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Chinese Physics B 2015年第11期24卷 422-427页

作者： mehdi ahmadi Sajjad Rashidi Dafeh Department of Physics Faculty of Science Vali-e-Asr University of Rafsanjan

In this work, ZnO nanorod arrays grown by an electrochemical deposition method are investigated. The crucial parameters of length, diameter, and density of the nanorods are optimized over the synthesize process and nanorods growth time. Crystalline structure, morphologies, and optical properties of ZnO nanorod arrays are studied by different techniques such as x-ray diffraction, scanning electron microscope, atomic force microscope, and UV-visible transmission spectra. The ZnO nanorod arrays are employed in an inverted bulk heterojunction organic solar cell of Poly （3-hexylthiophene）：[6- 6] Phenyl-（6） butyric acid methyl ester to introduce more surface contact between the electron transporter layer and the active layer. Our results show that the deposition time is a very important factor to achieve the aligned and uniform ZnO nanorods with suitable surface density which is required for effective infiltration of active area into the ZnO nanorod spacing and make a maximum interfacial surface contact for electron collection, as overgrowing causes nanorods to be too dense and thick and results in high resistance and lower visible light transmittance. By optimizing the thickness of the active layer on top of ZnO nanorods, an improved efficiency of 3.17% with a high FF beyond 60% was achieved.

关键词： electrochemical deposition density-controlled ZnO nanorods inverted polymer solar cells active area modification

Proposing two new methods to decrease lateral-torsional buckling in reduced beam section connections

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Frontiers of Structural and Civil Engineering 2022年第12期16卷 1581-1598页

作者： Samira EBRAHIMI Nasrin BAKHSHAYESH EGHBALI Mohammad mehdi ahmadi School of Civil Engineering College of EngineeringUniversity of TehranTehran ***Iran Department of Civil Engineering Ilam UniversityIlam 69391-77111Iran

Reduced web section(RWS)connections can prevent lateral-torsional buckling and web local buckling experienced by reduced beam section(RBS)*** RWS connections,removing a large portion of web can result in shear demand intolerance induced to plastic hinge *** present study aims to resolve the problems of RBS and RWS connections by proposing two new connections:(1)RBS with stiffener(RBS-ST)and(2)RBS with reduced web(RW-RBS)*** the first connection(RBS-ST),a series of stiffeners is connected to the beam in the reduced flange region,while the second connection(RW-RBS)considers both a reduction in flanges and a reduction in *** beam-to-column joints with three different connections,including RBS,RBS-ST,and RW-RBS connections were considered and simulated in *** to the results,RBS-ST and RW-RBS connections can decrease or even eliminate lateral-torsional buckling and web local buckling in RBS *** is important to note that RWRBS connection is more effective in long beams with smaller shear demands in the plastic hinge ***,results showed that RBS and RW-RBS connections experienced strength degradation at 4%to 5%drift,while no strength degradation was observed in RBS-ST connection until 8%drift.

关键词： RBS RBS-ST RW-RBS lateral-torsional buckling cyclic performance

Inverted polymer solar cells with employing of electrochemical-anodizing synthesized TiO_2 nanotubes

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Chinese Physics B 2016年第4期25卷 320-324页

作者： mehdi ahmadi Sajjad Rashidi Dafeh Hamed Fatehy Department of Physics Faculty of Science Vali-e-Asr University of Rafsanjan

An inverted structure of polymer solar cells based on Poly（3-hexylthiophene）（P3HT）：[6-6] Phenyl-（6） butyric acid methyl ester （PCBM） with using thin films of TiO2 nanotubes and nanoparticles as an efficient cathode buffer layer is developed. A total of three cells employing TiO2 thin films with different thickness values are fabricated. Two cells use layers of TiO2 nanotubes prepared via self-organized electrochemical-anodizing leading to thickness values of 203 and 423.7 nm, while the other cell uses only a simple sol-gel synthesized TiO2 thin film of nanoparticles with a thickness of 100 nm as electron transport layer. Experimental results demonstrate that TiO2 nanotubes with these thickness values are inefficient as the power conversion efficiency of the cell using 100-nm TiO2 thin film is 1.55%, which is more than the best power conversion efficiency of other cells. This can be a result of the weakness of the electrochemical anodizing method to grow nanotubes with lower thickness values. In fact as the TiO2 nanotubes grow in length the series resistance （Rs） between the active polymer layer and electron transport layer increases, meanwhile the fill factor of cells falls dramatically which finally downgrades the power conversion efficiency of the cells as the fill factor falls.

关键词： inverted polymer solar cells TiO2 nanotubes electrochemical-anodizing doctor blading

A multi-functional dynamic state estimator for error validation:measurement and parameter errors and sudden load changes

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Frontiers of Information Technology & Electronic Engineering 2016年第11期17卷 1218-1227页

作者： mehdi ahmadi JIRDEHI Reza HEMMATI Vahid ABBASI Hedayat SABOORI Department of Electrical Engineering Kermanshah University of Technology

We propose a new and efficient algorithm to detect, identify, and correct measurement errors and branch parameter errors of power systems. A dynamic state estimation algorithm is used based on the Kalman filter theory. The proposed algorithm also successfully detects and identifies sudden load changes in power systems. The method uses three normalized vectors to process errors at each sampling time: normalized measurement residual, normalized Lagrange multiplier, and normalized innovation vector. An IEEE 14-bus test system was used to verify and demonstrate the effectiveness of the proposed method. Numerical results are presented and discussed to show the accuracy of the method.

关键词： Dynamic state estimation Kalman filter Measurement errors Branch parameter errors Sudden load changes

Inverted organic solar cells with solvothermal synthesized vanadium-doped TiO2 thin films as efficient electron transport layer

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Chinese Physics B 2017年第9期26卷 406-410页

作者： mehdi ahmadi Sajjad Rashidi Dafeh Samaneh Ghazanfarpour Mohammad Khanzadeh Department of Physics Faculty of ScienceVali-e-Asr University of RafsanjanRafsanjanIran

We investigated the effects of using different thicknesses of pure and vanadium-doped thin films of TiO2 as the electron transport layer in the inverted configuration of organic photovoltaic cells based on poly（3-hexylthiophene） P3HT：[6-6] phenyl-（6） butyric acid methyl ester（PCBM）. 1% vanadium-doped TiO2nanoparticles were synthesized via the solvothermal method. Crystalline structure, morphology, and optical properties of pure and vanadium-doped TiO2 thin films were studied by different techniques such as x-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and UV–visible transmission spectrum. The doctor blade method which is compatible with roll-2-roll printing was used for deposition of pure and vanadium-doped TiO2 thin films with thicknesses of 30 nm and 60 nm. The final results revealed that the best thickness of TiO2 thin films for our fabricated cells was 30 nm. The cell with vanadium-doped TiO2 thin film showed slightly higher power conversion efficiency and great Jsc of 10.7 mA/cm^2 compared with its pure counterpart. In the cells using 60 nm pure and vanadium-doped TiO2 layers, the cell using the doped layer showed much higher efficiency. It is remarkable that the external quantum efficiency of vanadium-doped TiO2 thin film was better in all wavelengths.

关键词： inverted polymer solar cells electron transport layer vanadium-doped TiO2 thin films solvothermal

Comparison of accuracy and computational performance between the machine learning algorithms for rate of penetration in directional drilling well

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Petroleum Research 2021年第3期6卷 271-282页

作者： Omid Hazbeh Saeed Khezerloo-ye Aghdam Hamzeh Ghorbani Nima Mohamadian mehdi ahmadi Alvar Jamshid Moghadasi Faculty of Earth Sciences Shahid Chamran UniversityAhwazIran Department of Petroleum Engineering Amirkabir University of TechnologyTehranIran Young Researchers and Elite Club Ahvaz BranchIslamic Azad UniversityAhvazIran Young Researchers and Elite Club Omidiyeh BranchIslamic Azad UniversityOmidiyehIran Faculty of Engineering Department of Computer EngineeringShahid Chamran UniversityAhwazIran Petroleum Engineering Department Petroleum Industry UniversityAhvazIran

Oil and gas reservoirs are of the main assets of countries possessing *** from these reservoirs is one of the main concerns of engineers,which can be achieved by drilling oil and gas *** of hydrocarbon wells is one of the most expensive operations in the oil *** of the most important parameters affecting drilling cost is the rate of penetration(ROP).This paper predicts the rate of penetration using artificial intelligence and hybrid models on Kaboud oil field well#7 in the directional *** this study,different models were constructed through various approaches based on 1878 dataset obtained from drilling operation in the well#***,the accuracy of the constructed models was compared with each *** was found that the MLP-ABC algorithm predicts the rate of penetration more accurately,by far,as compared with other *** MLP-ABC algorithm achieves impressive ROP prediction accuracy(RMSE=0.007211 m/h;AAPD=0.1871%;R^(2)=1.000 for the testing subset).Consequently,it can be concluded that this method is applicable to predict the drilling rate in that oilfield.

关键词： Rate of penetration Artificial intelligence Directional drilling MLP Prediction

Data-Based Filters for Non-Gaussian Dynamic Systems With Unknown Output Noise Covariance

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IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 866-877页

作者： Elham Javanfar mehdi Rahmani the Department of Electrical Engineering Imam Khomeini International UniversityQazvin ***Iran

This paper proposes linear and nonlinear filters for a non-Gaussian dynamic system with an unknown nominal covariance of the output *** challenge of designing a suitable filter in the presence of an unknown covariance matrix is addressed by focusing on the output data set of the *** that data generated from a Gaussian distribution exhibit ellipsoidal scattering,we first propose the weighted sum of norms(SON)clustering method that prioritizes nearby points,reduces distant point influence,and lowers computational ***,by introducing the weighted maximum likelihood,we propose a semi-definite program(SDP)to detect outliers and reduce their impacts on each *** these weights paves the way to obtain an appropriate covariance of the output ***,two filtering approaches are presented:a cluster-based robust linear filter using the maximum a posterior(MAP)estimation and a clusterbased robust nonlinear filter assuming that output noise distribution stems from some Gaussian noise resources according to the ellipsoidal *** last,simulation results demonstrate the effectiveness of our proposed filtering approaches.

关键词： Data-based filter maximum likelihood estimation unknown covariance weighted maximum likelihood estimation weighted sum-of-norms clustering

Reinforcement Learning-Empowered Graph Convolutional Network Framework for Data Integrity Attack Detection in Cyber-Physical Systems

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 797-806页

作者： Edeh Vincent mehdi Korki mehdi Seyedmahmoudian Alex Stojcevski Saad Mekhilef School of Science Computingand Engineering TechnologiesSwinburne University of TechnologyMelbourneAustralia

The massive integration of communication and information technology with the large-scale power grid has enhanced the efficiency, safety, and economical operation of cyber-physical systems. However, the open and diversified communication environment of the smart grid is exposed to cyber-attacks. Data integrity attacks that can bypass conventional security techniques have been considered critical threats to the operation of the grid. Current detection techniques cannot learn the dynamic and heterogeneous characteristics of the smart grid and are unable to deal with non-euclidean data types. To address the issue, we propose a novel Deep-Q-Network scheme empowered with a graph convolutional network (GCN) framework to detect data integrity attacks in cyber-physical systems. The simulation results show that the proposed framework is scalable and achieves higher detection accuracy, unlike other benchmark techniques.

关键词： Deep reinforcement learning graph convolutional network heterogeneous smart grid network

Model Reference Adaptive Controller for Simultaneous Voltage and Frequency Restoration of Autonomous AC Microgrids

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Journal of Modern Power Systems and Clean Energy 2024年第4期12卷 1194-1202页

作者： Farahnaz ahmadi Yazdan Batmani Hassan Bevrani Department of Electrical Engineering University of KurdistanSanandajIran

In an autonomous droop-based microgrid,the sys-tem voltage and frequency(VaF)are subject to deviations as load *** the existence of various control methods aimed at correcting system frequency deviations at the second-ary control level without any communication network,the chal-lenges associated with these methods and their abilities to simul-taneously restore microgrid VaF have not been fully *** this paper,a multi-input multi-output(MIMO)model ref-erence adaptive controller(MRAC)is proposed to achieve VaF restoration while accurate power sharing among distributed generators(DGs)is *** proposed MRAC,without any communication network,is designed based on two meth-ods:droop-based and inertia-based *** the microgrid,the suggested design procedure is started by defining a model reference in which the control objectives,such as the desired settling time,the maximum tolerable overshoot,and steady-state error,are ***,a feedback-feedforward con-troller is established,of which the gains are adaptively tuned by some rules derived from the Lyapunov stability *** some simulations in MATLAB/SimPowerSystem Tool-box,the proposed MRAC demonstrates satisfactory perfor-mance.

关键词： AC microgid communication-free secondary control droop-based method inertia-based method model reference adaptive controller(MRAC) simultaneous voltage and frequency restoration

A novel mitigation measure for normal fault-induced deformations on pile-raft systems

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Earthquake Engineering and Engineering Vibration 2024年第1期23卷 15-33页

作者： Mohammadreza Jahanshahi Nowkandeh mehdi Ashtiani Faculty of Civil Engineering Babol Noshirvani University of TechnologyBabolIran

Evidence from recent earthquakes has shown destructive consequences of fault-induced permanent ground movement on *** observations have increased the demand for improvements in the design of structures that are dramatically vulnerable to surface fault *** this study a novel connection between the raft and the piles is proposed to mitigate the hazards associated with a normal fault on pile-raft systems by means of 3D finite element(FE)*** embarking on the parametric study,the strain-softening constitutive law used for numerical modeling of the sand has been validated against centrifuge test *** exact location of the fix-head and unconnected pile-raft systems relative to the outcropping fault rupture in the free-field is parametrically investigated,revealing different failure *** performance of the proposed connection for protecting the pile-raft system against normal fault-induced deformations is assessed by comparing the geotechnical and structural responses of both types of *** results indicate that the pocket connection can relatively reduce the cap rotation and horizontal and vertical displacements of the raft in most *** proposed connection decreases the bending moment response of the piles to their bending moment capacity,verging on a fault offset of 0.6 m at bedrock.

关键词： normal fault rupture failure mechanism pile-raft system pocket connection finite element modeling