To promote environmental sustainability, recycled construction concrete is suggested for civil infrastructure works. The aim of this study was to investigate the effects of vegetation type on water ...infiltration under extreme rainfall conditions in a proposed three-layer landfill cover system containing recycled concrete. Three soil columns, namely bare, covered with shrub (
Schefflera arboricola
), and covered with grass (
Cynodon dactylon
), were subjected to ponding tests. Each column was compacted with a bottom layer of silty soil, an intermediate layer of coarse recycled concrete aggregate, and an upper layer of fine recycled concrete aggregate. Water breakthrough occurred only in the bare cover system after 48 h of ponding, equivalent to a rainfall return period of greater than 1000 years in Hong Kong. Under the vegetated covers, suction maintained in the bottom silty soil layer was higher than under the bare cover by 49–52 kPa and hence no percolation was observed after 48 h of ponding. Comparing the two vegetated cover systems, suction maintained under the shrub cover was 2–12 kPa higher (2%–8% lower volumetric water content) than that under the grassed cover in the layers of recycled concrete. This implies that shrub cover can be more effective than grass cover in reducing water infiltration in humid climates.
Effect of nonmetallic solutes on {10–12} tension twin boundary (TB) are investigated using first-principles calculations. Fourteen kinds of interstitial sites near the {10–12} tension TB for four ...nonmetallic solutes such as C, N, O, and H are considered. The results show that the C and O atoms are much easier to segregate from the {10–12} tension TB to the octahedral site 1, causing the {10–12} tension TB more stable. The N atom is much easier to segregate from the {10–12} tension TB to the octahedral site 4, causing the {10–12} tension TB more stable. The H atom is much easier to segregate from the {10–12} tension TB to these 14 interstitial positions, causing the {10–12} tension TB more stable. The effect of C, N, or O atom on the stability of {10–12} tension TB is greater than that of H atom.
Graphical abstract
Zirconium alloys are subjected to a fast neutron flux in nuclear reactors, inducing the creation of a large number of point defects, both vacancy and self-interstitial. These point defects then ...diffuse and can be trapped by their different sinks or can cluster to form larger defects, such as vacancy and interstitial clusters. In this work, the trapping capability of small-vacancy clusters (two/three vacancies, V2/V3) in the α-Zr doped with alloying elements (Sn, Fe, Cr, and Nb) has been investigated by first-principle calculations. Calculation results show that for the supercells of α-Zr containing 142-zirconium atoms with the two-vacancy cluster, alloying elements of Sn and Nb in the second vacant site (V2) and Cr in the first vacant site (V1) are more easily trapped by two vacancies, respectively. However, the two sites are both captured more easily by two vacancies for Fe in the supercells of α-Zr containing 142-zirconium atoms inside due to the similar value of the Fermi level. For the supercells of α-Zr containing 141-zirconium atoms with the three-vacancy cluster, the alloying element of Sn in the third vacant site (V’3), Fe in the first vacant site (V’1), and Cr and Nb in the second vacant site (V’2) are more easily trapped by three vacancies, respectively.
Taking cold-tolerant rice cultivar 996 and cold-sensitive rice cultivar 4628 as test materials, a growth chamber experiment was conducted to investigate their pollen characters and flag leaf ...physiological and biochemical characteristics under the effects of low temperature stress. The plants were respectively treated with low temperature 19 degrees C (06:00-8:00; 19:00-23:00 )/21 degrees C (08:00-10:00; 16:00-19:00)/23 degrees C (10:00-16:00)/17 degrees C (23:00-06:00) and optimal temperature 24 degrees C (06:00-8:00; 19:00-23:00)/26 degrees C (08:00-10:00; 16:00-19:00)/30 degrees C (10:00-16:00)/22 degrees C (23:00-06:00) for seven days after heading. Low temperature stress decreased the anther dehiscence coefficient and pollen germination rate, as well as the sterile pollen rate of spikelets on middle and lower parts of panicles, with the anther dehiscence coefficient and pollen germination rate of cultivar 996 being significantly higher than those of cultivar 4628, indicating that cold-tolerant cultiv
•Strain, defects and crystal orientation relationship in the initial oxidation stage of zirconium alloy were investigated.•An In-situ oxidation test and a short time exposure corrosion test were ...carried out.•Compressive strain between semi-coherent planes of m, t and c-ZrO2 was detected in a range from 0.3% to 6%.•Tensile strain in c-ZrO2 was detected in a range from 0 to 1.34%.
An In-situ oxidation test and a short time exposure corrosion test of Zircaloy-4 were carried out. A lot of dislocations generated in the nucleation and growth process of ZrO2 are observed. Dislocations will be firstly distributed at the interface of ZrO2. With the growth of m-ZrO2 grains, the number of dislocations at the interface increases. When the grain size of ZrO2 reaches a critical value, the dislocations in the grains of ZrO2 begin to appear. A compressive strain between semi-coherent planes of oxides was detected in a range from −0.3% to −6%.
As one of the important structural materials in nuclear industry, the corrosion resistance of zirconium alloy limits their in-pile application. Therefore, it is necessary to investigate the corrosion ...mechanism of zirconium alloys. The zirconium-oxygen reaction at the O/M interface is one of the factors that affect the oxidation process. There are few reports in this regard. Ideally, the reaction process at the O/M interface has certain relevance with the initiation oxidation of zirconium, which provided a new way to investigate the reaction process by observing the initiation oxidation behaviours. To investigate the oxidation behaviours of zirconium alloy at the initial stage, in this paper, zircaloy-4 TEM thin foil specimens in 3 mm diameter were studied by TEM observation after heating in air condition with a vacuum of 3 Pa at 280 °C, 290 °C and 300 °C for 30 min exposures. The results show that, ZrO2 begin to nucleate at a size of 3–5 nm at a high Zr/O ratio of 10.4 and oxide layer formed while Zr/O was 4.6. As a result of stress caused by the P.B ratio of Zr, slip bands formed and a bcc structure sub-oxide b-ZrOx (a = 0.51 nm) grew up along with the slip bands was observed. At both sides of b-ZrOx, two hcp structure sub-oxides having the same a-axis lattice parameter and different c-axis lattice parameter were detected.
As one of the important structural materials in nuclear industry, the corrosion resistance of zirconium alloy limits their in-pile application. Therefore, it is necessary to investigate the corrosion ...mechanism of zirconium alloys. The zirconium-oxygen reaction at the O/M interface is one of the factors that affect the oxidation process. There are few reports in this regard. Ideally, the reaction process at the O/M interface has certain relevance with the initiation oxidation of zirconium, which provided a new way to investigate the reaction process by observing the initiation oxidation behaviours. To investigate the oxidation behaviours of zirconium alloy at the initial stage, in this paper, zircaloy-4 TEM thin foil specimens in 3 mm diameter were studied by TEM observation after heating in air condition with a vacuum of 3 Pa at 280 °C, 290 °C and 300 °C for 30 min exposures. The results show that, ZrO2 begin to nucleate at a size of 3-5 nm at a high Zr/O ratio of 10.4 and oxide layer formed while Zr/O was 4.6. As a result of stress caused by the P.B ratio of Zr, slip bands formed and a bcc structure sub-oxide b-ZrOx (a = 0.51 nm) grew up along with the slip bands was observed. At both sides of b-ZrOx, two hcp structure sub-oxides having the same a-axis lattice parameter and different c-axis lattice parameter were detected.
The microstructure evolutions of cascade annealing in α-Zr crystals at
, 400 K, and 500 K for energy of 2, 6 and 10 keV with initially driving directions
and
of the primary knocked atoms are ...investigated by using molecular dynamics simulations. The results show that the relaxation time (τ
r
) of cascades can play the role of an effective parameter for describing radiation damages during molecular dynamics simulations. τ
r
of cascade with the larger surface area but with the same volume is much smaller, which promotes faster recombination of defects during cascade annealing. Energy is a crucial factor in the formation of cascade displacements of atoms and appearing of defects compared with temperature and direction of movement for initially knocking atoms.
