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Forcing (other)
Forcing may refer to: Mathematics and science *Forcing (mathematics), a technique for obtaining independence proofs for set theory *Forcing (computability), a modification of Paul Cohen's original set theoretic technique of forcing to deal with the effective concerns in recursion theory *Forcing (horticulture), bringing a cultivated plant into growth outside of its natural season. *Forcing, driving a harmonic oscillator at a particular frequency *Cloud forcing, the difference between the radiation budget components for average cloud conditions and cloud-free conditions * Forcing bulbs, the inducement of plants to flower earlier than their natural season *Radiative forcing, the difference between the incoming radiation energy and the outgoing radiation energy in a given climate system Arts, entertainment, and media *Forcing (magic), a technique by which a magician forces one outcome from a card draw * Forcing, several distinct concepts within the game of contract bridge: ** Forcing b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forcing (mathematics)
In the mathematical discipline of set theory, forcing is a technique for proving consistency and independence (mathematical logic), independence results. Intuitively, forcing can be thought of as a technique to expand the set theoretical universe (mathematics), universe V to a larger universe V[G] by introducing a new "generic" object G. Forcing was first used by Paul Cohen (mathematician), Paul Cohen in 1963, to prove the independence of the axiom of choice and the continuum hypothesis from Zermelo–Fraenkel set theory. It has been considerably reworked and simplified in the following years, and has since served as a powerful technique, both in set theory and in areas of mathematical logic such as recursion theory. Descriptive set theory uses the notions of forcing from both recursion theory and set theory. Forcing has also been used in model theory, but it is common in model theory to define generic filter, genericity directly without mention of forcing. Intuition Forcing is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forcing (computability)
Forcing in computability theory is a modification of Paul Cohen's original set-theoretic technique of forcing to deal with computability concerns. Conceptually the two techniques are quite similar: in both one attempts to build generic objects (intuitively objects that are somehow 'typical') by meeting dense sets. Both techniques are described as a relation (customarily denoted \Vdash) between 'conditions' and sentences. However, where set-theoretic forcing is usually interested in creating objects that meet every dense set of conditions in the ground model, computability-theoretic forcing only aims to meet dense sets that are arithmetically or hyperarithmetically definable. Therefore, some of the more difficult machinery used in set-theoretic forcing can be eliminated or substantially simplified when defining forcing in computability. But while the machinery may be somewhat different, computability-theoretic and set-theoretic forcing are properly regarded as an application of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forcing (horticulture)
Forcing is the horticultural practice of bringing a cultivated plant into active growth outside of its natural growing season. Plants do not produce new growth or flowers (and hence fruit) during the winter, and many species only produce flowers or fruit for a very limited period. Forcing allows horticulturalists to produce these flowers and fruits at other times. This can be accomplished by cultural, physical, or chemical means, and is typically done to produce out-of-season flowers or fruit for display, consumption or sale. Forcing allows the more predictable production of products for sale, and can improve the quality of the products in some cases. Plants respond to different types of cues to break dormancy. Forcing usually involves manipulating the temperature of the plants. Forcing a certain plant may mean it needs a certain amount of time experiencing very cold weather, or experiencing hot weather prior to cold weather. They may also need to have a wet period or a dry period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harmonic Oscillator
In classical mechanics, a harmonic oscillator is a system that, when displaced from its equilibrium position, experiences a restoring force ''F'' proportional to the displacement ''x'': \vec F = -k \vec x, where ''k'' is a positive constant. The harmonic oscillator model is important in physics, because any mass subject to a force in stable equilibrium acts as a harmonic oscillator for small vibrations. Harmonic oscillators occur widely in nature and are exploited in many manmade devices, such as clocks and radio circuits. If ''F'' is the only force acting on the system, the system is called a simple harmonic oscillator, and it undergoes simple harmonic motion: sinusoidal oscillations about the equilibrium point, with a constant amplitude and a constant frequency (which does not depend on the amplitude). If a frictional force ( damping) proportional to the velocity is also present, the harmonic oscillator is described as a damped oscillator. Depending on the friction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cloud Forcing
Cloud feedback is a type of climate change feedback, where the overall cloud frequency, height, and the relative fraction of the different types of clouds are altered due to climate change, and these changes then affect the Earth's energy balance. On their own, clouds are already an important part of the climate system, as they consist of water vapor, which acts as a greenhouse gas and so contributes to warming; at the same time, they are bright and reflective of the Sun, which causes cooling. Clouds at low altitudes have a stronger cooling effect, and those at high altitudes have a stronger warming effect. Altogether, clouds make the Earth cooler than it would have been without them. If climate change causes low-level cloud cover to become more widespread, then these clouds will increase planetary albedo and contribute to cooling, making the overall cloud feedback ''negative'' (one that slows down the warming). But if clouds become higher and thinner due to climate change, then ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bulbs
In botany, a bulb is a short underground stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs during dormancy. In gardening, plants with other kinds of storage organ are also called ornamental bulbous plants or just ''bulbs''. Description The bulb's leaf bases, also known as scales, generally do not support leaves, but contain food reserves to enable the plant to survive adverse conditions. At the center of the bulb is a vegetative growing point or an unexpanded flowering shoot. The base is formed by a reduced stem, and plant growth occurs from this basal plate. Roots emerge from the underside of the base, and new stems and leaves from the upper side. Tunicate bulbs have dry, membranous outer scales that protect the continuous lamina of fleshy scales. Species in the genera ''Allium'', ''Hippeastrum'', '' Narcissus'', and ''Tulipa'' all ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiative Forcing
Radiative forcing (or climate forcing) is a concept used to quantify a change to the balance of energy flowing through a planetary atmosphere. Various factors contribute to this change in energy balance, such as concentrations of greenhouse gases and aerosols, and changes in surface albedo and solar irradiance. In more technical terms, it is defined as "the change in the net, downward minus upward, radiative flux (expressed in W/m2) due to a change in an external driver of climate change." These external drivers are distinguished from feedbacks and variability that are internal to the climate system, and that further influence the direction and magnitude of imbalance. Radiative forcing on Earth is meaningfully evaluated at the tropopause and at the top of the stratosphere. It is quantified in units of watts per square meter, and often summarized as an average over the total surface area of the globe. A planet in radiative equilibrium with its parent star and the rest of sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forcing (magic)
In stage magic, a force is a method of controlling a choice made by a spectator during a trick. Some forces are performed physically using sleight of hand, such as a trick where a spectator appears to select a random card from a deck but is instead handed a known card by the magician. Other forces use equivocation (or "the magician's choice") to create the illusion of a free decision in a situation where all choices lead to the same outcome. Equivocation Equivocation (or the magician's choice) is a verbal technique by which a magician gives an audience member an apparently free choice but frames the next stage of the trick in such a way that each choice has the same end result. An example of equivocation can be as follows: A performer deals two cards on a table and asks a spectator to select one. If the spectator chooses the card on the left, the performer will hand the card to the spectator. If they pick the card on the right, the performer will take that card as his own and hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contract Bridge
Contract bridge, or simply bridge, is a trick-taking game, trick-taking card game using a standard 52-card deck. In its basic format, it is played by four players in two Team game, competing partnerships, with partners sitting opposite each other around a table. Millions of people play bridge worldwide in clubs, bridge tournaments, tournaments, online and with friends at home, making it one of the world's most popular card games, particularly among Old Age, seniors. The World Bridge Federation (WBF) is the governing body for international competitive bridge, with numerous other bodies governing it at the regional level. The game consists of a number of , each progressing through four phases. The cards are to the players; then the players ''call'' (or ''bid'') in an seeking to take the , specifying how many tricks the partnership receiving the contract (the declaring side) needs to take to receive points for the deal. During the auction, partners use their bids to exchange infor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forcing Bid
In the card game contract bridge, a forcing bid is any that obliges the partner to bid over an intermediate opposing pass. Owing to the partnership's bidding system or a bridge convention A bridge convention is an agreement about an artificial or a set of related artificial calls. Calls made during the auction phase of a contract bridge game convey information about the player's card holdings. Calls may be " natural" (that is, are ..., partner must "keep the bidding open", i.e. not pass, thereby preventing his left-hand opponent from ending the auction with a pass and enabling the "forcing bidder" to bid further. A forcing bid that creates no further obligation is called ''forcing for one round''. A bid that is ''forcing and promises a rebid'' creates an obligation on the forcing bidder next round (typically, up to some level of the auction). A ''game forcing'' bids creates a mutual obligation to continue bidding at least to game level, or to double the opponents. All bridge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forcing Defense
A forcing defense in contract bridge aims to force declarer to repeatedly ruff the defenders' leads. If this can be done often enough, declarer eventually runs out of trumps and may lose control of the hand. A forcing defense is therefore applicable only to contracts played in a trump suit. The defense should try to make declarer ruff in the long trump hand. Unless declarer is playing for a dummy reversal, he usually intends to ruff losers in the short trump hand anyway. If the defense can shorten declarer's trumps sufficiently, it may wind up with more trumps than declarer. In that case, the defense will be able to pull any remaining trumps and run its own winners. A forcing defense is usually begun on the opening lead because the tempo is often important. It is indicated when: *The defense knows or suspects that the trump suit is breaking badly for declarer. *There is a side suit that declarer will have to ruff. *The defense has enough entries that it will be able to continue le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forcing Notrump
The forcing notrump is a bidding convention in the card game of bridge. In Standard American bidding, the response of 1NT to an opening bid of 1 or 1 shows 6 to 9 high card points (HCP) and is ''non-forcing''. Opener, with a balanced minimum, may pass the 1NT response and, if the opponents also pass, that will become the contract. A partnership may agree that this bid is ''forcing'' for one round; if the intervening opponent passes, opener must bid at least once more. This guarantees the responder at least one more opportunity to bid or pass. This mechanism allows the partnership to use the 1NT response for a greater variety of hands: in particular, ''invitational'' as well as ''minimum'' responder holdings. The forcing notrump is used over major suits only; 1NT is always standard and non-forcing over the minor suit In contract bridge the minor suits are diamonds () and clubs (). They are given that name because contracts made in those suits score less (20 per contracted trick ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
