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Main gases of the ionosphere (about 50 km; 31 miand above on this chart) vary considerably by altitude. The F layer or region, also known as the Appleton–Barnett layer, extends from about 150 km (93 mi) to more than 500 km (310 mi) above the surface of Earth. It is the layer with the highest electron density, which implies signals penetrating ...
Needles from the West Ford project compared to a stamp. Project West Ford (also known as Westford Needles and Project Needles) was a test carried out by Massachusetts Institute of Technology's Lincoln Laboratory on behalf of the United States military in 1961 and 1963 to create an artificial ionosphere above the Earth. [1]
This concrete is also known as "no-fines" or porous concrete. Mixing the ingredients in a carefully controlled process creates a paste that coats and bonds the aggregate particles. The hardened concrete contains interconnected air voids totaling approximately 15 to 25 percent. Water runs through the voids in the pavement to the soil underneath.
Layers of the ionosphere.The Kennelly–Heaviside layer is the E region. The Heaviside layer, [1] [2] sometimes called the Kennelly–Heaviside layer, [3] [4] named after Arthur E. Kennelly and Oliver Heaviside, is a layer of ionised gas occurring roughly between 90km and 150 km (56 and 93 mi) above the ground — one of several layers in the Earth's ionosphere.
The overall mass of concrete can be reduced by 35–50% depending on the design, [1] as a consequence of reduced slab mass, as well as lower requirements for vertical structure and foundations. Biaxial slabs commonly span up to 20 metres at a thickness of around 500 mm. [ citation needed ] The added strength also reduces the acoustic ...
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Air entrainment in concrete is the intentional creation of tiny air bubbles in a batch by adding an air entraining agent during mixing. A form of surfactant (a surface-active substance that in the instance reduces the surface tension between water and solids) it allows bubbles of a desired size to form.
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