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Improvement of mechanical behavior of buried pipelines subjected to strike-slip faulting using textured pipeline

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Frontiers of Structural and Civil Engineering 2019年第5期13卷 1105-1119页

作者： mahdi izadi Khosrow BARGI School of Civil Engineering College of EngineeringUniversity of TehranTehranIran

The present study investigates the mechanical behavior of a new generation of buried pipelines, dubbed the textured pipeline, which is subjected to strike-slip faulting. In conventional cylindrical pipelines, the axial and bending stresses brought about in their walls as a result of fault movement, lead to local buckling, which is construed as one of the major reasons contributing to pipeline failure. The present study has assessed 3-D numerical models of two kinds of buried textured pipelines, with 6 and 12 peripheral triangular facets, subjected to a strike-slip faulting normal to the axis of the pipelines, with and without internal pressure, with the two kinds of X65 and X80 steel, and with different diameter-to-thickness ratios. The results indicate that, because of specific geometry of this pipeline shell which is characterized by having lower axial stiffness and higher bending stiffness, compared to conventional cylindrical pipeline, they are considerably resistant to local (buckling. The results of this study can be conceived of as a first step toward comprehensive seismic studies on this generation of pipelines which aim at replacing the conventional cylindrical pipelines with textured ones in areas subjected to fault movement.

关键词： buried pipeline textured pipeline local buckling

Applying Sliding Mode Control to Suppress Double Frequency Voltage Ripples in Single-phase Quasi-Z-source Inverters

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CSEE Journal of Power and Energy Systems 2023年第2期9卷 671-681页

作者： Jaber Merrikhi Ahangarkolaei mahdi izadi Tohid Nouri Department of Electrical Engineering Sari BranchIslamic Azad UniversitySariIran Department of Electrical Engineering Shahriar BranchIslamic Azad UniversityShahriarIran

The inherent double-line frequency ripple(DFR)of the single-phase quasi-Z-Source inverter(qZSI)strongly affects performance and design of the whole system,which requires hardware improvement methods such as additional semiconductor components or increasing the volume of capacitors and *** a result,hardware solutions increase the price,and the volume and also reduces reliability of the *** this paper,as a non-hardware solution,a sliding mode control(SMC)method is presented to control the voltage of the qZSI *** suppress the DFR,a second-order harmonic is injected into the capacitor reference *** and experimental results show that the introduced controller will have satisfactory results in reducing the DFR without any hardware changes in the qZSI,such as increasing the volume of the capacitor and inductor,adding a semiconductor,or increasing the frequency.A simulation model and experimental prototype are provided to demonstrate the validation of the effectiveness of the proposed controller.

关键词： Double-frequency ripple quasi-Z-source inverter sliding mode control

Initial estimation of hydrate formation temperature of sweet natural gases based on new empirical correlation

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Journal of Natural Gas Chemistry 2012年第5期21卷 508-512页

作者： mohammad mahdi Ghiasi Petroleum University of Technology Ahwaz Faculty of PetroleumPost Box:63431AhwazIran

Production,processing and transportation of natural gases can be significantly affected by clathrate *** the gas analysis is crucial to predict the right conditions for hydrate ***,Katz gas gravity method can be used for initial estimation of hydrate formation temperature （HFT） under the circumstances of indeterminate gas *** far several correlations have been proposed for gas gravity method,in which the most accurate and reliable one has belonged to Bahadori and *** main objective of this study is to present a simple and yet accurate correlation for fast prediction of sweet natural gases HFT based on the fit to Katz gravity *** reviewing the error analysis results,one can discover that the new proposed correlation has the best estimation capability among the widely accepted existing correlations within the investigated range.

关键词： natural gas hydrates hydrate formation temperature gas gravity method empirical correlation

A new robust fuzzy method for unmanned flying vehicle control

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Journal of Central South University 2015年第6期22卷 2166-2182页

作者： Mojtaba Mirzaei mohammad Eghtesad mohammad mahdi Alishahi Department of Mechanical Engineering Shiraz University

A new general robust fuzzy approach was presented to control the position and the attitude of unmanned flying vehicles(UFVs). Control of these vehicles was challenging due to their nonlinear underactuated behaviors. The proposed control system combined great advantages of generalized indirect adaptive sliding mode control(IASMC) and fuzzy control for the UFVs. An on-line adaptive tuning algorithm based on Lyapunov function and Barbalat lemma was designed, thus the stability of the system can be guaranteed. The chattering phenomenon in the sliding mode control was reduced and the steady error was also alleviated. The numerical results, for an underactuated quadcopter and a high speed underwater vehicle as case studies, indicate that the presented adaptive design of fuzzy sliding mode controller performs robustly in the presence of sensor noise and external disturbances. In addition, online unknown parameter estimation of the UFVs, such as ground effect and planing force especially in the cases with the Gaussian sensor noise with zero mean and standard deviation of 0.5 m and 0.1 rad and external disturbances with amplitude of 0.1 m/s2 and frequency of 0.2 Hz, is one of the advantages of this method. These estimated parameters are then used in the controller to improve the trajectory tracking performance.

关键词： adaptive fuzzy sliding-mode control unmanned flying vehicle control underactuated system Lyapunov stability high speed underwater vehicle

Analyzing uncertainties involved in estimating collapse risk with and without considering uncertainty probability distribution parameters

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Earthquake Engineering and Engineering Vibration 2022年第1期21卷 101-116页

作者： mohammad Amin Bayari Naser Shabakhty Esmaeel izadi Zaman Abadi Department of Civil Engineering Najafabad BranchIslamic Azad UniversityNajafabad ***Iran School of Civil Engineering Iran University of Science and TechnologyTehran 16844Iran

In the present study,modified Ibarra,Medina and Krawinkler moment-rotation parameters are used for modeling the uncertainties in concrete moment frame *** of model parameters in a component and between two structural components were considered to analyze these *** the first step,the structural collapse responses were obtained by producing 281 samples for the uncertainties using the Latin hypercube sampling(LHS)method,considering the probability distribution of the uncertainties and performing incremental dynamic *** the second step,281 new samples were produced for the uncertainties by the central composite design(CCD)method without considering the probability distribution of the uncertainties and calculating the structural collapse ***,using the response surface method(RSM)and artificial neural network(ANN)for the two simulation modes,structural collapse responses were *** results indicated that the collapse responses at levels of 0 to 100%obtained from the two simulations have a high correlation coefficient of 98%.This suggests that random variables can be simulated without considering the probability distribution of uncertainties,by performing uncertainty analysis to determine structural collapse responses.

关键词： uncertainty analysis collapse response artificial neural network response surface method

Predicting seismic permanent displacement of soil walls under surcharge based on limit analysis approach

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Earthquake Engineering and Engineering Vibration 2018年第4期17卷 747-759页

作者： mohammad mahdi Aminpour mohammad Maleki Ali Ghanbari Faculty of Engineering Bu-Ali Sina University Faculty of Engineering Kharazmi University

Seismic permanent displacement of the soil walls plays an important role in design of these structures. Due to the increase in growth of urban areas and the limitations in use of flat grounds, many structures are built near slopes and retaining walls. During earthquakes, these structures can apply an additional surcharge on the wall. The intensity and location of the surcharge is of considerable importance on the seismic displacements of the soil wall. In this study, by using the limit analysis and upper bound theorem, seismic permanent displacement of the soil wall under surcharge has been analyzed. Thus, a formulation is presented for calculating the yield acceleration and seismic displacement for different surcharge conditions. The effect of seismic acceleration, surcharge intensity, its location and soil properties is investigated. A parameter called the ＂displacement coefficient＂ is proposed, and is a potential modification for Newmark’s sliding-block method.

关键词： limit analysis surcharge soil wall seismic displacement yield acceleration

Locational marginal price share: a new structural market power index

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Journal of Modern Power Systems and Clean Energy 2019年第6期7卷 1709-1720页

作者： mohammad Ebrahim HAJIABADI mahdi SAMADI Department of Electrical and Computer Engineering Hakim Sabzevari UniversitySabzevarIran

Market power is known as the ability of units and generation companies(GenCos)to change electricity price *** cleared in the definition,locational marginal price(LMP)is the most important key in market power ***,the main objective of the paper is to analyze market power of units and GenCos based on their abilities to change electricity *** the first step,using Karush-Kuhn-Tucker(KKT)conditions of Lagrangian method,LMP is decomposed into four main *** components indicate the share of each unit at the LMP of each *** values are calculated by the proposed analytical method,and cannot be obtained using simulation *** the second step,"unit-based LMP share(LMP_S)"index,which indicates the contribution factor of each unit at LMP of each bus,is proposed as a new structural market power *** index is also used as an effective tool to determine the most profitable coalition between two *** that,the market operator can predict highly potential ***,"GenCosbased LMP_S"index is *** this effective tool,the contribution of each GenCo,which owns multiple units at various buses,at the LMP of each bus is *** proposed market power indices are calculated on the IEEE24-bus test system and compared with some conventional structural market power *** profits of units due to change of unit’s strategies verify the accuracy of the proposed method.

关键词： Lagrange relaxation method Locational marginal price(LMP)share Market power Coalition

Assessment of liquefaction potential based on shear wave velocity:Strain energy approach

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第9期16卷 3733-3745页

作者： mohammad Hassan Baziar mahdi Alibolandi School of Civil Engineering Iran University of Science and TechnologyTehran16846-13114Iran

Liquefaction assessment based on strain energy is significantly superior to conventional stress-based *** main purpose of the present study is to investigate the correlation between shear wave velocity and strain energy capacity of silty *** dissipated energy until liquefaction occurs was calculated by analyzing the results of three series of comprehensive cyclic direct simple shear and triaxial tests on Ottawa F65,Nevada,and Firoozkuh sands with varying silt content by weight and relative ***,the shear wave velocity of each series was obtained using bender element or resonant column ***,for the first time,a liquefaction triggering criterion,relating to effective overburden normalized liquefaction capacity energy(WL=s’c)to effective overburden stresscorrected shear wave velocity(eVs1)has been *** accuracy of the proposed criteria was evaluated using in situ *** results confirm the ability of shear wave velocity as a distinguishing parameter for separating liquefied and non-liquefied soils when it is calculated against liquefaction capacity energy(WL=s’c).However,the proposed WL=s’c-Vs1 curve,similar to previously proposed cyclic resistance ratio(CRR)-Vs1 relationships,should be used conservatively for fields vulnerable to liquefaction-induced lateral spreading.

关键词： Liquefaction Strain energy capacity Shear wave velocity Cyclic triaxial test Cyclic direct simple shear test Resonant column test Bender element test

Improved rate-distortion optimized video coding using non-integer bit estimation and multiple Lambda search

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Frontiers of Computer Science 2016年第1期10卷 157-166页

作者： Sio Kei IM mohammad mahdi GHANDI MPI-QMUL Information Systems Research Centre Macao Polytechnic Institute Macao China Department of Electronic Systems Engineering University of Essex Colchestey CO4 3SQ UK

Many modern video encoders use the Lagrangian rate-distortion optimization （RDO） algorithm for mode deci- sions during the compression procedure. For each encoding stage, this approach involves minimizing a cost, which is a function of rate, distortion and a multiplier called Lambda. This paper proposes to improve the RDO process by applying two modifications. The first modification is to increase the ac- curacy of rate estimation, which is achieved by computing a non-integer number of bits for arithmetic coding of the syntax elements. This leads to a more accurate cost computation and therefore a better mode decision. The second modification is to search and adjust the value of Lambda based on the char- acteristics of each coding stage. For the encoder used, this paper proposes to search multiple values of Lambda for the intra-4x4 mode decision. Moreover, a simple shift in Lambda value is proposed for motion estimation. Each of these modi- fications offers a certain gain in RDO performance, and, when all are combined, an average bit-rate saving of up to 7.0% can be achieved for the H.264/AVC codec while the same concept is applicable to the H.265/HEVC codec as well. The extra added complexity is contained to a certain level, and is also adjustable according to the processing resources available.

关键词： rate distortion optimization Lambda adjust-ment non-integer bit estimation H.264/AVC H265/HEVCvideo coding