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Vortex analysis of water flow through gates by different vortex identification methods

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Journal of Hydrodynamics 2023年第1期35卷 112-124页

作者： Chun-ying Shen Rui-guo Yang Shan Qing Shi-hua He Faculty of Electrical Power Engineering Kunming University of Science and TechnologyKunming650500China

The pre-gate suction vortex,gate-bottom-edge transverse vortex,gate-slot vertical vortex,and downstream-of-gate return vortex are important factors affecting the flow instability of flat gates,which may lead to fatigue failure in severe cases.This study used the volume of fluid(VOF)model and large eddy simulation(LES)method to accurately capture the transient turbulence characteristics of flow under different water flow conditions and reveal the flow field and vortex structure.The Q—criterion,Omega(Ω)method,and latest third-generation Liutex vortex identification method were used to analyze and compare the pre-gate suction vortex,gate-slot vertical vortex,and downstream-of-gate return vortex,focusing on the ability of each vortex identification method to capture the flow field information and vortex characteristics.The results reveal that theΩmethod and Liutex method are less dependent on the threshold value,and the Liutex method captures a wide range of pre-gate vortices.Different flow conditions cause changes in the vortex structure of over-gate flow.When the relative opening of the gate is smaller,the intensity of the vortices in the flow field around the gate is greater,the return vortices downstream of the gate are more disordered,and the vortex changes are more violent,which in turn affects the efficient and stable operation of the gate.

关键词： Vortex features vortex identification methods Liutex Ωmethod Q-criterion large eddy simulation(LES)

On large action space in EV charging scheduling optimization

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Science China(Information Sciences) 2022年第2期65卷 45-60页

作者： Zhaoyu JIANG qing-shan JIA Xiaohong GUAN Center for Intelligent and Networked Systems Beijing National Research Center for Information Science and Technology Department of Automation Tsinghua University MOE KLINNS Lab Xi'an Jiaotong University

In order to reduce the air pollution by traditional fossil fuel and save the charging cost, much attention has been paid to the charging scheduling of electric vehicles(EVs) in the uncertain supplement of wind power and solar power. Owing to the randomness in the renewable power generation and the EV charging demand, simulation-based policy improvement(SBPI) has been well adopted for making charging decision. However, it is challenging to explore the large action space which grows exponentially with respect to the system scale. We consider this important problem in this paper and make the following contributions.First, we explore the structural property of the problem and develop an urgency index to rank the EVs.Second, we apply three methods to search in the action space. Third, we numerically demonstrate the performance of the urgency index and the search methods, and compare the SBPI methods with the CPLEXbased method. It shows that SBPI improves the base policies in all these cases.

关键词： EV simulation-based policy improvement large action space sampling

Instantaneous deformation characteristics of a single bubble in immiscible fluids

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Journal of Iron and Steel Research(International) 2022年第10期29卷 1601-1612页

作者： Jia-rui Xu Xiao-hui Zhang Shan Qing Hao Zhang Hua Wang Faculty of Metallurgical and Energy Engineering Kunming University of Science and TechnologyKunming650093YunnanChina National Local Joint Engineering Research Center of Energy Saving and Environmental Protection Technology in Metallurgy and Chemical Engineering Industry Kunming University of Science and TechnologyKunming650093YunnanChina

The passage of a rising bubble through immiscible fluids is encountered in bath smelting.In order to investigate characteristics of bubble deformation in immiscible fluids,the bubble shape change at the interface and the relationship between the bubble aspect ratio(E)and dimensionless number of forces were obtained.A three-dimensional model was established,and the free-floating behavior of a single bubble in immiscible fluids was numerically simulated by phase-field method.The simulation results are in good agreement with experimental results.The results indicate that when the bubble passes through the interface,the bubble shape is divided into four types in turn:“pear”,inverted“pear”,“convex”and“droplet”shape.In the lower liquid,the relationship of E to Weber number(We),Tadaki number(Ta),and Reynolds number(Re)is distributed between two intersecting lines.The relationship of E to Eötvös number(Eo),a dimensionless group,and Galilei number(Ga)is distributed near the lines with slopes of−3.325×10^(-5),−0.0855,and−8.73×10^(-4),respectively.In the upper liquid,the relationship of E to We,Ta,and Re is distributed between two parallel lines.Compared with gravity,the inertial force plays a leading role in the bubble shape in the lower and upper liquid.Compared with the viscous force,the surface tension dominates the bubble shape in the lower liquid.

关键词： Bubble shape Immiscible fluid Dimensionless number Phase-field method

Stability and Thermal Property Optimization of Propylene Glycol-Based MWCNT Nanofluids

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Fluid Dynamics & Materials Processing 2023年第9期19卷 2399-2416页

作者： Xi Wang Shan Qing Zhumei Luo Yiqin Liu Zichang Shi Jiachen Li Faculty of Metallurgical and Energy Engineering Kunming University of Science and TechnologyKunming650093China Faculty of Media and Information Engineering Yunnan Open UniversityKunming650093China

Propylene glycol-based MWCNT(multi-walled carbon nanotubes)nanoﬂuids were prepared in the framework of a two-step method and by using a suitable PVP(polyvinyl pyrrolidone)dispersant.The BBD(Box-Behnken design)model was exploited to analyze 17 sets of experiments and examine the sensitivity of the absorbance to three parameters,namely the concentration of MWCNT,the SN ratio(mass ratio of carbon nanotubes to sur-factants)and the sonication time.The results have revealed that,while the SN ratio and concentration of MWCNT have a strong effect on the absorbance,the inﬂuence of the sonication time is less important.The sta-tistical method of analysis of variance(ANOVA)was further used to determine the F-and p-values of the model.Five experiments were run to validate this approach.Since sample 2 was found to display the greatest absorbance,it was selected for stability monitoring as well as thermal conductivity and viscosity measurements.This sample has been found to be stable;the viscosity decreased with increasing temperature;the addition of MWCNT nano-particles was more effective in improving the thermal conductivity of propylene glycol than other methods in the literature.Moreover,the MWCNT nanoﬂuid based on propylene glycol exhibited higher thermal conductivity at low temperatures.

关键词： Propylene glycol thermal conductivity response surface methodology stability viscosity

Prediction and Optimization of the Thermal Properties of TiO_(2)/Water Nanofluids in the Framework of a Machine Learning Approach

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Fluid Dynamics & Materials Processing 2023年第8期19卷 2181-2200页

作者： Jiachen Li Wenlong Deng Shan Qing Yiqin Liu Hao Zhang Min Zheng Sate Key Laboratory of Complex Nonferrous Clean Utilization Kunming University of Science and TechnologyKunming650093China Faculty of Metallurgical and Energy Engineering Kunming University of Science and TechnologyKunming650093China Jiangxi Guoxing Intelligent Energy Co. Ganzhou330300China Faculty of Media and Information Engineering Yunnan Open UniversityKunming650500China

In this study,comparing multiple models of machine learning,a multiple linear regression(MLP),multilayer feed-forward artificial neural network(BP)model,and a radial-basis feed-forward artificial neural network(RBF-BP)model are selected for the optimization of the thermal properties of TiO_(2)/water nanofluids.In particular,the least squares support vector machine(LS-SVM)method and radial basis support vector machine(RB-SVM)method are implemented.First,curve fitting is performed by means of multiple linear regression in order to obtain bivariate correlation functions for thermal conductivity and viscosity of the nanofluid.Then the aforementioned models are used for a predictive analysis of the dependence of its thermal conductivity and viscosity on temperature and volume fraction.The results show that the least squares support vector machine(LS-SVM)has a prediction accuracy higher than the other models.The model predicts the thermal conductivity of TiO_(2)/water MSE=1.0853×10^(-6),R2=0.99864,MAE=0.00092,RMSE=0.00104,and the viscosity of TiO_(2)/water MSE=8.1397×10^(-6),R2=0.99995,MAE=0.00074,RMSE=0.0009.

关键词： Nanofluids viscosity thermal conductivity machine learning predictive modeling

A review on charging behavior of electric vehicles:data,model,and control

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Control Theory and Technology 2020年第3期18卷 217-230页

作者： qing-shan JIA Teng LONG Center for Intelligent and Networked Systems(CFINS) Department o f AutomationBeijing National Research Center for Information Science and Technology(BNRist)Tsinghua UniversityBeijing 100084China

The adoption and usage of electric vehicles(EVs)have emerged recently due to the increasing concerns on the greenhouse gas issues and energy revolution.As a part of the smart grid,EVs can provide valuable ancillary services beyond consumers of electricity.However,EVs are gradually considered as nonnegligible loads due to their increasing penetration,which may result in negative effects such as voltage deviations,lines saturation,and power losses.Relationship and interaction among EVs,charging stations,and micro grid have to be considered in the next generation of smart grid.Therefore,the topic of smart charging has been the focus of many works where a wide range of control methods have been developed.As one of the bases of simulation,the EV charging behavior and characteristics have also become the focus of many studies.In this work,we review the charging behavior of EVs from the aspects of data,model,and control.We provide the links for most of the data sets reviewed in this work,based on which interested researchers can easily access these data for further investigation.

关键词： Electric vehicle charging behavior data and model

Microporous metal-organic framework materials for efficient capture and separation of greenhouse gases

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Science China Chemistry 2023年第8期66卷 2181-2203页

作者： shan-qing Yang Tong-Liang Hu Banglin Chen School of Materials Science and Engineering National Institute for Advanced MaterialsNankai UniversityTianjin300350China Department of Chemistry University of Texas at San AntonioSan AntonioTexas78249-0698USA

The release of anthropogenic greenhouse gases into the atmosphere poses serious risks to the environment and human health,and is a global threat of growing concern.In order to ameliorate the greenhouse gas emission problems,the efficient capture and separation of these greenhouse gases are greatly meaningful.Metal-organic framework(MOF)materials,a relatively new kind of organic-inorganic hybrid porous materials with unique framework features,tunable pore environment and high surface areas,have been widely studied as regards their applicability to this implementation.And the well-defined structures of MOF materials greatly promote the understanding of structure-property relationships.In this review,we intend to provide a profound account of significant progress in the field of capture and separation of greenhouse gases using MOFs as adsorbents,including carbon dioxide,methane,nitrous oxide and fluorocompounds(such as perfluorocarbons,sulfur hexafluoride,hydrochlorocarbons,and hydrofluocarbons).The strategies used to realize the efficient capture and separation of greenhouse gases have been summarized,and the relationships between the frameworks,their capture and separation performances and mechanisms are discussed.Furthermore,the existing challenges and perspectives with regard to the development of MOF materials for the capture and separation of greenhouse gases and industrial practical application are outlined to further promote this very significant and active emerging topic.

关键词： porous materials metal-organic frameworks greenhouse gases capture and separation structure-property relationship

Secure analysis on artificial-noise-aided simultaneous wireless information and power transfer systems

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Frontiers of Information Technology & Electronic Engineering 2020年第11期21卷 1651-1660页

作者： Wei-min HOU qing-shan TANG School of Information Science and Engineering Hebei University of Science and TechnologyShijiazhuang 050018China School of Physics Electronic Science Changsha University of Science Sz TechnologyChangsha 410114China

In this paper,we investigate the secrecy outage performance in simultaneous wireless information and power transfer(SWIPT)systems taking artificial noise assistance into account.Multiple antennas in the source and a single antenna in both the legitimate receiver and the eavesdropper are assumed.Specifically,the transmitted signal at the source is composed of two parts,where the first part is the information symbols and the other is the noise for the eavesdropper.To avoid making noise in the legitimate receiver,these two parts in the transmitted signals are modulated into two orthogonal dimensions according to the instantaneous channel state between the source and the legitimate receiver.We derive an approximate closed-form expression for the secrecy outage probability(SOP)by adopting the Gauss-Laguerre quadrature(GLQ)method,where the gap between the exact SOP and our approximate SOP converges with increase of the summation terms in the GLQ.To obtain the secrecy diversity order and secrecy array gain for the considered SWIPT system,the asymptotic result of the SOP is also derived.This is tight in the high signal-to-noise ratio region.A novel and robust SOP approximation is also analyzed given a small variance of the signal-to-interference-plus-noise ratio at the eavesdropper.Some selected Monte-Carlo numerical results are presented to validate the correctness of the derived closed-form expressions.

关键词： Artificial noise Multi-antenna systems Secrecy outage probability Simultaneous wireless information and power transfer

Tuning d-spacing of graphene oxide nanofiltration membrane for effective dye/salt separation

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Rare Metals 2023年第2期42卷 418-429页

作者： Chao Xing Chang-Yu Liu Chao Lai shan-qing Zhang Center for Clean Environment and Energy School of Environment and ScienceGold Coast CampusGriffith UniversitySouthportQLD4222Australia School of Chemistry and Materials Science Jiangsu Normal UniversityXuzhou221116China School of Biotechnology and Health Sciences Wuyi UniversityJiangmen529020China

The interlayer spacing(i.e.,d-spacing)plays a crucial role in determining the selectivity and permeability of nanofiltration membranes.A high-throughput directional filtration can be achieved by designing and controlling the d-spacing.In this study,the d-spacing of a graphene oxide(GO)membrane was tuned and fixed to the desired value(approximately 0.79 nm)using a solution of polyethyleneimine(PEI)and GO at a PEI/GO mass ratio of15:1.The resultant PEI/GO was deposited on a polyacrylonitrile(PAN)substrate to form a robust composite nanofiltration membrane(a PEI/GO@PAN membrane).The as-prepared membrane exhibited an ultrahigh flux of117.8 L·m^(-2)·h^(-1),and the rejection values for Direct Red80(DR80)and Na_(2)SO_(4)reached 99.7%and<1.7%,respectively;these are desirable values for dye/salt separation.The PEI/GO@PAN membrane exhibited an excellent filtration performance,and had a longer lifespan and excellent reusability because of its reinforced nature.This work suggested that tuning the d-spacing with PEI would be an effective strategy to achieve the anticipated functions of nanofiltration membranes.

关键词： Separation Nanofiltration Graphene oxide Membrane d-spacing