omniomni/omni-engineering huggingface dataset:
Péclet number. In continuum mechanics, the Péclet number (, after Jean Claude Eugène Péclet) is a class of dimensionless numbers relevant in the study of transport phenomena in a continuum. It is defined to be the ratio of the rate of advection of a physical quantity by the flow to the rate of diffusion of the same quantity driven by an appropriate gradient. In the context of species or mass transfer, the Péclet number is the product of the Reynolds number and the Schmidt number (). In the context of the thermal fluids, the thermal Péclet number is equivalent to the product of the Reynolds number and the Prandtl number ().

The Péclet number is defined as:
 

For mass transfer, it is defined as:

Such ratio can also be re-written in terms of times, as a ratio between the characteristic temporal intervals of the system:

For    the diffusion happens in a much longer time compared to the advection, and therefore the latter of the two phenomena predominates in the mass transport. 

For heat transfer, the Péclet number is defined as:

where  is the characteristic length,  the local flow velocity,  the mass diffusion coefficient,  the Reynolds number,  the Schmidt number,  the Prandtl number, and  the thermal diffusivity,

where  is the thermal conductivity,  the density, and  the specific heat capacity.

In engineering applications the Péclet number is often very large. In such situations, the dependency of the flow upon downstream locations is diminished, and variables in the flow tend to become 'one-way' properties. Thus, when modelling certain situations with high Péclet numbers, simpler computational models can be adopted.

A flow will often have different Péclet numbers for heat and mass. This can lead to the phenomenon of double diffusive convection.

In the context of particulate motion the Péclet number has also been called Brenner number, with symbol , in honour of Howard Brenner.

The Péclet number also finds applications beyond transport phenomena, as a general measure for the relative importance of the random fluctuations and of the systematic average behavior in mesoscopic systems

See also
 Nusselt number

References

Convection
Dimensionless numbers of fluid mechanics
Dimensionless numbers of thermodynamics
Fluid dynamics
Heat conduction
Diffusivity. Diffusivity is a rate of diffusion, a measure of the rate at which particles or heat or fluids can spread.

It is measured differently for different mediums.

Diffusivity may refer to:
Thermal diffusivity, diffusivity of heat
Diffusivity of mass:
 Mass diffusivity, molecular diffusivity (often called "diffusion coefficient")
 Eddy diffusion, eddy diffusivity
Kinematic viscosity, characterising momentum diffusivity
Magnetic diffusivity

Dimensions and units

Diffusivity has dimensions of length2 / time, or m2/s in SI units and cm2/s in CGS units.

See also 
 Diffusibility

References

Former disambiguation pages converted to set index articles
Thermal diffusivity. In heat transfer analysis, thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure. It is a measure of the rate of heat transfer inside a material and has SI units of m2/s. It is an intensive property. Thermal diffusivity is usually denoted by lowercase alpha (), but , ,  (kappa), , ,,  are also used.

The formula is:

where
  is thermal conductivity (W/(m·K))
  is specific heat capacity (J/(kg·K))
  is density (kg/m3)
Together,  can be considered the volumetric heat capacity (J/(m3·K)).

As seen in the heat equation,

one way to view thermal diffusivity is as the ratio of the time derivative of temperature to its curvature, quantifying the rate at which temperature concavity is "smoothed out". Thermal diffusivity is a contrasting measure to thermal effusivity. In a substance with high thermal diffusivity, heat moves rapidly through it because the substance conducts heat quickly relative to its volumetric heat capacity or 'thermal bulk'.

Thermal diffusivity is often measured with the flash method. It involves heating a strip or cylindrical sample with a short energy pulse at one end and analyzing the temperature change (reduction in amplitude and phase shift of the pulse) a short distance away.

Thermal diffusivity of selected materials and substances

See also
 Heat equation
 Laser flash analysis
 Thermophoresis
 Thermal effusivity
 Thermal time constant

References

Heat transfer
Physical quantities
Heat conduction
Timeline of states of matter and phase transitions. This is a timeline of states of matter and phase transitions, specifically discoveries related to either of these topics.

Timeline

19th century 

 1879  Sir William Crookes first identifies plasma in laboratory
 1895 – Pierre Curie discovers that induced magnetization is proportional to magnetic field strength

20th century 
 1911 – Heike Kamerlingh Onnes discloses his research on superconductivity
 1912 – Peter Debye derives the T-cubed law for the low temperature heat capacity of a nonmetallic solid
 19241925  Bose–Einstein condensate was first predicted, generally, by Albert Einstein 
 1925 – Ernst Ising presents the solution to the one-dimensional Ising model 
 1928 – Felix Bloch applies quantum mechanics to electrons in crystal lattices, establishing the quantum theory of solids
 1929 – Paul Adrien Maurice Dirac  and Werner Karl Heisenberg develop the quantum theory of ferromagnetism
 1932 – Louis Eugène Félix Néel discovers antiferromagnetism
 1933 – Walther Meissner and Robert Ochsenfeld discover perfect superconducting diamagnetism
 1933–1937 – Lev Davidovich Landau develops the Landau theory of phase transitions
 1937 – Pyotr Leonidovich Kapitsa and John Frank Allen/Don Misener discover superfluidity
 1941 – Lev Davidovich Landau explains superfluidity
 1942 – Hannes Alfvén predicts magnetohydrodynamic waves in plasmas
 1944 – Lars Onsager publishes the exact solution to the two-dimensional Ising model
 1957 – John Bardeen, Leon Cooper, and Robert Schrieffer develop the BCS theory of superconductivity
 End of the 50s – Lev Davidovich Landau develops the theory of Fermi liquid
 1959 – Philip Warren Anderson predicts localization in disordered systems
 1972 – Douglas Osheroff, Robert C. Richardson, and David M. Lee discover that helium-3 can become a superfluid
 1974 – Kenneth G. Wilson develops the renormalization group technique for treating phase transitions
 1980 – Klaus von Klitzing discovers the quantum Hall effect
 1982 – Horst L. Störmer and Daniel C. Tsui discover the fractional quantum Hall effect
 1983 – Robert B. Laughlin explains the fractional quantum Hall effect
 1986 – Karl Alexander Müller and Georg Bednorz discover high critical temperature ceramic superconductors
 1995 – Eric Cornell and Carl Wieman produce the first Bose–Einstein condensate using rubidium atoms

21st century 

 2000 – CERN announced quark-gluon plasma, a new phase of matter.
 2023  Physicists from US and China discovered a new state of matter called the chiral bose-liquid state
 2024  Harvard researchers working with Quantinuum announced a new phase of matter non-Abelian topological order

References

States of Matter and Phase Transitions
Timeline of artificial satellites and space probes. This timeline of artificial satellites and space probes includes uncrewed spacecraft including technology demonstrators, observatories, lunar probes, and interplanetary probes. First satellites from each country are included. Not included are most Earth science satellites, commercial satellites or crewed missions.

Timeline

1950s

1960s

1970s

1980s

1990s

2000s

2010s

2020s

References

External links

Current and Upcoming Launches
Missions-NASA
Unmanned spaceflight discussion forum
Chronology of Lunar and Planetary Exploration (homepage)

Artificial satellites and space probes
Celestine (mineral). Celestine (the IMA-accepted name) or celestite is a mineral consisting of strontium sulfate (SrSO). The mineral is named for its occasional delicate blue color. Celestine and the carbonate mineral strontianite are the principal sources of the element strontium, commonly used in fireworks and in various metal alloys.

Etymology
Celestine derives its name from the Latin word caelestis meaning celestial which in turn is derived from the Latin word caelum meaning sky, air, weather, atmosphere and heaven.

Occurrence
Celestine occurs as crystals, and also in compact massive and fibrous forms. It is mostly found in sedimentary rocks, often associated with the minerals gypsum, anhydrite, and halite. On occasion in some localities, it may also be found with sulfur inclusions.

The mineral is found worldwide, usually in small quantities. Pale blue crystal specimens are found in Madagascar. White and orange variants also occurred at Yate, Bristol, UK, where it was extracted for commercial purposes until April 1991.

The skeletons of the protozoan Acantharea are made of celestine, unlike those of other radiolarians which are made of silica.

In carbonate marine sediments, burial dissolution is a recognized mechanism of celestine precipitation. It is sometimes used as a gemstone.

Geodes
Celestine crystals are found in some geodes. The world's largest known geode, a celestine geode  in diameter at its widest point, is located near the village of Put-in-Bay, Ohio, on South Bass Island in Lake Erie. The geode has been converted into a viewing cave, Crystal Cave, with the crystals which once composed the floor of the geode removed. The geode has celestine crystals as wide as  across, estimated to weigh up to  each.

Celestine geodes are understood to form by replacement of alabaster nodules consisting of the calcium sulfates gypsum or anhydrite. Calcium sulfate is sparingly soluble, but strontium sulfate is mostly insoluble. Strontium-bearing solutions that come into contact with calcium sulfate nodules dissolve the calcium away, leaving a cavity. The strontium is immediately precipitated as celestine, with the crystals growing into the newly formed cavity.

See also
 List of minerals

Footnotes

References

External links
 

Strontium minerals
Sulfate minerals
Orthorhombic minerals
Minerals in space group 62
Luminescent minerals
Evaporite
Gemstones
Baryte group
Minerals described in 1798
German submarine U-760. German submarine U-760 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II.

Her keel was laid down 5 August 1940 by the Kriegsmarinewerft of Wilhelmshaven, and she was commissioned  15 October 1942 with Oberleutnant zur See Otto-Ulrich Blum in command. Blum commanded her for her entire career in the Kriegsmarine.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-760 had a displacement of  when at the surface and  while submerged. She had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of  for use while surfaced, two Garbe, Lahmeyer & Co. RP 137/c double-acting electric motors producing a total of  for use while submerged. She had two shafts and two  propellers. The boat was capable of operating at depths of up to .

The submarine had a maximum surface speed of  and a maximum submerged speed of . When submerged, the boat could operate for  at ; when surfaced, she could travel  at . U-760 was fitted with five  torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one  SK C/35 naval gun, 220 rounds, and two twin  C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.

Service history
U-760 conducted two war patrols, but never sank or damaged a ship. On 26 February 1943 Obermaschinist Jakob Ippendorf died during an air attack in Wilhelmshaven. On 12 August 1943 Matrosenenobergefreiter Günter Werner was lost during an air attack in the North Atlantic.

On 8 September 1943, about  off Cape Finisterre, U-760 was sailing on the surface alongside  when they were attacked by Allied aircraft. U-760 fled into Vigo harbour and was taken under the guns of the .

Fate
International neutrality agreements allowed ships to spend up to 24 hours in neutral harbours to make emergency repairs, but U-760 was unable to get underway in time. She was interned at Ferrol for the remainder of World War II. The submarine engine was dismantled and used to generate electric energy for the city of Vigo's tram network. On 23 July 1945, the boat was taken to the United Kingdom for Operation Deadlight and was scuttled on 13 December 1945.

One other U-boat was interned in Spain during World War II: .

References

Bibliography

External links

German Type VIIC submarines
U-boats commissioned in 1942
Operation Deadlight
World War II submarines of Germany
Ships built in Wilhelmshaven
1942 ships
Maritime incidents in September 1943
Maritime incidents in December 1945
U-boats scuttled in 1945
German submarine U-463. German submarine U-463 was a Type XIV supply and replenishment U-boat ("Milchkuh") of Nazi Germany's Kriegsmarine during World War II.

Her keel was laid down on 8 March 1941 by Deutsche Werke of Kiel. She was launched on 20 December 1941 and commissioned on 2 April 1942 with Korvettenkapitän Leo Wolfbauer in command. Wolfbauer remained in charge for the boat's entire career.

Design
German Type XIV submarines were shortened versions of the Type IXDs they were based on. U-463 had a displacement of  when at the surface and  while submerged. The U-boat had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two Germaniawerft supercharged four-stroke, six-cylinder diesel engines producing a total of  for use while surfaced, two Siemens-Schuckert 2 GU 345/38-8 double-acting electric motors producing a total of  for use while submerged. She had two shafts and two propellers. The boat was capable of operating at depths of up to .

The submarine had a maximum surface speed of  and a maximum submerged speed of . When submerged, the boat could operate for  at ; when surfaced, she could travel  at . U-463 was not fitted with torpedo tubes or deck guns, but had two  SK C/30 anti-aircraft guns with 2500 rounds as well as a  C/30 guns with 3000 rounds. The boat had a complement of fifty-three.

Operational career
U-463 conducted five patrols. As a supply boat, she avoided combat.

First patrol
U-463 departed Kiel on her first patrol on 11 July 1942, arriving at St. Nazaire in occupied France on 3 September. She had gone the 'long' way round the British Isles, by way of the gap between Iceland and the Faeroe Islands, heading out into mid-Atlantic toward the Caribbean.

Second, third and fourth patrols
Her second foray took her into the middle of the Atlantic again, between 28 September 1942 and 11 November.

The submarine's next sortie was further south, passing the Azores on the outward journey to the north and to the south on the return. By now she was based at St. Nazaire once more.

Another uneventful patrol began on 4 March 1943, but when the U-boat returned to France on 17 April, she moved into Bordeaux.

Fifth patrol and loss
U-463s fifth patrol began with her departure from Le Verdon, (north of Bordeaux): She had barely cleared the Bay of Biscay, when she was attacked and sunk on 16 May 1943 by depth charges dropped by a British Halifax from 58 Squadron RAF Coastal Command, piloted by Wing Commander Wilfrid Oulton. All 57 of her crew died.

Wolfpacks
U-463 took part in one wolfpack, namely:
 Delphin (11 – 14 January 1943)

References

Bibliography

External links
 

German Type XIV submarines
U-boats commissioned in 1942
U-boats sunk in 1943
World War II submarines of Germany
Shipwrecks in the Bay of Biscay
1941 ships
World War II shipwrecks in the Atlantic Ocean
Ships built in Kiel
U-boats sunk by British aircraft
U-boats sunk by depth charges
Submarines lost with all hands
Maritime incidents in May 1943
Life-Line. "Life-Line" is  a short story by American author Robert A. Heinlein.  Published in the August 1939 edition of Astounding, it was Heinlein's first published short story.

The protagonist, Professor Hugo Pinero, builds a machine that will predict how long a person will live.  It does this by sending a signal along the world line of a person and detecting the echo from the far end.  Professor Pinero's invention has a powerful impact on the life insurance industry, as well as on his own life.

Pinero is mentioned in passing in the novels Time Enough for Love and Methuselah's Children when the practically immortal Lazarus Long mentions having been examined and being sent away because the machine is "broken".

Writing history
Heinlein was motivated to write the story by an editorial in Thrilling Wonder Stories magazine, in which Hugo Gernsback wrote that he wanted to foster new talent in the field, and that "We shall endeavor to present one amateur writer's story in each forthcoming issue [...] until further notice." Thrilling Wonder Stories'''s rate at the time was 0.5¢ per word. After Heinlein had written the 7,000-word story, he submitted it first to a rival magazine, Astounding, which paid 1¢ per word. Astounding bought the story, and at their higher rate, Heinlein was paid $70 ().

According to Virginia Heinlein's introductory biography of her husband in Grumbles from the Grave, upon receiving the check for the story Heinlein reportedly said, "How long has this racket been going on?" Later, Heinlein's authorized biography included a version of the story in which Thrilling Wonder Stories had advertised a $50 contest. The first known version of this story appeared in a 1985 interview published in Xignals, a science fiction newsletter.

"Life-Line" was later collected in The Worlds of Robert A. Heinlein (1966), Expanded Universe (1980), and in a Baen edition of The Man Who Sold The Moon'' (1987).

Reception
One particular paragraph from "Life-Line" is often quoted in reference to (and criticism of) modern intellectual property rights:

In the realm of science another passage has come to be quoted:

A television web series loosely based on the short story began in 2017.

References

External links 
 
 "Life-Line" on the Internet Archive

1939 short stories
Short stories by Robert A. Heinlein
Works originally published in Analog Science Fiction and Fact
IEC (disambiguation). IEC most commonly refers to the International Electrotechnical Commission.

IEC may also refer to:

Businesses and organisations
 Independent Election Commission, the Jordanian electoral commission
 Independent Election Commission, the South African electoral commission
 An independent ethics committee
  Institute of Catalan Studies (Institut d'Estudis Catalans)
 International Engineering Company, a Thai company
 Interstate Economic Committee, a Soviet committee
 Israel Electric Corporation
 Itumbiara Esporte Clube, a Brazilian football club

Education
 Independent educational consultant

In science and technology
 IEC connectors, electrical connectors
 IEC bus, for Commodore computers
 Inertial electrostatic confinement, in fusion energy
 Interactive evolutionary computation
 Ion exchange chromatography, a laboratory technique

Other uses
 Island Eastern Corridor, an expressway in Hong Kong
 In Ear Monitors, used in broadcasting and concerts.

See also
List of thermodynamic properties. In thermodynamics, a physical property is any property that is measurable, and whose value describes a state of a physical system. Thermodynamic properties are defined as characteristic features of a system, capable of specifying the system's state. Some constants, such as the ideal gas constant, , do not describe the state of a system, and so are not properties.  On the other hand, some constants, such as  (the freezing point depression constant, or cryoscopic constant), depend on the identity of a substance, and so may be considered to describe the state of a system, and therefore may be considered physical properties.

"Specific" properties are expressed on a per mass basis.  If the units were changed from per mass to, for example, per mole, the property would remain as it was (i.e., intensive or extensive).

Regarding work and heat

Work and heat are not thermodynamic properties, but rather process quantities: flows of energy across a system boundary. Systems do not contain work, but can perform work, and likewise, in formal thermodynamics, systems do not contain heat, but can transfer heat. Informally, however, a difference in the energy of a system that occurs solely because of a difference in its temperature is commonly called heat, and the energy that flows across a boundary as a result of a temperature difference is "heat".

Altitude (or elevation) is usually not a thermodynamic property.  Altitude can help specify the location of a system, but that does not describe the state of the system.  An exception would be if the effect of gravity need to be considered in order to describe a state, in which case altitude could indeed be a thermodynamic property.

See also
 Conjugate variables
 Dimensionless numbers
 Intensive and extensive properties
 Thermodynamic databases for pure substances
 Thermodynamic variable

References

Thermodynamic properties
Property (disambiguation). Property is the ownership of land, resources, improvements or other tangible objects, or intellectual property.

Property may also refer to:

Philosophy and science
 Property (philosophy), in philosophy and logic, an abstraction characterizing an object
Material properties, properties by which the benefits of one material versus another can be assessed
Chemical property, a material's properties that becomes evident during a chemical reaction
Physical property, any property that is measurable whose value describes a state of a physical system
Thermodynamic properties, in thermodynamics and materials science, intensive and extensive physical properties of substances
Mathematical property, a property is any characteristic that applies to a given set
Semantic property
Mental property, a property of the mind studied by many sciences and parasciences

Computer science
 Property (programming), a type of class member in object-oriented programming
 .properties, a Java Properties File to store program settings as name-value pairs
 Window property, data associated to a window in the X Window System
 Property of a Resource Description Framework class, possessing a value domain and range
 Linear time property, a property that a computer system must satisfy

Law and politics
 Real property, a piece of land defined by boundaries to which ownership is usually ascribed, including any improvements on this land
 Property rights (economics), a discussion of the role of property in economic theory
National Register of Historic Places property types, a site designated and classified by its type on the U.S. National Register of Historic Places
 Personal property, property that is moveable

Other uses
Property (novel), a novel by Valerie Martin
Theatrical property (commonly "prop") a portable object seen on stage or film set
Intel 430HX. The Intel 430HX (codenamed Triton II) is a chipset from Intel, supporting Socket 7 processors, including the Pentium and Pentium MMX. It is also known as i430HX and it was released in February 1996. The official part number is 82430HX.

Features
The 430HX chipset had all the features of the 430FX (Triton I) plus support for ECC, parity RAM, two-way SMP, USB, and then current PCI to improve speed.

It consists of one 82439HX TXC, the northbridge and one PIIX3, the southbridge. The 430HX chipset supported up to 512MB of RAM (64MB or 512MB cacheable depending on tag RAM size).

Gallery

Limitations
Not all 430HX boards allowed for tag RAM expansion, only allowing 64MB cacheable; 430HX also did not support the then-new SDRAM memory technology. Dual-voltage support, for Pentium MMX or AMD K6 CPUs, was also not mandatory on 430HX boards, requiring the use of an interposer to step down the voltage.

See also
 List of Intel chipsets

References

 , PC Guide.
 , PC Guide.
 Summary of P5 chipsets, comp.sys.intel, September 1996.
 
 

430HX