Study on Influence of Surface Plasma Activation of Quartz Fiber/Cyanate Ester Composite at Meter Range Working Distance

The surface of quartz fiber/cyanate ester composite at meter working distance was activated by plasma treatment technology. Influence of plasma treatment parameters on surface contact angle of the composite was investigated, as well as changes of surface morphology, intrinsic performance and membrane-based bonding strength. Results showed that surface contact angle of the composite decreased significantly after plasma treatment with nitrogen and argon. Moreover, activation effect of argon plasma was better than that of nitrogen plasma. With the increase of voltage, surface contact angle of composite became smaller and activation effect was better. After plasma treatment, glass transition temperature (Tg) and bending strength of the composite did not change, and intrinsic property of the composite was not damaged. After plasma treatment, surface roughness and specific surface area of the composite increased, and membrane-based bonding strength of the composite with Al coating increased significantly.

Study on Micro-Characteristics of Microbe-Induced Calcium Carbonate Solidified Loess

Microbial-induced carbonate precipitation (MICP) has outstanding characteristics in solidifying soil, such as good fluidity, ecological environmental protection, adjustable reaction, etc., making it have a good application prospect. As a typical silty clay, the composition of loess is fine, and the microstructure is quite different from that of sand. Previous research has found that the unconfined compressive strength of loess cured by MICP can be increased by nearly four times. In this paper, by comparing the changes of structural characteristics of undisturbed loess before and after MICP solidification, the mechanism of strength improvement of loess after MICP solidification is revealed from the microscopic level. Firstly, the microstructure of loess before and after solidification is tested by scanning electron microscope, and it is found that the skeleton particles of undisturbed loess are granular, and the soil particles coexist in direct contact and indirect contact, and the pores in soil are mainly overhead pores compared with the microstructure of solidified loess, it is found that the surface contact between aggregates increases obviously, and calcium carbonate generated by MICP is adsorbed around the point contact between aggregates, which makes the contact between soil particles change from point contact to surface contact. Then, Pores (Particles) and Cracks Analysis System (PCAS) is used to quantitatively analyze the pores of loess before and after solidification. The results show that the total pore area, the maximum total pore area and porosity of soil samples decrease, and the total number of pores decreases by 13.2% compared with that before MICP solidification, indicating that a part of calcium carbonate produced by MICP reaction accumulates in tiny pores, thus reducing the number of pores. One part is cemented between soil particles, which increases the contact area of particles. Therefore, some pores of loess solidified by MICP are filled and densified, the contact area between soil particles is increased, and the strength of loess under load is obviously improved.

Spatial distributions of <i>X</i>_CO₂ seasonal cycle amplitude and phase over northern high-latitude regions

Satellite-based observations of atmospheric carbon dioxide (CO2) provide measurements in remote regions, such as the biologically sensitive but undersampled northern high latitudes, and are progressing toward true global data coverage. Recent improvements in satellite retrievals of total column-averaged dry air mole fractions of CO2 (XCO2) from the NASA Orbiting Carbon Observatory 2 (OCO-2) have allowed for unprecedented data coverage of northern high-latitude regions, while maintaining acceptable accuracy and consistency relative to ground-based observations, and finally providing sufficient data in spring and autumn for analysis of satellite-observed XCO2 seasonal cycles across a majority of terrestrial northern high-latitude regions. Here, we present an analysis of XCO2 seasonal cycles calculated from OCO-2 data for temperate, boreal, and tundra regions, subdivided into 5∘ latitude by 20∘ longitude zones. We quantify the seasonal cycle amplitudes (SCAs) and the annual half drawdown day (HDD). OCO-2 SCAs are in good agreement with ground-based observations at five high-latitude sites, and OCO-2 SCAs show very close agreement with SCAs calculated for model estimates of XCO2 from the Copernicus Atmosphere Monitoring Services (CAMS) global inversion-optimized greenhouse gas flux model v19r1 and the CarbonTracker2019 model (CT2019B). Model estimates of XCO2 from the GEOS-Chem CO2 simulation version 12.7.2 with underlying biospheric fluxes from CarbonTracker2019 (GC-CT2019) yield SCAs of larger magnitude and spread over a larger range than those from CAMS, CT2019B, or OCO-2; however, GC-CT2019 SCAs still exhibit a very similar spatial distribution across northern high-latitude regions to that from CAMS, CT2019B, and OCO-2. Zones in the Asian boreal forest were found to have exceptionally large SCA and early HDD, and both OCO-2 data and model estimates yield a distinct longitudinal gradient of increasing SCA from west to east across the Eurasian continent. In northern high-latitude regions, spanning latitudes from 47 to 72∘ N, longitudinal gradients in both SCA and HDD are at least as pronounced as latitudinal gradients, suggesting a role for global atmospheric transport patterns in defining spatial distributions of XCO2 seasonality across these regions. GEOS-Chem surface contact tracers show that the largest XCO2 SCAs occur in areas with the greatest contact with land surfaces, integrated over 15–30 d. The correlation of XCO2 SCA with these land surface contact tracers is stronger than the correlation of XCO2 SCA with the SCA of CO2 fluxes or the total annual CO2 flux within each 5∘ latitude by 20∘ longitude zone. This indicates that accumulation of terrestrial CO2 flux during atmospheric transport is a major driver of regional variations in XCO2 SCA.

New Approaches to Increasing the Superhydrophobicity of Coatings Based on ZnO and TiO2

The work presented is devoted to new approaches to increasing the superhydrophobic properties of coatings based on zinc oxide (ZnO) and titanium dioxide (TiO2). There is an innovation in the use of inorganic coatings with a non-polar structure, high melting point, and good adhesion to ZnO, in contrast to the traditionally used polymer coatings with low performance characteristics. The maximum superhydrophobicity of the ZnO surface (contact angle of 173°) is achieved after coating with a layer of hematite (Fe2O3). The reason for the abnormally high hydrophobicity is a combination of factors: minimization of the area of contact with water (Cassie state) and the specific microstructure of a coating with a layer of non-polar Fe2O3. It was shown that the coating of ZnO structures with bimodal roughness with a gold (Au) layer that is 60-nm thick leads to an increase in the wetting contact angle from 145° to 168°. For clean surfaces of Au and hematite Fe2O3 films, the contact angle wets at no more than 70°. In the case of titanium oxide coatings, what is new lies in the method of controlled synthesis of a coating with a given crystal structure and a level of doping with nitrogen using plasma technologies. It has been shown that the use of nitrogen plasma in an open atmosphere with different compositions (molecular, atomic) makes it possible to obtain both a hydrophilic (contact angle of 73°) and a highly hydrophobic surface (contact angle of 150°).

Analysis of Tooth Surface Contact Stress of Involute Spur Gear

Through the establishment of a pair of spur gear contact models, based on Hertz contact theory, the tooth surface contact stress is calculated; then the Ansys finite element analysis software is used to simulate and analyse the stress distribution. Through the analysis and comparison of the two results, it is proved that the contact stress calculated by Hertz theory is relatively small, which is close to the results of the finite element simulation analysis. Theoretical calculation can verify the accuracy of the finite element simulation analysis model, and the finite element simulation analysis provides an effective way to accurately calculate the contact stress of the tooth surface.

HTR-10 OTTO Cycle Depletion Simulation Using Discrete Element Method Coupled Monte Carlo

Pebble bed reactor core contains 27,000 pebbles placed in a random position. Since the pebble insertion relies on gravity, the pebble placement pattern is irregular. Discrete Element Method used to simulate the pebble interaction and pebble movement during HTR-10 operation. Even though pebbles distributed randomly, the random generation of pebble positions used in most research does not mimic the actual pebble position and pebble surface contact. The Discrete Element Method provides a realistic interpretation of the pebble position by considering the pebble surface contact and gravity force. Each pebble coordinates from the Discrete Element Method obtained to construct Monte Carlo geometry of the HTR-10 core realistically. By coupling the DEM simulation with Monte Carlo simulation, it is possible to calculate the depletion while considering the core dynamic characteristic. The OTTO recirculation depletion calculation scheme with steady 10MW power for 368 days was constructed and demonstrated in this work. The DEM coupled Monte Carlo method allow one to track and predict each depleted fuel composition. Although the flux distribution change is slight in every timestep, the relation between flux and depleted U235 and Xe135 composition deserves to be taken into account. The calculation model in this work is comparable with the other calculation, but the timestep adjustment is needed to provide more accurate and representative results. Flux calculation and depletion simulation performed using the OpenMC program with ENDF/B-VIII.0 cross-section data. Please refer to digital version to view graph.