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Effect of Rolling on a Warm Compacted Ti_3SiC_2 Particulate Reinforced Cu Matrix Composite

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稀有金属材料与工程 2011年第S3期40卷 56-58页

作者： ngai Tungwai National Engineering Research Center of Near-net-shape Forming Technology for Metallic Materials South China University of Technology

Warm compaction was employed to fabricate a Ti3SiC2 particulate reinforced copper matrix composite for electro-friction application. Copper matrix composite reinforced with 5wt% of copper-coated Ti3SiC2 particulates were prepared by compacting mixed powder with a pressure of 700 MPa at 145 ℃, and then sintered at 1000 ℃ under cracked ammonia atmosphere for 60 min. In order to improve the density, rolling process was applied on the sintered samples, their density, hardness, electrical conductivity, ultimate tensile strength and tribological behaviors were studied. Results showed that the rolled composite with 30% deformation has a density of 8.28 g/cm3, a hardness of 1060 MPa (HB), an ultimate tensile strength of 288 MPa, an electrical resistivity of 7.0 ×10-8 Ω·m and a friction coefficient of 0.17.

关键词： Cu-Ti3SiC2 composite powder metallurgy electro-friction material

Universal properties of relaxation and diffusion in condensed matter

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Chinese Physics B 2017年第1期26卷 70-85页

作者： K L ngai State Key Laboratory of Metastable Materials Science and Technology. Yanshan University Qinhuangdao 066004 China

By and large the research communities today are not fully aware of the remarkable universality in the dynamic properties of many-body relaxation/diffusion processes manifested in experiments and simulations on condensed matter with diverse chemical compositions and physical structures. I shall demonstrate the universality first from the dynamic processes in glass-forming systems. This is reinforced by strikingly similar properties of different processes in contrasting interacting systems all having nothing to do with glass transition. The examples given here include glass-forming systems of diverse chemical compositions and physical structures, conductivity relaxation of ionic conductors（liquid, glassy, and crystalline）,translation and orientation ordered phase of rigid molecule, and polymer chain dynamics. Universality is also found in the change of dynamics when dimension is reduced to nanometer size in widely different systems. The remarkable universality indicates that many-body relaxation/diffusion is governed by fundamental physics to be unveiled. One candidate is classical chaos on which the coupling model is based, Universal properties predicted by this model are in accord with diverse experiments and simulations.

关键词： many-body relaxation/diffusion universal dynamics coupling model classical chaos

Advancing ion-exchange membranes to ion-selective membranes:principles,status,and opportunities

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Frontiers of Environmental Science & Engineering 2023年第2期17卷 145-171页

作者： Hanqing Fan Yuxuan Huang ngai Yin Yip Department of Earth and Environmental Engineering Columbia UniversityNew YorkNY 10027-6623USA Columbia Water Center Columbia UniversityNew YorkNY 10027-6623USA

Ion-exchange membranes(IEMs)are utilized in numerous established,emergent,and emerging applications for water,energy,and the *** article reviews the five different types of IEM selectivity,namely charge,valence,specific ion,ion/solvent,and ion/uncharged solute *** pathways to advance the selectivities through the sorption and migration mechanisms of transport in IEM are critically *** of the underlying principles governing transport,efforts to enhance selectivity by tuning the membrane structural and chemical properties are almost always accompanied by a concomitant decline in permeability of the desired *** the undesired crossover of solvent and neutral species is crucial to realize the practical implementation of several technologies,including bioelectrochemical systems,hypersaline electrodialysis desalination,fuel cells,and redox flow batteries,but the ion/solvent and ion/uncharged solute selectivities are relatively understudied,compared to the ion/ion *** fundamental understanding of the transport phenomena,specifically the factors underpinning structure-property-performance relationships,will be vital to guide the informed development of more selective *** in material and membrane design offer opportunities to utilize ion discrimination mechanisms that are radically different from conventional IEMs and potentially depart from the putative permeability-selectivity *** in IEM selectivity can contribute to meeting the aqueous separation needs of water,energy,and environmental challenges.

关键词： Ion-exchange membranes Selectivity Separations

A new thermomechanical coupled FDEM model for geomaterials considering continuum-discontinuum transitions

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第11期16卷 4654-4668页

作者： Zihan Liu Louis ngai Yuen Wong Department of Earth Sciences The University of Hong KongHong Kong China

A new thermomechanical(TM)coupled finite-discrete element method(FDEM)model,incorporating heat conduction,thermal cracking,and contact heat transfer,has been proposed for both continuous and discontinuous *** model incorporates a heat conduction model that can accurately calculate the thermal field in continuousediscontinuous transition processes within a finite element framework.A modified contact heat transfer model is also included,which accounts for the entire contact area of discrete *** align with the finite strain theory utilized in the FDEM mechanics module,the TM coupling module in the model is based on the multiplicative decomposition of the deformation *** proposed model has been applied to various scenarios,including heat conduction in both continuous and discontinuous media during transient states,thermal-induced strain and stress,and thermal cracking *** thermal field calculation model and the TM coupling model have been validated by comparing the numerical results with experiment findings and analytical *** numerical cases demonstrate the reliability of the proposed model convincingly,making it suitable for use across a wide range of continuous and discontinuous media.

关键词： Finite-discrete element method(FDEM) Thermomechanical(TM)coupling Thermal cracking Contact heat transfer Geomaterials

Adaptive quantile regression with precise risk bounds

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Science China Mathematics 2017年第5期60卷 875-896页

作者： TIAN MaoZai CHAN ngai Hang School of Statistics Lanzhou University of Finance and Economics School of Statistics and Information Xinjiang University of Finance and Economics Center for Applied Statistics School of StatisticsRenmin University of China Department of Statistics The Chinese University of Hong Kong

An adaptive local smoothing method for nonpaxametric conditional quantile regression models is considered in this paper. Theoretical properties of the procedure are examined. The proposed method is fully adaptive in the sense that no prior information about the structure of the model is assumed. The fully adaptive feature not only allows varying bandwidths to accommodate jumps or instantaneous slope changes, but also al- lows the algorithm to be spatially adaptive. Under general conditions, precise risk bounds for homogeneous and heterogeneous cases of the underlying conditional quantile curves are established. An automatic selection algo- rithm for locally adaptive bandwidths is also given, which is applicable to higher dimensional cases. Simulation studies and data analysis confirm that the proposed methodology works well.

关键词： adaptive smoothing automatic bandwidths conditional quantile risk bounds robustness

Preliminary estimation of rock-fall lateral dispersion by laboratory test

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第12期15卷 3343-3351页

作者： Louis ngai Yuen Wong Zhicheng Tang Department of Earth Sciences The University of Hong KongHong KongChina Faculty of Engineering China University of GeosciencesWuhan430074China

Lateral dispersion significantly directs the assessment of rockfall hazard and design of countermeasures. In the present study, the dependence of lateral dispersion on different controlling factors has been systematically evaluated by performing laboratory tests using three different rock block types, namely circular block, and two types of elliptical block. The three types of rock block are released onto an inclined surface with the identical initial status. Parallel, anti-parallel, and oblique impact tests set at slope angles of 22.5° and 45°are conducted to study the block-slope interaction of rockfall. Lateral dispersion of rockfall is less influenced by the block shape for the oblique impact, while the post-impact behaviors are greatly affected by the block shape. The key factors influencing the deviation of the post-impact trajectory direction are the slope angle (θ) and direction difference (Δφ). An empirical model is then developed to characterize the deviation distribution of lateral dispersion by 5th and 95th percentile values with the inclusion of the two key factors. Linear function can be used to describe the 5th percentile boundary, while hyperbolic function is good for the 95th percentile boundary, which need to be validated by field tests in the subsequent research.

关键词： Rockfall Block shape Slope angle Oblique impact Lateral dispersion

Pickering emulsions stabilized by biocompatible particles:A review of preparation,bioapplication,and perspective

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Particuology 2022年第5期20卷 110-120页

作者： Tong Zhang Fuguo Liu Jie Wu To ngai Department of Chemistry the Chinese University of Hong KongShatinN.T.Hong KongChina College of Food Science and Engineering Northwest A&F UniversityYangling 712100China State Key Laboratory of Biochemical Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing 700790China

The phenomenon of adsorption of solid particles at fluid interfaces to stabilize emulsions or foams have been known for more than a ***,particle-stabilized emulsions,often referred to as Pickering emulsions,are receiving growing attention as they are encountered in oil recovery and have long been used in personal care products and food *** the past 10 years the focus of the Pickering emulsion has also increasingly shifted to biomedical applications with thanks to novel syntheses of a wide range of biocompatible particle ***,a brief overview of the development of biocompatible particles is given for Pickering emulsion stabilization,including alginate,poly(lactic-co-gIycolic acid)(PLGA),and protein-based *** materials prepared by templating from emulsion stabilized with biocompatible particles include colloidal capsules and hierarchically porous *** is hoped that the understanding gained from the recent intense activity in the field will enable more researchers to modify existing materials and design new formulations,which would be beneficial for exploring more biological applications.

关键词： Biocompatible particle Pickering emulsion High internal phase emulsion(HIPE) Porous structure

Pathogenesis of pandemic H1N1 2009 influenza virusinfection and the implication on management

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Frontiers of Medicine 2010年第2期4卷 147-156页

作者： Kelvin Kai-Wang TO Iris wai-Sum LI Ivan Fan-ngai HUNG Vincent Chi-chung CHENG Kwok-Yung YUEN Carol Yu Center for Infection Department of MicrobiologyThe University of Hong KongHong Kong SARChina

The pandemic H1N12009 inﬂuenza virus has caused theﬁrst inﬂuenza pandemic of the 21st century,leading to disproportionate fatalities in the low-risk population despite the generally mild nature of the *** in science and technology have allowed very detailed study on the pathogenesis of this novel virus,and many have already been published in less than a year after the start of the *** generated from cell lines,animal models,and clinical data analysis has provided us with greater understanding of the behavior of this virus and the associated host *** new knowledge will allow us to formulate scientiﬁcally sound and evidence-based management plans.

关键词： inﬂuenza A virus,H1N1 subtype pandemic pathogenesis virulence factors immunity management,antiviral

Early-onset primary torsional dystonia in a 4-generation Chinese family with a mutation in the DYT1 gene

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Chinese Medical Journal 2005年第10期118卷 873-876页

作者： YEUNG wai Lan LAM Ching Wan CHENG wai Tsoi SIN ngai Chuen WONG Wing Kin WONG chun Nei TSE Ka Ming FOK Tai Fai Departments of Paediatrics Prince of Wales HospitalThe Chinese University of Hong KongHong KongChina Chemical Patholog Prince of Wales HospitalThe Chinese University of Hong KongHong KongChina Department of Paediatrics and Adolescent Medicine Queen Mary HospitalUniversity of Hong Kong Nuclear Medicine&PET Division Scanning DepartmentSt.Teresa’s HospitalHong KongChina

Primary torsion dystonia(PTD)is a clinically and genetically heterogeneous movement *** least thirteen different types of dystonia can be distinguished on a genetic basis.~1 The DYT1 gene was first mapped by Ozelius et al in 1989.~2(Kramer et)al^3 linked the same locus to PTD in 12 Ashkenazi Jewish families in *** patients with early-onset generalized PTD were caused by the same three base pair(GAG)deletion in the DYT1 gene on chromosome 9q34.^(1,4,5)The product of the gene is a protein called torsinA.~5(Although the)function of this protein is as yet uncertain,it is widely distributed throughout the brain with high levels in the substantia nigra compacta dopamine neurones.

关键词： DYT1 gene dystonia positron emission tomography