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Describing failure in geomaterials using second-order work approach

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Water Science and Engineering 2015年第2期8卷 89-95页

作者： Franois Nicot Félix Darve institut de Recherche en Sciences et Technologies de l'Environnement et de l'Agriculture(IRSTEA) Erosion Torrentielle Neige et Avalanches (ETNA)Geomechanics GroupGrenoble 38402 France Université Joseph Fourier (UJF)-institut national polytechnique de grenoble (INPG)-Centre national de la Recherche Scientifique (CNRS) Laboratoire SolsSolides Structures et RisquesGrenoble 38041 France

Geomaterials are known to be non-associated materials. Granular soils therefore exhibit a variety of failure modes, with diffuse or localized kinematical patterns. In fact, the notion of failure itself can be confusing with regard to granular soils, because it is not associated with an obvious phenomenology. In this study, we built a proper framework, using the second-order work theory, to describe some failure modes in geomaterials based on energy conservation. The occurrence of failure is defined by an abrupt increase in kinetic energy. The increase in kinetic energy from an equilibrium state, under incremental loading, is shown to be equal to the difference between the external second-order work,involving the external loading parameters, and the internal second-order work, involving the constitutive properties of the material. When a stress limit state is reached, a certain stress component passes through a maximum value and then may decrease. Under such a condition, if a certain additional external loading is applied, the system fails, sharply increasing the strain rate. The internal stress is no longer able to balance the external stress, leading to a dynamic response of the specimen. As an illustration, the theoretical framework was applied to the well-known undrained triaxial test for loose soils. The influence of the loading control mode was clearly highlighted. It is shown that the plastic limit theory appears to be a particular case of this more general second-order work theory. When the plastic limit condition is met, the internal second-order work is nil. A class of incremental external loadings causes the kinetic energy to increase dramatically, leading to the sudden collapse of the specimen, as observed in laboratory.

关键词： Failure in geomaterials Undrained triaxial loading path Second-order work Kinetic energy Plastic limit condition Control parameter

Characteristics and mechanism investigation on drag reduction of oblique riblets

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Journal of Central South University 2017年第6期24卷 1379-1386页

作者： GU Yun-qing FAN Tian-xing MOU Jie-gang WU Deng-hao ZHENG Shui-hua College of Mechanical and Engineering Zhejiang University of TechnologyHangzhou 310014China Zhijiang College Zhejiang University of TechnologyHangzhou 310024China institute national polytechnique of grenoble Joseph Fourier UniversityGrenoble 38031France

This work primarily focuses on the drag reduction characteristics and mechanism investigation of oblique riblets. First, a calculation model of the oblique riblets surface is established, and Reynolds stress model(RSM) turbulence model is used for numerical simulation of the oblique riblets flow field. Subsequently, the influence of inclination angle between flow direction and arrangement direction of riblets on friction resistance and drag reduction rate is further analyzed. Through the investigation of the distribution of shear stress, pressure stress and velocity in oblique riblets boundary layer, the oblique riblets drag reduction mechanism is finally revealed. Results show that, with increase of velocity and inclination angle, the pressure resistance increases obviously, along with the decreasing of the viscous resistance distinctly. The maximum drag reduction rate of the oblique riblets is 7.33%. Moreover, when the inclination angle increases, the wall shear stress reduces on oblique riblets surface; while differential pressure increases at both sides of oblique riblets tips. In addition, when inclination angle is small, the secondary vortex at oblique riblets tips will disappear soon. New vortices will be formed inside the oblique riblets and cause the decrease of viscosity resistance. Thus, oblique riblets show a better drag reduction effect and have an effective control on boundary layer.

关键词： oblique riblets drag reduction Reynolds stress model (RSM) secondary vortex numerical simulation

Generalisation,symbol specification and map evaluation:feedback from research done at COGIT laboratory,IGN France

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International Journal of Digital Earth 2011年第S1期4卷 25-41页

作者： C.Duchenea S.Christophe A.Ruas COGIT Laboratory Institut Geographique NationalSaint-MandeFrance Laboratory of Informatics grenoble(LIG) J.Fourier UniversityGrenobleFrance

This paper presents an overview of research studies made at the COGIT laboratory of IGN France in the fields of generalisation and symbol specification,particularly considering evaluation *** then discusses how generalisation and symbol specification *** it explores some possible adaptations of the presented works in generalisation and symbol specification to cartography in the context of crisis management.

关键词： automated cartography generalisation evaluation semiotics symbol specification

Effect of pumping chamber on performance of non-overload centrifugal pump

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Journal of Central South University 2015年第8期22卷 2989-2997页

作者：谷云庆牟介刚代东顺郑水华吴登昊蒋兰芳施瀚昱 WANG Evan College of Mechanical and Engineering Zhejiang University of Technology Engineering Research Center of Process Equipment and Its Re-manufacturing of Ministry of Education(Zhejiang University of Technology) Zhijiang College Zhejiang University of Technology institut national polytechnique of grenoble Joseph Fourier University

In order to specify the characteristics of un-overloaded centrifugal pumps, the IH100-65-200 pump was chosen as the model pump. Different calculation models for centrifugal pumps were established under different pumping chamber sectional parameters. In the numerical simulation of the centrifugal pumps flow field, the shaft power, head, efficiency, and the changes of the internal flow field under different sectional areas and sectional shapes were studied with the RNG k-ε turbulence model, and the influence of the pumping chamber section characteristics of the non-overloaded centrifugal pumps were analyzed. The results show that sectional areas have a significant impact on the non-overload characteristics of centrifugal pumps. The shaft power and head of centrifugal pump are increasing with a lager sectional area, by which the gradient of head curves decreases. The efficiency is improved under a large flow rate condition, but the head and the efficiency are reduced at a small flow rate. It is also observed that the sectional shapes have less influence on the shaft power, the hydraulic performance and flow field characteristics of a centrifugal pump.

关键词： centrifugal pumps sectional area sectional shape non-overload characteristics numerical simulation

Nano-confinement of biomolecules： Hydrophilic confinement promotes structural order and enhances mobility of water molecules

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Nano Research 2016年第2期9卷 273-281页

作者： Bachir Aoun Daniela Russo Argonne national Laboratory Chicago IL 60439 USA CNR-IOM c/o Institut Laue-Langevin 38400 Grenoble France institut Lumiere Matiere Universite de Lyon 69622 Lyon France

Molecular dynamics simulations have been used to investigate the confinement packing characteristics of small hydrophilic （N-acetyl-glycine-methylamide, Nagma） and hydrophobic （N-acetyl-leucine-methylamide, Nalma） biomolecules in large diameter single-wall carbon nanotubes （SWCNTs）. We find that hydrophilic biomolecules easily fill the nanotube and self organize into a geometrical configuration which reminds the water structural organization under SWCNT confinement. The packing of hydrophilic biomolecules inside the cylinder confines all water molecules in its core, which enhances their mobility. Conversely, hydrophobic biomolecules accommodate into the nanotubes with a trend for homogeneous filling, which generate unstable small pockets of water and drive toward a state of dehydration. These results shed light on key parameters important for the encapsulation of biomolecules with direct relevance for long-term storage and prevention of degradation.

关键词： nano-confinement protein folding hydration water carbon nanotube drug delivery

Axon guidance in regeneration of the mature central nervous system:step by step

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Neural Regeneration Research 2023年第12期18卷 2665-2666页

作者： Julia Schaeffer Noemie Vilallongue Stephane Belin Homaira Nawabi Univ.grenoble Alpes InsermU1216Grenoble Institut NeurosciencesGrenobleFrance

Unlocking axon regeneration in the injured central nervous system:In adult mammals,central nervous system(CNS)neurons fail to regenerate a?ter a lesion,whether it is traumatic–after spinal cord injury for example–or... 详细信息

关键词： traumatic system regeneration

Non-adiabatic approximations in time-dependent density functional theory: progress and prospects

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npj Computational Materials 2023年第1期9卷 1105-1119页

作者： Lionel Lacombe Neepa T.Maitra Laboratoire des Solides Irradiés École PolytechniqueInstitut Polytechnique de ParisF-91128 PalaiseauFrance Department of Physics Rutgers UniversityNewarkNJ 07102USA

Time-dependent density functional theory continues to draw a large number of users in a wide range of fields exploring myriad applications involving electronic spectra and *** in principle exact,the predictivity of the calculations is limited by the available approximations for the exchange-correlation *** particular,it is known that the exact exchange-correlation functional has memory-dependence,but in practise adiabatic approximations are used which ignore *** we review the development of non-adiabatic functional approximations,their impact on calculations,and challenges in developing practical and accurate memory-dependent functionals for general purposes.

关键词： dynamics adiabatic functional

A note on the regularity of the holes for permeability property through a perforated domain for the 2D Euler equations:Dedicated to Professor Jean-Yves Chemin on the Occasion of His 60th Birthday

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Science China Mathematics 2019年第6期62卷 1121-1142页

作者： Christophe Lacave Chao Wang institut Fourier Université Grenoble AlpesCNRS School of Mathematical Sciences Peking University

For equations of order two with the Dirichlet boundary condition, as the Laplace problem, the Stokes and the Navier-Stokes systems, perforated domains were only studied when the distance between the holes d_ε is equal to or much larger than the size of the holes ε. Such a diluted porous medium is interesting because it contains some cases where we have a non-negligible effect on the solution when(ε, d_ε) →(0, 0).Smaller distances were avoided for mathematical reasons and for these large distances, the geometry of the holes does not affect or rarely affect the asymptotic result. Very recently, it was shown for the 2D-Euler equations that a porous medium is non-negligible only for inter-holes distances much smaller than the sizes of the *** this result, the boundary regularity of holes plays a crucial role, and the permeability criterion depends on the geometry of the lateral boundary. In this paper, we relax slightly the regularity condition, allowing a corner, and we note that a line of irregular obstacles cannot slow down a perfect fluid in any regime such thatε ln d_ε→ 0.

关键词： ideal fluids homogenization in perforated domains shrinking obstacles and the porous medium domains with corners

The rise of 3D cellular spheroids: efficient culture via upward growth from a superamphiphobic surface

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national Science Review 2019年第6期6卷 1068-1069页

作者： Paul J.Dyson institut des Sciences et Ingénierie Chimiques Ecole Polytechnique Fédérale de Lausanne

Cell culture assays are extensively used in drug discovery and development programs, biomedical research, and in many others areas of science. Currently,2D monolayer cellular assays serve as the gold standard. However, while they provide seemingly indispensable information on drug activity, it is estimated that of the putative drug candidates selected

关键词： The rise of 3D cellular spheroids efficient culture via upward growth from a superamphiphobic surface