Magnesium hydride (MgH₂) has been considered as a potential material for storing hydrogen, but its practical application is still hindered by the kinetic and thermodynamic obstacles. Herein, Mn-based catalysts (MnCl₂ and Mn) are adopted and doped into MgH₂ to improve its hydrogen storage performance. The onset dehydrogenation temperatures of MnCl₂ and submicron-Mn-doped MgH₂ are reduced to 225 °C and 183 °C, while the un-doped MgH₂ starts to release hydrogen at 315 °C. Further study reveals that 10 wt% of Mn is the better doping amount and the MgH₂ + 10 wt% submicron-Mn composite can quickly release 6.6 wt% hydrogen in 8 min at 300 °C. For hydrogenation, the completely dehydrogenated composite starts to absorb hydrogen even at room temperature and almost 3.0 wt% H₂ can be rehydrogenated in 30 min under 3 MPa hydrogen at 100 °C. Additionally, the activation energy of hydrogenation reaction for the modified MgH₂ composite significantly decreases to 17.3 ± 0.4 kJ/mol, which is much lower than that of the primitive MgH₂. Furthermore, the submicron-Mn-doped sample presents favorable cycling stability in 20 cycles, providing a good reference for designing and constructing efficient solid-state hydrogen storage systems for future application.

Developing efficient and stable electrocatalysts for water splitting is highly desirable due to growing energy demands. Here, Au@RhCu nanodendrites with core‐shell nanostructure were facile generated via seed‐mediated method. Through composition optimization, the Au@Rh ₃ Cu nanodendrites show excellent hydrogen evolution reaction (HER) activity with an overpotential of 83 mV at the current density of 10 mA cm ⁻² , together with a small Tafel slope of 33.4 mV dec ⁻¹ . Meanwhile, the Au@Rh ₃ Cu nanocrystals are also a good oxygen evolution reaction (OER) catalyst with an overpotential of 415 mV (at 10 mA cm ⁻² ) and a Tafel slope of 127 mV dec ⁻¹ . Additionally, the Au@Rh ₃ Cu exhibits excellent stability for both HER and OER. Such attractive catalytic performance can be assigned to the large surface area produced by the unique core‐shell dendritic nanostructure, the synergistic effect between different metal elements and the positive influence of Au seeds. This work would offer a reliable pathway for the design of multimetallic core‐shell dendritic nanostructures as promising electrocatalysts toward water splitting.

High-pressure water mist fire extinguishing systems have some disadvantages, such as large space requirements and unsatisfactory suppression of pool fires in ships, which to some extent limit the effectiveness of extinguishing ship fires. Based on a confined space of 1.5 m × 1.5 m × 1.0 m, experimental studies were conducted on the flame characteristics of heptane pool fire suppression by low-pressure water mist (0.2-0.6 MPa) with different KCl concentrations (5%, 10%, 15%, and 20%). The results showed that low-pressure water mist can strengthen the flame combustion of pool fires, but low-pressure water mist containing KCl can effectively restrain the development of pool fires, in which a 20% mass fraction of KCl solution had the best extinguishing effect under a pressure of 0.6 MPa. A nonlinear expression for the extinguishing time of the flame based on the mass loss rate, the KCl solution concentration and the jet pressure was established. In addition, increasing the mass fraction of the KCl solution can improve the flame combustion stability and reduce the flame burning area. Moreover, an increase in the nozzle pressure shortened the fire extinguishing time by up to 80 s (0.6 MPa), suppressed the flame height, and improved the combustion process at the same time.

In recent years, with the concept of “green ship” put forward, it has been a major task for ship workers to improve ship propulsion efficiency and save fuel consumption. Combined propellers show higher propulsion efficiency and better energy saving effect, so they are favored by ship workers. This article using the computational fluid dynamics (CFD) software to the single propeller, tandem propellers and contra-rotating propellers was simulated in different speed coefficient, and forecast the propeller hydrodynamic performance, comparing single propeller, tandem propellers and contra-rotating propellers open water efficiency shows: the contra-rotating propellers and tandem propellers rear blade absorbing front blade axial velocity and trailing vortex energy, increase propeller thrust, to improve the efficiency of the propeller propulsion, energy conservation and emission reduction has important significance, also conforms to the concept of “green design” of the ship.

Electromagnetic valve train (EMVT) can realize independent, real-time and continuous valve motion regulation through the precise motion servo control, which has great potential to improve the efficiency of internal combustion engines. As an electromechanical integration device, EMVT is driven by electric energy, and the loss distribution is complex and changeable under different service conditions. Especially when the EMVT is used in exhaust system, the high gas pressure after combustion will increase the energy loss and operating temperature significantly. In order to improve the device performance, this study analyses the loss distribution and variation law of EMVT under different service conditions. First, the flux density is obtained by the 3D finite element simulation. In combination with the valve train dynamic Matlab/Simulink model, the copper loss and iron loss of EMVT under typical conditions are explored in detail. Then, the influence of the motion parameters (transition time) and condition parameters (gas pressure) on EMVT’s loss are calculated and analyzed significantly. In the end, the accuracy of the loss models and analysis results is verified by the experiment based on linear load simulator.