A size-adjustable trumpet-shaped riser was installed into a conventional airlift reactor to form a modified internal-loop airlift reactor (ILAR). The volumetric oxygen mass transfer coefficient (k L a) and gas holdup of the ILAR were heavily influenced by the height ratio of riser to static fluid level above the spargers (h/H), the cross-sectional area ratio of riser to downcomer (A r /A d ) and the superficial gas velocity in the riser (U g ) when deoxidized distilled water was used as the oxygen absorbent. An oxygen transfer rate of (2.17 ± 0.11) × 10 À5 kg m À3 s À1 , k L a of (27.88 ± 1.12) × 10 À3 s À1 and gas holdup of 0.031 were obtained with the ILAR of A r /A d = 1.09 and h/H = 0.73 at U g = 18 mm s À1 . As the well-constructed preset trumpet-shaped riser provided ideal conditions for complete circulation and blending of the fluid, enhanced oxygen transfer efficiency was achieved. The gas holdup and k L a were increased by 16.2% and 10.2% at 19°C, as compared with those of the conventional airlift reactor without this preset riser. The fluid rising velocity in the riser (V R ) and falling velocity in the downcomer (V D ) may be expressed by power-law functions of U g and A r /A d , respectively. These metrics indicate that the ILAR has better performance, as compared with a conventional airlift reaction, for oxygen transfer and microorganism culture for chemical engineering, biological fermentation and environmental protection.
In order to improve the accuracy and efficiency of the inspection of the appearance quality of the electrical connector in the acceptance process of the low frequency cable, the machine vision recognition technology is studied to realize the appearance quality inspection of the electrical connector on the existing low frequency cable, in order to improve the quality and efficiency of appearance inspection of low-frequency cable connectors, various kinds of defects such as slanting, missing and shrinking wires can be identified automatically.
Fujian provincial grid was connected into East China grid through two parallel tie lines of 500kV in 2002. Outof-step oscillation may occur between Fujian Province Grid andEast China grid under the critical contingencies. System separation devices have been installed on 500kV tie-lines between Fujian grid and East China grid to maintain system stability. As the newly built UHV Binjin DC transmission system was projected to come in service in 2014, power injected into East China grid through the system was gradually increased to its full capacity in accordance with the implementation of the project by three stages. The characteristics of out-of-step oscillation between Fujian grid and East China grid may be altered due to the significant changes involving tie lines, reinforcement and reconfiguration of local system as well as the scale of power injection. To investigate the characteristics of out-of-step oscillation, extreme contingencies contributing to out-of-step oscillation are identified based on the analysis of the practical grid operation. For each stage of Binjin transmission project, the center of out-of-step oscillation is determined through the simulation analysis of the oscillation characteristics for East China grid. The applicability of the existing system separation devices is evaluated, and system separation strategy is then reviewed for East China grid to accommodate the operation of UHV Binjin DC transmission project.
This article integrate the theoretical calculation of the power-frequency electromagnetic field intensity and radio interference intensity under transmission line, and analyze the factor which influence the value and distribution of the electromagnetic field, radio interference under transmission line, aiming to provide basis and reference for other environmental assessment of electromagnetism. The study shows that a reasonable selection of analog lines can get an accurate result as the theoretical calculation. Important factors of analog lines selection including: grade of voltage, current, height of line, location order of line, number of circuit, section area of line, number of bundle conductors.
Given the complexity of the soil environment, the evaluation of soil pollution should consider the comprehensive weight of multiple evaluation factors to obtain highly objective and scientific conclusions. In this paper, two main ways are proposed to comprehensively analyze the degree of heavy metal pollution in the region: the combination of subjective weight (the analytic hierarchy process method) and objective weight (the entropy method) to determine the combination weight, and the use of the TOPSIS method to quantify the relative relationship between samples and the soil background values in the study area and analyze the spatial and geographical distribution of heavy metal elements in the samples.Analysis results show that the weight ranking of 31 out of 56 samples in the study area is higher than that based on the soil background value of Hubei Province, indicating that 55.36% of the samples had a comprehensive pollution degree lower than the soil background value of Hubei Province. According to the spatial distribution of heavy metal pollution, the soil pollution status in the study area is poor, and some parts are polluted by heavy metals to a certain extent.
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