Rolling bearing composite fault diagnosis method based on EEMD fusion feature

Yixin Zhao,Yao Fan,Hu Li,Xuejin Gao 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.9

Aiming at the problem that the composite fault vibration signal of rolling bearing is complex and it is difficult to effectively extract the impact characteristics of the composite fault, a composite fault diagnosis method of rolling bearing based on multi-scale fuzzy entropy feature fusion is proposed. Compared with traditional fault feature extraction methods that can only extract single fault feature information, this method can increase the discrimination of composite fault features, effectively separate multiple composite fault features, and more comprehensively characterize composite fault feature information. First, the signal is processed by EEMD, getting a series of IMF components. Secondly, the energy and kurtosis index of the IMF component are calculated, the appropriate IMF component is selected through the correlation coefficient to obtain a new time series, the multi-scale fuzzy entropy is calculated, and feature fusion performed. Finally, the least square support vector machine is used to diagnose the fault of the fusion feature. The method is verified by a mechanical failure simulation test bench. The experimental results show that this method can quantitatively characterize the data information of fault signal, improve the anti-interference ability, have good feature extraction ability of composite fault of rolling bearings, and can effectively identify the type of composite fault. Compared with the method using multi-scale fuzzy entropy, energy and kurtosis index alone, the accuracy of fault diagnosis increases by 8.12 % and 11.65 %, respectively.

Spatial–Temporal Clustering and Optimization of Aircraft Descent and Approach Trajectories

Zhao Yang,Rong Tang,Yixin Chen,Bing Wang 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.6

This study presents a procedure for the spatial–temporal clustering and optimization of aircraft descent and approach trajectories. First, the spatial–temporal similarity between two trajectories is defined. Clustering analysis are conducted to identify the prevailing trajectories. The clustering centers obtained based on spatial–temporal distance are compared with those obtained based on the traditional Euclidean distance. Second, a multi-objective optimization model is established to minimize fuel consumption, aircraft emission and noise impact considering flight constraints. The Pareto solution that has the highest similarity with the prevailing trajectories is selected as the final optimized trajectory. The performance indicators of the optimized trajectory are compared with the average values of historic trajectories. It is found that travel time, fuel consumption and noise impact for the optimized trajectory are reduced by 5.34%, 0.96% and 11.86%, respectively. The percentages are 0.96%, 1.32%, 9.18%, 3.54% and 4.00% for CO2, SOx, NOx, CO and HC, respectively. Also, the performance indicators for the two clustering centers based on spatial–temporal distance are generally closer to average performance of original trajectories, as well as those of the optimized trajectories, as compared with the two clustering centers based on Euclidean distance. The spatial–temporal clustering methods may help to discover the valuable information that lies in those indicators associated with features reflected in time dimension.

A Virtual Resistance Based Reactive Power Sharing Strategy for Networked Microgrid

Yixin Zhu,Baoquan Liu,Feng Wang,Fang Zhuo,Yangjie Zhao 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Different from the traditional microgrid with a common ac bus, networked microgrid always suffers more serious reactive power sharing problems due to its complex inner configurations. In such a situation, the reactive power sharing errors among distributed generation (DG) units can’t be eliminated effectively. Thus, an advanced reactive power sharing strategy that employs communication and virtual resistance control is hereby proposed for networked microgrid. First of all, the relation between reactive power output and virtual impedance regulation (VRR) is discussed. After that, communication is introduced to assign reactive power reference to each DG unit for their respective VRR, which is able to compensate the mismatch in network. The method is immune to the load change during the regulation stage, and also to the time delay in communication channels. From the small signal analysis, it also can be seen that in the designed regulation range, VRR has no significant effect on the system stability. The feasibility and effectiveness of the proposed strategy are validated by the simulation and real time digital simulator (RTDS) test results from a 50 kVA networked microgrid system.

Attitude Control Design for Hypersonic Reentry Vehicles Subject to Control Direction Reversal via Sliding Mode Approach

Yixin Ding,Zongyi Guo,Yonglin Han,Jiaqi Wang,Jianguo Guo,Zequn Liu,Jinlong Zhao 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.2

This paper investigates the control direction reversal issue for the attitude control design for hypersonic reentry vehicles, and proposes a novel sliding mode control law which addresses the control direction switching and strong robustness requirement simultaneously. Firstly, the disturbance observer is introduced to estimate the unmatched uncertainties in the attitude model of hypersonic reentry vehicles, and then a periodic function-involved sliding mode control is presented and the bounded stability of the closed-loop system is guaranteed via Lyapunov stability theory. The merits of the proposed method lie in that the closed-loop system is stable even under the unknown control direction reversal, and the unmatched uncertainties can be addressed by the disturbance observer. Finally, the simulation verifies the effectiveness and superiority of the proposed control.

Design and Implementation of a Universal System Control Strategy Applicable to VSC-HVDC Systems

Yue Zhao,Libao Shi,Yixin Ni,Zheng Xu,Liang-Zhong Yao 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper proposes a universal system control strategy for voltage source converter (VSC) based high voltage direct current (HVDC) systems. The framework of the designed control strategy consists of five layer structures considering the topology and control characteristics of the VSC-HVDC system. The control commands sent from the topmost layer can be transmitted to the next layer based on the existing communication system. When the commands are sent to each substation, the following transmission of commands between the four lower layers are realized using the internal communication system while ignoring the communication delay. This hierarchical control strategy can be easily applied to any VSC-HVDC system with any topology. Furthermore, an integrated controller for each converter is designed and implemented considering all of the possible operating states. The modular-designed integrated controller makes it quite easy to extend its operating states if necessary, and it is available for any kind of VSC. A detailed model of a VSC-HVDC system containing a DC hub is built in the PSCAD/EMTDC environment. Simulation results based on three operating conditions (the start-up process, the voltage margin control method and the master-slave control method) demonstrate the flexibility and validity of the proposed control strategy.

Experimental and theoretical investigation of a new multistage countercurrent melt crystallizer with inclined sieve plates

Shui Wang,Guojing Zhao,Yizhen Du,Yixin Qu 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.6

A new multistage countercurrent melt crystallizer with sieve plates is proposed that combines the advantages of the TNO column crystallizer and the inclined column crystallizer. With the naphthalene-indene solid solution system, the purification process of organic materials in the new multistage countercurrent melt crystallizer with sieve plates under total reflux was investigated. Two of the influencing factors on the separation and purification performance in the new multistage countercurrent melt crystallizer with sieve plates were crystal settling velocity and crystal breakage, which were controlled by stirring speed, the sieve plates, the angle of the sieve plates, the diameter of the pores, particle sedimentation area, and the number of plates. The results of this study show that the optimum stirring speed was determined to be 20 rpm, sieve plates can obviously increase the separation and purification effect, the optimum angle of the sieve plates was determined to be 45o, the optimum diameter of the pores was determined to be 8 mm, the optimum particle sedimentation area was determined to be 0.5 r, and two plates in the crystallizer were shown to be the best.

Characteristics of Ground Surface Settlement of Double-Line Adjacent Metro Construction in Sandy Cobble Stratum: A Case Study of Beijing Airport Line

Xianjie Hao,Zhuowen Sun,Yixin Zhao,Yiqiang Kang,Qian Zhang,Jinguo Cheng,Yingnan Wei,Zeyu Chen 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.11

As a long-term urban transportation infrastructure, the stability of metro construction is very important. With the continuous expansion of urban metro network, metro adjacent construction is more and more frequently encountered. In this paper, taking the double-line adjacent construction problems encountered during excavation of Beijing New Airport Line metro in sandy cobble stratum as an example, the surface settlement caused by excavation of single-line metro and double-line adjacent metro is studied by computed tomography scan, electron microscope scanning, laboratory mechanical tests, orthogonal inversion and numerical simulation and other methods. The results show that 1) the sandy cobble particle size and sandy cobble distribution of Beijing sandy cobble samples are relatively dispersed, and the sandy cobble particle size is from 3 to 20 cm, of which the largest proportion is the sandy cobble particle size from 5 to 8 cm. 2) The internal friction angle of Beijing sandy cobble samples with different moisture content is from 27° to 40°, which is much larger than that of other soil samples. Even at the post-peak stage, the shear stress of some sandy cobble samples does not gradually tend to be gentle, but continuously increases or has secondary peaks. 3) For the excavation of double-line adjacent metro, the maximum settlement difference and the impact range of excavation are proposed as indicators to investigate the degree of interaction of the adjacent metro. 4) The results of numerical orthogonal analysis show that the width of surface settlement zone increases significantly with the increase of tunnel diameter and spacing when excavating adjacent metro in sandy cobble stratum, but the rate of increase with tunnel diameter (from 6 m to 14 m) almost reaches 2 times of the rate of increase with the spacing (from 3 m to 15 m). 5) The maximum settlement value of sandy cobble stratum increases with the increase of tunnel diameter and decreases with the increase of spacing. The orthogonal linear analysis shows that the influence of tunnel diameter on the maximum settlement value is much greater than the spacing. The maximum settlement increases with the increase of tunnel diameter, which is about 3.6 times of that with the decrease of spacing.

High-Temperature Oxidation Behavior of NiCoCrAlY Coatings Deposited by Laser Cladding on 304 Stainless Steel

Yuxin Li,Jinhao Nie,Yixin Yang,Peikang Bai,Hongjian Zhang,Zhanyong Zhao,Shouzheng Wei,Jie Cai,Qingfeng Guan 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.2

To improve the high-temperature resistance of the key hot-end parts of the steam turbine, NiCoCrAlY coatings were depositedon a 304 stainless steel substrate by laser cladding. The microstructure and high-temperature oxidation behavior of theNiCoCrAlY coatings were analyzed. The results showed that the NiCoCrAlY coatings contained γ/γ′ and β phases, and themicrostructure was mainly composed of elongated columnar crystals. In addition, after 100 h of oxidation at three differentoxidation temperatures (750, 850 and 950 °C), the coatings showed a relatively low oxidation rate, which was approximatelya quarter of the oxidation rate of the substrate. At the same time, the protective Cr2O3scales were formed on the coatingsurface. When the oxidation temperature was 850 °C, the FeCr2O4spinel formed and internal oxidation zone appeared,when the oxidation temperature reached 950 °C, the FeCr2O4spinel gathered in the local area on the surface of the Cr2O3scale and the internal oxidation was aggravated. In other words, as the oxidation temperature increased, the Fe element inthe matrix formed the FeCr2O4spinel, which accelerated the consumption of Cr element in the coatings and reduced theoverall oxidation resistance of the NiCoCrAlY coatings.

Single-cell characterization of macrophages in uveal melanoma uncovers transcriptionally heterogeneous subsets conferring poor prognosis and aggressive behavior

Li Ke,Sun Lanfang,Wang Yanan,Cen Yixin,Zhao Jingting,Liao Qianling,Wu Wencan,Sun Jie,Zhou Meng 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-

Uveal melanoma (UM) is the most frequent primary intraocular malignancy with high metastatic potential and poor prognosis. Macrophages represent one of the most abundant infiltrating immune cells with diverse functions in cancers. However, the cellular heterogeneity and functional diversity of macrophages in UM remain largely unexplored. In this study, we analyzed 63,264 single-cell transcriptomes from 11 UM patients and identified four transcriptionally distinct macrophage subsets (termed MΦ-C1 to MΦ-C4). Among them, we found that MΦ-C4 exhibited relatively low expression of both M1 and M2 signature genes, loss of inflammatory pathways and antigen presentation, instead demonstrating enhanced signaling for proliferation, mitochondrial functions and metabolism. We quantified the infiltration abundance of MΦ-C4 from single-cell and bulk transcriptomes across five cohorts and found that increased MΦ-C4 infiltration was relevant to aggressive behaviors and may serve as an independent prognostic indicator for poor outcomes. We propose a novel subtyping scheme based on macrophages by integrating the transcriptional signatures of MΦ-C4 and machine learning to stratify patients into MΦ-C4-enriched or MΦ-C4-depleted subtypes. These two subtypes showed significantly different clinical outcomes and were validated through bulk RNA sequencing and immunofluorescence assays in both public multicenter cohorts and our in-house cohort. Following further translational investigation, our findings highlight a potential therapeutic strategy of targeting macrophage subsets to control metastatic disease and consistently improve the outcome of patients with UM.

Sr-doping enhanced electrical transport and thermionic emission of single crystal 12CaO·7Al2O3 electride

Xin Zhang,Qi Feng,Jiping Zhao,Hong-liang Liu,Jichao Li,Yixin Xiao,Fan Li,Qingmei Lu 한국물리학회 2020 Current Applied Physics Vol.20 No.1

Sr-doped single crystals (C1-xSx)12A7:e− (x=0, 0.01, 0.02, 0.03) were successfully fabricated by floating zone method. It is found that Sr-doping decreases the reduction time from 30 h to 20 h. The maximum emission current of (C1-xSx)12A7:e− is greatly improved by 50% than that of the un-doped. The DFT calculations show Srdoping in C12A7 contributed to the free O2− in the cages spread out, leading to a short reduction time; increase the “window” between two adjacent cages that is conducive to the electrons in cages to escape. And the work function of the (C1-xSx)12A7:e− is lower than that of C12A7:e−.