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Effects of water content, water type and temperature on the rheological behaviour of slag-cement and fly ash-cement paste backfill

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International Journal of Mining Science and Technology 2020年第3期30卷 271-278页

作者： Yue Zhao abbas taheri Murat Karakus Zhongwei Chen An Deng School of Civil Environmental and Mining EngineeringThe University of AdelaideAdelaide 5005Australia School of Mechanical and Mining Engineering The University of QueenslandBrisbane 4072Australia

The pumping ability and placement performance of fresh cemented paste backfill(CPB) in underground mined cavities depend on its rheological properties. Hence, it is crucial to understand the rheology of fresh CPB slurry, which is related to CPB mixture design and the temperature underground. This paper presented an experimental study investigating the effects of binder type, content, water chemical properties and content, and temperature, on the rheological properties of CPB material prepared using the tailings of a copper mine in South Australia. Portland cement(PC), a newly released commercially manufactured cement called Minecem(MC) and fly ash(FA) were used as the binders added to the mine tailing materials. Various amounts of two different water types were added to the mixtures in the preparation of backfill material slurry. Six different temperatures ranging from 5 to 60 °C were to investigate the effect of temperature on CPB rheology. Overall, the increasing water content and decreasing temperature lead to lower yield stress. Based on the results obtained from the rheological properties of CPB slurry, it was found that at room temperature(25 °C), with regards to the unconfined compressive strength(UCS) performance, the replacement of 4% PC mixed CPB(28 days UCS 425 k Pa) to 3% MC mixed CPB(28 days UCS 519 k Pa), reduced the slurry yield stress from 210.7 to 178.5 Pa. The results also showed that the chemical composition of water affects the yield stress of CPB slurry and that MC mitigates the negative effect of mine-processed water(MW) and thus lead to improve the rheological properties of the slurry. However, the results suggested that the rheological properties of a mixture using MC is very sensitive to the water volume and temperature change. Therefore, using MC in backfill requires better quality control in slump mixing.

关键词： Cemented paste backfill Minecem Rheology Yield stress Fly ash Portland cement

Intermittent swelling and shrinkage of a highly expansive soil treated with polyacrylamide

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第1期14卷 252-261页

作者： Amin Soltani An Deng abbas taheri Brendan C.O’Kelly School of Engineering Information Technology and Physical SciencesFederation UniversityChurchillVIC3842Australia School of Civil Environmental and Mining EngineeringThe University of AdelaideAdelaideSA5005Australia Department of Civil Structural and Environmental EngineeringTrinity College DublinDublinD02 PN40Ireland

This laboratory study examines the potential use of an anionic polyacrylamide(PAM)-based material as an environmentally sustainable additive for the stabilization of an expansive soil from South *** experimental program consisted of consistency limits,sediment volume,compaction and oedometer cyclic swell-shrink tests,performed using distilled water and four different PAM-to-water solutions of P_(D)=0.1 g/L,0.2 g/L,0.4 g/L and 0.6 g/L as the mixing ***,the relative swelling and shrinkage strains were found to decrease with increasing number of applied swell-shrink cycles,with an‘elastic equilibrium’condition achieved on the conclusion of four *** propensity for swelling/shrinkage potential reduction(for any given cycle)was found to be in favor of increasing the PAM dosage up to P_(D)=0.2 g/L,beyond which the excess PAM molecules self-associate as aggregates,thereby functioning as a lubricant instead of a flocculant;this critical dosage was termed‘maximum flocculation dosage’(MFD).The MFD assertion was discussed and validated using the consistency limits and sediment volume properties,both exhibiting only marginal variations beyond the identified MFD of P_(D)=0.2 g/*** accumulated axial strain progressively transitioned from‘expansive’for the unamended soil to an ideal‘neutral’state at the MFD,while higher dosages demonstrated undesirable‘contractive’states.

关键词： Expansive soil Polyacrylamide(PAM) Consistency limits Sediment volume Swell-shrink cycles Swelling and shrinkage strains Accumulated axial strain

Evaluation of the propensity of strain burst in brittle granite based on post-peak energy analysis

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Underground Space 2021年第1期6卷 1-11页

作者： Selahattin Akdag Murat Karakus Giang D.Nguyen abbas taheri Thomas Bruning School of Civil Environmental and Mining EngineeringThe University of AdelaideAdelaideSAAustralia

The increasing demand for resources and depletion of near ground mineral resources caused deeper mining operations under highstress rock mass *** a result of this,strain burst,which is the sudden release of stored strain energy in the surrounding rock mass,has become more prevalent and created a considerable threat to workers and construction *** is,therefore,imperative to understand how strain burst mechanism and stored excess strain energy are affected due to the high confinement in deep underground *** this purpose,post-peak energy distributions for brittle rocks were investigated using a newly developed energy calculation method associated with acoustic emission(AE).A series of quasi-static uniaxial and triaxial compression tests controlled by the circumferential expansion were ***-back behaviour known as Class-II behaviour associated with energy evolution and the material response under self-sustaining failure were analysed on granites under a wide range of confining pressures(0–60 MPa).The experimental results underline that the energy evolution characteristics are strongly linked to *** elastic strain energy(dUE),energy consumed by dominating cohesion weakening(dUCW)and energy dissipated during mobilisation of frictional failure(dUFM)showed a rising trend as the confining pressure was *** intrinsic ejection velocity was proposed to express the propensity of strain burst that was purely determined by the excess strain energy released from Class II rock.

关键词： Strain burst Energy balance Class II failure mode Self-sustaining failure Triaxial compression test Circumferential strain control

Microstructural evolution,mechanical properties,and corrosion resistance of a heat-treated Mg alloy for the bio-medical application

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Journal of Magnesium and Alloys 2019年第1期7卷 80-89页

作者： Mohammad Janbozorgi Kimia Karimi taheri Ali Karimi taheri Department of Materials Science and Engineering Sharif University of TechnologyAzadi Ave.TehranIran School of Medicine Shahid Beheshti University of Medical ScienceTehranIran

During the recent years,some Mg based alloys have extensively been considered as a new generation of degradable and absorbable bio-medical *** this work,the Mg-2Zn-1Gd-1Ca(wt%)alloy as a new metallic bio-material was produced by the casting process followed by the heat *** samples of the alloy were solution treated at temperatures of 500,550,and 600°C and then quench aged at temperatures of 125,150,and 175°*** results of SEM-EDS examinations indicated that the alloy microstructure consists ofα-Mg matrix and the Ca_(2)Mg_(6)Zn_(3)and Mg_(3)Gd_(2)Zn_(3)secondary *** regard to the results of Vickers hardness test,the temperatures of 500°C and 150°C were selected as the optimum solutionizing and aging temperatures,***,the dissolution of casting precipitates and production of lattice distortion occurring after the solution treatment led to the reduction in ultimate shear strength up to 21%.But,the precipitation hardening and morphological changes taking place during the aging treatment improved the ultimate shear strength up to 32%.Furthermore,the results of electro-chemical and weight-loss measurements in a simulated body fluid indicated that the heat-treated alloy is a promising candidate for the Mg based alloys recently considered for the bio-medical applications.

关键词： Mg alloys Bio-medical applications Microstructural evolution Mechanical properties Corrosion resistance

Asperity-based modification on theory of contact mechanics and rubber friction for self-affine fractal surfaces

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Friction 2021年第6期9卷 1707-1725页

作者： Anahita EMAMI Seyedmeysam KHALEGHIAN Saied taheri Texas State University 601 University DriveSan MarcosTexas 78666USA Virginia Polytechnic Institute and State University 460 Old Turner Street BlacksburgBlacksburgVirginia 24061USA

Modeling the real contact area plays a key role in every tribological process,such as friction,adhesion,and *** between two solids does not necessarily occur everywhere within the apparent contact *** the multiscale nature of roughness,Persson proposed a theory of contact mechanics for a soft and smooth solid in contact with a rigid rough *** this theory,he assumed that the vertical displacement on the soft surface could be approximated by the height profile of the substrate *** this assumption gives an accurate pressure distribution at the interface for complete contact,when no gap exists between two surfaces,it results in an overestimation of elastic energy stored in the material for partial contact,which typically occurs in many practical *** issue was later addressed by Persson by including a correction factor obtained from the comparison of the theoretical results with molecular dynamics *** paper proposes a different approach to correct the overestimation of vertical displacement in Persson’s contact theory for rough surfaces with self-affine fractal *** results are compared with the correction factor proposed by *** main advantage of the proposed method is that it uses physical parameters such as the surface roughness characteristics,material properties,sliding velocity,and normal load to correct the *** method is also implemented in the theory of rubber *** results of the corrected friction model are compared with *** results confirm that the modified model predicts the friction coefficient as a function of sliding velocity more accurately than the original model.

关键词： contact area rubber friction self-affine fractals tribology surface roughness

On Zero Dynamics and Controllable Cyber-Attacks in Cyber-Physical Systems and Dynamic Coding Schemes as Their Countermeasures

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IEEE/CAA Journal of Automatica Sinica 2024年第11期11卷 2191-2203页

作者： Mahdi taheri Khashayar Khorasani Nader Meskin the Department of Electrical and Computer Engineering Concordia University the Department of Electrical Engineering Qatar University

In this paper, we study stealthy cyber-attacks on actuators of cyber-physical systems(CPS), namely zero dynamics and controllable attacks. In particular, under certain assumptions, we investigate and propose conditions under which one can execute zero dynamics and controllable attacks in the CPS. The above conditions are derived based on the Markov parameters of the CPS and elements of the system observability matrix. Consequently, in addition to outlining the number of required actuators to be attacked, these conditions provide one with the minimum system knowledge needed to perform zero dynamics and controllable cyber-attacks. As a countermeasure against the above stealthy cyber-attacks, we develop a dynamic coding scheme that increases the minimum number of the CPS required actuators to carry out zero dynamics and controllable cyber-attacks to its maximum possible value. It is shown that if at least one secure input channel exists, the proposed dynamic coding scheme can prevent adversaries from executing the zero dynamics and controllable attacks even if they have complete knowledge of the coding system. Finally, two illustrative numerical case studies are provided to demonstrate the effectiveness and capabilities of our derived conditions and proposed methodologies.

关键词： Controllable attacks cyber-physical systems(CPS) dynamic coding zero dynamics attacks stealthy cyber-attacks

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Partial oxidation of methane in Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.1)Ni_(0.1)O_(3-δ) ceramic membrane reactor

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Journal of Natural Gas Chemistry 2012年第5期21卷 519-525页

作者： Ensieh Ganji Babakhani Jafar Towfighi Zahra taheri Ali Nakhaei Pour Majid Zekordi Ali taheri Gas Department Research Institute of Petroleum Industry(RIPI)14665-137TehranIran Chemical Engineering Department Engineering FacultyUniversity of Tarbiat Modares14115-111TehranIran Chemistry and petrochemical Department Research Institute of Petroleum Industry(RIPI)14665-137TehranIran

Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3δ（BSCFNiO） perovskite oxides were synthesized using a combined EDTA-citrate complexation method,and then pressed into disk and applied in a membrane *** performance of the BSCFNiO membrane reactor was studied for partial oxidation of methane over Ni/α-Al 2 O 3 *** time dependence of oxygen permeation rate and catalytic performance of BSCFNiO membrane during the catalyst initiation stage were investigated at 850 *** unsteady state,oxygen permeation rate,methane conversion and CO selectivity were closely related to the state of the *** 300 min from the initial time,the reaction condition reached to steady state and oxygen permeation rate were obtained about 11.7cm 3 cm 2 min ***,the performance of membrane reactor was studied at the temperatures between 750 and 950 *** results demonstrated good performance for the membrane reactor,as CH 4 conversion and CO selectivity permeation rate reached 98% and 97.5%,respectively,and oxygen permeation rate was about 14.5 cm 3 cm 2 min 1 which was 6.8 times higher than that of air-helium *** of membrane surface by SEM after reaction showed that the original grains disappeared on both surfaces exposed to the air and reaction side,but XRD profile of the polished surface membrane indicated that the membrane bulk preserved the perovskite structure.

关键词： perovskite membrane reactor partial oxidation of methane

Specimen aspect ratio and progressive field strain development of sandstone under uniaxial compression by three-dimensional digital image correlation

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 599-610页

作者： H. Munoz A. taheri Deep Exploration Technologies Cooperative Research Centre (DET CRC) Export Park Adelaide Airport Adelaide SA 5950 Australia School of Civil Environmental & Mining Engineering The University of Adelaide Adelaide SA 5005 Australia

The complete stress-strain characteristics of sandstone specimens were investigated in a series of quasistatic monotonic uniaxial compression *** patterns development during pre-and post-peak behaviours in specimens with different aspect ratios was also *** stress,post-peak portion of stress-strain,brittleness,characteristics of progressive localisation and field strain patterns development were affected at different extents by specimen aspect *** patterns of the rocks were obtained by applying three-dimensional(3D) digital image correlation(DIC) *** conventional strain measurement using strain gauges attached to specimen,3D DIC allowed not only measuring large strains,but more importantly,mapping the development of field strain throughout the compression test,*** pre-and post-peak *** strain development in the surface of rock specimen suggests that strain starts localising progressively and develops at a lower rate in pre-peak ***,in post-peak regime,strains increase at different rates as local deformations take place at different extents in the vicinity and outside the localised *** extent of localised strains together with the rate of strain localisation is associated with the increase in rate of strength *** localisation and local inelastic unloading outside the localised zone both feature post-peak regime.

关键词： Uniaxial compression test Aspect ratio Strain patterns Digital image correlation(DIC)

Optimal operation of energy at hydrothermal power plants by simultaneous minimization of pollution and costs using improved ABC algorithm

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Frontiers in Energy 2015年第4期9卷 426-432页

作者： Homayoun EBRAHIMIAN Bahman taheri Nasser YOUSEFI Department of Engineering Ardabil Branch Islamic Azad University Ardabil 0451 Iran Young Researchers and Elite Club Ardabil Branch Islamic Azad University Ardabil 0451 Iran

The aim of this paper is simultaneous mini- mization of hydrothermal units to reach the best solution by employing an improved artificial bee colony （ABC） algorithm in a multi-objective function consisting of economic dispatch （ED） considering the valve-point effect and pollution function in power systems in view of the hot water of the hydro system. In this type of optimization problem, all practical constraints of units were taken into account as much as possible in order to comply with the reality. These constraints include the maximum and minimum output power of units, the constraints caused by the balance between supply and demand, the impact of pollution, water balance, uneven production curve con- sidering the valve-point effect and system losses. The proposed algorithm is applied on the studied system, and the obtained results indifferent operating conditions are analyzed. To investigate in various operating conditions, different load profiles in 12 h are taken into account. The obtained results are compared with those of the other methods including the genetfc algorithm （GA）, the Basu technique, and the improved genetic algorithm. Fast convergence is one of this improved algorithm features.

关键词： practical constraints of units pollution func-tion inlet steam valve up-ramp rate of units improvedABC algorithm