triple point

Noun

triple point (plural triple points)

1. The unique temperature and pressure at which the solid, liquid and gas phases of a substance are all in equilibrium.
   • A solid sublimes only when the pressure of its vapor is below that of the triple point for that substance.2006, David B. Troy, Paul Beringer, Remington: The Science and Practice of Pharmacy, →ISBN, page 179
2. A point where the incident shock wave, the reflected shock wave, the Mach stem, and one slipstream meet.
   • When the incident shock wave is at position “a” the second triple point, T, is still inside the zone where the vibrational degree of freedom has not yet reached its equilibrium and the dissociational degree of freedom is still frozen at that position, as its excitation can be assumed to start only...2007, Gabi Ben-Dor, Shock Wave Reflection Phenomena, →ISBN, page 198
   • A triple point may have a convex Mach stem, in which case the SS points upward.2012, George Emanuel, Shock Wave Dynamics: Derivatives and Related Topics, →ISBN, page 81
3. A point where a curve or surface intersects itself along three arcs.
   • The number of the distinguished edges whose orientations point towards the triple point is exactly one, or exactly two.1998, J. Scott Carter, Masahico Saito, Knotted Surfaces and Their Diagrams, →ISBN, page 162
   • A cubic surface with a triple point (a cubic cone) may or may not be rational.2007, Rida T Farouki, Pythagorean-Hodograph Curves: Algebra and Geometry Inseparable, →ISBN
4. The intersection of an occluded front, cold front, and warm front.
   • A further investigation is made of the reasonably-close relationship between some multiple tornado outbreaks in the British Isles and the passage of frontal-system triple points (TPs) using, principally, TORRO records and the hourly British Isles charts archived by the Meterorological Office at...1993, Meteorological and Geoastrophysical Abstracts
   • ...together at the point of occlusion, or triple point, where conditions are favorable for formation of a new cyclone, sometimes called a secondary cyclone.2002, Joseph M. Moran, Online weather studies, →ISBN, page 232
5. The point where two boundaries, such as a dry line, outflow boundary, or cold front, intersect.
   • Few, however, reach the African continent; some dissipate in the intertropical-front bulge east of southern Africa; others form triple points with the temperate fronts available for recurving anywhere between Australia and the Seychelles-Madagascar-Mascarenes (Reunion-Mauritius-Rodriguez) sector.1947, Maurice Adolph Garbell, Tropical and Equatorial Meteorology, page 205
   • It is concluded that the severe storms formed in close proximity to a "triple point" (TP), at which a synoptic cold front and "insolation-enhanced" warm front intersected.2006, The International Journal of Meteorology
6. (plate tectonics) A point where three plates intersect.
   • Such a 'piecrust model' has been used to explain the generation of triple points which can give rise to splitting of a continental body.2003, Neville Price, Major Impacts and Plate Tectonics, →ISBN, page 131
   • Microstructures like static mineral growth, equilibrated grain boundaries with triple points especially in quartz and feldspar fabric and the lack of plastic crystal lattice deformations even in quartz indicate that metamorphism outlasted deformation.2012, O. Oncken, C. Janssen, Basement Tectonics 11 Europe and Other Regions, →ISBN, page 43