Search

Aiming to address the problems of high cost, large size and complex structure of the traditional back-to-back three-level converter, this paper proposes a new dual-port three-level converter topology. This new topology reduces the number of switching devices and optimizes the system size through device multiplexing. Firstly, the operating principle of the proposed converter topology is analyzed in detail, outlining the six effective switching states, current flow paths, and corresponding dual-port output levels of the single leg, while also discussing and the voltage stresses of each switching device. Secondly, a level-shifting pulse width modulation for the proposed converter topology is investigated and designed, and the effect of modulating wave overlap is avoided by adding DC offsets. Thirdly, the key problems of the modulation scheme under both the common frequency and different frequency operation modes, such as the modulation regime range and phase angle difference constraints are analyzed. The principles for selecting DC offsets and constraint range of two-port modulation system in each operating mode are introduced. Finally, the different operating modes are verified using the DSP-FPGA-Typhoon HIL 402 experimental platform. The experimental results show that level-shifting pulse width modulation with DC offsets makes the output power quality of the converter better and the harmonic content lower on the premise of achieving stable output of voltage and current for the proposed converter topology.

Summary: A novel hybrid‐multiplexed fifteen‐switch converter (HM‐15SC) topology, which can simultaneously output a set of three‐phase AC and three sets of DC, is proposed to address the problems of a single type of power electronic converter and the complexity of coordinated control of AC/DC hybrid systems for smart grid. In this paper, we conduct a detailed analysis of the topology and operating principles of HM‐15SC. This includes an examination of the converter's effective switching states in relation to output voltage, current paths, and maximum voltage stress. In addition, a modulation strategy combining single‐leg independent model prediction current control (SL‐MPCC) and time‐sharing cooperative (TSC) ideas is proposed to establish a single‐leg AC current prediction model, which effectively reduces the prediction arithmetic under the premise of realizing three‐leg independent prediction control and optimal control of AC/DC hybrid outputs. Finally, we verify the feasibility and superiority of the proposed HM‐15SC topology and its modulation strategy using the Typhoon HIL 402 platform. [ABSTRACT FROM AUTHOR]

Rockburst, one of the leading types of disaster in mining and rock engineering causing serious injuries and the loss of property, frequently occurs, involving various features and complex evolutionary mechanisms. Compared to rockbursts occurring at mining faces, those occurring in main roadways cause more serious problems for mine production. This paper first analyzes the characteristics of rockbursts in main roadways using two case studies involving the Gaojiapu and Cuimu coal mines. The causes of rockbursts in main roadways were studied using microseismic monitoring, energy density cloud maps, and seismic velocity tomography. During the mining of the 22306 working face in the Cuimu coal mine, targeted measures, such as deep-hole blasting of the roof strata and deep-hole blasting of the coal seam, were implemented to prevent rockbursts in the main roadways. The effectiveness of these measures was verified through long-term analysis of tremor activities. The study found that the influence of mining at two working faces on both sides of main roadways was significantly greater than that from a single-sided working face. The intensity of the tremor activities occurring near the main roadways was correlated with the distance from the working face to the main roadways. The closer the working face was to the main roadways, the stronger the tremor activities were near the main roadways. According to the distribution range of the tremors, the influence area of working face mining exceeded 800 m, with tremors distributed linearly along the main roadways. Even five months after the completion of working face mining, there were still a large number of tremors near the main roadways, which gradually disappeared after another five months. Mining activities were the main reason for the occurrence of main roadway rockbursts and the stress concentration within the main roadways themselves was another reason for the occurrence of rockbursts. The influence of working face mining could be reduced by deep-hole blasting of roof strata and the stress concentration within main roadways themselves could be reduced by large-diameter drilling. Those joint preventive measures effectively prevented the occurrence of rockbursts in main roadways. This study is of important theoretical and practical significance for further studies of rockburst mechanisms and prevention in regard to main roadways in coal mines, and the findings are significant in terms of the enhancement of safety in coal mines. [ABSTRACT FROM AUTHOR]

The increasing global focus on carbon capture and storage (CCS) has highlighted the potential for offshore CO2 sequestration, particularly following recent successes in onshore projects. This research investigates the qualitative analysis of carbon trapping efficiency in offshore basins, employing a GEM simulator to incorporate factors such as aqueous solubility and geochemistry. The findings reveal that anticlines represent ideal geological structures for carbon storage, effectively trapping a significant portion of injected CO2. For effective mineralization, it is crucial to dissolve CO2 into saline aquifers to generate H+, which facilitates the release of Ca2+ and Al3+ from anorthite. This process leads to the dissolution of anorthite and the precipitation of kaolinite, while calcite transitions from a dissolved state to a precipitated state over time. The analysis indicates that structural trapping provides the highest storage contribution during the injection phase, whereas residual gas trapping becomes dominant by the end of the simulation. Notably, it is observed that the storage contribution of structural trapping decreases from 28.39% to 19.05%, and the percentage increase in storage contributions of residual gas, solubility, ionic, and mineral trapping are 4.12%, 3.25%, 1.69%, and 0.28% for CO2 plus water injection, thereby improving the long-term security of CO2 storage in offshore basins. It is most beneficial to optimize the layout and design of the injection well to ensure a uniform distribution of carbon dioxide and to increase the injection rate. [ABSTRACT FROM AUTHOR]

We previously demonstrated that glycyrrhizin (GL) suppressed inflammation and carcinogenesis in an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced murine model of colorectal cancer (CC). In this study, we found an accumulation of regulatory T cells (Tregs) in the spleen and suppression by GL in model mice. ICR mice were divided into four groups: Control, GL, CC, and GL-treated CC (CC+GL), and were sacrificed 20 weeks after AOM/DSS treatment. We measured spleen weight, areas of white and red pulp, and CD8+ T cells (cytotoxic T lymphocytes, CTL), and CD11c-positive cells (dendritic cells) in splenic tissues and forkhead box protein 3 (FoxP3)-positive cells (Tregs) in colorectal and splenic tissues. In all cases, the CC group showed a significant increase compared with those in Control group, and GL administration significantly attenuated this increase. These results indicate that Tregs accumulated in the spleen may participate in inflammation-related carcinogenesis by suppressing CTL. We also suggest that GL which binds to high-mobility group box 1 (HMGB1), suppresses carcinogenesis with decreasing Tregs in the spleen. Furthermore, there was an expression of FoxP3 in cancer cells, indicating that it may be involved in the malignant transformation of cancer cells. [ABSTRACT FROM AUTHOR]

To investigate the variations in wave velocity fields between impact and outburst coal seams, we analyzed the fluctuations in wave velocity under loading conditions for both coal types. A comprehensive methodology was developed to correct coal wave velocities in response to stress and gas presence, which was then applied to field assessments of hazardous regions. Our findings reveal significant differences in wave velocity alterations between impact and outburst coal seams during loading-induced failure. Gas pressure exhibits a negative correlation with wave velocity in outburst coal (correlation coefficient R2 = 0.86), whereas wave velocity in impact coal demonstrates a positive correlation with stress (R2 = 0.63). A robust methodology for correcting coal wave velocities in response to stress and gas presence was established to enable more accurate measurement of wave velocity changes. In field applications, seismic wave computed tomography identified stress anomalies that closelycorresponded with geological structures and mining operations, effectively pinpointing hazardous zones. The abnormal wave velocity coefficient ranges for outburst coal seams and impact coal seams are −0.6 to 0.25 and −0.35 to 0.16, respectively, which correspond well with the field stress distribution. [ABSTRACT FROM AUTHOR]