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1
Hassan, S. F. « O(d,d;R) deformations of complex structures and extended worldsheet supersymmetry ». Nuclear Physics B 454, no 1-2 (novembre 1995) : 86–102. http://dx.doi.org/10.1016/0550-3213(95)00384-5.
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BYTSENKO, A. A. « BRST-INVARIANT DEFORMATIONS OF GEOMETRIC STRUCTURES IN SIGMA MODELS ». International Journal of Modern Physics A 26, no 22 (10 septembre 2011) : 3769–80. http://dx.doi.org/10.1142/s0217751x11054231.
Texte intégralRésumé :
The closed string correlators can be constructed from the open ones using topological string theories as a model. The space of physical closed string states is isomorphic to the Hochschild cohomology of (A,Q) (operator Q of ghost number one), - this statement has been verified by means of computation of the Hochschild cohomology of the category of D -branes. We study a Lie algebra of formal vector fields Wn with its application to the perturbative deformed holomorphic symplectic structure in the A -model, and a Calabi-Yau manifold with boundaries in the B -model. We show that equivalent classes of deformations are describing by a Hochschild cohomology theory of the DG-algebra, [Formula: see text], [Formula: see text], which is defined to be the cohomology of (-1)nQ+d Hoch . Here [Formula: see text] is the initial non-deformed BRST operator while ∂ deform is the deformed part whose algebra is a Lie algebra of linear vector fields gl n. We assume that if in the theory exists a single D -brane then all the information associated with deformations is encoded in an associative algebra A equipped with a differential [Formula: see text]. In addition equivalence classes of deformations of these data are described by a Hochschild cohomology of (A,Q), an important geometric invariant of the (anti)holomorphic structure on X. We also discuss the identification of the harmonic structure (HT•(X); HΩ•(X)) of affine space X and the group [Formula: see text] (the HKR isomorphism), and bulk-boundary deformation pairing.
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BYTSENKO, A. A. « BRST-INVARIANT DEFORMATIONS OF GEOMETRIC STRUCTURES IN SIGMA MODELS ». International Journal of Modern Physics : Conference Series 03 (janvier 2011) : 75–86. http://dx.doi.org/10.1142/s2010194511001164.
Texte intégralRésumé :
The closed string correlators can be constructed from the open ones using topological string theories as a model. The space of physical closed string states is isomorphic to the Hochschild cohomology of (A, Q) (operator Q of ghost number one), - this statement has been verified by means of computation of the Hochschild cohomology of the category of D-branes. We study a Lie algebra of formal vector fields Wn with its application to the perturbative deformed holomorphic symplectic structure in the A-model, and a Calabi-Yau manifold with boundaries in the B-model. We show that equivalent classes of deformations are describing by a Hochschild cohomology theory of the DG-algebra [Formula: see text], [Formula: see text], which is defined to be the cohomology of (-1)n Q + d Hoch . Here [Formula: see text] is the initial non-deformed BRST operator while ∂deform is the deformed part whose algebra is a Lie algebra of linear vector fields gl n. We assume that if in the theory exists a single D-brane then all the information associated with deformations is encoded in an associative algebra A equipped with a differential [Formula: see text]. In addition equivalence classes of deformations of these data are described by a Hochschild cohomology of (A, Q), an important geometric invariant of the (anti)holomorphic structure on X. We also discuss the identification of the harmonic structure (HT•(X); HΩ•(X)) of affine space X and the group [Formula: see text] (the HKR isomorphism), and bulk-boundary deformation pairing.
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Cingolani, Matteo, Gioia Fusaro, Giulia Fratoni et Massimo Garai. « Influence of thermal deformations on sound absorption of three-dimensional printed metamaterials ». Journal of the Acoustical Society of America 151, no 6 (juin 2022) : 3770–79. http://dx.doi.org/10.1121/10.0011552.
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Acoustic metamaterials (AMMs) are designed with complex geometrical shapes to obtain unconventional sound-absorbing performances. As additive manufacturing is particularly suited to print complex structures in a more straightforward and controllable way, AMMs often exploit three-dimensional (3-D) printing techniques. However, when exposed to different temperature conditions, such structures can be affected by geometrical deformations, especially when they are polymer-based. This can cause a mismatch between the experimental data and the expected theoretical performance; therefore, it is important to take thermal effects into account. The present paper investigates the influence of thermal deformations on the sound absorption of three geometries: a coplanar spiral tube, a system with double coiled resonators, and a neck-embedded resonator. Measurements were performed on each 3-D printed specimen in the impedance tube after the samples had been placed in a climate chamber to modify the temperature settings (T = 10–50 °C). Numerical models, validated on the measurements, were employed to quantify the geometrical deformation of AMM structures through a multiphysics approach, highlighting the effects of thermal stress on the acoustic behavior. The main outcomes prove that the frequency shifts of sound absorption peaks depend on temperature configurations and follow exponential regressions, in accordance with previous literature on polymeric materials.
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Eriksen, Eivind. « Computing Noncommutative Deformations of Presheaves and Sheaves of Modules ». Canadian Journal of Mathematics 62, no 3 (1 juin 2010) : 520–42. http://dx.doi.org/10.4153/cjm-2010-015-6.
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AbstractWe describe a noncommutative deformation theory for presheaves and sheaves of modules that generalizes the commutative deformation theory of these global algebraic structures and the noncommutative deformation theory of modules over algebras due to Laudal.In the first part of the paper, we describe a noncommutative deformation functor for presheaves of modules on a small category and an obstruction theory for this functor in terms of global Hochschild cohomology. An important feature of this obstruction theory is that it can be computed in concrete terms in many interesting cases.In the last part of the paper, we describe a noncommutative deformation functor for quasi-coherent sheaves of modules on a ringed space (X,𝒜). We show that for any good A-affine open cover U of X, the forgetful functor QCoh𝒜 → PreSh(U,𝒜) induces an isomorphism of noncommutative deformation functors.Applications. We consider noncommutative deformations of quasi-coherent 𝒜-modules on X when (X,𝒜) = (X,𝒪X) is a scheme or (X,𝒜) = (X,𝒟) is a D-scheme in the sense of Beilinson and Bernstein. In these cases, we may use any open affine cover of X closed under finite intersections to compute noncommutative deformations in concrete terms using presheaf methods. We compute the noncommutative deformations of the left 𝒟X-module 𝒟X when X is an elliptic curve as an example.
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KAPUSTIN, ANTON. « TOPOLOGICAL STRINGS ON NONCOMMUTATIVE MANIFOLDS ». International Journal of Geometric Methods in Modern Physics 01, no 01n02 (avril 2004) : 49–81. http://dx.doi.org/10.1142/s0219887804000034.
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We identify a deformation of the N=2 supersymmetric sigma model on a Calabi–Yau manifold X which has the same effect on B-branes as a noncommutative deformation of X. We show that for hyperkähler X such deformations allow one to interpolate continuously between the A-model and the B-model. For generic values of the noncommutativity and the B-field, properties of the topologically twisted sigma-models can be described in terms of generalized complex structures introduced by N. Hitchin. For example, we show that the path integral for the deformed sigma-model is localized on generalized holomorphic maps, whereas for the A-model and the B-model it is localized on holomorphic and constant maps, respectively. The geometry of topological D-branes is also best described using generalized complex structures. We also derive a constraint on the Chern character of topological D-branes, which includes A-branes and B-branes as special cases.
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BYTSENKO, A. A., M. CHAICHIAN, A. TUREANU et F. L. WILLIAMS. « BRST-INVARIANT DEFORMATIONS OF GEOMETRIC STRUCTURES IN TOPOLOGICAL FIELD THEORIES ». International Journal of Modern Physics A 28, no 16 (28 juin 2013) : 1350069. http://dx.doi.org/10.1142/s0217751x13500693.
Texte intégralRésumé :
We study a Lie algebra of formal vector fields Wn with its application to the perturbative deformed holomorphic symplectic structure in the A-model, and a Calabi–Yau manifold with boundaries in the B-model. A relevant concept in the vertex operator algebra and the BRST cohomology is that of the elliptic genera (the one-loop string partition function). We show that the elliptic genera can be written in terms of spectral functions of the hyperbolic three-geometry (which inherits the cohomology structure of BRST-like operator). We show that equivalence classes of deformations are described by a Hochschild cohomology theory of the DG-algebra [Formula: see text], which is defined to be the cohomology of (-1)n Q + d Hoch . Here, [Formula: see text] is the initial nondeformed BRST operator while ∂ deform is the deformed part whose algebra is a Lie algebra of linear vector fields gl n. We discuss the identification of the harmonic structure (HT•(X);HΩ•(X)) of affine space X and the group [Formula: see text] (the HKR isomorphism), and bulk-boundary deformation pairing.
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Yuge, K., N. Iwai et N. Kikuchi. « Optimization of 2-D structures subjected to nonlinear deformations using the homogenization method ». Structural Optimization 17, no 4 (décembre 1999) : 286–99. http://dx.doi.org/10.1007/bf01207005.
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Correa, Francisco, et Olaf Lechtenfeld. « Algebraic integrability of PT -deformed Calogero models ». Journal of Physics : Conference Series 2038, no 1 (1 octobre 2021) : 012007. http://dx.doi.org/10.1088/1742-6596/2038/1/012007.
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Abstract We review some recents developments of the algebraic structures and spectral properties of non-Hermitian deformations of Calogero models. The behavior of such extensions is illustrated by the A 2 trigonometric and the D 3 angular Calogero models. Features like intertwining operators and conserved charges are discussed in terms of Dunkl operators. Hidden symmetries coming from the so-called algebraic integrability for integral values of the coupling are addressed together with a physical regularization of their action on the states by virtue of a PT -symmetry deformation.
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Vilfayeau, Jerome, David Crépin, François Boussu, Damien Soulat et Philippe Boisse. « Numerical Modelling of the Weaving Process for Textile Composite ». Key Engineering Materials 554-557 (juin 2013) : 472–77. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.472.
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Due to advancements made in 3D weaving process [1] and, in order to develop 3D textile structure as reinforcement of composite material for aeronautic application, a good prediction of the geometry and the mechanical properties of the 3D woven unit cell is required. Due to the complexity of these textile architectures, realistic geometric representations [2] of fabrics are often difficult to obtain especially for 3D woven fabrics, but these descriptions are necessary to define meshes for finite element computation [3]. At present, existing tools which model and define, early at a mesoscopic scale [4], the architecture of 3D fabrics don’t take into account the influence of the manufacturing process on the shape modification of the textile structure. Some numerical model exists for the braiding process [5] and the knitting process [6], but not yet for the weaving process. During the manufacturing process, fibres are subjected to significant deformations due to loads from the component of the loom or from the friction with the others fibres. These significant deformations lead to mechanical strength losses of the fabric. A numerical model of the different steps of the weaving process could predict these significant deformations and their influence on the geometry of the textile architecture. Thus, the objective of the NUMTISS project is to develop a numerical model of the deformation of the yarn during the weaving process. For the numerical modelling of the weaving process developed in finite element method, we considered all loom elements like rigid solid, and we will make the assumption that yarns are transverse isotropic elastic materials. Simulations of the process for a plain weave, a twill 2-2 and a satin 8 fabric have already been performed, as well as the simulation of orthogonal warp interlock structures. Then, to understand the kinematic motions of weaving process, the tracking of some strategic elements on the industrial weaving loom (reed, heddles, rapier,..) have been carried out. The tracking obtained from the video of the high speed camera will help us to define the numerical model of the weaving kinematic closer to reality. Correlations between numerical results and specific structures in glass fibres produced on the loom will be presented. The influence of each step of the manufacturing process on the characteristics of the textile structure could be analyzed [1]X. Chen, L. W. Taylor, L. J.Tsai. ”An overview on fabrication of three-dimensional woven textile preforms for composites”. Textile Research Journal, 2011, 81(9) 932–944 [2] SV Lomov, G Perie, DS Ivanov, I Verpoest and D Marsal. “Modeling three-dimensional fabrics and three-dimensional reinforced composites: challenges and solutions”. Textile Research Journal, 2011, 81(1) 28–41 [3] E. De Luycker, F. Morestin, P. Boisse, D. Marsal. « Simulation of 3D interlock composite performing”. Composite Structures, Volume 88, Issue 4, May 2009, Pages 615-623. [4] M. Ansar, W. Xinwei, Z. Chouwei. “Modeling strategies of 3D woven composites: A review”. Composite Structures 93 (2011) 1947–1963. [5] A. K. Pickett, J. Sirtautas, et A. Erber. « Braiding simulation and prediction of mechanical properties”. Applied Composite Materials, 2009. [6] M. Duhovic, D. Bhattacharyya. “Simulating the deformation mechanisms of knitted fabric composites”. Composites Part A : Applied Science and Manufacturing, 2006.
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Shaw, Amit, et D. Roy. « Improved Procedures for Static and Dynamic Analyses of Wrinkled Membranes ». Journal of Applied Mechanics 74, no 3 (10 avril 2006) : 590–94. http://dx.doi.org/10.1115/1.2338057.
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An analysis of large deformations of flexible membrane structures within the tension field theory is considered. A modification of the finite element procedure by Roddeman et al. (Roddeman, D. G., Drukker, J., Oomens, C. W. J., Janssen, J. D., 1987, ASME J. Appl. Mech. 54, pp. 884–892) is proposed to study the wrinkling behavior of a membrane element. The state of stress in the element is determined through a modified deformation gradient corresponding to a fictive nonwrinkled surface. The new model uses a continuously modified deformation gradient to capture the location orientation of wrinkles more precisely. It is argued that the fictive nonwrinkled surface may be looked upon as an everywhere-taut surface in the limit as the minor (tensile) principal stresses over the wrinkled portions go to zero. Accordingly, the modified deformation gradient is thought of as the limit of a sequence of everywhere-differentiable tensors. Under dynamic excitations, the governing equations are weakly projected to arrive at a system of nonlinear ordinary differential equations that is solved using different integration schemes. It is concluded that implicit integrators work much better than explicit ones in the present context.
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Romashko, Vasyl Mykolayovych, et Olena Vasylivna Romashko-Maistruk. « MAIN PARAMETERS OF THE UNIVERSAL CONCRETE STATE DIAGRAM IN THE REINFORCED CONCRETE ELEMENTS AND STRUCTURES ». Collected scientific works of Ukrainian State University of Railway Transport, no 199 (10 juin 2022) : 44–54. http://dx.doi.org/10.18664/1994-7852.199.2022.258672.
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This article presents the research results on the search and methodologicaljustification of the main parametric points of the universal dependence of the concrete deformationdiagram c c in reinforced concrete elements and structures. It is shown that, unlike others, thisdependence is not empirical, but obtained analytically using the hypothesis of "stiffness nonlinearity".The using expediency this hypothesis to describe the concrete stress-strain state in reinforcedconcrete elements and structures is substantiated by the results of experimental studies by otherauthors.The most important differences between the concrete deformation standard diagram c cand its state actual diagram in reinforced concrete elements and structures are reflected. It isindicated that the descending branch of the diagram c c reproduces the stresses redistributionfrom one concrete fiber to another. It is substantiated in detail why it is impossible to obtain adescending branch of the concrete deformation diagram for centrally loaded standard samples(concrete cylinders or prisms) under standard test conditions.The nature of the change in the secant modulus of concrete deformations in standard prototypesduring their testing is investigated. It has been established that the ratio between the initial modulusof concrete deformation Ec0 and the normalized modulus of elasticity Ec depends on the concreteclass. The numerical values of the indicated ratios for different classes of heavy concrete are determined and given. It is argued in detail why the compressed concrete ultimate deformability cumust be determined by the state diagram of the element or structure itself, and the concretedeformation descending branch should be limited by the criterion of ultimate bearing capacity(Fermat's criterion) dM / d(1/ r) 0. The reinforcement influence on the length of concretedeformation diagram descending branch of standard prism samples under axial load is estimated.
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KIM, SEUNG ROK, et JEONG SEO KOO. « A STUDY ON STRAIN RATE EFFECT IN COLLISION ANALYSIS OF ROLLING STOCK ». International Journal of Modern Physics B 22, no 09n11 (30 avril 2008) : 1423–30. http://dx.doi.org/10.1142/s0217979208046876.
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In this paper, the strain rate effect of energy absorption members in rolling stock is studied using the virtual testing model (VTM) for Korean high speed train (KHST). The VTM of KHST was simulated for two different strain rate conditions. The VTM is composed of FE models for structures, and nonlinear spring/damper models for dynamic components. To simplify numerical model for the full rake KHST, the first three units consist of full flexible multi-body dynamic models, and the remainder does 1-D spring/damper/mass models. To evaluate the strain rate effect of KHST, the crash simulation was performed under the accident scenario for a collision with a rigid mass of 15 tons at 110kph. The numerical results show that the overall crash response of the train is not largely affected as much as expected, but individual components have some different deformations according to strain rate. The deformation of the front end structure without strain rate effect is larger than that with it. However, the deformation of the rear end structure without strain rate effect is smaller than that with it. Finally, the intrusion of the driver's cabin is overestimated for no strain rate effect when compared to the case with it.
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McGreevy, Ryan, Abhishek Singharoy, Qufei Li, Jingfen Zhang, Dong Xu, Eduardo Perozo et Klaus Schulten. « xMDFF : molecular dynamics flexible fitting of low-resolution X-ray structures ». Acta Crystallographica Section D Biological Crystallography 70, no 9 (29 août 2014) : 2344–55. http://dx.doi.org/10.1107/s1399004714013856.
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X-ray crystallography remains the most dominant method for solving atomic structures. However, for relatively large systems, the availability of only medium-to-low-resolution diffraction data often limits the determination of all-atom details. A new molecular dynamics flexible fitting (MDFF)-based approach, xMDFF, for determining structures from such low-resolution crystallographic data is reported. xMDFF employs a real-space refinement scheme that flexibly fits atomic models into an iteratively updating electron-density map. It addresses significant large-scale deformations of the initial model to fit the low-resolution density, as tested with synthetic low-resolution maps of D-ribose-binding protein. xMDFF has been successfully applied to re-refine six low-resolution protein structures of varying sizes that had already been submitted to the Protein Data Bank. Finally,viasystematic refinement of a series of data from 3.6 to 7 Å resolution, xMDFF refinements together with electrophysiology experiments were used to validate the first all-atom structure of the voltage-sensing protein Ci-VSP.
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Marinkovic, Dragan, Manfred Zehn et Predrag Milic. « On the design of thermally loaded fiber optics feedthroughs ». Thermal Science 20, suppl. 5 (2016) : 1313–20. http://dx.doi.org/10.2298/tsci16s5313m.
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Thermo-mechanical design aspects of various structures exposed to cyclic thermal loading have a crucial impact on their lifetime. This is particularly valid for fiber optics feedthroughs that involve several materials with significantly different thermal expansion ratios. Thermal loading in such structures may give rise to non-trivial thermally induced deformations and therewith stresses, which can be adequately predicted and assessed only by a detailed 3-D numerical simulation. This paper considers a couple of design solutions of fiber optics feedthroughs, which have exhibited certain weaknesses in their application. Numerical simulation by means of the finite element method has been conducted to reveal the weak points of the design.
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Pakhomova, E. G., O. I. Kutsenko, A. S. Morozova et A. R. Timokhina. « Settlement Computation of Homogeneous Base ». Proceedings of the Southwest State University 23, no 6 (23 février 2020) : 90–98. http://dx.doi.org/10.21869/2223-1560-2019-23-6-90-98.
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Purpose of reseach. This article proposes the development of a new methodology for determining the settlement of a homogeneous foundation base on the basis of the layer-by-layer summation method, which reduces the amount of calculations performed.Methods. The boundary of the compressible stratum can be determined graphically from the condition that the additional stresses are equal to half the natural stresses. Knowing the value of the depth of the compressible stratum, we can determine the total value of the coefficients included in the well-known formula for calculating the settlement of the base by the method of layer-by-layer summation. Having determined the value of the specified coefficient in the layer located directly below the base of the foundation, we introduce the coefficient Kα, which reflects the proportion of sediment in the layer under consideration.Results. The application of the developed coefficient Kα allows determining the base settlement by calculating the deformations of one soil layer located directly below the base of the foundation, which greatly simplifies the design of underground structures. As an example, we consider a foundation, the average pressure under the sole of which is 1200 kPa, the laying depth d = 2 m, the base is homogeneous with a deformation modulus of 20 MPa and a specific gravity of γ = 18 kN / m3. The settlement of the building-basement system was calculated by the method of layer-bylayer summation and the critical analysis of the results was performed. When calculating precipitation by the method of layer-by-layer summation according to the known formulas given in SP 22.13330. 2016 “Foundations of buildings and structures”, it was obtained a draft value of 9 cm. When calculating the base deformations according to the proposed method, the boundary of the compressible thickness Hc = 5.7 m was graphically determined. The coefficient value was 0.203, and the draft was 9 cm.Conclusion. The settlement values determined in accordance with current regulatory documents and the developed methodology are the same, which allows us to conclude that the proposed method has a sufficient degree of reliability and can significantly facilitate the process of determining the deformations of the base of buildings and structures.
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Gigli, G., F. Mugnai, L. Leoni et N. Casagli. « <i>Brief communication</i> ; "Analysis of deformations in historic urban areas using terrestrial laser scanning" ; ». Natural Hazards and Earth System Sciences 9, no 6 (2 novembre 2009) : 1759–61. http://dx.doi.org/10.5194/nhess-9-1759-2009.
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Abstract. The terrestrial laser scanning (TLS) technique has been used to accurately reconstruct the 3-D shape of the walls and bastions of the historic city of Mdina (Malta) and underlying terrain. By applying this technique it has also been possible to extract additional quantitative information regarding weathering and deformational processes affecting the structures. Thus, with the aim of identifying the main instability mechanisms, a detailed 3-D crack distribution map has been drawn and the main displacement vectors have been defined.
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Cotti, Giordano, et Davide Guzzetti. « Results on the extension of isomonodromy deformations to the case of a resonant irregular singularity ». Random Matrices : Theory and Applications 07, no 04 (octobre 2018) : 1840003. http://dx.doi.org/10.1142/s2010326318400038.
Texte intégralRésumé :
We explain some results of [G. Cotti, B. A. Dubrovin and D. Guzzetti, Isomonodromy deformations at an irregular singularity with coalescing eigenvalues, preprint (2017); arXiv:1706.04808 .], discussed in our talk [G. Cotti, Monodromy of semisimple Frobenius coalescent structures, in Int. Workshop Asymptotic and Computational Aspects of Complex Differential Equations, CRM, Pisa, February 13–17, (2017).] in Pisa, February 2017. Consider an [Formula: see text] linear system of ODEs with an irregular singularity of Poincaré rank 1 at [Formula: see text] and Fuchsian singularity at [Formula: see text], holomorphically depending on parameter [Formula: see text] within a polydisk in [Formula: see text] centered at [Formula: see text]. The eigenvalues of the leading matrix at [Formula: see text], which is diagonal, coalesce along a coalescence locus [Formula: see text] contained in the polydisk. Under minimal vanishing conditions on the residue matrix at [Formula: see text], we show in [G. Cotti, B. A. Dubrovin and D. Guzzetti, Isomonodromy deformations at an irregular singularity with coalescing eigenvalues, preprint (2017); arXiv:1706.04808 .] that isomonodromic deformations can be extended to the whole polydisk, including [Formula: see text], in such a way that the fundamental matrix solutions and the constant monodromy data are well defined in the whole polydisk. These data can be computed just by considering the system at point of [Formula: see text], where it simplifies. Conversely, if the [Formula: see text]-dependent system is isomonodromic in a small domain contained in the polydisk not intersecting [Formula: see text], and if suitable entries of the Stokes matrices vanish, then [Formula: see text] is not a branching locus for the fundamental matrix solutions. The results have applications to Frobenius manifolds and Painlevé equations.
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ZHORNIK, Viktor I., et Svetlana A. KOVALIOVA. « ENERGY STATE ESTIMATION OF MECHANOCOMPOSITES CONTAINING FUSIBLE COMPONENTS BASED ON ANALYSIS OF FINE STRUCTURE PARAMETERS AND THERMAL EFFECTS ». Mechanics of Machines, Mechanisms and Materials 4, no 53 (décembre 2020) : 77–84. http://dx.doi.org/10.46864/1995-0470-2020-4-53-77-84.
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Energy state of composites obtained by mechanical alloying of the Cu-Sn and Fe-Ga powder mixtures during high-energy processing in the planetary ball mill is evaluated by the methods of X-ray diffraction analysis (XRD) and differential scanning calorimetry (DSC). It is shown that during mechanical alloying the total amount of accumulated energy can reach 80 % of the composite melting enthalpy. The greatest contribution to the structuralphase transformations is made by the phase changes of elastic deformations and grain boundaries. The obtained XRD data are consistent with the DSC data. Three endothermic effects are established at temperatures of 507, 792 and 905–1085 °C for the mechanocomposite with the composition Cu20Sn, the value of these thermal effects is significantly reduced (to 0.79, 16.29 and 36 J/g, respectively) relative to an alloy of similar composition obtained by metallurgical methods. The following criteria of estimation of the most probable processes of structural-phase transformations are proposed based on the energy state of mechanocomposites: the structure of the composite is activated at ΔEε << ΔEs; new phases (solid solutions, intermetallic compounds) are formed at ΔEε ≈ ΔEs; the structure ordering processes take place at ΔEε > ΔEs. The decrease in the values of the energy of elastic deformations ΔEε during prolonged mechanical alloying may indicate the increase of the role of the diffusion processes and the formation of ordered structures, which will contribute to the increase of thermal stability of the grain boundaries. According to these criteria, the dose of the introduced mechanical energy to obtain hardened mechanocomposites of the Cu-Sn composition is to meet the conditions: D ≥ 3.4 kJ/g for Cu-Sn mechanocomposites; D ≥ 37.8 kJ/g for Fe-Ga mechanocomposites.
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Pelham, Robert J., et Yu-li Wang. « High Resolution Detection of Mechanical Forces Exerted by Locomoting Fibroblasts on the Substrate ». Molecular Biology of the Cell 10, no 4 (avril 1999) : 935–45. http://dx.doi.org/10.1091/mbc.10.4.935.
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We have developed a new approach to detect mechanical forces exerted by locomoting fibroblasts on the substrate. Cells were cultured on elastic, collagen-coated polyacrylamide sheets embedded with 0.2-μm fluorescent beads. Forces exerted by the cell cause deformation of the substrate and displacement of the beads. By recording the position of beads during cell locomotion and after cell removal, we discovered that most forces were radially distributed, switching direction in the anterior region. Deformations near the leading edge were strong, transient, and variable in magnitude, consistent with active local contractions, whereas those in the posterior region were weaker, more stable, and more uniform, consistent with passive resistance. Treatment of cells with cytochalasin D or myosin II inhibitors caused relaxation of the forces, suggesting that they are generated primarily via actin–myosin II interactions; treatment with nocodazole caused no immediate effect on forces. Immunofluorescence indicated that the frontal region of strong deformation contained many vinculin plaques but no apparent concentration of actin or myosin II filaments. Strong mechanical forces in the anterior region, generated by locally activated myosin II and transmitted through vinculin-rich structures, likely play a major role in cell locomotion and in mechanical signaling with the surrounding environment.
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Wang, SF, JH Zhang, ZG Liu, XW Zhang, J. Hong, KG Nan et W. Wang. « Riveting parameter design that satisfies requirements for driven rivet head dimensions ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 229, no 13 (18 novembre 2014) : 2412–32. http://dx.doi.org/10.1177/0954406214559256.
Texte intégralRésumé :
Riveted joints are extensively adopted in designing aircraft structures. Riveting implies a squeezing process of the rivet with large plastic deformations to form the driven rivet head. The driven rivet head dimensions (height H, diameter D) depend on riveting force ( X1), rivet length and diameter tolerance ( X2 and X3), as well as rivet hole tolerance ( X4). Incorrect selection in these parameters could induce the excessive stress concentration that results in initial crack and also results in improper rivet head deformation leading to loose rivet. The present research is conducted on a MS2047AD6-6 rivet and 2.286 mm thick aluminum alloy sheets and mainly focuses on the design of riveting parameters X1, X2, X3, and X4 using the proposed three-step statistical experiment designs including fractional factorial design, steepest ascent design, and central composite design while satisfying the quality requirements for driven rivet head dimensions ( H, D) mentioned in Standard Aircraft Handbook. Fractional factorial design is used to evaluate the impact of riveting parameters X1, X2, X3, and X4 on H and D. Based on the effective ranges of the significant riveting parameters obtained from steepest ascent design, a five-level central composite design is proposed to derive the statistical relations between H, D and the significant riveting parameters, and the statistical models are used to find the feasible region resulting from the combination of the significant riveting parameters while satisfying the quality requirements for H and D. Finally, the feasible ranges of X1, X2, X3, and X4, namely [16,470 N 22,730 N], [−0.1491 mm 0.3891 mm], [−0.0466 mm 0.1216 mm], and [−0.0375 mm 0.2125 mm], are determined from the perspective of adjustable accuracy of X1 and that of the manufacturability for X2, X3, and X4. It implies that any combination of X1, X2, X3, and X4 that falls within this feasible region can result in a good quality riveted joins, namely that the quality requirements for the driven riveting head dimension ( H, D) can be satisfied.
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Jiang, Ke He, Bei Bei Sun et Xiao Bo Kang. « Simulations of Thermal Behaviors on a Power-Driven Turret ». Advanced Materials Research 139-141 (octobre 2010) : 961–64. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.961.
Texte intégralRésumé :
As core functional components of the medium and high grade CNC machine tools, the power-driven turret involves high technology and complicated structures. Traditionally, in the study of low speed turrets` performances, the effects of thermal influences are often negligible. However, on the high speed conditions, thermal effect cannot be neglected. This paper establishes the high speed turret 3-D Model and the Finite Element Model (FEM), and investigates and analyzes temperature fields and thermal deformations. Experimental measurements are implemented on the surfaces of the original model turret in order to compare with the simulation results, modified turret is analyzed, and thermal behaviors are proved to be available on the idle operating conditions. It manifests that the distributions of the thermal behaviors have intensive relations with the speeds of the transmission system.
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Gutierrez-Sagredo, Ivan, et Francisco Jose Herranz. « Cayley–Klein Lie Bialgebras : Noncommutative Spaces, Drinfel’d Doubles and Kinematical Applications ». Symmetry 13, no 7 (12 juillet 2021) : 1249. http://dx.doi.org/10.3390/sym13071249.
Texte intégralRésumé :
The Cayley–Klein (CK) formalism is applied to the real algebra so(5) by making use of four graded contraction parameters describing, in a unified setting, 81 Lie algebras, which cover the (anti-)de Sitter, Poincaré, Newtonian and Carrollian algebras. Starting with the Drinfel’d–Jimbo real Lie bialgebra for so(5) together with its Drinfel’d double structure, we obtain the corresponding CK bialgebra and the CK r-matrix coming from a Drinfel’d double. As a novelty, we construct the (first-order) noncommutative CK spaces of points, lines, 2-planes and 3-hyperplanes, studying their structural properties. By requiring dealing with real structures, we found that there exist 63 specific real Lie bialgebras together with their sets of four noncommutative spaces. Furthermore, we found 14 classical r-matrices coming from Drinfel’d doubles, obtaining new results for the de Sitter so(4,1) and anti-de Sitter so(3,2) as well as for some of their contractions. These geometric results were exhaustively applied onto the (3 + 1)D kinematical algebras, considering not only the usual (3 + 1)D spacetime but also the 6D space of lines. We established different assignations between the geometrical CK generators and the kinematical ones, which convey physical identifications for the CK contraction parameters in terms of the cosmological constant/curvature Λ and the speed of light c. We, finally, obtained four classes of kinematical r-matrices together with their noncommutative spacetimes and spaces of lines, comprising all κ-deformations as particular cases.
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Pöchtrager, M., G. Styhler-Aydın, M. Döring-Williams et N. Pfeifer. « AUTOMATED RECONSTRUCTION OF HISTORIC ROOF STRUCTURES FROM POINT CLOUDS – DEVELOPMENT AND EXAMPLES ». ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W2 (16 août 2017) : 195–202. http://dx.doi.org/10.5194/isprs-annals-iv-2-w2-195-2017.
Texte intégralRésumé :
The analysis of historic roof constructions is an important task for planning the adaptive reuse of buildings or for maintenance and restoration issues. Current approaches to modeling roof constructions consist of several consecutive operations that need to be done manually or using semi-automatic routines. To increase efficiency and allow the focus to be on analysis rather than on data processing, a set of methods was developed for the fully automated analysis of the roof constructions, including integration of architectural and structural modeling. Terrestrial laser scanning permits high-detail surveying of large-scale structures within a short time. Whereas 3-D laser scan data consist of millions of single points on the object surface, we need a geometric description of structural elements in order to obtain a structural model consisting of beam axis and connections. Preliminary results showed that the developed methods work well for beams in flawless condition with a quadratic cross section and no bending. Deformations or damages such as cracks and cuts on the wooden beams can lead to incomplete representations in the model. Overall, a high degree of automation was achieved.
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Ikeda, Kazutaka, Yuko Nakamori et Shinichi Orimo. « Hydriding Properties of the Mechanically Deformed Mg-Ni Alloys ». Materials Science Forum 503-504 (janvier 2006) : 499–504. http://dx.doi.org/10.4028/www.scientific.net/msf.503-504.499.
Texte intégralRésumé :
Mechanical deformations with/without elemental substitutions have been carried out on Mg-Ni-based alloys to improve their hydriding properties. The alloys Mg-x at.%Ni (x = 33, 38, 43 and 50) with different nanometer-scale structures were successively synthesized by mechanical milling of Mg2Ni mixed with various amounts of additional Ni, and the relations between their structural and hydriding properties were investigated in detail. By milling only Mg2Ni, nanostructured Mg2Ni composed of the intra- and inter-grain regions was obtained (x = 33). Amorphous MgNi (a-MgNi) as a third region was dispersed around the nanostructured Mg2Ni by milling of Mg2Ni mixed with additional Ni (x = 38 and 43), and the pure amorphous MgNi was homogeneously synthesized in equivalent composition (x = 50). The coordination numbers and interatomic distances of the Mg-D and Ni-D correlations in the amorphous MgNi-D show that deuterium occupies the interstitial tetrahedral site composed of nearly [2Mg2Ni]. According to the specific structural properties, there is obvious miscibility gap (plateau) pressure higher than 1 × 10-4 MPa at room temperature even in the amorphous phase, and the total hydrogen content reached up to 2.2 mass%. Further studies on an amorphous MgNi-based system were carried out to clarify the effect of the short-range ordering on the structural and hydriding properties due to substitution of Mg- and Ni-sites by various elements.
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Louadj, Samia, Ramdane Bahar et Nasser Laouami. « Numerical Analysis of Keddara Dam under Seismic Motion ». International Journal of Engineering Research in Africa 40 (décembre 2018) : 47–62. http://dx.doi.org/10.4028/www.scientific.net/jera.40.47.
Texte intégralRésumé :
The Boumerdes earthquake of May 21, 2003 in Algeria, which widely felt within a radius of ~ 400 km, caused damage in five provinces. Numerous structures have been devastated, others suffered of damages. Keddara rockfill dam which is situated approximately at 20 km from the epicentre was strongly shaken during this seismic event and can undergo significant deformations. In this study, numerical analysis of Keddara rockfill dam under Boumerdes earthquake is performed. It is mainly focus on the seismic amplification at different level of the dam under the main shock with dominant frequency close to the natural frequency of the dam. The low coherence between the input and the structural output indicates the need of nonlinear analysis of the dam under the spatial variation in excitation. Furthermore, the effect of plasticity on the seismic response is investigated by using maximum acceleration which is one of the most important properties selected. The analysis of the dam under stochastic non-uniform excitation is conducted using a 2-D finite difference modeling by using the software Fast Lagrangian Analysis of Continua (FLAC). The final results obtained after successive analyses on the dam configuration incorporating the nonlinear soil properties are presented.
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Nemat-Nasser, Sia, Jeom Yong Choi, Jon B. Isaacs et David W. Lischer. « Quasi-Static and Dynamic Buckling of Thin Cylindrical Shape-Memory Shells ». Journal of Applied Mechanics 73, no 5 (22 novembre 2005) : 825–33. http://dx.doi.org/10.1115/1.2165241.
Texte intégralRésumé :
To investigate the buckling behavior of thin and relatively thick cylindrical shape-memory shells, uniaxial compression tests are performed at a 295K initial temperature, using the CEAM/UCSD’s modified split Hopkinson bar systems and an Instron hydraulic testing machine. The quasi-static buckling response of the shells is directly observed and recorded using a digital camera with a close-up lens and two back mirrors. To document the dynamic buckling modes, a high-speed Imacon 200 framing camera is used. The shape-memory shells with an austenite-finish temperature of Af=281K, buckle gradually and gracefully in quasi-static loading, and fully recover upon unloading, showing a superelastic property, whereas when suitably annealed, the shells do not recover spontaneously upon unloading, but they do so once heated, showing a shape-memory effect. The thin shells had a common thickness of 0.125mm a common outer radius of 2.25mm (i.e., a common radius, R, to thickness, t, ratio, R∕t, of 18). A shell with the ratio of length, L, to diameter, D(L∕D) of 1.5 buckled under a quasi-static load by forming a nonsymmetric chessboard pattern, while with a L∕D of 1.95 the buckling started with the formation of symmetrical rings which then changed into a nonsymmetric chessboard pattern. A similar buckling mode is also observed under a dynamic loading condition for a shell with L∕D of 2. However, thicker shells, with 0.5mm thickness and radius 4mm(R∕t=8), buckled under a dynamic loading condition by the formation of a symmetrical ring pattern. For comparison, we have also tested shells of similar geometry but made of steel and aluminum. In the case of the steel shells with constrained end conditions, the buckling, which consists of nonsymmetric (no rings) folds (chessboard patterns), is sudden and catastrophic, and involves no recovery upon unloading. The gradual buckling of the shape-memory shells is associated with the stress-induced martensite formation and seems to have a profound effect on the unstable deformations of thin structures made from shape-memory alloys.
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Cheong, Yuen-Ki, Mariana P. Arce, Alejandro Benito, Daijie Chen, Noemi Luengo Crisóstomo, Laxmi V. Kerai, Guillermo Rodríguez et al. « Synergistic Antifungal Study of PEGylated Graphene Oxides and Copper Nanoparticles against Candida albicans ». Nanomaterials 10, no 5 (25 avril 2020) : 819. http://dx.doi.org/10.3390/nano10050819.
Texte intégralRésumé :
The coupling reactions of polyethylene glycol (PEG) with two different nano-carbonaceous materials, graphene oxide (GO) and expanded graphene oxide (EGO), were achieved by amide bond formations. These reactions yielded PEGylated graphene oxides, GO-PEG and EGO-PEG. Whilst presence of the newly formed amide links (NH-CO) were confirmed by FTIR stretches observed at 1732 cm−1 and 1712 cm−1, the associated Raman D- and G-bands resonated at 1311/1318 cm−1 and 1584/1595 cm−1 had shown the carbonaceous structures in both PEGylated products remain unchanged. Whilst SEM images revealed the nano-sheet structures in all the GO derivatives (GO/EGO and GO-PEG/EGO-PEG), TEM images clearly showed the nano-structures of both GO-PEG and EGO-PEG had undergone significant morphological changes from their starting materials after the PEGylated processes. The successful PEGylations were also indicated by the change of pH values measured in the starting GO/EGO (pH 2.6–3.3) and the PEGylated GO-PEG/EGO-PEG (pH 6.6–6.9) products. Initial antifungal activities of selective metallic nanomaterials (ZnO and Cu) and the four GO derivatives were screened against Candida albicans using the in vitro cut-well method. Whilst the haemocytometer count indicated GO-PEG and copper nanoparticles (CuNPs) exhibited the best antifungal effects, the corresponding SEM images showed C. albicans had, respectively, undergone extensive shrinkage and porosity deformations. Synergistic antifungal effects all GO derivatives in various ratio of CuNPs combinations were determined by assessing C. albicans viabilities using broth dilution assays. The best synergistic effects were observed when a 30:70 ratio of GO/GO-PEG combined with CuNPs, where MIC50 185–225 μm/mL were recorded. Moreover, the decreased antifungal activities observed in EGO and EGO-PEG may be explained by their poor colloidal stability with increasing nanoparticle concentrations.
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Narmashiri, Kambiz, Mohd Zamin Jumaat et Nor Hafizah Ramli Sulong. « Failure Modes of CFRP Flexural Strengthened Steel I-Beams ». Key Engineering Materials 471-472 (février 2011) : 590–95. http://dx.doi.org/10.4028/www.scientific.net/kem.471-472.590.
Texte intégralRésumé :
This paper presents the experimental and numerical studies on the flexural strengthened steel I-beams by using Carbon Fiber Reinforced Polymer (CFRP) strips. Nowadays, strengthening existing steel structures by using CFRP has been widely interested. One of the common usages of CFRP to strengthen steel beams is the flexural upgrading. In this case, CFRP strips are pasted on the tensile flange to improve flexural behaviors. The problems that are frequently reported for CFRP strengthened steel beams are the debonding, delaminating (peeling), and splitting. Identification these failure modes are essential to provide an appropriate level of safety for strengthened steel beams. To investigate the CFRP failure modes, four strengthened steel I-beams were chosen. The CFRP plates with different thicknesses in single and double (splice) layers were used. Both experimental test (four-points bending test) and numerical simulation (full 3D simulation with ANSYS) were employed. The incremental loading was applied until failure while deformations in the critical regions were recorded. The results reveal that for the CFRP flexural strengthened steel beams the following failure modes occurred: (a) debonding at the CFRP plate tips, (b) debonding below point loads, (c) delaminating at the ends of CFRP plate, and (d) splitting below point loads. The sequence of failure modes depended on the specifications of CFRP plate. Some recommendations are provided to overcome/retard these failures.
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Böhm, Stanislav, et Otto Exner. « Geometry at the aliphatic tertiary carbon atom : computational and experimental test of the Walsh rule ». Acta Crystallographica Section B Structural Science 60, no 1 (21 janvier 2004) : 103–7. http://dx.doi.org/10.1107/s010876810302826x.
Texte intégralRésumé :
The geometrical parameters of molecules of 2-substituted 2-methylpropanes and 1-substituted bicyclo[2.2.2]octanes were calculated at the B3LYP/6-311+G(d,p) level. They agreed reasonably well with the mean crystallographic values retrieved from the Cambridge Structural Database for a set of diverse non-cyclic structures with a tertiary C atom. The angle deformations at this C atom produced by the immediately bonded substituent are also closely related to those observed previously in benzene mono derivatives (either as calculated or as derived from crystallographic data). The calculated geometrical parameters were used to test the classical Walsh rule: It is evidently true that an electron-attracting substituent increases the proportion of C-atom p-electrons in the bond to the substituent and leaves more s-electrons to the remaining bonds; as a consequence the C—C—C angles at a tertiary carbon are widened and the C—C bonds shortened. However, this rule describes only part of the reality since the bond angles and lengths are controlled by other factors as well, for instance by steric crowding. Another imperfection of the Walsh rule is that the sequence of substituents does not correspond to their electronegativities, as measured by any known scale; more probably it is connected with the inductive effect, but then only very roughly.
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Jolivet, Laurent, Armel Menant, Vincent Roche, Laetitia Le Pourhiet, Agnès Maillard, Romain Augier, Damien Do Couto, Christian Gorini, Isabelle Thinon et Albane Canva. « Transfer zones in Mediterranean back-arc regions and tear faults ». BSGF - Earth Sciences Bulletin 192 (2021) : 11. http://dx.doi.org/10.1051/bsgf/2021006.
Texte intégralRésumé :
Slab tearing induces localized deformations in the overriding plates of subduction zones and transfer zones accommodating differential retreat in back-arc regions. Because the space available for retreating slabs is limited in the Mediterranean realm, slab tearing during retreat has been a major ingredient of the evolution of this region since the end of the Eocene. The association of detailed seismic tomographic models and extensive field observations makes the Mediterranean an ideal natural laboratory to study these transfer zones. We review in this paper the various structures in back-arc regions differential retreat from the Alboran Sea to the Aegean-Anatolian region and discuss them with the help of 3D numerical models to better understand the partitioning of deformation between high-angle and low-angle faults, as well as the 3-D kinematics of deformation in the middle and lower crusts. Simple, archetypal, crustal-scale strike-slip faults are in fact rare in these contexts above slab tears. Transfer zones are in general instead wide deformation zones, from several tens to several hundred kilometers. A partitioning of deformation is observed between the upper and the lower crust with low-angle extensional shear zones at depth and complex association of transtensional basins at the surface. In the Western Mediterranean, between the Gulf of Lion and the Valencia basin, transtensional strike-slip faults are associated with syn-rift basins and lower crustal domes elongated in the direction of retreat (a-type domes), associated with massive magmatic intrusions in the lower crust and volcanism at the surface. On the northern side of the Alboran Sea, wide E-W trending strike-slip zones in the brittle field show partitioned thrusting and strike-slip faulting in the external zones of the Betics, and E-W trending metamorphic core complexes in the internal zones, parallel to the main retreat direction with a transition in time from ductile to brittle deformation. On the opposite, the southern margin of the Alboran Sea shows short en-échelon strike-slip faults. Deep structures are not known there. In the Aegean-Anatolian region, two main tear faults with different degrees of maturity are observed. Western Anatolia (Menderes Massif) and the Eastern Aegean Sea evolved above a major left-lateral tear in the Hellenic slab. In the crust, the differential retreat was accommodated mostly by low-angle shear zones with a constant direction of stretching and the formation of a-type high-temperature domes exhumed from the middle and lower crust. These low-angle shear zones evolve through time from ductile to brittle. On the opposite side of the Aegean region, the Corinth and Volos Rift as well as the Kephalonia fault offshore, accommodate the formation of a dextral tear fault. Here, only the brittle crust can be observed, but seismological data suggest low-angle shear zones at depth below the rifts. We discuss the rare occurrence of pure strike-slip faults in these contexts and propose that the high heat flow above the retreating slabs and more especially above slab tears favors a ductile behavior with distributed deformation of the crust and the formation of low-angle shear zones and high-temperature domes. While retreat proceeds, aided by tears, true strike-slip fault system may localize and propagate toward the retreating trench, ultimately leading to the formation of new plate boundary, as shown by the example of the North Anatolian Fault.
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Ran, Ziv. « A BOGOMOLOV UNOBSTRUCTEDNESS THEOREM FOR LOG-SYMPLECTIC MANIFOLDS IN GENERAL POSITION ». Journal of the Institute of Mathematics of Jussieu 19, no 5 (9 novembre 2018) : 1509–19. http://dx.doi.org/10.1017/s1474748018000464.
Texte intégralRésumé :
We consider compact Kählerian manifolds $X$ of even dimension 4 or more, endowed with a log-symplectic holomorphic Poisson structure $\unicode[STIX]{x1D6F1}$ which is sufficiently general, in a precise linear sense, with respect to its (normal-crossing) degeneracy divisor $D(\unicode[STIX]{x1D6F1})$. We prove that $(X,\unicode[STIX]{x1D6F1})$ has unobstructed deformations, that the tangent space to its deformation space can be identified in terms of the mixed Hodge structure on $H^{2}$ of the open symplectic manifold $X\setminus D(\unicode[STIX]{x1D6F1})$, and in fact coincides with this $H^{2}$ provided the Hodge number $h_{X}^{2,0}=0$, and finally that the degeneracy locus $D(\unicode[STIX]{x1D6F1})$ deforms locally trivially under deformations of $(X,\unicode[STIX]{x1D6F1})$.
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Wilson, Matthew Coffie, Chiri G. Amedjoe et Simon K. Y. Gawu. « STRUCTURES OF BIRIMIAN AND TARKWAIAN ROCKS AT NORTH-WEST NEW DROBO – IMPLICATION ON DEFORMATION ». Malaysian Journal of Geosciences 6, no 1 (2022) : 36–44. http://dx.doi.org/10.26480/mjg.01.2022.36.44.
Texte intégralRésumé :
This research leads to identifying the microstructures, the deformation episodes (D) and foliation grades (S) of rocks in the study area. Different geological structures such as shear zones, foliations, micro-faults, crack-seal events, etc. have been identified in the study area. Different phases of deformation episodes and foliation grades have been studied to determine the deformation environments. Senses of shear such as dextral, CS, and CS’ as well as antithetic and synthetic micro-faults and boudins may be identified at the north-west New Drobo. Three (3) main deformational (D) events and foliation grades (S) in both the Tarkwaian sandstones and Birimian volcanic rocks may be identified as D1, D2 and D3 as well as S1, S2 and S3. Recrystallization of quartz and feldspar through bulging (BLG), subgrain boundary rotation (SBR) and grain boundary migration (GBM) have been observed at the study area. The overprinting relationships in the Birimian Supergroup may be identified with three (3) different deformational phases. The first deformation (D1) defines the formation of a vertical shortening, whilst the second deformation (D2) defines oblique shortening. Moreover, the third deformation (D3) is due to high strain rate causing brittle faulting.
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Xu, Wan Qiang, et Michael Ferry. « The Study on the Nucleation Behaviours in IF Steel by 3-D EBSD Tomography ». Materials Science Forum 654-656 (juin 2010) : 2334–37. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2334.
Texte intégralRésumé :
3-D FIB-EBSD tomography was used to analyze the structure and crystallography of nuclei, and nucleation process in 3-D space during annealing a cold rolled IF steel. It is revealed that the structure of nucleus at its very initial formation stage can be divided into two parts: (1) nucleation core, having a dislocation-contained subgrain structure, mainly bounded by low angle grain boundary with surrounding deformation subgrain, (2) newly-grown region, having a dislocation free structure, formed from high store energy deformation structures surrounding nucleus, and mainly bounded by high angle grain boundary.
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Qin, Dongxue, Lin Sang, Zihui Zhang, Shengyuan Lai et Yiping Zhao. « Compression Performance and Deformation Behavior of 3D-Printed PLA-Based Lattice Structures ». Polymers 14, no 5 (7 mars 2022) : 1062. http://dx.doi.org/10.3390/polym14051062.
Texte intégralRésumé :
The aim of this study is to fabricate biodegradable PLA-based composite filaments for 3D printing to manufacture bear-loading lattice structures. First, CaCO3 and TCP as inorganic fillers were incorporated into a PLA matrix to fabricate a series of composite filaments. The material compositions, mechanical properties, and rheology behavior of the PLA/CaCO3 and PLA/TCP filaments were evaluated. Then, two lattice structures, cubic and Triply Periodic Minimal Surfaces-Diamond (TPMS-D), were geometrically designed and 3D-printed into fine samples. The axial compression results indicated that the addition of CaCO3 and TCP effectively enhances the compressive modulus and strength of lattice structures. In particular, the TPMS-D structure showed superior load-carrying capacity and specific energy absorption compared to those of its cubic counterparts. Furthermore, the deformation behavior of these two lattice structures was examined by image recording during compression and computed tomography (CT) scanning of samples after compression. It was observed that pore structure could be well held in TPMS-D, while that in cubic structure was destroyed due to the fracture of vertical struts. Therefore, this paper highlights promising 3D-printed biodegradable lattice structures with excellent energy-absorption capacity and high structural stability.
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Negulescu, C., et E. Foerster. « Parametric studies and quantitative assessment of the vulnerability of a RC frame building exposed to differential settlements ». Natural Hazards and Earth System Sciences 10, no 9 (1 septembre 2010) : 1781–92. http://dx.doi.org/10.5194/nhess-10-1781-2010.
Texte intégralRésumé :
Abstract. The aim of this paper is to propose a simplified methodology to evaluate the mechanical performances of buildings exposed to landslide hazard, by using procedures inspired from the seismic risk analysis, such as the Capacity Spectrum Method (ATC 40, 1996). Landslide hazard involves so many aspects, that quantitative vulnerability assessment requires to consider one basic scenario at a time, i.e. one typology for the landslide hazard and one for the structural element considered. In this paper, we propose to assess vulnerability for simple one bay-one storey reinforced concrete (RC) frame structures subjected to differential settlements, using 2-D parametric nonlinear static time-history analyses. After a short review of methods used in practice to estimate building deformations induced by ground movements (e.g. differential settlements), we present the parametric studies carried out to identify the most relevant parameters, in order to predict the structural damage, as well as the methodology to develop analytical fragility curves, that can be used to quantitatively evaluate the structural vulnerability in landslide risk analyses. Different types of parameters that could influence structural behaviour have been examined in this analysis: foundation type (i.e. different combinations of links), cross-section geometry, section reinforcement degree, displacement magnitudes and displacement inclination angles. We show that the magnitude and inclination angle of displacements can be used as two relevant parameters for this type of landslide scenario. Based on these results, some simulations are conducted using the software SeismoStruct (SeismoSoft, 2003), and the proposed structural damage levels consider the local strain limits of steel and concrete constitutive materials. Some preliminary fragility curves are proposed with respect to the magnitude of differential ground displacement. It can be seen that the curves corresponding to limit states LS2 (moderate damage) and LS4 (complete damage) in the present study, correspond respectively to the "tolerable settlements" "observed intolerable settlements" curves proposed by Zhang and Ng (2005).
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Akahori, Takao. « Partially integrable almost CR structures ». Complex Manifolds 8, no 1 (1 janvier 2021) : 403–14. http://dx.doi.org/10.1515/coma-2020-0124.
Texte intégralRésumé :
Abstract Let (M, D) be a compact contact manifold with dim R M = 2n ≥ 5. This means that: M is a C ∞ differential manifold with dim R M = 2n ≥ 5. And D is a subbundle of the tangent bundle TM which satisfying; there is a real one form θ such that D = {X : X ∈ TM, θ(X) = 0}, and θ ^ Λ n−1(d ) ≠ 0 at every point of p of M. Especially, we assume that our D admits almost CR structure,(M, S). In this paper, inspired by the work of Matsumoto([M]), we study the difference of partially integrable almost CR structures from actual CR structures. And we discuss partially integrable almost CR structures from the point of view of the deformation theory of CR structures ([A1],[AGL]).
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Chen, Zhen, Chang You Li et Feng Ying Xu. « A Study on Dynamic Simulation of Litchi Pitting Process Based on ANSYS / LS-DYNA ». Advanced Materials Research 479-481 (février 2012) : 2557–63. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.2557.
Texte intégralRésumé :
To study the dynamic mechanical changes in litchi pitting process and improve the accuracy of litchi pitting, this paper established a 3-D solid assembly model of litchi, fixture and tool and conducted the finite element discrete of the model by using ANSYS / LS-DYNA software. In addition, the deformations and stress states of litchi’s multi-layer structure under the effects of tool and fixture were simulated and calculated by the LS-DYNA971 solver. The results showed that the deformations and stresses of litchi’s multi-layer structure changed with the increase of cutting depth, and appeared the maximum amplitude out of sync. When the litchi was gonna cut through, the stress amplitude of fruit pulp was the maximum among litchi’s multi-layer structure and the stress amplitude of fruit pulp was the minimum. Pulp would reach its maximum stress when cutting through the litchi, and because of its low strength, the breakage was prone to occur. The stress of fruit stone was large in the initial stage, and big fruit stone was easily led to the breakage for its overlarge stress. In pitting process, the deformation and slippage of litchi would take place with fixture clamping and tool pitting, so this is a complex dynamic deformation process. This study is urgent to make more comprehensive and systematic researches.
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Xue, Tengyun, Xiuli Xue, Sichun Long, Qiunan Chen, Shide Lu et Chaofeng Zeng. « Effect of Pre-Existing Underground Structures on Groundwater Flow and Strata Movement Induced by Dewatering and Excavation ». Water 15, no 4 (20 février 2023) : 814. http://dx.doi.org/10.3390/w15040814.
Texte intégralRésumé :
Based on an actual excavation of a metro station in Tianjin, China, a fluid–solid coupling numerical model was developed to study the characteristics of groundwater flow and strata movement induced by dewatering and excavation considering the barrier effect of pre-existing adjacent underground structures. Two parameters were selected for the model: the distance between the excavation and the existing underground structure (D), and the buried depth of the adjacent structure (H). By comparing the distribution of groundwater drawdown and deformation modes of the retaining structure and the strata under different working conditions, the influence mechanism of adjacent structures on the movement of groundwater and strata was revealed. The results show that the pile foundations have different effects on the groundwater flow and excavation deformation. Generally, the maximum groundwater drawdown could be enlarged by considering the adjacent underground structure, while the retaining structure deflection would be reduced and the ground settlement could be either enlarged or reduced. Additionally, as D decreases and H increases, a much greater groundwater drawdown and a much smaller retaining structure deflection would appear, which together affect the ground behavior. On the one hand, greater groundwater drawdown would lead to greater ground settlement by soil consolidation, while on the other hand, a smaller retaining structure deflection would lead to smaller ground settlement. Thus, a complex development of ground settlement would appear, and a specific analysis should be performed to assess this in practice, based on a specific H and D.
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GOLOVIN, A. A., A. A. NEPOMNYASHCHY et L. M. PISMEN. « NONPOTENTIAL EFFECTS IN NONLINEAR DYNAMICS OF MARANGONI CONVECTION ». International Journal of Bifurcation and Chaos 12, no 11 (novembre 2002) : 2487–500. http://dx.doi.org/10.1142/s021812740200600x.
Texte intégralRésumé :
Nonpotential effects in nonlinear evolution of Marangoni convection patterns are investigated analytically and numerically. Three manifestations of nonpotential effects are considered: (i) spatial modulations of hexagonal patterns; (ii) interaction between a short-scale hexagonal pattern and a long-scale slow deformational (Goldstone) mode; (iii) generation of the mean flow by the free-surface deformation in a large-scale Marangoni convection with poorly conducting boundaries. Nonpotential effects are shown to cause various secondary instabilities leading to skewed hexagonal structures, coexisting u- and d-hexagons, oscillating hexagonal patterns, spatially irregular cellular patterns, etc.
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Bischoff, Francis, Henrique Bursztyn, Hudson Lima et Eckhard Meinrenken. « Deformation spaces and normal forms around transversals ». Compositio Mathematica 156, no 4 (17 février 2020) : 697–732. http://dx.doi.org/10.1112/s0010437x1900784x.
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Given a manifold $M$ with a submanifold $N$, the deformation space ${\mathcal{D}}(M,N)$ is a manifold with a submersion to $\mathbb{R}$ whose zero fiber is the normal bundle $\unicode[STIX]{x1D708}(M,N)$, and all other fibers are equal to $M$. This article uses deformation spaces to study the local behavior of various geometric structures associated with singular foliations, with $N$ a submanifold transverse to the foliation. New examples include $L_{\infty }$-algebroids, Courant algebroids, and Lie bialgebroids. In each case, we obtain a normal form theorem around $N$, in terms of a model structure over $\unicode[STIX]{x1D708}(M,N)$.
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Sui, Shao Chun, Li Min Tang et Wang Wei Chu. « Application Study of the Aviation Structures’ Machining Deformation On-Line Measurement Technology ». Advanced Materials Research 381 (novembre 2011) : 38–43. http://dx.doi.org/10.4028/www.scientific.net/amr.381.38.
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Based on non-contact 3-D on-line measurement technology, the article studies the aviation structures’ machining deformation on-line measurement technology. The technology provide a effective way to measure the machining deformation, and the accuracy of the system can reach 0.05mm in 2000mm. Use the on-line measurement technology to get the 3-D shape of the structures after machining, and then compare the measurement result with the theoretical model to get the machining deformation. The deformation results provide the basis for the improvement of machining process.
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NICOLETTI, RICCARDO, et EMANUELE ORAZI. « GEOMETRIC IIA SUPERGRAVITY THEORIES IN THE STRING FRAME ». International Journal of Modern Physics A 26, no 26 (20 octobre 2011) : 4585–602. http://dx.doi.org/10.1142/s0217751x11054607.
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Using the geometric (rheonomic) approach based on the Free Differential Algebra, we derive the full type IIA D = 10 supergravity Lagrangian in the string frame, including the Romans' mass deformation, and containing the explicit four-fermion interactions, absent from the original Romans' paper. This provides a deeper insight into the group theoretical and algebraic structures of the theory. Moreover we provide the full set of supersymmetry transformation laws both in the Romans'-deformed and undeformed theories. The structure of the bosonic Free Differential Algebra for the HLW deformation is also presented.
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Lowe, John B., et Richard T. Baker. « Deformation of Ordered Mesoporous Silica Structures on Exposure to High Temperatures ». Journal of Nanomaterials 2014 (2014) : 1–13. http://dx.doi.org/10.1155/2014/754076.
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Ordered mesoporous silica materials are of interest for a wide range of applications. In many of these, elevated temperatures are used either in the preparation of the material or during its use. Therefore, an understanding of the effect of high temperature treatments on these materials is desirable. In this work, a detailed structural study is performed on silicas with three representative pore structures: a 2-D hexagonal pore arrangement (SBA-15), a continuous 3D cubic bimodal pore structure (KIT-6), and a 3D large cage pore structure (FDU-12). Each silica is studied as prepared and after treatment at a series of temperatures between 300 and 900°C. Pore structures are imaged using Transmission Electron Microscopy. This technique is used in conjunction with Small-Angle X-ray Diffraction, gas physisorption, and29Si solid state Nuclear Magnetic Resonance. Using these techniques, the pore size distributions, the unit cell dimensions of the mesoporous structures, and the relative occupancy of the distinct chemical environments of Si within them are cross correlated for the three silicas and their evolution with treatment temperature is elucidated. The physical and chemical properties before, during, and after collapse of these structures at high temperatures are described as are the differences in behavior between the three silica structures.
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Simitha, S., Shinto M. Francis, Jesly Jacob et Vibin Ipe Thomas. « Theoretical modelling of a deformation based concave square ring-square disc (SR-SD) silver structure for pressure sensing ». IOP Conference Series : Materials Science and Engineering 1263, no 1 (1 octobre 2022) : 012004. http://dx.doi.org/10.1088/1757-899x/1263/1/012004.
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A compact nanosensor that explores the tie-in between stress-induced deformation and optical resonance characteristics is theoretically proposed for pressure sensing. The structure modeling, electromagnetic (EM) wave simulation, and performance evaluations were carried out using the 2D finite element method (FEM). The proposed surface plasmon resonance (SPR) based metal-insulator-metal (MIM) model responds to the pressure induced on the top-facing side of an Ag concave square ring-square disc arrangement (Concave SR-SD) in terms of a structural curve-in into the insulator cavity. These deformations alter the electromagnetic field distributions and plasmonic resonance conditions, shifting the absorption cross-section profiles towards higher wavelengths. The shift in the resonant wavelength (Δλ) for specific measured deformations (d) exhibited by the normal SR-SD hinds at the application level perspective of the designed system in pressure sensing via its optomechanical correlation. Further, multiple parameters like insulator cavity width (W I ) and structure wise modifications in the outer ring structure are investigated for performance optimization, and subline sensitivity values (maximum) of 24.496 nm/MPa and 40.46 nm/MPa are observed from normal and concave SR-SD systems respectively. The suggested nano pressure sensor of suitable sensitivity and broad sensing range promises strong applicability in biomedicine, health monitoring, nanomechanics, chip-based devices, and nanoelectronics.
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Merkulov, Sergei, et Thomas Willwacher. « Classification of universal formality maps for quantizations of Lie bialgebras ». Compositio Mathematica 156, no 10 (octobre 2020) : 2111–48. http://dx.doi.org/10.1112/s0010437x20007381.
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We settle several fundamental questions about the theory of universal deformation quantization of Lie bialgebras by giving their complete classification up to homotopy equivalence. Moreover, we settle these questions in a greater generality: we give a complete classification of the associated universal formality maps. An important new technical ingredient introduced in this paper is a polydifferential endofunctor ${\mathcal {D}}$ in the category of augmented props with the property that for any representation of a prop ${\mathcal {P}}$ in a vector space $V$ the associated prop ${\mathcal {D}}{\mathcal {P}}$ admits an induced representation on the graded commutative algebra $\odot ^\bullet V$ given in terms of polydifferential operators. Applying this functor to the minimal resolution $\widehat {\mathcal {L}\textit{ieb}}_\infty$ of the genus completed prop $\widehat {\mathcal {L}\textit{ieb}}$ of Lie bialgebras we show that universal formality maps for quantizations of Lie bialgebras are in one-to-one correspondence with morphisms of dg props \[F: \mathcal{A}\textit{ssb}_\infty \longrightarrow {\mathcal{D}}\widehat{\mathcal{L}\textit{ieb}}_\infty \] satisfying certain boundary conditions, where $\mathcal {A}\textit{ssb}_\infty$ is a minimal resolution of the prop of associative bialgebras. We prove that the set of such formality morphisms is non-empty. The latter result is used in turn to give a short proof of the formality theorem for universal quantizations of arbitrary Lie bialgebras which says that for any Drinfeld associator $\mathfrak{A}$ there is an associated ${\mathcal {L}} ie_\infty$ quasi-isomorphism between the ${\mathcal {L}} ie_\infty$ algebras $\mathsf {Def}({\mathcal {A}} ss{\mathcal {B}}_\infty \rightarrow {\mathcal {E}} nd_{\odot ^\bullet V})$ and $\mathsf {Def}({\mathcal {L}} ie{\mathcal {B}}\rightarrow {\mathcal {E}} nd_V)$ controlling, respectively, deformations of the standard bialgebra structure in $\odot V$ and deformations of any given Lie bialgebra structure in $V$. We study the deformation complex of an arbitrary universal formality morphism $\mathsf {Def}(\mathcal {A}\textit{ssb}_\infty \stackrel {F}{\rightarrow } {\mathcal {D}}\widehat {\mathcal {L}\textit{ieb}}_\infty )$ and prove that it is quasi-isomorphic to the full (i.e. not necessary connected) version of the graph complex introduced Maxim Kontsevich in the context of the theory of deformation quantizations of Poisson manifolds. This result gives a complete classification of the set $\{F_\mathfrak{A}\}$ of gauge equivalence classes of universal Lie connected formality maps: it is a torsor over the Grothendieck–Teichmüller group $GRT=GRT_1\rtimes {\mathbb {K}}^*$ and can hence can be identified with the set $\{\mathfrak{A}\}$ of Drinfeld associators.
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Boman, F., A. Froment et P. Charlier. « Variations in the Thickness of the Cranial Vault in a Deformed Skull from Pre-Hispanic Ancón (Peru) ». Bulletins et Mémoires de la Société d'Anthropologie de Paris 28, no 3-4 (3 juin 2016) : 221–25. http://dx.doi.org/10.1007/s13219-016-0160-y.
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A medical tomodensitometric study (TDM) was performed on a dry skull from the necropolis of Ancón in Peru. The skull, housed at the Muséum national d'histoire naturelle in Paris, displays an anteroposterior, brachycephalic, oblique, asymmetric, and bilobar deformation. TDM permitted 3-D reconstructions of the skull, endocranium, and vault thickness. The external surface displayed deformation and asymmetry in the bone structures and the endocranium demonstrated deformation and asymmetry in the brain lobes and superficial structures. The TDM demonstration of abnormal variations and pronounced asymmetry in the thickness of the vault strongly suggested that the deformation was ante mortem. The 3-D TDM reconstructions also helped to reconstruct the device used to deform the head.
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Ji, Rong-Jian, Tao Li, Jian-Ming Yang et Jun Xu. « Sulfate Freeze–Thaw Resistance of Magnesium Potassium Phosphate Cement Mortar according to Hydration Age ». Materials 15, no 12 (13 juin 2022) : 4192. http://dx.doi.org/10.3390/ma15124192.
Texte intégralRésumé :
Concrete structures can be degraded by exposure to environmental stressors such as freeze–thaw cycling and salt corrosion. Magnesium potassium phosphate cement (MKPC) mortar is useful for the rapid repair of such structures but must acquire environmental resistance rapidly. In this study, the freeze–thaw resistance of MKPC mortar specimens of different hydration ages was tested in water and a 5% Na2SO4 solution. The strength, volume deformation, and water absorption rates were compared with those of full-age MKPC mortar specimens (28 d). The phase composition and microscopic morphology of the MKPC mortar specimens before and after corrosion were observed, and the corrosion-resistance mechanism was analyzed. After 225 freeze–thaw cycles in water and sulfate solution, the strength residual rates of the early-age specimen (1 d) were higher than those of the full-age specimen (28 d). The degree of strength attenuation in the 1 d specimen was lower in the sulfate environment than in the water environment. After 225 freeze–thaw cycles, the volume expansion rates of 1 d specimens in water or sulfate were 0.487% and 0.518%, respectively, while those of 28 d specimens were 0.963% and 1.308%. The comparison shows that the 1 d specimen had significantly better deformation resistance under freeze–thaw than the 28 d specimen. After 225 freeze–thaw cycles, the water absorption rates of 1 d specimens were 1.95% and 1.64% in water and sulfate solution, respectively, while those of 28 d specimens were 2.20% and 1.83%. This indicates that freeze–thaw cycling has a greater effect on the pore structure of fully aged mortar than on early-age mortar (1 d). Therefore, MKPC mortar is suitable for the rapid repair of concrete structures in harsh environments. The results form a theoretical basis for winter emergency repair projects. They also further the understanding of the application of MKPC-based materials in extreme environments.
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Liu, Minghui, Aiguo Yin et Cong Wan. « Prediction on Ground Settlement Deformation and Influence of Urban Buildings in the Construction Process of Existing Tunnel Reconstruction ». Wireless Communications and Mobile Computing 2022 (16 mars 2022) : 1–10. http://dx.doi.org/10.1155/2022/1292988.
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Surface deformation is one of the key issues in urban tunnel construction control, regardless of the construction method. The study on ground settlement deformation and urban buildings in the construction process of existing tunnel reconstruction is not many at present; moreover, rebuilding projects for older tunnels have more complicated planting conditions and limited construction methods. In this study, the construction method and process characteristics of an existing structure are analyzed. In addition, the ground settlement deformations and building displacements during construction are monitored. The results reveal that the method of the Peck formula for predicting the ground settlement deformation and urban buildings of existing tunnel reconstruction is feasible and effective based on fitting curve by monitoring data. A finite element model is established. The results show that the simulation values of the ground deformation are consistent with the measured values. The differences between the simulated and measured values of the maximum ground surface sedimentation are 4.9% and 0.72% for single-sided excavation and bilateral excavation, respectively. The maximum building settlement is -9.6 mm in the single-sided excavation, the deformation rates remain within 0.1 mm/d, and the maximum width change of the building crack occurs during the demolition of the existing tunnel concrete in the single-sided excavation (with a value of 0.45 mm); subsequently, the building crack exhibits a decreasing trend, indicating that the crack is stable. The results can provide a reference for construction control for existing tunnels.
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Lesueur, G., A. Marciniak, H. Gilles, S. Girard, M. Laroche, T. Merlet et M. Queguiner. « Polarization Optical Sensor for Dynamical Deformation Measurements on 1-D or 2-D Mechanical Structures ». IEEE Photonics Technology Letters 21, no 18 (septembre 2009) : 1311–13. http://dx.doi.org/10.1109/lpt.2009.2023508.
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