Search

In this article, we investigate a multi-user multiple-input-single-output full-duplex system with simultaneous wireless information and power transfer under the non-linear energy harvesting model, where channel state information is imperfect. Since the channel estimation error is considered in our proposed system, the self-interference cannot be canceled perfectly. For such a system, a robust optimization problem that maximizes the minimum average total harvested power by jointly optimizing the uplink and downlink beamforming matrices is formulated. As the problem is non-linear and non-convex under channel estimation errors, a novel Newton method based iterative optimization algorithm is proposed to solve it efficiently. In each iteration, the semidefinite relaxation technique and S-Procedure method are applied to obtain the optimal beamforming vectors, which are proved to be optimal solutions with rank-one. Simulation results reveal that the proposed robust design can achieve better system performance than the non-robust scheme, both of which are based on the non-linear energy harvesting model.

Medium-sized wall fire experiments were carried out using extruded polystyrene (XPS) panels to build an insulation layer to simulate the flame spread over the exterior thermal insulation system during the exposed stage. During the experiments, the influences of the wind direction on the lateral and vertical flame spread speed without fire barrier designs under the wind speed of 2.5m/s were studied quantitatively and qualitatively. According to the experimental results, it is found out the averaged peak lateral flame spread rate increases and the averaged peak vertical flame spread rate decreases when the angle between the wind direction and the wall increases from 0° to 60°. It can be seen from the analysis that the largest average lateral flame spread rate and the largest average vertical flame spread rate also show regular changes at same wind direction. This study results can provide valuable references for optimizing the fire safety design of exterior insulation system.

This paper analyzes the mechanism and characteristics of spontaneous combustion of coal and lists the technologies generally used for controlling spontaneous combustion of coal in recent years. Based on the analysis of the nature of aerosols, it proposes the feasibility of applying aerosol technology in this area

Spontaneous combustion is a fire disaster caused by being heated or self-heating and heat accumulation of combustible substances without the effect of external fire. The fire disaster of spontaneous combustion occupies a certain proportion in various kinds of fire accidents in the country. It is low in frequency, but these fire accidents usually occur in warehouse, open storage ground, chemical plant and seagoing freighter, and thus result in huge losses. This paper analyses the mechanism of spontaneous combustion of some common combustible substances and summarizes identification methods of spontaneous combustion caused by different types of combustible substances.