| 1. |
- Cao, Hongru, et al.
(författare)
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Unsupervised domain-share CNN for machine fault transfer diagnosis from steady speeds to time-varying speeds
- 2022
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Ingår i: Journal of manufacturing systems. - : Elsevier. - 0278-6125 .- 1878-6642. ; 62, s. 186-198
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Tidskriftsartikel (refereegranskat)abstract
- The existing deep transfer learning-based intelligent fault diagnosis studies for machinery mainly consider steady speed scenarios, and there exists a problem of low diagnosis efficiency. In order to overcome these limitations, an unsupervised domain-share convolutional neural network (CNN) is proposed for efficient fault transfer diagnosis of machines from steady speeds to time-varying speeds. First, a Cauchy kernel-induced maximum mean discrepancy based on unbiased estimation is developed for improving the efficiency and robustness of feature adaptation. Secondly, an unsupervised domain-share CNN is constructed to simultaneously extract the domain-invariant features from the source domain and the target domain. Finally, adjustable and segmented balance factors are designed to flexibly weigh the distribution-adaptation loss and cross-entropy loss to improve diagnosis accuracy and transferability. The proposed method analyzes raw vibration signals collected from bearings and gears under different rotating speeds. Results of case studies show that the proposed method can achieve higher diagnosis accuracy, faster convergence, and better robustness than the reported methods, which demonstrates its potential applications in machine fault transfer diagnosis from a steady speed condition to a time-varying speed condition.
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| 2. |
- Song, Qiang, et al.
(författare)
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Leader-following synchronization of coupled homogeneous and heterogeneous harmonic oscillators based on relative position measurements
- 2019
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Ingår i: IEEE Transactions on Control of Network Systems. - : IEEE. - 2325-5870. ; 6:1, s. 13-23
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the leader-following synchronization problem for a network of coupled harmonic oscillators by utilizing the relative position measurements between neighboring nodes, where the node dynamics can be either identical or nonidentical. For a homogeneous network with the same node dynamics, two types of first-order observer-based protocols are proposed to achieve leader-following synchronization in the network under some necessary and sufficient conditions, including some synchronization criteria for the homogeneous network subject to parameter uncertainty. For a heterogeneous network with different node dynamics, an output regulation approach is applied to solve the leader-following synchronization problem for the nominal network, based on which the robust synchronization of the uncertain network is investigated with an allowable bound being estimated for parameter uncertainties. Numerical examples are given to illustrate the correctness and the feasibility of the theoretical analysis.
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| 3. |
- Sumaila, U. Rashid, et al.
(författare)
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WTO must ban harmful fisheries subsidies
- 2021
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 374:6567, s. 544-544
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Wang, Jiaqi, et al.
(författare)
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Dynamic Response and Failure Analysis of Underground Openings to Oblique Wave Incidence
- 2024
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Ingår i: International Journal of Geomechanics. - : American Society of Civil Engineers (ASCE). - 1532-3641 .- 1943-5622. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- In deep underground mine, besides the high static in situ stress, openings such as stopes, drifts, and shafts in underground mine are also frequently subjected to dynamic waves coming from blasting and earthquake. The interactions of these waves with the opening boundaries can be under arbitrary incident angles and thus would induce different damages. In order to investigate the dynamic response of openings under the oblique incidence of blasting load, numerical modeling of wave incidence to a rectangular opening at different incident angles and the associated dynamic failure was carried out under various in situ stress states. The numerical model established by the discrete element code PFC2D was first validated against theoretical results for reflection of oblique wave incidence at the free surface at various incident angles. The simulation results showed that the reflected P wave causes spalling around the opening, and the subsequent reflected SV wave further promotes the propagation of tensile cracks. Among them, the opening with vertical wave incidence is the most seriously damaged, while wave incidence at 15° and 30° angles results in similar damage degree on the incident side of the opening. The damage of the opening at a 45° incident angle is light. With the increase of burial depth, the position of spalling at the incident side gets closer to the sidewall of the opening. When the buried depth is 1,200 m, the largest number of cracks around the opening is achieved for wave incidence at a 45° angle. This research can improve the understanding of the resulting failures from stress-wave incidence to the openings at arbitrary angles and contribute to the design of the opening in the deep underground.
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| 5. |
- Yang, Shuanghua, et al.
(författare)
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A new controllability index based on Hankel singular value
- 2020
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Ingår i: 21th IFAC World Congress. - : Elsevier. ; , s. 4662-4667
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a new controllability index based on the Hankel singular values (HSV) which is applicable for both single-input single-output (SISO) and multivariable processes. The new index quantifies the inherent performance limitation in terms of closed-loop response speed by associating it with the control effort, which is directly related to the inverse of the HSVs. It is also shown that for specific system there is a direct linear relationship between the inverse of the minimum Hankel singular value and desired closed loop pole locations. The controllability index is thereafter exemplified on several SISO examples systems to show some of its properties. Thereafter two well-known multivariable benchmark processes, quadruple tank and two-continuous-stirring-tank-reactor are used to show the effectiveness of the index. It is concluded that the index provides valuable insights to practitioners on the achievable performance of processes with actuator constraints, while being easy to use and requiring little computational effort.
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| 6. |
- Yu, Yang, et al.
(författare)
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Research of TE behaviour and compression property of porous Ni–Al–Cr intermetallic compounds in the β phase region
- 2023
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Ingår i: Journal of Materials Research and Technology. - : Elsevier Editora Ltda. - 2238-7854 .- 2214-0697. ; 25, s. 3537-3550
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Tidskriftsartikel (refereegranskat)abstract
- Ni–Al–Cr alloys in the β phase (B2–NiAl) region exhibit remarkable stability and mechanical property. Through thermal explosion (TE) reaction, Ni–Al–Cr intermetallic compounds with high porosity can be obtained. In this study, the focus lies on analyzing the macroscopic morphology, microstructure, phase distribution, TE behaviour, and the mechanical property of porous Ni–Al–Cr in the β phase region. Following the TE reaction, the Al-rich sintered product demonstrates a uniform phase composition and high porosity, reaching 44.39%. The vigorous TE reaction promotes the formation of interconnected pores, while the high porosity structure compromises the mechanical properties of the sample. Conversely, the Al-poor sintered product, due to a moderate TE reaction and low porosity structure, maintains its complete morphology and exhibits excellent compression resistance (yield stress reaching 538 MPa). This study offers valuable insights for the fabrication of porous Ni–Al–Cr materials with exceptional structure and performance.
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