Mechanism of Strength Formation of Unfired Bricks Composed of Aeolian Sand-Loess Composite.

Aeolian sand and loess are both natural materials with poor engineering-related properties, and no research has been devoted to exploring aeolian sand-loess composite materials. In this study, we used aeolian sand and loess as the main raw materials to prepare unfired bricks by using the pressing method, along with cement, fly ash, and polypropylene fiber. The effects of different preparation conditions on the physical properties of the unfired bricks were investigated based on compressive strength, water absorption, and softening tests and a freeze-thaw cycle test combined with X-ray diffraction and scanning electron microscope analysis to determine the optimal mixing ratio for unfired bricks, and finally, the effects of fibers on the durability of the unfired bricks were investigated. The results reveal that the optimal mixing ratio of the masses of aeolian sand-loess -cement -fly ash-polypropylene fiber-alkali activator-water was 56.10:28.05:9.17:2.40:0.4:0.003:4.24 under a forming pressure of 20 MPa. The composite unfired bricks prepared had a compressive strength of 14.5 MPa at 14 d, with a rate of water absorption of 8.8%, coefficient of softening of 0.92, and rates of the losses of frozen strength and mass of 15.93% and 1.06%, respectively, where these satisfied the requirements of environmentally protective bricks with strength grades of MU10-MU15. During the curing process, silicate and sodium silicate gels tightly connected the particles of aeolian sand and the loess skeleton, and the spatial network formed by the addition of the fibers inhibited the deformation of soil and improved the strength of the unfired bricks.

Design Consideration Investigation of Soft-Valve Pipe.

This paper focuses on investigating the configuration and parameter selection of the silicone pipe in soft valve. According to the working principles of soft valve, five configurations and four structural parameters of silicone pipes are proposed and analyzed. The relationship between the pipe configuration and breakthrough pressure is investigated through experimental tests. The influence of the structural parameters on the breakthrough pressure is revealed by experiments as well. Based on the revealed design considerations, a three-way soft valve is designed, fabricated and tested. The experimental results show that the designed pipes have great stability and good sealability, which ensures the three-way soft valve possesses high breakthrough pressure. Finally, two application tests of the three-way soft valve are carried out, which further confirm the effectiveness of designed pipe and designed soft valve.

Methane activation on single-atom Ir-doped metal nanoparticles from first principles.

The breaking of the C-H bond of CH4 is of great importance, and one of the most efficient strategies in heterogeneous catalysis is to alter the electronic structure of a surface by doping it with different metal elements or controlling the stoichiometry. We present an in-depth study on methane activation on pure metal and single-atom Ir-doped alloy nanoparticles, which are constructed based on (100), (110), (111) surfaces using density functional theory (DFT) calculations. DFT results show that the dissociation barriers of CH4 on the Ir-doped alloy surfaces are about 0.3-0.4 eV, much lower than those on the pure metal surfaces (i.e., 0.6-0.8 eV). DFT-based transition state theory further reveals the rates of the first C-H activation on single-atom Ir-doped alloy nanoparticles at the early stages. Importantly, a strong temperature dependence is mainly contributed by the proportion of the exposed (110) surface. The Ir-doped Pt nanoparticle is found to be an efficient catalyst for methane activation in potential industrial applications. These important results are helpful for further designing new metal catalysts for methane activation at the atomic/molecular level.

𝛍m-resolution thickness distribution measurement of transparent glass films by using a multi-wavelength phase-shift extraction method in the large lateral shearing interferometer.

In this paper, a precise phase-shift extraction method was introduced for the first time to measure the thickness distribution of transparent glass films. A spatial light modulator modulated the phases of the incident laser in a large lateral shearing interferometer. The phase shifting caused by the thickness of the films can be extracted ranging from 0 to 2π, in a recursive way suitable for real-time implementation. Incident lasers with different wavelengths were utilized to measure the spatial distribution of the thickness of the films, and they can be larger than one wavelength of the incident light. Both artificial and experimental results have verified that the resolution of the thickness measurement reaches up to 1 𝛍m.