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An investigation on prevalent strategies for XFEM-based numerical modeling of crack growth in porous media

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Frontiers of Structural and Civil Engineering 2021年第4期15卷 914-936页

作者： Mohammad REZANEZhAD seyed Ahmad LAJEVARDI Sadegh KARIMPOULI Mining Engineering Group Faculty of EngineeringUniversity of ZanjanZanjan45371-38791Iran Materials Engineering Group Faculty of EngineeringUniversity of ZanjanZanjan45371-38791Iran

Crack growth modeling has always been one of the major challenges in fracture *** all numerical methods,the extended finite element method(XFEM)has recently attracted much attention due to its ability to estimate the discontinuous deformation ***,XFEM modeling does not directly lead to reliable results,and choosing a strategy of implementation is inevitable,especially in porous *** this study,two prevalent XFEM strategies are evaluated:a)applying reduced Young’s modulus to pores and b)using different partitions to the model and enriching each part *** mention the advantages and limitations of each strategy via both analytical and experimental ***,the crack growth is modeled in a natural porous media(Fontainebleau sandstone).Our investigations proved that although both strategies can identically predict the stress distribution in the sample,the first strategy simulates only the initial crack propagation,while the second strategy could model multiple cracks *** strategies are reliable and highly accurate in calculating the stress intensity factor,but the second strategy can compute a more reliable reaction *** tests showed that the second strategy is a more accurate strategy in predicting the preferred crack growth path and determining the maximum strength of the sample.

关键词： numerical modeling extended finite element method porous media crack growth stress intensity factor

Passive Behavior of Ultra-Fine-Grained 1050 Aluminum Alloy Produced by Accumulative Roll Bonding in a Borate Buffer Solution

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Acta Metallurgica Sinica(English Letters) 2015年第10期28卷 1222-1229页

作者： Arash Fattah-alhosseini seyed Omid Gashti Department of Materials Engineering Bu-Ali Sina University

In this study, the effect of the ARB process on the passive behavior of ultra-fine-grained 1050 aluminum alloy in a borate buffer solution（p h 6.0） has been investigated. The result of the microhardness tests revealed that the microhardness values increase with an increasing number of ARB cycles. The potentiodynamic polarization plots revealed that the higher number of cycles for the specimens proceeds with the ARB process rather than annealing yield to lower corrosion and passive current densities and more noble corrosion potential values. Moreover, electrochemical impedance spectroscopy measurements showed that increasing the number of ARB cycles offers better conditions for forming the passive films.

关键词： Aluminum Polarization Passivation Electrochemical impedance spectroscopy (EIS)

Fabrication and Characterization of Willemite Scaffolds Using Corn Stalk as a Novel Bio Template for Bone Tissue Engineering Applications

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Journal of Bionic Engineering 2023年第1期20卷 16-29页

作者： Zahra Yahay seyed Mehdi Mirhadi Fariborz Tavangarian Department of Cellular Biotechnology Cell Science Research CenterRoyan Institute for BiotechnologyACECRIsfahan81593-58686Iran Department of Materials Engineering Shahreza BranchIslamic Azad UniversityShahrezaIsfahan86145-311Iran Mechanical Engineering Program School of ScienceEngineering and TechnologyPennsylvania State UniversityHarrisburgMiddletownPA17057USA

In this paper,we used Corn Stalk(CS)as a renewable and economical bio template to fabricate willemite scaffolds with the potential application in skull bone *** was used as a sacrificial template to synthesize the *** scaffolds with the chemical formula of Zn2SiO4 and pore size in the range of 3 to 10µm could be successfully synthesized by soaking CS in the willemite solution for 24 h and sintering at 950°C for 5 *** porosity of the samples was controlled by the soaking time(between 12 and 48 h)in the willemite solution from 5 to 35%,*** properties of these scaffolds showed a good approximation with cranial bone *** addition,cytotoxicity assays(MTT)were performed on human Bone Marrow Stromal cells(hBMSc)and A172 human glioblastoma cell lines by direct and indirect culture methods to estimate their toxicity for bone and nerve cells,*** Phosphatase(ALP)activity and DAPI/Phalloidin cell staining were also performed to investigate the efficiency of the scaffolds for bone tissue engineering *** results showed that the scaffolds had good biocompatibility with both hBMSC and A172 cells,noticeable improvement on ALP activity,and great apatite formation ability in Simulated Body Fluid(SBF).All the evidence ascertained that willemite scaffolds made by corn stalks could be a useful candidate for bone tissue engineering applications.

关键词： Corn stalk Bio template Bioactive ceramics-Scaffolds Bone tissue engineering

A shield against a monster:hepatitis C in hemodialysis patients

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World Journal of Gastroenterology 2009年第6期15卷 641-646页

作者： seyed-Moayed Alavian Baqiyatallah Research Center for Gastroenterology and Liver Disease Baqiyatallah Research Center for Gastroenterology and Liver DiseaseTehran ***Iran

hepatitis C virus(hCV)infection is highly prevalent among patients on hemodialysis(hD).The prevalence of hCV infection in hD patients varies markedly from country to *** factors are especially related to these high prevalence rates,such as blood transfusions and length of dialysis time. Nosocomial routes of transmission including the use of contaminated equipment and patient-to-patient exposure is considered more *** prophylactic measures have been suggested to avoid infection by hCV in the hD environment.

关键词： Dialysis Epidemiology hepatitis C virus Incidence Isolation Nosocomial transmission Prevalence Prevention Universal precaution

Droplets diameter distribution using maximum entropy formulation combined with a new energy-based sub-model

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Chinese Journal of Chemical Engineering 2016年第11期24卷 1625-1630页

作者： seyed Mostafa h.sseinalipour hadiseh Karimaei Ehsan Movahednejad Energy and Environmental Lab Dpt Mech. Eng. Iran University of Science and Technology 16846-13114 Narmak Tehran lran University of California Berkeley USA

The maximum entropy principle(MEP) is one of the first methods which have been used to predict droplet size and velocity distributions of liquid sprays. This method needs a mean droplets diameter as an input to predict the droplet size distribution. This paper presents a new sub-model based on the deterministic aspects of liquid atomization process independent of the experimental data to provide the mean droplets diameter for using in the maximum entropy formulation(MEF). For this purpose, a theoretical model based on the approach of energy conservation law entitled energy-based model(EBM) is presented. Based on this approach, atomization occurs due to the kinetic energy loss. Prediction of the combined model(MEF/EBM) is in good agreement with the available experimental data. The energy-based model can be used as a fast and reliable enough model to obtain a good estimation of the mean droplets diameter of a spray and the combined model(MEF/EBM) can be used to well predict the droplet size distribution at the primary breakup.

关键词： Mean droplets diameter Energy conservation Maximum entropy formulation (MEF) Size distribution Statistical thermodynamics Mathematical modeling

Design feasibility of gamma camera without collimator based on specific arrangement of the detectors

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Nuclear Science and Techniques 2016年第4期27卷 120-126页

作者： h.ssein Akbari-Lalimi seyed Ali Shafiei Geriatric Care Research Center Rafsanjan University of Medical Sciences Department of Medical Physics Mashhad University of Medical Sciences Department of Physiology and Pharmacology School of Medicine Qom University of Medical Sciences

In gamma camera and single-photon emission computerized tomography, the collimator removes most photons. here, a gamma camera without collimator utilizes a specific arrangement of detectors. Instead of bending beams(like a lens) or directing beams(by parallel hole collimator), changes are created in detectors' field of view(FOV), so that each detector's FOV looks different from others. Simulation proved this theory, with 98 detectors(2 cm 9 1.41 cm) arranged in a zigzag manner for Monte Carlo simulation. A radioactive source with energy of140 ke V was situated on the detectors' faces. Sixty projections, each 3(0 –179) apart, were simulated by Monte Carlo N-Particle(MCNP) 4C code, rotating detectors around a radioactive point. The band containing the radioactive source is clearly visible in each *** obtained after simulation in different projections were reconstructed, and point source location emerged correctly. Simulation of gamma camera with zigzag arrangement of detectors and MCNP-4C code demonstrated that one could string the space and determine radioactive source by image reconstruction without using collimators, solely through these special detectors' distribution.

关键词：探测器准直器 γ相机蒙特卡洛模拟计算机断层扫描单光子发射设计布置

A novel control strategy based on a look-up table for optimal operation of MTDC systems in post-contingency conditions

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Protection and Control of Modern Power Systems 2022年第1期7卷 40-50页

作者： seyed Mohsen Alavi Reza Ghazi Department of Electrical Engineering Ferdowsi University of MashhadMashhadIran

Multi terminal VSC-hVDC systems are a promising solution to the problem of connecting offshore wind farms to AC *** power sharing and appropriate control of DC-link voltages are essential and must be maintained dur-ing the operation of VSC-MTDC systems,particularly in post-contingency *** traditional droop control methods cannot satisfy these requirements,and accordingly,this paper proposes a novel centralized control strategy based on a look-up table to ensure optimal power sharing and minimum DC voltage deviation immediately during post-contingency conditions by considering converter *** also reduces destructive effects(e.g.,frequency devia-tion)on onshore AC grids and guarantees the stable operation of the entire MTDC *** proposed look-up table is an array of data that relates operating conditions to optimal droop coefficients and is determined according to N-1 contingency analysis and a linearized system *** constraints and contingencies such as wind power changes,converter outage,and DC line disconnection are considered in its formation *** performed on a 4-terminal VSC-MTDC system in the MATLAB-Simulink environment validate the effectiveness and superiority of the proposed control strategy.

关键词： Optimal power sharing DC voltage deviation Adaptive droop control Multi-terminal hVDC(MTDC) Voltage source converter(VSC)

Automatic recognition of sonar targets using feature selection in micro-Doppler signature

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Defence Technology（防务技术） 2023年第2期20卷 58-71页

作者： Abbas Saffari seyed-hamid Zahiri Mohammad Khishe Department of Electrical Engineering University of BirjandBirjandIran Department of Electrical Engineering Imam Khomeini Marine Science UniversityNowshahrIran

Currently,the use of intelligent systems for the automatic recognition of targets in the fields of defence and military has increased *** primary advantage of these systems is that they do not need human participation in target recognition *** paper uses the particle swarm optimization(PSO)algorithm to select the optimal features in the micro-Doppler signature of sonar *** microDoppler effect is referred to amplitude/phase modulation on the received signal by rotating parts of a target such as *** different targets'geometric and physical properties are not the same,their micro-Doppler signature is *** Inconsistency can be considered a practical issue(especially in the frequency domain)for sonar target *** using 128-point fast Fourier transform(FFT)for the feature extraction step,not all extracted features contain helpful *** a result,PSO selects the most optimum and valuable *** evaluate the micro-Doppler signature of sonar targets and the effect of feature selection on sonar target recognition,the simplest and most popular machine learning algorithm,k-nearest neighbor(k-NN),is used,which is called k-PSO in this paper because of the use of PSO for feature *** parameters measured are the correct recognition rate,reliability rate,and processing *** simulation results show that k-PSO achieved a 100%correct recognition rate and reliability rate at 19.35 s when using simulated data at a 15 dB signal-tonoise ratio(SNR)angle of 40°.Also,for the experimental dataset obtained from the cavitation tunnel,the correct recognition rate is 98.26%,and the reliability rate is 99.69%at ***,the k-PSO has an encouraging performance in automatically recognizing sonar targets when using experimental datasets and for real-world use.

关键词： Micro-Doppler signature Automatic recognition Feature selection k-NN PSO

Drilling cost optimization in a hydrocarbon field by combination of comparative and mathematical methods

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Petroleum Science 2009年第4期6卷 451-463页

作者： A.Bahari A.Baradaran seyed Iranian Central Oil Fields Company(ICOFC) Esfandiari St.Valiasr Ave. Behinkav Zharfa Consulting Engineers No.45Block 18Phase 2EkbatanTehranIran

In drilling operation, a large saving in time and money would be achieved by reducing the drilling time, since some of the costs are time-dependent. Drilling time could be minimized by raising the penetration rate. In the comparative optimization method, by using the records of the first drilled wells and comparing the criteria like penetration rate, cost per foot and specific energy, the drilling parameters of the next wells being drilled can be optimized in each depth interval. In the mathematical optimization technique, some numerical equations to model the penetration rate, bit wear rate and hydraulics would be used to minimize the drilling cost and time as much as possible and improve the results of the primary comparative optimization. In this research, as a case study the Iranian Khangiran gas field has been evaluated to optimize the drilling costs. A combination of the mentioned optimization techniques resulted in an optimal well which reduced the drilling time and cost considerably in comparison with the wells already drilled.

关键词： Optimization cost per foot penetration rate drilling performance