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Influence of surface cracking,anchor head profile,and anchor head size on cast-in headed anchors in geopolymer concrete

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Frontiers of Structural and Civil Engineering 2023年第8期17卷 1163-1187页

作者： Trijon KARMOKAR alireza MOYHEDDIN School of Engineering Edith Cowan UniversityPerth 6027Australia

In this study,the concrete cone capacity,concrete cone angle,and load–displacement response of cast-in headed anchors in geopolymer concrete are explored using numerical *** concrete damaged plasticity(CDP)model in ABAQUS is used to simulate the behavior of concrete *** tensile behavior of anchors in geopolymer concrete is compared with that in normal concrete as well as that predicted by the linear fracture mechanics(LFM)and concrete capacity design(CCD)*** results show that the capacity of the anchors in geopolymer concrete is 30%–40%lower than that in normal *** results also indicate that the CCD model overestimates the capacity of the anchors in geopolymer concrete,whereas the LFM model provides a much more conservative *** extent of the difference between the predictions by the numerical analysis and those of the above prediction models depends on the effective embedment depth of the anchor and the anchor head *** influence of concrete surface cracking on the capacity of the anchor is shown to depend on the location of the crack and the effective embedment *** influence of the anchor head profile on the tensile capacity of the anchors is found to be insignificant.

关键词： cast-in anchor concrete cone capacity geopolymer concrete head size surface crack anchor profile

Optimal State Estimation and Fault Diagnosis for a Class of Nonlinear Systems

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IEEE/CAA Journal of Automatica Sinica 2020年第2期7卷 517-526页

作者： Hamed Kazemi alireza Yazdizadeh Department of Electrical Engineering Shahid Beheshti UniversityTehran ***Iran

This study proposes a scheme for state estimation and,consequently,fault diagnosis in nonlinear ***,an optimal nonlinear observer is designed for nonlinear systems subject to an actuator or plant *** utilizing Lyapunov's direct method,the observer is proved to be optimal with respect to a performance function,including the magnitude of the observer gain and the convergence *** observer gain is obtained by using approximation of Hamilton-Jacobi-Bellman(HJB)*** approximation is determined via an online trained neural network(NN).Next a class of affine nonlinear systems is considered which is subject to unknown disturbances in addition to fault *** this case,for each fault the original system is transformed to a new form in which the proposed optimal observer can be applied for state estimation and fault detection and isolation(FDI).Simulation results of a singlelink flexible joint robot(SLFJR)electric drive system show the effectiveness of the proposed methodology.

关键词： Differential geometry fault detection and isolation(FDI) fault diagnosis neural network(NN) nonlinear observer and filter design optimal state estimation

Dynamic Positioning System Design for A Marine Vessel with Unknown Dynamics Subject to External Disturbances Including Wave Effect

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China Ocean Engineering 2020年第5期34卷 651-663页

作者： alireza HOSSEINNAJAD Mehdi LOUEIPOUR Department of Mechanical Engineering Isfahan University of TechnologyIsfahanIran Research Institute for Subsea Science and Technology Isfahan University of TechnologyIsfahanIran

In this paper, a new control system is proposed for dynamic positioning(DP) of marine vessels with unknown dynamics and subject to external disturbances. The control system is composed of a substructure for wave filtering and state estimation together with a nonlinear PD-type controller. For wave filtering and state estimation, a cascade combination of a modified notch filter and an estimation stage is considered. In estimation stage, a modified extended-state observer(ESO) is proposed to estimate vessel velocities and unknown dynamics. The main advantage of the proposed method is its robustness to model uncertainties and external disturbances and it does not require prior knowledge of vessel model parameters. Besides, the stability of the cascade structure is analyzed and input to state stability(ISS) is guaranteed. Later on, a nonlinear PD-type controller with feedforward of filtered estimated dynamics is utilized. Detailed stability analyses are presented for the closed-loop DP control system and global uniform ultimate boundedness is proved using large scale systems method. Simulations are conducted to evaluate the performance of the proposed method for wave filtering and state estimation and comparisons are made with two conventional methods in terms of estimation accuracy and the presence of uncertainties. Besides, comparisons are made in closed-loop control system to demonstrate the performance of the proposed method compared with conventional methods. The proposed control system results in better performance in the presence of uncertainties,external disturbance and even in transients when the vessel is subjected to sudden changes in environmental disturbances.

关键词： dynamic positioning environmental disturbances marine vessel state estimation unknown dynamics wave filtering

Presence of neodymium and gadolinium in cobalt ferrite lattice:Structural,magnetic and microwave features for electromagnetic wave absorbing

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Journal of Rare Earths 2020年第4期38卷 411-417页

作者： alireza Nikzad Roghaieh Parvizi Department of Physics College of SciencesYasouj UniversityYasouj75914-353Iran

In this work,neodymium substituted gadolinium-cobalt ferrite nanoparticles were synthesized by hydrothermal *** significant role of doping both the Nd3+and Gd3+ions to cobalt ferrite in manipulating the cation distribution and further in influencing structural and magnetic properties was experimentally studied and *** influence of Nd3+substitution was investigated with step of 0.02-0.1 into the optimized Gd-Co *** crystal structure formation and crystallite size were explored by X-ray diffraction analysis in which the crystallite size and lattice constant decrease with increasing the Nd3+*** microstructural properties were studied by field emission scanning electron microscopy and atomic force microscopy *** obtained structural and morphological results reveal that the substitution of Nd3+with more than 0.06 into the Gd-Co ferrites will change the material be havior and *** saturation magnetization and coercivity values were measured using a vibration sample magnetometer at room *** microwave absorption experiments demonstrate that the reflection loss properties enhance with increasing substitution of Nd3+cations in Gd-Co ferrite spinel *** research reports that the as-prepared Nd3+substituted Gd-Co ferrite compound stands as promising candidate for absorbing electromagnetic wave with a wider absorbing bandwidth of X-band.

关键词： Gd-Co nanoferrite Coercive field Microwave absorption Rare earths

Full Non-Rigid Group and Symmetry of Dimethyltrichlorophosphorus

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Chinese Journal of Chemistry 2005年第7期23卷 829-834页

作者： ASHRAFI alireza DepartmentofMathematics FacultyofScienceUniversityofKashanKashanIran

In this work, a simple method is described, by means of which it is possible to calculate character tables for the symmetry group of molecules consisting of a number of NH 3 groups attached to a rigid framework. The full non‐rigid group (f‐NRG) of dimethyltrichlorophosphorus with the symmetry group D 3h was studied. It has been proven that it is a group of order 216 with 27 conjugacy classes and its character table computed. Finally, thePermutation‐Inversion group of this molecule was calculated.

关键词： dimethyltrichlorophosphorus full non‐rigid group character table

Evolutionary Algorithms for Controller Tuning of Tert-Amyl-Methyl-Ether Reactive Distillation

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Journal of Systems Science and Systems Engineering 2020年第3期29卷 325-343页

作者： alireza Behroozsarand David AWood Faculty of Chemical Engineering Urmia University of TechnologyUrmiaIran DWA Energy Limited LincolnUnited Kingdom

Efficient tuning of the coefficients used by proportional-integral-derivative(PID)controllers enhances their *** highly non-linear systems,optimization algorithms are required to make the PID controllers more responsive to *** production of tert-amyl-methyl-ether(TAME),an essential additive for gasoline,in reactive distillation columns integrates highly non-linear reaction and separation *** the other hand,TAME distillation is an azeotrope distillation process,therefore non-linearity of this process is more complex than that of conventional ***-controller tuning methods applying a genetic algorithm(GA)and a particle swarm optimization(PSO)algorithm are compared using a dynamic simulation that integrates the optimization algorithms with the HYSYS process *** PID controller response trends are analyzed following the introduction of a significant disturbance to the TAME reactive distillation column(i.e.,a ten percent change in the methanol feed temperature).The PSO PID controller tuning method that minimizes the integral of the absolute error(IAE)as its objective function significantly outperforms the GA tuning *** novel PID-tuning methodology developed has more extensive application potential.

关键词： TAME azeotropic reactive distillation PID-controller tuning particle swarm optimization genetic algorithm real-time controller optimization

Multiobjective optimization scheme for industrial synthesis gas sweetening plant in GTL process

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Journal of Natural Gas Chemistry 2011年第1期20卷 99-109页

作者： alireza Behroozsarand Akbar Zamaniyan Department of Chemical Engineering Islamic Azad University Department of Natural Gas Conversion Gas Research Division Research Institute of Petroleum Industry (RIPI)

In industrial amine plants the optimized operating conditions are obtained from the conclusion of occurred events and challenges that are normal in the working units. For the sake of reducing the costs, time consuming, and preventing unsuitable accidents, the optimization could be performed by a computer program. In this paper, simulation and parameter analysis of amine plant is performed at first. The optimization of this unit is studied using Non-Dominated Sorting Genetic Algorithm-II in order to produce sweet gas with CO 2 mole percentage less than 2.0% and H 2 S concentration less than 10 ppm for application in Fischer-Tropsch synthesis. The simulation of the plant in HYSYS v.3.1 software has been linked with MATLAB code for real-parameter NSGA-II to simulate and optimize the amine process. Three scenarios are selected to cover the effect of （DEA/MDEA） mass composition percent ratio at amine solution on objective functions. Results show that sour gas temperature and pressure of 33.98 ？ C and 14.96 bar, DEA/CO 2 molar flow ratio of 12.58, regeneration gas temperature and pressure of 94.92 ？ C and 3.0 bar, regenerator pressure of 1.53 bar, and ratio of DEA/MDEA = 20%/10% are the best values for minimizing plant energy consumption, amine circulation rate, and carbon dioxide recovery.

关键词： amine plant multiobjective optimization Non-Dominated Sorting Genetic Algorithm amine circulation rate

Robust pre-specified time synchronization of chaotic systems by employing time-varying switching surfaces in the sliding mode control scheme

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Chinese Physics B 2016年第8期25卷 86-93页

作者： alireza Khanzadeh Mahdi Pourgholi Faculty of Electrical Engineering Shahid Beheshti University

In the conventional chaos synchronization methods, the time at which two chaotic systems are synchronized, is usually unknown and depends on initial conditions. In this work based on Lyapunov stability theory a sliding mode controller with time-varying switching surfaces is proposed to achieve chaos synchronization at a pre-specified time for the first time. The proposed controller is able to synchronize chaotic systems precisely at any time when we want. Moreover, by choosing the time-varying switching surfaces in a way that the reaching phase is eliminated, the synchronization becomes robust to uncertainties and exogenous disturbances. Simulation results are presented to show the effectiveness of the proposed method of stabilizing and synchronizing chaotic systems with complete robustness to uncertainty and disturbances exactly at a pre-specified time.

关键词： chaos synchronization finite time synchronization sliding mode controller time varying switching surfaces

Investigation of the stress rupture behavior of GTD-111 superalloy melted by VIM/VAR

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International Journal of Minerals,Metallurgy and Materials 2018年第9期25卷 1035-1041页

作者： Ainaz Agh alireza Amini Department of Materials Engineering Islamic Azad University Karaj Branch

The effects of vacuum induction melting(VIM) and vacuum arc remelting(VAR) processes on the microstructure and stress rupture properties of Ni-based GTD-111 superalloy were investigated. Samples of GTD-111 master alloy were melted in VIM and VAR furnaces and then poured into a preheated ceramic mold for VIM melt or into a water-cooled copper mold for VAR melt. The as-cast samples were examined radiographically to ensure that no casting defects were present in the final castings; the samples were then heat-treated using a standard heat-treatment cycle. The microstructure of the samples was investigated using optical microscopy and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy for microanalysis. On the basis of standard ASTM-E139, stress rupture tests were carried out at 1000°C under a stress of 300 MPa. The results showed that a γ matrix, fine γ′ precipitates, a γ–γ′ eutectic structure, carbide particles, and some harmful phases such as σ and η phases were present in the as-cast samples. The γ′ precipitates with cubic morphology appeared in the matrix after the standard heat-treatment process. The extent of segregation and the amount of γ–γ′ eutectic structure formed in the VAR-prepared sample were less than in the VIM-prepared sample. The results of stress rupture tests showed that the rupture time for the VAR sample was 43% longer than that for the VIM sample.

关键词： GTD-111 vacuum induction melting(VIM) vacuum arc remelting(VAR) stress rupture