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Jiawen Liu,정성재,Akbar Ali,엄석기 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.4
In this study, the microscopic transport properties of porous gas diffusion media (PGDMs) with capillary meniscus formation are evaluated using a statistical approach for electrochemical applications. The microscopic morphology of PGDM is stochastically modeled using randomly distributed carbon fibers and various meniscus formations. In particular, the meniscus formation of hydrophobic polytetrafl uorethylene (PTFE) agent enables the generation of highly elaborate microstructures in commercial PGDMs. A single-phase three-dimensional 19-velocity lattice Boltzmann method is applied to simulate the microscale mass transfer phenomena within the PGDMs. The mass transport characteristics (i.e., anisotropic permeability, tortuosity, and effective diffusion coefficient) of the PGDM samples with different PTFE content are statistically investigated as a function of untreated porosity (i.e., porosity before PTFE loading) of the PGDMs. The predicted results reveal an inverse relationship between anisotropic permeability and PTFE loading because the addition of PTFE decreases the bulk porosity of the PGDMs. In addition, the electrical and thermal conductivities of PGDMs are statistically estimated in both the in-plane and through-plane directions. The results show that the in-plane electrical and thermal conductivities are greater than those in the through-plane direction because of the carbon-fiber orientation. Moreover, the addition of PTFE has relatively larger effects on the through-plane electrical and thermal conductivities.
Jiawen Xu,Haodong Hong,Zhenyu Wang,Xinhu Sun,Yen Wei,Yu Liu 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.2
Microfluidic devices are critical in lab-on-chip, drug delivery, flexible sensors, etc. However, a formidable challenge remains in fabricating microfluidic channels with complex shapes during design and verification. Herein, we present a facile approach for manufacturing polystyrene (PS) templates by in-suit combining microscale electrohydrodynamic (EHD) printing and mesoscale direct ink writing (DIW). The desired multiscale filament width from 20 μm to > 1 mm could be obtained through appropriate voltage and pressure with continuous printing. The further process parameters for adjusting line width including deposition speed, auxiliary heating for DIW/EHD printing mode were investigated detailly. And we prove the stability and feasibility for producing microfluidics via the method by AFM, EDS and filling test. Based on the solubility of PS in the organic solvent, we can readily reconfigure the existing template by erasing and printing part of the patterns for better remanufacturing. Finally, the LM-filling PDMS microfluidic is experimented to demonstrate the future potential and advantage of the printing technology for fabricating the flexible microfluidic device.
Lu Li,Jiawen Zhu,Kui Yang,Zhuofei Xu,Ziduo Liu,Rui Zhou 한국미생물학회 2014 The journal of microbiology Vol.52 No.6
Actinobacillus pleuropneumoniae is an important porcinerespiratory pathogen causing great economic losses in thepig industry worldwide. Oxygen deprivation is a stress thatA. pleuropneumoniae will encounter during both early infectionand the later, persistent stage. To understand modulationof A. pleuropneumoniae gene expression in responseto the stress caused by anaerobic conditions, gene expressionprofiles under anaerobic and aerobic conditions werecompared in this study. The microarray results showed that631 genes (27.7% of the total ORFs) were differentially expressedin anaerobic conditions. Many genes encoding proteinsinvolved in glycolysis, carbon source uptake systems,pyruvate metabolism, fermentation and the electron respirationtransport chain were up-regulated. These changes ledto an increased amount of pyruvate, lactate, ethanol and acetatein the bacterial cells as confirmed by metabolite detection. Genes encoding proteins involved in cell surface structures,especially biofilm formation, peptidoglycan biosynthesisand lipopolysaccharide biosynthesis were up-regulatedas well. Biofilm formation was significantly enhancedunder anaerobic conditions. These results indicate that inductionof central metabolism is important for basic survivalof A. pleuropneumoniae after a shift to an anaerobic environment. Enhanced biofilm formation may contribute tothe persistence of this pathogen in the damaged anaerobichost tissue and also in the early colonization stage. Thesediscoveries give new insights into adaptation mechanismsof A. pleuropneumoniae in response to environmental stress.
Shin, Seungho,Liu, Jiawen,Akbar, Ali,Um, Sukkee Elsevier 2019 Journal of catalysis Vol.377 No.-
<P><B>Abstract</B></P> <P>Nanoscale transport characteristics and catalyst utilization of vertically aligned carbon nanotube (VACNT) catalyst layers (CLs) are evaluated using a fully statistical modeling approach based on the inherent random nature of the catalyst layer structures for fuel cell applications. Composite morphological structures of the catalyst layers are stochastically modeled with a 95% confidence level, and transport phenomena inside the catalyst layers are simulated using the D3Q19 lattice Boltzmann method (LBM). The effective diffusion coefficient of VACNT catalyst layers is predicted to be higher than that of the conventional catalyst layer, despite a relatively small pore diameter and a low-Knudsen diffusion coefficient. Consequently, the VACNT catalyst layers exhibit improved catalyst utilization compared to the conventional catalyst layers. These statistical results obtained from a series of numerical experiments confirm that the PEFC catalyst layers containing the VACNT catalyst supports can provide more efficient reactant transport, resulting in enhanced catalyst utilization for electrochemical reactions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A 3-dimensional Lattice Boltzmann method (LBM) was proposed for catalyst modeling. </LI> <LI> Structure–transport characteristics of catalyst layer were statistically predicted. </LI> <LI> VACNT catalyst layers can form more favorable pore structures for mass transport. </LI> <LI> Nanotube forest effects of VACNT catalyst layers induces lower Knudsen diffusion. </LI> <LI> Improved pore design and low tortuosity yield higher catalyst utilization in VACNT. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Reactive extraction of 2,3-butanediol from fermentation broth
Yanyang Wu,Yanjun Li,Jiawen Zhu,Jiaxian Liu 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.1
Biochemical 2,3-butanediol is a renewable material, but the lack of an effective separation process limits its industrial application. We developed an effective separation process to recover 2,3-butanediol from fermentation broth by reactive-extraction with ion-exchange resin HZ732 as catalyst. n-Butylaldehyde was used as both reactant and extractant. Feasible operation conditions were obtained as follows: room temperature, Ccat=200 g·L−1, three-stage cross-current extraction, with reactant ratio (VButylaldehyde : Vfermentation broth) 0.05 for each stage. Reactive-extraction can recover over 98% of 2,3-butanediol in the form of 2-propyl-4,5-dimethyl-1,3-dioxolane from fermentation broth. Then 2,3-butanediol was obtained by hydrolyzing 2-propyl-4,5-dimethyl-1,3-dioxolane and purified by vacuum distillation. The total yield rate of 2,3-butanediol through the process was over 94% and purity of final product reached 99%.
Yanyang Wu,Yanjun Li,Jiawen Zhu,Jiaxian Liu 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.1
An effective process was developed to separate 2,3-butanediol (2,3-BD) from fermentation broth (FB)by reactive-extraction. Propionaldehyde (PRA) was used as reactant and reaction product 2-ethyl-4,5-dimethyl-1,3-dioxolane (EDD) acted as extractant. HCl was selected as catalyst. Appropriate conditions were obtained by experiment as follows: 10 oC, CHCl=0.2mol·L−1, two-stage cross-current extraction, reactant volume ratio (VPRA : VFB) for first stage and second stage is 0.10 and 0.05, respectively. The yield rate of 2,3-butanediol for the whole process can reach 90%w/w, and 2,3-butanediol in the final product can be more than 99% w/w. The novel process required less solution and especially had advantages in treating dilute fermentation broth. Furthermore, equilibrium and kinetic study were investigated on the reaction of propionaldehyde and 2,3-butanediol to provide basic data for process development. The results reveal that reaction enthalpy and activation energy of the reaction were −21.84±2.38 KJ·mol−1 and 51.97±2.84 KJ·mol−1, respectively. Kinetics was well described by pseudo-homogeneous model.