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Li Weiwei,Zheng Wenyue,Ren Lulu,Li Huan,Zhao Xuetong,Wang Can,Li Jianying 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.1
Medium and high voltage XLPE cables were widely used in urban distribution network. The electric-thermal eff ect of the cable conductor and water in the running environment are two important factors that cause ageing of cable insulating material. In this work, accelerated electrical test (AET) and accelerated water tree test (AWTT) on 10 kV XLPE cable were carried out for 1440 h, 2880 h and 4320 h, respectively. The physicochemical and dielectric properties of both aged and unaged XLPE samples were tested. Physicochemical investigation of Fourier Transform Infrared (FTIR) spectroscopy and X-Ray Diff raction (XRD) show that higher carbonyl groups index, and lower crystallinity of the XLPE insulating materials were generated in AWTT process than that in AET process. The thermal decomposition process of the AWTT XLPE are complicated, presenting a multi-peak phenomenon in the diff erential thermogravimetry (DTG) curve. The insulating strength of the samples after AWTT is monotonically decreased from 23.03 kV to 21.74 kV with ageing time. The dielectric properties show that the permittivity and dielectric loss of AWTT samples increased more severely than that of AET samples, with a new dielectric relaxation peak appearing at around 100 Hz. The combination of physicochemical and dielectric results reveals that AWTT process leads to more serious degradation for XLPE insulating materials. A schematic illustration is given to elucidate the development of micro defects in XLPE during the AET and AWTT processes.
XIAOJUAN LIANG,WEIWEI HUAN,XIANGCHEN JIA,HAIJUN DING,YUXIANG YANG,XIANGNONG LIU 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.4
Pure nano-Fe3O4 and cobalt-doped nano-Fe3O4 particles are successfully synthesized by co-precipitation method using tetramethylammonium hydroxide (TMAOH) as alkali. Several key factors that may affect preparation are carefully discussed such as alkali concentration, alkali dosage, reaction temperature, iron salt solution concentration and dispersant agents. Such nano-Fe3O4 particles prepared have good dispersibility and a very narrow size distribution with the average diameter about 38 nm, which are proved to be cubic spinel Fe3O4 crystal by XRD pattern. It is also found that the addition of PEG-4000 surfactant can improve the dispersibility of nanoparticles. In our work, effects of cobalt dopant concentration on magnetic properties of cobalt-doped nano-Fe3O4 are also discussed. The result shows that the coercivity of cobalt-doped nanoparticles changes greatly with the variation of cobalt dopant concentration. The maximum coercivity reaches as high as 1628 Oe, which is very meaningful for preparation of materials with high coercivity.
Yi-Xiang Zhu,WEIWEI HUAN,Ling-yun Yao,Wan-Guo Yu,Ruihua Jiao,Yan-Hua Lu,Renxiang Tan 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.6
Fumigaclavine C (FC), which is produced by Aspergillus fumigatus, is a conidiation-associated ergot alkaloid with significant medical benefits. However, its application is restricted by low yields from submerged cultures. In this study, the technical feasibility of using molasses as a cost-effective ingredient for FC production in a two-stage culture of A. fumigatus was evaluated. The results indicated that molasses supplementation significantly enhanced FC accumulation by promoting conidiation and up-regulating hydroxymethylglutaryl-CoA reductase activity. Via the optimization of the two-stage process in the presence of molasses, FC production in shake flasks reached 226.9 mg/L, which was approximately three times that in the original medium (75.9 mg/L). The use of molasses as a cost-effective ingredient for FC fermentation was also successfully reproduced in a lab-scale bioreactor system in which the maximum FC production reached 215.0 mg/L. The FC production obtained in this study is the highest ever reported. This increased efficiency will enable large-scale production of FC and extend the application of molasses as a low-cost substrate for producing other conidiation-related secondary metabolites.