Laser-Induced Thermography for Quantitative Detection of Cracks in Building Materials

Laser-induced thermography is a an active technique using a laser source to heat a very small area on a side of a crack in a building material. The presence of a crack is easily detected as a sharp change in the temperature due to its insulating nature, but no information about its depth is directly available from the thermal image. The method described in this paper uses a heuristic form of the temperature on the surface of the heated specimen, which is transformed to a two-dimensional distribution. Then, a relation is used (called β -tool) between the thermal gap across the crack and the unknown depth of the damage. The purpose is that of making it possible to distinguish between shallow and deep fractures (more than 15mm deep).

Estimation of radon concentrations and associated radon doses by using active technique in drinking water sources of Abbottabad, KPK, Pakistan

In-situ measurement of radon concentration was carried out in three types of drinking water sources (spring, surface and bore/well). Water samples from all three sources were collected from the city of Abbottabad and its surroundings. Radon concentrations were measured through active technique, using the AB-5 series of portable radiation monitor (Pylon). The mean concentrations (ranges) of radon in the phosphate region were 13.4 ± 2.0 (9.1–23.6), 11.2 ± 1.5 (6.2–20.1) and 7.1 ± 0.9 (4.3–14) kBq m−3 in well, spring and surface waters, respectively. Similarly, the mean concentrations (ranges) of radon outside the phosphate region were 7.2 ± 1.0 (3.4–11.5), 5.4 ± 0.7 (2.5–8.9) and 3.1 ± 0.4 (1.7–5.8) kBq m−3 in well, spring and surface waters, respectively. The arithmetic mean values of radon concentration in drinking waters in the phosphate and non-phosphate parts or rocks were 10.76 ± 1.5 and 5.10 ± 0.70 kBq m−3, respectively. Respective doses of radon taken in by the people via water ingestion and inhalation were calculated as 0.029 ± 0.004 and 0.014 ± 0.002 mSv. The mean values of radon concentrations in drinking water samples collected from Abbottabad phosphate and non-phosphate rocks were below the US EPA Maximum Contamination Level (MCL) of 11.1 kBq m−3. The annual mean effective doses of all samples are lower than the reference level of 0.1 mSv a−1 for drinking water as recommended by WHO. Thus, the drinking water of Abbottabad and its surroundings is generally below the recommended levels as regards to radon-related health hazards.

Control of Wall Turbulence by Spinning Discs

This article is an extension to a previous paper of ours. It summarizes the main findingsand complements flow visualisations. An active technique for friction drag reduction in a turbulentchannel flow is studied by direct numerical simulations. The flow is modified by the steady rotationof rigid flush-mounted discs, located next to one another on the walls. The effect of the disc motionon the friction drag is investigated at a Reynolds number of Rτ =180, based on the friction velocity ofthe stationary-wall case and the half channel height. We compute a maximum drag reduction of 23%and a maximum net power saved of 10%, calculated by taking into account the power needed to rotatethe discs. The new Reynolds stress term induced by the disc rotation and generated by the velocitycomponents of the time averaged flow is shown to be instrumental for drag reduction.