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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]

Underwater electrical wire explosion is usually used as a source of underwater shock waves, and the generated shock wave intensity can be regulated by adopting a wire array. In this paper, the dynamics of the electrical explosion of two wires with different diameters connected in parallel were studied. The current flowing through each wire was measured to study the current distribution, and the self-emission image and laser backlight shadow image was obtained to observe the evolution of the wires. A numerical model was built to make explanations and predictions. The results showed that due to the presence of wire inductance and contact resistance between the wire and electrode, the wires are with different current densities and undergo asynchronous heating from the beginning of the discharge. Furthermore, the variation of current distribution among the wires was divided into six stages according to the moment the wire melted and exploded, and analyzed stage by stage. The unbalanced energy deposition results in obvious differences in thermal dynamic parameters, which explains the gradual "extinguishment" of the thinner wire in the self-emission image. [ABSTRACT FROM AUTHOR]

Recently, C4F7N mixtures have attracted attention as a promising SF6 alternative due to their low global warming potential and excellent electrical performance. In this study, we introduce a newly built experimental setup for pulsed Townsend measurements as well as the physical model for the acquisition of electron swarm parameters. The effective ionization rate coefficients, electron drift velocity, and density-normalized longitudinal diffusion coefficients in C4F7N and its mixtures with CO2 and N2 were obtained. The reduced critical electric field for pure C4F7N at 100 Pa is determined to be 1002 Td, while it decreases with increasing pressure because of the effect of ion kinetics during the discharge process. C4F7N shows good synergism with CO2 and N2. To have a dielectric strength equivalent to that of SF6, the mixing ratio of C4F7N in its mixtures with CO2 and N2 should be 18% and 12%, respectively. The results provide fundamental data for modeling discharges in C4F7N and its mixtures. [ABSTRACT FROM AUTHOR]

We present a computationally-efficient method for obtaining the fully spun-up state of a seasonally-varying global ocean biogeochemistry model. The solver uses a Newton–Krylov method to find the fixed points of the map that assigns to an initial state the value of the model state at the end of a one-year run. Apart from the preconditioner, which we describe in the paper, the method relies on a black-box public-domain Newton–Krylov solver that does not require the explicit construction of the model’s Jacobian matrix. Applied to the PO4 plus dissolved organic phosphorus (DOP) cycle of an Ocean Carbon Model Intercomparison Project II (OCMIP-2) type model, the solver is more than two orders of magnitude faster than the traditional time-stepping method for spinning up the model. The efficiency of the solver is illustrated by using the seasonally varying globally-gridded PO4 climatology to objectively optimize the parameters that control the mean lifetime of semi-labile DOP and the fraction of new production allocated to DOP. The optimization study demonstrates that the information in the seasonal variations of PO4 do not provide a significantly stronger constraint than the annually averaged data used in previous optimization studies.

HFO-1336mzz(E) is proposed as a novel alternative to SF6 due to its low greenhouse effect and high insulation strength. Typically, it is mixed with CO2 or Air to lower its boiling point to meet the minimum operating temperature. To better understand the thermophysical properties of the gases' arcing plasma, the composition, thermodynamic properties, transport properties, and net emission coefficient of 30% molar fraction of HFO-1336mzz(E) mixed with CO2 or Air at temperatures from 300 K to 30 000 K at 0.12 MPa are calculated. It is found that HFO-1336mzz(E) mixtures have similar turbulent energy dissipation and thermal interruption capability to the pure SF6. Analysis of radiation characteristics demonstrates that the HFO-1336mzz(E) mixtures at 0.12 MPa exhibit stronger radiation emission compared to SF6 at 0.1 MPa, which indicates good arc radiation dissipation capabilities within such mixtures. This study reports the properties of thermal plasma of HFO-1336mzz(E) mixtures for the first time. These findings not only provide fundamental data for further magneto-hydro-dynamic calculations for arcing process but also put forward the potential application of these mixtures as arc interruption medium in medium voltage switchgears. [ABSTRACT FROM AUTHOR]

During the arc breaking process of high-voltage circuit breakers, the eco-friendly SF6-alternative gases will inevitably decompose and generate various decomposition products. In some cases, this will contain solid by-products such as solid carbon, which will have a deterioration effect on the electrical insulation performance of the equipment. It has been found that adding a proper amount of O2 can effectively inhibit the formation of solid carbon. In this paper, based on the improved Gibbs free energy minimization method, a calculation model considering the solid decomposition products was established, and the arc plasma composition of CO2/O2 mixtures with the new eco-friendly gases, such as C4F7N, C5F10O, HFO-1234ze(E) and HFO-1336mzz(E), in local thermodynamic equilibrium state was calculated. The change of decomposition products with the initial O2 ratio is studied, and the criterion expression of inhibiting solid carbon formation is obtained. We also applied the method to the calculation of other SF6-alternative gases containing sulfur atoms such as NSF3 and CF3SO2F. Finally, we showed that solid carbon can be inhibited when a proper molecule formula is satisfied. This work may provide new ideas for further exploring the potential of SF6-alternative gases. [ABSTRACT FROM AUTHOR]

Recently, fluoronitrile C4F7N is regarded as a promising alternative gas for SF6, and its global warming potential (GWP) is extremely high. C4F7N has good insulation properties and a relatively low GWP, so it can be used as an insulation medium for gas-insulated switchgears. Some studies have been conducted on the decomposition pathway of C4F7N gas that may produce possible neutral molecules and free radicals, which helps understand the thermal decomposition of C4F7N. However, anions and cations will be produced under discharge conditions. In these cases, the decomposition pathway of C4F7N will be different. In this paper, the ionization decomposition pathway and the attachment decomposition pathway of C4F7N were first calculated, while the recombination processes of the cations and anions were also considered. The results can reveal the decomposition mechanism of C4F7N and the recombination mechanism of the stable products under discharge conditions. The energy changes of all the reactions were calculated, which reveals the difficulty of chemical reactions. To better investigate the formation mechanism of stable products, the partial discharge experiment was also carried out, and the decomposition products of C4F7N mixed gas were detected. Finally, the ionization energy and electron affinity energy of the stable products were also calculated, which can determine the difference in the total electronic energy between the neutral molecule and the ion. The results provide an important reference for studying the decomposition characteristics of C4F7N gas under discharge conditions from the theoretical aspect. [ABSTRACT FROM AUTHOR]