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Error detection and correction

In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels. Many communication channels are subject to channel noise, thus errors may be introduced during transmission from the source to a receiver. Error detection techniques allow detecting such errors, while error correction enables reconstruction of the original data in many cases. Error detection is the detection of errors caused by noise or other impairments during transmission from the transmitter to the receiver. Error correction is the detection of errors and reconstruction of the error-free data; the modern development of error correction codes is credited to Richard Hamming in 1947. A description of Hamming's code appeared in Claude Shannon's A Mathematical Theory of Communication and was generalized by Marcel J. E. Golay. All error-detection and correction schemes add some redundancy to a message, which receivers can use to check consistency of the delivered message, to recover data, determined to be corrupted.

Error-detection and correction schemes can be either non-systematic. In a systematic scheme, the transmitter sends the original data, attaches a fixed number of check bits, which are derived from the data bits by some deterministic algorithm. If only error detection is required, a receiver can apply the same algorithm to the received data bits and compare its output with the received check bits. In a system that uses a non-systematic code, the original message is transformed into an encoded message carrying the same information and that has at least as many bits as the original message. Good error control performance requires the scheme to be selected based on the characteristics of the communication channel. Common channel models include memoryless models where errors occur randomly and with a certain probability, dynamic models where errors occur in bursts. Error-detecting and correcting codes can be distinguished between random-error-detecting/correcting and burst-error-detecting/correcting.

Some codes can be suitable for a mixture of random errors and burst errors. If the channel characteristics cannot be determined, or are variable, an error-detection scheme may be combined with a system for retransmissions of erroneous data; this is known as automatic repeat request, is most notably used in the Internet. An alternate approach for error control is hybrid automatic repeat request, a combination of ARQ and error-correction coding. There are three major types of error correction. Automatic Repeat reQuest is an error control method for data transmission that makes use of error-detection codes, acknowledgment and/or negative acknowledgment messages, timeouts to achieve reliable data transmission. An acknowledgment is a message sent by the receiver to indicate that it has received a data frame; when the transmitter does not receive the acknowledgment before the timeout occurs, it retransmits the frame until it is either received or the error persists beyond a predetermined number of retransmissions.

Three types of ARQ protocols are Stop-and-wait ARQ, Go-Back-N ARQ, Selective Repeat ARQ. ARQ is appropriate if the communication channel has varying or unknown capacity, such as is the case on the Internet. However, ARQ requires the availability of a back channel, results in increased latency due to retransmissions, requires the maintenance of buffers and timers for retransmissions, which in the case of network congestion can put a strain on the server and overall network capacity. For example, ARQ is used on shortwave radio data links in the form of ARQ-E, or combined with multiplexing as ARQ-M. Forward error correction is a process of adding redundant data such as an error-correcting code to a message so that it can be recovered by a receiver when a number of errors were introduced, either during the process of transmission, or on storage. Since the receiver does not have to ask the sender for retransmission of the data, a backchannel is not required in forward error correction, it is therefore suitable for simplex communication such as broadcasting.

Error-correcting codes are used in lower-layer communication, as well as for reliable storage in media such as CDs, DVDs, hard disks, RAM. Error-correcting codes are distinguished between convolutional codes and block codes: Convolutional codes are processed on a bit-by-bit basis, they are suitable for implementation in hardware, the Viterbi decoder allows optimal decoding. Block codes are processed on a block-by-block basis. Early examples of block codes are repetition codes, Hamming codes and multidimensional parity-check codes, they were followed by a number of efficient codes, Reed–Solomon codes being the most notable due to their current widespread use. Turbo codes and low-density parity-check codes are new constructions that can provide optimal efficiency. Shannon's theorem is an important theorem in forward error correction, describes the maximum information rate at which reliable communication is possible over a channel that has a certain error probability or signal-to-noise ratio; this strict upper limit is expressed in terms of the channel capacity.

More the theorem says that there exist codes such that with increasing encoding length the

Craig Demmin

Craig Demmin is a retired Trinidad soccer defender who played professionally in Major League Soccer and the USL First Division. Demmin attended Belhaven University, playing on the men's soccer team from 1990 to 1993, he was 1993 First Team NAIA All American. In 1992, Demmin and his team mates won the NAIA national men's soccer championship. In 2008, he was inducted into the school's Athletic Hall of Fame. Demmin played for East Fife F. C. before playing in Major League Soccer for the Tampa Bay Mutiny in 2001. Demmin had two stints with the Rochester Raging Rhinos, was playing for the Virginia Beach Mariners at the time of their demise in 2006. Demmin was named to the A-League All-Star Team five times while playing for Rochester. Demmin represented the Trinidad and Tobago national team from 1995 to 2003. Demmin is an assistant coach with the Monroe Community College women's soccer team. On August 11, 2011, the Rochester Lancers named Demmin as assistant coach. 2001 Soccer America Craig Demmin at Major League Soccer Craig Demmin – FIFA competition record

Prezel Hardy

Prezel Hardy Jr. is an American sprinter who specializes in the 100 meters. At the 2009 World Youth Championships in Athletics in Brixen, Hardy won the 100 meters in 10.57 in the midst of heavy rain. Hardy attends Texas A&M University in Texas. At the 2009 Texas State high school meet he won the State 5A title in the 100 meters in 10.08 seconds, which would have bettered the World youth record of 10.23 set by Tamunosiki Atorudibo in 2002 and tied by Rynell Parson in 2007 had it not been for the wind assistance of 2.2 meters per second. However, his time made him the third fastest performer in high school history, behind only Jeffery Demps and J-Mee Samuels, a new Texas state record, beating the previous record set by Henry Neal of Greenville with a time of 10.15 seconds in 1990. He was named to the 2009 All-USA Field Team by USA Today. Hardy plans to participate in the 2012 Summer Olympics in London, he lists Tyson Gay as his athletic role model. At Ellison, Hardy is a member of the football varsity, playing running back and wide receiver.

Texas A&M Aggies bio

Blackmail (2005 film)

Blackmail is a 2005 Indian Hindi-language action thriller film directed by Anil Devgan, which stars Suniel Shetty, Ajay Devgn and Priyanka Chopra in the lead roles. The film is inspired by the 1996 Hollywood film Ransom; this was the second movie directed by Ajay Devgn's brother Anil Devgan. He directed Raju Chacha earlier in the year 2000. Inspector Abhay Rathod is an diligent police inspector employed with the Bombay police, he is assigned criminal don, Shekhar Mohan. Abhay entraps and arrests him, has him sentenced to a long jail term. Years Abhay is the Assistant Commissioner of Police, a happy family man with his wife and son Chirag. Shekhar Mohan is looking to seek vengeance against Abhay, he does taking him along with him. The objective for the kidnapping was to trace his lost son, whose information he feels, is with Abhay. After several attempts to get the answer, Shekhar tricks Abhay by making him feel that he has killed Chirag. Abhay's wife, informs Shekhar that Chirag is his son. Shekhar tries to get Chirag's affection and love.

Shekhar finds out that Chirag loves racing and takes him on various race courses where the child is thrilled to watch fast sports cars, soon starts a friendship with "Uncle" Shekhar. But, with Abhay and the police closing in fast, will Shekhar and Chirag be able to maintain their friendship? Suniel Shetty as Abhay Rathod Ajay Devgn as Shekhar Mohan Dia Mirza as Mrs. Anjali Mohan Priyanka Chopra as Mrs. Sanjana Rathod Parth Dave as Chirag Rathod Mukesh Rishi as Chhota Monalisa as Item girl All songs were composed by Himesh Reshammiya while all lyrics were penned by Sameer Track Listing Blackmail on IMDb

Dietmar Bonnen

Dietmar Bonnen is a German composer and pianist. Dietmar Bonnen studied fine arts in Cologne and Düsseldorf. In 1981 he founded the avantgarde-rock ensemble Fleisch, with whom he recorded several CDs with his own compositions. After two years of production he published a CD called “Bonnen spielt …” with organ music of the 20th century; this production was the first, which combined different organs and acoustics from different churches made possible by recording techniques taken from pop music. Beside works of György Ligeti, Paul Hindemith, Charles Ives and Max Reger, he played compositions written for this project and that cannot be performed on conventional organs, it contains premieres of two works of John Cage. Bonnen produced several CDs in several different musical genres, as for example the soundscape-composition “Bonnen in Beijing”, recorded 1993/94 for WDR in Beijing and Cologne. Other works present music of other composers in new arrangements. Examples are CDs with music of Frank Zappa, Hildegard von Bingen, Jimi Hendrix, Kurt Weill, Willie Dixon and Claudio Monteverdi.

Concerts in Europe, South America and Russia led to intensive collaborations with foreign artists and to the foundation of the “Russian-German Composers Quartet” with Alexei Aigui and Ivan Glebovich Sokolov from Moscow, Manfred Niehaus and Dietmar Bonnen from Cologne. Bonnen is the director of the chamber choir Les Saxosythes, he has more than 70 CD productions in different musical genres, composition commissions for different broadcasting companies and theatres to his name. Important for his own composing are the works of Johann Sebastian Bach, Jimi Hendrix, Pier Paolo Pasolini, Joseph Beuys and John Cage, whose pieces can be found in many of Bonnen's productions. Die Nachtwache Beijing Muspilli Algarabia Adagio Gazimagusa Knäuel Quatuor plus 2 Die Wolke des Vergessens Ouroboros i.m. J. C. Blau Früher, als wir die großen Ströme noch … with Peter Rühmkorf and Andreas Schilling Archangelos, Solovki Ben und seine Freunde im Konzert with Peter Hölscher and Andreas Schilling bukhara with Andreas Schilling Thai Ryoan-ji Medea Chronotopia archet-en-ciel axis with Arkady Marto New York City Museums Cycle Music I Forgot To Compose Meetings With Remarkable Melodies Sphera with Arkady Marto


Adamantinasuchus is an extinct genus of notosuchian crocodylomorph from and named after the Late Cretaceous Adamantina Formation of Brazil. It is known from holotype UFRJ-DG 107-R, collected by William Nava; the fossil consists of a partial skull, fragmentary limb bones and a few brokenen vertebrae, was found 25 km SW of the town of Marilia, near a reservoir dam. Adamantinasuchus was 60 cm long from nose to tail, would have only weighed a few kilograms. Adamantinasuchus's skull is quite well preserved; the right lower jaw is preserved, along with many of the teeth. The skull is small, only 60 mm long and around 30 mm high, but the elliptical orbits are large as long as the rostrum, which might suggest the animal was nocturnal; the premaxilla is covered in grooves and ridges, making it the most ornamented bone from the entire fossil. At the anterior end the premaxillae come together in a short triangular projection pointing ventrally and in another pointing dorsally; these would have been connected by a cartilaginous septum separating the two external nares, although this has not been preserved.

The premaxilla bears one caniniform tooth. The maxillary dentition appears to bear out this theory as it bears seven molariform teeth of varying sizes; the maxilla itself is triangular, with a long anteroposterior base at the ventral side of, a thin crest that covers the border of the dental alveoli. Towards the posterior end the maxilla is elongated, it forms a long suture with the jugal beneath the large orbits. There are two large foramina at the posterior end of the maxilla, three small foramina at the anterior end, close to the premaxillary-maxillary border where another foramen is located; the nasal bone is incompletely preserved. The nasal projects back far enough to contact the frontal bone with a short blade; the prefrontal is triangular, both left and right prefrontals are preserved, although the left prefrontal is only fragmentary. The prefrontal and frontal bones form a sinuous suture, although not a interdigitating one; the prefrontal's outer surface is smooth due to contact with a palpebral bone.

The lacrimal bone is small and has no distinguishing features, but contacts all of the nasal and frontal bones. The frontal is weakly convex in the middle and the anterior, but the posterior area of it is flattened. Although the parietal bone is not preserved, the interdigitating suture between parietal and frontal is still present, as is the crest across the bone here in the medial part; the postorbital is fragmentary. The jugal is thin, with three branches, its outer surface is smooth and there is a large foramen in the anterior section of the bone, close to the thin crest in the medial portion that comes to a slender edge. The jugal is arched medially, curving out laterally away from the orbit, is widest just behind the long suture with the maxilla, tapering to a bladelike portion at the posterior end; the postorbital bar is vertical, with an oval cross-section. The quadratojugal is just behind the laterotemporal fenestra, is slender and branched; the lower jaw as a whole is laterally compressed and curved anteroposteriorly, so that the narrow ventral surface is convex and the jaw forms a half-moon shape.

The mandibular fenestra is elliptical, does not excavate the dentary noticeably, rather remaining between angular and surangular. The dorsal end of the dentary extends posteriorly around part of the surangular; the surangular is tallest in the anterior portion. A lateral projection extends from it to cover the mandibular fenestra. At the posterior end the surangular is closer to cylindrical; the angular is medially excavated by the mandibular fenestra, forms a vertical contact zone with the dentary. The dentary carries three teeth on the preserved portion, which resemble those on the maxilla; the teeth are noticeably heterodont in Adamantinasuchus, with a mixture of incisiform and molariform teeth. The first two teeth in the premaxilla are incisiform; the third premaxillary tooth is caniniform and is much larger than the incisiform teeth, though it is a similar conical shape. Its tip points backwards, the crown bears small grooves. All seven maxillary teeth are molariform, though they vary in size.

All the maxillary teeth have one deep root, oval in cross-section, there is a slight constriction between this and the crown of the teeth, which are flattened obliquely to produce a spatulate shape. The outer surfaces of the maxillary teeth are smooth and bear a few grooves, whereas the inner surfaces are covered in denticles that grow smaller towards the tip of each tooth; the two large central molariform teeth have a second set of denticles around the base of the inner surfac