Generators info

Narrows Dam is a dam located 6 miles north of Murfreesboro, Arkansas and impounds the water of the Little Missouri River (Arkansas) to create Lake Greeson. Narrows Dam was authorized as a flood control and hydroelectric power project by the Flood Control Act of 1941. The dam is a feature of the comprehensive plan for the Ouachita River Basin. Lake Greeson is operated for hydroelectric power, recreation, and flood control. [1]

The powerhouse of the dam is located adjacent to the east abutment, and it has a total length of 151 feet. The equipment of the powerhouse is three 8,500 KWh generating machines. The powerhouse originally had two generators, but a third was placed in 1969. The average annual output is 28,000,000 KWh.

The dam is named due to its location on the river, The Narrows. During the dam’s construction many cemeteries and graveyards had to be removed due to the creation of the new lake. Narrows Dam is located by the Swaha, or Narrows Dam recreational area.

Lake Greeson is divided into three layers so Narrows Dam can work and operate properly. The bottom portion of the lake always remains full so the powerhouse has enough pressure to operate. The middle layer or “Power Storage” portion is used to regulate the flow of water running into the generators of the dam. The top portion or “Flood Storage” is usually empty unless holding floodwater. A spillway at top of the dam is used to regulate the top portion of the dam, the spillway contains walls to maneuver the flow of the water, and a stilling basin is placed at the foot of the spillway to dissipate erosion from the spillway water hitting the base of the dam. The spillway isn’t used much due to the fact that flooding can be regulated by other means, such as the flood control conduits.

Construction on the dam began on April 1947, the first bucket of concrete was poured in June 1948. The dam was finished in 1950, and dedicated on July 1951.

See also

• List of Arkansas dams and reservoirs

Acid test may refer to:

• Litmus test (chemistry), a common pH test
• a phrase that refers to a foolproof test that will accurately determine the validity of something
• Acid2, a Cascading Style Sheets test
• in petrology, using acid to test rock or soil for carbonates
• a method using aqua regia to determine if real gold is found
• The Electric Kool-Aid Acid Test, a novel written by Tom Wolfe
• the “Acid Tests” conducted by the Merry Pranksters (and chronicled by Tom Wolfe)
• Acid Test (Liquidity Ratio), a ratio used to determine the liquidity of a business entity.
• Acid Test (band), a Canadian alternative rock band best known for its collaborations with the film Highway 61
• “The Acid Test”, a short story by Ian Rankin.

Vibrational energy relaxation, or vibrational population relaxation, is a process in which the population distribution of molecules in vibrationally quantum states of high energy level caused by an external perturbation returns to the Maxwell-Boltzmann distribution.

In solution, the process proceeds with intra- and intermolecular energy transfer. The excess energy of the excited vibrational mode is transferred to the kinetic modes in the same molecule or to the surrounding molecules. Through this process, the initially excited vibrational mode moves to a vibrational state of a lower energy. The relaxation is called the longitudinal relaxation, and the time constant of the relaxation is called the longitudinal relaxation time, or T₁.

Vibrational energy relaxation has been studied with time-resolved spectroscopy. By the excitation of the pump pulse, the population distribution of the vibrationally excited state is made by infrared absorption or a Raman process when the molecule is in the electronic ground state. In addition, by the electronic transition, the molecule often moves to the vibrationally excited state of the electronic excited state. The process of the energy relaxation from these vibrationally excited states can be observed with the probe pulse, which is delayed from the pump pulse.

A bandwidth-limited pulse (also known as Fourier-transform-limited pulse, or more commonly, transform-limited pulse) is a pulse of a wave that has the minimum possible duration for a given spectral bandwidth. Optical pulses of this type can be generated by modelocked lasers. Bandwidth-limited pulses have a constant phase across all frequencies making up the pulse.

Any waveform can be disassembled into its spectral components by Fourier analysis or Fourier transformation.
The length of a pulse thereby is determined by its complex spectral components, which include not just their relative intensities, but also the relative positions (spectral phase) of these spectral components.

A bandwidth-limited pulse can only be kept together if the dispersion of the medium the wave is travelling through is zero; otherwise dispersion management is needed to revert the effects of unwanted spectral phase changes.

Keeping pulses bandwidth-limited is necessary to compress information in time or to achieve high field densities, as with ultrashort pulses in modelocked lasers.

End distortion: In start-stop teletypewriter operation, the shifting of the end of all marking pulses, except the stop pulse, from their proper positions in relation to the beginning of the next start pulse.

Shifting of the end of the stop pulse is a deviation in character time and rate rather than an end distortion.

Spacing end distortion is the termination of marking pulses before the proper time. Marking end distortion is the continuation of marking pulses past the proper time.

The magnitude of the distortion is expressed as a percentage of an ideal pulse length.

In abstract algebra, a free algebra is the noncommutative analogue of a polynomial ring (which may be regarded as a free commutative algebra).

Let R be a commutative ring. The free algebra on n indeterminates, {X₁, …, X_n}, is the ring spanned by all linear combinations of products of the variables. This ring is denoted R<X₁, …, X_n>. With the obvious scalar multiplication R<X₁, …, X_n> forms an algebra over R. Unlike in a polynomial ring, the variables do not commute. For example X₁X₂ does not equal X₂X₁.

More generally, one can construct the free algebra R<E> on any set E of generators. Since rings may be regarded as Z-algebras, a free ring on E can be defined as the free algebra Z<E>.

Over a field, the free algebra on n indeterminates can be constructed as the tensor algebra on an n-dimensional vector space. For a more general coefficient ring, the same construction works if we take the free module on n generators.

The construction of the free algebra on E is functorial in nature and satisfies an appropriate universal property. The free algebra functor is left adjoint to the forgetful functor from the category of R-algebras to the category of sets.

See also

• Tensor algebra
• Free object

References

A rhythmic unit is a durational pattern which occupies a period of time equivalent to a pulse or pulses on an underlying metric level, as opposed to a rhythmic gesture. Rhythmic units may be classified as:

1. Metric: even-note patterns, such as steady eighth notes or pulses.
2. Intrametric: confirming patterns, such as dotted eighth-sixteenth note and swing patterns.
3. Contrametric: non-confirming, or syncopated patterns.
4. Extrametric: irregular patterns, such as tuplets.

(DeLone et al. (Eds.), 1975, chap. 3)

References

• DeLone et al. (Eds.) (1975). Aspects of Twentieth-Century Music. Englewood Cliffs, New Jersey: Prentice-Hall. ISBN 0-13-049346-5.

An isolator switch is part of an electrical circuit and is most often found in industrial applications, however they are commonly fitted to domestic extractor fans when used in bathrooms in the UK. The switch does exactly what its name suggests in that it electrically isolates the circuit or circuits that are connected to it. Such a switch is not used normally as an instrument to turn on/off the circuit in the way that a light switch does. Either the switch isolates circuits that are continually powered or is a key element which enables an electrical engineer to safely work on the protected circuit.

Isolator switches may be fitted with the ability for the switch to padlock such that inadvertent operation is not possible (see: Lock and tag). In some designs the isolator switch has the additional ability to earth the isolated circuit thereby providing additional safety. Such an arrangement would apply to circuits which inter-connect power distribution systems where both end of the circuit need to be isolated.

Major difference between isolator and circuit breaker is that isolator is an off-load device, whereas circuit breaker is an on-load device.

The Pulse can refer to:

In radio:

• The Pulse of West Yorkshire, a UK radio station originally known as Pennine Radio.
• 94.7 The Pulse, an Australian community radio station from Geelong, Victoria formerly known as 3YYR.
• The Pulse (program), an Australian radio program.
• The Pulse (radio station), an American internet radio station specializing in Electronic music.
• The Pulse (ESPN Radio), a college basketball program airing on ESPN Radio, similar to the TV show (below).

In comics:

• The Pulse (comics), a Marvel comic book about a section of the Daily Bugle newspaper focusing on superheroes.
• The Pulse (comics news), a comic book news website at Comicon.com [1].

In TV:

• The Pulse (TV), a US teen television show.
• The Pulse (ESPN) A ESPN Television show.

In Novels:

• The Pulse was the name of the signal transmitted from cell phones that made people go crazy in Stephen King’s Cell.

Other

• The Pulse - A lifestyle and entertainment magazine - Worcester, MA
• The Pulse - A weekly local music and entertainment magazine - Minneapolis, MN (http://www.pulsetc.com)

Mohammad Azhar Khan (born September 7, 1955, Gujranwala, Punjab) is a former Pakistani cricketer who played in one Test in 1980.

A Bipolar Violation, or BPV, is an error in the transmission of a T1 signal where two pulses of the same polarity occur without an intervening pulse of the opposite polarity.

T1 signals are transmitted using a scheme called Alternate Mark Inversion (AMI), where a ONE is represented by a pulse, and a ZERO is represented by no pulse. Pulses-which represent ones-always alternate in polarity, so that if, for example two positive pulses are received in succession, the receiver knows that one or more bits were either added or deleted from the original signal.

B8ZS coding is a scheme used in addition to AMI, which allows longer strings of consecutive zeroes to be transmitted.

Gaussian Frequency Shift Keying (GFSK) is a type of Frequency Shift Keying modulation that utilizes a Gaussian filter to smooth positive/negative frequency deviations, which represent a binary 1 or 0. It is used by DECT, Bluetooth, Cypress WirelessUSB, Nordic Semiconductor and z-wave devices. For Bluetooth the minimum deviation is 115 kHz.

Generalization

In a GFSK modulator, everything is the same as a FSK modulator except that before the baseband pulses (-1, 1) go into the FSK modulator, it is passed through a gaussian filter to make the pulse smoother so to limit its spectral width. Gaussian filtering is one of the very standard ways for reducing the spectral width, it is called Pulse Shaping.

If we use -1 for fc-fd and 1 for fc+fd, once when we jump from -1 to 1 or 1 to -1, the modulated waveform changes rapidly, which introduces large out-of-band spectrum. If we change the pulse going from -1 to 1 as -1, -.98, -.93 ….. .96, .99, 1, and we use this smoother pulse to modulate the carrier, the out-of-band spectrum will be reduced. <ref>www.palowireless.com “GFSK Differences & Advantages over FSK Modulation”</ref>

The Fourier transform of a Gaussian curve results in a Gaussian curve.

References

A pulse wave is a kind of non-sinusoidal waveform that is similar to a square wave, but does not have the symmetrical shape associated with a perfect square wave. It is a term common to synthesizer programming, and is a typical waveform available on many synths. The exact shape of the wave is determined by the duty cycle of the oscillator.
The pulse wave is also known as the rectangular wave, the periodic version of the rectangular function.

See also

• Rectangular function
• Pulse-width modulation
• Sine wave
• Triangle wave
• Square wave

In abstract algebra, a generating set of a group <math>G</math> is a subset S such that every element of G can be expressed as the product of finitely many elements of S and their inverses.

More generally, if S is a subset of a group G, then <S>, the subgroup generated by <math>S</math>, is the smallest subgroup of G containing every element of S, meaning the intersection over all subgroups containing the elements of S; equivalently, <S> is the subgroup of all elements of G that can be expressed as the finite product of elements in S and their inverses.

If G = <S>, then we say S generates G; and the elements in S are called generators or group generators. If S is the empty set, then <S> is the trivial group {e}, since we consider the empty product to be the identity.

When there is only a single element x in S, <S> is usually written as <x>. In this case, <x> is the cyclic subgroup of the powers of x, a cyclic group, and we say this group is generated by x. Equivalent to saying an element x generates a group is saying that it has order |G|, or that <x> equals the entire group G.

Finitely generated group

If S is finite, then a group G = <S> is called finitely generated. The structure of finitely generated abelian groups in particular is easily described. Many theorems that are true for finitely generated groups fail for groups in general.

Every finite group is finitely generated since <G> = G. The integers under addition are an example of an infinite group which is finitely generated by both <1> and <-1>, but the group of rationals under addition cannot be finitely generated. No uncountable group can be finitely generated.

Different subsets of the same group can be generating subsets; for example, if p and q are integers with gcd(p, q) = 1, then <{p, q}> also generates the group of integers under addition (by Bézout’s identity).

While it is true that every quotient of a finitely generated group is finitely generated (simply take the images of the generators in the quotient), a subgroup of a finitely generated group need not be finitely generated. For example, let G be the free group in two generators, x and y (which is clearly finitely generated, since G = <{x,y}>), and let S be the subset consisting of all elements of G of the form yⁿxy⁻ⁿ, for n a natural number. Since <S> is clearly isomorphic to the free group in countable generators, it cannot be finitely generated. However, every subgroup of a finitely generated abelian group is in itself finitely generated. Rather more can be said about this though: the class of all finitely generated groups is closed under extensions. To see this, take a generating set for the (finitely generated) normal subgroup and quotient: then the generators for the normal subgroup, together with preimages of the generators for the quotient, generate the group.

Free group

The most general group generated by a set S is the group freely generated by S. Every group generated by S is isomorphic to a factor group of this group, a feature which is utilized in the expression of a group’s presentation.

Frattini subgroup

An interesting companion topic is that of non-generators. An element x of the group G is a non-generator if every set S containing x that generates G, still generates G when x is removed from S. In the integers with addition, the only non-generator is 0. The set of all non-generators forms a subgroup of G, the Frattini subgroup.

Examples

The group of units U(Z₉) is the group of all integers relatively prime to 9 under multiplication mod 9 (U₉ ={1,2,4,5,7,8}). All arithmetic here is done modulo 9. Seven is not a generator of U(Z₉), since

<math>\{7^i\pmod{9}\ |\ i \in \mathbb{N}\} = \{7,4,1\}.</math>

while 2 is, since:

<math>\{2^i\pmod{9}\ |\ i \in \mathbb{N}\} = \{2,4,8,7,5,1\}.</math>

On the other hand, the symmetric group of size n is not cyclic, so it is not generated by any one element. However, it is generated by the two permutations (1 2) and (1 2 3 … n). For example, for S₃ we have:

e = (1 2)(1 2)

(1 2) = (1 2)

(2 3) = (1 2)(1 2 3)

(1 3) = (1 2 3)(1 2)

(1 2 3) = (1 2 3)

(1 3 2) = (1 2)(1 2 3)(1 2)

Infinite groups can also have finite generating sets. The additive group of integers has 1 as a generating set. The element 2 is not a generating set, as the odd numbers will be missing. The two-element subset {3, 5} is a generating set, since (-5) + 3 + 3 = 1 (in fact, any pair of coprime numbers is, as a consequence of Bézout’s identity).

See also

• Cayley graph
• Generating set for related meanings in other structures
• Presentation of a group

External links

• Mathworld: Group generators

Pulse Repetition Frequency (PRF) is the number of pulses transmitted per second by a radar. The reciprocal of this is called the Pulse Repetition Time (PRT), Pulse Repetition Interval (PRI), or Inter-Pulse Period (IPP), which is the elapsed time from the beginning of one pulse to the beginning of the next pulse. PRF is important since it determines the maximum target range (R_max) and maximum Doppler velocity (V_max) that can be accurately determined by the radar.

Range ambiguity

A radar system determines range through the time delay between pulse transmission and reception by the relation:

<math>Range = \frac{c\tau}{2}</math>

For accurate range determination a pulse must be transmitted and reflected before the next pulse is transmitted. This gives rise to the maximum range limit:

<math>Max Range = \frac{c\tau_{PRT}}{2} = \frac{c}{2PRF} \qquad \begin{cases} \tau_{PRT} = \frac{1}{PRF} \end{cases}</math>

The maximum range also defines a range ambiguity for all detected targets. Because of the periodic nature of pulsed radar systems, it is impossible for a radar system to determine the difference between targets separated by integer multiples of the maximum range using a single PRF. More sophisticated radar systems avoid this problem through the use of multiple PRFs either simultaneously on different frequencies or on a single frequency with a changing PRT.

See also

• Radar
• Pulse-Doppler radar
• Weather radar

The Pulse can refer to:

In radio:

• The Pulse of West Yorkshire, a UK radio station originally known as Pennine Radio.
• 94.7 The Pulse, an Australian community radio station from Geelong, Victoria formerly known as 3YYR.
• The Pulse (program), an Australian radio program.
• The Pulse (radio station), an American internet radio station specializing in Electronic music.
• The Pulse (ESPN Radio), a college basketball program airing on ESPN Radio, similar to the TV show (below).

In comics:

• The Pulse (comics), a Marvel comic book about a section of the Daily Bugle newspaper focusing on superheroes.
• The Pulse (comics news), a comic book news website at Comicon.com [1].

In TV:

• The Pulse (TV), a US teen television show.
• The Pulse (ESPN) A ESPN Television show.

In Novels:

• The Pulse was the name of the signal transmitted from cell phones that made people go crazy in Stephen King’s Cell.

Other

• The Pulse - A lifestyle and entertainment magazine - Worcester, MA
• The Pulse - A weekly local music and entertainment magazine - Minneapolis, MN (http://www.pulsetc.com)

In mathematics, a (B, N) pair is a structure on groups of Lie type
that allows one to give uniform proofs of many results, instead of giving a large number of
case-by-case proofs. Roughly speaking, it shows that all such groups are similar to the
general linear group over a field. They were invented by the mathematician Jacques Tits, and are also sometimes known as Tits systems.

Definition

A (B, N) pair is a pair of subgroups B and N of a group G such that the following axioms hold:

• G is generated by B and N.
• The intersection H of B and N is a normal subgroup of N.
• The group W = N/H is generated by a set of elements w_i of order 2, for i in some non-empty set I.
• If w_i is one of the generators of W and w is any element of W, then w_iBw is contained in the union of Bw_iwB and BwB.
• No generator w_i normalizes B.

The idea of this definition is that B is an analogue of the upper triangular matrices of
the general linear group GL_n(K), H is an analogue of the diagonal matrices,
and N is an analogue of the normalizer of H.

The subgroup B is sometimes called the Borel subgroup, H is sometimes called the Cartan subgroup, and W is called the Weyl group.

The number of generators w_i is called the rank.

Examples

• Suppose that G is any doubly transitive permutation group on a set X with more than 2 elements. We let B be the subgroup of G fixing a point x, and we let N be the subgroup fixing or exchanging 2 points x and y. The subgroup H is then the set of elements fixing both x and y, and W has order 2 and its nontrivial element is represented by anything exchanging x and y.

• Conversely, if G has a BN pair of rank 1, then the action of G on the cosets of B is doubly transitive. So BN pairs of rank 1 are more or less the same as doubly transitive actions on sets with more than 2 elements.

• Suppose that G is the general linear group GL_n(K) over a field K. We take B to be the upper triangular matrices, H to be the diagonal matrices, and N to be the matrices with exactly one non-zero element in each row and column. There are n-1 generators w_i, represented by the matrices obtained by swapping two adjacent rows of a diagonal matrix.

• More generally, any group of Lie type has the structure of a BN-pair.

Properties of groups with a BN pair.

The map taking w to BwB is an isomorphism from the set of elements of W to the set of double cosets of B; this is the Bruhat decomposition G = BWB.

The subgroups of G containing B are called parabolic subgroups. There are exactly 2ⁿ of them, and they correspond to subsets of I.

Applications

BN-pairs can be used to prove that most groups of Lie type are simple. More precisely, if G has a BN-pair such that B is a solvable group, the intersection of all conjugates of B is trivial, and the set of generators of W cannot be decomposed into two non-empty commuting sets, then G is simple whenever it is a perfect group. In practice all of these conditions except for G being perfect are easy to check. Checking that G is perfect needs some slightly messy calculations (and in fact there are a few small groups of Lie type which are not perfect or simple). But showing that a group is perfect is usually far easier than showing it is simple.

References

The standard reference for BN pairs is:

• Bourbaki, Nicolas, Lie Groups and Lie Algebras: Chapters 4-6 (Elements of Mathematics), ISBN 3-540-42650-7

COmbined Diesel-eLectric And Gas (CODLAG) is a modification of the combined diesel and gas propulsion system for ships.

A CODLAG system employs electric motors which are connected to the propeller shafts (usually 2). The motors are powered by diesel generators. For higher speeds, a gas turbine powers the shafts via a cross-connecting gearbox; for cruise speed, the drive train of the turbine is disengaged with clutches.

This arrangement combines the diesel engines used for propulsion and for electric power generation, greatly reducing service cost, since it reduces the number of different diesel engines and electric motors require considerably less maintenance. Also electric motors work efficiently over a wide range of revolutions and can be connected directly to the propeller shaft so that simpler gearboxes can be used to combine the mechanical output of turbine and diesel-electric systems.

Another advantage of the diesel-electric transmission is that without the need of a mechanical connection, the diesel generators can be decoupled acousticly from the hull of the ship, making it less noisy. This has been used extensively by military submarines but surface naval vessels like anti-submarine vessels will benefit as well. Usually CODLAG ships are equipped with rechargeable batteries like diesel-electric submarines as well, allowing it to manoeuvre in silence without any heavy machinery running.

A system which employs the gas turbines as turbo generators, i.e. like the diesel engines without mechanical transmission to the propellers, is not classified as CODLAG. Some passenger ships like the RMS Queen Mary 2 use this configuration with a pool of diesel generators for the base load and turbo generators for peak power.

List of CODLAG ships

• Type 23 frigate (Royal Navy)
• F125 class frigate (German Navy)
• GTS Finnjet (Finnish cruiseferry)

See also

• Diesel-electric

The Joint Level Interface Protocol (JLIP) is a video equipment control data standard.

JLIP was JVC’s answer to the Sony Control L or LANC two-way serial bus. It is used to allow devices communicate with other, carrying control signals and exchanging data. JLIP jacks are now fitted to all new JVC camcorders, some older models, some VCRs and peripheral devices, like their new video printer.

The A2W reactor is a naval reactor used by the United States Navy to provide electricity generation and propulsion on warships. The A2W designation stands for:

• A = Aircraft carrier platform
• 2 = Second generation core designed by the contractor
• W = Westinghouse was the contracted designer

This nuclear reactor was used in the world’s first nuclear-powered aircraft carrier, the USS Enterprise (CVN-65). The four propulsion plants on Enterprise each contain two reactors, numbered 1A-1B, 4A - 4B, 2A - 2B, and 3A - 3B (numbered as they are located from fore to aft). Each propulsion plant is capable of operating on one reactor plant through most of the power range required to propel the ship at speeds in excess of 33 knots (61 km/h) (with a possible maximum speed up to approximately 35 knots; higher speeds such as the 40-50 knots sometimes rumored would rapidly become impossible due to hydrodynamic drag even if the reactors were capable of delivering enough power). Both reactors would be on-line to simultaneously provide maximum ship speed and plane launching capability.

Design and operation

The reactors are pressurized water reactors fueled by highly-enriched (upwards of 93%) U-235. Light water is used as both neutron-moderator and reactor coolant. Hafnium Control rods are used to control the operation of the reactor. Extracting the rods to a calculated height allows the reactor to reach “criticality” - the point at which the nuclear fission reactions reach a self-sustaining level. Thereafter, steam flow (from the steam generators) regulates reactor power as explained below. The control rods are “shimmed” in or out to regulate average coolant temperature or lowered to the bottom of the reactor vessel to shut the reactor down (either done in a slow controlled manner or dropped rapidly during what is referred to as a SCRAM to immediately shut the reactor down.

Much of the reactor power control during steady state operation comes as a result of the coolant water’s negative temperature coefficient. The “power” of the reactor is determined by the number of fission events that takes place in the fuel at any given moment. As the water heats up, it expands and becomes less dense which provides fewer molecules per volume to moderate the neutrons, hence fewer neutrons are slowed to the required thermal energies to sustain thermal fission. Conversely, when the coolant water temperature decreases, its density increases and a greater number of neutrons reach the required thermal energy, increasing the number of fissions per unit of time, creating more heat. This has the effect of allowing “steam demand” to control reactor power, requiring little intervention by the Reactor Operator for changes in the power demanded by the ship’s operations.

The hot water from the reactors is sent, via large pipes, into heat exchangers called steam generators. There the heat from the reactor coolant water is transferred, through tube walls, to water being fed into the steam generators from a separate feed system. In the A1W and A2W systems, the pressurized water reactor coolant is kept between 525 and 545 °F (274 and 285 °C). In the steam generators, the water from the feed system is converted to steam at 535 °F (279 °C) and a pressure of about 600 lb/in² (4 MPa). Once the reactor coolant water has given off its heat in the steam generators, it is returned, via large electric pumps (four per reactor), to the reactors to repeat the cycle.

Saturated steam at 600 lb/in² (4 MPa) is channeled from each steam generator to a common header, where the steam is then sent to the main engine, electrical generators, aircraft catapult system, and various auxiliaries. The main propulsion turbines are double-ended, in which the steam enters at the center and divides into two streams as it enters the actual turbine wheels, expanding and giving up its energy as it does so, causing the turbine to spin at high speed. The main shaft enters a reduction gear in which the high rotational velocity of the turbine shaft is stepped down to a usable turn rate for propelling the ship. The expended steam from the main engine and other auxiliaries enters condensers to be cooled into water and recycled to the feed system.

North Walsham Town F.C. are a football club based in North Walsham, England.

In the 2007-08 season, they are members of the Anglian Combination Premier Division.

PSR J2144-3933 is a pulsar about 180 parsecs (5.5 Em) from earth. It was previously thought to have a period of 2.84 seconds but is now known to have a period of 8.51 s, which is the longest of any known radio pulsar (the previous longest was that of PSR J1951+1123 at 5.09 s).

J2144-3933 is notable for other reasons: its mean pulse profile is very narrow in comparison to the pulse period with a half-intensity width of less than one degree of longitude. It also has the lowest spindown luminosity of any pulsar at about 3×10³¹ watts.

Writing in Nature, astrophysicists M. D. Young and coworkers consider this object and suggest that its existence throws current theories into doubt. They state:

Moreover, under the usual model assumptions, based on the neutron-star equations of state, this slowly rotating pulsar should not be emitting a radio beam. Therefore either the model assumptions are wrong, or current theories of radio emission must be revised —from Nature 400, 848–849 (26 August 1999); doi:10.1038/23650)

Master-View is the second studio album by Hexstatic. The CD version of the album includes 2 discs - a CD and a DVD.

Track listing

1. “Extra Life”
2. “Chase Me”
3. “Telemetron”
4. “L-Virata”
5. “Perfect Bird”
6. “Salvador”
7. “Living”
8. “Distorted Minds”
9. “That Track”
10. “Toys Are Us”
11. “Pulse”

DVD Track list

The DVD that accompanied the CD album contained the following tracks. A pair of 3-D film glasses were also included in the packaging for use with the 3D videos (tracks 13 - 18):

1. Extra Life (2D video)
2. Chase Me (2D video)
3. Telemetron (2D video)
4. L-Virata (2D video)
5. Perfect Bird (2D video)
6. Perfect Bird (Astroboy version) (2D video)
7. Salvador (2D video)
8. Living Stereo (2D video)
9. Distorted Minds (2D video)
10. That Track (2D video)
11. Toys Are Us (2D video)
12. Pulse (2D video)
13. Telemetron (3D video)
14. Salvador (3D video)
15. Living Stereo (3D video)
16. Distorted Minds (3D video)
17. That Track (3D video)
18. Pulse (3D video)
19. Extra Life (DVD audio)
20. Chase Me (DVD audio)
21. Telemetron (DVD audio)
22. L-Virata (DVD audio)
23. Perfect Bird (DVD audio)
24. Perfect Bird (Astroboy version) (DVD audio)
25. Salvador (DVD audio)
26. Living (DVD audio)
27. Living Stereo (DVD audio)
28. Living Stereo Eclectic Method remix (DVD audio)
29. Distorted Minds (DVD audio)
30. That Track (DVD audio)
31. That Track instrumental (DVD audio)
32. Toys Are Us (DVD audio)
33. Pulse (video mix) (DVD audio)
34. Pulse (CD mix) (DVD audio)
35. Master Mix (mix of the 2D videos listed above)

The DVD also contains the 3D version of the track “Deadly Media” from the previous album Rewind. It can only be viewed by directly accessing track 22 on the DVD using the DVD player’s remote control.

References

Track list on Ninja Tune website

Microinjector

This device provides the pressure which is needed to deliver the sample solution from the micropipette into the cells. It can be a mechanically or electronically regulated air pressure device or a simple glass syringe where the plunger is screw controlled for precise adjustments of the pressure and using air or oil filled connection tubing.

Slot time is a concept in computer networking. It is twice the time it takes for an electronic pulse (OSI Layer 1 - Physical) to travel the length of
the maximum theoretical distance between two nodes. In CSMA/CD networks such as ethernet, NICs wait a minimum of the slot time (which should be a constant, NOT dependent on the individual network -ie, it is a standard across all CSMA/CD networks that use a common NIC) before transmitting, allowing time (the maximum theoretical time - slot time) for the pulse to reach the NIC that intends to send.

Since a pulse will never exceed slot time (the maximum theoretical time for a frame to travel a network), the NIC waits a minimum of slot time before transmitting, in order to allow any pulse that was initiated at the time that the waiting NIC was requested to send, to reach the waiting NIC. By allowing the pulse to reach the waiting NIC, a local collision occurs rather than a late collision occurring. By having the collision occur at the NIC (local) and not on the wire (late) CSMA/CD implementation can take more control over the situation.

Some times for slot time include:

• Slot time is only applicable to half-duplex transmissions. Since slot time is the time required to wait for the medium to be free from transmissions, there is no time required to wait for full-duplex transmissions. 10 Gbit/s is a full duplex technology, so slot time is not applicable here.

See also: bit time

The Business Times , also known as the BT, is the name of two financial newspapers published in South East Asia:

• The Business Times of Singapore is an English language newspaper published since 1976 and online news service since 1995. It is widely considered to be the leading business daily in the region. It is part of the Singapore Press Holdings group.

• The Business Times of Kuala Lumpur has been published in Malaysia also since 1976. It is part of the New Straits Times publishing group.

External links

• Online edition of the Singapore Business times
• Online edition of Kuala Lumpur Business times
• Kuala Lumpur Business Times history timeline

A Bipolar Violation, or BPV, is an error in the transmission of a T1 signal where two pulses of the same polarity occur without an intervening pulse of the opposite polarity.

T1 signals are transmitted using a scheme called Alternate Mark Inversion (AMI), where a ONE is represented by a pulse, and a ZERO is represented by no pulse. Pulses-which represent ones-always alternate in polarity, so that if, for example two positive pulses are received in succession, the receiver knows that one or more bits were either added or deleted from the original signal.

B8ZS coding is a scheme used in addition to AMI, which allows longer strings of consecutive zeroes to be transmitted.

Doc-O-Matic is a commercial automatic documentation generator that creates fully cross linked documentation systems, including both Source Code Documentation, Online Help and User Manuals in PDF, browser-based Help, HTML Help, MS Help 2, Windows Help, RTF and XML. Doc-O-Matic supports all major project file formats as well as the following programming languages: C/[[C++]], C++/CLI, C#, Delphi, Java, IDL, VB.NET, JavaScript, MATLAB, ASP.NET, JSP.

See also

• Comparison of documentation generators

External links

Project Doc-O-Matic home page

A striplight lighting fixture is a long row of small lights. Usually theaters use roundels (pieces of colored glass) or gels to make these lights different colors. The unit can then be wired into several different circuits, allowing each bank of colored lights to be controlled by a separate dimmer on the lighting board. Striplights are often used to color a cyclorama, and are usually positioned behind the proscenium arch.

See also

• Stage lighting
• Stage lighting instrument

In mathematics, the expressions generator, generate, generated by and generating set can have several closely related technical meanings:

• generating set of a group, a set of group elements which are not contained in any subgroup of the group other than the entire group itself. See also group presentation.
• generating set of a ring: A subset S of a ring A generates A if the only subring of A containing S is A itself.
• generating set of an ideal in a ring.
• generating set of an algebra: If A is a ring and B is an A-algebra, then S generates B if the only sub-A-algebra of B containing S is B itself.
• generating set of a topological algebra: S is a generating set of a topological algebra A if the smallest closed subalgebra of A containing S is A itself??
• Elements of the Lie algebra to a Lie group are sometimes referred to as generators of the group, especially by physicists. The Lie algebra can be thought of as generating the group at least locally by exponentiation, but the Lie algebra does not form a generating set in the strict sense.
• The generator of any continuous symmetry implied by Noether’s theorem; the generators of a Lie group being a special case. In this case, a generator is sometimes called a charge or Noether charge, in analogy to the electric charge being the generator of the U(1) symmetry group of electromagnetism. Thus, for example, the color charges of quarks are the generators of the SU(3) color symmetry in quantum chromodynamics. More precisely, though, the term “charge” should apply only the to root system of a Lie group.
• In stochastic analysis, the infinitesimal generator of an Itō diffusion or more general Itō process.
• In topology, a collection of sets which generate the topology is called a subbase.
• In category theory there is also a notion of generator.

Usually the intended meaning will be clear from context.

In medicine, a person’s pulse is the throbbing of their arteries as an effect of the heart beat. It can be felt at the neck (carotid artery), at the wrist (radial artery), behind the knee (Popliteal artery), on the inside of the elbow (Brachial artery), near the ankle joint (Posterior Tibial artery), and a few other places.

Pressure waves move the artery walls, which are pliable; these waves are not caused by the forward movement of the blood. When the heart contracts, blood is ejected into the aorta and the aorta stretches. At this point the wave of distention (pulse wave) is pronounced but relatively slow-moving (3 to 6 m/s). As it travels towards the peripheral blood vessels, it gradually diminishes and becomes faster. In the large arterial branches, its velocity is 7 to 10 m/s; in the small arteries, it is 15 to 35 m/s. The pressure pulse is transmitted 15 or more times more rapidly than the blood flow.

The term pulse is also used, although incorrectly, to denote the frequency of the heart beat, usually measured in beats per minute. In most people, the pulse is an accurate measure of heart rate. Under certain circumstances, including arrhythmias, some of the heart beats are ineffective and the aorta is not stretched enough to create a palpable pressure wave. The pulse is too irregular and the heart rate can be (much) higher than the pulse rate. In this case, the heart rate should be determined by auscultation of the heart apex, in which case it is not the pulse. The pulse deficit (difference between heart beats and pulsations at the periphery) should be determined by simultaneous palpation at the radial artery and auscultation at the heart apex.

A normal pulse rate for a healthy adult, while resting, can range from 60 to 100 beats per minute (BPM). During sleep, this can drop to as low as 40 BPM; during strenuous exercise, it can rise as high as 200–220 BPM. Generally, pulse rates are higher in younger people. A resting heart rate for an infant is as high as or higher than an adult’s pulse rate during strenuous exercise.

Pulses are manually palpated with fingers. When palpating the carotid artery, the femoral artery or the brachial artery, the thumb may be used. However, the thumb has its own pulse which can interfere with detecting the patient’s pulse at other points, where two or three fingers should be used. Fingers or thumb must be placed near an artery and pressed gently against a firm structure, usually a bone, in order to feel the pulse.

An alternative way of finding the pulse rate is by palpating or listening to the heartbeat. This is most commonly done with the examiner’s palm or through a stethoscope. Before the invention of the stethoscope examiners would press their ear directly to the chest.

A collapsing pulse is a sign of hyperdynamic circulation.

Common pulse points

• radial pulse - located on the thumb side of the wrist (radial artery)
• ulnar pulse - located on the little finger side of the wrist (ulnar artery)
• carotid pulse - located in the neck (carotid artery). The carotid artery should be palpated gently. Stimulating its baroreceptors with vigorous palpitation can provoke severe bradycardia or even stop the heart in some sensitive persons. Also, a person’s two carotid arteries should not be palpated at the same time, to avoid a risk of fainting or brain ischemia.
• brachial pulse - located between the biceps and triceps, on the medial side of the elbow cavity frequently used in place of carotid pulse in infants (brachial artery)
• femoral pulse - located in the thigh (femoral artery)
• popliteal pulse - located behind the knee in the popliteal fossa, found by holding the bent knee. The patient bends the knee at approximately 120°, and the physician holds it in both hands to find the popliteal artery in the pit behind the knee.
• dorsalis pedis pulse - located on top of the foot (dorsalis pedis artery)
• tibialis posterior pulse - located in the back of the ankle behind the medial malleolus (posterior tibial artery).
• temporal pulse - located on the Temple (anatomy)|temple directly in front of the ear (superficial temporal artery)

The ease of palpability of a pulse is dictated by the patient’s blood pressure. If his or her systolic blood pressure is below 90 mmHg, the radial pulse will not be palpable. Below 80 mmHg, the brachial pulse will not be palpable. Below 60 mmHg, the carotid pulse will not be palpable. Since systolic blood pressure rarely drops that low, the lack of a carotid pulse usually indicates death. It is not unheard of, however, for patients with certain injuries, illnesses or other medical problems to be conscious and aware with no palpable pulse.

In mathematics, the middle-square method is a method of generating pseudorandom numbers. In practice it is not a good method, since its period is usually very short and it has some crippling weaknesses. The method was first suggested by John Von Neumann in 1946.

To generate a sequence of ten-digit pseudorandom numbers, you would create a ten-digit starting value and square it. The middle ten digits of the result would be the next number in the sequence. You would then square that, and so on.

Clearly, for a generator of n-digit numbers, the period can be no longer than 10ⁿ. If the middle ten digits are all zeroes, the generator then outputs zeroes forever. If the first half of a number in the sequence is zeroes, the subsequent numbers will be decreasing to zero. While these runs of zero are easy to detect, they occur too frequently for this method to be of practical use.

Von Neumann was aware of these problems, but for his purposes the middle-square method was quick (important for use on the ENIAC), and its errors were easy to detect (when it failed, it generally failed spectacularly).

See also

• Linear congruential generator
• Blum Blum Shub

Gaussian Frequency Shift Keying (GFSK) is a type of Frequency Shift Keying modulation that utilizes a Gaussian filter to smooth positive/negative frequency deviations, which represent a binary 1 or 0. It is used by DECT, Bluetooth, Cypress WirelessUSB, Nordic Semiconductor and z-wave devices. For Bluetooth the minimum deviation is 115 kHz.

Generalization

In a GFSK modulator, everything is the same as a FSK modulator except that before the baseband pulses (-1, 1) go into the FSK modulator, it is passed through a gaussian filter to make the pulse smoother so to limit its spectral width. Gaussian filtering is one of the very standard ways for reducing the spectral width, it is called Pulse Shaping.

If we use -1 for fc-fd and 1 for fc+fd, once when we jump from -1 to 1 or 1 to -1, the modulated waveform changes rapidly, which introduces large out-of-band spectrum. If we change the pulse going from -1 to 1 as -1, -.98, -.93 ….. .96, .99, 1, and we use this smoother pulse to modulate the carrier, the out-of-band spectrum will be reduced. <ref>www.palowireless.com “GFSK Differences & Advantages over FSK Modulation”</ref>

The Fourier transform of a Gaussian curve results in a Gaussian curve.

References

Leading Rating (or Leading Rate) is the most senior of the junior rates in the British Royal Navy. It is equal in status to Corporal, although for a long time was officially junior to that rank. The rate was introduced under the authority of Admiralty Circular No. 121 of 14 June 1853.

Leading Ratings are normally addressed as Leading Hand or using their branch title eg Leading Seaman, Leading Regulator etc.

The insignia worn by Leading Rates is a single fouled anchor, leading to the slang term Killick or Hooky used in reference to this rate.

In Celebration of the 154th Aniverseray of the introduction of the rate , 60 members of the Leading Hands and Corporals Mess of HMS Collingwood, attended a mess dinner on the Gun Deck of HMS Victory.

A golden unit or golden device is an ideal example of a device (such as a unit of measure) against which all later devices are tested and judged. The term “golden” is used to describe the precision of the device to standard specifications.

For example, in Paris there is a measure for the official “kilogram” unit of measurement. This is stored in a climate-controlled environment to prevent deviations.

External links and references

Defined

• http://literature.agilent.com/litweb/pdf/5988-6082EN.pdf (see page 25)

Examples of Use

• http://www.future-fab.com/documents.asp?grID=217&d_ID=927
• http://www-ee.eng.hawaii.edu/EEPage/Events/seminars.html

Operation Zeppelin is the name for two operations in World War II. It can either be:

• Operation Zeppelin (Allies), part of Operation Bodyguard, a deception plan with the object to keep the Germans occupied in the Balkans due to perceived Allied offensive, thereby reducing the number of German troops which would be otherwise engaged by the Allies in France during the Normandy invasion; or

• Operation Zeppelin (Assassination Plot), a scheme to assassinate Stalin on September 1944, involving anti-communist Russian prisoners of war.

The pain withdrawal reflex is an involuntary action in which the body reacts to pain by trying to move itself away from the source of the pain, to reduce or even eliminate that pain.

Although this is a reflex, there are two interesting aspects: (1) the body can be trained to over-ride that reflex; and (2) an unconscious body (or even drunk or drugged bodies) will not exhibit the reflex.

Advanced martial artists can use the pain withdrawal reflex to their advantage. Certain application of techniques - for example pressure points - can cause the body to react and move in a certain way, for increased effectiveness of the technique - or to allow a greater range of techniques.

Quodia is a performing group that uses multi-media tools to tell stories. Established by Trey Gunn of King Crimson and Joe Mendelson of Rise Robots Rise in 2003, Quodia tours throughout the world combining the mediums of music, film, sound design, literature and theater into a comprehensive and immersive performance experience. Their approach to storytelling is mythological and archetypical driven by high tech tools: laptops, keyboard, electronic percussion, the Warr guitar, video projectors and a massive screen.

External links

• Quodia homepage
• Trey Gunn homepage

Arlington High School can refer to one of several American high schools:

• Arlington High School (Arlington, Massachusetts)
• Arlington High School (Oregon)
• Arlington High School (Arlington, Tennessee)
• Arlington High School (Arlington, Texas)
• Arlington High School (Arlington, Washington)
• Arlington High School (Arlington Heights, Illinois)
• Arlington High School (Indianapolis, Indiana)
• Arlington High School (LaGrange, New York)
• Arlington High School (Nebraska)
• Arlington High School (Riverside, California)
• Arlington High School (Ohio)
• Arlington Senior High School Saint Paul, Minnesota

Natural Docs is a multi-language documentation generator. It is written in Perl and is available as free software under the terms of the GNU General Public License. It attempts to keep the comments written in source code just as readable as the generated documentation. It is written and maintained by Greg Valure.

Theoretically, it can generate documentation from any language that can support comments, or from plain text files. When executed, it can automatically document functions, variables, classes, and inheritance from ActionScript 2.0, C#, and Perl regardless of existing documentation in the source code. In all other languages, these need to be explicitly documented for them to be generated. It can generate documentation in HTML, either with frames or without.

Unlike Javadoc, it is not considered an industry standard for documenting in any language, although Javadoc compatibility is being developed for certain languages.<ref> Javadoc Support on NaturalDocs.org</ref> It is used by some hobbyists and companies, such as CNET Networks, Inc. and Iron Realms Entertainment.<ref>CNET’s Global Framework by CNET Networks, Inc. and generated documentation using Natural Docs</ref><ref>Rapture by Iron Realms Entertainment and generated documentation using Natural Docs</ref> It has gained popularity amongst ActionScript 2.0 developers because no other free documentation generator exists that fully supports ActionScript 2.0 and because it generates higher-quality output than similar generators that partially support the language, such as ROBODoc.

Example

This is an example of the documentation style:

/*
 * Function: Multiply
 *
 * Multiplies two integers.
 *
 * Parameters:
 *    x - The first integer.
 *    y - The second integer.
 *
 * Returns:
 *    The two integers multiplied together.
 *
 * See Also:
 *    <Divide>
 */

int Multiply (int x, int y)
   {  return x * y;  };

For comparison, this is how the same thing would be documented with Javadoc:

/**
 * Multiplies two integers.
 *
 * @param x The first integer.
 * @param y The second integer.
 * @return The two integers multiplied together.
 * @see Divide
 */ 	 

int Multiply (int x, int y)
   { return x * y; };

See also

• Comparison of documentation generators

Notes and references

Further reading

• Natural Docs Home Page
• List of features
• List of supported languages

The Bitterbynde is a fantasy trilogy by Australian writer Cecilia Dart-Thornton. It comprises The Ill-Made Mute, The Lady of the Sorrows, and The Battle of Evernight.

A ‘Bitterbynde’ refers to an unbreakable promise or oath.

Comic fantasy is a subgenre of fantasy that is primarily humorous in intent and tone. Usually set in imaginary worlds, comic fantasy often includes puns on and parodies of other works of fantasy. It is sometimes known as Low fantasy in contrast to High fantasy, which is primarily serious in intent and tone. The term “Low Fantasy” is used to represent other types of fantasy, however, so while comic fantasies may also correctly be classified as low fantasy, many examples of low fantasy are not comic in nature.

History

The subgenre rose in the latter half of the twentieth century. T.H. White’s works exemplify it,<ref>Lin Carter, ed. Kingdoms of Sorcery, p 121–2. Doubleday and Company Garden City, NY, 1976.</ref> L. Sprague de Camp and Fletcher Pratt’s Complete Enchanter stories are early exemplars. The overwhelming bulk of de Camp’s fantasy was comic.<ref>Carter. Kingdoms of Sorcery.</ref>

In more modern times, Piers Anthony’s Xanth books, Robert Asprin’s MythAdventures of Skeeve and Aahz books, Terry Pratchett’s Discworld, and Tom Holt’s books provide good examples. Not surprisingly there are also comic-strips/graphic novels in the humorous fantasy genre, including Chuck Whelon’s Pewfell series and the webcomic 8-Bit Theatre.

The subgenre has also been represented in television and film, such as in the comic fantasy television serial I Dream of Genie and the 1975 film Monty Python and the Holy Grail. A rare example on radio is the BBC’s Hordes of the Things.

References

Siv Jensen (born June 1, 1969 in Oslo) is the chairman of the Progress Party, the largest opposition party in Norway. She was appointed party chairman on May 6, 2006, after a long period of being next in leadership, after Carl I. Hagen, party’s chairman for 28 years, resigned in 2006. In September 2006 a political biography on Siv Jensen was released written by chief editor of the magazine Ny Tid, Martine Aurdal. Siv Jensen is also the most likely to run for Prime minister of Norway as well for the Norwegian Progress Party in the 2009 Norwegian Parliamentary election.

Siv Jensen has attended the Bilderberg meetings.

Siv Jensen has a sister, Nina Jensen.

External link

• Stortinget.no - Bio
  

Brandi Downs is a model who worked with Playboy in the early 1990s. She has also done swimsuit modeling for various publications, as well as appearing several times in the popular trading card series “Benchwarmers”.

Appearances in Playboy special editions

• Playboy’s Book of Lingerie Vol. 15 September 1990.
• Playboy’s Book of Lingerie Vol. 23 January 1992.
• Playboy’s Bathing Beauties April 1992.
• Playboy’s Book of Lingerie Vol. 29 January 1993.
• Playboy’s Girls of Summer ‘93 June 1993 - page 104.
• Playboy’s Book of Lingerie Vol. 32 July 1993.
• Playboy’s Book of Lingerie Vol. 35 January 1994.
• Playboy’s Bathing Beauties March 1994 - pages 48, 76.
• Playboy’s Book of Lingerie Vol. 38 July 1994.

PSR J2144-3933 is a pulsar about 180 parsecs (5.5 Em) from earth. It was previously thought to have a period of 2.84 seconds but is now known to have a period of 8.51 s, which is the longest of any known radio pulsar (the previous longest was that of PSR J1951+1123 at 5.09 s).

J2144-3933 is notable for other reasons: its mean pulse profile is very narrow in comparison to the pulse period with a half-intensity width of less than one degree of longitude. It also has the lowest spindown luminosity of any pulsar at about 3×10³¹ watts.

Writing in Nature, astrophysicists M. D. Young and coworkers consider this object and suggest that its existence throws current theories into doubt. They state:

Moreover, under the usual model assumptions, based on the neutron-star equations of state, this slowly rotating pulsar should not be emitting a radio beam. Therefore either the model assumptions are wrong, or current theories of radio emission must be revised —from Nature 400, 848–849 (26 August 1999); doi:10.1038/23650)

In kinematics, Euler’s rotation theorem states that, in three-dimensional space, any displacement of a rigid body such that a point on the rigid body remains fixed, is equivalent to a rotation about a fixed axis through that point. The theorem is named after Leonhard Euler.

In mathematical terms, this is a statement that, in 3D space, any two coordinate systems with a common origin are related by a rotation about some fixed axis. This also means that the product of two rotation matrices is again a rotation matrix. A (non-identity) rotation matrix has a real eigenvalue which is equal to unity. The eigenvector corresponding to this eigenvalue is the axis of rotation connecting the two systems.

Applications

Generators of rotations

Suppose we specify an axis of rotation by a unit vector [x, y, z] , and suppose we have an infinitely small rotation of angle Δθ  about that axis. To first order the rotation matrix ΔR  is represented as:

<math>\Delta R =

 \begin{bmatrix}
 1&0&0\\
 0&1&0\\
 0&0&1
 \end{bmatrix}

+

 \begin{bmatrix}
 0 & z&-y\\
 -z& 0& x\\
 y &-x& 0
 \end{bmatrix}\,\Delta \theta

= \mathbf{I}+\mathbf{A}\,\Delta \theta.
</math>

A finite rotation through angle θ about this axis may be seen as a succession of small rotations about the same axis. Approximating Δθ  as θ/N where N  is a large number, a rotation of θ about the axis may be represented as:

<math>R =\left(\mathbf{1}+\frac{\mathbf{A}\theta}{N}\right)^N

\approx e^{\mathbf{A}\theta}.</math>

It can be seen that Euler’s theorem essentially states that all rotations may be represented in this form. The product <math>\mathbf{A}\theta</math> is the “generator” of the particular rotation. Analysis is often easier in terms of these generators, rather than the full rotation matrix. Analysis in terms of the generators is known as the Lie algebra of the rotation group.

Quaternions

It follows from Euler’s theorem that the relative orientation of any pair of coordinate systems may be specified by a set of four numbers. Three of these numbers are the direction cosines that orient the eigenvector. The fourth is the angle about the eigenvector that separates the two sets of coordinates. Such a set of four numbers is called a quaternion.

While the quaternion as described above, does not involve complex numbers, if quaternions are used to describe two successive rotations, they must be combined using the non-commutative quaternion algebra derived by William Rowan Hamilton through the use of imaginary numbers.

Rotation calculation via quaternions has come to replace the use of direction cosines in Aerospace applications through their reduction of the required calculations, and their ability to minimize round-off errors. Also, in computer graphics the ability to perform spherical interpolation between quaternions with relative ease is of value.

See also

• Euler pole
• Euler angles
• Euler-Rodrigues parameters
• Rotation representation

Self-phase modulation (SPM) is a nonlinear optical effect of light-matter interaction.
An ultrashort pulse of light, when travelling in a medium, will induce a varying refractive index of the medium due to the optical Kerr effect. This variation in refractive index will produce a phase shift in the pulse, leading to a change of the pulse’s frequency spectrum.

Self-phase modulation is an important effect in optical systems that use short, intense pulses of light, such as lasers and optical fibre communications systems.

Theory

For an ultrashort pulse with a Gaussian shape and constant phase, the intensity at time t is given by I(t):

<math>I(t) = I_0 \exp \left(- \frac{t^2}{\tau^2} \right) </math>

where I₀ is the peak intensity, and τ is half the pulse duration.

If the pulse is travelling in a medium, the optical Kerr effect produces a refractive index change with intensity:

<math>n(I) = n_0 + n_2 \cdot I</math>

where n₀ is the linear refractive index, and n₂ is the second-order nonlinear refractive index of the medium.

As the pulse propagates, the intensity at any one point in the medium rises and then falls as the pulse goes past. This will produce a time-varying refractive index:

<math>\frac{dn(I)}{dt} = n_2 \frac{dI}{dt} = n_2 \cdot I_0 \cdot \frac{-2 t}{\tau^2} \cdot \exp\left(\frac{-t^2}{\tau^2} \right).</math>

This variation in refractive index produces a shift in the instantaneous phase of the pulse:

<math>\phi(t) = \omega_0 t - \frac{2 \pi}{\lambda_0} \cdot n(I) L</math>

where <math>\omega_0</math> and <math>\lambda_0</math> are the carrier frequency and (vacuum) wavelength of the pulse, and <math>L</math> is the distance the pulse has propagated.

The phase shift results in a frequency shift of the pulse. The instantaneous frequency ω(t) is given by:

<math>\omega(t) = \frac{d \phi(t)}{dt} = \omega_0 - \frac{2 \pi L}{\lambda_0} \frac{dn(I)}{dt},</math>

and from the equation for dn/dt above, this is:

<math>\omega(t) = \omega_0 + \frac{4 \pi L n_2 I_0}{\lambda_0 \tau^2} \cdot t \cdot \exp\left(\frac{-t^2}{\tau^2}\right).</math>

Plotting ω(t) shows the frequency shift of each part of the pulse. The leading edge shifts to lower frequencies (”redder” wavelengths), trailing edge to higher frequencies (”bluer”) and the very peak of the pulse is not shifted. For the centre portion of the pulse (between t = ±τ/2), there is an approximately linear frequency shift (chirp) given by:

<math>\omega(t) = \omega_0 + \alpha \cdot t</math>

where α is:

<math>\alpha = \left. \frac{d\omega}{dt} \right |_0 = \frac{4 \pi L n_2 I_0}{\lambda_0 \tau^2}.</math>

It is clear that the extra frequencies generated through SPM broaden the frequency spectrum of the pulse symmetrically. In the time domain, the envelope of the pulse is not changed, however in any real medium the effects of dispersion will simultaneously act on the pulse. In regions of normal dispersion, the “redder” portions of the pulse have a higher velocity than the “blue” portions, and thus the front of the pulse moves faster than the back, broadening the pulse in time. In regions of anomalous dispersion, the opposite is true, and the pulse is compressed temporally and becomes shorter. This effect can be exploited to some degree (until it diggs holes into the spectrum) to produce ultrashort pulse compression.

A similar analysis can be carried out for any pulse shape, such as the hyperbolic secant-squared (sech^{2</sub>) pulse profile generated by most ultrashort pulse lasers.}

If the pulse is of sufficient intensity, the spectral broadening process of SPM can balance with the temporal compression due to anomalous dispersion and reach an equilibrium state. The resulting pulse is called an optical soliton.

In metadata, time is a representation term used to specify a time of day in the in ISO 8601 time format.

Note that Time should not be confused with the DateAndTime representation term which requires that both the date and time to be supplied.

Metadata registries that use the time representation term

• NIEM
• ebXML
• GJXDM

See also

• metadata
• ISO/IEC 11179
• Representation term
• ISO 8601

Porcine zona pellucida is a form of zona pellucida extracted from the ovaries of pigs. Often referred to by the initials PZP.

The zona pellucida is a thick membrane that surrounds the unfertilized eggs of mammals. In order for an egg to be fertilized, sperm must first bind to, and then penetrate the zona pellucida. When porcine (pig) zona pellucida is injected into other mammals, antibodies are produced which attach to that animal’s zona pellucida, preventing the sperm from attaching to the egg, therefore preventing fertilization.

Porcine zona pellucida has been used in wildlife contraception since the late 1980s. Animals with which PZP has been employed in this context include elephants, feral horses, elk and whitetailed deer.

External links

• Google search “Porcine Zona Pellucida”
• Wildlife forever

SGPS can mean:

• Society of Graduate and Professional Students at Queen’s University
• Steam Generator Protection System
• Sygate Global Professional Services