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Analysis of humidity-dependent adhesion between a probe tip and a surface

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Particuology 2017年第4期15卷 91-97页

作者： Li Yang Junhui Hu Huapeng Xiao wenwen Quan College of Physics Science and Technology Guangxi Normal University Guilin 541004 China

Adhesive forces commonly exhibit a monotonic increase or a maximum with increasing relative humidity. However, anomalous behavior has been reported. Here, a numerical model of adhesive forces, comprised mainly of capillary and van der Waals forces, between a tip and a surface is established. It is described by a power law that considers the geometry, the liquid bridge wetting radius, the contact angle, and the separation distance. Capillary forces （sum of surface tension and Laplace pressure） and van der Waals forces are calculated. The latter cannot be neglected in the adhesion even at high humidity. Decrease in adhesion with increasing relative humidity can be attributed to a blunt tip shape, which is validated by experimental data. Specifically, the decrease in adhesion is attributed primarily to a transition from a rounded to a blunt tip shape. Structuring objects at the micro- or nanoscale can either increase or decrease adhesion as a function of relative humidity. This has a wide range of applications in robotic manipulation and can provide a better understanding of adhesion mechanisms in atomic force microscopy in ambient air.

关键词： Abnormality decrease Adhesive force Tip shape Capillary force Van der Waals force

DYNAMIC PRICING UNDER TEMPERATURE CONTROL FOR PERISHABLE FOODS

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Journal of Systems Science and Systems Engineering 2014年第3期23卷 252-265页

作者： wenwen Liu Wansheng Tang Lin Feng Jianxiong Zhang Institute of Systems Engineering Tianjin University

Consumers pay more and more attention to the quality of perishable roods, which is mainly affected by storage temperature. This paper presents a dynamic pricing model for perishable foods under temperature control. To maximize the total profit, the optimal price and storage temperature are obtained using Pontryagin＇s maximum principle. A static pricing model is provided to compare with the dynamic one. It is shown by a numerical example that the dynamic policy can make more revenue than the static one. Moreover, the managerial implications are analyzed and the effectiveness of the proposed method is demonstrated.

关键词： Temperature control dynamic pricing maximum principle perishable foods

Preparation and properties of tungsten-doped indium oxide thin films

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Rare Metals 2012年第2期31卷 158-163页

作者： Li, Yuan Wang, wenwen Zhang, Junying Wang, Rongming Department of Physics Beijing University of Aeronautics and Astronautics Beijing 100191 China

Tungsten-doped indium oxide (IWO) thin films were deposited on glass substrate by DC reactive magnetron sputtering. The effects of sputtering power and growth temperature on the structure, surface morphology, optical and electrical properties of IWO thin films were investigated. The thickness and surface morphology of the films are both closely dependent on the sputtering power and the substrate temperature. The transparency of the films decreases with the increase of the sputtering power but is not seriously influenced by substrate temperature. All the IWO thin film samples have high transmittance in near-infrared spectral range. With either the sputtering power or the growth temperature increases, the resistivity of the film decreases at the beginning and increases after the optimum parameters. The as-deposited IWO films with minimum resistivity of 6.4 10 4 cm were obtained at a growth temperature of225 C and sputteringpower of 40 W, with carrier mobility of 33.0 cm 2 V 1 s 1 and carrier concentration of 2.8 10 20 cm 3 and the average transmittance of about 81% in near-infrared region and about 87% in visible region.

关键词： In 2 O 3 : W thin film DC magnetron sputtering substrate temperature sputtering current optical and electrical properties

SHARP H?LDER CONTINUITY OF THE INTEGRATED DENSITY OF STATES FOR EXTENDED HARPER’S MODEL WITH A LIOUVILLE FREQUENCY

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Acta Mathematica Scientia 2019年第5期39卷 1240-1254页

作者： wenwen JIAN Yunfeng SHI School of Mathematical Sciences Fudan University Shanghai 200433 China School of Mathematical Sciences Peking University Beijing 100871 China

In this article, the non-self dual extended Harper's model with a Liouville frequency is considered. It is shown that the corresponding integrated density of states is 1/2-Holder continuous. As an application, the hom... 详细信息

关键词： extended Harper's model Liouville frequency 1/2-Holder continuity homogeneity

Organic Electrofluorescent Materials Using Pyridine-Containing Macrocyclic Compounds

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Journal of Materials Science & Technology 2008年第5期24卷 753-756页

作者： Tingxi LI Long FU wenwen YU Renhe HUANG School of Materials Science and Engineering Shandong University of Science ＆ Technology Qingdao 266510 China

Novel pyridine-containing macrocyclic compounds, such as 6,12,19,25-tetramethyl-7,11,20,24-dinitrilo-dibenzo [b,m]1,4,12,15-tetra-azacyclodoc osine （TMCD）, were synthesized and used as electron transport layer in organic electroluminescent devices. Devices with a structure of glass/indium-tin oxide/arylamine derivative/ tris（quinolinolato）aluminum（Ⅲ）（Alq）/TMCD/LiF/Al exhibited green emission from the Alq layer with external quantum efficiency of 0.84% and luminous efficiency of 1.3 lm/W. The derivatives of TMCD were synthesized and characterized as well. These compounds were also found to be useful as the electron-transporting materials in organic electroluminescent devices.

关键词： Pyridine-containing macrocyclic compound Organic electroluminescent Electron-transporting material

Surface modification of plasma nitriding on AlxCoCrFeNi high-entropy alloys

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Journal of Materials Science & Technology 2020年第13期47卷 140-145页

作者： jinxiong Hou wenwen Song Liwei Lan Junwei Qiao College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan030024China Steel Institute RWTH Aachen UniversityAachen52072Germany Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of EducationTaiyuan University of TechnologyTaiyuan030024China

Plasma nitriding is successfully employed in treating AlxCoCrFeNi high-entropy alloys(HEAs)with finelydivided Al content(i.e.,x values in molar ratio,x=0.1-0.8)to develop wear-resistant structural *** greatly removes the Al from the matrix that completely deplete the Ni-Al enriched phase,forming nanoscaled nitrides(AIN and CrN)precipitations near the *** promotes the hardness of present alloys with values widely ranging from 276 HV to 722 ***,the higher content the Al,the smaller thickness the nitrides layer,but the higher hardness due to the increased amount of hard nitrides phases and volume fraction of BCC ***,plasma nitriding considerably improves the wear re sistance of AlxCoCrFeNi HEAs by 4-18 times.

关键词： Plasma nitriding High-entropy alloy Microstructure Hardness Wear and tribology

Definition of spatial positions within foraging Greater White-fronted Geese flocks from an individual's perspective:Cost-benefit dynamics change with the distance to flock edge

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Avian Research 2022年第4期13卷 454-460页

作者： Mengzhen Wang wenwen Chen Chunlin Li jinming Zhao School of Life Science Huaibei Normal UniversityHuaibei235000China School of Resources and Environmental Engineering Anhui UniversityHefei230601China

The costs and benefits of group living are not evenly distributed among individuals that occupy different spatial positions within a group(central or peripheral).However,the definitions of central and peripheral positions may artificially mask the true dynamics of cost and benefit of *** wintering foraging Greater Whitefronted Geese(Anser albifrons)flocks as our study system,we measured individual spatial position within a flock as distance to the flock ***,we tested the effects of distance to edge on the antipredation cost and foraging benefit of individual goose using generalized linear mixed models(GLMMs).Flock size and number of neighbors and their interactions with distance to edge were included as fixed effects in *** we used piecewise regression to determine the threshold value of distance to edge to classify central and peripheral in*** results indicated distance to edge significantly affected percent of time spent on vigilance(vigilance time),percent of time spent on foraging(foraging time)and intake rate(pecks/min),whereas other factors had no *** found that the critical distance that predicted changes in behavior was around 2.5 *** 2.5 m or less from the edge of the group were more vigilant,and had less efficient foraging than more central in*** differences between central and peripheral individuals were more easily detected when the birds were classified by the method introduced in this study than by the traditional minimum convex polygon *** research provides researchers a dichotomous classification scheme that places individuals into peripheral and central positions from an individual's perspective.

关键词： Distance to edge Foraging time Intake rate Spatial position within a group Vigilance time

Significant influences of TiO_(2)crystal structures on NO_(2)and HONO emissions from the nitrates photolysis

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Journal of Environmental Sciences 2021年第4期33卷 198-206页

作者： wenwen Xu Wangjin Yang Chong Han He Yang Xiangxin Xue School of Metallurgy Northeastern UniversityShenyang 110819China

The emissions of NO_(2)and HONO from the KNO_(3)photolysis in the presence of TiO_(2)were measured using a round-shape reactor coupled to a NO_(x)***_(2)played important roles in the emission flux density of NO_(2)(R_(NO_(2)))and HONO(R HONO),depending on crystal structures and mass ratios of TiO_(2).R NO_(2)and R HONO significantly decreased with increasing the rutile and anatase mass ratios from 0 to 8 and 0.5 wt.%,***,with further increasing the anatase mass ratio to 8 wt.%,there was an increase in R_(NO_(2))and R HONO.R NO_(2)on KNO_(3)/TiO_(2)/SiO_(2)had positive correlation with the KNO_(3)mass(1–20 wt.%),irradiation intensity(80–400 W/m^(2))and temperature(278–308 K),while it had the maximum value at the relative humidity(RH)of 55%.R HONO on KNO_(3)/TiO_(2)/SiO_(2)slightly varied with the KNO_(3)mass and temperature,whereas it increased with the irradiation intensity and *** addition,the mechanism for NO_(2)and HONO emissions from the nitrates photolysis and atmospheric implications were discussed.

关键词： TiO_(2) Nitrates Photolysis NO_(2)

Lattice Boltzmann simulation of a laminar square jet in cross flows

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Chinese Journal of Chemical Engineering 2016年第11期24卷 1505-1512页

作者： Guoneng Li Youqu Zheng Huawen Yang wenwen Guo Yousheng Xu Department of Energy and Environment System Engineering Zhejiang University of Science and Technology

A three-dimensional, nineteen-velocity(D3Q19) Lattice Boltzmann Method(LBM) model was developed to simulate the fluid flow of a laminar square jet in cross flows based on the single relaxation time algorithm. The code was validated by the mathematic solution of the Poiseuille flow in a square channel, and was further validated with a previous well studied empirical correlation for the central trajectory of a jet in cross flows. The developed LBM model was found to be able to capture the dominant vortex, i.e. the Counter-rotating Vortex Pair(CVP) and the upright wake vortex. Results show that the incoming fluid in the cross flow channel was entrained into the leeside of the jet fluid, which contributes to the blending of the jet. That the spread width of the transverse jet decreases with the velocity ratio. A layer-organized entrainment pattern was found indicating that the incoming fluid at the lower position is firstly entrained into the leeside of the jet, and followed by the incoming fluid at the upper position.

关键词： Lattice Boltzmann method Square jet Cross flow Laminar flow