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Prediction of boundary shear stress distribution in straight open channels using velocity distribution

Water Science and Engineering 2021年第2期14卷 159-166页

作者： Behzad Malvandi mahmoud f.maghrebi Department of Civil Engineering Ferdowsi University of MashhadMashhad 91775-1111Iran

Conventional methods for measuring local shear stress on the wetted perimeter of open channels are related to the measurement of the very low velocity close to the *** near-zero velocity values with high fluctuations has always been a difficult task for fluid flow near solid *** solve the observation problems,a new model was developed to estimate the distribution of boundary shear stress from the velocity distribution in open channels with different cross-sectional *** estimate the shear stress at a point on the wetted perimeter by the model,the velocity must be measured at a point with a known normal distance to the *** experimental work of some other researchers on channels with various cross-sectional shapes,including rectangular,trapezoidal,partially full circular,and compound shapes,was used to evaluate the performance of the proposed *** exponent coefficients for the model were found using the multivariate Newton method with the minimum of the mean absolute percentage error(MAPE)between the model and experimental data as the objective ***,the calculated shear stress distributions along the wetted perimeter were compared with the experimental *** most important advantage of the proposed model is its inherent *** mean MAPE value for the seven selected cross-sections was 6.9%.The best results were found in the cross-sections with less discontinuity of the wetted perimeter,including the compound,trapezoidal,and partially full circular *** contrast,for the rectangular cross-section with an angle between the bed and walls of 90°,MAPE increased due to the large discontinuities.

关键词： Open channel Boundary shear stress Viscous shear stress Velocity distribution Velocity gradient

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New acoustic system for continuous measurement of river discharge and water temperature

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Water Science and Engineering 2010年第1期3卷 47-55页

作者： Kiyosi KAWANISI Arata KANEKO Shinya NIGO Mohammad SOLTANIASL mahmoud f. maghrebi Graduate School of Engineering Hiroshima University Ministry of Land InfrastructureTransport and Tourism(Kitaku) Civil Engineering Department Ferdowsi University of Mashhad

In many cases, river discharge is indirectly estimated from water level or streamflow velocity near the water surface. However, these methods have limited applicability. In this study, an innovative system, the fluvial acoustic tomography system （fATS）, was used for continuous discharge measurement. Transducers with a central frequency of 30 kHz were installed diagonally across the river. The system＇s significant functions include accurate measurement of the travel time of the transmission signal using a GPS clock and the attainment of a high signal-to-noise ratio as a result of modulation of the signal by the 10th order M-sequence. In addition, fATS is small and lightweight, and its power consumption is low. Operating in unsteady streamflow, fATS successfully measured the cross-sectional average velocity. The agreement between fATS and acoustic Doppler current profilers （ADCPs） on water discharge was satisfactory. Moreover, the temporal variation of the cross-sectional average temperature deduced from the sound speed of fATS was similar to that measured by a temperature sensor near the bank.

关键词： streamflow fluvial acoustic tomography cross-sectional average velocity unsteadyflow water temperature

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CfD modeling of reaction and mass transfer through a single pellet: Catalytic oxidative coupling of methane

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Journal of Natural Gas Chemistry 2011年第4期20卷 356-363页

作者： Siavash Seyednejadian Nakisa Yaghobi Ramin maghrebi Leila Vafajoo faculty of Chemical Engineering Azad University Tehran South Branch Iran Polymer and Petrochemical Institute

In this study a mathematical model of a small scale single pellet for the oxidative coupling of methane（OCM）over titanite pervoskite is *** method is based on a computational fluid dynamics（CfD）code which known as fluent may be adopted to model the reactions that take place inside the porous catalyst *** steady state single pellet model is coupled with a kinetic model and the intra-pellet concentration profiles of species are *** to achieving this goal,a nonlinear reaction network consisting of nine catalytic reactions and one gas phase reaction as an external program is successfully implemented to CfD-code as a reaction term in solving the *** study is based on the experimental design which is conducted in a differential reactor with a Sn/BaTiO3 catalyst（7-8 mesh） at atmospheric pressure,GHSV of 12000 h-1,ratio of methane to oxygen of 2,and three different temperatures of 1023,1048 and 1073 *** modeling results such as selectivity and conversion at the pellet exit are in good agreement with the experimental ***,it is suggested that to achieve high yield in OCM process the modeling of the single pellet should be considered as the heart of catalytic fixed bed reactor.

关键词： catalyst pellet oxidative coupling of methane modeling CfD catalytic reactions ethane

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Leakage Detection in Water Distribution Network Based on a New Heuristic Genetic Algorithm Model

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Journal of Water Resource and Protection 2013年第3期5卷 294-303页

作者： Ali Nasirian mahmoud f. maghrebi Siavash Yazdani Civil Engineering College Ferdowsi University of Mashhad Mashhad Iran Hydraulic Engineering Part Mahan Co. Mashhad Iran

The leakage control is an important task, because it is associated with some problems such as economic loss, safety concerns, and environmental damages. The pervious methods which have already been devised for leakage detection are not only expensive and time consuming, but also have a low efficient. As a result, the global leakage detection methods such as leak detection based on simulation and calibration of the network have been considered recently. In this research, leak detection based on calibration in two hypothetical and a laboratorial networks is considered. Additionally a novel optimization method called step-by-step elimination method (SSEM) combining with a genetic algorithm (GA) is introduced to calibration and leakage detection in networks. This method step-by-step detects and eliminates the nodes that provide no contribution in leakage among uncertain parameters of calibration of a network. The proposed method initiates with an ordinary calibration for a studied network, follow by elimination of suspicious nodes among adjusted parameters, then, the network is re-calibrated. finally the process is repeated until the numbers of unknown demands are equal to the desired numbers or the exact leakage locations and values are determined. These investigations illustrate the capability of this method for detecting the locations and sizes of leakages.

关键词： Calibration SSEM Water Distribution Leak Detection Genetic Algorithm

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CfD modeling of catalyst pellet for oxidative coupling of methane:Heat transfer and reaction

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Particuology 2013年第5期11卷 506-513页

作者： Ramin maghrebi Nakisa Yaghobi Siavash Seyednejadian Mitra H.Tabatabaei Department of Chemical Engineering South-Tehran Branch.Islamic Azad UniversityP.O.Box 11365/4435.TehranIran Iran Polymer and Petrochemical Institute P.O.Box 14965/115Tehran.Iran

This study deals with the phenomena occuring at single-pellet catalyst scale for the oxidative coupling of methane where heat transfer plays an important role. Computational fluid dynamics （CfD） is used for obtaining detailed rate and temperature profiles through the porous catalytic pellet where reaction and diffusion compete, lntra-particle temperature and concentration gradients were taken into account by solving heat transfer coupled with continuity equations in the catalyst pellet. In heat transfer, the energy term due to highly exothermic reaction was considered. Two external programs were successfully implemented into the CfD-code as kinetic and heat of reaction terms. Simulation results showed that reaction was favored at the beginning for the pellet, followed by diffusion predomination. The results of CfD simulation indicate that temperature variation within the catalyst pellet is 〈2 K due to exothermic oxidation. The results showed further that exothermic oxidation reactions occurred prior to endothermic coupling reaction in the pellet.

关键词： Catalyst pelletOxidative coupling of methaneModelingCfDKinetics

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Improved Performance for a Heterogeneous Satellite-Cooperative Network with Best Relay Node Selection

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China Communications 2019年第5期16卷 93-105页

作者： Pedram hajipour Ali Shahzadi Saeed Ghazi-maghrebi Department of Communication College of Electrical EngineeringYadegar-e-Imam Khomeini (RAH) Shahr-e-rey BranchIslamic Azad UniversityTehranIran. Department of Electrical and Computer Engineering Semnan UniversitySemnanIran. Department of Communication College of Electrical EngineeringYadegar-e-Imam Khomeini (RAH) Shahr-e-rey BranchIslamic Azad UniversityTehranIran

Nowadays, hybrid satellite-terrestrial cooperative network has emerged as a key technology to provide a great variety of communication services. The deployment of this network will improve coverage and capacity in remote areas. Despite the benefits of this network, by increasing the number of users, communication efficiency based on interference management is a major challenge in satellite-based system. Also, the direct links between satellite system and the terrestrial equipment do not always have desirable channel condition. In order to avoid serious throughput degradation, choosing a cooperative relay node is very important. In this paper, Stackelberg game is exploited for interference management that is raised by satellites in down link over terrestrial equipment. Then, for interference management between ground station and relay node with other mobile users, CVX is used to allocate optimum power. Also, the best relay node in this structure is selected based on the harmonic mean function. Thus, the performance of the heterogeneous satellite-cooperative network is investigated based on three benchmarks, namely, successful transmission, energy consumption and outage probability. finally, the simulation results showed the effect of proposed system model on the performance of next generation satellite networks.

关键词： heterogeneous Stackelberg game convex optimization relay node cooperative communication

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A STUDY Of THE CONCEPT Of DYNAMIC EQUIPMENT IN THE EARTHMOVING PROCESS BY A CONSIDERATION Of TIME,COST AND EMISSIONS

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Journal of Green Building 2013年第3期8卷 156-165页

作者： Mojtaba maghrebi Meysam Ebrahiminejad Eghbal Shakeri School of Civil and Environmental Engineering University of New South Wales(UNSW)Sydney2052Australia Department of Civil Engineering Ferdowsi University of MashhadMashhadKhorasan RazaviIran Department of Civil and Environmental Engineering Amirkabir University of Technology(Tehran Polytechnic)TehranIran

The earthmoving process is usually handled by a combination of multi-functional excavators and delivery *** to the principles of excavation,a specific machine is selected to dig the ***,due to the difficulties in the process,the digging process is split between different machines with different *** paper aims to introduce the concept of dynamic equipment for allocating different tasks in an operation to a *** concept is discussed and modelled via a discrete-event simulation method and is tested in a real earthmoving operation from three different perspectives:time,cost and *** results from the case study show that the use of dynamic equipment will lead to a decrease in cost and emissions and an increase in productivity.

关键词： CO_(2) Earthmoving Simulation Discrete-Event Productivity

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Lattice Boltzmann finite Volume formulation with Improved Stability

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Communications in Computational Physics 2012年第6期12卷 42-64页

作者： A.Zarghami M.J.maghrebi J.Ghasemi S.Ubertini Department of Mechanical Engineering Shahrood University of TechnologyShahroodIran Department of Mechanical Engineering Ferdowsi University of MashhadMashhadIran faculty of Engineering Zanjan UniversityZanjanIran Department of Technologies University of Naples"Parthenope"NaplesItaly

The most severe limitation of the standard Lattice Boltzmann Method is the use of uniform Cartesian grids especiallywhen there is a need for high resolutions near the body or *** the recent advances in lattice Boltzmann research to handle complex geometries,a particularly remarkable option is represented by changing the solution procedure from the original"stream and collide"to a finite volume ***,most of the presented schemes have stability *** paper presents a stable and accurate finite-volume lattice Boltzmann formulation based on a cell-centred *** enhance stability,upwind second order pressure biasing factors are used as flux correctors on a D2Q9 *** resulting model has been tested against a uniform flow past a cylinder and typical free shear flow problems at low and moderate Reynolds numbers:boundary layer,mixing layer and plane jet *** numerical results show a very good accuracy and agreement with the exact solution of the Navier-Stokes equation and previous numerical results and/or experimental *** in self-similar coordinates are also investigated and show that the timeaveraged statistics for velocity and vorticity express self-similarity at low Reynolds ***,the scheme is applied to simulate the flow around circular cylinder and the Reynolds number range is chosen in such a way that the flow is time *** agreement of the numerical results with previous results is satisfactory.

关键词： Lattice Boltzmann equation finite volume stability cell-centered scheme free shear flows

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Reconstruction of an Expert＇s Decision Making Expertise in Concrete Dispatching by Machine Learning

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Journal of Civil Engineering and Architecture 2013年第12期7卷 1540-1547页

作者： Mojtaba maghrebi Claude Sammut Travis Waller School of Civil and Environmental Engineering The University of New South Wales (UNSW) Kensington NSW 2052 Australia School of Computer Science Engineering The University of New South Wales (UNSW) Kensington NSW 2052 Australia National Information and Communications Technology Australia (NICTA) Sydney 20000 Australia

finding the optimum solution for dispatching in concrete delivery is computationally intractable because it is a NP-hard （non-deterministic polynomial-time hard） problem. Heuristic methods are required to obtain satisfactory solutions. Inefficiencies in mathematical modeling still make concrete dispatching difficult to solve. In reality, complex dispatching systems are mostly handled by human experts, who are able to manage the assigned tasks well. However, the high dependency on human expertise is a considerable challenge for RMC （ready mixed concrete） companies. In this paper, a logical reconstruction of an expert＇s decision making is achieved by two machine learning techniques： decision tree and rule induction. This paper focuses on the expert dispatcher＇s prioritization of customer orders. The proposed method has been tested on a simulation model consisting of a batch plant and three customers per day. The scenarios generated by the simulation model were given to a dispatch manager who was asked to prioritize the customers in each day. The scenarios and the decisions were then input to the machine learning programs, which created generalizations of the expert＇s decisions. Both decision trees and rules approach 80% accuracy in reproducing the human performance.

关键词： Machine learning logic reconstruction experts' behavior

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