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Mingming Li,Hua F. Xiao,Ming Cheng 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.2
Active damping (AD) methods with extra feedback provide a high rejection of the resonance peak caused by LCL-filters, and have the advantages of simple implementation and strong robustness. Among them, capacitor current proportional-feedback AD has been proved to be effective and robust with only a proportional calculation. However, a large capacitive current pulsation restricts the detection accuracy. Based on a theoretical derivation, the same damping effect but with a better rejection of grid harmonic can be obtained by grid-side inductor voltage differential-feedback AD. However, the measured inductor voltage usually contains a parasitic resistance voltage that is difficult to separated, and it deteriorates the performance of LCL-filters. To solve this problem, a differential-negative proportional method based on the vector relationship between the voltages of the grid-side inductor and its parasitic resistance is proposed in this paper. In addition, the influence of control delays is considered and a solution is given. Experimental results based on a 3 kW LCL-type grid-connected inverter prototype are provided to verify the effectiveness of the proposed method.
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Mingming Li,Chunlin Li,Chao Wu,Youlong Luo 보안공학연구지원센터 2015 International Journal of Grid and Distributed Comp Vol.8 No.2
Currently, the efficiency of the existing focused crawlers is not high because of their unsatisfactory precision. In this article, we analyze the URL analysis methods of the existing focused crawlers, and propose a URL analysis algorithm based on the semantic content and link clustering in cloud environment. In this algorithm, the download URLs are clustered with the philosophy of clustering on the basis of VSM to improve the precision of the focused crawler according to the correlation between download URLs and new URLs. The algorithm is evaluated on Heritrix3.10 compared with Best First Search algorithm and Shark Search algorithm. The experiment results demonstrate that the algorithm proposed can collect web pages related to the given topic accurately and effectively.Moreover, the algorithm has a good ability of learning which proves the possibility of this algorithm.
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Li Li,Huan Wang,Fenglin Hua,Mingming Wang,Yuanshuo Zhang,Hui Xi,Jing Yang,Zhiwang Yang,Ziqiang Lei 한국고분자학회 2021 Macromolecular Research Vol.29 No.9
An effective ternary organic-inorganic composite flame retardant of reduced graphene oxide-poly-dopamine@graphitic carbon nitride@10-(2,5-dihydroxyphenyl)- 10-H-9-oxa-10-phosphaphenanthrene-10-oxide (RGO-PDA@g-C3N4@ODOPB) was successfully fabricated by co-precipitation method. Its property concerning the intrinsic flame retardancy and the mechanical performance was well studied when it was used as co-additives in combination with ammonium polyphosphate (APP) in epoxy resin (EP) samples. The surface morphology and the structure of RGO-PDA@g-C3N4 @ODOPB were characterized by SEM, and the molecular structure and compositions were investigated by FT-IR, powder XRD and 1H NMR. TGA, limit oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test, and SEM were also used to investigate the thermal properties and flame retardancy of materials. As expected, the flame retardancy of EP was significantly heightened after adding of RGOPDA@ g-C3N4@ODOPB composites. It showed that with the 20% adding of RGO-PDA@g-C3N4@ODOPB/APP into EP led to the decreasing of the peak heat release rate and the total heat release at 78% and 62.5%, respectively. Meanwhile, the LOI value of the EP composites was as high as 29% and reached UL-94 V-0 rate. It was deemed that the excellent flame retardancy was attributed to the forming of compact and stable carbon layer, which was being catalytic carbonization by APP existed in the RGO-PDA@g-C3N4@ODOPB/APP composites. At the same time, the non-combustible gas released from thermal cracking of g-C3N4 during the combustion also benefited the flame retardant performance of EP.
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A Study on the Development Trends of Chinas Winter Sports Market in the Post COVID-19 Era
Mingming LI(이밍밍),Chen Lyu(려신) 한국체육과학회 2023 한국체육과학회지 Vol.32 No.6
The Winter sports market in China has been severely impacted by the COVID-19 pandemic. However, as China enters the postpandemic era, the market shows signs of growth and recovery. This study examines the development trends of Chinas winter sports market in the post COVID-19 era and predicts its trajectory. Through the utilization of big data methodologies and advanced text analysis techniques, data from various sources, including digital platforms and government reports, are collected and analyzed. The analysis reveals the primary emerging trends shaping the market. These trends encompass a strong emphasis on digitalization and innovative technologies, a focus on promoting consumption and driving market growth, the integration of winter sports and tourism, and the significance of regional development and collaboration. These findings provide valuable insights for policymakers, industry professionals, and researchers interested in understanding the evolving landscape of Chinas winter sports market.
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Jiang Mingming,Alugongo Gibson Maswayi,Xiao Jianxin,Li Congcong,Ma Yulin,Li Tingting,Cao Zhijun,Liu Dasen 아세아·태평양축산학회 2021 Animal Bioscience Vol.34 No.4
Objective: This study aimed to investigate the effect of stocking density on the behavior, productivity, and metabolism of periparturient Holstein cows as well as calf performance. Methods: A total of 48 periparturient cows were randomly assigned into three groups at 28 days (±3 days) before their expected calving date. The stocking densities of the groups, relative to the standard cubicle and feed bunk number, were i) 80% (13 cows), ii) 100% (16 cows), and iii) 120% (19 cows). Lying and rumination behavior was recorded using electronic data loggers and HR-Tags from d -21 (“d-” means days before calving) until the calving date, d 0. Lying time was assessed to determine the diurnal total hours spent lying per day. Rumination time was averaged in 2 hours interval periods over 24 hours during the experimental period. Results: Cows in the 80% group spent more time lying and ruminating between d -21 and d -7 and tended to ruminate more between d -14 and d 0. Calcium levels tended to be higher for cows in the 80% group, no other observable differences were found in monitored blood parameters. Moreover, 3.5% fat corrected milk and energy corrected milk yields were higher in 80% group in the first month of lactation. No other observable differences were found in the yield and composition of colostrum and milk in the first 10 months of lactation. The growth and performance of calves in the first week of life was not affected by stocking density of the dams. Conclusion: We concluded that lower stocking density may increase lying and ruminating behavior of prepartum Holstein cows. However, this did not translate into improved productivity and metabolism. Objective: This study aimed to investigate the effect of stocking density on the behavior, productivity, and metabolism of periparturient Holstein cows as well as calf performance.Methods: A total of 48 periparturient cows were randomly assigned into three groups at 28 days (±3 days) before their expected calving date. The stocking densities of the groups, relative to the standard cubicle and feed bunk number, were i) 80% (13 cows), ii) 100% (16 cows), and iii) 120% (19 cows). Lying and rumination behavior was recorded using electronic data loggers and HR-Tags from d -21 (“d-” means days before calving) until the calving date, d 0. Lying time was assessed to determine the diurnal total hours spent lying per day. Rumination time was averaged in 2 hours interval periods over 24 hours during the experimental period.Results: Cows in the 80% group spent more time lying and ruminating between d -21 and d -7 and tended to ruminate more between d -14 and d 0. Calcium levels tended to be higher for cows in the 80% group, no other observable differences were found in monitored blood parameters. Moreover, 3.5% fat corrected milk and energy corrected milk yields were higher in 80% group in the first month of lactation. No other observable differences were found in the yield and composition of colostrum and milk in the first 10 months of lactation. The growth and performance of calves in the first week of life was not affected by stocking density of the dams.Conclusion: We concluded that lower stocking density may increase lying and ruminating behavior of prepartum Holstein cows. However, this did not translate into improved productivity and metabolism.
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Research on Improved Schwarz Arc Model Considering Dynamic Arc Length
Li Jingli,Yuan Hao,Xu Mingming,Tian Fenglan,Wang Zijian,Ren Junyue 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3
Establishing an accurate arc model is significant for simulating arc characteristics and research on arc high impedance fault detection. This paper firstly expounds arc physical properties, and theoretically analyzes the relationship between arc length and arcing voltage. Then, the magnetohydrodynamic model of AC arc is established by COMSOL Multiphysics, and the influence of arc length on electric field intensity, temperature, voltage and current of arc plasma is analyzed. Secondly, based on the influence of arc length on arc, an improved Schwarz arc model considering dynamic arc length is proposed, which not only considers arc time constant and dissipated power as functions of arc conductance, but also introduces arc length. The comparison error of the arcing voltage of the improved Schwarz model with actual measured data is 5%. In addition, the arcing voltage is compared with calculation results of theoretical formula and simulation results of magnetohydrodynamic model, which verifies the validity of improved arc model. Finally, the improved arc model is compared with Mayr model, Schwarz model and cybernetic model from the perspectives of arc voltage and current, and analysis shows that the improved arc model is reasonable in simulating arcing voltage, arc steady-state combustion voltage, and current zero-break characteristics.
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Mingming Fei,Licheng Wang,Yalin Li,Yushuai Wei 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.4
The Jurassic marine sequences of the Qiangtang Basin in the northern part of the Tibet Plateau have the best petroleum exploration prospect. The prototype basin has undergone multi-stage and complicated tectonic events since the Cretaceous, especially the mid-Cretaceous tectonic event and the Cenozoic uplift of Tibetan Plateau. However, little information about the impact of these tectonic events on petroleum preservation has been done. In this paper, the burial and thermal histories modeling using vitrinite reflectance (Ro) are used to characterize the impact. The results showed that there is a regional falling of palaeotemperature in the Qiangtang Basin during the mid-Cretaceous indicating a regional tectonic event caused by the collision between Lhasa and Qiangtang blocks. However, the Cenozoic tectonic event caused by the uplift of Tibetan Plateau since 30 Ma was only recorded in the Southern Qiangtang Depression and not obvious in the Northern Qiangtang Depression, which indicates that uplift-denudation caused by the mid-Cretaceous tectonic event was extensive in whole Qiangtang Basin and more significant to the hydrocarbon accumulation than those in the Cenozoic. The event could damage the previously formed hydrocarbon traps and caused the leaking of cap-rocks for the dramatically denudation especially in the Southern Qiangtang Depression. We speculated that the Northern Qiangtang Depression has the lower thickness of denudation and barely influenced by the Cenozoic tectonic events and thus is primary exploration target for gas or gas hydrate.
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Kinetics of Horseradish Peroxidase-Catalyzed Nitration of Phenol in a Biphasic System
( Mingming Kong ),( Yang Zhang ),( Qida Li Runan Dong ),( Haijun Gao ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.2
The use of peroxidase in the nitration of phenols is gaining interest as compared with traditional chemical reactions. We investigated the kinetic characteristics of phenol nitration catalyzed by horseradish peroxidase (HRP) in an aqueous-organic biphasic system using n-butanol as the organic solvent and NO<sub>2</sub> - and H<sub>2</sub>O<sub>2</sub> as substrates. The reaction rate was mainly controlled by the reaction kinetics in the aqueous phase when appropriate agitation was used to enhance mass transfer in the biphasic system. The initial velocity of the reaction increased with increasing HRP concentration. Additionally, an increase in the substrate concentrations of phenol (0-2 mM in organic phase) or H<sub>2</sub>O<sub>2</sub> (0-0.1 mM in aqueous phase) enhanced the nitration efficiency catalyzed by HRP. In contrast, high concentrations of organic solvent decreased the kinetic parameter V<sub>max</sub>/K<sub>m</sub>. No inhibition of enzyme activity was observed when the concentrations of phenol and H<sub>2</sub>O<sub>2</sub> were at or below 10 mM and 0.1 mM, respectively. On the basis of the peroxidase catalytic mechanism, a double-substrate ping-pong kinetic model was established. The kinetic parameters were K<sub>m</sub> <sup>H2O2</sup> = 1.09 mM, K<sub>m</sub> <sup>PhOH</sup> = 9.45 mM, and V<sub>max</sub> = 0.196 mM/min. The proposed model was well fit to the data obtained from additional independent experiments under the suggested optimal synthesis conditions. The kinetic model developed in this paper lays a foundation for further comprehensive study of enzymatic nitration kinetics.
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An adaptive Kriging reliability analysis method based on novel condition likelihood function
Mingming Lu,Huacong Li,Linxiong Hong 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
To carry out the reliability analysis, whose performance functions are presented in a nonlinear form, many studies propose the reliability analysis methods involving the active Kriging model. Though some learning functions have been developed to refine the Kriging model around the limit state surface (LSS) effectively, most of them rely on the Kriging predictor and its variance. In this research, a new learning function, formed by the combination of the conditional likelihood function and clustering constrain function through adaptive weight coefficient, is raised to reconstruct Kriging by the candidate samples near the LSS. With the conditional likelihood function, the likelihood that the Kriging predictor reaches the LSS mainly contributes to the selection of the best next point. Three numerical applications with different complexities are used to investigate the validity of the proposed reliability method. In addition, the performance of the proposed reliability method is tested by an engineering application.
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