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The interrill erosion for a sandy loam soil

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International Journal of Sediment Research 2013年第3期28卷 329-337页

作者： Gabriella BALACCO dipartimento di ingegneria Civile Ambientaledel TerritorioEdile e di Chimica(DICATECh)Politecnico di BariBari Italy

This paper resumes a laboratory experience on a slope adjustable plot with the aim of examining the role of rainfall intensity and slope gradient for a sandy loam soil,typical of Southern Italy,with particular initial moisture *** results of the simulations performed show that a rainfall reduction causes a corresponding percentage reduction of sediment output.A similar behaviour can be attributed to slope gradient,while runoff moderately increases with rainfall intensity but it is not sensitive to slope *** also highlight that the degree of saturation can affect runoff and soil loss values.

关键词： Interrill erosion Runoff Slope gradient

Effects of near-fault ground motions on the nonlinear behaviour of reinforced concrete framed buildings

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Earthquake Science 2015年第4期28卷 285-302页

作者： Mirko Mazza dipartimento di ingegneria Civile Università della CalabriaArcavacata di Rende

The design provisions of current seismic codes are generally not very accurate for assessing effects of near-fault ground motions on reinforced concrete （r.c.） spatial frames, because only far-fault ground motions are considered in the seismic codes. Strong near-fault earth- quakes are characterized by long-duration （horizontal） pulses and high values of the ratio ~PGA of the peak value of the vertical acceleration, PGAv, to the analogous value of the horizontal acceleration, PGAH, which can become critical for girders and columns. In this work, six- and twelve-storey r.c. spatial frames are designed according to the provisions of the Italian seismic code, considering the horizontal seismic loads acting （besides the gravity loads） alone or in combination with the vertical ones. The non- linear seismic analysis of the test structures is performed using a step-by-step procedure based on a two-parameter implicit integration scheme and an initial stress-like itera- tive procedure. A lumped plasticity model based on the Haar-K^n~m principle is adopted to model the inelastic behaviour of the frame members. For the numerical investigation, five near-fault ground motions with high values of the acceleration ratio C^p6A are considered. Moreover, following recent seismological studies, which allow the extraction of the largest （horizontal） pulse from a near-fault ground motion, five pulse-type （horizontal） ground motions are selected by comparing the original ground motion with the residual motion after the pulse has been extracted. The results of the nonlinear dynamic analysis carried out on the test structures highlighted thathorizontal and vertical components of near-fault ground motions may require additional consideration in the seis- mic codes.

关键词： Near-fault ground motions Nonlineardynamic analysis r.c. spatial frames

APolygonal discontinuous Galerkin Formulation for Contact Mechanics in Fluid-Structure Interaction Problems

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Communications in Computational Physics 2021年第6期30卷 1-33页

作者： Stefano Zonca Paola FAntonietti Christian Vergara MOX Dipartimento di MatematicaPolitecnico di MilanoItaly LABS Dipartimento di ChimicaMateriali e Ingegneria Chimica“Giulio Natta”Politecnico di MilanoItaly

In this work,we propose a formulation based on the Polygonal discontinuous Galerkin(PolyDG)method for contact mechanics that arises in fluid-structure interaction *** particular,we introduce a consistent penalization approach to treat the frictionless contact between immersed structures that undergo large *** key feature of the method is that the contact condition can be naturally embedded in the PolyDG formulation,allowing to easily support polygonal/polyhedral *** proposed approach introduced a fixed background mesh for the fluid problem overlapped by the structure grid that is able to move independently of the fluid *** assess the validity of the proposed approach,we report the results of several numerical experiments obtained in the case of contact between flexible structures immersed in a fluid.

关键词： Polygonal discontinuous Galerkin method fluid-structure interaction contact mechanics

Nonlinear analysis of r.c. framed buildings retrofitted with elastomeric and friction bearings under near-fault earthquakes

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Earthquake Science 2015年第5期28卷 365-377页

作者： Mirko Mazza dipartimento di ingegneria Civile Universita della CalabriaPonte Bucci

Reinforced concrete （r.c.） framed buildings designed in compliance with inadequate seismic classifi- cations and code provisions present in many cases a high vulnerability and need to be retrofitted. To this end, the insertion of a base isolation system allows a considerable reduction of the seismic loads transmitted to the super- structure. However, strong near-fault ground motions, which are characterised by long-duration horizontal pulses, may amplify the inelastic response of the superstructure and induce a failure of the isolation system. The above considerations point out the importance of checking the effectiveness of different isolation systems for retrofitting a r.c. framed structure. For this purpose, a numerical inves- tigation is carried out with reference to a six-storey r.c. framed building, which, primarily designed （as to be a fixed-base one） in compliance with the previous Italian code （DM96） for a medium-risk seismic zone, has to be retrofitted by insertion of an isolation system at the base for attaining performance levels imposed by the current Italian code （NTC08） in a high-risk seismic zone. Besides the （fixed-base） original structure, three cases of base isolation are studied： elastomeric bearings acting alone （e.g. HDLRBs）; in-parallel combination of elastomeric and friction bearings （e.g. high-damping-laminated-rubber beatings, HDLRBs and steel-PTFE sliding bearings, SBs）; friction bearings acting alone （e.g. friction pendulum bearings, FPBs）. The nonlinear analysis of the fixed-base and base-isolated structures subjected to horizontal com- ponents of near-fault ground motions is performed for checking plastic conditions at the potential critical （end） sections of the girders and columns as well as critical conditions of the isolation systems. Unexpected high val- ues of ductility demand are highlighted at the lower floors of all base-isolated structures, while re-centring problems of the base isolation systems under near-fault earthquakes a

关键词： R.c. base-isolated structures Elastomericbearings Friction bearings Nonlinear dynamic analysis

Semisolid lead-antimony alloys for cars batteries

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Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1774-1779页

作者： A.POLA M.GELFI M.M OdiGELL R.ROBERTI dipartimento di ingegneria Meccanica e Industriale Università degli Studi di Brescia Aachener Verfahrenstechnik Chair of Mechanical Unit OperationsRWTH Aachen University

The application of semisolid process was investigated on Pb-Sb alloys that are normally used for metallic parts in car batteries, in order to increase their mechanical properties and corrosion *** semisolid behaviour of a Pb-4%Sb alloy was analysed by means of rheological and calorimetry differential scanning *** alloy was melted, treated by ultrasound to obtain the semisolid state and then poured into permanent *** of these samples were also heated in semisolid temperature range and injected in thixo-casting *** poured and injected samples were characterized by metallographic analysis, mechanical test and electrochemical corrosion *** results show an improvement of mechanical and corrosion resistance with respect to samples obtained by conventional casting technique.

关键词： Pb-based alloys semisolid metal corrosion resistance viscosity

Fractional-order systems without equilibria:The first example of hyperchaos and its application to synchronization

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Chinese Physics B 2015年第8期24卷 224-232页

作者： Donato Cafagna Giuseppe Grassi dipartimento ingegneria Innovazione Università del Salento

A challenging topic in nonlinear dynamics concerns the study of fractional-order systems without equilibrium *** particular, no paper has been published to date regarding the presence of hyperchaos in these systems. This paper aims to bridge the gap by introducing a new example of fractional-order hyperchaotic system without equilibrium points. The conducted analysis shows that hyperchaos exists in the proposed system when its order is as low as 3.84. Moreover, an interesting application of hyperchaotic synchronization to the considered fractional-order system is provided.

关键词： fractional-order systems equilibrium points hyperchaotic systems synchronization

Modeling of shear induced coarsening effects in semi-solid alloys

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Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1696-1701页

作者： M.MOdiGEL L A.POLA AVT Chair of Mechanical Process EngineeringRWTH Aachen University dipartimento di ingegneria Meccanica e Industriale Uni.degli Studi di Brescia

In long-term rheological shear experiments with semi-solid alloys, coarsening of the particles will falsify the interpretation of the experimental *** coarsening is intensified by the shear induced convection and the mean size of the particles is changed significantly during the experiments.A simple model has been set up which takes the influence of the convection into *** resulting growth law has been simplified for diffusion and convection dominated *** growth law was verified with shear experiments in a Searl-rheometer with A356 and tin-lead *** experiments demonstrated that under convection the growth follows a linear time law and that the rate constant depends on the root of the shear *** correction of experimental results to gain the true viscosity function is demonstrated for a shear jump experiment with A356.

关键词： microstructure coarsening Ostwald ripening flow function viscosity rheology semi-solid alloys

Navier-Stokes Spectral Solver in a Finite Cylinder

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Communications in Computational Physics 2010年第8期8卷 663-689页

作者： F.Auteri M.Biava L.Quartapelle Politecnico di Milano Dipartimento di Ingegneria AerospazialeVia La Masa 3420156 MilanoItaly

A primitive variable spectral method for simulating incompressible viscous flows inside a finite cylinder is *** element of originality of the proposed method is that the radial discretization of the Fourier coefficients depends on the Fourier mode,its dimension decreasing with the increase of the azimuthal modal *** principle was introduced independently by Matsushima and Marcus and by Verkley in polar coordinates and is adopted here for the first time to formulate a 3D cylindrical Galerkin projection method.A second element of originality is the use of a special basis of Jacobi polynomials introduced recently for the radial dependence in the solution of dirichlet *** this basis the radial operators are represented by matrices of minimal sparsity-diagonal stiffness and tridiagonal mass-provided here in closed form for the first time,and lead to a Helmholtz operator characterized by a favorable condition ***,a new method is presented for eliminating the singular behaviour of the solution originated by the rotation of the lid with respect to the cylindrical *** to these elements,the resulting Navier-Stokes spectral solver guarantees the differentiability to any order of the solution in the entire computational domain and does not suffer from the time-step stability restriction occurring in spectral methods with a point clustering close to the *** test examples are offered that demonstrate the spectral accuracy of the solution method under different representative conditions.

关键词： Navier-Stokes equations finite cylindrical domain spectral methods Jacobi and Legendre polynomials primitive variables projection method

Spectral Matrix Conditioning in Cylindrical and Spherical Elliptic Equations

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Numerical Mathematics(Theory,Methods and Applications) 2011年第2期4卷 113-141页

作者： F.Auteri L.Quartapelle Politecnico di Milano Dipartimento di Ingegneria AerospazialeVia La Masa 3420156 MilanoItaly

In the spectral solution of 3-D Poisson equations in cylindrical and spherical coordinates including the axis or the center,it is convenient to employ radial basis functions that depend on the Fourier wavenumber or on the latitudinal *** idea has been adopted by Matsushima and Marcus and by Verkley for planar problems and pursued by the present authors for spherical *** the dirichlet boundary value problem in both geometries,original bases have been introduced built upon Jacobi polynomials which lead to a purely diagonal representation of the radial second-order differential operator of all spectral *** note details the origin of such a diagonalization which extends to cylindrical and spherical regions the properties of the Legendre basis introduced by Jie Shen for Cartesian *** form expressions are derived for the diagonal elements of the stiffness matrices as well as for the elements of the tridiagonal mass matrices occurring in evolutionary ***,the bound on the condition number of the spectral matrices associated with the Helmholtz equation are determined,proving in a rigorous way one of the main advantages of the proposed radial bases.

关键词： Poisson equation cylindrical and spherical coordinates Fourier expansion spherical harmonics Jacobi polynomials spectral methods condition number