First, the general omen
(A) coal layer becomes wet, soft; help coal dripping occurs, the phenomenon of watering, and watering from small to large; sometimes appear to help iron rust coal water marks;
(B) reduced face temperature, or hydrogen sulfide odor occurrence or fog;
(3) Sometimes the smell of water is heard;
(4) The mine pressure is increased, and the roofing piece and the bottom drum are generated.
Second, the working surface floor limestone aquifer water inrush
(1) The pressure on the working surface is increased, the bottom plate is bulged, and the amount of the bottom drum is sometimes up to 500 mm or more;
(2) The crack in the bottom surface of the working surface is gradually increased;
(3) Water seepage along the fissures or coals. As the fissures increase, the amount of water increases. When the water seepage of the bottom plate increases to a certain extent, the coal seepage may stop. At this time, the water color is clear when it is clear, and when the bottom plate is active, the water becomes cloudy; when the bottom plate is stable, the water color becomes clear;
(4) The bottom plate is broken, and high-pressure water is sprayed along the crack, accompanied by a "beep" sound or a harsh underwater sound;
(5) The “bottom explosion†occurred in the bottom plate, accompanied by a loud noise, a large amount of groundwater poured out, and the water color was milky white or yellow.
Third, loose pore aquifer water inrush
(1) The water inrush from the water inrush, the dripping and the dripping phenomenon gradually increase, and it is observed that a small amount of fine sand is contained in the water;
(2) Local roofing occurs, the water volume suddenly increases and there is a flow of sand. The flowing sand is often intermittent, and the water color is mixed when it is clear. The general trend is that the amount of water and the amount of sand increase until a large amount of sand flows out;
(3) The roof is crushed and sanded. This phenomenon may affect the surface and cause collapse of the surface.
The above warnings are typical cases. In the process of specific water inrush accidents, they are not necessarily all manifested, so they should be carefully observed and carefully analyzed and judged.
Led street light, compared with the traditional lighting technology, led lamps and lanterns have higher efficiency, and longer service life.Thus become the preferred bulb type, in order to reduce the energy consumption of indoor/outdoor lighting, get energy saving effect.
For street lamps, higher efficiency and longer life are indispensable for cost reduction.Designed for the LED power supply switch power supply, also must have a high efficiency and durability, to ensure that it has as long as the LED life without maintenance.Here, the resonant converter is one of the most popular power supply topology, this is because compared with previous power supply topology, their performance has brought higher power efficiency, and can reduce EMI.Soft switch is an important characteristic of resonant converter.But the resonant converter used in parasitic diodes (bodydiode) can sometimes lead to system failure.Stored in the parasitic diodes charge must be clear, to avoid large current and voltage surge, including topology structure of high dv/dt and di/dt.
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