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Underwater pulsed spark discharge has been widely used in industrial fields as a source of shock waves or acoustic waves, and numerical modeling of the discharge and pressure wave characteristics is necessary to improve the application performance. In this paper, a numerical model is proposed that couples the circuit equation, the mass and energy conservation equations, and a momentum conservation equation based on the Rankine–Hugoniot conditions. A tabulated wide range equation of state and conductivity data of water are used, and various physical processes during the plasma channel expansion are considered, including the energy flow and mass exchange between the channel and the surrounding water due to thermal radiation, evaporation, and condensation. The model self-consistently solves the circuit current and voltage, the plasma channel parameters including composition, temperature, conductivity, pressure, etc., and the pressure profile at a certain distance from the discharge channel. The calculated results show good consistency with the experimental measurements, and three sets of experimental results from other literature are tested to further verify the applicability and effectiveness of the model. [ABSTRACT FROM AUTHOR]

We investigate the effects of specular reflection on the laser-induced breakdown (LIB) of copper, iron, and tungsten using fast photography and optical emission spectroscopy. The laser parameters include spot diameter ranging from 30.89 to 1589.33 μm, irradiance from 467.10 to 0.17 GW/cm2, with a single pulse of 6 ns duration and 21 mJ energy. As the laser spot defocuses, the plasma morphology changes from a single plasma near the target surface to a separated, independently evolving two-component plasma, and then to a single plasma suspended above. The defocusing distance for this transition is significantly influenced by specular reflectance. The separate plasma, comprising of a metallic component and an air component, occurs only under high specular reflectance conditions: ≥66.7% for copper, ≥51.4% for iron, and ≥44.9% for tungsten. The spectral emission of the metallic component initially increases and then decreases with reducing specular reflectance, due to a trade-off between enhanced surface absorption and reduced irradiance caused by surface roughening. LIB threshold irradiance increases with specular reflectance, rising from 0.31 to 1.22 GW/cm2 for copper, 0.24 to 0.70 GW/cm2 for iron, and 0.38 to 0.87 GW/cm2 for tungsten. These findings show the impact of sample pretreatment on LIB ignition and subsequent plasma evolution, offering insights into potential sources of inaccuracy in LIB applications. [ABSTRACT FROM AUTHOR]

Measurement of plasma parameters during the ablation phase in the Z-pinch is crucial for investigating the dynamic behaviors. In this study, optical Thomson scattering was employed to measure the temperature and velocity of the ablation plasma in a double-wire Z-pinch. The scattering spectra profiles were fitted using a model that considered the velocity distribution. The experimental results revealed the energy evolution of ablation plasma, the establishment of the global magnetic field and the development of axial non-uniformities. The precursor plasma was found to play a key role in strengthening the global magnetic field. A resistive layer near the wire core with a size of 1.5 mm was observed in the ablation plasma after the precursor plasma column formed. The plasma underwent rapid heating in this layer, the electron temperature rises from 17 eV to 22 eV. Upon leaving this layer, electron the temperature is stable at around 22 eV. The radial distribution of the ablation rate increases and decreases, indicating the axial motion of the ablation plasma, which could be caused by the tilt motion of the stream and the secondary modulation of the natural wavelength. [ABSTRACT FROM AUTHOR]

The synergy enhancement of magnetic-spatial confinement using a bar magnet pair was applied to fiber-optic laser-induced breakdown spectroscopy (FO-LIBS). By studying the plasma morphology and emission spectroscopy, the plasma temporal behaviors under free expansion, spatial confinement, and magnetic-spatial confinement have been carefully compared. Temperature distribution and pixel-to-pixel relative standard deviation (RSD) of plasma morphology under the combined effect of magnetic field and the reflected shock wave on fiber-optic laser-induced plasma were studied for the first time. The magnetic field was found to deform the plume mainly at the left and right sides, and the two high-intensity areas in FO-LIBS plasma rose from 8.7% to 13.8% and resisted being compressed together after the shock wave reflected. The magnetic-spatial confinements also demonstrated better enhancements in emission spectra than only spatial confinement, and the magnetic field tended to give around 20% and 50% additional enhancement on line intensity at the early and later stages of evolution, respectively. Besides, the self-reversed effect was significantly reduced in magnetic-spatial confinement, which can be explained by more evenly distributed temperatures calculated by spatially resolved spectra. Pixel-to-pixel RSD distribution of plasma morphology was studied, and it was found that the area of more fluctuated parts was reduced by 40% and concentrated on the left and right sides of the plasma in the magnetic field at the early stage. After the shock wave passed through, the two high-intensity areas were observed to fluctuate less due to the compression of the shock wave. Furthermore, shot-to-shot spectra fluctuation was also reduced by up to 50% under the magnetic-spatial confinement, which is consistent with the results of plasma morphology fluctuation. This study provides evidence of plasma emission signal enhancement and stabilization under magnetic-spatial confinement in the FO-LIBS system. [ABSTRACT FROM AUTHOR]

The proliferation of urbanization and the integration of new energy sources have stimulated the development of gas-insulated transmission lines and switchgear (GIL/GIS). In particular, the compact DC GIS in offshore converter platforms will significantly reduce footprints for DC switchyards, exhibit exceptional climatic resistance, and facilitate the cost-effective connection of remote offshore wind farms and submarine links. Nevertheless, insulators used in GIS/GIL always suffer from surface charge accumulation under DC stress, which could distort and enhance the local electric field and thus trigger a flashover at the gas–solid interface if it exceeds certain magnitude levels. This susceptibility becomes a major concern affecting the reliability of DC gas-insulated systems. Beyond these engineering-related challenges lie fundamental physics problems involving mechanisms of charge accumulation and charge-induced flashover which still require exploration. To this end, this paper presents an overview of recent advancements on this topic whilst highlighting relevant issues to be addressed. Specifically, the surface charge accumulation phenomena under DC fields are reviewed, and the charging mechanisms are summarized from macroscopic to microscopic perspectives. Further, the correlation between surface charge and surface flashover is discussed. Moreover, recent developments in tailoring methods for surface charging are also presented. Finally, perspectives are given on current research progress and future needs. [ABSTRACT FROM AUTHOR]

In this paper, Fe10Co25Ni34Cu23Al8 high-entropy-alloy nanoparticles have been synthesized by the in situ instantaneous electrical wire explosion method. Based on the thermodynamic parameters of the face-centered cubic phase of high-entropy-alloy, the parameters of the five kinds of wires were calculated and controlled, and the stable face-centered cubic structure with good crystallinity was synthesized in one step. The influence of the energy deposition during the electrical explosion on the nanoparticles and their electromagnetic absorption performance was explored. The results show that the face-centered cubic structure high-entropy-alloy with high crystallinity has better electromagnetic wave absorption performance when the energy deposition of the wires is increased. The minimum reflection loss can reach −39.37 dB at 15.34 GHz when the thickness is 1.9 mm and the effective absorption bandwidth is 6.63 GHz. It can provide a strategy for the microstructure and morphology design of high-entropy-alloy nanoparticles in electromagnetic wave absorption and magnetism in the electronics industry. [ABSTRACT FROM AUTHOR]

A rod pinch diode (RPD) is a feasible load configuration to generate a high-brightness, small-size hard x-ray radiation source. In this paper, the radiography performance of a wire-shorted low-impedance RPD on a compactly designed table-top driver (WRPD-1) is demonstrated for the first time. The driver consists of four high-power discharge branches connected in parallel, with each branch consisting of two metal-film capacitors and one multigap field-distortion switch in series. The four branches are triggered synchronously to generate a fast-rising current pulse: the inductance of the load section at the short circuit is ∼10 nH, and the short-circuit current amplitude is ∼325 kA at ±90 kV charging voltage, with a 10%-90% rise time of 110 ns. With a low-impedance RPD shorted by an 18-µm-diameter aluminum wire, a quasi-spherical x-ray focal spot with diameter <0.6 mm (width of the half-maximum grayscale) and a pulse duration of ∼25 ns (half-width of the radiation pulse) is obtained at ±70 kV charging voltage, and the imaging resolution excels 10 lp/mm under 1.56× magnification. According to the transmission-absorption x-ray spectrum estimation, the average emitted photon energy is ∼30 keV with a distinct peak in the 10-15 keV range that corresponds to the L-lines of tungsten, and the total energy of photons >10 keV reaches ∼1.16 J. The present results show that the device can serve well for the flash radiography diagnosis and potentially as an efficient light source for dynamic x-ray diffraction., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Computational Pathology (CPath) is an interdisciplinary science that augments developments of computational approaches to analyze and model medical histopathology images. The main objective for CPath is to develop infrastructure and workflows of digital diagnostics as an assistive CAD system for clinical pathology, facilitating transformational changes in the diagnosis and treatment of cancer that are mainly address by CPath tools. With evergrowing developments in deep learning and computer vision algorithms, and the ease of the data flow from digital pathology, currently CPath is witnessing a paradigm shift. Despite the sheer volume of engineering and scientific works being introduced for cancer image analysis, there is still a considerable gap of adopting and integrating these algorithms in clinical practice. This raises a significant question regarding the direction and trends that are undertaken in CPath. In this article we provide a comprehensive review of more than 800 papers to address the challenges faced in problem design all-the-way to the application and implementation viewpoints. We have catalogued each paper into a model-card by examining the key works and challenges faced to layout the current landscape in CPath. We hope this helps the community to locate relevant works and facilitate understanding of the field's future directions. In a nutshell, we oversee the CPath developments in cycle of stages which are required to be cohesively linked together to address the challenges associated with such multidisciplinary science. We overview this cycle from different perspectives of data-centric, model-centric, and application-centric problems. We finally sketch remaining challenges and provide directions for future technical developments and clinical integration of CPath. For updated information on this survey review paper and accessing to the original model cards repository, please refer to GitHub. Updated version of this draft can also be found from arXiv., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)