High Speed Wear of Gallium Nitride

This thesis observes the tribological properties of GaN at relatively high sliding speeds. We choose a model for a pin-on-disk and unit direction rotate sliding experiments. To fulfill that we assemble a new high speed tribometer and completed some successful tests. In the results of these tests, we can find several interesting tribological properties (coefficient of friction and wear rate) of GaN in relatively high speed and get some reliable information when the GaN sliding under some specific conditions. The results are compared to former tests on GaN in Lehigh tribology lab, and it is proved that the c-plane of GaN has a 60-degree periodical variation on wear rate. Also, we can record the highest and lowest wear rate on each different experiment and recorded the data working on the further researches of GaN. Focus on the high-speed parameters, and applied on difference loads, we also can use the slide surface of GaN to the further band bending researches

Favorable Fiscal Self-Sufficiency Enables Local Governments to Better Improve the Environmental Governance—Evidence from China’s Lower-Pollution Areas

With the rapid development of industrial economy, local governments in China have invested a large amount of financial funds in environmental protection. In the era of widespread use of clean energy, local governments have a greater responsibility to coordinate fiscal policies with industrial development policies to improve regional environment. Local governments with large fiscal surpluses would make more efforts to improve environmental efficiency, rather than attract heavily polluting industrial enterprises to develop their local economies, and more likely to promote the use of clean energy equipment and raise environmental awareness in government. This paper focuses on testing the impact of abundant fiscal revenue of local governments on the efficiency of regional environmental governance with the data in all prefecture-level cities of China’s Guangdong province from 2001 to 2020. We estimate local environmental governance efficiency score with super-efficiency SBM method, taking unexpected output into account. Then we find that fiscal affluence has significant positive effect on the efficiency of environmental governance and the environmental awareness of the government also has obvious help in improving local environmental efficiency. We hope that these findings will provide practical help for local governments to improve their fiscal policy agendas and the quality of environmental governance

Favorable Fiscal Self-Sufficiency Enables Local Governments to Better Improve the Environmental Governance—Evidence from China’s Lower-Pollution Areas

With the rapid development of industrial economy, local governments in China have invested a large amount of financial funds in environmental protection. In the era of widespread use of clean energy, local governments have a greater responsibility to coordinate fiscal policies with industrial development policies to improve regional environment. Local governments with large fiscal surpluses would make more efforts to improve environmental efficiency, rather than attract heavily polluting industrial enterprises to develop their local economies, and more likely to promote the use of clean energy equipment and raise environmental awareness in government. This paper focuses on testing the impact of abundant fiscal revenue of local governments on the efficiency of regional environmental governance with the data in all prefecture-level cities of China’s Guangdong province from 2001 to 2020. We estimate local environmental governance efficiency score with super-efficiency SBM method, taking unexpected output into account. Then we find that fiscal affluence has significant positive effect on the efficiency of environmental governance and the environmental awareness of the government also has obvious help in improving local environmental efficiency. We hope that these findings will provide practical help for local governments to improve their fiscal policy agendas and the quality of environmental governance

Efficient Sodium Transmembrane Permeation through Helically Folded Nanopores with Natural Channel-Like Ion Selectivity

The selective transmembrane permeation of sodium ions achieved by biomimetic chemistry shows great potential to solve the problem of sodium ion transport blockade in diseases, but its implementation faces enormous difficulties. Herein, we design and synthesize a series of helically folded nanopores by employing a quinoline-oxadiazole structural sequence to finely replicate the pentahydrate structure of sodium ions. Surprisingly, these nanopores are capable of achieving sodium transmembrane permeation with ion selectivity at the level of natural sodium channels, as observed in rationally designed nanopores (M1–M5) with Na+/K+ ion selectivity ratio of up to 20.4. Moreover, slight structural variations in nanopore structures can switch ion transport modes between the channel and carrier. We found that, compared to the carrier mode, the channel mode not only transports ions faster but also has higher ion selectivity during transmembrane conduction, clearly illustrating that the trade-off phenomenon between ion selectivity and transport activity does not occur between the two transport modes of channel and carrier. At the same time, we also found that the spatial position and numbers of coordination sites are crucial for the sodium ion selectivity of the nanopores. Moreover, carrier M1 reported in this work is totally superior to the commercial Na+ carrier ETH2120, especially in terms of Na+/K+ ion selectivity, thus being a potentially practical Na+ carrier. Our study provides a new paradigm on the rational design of sodium-specific synthetic nanopores, which will open up the possibility for the application of artificial sodium-specific transmembrane permeation in biomedicine and disease treatment

Polyethylene Microplastic Particles Alter the Nature, Bacterial Community and Metabolite Profile of Reed Rhizosphere Soils

With the wide use of polyethylene film, the influence of polyethylene microplastic particles produced by its weathering on the rhizosphere soil microenvironment has attracted more and more attention from scientific research circles. In this study, the effects of low (0.2% w/w), medium (1% w/w), and high (2% w/w) doses of polyethylene particles and the combined reed biomass (2% w/w) on soil environmental factors and bacterial communities and metabolites in the reed rhizosphere were evaluated by a 90-day pot microscopic simulation system. The shape and surface microstructure of polyethylene particles in each treatment group changed obviously. A high (2% w/w) dose of microplastics significantly increased the TKN, TOC, and TP in reed root soil. The addition of the biomass significantly improved the activities of urease and sucrase in the soil. The α diversity of bacteria was not significantly affected by the addition of LDPE microplastics and biomass, but the β diversity of the bacterial community and the relative abundance of the Candidatus_Roku Bacteria, Chloroflexi, Unclassified_Blastocatella_Genus were significantly changed by the addition of middle (1% w/w) and high (2% w/w) doses of microplastics. In addition, the spectrum analysis of the soil metabolites showed that the abundance of soil metabolites was changed in each treatment group, and the differential metabolites were significantly up-regulated or down-regulated. Our findings provide a scientific reference to elucidate the impact of LDPE microplastic particles on the inter-rooted soil microenvironment and improve our understanding of the potential risks of microplastics in soil ecosystems

Characteristics of underwater lighting based on white LEDs

This work systematically analyzed the application of LEDs in underwater white lighting. The characteristics of a RGB-LED and a phosphor-converted LED (PC-LED) have been compared in different water types. The green light shows the smallest attenuation, while the red light has the greatest attenuation coefficient. Such different attenuation effects at different wavelengths lead to the different spectra, CIE coordinates and color rendering index (CRI) of the two kinds of LEDs. With increasing distance, the illuminance of the PC-LED decreases much more rapidly than the RGB-LED due to the stronger attenuation of the wide phosphor-based yellow spectrum. However, the CIE coordinates calculated from the spectra of the PC-LED vary little due to the wider yellow spectrum. On the contrary, the CIE coordinates shift is very clear for the RGB-LED. What's more, the CRI of the RGB-LED increases at distances from 0 to 1.5m, and then decreases at longer distances, but the CRI of the PC-LED keeps decreasing at all distances, which can be explained by the variation of the R values of the color samples due to wavelength dependent light attenuation. This work will benefit the applications and designs of LED-based underwater lighting

Seasonal and Inter-Annual Variations of Stable Isotopic Characteristics of Rainfall and Cave Water in Shennong Cave, Southeast China, and Its Paleoclimatic Implication

Speleothem calcite stable oxygen isotope (delta O-18(C)) is one of the most widely used proxies in paleoclimate research, and understanding its seasonal-annual variability is very significant for palaeoclimate reconstruction. Five-year precipitation and karst cave water from 2016 to 2021 were monitored in Shennong cave, Jiangxi Province, Southeast China. The local meteoric water line (LMWL) is delta D = 8.20 x delta O-18 + 13.34, which is similar to the global meteoric water line. The stable hydrogen and oxygen isotope (delta D and delta O-18) characteristics of precipitation and cave water were studied. delta O-18 and delta D of precipitation and cave water show obvious seasonal variations. Lower precipitation delta O-18 and delta D generally occur during summer and autumn compared with higher delta O-18 and delta D values during winter and spring. Meanwhile, low precipitation delta O-18 values do not only appear in June-July when precipitation is the highest of the year but also appear in August-September when precipitation is limited. The back-trajectory analysis of monsoon precipitation moisture sources shows that the moisture uptake regions vary little on inter-annual scales; the water vapor of rainfall in June-July comes from the South China Sea and the Bay of Bengal, while the moisture source in August-September is mainly from the West Pacific and local area. The El Nino-Southern Oscillation is an important factor affecting the value of delta O-18 by modulating the percentage of summer monsoon precipitation in the annual precipitation and moisture source. The relationship between amount-weighted monthly mean precipitation delta O-18 and Nino-3.4 index shows that the East Asian summer monsoon (EASM) intensifies during La Nina phases, resulting in more precipitation in monsoon season (May to September, MJJAS) and lower delta O-18 values, and vice versa during El Nino phases