Mechanism and experiment of substituting high drainage roadway with directional long drilling group to extract pressure-relief gas

By establishing the numerical model in the vertical plane and the similar model in the horizontal plane of gas flow in goaf, the influence of high drainage roadway or drilling on the gas seepage field was analyzed, and the extraction mechanism was clarified. On this basis, the academic thought of directional long drilling group instead of high drainage roadway was put forward. And then using complex function theory, the permeation mechanical model of drilling group with circle distribution in the mining-induced fracture zone was established to explore the coupling relationship between the drilling quantity, extraction volume and the equivalent extraction rate of single drilling. Finally, combined with the concrete geological production conditions, the main parameters of directional long drilling group were determined. The distance between the drilling group center and the air-return roadway is 24 m, the height is 18 m, and the three drillings are in an approximate equilateral triangle distribution with a space of 8 m. The equivalent extraction square is 4.15 m2. It is shown that the effect of directional long drilling group is evident. The gas content in the upper comer is controlled below 0.95%, the content in the tail roadway is kept below the alarm value, and the content is over 50% in the drill, realizing the secure and effective extraction of coal and gas.

Research progress on the application of microneedle transdermal drug delivery system in dermatology

Transdermal drug delivery systems(TDDs)have the advantages on good local targeting,controlled and sustainable drug delivery.Hoewever,the stratum corneum,as the main skin barrier,severely limits the transdermal penetration of drugs and reduces bioavailability,which also limits their application.Microneedles(MNS)penetrate the stratum corneum and create several reversible microchannels in a minimally invasive manner to significantly improve the penetration of therapeutic agents,and are considered a milestone for effective transdermal drug delivery.As an emerging drug delivery modality,microneedle transdermal drug delivery systems have the advantages of being minimally invasive,safe,efficient,economical and convenient.In addition to the extensive research on microneedles for improving transdermal drug delivery,there is a growing interest in using them to manage and treat dermatological conditions.Being the largest organ in the human body,the skin acts as a barrier between the body and the external environment,while having an immense influence on appearance and self-confidence.Indeed,there is now a considerable body of evidence on how dermatological conditions can lead to psychological problems and a reduced quality of life.The utilisation of microneedle transdermal drug delivery systems for the management and treatment of dermatological conditions is of great therapeutic and commercial value.The principleof microneedle transdermal drug delivery systems and the progress of its clinical application in dermatology are reviewed here.