the-french-artist/wikipedia_20220301.simple_sentence_split huggingface dataset:
The archipelago and the island of Taiwan together formed the former Japanese territory of Formosa.
Yanshan University is a university in Qinhuangdao, Hebei, China.
Yan Shan University  official website
In physics, an insertion device is a group of magnets that can be placed on a straight segment of a particle accelerator to be a synchrotron light source.
They are called an "insertion devices" because they replace pipe that otherwise would hold the vacuum needed to maintain the particle beam path.
Many times, insertion devices are used on the circular path of a synchrotron or a storage ring.
There are two types of insertion devices.
Undulators make electromagnetic radiation that is tuned to a narrow frequency range.
Wigglers make a wide range of electromagnetic radiation frequencies.
In materials science, physics, chemistry, and molecular biology, a beamline leads to the experimental endstation utilizing particle beams from a particle accelerator, synchrotron light obtained from a synchrotron, or neutrons from a spallation source or research reactor.
Beamline in a particle accelerator
In particle accelerators, the beamline is usually housed in a tunnel and/or underground, cased inside a cement housing.
The beamline is usually cylindrical metal.
Typical names include, beam pipe, and/or a blank section called a drift tube.
This entire section must be under a good vacuum in order to have the beam travel for a long distance.
A survey and alignment crew carefully align the beamline segments by using a laser tracker.
All beamlines must be within micrometre tolerance.
Good alignment helps to prevent beam loss, and beam from colliding with the pipe walls, which creates secondary emissions and/or radiation.
Synchrotron radiation beamline
Regarding synchrotrons, a beamline is the instrumentation that carries beams of synchrotron radiation to an experimental end station, which uses the radiation produced by the bending magnets and insertion devices in the storage ring of a synchrotron light source.
A typical application for this kind of beamline is crystallography.
Scientists also use synchrotron light in many other ways.
A large synchrotron laboratory will have many beamlines, each optimized for a particular field of research.
The differences will depend on the type of insertion device (which, in turn, determines the intensity and spectral distribution of the radiation); the beam conditioning equipment; and the experimental end station.
A typical beamline at a modern synchrotron will be 25 to 100 m (82 ft to  328 ft) long from the storage ring to the end station, and may cost up to millions of US dollars.
For this reason, a synchrotron facility is often built in stages, with the first few beamlines at the start of operation, and other beamlines being added later as the funding permits.
The beamline elements are in radiation shielding enclosures, called hutches, which are the size of a small room (cabin).
A typical beamline consists of two hutches, an optical hutch for the beam conditioning elements and an experimental hutch, which houses the experiment.
Between hutches, the beam travels in a transport tube.
People are not allowed to enter hutches when the beam shutter is open and radiation can enter the hutch.
Hutches have complex safety systems with redundant  interlocking functions to make sure that no one is inside the hutch when the radiation is turned on.
The safety system will also shut down the radiation beam if the door to the hutch is accidentally opened when the beam is on.
In this case, the beam is turned off by dumping the electron beam circulating in the synchrotron.
So, opening one door will shut down all of the beamlines in the facility.
Windows - thin sheets of metal, often beryllium, which transmit almost all of the beam, but protect the vacuum within the storage ring from contamination
Slits - which control the physical width of the beam and its angular spread
Focusing mirrors - one or more mirrors, which may be flat, bent-flat, or toroidal, which helps to collimate (focus) the beam
Monochromators - devices based on diffraction by crystals which select particular wavelength bands and absorb other wavelengths, and which are sometimes tunable to varying wavelengths, and sometimes fixed to a particular wavelength
Spacing tubes - vacuum maintaining tubes which provide the proper space between optical elements, and shield any scattered radiation
Sample stages - for mounting and manipulating the sample under study and subjecting it to various external conditions, such a varying temperature, pressure etc.
Radiation detectors - for measuring the radiation which has interacted with the sample
The combination of beam conditioning devices controls the thermal load (heating caused by the beam) at the end station; the spectrum of radiation incident at the end station; and the focus or collimation of the beam.
Devices along the beamline which absorb significant power from the beam may need to be actively cooled by water, or liquid nitrogen.
Neutron beamline
An experimental end station in a neutron facility is called a neutron beamline.
Superficially, neutron beamlines differ from synchrotron radiation beamlines mostly by the fact that they use neutrons from a research reactor or a spallation source instead of photons.
The experiments usually measure neutron scattering from the sample under study.
Accelerator physics
Ion beam
:Category:Neutron facilities
Quadrupole magnet
Waveguide
Macromolecular Crystallography at Synchrotrons: An Historical Introduction
The Conférence des directeurs des écoles françaises d'ingénieurs (CDEFI) is a French association, established in 1976, of Grandes Écoles of engineering.
The CDEFI represents the administration of all the engineering institutions.
Fred Burton (born January 2, 1958) is STATFOR's vice president for intelligence.
STRATFOR is a global intelligence company.
Burton is thought to be "one of the world's foremost experts on security, terrorists and terrorist organizations."
This basically means that he is thought to be one of the world's best intelligence workers.
Washington asked Burton to help the investigation of the assassination of Israeli Prime Minister Yitzhak Rabin.
He used to be the deputy chief of the counter-terrorism part of the U.S. State Department's Diplomatic Security Service.
He also investigated the killing of Rabbi Meir Kahane, the al Qaeda New York City bombing plots before the September 11 attacks and the Libyan-backed terrorist attacks against diplomats in Sana'a and Khartoum.
He helped in the arrest of Ramzi Yousef, the mastermind of the first World Trade Center bombing in 1993.
Burton is the author of a memoir called Ghost: Confessions of a Counterterrorism Agent.
It was published by Random House in 2008.
Another memoir is Chasing Shadows: A Special Agent's Lifelong Hunt to Bring a Cold War Assassin to Justice, published by Palgrave Macmillan in 2011.
In August 2009 he was hired as the Texas Department of Public Safety's Assistant Director for Intelligence and Counter-Terrorism but left after 2 months.
This was because he wanted to work on his writing and speaking career.
STRATFOR website
Collimated light is light whose rays are parallel.
This light spreads slowly as it travels.
The word collimated is related to collinear, because all the rays in collimated light line up with each other.
Perfectly collimated light would not spread out with distance at all.
No real light is perfectly collimated.
Real light will spread a little as it travels.
Diffraction prevents anyone from creating a perfectly collimated beam.
Light can be roughly collimated by using a collimator – a device which narrows a beam of particles or waves.
The word "collimate" comes from the Latin verb collimare, which originated in a misreading of collineare, "to direct in a straight line".
Laser light from crystal and some gas lasers is highly collimated because it is formed in an optical cavity between two parallel mirrors, in addition to being coherent.
The divergence of high-quality laser beams is commonly less than 1 milliradian, and can be much less for large-diameter beams.
Laser diodes emit less collimated light due to their short cavity, and therefore higher collimation requires a collimating lens.
Synchrotron light
Synchrotron light is very collimated.
It is produced by bending relativistic electrons around a circular track.
Distant sources
Lenses and mirrors
A perfect parabolic mirror will bring parallel rays to a focus at a single point.
Conversely, a point source at the focus of a parabolic mirror will produce a beam of collimated light.
Since the source needs to be small, such an optical system cannot produce much optical power.
Spherical mirrors are easier to make than parabolic mirrors and they are often used to produce approximately collimated light.
Many types of lenses can also produce collimated light from point-like sources.
Pfister, J. & Kneedler, J.A. (s.d.).
A guide to lasers in the OR.
Hispanic (Spanish: Hispano, hispánico) is a word that originally meant a relationship to Hispania.
This is the Iberian Peninsula and includes Portugal, Andorra, Gibraltar and Spain.
Now the word is used with a more limited meaning.
In the United States it is often used to mean a person of (usually) mixed race with a Spanish surname.
In North America generally, the word Hispanic has lost its link to Spain and Portugal, and is mainly used to mean Latin America.
Hispanic has also been used to mean the culture and people of the former Spanish and Portuguese Empires in America.
Known as Hispanic America, this region includes Mexico, most of the Central and South American countries, and the Spanish-speaking island-nations of the Caribbean.
Muryeong of Baekje (462–523, r. 501–23), also known as Sama, was a 6th-century Korean king.
He was the 25th king of Baekje, which was one of the Three Kingdoms of Korea in ancient times.
The name Muryong means "military peace".
It is a name he got after death.
Events of Muryeong's reign
Muryeong's tomb is located in Gongju in South Chungcheong Province.
It has been studied by archeologists and historians.
This the only ancient tomb that has been positively identified among those of this period.
In 2001, Japan's Emperor Akihito acknowledged a distant relationship with Muryeong.
He explained, "I, on my part, feel a certain kinship with Korea, given the fact that it is recorded in the Chronicles of Japan that the mother of Emperor Kammu was of the line of King Muryong of Baekje."
Kim, Won-Yong. “
The Tomb of King Muryong of the Paekche Dynasty.”
Asian Pacific Quarterly of Cultural and Social Affairs (Seoul) 3:3 (Winter 1971): 34-46.
Paik, Seung-gil. "
Excavation of the Tomb of Paekche King Muryong."
Korea Journal 11:8 (August 1971): 48-51.
http://www.myj7000.jp-biz.net/clan/03/03013.htm#003
The Lilly Ledbetter Fair Pay Act of 2009  (LLFPA) is an Act of Congress about pay discrimination that was signed into law by President Barack Obama on January 29, 2009.
The bill amends the Civil Rights Act of 1964 stating that the 180-day statute of limitations for filing an equal-pay lawsuit regarding pay discrimination resets with each new discriminatory paycheck.
The law was a direct answer to the Ledbetter v. Goodyear Tire & Rubber Co., , a U.S. Supreme Court decision holding that the statute of limitations for presenting an equal-pay lawsuit begins on the date that the employer makes the initial discriminatory wage decision, not at the date of the most recent paycheck, as a lower court had ruled.
A first bill to amend the statutory limitations period and supersede the Ledbetter decision was introduced in the 110th United States Congress but was never enacted, as after having been passed by the House it failed to survive a cloture vote in the Senate due to the opposition of most of the Republican Senators.
During the campaign for the 2008 elections, the Democrats criticized Republicans for defeating the 2007 version of the bill, citing Republican presidential candidate John McCain's opposition.
Then-candidate Barack Obama supported the bill.
After the 2008 election gave the Democratic Party control of both the House and Senate, a new version of the bill was introduced in the first session of the 111th United States Congress and quickly passed both bodies.
It became the law signed by the new President Obama after he took office on January 20.
Court rulings
Lilly Ledbetter, a production supervisor at a Goodyear tire plant in Alabama, filed an equal-pay lawsuit seeking back pay for pay discrimination under Title VII of the Civil Rights Act of 1964.
She worked for that company for many years without learning that she was paid much less than the men holding the same job.
She filed the lawsuit six months before her early retirement in 1998.
The District court said her lawsuit was filed on time, but the Court of Appeals said her lawsuit was too late.
Ledbetter appealed the decision to the United States Supreme Court.
The Supreme Court ruled in 2007 by a 5-4 majority vote that Ledbetter's complaint was filed too late because the discriminatory decisions relating to pay had been made more than 180 days prior to the date she filed her charge, as explained by Justice Samuel Alito.
The minority position explained by Justice Ruth Bader Ginsburg proposed an interpretation according to which the law runs from the date of any paycheck that contains an amount affected by a prior discriminatory pay decision.
The Ledbetter decision was cited by federal judges in 300 cases before the LLFPA was passed.
These cases involved not only Title VII of the Civil Rights Act, but also the Age Discrimination in Employment Act, Fair Housing Act, Patsy T. Mink Equal Opportunity in Education Act and Eighth Amendment to the Constitution.
The case had never received much attention before going to the Supreme Court, but the Court's ruling ignited legal groups on the left and Democrats that took action to transform the Ledbetter case into a rallying issue for the left.
Some activists saw Lilly Ledbetter as an ideal standard-bearer in their attempt to persuade the public that the Supreme Court was moving too far to the right.
Among the first to criticize the Court's decision was Marcia Greenberger, president of the National Women's Law Center, that saw in the ruling a "setback for women and a setback for civil rights" and called Ginsburg's opinion a "clarion call to the American people that this slim majority of the court is headed in the wrong direction."
Debra Ness, president of the National Partnership for Women & Families, also condemned the decision, saying, “If employers can keep the discrimination hidden for a period of time, they can continue to discriminate without being held accountable.”
On the other side, the majority's findings were applauded by the US Chamber of Commerce, that called it a "fair decision" that "eliminates a potential wind-fall against employers by employees trying to dredge up stale pay claims."
The House Democrats were fast to react.
On June 12, the caucus spoke against the Supreme Court decision.
Claiming lead from Justice Ruth Ginsburg's minority opinion, which invited the Congress to take action by amending the law, the Democrats announced their intention to intervene: House Majority Leader Steny Hoyer and Education and Labor Committee Chairman George Miller said that a bill was to be passed to avoid future court rulings in line with Ledbetter, clearly putting that "a key provision of the legislation will make it clear that discrimination occurs not just when the decision to discriminate is made, but also when someone becomes subject to that discriminatory decision, and when they are affected by that discriminatory decision, including each time they are issued a discriminatory paycheck", as said by Rep. Miller.
The issue divided lawyers.
The American Bar Association passed a resolution supporting the new bill.
Other lawyers, such as Neal Mollen, argued that extending the term limit would put a strain on the chances of an adequate defense for the employers, as to defend themselves one "has to rely on documents and the memory of individuals, and neither of those is permanent.
If a disappointed employee can wait for many years before raising a claim of discrimination ... he or she can wait out the employer, that is ensure that the employer effectively unable to offer any meaningful defense to the claim".
Legislative history
The bill was re-introduced in the 111th Congress (as  and ) in January 2009.
It passed in the House of Representatives with 247 votes in support and 171 against.
The vote was nearly perfectly split along party lines, with only three Republicans voting in favor (Ed Whitfield of Kentucky, Don Young of Alaska and Chris Smith of New Jersey) and three Democrats voting nay (Travis Childers of Mississippi, Allen Boyd of Florida,  and Parker Griffith of Alabama).
The Senate voted 72 to 23 to invoke cloture on S. 181 on January 15, 2009. (
The vote to invoke cloture ends debate on a bill, and usually leads to a final vote within a few days.)
The Lilly Ledbetter Fair Pay Act passed the Senate, 61-36, on January 22, 2009.
The votes in favor included every Democratic senator (except Edward Kennedy of Massachusetts, who was absent from the vote because of health issues) and five Republican senators.
As president, Obama actively supported the bill.
The official White House blog said:
House Majority Leader Steny Hoyer announced that the House would vote on S.181 (the bill passed by the Senate) during the week of January 26, getting the bill to President Obama's desk sooner rather than later.
On January 27, the House passed S.181 by a 250-177 margin.
On January 29, Obama signed the bill into law.
It was the first act he signed as president, and it fulfilled his campaign pledge to nullify Ledbetter v. Goodyear.
However, some newspapers criticised him for signing it only two days after it was passed by the House.
The St. Petersburg Times which mentioned his campaign promise to give the public five days of notice to comment on legislation before he signed bills.
The White House through a spokesman answered that they would be "implementing this policy in full soon", and that  currently they were "working through implementation procedures and some initial issues with the congressional calendar".
The International Food Policy Research Institute (IFPRI) is an international agricultural research center to improve the understanding of national agricultural and food policies to promote the adoption of innovations in agricultural technology.
Additionally, IFPRI researches the role of agricultural and rural development in the overall development of a country.
IFPRI is an international research institutes funded in part by the Consultative Group on International Agricultural Research (CGIAR).
CGIAR is funded by governments, private businesses and foundations, and the World Bank.
IFPRI carries out food policy research.
IFPRI communicates in publications, bulletins, conferences, and other initiatives.
IFPRI was organized as a District of Columbia non-profit, non-stock corporation on March 5, 1975 and its first research bulletin was produced in February 1976.
IFPRI has offices in several developing countries, including China, Ethiopia, and India.
IFPRI has research staff working in many more countries around the world.
Research Areas
Products and Publications
IFPRI publishes books, research reports, but also newsletters, briefs, and fact sheets.
It is also involved in the collection of primary data and the compilation and processing of secondary data.
In 1993 IFPRI introduced its 2020 Vision Initiative.
IFPRI wants to reach food security for the world by 2020.
As of 2006 IFPRI produces the Global Hunger Index (GHI) yearly measuring the progress and failure of individual countries and regions in the fight against hunger.
The GHI is a collaboration of IFPRI, the Welthungerhilfe, and Concern Worldwide.
Development Strategy and Governance
Environment and Production Technology
Poverty, Health, and Nutrition
Knowledge, Capacity, and Innovation
Markets, Trade, and Institutions
The Agricultural Science and Technology Indicators (ASTI)
The CGIAR Systemwide Program on Collective Action and Property Rights (CAPRi)
Harvest Plus
HarvestChoice
CGIAR and its agencies, including IFPRI, have been criticized for their connections to Western governments and multinational agribusiness, although its research publications have also been cited by critics of agribusiness and Genetically Modified Organisms in agriculture.
IFPRI describes itself as "neither an advocate nor an opponent of genetically modified crops."
Adato, Michelle, and Ruth Meinzen-Dick.
Agricultural Research, Livelihoods, and Poverty: Studies of Economic and Social Impacts in Six Countries.
Johns Hopkins University Press, Baltimore, MD.
CGIAR Science Council Secretariat.
Fourth External Program and Management Review of the International Food Policy Research Institute (IFPRI).
Rome, Italy: CGIAR Science Council.
Farrar, Curtis.
The first ten years of IFPRI.
Washington, DC: IFPRI.
Lele, Uma J. 2004.
Policy Research in the CGIAR.
In The CGIAR at 31: An Independent Meta-Evaluation of the Consultative Group on International Agricultural Research, Chapter 11, pp.
Washington, DC: The World Bank.
Renkow, Mitch, and Derek Byerlee.
The impacts of CGIAR research: A review of recent evidence.
Food Policy, In Press, Corrected Proof.
Available online 20 May 2010.
von Braun, Joachim and Rajul Pandya-Lorch, Rajul, eds.
Food policy for the poor: Expanding the research frontiers, highlights from 30 years of IFPRI research.
von Grebmer, Klaus and Ingeborg Hovland.
Using 'systems awareness': a proposed mechanism for monitoring communications.
Evidence & Policy: A Journal of Research, Debate and Practice.
Vol 5 (3): 295–303
Event Centre rock (also known as arena rock, corporate rock, industry rock,or stadium rock) is a word to describe a form of rock music which is played, or intended to be played, in large venues, such as event centres, arenas, stadia, and open-air concert spaces.
In such a way, genres which traditionally fall within the categories of event centre rock tend to be (yet not always) loud and anthemic; event centre rock is most traditionally associated with heavy metal, progressive rock, hard rock, glam metal or pop rock genres.
Often, yet not always, event centre rock is categorised as being more mass-scale, commercially appealing, and radio-oriented music.
Due to the often commercial nature of event centre rock, it is occasionally called corporate rock.
Event centre rock is generally associated with the grand shows that artists and groups within the style would hold.
At these performances, large sound systems, and often elaborate lighting, additional effects and fireworks, would be included.
The 1970s and 80s were a major period in event centre rock.
Whilst event centre rock has seen large popularity over the years, especially from the 1960s to the 1980s, it has also been criticised for its often commercial and extravagant nature, especially with regards to the shows and concert tours that event centre rock bands and artists would have.
To some extent, genres such as pub rock, punk rock, indie rock and alternative rock grew as a reaction against the nature and aesthetic of event centre rock, opting for a less commercial and over-the-top style.
Famous bands associated with event centre rock include Kiss, Aerosmith, Journey, and Styx, amongst several others.
The Eagles
Martin Luther King Jr., a prominent American leader of the civil rights movement and Nobel Peace Prize winner, was shot and killed at the Lorraine Motel in Memphis, Tennessee, on April 4, 1968, at the age of 39.
King was rushed to St. Joseph's Hospital, where he died at 7:05 that evening.
He was a prominent leader of the Civil Rights Movement who was known for his use of nonviolence and civil disobedience.
James Earl Ray, a prisoner who ran away from the Missouri State Penitentiary, was arrested and charged with King's murder.
He was sentenced to 99 years in the Tennessee State Penitentiary.
He died in prison at the age of 70 due to liver failure.
The King family and others believe that a government conspiracy killed King, as Loyd Jowers said in 1993.
They believe that Ray was a scapegoat.
In 1999, the King family filed a wrongful death lawsuit against Jowers for $10,000,000.
During the trial, both the King family and Jowers gave evidence accusing the government of a conspiracy.
The government agencies that were accused could not defend themselves or respond, because they were not named as defendants.
Based on the evidence, the jury concluded that Jowers and "others were part of a conspiracy to kill King."
King had clearly made enemies in his rise to fame.
The Ku Klux Klan did what they could to hurt his reputation, especially in the South.
Even the FBI kept a close eye on him.
On the evening of April 4, 1968, King was standing on the balcony of his motel room in Memphis, Tennessee.
He was planning to lead a protest march to support garbage workers that were on strike.
At 6:01 p.m., King was shot.
The bullet entered through his right cheek, and travelled down his neck.
It cut the major vein and arteries in his neck before stopping in his shoulder.
Unconscious, he fell violently backwards onto the balcony.
Doctors cut open his chest and massaged his heart to try to keep blood and oxygen pumping through his body.
However, King never became conscious again.
He died at 7:05 p.m. According to Taylor Branch, King's autopsy showed that though he was only 39 years old, he had the heart of a 60-year-old man.
Civil disorder, including riots, happened after King's murder in at least 110 U.S. cities.
Washington, Chicago, and Baltimore had the most damage.
On June 10, 1968, James Earl Ray was arrested in London at Heathrow Airport.
Ray was extradited to the United States and charged with killing King.
On March 10, 1969, Ray told the court he was guilty, and was sentenced to 99 years in the Tennessee state penitentiary.
Ray later tried many times to take away his guilty plea and be tried by a jury, but he was unsuccessful.
The United States House of Representatives Select Committee on Assassinations was created in 1976 to look into the assassinations of John F. Kennedy and Martin Luther King, Jr., and the shooting of Governor George Wallace.
The Committee investigated until 1978, and put out a final report in 1979.
About the King assassination, the Committee decided:
James Earl Ray did kill King, with one rifle shot
"There is a likelihood" that this was the result of a conspiracy (probably between Ray and his brothers)
The U.S. government was not part of this conspiracy
In 1999, Coretta Scott King, King's widow, and the rest of King's family won their wrongful death lawsuit against Loyd Jowers and "other unknown co-conspirators" (other people who were part of the conspiracy).
Jowers claimed to have received $100,000 to arrange King's assassination.
The jury of six whites and six blacks found Jowers liable for King's murder.
They also found that governmental agencies were part of the assassination plot.
In 2000, the Department of Justice completed the investigation about Jowers' claims.
They did not find evidence to support the accusations about conspiracy.
The investigation report recommends no more investigation unless some reliable new facts are presented.
Department of Justice investigation on assassination
Shelby County Register of Deeds documents on the Assassination Investigation
Donald E. Wilkes, Jr. , Death of MLK Still a Mystery  (1987).
Donald E. Wilkes, Jr. , What are Facts of MLK Murder?
1960s crimes in the United States
1960s in Tennessee
History of Memphis, Tennessee
On 25 December 2011, there were a number of attacks on Christmas Day during church services in northern Nigeria.
There were bombings and shootings at churches in Madalla (near the capital, Abuja), Jos, Gadaka and Damaturu.
At least 39 people were killed.
The attacks were claimed by the Islamist group Boko Haram.
2010s explosions in Africa
2010s in Nigeria
Attacks on buildings and structures in Africa
Attacks on churches
Islamic terrorist incidents in Africa
Islamic terrorist incidents in the 2010s
Mass shootings in Africa
Mass shootings in the 2010s
Suicide bombings in Africa
Terrorist incidents in Africa in the 2010s
Albert Leo Schlageter (12 August 1894 — 26 May 1923) was a member of the German Freikorps.
His activities sabotaging French occupying troops after World War I led to his arrest and eventual execution by French forces.
His death created an image of martyrdom around him, which was cultivated by German nationalist groups, in particular the Nazi Party.
During the Third Reich, he was widely commemorated as a national hero.
Magnetic reluctance, or magnetic resistance, is a measurement used in the analysis of magnetic circuits.
It is like resistance in an electrical circuit, but rather than dissipating magnetic energy it stores magnetic energy.
As an electric field causes an electric current to follow the path of least resistance, a magnetic field causes magnetic flux to follow the path of least magnetic reluctance.
It is a scalar,
The term was coined in May 1888 by Oliver Heaviside.
The notion of “magnetic resistance” was first mentioned by James Joule and the term "magnetomotive force” (MMF) was first named by Bosanquet.
The idea for a magnetic flux law, similar to Ohm's law for closed electric circuits, is attributed to H. Rowland.
The total reluctance is equal to the ratio of the "magnetomotive force” (MMF) in a passive magnetic circuit to the magnetic flux in this circuit.
In an AC field, the reluctance is the ratio of the amplitude values for a sinusoidal MMF and magnetic flux. (
see phasors)
("R") is the reluctance in ampere-turns per weber (a unit that is equivalent to turns per henry).
("F") is the magnetomotive force (MMF) in ampere-turns
Φ ("Phi") is the magnetic flux in webers.
Magnetic flux always forms a closed loop, as described by Maxwell's equations, but the path of the loop depends on the reluctance of the surrounding materials.
Air and vacuum have high reluctance.
Easily magnetized materials such as soft iron have low reluctance.
The concentration of flux in low-reluctance materials forms strong temporary poles and causes mechanical forces that tend to move the materials towards regions of higher flux so it is always an attractive force (pull).
l is the length of the circuit in metres
is the permeability of free space, equal to  henry per metre
is the relative magnetic permeability of the material (dimensionless)
is the permeability of the material ()A is the cross-sectional area of the circuit in square metres
The inverse of reluctance is called permeance.
Air gaps can be created in the cores of certain transformers to reduce the effects of saturation.
This increases the reluctance of the magnetic circuit, and enables it to store more energy before core saturation.
This effect is also used in the flyback transformer.
Variation of reluctance is the principle behind the reluctance motor (or the variable reluctance generator) and the Alexanderson alternator.
In other words, the reluctance forces'' seek the most aligned magnetic circuit and a small air gap distance.
Multimedia loudspeakers are typically shielded magnetically, in order to reduce magnetic interference they make on televisions and other CRTs.
The speaker magnet is covered with a material such as soft iron to minimize the stray magnetic field.
Reluctance motors
Variable reluctance (magnetic) pickups
Dielectric complex reluctance
Magnetic capacitivity
Magnetic capacitance
Magnetic circuit
Magnetic complex reluctance
Reluctance motor
Triglav is a mountain in the Alps.
It is the highest mountain in Slovenia.
It is also the highest peak of the Julian Alps, in the southeastern part of the Alps.
Its name means "three-headed" in Slovene.
While this can describe the mountain, it is more likely the mountain was named for the Old Slovene god, Triglav.
The mountain is shown on the Flag of Slovenia.
Ampère's circuital law, discovered by André-Marie Ampère in 1826, relates the magnetic field around a closed loop to the electric current passing through the loop.
It is now one of Maxwell's equations, which form the basis of classical electromagnetism.
Original Ampère's circuital law
The law relates magnetic fields to electric currents that produce them.
A scientist can use Ampere's law to determine the magnetic field associated with a given current or current associated with a given magnetic field, if there is no time changing electric field present.
The law can be written in two forms, the "integral form" and the "differential form".
The forms are equivalent, and related by the Kelvin–Stokes theorem.
It can also be written in terms of either the B or H magnetic fields.
Again, the two forms are equivalent (see the "proof" section below).
Ampère's circuital law is now known to be a correct law of physics in a magnetostatic situation: The system is static except possibly for continuous steady currents within closed loops.
In all other cases the law is incorrect unless Maxwell's correction is included (see below).
Integral form
• is the vector dot product,  is the closed line integral around the closed curve C,  denotes an integral over the surface S enclosed by the curve C (the double integral sign is meant simply to denote that the integral is two-dimensional in nature);
B is the magnetic B-field in teslas, H is the magnetic H-field in ampere per metre;
If,enc is the net free current that penetrates through the surface S, Ienc is the total net current that penetrates through the surface S, including both free and bound current.
Jf is the free current density through the surface S enclosed by the curve C, J is the total current density through the surface S enclosed by the curve C, including both free and bound current;
dℓ is an infinitesimal element (a differential) of the curve C (i.e. a vector with magnitude equal to the length of the infinitesimal line element, and direction given by the tangent to the curve C), dS is the vector area of an infinitesimal element of surface S (that is, a vector with magnitude equal to the area of the infinitesimal surface element, and direction normal to surface S. The direction of the normal must correspond with the orientation of C by the right hand rule);
μ0 is the magnetic constant;
See below for further explanation of the curve C and surface S. There are a number of ambiguities in the above definitions that require clarification and a choice of convention.
First, three of these terms are associated with sign ambiguities: the line integral  could go around the loop in either direction (clockwise or counterclockwise); the vector area dS could point in either of the two directions normal to the surface; and Ienc is the net current passing through the surface S, meaning the current passing through in one direction, minus the current in the other direction—but either direction could be chosen as positive.
These ambiguities are resolved by the right-hand rule: With the palm of the right-hand toward the area of integration, and the index-finger pointing along the direction of line-integration, the outstretched thumb points in the direction that must be chosen for the vector area dS. Also the current passing in the same direction as dS must be counted as positive.
The right hand grip rule can also be used to determine the signs.
Second, there are infinitely many possible surfaces S that have the curve C as their border. (
Imagine a soap film on a wire loop, which can be deformed by moving the wire).
Which of those surfaces is to be chosen?
If the loop does not lie in a single plane, for example, there is no one obvious choice.
The answer is that it does not matter; it can be proven that any surface with boundary C can be chosen.
Differential form
By the Kelvin–Stokes theorem, this equation can also be written in a "differential form".
Again, this equation only applies in the case where the electric field is constant in time; see below for the more general form.
In SI units, the equation states:
is the curl operator.
Note on free current versus bound current
The electric current that arises in the simplest textbook situations would be classified as "free current."
For example, the law can apply to the current that passes through a wire or battery.
In contrast, "bound current" arises in the context of bulk materials that can be magnetized and/or polarized. (
All materials can to some extent.)
When a material is magnetized (for example, by placing it in an external magnetic field), the electrons remain bound to their respective atoms, but behave as if they were orbiting the nucleus in a particular direction, creating a microscopic current.
When the currents from all these atoms are put together, they create the same effect as a macroscopic current, circulating perpetually around the magnetized object.
This magnetization current JM is one contribution to "bound current".
When an electric field is applied, the positive and negative bound charges can separate over atomic distances in polarizable materials, and when the bound charges move, the polarization changes, creating another contribution to the "bound current", the polarization current JP.
The total current density J  due to free and bound charges is then:
with Jf the "free" or "conduction" current density.
There are often practical reasons for wanting to treat bound current differently from free current.
For example, the bound current usually originates over atomic dimensions, and one may wish to take advantage of a simpler theory intended for larger dimensions.
The result is that the more microscopic Ampère's law, expressed in terms of B and the microscopic current (which includes free, magnetization and polarization currents), is sometimes put into the equivalent form below in terms of H and the free current only.
For a detailed definition of free current and bound current, and the proof that the two formulations are equivalent, see the "proof" section below.
Shortcomings of the original formulation of Ampère's circuital law
Two issues regarding Ampère's law are important.
First, there is an issue regarding the continuity equation for electrical charge.
There is a theorem in vector calculus that states the divergence of a curl must always be zero.
which is non-zero for a time-varying charge density.
An example occurs in a capacitor circuit where time-varying charge densities exist on the plates.
Second, there is an issue regarding the propagation of electromagnetic waves.
For example, in free space, where
James Clerk Maxwell conceived of displacement current as a polarization current in the dielectric vortex sea, which he used to model the magnetic field with water (hydrodynamically) and with mechanical systems (mechanically).
He added this displacement current to Ampère's circuital law at equation (112) in his 1861 paper On Physical Lines of Force .
Displacement current
In a dielectric the above contribution to displacement current is also present, but a major contribution to the displacement current is related to the polarization of the individual molecules of the dielectric material.
Even though charges cannot flow freely in a dielectric, the charges in molecules can move a little under the influence of an electric field.
The positive and negative charges in molecules separate under the applied field, causing an increase in the state of polarization, expressed as the polarization density P.  A changing state of polarization is equivalent to a current.
where ε0 is the electric constant, εr the relative static permittivity, and P is the polarization density.
Substituting this form for D in the expression for displacement current, it has two components:
The first term on the right hand side is present everywhere, even in a vacuum.
It doesn't involve any actual movement of charge, but it nevertheless has an associated magnetic field, as if it were an actual current.
Some authors apply the name displacement current to only this contribution.
Maxwell's original explanation for displacement current focused upon the situation that occurs in dielectric media.
In the modern post-aether era, the concept has been extended to apply to situations with no material media present, for example, to the vacuum between the plates of a charging vacuum capacitor.
The displacement current is justified today because it serves several requirements of an electromagnetic theory:  correct prediction of magnetic fields in regions where no free current flows; prediction of wave propagation of electromagnetic fields; and conservation of electric charge in cases where charge density is time-varying.
For greater discussion see Displacement current.
Extending the original law: the Maxwell–Ampère equation
Treating free charges separately from bound charges, Ampère's equation including Maxwell's correction in terms of the H-field is (the H-field is used because it includes the magnetization currents, so JM does not appear explicitly, see H-field and also Note):
(integral form), where H is the magnetic H field (also called "auxiliary magnetic field", "magnetic field intensity", or just "magnetic field", D is the electric displacement field, and Jf is the enclosed conduction current or free current density.
In differential form,
in integral form.
In both forms J includes magnetization current density as well as conduction and polarization current densities.
That is, the current density on the right side of the Ampère–Maxwell equation is:
where current density JD is the displacement current, and J is the current density contribution actually due to movement of charges, both free and bound.
Because , the charge continuity issue with Ampère's original formulation is no longer a problem.
Because of the term in ε0∂E / ∂t, wave propagation in free space now is possible.
With the addition of the displacement current, Maxwell was able to hypothesize (correctly) that light was a form of electromagnetic wave.
See electromagnetic wave equation for a discussion of this important discovery.
Proof of equivalence
{| class="toccolours collapsible collapsed" width="80%" style="text-align:left"
Proof that the formulations of Ampère's law in terms of free current are equivalent to the formulations involving total current.
|In this proof, we will show that the equation
is equivalent to the equation
Note that we're only dealing with the differential forms, not the integral forms, but that is sufficient since the differential and integral forms are equivalent in each case, by the Kelvin–Stokes theorem.
We introduce the polarization density P, which has the following relation to E and D:
Next, we introduce the magnetization density M, which has the following relation to B and H:
and the following relation to the bound current:
is called the magnetization current density, and
is the polarization current density.
Taking the equation for B:
Consequently, referring to the definition of the bound current:
as was to be shown.
Ampère's law in cgs units
where c is the speed of light.
Biot–Savart law
Ampèrian magnetic dipole model
Electromagnetic wave equation
Bound charge
Simple Nature by Benjamin Crowell  Ampere's law from an online textbook
MISN-0-138 Ampere's Law  (PDF file) by Kirby Morgan for Project PHYSNET.
MISN-0-145 The Ampere–Maxwell Equation; Displacement Current  (PDF file) by J.S. Kovacs for Project PHYSNET.
The Ampère's Law Song (PDF file) by Walter Fox Smith; Main page, with recordings of the song.
A Dynamical Theory of the Electromagnetic Field  Maxwell's paper of 1864
The United States Air Force Academy (USAFA or Air Force) is an American military college.
It was created in 1954.
The Acadey is an accredited college for the undergraduate education of people who want to be officers for the United States Air Force.
The college is north of Colorado Springs in El Paso County.
The Academy's goal is "to educate, train, and inspire men and women to become officers of character, motivated to lead the United States Air Force in service to our nation."
It is the youngest of the five United States service academies.
The Academy had its first graduation in 1959.
Graduates of the Academy's four-year program get a Bachelor of Science degree.
Most become second lieutenants in the United States Air Force.
The Academy is one of the largest tourist attractions in Colorado.
More than a million people visit it each year.
Students are called "cadets".
The Air Force Academy is one of the most selective colleges in the United States.
U.S. News and World Report recently ranked it tied for 5th place in the category Undergraduate Engineering Programs.
Forbes magazine, in 2009, ranked the Academy the #2 public college in the United States and the #7 college overall in its "America's Best Colleges 2009" publication.
People wanting to study at the Academy are judged on their academic achievement, leadership, athletics and character.
They must pass a fitness test, pass a medical examination, and be nominated by the member of Congress where they live.
Recent classes have had about 1,400 cadets.
Normally, under 1,000 of the cadets will graduate.
The cost of going to the Academy, Housing and food are paid for by the U.S. government.
Cadets are paid monthly while at the Academy but they must be a part of the military for a number of years after they graduate.
The program at the Academy is based on the Air Force's core values.
These are  "Integrity First, Service Before Self, and Excellence in All We Do".
They are also  based on four "pillars of excellence": military training, academics, athletics and character development.
Cadets study military training and large curriculum in engineering, humanities, social sciences, basic sciences, military studies and physical education.
All cadets take part in athletics.
The academy has a character development and leadership curriculum.
The National Security Act of 1947 started the Air Force within the United States military.
Secretary of the Air Force W. Stuart Symington made an agreement where up to 25% of West Point and Annapolis graduates could ask to become officers in the new Air Force.
This was only meant to happen for a short time.
Disagreements between the parts of the military led to the creation of the Service Academy Board.
It was created by Secretary of Defense James Forrestal.
In January 1950, the Service Academy Board was controlled by Dwight D. Eisenhower.
He was the president of Columbia University at the time.
The board said that the two U.S. service academies were not able to train enough officers for the Air Force.
They decided that an air force academy was needed.
President Eisenhower signed a law on 1 April 1954 to begin building the Air Force Academy.
On 7 October 1975, President Gerald R. Ford signed a law that let women study at the United States service academies.
On 26 June 1976, 157 women went to the Air Force Academy. .
On 28 May 1980, 97 of them finished the program and graduated from the Academy.
They made up about 10% of the graduating class.
Women now make up about 20% of the classes.
The first Honor scandal happened in 1965.
A cadet who was leaving the Academy said that more than 100 cadets had been part of a cheating ring.
One hundred and nine cadets had to leave the Academy.
Cheating scandals were at the Academy again in 1967, 1972, 1984, 2004.
and 2007.
After each scandal, the Academy tried to learn why the cheating took place.
They also looked at complaints that the academic system put too much pressure on the cadets.
Changes were made to try to reduce the events from happening again.
In 2005, there were complaints that some Evangelical Christian cadets and staff were trying to convert others to their religion at the Academy.
Because of this and how the Air Force deals other religious issues, Academy graduate Michael L. Weinstein filed a lawsuit against the Air Force.
Bruegmann, Robert.
Modernism at Mid-Century: The Architecture of the United States Air Force Academy.
University of Chicago Press: 1995. .
Celebrating the U.S. Air Force Academy's Golden Anniversary, (Colorado Springs) Gazette, Special Edition, Spring 2004.
Contrails (various years)
Fagan, George V. Air Force Academy: An Illustrated History.
Johnson Books: 1988. .
Fifty Years of Excellence: Building Leaders of Character for the Nation, 2004.
Lui, Elizabeth Gill.
Spirit and Flight: A Photographic Salute to the United States Air Force Academy.
1996. .
Nauman, Robert Allen. (
On the Wings of Modernism: the United States Air Force Academy.
Urbana: University of Illinois Press. ;
OCLC 52542599
Schemo, Diana Jean.
Skies to Conquer: A Year Inside the Air Force Academy.
John Wiley & Sons, Inc.: 2010.
Official military website
USAFA Association of Graduates (Alumni organization)