| 释义 |
critical point
critical pointn.1. Physics The temperature and pressure at which the liquid and gaseous phases of a pure stable substance become identical. Also called critical state.2. Mathematics A value in the domain of a given function at which the function has a derivative of zero or a derivative that does not exist. For example, 1 is a critical point for the function x2 - 2x and 0 is a critical point for the function │ × │.critical point n 1. (General Physics) physics a. the point on a phase diagram that represents the critical state of a substanceb. another name for critical state 2. (Mathematics) maths the US name for stationary point crit′ical point`
n. the point at which a substance in one phase, as the liquid, has the same density, pressure, and temperature as in another phase, as the gaseous. [1875–80] critical point1. A key geographical point or position important to the success of an operation.
2. In point of time, a crisis or a turning point in an operation.
3. A selected point along a line of march used for reference in giving instructions.
4. A point where there is a change of direction or change in slope in a ridge or stream.
5. Any point along a route of march where interference with a troop movement may occur.Thesaurus| Noun | 1. | critical point - a crisis situation or point in time when a critical decision must be made; "at that juncture he had no idea what to do"; "he must be made to realize that the company stands at a critical point"crossroads, juncturecrisis - an unstable situation of extreme danger or difficulty; "they went bankrupt during the economic crisis"criticality - a critical state; especially the point at which a nuclear reaction is self-sustaining |
Translationscritical point
critical point[′krid·ə·kəl ′pȯint] (mathematics) A point at which the first derivative of a function is either 0 or does not exist. (petroleum engineering) A location on the drilling line which is subject to strain when the pipe is run into or pulled out of the drill hole. (physical chemistry) The temperature and pressure at which two phases of a substance in equilibrium with each other become identical, forming one phase. The temperature and pressure at which two ordinarily partially miscible liquids are consolute. Critical Point a point on a phase diagram corresponding to the critical state. The critical point of two-phase liquid-vapor equilibrium is the end point on the equilibrium curve and is characterized by the critical values of the temperature Tc, pressure Pc, and volume Vc (see Table 1). | Table 1. Parameters of the liquid-vapor critical point of some substances |
|---|
| | Tc
(oK)> | pc
(atm)* | Vc × 106
(m3 /mole) |
|---|
| * 1 atm = 1.01 × 106 N/m2 | | Helium........... | 5.3 | 2.26 | 57.8 | | Hydrogen........... | 33.0 | 12.8 | 61.8 | | Oxygen................. | 154.8 | 50.1 | 74.4 | | Nitrogen........... | 126.2 | 33.5 | 90.1 | | Carbon dioxide......... | 304.2 | 72.9 | 94.0 | | Propane............ | 369.9 | 42.0 | 200 | | Alcohol (ethyl)............ | 516.3 | 63.0 | 167 | | Bromine.............. | 584 | 102 | 144 | | Water........... | 647 | 218.3 | 56 | | Iodine........... | 785 | 116 | – | | Sulfur........... | 1313 | 116 | – | | Mercury........... | 1750 | 1,500 | 44 | | Cesium........... | 2030 | 115 | 332 |
The critical point is a particular case of the phase transition point and is characterized by the loss of thermodynamic stability with respect to the density or composition of the substance. On one side of the critical point the substance is homogeneous (usually when T > Tc); on the other it separates into phases. For mixtures or solutions a distinction should be made between the critical point of liquid-vapor equilibrium and the critical point of equilibrium of phases of different composition that are in the same state of aggregation (liquid-liquid or gas-gas). In this connection the critical point of mixtures (or solutions) is also characterized by the critical concentration xc. As a result of the increased number of parameters determining the system’s state, mixtures have not a critical point but rather a critical curve, whose points differ in the values of Tc, pc, Vc, and xc. Critical phenomena are observed in the region of the critical point. critical point The point between two bases from which it will take the same time to fly to either base.
An aircraft flying at flight level 350 has pressurization failure and is forced to descend to flight level 130. At critical point, it can either proceed to its destination airport or it can return to the airport of departure. It would take the same time to the either airport. The value of critical point will change if the aircraft is not incapacitated and can fly at the same altitude and speed.critical point
crit·i·cal pointa point at which two phases become identical; thus, at a given critical temperature and critical pressure, the liquid and gaseous state of a particular substance can no longer be differentiated.crit·i·cal point (kriti-kăl poynt) Stage at which two phases become identical; thus, at a given critical temperature and critical pressure, the liquid and gaseous states of a particular substance can no longer be differentiated. critical point
Synonyms for critical pointnoun a crisis situation or point in time when a critical decision must be madeSynonymsRelated Words |