Higher order correlations in a levitated nanoparticle phonon laser

We present theoretical and experimental investigations of higher order correlations of mechanical motion in the recently demonstrated optical tweezer phonon laser, consisting of a silica nanosphere trapped in vacuum by a tightly focused optical beam [R. M. Pettit et al., Nature Photonics 13, 402 (2019)]. The nanoparticle phonon number probability distribution is modeled with the master equation formalism in order to study its evolution across the lasing threshold. Up to fourth-order equal-time correlation functions are then derived from the probability distribution. Subsequently, the master equation is transformed into a nonlinear quantum Langevin equation for the trapped particle’s position. This equation yields the non-equal-time correlations, also up to fourth order. Finally, we present experimental measurements of the phononic correlation functions, which are in good agreement with our theoretical predictions. We also compare the experimental data to existing analytical Ginzburg-Landau theory where we find only a partial match

Two-dimensional convolution-based power system reliability assessment

With the rise in carbon emissions, it has become fashionable to construct a new power system using new energy as the primary raw material for power generation. This, however, might result in a significant rise in the number of system states and frequent changes in the system state. These issues raise the bar for the effectiveness of system dependability evaluation. Traditional evaluation procedures necessitate computing Optimal Power Flow (OPF) for many systems states one by one, which is unquestionably time-consuming. For that purpose, this research proposes a reliability evaluation approach based on two-dimensional convolutional networks. Branch circuit fault messages are analyzed with generator fault messages. Multiple channel state data from power system node admittance matrices, power generation, and energy demand are fed into a two-dimensional convolutional neural network. This is used to determine the regression connection between load curtailments and system status data and to forecast load curtailments. Finally, it is applied to the RTS-79 system, and experimental results demonstrate that the technique has certain advantages in terms of computing speed and accuracy

Magnetic properties of FeNi alloys for high-temperature thermomagnetic power generation

In this paper, the magnetic properties and heat transfer performance of Fe99.3-xNixMn0.4Si0.3 (x=33, 35, 37, 39, 41, 43) alloys near the Curie temperature (TC) were investigated. The results show that Curie temperature TC for the Fe99.3-xNixMn0.4Si0.3 alloys increases almost linearly from 450 K to 647 K with the Ni content increasing from x = 33 to x = 43. The maximum change rate of the magnetic induction (ΔB/ΔT) near the Curie temperature first increases and then decreases with the increasing Ni content. The maximum ΔB/ΔT value for Fe99.3-xNixMn0.4Si0.3 (x≥37) alloys is higher than that of the second-order phase transition materials (0.0202 T/K). Therefore, the Fe100-xNixMn0.4Si0.3 alloys are suitable for thermomagnetic power generation above 473 K. The energy conversion process of a platy sample (0.2×0.2×0.001 m3) for the alloy with x=37 in the static thermomagnetic power generation was simulated, and the maximum electromotive force of 1.47 V was generated in the simulation

The Effect of Different Atomic Substitution at Mn Site on Magnetocaloric Effect in Ni50Mn35Co2Sn13 Alloy

The effect of different atomic substitutions at Mn sites on the magnetic and magnetocaloric properties in Ni50Mn35Co2Sn13 alloy has been studied in detail. The substitution of Ni or Co for Mn atoms might lower the Mn content at Sn sites, which would reduce the d-d hybridization between Ni 3d eg states and the 3d states of excess Mn atoms at Sn sites, thus leading to the decrease of martensitic transformation temperature TM in Ni51Mn34Co2Sn13 and Ni50Mn34Co3Sn13 alloys. On the other hand, the substitution of Sn for Mn atoms in Ni50Mn34Co2Sn14 would enhance the p-d covalent hybridization between the main group element (Sn) and the transition metal element (Mn or Ni) due to the increase of Sn content, thus also reducing the TM by stabilizing the parent phase. Due to the reduction of TM, a magnetostructural martensitic transition from FM austenite to weak-magnetic martensite is realized in Ni51Mn34Co2Sn13 and Ni50Mn34Co2Sn14, resulting in a large magnetocaloric effect around room temperature. For a low field change of 3 T, the maximum ∆SM reaches as high as 30.9 J/kg K for Ni50Mn34Co2Sn14. A linear dependence of ΔSM upon μ0H has been found in Ni50Mn34Co2Sn14, and the origin of this linear relationship has been discussed by numerical analysis of Maxwell’s relation

Room temperature elastocaloric effect in polycrystalline Ni51Mn34In8Sn7 alloy

Room temperature elastocaloric effect in polycrystalline Ni51Mn34In8Sn7 allo