History.

The single quotation mark is traced to Ancient Greek practice, adopted and adapted by monastic copyists. In his seventh century encyclopedia, The, Isidore of Seville describes their use of the Greek "diplé" (a chevron) " ⟩ Diplé: our copyists place this sign in the books of the people of the Church, to separate or to indicate the quotations drawn from the Holy Scriptures".  The double quotation mark derives from a marginal notation used in fifteenth-century manuscript annotations to indicate a passage of particular importance (not necessarily a quotation); the notation was placed in the outside margin of the page and was repeated alongside each line of the passage. In his edition of the works of Aristotle, which appeared in 1483 or 1484, the Milanese Renaissance humanist Francesco Filelfo marked literal and appropriate quotes with oblique double dashes on the left margin of each line. Until then, literal quotations had been highlighted or not at the author's discretion. Non-verbal loans were marked on the edge. After the publication of Filelfo's edition, the quotation marks for literal quotations prevailed. During the seventeenth century this treatment became specific to quoted material, and it grew common, especially in Britain, to print quotation marks (now in the modern opening and closing forms) at the beginning and end of the quotation as well as in the margin; the French usage (see under Specific language features below) is a remnant of this. In most other languages, including English, the marginal marks dropped out of use in the last years of the eighteenth century. The usage of a pair of marks, opening and closing, at the level of lower case letters was generalized.  By the nineteenth century, the design and usage began to be specific within each region. In Western Europe the custom became to use the quotation mark pairs with the convexity pointing "outward." In Britain those marks were elevated to the same height as the top of capital letters:.  In France, by the end of the nineteenth century, the marks were modified to an angular shape:. Some authors claim that the reason for this was a practical one, in order to get a character that was clearly distinguishable from the apostrophes, the commas and the parentheses. Also, in other scripts, the angular quotation marks are distinguishable from other punctuation characters—the Greek breathing marks, the Armenian emphasis and apostrophe, the Arabic comma, decimal separator, thousands separator, etc. Other authors claim that the reason for this was an aesthetic one. The elevated quotation marks created an extra white space before and after the word that was considered aesthetically unpleasing, while the in-line quotation marks helped to maintain the typographical color, since the quotation marks had the same height and were aligned with the lower case letters. Nevertheless, while other languages do not insert a space between the quotation marks and the word(s), the French usage does insert them, even if it is a narrow space.  The "curved" quotation marks ('66-99') usage,, was exported to some non-Latin scripts, notably where there was some English influence, for instance in Native American scripts and Indic scripts. On the other hand, Greek, Cyrillic, Arabic and Ethiopic adopted the French 'angular' quotation marks,. The Far East angle bracket quotation marks,, are also a development of the in-line angular quotation marks.  In Central Europe, however, the practice was to use the quotation mark pairs with the convexity pointing "inward." The German tradition preferred the curved quotation marks, the first one at the level of the commas, the second one at the level of the apostrophes:. Alternatively, these marks could be angular and in-line with lower case letters, but still pointing inward:. Some neighboring regions adopted the German curved marks tradition with lower–upper alignment, while others made up a variant with the closing mark pointing rightward like the opening one,.  Sweden (and Finland) choose a convention where both marks equally pointed to the right but lined up both at the top level:.  In Eastern Europe there was a hesitation between the French tradition and the German tradition. The French tradition prevailed in North-Eastern Europe (Russia, Ukraine and Belarus), whereas the German tradition, or its modified version with the closing mark pointing rightward) has become dominant in South-Eastern Europe, i.e. the Balkan countries.  The single quotation marks re-emerged around 1800 as a means of indicating a secondary level of quotation. One could expect that the logic of using the corresponding single mark would be applied everywhere, but it was not. In some languages using the angular quotation marks, the usage of the single guillemet,, became obsolete, being replaced by double curved ones: ; the single ones still survive, for instance, in Switzerland. In Eastern Europe, the curved quotation marks,, are used as a secondary level when the angular marks, are used as a primary level.

In English.

In English writing, quotation marks are placed in pairs around a word or phrase to indicate:  In American writing, quotation marks are normally the double kind (the primary style). If quotation marks are used inside another pair of quotation marks, then single quotation marks are used. For example: If another set of quotation marks is nested inside single quotation marks, double quotation marks are used again, and they continue to alternate as necessary (though this is rarely done).  British publishing is regarded as more flexible about whether double or single quotation marks should be used. A tendency to use single quotation marks in British writing is thought to have arisen after the invention of steam-powered presses in the mid-19th century and the consequent rise of London and New York as very separate industrialized printing centres with distinct norms. However, "The King's English" in 1908 noted that the prevailing British practice was to use double marks for most purposes, and single ones for quotations within quotations. Different media now follow different conventions in the United Kingdom.  Different varieties and styles of English have different conventions regarding whether terminal punctuation should be written inside or outside the quotation marks; North American printing usually puts ending punctuation to the left of the closing quotation mark, whether it is part of the original quoted material or not, while styles elsewhere vary widely and have different rationales for placing it inside or outside, often a matter of house style.  Regarding their appearance, there are two types of quotation marks:  The closing single quotation mark is identical in form to the apostrophe and similar to the prime symbol. The double quotation mark is identical to the ditto mark in English-language usage. It is also similar to—and often used to represent—the double prime symbol. However, the quotation marks, the apostrophe, and the prime serve quite different purposes.

Summary table.

Other languages have similar conventions to English, but use different symbols or different placement.

Specific language features.

Dutch.

The standard form in the preceding table is taught in schools and used in handwriting. Most large newspapers have kept these quotation marks, but otherwise the alternative form with single or double “English-style” quotes is now often the only form seen in printed matter. Neutral (straight) quotation marks, and, are used widely, especially in texts typed on computers and on websites.  Although not generally common in the Netherlands any more, double angle (guillemet) quotation marks are still sometimes used in Belgium. Examples include the Flemish HUMO magazine and the Metro newspaper in Brussels.

German.

The symbol used as the left (typographical) quote in English is used as the right quote in Germany and Austria and a "low double comma" () (not used in English) is used for the left quote. Its single quote form () looks like a comma.  Some fonts, e.g. Verdana, were not designed with the flexibility to use an English left quote as a German right quote. Such fonts are therefore typographically incompatible with this German usage.  Double quotes are standard for denoting speech in German.  This style of quoting is also used in Bulgarian, Czech, Danish, Estonian, Georgian, Icelandic, Latvian, Lithuanian, Russian, Serbo-Croatian, Slovak, Slovene and in Ukrainian. This German double-quote style is also used in the Netherlands, but is falling out of fashion nowadays with the 'English-style' quotation marks being preferred. However, it still can be found on older shop signs and in most large newspapers.  Sometimes, especially in novels, guillemets (angle quotation mark sets) are used in Germany and Austria (albeit in reversed order from French):  In Switzerland, however, the French-style angle quotation mark sets are also used for German printed text: «A ‹B›?»

Finnish and Swedish.

In Finnish and Swedish, right quotes, called citation marks,, are used to mark both the beginning and the end of a quote. Double right-pointing angular quotes,, can also be used.  Alternatively, an en-dash followed by a (non-breaking) space can be used to denote the beginning of quoted speech, in which case the end of the quotation is not specifically denoted (see section Quotation dash below). A line-break should not be allowed between the en-dash and the first word of the quotation.

French.

French uses angle quotation marks (guillemets, or "duck-foot quotes"), adding a 'quarter-em space' within the quotes. However, many people now use the non-breaking space, because the difference between a non-breaking space and a four-per-em is virtually imperceptible (but also because the Unicode quarter-em space is breakable), and the quarter-em glyph is omitted from many fonts. Even more commonly, many people just put a normal (breaking) space between the quotation marks because the non-breaking space cannot be accessed easily from the keyboard; furthermore, many are simply not aware of this typographical refinement. Using the wrong type of space often results in a quotation mark appearing alone at the beginning of a line, since the quotation mark is treated as an independent word.  Sometimes, for instance on several French news sites such as "Libération", "Les Échos" or "Le Figaro", no space is used around the quotation marks. This parallels normal usage in other languages, e.g. Catalan, Polish, Portuguese, Russian, Spanish, or in German, French and Italian as written in Switzerland:  Initially, the French guillemet characters were not angle shaped but also used the comma (6/9) shape. They were different from English quotes because they were standing (like today's guillemets) "on" the baseline (like lowercase letters), and not above it (like apostrophes and English quotation marks) or hanging down from it (like commas). At the beginning of the nineteenth century, this shape evolved to look like small parentheses. The angle shape appeared later to increase the distinction and avoid confusions with apostrophes, commas and parentheses in handwritten manuscripts submitted to publishers. Unicode currently does not provide alternate codes for these 6/9 guillemets on the baseline, as they are considered to be form variants of guillemets, implemented in older French typography (such as the Didot font design). Also there was not necessarily any distinction of shape between the opening and closing guillemets, with both types pointing to the right (like today's French closing guillemets).  They must be used with non-breaking spaces, preferably narrow, if available, i.e. U+202F which is present in all up-to-date general-purpose fonts, but still missing in some computer fonts from the early years of Unicode, due to the belated encoding of U+202F (1999) after the flaw of not giving U+2008 non-breakable property as it was given to the related U+2007.  Legacy support of narrow non-breakable spaces was done at rendering level only, without interoperability as provided by Unicode support. High-end renderers as found in Desktop Publishing software should therefore be able to render this space using the same glyph as the breaking thin space U+2009, handling the non-breaking property internally in the text renderer/layout engine, because line-breaking properties are never defined in fonts themselves; such renderers should also be able to infer any width of space, and make them available as application controls, as is done with justifying/non-justifying.  In old-style printed books, when quotations span multiple lines of text (including multiple paragraphs), an additional closing quotation sign is traditionally used at the "beginning" of each line continuing a quotation; any right-pointing guillemet at the beginning of a line does not close the current quotation. This convention has been consistently used since the beginning of the 19th century by most book printers, but is no longer in use today. Such insertion of continuation quotation marks occurred even if there is a word hyphenation break. Given this feature has been obsoleted, there is no support for automatic insertion of these continuation guillemets in HTML or CSS, nor in word-processors. Old-style typesetting is emulated by breaking up the final layout with manual line breaks, and inserting the quotation marks at line start, much like pointy brackets before quoted plain text e-mail:  Unlike English, French does not set off unquoted material within a quotation by using a second set of quotation marks. Compare:  For clarity, some newspapers put the quoted material in italics:  The French Imprimerie nationale (cf. "Lexique des règles typographiques en usage à l'Imprimerie nationale", presses de l'Imprimerie nationale, Paris, 2002) does not use different quotation marks for nesting quotes:  In this case, when there should be two adjacent opening or closing marks, only one is written:  The use of English quotation marks is increasing in French and usually follows English rules, for instance in situations when the keyboard or the software context doesn't allow the use of guillemets. The French news site "L'Humanité" uses straight quotation marks along with angle ones.  English quotes are also used sometimes for nested quotations:  But the most frequent convention used in printed books for nested quotations is to style them in italics. Single quotation marks are much more rarely used, and multiple levels of quotations using the same marks is often considered confusing for readers:  Further, running speech does not use quotation marks beyond the first sentence, as changes in speaker are indicated by a dash, as opposed to the English use of closing and re-opening the quotation. (For other languages employing dashes, see section Quotation dash below.) The dashes may be used entirely without quotation marks as well. In general, quotation marks are extended to encompass as much speech as possible, including not just non-spoken text such as “he said” (as previously noted), but also as long as the conversion extends. However, the quotation marks end at the last spoken text, not extending to the end of paragraphs when the final part is not spoken.

Greek.

Greek uses angled quotation marks ( – "isagogiká"): and the quotation dash ( – "pávla"): which translate to:  A closing quotation mark,, is added to the beginning of each new quoted paragraph.  When quotations are nested, double and then single quotation marks are used:.

Hungarian.

According to current recommendation by the Hungarian Academy of Sciences the main Hungarian quotation marks are comma-shaped double quotation marks set on the base-line at the beginning of the quote and at apostrophe-height at the end of it for first level, (), reversed »French quotes« without space (the German tradition) for the second level, and thus the following nested quotation pattern emerges: ... and with third level:  In Hungarian linguistic tradition the meaning of a word is signified by "uniform (unpaired)" apostrophe-shaped quotation marks:  A quotation dash is also used, and is predominant in belletristic literature.

Polish.

According to current PN-83/P-55366 standard from 1983 (but not dictionaries, see below), "Typesetting rules for composing Polish text" ("Zasady składania tekstów w języku polskim") one can use either „ordinary Polish quotes” or «French quotes» (without space) for first level, and ‚single Polish quotes’ or «French quotes» for second level, which gives three styles of nested quotes:  There is no space on the internal side of quote marks, with the exception of "firet" (≈ em) space between two quotation marks when there are no other characters between them (e.g.,„ and ’”).  The above rules have not changed since at least the previous BN-76/7440-02 standard from 1976 and are probably much older. However, the part of the rules that concerns the use of guillemets conflicts with the Polish punctuation standard as given by dictionaries, including the "Wielki Słownik Ortograficzny PWN" recommended by the Polish Language Council. The PWN rules state:  In Polish books and publications, this style for use of guillemets (also known as »German quotes«) is used almost exclusively. In addition to being standard for second level quotes, guillemet quotes are sometimes used as first level quotes in headings and titles but almost never in ordinary text in paragraphs.  Another style of quoting is to use an em-dash to open a quote; this is used almost exclusively to quote dialogues, and is virtually the only convention used in works of fiction.  An en-dash is sometimes used in place of the em-dash, especially so in newspaper texts.

Portuguese.

Neither the Portuguese Language regulator nor the Brazilian prescribe what is the shape for quotation marks, they only prescribe when and how they should be used.  In Portugal, the angular quotation marks (ex. «quote») are traditionally used. They are the Latin tradition quotation marks, used normally by typographers. It is that also the chosen representation for displaying quotation marks in reference sources, and it is also the chosen representation from some sites dedicated to the Portuguese Language.  The "Código de Redação" for Portuguese-language documents published in the European Union prescribes three levels of quotation marks representation, :  However, the usage of English-style (ex. “quote” and ‘quote’) marks is growing in Portugal. That is probably due to the omnipresence of the English language and to the corresponding inability of some machines (mobile phones, cash registers, specific printers, calculators, etc.) to display the angular quotation marks.  In Brazil, however, the usage of angular quotation marks is little known, with almost solely the curved quotation marks (“quote” and ‘quote’) being used. This can be verified, for instance, in the difference between a Portuguese keyboard (which possesses a specific key for « and for ») and a Brazilian keyboard.  The Portuguese-speaking African countries tend to follow Portugal's conventions, not the Brazilian ones.  Other usages of quotation marks ( for double, for single) are obsolete..

Belarusian, Russian, and Ukrainian.

In Belarusian, Russian, and Ukrainian, angled quotation marks are used without spaces. In case of quoted material inside a quotation, rules and most noted style manuals prescribe the use of different kinds of quotation marks. However, Russian rules allow to use the same quotation marks for quoted material inside a quotation, and if inner and outer quotation marks fall together, then one of them should be omitted.  Right:  Permissible, when it is technically impossible to use different quotation marks:  It is common to use quotation dashes for dialogue, as well as within quotations for the reporting clause. For more details, see the on this topic.

Spanish.

Spanish uses angled quotation marks ( or ) as well, but always without the spaces.  And, when quotations are nested in more levels than inner and outer quotation, the system is: The use of English quotation marks is increasing in Spanish, and the "El País" style guide, which is widely followed in Spain, recommends them. Hispanic Americans often use them, owing to influence from the United States.

Chinese, Japanese, and Korean.

Corner brackets are well-suited for Chinese, Japanese, and Korean languages which are written in both vertical and horizontal orientations. China, South Korea, and Japan all use corner brackets when writing vertically. However, usages differ when writing horizontally: White corner brackets are used to mark quote-within-quote segments in case that the corner brackets are used.

Quotation dash.

Another typographical style is to omit quotation marks for lines of dialogue, replacing them with an initial dash:  This style is particularly common in Bulgarian, French, Greek, Hungarian, Polish, Portuguese, Romanian, Russian, Spanish, Swedish, Turkish, and Vietnamese. James Joyce always insisted on this style, although his publishers did not always respect his preference. Alan Paton used this style in "Cry, the Beloved Country" (and no quotation marks at all in some of his later work). Charles Frazier used this style for his novel "Cold Mountain" as well. Details for individual languages are given above.  The dash is often combined with ordinary quotation marks. For example, in French, a guillemet may be used to initiate running speech, with each change in speaker indicated by a dash, and a closing guillemet to mark the end of the quotation.  Dashes are also used in many modern English novels, especially those written in non-standard dialects. Some examples include:  In Italian, Catalan, Portuguese, Spanish, Ukrainian, Russian, Polish, Bulgarian, Georgian, Romanian, Lithuanian and Hungarian, the reporting clause in the middle of a quotation is separated with two additional dashes (also note that the initial quotation dash is followed by a single whitespace character as well as the fact that the additional quotation dashes for the middle main clause after the initial quotation dash are all with a single whitespace character on both of their sides):  In Finnish, on the other hand, a second dash is added when the quote continues after a reporting clause:  The Unicode standard introduced a separate character to be used as a quotation dash. In general it is the same length as an em-dash, and so this is often used instead. The main difference between them is that at least some software will insert a line break after an em dash, but not after a quotation dash. Both are displayed in the following table.

Electronic documents.

Different typefaces, character encodings and computer languages use various encodings and glyphs for quotation marks.

Typewriters and early computers.

"Ambidextrous" or "straight" quotation marks were introduced on typewriters to reduce the number of keys on the keyboard, and were inherited by computer keyboards and character sets. Some computer systems designed in the past had character sets with proper opening and closing quotes. However, the ASCII character set, which has been used on a wide variety of computers since the 1960s, only contains a straight single quote () and double quote ().  Many systems, such as the personal computers of the 1980s and early 1990s, actually drew these quotes like curved closing quotes on-screen and in printouts, so text would appear like this (approximately):  These same systems often drew the (free standing) grave accent (, U+0060) as an open quote glyph (actually a high-reversed-9 glyph, to preserve some usability as a grave when overstruck). Thus, using a grave accent instead of a quotation mark as the opening quote gave a proper appearance of single quotes at the cost of semantic correctness. Nothing similar was available for the double quote, so many people resorted to using two single quotes for double quotes, which would look approximately like the following:  The typesetting application TeX uses this convention for input files. The following is an example of TeX input which yields proper curly quotation marks.  The Unicode slanted/curved quotes described below are shown here for comparison:

Keyboard layouts.

Typographical quotation marks are almost absent on keyboards.  In typewriter keyboards, the curved quotation marks were not implemented. Instead, to save space, the straight quotation marks were invented as a compromise. Even in countries that did not use curved quotation marks, angular quotation marks were not implemented either.  Computer keyboards followed the steps of typewriter keyboards. Most computer keyboards do not have specific keys for curved quotation marks or angled quotation marks. This may also have to do with computer character sets:  In languages that use the curved “...” quotation marks, they are available in:  In languages that use the angular «...» quotation marks, they are available in:  In languages that use the corner bracket 「...」 quotation marks, they are available in:  In languages that use the angle bracket 《...》 they are available in:  In languages that use the curved „...“ quotation marks, they are available in:  In languages that use the curved „...” quotation marks, they are available in:  In languages that use the curved ”...” quotation marks, they are available in:

Curved quotes within and across applications.

Historically, support for curved quotes was a problem in information technology, primarily because the widely used ASCII character set did not include a representation for them.  The term'smart quotes',, is from the name in several word processors of a function aimed this problem: automatically converting straight quotes typed by the user into curved quotes, the feature attempts to be "smart" enough to determine whether the punctuation marked opening or closing. Since curved quotes are the typographically correct ones, word processors have traditionally offered curved quotes to users (at minimum as available characters). Before Unicode was widely accepted and supported, this meant representing the curved quotes in whatever 8-bit encoding the software and underlying operating system was using. The character sets for Windows and Macintosh used two different pairs of values for curved quotes, while ISO 8859-1 (historically the default character set for the Unixes and older Linux systems) has "no" curved quotes, making cross-platform and -application compatibility difficult.  Performance by these "smart quotes" features was far from perfect overall (variance potential by e.g. subject matter, formatting/style convention, user typing habits). As many word processors (including Microsoft Word and OpenOffice.org) have the function enabled by default, users may not have realized that the ASCII-compatible straight quotes they were typing on their keyboards ended up as something different (conversely users could incorrectly assume its functioning in other applications, e.g. composing emails).  The curved apostrophe is the same character as the closing single quote. "Smart quotes" features, however, wrongly convert initial apostrophes (as in 'tis, 'em, 'til, and '89) into "opening" single quotes. (An example of this error appears in the advertisements for the television show "'Til Death"). The two very different functions of this character can cause confusion, particularly in British styles, in which single quotes are the standard primary.  Unicode support has since become the norm for operating systems. Thus, in at least some cases, transferring content containing curved quotes (or any other non-ASCII characters) from a word processor to another application or platform has been less troublesome, provided all steps in the process (including the clipboard if applicable) are Unicode-aware. But there are still applications which still use the older character sets, or output data using them, and thus problems still occur.  There are other considerations for including curved quotes in the widely used markup languages HTML, XML, and SGML. If the encoding of the document supports direct representation of the characters, they can be used, but doing so can cause difficulties if the document needs to be edited by someone who is using an editor that cannot support the encoding. For example, many simple text editors only handle a few encodings or assume that the encoding of any file opened is a platform default, so the quote characters may appear as the generic replacement character or'mojibake' (gibberish). HTML includes a set of entities for curved quotes: codice_3 (left single), codice_4 (right single or apostrophe), codice_5 (low 9 single), codice_6 (left double), codice_7 (right double), and codice_8 (low 9 double). XML does not define these by default, but specifications based on it can do so, and XHTML does. In addition, while the HTML 4, XHTML and XML specifications allow specifying numeric character references in either hexadecimal or decimal, SGML and older versions of HTML (and many old implementations) only support decimal references. Thus, to represent curly quotes in XML and SGML, it is safest to use the decimal numeric character references. That is, to represent the double curly quotes use codice_9 and codice_10, and to represent single curly quotes use codice_11 and codice_12. Both numeric and named references function correctly in almost every modern browser. While using numeric references can make a page more compatible with outdated browsers, using named references are safer for systems that handle multiple character encodings (i.e. RSS aggregators and search results).

Usenet and email.

The style of quoting known as Usenet quoting uses the greater-than sign, prepended to a line of text to mark it as a quote. This convention was later standardized in RFC 3676, and was adopted subsequently by many email clients when automatically including quoted text from previous messages (in plain text mode).

Unicode code point table.

In Unicode, 30 characters are marked codice_13 by character property. They all have general category "Punctuation", and a subcategory Open, Close, Initial, Final or Other (codice_14). Several other Unicode characters with quotation mark semantics lack the character property.

Quotation marks, also known as quotes, quote marks, speech marks, inverted commas, or talking marks, are punctuation marks used in pairs in various writing systems to set off direct speech, a quotation, or a phrase. The pair consists of an opening quotation mark and a closing quotation mark, which may or may not be the same character.

引号(-{“”}- -{‘’}- -{「」}- -{『』}-,英文:quotation mark),标示引用、着重、特别用意的符号。


History.

SGI first used the IRIX name from the 1988 release 3.0 of the operating system for the SGI IRIS 4D series of workstations and servers. Previous releases are identified only by the release number prefixed by "4D1-", e.g. "4D1-2.2". The 4D1- prefix continued to be used in official documentation to prefix IRIX release numbers.  IRIX 3.x is based on UNIX System V Release 3 with 4.3BSD enhancements, and incorporates the 4Sight windowing system, based on NeWS and IRIS GL. SGI's own Extent File System (EFS) replaces the System V filesystem.  IRIX 4.0, released in 1991, replaces 4Sight with the X Window System (X11R4), the 4Dwm window manager providing a similar look and feel to 4Sight.  IRIX 5.0, released in 1993, incorporates certain features of UNIX System V Release 4, including ELF executables. IRIX 5.3 introduced the XFS journaling file system.  In 1994, IRIX 6.0 added support for the 64-bit MIPS R8000 processor, but is otherwise similar to IRIX 5.2. Later 6.x releases support other members of the MIPS processor family in 64-bit mode. IRIX 6.3 was released for the SGI O2 workstation only. IRIX 6.4 improved multiprocessor scalability for the Octane, Origin 2000, and Onyx2 systems. The Origin 2000 and Onyx2 IRIX 6.4 was marketed as "Cellular IRIX", although it only incorporates some features from the original Cellular IRIX distributed operating system project. IRIX development stabilized with IRIX 6.5, released in 1998. The last version of IRIX is 6.5.30, released in August 2006.  A 2001 "Computerworld" review found IRIX in a "critical" state. SGI had been moving its efforts to Linux and the Windows-based SGI Visual Workstation but MIPS and IRIX customers convinced SGI to continue to support its platform through 2006. On 6 September 2001, an SGI press release announced the end of the MIPS and IRIX product lines. Production ended on 29 December 2006, with final deliveries in March 2007, except by special arrangement. Support for these products ended in December 2013 and they will receive no further updates.  Much of IRIX's core technology has been open sourced and ported by SGI to Linux, including XFS. , due to the bankruptcy of Silicon Graphics in 2009 and its subsequent purchase by Rackable Systems, who later was purchased by HP Enterprise in 2016, all SGI-badged hardware produced after 2007 is incapable of running IRIX, being based on either IA-64 or x86-64 architecture and designed to run Red Hat Enterprise Linux or SUSE Linux Enterprise Server. HPE has not stated any public plans for IRIX development or source code release.

Features.

IRIX 6.5 is compliant with UNIX System V Release 4, UNIX 95, and POSIX (including 1e/2c draft 15 ACLs and Capabilities).  In the early 1990s, IRIX was a leader in Symmetric Multi-Processing (SMP), scalable from 1 to more than 1024 processors with a single system image. IRIX has strong support for real-time disk and graphics I/O. IRIX was widely used for the 1990s and 2000s, in the computer animation and scientific visualization industries due to its large application base and high performance. It still is relevant in a few legacy applications.  IRIX is one of the first Unix versions to feature a graphical user interface for the main desktop environment. IRIX Interactive Desktop uses the 4Dwm X window manager with a custom look designed using the Motif widget toolkit. IRIX is the originator of the industry standard OpenGL for graphics chips and Image processing libraries.  IRIX uses the MIPSPro Compiler for both its front end and back end. The compiler, also known in earlier versions as IDO (IRIS Development Option) was released in many versions, many of which are coupled to the OS version. The last version was 7.4.4m, designed for 6.5.19 or later. The compiler is designed to support parallel POSIX programming in C/C++, Fortran 77/90, and Ada. The Workshop GUI IDE is used for development. Other tools include Speedshop for performance tuning, and Performance Co-Pilot.

Hobbyist Use.

IRIX has attracted a small but dedicated fanbase of Silicon Graphics hardware who are attracted to various aspects of the operating system and corresponding hardware. This includes the operating system itself, especially its 3D graphics software such as Alias Maya/PowerAnimator and SoftImage, and the HPC elements of the hardware. This hobbyist community is notable for preserving various beta versions of Acclaim Entertainment games from a lot discovered in 2017 including Turok and NBA Jam.

IRIX ( ) is a discontinued operating system developed by Silicon Graphics (SGI) to run on the company's proprietary MIPS workstations and servers. It is a variety of UNIX System V with BSD extensions. In IRIX, SGI originated the XFS file system and the universally adopted industry-standard OpenGL graphics system.

IRIX是由硅谷图形公司(SGI)以System V与BSD延伸程序为基础所发展成的UNIX操作系统,IRIX可以在SGI公司的RISC型电脑上执行,即是采行32位元、64位元MIPS架构的SGI工作站、服务器。


Historical background.

Early attempts to claim a racial division between "masters" and "slaves", or the belief that a nation's ruling class is biologically superior to its ruled subjects, were made in the 18th century. Henri de Boulainvilliers in his book "History of the Ancient Government of France" (published posthumously in 1727) tried to prove that in France, the nobility represented the descendants of the old Frankish ruling class, whereas the rest of the population was descended from the subject Gauls. Therefore two qualitatively different races were confronting one another, and the only way to abolish the superiority of the Franks was to destroy their civilization. Classical liberal theorists such as Volney and Sieyès discredited this theory by showing that the French nobility consisted mostly of nouveaux riches who came from all parts of the country, and thus the idea of a racially-pure Frankish lineage was fraudulent.  In 1855, French count Arthur de Gobineau published his infamous work "An Essay on the Inequality of the Human Races". Expanding upon Boulainvilliers' use of ethnography to defend the Ancien Régime against the claims of the Third Estate, Gobineau divides the human species into three major groupings, white, yellow and black, claiming to demonstrate that "history springs only from contact with the white races." Among the white races, he distinguishes the Aryan race as the pinnacle of human development, the basis of all European aristocracies. However, inevitable miscegenation led to the "downfall of civilizations". The politically legitimist Gobineau was an enemy of democracy as much as he was an enemy of miscegenation.  Gobineau's influence was slight at first. In his letters to Alexis de Tocqueville, he complained that his book was being hushed up in France and was having a real effect only in the United States. Tocqueville, who rejected the book in spite of his friendship with Gobineau, pointed out to him that this was because the book chimed with the slave-owners' interests in the Southern states. However, in the 1880s the book gained popularity in Germany thanks to the efforts of Cosima Wagner. In 1899, Houston Stewart Chamberlain, a Germanophile Englishman and Cosima Wagner's son-in-law, published "The Foundations of the Nineteenth Century". Expanding upon Gobineau's earlier theories, he argued that that Western civilization is deeply marked by the influence of the Teutonic peoples. Chamberlain grouped all European peoples—not just Germans, but Celts, Slavs, Greeks, and Latins—into the "Aryan race", a race built on the ancient Proto-Indo-European culture. At the helm of the Aryan race, and, indeed, all races, he saw the Nordic or Teutonic peoples.  The "Übermensch" (German) ("Overman" or "Superman") is a concept in the philosophy of German philosopher Friedrich Nietzsche—he posited the "Übermensch" as a goal for humanity to set for itself in his 1883 book "Thus Spoke Zarathustra" (). However, Nietzsche never developed the concept on racial grounds. Instead, the "Übermensch" "seems to be the ideal aim of spiritual development more than a biological goal". Nazism distorted the concept's real meaning in order to make it fit its'master race' view.  By the late 19th and early 20th centuries, it was posited that the Indo-Europeans (who were generally referred to as Aryans) made up the highest branch of humanity because their civilization was its most technologically advanced. This reasoning was simultaneously intertwined with Nordicism which proclaimed that the "Nordic race" was the "purest" form of the said Aryan race. Today, this view is regarded as a form of scientific racism and contradicts the belief in racial equality by positing the view that one race is superior to all other races.

Eugenics.

Eugenics came to play a prominent role in this racial thought as a way to improve and maintain the purity of the Aryan master race. Eugenics was a concept adhered to by many thinkers in the 1910s, 1920s, and 1930s, such as Margaret Sanger, Marie Stopes, H. G. Wells, Woodrow Wilson, Theodore Roosevelt, Madison Grant, Émile Zola, George Bernard Shaw, John Maynard Keynes, John Harvey Kellogg, Linus Pauling, and Sidney Webb. Human "dog and pony show" type events (organized by advocates of eugenics), where men and women appeared on stage in swimsuits in eugenic competitions (only Nordic Aryans were allowed to enter) to be evaluated for their physical and mental qualities as marriage partners, were common throughout Europe and North America in the 1920s. The Nazis took this concept to a further extreme by establishing a program to systematically genetically enhance the Nordic Aryans themselves through a program of Nazi eugenics, based on the eugenics laws of the US state of California, to create a super race.

Hierarchy.

The modern concept of the "master race" is generally derived from a 19th-century racial theory, which posited a hierarchy of races that was based on darkness of skin color. This 19th-century concept was initially developed by Count Joseph Arthur De Gobineau. Gobineau's basic concept, as further refined and developed in Nazism, placed black Indigenous Australians and Equatorial Africans at the bottom of the hierarchy, while white Northern and Western Europeans (which consisted of Germans, Swedes, Icelanders, Norwegians, Danes, British, Irish, Dutch, Belgian and Northern French) were placed at its top; olive skinned white Southern Europeans (who consisted of Southern French, Portuguese, Spaniards, Italians, Romanians, and Greeks, i.e., those who were called the Mediterranean race, were regarded as another sub-race of the Caucasian race) and placed in its upper middle ranks; and the Semitic and Hamitic races (supposed sub-races of the Caucasian race) were placed in its lower-middle ranks (because the Jews, were Semites, the Nazis believed their cleverness made them extremely dangerous—they had their own plan for Jewish world domination, a conspiracy which needed to be opposed by all thoughtful Aryans). Slavs such as Poles and Russians were not considered Aryans; and neither were the members of the Mongoloid race (including its offshoots such as Malayans, American Indians) and mixed-race people such as Eurasians, the bronze Mestizos, Mulattos, Afro-Asians, and Zambos were placed in its lower middle ranks. However, the Japanese were considered honorary Aryans.  In their attempt to scientifically prove the racial inferiority of Slavs, German (and Austrian) racial scientists were forced to gloss over their findings which consistently proved that Early Slavs were dolicocephalic and fair haired, i.e., "Nordic", while the South Slavic "Dinaric" sub-race was often viewed favourable. Nazis used the term "Slavic race", and considered Slavs to be non-Aryan The concept of a Slavic "Untermensch" accompanied their political goals, and it was particularly aimed at Poles and Russians. Germany's immediate goal was "Drang nach Osten" or expansion into the East, which was the first phase in its ultimate plan to conquer Europe, and Ukraine's "chernozem" (black earth) soil was regarded as a particularly desirable zone for colonization by the ""Herrenvolk"" (master race).  In relation to the Nazis belief in racial purity, author and historian Lucy Dawidowicz wrote:

'Master race' in the United States.

In the United States, the concept of'master race' arose within the context of master-slave race relations in the slavery-based society of historical America – particularly in the South in the mid-19th century. It was based upon both the experience of slavery and the, but also on the relations between whites in the South and North, particularly during the American Civil War.  Benjamin W. Leigh, representing Virginia in the United States Senate, said in a speech of January 19, 1836: There has been in Virginia as earnest a desire to abolish slavery as exists any where at this day. It commenced with the Revolution, and many of our ablest and most influential men were active in recommending it, and in devising plans for the accomplishment of it. The Legislature encouraged and facilitated emancipation by the owners, and many slaves were so emancipated. The leaning of the courts of justice was always "in favorem libertatis". This disposition continued until the impracticability of effecting a general emancipation, without incalculable mischief to the master race, and danger of utter destruction to the other, and the evils consequent on partial emancipations, became too obvious to the Legislature, and to the great majority of the people, to be longer disregarded.  The Oxford English Dictionary records that William J. Grayson used the phrase "master race" in his poem "The Hireling and the Slave" (1855): <poem> For these great ends hath Heaven’s supreme command Brought the black savage from his native land, Trains for each purpose his barbarian mind, By slavery tamed, enlightened, and refined; Instructs him, from a master-race, to draw Wise modes of polity and forms of law, Imbues his soul with faith, his heart with love, Shapes all his life by dictates from above </poem>  where the phrase denotes the relation between the white masters and negro slaves. By 1860 Virginian author George Fitzhugh was using the "challenging phrase "master race", which soon came to mean considerably more than the ordinary master-slave relationship". Fitzhugh, along with a number of southern writers, used the term to differentiate Southerners from Northerners, based on the dichotomy that Southerners were supposedly descendants of Normans / Cavaliers whereas Northerners were descendants of Anglo-Saxons / Puritans.  In 1861, the Southern press bragged that Northern soldiers would "encounter a master race" and knowledge of this fact would cause Northern soldiers' "knees to tremble". The "Richmond Whig" in 1862 proclaimed that "the master race of this continent is found in the southern states", and in 1863 the "Richmond Examiner" stated that "there are slave races born to serve, master races born to govern".  In the works of John H. Van Evrie, a Northern supporter of the Confederacy, the term was interchangeable with white supremacy, notably in "White Supremacy and Negro Subordination, Or, Negroes a Subordinate Race and (so-called) slavery its normal condition" (1861). In "Subgeneation: the theory of the normal relations of the races; an answer to miscegenation" (1864) Van Evrie created the words "subgen" to describe what he considered to be the "inferior races" and "subgeneation" to describe the ‘normal’ relation of such inferior races to whites, something which he considered to be the "very corner-stone of democracy"; but these words never entered the dictionary.  The racial term "Untermensch" originates from the title of Klansman Lothrop Stoddard's 1922 book "The Revolt Against Civilization: The Menace of the Under-man". It was later adopted by the Nazis from that book's German version "Der Kulturumsturz: Die Drohung des Untermenschen" (1925). An advocate of the U.S. immigration laws that favored Northern Europeans, Stoddard wrote primarily on the alleged dangers posed by "colored" peoples to white civilization, with his most famous book "The Rising Tide of Color Against White World-Supremacy" in 1920. Alfred Rosenberg was the leading Nazi who attributed the concept of the East-European "under man" to Stoddard. As the Nazi Party's chief racial theorist, Rosenberg oversaw the construction of a human racial "ladder" that justified Hitler's racial and ethnic policies. Referring to Russian communists, Rosenbeg wrote in his "Der Mythus des 20. Jahrhunderts" (1930) that "this is the kind of human being that Lothrop Stoddard has called the 'under man.'" ["...den Lothrop Stoddard als 'Untermenschen' bezeichnete."]

Nordicism.

The origins of the Nazi version of the theory of the master race were in the 19th-century racial theories of Count Joseph Arthur De Gobineau, who argued that cultures degenerated when distinct races mixed. It was believed at this time that the peoples of Southern Europe were racially mixed with non-European Moors from across the Mediterranean Sea, while the peoples of Northern Europe and Western Europe remained pure. Proponents of the Nordic theory further argued that Nordic peoples had developed an innate toughness and determination due to the harsh, challenging climate in which they evolved.  The philosopher Arthur Schopenhauer was one of the earliest proponents of a theory presenting a hierarchical racial model of history, attributing civilisational primacy to the "white races" who gained their sensitivity and intelligence by refinement in the rigorous north.  The highest civilisation and culture, apart from the Ancient Indians and Egyptians, are found exclusively among the white races; and even with many dark peoples, the ruling caste or race is fairer in colour than the rest and has, therefore, evidently immigrated, for example, the Brahmins, the Incas, and the rulers of the South Sea Islands. All this is because necessity is the mother of invention because those tribes that emigrated early to the north and there gradually became white, had to develop all their intellectual powers and invent and perfect all the arts in their struggle with need, want and misery, which in their many forms were brought about by the climate. This they had to do in order to make up for the parsimony of nature and out of it all came their high civilisation.  Despite this, he was adamantly against differing treatment of races, was fervently anti-slavery, and supported the abolitionist movement in the United States. He describes the treatment of "[our] innocent black brothers whom force and injustice have delivered into [the slave-master's] devilish clutches" as "belonging to the blackest pages of mankind's criminal record".  Hans Frank, Hitler's personal lawyer, stated that Hitler carried a copy of Schopenhauer's book "The World as Will and Representation" with him wherever he went throughout World War I. The postulated superiority of these people was said to make them born leaders, or a "master race". Other authors included Guido von List, his associate Lanz von Liebenfels, and the British-born German racial theorist Houston Stewart Chamberlain, all of whom felt that the white race in general and Germanic peoples in particular were superior to others, and that given the purification of both the white race and the German people from the other races which were "polluting" them, a new millenarian age of Aryan god-men would arrive.  Nazi policy stressed the superiority of the Germanic "Ubermenschen" (superhuman) Nordic race, a sub-race of the European population defined by anthropometric models of racial difference. The Nordic race was said to comprise only the Germanic peoples: Scandinavians and the rest of the Nordic countries (Norwegians, Swedes, Danes, Icelanders, and Faroese), ethnic Germans (including Austrians, Banat Swabians, as well as Sudeten, Baltic and Volga Germans), Alemannic Swiss, Liechtensteiners, Luxembourgers, the Dutch, Flemings, Afrikaners, Frisians and the English.  The Nazi racial theorist Hans F. K. Günther first defined "Nordic thought" in his programmatic book "Der Nordische Gedanke unter den Deutschen". The fact that Germans were not purely Nordic was acknowledged by Günther in his book "Rassenkunde des deutschen Volkes" (1922) ("Racial Science of the German People"), in which he described the German people as being made up of all five of his European racial categories: Nordic, Mediterranean, Dinaric, Alpine, and East Baltic. Most official Nazi comments on the Nordic race were based on Günther's works, and Alfred Rosenberg presented Günther with a medal for his work in anthropology.  Although the physical ideal of these racial theorists was typically the tall, fair-haired and light-eyed Nordic individual, such theorists accepted the fact that a considerable variety of hair and eye colour existed within the racial categories they recognised. For example, Adolf Hitler and many Nazi officials had dark hair and were still considered members of the Aryan race under Nazi racial doctrine, because the determination of an individual's racial type depended on a preponderance of many characteristics in an individual rather than on just one defining feature.  Hitler and Himmler planned to use the SS as the basis for the racial "regeneration" of Europe following the final victory of Nazism. The SS was to be a racial elite chosen on the basis of "pure" Nordic qualities.  Giuseppe Sergi (1841–1936) was an Italian anthropologist of the early twentieth century, best known for his opposition to Nordicism in his books on the racial identity of ancient Mediterranean peoples. His concept of the Mediterranean race became important to the modelling of racial difference in the early twentieth century.

Aryanism and Nazism.

The term Aryan derives from the Sanskrit word (ā́rya), which derived from "arya", the original Indo-Iranian autonym. Also, the word "Iran" is the Persian word for land/place of the "Aryan" (see also Iranian peoples).  Following the ideas of Gobineau and others, the Nazi theorist Alfred Rosenberg determined that these people, who, he claimed, were originally from Atlantis, were a dynamic warrior people who dwelt in northern climates on the North German Plain in prehistoric times, from which they migrated southeast by riding their chariots, eventually reaching Ukraine, Iran, and then India. They were supposed to be the ancestors of the ancient Germanic tribes, who shared their warrior values. Rosenberg claimed that Christianity was an alien Semitic slave-morality which was inappropriate for the warrior Aryan master race and he thus supported a melange of aspects of Hindu Vedic and Zoroastrian teachings (both of these religions having been organised by Aryans), along with pre-Christian European Odinistic paganism, which he also considered distinctively Aryan in character.  In Nazi Germany, the Nuremberg Race Laws of 1935 forbade sexual relations and marriage between an "Aryan" and a "non-Aryan" in order to maintain the purity of the Aryan race. Such relations became a punishable crime known as "Rassenschande" or "racial shame". The League of German Girls was particularly regarded as instructing girls to avoid "Rassenschande", which was treated with particular importance for young females. Aryans found guilty of this crime could face incarceration in a concentration camp, while non-Aryans could face the death penalty. The Nazis recognized the Germanic people as the master race, and several policies were implemented in order to improve and maintain the Germanic-Nordic ubermenschen Aryan "master race", including the practice of eugenics. In order to eliminate "defective" citizens, the T-4 Euthanasia Program was administered by Karl Brandt in order to rid the country of the intellectually disabled or those born with genetic deficiencies, as well as those deemed racially inferior. Additionally, a programme of compulsory sterilisation was undertaken which resulted in forced operations being performed on hundreds of thousands of individuals. Many of these policies are generally seen as being related to what eventually became known as the Holocaust.  The Nazis also undertook measures to increase the number of Nordics in Germany. The Lebensborn program was only open to German women who fit the Nordic profile. During the Nazi occupation of Poland, the Nazis took young Nordic-looking Polish children who were classified as being descended from ethnic German settlers in order to determine whether or not they were "racially valuable". If that were the case, the young children were taken back to these Lebensborn houses so they could be raised as Germans.  In Nazi Germany, there existed an official document which certified that its owner was Aryan, the so-called Aryan certificate that could also be obtained by citizens of other countries. It states in the section "Racial Tenet" ("Rassegrundsatz"):  For the "Greater Aryan certificate" people had to prove that reaching back to January 1, 1800 ""none of their paternal nor their maternal ancestors had Jewish or colored blood"" (SS officers had to prove this reaching back to 1750).

Mediterranean race.

The fact that the Mediterranean race was responsible for the most important of ancient western civilisations was a problem for the promoters of Nordic superiority. According to Giuseppe Sergi, the Mediterranean race was the "greatest race of the world" and was singularly responsible for the most accomplished civilisations of ancient times, including those of Mesopotamia, Persia, Egypt, Greece, Phoenicia, Carthage, and Rome. The Mediterranean race was also a major influence to the outside world in the modern era: during the 16th century, Spain and Portugal established the first global empires in Western history, setting both nations in the highest level of political and economic powers in Europe.  Charles Gabriel Seligman also stated that "it must, I think, be recognised that the Mediterranean race has actually more achievements to its credit than any other race, since it is responsible for by far the greater part of Mediterranean civilisation, certainly before 1000 BC (and probably much later), and so shaped not only the Aegean cultures, but those of Western as well as the greater part of Eastern Mediterranean lands, while the culture of their near relatives, the Hamitic pre-dynastic Egyptians, formed the basis of that of Egypt."  The Nazis explained this by pointing out that the original Latins and Greeks were Indo-European Nordic tribes which had migrated into Italy and Greece, respectively. The Nazis also claimed that the Spanish and Portuguese Empires were examples of Nordic power since, at the time, their governments were run by the descendants of the Germanic Visigoths who invaded Spain and Portugal fifteen centuries earlier. However, they did admit that the masses of people who lived during the flowering of these four civilizations were Mediterranean. And Germans of all European races were classified as Aryans.

Master race in fiction.

Aryan master race ideology was common throughout the educated and literate strata of the Western world until the post-World War II era. Such theories were commonplace in early-20th century fantasy literature.  In the 1920s and 1930s, the original "Buck Rogers" stories and newspaper cartoons, Buck Rogers, in his adventures in the 25th century that take place on Earth, fights for "Aryan-Americans" from the liberated zone around Niagara, New York, against the "Red Mongol Empire," a Chinese empire of the future which rules most of North America.  In the 1930s, both educational and storybooks for children in Germany taught their readers about the master race. In the "Sun Koh" science fiction series, the protagonist Koh says things like "My forefathers were Aryan", and in a story about Atlantis, he says, "If our Atlantis once again rises out of the sea, then we will get from there the blond, steel-hard men with the pure blood and will create with them the master race, which will finally rule the earth." The German writer Michael Ende, who was born in 1929 and grew up reading such books, wrote his classic novel "Jim Button and Luke the Engine Driver" in the 1950s, as a way of opposing the Nazi propaganda he was taught. "Frankfurter Allgemeine Zeitung" writer Julia Voss wrote a book on Jim Button, uncovering Ende's many references to Nazi symbols in that book. Voss shows how Ende upends the Nazi belief that Atlantis was the original home of the Aryan race by creating his own submerged city and making it rise, but not to restore Aryan master-race rule over the earth, rather it becomes a multi-racial paradise with Jim Button, who is black and a descendant of the Magi Caspar, as its king.  In the 1948 film "Rope" by Alfred Hitchcock, one of the central characters, Brandon Shaw, is a firm believer in the master race ideology.  In the "Doctor Who series," the Doctor's frequent enemies, the Daleks, consider themselves a master race which must purge the universe of all other life forms; Terry Nation explicitly modeled them on the Nazis. In the 2009 special "The End of Time", when the Master transforms the entire human race into copies of himself, he claims that there is no human race, but only "the Master race".  In the "Harry Potter" series, while the parallels were not originally intentional, there is much similarity between Lord Voldemort's pureblood ideology and the master race ideology of the Nazis, with wizards being "pure" and anyone with Muggle (non-wizard) blood being considered "half-blood" or "mudblood", a word treated the same way a racial slur would be treated in the real world (Neo-Nazis call non-white people "mud people").  In the film "Lethal Weapon 2", the Master Race is a criminal organization of corrupt South-Afrikaners from South Africa led by its consul-general Arjen Rudd that smuggles illegal gold krugerrands in the United States of America via Los Angeles Harbor.

References.

Informational notes Citatons Bibliography

The master race (, also referred to as "master people") is a concept in Nazi ideology in which the putative Nordic or Aryan races, predominant among Germans and other northern European peoples, are deemed the highest in racial hierarchy. Members of this alleged master race were referred to as Herrenmenschen ("master humans").

优等民族(,)是一个纳粹主义种族概念,这一概念将德国人之中的北欧人种或雅利安人,认定为在假定的种族层级中最高的一支。纳粹认为史前时代的北欧人种在北德平原上定居,其源头可追溯到亚特兰蒂斯文明。


Laboratory funnels.

There are many different kinds of funnels that have been adapted for specialised applications in the laboratory. Filter funnels, thistle funnels (shaped like thistle flowers), and dropping funnels have stopcocks which allow the fluids to be added to a flask slowly. For solids, a powder funnel with a wide and short stem is more appropriate as it does not clog easily.  When used with filter paper, filter funnels, Büchner and Hirsch funnels can be used to remove fine particles from a liquid in a process called filtration. For more demanding applications, the filter paper in the latter two may be replaced with a sintered glass frit. Separatory funnels are used in liquid-liquid extractions. The Tullgren funnel is used to collect arthropods from plant litter or similar material.

Construction.

Glass is the material of choice for laboratory applications due to its inertness compared with metals or plastics. However, plastic funnels made of nonreactive polyethylene are used for transferring aqueous solutions. Plastic is most often used for powder funnels that do not come into contact with solvent in normal use.

Culture.

The inverted funnel is a symbol of madness. It appears in many Medieval depictions of the mad; for example, in Hieronymus Bosch's "Ship of Fools" and "Allegory of Gluttony and Lust". The Cebuano word for inverted funnel is ""; such devices are sometimes used as timers.  In popular culture, the Tin Woodman in L. Frank Baum's novel "The Wonderful Wizard of Oz" (and in most dramatizations of it) uses an inverted funnel for a hat, though that is never specifically mentioned in the story—it originated in W. W. Denslow's original illustrations for the book.  In the East Coast of the United States, "beer funnel" is another term for "beer bong". "Funneling" a beer involves pouring an entire beer into a funnel attached to a tube, in which a person then consumes the beer via the tube.  In the computing world, a funnel is frequently used as the icon for the filter functionality.

External links.

<br

A funnel is a tube or pipe that is wide at the top and narrow at the bottom, used for guiding liquid or powder into a small opening.

漏斗是一个筒型物体,被用作把液体及幼粉状物体注入入口较细小的容器。在漏斗咀部较细小的管状部分可以有不同长度。漏斗通常以不锈钢或塑胶制造,但纸制漏斗亦有时被使用于难以彻底清洗的物质,例如引擎机油。一些漏斗在咀部设有可控制的活门,让使用者可控制流质流入的速度。漏斗常见于厨房;在实验室也可找到漏斗,有时会使用滤纸以隔滤结晶物等化学物质。


Historical cycles.

Historically successful combined cycles have used mercury vapour turbines, magnetohydrodynamic generators and molten carbonate fuel cells, with steam plants for the low temperature "bottoming" cycle. Very low temperature bottoming cycles have been too costly due to the very large sizes of equipment needed to handle the large mass flows and small temperature differences. However, in cold climates it is common to sell hot power plant water for hot water and space heating. Vacuum-insulated piping can let this utility reach as far as 90km. The approach is called "combined heat and power" (CHP).  In stationary and marine power plants, a widely used combined cycle has a large gas turbine (operating by the Brayton cycle). The turbine's hot exhaust powers a steam power plant (operating by the Rankine cycle). This is a "combined cycle gas turbine" (CCGT) plant. These achieve a best-of-class real (see below) thermal efficiency of around 64% in base-load operation. In contrast, a single cycle steam power plant is limited to efficiencies from 35 to 42%. Many new power plants utilize CCGTs. Stationary CCGTs burn natural gas or synthesis gas from coal. Ships burn fuel oil.  Multiple stage turbine or steam cycles can also be used, but CCGT plants have advantages for both electricity generation and marine power. The gas turbine cycle can often start very quickly, which gives immediate power. This avoids the need for separate expensive peaker plants, or lets a ship maneuver. Over time the secondary steam cycle will warm up, improving fuel efficiency and providing further power.  In November 2013, the Fraunhofer Institute for Solar Energy Systems ISE assessed the levelised cost of energy for newly built power plants in the German electricity sector. They gave costs of between 78 and 100 €/MWh for CCGT plants powered by natural gas. In addition the capital costs of combined cycle power is relatively low, at around $1000/kW, making it one of the cheapest types of generation to install.

Basic combined cycle.

The thermodynamic cycle of the basic combined cycle consists of two power plant cycles. One is the Joule or Brayton cycle which is a gas turbine cycle and the other is Rankine cycle which is a steam turbine cycle. The cycle 1-2-3-4-1 which is the gas turbine power plant cycle is the topping cycle. It depicts the heat and work transfer process taking place in high temperature region.  The cycle a-b-c-d-e-f-a which is the Rankine steam cycle takes place at a low temperature and is known as the bottoming cycle. Transfer of heat energy from high temperature exhaust gas to water and steam takes place by a waste heat recovery boiler in the bottoming cycle. During the constant pressure process 4-1 the exhaust gases in the gas turbine reject heat. The feed water, wet and super heated steam absorb some of this heat in the process a-b, b-c and c-d.

Steam generators.

The steam power plant gets its input heat from the high temperature exhaust gases from gas turbine power plant. The steam generated thus can be used to drive steam turbine. The Waste Heat Recovery Boiler (WHRB) has 3 sections: Economiser, evaporator and superheater.

Cheng cycle.

The Cheng cycle is a simplified form of combined cycle where the steam turbine is eliminated by injecting steam directly into the combustion turbine. This has been used since the mid 1970s and allows recovery of waste heat with less total complexity, but at the loss of the additional power and redundancy of a true combined cycle system. It has no additional steam turbine or generator, and therefore it cannot use it as a backup or supplementary power. It is named after American Professor D. Y. Cheng who patented the design in 1976.

Design principles.

The efficiency of a heat engine, the fraction of input heat energy that can be converted to useful work, is limited by the temperature difference between the heat entering the engine and the exhaust heat leaving the engine.  In a thermal power station, water is the working medium. High pressure steam requires strong, bulky components. High temperatures require expensive alloys made from nickel or cobalt, rather than inexpensive steel. These alloys limit practical steam temperatures to 655 °C while the lower temperature of a steam plant is fixed by the temperature of the cooling water. With these limits, a steam plant has a fixed upper efficiency of 35–42%.  An open circuit gas turbine cycle has a compressor, a combustor and a turbine. For gas turbines the amount of metal that must withstand the high temperatures and pressures is small, and lower quantities of expensive materials can be used. In this type of cycle, the input temperature to the turbine (the firing temperature), is relatively high (900 to 1,400 °C). The output temperature of the flue gas is also high (450 to 650 °C). This is therefore high enough to provide heat for a second cycle which uses steam as the working fluid (a Rankine cycle).  In a combined cycle power plant, the heat of the gas turbine's exhaust is used to generate steam by passing it through a heat recovery steam generator (HRSG) with a live steam temperature between 420 and 580 °C. The condenser of the Rankine cycle is usually cooled by water from a lake, river, sea or cooling towers. This temperature can be as low as 15 °C.

Typical size of CCGT plants.

Plant size is important in the cost of the plant. The larger plant sizes benefit from economies of scale (lower initial cost per kilowatt) and improved efficiency.  For large-scale power generation, a typical set would be a 270 MW primary gas turbine coupled to a 130 MW secondary steam turbine, giving a total output of 400 MW. A typical power station might consist of between 1 and 6 such sets.  Gas turbines for large-scale power generation are manufactured by at least four separate groups – General Electric, Siemens, Mitsubishi-Hitachi, and Ansaldo Energia. These groups are also developing, testing and/or marketing gas turbine sizes in excess of 300 MW (for 60 Hz applications) and 400 MW (for 50 Hz applications). Combined cycle units are made up of one or more such gas turbines, each with a waste heat steam generator arranged to supply steam to a single or multiple steam turbines, thus forming a combined cycle block or unit. Combined cycle block sizes offered by three major manufacturers (Alstom, General Electric and Siemens) can range anywhere from 50 MW to well over 1300 MW with costs approaching $670/kW.

Unfired boiler.

The heat recovery boiler is item 5 in the COGAS figure shown above. Hot gas turbine exhaust enters the super heater, then passes through the evaporator and finally through the economiser section as it flows out from the boiler. Feed water comes in through the economizer and then exits after having attained saturation temperature in the water or steam circuit. Finally it flows through the evaporator and super heater. If the temperature of the gases entering the heat recovery boiler is higher, then the temperature of the exiting gases is also high.

Dual pressure boiler.

In order to remove the maximum amount of heat from the gasses exiting the high temperature cycle, a dual pressure boiler is often employed. It has two water/steam drums. The low-pressure drum is connected to the low-pressure economizer or evaporator. The low-pressure steam is generated in the low temperature zone of the turbine exhaust gasses. The low-pressure steam is supplied to the low-temperature turbine. A super heater can be provided in the low-pressure circuit.  Some part of the feed water from the low-pressure zone is transferred to the high-pressure economizer by a booster pump. This economizer heats up the water to its saturation temperature. This saturated water goes through the high-temperature zone of the boiler and is supplied to the high-pressure turbine.

Supplementary firing.

The HRSG can be designed to burn supplementary fuel after the gas turbine. Supplementary burners are also called "duct burners". Duct burning is possible because the turbine exhaust gas (flue gas) still contains some oxygen. Temperature limits at the gas turbine inlet force the turbine to use excess air, above the optimal stoichiometric ratio to burn the fuel. Often in gas turbine designs part of the compressed air flow bypasses the burner in order to cool the turbine blades. The turbine exhaust is already hot, so a regenerative air preheater is not required as in a conventional steam plant. However, a fresh air fan blowing directly into the duct permits a duct-burning steam plant to operate even when the gas turbine cannot.  Without supplementary firing, the "thermal efficiency" of a combined cycle power plant is higher. But more flexible plant operations make a marine CCGT safer by permitting a ship to operate with equipment failures. A flexible stationary plant can "make more money." Duct burning raises the flue temperature, which increases the quantity or temperature of the steam (e.g. to 84 bar, 525 degree Celsius). This improves the efficiency of the steam cycle. Supplementary firing lets the plant respond to fluctuations of electrical load, because duct burners can have very good efficiency with partial loads. It can enable higher steam production to compensate for the failure of another unit. Also, coal can be burned in the steam generator as an economical supplementary fuel.  Supplementary firing can raise exhaust temperatures from 600 °C (GT exhaust) to 800 or even 1000 °C. Supplemental firing does not raise the efficiency of most combined cycles. For single boilers it can raise the efficiency if fired to 700–750 °C; for multiple boilers however, the flexibility of the plant should be the major attraction.  "Maximum supplementary firing" is the condition when the maximum fuel is fired with the oxygen available in the gas turbine exhaust.

Fuel for combined cycle power plants.

Combined cycle plants are usually powered by natural gas, although fuel oil, synthesis gas or other fuels can be used. The supplementary fuel may be natural gas, fuel oil, or coal. Biofuels can also be used. Integrated solar combined cycle power stations combine the energy harvested from solar radiation with another fuel to cut fuel costs and environmental impact (See: ISCC section). Many next generation nuclear power plants can use the higher temperature range of a Brayton top cycle, as well as the increase in thermal efficiency offered by a Rankine bottoming cycle.  Where the extension of a gas pipeline is impractical or cannot be economically justified, electricity needs in remote areas can be met with small-scale combined cycle plants using renewable fuels. Instead of natural gas, these gasify and burn agricultural and forestry waste, which is often readily available in rural areas.

Managing Low-grade fuels in turbines.

Gas turbines burn mainly natural gas and light oil. Crude oil, residual, and some distillates contain corrosive components and as such require fuel treatment equipment. In addition, ash deposits from these fuels result in gas turbine deratings of up to 15%. They may still be economically attractive fuels however, particularly in combined-cycle plants.  Sodium and potassium are removed from residual, crude and heavy distillates by a water washing procedure. A simpler and less expensive purification system will do the same job for light crude and light distillates. A magnesium additive system may also be needed to reduce the corrosive effects if vanadium is present. Fuels requiring such treatment must have a separate fuel-treatment plant and a system of accurate fuel monitoring to assure reliable, low-maintenance operation of gas turbines.

Configuration.

Combined-cycle systems can have single-shaft or multi-shaft configurations. Also, there are several configurations of steam systems.  The most fuel-efficient power generation cycles use an unfired heat recovery steam generator (HRSG) with modular pre-engineered components. These unfired steam cycles are also the lowest in initial cost, and they are often part of a single shaft system that is installed as a unit.  Supplementary-fired and multishaft combined-cycle systems are usually selected for specific fuels, applications or situations. For example, cogeneration combined-cycle systems sometimes need more heat, or higher temperatures, and electricity is a lower priority. Multishaft systems with supplementary firing can provide a wider range of temperatures or heat to electric power. Systems burning low quality fuels such as brown coal or peat might use relatively expensive closed-cycle helium turbines as the topping cycle to avoid even more expensive fuel processing and gasification that would be needed by a conventional gas turbine.  A typical single-shaft system has one gas turbine, one steam turbine, one generator and one heat recovery steam generator (HRSG). The gas turbine and steam turbine are both coupled in tandem to a single electrical generator on a single shaft. This arrangement is simpler to operate, smaller, with a lower startup cost.  Single-shaft arrangements can have less flexibility and reliability than multi-shaft systems. With some expense, there are ways to add operational flexibility: Most often, the operator desires to operate the gas turbine as a peaking plant. In these plants, the steam turbine's shaft can be disconnected with a synchro-self-shifting (SSS) clutch, for start up or for simple cycle operation of the gas turbine. Another less common set of options enable more heat or standalone operation of the steam turbine to increase reliability: Duct burning, perhaps with a fresh air blower in the duct and a clutch on the gas turbine side of the shaft.  A multi-shaft system usually has only one steam system for up to three gas turbines. Having only one large steam turbine and heat sink has economies of scale and can have lower cost operations and maintenance. A larger steam turbine can also use higher pressures, for a more efficient steam cycle. However, a multi-shaft system is about 5% higher in initial cost.  The overall plant size and the associated number of gas turbines required can also determine which type of plant is more economical. A collection of single shaft combined cycle power plants can be more costly to operate and maintain, because there are more pieces of equipment. However, it can save interest costs by letting a business add plant capacity as it is needed.  Multiple-pressure reheat steam cycles are applied to combined-cycle systems with gas turbines with exhaust gas temperatures near 600 °C. Single- and multiple-pressure non-reheat steam cycles are applied to combined-cycle systems with gas turbines that have exhaust gas temperatures of 540 °C or less. Selection of the steam cycle for a specific application is determined by an economic evaluation that considers a plant's installed cost, fuel cost and quality, duty cycle, and the costs of interest, business risks, and operations and maintenance.

Efficiency of CCGT plants.

By combining both gas and steam cycles, high input temperatures and low output temperatures can be achieved. The efficiency of the cycles add, because they are powered by the same fuel source. So, a combined cycle plant has a thermodynamic cycle that operates between the gas-turbine's high firing temperature and the waste heat temperature from the condensers of the steam cycle. This large range means that the Carnot efficiency of the cycle is high. The actual efficiency, while lower than the Carnot efficiency, is still higher than that of either plant on its own.  The electric efficiency of a combined cycle power station, if calculated as electric energy produced as a percentage of the lower heating value of the fuel consumed, can be over 60% when operating new, i.e. unaged, and at continuous output which are ideal conditions. As with single cycle thermal units, combined cycle units may also deliver low temperature heat energy for industrial processes, district heating and other uses. This is called cogeneration and such power plants are often referred to as a combined heat and power (CHP) plant.  In general, combined cycle efficiencies in service are over 50% on a lower heating value and Gross Output basis. Most combined cycle units, especially the larger units, have peak, steady-state efficiencies on the LHV basis of 55 to 59%.

Difference between HHV and LHV.

To avoid confusion, the efficiency of heat engines and power stations should be stated relative to the Higher Heating Value (HHV) or Lower Heating Value (LHV) of the fuel, to include or exclude the heat that can be obtained from condensing the flue gas. It should also be specified whether Gross output at the generator terminals or Net Output at the power station fence is being considered.  The LHV figure is not a computation of electricity net energy compared to energy content of fuel input; it is 11% higher than that. The HHV figure is a computation of electricity net energy compared to energy content of fuel input. If the LHV approach were used for some new condensing boilers, the efficiency would calculate to be over 100%. Manufacturers prefer to cite the higher LHV efficiency, e.g. 60%, for a new CCGT, but utilities, when calculating how much electricity the plant will generate, divide this by 1.11 to get the real HHV efficiency, e.g. 54%, of that CCGT. Coal plant efficiencies are computed on a HHV basis since it doesn't make nearly as much difference for coal burn, as for gas.  The difference between HHV and LHV for gas, can be estimated (using US customary units) by 1055Btu/Lb * w, where w is the lbs of water after combustion per lb of fuel. To convert the HHV of natural gas, which is 23875 Btu/lb, to an LHV (methane is 25% hydrogen) would be: 23875 – (1055*0.25*18/2) = 21500. Because the efficiency is determined by dividing the energy output by the input, and the input on an LHV basis is smaller than the HHV basis, the overall efficiency on an LHV basis is higher. Therefore using the ratio of 23875/21500 = 1.11 one can convert the HHV to an LHV.  A real best-of-class baseload CCGT efficiency of 54%, as experienced by the utility operating the plant, translates to 60% LHV as the manufacturer's published headline CCGT efficiency.

Boosting efficiency.

Efficiency of the turbine is increased when combustion can run hotter, so the working fluid expands more. Therefore efficiency is limited by whether the first stage of turbine blades can survive higher temperatures. Cooling and materials research are continuing. A common technique, adopted from aircraft, is to pressurise hot-stage turbine blades with coolant. This is also bled-off in proprietary ways to improve the aerodynamic efficiencies of the turbine blades. Different vendors have experimented with different coolants. Air is common but steam is increasingly used. Some vendors might now utilize single-crystal turbine blades in the hot section, a technique already common in military aircraft engines.  The efficiency of CCGT and GT can also be boosted by pre-cooling combustion air. This increases its density, also increasing the expansion ratio of the turbine. This is practised in hot climates and also has the effect of increasing power output. This is achieved by evaporative cooling of water using a moist matrix placed in the turbine's inlet, or by using Ice storage air conditioning. The latter has the advantage of greater improvements due to the lower temperatures available. Furthermore, ice storage can be used as a means of load control or load shifting since ice can be made during periods of low power demand and, potentially in the future the anticipated high availability of other resources such as renewables during certain periods.  Combustion technology is a proprietary but very active area of research, because fuels, gasification and carburation all affect fuel efficiency. A typical focus is to combine aerodynamic and chemical computer simulations to find combustor designs that assure complete fuel burn up, yet minimize both pollution and dilution of the hot exhaust gases. Some combustors inject other materials, such air or steam, to reduce pollution by reducing the formation of nitrates and ozone.  Another active area of research is the steam generator for the Rankine cycle. Typical plants already use a two-stage steam turbine, reheating the steam between the two stages. When the heat-exchangers' thermal conductivity can be improved, efficiency improves. As in nuclear reactors, tubes might be made thinner (e.g. from stronger or more corrosion-resistant steel). Another approach might use silicon carbide sandwiches, which do not corrode.  There is also some development of modified Rankine cycles. Two promising areas are ammonia/water mixtures, and turbines that utilize supercritical carbon dioxide.  Modern CCGT plants also need software that is precisely tuned to every choice of fuel, equipment, temperature, humidity and pressure. When a plant is improved, the software becomes a moving target. CCGT software is also expensive to test, because actual time is limited on the multimillion-dollar prototypes of new CCGT plants. Testing usually simulates unusual fuels and conditions, but validates the simulations with selected data points measured on actual equipment.

Competition.

There is active competition to reach higher efficiencies. Research aimed at turbine inlet temperature has led to even more efficient combined cycles.  Nearly 60% LHV efficiency (54% HHV efficiency) was reached in the Baglan Bay power station, using a GE H-technology gas turbine with a NEM 3 pressure reheat boiler, using steam from the heat recovery steam generator (HRSG) to cool the turbine blades.  In May 2011 Siemens AG announced they had achieved a 60.75% efficiency with a 578 megawatt SGT5-8000H gas turbine at the Irsching Power Station.  The Chubu Electric’s Nishi-ku, Nagoya power plant 405 MW 7HA is expected to have 62% gross combined cycle efficiency.  The General Electric 9HA claimed 41.5% simple cycle efficiency and 61.4% in combined cycle mode, with a gas turbine output of 397 MW to 470 MW and a combined output of 592 MW to 701 MW. Its firing temperature is between, its overall pressure ratio is 21.8 to 1. It is used by Électricité de France in Bouchain. On April 28, 2016, this plant was certified by Guinness World Records as the worlds most efficient combined cycle power plant at 62.22%.  In January 2017, Mitsubishi claimed a LHV efficiency of greater than 63% for some members of its J Series turbines.  In December 2017, GE claimed 64% in its latest 826 MW HA plant, up from 63.7%. They said this was due to advances in additive manufacturing and combustion. Their press release said that they planned to achieve 65% by the early 2020s.

Natural gas integrated power and syngas (hydrogen) generation cycle.

A natural gas integrated power & syngas (hydrogen) generation cycle utilizes semi-closed (sometimes called closed) gas turbine cycles where fuel is combusted with pure oxygen in a presence of the working fluid of the cycle which is a mix of combustion products CO and HO (steam).  The integrated cycle implies that, before combustion, methane (primer natural gas component) is mixed with working fluid and converted into syngas (mix of H and CO) in a catalytic adiabatic (without an indirect heat supply) reactor by using sensible heat of the hot working fluid leaving, in the simplest case, the gas turbine outlet. The largest part of produced syngas (about 75%) is directed into the combustion chamber of the gas-turbine cycle to generate power, but another part of syngas (about 25%) is withdrawn from the power generation cycle as hydrogen, carbon monoxide, or their blend to produce chemicals, fertilizers, synthetic fuels, and etc. The thermodynamic benefit owing to this modification is substantiated by exergy analysis. There are numerous technological options to separate syngas from working fluid and withdraw it from the cycle (e.g., condensing vapors and removing liquids, taking out gases and vapors by membrane and pressure swing adsorption separation, amine gas treating, and glycol dehydration).  All the environmental advantages of semi-closed gas turbine cycles as to an absence of NO and the release of non-diluted (in N) CO in the flue gas stay the same. An effect of integration becomes apparent with the following clarification. Assigning the efficiency of syngas production in the integrated cycle a value equal to a regular syngas production efficiency through steam-methane reforming (some part of methane is combusted to drive endothermic reforming), the net-power generation efficiency (with accounting for the consumed electricity required to separate air) can reach levels higher than 60% at a maximum temperature in the cycle (at the gas turbine inlet) of about 1300C.  The natural gas integrated cycle with adiabatic catalytic reactor was firstly proposed at Chemistry Department of Moscow State Lomonosov University (Russia) in Prof. M. Safonov (late) group by M. Safonov, M. Granovskii, and S. Pozharskii in 1993.

Integrated gasification combined cycle (IGCC).

An integrated gasification combined cycle, or IGCC, is a power plant using synthesis gas (syngas). Syngas can be produced from a number of sources, including coal and biomass. The system uses gas and steam turbines, the steam turbine operating off of the heat left over from the gas turbine. This process can raise electricity generation efficiency to around 50%.

Integrated solar combined cycle (ISCC).

An Integrated Solar Combined Cycle (ISCC) is a hybrid technology in which a solar thermal field is integrated within a combined cycle plant. In ISCC plants, solar energy is used as an auxiliary heat supply, supporting the steam cycle, which results in increased generation capacity or a reduction of fossil fuel use.  Thermodynamic benefits are that daily steam turbine startup losses are eliminated.  Major factors limiting the load output of a combined cycle power plant are the allowed pressure and temperature transients of the steam turbine and the heat recovery steam generator waiting times to establish required steam chemistry conditions and warm-up times for the balance of plant and the main piping system. Those limitations also influence the fast start-up capability of the gas turbine by requiring waiting times. And waiting gas turbines consume gas. The solar component, if the plant is started after sunshine, or before, if there is heat storage, allows the preheat of the steam to the required conditions. That is, the plant is started faster and with less consumption of gas before achieving operating conditions. Economic benefits are that the solar components costs are 25% to 75% those of a Solar Energy Generating Systems plant of the same collector surface.  The first such system to come online was the Archimede combined cycle power plant, Italy in 2010, followed by Martin Next Generation Solar Energy Center in Florida, and in 2011 by the Kuraymat ISCC Power Plant in Egypt, Yazd power plant in Iran, Hassi R'mel in Algeria, Ain Beni Mathar in Morocco. In Australia CS Energy’s Kogan Creek and Macquarie Generation’s Liddell Power Station started construction of a solar Fresnel boost section (44 MW and 9 MW), but the projects never became active.

Bottoming cycles.

In most successful combined cycles, the bottoming cycle for power is a conventional steam Rankine cycle.  It is already common in cold climates (such as Finland) to drive community heating systems from a steam power plant's condenser heat. Such cogeneration systems can yield theoretical efficiencies above 95%.  Bottoming cycles producing electricity from the steam condenser's heat exhaust are theoretically possible, but conventional turbines are uneconomically large. The small temperature differences between condensing steam and outside air or water require very large movements of mass to drive the turbines.  Although not reduced to practice, a vortex of air can concentrate the mass flows for a bottoming cycle. Theoretical studies of the Vortex engine show that if built at scale it is an economical bottoming cycle for a large steam Rankine cycle power plant.

A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turbine (CCGT) plant. The same principle is also used for marine propulsion, where it is called a "combined gas and steam (COGAS)" plant. Combining two or more thermodynamic cycles improves overall efficiency, which reduces fuel costs.

复循环(英语:Combined cycle),又称-{zh-hk:复合循环; zh-tw:复合循环; zh-cn:复合循环;}-或者-{zh-hk:联合循环; zh-tw:联合循环; zh-cn:联合循环;}-,是一种使用多种热力学循环串联来获得更高热效率的方式,将其转换成机械能。比如在发电时,前一级产生的废气被用来驱动下一级热机推动发电机,提高了燃料的效率。