Water Disaster Types and Water Control Measures of Hanxing Coal Mine Area

AbstractHanxing coal mine area is a typical karst high-water deposit. With further exploration of under-group coal seams, various threats of water disasters came. Coal water disasters can be divided into five types through comprehensive study on geological and hydro-geological conditions of the coal mine area. The five kinds of water disasters are surfer water disaster, coal roof aquifer water disaster, coal floor high-pressure Ordovician karst water disaster, goaf water disaster and karst collapse column water disaster. For all types of water disasters, corresponding water control measures were proposed and these water control measures are of great theoretical and realistic significance to the mine safety and high-level decision in Hanxing coal mine area

Rapid Maxillary Anterior Teeth Retraction En Masse by Bone Compression: A Canine Model

The present study sought to establish an animal model to study the feasibility and safety of rapid retraction of maxillary anterior teeth en masse aided by alveolar surgery in order to reduce orthodontic treatment time.Extraction of the maxillary canine and alveolar surgery were performed on twelve adult beagle dogs. After that, the custom-made tooth-borne distraction devices were placed on beagles' teeth. Nine of the dogs were applied compression at 0.5 mm/d for 12 days continuously. The other three received no force as the control group. The animals were killed in 1, 14, and 28 days after the end of the application of compression.The tissue responses were assessed by craniometric measurement as well as histological examination. Gross alterations were evident in the experimental group, characterized by anterior teeth crossbite. The average total movements of incisors within 12 days were 4.63±0.10 mm and the average anchorage losses were 1.25±0.12 mm. Considerable root resorption extending into the dentine could be observed 1 and 14 days after the compression. But after consolidation of 28 days, there were regenerated cementum on the dentine. There was no apparent change in the control group. No obvious tooth loosening, gingival necrosis, pulp degeneration, or other adverse complications appeared in any of the dogs.This is the first experimental study for testing the technique of rapid anterior teeth retraction en masse aided by modified alveolar surgery. Despite a preliminary animal model study, the current findings pave the way for the potential clinical application that can accelerate orthodontic tooth movement without many adverse complications.It may become a novel method to shorten the clinical orthodontic treatment time in the future

Effects of guide vane thickness on pressure pulsation of mixed-flow pump in pumped-storage power station

The pressure pulsation is one of the key factors affecting instability operation and vibration of large mixed-flow pump units in pumped-storage power station. The unsteady flow field in a mixed-flow pump with different guide vane thicknesses was numerically simulated based on the standard k-ε turbulence model, the SIMPLE algorithm and the sliding mesh technique. By setting pressure measurement points, the pressure pulsation characteristics in the impeller inlet, outlet and the middle of guide vane were discussed and the influence of the guide vanes’ thickness on pressure pulsation was analyzed. The results show that the type of numerical simulation grid, turbulence model can accurately predict the internal flow characteristics of the mixed-flow pump. The dominant frequency of pressure pulsation was approximate to the impeller blade passing frequency. The thickness of the guide vane have less influence on pressure pulsation in the inlet of impeller, and have more influence on pressure pulsation in the middle of guide vane. Compared with the thinning guide vanes, the pressure pulsation amplitude of the thicken guide vane increase 7.8 %. Therefore, appropriately reducing the thickness of guide vane is beneficial to the stability of the internal flow of guide vane

Hydrocarbon Generation Potential Evaluation of Coal Shale Gas of Permo-Carboniferous in Jiyang Depression

This paper studied the residual strata distribution of Carboniferous-Permian in Jiyang Depression, the organic geochemical characteristics of shale and the correlation of hydrocarbon-generating potential of shale by applying geochemistry, petroleum geology and coal geology, for study hydrocarbon generation potential of Permo-Carboniferous coal shale in Jiyang Depression. The results show that the thickness of Carboniferous-Permian residual strata in Jiyang Depression is generally 200-800 m, the thickest can reach 900 m; coal shale has good organic matter abundance and is type III kerogen, which is conducive to gas generation, and organic matter maturity reaches maturity-higher maturity stage; Benxi Formation and Taiyuan Formation have better hydrocarbon generation potential; medium to good hydrocarbon source rocks can be found in every sag of Shanxi Formation hydrocarbon source rocks, but the scope is limited, and the overall evaluation is still medium. Compared with other areas in China, it is found that the hydrocarbon-generating capacity of coal-bearing shale of Carboniferous-Permian in Jiyang Depression is generally at a medium level, which has a certain shale gas exploration potential