Some alternative refrigerants with excellent environmental performance often have different flammable limits. When refrigerant leaks, the external space may have a certain explosion risk if the refrigerant is not diffused timely. To understand the leakage and diffusion characteristics of the refrigerant, an improved gas leakage model was proposed in this paper, and the accuracy verification of the improved model was developed. Based on the above works, taking R290 as the research object, the variation law of the field strength between the leaked gas and external space and the influence of different initial leakage pressures on the field strength characteristics were analyzed. The simulation results showed that when the initial leakage pressure was 2 MPa, the R290 gas entered the external space as a supersonic jet, the gas underwent continuous expansion and compression processes in the near-field area and a Mach disk was formed within the flow area. During this process, parameters, such as the temperature, pressure, velocity and density of the leaked R290 gas, changed dramatically, and then the gas gradually returned to room temperature and normal pressure through interaction with the external space. The flammable area formed by the leaked R290 was mainly concentrated in the local flow area below the leak hole, and the existence of the Mach disk caused the R290 high concentration area to increase. With the increase in the initial leakage pressure, the distance from the Mach disk to the leak hole and the circumferential diameter of the Mach disk increased, and the flammable area increased slightly in the horizontal direction, whereas the flammable area increased significantly in the vertical direction.

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We propose UWash, an intelligent solution upon smartwatches, to assess handwashing for the purpose of raising user's awareness and cultivating habits in high-quality handwashing. UWash can identify the onset/offset of handwashing, measure the duration of each gesture, and score each gesture as well as the entire procedure in accordance with the WHO guidelines. Technically, we address the task of handwashing assessment as the semantic segmentation problem in computer vision, and propose a lightweight UNet-like network, only 496KBits, to achieve it effectively. Experiments over 51 subjects show that UWash achieves the accuracy of 92.27% on sample-wise handwashing gesture recognition, <0.5 seconds error in onset/offset detection, and <5 out of 100 points error in scoring in the user-dependent setting, while remains promising in the cross-user evaluation and in the cross-user-cross-location evaluation.

With the development of the alternative refrigerant technology, the thermophysical properties of hydrofluoroolefin (HFO) refrigerants have attracted much attention. Among these thermophysical properties, the thermal conductivity of refrigerants is a key parameter of phase change and convective heat transfer process of refrigeration cycle and also an important basis for the selection of alternative refrigerants. Therefore, studies on the thermal conductivity of refrigerants are of great significance. At present, many studies emphasized on the thermal conductivity of refrigerants, but there is no public report on the investigation of the saturated liquid thermal conductivity of HFO-1336mzz(E). On the basis of the current state, the thermal conductivities of HFO-1336mzz(E) by means of the general models were first predicted, then the thermal conductivities of the saturated liquid phase of HFO-1336mzz(E) in the temperature range of 253.15−353.15 K were measured based on the transient hot wire method. A comparison of prediction and experimental data was developed, and a special equation of the saturated liquid thermal conductivity for HFO-1336mzz(E) was recommended.