Speed bumps (or traffic thresholds or speed breakers or sleeping policemen) are the common name for a family of traffic calming devices that use vertical deflection to slow motor-vehicle traffic in order to improve safety conditions. Variations include the speed hump, speed cushion, and speed table.

The use of vertical deflection devices is widespread around the world, and they are most commonly found to enforce a low speed limit, under 40 km/h (25 mph) or lower.

Although speed bumps are effective in keeping vehicle speeds down, their use is sometimes controversial—as they can increase traffic noise, may damage vehicles if traversed at too great a speed, and slow emergency vehicles. Poorly-designed speed bumps that stand too tall or with too-sharp an angle can be disruptive for drivers, and may be difficult to navigate for vehicles with low ground clearance, even at very low speeds. Many sports cars have this problem with such speed bumps. Speed bumps can also pose serious hazards to motorcyclists and bicyclists if they are not clearly visible, though in some cases a small cut across the bump allows those vehicles to traverse without impediment.

Arthur Holly Compton was a physicist and winner of the Nobel Prize in physics in 1927 for his discoveries resulting in major changes in electromagnetic theory. He is commonly known for his work on the Compton Effect with X-rays. He also invented what he called "traffic control bumps," the basic design for the speed hump, in 1953. Compton began designs on the speed bump after noticing the speed at which motorists passed *ings Hall at Washington University in St. Louis, Missouri, where he was chancellor.

In room and pillar mining, tunnels are advanced in a rectangular pattern resembling city streets (tunnels), leaving behind blocks (pillars) of coal. To a miner, a partially completed tunnel resembles a room dug into the coal seam. As mining proceeds, the weight of rock overburden previously supported by coal mined from rooms is redistributed to pillars. If that weight exceeds the strength of a pillar, the pillar can fail by crushing or exploding. An explosive failure is called a "bump."

https://archives.novascotia.ca/meninmines/disasters/
The miner's life has always been a dark, dangerous and precarious one, carried out in the earth's margins and depths, usually far underground — and in the case of Nova Scotia's coal mines, frequently in dank subterranean tunnels stretching for kilometres out beneath the Atlantic Ocean. Sweat from the miner's brow has often been mingled with blood on the coal or gold.

Over nearly three centuries of mining activity in Nova Scotia [新斯科舍，拉丁语意为'新苏格兰"是加拿大东南部的一省], countless numbers of miners and quarrymen have been killed in disasters large and small. Major coal-mining catastrophes in the last 130 years include:

• Drummond Colliery Disaster, Westville, 1873 (60-70 deaths)
• Foord Pit Explosion, Stellarton, 1880 (50 deaths)
• Springhill Mine Disaster, 1891 (125 deaths)
• Dominion No. 12 Colliery Explosion, New Waterford, 1917 (65 deaths)
• Albion Mine Explosion, Stellarton, 1918 (88 deaths)
• cable break in mine shaft, Sydney Mines, 1938 (20 deaths)
• Springhill Explosion, 1956 (39 deaths)
• Springhill Bump, 1958 (74 or 75 deaths)
• Westray Coal Mine Explosion, Plymouth, 1992 (26 deaths)

六级/考研单词: threshold, vertical, cushion, enforce, controversy, disrupt, navigate, clearance, pose, hazard, physics, notify, chancellor, pillar, tunnel, resemble, dig, crush, explode, archive, subway, seldom, sweat, forehead, mingle, innumerable, catastrophe, pit, shaft