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1
Saxena, Arushi, Eunseo Choi, Christine A. Powell et Khurram S. Aslam. « Seismicity in the central and southeastern United States due to upper mantle heterogeneities ». Geophysical Journal International 225, no 3 (10 mars 2021) : 1624–36. http://dx.doi.org/10.1093/gji/ggab051.
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SUMMARY Sources of stress responsible for earthquakes occurring in the Central and Eastern United States (CEUS) include not only far-field plate boundary forces but also various local contributions. In this study, we model stress fields due to heterogeneities in the upper mantle beneath the CEUS including a high-velocity feature identified as a lithospheric drip in a recent regional P-wave tomography study. We calculate velocity and stress distributions from numerical models for instantaneous 3-D mantle flow. Our models are driven by the heterogeneous density distribution based on a temperature field converted from the tomography study. The temperature field is utilized in a composite rheology, assumed for the numerical models. We compute several geodynamic quantities with our numerical models: dynamic topography, rate of dynamic topography, gravitational potential energy (GPE), differential stress, and Coulomb stress. We find that the GPE, representative of the density anomalies in the lithosphere, is an important factor for understanding the seismicity of the CEUS. When only the upper mantle heterogeneities are included in a model, differential and Coulomb stress for the observed fault geometries in the CEUS seismic zones acts as a good indicator to predict the seismicity distribution. Our modelling results suggest that the upper mantle heterogeneities and structure below the CEUS have stress concentration effects and are likely to promote earthquake generation at preexisting faults in the region’s seismic zones. Our results imply that the mantle flow due to the upper-mantle heterogeneities can cause stress perturbations, which could help explain the intraplate seismicity in this region.
2
Moore, Peter L., Neal R. Iverson et Denis Cohen. « Ice flow across a warm-based/cold-based transition at a glacier margin ». Annals of Glaciology 50, no 52 (2009) : 1–8. http://dx.doi.org/10.3189/172756409789624319.
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AbstractWhere polythermal glaciers have frozen margins that buttress otherwise temperate-based sliding ice, longitudinal compression can strongly influence ice-flow trajectory, and consequently sediment transport paths. Past efforts to model flow in the vicinity of a basal thermal transition (BTT) have generally relied on simplified boundary conditions or rheological idealizations, making these model results difficult to apply to real glacier termini. Herein, we present results of numerical simulations using a power-law rheology and with boundary conditions that better represent the frozen margin. Model results indicate that a transition to a non-sliding frozen margin causes a decline in surface velocity made possible by upward ice flow, implying either enhanced ablation for steady-state simulations or the formation of a surface bulge. Permitting ice loss by ablation combined with numerical smoothing of the basal slip transition subdues basal stress concentrations and thereby inhibits development of structural discontinuities such as thrust faults. Upward ice flow is accommodated by vertical extension up-glacier of the BTT. This strain regime can potentially account for key structural features in polythermal glacier termini without appealing to thrusting.
3
Preuss, Simon, Jean Paul Ampuero, Taras Gerya et Ylona van Dinther. « Characteristics of earthquake ruptures and dynamic off-fault deformation on propagating faults ». Solid Earth 11, no 4 (22 juillet 2020) : 1333–60. http://dx.doi.org/10.5194/se-11-1333-2020.
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Abstract. Natural fault networks are geometrically complex systems that evolve through time. The evolution of faults and their off-fault damage patterns are influenced by both dynamic earthquake ruptures and aseismic deformation in the interseismic period. To better understand each of their contributions to faulting we simulate both earthquake rupture dynamics and long-term deformation in a visco-elasto-plastic crust subjected to rate- and state-dependent friction. The continuum mechanics-based numerical model presented here includes three new features. First, a 2.5-D approximation is created to incorporate the effects of a viscoelastic lower crustal substrate below a finite depth. Second, we introduce a dynamically adaptive (slip-velocity-dependent) measure of fault width to ensure grid size convergence of fault angles for evolving faults. Third, fault localization is facilitated by plastic strain weakening of bulk rate and state friction parameters as inspired by laboratory experiments. This allows us to simulate sequences of episodic fault growth due to earthquakes and aseismic creep for the first time. Localized fault growth is simulated for four bulk rheologies ranging from persistent velocity weakening to velocity strengthening. Interestingly, in each of these bulk rheologies, faults predominantly localize and grow due to aseismic deformation. Yet, cyclic fault growth at more realistic growth rates is obtained for a bulk rheology that transitions from velocity-strengthening friction to velocity-weakening friction. Fault growth occurs under Riedel and conjugate angles and transitions towards wing cracks. Off-fault deformation, both distributed and localized, is typically formed during dynamic earthquake ruptures. Simulated off-fault deformation structures range from fan-shaped distributed deformation to localized splay faults. We observe that the fault-normal width of the outer damage zone saturates with increasing fault length due to the finite depth of the seismogenic zone. We also observe that dynamically and statically evolving stress fields from neighboring fault strands affect primary and secondary fault growth and thus that normal stress variations affect earthquake sequences. Finally, we find that the amount of off-fault deformation distinctly depends on the degree of optimality of a fault with respect to the prevailing but dynamically changing stress field. Typically, we simulate off-fault deformation on faults parallel to the loading direction. This produces a 6.5-fold higher off-fault energy dissipation than on an optimally oriented fault, which in turn has a 1.5-fold larger stress drop. The misalignment of the fault with respect to the static stress field thus facilitates off-fault deformation. These results imply that fault geometries bend, individual fault strands interact, and optimal orientations and off-fault deformation vary through space and time. With our work we establish the basis for simulations and analyses of complex evolving fault networks subject to both long-term and short-term dynamics.
4
Le Pourhiet, L., B. Huet, L. Labrousse, K. Yao, P. Agard et L. Jolivet. « Strain localisation in mechanically layered rocks beneath detachment zones : insights from numerical modelling ». Solid Earth 4, no 1 (17 avril 2013) : 135–52. http://dx.doi.org/10.5194/se-4-135-2013.
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Abstract. We have designed a series of fully dynamic numerical simulations aimed at assessing how the orientation of mechanical layering in rocks controls the orientation of shear bands and the depth of penetration of strain in the footwall of detachment zones. Two parametric studies are presented. In the first one, the influence of stratification orientation on the occurrence and mode of strain localisation is tested by varying initial dip of inherited layering in the footwall with regard to the orientation of simple shear applied at the rigid boundary simulating a rigid hanging wall, all scaling and rheological parameter kept constant. It appears that when Mohr–Coulomb plasticity is being used, shear bands are found to localise only when the layering is being stretched. This corresponds to early deformational stages for inital layering dipping in the same direction as the shear is applied, and to later stages for intial layering dipping towards the opposite direction of shear. In all the cases, localisation of the strain after only γ=1 requires plastic yielding to be activated in the strong layer. The second parametric study shows that results are length-scale independent and that orientation of shear bands is not sensitive to the viscosity contrast or the strain rate. However, decreasing or increasing strain rate is shown to reduce the capacity of the shear zone to localise strain. In the later case, the strain pattern resembles a mylonitic band but the rheology is shown to be effectively linear. Based on the results, a conceptual model for strain localisation under detachment faults is presented. In the early stages, strain localisation occurs at slow rates by viscous shear instabilities but as the layered media is exhumed, the temperature drops and the strong layers start yielding plastically, forming shear bands and localising strain at the top of the shear zone. Once strain localisation has occured, the deformation in the shear band becomes extremely penetrative but the strength cannot drop since the shear zone has a finite thickness.
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Andrea Bizzarri, Alberto Petri et Andrea Baldassarri. « Earthquake dynamics constrained from laboratory experiments : new insights from granular materials ». Annals of Geophysics 64, no 4 (16 novembre 2021) : SE441. http://dx.doi.org/10.4401/ag-8613.
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The traction evolution is a fundamental ingredient to model the dynamics of an earthquake rupture which ultimately controls, during the coseismic phase, the energy release, the stress redistribution and the consequent excitation of seismic waves. In the present paper we explore the use of the friction behavior derived from laboratory shear experiments performed on granular materials at low normal stress. We find that the rheological properties emerging from these laboratory experiments can not be described in terms of preexisting governing models already presented in literature; our results indicate that neither rate–and state–dependent friction laws nor nonlinear slip–dependent models, commonly adopted for modeling earthquake ruptures, are able to capture all the features of the experimental data. Then, by exploiting a novel numerical approach, we directly incorporate the laboratory data into a code to simulate the fully dynamic propagation of a 3–D slip failure. We demonstrate that the rheology of the granular material, imposed as fault boundary condition, is dynamically consistent. Indeed, it is able to reproduce the basic features of a crustal earthquake, spontaneously accelerating up to some terminal rupture speed, both sub– and supershear.
6
Finzi, Yaron, Elizabeth H. Hearn, Yehuda Ben-Zion et Vladimir Lyakhovsky. « Structural Properties and Deformation Patterns of Evolving Strike-slip Faults : Numerical Simulations Incorporating Damage Rheology ». Pure and Applied Geophysics 166, no 10-11 (30 juin 2009) : 1537–73. http://dx.doi.org/10.1007/s00024-009-0522-1.
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Seol, D. E., et C. G. Kang. « Numerical Analysis of Two-Phase Thermal Flow for Rheology Forging Process ». Solid State Phenomena 116-117 (octobre 2006) : 673–76. http://dx.doi.org/10.4028/www.scientific.net/ssp.116-117.673.
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The algorithm two-phase flow model, developed in this study, gives die filling patterns, velocity, temperature and solid fraction of rheology material during rheology forging process. To calculate the velocity and temperature fields, the respective governing equations corresponding to the liquid and solid region were adapted. Therefore, respective numerical models considering the solid and liquid phase co-existent within the rheology material have been developed to predict the defects of part manufactured by the rheology forging process. This study has focused on the simulation of the rheology forging process and calculation of the velocity profiles and temperature distribution. And, to predict the liquid segregation in the part, the deviation of velocity between liquid and solid region in the two-phase flow model was analysed.
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Zhang, De-Han. « Numerical analysis model of horizontal displacement of active faults ». Acta Seismologica Sinica 6, no 3 (août 1993) : 601–8. http://dx.doi.org/10.1007/bf02650399.
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Chen, Ge, Xiao Cong Ren et Xiao Zheng. « Numerical Simulation of Flaxseed and Cottonseed Oil Cakes ». Applied Mechanics and Materials 687-691 (novembre 2014) : 631–36. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.631.
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The pressed oil-extraction process is essentially a process of oil seepage through porous cake-shaped media. Permeability of seepage field changes along with the change of porous media caused by press pressure. The change of permeability affects fluid pressure and effective pressure of oil cake pores, which means that porosity is influenced. On the contrary, the change of porosity also has an impact on permeability. The interaction between the seepage and rheology fields is termed as fluid-solid coupling. If rheology of oil cakes is considered, the fluid-solid coupling seepage with the rheological properties is the essence of the pressed oil-extraction process. In the present study, we studied a permeability model based on the deformable and rheological properties of oilseed cakes and the effective stress. The seepage and rheology fields were analyzed by alternative application of the finite difference and finite element methods. The finite element calculation model of nonlinear rheology field was established by the time step-initial strain method. We used flax and cotton seeds as examples to perform numerical simulation and calculate the displacement and pore fluid pressure dissipation of flaxseed and cottonseed oil during the press process.
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Gallo-Molina, Juan Pablo, Karel Lesage et Ingmar Nopens. « Numerical Validation of a Population Balance Model Describing Cement Paste Rheology ». Materials 13, no 5 (10 mars 2020) : 1249. http://dx.doi.org/10.3390/ma13051249.
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Rheology control is essential during the period in which cement and concrete pastes are encountered in the fresh state, due to the fact that it directly affects workability, initial placement and the structural performance of the hardened material. Optimizations of clinker formulations and reductions in cement-to-water ratios induced by economic and environmental considerations have a significant effect in rheology, which invokes the need for mechanistic models capable of describing the effect of multiple relevant phenomena on the observed paste flow. In this work, the population balance framework was implemented to develop a model able to relate the transient microstructural evolution of cement pastes under typical experimental conditions with its macroscopic rheological responses. Numerical details and performance are assessed and discussed. It was found that the model is capable of reproducing experimentally observed flow curves by using measured cluster size distribution information. It is also able to predict the complex rheological characteristics typically found in cement pastes. Furthermore, a spatially resolved scheme was proposed to investigate the nature of flow inside a parallel-plates rheometer geometry with the objective of assessing the ability of the model of qualitatively predicting experimentally observed behavior and to gain insight into the effect of possible secondary flows.
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Sorokin, Valery, Alexey Yaschenko, Georgy Mushkarev et Victor Novikov. « Telluric Currents Generated by Solar Flare Radiation : Physical Model and Numerical Estimations ». Atmosphere 14, no 3 (24 février 2023) : 458. http://dx.doi.org/10.3390/atmos14030458.
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The current studies of solar-terrestrial relations and possible impact of space weather on the seismic activity are based on statistical analysis without detailed consideration of possible physical mechanism that results in fuzzy and contradictory conclusions. We propose to consider a hypothesis of electromagnetic earthquake triggering by a sharp rise of telluric currents in lithosphere including crust faults due to interaction of solar flare X-ray radiation with ionosphere-atmosphere-lithosphere system resulted in a rise of telluric currents in the crust faults. This hypothesis is based on field and laboratory experiments carried out in Russia within the last forty years and clearly demonstrated a possibility of earthquake triggering by electric current injected into the fault. We developed a mathematical model and computer code for numerical estimations of telluric currents generated by solar flare radiations. The obtained numerical results demonstrate that solar flares can cause variations in the density of telluric currents in the crust faults, comparable to the current densities generated in the Earth’s crust by artificial pulsed power sources capable to trigger earthquakes. Consequently, the triggering of seismic events is possible not only by artificial sources of electric current, but also by ionospheric disturbances caused by strong solar flares.
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Khorsand, M. R., F. Rashidi, F. Goharpey, M. Mirzazadeh et E. Amani. « Numerical Predictions of Viscoelastic Fluid in Pipe Flow Using Extended Pom-Pom Model ». Nihon Reoroji Gakkaishi 39, no 1_2 (2011) : 75–85. http://dx.doi.org/10.1678/rheology.39.75.
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Vieli, Andreas, Antony J. Payne, Zhijun Du et Andrew Shepherd. « Numerical modelling and data assimilation of the Larsen B ice shelf, Antarctic Peninsula ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 364, no 1844 (31 mai 2006) : 1815–39. http://dx.doi.org/10.1098/rsta.2006.1800.
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In this study, the flow and rheology of pre-collapse Larsen B ice shelf are investigated by using a combination of flow modelling and data assimilation. Observed shelf velocities from satellite interferometry are used to constrain an ice shelf model by using a data assimilation technique based on the control method. In particular, the ice rheology field and the velocities at the inland shelf boundary are simultaneously optimized to get a modelled flow and stress field that is consistent with the observed flow. The application to the Larsen B ice shelf shows that a strong weakening of the ice in the shear zones, mostly along the margins, is necessary to fit the observed shelf flow. This pattern of bands with weak ice is a very robust feature of the inversion, whereas the ice rheology within the main shelf body is found to be not well constrained. This suggests that these weak zones play a major role in the control of the flow of the Larsen B ice shelf and may be the key to understanding the observed pre-collapse thinning and acceleration of Larsen B. Regarding the sensitivity of the stress field to rheology, the consistency of the model with the observed flow seems crucial for any further analysis such as the application of fracture mechanics or perturbation model experiments.
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Liang, Shi Chuan, Xin Sheng Zhao, Sheng Li, Li Hua Feng, Xue Liang Liu et Xiao Min Qin. « The Application of GMS in Numerical Simulation of Groundwater and Faults Disposing in Gaizi River Source ». Advanced Materials Research 518-523 (mai 2012) : 4047–56. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.4047.
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GMS (Groundwater Modeling System) is a popular software of groundwater simulation and it also has good compatibility with ARCGIS data. The barrier term , lies in 3D Grids’ MODFLOW module, was developed to simulate thin ,vertical ,low-permeability features that impede the horizontal flow of groundwater .In Gaizi river study area ,the faults ,distributed nearly north-south ,have obstructive effects on groundwater. Using barrier borderline to tackle the faults, imitating study area’s groundwater, and the reckoning indicate that the faults have a prominent effect on subsurface flow. Using barrier borderline to handle faults can reflect faults’ effect perfectly in model.
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Finzi, Yaron, Hans Muhlhaus, Lutz Gross et Artak Amirbekyan. « Shear Band Formation in Numerical Simulations Applying a Continuum Damage Rheology Model ». Pure and Applied Geophysics 170, no 1-2 (3 avril 2012) : 13–25. http://dx.doi.org/10.1007/s00024-012-0463-y.
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Lagrée, P. Y., L. Staron et S. Popinet. « The granular column collapse as a continuum : validity of a two-dimensional Navier–Stokes model with a μ(I)-rheology ». Journal of Fluid Mechanics 686 (27 septembre 2011) : 378–408. http://dx.doi.org/10.1017/jfm.2011.335.
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AbstractThere is a large amount of experimental and numerical work dealing with dry granular flows (such as sand, glass beads, etc.) that supports the so-called $\ensuremath{\mu} (I)$-rheology. The reliability of the $\ensuremath{\mu} (I)$-rheology in the case of complex transient flows is not fully ascertained, however. From this perspective, the granular column collapse experiment provides an interesting benchmark. In this paper we implement the $\ensuremath{\mu} (I)$-rheology in a Navier–Stokes solver (Gerris) and compare the resulting solutions with both analytical solutions and two-dimensional contact dynamics discrete simulations. In a first series of simulations, we check the numerical model in the case of a steady infinite two-dimensional granular layer avalanching on an inclined plane. A second layer of Newtonian fluid is then added over the granular layer in order to recover a close approximation of a free-surface condition. Comparisons with analytical and semi-analytical solutions provide conclusive validation of the numerical implementation of the $\ensuremath{\mu} (I)$-rheology. In a second part, we simulate the unsteady two-dimensional collapse of granular columns over a wide range of aspect ratios. Systematic comparisons with discrete two-dimensional contact dynamics simulations show good agreement between the two methods for the inner deformations and the time evolution of the shape during most of the flow, while a systematic underestimation of the final run-out is observed. The experimental scalings of spreading of the column as a function of the aspect ratio available from the literature are also recovered. A discussion follows on the performances of other rheologies, and on the sensitivity of the simulations to the parameters of the $\ensuremath{\mu} (I)$-rheology.
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Li, Juan, et Bai Lin Zheng. « Numerical Analysis on Effect of Rock Rheology on Fully-Grounded MFRP Bolt Stress ». Advanced Materials Research 594-597 (novembre 2012) : 362–65. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.362.
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As to the time effect of prestress in bolt in geotechnical engineering, the stress distribution in fully-grounded MFRP bolt and its trend influenced by rock rheology is obtained by FEM. The Burgers body which is able to model the primary and secondary creep regions of the rock mass is applied to analyze the time effect of prestress in MFRP bolt. The results show that rock rheology has a great effect on MFRP bolt stress.
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Arattano, M., L. Franzi et L. Marchi. « Influence of rheology on debris-flow simulation ». Natural Hazards and Earth System Sciences 6, no 4 (12 juin 2006) : 519–28. http://dx.doi.org/10.5194/nhess-6-519-2006.
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Abstract. Systems of partial differential equations that include the momentum and the mass conservation equations are commonly used for the simulation of debris flow initiation, propagation and deposition both in field and in laboratory research. The numerical solution of the partial differential equations can be very complicated and consequently many approximations that neglect some of their terms have been proposed in literature. Many numerical methods have been also developed to solve the equations. However we show in this paper that the choice of a reliable rheological model can be more important than the choice of the best approximation or the best numerical method to employ. A simulation of a debris flow event that occurred in 2004 in an experimental basin on the Italian Alps has been carried out to investigate this issue. The simulated results have been compared with the hydrographs recorded during the event. The rheological parameters that have been obtained through the calibration of the mathematical model have been also compared with the rheological parameters obtained through the calibration of previous events, occurred in the same basin. The simulation results show that the influence of the inertial terms of the Saint-Venant equation is much more negligible than the influence of the rheological parameters and the geometry. A methodology to quantify this influence has been proposed.
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Dansereau, Véronique, Jérôme Weiss, Pierre Saramito et Philippe Lattes. « A Maxwell elasto-brittle rheology for sea ice modelling ». Cryosphere 10, no 3 (1 juillet 2016) : 1339–59. http://dx.doi.org/10.5194/tc-10-1339-2016.
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Abstract. A new rheological model is developed that builds on an elasto-brittle (EB) framework used for sea ice and rock mechanics, with the intent of representing both the small elastic deformations associated with fracturing processes and the larger deformations occurring along the faults/leads once the material is highly damaged and fragmented. A viscous-like relaxation term is added to the linear-elastic constitutive law together with an effective viscosity that evolves according to the local level of damage of the material, like its elastic modulus. The coupling between the level of damage and both mechanical parameters is such that within an undamaged ice cover the viscosity is infinitely large and deformations are strictly elastic, while along highly damaged zones the elastic modulus vanishes and most of the stress is dissipated through permanent deformations. A healing mechanism is also introduced, counterbalancing the effects of damaging over large timescales. In this new model, named Maxwell-EB after the Maxwell rheology, the irreversible and reversible deformations are solved for simultaneously; hence drift velocities are defined naturally. First idealized simulations without advection show that the model reproduces the main characteristics of sea ice mechanics and deformation: strain localization, anisotropy, intermittency and associated scaling laws.
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Benzi, Roberto, Mauro Sbragaglia, Massimo Bernaschi et Sauro Succi. « Shear banding from lattice kinetic models with competing interactions ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 369, no 1945 (28 juin 2011) : 2439–47. http://dx.doi.org/10.1098/rsta.2011.0058.
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We present numerical simulations based on a Boltzmann kinetic model with competing interactions, aimed at characterizing the rheological properties of soft-glassy materials. The lattice kinetic model is shown to reproduce typical signatures of driven soft-glassy flows in confined geometries, such as Herschel–Bulkley rheology, shear banding and hysteresis. This lends further credit to the present lattice kinetic model as a valuable tool for the theoretical/computational investigation of the rheology of driven soft-glassy materials under confinement.
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Cao, Anye, Yaoqi Liu, Siqi Jiang, Qi Hao, Yujie Peng, Xianxi Bai et Xu Yang. « Numerical Investigation on Influence of Two Combined Faults and Its Structure Features on Rock Burst Mechanism ». Minerals 11, no 12 (19 décembre 2021) : 1438. http://dx.doi.org/10.3390/min11121438.
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With the increase in coal mining depth, engineering geological conditions and the stress environment become more complex. Many rock bursts triggered by two combined faults have been observed in China, but the mechanism is not understood clearly. The focus of this research aims at investigating the influence of two combined faults on rock burst mechanisms. The six types of two combined faults were first introduced, and two cases were utilized to show the effects of two combined faults types on coal mining. The mechanical response of the numerical model with or without combined faults was compared, and a conceptual model was set up to explain the rock burst mechanism triggered by two combined faults. The influence of fault throw, dip, fault pillar width, and mining height on rock burst potential was analyzed. The main control factors of rock burst in six models that combined two faults were identified by an orthogonal experiment. Results show that six combinations of two faults can be identified, including stair-stepping fault, imbricate fault, graben fault, horst fault, back thrust fault, and ramp fault. The particular roof structure near the two combined faults mining preventing longwall face lateral abutment pressure from transferring to deep rock mass leads to stress concentration near the fault areas. Otherwise, a special roof structure causing the lower system stiffness of mining gives rise to the easier gathering of elastic energy in the coal pillars, which makes it easier to trigger a rock burst. There is a nonlinear relationship between fault parameters and static or dynamic load for graben faults mining. The longwall face has the highest rock burst risk when the fault throw is between 6 and 8 m, the fault dip is larger than 65°, the mining height is greater than 6 m, and the coal pillar width is less than 50 m. The stair-stepping, imbricate, horst, and ramp fault compared to the other fault types will produce higher dynamic load stress during longwall retreat. Fault pillar width is the most significant factor for different two combined faults, leading to the rise of static load stress and dynamic proneness.
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PANIKAVEETIL, FUAAD, AHAMED KUTTY, RAJESH KOPPOLU, AGNE SWERIN, FREDRIK LUNDELL et MARTTI TOIVAKKA. « Numerical analysis of slot die coating of nanocellulosic materials ». November 2020 19, no 11 (1 décembre 2020) : 575–82. http://dx.doi.org/10.32964/tj19.11.575.
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Nanocellulosic coatings as a food packaging material are of commercial interest due to their nontoxic nature, renewability, and excellent barrier properties. Complex shear-thinning rheology poses challenges in designing and sizing equipment to pump, mix, and process the suspension and actual coating process. This study aims to determine the effectiveness of computational fluid dynamics (CFD) in predicting nanocellulosic suspension flow in light of existing rheological data. We employ and compare three distinct rheological models to characterize the rheology and flow of nanocellulose suspensions through a slot die coater, where the model parameters are established from existing slot rheometry measurements. A volume-of-fluid (VoF) based finite volume method is employed to simulate the flow in a slot die operated in an unconventional metering mode. Results with the Casson model predict the presence of unyielded regions in the flow, which was not captured using the power law model. These stagnation regions will incur coatability issues stemming from flow intermittencies and lead to potential defects in the coating layer, including fracture. The results suggest that a rheological model that includes yield stress should be considered while modeling such flows. A need for better rheological data to model nanocellulosic flows, especially at high consistencies and shear rates, is also highlighted.
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Yin, Xiu, Xiyu Liu, Minghe Sun, Jianping Dong et Gexiang Zhang. « Fuzzy Reasoning Numerical Spiking Neural P Systems for Induction Motor Fault Diagnosis ». Entropy 24, no 10 (28 septembre 2022) : 1385. http://dx.doi.org/10.3390/e24101385.
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The fuzzy reasoning numerical spiking neural P systems (FRNSN P systems) are proposed by introducing the interval-valued triangular fuzzy numbers into the numerical spiking neural P systems (NSN P systems). The NSN P systems were applied to the SAT problem and the FRNSN P systems were applied to induction motor fault diagnosis. The FRNSN P system can easily model fuzzy production rules for motor faults and perform fuzzy reasoning. To perform the inference process, a FRNSN P reasoning algorithm was designed. During inference, the interval-valued triangular fuzzy numbers were used to characterize the incomplete and uncertain motor fault information. The relative preference relationship was used to estimate the severity of various faults, so as to warn and repair the motors in time when minor faults occur. The results of the case studies showed that the FRNSN P reasoning algorithm can successfully diagnose single and multiple induction motor faults and has certain advantages over other existing methods.
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Li, Guan Min. « Robust H∞ Control with Actuator Faults ». Advanced Materials Research 499 (avril 2012) : 428–33. http://dx.doi.org/10.4028/www.scientific.net/amr.499.428.
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This paper concernes with the robust H∞ control design problem for linear systems with actuator faults. A more practical model of actuator faults than outage is considered. An linear matrix inequality (LMI) approach of designing robust controller is presented for actuator faults. The resulting control systems are robust in that they provide guaranteed asymptotic stability and H∞ performance when actuator faults occur and the performance in the normal case is optimized. A numerical example illustrates the effectiveness and the necessity of robust control.
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Li, Liming, Xianrui Li, Fanyan Yang, Lili Pan et Jingxiong Tian. « Numerical simulation of contemporary kinematics at the northeastern Tibetan Plateau and its implications for seismic hazard assessment ». Solid Earth 13, no 9 (31 août 2022) : 1371–91. http://dx.doi.org/10.5194/se-13-1371-2022.
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Abstract. The slip rates of active faults in the northeastern Tibetan Plateau (NETP) require clarification to understand the lateral expansion of the Tibetan Plateau and assess the seismic hazards in this region. To obtain the continuous slip rates of active faults at the NETP, we constructed a three-dimensional (3D) numerical geomechanics model that includes a complex 3D fault system. The model also accounts for the physical rock properties, gravity fields, fault friction coefficients, initial stress, and boundary conditions. Following this, we present the long-term kinematics of NETP based on the horizontal and vertical velocities and fault slip rates acquired from the model. The fault kinematic characteristics indicate that the Laohushan, middle–southern Liupanshan, and Guguan–Baoji faults, as well as the junction area of the Maxianshan and Zhuanglanghe faults, are potential hazard areas for strong earthquakes. However, as these faults are currently in the stress accumulation stage, they are unlikely to cause a strong earthquake in the short term. In contrast, it is likely that the Jinqiangshan–Maomaoshan fault will generate a earthquake with a surface-wave magnitude (MS) of 7.1–7.3 in the coming decades. In addition, the velocity profiles across the NETP imply that the plate rotation is the primary deformation mechanism of the NETP even though the intra-block straining and faulting are non-negligible.
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Chen, Haoran, Xin Lin, Guanhua Li, Jianyuan Xu, Hui Li et Shuai Wang. « Experimental Research and Numerical Simulation of Single Soil-Arc-Grounding-Fault in Distribution Networks ». Wireless Communications and Mobile Computing 2021 (5 novembre 2021) : 1–21. http://dx.doi.org/10.1155/2021/1875068.
Texte intégralRésumé :
Among the distribution network faults, single-phase grounding faults have the greatest probability. The faults are often accompanied by arcs in the grounding point soil. This type of fault current has a small amplitude and seldom can obtain field record data. A soil arc grounding fault is tested on a realistic-distribution-network-experimental-platform (RDNEP), and it is concluded that the soil-arc-grounding-fault (SAGF) has three main characteristics: hysteresis, nonlinearity, and asymmetry. By comparing with the characteristics of common arc models, it is pointed out that common arc models cannot accurately fit the characteristics of SAGF. This paper proposes and establishes a double exponential function arc model. Through the comparison of simulation waveforms with experimental data, it is verified that the numerical simulation method proposed in this paper can simulate the development process of SAGF more accurately. Furthermore, the equivalence of RDNEP is verified on the real distribution network system (RDNS). On this basis, analyzed the arc characteristic changes of different SAGF development cycles. Finally, by studying the applicability of the proposed model in simulating ground faults in grass and gravel roads, it is verified that the model proposed in this paper has a strong generalization capability. The research has laid a theoretical foundation for a detection algorithm that is based on the characteristics of SAGF.
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Wang, Wenyi, et Albert K. Wong. « Autoregressive Model-Based Gear Fault Diagnosis ». Journal of Vibration and Acoustics 124, no 2 (26 mars 2002) : 172–79. http://dx.doi.org/10.1115/1.1456905.
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This paper presents a model-based technique for the detection and diagnosis of gear faults. Based on the signal averaging technique, the proposed technique first establishes an autoregressive (AR) model on the vibration signal of the gear of interest in its healthy-state. The model is then used as a linear prediction error filter to process the future-state signal from the same gear. The health condition of the gear is diagnosed by characterizing the error signal between the filtered and unfiltered signals. The technique is validated using both numerical simulation and experimental data. The results show that the AR model technique is an effective tool in the detection and diagnosis of gear faults and it may lead to an effective solution for in-flight diagnosis of helicopter transmissions.
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Tang, Jin-bo, Peng-zhi Lin et Peng Cui. « Depth-resolved numerical model of dam break mud flows with Herschel-Bulkley rheology ». Journal of Mountain Science 19, no 4 (avril 2022) : 1001–17. http://dx.doi.org/10.1007/s11629-021-7218-0.
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UTKIN, LEV V., SERGEY V. GUROV et MAXIM I. SHUBINSKY. « A FUZZY SOFTWARE RELIABILITY MODEL WITH MULTIPLE-ERROR INTRODUCTION AND REMOVAL ». International Journal of Reliability, Quality and Safety Engineering 09, no 03 (septembre 2002) : 215–27. http://dx.doi.org/10.1142/s0218539302000780.
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A fuzzy software reliability model is proposed where the time intervals between the software failures are taken as the fuzzy variables governed by a membership function. The model takes into account the following assumptions: new faults may be introduced into the software during debugging processes, the number of faults removed after a failure may be greater than one, and there is a growth of human experience during debugging. The model can be considered as an extension of the model developed by Cai, Wen and Zhang. An efficient algorithm is presented for estimating parameters of the model. The numerical examples validate the proposed model.
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Yang, Jing, Guo Xie, Yanxi Yang, Qijun Li et Cheng Yang. « A multilevel recovery diagnosis model for rolling bearing faults from imbalanced and partially missing monitoring data ». Mathematical Biosciences and Engineering 20, no 3 (2023) : 5223–42. http://dx.doi.org/10.3934/mbe.2023242.
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<abstract> <p>As an indispensable part of large Computer Numerical Control machine tool, rolling bearing faults diagnosis is particularly important. However, due to the imbalanced distribution and partially missing of collected monitoring data, such diagnostic issue generally emerging in manufacturing industry is still hardly to be solved. Thus, a multilevel recovery diagnosis model for rolling bearing faults from imbalanced and partially missing monitoring data is formulated in this paper. Firstly, a regulable resampling plan is designed to handle the imbalanced distribution of data. Secondly, a multilevel recovery scheme is formed to deal with partially missing. Thirdly, an improved sparse autoencoder based multilevel recovery diagnosis model is built to identify the health status of rolling bearings. Finally, the diagnostic performance of the designed model is verified by artificial faults and practical faults tests, respectively.</p> </abstract>
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Guo, Jinjin, Juntong Qi et Chong Wu. « Robust fault diagnosis and fault-tolerant control for nonlinear quadrotor unmanned aerial vehicle system with unknown actuator faults ». International Journal of Advanced Robotic Systems 18, no 2 (1 mars 2021) : 172988142110027. http://dx.doi.org/10.1177/17298814211002734.
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This article addresses the problem that quadrotor unmanned aerial vehicle (UAV) actuator faults, including small-amplitude bias faults and gain degradation, cannot be detected in time. A hybrid observer, which combines the fast convergence from adaptive observer and the strong robustness from sliding mode observer, is proposed to detect and estimate UAV actuator faults accurately with model uncertainties and disturbances. A nonlinear quadrotor UAV model with model uncertainties and disturbances is considered and a more precise unified expression for actuator faults that do not require knowing where the upper or lower bound is provided. The original system is decomposed into two subsystems by coordinate transformation to improve detection accuracy for small amplitude bias faults and avoid external influences. The hybrid observer is then designed to estimate subsystem states and faults with good stability by selecting a Lyapunov function. A fault-tolerant controller is obtained depending on fault estimation by compensating the normal controller (proportion integral differential [PID] controller). Several numerical simulations confirmed that unknown actuator faults can be accurately detected, estimated, and compensated for even under disturbance conditions.
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Niu, Xiaojing, et Xiping Yu. « A NUMERICAL MODEL FOR WAVE PROPAGATION OVER MUDDY SLOPE ». Coastal Engineering Proceedings 1, no 32 (29 janvier 2011) : 27. http://dx.doi.org/10.9753/icce.v32.waves.27.
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A numerical model for the interaction between waves and muddy seabed is developed, in which the motion of the movable mud and the motion of water are solved simultaneously. The governing equations for both water and the mud are the continuity equation and the equations of motion for incompressible fluids. Water is treated as a Newtonian fluid, while a visco-elastic-plastic model is used to describe the rheology of the mud. Both the interface between water and the mud and the free water surface are traced by the VOF (Volume of Fluid) method. The numerical method is based on the well-known SMAC method. The numerical model is applied to simulate wave propagation over a muddy slope, and the numerical results are in reasonable agreement with the experimental data. The present model is proved better performance than the traditional analytic model in case that topography change is not negligible.
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Luo, Yue Gang, Song He Zhang, Hong Liang Yao et Bang Chun Wen. « Application of Model Based Diagnosis in Two-Span Rotor System with Two Unbalance Faults ». Advanced Materials Research 199-200 (février 2011) : 780–83. http://dx.doi.org/10.4028/www.scientific.net/amr.199-200.780.
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The model based fault identification method was used to identify the two unbalance faults in two-span rotor system. The unbalance location and magnitude were identified using least squares fitting approach by the system’s transient residual vibration. The all-phasic FFT technique was used to analyze the original phases of vibration signals. The unbalance location and magnitude of the rotor system can be detected by using only a few sensors. Numerical simulations and experiment on rotor system with two unbalance faults were used, which proved the efficiency of the method.
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Hsu, Tian-Jian, Xiao Yu, Celalettin E. Ozdemir et S. Balachandar. « A 3D NUMERICAL INVESTIGATION OF FINE SEDIMENT TRANSPORT IN AN OSCILLATORY CHANNEL ». Coastal Engineering Proceedings 1, no 33 (15 décembre 2012) : 9. http://dx.doi.org/10.9753/icce.v33.sediment.9.
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Recent findings on a diverse range of muddy seabed states revealed by 3D, turbulence-resolving simulations are first reviewed. These transitions have critical implications to offshore delivery of fine sediment in the ocean and wave dissipation. Assuming a small particle Stokes number, the Equilibrium approximation to the Eulerian two-phase flow equations is applied. The resulting simplified equations are solved with a high-accuracy pseudo-spectral scheme in an idealized oscillatory bottom boundary layer (OBBL). For a typical energetic muddy shelf, the Stokes Reynolds number Re is no more than 1000 and all of the scales of flow turbulence and their interaction with sediments are resolved. With increasing sediment availability or settling velocity, the seabed state evolves from well-mixed sediment distribution, to the formation of lutocline and a complete laminarization of the OBBL. More recently, we further include rheological stress in the simulations in order to study the interplay between turbulence and rheology in determining the flow regimes and hydrodynamic dissipation. To include rheological stress, we extend the numerical model with a hybrid spectral and compact finite difference scheme. A sixth-order compact finite difference is implemented in vertical direction to keep the spectral-like accuracy. The model is validated with analytical solutions using simple Newtonian rheology in laminar condition. Preliminary results at Re=600 reveal that when rheology is incorporated, high viscosity can trigger earlier laminarization of OBBL. When OBBL is laminarized, sediments settle and higher concentration is accumulated near the bed that further enhances viscosity and hydrodynamic dissipation. Our preliminary finding that rheology encourages laminarization may explain why large attenuation of surface waves over muddy seabed is ubiquitous and the highest dissipation rate is often observed during the waning stage of a storm.
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Shimizu, Yoshiyuki, Kosuke Masuda et Tadayoshi Sadakane. « Multi-Visco-Elastic Contact Model in Discrete Element Method - Numerical Simulations of Margarine’s Dynamics during Manufacturing Process - ». Nihon Reoroji Gakkaishi 42, no 3 (2014) : 177–83. http://dx.doi.org/10.1678/rheology.42.177.
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Li, Xiaotian, Zhurui Gao, Shengjun Zhang et Junshi Li. « The extension of thixotropy of cement paste under vibration : a shear-vibration equivalent theory ». Science and Engineering of Composite Materials 27, no 1 (8 novembre 2020) : 367–73. http://dx.doi.org/10.1515/secm-2020-0040.
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AbstractThe rheology of cement paste under vibration follows the transformation from Bingham model to Hershel-Bulkly model to Power-Law model. Most of the existing research is obtained through a large number of experiments in the data fitting process, and cannot express the time-varying characteristics of viscosity. Furthermore, thixotropy of cement paste is based on static experiment and cannot be applied under vibration. In this paper a shear-vibration equivalent theory is proposed, which consider the effect of vibration is the same as the shear effect on the viscosity change of cement paste. Combining vibrational shear equivalent theory and HI theory, the rheological changes of cement paste under vibration are obtained through numerical simulation. This theory has been verified by a series of experiments with numerical simulations, and can be used to study the rheology of concrete under vibration.
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Xiao, Yancai, et Zhe Hua. « Misalignment Fault Prediction of Wind Turbines Based on Combined Forecasting Model ». Algorithms 13, no 3 (1 mars 2020) : 56. http://dx.doi.org/10.3390/a13030056.
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Due to the harsh working environment of wind turbines, various types of faults are prone to occur during long-term operation. Misalignment faults between the gearbox and the generator are one of the latent common faults for doubly-fed wind turbines. Compared with other faults like gears and bearings, the prediction research of misalignment faults for wind turbines is relatively few. How to accurately predict its developing trend has always been a difficulty. In this paper, a combined forecasting model is proposed for misalignment fault prediction of wind turbines based on vibration and current signals. In the modelling, the improved Multivariate Grey Model (IMGM) is used to predict the deterministic trend and the Least Squares Support Vector Machine (LSSVM) optimized by quantum genetic algorithm (QGA) is adopted to predict the stochastic trend of the fault index separately, and another LSSVM optimized by QGA is used as a non-linear combiner. Multiple information of time-domain, frequency-domain and time-frequency domain of the wind turbine’s vibration or current signals are extracted as the input vectors of the combined forecasting model and the kurtosis index is regarded as the output. The simulation results show that the proposed combined model has higher prediction accuracy than the single forecasting models.
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Dontsov, E. V., S. A. Boronin, A. A. Osiptsov et D. Yu Derbyshev. « Lubrication model of suspension flow in a hydraulic fracture with frictional rheology for shear-induced migration and jamming ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 475, no 2226 (juin 2019) : 20190039. http://dx.doi.org/10.1098/rspa.2019.0039.
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We developed a model for suspension flow in a hydraulic fracture, taking into account frictional rheology to capture the effects of shear-induced particle migration, jamming and transition to close packing. One of the key issues with the existing slurry rheology models is that each of them diverges near the close packing limit, which is typically resolved in numerical simulations via a pragmatic (and mostly unjustified) regularization. Another drawback of the family of existing models for proppant transport in fractures is the assumption of a uniform cross-flow concentration profile, which neglects the effects of shear-induced migration. We developed a self-consistent model for slurry flow with a constitutive relation for suspension rheology, which is applicable in the entire range of particle volume concentration, from dilute suspension through dense suspension to the close packing limit. In addition, we investigated the influence of various constitutive relations for the suspension rheology on the final model for the slurry flow. The selected model for slurry flow was implemented into a two-dimensional lubrication model of proppant transport in a fracture (based on the two-continua approach), and illustrative simulations were conducted in comparison with the family of existing suspension rheology models (having a singularity). Validation against laboratory experiments is discussed.
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Thote, Pankaj B., Mohammad Ashar, Afsar Khan et Chandrakant Rathore. « Hardware Model of IDMT Protection Scheme Using Numerical Relay ». SAMRIDDHI : A Journal of Physical Sciences, Engineering and Technology 13, no 01 (30 juin 2021) : 42–47. http://dx.doi.org/10.18090/samriddhi.v13i01.8.
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Protection plays a crucial role in power system engineering, especially current protection. Hence, the authors have modelled and simulated various operating characteristics of overcurrent relay in MATrix LABoratory (MATLAB)/Simulink environment in this paper. The proposed work has been divided in two phases. In the first part, modeling of Inverse Definite Minimum Time (IDMT) overcurrent relay on MATLAB/Simulink platform has been done, and the simulation has been carried out. The second part IDMT type overcurrent relay has been implemented on AVR microcontroller with intelligent current sensing techniques and control for validation of the simulation results. Different types of faults and different IDMT fault characteristics on the developed model have been tested. The results obtained with the hardware model and Simulink model are compared, and it is noted that both results are in line with each other.
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Wang, Jingquan, Xingxing Zou, Xiaowei Yan et Shuai Li. « Integrated Analysis Model for the Seismic Responses of Cable-Stayed Bridges Near Active Faults ». Journal of Earthquake and Tsunami 09, no 01 (mars 2015) : 1550002. http://dx.doi.org/10.1142/s1793431115500025.
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To study the special behaviors of seismic responses regarding a cable-stayed bridge under an active fault earthquake, a novel numerical algorithm named Structure-Medium-Fault (SMF) Integrated Model, in which the interaction of the three parts can be considered, is proposed. The mechanical simplification of causative faults' rupture, numerical simulation of stress wave propagation and the artificial boundary conditions (ABC) for the infinite body laid the groundwork of this model. Initially, the mechanical model for the structures and earth medium was established. Afterwards, the equivalent initial stresses of causative seismic sources can be calculated according to the monitored data of active faults. Thirdly, the function of the equivalent initial stress of seismic source time was derived by the second derivation of Brune source function. Finally, the viscoelastic boundary was chosen for the model as ABC. A cable-stayed bridge (600 m main span) above the causative fault was analyzed using the novel model. Consequently, vertical effect, velocity pulse effect and directivity effect were all confirmed by the analytical results. The model can reflect the mutual influences of near-fault structures, medium and causative faults. The seismic responses of the bridge under a near-fault earthquake can thus be obtained.
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Röckel, Luisa, Steffen Ahlers, Sophia Morawietz, Birgit Müller, Karsten Reiter, Oliver Heidbach, Andreas Henk, Tobias Hergert et Frank Schilling. « Slip tendency analysis of major faults in Germany ». Safety of Nuclear Waste Disposal 1 (10 novembre 2021) : 77–78. http://dx.doi.org/10.5194/sand-1-77-2021.
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Abstract. Natural seismicity and tectonic activity are important processes for the site-selection and for the long-term safety assessment of a nuclear waste repository, as they can influence the integrity of underground structures significantly. Therefore, it is crucial to gain insight into the reactivation potential of faults. The two key factors that control the reactivation potential are (a) the geometry and properties of the fault such as strike direction and friction angle, and (b) the orientations and magnitudes of the recent stress field and future changes to it due to exogenous processes such as glacial loading as well as anthropogenic activities in the subsurface. One measure of the reactivation potential of faults is the ratio of resolved shear stress to normal stresses at the fault surface, which is called slip tendency. However, the available information on fault properties and the stress field in Germany is sparse. Geomechanical numerical modelling can provide a prediction of the required 3D stress tensor in places without stress data. Here, we present slip tendency calculations on major faults based on a 3D geomechanical numerical model of Germany and adjacent regions of the SpannEnD project (Ahlers et al., 2021). Criteria for the selection of faults relevant to the scope of the SpannEnD project were identified and 55 faults within the model area were selected. For the selected faults, simplified geometries were created. For a subset of the selected faults, vertical profiles and seismic sections could be used to generate semi-realistic 3D fault geometries. Slip tendency calculations using the stress tensor from the SpannEnD model were performed for both 3D fault sets. The slip tendencies were calculated without factoring in pore pressure and cohesion, and were normalized to a coefficient of friction of 0.6. The resulting values range mainly between 0 and 1, with 6 % of values larger than 0.4. In general, the observed slip tendency is slightly higher for faults striking in the NW and NNE directions than for faults of other strikes. Normal faults show higher slip tendencies than reverse and strike slip faults for the majority of faults. Seismic events are generally in good agreement with the regions of elevated slip tendencies; however, not all seismicity can be explained through the slip tendency analysis.
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Murillo-Soto, Luis D., et Carlos Meza. « Automated Fault Management System in a Photovoltaic Array : A Reconfiguration-Based Approach ». Energies 14, no 9 (23 avril 2021) : 2397. http://dx.doi.org/10.3390/en14092397.
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This work proposes an automated reconfiguration system to manage two types of faults in any position inside the solar arrays. The faults studied are the short-circuit to ground and the open wires in the string. These faults were selected because they severely affect power production. By identifying the affected panels and isolating the faulty one, it is possible to recover part of the power loss. Among other types of faults that the system can detect and locate are: diode short-circuit, internal open-circuit, and the degradation of the internal parasitic serial resistance. The reconfiguration system can detect, locate the above faults, and switch the distributed commutators to recover most of the power loss. Moreover, the system can return automatically to the previous state when the fault has been repaired. A SIMULINK model has been built to prove this automatic system, and a simulated numerical experiment has been executed to test the system response to the faults mentioned. The results show that the recovery of power is more than 90%, and the diagnosis accuracy and sensitivity are both 100% for this numerical experiment.
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Winstanley, H. F., M. Chapwanya, M. J. McGuinness et A. C. Fowler. « A polymer–solvent model of biofilm growth ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 467, no 2129 (décembre 2010) : 1449–67. http://dx.doi.org/10.1098/rspa.2010.0327.
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We provide and analyse a model for the growth of bacterial biofilms based on the concept of an extracellular polymeric substance as a polymer solution, whose viscoelastic rheology is described by the classical Flory–Huggins theory. We show that one-dimensional solutions exist, which take the form at large times of travelling waves, and we characterize their form and speed in terms of the describing parameters of the problem. Numerical solutions of the time-dependent problem converge to the travelling wave solutions.
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Leng, Jianqiao, Xindi Sun, Mingzhen Wei et Baojun Bai. « A Novel Numerical Model of Gelant Inaccessible Pore Volume for In Situ Gel Treatment ». Gels 8, no 6 (13 juin 2022) : 375. http://dx.doi.org/10.3390/gels8060375.
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Inaccessible pore volume (IAPV) can have an important impact on the placement of gelant during in situ gel treatment for conformance control. Previously, IAPV was considered to be a constant factor in simulators, yet it lacked dynamic characterization. This paper proposes a numerical simulation model of IAPV. The model was derived based on the theoretical hydrodynamic model of gelant molecules. The model considers both static features, such as gelant and formation properties, and dynamic features, such as gelant rheology and retention. To validate our model, we collected IAPV from 64 experiments and the results showed that our model fit moderately into these lab results, which proved the robustness of our model. The results of the sensitivity test showed that, considering rheology and retention, IAPV in the matrix dramatically increased when flow velocity and gelant concentration increased, but IAPV in the fracture maintained a low value. Finally, the results of the penetration degree showed that the high IAPV in the matrix greatly benefited gelant placement near the wellbore situation with a high flow velocity and gelant concentration. By considering dynamic features, this new numerical model can be applied in future integral reservoir simulators to better predict the gelant placement of in situ gel treatment for conformance control.
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Zhong, Shijie, et Michael Gurnis. « Interaction of weak faults and non-newtonian rheology produces plate tectonics in a 3D model of mantle flow ». Nature 383, no 6597 (septembre 1996) : 245–47. http://dx.doi.org/10.1038/383245a0.
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Tchomeni, Bernard Xavier, et Alfayo Alugongo. « Numerical and experimental diagnosis of complex rotor system by time-frequency techniques ». MATEC Web of Conferences 169 (2018) : 01015. http://dx.doi.org/10.1051/matecconf/201816901015.
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This paper describes the application of Discrete Wavelet Transform (DWT) to identify various types of nonlinear damage caused by, unbalance, rotor-stator contact and a breathing crack in rotating machinery. Multiple faults have been investigated based on numerical and experimental signal analysis using Fast Fourier Transform (FFT) and DWT. A four degree of freedom fully coupled model of the rotor-stator system that includes the nonlinear damage in the rotor vibrations was established using Energy principles. Existence of high system nonlinearity could not allow exhaustive discrimination of rub and crack by classical FFT. Therefore, the DWT was employed. The results provide detailed feature analysis of the fault signals. Practical vibration measurements through a data acquisition system interfaced with Rotor Kit-4 and crack simulator provided the test data. Experimental Time-Frequency analysis gave more realistic faults responses with variable faults features. Irregularity of orbit, harmonic peaks in the presence of rub and crack were unique and distinguished periodic motion from other types of motion. The presence of a crack shifted the critical speed location and exhibited sub-harmonic components, which were more prominent with rub in vibration response. The detailed decomposition signal by DWT method established inherent feature patterns that effectively discriminated the multiple faults.
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Cuomo, Sabatino, Manuel Pastor, Leonardo Cascini et Giuseppe Claudio Castorino. « Interplay of rheology and entrainment in debris avalanches : a numerical study ». Canadian Geotechnical Journal 51, no 11 (novembre 2014) : 1318–30. http://dx.doi.org/10.1139/cgj-2013-0387.
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Flow-type landslides are a major global hazard. They occur worldwide, and are responsible for a large number of casualties, significant structural damage to property and infrastructure, and economic losses. The features of debris avalanches are particularly important, as they involve open slopes and affect triangular source areas when initial slides turn into avalanches through further failures or eventual soil entrainment. In this paper, the propagation stage of debris avalanches is numerically modelled to provide information such as the propagation pattern of the mobilized material and its velocity, thickness, and run-out distance. The use of a “depth-integrated” model has the following advantages: (i) it adequately accommodates the irregular topography of real slopes, which greatly affects the evolution of the propagation stage; and (ii) it is less time consuming than full three-dimensional approaches. The model is named “GeoFlow_SPH” and has previously been applied to theoretical, experimental, and real case histories. The behaviour of debris avalanches is analysed with particular attention to the apical angle, one of the main features of this type of landslide, in relation to soil rheology, hillslope geometry, and the geometric aspect ratio of the triggering area. The role of bed entrainment is also investigated with reference to differences in steepness of the uppermost parts of open slopes. First, simplified benchmark slopes are analysed using both water-like materials (with negligible shear strength) and debris-type materials (saturated frictional soil). Next, the paper addresses three important case studies from the Campania region of southern Italy (Cervinara, Nocera Inferiore, and Sarno), where debris avalanches occur in pyroclastic soils that originated from the eruptive products of the Mount Vesuvius volcano. In all of the cases analysed, the effects of erosion rate are compared with those of simulated soil propagation height, run-out distance, and velocity. In a novel contribution to the existing research, the results obtained from analysis of both the benchmark slopes and the real case histories indicate that landslide propagation depends on the interplay of rheology and bed entrainment. In particular, increased erosion growth rates correspond to shorter run-out distances, lower velocities, and larger propagation depths. It is further shown that erosion depth increases with either friction angle or the consolidation coefficient of pore-water pressure; the latter reduces bed entrainment but does not significantly affect the apical angle of debris avalanches. Globally, the results are particularly satisfactory because they indicate that the GeoFlow_SPH model is a suitable tool for the analysis and forecasting of debris avalanches.
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Yamamoto, Takehiro, et Kazuhiro Sawa. « Numerical Analysis of Shear Banding Flow of Wormlike Micelle Solutions between Parallel Channels using a Network Scission Model ». Nihon Reoroji Gakkaishi 39, no 3 (2011) : 105–11. http://dx.doi.org/10.1678/rheology.39.105.
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Zhang, Jun Hong, Liang Ma, Jie Wei Lin et Gui Chang Zhang. « Dynamic Analysis of Flexible Rotor-Ball Bearings System with Unbalance-Misalignment-Rubbing Coupling Faults ». Applied Mechanics and Materials 105-107 (septembre 2011) : 448–53. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.448.
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Dynamic responses of flexi rotor-ball-bearing system under unbalance misalignment rubbing coupling faults are studied. Coupling faults dynamic control model of flexi-multi-system of rotor-ball-bearing system is established, based on finite element analysis and numerical integral combined simulate method. Then nonlinear bearing force and rub-impact force models are programmed in MATLAB. Analysis and compare vibration characteristics of system while under faults-free, unbalance and rub-impact faults. The result demonstrates that when system under unbalance faults, vibration frequency brought by eccentric mass is agreed with rotating speed frequency, its fundamental frequency wave add high frequency component, can show the characteristics of unbalance-rubbing faults efficiently; when system under misalignment faults, with frequency double vibration and high harmonics; when system under unbalance-misalignment-rubbing coupling faults, support force of shafting of rotor system appears high frequency responses like saw tooth based on sine wave, causing aggravation of rub-impact faults.
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Long, Haihui, et Jiankang Zhao. « Robust constrained fault-tolerant attitude control for flexible spacecraft ». Proceedings of the Institution of Mechanical Engineers, Part G : Journal of Aerospace Engineering 232, no 16 (9 octobre 2017) : 3011–23. http://dx.doi.org/10.1177/0954410017733291.
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In this paper, robust constrained fault-tolerant attitude controllers are proposed for flexible spacecraft subjected to external disturbance, model uncertainty, input saturation, and actuator faults. Three types of actuator faults of spacecraft, i.e. partial loss of effectiveness, stuck fault, and outage fault, are modeled explicitly. To handle these actuator faults, a significant lemma is proposed and rigorous proof is conducted at length. By introducing two e-modification parameter update laws to online estimate the unknown parameters caused by actuator faults, constrained fault-tolerant attitude controllers of flexible spacecraft are designed to accommodate these faults without the need of any prior information about these faults. The proposed controllers can achieve the disturbance attenuation in the sense of [Formula: see text] gain. The effectiveness of the proposed algorithms is assessed through numerical simulations.