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Teaching solid mechanics to artificial intelligence—a fast solver for heterogeneous materials

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npj Computational Materials 2021年第1期7卷 899-908页

作者： Jaber Rezaei Mianroodi nima h.s.boni Dierk Raabe Microstructure Physics and Alloy Design Max-Planck-Institut für EisenforschungDüsseldorfGermany DeepMetis BerlinGermany

We propose a deep neural network(DNN)as a fast surrogate model for local stress calculations in inhomogeneous non-linear *** show that the DNN predicts the local stresses with 3.8%mean absolute percentage error(MAPE)for the case of heterogeneous elastic media and a mechanical contrast of up to factor of 1.5 among neighboring domains,while performing 103 times faster than spectral *** DNN model proves suited for reproducing the stress distribution in geometries different from those used for *** the case of elasto-plastic materials with up to 4 times mechanical contrast in yield stress among adjacent regions,the trained model simulates the micromechanics with a MAPE of 6.4%in one single forward evaluation of the network,without any *** results reveal an efficient approach to solve non-linear mechanical problems,with an acceleration up to a factor of 8300 for elastic-plastic materials compared to typical solvers.

关键词： artificial network faster

Probabilistic safety assessment of self-centering steel braced frame

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Frontiers of structural and Civil Engineering 2018年第1期12卷 163-182页

作者： Navid RAhGOZAR nima RAhGOZAR Abdolreza s. MOGhADAM Department of structural Engineering Science and Research Branch Islamic Azad University Tehran Iran structural Engineering Research Center International Institute of Earthquake Engineering and Seismology (IIEES) Tehran Iran

The main drawback of conventional braced frames is implicitly accepting structural damage under the design earthquake load, which leads to considerable economic losses. Controlled rocking self-centering system as a modem low-damage system is capable of minimizing the drawbacks of conventional braced frames. This paper quantifies main limit states and investigates the seismic performance of self-centering braced frame using a Probabilistic safety Assessment procedure. Margin of safety, confidence level, and mean annual frequency of the self-centering archetypes for their main limit states, including PT yield, fuse fracture, and global collapse, are established and are compared with their acceptance criteria. Considering incorporating aleatory examined. Results of the investigation indicate that the provide the adequate margin of safety against exceeding and epistemic uncertainties, the efficiency of the system is design of low- and mid-rise self-centering archetypes could the undesirable limit-states.

关键词： self-centering steel braced frame mean annual frequency safety assessment confidence level margin of safety

Low pressure mercury–argon electrodeless fluorescent lamp simulation using the finite volume method

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Plasma science and Technology 2018年第10期20卷 98-103页

作者： nima VAZIRI Department of Physics Karaj Branch Islamic Azad University

A finite volume model of a low pressure Ar-hg electrodeless lamp with external coils is established. The physical configuration is similar to the OsRAM/ENDURA 70 W lamp. A Maxwellian energy distribution is assumed. Two dimensional behaviors of the most important plasma parameters such as the electron density, the electron temperature and the most important mercury states are discussed. Results are in good agreement with former studies and the general understanding in this area. Also, the influence of the argon pressure is studied. Based on the simulation, the population of the main resonance state, hg （63p1） depends on the argon pressure and the optimized value is about 300 mTorr.

关键词： electrodeless lamp Ar-hg discharge electric discharge lamp

A New Formulation of the scaled Boundary Finite Element Method for heterogeneous Media:Application to heat Transfer Problems

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Acta Mechanica solida sinica 2024年第2期37卷 285-296页

作者： nima Noormohammadi Nazanin Pirhaji Khouzani Department of Civil Engineering Isfahan University of TechnologyIsfahan84156-83111Iran

The solution to heat transfer problems in two-dimensional heterogeneous media is attended based on the scaled boundary finite element method(sBFEM)coupled with equilibrated basis functions(EqBFs).The sBFEM reduces the model order by scaling the boundary solution onto the inner *** this end,tri-lateral elements are emanated from a scaling center,followed by the development of a semi-analytical solution along the radial direction and a finite element solution along the circumferential/boundary *** discretization is thus limited to the boundaries of the model,and the semi-analytical radial solution is found through the solution of an eigenvalue problem,which restricts the methods’applicability to heterogeneous *** this research,we first extracted the sBFEM formulation considering the heterogeneity of the ***,we replaced the semi-analytical radial solution with the EqBFs and removed the eigenvalue solution step from the *** varying coefficients of the partial differential equation(PDE)resulting from the heterogeneity of the media are replaced by a finite series in the radial and circumferential directions of the element.A weighted residual approach is applied to the radial *** equilibrated radial solution series is used in the new formulation of the sBFEM.

关键词： scaled boundary finite element method Equilibrated basis functions heat transfer

Corrosion control in underground concrete structures using double waterproofing shield system (DWs)

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International Journal of Mining science and Technology 2013年第4期23卷 590-598页

作者： nima Ghafari Mapua Institute of Technology School of Civil Environmental and Geological Engineering Intramuros Manila 1002 Philippines

high level of structural and waterproofng stability leads to long-term service life in underground *** between aggressive groundwater with tunnel causes corrosion and damage in concrete structure due to steel reinforcement corrosion and concrete *** study introduces a double waterproofng shield system(DWs)as an innovative solution to waterproofng and structural failures in underground concrete *** this method,ordinary shotcrete mixture replaces by an organic polymer concrete(OPC)to construct a water-resistant temporary support right after each partial *** groups of specimens including reference concrete and OPC specimens were provided and tested in accordance with AsTM C *** parameters including porosity,pore volume,permeability and hydraulic conductivity have been *** show a remarkable reduction in mentioned parameters for OPC compared with ordinary *** in waterproofng performance of temporary support corresponds to a healthy fnal lining and increase in service life of the structure.

关键词： Corrosion Final lining structure Organic polymer concrete (OPC) Underground concrete structure Waterproofing shield Water-resistant temporary support

An artificial neural network for surrogate modeling of stress fields in viscoplastic polycrystalline materials

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npj Computational Materials 2023年第1期9卷 1981-1990页

作者： Mohammad s.Khorrami Jaber R.Mianroodi nima h.s.boni Pawan Goyal Bob svendsen Peter Benner Dierk Raabe Microstructure Physics and Alloy Design Max-Planck-Institut für EisenforschungDüsseldorfGermany Ergodic Labs Lohmühlenstraße 6512435 BerlinGermany Computational Methods in systems and Control Theory Max Planck Institute for Dynamics of Complex Technical SystemsMagdeburgGermany Material Mechanics RWTH Aachen UniversityAachenGermany

The purpose of this work is the development of a trained artificial neural network for surrogate modeling of the mechanical response of elasto-viscoplastic grain *** this end,a U-Net-based convolutional neural network(CNN)is trained using results for the von Mises stress field from the numerical solution of initial-boundary-value problems(IBVPs)for mechanical equilibrium in such microstructures subject to quasi-static uniaxial *** resulting trained CNN(tCNN)accurately reproduces the von Mises stress field about 500 times faster than numerical solutions of the corresponding IBVP based on spectral *** of the tCNN to test cases based on microstructure morphologies and boundary conditions not contained in the training dataset is also investigated and discussed.

关键词： methods boundary faster

Investigating a potential reservoir landslide and suggesting its treatment using limit-equilibrium and numerical methods

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Journal of Mountain science 2017年第3期14卷 432-441页

作者： nima BABANOURI hesam DEhGhANI Department of Mining Engineering Hamedan University of Technology***HamedanIran

A reservoir landslide not only reduces the water storage capacity, but also causes extensive damages to the dam body, power/water transmission lines, roads, and other infrastructures. The Latian Dam, located 35 km north east of Tehran （Iran）, is one of the cases which has encountered serious problems with instability of its rock abutments. This paper addresses the stability analysis of the right abutment of the Latian Dam using limit equilibrium and numerical methods. Geomechanical characteristics of the rock abutment were first estimated based on engineering classification of the rock mass. Different search methods were examined for locating the critical circular/non-circular slip surface in conjunction with the general limit equilibrium method. The effect of variabi]ity of rock mass properties, water table, and earthquake load on the factor of safety （Fs） and probability of failure （PF） was studied. In the event of rapid drawdown in the reservoir, the limit equilibrium analysis calculated Fs=1.067 and PF=21.1%, and the numerical analysis returned Fs=1.01. The results of the analyses suggest that the right abutment of the Latian Dam is prone to slide and needs treatment. Investigations demonstrated that a slope reduction by 15° at the upper part of the abutment would meet stability conditions even in the worst-case scenario （Fs=1.297 and PF=2.07%）.

关键词： Reservoir landslide Limit equilibrium Numerical modeling Reliability slope stabilization

synthesis and characterization of carbon-coated cobalt ferrite nanoparticles

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International Journal of Minerals,Metallurgy and Materials 2016年第9期23卷 1104-1111页

作者： hamed Bakhshi Ali shokuhfar nima Vahdati Advanced Materials and Nanotechnology Lab Department of Materials Science and Engineering K.N.Toosi University of Technology Department of Materials science and Engineering Saveh Branch Islamic Azad University

Cobalt ferrite nanoparticles（CFNPs） were prepared via a reverse micelle method. The CFNPs were subsequently coated with carbon shells by means of thermal chemical vapor deposition（TCVD）. In this process, acetylene gas（C2h2） was used as a carbon source and the coating was carried out for 1, 2, or 3 h at 750℃. The Ar/C2h2 ratio was 10：1. heating during the TCVD process resulted in a NP core size that approached 30 nm; the thickness of the shell was less than 10 nm. The composition, structure, and morphology of the fabricated composites were characterized using X-ray diffraction, simultaneous thermal analysis, transmission electron microscopy, high-resolution transmission electron microscopy, and selected-area diffraction. A vibrating sample magnetometer was used to survey the samples＇ magnetic properties. The deposited carbon shell substantially affected the growth and magnetic properties of the CFNPs. Micro-Raman spectroscopy was used to study the carbon coating and revealed that the deposited carbon comprised graphite, multiwalled carbon nanotubes, and diamond-like carbon. With an increase in coating time, the intensity ratio between the amorphous and ordered peaks in the Raman spectra decreased, which indicated an increase in crystallite size.

关键词： nanoparticles cobalt ferrite carbon coatings chemical vapor deposition Raman spectroscopy

A Two-stage Adaptive Robust Model for Residential Micro-ChP Expansion Planning

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Journal of Modern Power systems and Clean Energy 2021年第4期9卷 826-836页

作者： Fatemeh Teymoori hamzehkolaei nima Amjady Bahareh Bagheri Department of Electrical Engineering Semnan UniversitySemnanIran

This paper addresses the planning problem of residential micro combined heat and power (micro-ChP) systems (including ‎micro-generation units, auxiliary boilers, and thermal storage tanks) considering the associated technical and economic factors. since the accurate values of the thermal and electrical loads of this system cannot be exactly predicted for the planning horizon, the thermal and electrical load uncertainties are modeled using a two-stage ‎adaptive robust optimization method based on a ‎polyhedral uncertainty set. A solution method, which is composed of column-and-constraint generation (C&CG) algorithm ‎and block coordinate descent (BCD) method, is proposed to efficiently solve this adaptive robust optimization model. Numerical results ‎from a practical case study show the effective performance of the proposed adaptive robust model for residential micro-ChP planning and its solution method.

关键词： Micro combined heat and power(micro-ChP)planning two-stage adaptive robust optimization model block coordinate descent method polyhedral uncertainty set