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Molecular Dynamics Simulation of Behaviours of Non-Polar Droplets Merging and Interactions with Hydrophobic Surfaces

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Journal of Bionic Engineering 2008年第4期5卷 271-281页

作者： y.y. yan c.y. Ji School of the Built Environment University of Nottingham Nottingham NG7 2RD UK

This paper presents a molecular dynamics simulation of the behaviours of non-polar droplets merging and also the fluid molecules interacting with a hydrophobic surface. Such behaviours and transport phenomena are popular in general microchannel flow boiling and two-phase flow. The droplets are assumed to be composed of Lennards-Jones type molecules. Periodic boundary conditions are applied in three coordinate directions of a 3-D system, where there exist two liquid droplets and their vapour. The two droplets merge when they come within the prescribed small distance. The merging of two droplets apart from each other at different initial distances is tested and the possible larger （or critical） non-dimensional distance, in which droplets merging can occur, is discussed. The evolution of the merging process is simulated numerically by employing the Molecular Dynamics （MD） method. For interactions with hydrophobic solid wall, a system with fluid confined between two walls is used to study the wetting phenomena of fluid and solid wall. The results are compared with those of hydrophilic wall to show the unique characteristics of hydrophobic interactions by microscopic methods.

关键词： molecular dynamics simulation mist flow droplets merging hydrophobic wetting

Ultra‑Transparent and Multifunctional IZVO Mesh Electrodes for Next‑Generation Flexible Optoelectronics

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Nano-Micro Letters 2025年第1期17卷 293-309页

作者： Kiran A.Nirmal Tukaram D.Dongale Atul c.Khot chenjie yao Nahyun Kim Tae Geun Kim School of Electrical Engineering Korea UniversityAnam‑ro 145Seongbuk‑guSeoulRepublic of Korea computational Electronics and Nanoscience Research Laboratory School of Nanoscience and BiotechnologyShivaji UniversityKolhapur 416004India

Mechanically durable transparent electrodes are essential for achieving long-term stability in flexible optoelectronic ***,they are crucial for applications in the fields of energy,display,healthcare,and soft *** meshes represent a promising alternative to traditional,brittle,metal oxide conductors due to their high electrical conductivity,optical transparency,and enhanced mechanical *** this paper,we present a simple method for fabricating an ultra-transparent conducting metal oxide mesh electrode using selfcracking-assisted *** this method,we produced an electrode with ultra-transparency(97.39%),high conductance(Rs=21.24Ωsq^(−1)),elevated work function(5.16 eV),and good mechanical *** also evaluated the effectiveness of the fabricated electrodes by integrating them into organic photovoltaics,organic light-emitting diodes,and flexible transparent memristor devices for neuromorphic computing,resulting in exceptional device *** addition,the unique porous structure of the vanadium-doped indium zinc oxide mesh electrodes provided excellent flexibility,rendering them a promising option for application in flexible optoelectronics.

关键词： Self-cracking template Vanadium-doped indium zinc oxide mesh Organic solar cells Organic light-emitting diodes Flexible transparent memory

Improving maintenance efficiency and safety through a human-centric approach

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Advances in Manufacturing 2021年第1期9卷 104-114页

作者： c.y.Siew S.K.Ong A.y.c.Nee Graduate School for Integrative Sciences and Engineering National University of Singapore28 Medical DriveSingapore 117456Singapore Department of Mechanical Engineering National University of Singapore9 Engineering Drive 1Singapore 117576Singapore

This paper presents an adaptive human-machine interface(HMI)that can provide appropriate sets of digital maintenanceinformation and guidance to an operator during *** takes into consideration the expertise level of the operator and the maintenance context and *** proposed human-centric methodology considers the heart rate,intention,and expertise level of the operator,which can be captured using sensors during maintenance.A set of rules is formulated based on the sensor data to infer the state of the operator during a maintenance *** on the operator state,the adaptive HMI can augment the operator's senses using a scheme that combines visual,audio,and haptic guidance cues during maintenance to enhance the operator's ability to perceive information and perform maintenance *** schemes of visual,audio,and haptic cues are developed based on a comparison of the best practices obtained from experienced operators.

关键词： Augmented reality(AR) Ergonomics Product development Maintenance

Analytical modeling of effect of interlayer on effective moduli of layered graphene-polymer nanocomposites

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Journal of Materials Science & Technology 2017年第8期33卷 827-833页

作者： c.c.Roach y.c.Lu Department of Mechanical Engineering University of KentuckyLexingtonKY 40506-0503USA

Nanocomposites enhanced with two-dimensional, layered graphene fillers are a new class of engineering materials that exhibit superior properties and characteristics to composites with conventional ***, the roles of ＂interlayers＂ in layered graphene fillers have yet to be fully explored. This paper examines the effect of interlayers on mechanical properties of layered graphene polymer *** an effective filler, the fundamental properties（in-plane young＇s modulus E（L1）, out-of-plane young＇s modulus E（L2）; shear modulus G（L12）, major Poisson＇s ratio V（L12）） of the layered graphene were computed by using the Arridge＇s lamellar model. The effects of interlayers on effective moduli of layered graphene epoxy composites were examined through the Tandon-Weng model. The properties of the interlayer show noticeable impact on elastic properties of the composites, particular the out-of-plane properties（young＇s modulus E2 and shear modulus G（12））. The interlayer spacing is seen to have much great influence on properties of the composites. As the interlayer spacing increases from 0.34 nm to 2 nm, all elastic properties of the composites have been greatly decreased.

关键词： Interlayer Layered graphene Nanocomposite Effective moduli

Finite element analysis of the effect of interlayer on interfacial stress transfer in layered graphene nanocomposites

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Journal of Materials Science & Technology 2019年第6期35卷 1147-1152页

作者： c.c.Roach y.c.Lu Department of Mechanical Engineering University of Kentucky

Understanding the roles of interlayers in reinforcement efficiencies by layered graphene is very important in order to produce strong and light graphene based nanocomposites. The present paper uses the finite element method to evaluate the interfacial strain transfers and reinforcement efficiencies in layered graphene-polymer composites. Results indicate that the presence of compliant interlayers in layered graphene plays significant roles in the transfers of strain/stress from matrix to graphene and subsequently the reinforcement effectiveness of layered graphene. In general, the magnitude of shear strain transferred onto the rigid graphene decreases as the thickness of the interlayer increases. This trend becomes insignificant as the graphene becomes sufficiently large(s>25,000). The shear strain at the interface of graphene-matrix is also greatly influenced by the interlayer modulus. A stiffer interlayer would result in a higher shear strain transferred on the graphene. The performance of the interlayers is further affected by the property of the composite and the architecture of the layered graphene stack. If a composite contains more graphene phase, the efficiency of reinforcement by a layered graphene becomes improved. If a graphene stack contains more interlayers, the effectiveness of reinforcement at the edges of the graphene becomes negatively affected.

关键词： Interlayer Layered graphene Nanocomposites Interfacial stress transfer Finite element method

Two sides of the heliopause

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Science china Earth Sciences 2011年第12期54卷 1830-1844页

作者： WHANG y. c catholic University of America

Interaction of the solar wind with the interstellar medium leads to the formation of the heliosphere and termination shock. This article addresses three aspects of the plasma and magnetic field on two sides of the heliopause：（1） The interstellar magnetic field surrounding the heliopause. In the limit of very low plasma β-ratio an analytical solution is obtained for the 3D interstellar magnetic field by means of a line dipole method. The undisturbed magnetic field in the upstream is allowed to have an arbitrary inclination angle. The solution describes the heliosphere as having a blunt-nosed geometry on the upwind side and approaching a cylindrical geometry on the downwind side. The distortion of the magnetic field can penetrate very deep into the interstellar space. （2） Interaction of the interstellar neutral hydrogen with the global solar wind. The ionization process leads to removal of interstellar neutral hydrogen in the heliosphere： on the upwind side, 90% of hydrogen depletion occurs inside 60 AU, the hydrogen density changes rapidly inside 10 AU. A hydrogen cavity forms inside -4 AU; the cavity extends on the downwind side to form a long cavity wake. Outside the cavity and cavity wake, pickup protons are produced, they cause deceleration and heating of the solar wind. The wind speed and temperature also increase steadily with heliolatitude caused by the latitudinal increase in wind speed at the inner boundary. （3） The global geometry of the termination shock. The termination shock has been treated as having a closed geometry in previous heliosphere models. This study presents a new perspective that the global termination shock may have a bow-shaped open geometry. The termination shock forms on the upwind side because the forward motion of the supersonic solar wind is blocked at the blunt-nosed heliopause. However, the heliopause likely to be open on the downwind side; the motion of the supersonic solar wind is unobstructed for shock formation. Thus, the globa

关键词： solar wind interstellar medium magnetic fields plasmas magnetohydrodynamics (MHD)

Study on the wind field and pollutant dispersion in street canyons using a stable numerical method

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Journal of Environmental Sciences 2005年第3期17卷 488-490页

作者： Dennis y.c. LEUNG Department of Mechanical Engineering the University of Hong Kong Hong Kong China

A stable finite element method for the time dependent Navier-Stokes equations was used for studying the wind flow and pollutant dispersion within street canyons. A three-step fractional method was used to solve the velocity field and the pressure field separately from the governing equations. The Streamline Upwind Petrov-Galerkin(SUPG) method was used to get stable numerical results. Numerical oscillation was minimized and satisfactory results can be obtained for flows at high Reynolds numbers. Simulating the flow over a square cylinder within a wide range of Reynolds numbers validates the wind field model. The Strouhal numbers obtained from the numerical simulation had a good agreement with those obtained from experiment. The wind field model developed in the present study is applied to simulate more complex flow phenomena in street canyons with two different building configurations. The results indicated that the flow at rooftop of buildings might not be assumed parallel to the ground as some numerical modelers did. A counter-clockwise rotating vortex may be found in street canyons with an inflow from the left to right. In addition, increasing building height can increase velocity fluctuations in the street canyon under certain circumstances, which facilitate pollutant dispersion. At high Reynolds numbers, the flow regimes in street canyons do not change with inflow velocity.

关键词： finite element method Streamline Upwind Petrov-Galerkin method three-step fractional method

Effects of building aspect ratio,diurnal heating scenario,and wind speed on reactive pollutant dispersion in urban street canyons

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Journal of Environmental Sciences 2012年第12期24卷 2091-2103页

作者： Nelson y.O.Tong Dennis y.c.Leung Department of Mechanical Engineering The University of Hong Kong

A photochemistry coupled computational fluid dynamics （cFD） based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario （solar radiation affections in nighttime, daytime, and sun-rise/set）, wind speed, building aspect ratio （building-height-to-street-width）, and dispersion of reactive gases, specifically nitric oxide （NO）, nitrogen dioxide （NO2） and ozone （O3） such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO2 and 03. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of 03 concentrations into the street canyons along windward walls under all diurnal heating scenarios. comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.

关键词： photochemistry reactive pollutant dispersion building aspect ratio diurnal heating scenario wind speed urban streetcanyon

MEcHANIcAL PROPERTIES OF Ti_3Sic_2 AT HIGH TEMPERATURE

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Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 465-470页

作者： y.W.Bao y.c.Zhou Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 ChinaShenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

creep and stress relaxation behavior, the elastic modulus and fracture toughness of machinable Ti3Sic2 at various temperatures from 20 to 1250℃ were investigated by means of three-point bending tests. The experiments were performed respectively at: (i) fixed stress and changed temperatures, and (ii) fixed temperature and changed stresses. A creep resistance parameter that represents the probability of creep deformation in a given condition was defined as a function of both applied stress and the threshold stress, varying in a range from 0 to 1. Elastic modulus at high temperatures was measured through comparing relative slopes of loading curves in cyclic loading curve. The fracture toughness measured by SENB method showed a stable value in the range of 25-1000℃, but over 1000℃, it declined abruptly from -6.7MPa·m1/2 to -2.0MPa·m1/2 at 1200℃.

关键词： high-temperature Ti3Sic2 creep stress relaxation fracture toughness