Investigation on millimeter-scale W1/O/W2 compound droplets generation in a co-flowing device with one-step structure

Dawei Pan,Qiang Chen,Yinjuan Zhang,Bo Li 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.84 No.-

Millimeter-scale W1/O/W2 compound droplets generation in a co-flowing microfluidic device with onestepstructure was symmetrically observed through experiments, and the formation process isdistinguished according to the variation law of thread tip velocity. Specially, under a wide range ofoperation conditions, W1/O/W2 compound droplets form accompanying with the generation of oil phasedroplet. The formation ratio of compound droplets to oil phase droplet always depends on the outerphase Capillary number, Caw2, and theflow rate ratio, R, of middle to inner phases, and thus theflowpattern diagram is obtained. Further the influences of all phasesflow rates, outer phase viscosity as wellas the interfacial tension on the formation period and geometric sizes are extensively studied. Finally, aprediction correlation for dimensionless inner and outer diameters with several dimensionless numbersis also obtained. The results could provide an experimental basis for controllably preparing monodispersecompound droplets with millimeter-scale.

Flow patterns of solid in water in oil (S/W/O) compound droplets formation in a microfluidic device with perpendicular shear

Dawei Pan,Qiang Chen,Lan Xu,Can Yang,Meifang Liu,Weixing Huang,Bo Li 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.75 No.-

Theflow patterns and corresponding breakup dynamics of solid in water in oil compound droplets underperpendicular shear force were experimentally investigated in a microfluidic device. Three typicalflowpatterns, namely double-encapsulation, plugs, and cobbles, were found and be quantitativelydistinguished by the capillary number (Cac) of continuous phase and theflow rate ratio (R) ofcontinuous phase to dispersed phase. It is found that, under all offlow regimes, the consecutive entry ofsolid particles leads d1 (the neck thickness along the center of the side channel) varying periodically. Inthe double-encapsulation regime, the neck thickness (d2) between thefirst and second particle increasesas the interface deformation recovers driven by the interfacial tension force, whereas the neck thickness(d3) between the second and third particle decreases to break off because the neck has been stretchedlong to become thin enough. As for the cobbles regime, hydrostatic pressure difference still remainsdominant, but not a shearing force. Specially, different from the W/O droplet formation, it suggests thatvarious breakup dynamics are always caused by a non-free deformation of S/W interface and the largediameter of solid particle. Finally, theflow pattern diagrams dependent on Cac and R are obtained.

V₂O₅ xerogel electrodes with much enhanced lithium-ion intercalation properties with N₂ annealing

Liu, Dawei,Liu, Yanyi,Garcia, Betzaida Batalla,Zhang, Qifeng,Pan, Anqiang,Jeong, Yoon-Ha,Cao, Guozhong The Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.46

<p>V<SUB>2</SUB>O<SUB>5</SUB> xerogel films were fabricated by casting V<SUB>2</SUB>O<SUB>5</SUB> sols onto FTO glass substrates and annealing at 300 °C for 3 hours in nitrogen and air. The films annealed in nitrogen and air possessed different grain size and crystallinity. Optical absorption measurements and electrochemical impedance analyses revealed a reduced optical bandgap and enhanced electrical conductivity of N<SUB>2</SUB> annealed V<SUB>2</SUB>O<SUB>5</SUB> film. Lithium ion intercalation measurements showed that at a charge/discharge current density of 600 mAg<SUP>−1</SUP>, the N<SUB>2</SUB> annealed sample possessed noticeably better lithium ion storage capability. In contrast to the air annealed sample, which started with a discharge capacity of 152 mAhg<SUP>−1</SUP> but after 50 cycles the capacity had decreased to a low value of only 44 mAhg<SUP>−1</SUP>, the N<SUB>2</SUB> annealed sample started with a low value of 68 mAhg<SUP>−1</SUP> but the capacity increased sharply to a high value of 158 mAhg<SUP>−1</SUP> at the 24<SUP>th</SUP> cycle, followed by little capacity degradation in later cycles and after 50 cycles, the discharge capacity was still as high as 148 mAhg<SUP>−1</SUP>. Much improved lithium ion intercalation capacity and cyclic stability could be attributed to surface defects V<SUP>4+</SUP> and/or V<SUP>3+</SUP> and associated oxygen vacancies introduced by N<SUB>2</SUB> annealing as well as much less crystallized vanadium oxide.</p> <P>Graphic Abstract</P><P>V<SUB>2</SUB>O<SUB>5</SUB> films annealed in N<SUB>2</SUB> exhibited a much improved lithium ion intercalation capability as compared to counterparts annealed in air, highly favoring potential application as lithium ion battery electrodes. <img src='http://pubs.rsc.org/ej/JM/2009/b914436f/b914436f-ga.gif'> </P>

Utilizing Structural Equation Modeling and Segmentation Analysis in Real-time Crash Risk Assessment on Freeways

Chengcheng Xu,Dawei Li,Zhibin Li,Wei Wang,Pan Liu 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.7

The study aimed to utilize Structural Equation Modeling (SEM) and K-means clustering for predicting real-time crash risks onfreeways. The SEM was used to transform a number of correlated traffic variables into four independent latent traffic factors, and toestablish the interrelationships among the traffic variables and crash risks. The segmentation analysis based on K-means clusteringwas then conducted to investigate the main traffic factors affecting crash risks in various traffic regimes. It was found that: (a) Themeasurement equations in SEM can effectively account for the correlations among traffic variables by transforming numerouscorrelated traffic variables into several latent traffic variables; (b) The SEM can both capture the direct and indirect effects of trafficflow variables on crash risks. This promotes a better understanding how traffic conditions affect crash risks; (c) The SEM producesmore accurate estimates of crash risks than existing modeling technique. It can increase the crash prediction accuracy by an averageof 7.6% compared with the commonly used logistic regression; and (d) Segmentation analysis results suggested that the trafficfactors contributing to crash risks are various across different traffic regimes. The proactive crash prevention strategies for differenttraffic regimes were discussed based on the findings in the segmentation analysis

Study of the Key Technology of Ghost Imaging Based on Rosette Scanning

Zhang, Leihong,Kang, Yi,Pan, Zilan,Liang, Dong,Li, Bei,Zhang, Dawei,Ma, Xiuhua Optical Society of Korea 2017 Current Optics and Photonics Vol.1 No.5

Ghost imaging offers great potential, with respect to standard imaging, for imaging objects in optically harsh or noisy environments. It can solve the problems that are difficult to solve by conventional imaging techniques. Recently, it has become a hot topic in quantum optics. In this paper, we propose a scheme for ghost imaging based on rosette scanning, named rosette ghost imaging. Sampling a small area sampling instead of the whole object, the instantaneous field of view of rosette scanning is used as the modulation light field in ghost imaging. This scheme reduces energy loss, the number of samples, and the sampling time, while improving the quality of the reconstructed image.

Equilibrium, kinetic and mechanism studies on the biosorption of Cu2+ and Ni2+ by sulfur-modified bamboo powder

Tian Ai,Xiaojun Jiang,Hongmei Yu,Hong-Bo Xu,Dawei Pan,Qingyu Liu,Dongyu Chen,Jinyang Li 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.2

Two biosorbents were prepared using bamboo powder modified with mercaptoacetic acid and carbondisulfide, which exhibits strong adsorption properties for Cu2+ and Ni2+. The obtained materials were characterized byFTIR. Maximum adsorption for both metals was found to occur around pH 5.0-6.5. The kinetic data followed thepseudo-second-order model. The maximum adsorption capacities of Cu2+ and Ni2+ on mercaptoacetic acid modifiedbamboo powder determined from Langmuir isotherm were 103.97mg g−1 and 61.35mg g−1, respectively. While oncarbon disulfide modified bamboo powder were 128.21mg g−1 and 56.82mg g−1, respectively. The adsorption mechanismanalysis revealed that the most possible adsorption mode of Cu2+ was coordination, and Ni2+ was ion exchange. The obtained adsorbents could effectively remove Cu2+ and Ni2+ from industrial electroplating wastewater and could beused repeatedly for more than five cycles.