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Ammunition | Design | For example, ammunition for hunting can be designed to expand inside a target, maximizing the damage inflicted by one round. Anti-personnel shells are designed to fragment into many pieces and can affect a large area. Armor-piercing rounds are specially hardened to penetrate armor, while smoke ammunition covers an area with a fog that screens people from view. More generic ammunition (e.g., 5.56×45mm NATO) can often be altered slightly to give it a more specific effect (e.g., tracer, incendiary), whilst larger explosive rounds can be altered by using different fuzes. |
Ammunition | Components | The components of ammunition intended for rifles and munitions may be divided into these categories: fuze or primer explosive materials and propellants projectiles of all kinds cartridge casing Fuzes The term fuze refers to the detonator of an explosive round or shell. The spelling is different in British English and American English (fuse/fuze respectively) and they are unrelated to a fuse (electrical). A fuse was earlier used to ignite the propellant (e.g., such as on a firework) until the advent of more reliable systems such as the primer or igniter that is used in most modern ammunition. |
Ammunition | Components | The fuze of a weapon can be used to alter how the ammunition works. For example, a common artillery shell fuze can be set to "point detonation" (detonation when it hits a target), delay (detonate after it has hit and penetrated a target), time-delay (explode a specified time after firing or impact) and proximity (explode above or next to a target without hitting it, such as for airburst effects or anti-aircraft shells). These allow a single ammunition type to be altered to suit the situation it is required for. There are many designs of a fuze, ranging from simple mechanical to complex radar and barometric systems. |
Ammunition | Components | Fuzes are usually armed by the acceleration force of firing the projectile, and usually arm several meters after clearing the bore of the weapon. This helps to ensure the ammunition is safer to handle when loading into the weapon and reduces the chance of the detonator firing before the ammunition has cleared the weapon. |
Ammunition | Components | Propellant or explosive The propellant is the component of ammunition that is activated inside the weapon and provides the kinetic energy required to move the projectile from the weapon to the target. Before the use of gunpowder, this energy would have been produced mechanically by the weapons system (e.g., a catapult or crossbow); in modern times, it is usually a form of chemical energy that rapidly burns to create kinetic force, and an appropriate amount of chemical propellant is packaged with each round of ammunition. In recent years, compressed gas, magnetic energy and electrical energy have been used as propellants. |
Ammunition | Components | Until the 20th-century, gunpowder was the most common propellant in ammunition. However, it has since been replaced by a wide range of fast-burning compounds that are more reliable and efficient.
The propellant charge is distinct from the projectile charge which is activated by the fuze, which causes the ammunition effect (e.g., the exploding of an artillery round). |
Ammunition | Components | Cartridge case or container The cartridge is the container that holds the projectile and propellant. Not all ammunition types have a cartridge case. In its place, a wide range of materials can be used to contain the explosives and parts. With some large weapons, the ammunition components are stored separately until loaded into the weapon system for firing. With small arms, caseless ammunition can reduce the weight and cost of ammunition, and simplify the firing process for increased firing rate, but the maturing technology has functionality issues. |
Ammunition | Components | Projectile The projectile is the part of the ammunition that leaves the weapon and has the effect on the target. This effect is usually either kinetic (e.g., as with a standard bullet) or through the delivery of explosives. |
Ammunition | Storage | An ammunition dump is a military facility for the storage of live ammunition and explosives that will be distributed and used at a later date. Such a storage facility is extremely hazardous, with the potential for accidents when unloading, packing, and transferring the ammunition. In the event of a fire or explosion, the site and its surrounding area is immediately evacuated and the stored ammunition is left to detonate itself completely with limited attempts at firefighting from a safe distance. In large facilities, there may be a flooding system to automatically extinguish a fire or prevent an explosion. Typically, an ammunition dump will have a large buffer zone surrounding it, to avoid casualties in the event of an accident. There will also be perimeter security measures in place to prevent access by unauthorized personnel and to guard against the potential threat from enemy forces. |
Ammunition | Storage | A magazine is a place where a quantity of ammunition or other explosive material is stored temporarily prior to being used. The term may be used for a facility where large quantities of ammunition are stored, although this would normally be referred to as an ammunition dump. Magazines are typically located in the field for quick access when engaging the enemy. The ammunition storage area on a warship is referred to as the "ship's magazine". On a smaller scale, magazine is also the name given to the ammunition storage and feeding device of a repeating firearm. |
Ammunition | Storage | Gunpowder must be stored in a dry place (stable room temperature) to keep it usable, as long as for 10 years. It is also recommended to avoid hot places, because friction or heat might ignite a spark and cause an explosion. |
Ammunition | Common types | Small arms The standard weapon of a modern soldier is an assault rifle, which, like other small arms, uses cartridge ammunition in a size specific to the weapon. Ammunition is carried on the person in box magazines specific to the weapon, ammunition boxes, pouches or bandoliers. The amount of ammunition carried is dependent on the strength of the soldier, the expected action required, and the ability of ammunition to move forward through the logistical chain to replenish the supply. A soldier may also carry a smaller amount of specialized ammunition for heavier weapons such as machine guns and mortars, spreading the burden for squad weapons over many people. Too little ammunition poses a threat to the mission, while too much limits the soldier's mobility also being a threat to the mission. |
Ammunition | Common types | Shells A shell is a payload-carrying projectile which, as opposed to a shot, contains explosives or other fillings, in use since the 19th century. |
Ammunition | Common types | Artillery Artillery shells are ammunition that is designed to be fired from artillery which has an effect over long distances, usually indirectly (i.e., out of sight of the target). There are many different types of artillery ammunition, but they are usually high-explosive and designed to shatter into fragments on impact to maximize damage. The fuze used on an artillery shell can alter how it explodes or behaves so it has a more specialized effect. Common types of artillery ammunition include high explosive, smoke, illumination, and practice rounds. Some artillery rounds are designed as cluster munitions. Artillery ammunition will almost always include a projectile (the only exception being demonstration or blank rounds), fuze and propellant of some form. When a cartridge case is not used, there will be some other method of containing the propellant bags, usually a breech-loading weapon; see Breechloader. |
Ammunition | Common types | Tank Tank ammunition was developed in WWI as tanks first appeared on the battlefield. However, as tank-on-tank warfare developed (including the development of anti-tank warfare artillery), more specialized forms of ammunition were developed such as high-explosive anti-tank (HEAT) warheads and armour-piercing discarding sabot (APDS), including armour-piercing fin-stabilized discarding sabot (APFSDS) rounds. The development of shaped charges has had a significant impact on anti-tank ammunition design, now common in both tank-fired ammunition and in anti-tank missiles, including anti-tank guided missiles. |
Ammunition | Common types | Naval Naval weapons were originally the same as many land-based weapons, but the ammunition was designed for specific use, such as a solid shot designed to hole an enemy ship and chain-shot to cut rigging and sails. Modern naval engagements have occurred over far longer distances than historic battles, so as ship armor has increased in strength and thickness, the ammunition to defeat it has also changed. Naval ammunition is now designed to reach very high velocities (to improve its armor-piercing abilities) and may have specialized fuzes to defeat specific types of vessels. However, due to the extended ranges at which modern naval combat may occur, guided missiles have largely supplanted guns and shells. |
Ammunition | Logistics | With every successive improvement in military arms, a corresponding modification has occurred in the method of supplying ammunition in the quantity required. As soon as projectiles were required (such as javelins and arrows), there needed to be a method of replenishment. When non-specialized, interchangeable or recoverable ammunition was used (e.g., arrows), it was possible to pick up spent arrows (both friendly and enemy) and reuse them. However, with the advent of explosive or non-recoverable ammunition, this was no longer possible and new supplies of ammunition would be needed. |
Ammunition | Logistics | The weight of ammunition required, particularly for artillery shells, can be considerable, causing a need for extra time to replenish supplies. In modern times, there has been an increase in the standardization of many ammunition types between allies (e.g., the NATO Standardization Agreement) that has allowed for shared ammunition types (e.g., 5.56×45mm NATO). |
Ammunition | Environmental problems | As of 2013, lead-based ammunition production is the second-largest annual use of lead in the US, accounting for over 60,000 metric tons consumed in 2012. In contrast to the closed-loop nature of the largest annual use of lead (i.e. for lead-acid batteries, nearly all of which are, at the end of their lives, collected and recycled into new lead-acid batteries), the lead in ammunition ends up being almost entirely dispersed into the natural environment. For example, lead bullets that miss their target or remain in a carcass or body that was never retrieved can very easily enter environmental systems and become toxic to wildlife. The US military has experimented with replacing lead with copper as a slug in their green bullets which reduces the dangers posed by lead in the environment as a result of artillery. Since 2010, this has eliminated over 2000 tons of lead in waste streams.Hunters are also encouraged to use monolithic bullets, which exclude any lead content. |
Ammunition | Unexploded ordnance | Unexploded ammunition can remain active for a very long time and poses a significant threat to both humans and the environment. |
Generalized minimal residual method | Generalized minimal residual method | In mathematics, the generalized minimal residual method (GMRES) is an iterative method for the numerical solution of an indefinite nonsymmetric system of linear equations. The method approximates the solution by the vector in a Krylov subspace with minimal residual. The Arnoldi iteration is used to find this vector. |
Generalized minimal residual method | Generalized minimal residual method | The GMRES method was developed by Yousef Saad and Martin H. Schultz in 1986. It is a generalization and improvement of the MINRES method due to Paige and Saunders in 1975. The MINRES method requires that the matrix is symmetric, but has the advantage that it only requires handling of three vectors. GMRES is a special case of the DIIS method developed by Peter Pulay in 1980. DIIS is applicable to non-linear systems. |
Generalized minimal residual method | The method | Denote the Euclidean norm of any vector v by ‖v‖ . Denote the (square) system of linear equations to be solved by The matrix A is assumed to be invertible of size m-by-m. Furthermore, it is assumed that b is normalized, i.e., that ‖b‖=1 The n-th Krylov subspace for this problem is where r0=b−Ax0 is the initial error given an initial guess x0≠0 . Clearly r0=b if x0=0 GMRES approximates the exact solution of Ax=b by the vector xn∈Kn that minimizes the Euclidean norm of the residual rn=b−Axn The vectors r0,Ar0,…An−1r0 might be close to linearly dependent, so instead of this basis, the Arnoldi iteration is used to find orthonormal vectors q1,q2,…,qn which form a basis for Kn . In particular, q1=‖r0‖2−1r0 Therefore, the vector xn∈Kn can be written as xn=x0+Qnyn with yn∈Rn , where Qn is the m-by-n matrix formed by q1,…,qn . In other words, finding finding the n-th approximation of the solution (i.e., xn ) is reduced to finding the vector yn , which is determined via minimizing the residue as described below. |
Generalized minimal residual method | The method | The Arnoldi process also constructs H~n , an ( n+1 )-by- n upper Hessenberg matrix which satisfies an equality which is used to simplify the calculation of yn (see below). Note that, for symmetric matrices, a symmetric tri-diagonal matrix is actually achieved, resulting in the MINRES method.
Because columns of Qn are orthonormal, we have where is the first vector in the standard basis of Rn+1 , and r0 being the first trial vector (usually zero). Hence, xn can be found by minimizing the Euclidean norm of the residual This is a linear least squares problem of size n. |
Generalized minimal residual method | The method | This yields the GMRES method. On the n -th iteration: calculate qn with the Arnoldi method; find the yn which minimizes ‖rn‖ compute xn=x0+Qnyn repeat if the residual is not yet small enough.At every iteration, a matrix-vector product Aqn must be computed. This costs about 2m2 floating-point operations for general dense matrices of size m , but the cost can decrease to O(m) for sparse matrices. In addition to the matrix-vector product, O(nm) floating-point operations must be computed at the n -th iteration. |
Generalized minimal residual method | Convergence | The nth iterate minimizes the residual in the Krylov subspace Kn . Since every subspace is contained in the next subspace, the residual does not increase. After m iterations, where m is the size of the matrix A, the Krylov space Km is the whole of Rm and hence the GMRES method arrives at the exact solution. However, the idea is that after a small number of iterations (relative to m), the vector xn is already a good approximation to the exact solution. |
Generalized minimal residual method | Convergence | This does not happen in general. Indeed, a theorem of Greenbaum, Pták and Strakoš states that for every nonincreasing sequence a1, ..., am−1, am = 0, one can find a matrix A such that the ‖rn‖ = an for all n, where rn is the residual defined above. In particular, it is possible to find a matrix for which the residual stays constant for m − 1 iterations, and only drops to zero at the last iteration. |
Generalized minimal residual method | Convergence | In practice, though, GMRES often performs well. This can be proven in specific situations. If the symmetric part of A, that is (AT+A)/2 , is positive definite, then where λmin(M) and λmax(M) denote the smallest and largest eigenvalue of the matrix M , respectively.If A is symmetric and positive definite, then we even have where κ2(A) denotes the condition number of A in the Euclidean norm. |
Generalized minimal residual method | Convergence | In the general case, where A is not positive definite, we have where Pn denotes the set of polynomials of degree at most n with p(0) = 1, V is the matrix appearing in the spectral decomposition of A, and σ(A) is the spectrum of A. Roughly speaking, this says that fast convergence occurs when the eigenvalues of A are clustered away from the origin and A is not too far from normality.All these inequalities bound only the residuals instead of the actual error, that is, the distance between the current iterate xn and the exact solution. |
Generalized minimal residual method | Extensions of the method | Like other iterative methods, GMRES is usually combined with a preconditioning method in order to speed up convergence. |
Generalized minimal residual method | Extensions of the method | The cost of the iterations grow as O(n2), where n is the iteration number. Therefore, the method is sometimes restarted after a number, say k, of iterations, with xk as initial guess. The resulting method is called GMRES(k) or Restarted GMRES. For non-positive definite matrices, this method may suffer from stagnation in convergence as the restarted subspace is often close to the earlier subspace. |
Generalized minimal residual method | Extensions of the method | The shortcomings of GMRES and restarted GMRES are addressed by the recycling of Krylov subspace in the GCRO type methods such as GCROT and GCRODR.
Recycling of Krylov subspaces in GMRES can also speed up convergence when sequences of linear systems need to be solved. |
Generalized minimal residual method | Comparison with other solvers | The Arnoldi iteration reduces to the Lanczos iteration for symmetric matrices. The corresponding Krylov subspace method is the minimal residual method (MinRes) of Paige and Saunders. Unlike the unsymmetric case, the MinRes method is given by a three-term recurrence relation. It can be shown that there is no Krylov subspace method for general matrices, which is given by a short recurrence relation and yet minimizes the norms of the residuals, as GMRES does. |
Generalized minimal residual method | Comparison with other solvers | Another class of methods builds on the unsymmetric Lanczos iteration, in particular the BiCG method. These use a three-term recurrence relation, but they do not attain the minimum residual, and hence the residual does not decrease monotonically for these methods. Convergence is not even guaranteed.
The third class is formed by methods like CGS and BiCGSTAB. These also work with a three-term recurrence relation (hence, without optimality) and they can even terminate prematurely without achieving convergence. The idea behind these methods is to choose the generating polynomials of the iteration sequence suitably.
None of these three classes is the best for all matrices; there are always examples in which one class outperforms the other. Therefore, multiple solvers are tried in practice to see which one is the best for a given problem. |
Generalized minimal residual method | Solving the least squares problem | One part of the GMRES method is to find the vector yn which minimizes Note that H~n is an (n + 1)-by-n matrix, hence it gives an over-constrained linear system of n+1 equations for n unknowns. |
Generalized minimal residual method | Solving the least squares problem | The minimum can be computed using a QR decomposition: find an (n + 1)-by-(n + 1) orthogonal matrix Ωn and an (n + 1)-by-n upper triangular matrix R~n such that The triangular matrix has one more row than it has columns, so its bottom row consists of zero. Hence, it can be decomposed as where Rn is an n-by-n (thus square) triangular matrix. |
Generalized minimal residual method | Solving the least squares problem | The QR decomposition can be updated cheaply from one iteration to the next, because the Hessenberg matrices differ only by a row of zeros and a column: where hn+1 = (h1,n+1, …, hn+1,n+1)T. This implies that premultiplying the Hessenberg matrix with Ωn, augmented with zeroes and a row with multiplicative identity, yields almost a triangular matrix: This would be triangular if σ is zero. To remedy this, one needs the Givens rotation where With this Givens rotation, we form Indeed, is a triangular matrix with rn+1,n+1=ρ2+σ2 Given the QR decomposition, the minimization problem is easily solved by noting that Denoting the vector βΩne1 by with gn ∈ Rn and γn ∈ R, this is The vector y that minimizes this expression is given by Again, the vectors gn are easy to update. |
Generalized minimal residual method | Example code | Regular GMRES (MATLAB / GNU Octave) |
Generalized minimal residual method | Notes | A. Meister, Numerik linearer Gleichungssysteme, 2nd edition, Vieweg 2005, ISBN 978-3-528-13135-7.
Y. Saad, Iterative Methods for Sparse Linear Systems, 2nd edition, Society for Industrial and Applied Mathematics, 2003. ISBN 978-0-89871-534-7.
Y. Saad and M.H. Schultz, "GMRES: A generalized minimal residual algorithm for solving nonsymmetric linear systems", SIAM J. Sci. Stat. Comput., 7:856–869, 1986. doi:10.1137/0907058.
S. C. Eisenstat, H.C. Elman and M.H. Schultz, "Variational iterative methods for nonsymmetric systems of linear equations", SIAM Journal on Numerical Analysis, 20(2), 345–357, 1983.
J. Stoer and R. Bulirsch, Introduction to numerical analysis, 3rd edition, Springer, New York, 2002. ISBN 978-0-387-95452-3.
Lloyd N. Trefethen and David Bau, III, Numerical Linear Algebra, Society for Industrial and Applied Mathematics, 1997. ISBN 978-0-89871-361-9. |
Generalized minimal residual method | Notes | Dongarra et al. , Templates for the Solution of Linear Systems: Building Blocks for Iterative Methods, 2nd Edition, SIAM, Philadelphia, 1994 Amritkar, Amit; de Sturler, Eric; Świrydowicz, Katarzyna; Tafti, Danesh; Ahuja, Kapil (2015). "Recycling Krylov subspaces for CFD applications and a new hybrid recycling solver". Journal of Computational Physics 303: 222. doi:10.1016/j.jcp.2015.09.040 Imankulov T, Lebedev D, Matkerim B, Daribayev B, Kassymbek N. Numerical Simulation of Multiphase Multicomponent Flow in Porous Media: Efficiency Analysis of Newton-Based Method. Fluids. 2021; 6(10):355. https://doi.org/10.3390/fluids6100355 |
Geologic Calendar | Geologic Calendar | The Geologic Calendar is a scale in which the geological lifetime of the Earth is mapped onto a calendrical year; that is to say, the day one of the Earth took place on a geologic January 1 at precisely midnight, and today's date and time is December 31 at midnight. On this calendar, the inferred appearance of the first living single-celled organisms, prokaryotes, occurred on a geologic February 25 around 12:30 pm to 1:07 pm, dinosaurs first appeared on December 13, the first flower plants on December 22 and the first primates on December 28 at about 9:43 pm. The first Anatomically modern humans did not arrive until around 11:48 p.m. on New Year's Eve, and all of human history since the end of the last ice-age occurred in the last 82.2 seconds before midnight of the new year. A variation of this analogy instead compresses Earth's 4.6 billion year-old history into a single day: While the Earth still forms at midnight, and the present day is also represented by midnight, the first life on Earth would appear at 4:00 am, dinosaurs would appear at 10:00 pm, the first flowers 10:30 pm, the first primates 11:30 pm, and modern humans would not appear until the last two seconds of 11:59 pm. A third analogy, created by University of Washington paleontologist Peter Ward and astronomer Donald Brownlee, who are both famous for their Rare Earth hypothesis, for their book The Life and Death of Planet Earth, alters the calendar so it includes the Earth's future leading up to the Sun's death in the next 5 billion years. As a result, each month now represents 1 of 12 billion years of the Earth's life. According to this calendar, the first life appears in January, and the first animals first appeared in May, with the present day taking place on May 18, even though the Sun won't destroy Earth until December 31, all animals will die out by the end of May. |
Alpha-1,3-glucan synthase | Alpha-1,3-glucan synthase | In enzymology, an alpha-1,3-glucan synthase (EC 2.4.1.183) is an enzyme that catalyzes the chemical reaction UDP-glucose + [alpha-D-glucosyl-(1-3)]n ⇌ UDP + [alpha-D-glucosyl-(1-3)]n+1Thus, the two substrates of this enzyme are UDP-glucose and [[[alpha-D-glucosyl-(1-3)]n]], whereas its two products are UDP and [[[alpha-D-glucosyl-(1-3)]n+1]].
This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. The systematic name of this enzyme class is UDP-glucose:alpha-D-(1-3)-glucan 3-alpha-D-glucosyltransferase. Other names in common use include uridine diphosphoglucose-1,3-alpha-glucan glucosyltransferase, and 1,3-alpha-D-glucan synthase. |
Opaline glass | Opaline glass | The term "opaline" refers to a number of different styles of glassware. |
Opaline glass | Opaline glass | By opaline glass we mean a milky glass, which can be white or colored, and is made translucent or opaque by adding particular phosphates or oxides during the mixing. In France, the term "opaline" is used to refer to multiple types of glass, and not specifically antique colored crystal or semi-crystal, as is commonly thought, with 'opaline' often a mistakenly-given term referring to the color of a particular type of glass, rather than the age, origin or content of the glass. |
Opaline glass | Description | To make the opaline glass, opacifying substances are added, such as: sodium phosphate, sodium chloride, calcium phosphate, calcium chloride, tin oxide and talc. The glass can thus take on different colors and have varying shades of color, depending on the quantity of the added substance: from white to gray, to pink, to lavender green, to golden yellow, to light blue, up to blue and black. |
Opaline glass | History | The first objects in opaline glass were made in Murano in the sixteenth century, with the addition of calcium phosphate, resulting from the calcination of bones. The technique did not remain secret and was copied in Germany, where this glass was known as bein glass. Opaline glass was produced in large quantities in France in the nineteenth century and reached the apex of diffusion and popularity during the empire of Napoleon III; but the pieces made in the period of Napoleon I, which are translucent, are the most sought after by the antiques market. |
Opaline glass | History | The production centers were in Le Creusot, in Baccarat, in Saint-Louis-lès-Bitche. In England it was produced in the eighteenth century, in Bristol. From the mid-nineteenth century opaque opal glass objects came into fashion. At the Sèvres Porcelain Manufactory, a production line in white milk glass, decorated by hand, was experimented with, which attempted to imitate the transparency of Chinese porcelain. |
Opaline glass | History | With this particular glass objects of common use were handcrafted: vases, bowls, cups, goblets, carafes, perfume bottles, boxes, lamps. Some objects were also decorated in cold enamel, with flowers, with landscapes, with birds. Sometimes a bronze or silver support was added to the opal vase. Most green or yellow opaline glass are uranium glass. |
Opaline glass | 19th century opaline glass | Many different pieces were produced in opaline glass, including vases, bowls, cups, coupes, decanters, perfume bottles, boxes, clocks and other implements.
All opaline glass is hand-blown and has a rough or polished pontil on the bottom. There are no seams and no machine engraving, and most opaline glass is not branded or signed. Many pieces of opaline glass are decorated with gilding. Some with handpainted flowers or birds. Several have bronze ormolu mounts, rims, hinges or holders. |
Opaline glass | Later opaline glass | The French factory Portieux Vallérysthal in 1930 has put opal glass objects on the market in a particular blue-azure color. Some pieces have decorations in pure gold or polychrome enamels and are sometimes equipped with supports or hinges in gilded bronze (sets of plates, cruets, sets of glasses and cups, boxes, lamps, flacons, chandeliers). The blue-blue color of the glass is inspired by that of the American robin's egg. |
Opaline glass | Later opaline glass | In the late 20th century the venetian master glassmaker Vincenzo Nason, began producing a similar type of glass, labelled 'Veritable Opaline de Murano'. |
The Kitchen Cabinet (radio show) | The Kitchen Cabinet (radio show) | The Kitchen Cabinet is a BBC Radio 4 programme hosted by Jay Rayner in which members of the public can put questions to a panel of experts about food and cooking. |
The Kitchen Cabinet (radio show) | History | The programme was first broadcast on 7 Feb 2012; as of February 2023 it is in its 39th series. It is a Somethin' Else production. |
The Kitchen Cabinet (radio show) | Format | The show is a similar format to the long established Gardeners Question Time, coming from public venues at interesting 'food locations' in Britain in front of an audience. Panel members have included the food historian Professor Peter Barham, James 'Jocky' Petrie, the former Head of Creative Development for Heston Blumenthal and food writer Tim Hayward. |
Netflix Prize | Netflix Prize | The Netflix Prize was an open competition for the best collaborative filtering algorithm to predict user ratings for films, based on previous ratings without any other information about the users or films, i.e. without the users being identified except by numbers assigned for the contest. |
Netflix Prize | Netflix Prize | The competition was held by Netflix, a video streaming service, and was open to anyone who is neither connected with Netflix (current and former employees, agents, close relatives of Netflix employees, etc.) nor a resident of certain blocked countries (such as Cuba or North Korea). On September 21, 2009, the grand prize of US$1,000,000 was given to the BellKor's Pragmatic Chaos team which bested Netflix's own algorithm for predicting ratings by 10.06%. |
Netflix Prize | Problem and data sets | Netflix provided a training data set of 100,480,507 ratings that 480,189 users gave to 17,770 movies. Each training rating is a quadruplet of the form <user, movie, date of grade, grade>. The user and movie fields are integer IDs, while grades are from 1 to 5 (integer) stars.The qualifying data set contains over 2,817,131 triplets of the form <user, movie, date of grade>, with grades known only to the jury. A participating team's algorithm must predict grades on the entire qualifying set, but they are informed of the score for only half of the data: a quiz set of 1,408,342 ratings. The other half is the test set of 1,408,789, and performance on this is used by the jury to determine potential prize winners. Only the judges know which ratings are in the quiz set, and which are in the test set—this arrangement is intended to make it difficult to hill climb on the test set. Submitted predictions are scored against the true grades in the form of root mean squared error (RMSE), and the goal is to reduce this error as much as possible. Note that, while the actual grades are integers in the range 1 to 5, submitted predictions need not be. Netflix also identified a probe subset of 1,408,395 ratings within the training data set. The probe, quiz, and test data sets were chosen to have similar statistical properties. |
Netflix Prize | Problem and data sets | In summary, the data used in the Netflix Prize looks as follows: Training set (99,072,112 ratings not including the probe set; 100,480,507 including the probe set) Probe set (1,408,395 ratings) Qualifying set (2,817,131 ratings) consisting of: Test set (1,408,789 ratings), used to determine winners Quiz set (1,408,342 ratings), used to calculate leaderboard scoresFor each movie, the title and year of release are provided in a separate dataset. No information at all is provided about users. In order to protect the privacy of the customers, "some of the rating data for some customers in the training and qualifying sets have been deliberately perturbed in one or more of the following ways: deleting ratings; inserting alternative ratings and dates; and modifying rating dates."The training set is constructed such that the average user rated over 200 movies, and the average movie was rated by over 5000 users. But there is wide variance in the data—some movies in the training set have as few as 3 ratings, while one user rated over 17,000 movies.There was some controversy as to the choice of RMSE as the defining metric. Would a reduction of the RMSE by 10% really benefit the users? It has been claimed that even as small an improvement as 1% RMSE results in a significant difference in the ranking of the "top-10" most recommended movies for a user. |
Netflix Prize | Prizes | Prizes were based on improvement over Netflix's own algorithm, called Cinematch, or the previous year's score if a team has made improvement beyond a certain threshold. A trivial algorithm that predicts for each movie in the quiz set its average grade from the training data produces an RMSE of 1.0540. Cinematch uses "straightforward statistical linear models with a lot of data conditioning."Using only the training data, Cinematch scores an RMSE of 0.9514 on the quiz data, roughly a 10% improvement over the trivial algorithm. Cinematch has a similar performance on the test set, 0.9525. In order to win the grand prize of $1,000,000, a participating team had to improve this by another 10%, to achieve 0.8572 on the test set. Such an improvement on the quiz set corresponds to an RMSE of 0.8563. |
Netflix Prize | Prizes | As long as no team won the grand prize, a progress prize of $50,000 was awarded every year for the best result thus far. However, in order to win this prize, an algorithm had to improve the RMSE on the quiz set by at least 1% over the previous progress prize winner (or over Cinematch, the first year). If no submission succeeded, the progress prize was not to be awarded for that year. |
Netflix Prize | Prizes | To win a progress or grand prize a participant had to provide source code and a description of the algorithm to the jury within one week after being contacted by them. Following verification the winner also had to provide a non-exclusive license to Netflix. Netflix would publish only the description, not the source code, of the system. (To keep their algorithm and source code secret, a team could choose not to claim a prize.) The jury also kept their predictions secret from other participants. A team could send as many attempts to predict grades as they wish. Originally submissions were limited to once a week, but the interval was quickly modified to once a day. A team's best submission so far counted as their current submission. |
Netflix Prize | Prizes | Once one of the teams succeeded to improve the RMSE by 10% or more, the jury would issue a last call, giving all teams 30 days to send their submissions. Only then, the team with best submission was asked for the algorithm description, source code, and non-exclusive license, and, after successful verification; declared a grand prize winner.
The contest would last until the grand prize winner was declared. Had no one received the grand prize, it would have lasted for at least five years (until October 2, 2011). After that date, the contest could have been terminated at any time at Netflix's sole discretion. |
Netflix Prize | Progress over the years | The competition began on October 2, 2006. By October 8, a team called WXYZConsulting had already beaten Cinematch's results.By October 15, there were three teams who had beaten Cinematch, one of them by 1.06%, enough to qualify for the annual progress prize. By June 2007 over 20,000 teams had registered for the competition from over 150 countries. 2,000 teams had submitted over 13,000 prediction sets.Over the first year of the competition, a handful of front-runners traded first place. The more prominent ones were: WXYZConsulting, a team of Wei Xu and Yi Zhang. (A front runner during November–December 2006.) ML@UToronto A, a team from the University of Toronto led by Prof. Geoffrey Hinton. (A front runner during parts of October–December 2006.) Gravity, a team of four scientists from the Budapest University of Technology (A front runner during January–May 2007.) BellKor, a group of scientists from AT&T Labs. (A front runner since May 2007.) Dinosaur Planet, a team of three undergraduates from Princeton University. (A front runner on September 3, 2007 for one hour before BellKor snatched back the lead.)On August 12, 2007, many contestants gathered at the KDD Cup and Workshop 2007, held at San Jose, California. During the workshop all four of the top teams on the leaderboard at that time presented their techniques. The team from IBM Research — Yan Liu, Saharon Rosset, Claudia Perlich, and Zhenzhen Kou — won the third place in Task 1 and first place in Task 2. |
Netflix Prize | Progress over the years | Over the second year of the competition, only three teams reached the leading position: BellKor, a group of scientists from AT&T Labs. (front runner during May 2007 - September 2008.) BigChaos, a team of Austrian scientists from commendo research & consulting (single team front runner since October 2008) BellKor in BigChaos, a joint team of the two leading single teams (A front runner since September 2008) 2007 Progress Prize On September 2, 2007, the competition entered the "last call" period for the 2007 Progress Prize. Over 40,000 teams from 186 countries had entered the contest. They had thirty days to tender submissions for consideration. At the beginning of this period the leading team was BellKor, with an RMSE of 0.8728 (8.26% improvement), followed by Dinosaur Planet (RMSE = 0.8769; 7.83% improvement), and Gravity (RMSE = 0.8785; 7.66% improvement). In the last hour of the last call period, an entry by "KorBell" took first place. This turned out to be an alternate name for Team BellKor.On November 13, 2007, team KorBell (formerly BellKor) was declared the winner of the $50,000 Progress Prize with an RMSE of 0.8712 (8.43% improvement). The team consisted of three researchers from AT&T Labs, Yehuda Koren, Robert Bell, and Chris Volinsky. As required, they published a description of their algorithm. |
Netflix Prize | Progress over the years | 2008 Progress Prize The 2008 Progress Prize was awarded to the team BellKor. Their submission combined with a different team, BigChaos achieved an RMSE of 0.8616 with 207 predictor sets. |
Netflix Prize | Progress over the years | The joint-team consisted of two researchers from commendo research & consulting GmbH, Andreas Töscher and Michael Jahrer (originally team BigChaos) and three researchers from AT&T Labs, Yehuda Koren, Robert Bell, and Chris Volinsky (originally team BellKor). As required, they published a description of their algorithm.This was the final Progress Prize because obtaining the required 1% improvement over the 2008 Progress Prize would be sufficient to qualify for the Grand Prize. The prize money was donated to the charities chosen by the winners. |
Netflix Prize | Progress over the years | 2009 On June 26, 2009 the team "BellKor's Pragmatic Chaos," a merger of teams "Bellkor in BigChaos" and "Pragmatic Theory," achieved a 10.05% improvement over Cinematch (a Quiz RMSE of 0.8558). The Netflix Prize competition then entered the "last call" period for the Grand Prize. In accord with the Rules, teams had thirty days, until July 26, 2009 18:42:37 UTC, to make submissions that will be considered for this Prize.On July 25, 2009 the team "The Ensemble," a merger of the teams "Grand Prize Team" and "Opera Solutions and Vandelay United," achieved a 10.09% improvement over Cinematch (a Quiz RMSE of 0.8554).On July 26, 2009, Netflix stopped gathering submissions for the Netflix Prize contest.The final standing of the Leaderboard at that time showed that two teams met the minimum requirements for the Grand Prize. "The Ensemble" with a 10.10% improvement over Cinematch on the Qualifying set (a Quiz RMSE of 0.8553), and "BellKor's Pragmatic Chaos" with a 10.09% improvement over Cinematch on the Qualifying set (a Quiz RMSE of 0.8554). The Grand Prize winner was to be the one with the better performance on the Test set. |
Netflix Prize | Progress over the years | On September 18, 2009, Netflix announced team "BellKor's Pragmatic Chaos" as the prize winner (a Test RMSE of 0.8567), and the prize was awarded to the team in a ceremony on September 21, 2009. "The Ensemble" team had matched BellKor's result, but since BellKor submitted their results 20 minutes earlier, the rules award the prize to BellKor.The joint-team "BellKor's Pragmatic Chaos" consisted of two Austrian researchers from Commendo Research & Consulting GmbH, Andreas Töscher and Michael Jahrer (originally team BigChaos), two researchers from AT&T Labs, Robert Bell, and Chris Volinsky, Yehuda Koren from Yahoo! (originally team BellKor) and two researchers from Pragmatic Theory, Martin Piotte and Martin Chabbert. As required, they published a description of their algorithm.The team reported to have achieved the "dubious honors" (sic Netflix) of the worst RMSEs on the Quiz and Test data sets from among the 44,014 submissions made by 5,169 teams was "Lanterne Rouge," led by J.M. Linacre, who was also a member of "The Ensemble" team. |
Netflix Prize | Cancelled sequel | On March 12, 2010, Netflix announced that it would not pursue a second Prize competition that it had announced the previous August. The decision was in response to a lawsuit and Federal Trade Commission privacy concerns. |
Netflix Prize | Cancelled sequel | Privacy concerns Although the data sets were constructed to preserve customer privacy, the Prize has been criticized by privacy advocates. In 2007 two researchers from The University of Texas at Austin were able to identify individual users by matching the data sets with film ratings on the Internet Movie Database.On December 17, 2009, four Netflix users filed a class action lawsuit against Netflix, alleging that Netflix had violated U.S. fair trade laws and the Video Privacy Protection Act by releasing the datasets. There was public debate about privacy for research participants. On March 19, 2010, Netflix reached a settlement with the plaintiffs, after which they voluntarily dismissed the lawsuit. |
TrashMail | TrashMail | TrashMail is a free disposable e-mail address service created in 2002 by Stephan Ferraro, a computer science student at Epitech Paris which belongs now to Ferraro Ltd. The service provides temporary email addresses that can be abandoned if they start receiving email spam. It mainly forwards emails to a real hidden email address. |
TrashMail | Description | TrashMail receives emails and forwards them to a real hidden email address. On account creation there is the option to set a number of total forwards and a date when the disposable email expires. For each forwarded email the counter is decreased by 1. When the counter reaches 0 or the date limit is expired then the temporary email address will be deleted. |
TrashMail | Description | After the temporary email address is deleted, any incoming email is rejected by the SMTP code 550 5.1.1. TrashMail also provides a free open-source add-on for Mozilla Firefox available from the official store. The email registration and community forum are provided by HTTPS (SSL over HTTP) access to protect privacy. Additionally the SMTP server communication has TLS enabled by default. |
TrashMail | Description | As many spammers rely on harvested email addresses, the best method of avoiding spam is not to publish one's real email address. By providing a temporary address, TrashMail allows users to protect their real email. |
TrashMail | Extras | TrashMail differs from other disposable email address services in its possibility to use the Challenge-Response System for each free disposable email address. Additionally, it provides real-time spam stats on its main page. It is possible to verify the current incoming spam amount on this site. |
TrashMail | Software | TrashMail can be used via the web. However an API is provided and documented on the forum which explains how to write custom software to use for the free service. A Mozilla Firefox add-on for the service is available. |
Compressed air filters | Compressed air filters | Compressed air filters, often referred to as line filters, are used to remove contaminants from compressed air after compression has taken place.
When the filer is combined with a regulator and an oiler, it is called an air set.Air leaving a standard screw or piston compressor will generally have a high water content, as well as a high concentration of oil and other contaminants. There are many different types of filters, suitable for different pneumatics applications. |
Compressed air filters | Working principle | Unfiltered compressed air frequently contains dust, oil, rust, moisture and other harmful substances, and therefore requires filtration. In the first stage of filtration, the compressed air passes through a tube-shaped mesh filter, which creates a coalescence effect. Here bigger particles are adsorbed on the filter and the water will condense into larger droplets, which can then pass into the separation chamber. The compressed air is slowed down, which makes the particles condense on a honeycomb-like pad, allowing the water droplets to travel to the bottom of the drainage system and through an automatic or electric drain valve to the discharge. In the first filtration stage more than 95% of the water droplets, oil and large particles are removed. This practice is most common for removing water, but is also used for removing oil.In the second filtration stage, the air is passed through a fiber filter. This process generates thousands of small vortices and other disturbances that cause the airflow to be less uniform. In doing this, the air comes into contact with more surface area of the filtration medium. Fine particulate is then captured because it will not fit through the small pores in the fiber filter. However, there will be a small pressure drop due to the added resistance to the airflow. |
Compressed air filters | Types of filters | Particulate filters Particulate compressed air filters are used to remove dust and particles from the air.
Activated carbon filters Activated carbon filters utilize a composite carbon material to remove gases and odors from the air. They are used in factories where food is produced or for breathing gas. |
Compressed air filters | Types of filters | Coalescing filters High oil compressed air coalescing filters remove water and oil aerosols by coalescing the aerosols into droplets. This happens partially because of tortuous path and pressure drop. Coalescers remove both water and oil aerosols from the air stream, and are rated at particulate contamination through direct interception. Filtration of oil, water aerosols, dust and dirt particles to 0.01 µm the best achievable in industry. |
Compressed air filters | Types of filters | Cold coalescing filters Cold coalescing filters are coalescing filters operated at around 35 °F (2 °C), allowing them to be more effective at removing moistures.
Compressed intake filters Intake filters are the first line of defense in filtering. These filters can remove contaminants down to 0.3 µm and can remove chemical contaminants. |
Gum over platinum | Gum over platinum | Gum over platinum is a historical chemical photographic process, which was commonly used in art photography. It is a very complex process, in which a specially treated platinum print photograph is coated with washes of gum arabic, then re-exposed to the same photographic negative. The finished process results in a sepia toned print, and is said to impart added luminosity and depth. It is sometimes called "pigment over platinum". |
Gum over platinum | Gum over platinum | To sensitize the gum arabic it must first be placed in contact with ammonium or potassium dichromate. Gum arabic is not photosensitive by itself. To clear the chromic acid, the print is washed in 1% potassium metabisulfite after proper development in water. Interested individuals should read up on the process before attempting, as the chromic acids are very dangerous to work with. |
Gum over platinum | Gum over platinum | The mechanics of the gum portion is not entirely known; what occurs is the exposed gum is hardened and becomes water-insoluble. Upon washing, the unexposed portions wash away, leaving the white paper exposed.
The technique is related to platinum printing. |
Lock-on (protest tactic) | Lock-on (protest tactic) | A lock-on is a technique used by protesters to make it difficult to remove them from their place of protest. It often involves improvised or specially designed and constructed hardware, although a basic lock-on is the human chain which relies simply on hand grip. |
Lock-on (protest tactic) | Objective | In American protest movements dating from the 1960s and 1970s, the term lockdown applies to a person's attaching themself to a building, object, fence or other immobile object.
The safe removal of the protesters necessitates the involvement of skilled technicians, and is often time-consuming. |
Lock-on (protest tactic) | Objective | The lock-on chosen by the protester may be the difference between being arrested or not, or may vary the kind or number of charges brought against them by the police. If a protester can remove themselves when asked to by the police, they may stand a better chance of not being arrested. However, if they can remove themselves and they choose not to, they may receive a charge for refusing to remove themselves from the lock-on. |
Lock-on (protest tactic) | Objective | Locking on is a very successful means of slowing down operations that are perceived by the protesters to be illegal or immoral. It is also often used to allow time for journalists to arrive to record the scene and take statements from the group's spokespeople. |
Lock-on (protest tactic) | Devices | Lock-ons were originally performed with chains and handcuffs, but other devices have been introduced, including tripods and tubes or pipes with handholds built in to link a person to an object or to create chains of people. Other common hardware includes padlocks, U-locks and other bicycle locks, lockboxes and tripods and platforms and other rigging in tree sitting.A more complicated lock-on is the sleeping dragon, which involves protesters putting their limbs through pipes containing concrete, or a mixture of steel and concrete, and is only limited by the imagination and ingenuity of those making the lock-on. The protester can choose between a type that will allow them to willingly remove themselves or a type that requires machinery to remove them. Devices can be buried as an additional barrier to removal. A car dragon is a car concreted into place after removing the wheels, where protestors can then lock-on to a further device fixed to the car. |
Lock-on (protest tactic) | Opposition in law | In the United Kingdom in May 2023, the Public Order Act 2023 made it a criminal offence for a person to "attach themselves to another person, to an object or to land" with the intention of causing serious disruption. "Going equipped" with such an aim was also criminalised. |
Proprotein convertase subtilisin/kexin type 1 inhibitor | Proprotein convertase subtilisin/kexin type 1 inhibitor | Proprotein convertase subtilisin/kexin type 1 inhibitor is a protein by the name of proSAAS that in humans is encoded by the PCSK1N gene. |
Proprotein convertase subtilisin/kexin type 1 inhibitor | Function | This protein is expressed largely in cells possessing a regulated secretory pathway, such as endocrine/neuroendocrine cells and neurons. The intact proSAAS protein, as well as the carboxyy-terminal peptide containing the inhibitory hexapeptide LLRVKR, functions as an inhibitor of prohormone convertase 1/3, which accomplishes the initial proteolytic cleavage of peptide precursors. ProSAAS is further processed at the N- and C-termini into multiple short peptides, leaving the central segment intact. This central, unprocessed portion of the protein may function as a neural- and endocrine-specific chaperone due to its potent ability to block the aggregation of beta amyloid and alpha synuclein in vitro, and to block oligomer cytotoxicity in cells. Recent data show that nigral proSAAS expression blocks the deterioration of the striatonigral pathway in a synuclein rat model of Parkinson's disease. ProSAAS also oligomerizes and undergoes liquid-liquid phase separation. |
Proprotein convertase subtilisin/kexin type 1 inhibitor | Function | Differential expression of this gene may be associated with obesity. |
Yale–Brown Obsessive Compulsive Scale | Yale–Brown Obsessive Compulsive Scale | The Yale–Brown Obsessive–Compulsive Scale (Y-BOCS) is a test to rate the severity of obsessive–compulsive disorder (OCD) symptoms. |
Yale–Brown Obsessive Compulsive Scale | Yale–Brown Obsessive Compulsive Scale | The scale, which was designed by Wayne K. Goodman and his colleagues, is used extensively in research and clinical practice to both determine severity of OCD and to monitor improvement during treatment. This scale, which measures obsessions separately from compulsions, specifically measures the severity of symptoms of obsessive–compulsive disorder without being biased towards or against the type of content the obsessions or compulsions might present. Following the original publication, the total score is usually computed from the subscales for obsessions (items 1–5) and compulsions (items 6–10), but other algorithms exist. |
Yale–Brown Obsessive Compulsive Scale | Accuracy and modifications | Goodman and his colleagues have developed the Yale–Brown Obsessive–Compulsive Scale—Second Edition (Y-BOCS-II) in an effort to modify the original scale which, according to Goodman, "[has become] the gold standard measure of obsessive–compulsive disorder (OCD) symptom severity". In creating the Y-BOCS-II, changes were made "to the Severity Scale item content and scoring framework, integrating avoidance into the scoring of Severity Scale items, and modifying the Symptom Checklist content and format". After reliability tests, Goodman concluded that "Taken together, the Y-BOCS-II has excellent psychometric properties in assessing the presence and severity, of obsessive–compulsive symptoms. Although the Y-BOCS remains a reliable and valid measure, the Y-BOCS-II may provide an alternative method of assessing symptom presence and severity."Studies have been conducted by members of the Iranian Journal of Psychiatry and Clinical Psychology to determine the accuracy of the Yale–Brown Obsessive–Compulsive Scale (specifically as it appears in its Persian format). The members applied the scale to a group of individuals and, after ensuring a normal distribution of data, a series of reliability tests were performed. According to the authors, "[the] results supported satisfactory validity and reliability of translated form of Yale–Brown Obsessive–Compulsive Scale for research and clinical diagnostic applications". |
Yale–Brown Obsessive Compulsive Scale | Children's version | The children's version of the Y-BOCS, or the Children's Yale–Brown Obsessive–Compulsive Scales (CY-BOCS), is a clinician-report questionnaire designed to assess symptoms of obsessive–compulsive disorder from childhood through early adolescence.The CY-BOCS contains 70 questions and takes about 15 to 25 minutes. Each question is designed to ask about symptoms of obsessive–compulsive behavior, though the exact breakdown of questions is unknown. For each question, children rate the degree to which the question applies on a scale of 0–4. Based on research, this assessment has been found to be statistically valid and reliable, but not necessarily helpful. |
Yale–Brown Obsessive Compulsive Scale | Children's version | Other versions The CY-BOCS has been adapted into several self- and parent-report versions, designed to be completed by parent and child working together, although most have not been psychometrically validated. However, these versions still ask the child to rate the severity of their obsessive–compulsive behaviors and the degree to which each has been impairing. While this measure has been found to be useful in a clinic setting, scores and interpretations are taken with a grain of salt, given the lack of validation.Another version, which is parent-focused, is similar to the original CY-BOCS and is administered to both parent and child by the clinician. This version was distributed by Solvay Pharmaceuticals in the late 1990s, creating an association between the measure and a number of pharmaceutical groups that has caused it to be avoided by most clinicians. Severity cutoff scores for this version have not been empirically determined. |
Coiled sewn sandals | Coiled sewn sandals | Coiled sewn sandals are an ancient Egyptian footwear constructed using a technique similar to that used in basket weaving with a technique whereby coils were sewn together with the same material used in construction of the coils. The shoes were typically woven using halfa grass. |
Nissan RD engine | Nissan RD engine | The Nissan RD engine series is basically a Nissan RB engine design, except that it is only a single overhead cam six-cylinder diesel engine. It was the successor to the Nissan LD and SD six-cylinder engines and was joined by the six-cylinder Nissan TD engine.
From 1997 onwards the turbocharged versions were fitted with electronic fuel injection. The turbodiesel version known as the RD28T (or RD28ET with electronic fuel injection) and were also fitted to the Nissan Safari (also known as the Nissan Patrol) off-road vehicle. |