检索结果-南通市图书馆

Voltage control strategy for an uncertain mobile robot

在线全文

学校读者我要写书评

暂无评论

International Journal of Intelligent Computing and Cybernetics 2014年第4期7卷 436-452页

作者： Mohammad Mehdi Fateh ali Asghar arab Department of Electrical Engineering University of ShahroodShahroodIran Electrical and Robotic Engineering Shahrood University of TechnologyShahroodIran

Purpose–The uncertainty and nonlinearity are the challenging problems for the control of a nonholonomic wheeled mobile *** overcome these problems,many valuable methods have been proposed by using two control loops namely the kinematic control and the torque control so *** majority of the proposed approaches the dynamics of actuators is omitted for simplicity in the control *** drawback degrades the control performance in high-velocity tracking *** the other hand,to guarantee stability and overcome uncertainties,the control methods become computationally extensive and may be impractical due to using all *** purpose of this paper is to design a simple controller with guaranteed stability for overcoming the nonlinearity,uncertainty and actuator ***/methodology/approach–The control design includes two control loops,the kinematic control loop and the novel dynamic control *** dynamic control loop uses the voltage control strategy instead of the torque control *** of the robot orientation,robot position,robot linear and angular velocity,and motor currents are given to the control ***–To improve the precision,the dynamics of motors are taken into *** most important advantages of the proposed control law is that it is free from the robot dynamics,thereby the controller is simple,fast response and robust with ignorable tracking *** control approach is verified by stability *** results show the effectiveness of the proposed control applied on an uncertain nonholonomic wheeled mobile robot driven by permanent magnet dc motors.A comparison with an adaptive sliding-mode dynamic control approach confirms the superiority of the proposed approach in terms of precision,simplicity of design and ***/value–The originality of the paper is to present a new control design for an uncertain nonholonomic wheeled mobile robot by using voltage control strategy in replac

关键词： Nonlinear control Robust control Actuator dynamics Nonholonomic wheeled robot Robotics

High strain rate deformation of explosion-welded Ti6Al4V/pure titanium

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2020年第3期16卷 678-688页

作者： Yan-song Guo Peng-wan Chen ali arab Qiang Zhou Yasir Mahmood State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081PR China

Multilayer materials are widely used in military,automobile and aerospace *** this paper,the response of an explosion-welded Ti6Al4V/pure titanium with a flat interface to dynamic loading is *** SHPB apparatus is ***,the dynamic behaviour of a bimetal sample is explored with a DIC system coupled to the *** indicates that in the bimetal sample pure titanium is deformed and failed before *** stress curve of the sample shows two different peaks in a striker velocity higher than the 18.3 m/*** the incident wave encounters the interface of the Ti6Al4V/pure titanium sample,only a small fraction of the wave is reflected owing to similar *** the direct interpretation stress-strain curve is unreasonable in this case because of unhomogenised plastic *** micro structure of the sample is investigated after *** adiabatic shear band is formed in the pure titanium side before failure,and the interface of the sample remains intact under different loading *** FEM simulation result for the sample is in good agreement with experimental observations.

关键词： Explosion welded Dynamic behaviour SHPB Titanium alloy

Histological and biochemical alterations in early-stage lobar ischemia-reperfusion in rat liver

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2009年第16期15卷 1951-1957页

作者： Hossein ali arab Farhang Sasani Mohammad Hossein Rafiee Ahmad Fatemi Abbas Javaheri Department of Pharmacology Faculty of Veterinary MedicineUniversity of Tehran Department of Pathology Faculty of Veterinary MedicineUniversity of Tehran Faculty of Veterinary Medicine University of Semnan

AIM:To investigate the structural and biochemical changes in the early stage of reperfusion in the rat livers exposed to lobar ischemia-reperfusion (IR).METHODS: The median and left lobes of the liver were subjected to 60 min ischemia followed by 5, 10, 30, 45, 60 and 120 min reperfusion. Blood samples were taken at different time intervals to test enzyme activities and biochemical alterations induced by reperfusion. At the end of each reperfusion period, the animals were killed by euthanasia and tissue samples were taken for histological examination and immunohistochemistry. RESULTS: Cell vacuolation, bleb formation and focal hepatitis were the most important changes occur during ischemia. While some changes including bleb formation were removed during reperfusion, other alterations including portal hepatitis, inflammation and the induction of apoptosis were seen during this stage. The occurrence of apoptosis, as demonstrated by apoptotic cells and bodies, was the most important histological change during reperfusion. The severity of apoptosis was dependent on the time of reperfusion, and by increasing the time of reperfusion,the numbers of apoptotic bodies was significantly enhanced. The amounts of lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, creatinine and urea were significantly increased in serum obtained from animals exposed to hepatic ***: Inflammation and subsequent apoptotic cell death were the most important changes in early-stage hepatic reperfusion injury, and the number of apoptotic bodies increased with time of reperfusion.

关键词：缺血再灌注大鼠肝脏组织学变化生化改变早期诱导细胞凋亡再灌注期间炎症反应

Effects of La_(2)O_(3) addition on microstructure development and physical properties of harder ZTA-CeO_(2) composites with sustainable high fracture toughness

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Rare Earths 2021年第7期39卷 844-849,I0003页

作者： Zhwan Dilshad Ibrahim Sktani Nik Akmar Rejab Abdul Fatah Zulkarnain Rosli ali arab Zainal Arifin Ahmad Department of Mechanical and Energy Engineering Erbil Technical Engineering CollegeErbil Polytechnic UniversityErbil44001Iraq Structural Materials Niche Area School of Materials and Mineral Resources EngineeringEngineering CampusUniversiti Sains Malaysia14300Nibong TebalPenangMalaysia State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

The influence of La_(2)O_(3) inclusion(0-3 wt%) on the micro structure,phase formation and mechanical properties of zirconia toughed alumina(ZTA) added with 5.0 wt% CeO_(2) was *** CeO_(2) composites were sintered at 1600℃ for 4 *** microstructure,phase formation,density,fracture toughness and hardness properties were characterised through FESEM,Microscopy Image Analysis Software and XRD diffractometer,Archimedes principle and Vickers indentation technique,*** XRD,image processing and FESEM reveal the existence of LaAl_(11)O_(18).The addition of La_(2)O_(3) incites the sintering,microstructure refinement,densification of ZTA-CeO_(2) matrix and phase ***,the hardness of ZTA-CeO_(2) ceramics is increased rapidly based on refinement of Al_(2)O_(3) grains,densification of ZTA-CeO_(2) composites and porosity *** is observed that the fracture toughness is enhanced through in situ formation of elongated LaAl_(11)O_(18) *** addition of 0.7 wt% La_(2)O_(3) culminated in the achievement of the optimum findings for density(4.41 g/cm^(3)),porosity(0.46%),hardness(1792 HV) and fracture toughness(8.8 MPa·m^(1/2)).Nevertheless,excess La_(2)O_(3) is proven to be detrimental as it displays poor mechanical properties due to the poor compactness of numerous LaAl_(11)O_(18) grains,coarsening of Al_(2)O_(3) grains and decline in density.

关键词： ZTA-CeO_(2) Ceramic composite Microstructural design Fracture toughness Vickers hardness Rare earths

Mechanical behavior and failure mechanism of polyurea nanocomposites under quasi-static and dynamic compressive loading

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2021年第2期17卷 495-504页

作者： Qiang Liu Peng-wan Chen Yan-song Guo Jian-jun Su Lu Han ali arab Jian-fei Yuan State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Xi’an Modern Chemistry Research Institute Xi’an 710065China

Polyurea is an elastomeric material that can be applied to enhance the protection ability of structures under blast and impact *** order to study the compressive mechanical properties of SiC/polyurea nanocomposites under quasi-static and dynamic loading,a universal testing machine and split Hopkinson pressure bar(SHPB)apparatus were used *** stress-strain curves were obtained on polyurea and its composites at strain rates of 0.001e8000 s*** results of the experiment suggested that increase in the strain rates led to the rise of the flow stress,compressive strength,strain rate sensitivity and strain *** indicates that all of the presented materials were dependent on strain ***,these mechanical characters were enhanced by incorporating a small amount of SiC into polyurea *** relation between yield stress and strain rates were established using the power law ***,in order to investigate the fracture surfaces and inside information of failed specimens,scanning electron microscopy(SEM)and micro X-ray computed tomography(micro-CT)were used *** voids,crazes,micro-cracks and cracking were observed in fracture *** the other hand,the cracking propagation was found in the micro-CT slice *** is essential to understand the deformation and failure mechanisms in all the polyurea materials.

关键词： Polyurea nanocomposites Mechanical properties Strain rate Micro-CT Failure

Effects of different periods of renal ischemia on liver as a remote organ

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2009年第9期15卷 1113-1118页

作者： Mehri Kadkhodaee Fereshteh Golab Maryam Zahmatkesh Rana Ghaznavi Mehdi Hedayati Hossein ali arab Seyed Naser Ostad Manoocher Soleimani Department of Physiology School of MedicineTehran University of Medical Sciences14155-6447TehranIran Endocrine and Metabolism Research Center Shahid Beheshti University of Medical Sciences193954763TehranIran Department of Pharmacology School of Veterinary MedicineTehran University141556453 TehranIran Cell culture laboratory Faculty of PharmacyTehran University of Medical Sciences14155-6447TehranIran Department of Medicine University of CincinnatiMSB G259 OHUnited States

AIM:To assess the hepatic changes after induction of different periods of renal ischemia. METHODS:Rats were subjected to either sham operation or ischemia (30,45 and 60 min) followed by 60 min reperfusion. Liver and renal functional indices were measured. Hepatic glutathione (GSH) and ferric reducing antioxidant power levels and the concentration of interleukin (IL)-10 and tumor necrosis factor (TNF-α) were evaluated. Portions of liver and kidney tissues were fixed for histological evaluation. RESULTS:Forty-five minutes renal ischemia followed by 60 min reperfusion caused significant changes in liver structure and a significant reduction in renalfunction. These rats showed a significant decrease in liver GSH,as well as a significant increase in TNF-α and IL-10 concentrations. These results demonstrated that renal ischemia caused changes in liver histology,function,oxidative stress and inflammatory status,which led to a reduction in hepatic antioxidant capacity. With 30 min ischemia,the magnitude of these changes was less than those with 45 or 60 min ***:A minimum of 45 min ischemia is needed to study the effects of renal injury on the liver as a remote organ.

关键词：肾缺血再灌注肝脏结构器官肿瘤坏死因子肾功能指标 GSH含量白细胞介素组织学评价

Genuine entanglement under squeezed generalized amplitude damping channels with memory

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2024年第2期33卷 158-163页

作者： Mazhar ali Department of Electrical Engineering Faculty of EngineeringIslamic University MadinahMadinah 107Saudi Arabia

We study genuine entanglement among three qubits undergoing a noisy process that includes dissipation, squeezing,and decoherence. We obtain a general solution and analyze the asymptotic quantum states. We find that most of these asymptotic states can be genuinely entangled depending upon the parameters of the channel, memory parameter, and the parameters of the initial states. We study Greenberger–Horne–Zeilinger(GHZ) states and W states, mixed with white noise,and determine the conditions for them to be genuinely entangled at infinity. We find that for these mixtures, it is possible to start with a bi-separable state(with a specific mixture of white noise) and end with genuine entangled states. However, the memory parameter μ must be very high. We find that in contrast to the two-qubit case, none of the three-qubit asymptotic states for n → ∞ are genuinely entangled.

关键词： genuine entanglement squeezed thermal baths multipartite states

Heat transfer analysis in particle-laden flows using the immersed boundary method

在线全文

学校读者我要写书评

暂无评论

Particuology 2024年第7期90卷 394-403页

作者： ali Abbas Zaidi Department of Mechanical Engineering University of Manitoba75A Chancellors CircleWinnipegR3T 5V6Canada

This paper investigates an efficient immersed boundary method(IBM)for multiple-core CPU machines with local grid refinement for the calculation of heat transfer between fluids and finite-sized *** fluid momentum equations are solved by using the fractional step method,while the energy equation is solved by employing the second-order Adams-Bashforth *** efficient load balancing between the CPU cores,the coupling between particles and fluid is obtained by applying the body force in the fluid equations,which depends on the solid volume fraction of particles contained in each grid cell,and then by linearly interpolating the particle temperature and velocity on the fluid grid cell(in place of the delta function commonly used in literature).Several test cases from the literature are studied,and good agreement is observed between the simulation results and the ***,a scaling study on multiple core machines is performed,demonstrating the proposed IBM's capabilities for a significant reduction in processing time.

关键词： Heat transfer Immersed boundary method Particle resolved direct numerical simulations Fluid solid interactions

Simulation of the deformable lateral boundaries in biaxial test using DEM

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2024年第5期88卷 161-175页

作者： ali Momeni Barry Clarke Yong Sheng ali Hassanpour WSP 3 Wellington PlaceLeedsLS1 4APUK Hull University HullHU6 7RXUK School of Civil Engineering University of LeedsLeedsLS2 9JTUK School of Computer Science University of HullHullHU6 7RXUK School of Chemical and Process Engineering University of LeedsLeedsLS2 9JTUK

Applying the discrete element method(DEM)in soil mechanics can provide abundant information at the particle-scale and facilitates illustration of the macro-mechanical behaviour of soils based on the inter-particle *** triaxial test is one of the most common laboratory methods to study the macro-mechanical behaviour of particulate materials such as ***,many problems in geotechnical design can be assumed and simplified as a plane strain *** a biaxial test can be conducted to reproduce the macro-mechanical behaviour of soil,where the sample is enclosed by two horizontal rigid platens and a vertical latex membrane,which is a deformable continuous element and allows the enclosed specimen to deform freely while maintaining confining stress during *** paper presents an algorithm to represent physical and mechanical characteristics of latex membrane in the 2D DEM simulation of biaxial test using the PFC^(2D) *** investigate the impact of the lateral boundary conditions on the micro-macro mechanical behaviours of soil samples,two sets of DEM biaxial tests are conducted,*** rigid and deformable lateral boundary *** DEM modeling results indicate that the lateral boundary conditions have a significant effect on the micro-scale fabric properties,thickness and inclination of the shear *** comparison between these two simulations also demonstrates that the lateral boundary conditions play a major role in the peak and post-peak stress-strain behaviours as well as the dilation and critical state behaviours of granular soils.

关键词： Discrete element method Biaxial test Deformable boundaries Shear band Critical state Fabric anisotropy Geometrical stability index