Research on Influence of Matrix Component on the Mechanical Behavior of Multiaxial Warp-knitted Composites

Jiawei Chen,Xiaoping Gao,Ke Zhao,Wei Wu 한국섬유공학회 2022 Fibers and polymers Vol.23 No.11

The mass ratio of curing agent to epoxy resin is one of the important factors affecting the behavior of matrix andcomposites. In this paper, the solution of curing agent to epoxy resin with different mass ratio (0.25, 0.30, 0.35 and 0.40) wasselected as matrix, quadriaxial warp-knitted fabric was selected as reinforcement, and the composites were manufactured byapplying vacuum assisted film infusion. Then the tensile and bending behavior of the composites was experimentallyinvestigated, and the curing degree and failure mechanism of the composites were analyzed with respect to thethermodynamic properties and the microscopic failure morphologies. The optimal mass ratio was obtained by applyingnonlinear fitting and verified by experiment, and a mathematical model was derived to predict the relationship between thestrength and the mass ratio. The results showed that the thermal stability, curing degree, tensile and bending strength of thespecimens increase firstly and then decrease with increase of the mass ratio. According to the tensile and bending strengthresults, the optimum mass ratio were obtained as 0.31 and 0.33 by applying nonlinear fitting to the experiment data. Theresults could lay a theoretical foundation for optimizing the mass ratio of matrix components, and improve the strength ofcomposites.

Investigation on the Influence of Temperature on Starting Torque of Magnetic Fluid Seal

Jiawei Chen,Decai Li,Du Hao 한국자기학회 2018 Journal of Magnetics Vol.23 No.3

The widest application of magnetic fluid is in magnetic fluid seals. The starting torque varying with temperature of magnetic fluid seal has limited its application in special seal field such as military industry. This paper firstly measure the starting torque of magnetic fluid seals under different temperature conditions from −55 oC to 70 ℃ after holding for 2.5 hours in a closed environment with uniform temperature. And the law of starting torque with temperature change is studied experimentally. The results show that the starting torque of the magnetic fluid seal changes unobvious at 25 ℃ or higher temperature. The starting toque of magnetic fluid seal increases with the decrease of temperature, and the causes of which are analyzed. The results of this study provide experimental and theoretical reference for reducing the staring torque of magnetic fluid seal in low temperature environment.

The Stability, and Efficacy Against Penicillin-Resistant Enterococcus faecium, of the Plectasin Peptide Efficiently Produced by Escherichia coli

( Xin Chen ),( Yaoan Wen ),( Ling Li ),( Jiawei Shi ),( Zhe Zhu ),( Yuwen Luo ),( Yun Li ),( Rui Chen ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.7

Plectasin, the first defensin extracted from a fungus (the saprophytic ascomycetePseudoplectania nigrella), is attractive as a prospective antimicrobial agent. The purpose of this study was to establish a bacterium-based production system and evaluate the antimicrobial activity of the resulting plectasin. A gene encoding plectasin, with the codon preference ofEscherichia coli, was optimized based on its amino acid sequence, synthesized using genesplicing with overlap extension PCR, and inserted into the expression vector pGEX-4T-1. The fusion protein was expressed in the soluble fraction of E. coli and purified using glutathione Stransferaseaffinity chromatography. Plectasin was cleaved from the fusion protein with thrombin and purified by ultrafiltration. The purified plectasin showed strong, concentrationdependent antimicrobial activity against gram-positive bacteria, including antibiotic-resistant bacteria, especially penicillin-resistant Enterococcus faecium. This antimicrobial activity wasequal to chemically synthesized plectasin and was maintained over a wide range of pH and temperatures. This soluble recombinant expression system in E. coli is effective for producing plectasin at a relatively lower cost, and higher purity and efficiency than prior systems, and might provide a foundation for developing a large-scale production system. Overall, plectasin shows potential as a novel, high-performance, and safe antibiotic for the treatment of refractory diseases caused by drug-resistant bacterial strains.

Crack identification in short shafts using wavelet-based element and neural networks

Jiawei Xiang,Xuefeng Chen,Lianfa Yang 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.5

The rotating Rayleigh-Timoshenko beam element based on B-spline wavelet on the interval (BSWI) is constructed to discrete short shaft and stiffness disc. The crack is represented by nondimensional linear spring using linear fracture mechanics theory. The wavelet-based finite element model of rotor system is constructed to solve the first three natural frequencies functions of normalized crack location and depth. The normalized crack location, normalized crack depth and the first three natural frequencies are then employed as the training samples to achieve the neural networks for crack diagnosis. Measured natural frequencies are served as inputs of the trained neural networks and the normalized crack location and depth can be identified. The experimental results of fatigue crack in short shaft is also given.

Removal of norfloxacin by combining persulfate with nano zero-valent iron modified by activated carbon and copper nanocomposite

Jiawei Zhang,Yong Chen,Jingzhuo Liang,Hui Xu 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.5

Study on damage detection software of beam-like structures

Jiawei Xiang,Zhansi Jiang,Yanxue Wang,Xuefeng Chen 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.1

A simply structural damage detection software is developed to identification damage in beams. According to linear fracture mechanics theory, the localized additional flexibility in damage vicinity can be represented by a lumped parameter element. The damaged beam is modeled by waveletbased elements to gain the first three frequencies precisely. The first three frequencies influencing functions of damage location and depth are approximated by means of surface-fitting techniques to gain damage detection database of forward problem. Then the first three measured natural frequencies are employed as inputs to solve inverse problem and the intersection of the three frequencies contour lines predict the damage location and depth. The DLL (Dynamic Linkable Library) file of damage detection method is coded by C++ and the corresponding interface of software is coded by virtual instrument software LabVIEW. Finally, the software is tested on beams and shafts in engineering. It is shown that the presented software can be used in actual engineering structures.

Crack identification in short shafts using wavelet-based element and neural networks

Xiang, Jiawei,Chen, Xuefeng,Yang, Lianfa Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.5

The rotating Rayleigh-Timoshenko beam element based on B-spline wavelet on the interval (BSWI) is constructed to discrete short shaft and stiffness disc. The crack is represented by non-dimensional linear spring using linear fracture mechanics theory. The wavelet-based finite element model of rotor system is constructed to solve the first three natural frequencies functions of normalized crack location and depth. The normalized crack location, normalized crack depth and the first three natural frequencies are then employed as the training samples to achieve the neural networks for crack diagnosis. Measured natural frequencies are served as inputs of the trained neural networks and the normalized crack location and depth can be identified. The experimental results of fatigue crack in short shaft is also given.

Static and vibration analysis of thin plates by using finite element method of B-spline wavelet on the interval

Xiang, Jiawei,He, Zhengjia,He, Yumin,Chen, Xuefeng Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.25 No.5

A finite element method (FEM) of B-spline wavelet on the interval (BSWI) is used in this paper to solve the static and vibration problems of thin plate. Instead of traditional polynomial interpolation, the scaling functions of two-dimensional tensor product BSWI are employed to construct the transverse displacements field. The method combines the accuracy of B-spline functions approximation and various basis functions for structural analysis. Some numerical examples are studied to demonstrate the proposed method and the numerical results presented are in good agreement with the solutions of other methods.

Study on damage detection software of beam-like structures

Xiang, Jiawei,Jiang, Zhansi,Wang, Yanxue,Chen, Xuefeng Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.1

A simply structural damage detection software is developed to identification damage in beams. According to linear fracture mechanics theory, the localized additional flexibility in damage vicinity can be represented by a lumped parameter element. The damaged beam is modeled by wavelet-based elements to gain the first three frequencies precisely. The first three frequencies influencing functions of damage location and depth are approximated by means of surface-fitting techniques to gain damage detection database of forward problem. Then the first three measured natural frequencies are employed as inputs to solve inverse problem and the intersection of the three frequencies contour lines predict the damage location and depth. The DLL (Dynamic Linkable Library) file of damage detection method is coded by C++ and the corresponding interface of software is coded by virtual instrument software LabVIEW. Finally, the software is tested on beams and shafts in engineering. It is shown that the presented software can be used in actual engineering structures.

Size-Controlled Silver Nanoparticles Confined in Ordered Mesoporous Silica and Their Enhanced Catalytic Activities

Xiaofei Zhou,Jiawei Wan,Yefeng Liu,Di Liu,Hong Wang,Xiaoyong Lai,Yanzhao Zou,Guo Lin,Jian Chen 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.9

A cooperative assembly route has been developed, by which silver nanoparticles with controlled sizes are incorporated into the channels of ordered cubic mesoporous silica (KIT-6) with different pore sizes (4.3–6.4 nm). The samples were characterized by XRD, TEM, FT-IR, UV-Vis and N2 physisorption. The pore wall of mesoporous silica can efficiently confine the growth of silver nanoparticles within the channels and their average sizes decreased with the pore size reduction of KIT-6. Catalytic activities of the resultant Ag/KIT-6-x (x stands for hydrothermal temperature) composite for reducing harmful organic dye Rhodamine B (Rh B) by sodium borohydride (NaBH4) were investigated. All the Ag/KIT-6 composite samples show great catalytic activities, among which Ag/KIT-6-80 with higher loading and smaller size of Ag nanoparticles exhibits higher catalytic activity than those of Ag/KIT-6-60 and Ag/KIT-6-100.