A barcode or bar code is a method of representing data in a visual, machine-readable form. Barcodes represented data by varying the widths and spacings of parallel lines; these barcodes, now referred to as linear or one-dimensional, can be scanned by special optical scanners, called barcode readers. Two-dimensional variants were developed, using rectangles, dots and other geometric patterns, called matrix codes or 2D barcodes, although they do not use bars as such. 2D barcodes can be read or deconstructed using application software on mobile devices with inbuilt cameras, such as smartphones. The barcode was invented by Norman Joseph Woodland and Bernard Silver and patented in the US in 1951; the invention was based on Morse code, extended to thin and thick bars. However, it took over twenty years. An early use of one type of barcode in an industrial context was sponsored by the Association of American Railroads in the late 1960s. Developed by General Telephone and Electronics and called KarTrak ACI, this scheme involved placing colored stripes in various combinations on steel plates which were affixed to the sides of railroad rolling stock.

Two plates were used per car, one on each side, with the arrangement of the colored stripes encoding information such as ownership, type of equipment, identification number. The plates were read by a trackside scanner, located for instance, at the entrance to a classification yard, while the car was moving past; the project was abandoned after about ten years because the system proved unreliable after long-term use. Barcodes became commercially successful when they were used to automate supermarket checkout systems, a task for which they have become universal; the Uniform Grocery Product Code Council had chosen, in 1973, the barcode design developed by George Laurer. Laurer's barcode, with vertical bars, printed better than the circular barcode developed by Woodland and Silver, their use has spread to many other tasks that are generically referred to as automatic identification and data capture. The first scanning of the now-ubiquitous Universal Product Code barcode was on a pack of Wrigley Company chewing gum in June 1974 at a Marsh supermarket in Troy, Ohio.

QR codes, a specific type of 2D barcode, have become popular. Other systems have made inroads in the AIDC market, but the simplicity and low cost of barcodes has limited the role of these other systems before technologies such as radio-frequency identification became available after 1995. In 1948 Bernard Silver, a graduate student at Drexel Institute of Technology in Philadelphia, Pennsylvania, US overheard the president of the local food chain, Food Fair, asking one of the deans to research a system to automatically read product information during checkout. Silver told his friend Norman Joseph Woodland about the request, they started working on a variety of systems, their first working system used ultraviolet ink, but the ink faded too and was expensive. Convinced that the system was workable with further development, Woodland left Drexel, moved into his father's apartment in Florida, continued working on the system, his next inspiration came from Morse code, he formed his first barcode from sand on the beach.

"I just extended the dots and dashes downwards and made narrow lines and wide lines out of them." To read them, he adapted technology from optical soundtracks in movies, using a 500-watt incandescent light bulb shining through the paper onto an RCA935 photomultiplier tube on the far side. He decided that the system would work better if it were printed as a circle instead of a line, allowing it to be scanned in any direction. On 20 October 1949, Woodland and Silver filed a patent application for "Classifying Apparatus and Method", in which they described both the linear and bull's eye printing patterns, as well as the mechanical and electronic systems needed to read the code; the patent was issued on 7 October 1952 as US Patent 2,612,994. In 1951, Woodland continually tried to interest IBM in developing the system; the company commissioned a report on the idea, which concluded that it was both feasible and interesting, but that processing the resulting information would require equipment, some time off in the future.

IBM offered to buy the patent. Philco purchased the patent in 1962 and sold it to RCA sometime later. During his time as an undergraduate, David Collins worked at the Pennsylvania Railroad and became aware of the need to automatically identify railroad cars. After receiving his master's degree from MIT in 1959, he started work at GTE Sylvania and began addressing the problem, he developed a system called KarTrak using blue and red reflective stripes attached to the side of the cars, encoding a six-digit company identifier and a four-digit car number. Light reflected off; the Boston and Maine Railroad tested the KarTrak system on their gravel cars in 1961. The tests continued until 1967, when the Association of American Railroads selected it as a standard, Automatic Car Identification, across the entire North American fleet; the installations began on 10 October 1967. However, the economic downturn and rash of bankruptcies in the industry in the early 1970s slowed the rollout, it was not until 1974 that 95% of the fleet was labeled.

To add to its woes, the system was found to be fooled by dirt in certain applications, which affected accuracy. The AAR abandoned the system in the late 1970s, it was not until the mid-1980s that they in

In statistics, the Ramsey Regression Equation Specification Error Test test is a general specification test for the linear regression model. More it tests whether non-linear combinations of the fitted values help explain the response variable; the intuition behind the test is that if non-linear combinations of the explanatory variables have any power in explaining the response variable, the model is misspecified in the sense that the data generating process might be better approximated by a polynomial or another non-linear functional form. The test was developed by James B. Ramsey as part of his Ph. D. thesis at the University of Wisconsin–Madison in 1968, published in the Journal of the Royal Statistical Society in 1969. Consider the model y ^ = E = β x; the Ramsey test tests whether 2, 3, …, k has any power in explaining y. This is executed by estimating the following linear regression y = α x + γ 1 y ^ 2 + ⋯ + γ k − 1 y ^ k + ε, testing, by a means of a F-test whether γ 1 through γ k − 1 are zero.

If the null-hypothesis that all γ coefficients are zero is rejected the model suffers from misspecification. Harvey–Collier test Long, J. Scott. "Some Specification Tests for the Linear Regression Model". In Bollen, Kenneth A.. Testing Structural Equation Models. London: Sage. pp. 66–110. ISBN 0-8039-4506-X. Thursby, J. G.. "Some Properties of Tests for Specification Error in a Linear Regression Model". Journal of the American Statistical Association. 72: 635–641. Doi:10.1080/01621459.1977.10480627. JSTOR 2286231. Wooldridge, Jeffrey M.. Introductory Econometrics – A Modern Approach. Cengage Learning. Pp. 273–278. ISBN 978-1-305-27010-7

The 7th Air Division was a land-based aviation force of the Imperial Japanese Army. The division was formed on 29 January 1943 in the Netherlands East Indies as part of the Eighth Area Army, it was incorporated into the Fourth Air Army based at Rabaul on 28 July 1943. The division moved its headquarters to Wewak in June 1943; the division was disbanded 24 July 1945. Lt. General Einosuke Sudō Lt. General Chōji Shirokane 59th Hikō Sentai 5th Hikō Sentai 7th Hikō Sentai 61st Hikō Sentai List of air divisions of the Imperial Japanese Army Shindo, Hiroyuki. 2001, Japanese air operations over New Guinea during the Second World War, Journal of the Australian War Memorial. Rekishi Dokuhon, Document of the war No. 42 Overview of Imperial Japanese Army Units, Shin-Jinbutsuoraisha Co. Ltd. Tōkyō, Japan, 1998, ISBN 4-404-02639-0