements of the unpoled ceramic material. The method is based on the observation that the softening in a ferroelectric phase with respect to the paraelectric phase is of piezoelectric origin, and is tested on BaTiO3. The angular averages of the piezoelectric softening in unpoled ceramics are calculated for ferroelectric phases of different symmetries. The expression of the orientational average with the piezoelectric and dielectric constants of single crystal tetragonal BaTiO3 from the literature reproduces well the softening of the Young's modulus of unpoled ceramic BaTiO3, after a correction for the porosity. The agreement is good in the temperature region sufficiently far from the Curie temperature and from the transition to the orthorhombic phase, where the effect of fluctuations should be negligible, but deviations are found outside this region, and possible reasons for this are discussed. This validates the determination of the piezoelectric response by means of purely elastic measurements on unpoled samples. The method is indirect and, for quantitative assessments, requires the knowledge of the dielectric tensor. On the other hand, it does not require poling of the sample, and therefore is insensitive to inaccuracies from incomplete poling, and can even be used with materials that cannot be poled, for example, due to excessive electrical conductivity. While the proposed example of the Young's modulus of a ceramic provides an orientational average of all the single crystal piezoelectric constants, a Resonant Ultrasound Spectroscopy measurement of a single unpoled ceramic sample through the ferroelectric transition can in principle measure all the piezoelectric constants, together with the elastic ones.
Elastic-plastic response of a piping system due to simulated double-ended guillotine break events
International Nuclear Information System (INIS)
Kussmaul, K.; Diem, H.; Hunger, H.; Katzenmeier, G.
1987-01-01
From the blowdown experiments performed on the HDR feedwater line with feedwater check valve the conclusion can be drawn that high transient loads of up to plastic strains of 3%, acting on an initially integer piping system, can be sustained without loss of integrity for a low number of load cycles due to the plasticizing capacity of the pipework materials nowadays used in the reactor technology. In the experiments carried out with ferritic piping of ND 400 pressure peaks up to about 31,5 mPA were achieved which resulted in excessive strains of up to 3%. By nonlinear finite element computations (ABAQUS) it was possible to describe the elastic-plastic behaviour of the piping in a good approximation. On account of the safety margins proved in the experiments, potential inaccuracies in theoretical structure analyses are recommended so as to be on the safe side. On the other hand, it appears that designing pipework with reference to elastic stress categories does not adequately take into account the actual reserves of the pipework material
Rahmani, O.; Shokrnia, M.; Golmohammadi, H.; Hosseini, S. A. H.
2018-02-01
Transverse forced vibration of a single-walled carbon nanotube (SWCNT) under excitation of a moving harmonic load has been analyzed based on modified nonlocal elasticity theory. In the parametric study, influences of nonlocal parameter, velocity of the moving load, excitation frequency, order of derivative and their interactive effects on forced deflection of the nanotube have been investigated in details. Numerical amounts of the dimensionless static deflection of the SWCNT have been calculated and compared with those of existing papers and an excellent agreement has been achieved. The results show that the variation of N affects the dynamic deflection and natural frequency of SWCNTs, significantly. Also by amplification of the excitation frequency, differences between the amounts of dynamic deflection become smaller for various values of N . Furthermore, decreasing the frequency ratio causes a reduction of the maximum deflection and increasing the frequency ratio causes an increase of the maximum deflection for values of load velocity which are greater than a specified value.
Knight, Norman F., Jr.; Song, Kyongchan; Elliott, Kenny B.; Raju, Ivatury S.; Warren, Jerry E.
2012-01-01
Elastic-plastic, large-deflection nonlinear stress analyses are performed for the external hat-shaped stringers (or stiffeners) on the intertank portion of the Space Shuttle s external tank. These stringers are subjected to assembly strains when the stringers are initially installed on an intertank panel. Four different stringer-feet configurations including the baseline flat-feet, the heels-up, the diving-board, and the toes-up configurations are considered. The assembly procedure is analytically simulated for each of these stringer configurations. The location, size, and amplitude of the strain field associated with the stringer assembly are sensitive to the assumed geometry and assembly procedure. The von Mises stress distributions from these simulations indicate that localized plasticity will develop around the first eight fasteners for each stringer-feet configuration examined. However, only the toes-up configuration resulted in high assembly hoop strains.
Elastic-plastic response of a piping system due to simulated double-ended guillotine break events
International Nuclear Information System (INIS)
Kussmaul, K.; Diem, H.; Hunger, H.; Katzenmeier, G.
1987-01-01
From the blowdown experiments performed on the HDR feedwater line with feedwater check valve the conclusion can be drawn that high transient loads of up to plastic strains of 3%, acting on an initially integer piping system, can be sustained without loss of integrity for a low number of load cycles due to the plasticizing capacity of the pipework materials nowadays used in reactor technology. In the experiments carried out with ferritic piping of ND 400 pressure peaks up to about 31,5 MPa were achieved which resulted in excessive strains of up to 3%. By nonlinear finite element computations (ABAQUS) it was possible to describe the elastic-plastic behaviour of the piping in a good approximation. (orig./GL)
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 (appearance in a 5-point severity scale. The XPL platform may offer advanced solutions to compromised skin barrier function, pharmaceutical delivery and wound dressings.
Characterizing the Quasi-Static and Dynamic Response of a Non-Contact Magneto-Elastic Torque Sensor
Muller, Brooks
Advances in the development of rolled-sheet magnetostrictive materials led to testing of a prototype wireless magneto-elastic torque (WiMET) sensor using the iron alloy Galfenol. As torque was applied to a shaft, stress-induced changes in the magnetic state of Galfenol that was bonded to the shaft were proportional to the applied torque. Building on that work, this thesis investigates strategies to improve both repeatability and the signal to noise ratio of WiMET sensor output. Multi-physics models of WiMET stress and magnetic states under applied torques are used to improve understanding of sensor operation. Testing to validate simulations is performed using Galfenol and Alfenol, a newer rolled-sheet alloy, for torsional loads of 0 - 200 in-lb, and under quasi-static and dynamic (0 - 2000 RPM) loading conditions. The experimental results presented support the potential of WiMET sensor use for dynamic torque measurement and health monitoring of drive train systems.
Ullm, Sandra; Krüger, Anne; Tondera, Christoph; Gebauer, Tim P; Neffe, Axel T; Lendlein, Andreas; Jung, Friedrich; Pietzsch, Jens
2014-12-01
Hydrogels prepared from gelatin and lysine diisocyanate ethyl ester provide tailorable elastic properties and degradation behavior. Their interaction with human aortic endothelial cells (HAEC) as well as human macrophages (Mɸ) and granulocytes (Gɸ) were explored. The experiments revealed a good biocompatibility, appropriate cell adhesion, and cell infiltration. Direct contact to hydrogels, but not contact to hydrolytic or enzymatic hydrogel degradation products, resulted in enhanced cyclooxygenase-2 (COX-2) expression in all cell types, indicating a weak inflammatory activation in vitro. Only Mɸ altered their cytokine secretion profile after direct hydrogel contact, indicating a comparably pronounced inflammatory activation. On the other hand, in HAEC the expression of tight junction proteins, as well as cytokine and matrix metalloproteinase secretion were not influenced by the hydrogels, suggesting a maintained endothelial cell function. This was in line with the finding that in HAEC increased thrombomodulin synthesis but no thrombomodulin membrane shedding occurred. First in vivo data obtained after subcutaneous implantation of the materials in immunocompetent mice revealed good integration of implants in the surrounding tissue, no progredient fibrous capsule formation, and no inflammatory tissue reaction in vivo. Overall, the study demonstrates the potential of gelatin-based hydrogels for temporal replacement and functional regeneration of damaged soft tissue. Copyright © 2014 Elsevier Ltd. All rights reserved.
Elastic properties of spherically anisotropic piezoelectric composites
International Nuclear Information System (INIS)
En-Bo, Wei; Guo-Qing, Gu; Ying-Ming, Poon
2010-01-01
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. (condensed matter: structure, thermal and mechanical properties)
International Nuclear Information System (INIS)
Mackey, T.C.; Abatt, F.G.; Johnson, K.I.
2009-01-01
The purpose of this study was to determine the sensitivity of the dynamic response of the Hanford double-shell tanks (DSTs) to the assumptions regarding the constitutive properties of the contained waste. In all cases, the waste was modeled as a uniform linearly elastic material. The focus of the study was on the changes in the modal response of the tank and waste system as the extensional modulus (elastic modulus in tension and compression) and shear modulus of the waste were varied through six orders of magnitude. Time-history analyses were also performed for selected cases and peak horizontal reaction forces and axial stresses at the bottom of the primary tank were evaluated. Because the analysis focused on the differences in the responses between solid-filled and liquid-filled tanks, it is a comparative analysis rather than an analysis of record for a specific tank or set of tanks. The shear modulus was varied between 4 x 10 3 Pa and 4.135 x 10 9 Pa. The lowest value of shear modulus was sufficient to simulate the modal response of a liquid-containing tank, while the higher values are several orders of magnitude greater than the upper limit of expected properties for tank contents. The range of elastic properties used was sufficient to show liquid-like response at the lower values, followed by a transition range of semi-solid-like response to a clearly identifiable solid-like response. It was assumed that the mechanical properties of the tank contents were spatially uniform. Because sludge-like materials are expected only to exist in the lower part of the tanks, this assumption leads to an exaggeration of the effects of sludge-like materials in the tanks. The results of the study show that up to a waste shear modulus of at least 40,000 Pa, the modal properties of the tank and waste system are very nearly the same as for the equivalent liquid-containing tank. This suggests that the differences in critical tank responses between liquid-containing tanks and tanks
Cabrera-Fischer, Edmundo I; Bia, Daniel; Zócalo, Yanina; Wray, Sandra; Armentano, Ricardo
2013-12-01
There is a relationship between the intra-aortic balloon pumping (IABP) benefits and the dynamic behavior of muscular arteries, which is associated with induced changes on the vessel walls through an endothelial-dependent mechanism. The arterial wall elastic behavior is influenced by adventitial function; however, no studies were performed in order to elucidate if this layer plays a role in the changes determined by IABP. Our aim was to quantify acute IABP effects on the mechanical properties of muscular arteries in induced acute heart failure (AHF), before and after adventitia removal. Pressure and diameter were recorded in the iliac arteries (IA) of sheep (n = 7), before and during 1:2 IABP: (i) in control state (CS) with intact IA, (ii) in CS after IA adventitia removal, and (iii) in de-adventitialized IA after AHF. Conduit function, compliance and arterial distensibility were calculated in each state. During CS, IABP resulted in intact IA dilatation and in an increase in conduit function, compliance and distensibility; adventitial removal determined an increase of arterial stiffness with respect to the CS, which decreased when IABP was used; the increase in arterial stiffness observed after adventitia removal was also detected in AHF state; IABP improves conduit function and arterial stiffness in de-adventitialized arteries, both before and during AHF. However, the improvement in these properties was lower than in intact arteries. Before and after AHF induction, the improvements of conduit function and arterial distensibility determined by IABP in intact IA were significantly reduced after adventitia removal. Adventitial layer integrity would be necessary to maximize IABP-related beneficial effects on arterial system properties. © 2013 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation.
Zhao, Xin
2013-05-01
Elastic rods have been studied intensively since the 18th century. Even now the theory of elastic rods is still developing and enjoying popularity in computer graphics and physical-based simulation. Elastic rods also draw attention from architects. Architectural structures, NODUS, were constructed by elastic rods as a new method of form-finding. We study discrete models of elastic rods and NODUS structures. We also develop computational tools to find the equilibria of elastic rods and the shape of NODUS. Applications of elastic rods in forming torus knot and closing Bishop frame are included in this thesis.
Elastic and viscoplastic properties
International Nuclear Information System (INIS)
Lebensohn, R.A.
2015-01-01
In this chapter, we review crystal elasticity and plasticity-based self-consistent theories and apply them to the determination of the effective response of polycrystalline aggregates. These mean-field formulations, which enable the prediction of the mechanical behaviour of polycrystalline aggregates based on the heterogeneous and/or directional properties of their constituent single crystal grains and phases, are ideal tools to establish relationships between microstructure and properties of these materials, ubiquitous among fuels and structural materials for nuclear systems. (author)
Cheng, Hongyang; Pellegrino, Antonio; Magnanimo, Vanessa
2017-01-01
A novel approach is presented for calibrating discrete element method (DEM) simulations of granular materials based on the sequential Bayesian parameter estimation over the experimental stress–strain responses. The initial DEM packing is bridged with microscopic computed tomography (microCT) images
Tissue elasticity and the ageing elastic fibre
Sherratt, Michael J.
2009-01-01
The ability of elastic tissues to deform under physiological forces and to subsequently release stored energy to drive passive recoil is vital to the function of many dynamic tissues. Within vertebrates, elastic fibres allow arteries and lungs to expand and contract, thus controlling variations in blood pressure and returning the pulmonary system to a resting state. Elastic fibres are composite structures composed of a cross-linked elastin core and an outer layer of fibrillin microfibrils. Th...
Showa, Sarudzai P; Nyabadza, Farai; Hove-Musekwa, Senelani D; Magombedze, Gesham
2014-01-01
Background The presence of an asymptomatic phase in an HIV infection indicates that the immune system can partially control the infection. Determining the immune mechanisms that contribute significantly to the partial control of the infection enhance the HIV infection intervention strategies and is important in vaccine development. Towards this goal, a discrete time HIV model, which incorporates the life cycle aspects of the virus, the antibody (humoral) response and the cell-mediated immune ...
International Nuclear Information System (INIS)
Darling, T.W.; Migliori, A.; Moshopoulou, E.G.; Trugman, S.A.; Neumeier, J.J.; Sarrao, J.L.; Bishop, A.R.; Thompson, J.D.
1998-01-01
We have measured the (cubic-lattice-approximation) elastic moduli of optical melt-zone-grown single-crystal La 0.83 Sr 0.17 MnO 3 using resonant ultrasound spectroscopy. We observe the structural transition at 285 K to be hysteretic in the ambient (almost zero) magnetic field. A second elastic feature at the ferromagnetic T c 265 K, a third at 252 K, and a fourth in magnetic field at 220 K are also observed in this sample, which sits in a particularly complex region in composition space. The application of a magnetic field changes some of the elastic moduli significantly between 220 K and 285 K. By determining the complete elastic tensor, we identify which cubic crystallographic distortions are strongest at each elastic anomaly and which are sensitive to magnetic field. We also determine which bonds play a role in each of the observed features. copyright 1998 The American Physical Society
Directory of Open Access Journals (Sweden)
Mustapha Lahmar
2015-04-01
Full Text Available On the basis of the V. K. Stokes micro-continuum theory, the effects of couple stresses on the nonlinear dynamic response of the unbalanced Jeffcott’s flexible rotor supported by layered hydrodynamic journal bearings is presented in this paper. A nonlinear transient modified Reynolds’ equation is derived and discretized by the finite element method to obtain the fluid-film pressure field as well as the film thickness by means of the implicit Euler method. The nonlinear orbits of the rotor center are determined by solving the nonlinear differential equations of motion with the explicit Euler’s scheme taking into account the flexibility of rotor. According to the obtained results, the combined effects of couple stresses due to the presence of polymer additives in lubricant and the pressure dependent viscosity on the nonlinear dynamic response of the rotor-bearing system are significant and cannot be ignored or overlooked. As expected, these effects are more noticeable for polymers characterized by higher length molecular chains.
Chen, Pei-Tai; Lin, Chorng-Shyan; Yang, Tachung
2002-09-01
Using a coupled BEM/FEM, this work describes a numerical method to compute the response and acoustic radiation for structures partially immersed in fluid. The structures and their responses are assumed to be symmetric about a symmetric plane. A symmetric complex matrix derived from the BEM and a reciprocal principle for surface acoustics is also used to represent the acoustic loading against the structures. In addition, selecting a proper Green's function based on image source method satisfies the boundary conditions of pressure release on the fluid surface and null normal velocity on the symmetric plane. Moreover, a boundary integral equation emerges when the field point approaches the structural surface where the normal derivative of the Green's function over partial, infinitesimal spheres is evaluated. These limiting values depend on locations of the field point on the surface. Owing to the symmetry of the acoustic loading matrix, the matrix for the coupled BEM/FEM is a banded, symmetric one, thereby allowing us to employ a variable banded storage method and invert of the matrix. Doing so markedly increases computational efficiency. Furthermore, an analytical solution of a spherical thin shell with the lower semi-sphere immersed in water is carried out by characteristic function expansions for shell equation and acoustic loading. These analytical solutions compare with the results obtained from the proposed numerical method. A good correlation for low frequencies is obtained and minor discrepancies are observed with an increasing frequency.
Eringen's theory of Nonlocal Elasticity (cont…)
Indian Academy of Sciences (India)
Eringen's theory of Nonlocal Elasticity (cont…) Integro-Partial differential equations of the above linear nonlocal elasticity have been proposed leading to singular partial differential equations of a special class of ... The scale coefficient in the modeling will lead to small-scale effect on the response of structures in nano-size.
Tissue elasticity and the ageing elastic fibre.
Sherratt, Michael J
2009-12-01
The ability of elastic tissues to deform under physiological forces and to subsequently release stored energy to drive passive recoil is vital to the function of many dynamic tissues. Within vertebrates, elastic fibres allow arteries and lungs to expand and contract, thus controlling variations in blood pressure and returning the pulmonary system to a resting state. Elastic fibres are composite structures composed of a cross-linked elastin core and an outer layer of fibrillin microfibrils. These two components perform distinct roles; elastin stores energy and drives passive recoil, whilst fibrillin microfibrils direct elastogenesis, mediate cell signalling, maintain tissue homeostasis via TGFβ sequestration and potentially act to reinforce the elastic fibre. In many tissues reduced elasticity, as a result of compromised elastic fibre function, becomes increasingly prevalent with age and contributes significantly to the burden of human morbidity and mortality. This review considers how the unique molecular structure, tissue distribution and longevity of elastic fibres pre-disposes these abundant extracellular matrix structures to the accumulation of damage in ageing dermal, pulmonary and vascular tissues. As compromised elasticity is a common feature of ageing dynamic tissues, the development of strategies to prevent, limit or reverse this loss of function will play a key role in reducing age-related morbidity and mortality.
Buschmann, Johanna; Calcagni, Maurizio; Bürgisser, Gabriella Meier; Bonavoglia, Eliana; Neuenschwander, Peter; Milleret, Vincent; Giovanoli, Pietro
2015-05-01
Tendon rupture repair is a surgical field where improvements are still required due to problems such as repeat ruptures, adhesion formation and joint stiffness. In the current study, a reversibly expandable and contractible electrospun tube based on a biocompatible and biodegradable polymer was implanted around a transected and conventionally sutured rabbit Achilles tendon. The material used was DegraPol® (DP), a polyester urethane. To make DP softer, more elastic and surgeon-friendly, the synthesis protocol was slightly modified. Material properties of conventional and new DP film electrospun meshes are presented. At 12 weeks post-surgery, tenocyte and tenoblast density, nuclei and width, collagen fibre structure and inflammation levels were analyzed histomorphometrically. Additionally, a comprehensive histological scoring system by Stoll et al. (2011) was used to compare healing outcomes. Results showed that there were no adverse reactions of the tendon tissue following the implant. No differences were found whether the DP tube was applied or not for both traditional and new DP materials. As a result, the new DP material was shown to be an excellent carrier for delivery of growth factors, stem cells and other agents responsible for tendon healing. Copyright © 2015 John Wiley & Sons, Ltd.
Ungár, Tamás; Harjo, Stefanus; Kawasaki, Takuro; Tomota, Yo; Ribárik, Gábor; Shi, Zengmin
2017-01-01
Based on high-resolution neutron diffraction experiments, we will show that in lath martensite steels, the initially homogeneous dislocation structure, i.e., homogeneous on the length scale of grain size, is disrupted by plastic deformation, which, in turn, produces a composite on the length scale of martensite lath packets. The diffraction patterns of plastically strained martensitic steel reveal characteristically asymmetric peak profiles in the same way as has been observed in materials with heterogeneous dislocation structures. The quasi homogeneous lath structure, formed by quenching, is disrupted by plastic deformation producing a composite structure. Lath packets oriented favorably or unfavorably for dislocation glide become soft or hard. Two lath packet types develop by work softening or work hardening in which the dislocation densities become smaller or larger compared to the initial average dislocation density. The decomposition into soft and hard lath packets is accompanied by load redistribution and the formation of long-range internal stresses between the two lath packet types. The composite behavior of plastically deformed lath martensite opens a new way to understand the elastic-plastic response in this class of materials.
DEFF Research Database (Denmark)
Hansen, Mads Fogtmann; Fagertun, Jens; Larsen, Rasmus
2011-01-01
This paper presents a fusion of the active appearance model (AAM) and the Riemannian elasticity framework which yields a non-linear shape model and a linear texture model – the active elastic appearance model (EAM). The non-linear elasticity shape model is more flexible than the usual linear subs...
International Nuclear Information System (INIS)
Mermaz, M.C.
1984-01-01
Diffraction and refraction play an important role in particle elastic scattering. The optical model treats correctly and simultaneously both phenomena but without disentangling them. Semi-classical discussions in terms of trajectories emphasize the refractive aspect due to the real part of the optical potential. The separation due to to R.C. Fuller of the quantal cross section into two components coming from opposite side of the target nucleus allows to understand better the refractive phenomenon and the origin of the observed oscillations in the elastic scattering angular distributions. We shall see that the real part of the potential is responsible of a Coulomb and a nuclear rainbow which allows to determine better the nuclear potential in the interior region near the nuclear surface since the volume absorption eliminates any effect of the real part of the potential for the internal partial scattering waves. Resonance phenomena seen in heavy ion scattering will be discussed in terms of optical model potential and Regge pole analysis. Compound nucleus resonances or quasi-molecular states can be indeed the more correct and fundamental alternative
The elastic theory of a single DNA molecule
Indian Academy of Sciences (India)
We study the elastic responses of double- (ds) and single-stranded (ss) DNA at external force ﬁelds. A double-strand-polymer elastic model is constructed and solved by path integral methods and Monte Carlo simulations to understand the entropic elasticity, cooperative extensibility, and supercoiling property of dsDNA.
The elastic theory of a single DNA molecule
Indian Academy of Sciences (India)
Abstract. We study the elastic responses of double- (ds) and single-stranded (ss) DNA at exter- nal force fields. A double-strand-polymer elastic model is constructed and solved by path integral methods and Monte Carlo simulations to understand the entropic elasticity, cooperative extensibil- ity, and supercoiling property of ...
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 uncompensated own and cross price-elasticity of demand are here derived for bundle of goods, using the differential approach to demand analysis. Key parameters are: the elasticity of the marginal utility of...
Theory of Spacetime Elasticity
Gusev, Andrei A.; Lurie, Sergey A.
We present the theory of spacetime elasticity and demonstrate that it involves traditional thermoelasticity. Assuming linear-elastic constitutive behavior and using spacetime transversely-isotropic elastic constants, we derive all principal thermodynamic relations of classical thermoelasticity. We introduce the spacetime principle of virtual work, and use it to derive the equations of motion for both reversible and dissipative thermoelastic dynamics. We show that spacetime elasticity directly implies the Fourier and the Maxwell-Cattaneo laws of heat conduction. However, spacetime elasticity is richer than classical thermoelasticity, and it advocates its own equations of motion for coupled thermoelasticity, complemented by the spectrum of boundary and interface conditions. We argue that the presented framework of spacetime elasticity should prove adequate for describing the thermoelastic phenomena occurring at low temperatures, for interpreting the results of molecular simulations of heat conduction in solids, and also for the optimal heat and stress management in the microelectronic components and the thermoelectric devices.
Paro, Alberto
2013-01-01
Written in an engaging, easy-to-follow style, the recipes will help you to extend the capabilities of ElasticSearch to manage your data effectively.If you are a developer who implements ElasticSearch in your web applications, manage data, or have decided to start using ElasticSearch, this book is ideal for you. This book assumes that you've got working knowledge of JSON and Java
DEFF Research Database (Denmark)
Andersen, Lars; Nielsen, Søren R. K.
2003-01-01
The paper deals with the boundary element method formulation of the steady-state wave propagation through elastic media due to a source moving with constant velocity. The Greens' function for the three-dimensional full-space is formulated in a local frame of reference following the source. This i...
Haber, Cassandra Kay; Ritchie, Laura J; Strike, Siobhan C
2018-04-01
In a dynamic elastic response prosthesis (DERP), spring-like properties aim to replace the loss of musculature and soft tissues and optimise dynamic movement biomechanics, yet higher intact limb (IL) loading exists. It is unknown how amputees wearing a DERP will perform in start-stop movements and how altering the prosthetic stiffness will influence the performance and loading. This study assessed movement dynamics through comparisons in spatiotemporal, kinematic and kinetic variables and leg stiffness of intact, prosthetic and control limbs. The effect of prosthetic stiffness on movement dynamics was also determined. Eleven male unilateral transtibial amputees performed a start-stop task with one DERP set at two different stiffness - Prescribed and Stiffer. Eleven control participants performed the movement with the dominant limb. Kinematic and kinetic data were collected by a twelve-camera motion capture system synchronised with a Kistler force platform. Selected variables were compared between intact, prosthetic and control limbs, and against prosthetic stiffness using ANOVA and effect size. Pearson's Correlation was used to analyse relationship between leg stiffness and prosthetic deflection. Amputees showed a more horizontal approach to the bound during the start-stop movement, with lower horizontal velocities and a longer stance time on the IL compared to controls. In both stiffness conditions, the IL showed selected higher anteroposterior and vertical forces and impulses when compared to the controls. Leg stiffness was not significantly different between limbs as a result of the interplay between angle swept and magnitude of force, even with the change in prosthetic stiffness. A main effect for prosthetic stiffness was found only in higher impact forces of the prosthetic limb and more horizontal touchdown angles of the IL when using the prescribed DERP. In conclusion, amputees achieve the movement with a horizontal approach when compared to controls which
Paro, Alberto
2015-01-01
If you are a developer who implements ElasticSearch in your web applications and want to sharpen your understanding of the core elements and applications, this is the book for you. It is assumed that you've got working knowledge of JSON and, if you want to extend ElasticSearch, of Java and related technologies.
DEFF Research Database (Denmark)
Pan, E.; Chen, J.Y.; Bevis, M.
2015-01-01
We present an analytical solution for the elastic deformation of an elastic, transversely isotropic, layered and self-gravitating Earth by surface loads. We first introduce the vector spherical harmonics to express the physical quantities in the layered Earth. This reduces the governing equations...... the correctness of our solution and the implementation. We also calculate the load Love numbers (LLNs) of the PREM Earth for different degrees of the Legendre function for both isotropic and transversely isotropic, layered mantles with different core models, demonstrating for the first time the effect of Earth...... to a linear system of equations for the expansion coefficients. We then solve for the expansion coefficients analytically under the assumption (i.e. approximation) that in the mantle, the density in each layer varies as 1/r (where r is the radial coordinate) while the gravity is constant and that in the core...
Gelb, Arthur F; Yamamoto, Alfred; Verbeken, Eric K; Nadel, Jay A
2015-08-01
Investigators believe most patients with asthma have reversible airflow obstruction with treatment, despite airway remodeling and hyperresponsiveness. There are smokers with chronic expiratory airflow obstruction despite treatment who have features of both asthma and COPD. Some investigators refer to this conundrum as the asthma-COPD overlap syndrome (ACOS). Furthermore, a subset of treated nonsmokers with moderate to severe asthma have persistent expiratory airflow limitation, despite partial reversibility. This residuum has been assumed to be due to large and especially small airway remodeling. Alternatively, we and others have described reversible loss of lung elastic recoil in acute and persistent loss in patients with moderate to severe chronic asthma who never smoked and its adverse effect on maximal expiratory airflow. The mechanism(s) responsible for loss of lung elastic recoil and persistent expiratory airflow limitation in nonsmokers with chronic asthma consistent with ACOS remain unknown in the absence of structure-function studies. Recently we reported a new pathophysiologic observation in 10 treated never smokers with asthma with persistent expiratory airflow obstruction, despite partial reversibility: All 10 patients with asthma had a significant decrease in lung elastic recoil, and unsuspected, microscopic mild centrilobular emphysema was noted in all three autopsies obtained although it was not easily identified on lung CT scan. These sentinel pathophysiologic observations need to be confirmed to further unravel the epiphenomenon of ACOS. The proinflammatory and proteolytic mechanism(s) leading to lung tissue breakdown need to be further investigated.
Directory of Open Access Journals (Sweden)
Lorenzo Sabatelli
Full Text Available 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.
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.
Elastic scattering phenomenology
Energy Technology Data Exchange (ETDEWEB)
Mackintosh, R.S. [The Open University, School of Physical Sciences, Milton Keynes (United Kingdom)
2017-04-15
We argue that, in many situations, fits to elastic scattering data that were historically, and frequently still are, considered ''good'', are not justifiably so describable. Information about the dynamics of nucleon-nucleus and nucleus-nucleus scattering is lost when elastic scattering phenomenology is insufficiently ambitious. It is argued that in many situations, an alternative approach is appropriate for the phenomenology of nuclear elastic scattering of nucleons and other light nuclei. The approach affords an appropriate means of evaluating folding models, one that fully exploits available empirical data. It is particularly applicable for nucleons and other light ions. (orig.)
Elastic magnetic electron scattering
International Nuclear Information System (INIS)
Sick, I.
1985-01-01
The paper surveys the field of elastic magnetic electron scattering. Magnetic scattering as a configuration analyzer; magnetic form factors of high multipole order; absolute spectroscopic factors; and non-nucleonic constituents; are all discussed. (U.K.)
Statistical mechanics of elasticity
Weiner, JH
2012-01-01
Advanced, self-contained treatment illustrates general principles and elastic behavior of solids. Topics include thermoelastic behavior of crystalline and polymeric solids, interatomic force laws, behavior of solids, and thermally activated processes. 1983 edition.
An analytical description for the elastic compression of metallic polyhedral nanoparticles
Directory of Open Access Journals (Sweden)
L. Yang
2016-08-01
Full Text Available Metallic nanoparticles are usually polyhedrons instead of perfect spheres, which presents a challenge to characterize their elastic response. In the present paper, the elastic compression of truncated octahedral nanoparticles is investigated through finite element calculations and atomic simulations. An analytical expression of load is obtained for octahedral particles, which is linearly proportional to indent depth, instead of the 3/2 power law relation predicted by Hertzian model for elastic sphere. Comparisons with molecular dynamics simulations demonstrate that the obtained relation can predict the elastic response of polyhedral nanoparticles. This study is helpful to measure the elastic properties of polyhedral nanoparticles, and characterize their elastic response.
Kuc, Rafal
2013-01-01
A practical tutorial that covers the difficult design, implementation, and management of search solutions.Mastering ElasticSearch is aimed at to intermediate users who want to extend their knowledge about ElasticSearch. The topics that are described in the book are detailed, but we assume that you already know the basics, like the query DSL or data indexing. Advanced users will also find this book useful, as the examples are getting deep into the internals where it is needed.
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.
Orthodontic elastic materials.
Wong, A K
1976-04-01
Latex elastics and synthetic elastomers have certain similarities and differences. In the fracture tests the latex elastics showed a greater amount of loss in strength than plastic elastomers when stretched over a 21 day period. There is a great variability, as much as 50%, in the tensile strength of the plastic materials taken from the same batch and stretched under the same conditions. The Ormco Power Chain was more resilient than the Unitek AlastiK chain. The Unitek AlastiKs had more force and stretched less. The force decay of synthetic elastomers, stretched over a specific length and time, exhibited a great loss in force. This loss could be as great as 73% during the first day. The decay of force continued at a slower rate during the rest of the 21 day period. Unitek AlastiK C2 double links, when stretched 17 millimeters, had a higher initial force averaging 641 grams (22.5 ounces) than the Ormco Power Chain which averages 342 grams (12.0 ounces). In one day the force was reduced to 171 grams (6.0 ounces) for both materials. The elastic materials within the same batch showed a great variation in the modulus of elasticity under different test conditions. The approximate force generated when stretched dry, within the elastic limit, was 22 grams per millimeter for 3/16 inches heavy latex elastics. The Unitek AlastiK C2 gave a force of 89 grams per millimeter, while the Ormco Power Chain had a value of 46 grams per millimeter. The modulus of elasticity of all of the materials was much lower after immersion in the water bath. The force decay under constant force application to latex, elastic, polymer chains, and tied loops showed that the greatest amount of force decay occurred during the first three hours in the water bath. The forces remained relatively the same throughout the rest of the test period. The elastic materials undergo permanent deformation in shape. The synthetic elastomers exhibited plastic deformation when the elastomers were stretched 17
Nonlinear elastic waves in materials
Rushchitsky, Jeremiah J
2014-01-01
The main goal of the book is a coherent treatment of the theory of propagation in materials of nonlinearly elastic waves of displacements, which corresponds to one modern line of development of the nonlinear theory of elastic waves. The book is divided on five basic parts: the necessary information on waves and materials; the necessary information on nonlinear theory of elasticity and elastic materials; analysis of one-dimensional nonlinear elastic waves of displacement – longitudinal, vertically and horizontally polarized transverse plane nonlinear elastic waves of displacement; analysis of one-dimensional nonlinear elastic waves of displacement – cylindrical and torsional nonlinear elastic waves of displacement; analysis of two-dimensional nonlinear elastic waves of displacement – Rayleigh and Love nonlinear elastic surface waves. The book is addressed first of all to people working in solid mechanics – from the students at an advanced undergraduate and graduate level to the scientists, professional...
Energy Technology Data Exchange (ETDEWEB)
Atac, Hamza [Temple University, Philadelphia, PA
2017-12-01
The Coulomb Sum is defined by the quasi-elastic nucleon knock-out process and it is the integration of the longitudinal response function over the energy loss of the incident electron. The Coulomb sum goes to the total charge at large q. The existing measurements of the Coulomb Sum Rule show disagreement with the theoretical calculations for the medium and heavy nuclei. To find the reason behind the disagreement might answer the question of whether the properties of the nucleons are affected by the nuclear medium or not. In order to determine the Coulomb Sum in nuclei, a precision measurement of inclusive electron scattering in the quasi-elastic region was performed at the Thomas Jefferson National Accelerator Facility. Incident electrons with energies ranging from 0.4 GeV to 4 GeV scattered off 4He,12C,56Fe and 208Pb nuclei at four scattering angles (15 deg.; 60 deg.; 90 deg.; 120 deg.) and scattered energies ranging from 0.1 GeV to 4 GeV. The Born cross sections were extracted for the Left High Resolution Spectrometer (LHRS) and the Right High Resolution Spectrometer 56Fe data. The Rosenbluth separation was performed to extract the transverse and longitudinal response functions at 650 MeV three-momentum transfer. The preliminary results of the longitudinal and transverse functions were extracted for 56Fe target at 650 MeV three-momentum transfer.
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.
International Nuclear Information System (INIS)
Das, Y.C.; Kedia, K.K.
1977-01-01
No realistic analytical work in the area of Shells on Elastic Foundations has been reported in the literature. Various foundation models have been proposed by several authors. These models involve one or more than one parameters to characterise the foundation medium. Some of these models cannot be used to derive the basic equations governing the behaviour of shells on elastic foundations. In the present work, starting from an elastic continuum hypothesis, a mathematical model for foundation has been derived in curvilinear orthogonal coordinates by the help of principle of virtual displacements, treating one of the virtual displacements as known to satisfy certain given conditions at its edge surfaces. In this model, several foundation parameters can be considered and it can also be used for layered medium of both finite and infinite thickness. (Auth.)
Elastic anisotropy of crystals
Directory of Open Access Journals (Sweden)
Christopher M. Kube
2016-09-01
Full Text Available 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 provides an anisotropy table giving the values of AL for 2,176 crystallite compounds.
Elastic plastic fracture mechanics
International Nuclear Information System (INIS)
Simpson, L.A.
1978-07-01
The application of linear elastic fracture mechanics (LEFM) to crack stability in brittle structures is now well understood and widely applied. However, in many structural materials, crack propagation is accompanied by considerable crack-tip plasticity which invalidates the use of LEFM. Thus, present day research in fracture mechanics is aimed at developing parameters for predicting crack propagation under elastic-plastic conditions. These include critical crack-opening-displacement methods, the J integral and R-curve techniques. This report provides an introduction to these concepts and gives some examples of their applications. (author)
Rogozinski, Marek
2014-01-01
This book is a detailed, practical, hands-on guide packed with real-life scenarios and examples which will show you how to implement an ElasticSearch search engine on your own websites.If you are a web developer or a user who wants to learn more about ElasticSearch, then this is the book for you. You do not need to know anything about ElastiSeach, Java, or Apache Lucene in order to use this book, though basic knowledge about databases and queries is required.
Lai, Yun
2011-06-26
Metamaterials can exhibit electromagnetic and elastic characteristics beyond those found in nature. In this work, we present a design of elastic metamaterial that exhibits multiple resonances in its building blocks. Band structure calculations show two negative dispersion bands, of which one supports only compressional waves and thereby blurs the distinction between a fluid and a solid over a finite frequency regime, whereas the other displays super anisotropy-in which compressional waves and shear waves can propagate only along different directions. Such unusual characteristics, well explained by the effective medium theory, have no comparable analogue in conventional solids and may lead to novel applications. © 2011 Macmillan Publishers Limited. All rights reserved.
Directory of Open Access Journals (Sweden)
Sergio Cesare Masin
2010-01-01
Full Text Available 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 either in series or in parallel. This total elongation was longer for serial than for parallel springs, and increased proportionally to the number of serial springs and inversely proportionally to the number of parallel springs. The results suggest that participants integrated load weight with imagined elasticity rather than with spring length.
Measuring global gasoline and diesel price and income elasticities
International Nuclear Information System (INIS)
Dahl, Carol A.
2012-01-01
Price and income elasticities of transport fuel demand have numerous applications. They help forecast increases in fuel consumption as countries get richer, they help develop appropriate tax policies to curtail consumption, help determine how the transport fuel mix might evolve, and show the price response to a fuel disruption. Given their usefulness, it is understandable why hundreds of studies have focused on measuring such elasticities for gasoline and diesel fuel consumption. In this paper, I focus my attention on price and income elasticities in the existing studies to see what can be learned from them. I summarize the elasticities from these historical studies. I use statistical analysis to investigate whether income and price elasticities seem to be constant across countries with different incomes and prices. Although income and price elasticities for gasoline and diesel fuel are not found to be the same at high and low incomes and at high and low prices, patterns emerge that allow me to develop suggested price and income elasticities for gasoline and diesel demand for over one hundred countries. I adjust these elasticities for recent fuel mix policies, and suggest an agenda of future research topics. - Research highlights: ► Surveyed econometric studies of transport fuel demand. ► Developed price elasticities of demand for gasoline and diesel fuel for 120 countries. ► Developed income elasticities of demand for gasoline and diesel fuel for 120 countries. ► Suggested a research agenda for future work.
The Measurement of Tax Elasticity in India: A Time Series Approach
Acharya, Hem
2011-01-01
Revenue generation is an important goal of tax reform. The built-in responsiveness of revenues to changes in income, tax elasticity, provides very critical information for tax policy formulation. This paper utilises a time series approach to empirically estimate tax elasticities for India for the period 1991-2010. Tax elasticities are computed for income, turnover, excise, import and total taxes for the post-reform period. The elasticity coefficients reveal a low responsiveness of taxes to i...
The real-time price elasticity of electricity
Lijesen, M.G.
2007-01-01
The real-time price elasticity of electricity contains important information on the demand response of consumers to the volatility of peak prices. Despite the importance, empirical estimates of the real-time elasticity are hardly available. This paper provides a quantification of the real-time
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…
Norsworthy, Mark A.; Ruch, Marc L.; Hamel, Michael C.; Clarke, Shaun D.; Hausladen, Paul A.; Pozzi, Sara A.
2018-03-01
We present the first measurements of energy-dependent light output from carbon recoils in the liquid organic scintillator EJ-309. For this measurement, neutrons were produced by an associated particle deuterium-tritium generator and scattered by a volume of EJ-309 scintillator into stop detectors positioned at four fixed angles. Carbon recoils in the scintillator were isolated using triple coincidence among the associated particle detector, scatter detector, and stop detectors. The kinematics of elastic and inelastic scatter allowed data collection at eight specific carbon recoil energies between 2.86 and 3.95 MeV. We found the light output caused by carbon recoils in this energy range to be approximately 1.14% of that caused by electrons of the same energy, which is comparable to the values reported for other liquid organic scintillators. A comparison of the number of scattered neutrons at each angle to a Monte Carlo N-Particle eXtended simulation indicates that the ENDF/B-VII.1 evaluation of differential cross sections for 14.1 MeV neutrons on carbon has discrepancies with the experiment as large as 55%, whereas those reported in the JENDL-4.0u evaluation agree with experiment.
Non-linear elastic deformations
Ogden, R W
1997-01-01
Classic in the field covers application of theory of finite elasticity to solution of boundary-value problems, analysis of mechanical properties of solid materials capable of large elastic deformations. Problems. References.
Designing interactively with elastic splines
DEFF Research Database (Denmark)
Brander, David; Bærentzen, Jakob Andreas; Fisker, Ann-Sofie
2018-01-01
We present an algorithm for designing interactively with C1 elastic splines. The idea is to design the elastic spline using a C1 cubic polynomial spline where each polynomial segment is so close to satisfying the Euler-Lagrange equation for elastic curves that the visual difference becomes neglig...... negligible. Using a database of cubic Bézier curves we are able to interactively modify the cubic spline such that it remains visually close to an elastic spline....
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 delasticity) and a=1-4/9(2-d)+... (long-ranged elasticity). We show how the dynamical theory recovers the avalanche-size distribution
Elasticity in Elastics-An in-vitro study.
Kamisetty, Supradeep Kumar; Nimagadda, Chakrapani; Begam, Madhoom Ponnachi; Nalamotu, Raghuveer; Srivastav, Trilok; Gs, Shwetha
2014-04-01
Orthodontic tooth movement results from application of forces to teeth. Elastics in orthodontics have been used both intra-orally and extra- orally to a great effect. Their use, combined with good patient co-operation provides the clinician with the ability to correct both anteroposterior and vertical discrepancies. Force decay over a period of time is a major problem in the clinical usage of latex elastics and synthetic elastomers. This loss of force makes it difficult for the clinician to determine the actual force transmitted to the dentition. It's the intent of the clinician to maintain optimal force values over desired period of time. The majority of the orthodontic elastics on the market are latex elastics. Since the early 1990s, synthetic products have been offered in the market for latex-sensitive patients and are sold as nonlatex elastics. There is limited information on the risk that latex elastics may pose to patients. Some have estimated that 0.12-6% of the general population and 6.2% of dental professionals have hypersensitivity to latex protein. There are some reported cases of adverse reactions to latex in the orthodontic population but these are very limited to date. Although the risk is not yet clear, it would still be inadvisable to prescribe latex elastics to a patient with a known latex allergy. To compare the in-vitro performance of latex and non latex elastics. Samples of 0.25 inch, latex and non latex elastics (light, medium, heavy elastics) were obtained from three manufacturers (Forestadent, GAC, Glenroe) and a sample size of ten elastics per group was tested. The properties tested included cross sectional area, internal diameter, initial force generated by the elastics, breaking force and the force relaxation for the different types of elastics. Force relaxation testing involved stretching the elastics to three times marketed internal diameter (19.05 mm) and measuring force level at intervals over a period of 48 hours. The data were
Introduction to linear elasticity
Gould, Phillip L
2013-01-01
Introduction to Linear Elasticity, 3rd Edition, provides an applications-oriented grounding in the tensor-based theory of elasticity for students in mechanical, civil, aeronautical, and biomedical engineering, as well as materials and earth science. The book is distinct from the traditional text aimed at graduate students in solid mechanics by introducing the subject at a level appropriate for advanced undergraduate and beginning graduate students. The author's presentation allows students to apply the basic notions of stress analysis and move on to advanced work in continuum mechanics, plasticity, plate and shell theory, composite materials, viscoelasticity and finite method analysis. This book also: Emphasizes tensor-based approach while still distilling down to explicit notation Provides introduction to theory of plates, theory of shells, wave propagation, viscoelasticity and plasticity accessible to advanced undergraduate students Appropriate for courses following emerging trend of teaching solid mechan...
Bashur, Chris A.; Venkataraman, Lavanya; Ramamurthi, Anand
2012-01-01
Cardiovascular tissues exhibit architecturally complex extracellular matrices, of which the elastic matrix forms a major component. The elastic matrix critically maintains native structural configurations of vascular tissues, determines their ability to recoil after stretch, and regulates cell signaling pathways involved in morphogenesis, injury response, and inflammation via biomechanical transduction. The ability to tissue engineer vascular replacements that incorporate elastic matrix super...
Two Propositions on the Application of Point Elasticities to Finite Price Changes.
Daskin, Alan J.
1992-01-01
Considers counterintuitive propositions about using point elasticities to estimate quantity changes in response to price changes. Suggests that elasticity increases with price along a linear demand curve, but falling quantity demand offsets it. Argues that point elasticity with finite percentage change in price only approximates percentage change…
Elastic properties of Gum Metal
International Nuclear Information System (INIS)
Kuramoto, Shigeru; Furuta, Tadahiko; Hwang, Junghwan; Nishino, Kazuaki; Saito, Takashi
2006-01-01
In situ X-ray diffraction measurements under tensile loading and dynamic mechanical analysis were performed to investigate the mechanisms of elastic deformation in Gum Metal. Tensile stress-strain curves for Gum Metal indicate that cold working substantially decreases the elastic modulus while increasing the yield strength, thereby confirming nonlinearity in the elastic range. The gradient of each curve decreased continuously to about one-third its original value near the elastic limit. As a result of this decrease in elastic modulus and nonlinearity, elastic deformability reaches 2.5% after cold working. Superelasticity is attributed to stress-induced martensitic transformations, although the large elastic deformation in Gum Metal is not accompanied by a phase transformation
Impact loads on beams on elastic foundations
International Nuclear Information System (INIS)
Kameswara Rao, N.S.V.; Prasad, B.B.
1975-01-01
Quite often, complex structural components are idealised as beams in engineering analysis and design. Also, equations governing the responses of shallow shells are mathematically equivalent to the equations governing the responses of beams on elastic foundations. Hence with possible applications in several technical disciplines, the behaviour of beams on elastic foundations subjected to impact loads is studied in detail in the present investigation both analytically and experimentally. The analytical methods include analysis and energy method. The effect of foundation parameters (stiffness, and damping constants) on the dynamic responses of the beam-foundation system has been analysed. In modal analysis, the free-vibration equation has been solved by replacing the applied impulse by suitable initial conditions and the solution has been obtained as the linear combination of an infinite sequence of discrete eigen-vectors. In the energy method, the beam-foundation system is treated to be under forced vibrations and the forcing function has been obtained using the Hertz's law of impact. In the case of free-free end conditions of the beam, the rigid body modes and the elastic modes have been superposed to obtain the total response. The responses predicted using modal analysis are higher than those obtained using energy method. From the present study it is observed that model analysis is preferable to energy method. (Auth.)
Mathematical foundations of elasticity
Marsden, Jerrold E
1994-01-01
This advanced-level study approaches mathematical foundations of three-dimensional elasticity using modern differential geometry and functional analysis. It is directed to mathematicians, engineers and physicists who wish to see this classical subject in a modern setting with examples of newer mathematical contributions. Prerequisites include a solid background in advanced calculus and the basics of geometry and functional analysis.The first two chapters cover the background geometry ― developed as needed ― and use this discussion to obtain the basic results on kinematics and dynamics of con
1995-01-01
7.2 Planetary rover 75 7.3 Biped Robot 76 8 Conclusions 77 8.1 Review of Thesis 77 8.2 Further Work 77 List of Figures 1-1 Schematic of...have only four degrees of freedom, and a simple gripper. 75 76 CHAPTER 7. APPLICATIONS Figure 7-1: Photograph of robot arm 7.3 Biped Robot ...Another group at MIT is building a biped walking robot using series elastic actuators. The design of the actuators differs in that instead of using a
WE-E-9A-01: Ultrasound Elasticity
Energy Technology Data Exchange (ETDEWEB)
Emelianov, S [University of Texas at Austin, Austin, TX (United States); Hall, T [University of WI-Madison, Madison, WI (United States); Bouchard, R [UT MD Anderson Cancer Center and UTHSC at Houston Graduate School of Biomed, Houston, TX (United States)
2014-06-15
Principles and techniques of ultrasound-based elasticity imaging will be presented, including quasistatic strain imaging, shear wave elasticity imaging, and their implementations in available systems. Deeper exploration of quasistatic methods, including elastic relaxation, and their applications, advantages, artifacts and limitations will be discussed. Transient elastography based on progressive and standing shear waves will be explained in more depth, along with applications, advantages, artifacts and limitations, as will measurement of complex elastic moduli. Comparisons will be made between ultrasound radiation force techniques, MR elastography, and the simple A mode plus mechanical plunger technique. Progress in efforts, such as that by the Quantitative Imaging Biomarkers Alliance, to reduce the differences in the elastic modulus reported by different commercial systems will be explained. Dr. Hall is on an Advisory Board for Siemens Ultrasound and has a research collaboration with them, including joint funding by R01CA140271 for nonlinear elasticity imaging. Learning Objectives: Be reminded of the long history of palpation of tissue elasticity for critical medical diagnosis and the relatively recent advances to be able to image tissue strain in response to an applied force. Understand the differences between shear wave speed elasticity measurement and imaging and understand the factors affecting measurement and image frame repletion rates. Understand shear wave propagation effects that can affect measurements, such as essentially lack of propagation in fluids and boundary effects, so important in thin layers. Know characteristics of available elasticity imaging phantoms, their uses and limitations. Understand thermal and cavitational limitations affecting radiation force-based shear wave imaging. Have learning and references adequate to for you to use in teaching elasticity imaging to residents and technologists. Be able to explain how elasticity measurement
WE-E-9A-01: Ultrasound Elasticity
International Nuclear Information System (INIS)
Emelianov, S; Hall, T; Bouchard, R
2014-01-01
Principles and techniques of ultrasound-based elasticity imaging will be presented, including quasistatic strain imaging, shear wave elasticity imaging, and their implementations in available systems. Deeper exploration of quasistatic methods, including elastic relaxation, and their applications, advantages, artifacts and limitations will be discussed. Transient elastography based on progressive and standing shear waves will be explained in more depth, along with applications, advantages, artifacts and limitations, as will measurement of complex elastic moduli. Comparisons will be made between ultrasound radiation force techniques, MR elastography, and the simple A mode plus mechanical plunger technique. Progress in efforts, such as that by the Quantitative Imaging Biomarkers Alliance, to reduce the differences in the elastic modulus reported by different commercial systems will be explained. Dr. Hall is on an Advisory Board for Siemens Ultrasound and has a research collaboration with them, including joint funding by R01CA140271 for nonlinear elasticity imaging. Learning Objectives: Be reminded of the long history of palpation of tissue elasticity for critical medical diagnosis and the relatively recent advances to be able to image tissue strain in response to an applied force. Understand the differences between shear wave speed elasticity measurement and imaging and understand the factors affecting measurement and image frame repletion rates. Understand shear wave propagation effects that can affect measurements, such as essentially lack of propagation in fluids and boundary effects, so important in thin layers. Know characteristics of available elasticity imaging phantoms, their uses and limitations. Understand thermal and cavitational limitations affecting radiation force-based shear wave imaging. Have learning and references adequate to for you to use in teaching elasticity imaging to residents and technologists. Be able to explain how elasticity measurement
Modeling Pseudo-elastic Behavior of Springback
International Nuclear Information System (INIS)
Xia, Z. Cedric
2005-01-01
constant. In the context of this investigation we refer psuedoelastic behavior in the most general sense as any deviation from linearity in the unloading curve. The non-linearity leads to a hysteresis loop upon reloading. The approach is based on the non-conventional theory with a vanishing elastic region as advanced by Dafalias and Popov. The treatment is purely phenomenological where we don't distinguish between macroscopic plasticity and micro-plasticity. The macroscopic uniaxial stress-strain curve is used to define effective plastic response in the same manner as classical plasticity theory except that the nonlinearity during unloading and reloading are incorporated into plasticity. It is shown that such models can be easily formulated within the context of elastoplasticity without violating any physical mechanisms of deformation. Springback for a plane strain bending model is used to demonstrate the potential effect if such a model is applied
Negative stiffness honeycombs as tunable elastic metamaterials
Goldsberry, Benjamin M.; Haberman, Michael R.
2018-03-01
Acoustic and elastic metamaterials are media with a subwavelength structure that behave as effective materials displaying atypical effective dynamic properties. These material systems are of interest because the design of their sub-wavelength structure allows for direct control of macroscopic wave dispersion. One major design limitation of most metamaterial structures is that the dynamic response cannot be altered once the microstructure is manufactured. However, the ability to modify wave propagation in the metamaterial with an external stimulus is highly desirable for numerous applications and therefore remains a significant challenge in elastic metamaterials research. In this work, a honeycomb structure composed of a doubly periodic array of curved beams, known as a negative stiffness honeycomb (NSH), is analyzed as a tunable elastic metamaterial. The nonlinear static elastic response that results from large deformations of the NSH unit cell leads to a large variation in linear elastic wave dispersion associated with infinitesimal motion superposed on the externally imposed pre-strain. A finite element model is utilized to model the static deformation and subsequent linear wave motion at the pre-strained state. Analysis of the slowness surface and group velocity demonstrates that the NSH exhibits significant tunability and a high degree of anisotropy which can be used to guide wave energy depending on static pre-strain levels. In addition, it is shown that partial band gaps exist where only longitudinal waves propagate. The NSH therefore behaves as a meta-fluid, or pentamode metamaterial, which may be of use for applications of transformation elastodynamics such as cloaking and gradient index lens devices.
Nonlinear elastic behavior of rocks revealed by dynamic acousto-elastic testing
Shokouhi, Parisa; Riviere, Jacques; Guyer, Robert; Johnson, Paul
2017-04-01
Nonlinear elastic behavior of rocks is studied at the laboratory scale with the goal of illuminating observations at the Earth scale, for instance during strong ground motion and earthquake slip processes. A technique called Dynamic Acousto-Elastic Testing (DAET) is used to extract the nonlinear elastic response of disparate rocks (sandstone, granite and soapstone). DAET is the dynamic analogous to standard (quasi-static) acousto-elastic testing. It consists in measuring speed of sound with high-frequency low amplitude pulses (MHz range) across the sample while it is dynamically loaded with a low frequency, large amplitude resonance (kHz range). This particular configuration provides the instantaneous elastic response over a full dynamic cycle and reveals unprecedented details: instantaneous softening, tension/compression asymmetry as well as hysteretic behaviors. The strain-induced modulation of ultrasonic pulse velocities ('fast dynamics') is analyzed to extract nonlinearity parameters. A projection method is used to extract the harmonic content and a careful comparison of the fast dynamics response is made. In order to characterize the rate of elastic recovery ('slow dynamics'), we continue to monitor the ultrasonic wave velocity for about 30 minutes after the low-frequency resonance is turned off. In addition, the frequency, pressure and humidity dependences of the nonlinear parameters are reported for a subset of samples. We find that the nonlinear components can be clustered into two categories, which suggests that two main mechanisms are at play. The first one, related to the second harmonic, is likely related to the opening/closing of microstructural features such as cracks and grain/grain contacts. In contrast, the second mechanism is related to all other nonlinear parameters (transient softening, hysteresis area and higher order harmonics) and may arise from shearing mechanisms at grain interfaces.
Advances in biomimetic regeneration of elastic matrix structures.
Sivaraman, Balakrishnan; Bashur, Chris A; Ramamurthi, Anand
2012-10-01
Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of normal native elastic tissues in the body. In diseased tissues, the chronic overexpression of proteolytic enzymes can cause significant matrix degradation, to further limit the accumulation and quality (e.g., fiber formation) of newly deposited elastic matrix. This review provides an overview of the role and importance of elastin and elastic matrix in soft tissues, the challenges to elastic matrix generation in vitro and to regenerative elastic matrix repair in vivo, current biomolecular strategies to enhance elastin deposition and matrix assembly, and the need to concurrently inhibit proteolytic matrix disruption for improving the quantity and quality of elastogenesis. The review further presents biomaterial-based options using scaffolds and nanocarriers for spatio-temporal control over the presentation and release of these biomolecules, to enable biomimetic assembly of clinically relevant native elastic matrix-like superstructures. Finally, this review provides an overview of recent advances and prospects for the application of these strategies to regenerating tissue-type specific elastic matrix structures and superstructures.
Design guidance for elastic followup
Energy Technology Data Exchange (ETDEWEB)
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.
Energy Technology Data Exchange (ETDEWEB)
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.
Elastic regimes of subisostatic athermal fiber networks
Licup, A. J.; Sharma, A.; MacKintosh, F. C.
2016-01-01
Athermal models of disordered fibrous networks are highly useful for studying the mechanics of elastic networks composed of stiff biopolymers. The underlying network architecture is a key aspect that can affect the elastic properties of these systems, which include rich linear and nonlinear elasticity. Existing computational approaches have focused on both lattice-based and off-lattice networks obtained from the random placement of rods. It is not obvious, a priori, whether the two architectures have fundamentally similar or different mechanics. If they are different, it is not clear which of these represents a better model for biological networks. Here, we show that both approaches are essentially equivalent for the same network connectivity, provided the networks are subisostatic with respect to central force interactions. Moreover, for a given subisostatic connectivity, we even find that lattice-based networks in both two and three dimensions exhibit nearly identical nonlinear elastic response. We provide a description of the linear mechanics for both architectures in terms of a scaling function. We also show that the nonlinear regime is dominated by fiber bending and that stiffening originates from the stabilization of subisostatic networks by stress. We propose a generalized relation for this regime in terms of the self-generated normal stresses that develop under deformation. Different network architectures have different susceptibilities to the normal stress but essentially exhibit the same nonlinear mechanics. Such a stiffening mechanism has been shown to successfully capture the nonlinear mechanics of collagen networks.
Price Elasticity of Alcohol Demand in India.
Kumar, Santosh
2017-05-01
Using a household survey conducted in 2014, this study estimates price elasticity of demand (PED) for beer, country liquor and spirits in India. Ordinary least-square models were used to estimate the responsiveness in alcohol demand due to price change. A large number of control variables were included to adjust for potential confounding in the model. Inter-district variation in alcohol consumption is adjusted for by including district fixed effects. Alcohol prices are negatively associated with demand for alcoholic beverages. The PED ranged from -0.14 for spirits to -0.46 for country liquor. Low level of education was positively associated with spirits consumption. The magnitude of elasticity varied by rural-urban, education and gender. Results indicate that a policy mix of price controls and awareness campaigns would be most effective in tackling the adverse effects of harmful drinking in India. The demand for beer, country liquor and spirits is negatively associated with its own price. The elasticity estimates ranged from -0.14 for spirits to -0.44 for country liquor. The elasticity estimates varied by rural-urban, gender and by education levels of the drinkers. © The Author 2017. Medical Council on Alcohol and Oxford University Press. All rights reserved
Recent advances in elasticity, viscoelasticity and inelasticity
Rajagopal, KR
1995-01-01
This is a collection of papers dedicated to Prof T C Woo to mark his 70th birthday. The papers focus on recent advances in elasticity, viscoelasticity and inelasticity, which are related to Prof Woo's work. Prof Woo's recent work concentrates on the viscoelastic and viscoplastic response of metals and plastics when thermal effects are significant, and the papers here address open questions in these and related areas.
Multisoliton solutions, completely elastic collisions and non-elastic ...
Indian Academy of Sciences (India)
We discuss the nature of solitonsolutions before and after their interactions, and present their fusion (non-elastic) and elastic collisions of the soliton solutions. ... Department of Mathematics, Pabna University of Science and Technology, Pabna 6600, Bangladesh; School of Mathematics and Physics, University of ...
Directory of Open Access Journals (Sweden)
Vebil Yıldırım
2017-10-01
Full Text Available A broad parametric study is carried out to investigate the effects of both the inhomogeneity parameter, and a profile index of Stodola’s hyperbolic function on the static response of such structures subjected to both the inner and outer pressures. The investigation is based on the analytical formulas lately published by the author. The effects of those parameters on the variation of the radial displacement, the radial and hoop stresses are all graphically illustrated for an annulus pressurized at its both surfaces. It is observed that, especially, the variation of the hoop stress in radial coordinate is closely sensible to variation of those parameters. For the chosen problems it was observed that one of two materials whose Young’s modulus is higher than the other is better to locate at the inner surface of the disc having divergent profile to get reasonable maximum hoop stresses. However much smaller radial displacements may be obtained by using positive inhomogeneity indexes for all discs whose surfaces host a material whose Young’s modulus is smaller than the other. To reach a final decision, analytical formulas such as those used in the present study together with a failure criteria such as Von Mises and Tresca become indispensable means in a design process.
Engelbrecht, Jüri
2015-01-01
This book addresses the modelling of mechanical waves by asking the right questions about them and trying to find suitable answers. The questions follow the analytical sequence from elementary understandings to complicated cases, following a step-by-step path towards increased knowledge. The focus is on waves in elastic solids, although some examples also concern non-conservative cases for the sake of completeness. Special attention is paid to the understanding of the influence of microstructure, nonlinearity and internal variables in continua. With the help of many mathematical models for describing waves, physical phenomena concerning wave dispersion, nonlinear effects, emergence of solitary waves, scales and hierarchies of waves as well as the governing physical parameters are analysed. Also, the energy balance in waves and non-conservative models with energy influx are discussed. Finally, all answers are interwoven into the canvas of complexity.
Approximation by planar elastic curves
DEFF Research Database (Denmark)
Brander, David; Gravesen, Jens; Nørbjerg, Toke Bjerge
2016-01-01
We give an algorithm for approximating a given plane curve segment by a planar elastic curve. The method depends on an analytic representation of the space of elastic curve segments, together with a geometric method for obtaining a good initial guess for the approximating curve. A gradient-driven...
Nonlinear Elasticity of Doped Semiconductors
2017-02-01
AFRL-RY-WP-TR-2016-0206 NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS Mark Dykman and Kirill Moskovtsev Michigan State University...2016 4. TITLE AND SUBTITLE NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS 5a. CONTRACT NUMBER FA8650-16-1-7600 5b. GRANT NUMBER 5c. PROGRAM...vibration amplitude. 15. SUBJECT TERMS semiconductors , microresonators, microelectromechanical 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF
Blocky inversion of multichannel elastic impedance for elastic parameters
Mozayan, Davoud Karami; Gholami, Ali; Siahkoohi, Hamid Reza
2018-04-01
Petrophysical description of reservoirs requires proper knowledge of elastic parameters like P- and S-wave velocities (Vp and Vs) and density (ρ), which can be retrieved from pre-stack seismic data using the concept of elastic impedance (EI). We propose an inversion algorithm which recovers elastic parameters from pre-stack seismic data in two sequential steps. In the first step, using the multichannel blind seismic inversion method (exploited recently for recovering acoustic impedance from post-stack seismic data), high-resolution blocky EI models are obtained directly from partial angle-stacks. Using an efficient total-variation (TV) regularization, each angle-stack is inverted independently in a multichannel form without prior knowledge of the corresponding wavelet. The second step involves inversion of the resulting EI models for elastic parameters. Mathematically, under some assumptions, the EI's are linearly described by the elastic parameters in the logarithm domain. Thus a linear weighted least squares inversion is employed to perform this step. Accuracy of the concept of elastic impedance in predicting reflection coefficients at low and high angles of incidence is compared with that of exact Zoeppritz elastic impedance and the role of low frequency content in the problem is discussed. The performance of the proposed inversion method is tested using synthetic 2D data sets obtained from the Marmousi model and also 2D field data sets. The results confirm the efficiency and accuracy of the proposed method for inversion of pre-stack seismic data.
International Nuclear Information System (INIS)
Perreard, I M; Weaver, J B; Paulsen, K D; Pattison, A J; McGarry, M D J; Doyley, M; Barani, Z; Van Houten, E E
2010-01-01
The mechanical model commonly used in magnetic resonance elastography (MRE) is linear elasticity. However, soft tissue may exhibit frequency- and direction-dependent (FDD) shear moduli in response to an induced excitation causing a purely linear elastic model to provide an inaccurate image reconstruction of its mechanical properties. The goal of this study was to characterize the effects of reconstructing FDD data using a linear elastic inversion (LEI) algorithm. Linear and FDD phantoms were manufactured and LEI images were obtained from time-harmonic MRE acquisitions with variations in frequency and driving signal amplitude. LEI responses to artificially imposed uniform phase shifts in the displacement data from both purely linear elastic and FDD phantoms were also evaluated. Of the variety of FDD phantoms considered, LEI appeared to tolerate viscoelastic data-model mismatch better than deviations caused by poroelastic and anisotropic mechanical properties in terms of visual image contrast. However, the estimated shear modulus values were substantially incorrect relative to independent mechanical measurements even in the successful viscoelastic cases and the variations in mean values with changes in experimental conditions associated with uniform phase shifts, driving signal frequency and amplitude were unpredictable. Overall, use of LEI to reconstruct data acquired in phantoms with FDD material properties provided biased results under the best conditions and significant artifacts in the worst cases. These findings suggest that the success with which LEI is applied to MRE data in tissue will depend on the underlying mechanical characteristics of the tissues and/or organs systems of clinical interest.
Morphoelasticity: A theory of elastic growth
Goriely, Alain
2011-10-11
This chapter is concerned with the modelling of growth processes in the framework of continuum mechanics and nonlinear elasticity. It begins by considering growth and deformation in a one-dimensional setting, illustrating the key relationship between growth, the elastic response of the material, and the generation of residual stresses. The general three-dimensional theory of morphoelasticity is then developed from conservation of mass and momentum balance equations. In the formulation, the multiplicative decomposition of the deformation tensor, the standard approach in morphoelasticity, is derived in a new way. A discussion of continuous growth is also included. The chapter concludes by working through a sample problem of a growing cylindrical tube. A stability analysis is formulated, and the effect of growth on mucosal folding, a commonly seen instability in biological tubes, is demonstrated.
Application of elasticity theory at Sandia Labortories
International Nuclear Information System (INIS)
Davison, L.
1975-01-01
Examples are given of the application of linear elasticity theory to the solution of practical problems encountered at Sandia Laboratories. It is being applied to a very broad range of problems: those in one, two, and three spatial dimensions, some involving static and some dynamic response, to materials having isotropic and anisotropic symmetry, to homogeneous and inhomogeneous bodies, etc. Various extensions of the theory to include electric, magnetic and thermal effects, to account for material microstructure, for radiation and spall damage, chemical reactions, and other phenomena have been developed and/or applied. In some applications linear elasticity represents the physics of a problem well and is the theory of choice. In others the theory was used because it lent insight into a larger problem that was also attacked by means of other theories and/or experiment, and in some cases it serves as a part of a more encompassing theory
bessel functions for axisymmetric elasticity problems of the elastic
African Journals Online (AJOL)
HOD
. ) ( ) r. (. ) ( ). The governing partial differential equation for axisymmetric elasticity problems are the strain- displacement equations, the differential equations of equilibrium and the material constitutive laws, subject to the displacement and ...
Strain fluctuations and elastic constants
Energy Technology Data Exchange (ETDEWEB)
Parrinello, M.; Rahman, A.
1982-03-01
It is shown that the elastic strain fluctuations are a direct measure of elastic compliances in a general anisotropic medium; depending on the ensemble in which the fluctuation is measured either the isothermal or the adiabatic compliances are obtained. These fluctuations can now be calculated in a constant enthalpy and pressure, and hence, constant entropy, ensemble due to recent develpments in the molecular dynamics techniques. A calculation for a Ni single crystal under uniform uniaxial 100 tensile or compressive load is presented as an illustration of the relationships derived between various strain fluctuations and the elastic modulii. The Born stability criteria and the behavior of strain fluctuations are shown to be related.
High energy elastic hadron scattering
International Nuclear Information System (INIS)
Fearnly, T.A.
1986-04-01
The paper deals with the WA7 experiment at the CERN super proton synchrotron (SPS). The elastic differential cross sections of pion-proton, kaon-proton, antiproton-proton, and proton-proton at lower SPS energies over a wide range of momentum transfer were measured. Some theoretical models in the light of the experimental results are reviewed, and a comprehensive impact parameter analysis of antiproton-proton elastic scattering over a wide energy range is presented. A nucleon valence core model for high energy proton-proton and antiproton-proton elastic scattering is described
Estimating Price Elasticity using Market-Level Appliance Data
Energy Technology Data Exchange (ETDEWEB)
Fujita, K. Sydny [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2015-08-04
This report provides and update to and expansion upon our 2008 LBNL report “An Analysis of the Price Elasticity of Demand for Appliances,” in which we estimated an average relative price elasticity of -0.34 for major household appliances (Dale and Fujita 2008). Consumer responsiveness to price change is a key component of energy efficiency policy analysis; these policies influence consumer purchases through price both explicitly and implicitly. However, few studies address appliance demand elasticity in the U.S. market and public data sources are generally insufficient for rigorous estimation. Therefore, analysts have relied on a small set of outdated papers focused on limited appliance types, assuming long-term elasticities estimated for other durables (e.g., vehicles) decades ago are applicable to current and future appliance purchasing behavior. We aim to partially rectify this problem in the context of appliance efficiency standards by revisiting our previous analysis, utilizing data released over the last ten years and identifying additional estimates of durable goods price elasticities in the literature. Reviewing the literature, we find the following ranges of market-level price elasticities: -0.14 to -0.42 for appliances; -0.30 to -1.28 for automobiles; -0.47 to -2.55 for other durable goods. Brand price elasticities are substantially higher for these product groups, with most estimates -2.0 or more elastic. Using market-level shipments, sales value, and efficiency level data for 1989-2009, we run various iterations of a log-log regression model, arriving at a recommended range of short run appliance price elasticity between -0.4 and -0.5, with a default value of -0.45.
Grandin, R.; Socquet, A.; Doin, M.-P.; Jacques, E.; de Chabalier, J.-B.; King, G. C. P.
2010-09-01
Interferometric synthetic aperture radar (InSAR) data spanning the time intervals separating thirteen dike intrusions in the Manda Hararo-Dabbahu rift (Afar, Ethiopia) from 2005 to 2009 show that transient deformation occurs in the inter-diking period. This deformation can be explained by the presence of seven inflating or deflating pressure sources. By combining the data acquired on four different InSAR tracks, through time-dependent elastic models, we are able to track these deformation modes with a time resolution smaller than 1 month. Sustained deflation of a deep magma reservoir at Dabbahu in the 6 months following the main rifting event of 2005, and slow decelerating post-eruptive re-inflation of two shallow magma reservoirs below Dabbahu and Gabho volcanoes, are monitored. A deflation signal of deep origin on the neighboring rift system is also detected, possibly caused by outflow of material from a preexisting reservoir into the deep plate boundary. In contrast, rapidly evolving deformation is observed at the center of the Manda Hararo rift segment. Transient deformation events are monitored in the weeks/months following the diking events, with pulses of localized rift opening after the dike intrusions, followed by an exponential-like decay of opening rate. This signal may be associated with the replenishment of the central magma reservoir involved in feeding the 2005-2009 dikes. Alternatively, the predominantly horizontal mode of deformation suggests an interaction between the response of the lithosphere to tectonic strain accumulation, and the process of hydraulic connectivity within the central magma plumbing system.
Model-Based Reconstructive Elasticity Imaging Using Ultrasound
Directory of Open Access Journals (Sweden)
Salavat R. Aglyamov
2007-01-01
Full Text Available Elasticity imaging is a reconstructive imaging technique where tissue motion in response to mechanical excitation is measured using modern imaging systems, and the estimated displacements are then used to reconstruct the spatial distribution of Young's modulus. Here we present an ultrasound elasticity imaging method that utilizes the model-based technique for Young's modulus reconstruction. Based on the geometry of the imaged object, only one axial component of the strain tensor is used. The numerical implementation of the method is highly efficient because the reconstruction is based on an analytic solution of the forward elastic problem. The model-based approach is illustrated using two potential clinical applications: differentiation of liver hemangioma and staging of deep venous thrombosis. Overall, these studies demonstrate that model-based reconstructive elasticity imaging can be used in applications where the geometry of the object and the surrounding tissue is somewhat known and certain assumptions about the pathology can be made.
The real-time price elasticity of electricity
International Nuclear Information System (INIS)
Lijesen, Mark G.
2007-01-01
The real-time price elasticity of electricity contains important information on the demand response of consumers to the volatility of peak prices. Despite the importance, empirical estimates of the real-time elasticity are hardly available. This paper provides a quantification of the real-time relationship between total peak demand and spot market prices. We find a low value for the real-time price elasticity, which may partly be explained from the fact that not all users observe the spot market price. If we correct for this phenomenon, we find the elasticity to be fairly low for consumers currently active in the spot market. If this conclusion applies to all users, this would imply a limited scope for government intervention in supply security issues. (Author)
Astronomical optics and elasticity theory
Lemaitre, Gerard Rene
2008-01-01
Astronomical Optics and Elasticity Theory provides a very thorough and comprehensive account of what is known in this field. After an extensive introduction to optics and elasticity, the book discusses variable curvature and multimode deformable mirrors, as well as, in depth, active optics, its theory and applications. Further, optical design utilizing the Schmidt concept and various types of Schmidt correctors, as well as the elasticity theory of thin plates and shells are elaborated upon. Several active optics methods are developed for obtaining aberration corrected diffraction gratings. Further, a weakly conical shell theory of elasticity is elaborated for the aspherization of grazing incidence telescope mirrors. The very didactic and fairly easy-to-read presentation of the topic will enable PhD students and young researchers to actively participate in challenging astronomical optics and instrumentation projects.
Uniqueness theorems in linear elasticity
Knops, Robin John
1971-01-01
The classical result for uniqueness in elasticity theory is due to Kirchhoff. It states that the standard mixed boundary value problem for a homogeneous isotropic linear elastic material in equilibrium and occupying a bounded three-dimensional region of space possesses at most one solution in the classical sense, provided the Lame and shear moduli, A and J1 respectively, obey the inequalities (3 A + 2 J1) > 0 and J1>O. In linear elastodynamics the analogous result, due to Neumann, is that the initial-mixed boundary value problem possesses at most one solution provided the elastic moduli satisfy the same set of inequalities as in Kirchhoffs theorem. Most standard textbooks on the linear theory of elasticity mention only these two classical criteria for uniqueness and neglect altogether the abundant literature which has appeared since the original publications of Kirchhoff. To remedy this deficiency it seems appropriate to attempt a coherent description ofthe various contributions made to the study of uniquenes...
Sivak, David Alexander
DNA bending elasticity on length scales of tens of basepairs is of critical importance in numerous biological contexts. Even the simplest models of DNA bending admit of few simple analytic results, thus there is a need for numerical methods to calculate experimental observables, such as distance distributions, forces, FRET efficiencies, and timescales of particular large-scale motions. We have implemented and helped develop a coarse-grained representation of DNA and various other covalently-linked groups that allows simple calculation of such observables for varied experimental systems. The simple freely-jointed chain (FJC) model and extremely coarse resolution proved useful in understanding DNA threading through nanopores, identifying steric occlusion by other parts of the chain as a prime culprit for slower capture as distance to the pore decreased. Enhanced sampling techniques of a finer resolution discrete wormlike chain (WLC) model permitted calculation of cyclization rates for small chains and identified the ramifications of a thermodynamically-sound treatment of thermal melts. Adding treatment of double-stranded DNA's helical nature and single-stranded DNA provided a model system that helped demonstrate the importance of statistical fluctuations in even highly-stressed DNA mini-loops, and allowed us to verify that even these constructs show no evidence of excitation-induced softening. Additional incorporation of salt-sensitivity to the model allowed us to calculate forces and FRET efficiencies for such mini-loops and their uncircularized precursors, thereby furthering the understanding of the nature of IHF binding and bending of its recognition sequence. Adding large volume-excluding spheres linked to the ends of the dsDNA permits calculation of distance distributions and thus small-angle X-ray scattering, whereby we demonstrated the validity of the WLC in describing bending fluctuations in DNA chains as short as 42 bp. We also make important connections
Integrodifferential relations in linear elasticity
Kostin, Georgy V
2012-01-01
This work treats the elasticity of deformed bodies, including the resulting interior stresses and displacements.It also takes into account that some of constitutive relations can be considered in a weak form. To discuss this problem properly, the method of integrodifferential relations is used, and an advanced numerical technique for stress-strain analysis is presented and evaluated using various discretization techniques. The methods presented in this book are of importance for almost all elasticity problems in materials science and mechanical engineering.
Protein crystallization image classification with elastic net
Hung, Jeffrey; Collins, John; Weldetsion, Mehari; Newland, Oliver; Chiang, Eric; Guerrero, Steve; Okada, Kazunori
2014-03-01
Protein crystallization plays a crucial role in pharmaceutical research by supporting the investigation of a protein's molecular structure through X-ray diffraction of its crystal. Due to the rare occurrence of crystals, images must be manually inspected, a laborious process. We develop a solution incorporating a regularized, logistic regression model for automatically evaluating these images. Standard image features, such as shape context, Gabor filters and Fourier transforms, are first extracted to represent the heterogeneous appearance of our images. Then the proposed solution utilizes Elastic Net to select relevant features. Its L1-regularization mitigates the effects of our large dataset, and its L2- regularization ensures proper operation when the feature number exceeds the sample number. A two-tier cascade classifier based on naïve Bayes and random forest algorithms categorized the images. In order to validate the proposed method, we experimentally compare it with naïve Bayes, linear discriminant analysis, random forest, and their two-tier cascade classifiers, by 10-fold cross validation. Our experimental results demonstrate a 3-category accuracy of 74%, outperforming other models. In addition, Elastic Net better reduces the false negatives responsible for a high, domain specific risk. To the best of our knowledge, this is the first attempt to apply Elastic Net to classifying protein crystallization images. Performance measured on a large pharmaceutical dataset also fared well in comparison with those presented in the previous studies, while the reduction of the high-risk false negatives is promising.
Effective stress law for anisotropic elastic deformation
International Nuclear Information System (INIS)
Carroll, M.M.
1979-01-01
An effective stress law is derived analytically to describe the effect of pore fluid pressure on the linearly elastic response of saturated porous rocks which exhibit anisotropy. For general anisotropy the difference between the effective stress and the applied stress is not hydrostatic. The effective stress law involves two constants for transversely isotropic response and three constants for orthotropic response; these constants can be expressed in terms of the moduli of the porous material and of the solid material. These expressions simplify considerably when the anisotropy is structural rather than intrinsic, i.e., in the case of an isotropic solid material with an anisotropic pore structure. In this case the effective stress law involves the solid or grain bulk modulus and two or three moduli of the porous material, for transverse isotropy and orthotropy, respectively. The law reduces, in the case of isotropic response, to that suggested by Geertsma (1957) and by Skempton (1961) and derived analytically by Nur and Byerlee
Temperature dependence of elastic properties of paratellurite
International Nuclear Information System (INIS)
Silvestrova, I.M.; Pisarevskii, Y.V.; Senyushenkov, P.A.; Krupny, A.I.
1987-01-01
New data are presented on the temperature dependence of the elastic wave velocities, elastic stiffness constants, and thermal expansion of paratellurite. It is shown that the external pressure appreciably influences the elastic properties of TeO 2 , especially the temperature dependence of the elastic modulus connected with the crystal soft mode. (author)
Comparison of elastic and inelastic analyses
International Nuclear Information System (INIS)
Ammerman, D.J.; Heinstein, M.W.; Wellman, G.W.
1992-01-01
The use of inelastic analysis methods instead of the traditional elastic analysis methods in the design of radioactive material (RAM) transport packagings leads to a better understanding of the response of the package to mechanical loadings. Thus, better assessment of the containment, thermal protection, and shielding integrity of the package after a structure accident event can be made. A more accurate prediction of the package response can lead to enhanced safety and also allow for a more efficient use of materials, possibly leading to a package with higher capacity or lower weight. This paper discusses the advantages and disadvantages of using inelastic analysis in the design of RAM shipping packages. The use of inelastic analysis presents several problems to the package designer. When using inelastic analysis the entire nonlinear response of the material must be known, including the effects of temperature changes and strain rate. Another problem is that there currently is not an acceptance criteria for this type of analysis that is approved by regulatory agencies. Inelastic analysis acceptance criteria based on failure stress, failure strain , or plastic energy density could be developed. For both elastic and inelastic analyses it is also important to include other sources of stress in the analyses, such as fabrication stresses, thermal stresses, stresses from bolt preloading, and contact stresses at material interfaces. Offsetting these added difficulties is the improved knowledge of the package behavior. This allows for incorporation of a more uniform margin of safety, which can result in weight savings and a higher level of confidence in the post-accident configuration of the package. In this paper, comparisons between elastic and inelastic analyses are made for a simple ring structure and for a package to transport a large quantity of RAM by rail (rail cask) with lead gamma shielding to illustrate the differences in the two analysis techniques
Price-elastic demand in deregulated electricity markets
Energy Technology Data Exchange (ETDEWEB)
Siddiqui, Afzal S.
2003-05-01
The degree to which any deregulated market functions efficiently often depends on the ability of market agents to respond quickly to fluctuating conditions. Many restructured electricity markets, however, experience high prices caused by supply shortages and little demand-side response. We examine the implications for market operations when a risk-averse retailer's end-use consumers are allowed to perceive real-time variations in the electricity spot price. Using a market-equilibrium model, we find that price elasticity both increases the retailers revenue risk exposure and decreases the spot price. Since the latter induces the retailer to reduce forward electricity purchases, while the former has the opposite effect, the overall impact of price responsive demand on the relative magnitudes of its risk exposure and end-user price elasticity. Nevertheless, price elasticity decreases cumulative electricity consumption. By extending the analysis to allow for early settlement of demand, we find that forward stage end-user price responsiveness decreases the electricity forward price relative to the case with price-elastic demand only in real time. Moreover, we find that only if forward stage end-user demand is price elastic will the equilibrium electricity forward price be reduced.
Thermodynamic analysis of elastic-plastic deformation
International Nuclear Information System (INIS)
Lubarda, V.
1981-01-01
The complete set of constitutive equations which fully describes the behaviour of material in elastic-plastic deformation is derived on the basis of thermodynamic analysis of the deformation process. The analysis is done after the matrix decomposition of the deformation gradient is introduced into the structure of thermodynamics with internal state variables. The free energy function, is decomposed. Derive the expressions for the stress response, entropy and heat flux, and establish the evolution equation. Finally, we establish the thermodynamic restrictions of the deformation process. (Author) [pt
Price and income elasticities of residential energy demand in Germany
International Nuclear Information System (INIS)
Schulte, Isabella; Heindl, Peter
2017-01-01
We apply a quadratic expenditure system to estimate price and expenditure elasticities of residential energy demand (electricity and heating) in Germany. Using official expenditure data from 1993 to 2008, we estimate an expenditure elasticity for electricity of 0.3988 and of 0.4055 for space heating. The own price elasticity for electricity is −0.4310 and −0.5008 in the case of space heating. Disaggregation of households by expenditure and socio-economic composition reveals that the behavioural response to energy price changes is weaker (stronger) for low-income (top-income) households. There are considerable economies of scale in residential energy use but scale effects are not well approximated by the new OECD equivalence scale. Real increases in energy prices show a regressive pattern of incidence, implying that the welfare consequences of direct energy taxation are larger for low income households. The application of zero-elasticities in assessments of welfare consequences of energy taxation strongly underestimates potential welfare effects. The increase in inequality is 22% smaller when compared to the application of disaggregated price and income elasticities as estimated in this paper. - Highlights: • We estimate price, income, and expenditure elasticities for residential energy demand in Germany. • We differentiate elasticities by income groups and household type. • Electricity and space heating are necessary goods since the expenditure elasticities are smaller than unity. • Low-income households show a weaker reaction to changing prices when compared to high-income households. • Direct energy taxation has regressive effects, meaning that larger burdens fall upon low-income households.
Appraisal of elastic follow up
International Nuclear Information System (INIS)
Roche, R.L.
1981-01-01
Elastic computations are widely used in structural analysis, and their results are used when material behaviour is non elastic. The current practice is the partition of the computed stress between primary and secondary stress. The basic characteristic of primary stress is that it is not self limiting. On the contrary the basic characteristic of a secondary stress is that it is self limiting, and failure from one application of the stress is not to be expected. It must be emphasized that self limitation is not sufficient and that it is also necessary that strains are small enough to avoid any material disorder. Unfortunately, elastic computations do not give real strain distribution and computed strain in highly stressed areas can be magnified under conditions of plastic temperature is high enough, an undesirable amount of creep occurs in areas of reduced strength and failure can happen. In creep range, to avoid elastic follow up, the most important part of elastically computed stress is considered as primary. This practice is over conservative, and the aim of this paper is to provide indications to choise what fraction of a self limiting stress can be considered as secondary. (orig./GL)
Spherically symmetric elasticity in relativity
Energy Technology Data Exchange (ETDEWEB)
Carot, J [Departament de Fisica, Universitat de les Illes Balears, Cra Valldemossa pk 7.5, E-07122 Palma (Spain); Brito, I; Vaz, E G L R, E-mail: jcarot@uib.ca, E-mail: ireneb@mct.uminho.p, E-mail: evaz@mct.uminho.p
2010-05-01
The relativistic theory of elasticity is reviewed within the spherically symmetric context with a view towards the modelling of star interiors possessing elastic properties such as the ones expected in neutron stars. Emphasis is placed on generality in the main sections of the paper, and the results are then applied to specific examples. Along the way, a few general results for spacetimes admitting isometries are deduced, and their consequences are fully exploited in the case of spherical symmetry relating them next to the the case in which the material content of the spacetime is some elastic material. This paper extends and generalizes the pioneering work by Magli and Kijowski [1], Magli [2] and [3], and complements, in a sense, that by Karlovini and Samuelsson in their interesting series of papers [4], [5] and [6].
Complex variable methods in elasticity
England, A H
2003-01-01
The plane strain and generalized plane stress boundary value problems of linear elasticity are the focus of this graduate-level text, which formulates and solves these problems by employing complex variable theory. The text presents detailed descriptions of the three basic methods that rely on series representation, Cauchy integral representation, and the solution via continuation. Its five-part treatment covers functions of a complex variable, the basic equations of two-dimensional elasticity, plane and half-plane problems, regions with circular boundaries, and regions with curvilinear bounda
International Nuclear Information System (INIS)
Gale, J.; Tiselj, I.
2002-01-01
One dimensional two-fluid six-equation model of two-phase flow, that can be found in computer codes like RELAP5, TRAC, and CATHARE, was upgraded with additional terms, which enable modelling of the pressure waves in elastic pipes. It is known that pipe elasticity reduces the propagation velocity of the shock and other pressure waves in the piping systems. Equations that include the pipe elasticty terms are used in WAHA code, which is being developed within the WAHALoads project of 5't'h EU research program.(author)
CONFERENCE: Elastic and diffractive scattering
International Nuclear Information System (INIS)
White, Alan
1989-01-01
Elastic scattering, when particles appear to 'bounce' off each other, and the related phenomena of diffractive scattering are currently less fashionable than the study of hard scattering processes. However this could change rapidly if unexpected results from the UA4 experiment at the CERN Collider are confirmed and their implications tested. These questions were highlighted at the third 'Blois Workshop' on Elastic and Diffractive Scattering, held early in May on the Evanston campus of Northwestern University, near Chicago
ELASTIC AND SAFETY CLUTCH WITH RADIAL TAPERED ROLLER AND METALLIC ELASTIC ELEMENTS AXIALLY ARRANGED
STROE Ioan
2014-01-01
The paper presents a new type of clutch named `Elastic and Safety Clutch` that can accomplish the functions of the elastic and those of the safety clutches, but it is not a combined clutch. The proposed clutch is an elastic and safety clutch with metallic intermediate elements. The paper presents the elastic and safety clutch with radial tapered roller and metallic elastic elements axially arranged. The design and verification computing relations of the elastic and safety...
Impact loads on beams on elastic foundations
International Nuclear Information System (INIS)
Kameswara Rao, N.S.V.; Prasad, B.B.
1975-01-01
The behavior of beams on elastic foundations subjected to impact loads is studied in detail. The effect of foundation parameters (stiffness, and damping constants) on the dynamic response of the beam-foundation system has been analyzed. In modal analysis, the free-vibration equation has been solved by replacing the applied impulse by suitable initial conditions and the solution has been obtained as the linear combination of an infinite sequence of discrete eigen-vectors. In the energy method, the beam-foundation system is treated to be under forced vibrations and the forcing function has been obtained using the Hertz's law of impact. In the case of free-free end conditions of the beam, the rigid body modes and the elastic modes have been superposed to obtain the total response. A model of an Euler-Bernoulli beam resting on Winkler foundation has been subjected to impact loads using an impact testing machine and the responses such as deflection, strain velocity and acceleration have been measured with electronic instrumentation suited for shock and vibration. The analytical and experimental results are found to be in good agreement, thus showing the applicability of modal analysis and energy method to impact problems. The effect of foundation modulus is to increase the natural frequencies of the system. However, this effect diminishes as the mode number increases. The responses such as deflection, strain and stresses in the beam increase with increasing velocities of impact. If the system is overdamped the motion is aperiodic, and if the system is underdamped the motion is oscillatory. The beam response is greatly reduced by the damping in the foundation medium. From the present study it is observed that modal analysis is preferable to energy method
Analysis of price and income elasticities for cereals food crops in an ...
African Journals Online (AJOL)
The objective of the study is to estimate the price and income elasticities of cereals food crops in the study area. The results of the price and income elasticities of demand suggest that urban households in general are responsive to changes in own price and income in adjusting their consumption patterns. It was shown that ...
Nonlinear theory of elastic shells
International Nuclear Information System (INIS)
Costa Junior, J.A.
1979-08-01
Nonlinear theory of elastic shells is developed which incorporates both geometric and physical nonlinearities and which does not make use of the well known Love-Kirchhoff hypothesis. The resulting equations are formulated in tensorial notation and are reduced to the ones of common use when simplifying assumptions encountered in the especific litterature are taken. (Author) [pt
Duration of an Elastic Collision
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…
Reference-based transitions in short-run price elasticity
K.H. Pauwels (Koen); Ph.H.B.F. Franses (Philip Hans); S. Srinivasan (Shuba)
2003-01-01
textabstractMarketing literature has long recognized that price response need not be monotonic and symmetric, but has yet to provide generalizable market-level insights on reference price type, asymmetric thresholds and sign and magnitude of elasticity transitions. In this paper, we introduce smooth
Price elasticity of demand for psychiatric consultation in a Nigerian ...
African Journals Online (AJOL)
Objective: This paper addresses price elasticity of demand (PED) in a region where most patients make payments for consultations out of pocket. PED is a measure of the responsiveness of the quantity demanded of goods or services to changes in price. The study was done in the context of an outpatient psychiatric clinic in ...
Heart transplantation and arterial elasticity
Directory of Open Access Journals (Sweden)
Colvin-Adams M
2013-12-01
Full Text Available Monica Colvin-Adams,1 Nonyelum Harcourt,1 Robert LeDuc,2 Ganesh Raveendran,1 Yassir Sonbol,3 Robert Wilson,1 Daniel Duprez11Cardiovascular Division, University of Minnesota, Minneapolis, MN, USA; 2Division of Biostatistics University of Minnesota, Minneapolis, MN, USA; 3Cardiovascular Division, St Luke's Hospital System, Sugar Land, TX, USAObjective: Arterial elasticity is a functional biomarker that has predictive value for cardiovascular morbidity and mortality in nontransplant populations. There is little information regarding arterial elasticity in heart transplant recipients. This study aimed to characterize small (SAE and large (LAE artery elasticity in heart transplant recipients in comparison with an asymptomatic population free of overt cardiovascular disease. A second goal was to identify demographic and clinical factors associated with arterial elasticity in this unique population.Methods: Arterial pulse waveform was registered noninvasively at the radial artery in 71 heart transplant recipients between 2008 and 2010. SAEs and LAEs were derived from diastolic pulse contour analysis. Comparisons were made to a healthy cohort of 1,808 participants selected from our prevention clinic database. Multiple regression analyses were performed to evaluate associations between risk factors and SAE and LAE within the heart transplant recipients.Results: LAE and SAE were significantly lower in heart transplant recipients than in the normal cohort (P <0.01 and P < 0.0001, respectively. Female sex and history of ischemic cardiomyopathy were significantly associated with reduced LAE and SAE. Older age and the presence of moderate cardiac allograft vasculopathy were also significantly associated with reduced SAE. Transplant duration was associated with increased SAE.Conclusion: Heart transplants are associated with peripheral endothelial dysfunction and arterial stiffness, as demonstrated by a significant reduction in SAE and LAE when compared with a
Visco-piezo-elastic parameter estimation in laminated plate structures
DEFF Research Database (Denmark)
Araujo, A. L.; Mota Soares, C. M.; Herskovits, J.
2009-01-01
A parameter estimation technique is presented in this article, for identification of elastic, piezoelectric and viscoelastic properties of active laminated composite plates with surface-bonded piezoelectric patches. The inverse method presented uses experimental data in the form of a set...... determining the material parameters for the best fit. The solution of the inverse problem is obtained by gradient-based optimization techniques, through constrained minimization of an error functional, which expresses the deviation of the numerical model's response with respect to the experimentally measured...... data. Results are presented for the estimation of elastic, piezoelectric and viscoelastic properties in laminated plates....
A general solution to some plane problems of micropolar elasticity
DEFF Research Database (Denmark)
Warren, William E.; Byskov, Esben
2008-01-01
that micropolar effects are most significant in material regions subjected to large deformation gradients. Specific results are presented for the classical crack problem, the half plane loaded uniformly on the surface, Flamant's problem, and the circular cylinder compressed by equal and opposite oncentrated......We obtain a general solution to the field equations of plane micropolar elasticity for materials characterized by a hexagonal or equilateral triangular structure. These materials exhibit 3-fold symmetry in the plane and the elastic response is isotropic. Utilizing two displacement potential...
Elastic least-squares reverse time migration
Feng, Zongcai
2016-09-06
Elastic least-squares reverse time migration (LSRTM) is used to invert synthetic particle-velocity data and crosswell pressure field data. The migration images consist of both the P- and Svelocity perturbation images. Numerical tests on synthetic and field data illustrate the advantages of elastic LSRTM over elastic reverse time migration (RTM). In addition, elastic LSRTM images are better focused and have better reflector continuity than do the acoustic LSRTM images.
Spectral control of elastic dynamics in metallic nano-cavities.
Ulrichs, Henning; Meyer, Dennis; Döring, Florian; Eberl, Christian; Krebs, Hans-Ulrich
2017-09-06
We show how the elastic response of metallic nano-cavities can be tailored by tuning the interplay with an underlying phononic superlattice. In particular, we exploit ultrafast optical excitation in order to address a resonance mode in a tungsten thin film, grown on top of a periodic MgO/ZrO 2 multilayer. Setting up a simple theoretical model, we can explain our findings by the coupling of the resonance in the tungsten to an evanescent surface mode of the superlattice. To demonstrate a second potential benefit of our findings besides characterization of elastic properties of multilayer samples, we show by micromagnetic simulation how a similar structure can be utilized for magneto-elastic excitation of exchange-dominated spin waves.
Vibrations of Elastic Systems With Applications to MEMS and NEMS
Magrab, Edward B
2012-01-01
This work presents a unified approach to the vibrations of elastic systems as applied to MEMS devices, mechanical components, and civil structures. Applications include atomic force microscopes, energy harvesters, and carbon nanotubes and consider such complicating effects as squeeze film damping, viscous fluid loading, in-plane forces, and proof mass interactions with their elastic supports. These effects are analyzed as single degree-of-freedom models and as more realistic elastic structures. The governing equations and boundary conditions for beams, plates, and shells with interior and boundary attachments are derived by applying variational calculus to an expression describing the energy of the system. The advantages of this approach regarding the generation of orthogonal functions and the Rayleigh-Ritz method are demonstrated. A large number of graphs and tables are given to show the impact of various factors on the systems’ natural frequencies, mode shapes, and responses.
Health care demand elasticities by type of service.
Ellis, Randall P; Martins, Bruno; Zhu, Wenjia
2017-09-01
We estimate within-year price elasticities of demand for detailed health care services using an instrumental variable strategy, in which individual monthly cost shares are instrumented by employer-year-plan-month average cost shares. A specification using backward myopic prices gives more plausible and stable results than using forward myopic prices. Using 171 million person-months spanning 73 employers from 2008 to 2014, we estimate that the overall demand elasticity by backward myopic consumers is -0.44, with higher elasticities of demand for pharmaceuticals (-0.44), specialists visits (-0.32), MRIs (-0.29) and mental health/substance abuse (-0.26), and lower elasticities for prevention visits (-0.02) and emergency rooms (-0.04). Demand response is lower for children, in larger firms, among hourly waged employees, and for sicker people. Overall the method appears promising for estimating elasticities for highly disaggregated services although the approach does not work well on services that are very expensive or persistent. Copyright © 2017 Elsevier B.V. All rights reserved.
On Elasticity Measurement in Cloud Computing
Directory of Open Access Journals (Sweden)
Wei Ai
2016-01-01
Full Text Available Elasticity is the foundation of cloud performance and can be considered as a great advantage and a key benefit of cloud computing. However, there is no clear, concise, and formal definition of elasticity measurement, and thus no effective approach to elasticity quantification has been developed so far. Existing work on elasticity lack of solid and technical way of defining elasticity measurement and definitions of elasticity metrics have not been accurate enough to capture the essence of elasticity measurement. In this paper, we present a new definition of elasticity measurement and propose a quantifying and measuring method using a continuous-time Markov chain (CTMC model, which is easy to use for precise calculation of elasticity value of a cloud computing platform. Our numerical results demonstrate the basic parameters affecting elasticity as measured by the proposed measurement approach. Furthermore, our simulation and experimental results validate that the proposed measurement approach is not only correct but also robust and is effective in computing and comparing the elasticity of cloud platforms. Our research in this paper makes significant contribution to quantitative measurement of elasticity in cloud computing.
Thermodynamic parameters of elasticity and electrical conductivity ...
African Journals Online (AJOL)
The thermodynamic parameters (change in free energy of elasticity, DGe; change in enthalpy of elasticity, DHe; and change in entropy of elasticity, DSe) and the electrical conductivity of natural rubber composites reinforced separately with some agricultural wastes have been determined. Results show that the reinforced ...
short communication thermodynamic parameters of elasticity
African Journals Online (AJOL)
a
ABSTRACT. The thermodynamic parameters (change in free energy of elasticity, AGe; change in enthalpy of elasticity, AHe; and change in entropy of elasticity, ASe) and the electrical conductivity of natural rubber composites reinforced separately with some agricultural wastes have been determined. Results show that the ...
Applications of super elasticity in vibrational control
International Nuclear Information System (INIS)
Soul, H
2005-01-01
In this work, the possibilities of using shape memory alloys (SMA) as passive dampers devices in mechanicals vibrations problems are studied.The property that is exploited is the super elastic effect, by wich strains of the order of 10% can be obtained.The relationship between stress and strain means that this is an inelastic process.Nevertheless when load is removed the material recoveries its original dimension, presenting zero or almost zero permanent strain relative to others common materials, describing in its stress-strain diagram an important hysteretic loop.This features occurs basically because in well suited conditions the SMA can undergo martensitic transformations induced by stress.A series of uniaxial tension tests in commercial NiTi wires are performed, in order to characterize the super elastic behavior of the material.The influence of variables as ambient temperature, strain rate, strain levels and number of tension cycles accumulated are studied paying attention to the dissipative capacity of the material defined by means of the shape of the hysteretic loop.The influence on the damping capacity of the thermal effects associated with the martensitic transformation are evaluated by performing experiments at different transformation rates.Results are rationalized in terms of a model considering the interaction between a source term (heat of transformation), heat convection to the ambient and conduction along the wire.Some numerical results are obtained and discussed. For a performance evaluation in devices applications a simplified model of super elasticity is proposed.Then, the response of an elastic frame structure endowed with SMA tensors is evaluated following the model behavior when seismic movement is imposed at the base.The obtained results verify the possibility of using SMA as kernel elements in vibration control.This conclusion is experimentally verified in a prototype of the structure specially designed and constructed for this work
Almanna Lubis, Luluan; Ghosh, Deva P.; Hermana, Maman
2016-07-01
The elastic and electrical properties of low resistivity pays clastics reservoirs in Malay Basin are strongly dependent on the complex nature of the clay content, either dispersed or laminated/layered. Estimating the hydrocarbon pore volume from conventional electrical log, i.e. resistivity log, is quite a challenge. The low elastic impedance contrast also found as one of the challenge thus create a problem to map the distribution of the low resistivity reservoirs. In this paper, we evaluate the electrical properties and elastic rock properties to discriminate the pay from the adjacent cap rock or shale. Forward modeling of well log responses including electrical properties are applied to analyze the nature of the possible pays on laminated reservoir rocks. In the implementation of rock properties analysis, several conventional elastic properties are comparatively analyzed for the sensitivity and feasibility analysis on each elastic parameters. Finally, we discussed the advantages of each elastic parameters in detail. In addition, cross-plots of elastic and electrical properties attributes help us in the clear separation of anomalous zone and lithologic properties of sand and shale facies over conventional elastic parameter crossplots attributes. The possible relationship on electrical and elastic properties are discussed for further studies.
Elasticity of Long Distance Travelling
DEFF Research Database (Denmark)
Knudsen, Mette Aagaard
2011-01-01
With data from the Danish expenditure survey for 12 years 1996 through 2007, this study analyses household expenditures for long distance travelling. Household expenditures are examined at two levels of aggregation having the general expenditures on transportation and leisure relative to five other...... aggregated commodities at the highest level, and the specific expenditures on plane tickets and travel packages at the lowest level. The Almost Ideal Demand System is applied to determine the relationship between expenditures on transportation and leisure and all other purchased non-durables within...... packages has higher income elasticity of demand than plane tickets but also higher than transportation and leisure in general. The findings within price sensitiveness are not as sufficient estimated, but the model results indicate that travel packages is far more price elastic than plane tickets which...
Transient waves in visco-elastic media
Ricker, Norman
1977-01-01
Developments in Solid Earth Geophysics 10: Transient Waves in Visco-Elastic Media deals with the propagation of transient elastic disturbances in visco-elastic media. More specifically, it explores the visco-elastic behavior of a medium, whether gaseous, liquid, or solid, for very-small-amplitude disturbances. This volume provides a historical overview of the theory of the propagation of elastic waves in solid bodies, along with seismic prospecting and the nature of seismograms. It also discusses the seismic experiments, the behavior of waves propagated in accordance with the Stokes wave
Kaspar, Jan; Deile, M
The seemingly simple elastic scattering of protons still presents a challenge for the theory. In this thesis we discuss the elastic scattering from theoretical as well as experimental point of view. In the theory part, we present several models and their predictions for the LHC. We also discuss the Coulomb-hadronic interference, where we present a new eikonal calculation to all orders of alpha, the fine-structure constant. In the experimental part we introduce the TOTEM experiment which is dedicated, among other subjects, to the measurement of the elastic scattering at the LHC. This measurement is performed primarily with the Roman Pot (RP) detectors - movable beam-pipe insertions hundreds of meters from the interaction point, that can detect protons scattered to very small angles. We discuss some aspects of the RP simulation and reconstruction software. A central point is devoted to the techniques of RP alignment - determining the RP sensor positions relative to each other and to the beam. At the end we pres...
Biomimetic heterogenous elastic tissue development.
Tsai, Kai Jen; Dixon, Simon; Hale, Luke Richard; Darbyshire, Arnold; Martin, Daniel; de Mel, Achala
2017-01-01
There is an unmet need for artificial tissue to address current limitations with donor organs and problems with donor site morbidity. Despite the success with sophisticated tissue engineering endeavours, which employ cells as building blocks, they are limited to dedicated labs suitable for cell culture, with associated high costs and long tissue maturation times before available for clinical use. Direct 3D printing presents rapid, bespoke, acellular solutions for skull and bone repair or replacement, and can potentially address the need for elastic tissue, which is a major constituent of smooth muscle, cartilage, ligaments and connective tissue that support organs. Thermoplastic polyurethanes are one of the most versatile elastomeric polymers. Their segmented block copolymeric nature, comprising of hard and soft segments allows for an almost limitless potential to control physical properties and mechanical behaviour. Here we show direct 3D printing of biocompatible thermoplastic polyurethanes with Fused Deposition Modelling, with a view to presenting cell independent in-situ tissue substitutes. This method can expeditiously and economically produce heterogenous, biomimetic elastic tissue substitutes with controlled porosity to potentially facilitate vascularisation. The flexibility of this application is shown here with tubular constructs as exemplars. We demonstrate how these 3D printed constructs can be post-processed to incorporate bioactive molecules. This efficacious strategy, when combined with the privileges of digital healthcare, can be used to produce bespoke elastic tissue substitutes in-situ, independent of extensive cell culture and may be developed as a point-of-care therapy approach.
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.
Motivation and compliance with intraoral elastics.
Veeroo, Helen J; Cunningham, Susan J; Newton, Jonathon Timothy; Travess, Helen C
2014-07-01
Intraoral elastics are commonly used in orthodontics and require regular changing to be effective. Unfortunately, poor compliance with elastics is often encountered, especially in adolescents. Intention for an action and its implementation can be improved using "if-then" plans that spell out when, where, and how a set goal, such as elastic wear, can be put into action. Our aim was to determine the effect of if-then plans on compliance with elastics. To identify common barriers to compliance with recommendations concerning elastic wear, semistructured interviews were carried out with 14 adolescent orthodontic patients wearing intraoral elastics full time. Emerging themes were used to develop if-then plans to improve compliance with elastic wear. A prospective pilot study assessed the effectiveness of if-then planning aimed at overcoming the identified barriers on compliance with elastic wear. Twelve participants were randomized equally into study and control groups; the study group received information about if-then planning. The participants were asked to collect used elastics, and counts of these were used to assess compliance. A wide range of motivational and volitional factors were described by the interviewed participants, including the perceived benefits of elastics, cues to remember, pain, eating, social situations, sports, loss of elastics, and breakages. Compliance with elastic wear was highly variable among patients. The study group returned more used elastics, suggesting increased compliance, but the difference was not significant. The use of if-then plans might improve compliance with elastic wear when compared with routine clinical instructions. Copyright © 2014 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.
Localization of elastic layers by correlated disorder
International Nuclear Information System (INIS)
Balents, L.
1993-01-01
The equilibrium behavior of a system of elastic layers under tension in the presence of correlated disorder is studied using functional renormalization group techniques. The model exhibits many of the features of the Bose-glass phase of type-II superconductors induced by columnar defects, but may be more directly applicable to charge density waves, incommensurate striped magnetic phases, stacked membranes under tension, vicinal crystal surfaces, or superconducting ''vortex-chains''. Below five dimensions, an epsilon expansion for the stable zero-temperature fixed point yields the properties of the glassy phase. Transverse to the direction of correlation, the randomness induces logarithmic growth of displacements. The absence of a response to a weak applied transverse field (transverse Meissner effect) is demonstrated analytically. In this simple model, the localized phase is stable to point disorder, in contrast to the behavior in the presence of dislocations, in which the converse is believed to be true. (orig.)
Hydrodynamic analysis of elastic floating collars in random waves
Bai, Xiao-dong; Zhao, Yun-peng; Dong, Guo-hai; Li, Yu-cheng
2015-06-01
As the main load-bearing component of fish cages, the floating collar supports the whole cage and undergoes large deformations. In this paper, a mathematical method is developed to study the motions and elastic deformations of elastic floating collars in random waves. The irregular wave is simulated by the random phase method and the statistical approach and Fourier transfer are applied to analyze the elastic response in both time and frequency domains. The governing equations of motions are established by Newton's second law, and the governing equations of deformations are obtained based on curved beam theory and modal superposition method. In order to validate the numerical model of the floating collar attacked by random waves, a series of physical model tests are conducted. Good relationship between numerical simulation and experimental observations is obtained. The numerical results indicate that the transfer function of out-of-plane and in-plane deformations increase with the increasing of wave frequency. In the frequency range between 0.6 Hz and 1.1 Hz, a linear relationship exists between the wave elevations and the deformations. The average phase difference between the wave elevation and out-of-plane deformation is 60° with waves leading and the phase between the wave elevation and in-plane deformation is 10° with waves lagging. In addition, the effect of fish net on the elastic response is analyzed. The results suggest that the deformation of the floating collar with fish net is a little larger than that without net.
Characterization of the elastic displacement demand: Case study - Sofia city
International Nuclear Information System (INIS)
Paskaleva, I.; Kouteva, M.; Vaccari, F.; Panza, G.F.
2008-02-01
The results of the study on the seismic site response in a part of the metropolitan Sofia are discussed. The neo-deterministic seismic hazard assessment procedure has been used to compute realistic synthetic waveforms considering four earthquake scenarios, with magnitudes M = 3.7, M = 6.3 and M = 7.0. Source and site specific ground motion time histories are computed along three investigated cross sections, making use of the hybrid approach, combining the modal summation technique and the finite differences scheme. Displacement and acceleration response spectra are considered. These results are validated against the design elastic displacement response spectra and displacement demand, recommended in Eurocode 8. The elastic response design spectrum from the standard pseudo-acceleration, versus natural period, Tn, format is converted to the Sa - Sd format. The elastic displacement response spectra and displacement demand are discussed with respect to the earthquake magnitude, the seismic source-to-site distance, seismic source mechanism, and the local geological site conditions. (author)
Examining the short-run price elasticity of gasoline demand in the United States
Brannan, Michael James
Estimating the consumer demand response to changes in the price of gasoline has important implications regarding fuel tax policies and environmental concerns. There are reasons to believe that the short-run price elasticity of gasoline demand fluctuates due to changing structural and behavioral factors. In this paper I estimate the short-run price elasticity of gasoline demand in two time periods, from 2001 to 2006 and from 2007 to 2010. This study utilizes data at both the national and state levels to produce estimates. The short-run price elasticities range from -0.034 to -0.047 during 2001 to 2006, compared to -0.058 to -0.077 in the 2007 to 2010 period. This paper also examines whether there are regional differences in the short-run price elasticity of gasoline demand in the United States. However, there appears to only be modest variation in price elasticity values across regions.
Wave propagation in elastic solids
Achenbach, Jan
1984-01-01
The propagation of mechanical disturbances in solids is of interest in many branches of the physical scienses and engineering. This book aims to present an account of the theory of wave propagation in elastic solids. The material is arranged to present an exposition of the basic concepts of mechanical wave propagation within a one-dimensional setting and a discussion of formal aspects of elastodynamic theory in three dimensions, followed by chapters expounding on typical wave propagation phenomena, such as radiation, reflection, refraction, propagation in waveguides, and diffraction. The treat
Material variability in elastic assessment
International Nuclear Information System (INIS)
Riou, B.; Sperandio, M.; Guinovart, J.
1997-01-01
The structures of Fast Reactors (FRs) are subjected to high temperatures and their design is checked mainly against elastic rules. The aim of this paper is to study the influence of uncertainties in material properties on creep-fatigue assessment according to the elastic route of the RCC-MR code, so as to evaluate the subsequent margins. This work has been conducted by FRAMATOME, in cooperation with GEC, NNC and SIEMENS, in the frame of the activities of the Working Group on Codes and standards of DG XI/C (Nuclear Safety of Installations). The material considered is the 316L(N) austenitic stainless steel (RCC-MR 1S type material). The work is divided into two phases: the first one consists of the identification of the scatterband of material properties used in the elastic creep-fatigue assessment route of the RCC-MR code and the second of the study of the influence of the scatter on the results of elastic calculations and creep-fatigue assessment, with the aim to evaluate the difference in lifetime as a function of the set of material properties used and the relative importance of each material property. The latter will be based on one example of application typical of FRs structure. The example chosen consists of a plate to shell junction subjected to a thermal transient. Calculations are carried out using design material properties, mean material properties and properties leading to minimum and maximum life duration. Results of creep-fatigue analyses with material properties leading to minimum life duration are shown to be similar to those with design material properties, giving results of the same order to magnitude. Results with mean material properties and properties leading to maximum life duration exhibit significant margins compared to design analyses. Sensitivity analyses carried out on the basis of the maximum and minimum material property values show that properties which are the most significant for creep-fatigue assessment are the S r curves, the K s
Surface elastic properties in silicon nanoparticles
Melis, Claudio; Giordano, Stefano; Colombo, Luciano
2017-09-01
The elastic behavior of the external surface of a solid body plays a key role in nanomechanical phenomena. While bulk elasticity enjoys the benefits of a robust theoretical understanding, many surface elasticity features remain unexplored: some of them are here addressed by blending together continuum elasticity and atomistic simulations. A suitable readdressing of the surface elasticity theory allows to write the balance equations in arbitrary curvilinear coordinates and to investigate the dependence of the surface elastic parameters on the mean and Gaussian curvatures of the surface. In particular, we predict the radial strain induced by surface effects in spherical and cylindrical silicon nanoparticles and provide evidence that the surface parameters are nearly independent of curvatures and, therefore, of the surface conformation.
Elasticities of Turkish Exports and Imports
Ayla Ogus; Niloufer Sohrabji
2009-01-01
The Turkish current account has been exploding in the last few years leading to concerns of a crisis. One of the primary factors identified in the rising deficits is the appreciating lira. In addition, income elasticity of exports and imports can also shed light on continuing trade deficits. In this paper we analyze exchange rate and income elasticity of Turkish imports and exports. We find a significant gap between domestic and foreign income elasticities (for exports and imports respectivel...
Elastic properties of graphite and interstitial defects
International Nuclear Information System (INIS)
Ayasse, J.-B.
1977-01-01
The graphite elastic constants C 33 and C 44 , reflecting the interaction of the graphitic planes, were experimentally measured as a function of irradiation and temperature. A model of non-central strength atomic interaction was established to explain the experimental results obtained. This model is valid at zero temperature. The temperature dependence of the elastic properties was analyzed. The influence of the elastic property variations on the specific heat of the lattice at very low temperature was investigated [fr
Elegent -- an elastic event generator
Kašpar, Jan
2014-01-01
Although elastic scattering of nucleons may look like a simple process, it presents a long-lasting challenge for theory. Due to missing hard energy scale, the perturbative QCD can not be applied. Instead, many phenomenological/theoretical models have emerged. In this paper we present a unified implementation of some of the most prominent models in a C++ library, moreover extended to account for effects of the electromagnetic interaction. The library is complemented with a number of utilities. For instance, programs to sample many distributions of interest in four-momentum transfer squared, t, impact parameter, b, and collision energy sqrt(s). These distributions at ISR, SppS, RHIC, Tevatron and LHC energies are available for download from the project web site. Both in the form of ROOT files and PDF figures providing comparisons among the models. The package includes also a tool for Monte-Carlo generation of elastic scattering events, which can easily be embedded in any other program framework.
Continuum mechanics elasticity, plasticity, viscoelasticity
Dill, Ellis H
2006-01-01
FUNDAMENTALS OF CONTINUUM MECHANICSMaterial ModelsClassical Space-TimeMaterial BodiesStrainRate of StrainCurvilinear Coordinate SystemsConservation of MassBalance of MomentumBalance of EnergyConstitutive EquationsThermodynamic DissipationObjectivity: Invariance for Rigid MotionsColeman-Mizel ModelFluid MechanicsProblems for Chapter 1BibliographyNONLINEAR ELASTICITYThermoelasticityMaterial SymmetriesIsotropic MaterialsIncompressible MaterialsConjugate Measures of Stress and StrainSome Symmetry GroupsRate Formulations for Elastic MaterialsEnergy PrinciplesGeometry of Small DeformationsLinear ElasticitySpecial Constitutive Models for Isotropic MaterialsMechanical Restrictions on the Constitutive RelationsProblems for Chapter 2BibliographyLINEAR ELASTICITYBasic EquationsPlane StrainPlane StressProperties of SolutionsPotential EnergySpecial Matrix NotationThe Finite Element Method of SolutionGeneral Equations for an Assembly of ElementsFinite Element Analysis for Large DeformationsProblems for Chapter 3Bibliograph...
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
A new approach to ultrasonic elasticity imaging
Hoerig, Cameron; Ghaboussi, Jamshid; Fatemi, Mostafa; Insana, Michael F.
2016-04-01
Biomechanical properties of soft tissues can provide information regarding the local health status. Often the cells in pathological tissues can be found to form a stiff extracellular environment, which is a sensitive, early diagnostic indicator of disease. Quasi-static ultrasonic elasticity imaging provides a way to image the mechanical properties of tissues. Strain images provide a map of the relative tissue stiffness, but ambiguities and artifacts limit its diagnostic value. Accurately mapping intrinsic mechanical parameters of a region may increase diagnostic specificity. However, the inverse problem, whereby force and displacement estimates are used to estimate a constitutive matrix, is ill conditioned. Our method avoids many of the issues involved with solving the inverse problem, such as unknown boundary conditions and incomplete information about the stress field, by building an empirical model directly from measured data. Surface force and volumetric displacement data gathered during imaging are used in conjunction with the AutoProgressive method to teach artificial neural networks the stress-strain relationship of tissues. The Autoprogressive algorithm has been successfully used in many civil engineering applications and to estimate ocular pressure and corneal stiffness; here, we are expanding its use to any tissues imaged ultrasonically. We show that force-displacement data recorded with an ultrasound probe and displacements estimated at a few points in the imaged region can be used to estimate the full stress and strain vectors throughout an entire model while only assuming conservation laws. We will also demonstrate methods to parameterize the mechanical properties based on the stress-strain response of trained neural networks. This method is a fundamentally new approach to medical elasticity imaging that for the first time provides full stress and strain vectors from one set of observation data.
Demand elasticity of oil in Barbados
International Nuclear Information System (INIS)
Moore, Alvon
2011-01-01
The importation of oil is a significant component of Barbados' imports, rising from 7% of imports in 1998 to over 20% in 2009. This increase has impacted greatly on the level of foreign reserves. As a price-taker, relying entirely on imported oil for our energy needs could prove a continuous drain on the economy. With a view to formulating an appropriate energy policy for Barbados, this paper analyses the demand for oil using monthly data from 1998 to 2009. The paper estimates the elasticities of demand for oil by employing single equation cointegration approach and comparing the results with countries that rely heavily on imported oil and whose policy objective are to alter their energy structure to rely less on imported oil. The results show that the demand for oil imports is price inelastic in the long run. The consumption of oil is responsive to past consumption, prices, income, electricity consumption and the number of appliances imported in the short-run. A policy framework to reduce the use of oil for electricity consumption via alternative energy sources should be considered and the taxation of oil imports given its elasticity is a good source of revenue. - Highlights: → Demand for oil is price inelastic in the long-run (-0.552). → The relationship between oil demand and income is insignificant in the long run. → As electricity consumption increases by 1%, the demand for oil rises by 1.43%. → Need to determine if investments in alternative sources can offset demand for oil. → Investment in alternative resources may be required before gains are realised.
Effective medium theory for elastic matrix composites containing dispersed particulates
International Nuclear Information System (INIS)
Jhon, M.S.; Metz, R.J.; Freed, K.F.
1988-01-01
We describe a new, effective medium theory to study the wave propagation and mechanical properties of a composite system with dispersed particulates. One main emphasis here is in formulating the theory and in analyzing the structure of the contribution of the fillers to the elastic response. By constructing the elastic propagator (whose fluid mechanical counterpart is known as the Oseen tensor), we show that an analogy between the theoretical description of the particulate system and of suspension rheology exists when the former corresponds to a high-rigidity solid matrix (or, analogously, when the Poisson ratio is close to 1/2) in steady state. The effective Lame constants for this case are derived by combining this analogy with the theory developed by Freed and Muthukumar for the rheology of a suspension of spheres. The analogy is also useful in our new prediction of the phenomenon of elastic screening, the possible existence of a cutoff frequency below which elastic waves cannot propagate in the filler system
Vector-based excitation amplitude imaging condition for elastic RTM
Zhou, Jinju; Wang, Deli
2017-12-01
In recent years, many studies have focused on elastic reverse time migration (RTM). In response to the problems associated with elastic RTM, we propose a new procedure for 2D elastic multicomponent RTM. In this new method, decomposed P- and S-wave components are obtained from the decoupled propagation of the source and receiver wavefields, which allows the expedient calculation of the Poynting vectors and the incident and reflection angles of the P- and S-waves. In addition, we deduce the vector-based excitation amplitude imaging condition. This process automatically accounts for the particle vibration directions when determining the angle-dependent signed reflection coefficients, and does not require the sign to be determined apart from the value of the reflection coefficients. This concept was further extended to the source-normalized crosscorrelation imaging condition. The reflection coefficient of the layered model test was in agreement with the Zoeppritz theory, the PP and PS wave images of the Marmousi II model were clear, and the PS wave images had higher resolution and richer details. In addition, since the calculated reflection coefficients are angle-dependent, they can be easily used for the extraction of angle-domain common-image gathers. Moreover, the imaging condition avoids the polarization reversal in PS wave images and does not require all of the source wavefield data. Consequently, the computation and storage requirements are significantly reduced, which will facilitate the use of the elastic RTM in practice.
Separating growth from elastic deformation during cell enlargement
Energy Technology Data Exchange (ETDEWEB)
Proseus, T.E.; Boyer, J.S. (Univ. of Delaware, Lewes, DE (United States). Coll. of Marine Studies); Ortega, J.K.E. (Univ. of Colorado, Denver, CO (United States). Dept. of Mechanical Engineering)
1999-02-01
Plants change size by deforming reversibly (elastically) whenever turgor pressure changes, and by growing. The elastic deformation is independent of growth because it occurs in nongrowing cells. Its occurrence with growth has prevented growth from being observed alone. The authors investigated whether the two processes could be separated in internode cells of Chara corallina Klien ex Willd., em R.D.W. by injecting or removing cell solution with a pressure probe to change turgor while the cell length was continuously measured. Cell size changed immediately when turgor changed, and growth rates appeared to be altered. Low temperature eliminated growth but did not alter the elastic effects. This allowed elastic deformation measured at low temperature to be subtracted from elongation at warm temperature in the same cell. After te subtraction, growth alone could be observed for the first time. Alternations in turgor caused growth to change rapidly to a new, steady rate with no evidence of rapid adjustments in wall properties. This turgor response, together with the marked sensitivity of growth to temperature, suggested that the growth rate was not controlled by inert polymer extension but rather by the biochemical reactions that include a turgor-sensitive step.
Bayesian Analysis of Demand Elasticity in the Italian Electricity Market
Directory of Open Access Journals (Sweden)
Maria Chiara D'Errico
2015-09-01
Full Text Available The liberalization of the Italian electricity market is a decade old. Within these last ten years, the supply side has been extensively analyzed, but not the demand side. The aim of this paper is to provide a new method for estimation of the demand elasticity, based on Bayesian methods applied to the Italian electricity market. We used individual demand bids data in the day-ahead market in the Italian Power Exchange (IPEX, for 2011, in order to construct an aggregate demand function at the hourly level. We took into account the existence of both elastic and inelastic bidders on the demand side. The empirical results show that elasticity varies significantly during the day and across periods of the year. In addition, the elasticity hourly distribution is clearly skewed and more so in the daily hours. The Bayesian method is a useful tool for policy-making, insofar as the regulator can start with a priori historical information on market behavior and estimate actual market outcomes in response to new policy actions.
Determination of corneal elasticity coefficient using the ORA database.
Avetisov, Sergei E; Novikov, Ivan A; Bubnova, Irina A; Antonov, Alexei A; Siplivyi, Vladimir I
2010-07-01
To propose a new approach for the study of corneal biomechanics using the Reichert Ocular Response Analyzer (ORA) database, which is based on changes in velocity retardation in the central cornea at the peak of flattening. The ORA applanation curve was analyzed using a mathematical technique, which allowed calculation of the elasticity coefficient (Ke), which is primarily characteristic of the elastic properties of the cornea. Elasticity coefficient values were obtained in patients with presumably different biomechanical properties of the cornea: "normal" cornea (71 eyes, normal group), keratoconus (34 eyes, keratoconus group), LASIK (36 eyes, LASIK group), and glaucoma with elevated and compensated intraocular pressure (lOP) (38 eyes, glaucoma group). The mean Ke value in the normal group was 11.05 +/- 1.6, and the corneal thickness correlation coefficient r2 was 0.48. In the keratoconus group, the mean Ke value was 4.91 +/- 1.87 and the corneal thickness correlation coefficient r2 was 0.47. In the LASIK group, Ke and r2 were 5.99 +/- 1.18 and 0.39, respectively. In the glaucoma group, the same eyes that experienced a two-fold reduction in lOP developed a statistically significant reduction in the Ke (1.06 times lower), whereas their corneal hysteresis value increased 1.25 times. The elasticity coefficient calculated using the ORA applanation curve can be used in the evaluation of corneal biomechanical properties.
Elastic moduli and elastic anisotropy of cold sprayed metallic coatings
Czech Academy of Sciences Publication Activity Database
Seiner, Hanuš; Cizek, J.; Sedlák, Petr; Huang, R.; Cupera, J.; Dlouhý, I.; Landa, Michal
2016-01-01
Roč. 291, April (2016), s. 342-347 ISSN 0257-8972 R&D Projects: GA ČR GA13-13616S; GA ČR(CZ) GA13-35890S Grant - others:NETME Centre Plus - národní program udržitelnosti(CZ) LO1202 Institutional support: RVO:61388998 Keywords : kinetic spray * CGDS * elastic properties * metals and alloys * deposition * resonant ultrasound spectroscopy Subject RIV: JG - Metallurgy Impact factor: 2.589, year: 2016 http://ac.els-cdn.com/S0257897216301165/1-s2.0-S0257897216301165-main.pdf?_tid=1083617a-017f-11e6-92e7-00000aacb361&acdnat=1460555773_2e80d3df20843f3af649bf3ac71c8844
Advances in biomimetic regeneration of elastic matrix structures
Sivaraman, Balakrishnan; Bashur, Chris A.; Ramamurthi, Anand
2012-01-01
Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of no...
A Reformulation of Nonlinear Anisotropic Elasticity for Impact Physics
2014-02-01
simple shear are compared in figures 3a, b, and c, respectively. Stresses are normalized by ambient bulk modulus B0; Poisson’s ratio is . Stresses...0 is the ambient pressure derivative of the tangent bulk modulus. The pressure-volume response of the Eulerian model similar is similar to the...Magazine A 2000, 80, 2827–2840. 9. Gregoryanz, E.; Hemley, R. J.; Mao , H.; Gillet, P. High Pressure Elasticity of -Quartz: Instability and
The everyday elasticity of compliance in a symptomless disease
DEFF Research Database (Denmark)
Felde, Lina Hoel
2011-01-01
Medically, compliance refers to the extent to which a patient's response to medical advice coincides with doctors' orders. Rather than this absolute standard, this article treats compliance as an institutionally available discourse continually figured in practice. The aim of this article...... give-and-take. This elasticity of compliance reveals a reflexive critique of medical compliance as a moral standard and leads us to discuss how people are adequately compliant in everyday moral contexts....
Quasi-experimental taxation elasticities of US gasoline demand
International Nuclear Information System (INIS)
Goel, R.K.
1994-01-01
Taxation elasticities provide inputs in public policy aimed at raising revenues. Using the quasi-experimental method, this paper calculates gasoline taxation elasticities for the USA over 1952-86. The medium (mean) elasticity over this period is found to be -0.075 (-0.122). However, the elasticity following the oil shock of 1973 is found to be statistically different from the pre-shock elasticity. Reasons for this change in elasticity are discussed. The implication of this analysis is that tax policies based on price elasticities, rather than on tax elasticities, might be using an inappropriate elasticity estimate and consequently misinterpreting the government's ability to raise tax revenues. (author)
Contribution of domain 30 of tropoelastin to elastic fiber formation and material elasticity.
Muiznieks, Lisa D; Miao, Ming; Sitarz, Eva E; Keeley, Fred W
2016-05-01
Elastin is a fibrous structural protein of the extracellular matrix that provides reversible elastic recoil to vertebrate tissues such as arterial vessels, lung, and skin. The elastin monomer, tropoelastin, contains a large proportion of intrinsically disordered and flexible hydrophobic sequences that collectively are responsible for the initial phase separation of monomers during assembly, and are essential for driving elastic recoil. While structural disorder of hydrophobic sequences is controlled by a high proline and glycine residue composition, hydrophobic domain 30 of human tropoelastin is atypically proline-poor, and forms β-sheet amyloid-like fibrils as an individual peptide. We explored the contribution of confined regions of secondary structure at the location of domain 30 in human tropoelastin to fiber assembly and mechanical properties using a set of mutations designed to inhibit or enhance the propensity of β-sheet formation at this location. Our data support a dual role for confined β-sheet secondary structure in domain 30 of tropoelastin in guiding the formation of fibers, and as a determinant of stiffness and viscoelastic properties of cross-linked materials. Together, these results suggest a mechanism for specificity in fiber assembly, and elucidate structure-function relationships for the rational design of elastomeric biomaterials with defined mechanical properties. © 2016 Wiley Periodicals, Inc.
Elastic Properties of Nucleic Acids by Single-Molecule Force Spectroscopy.
Camunas-Soler, Joan; Ribezzi-Crivellari, Marco; Ritort, Felix
2016-07-05
We review the current knowledge on the use of single-molecule force spectroscopy techniques to extrapolate the elastic properties of nucleic acids. We emphasize the lesser-known elastic properties of single-stranded DNA. We discuss the importance of accurately determining the elastic response in pulling experiments, and we review the simplest models used to rationalize the experimental data as well as the experimental approaches used to pull single-stranded DNA. Applications used to investigate DNA conformational transitions and secondary structure formation are also highlighted. Finally, we provide an overview of the effects of salt and temperature and briefly discuss the effects of contour length and sequence dependence.
Optimization Of Elastic Bridge Trusses
Directory of Open Access Journals (Sweden)
Ignas Rimkus
2013-12-01
Full Text Available The article analyzes the problems of optimizing elastic bridgetrusses, which is a tool for seeking the establishment of theminimum volume (mass of construction and optimization of thecross-section area and height as well as the structure of the truss.It has been formulated as a nonlinear discrete mathematical programmingproblem. The upper band of the truss works not onlyfor compression but also for bending. The cross-sections of theelements are designed from rolled steel sections. Mathematicalmodels are prepared by using the finite element method and complyingwith requirements for the strength, stiffness and stabilityof the structure. The formulated problems are solved referringto an iterative process and applying the mathematical softwarepackage “MATLAB” along with routine “fmincon”. The ratio ofbuckling is corrected in every case of iteration. Requirementsfor cross-section assortment (discretion are fulfilled employingthe branch and bound method.
Mathematical methods for elastic plates
Constanda, Christian
2014-01-01
Mathematical models of deformation of elastic plates are used by applied mathematicians and engineers in connection with a wide range of practical applications, from microchip production to the construction of skyscrapers and aircraft. This book employs two important analytic techniques to solve the fundamental boundary value problems for the theory of plates with transverse shear deformation, which offers a more complete picture of the physical process of bending than Kirchhoff’s classical one. The first method transfers the ellipticity of the governing system to the boundary, leading to singular integral equations on the contour of the domain. These equations, established on the basis of the properties of suitable layer potentials, are then solved in spaces of smooth (Hölder continuous and Hölder continuously differentiable) functions. The second technique rewrites the differential system in terms of complex variables and fully integrates it, expressing the solution as a combination of complex ana...
Wrinkling of Pressurized Elastic Shells
Vella, Dominic
2011-10-01
We study the formation of localized structures formed by the point loading of an internally pressurized elastic shell. While unpressurized shells (such as a ping-pong ball) buckle into polygonal structures, we show that pressurized shells are subject to a wrinkling instability. We study wrinkling in depth, presenting scaling laws for the critical indentation at which wrinkling occurs and the number of wrinkles formed in terms of the internal pressurization and material properties of the shell. These results are validated by numerical simulations. We show that the evolution of the wrinkle length with increasing indentation can be understood for highly pressurized shells from membrane theory. These results suggest that the position and number of wrinkles may be used in combination to give simple methods for the estimation of the mechanical properties of highly pressurized shells. © 2011 American Physical Society.
Multidiscipline simulation of elastic manipulators
Directory of Open Access Journals (Sweden)
T. Rølvåg
1992-10-01
Full Text Available This paper contributes to multidiscipline simulation of elastic robot manipulators in FEDEM. All developments presented in this paper are based on the formulations in FEDEM, a simulation system developed by the authors which combines finite element, mechanism and control analysis. In order to establish this general simulation system as an efficient multidiscipline robot design tool a robot control system including a high level robot programming language, interpolation algorithms, path generation algorithms, forward and inverse kinematics, control systems, gear and transmission models are implemented. These new features provide a high level of integration between traditionally separate design disciplines from the very beginning of the design and optimization process. Several simulations have shown that high fidelity mathematical models can be derived and used as a basis for dynamic analysis and controller design in FEDEM.
Price elasticity of natural gas demand in the power generation sector
International Nuclear Information System (INIS)
McArdle, P.F.
1990-01-01
Today, the demand for energy by the electric generation sector is highly competitive and price-responsive. Previous estimates of the price elasticity of natural gas demand in this sector have focused primarily on data from the 1960s and 1970s. Such estimates fail to take full account of economic, regulatory, and legislative developments that have altered the structure of the electric generation market during the 1980s. Structural changes include an increased ability of utilities to choose among generating options, the increase in non-utility generators, the amending of the Fuel Use Act, and a more competitive market for electricity. An accurate estimate of price elasticity requires a refocusing on data from the post-1983 period. The purpose of this paper is to answer two questions: how price responsive (elastic) is natural gas demand in this market; and what changes in natural gas demand elasticity have occurred over time
An analysis of gasoline demand elasticities at the national and local levels in Mexico
International Nuclear Information System (INIS)
Crotte, Amado; Noland, Robert B.; Graham, Daniel J.
2010-01-01
The majority of evidence on gasoline demand elasticities is derived from models based on national data. Since the largest growth in population is now taking place in cities in the developing world it is important that we understand whether this national evidence is applicable to demand conditions at the local level. The aim of this paper is to estimate and compare gasoline per vehicle demand elasticities at the national and local levels in Mexico. National elasticities with respect to price, income, vehicle stock and metro fares are estimated using both a time series cointegration model and a panel GMM model for Mexican states. Estimates for Mexico City are derived by modifying national estimates according to mode shares as suggested by, and by estimating a panel Within Groups model with data aggregated by borough. Although all models agree on the sign of the elasticities the magnitudes differ greatly. Elasticities change over time and differ between the national and local levels, with smaller price responses in Mexico City. In general, price elasticities are smaller than those reported in the gasoline demand surveys, a pattern previously found in developing countries. The fact that income and vehicle stock elasticities increase over time may suggest that vehicles are being used more intensively in recent years and that Mexico City residents are purchasing larger vehicles. Elasticities with respect to metro fares are negligible, which suggests little substitution between modes. Finally, the fact that fuel efficiency elasticities are smaller than vehicle stock elasticities suggests that vehicle stock size, rather than its composition, has a larger impact on gasoline consumption in Mexico City. (author)
Wave propagation in elastic layers with damping
DEFF Research Database (Denmark)
Sorokin, Sergey; Darula, Radoslav
2016-01-01
The conventional concepts of a loss factor and complex-valued elastic moduli are used to study wave attenuation in a visco-elastic layer. The hierarchy of reduced-order models is employed to assess attenuation levels in various situations. For the forcing problem, the attenuation levels are found...
2010-01-01
... 7 Agriculture 2 2010-01-01 2010-01-01 false Elasticity. 29.6013 Section 29.6013 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Definitions § 29.6013 Elasticity. The flexible, springy nature of the tobacco leaf to...
Solitary waves on nonlinear elastic rods. I
DEFF Research Database (Denmark)
Sørensen, Mads Peter; Christiansen, Peter Leth; Lomdahl, P. S.
1984-01-01
Acoustic waves on elastic rods with circular cross section are governed by improved Boussinesq equations when transverse motion and nonlinearity in the elastic medium are taken into account. Solitary wave solutions to these equations have been found. The present paper treats the interaction between...
Elastic least-squares reverse time migration
Feng, Zongcai
2017-03-08
We use elastic least-squares reverse time migration (LSRTM) to invert for the reflectivity images of P- and S-wave impedances. Elastic LSRTMsolves the linearized elastic-wave equations for forward modeling and the adjoint equations for backpropagating the residual wavefield at each iteration. Numerical tests on synthetic data and field data reveal the advantages of elastic LSRTM over elastic reverse time migration (RTM) and acoustic LSRTM. For our examples, the elastic LSRTM images have better resolution and amplitude balancing, fewer artifacts, and less crosstalk compared with the elastic RTM images. The images are also better focused and have better reflector continuity for steeply dipping events compared to the acoustic LSRTM images. Similar to conventional leastsquares migration, elastic LSRTM also requires an accurate estimation of the P- and S-wave migration velocity models. However, the problem remains that, when there are moderate errors in the velocity model and strong multiples, LSRTMwill produce migration noise stronger than that seen in the RTM images.
Plane strain problem in microstretch elastic solid
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
stress, couple stress and first moment, which are also shown graphically. The results of micropolar elasticity are deduced as a special case from the present formulation. Keywords. Eigenvalue; microstretch elastic solid; two-dimensional plane problem; integral transform; impulsive force. 1. Introduction. It is well known that ...
Modelling the elastic properties of cellulose nanopaper
DEFF Research Database (Denmark)
Mao, Rui; Goutianos, Stergios; Tu, Wei
2017-01-01
The elastic modulus of cellulose nanopaper was predicted using a two-dimensional (2D) micromechanical fibrous network model. The elastic modulus predicted by the network model was 12 GPa, which is well within the range of experimental data for cellulose nanopapers. The stress state in the network...
Elasticity of a quantum monolayer solid
DEFF Research Database (Denmark)
Bruch, Ludwig Walter
1992-01-01
A perturbation-theory formulation of the zero-temperature elastic constants is used to verify symmetry relations for a (monolayer) triangluar lattice. A generalization of the Cauchy relation between the two elastic constants of the triangular lattice with central-pair-potential interactions...
Elastic properties and electron transport in InAs nanowires
Energy Technology Data Exchange (ETDEWEB)
Migunov, Vadim
2013-02-22
was found that the lattice distortion due to stacking fault does not affect the Young's modulus significantly. The effect of electron density redistribution is suggested as the main aspect which is responsible for an enhancement of the Young's modulus by up to 200%. This study suggests that both electrical and elastic properties of the InAs nanowires can be tuned by changing the defect density.
Reappraising elastic thickness variation at oceanic trenches
Bry, Madeleine; White, Nicky
2007-08-01
We reassess the variation of elastic thickness as a function of lithospheric plate age using a global database of bathymetric and free-air gravity profiles which are perpendicular to oceanic trenches. As in many previous studies, our starting point is the well-known floating elastic plate model. In order to remove the influence of short-wavelength features not associated with lithospheric bending, adjacent profiles from 10-Myr bins have been stacked together to construct average profiles with standard deviations. Each average profile was then inverted in a two-stage procedure. First, singular value decomposition was used to determine two unknown flexural parameters, together with a regional slope and offset, for any given elastic thickness. This procedure was repeated for a range of elastic thicknesses. Second, residual misfit was plotted as a function of elastic thickness, and the global minimum was identified. This two-stage procedure makes no prior assumptions about magnitude of the load, size of the bending moment, or whether the elastic plate is broken/continuous. We obtained excellent fits between theory and observation for both bathymetric and gravity profiles from lithosphere with an age range of 0-150 Ma. The shape of the residual misfit function indicates the degree of confidence we have in our elastic thickness estimates. The lower limit of elastic thickness is usually well determined but upper limits are often poorly constrained. Inverse modeling was carried out using a range of profile lengths (250-300, 500, and 700 km). In general, our estimates show no consistent increase of elastic thickness as a function of plate age. This surprising result is consistent with recent reassessments of elastic thickness beneath seamounts and implies either that elastic thickness is independent of plate age or that elastic thickness cannot be measured with sufficient accuracy to reveal such a relationship. Modeling of short free-air gravity profiles (250-300 km) does
Defining Elastic Fiber Interactions by Molecular Fishing
Cain, Stuart A.; McGovern, Amanda; Small, Elaine; Ward, Lyle J.; Baldock, Clair; Shuttleworth, Adrian; Kielty, Cay M.
2009-01-01
Deciphering interacting networks of the extracellular matrix is a major challenge. We describe an affinity purification and mass spectrometry strategy that has provided new insights into the molecular interactions of elastic fibers, essential extracellular assemblies that provide elastic recoil in dynamic tissues. Using cell culture models, we defined primary and secondary elastic fiber interaction networks by identifying molecular interactions with the elastic fiber molecules fibrillin-1, MAGP-1, fibulin-5, and lysyl oxidase. The sensitivity and validity of our method was confirmed by identification of known interactions with the bait proteins. Our study revealed novel extracellular protein interactions with elastic fiber molecules and delineated secondary interacting networks with fibronectin and heparan sulfate-associated molecules. This strategy is a novel approach to define the macromolecular interactions that sustain complex extracellular matrix assemblies and to gain insights into how they are integrated into their surrounding matrix. PMID:19755719
Modelling elasticity in solids using active cubes - application to simulated operations
DEFF Research Database (Denmark)
Bro-Nielsen, Morten
1995-01-01
The paper describes an approach to elastic modelling of human tissue based on the use of 3D solid active models-active cubes (M. Bro-Nielsen, 1994)-and a shape description based on the metric tensor in a solid. Active cubes are used because they provide a natural parameterization of the surface a....... The application of this approach to modelling the elastic deformation of human tissue in response to movement of bones is demonstrated...
New empirical generalizations on the determinants of price elasticity
Bijmolt, THA; Van Heerde, HJ; Pieters, RGM
The importance of pricing decisions for firms has fueled an extensive stream of research on price elasticities. In an influential meta-analytical study, Tellis (1988) summarized price elasticity research findings until 1986. However, empirical generalizations on price elasticity require
Effect of Intrinsic Ripples on Elasticity of the Graphene Monolayer.
Lee, Seungjun
2015-12-01
The effect of intrinsic ripples on the mechanical response of the graphene monolayer is investigated under uniaxial loading using molecular dynamics (MD) simulations with a focus on nonlinear behavior at a small strain. The calculated stress-strain response shows a nonlinear relation through the entire range without constant slopes as a result of the competition between ripple softening and bond stretching hardening. For a small strain, entropic contribution is dominant due to intrinsic ripples, leading to elasticity softening. As the ripples flatten at increasing strain, the energetic term due to C-C bonds stretching competes with the entropic contribution, followed by energetic dominant deformation. Elasticity softening is enhanced at increased temperature as the ripple amplitude increases. The study shows that the intrinsic ripple of graphene affects elasticity. This result suggests that a change of ripple amplitudes due to various environmental conditions such as temperature, and substrate interactions can lead to a change of the mechanical properties of graphene. The understanding of the rippling effect on the mechanical behavior of 2D materials is useful for strain-based ripple manipulation for their engineering applications.
Elastically driven intermittent microscopic dynamics in soft solids
Bouzid, Mehdi; Colombo, Jader; Barbosa, Lucas Vieira; Del Gado, Emanuela
2017-06-01
Soft solids with tunable mechanical response are at the core of new material technologies, but a crucial limit for applications is their progressive aging over time, which dramatically affects their functionalities. The generally accepted paradigm is that such aging is gradual and its origin is in slower than exponential microscopic dynamics, akin to the ones in supercooled liquids or glasses. Nevertheless, time- and space-resolved measurements have provided contrasting evidence: dynamics faster than exponential, intermittency and abrupt structural changes. Here we use 3D computer simulations of a microscopic model to reveal that the timescales governing stress relaxation, respectively, through thermal fluctuations and elastic recovery are key for the aging dynamics. When thermal fluctuations are too weak, stress heterogeneities frozen-in upon solidification can still partially relax through elastically driven fluctuations. Such fluctuations are intermittent, because of strong correlations that persist over the timescale of experiments or simulations, leading to faster than exponential dynamics.
Strain gradient elasticity within the symmetric BEM formulation
Directory of Open Access Journals (Sweden)
S. Terravecchia,
2014-07-01
Full Text Available The symmetric Galerkin Boundary Element Method is used to address a class of strain gradient elastic materials featured by a free energy function of the (classical strain and of its (first gradient. With respect to the classical elasticity, additional response variables intervene, such as the normal derivative of the displacements on the boundary, and the work-coniugate double tractions. The fundamental solutions - featuring a fourth order partial differential equations (PDEs system - exhibit singularities which in 2D may be of the order 1/ r 4 . New techniques are developed, which allow the elimination of most of the latter singularities. The present paper has to be intended as a research communication wherein some results, being elaborated within a more general paper [1], are reported.
Black hole elasticity and gapped transverse phonons in holography
Alberte, Lasma; Ammon, Martin; Baggioli, Matteo; Jiménez, Amadeo; Pujolàs, Oriol
2018-01-01
We study the elastic response of planar black hole (BH) solutions in a simple class of holographic models with broken translational invariance. We compute the transverse quasi-normal mode spectrum and the propagation speed of the lowest energy mode. We find that the speed of the lowest mode relates to the BH rigidity modulus as dictated by elasticity theory. This allows to identify these modes as transverse phonons — the pseudo Goldstone bosons of spontaneously broken translational invariance. In addition, we show that these modes have a mass gap controlled by an explicit source of the translational symmetry breaking. These results provide a new confirmation that the BHs in these models do exhibit solid properties that become more manifest at low temperatures. Also, by the AdS/CFT correspondence, this allows to extend the standard results from the effective field theory for solids to quantum-critical materials.
Role of estrogen receptor-α on food demand elasticity.
Minervini, Vanessa; Rowland, Neil E; Robertson, Kimberly L; Foster, Thomas C
2015-05-01
Estrogens have been shown to have an inhibitory effect on food intake under free-feeding conditions, yet the effects of estrogens on food-maintained operant responding have been studied to a much lesser extent and, thus, are not well understood. Therefore, the purpose of the present experiment was to use a behavioral economics paradigm to assess differences in demand elasticity between mice with knockout of the estrogen receptor subtype α, knockout of subtype β, and their wild type controls. The mice responded in a closed economy, and the price of food was increased by increasing the fixed-ratio response requirement every four sessions. Overall, we found that mice with the knockout of receptor subtype α had the most elastic demand functions. Therefore, under these conditions, estrogens increased food seeking via activation of the receptor subtype α. The results were inconsistent with those reported by previous studies that employed free-feeding conditions. © Society for the Experimental Analysis of Behavior.
Soft Elasticity in Main Chain Liquid Crystal Elastomers
Directory of Open Access Journals (Sweden)
Anselm C. Griffin
2013-06-01
Full Text Available Main chain liquid crystal elastomers exhibit several interesting phenomena, such as three different regimes of elastic response, unconventional stress-strain relationship in one of these regimes, and the shape memory effect. Investigations are beginning to reveal relationships between their macroscopic behavior and the nature of domain structure, microscopic smectic phase structure, relaxation mechanism, and sample history. These aspects of liquid crystal elastomers are briefly reviewed followed by a summary of the results of recent elastic and high-resolution X-ray diffraction studies of the shape memory effect and the dynamics of the formation of the smectic-C chevron-like layer structure. A possible route to realizing auxetic effect at molecular level is also discussed.
Mechanical modeling and characteristic study for the adhesive contact of elastic layered media
Zhang, Yuyan; Wang, Xiaoli; Tu, Qiaoan; Sun, Jianjun; Ma, Chenbo
2017-11-01
This paper investigates the adhesive contact between a smooth rigid sphere and a smooth elastic layered medium with different layer thicknesses, layer-to-substrate elastic modulus ratios and adhesion energy ratios. A numerical model is established by combining elastic responses of the contact system and an equation of equivalent adhesive contact pressure which is derived based on the Hamaker summation method and the Lennard–Jones intermolecular potential law. Simulation results for hard layer cases demonstrate that variation trends of the pull-off force with the layer thickness and elastic modulus ratio are complex. On one hand, when the elastic modulus ratio increases, the pull-off force decreases at smaller layer thicknesses, decreases at first and then increases at middle layer thicknesses, while increases monotonously at larger layer thicknesses. On the other hand, the pull-off force decreases at first and then increases with the increase in the layer thickness. Furthermore, a critical layer thickness above which the introduction of hard layer cannot reduce adhesion and an optimum layer thickness under which the pull-off force reaches a minimum are found. Both the critical and optimum layer thicknesses become larger with an increase in the Tabor parameter, while they tend to decrease with the increase in the elastic modulus ratio. In addition, the pull-off force increases sublinearly with the adhesion energy ratio if the layer thickness and elastic modulus ratio are fixed.
Elastic metamaterial beam with remotely tunable stiffness
Qian, Wei; Yu, Zhengyue; Wang, Xiaole; Lai, Yun; Yellen, Benjamin B.
2016-02-01
We demonstrate a dynamically tunable elastic metamaterial, which employs remote magnetic force to adjust its vibration absorption properties. The 1D metamaterial is constructed from a flat aluminum beam milled with a linear array of cylindrical holes. The beam is backed by a thin elastic membrane, on which thin disk-shaped permanent magnets are mounted. When excited by a shaker, the beam motion is tracked by a Laser Doppler Vibrometer, which conducts point by point scanning of the vibrating element. Elastic waves are unable to propagate through the beam when the driving frequency excites the first elastic bending mode in the unit cell. At these frequencies, the effective mass density of the unit cell becomes negative, which induces an exponentially decaying evanescent wave. Due to the non-linear elastic properties of the membrane, the effective stiffness of the unit cell can be tuned with an external magnetic force from nearby solenoids. Measurements of the linear and cubic static stiffness terms of the membrane are in excellent agreement with experimental measurements of the bandgap shift as a function of the applied force. In this implementation, bandgap shifts by as much as 40% can be achieved with ˜30 mN of applied magnetic force. This structure has potential for extension in 2D and 3D, providing a general approach for building dynamically tunable elastic metamaterials for applications in lensing and guiding elastic waves.
Elastic metamaterial beam with remotely tunable stiffness
International Nuclear Information System (INIS)
Qian, Wei; Yu, Zhengyue; Wang, Xiaole; Lai, Yun; Yellen, Benjamin B.
2016-01-01
We demonstrate a dynamically tunable elastic metamaterial, which employs remote magnetic force to adjust its vibration absorption properties. The 1D metamaterial is constructed from a flat aluminum beam milled with a linear array of cylindrical holes. The beam is backed by a thin elastic membrane, on which thin disk-shaped permanent magnets are mounted. When excited by a shaker, the beam motion is tracked by a Laser Doppler Vibrometer, which conducts point by point scanning of the vibrating element. Elastic waves are unable to propagate through the beam when the driving frequency excites the first elastic bending mode in the unit cell. At these frequencies, the effective mass density of the unit cell becomes negative, which induces an exponentially decaying evanescent wave. Due to the non-linear elastic properties of the membrane, the effective stiffness of the unit cell can be tuned with an external magnetic force from nearby solenoids. Measurements of the linear and cubic static stiffness terms of the membrane are in excellent agreement with experimental measurements of the bandgap shift as a function of the applied force. In this implementation, bandgap shifts by as much as 40% can be achieved with ∼30 mN of applied magnetic force. This structure has potential for extension in 2D and 3D, providing a general approach for building dynamically tunable elastic metamaterials for applications in lensing and guiding elastic waves
Microstructural evolution in inhomogeneous elastic media
International Nuclear Information System (INIS)
Jou, H.J.; Leo, P.H.; Lowengrub, J.S.
1997-01-01
We simulate the diffusional evolution of microstructures produced by solid state diffusional transformations in elastically stressed binary alloys in two dimensions. The microstructure consists of arbitrarily shaped precipitates embedded coherently in an infinite matrix. The precipitate and matrix are taken to be elastically isotropic, although they may have different elastic constants (elastically inhomogeneous). Both far-field applied strains and mismatch strains between the phases are considered. The diffusion and elastic fields are calculated using the boundary integral method, together with a small scale preconditioner to remove ill-conditioning. The precipitate-matrix interfaces are tracked using a nonstiff time updating method. The numerical method is spectrally accurate and efficient. Simulations of a single precipitate indicate that precipitate shapes depend strongly on the mass flux into the system as well as on the elastic fields. Growing shapes (positive mass flux) are dendritic while equilibrium shapes (zero mass flux) are squarish. Simulations of multiparticle systems show complicated interactions between precipitate morphology and the overall development of microstructure (i.e., precipitate alignment, translation, merging, and coarsening). In both single and multiple particle simulations, the details of the microstructural evolution depend strongly o the elastic inhomogeneity, misfit strain, and applied fields. 57 refs., 24 figs
Application of numerical methods to elasticity imaging.
Castaneda, Benjamin; Ormachea, Juvenal; Rodríguez, Paul; Parker, Kevin J
2013-03-01
Elasticity imaging can be understood as the intersection of the study of biomechanical properties, imaging sciences, and physics. It was mainly motivated by the fact that pathological tissue presents an increased stiffness when compared to surrounding normal tissue. In the last two decades, research on elasticity imaging has been an international and interdisciplinary pursuit aiming to map the viscoelastic properties of tissue in order to provide clinically useful information. As a result, several modalities of elasticity imaging, mostly based on ultrasound but also on magnetic resonance imaging and optical coherence tomography, have been proposed and applied to a number of clinical applications: cancer diagnosis (prostate, breast, liver), hepatic cirrhosis, renal disease, thyroiditis, arterial plaque evaluation, wall stiffness in arteries, evaluation of thrombosis in veins, and many others. In this context, numerical methods are applied to solve forward and inverse problems implicit in the algorithms in order to estimate viscoelastic linear and nonlinear parameters, especially for quantitative elasticity imaging modalities. In this work, an introduction to elasticity imaging modalities is presented. The working principle of qualitative modalities (sonoelasticity, strain elastography, acoustic radiation force impulse) and quantitative modalities (Crawling Waves Sonoelastography, Spatially Modulated Ultrasound Radiation Force (SMURF), Supersonic Imaging) will be explained. Subsequently, the areas in which numerical methods can be applied to elasticity imaging are highlighted and discussed. Finally, we present a detailed example of applying total variation and AM-FM techniques to the estimation of elasticity.
Integrated magnetic and elastic force systems.
Bourauel, Christoph; Köklü, Saduman O; Vardimon, Alexander D
2002-08-01
Magnetic force increases as the distance (d) of the force- generating elements (F approximately 1/d(2)) decreases, whereas elastic force decreases as the distance decreases (F approximately kd). These opposing characteristics suggest that combining both force systems will establish an integrated system with a long-range working ability. The objective of this study was to determine the vertical closure force (F(X)) and the transverse axis moment (M(Y)) of an integrated force system, ie, attracting magnets with elastics (vertical or Classes II and III). F(X) and M(Y) were examined on the orthodontic measurement and simulation system. It was found that the integrated force system had a positive closure force (+F(X)) that never declined to 0 and a long working range. Three regions characterized the force-deflection curve of F(X): the magnetic region (0-3 mm, for magnets with 3/16-in medium elastics), in which the decline in magnetic force was larger than the increase in elastic force (6.3-2.5 N); the constant region (3-7 mm), in which the decline in magnetic force equaled the increase in elastic force (2.5-2.9 N); and the elastic region (7-10 mm), in which there was only an increase in elastic force (2.9-3.5 N). The transverse axis moment (+M(Y)), which tends to close the bite, developed especially in magnets with a single vertical elastic. Clinically, inactivation of vertical elastics by closing the mouth can be overruled by the integrated force system because it exerts adequate force level at both short and long distances.
Elastic/Inelastic Measurement Project
Energy Technology Data Exchange (ETDEWEB)
Yates, Steven [Univ. of Kentucky, Lexington, KY (United States); Hicks, Sally [Univ. of Dallas, TX (United States); Vanhoy, Jeffrey [U.S. Naval Academy, Annapolis, MD (United States); McEllistrem, Marcus [Univ. of Kentucky, Lexington, KY (United States)
2016-03-01
The work scope involves the measurement of neutron scattering from natural sodium (^{23}Na) and two isotopes of iron, ^{56}Fe and ^{54}Fe. Angular distributions, i.e., differential cross sections, of the scattered neutrons will be measured for 5 to 10 incident neutron energies per year. The work of the first year concentrates on ^{23}Na, while the enriched iron samples are procured. Differential neutron scattering cross sections provide information to guide nuclear reaction model calculations in the low-energy (few MeV) fast-neutron region. This region lies just above the isolated resonance region, which in general is well studied; however, model calculations are difficult in this region because overlapping resonance structure is evident and direct nuclear reactions are becoming important. The standard optical model treatment exhibits good predictive ability for the wide-region average cross sections but cannot treat the overlapping resonance features. In addition, models that do predict the direct reaction component must be guided by measurements to describe correctly the strength of the direct component, e.g., β_{2} must be known to describe the direct component of the scattering to the first excited state. Measurements of the elastic scattering differential cross sections guide the optical model calculations, while inelastic differential cross sections provide the crucial information for correctly describing the direct component. Activities occurring during the performance period are described.
Elastic/Inelastic Measurement Project
International Nuclear Information System (INIS)
Yates, Steven; Hicks, Sally; Vanhoy, Jeffrey; McEllistrem, Marcus
2015-12-01
The work scope involves the measurement of neutron scattering from natural sodium ( 23 Na) and two isotopes of iron, 56 Fe and 54 Fe. Angular distributions, i.e., differential cross sections, of the scattered neutrons will be measured for 5 to 10 incident neutron energies per year. The work of the first year concentrates on 23 Na, while the enriched iron samples are procured. Differential neutron scattering cross sections provide information to guide nuclear reaction model calculations in the low-@@energy (few MeV) fast-@@neutron region. This region lies just above the isolated resonance region, which in general is well studied; however, model calculations are difficult in this region because overlapping resonance structure is evident and direct nuclear reactions are becoming important. The standard optical model treatment exhibits good predictive ability for the wide-@@region average cross sections but cannot treat the overlapping resonance features. In addition, models that do predict the direct reaction component must be guided by measurements to describe correctly the strength of the direct component, e.g., @@ 2 must be known to describe the direct component of the scattering to the first excited state. Measurements of the elastic scattering differential cross sections guide the optical model calculations, while inelastic differential cross sections provide the crucial information for correctly describing the direct component. Activities occurring during the performance period are described.
Highly elastic conductive polymeric MEMS
Ruhhammer, J.; Zens, M.; Goldschmidtboeing, F.; Seifert, A.; Woias, P.
2015-02-01
Polymeric structures with integrated, functional microelectrical mechanical systems (MEMS) elements are increasingly important in various applications such as biomedical systems or wearable smart devices. These applications require highly flexible and elastic polymers with good conductivity, which can be embedded into a matrix that undergoes large deformations. Conductive polydimethylsiloxane (PDMS) is a suitable candidate but is still challenging to fabricate. Conductivity is achieved by filling a nonconductive PDMS matrix with conductive particles. In this work, we present an approach that uses new mixing techniques to fabricate conductive PDMS with different fillers such as carbon black, silver particles, and multiwalled carbon nanotubes. Additionally, the electrical properties of all three composites are examined under continuous mechanical stress. Furthermore, we present a novel, low-cost, simple three-step molding process that transfers a micro patterned silicon master into a polystyrene (PS) polytetrafluoroethylene (PTFE) replica with improved release features. This PS/PTFE mold is used for subsequent structuring of conductive PDMS with high accuracy. The non sticking characteristics enable the fabrication of delicate structures using a very soft PDMS, which is usually hard to release from conventional molds. Moreover, the process can also be applied to polyurethanes and various other material combinations.
SIMULATION OFTHERMO-ELASTICS PROPERTIESOFTHERMALBARRIERCOATINGS
Directory of Open Access Journals (Sweden)
A.M.Ferouani M. Ferouani
2015-07-01
Full Text Available Thermal barrier coatings are used to protect different parts in compressors and turbines from heat. They are generally composed of two layers, one metallic layer providing resistance to heat corrosion and oxidation, and one thermally insulating ceramic layer. Two different techniques are industrially used. Plasma spray results in a lamellar structure granting a low thermal conductivity, but with a low thermal expansion compliance. Electron Beam Physical Vapour Deposition generates a columnar structure allowing a better accommodation of the thermal expansion stresses, entailing improved lifetime of the coating, but with a higher thermal conductivity. The aim of the paper presented here is to develop a procedure of analysis based on the micro structural observation for the prediction of the properties of new coatings in court of industrial development and to predict the effect of the posterior thermal treatment on the properties of the coatings carried out. For a given coating, one has to calculate linear elasticity and its evolution with the temperature as well as thermal expansion, aiming at predicting different parameters related to the in service deterioration.
Robust Force Control of Series Elastic Actuators
Directory of Open Access Journals (Sweden)
Andrea Calanca
2014-07-01
Full Text Available Force-controlled series elastic actuators (SEA are widely used in novel human-robot interaction (HRI applications, such as assistive and rehabilitation robotics. These systems are characterized by the presence of the “human in the loop”, so that control response and stability depend on uncertain human dynamics, including reflexes and voluntary forces. This paper proposes a force control approach that guarantees the stability and robustness of the coupled human-robot system, based on sliding-mode control (SMC, considering the human dynamics as a disturbance to reject. We propose a chattering free solution that employs simple task models to obtain high performance, comparable with second order solutions. Theoretical stability is proven within the sliding mode framework, and predictability is reached by avoiding the reaching phase by design. Furthermore, safety is introduced by a proper design of the sliding surface. The practical feasibility of the approach is shown using an SEA prototype coupled with a human impedance in severe stress tests. To show the quality of the approach, we report a comparison with state-of-the-art second order SMC, passivity-based control and adaptive control solutions.
Elasticity of Substitution and Antidumping Measures
DEFF Research Database (Denmark)
Drud Hansen, Jørgen; Meinen, Philipp; Nielsen, Jørgen Ulff-Møller
therefore also vary inversely with the elasticity of substitution at least for countries which have a strong focus on prices in the determination of their anti-dumping measures. We test this for ten countries from 1990 to 2009 using data on anti-dumping from Chad Bown (2010) and US-data at 8-digit level......Abstract This paper analyzes the role of the elasticity of substitution for anti-dumping decisions across countries. In monopolistic competition models with cost heterogeneous firms across countries, price differences vary inversely with the elasticity of substitution. Anti-dumping duties should...
Elastic and inelastic psi production by muons
International Nuclear Information System (INIS)
Loken, S.C.
1981-06-01
Results are presented on the elastic and inelastic production of psi (3.1). The elastic data are qualitative agreement with the predictions of photon-gluon fusion but have a steeper dependence on Q 2 than the model predicts. A QCD calculation accounts well for the shape of the inelastic data in inelasticity, Q 2 and E/sub γ/, but fails to account for the absolute cross section. At 209 GeV, the cross-section for elastic psi production is 0.36 +- 0.07 nb; for inelastic, 0.28 +- 0.06nb
Defects in Static Elasticity of Quasicrystals
Directory of Open Access Journals (Sweden)
Qin Xu
2017-12-01
Full Text Available A review on mathematical elasticity of quasicrystals is given. In this review, the focus is on various defects of quasicrystals. Dislocation and crack are two classes of typical topological defects, while their existence has great influence on the mechanical behavior of quasicrystals. The analytic and numerical solutions of dislocations and crack in quasicrystals are the core of the static and dynamic elasticity theory, and this paper gives a comprehensive review on the solutions for dislocations and crack with different configurations in different various important quasicrystalline systems. We review some results in linear elasticity of quasicrystals, referring to different boundary value problems. We also add some new achievements.
Marangoni elasticity of flowing soap films
Kim, Ildoo; Mandre, Shreyas
2017-08-01
We measure the Marangoni elasticity of a flowing soap film to be 22 mN/m irrespective of its width, thickness, flow speed, or the bulk soap concentration. We perform this measurement by generating an oblique shock in the soap film and measuring the shock angle, flow speed, and thickness. We postulate that the elasticity is constant because the film surface is crowded with soap molecules. Our method allows nondestructive measurement of flowing soap film elasticity and the value 22 mN/m is likely applicable to other similarly constructed flowing soap films.
Bashur, Chris A; Venkataraman, Lavanya; Ramamurthi, Anand
2012-06-01
Cardiovascular tissues exhibit architecturally complex extracellular matrices, of which the elastic matrix forms a major component. The elastic matrix critically maintains native structural configurations of vascular tissues, determines their ability to recoil after stretch, and regulates cell signaling pathways involved in morphogenesis, injury response, and inflammation via biomechanical transduction. The ability to tissue engineer vascular replacements that incorporate elastic matrix superstructures unique to cardiac and vascular tissues is thus important to maintaining vascular homeostasis. However, the vascular elastic matrix is particularly difficult to tissue engineer due to the inherently poor ability of adult vascular cells to synthesize elastin precursors and organize them into mature structures in a manner that replicates the biocomplexity of elastic matrix assembly during development. This review discusses current tissue engineering materials (e.g., growth factors and scaffolds) and methods (e.g., dynamic stretch and contact guidance) used to promote cellular synthesis and assembly of elastic matrix superstructures, and the limitations of these approaches when applied to smooth muscle cells, the primary elastin-generating cell type in vascular tissues. The potential application of these methods for in situ regeneration of disrupted elastic matrix at sites of proteolytic vascular disease (e.g., abdominal aortic aneurysms) is also discussed. Finally, the review describes the potential utility of alternative cell types to elastic tissue engineering and regenerative matrix repair. Future progress in the field is contingent on developing a thorough understanding of developmental elastogenesis and then mimicking the spatiotemporal changes in the cellular microenvironment that occur during that phase. This will enable us to tissue engineer clinically applicable elastic vascular tissue replacements and to develop elastogenic therapies to restore homeostasis in
International Nuclear Information System (INIS)
Sancho, Ferran
2010-01-01
There is a considerable body of literature that has studied whether or not an adequately designed tax swap, whereby an ecotax is levied and some other tax is reduced while keeping government income constant, may achieve a so-called double dividend, that is, an increase in environmental quality and an increase in overall efficiency. Arguments in favor and against are abundant. Our position is that the issue should be empirically studied starting from an actual, non-optimal tax system structure and by way of checking the responsiveness of equilibria to revenue neutral tax regimes under alternate scenarios regarding technological substitution. With the use of a CGE model, we find that the most critical elasticity for achieving a double dividend is the substitution elasticity between labor and capital whereas the elasticity that would generate the highest reduction in carbon dioxide emissions is the substitution elasticity among energy goods. (author)
Metric elasticity in a collapsing star: Gravitational radiation coupled to torsional motion
International Nuclear Information System (INIS)
Gerlach, U.H.; Scott, J.F.
1986-01-01
Torsional oscillatory matter motion as well as differential rotation couple via the linearized Einstein field equations to the gravitational degrees of freedom. For an arbitrary spherically symmetric background, such as that of a wildly pulsating or a catastrophically collapsing star, we exhibit (a) the strain tensor and (b) the corresponding stress-energy tensor. It is found that in the star there are two elasticity tensors. One expresses the familiar elasticity of matter, the other expresses the elasticity of the geometry. This metric elasticity is responsible for coupling the gravitational and matter degrees of freedom. The two coupled scalar wave equations for these degrees of freedom are exhibited. Also exhibited are their characteristics as well as the junction conditions for their solutions across any spherical surface of discontinuity
Predicting elastic properties of β-HMX from first-principles calculations.
Peng, Qing; Rahul; Wang, Guangyu; Liu, Gui-Rong; Grimme, Stefan; De, Suvranu
2015-05-07
We investigate the performance of van der Waals (vdW) functions in predicting the elastic constants of β cyclotetramethylene tetranitramine (HMX) energetic molecular crystals using density functional theory (DFT) calculations. We confirm that the accuracy of the elastic constants is significantly improved using the vdW corrections with environment-dependent C6 together with PBE and revised PBE exchange-correlation functionals. The elastic constants obtained using PBE-D3(0) calculations yield the most accurate mechanical response of β-HMX when compared with experimental stress-strain data. Our results suggest that PBE-D3 calculations are reliable in predicting the elastic constants of this material.
Using GPS and GRACE data to assess Solid Earth elastic parameters at regional scale
DEFF Research Database (Denmark)
Barletta, Valentina Roberta; Borghi, A.; Aoudia, A.
2012-01-01
response, by convolution with suitable elastic green functions, relying on selected Earth model and related layering and elastic parameters. We calculate at regional scale the time series of monthly uplift associated with the mass redistribution observed by GRACE implementing the high resolution technique......We propose a way to combine GPS and GRACE data for regional scale cross check and validation especially of the most commonly used PREM (Preliminary Earth Reference Model). In form of h and k Love numbers, global PREM is very often used to simulate elastic rebound due to present-day ice mass loss......, to derive the mass distribution produced by the observed GRACE time series, and it is also used for atmospheric loading correction both in GPS and in GRACE dealiasing products. GRACE data provide load estimates, usually given as water equivalent mass distribution, from which one derives the Earth elastic...
Energy Technology Data Exchange (ETDEWEB)
Sancho, Ferran, E-mail: Ferran.Sancho@uab.ca [Departament d' Economia, Universitat Autonoma de Barcelona, 08193-Bellaterra (Spain)
2010-06-15
There is a considerable body of literature that has studied whether or not an adequately designed tax swap, whereby an ecotax is levied and some other tax is reduced while keeping government income constant, may achieve a so-called double dividend, that is, an increase in environmental quality and an increase in overall efficiency. Arguments in favor and against are abundant. Our position is that the issue should be empirically studied starting from an actual, non-optimal tax system structure and by way of checking the responsiveness of equilibria to revenue neutral tax regimes under alternate scenarios regarding technological substitution. With the use of a CGE model, we find that the most critical elasticity for achieving a double dividend is the substitution elasticity between labor and capital whereas the elasticity that would generate the highest reduction in carbon dioxide emissions is the substitution elasticity among energy goods.
Energy Technology Data Exchange (ETDEWEB)
Sancho, Ferran [Departament d' Economia, Universitat Autonoma de Barcelona, 08193-Bellaterra (Spain)
2010-06-15
There is a considerable body of literature that has studied whether or not an adequately designed tax swap, whereby an ecotax is levied and some other tax is reduced while keeping government income constant, may achieve a so-called double dividend, that is, an increase in environmental quality and an increase in overall efficiency. Arguments in favor and against are abundant. Our position is that the issue should be empirically studied starting from an actual, non-optimal tax system structure and by way of checking the responsiveness of equilibria to revenue neutral tax regimes under alternate scenarios regarding technological substitution. With the use of a CGE model, we find that the most critical elasticity for achieving a double dividend is the substitution elasticity between labor and capital whereas the elasticity that would generate the highest reduction in carbon dioxide emissions is the substitution elasticity among energy goods. (author)
A comparison of time-history elastic plastic piping analysis with measurement
International Nuclear Information System (INIS)
Scavuzzo, R.J.; Sansalone, K.H.
1992-01-01
The GE/ETEC Green piping system was subjected to high seismic inputs from hydraulic sleds at each pipe foundation. These inputs were high enough to force bending stresses into the plastic regime. Strain gages recorded the pipe response at various positions within the system. The ABAQUS finite element code was used to model this piping system and the dynamic input. Problems associated with the dynamic input are discussed. Various types of finite elements were evaluated for accurancy. Both an elastic time-history analysis and an elastic-plastic time-history analysis of the system were conducted. Results of these analyses are compared to each other and the experimental data. These comparisons indicated that elastic analysis of dynamic strains are conservative at all points of comparison and that there is good agreement between the nonlinear elastic-plastic analysis and experimental data. (orig.)
Elasticity of population growth with respect to the intensity of biotic or abiotic driving factors.
Lee, Charlotte T
2017-04-01
Demographic analysis can elucidate how driving factors, such as climate or species interactions, affect populations. One important question is how growth would respond to future changes in the mean intensity of a driving factor or in its variability, such as might be expected in a fluctuating and shifting climate. Here I develop an approach to computing new stochastic elasticities to address this question. The linchpin of this novel approach is the multidimensional demographic difference that expresses how a population responds to change in the driving factor between two discrete levels of intensity. I use this difference to design a perturbation matrix that links data from common empirical sampling schemes with rigorous theory for stochastic elasticities. Although the starting point is a difference, the products of this synthesis are true derivatives: they are elasticity with respect to the mean intensity of a driving factor, and elasticity with respect to variability in a driving factor. Applying the methods to published data, I demonstrate how these new elasticities can shed light on growth rate response within and at the boundary of the previously observed range of the driving factor, thus helpfully indicating nonlinearity in the observed and in the potential future response. The stochastic approach simplifies in a fixed environment, yielding a compact formula for deterministic elasticity to a driving factor. © 2017 by the Ecological Society of America.
Ye, Wei; Liu, Yifei
2018-04-01
This work formulates the solutions to the elastic and piezoelectric fields around a quantum wire (QWR) with interface elasticity effect. Closed-form solutions to the piezoelectric potential field of zincblende QWR/matrix heterostructures grown along [111] crystallographic orientation are found and numerical results of InAs/InP heterostructures are provided as an example. The piezoelectric potential in the matrix depends on the interface elasticity, the radius and stiffness of the QWR. Our results indicate that interface elasticity can significantly alter the elastic and piezoelectric fields near the interface. Additionally, when the elastic property of the QWR is considered to be anisotropic in contrary to the common isotropic assumption, piezoelectric potentials are found to be distinct near the interface, but the deviations are negligible at positions far away from the interface.
Elastic and inelastic heavy ion scattering
International Nuclear Information System (INIS)
Toepffer, C.; University of the Witwatersrand, Johannesburg; Richter, A.
1977-02-01
In the field of elastic and inelastic heavy ion scattering, the following issues are dealt with: semiclassical descriptive approximations, optical potentials, barriers, critical radii and angular momenta, excitation functions and the application to superheavy ions and high energies. (WL) [de
Biomolecular analysis of elastic fibre molecules.
Cain, Stuart A; Raynal, Bertrand; Hodson, Nigel; Shuttleworth, Adrian; Kielty, Cay M
2008-05-01
Elastic fibres are macromolecular extracellular matrix assemblies that endow dynamic connective tissues such as arteries, lungs and skin with the property of elastic recoil. Here, we describe how we have purified elastic fibre molecules and then analysed them using a range of biochemical and biomolecular approaches. Such approaches have provided powerful insights into the complex hierarchical processes of extracellular matrix assembly. We outline molecular interaction and kinetics assays using Biacore, biophysical approaches such as multi-angle laser light scattering and analytical ultracentrifugation which provide information on molecular and macromolecular shape and mass in solution, the visualisation of molecules and assemblies using microscopy approaches such as atomic force microscopy and environmental scanning electron microscopy, and compositional analysis of macromolecular complexes using mass spectrometry. Data from these in vitro analytical approaches can be combined to develop powerful new models of elastic fibre assembly.
Elastic spheres can walk on water
Belden, Jesse; Hurd, Randy C.; Jandron, Michael A.; Bower, Allan F.; Truscott, Tadd T.
2016-02-01
Incited by public fascination and engineering application, water-skipping of rigid stones and spheres has received considerable study. While these objects can be coaxed to ricochet, elastic spheres demonstrate superior water-skipping ability, but little is known about the effect of large material compliance on water impact physics. Here we show that upon water impact, very compliant spheres naturally assume a disk-like geometry and dynamic orientation that are favourable for water-skipping. Experiments and numerical modelling reveal that the initial spherical shape evolves as elastic waves propagate through the material. We find that the skipping dynamics are governed by the wave propagation speed and by the ratio of material shear modulus to hydrodynamic pressure. With these insights, we explain why softer spheres skip more easily than stiffer ones. Our results advance understanding of fluid-elastic body interaction during water impact, which could benefit inflatable craft modelling and, more playfully, design of elastic aquatic toys.
ELASTIC CHARACTERIZATION OF Eucalyptus citriodora WOOD
Directory of Open Access Journals (Sweden)
Adriano Wagner Ballarin
2003-01-01
Full Text Available This paper contributed to the elastic characterization of Eucalyptus citriodora grown inBrazil, considering an orthotropic model and evaluating its most important elastic constants.Considering this as a reference work to establish basic elastic ratios — several important elasticconstants of Brazilian woods were not determined yet - the experimental set-up utilized one tree of 65years old from plantations of “Horto Florestal Navarro de Andrade”, at Rio Claro-SP, Brazil. All theexperimental procedures attended NBR 7190/97 – Brazilian Code for wooden structures –withconventional tension and compression tests. Results showed statistical identity between compressionand tension modulus of elasticity. The relation observed between longitudinal and radial modulus ofelasticity was 10 (EL/ER ≈ 10 and same relation, considering shear modulus (modulus of rigidity was20 (EL/GLR ≈ 20. These results, associated with Poisson’s ratios herein determined, allow theoreticalmodeling of wood mechanical behavior in structures.
Appendix C demand elasticities for highway travel.
2000-04-12
An elasticity summarizes a large amount of information in a single number. Levels and : distribution of incomes, price levels of the specific good and of substitute and complementary : goods, preferences and tastes, transaction costs, etc., can, cete...
Elastic scattering of slow positrons by helium
International Nuclear Information System (INIS)
Amusia, M.Ya.; Cherepkov, N.A.; Chernysheva, L.V.; Shapiro, S.G.
1976-01-01
The s-, p-, d- and f-wave phaseshifts for elastic scattering of slow positrons by He are calculated using a simplified version of the random phase approximation with exchange, with virtual positronium formation effect taken into account. (author)
Elastic form factors at higher CEBAF energies
Energy Technology Data Exchange (ETDEWEB)
Petratos, G.G. [Kent State Univ., OH (United States)
1994-04-01
The prospects for elastic scattering from few body systems with higher beam energies at CEBAF is presented. The deuteron and{sup 3}He elastic structure functions A(Q{sup 2}) can be measured at sufficiently high momentum transfers to study the transition between the conventional meson-nucleon and the constituent quark-gluon descriptions. Possible improvements in the proton magnetic form factor data are also presented.
Damping elastic oscillations of digging mechanism
Kuznetsov, N. K.; Makhno, D. E.; Iov, I. A.
2017-10-01
The article studies methods for reducing dynamic loading and elastic oscillations of excavator buckets using dampers. The authors suggest a structural scheme for damping bucket oscillations using a damping device installed in a running gear of the traction cable. The results of numerical efficiency simulation are presented. The article shows that the system helps to reduce intensity of elastic oscillations and a transition period in acceleration and deceleration modes.
Global Value Chains and Trade Elasticities
Byron S. Gangnes; Alyson C. Ma; Ari Van Assche
2014-01-01
Previous studies have argued that global value chains (GVCs) have increased the sensitivity of trade to external business cycle shocks. This may occur either because GVC trade is concentrated in durable goods industries, which are known to have high income elasticities (a composition effect), or because, within industries, GVC trade has a higher income elasticity than regular trade (a supply chain effect). Using Chinese trade data across customs regimes and industries during the period 1995-2...
Flow of Tunable Elastic Microcapsules through Constrictions
do Nascimento, D?bora F.; Avenda?o, Jorge A.; Mehl, Ana; Moura, Maria J. B.; Carvalho, Marcio S.; Duncanson, Wynter J.
2017-01-01
We design and fabricate elastically tunable monodisperse microcapsules using microfluidics and cross-linkable polydimethylsiloxane (PDMS). The overall stiffness of the microcapsules is governed by both the thickness and cross-link ratio of the polymer shell. Flowing suspensions of microcapsules through constricted spaces leads to transient blockage of fluid flow, thus altering the flow behavior. The ability to tune microcapsule mechanical properties enables the design of elastic microcapsules...
High multipolarity elastic magnetic electron scattering
International Nuclear Information System (INIS)
DeVries, H.; DeWitt-Huberts, P.; Dieperink, A.E.L.; Donnelly, T.W.
1977-01-01
Elastic magnetic electron scattering calculations were performed for 93 Nb and 87 Sr. A comparison is made between proton and neutron radial distributions for a given shell obtained by measurements on odd-proton and odd-neutron nuclei as above in the same region of the periodic table. The experimental data are from previous work in the presented plots of the electron elastic magnetic scattering for strontium 87 as functions of momentum transfer. 5 references
A Linear Theory for Pretwisted Elastic Beams
DEFF Research Database (Denmark)
Krenk, Steen
1983-01-01
contains a general system of differential equations and gives explicit solutions for homogenous extension, torsion, and bending. The theory accounts explicitly for the shear center, the elastic center, and the axis of pretwist. The resulting torsion-extension coupling is in agreement with a recent...... asymptotic result from three-dimensional elasticity apart from the limitation imposed by neglecting deformations of the cross sections in their own plane....
Stress transmission through a model system of cohesionless elastic grains
Da Silva, Miguel; Rajchenbach, Jean
2000-08-01
Understanding the mechanical properties of granular materials is important for applications in civil and chemical engineering, geophysical sciences and the food industry, as well as for the control or prevention of avalanches and landslides. Unlike continuous media, granular materials lack cohesion, and cannot resist tensile stresses. Current descriptions of the mechanical properties of collections of cohesionless grains have relied either on elasto-plastic models classically used in civil engineering, or on a recent model involving hyperbolic equations. The former models suggest that collections of elastic grains submitted to a compressive load will behave elastically. Here we present the results of an experiment on a two-dimensional model system-made of discrete square cells submitted to a point load-in which the region in which the stress is confined is photoelastically visualized as a parabola. These results, which can be interpreted within a statistical framework, demonstrate that the collective response of the pile contradicts the standard elastic predictions and supports a diffusive description of stress transmission. We expect that these findings will be applicable to problems in soil mechanics, such as the behaviour of cohesionless soils or sand piles.
Income Elasticity Literature Review | Science Inventory | US ...
Following advice from the SAB Council, when estimating the economic value of reductions in air pollution-related mortality and morbidity risk, EPA accounts for the effect of personal income on the willingness to pay to reduce the risk of adverse health outcomes. These income growth adjustment factors are calculated using a combination of income elasticity estimates and income growth projections, both of which have remained essentially unchanged since 1999. These income elasticity estimates vary according to the severity of illness. EPA recently received advice from the SAB regarding the range of income elasticities to apply as well as the research standards to use when selecting income elasticity estimates. Following this advice, EPA consulted with a contractor to update its income elasticity and income growth projections, and generate new income growth adjustment factors. The SAB would evaluate the income elasticity estimates identified in the EPA-provided literature review, determining the extent to which these estimates are appropriate to use in human health benefits assessments.
New insights into elastic fiber assembly.
Wagenseil, Jessica E; Mecham, Robert P
2007-12-01
Elastic fibers provide recoil to tissues that undergo repeated stretch, such as the large arteries and lung. These large extracellular matrix (ECM) structures contain numerous components, and our understanding of elastic fiber assembly is changing as we learn more about the various molecules associated with the assembly process. The main components of elastic fibers are elastin and microfibrils. Elastin makes up the bulk of the mature fiber and is encoded by a single gene. Microfibrils consist mainly of fibrillin, but also contain or associate with proteins such as microfibril associated glycoproteins (MAGPs), fibulins, and EMILIN-1. Microfibrils were thought to facilitate alignment of elastin monomers prior to cross-linking by lysyl oxidase (LOX). We now know that their role, as well as the overall assembly process, is more complex. Elastic fiber formation involves elaborate spatial and temporal regulation of all of the involved proteins and is difficult to recapitulate in adult tissues. This report summarizes the known interactions between elastin and the microfibrillar proteins and their role in elastic fiber assembly based on in vitro studies and evidence from knockout mice. We also propose a model of elastic fiber assembly based on the current data that incorporates interactions between elastin, LOXs, fibulins and the microfibril, as well as the pivotal role played by cells in structuring the final functional fiber. Copyright 2008 Wiley-Liss, Inc.
TOPICAL REVIEW: Inverse problems in elasticity
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.
Elastic reflection waveform inversion with variable density
Li, Yuanyuan
2017-08-17
Elastic full waveform inversion (FWI) provides a better description of the subsurface than those given by the acoustic assumption. However it suffers from a more serious cycle skipping problem compared with the latter. Reflection waveform inversion (RWI) provides a method to build a good background model, which can serve as an initial model for elastic FWI. Therefore, we introduce the concept of RWI for elastic media, and propose elastic RWI with variable density. We apply Born modeling to generate the synthetic reflection data by using optimized perturbations of P- and S-wave velocities and density. The inversion for the perturbations in P- and S-wave velocities and density is similar to elastic least-squares reverse time migration (LSRTM). An incorrect initial model will lead to some misfits at the far offsets of reflections; thus, can be utilized to update the background velocity. We optimize the perturbation and background models in a nested approach. Numerical tests on the Marmousi model demonstrate that our method is able to build reasonably good background models for elastic FWI with absence of low frequencies, and it can deal with the variable density, which is needed in real cases.
THE ELASTICITY OF EXPORT DEMAND FOR US COTTON
Paudel, Laxmi; Houston, Jack E.; Adhikari, Murali; Devkota, Nirmala
2004-01-01
There exist conflicting views among the researchers about the magnitudes of US cotton export demand elasticity, ranging from the highly inelastic to highly elastic. An Armington model was used to analyze the export demand elasticity of US Cotton. Our analysis confirms an elastic nature of US cotton export demand.
Cell visco-elasticity measured with AFM and optical trapping at sub-micrometer deformations.
Directory of Open Access Journals (Sweden)
Schanila Nawaz
Full Text Available The measurement of the elastic properties of cells is widely used as an indicator for cellular changes during differentiation, upon drug treatment, or resulting from the interaction with the supporting matrix. Elasticity is routinely quantified by indenting the cell with a probe of an AFM while applying nano-Newton forces. Because the resulting deformations are in the micrometer range, the measurements will be affected by the finite thickness of the cell, viscous effects and even cell damage induced by the experiment itself. Here, we have analyzed the response of single 3T3 fibroblasts that were indented with a micrometer-sized bead attached to an AFM cantilever at forces from 30-600 pN, resulting in indentations ranging from 0.2 to 1.2 micrometer. To investigate the cellular response at lower forces up to 10 pN, we developed an optical trap to indent the cell in vertical direction, normal to the plane of the coverslip. Deformations of up to two hundred nanometers achieved at forces of up to 30 pN showed a reversible, thus truly elastic response that was independent on the rate of deformation. We found that at such small deformations, the elastic modulus of 100 Pa is largely determined by the presence of the actin cortex. At higher indentations, viscous effects led to an increase of the apparent elastic modulus. This viscous contribution that followed a weak power law, increased at larger cell indentations. Both AFM and optical trapping indentation experiments give consistent results for the cell elasticity. Optical trapping has the benefit of a lower force noise, which allows a more accurate determination of the absolute indentation. The combination of both techniques allows the investigation of single cells at small and large indentations and enables the separation of their viscous and elastic components.
Liu, Jianyu; Zhang, Qiang; Zhang, Yongqiang; Chen, Xi; Li, Jianfeng; Aryal, Santosh K.
2017-10-01
Climatic elasticity has been widely applied to assess streamflow responses to climate changes. To fully assess impacts of climate under global warming on streamflow and reduce the error and uncertainty from various control variables, we develop a four-parameter (precipitation, catchment characteristics n, and maximum and minimum temperatures) climatic elasticity method named PnT, based on the widely used Budyko framework and simplified Makkink equation. We use this method to carry out the first comprehensive evaluation of the streamflow response to potential climate change for 372 widely spread catchments in China. The PnT climatic elasticity was first evaluated for a period 1980-2000, and then used to evaluate streamflow change response to climate change based on 12 global climate models under Representative Concentration Pathway 2.6 (RCP2.6) and RCP 8.5 emission scenarios. The results show that (1) the PnT climatic elasticity method is reliable; (2) projected increasing streamflow takes place in more than 60% of the selected catchments, with mean increments of 9% and 15.4% under RCP2.6 and RCP8.5 respectively; and (3) uncertainties in the projected streamflow are considerable in several regions, such as the Pearl River and Yellow River, with more than 40% of the selected catchments showing inconsistent change directions. Our results can help Chinese policy makers to manage and plan water resources more effectively, and the PnT climatic elasticity should be applied to other parts of the world.
Elastic interaction between defects during dynamic aging of stainless steels
International Nuclear Information System (INIS)
Journaux, J.; Monteiro, S.N.
1977-01-01
The study of the mechanical properties through traction tests, at temperatures above room temperature in 316 type stainless steel emphasizes the existence of the dynamic aging phenomenon (Portevin-Lechantelier effect). The present paper explains in a general way the fundamental causes of this effect by examining the elastic interactions that occur between the solute atoms in solid solution and the crystal dislocations. These interactions, which are present only at a certain temperature range, are responsible for the improvement of the mechanical properties always noticed in the alloys showing this phenomenon. (F.R.) [pt
Is the Armington Elasticity Really Constant across Importers?
Yilmazkuday, Hakan
2009-01-01
This paper shows that the Armington elasticity, which refers to both the elasticity of substitution across goods and the price elasticity of demand under the assumption of a large number of varieties, systematically changes from one importer country to another in an international trade context. Then a natural question to ask is "What determines the Armington elasticity?" The answer comes from the distinction between the elasticity of demand with respect to the destination price (i.e., the Arm...
Role of Elastic Compatibility and Disorder in Texture Evolution in Martensitic Materials.
Kerr, W. C.; Shenoy, S. R.; Saxena, A.; Swart, P. J.; Bishop, A. R.; Killough, M. G.
1997-03-01
Based on a k-space analysis of the 2D elastic compatibility condition, we derive an anisotropic long-range elastic interaction that is responsible for twinning in martensitic materials. This 2D condition is operational only for textures that have nonzero "elastic quadrupole" moment such as twins impinging on a martensite-austenite interface or tweed intersections. The long-range interaction, previously obtained (G.R. Barsch, B. Horovitz, and J.A. Krumhansl, PRL 59, 1251 (1987); PR B 43, 1021 (1991).) by integrating out the elastic fringing field energy contribution in the austenite, is thus shown as a direct consequence of elastic compatibility. Using both annealed and quenched averaging over compositional disorder, we derive an effective cross-gradient elastic energy contribution that is fourth-order in gradient and second-order in strain. The coefficient of this term is negative in a limited temperature range, indicating the presence of tweed texture and its coarsening with cooling. These results are borne out by integration of the equations of motion for rectangular and shear strains, obtained from the Ginzburg-Landau functional with the compatibility condition.
New pure shear elastic surface waves in magneto-electro-elastic half-space
Melkumyan, Arman
2006-01-01
Pure shear surface waves guided by the free surface of a magneto-electro-elastic material are investigated. Three surface waves are obtained for various magneto-electrical conditions on the free surface of the magneto-electro-elastic half-space. The velocities of propagation and the existence conditions for each of these waves are obtained in explicit exact form.
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.
Probing hysteretic elasticity in weakly nonlinear materials
Energy Technology Data Exchange (ETDEWEB)
Johnson, Paul A [Los Alamos National Laboratory; Haupert, Sylvain [UPMC UNIV PARIS; Renaud, Guillaume [UPMC UNIV PARIS; Riviere, Jacques [UPMC UNIV PARIS; Talmant, Maryline [UPMC UNIV PARIS; Laugier, Pascal [UPMC UNIV PARIS
2010-12-07
Our work is aimed at assessing the elastic and dissipative hysteretic nonlinear parameters' repeatability (precision) using several classes of materials with weak, intermediate and high nonlinear properties. In this contribution, we describe an optimized Nonlinear Resonant Ultrasound Spectroscopy (NRUS) measuring and data processing protocol applied to small samples. The protocol is used to eliminate the effects of environmental condition changes that take place during an experiment, and that may mask the intrinsic elastic nonlinearity. As an example, in our experiments, we identified external temperature fluctuation as a primary source of material resonance frequency and elastic modulus variation. A variation of 0.1 C produced a frequency variation of 0.01 %, which is similar to the expected nonlinear frequency shift for weakly nonlinear materials. In order to eliminate environmental effects, the variation in f{sub 0} (the elastically linear resonance frequency proportional to modulus) is fit with the appropriate function, and that function is used to correct the NRUS calculation of nonlinear parameters. With our correction procedure, we measured relative resonant frequency shifts of 10{sup -5} , which are below 10{sup -4}, often considered the limit to NRUS sensitivity under common experimental conditions. Our results show that the procedure is an alternative to the stringent control of temperature often applied. Applying the approach, we report nonlinear parameters for several materials, some with very small nonclassical nonlinearity. The approach has broad application to NRUS and other Nonlinear Elastic Wave Spectroscopy approaches.
Population and energy elasticity of tornado casualties
Fricker, Tyler; Elsner, James B.; Jagger, Thomas H.
2017-04-01
Tornadoes are capable of catastrophic destruction and mass casualties, but there are yet no estimates of how sensitive the number of casualties are to changes in the number of people in harm's way or to changes in tornado energy. Here the relationship between tornado casualties (deaths and injuries), population, and energy dissipation is quantified using the economic concept of "elasticity." Records of casualties from individual tornadoes over the period 2007-2015 are fit to a regression model. The coefficient on the population term (population elasticity) indicates that a doubling in population increases the casualty rate by 21% [(17, 24)%, 95% credible interval]. The coefficient on the energy term (energy elasticity) indicates that a doubling in energy dissipation leads to a 33% [(30, 35)%, 95% credible interval] increase in the casualty rate. The difference in elasticity values show that on average, changes in energy dissipation have been relatively more important in explaining tornado casualties than changes in population. Assuming no changes in warning effectiveness or mitigation efforts, these elasticity estimates can be used to project changes in casualties given the known population trends and possible trends in tornado activity.
Vascular elastic photoacoustic tomography in humans
Hai, Pengfei; Zhou, Yong; Liang, Jinyang; Li, Chiye; Wang, Lihong V.
2016-03-01
Quantification of vascular elasticity can help detect thrombosis and prevent life-threatening conditions such as acute myocardial infarction or stroke. Here, we propose vascular elastic photoacoustic tomography (VE-PAT) to measure vascular elasticity in humans. VE-PAT was developed by incorporating a linear-array-based photoacoustic computed tomography system with a customized compression stage. By measuring the deformation of blood vessels under uniaxial loading, VE-PAT was able to quantify the vascular compliance. We first demonstrated the feasibility of VE-PAT in blood vessel phantoms. In large vessel phantoms, VE-PAT detected a decrease in vascular compliance due to simulated thrombosis, which was validated by a standard compression test. In small blood vessel phantoms embedded 3 mm deep in gelatin, VE-PAT detected elasticity changes at depths that are difficult to image using other elasticity imaging techniques. We then applied VE-PAT to assess vascular compliance in a human subject and detected a decrease in vascular compliance when an occlusion occurred downstream from the measurement point, demonstrating the potential of VE-PAT in clinical applications such as detection of deep venous thrombosis.
MAXIMIZING OPTO-ELASTIC INTERACTION
DEFF Research Database (Denmark)
Gersborg, Allan Roulund; Sigmund, Ole
2008-01-01
This contribution is concerned with topology optimization of a coupled optical and mechanical problem in photonic crystals. It is motivated by the potential gain in functionality of optical devices where the mechanical loading influences the optical response by distorting the geometry and through...
Grimes, Craig A. (Inventor); Stoyanov, Plamen G. (Inventor)
2002-01-01
An analyte, viscosity, or temperature sensing apparatus for operative arrangement within a time-varying magnetic field, including a sensor with an outer surface that is chemically, frictionally, or thermally responsive and adhered to a base magnetostrictive element, and a receiver to measure a first and second value for magneto-elastic emission intensity of the sensor taken at, respectively, a first and second interrogation frequency. A change in mass or a change in material stiffness of the sensor due to the responsiveness, the viscosity and mass density of a fluid therearound, or the temperature, can be identified. The receiver, alternatively, measures a plurality of successive values for magneto-elastic emission intensity of the sensor taken over an operating range of successive interrogation frequencies to identify a value for the sensor's magneto-elastic resonant frequency (a fundamental frequency or harmonic thereof). Several sensors in an ordered array will provide a package of information.
Vibrational Analysis of Curved Single-Walled Carbon Nanotube on a Pasternak Elastic Foundation
DEFF Research Database (Denmark)
Mehdipour, I.; Barari, Amin; Kimiaeifar, Amin
2012-01-01
Continuum mechanics and an elastic beam model were employed in the nonlinear force vibrational analysis of an embedded, curved, single-walled carbon nanotube. The analysis considered the effects of the curvature or waviness and midplane stretching of the nanotube on the nonlinear frequency....... By utilizing He’s Energy Balance Method (HEBM), the relationships of the nonlinear amplitude and frequency were expressed for a curved, single-walled carbon nanotube. The amplitude frequency response curves of the nonlinear free vibration were obtained for a curved, single-walled carbon nanotube embedded...... in a Pasternak elastic foundation. Finally, the influence of the amplitude of the waviness, midplane stretching nonlinearity, shear foundation modulus, surrounding elastic medium, radius, and length of the curved carbon nanotube on the amplitude frequency response characteristics are discussed. As a result...
Energy Technology Data Exchange (ETDEWEB)
Cheng, Guang; Sun, Xin; Wang, Yuxin; Tay, See Leng; Gao, Wei
2017-01-01
A new inverse method was proposed to calculate the anisotropic elastic-plastic properties (flow stress) of thin electrodeposited Ag coating utilizing nanoindentation tests, previously reported inverse method for isotropic materials and three-dimensional (3-D) finite element analyses (FEA). Indentation depth was ~4% of coating thickness (~10 μm) to avoid substrate effect and different indentation responses were observed in the longitudinal (L) and the transverse (T) directions. The estimated elastic-plastic properties were obtained in the newly developed inverse method by matching the predicted indentation responses in the L and T directions with experimental measurements considering indentation size effect (ISE). The results were validated with tensile flow curves measured from free-standing (FS) Ag film. The current method can be utilized to characterize the anisotropic elastic-plastic properties of coatings and to provide the constitutive properties for coating performance evaluations.
Improved Systematic of pp Elastic Scattering Data
Uzhinsky, V.
2012-01-01
Unified systematic of elastic scattering data (USESD) proposed by the authors (arxiv:1111.4984 [hep-ph]) is based on symmetrized 2-dimensional Fermi distribution for pp elastic scattering amplitude in the impact parameter representation. It allows to describe differential cross sections of the reactions up to |t| ~ 1.75 (GeV/c)$^2$. To extend it to higher |t| values we consider a two coherent exponential parametrization of the cross sections and show that it cannot describe the cross sections at small |t| at $P_{lab}>$ 10 GeV/c. We extract a description of high |t| region from the parameterization and couple it with USESD. As a result, we obtained a good description of all pp elastic scattering data at $P_{lab}>$ 10 GeV/c. It can be easily used in Glauber Monte Carlo codes for calculations of nucleus-nucleus interaction properties.
Facies Constrained Elastic Full Waveform Inversion
Zhang, Z.
2017-05-26
Current efforts to utilize full waveform inversion (FWI) as a tool beyond acoustic imaging applications, for example for reservoir analysis, face inherent limitations on resolution and also on the potential trade-off between elastic model parameters. Adding rock physics constraints does help to mitigate these issues. However, current approaches to add such constraints are based on averaged type rock physics regularization terms. Since the true earth model consists of different facies, averaging over those facies naturally leads to smoothed models. To overcome this, we propose a novel way to utilize facies based constraints in elastic FWI. A so-called confidence map is calculated and updated at each iteration of the inversion using both the inverted models and the prior information. The numerical example shows that the proposed method can reduce the cross-talks and also can improve the resolution of inverted elastic properties.
Alumina strength degradation in the elastic regime
International Nuclear Information System (INIS)
Furnish, Michael D.; Chhabildas, Lalit C.
1998-01-01
Measurements of Kanel et al. [1991] have suggested that deviatoric stresses in glasses shocked to nearly the Hugoniot Elastic Limit (HEL) relax over a time span of microseconds after initial loading. 'Failure' (damage) waves have been inferred on the basis of these measurements using time-resolved manganin normal and transverse stress gauges. Additional experiments on glass by other researchers, using time-resolved gauges, high-speed photography and spall strength determinations have also lead to the same conclusions. In the present study we have conducted transmitted-wave experiments on high-quality Coors AD995 alumina shocked to roughly 5 and 7 GPa (just below or at the HEL). The material is subsequently reshocked to just above its elastic limit. Results of these experiments do show some evidence of strength degradation in the elastic regime
Path independent integrals in equilibrium electro-chemo-elasticity
Zhang, Min; Qu, Jianmin; Rice, James R.
2017-10-01
By using the Noether's first theorem, this paper constructed two types of path-independent integrals in equilibrium electro-chemo-elasticity and proved their uniqueness. These path-independent integrals are the electro-chemo-elastic extensions of the classical J- and L-integrals in elasticity. Similar to their elastic counterparts, the electro-chemo-elastic J- and L-integrals represent energy release when a crack or a cavity undergoes a translation and rotation, respectively. Also shown in this paper is that the M-integral in elasticity cannot be extended to electro-chemo-elasticity. Results of this study established a theoretical foundation for energy conservation laws in equilibrium electro-chemo-elasticity. Such conservation laws are useful in modeling various phenomena in electro-chemo-elastic systems. In addition, the path-independent integrals obtained here provide a theoretical tool for understanding and a practical tool for numerical evaluation of singular fields.
Fully coupled heat conduction and deformation analyses of visco-elastic solids
Khan, Kamran
2012-04-21
Visco-elastic materials are known for their capability of dissipating energy. This energy is converted into heat and thus changes the temperature of the materials. In addition to the dissipation effect, an external thermal stimulus can also alter the temperature in a viscoelastic body. The rate of stress relaxation (or the rate of creep) and the mechanical and physical properties of visco-elastic materials, such as polymers, vary with temperature. This study aims at understanding the effect of coupling between the thermal and mechanical response that is attributed to the dissipation of energy, heat conduction, and temperature-dependent material parameters on the overall response of visco-elastic solids. The non-linearly viscoelastic constitutive model proposed by Schapery (Further development of a thermodynamic constitutive theory: stress formulation, 1969,Mech. Time-Depend. Mater. 1:209-240, 1997) is used and modified to incorporate temperature- and stress-dependent material properties. This study also formulates a non-linear energy equation along with a dissipation function based on the Gibbs potential of Schapery (Mech. Time-Depend. Mater. 1:209-240, 1997). A numerical algorithm is formulated for analyzing a fully coupled thermo-visco-elastic response and implemented it in a general finite-element (FE) code. The non-linear stress- and temperature-dependent material parameters are found to have significant effects on the coupled thermo-visco-elastic response of polymers considered in this study. In order to obtain a realistic temperature field within the polymer visco-elastic bodies undergoing a non-uniform heat generation, the role of heat conduction cannot be ignored. © Springer Science+Business Media, B. V. 2012.
Magneto-elastic interactions in terbium
DEFF Research Database (Denmark)
Jensen, J.
1971-01-01
Making use of the Hamiltonian for linear magneto-elastic coupling which has been proposed by Callen and Callen, expressions are deduced for changes in the velocity of acoustic waves in a terbium crystal, due to ferromagnetic ordering and the application of an external magnetic field. These calcul......Making use of the Hamiltonian for linear magneto-elastic coupling which has been proposed by Callen and Callen, expressions are deduced for changes in the velocity of acoustic waves in a terbium crystal, due to ferromagnetic ordering and the application of an external magnetic field...
The elastic modulus of isolated polytetrafluoroethylene filaments
Directory of Open Access Journals (Sweden)
Patrick Drawe
2014-09-01
Full Text Available We report vibrational Raman spectra of small extended perfluoro-n-alkanes (CnF2n+2 with n = 6, 8–10, 12–14 isolated in supersonic jet expansions and use wavenumbers of longitudinal acoustic vibrations to extrapolate the elastic modulus of cold, isolated polytetrafluoroethylene filaments. The derived value E = 209(10 GPa defines an upper limit for the elastic modulus of the perfectly crystalline, noninteracting polymer at low temperatures and serves as a benchmark for quantum chemical predictions.
An introduction to the theory of elasticity
Atkin, R J
2005-01-01
Thanks to intense research activity in the field of continuum mechanics, the teaching of subjects such as elasticity theory has attained a high degree of clarity and simplicity. This introductory volume offers upper-level undergraduates a perspective based on modern developments that also takes into account the limited mathematical tools they are likely to have at their disposal. It also places special emphasis on areas that students often find difficult upon first encounter. An Introduction to the Theory of Elasticity provides an accessible guide to the subject in a form that will instill a f
Elasticity of some mantle crystal structures. II.
Wang, H.; Simmons, G.
1973-01-01
The single-crystal elastic constants are determined as a function of pressure and temperature for rutile structure germanium dioxide (GeO2). The data are qualitatively similar to those of rutile TiO2 measured by Manghnani (1969). The compressibility in the c direction is less than one-half that in the a direction, the pressure derivative of the shear constant is negative, and the pressure derivative of the bulk modulus has a relatively high value of about 6.2. According to an elastic strain energy theory, the negative shear modulus derivative implies that the kinetic barrier to diffusion decreases with increasing pressure.
Gradient Elasticity Formulations for Micro/Nanoshells
Directory of Open Access Journals (Sweden)
Bohua Sun
2014-01-01
Full Text Available The focus of this paper is on illustrating how to extend the second author’s gradient theory of elasticity to shells. Three formulations are presented based on the implicit gradient elasticity constitutive relation 1 -ld2∇2σij=Cijkl(1-ls2∇2εkl and its two approximations 1+ls2∇2-ld2∇2σij=Cijklεkl and σij=Cijkl(1+ld2∇2-ls2∇2εkl.
Superpropulsion of Droplets and Soft Elastic Solids
Raufaste, Christophe; Chagas, Gabriela Ramos; Darmanin, Thierry; Claudet, Cyrille; Guittard, Frédéric; Celestini, Franck
2017-09-01
We investigate the behavior of droplets and soft elastic objects propelled with a catapult. Experiments show that the ejection velocity depends on both the projectile deformation and the catapult acceleration dynamics. With a subtle matching given by a peculiar value of the projectile/catapult frequency ratio, a 250% kinetic energy gain is obtained as compared to the propulsion of a rigid projectile with the same engine. This superpropulsion has strong potentialities: actuation of droplets, sorting of objects according to their elastic properties, and energy saving for propulsion engines.
Elasticity and clustering in concentrated depletion gels.
Ramakrishnan, S; Chen, Y-L; Schweizer, K S; Zukoski, C F
2004-10-01
X-ray scattering and rheology are employed to study the volume fraction dependence of the collective structure and elastic moduli of concentrated nanoparticle-polymer depletion gels. The nonequilibrium gel structure consists of locally densified nonfractal clusters and narrow random interfaces. The elastic moduli display a power law dependence on volume fraction with effective exponents that decrease with increasing depletion attraction strength. A microscopic theory that combines local structural information with a dynamic treatment of gelation is in good agreement with the observations.
Price elasticity and medication use: cost sharing across multiple clinical conditions.
Gatwood, Justin; Gibson, Teresa B; Chernew, Michael E; Farr, Amanda M; Vogtmann, Emily; Fendrick, A Mark
2014-11-01
To address the impact that out-of-pocket prices may have on medication use, it is vital to understand how the demand for medications may be affected when patients are faced with changes in the price to acquire treatment and how price responsiveness differs across medication classes. To examine the impact of cost-sharing changes on the demand for 8 classes of prescription medications. This was a retrospective database analysis of 11,550,363 commercially insured enrollees within the 2005-2009 MarketScan Database. Patient cost sharing, expressed as a price index for each medication class, was the main explanatory variable to examine the price elasticity of demand. Negative binomial fixed effect models were estimated to examine medication fills. The elasticity estimates reflect how use changes over time as a function of changes in copayments. Model estimates revealed that price elasticity of demand ranged from -0.015 to -0.157 within the 8 categories of medications (P less than 0.01 for 7 of 8 categories). The price elasticity of demand for smoking deterrents was largest (-0.157, P less than 0.0001), while demand for antiplatelet agents was not responsive to price (P greater than 0.05). The price elasticity of demand varied considerably by medication class, suggesting that the influence of cost sharing on medication use may be related to characteristics inherent to each medication class or underlying condition.
Marangoni and Gibbs elasticity of flowing soap films
Kim, Ildoo; Sane, Aakash; Mandre, Shreyas
2017-11-01
A flowing soap film has two elasticities. Marangoni elasticity dynamically stabilizes the film from sudden disturbance, and Gibbs elasticity is an equilibrium property that influences the film's persistence over time. In our experimental investigation, we find that Marangoni elasticity is 22 mN/m independent of the film thickness. On the other hand, Gibbs elasticity depends both on the film thickness and the soap concentration. Interestingly, the soap film made of dilute soap solution has the greater Gibbs elasticity, which is not consistent to the existing theory. Such discrepancy is originated from the flowing nature of our soap films, in which surfactants are continuously replenished.
DEFF Research Database (Denmark)
Abdallah, Imad; Sudret, Bruno; Lataniotis, Christos
2015-01-01
Fusing predictions from multiple simulators in the early stages of the conceptual design of a wind turbine results in reduction in model uncertainty and risk mitigation. Aero-servo-elastic is a term that refers to the coupling of wind inflow, aerodynamics, structural dynamics and controls. Fusing...... the response data from multiple aero-servo-elastic simulators could provide better predictive ability than using any single simulator. The co-Kriging approach to fuse information from multifidelity aero-servo-elastic simulators is presented. We illustrate the co-Kriging approach to fuse the extreme flapwise...... bending moment at the blade root of a large wind turbine as a function of wind speed, turbulence and shear exponent in the presence of model uncertainty and non-stationary noise in the output. The extreme responses are obtained by two widely accepted numerical aero-servo-elastic simulators, FAST...
Toward an Elasticity of Chip-N-Saw: Demand and Supply Models of Chip-N-Saw Stumpage in Louisiana
Directory of Open Access Journals (Sweden)
Shaun M. Tanger
2018-04-01
Full Text Available Softwood chip-n-saw (CNS is a relatively new stumpage product in the sawtimber- and pulpwood-dominated stumpage markets in the U.S. South. Based on a quarterly data series from 2003 to 2016, this study estimates the demand and supply models of the softwood CNS stumpage market in Louisiana. The two-stage least squares (2SLS results reveal that own price elasticity of demand (PED is price elastic, and the cross-price elasticity (XEDwith sawtimber approaches unit elasticity. On the supply side, CNS is price inelastic in supply (PES, but more responsive to own price changesthan sawtimber quantity supplied. Further, severance tax increases are found to decrease the supply of CNS, indicating that suppliers are responsive to severance tax incidence. As the first empirical estimation of CNS, the findings should be of interest to those involved in the analysis of Southeastern stumpage markets.
Elasticity and elctro-magneto-elasticity of general-relativistic systems
International Nuclear Information System (INIS)
Maugin, G.A.
1978-01-01
The interest for a genuine continuum mechanics and, more restrictively, elasticity of general-relativistic systems is demonstrated in cases where the Einsteinian gravitational picture cannot be deleted, e.g., in 'elastic' gravitational-wave detectors and in the study of elastic oscillations of solid stars. The same foundations, constitutive theory, and methodology (superimposition of perturbations on finite initial states) apply to both cases, which also demand a generalization to comprehend electrodynamical-mechanical couplings, electroelasticity in the first case (use of piezoelectricity), and magnetoelasticity in the second case (presence of extremely intense magnetic fields). (author)
Stressed-deformed state of mountain rocks in elastic stage and between elasticity
Directory of Open Access Journals (Sweden)
Samedov A.M.
2017-12-01
Full Text Available The problems of the stress-strain state of rocks in the elastic stage and beyond the elastic limits, and the ways of schematizing the tension and compression diagrams were reviewed in the article. To simplify calculations outside the elastic range, the tension (compression diagrams are usually schematized, i.e. are replaced by curved smooth lines having a fairly simple mathematical expression and at the same time well coinciding with the experimentally obtained diagrams. When diagram is to be schematized, it is necessary to take a constant temperature of superheated water steam if a rock test is planned in a relaxed form. Note that when the diagram is schematizing, the difference between the limits of proportionality and fluidity is erased. This allows the limit of proportionality to be considered the limit of fluidity. Schematicization can be carried out in the area where the tensile strength (compression is planned to be destroyed with the established weakening of rocks by exposure to water steam or chemical reagents. Samples of rocks in natural form were tested and weakened by means of superheated water steam (220 °C and more and chemical reagents for tension and compression. The data are obtained, the diagrams of deformation are constructed and schematized in the elastic stage and beyond the elastic limit. Based on the schematic diagrams of deformation, the components of stress and strain were composed in the elastic stage and beyond the elastic limit. It is established in the publication that rocks under compression and stretching deform, both within the elastic stage, and beyond the limits of elasticity. This could be seen when the samples, both in natural and in weakened state, with superheated water steam (more than 220 °C or chemical reagents were tested. In their natural form, they are mainly deformed within the elastic stage and are destroyed as a brittle material, and in a weakened form they can deform beyond the elastic stage and
Elasticity, viscosity, and deformation of orbital fat
I. Schoemaker (Ivo); P.P.W. Hoefnagel (Pepijn); T.J. Mastenbroek (Tom); C.F. Kolff (Cornelis); S. Schutte (Sander); F.C.T. van der Helm (Frans); S.J. Picken (Stephen); A.F.C. Gerritsen (Anton); P.A. Wielopolski (Piotr); H. Spekreijse (Henk); H.J. Simonsz (Huib)
2006-01-01
textabstractPURPOSE. For development of a finite element analysis model of orbital mechanics, it was necessary to determine the material properties of orbital fat and its degree of deformation in eye rotation. METHODS. Elasticity and viscosity of orbital fat of eight orbits of four calves and two
Vibrations of a pipe on elastic foundations
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
This new term is opposed to the centrifugal term U2w,xx and has a strong effect on the stability. Lilkova-Markova & Lolov (2003) investigated the influence of the transverse force at the free end of the dynamic stability of a cantilevered pipe placed on a Winkler elastic foundation. In this paper, two cases of cantilevered pipes ...
A mixed system of equations of elasticity
Shul'ga, M. O.
2010-09-01
A mixed system of six equations of elasticity is represented as a Hamiltonian (canonical) operator system in one of the spatial coordinates. It is shown that this system is the Euler equations for the Hellinger-Reissner principle with an appropriately modified integrand. One more functional with an operator integrand from which the canonical operator system can be derived is set up
The theory of elastic waves and waveguides
Miklowitz, J
1984-01-01
The primary objective of this book is to give the reader a basic understanding of waves and their propagation in a linear elastic continuum. The studies of elastodynamic theory and its application to fundamental value problems should prepare the reader to tackle many physical problems of general interest in engineering and geophysics, and of particular interest in mechanics and seismology.
Some remarks on elastic fracture mechanics
International Nuclear Information System (INIS)
Destuynder, P.; Djaoua, M.; Lescure, S.
1981-12-01
A thermodynamical approach of propagation law in elastic media is given in this paper. From a particular choice of an energy dissipation potential, we deduce some propagation laws corresponding to particular loading cases. Finally a new computational method of the energy release rate is suggested and discussed from a computational point of view [fr
Elastic magnetic form factors of exotic nuclei
International Nuclear Information System (INIS)
Dong Tiekuang; Guo Yanqing; Ren Zhongzhou
2007-01-01
How to identify the orbital of the valence nucleon(s) of exotic nuclei is an important problem. The elastic magnetic electron scattering is an excellent probe to determine the valence structure of odd-A nuclei. The relativistic mean-field theory has been successfully applied to systematic studies of the elastic charge electron scattering from even-even exotic nuclei. The extension of this method to investigate the elastic magnetic electron scattering from odd-A exotic nuclei is a natural generalization. The experimental form factors of 17 O and 41 Ca are reproduced very well with the help of the spectroscopic factors which are introduced into the relativistic treatment of the magnetic electron scattering for the first time. The emphases are put on the magnetic form factors of 15,17,19 C, 23 O, 17 F, and 49,59 Ca calculated in the relativistic impulse approximation. Great differences have been found in the form factors of the same nucleus with different configurations. Therefore, the elastic magnetic electron scattering can be used to determine the orbital of the last nucleon of odd-A exotic nuclei. Our results can provide references for the electron scattering from exotic nuclei in the near future
Elastic proton-proton scattering at RHIC
Energy Technology Data Exchange (ETDEWEB)
Yip, K.
2011-09-03
Here we describe elastic proton+proton (p+p) scattering measurements at RHIC in p+p collisions with a special optics run of {beta}* {approx} 21 m at STAR, at the center-of-mass energy {radical}s = 200 GeV during the last week of the RHIC 2009 run. We present preliminary results of single and double spin asymmetries.
Vibrations of a pipe on elastic foundations
Indian Academy of Sciences (India)
A cantilevered pipe subjected to external transverse (or lateral) force is investigated. Two cases of elastic foundations are considered: rotational and both linear and rotational. The major ﬁndings are the variations in frequency with ﬂow velocity and displacements at different points and times.
On elastic structural elements for nuclear reactors
International Nuclear Information System (INIS)
Povolo, F.
1978-03-01
The in-pile stress-relaxation behaviour of materials usually employed for the elastic structural elements, in nuclear reactors, is critically reviewed and the results are compared with those obtained in commercial zirconium alloys irradiated under similar conditions. Finally, it is shown that, under certain conditions, some zirconium alloys may be used as an alternative material for these structural elements. (orig.) [de
Elastic and inelastic electron and muon scattering
International Nuclear Information System (INIS)
Hand, L.N.
1977-01-01
The current status of experiments in the field of elastic and inelastic electron and muon scattering is discussed. The talk is divided into discussions of the single arm inclusive experiments at SLAC and Fermilab; the multiparticle inclusive experiments at SLAC, Fermilab und Cornell, and a description of selected results from exclusive channel measurements on electroproduced final states. (orig.) [de
Elastic electron scattering and muonic atoms
International Nuclear Information System (INIS)
Sick, I.
1975-01-01
The discussion of elastic electron scattering covers (e,e) at large q, linked to it the investigation of isotone pairs, and experiments concerning the higher multipole moments of the ground state density. The corresponding μ-x-ray work is discussed in parallel
On the K+-nucleus elastic scattering
International Nuclear Information System (INIS)
Ning, P.; Men, D.
1991-01-01
In this paper conventional and unconventional nuclear medium effects in the K + scattering are briefly reviewed. Microscopic calculations of the K + elastic scattering on 4 He, 12 C, 40 Ca, 120 Sn at 800 MeV/c are performed and then possible swellings of nucleons in nuclei are discussed
PNESD proton nucleus elastic scattering data
International Nuclear Information System (INIS)
DayDay, N.
1979-12-01
The data file PNESD contains numerical data and the related bibliography for the differential elastic cross sections, polarization and integral nonelastic cross sections for protons of 3 MeV to 1000 MeV incident on natural elements and their isotopes. The file can be obtained on magnetic tape free of charge from the IAEA Nuclear Data Section. (author)
Thickness dependence of nanofilm elastic modulus
Czech Academy of Sciences Publication Activity Database
Fedorchenko, Alexander I.; Wang, A. B.; Cheng, H.H.
2009-01-01
Roč. 94, č. 15 (2009), s. 152111-152113 ISSN 0003-6951 Institutional research plan: CEZ:AV0Z20760514 Keywords : nanofilm * elastic modulus * thickness dependence Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.554, year: 2009 http://link.aip.org/link/?APPLAB/94/152111/1
Titanium Elastic Nails Successfully Splint Subsequent Femoral ...
African Journals Online (AJOL)
The current trend in the management of fractures in children with osteogenesis imperfecta (OI) is the use of expandable nails. These may not be widely available in resource- constrained settings. We report a case of a 9 year old female with a peri-prosthetic fracture treated with premeasured pre-contoured titanium elastic ...
Dielectric, elastic, anelastic and conductivity behaviour of ...
Indian Academy of Sciences (India)
The presence of two phases was confirmed by X-ray diffraction. The temperature variation of dielectric constant, ', dielectric loss, tan , d.c. conductivity, a.c. conductivity, elastic and anelastic behaviour of ferrite–ferroelectric composites were studied in the temperature range 30–350°C. The a.c. conductivity measurements ...
Flexoelectricity and elasticity of asymmetric biomembranes.
Petrov, Alexander G; Sachs, Frederick
2002-02-01
In view of the well-established charge and dipolar asymmetry of the two leaflets of a native membrane, the theory of flexoelectricity (and curvature elasticity) is extended to take into account this asymmetry using linear and nonlinear forms of the Poisson-Boltzmann equation. The results are discussed with respect to data from atomic force microscopy studies of electromotility in biomembranes.
Mechanical behaviour of nanoparticles: Elasticity and plastic ...
Indian Academy of Sciences (India)
2015-06-03
Jun 3, 2015 ... As such, related research topics have become increasingly prominent in recent years. In this review on the mechanical behaviour of nanoparticles, the main investigation approaches are first briefly presented. The main results in terms of elasticity and plastic deformation mechanisms are then reported and ...
Hydrodynamics and Elasticity of Charged Black Branes
DEFF Research Database (Denmark)
Gath, Jakob
We consider long-wavelength perturbations of charged black branes to first order in a uidelastic derivative expansion. At first order the perturbations decouple and we treat the hydrodynamic and elastic perturbations separately. To put the results in a broader perspective, we present the rst...
Bending rate damping in elastic systems
Banks, H. T.; Wang, Y.; Fabiano, R. H.
1989-01-01
Preliminary results of an investigation of the bending rate damping model for elastic structures are presented. A model for which the internal damping term is physically plausible and which can accomodate cantilevered boundary conditions is discussed. The model formulation and mathematical foundations are given, and numerical results are discussed.
Solitary waves on nonlinear elastic rods. II
DEFF Research Database (Denmark)
Sørensen, Mads Peter; Christiansen, Peter Leth; Lomdahl, P. S.
1987-01-01
In continuation of an earlier study of propagation of solitary waves on nonlinear elastic rods, numerical investigations of blowup, reflection, and fission at continuous and discontinuous variation of the cross section for the rod and reflection at the end of the rod are presented. The results...
First-principles elasticity of monocarboaluminate hydrates
Moon, J.
2014-07-01
The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.
Comparison of elastic and inelastic analyses
International Nuclear Information System (INIS)
Ammerman, D.J.; Heinstein, M.W.; Wellman, G.W.
1993-01-01
In this paper, comparisons between elastic and inelastic analyses are made for a simple ring structure and for a package to transport a large quantity of RAM by rail (rail cask) with lead gamma shielding to illustrate the differences in the two analysis techniques. (J.P.N.)
Elastic kirchhoff migration for vertical seismic profiles
International Nuclear Information System (INIS)
Keho, T.H.; Wu, R.S.
1987-01-01
Elastic Kirchhoff migration is implemented for the VSP recording geometry. The resulting migration formula requires measurement of the stress as well as the displacement. Since stress is not measured in a VSP, and in many cases the horizontal component of displacement is not measured, approximate migration formulas are given for these cases. The elastic migration formula for the case where only the vertical components are available, is the same as the acoustic migration formula, where the pressure data are replaced by the magnitudes of the elastic data as reconstructed from the vertical components, and the acoustic Green's functions are replaced with either the P or S wave elastic Green's functions. Two expressions for migration of two component displacement data are presented. In the first, the terms involving traction data are simply ignored. In the second, an improved backpropagation operator for the displacement field is obtained by replacing the traction data in the Kirchhoff integral by displacement data using Hooke's law. The migration expressions for the cases where two component data are available produce images which are less contaminated by artifacts than the migration images of one component data
Hadron elastic scattering at small angles
2002-01-01
This experiment is an extension of the measurements of the WA9 experiment up to the highest energies available in the North Area. It will measure the differential cross-section for hadron elastic scattering in the t-range 0.002-0.05 (GeV/c)$^{2}$ using an ionization chamber for the measurement of the energy and the angle of the recoil and a magnet-WC spectrometer to measure the momentum and direction of the forward particle. From these measurements will be obtained the ratio $\\rho$ of the real to imaginary parts of the forward elastic amplitude and the exponential slope parameter b of the hadronic amplitude at small t. The precision expected in these measurements is $\\Delta \\rho \\approx \\pm 0.01$ and $\\Delta$b $\\approx \\pm 0.2$ (GeV/c)$^{-2}$. \\\\ \\\\ The experimental programme includes: \\\\\\\\ i) measurements of $\\rho$ and b for $\\pi$p elastic scattering at incident momenta between 150 GeV/c and 300 GeV/c; \\\\ ii) measurements of $\\rho$ and b for $\\pi^{+}$p and pp elastic scattering at incident momenta between 5...
Elasticity problems in domains with nonsmooth boundaries
Esparza, D
2001-01-01
In the present work we study the behaviour of elastic stress fields in domains with non-regular boundaries. We consider three-dimensional problems in elastic media with thin conical defects (inclusions or cavities) and analyse the stress singularity at their vertices. To construct asymptotic expansions for the stress and displacement fields in terms of a small parameter epsilon related to the 'thickness' of the defect, we employ a technique based on the work by Kondrat'ev, Maz'ya, Nazarov and Plamenevskii. We first study the stress distribution in an elastic body with a thin conical notch. We derive an asymptotic representation for the stress singularity exponent by reducing the original problem to a spectral problem for a 9x9 matrix. The elements of this matrix are found to depend upon the geometry of the cross-section of the notch and the elastic properties of the medium. We specify the sets of eigenvalues and the corresponding eigenvectors for a circular, elliptical, 'triangular' and 'square' cross-section...
Approximate analysis of rigid plate loading on elastic multi-layered systems
CSIR Research Space (South Africa)
Maina, JW
2008-07-01
Full Text Available Games software is well known for its capability to compute responses for uniformly distributed load acting on the surface of a multi-layered linear elastic system. In this study a method was developed to approximate rigid plate loading to be used...
Jamari, Jamari; Schipper, Dirk J.
2007-01-01
This paper presents theoretical and experimental results of the residual or plastic deformation and the plastic contact area of an elastic–plastic contact of ellipsoid bodies after unloading. There are three regime responses of the deformation and contact area: elastic, elastic–plastic and fully
Precursor of pion condensation: The softening of the quasi-elastic peak
International Nuclear Information System (INIS)
Alberico, W.M.; Ericson, M.; Molinari, A.
1980-01-01
The phase transition of pion condensation is heralded in the disordered phase by an increase in the life time of the fluctuations for the staggered magnetization. This precursor phenomenon entails, in ordinary nuclei, a showing down of the nuclear quasi-elastic response when observed with spin-sensitive probes. (orig.)
Liu, Yan; Zhang, Kaihuan; Ma, Jinghong; Vancso, Gyula J.
2017-01-01
Hydrogels with rapid and strong response to external stimuli and possessing high elasticity and strength have been considered as platform materials for numerous applications, e.g., in biomaterials engineering. Thermoresponsive hydrogels based on semi-interpenetrating polymer networks (semi-IPN)
International Nuclear Information System (INIS)
Berryman, J.G.
1997-01-01
Eshelby close-quote s formula gives the response of a single ellipsoidal elastic inclusion in an elastic whole space to a uniform strain imposed at infinity. Using a linear combination of results from two simple thought experiments, we show how this formula may be generalized to both poroelasticity and thermoelasticity. The resulting new formulas are important for applications to analysis of poroelastic and thermoelastic composites, including but not restricted to rocks. copyright 1997 The American Physical Society
Failure above and Below the Elastic Limit in AD995
Bourne, N. K.; Millett, J. C. F.; Chen, M. W.; Dandekar, D. P.; McCauley, J. W.
2007-12-01
There is an ongoing interest in identifying inexpensive armour materials for use in the protection of personnel and vehicles. The response of AD995 under shock loading is one of the materials most extensively investigated. Over recent years, workers have reported failure occurring in various polycrystalline ceramics behind the shock front. This phenomenon has been investigated using embedded stress sensors and a recovery technique that has allowed observation of the microstructure above and below the Hugoniot Elastic Limit (HEL) and these results are brought together here to explain the observed behaviour. The failure front velocity is found to change with the applied stress, in particular it slows as the HEL is exceeded. The microstructure shows the response below the HEL is dominated by intergranular failure whilst above it, the grains exhibit plasticity (including twinning). The HEL is thus shown to be characteristic of alumina viewed as a composite with randomly oriented alumina grains.
Elastic versus acoustic inversion for marine surveys
Mora, Peter
2018-04-24
Full Wavefield Inversion (FWI) is a powerful and elegant approach for seismic imaging that is on the way to becoming the method of choice when processing exploration or global seismic data. In the case of processing marine survey data, one may be tempted to assume acoustic FWI is sufficient given that only pressure waves exist in the water layer. In this paper, we pose the question as to whether or not in theory – at least for a hard water bottom case – it should be possible to resolve the shear modulus or S-wave velocity in a marine setting using large offset data. We therefore conduct numerical experiments with idealized marine data calculated with the elastic wave equation. We study two cases, FWI of data due to a diffractor model, and FWI of data due to a fault model. We find that at least in idealized situation, elastic FWI of hard waterbottom data is capable of resolving between the two Lamé parameters λ and μ. Another numerical experiment with a soft waterbottom layer gives the same result. In contrast, acoustic FWI of the synthetic elastic data results in a single image of the first Lamé parameter λ which contains severe artefacts for diffraction data and noticable artefacts for layer reflection data. Based on these results, it would appear that at least, inversions of large offset marine data should be fully elastic rather than acoustic unless it has been demonstrated that for the specific case in question (offsets, model and water depth, practical issues such as soft sediment attenuation of shear waves or computational time), that an acoustic only inversion provides a reasonably good quality of image comparable to that of an elastic inversion. Further research with real data is required to determine the degree to which practical issues such as shear wave attenuation in soft sediments may affect this result.
Cost Optimal Elastic Auto-Scaling in Cloud Infrastructure
Mukhopadhyay, S.; Sidhanta, S.; Ganguly, S.; Nemani, R. R.
2014-12-01
Today, elastic scaling is critical part of leveraging cloud. Elastic scaling refers to adding resources only when it is needed and deleting resources when not in use. Elastic scaling ensures compute/server resources are not over provisioned. Today, Amazon and Windows Azure are the only two platform provider that allow auto-scaling of cloud resources where servers are automatically added and deleted. However, these solution falls short of following key features: A) Requires explicit policy definition such server load and therefore lacks any predictive intelligence to make optimal decision; B) Does not decide on the right size of resource and thereby does not result in cost optimal resource pool. In a typical cloud deployment model, we consider two types of application scenario: A. Batch processing jobs → Hadoop/Big Data case B. Transactional applications → Any application that process continuous transactions (Requests/response) In reference of classical queuing model, we are trying to model a scenario where servers have a price and capacity (size) and system can add delete servers to maintain a certain queue length. Classical queueing models applies to scenario where number of servers are constant. So we cannot apply stationary system analysis in this case. We investigate the following questions 1. Can we define Job queue and use the metric to define such a queue to predict the resource requirement in a quasi-stationary way? Can we map that into an optimal sizing problem? 2. Do we need to get into a level of load (CPU/Data) on server level to characterize the size requirement? How do we learn that based on Job type?
Household demand elasticities for meat products in Uruguay
Energy Technology Data Exchange (ETDEWEB)
Lanfranco, B. A.; Rava, C.
2014-06-01
This article analyzed the demand for meats at household level over the past decade in Uruguay, a country that exhibits a very high per capita consumption of these products. In particular, the consumption of beef is one of the highest in the world and only comparable to Argentina. The analysis involved a two-step estimation of an incomplete system of censored demand equations using household data from the last available national income and expenditure survey (2005/06). Thirteen meat products were included in the analysis: six broad beef products (de boned hindquarter cuts, bone-in hindquarter cuts, ground beef, rib plate, bone-in forequarter cuts, and other beef cuts), four products from other meats (sheep, pork, poultry, and fish), and three generic mixed-meat products. A complete set of short-term income, own-price and cross-price elasticities were computed and reported along with their 90% confidence intervals (CI). The results were consistent with both economic theory and empirical evidence as well as with the expected behavior, considering the relevance of these products, particularly beef, in the diet of Uruguayan consumers. All meat items were necessary goods and evidenced income-inelastic responses, which was expected given their high consumption level. All meats behaved as normal goods although exhibiting different reactions to changes in price. In general, beef cuts were more price elastic than other more broadly defined products. The more specific and dis aggregated the meat product the higher its corresponding direct price elasticity. The complement/substitute relationships found in this study were highly depended on the specific product combinations. (Author)
Household demand elasticities for meat products in Uruguay
Directory of Open Access Journals (Sweden)
Bruno A. Lanfranco
2014-01-01
Full Text Available This article analyzed the demand for meats at household level over the past decade in Uruguay, a country that exhibits a very high per capita consumption of these products. In particular, the consumption of beef is one of the highest in the world and only comparable to Argentina. The analysis involved a two-step estimation of an incomplete system of censored demand equations using household data from the last available national income and expenditure survey (2005/06. Thirteen meat products were included in the analysis: six broad beef products (deboned hindquarter cuts, bone-in hindquarter cuts, ground beef, rib plate, bone-in forequarter cuts, and other beef cuts, four products from other meats (sheep, pork, poultry, and fish, and three generic mixed-meat products. A complete set of short-term income, own-price and cross-price elasticities were computed and reported along with their 90% confidence intervals (CI. The results were consistent with both economic theory and empirical evidence as well as with the expected behavior, considering the relevance of these products, particularly beef, in the diet of Uruguayan consumers. All meat items were necessary goods and evidenced income-inelastic responses, which was expected given their high consumption level. All meats behaved as normal goods although exhibiting different reactions to changes in price. In general, beef cuts were more price elastic than other more broadly defined products. The more specific and disaggregated the meat product the higher its corresponding direct price elasticity. The complement/substitute relationships found in this study were highly depended on the specific product combinations.
A-thermal elastic behavior of silicate glasses.
Rabia, Mohammed Kamel; Degioanni, Simon; Martinet, Christine; Le Brusq, Jacques; Champagnon, Bernard; Vouagner, Dominique
2016-02-24
Depending on the composition of silicate glasses, their elastic moduli can increase or decrease as function of the temperature. Studying the Brillouin frequency shift of these glasses versus temperature allows the a-thermal composition corresponding to an intermediate glass to be determined. In an intermediate glass, the elastic moduli are independent of the temperature over a large temperature range. For sodium alumino-silicate glasses, the a-thermal composition is close to the albite glass (NaAlSi3O8). The structural origin of this property is studied by in situ high temperature Raman scattering. The structure of the intermediate albite glass and of silica are compared at different temperatures between room temperature and 600 °C. When the temperature increases, it is shown that the high frequency shift of the main band at 440 cm(-1) in silica is a consequence of the cristobalite-like alpha-beta transformation of 6-membered rings. This effect is stronger in silica than bond elongation (anharmonic effects). As a consequence, the elastic moduli of silica increase as the temperature increases. In the albite glass, the substitution of 25% of Si(4+) ions by Al(3+) and Na(+) ions decreases the proportion of SiO2 6-membered rings responsible for the silica anomaly. The effects of the silica anomaly balance the anharmonicity in albite glass and give rise to an intermediate a-thermal glass. Different networks, formers or modifiers, can be added to produce different a-thermal glasses with useful mechanical or chemical properties.
Elastic ring deformation and pedestal contact status analysis of elastic ring squeeze film damper
Zhang, Wei; Ding, Qian
2015-06-01
This paper investigates the dynamic parametric characteristic of the elastic ring squeeze film damper (ERSFD). Firstly, the coupled oil film Reynolds equations and dynamic equations of an ERSFD supported rotor system are established. The finite differential method and numerical simulation are used to analyze the oil film pressure distribution, bearing capacity of ERSFD, oil film stiffness and damping characteristics during a vibration period. Then, based on the oil film pressure results, the deformation of elastic ring is revealed by the finite element method. Finally, pedestal contact status is analyzed according to the change of oil film thickness during a vibration period. The results reveal that the oil film pressure is sectionally continuous, the deformation of elastic ring is complex under the compression of inner and outer oil film, and different pedestal contacts occur in a vibration period. The level of nonlinearity of the bearing capacity, oil film stiffness and damping can be effectively lightened by application of the elastic ring.
A meta-analysis of the price elasticity of gasoline demand. A SUR approach
International Nuclear Information System (INIS)
Brons, Martijn; Rietveld, Piet; Nijkamp, Peter; Pels, Eric
2008-01-01
Automobile gasoline demand can be expressed as a multiplicative function of fuel efficiency, mileage per car and car ownership. This implies a linear relationship between the price elasticity of total fuel demand and the price elasticities of fuel efficiency, mileage per car and car ownership. In this meta-analytical study we aim to investigate and explain the variation in empirical estimates of the price elasticity of gasoline demand. A methodological novelty is that we use the linear relationship between the elasticities to develop a meta-analytical estimation approach based on a Seemingly Unrelated Regression (SUR) model with Cross Equation Restrictions. This approach enables us to combine observations of different elasticities and thus increase our sample size. Furthermore, it allows for a more detailed interpretation of our meta-regression results. The empirical results of the study demonstrate that the SUR approach leads to more precise results (i.e., lower standard errors) than a standard meta-analytical approach. We find that, with mean short run and long run price elasticities of - 0.34 and - 0.84, respectively, the demand for gasoline is not very price sensitive. Both in the short and the long run, the impact of a change in the gasoline price on demand is mainly driven by responses in fuel efficiency and mileage per car and to a slightly lesser degree by changes in car ownership. Furthermore, we find that study characteristics relating to the geographic area studied, the year of the study, the type of data used, the time horizon and the functional specification of the demand equation have a significant impact on the estimated value of the price elasticity of gasoline demand. (author)
Forced excitation and active control for the measurement of fluid-elastic forces
International Nuclear Information System (INIS)
Caillaud, Sebastien
1999-01-01
The action of a fluid flow on a tubes bundle is commonly decomposed into a random turbulent excitation and a fluid-elastic excitation. The fluid-elastic forces which are coupled to the tubes movement can be experimentally determined from an analysis of the vibratory response of the structure excited by turbulent forces. For low flow velocities, the turbulent excitation can be insufficient to make the tube significantly vibrate and to permit a correct vibratory analysis. On the opposite side, the structure can become unstable for high flow velocities: the fluid-elastic forces make the fluid-structure damping system fall towards zero. Two experimental methods are proposed in order to extend the considered flow rate. An additional excitation force allows to increase the tube vibration level for improving the signal-noise ratio at low velocities. When the tube is submitted to fluid-elastic instability, an artificial damping contribution by active control allows to stabilize it. Methods are implemented on a flexible tube inserted into rigid tubes bundle water and water-air transverse flows. Two actuator technologies are used: an electromagnetic exciter and piezoelectric actuators. The additional excitation method shows that the fluid-elastic forces remain insignificant at low velocity single phase flow. With the active control method, it is possible to carry out tests beyond the fluid-elastic instability. In two-phase flow, the stabilization of the structure is observed for low vacuum rates. The obtained new results are analyzed with the literature expected results in terms of fluid-elastic coupling and turbulent excitation. (author) [fr
Importance of elastic finite-size effects: Neutral defects in ionic compounds
Burr, P. A.; Cooper, M. W. D.
2017-09-01
Small system sizes are a well-known source of error in density functional theory (DFT) calculations, yet computational constraints frequently dictate the use of small supercells, often as small as 96 atoms in oxides and compound semiconductors. In ionic compounds, electrostatic finite-size effects have been well characterized, but self-interaction of charge-neutral defects is often discounted or assumed to follow an asymptotic behavior and thus easily corrected with linear elastic theory. Here we show that elastic effects are also important in the description of defects in ionic compounds and can lead to qualitatively incorrect conclusions if inadequately small supercells are used; moreover, the spurious self-interaction does not follow the behavior predicted by linear elastic theory. Considering the exemplar cases of metal oxides with fluorite structure, we show that numerous previous studies, employing 96-atom supercells, misidentify the ground-state structure of (charge-neutral) Schottky defects. We show that the error is eliminated by employing larger cells (324, 768, and 1500 atoms), and careful analysis determines that elastic, not electrostatic, effects are responsible. The spurious self-interaction was also observed in nonoxide ionic compounds irrespective of the computational method used, thereby resolving long-standing discrepancies between DFT and force-field methods, previously attributed to the level of theory. The surprising magnitude of the elastic effects is a cautionary tale for defect calculations in ionic materials, particularly when employing computationally expensive methods (e.g., hybrid functionals) or when modeling large defect clusters. We propose two computationally practicable methods to test the magnitude of the elastic self-interaction in any ionic system. In commonly studied oxides, where electrostatic effects would be expected to be dominant, it is the elastic effects that dictate the need for larger supercells: greater than 96 atoms.
Study of the Quasi-Elastic Scattering in the NOvA Detector Prototype
Energy Technology Data Exchange (ETDEWEB)
Betancourt, Minerba [Univ. of Minnesota, Minneapolis, MN (United States)
2013-06-01
NOvA is a 810 km long base-line neutrino oscillation experiment with two detectors (far 14 KTon and near detector 300 Ton) currently being installed in the NUMI o -axis neutrino beam produced at Fermilab. A 222 Ton prototype NOvA detector (NDOS) was built and operated in the neutrino beam for over a year to understand the response of the detector and its construction. The goal of this thesis is to study the muon neutrino interaction data collected in this test, specifically the identification of quasi-elastic charged-current interactions and measure the behavior of the quasi-elastic muon neutrino cross section.
Rotation, inversion and perversion in anisotropic elastic cylindrical tubes and membranes
Goriely, A.
2013-03-06
Cylindrical tubes and membranes are universal structural elements found in biology and engineering over a wide range of scales.Working in the framework of nonlinear elasticity, we consider the possible deformations of elastic cylindrical shells reinforced by one or two families of fibres. We consider both small and large deformations and the reduction from thick cylindrical shells (tubes) to thin shells (cylindrical membranes). In particular, a number of universal parameter regimes can be identified where the response behaviour of the cylinder is qualitatively different. This include the possibility of inversion of twist or axial strain when the cylinder is subject to internal pressure. Copyright © The Royal Society 2013.
Elastic electron scattering from the DNA bases: cytosine and thymine
International Nuclear Information System (INIS)
Colyer, C J; Bellm, S M; Lohmanny, B; Blanco, F; Garcia, G
2012-01-01
Relative elastic differential cross sections for elastic scattering from cytosine and thymine have been measured using the crossed beam method. The experimental data are compared with theoretical cross sections calculated by the screen corrected additivity rule method.
Controlling elastic waves with small phononic crystals containing rigid inclusions
Peng, Pai
2014-05-01
We show that a two-dimensional elastic phononic crystal comprising rigid cylinders in a solid matrix possesses a large complete band gap below a cut-off frequency. A mechanical model reveals that the band gap is induced by negative effective mass density, which is affirmed by an effective medium theory based on field averaging. We demonstrate, by two examples, that such elastic phononic crystals can be utilized to design small devices to control low-frequency elastic waves. One example is a waveguide made of a two-layer anisotropic elastic phononic crystal, which can guide and bend elastic waves with wavelengths much larger than the size of the waveguide. The other example is the enhanced elastic transmission of a single-layer elastic phononic crystal loaded with solid inclusions. The effective mass density and reciprocal of the modulus of the single-layer elastic phononic crystal are simultaneously near zero. © CopyrightEPLA, 2014.
Branicio, Paulo S.; Vastola, Guglielmo; Jhon, Mark H.; Sullivan, Michael B.; Shenoy, Vivek B.; Srolovitz, David J.
2016-10-01
The deformation of graphene due to the chemisorption of hydrogen atoms on its surface and the long-range elastic interaction between hydrogen atoms induced by these deformations are investigated using a multiscale approach based on first principles, empirical interactions, and continuum modeling. Focus is given to the intrinsic low-temperature structure and interactions. Therefore, all calculations are performed at T =0 , neglecting possible temperature or thermal fluctuation effects. Results from different methods agree well and consistently describe the local deformation of graphene on multiple length scales reaching 500 Å . The results indicate that the elastic interaction mediated by this deformation is significant and depends on the deformation of the graphene sheet both in and out of plane. Surprisingly, despite the isotropic elasticity of graphene, within the linear elastic regime, atoms elastically attract or repel each other depending on (i) the specific site they are chemisorbed; (ii) the relative position of the sites; (iii) and if they are on the same or on opposite surface sides. The interaction energy sign and power-law decay calculated from molecular statics agree well with theoretical predictions from linear elasticity theory, considering in-plane or out-of-plane deformations as a superposition or in a coupled nonlinear approach. Deviations on the exact power law between molecular statics and the linear elastic analysis are evidence of the importance of nonlinear effects on the elasticity of monolayer graphene. These results have implications for the understanding of the generation of clusters and regular formations of hydrogen and other chemisorbed atoms on graphene.
elastic analysis of tall reinforced concrete frames on elastic sub-base
African Journals Online (AJOL)
Dr Obe
distribution of internal forces in the structural members as well as in their deflections. Presently, there is lack of ... basis for this design of structures. The main objective, here is to find out about the behaviours of. ... Fig.1. principles of beam on elastic sub –base. a. Settlement of beam –axis b. Beam on elastic sub – base using ...
Directory of Open Access Journals (Sweden)
Supakorn Tirapat
2017-01-01
Full Text Available This paper presents the analysis of a layered elastic half space under the action of axisymmetric surface loading and the influence of the surface energy effects. The boundary value problems for the bulk and the surface are formulated based on classical linear elasticity and a complete Gurtin-Murdoch constitutive relation. An analytical technique using Love’s representation and the Hankel integral transform is employed to derive an integral-form solution for both displacement and stress fields. An efficient numerical quadrature is then applied to accurately evaluate all involved integrals. Selected numerical results are presented to portray the influence of various parameters on elastic fields. Numerical results indicate that the surface stress displays a significant influence on both displacement and stress fields. It is also found that the layered half space becomes stiffer with the presence of surface stresses. In addition, unlike the classical elasticity solution, size-dependent behavior of elastic fields is noted. The present analytical solutions provide fundamental understanding of the influence of surface energy on layered elastic materials. It can also be used as a benchmark solution for the development of numerical techniques such as FEM and BEM, for analysis of more complex problems involving a layered medium under the influence of surface energy effects.
Energy Technology Data Exchange (ETDEWEB)
Sargsyan, V.V. [International Center for Advanced Studies, Yerevan State University (Armenia); Adamian, G.G.; Antonenko, N.V., E-mail: adamian@theor.jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); Gomes, P.R.S. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Fisica
2014-07-01
We suggest simple and useful methods to extract reaction and capture (fusion) cross sections from the experimental elastic and quasi-elastic backscattering data.The direct measurement of the reaction or capture (fusion) cross section is a difficult task since it would require the measurement of individual cross sections of many reaction channels, and most of them could be reached only by specific experiments. This would require different experimental setups not always available at the same laboratory and, consequently, such direct measurements would demand a large amount of beam time and would take probably some years to be reached. Because of that, the measurements of elastic scattering angular distributions that cover full angular ranges and optical model analysis have been used for the determination of reaction cross sections. This traditional method consists in deriving the parameters of the complex optical potentials which fit the experimental elastic scattering angular distributions and then of deriving the reaction cross sections predicted by these potentials. Even so, both the experimental part and the analysis of this latter method are not so simple. In the present work we present a much simpler method to determine reaction and capture (fusion) cross sections. It consists of measuring only elastic or quasi-elastic scattering at one backward angle, and from that, the extraction of the reaction or capture cross sections can easily be performed. (author)
Mechanical critical phenomena and the elastic response of fiber networks
Mackintosh, Fred
The mechanics of cells and tissues are largely governed by scaffolds of filamentous proteins that make up the cytoskeleton, as well as extracellular matrices. Evidence is emerging that such networks can exhibit rich mechanical phase behavior. A classic example of a mechanical phase transition was identified by Maxwell for macroscopic engineering structures: networks of struts or springs exhibit a continuous, second-order phase transition at the isostatic point, where the number of constraints imposed by connectivity just equals the number of mechanical degrees of freedom. We present recent theoretical predictions and experimental evidence for mechanical phase transitions in in both synthetic and biopolymer networks. We show, in particular, excellent quantitative agreement between the mechanics of collagen matrices and the predictions of a strain-controlled phase transition in sub-isostatic networks.
Influence of elastic supports on non-linear steady-state vibrations of Zener material plates
Litewka, Przemysław; Lewandowski, Roman
2018-01-01
The paper reports numerical results of analyses of steady-state harmonic vibrations of von Kármán non-linear plates made from Zener material with various elastic support conditions. Influences of shear deformation and rotary inertia are taken into account, thus the model is able to predict the behaviour of plates with a moderate thickness. The amplitude equation for the plate is obtained using the time-averaged principle of virtual work for the assumed harmonic form of excitation and plate displacements as well as the harmonic balance method for Zener material and non-linear elastic supports. Plates are discretised using 8-noded rectangular plate finite elements. The discretised amplitude equation is solved for the response curves using a path-following method. Results of two numerical examples are presented and the qualitative and quantitative influence of support elastic properties is discussed.
A non-linear elastic constitutive framework for replicating plastic deformation in solids.
Energy Technology Data Exchange (ETDEWEB)
Roberts, Scott Alan; Schunk, Peter Randall
2014-02-01
Ductile metals and other materials typically deform plastically under large applied loads; a behavior most often modeled using plastic deformation constitutive models. However, it is possible to capture some of the key behaviors of plastic deformation using only the framework for nonlinear elastic mechanics. In this paper, we develop a phenomenological, hysteretic, nonlinear elastic constitutive model that captures many of the features expected of a plastic deformation model. This model is based on calculating a secant modulus directly from a materials stress-strain curve. Scalar stress and strain values are obtained in three dimensions by using the von Mises invariants. Hysteresis is incorporated by tracking an additional history variable and assuming an elastic unloading response. This model is demonstrated in both single- and multi-element simulations under varying strain conditions.
Modeling of Distributed Sensing of Elastic Waves by Fiber-Optic Interferometry
Directory of Open Access Journals (Sweden)
Just Agbodjan Prince
2016-09-01
Full Text Available This paper deals with the transduction of strain accompanying elastic waves in solids by firmly attached optical fibers. Stretching sections of optical fibers changes the time required by guided light to pass such sections. Exploiting interferometric techniques, highly sensitive fiber-optic strain transducers are feasible based on this fiber-intrinsic effect. The impact on the actual strain conversion of the fiber segment’s shape and size, as well as its inclination to the elastic wavefront is studied. FEM analyses show that severe distortions of the interferometric response occur when the attached fiber length spans a noticeable fraction of the elastic wavelength. Analytical models of strain transduction are presented for typical transducer shapes. They are used to compute input-output relationships for the transduction of narrow-band strain pulses as a function of the mechanical wavelength. The described approach applies to many transducers depending on the distributed interaction with the investigated object.
Towards an Aero-Propulso-Servo-Elasticity Analysis of a Commercial Supersonic Transport
Connolly, Joseph W.; Kopasakis, George; Chwalowski, Pawel; Sanetrik, Mark D.; Carlson, Jan-Renee; Silva, Walt A.; McNamara, Jack
2016-01-01
This paper covers the development of an aero-propulso-servo-elastic (APSE) model using computational fluid dynamics (CFD) and linear structural deformations. The APSE model provides the integration of the following two previously developed nonlinear dynamic simulations: a variable cycle turbofan engine and an elastic supersonic commercial transport vehicle. The primary focus of this study is to provide a means to include relevant dynamics of a turbomachinery propulsion system into the aeroelastic studies conducted during a vehicle design, which have historically neglected propulsion effects. A high fidelity CFD tool is used here for the integration platform. The elastic vehicle neglecting the propulsion system serves as a comparison of traditional approaches to the APSE results. An overview of the methodology is presented for integrating the propulsion system and elastic vehicle. Static aeroelastic analysis comparisons between the traditional and developed APSE models for a wing tip detection indicate that the propulsion system impact on the vehicle elastic response could increase the detection by approximately ten percent.
Wu, Yun-Hui; Liu, Hai-Zhou; Chen, Song; Dong, Xu-Chu; Wang, Ping-Ping; Liu, Shu-Qi; Lin, Yong; Wei, Yong; Liu, Lan
2017-06-14
It is a great challenge to fabricate piezoresistive sensors that possess high elasticity, large-area compliance, and excellent detectability to satisfy both extremely tiny and large human activity monitoring. Herein, a novel and facile strategy is reported to manufacture highly elastic channel crack-based gold@PU sponge piezoresistive material. The elastic 3D conductive network is successfully prepared by gold ion sputtering, and channel cracks are skillfully designed on the 3D sponge skeletons. Such novel structure makes these fabricated sensors are capable of monitoring both tiny and large human motions, which originate from the nanocrack joint sensing mechanism and physical contact of conductive interconnected network. Meanwhile, our sensors possess excellent elasticity, fast response time (9 ms), and ultralow detection limit (0.568 Pa), as well as good reproducibility over 1000 cycles. The desirable elasticity of channel crack-based gold@PU sensor is comparable to recently reported pressure sensors, together with advantages of reliable fabrication and large-area compliance, makes them attractive in various electronic devices, for example, biological health monitoring, sport performance monitoring, and man-machine interfaces.
Directory of Open Access Journals (Sweden)
M. Mohammadi
Full Text Available In this study, the vibration behavior of annular and circular graphene sheet coupled with temperature change and under in-plane pre-stressed is studied. Influence of the surrounding elastic medium 011 the fundamental frequencies of the single-layered graphene sheets (SLGSs is investigated. Both Winkler-type and Pasternak- type models are employed to simulate the interaction of the graphene sheets with a surrounding elastic medium. By using the nonlocal elasticity theory the governing equation is derived for SLGSs. The closed-form solution for frequency vibration of circular graphene sheets lias been obtained and nonlocal parameter, inplane pre-stressed, the parameters of elastic medium and temperature change appears into arguments of Bessel functions. The results are subsequently compared with valid result reported in the literature and the molecular dynamics (MD results. The effects of the small scale, pre-stressed, mode number, temperature change, elastic medium and boundary conditions on natural frequencies are investigated. The non-dimensional frequency decreases at high temperature case with increasing the temperature change for all boundary conditions. The effect of temperature change 011 the frequency vibration becomes the opposite at high temperature case in compression with the low temperature case. The present research work thus reveals that the nonlocal parameter, boundary conditions and temperature change have significant effects on vibration response of the circular nanoplates. The present results can be used for the design of the next generation of nanodevices that make use of the thermal vibration properties of the graphene.
Structure, energetics, and elasticity of phase Egg: insights from theory and experiments
Mookherjee, M.; Panero, W. R.; Wunder, B.; Jahn, S.; Koch-Müller, M.
2017-12-01
Phase Egg is a hydrous aluminosilicate mineral with AlSiO3(OH) stoichiometry. It is likely to be stable in subducted sediments that could be modeled in a Al2O3-SiO2-H2O (ASH) ternary system. Therefore, phase Egg is an important candidate phase for transporting water into the deep Earth. In order to constrain the amount of water subducted and the degree of slab hydration, we need to understand the elasticity of hydrous phases including phase Egg and correlate them to geophysical observations. The elasticity of phase Egg is related to the crystal structure and its response to pressure and temperature. The crystal structure of phase Egg has a monoclinic (P21/n) space group symmetry. Based on high-pressure experiments and phase relations in the ASH ternary, phase Egg is likely to be stable above 11 GPa. In this study we explored the elasticity of phase Egg using first principles simulations based on density functional theory. We notice anomalous behavior of elasticity of phase Egg at mantle transition zone depths ( 15 GPa). Such anomalous behavior in the elasticity is related to changes in the hydrogen bonding O-H…O configurations and has also been documented with spectroscopic methods. Acknowledgement: MM is supported by US NSF awards EAR-1634422.
Estimating elasticities of demand for natural gas in the European household sector
International Nuclear Information System (INIS)
Nilsen, Odd Bjarte; Asche, Frank; Tveteras, Ragnar
2005-01-01
This paper analyzes the residential natural gas demand in 12 European countries using a dynamic loglinear demand model, which allows for country-specific elasticity estimates in the short-run and long run. The explanatory variables include a heating degree days index, real prices of natural gas, light fuel oil, electricity, and real private income per capita. Our data set is a country panel with annual observations from 1978 to 2002. Short panel data sets like this represents a challenge for econometric estimation, as standard estimators often provide implausible estimates of elasticities. The demand model is estimated using both homogeneous and heterogeneous estimators, with a particular focus on the shrinkage estimator (an empirical Bayes estimator). The shrinkage short-run own-price and income elasticity tend to be very inelastic, but with greater long-run responsiveness. We provide support for employing a heterogeneous estimator such as the shrinkage estimator. But the empirical results also motivate a further scrutiny of its properties. We also consider the problem of reporting t-statistics of shrinkage estimators in the empirical Bayes (EB) framework and the problem of using the delta method to approximate the elasticities. The delta method biases upward the t-statistics of the shrinkage elasticities. An alternative approach, the bootstrap sampling methods obtained more reliable confidence intervals. We call into question - is the traditional way of constructing confidence intervals or t-statistics of the shrinkage estimator to naive. (Author)
Elastic properties of Thiel-embalmed human ankle tendon and ligament.
Liao, Xiaochun; Kemp, Sandy; Corner, George; Eisma, Roos; Huang, Zhihong
2015-10-01
Thiel embalming is recommended as an alternative to formalin-based embalming because it preserves tissue elasticity, color, and flexibility in the long term, with low infection and toxicity risk. The degree to which Thiel embalming preserves elasticity has so far been assessed mainly by subjective scoring, with little quantitative verification. The aim of this study is to quantify the effect of Thiel embalming on the elastic properties of human ankle tendons and ligament. Biomechanical tensile tests were carried out on six Thiel-embalmed samples each of the peroneus longus, peroneus brevis, and calcaneal tendons, and the calcaneofibular ligament, with strain rates of 0.25%s(-1), 2%s(-1), and 8%s(-1). The stress-strain relationship was calculated from the force-extension response with cross-sectional area and gauge length. Young's modulus was determined from the stress-strain curve. The results showed that the tendon and ligament elasticity were lower after Thiel embalming than the literature values for fresh nonembalmed tendons and ligament. The biomechanical tensile test showed that the measured elasticity of Thiel-embalmed tendons and ligaments increased with the strain rate. The Thiel embalming method is useful for preserving human ankle tendons and ligaments for anatomy and surgery teaching and research, but users need to be aware of its softening effects. The method retains the mechanical strain rate effect on tendons and ligament. © 2015 Wiley Periodicals, Inc.
Theory of the change of elastic constants by interstitials
International Nuclear Information System (INIS)
Breuer, N.; Dederichs, P.H.; Lehmann, C.; Leibfried, G.; Scholz, A.
1975-01-01
The theory of the change of elastic constants by point-defects, in particular by interstitials, is briefly summarized. The typical effects of spring changes in a defect lattice on the elastic data are discussed qualitatively. Numerical results for the change of elastic constants by self-interstitials and vacancies are given and compared with experimental data for Cu and Al
Coupling of Elastic Isotropic Medium Parameters in Iterative Linearized Inversion
Anikiev, D.V.; Kashtan, B.M.; Mulder, W.A.; Troyan, V.N.
2014-01-01
An elastic isotropic medium is described with three parameters. In seismic migration the perturbation of one elastic parameter affects the images of all the three, which means that these parameters are coupled. For an effective quantitative reconstruction of the true elastic medium reflectivity one
Magneto-elastic interaction in cubic helimagnets with B20 structure
International Nuclear Information System (INIS)
Maleyev, S V
2009-01-01
The magneto-elastic interaction in cubic helimagnets with B 20 symmetry is considered. It is shown that this interaction is responsible for a negative contribution to the square of the spin-wave gap Δ and it alone appears to disrupt the assumed helical structure. It is suggested that competition between the positive part of Δ I 2 , which stems from magnon-magnon interaction, and its negative magneto-elastic part leads to the quantum phase transition observed at high pressure in MnSi and FeGe. This transition has to occur when Δ 2 →0. For MnSi it was shown using rough estimations that at ambient pressure both parts Δ I and |Δ ME | are comparable with the experimentally observed gap. The magneto-elastic interaction is responsible for 2k modulation of the lattice where k is the helix wavevector and contributes to the magnetic anisotropy. Properties of the magnetic state above the quantum phase transition are also discussed. Experimental observation of the lattice modulation by x-ray and neutron scattering allows the determination of the strength of the anisotropic part of the magneto-elastic interaction responsible for the above phenomena and the lattice helicity.
Magneto-elastic interaction in cubic helimagnets with B20 structure.
Maleyev, S V
2009-04-08
The magneto-elastic interaction in cubic helimagnets with B 20 symmetry is considered. It is shown that this interaction is responsible for a negative contribution to the square of the spin-wave gap Δ and it alone appears to disrupt the assumed helical structure. It is suggested that competition between the positive part of Δ(I)(2), which stems from magnon-magnon interaction, and its negative magneto-elastic part leads to the quantum phase transition observed at high pressure in MnSi and FeGe. This transition has to occur when [Formula: see text]. For MnSi it was shown using rough estimations that at ambient pressure both parts Δ(I) and |Δ(ME)| are comparable with the experimentally observed gap. The magneto-elastic interaction is responsible for 2k modulation of the lattice where k is the helix wavevector and contributes to the magnetic anisotropy. Properties of the magnetic state above the quantum phase transition are also discussed. Experimental observation of the lattice modulation by x-ray and neutron scattering allows the determination of the strength of the anisotropic part of the magneto-elastic interaction responsible for the above phenomena and the lattice helicity.
Snap-buckling in asymmetrically constrained elastic strips
Sano, Tomohiko G.; Wada, Hirofumi
2018-01-01
When a flat elastic strip is compressed along its axis, it is bent in one of two possible directions via spontaneous symmetry breaking, forming a cylindrical arc. This is a phenomenon well known as Euler buckling. When this cylindrical section is pushed in the other direction, the bending direction can suddenly reverse. This instability is called "snap-through buckling" and is one of the elementary shape transitions in a prestressed thin structure. Combining experiments and theory, we study snap-buckling of an elastic strip with one end hinged and the other end clamped. These asymmetric boundary constraints break the intrinsic symmetry of the strip, generating mechanical behaviors, including largely hysteretic but reproducible force responses and switchlike discontinuous shape changes. We establish the set of exact analytical solutions to fully explain all our major experimental and numerical findings. Asymmetric boundary conditions arise naturally in diverse situations when a thin object is in contact with a solid surface at one end. The introduction of asymmetry through boundary conditions yields new insight into complex and programmable functionalities in material and industrial design.
Mechanisms of elastic wave generation in solids by ion impact
International Nuclear Information System (INIS)
Deemer, B.; Murphy, J.; Claytor, T.
1990-01-01
This study is directed at understanding the mechanisms of acoustic signal generation by modulated beams of energetic ions as a function of ion energy. Interaction of ions with solids initiates a range of processes including sputtering, ion implantation, ionization, both internal and external, as well as thermal deposition in the solid. Accumulated internal stress also occurs by generation of dislocations resulting from, inelastic nuclear scattering of the incident ion beam. With respect to elastic wave generation, two potential mechanisms are thermoelastic induced stress and momentum transfer. The latter process includes contributions of momentum transfer from the incident beam and from ions ejected via sputtering. Other aspects of the generation process include the potential for shock wave generation since the mean particle velocity for a wide range of ion energies exceeds the velocity of sound in solids. This study seeks to distinguish the contribution of these mechanisms by studying the signature, angular distribution and energy dependence of the elastic wave response in the time domain and to use this information to understand technologically important processes such as implantation and sputtering
Elastic Model Transitions Using Quadratic Inequality Constrained Least Squares
Orr, Jeb S.
2012-01-01
A technique is presented for initializing multiple discrete finite element model (FEM) mode sets for certain types of flight dynamics formulations that rely on superposition of orthogonal modes for modeling the elastic response. Such approaches are commonly used for modeling launch vehicle dynamics, and challenges arise due to the rapidly time-varying nature of the rigid-body and elastic characteristics. By way of an energy argument, a quadratic inequality constrained least squares (LSQI) algorithm is employed to e ect a smooth transition from one set of FEM eigenvectors to another with no requirement that the models be of similar dimension or that the eigenvectors be correlated in any particular way. The physically unrealistic and controversial method of eigenvector interpolation is completely avoided, and the discrete solution approximates that of the continuously varying system. The real-time computational burden is shown to be negligible due to convenient features of the solution method. Simulation results are presented, and applications to staging and other discontinuous mass changes are discussed
Elastic and Inelastic Scattering of Neutrons using a CLYC array
Brown, Tristan; Doucet, E.; Chowdhury, P.; Lister, C. J.; Wilson, G. L.; Devlin, M.; Mosby, S.
2015-10-01
CLYC scintillators, which have dual neutron and gamma response, have recently ushered in the possibility of fast neutron spectroscopy without time-of-flight (TOF). A 16-element array of 1'' x 1'' 6Li-depleted CLYC crystals, where pulse-shape-discrimination is achieved via digital pulse processing, has been commissioned at UMass Lowell. In an experiment at LANSCE, high energy neutrons were used to bombard 56Fe and 238U targets, in order to measure elastic and inelastic neutron scattering cross sections as a function of energy and angle with the array. The array is placed very close to the targets for enhanced geometrical solid angles for scattered neutrons compared to standard neutron-TOF measurements. A pulse-height spectrum of scattered neutrons in the detectors is compared to the energy of the incident neutrons, which is measured via the TOF of the pulsed neutrons from the source to the detectors. Recoil corrections are necessary to combine the energy spectra from all the detectors to obtain angle-integrated elastic and inelastic cross-sections. The detection techniques, analysis procedures and results will be presented. Supported by NNSA-SSAA program through DOE Grant DE-NA00013008.
Structural changes in elastically stressed crystallites under irradiation
International Nuclear Information System (INIS)
Zolnikov, K.P.; Korchuganov, A.V.; Kryzhevich, D.S.; Chernov, V.M.; Psakhie, S.G.
2015-01-01
The response of elastically stressed iron and vanadium crystallites to atomic displacement cascades was investigated by molecular dynamics simulation. Interatomic interaction in vanadium was described by a many-body potential calculated in the Finnis–Sinclair approximation of the embedded atom method. Interatomic interaction in iron was described by a many-body potential constructed in the approximation of valence-electron gas. The crystallite temperature in the calculations was varied from 100 to 600 K. The elastically stressed state in the crystallites was formed through uniaxial tension by 4–8% such that their volume remained unchanged. The energy of a primary knock-on atom was varied from 0.5 to 50 keV. It is shown that the lower the temperature and the higher the strain degree of an initial crystallite, the lower the threshold primary knock-on atom energy for plastic deformation generation in the crystallite. The structural rearrangements induced in the crystallites by an atomic displacement cascade are similar to those induced by mechanical loading. It is found that the rearrangements are realized through twinning
Elastic Multi-scale Mechanisms: Computation and Biological Evolution.
Diaz Ochoa, Juan G
2018-01-01
Explanations based on low-level interacting elements are valuable and powerful since they contribute to identify the key mechanisms of biological functions. However, many dynamic systems based on low-level interacting elements with unambiguous, finite, and complete information of initial states generate future states that cannot be predicted, implying an increase of complexity and open-ended evolution. Such systems are like Turing machines, that overlap with dynamical systems that cannot halt. We argue that organisms find halting conditions by distorting these mechanisms, creating conditions for a constant creativity that drives evolution. We introduce a modulus of elasticity to measure the changes in these mechanisms in response to changes in the computed environment. We test this concept in a population of predators and predated cells with chemotactic mechanisms and demonstrate how the selection of a given mechanism depends on the entire population. We finally explore this concept in different frameworks and postulate that the identification of predictive mechanisms is only successful with small elasticity modulus.
Elastic Instability and Sound Dispersion in Amorphous Solids
Degiuli, Eric; Laversanne-Finot, Adrien; During, Gustavo; Lerner, Edan; Wyart, Matthieu
2014-03-01
Connectedness and applied stress are key characteristics of amorphous solids at zero temperature. Rigidity can be lost either through unjamming as connectedness is decreased, or buckling as stress is increased. We present an effective medium theory which describes elastic behaviour in proximity to both unjamming and buckling. The theory successfully predicts (i) the dependence of the boson peak on pressure and coordination, (ii) negative sound dispersion and a kink in sound attenuation near the boson peak, as observed experimentally in molecular glasses, (iii) a characteristic frequency ω0 that vanishes at a critical pressure, and (iv) the previously derived stability diagram for T = 0 amorphous solids. Our predictions for sound dispersion are similar to disorder-based approaches to the boson peak, however we resolve two inconsistencies of these approaches: (i) since disorder is secondary to connectedness and stress in our theory, we explain why some crystals and glasses have similar elasticity, and (ii) we explain the natural emergence of a mesoscopic length scale visible in response, which is absent in static structure.
Fabrication of hydrogels with elasticity changed by alkaline phosphatase for stem cell culture.
Toda, Hiroyuki; Yamamoto, Masaya; Uyama, Hiroshi; Tabata, Yasuhiko
2016-01-01
The objective of this study is to design hydrogels whose elasticity can be changed by alkaline phosphatase (ALP) in cell culture and evaluate the effect of hydrogel elasticity on an osteogenic gene expression of cells. Hydrogels were prepared by the radical polymerization of acrylamide (AAm), N,N'-methylenebisacrylamide (BIS), and Phosmer™M containing phosphate groups (PE-PAAm hydrogels). The storage modulus of PE-PAAm hydrogels prepared was changed by the preparation conditions. When human mesenchymal stem cells (hMSC) were cultured on the ALP-responsive PE-PAAm hydrogels in the presence or absence of ALP, the morphology of hMSC was observed and one of the osteogenic differentiation markers, Runx2, was evaluated. By ALP addition into the culture medium, the morphology of hMSC was changed into an elongated shape without cell damage. ALP addition modified the level of Runx2 gene expression, which was influenced by the modulus of PE-PAAm hydrogels. It is concluded that the elasticity change of hydrogel substrates in cell culture had an influence on the Runx2 gene expression of hMSC. Stem cells sense the surface elasticity of culture substrates, and their differentiation fate is biologically modified by substrate properties. Most of experiments have been performed in static conditions during cell culture, while the in vivo microenvironment is dynamically changed. In this study, we established to design an enzyme-responsive hydrogel whose elasticity can be changed by alkaline phosphatase (ALP) in cell culture to mimic in vivo conditions. As a result, the cells were deformed and the gene expression level of an osteogenic maker, Runx2, was modified by ALP treatment. This is the novel report describing to demonstrate that the dynamic alteration of hydrogel substrate elasticity could modulate the osteoblastic gene expression of human MSC in vitro. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Elastic K-means using posterior probability.
Zheng, Aihua; Jiang, Bo; Li, Yan; Zhang, Xuehan; Ding, Chris
2017-01-01
The widely used K-means clustering is a hard clustering algorithm. Here we propose a Elastic K-means clustering model (EKM) using posterior probability with soft capability where each data point can belong to multiple clusters fractionally and show the benefit of proposed Elastic K-means. Furthermore, in many applications, besides vector attributes information, pairwise relations (graph information) are also available. Thus we integrate EKM with Normalized Cut graph clustering into a single clustering formulation. Finally, we provide several useful matrix inequalities which are useful for matrix formulations of learning models. Based on these results, we prove the correctness and the convergence of EKM algorithms. Experimental results on six benchmark datasets demonstrate the effectiveness of proposed EKM and its integrated model.
Magneto-elastic torsional oscillations of magnetars
International Nuclear Information System (INIS)
Gabler, Michael; Cerda-Duran, Pablo; Mueller, Ewald; Font, Jose A; Stergioulas, Nikolaos
2011-01-01
We extend a general-relativistic ideal magneto-hydrodynamical code to include the effects of elasticity. Using this numerical tool we analyse the magneto-elastic oscillations of highly magnetised neutron stars (magnetars). In simulations without magnetic field we are able to recover the purely crustal shear oscillations within an accuracy of about a few per cent. For dipole magnetic fields between 5 x 10 13 and 10 15 G the Alfven oscillations become modified substantially by the presence of the crust. Those quasi-periodic oscillations (QPOs) split into three families: Lower QPOs near the equator, Edge QPOs related to the last open field line and Upper QPOs at larger distance from the equator.
Mathematical methods in electro-magneto-elasticity
Bardzokas, DI; Filshtinsky, LA
2007-01-01
The mechanics of Coupled Fields is a discipline at the edge of modern research connecting Continuum Mechanics with Solid State Physics. It integrates the Mechanics of Continuous Media, Heat Conductivity and the theory of Electromagnetism that are usually studied separately. For an accurate description of the influence of static and dynamic loadings, high temperatures and strong electromagnetic fields in elastic media and constructive installations, a new approach is required; an approach that has the potential to establish a synergism between the above mentioned fields. Throughout the book a vast number of problems are considered: two-dimensional problems of electro-magneto-elasticity as well as static and dynamical problems for piecewise homogenous compound piezoelectric plates weakened by cracks and openings. The boundary conditions, the constructive equations and the mathematical methods for their solution are thoroughly presented, so that the reader can get a clear quantitative and qualitative understandi...
Elastic wave scattering methods: assessments and suggestions
International Nuclear Information System (INIS)
Gubernatis, J.E.
1985-01-01
The author was asked by the meeting organizers to review and assess the developments over the past ten or so years in elastic wave scattering methods and to suggest areas of future research opportunities. He highlights the developments, focusing on what he feels were distinct steps forward in our theoretical understanding of how elastic waves interact with flaws. For references and illustrative figures, he decided to use as his principal source the proceedings of the various annual Reviews of Progress in Quantitative Nondestructive Evaluation (NDE). These meetings have been the main forum not only for presenting results of theoretical research but also for demonstrating the relevance of the theoretical research for the design and interpretation of experiment. In his opinion a quantitative NDE is possible only if this relevance exists, and his major objective is to discuss and illustrate the degree to which relevance has developed
Data-Driven Problems in Elasticity
Conti, S.; Müller, S.; Ortiz, M.
2018-01-01
We consider a new class of problems in elasticity, referred to as Data-Driven problems, defined on the space of strain-stress field pairs, or phase space. The problem consists of minimizing the distance between a given material data set and the subspace of compatible strain fields and stress fields in equilibrium. We find that the classical solutions are recovered in the case of linear elasticity. We identify conditions for convergence of Data-Driven solutions corresponding to sequences of approximating material data sets. Specialization to constant material data set sequences in turn establishes an appropriate notion of relaxation. We find that relaxation within this Data-Driven framework is fundamentally different from the classical relaxation of energy functions. For instance, we show that in the Data-Driven framework the relaxation of a bistable material leads to material data sets that are not graphs.
Diffraction by an immersed elastic wedge
Croisille, Jean-Pierre
1999-01-01
This monograph presents the mathematical description and numerical computation of the high-frequency diffracted wave by an immersed elastic wave with normal incidence. The mathematical analysis is based on the explicit description of the principal symbol of the pseudo-differential operator connected with the coupled linear problem elasticity/fluid by the wedge interface. This description is subsequently used to derive an accurate numerical computation of diffraction diagrams for different incoming waves in the fluid, and for different wedge angles. The method can be applied to any problem of coupled waves by a wedge interface. This work is of interest for any researcher concerned with high frequency wave scattering, especially mathematicians, acousticians, engineers.
Plane micropolar elasticity with surface flexural resistance
Gharahi, Alireza; Schiavone, Peter
2018-03-01
We propose a linear surface/interface model for plane deformations of a micropolar elastic solid based on a higher-order surface elasticity theory capable of incorporating bending and twisting effects. The surface/interface is modeled as a bending-resistant Kirchhoff micropolar thin shell perfectly bonded to the boundary of the solid. It is anticipated that by combining micropolar bulk and surface effects in this way, the enhanced model will most accurately capture the essential characteristics (in particular, size dependency) required in the modeling of materials with significant microstructure as well as in the modeling of classes of nanomaterials. The corresponding boundary value problems are particularly interesting in that they involve boundary conditions of order higher than that of the governing field equations. We illustrate our theory by analyzing the simple problem of a circular hole in a micropolar sheet noting, in particular, the extent to which surface effects and micropolar properties each contribute to the deformation of the sheet.
Plutonium Elastic Moduli, Electron Localization, and Temperature
International Nuclear Information System (INIS)
Migliori, Albert; Mihut-Stroe, Izabella; Betts, Jon B.
2008-01-01
In almost all materials, compression is accompanied naturally by stiffening. Even in materials with zero or negative thermal expansion, where warming is accompanied by volume contraction it is the volume change that primarily controls elastic stiffness. Not so in the metal plutonium. In plutonium, alloying with gallium can change the sign of thermal expansion, but for the positive thermal- expansion monoclinic phase as well as the face-centered-cubic phase with either sign of thermal expansion, and the orthorhombic phase, recent measurements of elastic moduli show soften on warming by an order of magnitude more than expected, the shear and compressional moduli track, and volume seems irrelevant. These effects point toward a novel mechanism for electron localization, and have important implication for the pressure dependence of the bulk compressibility. (authors)
Elastic path controller for assistive devices.
Long, B; Rebsamen, B; Burdet, E; Yu, H; Teo, C L
2005-01-01
Robotic assistive devices that constrain motion along pre-defined paths are useful in reducing maneuvering efforts by human. This paper introduces an Elastic Path Controller (EPC) that adds "elasticity" to the path following and enables dynamic modification of the paths. This permits the users to compensate for changes in the environment such as introduction of new obstacles or for errors in position sensing. The experiments performed on a Scooter cobot show that users can learn to use this novel tool to modify and design guiding paths in a relatively simple way. The operators use the EPC by pushing/pulling against the guided paths to produce the desired deformations. Then, by just dropping the forces and trusting the path controller, they will be brought back to the guided paths.
Elastic softness of hybrid lead halide perovskites
Ferreira, A. C.
2018-01-26
Much recent attention has been devoted towards unravelling the microscopic optoelectronic properties of hybrid organic-inorganic perovskites (HOP). Here we investigate by coherent inelastic neutron scattering spectroscopy and Brillouin light scattering, low frequency acoustic phonons in four different hybrid perovskite single crystals: MAPbBr3, FAPbBr3, MAPbI3 and α-FAPbI3 (MA: methylammonium, FA: formamidinium). We report a complete set of elastic constants caracterized by a very soft shear modulus C44. Further, a tendency towards an incipient ferroelastic transition is observed in FAPbBr3. We observe a systematic lower sound group velocity in the technologically important iodide-based compounds compared to the bromide-based ones. The findings suggest that low thermal conductivity and hot phonon bottleneck phenomena are expected to be enhanced by low elastic stiffness, particularly in the case of the ultrasoft α-FAPbI3.
Elastic passive source localization using rotational motion
Li, Zhenhua; van der Baan, Mirko
2017-11-01
As a complement to traditional particle velocity recordings, rotational motion provides information on the spatial gradient of particle displacement motion which aids in imaging passive sources using elastic waves. Event localization is for instance important in earthquake seismology and detection of microseismic events during hydraulic fracturing treatments of hydrocarbon reservoirs or injection of carbon dioxide (CO2) in depleted reservoirs. We propose an elastic reverse time extrapolation technique for passive event localization incorporating a new representation-theorem-based expression that explicitly uses recordings from rotational and particle velocity sensors either simultaneously or separately, leading to enhanced imaging results. We also introduce a novel focusing criterion based on the energy flux which is insensitive to polarity reversals due to non-isotropic source mechanisms. Energy flux combined with the Hough transform leads to a convenient and stable criterion for automatically detecting both event locations and origin times.
Anticavitation and Differential Growth in Elastic Shells
Moulton, Derek E.
2010-07-22
Elastic anticavitation is the phenomenon of a void in an elastic solid collapsing on itself. Under the action of mechanical loading alone typical materials do not admit anticavitation. We study the possibility of anticavitation as a consequence of an imposed differential growth. Working in the geometry of a spherical shell, we seek radial growth functions which cause the shell to deform to a solid sphere. It is shown, surprisingly, that most material models do not admit full anticavitation, even when infinite growth or resorption is imposed at the inner surface of the shell. However, void collapse can occur in a limiting sense when radial and circumferential growth are properly balanced. Growth functions which diverge or vanish at a point arise naturally in a cumulative growth process. © 2010 Springer Science+Business Media B.V.
The multiple V-shaped double peeling of elastic thin films from elastic soft substrates
Menga, N.; Afferrante, L.; Pugno, N. M.; Carbone, G.
2018-04-01
In this paper, a periodic configuration of V-shaped double peeling process is investigated. Specifically, an elastic thin film is detached from a soft elastic material by applying multiple concentrated loads periodically distributed with spatial periodicity λ. The original Kendall's idea is extended to take into account the change in elastic energy occurring in the substrate when the detachment fronts propagate. The symmetric configuration typical of a V-peeling process causes the energy release rate to be sensitive to variations of the elastic energy stored in the soft substrate. This results in an enhancement of the adhesion strength because part of the external work required to trigger the peeling mechanism is converted in substrate elastic energy. A key role is played by both spatial periodicity λ and elasticity ratio E/Eh, between tape and substrate elastic moduli, in determining the conditions of stable adhesion. Indeed, the presence of multiple peeling fronts determines a modification of the mechanism of interaction, because deformations close to each peeling front are also affected by the stresses related to the other fronts. Results show that the energy release rate depends on the detached length of the tape so that conditions can be established which lead to an increase of the supported load compared to the classical peeling on rigid substrates. Finally, we also find that for any given value of the load per unit length, an optimum value of the wavelength λ exists that maximizes the tolerance of the system, before unstable propagation of the peeling front can occur.
Elasticity, viscosity, and deformation of orbital fat
Schoemaker, Ivo; Hoefnagel, Pepijn; Mastenbroek, Tom; Kolff, Cornelis; Schutte, Sander; Helm, Frans; Picken, Stephen; Gerritsen, Anton; Wielopolski, Piotr; Spekreijse, Henk; Simonsz, Huib
2006-01-01
textabstractPURPOSE. For development of a finite element analysis model of orbital mechanics, it was necessary to determine the material properties of orbital fat and its degree of deformation in eye rotation. METHODS. Elasticity and viscosity of orbital fat of eight orbits of four calves and two orbits of one rhesus monkey were measured with a parallel-plate rheometer. The degree of deformation of orbital fat was studied in two human subjects by magnetic resonance imaging (MRI) through the o...
Wilhelmy plate artifacts in elastic monolayers
Witten, T. A.; Wang, Jin; Pocivavsek, L.; Lee, K. Y. C.
2010-01-01
A recent article [L. Pocivavsek et al., Soft Matter4, 2019 (2008)] by some of us pointed out difficulties in interpreting Wilhelmy plate measurements on elastic Langmuir monolayers that support anisotropic stress. Using a simplified geometry it showed conditions in which the Wilhelmy plate measures significantly different stress from the ambient stress. We correct a serious error in this analysis and strengthen its conclusion, showing that the Wilhelmy stress and the ambient stress can have opposite signs.
Nucleon elastic and quasielastic scattering on vanadium
International Nuclear Information System (INIS)
Titarenko, N.N.; Isakov, A.G.; Rudenskaya, E.O.
1988-01-01
A unified set of parameters of the neutron optical potential for the 51 V nucleus is searched in the energy range 10 keV - 32 MeV so as to obtain a good agreement with all the available data. These include neutron strength function and elastic scattering data, as well as the neutron total cross sections and (p,n) isobaric analog state quasielastic scattering data
Serpentine locomotion through elastic energy release
Dal Corso, Francesco; Misseroni, Diego; Pugno, Nicola; Movchan, A. B.; Movchan, N. V.; Bigoni, Davide
2017-01-01
A model for serpentine locomotion is derived from a novel perspective based on concepts from configurational mechanics. The motion is realized through the release of the elastic energy of a deformable rod, sliding inside a frictionless channel, which represents a snake moving against lateral restraints. A new formulation is presented, correcting previous results and including situations never analysed so far, as in the cases when the serpent's body lies only partially inside the restraining c...
Coulomb correction to elastic. alpha. -. alpha. scattering
Energy Technology Data Exchange (ETDEWEB)
Bera, P.K.; Jana, A.K.; Haque, N.; Talukdar, B. (Department of Physics, Visva-Bharati University, Santiniketan-731235, West Bengal, India (IN))
1991-02-01
The elastic {alpha}-{alpha} scattering is treated within the framework of a generalized phase-function method (GPFM). This generalization consists in absorbing the effect of Coulomb interaction in the comparison functions for developing the phase equation. Based on values of scattering phase shifts computed by the present method, it is concluded that the GPFM provides an uncomplicated approach to rigorous Coulomb correction in the {alpha}-{alpha} scattering.
Graphene nanoribbon as an elastic damper
Evazzade, Iman; Lobzenko, Ivan P.; Saadatmand, Danial; Korznikova, Elena A.; Zhou, Kun; Liu, Bo; Dmitriev, Sergey V.
2018-05-01
Heterostructures composed of dissimilar two-dimensional nanomaterials can have nontrivial physical and mechanical properties which are potentially useful in many applications. Interestingly, in some cases, it is possible to create heterostructures composed of weakly and strongly stretched domains with the same chemical composition, as has been demonstrated for some polymer chains, DNA, and intermetallic nanowires supporting this effect of two-phase stretching. These materials, at relatively strong tension forces, split into domains with smaller and larger tensile strains. Within this region, average strain increases at constant tensile force due to the growth of the domain with the larger strain, at the expense of the domain with smaller strain. Here, the two-phase stretching phenomenon is described for graphene nanoribbons with the help of molecular dynamics simulations. This unprecedented feature of graphene that is revealed in our study is related to the peculiarities of nucleation and the motion of the domain walls separating the domains of different elastic strain. It turns out that the loading–unloading curves exhibit a hysteresis-like behavior due to the energy dissipation during the domain wall nucleation and motion. Here, we put forward the idea of implementing graphene nanoribbons as elastic dampers, efficiently converting mechanical strain energy into heat during cyclic loading–unloading through elastic extension where domains with larger and smaller strains coexist. Furthermore, in the regime of two-phase stretching, graphene nanoribbon is a heterostructure for which the fraction of domains with larger and smaller strain, and consequently its physical and mechanical properties, can be tuned in a controllable manner by applying elastic strain and/or heat.
Elastic scintillation materials based on polyorganosiloxane
International Nuclear Information System (INIS)
Grinev, B.V.; Andryushchenko, L.A.; Shershukov, V.M.; Ulanenko, K.B.; Minakova, R.A.; Sevastjanova, I.V.
1994-01-01
The developed elastic scintillators based on polymethyl-phenylsiloxane rubber are characterized by an elevated light output and a low toxicity. The increase of their light output is achieved by raising the content of phenyl chains, varying the chemical structure of luminescent additions and using isopropylnaphthalene. This high-boiling solvent introduced into the scintillation siloxane compositions is confined within siloxane matrix after the hardening of the rubber
On the elastic stiffness of grain boundaries
International Nuclear Information System (INIS)
Zhang Tongyi; Hack, J.E.
1992-01-01
The elastic softening of grain boundaries is evaluated from the starting point of grain boundary energy. Several examples are given to illustrate the relationship between boundary energy and the extent of softening. In general, a high grain boundary energy is associated with a large excess atomic volume in the boundary region. The consequent reduction in grain boundary stiffness can represent a significant fraction of that observed in bulk crystals. (orig.)
Thermal elastic deformations of the planet Mercury.
Liu, H.-S.
1972-01-01
The variation in solar heating due to the resonance rotation of Mercury produces periodic elastic deformations on the surface of the planet. The thermal stress and strain fields under Mercury's surface are calculated after certain simplifications. It is found that deformations penetrate to a greater depth than the variation of solar heating, and that the thermal strain on the surface of the planet pulsates with an amplitude of .004 and a period of 176 days.
Intersite elastic coupling and invar effect
Khomskii, D. I.; Kusmartsev, F. V.
2004-01-01
The invar phenomenon (very small thermal expansion in some iron alloys or compounds) is usually explained by the thermally-induced transitions between different spin states of Fe, having different atomic volumes. We consider these processes taking into account elastic interaction between Fe atoms in different spin states. Inclusion of these interactions explains why thermal expansion may be close to zero in a broad temperature interval and thus gives rise to the invar effect.
Studies of elastic-plastic instabilities
DEFF Research Database (Denmark)
Tvergaard, Viggo
1999-01-01
Analyses of plastic instabilities are reviewed, with focus on results in structural mechanics as well as continuum mechanics. First the basic theories for bifurcation and post-bifurcation behavior are briefly presented. Then, localization of plastic flow is discussed, including shear band formation...... in solids, localized necking in biaxially stretched metal sheets, and the analogous phenomenon of buckling localization in structures. Also some recent results for cavitation instabilities in elastic-plastic solids are reviewed....
Price Elasticities of Food Demand: Compensated vs Uncompensated.
Clements, Kenneth W; Si, Jiawei
2016-11-01
Two recent studies have provided a comprehensive review/summary of a large number of estimates of the price elasticity of food consumption using a meta-regression approach. In this letter, we introduce a way of removing the income effect from these elasticities to recover the compensated elasticities. Although the income effect is small, the compensated elasticities vary by income group. Both types of elasticity should possibly be considered when assessing the impact of policy changes on food consumption. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
Are rapid changes in brain elasticity possible?
Parker, K. J.
2017-09-01
Elastography of the brain is a topic of clinical and preclinical research, motivated by the potential for viscoelastic measures of the brain to provide sensitive indicators of pathological processes, and to assist in early diagnosis. To date, studies of the normal brain and of those with confirmed neurological disorders have reported a wide range of shear stiffness and shear wave speeds, even within similar categories. A range of factors including the shear wave frequency, and the age of the individual are thought to have a possible influence. However, it may be that short term dynamics within the brain may have an influence on the measured stiffness. This hypothesis is addressed quantitatively using the framework of the microchannel flow model, which derives the tissue stiffness, complex modulus, and shear wave speed as a function of the vascular and fluid network in combination with the elastic matrix that comprise the brain. Transformation rules are applied so that any changes in the fluid channels or the elastic matrix can be mapped to changes in observed elastic properties on a macroscopic scale. The results are preliminary but demonstrate that measureable, time varying changes in brain stiffness are possible simply by accounting for vasodynamic or electrochemical changes in the state of any region of the brain. The value of this preliminary exploration is to identify possible mechanisms and order-of-magnitude changes that may be testable in vivo by specialized protocols.
Nonlinear elasticity of disordered fiber networks
Feng, Jingchen; Levine, Herbert; Mao, Xiaoming; Sander, Leonard M.
One of the most striking mechanical properties in disordered biopolymer gels is strong nonlinearities. In the case of athermal gels (such as collagen- I) the nonlinearity has long been associated with a crossover from a bending dominated to a stretching dominated regime of elasticity. The physics of this crossover is related to the existence of a central-force isostatic point and to the small bending modulus for most gels. This crossover induces scaling behavior for the elastic moduli. In particular, for linear elasticity such a scaling law has been demonstrated by Broedersz et al. We generalize the scaling to the nonlinear regime with a two-parameter scaling law involving three critical exponents. We do numerical testing of the scaling law for two disordered lattice models, and find a good scaling collapse for the shear modulus in both the linear and nonlinear regimes. We compute all the critical exponents for the two lattice models and discuss the applicability of our results to real systems.
Environmental bias and elastic curves on surfaces
International Nuclear Information System (INIS)
Guven, Jemal; María Valencia, Dulce; Vázquez-Montejo, Pablo
2014-01-01
The behavior of an elastic curve bound to a surface will reflect the geometry of its environment. This may occur in an obvious way: the curve may deform freely along directions tangent to the surface, but not along the surface normal. However, even if the energy itself is symmetric in the curve's geodesic and normal curvatures, which control these modes, very distinct roles are played by the two. If the elastic curve binds preferentially on one side, or is itself assembled on the surface, not only would one expect the bending moduli associated with the two modes to differ, binding along specific directions, reflected in spontaneous values of these curvatures, may be favored. The shape equations describing the equilibrium states of a surface curve described by an elastic energy accommodating environmental factors will be identified by adapting the method of Lagrange multipliers to the Darboux frame associated with the curve. The forces transmitted to the surface along the surface normal will be determined. Features associated with a number of different energies, both of physical relevance and of mathematical interest, are described. The conservation laws associated with trajectories on surface geometries exhibiting continuous symmetries are also examined. (paper)
Fringe instability in constrained soft elastic layers.
Lin, Shaoting; Cohen, Tal; Zhang, Teng; Yuk, Hyunwoo; Abeyaratne, Rohan; Zhao, Xuanhe
2016-11-04
Soft elastic layers with top and bottom surfaces adhered to rigid bodies are abundant in biological organisms and engineering applications. As the rigid bodies are pulled apart, the stressed layer can exhibit various modes of mechanical instabilities. In cases where the layer's thickness is much smaller than its length and width, the dominant modes that have been studied are the cavitation, interfacial and fingering instabilities. Here we report a new mode of instability which emerges if the thickness of the constrained elastic layer is comparable to or smaller than its width. In this case, the middle portion along the layer's thickness elongates nearly uniformly while the constrained fringe portions of the layer deform nonuniformly. When the applied stretch reaches a critical value, the exposed free surfaces of the fringe portions begin to undulate periodically without debonding from the rigid bodies, giving the fringe instability. We use experiments, theory and numerical simulations to quantitatively explain the fringe instability and derive scaling laws for its critical stress, critical strain and wavelength. We show that in a force controlled setting the elastic fingering instability is associated with a snap-through buckling that does not exist for the fringe instability. The discovery of the fringe instability will not only advance the understanding of mechanical instabilities in soft materials but also have implications for biological and engineered adhesives and joints.
Elastic energy of polyhedral bilayer vesicles.
Haselwandter, Christoph A; Phillips, Rob
2011-06-01
In recent experiments [M. Dubois, B. Demé, T. Gulik-Krzywicki, J.-C. Dedieu, C. Vautrin, S. Désert, E. Perez, and T. Zemb, Nature (London) 411, 672 (2001)] the spontaneous formation of hollow bilayer vesicles with polyhedral symmetry has been observed. On the basis of the experimental phenomenology it was suggested [M. Dubois, V. Lizunov, A. Meister, T. Gulik-Krzywicki, J. M. Verbavatz, E. Perez, J. Zimmerberg, and T. Zemb, Proc. Natl. Acad. Sci. USA 101, 15082 (2004)] that the mechanism for the formation of bilayer polyhedra is minimization of elastic bending energy. Motivated by these experiments, we study the elastic bending energy of polyhedral bilayer vesicles. In agreement with experiments, and provided that excess amphiphiles exhibiting spontaneous curvature are present in sufficient quantity, we find that polyhedral bilayer vesicles can indeed be energetically favorable compared to spherical bilayer vesicles. Consistent with experimental observations we also find that the bending energy associated with the vertices of bilayer polyhedra can be locally reduced through the formation of pores. However, the stabilization of polyhedral bilayer vesicles over spherical bilayer vesicles relies crucially on molecular segregation of excess amphiphiles along the ridges rather than the vertices of bilayer polyhedra. Furthermore, our analysis implies that, contrary to what has been suggested on the basis of experiments, the icosahedron does not minimize elastic bending energy among arbitrary polyhedral shapes and sizes. Instead, we find that, for large polyhedron sizes, the snub dodecahedron and the snub cube both have lower total bending energies than the icosahedron.
Wave anisotropy of shear viscosity and elasticity
Rudenko, O. V.; Sarvazyan, A. P.
2014-11-01
The paper presents the theory of shear wave propagation in a "soft solid" material possessing anisotropy of elastic and dissipative properties. The theory is developed mainly for understanding the nature of the low-frequency acoustic characteristics of skeletal muscles, which carry important diagnostic information on the functional state of muscles and their pathologies. It is shown that the shear elasticity of muscles is determined by two independent moduli. The dissipative properties are determined by the fourth-rank viscosity tensor, which also has two independent components. The propagation velocity and attenuation of shear waves in muscle depend on the relative orientation of three vectors: the wave vector, the polarization vector, and the direction of muscle fiber. For one of the many experiments where attention was distinctly focused on the vector character of the wave process, it was possible to make a comparison with the theory, estimate the elasticity moduli, and obtain agreement with the angular dependence of the wave propagation velocity predicted by the theory.
Price elasticity of tobacco products among economic classes in India, 2011-2012.
Selvaraj, Sakthivel; Srivastava, Swati; Karan, Anup
2015-12-09
The objectives of this study are to: (1) examine the pattern of price elasticity of three major tobacco products (bidi, cigarette and leaf tobacco) by economic groups of population based on household monthly per capita consumption expenditure in India and (2) assess the effect of tax increases on tobacco consumption and revenue across expenditure groups. Data from the 2011-2012 nationally representative Consumer Expenditure Survey from 101,662 Indian households were used. Households which consumed any tobacco or alcohol product were retained in final models. The study draws theoretical frameworks from a model using the augmented utility function of consumer behaviour, with a two-stage two-equation system of unit values and budget shares. Primary outcome measures were price elasticity of demand for different tobacco products for three hierarchical economic groups of population and change in tax revenue due to changes in tax structure. We finally estimated price elasticity of demand for bidi, cigarette and leaf tobacco and effects of changes in their tax rates on demand for these tobacco products and tax revenue. Own price elasticities for bidi were highest in the poorest group (-0.4328) and lowest in the richest group (-0.0815). Cigarette own price elasticities were -0.832 in the poorest group and -0.2645 in the richest group. Leaf tobacco elasticities were highest in the poorest (-0.557) and middle (-0.4537) groups. Poorer group elasticities were the highest, indicating that poorer consumers are more price responsive. Elasticity estimates show positive distributional effects of uniform bidi and cigarette taxation on the poorest consumers, as their consumption is affected the most due to increases in taxation. Leaf tobacco also displayed moderate elasticities in poor and middle tertiles, suggesting that tax increases may result in a trade-off between consumption decline and revenue generation. A broad spectrum rise in tax rates across all products is critical for
Price elasticity of tobacco products among economic classes in India, 2011–2012
Selvaraj, Sakthivel; Srivastava, Swati; Karan, Anup
2015-01-01
Objectives The objectives of this study are to: (1) examine the pattern of price elasticity of three major tobacco products (bidi, cigarette and leaf tobacco) by economic groups of population based on household monthly per capita consumption expenditure in India and (2) assess the effect of tax increases on tobacco consumption and revenue across expenditure groups. Setting Data from the 2011–2012 nationally representative Consumer Expenditure Survey from 101 662 Indian households were used. Participants Households which consumed any tobacco or alcohol product were retained in final models. Primary outcome measures The study draws theoretical frameworks from a model using the augmented utility function of consumer behaviour, with a two-stage two-equation system of unit values and budget shares. Primary outcome measures were price elasticity of demand for different tobacco products for three hierarchical economic groups of population and change in tax revenue due to changes in tax structure. We finally estimated price elasticity of demand for bidi, cigarette and leaf tobacco and effects of changes in their tax rates on demand for these tobacco products and tax revenue. Results Own price elasticities for bidi were highest in the poorest group (−0.4328) and lowest in the richest group (−0.0815). Cigarette own price elasticities were −0.832 in the poorest group and −0.2645 in the richest group. Leaf tobacco elasticities were highest in the poorest (−0.557) and middle (−0.4537) groups. Conclusions Poorer group elasticities were the highest, indicating that poorer consumers are more price responsive. Elasticity estimates show positive distributional effects of uniform bidi and cigarette taxation on the poorest consumers, as their consumption is affected the most due to increases in taxation. Leaf tobacco also displayed moderate elasticities in poor and middle tertiles, suggesting that tax increases may result in a trade-off between consumption decline and
In Silico Measurement of Elastic Moduli of Nematic Liquid Crystals
Sidky, Hythem; de Pablo, Juan J.; Whitmer, Jonathan K.
2018-03-01
Experiments on confined droplets of the nematic liquid crystal 5CB have questioned long-established bounds imposed on the elastic free energy of nematic systems. This elasticity, which derives from molecular alignment within nematic systems, is quantified through a set of moduli which can be difficult to measure experimentally and, in some cases, can only be probed indirectly. This is particularly true of the surfacelike saddle-splay elastic term, for which the available experimental data indicate values on the cusp of stability, often with large uncertainties. Here, we demonstrate that all nematic elastic moduli, including the saddle-splay elastic constant k24, may be calculated directly from atomistic molecular simulations. Importantly, results obtained through in silico measurements of the 5CB elastic properties demonstrate unambiguously that saddle-splay elasticity alone is unable to describe the observed confined morphologies.
The elasticity of demand for gasoline in China
International Nuclear Information System (INIS)
Lin, C.-Y. Cynthia; Zeng, Jieyin
2013-01-01
This paper estimates the price and income elasticities of demand for gasoline in China. Our estimates of the intermediate-run price elasticity of gasoline demand range between −0.497 and −0.196, and our estimates of the intermediate-run income elasticity of gasoline demand range between 1.01 and 1.05. We also extend previous studies to estimate the vehicle miles traveled (VMT) elasticity and obtain a range from −0.882 to −0.579. - highlights: • The price elasticity of demand for gasoline in China is between −0.497 and −0.196. • The income elasticity of demand for gasoline in China is between 1.01 and 1.05. • The price elasticity of demand for VMT in China is between −0.882 and −0.579
Rubin, M. B.; Vorobiev, O.; Vitali, E.
2016-07-01
A large deformation thermomechanical model is developed for shock loading of a material that can exhibit elastic and inelastic anisotropy. Use is made of evolution equations for a triad of microstructural vectors mathbf{m}i (hbox {i}=1,2,3) which model elastic deformations and directions of anisotropy. Specific constitutive equations are presented for a material with orthotropic elastic response. The rate of inelasticity depends on an orthotropic yield function that can be used to model weak fault planes with failure in shear and which exhibits a smooth transition to isotropic response at high compression. Moreover, a robust, strongly objective numerical algorithm is proposed for both rate-independent and rate-dependent response. The predictions of the continuum model are examined by comparison with exact steady-state solutions. Also, the constitutive equations are used to obtain a simplified continuum model of jointed rock which is compared with high fidelity numerical solutions that model a persistent system of joints explicitly in the rock medium.
Growth-induced axial buckling of a slender elastic filament embedded in an isotropic elastic matrix
O'Keeffe, Stephen G.
2013-11-01
We investigate the problem of an axially loaded, isotropic, slender cylinder embedded in a soft, isotropic, outer elastic matrix. The cylinder undergoes uniform axial growth, whilst both the cylinder and the surrounding elastic matrix are confined between two rigid plates, so that this growth results in axial compression of the cylinder. We use two different modelling approaches to estimate the critical axial growth (that is, the amount of axial growth the cylinder is able to sustain before it buckles) and buckling wavelength of the cylinder. The first approach treats the filament and surrounding matrix as a single 3-dimensional elastic body undergoing large deformations, whilst the second approach treats the filament as a planar, elastic rod embedded in an infinite elastic foundation. By comparing the results of these two approaches, we obtain an estimate of the foundation modulus parameter, which characterises the strength of the foundation, in terms of the geometric and material properties of the system. © 2013 Elsevier Ltd. All rights reserved.
A comparison between different finite elements for elastic and aero-elastic analyses
Directory of Open Access Journals (Sweden)
Mohamed Mahran
2017-11-01
Full Text Available In the present paper, a comparison between five different shell finite elements, including the Linear Triangular Element, Linear Quadrilateral Element, Linear Quadrilateral Element based on deformation modes, 8-node Quadrilateral Element, and 9-Node Quadrilateral Element was presented. The shape functions and the element equations related to each element were presented through a detailed mathematical formulation. Additionally, the Jacobian matrix for the second order derivatives was simplified and used to derive each element’s strain-displacement matrix in bending. The elements were compared using carefully selected elastic and aero-elastic bench mark problems, regarding the number of elements needed to reach convergence, the resulting accuracy, and the needed computation time. The best suitable element for elastic free vibration analysis was found to be the Linear Quadrilateral Element with deformation-based shape functions, whereas the most suitable element for stress analysis was the 8-Node Quadrilateral Element, and the most suitable element for aero-elastic analysis was the 9-Node Quadrilateral Element. Although the linear triangular element was the last choice for modal and stress analyses, it establishes more accurate results in aero-elastic analyses, however, with much longer computation time. Additionally, the nine-node quadrilateral element was found to be the best choice for laminated composite plates analysis.
A comparison between different finite elements for elastic and aero-elastic analyses.
Mahran, Mohamed; ELsabbagh, Adel; Negm, Hani
2017-11-01
In the present paper, a comparison between five different shell finite elements, including the Linear Triangular Element, Linear Quadrilateral Element, Linear Quadrilateral Element based on deformation modes, 8-node Quadrilateral Element, and 9-Node Quadrilateral Element was presented. The shape functions and the element equations related to each element were presented through a detailed mathematical formulation. Additionally, the Jacobian matrix for the second order derivatives was simplified and used to derive each element's strain-displacement matrix in bending. The elements were compared using carefully selected elastic and aero-elastic bench mark problems, regarding the number of elements needed to reach convergence, the resulting accuracy, and the needed computation time. The best suitable element for elastic free vibration analysis was found to be the Linear Quadrilateral Element with deformation-based shape functions, whereas the most suitable element for stress analysis was the 8-Node Quadrilateral Element, and the most suitable element for aero-elastic analysis was the 9-Node Quadrilateral Element. Although the linear triangular element was the last choice for modal and stress analyses, it establishes more accurate results in aero-elastic analyses, however, with much longer computation time. Additionally, the nine-node quadrilateral element was found to be the best choice for laminated composite plates analysis.
DEFF Research Database (Denmark)
Gaihede, Michael Lyhne; Donghua, Liao; Gregersen, H.
2007-01-01
The quasi-static elastic properties of the tympanic membrane system can be described by the areal modulus of elasticity determined by a middle ear model. The response of the tympanic membrane to quasi-static pressure changes is determined by its elastic properties. Several clinical problems are r...... finite element analyses. In vivo estimates of Young's modulus in this study were a factor 2-3 smaller than previously found in vitro. No significant age-related differences were found in the elastic properties as expressed by the areal modulus.......The quasi-static elastic properties of the tympanic membrane system can be described by the areal modulus of elasticity determined by a middle ear model. The response of the tympanic membrane to quasi-static pressure changes is determined by its elastic properties. Several clinical problems...... are related to these, but studies are few and mostly not comparable. The elastic properties of membranes can be described by the areal modulus, and these may also be susceptible to age-related changes reflected by changes in the areal modulus. The areal modulus is determined by the relationship between...
Elastic and inelastic neutron cross-sections
International Nuclear Information System (INIS)
Wilmore, D.
1967-01-01
Computer programmes have been developed for the calculation of elastic and inelastic scattering of particles from nuclei. These programmes are written in the S2 dialect of FORTRAN, and run on an IBM-7030 computer. One programme calculates the shape elastic cross-section, the total cross-section and the absorption cross-section according to the optical model. The time taken in performing an optical calculation depends mainly upon the efficiency of the method used to perform the integration of the radial Schroedinger equation. A method is used which takes advantage of the absence of the first derivative term, and this gives a great improvement over more general methods. A least-squares fitting procedure is used which enables any number of parameters to be varied. The number of optical model calculations which are needed for a least-squares fit is less than with usual methods. Another programme will calculate compound nucleus reactions according to the Hauser-Feshbach theory, with or without the fluctuation correction. This programme will accept target and projectiles of any spin and parity, so that deuteron and alpha channels, as well as nucleon channels, may be taken into account. A third programme enables least-squares fits of elastic scattering to be done by taking into account the compound elastic contribution as calculated by the Hauser-Feshbach theory. The use of these programmes is illustrated by the analysis of the inelastic scattering of neutrons from 238 U. The elastic scattering cross-sections were used to obtain optical potentials by a least-squares fitting method. These potentials were subsequently used to predict the inelastic cross-sections to a large number of excited states. The results using the fluctuation correction are in good agreement with experiment. A further example of their use is shown in the analysis of neutron and proton scattering from light nuclei. Proton cross-sections were analysed to obtain potentials which were then used to
Elasticity of fluorite at high temperatures
Eke, J.; Tennakoon, S.; Mookherjee, M.
2017-12-01
Fluorite (CaF2) is a simple halide with cubic space group symmetry (Fm-3m) and is often used as an internal pressure calibrant in moderate high-pressure/high-temperature experiments [1]. In order to gain insight into the elastic behavior of fluorite, we have conducted Resonant Ultrasound Spectroscopy (RUS) on a single crystal of fluorite with rectangular parallelepiped geometry. Using single crystal X-ray diffraction, we aligned the edges of the rectangular parallelepiped with [-1 1 1], [-1 1 -2], and [-1 -1 0] crystallographic directions. We conducted the RUS measurements up to 620 K. RUS spectra are influenced by the geometry, density, and the full elastic moduli tensor of the material. In our high-temperature RUS experiments, the geometry and density were constrained using thermal expansion from previous studies [2]. We determined the elasticity by minimizing the difference between observed resonance and calculated Eigen frequency using Rayleigh-Ritz method [3]. We found that at room temperature, the single crystal elastic moduli for fluorite are 170, 49, and 33 GPa for C11, C12, and C44 respectively. At room temperatures, the aggregate bulk modulus (K) is 90 GPa and the shear modulus (G) is 43 GPa. We note that the elastic moduli and sound wave velocities decrease linearly as a function of temperature with dVP /dT and dVS /dT being -9.6 ×10-4 and -5.0 ×10-4 km/s/K respectively. Our high-temperature RUS results are in good agreement with previous studies on fluorite using both Ultrasonic methods and Brillouin scattering [4,5]. Acknowledgement: This study is supported by US NSF awards EAR-1639552 and EAR-1634422. References: [1] Speziale, S., Duffy, T. S. 2002, Phys. Chem. Miner., 29, 465-472; [2] Roberts, R. B., White, G. K., 1986, J. Phys. C: Solid State Phys., 19, 7167-7172. [3] Migliori, A., Maynard, J. D., 2005, Rev. Sci. Instrum., 76, 121301. [4] Catlow, C. R. A., Comins, J. D., Germano, F. A., Harley, R. T., Hayes, W., 1978, J. Phys. C Solid State Phys
Tip velocity tracking control for elastic manipulators
Sever, Manfred Dieter Martin
A unique approach to tip velocity control of an elastic robotic manipulator is presented. This method has potential application in teleoperation control and in applications where the trajectory is generated in real-time. Control is effected by reducing the tip velocity tracking error between the desired tip velocity and the measured tip velocity. Thus, in teleoperation, the concept of dead reckoning is used, so that while the manipulator's desired tip velocity is specified, the goal is for the tip to follow a path, leading toward a desired terminal position. This is done by concentrating the controller's effort on the manipulator tip while allowing the manipulator's links to deform., The controller utilizes a gain scheduling scheme to arrive at an appropriate feedback law. The control algorithm is implemented using a parallel-processing scheme on a multiprocessor system which consists of INMOS TransputersRTM . Experimental results are obtained using Radius, the Space Robotics Laboratory Facility at the University of Toronto Institute for Aerospace Studies. Radius was designed to serve specifically as a test-bed for the development and evaluation of control methods for elastic manipulators. For the present work Radius is configured as a two-link manipulator with both links structurally flexible. One of the trajectories used for the simulations and experiment is a square, which is quite difficult for an elastic manipulator to execute. This box trajectory is more demanding than trajectories typically executed by Canadarm and so link elasticity becomes an important consideration. The effect of elasticity is demonstrated using an independent joint PD controller. In simulation, excellent tip velocity tracking was achieved using the proposed controller. In the experiment, reasonable accuracy in following the desired tip path was attained, however, disturbances, mainly a result of unmodeled joint dynamics, caused degraded performance. The controller may be improved by
The everyday elasticity of compliance in a symptomless disease
DEFF Research Database (Denmark)
Felde, Lina Hoel
2011-01-01
Medically, compliance refers to the extent to which a patient's response to medical advice coincides with doctors' orders. Rather than this absolute standard, this article treats compliance as an institutionally available discourse continually figured in practice. The aim of this article...... is to describe people's everyday elasticity of compliance in shifting contexts in everyday life. The empirical material presented, based on interviews with people with elevated cholesterol, suggests that people with symptomless diseases can be perceived to be living in a virtual 'temporal limbo', living 'here...... and now' in the present from one episode to the next. Present-bound conditions create, from moment to moment, a temporal limbo that challenges and conditions the participants' constructions of compliance. Using three contexts as examples, this article empirically demonstrates how people with a symptomless...
Directory of Open Access Journals (Sweden)
Woo-Young Jung
2013-01-01
Full Text Available Based on a nonlocal elasticity theory, a model for sigmoid functionally graded material (S-FGM nanoscale plate with first-order shear deformation is studied. The material properties of S-FGM nanoscale plate are assumed to vary according to sigmoid function (two power law distribution of the volume fraction of the constituents. Elastic theory of the sigmoid FGM (S-FGM nanoscale plate is reformulated using the nonlocal differential constitutive relations of Eringen and first-order shear deformation theory. The equations of motion of the nonlocal theories are derived using Hamilton’s principle. The nonlocal elasticity of Eringen has the ability to capture the small scale effect. The solutions of S-FGM nanoscale plate are presented to illustrate the effect of nonlocal theory on bending and vibration response of the S-FGM nanoscale plates. The effects of nonlocal parameters, power law index, aspect ratio, elastic modulus ratio, side-to-thickness ratio, and loading type on bending and vibration response are investigated. Results of the present theory show a good agreement with the reference solutions. These results can be used for evaluating the reliability of size-dependent S-FGM nanoscale plate models developed in the future.
Singal, Kalpesh; Rajamani, Rajesh; Ahmadi, Mahdi; Serdar Sezen, A; Bechtold, Joan E
2015-02-01
This paper presents a novel Hall-effect-based magnetic sensor for handheld measurement of either elasticity or tension in soft tissues. A theoretical model is developed for the mechanical interaction of the sensor with the tissue, and conditions are established under which the separate effects of tension or elasticity can be measured. A model of the magnetic field within the sensor is developed and a technique to estimate the sensor response in the presence of multiple magnets is established. This paper then provides analytical sensor responses and compares them with experimental results obtained on synthetic materials. It is found that the sensor can measure tension values upto 100 N with a resolution of 10 N in handheld operation and elasticity of upto 0.87 MPa with a resolution of 0.02 MPa. Significant experimental characterization and statistical analysis of sensor repeatability is performed. The viability of this sensor to make tension and elasticity measurements with biological tissues is then demonstrated using turkey tendons and fresh swine tissues.
Transient Vibrations of an Elastic Cylinder Inserted in the Elastic Medium
Directory of Open Access Journals (Sweden)
Sulym Heorgij
2016-06-01
Full Text Available Using method of Laguerre polynomials we have obtained the solution of the dynamic problem of the theory of elasticity for elastic cylinder inserted into massive body modeled as a space. The source of non-stationary processes in composite is high intensity force load of the inner surface of the cylinder. On the surface separation of materials of space and cylinder the conditions of ideal mechanical contact are satisfied. The solution is obtained as series of Laguerre polynomials, which coefficients are found from recurrent relations. The results of numerical analysis of transient stress-strain state in elastic space with cylindrical insertion might be used for the technological process of hydraulic fracturing during shale gas extraction.
Vibration of an Elastic Circular Plate on an Elastic Half Space
DEFF Research Database (Denmark)
Krenk, Steen; Schmidt, H.
1981-01-01
, but the method is easily extended to more general plate theories as well as nonsymmetric oscillations. The results include displacement and phase curves for rigid disks, power input for elastic plates, and typical stress and deformation distributions at selected phase angles. The results show considerable......The axisymmetric problem of a vibrating elastic plate on an elastic half space is solved by a direct method, in which the contact stresses and the normal displacements of the plate are taken as the unknown functions. First, the influence functions that give the displacements in terms...... of the stresses are determined for the half space and the plate. Displacement continuity then takes the form of an integral equation. Due to the half space the kernel is weakly singular, and a special solution technique that accounts for this is employed. The solution implies a direct matrix relation between...
Meta-Analysis of the Oil Price Elasticity of the GDP for Policy Analysis: Documentation
Energy Technology Data Exchange (ETDEWEB)
Leiby, Paul Newsome [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bowman, David Charles [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Oladosu, Gbadebo A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Uria Martinez, Rocio [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Johnson, Megan M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2017-08-01
Given the important role of oil in economic activities, policy makers are interested in estimates of the potential damage to the economy from oil price shocks, particularly during periods of rapid and large increases that accompany severe shocks. Such estimates are needed to quantify the economic costs of oil price shocks, and to evaluate the potential benefits of alternative policy responses. Although research on the economic impacts of oil price shocks is extensive and has generally found that large increases in oil prices exert negative economic impacts, the range of estimates, summarized by the oil price elasticity of the GDP or other aggregate measure of economic activity, is very wide. There are also conditions under which the relationship between the oil price and the economy could be positive. The range of estimates of the oil price elasticity of the GDP for the United States is typified by averages from the studies of Hamilton (2005, 2012) and Kilian and Vigfusson (2014), in which the implied elasticities were -0.014 to - 0.069 and +0.004 to -0.052, respectively. We employ a meta-regression approach to systematically summarize available estimates of the oil price elasticity of the GDP for oil importing economies, and examine the role of key factors. The resulting regression model was used to estimate the oil price elasticity of the GDP for the United States. Based on this we estimate the mean elasticity for the United States at -0.0238, with a 68% confidence interval of -0.0075 to -0.0402, four quarters after a shock.
Elastic waves and transition to elastic turbulence in a two-dimensional viscoelastic Kolmogorov flow
Berti, S.; Boffetta, G.
2010-09-01
We investigate the dynamics of the two-dimensional periodic Kolmogorov flow of a viscoelastic fluid, described by the Oldroyd-B model, by means of direct numerical simulations. Above a critical Weissenberg number the flow displays a transition from stationary to randomly fluctuating states, via periodic ones. The increasing complexity of the flow in both time and space at progressively higher values of elasticity accompanies the establishment of mixing features. The peculiar dynamical behavior observed in the simulations is found to be related to the appearance of filamental propagating patterns, which develop even in the limit of very small inertial nonlinearities, thanks to the feedback of elastic forces on the flow.
Mechanics of Fluctuating Elastic Plates and Fiber Networks
Liang, Xiaojun
Lipid membranes and fiber networks in biological systems perform important mechanical functions at the cellular and tissue levels. In this thesis I delve into two detailed problems--thermal fluctuation of membranes and non-linear compression response of fiber networks. Typically, membrane fluctuations are analysed by decomposing into normal modes or by molecular simulations. In the first part of my thesis, I propose a new semi-analytic method to calculate the partition function of a membrane. The membrane is viewed as a fluctuating von Karman plate and discretized into triangular elements. Its energy is expressed as a function of nodal displacements, and then the partition function and co-variance matrix are computed using Gaussian integrals. I recover well-known results for the dependence of the projected area of a lipid bilayer membrane on the applied tension, and recent simulation results on the ependence of membrane free energy on geometry, spontaneous curvature and tension. As new applications I use this technique to study a membrane with heterogeneity and different boundary conditions. I also use this technique to study solid membranes by taking account of the non-linear coupling of in-plane strains with out-of-plane deflections using a penalty energy, and apply it to graphene, an ultra-thin two-dimensional solid. The scaling of graphene fluctuations with membrane size is recovered. I am able to capture the dependence of the thermal expansion coefficient of graphene on temperature. Next, I study curvature mediated interactions between inclusions in membranes. I assume the inclusions to be rigid, and show that the elastic and entropic forces between them can compete to yield a local maximum in the free energy if the membrane bending modulus is small. If the spacing between the inclusions is less than this local maximum then the attractive entropic forces dominate and the separation between the inclusions will be determined by short range interactions; if the
Elasticity of a Filament with Kinks
Razbin, Mohammadhosein
2017-12-01
Using the wormlike chain model, we analytically study the elasticity of a filament with kinks. We calculate the position probability density function and the force constant of a kinked filament with a general kink angle. Then, using the mathematical induction, we obtain the positional-orientational probability density function of a filament with regular kinks. For this filament, we compute the force constant in two different directions. In longitudinal direction of the filament, the force constant is proportional to the inverse of the number of the segments, i.e., 1 / m, while in transverse direction, it is proportional to 1/m^3.
Martensitic textures: Multiscale consequences of elastic compatibility
International Nuclear Information System (INIS)
Shenoy, S.R.; Lookman, T.; Saxena, A.; Bishop, A.R.
2001-03-01
We show that a free energy entirely in the order-parameter strain variable(s), rather than the displacement field, provides a unified understanding of martensitic textures. We use compatibility equations, linking the strain tensor components in the bulk and at interfaces, that induce anisotropic order-parameter strain interactions. These two long-range bulk/interface potentials, together with local compositional fluctuations, drive the formation of global elastic textures. Relaxational simulations show the spontaneous formation (and evolution under stress/temperature quenches) of equal width parallel twins, branched twins, and tweed, including characteristic scaling of twin width with twin length. (author)
Local Tensor Radiation Conditions For Elastic Waves
DEFF Research Database (Denmark)
Krenk, S.; Kirkegaard, Poul Henning
2001-01-01
A local boundary condition is formulated, representing radiation of elastic waves from an arbitrary point source. The boundary condition takes the form of a tensor relation between the stress at a point on an arbitrarily oriented section and the velocity and displacement vectors at the point....... The tensor relation generalizes the traditional normal incidence impedance condition by accounting for the angle between wave propagation and the surface normal and by including a generalized stiffness term due to spreading of the waves. The effectiveness of the local tensor radiation condition...
Elasticity of semiflexible polymers in two dimensions
Prasad, Ashok; Hori, Yuko; Kondev, Jané
2005-10-01
We study theoretically the entropic elasticity of a semiflexible polymer, such as DNA, confined to two dimensions. Using the worm-like-chain model we obtain an exact analytical expression for the partition function of the polymer pulled at one end with a constant force. The force-extension relation for the polymer is computed in the long chain limit in terms of Mathieu characteristic functions. We also present applications to the interaction between a semiflexible polymer and a nematic field, and derive the nematic order parameter and average extension of the polymer in a strong field.
Molecular sieves analysis by elastic recoil detection
International Nuclear Information System (INIS)
Salah, H.; Azzouz, A.
1992-01-01
The opportunity of water determination in zeolites via hydrogen detection using the elastic recoil detection analysis (ERDA) was investigated. The radiation effect upon the desorption rate of hydrogen in miscellaneous types of zeolites, e.g. Y-Faujasite, ZSM-5, SK, etc. and in a natural clay, e.g. an Algerian bentonite was discussed. Quantitative measurements were carried out in order to determine the amount and distribution shape of hydrogen in each material. Various explanations dealing with hydration and constitution water in such a crystalline framework were proposed. The experimental results are in a good agreement with the corresponding theoretical values
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
International Nuclear Information System (INIS)
Gajewski, W.; Swiecki, M.
1975-01-01
This paper is devoted to the description of the present status of our knowledge about π meson elastic form factor. In the first section there is given a definition of the form factor on the basis of electromagnetic interactions, and its extension to weak and strong interactions. Next, there are reviewed theoretical models, which on the assumption of analyticity predict features of π meson form factor. In the last sections the results of experimental investigaton of π meson form factor are described with the stress on the results of the recent experiment made on Serpukhov accelerator in order to measure the π meson electromagnetic radius. (author)
Elastic lattice in an incommensurate background
International Nuclear Information System (INIS)
Dickman, R.; Chudnovsky, E.M.
1995-01-01
We study a harmonic triangular lattice, which relaxes in the presence of an incommensurate short-wavelength potential. Monte Carlo simulations reveal that the elastic lattice exhibits only short-ranged translational correlations, despite the absence of defects in either lattice. Extended orientational order, however, persists in the presence of the background. Translational correlation lengths exhibit approximate power-law dependence upon cooling rate and background strength. Our results may be relevant to Wigner crystals, atomic monolayers on crystals surfaces, and flux-line and magnetic bubble lattices
Elastic lattice in a random potential
Energy Technology Data Exchange (ETDEWEB)
Chudnovsky, E.M.; Dickman, R. [Department of Physics and Astronomy, Lehman College, CUNY, Bedford Park Boulevard West, Bronx, New York 10468-1589 (United States)
1998-02-01
Using Monte Carlo simulations, we study the properties of an elastic triangular lattice subject to a random background potential. As the cooling rate is reduced, we observe a rather sudden crossover between two different glass phases, with exponential decay of translational correlations, the other with power-law decay. Contrary to predictions derived for continuum models, no evidence of a crossover in the mean-square displacement B(r) from the quadratic growth at small r to the logarithmic growth at large r is found. {copyright} {ital 1998} {ital The American Physical Society}
Elastic lattice in a random potential
International Nuclear Information System (INIS)
Chudnovsky, E.M.; Dickman, R.
1998-01-01
Using Monte Carlo simulations, we study the properties of an elastic triangular lattice subject to a random background potential. As the cooling rate is reduced, we observe a rather sudden crossover between two different glass phases, with exponential decay of translational correlations, the other with power-law decay. Contrary to predictions derived for continuum models, no evidence of a crossover in the mean-square displacement B(r) from the quadratic growth at small r to the logarithmic growth at large r is found. copyright 1998 The American Physical Society
Marginal elasticity of periodic triangulated origami
Chen, Bryan; Sussman, Dan; Lubensky, Tom; Santangelo, Chris
Origami, the classical art of folding paper, has inspired much recent work on assembling complex 3D structures from planar sheets. Origami, and more generally hinged structures with rigid panels, where all faces are triangles have special properties due to having a bulk balance of mechanical degrees of freedom and constraints. We study two families of periodic triangulated origami structures, one based on the Miura ori and one based on a kagome-like pattern due to Ron Resch. We point out the consequences of the balance of degrees of freedom and constraints for these ''metamaterial plates'' and show how the elasticity can be tuned by changing the unit cell geometry.
2013-01-01
Valitsus saatis riigikokku eelnõu, mille kohaselt võib Eesti saata Euroopa Liidu väljaõppemissioonile Malis kuni 10 kaitseväelast. Kaitsevägi panustaks staabiohvitseridega, kelle peamiseks ülesandeks on osaleda Mali üksustele erinevate riikide poolt läbiviidava väljaõppe planeerimise ja nõustamise protsessides ning väljaõppemeeskonnaga, kelle ülesandeks on viia läbi Mali üksustele mitmesugust sõjalist väljaõpet
Ugarte, M; Hussain, A A; Marshall, J
2006-05-01
To investigate the mechanical properties (stress-strain relation, elasticity, hysteresis, response to stress spikes and drops) of isolated human Bruch's membrane-choroid, as well as the effect of ageing and aged related macular degeneration (AMD). 13 Bruch's membrane-choroid complexes were obtained from human donors (21-97 years). Two samples (aged 85 and 95) showed signs of AMD including large, soft drusen, choroidal neovascularisation, and/or disciform scars. Various hydrostatic pressures (stress) were applied to the choroidal surface of mid-peripheral samples mounted in a modified open Ussing chamber. Linear scans of the tissue were recorded by optical coherence tomography (OCT) and the pressure induced deformation (strain), elasticity, hysteresis, and response to pressure spikes and drops measured. The elasticity of human Bruch's membrane-choroid complex decreased linearly with ageing (precoil capacity of Bruch's membrane-choroid was not affected by ageing. The response to pressure spikes/drops was similar in age matched normal and AMD eyes. The results suggest that although the aged induced decrease in Bruch's membrane elasticity may contribute to breaks in this membrane in AMD leading to neovascularisation this is not sufficient. The presence of other factors is required for its development. The elasticity of Bruch's membrane-choroid complex decreases with age while recoil capacity does not. The decrease was not exaggerated in AMD.
Grebenstein, Patricia E.; Burroughs, Danielle; Roiko, Samuel A.; Pentel, Paul R.; LeSage, Mark G.
2015-01-01
Background The FDA is considering reducing the nicotine content in tobacco products as a population-based strategy to reduce tobacco addiction. Research is needed to determine the threshold level of nicotine needed to maintain smoking and the extent of compensatory smoking that could occur during nicotine reduction. Sources of variability in these measures across sub-populations also need to be identified so that policies can take into account the risks and benefits of nicotine reduction in vulnerable populations. Methods The present study examined these issues in a rodent nicotine self- administration model of nicotine reduction policy to characterize individual differences in nicotine reinforcement thresholds, degree of compensation, and elasticity of demand during progressive reduction of the unit nicotine dose. The ability of individual differences in baseline nicotine intake and nicotine pharmacokinetics to predict responses to dose reduction was also examined. Results Considerable variability in the reinforcement threshold, compensation, and elasticity of demand was evident. High baseline nicotine intake was not correlated with the reinforcement threshold, but predicted less compensation and less elastic demand. Higher nicotine clearance predicted low reinforcement thresholds, greater compensation, and less elastic demand. Less elastic demand also predicted lower reinforcement thresholds. Conclusions These findings suggest that baseline nicotine intake, nicotine clearance, and the essential value of nicotine (i.e. elasticity of demand) moderate the effects of progressive nicotine reduction in rats and warrant further study in humans. They also suggest that smokers with fast nicotine metabolism may be more vulnerable to the risks of nicotine reduction. PMID:25891231
Pricing perpetual American options under multiscale stochastic elasticity of variance
International Nuclear Information System (INIS)
Yoon, Ji-Hun
2015-01-01
Highlights: • We study the effects of the stochastic elasticity of variance on perpetual American option. • Our SEV model consists of a fast mean-reverting factor and a slow mean-revering factor. • A slow scale factor has a very significant impact on the option price. • We analyze option price structures through the market prices of elasticity risk. - Abstract: This paper studies pricing the perpetual American options under a constant elasticity of variance type of underlying asset price model where the constant elasticity is replaced by a fast mean-reverting Ornstein–Ulenbeck process and a slowly varying diffusion process. By using a multiscale asymptotic analysis, we find the impact of the stochastic elasticity of variance on the option prices and the optimal exercise prices with respect to model parameters. Our results enhance the existing option price structures in view of flexibility and applicability through the market prices of elasticity risk
Token-Aware Completion Functions for Elastic Processor Verification
Directory of Open Access Journals (Sweden)
Sudarshan K. Srinivasan
2009-01-01
Full Text Available We develop a formal verification procedure to check that elastic pipelined processor designs correctly implement their instruction set architecture (ISA specifications. The notion of correctness we use is based on refinement. Refinement proofs are based on refinement maps, which—in the context of this problem—are functions that map elastic processor states to states of the ISA specification model. Data flow in elastic architectures is complicated by the insertion of any number of buffers in any place in the design, making it hard to construct refinement maps for elastic systems in a systematic manner. We introduce token-aware completion functions, which incorporate a mechanism to track the flow of data in elastic pipelines, as a highly automated and systematic approach to construct refinement maps. We demonstrate the efficiency of the overall verification procedure based on token-aware completion functions using six elastic pipelined processor models based on the DLX architecture.
Irrigation water demand: A meta-analysis of price elasticities
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.
Remarks on stability of magneto-elastic shocks
Directory of Open Access Journals (Sweden)
Włodzimierz Domański
2015-12-01
Full Text Available The problem of stability of plane shock waves for a model of perfect magnetoelasticityis investigated. Important mathematical properties, like loss of strict hyperbolicityand loss of genuine nonlinearity, and their consequences for the stability ofmagneto-elastic shocks are discussed. It is shown that some of these shocks do not satisfyclassical Lax stability conditions. Both compressible and incompressible models ofmagneto-elasticity are discussed.[b]Keywords[/b]: perfect magneto-elasticity, shock waves, stability conditions
On Finite Element Computations of Contact Problems in Micropolar Elasticity
Eremeyev, Victor A.; Skrzat, Andrzej; Stachowicz, Feliks
2016-01-01
Within the linear micropolar elasticity we discuss the development of new finite element and its implementation in commercial software. Here we implement the developed 8-node hybrid isoparametric element into ABAQUS and perform solutions of contact problems. We consider the contact of polymeric stamp modelled within the micropolar elasticity with an elastic substrate. The peculiarities of modelling of contact problems with a user defined finite element in ABAQUS are discussed. The provided co...
Elastic constants and internal friction of fiber-reinforced composites
International Nuclear Information System (INIS)
Ledbetter, H.M.
1982-01-01
We review recent experimental studies at NBS on the anisotropic elastic constants and internal friction of fiber-reinforced composites. Materials that were studied include: boron-aluminum, boron-epoxy, graphite-epoxy, glass-epoxy, and aramid-epoxy. In all cases, elastic-constant direction dependence could be described by relationships developed for single crystals of homogeneous materials. Elastic stiffness and internal friction were found to vary inversely
Consumer Brand Choice: Individual and Group Analyses of Demand Elasticity
Oliveira-Castro, Jorge M; Foxall, Gordon R; Schrezenmaier, Teresa C
2006-01-01
Following the behavior-analytic tradition of analyzing individual behavior, the present research investigated demand elasticity of individual consumers purchasing supermarket products, and compared individual and group analyses of elasticity. Panel data from 80 UK consumers purchasing 9 product categories (i.e., baked beans, biscuits, breakfast cereals, butter, cheese, fruit juice, instant coffee, margarine and tea) during a 16-week period were used. Elasticity coefficients were calculated fo...
Analysis of flexible layered shallow shells on elastic foundation
Stupishin, L.; Kolesnikov, A.; Tolmacheva, T.
2017-05-01
This paper contains numerical analysis of a layered geometric nonlinear flexible shallow shell based on an elastic foundation. Rise of arch in the center of the shell, width, length and type of support are given. The design variable is taken to be the thickness of the shallow shell, the form of the middle surface forming and the characteristic of elastic foundations. Critical force coefficient and stress of shells are calculated by Bubnov-Galerkin. Stress, characteristic of elastic foundations - thickness dependence are presented.
Abnormal linear elasticity in polycrystalline phosphorene.
Liu, Ning; Pidaparti, Ramana; Wang, Xianqiao
2018-03-14
Phosphorene, also known as monolayer black phosphorous, has been widely used in electronic devices due to its superior electrical properties. However, its relatively low Young's modulus, low fracture strength and susceptibility to structural failure has limited its application in nano devices. Therefore, in order to design more mechanically reliable devices that utilize phosphorene, it is necessary to explore the mechanical properties of polycrystalline phosphorene. Here molecular dynamics simulations are performed to study the effect of grain size on the mechanical performance of polycrystalline phosphorene sheets. Unlike other two-dimension materials with planar crystalline structure, polycrystalline phosphorene sheets are almost linear elastic, resulting from its high bending stiffness due to its intrinsic buckled crystalline structure. Moreover, the percentage increase of stiffness for polycrystalline phosphorene associated with the increase of grain size from 2 to 12 nm is only 15.9%, much smaller than that for other two-dimension materials with planar crystalline structure. This insensitivity could be attributed to the small difference between the elastic modulus of the crystalline phase and amorphous phase of polycrystalline phosphorene. In addition, the strength deduction obeys well a logarithm relation of grain size, well explained by the dislocation pile-up theory analogous to that of polycrystalline graphene. Overall, our findings provide a better understanding of mechanical properties of polycrystalline phosphorene and establish a guideline for manufacturing and designing novel phosphorene-based nano devices and nano structures.
Elastic models application for thorax image registration
International Nuclear Information System (INIS)
Correa Prado, Lorena S; Diaz, E Andres Valdez; Romo, Raul
2007-01-01
This work consist of the implementation and evaluation of elastic alignment algorithms of biomedical images, which were taken at thorax level and simulated with the 4D NCAT digital phantom. Radial Basis Functions spatial transformations (RBF), a kind of spline, which allows carrying out not only global rigid deformations but also local elastic ones were applied, using a point-matching method. The applied functions were: Thin Plate Spline (TPS), Multiquadric (MQ) Gaussian and B-Spline, which were evaluated and compared by means of calculating the Target Registration Error and similarity measures between the registered images (the squared sum of intensity differences (SSD) and correlation coefficient (CC)). In order to value the user incurred error in the point-matching and segmentation tasks, two algorithms were also designed that calculate the Fiduciary Localization Error. TPS and MQ were demonstrated to have better performance than the others. It was proved RBF represent an adequate model for approximating the thorax deformable behaviour. Validation algorithms showed the user error was not significant