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The Ritz variational-perturbational method is developed for calculating relativistic energy levels of ions embedded in plasmas. With a review of the one-electron atom problem, hydrogen-like ions are studied, and He-like and Li-like ions are studied at the effective charge approximation. For the outer shell excited states, the results agree well with other theoretical results and experimental data. PACS Nos.: 52.25.Vy, 52.40.Mj, 52.27.Gr. Nous developpons la methode variation-perturbation de Ritz pour calculer les niveaux d'energie relativistes d'ions dans du plasma. Suite a une revue du probleme de l'atome a un electron, nous etudions les atomes de type hydrogene, alors que les ions de type He et Li sont etudies dans l'approximation de la charge effective. Pour les etats dans les couches exterieures, les resultats agreent avec l'experience et d'autres theories. [Traduit par la Redaction], 1. Introduction In recent years, study of the heavy-ion-plasma interaction has drawn considerable interest. For example, X-ray source devices [1], ion-wall interaction in magnet confinement fusion [2, 3], heavyion driven [...]

Rayleigh waves can be used to detect surface defects effectively. However, the Rayleigh wave imaging quality is often poor due to the low reflected energy when using a single probe. To accomplish high-resolution imaging of surface defects, we propose a total focusing method with Rayleigh waves (TFMRW) combined with principal component analysis (PCA), in an approach called TFMRW-PCA. Firstly, the propagation characteristics of Rayleigh waves are analysed using simulation, and full matrix capture (FMC) data are obtained. Secondly, we use the Fermat principle to calculate the time of flight of the ultrasonic waves, and an improved TFM (TFMRW) algorithm is established to post-process the FMC data. Finally, PCA is used to separate the interference wave from the signal after processing by the TFMRW algorithm. In this paper, the effect of the quantity of elements and the location of the defect on the imaging results are analysed through simulation and experiment. The results show that TFMRW can accurately characterise the surface defects in the sample, with an average defect size error of 0.14 mm2. Moreover, when combined with PCA, the average API value is reduced by 0.06 and the average signal-to-noise ratio (SNR) is increased by 6.26 dB. [ABSTRACT FROM AUTHOR]

The hydrophobic encapsulation method is one of the common methods to ensure the regular operation of electronics under water. However, the hydrogel underwater sensors prepared by hydrophobic encapsulation still suffer from weak interfacial bonding. Here, we developed a high toughness and low hysteresis, dual-physically cross-linked structure hydrogel that was hydrophobically regulated by an MXene. The introduction of an MXene into the hydrogel can not only enhance the conductivity as a conductive filler, but also improve the mechanical properties as a physical cross-linking point. At the same time, the hydrophobic fluorine groups of the MXene can regulate the hydrophobic properties and enhance the bonding strength with the hydrophobic layer. In this way, a hydrophobic encapsulation structure hydrogel–elastomer hybrid was constructed, which showed a maximum bonding strength of 34.19 ± 1 N m−1, and excellent anti-drying (7d, ≤5.5%), and anti-swelling (7d, ≤0.07) properties. Furthermore, the core–shell structure hybrid fiber sensor exhibited excellent conductivity, sensitivity, and long-term stability performance in harsh environments, such as underwater, acid (pH = 1), alkali (pH = 14), salt solution (1 M NaCl), and alcohol solution. It provides a reliable opportunity for underwater smart wearable sensors using hydrogels with high flexibility. [ABSTRACT FROM AUTHOR]

Previous hydrocyclone optimizations often overlooked crucial objectives interactions, thereby weakening the overall system performance. This study presents a framework that integrates meta-heuristic algorithms with preference-informed decision-making to simultaneously optimize key performance objectives. Meta-heuristics identify comprehensive Pareto-optimal sets, while preference-informed decision-making evaluates each solution's overall separation performance according to specific separation preferences. Supported by computational fluid dynamics, the study quantifies the trade-off between optimal overall separation performance and pressure drop, enabling the attainment of optimal overall separation performance at any pressure drop within the Pareto-optimal set. Among the evaluated algorithms, the strength Pareto evolutionary algorithm 2 (SPEA2) stands out for its exceptional diversity and convergence. With this framework, the study circumvents excessive compromises on neglected but crucial objectives, especially highlighting the significant adverse effects of overlooking water split or cut size. Overall, this study provides an integrated approach for developing energy-efficient hydrocyclones that maximize overall separation performance tailored to specific separation requirements. [Display omitted] • Optimizing four objectives mitigates the loss in overall performance compared to two. • SPEA2 generates a more well-distributed Pareto optimal set than other algorithms. • Both preferred separation performance objectives and overall performance improve. • A moderate preference for the weighting ratio of water split enhances the cut size. [ABSTRACT FROM AUTHOR]

Mixed-cation lead mixed-halide perovskites simultaneously possess structural stability and high power conversion efficiency. A thorough study of both carrier and exciton dynamics is needed to understand the photophysical properties that underpin its superior photovoltaic performance. By utilizing a broadband transient absorption spectroscopy, we observe the carrier and exciton dynamics in a FA0.85Cs0.15Pb(I0.97Br0.03)3 (FCPIB) perovskite by simultaneously resolving the carrier and exciton contribution to the transient change of the absorption spectra, from which the carrier density and exciton oscillator strength can be determined. Our data reveal a quick and significant conversion of the photogenerated carriers to excitons, on top of the usual carrier recombination process. Moreover, the decay of carrier density shows a change of kinetics from a second-order recombination at high pump fluence to a third-order recombination at low pump fluence. Our analysis utilizes band anharmonicity, presents an independent determination of electronic temperature and quasi-Fermi energy, and reveals an interesting interplay among the processes of carrier cooling, exciton formation/decay and carrier recombination, all as a function of time after photoexcitation. Our work demonstrates the use of pump fluence as a knob to tune the relative populations of carriers and excitons in halide perovskite materials. Lead halide perovskites have many suitable features as materials for solar cells and a better understanding of the underlying physics will help engineer improved performance values. Here, the authors use broadband transient absorption spectroscopy to probe the excited state dynamics of mixed-halide perovskites and the role of excitons and carriers. [ABSTRACT FROM AUTHOR]

The 2 p photoionization of sodium atoms from the initial states 2 p 63 p 1/2,3/2 have been investigated, with special emphasis placed on the relaxation and correlation effects. To understand the details of the spectra, a series of ab initio calculations based on the multi-configuration Diracâ€"Fock method have been performed. Theoretical predictions have been compared with the high-resolution spectra measured using a synchrotron radiation source, and suitable agreement between experiment and theory has enabled the identification of fine-structure spectra. The prominent influence of the relaxation and correlation effects on the photoelectron spectra has been analysed according to the detailed calculations. [ABSTRACT FROM AUTHOR]