Particulate matter with an aerodynamic diameter less than 2.5μm (PM_2.5) is currently a major air pollutant that has been raising public attention. Studies have found that short/long-term exposure to PM_2.5 lead detrimental health effects. Since people in most region of the world spend a large proportion of time in dwellings, personal exposure to PM_2.5 in home microenvironment should be carefully investigated. The objective of this review is to investigate and summary studies in terms of personal exposure to indoor PM_2.5 pollutants from the literature between 2000 and 2021. Factors from both outdoor and indoor environment that have impact on indoor PM_2.5 levels were explicated. Exposure studies were verified relating to individual activity pattern and exposure models. It was found that abundant investigations in terms of personal exposure to indoor PM_2.5 is affected by factors including concentration level, exposure duration and personal diversity. Personal exposure models, including microenvironment model, mathematical model, stochastic model and other simulation models of particle deposition in different regions of human airway are reviewed. Further studies joining indoor measurement and simulation of PM_2.5 concentration and estimation of deposition in human respiratory tract are necessary for individual health protection.

This study investigated the heat transfer mechanism and preservation quality of axisymmetric vegetables during cold shock treatment (CST). A simulation model of heat transfer was developed based on geometrical and biological characteristics of the vegetables by finite element difference method. CST for cucumbers and carrots with cold water at 0°C (40 min), 2°C (20, 40 and 60 min) and 4°C (40 min) was conducted to evaluate the relationships between heat transfer characteristics and preservation quality. The comparative analysis shown that the simulated results agreed well with measured results. Meanwhile, in terms of weight loss, firmness and POD activity, CST with cold water at 2°C for 40 min could achieve the most positive effect on preserving cucumbers. The cucumber during treatment experienced whole variable temperature stage and appropriate constant temperature stage so as to reach optimal preservation quality.

In order to achieve efficient utilization of solar energy resources, this study combines the trans-critical organic Rankine cycle (ORC) power cycle (TORC) with the trans-critical CO₂ refrigeration cycle (TCO₂). Additionally, a comprehensive three-level index decision evaluation system is developed based on system safety and environmental protection, thermodynamics, and techno-economic performance. The evaluation focuses on typical medium- and high-temperature solar energy applications and considers six organic working gases. The evaluation results demonstrate that the R600 + CO₂ solution outperformed the others. This solution achieved a maximum net output power (P_net) of 1531.31 kW and 2306.43 kW, a maximum coefficient of performance (COP) of 3.16, a predicted payback period of 2.651 years and 2.033 years, and a benefit–investment ratio of 4.533 and 5.773.

In order to explore the reasons for preservation effect of hot water treatment on cherries, intermittent treatment was introduced to amplify the heat transfer factor. Cherries were immersed in hot water (42℃) for 10 (C1), 15 min (C2) continuously, or for 10 (IN1), 15 (IN2) min intermittently, respectively, and the intermittent treatment was realized through the temperature return process by room temperature water (20 °C) after every 5 min continuous treatment. Results showed that Group IN1, IN2 and C1 performed better than the untreated Group CK, and Group IN1 performed the best. At the fifteenth day, the weight loss ratio, browning index and respiration intensity of Group IN were 83.1%, 62.3% and 71% of that of Group CK, respectively, the soluble solid and titratable acid content of Group IN1 were effectively preserved, and Group IN1 also maintained good hardness, brittleness and cellular microstructure. The poor-quality and severe cell damage indicated that Group C2 had the worst performance and showed irreversible thermal damage. Continuously 15 min soaking in hot water exceeded the safety threshold time of treatment for the cherries, and under the same valid treatment time period, intermittent treatment showed positive performance and avoided irreversible thermal damage. Key words: Cherry, Intermittent hot water treatment, Quality, Heat transfer characteristics