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Wei Chen,Shan He,Jing Cheng,Zhi Yuan,Xueqin Yan 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.2
Under weak grid conditions, there is a strong nonlinear coupling between phase-locked loops (PLLs) and the doubly-fed induction generators (DFIGs), and the influence of its dynamic characteristics on system stability cannot be ignored. For a system to be stable, the dynamic properties must be considered. First, based on instantaneous power theory, the subsynchronous frequency component of power oscillation in a three-phase symmetrical system with the participation of a PLL is deduced. Second, the PLL transient stability is studied under two power grid structures. Third, to connect with the power grid model, a DFIG with a PLL structure is established, and the phase disturbance of the PLL is used as the excitation signal. In the rotor current inner loop and the voltage outer loop transfer processes, the PLL phase disturbance component plays a role. A d-axis structure block diagram of the current loop with the PLL phase disturbance component is constructed, and the disturbance transfer function is deduced. The influence mechanism of the PLL control parameters on system power oscillation is investigated. Finally, the modeling simulation verifies the validity of the theoretical analysis
Taichi Chen,Hongzhi Xia,Shixiu Cui,Xueqin Lv,Xueliang Li,Yanfeng Liu,Jianghua Li,Guocheng Du,Long Liu 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.5
Vitamin K2 (menaquinone) is an essential vitamin existing in the daily diet, and menaquinone-7 (MK- 7) is an important form of it. In a recent work, we engineered the synthesis modules of MK-7 in Bacillus subtilis, and the strain BS20 could produce 360 mg/l MK-7 in shake flasks, while the methylerythritol phosphate (MEP) pathway, which provides the precursor isopentenyl diphosphate for MK-7 synthesis, was not engineered. In this study, we overexpressed five genes of the MEP pathway in BS20 and finally obtained a strain (BS20DFHG) with MK-7 titer of 415 mg/l in shake flasks. Next, we optimized the fermentation process parameters (initial pH, temperature and aeration) in an 8-unit parallel bioreactor system consisting of 300-ml glass vessels. Based on this, we scaled up the MK-7 production by the strain BS20DFHG in a 50-l bioreactor, and the highest MK-7 titer reached 242 mg/l. Here, we show that the engineered strain BS20DFHG may be used for the industrial production of MK-7 in the future.
Effects of Exocellobiohydrolase CBHA on Fermentation of Tobacco Leaves
Xu Xueqin,Wang Qianqian,Yang Longyan,Chen Zhiyan,Zhou Yun,Feng Hui,Zhang Peng,Wang Jie 한국미생물·생명공학회 2024 Journal of microbiology and biotechnology Vol.34 No.8
The quality of tobacco is directly affected by macromolecular content, fermentation is an effective method to improve biochemical properties. In this study, we utilized CBHA (cellobiohydrolase A) glycosylase, which was expressed by Pichia pastoris, as an additive for fermentation. The contents of main chemical components of tobacco leaves after fermentation were determined, and the changes of microbial community structure and abundance in tobacco leaves during fermentation were analyzed. The relationship between chemical composition and changes in microbial composition was investigated, and the function of bacteria and fungi in fermentation was predicted to identify possible metabolic pathways. After 48 h of CBHA fermentation, the contents of starch, cellulose and total nitrogen in tobacco leaf decreased by 17.60%, 28.91% and 16.05%, respectively. The microbial community structure changed significantly, with Aspergillus abundance decreasing significantly, while Filobasidum, Cladosporium, Bullera, Komagataella, etc., increased in CBHA treated group. Soluble sugar was most affected by microbial community in tobacco leaves, which was negatively correlated with starch, cellulose and total nitrogen. During the fermentation process, the relative abundance of metabolism-related functional genes increased, and the expressions of cellulase and endopeptidase also increased. The results showed that the changes of bacterial community and dominant microbial community on tobacco leaves affected the content of chemical components in tobacco leaves, and adding CBHA for fermentation had a positive effect on improving the quality of tobacco leaves.
Research on the application of nanocomposite materials in children's physical exercise equipment
Huanxiang Ding,Xueqin Wang,Xiaodao Chen Techno-Press 2023 Advances in nano research Vol.14 No.3
Combating the worldwide environmental threat of plastic waste pollution has become a priority. Plastic pollution has the potential to impact land, rivers, and seas, since many marine and terrestrial organisms have perished as a result of plastic's non-biodegradability and soil dangers. For this consumption, it seems required to manufacture and use new renewable resources. Renewable materials for diverse applications have been created utilizing nanotechnology, which may replace conventional materials for children's activities and sports equipment. This study investigates and suggests that nanotechnology-based materials be replaced with conventional materials to save the environment in manufacturing equipment for children's physical activities. On the basis of the mechanical sciences, a stability study of the bending behavior of small-scale structures will be performed for the various recommended materials.
Modeling of active magnetic bearing in rotating payload satellite considering shaft motion coupling
Yatao Zhao,Xueqin Chen,Feng Wang,Cheng Wei,Yang Zhao 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11
This paper establishes the refined dynamic model of the five degree-of-freedom active magnetic bearing used in the earth-oriented satellite system with an unbalanced rotating payload based on the more refined air gap change model for stator motion. The disturbance effects of the thrust active magnetic bearing and the coupling effects of shaft motion are analyzed by the equivalent stiffness and damping model, especially when the satellite system is in the fine pointing phase. Numerical simulation results are provided to verify the accuracy of the proposed simplified stiffness and damping model, the disturbance term effects on active magnetic bearing, and the significance of the refined magnetic bearing dynamic model for improving the payload working ability in the fine pointing phase.
Qingxian Jia,Huayi Li,Yingchun Zhang,Xueqin Chen 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.2
This paper addresses the problem of observer-based sensor fault reconstruction for discrete-time systems subject to external disturbances via a descriptor system approach. First, an augmented descriptor system is formulated by letting the sensor fault term be an auxiliary state vector; then a discrete-time descriptor state observer is constructed to achieve concurrent reconstructions of original system states and sensor faults. Sufficient and necessary conditions for the asymptotic stability of the proposed observer are explicitly provided. To broaden its application scope, less restrictive existence conditions are further discussed. Further, sufficient conditions for the robust stability of the proposed observer are formulated in terms of linear matrix inequalities (LMIs) that can be conveniently solved using LMI optimization techniques. After that, an extension of the proposed linear approach to discrete-time nonlinear systems with Lipschitz constraint is investigated. At last, two illustrative examples are given to verify the effectiveness of the proposed techniques.