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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

Identification of Pitch Dynamics of An Autonomous Underwater Vehicle Using Sensor Fusion

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China Ocean Engineering 2019年第5期33卷 563-572页

作者： Seid Farhad Abtahi mohammad Mehdi alishahi Ehsan Azadi Yazdi Department of Mechanical Engineering Shiraz University

This paper presents a method for identification of the hydrodynamic coefficients of the dive plane of an autonomous underwater vehicle. The proposed identification method uses the governing equations of motion to estimate the coefficients of the linear damping, added mass and inertia, cross flow drag and control. Parts of data required by the proposed identification method are not measured by the onboard instruments. Hence, an optimal fusion algorithm is devised which estimates the required data accurately with a high sampling rate. To excite the dive plane dynamics and obtain the required measurements, diving maneuvers should be performed. Hence, a reliable controller with satisfactory performance and stability is needed. A cascaded controller is designed based on the coefficients obtained using a semi-empirical method and its robustness to the uncertainties is verified by the μ-analysis method. The performance and accuracy of the identification and fusion algorithms are investigated through 6-DOF numerical simulations of a realistic autonomous underwater vehicle.

关键词： autonomous underwater vehicles hydrodynamic coefficients system identification robust control sensor fusion parameter estimation numerical methods

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

Reliable control of discrete-time linear systems with actuator failure

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Journal of Control and Decision 2020年第4期7卷 345-358页

作者： mohammad mahdi Share Pasand Department of Electrical and Electronics Faculty of ElectricalMechanical and Civil EngineeringStandard Research InstitutePO Box 31585-163AlborzIran

A sufficient condition is given for robust stability of a discrete linear system in which an arbitrary portion of input channel is permanently attenuated or disconnected due to actuator *** partial disconnection/attenuation of the control input,is modelled as uncertainty and dealt with via a robust control *** proposed method enables one to design a controller in such a way that the closed loop system remains stable when any combination of input signals is disconnected if the open loop system is stable and fulfils some additional *** is shown that the linear quadratic regulator can guarantee reliable closed loop with some specific choices for weighting *** result is extended to unstable systems by assuming additional constraints on the failed *** to previously established results,the proposed conditions are easier to verify and applicable to a wider class of *** example is also included.

关键词： Reliable control robust control linear matrix inequality actuator failure

Risk factors for congenital nasolacrimal duct obstruction in children under two years of age

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国际眼科杂志 2025年第1期25卷 17-23页

作者： Rozhin Kasiri Gholamreza Khataminia Ali Kasiri mohammad Sadegh Mirdehghan mohammad Armin Kasiri Infectious Ophthalmologic Research Center Ahvaz Jundishapur University of Medical SciencesAhvaz ***Iran Islamic Azad University Tehran Medical Sciences Tehran ***Iran

·AIM:To identify various risk factors that may play a significant role in the development of congenital nasolacrimal duct obstruction(CNLDO).·METHODS:This observational case-control study included a case group of 122 children less than two years of age with CNLDO who underwent probing and irrigation treatment at the ophthalmology department of Imam Khomeini Hospital in Ahvaz,Iran,from June 2022 to June2024.A control group of 122 age-matched children without CNLDO was also included for *** was collected from the children's medical records.·RESULTS:The study found a significant correlation between the occurrence of CNLDO and several maternal factors,such as preeclampsia,the use of levothyroxine,hypothyroidism,having more than three pregnancies(gravidity>3),natural pregnancy,and gestational diabetes ***,in children,factors,such as oxygen therapy,anemia,reflux,jaundice,and a family history of CNLDO in first-degree relatives were associated with CNLDO,and maternal preeclampsia and hypothyroidism were found to significantly increase the risk of developing CNLDO in children.·CONCLUSION:Given that CNLDO affects both premature and full-term children,the present findings may potentially facilitate the early identification of children and infants at risk of nasolacrimal duct obstruction,thereby preventing the onset of chronic dacryocystitis.

关键词： risk factors congenital nasolacrimal duct obstruction children

Study of acoustic bubble cluster dynamics using a lattice Boltzmann model

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Chinese Physics B 2015年第2期24卷 263-270页

作者： mahdi Daemi mohammad Taeibi-Rahni Hamidreza Massah Aerospace Engineering Department Sharif University of Technology Physics Department Ferdowsi University

The search for the development of a reliable mathematical model for understanding bubble dynamics behavior is an ongoing endeavor.A long list of complex phenomena underlies the physics of this *** the past decades,the lattice Boltzmann method has emerged as a promising tool to address such *** this regard,we have applied a 121-velocity multiphase lattice Boltzmann model to an asymmetric cluster of bubbles in an acoustic field.A problem as a benchmark is studied to check the consistency and applicability of the *** problem of interest is to study the deformation and coalescence phenomena in bubble cluster dynamics,as well as the screening effect on an acoustic multibubble *** has been observed that the LB model is able to simulate the combination of the three aforementioned phenomena for a bubble cluster as a whole and for every individual bubble in the cluster.

关键词： multiphase lattice Boltzmann model acoustic field multi-bubble bubble cluster dynamics cavitation