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RISS 인기검색어
- 검색키워드
- 저자 : Huafeng Liu (검색결과 4 건)
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Maximum Likelihood-based Multi-innovation Stochastic Gradient Method for Multivariable Systems
Huafeng Xia,Yan Ji,Yanjun Liu,Ling Xu 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.3
This paper considers the parameter estimation problems for multivariable controlled autoregressive moving average systems. By means of the decomposition technique, a multivariable system is transformed into several identification submodels according to the number of outputs. A maximum likelihood extended stochastic gradient identification algorithm is derived for identifying each subsystem by using the maximum likelihood principle. In order to improve the convergence rate, a multivariable maximum likelihood-based muti-innovation stochastic gradient algorithm is proposed. The proposed algorithms can generate more accurate parameter estimates compared with the multivariable extended stochastic gradient algorithm. The illustrative simulation results show that the proposed methods work well.
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Preparation and enzymatic activity of Fe3O4-IDA-Ni/NAD kinase magnetic catalyst
Changxia Liu,Yadi Yang,Huafeng Gao,Xiaoshuang Bai,Zheng-Jun Li 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.3
The use of oxidoreductases as biocatalysts for industrial production of valuable compounds has a strong demand for NADP. Herein, we prepared superparamagnetic NAD kinase catalyst to synthesize NADP in vitro. First, Fe3O4 particles were synthesized through a solvothermal method, followed by the chemical modification with epichlorohydrin, iminodiacetic acid, and Ni2+ to yield functional Fe3O4 sub-microspheres. Subsequently, NAD kinase of Escherichia coli was overexpressed and immobilized on to the surface of magnetic sub-microspheres. The immobilized NAD kinase was used to catalyze the conversion of NAD to NADP in a cell-free system. Under optimal condition, the conversion ratio of NAD reached 91.7% and remained at 86.3% after repeated use for five times. Our study revealed that the novel magnetic NAD kinase catalyst possessed favorable properties for magnetic manipulation and NADP production.
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Zengcheng Yu,Yuqin Xiao,Huafeng Tian,Shilin Liu,Jian Zeng,Xiaogang Luo 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.10
Using agricultural wastes (bagasse) and polyol derived from soy oil as raw materials to develop biodegradable rigid polyurethane foams (RPUFs) is beneficial to reduce the dependence on petroleum resources and promote the sustainable socioeconomic and environmental development. This study focuses on bagasse as a functional filler to improve and control the mechanical properties and biodegradability of the RPUFs. With the increasing levels of bagasse content, the density and mechanical properties of RPUFs increase. The biodegradation of RPUFs has a greater enhancement compared to the foam without bagasse, and all bio-foams have excellent thermal insulation properties. All changes in foam performance are due to the fact that the active hydroxyl groups on bagasse react with excess isocyanate to form urethane, which affects the structure of RPUFs. In this study, scientific design and molecular regulation theory were applied to improve the utilization value of bagasse and develop high-performance biodegradable RPUFs for thermal insulation materials
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Novel Method to Improve the Microstructure and Mechanical Properties of 45 Steel
Tao Gu,Shuaixin Zhang,Yuhong Zhao,Yurong Yang,Huafeng Liu,Li Wu,Jianhua Liu,Hua Hou 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4
Aiming at the problems of poor hardenability and low mechanical strength of 45 steel after quenching and tempering atnormal pressure, 45 steel was quenched and tempered under high pressure. The microstructure of 45 steel after high pressurequenching and tempering was analyzed by optical microscope, scanning electron microscope and transmission electronmicroscope, its hardness and compressive strength were tested by hardness tester and electronic universal testing machine,and compared with samples treated by the same process under atmospheric pressure. The results show that uniform andcompact tempered sorbite can be obtained after high pressure quenching and tempering of 45 steel, and the precipitatedgranular carbides are finely dispersed, thus improving the mechanical properties of 45 steel. Under a pressure of 3 GPa,quenching at 900 °C for 15 min and 550 °C for 60 min tempering, the hardness and compressive yield strength of 45 steelwere 36.3 HRC and 971 MPa, respectively, which were respectively 25.17% and 20.77% higher than the corresponding valuesobtained with the same process under atmospheric pressure quenching and tempering. This work provides a new method toeffectively improve the mechanical properties of 45 steel.
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