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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

Study on failure mechanism of room and pillar with different shapes and configurations under uniaxial test and numerical simulation compression using experimental test and numerical simulation

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Underground Space 2023年第2期9卷 105-121页

作者： Vahab Sarfarazi nima babanouri Shahin Fattahi Kaveh Asgari Department of Mining Engineering Hamedan University of TechnologyHamedanIran Department of Mining Engineering Shahid Bahonar University of KermanKermanIran

Experimental and discrete element methods were used to investigate the failure behavior of room and pillar with different configura-tions under uniaxial *** samples with dimension of 15 cm×15 cm×5 cm were *** the specimens,rooms and pillars with different configurations were *** room dimension was 1 cm×1 cm,and the pillar dimension was according to the room *** different configurations were chosen for rooms and *** axial load was applied to the model by rate of 0.05 mm/*** results show that the failure process was mostly governed by both the non-persistent joint angle and joint *** compressive strength of the specimens was related to the fracture pattern and failure mechanism of the *** was shown that the shear behaviour of pillars was related to the number of the induced tensile cracks,which increased by increasing the room *** compressive strength of samples increased with the increase of the room *** failure pattern and failure strength are similar in both methods,i.e.,the experimental testing and the numerical simulation.

关键词： PFC2D Physical test Rock pillar

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

Nonlinear integral resonant controller for vibration reduction in nonlinear systems

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Acta Mechanica Sinica 2016年第5期32卷 925-934页

作者： Ehsan Omidi S.nima Mahmoodi Nonlinear Intelligent Structures Laboratory Department of Mechanical Engineering The University of Alabama

A new nonlinear integral resonant controller（NIRC） is introduced in this paper to suppress vibration in nonlinear oscillatory smart structures. The NIRC consists of a first-order resonant integrator that provides additional damping in a closed-loop system response to reduce highamplitude nonlinear vibration around the fundamental resonance frequency. The method of multiple scales is used to obtain an approximate solution for the closed-loop *** closed-loop system stability is investigated using the resulting modulation equation. Finally, the effects of different control system parameters are illustrated and an approximate solution response is verified via numerical simulation *** advantages and disadvantages of the proposed controller are presented and extensively discussed in the results. The controlled system via the NIRC shows no high-amplitude peaks in the neighboring frequencies of the resonant mode,unlike conventional second-order compensation *** makes the NIRC controlled system robust to excitation frequency variations.

关键词： Active vibration control Cantilever Highamplitude oscillation Method of multiple scales Nonlinear vibration Piezoelectric actuator Smart structure

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

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

Seismic demand evaluation of medium ductility RC moment frames using nonlinear procedures

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Earthquake Engineering and Engineering Vibration 2013年第3期12卷 399-409页

作者： Hosein Ghaffarzadeh nima Talebian Roya Kohandel Faculty of Civil Engineering University of TabrizTabriz Iran Faculty of Civil Engineering Universiti Teknologi Malaysia81310 UTM Skudai Johor Malaysia

Performance-based earthquake engineering is a recent focus of research that has resulted in widely developed design methodologies due to its ability to realistically simulate structural response characteristics. Precise prediction of seismic demands is a key component of performance-based design methodologies. This paper presents a seismic demand evaluation of reinforced concrete moment frames with medium ductility. The accuracy of utilizing simplified nonlinear static analysis is assessed by comparison against the results of time history analysis on a number of frames. Displacement profiles, drift demand and maximum plastic rotation were computed to assess seismic demands. Estimated seismic demands were compared to acceptance criteria in FEMA 356. The results indicate that these frames have sufficient capacity to resist interstory drifts that are greater than the limit value.

关键词： seismic demand evaluation pushover analysis time history analysis plastic rotations FEMA 356

Heterogeneous particle structure formation during post-crystallization of spray-dried powder

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Particuology 2016年第4期14卷 72-79页

作者： nima Yazdanpanah Tim A.G. Langrish School of Chemical & Biomolecular Engineering The University of Sydney Sydney 2006. NSW. Australia

The formation of heterogeneous particle structure in skim milk powder has been investigated in a post- crystallization facility using experimental and a mathematical model. Various processing conditions were used to produce these heterogeneous structures. The experimental process parameters were used as initial and boundary conditions for the model. The modelled data agreed well with the experimental data. The experimental and modelling results show that the powder processed at high water activity （aw = 0.7） with low initial moisture content （X0 = 0.01 kg/kg） developed a crystalline surface layer while the core of the particle remained amorphous. This structure is referred to as an egg-shell structure. The powder that was processed at low water activity （αw = 0.1） with high initial moisture content （X0 = 0.2 kg/kg） developed a crystalline core while the surface of the particle remained amorphous. This structure is referred to as an egg-yolk structure. Understanding the dependency of particle microstructures on the processing conditions could be useful when developing procedures to control the drying equipment because the particle microstructure affects the physicochemical properties of the powder and potential applications and behaviour of the powder.

关键词： Heterogeneous structure Microstructure modification Post-crystallization Phase change Complex domain matrix