National Institute of Standards and Technology

The National Institute of Standards and Technology (NIST) is a physical sciences laboratory, and a non-regulatory agency of the United States Department of Commerce. Its mission is to promote innovation and industrial competitiveness. NIST's activities are organized into laboratory programs that include nanoscale science and technology, engineering, information technology, neutron research, material measurement, and physical measurement. The American AI initiative[2] has called NIST to lead the development of appropriate technical standards for reliable, robust, trustworthy, secure, portable, and interoperable AI systems.

Institute of Standards and Technology (NIST)
NIST logo
Agency overview
FormedMarch 3, 1901 (as National Bureau of Standards), became NIST in 1988
HeadquartersGaithersburg, Maryland, U.S.
39°07′59″N 77°13′25″W / 39.13306°N 77.22361°W
Employees2900
Annual budget$1.2 billion (2018)[1]
Agency executive
  • Walter Copan, Under Secretary of Commerce for Standards and Technology and Director of NIST
Parent agencyDepartment of Commerce
Websitewww.nist.gov

History

Background

The Articles of Confederation, ratified by the colonies in 1781, contained the clause, "The United States in Congress assembled shall also have the sole and exclusive right and power of regulating the alloy and value of coin struck by their own authority, or by that of the respective states—fixing the standards of weights and measures throughout the United States". Article 1, section 8, of the Constitution of the United States (1789), transferred this power to Congress; "The Congress shall have power...To coin money, regulate the value thereof, and of foreign coin, and fix the standard of weights and measures".

In January 1790, President George Washington, in his first annual message to Congress stated that, "Uniformity in the currency, weights, and measures of the United States is an object of great importance, and will, I am persuaded, be duly attended to", and ordered Secretary of State Thomas Jefferson to prepare a plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States, afterwards referred to as the Jefferson report. On October 25, 1791, Washington appealed a third time to Congress, "A uniformity of the weights and measures of the country is among the important objects submitted to you by the Constitution and if it can be derived from a standard at once invariable and universal, must be no less honorable to the public council than conducive to the public convenience", but it was not until 1838, that a uniform set of standards was worked out.

In 1821, John Quincy Adams had declared "Weights and measures may be ranked among the necessities of life to every individual of human society".[3] From 1830 until 1901, the role of overseeing weights and measures was carried out by the Office of Standard Weights and Measures, which was part of the United States Department of the Treasury.[4]

Bureau of Standards

In 1901, in response to a bill proposed by Congressman James H. Southard (R, Ohio), the National Bureau of Standards was founded with the mandate to provide standard weights and measures, and to serve as the national physical laboratory for the United States. (Southard had previously sponsored a bill for metric conversion of the United States.) [5]

Wheeled chart of National Bureau of Standards activities, 1915
Chart of NBS activities, 1915

President Theodore Roosevelt appointed Samuel W. Stratton as the first director. The budget for the first year of operation was $40,000. The Bureau took custody of the copies of the kilogram and meter bars that were the standards for US measures, and set up a program to provide metrology services for United States scientific and commercial users. A laboratory site was constructed in Washington, DC, and instruments were acquired from the national physical laboratories of Europe. In addition to weights and measures, the Bureau developed instruments for electrical units and for measurement of light. In 1905 a meeting was called that would be the first "National Conference on Weights and Measures".

Initially conceived as purely a metrology agency, the Bureau of Standards was directed by Herbert Hoover to set up divisions to develop commercial standards for materials and products.[5]page 133 Some of these standards were for products intended for government use, but product standards also affected private-sector consumption. Quality standards were developed for products including some types of clothing, automobile brake systems and headlamps, antifreeze, and electrical safety. During World War I, the Bureau worked on multiple problems related to war production, even operating its own facility to produce optical glass when European supplies were cut off. Between the wars, Harry Diamond of the Bureau developed a blind approach radio aircraft landing system. During World War II, military research and development was carried out, including development of radio propagation forecast methods, the proximity fuze and the standardized airframe used originally for Project Pigeon, and shortly afterwards the autonomously radar-guided Bat anti-ship guided bomb and the Kingfisher family of torpedo-carrying missiles.

SpectroscopyResearch 012
A mass spectrometer in use at the NBS in 1948.

In 1948, financed by the United States Air Force, the Bureau began design and construction of SEAC, the Standards Eastern Automatic Computer. The computer went into operation in May 1950 using a combination of vacuum tubes and solid-state diode logic. About the same time the Standards Western Automatic Computer, was built at the Los Angeles office of the NBS by Harry Huskey and used for research there. A mobile version, DYSEAC, was built for the Signal Corps in 1954.

Due to a changing mission, the "National Bureau of Standards" became the "National Institute of Standards and Technology" in 1988.[4]

Following September 11, 2001, NIST conducted the official investigation into the collapse of the World Trade Center buildings.

Constitution

NIST, known between 1901 and 1988 as the National Bureau of Standards (NBS), is a measurement standards laboratory, also known as a National Metrological Institute (NMI), which is a non-regulatory agency of the United States Department of Commerce. The institute's official mission is to:[6]

Promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.

— NIST

NIST had an operating budget for fiscal year 2007 (October 1, 2006 – September 30, 2007) of about $843.3 million. NIST's 2009 budget was $992 million, and it also received $610 million as part of the American Recovery and Reinvestment Act.[7] NIST employs about 2,900 scientists, engineers, technicians, and support and administrative personnel. About 1,800 NIST associates (guest researchers and engineers from American companies and foreign countries) complement the staff. In addition, NIST partners with 1,400 manufacturing specialists and staff at nearly 350 affiliated centers around the country. NIST publishes the Handbook 44 that provides the "Specifications, tolerances, and other technical requirements for weighing and measuring devices".

Metric system

The Congress of 1866 made use of the metric system in commerce a legally protected activity through the passage of Metric Act of 1866.[8] On May 20, 1875, 17 out of 20 countries signed a document known as the Metric Convention or the Treaty of the Meter, which established the International Bureau of Weights and Measures under the control of an international committee elected by the General Conference on Weights and Measures.[9]

Organization

NIST AML building
Advanced Measurement Laboratory Complex in Gaithersburg
NIST in the mist
Boulder Laboratories

NIST is headquartered in Gaithersburg, Maryland, and operates a facility in Boulder, Colorado. NIST's activities are organized into laboratory programs and extramural programs. Effective October 1, 2010, NIST was realigned by reducing the number of NIST laboratory units from ten to six.[10] NIST Laboratories include:[11]

Extramural programs include:

  • Hollings Manufacturing Extension Partnership (MEP), a nationwide network of centers to assist small and mid-sized manufacturers to create and retain jobs, improve efficiencies, and minimize waste through process improvements and to increase market penetration with innovation and growth strategies;
  • Technology Innovation Program (TIP), a grant program where NIST and industry partners cost share the early-stage development of innovative but high-risk technologies;
  • Baldrige Performance Excellence Program, which administers the Malcolm Baldrige National Quality Award, the nation's highest award for performance and business excellence.

NIST's Boulder laboratories are best known for NIST‑F1, which houses an atomic clock. NIST‑F1 serves as the source of the nation's official time. From its measurement of the natural resonance frequency of cesium—which defines the second—NIST broadcasts time signals via longwave radio station WWVB near Fort Collins, Colorado, and shortwave radio stations WWV and WWVH, located near Fort Collins and Kekaha, Hawaii, respectively.[12]

NIST also operates a neutron science user facility: the NIST Center for Neutron Research (NCNR). The NCNR provides scientists access to a variety of neutron scattering instruments, which they use in many research fields (materials science, fuel cells, biotechnology, etc.).

The SURF III Synchrotron Ultraviolet Radiation Facility is a source of synchrotron radiation, in continuous operation since 1961. SURF III now serves as the US national standard for source-based radiometry throughout the generalized optical spectrum. All NASA-borne, extreme-ultraviolet observation instruments have been calibrated at SURF since the 1970s, and SURF is used for measurement and characterization of systems for extreme ultraviolet lithography.

The Center for Nanoscale Science and Technology (CNST) performs research in nanotechnology, both through internal research efforts and by running a user-accessible cleanroom nanomanufacturing facility. This "NanoFab" is equipped with tools for lithographic patterning and imaging (e.g., electron microscopes and atomic force microscopes).

Committees

NIST has seven standing committees:

Projects

NIST HipHopAtomLogo
A 40 nm wide NIST logo made with cobalt atoms

Measurements and standards

As part of its mission, NIST supplies industry, academia, government, and other users with over 1,300 Standard Reference Materials (SRMs). These artifacts are certified as having specific characteristics or component content, used as calibration standards for measuring equipment and procedures, quality control benchmarks for industrial processes, and experimental control samples.

Handbook 44

NIST publishes the Handbook 44 each year after the annual meeting of the National Conference on Weights and Measures (NCWM). Each edition is developed through cooperation of the Committee on Specifications and Tolerances of the NCWM and the Weights and Measures Division (WMD) of the NIST. The purpose of the book is a partial fulfillment of the statutory responsibility for "cooperation with the states in securing uniformity of weights and measures laws and methods of inspection".

NIST has been publishing various forms of what is now the Handbook 44 since 1918 and began publication under the current name in 1949. The 2010 edition conforms to the concept of the primary use of the SI (metric) measurements recommended by the Omnibus Foreign Trade and Competitiveness Act of 1988.[13][14]

Homeland security

NIST is developing government-wide identity document standards for federal employees and contractors to prevent unauthorized persons from gaining access to government buildings and computer systems.

World Trade Center collapse investigation

In 2002, the National Construction Safety Team Act mandated NIST to conduct an investigation into the collapse of the World Trade Center buildings 1 and 2 and the 47-story 7 World Trade Center. The "World Trade Center Collapse Investigation", directed by lead investigator Shyam Sunder,[15] covered three aspects, including a technical building and fire safety investigation to study the factors contributing to the probable cause of the collapses of the WTC Towers (WTC 1 and 2) and WTC 7. NIST also established a research and development program to provide the technical basis for improved building and fire codes, standards, and practices, and a dissemination and technical assistance program to engage leaders of the construction and building community in implementing proposed changes to practices, standards, and codes. NIST also is providing practical guidance and tools to better prepare facility owners, contractors, architects, engineers, emergency responders, and regulatory authorities to respond to future disasters. The investigation portion of the response plan was completed with the release of the final report on 7 World Trade Center on November 20, 2008. The final report on the WTC Towers—including 30 recommendations for improving building and occupant safety—was released on October 26, 2005.[16]

Election technology

NIST works in conjunction with the Technical Guidelines Development Committee of the Election Assistance Commission to develop the Voluntary Voting System Guidelines for voting machines and other election technology.

People

Four scientific researchers at NIST have been awarded Nobel Prizes for work in physics: William D. Phillips in 1997, Eric A. Cornell in 2001, John L. Hall in 2005 and David J. Wineland in 2012, which is the largest number for any US government laboratory. All four were recognized for their work related to laser cooling of atoms, which is directly related to the development and advancement of the atomic clock. In 2011, Dan Shechtman was awarded the Nobel in chemistry for his work on quasicrystals in the Metallurgy Division from 1982 to 1984. In addition, John Cahn was awarded the 2011 Kyoto Prize for Materials Science, and the National Medal of Science has been awarded to NIST researchers Cahn (1998) and Wineland (2007). Other notable people who have worked at NIST include:

Directors

Since 1989, the director of NIST has been a Presidential appointee and is confirmed by the United States Senate,[17] and since that year the average tenure of NIST directors has fallen from 11 years to 2 years in duration. Since the 2011 reorganization of NIST, the director also holds the title of Under Secretary of Commerce for Standards and Technology. Fifteen individuals have officially held the position (in addition to four acting directors who have served on a temporary basis).

Controversial Backdoored NIST Standard

The Guardian and The New York Times reported that NIST allowed the National Security Agency (NSA) to insert a cryptographically secure pseudorandom number generator called Dual EC DRBG into NIST standard SP 800-90 that had a kleptographic backdoor that the NSA can use to covertly predict the future outputs of this pseudorandom number generator thereby allowing the surreptitious decryption of data.[18] Both papers report[19][20] that the NSA worked covertly to get its own version of SP 800-90 approved for worldwide use in 2006. The whistle-blowing document states that "eventually, NSA became the sole editor". The reports confirm suspicions and technical grounds publicly raised by cryptographers in 2007 that the EC-DRBG could contain a kleptographic backdoor (perhaps placed in the standard by NSA).[21]

NIST responded to the allegations, stating that "NIST works to publish the strongest cryptographic standards possible" and that it uses "a transparent, public process to rigorously vet our recommended standards".[22] The agency stated that "there has been some confusion about the standards development process and the role of different organizations in it...The National Security Agency (NSA) participates in the NIST cryptography process because of its recognized expertise. NIST is also required by statute to consult with the NSA."[23] Recognizing the concerns expressed, the agency reopened the public comment period for the SP800-90 publications, promising that "if vulnerabilities are found in these or any other NIST standards, we will work with the cryptographic community to address them as quickly as possible”.[24] Due to public concern of this cryptovirology attack, NIST rescinded the EC-DRBG algorithm from the NIST SP 800-90 standard.[25]

Publications

See also

References

  1. ^ Corrigan, Jack (March 23, 2018). "Defense R&D Gets a Huge Boost Under the 2018 Omnibus". Nextgov. Archived from the original on May 14, 2018. Retrieved September 22, 2018.
  2. ^ <https://www.whitehouse.gov/articles/accelerating-americas-leadership-in-artificial-intelligence/>
  3. ^ NBS special publication 447 Archived October 17, 2011, at the Wayback Machine-Retrieved September 28, 2011
  4. ^ a b Records of the National Institute of Standards and Technology (NIST) Archived October 19, 2017, at the Wayback Machine, National Archives and Records Administration website, (Record Group 167), 1830–1987.
  5. ^ a b John Perry, The Story of Standards, Funk and Wagnalls, 1953, Library of Congress Cat. No. 55-11094, p. 123
  6. ^ NIST General Information. Archived August 23, 2016, at the Wayback Machine Retrieved on August 21, 2010.
  7. ^ "NIST Budget, Planning and Economic Studies". National Institute of Standards and Technology. October 5, 2010. Archived from the original on September 22, 2010. Retrieved October 6, 2010.
  8. ^ "Weights and Measures Standards of the United States a brief history" (PDF). ts.nist.gov. p. 41. Archived from the original (PDF) on October 26, 2011. Retrieved September 28, 2011.
  9. ^ "Weights and Measures Standards of the United States a brief history" (PDF). ts.nist.gov. p. 22. Archived from the original (PDF) on October 26, 2011. Retrieved September 28, 2011.
  10. ^ NIST Strengthens Laboratory Mission Focus with New Structure Archived August 28, 2016, at the Wayback Machine
  11. ^ NIST Laboratories Archived August 26, 2016, at the Wayback Machine. National Institute of Standards and Technology. Retrieved on May 10, 2016.
  12. ^ [1]. NIST. Retrieved on March 18, 2014.
  13. ^ Handbook 44 Archived October 20, 2011, at the Wayback Machine- "Forward; page 5" Retrieved: September 28, 2011
  14. ^ 100th Congress (1988) (June 16, 1988). "H.R. 4848". Legislation. GovTrack.us. Retrieved September 28, 2011. Omnibus Trade and Competitiveness Act of 1988
  15. ^ Eric Lipton (August 22, 2008). "Fire, Not Explosives, Felled 3rd Tower on 9/11, Report Says". New York Times. Archived from the original on March 9, 2011.
  16. ^ "Final Reports of the Federal Building and Fire Investigation of the World Trade Center Disaster". National Institute of Standards and Technology. October 2005. Archived from the original on November 24, 2005.
  17. ^ "2012 Plum Book". Government Printing Office. 2012. Archived from the original on November 30, 2016. Retrieved December 2, 2016.
  18. ^ Konkel, Frank (September 6, 2013). "What NSA's influence on NIST standards means for feds". FCW. 1105 Government Information Group. Archived from the original on September 10, 2013. Retrieved September 10, 2013.
  19. ^ James Borger; Glenn Greenwald (September 6, 2013). "Revealed: how US and UK spy agencies defeat internet privacy and security". The Guardian. The Guardian. Archived from the original on September 18, 2013. Retrieved September 7, 2013.
  20. ^ Nicole Perlroth (September 5, 2013). "N.S.A. Able to Foil Basic Safeguards of Privacy on Web". The New York Times. Retrieved September 7, 2013.
  21. ^ Schneier, Bruce (November 15, 2007). "Did NSA Put a Secret Backdoor in New Encryption Standard?". Wired. Condé Nast. Archived from the original on September 19, 2012. Retrieved September 10, 2013.
  22. ^ Byers, Alex. "NSA encryption info could pose new security risk – NIST weighs in". Politico. Archived from the original on September 27, 2013. Retrieved September 10, 2013.
  23. ^ Perlroth, Nicole. "Government Announces Steps to Restore Confidence on Encryption Standards". New York Times. Archived from the original on October 29, 2013. Retrieved September 11, 2013.
  24. ^ Office of the Director, NIST (September 10, 2013). "Cryptographic Standards Statement". National Institute of Standsards in Technology. Archived from the original on September 12, 2013. Retrieved September 11, 2013.
  25. ^ "NIST Removes Cryptography Algorithm from Random Number Generator Recommendations". National Institute of Standards and Technology. April 21, 2014. Archived from the original on August 29, 2016.

External links

Advanced Encryption Standard process

The Advanced Encryption Standard (AES), the symmetric block cipher ratified as a standard by National Institute of Standards and Technology of the United States (NIST), was chosen using a process lasting from 1997 to 2000 that was markedly more open and transparent than its predecessor, the Data Encryption Standard (DES). This process won praise from the open cryptographic community, and helped to increase confidence in the security of the winning algorithm from those who were suspicious of backdoors in the predecessor, DES.

A new standard was needed primarily because DES has a relatively small 56-bit key which was becoming vulnerable to brute-force attacks. In addition, the DES was designed primarily for hardware and is relatively slow when implemented in software. While Triple-DES avoids the problem of a small key size, it is very slow even in hardware, it is unsuitable for limited-resource platforms, and it may be affected by potential security issues connected with the (today comparatively small) block size of 64 bits.

Box–Jenkins method

In time series analysis, the Box–Jenkins method, named after the statisticians George Box and Gwilym Jenkins, applies autoregressive moving average (ARMA) or autoregressive integrated moving average (ARIMA) models to find the best fit of a time-series model to past values of a time series.

Dataplot

Dataplot is a public domain software system for scientific visualization and statistical analysis. It was developed at the National Institute of Standards and Technology. Dataplot's source code is available.

EXPRESS (data modeling language)

EXPRESS is a standard data modeling language for product data. EXPRESS is formalized in the ISO Standard for the Exchange of Product model STEP (ISO 10303), and standardized as ISO 10303-11.

Federal Information Processing Standards

For the county code, see FIPS county code.Federal Information Processing Standards (FIPS) are publicly announced standards developed by the United States federal government for use in computer systems by non-military government agencies and government contractors.FIPS standards are issued to establish requirements for various purposes such as ensuring computer security and interoperability, and are intended for cases in which suitable industry standards do not already exist. Many FIPS specifications are modified versions of standards used in the technical communities, such as the American National Standards Institute (ANSI), the Institute of Electrical and Electronics Engineers (IEEE), and the International Organization for Standardization (ISO).

Information model

An information model in software engineering is a representation of concepts and the relationships, constraints, rules, and operations to specify data semantics for a chosen domain of discourse. Typically it specifies relations between kinds of things, but may also include relations with individual things. It can provide sharable, stable, and organized structure of information requirements or knowledge for the domain context.

JILA

JILA, formerly known as the Joint Institute for Laboratory Astrophysics, is a physical science research institute in the United States. JILA is located on the University of Colorado Boulder campus. JILA was founded in 1962 as a joint institute of The University of Colorado Boulder and the National Institute of Standards & Technology

MNIST database

The MNIST database (Modified National Institute of Standards and Technology database) is a large database of handwritten digits that is commonly used for training various image processing systems. The database is also widely used for training and testing in the field of machine learning. It was created by "re-mixing" the samples from NIST's original datasets. The creators felt that since NIST's training dataset was taken from American Census Bureau employees, while the testing dataset was taken from American high school students, it was not well-suited for machine learning experiments. Furthermore, the black and white images from NIST were normalized to fit into a 28x28 pixel bounding box and anti-aliased, which introduced grayscale levels.

The MNIST database contains 60,000 training images and 10,000 testing images. Half of the training set and half of the test set were taken from NIST's training dataset, while the other half of the training set and the other half of the test set were taken from NIST's testing dataset.

There have been a number of scientific papers on attempts to achieve the lowest error rate; one paper, using a hierarchical system of convolutional neural networks, manages to get an error rate on the MNIST database of 0.23%. The original creators of the database keep a list of some of the methods tested on it. In their original paper, they use a support vector machine to get an error rate of 0.8%. An extended dataset similar to MNIST called EMNIST has been published in 2017, which contains 240,000 training images, and 40,000 testing images of handwritten digits and characters.

Metre

The metre (British spelling and BIPM spelling) or meter (American spelling) (from the French unit mètre, from the Greek noun μέτρον, "measure") is the base unit of length in the International System of Units (SI). The SI unit symbol is m. The metre is defined as the length of the path travelled by light in vacuum in 1/299 792 458 of a second.The metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole – as a result the Earth's circumference is approximately 40,000 km today. In 1799, it was redefined in terms of a prototype metre bar (the actual bar used was changed in 1889). In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted.

The imperial inch is defined as 0.0254 metres (2.54 centimetres or 25.4 millimetres). One metre is about ​3 3⁄8 inches longer than a yard, i.e. about ​39 3⁄8 inches.

Partial autocorrelation function

In time series analysis, the partial autocorrelation function (PACF) gives the partial correlation of a stationary time series with its own lagged values, regressed the values of the time series at all shorter lags. It contrasts with the autocorrelation function, which does not control for other lags.

This function plays an important role in data analysis aimed at identifying the extent of the lag in an autoregressive model. The use of this function was introduced as part of the Box–Jenkins approach to time series modelling, whereby plotting the partial autocorrelative functions one could determine the appropriate lags p in an AR (p) model or in an extended ARIMA (p,d,q) model.

Personal data

Personal data, also known as personal information, personally identifying information (PII), or sensitive personal information (SPI), is any information relating to an identifiable person.

The abbreviation PII is widely accepted in the United States, but the phrase it abbreviates has four common variants based on personal / personally, and identifiable / identifying. Not all are equivalent, and for legal purposes the effective definitions vary depending on the jurisdiction and the purposes for which the term is being used. Under European and other data protection regimes, which centre primarily around the General Data Protection Regulation, the term "personal data" is significantly broader, and determines the scope of the regulatory regime.National Institute of Standards and Technology Special Publication 800-122 defines personally identifying information as "any information about an individual maintained by an agency, including (1) any information that can be used to distinguish or trace an individual's identity, such as name, social security number, date and place of birth, mother's maiden name, or biometric records; and (2) any other information that is linked or linkable to an individual, such as medical, educational, financial, and employment information." So, for example, a user's IP address is not classed as PII on its own, but is classified as linked PII. However in the European Union, the IP address of an Internet subscriber may be classed as personal data.The concept of PII has become prevalent as information technology and the Internet have made it easier to collect PII leading to a profitable market in collecting and reselling PII. PII can also be exploited by criminals to stalk or steal the identity of a person, or to aid in the planning of criminal acts. As a response to these threats, many website privacy policies specifically address the gathering of PII, and lawmakers such as the European Parliament have enacted a series of legislation such as the General Data Protection Regulation (GDPR) to limit the distribution and accessibility of PII.Personally identifying information is a legal concept, not a technical concept, and it is not utilised in all jurisdictions. Because of the versatility and power of modern re-identification algorithms, the absence of PII data does not mean that the remaining data does not identify individuals. While some attributes may not be uniquely identifying on their own, any attribute can be potentially identifying in combination with others. These attributes have been referred to as quasi-identifiers or pseudo-identifiers. While such data may not constitute PII in the United States, it is highly likely to remain personal data under European data protection law.

Physical constant

A physical constant, sometimes fundamental physical constant or universal constant, is a physical quantity that is generally believed to be both universal in nature and have constant value in time. It is contrasted with a mathematical constant, which has a fixed numerical value, but does not directly involve any physical measurement.

There are many physical constants in science, some of the most widely recognized being the speed of light in vacuum c, the gravitational constant G, the Planck constant h, the electric constant ε0, and the elementary charge e. Physical constants can take many dimensional forms: the speed of light signifies a maximum speed for any object and its dimension is length divided by time; while the fine-structure constant α, which characterizes the strength of the electromagnetic interaction, is dimensionless.

The term fundamental physical constant is sometimes used to refer to universal but dimensioned physical constants such as those mentioned above. Increasingly, however, physicists reserve the use of the term fundamental physical constant for dimensionless physical constants, such as the fine-structure constant α.

Physical constant in the sense under discussion in this article should not be confused with other quantities called "constants" that are assumed to be constant in a given context without the implication that they are fundamental, such as the "time constant" characteristic of a given system, or material constants, such as the Madelung constant, electrical resistivity, and heat capacity.

The International Bureau of Weights and Measures decided to redefine several SI base units as from 20 May 2019 by fixing the SI value of several physical constants, including the Planck constant, h, the elementary charge, e, the Boltzmann constant, kB, and the Avogadro constant, NA. The new fixed values are based on the best measurements of the constants based on the earlier definitions, including the kilogram, to ensure minimal impact. As a consequence, the uncertainty in the value of many physical constants when expressed in SI units will reduce substantially.

Precision engineering

Precision engineering is a subdiscipline of electrical engineering, software engineering, electronics engineering, mechanical engineering, and optical engineering concerned with designing machines, fixtures, and other structures that have exceptionally high tolerances, are repeatable, and are stable over time. These approaches have applications in machine tools, MEMS, NEMS, optoelectronics design, and many other fields.

Process Specification Language

The Process Specification Language (PSL) is a set of logic terms used to describe processes. The logic terms are specified in an ontology that provides a formal description of the components and their relationships that make up a process. The ontology was developed at the National Institute of Standards and Technology (NIST), and has been approved as an international standard in the document ISO 18629.

The Process Specification Language can be used for the representation of manufacturing, engineering and business processes, including production scheduling, process planning, workflow management, business process reengineering, simulation, process realization, process modelling, and project management. In the manufacturing domain, PSL's objective is to serve as a common representation for integrating several process-related applications throughout the manufacturing process life cycle.

Regression validation

In statistics, regression validation is the process of deciding whether the numerical results quantifying hypothesized relationships between variables, obtained from regression analysis, are acceptable as descriptions of the data. The validation process can involve analyzing the goodness of fit of the regression, analyzing whether the regression residuals are random, and checking whether the model's predictive performance deteriorates substantially when applied to data that were not used in model estimation.

Run chart

A run chart, also known as a run-sequence plot is a graph that displays observed data in a time sequence. Often, the data displayed represent some aspect of the output or performance of a manufacturing or other business process. It is therefore a form of line chart.

Slash distribution

In probability theory, the slash distribution is the probability distribution of a standard normal variate divided by an independent standard uniform variate. In other words, if the random variable Z has a normal distribution with zero mean and unit variance, the random variable U has a uniform distribution on [0,1] and Z and U are statistically independent, then the random variable XZ / U has a slash distribution. The slash distribution is an example of a ratio distribution. The distribution was named by William H. Rogers and John Tukey in a paper published in 1972.

The probability density function (pdf) is

where φ(x) is the probability density function of the standard normal distribution. The result is undefined at x = 0, but the discontinuity is removable:

The most common use of the slash distribution is in simulation studies. It is a useful distribution in this context because it has heavier tails than a normal distribution, but it is not as pathological as the Cauchy distribution.

Statistical graphics

Statistical graphics, also known as graphical techniques, are graphics in the field of statistics used to visualize quantitative data.

WWVH

WWVH is the callsign of the U.S. National Institute of Standards and Technology's shortwave radio time signal station in Kekaha, on the island of Kauai in the state of Hawaii.

WWVH is the Pacific sister station to WWV, and has a similar broadcast format. Like WWV, WWVH's main function is the dissemination of official U.S. Government time, through exactly the same methods as found on WWV's signal.

To minimize interference with the WWV broadcasts on the same frequencies, WWVH's broadcasts on 5, 10 and 15 MHz are directional, pointed primarily west. Despite this strategy, in certain places, particularly on the west coast of North America; and at certain times, due to ionospheric conditions, the listener can actually hear both WWV and WWVH on the same frequency at the same time. The information modulated on the carrier is modified to reduce confusion if both are received simultaneously. In particular, voice announcements on one correspond to silent periods on the other. WWVH uses a female voice to distinguish itself from WWV, which uses a male voice. WWVH time signals can also be accessed by telephone.

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