Three Phase
Three-phase electric power is a common method of alternating-current electric power transmission.[1] It is a type of polyphase system, and is the most common method used by electric power distribution grids worldwide to distribute power. It is also used to power large motors and other large loads. A three-phase system is generally more economical than others because it uses less conductor material to transmit electric power than equivalent single-phase or two-phase systems at the same voltage.[2]
In a three-phase system, three circuit conductors carry three alternating currents (of the same frequency) which reach their instantaneous peak values at different times. Taking one conductor as the reference, the other two currents are delayed in time by one-third and two-thirds of one cycle of the electrical current. This delay between "phases" has the effect of giving constant power transfer over each cycle of the current, and also makes it possible to produce a rotating magnetic field in an electric motor.
NFPA 704
NFPA 704 is a standard maintained by the
U.S.-based
National Fire Protection Association. It defines the colloquial "
fire diamond" used by emergency personnel to quickly and easily identify the risks posed by nearby hazardous materials. This is necessary to help determine what, if any, specialty equipment should be used, procedures followed, or precautions taken during the first moments of an emergency response.
Vela6911
The
Vela Incident (sometimes referred to as the
South Atlantic Flash) was an as-yet unidentified
double flash of
light detected by a
United States Vela satellite on
September 22,
1979. It has been speculated that the double flash, characteristic of a nuclear explosion, was the result of a
nuclear weapons test. A US presidential panel concluded that it "was probably not from a nuclear explosion, although [it cannot be ruled] out that this signal was of nuclear origin"
[1], but others examining the data "including DIA, the national laboratories, and contractors reached a very different conclusion - that the data supported the conclusion that on September 22, 1979 Vela 6911 had detected a nuclear detonation."
[2]
Uncanny Valley
The
uncanny valley is a hypothesis that when
robots and other facsimiles of humans look and act almost, but not entirely, like actual humans, it causes a response of revulsion among human observers. The "valley" in question is a dip in a proposed graph of the positivity of human reaction as a function of a robot's lifelikeness. It was introduced by
Japanese roboticist
Masahiro Mori in
1970, and has been linked to
Ernst Jentsch's concept of "
the uncanny" identified in a
1906 essay, "On the Psychology of the Uncanny." Jentsch's conception is famously elaborated upon by
Sigmund Freud in a
1919 essay, simply entitled "The Uncanny" ("
Das Unheimliche"). A similar problem exists in realistic
3D computer animation, such as with the film
The Polar Express.
[1]
Indifference Curves
In
microeconomic theory, an
indifference curve is a
graph showing different bundles of
goods, each measured as to quantity, between which a consumer is
indifferent. That is, at each point on the curve, the consumer has no
preference for one bundle over another. In other words, they are all equally preferred. One can equivalently refer to each point on the indifference curve as rendering the same level of
utility (satisfaction) for the consumer. Utility is then a device to represent
preferences rather than something from which preferences come (Geanakoplis, 1987, p. 117). The main use of indifference curves is in the
representation of potentially observable
demand patterns for individual consumers over commodity bundles (Böhm and Haller, 1987, p. 785).
Carnot Cycle
The Carnot cycle is a particular thermodynamic cycle, modeled on the hypothetical Carnot heat engine, proposed by Nicolas Léonard Sadi Carnot in 1824 and expanded upon by Benoit Paul Émile Clapeyron in the 1830s and 40s.
Every thermodynamic system exists in a particular state. A thermodynamic cycle occurs when a system is taken through a series of different states, and finally returned to its initial state. In the process of going through this cycle, the system may perform work on its surroundings, thereby acting as a heat engine.
A heat engine acts by transferring energy from a warm region to a cool region of space and, in the process, converting some of that energy to mechanical work. The cycle may also be reversed. The system may be worked upon by an external force, and in the process, it can transfer thermal energy from a cooler system to a warmer one, thereby acting as a Heat Pump rather than a heat engine.
The Carnot cycle is the most efficient cycle possible for converting a given amount of thermal energy into work or, conversely, for using a given amount of work for refrigeration purposes.
Methane Clathrate
Methane clathrate, also called methane hydrate or methane ice, is a solid form of water that contains a large amount of methane within its crystal structure (a clathrate hydrate). Originally thought to occur only in the outer regions of the Solar System where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under sediments on the ocean floors of Earth. [1]
