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Application of physics-informed neural network in the analysis of hydrodynamic lubrication

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Friction 2023年第7期11卷 1253-1264页

作者： Yang ZHAO Liang GUO patrick Pat Lam wong School of Automotive and Transportation Engineering Shenzhen PolytechnicShenzhen 518055China School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200444China Department of Mechanical Engineering City University of Hong KongHong KongChina

The last decade has witnessed a surge of interest in artificial neural network in many different areas of scientific *** the rapid expansion in the application of neural networks,few efforts have been carried out to introduce such a powerful tool into lubrication ***,this work aims to apply the physics-informed neural network(PINN)to the hydrodynamic lubrication *** 2D Reynolds equation is *** PINN is a meshless method and does not require big data for network training compared with classical *** results are consistent with those obtained by experiments and the finite element ***,we envision that the PINN method will have great application potential in lubrication and bearing research.

关键词： physics-informed neural network hydrodynamic lubrication slider bearing

Identifying the optimal interfacial parameter correlated with hydrodynamic lubrication

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Friction 2016年第4期4卷 347-358页

作者： Liang GUO patrick wong Feng GUO Department of Mechanical and Biomedical Engineering City University of Hong Kong Hong Kong China Mechanical Engineering Department Qingdao Technological University Qingdao 266033 China

The effects of boundary (liquid/solid) slip on hydrodynamics are well recognized. However, it is extremely difficult to quantify in-situ boundary slip in a lubrication contact. Therefore, an effective interfacial parameter that is well correlated with the lubrication effect is of practical significance. This paper presents an examination of common interfacial parameters, including surface tension, contact angle, contact angle hysteresis, and a recently proposed spreading parameter. Specimen surfaces of different hydro/oleophobicity were prepared and characterized using the aforementioned interfacial parameters. These samples were further used as bearing surfaces in hydrodynamic lubrication tests. The correlations of these parameters with the measured lubricating film thickness were examined and compared. The key parameter closely related to the hydrodynamic effect was identified.

关键词： bearing slip oleophobicity thin hydrodynamic film

Stripe theory based numerical method for solving asymmetrical hysteresis of friction force in linear rolling guideways

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Science China(Technological Sciences) 2016年第9期59卷 1320-1327页

作者： ZHAO Yang XI YinHu MAO JunHong wong patrick Pat Lam Theory of Lubrication and Bearing Institute Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System Xi'an Jiaotong University Department of Mechanical and Biomedical Engineering City University of Hong Kong

Linear rolling guideways(LRGs) play an important role in precision engineering. In the pre-rolling region, the hysteretic friction force exerts great impacts on the positioning accuracy. Numerical and experimental studies of the hysteresis of friction force are presented in this paper. A model, which is based on the stripe theory and the simplified theory of rolling contact, is built to describe the transient hysteresis of the friction force. Then, the model is modified by taking the anelasticity effect into consideration. Experimentally, a linear motor direct-drive setup is utilized to measure the transient asymmetrical hysteresis of the friction force in the pre-rolling region of an LRG. The influences of the pre-rolling displacement and the dwelling time on the asymmetrical hysteresis of the friction force are studied. The numerical and experimental results are well correlated, which shows good accuracy of the model. The transient asymmetrical hysteresis of friction force in the pre-rolling region of LRGs can thus be determined using the model.

关键词：直线滚动导轨摩擦力数值方法纹理不对称滞回求解滞后现象

Guest editorial: Special issue on thin film lubrication

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Friction 2016年第4期4卷 277-279页

作者： Feng GUO patrick wong Jianbin LUO School of Mechanical Engineering Qingdao University of Technology Qingdao 266520 China Department of Mechanical and Biomedical Engineering City University of Hong Kong Hong Kong China State Key Laboratory of Tribology Tsinghua University Beijing 100084 China

It has been well accepted that the lubrication in tribopairs is dominated by different regimes under different conditions,mainly involving hydrodynamic lubrication (HDL),elastohydrodynamic lubrication (EHL),thin film lubrication (TFL),and boundary lubrication (BL).Thin film lubrication is a lubrication regime with lubricant film thickness ranging from a few nanometers to tens of nanometers,which bridges the gap between boundary lubrication and elastohydrodynamic lubrication.

关键词： Lubrication

Effects of La^(3+) and Gd^(3+) on Ca^(2+) influx in rat hepatoma H-35 cells

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Chinese Science Bulletin 1999年第4期44卷 331-335页

作者： wong patrick C. L. Department of Biochemistry The University of Hong Kong

Effects of La93+) and Gd3+ on Ca2+ influx were investigated in rat hepatoma H-35 cells by measuring the initial rate of45Ca2+ uptake. It was found that the maximum initial rate of Ca2+ uptake was increased six- to ten-fold at low concentrations of La3+ and Gd3+. Kinetic analyses by measuring the initial rate of Ca2+ influx at different external Ca2+ concentrations indicated the existence of two intracellular exchangeable components in the basal Ca2+ system, with low and high affinities for Ca2+,and only one class of Ca2+ binding sites was observed in the La3+- or Gd3+-treated cells. For high affinity, La3+ and Gd3+ increased both kinetic parameters Km and V(max of basal Ca2+ influx. La3+ and Gd3+ compete directly with Ca2+ for Ca2+ binding site for low affinity. The kinetics is competitive.

关键词： La3+ Gd3+ rat hepatoma H-35 cells Ca2+ influx.

Low phase noise K-band signal generation using polarization diverse single-soliton integrated microcombs

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Photonics Research 2024年第6期12卷 1175-1185页

作者： ALWALEED ALDHAFEERI HSIAO-HSUAN CHIN TRISTAN MELTON DONG IL LEE ALLEN CHU WENTING WANG MINGBIN YU patrick GUO-QIANG LO DIM-LEE Kwong CHEE WEI wong Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory University of CaliforniaLos AngelesCalifornia 90095USA Institute of Microelectronics A*STARSingapore 117865Singapore State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technologyand Shanghai Industrial Technology Research InstituteShanghai 200050China

Frequency microcombs with microwave and millimeter-wave repetition rates provide a compact solution for coherent communication and information *** implementation of these microcombs using a CMOS-compatible platform further paves the way for large-scale photonic integration and ***,we demonstrate free-running soliton microcombs with K-band repetition rates with very low phase noise over a 4 GHz pump detuning range reaching−117(−123)dBc/Hz at 10 kHz offset for a 19.7(10)GHz carrier without active pump stabilization,exceeding commercial electronic microwave oscillators at frequency offsets above 40 *** minimum laser noise to soliton microwave signal transduction factor observed is−*** noise performance is achieved using a hybridized dual-mode for soliton generation to achieve passive thermal stabilization and minimal soliton spectrum shift from prior Raman scattering and dispersive wave *** further examine the locking of the repetition rate to an external ultrastable photonic oscillator to illustrate the feasibility of phase noise suppression below the thermorefractive noise limits of microresonator frequency combs.

关键词： pump polarization millimeter

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亚洲金融中心之争或见分晓

商业周刊（中文版） 2023年第22期 42-44页

作者： Francis Chan patrick wong 不详

在竞逐亚洲最大金融中心的比拼中,中国香港与中国内地的关系逐步加深有望增强其相对于新加坡的优势。新加坡与西方关系融洽,这将帮助其在更广泛的全球商业领域获得额外的吸引力。

关键词：全球商业金融中心中国香港新加坡亚洲吸引力

Doubling over ten years of central obesity in Hong Kong Chinese working men

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Chinese Medical Journal 2007年第13期120卷 1151-1154页

作者： KO Gary Tin-choi CHAN Juliana CHAN Amy wong patrick HUI Stanley CHOW Ferrie TONG Spencer CHAN Cecilia Department of Medicine Alice HML Nethersole HospitalHong Kong SAR China The Chinese University of Hong Kong Hong Kong SARChina Hong Kong Hospital Authority Hong Kong SARChina The University of Hong Kong Hong Kong SARChina

Obesity is now an epidemic in most parts of the world. In this cross sectional study, we report the most recent data on obesity in Hong Kong Chinese working population and compare the changes over 10 years. Methods Between July 2000 and March 2002, 5882 adult subjects from the working class in Hong Kong were recruited （2716 men （46.2%） and 3166 women （53.8%））. They were randomly selected using computer generated codes according to the distribution of occupational groups. Results of this study were compared with the data collected from a prevalence survey for cardiovascular risk factors in a Hong Kong Chinese working population conducted in 1990 （1513 subjects, 910 men （60.1%） and 603 women （39.9%））. Results Standardized percentages of overweight, obesity, and central obesity, in Hong Kong Chinese working population were 59.7%, 35.0%, 26.7% in men and 32.0%, 21.7%, 26.7% in women. Compared to the data collected in 1990, the percentage of obesity increased by 5% in men and reduced by 6% in women. The percentage of central obesity doubled in men （from 12.2% to 26.7%） but remained stable in women.Conclusions There is a doubling of the percentage of central obesity in Hong Kong Chinese working men over previous decade. Education and proper lifestyle modification program to tackle this social health issue are urgently indicated.

关键词： obesity prevalence Hong Kong Chinese working population health promotion

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多孔灰岩局部化变形的精细化描述与数字表征

大地构造与成矿学 2024年第3期48卷 547-556页

作者：武岳彪孟范宝王岳军 patrick Baud 黄庭芳中山大学地球科学与工程学院广东珠海519082 香港中文大学理学院地球与环境科学课程中国香港999077 Universitéde Strasbourg CNRSInstitute Terre et Environnement de StrasbourgUMR 70635 Rue RenéDescartesStrasbourg cedex 67084France Department of Geosciences Stony Brook UniversityStony Brook NY 11794USA

压实带是一种典型的应变局部化现象,影响储层流体的封存、输运以及地下岩体的稳定性。多孔灰岩局部化变形的相关研究一直是难点,不像砂岩样品可以通过明显的声发射信号特征来分析与表征压实带的形成与演化规律。本文利用动态CT技术,实... 详细信息

压实带是一种典型的应变局部化现象,影响储层流体的封存、输运以及地下岩体的稳定性。多孔灰岩局部化变形的相关研究一直是难点,不像砂岩样品可以通过明显的声发射信号特征来分析与表征压实带的形成与演化规律。本文利用动态CT技术,实时监测灰岩局部化变形到宏观失稳的演化过程,重点描述压实带形成初期的局部化变形特征,涵盖了应变量>5%的变形部分特征。在灰岩变形过程中可以识别两处明显非弹性变形阶段:即初始大孔隙坍塌阶段和后续压实带形成过程,利用图像体积互相关技术定量表征压实带的演化特征,精细化描述压实带形成过程的微观破裂特征,系统分析离散压实带内的连通孔隙分布规律,发现连通孔隙与局部化变形有紧密联系,并基于CT扫描的孔隙网络数据,利用纳维斯特斯方程计算绝对渗透率,以渗透率为参考指标,研究局部化变形引起的损伤程度。

关键词：局部化变形 CT技术灰岩孔隙网络