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The VSC-HVDC system can damp the inter-area low-frequency oscillation effectively. To enhance the ability of the VSC-HVDC supplementary control, this article proposes a unified low-frequency oscillation controller design using the robustness theory. The unified control strategy uses both the active power control and reactive power control loop of the VSC to expand the supplementary control dimensions. To design the controller, the TLS-ESPRIT identification method is used to obtain the system small signal model and the oscillation characteristic. Based on the model identified out, the linear matrix inequality method based robust control theory is applied for the controller design, and the robust controllers for active power control and reactive power control loop are both designed to improve the control effect. Finally, the simulation results show that the controller can reach better control effect and the robustness can also be guaranteed.

Real-time precise orbits of low earth orbit (LEO) satellites are becoming indispensable with the rapid development of real-time Earth observation application and LEO enhanced precise point positioning. Currently, GNSS-based precise orbit determination is a widely used method for LEO onboard navigation. However, the real-time LEO satellite orbits are usually obtained by ambiguity-float solution even when the GNSS augmentation corrections are considered. In this study, we perform LEO ambiguity-fixed multi-GNSS real-time precise orbit determination (RTPOD) based on square root information filter. One month of onboard GPS + Galileo observations from Sentinel-6A and real-time products of the Centre National d’Etudes Spatiales (CNES) are used to investigate the contribution of integer ambiguity resolution (IAR). The benefit of dual-system combination on LEO RTPOD is firstly evaluated. The combination of GPS and Galileo dual-system contributes to more visible GNSS satellites and better observation geometry for LEO RTPOD, which results in an evident accuracy improvement of 19% over GPS and a convergence time reduction of 43% and 41% compared to the GPS and Galileo solutions respectively. Considering the short arc of onboard GNSS observations and imperfections in GNSS real-time products, we propose a strict IAR quality control method to avoid fixing the ambiguity to the wrong values. The results indicate that the IAR quality control method we used can effectively reduce the wrong fixing risk and increase the robustness of the IAR solution. Using onboard GPS and Galileo observations, the 3D orbit accuracy of the ambiguity-fixed solution is significantly improved from 5.17 to 3.61cm, by 30%, compared to the ambiguity-float solution. Furthermore, the application of IAR also achieves a faster convergence to the centimeter-level orbit. [ABSTRACT FROM AUTHOR]

When using electromagnetic detection method to detect the damage of mine wire rope, the detection signal contains a lot of noise. Moreover, there are spikes and mutations interference, which increase the difficulty of damage identification. Therefore, it is necessary to reduce the noise of the original detection signal. The commonly used Fourier transform cannot process the operating wire rope detection signal. The wavelet transform has problems of poor translation invariance and frequency aliasing, which affect the detection accuracy. This paper proposes a method for mine wire rope damage detection based on dual-tree complex wavelet transform. Firstly, a dual-tree complex wavelet high and low pass filter is constructed by Q-shift method, and the original signal is decomposed by 3-layer dual-tree complex wavelet to obtain the high and low frequency signal components. Secondly, a soft threshold method with minimax variance is used to reduce the noise of the decomposed signal. Finally, the noise reduction signal is reconstructed. A wire rope damage detection test platform is built in the laboratory environment to verify the noise reduction performance of the wire rope damage detection signal processing method based on dual-tree complex wavelet transform. The results show that the method can reduce the number of spikes and mutations in the detection signal effectively and make the signal stable. The noise reduction effect is better than that of classical wavelet transform. The method increases the signal peak value at the singularity point, which is beneficial to the subsequent feature extraction.

Background and objectives: To evaluate and compare the surface roughness and elastic modulus in ceramic and resin composite CAD/CAM materials during thermal ageing. Materials and Methods: Four ceramic and resin composite CAD/CAM materials (Lava Ultimate HT and LT, VITA ENAMIC HT, and LT) were selected for this study. The specimens were treated with the aim of measuring the surface roughness and mechanical properties. Before and after the accelerated ageing protocol (5,000 cycles, 5°C and 55°C), the specimens were subjected to nanoindentation and a 3D profilometer. Results: The surface roughness of the Ultimate HT before and after ageing ranged from 118.48±12.87 to 123.42±10.68 nm without any statistically significant differences (p ˂ 0.05). The surface roughness of the Ultimate LT before and after ageing ranged from 90.18±10.57 to 96.91±6.28 nm without any statistically significant differences (p ˂ 0.05). The Ra of the ENAMIC HT before and after ageing ranged from 87.84±6.67 to 167.65±21.80 nm with statistically significant differences (p ˂ 0.05). The Ra of the ENAMIC LT before and after ageing ranged from 72.96±6.61 to 97.75±10.23 nm with statistically significant differences (p ˂ 0.05). The ENAMIC HT and LT had an elastic modulus nearly twice as much as the Ultimate HT and LT, respectively. Conclusions: The thermal ageing did not affect the elastic modulus. The thermal ageing increased the Ra in the ENAMIC HT and LT Group, but did not affect the Ra in the Ultimate HT and LT Group.

Although reducing students' aggressive behaviors and improving their creativity are both important commitments of educators, they are usually treated independently as unrelated tasks. However, cumulative evidence suggests potential links between aggression and creativity, not only from the perspectives of personality traits and psychological development, but also from their shared cognitive mechanisms. This implies that there may be an approach to achieving these two goals through a single intervention. Moreover, this new approach may overcome the limitation of the usually adopted aggression intervention, which is limited in its regulatory effectiveness and might bring about some disadvantageous impacts on creativity that are closely associated with aggression. To test this possibility, the present study implemented a four‐session, 2‐week creative thinking training (CTT) intervention for students with high aggression scores to examine whether it could simultaneously downregulate aggression and increase creativity. Our results demonstrate that, compared to the control group, the intervention group experienced significant improvements in creativity and a reduction in aggression following the CTT intervention. Furthermore, our findings suggest that this regulatory effect can persist for up to 6 months. The CTT‐induced creativity change (increase) could significantly correlate with and predict the CTT‐induced aggression decrease, thus suggesting that the CTT could transform aggression into creativity. [ABSTRACT FROM AUTHOR]