The Cosmic-Ray Observations of December 4, 1957
A RECENT communication from Legrand and Helary1 reports an increase in the total component of cosmic radiation at Paris on December 4, 1957. The increase amounted to about 18 per cent and extended over three hours with the maximum occurring at 2245 U.T. A small increase in the nucleonic component at Thule preceded the Paris event by about three hours. Optical and radio data indicate a flare of importance 1 on the western hemisphere of the Sun at 1657 U.T. (ref. 2).
Ionospheric Disturbance at the Time of Cosmic Ray Increases
IN a recent communication Legrand and Helary1 have reported the occurrence of an anomalous increase in the intensity of the total cosmic ray component at the Paris Cosmic Ray Survey Station on December 4, 1957. At about the same time an increase was also observed in the intensity of the nucleonic component at Thule, Greenland. This cosmic ray event was further described as being analogous to one which was observed at Paris on January 21, 1957 (ref. 2). It has been suggested that these events are manifestations of the precipitation into the Earth's atmosphere of high-energy protons which emanate from the disturbed Sun.
Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet
In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.