Hole Stemming

S. J. Pennycook. EMSA Bulletin. 19, 67, 1989. A summary of compositional imaging using a high-angle annular dark-field detector in a field emission STEM instrument published by the Electron Microscopy Society of America, Box EMSA Woods Hole, MA 02543. 

A 12S-ml. distilling flask is fitted (Note 1) with a condenser set for distillation and with a long-stem dropping funnel. The condenser is connected by means of an adapter to a 250-ml. Erlenmeyer flask. Through a second hole in the stopper of the... 

Decoking is a routine daily occurrence accomplished by a high-pressure water jet. First the top and bottom heads of the coke drum are removed then a hole is drilled in the coke from top to hottom.. A rotating stem is lowered through the hole, spraying a jet high-pressure water sidewavs... 

BHA — Change bottom hole assembly DMF — Down hole motor failure DSF — Drill string failure DST — Drill stem test DTF — Down hole tool failure LOG — Run logs CM — Condition mud CP — Core point DP — Drill plug FM — Formation change... 

Downhole drilling tools are the components of the lower part of a drill string used in normal drilling operations such as the drill bits, drill collars, stabilizers, shock absorbers, hole openers, underreamers, drilling jars as well as a variety of drill stem subs. 

Let us introduce another early example by Slater, 1951, where the electron density is exploited as the central quantity. This approach was originally constructed not with density functional theory in mind, but as an approximation to the non-local and complicated exchange contribution of the Hartree-Fock scheme. We have seen in the previous chapter that the exchange contribution stemming from the antisymmetry of the wave function can be expressed as the interaction between the charge density of spin o and the Fermi hole of the same spin... 

It was early recognised that an explosive is more hazardous in a coal mine if it is fired in a borehole from which the stemming is omitted or blown out early by the explosive than if it is fired in a properly stemmed hole and does adequate work in bringing down rock or coal. The tests which led to the original permitted explosives, now called P1 explosives, were therefore designed to test the product under these conditions. 

Figure 14.10 illustrates the method of seismic prospecting on land by what is known as reflection shooting. A hole usually 10 to 12 cm in diameter is drilled to a depth of 15 to 30 m. The charge of explosive is likely to be 5 to 12-5 kg and the stemming used is usually water. As the explosive must fire under a depth of water which may exceed 45 m, special varieties of gelatines are employed (see p. 53). Alternatively, a powder explosive can be sealed into pressure-resistant metal containers. Special detonators are also employed, not only to withstand the possible head of water, but also to have a specially short bursting time (see p. 113). 

Signs Plants infected with citrus canker have characteristic lesions on leaves, stems, and fruit with raised, brown water-soaked margins usually with a yellow hallow effect around the lesion. Incubation is typically 14-60 days. Older lesions may fall out, creating a shot-hole effect. Fruit production declines and then stops. The disease ultimately kills the tree. 

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