Metal Magnetic Memory (MMM) testing method has its own effective and unique advantages on the research of extension of metal crack. The array magnetic memory testing sensor designed and assembled in accordance with specific conditions, could evidently enhance testing-efficiency, such as for components with complex shape or large surface area, and may simplify the test equipment correspondingly. A kind of array magnetic memory sensor with Hall elements as core components was designed and an experiment on metal magnetic memory testing on extension of metal crack was executed. The experiment results indicate that the magnetic memory testing technique could effectively monitor and qualitatively evaluate the progress of metal crack extension.
We adopted self-rating symptom scale to evaluate 242 students from medical colleges who took part in association activities for 16 weeks. Results indicate: the depression and anxiety of students joining martial art association were significantly improved; students joining football and ping-pong ball associations had significantly improved interpersonal relationship, depression and anxiety; students joining fitness exercises and sport dancing association had more comprehensive improvement in mental status.
With the rapid improvement of urbanization and the acceleration of urban-rural integration, environmental problems in China call for urgent actions. One of the important factors of non-effective treatment of Chinese urban pollution is due to the lagging of construction of urban environmental infrastructure. By analysis, this paper concludes that the limited number of investment entities, rare amount of capital investment and poor investment effectiveness account for the slow pace of construction of urban environmental infrastructure in China. Considering this, the government should allocate a larger share of fiscal capital investment, adopt preferential taxation policy and green financial policy, and perform public-private cooperation to smoothen the construction of urban environmental infrastructure.
Three typical external carbon sources (i.e. leachate, hydrolysates from primary sludge and starch solution) with regard to the denitrification process were investigated respectively in sequencing batch reactors (SBR) and their denitrification properties were compared to provide the optimum substrate suited for nitrogen removal processes. The variations of nitrogen were examined and nitrate utility ratio as well as carbon consumption rate was exhibited, denitrification kinetics regarding leachate was also analyzed by use of zero-order kinetic model. The experimental results indicated that the similar denitrification trend was achieved between hydrolysates from primary sludge and starch solution other than leachate as carbon source in denitrification system. The nitrate was not entirely degraded and the nitrite generated permanent accumulation. Compared with other carbon sources, leachate in steady operation showed the highest nitrate removal concentration and rate in phase I with an average of 13 mg/L and 86%, respectively. In phase II, the maximum nitrate and carbon decomposition rates were 0.088 g N/g VSS•d and 0.848 g TOC/g VSS•d respectively occurring at leachate as substrate. Thus, stable leachate was considered as the most suitable carbon source in comparison with other substrates.
Effective stage-to-stage isolation is typically accomplished by setting a bridge plug in a properly cemented casing between stages. This isolation plays a vital role in a horizontal well multistage fracturing completion. Failure of isolation not only impacts the well productivity but also wastes fracturing materials. The challenges isolation failure poses for stimulation effectiveness include both detection and remediation. First, there has been historically no reliable and cost-effective solution to detect stage-to-stage isolation onsite. One may only start to realize this problem when inconsistent production is observed. Second, existing remedial actions are seldom satisfying in case of an isolation failure. Most commonly, a new plug is set to replace the failed one. However, because the perforation clusters of an unstimulated stage may create irregularities in well inside diameter (ID) (e.g., casing deformation or burr), there is a risk that the plug will be damaged or become stuck when it passes the perforation area. Also, when the plug passes a perforation cluster, the perforations start to take in the pump-down fluid, which can increase the difficulty of the pump-down job. A novel remedial action uses high-frequency pressure monitoring (HFPM) and diversion to solve both challenges. The stage isolation integrity is evaluated in quasi-real time by analyzing the water hammer after the pump shutdown. In the case of a plug failure, large-particle fracture diversion materials and techniques can establish temporary wellbore isolation through a quick and simple delivery process. To close the cycle, the effect of the diversion can be evaluated by HFPM, which can reveal the fluid entry point of the treatment fluid after diversion. The technique was applied to two cases in Ordos basin in which wellbore isolation failure interrupted the operation. The problem identification, development of the solution workflow, and observation from treatment analysis are discussed. In both cases, the stage-to-stage isolation was recovered, and the drilled sand body was successfully stimulated without involving costly and time-consuming well intervention. The stimulation operation of the entire well was successfully resumed in a timely manner.
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