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Junhong Chen,Mingwei Yan, Yong Li,Zhijian Li,Jindong Su,Bin Li,Jialin Sun 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.5
Periclase-hercynite bricks were prepared from fused or reaction-sintered hercynite. The microstructure of the obtained brickswas studied and their thermal conductivity in the simulated on-site condition was tested. The results show that the mutualdiffusion of Fe or Al from hercynite and Mg from periclase forms more pores in the material. Compared with the brickprepared from fused hercynite, the brick from reaction-sintered hercynite has smaller pore size. The thermal conductivitysimulation test of the two bricks at 1550 oC shows that the cold end temperature of the brick synthesized from the reactionsinteredhercynite is 40 oC lower than that of the brick from the fused hercynite. Thus, in consideration of reducing the shelltemperature of the cement rotary kilns, the reaction-sintered hercynite is more favorable for the production of periclasehercynitebricks.
Structure of hercynite prepared with existence of metal Fe
Junhong Chen,Dongfang Liu,Mingwei Yan, Yong Li,Jindong Su,Bin Li,Jialin Sun 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.12
In this work, raw materials analytically pure Al2O3 and analytically pure Fe2O3 were mixed in FeO: Al2O3 molar ratio of 1 : 1and pressed into specimens. The specimens were embedded in analytically pure metal Fe powders and fired slowly to 1650 oCin air atmosphere, and then soaked at 1650 oC for 5 hrs. The fired specimens were investigated by XRD, SEM, and EDS. Theresults show that the specimen synthesized at high temperatures in melting Fe is composed of hercynite and wüstite (FenO(n ≤ 1)); FenO disperses in hercynite; hercynite crystals develop well and are mostly perfect octahedron with grain size around50μm. The hercynite has Fe/Al ratio smaller than 1/2, which is non-stoichimetric. With the existence of melting Fe, althoughthe raw materials are theoretically batched according to FeO·Al2O3, FenO is still excess, so the hercynite obtained is Al-rich.
DNA-Recombinant Azurin Conjugation as a Biomemory Platform with Enhanced Sensitivity
Chen, Qi,Yoo, Si-Youl,Lee, Taek,Kim, Sang-Uk,Nam, Eun Sook,Min, Junhong,Choi, Jeong-Woo American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.11
<P>Biocomputing devices with DNA, protein/enzymes and other biomaterials have been studied to develop unconventional computing devices. However, the high sensitivity of these devices is still in doubt due to difficulty detecting the efficient electron transfer between biomolecules and the device surface. In this study, oligonucleotides were introduced to the recombinant azurin to enhance the current signal. The recombinant azurin self-assembled on the gold surface due to the formation of gold-sulfur covalent bonds. Single stranded DNA (ssDNA) sequences were further conjugated with self-assembled recombinant azurin via a chemical linker. The fabricated biofilm was confirmed by cyclic voltammetry (CV) and atomic force microscopy (AFM). Moreover, enhancement of the electrochemical signal sensitivity and durability to harsh pH conditions were achieved by conjugation with biomolecular oligonucleotides that can contain Pb2+. The biofilm consisting of DNA and recombinant azurin was further verified to be a suitable platform for biomemory. The sensitivity and durability of the biomemory platform was enhanced by simply by introducing DNA into the system, without any other labels or nanoparticles. The proposed biofilm can be applied to bioelectronics devices such as bioprocessors and biocomputers.</P>
Chen, Jianqiao,Peng, Wenjie,Ge, Rui,Wei, Junhong Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.4
The present paper addresses the optimal design of composite laminates with the aim of minimizing free-edge delamination stresses. A technique involving the application of particle swarm optimization (PSO) integrated with FEM was developed for the optimization. Optimization was also conducted with the zero-order method (ZOM) included in ANSYS. The semi-analytical method, which provides an approximation of the interlaminar normal stress of laminates under in-plane load, was used to partially validate the optimization results. It was found that optimal results based on ZOM are sensitive to the starting design points, and an unsuitable initial design set will lead to a result far from global solution. By contrast, the proposed method can find the global optimal solution regardless of initial designs, and the solutions were better than those obtained by ZOM in all the cases investigated.
Fuzzy reliability analysis of laminated composites
Chen, Jianqiao,Wei, Junhong,Xu, Yurong Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.22 No.6
The strength behaviors of Fiber Reinforced Plastics (FRP) Composites can be greatly influenced by the properties of constitutive materials, the laminate structures, and load conditions etc, accompanied by many uncertainty factors. So the reliability study on FRP is an important subject of research. Many achievements have been made in reliability studies based on the probability theory, but little has been done on the roles played by fuzzy variables. In this paper, a fuzzy reliability model for FRP laminates is established first, in which the loads are considered as random variables and the strengths as fuzzy variables. Then a numerical model is developed to assess the fuzzy reliability. The Monte Carlo simulation method is utilized to compute the reliability of laminas under the maximum stress criterion. In the second part of this paper, a generalized fuzzy reliability model (GFRM) is proposed. By virtue of the fact that there may exist a series of states between the failure state and the function state, a fuzzy assumption for the structure state together with the probabilistic assumption for strength parameters is adopted to construct the GFRM of composite materials. By defining a generalized limit state function, the problem is converted to the conventional reliability formula that enables the first-order reliability method (FORM) applicable in calculating the reliability index. Several examples are worked out to show the validity of the models and the efficiency of the methods proposed in this paper. The parameter sensitivity analysis shows that some of the mean values of the strength parameters have great influence on the laminated composites' reliability. The differences resulting from the application of different failure criteria and different fuzzy assumptions are also discussed. It is concluded that the GFRM is feasible to use, and can provide an effective and synthetic method to evaluate the reliability of a system with different types of uncertainty factors.
Jianqiao Chen,Wenjie Peng,Junhong Wei,Rui Ge 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.4
The present paper addresses the optimal design of composite laminates with the aim of minimizing free-edge delamination stresses. A technique involving the application of particle swarm optimization (PSO) integrated with FEM was developed for the optimization. Optimization was also conducted with the zero-order method (ZOM) included in ANSYS. The semi-analytical method, which provides an approximation of the interlaminar normal stress of laminates under in-plane load, was used to partially validate the optimization results. It was found that optimal results based on ZOM are sensitive to the starting design points, and an unsuitable initial design set will lead to a result far from global solution. By contrast, the proposed method can find the global optimal solution regardless of initial designs, and the solutions were better than those obtained by ZOM in all the cases investigated.
( Zhan Gao ),( Junhong Chen ),( Yuhua Xu ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.10
This article investigates the problem of opportunistic spectrum access in dynamic environment, in which the signal-to-noise ratio (SNR) is time-varying. Different from existing work on continuous feedback, we consider more practical scenarios in which the transmitter receives an Acknowledgment (ACK) if the received SNR is larger than the required threshold, and otherwise a Non-Acknowledgment (NACK). That is, the feedback is discrete. Several applications with different threshold values are also considered in this work. The channel selection problem is formulated as a non-cooperative game, and subsequently it is proved to be a potential game, which has at least one pure strategy Nash equilibrium. Following this, a multi-agent Q-learning algorithm is proposed to converge to Nash equilibria of the game. Furthermore, opportunistic spectrum access with multiple discrete feedbacks is also investigated. Finally, the simulation results verify that the proposed multi-agent Q-learning algorithm is applicable to both situations with binary feedback and multiple discrete feedbacks.
Lee, Taek,Chung, Yong-Ho,Chen, Qi,El-Said, Waleed Ahmed,Min, Junhong,Choi, Jeong-Woo American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.5
<P>We developed surface modification tools for the fabrication of a bioelectronic device which consists of a myoglobin monolayer self-assembled on an 11-MUA layer. To utilize a single protein as the active element, it was necessary to reduce protein aggregation on the protein layer in the nanobio electronic device, which was developed in our previous study and shown to display basic biomemory functions. Here, the reduction of myoglobin aggregation was accomplished by using 3-(3-cholamidopropyl) dimethylammonio-1-propanesulfonate (CHAPS) to fabricate a well-defined protein layer on the bioelectronic device. We investigated two different surface modification methods for making well oriented biofilm. The effects of CHAPS on the formation of a myoglobin layer self-assembled on an 11-MUA layer were examined by atomic force microscopy and Raman spectroscopy. The size of the myoglobin aggregates was reduced from 200 similar to 250 nm to 10 similar to 40 nm depending on treatment method. The sustaining redox property of the CHAPS treated myoglobin layer was examined using cyclic voltammetry. Using these techniques, we found that after surfactant CHAPS treatment, protein aggregation was dramatically reduced and the protein layer still maintained its inherent electrochemical properties.</P>