Pinch point
Pinch point may refer to:
See also
Pinch point (mathematics)
In geometry, a pinch point or cuspidal point is a type of singular point on an algebraic surface.
The equation for the surface near a pinch point may be put in the form
where [4] denotes terms of degree 4 or more and 
is not a square in the ring of functions.
For example the surface 
near the point 
, meaning in coordinates vanishing at that point, has the form above. In fact, if 
and 
then {
} is a system of coordinates vanishing at then 
is written in the canonical form.
The simplest example of a pinch point is the hypersurface defined by the equation 
called Whitney umbrella.
The pinch point (in this case the origin) is a limit of normal crossings singular points (the -axis in this case). These singular points are intimately related in the sense that in order to resolve the pinch point singularity one must blow-up the whole -axis and not only the pinch point.
See also
References
Pinch point (economics)
A pinch-point is the level of inventories of a commodity or product below which consumers of that commodity or product become concerned about security of supply. When inventories are below the pinch-point, small changes in the balance of supply and demand can cause large changes in the price of the commodity or product.
The term was suggested in 1988 by Walter Curlook (Executive Vice-President of Inco Ltd) and was first published by Raymond Goldie with Rob Maiman in 1990. In 2000 Raymond Goldie trademarked the term.
References
Digging bar
A digging bar is a long, straight metal bar used as a hand tool to deliver blows to break up and loosen hard or compacted materials (e.g., soil, rocks, concrete, ice) or as a lever to move objects. Digging bars are known by various other names depending on locale, structural features, and intended purpose. In Britain, Australia and New Zealand the tool is referred to as a crowbar, pry bar, or just a bar. In North America digging bars have various names including slate bar, shale bar, pinch point bar, and San Angelo bar. In Russian, it is typically called a lom (лом).
Uses
Common uses of digging bars include breaking up clay, concrete, frozen ground, and other hard materials, moving or breaking up tree roots and obstacles, and making holes in the ground for fence posts. They are often used where space would not allow use of a pickaxe.
Materials and construction
The ends of a digging bar are shaped during manufacturing to make them useful for various purposes. Typically, each end has a different shape so as to provide two different tool functions in one tool. Common end shapes include:
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