| 1. |
- Kristan, Matej, et al.
(author)
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The first visual object tracking segmentation VOTS2023 challenge results
- 2023
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In: 2023 IEEE/CVF International conference on computer vision workshops (ICCVW). - : Institute of Electrical and Electronics Engineers Inc.. - 9798350307443 - 9798350307450 ; , s. 1788-1810
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Conference paper (peer-reviewed)abstract
- The Visual Object Tracking Segmentation VOTS2023 challenge is the eleventh annual tracker benchmarking activity of the VOT initiative. This challenge is the first to merge short-term and long-term as well as single-target and multiple-target tracking with segmentation masks as the only target location specification. A new dataset was created; the ground truth has been withheld to prevent overfitting. New performance measures and evaluation protocols have been created along with a new toolkit and an evaluation server. Results of the presented 47 trackers indicate that modern tracking frameworks are well-suited to deal with convergence of short-term and long-term tracking and that multiple and single target tracking can be considered a single problem. A leaderboard, with participating trackers details, the source code, the datasets, and the evaluation kit are publicly available at the challenge website1
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| 2. |
- Liu, Shentan, et al.
(author)
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Acorus calamus L. constructed wetland-microbial fuel cell for Cr(VI)-containing wastewater treatment and bioelectricity production
- 2022
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In: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437. ; 10:3
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Journal article (peer-reviewed)abstract
- Due to chemical agents consumption and energy demand during traditional Cr(VI)-containing wastewater treatments, it is essential to explore a cost-effective and sustainable technique to remove Cr(VI) from wastewater. Combining of phytoremediation and bio-electrochemical technology, an Acorus calamus L. constructed wetland-microbial fuel cell (CW-MFC) was ingeniously designed to purify Cr(VI)-containing wastewater and harvest bioelectricity, and possible Cr(VI) removal routes were explored. Acorus calamus L. increased the CW-MFC voltage by approximately 69.75%, and maximum power density reached 36.43 mW m-2. After 9 h, the planted CW-MFC achieved Cr(VI) removal efficiency of 98.92% at an influent Cr(VI) concentration of 12.07 mg/L, while only 76.43% of the Cr(VI) was eliminated in the unplanted CW-MFC. The Cr(VI) removal was achieved mainly through bio-electrochemical reduction and plant uptake, which accounted for 53-67% and 22-33%, respectively. The addition of low concentrations of Cr(VI) improved the CW-MFC power generation, while high levels of Cr(VI) resulted in power decline. The highest maximum power density of 46.63 mW m-2 was observed when influent Cr(VI) concentration was 6.69 mg/L. The CW-MFC's Cr(VI) removal conformed to the first-order reaction kinetics, and a high rate constant of 0.2887 h-1 was achieved even at a Cr(VI) concentration of 18.21 mg/L. The main removal pathway of Cr was associated with cathodic bio-electrochemical reduction of Cr(VI) to Cr(III) and Cr(OH)3 precipitation, and the final fate of Cr was comprehensively analyzed. The obtained research results provide an important reference for the practical application of CW-MFC in Cr(VI)-containing wastewater treatment.
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| 3. |
- Zhu, Lianghong, et al.
(author)
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Phase Current Reconstruction Error Suppression Method for Single DC-Link Shunt PMSM Drives at Low-Speed Region
- 2022
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In: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 37:6, s. 7067-7081
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Journal article (peer-reviewed)abstract
- The extensive application of vector phase shift modulation method in permanent magnet synchronous motor drive systems with single dc-link current sensor results in obvious current ripple in the low-speed region. The patterns of these ripples vary greatly in different sectors, leading to nonnegligible phase current reconstruction errors. In this article, an estimation of the local average current change rate (ELAC(2)R) based reconstruction error suppression method within the switching cycle is proposed to resolve this problem. By comparing the actual and the ideal sampling points, the increase of current ripple and the reconstruction error caused by the combination of the vector phase shift and the single current sensor sampling in the low-speed region are modelled and analyzed. Then according to equivalent modelling of the current ripple between the ideal and the actual sampling points, the more accurate phase current information can be quickly obtained based on the sampling value. The compensation process is significantly simplified and the computation burden of the processor is reduced. Experimental results show that the performance of current reconstruction can be improved effectively with less harmonic content with the proposed method.
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| 4. |
- Chen, Feifan, et al.
(author)
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Dynamics Enhancement for Power Synchronization Control with Asymmetric AC Voltage Controller in Strong Grids
- 2023
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In: 2023 IEEE Conference on Control Technology and Applications, CCTA 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1066-1070
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Conference paper (peer-reviewed)abstract
- Power synchronization control (PSC) is designed for weak grid connections originally and its performance is weakened when connected to a strong grid. In this paper, an asymmetric AC voltage controller (AVC) is proposed to improve the performance of PSC in strong grids. The improvement is achieved by adding a coupling from d-axis to q-axis to the voltage control part. The effect of this d-to-q coupling is explained by small signal modeling. It is found that the asymmetric AVC gives an effective improvement in damping the low-frequency oscillation and stability robustness against the grid strengths. Theoretical analysis and experiments verify the effectiveness of the proposed asymmetric AVC.
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| 5. |
- Chen, Feifan, et al.
(author)
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Enhanced Q-Axis Voltage-Integral Damping Control for Fast PLL-Synchronized Inverters in Weak Grids
- 2024
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In: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 39:1, s. 424-435
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Journal article (peer-reviewed)abstract
- The phase-locked loop (PLL) is a commonly used synchronization control method for grid-tied inverters. The PLL-synchronized inverters tend to have poor stability robustness with weak grid interconnections, especially when the PLL is designed with a high control bandwidth. To tackle this challenge, this article proposes an enhanced q-axis voltage-integral damping control, which not only stabilizes PLL-synchronized inverters in weak grids but also lifts the restriction on PLL bandwidth. This superior feature enables inverters to operate stably in ultraweak grids and with a superior transient response. The experimental tests confirm the performance of the method with 400-Hz PLL bandwidth under a short-circuit ratio of 1.28 of the grids.
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| 6. |
- Chen, Feifan, et al.
(author)
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Impedance Modeling for Quadrature-Axis Active Damping of PLL Dynamics
- 2022
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In: 2022 IEEE 23RD WORKSHOP ON CONTROL AND MODELING FOR POWER ELECTRONICS (COMPEL 2022). - : IEEE.
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Conference paper (peer-reviewed)abstract
- When grid-following voltage source converters (VSCs) operate in inverter mode, the phase-locked loop (PLL) dynamics introduce a negative-real-part impedance, which may lead to the instability of the closed-loop system, especially in a weak-grid connection. This undesirable property of the PLL may be offset by so-called active damping. Nevertheless, the interaction between the active damping and the adverse PLL impact is not fully understood. To this end, the properties of different active-damping methods are analyzed, with the focus on the q-to-q coupling of the input admittance. One important finding is that adding an integrator to the q-axis active damper can improve the system performance in a weak-grid connection. Simulations and experimental results verify the theoretical analysis.
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| 7. |
- Chen, Feifan, et al.
(author)
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Pitfalls of Using Passivity Index to Guide Grid-connected Inverter Control Design in Low-frequency Region
- 2023
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In: 2023 IEEE Energy Conversion Congress and Exposition, ECCE 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 758-764
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Conference paper (peer-reviewed)abstract
- The main purpose of this article is to elaborate on the pitfalls of using the frequency-domain passivity theories in grid-inverter interactions within the low-frequency range. It mainly covers the relationship between the passivity index and stability, considerations for control design guided by optimizing the passivity index, and issues with a negative infinite index. It is advised to exercise caution when applying passivity theory in the low-frequency range. These conclusions have been substantiated through numerical and experimental studies.
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| 8. |
- Zou, Yangfan, et al.
(author)
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Characterizations of dissimilar refill friction stir spot welding 2219 aluminum alloy joints of unequal thickness
- 2022
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In: JOURNAL OF MANUFACTURING PROCESSES. - : ELSEVIER SCI LTD. - 1526-6125. ; 79, s. 91-101
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Journal article (peer-reviewed)abstract
- Refill friction stir spot welding (RFSSW) is a relatively new solid-state spot welding technology. Reliability of the joint is mainly affected by the macroscopic characteristics and microstructure evolution. This method can be applied to weld plates with different thicknesses. However, the temperature distribution, microstructure and mechanical properties of joints with different thicknesses remain unclear. In the present study, 2 mm thick 2219-O aluminum alloy plates were successfully welded to 2219-C10S plates of various thicknesses (4 mm, 10 mm and 14 mm) via the RFSSW method. The effect of lower 2219-C10S plate thickness on the temperature distribution, microstructure, mechanical properties and fracture behavior of RFSSWed joints was evaluated by both experi-mental and simulation methods. The results indicated that the peak temperature decreased, and the isothermal zone became larger as the thickness of the lower plate increased. A relatively flat hook configuration could be identified in the cross-section of the joint fabricated using a 4 mm thick lower plate, while an upward hook was observed for the joints fabricated using a 10 and 14 mm thick lower plate. Lower plate thickness scarcely affected hardness of the upper plate, but HAZ width of the lower plate becomes narrower with increasing lower sheet thickness. The lap-shear load of the joints fabricated using a lower plate thicknesses of 4, 10 and 14 mm was 7.4 +/- 0.3 kN, 6.7 +/- 0.2 kN, and 6.4 +/- 0.4 kN, respectively, all of them failed as a plug fracture mode. According to the simulation results, tensile and compressive stresses were mainly distributed along the direction of the force on both sides of the weld nugget. While shear stress was primarily distributed in the direction perpendicular to the external force. Furthermore, bending stress was also identified in the joints, which increased with the in -crease of the lower plate thickness.
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