Non-Contact Experiment Investigation of the Interaction between the Soil and Underground Granary Subjected to Water Buoyancy

The buoyancy of underwater can cause the underground granary to overall float, or even overturn, and the interaction between the soil and underground granary is the key to its stability. This paper introduces a non-contact experiment system utilizing the digital image correlation (DIC) technology and particle image velocity (PIV) technology, and its measurement accuracy is analyzed. Then, this system is employed to study the granary displacement and the soil deformation around the granary subjected to the buoyancy of water. Results show that with the increase of the degree of compaction of the soil around the granary, the floating water level increases by 10.77% and the vertical displacement decreases by 17%. When the soils around the granary are loose sands, the soil deformation range shows an obvious inverted triangle. When the soils are medium dense sands, the soil deformation zone concentrates at the junction of the conical granary bottom and granary wall. When the soils are dense sands, the disturbed range of the soil obviously reduces, and the soil deformation concentrates on both sides of the granary wall and is distributed symmetrically. Finally, taking the medium dense sands around the granary as an example, the reasons for the unstable failure of the granary subjected to buoyancy are discussed, assisted by the soil pressure theory of retaining wall. With the granary increasingly inclining, the soil deviating from the inclined direction of the granary loses its support, which drives the soils to reach the active limit state. The soil in the inclined direction of the granary is squeezed, resulting in passive soil pressure on the granary wall. The soil deformation increases continuously to a passive limit equilibrium state, and the soil continuously develops a sliding surface, resulting in the unstable failure of the granary. This research is expected to provide the technical guidance for the design and popularization of underground granaries.

Interrogating the health condition of rails using the narrowband Rayleigh waves emitted by an innovative design of non-contact laser transduction system

The article reports an innovative optical system that is designed to interrogate the health condition of macroscopically intact rail specimens by measuring its inherent nonlinearity using the narrowband Rayleigh waves. A line-arrayed pattern is developed through the optical system that generates narrowband Rayleigh waves with high power on the surface of the rail. As a result of lattice-anharmonicity, a second harmonic is produced in the wave that is sensed by a scanning laser Doppler vibrometer. The spectral amplitudes of the first and generated second harmonics are used to calculate the inherent nonlinearity using an amplitude-based nonlinearity equation. These measurements are carried out on the head, web, and foot of the rail. The performance of the non-contact experiment is also compared with that of a contact experiment carried out using wedge transducers. The experimentally evaluated nonlinearity of the rail steel is further compared with that obtained using a physics-based nonlinearity equation that relies on the higher-order elastic constants. Agreement of the results shows that the new optical system is effective in generating Rayleigh waves in rails and thereby measuring the inherent nonlinearity of the rail track. The estimation of inherent nonlinearity may help in diagnosing the health status of the macroscopically intact rail specimens in terms of their microstructural consistency and level of dissolved impurities before fixing them on a track.

Adolescents’ face mask usage and contact transmission in novel Coronavirus

The global outbreak of coronavirus has become an international public health threat. Prevention is of paramount importance to contain its spread. This study observes face mask wearing behavior and contact transmission problems in Taiwan. Teachers track student status in class. In addition to measuring body temperature and regular disinfection, classrooms require ventilation wear mask, provide alcohol spray and avoid sharing the microphone. Both questionnaire surveys and experimental were utilized. A total of 160 adults residing in Taiwan participated in the survey. The dye simulated the possible virus area on the mask surface during usage. Subjects were required to complete a questionnaire and simulate the spread of contact transmission when using a computer. Eighty-one % of respondents reported consistent use of surgical masks several times a day. They reported taking their masks off in relatively safe areas. Most people reported using one mask per day and storing the masks in their pockets. As a result, masks surface become a contamination source. In the contact experiment, ten adults were requested to don and doff a surgical mask while doing a word processing task. The extended contamination areas were recorded and identified by image analysis. The results show an average contamination area of the workspace is significant 530 cm2. When the hand touches the surface of the mask, it may spread the virus to the subsequent contact area.

Electrical Erosion Characteristics of Pt-Ir-Zr Alloy Contact under DC Load

The analysis of electrical erosion characteristics of contacts under DC load is conducive to the in-depth study of the arc erosion mechanism. Through the electrical contact experiment, the electrical erosion status of the Pt-Ir-Zr alloy under DC load of 25V/15A is studied in this paper. The results show that: the contacts have excellent anti-welding behavior and lower loss on arc ablation. The separation acceleration of the breaking process between the movable and static contacts is 154.32μm/ms2. The arc erosion surfaces of the material show a large number of paste-like coagulum and bubbles. There are some micro-cracks existing on the surface of the Pt-Ir-Zr alloy contacts. The obvious material transfer phenomenon occurs between the movable and static contacts under DC load.