omniomni/omni-engineering huggingface dataset:
Aventurescence. In gemology, aventurescence (sometimes called aventurization) is an optical reflectance effect seen in certain gems. The effect amounts to a metallic glitter, arising from minute, preferentially oriented mineral platelets within the material. These platelets are so numerous that they also influence the material's body colour. In aventurine quartz, chrome-bearing fuchsite produces a green stone, and various iron oxides produce a red stone.

The words aventurine and aventurescence derive from the Italian "a ventura", meaning "by chance". This is an allusion to the chance discovery of aventurine glass (goldstone) at some point in the 18th century. Goldstone is still manufactured today as an artificial imitation of the later discoveries aventurine quartz and aventurine feldspar (sunstone).

See also

References
 Webster, R. (2000). Gems: Their sources, descriptions and identification (5th ed.), p 231. Great Britain: Butterworth-Heinemann.

Gemology
Optical phenomena
George Woltman. George Woltman (born November 10, 1957) is the founder of the Great Internet Mersenne Prime Search (GIMPS), a distributed computing project researching Mersenne prime numbers using his software Prime95. He graduated from the Massachusetts Institute of Technology (MIT) with a degree in computer science. He lives in North Carolina. His mathematical libraries created for the GIMPS project are the fastest known for multiplication of large integers, and are used by other distributed computing projects as well, such as Seventeen or Bust.

He also worked on a TTL version of Maze War while a student at MIT.  Later he worked as a programmer for Data General.

See also 
 Prime95

References

External links 
 The Prime Pages Titan Biography
 GIMPS home page

1957 births
Living people
Great Internet Mersenne Prime Search
20th-century American mathematicians
21st-century American mathematicians
MIT School of Engineering alumni
Sodium percarbonate. Sodium percarbonate or sodium carbonate peroxide is a chemical substance with empirical formula . It is an adduct of sodium carbonate ("soda ash" or "washing soda") and hydrogen peroxide (that is, a perhydrate) whose formula is more properly written as . It is a colorless, crystalline, hygroscopic and water-soluble solid.  It is sometimes abbreviated as SPC. It contains 32.5% by weight of hydrogen peroxide.

The product is used in some eco-friendly bleaches and other cleaning products.

History
Sodium percarbonate was first prepared in 1899 by Ukrainian chemist Sebastian Moiseevich Tanatar (7 October 1849 – 30 November 1917).

Structure
At room temperature, solid sodium percarbonate has the orthorhombic crystal structure, with the Cmca crystallographic space group.  The structure changes to Pbca as the crystals are cooled below about −30 °C.

Chemistry
Dissolved in water, sodium percarbonate yields a mixture of hydrogen peroxide (which eventually decomposes to water and oxygen), sodium cations (), and carbonate ().

Production
Sodium percarbonate is produced industrially by crystallization of a solution of sodium carbonate and hydrogen peroxide,  with proper control of the pH and concentrations.  This is also a convenient laboratory method.

Alternatively, dry sodium carbonate may be treated directly with concentrated hydrogen peroxide solution.

It may also be formed from a process starting from sodium peroxide; when absolute ethyl alcohol reacts with sodium peroxide at 0°C, a perhydroxide is produced.

Carbon dioxide converts it into sodium hydrogen percarbonate.

World production capacity of this compound was estimated at several hundred thousand tons for 2004.

Uses
As an oxidizing agent, sodium percarbonate is an ingredient in a number of home and laundry cleaning products, including non-chlorine bleach products such as Oxyper, OxiClean, Tide laundry detergent, and Vanish.

Many commercial products mix a percentage of sodium percarbonate with sodium carbonate. The average "Oxy" product in the supermarket contains 35–40% sodium percarbonate with about 5% active oxygen when titrated.

Sodium percarbonate is also used as a cleaning agent in homebrewing.

Sodium percarbonate can be used in organic synthesis as a convenient source of anhydrous H2O2, in particular in solvents that cannot dissolve the carbonate but can leach the H2O2 out of it.  A method for generating trifluoroperacetic acid in situ for use in Baeyer–Villiger oxidations from sodium percarbonate and trifluoroacetic anhydride has been reported; it provides a convenient and cheap approach to this reagent without the need to obtain highly concentrated hydrogen peroxide.

References

External links
 Organic Chemistry Portal: Sodium percarbonate
 Consumer Product Information Database: Sodium percarbonate

Sodium compounds
Hydrogen peroxide
Carbonates
Cleaning product components
Antiseptics
Bleaches
Oxidizing agents
IMU. IMU may refer to:

Science and technology
Inertial measurement unit, a device that measures acceleration and rotation, used for example to maneuver modern vehicles including motorcycles, missiles, air- and spacecraft

Businesses and organizations
I Measure U, a New Zealand company that develops inertial measurement units
Indiana Memorial Union, on the Indiana University Bloomington campus
International Mathematical Union
Irish Medical Union, since renamed the Irish Medical Organisation
Islamic Movement of Uzbekistan, Afghan Militant group
Italian Mathematical Union

Education
Indian Maritime University, a public university in India
Inner Mongolia University, a public university in China
International Medical University, a private university in Malaysia
Istanbul Medipol University, a private university in Turkey

Other uses
Initial markup, in business
Intensive Management Unit, a type of prison in the United States, usually practicing solitary confinement
Interurban Multiple Units, used by Queensland Rail

See also
Imu, a type of underground oven used in Hawaiian cooking
SPITBOL. SPITBOL (Speedy Implementation of SNOBOL) is a compiled implementation of the SNOBOL4 programming language. Originally targeted for the IBM System/360 and System/370 family of computers, it has now been ported to most major microprocessors including the SPARC. It was created by Robert Dewar and Ken Belcher, who were then at the Illinois Institute of Technology.

Prior to the development of SPITBOL, SNOBOL4 was thought to be slow, memory-intensive, and impossible to compile due to its dynamic nature. While delayed binding prevents everything from being determined at compile time, SPITBOL adopts various strategies for making decisions as early as possible. Recent versions of the SPITBOL compiler are available. Since 2001 the source code for the original SPITBOL 360 compiler has been made available under the GNU General Public License.

MACRO SPITBOL is an implementation of SPITBOL written in the 1970s by Robert Dewar and Anthony P. McCann. MACRO SPITBOL is coded in MINIMAL, an assembly language for an abstract machine. The instruction set is carefully defined to allow some latitude in its implementation, so that hardware operations favorable to string processing can be exploited.

An implementation of MINIMAL that was designed for interpretation on microcomputers was done by translating MINIMAL into MICRAL using a translator that was itself implemented in SPITBOL. The MICRAL version of MACRO SPITBOL, together with the MICRAL interpreter ran in under 40K bytes. This extreme object code compression of MICRAL is achieved using a set of machine code macro substitutions that minimizes the space required for the object code and macro table. The complexity of known algorithms for an optimal solution to this problem are high, but efficient heuristics attain near-optimal results.

The source code for MACRO SPITBOL was released under the GNU General Public License on April 17, 2009.

References

Compilers
Pattern matching programming languages
SNOBOL programming language family
Monongahela Connecting Railroad. The Monongahela Connecting Railroad  or Mon Conn was a three-mile industrial railroad line in Pittsburgh, Pennsylvania. It was a subsidiary of the Jones & Laughlin Steel Company and a large portion of its work was for its parent company, though it also served other industries along the line.

History
The railroad is possibly best known for its Hot Metal Bridge, which was used to carry molten iron across the Monongahela River from J&L's Eliza Furnaces to the Bessemer converters (later, open hearth furnaces) and rolling mills at J&L's South Side facility.

In 1966, the company was involved in construction of the Pittsburgh Tri-Port Terminal, which had been created "to offer prompt movement of products for rail, truck and river delivery," and was slated to be "used to load or unload river barges for transfer to trucks or railroad," and was "intended to reduce truck traffic over city streets."

The railroad was also a dieselization pioneer, buying many early diesel locomotives from Alco, General Electric and other manufacturers.

The Monongahela Connecting Railroad was acquired by real estate firm Almono in 2002, who ceased providing common carrier services the following year.

The Monongahela River bridge has been converted to a two-lane automobile bridge, with the adjacent hot metal bridge converted for bicycles. The bridges are collectively called the Hot Metal Bridge. The railroad served a few small industrial customers along the north/east (right downstream) bank of the river.

Joseph L. Sorensen was Vice President of the Monongahela Connecting Railroad from 1948 until 1952.

See also 

 Monongahela Railway, not to be confused with the Monongahela Connecting Railroad.

References

External links 
Holth, Nathan and McOmber, Rick, et al. "Hot Metal Street Bridge: Monongahela Connecting Railroad Bridge." Historic Bridges, 2011, 2016 and 2021 (retrieved online January 7, 2023).
Lundsten, Carsten S. "Monongahela Connecting RailRoad," in "Western Pennsylvanian Railroads," February 3, 2008 (retrieved online January 7, 2023).

Defunct Pennsylvania railroads
Switching and terminal railroads
History of Allegheny County, Pennsylvania
Transportation in Pittsburgh
Re-order buffer. A re-order buffer (ROB) is a hardware unit used in an extension to Tomasulo's algorithm to support out-of-order and speculative instruction execution.  The extension forces instructions to be committed in-order.

The buffer is a circular buffer (to provide a FIFO instruction ordering queue) implemented as an array/vector (which allows recording of results against instructions as they complete out of order).

There are three stages to the Tomasulo algorithm: "Issue", "Execute", "Write Result". In an extension to the algorithm, there is an additional "Commit" stage. During the Commit stage, instruction results are stored in a register or memory. The "Write Result" stage is modified to place results in the re-order buffer. Each instruction is tagged in the reservation station with its index in the ROB for this purpose.

The contents of the buffer are used for data dependencies of other instructions scheduled in the buffer. The head of the buffer will be committed once its result is valid. Its dependencies will have already been calculated and committed since they must be ahead of the instruction in the buffer though not necessarily adjacent to it. Data dependencies between instructions would normally stall the pipeline while an instruction waits for its dependent values. The ROB allows the pipeline to continue to process other instructions while ensuring results are committed in order to prevent data hazards such as read ahead of write (RAW), write ahead of read (WAR) and write ahead of write (WAW). 

There are additional fields in every entry of the buffer to support the extended algorithm:
 Instruction type (jump, store to memory, store to register)
 Destination (either memory address or register number)
 Result (value that goes to destination or indication of a (un)successful jump)
 Validity (does the result already exist?)

The consequences of the re-order buffer include precise exceptions and easy rollback control of target address mis-predictions (branch or jump). When jump prediction is not correct or a nonrecoverable exception is encountered in the instruction stream, the ROB is cleared of all instructions (by setting the circular queue tail to the head) and reservation stations are re-initialized.

References

External links
Hardware Based Speculation - Prof. Dr. Ben H. Juurlink
Reorder Buffer

Instruction processing
SpeakEasy. SpeakEasy was a United States military project to use software-defined radio technology to make it possible to communicate with over 10 different types of military radios from a single system.

History

"The SpectrumWare project applied a software-oriented wireless communications approach with distributed signal processing. The research direction of the SpectrumWare project was heavily influenced by two software radio efforts: the military SpeakEasy project and the commercial products of the Steinbrecher Corporation.

According to Upmal and Lackey in “SPEAKeasy, the Military Software Radio” IEEE Communications Magazine (NY: IEEE Press) 1995, the SpeakEasy project was started in 1991 and was the first large-scale software radio. SpeakEasy was motivated in large part by the communications interoperability problems that resulted from different branches of the military services having dissimilar (non-interoperable) radio systems. This lack of communications interoperability can be directly linked to casualties in several conflicts. SpeakEasy had a very aggressive goal of implementing ten different radio waveforms in software on a single platform. The designers chose the fastest DSP available at the time, the Texas Instruments TMS320C40 processor, which ran at 40 MHz. Since this was not enough processing power to implement all of the waveform processing, the system boards were designed to each support four ’C40s as well as some FPGAs.

In 1994, Phase I was successfully demonstrated; however it involved several hundred processors and filled the back of a truck. Moore’s Law provides a doubling in speed every eighteen months, and since it had taken three years to build the system and write all of the software, two doublings had taken place. This seemed to indicate that the number of processors could be reduced by a factor of four. However, SpeakEasy could not take advantage of these newer faster processors, and the reason was the software.

The software was tied to ’C40 assembly language, plus all of the specialized glue code to get four C40s to work together with the code for the particular chosen FPGA. The observation was that it had taken three years to write software for a platform that Moore’s Law made obsolete in eighteen months. Further-more, a software radio pushes most of the complexity of the radio into software, so the software development could easily become the largest, most expensive part of the system. These observations led to software portability being a key goal of the SpectrumWare project."

See also
 Software Communications Architecture (SCA)
 European Secure Software-defined Radio (ESSOR) http://www.occar.int/36
 Joint Radio System of the German Armed Forces (SVFuA) 
 GNU Radio

References

Military radio systems of the United States
Software-defined radio
Concept car. A concept car (also known as a concept vehicle or show vehicle) is a car made to showcase new styling or new technology. Concept cars are often exhibited at motor shows to gauge customer reaction to new and radical designs which may or may not be produced. 

General Motors designer Harley Earl is generally credited with inventing the concept car, and did much to popularize it through its traveling Motorama shows of the 1950s.

Concept cars never go into production directly. In modern times, all would have to undergo many changes before the design is finalized for the sake of practicality, safety, regulatory compliance, and cost. A "production-intent" prototype, as opposed to a concept vehicle, serves this purpose.

Design 

Concept cars are often radical in engine or design. Some use non-traditional, exotic, or expensive materials, ranging from paper to carbon fiber to refined alloys. Others have unique layouts, such as gullwing doors, three or five (or more) wheels, or special abilities not usually found on cars. Because of these often impractical or unprofitable leanings, many concept cars never get past scale models or even drawings. Other more traditional concepts can be developed into fully drivable (operational) vehicles with a working drivetrain and accessories. The state of most concept cars lies somewhere in between and does not represent the final product. A very small proportion of concept cars are functional to any useful extent, and some cannot move safely at speeds above .

Inoperative "mock-ups" are usually made of wax, clay, metal, fiberglass, plastic, or a combination thereof.

If drivable, the drivetrain is often borrowed from a production vehicle from the same company or may have defects and imperfections in design. They can also be quite refined, such as General Motors' Cadillac Sixteen concept.

Notable concept cars

See also 
 Concept art
 List of Alfa Romeo concept cars
 List of Audi concept cars
 List of BMW concept vehicles
 List of Citroën concept cars
 List of Dodge concept vehicles
 List of Lamborghini concept vehicles
 List of Lancia concept cars
 Pre-production car
 Production vehicle
 Product lifecycle management
 Proof-of-concept
 Show car

References

Works cited

External links 

 

 
Articles containing video clips
Automotive terminology
Automotive design
Dynabook. The KiddiComp concept, envisioned by Alan Kay in 1968 while a PhD candidate, and later developed and described as the Dynabook in his 1972 proposal "A personal computer for children of all ages", outlines the requirements for a conceptual portable educational device that would offer similar functionality to that now supplied via a laptop computer or (in some of its other incarnations) a tablet or slate computer with the exception of the requirement for any Dynabook device offering near eternal battery life. Adults could also use a Dynabook, but the target audience was children.

Though the hardware required to create a Dynabook is here today, Alan Kay still thinks the Dynabook hasn't been invented yet, because key software and educational curricula are missing.  When Microsoft came up with its tablet PC in 2001, Kay was quoted as saying "Microsoft's Tablet PC, the first Dynabook-like computer good enough to criticize".

In 1989, Toshiba released a sub-notebook computer called DynaBook, inspired by the concept. Kay was personally gifted a unit and was a guest of Toshiba. The company released notebook computers under the DynaBook brand in Japan; in 2018, Sharp acquired a majority stake in Toshiba's PC business, now named Dynabook Inc. and has marketed notebooks worldwide under the Dynabook name.

Original concept 

Describing the idea as "A Personal Computer For Children of All Ages", Kay wanted the Dynabook concept to embody the learning theories of Jerome Bruner and some of what Seymour Papert— who had studied with developmental psychologist Jean Piaget and who was one of the inventors of the Logo programming language — was proposing. This concept was created two years before the founding of Xerox PARC. The ideas led to the development of the Xerox Alto prototype, which was originally called "the interim Dynabook".  It embodied all the elements of a graphical user interface, or GUI, as early as 1972. The software component of this research was Smalltalk, which went on to have a life of its own independent of the Dynabook concept.

The hardware on which the programming environment ran was relatively irrelevant.

At the same time, Kay tried in his 1972 article to identify existing hardware components that could be used in a Dynabook, including screens, processors and storage memory. For example:

The Dynabook vision was most fully laid out in Kay’s 1977 article "Personal Dynamic Media", co-authored with collaborator (and Smalltalk co-inventor) Adele Goldberg.

In 2019, Kay gave a detailed answer to a question on Quora, about the origins of the Dynabook concept.

Later works 
Since the late 1990s, Kay has been working on the Squeak programming system, an open source Smalltalk-based environment which could be seen as a logical continuation of the Dynabook concept.

He was actively involved in the One Laptop Per Child project, which uses Smalltalk, Squeak, and the concepts of a computer for learning.

References

External links 
 .
 .
 
 .
 .
  about the Dynabook project and vision
 .
 .

History of human–computer interaction
Tablet computers
User interfaces
Xerox computers
History of computing hardware
Early laptops
List of refractive indices. Many materials have a well-characterized refractive index, but these indices often depend strongly upon the frequency of light, causing optical dispersion. Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength (λ) of 589 nanometers.

There are also weaker dependencies on temperature, pressure/stress, etc., as well on precise material compositions (presence of dopants, etc.); for many materials and typical conditions, however, these variations are at the percent level or less. Thus, it's especially important to cite the source for an index measurement if precision is required.

In general, an index of refraction is a complex number with both a real and imaginary part, where the latter indicates the strength of absorption loss at a particular wavelength—thus, the imaginary part is sometimes called the extinction coefficient . Such losses become particularly significant, for example, in metals at short (e.g. visible) wavelengths, and must be included in any description of the refractive index.

List

See also
Sellmeier equation
Corrective lens#Ophthalmic material property tables
Optical properties of water and ice

References

External links 
International Association for the Properties of Water and Steam
Ioffe institute, Russian Federation 
Crystran, United Kingdom
Jena University, Germany
Hyperphysics list of refractive indices
Luxpop: Index of refraction values and photonics calculations
Kaye and Laby Online Provided by the National Physical Laboratory, UK
List of Refractive Indices of Solvents

Physics-related lists
Optics
Relaxation. Relaxation stands quite generally for a release of tension, a return to equilibrium.

In the sciences, the term is used in the following ways:
 Relaxation (physics), and more in particular:
 Relaxation (NMR), processes by which nuclear magnetization returns to the equilibrium distribution
 Dielectric relaxation, the delay in the dielectric constant of a material
 Vibrational energy relaxation, the process by which molecules in high energy quantum states return to the Maxwell-Boltzmann distribution
 Chemical relaxation methods, related to temperature jump
 Relaxation oscillator, a type of electronic oscillator

In mathematics:
 Relaxation (approximation), a technique for transforming hard constraints into easier ones
 Relaxation (iterative method), a technique for the numerical solution of equations
 Relaxation (extension method), a technique for a natural extension in mathematical optimization or variational problems

In computer science:
 Relaxation (computing), the act of substituting alternative program code during linking

In physiology, hypnosis, meditation, recreation:
 Relaxation (psychology), the emotional state of low tension
 Relaxation technique, an activity that helps a person to relax 

In ecclesiastical law:
 Relaxation in person, transfer of a condemned person so that secular authorities execute a death sentence

See also
 Leisure
 Tension (music)
 Relaxation response (disambiguation)
 Relax (disambiguation)