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Cracks coalescence mechanism and cracks propagation paths in rock-like specimens containing pre-existing random cracks under compression

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Journal of Central South University 2014年第6期21卷 2404-2414页

作者： Hadi Haeri Kourosh shahriar Mohammad Fatehi Marji Parviz Moarefvand Department of Mining Engineering Science and Research BranchIslamic Azad University Department of Mining and Metallurgical Engineering Amirkabir University of Technology Mine Exploitation Engineering Department Faculty of Mining and MetallurgyInstitution of EngineeringYazd University

The mechanism of cracks propagation and cracks coalescence due to compressive loading of the brittle substances containing pre-existing cracks(flaws)was modeled experimentally using specially made rock-like specimens from Portland Pozzolana Cement(PPC).The breakage process of the specimens was studied by inserting single and double flaws with different inclination angles at the center and applying uniaxial compressive stress at both ends of the *** first crack was oriented at 50° from the horizontal direction and kept constant throughout the analysis while the orientation of the second crack was *** is experimentally observed that the wing cracks are produced at the first stage of loading and start their propagation toward the direction of uniaxial compressive *** secondary cracks may also be produced in form of quasi-coplanar and/or oblique cracks in a stable *** secondary cracks may eventually continue their propagation in the direction of maximum principle *** experimental works were also simulated numerically by a modified higher order displacement discontinuity method and the cracks propagation and cracks coalescence were studied based on Mode I and Mode II stress intensity factors(SIFs).It is concluded that the wing cracks initiation stresses for the specimens change from 11.3 to 14.1 MPa in the case of numerical simulations and from 7.3 to 13.8 MPa in the case of experimental *** is observed that cracks coalescence stresses change from 21.8 to 25.3 MPa and from 19.5 to 21.8 MPa in the numerical and experimental analyses,*** some of the numerical and experimental results with those recently cited in the literature validates the results obtained by the proposed ***,a numerical simulation was accomplished to study the effect of confining pressure on the crack propagation process,showing that the SIFs increase and the crack initiation angles change in this case.

关键词：裂纹扩展传播路径压缩载荷机制标本聚结数值模拟岩样

Thermo-hydro-mechanical modeling of fault discontinuities using zero-thickness interface element

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第1期12卷 74-88页

作者： Ali Ranjbar Hossein Hassani Kourosh shahriar Mohammad Javad Ameri Shahrabi Department of Petroleum Engineering Amirkabir University of TechnologyTehranIran Department of Mining and Metallurgy Engineering Amirkabir University of TechnologyTehranIran

In this paper,a coupled thermo-hydro-mechanical(THM)simulation in a faulted deformable porous medium is *** model involves solving the mass conservation,linear momentum balance,and energy balance equations which are derived from the Biot’s consolidation *** pore pressure,solid displacement,and temperature are chosen as initial variables in these equations,and the finite element method in combination with the interface element is used for spatial discretization of continuous and discontinuities(fault)parts of the medium to solve the *** main purpose of this study is providing precise formulations,applicability,and ability of the triple-node zero-thickness interface element in THM modeling of *** should be noted that the system of equations is solved using a computer code written in Matlab *** order to verify the developed method,simulations of index problems such as Mandel’s problem,and coupled modeling of a faulted porous medium and a faulted aquifer are *** modeling results obtained from the developed method show a very good agreement with those by other modeling methods,which indicates its accuracy.

关键词： Thermo-hydro-mechanical(THM) simulation Geomechanical coupling Zero-thickness element Joint element Finite element

Interplay between cold densification and malic acid addition (C4H6O5) for the fabrication of near-isotropic MgB2 conductors for magnet application

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Journal of Magnesium and Alloys 2020年第2期8卷 493-498页

作者： md.shahriar A.Hossain Carmine Senatore Yusuke Yamauchi Mislav Mustapic Daniel Gajda Dipak Patel Aslam Khan Jung Ho Kim Andrzej J Morawski Rene Flukiger School of Mechanical and Mining Engineering The University of QueenslandBrisbaneQLD 4072Australia Department of Quantum Matter Physics(DQMP) University of GenevaGenevaSwitzerland Key Laboratory of Eco-chemical Engineering College of Chemistry and Molecular EngineeringQingdao University of Science and TechnologyQingdao 266042China School of Chemical Engineering and Australian Institute for Bioengineering and Nanotechnology(AIBN) The University of QueenslandBrisbaneQLD 4072Australia International Center for Materials Nanoarchitectonics(WPI-MANA) National Institute for Materials Science(NIMS)1-1 NamikiTsukubaIbaraki 305-0044Japan University of Osjek Departiment of Physics31000OsijekCroatia Institute of Low Temperature and Structure Research PAS Okolna 250-422 WroclawPoland Research Center for Functional Materials National Institute for Materials Science(NIMS)1-2-1 SengenTsukubaIbaraki 305-0047Japan King Abdullah Institute for Nanotechnology King Saud UniversityRiyadh11451Saudi Arabia Australian Institute for Innovative Materials(AIIM) University of WollongongSquires WayNorth WollongongNSW 2500Australia Institute of High Pressure Physics Polish Academy of Sciences(PAS)Sokoiowska 29/3701-142 WarsawPoland

The effect of cold high pressure densification(CHPD)on anisotropy of the critical current density(Jc)in《in situ》single core binary and alloyed MgB2 tapes has been determined as a function of temperatures at 4.2 K,20 K and 25 K as well as at applied magnetic fields up to 19 *** study includes binary and C4H6O5(malic acid)doped MgB2 tapes before and after *** is remarkable that the CHPD process not only improved the Jc values,in particular at the higher magnetic fields,but also decreased the anisotropy ratio,Г=JC^///JC^⊥In binary MgB2 tapes,the anisotropy factor F increases with higher aspect ratios,even after applying *** malic acid(C4H6O5)doped tapes,however,the application of CHPD leads only to small enhancements ofГ,even for higher aspect *** is attributed to the higher carbon content in the MgB2 filaments,which in turn is a consequence of the reduced chemical reaction path in the densified *** all applied field values,it was found that CHPD processed C4H6O5 doped tapes exhibit an almost isotropic *** constitutes an advantage in view of industrial magnet applications using wires with square or slightly rectangular configuration.

关键词： Magnesium diboride Cold high pressure densification Anisotropy Tapes Critical current density

Synthesis, Characterization, Spectroscopy and Study of Antimicrobial Properties of Two New Substituted Trichloroaluminate(Ⅲ) Complexes [AlCl_3X]^- (X = SCN^-, CN^-)

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Chinese Journal of Structural Chemistry 2013年第1期32卷 67-72页

作者： Zahra Shokri Aghbolagh shahriar Ghammamy Sajjad Sedaghat Shahram Jahandide Young Research Club Takestan Branch Islamic Azad University Takestan Iran Department of Chemistry Faculty of Science Islamic Azad University Malard Branch Malard Iran Department of Chemistry Faculty of Science Islamic Azad University Ardabil Branch Ardabil Iran

The synthesis and characterization of two new aluminate（Ⅲ） complexes with general formula K[AlCl3X] are reported. These compounds derived from aluminate trichloride and related salts. Potassium trichlorothiocyanoaluminate, PCTA, and potassium trichlorocyanatoalu-minate, PCCA, are two new ionic aluminate complexes. They can be easily synthesized in a nearly quantitative yield by using the direct reaction of AlCl3 and KX. The complexes were characterized by physico-chemical and spectroscopic methods. Theoretical calculations have been used for the extraction of structural and spectroscopic data of these new synthesized complexes. The antibacterial activities of such compounds were studied against the Staphylococcus aureus, Escherichia coli, Staphylococcus Epidermidis, Estreptococo B and Shigella.

关键词： aluminate compounds synthesis characterization PCTA PCCA theoretical calculation antibacterial activities

Extreme climate projections over the transboundary Koshi River Basin using a high resolution regional climate model

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Advances in Climate Change Research 2017年第3期8卷 199-211页

作者： Rupak RAJBHANDARI Arun Bhakta SHRESTHA Santosh NEPAL shahriar WAHID REN Guo-Yu Department of Meteorology Tri-Chandra Campus Tribhuvan University Kathmandu Nepal International Centre for Integrated Mountain Development Kathmandu Nepal National Climate Center China Meteorological Administration Beijing 100081 China

The high-resolution climate model Providing REgional Climates for Impacts Studies (PRECIS) was used to project the changes in futureextreme precipitation and temperature over the Koshi River Basin for use in impact assessments. Three outputs of the Quantifying Uncertaintiesin Model Prediction (QUMP) simulations using the Hadley Centre Couple Model (HadCM3) based on the IPCC SRES A1B emission scenario were used to project the future climate. The projections were analysed for three time slices, 2011e2040 (near future), 2041e2070 (mid-century), and 2071e2098 (distant future). The results show an increase in the future frequency and intensity of climate extremes events such as dry days, consecutive dry days, and very wet days (95th percentile), with greater increases over the southern plains than in the mountainous area to the north. A significant decrease in moderate rainfall days (75th percentile) is projected over the middle (high) mountain and trans-Himalaya areas. Increases are projected in both the extreme maximum and extreme minimum temperature, with a slightly higher rate in minimum temperature. The number of warm days is projected to increase throughout the basin, with more rapid rates in the trans-Himalayan and middle mountain areas than in the plains. Warm nights are also projected to increase, especially in the southern plains. A decrease is projected in cold days and cold nights indicating overall warming throughout the basin.

关键词： Climate change Climate projection Koshi basin PRECIS Extreme climate

An estimation of the penetration rate of rotary drills using the Specific Rock Mass Drillability index

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International Journal of Mining Science and Technology 2012年第2期22卷 187-193页

作者： Cheniany Alireza Hasan Khoshrou Seyed shahriar Kourosh Khademi Hamidi Jafar Department of Mining and Metallurgy Engineering Amirkabir University of TechnologyTehranIran Mining Engineering Department Faculty of EngineeringTarbiat Modares UniversityTehranIran

The main purpose of the present study was to provide a practical,convenient drillability prediction model based on rock mass characteristics,geological sampling from blast holes,and drill operational *** equations that predict drill penetration rate have been developed using statistical analyses of data from the Sarcheshmeh Copper *** parameters of the rock or rock mass,including uniaxial compressive strength(UCS) of the rock,Schmidt hammer hardness value,quartz content,fragment size(d80),alteration,and joint dip,are included in the model along with two operational parameters of the rotary drill,bit rotational speed and *** parameters were used to predict values of the newly developed Specific Rock Mass Drillability(SRmd) *** measured SRmd values to those predicted by the multi-parameter linear,or nonlinear,regression models showed good *** correlation coefficients were 0.82 and 0.81,respectively.

关键词：可钻性指标岩体预测模型估计机率旋转渗透数据统计分析

3-D numerical modelling of Domino failure of hard rock pillars in Fetr6 Chromite Mine, Iran, and comparison with empirical methods

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Journal of Central South University 2013年第2期20卷 541-549页

作者： S.Dehghan K.shahriar P.Maarefvand K.Goshtasbi Department of Mining Engineering Science and Research BranchIslamic Azad University Department of Mining and Metallurgical Engineering Amirkabir University of Technology Department of Mining Engineering Tarbiat Modares University

Fetr6 is an underground mine using the stope-and-pillar mining method. As there was some evidence regarding pillar failure in this mine, improving works such as roof support and replacing existing pillars with concrete pillars (CP) were carried out. During the construction of the second CP, in the space between the remaining pillars, one of the pillars failed leading to the progressive failure of other pillars until 4 000 m 2 of mine had collapsed within a few minutes. In this work, this phenomenon is described by applying both numerical and empirical methods and the respective results are compared. The results of numerical modelling are found to be closer to the actual condition than those of the empirical method. Also, a width-to-height (W/H) ratio less than 1, an inadequate support system and the absence of a detailed program for pillar recovery are shown to be the most important causes of the Domino failure in this mine.

关键词： Domino 数值模拟支柱 3-D 铬矿故障伊朗岩石

Comparative evaluation of impacts of climate change and droughts on river flow vulnerability in Iran

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Water Science and Engineering 2020年第4期13卷 265-274页

作者： Zahra Noorisameleh shahriar Khaledi Alireza Shakiba Parviz Zeaiean Firouzabadi William AGough MMonirul Qader Mirza Faculty of Earth Sciences Shahid Beheshti UniversityTehran ***Iran Department of Physical and Environmental Sciences University of Toronto ScarboroughToronto M1C 1A4Canada Faculty of Geographical Sciences Kharazmi UniversityTehran 15719-14911Iran

Rivers in arid and semi-arid regions are threatened by droughts and climate *** study focused on a comparative evaluation of the impacts of climate change and droughts on the vulnerability of river flows in three basins with diverse climates in *** standardized precipitation-evapotranspiration index(SPEI)and precipitation effectiveness variables(PEVs)extracted from the conjunctive precipitation effectiveness index(CPEI)were used to analyze the drought *** investigate hydrological droughts in the basins,the normalized difference water index(NDWI)and the streamflow drought index(SDI)were calculated and *** effects of droughts were assessed under various representative concentration pathway(RCP)*** in the number of wet days and precipitation depth restricted hydrological droughts,whereas an increasing number of dry days amplified their *** projected increases in dry days and precipitation over short durations throughout a year under future climate scenarios would produce changes in drought and flood periods and ultimately impact the frequency and severity of hydrological *** RCP 4.5,an increase in the frequencies of moderate and severe meteorological/hydrological droughts would further affect the Central Desert *** RCPs 2.6 and 8.5,the frequencies of severe and extreme droughts would increase,but the drought area would be smaller than that under RCP 4.5,demonstrating less severe drought *** to the shallow depths of most rivers,SDI was found to be more feasible than NDWI in detecting hydrological droughts.©2020 Hohai *** and hosting by Elsevier *** is an open access article under the CC BY-NC-ND license(http://***/licenses/by-nc-nd/4.0/).

关键词： Climate change River flow Precipitation Drought index Standardized precipitation-evapotranspiration index Iran

Can patients with non-convulsive seizure be identifi ed in the emergency department?

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World Journal of Emergency Medicine 2017年第3期8卷 190-194页

作者： Gholamreza Sadeghipoor Roodsari Geetha Chari Bryan Mera shahriar Zehtabchi Department of Emergency Medicine State University of New York Downstate Medical Center Department of Neurology State University of New York Downstate Medical Center

BACKGROUND: Non-convulsive seizure(NCS) is an underdiagnosed, potentially treatable emergency with significant mortality and morbidity. The objective of this study is to examine the characteristics of patients with NCS presenting with altered mental status(AMS) and diagnosed with electroencephalography(EEG), to identify the factors that could increase the pre-test probability of ***: Retrospective study using the data collected prospectively. Inclusion criteria: patients older than 13 years with AMS. Exclusion criteria:(1) immediately correctable AMS(e.g., hypoglycemia, opiod overdose);(2) inability to undergo EEG;(3) hemodynamic instability. Outcomes compared between NCS and non-NCS cases: vital signs, lactate level, gender, witnessed seizure, use of anticonvulsive in the field or in the ED, history of seizure or stroke, head injury, abnormal neurological finding and new abnormal findings on head CT. Data presented as medians and quartiles for categorical and percentages with 95%CI for continuous variables. Univariate analyses were performed with Man-Whitney U and Fisher's Exact tests. A multivariate analysis model was used to test the predictive value of clinical variables in identifying ***: From 332 patients(median age 66 years, quartiles 50–78), 16 were diagnosed with NCS(5%, 95%CI 3%–8%). Only age was signifi cantly different between the NCS vs. non-NCS groups in both univariate(P=0.032) and multivariate analyses(P=0.016).CONCLUSION: Other than age, no other clinically useful variable could identify patients at high risk of NCS. ED physicians should have a high suspicion for NCS and should order EEG for these patients more liberally.

关键词： Altered mental status Seizure Non-convulsive Electroencephalography