Numerical Simulation Of Three-dimension Unsteady Flow In The Compression Chambers Of A Scroll Compressor

Due to the movement of orbiting scroll and leakage in scroll compressor chambers, the unsteady flow has significant influence on compression process. It\u27s necessary to takes account of both flow and thermodynamics process in analysis of compression. This paper has carried out a numerical simulation of the whole compression process in scroll compressor, involving suction, compression and discharge process. By solving mass, momentum and energy equations of the refrigerant, the velocity, pressure and temperature distribution in all compression chambers throughout the entire compression cycle has been obtained, which takes account of all the influence of flow and thermodynamics process. The field quantities have shown nonuniform distribution in every compression chamber, and leakage between different chambers is obvious. Further, the overall parameters, such as mass flow rate, discharge temperature and compression power consumption, have been calculated from the field quantities. The general comparisons between numerical and experimental results show a reasonable good agreement. The research is useful for the optimal design of the compressor geometric structure

Soil nitrogen sequestration in a long-term fertilizer experiment in central China

Aim of study: To evaluate the effects of a long-term manuring and fertilization experiment on the soil total N concentration and its storage and sequestration rates in the rice-wheat cropping system.Area of study: A rice-wheat rotation area in central China.Material and methods: A 35-yr long-term fertilizer experiment was conducted with 9 treatments: unfertilized (Control), N, P, and K fertilizers, manure (M) and M combined with N, P, and K fertilizers treatments. Soil total N input amount, total N concentration, total N storage amount and N sequestration rate in soil were calculated.Main results: The soil total N input amount, N concentration, N storage amount and N sequestration rate were significantly influenced by M and chemical fertilizers. In total, 0.017-0.021 g N/kg soil accumulated in the organic M plots, whereas only 0.005-0.007 g in chemical fertilizer alone plots. The highest soil total N storage amount was 6.09 t/hain the M alone plot, and the lowest value was 4.46 tN/ha in the N fertilizer alone plot. The highest N sequestration rate in soil was 0.061 t N/ha/yr in the high amount M plus NPK fertilizers plot, and the lowest value was 0.002 tN/ha/yr in the N fertilizer alone plot. A significant nonlinear regression relationship existed between the total N sequestration rate in soil and annual total N input amount. Moreover, the average soil total N concentration was significantly positively correlated with the average grain yield of crop and soil organic C concentration. The soil total N sequestration rate in M alone or M combined with inorganic fertilizer treatments were increased compared with inorganic fertilizer alone treatments.Research highlights: Considering crop yields and total N sequestration rate in soil, the use of manure combined with inorganic fertilizer should be recommended in the rice-wheat cropping system

Bivariate Correlation Analysis of the Chemometric Profiles of Chinese Wild Salvia miltiorrhiza Based on UPLC-Qqq-MS and Antioxidant Activities

To better understand the mechanisms underlying the pharmacological actions of Salvia miltiorrhiza, correlation between the chemical profiles and in vitro antioxidant activities in 50 batches of wild S. miltiorrhiza samples was analyzed. Our ultra-performance liquid chromatography–tandem mass spectrometry analysis detected twelve phenolic acids and five tanshinones and obtained various chemical profiles from different origins. In a principal component analysis (PCA) and cluster analysis, the tanshinones cryptotanshinone, tanshinone IIA and dihydrotanshinone I exhibited higher weights in PC1, whereas the phenolic acids danshensu, salvianolic acids A and B and lithospermic acid were highly loaded in PC2. All components could be optimized as markers of different locations and might be suitable for S. miltiorrhiza quality analyses. Additionally, the DPPH and ABTS assays used to comprehensively evaluate antioxidant activities indicated large variations, with mean DPPH and ABTS scavenging potencies of 32.24 and 23.39 μg/mL, respectively, among S. miltiorrhiza extract solutions. Notably, samples that exceeded the mean IC50 values had higher phenolic acid contents. A correlation analysis indicated a strong correlation between the antioxidant activities and phenolic acid contents. Caffeic acid, danshensu, rosmarinic acid, lithospermic acid and salvianolic acid B were major contributors to antioxidant activity. In conclusion, phenolic compounds were the predominant antioxidant components in the investigated plant species. These plants may be sources of potent natural antioxidants and beneficial chemopreventive agents

Key role of Nb5+ in achieving water-resistant red emission in K2Ta1-xNbxF7:Mn4+ phosphors

Mn4+-activated fluoride is one of the most important red phosphors for white light-emitting diodes (WLEDs) with high color rendering index (CRI). Due to a lack of water resistance, their potential applications are limited. Although surface coating strategies improve the waterproof stability of fluoride red phosphors, they have downsides. It was found that Nb5+ plays an important role in improving the water resistance of Mn4+-activated oxyfluorides by preventing the hydrolysis of [MnF6]2-. In this work, the influence of Nb5+ on the waterproof stability of Mn4+-activated fluorides was explored. A set of synthesized K2Ta1-xNbxF7:Mn4+ phosphors exhibit tunable and superior water resistance. The photoluminescence (PL) intensity of the representative sample K2Ta0.6Nb0.4F7:5%Mn4+ remains nearly 100% of its initial value even after being immersed in water for 60 min, which is significantly higher than the commercial K2SiF6:Mn4+ red phosphor (8.7%). Our findings open up new possibilities for the development of waterproof fluoride red phosphors. © 2023 Elsevier Ltd and Techna Group S.r.l