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In telecommunication, an optical time domain reflectometer (OTDR) is an optoelectronic instrument used to characterize an optical fiber.

An OTDR injects a series of optical pulses into the fiber under test. It also extracts, from the same end of the fiber, light that is scattered back and reflected back from points in the fiber where the index of refraction changes. (This is equivalent to the way that an electronic TDR measures reflections caused by changes in the impedance of the cable under test.) The intensity of the return pulses is measured and integrated as a function of time, and is plotted as a function of fiber length.

An OTDR may be used for estimating the fiber’s length and overall attenuation, including splice and mated-connector losses. It may also be used to locate faults, such as breaks.

See also

• Time-domain reflectometer
• Optical return loss

[1] Stockists of OTDR Equipment

In telecommunication, attack time is the time between (a) the instant that a signal at the input of a device or circuit exceeds the activation threshold of the device or circuit and (b) the instant that the device or circuit reacts in a specified manner, or to a specified degree, to the input. Attack time occurs in devices such as clippers, peak limiters, compressors, and voxes.

See also

• Federal Standard 1037C
• Fall time

DRI may stand for:

• Darden Restaurants, Inc., NYSE stock symbol
• Directorate of revenue intelligence
• Declarative Referential Integrity
• Desert Research Institute
• Dietary Reference Intake
• Digital Range Increase
• Digital Recorders, Inc.
• Digital Research, Inc.
• Direct reduced iron
• Direct Rendering Infrastructure - In computing, DRI is an interface used in the X Window System.
• Directly Responsible Individual
• Digital Rights Interface
• Dirty Rotten Imbeciles, a United States hardcore punk/thrash metal band
• Doncaster Royal Infirmary, a hospital in Doncaster, South Yorkshire, UK.
• Dopamine reuptake inhibitor (Bupropion or Wellbutrin®)

1. Redirect Reduction potential 

This is a redirect from a title that is an alternative name, a pseudonym, a nick name or a synonym.

It leads to the title in accordance with the naming conventions for common names and can help writing.

For more information, follow the category link.

Magnetic complex impedance is the complex value, which is equal to the relation of the complex effective or amplitude value of a sinusoidal magnetic tension on the passive magnetic circuit or its element and accordingly the complex effective or amplitude value of a sinusoidal magnetic current in this circuit or in this element.

Magnetic complex impedance [1, 2] is measuring in units – [<math>\frac{1}{\Omega}</math>] and determining by the formula:

<math>Z_M = \frac{\dot N}{\dot {I}_M} = \frac{\dot {N}_m}{\dot {I}_Mm} = z_M e^{j\phi}</math>

where
<math>z_M = \frac{N}{I_M} = \frac{N_m}{I_{Mm}}</math> is the relation of the effective or amplitude value of a magnetic tension and accordingly of the effective or amplitude magnetic current is naming as the full magnetic resistance (magnetic impedance). The full magnetic resistance (magnetic impedance) is equal to the modulus of the complex magnetic impedance. The argument of a complex magnetic impedance is equal to the difference of the phases of the magnetic tension and magnetic current <math>\phi = \beta - \alpha</math>.
Complex magnetic impedance can be presented in following form:

<math>Z_M = z_M e^{j\phi} = z_M \cos \phi + jz_M \sin \phi = r_M + jx_M </math>

where
<math>r_M = z_M \cos \phi</math> is the real part of the complex magnetic impedance, naming as the effective magnetic resistance;
<math>x_M = z_M \sin \phi</math> is the imaginary part of the complex magnetic impedance, naming as the reactive magnetic resistance.
The full magnetic resistance (magnetic impedance) is equal

<math>z_M = \sqrt{r_{M}^2 + x_{M}^2}</math> , <math>\phi = \arctan {\frac{x_M}{r_M}}</math>

References

• Popov V. P. The Principles of Theory of Circuits. – M.: Higher School, 1985, 496 p. (In Russian).
• Küpfmüller K. Einführung in die theoretische Elektrotechnik, Springer-Verlag, 1959.

A humbler is a BDSM “cock and ball torture” and physical restraint device used to restrict the movement of a submissive male participant in a BDSM scene.

The humbler consists of a testicle cuff device that clamps around the base of the scrotum, mounted in the centre of a bar that passes behind the thighs at the base of the buttocks. This forces the wearer to keep his legs folded forward, as any attempt to straighten the legs even slightly pulls directly on the scrotum, causing considerable discomfort (extreme pain).

Medical dangers

Because of the strong muscles and substantial mechanical advantage of the legs, this device can cause permanent physical damage. Damage can also occur if worn for an extended period of time—all the other dangers of the use of testicle cuffs and other forms of physical restraint also apply to this device.

In mathematics, the point <math>\tilde \mathbf{x}\in \mathbb{R}^n</math> is an equilibrium point for the differential equation

<math>\frac{d\mathbf{x}}{dt} = \mathbf{f}(t,\mathbf{x})</math>

if <math>\mathbf{f}(t,\tilde\mathbf{x})=0</math> for all <math>t\,\!</math>.

Similarly, the point <math>\tilde \mathbf{x}\in \mathbb{R}^n</math> is an equilibrium point (or fixed point) for the difference equation

<math>\mathbf{x}_{k+1} = \mathbf{f}(k,\mathbf{x}_k)</math>

if <math>\mathbf{f}(k,\tilde\mathbf{x})= \tilde\mathbf{x}</math> for <math>k=0,1,2,\ldots</math>.

Equilibria can be classified by looking at the signs of the eigenvalues of the linearization of the equations about the equilibria. That is to say, by evaluating the Jacobian matrix at each of the equilibrium points of the system, and then finding the resulting eigenvalues, the equilibria can be categorized. Then the behavior of the system in the neighborhood of each equilibrium point can be qualitatively determined, (or even quantitatively determined, in some instances, by finding the eigenvector(s) associated with each eigenvalue).

An equilibrium point is hyperbolic if none of the eigenvalues have zero real part. If all eigenvalues have negative real part, the equilibrium is a stable node. If all have positive real part, the equilibrium is an unstable node. If at least one eigenvalue has negative real part and at least one has positive real part, the equilibrium is a saddle point.

Things known as a Viewer include:

• For television viewers, see ratings or Nielsen ratings
• File viewer, a piece of computer software that displays the data stored in a computer file in a human-friendly form.
• Image viewer, a computer program that displays a stored graphical image.
• Pocket viewer, a model range of Personal Digital Assistants developed by Casio
• ViEWER, a computer program written for the purposes of studying visual perception in a 3-D environment

A spinal fixation device is a rigid or semi-rigid mechanical support system which is surgically implanted into the vertebral column in order to obtain stabilization of spinal fractures, correction of spinal deformities, or treatment of degenerative spinal disease. The implanted fixation device may consist of rods, plates, screws and/or interbody constructs such that the surgeon can obtain optimum fixation in each case. The implanted fixation device can be made of a rigid or semi-rigid biologically compatible material, such as titanium alloy.

Alternatively, a resorbable spinal fixation device can be used for temporary spinal fixation. Though such devices are not common in the US, they are composed of bioresorbable material such as a polymer that can produce acidic products upon hydrolytic degradation, the device needs to include a neutralization compound, or buffering agent, in sufficiently high concentration to decrease the rate of pH change as the device degrades, in order to prevent sterile abscess formation caused by the accumulation of unbuffered acidic products in the area of the implant.

Sialography is the radiographic examination of the salivary glands. It usually involves the injection of a small amount of contrast medium into the salivary ducts of a single gland, followed by routine X-ray projections.

How is the Test Performed?

The test is performed in a hospital radiology department or in the health care provider’s office by an X-ray technician. You may be given a sedative before the procedure.

You will be asked to lie on your back on the X-ray table. An X-ray is taken before the contrast material is injected to ensure that no stones are present to stop the contrast material from entering the ducts. A catheter (a small flexible tube) will be inserted through your mouth and into the duct of the salivary gland. A contrast medium in then injected into the duct so that the duct will show up on the X-ray. X-rays will be taken from a number of positions.

You may be given lemon juice by mouth to help stimulate the production of saliva. Pictures are repeated to examine the drainage of the saliva into the mouth.

The Ministry of Plenty (in Newspeak, Miniplenty) is one of the ministries from George Orwell’s novel Nineteen Eighty-Four that governs Oceania. The other ministries are the Ministry of Truth, the Ministry of Peace and the Ministry of Love.

The Ministry of Plenty is in charge of Oceania’s economy. It oversees public access to food, supplies, and goods. It is also in charge of rationing these goods. As told in Goldstein’s book, the economy of Oceania is very important, and it’s necessary to have the public continually create useless and synthetic supplies or weapons for use in the war, while they have no access to the means of production. This is the central theme of Oceania’s idea that a poor, weak populace is easier to rule over than a wealthy, powerful populace. Telescreens often make reports on how Big Brother has been able to increase economic productivity, even when productivity has actually gone down (see Ministry of Truth).

The Ministry hands out statistics which are “nonsense”. When Winston is adjusting some Ministry of Plenty’s figures, he explains this:

This system of ludicrous quotas and falsified results is a reference to the quotas of the planned economy and other statistical falsifications (such as the 1937 Census) of the Soviet Union under Joseph Stalin. Like the other ministries, the Ministry of Plenty does the opposite of its name, since it is in charge of maintaining poverty and financial shortages.

Clamp may refer to:

• Clamp (tool), a device used to hold an object in a fixed position.
• Storage clamp, an agricultural root crop storage.
• Clamp meter, a device for measuring electric current.
• Riser clamp, a device used to support vertical piping
• Clamp (manga artists), a team of four female mangaka.
• Shirley Clamp, a Swedish pop singer
• Sliding clamp, a protein involved in DNA-replication.
• Wheel clamp, a device used with road vehicles to either help prevent theft or enforce parking restrictions.
• clampf or clampi, color amplitude[1] data types in OpenGL.
• Clamp is a character in the television show Galaktik Football.

The Laws is Plato’s last and longest dialogue. The question asked at the beginning is not “What is law?” as one would expect- that is the question of the Minos. The kick-off question is rather, “Who is given the credit for laying down your laws?”

It is generally agreed that Plato wrote this dialogue as an old man, having failed in his effort in Syracuse on the island of Sicily to guide a tyrant’s rule, instead having been thrown in prison. These events are alluded to in the Seventh Letter.

Summary

The setting

Unlike most of Plato’s dialogues, Socrates does not appear in the Laws. This is fitting because the dialogue takes place on the island of Crete, and Socrates never appears outside of Athens in Plato’s writings, except in the Phaedrus, where he is just outside the city’s walls. Instead of Socrates we have the Athenian Stranger (in Greek, ‘xenos’) and two other old men, an ordinary Spartan citizen (Megillos) and a Cretan politician and lawgiver (Kleinias) from Knossos.

The Athenian Stranger, who is much like Socrates but whose name is never given, joins the other two on their religious pilgrimage to the cave of Zeus. The entire dialogue takes place during this journey, which mimics the action of Minos, who is said by the Cretans to have made their ancient laws, who walked this path every nine years in order to receive instruction from Zeus on lawgiving. It is also said to be the longest day of the year, allowing for a densely-packed twelve chapters.

By the end of the third chapter Kleinias announces that he has in fact been given the charge of laying down laws for a new Cretan colony, and that he would like the Stranger’s assistance. The rest of the dialogue proceeds with the three old men, walking towards the cave and making laws for this new city.

Topics

The questions of the Laws are without limit:

• Divine revelation, divine law and lawgiving
• The role of intelligence in lawgiving
• The relations of philosophy, religion, and politics
• The role of music, exercise and dance in education
• Natural law and natural right
• …

The dialogue uses primarily the Athenian and Spartan (Lacedaemonian) law systems as background for pinpointing a choice of laws, which the speakers imagine as a more or less coherent set for the new city they are talking about.

Comparisons

…to other dialogues by Plato

The Laws is similar to and yet in opposition to the Republic. It is similar in that both dialogues concern the making of a city in speech, but different in that the one city is ideal, and the other a real, practical city. The city of the Laws is described as “second best,” whereas the beautiful city of the Republic is the best possible city. The city of the Laws differs in its allowance of private property and private families, and in the very existence of written laws, from the city of the Republic, with its communistic property-system, possession of women in common, and absence of written law. Also, whereas the Republic is a dialogue between Socrates and many young men (Cephalus goes to bed early, after attending to his boring old sacrifices), the Laws is a discussion among old men, where children are not allowed and there is always a pretence of piety and ritualism. All in all, while the Laws is more similar to the Republic than any other dialogue, they are so different that the Laws needs to be considered in its own right, as Plato’s most serious and comprehensive contribution to political philosophy.

It has the sense of a writer trying to get everything into his last work, yet its structure is comparable to the Symposium in its beauty and grace.

Traditionally, the Minos is thought to be the preface, and the Epinomis the epilogue, to the Laws, but both may be spurious.

In The Laws, Plato takes a harsh view of homosexuality, and proposes to legislate against it. This is a stark contrast to the Symposium and the Phaedrus, both of which seem to present homosexuality in a positive light.

…to other ancient accounts of Greek law systems

Plato was not the only Ancient Greek author writing about the law systems of his day, and making comparisons between the Athenian and the Lacedaemonian/Spartan laws. Notably, The Polity of the Athenians and the Lacedaemonians, by Xenophon, another of Socrates’ pupils, has also survived.

Some centuries later Plutarch would also devote attention to the topic of Ancient Greek law systems, e.g. in his Life of Lykurgus. Lykurgus (or: Lycurgus) was the legendary law-giver of the Lacedaemonians. Plutarch compares Lycurgus (and his Spartan laws) to the law system Numa Pompilius introduced in Rome around 700 BC.

Both Xenophon and Plutarch are stark admirers of the Spartan system, showing less reserve than Plato in expressing that admiration.

See also

See also

Political content

• List of classics of political philosophy - List of writings (similar to the Laws) on political philosophy.
• Mixed government
• The Open Society and Its Enemies - Karl Popper attacking a totalitarian undercurrent in Plato’s “political” works.

Other aspects

• Gymnasium (ancient Greece) and Gymnopaedia - Military exercise, sports and dancing as an educational asset.

External references

Regarding Plato’s The Laws

• Pangle, Thomas L., 1980. The Laws of Plato, Translated, with Notes and an Interpretive Essay, New York, Basic Books.
• , a 19th century translation.

Other ancient texts about law systems

• (The text about Lykurgus is in Volume I of the Lives)

The Crystal River 3 Nuclear Generation Station is a nuclear power plant, part of the Crystal River Energy Complex located in Citrus County, Florida near Crystal River, Florida. The site consists of approximately 4,700 acres (19 km²) and contains a single pressurized water reactor sharing the site with 4 fossil-fueled generators. The reactor is rated to produce 842 megawatts of electric power. It is a Babcock and Wilcox pressurized water reactor.

Crystal River 3 was originally owned by Florida Progress Corporation (and operated by its subsidiary, Florida Power Corporation) but, in 2000, it was bought by Carolina Power & Light to form the new company, Progress Energy, which currently runs the plant.

In December 2006, Florida Progress purchased 3,000 acres of land seven miles from the Gulf of Mexico and eight miles north of the existing Crystal River plant in preparation for the potential construction of a new nuclear power reactor. A formal decision has not yet been made. Critics lament the low-lying location of the site. Levy County officials have welcomed the potential plant in an effort to bring jobs to the impoverished county.

External links

• DoE Page
• NukeWorker

• [1]

RBST or rBST may refer to:

• Randomized binary search tree, a computer data structure
• Rare Breeds Survival Trust, a UK charity
• Recombinant bovine somatotropin (usually “rBST”), a synthetic growth hormone that is injected into a cow to increase its milk production

In signal processing and telecommunication, the term pulse duration has the following meanings:

1. In a pulse waveform, the interval between (a) the time, during the first transition, that the pulse amplitude reaches a specified fraction (level) of its final amplitude, and (b) the time the pulse amplitude drops, on the last transition, to the same level.

   Note: The interval between the 50% points of the final amplitude is usually used to determine or define pulse duration, and this is understood to be the case unless otherwise specified. Other fractions of the final amplitude, e.g., 90% or 1/e, may also be used, as may the root mean square (rms) value of the pulse amplitude. Deprecated synonyms: pulse length, pulse width.

2. In radar, measurement of pulse transmission time in microseconds, that is, the time the radar’s transmitter is energized during each cycle.

Source: From Federal Standard 1037C and from MIL-STD-188 and from the Department of Defense Dictionary of Military and Associated Terms

mIRCStats is an IRC Log analyzing and statistics creating tool created by Mikko Auvinen. The program takes log files, which are IRC conversations written to a file by an IRC client. mIRCStats was originally developed to analyze mIRC logs, but since its beginning new parsers for different IRC clients have been written.

Features

mIRCStats is capable of creating extensive statistics on fields such as URLs, foul words, words written by nickname, among others.

Criticism

Some people who use other tools like pisg criticize mIRCStats claiming that is pressuposes mIRCStats. However, those people do not actively attack it.

See also

• mIRC
• IRC

External links

• mIRCStats homepage

Visualization can refer to

psychology:

• The process of creating internal mental images (internal visualization and imagination)
• Spatial Visualization Ability

spiritual disciplines:

• The engaging of one’s imagination within the body-mind to effect changes in consciousness.

technology:

• Visualization (graphic), as in any technique for creating images, diagrams, or animations to communicate any message.
• Scientific visualization, an area of computer graphics that is concerned with the presentation of potentially huge quantities of laboratory, simulation or abstract data to aid cognition, hypotheses building, and reasoning
• Knowledge visualization, a sub discipline of Information Design and Instructional Message Design.
  
• Product visualization, visualization software technology for manufacture of components and large assemblies of products.
• Music visualization, a feature found in some media player software applications.

This article is related to signal processing. For other meanings of the word Decimation, please see Decimation (disambiguation).

In digital signal processing, decimation is a technique for reducing the number of samples in a discrete-time signal.

Decimation is a two-step process:

1. Low-pass anti-aliasing filter
2. Downsampling

An example of decimation: the frequency of a recorded sound can be raised an octave (in other words, doubled in frequency) by eliminating every other sample without changing the sampling rate. This will result in aliasing if the sound contains overtones whose (doubled) frequency will exceed half the sampling rate. Decimation aliasing can be avoided by eliminating those overtones.

The same principle applies to eliminating samples at other intervals.

See also

• Digital signal processing
• Signal processing

Jeanatope is iodinated I-125 human serum albumin, typically injected to aid in the determination of total blood and plasma volume. I-125 is a radioactive isotope of Iodine, it decays by electron capture with a physical half-life of 60.14 days. The biologic half-life in normal individuals for I-125 has been reported to be approximately 14 days.

Iodinated I-131 albumin (Volumex®, Daxor) is used for a similar purpose.

External links

• Jeanatope at isotexdiagnostics.com

A CO-oximeter is a device for of detecting hypoxia, a medical condition relating to oxygen deficiency at tissue level. It is an enhanced version of a pulse oximeter operating with more than two wavelengths.

The device measures absorption at several wavelengths to distinguish oxyhemoglobin from carboxyhemoglobin and determine the oxyhemoglobin saturation: the percentage of oxygenated Hb compared to the total amount of Hb, including carboxy-Hb, met-Hb, oxy-Hb, and reduced Hb. When a patient presents with carbon monoxide poisoning, the CO-oximeter will detect this Hb and will report the oxyhemoglobin saturation as markedly reduced.

See also

Pulse oximeter

Electronic instrumentation refers to measuring instruments used to measure the properties of electrical devices.

See also

• Ammeter
• Meter (electronics)
  
• Moving coil meter
• Multimeter
• Ohmmeter
• Oscilloscope
• Spectrum analyzer
• Voltmeter

• Instrumentation engineering

Other uses

• Communications-electronics
• Electron microscope
• Electronic amplifier
• Electronic deception
• Instrument Landing System
• Instrumentation amplifier
• Instrumentation, Systems, and Automation Society
• Measuring instrument
• Micro Instrumentation and Telemetry Systems
• Popular Electronics

EEG topography is a neuroimaging technique in which a large number of EEG electrodes are placed onto the head, following a geometrical array of even-spaced points. A special software inside the apparatus’ computer, plots the activity on a color screen or printer, by coding the amount of activity in several tones of color (for example, black and blue might depict low EEG amplitude, while yellow and red might depict larger amplitudes). The spatial points lying between electrodes are calculated by mathematical techniques of interpolation (calculating intermediary values on the basis on the value of its neighbors), and thus a smooth gradation of colors is achieved.

This approach gives a much more accurate and representative view of the location of alterations of rhythm, amplitude, etc., in relation to the surface of the skull. Neurologists working with the EEG brain topographic system were soon able to differentiate several kinds of diagnoses (including some mental diseases whose biological origin, or etiology, was previously unknown). Pinpointing the exact location of EEG alterations was also made much easier. In addition, the use of the cinè mode (animations using several sequential pictures taken from the brain maps) made possible the dynamic study of brain function in action.

History

EEG brain topography was invented by William Grey Walter, who, in 1936, proved that, by using a larger number of electrodes pasted to the scalp, each one having a small size, and a triangulation algorithm, it was possible to identify abnormal electrical activity in the brain areas around a tumor, and diminished activity inside it. Impressed with the possibilities of building bidimensional maps of the EEG activity over the brain surface, Grey Walter invented the toposcope in 1957.

This was a remarkably complex device and showed Grey Walter’s inventiveness (besides being a physician, he was also an engineer). It had 22 cathode ray tubes (similar to a TV tube), each of them connected to a pair of electrodes attached to the skull. The electrodes (and their corresponding tubes) were arranged in a bidimensional geometrical array, such as that each tube was able to depict the intensity of the several rhythms which compose the EEG in a particular area of the brain (the frontal, parietal and occipital lobes, etc.). This array of CRT tubes, were photographed face up, so that a kind of phosphorescent spiral display showed simultaneously which kind of rhythm was present in a particular part of the brain.

Medical applications

EEG brain topography is not performed in all cases requiring a recording of the brain activity. Initially its main indication was to determine the presence of tumors and focal disease of the brain (including arteriovenous mal-formations and stroke), but today other imaging technologies have replaced the EEG to describe changes in brain structure. There are several neurosurgical procedures that rely on topographic EEG to localize electro-functional problems, such as epilepsy, before and during surgery. It is also appropriate when disturbances in consciousness and vigilance are present, such as narcolepsy (the abrupt onset of sleep), coma, etc.. In addition, EEG brain topography is being increasingly used to monitor the effects of withdrawal of psychoactive drugs, and in infectious diseases of the brain, such as meningitis, as well as to follow up patients who where subjected to brain operations. In psychiatry, EEG brain topography has been of value in identifying disorders of biological origin, such as schizophrenia, dementias, hyperactivity and depression, brain atrophy and attention deficit disorders in children.

Today, there are many commercial EEG brain topography systems in use. They are generally installed in Windows- or Macintosh-based microcomputer platforms, and can be easily operated by technicians or physicians, due to the graphical software which comes with the package. This software is highly flexible, permitting the programming of many recording configurations and parameters, as well as to build a reference database of images, composed of typical patient cases in several pathologies. Usually, the multichannel records can be shown side by side with the reconstructed topographical brain map. In addition, several maps taken in different epochs can be displayed side by side.

There are several very-well researched databases of normal subjects, with which the physician may accurately determine whether a patient’s EEG is abnormal. That research, conducted principally at Harvard, New York University, and the National Institute of Health extends from the 1970’s forward and is intensely active today at a number of international sites. A recent development is three-dimensional analysis, allowing localization of an EEG source deep within the brain.

Source

• Renato M.E. Sabbatini, Mapping the Brain. Brain & Mind Magazine, September/November 1997 (reproduced with permission).

A computer museum is a collection of vintage computer hardware and software. Computer museums are rarely physical museums, but rather personal collections owned by retrocomputing hobbyists. Many computer museums are freely available to view publicly online through websites. Computers often found in computer museums include Apple IIs, older Apple Macintoshes, Commodore International’s, Amigas, IBM PCs and more rare computers such as the Osborne 1.

The largest computer museum in the world is the Computer History Museum, which preserves and presents the computing revolution and its impact on the human experience. The Computer History Museum has the largest number of exhibits and collections of any other computer museum. Most public computer museums include the Apple I and Altair 8800 as exhibits.

Computer museum websites are widely popular because they document a large number of computers. The most popular is old-computers.com, first opened online in 1996. As of 2006, it includes 935 computers, 84 consoles and 98 pongs. However, old-computers.com is missing many vintage systems such as the Macintosh Classic from 1990.

Microsoft have their own computer museum at their headquarters which is open to the public, and at one time Apple Computer also had a museum open to the public.

Some computer museums

This list is incomplete. See also .

• American Computer Museum, the oldest currently operating one
• Computer History Museum, the largest
• DigiBarn Computer Museum in Boulder Creek, California
• Rhode Island Computer Museum
• The Computer Museum, Boston, closed in 1999
• Personal Computer Museum in Brantford, Ontario, Canada

See also

• Retrocomputing
• History of computing
• Timeline of computing

External links

• The Computer History Museum
• Heinz Nixdorf MuseumsForum
• The Museum of Computing

A pacemaker action potential is the kind of action potential that provides a reference rhythm for the network. This contrasts with pacemaker potential or current which drives rhythmic modulation of firing rate.

Some pacemaker action potentials generate rhythms for the heart beat (sino-atrial node) or the circadian rhythm in the suprachiasmatic nucleus.

The Market Weighton canal ran 9.5 miles from the River Humber to where it terminated near Market Weighton. It gained its Act of Parliament in 1772 and opened in 1782. The 3.5 miles closest to Market Weighton was abandoned in 1900 and the right of navigation through the Humber lock was lost in 1971. However as of 2002 the lock was passable and the canal usable up to the junction with the River Foulness where silt made it impassable. [1]

See also

• Canals of Great Britain
• History of the British canal system

Electronic systems are groupings of electronic circuits and components which are designed to accomplish one or more complex functions. Examples include telecommunication systems, computer systems, power distribution systems, radar systems, electronic music systems, and many others.

Electronic Systems may also refer to one of several organizations, including:

• Goodrich Electronic Systems, a division of the Goodrich Corporation.
• Marconi Electronic Systems, a former business of GEC. Now part of BAE Systems.
• Northrop Grumman Electronic Systems, a business of Northrop Grumman
• Electronic Systems, a former business of Raytheon
• Electronic Systems Center, a unit of the USAF located at Hanscom AFB

Lt. Col. Milo E. Rowell (July 25, 1903 - October 7, 1977) was an American lawyer and Army officer best known for his role in drafting the Constitution of Japan.

Born in Fresno, California, Rowell graduated from Stanford University and Harvard Law School, and returned to Fresno in 1926 to open a private law practice there. He enlisted in the Army in 1943, where he studied occupation administration and also commanded troops in the Philippines.

Following Japan’s surrender in 1945, Rowell moved to Tokyo and joined the occupation authority under Douglas MacArthur as Chief of Judicial Affairs. In this capacity, he worked with Brig. Gen. Courtney Whitney to prepare a draft constitution for the Diet of Japan to approve. Rowell extensively analyzed the existing Meiji Constitution, balancing it with the demands of Japanese lawyers to form a draft that was acceptable to both the Japanese government and the GHQ.

Rowell donated his papers to the University of Tokyo in 1965. They now serve as one of the key legislative history sources in Japanese constitutional law.

Near Vertical Incidence Skywave, or NVIS, is a radio antenna configuration that provides usable signals in the range between groundwave and skywave distances (usually
30 to 400 miles, or 50 to 650 km). The usable frequencies are between 1.8 MHz and
15 MHz. with the most common use being between 3.5 MHz and 7.3 MHz.

NVIS configuration is a horizontally polarized (parallel with the surface of the earth) radiating element that is from 1/20th wavelength to 1/8th wavelength above the ground. That proximity to the ground forces the majority of the radiation to go straight up. Overall efficiency of the antenna can be increased by placing a ground wire slightly longer than the antenna, parallel to and directly underneath the antenna. While the ground wire is not necessary under good to excellent propagation conditions, antenna gain in the 3 dB to 6 dB range are common when the ground wire is used.

Significant increases in communication will be realized when both the transmitting station and the receiving station use NVIS configuration for their antennas.

NVIS is most useful in mountainous areas where line of sight
propagation at VHF or UHF frequencies is ineffective or when the
communication distance is beyond ground wave (more than 50 miles)
and less than sky-wave (300 to 1500 miles). More simply stated, NVIS
communication is most effective for regional use. This may be used to
handle emergency communication or simply for fun.

External links

• QSL.net Article
• Build an NVIS antenna yourself
• Using NVIS in antenna manufacturing
• Stealthy NVIS Antenna System

Reference

The Arkwright Scholarship is a scholarship for engineering given to pupils studying A Levels or Highers in the United Kingdom. It is named after the famed 18th Century engineer, Richard Arkwright. Engineering companies give £1000 per scholar. This is then divided between the school, the scholar and the Arkwright Scholarships Trust (the administrative body that sorts out the scholarships). About £450 goes to both the school and the scholar (£225 a year for two years), and £100 goes to the Trust.

To achieve the scholarship, the student must go through a 3 stage selection process. The first stage is an extended application form, where pupils have to describe their GCSE Technology Project, explain how engineering is an interest in their lives, and usual personal details. Stage Two is a two-hour exam, which focuses on the design stage of a system. The final stage is an interview at a University renowned for engineering.

In 2004, 166 Scholarships were awarded, this was brought down from over 500 candidates.

External links

• The Arkwright Trust

Polling, or polled operation, in computer science, refers to actively sampling the status of an external device by a client program as a synchronous activity. Polling is most often used in terms of I/O, and is also referred to as polled I/O.

Polled I/O is a system by which an operating system (OS) waits and monitors a device until the device is ready to read. In early computer systems, when a program would want to read a key from the keyboard, it would constantly poll the keyboard status port until a key was available; due to lack of multiple processes such computers could not do other operations while waiting for the keyboard. The solution and alternative to this approach is for the device controller to generate an interrupt when the device was ready to transfer data. The CPU handles this interrupt and the OS knows to fetch the data from the relevant device registers. This solution is called interrupt-driven I/O.

Another example of polling can be found in many online chat solutions where a server must queue messages and wait to be asked by a client. This is the most common mechanism for chat utilizing the Ajax web communications technique. Also fetching RSS-Feeds uses the pattern.

Polled reads are data transfers queued on the server system until activated or triggered by the client when needed.

In telecommunication and electronics, the term duty cycle has the following meanings:

Duty cycle is the proportion of time during which a component, device, or system is operated. Suppose a disk drive operates for 1 second, then is shut off for 99 seconds, then is run for 1 second again, and so on. The drive runs for one out of 100 seconds, or 1/100 of the time, and its duty cycle is therefore 1/100, or 1 percent.

In a periodic phenomenon, the ratio of the duration of the phenomenon in a given period to the period.

duty cycle <math> D = \frac{\tau}{T} \ </math>

where

D is the so-called duty cycle;

<math>\tau</math> is the duration that the function is non-zero;

<math>\Tau</math> is the period of the function.

For example, in an ideal pulse train (one having rectangular pulses), the duty cycle is the pulse duration divided by the pulse period. For a pulse train in which the pulse duration is 1 μs and the pulse period is 4 μs, the duty cycle is 0.25. The duty cycle of a square wave is 0.5, or 50%.

For another example, the duty cycle for a piece of electrical equipment (such as an electric motor) is the period for which it may be operated without deleterious effects, such as from overheating.

In a continuously variable slope delta (CVSD) modulation converter, the mean proportion of binary “1″ digits at the converter output in which each “1″ indicates a run of a specified number of consecutive bits of the same polarity in the digital output signal.

Some music synthesizers vary the duty cycle of their audio-frequency oscillators to obtain a subtle effect on the tone colors. This technique is known as Pulse-width modulation (PWM.)

ACC is a near-C compiler for the MS-DOS operating system on the IBM PC line of computers for programs. The compiler and compiled programs will run on any Intel 80386 or above PC running MS-DOS. Included with the compiler are a 386 assembler and a linker for combining multiple object files. There are also two libraries, which are a protected mode DOS extender (based on Thomas Pytel’s, AKA Tran’s PMODE30B + PMODE307 DOS extenders), and a library of functions callable by C programs.

Pointers are 4 bytes, and can access all available memory. All memory can be allocated too. The compiler, assembler and linker are all very small and reportedly very fast.

In mathematics, a module is a finitely-generated module if it has a finite generating set.

Intuitive introduction

Informally, modules are an abstraction of the concept of a number of directions, together with distances (or coefficients) in each direction. A generating set is a list which spans all the possible directions. A finitely-generated module is one for which there is a finite generating set.

This image should nonetheless be used with care, because in a given module “distance” might not be interpreted as a continuous quantity (see examples 2 and 3 below of modules where “distance” is always a whole number). In some modules counter-intuitive things might happen if you travel far enough in one direction (for example in some modules you will get back to where you started). See also torsion modules.

Example 1.: Consider ordinary map co-ordinates, East-West and North-South. Only two directions are required to span the whole map. Ignoring obstructions, you could get to any point on the map by travelling some distance East-West and then some other distance North-South. Thus we say that the whole area of the map is generated by the set {1 mile east, 1 mile north} together with coefficients from the real numbers. The map can be described as a finitely generated module (in fact, a 2-generator module) — although for technical reasons it has to go as far as you like in all directions.

Example 2. (not finitely generated module). Consider the positive rational numbers written as powers of prime numbers. So for example we express 18 as 2.3², 7/6 as 7.2^-1.3^-1 and so on. Here, the prime numbers are the “directions”, and the exponent of each prime is the coefficient. When described in this way, the positive rationals form a module (over the integers). A finite generating set would be a finite set of rational numbers which could, by raising them to any integer power and multiplying them together, be used to express any rational number. No such set exists, because there are infinitely many prime numbers, and no finite set of rational numbers can generate them all. Hence this is not a finitely-generated module.

Example 3. Take the positive rational numbers which (after simplification) contain only the primes 2 and 3. So for instance 6, 10/45=2/9 and 1/12 belong to this set. This is a module over the integers, which is also finitely generated. A set of generators is, for example, {2,3}. Another one would be {2,1/6}.

Formal definition

The left R-module M is finitely-generated if and only if there exist a₁, a₂, …, a_n in M such that for all x in M, there exist r₁, r₂, …, r_n in R with x = r₁a₁ + r₂a₂ + … + r_na_n.

The set {a₁, a₂, …, a_n} is referred to as a generating set for M in this case.

In the case where the module M is a vector space over a field R, and the generating set is linearly independent, n is well-defined and is referred to as the dimension of M (well-defined means that any linearly independent generating set has n elements: this is the dimension theorem for vector spaces).

Some facts

Finitely generated modules over the ring of integers Z coincide with the finitely generated abelian groups; these are completely classified. The same is true for the finitely generated modules over any principal ideal domain; see the structure theorem.

Every homomorphic image of a finitely generated module is finitely generated. In general, submodules of finitely generated modules need not be finitely generated. (As an example, consider the ring R=Z[X₁,X₂,…] of all polynomials in countably many variables. R itself is a finitely-generated R-module [with {1} as generating set]. Consider the submodule K consisting of all those polynomials without constant term. Since every polynomial contains only finitely many variables, the R-module K is not finitely generated.) However, if the ring R is Noetherian, then every submodule of a finitely generated module is again finitely generated (and indeed this property characterizes Noetherian rings).

If M is a module which has a finitely-generated submodule K such that the factor module M/K is finitely generated, then M itself is finitely-generated.

Finitely-presented and coherent modules

Another formulation is this: a finitely-generated module M is one for which there is a surjective module homomorphism

φ : R^k → M.

A finitely-presented module M is one for which the kernel of φ can also be taken to be finitely-generated. If this is the case, we essentially have M specified using finitely many generators (the images of the k generators of R^k) and finitely many relations (the generators of ker(φ)). A coherent module M is one that is finitely-generated and such that the kernel of any map R^k → M (not necessarily surjective) is also finitely-generated.

Over any ring R, coherent modules are finitely-presented, and finitely-presented modules are finitely-generated. For a noetherian ring R, all three conditions are actually equivalent.

Although coherence seems like a more cumbersome condition than the other two, it is nicer than them since the category of coherent modules is an abelian category, while, in general, neither finitely-generated nor finitely-presented modules form an abelian category.

In computer science, statistical computing and bioinformatics, the Baum-Welch algorithm is used to find the unknown parameters of a hidden Markov model (HMM). It makes use of the forward-backward algorithm and is named for Leonard E. Baum and Lloyd Welch.

Explanation

The Baum-Welch algorithm is a generalized expectation-maximization (GEM) algorithm. It can compute maximum likelihood estimates and posterior mode estimates for the parameters (transition and emission probabilities) of an HMM, when given only emissions as training data.

The algorithm has two steps:

1. Calculating the forward probability and the backward probability for each HMM state;
2. On the basis of this, determining the frequency of the transition-emission pair values and dividing it by the probability of the entire string. This amounts to calculating the expected count of the particular transition-emission pair. Each time a particular transition is found, the value of the quotient of the transition divided by the probability of the entire string goes up, and this value can then be made the new value of the transition.

References

The algorithm was introduced in the paper:

• L. E. Baum, T. Petrie, G. Soules, and N. Weiss, “A maximization technique occurring in the statistical analysis of probabilistic functions of Markov chains,” Ann. Math. Statist., vol. 41, no. 1, pp. 164–171, 1970.

The Shannon Lecture by Welch:

• Hidden Markov Models and the Baum-Welch Algorithm, IEEE Information Theory Society Newsletter, Dec. 2003.

See also

• Forward-backward algorithm
• Viterbi algorithm

External links

• An Interactive Spreadsheet for Teaching the Forward-Backward Algorithm (spreadsheet and article with step-by-step walkthrough)

The long-term stability of an oscillator, the degree of uniformity of frequency over time, when the frequency is measured under identical environmental conditions, such as supply voltage, load, and temperature. Long-term frequency changes are caused by changes in the oscillator elements that determine frequency, such as crystal drift, inductance changes, and capacitance changes.

The term Hodometer may refer to:

• Hodometer,

an older name for an Odometer, a device for measuring the distance travelled by a vehicle.

The Skewb Diamond is an octahedron-shaped puzzle similar to the Rubik’s Cube. It has 14 movable pieces which can be rearranged in a total of 138,240 possible combinations. This puzzle is the dual polyhedron of the Skewb.

Description

The Skewb Diamond has 6 octahedral corner pieces and 8 triangular face centers. All pieces can move relative to each other. It is a deep-cut puzzle: its planes of rotation bisect it.

The purpose of the puzzle is to scramble its colors, and then restore it to its original solved state.

See also

• Rubik’s cube
• Pyraminx
• Megaminx
• Skewb
• Dogic

External links

• Jaap’s Skewb Diamond page

In finance and economics, nominal interest rate or nominal rate of interest refers to the rate of interest before adjustment for inflation (in contrast with the real interest rate); or, for interest rates “as stated” without adjustment for the full effect of compounding (also referred to as the nominal annual rate). An interest rate is called nominal if the frequency of compounding (e.g. a month) is not identical to the basic time unit (normally a year).

Nominal and real interest rates

The nominal interest rate (unadjusted for inflation) includes compensation for the lender’s lost value due to inflation, whereas the real interest rate excludes inflation. The real interest rate therefore expresses the cost of borrowed funds after the expected erosion of the value of those funds due to the rise in the general price level.

The relationship between real and nominal interest rates can be described in the equation:

• <math>(1+r)(1+i)=(1+R)</math> where r is the real interest rate, i is the inflation rate, and R is the nominal interest rate.Richard A. Brealey and Steward C. Meyer. Principles of Corporate Finance, Sixth Edition. Irwin McGraw-Hill, London, 2000. p. 49.

• A common approximation for the real interest rate is:

real interest rate = nominal interest rate - expected inflation

In this analysis, the nominal rate is the stated rate, and the real interest rate is the interest after the expected losses due to inflation. Since the future inflation rate can only be estimated, the ex ante and ex post (before and after the fact) real interest rates may be different; the premium paid to actual inflation may be higher or lower. In contrast, the nominal interest rate is known in advance.

Nominal and effective interest rates

The nominal interest rate is the periodic interest rate times the number of periods per year; for example, a nominal annual interest rate of 12% based on monthly compounding means a 1% interest rate per month (compounded).[1]
Contemporary Financial Management (with Thomson One - Business School Edition and Infotrac) By R. Charles Moyer, James R. McGuigan, William J. Kretlow, pg. 163] A nominal interest rate for compounding periods less than a year is always higher than the equivalent rate with annual compounding.A nominal rate without the compounding frequency is not fully defined: for any interest rate, the effective interest rate cannot be specified without knowing the compounding frequency and the rate. Although some conventions are used where the compounding frequency is understood, consumers in particular may fail to understand the importance of knowing the effective rate.

Nominal interest rates are not comparable unless the compounding periods are the same; effective interest rates correct for this by “converting” nominal rates into annual compound interest. In many cases, depending on local regulations, interest rates as quoted by lenders and in advertisements are based on nominal, not effective, interest rates, and hence may understate the interest rate compared to the equivalent effective annual rate.

The term should not be confused with simple interest (as opposed to compound interest). Simple interest is interest that is not compounded.

The effective interest rate is always calculated as if compounded annually. The effective rate is calculated in the following way, where r is the effective rate, i the nominal rate, and n the number of compounding periods per year (for example, 12 for monthly compounding):

<math> r \ = \ (1+i/n)^n - 1</math>

Examples

Monthly compounding

A nominal interest rate of 6% compounded monthly is equivalent to an effective interest rate of 6.17%. 6% monthly is credited as 6%/12 = 0.5% every month. After one year, the initial capital is increased by the factor (1+0.005)¹² ≈ 1.0617.

Daily compounding

A loan with daily compounding will have a substantially higher rate in effective annual terms. For a loan with a 10% nominal annual rate and daily compounding, the effective annual rate is 10.516%. For a loan of $10,000 (paid at the end of the year in a single lump sum), the borrower would pay $51.56 more than one who was charged 10% interest, compounded annually.

See also

• Time value of money
• Interest
• Compound interest
• Effective interest rate
• List of finance topics
• Real interest rate
• Real versus nominal value

References

A device file or special file is an interface for a device driver that appears in a file system as if it were an ordinary file. This allows software to interact with the device driver using standard input/output system calls, which simplifies many tasks.

Device files often provide simple interfaces to peripheral devices, such as printers. But they can also be used to access specific resources on those devices, such as disk partitions. Finally, device files are useful for accessing system resources that have no connection with any actual device such as data sinks and random number generators.

Unix special files

There are two general kinds of device nodes in Unix-like operating systems, known as character special files and block special files. The difference between them lies in how data written to them and read from them is processed by the operating system and hardware. These together can be called device special files in contrast to named pipes, which are not connected to a device but are not ordinary files either.

MS-DOS device files

MS-DOS borrowed the concept of special files from Unix, but renamed them device files. Because early versions of MS-DOS did not support a directory hierarchy, device files were distinguished from regular files by making their names reserved words. This means that certain file names are reserved for device files, and cannot be used to name new files or directories.
The reserved names themselves are chosen to be compatible with “special files” handling of PIP command in CP/M.

Some device files are listed below:

Reserved words cannot even be used with extensions, so that file names like “nul.doc” and “con.htm” are invalid. This has been known to confuse some users or to cause programmatic construction of file names to fail.

Macquarie Graduate School of Management (MGSM) is Macquarie University’s business school.

MGSM is a leading business school in Australia and the Asia-Pacific region. Offering a range of programs in Sydney, Singapore and Hong Kong, MGSM’s comprehensive suite of management programs are innovative and practical and include:

   * Postgraduate Programs - including the MBA.
   * Research Programs - including the DBA.
   * Executive Education Programs - open enrolment programs.
   * Customised Corporate Programs - degree and non-degree programs.

MGSM has two campuses in Sydney, one at Macquarie University in Macquarie Park, North Ryde and one in the CBD, near Circular Quay. These exceptional venues meet the requirements of students and cater for corporate conference and training needs. The Macquarie Park venue features a 4-star hotel, dining rooms, bar and restaurant.

[1].

MGSM currently has around 1,800 graduate students enrolled[2]. The current dean is Professor Roy Green.

External links

• Macquarie Graduate School of Management

Chas. T. Main Inc. was founded in 1893 by Charles T. Main, an engineer for the textile mills of New England. In addition to the traditional business of water and steam power, Main soon expanded into the new field of hydroelectric generators. It rose to become a world-wide player in the utility industries, providing many wide-ranging engineering services. For example, in the mid-1950’s Charles T. Main was responsible for the building of a hydro-electric plant in Turkey, a plant visited by the Shah of Iran during his effort to modernize Iran.

According to John Perkins, Main Inc. was additionally a consulting firm, which trapped Third World countries into international debts they could not repay. He published his account in “Confessions of an Economic Hit Man”.

In the late 1980s, mismanagement lead to the downfall of Main and it was bought by Parsons Corporation of Pasadena, California.

Chas T. Main, Inc. changed its name to Parsons Main, Inc. in January of 1992.

Hibernation induction trigger (hibernation inducement trigger or HIT) is a substance found in the blood of hibernating animals. If blood is taken from a hibernating squirrel in the winter and injected into another squirrel in the spring, the normally active squirrel goes into hibernation. HIT can also be found in the blood of hibernating bears.

Researchers were able to prolong the life of an isolated pig’s heart with HIT. This may have potentially important implications for organ transplant, as it could allow organs to survive for up to 18 or more hours, outside the human body. This would be a great improvement from the current 6 hours.

NASA is co-funding research into HIT, with an eye to long-duration space travel for humans.

Chemically, HIT is an opioid-like substance.

See also

• Suspended animation
• Premature burial

External links and sources

• Potential medical usage
• Harvested human Lung Preservation With the Use of Hibernation Trigger Factors

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In probability theory, an elementary event or atomic event is a subset of a sample space that contains only one element. It is important to note that an elementary event is still a set containing an element of the sample space, not that element itself. However, elementary events are often written as elements rather than sets for simplicity, where this is unambiguous.

Examples of sample spaces, S, and elementary events include:

• If objects are being counted, and the sample space S = {0, 1, 2, 3, …} (the natural numbers), then the elementary events are all sets {k}, where k ∈ N.
• If a coin is tossed twice, S = {HH, HT, TH, TT}, H for heads and T for tails, and the elementary events are {HH}, {HT}, {TH} and {TT}.
• If X is a normally distributed random variable, S = (-∞, +∞), the real numbers, and the elementary events are all sets {x}, where x ∈ R. This example shows that a continuous probability distribution is not determined by the probabilities assigned to atomic events, since all of those are zero.

Elementary events may have probabilities that are strictly positive, zero, undefined, or any combination thereof. For instance, any discrete probability distribution is determined by the probabilities it assigns to what may be called elementary events. In contrast, all elementary events have probability zero under any continuous distribution. Mixed distributions, being neither entirely continuous nor entirely discrete, may contain atoms, which can be thought of as elementary (that is, atomic) events with non-zero probabilities. Under the measure-theoretic definition of a probability space, the probability of an elementary event need not even be defined, since mathematicians distinguish between the sample space S and the events of interest, defined by the elements of a σ-algebra on S.

In probability theory and statistics, the moment-generating function of a random variable X is

<math>M_X(t)=E\left(e^{tX}\right), \quad t \in \mathbb{R},</math>

wherever this expectation exists. The moment-generating function generates the moments of the probability distribution.

For vector-valued random variables X with real components, the moment-generating function is given by

<math> M_X(\mathbf{t}) = E\left( e^{\langle \mathbf{t}, \mathbf{X}\rangle}\right) </math>

where t is a vector and <math>\langle \mathbf{t} , \mathbf{X}\rangle</math> is the dot product.

Provided the moment-generating function exists in an interval around t = 0, the nth moment is given by

<math>E\left(X^n\right)=M_X^{(n)}(0)=\left.\frac{\mathrm{d}^n M_X(t)}{\mathrm{d}t^n}\right|_{t=0}.</math>

If X has a continuous probability density function f(x) then the moment generating function is given by

<math>M_X(t) = \int_{-\infty}^\infty e^{tx} f(x)\,\mathrm{d}x</math>

<math> = \int_{-\infty}^\infty \left( 1+ tx + \frac{t^2x^2}{2!} + \cdots\right) f(x)\,\mathrm{d}x</math>

<math> = 1 + tm_1 + \frac{t^2m_2}{2!} +\cdots,</math>

where <math>m_i</math> is the ith moment. <math>M_X(-t)</math> is just the two-sided Laplace transform of f(x).

Regardless of whether the probability distribution is continuous or not, the moment-generating function is given by the Riemann-Stieltjes integral

<math>M_X(t) = \int_{-\infty}^\infty e^{tx}\,dF(x)</math>

where F is the cumulative distribution function.

If X₁, X₂, …, X_n is a sequence of independent (and not necessarily identically distributed) random variables, and

<math>S_n = \sum_{i=1}^n a_i X_i,</math>

where the a_i are constants, then the probability density function for S_n is the convolution of the probability density functions of each of the X_i and the moment-generating function for S_n is given by

<math>

M_{S_n}(t)=M_{X_1}(a_1t)M_{X_2}(a_2t)\cdots M_{X_n}(a_nt).
</math>

Related to the moment-generating function are a number of other transforms that are common in probability theory, including the characteristic function and the probability-generating function.

The cumulant-generating function is the logarithm of the moment-generating function.

See also

• Characteristic function
• Cumulant generating function
• Factorial moment generating function
• Rate function

In the algebraic axiomatization of probability theory, the primary concept is not that of probability of an event, but rather that of a random variable. Probability distributions are determined by assigning an expectation to each random variable. The measurable space and the probability measure arise from the random variables and expectations by means of well-known representation theorems of analysis. One of the important features of the algebraic approach is that apparently infinite-dimensional probability distributions are not harder to formalize than finite-dimensional ones.

Random variables are assumed to have the following properties:

1. complex constants are random variables;
2. the sum of two random variables is a random variable;
3. the product of two random variables is a random variable;
4. addition and multiplication of random variables are both commutative; and
5. there is a notion of conjugation of random variables, satisfying (ab)^* = b^* a^* and a^** = a for all random variables a, b, and coinciding with complex conjugation if a is a constant.

This means that random variables form complex abelian *-algebras. If a = a^*, the random variable a is called “real”.

An expectation E on an algebra A of random variables is a normalized, positive linear functional. What this means is that

1. E(k) = k where k is a constant;
2. E(a^* a) ≥ 0 for all random variables a;
3. E(a + b) = E(a) + E(b) for all random variables a and b; and
4. E(za) = zE(a) if z is a constant.

References

• Peter Whittle, Probability via Expectation, Fourth Edition, Springer, 2000

Pulse generators can either be internal circuits or pieces of electronic test equipment used to generate pulses.

Features

Simple pulse generators usually allow control of the pulse repetition rate (frequency), pulse width, delay with respect to an internal or external trigger and the high- and low-voltage levels of the pulses. More-sophisticated pulse generators may allow control over the rise time and fall time of the pulses. Pulse generators may use digital techniques, analog techniques, or a combination of both techniques to form the output pulses. For example, the pulse repetition rate and duration may be digitally controlled but the pulse amplitude and rise and fall times may be determined by analog circuitry in the output stage of the pulse generator. With correct adjustment, pulse generators can also produce a 50% duty cycle square wave. Pulse generators are generally single-channel providing one frequency, delay, width and output. To produce multiple pulses, these simple pulse generators would have to be ganged in series or in parallel.

A new family of pulse generators can produce multiple-channels of independent widths and delays and independent outputs and polarities. Often called digital delay/pulse generators, the newest designs even offer differing repetition rates with each channel. These digital delay generators are useful in synchronizing, delaying, gating and triggering multiple devices usually with respect to one event.

Pulse generators are generally voltage sources, with true current pulse generators being available only from a few suppliers.

Applications

These pulses can then be injected into a device under test and used as a stimulus or clock signal or analyzed as they progress through the device, confirming the proper operation of the device or pinpointing a fault in the device. Pulse generators are also used to drive devices such as switches, lasers and optical components, modulators, intensifiers as well as resistive loads.

The output of a pulse generator may also be used as the modulation signal for a signal generator.

Pirate broadcasting is unlicensed broadcasting of radio and television. Pirate radio is by far the most common, as less equipment is usually necessary, and lower power is usually required to create a usable signal. Some pirate television outlets have existed, however.

Pirate broadcasting can also refer to broadcast signal intrusion which is when a licensed broadcast signal is overridden by an unauthorized signal.