In this paper, we propose a cross-correlation method applied to multistatic ground penetrating radar (GPR) data sets to detect road pavement damage. Pavement cracks and delamination cause variations in electromagnetic wave propagation. The proposed method can detect velocity change using cross-correlation of data traces at different times. An artificially damaged airport taxiway model was measured, and the method captures the positions of damaged parts.

The demand for non-destructive inspection of the thermal insulation layer of Japanese houses has been increasing. Surface temperature measurement is commonly used for estimating the condition of the thermal insulation layer that is located inside the walls. However, the accuracy needs to be improved because this approach only considers the surface information. To evaluate the thermal insulation layer inside the walls, a millimeter-wave tomography system is proposed for measuring the water content. The system can provide ∼10 mm range resolution to differentiate the reflections from the thermal insulation layer behind the external wall. The Lichtenecker-Rother model is applied for the quantitative evaluation of the water content using the reflected signal. The proposed model is consistent with the experimental data, confirming that a maximum error of 16.0% is obtained. It is also demonstrated that the water content distribution can be visualized with a range resolution of 10.6 mm.

Based on the semiclassical theory, we deduce the expressions of stimulated absorption, stimulated amplification and threshold by using density matrix equation in the Er3+-doped fibers. Meaningful results have been given and some phenomena occuring in experiments are explained theoretically.