Sensitive skin is characterized by uncomfortable sensations in response to a number of factors. We performed a large-scale study to investigate the prevalence of sensitive skin at all ages and the impacts of related factors across China. Methods: A nationwide sampling of the Chinese population aged over 18 was conducted. Subjects were categorized into sensitive and non-sensitive groups, and critical differences between these two groups were investigated. Results: In total, 22,085 questionnaires were collected from Chinese women with sensitive skin. The prevalence of sensitive skin is 49.6% and is associated with age, skin type, geographic area of subjects, and other factors. Heavy life stress and the application of several cosmetic products also affect the prevalence of sensitive skin. Conclusion: Having a combination or oily skin type, living in the municipalities, being under heavy stress, and applying several cosmetic products will increase skin stress and contribute to the occurrence of sensitive skin.

The isothermal curing of polymethacrylimide (PMI) is studied through the use of dynamic mechanical analysis (DMA). Based on the growth rate of measured dynamic mechanical property, the relative conversion is defined to investigate the evolution of storage modulus at different curing temperatures. Hsich's nonequilibrium thermodynamic fluctuation theory, Avrami equation, and isoconversional methods are used to analyze isothermal cure kinetics of PMI. The results show that there are different increase modes of at low temperature range and high temperature range, respectively. In low temperature range, the relative conversion curves include a transitional stage which is found to be strongly frequency-dependent, but this stage is not observed in the relative conversion curve in high temperature range. During the isothermal curing process, the relative evolution of can be described by Hsich's nonequilibrium thermodynamic fluctuation theory and Avrami equation. Moreover, the values and evolutions of activation energy are different in two temperature ranges, which suggest that the curing mechanism probably has changed.

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To investigate the effects of charge size on the slow cook‐off characteristics of trilobite ammonium perchlorate (AP)/hydroxyl‐terminated polybutadiene (HTPB) composite propellant with slits, a cook‐off model of three‐dimensional base bleed unit is developed based on the two‐step decomposition reaction mechanism of AP/HTPB propellant at the external heating rates from 3.3 to 9 K/h. The charge length of AP/HTPB propellant is 72 mm with 43 mm to 53 mm in grain diameter, and the grain diameter is 43 mm with 72 mm to 90 mm in charge length, respectively. The results show that heating rate and charge size determine the ignition position of AP/HTPB propellant. The effects of charge size on the ignition position and cook‐off temperature are small at the heating rate of 3.3 K/h. As the heating rate increases to 4.6 K/h–6 K/h, with the grain diameter and charge length extending, the ignition position gradually moves from the inner wall to the surface near the slit, meanwhile the cook‐off temperature changes obviously. When the heating rate increases to 9 K/h, the ignition position of AP/HTPB propellant at different charge sizes all occurs on the outer interface between the propellant and slit, there is no obvious influence of different charge sizes on the ignition temperature of AP/HTPB propellant. Additionally, the law of ignition time of AP/HTPB propellant to charge size is the same at different heating rates.

Moving beyond the prior studies on destinations, this study identifies people's perceptions of and attachments to their places of origin to theoretically address how social groups defined by environmental experiences perceive the environment and how these perceptions affect their attachment. Villages in inland China are empirically examined as shared places of origin for stayers, outmigrants and returnees. This study confirms a positive relationship between the frequency and intensity of people‐environment interactions and the levels of environmental perception, as shown by the decreasing perception levels among stayers, returnees and outmigrants. Environmental perception occurs when individuals selectively perceive environmental features that have special meaning to them in meeting their functional needs. Such selectivity leads to differences in the environmental perception variables that significantly affect group attachment. The village attachment of both outmigrants and stayers is significantly affected by their perception of socioeconomic environmental features, while the perception of physical environmental features is only significant for returnees. The strong impact of social environmental features on outmigrants’ level of attachment confirms the rootedness of such attachment to one's place of origin and challenges the belief that mobility and attachment to place are negatively related.