Drilling is a widely used machining process. As the hole drilling operation progresses, a drill-bit gradually degrades until it breaks at the end of its life. Replacing a drill-bit after it is breakage can be costly in certain special applications. At the same time an early tool replacement decision may lead to lower tool life utilisation. This calls for methods that enable accurate prediction ...

The internal pressure of simple bone cysts was found to be slightly higher than the normal pressure of the bone marrow in the contralateral limb. The pressure within the cyst was measured during drilling with a Kirschner wire; it gradually decreased as the number of drill-holes increased. The PO2 of the cyst fluid was markedly lower than that of either venous or arterial blood measured synchron...

Previous studies have established that the selection of gas extraction borehole parameters is crucial for effectiveness extraction. To more accurately determine reasonable radius boreholes in coal seam, this study was based on actual occurrence conditions body. A coal-seam gas-seepage model, considering dynamic changes permeability under gas–solid coupling conditions, constructed. It combined w...