omniomni/omni-engineering huggingface dataset:
Counter-electromotive force. Counter-electromotive force (counter EMF, CEMF, back EMF), is the electromotive force (EMF) manifesting as a voltage that opposes the change in current which induced it. CEMF is the EMF caused by electromagnetic induction.

Details
For example, the voltage appearing across an inductor or coil is due to a change in current which causes a change in the magnetic field within the coil, and therefore the self-induced voltage. The polarity of the voltage at every moment opposes that of the change in applied voltage, to keep the current constant.

The term back electromotive force is also commonly used to refer to the voltage that occurs in electric motors where there is relative motion between the armature and the magnetic field produced by the motor's field coils or permanent magnet field, thus also acting as a generator while running as a motor. This effect is not due to the motor's inductance, which generates a voltage in opposition to a changing current via Faraday's law, but a separate phenomenon. That is, the back-EMF is also due to inductance and Faraday's law, but occurs even when the motor current is not changing, and arises from the geometric considerations of an armature spinning in a magnetic field. 

This voltage is in series with and opposes the original applied voltage and is called "back-electromotive force" (by Lenz's law). With a lower overall voltage across the motor's internal resistance as the motor turns faster, the current flowing into the motor decreases. One practical application of this phenomenon is to indirectly measure motor speed and position, as the back-EMF is proportional to the rotational speed of the armature.

In motor control and robotics, back-EMF often refers most specifically to actually using the voltage generated by a spinning motor to infer the speed of the motor's rotation, for use in better controlling the motor in specific ways.

To observe the effect of back-EMF of a motor, one can perform this simple exercise: with an incandescent light on, cause a large motor such as a drill press, saw, air conditioner compressor, or vacuum cleaner to start.  The light may dim briefly as the motor starts.  When the armature is not turning (called locked rotor) there is no back-EMF and the motor's current draw is quite high.  If the motor's starting current is high enough, it will pull the line voltage down enough to cause noticeable dimming of the light.

References

External links
Counter-electromotive-force in access control applications

Electromagnetism
Rickardite. Rickardite is a telluride mineral, a copper telluride (Cu7Te5) or Cu3-x (x = 0 to 0.36)Te2. It was first described for an occurrence in the Good Hope Mine, Vulcan district, Gunnison County, Colorado, US, and named for mining engineer Thomas Arthur Rickard (1864–1953).  It is a low temperature hydrothermal mineral that occurs associated with vulcanite, native tellurium, cameronite, petzite, sylvanite, berthierite, pyrite, arsenopyrite and bornite.

See also
 List of minerals

References

D. M. Chizhikov and V. P. Shchastlivyi, 1966, Tellurium and Tellurides, Nauka Publishing, Moscow 

Copper(I,II) minerals
Telluride minerals
Orthorhombic minerals
Minerals in space group 59
Minerals described in 1903
Kelvin–Voigt material. A Kelvin–Voigt material, also called a Voigt material, is the most simple model viscoelastic material showing typical rubbery properties. It is purely elastic on long timescales (slow deformation), but shows additional resistance to fast deformation. The model was developed independently by the British physicist Lord Kelvin in 1865 and by the German physicist Woldemar Voigt in 1890.

Definition 

The Kelvin–Voigt model, also called the Voigt model, is represented by a purely viscous damper and purely elastic spring connected in parallel as shown in the picture.

If, instead, we connect these two elements in series we get a model of a Maxwell material.

Since the two components of the model are arranged in parallel, the strains in each component are identical:

where the subscript D indicates the stress-strain in the damper and the subscript S indicates the stress-strain in the spring. Similarly, the total stress will be the sum of the stress in each component:

From these equations we get that in a Kelvin–Voigt material, stress σ, strain ε and their rates of change with respect to time t are governed by equations of the form:

or, in dot notation:

where E is a modulus of elasticity and  is the viscosity. The equation can be applied either to the shear stress or normal stress of a material.

Effect of a sudden stress 

If we suddenly apply some constant stress  to Kelvin–Voigt material, then the deformations would approach the deformation for the pure elastic material  with the difference decaying exponentially:

where t is time and  is the retardation time.

If we would free the material at time , then the elastic element would retard the material back until the deformation becomes zero. The retardation obeys the following equation:

The picture shows the dependence of the dimensionless deformation  
on dimensionless time . In the picture the stress on the material is loaded at time , and released at the later dimensionless time .

Since all the deformation is reversible (though not suddenly) the Kelvin–Voigt material is a solid.

The Voigt model predicts creep more realistically than the Maxwell model, because in the infinite time limit the strain approaches a constant:

while a Maxwell model predicts a linear relationship between strain and time, which is most often not the case. Although the Kelvin–Voigt model is effective for predicting creep, it is not good at describing the relaxation behavior after the stress load is removed.

Dynamic modulus 

The complex dynamic modulus of the Kelvin–Voigt material is given by:

Thus, the real and imaginary components of the dynamic modulus are referred to as storage modulus  and  respectively:

Note that  is constant, while  is directly proportional to frequency (where time-scale  is the constant of proportionality). Often, this constant  multiplied with angular frequency  is called the loss modulus .

References

See also 
Burgers material
Generalized Maxwell model
Maxwell material
Standard linear solid model

Non-Newtonian fluids
Materials science
William Thomson, 1st Baron Kelvin
Flying column. A flying column is a small, independent, military land unit capable of rapid mobility and usually composed of all arms. It is often an ad hoc unit, formed during the course of operations.

The term is usually, though not necessarily, applied to forces less than the strength of a brigade. As mobility is its primary purpose, a flying column is accompanied by the minimum of equipment. It generally uses suitable fast transport; historically, horses were used, with trucks and helicopters replacing them in modern times.

History

Flying columns are mentioned by Sun Tzu in his Art of War in such a fashion that indicates it was not a new concept at the time of his writing. This dates to at least the middle 6th century BC, and possibly the late 8th century BC.

The Roman army made good use of the flying columns in the early imperial era. One such commander, the proconsul Germanicus Caesar used flying columns to great effect in the early stages of the campaign against one of Rome's greatest enemies, Arminius. Scouts, raiders, and screening forces were used against the Germanic tribes responsible for destroying three Roman legions (the 17th, 18th, and 19th) in the Battle of the Teutoburg Forest.

Boer kommandos in 17th–20th-century South Africa may be regarded as a form of flying column (unlike commandos in the more recent sense). The mobile columns employed against Boer forces, by British Empire forces in the South African War of 1899–1902, were usually of the strength of two battalions of infantry, a battery of artillery, and a squadron of cavalry, almost exactly half that of a Mixed brigade.

Flying columns have also been used in guerrilla warfare, notably the mobile armed units of the Irish Republican Army during the Irish War of Independence 1919–1921.During this period, the most successful Irish flying columns in terms of casualties inflicted on the police and military were the west Connemara, the south Mayo and the west Mayo column under the command of Michael Kilroy.

In 1919, Polish officer Stanisław Maczek created a flying company made of a battle-hardened infantry, using horses for mobility, and a lot of machineguns for fire power. They were part of the 4th Infantry Division (Poland).

In the 1920s, Defence Scheme No. 1, the proposed Canadian response to an invasion by the United States, Lt. Col. James "Buster" Brown suggested "immediate dispatch of flying columns on the declaration of war" in order to counter-invade across the border and enact a scorched earth policy, forcing the US to divert military resources towards the defense of its northern cities.

During and shortly after the Anglo-Iraqi War of 1941, British forces employed flying columns code-named Kingcol, Mercol and Gocol. Kingcol advanced into Iraq from Jordan and Palestine.

See also

Notes

References

Attribution:

Further reading

Land warfare
Irish War of Independence
Guerrilla wars
Second Boer War
Science for Peace. Science for Peace is organization of scientists, engineers, social scientists  and scholars working together to promote peace worldwide. It was co-founded by mathematical psychologist Anatol Rapoport, and physicist Eric Fawcett, both former professors at the University of Toronto.  It is based in Toronto, Ontario. Some of the activities undertaken include lectures, workshops, administering the Franz Blumenfeld Peace Education Fund, and hosting the biannual Eric Fawcett Memorial Forum.

See also
Peace and conflict studies
Peace Magazine

External links
 Science for Peace website
 History of Science for Peace
Science for Peace archival papers held at the University of Toronto Archives and Records Management Services
Archival papers of University of Toronto professors involved in Science for Peace are held at the University of Toronto Archives and Records Management Services, including Anatol Rapoport, L. Terrell Gardner, and Derek Paul.

Scientific organizations based in Canada
Airware. Airware (incorporated as Unmanned Innovation, Inc.) was an American venture-funded startup that provided commercial unmanned aerial vehicles for enterprises. The company ceased operations on September 14, 2018.

Airware was founded in 2011 in Newport Beach, California, by Jonathan Downey. The company relocated to San Francisco in January 2014.

The company produced enterprise drones which combine hardware, on-aircraft and mobile software, and cloud services. Downey has stated the company is focused on building systems for drones for commercial uses, including anti-poaching efforts, infrastructure inspections, and precision agriculture.

History
Airware was founded by Downey in 2011 out of a frustration with the "inflexible and costly" autopilot systems for unmanned aircraft.

Airware was incubated at both Lemnos Labs and Y Combinator. In March 2016, the company announced a $30 million Series C round of financing led by Next World Capital with Andreessen Horowitz, Kleiner Perkins Caufield & Byers and Cisco Systems executive chairman John T. Chambers. Andreessen Horowitz partner Martin Casado, Kleiner Perkins Caufield & Byers partner Mike Abbott, and John T. Chambers are members of the company's board. In 2015, Airware launched a new venture fund for commercial drones to support "scaling the use of drones across a variety of commercial applications." Airware purchased Redbird, a drone analytics software company, in 2016. On September 14, 2018, Airware announced it was ceasing operations effective immediately.

Products and services
Airware offered enterprise drone services combining hardware, on-aircraft and mobile software, and cloud services for industries like mining, insurance, and construction. Airware offered navigation software for drones, table software to guide and monitors drones in flight, and cloud services to store and manage the information gathered by drones. Where most software is designed for specific models of drones, Airware was developing a platform that enables compatibility across aircraft. The company previously collaborated with commercial drone manufacturers to integrate its autopilot hardware and software, then consulted directly with enterprise clients to identify solutions and to ensure regulatory compliance.

References

Further reading
 
 
 
 "Why Is America Losing the Commercial Drone Wars?". June/July/August 2015. Washington Monthly.
 
 
 "Caterpillar invests in Airware bringing drone tech to mining and construction enterprises". February 2, 2017. TechCrunch.

External links
 Official website

Aerospace companies of the United States
Technology companies based in the San Francisco Bay Area
2011 establishments in California
Electronics companies established in 2011
Unmanned aerial vehicle manufacturers
American companies established in 2011
2018 disestablishments in California
American companies disestablished in 2018
Electronics companies disestablished in 2018
Spike driver. A spike driver (also known as a spiker) is a piece of rail transport maintenance of way equipment. Its purpose is to drive rail spikes into the ties on a rail track to hold the rail in place. Many different sizes of spikers are manufactured and in use around the world.

History 
Historically, spikers was the slang-name for the rail workers who drove in the spikes after the gandy dancers laid the track on the tie. Spikes are used to hold the rail in gauge and keep it connected to the ties. Before the development of automated spikers, this task was done entirely by hand using pickaxes to drive the spikes into the ties. This process was slow and not easy to learn (at the driving of the golden spike that marked the completion of the first transcontinental railroad in 1869, several executives of the companies building the railroad tried and failed to drive in the final spike, showing how difficult a task it was).

To make the process of driving spikes faster and easier, automated self-propelled machines that travel on the rails were developed in the 1900s. These machines can insert spikes far faster than by hand. Brian Solomon writes that, "Spike drivers take less time to accomplish their tasks than it takes to read about it."

Method of operation 
When in operation, a spiker works by using rams to drive spikes into the ties, using either compressed air or hydraulics to power the rams. The spiker uses chutes to automatically feed spikes to the rams, which are present on both sides of the machine to allow spikes to be inserted on both rails at the same time. A worker will periodically add fresh spikes to the chutes as needed to keep the machine supplied. On larger spikers, spikes are supplied from a feed bin, eliminating the need to add spikes by hand. Railroad workers operate the machine by directing the rams and moving the spiker, which is usually self-propelled and powered by a diesel engine. The process is as follows:

 The spiker moves to a tie that needs spikes inserted. The spiker uses claws to grab the tie and hold it in place.
 Workers use a joystick to direct the rams to the locations where spikes are to be inserted, and then activate the rams to drive the spikes into the rail.
 The spiker releases the tie, and moves on to the next tie to repeat the process.

A typical spiker has controls on both sides of the machine, allowing it to operate when only one of the two rails needs spikes inserted.

Manufacturers of spikers 

 Harsco
 Nordco

References 

Maintenance of way equipment
Rail fastening systems
Acetone (data page). This page provides supplementary chemical data on acetone.

Material Safety Data Sheet  

The handling of this chemical may incur notable safety precautions. It is highly recommended that you seek the Material Safety Datasheet (MSDS) for this chemical from a reliable source and follow its directions. 
Mallinckrodt Baker
Science Stuff

Structure and properties

Thermodynamic properties

Vapor pressure of liquid

Table data obtained from CRC Handbook of Chemistry and Physics 44th ed.

Distillation data
See also:
 Carbon tetrachloride (data page)
 Butanone (data page)

Spectral data

References 

Chemical data pages
Chemical data pages cleanup
Philip Bono. Philip Bono (13 January 1921 – 23 May 1993) was a Douglas Aircraft Company engineer. He was a pioneer of reusable vertical landing single-stage to orbit launch vehicles. As a visionary designer, he is credited with inventing the first version of a recoverable single-stage spacecraft booster, and his contributions influenced spacecraft design.

Bono pursued single-stage space launch as simpler and cheaper. He realized to do this he would need to use high specific impulse liquid hydrogen/liquid oxygen rocket engines. Afterwards he proposed to make these vehicles reusable. From his ROOST design onwards Bono advocated space launch vehicles without wings, usually using rocket-assisted vertical takeoff and landing (VTVL). According to his estimates, wings consisted mostly of dead weight that decreased launch payload mass. He patented a reusable plug nozzle rocket engine which had dual use as a heat shield for atmospheric reentry. His early 1960s concepts influenced later designs like the 1990s Delta Clipper, also from Douglas.

Birth, education and career
Philip Bono was born in Brooklyn, New York, on 13 January 1921.  He graduated from the University of Southern California in 1947 with a degree in mechanical engineering.  After graduation, Bono worked as a research and systems analyst for North American Aviation.  Bono began working for Douglas Aircraft company in 1960. After the merger of McDonnell Aircraft and the Douglas Aircraft Company, he worked for McDonnell Douglas Astronautics from 1966 until 1988.

Philip Bono died on 23 May 1993 at the age of 72. He was a resident of Costa Mesa, California, at the time of his death.

Less than three months after Bono's death, the first launch vehicle based on his designs, the McDonnell Douglas DC-X (Delta Clipper) began a largely successful series of test flights. The DC-X was a vertical-takeoff and vertical landing vehicle. The series of test flights began on 18 August 1993 and continued until the upgraded version of the launch vehicle (renamed the DC-XA) tipped over on landing on July 31, 1996.

Among Bono's visionary designs was a 1960 Boeing design for a crewed Mars spacecraft capable of carrying eight.

Designs

 One Stage Orbital Space Truck (OOST) 
 Recoverable One Stage Orbital Space Truck (ROOST) 
 Reusable Orbital Module, Booster, and Utility Shuttle (ROMBUS) 
 Ithacus
 Pegasus 
 Hyperion
 SASSTO 
 Mars Glider

Hyperion was HTVL, the others VTVL.

Bibliography

Patents

 US Patent D201773, Recoverable Single Stage Spacecraft Booster, July 27, 1965
 US Patent 3295790, Recoverable Single Stage Spacecraft Booster, January 3, 1967

References

External links
 Philip Bono Collection, Flickr, San Diego Air and Space Museum Archives

1921 births
1993 deaths
American aerospace engineers
Single-stage-to-orbit
20th-century American engineers
USS Converse (DD-291). USS Converse (DD-291) was a  built for the United States Navy during World War I.

Description
The Clemson class was a repeat of the preceding  although more fuel capacity was added. The ships displaced  at standard load and  at deep load. They had an overall length of , a beam of  and a draught of . They had a crew of 6 officers and 108 enlisted men.

Performance differed radically between the ships of the class, often due to poor workmanship. The Clemson class was powered by two steam turbines, each driving one propeller shaft, using steam provided by four water-tube boilers. The turbines were designed to produce a total of  intended to reach a speed of . The ships carried a maximum of  of fuel oil which was intended gave them a range of  at .

The ships were armed with four 4-inch (102 mm) guns in single mounts and were fitted with two  1-pounder guns for anti-aircraft defense. In many ships a shortage of 1-pounders caused them to be replaced by 3-inch (76 mm) guns. Their primary weapon, though, was their torpedo battery of a dozen 21 inch (533 mm) torpedo tubes in four triple mounts. They also carried a pair of depth charge rails. A "Y-gun" depth charge thrower was added to many ships.

Construction and career
Converse named for George A. Converse, was launched 28 November 1919 by Bethlehem Shipbuilding Corporation, Squantum, Massachusetts; sponsored by Miss E. C. Colt; commissioned 28 April 1920 and reported to the Atlantic Fleet. Converse was placed in reserve status 11 June 1920 operating in New England waters with 50 percent of her complement on training cruises for members of the Naval Reserve.

After testing the Arma gyro compass, Converse operated from 15 November 1921 with Scouting Fleet. Returned to full commission 1 July 1922, she cruised on the east coast and in Caribbean waters. Converse sailed from Newport, Rhode Island 18 June 1924 to join U.S. Naval Forces in European Waters, visiting Antwerp, Amsterdam, Cherbourg and Southampton before returning to New York 16 July 1925.

In 1926 and 1927 Converse again served as training ship for the Naval Reserve making two cruises each summer to Newport and the Caribbean. From 23 February 1927 she tested the Flettner rudder during her cruising. In 1928 Converse was designated as Experimental Ship, Scouting Fleet. She made test runs for the Bureau of Engineering in the Potomac River and Chesapeake Bay, then fired experimental torpedoes at Newport and Charleston, South Carolina. She rejoined her squadron at Norfolk, Virginia 4 January 1929 for regular operations until decommissioned at Philadelphia 1 May 1930. She was sold 17 January 1931 to be scrapped in accordance with the London Naval Treaty which called for the limitation and reduction of naval armaments.

Notes

References

External links
http://www.navsource.org/archives/05/291.htm

Clemson-class destroyers
Ships built in Quincy, Massachusetts
1919 ships
USS Charles Ausburn (DD-294). USS Charles Ausburn (DD-294) was a  built for the United States Navy during World War I.

Construction and career
Charles Ausburn, named for Charles Lawrence Ausburne, was launched 18 December 1919 by Bethlehem Shipbuilding Corporation, Squantum, Massachusetts; sponsored by Mrs. D. K. Ausburn; and commissioned 23 March 1920. Assigned to the Atlantic Fleet, Charles Ausburn operated from Charleston, South Carolina, Norfolk, Virginia and Newport, Rhode Island along the Atlantic coast and in the Caribbean through 1924, serving with a reduced complement from October 1920 to May 1922. During those years, as she participated in fleet exercises and training maneuvers, she aided in the development and application of new ideas in naval warfare. In the fall of 1923, Charles Ausburn was equipped to carry a seaplane, with which she performed experiments in the rapidly developing field of naval aviation.

In late summer of 1924, Charles Ausburn cruised to northern latitudes to provide plane guard service in the round-the-world flight of Army aircraft, maintaining stations off Greenland and Newfoundland. On 18 June 1925, she sailed from Boston for a year of duty off Europe and in the Mediterranean, visiting at a large number of ports before her return to New York 11 July 1926. She continued her operations with the fleet, often providing facilities for the training of reservists, until 1 May 1930, when she was decommissioned at Philadelphia. There she was sold 17 January 1931.

Notes

References

External links
http://www.navsource.org/archives/05/294.htm

Clemson-class destroyers
Ships built in Quincy, Massachusetts
1919 ships