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This article establishes an experimental platform for study of the thermal storage characteristics of solid thermal storage materials in low pressure environments. The experimental results show that under the influence of the thermal inertia of the heating section in low pressure environments, the thermal storage rates of thermal storage materials first increase to the peak, and then gradually decrease with the increase or decrease of the temperature of the thermal storage bricks. Air pressure has a significant impact on the heat storage rate of thermal bricks: compared to a 101kPa atmospheric pressure environment, under the same heating temperature, the heat storage time of 80kPa and 40kPa is significantly increased, and the lower the air pressure, the longer the heat storage time required.

Aiming at the fault overcurrent problem existing in the current arrangement scheme of the bridge arm reactor in the modular multilevel converter (MMC) of the bipolar flexible DC transmission system, the influence of the bridge arm reactor in different positions on the converter fault current is analyzed in this paper, and the mathematical expression of fault current component is derived. A scheme of placing the bridge arm reactor near the DC connection point is proposed. The study shows that the arrangement of bridge arm reactor near the DC connection point can effectively limit the rise rate of fault current, reducing the overcurrent level of the bridge arm module without increasing larger costs. However, when the bridge arm reactor is arranged close to the DC connection point, the short circuit fault of the bridge arm reactor wall bushing cannot be detected in time by the existing protection strategy, which brings potential threats to the MMC. A protection strategy, which can effectively identify the short circuit fault of the bridge arm reactor wall bushing is proposed in this paper. Finally, the correlation analysis and protection strategy are verified by PSCAD/EMTDC simulation.

In this article, we systematically study the high-order stability for a stochastic reaction-diffusion equation under random fluctuation. We obtain the convergence of solutions and upper semi-continuity of random attractors for the fluctuation equations in the initial space L2(ℝN), without an additional assumption on the nonlinearity. By means of a splitting method, we technically prove that the Lp∩H1-difference of solutions is controlled by the L2-difference of initial values near the initial time, where p , p > 2 , is the dissipation exponent of the nonlinearity. This along with the L2-stability is sufficient for us to establish the Lp∩H1-stability of random attractors. By utilizing some iteration arguments, we show that the solution is uniformly bounded on a bounded interval near the initial time in Lδ(ℝN) for arbitrary δ > p, in which space the convergence of solutions and the upper semi-continuity of random attractors are also established. [ABSTRACT FROM AUTHOR]

In this article, we systematically study the high-order stability for a stochastic reaction-diffusion equation under random fluctuation. We obtain the convergence of solutions and upper semi-continuity of random attractors for the fluctuation equations in the initial space L2(ℝN), without an additional assumption on the nonlinearity. By means of a splitting method, we technically prove that the Lp∩H1-difference of solutions is controlled by the L2-difference of initial values near the initial time, where p , p > 2 , is the dissipation exponent of the nonlinearity. This along with the L2-stability is sufficient for us to establish the Lp∩H1-stability of random attractors. By utilizing some iteration arguments, we show that the solution is uniformly bounded on a bounded interval near the initial time in Lδ(ℝN) for arbitrary δ > p, in which space the convergence of solutions and the upper semi-continuity of random attractors are also established. [ABSTRACT FROM AUTHOR]

Thin-walled connection structures are commonly used in the hot-end components of aerospace vehicles. Large deflection nonlinear responses and fatigue failure occur due to their discontinuous mass distribution and prominent cross-sectional changes under the action of complex thermal, aerodynamic, and noise loads. A thermoacoustic fatigue test was carried out to obtain the acoustic and vibration responses and fatigue life changes of the connection structure under heat flow conditions in engineering applications. The high-temperature acoustic fatigue test system of aviation thin-walled structures was used, taking the high-temperature alloy thin-walled plate-load-bearing frame bolted connection structure as the research object. As a result, the vibration response and fatigue life under different thermoacoustic loads were obtained. The contact finite element method was used to simulate the connection pre-tightening force, and the coupled finite element/boundary element method was used to calculate the acoustic and vibration response of the heat flow conditions. The changing rules of the frequency response peak value at the critical point of the thin-walled connection structure under the effects of different temperature fields, fluid fields, and sound fields were obtained through the processing and analysis of the calculation results. Considering the structural vibration fatigue damage mechanism, this study employed an improved rainflow counting method to compute the rainflow circulation matrix (RFM) and rainflow damage matrix (RFD) of the vibration stress time history at critical points within the structure framework. Said method was combined with Miner's linear cumulative damage theory to estimate the fatigue life under various thermal-fluid-acoustic coupled loads. A comprehensive analysis validates the accuracy of the established numerical simulation calculation model in identifying critical connection points within structures subjected to pre-tightening forces. This model effectively characterizes thermal, aerodynamic, and acoustic loads on high-temperature alloy thin-walled-load-bearing frame bolted connection structures. It delineates the relationship between vibration response and fatigue life while assessing the impact of three distinct load parameters. [ABSTRACT FROM AUTHOR]

The interlayer properties of the CRTS III slab track during construction directly affect its long-term service condition. This article introduces time-varying coefficients that characterize the early properties of the interface between track slab and SCC to improve the bilinear CZM. Based on this, an interlayer property evolution model of the CRTS III slab track during construction is established. The evolution mechanism of interlayer properties under complex loads and the influence mechanism of key parameters on them are revealed. The results show that after SCC pouring, the interlayer damage at the corner of the slab becomes a sensitive area due to the combined effects of SCC shrinkage and temperature gradients. Interlayer damage initially manifests at the corner of the slab before progressively spreading toward the center of the slab, influencing the composite performance and force transmission characteristics of the track structure. The interlayer bonding property, shrinkage performance of SCC, and construction temperature substantially affect interlayer damage evolution. To reduce the risk of damage, mineral admixtures and expansion agents can be added as additives to improve the bonding property and minimize shrinkage of SCC. Insulation measures should be taken for SCC during low-temperature construction, and SCC pouring construction below 0 °C and above 30 °C should be avoided. [ABSTRACT FROM AUTHOR]

In this paper, we study the Wong-Zakai approximation of a non-autonomous stochastic reaction-diffusion equation driven by an additive white noise and a general nonlinearity. Firstly by a decomposition technique of the nonlinearity, we obtain the convergence of solutions of the Wong-Zakai approximation equations in the initial space, and then the upper semi-continuity of random attractors of the approximation equations is followed. Secondly by this decomposition trick we also technically obtain the difference estimate of solutions near the initial time in $ L^p({\mathbb{R}}^N) $, in terms of the $ L^2 $-initial values and the Wong-Zakai approximation degree, where $ p $ is the growth exponent of the nonlinearity. By this and the $ L^2 $-upper semi-continuity we establish the upper semi-continuity of random attractors in $ L^p({\mathbb{R}}^N) $. Thirdly with some additional hypothesis on the coefficients, by an induction argument we prove that the solutions are bounded near the initial time in $ L^l(\mathbb{R}^N) $ for arbitrary $ l> p $, in which the the upper semi-continuity of random attractors is also established. Our conclusions largely improve the related results. [ABSTRACT FROM AUTHOR]