Energy and exergy analysis of a modified three-stage auto-cascade refrigeration cycle using low-GWP refrigerants for sustainable development.

This study proposed a modified three-stage auto-cascade refrigeration cycle (MTARC) operating with environmentally benign zeotropic mixture of R1234yf/R170/R14 at the refrigeration temperature level of - 80 °C. Compared with the conventional three-stage auto-cascade refrigeration cycle (CTARC), MTARC incorporates an additional pressure regulator between the condenser and separator to realize phase separation at a lower pressure and temperature. A comprehensive evaluation of energy and exergy performance of the two cycles was conducted theoretically. Under a typical working condition, the cooling capacity, COP and exergy efficiency of the MTARC are improved by 15.85%, 11.69% and 7.65% in comparison with the CTARC, respectively. In addition, a lower evaporating temperature was also obtained by the MTARC under the same operating condition. When the intermediate pressure drops from 2 to 1 MPa, the cooling capacity, COP and exergy efficiency are improved by 35.43%, 25.25% and 16.74%, respectively, for the MTARC, meanwhile the compressor outlet temperature increases 19.93 °C from 92.27 to 112.20 °C. Therefore, the selection of the intermediate pressure should be comprehensively considered to ensure a desirable cycle performance and a proper working condition for the compressor. The proposed modified cycle offers new pathways for designing innovative cryogenic refrigeration systems, thereby potentially improving the energy economy in a myriad of modern energy applications for sustainability concerns.

[Spatio-temporal Variation Characteristics Monitored by Remotely Sensed Technique of PM2.5 Concentration and Its Influencing Factor Analysis in Sichuan Basin, China].

The spread of atmospheric pollutants in the Sichuan Basin is difficult because of its unique topography, static wind, high humidity, and other meteorological conditions. Owing to the acceleration of urbanization and industrialization, PM2.5 pollution in the region is becoming increasingly severe, and the Sichuan Basin has become one of the key areas of national air pollution prevention and control. In this study, based on the remote sensing inversion product of PM2.5 concentration, spatial autocorrelation and gray correlation analyses are used to evaluate the spatial and temporal distribution characteristics and influencing factors of PM2.5 concentration in the Sichuan Basin. The results show that PM2.5 concentration has significant spatial aggregation; the high-high aggregation types are concentrated, low-low aggregation types are more dispersed, and coniferous forest has a significantly higher inhibitory effect on the absorption of PM2.5 than the shrub, grassland, and other vegetation types. The main meteorological factors affecting PM2.5 concentration in the Sichuan Basin are wind speed and temperature; population density and economic scale are the main human-activity factors affecting PM2.5 concentration in the Sichuan Basin, and the change in the industrial structure and scale also has a certain influence on the PM2.5 concentration.

[Spatiotemporal variation and driving factors of growing season NDVI in the Tibetan Pla-teau, China.] / 青藏高原植被生长季NDVIæ—¶ç©ºå˜åŒ–ä¸Žå½±å“å› ç´ .

It is important to understand the response of vegetation to climate change in Tibetan Pla-teau (TP), an ecological barrier for China and Asia. The spatiotemporal variation of the normalized difference vegetation index (NDVI) of vegetation growing season were analyzed based on the gro-wing season NDVI retrieved from MOD09A1. The relationship between NDVI and climate factors was analyzed by combining the data of meteorological stations in TP from 2001 to 2018. The results showed that NDVI in the growing season showed a slow upward trend during the study period. There was substantial interannual variation of NDVI in different climate regions. The fluctuation magnitude of NDVI value was plateau humid climate region>semi-humid climate region>semi-arid climate region>arid climate region. The proportion of area with increasing and decreasing NDVI in humid climate region, semi-humid climate region, arid climate region, semi-arid climate region on TP were 1.4% and 1.9%, 4.9% and 1.5%, 16.4% and 0.8%, 7.0% and 2.0%, respectively. The areas of increasing NDVI in arid and semi-arid climate region was significantly larger than humid and semi-humid region. Temperature was the leading factor affecting the change of NDVI in humid and semi-humid region. The impact of precipitation on NDVI was significantly stronger than that of other climate factors in arid region. The impact of air temperature in growing season on NDVI was stronger than that of precipitation and relative humidity.

Lingual-occlusal surface position predicts retroglossal obstruction in patients with obstructive sleep apnea hypopnea syndrome.

CONCLUSION: Lingual-occlusal surface position was significantly related to retroglossal obstruction, and lingual-occlusal surface position may be an available reference in clinical practice for the preliminary assessment of retroglossal obstruction. OBJECTIVE: To investigate the relationship between lingual-occlusal surface position and retroglossal obstruction in patients with obstructive sleep apnea hypopnea syndrome (OSAHS). MATERIALS AND METHODS: A total of 140 patients with OSAHS diagnosed by polysomnography (PSG) were enrolled. Lingual-occlusal surface position was evaluated and classified into three types. Airway computed tomograpy (CT) was performed to measure the retroglossal cross-sectional area and inner diameter. The PSG was repeated after the nasopharyngeal tube insertion (NPT-PSG). The NPT-PSG results, CT-measured data and incidence of retroglossal obstruction were compared among the different lingual-occlusal surface positions groups. RESULTS: The demographics of OSAHS patients with different lingual-occlusal surface positions was similar. As lingual-occlusal surface position type varied from type I to type III, retroglossal cross-sectional area and inner diameter decreased, retroglossal airway obstruction rate increased, apnea hypopnea index (AHI) measured by NPT-PSG increased, and lowest oxygen saturation (LaSO2) decreased.