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A coupled CFD simulation approach for investigating the pyrolysis process in industrial naphtha thermal cracking furnaces

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Chinese Journal of Chemical Engineering 2022年第4期35卷 528-542页

作者： mohsen Rezaeimanesh Ali Asghar Ghoreyshi S.m.Peyghambarzadeh seyed Hassan Hashemabadi Chemical Engineering Department Babol Noshirvani University of TechnologyShariati Ave.47148-71167 BabolIran Department of Chemical Engineering Mahshahr BranchIslamic Azad UniversityMahshahrIran Computational Fluid Dynamics(CFD)Research Laboratory School of ChemicalPetroleum and Gas EngineeringIran University of Science and Technology(IUST)TehranIran

In the steam thermal cracking of naphtha,the hydrocarbon stream flows inside tubular reactors and is exposed to flames of a series of burners in the *** this paper,a full three-dimensional computational fluid dynamics(CFD)model was developed to investigate the process variables in the firebox and reactor coil of an industrial naphtha *** comprehensive CFD model consists of a standard k-εturbulence model accompanied by a molecular kinetic reaction for cracking,detailed combustion model,and radiative *** order to improve the steam cracking performance,the model is solved using a proposed iterative *** respect to temperature,product yield and specially propylene-toethylene ratio(P/E),the simulation results agreed well with industrial data obtained from a mega olefin plant of a petrochemical *** deviation of P/E results from industrial data was less than 2%.The obtained velocity,temperature,and concentration profiles were used to investigate the residence time,coking rate,coke concentration,and some other *** coke concentration at coil exit was1.9×10^(-3)%(mass)and the residence time is calculated to be 0.29 *** results can be used as a scientific guide for process engineers.

关键词： Naphtha thermal cracking CFD modeling Systems engineering Residence time Product yield

Woody Species Diversity and Forest Structure from Lowland to montane Forest in Hyrcanian Forest Ecoregion

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Journal of mountain Science 2013年第4期10卷 609-620页

作者： seyed.mohammad JAFARI Shahin ZARRE seyed Kazem ALAVIPANAH School of Biology and Center of Excellence in Phylogeny of Living Organisms College of Science University of TehranP.O. Box 14155-6455 Tehran Iran School of Biology and Center of Excellence in Phylogeny of Living Organisms College of Science University of TehranTehran Iran Department of Cartography Faculty of Geography University of TehranTehran Iran

Alborz mountains host Caspian Hyrcanian forest ecoregion along the northern slopes and forest steppe ecoregion in highlands. Hyrcanian forest covers the southeastern part of Caucasus biodiversity hotspot and is of great biogeographic importance. Altitudinal pattern and correlation between woody species biodiversity （DIV）, forest structure （（stem density （DEN）, mean basal area （mBA） and mean height class （mHC）） and disturbance （DIS） were explored along 2,4oo m altitudinal gradient in Hyrcanian relict forest, Central Alborz mountains. Vegetation changes from lowland forest （LoF） to mid- altitude forest （miF） and montane forest （moF） in this area. The altitudinal gradient was divided into twelve 200 m elevational belts. Point centered quarter method （PCQm） with 96 sampling points and 83 vegetation samples by plot method （Pm） were used to record field data. Shannon-Wiener index and Pearson coefficient were used for diversity and correlation analysis. The results showed that DEN decreased linearly, mBA and mHC showed relatively hump shaped and DIS showed a reverse hump shaped pattern of change along altitudinal gradient. Woody species diversity decreased non-steadily from LoF to moF. Transitional vegetations of Carpinus-Fagus and Fagus-Quercus represented higher diversity of woody taxa compared to adjacent homogenous communities. Significant correlation was observed between altitude and all parameters： DEN with mBA, DIS and DIV; mBA with DIS; mHC with DIS along with DIV; and DIS with DIV at the study area scale. Surprisingly,correlation between studied parameters differed within each vegetation type. Altitude probably acts as a proxy for human and environmental driving forces in this area. Stability of warm and wet condition, season length, soil depth along with forest accessibility probably influences the altitudinal pattern of the studied parameters. Disturbance affects forest structure and consequently diversity; especially in lowlands. The obtained results recommend

关键词： Alborz mountains Biodiversity Forestmensuration Hyrcanian forest Disturbance

Electrodeposition of nanostructured Ti/(Ru+Ti+Ce)O_2 coatings

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Rare metals 2018年第1期37卷 13-20页

作者： seyed.mostafa Peyghambari mardali Yousefpour Faculty of materials and metallurgical Engineering Semnan University

A nanostructured ternary coating of Ti/（Ru ＋ Ti ＋ Ce）O2 was prepared by the conventional electrodeposition on the titanium substrate as the cathode with different numbers of coating layers. The main objective of this work was to study nanostructured coatings of ceramic materials. For this purpose, the amount of precursor materials in the electrolyte was a variable parameter. Furthermore, the salt of TiCl4/RuCl3·xH2 O/Ce（NO3）3·6 H2 O with different amounts, hydrogen peroxide, methanol, and distilled water were used as an aqueousunaqueous bath. In addition, the coated samples were put to heat at 300, 450, 650, and 850℃ in an electric furnace for1 h. The crystalline phase of the coating was characterized by X-ray diffraction（XRD）. The chemical composition and microstructure of the coating were studied using energydispersive spectroscopy（EDS） and scanning electron microscopy analysis（SEm）. moreover, the electrochemical measurement of Ti/（Ru ＋ Ti ＋ Ce）O2 coatings was carried out. Results show that with the increase in the number of coating layers, the quality of morphology is ***, the best quality of coatings is obtained at six layers on the titanium substrate with electrolyte including TiO2/RuO2/CeO2 with the molar ratio of 70：5：25 after heat treatment at 450 ℃ for 1 h. Besides,with the increase in Ce02 content from 5 wt% to 25 wt% and the number of coating layers, higher thickness of about（20.0±0.1） μm and minimum over potential for chlorine evolution were obtained.

关键词： Oxides Coating Heat treatment Interface Thin films

Simulation of quantum-well slipping effect on optical bandwidth in transistor laser

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Chinese Optics Letters 2009年第5期7卷 435-436页

作者： Hassan Kaatuzian seyed Iman Taghavi Photonics Research Laboratory Electrical Engineering DepartmentAmirkabir University of Technology

An optical bandwidth analysis of a quantum-well （16 nm） transistor laser with 150-μm cavity length using a charge control model is reported in order to modify the quantum-well location through the base region. At constant bias current, the simulation shows significant enhancement in optical bandwidth due to moving the quantum well in the direction of collector-base junction. No remarkable resonance peak, limiting factor in laser diodes, is observed during this modification in transistor laser structure. The method can be utilized for transistor laser structure design.

关键词： well Simulation of quantum-well slipping effect on optical bandwidth in transistor laser

Characteristics of a multi-component mgO-based bioceramic coating synthesized in-situ by plasma electrolytic oxidation

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Journal of magnesium and Alloys 2021年第5期9卷 1611-1625页

作者： Nasrinsadat Azarian seyed.mohammad mousavi Khoei Department of mining and metallurgical Engineering Amirkabir University of Technology(Tehran Polytechnic)P.O.Box 15875-4413TehranIran

Plasma electrolytic oxidation(PEO)has held great potential for the advancement of biodegradable implants,as it helps in developing porous bioceramic coatings on the surface of magnesium *** this research work,mgO-based bioceramic coatings containing the Si,P,Ca,Na,and F elements have been successfully fabricated on an AZ31 magnesium alloy plate utilizing the PEO *** characteristic current-voltage behavior of the samples during the process was surveyed in an electrolyte containing Ca(H_(2)PO_(4))_(2),Na_(2)SiO_(3)·9H_(2)O,Na_(3)PO_(4)·12H_(2)O,NaF,and KOH with a pH of 12.5 and electrical conductivity of 20 mS/cm^(-1).The results revealed that applying a voltage of 350-400 V(that is 50-100 V higher than the breakdown limit)could greatly facilitate the synthesis of a PEO ceramic coating with fewer defects and more uniform *** resulting coating was a compositionally graded bioceramic layer with a thickness in the range of 3.5±0.4 to 6.0±0.7µm,comprising the above-mentioned elements as promising bioactive *** synthesized ceramic features were investigated in terms of the elemental distribution of components through the thickness,which indicated a gradual rise in the Si and P contents and,conversely,a decline in the F content towards the outer *** growth mechanism of the PEO coating has been discussed accordingly.

关键词： Az31 magnesium alloy Plasma electrolytic oxidation Bioceramic Coating mgO-based ceramic

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

AFAR:adaptive fuzzy ant-based routing for communication networks

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第12期9卷 1666-1675页

作者： seyed Javad mIRABEDINI mohammad TESHNEHLAB m.H.SHENASA Ali mOVAGHAR Amir masoud RAHmANI Engineering Department Science and Research BranchIslamic Azad UniversityTehranIran Control Department K.N.Toosi Technology UniversityTehranIran Computer Department Sharif UniversitTehranIran

We propose a novel approach called adaptive fuzzy ant-based routing (AFAR), where a group of intelligent agents (or ants) builds paths between a pair of nodes, exploring the network concurrently and exchanging obtained information to up-date the routing tables. Routing decisions can be made by the fuzzy logic technique based on local information about the current network state and the knowledge constructed by a previous set of behaviors of other agents. The fuzzy logic technique allows multiple constraints such as path delay and path utilization to be considered in a simple and intuitive way. Simulation tests show that AFAR outperforms OSPF, AntNet and ASR, three of the currently most important state-of-the-art algorithms, in terms of end-to-end delay, packet delivery, and packet drop ratio. AFAR is a promising alternative for routing of data in next generation networks.

关键词： Adaptive fuzzy routing algorithm Swarm intelligence Routing table Communication network Packet delay,Throughput

modelling the impact of timelines of testing and isolation on disease control

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Infectious Disease modelling 2023年第1期8卷 58-71页

作者： Ao Li Zhen Wang seyed.m.moghadas Agent-Based modelling Laboratory York UniversityTorontoOntarioM3J 1P3Canada

Testing and isolation remain a key component of public health responses to both persistent and emerging infectious *** the value of these measures have been demonstrated in combating recent outbreaks including the COVID-19 pandemic and monkeypox,their impact depends critically on the timelines of testing and start of isolation during the course of *** investigate this impact,we developed a delay differential model and incorporated age-since-symptom-onset as a parameter for delay in *** then used the model to compare the outcomes of reverse-transcription polymerase chain reaction(RT-PCR)and rapid antigen(RA)testing methods when isolation starts either at the time of testing or at the time of test *** the model with estimates of SARS-CoV-2 infection and diagnostic sensitivity of the tests,we found that the reduction of disease transmission using the RA test can be comparable to that achieved by applying the RT-PCR *** constraints and inevitable delays associated with sample collection and laboratory assays in RT-PCR testing post symptom onset,self-administered RA tests with short turnaround times present a viable alternative for timely isolation of infectious cases.

关键词： Testing Isolation Delay equations Simulations Turnaround time

Stability and thermal conductivity of water-based carbon nanotube nanofluids

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Particuology 2015年第5期13卷 59-65页

作者： mansoor Farbod Ameneh Ahangarpour seyed Gholamreza Etemad Department of Physics Shahid-Chamran University Department of Chemical Engineering Isfahan University of Technology

Water-based nanofluids were prepared with multi walled carbon nanotubes （mWCNTs） of different lengths in concentrations of 0,1,0,25 and 0,5 vol%, To improve their dispersibility, pristine mWCNTs were functionalized and cut into small lengths by reflux in an oxidizing mixture of 3：1 sulfuric and nitric acids, The initial length of the carbon nanotubes （CNTs; 10-15 μm） was reduced to 203, 171 and 134nm after 1, 2 and 4 h of reflux, respectively, Surface modification and the reduced length of the CNTs, improved the stability of the nanofluids with no significant sedimentation observed after 80 days. Furthermore, the thermal conductivities of nanofluids prepared using refluxed CNTs, were higher than that of the pristine CNTs. The thermal conductivity also increased with the nanofluid temperature, The nanofluid prepared with 1 h refluxed CNTs had the highest thermal conductivity, The enhanced thermal conductivity and stabilitv of the nanofluids was attributed to the decreased length of CNTs.

关键词： Nanofluids Thermal conductivity Stability Carbon nanotubes Refluxing time