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Gd impurity effect on the magnetic and electronic properties of hexagonal Sr ferrites: A case study by DFT

Chinese Physics B 2020年第7期29卷 521-527页

作者： Masomeh Taghipour Mohammad Yousefi reza fazaeli Masoud Darvishganji Department of Chemistry Science and Research BranchIslamic Azad UniversityTehranIran Department of Chemistry Yadegar-e-Imam Khomeni(RAH)shahr-e-Rey BranchIslamic Azad UniversityTehranIran Department of Chemistry South Tehran BranchIslamic Azad UniversityTehranIran Department of Chemistry Qaemshahr BranchIslamic Azad UniversityQaemshahrIran

The electronic and magnetic properties of strontium hexa-ferrite(SrFe12O19)are studied in pure state(SrFe12O19)and with dopant in the positions 2 and 3 of Fe atoms(SrGdFe11O19-I and SrGdFe11O19-Ⅱ,respectively)by utilizing a variety of the density functional theory(DFT)approaches including the Perdew-Burke-Ernzerhof generalized gradient approximation(PBE-GGA)and GGA plus Hubbard U parameter(GGA+U).The pure SrFe12O19 is a hard magnetic half-metal with an integer magnetic moment of 64.00μB,while using the GGA+U functional,the magnetic intensity increases,resulting in a magnetic semiconductor with a high integer magnetic moment of 120μ*** doping the Gd atom in the two different positions of Fe,the magnetic moment is increased to 71.68μB and 68.00μB,*** magnetic moment increases and remains an integer;hence,SrGdFe11O19-Ⅱcan be very useful for application in magnetic ***,applying the Hubbard parameter turns SrGdFe11O19-I and SrGdFe11O19-Ⅱto magnetic semiconductors with a magnetic moment of 124μB,and the energy gap of both doped structures at spin down is found to be less than the pure *** studying the electronic density diagram of the atoms of the crystal,it is found that the major effect to create magnetization in the pure case is due to the Fe ***,in the doped case,the elements Gd and Fe have the highest moment in the crystal respectively.

关键词： magnetic properties density functional theory half-metal doping

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4E analysis and optimization of cold thermal-energy storage under partial operating mode and demand-limiting mode for air-conditioning systems

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Clean Energy 2023年第3期7卷 582-594页

作者： Salar Hosseinjany Hossien Ahmadi-Danesh-Ashtiani Ahmad Khoshgard reza fazaeli Department of Mechanical Engineering South Tehran BranchIslamic Azad UniversityTehranIran Department of Chemical Engineering South Tehran BranchIslamic Azad UniversityTehranIran

Cold thermal energy storage is an active method for reducing the peak electrical demand and electricity consumption of air *** paper investigates two different cases:partial operating mode-load levelling(POM-LL)and demand-limiting mode(DLM).4E(energy,exergy,economic,environment)analyses along with a multi-objective optimization process based on a genetic algorithm is applied to determine optimal design *** efficiency,total annual cost and payback-period time are considered as objective functions in this *** results have shown that POM and DLM decreased the electricity consumption by 10.36%and 11.29%,respectively,resulting in raising the annual costs by 11.08%and 11.42%.Also,their annual payback periods were 4.36 and 4.18 years *** addition,using off-peak hours instead of on-peak hours for electricity consumption and reducing electricity consump-tion are the two main ways of decreasing CO_(2) emissions during electricity ***,the CO_(2) emissions through POM and DLM are 13.31%and 13.72%less than those of conventional systems,respectively.

关键词： partial operating mode cold thermal storage load levelling demand-limiting mode

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Nonlinear phenomena in vibrations of embedded carbon nanotubes conveying viscous fluid

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Nanotechnology and Precision Engineering 2024年第1期7卷 44-54页

作者： reza Ebrahimi Mechanical Engineering Faculty of EngineeringYasouj UniversityYasouj 75918-74831Iran

Various nonlinear phenomena such as bifurcations and chaos in the responses of carbon nanotubes(CNTs)are recognized as being major contributors to the inaccuracy and instability of nanoscale mechanical ***,the main purpose of this paper is to predict the nonlinear dynamic behavior of a CNT conveying viscousﬂuid and supported on a nonlinear elastic *** proposed model is based on nonlocal Euler–Bernoulli beam *** Galerkin method and perturbation analysis are used to discretize the partial differential equation of motion and obtain the frequency-response equation,respectively.A detailed parametric study is reported into how the nonlocal parameter,foundation coefﬁcients,ﬂuid viscosity,and amplitude and frequency of the external force inﬂuence the nonlinear dynamics of the ***,quasi-periodic,and chaotic behaviors and hardening nonlinearity are revealed by means of the vibration time histories,frequency-response curves,bifurcation diagrams,phase portraits,power spectra,and Poincaré***,the results show that it is possible to eliminate irregular motion in the whole range of external force amplitude by selecting appropriate parameters.

关键词： Nonlinear vibration Carbon nanotubes Nonlocal effect Viscousﬂuid Nonlinear elastic medium

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Temperature-jump tensile tests to induce optimized TRIP/TWIP effect in a metastable austenitic stainless steel

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International Journal of Minerals,Metallurgy and Materials 2024年第9期31卷 2025-2036页

作者： Mohammad Javad Sohrabi Hamed Mirzadeh Saeed Sadeghpour Abdol reza Geranmayeh reza Mahmudi School of Metallurgy and Materials Engineering College of EngineeringUniversity of Tehran14395-515TehranIran Centre for Advanced Steels Research Materials and Mechanical EngineeringUniversity of Oulu90014 OuluFinland

In the present work,plastic deformation mechanisms were initially tailored by adjusting the deformation temperature in the range of 0 to 200℃ in AISI 304L austenitic stainless steel,aiming to optimize the strength-ductility *** was shown that the combined twinning-induced plasticity(TWIP)/transformation-induced plasticity(TRIP)effects and a wider strain range for the TRIP effect up to higher strains by adjusting the deformation temperature are good strategies to improve the strength-ductility synergy of this metastable stainless *** this regard,by consideration of the observed temperature-dependency of plastic deformation,the controlled sequence of TWIP and TRIP effects for archiving superior strength-ductility trade-off was intended by the pre-designed temperature jump tensile ***,the optimum tensile toughness of 846 MJ/m^(3) and total elongation to 133% were obtained by this strategy via exploiting the advantages of the TWIP effect at 100℃ and the TRIP effect at 25℃ at the later stages of the ***,a deformation-temperature-transformation(DTT)diagram was developed for this metastable ***,based on work-hardening analysis,it was found that the main phenomenon constraining further improvement in the ductility and strengthening was the yielding of the deformation-induced α′-martensite.

关键词： metastable stainless steels transformation-induced plasticity twinning-induced plasticity stacking fault energy mechanical properties

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Resilence Control of DC Microgrid Integrated with Multi-Nanogrids Considering Connected-Islanded States

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 786-796页

作者： Hossien Faraji reza Hemmati Pierluigi Siano Department of Electrical Engineering Amirkabir University of TechnologyTehranIran Department of Electrical Engineering Kermanshah University of TechnologyKermanshahIran Department of Management&Innovation Systems University of Salernoand also with the Department of Electrical and Electronic Engineering ScienceUniversity of JohannesburgJohannesburg 2006South Africa

In this paper, a DC microgrid (DCMG) integrated with a set of nano-grids (NG) is studied. DCMG exchanges predetermined active and reactive power with the upstream network. DCMG and NGs are coordinately controlled and managed in such a way the exchanged P-Q power with external grid are kept on scheduled level following all events and operating conditions. The proposed control system, in addition to the ability of mutual support between DCMG and NGs, makes NGs support each other in critical situations. On the other hand, in all operating conditions, DCMG not only feeds three-phase loads with time-varying active and reactive power on the grid side but also injects constant active power into the grid. During events, NGs support each other, NGs support DCMG, and DCMG supports NGs. Such control strategies are realized by the proposed control method to increase resilience of the system. For these purposes, all resources and loads in DCMG and NGs are equipped with individual controllers. Then, a central control unit analyzes, monitors, and regularizes performance of individual controllers in DCMG and NGs. Nonlinear simulations show the proposed model can effectively control DCMG and NGs under normal and critical conditions.

关键词： Control system DC microgrid nanogrid resilience

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Interplay between temperature-dependent strengthening mechanisms and mechanical stability in high-performance austenitic stainless steels

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International Journal of Minerals,Metallurgy and Materials 2024年第10期31卷 2182-2188页

作者： Mohammad Javad Sohrabi Hamed Mirzadeh Saeed Sadeghpour Milad Zolfipour Aghdam Abdol reza Geranmayeh reza Mahmudi School of Metallurgy and Materials Engineering College of EngineeringUniversity of Tehran14395-515 TehranIran Centre for Advanced Steels Research Materials and Mechanical EngineeringUniversity of Oulu90014 OuluFinland Department of Mechanical Engineering College of EngineeringUniversity of Tehran14395-515 TehranIran

The effects of deformation temperature on the transformation-induced plasticity(TRIP)-aided 304L,twinning-induced plasti-city(TWIP)-assisted 316L,and highly alloyed stable 904L austenitic stainless steels were compared for the first time to tune the mechan-ical properties,strengthening mechanisms,and strength-ductility *** this purpose,the scanning electron microscopy(SEM),electron backscattered diffraction(EBSD),X-ray diffraction(XRD),tensile testing,work-hardening analysis,and thermodynamics calcu-lations were *** induced plasticity effects led to a high temperature-dependency of work-hardening behavior in the 304L and 316L stainless *** the deformation temperature increased,the metastable 304L stainless steel showed the sequence of TRIP,TWIP,and weakening of the induced plasticity mechanism;while the disappearance of the TWIP effect in the 316L stainless steel was also ***,the solid-solution strengthening in the 904L superaustenitic stainless steel maintained the tensile properties over a wide temper-ature range,surpassing the performance of 304L and 316L stainless *** this regard,the dependency of the total elongation on the de-formation temperature was less pronounced for the 904L alloy due to the absence of additional plasticity *** results re-vealed the importance of solid-solution strengthening and the associated high friction stress for superior mechanical behavior over a wide temperature range.

关键词： austenitic stainless steels mechanical behavior stacking fault energy metastability mechanical twinning

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Particle size distribution in a multi-zone circulating fluidized bed polymerization reactor

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PARTICUOLOGY 2024年第10期93卷 291-299页

作者： Hadadiyan, Mohammadhossein Mostou, Navid Marandi, reza Univ Tehran Coll Engn Proc Design & Simulat Res Ctr Sch Chem Engn POB 11155-4563 Tehran Iran Natl Petrochem Co Petrochem Res & Technol Co Polymer Res Grp POB 14358-84711 Tehran Iran

This research focuses on modeling a multi-zone circulating reactor (MZCR) in the polypropylene production process. In these reactors, designed for polyolefin production, small catalyst particles (20-300 mm) initiate polymerization in the presence of monomer gas. The reactor consists of two main regions: the riser and the downer. The riser operates in the fast fluidization and the downer is in the moving bed regime. Employing the two-fluid model with the Eulerian-Eulerian approach, the dynamics of both solid and gas phases were modeled by applying Newton's laws of motion and assuming spherical particles. The population balance of particles within the reactor was also coupled with the equations of motion. The simultaneous solution of these equations provides valuable insights into particle and fluid behavior, revealing trends such as the growth of polymer particles. Furthermore, the impact of various operating conditions was explored. This study also examined the effects of design parameters (gas inlet velocity, average inlet diameter, and temperature) on the system performance. For instance, it was shown that in the case where the solid circulation flux is 30 kg/(m2 2 s) the velocity of particles in the bed increases from 0.4 at the inlet to 1.1 m/s in the fully developed zone, when it is 43 kg/(m2 2 s) the velocity of particles increases from 0.3 to 1.4 m/s, and when it is 55 kg/(m2 2 s), it is increased from 0.22 to 1.5 m/s. Additionally, trends in particle size distribution based on temperature adjustments were revealed. This study showed that higher temperatures accelerate the polymerization reaction rate, promoting faster growth kinetics and the formation of larger particles. (c) 2024 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

关键词： Fluidization Polymerization Gas-solid flow Multi-zone circulating reactor (MZCR) CFD-PBM Two-fluid model GAS-PHASE POLYMERIZATION CFD SIMULATION 2-FLUID MODEL HYDRODYNAMICS FLOW DYNAMICS SOLIDS PBM

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Changes in climatic conditions drive variations in arbuscular mycorrhizal fungi diversity and composition in semi-arid oak forests

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Journal of Forestry Research 2024年第5期35卷 106-119页

作者： Nahid Jafarian Javad Mirzaei reza Omidipour Yahya Kooch Department of Forest Science Faculty of AgricultureIlam UniversityIlam 69315-516Iran Department of Range and Watershed Management Faculty of AgricultureIlam UniversityIlam 69315-516Iran Faculty of Natural Resources and Marine Sciences Tarbiat Modares UniversityNoor 46417-76489MazandaranIran

Arbuscular mycorrhizal fungi(AMF)play a vital role in plant productivity and ecosystem ***,their responses to abiotic factors(i.e.,climate,physiography,and soil properties)are unknown,especially across climatic gradients and slope aspects in arid and semi-arid *** this study,using 60 composite soil samples,direct and indirect effects of climate factors and slope aspects on AMF diversity,composition and spore density were *** findings indicate that climate has a more direct influ-ence on soil properties(P<0.001)in comparison to slope aspect(P=0.449).In contrast,climate significantly affected AMF diversity and composition,with the highest diversity in dryer *** pH had the highest correlation with different facets of AMF *** equation modeling(SEM)indicated that only a small part of the variation in AMF diversity and spore density could be explained by climate characteristics,slope aspect and soil *** on SEM results,climate was the most important determinant of AMF diversity and spore density;slope aspect had a less critical *** outputs suggest that variations in AMF diversity are derived by the direct effects of climate and the indirect effect of soil chemical *** addition,with increasing dryness,sporulation and AMF diversity increased.

关键词： AMF diversity and composition Physiographic factors Semi-arid ecosystems Zagros forest

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Movement Trend Alterations in the Periaqueductal Gray(PAG)-Employed Ratbot Navigation Are Correlated with Stimulation Parameters

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Journal of Bionic Engineering 2024年第2期21卷 866-876页

作者： Sina Khajei Abed Khorasani Mohammad reza Afarinesh Vahid Sheibani Neuroscience Research Center Institute of NeuropharmacologyKerman University of Medical SciencesKerman***Iran Cognitive Neuroscience Research Center Institute of NeuropharmacologyKerman University of Medical SciencesKerman***Iran

In previous studies,Periaqueductal Gray(PAG)stimulation was used to stop ratbots from *** to the homology between the PAG and the intercollicular nucleus,which has been used for forward movement in birds,we investigated the possibility of PAG application to induce forward locomotion for the first *** a corridor maze,the traveled distances via PAG electrical stimulation were examined in nine Wistar male rats during three sessions.A custom-designed stimulator was developed to apply the *** results showed reductions in responses to stimulation over ***,the traveled distances had negative slopes during the consecutive trials(in 8 out of the 9 rats),and the slope mean was significantly different from *** was a strong correlation between the stimulation parameters(electric Charge per Phase(CPP)and the Number of Pulses(NP))and the observed *** negative Movement Slopes(MS)were highly correlated with the CPP and the NP,as the Pearson's linear correlation coefficients were−0.87 and−0.79,*** MS-CPP coefficients of determination(R-squared)were also between 0.76 and *** addition,the MS-NP coefficients of determination were between 0.63 and ***,it is concluded that the electrical stimulation parameters influence the behavioral outcomes ***,the PAG area may be considered a suitable candidate for forward locomotion control in the future if the area is harnessed effectively to prevent undesirable chaotic behaviors.

关键词： Periaqueductal Gray(PAG) Navigation Ratbot Animal-robot Forward locomotion Movement slope

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Characteristics of turbulent flow in 3-D pools in the presence of submerged rigid vegetation in channel bed

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Journal of Hydrodynamics 2024年第1期36卷 158-169页

作者： Kourosh Nosrati Hossein Afzalimehr Jueyi Sui Hamid reza Reisifar Natural Disasters Prevention Research Center Faculty of Civil EngineeringIran University of Science and TechnologyTehranIran School of Engineering University of Northern British ColumbiaPrince GeorgeCanada

In this study,the interaction between 3-D bedforms and submerged rigid vegetation has been *** laboratory experiments were conducted to study the distribution of flow velocity,Reynolds shear stress,turbulent kinetic energy,and skewness coefficients for a constant density of *** showed that the velocity profile in the pool section deviates from those in the upstream section of the *** has been found that the dip parameter varied between 0.6H and 0.9H depending on various factors including bed roughness,vegetation distribution,and pool entrance/exit ***,scattered vegetation in the pool and differences in slopes created non-uniform flow ***,in the wake region behind each vegetated element,flow velocity reduced significantly,and small-scale eddies are formed,causing increased *** decreasing the entrance slope and bed roughness,relatively uniform flow and weaker turbulence was resulted,but the random distribution of vegetated elements counteracted this balance and intensified *** the decrease in the pool entrance slope,the contribution of sweep event decreased and the contribution of ejection event increased.

关键词： Submerged rigid vegetation 3-D pool Reynolds shear stress skewness coefficients

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