Summary The effective stress concept for solid‐fluid 2‐phase media was revisited in this work. In particular, the effects of the compressibility of both the pore fluid and the soil particles were studied under 3 different conditions, i.e., undrained, drained, and unjacketed conditions based on a Biot‐type theory for 2‐phase porous media. It was confirmed that Terzaghi effective stress holds at the moment when soil grains are assumed to be incompressible and when the compressibility of the pore fluid is small enough compared to that of the soil skeleton. Then, isotropic compression tests for dry sand under undrained conditions were conducted within the triaxial apparatus in which the changes in the pore air pressure could be measured. The ratio of the increment in the cell pressure to the increment in the pore air pressure, m, corresponds to the inverse of the B value by Bishop and was obtained during the step loading of the cell pressure. In addition, the m values were evaluated by comparing them with theoretically obtained values based on the solid‐fluid 2‐phase mixture theory. The experimental m values were close to the theoretical values, as they were in the range of approximately 40 to 185, depending on the cell pressure. Finally, it was found that the soil material with a highly compressible pore fluid, such as air, must be analyzed with the multi‐phase porous mixture theory. However, Terzaghi effective stress is practically applicable when the compressibilities of both the soil particles and the pore fluid are small enough compared to that of the soil skeleton.

Structural and electrical properties of Al-doped MgxZn1−xO films were improved by post-annealing with supplying Zn vapor. The Al-doped MgxZn1−xO films were deposited on glass substrates by a sol-gel method. The substrates were dip-coated with a precursor solution and were dried on a hotplate at 270 °C for 10 min. This dip-coating and drying process was repeated 10 times, and the Al-doped MgxZn1−xO films were obtained after calcination in air at 500 °C for 1 h. The as-grown films were post-annealed in H2 at 400 °C for 20 min. To supply zinc vapor, a glass slide with a thermally evaporated Zn layer (Zn cap) was put on the sample surface during the post-annealing. The as-grown films had the wurtzite structure with the c-axis perpendicular to the substrate surface, but the intensity of the (002) diffraction peak decreased with increasing Mg content (x). The crystallinity of the films was improved after the post-annealing with a Zn cap, which was observed when x was below 0.1. The resistivity and carrier concentration of the film (x = 0.1) after the post-annealing with a Zn cap was 6.0 × 10−3 Ωcm and 5.7 × 1019 cm−3, respectively. On the other hand, the resistivity of the film (x = 0.1) after the post-annealing without a Zn cap was 6.6 × 102 Ωcm. Transmittance spectra in the visible range were not affected by the post-annealing. The optical bandgap of the film (x = 0.1) after the post-annealing with a Zn cap was 3.41 eV.

ZnO films consisting of nanoparticles were obtained by the sol–gel dip-coating method using citric acid and ethylenediaminetetraacetic acid (EDTA) as additives. The size of the nanoparticles was decreased by using the additives, and continuous ZnO films were formed when citric acid was added to a precursor solution. The crystallinity of the ZnO films depended on the additives and pre-annealing temperature to dry the precursor solution. When the pre-annealing temperature was at 260 °C, ZnO films with preferred c-axis orientation were obtained regardless of the additives. At the pre-annealing temperature of 120 °C, the additives prevented the crystallization of ZnO. The ZnO film pre-annealed at 120 °C was directly patterned by light irradiation from a high-pressure mercury lamp during pre-annealing. EDTA in the precursor solution improved the patterning selectivity.