Geography Canberra covers an area of 805.6 square kilometres and is located near the Brindabella Ranges approximately 150 kilometres inland from Australia's east coast. The highest point is Mount Majura at 888 metres. Climate Canberra experiences hot, quite dry summers, and cold winters with heavy fog and frequent frosts, with a rare spot of snow. Light snow falls in the city in one out of approximately three winters but is usually not widespread and quickly dissipates. Culture Canberra is home to many national monuments and institutions such as : the Australian War Memorial, the National Gallery of Australia, the National Portrait Gallery, the National Library of Australia, the National Archives of Australia, the National Museum of Australia. The End
none 1 ms 12v zener 1.5 ms 6v zener 2.2 ms diode 5.5 ms These numbers were obtained by switching off the relay coil and measur- ing the time until the contacts open. You can see that the higher the flyback voltage is allowed to rise, the faster the field dissipates and the faster the con- tacts open. Solenoids, Relays, and Other Analog Outputs 139 140 Analog Interfacing to Embedded Microprocessors Figure 6.2 Using a zener clamp to speed up relay release time. Tranzorbs can also be used to clamp a relay or solenoid. A Tranzorb is a zener-like device that is used for clamping high-energy transients. A Tranzorb
reactions. The latter set is regularly used in petrochemical plants and oil refineries. Wells are drilled into oil reservoirs to extract the crude oil. "Natural lift" production methods that rely on the natural reservoir pressure to force the oil to the surface are usually sufficient for a while after reservoirs are first tapped. In some reservoirs, such as in the Middle East, the natural pressure is sufficient over a long time. The natural pressure in most reservoirs, however, eventually dissipates. Then the oil must be extracted using "artificial lift" means. Over time, these "primary" methods become less effective and "secondary" production methods may be used. A common secondary method is "waterflood" or injection of water into the reservoir to increase pressure and force the oil to the drilled shaft or "wellbore." Eventually "tertiary" or "enhanced" oil recovery methods may be used to increase the oil's flow characteristics by injecting
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