omniomni/omni-engineering huggingface dataset:
Leuco dye. A leuco dye (from the Greek λευκό leuko: white ) is a dye which can switch between two chemical forms, one of which is colorless. Reversible transformations can be caused by heat, light or pH, resulting in examples of thermochromism, photochromism and halochromism, respectively. Irreversible transformations typically involve reduction or oxidation. The colorless form is sometimes referred to as the leuco form.

Leuco dyes form the basis of thermal printer papers and certain pH indicators.

Examples
The most common example is in applying sulfur dyes and vat dyes, with indigo being a classic case. This is characteristically purple but is also completely insoluble in water, meaning that it cannot be applied to clothes directly. It is instead reduced to indigo white (sometimes Leucoindigo), which is water-soluble but colorless. When a submerged fabric is removed from a dyebath of white indigo the dye quickly combines with oxygen in the air and reverts to the insoluble, intensely colored indigo. The reduction step is typically achieved with sodium dithionite, hydroxyacetone and hydrogen, or by electrochemical methods.

The spiro form of an oxazine is a colorless leuco dye; the conjugated system of the oxazine and another aromatic part of the molecule is separated by an sp3-hybridized "spiro" carbon. After protonating a part of the molecule, irradiation with UV light (see Photochromism), or introducing other kind of such change, the bond between the spiro carbon and the oxazine interrupts, the ring opens, the spiro carbon achieves sp2 hybridization and becomes planar, the aromatic group rotates, aligns its π-orbitals with the rest of the molecule, and a conjugated system forms, with ability to absorb photons of visible light, and therefore appear colorful.

Another example of a leuco dye is the crystal violet lactone, which in its lactone form is colorless or slightly yellowish, but in low pH, when it is protonated, it becomes intensely violet. Other examples are phenolphthalein and thymolphthalein, colorless in acidic to neutral pH, but becoming pink and blue in alkaline environment. Other example are many redox indicators, which undergo reversible color change between colored and colorless form at a specific electrode potential.

See also
Flexplay, trademark for a DVD-compatible optical video disk format that uses leuco dye to intentionally "wear away" after a limited number of playings.
Hypercolor, clothing that changes color with heat

References

Dyes
Iron(II) fluoride. Iron(II) fluoride or ferrous fluoride is an inorganic compound with the molecular formula FeF2.  It forms a tetrahydrate FeF2·4H2O that is often referred to by the same names.  The anhydrous and hydrated forms are white crystalline solids.

Structure and bonding
Anhydrous FeF2 adopts the TiO2 rutile structure. As such, the iron cations are octahedral and fluoride anions are trigonal planar.

The tetrahydrate can exist in two structures, or polymorphs. One form is rhombohedral and the other is hexagonal, the former having a disorder.

Like most fluoride compounds, the anhydrous and hydrated forms of iron(II) fluoride feature high spin metal center. Low temperature neutron diffraction studies show that the FeF2 is antiferromagnetic. Heat capacity measurements reveal an event at 78.3 K corresponding to ordering of antiferromagnetic state.

Selected physical properties 
FeF2 sublimes between 958 and 1178 K. Using Torsion and Knudsen methods, the heat of sublimation was experimentally determined and averaged to be 271 ± 2 kJ mole−1.

The following reaction is proposed in order to calculate the atomization energy for Fe+:
FeF2 + e  →   Fe+ +  F2 (or 2F)  +  2e

Synthesis and reactions
The anhydrous salt can be prepared by reaction of ferrous chloride with anhydrous hydrogen fluoride.  It is slightly soluble in water (with solubility product Ksp = 2.36×10−6 at 25 °C) as well as dilute hydrofluoric acid, giving a pale green solution. It is insoluble in organic solvents.

The tetrahydrate can be prepared by dissolving iron in warm hydrated hydrofluoric acid and precipitating the result by addition of ethanol.  It oxidizes in moist air to give, inter alia, a hydrate of iron(III) fluoride, (FeF3)2·9H2O.

Uses
FeF2 is used to catalyze some organic reactions.

Battery research
FeF2 has been investigated as a cathode material for both lithium-ion and fluoride-ion batteries. Unlike conventional metal oxides, which rely on an intercalation-based lithium storage mechanism, FeFX (x = 2, 3) operates via a complex conversion mechanism, resulting in higher energy density. Fluoride cathodes are stable up to 1000°C. Stability not only enhances safety and lowers the risk of thermal runaway.

FeFX exhibits distinctive phase evolution, intermediate phases, and morphological transformations during lithiation and delithiation. A stable lattice of fluoride anions is maintained throughout charge and discharge cycles, consistent with high cycling reversibility.

References

External links
National Pollutant Inventory - Fluoride and compounds fact sheet

Fluorides
Metal halides
Iron(II) compounds
Screenless hammer mill. The screenless hammer mill, like regular hammer mills, is used to pound grain. However, rather than a screen, it uses air flow to separate small particles from larger ones. 

Conventional hammer mills in poor and remote areas, such as many parts of Africa, suffer from the problem that screens break easily, and cannot be easily bought, made or repaired. Thus regular hammer mills break down and fall into disuse. The screenless hammer mill uses air flow to separate small particles from larger ones, rather than a screen, and is thus more reliable. 

The screenless hammer mill is claimed to be 25% cheaper  and much more energy efficient than regular hammer mills, as well as more reliable. 

It was designed by Amy Smith of MIT.

See also 
 Appropriate technology

External links
Mill Field Testing in Senegal
Necessity Is the Mother of Invention
A MacGyver for the Third World

References 

Appropriate technology
American inventions
Grinding mills
Cobalt(II) fluoride. Cobalt(II) fluoride is a chemical compound with the formula (CoF2). It is a pink crystalline solid compound which is antiferromagnetic at low temperatures (TN=37.7 K) The formula is given for both the red tetragonal crystal, (CoF2), and the tetrahydrate red orthogonal crystal, (CoF2·4H2O). CoF2 is used in oxygen-sensitive fields, namely metal production. In low concentrations, it has public health uses.
CoF2 is sparingly soluble in water. The compound can be dissolved in warm mineral acid, and will decompose in boiling water. Yet the hydrate is water-soluble, especially the di-hydrate CoF2·2H2O and tri-hydrate CoF2·3H2O forms of the compound. The hydrate will also decompose with heat.

Like some other metal difluorides, CoF2 crystallizes in the rutile structure, which features octahedral Co centers and planar fluorides.

Preparation
Cobalt(II) fluoride can be prepared from anhydrous cobalt(II) chloride or cobalt(II) oxide in a stream of hydrogen fluoride:

CoCl2  + 2HF  →  CoF2  + 2HCl
CoO + 2HF → CoF2  + H2O

It is produced in the reaction of cobalt (III) fluoride with water.

The tetrahydrate cobalt(II) fluoride is formed by dissolving cobalt(II) in hydrofluoric acid. The anhydrous fluoride can be extracted from this by dehydration. Other synthesis can occur at higher temperatures. It has been shown that at 500 °C fluorine will combine with cobalt producing a mixture of CoF2   and CoF3.

Uses
Cobalt(II) fluoride can be used as a catalyst to alloy metals. It is also used for optical deposition, of which it tremendously improves optical quality. Cobalt(II) fluoride is available in most volumes in an ultra high purity composition. High purity compositions improve optical qualities and its usefulness as a standard.

Analysis
To analyze this compound, Cobalt (II) fluoride can be dissolved in nitric acid. The solution is then diluted with water until appropriate concentration for AA or ICP spectrophotometry for the cobalt. A small amount of salt can be dissolved in cold water and analyzed for fluoride ion by a fluoride ion-selective electrode or ion chromatography.

Chemical properties
CoF2 is a weak Lewis acid. Cobalt(II) complexes are usually octahedral or tetrahedral. As a 19-electron species it is a good reducing agent, fairly oxidizable into an 18-electron compound. Cobalt(II) fluoride can be reduced by hydrogen at a 300 °C.

References

External links

 National Pollutant Inventory - Cobalt fact sheet
National Pollutant Inventory - Fluoride and compounds fact sheet

Fluorides
Metal halides
Cobalt(II) compounds
C. Illies & Co.. C. Illies & Co. (Illies GmbH & Co. KG) is an engineering and trading house for the export of investment goods, based in Hamburg, Germany, established in 1859.

The company is privately owned with more than 400 employees in Hamburg/Germany, Japan, China, Korea, Taiwan, United Arab Emirates, Vietnam, India, Indonesia, Russia, Kazakhstan, Uzbekistan and Italy.

Further reading
 Johannes Bähr, Jörg Lesczenski, Katja Schmidtpott: Handel ist Wandel – 150 Jahre C. Illies & Co, München 2013, . (reviews: Japan Markt, H-Net) (German)
 Käthe Molsen: C. Illies & Co., 1859-1959: ein Beitrag zur Geschichte des deutsch-japanischen Handels. Verlag Hanseatischer Merkur, 1959 (German)

External links
Official website

Illies
Companies based in Hamburg
Government Polytechnic Nashik. The Government Polytechnic, Nashik is a public polytechnic college in Nashik, Maharashtra, India. It is an autonomous institution run by the Government of Maharashtra and offers diploma, post diploma and certificate programs in engineering & technology. The college is accredited by the All India Council for Technical Education (AICTE) and affiliated with the Maharashtra State Board of Technical Education (MSBTE). It is also a member of Indian Society for Technical Education (ISTE).

Programs Offered
Full Time Diploma Program (3-year):

Mechanical Engineering
Electrical Engineering
Civil Engineering
Plastic Engineering
Computer Engineering
Automobile Engineering
Electronics & Telecommunication Engineering
Information Technology
Dress Designing & Garment Manufacturing
Interior designing & decoration (2-year)

Part Time Certificate Courses (1-year):

PGD in IT
Short term Course in IT
Certificate Course in IT
System Analysis & Applications

External links
Official website

Universities and colleges in Maharashtra
Education in Nashik
Charles Wilson Dyson. Rear Admiral Charles Wilson Dyson (January 2, 1861 - October 25, 1930) was an American naval officer and engineer.

Biography
Dyson graduated from the United States Naval Academy in June 1883.  He was well known for his achievements in the field of engineering.  His designs covered machinery for naval vessels of all types, including Saratoga (CV-3) and Lexington (CV-2). He wrote extensively for technical magazines and revised Durand's treatise on Marine Engineering. For his meritorious service while in charge of the Division of Design of the Bureau of Steam Engineering during World War I, he was awarded the Navy Cross and the Distinguished Service Medal.

Dyson was retired December 2, 1925, and died in Washington, D.C., October 25, 1930.

Namesake
In 1942, the destroyer USS Dyson (DD-572) was named in his honor.

References

External links
 

1861 births
1930 deaths
Recipients of the Navy Cross (United States)
Recipients of the Navy Distinguished Service Medal
United States Naval Academy alumni
United States Navy admirals
United States Navy personnel of World War I
People from Cambridge, Maryland
Échirolles. Échirolles (; ) is a commune in the Isère department, southeastern France. Part of the Grenoble urban unit (agglomeration), it is the second-largest suburb of the city of Grenoble, which is immediately to its north.

History
A former industrial village had the majority of its inhabitants work in the viscose factories, a fabric that was invented in Échirolles in 1884 by the French scientist and industrial Hilaire de Chardonnet, before becoming universally famous. The process for manufacturing viscose was then patented by three British scientists, Charles Frederick Cross, Edward John Bevan and Clayton Beadle, in 1891.

Population

Personalities
 Thernand Bakouboula footballer
 Seynabou Benga handball player
 Stephane Biakolo footballer
 Talel Chedly (b. 1978), footballer
 Vincent Clerc (b. 1981), rugby footballer of Stade Toulousain and of the France national team.
 Mélissa Theuriau (b. 1978), journalist and television producer.
 Calogero (b. 1971), pop/rock singer, composer and songwriter.
 Laure Péquegnot (b. 1975), skier.
 Gérald Hustache-Mathieu (b. 1968), film director and scenarist.
 David di Tommaso (1979–2005), football player.
 Sami Bouajila (b. 1966), actor.
 Guilbaut Colas (b. 18 June 1983), freestyle skier.
 David Lazzaroni (b. 4 February 1985), ski jumper.
 Sandrine Aubert (b. 6 October 1982), alpine skier.
 Jonathan Tinhan (b. 1 June 1989), footballer.
 Kévin Aymoz (b. 1 August 1997), figure skater
 Matteo Tomasi (b. 16 October 1998), footballer.

International relations
Échirolles is twinned with:
  Grugliasco, Italy
  Honhoue, Benin
  Kimberley, England

See also
Musée Géo-Charles
Cellatex

References

External links

 Official website
 Official website of the Paroisse Charles de Foucauld in Échirolles
 Museum of viscose in Échirolles

Communes of Isère
Arpitania
Constant speed drive. A constant speed drive (CSD) also known as a constant speed generator, is a type of transmission that takes an input shaft rotating at a wide range of speeds, delivering this power to an output shaft that rotates at a constant speed, despite the varying input. They are used to drive mechanisms, typically electrical generators, that require a constant input speed.

The term is most commonly applied to hydraulic transmissions found in the accessory drives of gas turbine engines, such as aircraft jet engines. On modern aircraft, the CSD is often combined with a generator into a single unit known as an integrated drive generator (IDG).

Mechanism
CSDs are mainly used on airliner and military aircraft jet engines to drive the alternating current (AC) electrical generator. In order to produce the proper voltage at a constant AC frequency, usually three-phase 115 VAC at 400 Hz, an alternator needs to spin at a constant specific speed (typically 6,000 RPM for air-cooled generators). Since the jet engine gearbox speed varies from idle to full power, this creates the need for a constant speed drive (CSD).  The CSD takes the variable speed output of the accessory drive gearbox and hydro-mechanically produces a constant output RPM.

Different systems have been used to control the alternator speed. Modern designs are mostly hydrokinetic, but early designs often took advantage of the bleed air available from the engines. Some of these were mostly mechanically powered, with an air turbine to provide a vernier speed adjustment. Others were purely turbine-driven.

Integrated drive generator
On aircraft such as the Airbus A310, Airbus A320 family, Airbus A320neo, Airbus A330, Airbus A330neo, Airbus A340, Boeing 737 Next Generation, 747, 757, 767 and 777, an integrated drive generator (IDG) is used. This unit is simply a CSD and an oil cooled generator inside the same case. Troubleshooting is simplified as this unit is the line-replaceable electrical generation unit on the engine.

Manufacturers
Collins Aerospace (formerly UTC Aerospace Systems (formerly Hamilton Sundstrand)) is an American manufacturer of CSD and IDG units.

Alternatives
A variable-speed constant-frequency (VSCF) generator can be used to provide AC power using an electronic tap converter.

Variable Frequency Starter Generator (VFSG) used primarily on the Boeing 787 are both used for electric start and electric generation.

An electronic Power inverter can take a variable frequency and voltage AC or variable voltage DC input, e.g. from a permanent magnet generator, and convert it to fixed RMS voltage and frequency AC.

See also
 Centrifugal governor 
 Continuously variable transmission

References

Jet engine technology
Aircraft components
Aerospace engineering
Vehicle technology
IBM Peterlee Relational Test Vehicle. PRTV (Peterlee Relational Test Vehicle) was the world's first relational database management system that could handle significant data volumes. 

It was a relational query system with powerful query facilities, but very limited update facility and no simultaneous multiuser facility. PRTV was a successor from the very first relational implementation, IS1.

Features
PRTV included several firsts in the relational database area:
 implemented relational optimizer
 implemented cost-based relational optimizer
 handle tables of 1,000 rows up to 10,000,000 rows
 user-defined functions (UDFs) within an RDB (also a large suite of built-in functions such as trigonometric and statistical)
 geographic information system based on an RDB (using UDFs such as point-in-polygon).

PRTV was based on a relational algebra, Information Systems Base Language (ISBL) and followed the relational model very strictly.  Even features such as user-defined functions were formalized within that model.  The PRTV team also introduced surrogates to the relational model to help formalize relational update operations; and a formalisation for updating through views.  However neither of these was implemented within PRTV.  PRTV emphatically did not implement NULL values, because this conception was introduced only in 1979.

PRTV was itself never available as a product, but the Urban Management System built on it was available as a limited IBM product.

Implementation
PRTV was written in a mixture of languages. The higher layers were written in MP/3 and PL/I, whereas the lower layers were written in PL/I and System/370 assembler language. MP/3 was a macro processing language developed at Peterlee from 1973 onwards, similar to ML/I or TRAC. PRTV ran on System/370 IBM mainframes.

References

Peterlee Relational Test Vehicle (PRTV)
IBM mainframe software
Relational database management systems
List of textbooks in thermodynamics and statistical mechanics. A list of notable textbooks in thermodynamics and statistical mechanics, arranged by category and date.

Only or mainly thermodynamics

Both thermodynamics and statistical mechanics 

 
 2e Kittel, Charles; and Kroemer, Herbert (1980) New York: W.H. Freeman 
 2e (1988) Chichester: Wiley , .
 (1990) New York: Dover 

Stephen G. Brush (1976) The Kind of Motion We Call Heat  I-II North-Holland ISBN 0-444-87008-3

Statistical mechanics 
 . 2e (1936) Cambridge: University Press; (1980) Cambridge University Press. 
 ; (1979) New York: Dover 
  Vol. 5 of the Course of Theoretical Physics. 3e (1976) Translated by J.B. Sykes and M.J. Kearsley (1980) Oxford : Pergamon Press. 
 . 3e (1995) Oxford: Butterworth-Heinemann 
 . 2e (1987) New York: Wiley 
 . 2e (1988) Amsterdam: North-Holland . 2e (1991) Berlin: Springer Verlag , 
 ; (2005) New York: Dover 
 
2e (2000) Sausalito, Calif.: University Science 

 
2e (1998) Chichester: Wiley 

 
 
 
 
 S. R. De Groot, P. Mazur (2011)  Non-Equilibrium Thermodynamics, Dover Books on Physics, ISBN 978-0486647418.

Specialized topics

Kinetic theory 
  Vol. 10 of the Course of Theoretical Physics (3rd Ed). Translated by J.B. Sykes and R.N. Franklin (1981) London: Pergamon ,

Quantum statistical mechanics

Mathematics of statistical mechanics 

 Translated by G. Gamow (1949) New York: Dover 
 . Reissued (1974), (1989); (1999) Singapore: World Scientific 
; (1984) Cambridge: University Press . 2e (2004) Cambridge: University Press

Miscellaneous
 
(available online here)

Historical
  (1896, 1898) Translated by Stephen G. Brush (1964) Berkeley: University of California Press; (1995) New York: Dover 
 
 Translated by J. Kestin (1956) New York: Academic Press.
  German Encyclopedia of Mathematical Sciences. Translated by Michael J. Moravcsik (1959) Ithaca: Cornell University Press; (1990) New York: Dover

See also

List of textbooks on classical mechanics and quantum mechanics
List of textbooks in electromagnetism
List of books on general relativity

Further reading

References

External links 
 Statistical Mechanics and Thermodynamics Texts Clark University curriculum development project

Lists of science textbooks
 
Mathematics-related lists
Physics-related lists
 
Textbooks
Textbooks
Combined gas and gas. Combined gas turbine and gas turbine (COGAG) is a type of propulsion system for ships using two gas turbines connected to a single propeller shaft. A gearbox and clutches allow either of the turbines to drive the shaft or both of them combined. Marine usage of COGAG systems are similar to those found ashore.

Description

A COGAG system consists of two gas turbines, each connected to a reduction gearbox. These are each attached to a coupling with both connected to larger gearbox and then to the ship's propeller.

Advantages and disadvantages
Advantages of the system include a large degree of automation along with quick startup time, they are easier to silence and protect from shock. Compared to combined diesel and gas (CODAG) or combined diesel or gas (CODOG), COGAG systems have a smaller footprint but a much lower fuel efficiency at cruise speed and for CODAG systems it is also somewhat lower for high speed dashes. Issues with COGAG systems include their complexity and gearbox issues and high fuel use.

List of COGAG ships 
 guided-missile destroyer (Indian Navy)
 (aircraft carrier) (Indian Navy)
Type 22 frigate (Batch 3)  (Royal Navy)
 (Royal Navy)
 (Italian Navy)
 (Japan Maritime Self-Defense Force), and subsequent destroyer classes
 (Japan Maritime Self-Defense Force), helicopter carrier
 (Japan Maritime Self-Defense Force), helicopter carrier
Type 055 destroyer (People's Liberation Army Navy)
 (Russian Navy)
 (Republic of Korea Navy)
 (Royal Norwegian Navy)
 (United States Navy)
 (United States Navy)

Citations

References
 
 
 

Marine propulsion