Relevant bibliographies by topics / Hybrid variational formulation / Journal articles
To see the other types of publications on this topic, follow the link: Hybrid variational formulation.

Journal articles on the topic 'Hybrid variational formulation'

Author: Grafiati
Published: 13 February 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'Hybrid variational formulation.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Davi', G. "A hybrid displacement variational formulation of BEM for elastostatics." Engineering Analysis with Boundary Elements 10, no. 3 (January 1992): 219–24. http://dx.doi.org/10.1016/0955-7997(92)90005-r.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Jirousek, J. "Variational formulation of two complementary hybrid-Trefftz FE models." Communications in Numerical Methods in Engineering 9, no. 10 (October 1993): 837–45. http://dx.doi.org/10.1002/cnm.1640091007.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Lu, Pin, and O. Mahrenholtz. "A modified hybrid displacement variational formulation of BEM for elasticity." Mechanics Research Communications 20, no. 5 (September 1993): 425–29. http://dx.doi.org/10.1016/0093-6413(93)90034-l.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Cartier, J., and M. Peybernes. "Mixed Variational Formulation and Mixed-Hybrid Discretization of the Transport Equation." Transport Theory and Statistical Physics 39, no. 1 (January 13, 2010): 1–46. http://dx.doi.org/10.1080/00411450.2010.529630.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Gustafsson, N., J. Bojarova, and O. Vignes. "A hybrid variational ensemble data assimilation for the HIgh Resolution Limited Area Model (HIRLAM)." Nonlinear Processes in Geophysics 21, no. 1 (February 26, 2014): 303–23. http://dx.doi.org/10.5194/npg-21-303-2014.

Full text
Abstract:
Abstract. A hybrid variational ensemble data assimilation has been developed on top of the HIRLAM variational data assimilation. It provides the possibility of applying a flow-dependent background error covariance model during the data assimilation at the same time as full rank characteristics of the variational data assimilation are preserved. The hybrid formulation is based on an augmentation of the assimilation control variable with localised weights to be assigned to a set of ensemble member perturbations (deviations from the ensemble mean). The flow-dependency of the hybrid assimilation is demonstrated in single simulated observation impact studies and the improved performance of the hybrid assimilation in comparison with pure 3-dimensional variational as well as pure ensemble assimilation is also proven in real observation assimilation experiments. The performance of the hybrid assimilation is comparable to the performance of the 4-dimensional variational data assimilation. The sensitivity to various parameters of the hybrid assimilation scheme and the sensitivity to the applied ensemble generation techniques are also examined. In particular, the inclusion of ensemble perturbations with a lagged validity time has been examined with encouraging results.
APA, Harvard, Vancouver, ISO, and other styles
6

Bhatia, Anand K. "Scattering and Its Applications to Various Atomic Processes: Elastic Scattering, Resonances, Photoabsorption, Rydberg States, and Opacity of the Atmosphere of the Sun and Stellar Objects." Atoms 8, no. 4 (November 6, 2020): 78. http://dx.doi.org/10.3390/atoms8040078.

Full text
Abstract:
A scattering process can be a natural process or a process carried out in a laboratory. The scattering of particles from targets has resulted in important discoveries in physics. We discuss various scattering theories of electrons and positrons and their applications to elastic scattering, resonances, photoabsorption, excitation, and solar and stellar atmospheres. Among the most commonly employed approaches are the Kohn variational principle, close-coupling approximation, method of polarized orbitals, R-matrix formulation, and hybrid theory. In every formulation, an attempt is made to include exchange, long-range and short-range correlations, and to make the approach variationally correct. The present formulation, namely, hybrid theory, which is discussed in greater detail compared to other approximations, includes exchange, long-range correlations, and short-range correlations at the same time, and is variationally correct. It was applied to calculate the phase shifts for elastic scattering, the resonance parameters of two-electron systems, photoabsorption in two-electron systems, excitation of atomic hydrogen by an electron and positron impact, and to study the opacity of the Sun’s atmosphere. Calculations of polarizabilities, Rydberg states, and bound states of atoms are also discussed.
APA, Harvard, Vancouver, ISO, and other styles
7

Felippa, Carlos A. "Parametrized multifield variational principles in elasticity: II. Hybrid functionals and the free formulation." Communications in Applied Numerical Methods 5, no. 2 (February 1989): 89–98. http://dx.doi.org/10.1002/cnm.1630050205.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Ma, Yongqi, Yankai Zhou, Yi Dong, and Wei Feng. "Hybrid Natural Element Method for Elastic Large Deformation Problems." International Journal of Applied Mechanics 08, no. 04 (June 2016): 1650044. http://dx.doi.org/10.1142/s1758825116500447.

Full text
Abstract:
Elastic large deformation analysis based on the hybrid natural element method (HNEM) is presented in this paper. The natural neighbor interpolation is adopted to construct the shape functions for the HNEM. The incremental formulation of Hellinger–Reissner variational principle is used to derive discrete system of incremental equations under the total Lagrangian formulation. And the Newton-Raphson iteration is applied to solve these incremental equations. Compared with the natural element method (NEM), the HNEM can directly obtain nodal stresses of higher precision, which will bring advantage in the iteration process and improve computational efficiency in solving elastic large deformation problems. Some numerical examples demonstrate the validity of the HNEM for elastic large deformation problems.
APA, Harvard, Vancouver, ISO, and other styles
9

Kotsuki, Shunji, and Craig H. Bishop. "Implementing Hybrid Background Error Covariance into the LETKF with Attenuation-Based Localization: Experiments with a Simplified AGCM." Monthly Weather Review 150, no. 1 (January 2022): 283–302. http://dx.doi.org/10.1175/mwr-d-21-0174.1.

Full text
Abstract:
Abstract Recent numerical weather prediction systems have significantly improved medium-range forecasts by implementing hybrid background error covariance, for which climatological (static) and ensemble-based (flow-dependent) error covariance are combined. While the hybrid approach has been investigated mainly in variational systems, this study aims at exploring methods for implementing the hybrid approach for the local ensemble transform Kalman filter (LETKF). Following Kretschmer et al., the present study constructed hybrid background error covariance by adding collections of climatological perturbations to the forecast ensemble. In addition, this study proposes a new localization method that attenuates the ensemble perturbation (Z-localization) instead of inflating observation error variance (R-localization). A series of experiments with a simplified global atmospheric model revealed that the hybrid LETKF resulted in smaller forecast errors than the LETKF, especially in sparsely observed regions. Due to the larger ensemble enabled by the hybrid approach, optimal localization length scales for the hybrid LETKF were larger than those for the LETKF. With the LETKF, the Z-localization resulted in similar forecast errors as the R-localization. However, Z-localization has an advantage in enabling us to apply different localization scales for flow-dependent perturbation and climatological static perturbations with the hybrid LETKF. The optimal localization for climatological perturbations was slightly larger than that for flow-dependent perturbations. This study also proposes optimal eigendecomposition (OED) ETKF formulation to reduce computational costs. The computational expense of the OED ETKF formulation became significantly smaller than that of standard ETKF formulations as the number of climatological perturbations was increased beyond a few hundred.
APA, Harvard, Vancouver, ISO, and other styles
10

Zhang, Bin, Apostolos S. Papageorgiou, and John L. Tassoulas. "A hybrid numerical technique, combining the finite-element and boundary-element methods, for modeling the 3D response of 2D scatterers." Bulletin of the Seismological Society of America 88, no. 4 (August 1, 1998): 1036–50. http://dx.doi.org/10.1785/bssa0880041036.

Full text
Abstract:
Abstract A hybrid formulation of the 2.5D elastodynamic scattering problem combining the finite-element method and boundary integral equation method is presented and validated. The formulation of the 2.5D boundary integral equation method that is used was presented in detail by Papageorgiou and Pei (1998) and is an extension of the discrete wavenumber boundary integral equation method originally proposed by Kawase (1988) for 2D scattering problems. Modeling of the wave field in the domain of the scatterer is based on the variational principle of virtual displacements, and discretization of the domain is accomplished using the finite-element method. The formulation may be used to study the wave field in models of sedimentary deposits (e.g., valleys) or topography (e.g., canyons or ridges) with a 2D variation in structure but obliquely incident plane waves. The hybrid method exploits the versatility of the finite element method for modeling the scatterer and the effectiveness of the boundary integral equation method for taking care of the radiation condition in the half-space. The advantage of the 2.5D formulation is that it provides the means for calculations of 3D wave fields in scattering problems by requiring a storage comparable to that of the corresponding 2D calculations.
APA, Harvard, Vancouver, ISO, and other styles
11

Botha, M. M., and J. M. Jin. "On the Variational Formulation of Hybrid Finite Element-Boundary Integral Techniques for Electromagnetic Analysis." IEEE Transactions on Antennas and Propagation 52, no. 11 (November 2004): 3037–47. http://dx.doi.org/10.1109/tap.2004.835140.

Full text
APA, Harvard, Vancouver, ISO, and other styles
12

Liu, G. R., and Y. T. Gu. "Coupling of element free Galerkin and hybrid boundary element methods using modified variational formulation." Computational Mechanics 26, no. 2 (August 17, 2000): 166–73. http://dx.doi.org/10.1007/s004660000164.

Full text
APA, Harvard, Vancouver, ISO, and other styles
13

Yahia, Mohamed, Jun Wu Tao, and Hedi Sakli. "COMPLEX RECTANGULAR FILTER DESIGN USING HYBRID FINITE ELEMENT METHOD AND MODIFIED MULTIMODAL VARIATIONAL FORMULATION." Progress In Electromagnetics Research C 44 (2013): 55–66. http://dx.doi.org/10.2528/pierc13072904.

Full text
APA, Harvard, Vancouver, ISO, and other styles
14

Sze, K. Y. "Finite element formulation by parametrized hybrid variational principles: Variable stiffness and removal of locking." International Journal for Numerical Methods in Engineering 37, no. 16 (August 30, 1994): 2797–818. http://dx.doi.org/10.1002/nme.1620371607.

Full text
APA, Harvard, Vancouver, ISO, and other styles
15

Barhorst, A. A., and L. J. Everett. "Contact/Impact in Hybrid Parameter Multiple Body Mechanical Systems." Journal of Dynamic Systems, Measurement, and Control 117, no. 4 (December 1, 1995): 559–69. http://dx.doi.org/10.1115/1.2801115.

Full text
Abstract:
The multiple motion regime (free/constrained) dynamics of hybrid parameter multiple body (HPMB) systems is addressed. Impact response has characteristically been analyzed using impulse-momentum techniques. Unfortunately, the classical methods for modeling complex HPMB systems are energy based and have proven ineffectual at modeling impact. The problems are exacerbated by the problematic nature of time varying constraint conditions. This paper outlines the reformulation of a recently developed HPMB system modeling methodology into an impulse-momentum formulation, which systematically handles the constraints and impact. The starting point for this reformulation is a variational calculus based methodology. The variational roots of the methodology allows rigorous equation formulation which includes the complete nonlinear hybrid differential equations and boundary conditions. Because the methodology presented in this paper is formulated in the constraint-free subspace of the configuration space, both holonomic and nonholonomic constraints are automatically satisfied. As a result, the constraint-addition/deletion algorithms are not needed. Generalized forces of constraint can be directly calculated via the methodology, so the condition for switching from one motion regime to another is readily determined. The resulting equations provides a means to determine after impact velocities (and velocity fields for distributed bodies) which provide the after collision initial conditions. Finally the paper demonstrates, via example, how to apply the methodology to contact/impact in robotic manipulators and structural systems.
APA, Harvard, Vancouver, ISO, and other styles
16

Halliday, P. J., and K. Grosh. "Dynamic Response of Complex Structural Intersections Using Hybrid Methods." Journal of Applied Mechanics 66, no. 3 (September 1, 1999): 653–59. http://dx.doi.org/10.1115/1.2791518.

Full text
Abstract:
A novel application of Lagrange multipliers to couple domains modeled independently with linear elastodynamic and reduced-order theories is presented herein. This method is developed from a variational formulation of the continuous problem and is easily implemented within a finite element code. Applications include, but are not limited to, modeling of inhomogeneities such as joints, cracks, holes, and welds within a frame-like structure. Results from this method compare well with a full elastodynamic discretization and existing methods for modeling such problems.
APA, Harvard, Vancouver, ISO, and other styles
17

Qin, Qing-Hua. "Trefftz Finite Element Method and Its Applications." Applied Mechanics Reviews 58, no. 5 (September 1, 2005): 316–37. http://dx.doi.org/10.1115/1.1995716.

Full text
Abstract:
This paper presents an overview of the Trefftz finite element and its application in various engineering problems. Basic concepts of the Trefftz method are discussed, such as T-complete functions, special purpose elements, modified variational functionals, rank conditions, intraelement fields, and frame fields. The hybrid-Trefftz finite element formulation and numerical solutions of potential flow problems, plane elasticity, linear thin and thick plate bending, transient heat conduction, and geometrically nonlinear plate bending are described. Formulations for all cases are derived by means of a modified variational functional and T-complete solutions. In the case of geometrically nonlinear plate bending, exact solutions of the Lamé-Navier equations are used for the in-plane intraelement displacement field, and an incremental form of the basic equations is adopted. Generation of elemental stiffness equations from the modified variational principle is also discussed. Some typical numerical results are presented to show the application of the finite element approach. Finally, a brief summary of the approach is provided and future trends in this field are identified. There are 151 references cited in this revised article.
APA, Harvard, Vancouver, ISO, and other styles
18

Wang, Ke Yong. "A Four-Node Hybrid-Trefftz Plane Elasticity Element with Fundamental Analytical Solutions." Advanced Materials Research 279 (July 2011): 194–99. http://dx.doi.org/10.4028/www.scientific.net/amr.279.194.

Full text
Abstract:
A new four-node hybrid-Trefftz element is developed for plane elasticity problems. From the Airy stress function, the fundamental analytical solutions of the governing equation are derived as Trefftz functions for the intra-element (Trefftz) displacement field. Together with an independent frame displacement field along the element boundary, the element formulation is then constructed following the modified variational functional. Several numerical examples indicate that the proposed element exhibits good performance.
APA, Harvard, Vancouver, ISO, and other styles
19

Kleist, Daryl T., and Kayo Ide. "An OSSE-Based Evaluation of Hybrid Variational–Ensemble Data Assimilation for the NCEP GFS. Part II: 4DEnVar and Hybrid Variants." Monthly Weather Review 143, no. 2 (February 1, 2015): 452–70. http://dx.doi.org/10.1175/mwr-d-13-00350.1.

Full text
Abstract:
Abstract This work describes the formulation of a hybrid four-dimensional ensemble--variational (4DEnVar) algorithm and initialization options utilized within the National Centers for Environmental Prediction global data assimilation system. Initialization schemes that are proposed for use are the tangent-linear normal mode constraint, weak constraint digital filter, and a combination thereof. An observing system simulation experiment is carried out to evaluate the impact of utilizing hybrid 4DEnVar with various initialization techniques. The experiments utilize a dual-resolution configuration, where the ensemble is run at roughly half the resolution of the deterministic component. It is found that by going from 3D to 4D, analysis error is reduced for most variables and levels. The inclusion of a time-invariant static covariance when used without a normal mode–based strong constraint is found to have a small, positive impact on the analysis. The experiments show that the weak constraint digital filter degrades the quality of analysis, due to the use of hourly states to prescribe high-frequency noise. It is found that going from 3D to 4D ensemble covariances has a relatively larger impact in the extratropics, whereas the original inclusion of ensemble-based covariances was found to have the largest impact in the tropics. The improvements found in going from 3D to 4D covariances in the hybrid EnVar formulation are not as large as was found in Part I from the original introduction of the hybrid algorithm. The analyses generated by the 4D hybrid scheme are found to yield slightly improved extratropical height and wind forecasts, with smaller impacts on other variables and in general in the tropics.
APA, Harvard, Vancouver, ISO, and other styles
20

NICOLAU, J. B., and E. VAN GROESEN. "HYBRID ANALYTIC-NUMERIC METHOD FOR LIGHT THROUGH A BOUNDED PLANAR DIELECTRIC STRUCTURE." Journal of Nonlinear Optical Physics & Materials 14, no. 02 (June 2005): 161–76. http://dx.doi.org/10.1142/s021886350500261x.

Full text
Abstract:
We present a hybrid analytic-numeric method to calculate the transmission and reflection of light that is fluxed into a bounded complicated optical structure surrounded by air. The solution is obtained by numerical calculations inside a square containing the structure and by analytical calculations outside the square. For solving the 2D Helmholtz equation we formulate transparent-influx boundary conditions (TIBCs) on the boundaries of the square; these are incorporated into a variational formulation of the Helmholtz equation to obtain a FEM-implementation for the interior calculations.
APA, Harvard, Vancouver, ISO, and other styles
21

Oddo, Paolo, Andrea Storto, Srdjan Dobricic, Aniello Russo, Craig Lewis, Reiner Onken, and Emanuel Coelho. "A hybrid variational-ensemble data assimilation scheme with systematic error correction for limited-area ocean models." Ocean Science 12, no. 5 (October 14, 2016): 1137–53. http://dx.doi.org/10.5194/os-12-1137-2016.

Full text
Abstract:
Abstract. A hybrid variational-ensemble data assimilation scheme to estimate the vertical and horizontal parts of the background error covariance matrix for an ocean variational data assimilation system is presented and tested in a limited-area ocean model implemented in the western Mediterranean Sea. An extensive data set collected during the Recognized Environmental Picture Experiments conducted in June 2014 by the Centre for Maritime Research and Experimentation has been used for assimilation and validation. The hybrid scheme is used to both correct the systematic error introduced in the system from the external forcing (initialisation, lateral and surface open boundary conditions) and model parameterisation, and improve the representation of small-scale errors in the background error covariance matrix. An ensemble system is run offline for further use in the hybrid scheme, generated through perturbation of assimilated observations. Results of four different experiments have been compared. The reference experiment uses the classical stationary formulation of the background error covariance matrix and has no systematic error correction. The other three experiments account for, or not, systematic error correction and hybrid background error covariance matrix combining the static and the ensemble-derived errors of the day. Results show that the hybrid scheme when used in conjunction with the systematic error correction reduces the mean absolute error of temperature and salinity misfit by 55 and 42 % respectively, versus statistics arising from standard climatological covariances without systematic error correction.
APA, Harvard, Vancouver, ISO, and other styles
22

Dumont, N. A. "The Hybrid Boundary Element Method: An Alliance Between Mechanical Consistency and Simplicity." Applied Mechanics Reviews 42, no. 11S (November 1, 1989): S54—S63. http://dx.doi.org/10.1115/1.3152408.

Full text
Abstract:
The most important features of a new numerical method are outlined. The mechanical, or variational consistency of the hybrid finite element method is extended to the conventional boundary element formulation, giving rise to naturally established symmetric force-displacement relations. The computational effort for the complete solution of a given problem, according to this method, is in some cases only a small fraction of the effort needed with traditional methods. This paper also outlines briefly the types of analyses which may be advantageously performed with this new method, many of which are already being implemented by the author and co-workers. Some numerical examples are provided.
APA, Harvard, Vancouver, ISO, and other styles
23

Liu, Chengsi, and Ming Xue. "Relationships among Four-Dimensional Hybrid Ensemble–Variational Data Assimilation Algorithms with Full and Approximate Ensemble Covariance Localization." Monthly Weather Review 144, no. 2 (February 1, 2016): 591–606. http://dx.doi.org/10.1175/mwr-d-15-0203.1.

Full text
Abstract:
Abstract Ensemble–variational data assimilation algorithms that can incorporate the time dimension (four-dimensional or 4D) and combine static and ensemble-derived background error covariances (hybrid) are formulated in general forms based on the extended control variable and the observation-space-perturbation approaches. The properties and relationships of these algorithms and their approximated formulations are discussed. The main algorithms discussed include the following: 1) the standard ensemble 4DVar (En4DVar) algorithm incorporating ensemble-derived background error covariance through the extended control variable approach, 2) the 4DEnVar neglecting the time propagation of the extended control variable (4DEnVar-NPC), 3) the 4D ensemble–variational algorithm based on observation space perturbation (4DEnVar), and 4) the 4DEnVar with no propagation of covariance localization (4DEnVar-NPL). Without the static background error covariance term, none of the algorithms requires the adjoint model except for En4DVar. Costly applications of the tangent linear model to localized ensemble perturbations can be avoided by making the NPC and NPL approximations. It is proven that En4DVar and 4DEnVar are mathematically equivalent, while 4DEnVar-NPC and 4DEnVar-NPL are mathematically equivalent. Such equivalences are also demonstrated by single-observation assimilation experiments with a 1D linear advection model. The effects of the non-flow-following or stationary localization approximations are also examined through the experiments. All of the above algorithms can include the static background error covariance term to establish a hybrid formulation. When the static term is included, all algorithms will require a tangent linear model and an adjoint model. The first guess at appropriate time (FGAT) approximation is proposed to avoid the tangent linear and adjoint models. Computational costs of the algorithms are also discussed.
APA, Harvard, Vancouver, ISO, and other styles
24

Wu, Wenan, and Hong Zheng. "Mixed multiscale three-node triangular elements for incompressible elasticity." Engineering Computations 36, no. 8 (October 7, 2019): 2859–86. http://dx.doi.org/10.1108/ec-10-2018-0488.

Full text
Abstract:
Purpose This study aims to introduce the hybrid finite element (FE) – meshfree method and multiscale variational principle into the traditional mixed FE formulation, leading to a stable mixed formulation for incompressible linear elasticity which circumvents the need to satisfy inf-sup condition. Design/methodology/approach Using the hybrid FE–meshfree method, the displacement and pressure are interpolated conveniently with the same order so that a continuous pressure field can be obtained with low-order elements. The multiscale variational principle is then introduced into the Galerkin form to obtain stable and convergent results. Findings The present method is capable of overcoming volume locking and does not exhibit unphysical oscillations near the incompressible limit. Moreover, there are no extra unknowns introduced in the present method because the fine-scale unknowns are eliminated using the static condensation technique, and there is no need to evaluate any user-defined stability parameter as the classical stabilization methods do. The shape functions constructed in the present model possess continuous derivatives at nodes, which gives a continuous and more precise stress field with no need of an additional smooth process. The shape functions in the present model also possess the Kronecker delta property, so that it is convenient to impose essential boundary conditions. Originality/value The proposed model can be implemented easily. Its convergence rates and accuracy in displacement, energy and pressure are even comparable to those of second-order mixed elements.
APA, Harvard, Vancouver, ISO, and other styles
25

Li, Xiaolin. "Numerical Solution of Solid Mechanics Problems Using a Boundary-Only and Truly Meshless Method." Mathematical Problems in Engineering 2012 (2012): 1–16. http://dx.doi.org/10.1155/2012/298903.

Full text
Abstract:
Combining the hybrid displacement variational formulation and the radial basis point interpolation, a truly meshless and boundary-only method is developed in this paper for the numerical solution of solid mechanics problems in two and three dimensions. In this method, boundary conditions can be applied directly and easily. Besides, it is truly meshless, that is, it only requires nodes generated on the boundary of the domain, and does not require any element either for variable interpolation or for numerical integration. Some numerical examples are presented to demonstrate the efficiency of the method.
APA, Harvard, Vancouver, ISO, and other styles
26

Kulikov, G. M., and S. V. Plotnikova. "Exact geometry SaS solid-shell element for 3D stress analysis of FGM piezoelectric structures." Curved and Layered Structures 5, no. 1 (June 1, 2018): 116–35. http://dx.doi.org/10.1515/cls-2018-0009.

Full text
Abstract:
Abstract A hybrid-mixed functionally graded material (FGM) piezoelectric four-node solid-shell element through the sampling surfaces (SaS) method is proposed. The SaS formulation is based on choosing inside the shell N SaS parallel to the middle surface in order to introduce the displacements and electric potentials of these surfaces as fundamental shell unknowns. Such choice of unknowns with the use of Lagrange polynomials of degree N-1 in through-thickness interpolations of the displacements, strains, electric potential, electric field and material properties leads to a robust FGM piezoelectric shell formulation. The inner SaS are located at Chebyshev polynomial nodes that make it possible to minimize uniformly the error due to Lagrange interpolation. To implement the effective analytical integration throughout the element, the extended assumed natural strain (ANS) method is employed. As a result, the piezoelectric four-node solid-shell element exhibits a superior performance in the case of coarse meshes. To circumvent shear and membrane locking, the hybrid stress-strain solid-shell formulation via the Hu-Washizu variational principle is employed. The developed solid-shell element could be useful for the 3D stress analysis of FGMstructures because the SaS method allows obtaining the solutions with a prescribed accuracy, which asymptotically approach the exact solutions of electroelasticity as the number of SaS tends to infinity.
APA, Harvard, Vancouver, ISO, and other styles
27

Hua, X., and C. W. S. To. "Simple and Efficient Tetrahedral Finite Elements With Rotational Degrees of Freedom for Solid Modeling." Journal of Computing and Information Science in Engineering 7, no. 4 (July 29, 2007): 382–93. http://dx.doi.org/10.1115/1.2798120.

Full text
Abstract:
A mixed variational principle and derivation of two simple and efficient tetrahedral finite elements with rotational degrees of freedom (DOF) are presented. Each element has four nodes. Every node has six DOF, which include three translational and three rotational DOF. Each element is capable of providing six rigid-body modes. The rotational DOF are based on the displacement formulation, while the translational DOF are hinged on the hybrid strain Hellinger–Reissner functional. Explicit expressions for stiffness matrices are obtained. Element performance has been evaluated with benchmark problems, indicating that they have superior accuracy compared with other lower-order tetrahedral elements.
APA, Harvard, Vancouver, ISO, and other styles
28

Yaremchuk, Max, Dmitri Nechaev, and Chudong Pan. "A Hybrid Background Error Covariance Model for Assimilating Glider Data into a Coastal Ocean Model." Monthly Weather Review 139, no. 6 (June 1, 2011): 1879–90. http://dx.doi.org/10.1175/2011mwr3510.1.

Full text
Abstract:
Abstract A hybrid background error covariance (BEC) model for three-dimensional variational data assimilation of glider data into the Navy Coastal Ocean Model (NCOM) is introduced. Similar to existing atmospheric hybrid BEC models, the proposed model combines low-rank ensemble covariances with the heuristic Gaussian-shaped covariances to estimate forecast error statistics. The distinctive features of the proposed BEC model are the following: (i) formulation in terms of inverse error covariances, (ii) adaptive determination of the rank m of with information criterion based on the innovation error statistics, (iii) restriction of the heuristic covariance operator to the null space of , and (iv) definition of the BEC magnitudes through separate analyses of the innovation error statistics in the state space and the null space of . The BEC model is validated by assimilation experiments with simulated and real data obtained during a glider survey of the Monterey Bay in August 2003. It is shown that the proposed hybrid scheme substantially improves the forecast skill of the heuristic covariance model.
APA, Harvard, Vancouver, ISO, and other styles
29

Kulikov, GM, SV Plotnikova, and E. Carrera. "Modeling and analysis of spiral actuators by exact geometry piezoelectric solid-shell elements." Journal of Intelligent Material Systems and Structures 31, no. 1 (October 14, 2019): 53–70. http://dx.doi.org/10.1177/1045389x19880014.

Full text
Abstract:
An exact geometry four-node piezoelectric solid-shell element through the sampling surfaces formulation is proposed. The sampling surfaces formulation is based on choosing inside the shell N – 2 sampling surfaces parallel to the middle surface and located at Chebyshev polynomial nodes to introduce the displacements and electric potentials of these surfaces as fundamental shell unknowns. The bottom and top surfaces are also included into a set of sampling surfaces. Such choice of unknowns with the use of Lagrange polynomials of degree N – 1 in the through-the-thickness interpolations of displacements, strains, electric potential, and electric field yields a robust piezoelectric shell formulation. To implement efficient analytical integration throughout the solid-shell element, the extended assumed natural strain method is employed. The developed hybrid-mixed four-node piezoelectric solid-shell element is based on the Hu-Washizu variational principle and shows the excellent performance for coarse mesh configurations. It can be useful for the 3D stress analysis of piezoelectric shells with variable curvatures, in particular for the modeling and analysis of spiral actuators.
APA, Harvard, Vancouver, ISO, and other styles
30

Kuhl, David D., Thomas E. Rosmond, Craig H. Bishop, Justin McLay, and Nancy L. Baker. "Comparison of Hybrid Ensemble/4DVar and 4DVar within the NAVDAS-AR Data Assimilation Framework." Monthly Weather Review 141, no. 8 (July 25, 2013): 2740–58. http://dx.doi.org/10.1175/mwr-d-12-00182.1.

Full text
Abstract:
Abstract The effect on weather forecast performance of incorporating ensemble covariances into the initial covariance model of the four-dimensional variational data assimilation (4D-Var) Naval Research Laboratory Atmospheric Variational Data Assimilation System-Accelerated Representer (NAVDAS-AR) is investigated. This NAVDAS-AR-hybrid scheme linearly combines the static NAVDAS-AR initial background error covariance with a covariance derived from an 80-member flow-dependent ensemble. The ensemble members are generated using the ensemble transform technique with a (three-dimensional variational data assimilation) 3D-Var-based estimate of analysis error variance. The ensemble covariances are localized using an efficient algorithm enabled via a separable formulation of the localization matrix. The authors describe the development and testing of this scheme, which allows for assimilation experiments using differing linear combinations of the static and flow-dependent background error covariances. The tests are performed for two months of summer and two months of winter using operational model resolution and the operational observational dataset, which is dominated by satellite observations. Results show that the hybrid mode data assimilation scheme significantly reduces the forecast error across a wide range of variables and regions. The improvements were particularly pronounced for tropical winds. The verification against radiosondes showed a greater than 0.5% reduction in vector wind RMS differences in areas of statistical significance. The verification against self-analysis showed a greater than 1% reduction from verifying against analyses between 2- and 5-day lead time at all eight vertical levels examined in areas of statistical significance. Using the Navy's summary of verification results, the Navy Operational Global Atmospheric Prediction System (NOGAPS) scorecard, the improvements resulted in a score (+1) that justifies a major system upgrade.
APA, Harvard, Vancouver, ISO, and other styles
31

Wu, Wan-Shu, David F. Parrish, Eric Rogers, and Ying Lin. "Regional Ensemble–Variational Data Assimilation Using Global Ensemble Forecasts." Weather and Forecasting 32, no. 1 (January 4, 2017): 83–96. http://dx.doi.org/10.1175/waf-d-16-0045.1.

Full text
Abstract:
Abstract At the National Centers for Environmental Prediction, the global ensemble forecasts from the ensemble Kalman filter scheme in the Global Forecast System are applied in a regional three-dimensional (3D) and a four dimensional (4D) ensemble–variational (EnVar) data assimilation system. The application is a one-way variational method using hybrid static and ensemble error covariances. To enhance impact, three new features have been added to the existing EnVar system in the Gridpoint Statistical Interpolation (GSI). First, the constant coefficients that assign relative weight between the ensemble and static background error are now allowed to vary in the vertical. Second, a new formulation is introduced for the ensemble contribution to the analysis surface pressure. Finally, in order to make use of the information in the ensemble mean that is disregarded in the existing EnVar in GSI, the trajectory correction, a novel approach, is introduced. Relative to the application of a 3D variational data assimilation algorithm, a clear positive impact on 1–3-day forecasts is realized when applying 3DEnVar analyses in the North American Mesoscale Forecast System (NAM). The 3DEnVar DA system was operationally implemented in the NAM Data Assimilation System in August 2014. Application of a 4DEnVar algorithm is shown to further improve forecast accuracy relative to the 3DEnVar. The approach described in this paper effectively combines contributions from both the regional and the global forecast systems to produce the initial conditions for the regional NAM system.
APA, Harvard, Vancouver, ISO, and other styles
32

DRONIOU, JEROME, ROBERT EYMARD, THIERRY GALLOUET, and RAPHAELE HERBIN. "GRADIENT SCHEMES: A GENERIC FRAMEWORK FOR THE DISCRETISATION OF LINEAR, NONLINEAR AND NONLOCAL ELLIPTIC AND PARABOLIC EQUATIONS." Mathematical Models and Methods in Applied Sciences 23, no. 13 (September 16, 2013): 2395–432. http://dx.doi.org/10.1142/s0218202513500358.

Full text
Abstract:
Gradient schemes are nonconforming methods written in discrete variational formulation and based on independent approximations of functions and gradients, using the same degrees of freedom. Previous works showed that several well-known methods fall in the framework of gradient schemes. Four properties, namely coercivity, consistency, limit-conformity and compactness, are shown in this paper to be sufficient to prove the convergence of gradient schemes for linear and nonlinear elliptic and parabolic problems, including the case of nonlocal operators arising for example in image processing. We also show that the schemes of the Hybrid Mimetic Mixed family, which include in particular the Mimetic Finite Difference schemes, may be seen as gradient schemes meeting these four properties, and therefore converges for the class of above-mentioned problems.
APA, Harvard, Vancouver, ISO, and other styles
33

Ali, Bagh, Rizwan Ali Naqvi, Dildar Hussain, Omar M. Aldossary, and Sajjad Hussain. "Magnetic Rotating Flow of a Hybrid Nano-Materials Ag-MoS2 and Go-MoS2 in C2H6O2-H2O Hybrid Base Fluid over an Extending Surface Involving Activation Energy: FE Simulation." Mathematics 8, no. 10 (October 9, 2020): 1730. http://dx.doi.org/10.3390/math8101730.

Full text
Abstract:
Numeric simulations are performed for a comparative study of magnetohydrodynamic (MHD) rotational flow of hybrid nanofluids (MoS2-Ag/ethyleneglycol-water (50–50%) and MoS2-Go/ethyleneglycol-water (50–50%)) over a horizontally elongated plane sheet. The principal objective is concerned with the enhancement of thermal transportation. The three-dimensional formulation governing the conservation of mass, momentum, energy, and concentration is transmuted into two-dimensional partial differentiation by employing similarity transforms. The resulting set of equations (PDEs) is then solved by variational finite element procedure coded in Matlab script. An intensive computational run is carried out for suitable ranges of the particular quantities of influence. The primary velocity component decreases monotonically and the magnitude of secondary velocity component diminishes significantly when magnetic parameter, rotational parameter, and unsteadiness parameter are incremented. Both the primary and secondary velocities are smaller in values for the hybrid phase Ag-MoS2 than that of hybrid phase Go-MoS2 but the nanoparticle concentration and temperature are higher for hybrid phase Ag-MoS2. The increased values of parameters for thermophoresis, Brownian motion, shape factor, and volume fraction of ϕ2 made significant improvement in the temperature of the two phases of nano liquids. Results are also computed for the coefficients of skin friction(x, y-directions), Nusselt number, and Sherwood number. The present findings manifest reasonable comparison to their existing counterparts. Some of the practical engineering applications of the present analysis may be found in high-temperature nanomaterial processing technology, crystal growing, extrusion processes, manufacturing and rolling of polymer sheets, academic research, lubrication processes, and polymer industry.
APA, Harvard, Vancouver, ISO, and other styles
34

Nikolaidis, Pavlos. "Variational Bayes to Accelerate the Lagrange Multipliers towards the Dual Optimization of Reliability and Cost in Renewable Energy Systems." Algorithms 16, no. 1 (December 29, 2022): 20. http://dx.doi.org/10.3390/a16010020.

Full text
Abstract:
Renewable energy sources are constantly increasing in the modern power systems. Due to their intermittent and uncertain potential, increased spinning reserve requirements are needed to conserve the reliability. On the other hand, each action towards efficiency improvement and cost reduction contradicts the participation of variable resources in the energy mix, requiring more accurate tools for optimal unit commitment. By increasing the renewable contribution, not only does the overall system inertia decrease with the decreasing conventional generation, but more generators that are expensive are also introduced. This work provides a radically different approach towards a tractable optimization task based on the framework of Lagrange relaxation and variational Bayes. Following a dual formulation of reliability and cost, the Lagrange multipliers are accelerated via a machine learning mechanism, namely, variational Bayesian inference. The novelty in the proposed approach stems from the employed acquisition function and the effect of the Gaussian process. The obtained results show great improvements compared with the Lagrange relaxation alternative, which can reach over USD 1 M in production cost credits at the least number of function evaluations. The proposed hybrid method promises global solutions relying on a proper acquisition function that is able to move towards regions with minimum objective value and maximum uncertainty.
APA, Harvard, Vancouver, ISO, and other styles
35

Wu, Chih-Ping, and Shuang Ding. "Coupled thermo-electro-mechanical analysis of sandwiched hybrid functionally graded elastic material and piezoelectric plates under thermal loads." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 10 (May 18, 2017): 1851–70. http://dx.doi.org/10.1177/0954406217710674.

Full text
Abstract:
Based on Reissner’s mixed variational theorem, a weak-form formulation of finite layer methods is developed for the three-dimensional coupled thermo-electro-mechanical analysis of simply-supported, functionally graded elastic material plates integrated with surface-bonded piezoelectric layers and under thermal loads. The material properties of the functionally graded elastic material core are assumed to obey the power-law distributions varying through-the-thickness coordinate of the core according to the volume fractions of the constituents, and those of the functionally graded elastic material core and piezoelectric face sheets are also temperature dependent. The effective material properties of the functionally graded elastic material are estimated using the Mori-Tanaka scheme. Two different thermal conditions, i.e. the convection conditions and specified temperature conditions, on the top and bottom surfaces of the plate are considered. The accuracies and convergence rates of the finite layer methods with various orders used for expanding the elastic and electric variables in the thickness direction are assessed by comparing their solutions with the exact three-dimensional ones available in the literature.
APA, Harvard, Vancouver, ISO, and other styles
36

Wang, Xuguang, and Ting Lei. "GSI-Based Four-Dimensional Ensemble–Variational (4DEnsVar) Data Assimilation: Formulation and Single-Resolution Experiments with Real Data for NCEP Global Forecast System." Monthly Weather Review 142, no. 9 (September 2014): 3303–25. http://dx.doi.org/10.1175/mwr-d-13-00303.1.

Full text
Abstract:
A four-dimensional (4D) ensemble–variational data assimilation (DA) system (4DEnsVar) was developed, building upon the infrastructure of the gridpoint statistical interpolation (GSI)-based hybrid DA system. 4DEnsVar used ensemble perturbations valid at multiple time periods throughout the DA window to estimate 4D error covariances during the variational minimization, avoiding the tangent linear and adjoint of the forecast model. The formulation of its implementation in GSI was described. The performance of the system was investigated by evaluating the global forecasts and hurricane track forecasts produced by the NCEP Global Forecast System (GFS) during the 5-week summer period assimilating operational conventional and satellite data. The newly developed system was used to address a few questions regarding 4DEnsVar. 4DEnsVar in general improved upon its 3D counterpart, 3DEnsVar. At short lead times, the improvement over the Northern Hemisphere extratropics was similar to that over the Southern Hemisphere extratropics. At longer lead times, 4DEnsVar showed more improvement in the Southern Hemisphere than in the Northern Hemisphere. The 4DEnsVar showed less impact over the tropics. The track forecasts of 16 tropical cyclones initialized by 4DEnsVar were more accurate than 3DEnsVar after 1-day forecast lead times. The analysis generated by 4DEnsVar was more balanced than 3DEnsVar. Case studies showed that increments from 4DEnsVar using more frequent ensemble perturbations approximated the increments from direct, nonlinear model propagation better than using less frequent ensemble perturbations. Consistently, the performance of 4DEnsVar including both the forecast accuracy and the balances of analyses was in general degraded when less frequent ensemble perturbations were used. The tangent linear normal mode constraint had positive impact for global forecast but negative impact for TC track forecasts.
APA, Harvard, Vancouver, ISO, and other styles
37

Bunoiu, Renata, Giuseppe Cardone, and Sergey A. Nazarov. "Scalar problems in junctions of rods and a plate." ESAIM: Mathematical Modelling and Numerical Analysis 52, no. 2 (March 2018): 481–508. http://dx.doi.org/10.1051/m2an/2017047.

Full text
Abstract:
In this work we deal with a scalar spectral mixed boundary value problem in a spacial junction of thin rods and a plate. Constructing asymptotics of the eigenvalues, we employ two equipollent asymptotic models posed on the skeleton of the junction, that is, a hybrid domain. We, first, use the technique of self-adjoint extensions and, second, we impose algebraic conditions at the junction points in order to compile a problem in a function space with detached asymptotics. The latter problem is involved into a symmetric generalized Green formula and, therefore, admits the variational formulation. In comparison with a primordial asymptotic procedure, these two models provide much better proximity of the spectra of the problems in the spacial junction and in its skeleton. However, they exhibit the negative spectrum of finite multiplicity and for these “parasitic” eigenvalues we derive asymptotic formulas to demonstrate that they do not belong to the service area of the developed asymptotic models.
APA, Harvard, Vancouver, ISO, and other styles
38

Norouzzadeh, Amir, Mohammad Faraji Oskouie, Reza Ansari, and Hessam Rouhi. "Integral and differential nonlocal micromorphic theory." Engineering Computations 37, no. 2 (August 19, 2019): 566–90. http://dx.doi.org/10.1108/ec-01-2019-0008.

Full text
Abstract:
Purpose This paper aims to combine Eringen’s micromorphic and nonlocal theories and thus develop a comprehensive size-dependent beam model capable of capturing the effects of micro-rotational/stretch/shear degrees of freedom of material particles and nonlocality simultaneously. Design/methodology/approach To consider nonlocal influences, both integral (original) and differential versions of Eringen’s nonlocal theory are used. Accordingly, integral nonlocal-micromorphic and differential nonlocal-micromorphic beam models are formulated using matrix-vector relations, which are suitable for implementing in numerical approaches. A finite element (FE) formulation is also provided to solve the obtained equilibrium equations in the variational form. Timoshenko micro-/nano-beams with different boundary conditions are selected as the problem under study whose static bending is addressed. Findings It was shown that the paradox related to the clamped-free beam is resolved by the present integral nonlocal-micromorphic model. It was also indicated that the nonlocal effect captured by the integral model is more pronounced than that by its differential counterpart. Moreover, it was revealed that by the present approach, the softening and hardening effects, respectively, originated from the nonlocal and micromorphic theories can be considered simultaneously. Originality/value Developing a hybrid size-dependent Timoshenko beam model including micromorphic and nonlocal effects. Considering the nonlocal effect based on both Eringen’s integral and differential models proposing an FE approach to solve the bending problem, and resolving the paradox related to nanocantilever.
APA, Harvard, Vancouver, ISO, and other styles
39

Pannekoucke, Olivier. "Heterogeneous Correlation Modeling Based on the Wavelet Diagonal Assumption and on the Diffusion Operator." Monthly Weather Review 137, no. 9 (September 1, 2009): 2995–3012. http://dx.doi.org/10.1175/2009mwr2783.1.

Full text
Abstract:
Abstract This article discusses several models for background error correlation matrices using the wavelet diagonal assumption and the diffusion operator. The most general properties of filtering local correlation functions, with wavelet formulations, are recalled. Two spherical wavelet transforms based on Legendre spectrum and a gridpoint spherical wavelet transform are compared. The latter belongs to the class of second-generation wavelets. In addition, a nonseparable formulation that merges the wavelets and the diffusion operator model is formally proposed. This hybrid formulation is illustrated in a simple two-dimensional framework. These three formulations are tested in a toy experiment on the sphere: a large ensemble of perturbed forecasts is used to simulate a true background error ensemble, which gives a reference. This ensemble is then applied to compute the required parameters for each model. A randomization method is utilized in order to diagnose these different models. In particular, their ability to represent the geographical variations of the local correlation functions is studied by diagnosis of the local length scale. The results from these experiments show that the spectrally based wavelet formulation filters the geographical variations of the local correlation length scale but it is less able to represent the anisotropy. The gridpoint-based wavelet formulation is also able to represent some parts of the geographical variations but it appears that the correlation functions are dependent on the grid. Finally, the formulation based on the diffusion represents quite well the local length scale.
APA, Harvard, Vancouver, ISO, and other styles
40

Chang, Gang-Len, Chien-Yu Chen, and Cesar Perez. "Hybrid Model for Estimating Permitted Left-Turn Saturation Flow Rate." Transportation Research Record: Journal of the Transportation Research Board 1566, no. 1 (January 1996): 54–63. http://dx.doi.org/10.1177/0361198196156600107.

Full text
Abstract:
This study explored the integration of analytical formulations with simulation results for estimating the complex permitted saturation flow rate. The proposed hybrid model captured most tractable interactions between the permitted flow rate and the opposing flows with the widely used formulation by Drew, which serves as one of the primary explanatory variables. To further consider the complex interactions between the permitted flow rate and all other associated factors, which often are not consistent with the assumptions used in analytical derivations, this study modeled the intractable relations as multiplicative adjustment terms and estimated their parameters with log-linear regression. Such a hybrid formulation offers the flexibility to incorporate various additional critical factors on the permitted flow rate, including the variation of driving behavior, the number of opposing lanes, the progression quality, and the heavy vehicle percentage. The preliminary tests with extensive simulation experiments have shown very promising results.
APA, Harvard, Vancouver, ISO, and other styles
41

Alduncin, Gonzalo. "Macro-Hybrid Variational Formulations of Constrained Boundary Value Problems." Numerical Functional Analysis and Optimization 28, no. 7-8 (August 14, 2007): 751–74. http://dx.doi.org/10.1080/01630560701493206.

Full text
APA, Harvard, Vancouver, ISO, and other styles
42

Cao, Changyong, and Qing-Hua Qin. "Hybrid Fundamental Solution Based Finite Element Method: Theory and Applications." Advances in Mathematical Physics 2015 (2015): 1–38. http://dx.doi.org/10.1155/2015/916029.

Full text
Abstract:
An overview on the development of hybrid fundamental solution based finite element method (HFS-FEM) and its application in engineering problems is presented in this paper. The framework and formulations of HFS-FEM for potential problem, plane elasticity, three-dimensional elasticity, thermoelasticity, anisotropic elasticity, and plane piezoelectricity are presented. In this method, two independent assumed fields (intraelement filed and auxiliary frame field) are employed. The formulations for all cases are derived from the modified variational functionals and the fundamental solutions to a given problem. Generation of elemental stiffness equations from the modified variational principle is also described. Typical numerical examples are given to demonstrate the validity and performance of the HFS-FEM. Finally, a brief summary of the approach is provided and future trends in this field are identified.
APA, Harvard, Vancouver, ISO, and other styles
43

Wang, L.-P., J.-S. Wang, Y.-W. Li, and Y. Lu. "Kinematic and dynamic equations of a planar parallel manipulator." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 217, no. 5 (May 1, 2003): 525–31. http://dx.doi.org/10.1243/095440603765226812.

Full text
Abstract:
This paper presents an inverse dynamic formulation using the Newton-Euler approach for a planar parallel manipulator, which is used in a new five-axis hybrid machine tool. The inverse kinematics of the manipulator is given and the velocity and the acceleration formulae are derived. The driving forces acting on the legs are determined according to the dynamic formulation. The formulation has been implemented in a program and has been used for some typical trajectories planned for a numerical simulation experiment. The simulation results reveal the nature of the variation of the driving forces in the hybrid machine tool and justify the dynamic control model. The dynamic modelling approach presented in this paper can also be applied to other parallel manipulators with less than six degrees of freedom.
APA, Harvard, Vancouver, ISO, and other styles
44

Beitelshees, Marie, Andrew Hill, Yi Li, Mingfu Chen, Mahmoud Kamal Ahmadi, Randall J. Smith, Stelios T. Andreadis, Pooya Rostami, Charles H. Jones, and Blaine A. Pfeifer. "Antigen delivery format variation and formulation stability through use of a hybrid vector." Vaccine: X 1 (April 2019): 100012. http://dx.doi.org/10.1016/j.jvacx.2019.100012.

Full text
APA, Harvard, Vancouver, ISO, and other styles
45

Valido, Aníbal J. J., and João Barradas Cardoso. "Design variation of thin-walled composite beam cross-section properties." Multidiscipline Modeling in Materials and Structures 12, no. 3 (October 10, 2016): 558–76. http://dx.doi.org/10.1108/mmms-12-2015-0081.

Full text
Abstract:
Purpose The purpose of this paper is to present a design sensitivity analysis continuum formulation for the cross-section properties of thin-walled laminated composite beams. These properties are expressed as integrals based on the cross-section geometry, on the warping functions for torsion, on shear bending and shear warping, and on the individual stiffness of the laminates constituting the cross-section. Design/methodology/approach In order to determine its properties, the cross-section geometry is modeled by quadratic isoparametric finite elements. For design sensitivity calculations, the cross-section is modeled throughout design elements to which the element sensitivity equations correspond. Geometrically, the design elements may coincide with the laminates that constitute the cross-section. Findings The developed formulation is based on the concept of adjoint system, which suffers a specific adjoint warping for each of the properties depending on warping. The lamina orientation and the laminate thickness are selected as design variables. Originality/value The developed formulation can be applied in a unified way to open, closed or hybrid cross-sections.
APA, Harvard, Vancouver, ISO, and other styles
46

Lamuraglia, Raffaella, Andrea Campostrini, Elena Ghedini, Alessandra De Lorenzi Pezzolo, Alessandro Di Michele, Giulia Franceschin, Federica Menegazzo, Michela Signoretto, and Arianna Traviglia. "A New Green Coating for the Protection of Frescoes: From the Synthesis to the Performances Evaluation." Coatings 13, no. 2 (January 26, 2023): 277. http://dx.doi.org/10.3390/coatings13020277.

Full text
Abstract:
This work presents the formulation and characterization of a new product for the protection of outdoor frescoes from aggressive environmental agents. The formulation is designed as an innovative green coating, prepared through a zero-waste one-pot-synthetic method to form silver nanoparticles (AgNPs) directly in a chitosan-based medium. The AgNPs are seeded and grown in a mixed hydrogel of chitosan, azelaic, and lactic acid, by the reduction of silver nitrate, and using calcium hydroxide as precipitating agent. The rheological properties of this coating base are optimized by the addition of a solvent mixture of glycerol and ethanol with a 1:1 volume ratio. The new formulation and two commercial products (Paraloid® B72 and Proconsol®) are then applied by brush to ad hoc mock-ups to be evaluated for chemical stability, color and gloss variations, morphological variation, hydrophobicity, and water vapor permeability via Fourier-transform infrared spectroscopy (FT-IR) in attenuated total reflection (ATR) mode, spectrophotometer analysis, stereomicroscope observations, UNI EN 15802, and UNI EN 15803, respectively. The results show that the application of the hybrid chitosan-AgNPs coating is promising for the protection of outdoor frescoes and that it can underpin the development of new products that address the lack of conservation strategies specifically designed for wall painting.
APA, Harvard, Vancouver, ISO, and other styles
47

Moreno-Guerra, Mario R., Oscar Martínez-Romero, Luis Manuel Palacios-Pineda, Daniel Olvera-Trejo, José A. Diaz-Elizondo, Eduardo Flores-Villalba, Jorge V. L. da Silva, Alex Elías-Zúñiga, and Ciro A. Rodriguez. "Soft Tissue Hybrid Model for Real-Time Simulations." Polymers 14, no. 7 (March 30, 2022): 1407. http://dx.doi.org/10.3390/polym14071407.

Full text
Abstract:
In this article, a recent formulation for real-time simulation is developed combining the strain energy density of the Spring Mass Model (SMM) with the equivalent representation of the Strain Energy Density Function (SEDF). The resulting Equivalent Energy Spring Model (EESM) is expected to provide information in real-time about the mechanical response of soft tissue when subjected to uniaxial deformations. The proposed model represents a variation of the SMM and can be used to predict the mechanical behavior of biological tissues not only during loading but also during unloading deformation states. To assess the accuracy achieved by the EESM, experimental data was collected from liver porcine samples via uniaxial loading and unloading tensile tests. Validation of the model through numerical predictions achieved a refresh rate of 31 fps (31.49 ms of computation time for each frame), achieving a coefficient of determination R2 from 93.23% to 99.94% when compared to experimental data. The proposed hybrid formulation to characterize soft tissue mechanical behavior is fast enough for real-time simulation and captures the soft material nonlinear virgin and stress-softened effects with high accuracy.
APA, Harvard, Vancouver, ISO, and other styles
48

Zhdanov, Dmitry V., and Denys I. Bondar. "Joint quantum–classical Hamilton variational principle in the phase space." Journal of Physics A: Mathematical and Theoretical 55, no. 10 (February 17, 2022): 104001. http://dx.doi.org/10.1088/1751-8121/ac4ce7.

Full text
Abstract:
Abstract We show that the dynamics of a closed quantum system obeys the Hamilton variational principle. Even though quantum particles lack well-defined trajectories, their evolution in the Husimi representation can be treated as a flow of multidimensional probability fluid in the phase space. By introducing the classical counterpart of the Husimi representation in a close analogy to the Koopman–von Neumann theory, one can largely unify the formulations of classical and quantum dynamics. We prove that the motions of elementary parcels of both classical and quantum Husimi fluid obey the Hamilton variational principle, and the differences between associated action functionals stem from the differences between classical and quantum pure states. The Husimi action functionals are not unique and defined up to the Skodje flux gauge fixing (Skodje et al 1989 Phys. Rev. A 40 2894). We demonstrate that the gauge choice can dramatically alter flux trajectories. Applications of the presented theory for constructing semiclassical approximations and hybrid classical–quantum theories are discussed.
APA, Harvard, Vancouver, ISO, and other styles
49

Alshaya, Abdullah, and Shiang-Jiun Lin. "Hybrid stress analysis of a near-surface circular hole in finite structures." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 7 (December 4, 2019): 1366–81. http://dx.doi.org/10.1177/0954406219892995.

Full text
Abstract:
The ability to stress-analyze complicated structures from recorded load-induced temperatures is demonstrated. The considered structures have a near-surface hole and subjected to a concentrated load. The complexity of the structure is simplified by conformal mapping, the traction-free condition on the boundary of the hole is analytically satisfied by analytic continuation, and the equilibrium and compatibility conditions are satisfied by means of Airy stress function in complex-variable formulation. For isotropic member that is cyclically loaded within its elastic range, the produced in-phase temperature variations are linearly proportional to the local changes in the normal stresses. Even though no recorded thermal data were used at or near to the edges, the present hybrid method simultaneously separates the load-induced temperatures into the individual stress components, determines reliably the boundary stress and hence the stress concentration, and smooths the measured input data. Unlike prior capabilities of using geometrical symmetry to simply the stress function representation, the present analysis retains all the terms in the stress functions. Therefore, the considered hybrid stress analysis approach of such complex structures extends significantly the applicability of thermoelastic stress analysis compared to prior capabilities and is considered to be the most complicated formulation of the hybrid complex-variable method to date. To support the reliability of the present hybrid method, the results were compared with finite element predictions and previous results based on Mitchell solution.
APA, Harvard, Vancouver, ISO, and other styles
50

CHEN, MENG-CHENG, JIAN-JUN ZHU, and K. Y. SZE. "FINITE ELEMENT ANALYSIS OF PIEZOELECTRIC ELASTICITY WITH SINGULAR INPLANE ELECTROELASTIC FIELDS." International Journal of Computational Methods 03, no. 01 (March 2006): 115–35. http://dx.doi.org/10.1142/s0219876206000837.

Full text
Abstract:
An ad hoc one-dimensional finite element formulation is developed for the eigenanalysis of inplane singular electroelastic fields at material and geometric discontinuities in piezoelectric elastic materials by using the eigenfunction expansion procedure and the weak form of the governing equations for prismatic sectorial domains composed of piezoelectrics, composites or air. The order of the electroelastic singularities and the angular variation of the stress and electric displacement fields are obtained with the formulation. The influence of wedge angle, polarization orientation, material types, and boundary and interface conditions on the singular electroelastic fields and the order of their singularity are also examined. The simplicity and accuracy of the formulation are demonstrated by comparison to several analytical solutions for piezoelectric and composite multi-material wedges. The nature and speed of convergence suggests that the present eigensolution could be used in developing hybrid elements for use along with standard elements to yield accurate and computationally efficient solutions to problems having complex global geometries leading to singular electroelastic states.
APA, Harvard, Vancouver, ISO, and other styles
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography