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418 results on '"Zhu Minggang"'

123. The study on thermal expansion of sintered [Sm.sub.2][Co.sub.17] magnets

Author

Li, Anhua, Li, Wei, Wang, Huijie, Zhu, Minggang, Pan, Wei, and Lee, Dong

Subjects
Cobalt -- Analysis, Cobalt -- Thermal properties, Anisotropy -- Analysis, Anisotropy -- Thermal properties, Sintering -- Analysis, Sintering -- Thermal properties, Business, Electronics, Electronics and electrical industries
Published
2009

124. Combining active control and synchrophasing for vibration isolation of a floating raft system: An experimental demonstration.

Author

Yang, Tiejun, Wu, Lei, Li, Xinhui, Zhu, Minggang, Liu, Zhigang, and Brennan, Michael J

Subjects
ACTIVE noise & vibration control, VIBRATION isolation, HYDRAULIC control systems, RAFTS, ACOUSTIC radiation, RISER pipe
Abstract

Vibration isolation of a floating raft system typically found in a marine application is of concern in this paper. Housed on the raft are electrical motors each driving two counter rotating shafts with eccentric masses attached. An experimental study is described in which vibration transmitted to a large-scale, laboratory-based hull-like structure is attenuated by using three measures. They are, the use of vibration isolators between the raft and the hull-like structure, adjustment of the phase of the electrical supply between the motors to minimize vibration transmitted through the isolators, and the application of an active vibration control system using hydraulic actuators placed in parallel with the isolators. The results show that this combination of measures is extremely effective at reducing the vibration transmission to the hull-like structure, and consequent reduction the sound radiation. It is more effective than the application of any of the vibration control measures applied by themselves. [ABSTRACT FROM AUTHOR]

Published
2021
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142. Effects of Oxygen Contents on the Microstructures of High-Performance SmCo 2:17-Type Sintered Permanent Magnet

Author

Zhu Minggang, Hongsheng Chen, Kuikui Song, Sun Wei, Li Wei, Nengjun Yu, and Fang Yikun

Subjects
Magnetization, Materials science, Magnet, Demagnetizing field, Analytical chemistry, Coercivity, Type (model theory), Magnetic hysteresis, Temperature coefficient, Intensity (heat transfer)
Abstract

Precipitation-hardened Sm 2 Co 17 based sintered permanent magnet has been attracting a great deal of attention due to its distinguished high temperature magnetic properties, extremely low temperature coefficient, excellent corrosion resistance and oxidation resistance [1]–[3]. In this study, magnetic properties and microstructures of Sm-Co 17 -based sintered permanent magnets with the nominal composition Sm(Co bal Fe 0.245 Cu 0.07 Zr 0.02 ) 7.8 have been investigated. The magnets were prepared using the conventional powder metallurgy method, in which the pulverizing of powder is jet-milling and ball-milling, respectively. The typical demagnetization curves of the sintered magnets obtained by jet-milled and ball-milled powders are shown in Fig. 1. The corresponding magnetic properties of the magnets made of ball-milled powders (the magnet is designated as $\mathrm{M}_{\mathrm{b}})$ , are: the remanent magnetic polarization intensity J r =1.157 T (11.57 kGs), the intrinsic coercivity $\mathrm{H}_{\mathrm{c}\mathrm{j}}=752$ kA/m (9.46 kOe), and the maximum magnetic energy product $(\text{BH})_{\max}=221$ kJ/m3(27.8 MGOe), while that of jet-milled powder (the magnet is designated as M j ) are: $\mathrm{J}_{\mathrm{r}}=1.146$ T (11.46 kGs), $\mathrm{H}_{\mathrm{c}\mathrm{j}}=2497$ kA/m (31.37 kOe), and $(\text{BH})_{\max}=251.7$ kJ/m3(31.64 MGOe). The cause of such a significant difference between the two kinds of samples is expected as the existed deviation in effective chemical compositions, due to the different oxygen contents introduced during fabrication for the two kinds of magnets: ∼2800 and ∼1300 ppm.

Published
2016

147. Active Control of Broadband Noise Inside a Car Using a Causal Optimal Controller.

Author

Zhu, Liping, Yang, Tiejun, Li, Xinhui, Pang, Lihong, and Zhu, Minggang

Subjects
ACTIVE noise control, NOISE control, QUANTUM coherence
Abstract

This paper investigates active broadband noise control inside vehicles with a multichannel controller. The noncausal inversion of a practical nonminimum-phase secondary path is formulated, and its influence on noise-reduction performance is analyzed. Based on multiple coherence between reference signals and undesired noise, a novel formulation for identifying primary paths with correlated excitation signals is presented and a causal optimal controller is proposed. Meanwhile, the proposed controller can be used as an accurate predictor to estimate the maximal achievable noise reduction and provide a reference to improve the control systems. The robustness of the proposed algorithm is examined by varying the uncertainty of primary paths. Finally, the performance of the proposed causal optimal controller is validated using the data measured in a car. The results show that the proposed algorithm outperforms traditional algorithms and achieves a significant broadband noise reduction in time-invariant systems. [ABSTRACT FROM AUTHOR]

Published
2019
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148. Optimizing temperature coefficient of Sm2Co17-type magnets through adjusting the isothermal aging process

Author

Wang, Chao, Hu, Die, Li, Qiangfeng, Fang, Yikun, Zheng, Meng, Wang, Lei, Chen, Hongsheng, Zhao, Lei, Wang, Haizhou, Zhu, Minggang, and Li, Wei

Abstract

The high-temperature magnetic performance and microstructure of Sm1–xGdx(CobalFe0.09Cu0.09Zr0.025)7.2(x = 0.3, 0.5) magnets were investigated. With the isothermal aging time decreasing from 11 to 3 h, the temperature coefficient of intrinsic coercivity in the temperature range of 25–500 °C, β25–500 °C, was optimized from −0.167%/°C to −0.112%/°C for x = 0.3 magnets. The noticeable enhancement (∼33%) of temperature stability is correlated with the increased content of 1:5H cell boundary phase and its relatively high Curie temperature as well. However, for the x = 0.5 magnet, it is found that the presence of Sm5Co19phases and wider nanotwin variants hinder the formation of 1:5H cell boundary phase. The insufficient 1:5H is not beneficial to the proper redistribution of Cu in cell boundary, making the x = 0.5 magnet difficult to achieve higher temperature stability. Consequently, the approach of adjusting the isothermal aging process can offer guidance for attaining superior magnetic performance in the temperature range from 25 to 500 °C for Gd-substituted Sm2Co17-type magnets.

Published
2024
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149. Optimization of microstructures and magnetic properties of Sm(CobalFe0.227Cu0.07Zr0.023)7.6magnets by sintering treatment

Author

Song, Kuikui, Sun, Wei, Fang, Yikun, Wang, Shuai, Yu, Nengjun, Zhang, Meiling, Zhu, Minggang, and Li, Wei

Abstract

Magnetic properties and microstructures of Sm(CobalFe0.227Cu0.07Zr0.023)7.6sintered magnets were optimized by sintering treatment. Results show that the knee-point magnetic field, Hknee, is twofold up and the intrinsic coercivity Hcjincreases by 40%, ranging from 21.64 to 30.39 kOe at the cost of a little decrease of Brfrom 10.84 to 10.31 kGs with sintering temperature decreasing from 1488 to 1473 K. And the average domain width is narrower and more uniform for the specimen sintered at 1473 K than that of the specimen sintered at 1488 K. It is impressive that the density of lamellar phase increases from ∼0.050 to ∼0.058 nm−1with the sintering temperature decreasing from 1488 to 1473 K. Moreover, the average cellular size is about ∼84 nm for the magnets sintered at 1473 K, which is 80% of that of the magnets sintered at 1488 K (∼97 nm). And the cell boundary width of the magnets sintered at 1473 K (∼7 nm) is only half average width of the magnets sintered at 1488 K (∼14 nm). It is found that the Cu content in the cell boundaries is much higher (∼17 at%) in the magnets sintered at 1473 K compared to that of the magnets sintered at 1488 K (∼10 at%). It can be concluded that smaller cells and narrower cell boundaries together with higher gradient of Cu content are key points for obtaining the optimum Hkneeand Hcj.

Published
2024
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150. Microstructure, microchemistry, and micro-magnetism of Dy grain boundary diffused (Nd, Ce)–Fe–B magnets

Author

Xiao, Yifei, Zhang, Lele, Liu, Tao, Sun, Qisong, Song, Xiaolong, Fang, Yikun, Li, Anhua, Zhu, Minggang, and Li, Wei

Abstract

The microstructure of (Nd, Ce)–Fe–B sintered magnets with different diffusion depths was characterized by a magnetic force microscope, and the relationship between the magnetic properties and the local structure of grain boundary diffused magnets is discussed. The domains perpendicular to the c-axis (easy magnetization direction) show a typical maze-like pattern, while those parallel to the c-axis show the characteristics of plate domains. The significant gradient change is shown in the concentration of Dy with the direction of diffusion from the surface to the interior. Dy diffuses along grain boundaries and (Dy, Nd)2Fe14B layer with a high anisotropy field formed around the grains. Through in-situelectron probe micro-analysis/magnetic force microscopy (EPMA/MFM), it is found that the average domain width decreases, and the proportion of single domain grains increases as diffusion depth increases. This is caused by both the change of concentration and distribution of Dy. The grain boundary diffusion process changes the microstructure and microchemistry inside the magnet, and these local magnetism differences can be reflected by the configuration of the magnetic domain structure.

Published
2024
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