QUANTITATIVE REMOTE SENSING ANALYSIS OF THERMAL ENVIRONMENT CHANGES IN THE MAIN URBAN AREA OF Guilin BASED ON GEE

The dynamic change of urban thermal environment caused by the change of land use type has become one of the important problems of urban ecological environment protection. In Guilin city as research area, based on the Google Earth Engine (GEE), the random forest algorithm was used to classify the land use classification of Landsat remote sensing images in 2010, 2014 and 2018, and the mono-window algorithm was used to calculate the surface temperature. The surface vegetation was solved according to the NDVI pixel binary model. Coverage, and finally dynamic statistics and comparative analysis of land use, vegetation cover and surface temperature. The main results as follows. (1) From 2010 to 2018, the average temperature in the main urban area of Guilin is on the rise (increased by 1.29 °C), and the temperature zones in each class are converted from low temperature zone, lower temperature zone and medium temperature zone to higher temperature zone and high temperature zone. (2) Lower temperature zone and the low temperature zone is mainly distributed in vegetation and water body coverage areas, while the medium temperature zone, higher temperature zone and the high temperature zone are mainly distributed in construction land and unused land cover area. (3) High vegetation cover area in 2014–2018 (reduced by 31.34%) The main reason for the sharp decline is the substantial increase in the area of construction land (expansion 30.19%). (4) GEE-based random forest algorithm Land use classification had higher classification accuracy (more than 80% in all three periods). The results can provide scientific basis for improving urban thermal environment and scientific reference for the development strategy of Guilin city.

Oxygen-Enriched Combustion Characteristics of Lignite: A Case Study of the Pingzhuang Lignite from Inner Mongolia, China

Combustion curves of lignite samples from China in four different particle sizes and Oxygen-enriched condition were analyzed using non-isothermal thermogravimetric method. The lignite samples separated into -150+100 μm, -100+75 μm, -75+50 μm, and -50μm sizes. Combustion profiles shift to lower temperature zone as particle size decrease. Combustion profiles have little difference when the particle size below 100 μm in oxygen atmosphere; Oxygen-enriched combustion experiment were carried out in O2/N2 mixture atmospheres with the volume fraction of oxygen was 21%, 30%, 40%, 50%, 60% and 70%, respectively. As oxygen concentration increase profiles shift to lower temperature zone. and gets the proper range of oxygen concentration is about 50%.

Kinetic Simulation of the Promoted Effect of Methanol on the NOxOUT Process

Subscript textThe kinetic model for simulating the mechanism of the promoted effect of methanol on the NOxOUT process has been established and it mainly includes the optimal sub-mechanisms respectively for the NOxOUT process and the chemical reaction of methanol. The oxygen concentration does not obviously influence the maximum NO reduction efficiency in the range of 1-6 %, but the temperature window is overall shifted to lower temperature zone with oxygen concentration increased. Meanwhile, the mole ratio of urea to nitric oxide by a factor of 2 should be maintained between 1.5 and 2 from both the efficiency and running cost view. Also, ample residence time of 300/T-400/T s must be guaranteed for the reduction occurring thoroughly. Methanol does not compromise the maximum NO reduction efficiency and broadens the temperature window towards low temperature zone. The promoted mechanism of methanol on the NOxOUT process is the abundant OH formation through the methanol regenerative reaction of CH2OH/CH3O+H2O=CH3OH+OH and methanol should be maintained at 50-100 ppm for an obvious promoted effect. During the co-injection of methanol and urea, the “ammonia slip” is depressed, especially at 1173 K where the promoted effect on NO reduction is obvious, but emission of nitrous oxide is also markedly increased at this temperature.

Fabrication of Single Crystalline Cadmium Nanowires by a Facile Low Temperature Vapor Phase Method

Single-crystalline cadmium nanowires were successfully fabricated by vaporization of cadmium metal powders in a horizontal quartz tube furnace at 250 °C. The vaporization was carried out for 30 minutes and yielded nanowires of diameters of 80 to 250 nm and lengths up to several tens of microns. The nanowires were deposited on a Si (111) substrate kept at the lower temperature zone (150–175 °C) of the furnace. When the deposition temperature was lower than this, hexagonal nanodisks were produced. The possible mechanism for the formation of the obtained nanostructures is discussed.