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Progressive collapse resisting capacity of reinforced concrete load bearing wall structures

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Journal of Central South University 2015年第7期22卷 2730-2738页

作者： Alireza Rahai Alireza shahin Farzad Hatami Department of Civil Engineering Amirkabir University of Technology (Tehran Polytechnic) No.424 Structural & Earthquake Research Center (SERC) Amirkabir University of Technology No.424

Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.

关键词： reinforced concrete(RC) load bearing wall structure progressive collapse fiber sections nonlinear analysis load factor method

Evaluation of the ECMWF Precipitation Product over Various Regions of Iran

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Journal of Meteorological Research 2021年第6期35卷 1125-1135页

作者： Aminreza NESHAT shahin SHOBEIRI Ahmad SHARAFATI Department of Geographic Information System Remote SensingFaculty of Natural Resources and EnvironmentScience and Research BranchIslamic Azad UniversityTehranIran Department of Civil Engineering Science and Research BranchIslamic Azad UniversityTehranIran

Easy access to accurate and reliable climate data is a crucial concern in hydrological *** this regard,gridded climate data have recently been provided as an alternative to observational ***,those data should be first evaluated and corrected to guarantee their validity and *** study offered a new approach to assess the ECMWF gridded precipitation data based on some indicators,including correlation coefficient(CC),normalized root-mean-square error(NRMSE),and absolute error(AE)in daily and monthly intervals(2007-2017)across different climatic and geographical areas of ***,an artificial neural network(ANN)model was utilized to correct the ECMWF precipitation *** to the results,NRMSE was less than 2(in 93%of stations)and 5(in63%of stations)on monthly and daily scales,***,CC was above 0.6 in 58%and 94%of stations on daily and monthly scales,*** AE values were from-0.5 to 0.5,in 80%(daily scale)and 50%(monthly scale)of *** corrected the ECMWF precipitation product by ANN,the number of stations with NRMSE less than 5 increased from 63%to 74%on the daily timescale,whereas the number of stations with NRMSE less than 2 reached 95%from 93%on the monthly *** results also showed that the number of stations with CC more than 0.6 increased from 58%to 87%on the daily timescale.

关键词： ECMWF gridded precipitation data artificial neural network(ANN) Iran

Angiographic characteristics of central serous chorioretinopathy in an Egyptian population

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International Journal of Ophthalmology(English edition) 2013年第3期6卷 342-345页

作者： Maha M shahin Mansoura Faculty of Medicine Mansoura University

· AIM: To describe and analyze the demographic characteristics and to determine the angiographic features of acute central serous chorioretinopathy(CSCR) in an Egyptian population. ·METHODS: A series of consecutive patients presenting with acute idiopathic CSCR to Mansoura Ophthalmology Center Mansoura University who underwent fluorescein angiography (FA) within a 3 -year -period (between January 1, 2007 and December 31, 2009) was retrospectively studied. Patient demographics and angiographic features were studied. Results were compared to those of other Western and Asian populations. ·RESULTS: Fluorescein angiograms of 86 patients were analyzed. 91% were males. The age range of patients was 24 -49 years, with a mean age of (38±6) years. The right eye was the presenting eye in 47% of patients. Eighty seven percent of eyes showed delayed choroidal filling. Thirty -five percent of patients had more than one point of leakage. The macula was the most common site of fluorescein leakage seen in 79% of patients. Peripheral leakage was seen in 14% of patients while peripapillary leakage was seen in 12% of patients. The inkblot leakage pattern was found in 53% of patients. The presenting eye had RPE atrophic changes in 84% of cases. The other eye was assessed in 44 patients (51%). Fifty-five percent of them had signs of RPE atrophic changes. ·CONCLUSION: In the Egyptian population, CSCR is seen at younger age with higher male -to -female ratio and more frequent smokestack leaks than other populations. Despite younger age group, this series of patient showed higher frequency of bilateral and multifocal disease compared to other studies. Roles of psychological stress and choroidal ischemia in pathogenesis of CSCR need further evaluation. ·

关键词： choroidal circulation central serous chorioretinopathy epidemiology fluorescein angiography medical retina

Nano-tribological behavior of graphene nanoplatelet-reinforced magnesium matrix nanocomposites

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Journal of Magnesium and Alloys 2021年第3期9卷 895-909页

作者： Mohammad shahin Khurram Munir Cuie Wen Yuncang Li School of Engineering RMIT UniversityMelbourneVIC 3001Australia

The corrosion resistance and wear resistance of metallic biomaterials are critically important for orthopedic hard-tissue replacement applications because the lack of such properties not only adversely affects their mechanical integrity but also allows the release of wear debris into the human *** this study,the potential of zirconium(Zr)as an alloying element and graphene nanoplatelets(GNPs)as a nano-reinforcement material were investigated in relation to improving the tribological performance of pure magnesium(Mg).The GNPs-reinforced Mg matrix nanocomposites(MNCs)were fabricated using powder *** indicate that additions of 0.5 wt.%Zr and0.1 wt.%GNPs to Mg matrices significantly improved the wear resistance by 89%and 92%at 200μN load,60%and 80%at 100μN load,and 94%and 93%at 50μN load,respectively,as compared to the wear resistance of pure *** wear depth and coefficient of friction of the MNC containing 0.5 wt.%Zr and 0.1 wt.%GNPs(Mg0.5 Zr0.1 GNPs MNC)were considerably reduced as compared to pure Mg and Mg0.5 *** results demonstrate that the Mg0.5 Zr0.1 GNPs MNC is promising for orthopedic applications in relation to its excellent tribological performance.

关键词： Coefficient of friction Graphene nanoplatelet Magnesium matrix nanocomposite Wear

Effect of overburden pressure on determination of reservoir rock types using RQI/FZI,FZI^* and Winland methods in carbonate rocks

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Petroleum Science 2019年第6期16卷 1403-1416页

作者： Aboozar Soleymanzadeh Saeed Parvin shahin Kord Ahwaz Faculty of Petroleum Petroleum University of Technology(PUT)AhwazIran

Rock typing is an important tool in evaluation and performance prediction of *** techniques such as flow zone indicator(FZI),FZI~*and Winland methods are used to categorize reservoir rocks into distinct rock ***,these methods are applied to petrophysical data that are measured at a pressure other than reservoir *** the pressure changes the pore structure of rock,the effect of overburden pressure on rock typing should be *** this study,porosity and permeability of 113 core samples were measured at five different *** investigate the effect of pressure on determination of rock types,FZI,FZI~*and Winland methods were *** indicated that although most of the samples remain in the same rock type when pressure changes,some of them show different *** are related to the mineralogy and changes in pore system of the samples due to pressure ***,the number of rock types increases with increasing ***,the effect of overburden pressure on determination of rock types is more clearly observed in the Winland and FZI~****,results revealed that a more precise reservoir dynamic simulation can be obtained by considering the reservoir rock typing process at reservoir conditions.

关键词： Overburden pressure Carbonate rocks Rock type Reservoir quality index Flow zone indicator Winland method

Mechanical and corrosion properties of graphene nanoplatelet–reinforced Mg–Zr and Mg–Zr–Zn matrix nanocomposites for biomedical applications

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Journal of Magnesium and Alloys 2022年第2期10卷 495-514页

作者： Mohammad shahin Cuie Wen Khurram Munir Yuncang Li School of Engineering RMIT UniversityMelbourneVictoria 3001Australia

Magnesium(Mg)-based biomaterials have gained acceptability in fracture fixation due to their ability to naturally degrade in the body after fulfilling the desired ***,pure Mg not only degrades rapidly in the physiological environment,but also evolves hydrogen gas during *** this study,Mg0.5Zr and Mg0.5ZrxZn(x=1–5 wt.%)matrix nanocomposites(MNCs)reinforced with different contents(0.1–0.5 wt.%)of graphene nanoplatelets(GNP)were manufactured via a powder metallurgy technique and their mechanical and corrosion properties were *** increase in GNP concentration from 0.2 wt.%to 0.5 wt.%added to Mg0.5Zr matrices resulted in decreases in the compressive yield strength and corrosion resistance in Hanks’Balanced Salt Solution(HBSS).On the other hand,a higher concentration(4–5 wt.%)of Zn added to Mg0.5Zr0.1GNP resulted in an increase in ductility but a decrease in compressive yield ***,an addition of 0.1 wt.%GNPs to Mg0.5Zr3Zn matrices gave excellent ultimate compressive strength(387 MPa)and compressive yield strength(219 MPa).Mg0.5Zr1Zn0.1GNP and Mg0.5Zr3Zn0.1GNP nanocomposites exhibited 29%and 34%higher experimental yield strength,respectively,as compared to the theoretical yield strength of Mg0.5Zr0.1GNP calculated by synergistic strengthening mechanisms including the difference in thermal expansion,elastic modulus,and geometry of the particles,grain refinement,load transfer,and precipitation of GNPs in the Mg *** corrosion rates of Mg0.5Zr1Zn0.1GNP,Mg0.5Zr3Zn0.1GNP,Mg0.5Zr4Zn0.1GNP,and Mg0.5Zr5Zn0.1GNP measured using potentiodynamic polarization were 7.5 mm/y,4.1 mm/y,6.1 mm/y,and 8.0 mm/y,***,hydrogen gas evolution tests also demonstrated that Mg0.5Zr3Zn0.1GNP exhibited a lower corrosion rate(1.5 mm/y)than those of Mg0.5Zr1Zn0.1GNP(3.8 mm/y),Mg0.5Zr4Zn0.1GNP(1.9 mm/y),and Mg0.5Zr5Zn0.1GNP(2.2 mm/y).This study demonstrates the potential of GNPs as effective nano-reinforcement particulates for improv

关键词： Biodegradation Graphene nanoplatelet Magnesium metal matrix composite Mg–Zr–Zn alloy Strengthening mechanism

A Review on Self-healing in Modern Power Distribution Systems

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Journal of Modern Power Systems and Clean Energy 2023年第6期11卷 1719-1733页

作者： Seyed Ali Arefifar Md shahin Alam Abdullah Hamadi IEEE Department of Electrical and Computer Engineering Oakland UniversityRochesterUSA Department of Energy and Technology Odessa CollegeOdessaUSA School of Engineering and Technology Western Illinois UniversityMacombUSA

The ever-increasing dependence on electrical power has posed more challenges to power system engineers to deliver secure, stable, and sustained energy to electricity consumers. Due to the increasing occurrence of short-and long-term power interruptions in the power system, the need for a systematic approach to mitigate the negative impacts of such events is further manifested. Self-healing and its control strategies are generally accepted as a solution for this concern. Due to the importance of self-healing subject in power distribution systems, this paper conducts a comprehensive literature review on self-healing from existing published papers. The concept of self-healing is briefly described, and the published papers in this area are categorized based on key factors such as self-healing optimization goals, available control actions, and solution methods. Some proficient techniques adopted for self-healing improvements are also classified to have a better comparison and selection of methods for new investigators. Moreover, future research directions that need to be explored to improve self-healing operations in modern power distribution systems are investigated and described at the end of this paper.

关键词： Self-healing distributed generator renewable energy source microgrid optimization reconfiguration service restoration automation system

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

Hydrothermal analysis of non-Newtonian fluid flow(blood)through the circular tube under prescrib e d non-uniform wall heat flux

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Theoretical & Applied Mechanics Letters 2022年第4期12卷 275-285页

作者： shahin Faghiri shahin Akbari Mohammad Behshad Shafii Kh.Hosseinzadeh Department of Mechanical Engineering Sharif University of TechnologyTehranIran Sharif Energy Water and Environment Institute(SEWEI)TehranIran

The present article aims to investigate the Graetz-Nusselt problem for blood as a non-Newtonian fluid obeying the power-law constitutive equation and flowing inside the axisymmetric tube subjected to nonuniform surface heat *** the flow field is determined by solving the continuity and the momentum equations,the energy equation is handled by employing the separation of variables *** resulting Eigen functions and Eigen values are numerically calculated using MATLAB built-in solver *** analysis is first conducted for the situation of constant heat flux and subsequently generalized to apply to the case of sinusoidal variation of wall heat flux along the tube length,using Duhamel’s ***,an approximate analytic solution is determined,employing an integral approach to solve the boundary layer *** respect to the comparison,the results of approximate solution display acceptable congruence with those of exact solution with an average error of 7.4%.Interestingly,with decreasing the power-law index,the discrepancy between the two presented methods significantly ***,the influences of the controlling parameters such as surface heat flux and power-law index on the non-Newtonian fluid flow’s thermal characteristics and structure are elaborately *** is found that switching from constant wall heat flux to non-uniform wall heat flux that sinusoidally varies along the tube length significantly improves the simulation’s accuracy due to the better characterization of the heat transport phenomenon in non-Newtonian fluid flow through the *** the presence of sinusoidally varying wall heat flux with an amplitude of 200 W/m 2 and when the power-law index is 0.25,the maximum arterial wall temperature is found to be about 311.56 K.

关键词： Non-newtonian fluid Power-law model Non-uniform heat flux Analytical solution