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Determination of Hund's coupling in 5d oxides using resonant inelastic x-ray scattering
Yuan, Bo,Clancy, J. P.,Cook, A. M.,Thompson, C. M.,Greedan, J.,Cao, G.,Jeon, B. C.,Noh, T. W.,Upton, M. H.,Casa, D.,Gog, T.,Paramekanti, A.,Kim, Young-June American Physical Society 2017 Physical Review B Vol.95 No.23
<P>We report resonant inelastic x-ray scattering (RIXS) measurements on ordered double-perovskite samples containing Re5+ and Ir5+ with 5d(2) and 5d(4) electronic configurations, respectively. In particular, the observedRIXS spectra of Ba2YReO6 and Sr2MIrO6 (M = Y, Gd) show sharp intra-t(2g) transitions, which can be quantitatively understood using a minimal 'atomic' Hamiltonian incorporating spin-orbit coupling. and Hund's coupling J(H). Our analysis yields lambda = 0.38(2) eV with J(H) = 0.26(2) eV for Re5+ and lambda = 0.42(2) eV with J(H) = 0.25(4) eV for Ir5+. Our results provide sharp estimates for Hund's coupling in 5d oxides and suggest that it should be treated on equal footing with spin-orbit interaction in multiorbital 5d transition-metal compounds.</P>
Yuanbo Xu,Zongyan Cai,Xiaoyan Cai,Kai Ding 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6
Previous research has shown that minimum entropy deconvolution (MED) is an effective technique for detecting impulse-like signals, such as the bearing fault and gear fault signals. However, some problems still exist in this technique. With the aim of overcoming these limitations, in this paper, an enhanced MED called multipoint optimal minimum entropy deconvolution adjusted (MOMEDA) is proposed. MOMEDA can succeed in detecting multiple impulses. Unfortunately, according to some simulations and real tests in this work, the results of applying this technique to the fault signals directly were grudgingly acceptable but not very satisfactory, especially under a harsh working condition. This means that MOMEDA is a little sensitive to intensive background noise and vibration interference. To overcome this drawback, a novel mode decomposition method, named time-varying filtering for empirical mode decomposition (TVFEMD), is applied to adaptively eliminate background noise and vibration interference prior to using MOMEDA. According to this proposed method, the weak bearing fault features can be identified clearly. The proposed approach is utilized in bearing fault detection of a spur gearbox and the results show its superiority and effectiveness.
Yuanbo Chu,Changchun Huo,Fu Zhang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.9
The barrel pitching system (BPS) is a typical electro-hydraulic servo control system. In actual service, the primary control difficulty is how to effectively restrain the influence of the barrel’s unbalanced torque (UT) and bumpy road (BR). Furthermore, with the extension of service life, the gradual depletion behavior, such as erosion wear (EW), will induce the core parameter’s decay of the servo valve. All of which will seriously deteriorate the barrel pitching system’s control performance. For this purpose, a new cascade control method based on active disturbance rejection control (ADRC) and proportional integral derivative (PID) for the vehicle mounted and unbalanced BPS is proposed. In this paper, the working mechanism is analyzed and the mathematical model of the BPS is established. Moreover, the sensitivity equation of BR and EW about the BPS is constructed and their influence are respectively dissected, then the evolution model and law of core parameters under the condition of BR and EW are deduced and researched. In the process of controller design, the correction element and isolation element are, respectively, used for compensating and suppressing the influence of EW and BR, then the ADRC and PID are synthesized to obtained the cascade control for the BPS. Finally, the effectiveness of the proposed method is verified through simulation experiments.
New discovery of pulse arc shape of sheet tungsten electrode
Li Yuanbo,Ye Tao 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5
The synergistic effect of sheet tungsten electrode and pulse current can further reduce the heat input, effectively regulate the arc plasma jet behavior, change the arc flow characteristics, and produce a new arc shape which the arc would shrink at the electrode and expand in the middle of the arc column. The main reason for the new arc shape is the interaction between cathode and anode jets; when these two meet in the middle of the arc column, the velocity decreases significantly and results in a stagnation layer. The intensity of the cathode jet changes with the peak current, argon flow rate, and arc length, causing the stagnation layer to migrate along the arc length direction.
Combined effect of fine aggregate and silica fume on properties of Portland cement pervious concrete
Zhang, Yuanbo,Zhang, Wuman,Zhang, Yingchen Techno-Press 2019 Advances in concrete construction Vol.8 No.1
Portland cement pervious concrete has been expected to have good water permeability, mechanical properties and abrasion resistance at the same time when Portland cement pervious concrete is applied to the actual vehicle pavement. In this study, the coarse aggregate and cement were replaced by the fine aggregate and the silica fume to improve actual road performance Portland cement pervious concrete. The Mechanical properties, the water permeability and the abrasion resistance of Portland cement pervious concrete were investigated. The results show that the compressive strength, the flexural strength and the abrasion resistance are increased when the fine aggregate and the silica fume are added to Portland cement pervious concrete separately. However, the porosity and the water permeability are decreased simultaneously. With assistance of silica fume and fine aggregate simultaneously, Portland cement pervious concrete could achieve a higher strength. The compressive strength, the flexural strength and the abrasion resistance of Portland cement pervious concrete mixed with 5% fine aggregates and 8% silica fume are increased by 93.1%, 65% and 65.2%, respectively. The porosity and the water permeability are decreased by 22.4% and 85% when Portland cement pervious concrete is mixed with 5% fine aggregate and 8% silica fume. Therefore, the replacement ratio of the fine aggregates and the silica fume should be considered comprehensively and determined on the premise of ensuring the water permeability coefficient.
Kun Wu,Yuanbo Xu,Na Yang,Liang Zhao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3
Fault signals measured from a damaged rolling bearing usually exhibit amplitude modulation (AM)-frequency modulation (FM) properties. For this kind of signal, the demodulation technique is an effective and common method. In the demodulation techniques, a variety of energy operator (EO) tools have been available due to high computational efficiency and self-adaptability to transient signals. Hence, an alternative energy measure is proposed in this work. The new demodulation technique is achieved by combining a multiresolution higherorder symmetric difference sequence with the envelope-derivative operator (EDO). The multiresolution higher-order symmetric envelope-derivative operator (MHOS-EDO) can extract the weak bearing fault characteristics in a harsh environment without any pre-filtering. Especially in the presence of vibration interferences, its unique energy transformation can eliminate the influence of vibration interferences, so that the vibration interferences will no longer appear in the energy spectrum. Through simulation and practical experiments, the superiority of MHOS-EDO in dealing with noise and interfering components is demonstrated. Meanwhile, the comparison results reveal that the MHOS-EDO outperforms some previous EO and some other bearing fault identification methods.