Flexible membranes with a hierarchical nanofiber/microsphere structure for oil adsorption and oil/water separation

Jiefeng Gao,Bei Li,Ling Wang,Xuewu Huang,Huaiguo Xue 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.68 No.-

Oil spill and oily wastewater have now become a serious threat to the freshwater and marine environments. Porous materials with super-hydrophobicity and super-oleophilicity are good candidates for the oil adsorption and oil/water separation. Here, flexible hybrid nanofibrous membrane (FHNM) containing SiO2/polyvinylidene fluoride (PVDF) microspheres was prepared by simultaneous electrospinning and electrospraying. The obtained FHNM combined the flexibility of the nanofiber mat and super-hydrophobicity of the microspheres, which could not be achieved by either only electrospinning or only electrospraying. It was found that when the weight ratio between the SiO2 and PVDF reached a critical value, the SiO2 nanoparticles were present on the PVDF microsphere surface, significantly improving the surface roughness and hence the contact angle of the FHNM. Compared with the pure electrospun PVDF nanofiber mat, most of the FHNMs have a higher oil adsorption capacity. The FHNM could separate the oil with water quickly under the gravity and displayed a high efficiency and good reusability for the oil/water separation. More importantly, the FHNM could not only separate the oil with the pure water but also the corrosive solution including the salt, acid and alkali solution.

Affinity Propagation Algorithm Based on Locality Preserving Projections and Particle Swarm Optimization

Lele Liu,Zhiping Zhou,Jiefeng Wang 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.6

Affinity propagation algorithm is a new powerful and effective clustering method. One of the major problems in clustering is the determination of the optimal number of clusters. In this paper, the particle swarm optimization algorithm is utilized to cope with this problem by using the parameter p as each particle and Silhouette index as the fitness, which can search for the optimal value of p and determine the optimal number of clusters automatically. Moreover, the problem of information overlap is the main drawback of affinity propagation algorithm in dealing with complex structure or high dimensional data for clustering. Hence the enhanced Locality preserving projections method is proposed to integrate with affinity propagation algorithm to reduce the dimension of the data as a processing step. As the result of experiment shows, the proposed method can simultaneously obtain the optimal number of clusters accurately and improve the clustering accuracy by eliminating the redundant information of the data without losing the internal nonlinear structure.

Hierarchical polyurethane/RGO/BiOI fiber composite as flexible, selfsupporting and recyclable photocatalysts for RhB degradation under visible light

Meng Lan,Manli Wang,Nan Zheng,Xiaoli Dong,Yu Wang,Jiefeng Gao 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-

Increasing organic pollutants have seriously affected the ecological environment and human health, photocatalytictechnology is considered as one of the most effective and environmentally friendly treatmentmethods. In this work, a novel hierarchical polyurethane (PU)/reduced graphene oxide (RGO)/bismuthoxyiodide (BiOI) composite fiber photocatalyst is constructed via an energy-saving route consisted ofultrasonic-assisted and co-precipitation method by utilizing PU nanofibers as substrate. The RGO are firstevenly wrapped in the PU nanofiber surface and BiOI nanosheets are then uniformly grown on the PU/RGO surface to form the hierarchical PU/RGO/BiOI composite fibers with a core–shell structure. The composition,morphology and electrochemical performance of the obtained PU/RGO/BiOI were characterizedby XRD, XPS, SEM, BET, I-t and EIS. Benefited from the high specific surface area of the PU nanofiber andthe excellent electron transfer ability of the RGO, a remarkable photocatalytic activity was achieved forthe PU/RGO/BiOI composite fibers and the degradation rate of RhB is 93.2% within 180 min. Notably, comparedto the traditional suspended nanoparticles, the PU/RGO/BiOI fibers exhibit excellent flexibility andself-supporting property, and can be easily separated and recovered from the contaminated water. Thus,the obtained PU/RGO/BiOI composite fibers with high photocatalytic activity and easily separable propertyare expected to possess great potential in water purification.

Stretchable, electrically conductive and superhydrophobic/superoleophilic nanofibrous membrane with a hierarchical structure for efficient oil/water separation

Xuewu Huang,Bei Li,Xin Song,Ling Wang,Yue Shi,Mingjun Hu,Jiefeng Gao,Huaiguo Xue 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.70 No.-

Aflexible, stretchable and electrically conductive nanofiber composite with superhydrophobicity wasfabricated by ultrasonication induced carbon nanotubes (CNTs) decoration onto the polymer nanofiber,followed by methyltrichlorosilane (MTS) modification. The introduction of CNTs and polysiloxanederived from MTS improved the superhydrophobicity, conductivity, thermal stability and mechanicalproperties of the nanofibrous membrane. The superhydrophobicity and electrical conductivity could bemaintained during the cyclic stretching. The nanofiber composite membrane could be utilized toseparate the oil from the oil/water mixture regardless of pH of water, exhibiting a largeflux, highefficiency and good recyclability.

Numerical study on flow and heat transfer behavior of vortex and film composite cooling

Li Liang,Du Changhe,Chen Xiuxiu,Wang Jiefeng,Fan Xiaojun 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.6

The complete vortex and film composite cooling model is established to study the flow and heat transfer behavior. Influences of coolant Reynolds number, film hole diameter and inject angle on vortex and film composite cooling property are thoroughly discussed. Results show that the vortex nozzle coolant mass flux increases along the vortex chamber axial direction, while the film hole coolant mass flux and blowing ratio decrease along the vortex chamber axial direction. The internal heat transfer intensity will increase along the vortex chamber axial direction. The adiabatic film cooling efficiency decreases downstream due to counter rotating vortex pairs (CRVP) lift off wall effects. The coolant rotational velocity in vortex chamber increases with the increasing Reynolds number, thus leading to obvious heat transfer enhancement. An increase in Reynolds number results in an increase in CVRP intensity, hence the adiabatic film cooling efficiency will turn lower. The coolant rotational velocity and internal heat transfer intensity will decrease with the increase of film hole diameter. The CRVP intensity and film hole jet coolant mass flux increases with the increasing film hole diameter, leading to an increase in adiabatic film cooling efficiency. The rotational coolant flow and heat transfer intensity are not sensitive to inject angle. As the inject angle increases, the CRVP intensity changes little and the inject coolant owns larger inclined angle with gas mainstream flow, therefore the adiabatic film cooling efficiency will increase.

A numerical method for estimating the elastic modulus of recycled concrete

Xinzhu Zhou,Jianjun Zheng,Ting Chen,Jian Zhang,Chuanyang Wang,Jiefeng Wu 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.3

This paper aims at presenting a numerical method for estimating the elastic modulus of recycled concrete with crushed aggregates. In the method, polygonal aggregates following a given sieve curve are generated, and placed into a square simulation element with the aid of the periodic boundary condition and the overlap criterion of two polygonal aggregates. The mesostructure of recycled concrete is reconstructed by embedding an old interfacial transition zone (ITZ) layer inside each recycled aggregate and by coating all the aggregates with a new ITZ layer. The square simulation element is discretized into a regular grid and a representative point is selected from each sub-element. The iterative method is combined with the fast Fourier transform to evaluate the elastic modulus of recycled concrete. After the validity of the numerical method is verified with experimental results, a sensitivity analysis is conducted to evaluate the effects of key factors on the elastic modulus of recycled concrete. Numerical results show that the elastic modulus of recycled concrete increases with the increase of the total aggregate content and the elastic moduli of old and new ITZ but decreases with increasing the replacement ratio of recycled aggregate and the thicknesses of old and new ITZ. It is also shown that, for a replacement ratio of recycled aggregate smaller than 0.3, the elastic modulus of recycled concrete is reduced by no more than 10%.

An Unstructured Kinetic Model to Study NaCl Effect on Volatile Ester Fermentation by Candida etchellsii for Soy Sauce Production

Jie Feng,Xiao-Bei Zhan,Dong Wang,Li-Min Zhang,Chi Chung Lin 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.2

Salt-tolerant aromatic yeast is an important microorganism arising from the solid state fermentation of soy sauce. The fermentation kinetics of volatile esters by Candida etchellsii was studied in a batch system. The data obtained from the fermentation were used for determining the kinetic parameters of the model. Batch experimental results at four NaCl levels (180, 200, 220, and 240 g/L) were used to formulate the parameter estimation model. The kinetic parameters of the model were optimized by specifically designed Runge-Kutta Genetic Algorithms (GA). The resulting mathematical model for volatile ester production, cell growth and glucose consumption simulates the experimental data well. The resulting new model was capable of explaining the behavior of volatile ester fermentation. The optimized parameters (μo, Xmax, Ki, α, β, YX/S, m, and YP/S) were characterized by a correlation of functions assuming salinity dependence. The kinetic models optimized by GA describe the batch fermentation process adequately, as demonstrated by our experimental results.