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Uniform surface polished method of complex holes in abrasive flow machining

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中国有色金属学会会刊：英文版 2009年第B09期19卷 250-257页

作者： Lung TSAI Kuo-Zoo L IANG chun-ho liu Department of Mechanical Engineering Ching Yun University

Abrasive flow machining(AFM) is an effective method that can remove the recasting layer produced by wire electrical discharge machining(WEDM). however, the surface roughness will not be easily uniform when a complex hole is polished by this method. CFD numerical method is aided to design good passageways to find the smooth roughness on the complex hole in AFM. Through the present method, it reveals that the shear forces in the polishing process and the flow properties of the medium in AFM play the roles in controlling the roughness on the entire surface. A power law model was firstly set up by utilizing the effect of shear rates on the medium viscosities, and the coefficients of the power law would be found by solving the algebraic equation from the relations between the shear rates and viscosities. Then the velocities, strain rates and shear forces of the medium acting on the surface would be obtained in the constant pressure by CFD software. Finally, the optimal mold core put into the complex hole could be designed after these simulations. The results show that the shear forces and strain rates change sharply on the entire surface if no mold core is inserted into the complex hole, whereas they hardly make any difference when the core shape is similar to the complex hole. Three experimental types of mold core were used. The results demonstrate that the similar shape of the mold core inserted into the hole could find the uniform roughness on the surface.

关键词：表面抛光磨料流加工表面粗糙度原子力显微镜计算机辅助设计 CFD软件介质粘度电火花加工

Computational fluid dynamics simulation of the wind flow over an airport terminal building

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第6期11卷 389-401页

作者： chun-ho liu Dennis Y.C.LEUNG Alex C.S.MAN P.W.CHAN Department of Mechanical Engineering The University of Hong Kong hong Kong Observatory

Turbulence in the wake generated by wind flow over buildings or obstacles may produce complex flow patterns in downstream *** include the recirculating flow and wind deficit areas behind an airport terminal building and their potential impacts on the aircraft landing on nearby runways.A computational fluid dynamics(CFD) simulation of the wind flow over an airport terminal building was performed in this study of the effect of the building wake on landing *** normal meteorological conditions,the studied airport terminal building causes limited effects on landing aircraft because most of the aircraft have already landed before entering the turbulent wake *** simulating the approach of a tropical cyclone,additional CFD sensitivity tests were performed to study the impacts of building wake under extreme meteorological *** was found that,in a narrow range of prevalent wind directions with wind speeds larger than a certain threshold value,a substantial drop in wind speed(>3.6 m/s) along the glide path of aircraft was observed in the building *** CFD results also showed that under the most critical situation,a drop in wind speed as large as 6.4 m/s occurred right at the touchdown point of landing aircraft on the runway,an effect which may have a significant impact on aircraft *** study indicated that a comprehensive analysis of the potential impacts of building wake on aircraft operations should be carried out for airport terminals and associated buildings in airfields to ensure safe aviation operation under all meteorological conditions and to facilitate implementation of precautionary measures.

关键词： Aviation safety Building aerodynamics Computational fluid dynamics (CFD) k-e turbulence model Tropicalcyclone

Physio-chemical modeling of the NO_(x)-O_(3) photochemical cycle and the air pollutants’ reactive dispersion around an isolated building

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建筑模拟(英文) 2023年第9期16卷 1735-1758页

作者： Yunfei Fu Xisheng Lin Xing Zheng Liangzhu Wang chun-ho liu Xuelin Zhang Cruz Y.Li K.T.Tse Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina Future Cities Lab Global Singapore-ETH CentreSingapore 138602 Department of Building Civil and Environmental Engineering at Concordia UniversityMontrealQuebecCanada Department of Mechanical Engineering The University of Hong KongPok-fu-lam RoadHong KongChina Department of Civil Engineering Chongqing UniversityChongqingChina School of Atmospheric Sciences Sun Yat-sen UniversityZhuhaiChina

A numerical physio-chemical model of the NO_(x)-O_(3) photochemical cycle in the near-wake region of an isolated residential/office building has been presented in this *** investigation delves into the dispersion of reactive air pollutants through the lens of fluid phenomenology and its impact on chemical reactivity,formation,transport,deposition,and *** fluid dynamics(CFD)simulations were conducted for the ground-point-source(GES)and roof-pointsource(RES)*** show that the Damköhler number(Da),which quantifies pollutants’physio-chemical timescales,displays a strong inverse proportionality with the magnitude and spread of NO–increasing Da reduces human exposure to the toxic NO and NO_(2) *** different wind directions were considered,the dispersion range of NO exhibited varying shrinking directions as Da ***,as Da increases,the concentration ratio KNO_(2)/KNO_(x),which quantifies the production of NO_(2) resulting from NO depletion,forms sharp high-low gradients near emission *** GES,the dispersion pattern is governed by the fluid’s phenomenological *** RES,the intoxicated area emanates from the building’s leading-edge,with the lack of shielding inhibiting pollutant interactions in the near-wake,resulting in scant physio-chemical *** NO_(2)/NO_(x) distribution follows a self-similar,stratified pattern,exhibiting consistent layering gradients and attributing to the natural deposition of the already-reacted pollutants rather than in-situ *** the end,building design guidelines have been proposed to reduce pedestrian and resident exposure to NO_(x)-O_(3).

关键词： reactive pollutant dispersion NO_(x)-O_(3)cycle air pollution isolated building physio-chemical modelling

Turbulent flows over real heterogeneous urban surfaces:Wind tunnel experiments and Reynolds-averaged Navier-Stokes simulations

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Building Simulation 2021年第5期14卷 1345-1358页

作者： Wai-Chi Cheng chun-ho liu Yat-Kiu ho Ziwei Mo Zhangquan Wu Wenye Li Lilian Y.L.Chan W.K.Kwan Hing Tuen Yau School of Atmospheric Sciences and Guangdong Province Key Laboratory for Climate Change and Natural Disaster StudiesSun Yat-sen UniversityZhuhaiChina Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) ZhuhaiChina Department of Mechanical Engineering The University of Hong KongHong KongChina Information Technology Services The University of Hong KongHong KongChina

Wind tunnel experiment and steady-state Reynolds-averaged Navier-Stokes(RANS)approaches are used to examine the urban boundary layer(UBL)development above Kowloon Peninsula,hong Kong Special Administrative Region(HKSAR).The detailed urban morphology is resolved by computational fluid dynamics(CFD)and is fabricated by 3D-printing(reduced scale)for wind tunnel *** from the majority existing results based on idealized,homogeneous urban geometries,it was found that the wind and turbulence in the UBL over downtown Kowloon are characterized by the wake behind several high-rise *** particular,local maxima of turbulence kinetic energy(TKE)and shear stress are found at the roof level of those high-rise *** the downstream region where the flows are already adjusted to the urban surfaces,the urban roughness sublayer(URSL)can be further divided into two layers based on the structures of the mixing length/m,effective drag Dx and dispersive *** the lower URSL(z<100 m),lm is rather uniform,and the Reynolds stress and dispersive stress are *** the upper URSL(100 m z s 300 m),on the contrary,lm is peaked at the mid-height and the magnitude of dispersive stress is smaller than that of the Reynolds stress(<30%).The effective drag Dx is negligible in the upper URSL.

关键词： computational fluid dynamics(CFD) real urban morphology urban boundary layer(UBL) urban canopy model(UCM) wind tunnel experiments

Pb induced dislocation defects of PtCo systems: Strain-triggered oxygen reduction reaction for PEMFC

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Nano Research 2024年第4期17卷 2462-2472页

作者： chun Jin Qiheng Wang Jingjun liu Beijing Key Laboratory of Electrochemical Process and Technology for Materials Beijing 100029China Beijing University of Chemical Technology Beijing 100029China

Design and development of advanced electrocatalysts with high performance and low Pt consumption are crucial for reducing the kinetic energy barrier of the cathode oxygen reduction reaction(ORR)and improving the efficiency of proton exchange membrane fuel cells(PEMFC).In this study,we demonstrate a Pb-modulated PtCo system for efficient ORR,in which the inclusion of Pb in ternary alloys induces dislocation defects due to the significant difference in atomic ***-PtCoPb was confirmed to exhibit significantly higher ORR activity and stability in acidic *** practical PEMFC applications,it outperforms the corresponding commercial Pt/C with a mass activity of 0.58 A·mgPt^(-1),making it a promising alternative to state-of-the-art Pt-based *** combination of experimental results and density functional theory(DFT)calculations offers valuable atomic-level insights into the dislocation *** with a larger atomic radius is located in the lattice stretching region below the dislocation slip plane,forming a structure similar to a Cottrell atmosphere,which reduces the dislocation energy and puts the system in a lower energy *** Cottrell atmosphere pins the dislocation structure and stabilizes the ternary *** adjusting the amount of added Pb,a moderate level of dislocation density induces a tuned strain effect,thereby enhancing the electrocatalytic mechanism by optimizing the electronic structure of the alloy surface and the adsorption and desorption of oxygen *** work provides valuable insights into the design and development of lattice dislocation defect structures to trigger strain effects for improving ORR performance.

关键词： dislocation defect strain effect Pb-modulated oxygen reduction reaction

Differential Evolution Hemivariational Inequalities with Anti-periodic Conditions

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Acta Mathematica Sinica,English Series 2024年第4期40卷 1143-1160页

作者： Jing ZHAO chun Mei GAN Zhen Hai liu School of Mathematics and Quantitative Economics Guangxi University of Finance and EconomicsNanning 530003P.R.China Guangxi Colleges and Universities Key Laboratory of Optimization Control and Engineering Calculation Guangxi Minzu UniversityNanning 530006P.R.China

The goal of this paper is to deal with a new dynamic system called a differential evolution hemivariational inequality(DEHVI)which couples an abstract parabolic evolution hemivariational inequality and a nonlinear differential equation in a Banach ***,by apply ing surjectivity result for pseudomonotone multivalued mappins and the properties of Clarke's subgradient,we show the nonempty of the solution set for the parabolic hemivariational ***,some topological properties of the solution set are established such as boundedness,closedness and ***,we explore the upper semicontinuity of the solution ***,we prove the solution set of the system(DEHVI)is nonempty and the set of all trajectories of(DEHVI)is weakly compact in C(I,X).

关键词： Differential parabolic hemivariational inequality Clarke subdifferential hyperbolicparabolic system parabolic-parabolic system existence result

Enhanced Fenton-like process over Cu/L(+)-ascorbic acid co-doping mesoporous silica for toxicity reduction of emerging contaminants

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Frontiers of Environmental Science & Engineering 2024年第4期18卷 49-60页

作者： Yuhang liu Wenxuan Deng Xiaojun Wu chun Hu Lai Lyu Key Laboratory for Water Quality and Conservation of the Pearl River Delta(Ministry of Education) Institute of Environmental Research at Greater BayGuangzhou UniversityGuangzhou 510006China

Effective removal of emerging contaminants(ECs)to minimize their impacts on human health and the natural environment is a global *** the removal of ECs in water,we fabricated a seaweed spherical microsphere catalyst with Cu cation-πstructures by in situ doping of Cu species and ascorbic acid in mesoporous silica(Cu-C-MSNs)via a hydrothermal *** results indicate that bisphenol A(BPA)is substantially degraded within 5 min under natural conditions,with its biological toxicity considerably ***,industrial wastewater could also be effectively purified by Cu-C-MSNs/H_(2)O_(2) *** presence of metal sites and the complexation of ECs via cation-πinteraction andπ-πstacking on the catalyst surface were directly responsible for the polarization distribution of electrons,thus activating H_(2)O_(2) and dissolved oxygen(DO).The removal of contaminants could be attributed primarily to 1)the activation of H_(2)O_(2) into ^(·)OH to attack the contaminants and 2)self-cleavage because of the transfer of electrons from the contaminants to the *** study provides an innovative solution for the effective treatment of ECs and has positive implications for easing global environmental crises.

关键词： Cation-πstructures Polarization electric field Fenton-like process Contaminants cleavage

Relationship Between Short-chain Fatty Acids and Parkinson’s Disease:A Review from Pathology to Clinic

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Neuroscience Bulletin 2024年第4期40卷 500-516页

作者： Wen-Xiang Duan Fen Wang Jun-Yi liu chun-Feng liu Department of Neurology and Clinical Research Center of Neurological Disease The Second Affiliated Hospital of Soochow UniversitySuzhou215004China Department of Neurology Dushu Lake Hospital affiliated to Soochow UniversitySuzhou215125China Jiangsu Key Laboratory of Neuropsychiatric Diseases and Institute of Neuroscience Soochow UniversitySuzhou215123China

Parkinson’s disease(PD)is a complicated neurodegenerative disease,characterized by the accumulation ofα-synuclein(α-syn)in Lewy bodies and neurites,and massive loss of midbrain dopamine *** evidence suggests that gut microbiota and microbial metabolites are involved in the development of *** these,short-chain fatty acids(SCFAs),the most abundant microbial metabolites,have been proven to play a key role in brain-gut *** this review,we analyze the role of SCFAs in the pathology of PD from multiple dimensions and summarize the alterations of SCFAs in PD patients as well as their correlation with motor and non-motor *** research should focus on further elucidating the role of SCFAs in neuroinflammation,as well as developing novel strategies employing SCFAs and their derivatives to treat PD.

关键词： Parkinson’s disease Short-chain fatty acids Microbial metabolites Brain-gut-microbiota axis

A multiscale adaptive framework based on convolutional neural network: Application to fluid catalytic cracking product yield prediction

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Petroleum Science 2024年第4期21卷 2849-2869页

作者： Nan liu chun-Meng Zhu Meng-Xuan Zhang Xing-Ying Lan State Key Laboratory of Heavy Oil Processing China University of Petroleum (Beijing) College of Artificial Intelligence China University of Petroleum (Beijing)

Since chemical processes are highly non-linear and multiscale, it is vital to deeply mine the multiscale coupling relationships embedded in the massive process data for the prediction and anomaly tracing of crucial process parameters and production indicators. While the integrated method of adaptive signal decomposition combined with time series models could effectively predict process variables, it does have limitations in capturing the high-frequency detail of the operation state when applied to complex chemical processes. In light of this, a novel Multiscale Multi-radius Multi-step Convolutional Neural Network(Msrt Net) is proposed for mining spatiotemporal multiscale information. First, the industrial data from the Fluid Catalytic Cracking(FCC) process decomposition using Complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN) extract the multi-energy scale information of the feature subset. Then, convolution kernels with varying stride and padding structures are established to decouple the long-period operation process information encapsulated within the multi-energy scale data. Finally, a reconciliation network is trained to reconstruct the multiscale prediction results and obtain the final output. Msrt Net is initially assessed for its capability to untangle the spatiotemporal multiscale relationships among variables in the Tennessee Eastman Process(TEP). Subsequently, the performance of Msrt Net is evaluated in predicting product yield for a 2.80 × 10～6 t/a FCC unit, taking diesel and gasoline yield as examples. In conclusion, Msrt Net can decouple and effectively extract spatiotemporal multiscale information from chemical process data and achieve a approximately reduction of 30% in prediction error compared to other time-series models. Furthermore, its robustness and transferability underscore its promising potential for broader applications.

关键词： Fluid catalytic cracking Product yield Data-driven modeling Multiscale prediction Data decomposition Convolution neural network