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Differentiated services

Differentiated services or DiffServ is a computer networking architecture that specifies a mechanism for classifying and managing network traffic and providing quality of service (QoS) on modern IP networks. DiffServ can, for example, be used to provide low-latency to critical network traffic such as voice or streaming media while providing best-effort service to non-critical services such as web traffic or file transfers.

DiffServ uses a 6-bit differentiated services code point (DSCP) in the 6-bit differentiated services field (DS field) in the IP header for packet classification purposes. The DS field, together with the ECN field, replaces the outdated IPv4 TOS field.

Background
Modern data networks carry many different types of services, including voice, video, streaming music, web pages and email. Many of the proposed QoS mechanisms that allowed these services to co-exist were both complex and failed to scale to meet the demands of the public Internet. In December 1998, the IETF replaced the TOS and IP precedence fields in the IPv4 header with the DS field, which was later split to refer to only the top 6 bits with the ECN field in the bottom two bits. In the IPv6 header the DS field is part of the Traffic Class field where it occupies the 6 most significant bits.

In the DS field, a range of eight values (class selectors) is used for backward compatibility with the former IPv4 IP precedence field. Today, DiffServ has largely supplanted TOS and other layer-3 QoS mechanisms, such as integrated services (IntServ), as the primary architecture routers use to provide QoS.

Traffic management mechanisms
DiffServ is a coarse-grained, class-based mechanism for traffic management. In contrast, IntServ is a fine-grained, flow-based mechanism. DiffServ relies on a mechanism to classify and mark packets as belonging to a specific class. DiffServ-aware routers implement per-hop behaviors (PHBs), which define the packet-forwarding properties associated with a class of traffic. Different PHBs may be defined to offer, for example, low-loss or low-latency service.

Rather than differentiating network traffic based on the requirements of an individual flow, DiffServ operates on the principle of traffic classification, placing each data packet into one of a limited number of traffic classes. Each router on the network is then configured to differentiate traffic based on its class. Each traffic class can be managed differently, ensuring preferential treatment for higher-priority traffic on the network. The premise of Diffserv is that complicated functions such as packet classification and policing can be carried out at the edge of the network by edge routers. Since no classification and policing is required in the core routers, functionality there can then be kept simple. Core routers simply apply PHB treatment to packets based on their markings. PHB treatment is achieved by core routers using a combination of scheduling policy and queue management policy.

A group of routers that implement common, administratively defined DiffServ policies are referred to as a DiffServ domain.

While DiffServ does recommend a standardized set of traffic classes, the DiffServ architecture does not incorporate predetermined judgments of what types of traffic should be given priority treatment. DiffServ simply provides a framework to allow classification and differentiated treatment. The standard traffic classes (discussed below) serve to simplify interoperability between different networks and different vendors' equipment.

Classification and marking
Network traffic entering a DiffServ domain is subjected to classification and conditioning. A traffic classifier may inspect many different parameters in incoming packets, such as source address, destination address or traffic type and assign individual packets to a specific traffic class. Traffic classifiers may honor any DiffServ markings in received packets or may elect to ignore or override those markings. For tight control over volumes and type of traffic in a given class, a network operator may choose not to honor markings at the ingress to the DiffServ domain. Traffic in each class may be further conditioned by subjecting the traffic to rate limiters, traffic policers or shapers.

The per-hop behavior is determined by the DS and ECN fields in the IP header. The DS field contains the 6-bit DSCP value. Explicit Congestion Notification (ECN) occupies the least-significant 2 bits of the IPv4 TOS field and IPv6 traffic class (TC) field.

In theory, a network could have up to 64 different traffic classes using the 64 available DSCP values. The DiffServ RFCs recommend, but do not require, certain encodings. This gives a network operator great flexibility in defining traffic classes. In practice, however, most networks use the following commonly defined per-hop behaviors:
 * Default Forwarding (DF) PHB — which is typically best-effort traffic
 * Expedited Forwarding (EF) PHB — dedicated to low-loss, low-latency traffic
 * Assured Forwarding (AF) PHB — gives assurance of delivery under prescribed conditions
 * Class Selector PHBs — which maintain backward compatibility with the IP precedence field.

Default Forwarding
A default forwarding (DF) PHB is the only required behavior. Essentially, any traffic that does not meet the requirements of any of the other defined classes uses DF. Typically, DF has best-effort forwarding characteristics. The recommended DSCP for DF is 0.

Expedited Forwarding
The IETF defines Expedited Forwarding (EF) behavior in. The EF PHB has the characteristics of low delay, low loss and low jitter. These characteristics are suitable for voice, video and other realtime services. EF traffic is often given strict priority queuing above all other traffic classes. Because an overload of EF traffic will cause queuing delays and affect the jitter and delay tolerances within the class, admission control, traffic policing and other mechanisms may be applied to EF traffic. The recommended DSCP for EF is 101110B (46 or 2EH).

Voice Admit
The IETF defines Voice Admit behavior in. The Voice Admit PHB has identical characteristics to the Expedited Forwarding PHB. However, Voice Admit traffic is also admitted by the network using a Call Admission Control (CAC) procedure. The recommended DSCP for voice admit is 101100B (44 or 2CH).

Assured Forwarding
The IETF defines the Assured Forwarding (AF) behavior in and. Assured forwarding allows the operator to provide assurance of delivery as long as the traffic does not exceed some subscribed rate. Traffic that exceeds the subscription rate faces a higher probability of being dropped if congestion occurs.

The AF behavior group defines four separate AF classes with all traffic within one class having the same priority. Within each class, packets are given a drop precedence (high, medium or low, where higher precedence means more dropping). The combination of classes and drop precedence yields twelve separate DSCP encodings from AF11 through AF43 (see table).

Some measure of priority and proportional fairness is defined between traffic in different classes. Should congestion occur between classes, the traffic in the higher class is given priority. Rather than using strict priority queuing, more balanced queue servicing algorithms such as fair queuing or weighted fair queuing are likely to be used. If congestion occurs within a class, the packets with the higher drop precedence are discarded first. To prevent issues associated with tail drop, more sophisticated drop selection algorithms such as random early detection are often used.

Class Selector
DF= Default Forwarding

Prior to DiffServ, IPv4 networks could use the IP precedence field in the TOS byte of the IPv4 header to mark priority traffic. The TOS octet and IP precedence were not widely used. The IETF agreed to reuse the TOS octet as the DS field for DiffServ networks, later splitting it into the DS field and ECN field. In order to maintain backward compatibility with network devices that still use the Precedence field, DiffServ defines the Class Selector PHB.

The Class Selector code points are of the binary form 'xxx000'. The first three bits are the IP precedence bits. Each IP precedence value can be mapped into a DiffServ class. IP precedence 0 maps to CS0, IP precedence 1 to CS1, and so on. If a packet is received from a non-DiffServ-aware router that used IP precedence markings, the DiffServ router can still understand the encoding as a Class Selector code point.

Specific recommendations for use of Class Selector code points are given in RFC 4594.

Configuration guidelines
offers detailed and specific recommendations for the use and configuration of code points. Other RFCs such as have updated these recommendations.

sr+bs = single rate with burst size control.

Design considerations
Under DiffServ, all the policing and classifying are done at the boundaries between DiffServ domains. This means that in the core of the Internet, routers are unhindered by the complexities of collecting payment or enforcing agreements. That is, in contrast to IntServ, DiffServ requires no advance setup, no reservation, and no time-consuming end-to-end negotiation for each flow.

The details of how individual routers deal with the DS field are configuration specific, therefore it is difficult to predict end-to-end behavior. This is complicated further if a packet crosses two or more DiffServ domains before reaching its destination. From a commercial viewpoint, this means that it is impossible to sell different classes of end-to-end connectivity to end users, as one provider's Gold packet may be another's Bronze. DiffServ or any other IP-based QoS marking does not ensure the quality of the service or a specified service-level agreement (SLA). By marking the packets, the sender indicates that it wants the packets to be treated as a specific service, but there is no guarantee this happens. It is up to all the service providers and their routers in the path to ensure that their policies will take care of the packets in an appropriate fashion.

Bandwidth broker
A Bandwidth Broker in the framework of DiffServ is an agent that has some knowledge of an organization's priorities and policies and allocates bandwidth with respect to those policies. In order to achieve an end-to-end allocation of resources across separate domains, the Bandwidth Broker managing a domain will have to communicate with its adjacent peers, which allows end-to-end services to be constructed out of purely bilateral agreements.

DiffServ RFCs

 * — Definition of the differentiated services field (DS field) in the IPv4 and IPv6 headers. Note that the DS field of 8 bits (the bottom two unused) in was later split into the current 6-bit DS field and a separate 2-bit ECN field.
 * — An architecture for differentiated services.
 * — Assured forwarding PHB group.
 * — Differentiated services and tunnels.
 * — Definition of differentiated services per-domain behaviors and rules for their specification.
 * — Per hop behavior identification codes. (Obsoletes.
 * — An expedited forwarding PHB. (Obsoletes .)
 * — Supplemental information for the new definition of the EF PHB (expedited forwarding per-hop behavior).
 * — New Terminology and Clarifications for Diffserv. (Updates, and .)
 * — Configuration Guidelines for DiffServ Service Classes.
 * — A differentiated services code point (DSCP) for capacity-admitted traffic. (Updates and .)
 * — A Lower-Effort Per-Hop Behavior (LE PHB) for Differentiated Services. (Updates and, obsoletes .)

DiffServ Management RFCs

 * — Management information base for the differentiated services architecture.
 * — An informal management model for differentiated services routers.
 * — Differentiated services quality of service policy information base.

title: Differentiated services


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Road verge

A road verge is a strip of groundcover consisting of grass or garden plants, and sometimes also shrubs and trees, located between a roadway and a sidewalk. Verges are known by dozens of other names such as grass strip, nature strip or curb strip, the usage of which is often quite regional.

Road verges are often considered public property, with maintenance usually being a municipal responsibility. Some local authorities, however, require abutting property owners to help maintain (e.g. watering, mowing, edging, trimming/pruning and weeding) their respective verge areas, as well as clean the adjunct footpaths and gutters, as a form of community work.

Benefits of having road verges include visual aesthetics, increased safety and comfort of sidewalk users, protection from spray from passing vehicles, and a space for benches, bus shelters, street lights, and other public amenities. Verges are also often part of sustainability for water conservation or the management of urban runoff and water pollution  and can provide useful wildlife habitat. Snow that has been ploughed off the street in colder climates often is stored in the area of the verge by default.

In the British Isles, road verges serve as important habitats for a range of florae, including rare wildflowers. In the UK, around 700 different species of wildflower can be found growing on verges, including 29 of the country's 52 species of orchid. Verges can also support a wide range of animals and plants that may have been displaced from their usual grassland habitats, as the soil is not extensively fertilised and relatively undisturbed by human activity. Animals that reside on verges range from small insects and amphibians, to larger reptiles, mammals and birds, which rely on verges as a corridor connecting areas of undamaged habitat. As a result, verges may be managed by local areas to encourage biodiversity and conserve the ecosystems that rely on them.

The main disadvantage of a road verge is that the right-of-way must be wider, increasing the cost of the road. In some localities, a wider verge offers opportunity for later road widening, should the traffic usage of a road demand this. For this reason, footpaths are usually sited a significant distance from the curb.

Certain nutrient amounts in a verge's soil can be influenced by the amount of traffic on the road it sits beside; roads with heavier traffic tend to have more nitrate in the soil due to nitrogen compounds from air pollution leaching out of the atmosphere and into the ground.

Sustainable urban and landscape design
In urban and suburban areas, urban runoff from private and civic properties can be guided by grading and bioswales for rainwater harvesting collection and bioretention within the "tree-lawn" – parkway zone in rain gardens. This is done for reducing runoff of rain and domestic water: for their carrying waterborne pollution off-site into storm drains and sewer systems; and for the groundwater recharge of aquifers.

In some cities, such as Santa Monica, California, city code mandates specify: "Parkways, the area between the outside edge of the sidewalk and the inside edge of the curb which are a component of the Public Right of Way (PROW) – that the landscaping should require little or no irrigation and the area produce no runoff."

For Santa Monica, another reason for this use of "tree-lawns" is to reduce current beach and Santa Monica Bay ocean pollution that is measurably higher at city outfalls. New construction and remodeling projects needing building permits require that landscape design submittals include garden design plans showing the means of compliance.

In some cities and counties, such as Portland, Oregon, street and highway departments are regrading and planting rain gardens in road verges to reduce boulevard and highway runoff. This practice can be useful in areas with either independent Storm sewers or combined storm and sanitary sewers, reducing the frequency of pollution, treatment costs, and released overflows of untreated sewage into rivers and oceans during rainstorms.

Rural roadsides
In some countries, the road verge can be a corridor of vegetation that remains after adjacent land has been cleared. Considerable effort in supporting conservation of the remnant vegetation is prevalent in Australia, where significant tracts of land are managed as part of the roadside conservation strategies by government agencies.

Terminology
The term verge has many synonyms and dialectal differences. Some dialects and idiolects lack a specific term for this area, instead using a circumlocution.

Terms used include:

 * Berm: Pennsylvania, northern Indiana, Ohio, Michigan, Wisconsin, New Zealand
 * Besidewalk
 * Boulevard: Detroit, Michigan; North Dakota; Minnesota; Iowa; Illinois; Ohio; Wisconsin; United States Upper Midwest; Winnipeg, and western Canada; Toronto, Ontario; Markham, Ontario; Kitchener, Ontario
 * Boulevard strip: U.S. Upper Midwest
 * Common: New England, generally describes a large strip of grass. Also refers to park-like common-use green spaces in small town centers.
 * Curb lawn: Kalamazoo, Michigan; Elyria, Ohio; Miami County, Ohio; Greenville, South Carolina
 * Curb strip: New Jersey, New York, North Carolina, Florida, Ohio, Indiana, Massachusetts, Michigan, Iowa, Kansas, Nebraska, Oregon, Washington
 * Devil strip or devilstrip: Akron, Ohio; Northeast Ohio.  This term was once used more widely to refer to the space between tracks on a streetcar line, a space not wide enough to stand in as cars passed.
 * Drivestrip or Drive Strip
 * Extension lawn: Ann Arbor, Michigan
 * Furniture zone, also landscape zone: a term used by urban planners, indicating its suitability for "street furniture" such as utility poles and fire hydrants, as well as trees or planters
 * Grassplot: East Coast of the United States, Pennsylvania
 * Hellstrip
 * Island strip: Long Island, New York
 * Long acre – a traditional term for wide grassy road verges, used by grazing herds or flocks moving from place to place
 * Median: Washington, Oregon
 * Mow strip: SF East Bay Area Northern California
 * Nature strip: Australia
 * Neutral ground: U.S. Gulf states
 * Park strip: Ohio
 * Parking: Illinois, Iowa, Western United States
 * Parking strip: Washington, Oregon, Utah, much of California
 * Parkrow: Iowa, Oregon
 * Parkway: Grand Rapids, Michigan; Greater Los Angeles; San Francisco Bay Area; West Coast of the United States; Casper, Wyoming; Ohio; Illinois; Missouri; Florida; Texas
 * Parkway strip: Austin, Texas; Fort Collins, Colorado
 * Planter zone: SmartCode/New Urbanist terminology
 * Planting strip: Berkeley, California, Seattle, Washington
 * Right-of-way: Wisconsin, Illinois
 * Road allowance: Ottawa, Canada
 * Road verge: Australia
 * Roadside: Australia
 * Shoulder
 * Sidewalk lawn: Georgia
 * Sidewalk plot: Virginia, Maryland, Indiana, Tennessee
 * Sidewalk strip: California, North Carolina, Oregon, Utah, Washington
 * Sidewalk taint: Central Indiana
 * Street lawn: Ohio
 * Subway: Western New York
 * Swale: South Florida
 * Terrace: U.S. Great Lakes region, Missouri
 * Tree belt: Massachusetts
 * Tree box: Washington, DC
 * Tree lawn or treelawn: Ohio, Indiana, New York, and elsewhere
 * Verge: UK, New Zealand, South Africa, Western Australia

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Road verge


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Gambit

A gambit (from Italian gambetto, the act of tripping someone with the leg to make them fall) is a chess opening in which a player sacrifices with the aim of achieving a subsequent  advantage.

The word gambit is also sometimes used to describe similar tactics used by politicians or business people in a struggle with rivals in their fields, for example: "The early election was a risky gambit by Theresa May."

Terminology
The Spanish word gambito was originally applied to chess openings in 1561 by Ruy López de Segura, from an Italian expression dare il gambetto (to put a leg forward in order to trip someone). In English, the word first appeared in Francis Beale's 1656 translation of a Gioachino Greco manuscript, The Royall Game of Chesse-play ("illustrated with almost one hundred Gambetts" ). The Spanish gambito led to French gambit, which has influenced the English spelling of the word. The metaphorical sense of the word as "opening move meant to gain advantage" was first recorded in English in 1855.

Gambits are more commonly played by White. Some well-known examples of a gambit are the King's Gambit (1.e4 e5 2.f4) and Evans Gambit (1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.b4). A gambit employed by Black may also be named a gambit, e.g. the Latvian Gambit (1.e4 e5 2.Nf3 f5), or Englund Gambit (1.d4 e5); but is sometimes named a "countergambit", e.g. the Albin Countergambit (1.d4 d5 2.c4 e5) and Greco Countergambit (the original name for the Latvian Gambit). Not all opening lines involving the sacrifice of material are named as gambits, for example the main line of the Two Knights Defense (1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 d5 5.exd5 Na5) in which Black sacrifices a pawn for active play is known as the "Knorre Variation", though it may be described as a "gambit". On the other hand, the Queen's Gambit (1.d4 d5 2.c4) is not a true gambit as Black cannot hold the pawn without incurring a disadvantage. As is often the case with chess openings, nomenclature is inconsistent.

Strategy

Gambits are described as being "offered" to an opponent, and that offer is then said to be either "accepted" or "declined".

In modern chess, the typical response to a moderately sound gambit is to accept the material and give the material back at an advantageous time. For gambits that are less sound, the accepting player is more likely to try to hold on to their extra material. A rule of thumb often found in various primers on chess suggests that a player should get three moves (see tempo) of for a sacrificed pawn, but it is unclear how useful this general maxim is since the "free moves" part of the compensation is almost never the entirety of what the gambiteer gains. Often, a gambit can be declined with no disadvantage.

Soundness
A gambit is said to be 'sound' if it is capable of procuring adequate concessions from the opponent. There are three general criteria in which a gambit is often said to be sound:
 * 1) Time gain: the player accepting the gambit must take time to procure the sacrificed material and possibly must use more time to reorganize their pieces after the material is taken.
 * 2) Generation of differential activity: often a player accepting a gambit will decentralize their pieces or pawns and their poorly placed pieces will allow the gambiteer to place their own pieces and pawns on squares that might otherwise have been inaccessible. In addition, bishops and rooks can become more active simply because the loss of pawns often gives rise to open  and . Former world champion Mikhail Tal once reportedly told Mikhail Botvinnik that he had sacrificed a pawn because it was simply in the way.
 * 3) Generation of positional weaknesses: finally, accepting a gambit may lead to a compromised pawn structure, holes or other positional deficiencies.

An example of a sound gambit is the Scotch Gambit: 1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Bc4. Here Black can force White to sacrifice a pawn speculatively with 4...Bb4+, but White gets very good compensation for one pawn after 5.c3 dxc3 6.bxc3, or for two pawns after 6.0-0 inviting 6...cxb2 7.Bxb2, due to the development advantage and attacking chances against the black king. As a result, Black is often advised not to try to hold on to the extra pawn. A more dubious gambit is the so-called Halloween Gambit: 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Nxe5 Nxe5 5.d4. Here the investment (a knight for just one pawn) is too large for the moderate advantage of having a strong center.

Examples

 * King's Gambit: 1.e4 e5 2.f4
 * Queen's Gambit: 1.d4 d5 2.c4
 * Evans Gambit: 1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.b4
 * Rousseau Gambit: 1.e4 e5 2.Nf3 Nc6 3.Bc4 f5
 * Smith–Morra Gambit: 1.e4 c5 2.d4 intending 2...cxd4 3.c3 dxc3 4.Nxc3
 * Two Knights Defense: 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 d5 with 5.exd5 Na5 6.Bb5+ c6 7.dxc6 bxc6 likely to follow
 * Blackmar–Diemer Gambit (BDG): 1.d4 d5 2.e4 dxe4 3.Nc3 followed by 4.f3
 * From's Gambit: 1.f4 e5
 * Staunton Gambit: 1.d4 f5 2.e4
 * Budapest Gambit: 1.d4 Nf6 2.c4 e5
 * Scotch Gambit: 1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Bc4
 * Latvian Gambit: 1.e4 e5 2.Nf3 f5
 * Danish Gambit: 1.e4 e5 2.d4 exd4 3. c3
 * Blackburne Shilling Gambit: 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nd4
 * This is not a true gambit by Black, since after 4.Nxe5 Qg5 Black wins material. White can play a gambit themselves with 5.Bxf7+! Ke7 6.0-0! Qxe5 7.Bxg8 Rxg8 8.c3 Nc6 9.d4, when White's two pawns and rolling pawn center, combined with Black's misplaced king, give White strong compensation for the sacrificed bishop.

 * Elephant Gambit: 1.e4 e5 2.Nf3 d5!?
 * Englund Gambit: 1.d4 e5?!
 * Italian Gambit: 1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.d4
 * Fried Liver Attack: 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 d5 5.exd5 Nxd5 6.Nxf7 Kxf7
 * Albin Countergambit: 1.d4 d5 2.c4 e5
 * Benko Gambit: 1.d4 Nf6 2.c4 c5 3.d5 b5
 * Milner Barry Gambit: 1.e4 e6 2.d4 d5 3.e5 c5 4.c3 Nc6 5.Nf3 Qb6 6.Bd3 cxd4 7.cxd4 Bd7 8.Nc3 Nxd4 9.Nxd4 Qxd4
 * Vienna Gambit: 1.e4 e5 2.Nc3 Nf6 3.f4

title: Gambit


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Delaunay-Belleville

Automobiles Delaunay-Belleville was a French luxury automobile manufacturer at Saint-Denis, France, north of Paris. At the beginning of the 20th century they were among the most prestigious cars produced in the world, and perhaps the most desirable French marque.

History
Julien Belleville had been a maker of marine boilers from around 1850. Louis Delaunay joined the firm in 1867 and married Belleville's daughter. He changed his name to Delaunay-Belleville and succeeded his father-in-law in charge of the company.

S.A. des Automobiles Delaunay-Belleville was formed in 1903 by Louis Delaunay and. Barbarou's family owned the boiler making company Belleville in Saint-Denis, with boiler design influences inspired by the company. Barbarou, then 28, had experience working for Clément, Lorraine-Dietrich and Benz and was responsible for design and styling, including the trademark round grille shell. The first car was exhibited at the 1904 Paris Salon, and it received enormous acclaim.

The company started with three models, all four-cylinders: a live axled 16 hp and a 24 hp and 40 hp model, both chain-driven. These were likely the first automobiles to have pressure-lubricated camshafts. The bodies were attached with just four bolts, and the brakes were water-cooled, from a 2 impgal reservoir.

Delaunay-Belleville were a prestige marque, and one of the world's leaders, from the outset, and by 1906, Emperor Nicholas II of Russia had purchased a 40. Other royal owners included King George I of Greece and King Alphonso XIII of Spain.

The first French car maker to offer a six-cylinder engine, Delaunay-Belleville's 70 hp became available only in 1909, and then only in small numbers, remaining in limited production until 1912. This model came to be known as the Type SMT, or Sa Majesté le Tsar, because Nicholas purchased one of the last 70s built. He also ordered another in 1909; the demand for a silent starter, operable from the driving seat, became known as a Barbey starter, and was made standard at the end of 1910.

Like most prestige marques, the cars were sold as bare chassis and bodies were coachbuilt for them. Between 1906 and 1914, British imports were mainly bodied by Shinnie Brothers, a Burlington Coachbuilders subsidiary, in Aberdeen, then shipped to London for sale.

Postwar, Continental bodies gained popularity, at least in Britain, as Belgium's D'Ieteren Frères became most associated with the company: their landaulette, on a 26 hp chassis, was priced in Britain at £900, pitting them between Napier and Rolls-Royce.

In 1919, the company offered the P4, a 2 litre sidevalve 10 hp four-cylinder, undoubtedly the most expensive voiturette on the market, as well as a 2.6 litre OHC 15.9 hp four, the P4B, in 1922.

After Barbarou resigned, Delaunay-Belleville quality began to slip. New four-cylinder pushrod overhead valve 14/40 and 16/60 models appeared in 1926, and the pre-war 20 hp and 10 hp six-cylinder models continued to be produced until 1927. The last gasps were the 3180 cc 21 hp six of 1928 and the 3619 cc 21/75 OHV six of 1930. In 1931, Continental engines, imported from the US, were offered, being quieter and cheaper.

By the late 1920s, Delaunay-Belleville had lost its prestige, and converted to truck and military vehicle production. In 1936 the previously separate car company was merged with the Delaunay-Belleville parent. Production of the Delaunay-Belleville RI-6 continued through the late 1930s and was revived after the Second World War. This was a six-cylinder-engined car strongly resembling the Mercedes-Benz 230, featuring independent suspension all-round; revived postwar, it featured Cotal preselector gearbox and a front grille design apparently copied from the 1939 Buick. However, the business was in decline: anyone buying a RI-6 in the 1940s would have done so in the knowledge after-sales service might disappear soon. Six cars were completed in 1947 and only four during the first part of 1948.

The company continued to advertise new cars for sale until 1950, but the factory was sold to Robert de Rovin in 1948 and thereafter used to make cyclecars.

title: Delaunay-Belleville


text:
Far-infrared astronomy

Far-infrared astronomy is the branch of astronomy and astrophysics that deals with objects visible in far-infrared radiation (extending from 30 μm towards submillimeter wavelengths around 450 μm).

In the far-infrared, stars are not especially bright, but emission from very cold matter (140 Kelvin or less) can be observed that is not seen at shorter wavelengths. This is due to thermal radiation of interstellar dust contained in molecular clouds.

These emissions are from dust in circumstellar envelopes around numerous old red giant stars. The Bolocam Galactic Plane Survey mapped the galaxy for the first time in the far-infrared.

Telescopes
On 22 January 2014, European Space Agency scientists reported the detection, for the first definitive time, of water vapor on the dwarf planet, Ceres, largest object in the asteroid belt. The detection was made by using the far-infrared abilities of the Herschel Space Observatory. The finding is unexpected because comets, not asteroids, are typically considered to "sprout jets and plumes". According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids."

The Earth's atmosphere is opaque over most of the far-infrared, so most far-infrared astronomy is performed by satellites such as the Herschel Space Observatory, Spitzer Space Telescope, IRAS, and Infrared Space Observatory. Upper-atmosphere observations are also possible, as conducted by the airborne SOFIA telescope.

Ground-based observations are limited to submillimetre wavelengths using high-altitude telescopes such as the James Clerk Maxwell Telescope, the Caltech Submillimeter Observatory, the High Elevation Antarctic Terahertz Telescope and the Submillimeter Array.

title: Far-infrared astronomy


text:
Nell Carter

Nell Carter (born Nell Ruth Hardy; September 13, 1948 – January 23, 2003) was an American actress and singer.

Carter began her career in 1970, singing in the theater, and later began work on television. She was best known for her role as Nell Harper on the sitcom Gimme a Break!, which aired from 1981 to 1987. Carter received two Emmy and two Golden Globe award nominations for her work on the series. Prior to Gimme a Break!, Carter won a Tony Award for Best Performance by a Featured Actress in a Musical in 1978 for her performance in the Broadway musical Ain't Misbehavin' as well as a Primetime Emmy Award for her reprisal of the role on television in 1982.

Early life
Nell Ruth Hardy was born on September 13, 1948 in Birmingham, Alabama, one of nine children born to Edna Mae and Horace Hardy. She was born into a Catholic family and raised Presbyterian. Carter later self-identified as Pentecostal and as Jewish.

At the age of two, Hardy witnessed her father's electrocution when he stepped on a live power line.

As a child, she began singing on a local gospel radio show and was also a member of the church choir. At age 15, she began performing at area coffee houses, and later joined the Renaissance Ensemble that played at coffee houses and gay bars.

On July 5, 1965 at the age of 16, Hardy was raped at gunpoint by a man whom she knew. She became pregnant as a result of the rape and gave birth to daughter Tracy the next year. Finding raising a baby alone too difficult, she sent her child to live with her older sister Willie. She later claimed that Tracy was the product of a brief marriage, but she revealed the truth in a 1994 interview.

Broadway work
At age 19, Hardy changed her surname to Carter and left Birmingham, Alabama, moving to New York City with the Renaissance Ensemble, where she sang in coffee shops, nightclubs and bathhouses before landing her first Broadway role in 1971.

Carter made her Broadway debut in the 1971 rock opera Soon, which closed after three performances. She was the music director for the 1974 Westbeth Playwrights Feminist Collective's production of What Time of Night It Is. Carter appeared with Bette Davis in the 1974 stage musical Miss Moffat, based on Davis' earlier film The Corn Is Green, but the show closed before reaching Broadway.

Carter became a star for her role in the musical Ain't Misbehavin, for which she won a Tony Award in 1978. She later won an Emmy for the same role in a televised performance in 1982.

In 1978, Carter was cast as Effie White in the Broadway musical Dreamgirls but departed the production during development to take a television role on Ryan's Hope. When Dreamgirls premiered in late 1981, Jennifer Holliday had taken the lead role.

Carter's additional Broadway credits include Dude and the 20th-anniversary production of Annie, in which she played Miss Hannigan.

Film and television
In 1979, Carter had a part in the Miloš Forman-directed musical adaptation of Hair and her voice is heard on the film's soundtrack.

In 1981, she took a role on the NBC action comedy television series The Misadventures of Sheriff Lobo before landing the lead role of Nell Harper on the sitcom Gimme a Break!.

Gimme a Break!
Carter became best known to audiences for her lead role in the NBC television series Gimme a Break!, in which she played a housekeeper for a widowed police chief (Dolph Sweet) and his three daughters. The show earned Carter nominations for a Golden Globe and an Emmy Award. A total of 137 episodes of Gimme a Break! were produced over a run of six seasons, airing from 1981 to 1987.

In August 1987 after the cancellation of Gimme a Break!, Carter returned to the nightclub circuit with a five-month national tour with comedian Joan Rivers.

Further television work
In 1989, Carter played the assistant to a banquet-hall owner in an unsuccessful pilot for NBC titled Morton's by the Bay, which aired as a one-time special that May. In October, she performed "The Star-Spangled Banner" before Game 4 of the 1989 World Series in San Francisco.

In 1990, Carter starred in the CBS comedy You Take the Kids. The series, which was perceived as the black answer to Roseanne with its portrayal of a working-class black family, featured Carter as a crass, no-nonsense mother and wife. You Take the Kids faced poor ratings and reviews and only ran from December 1990 to January 1991.

During the early 1990s, Carter appeared in low-budget movies, television specials and game shows such as Match Game '90 and To Tell the Truth. She costarred in Hangin' with Mr. Cooper from 1993 to 1995.

In the mid-1990s, Carter appeared on Broadway in a revival of Annie as Miss Hannigan. She was upset when commercials promoting the show used white actress Marcia Lewis as Miss Hannigan. The producers stated that the commercials, which were created during an earlier production, were too costly to reshoot. However, Carter felt that racism played a part in the decision. She told the New York Post: "Maybe they don't want audiences to know Nell Carter is black. ... It hurts a lot. I've asked them nicely to stop it—it's insulting to me as a black woman." Carter was later replaced by Sally Struthers.

Later years
In 2001, Carter appeared as a special guest star on the pilot episode of Reba and continued with the show, making three appearances in Season 1. The following year, Carter made two appearances on Ally McBeal.

In 2002, she rehearsed for a production of Raisin, a stage musical based on A Raisin in the Sun in Long Beach, California. She appeared in the 2003 film Swing. Her final onscreen appearance was in the comedy film Back by Midnight, released in 2005, two years after her death. Nell's final recording project was a duet with Jay Levy, produced by Jay Levy for the 1998 Warner/Rhino Album To Life!: Songs of Chanukah and Other Jewish Celebrations.

Death
On January 23, 2003 at the age of 54, Carter collapsed and died at her home in Beverly Hills. Her son Joshua discovered her body that night. Per a provision in Carter's will, no autopsy was performed. Using blood tests, X-rays and a cursory physical examination, the Los Angeles County coroner's office ruled that Carter's death was the likely result of "probable arteriosclerotic heart disease, with diabetes a contributing condition."

Carter's friend Ann Kaser inherited her property and custody of her two sons. Carter is interred at Hillside Memorial Park Cemetery in Los Angeles.

Personal life
Carter attempted suicide in the early 1980s, and around 1985 she entered a drug-detoxification facility to break a longstanding cocaine addiction. Her brother Bernard died of complications from AIDS in 1989.

Carter married mathematician and lumber executive George Krynicki, and she converted to Judaism in 1982. She filed for divorce from Krynicki in 1989 and the divorce was finalized in 1992.

Carter had three children: daughter Tracy and sons Joshua and Daniel. She adopted both Joshua and Daniel as newborns over a four-month period. She attempted to adopt twice more, but both adoptions failed. In her first attempt, she allowed a young pregnant woman to move into her home with the plan that she would adopt the child, but the mother decided to keep the baby. Carter also had three miscarriages.

In 1992, Carter had surgery to repair two aneurysms. She married Roger Larocque in June 1992 but divorced him the next year. Carter declared bankruptcy in 1995 and again in 2002.

Stage credits

 * Soon (1971), Broadway
 * The Wedding of Iphigenia (1971), off-Broadway
 * Dude (1972), Broadway
 * Miss Moffat (1974), closed on the road
 * Be Kind to People Week (1975), off-Broadway
 * Tom Eyen's Dirtiest Musical (1975), off-Broadway
 * Don't Bother Me, I Can't Cope (1976), San Francisco
 * Ain't Misbehavin' (1978), Manhattan Theatre Club, Broadway and U.S. national tour
 * One Night Only (1979), workshop
 * Black Broadway (1979), Avery Fisher Hall
 * Black Broadway (1980), The Town Hall
 * Ain't Misbehavin'  (1988), Broadway
 * Hello, Dolly! (1991), Long Beach Civic Light Opera
 * Annie (1997), Broadway and U.S. national tour
 * South Pacific (2001), Pittsburgh Civic Light Opera
 * The Vagina Monologues (2001), Madison Square Garden

title: Nell Carter


text:
Talk:Fermat number

Proof of the theorem of Edouard Lucas
In the sketch of proof of the theorem I propose to replace the last sentence : "Since an odd power of 2 is a quadratic residue (mod p), so is 2 itself." by "Since an even power of 2 is a quadratic residue (mod p), so is 2 itself." which seems (to me) more accurate. JFM79.93.171.237 (talk) 15:30, 16 December 2010 (UTC)
 * No, that's an incorrect argument. An even power of every element is a quadratic residue, this does not imply anything about the element's being quadratic residue. If an odd power a2k+1 = b2 is a quadratic residue, then a is a quadratic residue, since a = (ba−k)2. Anyway, the power in question, 1 + 2n−1, is odd indeed.—Emil J. 15:45, 16 December 2010 (UTC)

Excuse me, I mean : from the last formula I get (1+22 n-1 )2. 2- 2 n-1 =2 (mod p), then 2 is a square if n > 1 (without using the fact that odd powers of 2 are residues mod p, I use only that 2 is invertible mod p). JFM —Preceding unsigned comment added by 79.93.171.86 (talk) 17:24, 22 December 2010 (UTC)

In fact, we can get an explicit value of r such that r^2 = 2 (mod Fn). Let i = 2^(2^(n-1)). Then i^2 = -1 (mod Fn). i exists for n≥1. Let q = 2^(2^(n-2)). Then q^2 = i, and q^4 = -1 (mod Fn). q exists for n≥2. Now (i-1)^2 = -2i (mod Fn) by direct algebraic expansion. So let r = q(i-1). Then r^2 = 2 (mod Fn). r exists for n≥2. 86.4.253.180 (talk) 00:45, 20 September 2013 (UTC)

In its present form this sketch of the proof is not well organized and has a significant gap. One needs precisely that the multiplicative order of 2 in G is 2n+1, not merely that this is divisible by the order of 2, to conclude p-1 is divisible by that power of 2. If no one objects, I will fix that gap. Further it seems a bit misplaced to lump this proof sketch with "other results" when it has been mentioned more than once already, including early in the article as a whole. Hardmath (talk) 14:27, 23 April 2019 (UTC)

Perhaps a simpler way to get an explicit value of r such that r^2 = 2 (mod Fn) is to define q = 2^(n-2), which clearly exists for n≥2. Then 4q = -1 (mod Fn), and let r = 2^(3q) - 2^q (mod Fn). Then by direct algebra: r^2 = 2^(6q) - 2*2^(4q) + 2^(2q) = (2^(4q) + 1)* 2^(2q) - 2*2^(4q)= Fn * 2^(2q) - 2*(Fn - 1) = 2 (mod Fn). 86.11.96.95 (talk) 01:36, 11 February 2022 (UTC)

Non-sensical heuristic for the infinitude of Fermat primes
The heuristic for the infinitude starts of with : "Suppose we regard the conditional probability that n is prime, given that we know all its prime factors are 1 modulo M, as at least CM/ln(n)."

This is non-sense. The number of integers up to x all of whose prime factors are congruent to 1 mod M is equal to roughly x / (\log x)^{1 - 1/\varphi(M)} on the other hand the number of integer that are prime and all of whose prime factors are congruent to 1 mod M is (1/\varphi(M)) * x / (\log x). Therefore the conditional probability of x being prime given that all of its prime factors are = 1 (mod M) is the latter divided by the former, that is (\log x)^{-1/\varphi(M)} / \varphi(M). Taking x = F_n and M = 2^n we now see that this conditional probability summed over all n converges very nicely.

I am therefore removing the non-sensical heuristic for the infinitude. — Preceding unsigned comment added by 132.204.90.25 (talk) 03:54, 5 March 2019 (UTC)

Sequence of Fermat numbers
I notice editor DVdm has reverted the specification that these numbers are terms in a numerical sequence as non-beeing sourced. I think that this aspect is easily noticeable without source like the statement "The cloudless sky is blue" which is considered a common fact not needing citation, as specified in some wikirules.--109.166.129.57 (talk) 14:32, 10 September 2019 (UTC)

Main motivation of study by Fermat
Among the edits reverted by user DVdm is the specification of main motivation of the study of these type of numbers by Fermat which I agree it might need a citation from a source. The info inserted in the introductory paragraphs of the article is already in a section below, but without explicit acknowledgement of main motivation of study.--109.166.129.57 (talk) 14:38, 10 September 2019 (UTC)

I understand that main aspect needing a citation concerns the simple enumeration procedure used by Fermat when formulating the conjecture.--109.166.129.57 (talk) 15:13, 10 September 2019 (UTC)

F5 factorization date
I've asked for clarification about the date of 1732 for the "full factorizaton" of $F_5$. Although Euler found the factor 641 in 1732, there is no indication he even tried to prove the other factor 6700741 prime. Refer to C. Edward Sandifer's book How Euler Did Even More ([]). The earliest I've heard this number being published as prime is with Dase's catalog in 1861. — Preceding unsigned comment added by Casu Marzu (talk • contribs) 16:55, 13 April 2020 (UTC)

It is proven that there are only 5 Fermat primes.
See this article, Fermat numbers 2^(2^n)+1 is not prime for n>=5, thus there are only 5 Fermat primes: 3, 5, 17, 257, 65537. 2402:7500:92C:4EB9:78DA:44AC:3879:8299 (talk) 19:22, 8 October 2021 (UTC)

 * Please read the article.—Anita5192 (talk) 20:23, 8 October 2021 (UTC)

 * There are infinity solution in Real numbers pair k1 & k2, but no guarantee in Natural numbers where are we looking for --Ming mm (talk) 13:58, 14 October 2021 (UTC)

Bad definition
I do believe that Fermat numbers are defined as $2^n + 1$, and NOT as $2^{2^n} + 1$. Fermat primes are primes that happen to be Fermat numbers... and they (proven) take the form $2^{2^m}+1$. Thus Fermat primes are prime Fermat numbers of the form $2^n+1$ where necessarily $n=2^m$. — Preceding unsigned comment added by 134.204.1.226 (talk) 20:22, 5 November 2021 (UTC)

Semi-protected edit request on 12 November 2021
Vizz01 (talk) 05:05, 12 November 2021 (UTC)

 * Request denied. You did not specify a "complete and specific description." The next time you make a request, please read the instructions that were in the template above.—Anita5192 (talk) 05:58, 12 November 2021 (UTC)

I added F12 entry (last line in table below) at https://en.wikipedia.org/wiki/Fermat_number#Factorization_of_Fermat_numbers

What can be more "complete and specific description" ? Anita5192 Can you please elaborate ? Here is the edit again since it most likely disappeared when the request was denied.

 * - valign="top"
 * F0 ||=|| 21||+||1 ||=||3 is prime||
 * - valign="top"
 * F1 ||=|| 22||+||1 ||=||5 is prime||
 * - valign="top"
 * F2 ||=|| 24||+||1 ||=||17 is prime||
 * - valign="top"
 * F3 ||=|| 28||+||1 ||=||257 is prime||
 * - valign="top"
 * F4 ||=|| 216||+||1 ||=||65,537 is the largest known Fermat prime||
 * - valign="top"
 * F5 ||=|| 232||+||1 ||=||4,294,967,297||
 * - style="background:white; color:#700000"
 * || || || || ||=||641 × 6,700,417 (fully factored 1732 )
 * - valign="top"
 * F6 ||=|| 264||+||1 ||=||18,446,744,073,709,551,617 (20 digits) ||
 * - style="background:white; color:#700000"
 * || || || || ||=||274,177 × 67,280,421,310,721 (14 digits) (fully factored 1855)
 * - valign="top"
 * F7 ||=|| 2128||+||1 ||=||340,282,366,920,938,463,463,374,607,431,768,211,457 (39 digits)||
 * - style="background:white; color:#700000"
 * || || || || ||=||59,649,589,127,497,217 (17 digits) × 5,704,689,200,685,129,054,721 (22 digits) (fully factored 1970)
 * - valign="top"
 * F8 ||=|| 2256||+||1 ||=||115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129, 639,937 (78 digits)||
 * - style="background:white; color:#700000; vertical-align:top"
 * || || || || ||=||1,238,926,361,552,897 (16 digits) × 93,461,639,715,357,977,769,163,558,199,606,896,584,051,237,541,638,188,580,280,321 (62 digits) (fully factored 1980)
 * - valign="top"
 * F9 ||=|| 2512||+||1 ||=||13,407,807,929,942,597,099,574,024,998,205,846,127,479,365,820,592,393,377,723,561,443,721,764,0 30,073,546,976,801,874,298,166,903,427,690,031,858,186,486,050,853,753,882,811,946,569,946,433,6 49,006,084,097 (155 digits)||
 * - style="background:white; color:#700000; vertical-align:top"
 * || || || || ||=|| 2,424,833 × 7,455,602,825,647,884,208,337,395,736,200,454,918,783,366,342,657 (49 digits) × 741,640,062,627,530,801,524,787,141,901,937,474,059,940,781,097,519,023,905,821,316,144,415,759, 504,705,008,092,818,711,693,940,737 (99 digits) (fully factored 1990)
 * - valign="top"
 * F10 ||=|| 21024||+||1
 * =||179,769,313,486,231,590,772,930...304,835,356,329,624,224,137,217 (309 digits)||
 * - style="background:white; color:#700000; vertical-align:top"
 * || || || || ||=||45,592,577 × 6,487,031,809 × 4,659,775,785,220,018,543,264,560,743,076,778,192,897 (40 digits) × 130,439,874,405,488,189,727,484...806,217,820,753,127,014,424,577 (252 digits) (fully factored 1995)
 * - valign="top"
 * F11 ||=|| 22048||+||1
 * =||32,317,006,071,311,007,300,714,8...193,555,853,611,059,596,230,657 (617 digits)||
 * - style="background:white; color:#700000; vertical-align:top"
 * || || || || ||=|| 319,489 × 974,849 × 167,988,556,341,760,475,137 (21 digits) × 3,560,841,906,445,833,920,513 (22 digits) × 173,462,447,179,147,555,430,258...491,382,441,723,306,598,834,177 (564 digits) (fully factored 1988)
 * - valign="top"
 * F12 ||=|| 24096||+||1
 * =||1,044,388,881,413,152,506,691,75...243,804,708,340,403,154,190,337 (1234 digits)||
 * - style="background:white; color:#700000; vertical-align:top"
 * || || || || ||=|| 114,689 × 26,017,793 × 63,766,529 × 190,274,191,361 × 1,256,132,134,125,569 × 568,630,647,535,356,955,169,033,410,940,867,804,839,360,742,060,818,433 × 40,386,086,203,521,847,842,442,0...117,418,021,434,702,300,430,337 (1133 digits) (last factor is a not-yet-factored composite)
 * }
 * Red information icon with gradient background.svg Not done: The 1213-digit factor is composite. It has the known prime factors 190274191361 and 1256132134125569, but it's still not fully factored. Your first request  was rejected because it was empty. PrimeHunter (talk) 07:46, 13 November 2021 (UTC)
 * Red information icon with gradient background.svg Not done: The 1213-digit factor is composite. It has the known prime factors 190274191361 and 1256132134125569, but it's still not fully factored. Your first request  was rejected because it was empty. PrimeHunter (talk) 07:46, 13 November 2021 (UTC)

Agreed and updated the most complete known factors above. Thanks PrimeHunter for your very valid point.
 * We list F0 to F11 and say "only F0 to F11 have been completely factored. I think it would be a little odd to stop at F12. All numbers from F12 to F19 are partially factored. We link http://www.prothsearch.com/fermat.html which has all known factors. PrimeHunter (talk) 06:52, 16 November 2021 (UTC)

Header intro-section, missing reference/link
In the header/intro section we have: “If 2k + 1 is prime and k > 0, then k must be a power of 2” which is not justified or referenced. It would be useful to link to the section below: Other theorems about Fermat numbers where the introductory statement is immediately proved. 91.125.173.22 (talk) 11:51, 13 November 2021 (UTC)

Finite fermat primes, but irrational reciprocal sum?
The page states at the same time that heuristics suggest F4 to be the last Fermat prime and that the sum of the reciprocals of the Fermat primes is irrational. This can't happen if there are finitely many of them. 69.176.153.154 (talk) 00:23, 11 January 2023 (UTC)

 * It does not specify that the sum must include only primes. All the composite Fermat numbers (e.g. 4294967297) are includeed as well –LaundryPizza03 ( d c̄ ) 00:25, 11 January 2023 (UTC)

title: Talk:Fermat number


text:
KHTML

KHTML is a discontinued browser engine that was developed by the KDE project. It originated as the engine of the Konqueror browser in the late 1990s, but active development ceased in 2016. It was officially discontinued in 2023.

Built on the KParts framework and written in C++, KHTML had relatively good support for Web standards during its prime. Engines forked from KHTML are used by most of the browsers that are widely used today, including WebKit (Safari) and Blink (Google Chrome, Chromium, Microsoft Edge, Opera, Vivaldi and Brave).

Origins
KHTML was preceded by an earlier engine called khtmlw or the KDE HTML Widget, developed by Torben Weis and Martin Jones, which implemented support for HTML 3.2, HTTP 1.0, and HTML frames, but not the DOM, CSS, or JavaScript.

KHTML itself came into existence on November 4, 1998, as a fork of the khtmlw library, with some slight refactoring and the addition of Unicode support and changes to support the move to Qt 2. Waldo Bastian was among those who did the work of creating that early version of KHTML.

Re-write and improvement
The real work on KHTML actually started between May and October 1999, with the realization that the choice facing the project was "either do a significant effort to move KHTML forward or to use Mozilla" and with adding support for JavaScript as the highest priority. So in May 1999, Lars Knoll began doing research with an eye toward implementing the DOM specification, finally announcing on August 16, 1999 that he had checked in what amounted to a complete rewrite of the KHTML library—changing KHTML to use the standard DOM as its internal document representation. That in turn allowed the beginnings of JavaScript support to be added in October 1999, followed shortly afterwards with the integration of KJS by Harri Porten.

In the closing months of 1999 and first few months of 2000, Knoll did further work with Antti Koivisto and Dirk Mueller to add CSS support and to refine and stabilize the KHTML architecture, with most of that work being completed by March 2000. Among other things, those changes enabled KHTML to become the second browser after Internet Explorer to correctly support Hebrew and Arabic and languages written right-to-left —before Mozilla had such support.

KDE 2.0 was the first KDE release (on October 23, 2000) to include KHTML (as the rendering engine of the new Konqueror file and web browser, which replaced the monolithic KDE File Manager).

Other modules
KSVG was first developed in 2001 by Nikolas Zimmermann and Rob Buis; however, by 2003, it was decided to fork the then-current KSVG implementation into two new projects: KDOM/KSVG2 (to improve the state of DOM rendering in KHTML underneath a more formidable SVG 1.0 render state) and Kcanvas (to abstract any rendering done within khtml/ksvg2 in a single shared library, with multiple backends for it, e.g., Cairo/Qt, etc.).

KSVG2 is also a part of WebKit.

Sunsetting
KHTML was scheduled to be removed in KDE Frameworks 6. Active development ended in 2016, just the necessary maintenance to work with updates to Frameworks 5. It was officially discontinued in 2023.

Standards compliance
The following standards are supported by the KHTML engine:

 * HTML 4.01
 * HTML 5 support
 * CSS 1
 * CSS 2.1 (screen and paged media)
 * CSS 3 Selectors (fully as of KDE 3.5.6 )
 * CSS 3 Other (multiple backgrounds, box-sizing and text-shadow)
 * PNG, MNG, JPEG, GIF graphic formats
 * DOM 1, 2 and partially 3
 * ECMA-262/JavaScript 1.5
 * Partial Scalable Vector Graphics support

Descendants
KHTML and KJS were adopted by Apple in 2002 for use in the Safari web browser. Apple publishes the source code for their fork of the KHTML engine, called WebKit. In 2013, Google began development on a fork of WebKit, called Blink.

title: KHTML


text:
Ultraviolet astronomy

Ultraviolet astronomy is the observation of electromagnetic radiation at ultraviolet wavelengths between approximately 10 and 320 nanometres; shorter wavelengths—higher energy photons—are studied by X-ray astronomy and gamma-ray astronomy. Ultraviolet light is not visible to the human eye. Most of the light at these wavelengths is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space.

Overview
Ultraviolet line spectrum measurements (spectroscopy) are used to discern the chemical composition, densities, and temperatures of the interstellar medium, and the temperature and composition of hot young stars. UV observations can also provide essential information about the evolution of galaxies. They can be used to discern the presence of a hot white dwarf or main sequence companion in orbit around a cooler star.

The ultraviolet universe looks quite different from the familiar stars and galaxies seen in visible light. Most stars are actually relatively cool objects emitting much of their electromagnetic radiation in the visible or near-infrared part of the spectrum. Ultraviolet radiation is the signature of hotter objects, typically in the early and late stages of their evolution. In the Earth's sky seen in ultraviolet light, most stars would fade in prominence. Some very young massive stars and some very old stars and galaxies, growing hotter and producing higher-energy radiation near their birth or death, would be visible. Clouds of gas and dust would block the vision in many directions along the Milky Way.

Space-based solar observatories such as SDO and SOHO use ultraviolet telescopes (called AIA and EIT, respectively) to view activity on the Sun and its corona. Weather satellites such as the GOES-R series also carry telescopes for observing the Sun in ultraviolet.

The Hubble Space Telescope and FUSE have been the most recent major space telescopes to view the near and far UV spectrum of the sky, though other UV instruments have flown on smaller observatories such as GALEX, as well as sounding rockets and the Space Shuttle.

Pioneers in ultraviolet astronomy include George Robert Carruthers, Robert Wilson, and Charles Stuart Bowyer.

Ultraviolet space telescopes

 * 🇺🇸 - Far Ultraviolet Camera/Spectrograph on Apollo 16 (April 1972)
 * 🇺🇸 + ESRO - TD-1A (135-286 nm; 1972–1974)
 * 🇺🇸 - Orbiting Astronomical Observatory (#2:1968-73. #3:1972-1981)
 * - Orion 1 and Orion 2 Space Observatories (#1: 200-380 nm, 1971; #2: 200-300 nm, 1973)
 * 🇺🇸 + 🇳🇱 - Astronomical Netherlands Satellite (150-330 nm, 1974–1976)
 * 🇺🇸 + 🇪🇺 - International Ultraviolet Explorer (115-320 nm, 1978–1996)
 * - Astron-1 (150-350 nm, 1983–1989)
 * - Glazar 1 and 2 on Mir (in Kvant-1, 1987–2001)
 * 🇺🇸 - FAUST (140-180 nm, in ATLAS-1 Spacelab aboard STS-45 mission, March 1992)
 * 🇺🇸 - EUVE (7-76 nm, 1992–2001)
 * 🇺🇸 - FUSE (90.5-119.5 nm, 1999–2007)
 * 🇺🇸 + 🇪🇺 - Extreme ultraviolet Imaging Telescope (on SOHO imaging Sun at 17.1, 19.5, 28.4, and 30.4 nm)
 * 🇺🇸 + 🇪🇺 - Hubble Space Telescope (various 115-800 nm,1990-1997-) (STIS 115–1030 nm, 1997–) (WFC3 200-1700 nm, 2009–)
 * 🇺🇸 - Swift Gamma-Ray Burst Mission (170–650 nm, 2004- )
 * 🇺🇸 - Hopkins Ultraviolet Telescope (flew in 1990 and 1995)
 * 🇩🇪 - ROSAT XUV (17-210eV) (30-6 nm, 1990–1999)
 * 🇺🇸 - Far Ultraviolet Spectroscopic Explorer (90.5-119.5 nm, 1999–2007)
 * 🇺🇸 - Galaxy Evolution Explorer (135–280 nm, 2003–2012)
 * 🇯🇵 - Hisaki (130-530 nm, 2013 - 2023)
 * 🇨🇳 - Lunar-based ultraviolet telescope (LUT) (on Chang'e 3 lunar lander, 245-340  nm, 2013 -)
 * 🇮🇳 - Astrosat (130-530 nm, 2015 -)
 * 🇺🇸 - Colorado Ultraviolet Transit Experiment (CUTE) - (255-330 nm spectrograph, 2021- )
 * 🇩🇪 - Public Telescope (PST) (100-180 nm, Proposed 2015, EU funded study )
 * 🇺🇸 - Viewpoint-1 SpaceFab.US (200-950 nm, Launch planned 2022)

See also List of ultraviolet space telescopes

Ultraviolet instruments on planetary spacecraft

 * 🇺🇸 - UVIS (Cassini) - 1997 (at Saturn from 2004 to 2017)
 * 🇺🇸 - MASCS (MESSENGER) - 2004 (at Mercury from 2011 to 2015)
 * 🇺🇸 - Alice (New Horizons) - 2006 (Pluto flyby in 2015)
 * 🇺🇸 - UVS (Juno) - 2011 (at Jupiter since 2016)
 * 🇺🇸 - IUVS (MAVEN) - 2013 (at Mars since 2014)

title: Ultraviolet astronomy