Since most coalfields in China are commonly characterized by high gas content and low permeability, there is an urgent need to improve coal seam permeability and further enhance coal bed methane (CBM) extraction efficiency. As an emerging fracturing technology, the CO2 gas fracturing (CGF) technology has been widely used because of its advantages of low cost, environmental protection and high fragmentation efficiency. In order to improve the fracturing ability of CGF technique and optimize the release orifices of discharge head, computational fluid dynamics model was used in this paper to simulate the flow fields of dynamic pressure of gas jet released from the orifices with different structures and other geometrical parameters. The results show that the orifice structure has a great influence on the flow field of gas jet, but little influence on the magnitude of the dynamic pressure. Besides, the maximum dynamic pressure of gas jet linearly decreases with the increase in the number of release orifices. Based on a series of simulation results, the discharge head which has single group of orifices with structure c, diameter of 24 mm can be identified as the best choice for fieldwork. Then, two field experiments were conducted in Pingdingshan and Changping coal mines to evaluate the enhanced CBM extraction efficiency by CGF. The results indicate that the CGF can effectively create a large number of cracks in a large range around the fracturing borehole in the coal seam and further significantly improve the permeability. And the CBM extraction efficiency can be improved to a higher level from a lower level and maintained for a long time. Besides, the effective influence radii caused by CGF in Pingdingshan and Changping coal mines are 15.19 m and 12.5 m, respectively. Compared with other fracturing techniques, the CGF technique has a promising application prospect.
We use the Richardson-Lucy deconvolution algorithm to extract one-dimensional(1 D) spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) spectrum images. Compared with other deconvolution algorithms, this algorithm is much faster. The application on a real LAMOST image illustrates that the 1 D spectrum resulting from this method has a higher signal-to-noise ratio and resolution than those extracted by the LAMOST pipeline. Furthermore, our algorithm can effectively suppress the ringings that are often present in the 1 D resulting spectra generated by other deconvolution methods. 相似文献
Creating appropriate colour schemes is challenging for both novice and experienced cartographers. This paper introduces an artificial bee colony (ABC) algorithm to automatically create various colour schemes. Colour scheme creation is treated as a constrained search problem in a continuous colour space. We considered the gamut of the target device and a series of cartographic rules, such as convention, discrimination, contrast, perceptual uniformity and brightness mirror, in the ABC algorithm and presented detailed initialization, fitness definition, local exploration, and global exploration methods for creating qualitative, sequential and diverging colour schemes. The proposed method is evaluated with a case study, and the results indicate that compared with the brute force search method, the proposed method can create satisfying colour schemes of similar quality but significantly improved efficiency. 相似文献
Precipitation is usually the primary source of water for the hydrological cycle in a semiarid area. However, dew occurs frequently and affects water circulation dramatically in the west of Jilin Province in China. Measurements of the amount of dew formed and precipitation were carried out from July 2012 to October 2013 in the Momoge Natural Reserve. The results indicated that moisture from primary precipitation in the summer originated from the East Asian monsoon and was affected by the atmospheric circulation in the middle and high latitudes of Eurasia in the winter. The dew amount was approximately 19.44 mm (approximately 5% of the total rainfall amount), consisting of the evapotranspiration in the local area and atmospheric moisture. Dew also supplies nutrients to the local vegetation. The maximum contribution of total nitrogen, total phosphorus, and potassium in unit corn area could reach 288.60, 27.46, and 291.63 mg/m2 in half a month, respectively. The wind speed, relative humidity, and lowest temperature were the primary factors that dramatically affected dew formation and amount. As an additional source of fresh water, dew not only had a positive impact on the ecosystem in arid and semiarid zones but also played an important role in the local water cycle and other ecological processes. This research has important implications for water circulation and land use management. 相似文献
Geotechnical and Geological Engineering - The fluctuation in reservoir water level is one of the key external factors affecting the stability of slopes. Finite element models are established for... 相似文献