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Numerical investigation for the suitable choice of bubble diameter correlation for EMMS/bubbling drag model

Chinese Journal of Chemical Engineering 2022年第7期35卷 254-270页

作者： nouman ahmad Jianqiang Deng Muhammad Adnan Shaanxi Key Laboratory of Energy Chemical Process Intensification Xi’an 710049China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China

Mesoscale bubbles exist inherently in bubbling fluidized beds and hence should be considered in the constitutive modeling of the drag *** energy minimization multiscale bubbling(EMMS/bubbling)drag model takes the effects of mesoscale structures(i.e.,bubbles)into the modeling of drag coefficient and thus improves the coarse-grid simulation of bubbling and turbulent fluidized ***,its dependence on the bubble diameter correlation has not been thoroughly *** hydrodynamic disparity between homogeneous and heterogeneous fluidization is accounted for by the heterogeneity index,H_(d),which can be affected by choice of bubble diameter *** this choice of bubble diameter correlation influences the model prediction calls for further fundamental *** article incorporated seven different bubble diameter correlations into EMMS/bubbling drag model and studied their effects on H_(d).The performance of these correlations has been compared with the correlation used previously by EMMS/bubbling drag *** found that some of the correlations predicted lower Hd by order of a magnitude than the correlation used by the original EMMS/bubbling *** on such analysis,we proposed a modification in the EMMS drag model for bubbling and turbulent fluidized beds.A computational fluid dynamics(CFD)simulation using two-fluid model with the modified EMMS/bubbling drag model was performed for two bubbling and one turbulent fluidized *** distribution,time averaged solid concentration and axial solid concentration profiles were studied and compared with the previous version of the EMMS/bubbling drag model and experimental *** found that the right choice of bubble diameter correlations can significantly improve the results for CFD simulations.

关键词： Mesoscale Bubbles Energy minimization multiscale(EMMS) Heterogeneity index Bubbling fluidized bed

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Sensitivity analysis of a dense discrete phase model for 3D simulations of a tapered fluidized bed

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Particuology 2024年第11期94卷 59-83页

作者： Muhammad Adnan nouman ahmad Pornpote Piumsomboon Benjapon Chalermsinsuwan Fuel Research Center Department of Chemical TechnologyFaculty of ScienceChulalongkorn UniversityBangkok10330Thailand School of Chemical and Materials Engineering National University of Sciences and TechnologyIslamabad44000Pakistan Advanced Computational Fluid Dynamics Research Unit Chulalongkorn UniversityBangkok10330Thailand

This study aims to conduct a sensitivity analysis of closure models and modeling parameters for the Dense Discrete Phase Modeling(DDPM)approach in order to investigate the hydrodynamics of a 3D lab-scale Tapered Fluidized Bed(TFB).The closure models and model parameters under investigation include the gas-solid drag force,viscous models,particle-particle interaction models,restitution coefficient,specularity coefficient,and rebound *** primary objective of this sensitivity analysis is to optimize the numerical model's *** numerical results,in terms of axial and lateral Solid Volume Fraction(SVF)profiles obtained from the sensitivity analysis,indicate that the drag force and restitution coefficient significantly influence the hydrodynamics of the *** selecting these parameters could result in the improved performance of the numerical ***,the sensitivity of turbulence models,particle-particle interaction models,specularity coefficient,and rebound coefficient has a lesser impact on the hydrodynamics *** work concludes with the recommendation of a set of closure models and modeling parameters that offer the most accurate prediction of the hydrodynamics of the TFB.

关键词： Sensitivity analysis Dense discrete phase model Sub-models Modeling parameters Tapered fluidized bed Hydrodynamics

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Hydrodynamics in commercial-scale internally circulating fluidized beds with different central downcomer outlets

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Particuology 2020年第4期18卷 120-131页

作者： Zhenliang Meng Mengxi Liu nouman ahmad Wei Wang Chunxi Lu State Key Laboratory of Heavy Oil Processing China University of Petroleum-BeijingBeijing 102249China State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Standpipes,or downcomers,are commonly used in fluidized beds to transport *** outlet structure of the downcomer greatly affects the performance of flow from it and even overall reactor *** this study,the hydrodynamics in commercial-scale internally circulating fluidized beds(ICFBs)with central downcomers having different outlet structures was investigated using computational fluid dynamics simulations with an energy minimization multi-scale drag *** predicted results closely agreed with experimental *** showed that in an ICFB with a downcomer outlet directly open to the bed(model A),nearly 12.7%to 5.4%of the gas in the draft tube bypasses into the *** the ICFB models B and C with a conic baffle below the downcomer,the gas bypass is significantly weakened or even eliminated when the diameter of the conic baffle is 1.1 times that of the downcomer(model C).In addition,the solids circulation mass flux in ICFBs increased by about 62.5%,from 126.8 kg/(m2 s)in model A to 206 kg/(m2 s)in model C.

关键词： Internally circulating fluidized bed Downcomer outlet EMMS CFD Particles flow

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DFT Study for Hydrogen Storage as an Alternative Fuel Source

DFT Study for Hydrogen Storage as an Alternative Fuel Source

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作者： nouman ahmad 北京化工大学

学位级别：硕士

本文对镧修饰的乙烯分子在储存氢气方面的可行性进行了研究。我们对镧修饰的乙烯分子在储氢前后的结构、HOMO-LUMO轨道、密立根电荷、分态密度等电子性质进行了研究。研究发现乙烯分子可以吸附两个镧原子,而且每个镧原子可以吸附6个氢...

本文对镧修饰的乙烯分子在储存氢气方面的可行性进行了研究。我们对镧修饰的乙烯分子在储氢前后的结构、HOMO-LUMO轨道、密立根电荷、分态密度等电子性质进行了研究。研究发现乙烯分子可以吸附两个镧原子,而且每个镧原子可以吸附6个氢气分子,相当于7.34wt%的储氢量。镧原子和氢气分子之间的相互作用为库巴斯作用。在第二章中,我们详细地讨论了密度泛函理论和第一性原理分子动力学。在第三章中,我们讨论了液态储氢技术、物理和化学储氢技术。在第四种中,我们罗列和讨论了不同的高表面储氢材料的文献。在第五章中,我们讨论了镧修饰的乙烯分子在储氢方面的表现。

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Extending the EMMS/bubbling model to fluidization of binary particle mixture: Formulation and steady-state validation

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Chinese Journal of Chemical Engineering 2019年第1期27卷 54-62页

作者： nouman ahmad Yujie Tian Bona Lu Kun Hong Haifeng Wang Wei Wang State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences Jiangsu Provincial Engineering Laboratory for Advanced Materials of Salt Chemical Industry Huaiyin Institute of Technology

The EMMS/bubbling model originally proposed for fluidization of monodisperse particles is extended to fluidization of binary particle mixture in this *** dense and dilute phases are considered to comprise of two types of particles differing in size and/or *** equations and the stability condition are then formulated and solved by using an optimization numerical *** effects of bubble diameter are first investigated and a suitable bubble diameter correlation is *** validation for steady state behavior shows the extended model can fairly capture the overall hydrodynamic behaviors in terms of volume fraction of bubbles and average bed voidage for both monodisperse and binary particle *** encourages us to integrate this model with CFD for more validations in the future.

关键词： EMMS Binary mixture Fluidization Mesoscale structure

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基于EMMS介尺度模型的双分散鼓泡流化床的模拟

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化工学报 2019年第5期70卷 1682-1692页

作者：佟颖 ahmad nouman 鲁波娜王维中国科学院过程工程研究所多相复杂系统国家重点实验室北京100190 中国科学院大学中丹学院北京100049 中国科学院洁净能源创新院辽宁大连116023

双分散气固鼓泡流化床中颗粒通常具有不同粒径或密度,导致产生颗粒偏析等现象,影响传递和反应行为。颗粒分离和混合与气泡运动密不可分,其中相间曳力起关键作用。最近ahmad等提出了一种基于气泡结构的双分散介尺度曳力模型,能成功预测... 详细信息

双分散气固鼓泡流化床中颗粒通常具有不同粒径或密度,导致产生颗粒偏析等现象,影响传递和反应行为。颗粒分离和混合与气泡运动密不可分,其中相间曳力起关键作用。最近ahmad等提出了一种基于气泡结构的双分散介尺度曳力模型,能成功预测双分散鼓泡流化床的床层膨胀系数。本研究耦合该曳力模型与连续介质方法,模拟了两种不同的双分散鼓泡流化床,通过分析不同流化状态下的气泡运动、颗粒浓度比的轴向分布等参数,进一步检验模型的适用性。研究表明,当双分散颗粒处于完全流化状态时,耦合双分散介尺度曳力模型可合理预测不同颗粒的分离现象;而其处于过渡流化状态时,新曳力模型和传统模型均无法获得合理结果,此时调节固固曳力可改进模拟结果。

关键词：双分散颗粒流化床介尺度曳力计算流体力学 EMMS

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Observed failure modes of unreinforced masonry buildings during the 2015 Hindu Kush earthquake

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Earthquake Engineering and Engineering Vibration 2019年第2期18卷 301-314页

作者： Najif Ismail nouman Khattak Department of Civil and Environmental Engineering United Arab Emirates University

On 26 th October 2015, an Mw 7.5 earthquake struck northern Pakistan, with its epicenter located 45 km southwest of Jarm in the Hindu Kush region of Afghanistan. The earthquake resulted from reverse faulting at a depth of 210 km, resulting in 280 fatalities and substantial damage to some 109,123 buildings. Regional seismicity, characteristics of recorded strong motions, damage statistics, and building performance observations are presented. Earthquake damage was mostly constrained to seismic-deficient unreinforced masonry(URM) buildings. Typical failure modes included toppled minarets, partial or complete out of plane collapse of URM walls, diagonal shear cracking in piers, flexural cracking in spandrels, corner damage, pounding damage, and damage due to ground settlement. The majority of human loss resulted due to failure of URM walls and subsequent roof collapse. URM buildings located in rural hilly areas closer to the epicenter suffered more intense and frequent damage than urban URM buildings located farther away in larger cities.

关键词： Pakistan earthquake performance masonry buildings failure

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An Inception Module CNN Classifiers Fusion Method on Pulmonary Nodule Diagnosis by Signs

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Tsinghua Science and Technology 2020年第3期25卷 368-383页

作者： Guangyuan Zheng Guanghui Han nouman Qadeer Soomro the Beijing Key Laboratory of Intelligent Information Technology School of Computer Science and TechnologyBeijing Institute of TechnologyBeijing 100081China the School of Information Technology Shangqiu Normal UniversityShangqiu 476000China the School of Biomedical Engineering Sun Yat-sen UniversityGuangzhou 510006China the Department of Software Engineering Mehran University of Engineering and TechnologySZAB CampusKhairpur Mir's66020Pakistan

A "sign" on a lung CT image refers to a radiologic finding that suggests a pathological progression of some specific disease. Analysis of CT signs is helpful to understand the pathological origin of the lesion. In-depth study of lung nodules classification with different CT signs will help to distinguish benign and malignant nodules more clearly and accurately. To this end, we propose an Inception module-based ensemble classification method for pulmonary nodule diagnosis with different nodule signs. We first construct a Convolutional Neural Network(CNN) classifier adopting Inception modules and pre-train it on ImageNet. We then fine-tune this pre-trained classifier on 10 different lung nodule sign sample sets, and fuse these 10 classifiers with an artificial immune ensemble algorithm. The overall sensitivity, specificity, and accuracy of our proposed Artificial Immune Algorithm-based Inception Networks Fusion(AIA-INF) algorithm are 82.22%, 93.17%, and 88.67%, respectively, which are significantly higher than those of the alternative Bagging and Boosting methods. The experimental results show that our Inception-based ensemble classifier offers promising performance, and compared with other CADx systems, this scheme can offer a more detailed reference for diagnosis, and can be valuable for junior radiologist training.

关键词： sign lung cancer pulmonary nodule Convolutional Neural Network(CNN) Artificial Immune Algorithm(AIA)

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Experimental study on repeatedly loaded foundation soil strengthened by wraparound geosynthetic reinforcement technique

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第4期13卷 899-911页

作者： Muhammad nouman Amjad Raja Sanjay Kumar Shukla Geotechnical and Geoenvironmental Engineering Research Group School of EngineeringEdith Cowan UniversityJoondalupPerthWA 6027Australia Department of Civil Engineering School of EngineeringUniversity of Management and TechnologyLahorePakistan Civil Engineering Department Delhi Technological UniversityDelhiIndia

In the recent past,the potential benefits of wraparound geosynthetic reinforcement technique for constructing the reinforced soil foundations have been *** paper presents the experimental study on the behaviour of model strip footing resting on sandy soil bed reinforced with geosynthetic in wraparound and planar forms under monotonic and repeated *** geosynthetic layers were laid according to the reinforcement ratio to minimise the scale *** is found that for the same amount of reinforcement material,the wraparound reinforced model resulted in less settlement in comparison to planar reinforced *** efficiency of wraparound reinforced model increased with the increase in load amplitude and the rate of total cumulative settlement substantially decreased with the increase in number of load *** wraparound reinforced model has shown about 45% lower average total settlement in comparison to unreinforced model,while the double-layer reinforced model has about 41% lower average total settlement at the cost of approximately twice the material and 1.5 times the occupied land width ***,wraparound models have shown much greater stability in comparison to their counterpart models when subjected to incremental repeated loading.

关键词： Geosynthetics Repeated loads Wraparound reinforcement technique Model tests Footing settlement Bearing capacity Reinforcement ratio Strip footing

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Distinguish Fritillaria cirrhosa and nonFritillaria cirrhosa using laser-induced breakdown spectroscopy

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Plasma Science and Technology 2021年第8期23卷 161-166页

作者： Kai WEI Xutai CUI Geer TENG Mohammad nouman KHAN Qianqian WANG School of Optics and Photonics Beijing Institute of TechnologyBeijing 100081People's Republic of China Key Laboratory of Photonic Information Technology Ministry of Industry and Information TechnologyBeijing Institute of TechnologyBeijing 100081People's Republic of China

As traditional Chinese medicines,Fritillaria from different origins are very similar and it is difficult to distinguish *** this study,the laser-induced breakdown spectroscopy combined with learning vector quantization(LIBS-LVQ)was proposed to distinguish the powdered samples of Fritillaria cirrhosa and non-Fritillaria *** also studied the performance of linear discriminant analysis,and support vector machine on the same data *** these three classifiers,LVQ had the highest correct classification rate of 99.17%.The experimental results demonstrated that the LIBS-LVQ model could be used to differentiate the powdered samples of Fritillaria cirrhosa and non-Fritillaria cirrhosa.

关键词： laser-induced breakdown spectroscopy(LIBS) learning vector quantization chemometric models robustness of model

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