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For the entire intercalation/deintercalation range of Na 4 VP 2 O 9 , quantum mechanics is applied to investigate sodium transport mechanism and a machine learning force field is used instead of ab initio method to offers an applicable method for the full understanding of the complicated Na + movements dynamically. It shows chain of '8′ shaped units horizontally and repeated alternating round aggregate and '8′ shaped long chain vertically. For primitive Na 4 VP 2 O 9 , facile Na+ transportation along a-axis is observed with an energy barrier of 0.16 V. As a cathode material, Na 3 VP 2 O 9 also shows fast Na + diffusion with a minimal diffusion energy barrier 0.27 eV along a-axis. However, for the fully sodiated state of Na 4 VP 2 O 9 , Na+ diffusion in the lattice is significantly restricted with an energy barrier of 0.92 eV along b-axis. Accordingly, the sodium ion diffusion coefficients at room temperature for Na 3 VP 2 O 9 , Na 4 VP 2 O 9 and Na 5 VP 2 O 9 are 1.2 × 10−9 cm2 s−1, 5.9 × 10−9 cm2 s−1 and 8.2 × 10−11 cm2 s−1, respectively. The formation energy convex hull originated from the removal of Na1 sites and the occupation of E 8c O 8 cavities reveals an intermediate phase, Na 3.5 VP 2 O 9 , for the Na x VP 2 O 9 (3 ≤ x ≤ 4) and three intermediate phases, Na 4.5 VP 2 O 9 , Na 4.625 VP 2 O 9 and Na 4.75 VP 2 O 9 , for the Na x VP 2 O 9 (4 ≤ x ≤ 5). [Display omitted] • A machine learning force field with ab initio accuracy in MD simulations • Phase evolution for the Na x VP 2 O 9 (3 ≤ x ≤ 5) cycle • Complete diffusion mechanism [ABSTRACT FROM AUTHOR]

Fault diagnosis and location play a pivotal role in expediting fault restoration and enhancing power system resilience. However, integrating distributed generation and diverse load profiles has led to more complicated distribution networks, intensifying fault diagnosis and location challenges. Hence, there is a need to transform traditional distribution networks into resilient active ones that actively guide and utilize distributed energy resources, possessing active control and operational capabilities. This paper comprehensively reviews fault diagnosis and location techniques in distribution networks, focusing on faulted line selection, fault section estimation, and accurate fault location. It provides an in-depth analysis of current fault diagnosis and location techniques, along with an assessment of their challenges, summarizing and evaluating the current research status at both local and international levels. To address existing fault diagnosis and location technologies limitations, a method utilizing micro-phasor measurement units (μPMUs) to enhance situational awareness and state estimation of active distribution networks is proposed. The paper also provides a comprehensive analysis of the optimized configuration strategy for achieving network observability and fault diagnosis using limited μPMU, in addition to comparing and analyzing the advantages and disadvantages of typical solution algorithms for the optimal PMU placement (OPP) problem. In response to extreme disturbance scenarios in active distribution networks, resilience enhancement strategies are proposed from three perspectives: fault prevention, fault response, and fault restoration. Finally, a summary and outlook on current research methods for fault diagnosis and location, as well as the challenges and future research directions in resilience enhancement strategies, are provided. [Display omitted] • Review fault diagnosis, section estimation, and accurate fault location methods. • Improving power system resilience through fault diagnosis and location. • Strategies using limited μPMUs to enhance distribution network situation awareness. • Comprehensive methods for power system resilience in extreme disasters. [ABSTRACT FROM AUTHOR]

X-ray communication (XCOM) is a novel space communication method with great potential. X-rays have much shorter wavelengths than both infrared and radio. In principle, XCOM can send more data for the same amount of transmission power, which could permit more efficient gigabits-per-second data rates for deep space missions. Besides, X-rays can pierce the hot plasma sheath that builds up as spacecraft hurdle through Earth's atmosphere at hypersonic speeds. However, some current technical limitations have made X-ray communication unable to fully release its theoretical advantages in space communications. Among them, the modulation of X-ray emission impacts significantly. For the requirements of high-flux, collimation, quasi-monochromatic X-ray emissions, as well as the exploration of X-ray frequency modulation, we propose an X-ray frequency modulation method for generating different energy X-rays by controlling the electron beam deflection based on an external electrostatic field. Different from all traditional on-off control methods, this scheme uses two specific X-ray energies indicate the digital signal 0 and 1, which makes X-ray frequency modulation possible. Based on this, we simulated the emission flux and energy distribution of two different targets. Simulation results indicate that this X-ray modulation method produce X-rays with up to 50 GHz modulation frequency, 1014 cps X-ray emission flux, 99% monochrome, and 1.5 mrad divergence angle. Through this modulator, not only the communication distance and communication speed experience significant increases, but also the concept of X-ray communication, X-ray ranging and X-ray navigation can be realized as a three-in-one mission. [ABSTRACT FROM AUTHOR]