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Improved Methods for In-situ Measurement Railway Noise Barrier Insertion Loss

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第1期35卷 58-68页

作者： Li Qiutong Duhamel Denis Luo Yanyun Yin Honoré Université Paris-Est Laboratoire NavierENPC-IFSTTAR-CNRS Institute of Railway Transit Tongji University

Many countries which seek to understand the acoustic performance of railway noise barriers have established standards for the conduct of in-situ ***,there are no universally acknowledged receiver positions for the evaluation of the barrier performance,a fact which may be leading to uncertainty over the noise reduction capabilities of available *** terms of the descriptor of the barrier performance,the general recommendation is the A-weighted sound pressure level,although the latter is considered to underestimate low frequencies for railway noise ***,in this study,the comparison of receiver positions and the descriptors among existing Chinese,ISO and European standards were *** upon a combination of diffraction theory and standards,a rearrangement of receiver positions and one-third-octave-band analysis were *** addition,in line with improved methods,an in-situ measurement of insertion loss for a 1.5 mhigh railway noise barrier was designed and *** results of the experiment validate as effective and applicable the new receiver *** results also suggest that one-third-octave-band analysis is indispensable.

关键词： railway noise noise barrier in-situ experiment A-weighting insertion loss one-third-octave-band analysis grid receiver positions

Stable and accurate schemes for smoothed dissipative particle dynamics

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Applied Mathematics and Mechanics(English Edition) 2018年第1期39卷 83-102页

作者： G. FAURE G. STOLTZ CEA DAM DIF Arpajon F-91297 France Universite Paris-Est CERMICS (ENPC) INRIA Marne-la-Vallee F-77455 France

Smoothed dissipative particle dynamics （SDPD） is a mesoscopic particle method that allows to select the level of resolution at which a fluid is simulated. The numerical integration of its equations of motion still suffers from the lack of numerical schemes satisfying all the desired properties such as energy conservation and stability. Similarities between SDPD and dissipative particle dynamics with energy （DPDE） con- servation, which is another coarse-grained model, enable adaptation of recent numerical schemes developed for DPDE to the SDPD setting. In this article, a Metropolis step in the integration of the fluctuation/dissipation part of SDPD is introduced to improve its stability.

关键词： smoothed dissipative particle dynamics (SDPD) numerical integration Metropolis algorithm

Elastic behavior of saturated porous materials under undrained freezing

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Acta Mechanica Sinica 2013年第6期29卷 827-835页

作者： Qiang Zeng Teddy Fen-Chong Ke-Fei Li Civil Engineering Department Tsinghua University Universit Paris-Est Laboratoire Navier(UMR 8205)CNRSENPCIFSTTAR2 alle KeplerF-77420 Champs-sur-MarneFrance

The elastic behavior of saturated porous materi- als under undrained freezing is investigated by using a poro- mechanical approach. Thermodynamic equilibria are used to describe the crystallization process of the partially frozen solution in bulk state and confined state in pores. By phase transition at freezing, fusion energy, thermal contraction of solid, solution and ice crystals, volume changes of crystallization build up remarkable pore pressure that induces expansion or shrinkage of solid matrix. Owing to the lower chemical potential when pore water mixes with salts, fewer ice forms in pores. Penetration of ice into the porous materials increases the capillary pressure, but limits effect on the pore liquid pressure and the strain of solid matrix. On the contrary, the pore pressure induced by solution density rises as salt concentration increases and causes significant shrinkage of solid matrix.

关键词： Poromechanics Crystallization Cement Salt solution

Strength criterion of porous media: Application of homogenization techniques

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第1期9卷 62-73页

作者： L. Dormieux E. Lemarchand D. Kondo S. Brach CNRS UMR 8205 ENPC Laboratoire Navier 6 et 8 avenue Blaise Pascal 77455 Marne-la-Vallée France UPMC Institut Jean le Rond d’Alembert Paris France

The present paper aims at giving some general ideas concerning the micromechanical approach of the strength of a porous material. It is shown that its determination theoretically amounts to solving a nonlinear boundary value problem defined on a representative elementary volume(REV). The principle of nonlinear homogenization is illustrated based on the case of a solid phase having a Green’s strength criterion. An original refinement of the so-called secant method(based on two reference strains) is also provided. The paper also describes the main feature of the Gurson’s model which implements the principle of limit analysis on a conceptual model of hollow sphere. The last part of the paper gives some ideas concerning poromechanical couplings.

关键词： Strength criterion Porous media Homogenization techniques Nonlinear behavior Limit analysis Gurson’s model

Continuous Ethanol Fermentation at Very High Gravity in the Presence of <i>Saccharomyces cerevisiae</i>: A Bifurcation Analysis

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Journal of Sustainable Bioenergy Systems 2018年第4期8卷 116-126页

作者： Ghanem-Lakhal Abdelghani Département de Génie des Procédés ENPC Constantine Algérie

In this paper, a study of the bifurcation analysis of fermentation of sugar to ethanol in presence of Saccharomyces cerivisiae at very high gravity is described. The bifurcation analysis was done for a concentration 280 gl−1 of sugar, and the dilution rate was taken as the parameter of bifurcation. Two Hopf bifurcations (HB) at 280 gl−1 were found. At dilution rate of 0.027 h−1 the system exhibits damped oscillations and not sustained oscillations as previously reported because the system is close to a point of attraction, and we can attenuate these oscillations by the choice of initial conditions. The system exhibits sustained oscillations between the two Hopf Bifurcations, the first at 0.08028 h−1 and the second at 0.04395 h−1. These oscillations are the consequence of synchrony between the daughter and the mother yeast. Indeed, it is better to take a dilution rate between the two Hopf bifurcations (self sustained oscillations), in order to increase the ethanol productivity.

关键词： Bifurcation Ethanol Fermentation Saccharomyces cerevisiae Very High Gravity

城市交通“战略技术经济模型”(STEM)——巴黎大区交通政策探索

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交通与港航 2020年第1期7卷 26-32页

作者：李盛法国enpc/LVMT

城市交通的投资和管理是交通决策的重大问题,如何在不同的供给、需求结构下,制定合理可行、与时俱进的交通政策是管理者需长期面对的课题。交通系统管治的内涵因城市发展阶段而变化,但究其理论根本是使边际出行在各种出行方式中所造成... 详细信息

城市交通的投资和管理是交通决策的重大问题,如何在不同的供给、需求结构下,制定合理可行、与时俱进的交通政策是管理者需长期面对的课题。交通系统管治的内涵因城市发展阶段而变化,但究其理论根本是使边际出行在各种出行方式中所造成的社会成本的增量相等。STEM(Strategic Technical-Economic Model)模型为决策提供了这样一个理论和操作工具,并以此为基础模拟了巴黎大区的几项交通政策。交通税费的合理配置能够有效缩减私人成本和社会成本的分离,使出行消耗的社会资源内部化,从而实现城市交通系统的最优运行。

关键词：交通系统管治边际社会成本环境成本交通拥堵费

Three-dimensional simulation of horseshoe vortex and local scour around a vertical cylinder using an unstructured finite-volume technique

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International Journal of Sediment Research 2020年第3期35卷 295-306页

作者： Wei Zhang Miguel Uh Zapata Xin Bai Damien Pham-Van-Bang Kim Dan Nguyen Laboratory for Hydraulics Saint-Venant (LHSV ENPC-EDF R&D-Cerema)University Paris-Est CONACYT Centro de Investigacion en Matematicas A.C.(CIMAT)Unidad Merida 3. Laboratory for Hydraulics and Environment (LHE)Institut National de La Recherche ScientifiqueUniversite Du Quebec

A Large Eddy Simulation model is developed to simulate the hydrodynamics and scour process around a circular *** Navier-Stokes solver is based on the projection method and a second-order unstructured finite-volume method.A sigma-coordinate system is used to obtain an accurate representation of the evolution of the sediment-water *** erosion is simulated by solving the sediment continuity equation using a mass-conservating sand-slide algorithm and a bedload transport rate,which is based on a description of physical processes(Engelund & Freds(?)e,1976).Simulations of flow around a vertical cylinder for free-slip bed,rigid bed,and live-bed cases are *** mean velocity profile and shear stress validate the accuracy of this *** vortex and lee-wake vortex shedding structure are simulated,and the results are thoroughly discussed in *** formation and the temporal development of the scour hole and other topographic bed features are successfully *** current paper reports the first known investigation of both scour evolution and coherent structure using large-eddy simulation.

关键词： Non-hydrostatic flows Horseshoe vortex Wake region Scouring Bedload transport

Pseudo-static stability analysis of rock slopes reinforced by passive bolts using the generalized Hoek-Brown criterion

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 659-670页

作者： Mounir Belghali Zied Saada Denis Garnier Samir Maghous Laboratoire de Génie Civil ENIT Université de Tunis El Manar Tunis Tunisia Université Paris-Est Laboratoire Navier (UMR8205) ENPC-IFSTTAR-CNRS Marne-la-Vallée France Department of Civil Engineering Federal University of Rio Grande do Sul Av. Osvaldo Aranha 99 Porto Alegre RS 90350-190 Brazil

The stability analysis of passive bolt-reinforced rock slopes under seismic loads is investigated within the framework of the kinematic approach of limit analysis theory.A pseudo-static method is adopted to account for the inertial forces induced in the rock mass by seismic *** strength properties of the rock material are described by a modified Hoek-Brown strength criterion,whereas the passive bolts are modeled as bar-like inclusions that exhibit only resistance to tensile-compressive *** advantage of the ability to compute closed-form expressions for the support functions associated with the modified Hoek-Brown strength criterion,a rotational failure mechanism is implemented to derive rigorous lower bound estimates for the amount of reinforcement strength to prevent slope *** approach is then applied to investigating the effects of relevant geometry,strength and loading parameters in light of a preliminary parametric *** accuracy of the approach is assessed by comparison of the lower bound estimates with finite element limit analysis solutions,thus emphasizing the ability of the approach to properly predict the stability conditions and to capture the essential features of deformation localization ***,the extension of the approach to account for slipping at the interface between reinforcements and surrounding rock mass is outlined.

关键词： Reinforced rock slope Modified Hoek-Brown criterion Seismic loading Limit analysis Rotational failure mechanism

CREEP BEHAVIOUR IN THERMAL AND MECHANICAL CONSOLIDATION TESTS ON BOOM CLAY

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CREEP BEHAVIOUR IN THERMAL AND MECHANICAL CONSOLIDATION TEST...