Dry response and acclimated characteristics of people ascending the Tibetan Plateau.

Due to a long period of low humidity, exposure to the dry environment of the Tibetan Plateau can cause skin and respiratory diseases and threaten human health. To examine the characteristics of acclimatization response to humidity comfort in visitors to the Tibetan Plateau based on an examination of the targeted effect and mechanism of the dry environment. A scale corresponding to local dryness symptoms was proposed. Eight participants were selected to conduct a two-week plateau experiment and a one-week plain experiment under six humidity ratios, respectively, to explore the characteristics of dry response and acclimatization of people entering the plateau. The results indicate that duration has a significant effect on human dry response. On the sixth day after entering Tibet, the degree of dryness reached the maximum, and acclimatization to the plateau environment began on the 12th day. The sensitivity of different body parts to the change in a dry environment was different. When the indoor humidity ratio increased from 9.04 g/kg to 21.77 g/kg, the symptoms of dry skin were most significantly relieved by 0.5 units of scale. After de-acclimatization, the degree of dryness in the eyes was most significantly alleviated, reducing by nearly one scale. The analysis of human symptom indicators in a dry environment shows that subjective and physiological indices are influential and essential in measuring human comfort in a dry environment. This study extends our understanding of dry environment responses and cognition of human comfort and lays a solid foundation for humid built environments in the plateau.

Identification of local thermal conditions for sleeping comfort improvement in neutral to cold indoor thermal environments.

The effect of the thermal environment on sleep quality has attracted considerable attention, as sleep forms one-third of human lifetime and the occupied space is largely constrained during sleep. With an increasing development of partial space regulation and task air conditioning systems and devices, thermal comfort demand concerning local thermal conditions has attracted more and more attention. In the present study, experiment was conducted and data mining technologies were performed to investigate correlations between local thermal conditions and whole body thermal comfort in sleeping state. The identification of local thermal condition included two steps: the first step was to clarify thermal sensation links between local and covered body, and the second step was to identify local thermal sensation inclination towards different thermal comfort levels. Thermal sensation correlations among local body parts and covered body were obtained. Back, face, and thigh were identified as three dominant linear-correlated local parts with weighting factors 0.488, 0.388, and 0.152, respectively; in addition, chest, arm, leg and foot were found as non-negligible local parts in the estimation of covered body thermal sensation. By dividing the sleeping human body into three parts as head, trunk and extremity, the proper local thermal sensations and their coupling relationships for whole body sleeping thermal comfort have been elaborated by three rules. The present study provides implications in sleeping thermal environment regulation in neutral to cold indoor conditions.

A diffusivity model for predicting VOC diffusion in porous building materials based on fractal theory.

Most building materials are porous media, and the internal diffusion coefficients of such materials have an important influences on the emission characteristics of volatile organic compounds (VOCs). The pore structure of porous building materials has a significant impact on the diffusion coefficient. However, the complex structural characteristics bring great difficulties to the model development. The existing prediction models of the diffusion coefficient are flawed and need to be improved. Using scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests of typical porous building materials, this study developed a new diffusivity model: the multistage series-connection fractal capillary-bundle (MSFC) model. The model considers the variable-diameter capillaries formed by macropores connected in series as the main mass transfer paths, and the diameter distribution of the capillary bundles obeys a fractal power law in the cross section. In addition, the tortuosity of the macrocapillary segments with different diameters is obtained by the fractal theory. Mesopores serve as the connections between the macrocapillary segments rather than as the main mass transfer paths. The theoretical results obtained using the MSFC model yielded a highly accurate prediction of the diffusion coefficients and were in a good agreement with the VOC concentration measurements in the environmental test chamber.