Thursday, January 23, 2014

Ancient Stone Bridge Surveying by Ground-Penetrating Radar and Numerical Modeling Methods

Solla, M., Riveiro, B., Lorenzo, H., and Armesto, J. (2014). ”Ancient Stone Bridge Surveying by Ground-Penetrating Radar and Numerical Modeling Methods.” J. Bridge Eng., 19(1), 110–119.

Bridges are considered necessary engineering structures because they connect separated lands to improve economic and social development. In Spain, many of the bridges in service within the network of transport are masonry arch bridges built in ancient times. In addition to their age, the stability of these remaining bridges is questionable because of the changing loading conditions; therefore, they require periodic assessment of the condition state. Moreover, some of these bridges are considered a part of the cultural heritage of a region, so nondestructive evaluation is required to preserve their historical character. In this work, a medieval stone bridge in the Galician territory of Spain was evaluated using ground-penetrating radar, supported by a detailed geometric survey performed through a terrestrial laser scanner. The results revealed unknown geometrical data and hidden characteristics, including the thickness of ring stones in the interior of the vault, as well as the presence of ancient arches and restorations. To assist in the interpretation, finite-difference time-domain modeling was used, where realistic models were built from the accurate geometry provided. The synthetic data obtained were compared with the field data, which allowed for the identification of unknown structural details.

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Tuesday, January 7, 2014

SCR-270 radar

SCR-270 Early Warning radar

From Wikipedia, the free encyclopedia

SCR-270: Similar to the model that detected the attacking Pearl Harbor planes (the actual Opana antenna was nine dipoles high by four wide, instead of the eight-by-four configuration shown here). The scale for reading the direction the antenna is pointing to can be seen at the base.

The SCR-270 (Signal Corps Radio model 270) was one of the first operational early warning radars. It was the U.S. Army's primary long-distance radar throughout World War II and was deployed around the world. It is also known as the Pearl Harbor Radar, since it was a SCR-270 set that detected the incoming raid about half an hour before the attack commenced.