检索结果-南通市图书馆

Robust Control of Robotic Manipulators in the Task-Space Using an Adaptive Observer Based on Chebyshev Polynomials

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2020年第5期33卷 1360-1382页

作者： GHOLIPOUR reza FATEH Mohammad Mehdi Department of Electrical and Robotic Engineering Shahrood University of Technology*** ShahroodIran

In this paper,an adaptive observer for robust control of robotic manipulators is *** lumped uncertainty is estimated using Chebyshev ***,the uncertainty upper bound is required in designing observer-controller ***,obtaining this bound is a challenging *** solve this problem,many uncertainty estimation techniques have been proposed in the literature based on neuro-fuzzy *** an alternative,in this paper,Chebyshev polynomials have been applied to uncertainty estimation due to their simpler structure and less computational *** on strictly-positive-rea Lyapunov theory,the stability of the closed-loop system can be *** Chebyshev coefficients are tuned based on the adaptation rules obtained in the stability ***,to compensate the truncation error of the Chebyshev polynomials,a continuous robust control term is designed while in previous related works,usually a discontinuous term is *** SCARA manipulator actuated by permanent magnet DC motors is used for computer *** results reveal the superiority of the designed method.

关键词： Adaptive observer Chebyshev polynomials electrically driven robot manipulators robust control uncertainty estimation

Experimental investigation of different brines imbibition influences on co-and counter-current oil flows in carbonate reservoirs

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2021年第5期34卷 17-29页

作者： Pouyan Ahmadi Mohammad reza Aghajanzadeh Masoud Riazi Mohammad reza Malayeri Mohammad Sharifi Enhanced Oil Recovery(EOR)Research Centre IOR/EOR Research InstituteShiraz UniversityShirazIran Helmholtz Centre for Environmental Research-UFZ LeipzigGermany Department of Petroleum Engineering Amirkabir University of TechnologyTehranIran Institut für Verfahrenstechnik und Umwelttechnik Technische Universität DresdenGermany

Imbibition of water,as wetting phase in oil-wet fractured carbonate reservoirs,plays a key role in fluid flow between matrix and fracture *** type of injected seawater and its chemistry would profoundly influence the imbibition *** this study,the impact of smart water(a brine that its ions have been adjusted to facilitate oil recovery)and low salinity water on co-and counter-current imbibition processes for oil-wet carbonate cores has been experimentally *** results show an increase of about 10% in oil recovery for co-and counter-currents for smart seawater imbibition compared to that of low salinity *** addition,as a result of the influence of co-and counter-current on each other,by co-current removal from one core face,the countercurrent in the other face would be intensified by as much as about 75%.A close examination of different lengths(5,7 and 9 cm)of carbonate cores with the same permeability revealed that by decreasing porous medium length,the amount of counter-current producing oil would be decreased so that in the 5 cm core,counter current oil production will not *** similar core lengths by increasing permeability,the share of counter current flow would be decreased approximately 18% since the capillary pressure could not overcome non-wetting phase viscous *** the role of matrix length along with a modified brine(which is designed according to the matrix mixture)strengthen the relevant mechanisms to have more oil production so that the higher thickness of matrix causes the higher amount of co-current oil producing and consequently more total recovery.

关键词： Smart water Co-current Counter current Wettability alteration Oil recovery

Hot compression deformation behavior of AISI 321 austenitic stainless steel

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2013年第6期20卷 529-534页

作者： Mehdi Haj Hojjatollah Mansouri reza Vafaei Golam reza Ebrahimi Ali Kanani Department of Materials Engineering Malek Ashtar University of Technology Department of Materials and Polymer Engineering Faculty of Engineering Hakim Sabzevari University

The hot compression behavior of AISI 321 ll00~C and the strain rates of 0.01-1 s-1 using a Baehr austenitic stainless steel was studied at the temperatures of 950- DIL-805 deformation dilatometer. The hot deformation equations and the relationship between hot deformation parameters were obtained. It is found that strain rate and deformation temperature significantly influence the flow stress behavior of the steel. The work hardening rate and the peak value of flow stress increase with the decrease of deformation temperature and the increase of strain rate. In addition, the activation energy of deformation （Q） is calculated as 433.343 kJ/mol. The microstructural evolution during deformation indicates that, at the temperature of 950~C and the strain rate of 0.01 s-1, small circle-like precipitates form along grain boundaries; but at the temperatures above 950~C, the dissolution of such precipitates occurs. Energy-dispersive X-ray analyses indicate that the precipitates are complex carbides of Cr, Fe, Mn, Ni, and Ti.

关键词： austenitic stainless steel deformation constitutive equations microstructural evolution activation energy

The impact of Persian oak (Quercus brantii Lindl.) on soil characteristics in a declining forest

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2020年第6期31卷 2359-2366页

作者： reza Soleimani Ahmad Hosseini Crop and Horticultural Science Research Department Ilam Agricultural and Natural Resources Research and Education CenterAREEOIlamIran Forests and Rangelands Research Department Ilam Agricultural and Natural Resources Research and Education CenterAREEOIlamIran

Root activity has an important impact on soil development but we have little knowledge of the interaction of the root zone and soil genetic *** aim of this investigation was to study the interactions between soil chemical characteristics and root zone processes in a declining Persian oak forest(Quercus brantii Lindl.).A randomized complete block design was used to investigate the long-term eff ect of Persian oak on soil horizons,and the chemical and biological properties in two soil zones(under and outside the canopy).Results indicate that the rhizosphere zone had signifi cantly higher total organic carbon(TOC)than outside the canopy soil in the upper soil *** subsurface horizons,water-extractable organic carbon values were signifi cantly higher in rhizosphere than in non-rhizospheric *** biomass carbon(MBC)values in the rhizospheric zone decreased from the fi rst to the second *** MBC/TOC ratio indicated signifi-cant diff erences between the rhizosphere and soils outside of the canopy,with the exception of the subsurface *** the subsurface horizon of the rhizosphere,there was greater respiration of organic carbon(ΣCO 2/TOC)than in outside of canopy *** addition,root processes infl uenced pH,nitrogen fractions,and availability of phosphorus,potassium,iron,zinc and *** erences in soil characteristics between rhizospheric and non-rhizospheric zones were signifi cant in surface horizons due to higher root density than in deeper soil *** fi ndings indicate that Persian oak(Quercus brantii Lindl.)roots infl uenced the main soil chemical properties,even in calcareous soils.

关键词： Declining forest Persian oak Rhizosphere Soil horizons

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

在线全文

学校读者我要写书评

暂无评论

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

Application of a fuzzy analytical hierarchy process to the prediction of vibration during rock sawing

在线全文

学校读者我要写书评

暂无评论

Mining Science and Technology 2011年第5期21卷 611-619页

作者： Mikaeil reza Ataei Mohammad Yousefi reza Faculty of Mining Petroleum & Geophysics Shahrood University of Technology Shahrood 36155-316 Iran Faculty of Mining Petroleum & Geophysics Shahrood University of Technology Shahrood 36155-316 Iran Faculty of Mechanics Sharif University of Technology Tehran Irana

A new predictive model for evaluating the vibration of a sawing machine was developed using a new rock classification system. The predictors are machine parameters and a rock sawability index. The new rock classification system includes four major parameters of the rock： uniaxial compressive strength, abrasiv- ity index, mean MoWs hardness, and Young＇s modulus. The FAHP approach was used when determining the weights of these parameters by six decision makers. Two groups of carbonate rocks were sawn using a fully-instrumented laboratory sawing rig at different feed rates and depths of cut. During the sawing trials system vibration was monitored as a measure of saw performance. Then, a new statistical model was obtained by multiple regression on the machining parameters and the rock sawability index. The model is very useful for the evaluation of the system vibration, and for selecting suitable machining parameters, from a limited set of mechanical properties.

关键词： Sawability FAHP Classification Vibration

3D numerical parametric study of the influence of open-pit mining sequence on existing tunnels

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2017年第3期27卷 459-466页

作者： Beyabanaki Amir reza Gall Vojtech McMillen Jacobs Associates San Francisco CA 94105 USA Gall Zeidler Consultants Ashburn VA 20147 USA

The development of open-pit mines can adversely affect and even damage existing access tunnels. To ensure the safety and serviceability of them, it is essential to know potential adverse effects of the mining sequence on existing tunnels such as displacements of the lining and additional loads on the lining. In this paper, three-dimensional numerical parametric study is performed to explore this complex interaction. This study investigates the effects of different parameters that may affect the tunnel response. These parameters are： excavation sequence method, horizontal/vertical stress ratio, slope angle, and tunnel diameter. This study shows that the mining sequence affects the stability of the tunnels. The open-pit mining activities lead to both higher axial forces in rock bolts and normal forces and bending moments in the lining. The results of the analysis also demonstrate that the mining sequence causes tunnel heave and significant tensile forces in the lining. Based on the study in this paper a better understanding of the interaction between oDen-oit minin~ seouence and tunnels will he ohtained

关键词： Three-dimensionalNumerical parametric studyExisting tunnelOpen-pit mining sequenceModeling

Alleviation of spike stall in axial compressors utilizing grooved casing treatment

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2015年第3期28卷 649-658页

作者： reza Taghavi-Zenouz Sarallah Abbasi School of Mechanical Engineering Iran University of Science and Technology School of Mechanical Engineering Arak University of Technology

Abstract This article deals with application of grooved type casing treatment for suppression of spike stall in an isolated axial compressor rotor blade row. The continuous grooved casing treatment covering the whole compressor circumference is of 1.8 mm in depth and located between 90% and 108% chord of the blade tip as measured from leading edge. The method of investigation is based on time-accurate three-dimensional full annulus numerical simulations for cases with and without casing treatment. Discretization of the Navier Stokes equations has been carried out based on an upwind second-order scheme and k-a-SST （Shear Stress Transport） turbulence modeling has been used for estimation of eddy viscosity. Time-dependent flow structure results for the smooth casing reveal that there are two criteria for spike stall inception known as leading edge spillage and trailing edge backftow, which occur at specific mass flow rates in near-stall conditions. In this case, two dominant stall cells of different sizes could be observed. The larger one is caused by the spike stall covering roughly two blade passages in the circumferential direction and about 25% span in the radial direction. Spike stall disturbances are accompanied by lower frequencies and higher amplitudes of the pressure signals. Casing treatment causes flow blockages to reduce due to allevi- ation of backflow regions, which in turn reduces the total pressure loss and increases the axial veloc- ity in the blade tip gap region, as well as tip leakage flow fluctuation at higher frequencies and lower amplitudes. Eventually, it can be concluded that the casing treatment of the stepped tip gap type could increase the stall margin of the compressor. This fact is basically due to retarding the movement of the interface region between incoming and tip leakage flows towards the rotor leading edge Diane and suttressing the reversed flow around the blade trailing edee.

关键词： Axial compressor Casing treatment Frequency spectrum Spike stall inception Tip leakage flow

Phase type delay distribution with PU return and sensing error in CR networks

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2017年第10期24卷 2314-2321页

作者： Mohammad reza Amini Hemati Farzad Department of Electrical Engineering College of EngineeringBorujerd BranchIslamic Azad UniversityBorujerdIran

Many studies have been done in cognitive radios to maximize the network efficiency. There is always a trade-off between sensing and transmission time which has been addressed fully in the literature. There is also some missed idle times during the waiting phase when secondary user finds the channel busy. Therefore, the longer the transmission time is, the higher the successfully delivered bits would be and the higher the missed idle times in the waiting stage would be expected. In this work, we formulate these missed idle times to addressed this trade-off. Furthermore, interference due to PU re-occupancy is modelled in successful transmitted time and in collision probability. Moreover, we derive secondary user's packet delay distribution using phase type model at which retransmission due to collision results from both sensing error and PU re-occupancy is considered. Thanks to derived delay distribution, any statistical moments of delay could be found as a closed form mathematical expression. These moments can be used as constraints for applications with delay sensitive packets. Numerical results are given to clarify the network metrics. Finally, the optimized values for sensing and transmission time are computed using genetic algorithm in order to maximize access efficiency.

关键词： phase type distribution spectrum sensing cognitive radio access efficiency