Respiratory droplet characteristics are key to determine the droplet-bornepathogen transmission, which provide scientific basis for formulating the disease prevention from droplet transmission and control measures. Through studying the data information from existing documents, this paper gives the respiratory droplet characteristics, like size, concentration, velocity, etc. Meanwhile, droplet evaporation,droplet-bornepathogen activity and their transmission are discussed. The droplet size is no significant difference with human health level, gender and age. The size of droplets produced by health people is between 0.1 and 10μm, it produced by patientsis between 0.05 and 10μm, and the patients' dropletconcentration is higher. The coughed droplet concentrations change with the size into a peak rule. The velocity of the cough droplets is the biggest, the range of 10 to 25m/s, the transmission distance is more than 2m.

Latent heat storage with phase change material is a superior way of storing thermal energy because of its high thermal storage density, isothermal nature of the storage process, and easy control. In recent years, latent heat storage systems have been increasingly used in building energy conservation, solar heating systems, and waste heat recovery systems. The water tank as a key component of solar heating systems has been widely applied in practical applications. This article first reviews the research on the water tank integrated with phase change material in terms of existing research methods and heat transfer enhancing technologies and then summarizes the applications of various phase change material-based water tanks. Finally, the further research suggestions on the phase change material-based water tank are proposed in this article. The successful completion of this review will not only deepen the understanding on the research development of phase change material-based water tank but also promote practical applications of such water tanks in solar heating systems.

For the fabrication of high performance graphene devices, the transfer process with clean surface without too many PMMA residues is of paramount importance in that it is has great impact on graphene interface. In this paper, a graphene heat-free-transfer process is proposed for the first time in order to get a decently clean surface. The evaluation of PMMA residues as a function of baking temperature is carried out. Experimental results clearly show that baking at higher temperature leads to more PMMA residues on graphene. In order to reduce these residues on graphene, a heat-free-transfer process is presented, in which the baking step is skipped. Thanks to both the step of anisole recoating and the abolishment of DI water rinsing, this heat-free-transfer overcomes the crack issue occurred to transferred graphene. It has been proven that, by adopting this heat-free-transfer process, the PMMA residues are notably reduced and the surface roughness of transferred graphene is improved, which in turn improves the interface of graphene. This improved interface is ought to be beneficial for the fabrication of high performance graphene devices.

The heat-source tower heat pump (HSTHP), as a novel energy-saving unit, extracts low-grade thermal energy from air that can be a promising alternative of boiler in Yangtze River basin, China. A numerical model for analysis of the heat and mass transfer characteristics of a counter-flow heat source tower (CFHST) operating in winter is developed and validated by using experimental results. In this proposed numerical model, the changeable Lewis number is considered, and the effects of various operating, environmental including inlet air dry bulb temperature, inlet air humidity ratio, inlet air flow rate, inlet solution temperature and inlet solution flow rate on the thermal behavior of the heat source tower are studied. Furthermore, the proposed model will also be used to analyze the impact of the porosity and spacing of packing on the heat exchange in the CFHST. Finally, the moisture transfer characteristics inside CFHST under various environmental conditions are also studied. This work can provide a theoretical foundation for performance evaluation and practical design of CFHST.