In the field of pico-projectors there is a delicate compromise between size, price and capabilities. Photo: Tom Sawyer Small size, low cost and fair picture make it desirable, despite weaknesses. One must expect sacrifices for 3M’s MPro 150’s $300 price and tiny size, considering full-sized projectors run up to $3,000 and can weigh as much as 25 lbs. With limited viewing options—only 12 lumens and unsupportive of most video codecs—the unit is hard to use and its image hard to see in normally lit rooms. But we found it bright enough for small meetings in a typically dim conference room.
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.