Hydrodynamic Performance of Open-frame Deep Sea Remotely Operated Vehicles Based on Computational Fluid Dynamics Method

The resistance performance and motion stability of deep sea remotely operated vehicles (ROVs) subjected to underwater motion conditions are studied on the basis of the unsteady Reynolds-averaged Navier-Stokes method combined with the six-degree-of-freedom equation of motion to quickly and accurately predict them. In the modeling process, we consider the complexity of ROV geometry and thus reduce the model to a series of regular geometries to maximize the position and weight of the original components. The grid and value slots of an ROV are divided, and the surface is reconstructed. The forward, backward, transverse, floating, and submerged resistance of ROVs are simulated and compared with existing experimental forces to determine the accuracy of the calculation method. Then, the oblique navigation of the ROV on the horizontal and vertical planes is studied. Furthermore, the motion response of the ROV to direct horizontal motion, heave, pitch, and yaw are studied. The force, moment, and motion time curves are obtained. The stability of ROV motion is analyzed to provide technical support for the safety of ROVs.

Resistance and Endurance Exercise Training Induce Differential Changes in Gut Microbiota Composition in Murine Models

Background: The effect of resistance training on gut microbiota composition has not been explored, despite the evidence about endurance exercise. The aim of this study was to compare the effect of resistance and endurance training on gut microbiota composition in mice.Methods: Cecal samples were collected from 26 C57BL/6N mice, divided into three groups: sedentary (CTL), endurance training on a treadmill (END), and resistance training on a vertical ladder (RES). After 2 weeks of adaption, mice were trained for 4 weeks, 5 days/week. Maximal endurance and resistance capacity test were performed before and after training. Genomic DNA was extracted and 16S Ribosomal RNA sequenced for metagenomics analysis. The percentages for each phylum, class, order, family, or genus/species were obtained using an open-source bioinformatics pipeline.Results: END showed higher diversity and evenness. Significant differences among groups in microbiota composition were only observed at genera and species level. END showed a significantly higher relative abundance of Desulfovibrio and Desulfovibrio sp., while Clostridium and C. cocleatum where higher for RES. Trained mice showed significantly lower relative abundance of Ruminococcus gnavus and higher of the genus Parabacteroides compared to CTL. We explored the relationship between relative taxa abundance and maximal endurance and resistance capacities after the training period. Lachnospiraceae and Lactobacillaceae families were negatively associated with endurance performance, while several taxa, including Prevotellaceae family, Prevotella genus, and Akkermansia muciniphila, were positively correlated. About resistance performance, Desulfovibrio sp. was negatively correlated, while Alistipes showed a positive correlation.Conclusion: Resistance and endurance training differentially modify gut microbiota composition in mice, under a high-controlled environment. Interestingly, taxa associated with anti- and proinflammatory responses presented the same pattern after both models of exercise. Furthermore, the abundance of several taxa was differently related to maximal endurance or resistance performance, most of them did not respond to training.

The Fire Resistance Performance of Concrete Columns With Different Compressive Strength

Four full concrete columns have been created Tested below high temperature for The fire resistance of concrete elements in concrete with particular compressive strengths. The standard concrete with compressive strength values of C25 were made of one of the four specimens, while the rest were made of C35, C60 and C75 respectively, respectively. During simulation of Within the laboratory furnace, the same For the specimens, axial forces were applied. Many experimental outcomes parameters were evaluated in contrast, including temperature changes, Vertical moving, side deflection, fire resistance and Failed properties of the specimen. The results have shown a rise in the compressive strength of the concrete for the concrete columns from the outside up to the inside of the column the same cross section of the lower compressive forces of concrete display better fire resistance efficiency with the same initial axial strength ratio. The C35, C60 and C75 columns' fire resistance is higher than standard concrete columns. The initial and secant rigidity of the columns of Reinforced concrete (RC) has also The percentage decreased dramatically after fire exposure and the temperature increased from 25 to 750 ° C.

Gas Well Deliquification in the Presence of High Content of Condensate: From Laboratory to Field Test

Two foaming formulations, an amphoteric surfactant (noted as Fam) and a blend of anionic-cationic-amphoteric surfactants (noted as Facam) have been prepared and tested at lab and in field in the presence of high content of condensate (60 vol% on average). Foam height with Facam are close to those with Fam. Although Fam has better foam stability without condensate, the half-life of the foam (t1/2) decreases by 50% in presence of condensate. Foam generated by Facam shows better oil resistance performance due to negative spreading coefficient (S). Liquid unloading efficiency with Facam are close to those with Fam at lab. Nevertheless in field application, Facam is more efficient than Fam for the deliquification in the gas well. The depth of gas well is 2126 m. Foaming formulations were injected respectively from casing pipe with injection amount of 1-2kg/day. The pressure difference between casing and tubing pipes (ΔPc-t) decreased from 1.0 MPa to 0.28 MPa, and the decline of gas production was slowed down after the injection of Facam in the gas well. As a contrast, both theΔPc-t and decline rate of gas production were increased with Fam. Foam resistance to condensate is a factor, while emulsion viscosity is inferred to be another crucial factor for the performance of formulations in the deliquification process.

Experience Study on Long-Life Microsurfacing with High Water Resistance Performance

Microsurfacing is a standard preventive maintenance technology developed on the basis of slurry sealing technology. However, the high temperature and rainy season in Guangdong Province affect its expanded application because of its low water resistance and short service life. So, high-performance microsurfacing, a new microsurfacing technology, has been developed. The key to this technique is an appropriate proportion of water-based epoxy resin and waterborne epoxy curing agent, which could generate a chemical reaction to form a high-performance bonding network structure of space. And indoor wet-wheel wear test shows that its antiwear ability and resistance to water damage are evidently increased (to over 50%) compared with the conventional microsurfacing. Furthermore, from the long-term road performance results, the antisliding and water resistance performance of high-performance microsurfacing is much higher than the conventional technique.