باصوفان  هي قرية سوريّة تتبع إداريّاً لمحافظة حلب منطقة عفرين ناحية مركز عفرين. بلغ تعداد سكانها 901 نسمة حسب التعداد السكاني لعام 2004، و2,059 نسمة حسب قيود السجل المدني لنهاية عام 2005. سكانها من الكرد الإيزيديين.

باصوفان

باصوفان قرية سورية تتبع منطقة عفرين في محافظة حلب. تتميز بهوائها النقي وجوّها اللطيف وجمال الطبيعة وكانت مقصداً لقضاء فترة الصيف وخاصة المصطافين من مدينة حلب.
تقع قرية باصوفان بمقربة من قلعة سمعان حوالي 4 كم
على سفح هضبي متباين محليا يطلق على اسم المنطقة (جبل ليلون). فيها بقايا أثرية لأبنية وسوق وجدران كنيسة ومدافن وصهاريج أثرية منحوتة في الصخر، ومعاصر قديمة للزيوت، بالإضافة إلى مزار مرقد للشيخ علي.

التصنيف التاريخي

صوفان سُكنت منذ العصور القديمة وتعود للعصر البيزنطي-الروماني وفيها العديد من الأثار.
 يقال إن Sofan تعني«قس» وهو رجل دين مسيحي، وكامل الاسم يعني «بيت القس».

أما الأسدي فيقول نقلا عن الأب شلحت إنه من الآرامية: بيت شوفْنا: بيت القطر، /ج 2، ص 32 /.

أما الخوري برصوم /ص 58 / فيقول أنه بمعنى «الحد أو النهاية»،
ولكن حسب رأيه أن الاسم بمعنى «بيت الملاح أو بيت الصابون» محل تصنيع الصابون لوجود أشجار الزيتون حولها.

وهنالك رواية أخرى تقول: أنه كان يسكن في موقع القرية بعض المتصوفة من أتباع الديانة الإيزيدية، وكان سكان القرى المجاورة يقصدونهم لأجل شفاء مرضاهم بالأدعية، فيقولون حينها:
لنذهب إلى عند الصوفيين Ba sofiyan , ثم أدمجت الكلمتان وأصبحتا اسما للمكانBasofan و Basofiyan .

كما أن شيخ علي أحد شيوخ الإيزيديين كان يقول: بأن أصلها من «بازيوان» وهي اسم قرية في منطقة خالتان في شمالي كردستان، جاء منها أوائل سكانها الإيزيديين، ثم حرف الاسم مع الزمن إلى باسوفان، وأعتقد أن هذا الرأي لايناقض رواية الأهالي بصدد وجود متصوفين فيها وربما كانوا من تلك القرية أو وافدين من منطقتهم الأصلية خالتان.

- قرية كبيرة تقع على سطح جبل ليلون. فيها بقايا أثرية لأبنية وسوق وجدران كنيسة ومد افن وصهاريج أثرية منقورة في الصخر، ومعاصر قديمة للزيوت والخمور. سكانها من الأكراد الإيزيدية، يوجد مزار شيخ علي في وسطها.

السكان
إجمالي عدد سكان القرية يقارب 2000 شخص معظمهم يتبعون الديانة الإزيدية.
وقد هاجر أغلب سكان باصوفان إلى أوروبا خصوصا بعد الأحداث الأخيرة التي وقعت عام 2011 في سوريا، واستقر أغلبهم في ألمانيا.

نبذة عن الموقع

تقع باصوفان على مسافة /4/كم من الجهة الشرقية الشمالية لقلعة سمعان، من أهم آثارها كنيسة القديس فوقاس التي يعود تاريخها لعام 491-496 ميلادية وأثار لأبنية تاريخية قديمة كما تضم حصنا صغيرا.

وأهم ما يميزها عن غيرها أثار مميزة مثل وجود أعمدة بأخاديد حلزونية وفيها بعض القبور المدافن القديمة.

كما انها تشتهر بزراعة الزيتون وععد من أنواع الأشجار المثمرة،

ويمكن الوصول إليها من طريق قلعة سمعان باصوفان أو من طريق حلب اعزاز عند مفرق حيان مروراً بقرية برج حيدر.

أماكن مأهولة في منطقة عفرين
المدن المنسية
بلدات في محافظة حلب
قرى محافظة حلب
تجمعات كردية في محافظة حلب

باصوفان


Lev Alexandrovich Polyakov (24 de abril de 1927, Morshansk, província de Tambov, URSS - 26 de janeiro de 2001, Moscou, Rússia) - ator de teatro e cinema soviético e russo. Artista do Povo da Federação Russa (1996).

Biografia
Lev Polyakov nasceu em 24 de abril de 1927 em Morshansk .

Inicialmente, Lev Aleksandrovich Polyakov sonhava com uma carreira militar. Ele estudou na escola técnica de aviação e depois na Escola Superior Naval de Baku. Mas a atuação amadora e o amor pelo teatro decidiram a escolha pela profissão de ator. Polyakov entrou na Escola de Teatro de Arte de Moscou e tocou no BDT por 2 anos .

Em meados da década de 1950, Lev Polyakov começou a atuar ativamente em filmes.

Em 1958 ele se formou na VGIK (oficina de Sergei Gerasimov e Tamara Makarova ) e entrou no Film Actor Theatre Studio .

Lutou com um golpe. O ator morreu aos 74 anos de um derrame em 26 de janeiro de 2001 em uma das clínicas da capital. Três anos antes, em 1998, seu único filho Nikita e sua esposa Inna Vykhodtseva desapareceram na República Dominicana durante o tsunami .

A urna com as cinzas do ator foi enterrada em um columbário no cemitério de Vagankovsky.

Família

 Esposa - atriz do Teatro-Estúdio do ator de cinema Inna Vykhodtseva
 Filho Nikita (1960-1998), tradutor, formado pelo Instituto Maurice Thorez. Ele morreu na República Dominicana durante o tsunami em 1998.

Filmografia

 1957 : Histórias sobre Lenin são encomendadas por Baryshev
 1958 : Ataman Kodr - Todor Tobultok
 1958 : O Caso do "Motley" - Rastyagaev
 1958 : Road to the Festival (curta)
 1960 : Midshipman Panin - oficial georgianos
 1961 : Duas Vidas - Nikolai Ignatiev
 1962 : Colegas - Dr. Stolbov
 1962 : Balada Gussar - Peter Pelyov
 1964 : Os mísseis não devem decolar - Sargento do Exército dos EUA Eugene
 1964 : Wick (episódio nº 19 "Berries") - noivo
 1964 : Fuga do Paraíso - Pavel
 1965 : A Última Noite no Paraíso - Pavel
 1965 - 1967 : Guerra e Paz - Lauriston
 1965 : Como você se chama agora? — Peter Sizov / Paul Krause
 1965 : Sobre o que a taiga estava calada - Padre Nikolai
 1966 : Dias alegres de Rasplyuev - policial de Kachala
 1966 : Mel selvagem - chefe da expedição geológica
 1966 : Tiro - Major
 1967 : Nikolai Bauman - Evgeny Kotov
 1967 : The Places Are Quiet - Tom, American Sailor (sem créditos)
 1967 : Sergei Lazo - Vishnyakov
 1968 : Mão de diamante - capitão do navio "Mikhail Svetlov"
 1968 : Crash - Zipunov , Savinkovets
 1968 : Novas aventuras do indescritível - um oficial de chapéu
 1968 : Uma Chance em Mil - Otto
 1968 : Escudo e espada - Major Gerlach, vice-chefe da escola Abwehr
 1968 - 1972 : Libertação - General Andrey Grechko
 1969 : Ajudante de Sua Excelência - Zagladin
 1969 : Montanhas, montanhas , minha estrela é uma amante em filmes mudos
 1970 : Waterloo ( Itália , URSS) - Kellerman (sem créditos)
 1970 : Carrossel - Anatole, noivo da princesa Bibulova
 1970 : O trem para amanhã - um funcionário do Conselho de Comissários do Povo
 1970 : Mensageiros da Eternidade - Capitão
 1970 : Coração da Rússia - Bolchevique em Smolny (sem créditos)
 1971 : A Coroa do Império Russo, ou Elusive Again - Oficial Caolho
 1971 : O preço dos segundos rápidos - episódio
 1971 : As sombras desaparecem ao meio -dia - Anisim Shatrov
 1972 : O Último Guia - episódio
 1972 : Sveaborg - Grão-Duque Nikolai Nikolaevich
 1973 : E no Oceano Pacífico... - Semyon
 1973 : Oceano - Svetlichny Andrey Pavlovich, capitão do segundo escalão
 1973 : Parada (curta)
 1974 : Chamado Eterno - Membro do Bureau (sem créditos)
 1974 : Livre - arbítrio (curta)
 1975 : A Corrida do Sr. McKinley - Amigo do McKinley
 1975 : Não pode ser! (conto "Crime e Castigo") - investigador
 1976 : A Vida e Morte de Ferdinand Luce como Kurt, o Homem de Bauer
 1977 : Frente por linha de frente - Friedrich von Bützow, engenheiro tenente-coronel alemão
 1977 : Incógnito de São Petersburgo - gendarme
 1978 : Temporada de veludo (URSS, Suíça ) - François, assistente de Nicholas
 1979 : Pequenas Tragédias - Espectadores no Teatro
 1980 : Labirinto da noite - maitre d'''
 1980 : Caso contrário é impossível - um participante da reunião 1980 : Casket of Mary Medici - perito forense Nikolai Ivanovich Krelin 1981 : Frente atrás das linhas inimigas - Friedrich von Bützow, um engenheiro alemão que se tornou um oficial de inteligência soviético 1983 : Domingo Ansioso - comandante da brigada de incêndio naval Chelobov 1984 : História europeia - jornalista 1984 : Almas Mortas - Vice-Governador 1984 : Despedida - Ministro Andrei Ivanovich 1985 : Perigoso para a vida! - tenente-coronel, chefe do departamento de polícia 1985 : Shores in the fog (URSS, Bulgária ) - Akulinichev 1985 : Bagration - episódio 1985 : Will - soldado 1986 : Cara a Cara - Cairns 1986 : Tempo para os filhos - Kovalenko 1987 : Zagon (URSS, Síria ) - chefe da guarda pessoal do presidente 1987 : Kreutzer Sonata - parente no casamento 1988 : Pilotos ( URSS , Tchecoslováquia ) - episódio 1989 : Detetive particular, ou Operação "Cooperação" - N. I. Okayomov 1989 : Mayhem - Throaty 1990 : Meninos - médico 1991 : Como você vive, carpa? - Gleb, vizinho no país 1992 : Piratas do Ar - episódio 1995 : Jovem camponesa - Lev Dmitrich Kolbin Atuação de voz

 1975  - Convidados não convidados ( Georgia-film ) - Guitarra principal (papel de Ramaz Chkhikvadze)
 1973  - Tailwind ( URSS , Checoslováquia ) - Rosher (o papel de Joseph Langmiller)
 1967  - Onde está o terceiro rei? ( Polônia )
 1962  - Mestre e Servo ( Armenfilm ) (curta) - Cocheiro (papel de Armen Khostikyan)
 1961  - Divórcio em italiano ( Itália ) - Rosário'' (o papel de Lando Budzanka)

Prêmios

 Artista Homenageado da RSFSR (25.07.1988)
 Artista do Povo da Federação Russa (30.08.1996)

Ligações externas

Referências
Atores da Rússia
Nascidos em 1927
Mortos em 2006

Lev Polyakov


Douglas Richard Hurd, baron Hurd af Westwell CH CBE PC (født 8. marts 1930 i Marlborough, Wiltshire, England) er en britisk konservativ politiker, der har været minister i Margaret Thatchers og John Majors regeringer. Han har blandt andet været indenrigsminister og udenrigsminister.

Medlem af Parlamentet

Medlem af Underhuset
I 1974–1997 var Douglas Hurd medlem af Underhuset for Oxfordshire. Fra 1974 til 1983 repræsenterede han Mid Oxfordshire. Efter en omlægning af valgkredsene kom han til at repræsentere Witney-kredsen frem til 1997. Fra 2001 er den senere premierminister David Cameron valgt i Witney-kredsen.

Medlem af Overhuset
I 1997 fik Douglas Hurd titlen baron Hurd af Westwell, og han blev medlem af Overhuset.

Poster som minister

Europaminister
I 1979–1983 var Douglas Hurd Storbritanniens første Europaminister.

Minister for Nordirland
Douglas Hurd var minister for Nordirland i 1984–1985.

Indenrigsminister
Douglas Hurd var indenrigsminister i 1985–1989.

Udenrigsminister
Douglas Hurd var udenrigsminister i 1989–1995.

Britiske konservative politikere
Europaministre fra Storbritannien
Britiske ministre for Nordirland
Indenrigsministre fra Storbritannien
Udenrigsministre fra Storbritannien

Douglas Hurd, baron Hurd af Westwell


Paracymbiomma caecus est une espèce d'araignées aranéomorphes de la famille des Prodidomidae.

Distribution
Cette espèce est endémique du Pará au Brésil. Elle se rencontre à Canaã dos Carajás dans des grottes.

Description
Le mâle holotype mesure  et la femelle paratype . Cette araignée est anophthalme.

Systématique et taxinomie
Cette espèce a été décrit par Rodrigues, Cizauskas et Rheims en 2018.

Publication originale
 Rodrigues, Cizauskas & Rheims, 2018 : « Description of Paracymbiomma gen. nov., a new genus of prodidomid spiders from the Neotropical region (Araneae: Prodidomidae) including a new troglobite species. » Zootaxa, , .

Liens externes

Notes et références

Prodidomidae
Espèce d'araignées (nom scientifique)
Faune endémique du Pará

Paracymbiomma caecus


5155 Denisyuk este un asteroid din centura principală de asteroizi.

Descriere
5155 Denisyuk este un asteroid din centura principală de asteroizi. A fost descoperit pe  la Observatorul de Astrofizică din Crimeea de Tamara Smirnova. El prezintă o orbită caracterizată de o semiaxă mare de 3,12 ua, o excentricitate de 0,13 și o înclinație de 6,1° în raport cu ecliptica.

Vezi și
 Lista planetelor minore: 5001-6000
 Centura de asteroizi

Referințe

Obiecte astronomice descoperite în 1972
Centura de asteroizi

5155 Denisyuk


Roksana Emilia Węgiel (født 11. januar 2005) er en polsk sanger som repræsenterede Polen og vandt Junior Eurovision Song Contest 2018 med sangen "Anyone I Want To Be" sangen opnåede 215 point. Roksana vandt også den første sæson af den polske udgave af Voice Junior. Efter hendes sejr i 2018 blev hun også vært i Junior Eurovision Song Contest 2019 sammen med Ida Nowakowska og Aleksander Sikora.

Diskografi

 Roksana Węgiel (2019)
 13+5 (2023)

Noter

Eksterne henvisninger

Sangere fra Polen

Roksana Węgiel


«إنغليش أم فتز أم بيرسي»  هي الحلقة الخامسة من المسلسل التلفزيوني بريزون بريك. بُثّت الحلقة في 19 سبتمبر 2005 في الولايات المتحدة. أخرج الحلقة راندل زسك وكتبها زاك إسترن. تستهدف «إنغليش أم فتز أم بيرسي» جزءًا آخرًا من خطة مايكل سكوفيلد للهرب، وهي أي شارع محيط بالمستوصف سيسلكونه من بين إنغليش وفتز وبيرسي. أيضا تنعطف قضية إعدام لينكلون بوروز منعطفا آخرا، حيث يقوم العميلان بول وهيل بابتزاز المأمور بوب لنقل مايكل خارج إصلاحية نهر فوكس.

القصة
يخبر مايكل سكوفيلد الفريق -الذي يتكون إلى الآن من جون أبروزي ولينكون بوروز وفرناندو سوكري- بأن عليهم اختيار واحد من الشوارع المحيطة بالمستوصف وهي إنغليش وفتز وبيرسي، وهذه الأسماء الثالثة مكتوبة على وشم ساعده. في هذه الأثناء، يقابل عميلا المباحث بول وهيل المأمور بوب طالبين نقل مايكل سكوفيلد. يرفض بوب الطلب، لكن العميل يواصل ابتزازه مهددا بفضح القضية التي واجهها في توليدو لزوجته. يعود مايكل إلى زنزانته واجدا بوب الذي يخبره أن سلطات عليا تريد نقله خارج إصلاحية نهر فوكس. يعزم مايكل على أخذ نصيحة تشارلز ويستمورلاند -بصفته أقدم سجين في الإصلاحية- حول تعطيل النقل، فينصحه بأن يكتب رسالة إلى بوب وأن يذكر أنه مصاب بالتهاب الجيوب الأنفية، لأن ذلك سيعطل النقل على الأقل لشهر ريثما يتم البت فيه. لكن بول وهيل يواصلان ابتزاز بول، ويأمرانه بأن يرمي الرسالة التي أرسلها مايكل، فيفعل بوب ذلك. يواصل نيك سافرين وفيرونيكا دونوفان التحقيقات ويحاولان إيجاد أسباب قانونية لتبرئة لينكون. يعرضان الشريط الذي يحتوي حادث القتل على أحد الخبراء، فيخبرهما أن صوت إطلاق النار مركب، لكنه بحاجة إلى الشريط الأصل ليشهد أمام المحكمة. يعودان ليأخذا الشريط الأصل فيجدان المخزن مدمرًا بسبب «حادث تهريب» نتج عن انكسار إحدى الأنابيب. عندما يعودان إلى شقة فيرونيكا، يكتشفان أن الشريط سرق، فتشك فيرونيكا بتورط نيك في ذلك.

يطلب مايكل من جون نسخة من مفتاح مكتب المأمور بوب. يحصل جون على نسخة المفتاح بعد أن تمكن أحد رفاقه من طبع المفتاح على قطعة فلين ثم إذابة قطعة بلاستيكية على القالب حتى تجف. في الليل، أخبر مايكل المأمور بوب بينما كان يبني نموذج تاج محل بأن البناء سوف ينهار إذا لم يبقَ هناك ممسكا إحدى القطع حتى يجف الغراء. يغادر بوب مكتبه فيغادر مايكل فورا مستخدما نسخته من المفتاح عبر البوابة الخلفية متجها إلى السطح. لاحظ براد بيليك فقد مايكل أثناء عد السجناء، فيبلغ السلطات بوجود هارب فتحاصر سيارات الشرطة المكان، لكن هذا كله كان من تخطيط مايكل. يلاحظ مايكل من السطح أن شارع فتز خالي من سيارات الشرطة، فيعزم على أن يسلكوه عند الهرب. يعود مايكل إلى مكتب المأمور قبل لحظات من دخول بيليك، فيجده ممسكا بالقطعة منتظرا جفافها، لم يشك أحد أنه كان هناك طوال المدة السابقة. لكن المأمور بوب يخبر مايكل بأنه سوف ينقل، فيصاب مايكل بالفزع. في الصباح التالي، وبينما كان مايكل على وشك أن يُنقل، يقرر بوب إلغاء النقل. ويعترف لزوجته بالقضية قبل أن يخبرها العميل بول.

مراجع

وصلات خارجية

 الملخص الرسمي للحلقة الخامسة من الموسم الأول من قناة فوكس

حلقات بريزون بريك
حلقات تلفزيونية أمريكية في 2005

إنغليش أم فتز أم بيرسي (بريزون بريك)


Parc ist eine U-Bahn-Station in Montreal. Sie befindet sich im Arrondissement Villeray–Saint-Michel–Parc-Extension an der Avenue Ogilvy, beim Gare Parc von exo. Hier verkehren Züge der blauen Linie 2. Im Jahr 2019 nutzten 3.101.394 Fahrgäste die Station, was dem 41. Rang unter den insgesamt 68 Stationen der Metro Montreal entspricht.

Bauwerk

Die vom Architekturbüro Blouin, Blouin & Associés entworfene Station entstand in offener Bauweise. Die Verteilerebene erstreckt sich unter einer Arkade mit weit gespannten Bögen, deren Rippen mit langen fluoreszierenden Leuchtkörpern versehen sind. Große runde Öffnungen in der Trennwand ermöglichen von dort aus einen Blick auf die Bahnsteige. Ein verglaster Lichtschacht lässt das Tageslicht auf die Verteilerebene scheinen. Der Eingang zur Station ist in den ehemaligen Rauchsalon des Bahnhofs Parc integriert. Das Gebäude im Art-déco-Stil war in den 1930er Jahren im Auftrag der Canadian Pacific Railway erbaut worden.

In 15,1 Metern Tiefe befindet sich die Bahnsteigebene mit zwei Seitenbahnsteigen. Die Entfernungen zu den benachbarten Stationen, jeweils von Stationsende zu Stationsanfang gemessen, betragen 490,60 Meter bis De Castelnau und 727,60 Meter bis Acadie. Es bestehen Anschlüsse zu fünf Buslinien und zwei Nachtbuslinien der Société de transport de Montréal. Außerdem kann im angrenzenden Gare Parc zu den exo-Vorortszügen nach Montreal Lucien-L'Allier bzw. Saint-Jérôme umgestiegen werden. Sehenswürdigkeiten in der Nähe sind das Stade IGA und der Parc Jarry.

Kunst
Durch die gesamte Station (mit Ausnahme des Eingangsbereichs) ziehen sich Wandfriese, bestehend aus gebranntem Email auf Stahlplatten. Das Werk von Huguette Desjardins stellt weiße Muster dar, die von verschiedenfarbig bemalten, dreieckig hervorstehenden Kanten unterbrochen werden. Fahrgäste, die daran vorbeigehen oder im Zug vorbeifahren, erhalten so den Eindruck einer fließenden Bewegung, die sich je nach Blickwinkel verändert.

Im Lichtschacht der Verteilerebene hängt das Kunstwerk Métamorphose d'Icare ("Verwandlung des Ikarus") von Claire Sarrasin. Es besteht aus einer halbrunden Acrylplatte, in der bunt bemalte Elemente aus Seide und Flüssigkristallen eingeschlossen sind. Das Werk erinnert an sich ausfaltende Flügel. Zahlreiche Spiegel reflektieren das einfallende, verschiedenfarbige Licht auf die gegenüberliegenden Wände.

Geschichte
Die Eröffnung der Station erfolgte am 15. Juni 1987, zusammen mit dem kurzen Teilstück bis De Castelnau. Etwas mehr als ein halbes Jahr lang war Parc die südliche Endstation der blauen Linie, bis zur Eröffnung des Teilstücks nach Snowdon am 4. Januar 1988. Namensgeber ist die Avenue du Parc, eine bedeutende Hauptstraße, deren westliches Ende sich in unmittelbarer Nachbarschaft der Station befindet. Benannt ist sie nach dem Parc du Mont-Royal. Im Jahr 2007 schlug Bürgermeister Gérald Tremblay vor, die Straße (und somit auch die Station) nach dem früheren Premierminister Robert Bourassa zu benennen, was jedoch auf heftigen Widerstand stieß.

Weblinks

 Seite der STM über die Station Parc (französisch)
 Detaillierte Informationen zur Station Parc (französisch)

Einzelnachweise

Station der Metro Montreal
Bauwerk des Art déco in Kanada
Erbaut in den 1980er Jahren

Parc (Metro Montreal)


أوكتونيون Octonion في الرياضيات هي امتداد كعملية غير تجميعية للكواتيرنيون. أبعادها الثمانية الحقيقية الجبرية في حقل الأعداد الحقيقية هو أوسع حقل بعدي من الممكن الحصول عليه باستخدام إنشاء كايلي-ديكسون. يرمز جبرياً إلى الأوكتونيون بالرمز O أو بالحرف العريض .

ربما بسبب أن الأوكتونيون لاتحقق الخاصة التجميعية لعملية الضرب، فإنها تجذب اهتماماً أقل من الكواتيرنيون، ولكن وعلى الرغم من شهرتها الضئيلة هذه فإن الأوكتونيون لها تطبيقات عدة في مجالات نظرية الأوتار، النسبية الخاصة، المنطق الكوانتي.

التاريخ
تم اكتشاف الأوكتونيون في عام 1843 من قبل العالم جون ت. غرافس، صديق ويليام هاملتون مكتشف الكواتيرنيون.

التعريف
من الممكن اعتبار الأوكتونيون على أنها مجموعات ثمانية (مثل الألحان الثمانية المعد لثماني آلات موسيقية أو مغنينن) من الأعداد الحقيقية. كل أوكتونيون هي اندماج خطي حقيقي لوحدات الزمرة الثمانية البسيطة {1, i, j, k, l, il, jl, kl}، وعليه فإن أي أوكتونيون x يكون ممكن الكتابة على الشكل التالي:

ذات مكافئ حقيقي xa.

عملية جمع الأوكتونيون تتم بجمع المكافئات المتوافقة، تماماً مثل الأعداد العقدية وكواتيرنيون. عملية الضرب في الأوكتونيون محددة بشكل كامل بجدول الضرب التالي:

إنشاء كايلي-ديكسون
هناك طريقة أكثر منطقية في تعريف الأوكتونيون باستخدام إنشاء كايلي-ديكسون. حيث كما أنه من الممكن تعريف الكواتيرنيون على أنها زوج من الأعداد العقدية، يمكن تعريف الأوكتونيون على أنها زوج من الكواتيرنيون. حيث يعطى جداء زوجين من الكواتيرنيون (a, b) و(c, d) على النحو التالي:

حيث  هو نظير الكواتيرنيون z.

النظير، الطويلة، المقلوب
يعطى نظير الأوكتونيون التالية

بالعلاقة:

يعرف الجزء الحقيقي للأوكتونيون x بالعلاقة:

½x + x*) = x0)

كما يعرف الجزء التخيلي بالعلاقة:

½(x - x*)

تعطى طويلة الأوكتونيون x بالعلاقة:

يعطى الجذر التربيعي هنا بالعلاقة:  وهو دائماً عدد حقيقي غير سالب:

وهذه الطويلة تتوافق مع الطويلة في الفضاء الإقليدي من البعد الثامن R8.

إن وجود طويلة للأوكتونيون يتطلب وجود مقلوب لكل أوكتونيون غير صفري. حيث يعطى مقلوب x ≠ 0 بالعلاقة:

وهي تحقق

.

مراجع

جبر

أوكتونيون


Béatrice Ahyi Aguessy, née en 1934 à Abomey et morte le , est la première femme gynécologue-obstétricienne du Bénin.

Biographie
Née en 1934 au Bénin, Béatrice Ahyi après un baccalauréat série D science expérimentale en 1958, entre en faculté de médecine de Dakar comme . Quatre années d'étude plus tard, elle s'installe à Paris pour continuer ses études où en 1968 elle passe sa thèse en médecine. Quatre années après, elle réussit au diplôme de gynécologie-obstétrique puis devient trois ans plus tard spécialiste en stérilité. Parallèlement, elle a évolué dans plusieurs domaines liés toujours a la médecine comme : médecine du travail, médecine pénitentiaire et planning familial. Elle forme plusieurs générations de médecins a l'université du Bénin.

Vie privée
Béatrice Ahyi Aguessy est l'épouse du professeur Honorat Aguessy.''

Vie associative
Fondatrice du Sort Optimisme Club, elle milite pour la lutte contre le cancer du sein mais aussi contre celui du col de l'utérus en sensibilisant les femmes.

Décès et hommages
Le 11 janvier 2019, à l'âge de 85 ans, Béatrice Ahyi Aguessy tire sa révérence et est inhumée le 9 février 2019 à Ouidah. Lors des cérémonies, l'ancien président de la république du Bénin Boni Yayi et La Ligue panafricaine UMOJA lui rendent hommage.

Notes et références

Liens externes

Femme médecin béninoise
Obstétricien
Étudiant de l'université Cheikh-Anta-Diop
Étudiant de la faculté de médecine de Paris
Naissance en avril 1934
Naissance à Abomey
Décès en janvier 2019
Décès à 84 ans

Béatrice Ahyi Aguessy


The Vampire Diaries , o dramă supranaturală americană de o oră, a fost reînnoită oficial pentru un al treilea sezon de către The CW în data de 26 aprilie 2011, difuzată din 15 septembrie 2011 până în data de 10 mai 2012.  Cel de-al treilea sezon a constat din 22 de episoade și s-a axat pe povestea originii lui Klaus , relația sa cu familia și revelarea mai mult despre familia originală.  Cel de-al treilea sezon a fost deschis pentru recenziile generale pozitive.  Sezonul are un decalaj de la ultimul sezon și începe cu data de 18 ani a lui Elena Gilbert , cu revenirea tuturor regizoarelor seriei, cu excepția lui Sara Canning cărei personaj Jenna Sommers a fost ucis în sezonul trecut.  Caracterul lui Klaus Joseph Morgan a devenit o serie regulată în loc să se întoarcă ca personaj recurent.
Nina Dobrev as Elena Gilbert (22 episodes) / Katherine Pierce (5 episodes)
Paul Wesley as Stefan Salvatore (22 episodes)
Ian Somerhalder as Damon Salvatore (22 episodes)
Steven R. McQueen as Jeremy Gilbert (14 episodes)
Kat Graham as Bonnie Bennett (17 episodes)
Zach Roerig as Matt Donovan (15 episodes)
Candice Accola as Caroline Forbes (19 episodes)
Michael Trevino as Tyler Lockwood (himself; possessed by Klaus) (15 episodes)
Matt Davis (himself; possessed by Klaus) as Alaric Saltzman (18 episodes)
Joseph Morgan as Niklaus Mikaelson (18 episodes)

recurent

Claire Holt as Rebekah Mikaelson (herself; possessed by Esther) (17 episodes)
Susan Walters as Carol Lockwood (10 episodes)
Torrey DeVitto as Dr. Meredith Fell (9 episodes)
Marguerite MacIntyre as Sheriff Elizabeth|"Liz" Forbes (7 episodes)
Malese Jow as Annabelle "Anna" (6 episodes)
Daniel Gillies as Elijah Mikaelson (6 episodes)
Alice Evans as Esther (6 episodes)
Sebastian Roché as Mikael (5 episodes)
Persia White as Abby Bennett Wilson (5 episodes)
Kayla Ewell as Vicki Donovan (4 episodes)
Nathaniel Buzolic as Kol Mikaelson (4 episodes)
Casper Zafer as Finn Mikaelson (4 episodes)
Jack Coleman as Bill Forbes (5 episodes)

Robert Ri'chard as Jamie Wilson (3 episodes)
Cassidy Freeman as Sage (3 episodes)
Kimberly Drummond as Mindy (3 episodes)
David Gallagher as Ray Sutton (2 episodes)
Taylor Kinney as Mason Lockwood (2 episodes)
Zane Stephens as Tony (2 episodes)
Daniel Newman as Daniel Warren (2 episodes)
Kelly Hu as Pearl (1 episode)
Arielle Kebbel as Alexia "Lexi" Branson (1 episode)
Jasmine Guy as Sheila Bennett (1 episode)
Stephen Martines as Frederick (1 episode)
Dawn Olivieri as Andie Starr (1 episode)
Cherilyn Wilson as Sofie (1 episode)
Lauren Cohan as Rosemary "Rose" (1 episode)
Sara Canning as Jenna Sommers (1 episode)

episoade
 Pe 26 aprilie 2011, The CW a reînnoit oficial The Vampire Diaries pentru un al treilea sezon.   Pe 19 mai 2011, odată cu dezvăluirea programului CW 2011-12, a fost anunțat că seria va rămâne joi la ora 20:00 Est / 7:00 pm Central, în calitate de plumb al <i id="mwIA">Cercului Secret,</i> care este de asemenea produs de Kevin Williamson .   Kevin Williamson, Julie Plec , Leslie Morgenstein și Bob Levy sunt producători executivi ai serialului.

piesă turnată
Serialele sunt Nina Dobrev , Elena Gilbert si Katherine Pierce, Paul Wesley , Stefan Salvatore si Silas, Ian Somerhalder , Damon Salvatore, Steven R. McQueen , Jeremy Gilbert, Kat Graham , Bonnie Bennett, Candice Accola , Caroline Forbes, Zach Roerig , Matt Donovan, Michael Trevino ca Tyler Lockwood, Matt Davis ca Alaric Saltzman și Joseph Morgan ca și Klaus.

David Gallagher, al 7-lea cer, a fost prezentat ca vârcolac Ray Sutton, care are o rulare cu Klaus în Tennessee.   Actrița australiană, Claire Holt, a fost distribuită ca Rebekah, sora lui Klaus și a lui Ilie, un vampir frumos care a avut plăcerea companiei lui Stefan în primele zile când a fost sărbătorit cu sânge uman.   Sebastian Roché a fost, de asemenea, distribuit ca Mikael un vanator de vampiri, care este mai exact după fiul său Klaus.  El se hrănește cu vampiri și îl vânează pe Klaus.   Mai târziu, se dezvăluie că el este tatăl originalilor și tatălui vitreg al lui Klaus.  Când planul său de a ucide pe Klaus, Mikael este ucis de Klaus.   Heroes star Jack Coleman a fost distribuit ca Bill, fostul rezident al Mystic Falls și tatăl vampirii rezidenți Caroline, care crede că fiica sa a devenit monstru, dar mai târziu o acceptă.

Alice Evans sa alăturat distribuției ca vrăjitoare originară, Esther, mama lui Klaus.  A fost prima dată vazută într-o retrospectivă în episodul opt.   Daniel Gillies se va întoarce, de asemenea, apărând prima dată într-o retrospectivă în timpul episodului opt ca fratele lui Klaus, Ilie.   Persia White a fost distribuită ca mamă a lui Bonnie, Abby Bennett.   La 10 noiembrie 2011, a fost anunțată că soția lui Paul Wesley, Torrey DeVitto, a fost distribuită ca Meredith Fell (bazată pe Meredith Sulez de la romanul sursă), un tânăr doctor fascinat de Alaric, când observă cât de repede se recuperează de la un accident .  Folosește sângele vampir pentru a vindeca oamenii și începe să se întâlnească cu Alaric.   Pe 16 noiembrie 2011, a fost anunțat că Robert Ri'chard a fost distribuit ca Jamie un interes nou pentru iubitul rezident Bonnie.   La 22 noiembrie 2011, a fost anunțat că Daniel Newman a fost distribuit ca Daniel Warren, care apare într-un singur episod.   Actorul australian Nathaniel Buzolic a fost distribuit pentru a juca Klaus și fratele lui Eli, Kol  iar actorul englez Caspar Zafer a fost distribuit ca celălalt frate Finn.   Pe 13 ianuarie 2012, a fost anunțat că Cassidy Freeman a fost distribuit ca Sage.   Pe 31 martie 2012, Sara Canning a fost confirmată să se întoarcă în rolul Jenna Sommers într-o retrospectivă în ultimul episod al sezonului "The Departed".   Pe 9 aprilie 2012, Jason MacDonald și Erin Beute au fost confirmați ca părinți ai Elenei, vor apărea într-o retrospectivă în ultimul episod al sezonului.   Lauren Cohan a reapărut în episodul "Heart of Darkness", ca fantoma Rose, să îl contacteze pe Jeremy și să-l găsească pe Mary, care la transformat pe Rose într-un vampir.

storylines
Sezonul trei începe după moartea Jennei si ceremonia care a condus la crearea lui Klaus fiind primul hibrid care i-a afectat puternic pe Alaric, Elena și Jeremy.  Stefan se află într-o situație dificilă, unde nu-si poate controla nevoile pentru sângele uman și continuă să devină un personaj mai întunecat.  În încercarea de ai ajuta pe Stefan, Elena și Damon incep să petreacă timp împreună și încep să-și dea seama că au sentimente unul pentru celalalt.  Ambii se simt vinovați de asta și nu vorbesc despre asta cu voce tare, dar este un adevăr tăcut între cei doi.

Jeremy are încă probleme cu fantomele sale și încearcă să-i transmită un mesaj important.  El și Bonnie devin din ce în ce mai îndepărtați, deoarece distragerea fantomelor din trecutul său în viața de zi cu zi îl distrage.

Klaus intentionează să creeze o armată de hibrizi (jumătate de vârcolac, jumatate vampir) care îi sunt chemați.

La inceput el il insista pe Stefan sa-l ajute, dar Stefan in cele din urma pleaca.  Sezonul se concentrează, de asemenea, asupra modului în care familia originală de vampiri a devenit vampiri de către tatăl lor, Michael Mikaelson, cerându-i lui Esther să devină mai puternici decât vecinii lor vârcolaci.

De asemenea se adâncește mai adânc în fiziologia familiei, în mod specific frații și arată motivul din spatele motto-ului lor "Always and Forever" și cum se formează legături între unii frați.

Evaluări

DVD și Blu-ray de presă

Referințe

Pages with unreviewed translations

Seriale de televiziune din 2011
Seriale de televiziune fantastice
Filme cu vampiri
Seriale de televiziune The CW Television Network
Emisiuni de televiziune cu vampiri

The Vampire Diaries (sezonul 3)


අග්‍රාමාත්‍යය යනු ස්වීඩනයෙහි රජයෙහි ප්‍රධානියා වෙයි. 1876 වසරෙහිදී අග්‍රාමාත්‍යය තනතුර ස්ථාපනය කිරීමට පෙර, එහි රාජ්‍ය නායකයාවූ  රජ වෙතින් පරිබාහිරව රජයෙහි නායකයෙක් ස්වීඩනය සතු නොවූ අතර රජතුමා වෙත විධායක අධිකාරිය පැවරිණි. 1866 වසරෙහිදි ශතවර්ෂ ගණනක් පැරණි රික්ස්ඩා ඔෆ් දි එස්ටේට්ස් වෙනුවෙන් සංස්ථාපිත නව ද්වීමණ්ඩල රික්ස්ඩා නිර්මාතෘ  ලුවී යෑර්හඩ ඩො යෑර්, 1876 වසරෙහිදී පළමු නිල දරන්නා විය.

පාර්ලිමේන්තු ක්‍රමයන්හි බොහෝ අග්‍රාමාත්‍යවරුන්ට වෙනස් වශයෙන් ස්වීඩනයෙහි අග්‍රාමාත්‍යවරයා නීති ප්‍රකාර සහ තත්වාකාර ප්‍රධාන විධායකයා වෙයි. මෙය මෙසේ වන්නේ  රාජ්‍ය ලිඛිතය විසින් පැහැදිලි ලෙසින් විධායක බලය රජය වෙත පවරන අතර, එහි නායකයා අග්‍රාමාත්‍යවරයා වන හෙයිනි.

ස්වීඩනයෙහි අග්‍රාමාත්‍යවරයා


In der Liste der Kulturdenkmale in Cracau sind alle Kulturdenkmale des zur Stadt Magdeburg gehörenden Stadtteils Cracau aufgelistet. Grundlage ist das Denkmalverzeichnis des Landes Sachsen-Anhalt, das auf Basis des Denkmalschutzgesetzes vom 21. Oktober 1991 erstellt und seither laufend ergänzt wurde. (Stand: 31. Dezember 2022)

Denkmale

|}

Ehemalige Denkmale
Die nachfolgenden Objekte waren ursprünglich ebenfalls denkmalgeschützt oder wurden in der Literatur als Kulturdenkmale geführt. Die Denkmale bestehen heute jedoch nicht mehr, ihre Unterschutzstellung wurde aufgehoben oder sie werden nicht mehr als Denkmale betrachtet.

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Legende

Weblinks

 Digitales Denkmalverzeichnis der Stadt Magdeburg
 Denkmalinformationssystem Sachsen-Anhalt

Einzelnachweise

Cracau

Liste der Kulturdenkmale in Cracau (Magdeburg)


Subunitate reprezintă o subdiviziune a unei unități militare, economice sau administrative
 Subunitate (categorie militară)
 Subunitate de pompieri
 Subunitate administrativ-teritorială
 Subunitate economică

Subunitate


KrasAir (En ruso: Красаир) también conocida como Krasnoyarsk Airlines (Красноярские авиалинии) fue una aerolínea rusa basada en el Aeropuerto Internacional de Krasnoyarsk-Yemelyanovo. Operaba servicios regulares de pasajeros y carga a nivel nacional e internacional, así como también vuelos chárter de pasajeros y carga de carácter internacional desde su base en el Aeropuerto Internacional de Krasnoyarsk-Yemelyanovo. En 2008 la aerolínea perdió liquidez, después de la cancelación de la mayoría de sus vuelos y diversos problemas financieros y legales, la aerolínea dejó de existir en octubre del 2008.

Historia

La aerolínea se fundó en 1967 como la división de Aeroflot-Krasnoyarsk, durante el periodo comprendido entre su fundación y la caída de la Unión Soviética, la aerolínea operó diversos aparatos como los Tu-134, Tu-154, An-24, An-26, Yak-40 y, durante algunos meses, Yak-42. Tras los sucesos de 1991, la aerolínea fue privatizada y se nombró como director a Boris Abramovich y su hermano, Alexander Abramovich, fue nombrado como el mayor accionista de la aerolínea. Los hermanos Abramovich llevaron a cabo una campaña de ampliación extenuante, sumando una gran cantidad de nuevos destinos a la aerolínea, así como la compra de nuevos aparatos de fabricación occidental y de fabricación rusa más modernos. Esta expansión desembocó en la creación de la alianza de AirUnion en 2005, esta fue la primera alianza de aerolíneas íntegramente rusa, formando parte de esta Domodedovo Airlines, Omskavia, Samara Airlines, Sibaviatrans y la misma KrasAir. Esta se convirtió en la tercera aerolínea más importante de Rusia. En esta alianza, todas las aerolíneas miembro eran controladas por KrasAir.

En 2006 KrasAir trato de extenderse al extranjero, comprando parte de la ahora extinta aerolínea bandera húngara Malév durante el proceso de privatización de esta. La compra de las acciones fue anulada inicialmente por las autoridades húngaras, quienes cancelaron la compra pocos días antes de que se concretara la compra en febrero de 2007. Durante 2006 KrasAir transporto a 1.118.543 de pasajeros en sus destinos domésticos e internacionales, y AirUnion transporto a 3,342,815 de pasajeros en destinos domésticos e internacionales.

KrasAir también participó en una inversión conjunta con el Banco Europeo para la Reconstrucción y el Desarrollo para crear una aerolínea de bajo costo en Rusia, la primera del país. La aerolínea fue llamada Sky Express. Esta filial estuvo basada en el Aeropuerto Internacional de Moscú-Vnúkovo y operaba inicialmente una flota de 44 Boeing 737-300/500, KrasAir tenía un 40% de esta aerolínea.

En junio y agosto de 2008 las flotas de KrasAir y de las otras aerolíneas miembros de AirUnion fueron detenidas en tierra luego de que los proveedores de combustible negaran créditos para poder reabastecer a los aviones de la alianza, ya que estos tenían una deuda de unos 80 millones de rublos. En junio, KrasAir y su principal proveedor de combustible, la también basada en Krasnoyarsk Sibir Avia Services, llegaron un acuerdo para reanudar el suministro de combustible con la condición de que la deuda de KrasAir no excediera los 100 millones de rublos. En agosto la deuda de KrasAir rondaba los 223 millones de rublos, y el 19 de agosto, Sibir Avia Services detuvo el suministro de combustible nuevamente, dejando a miles de pasajeros varados en los aeropuertos. KrasAir responsabilizo a las compañías petroleras de la crisis. A los seis meses del 2008, un 54% de los gastos de la aerolínea lo representaban los gastos de combustible. Los vuelos de Omskavia y Sibaviatrans también fueron suspendidos en sus respectivos aeropuertos.

Algunos analistas dijeron que la crisis del combustible se resolvería con la intervención de Rostechhologii, una nueva conglomeración del estado que había tenido varias negociaciones con varias compañías de AirUnion, incluyendo a KrasAir. A pesar de esto, el estado prefería una declaración formal de bancarrota de parte de AirUnion, lo que llevaría a una intervención por parte del estado, asumiendo al mando de todas las aerolíneas pertenecientes a la alianza. El 24 de agosto, el primer ministroVladímir Putin hizo referencia a la situación de la aerolínea, autorizando a Serguéi Ivanov a utilizar fondos del estado para ayudar a la alianza.

El 26 de agosto las agencias de noticias informaron que, al parecer, la bancarrota era inevitable, ya que Rostechhologii se negó a pagar las deudas de AirUnion, por lo que sus flotas permanecieron en tierra. Ese mismo día, el Ministerio de Transporte ruso habló con Aeroflot, Transaero, S7 y Rossiya para que estas tomaran las rutas operadas anteriormente por KrasAir.

El 27 de octubre KrasAir perdió a la mayoría de sus tripulaciones de cabina debido a una huelga generalizada. Finalmente, el 1 de noviembre KrasAir dejó de existir, junto con Omskavia, Domodedovo Airlines y Sibaviatrans, todas miembros de AirUnion, que también dejó de existir.

Flota

Destinos

Enlaces externos

 Sitio oficial de la aerolínea (Cerrada)
 Problemas con la adquisición de Malev por parte de KrasAir
 The Budapest Times-
 Primera aerolínea de bajo coste en Rusia
 Crisis en KrasAir debido a los precios del combustible
 La bancarrota es inevitable para KrasAir
 KrasAir deja de existir debido a crisis de combustibles

Aerolíneas desaparecidas de Rusia
Aerolíneas fundadas en 1993
Aerolíneas desaparecidas en 2008

KrasAir


Impardonnable est un nom notamment porté par :
 Impardonnable, film de Nora Fingscheidt sorti en 2021 ;
 Impardonnable, épisode d'Angel diffusé en 2002 ;
 Impardonnables, film d'André Téchiné sorti en 2011.

Voir aussi

Impardonnable


James Prinsep යනු ඉංදියාවේ බ්‍රාහ්මී අක්‌ෂර හඳුනා ගැනීමේ පුරෝගාමියෙකු වූ ඉංගී්‍රසි ජාතිකයෙකි.

මූලාශ්‍ර

ආශ්‍රිත
 ඇලොයිස් ඇන්ටොන් ෆියුහර්
 ඇලෙක්සැන්ඩර් කනිංහැම්

James Prinsep


Jaume Pujol Balcells (Guissona, 8 de fevereiro de 1944) - padre católico espanhol, arcebispo de Tarragona nos anos 2004-2019.

Foi ordenado sacerdote em 5 de agosto de 1973 pelo Cardeal Vicente Henrique e Tarancón. Incardinado na prelazia do Opus Dei, trabalhou principalmente na Universidade de Navarra, em Pamplona. A partir de 1997, dirigiu o Instituto de Ciências Religiosas daquela universidade.

Em 15 de junho de 2004, o Papa João Paulo II o nomeou Arcebispo Ordinário da Arquidiocese de Tarragona. Foi ordenado bispo pelo então Núncio Apostólico na Espanha, Dom Manuel Monteiro de Castro.

Em 4 de maio de 2019, o Papa aceitou sua renúncia ao cargo, apresentada com base em sua idade.

Ver também

{[commons|Category:Jaume Pujol Balcells}}

Arcebispos católicos da Espanha

Jaume Pujol Balcells


Four-wheel drive, also called 4×4 ("four by four") or 4WD, refers to a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, and is typically linked via a transfer case providing an additional output drive shaft and, in many instances, additional gear ranges.

A four-wheel drive vehicle with torque supplied to both axles is described as "all-wheel drive" (AWD). However, "four-wheel drive" typically refers to a set of specific components and functions, and intended off-road application, which generally complies with modern use of the terminology.

Definitions
Four-wheel-drive systems were developed in many different markets and used in many different vehicle platforms. There is no universally accepted set of terminology that describes the various architectures and functions. The terms used by various manufacturers often reflect marketing rather than engineering considerations or significant technical differences between systems. SAE International's standard J1952 recommends only the term "all-wheel drive" with additional subclassifications that cover all types of AWD/4WD/4x4 systems found on production vehicles.

4×4
"Four-by-four" or "4×4" is frequently used to refer to a class of vehicles in general. Syntactically, the first figure indicates the total number of axle ends and the second indicates the number of axle ends that are powered. Accordingly, 4×2 means a four-wheel vehicle that transmits engine torque to only two axle ends: the front two in front-wheel drive or the rear two in rear-wheel drive. Similarly, a 6×4 vehicle has three axles, two of which provide torque to two axle ends each. If this vehicle were a truck with dual rear wheels on two rear axles, so actually having ten wheels, its configuration would still be formulated as 6x4. During World War II, the U.S. military would typically use spaces and a capital 'X' – as "4 X 2" or "6 X 4".

4WD
Four-wheel drive (4WD) refers to vehicles with two axles providing torque to four axle ends. In the North American market, the term generally refers to a system optimized for off-road driving conditions. The term "4WD" is typically designated for vehicles equipped with a transfer case that switches between 2WD and 4WD operating modes, either manually or automatically.

AWD

All-wheel drive (AWD) was historically synonymous with "four-wheel drive" on four-wheeled vehicles, and six-wheel drive on 6×6s, and so on, being used in that fashion at least as early as the 1920s. Today in North America, the term is applied to both heavy vehicles and light passenger vehicles. When referring to heavy vehicles, the term is increasingly applied to mean "permanent multiple-wheel drive" on 2×2, 4×4, 6×6, or 8×8 drive-train systems that include a differential between the front and rear drive shafts. This is often coupled with some sort of antislip technology, increasingly hydraulic-based, that allows differentials to spin at different speeds, but still be capable of transferring the torque from a wheel with poor traction to one with better. Typical AWD systems work well on all surfaces, but are not intended for more extreme off-road use. When used to describe AWD systems in light passenger vehicles, it refers to a system that applies torque to all four wheels (permanently or on-demand) or is targeted at improving on-road traction and performance (particularly in inclement conditions), rather than for off-road applications.

Some all-wheel drive electric vehicles use one motor for each axle, thereby eliminating a mechanical differential between the front and rear axles. An example of this is the dual-motor variant of the Tesla Model S, which controls the torque distribution between its two motors electronically.

SAE recommended practices
According to the SAE International standard J1952, AWD is the preferred term for all the systems described above. The standard subdivides AWD systems into three categories.

Part-time AWD systems require driver intervention to couple and decouple the secondary axle from the primarily driven axle, and these systems do not have a center differential (or similar device). The definition notes that part-time systems may have a low range.

Full-time AWD systems drive both front and rear axles at all times via a center (interaxle) differential. The torque split of that differential may be fixed or variable depending on the type of center differential. This system can be used on any surface at any speed. The definition does not address the inclusion or exclusion of a low-range gear.

On-demand AWD systems drive the secondary axle via an active or passive coupling device or "by an independently powered drive system". The standard notes that in some cases, the secondary drive system may also provide the primary vehicle propulsion. An example is a hybrid AWD vehicle where the primary axle is driven by an internal combustion engine and the secondary axle is driven by an electric motor. When the internal combustion engine is shut off, the secondary, electrically driven axle is the only driven axle. On-demand systems function primarily with only one powered axle until torque is required by the second axle. At that point, either a passive or active coupling sends torque to the secondary axle.

In addition to the above primary classifications, the J1952 standard notes secondary classifications resulting in a total of eight systems, designated as:
Part-time nonsynchro
Part-time synchro
Full-time fixed torque
Full-time variable-torque passive
Full-time variable-torque active
On-demand synchro variable-torque passive
On-demand synchro variable-torque active
On-demand independently powered variable-torque active

Design

Differentials

Two wheels fixed to the same axle (but on the opposite axle ends) need to turn at different speeds as a vehicle goes around a curve. The reason is that the wheel that is located on the inner side of the curve needs to travel less distance than the opposite wheel for the same duration of time. However, if both wheels are connected to the same axle driveshaft, they always have to spin at the same speed relative to each other. When going around a curve, this either forces one of the wheels to slip, if possible, to balance the apparent distance covered, or creates uncomfortable and mechanically stressful wheel hop. To prevent this, the wheels are allowed to turn at different speeds using a mechanical or hydraulic differential. This allows one driveshaft to independently drive two output shafts, axles that go from the differential to the wheel, at different speeds.

The differential does this by distributing angular force (in the form of torque) evenly, while distributing angular velocity (turning speed) such that the average for the two output shafts is equal to that of the differential ring gear. When powered, each axle requires a differential to distribute power between the left and right sides. When power is distributed to all four wheels, a third or 'center' differential can be used to distribute power between the front and rear axles.

The described system handles extremely well, as it is able to accommodate various forces of movement and distribute power evenly and smoothly, making slippage unlikely. Once it does slip, however, recovery is difficult. If the left front wheel of a 4WD vehicle slips on an icy patch of road, for instance, the slipping wheel spins faster than the other wheels due to the lower traction at that wheel. Since a differential applies equal torque to each half-shaft, power is reduced at the other wheels, even if they have good traction. This problem can happen in both 2WD and 4WD vehicles, whenever a driven wheel is placed on a surface with little traction or raised off the ground. The simplistic design works acceptably well for 2WD vehicles. It is much less acceptable for 4WD vehicles, because 4WD vehicles have twice as many wheels with which to lose traction, increasing the likelihood that it may happen. 4WD vehicles may also be more likely to drive on surfaces with reduced traction. However, since torque is divided between four wheels rather than two, each wheel receives roughly half the torque of a 2WD vehicle, reducing the potential for wheel slip.

Limiting slippage

Many differentials have no way of limiting the amount of engine power that gets sent to their attached output shafts. As a result, if a tire loses traction on acceleration, either because of a low-traction situation (e.g., driving on gravel or ice) or the engine power overcomes available traction, the tire that is not slipping receives little or no power from the engine. In very low-traction situations, this can prevent the vehicle from moving at all. To overcome this, several designs of differentials can either limit the amount of slip (these are called 'limited-slip' differentials) or temporarily lock the two output shafts together to ensure that engine power reaches all driven wheels equally.

Locking differentials work by temporarily locking together a differential's output shafts, causing all wheels to turn at the same rate, providing torque in case of slippage. This is generally used for the center differential, which distributes power between the front and the rear axles. While a drivetrain that turns all wheels equally would normally fight the driver and cause handling problems, this is not a concern when wheels are slipping.

The two most common factory-installed locking differentials use either a computer-controlled multiplate clutch or viscous coupling unit to join the shafts, while other differentials are more commonly used on off-road vehicles generally use manually operated locking devices. In the multi-plate clutch, the vehicle's computer senses slippage and locks the shafts, causing a small jolt when it activates, which can disturb the driver or cause additional traction loss. In the viscous coupling differentials, the shear stress of high shaft speed differences causes a dilatant fluid in the differential to become solid, linking the two shafts. This design suffers from fluid degradation with age and from exponential locking behavior. Some designs use gearing to create a small rotational difference that hastens torque transfer.

A third approach to limiting slippage is taken by a Torsen differential, which allows the output shafts to receive different amounts of torque. This design does not provide for traction when one wheel is spinning freely, where no torque exists, but provides excellent handling in less extreme situations. A typical Torsen II differential can deliver up to twice as much torque to the high-traction side before traction is exceeded at the low-traction side.

A fairly recent innovation in automobiles is electronic traction control. It typically uses a vehicle's braking system to slow a spinning wheel. This forced slowing emulates the function of a limited-slip differential, and by using the brakes more aggressively to ensure wheels are being driven at the same speed, can also emulate a locking differential. This technique normally requires wheel sensors to detect when a wheel is slipping, and only activates when wheel slip is detected. Therefore, typically no mechanism exists to actively prevent wheel slip (i.e., locking the differential in advance of wheel slip is not possible); rather, the system is designed to expressly permit wheel slip to occur, and then to attempt to send torque to the wheels with the best traction. If preventing all-wheel slip is a requirement, this is a limiting design.

Operating modes
The architecture of an AWD/4WD system can be described by showing its possible operating modes. A single vehicle may have the ability to operate in multiple modes depending on driver selection. The different modes are:
Two-wheel drive mode – In this mode, only one axle (typically the rear axle) is driven. The drive to the other axle is disconnected. The operating torque split ratio is 0:100.
Four-wheel drive mode – Here, depending on the nature of torque transfer to the axles, three submodes (below) can be defined.
Part-time mode – The front and rear axle drives are rigidly coupled in the transfer case. Since the driveline does not permit any speed differentiation between the axles and would cause driveline wind-up, this mode is recommended only for part-time use in off-road or loose-surface conditions where driveline wind-up is unlikely. Up to full torque could go to either axle, depending on the road conditions and the weight over the axles.
Full-time mode – Both axles are driven at all times, but an interaxle differential permits the axles to turn at different speeds as needed. This allows the vehicle to be driven full-time in this mode, regardless of the road surface, without fear of driveline wind-up. With standard bevel-gear differentials, the torque split is 50:50. Planetary differentials can provide asymmetric torque splits as needed. A system that operates permanently in the full-time mode is sometimes called all-the-time 4WD, all-wheel drive, or AWD. If the interaxle differential is locked out, then the mode reverts to a part-time mode.
On-demand mode – In this mode, the transfer case operates primarily in the 2WD mode. Torque is transferred to the secondary axle as needed by modulating the transfer clutch from open to a rigidly coupled state, while avoiding any driveline wind-up. The torque modulation may be achieved by active electronic/hydraulic control systems, or by passive devices, based on wheel slip or wheel torque, as described in the section on traction control systems.
In addition to these basic modes, some implementations can combine these modes. The system could have a clutch across the center differential, for example, capable of modulating the front axle torque from a full-time mode with the 30:70 torque split of the center differential to the 0:100 torque split of the 2WD mode.

History

Late 1800s
In 1893, before the establishment of the modern automotive industry in Britain, English engineer Bramah Joseph Diplock patented a four-wheel drive system for a steam-powered traction engine, including four-wheel steering and three differentials, which was subsequently built. The development also incorporated Bramah's Pedrail wheel system in what was one of the first four-wheel drive automobiles to display an intentional ability to travel on challenging road surfaces. It stemmed from Bramagh's previous idea of developing an engine that would reduce the amount of damage to public roads.

Ferdinand Porsche designed and built a four-wheel-driven electric vehicle for the k. u. k. Hofwagenfabrik Ludwig Lohner & Co. in Vienna in 1899, presented to the public during the 1900 World Exhibition in Paris. The vehicle was a series hybrid car that used an electric hub motor at each wheel, powered by batteries, which were in turn charged by a gasoline-engine generator. It was clumsily heavy, and due to its unusual status, the so-called Lohner–Porsche is not frequently given its credit as the first four-wheel driven automobile.

1900s–1920s

The world's first four-wheel-drive car directly powered by an internal-combustion engine, and the first with a front-engine, four-wheel-drive layout, was the Dutch Spyker 60 H.P., Commissioned for the Paris to Madrid race of 1903, it was presented that year by brothers Jacobus and Hendrik-Jan Spijker of Amsterdam. The two-seat sports car featured permanent four-wheel drive and was also the first car equipped with a six-cylinder engine, as well as four-wheel braking. Later used as a hill-climb racer, it is now an exhibit in the Louwman Museum (the former Nationaal Automobiel Museum) in the Hague, the Netherlands.

Designs for four-wheel drive in America first came from the Twyford Motor Car Company.

The Reynolds-Alberta Museum has a four-wheel-drive vehicle, named "Michigan", from 1905 in unrestored storage.

The first four-wheel-drive vehicles to go into mass production were built by (what became) the American Four Wheel Drive Auto Company (FWD) of Wisconsin, founded in 1908. (not to be confused with the term "FWD" as an acronym for front-wheel-drive)
Along with the 1- and 2-ton Nash Quad (see below), the 3-ton FWD Model B became a standard military four-wheel-drive truck for the U.S. Army in World War I. Some 16,000 FWD Model B trucks were built for the British and American armies during World War I – about half by FWD and the rest by other licensed manufacturers. Only about 20% of the trucks built were four-wheel drives, but the 4x4s were more often on the front lines.

About 11,500 of the Jeffery / Nash Quad trucks were built for similar use between 1913 and 1919. The Quad not only came with four-wheel-drive and four-wheel brakes, but also featured four-wheel steering. The Quad was one of the first successful four-wheel drive vehicles ever to be made, and its production continued for 15 years with a total of 41,674 units made by 1928.

Daimler-Benz also has a history in four-wheel drive. After the Daimler Motoren Gesellschaft had built a four-wheel-driven vehicle called Dernburg-Wagen, also equipped with four-wheel steering, in 1907, that was used by German colonial civil servant, Bernhard Dernburg, in Namibia; Mercedes and BMW, in 1926, introduced some rather sophisticated four-wheel drives, the G1, the G4, and G4 following. Mercedes and BMW developed this further in 1937.

1930s

The American Marmon-Herrington Company was founded in 1931 to serve a growing market for moderately priced four-wheel-drive vehicles. Marmon-Herrington specialized in converting Ford trucks to four-wheel drive and got off to a successful start by procuring contracts for military and commercial aircraft refueling trucks, 4×4 chassis for towing light weaponry, and an order from the Iraqi Pipeline Company for what were the largest trucks built at the time.

The early Marmon-Herringtons proved to be the exception to the rule — 4WD cars and trucks developed in the 1930s were mainly built for governments, with (future) warfare applications in mind.

Dodge developed its first four-wheel-drive truck in 1934 — a military  ton designated K-39-X-4(USA), of which 796 units were built for the U.S. Army in several configurations. Timken supplied front axles and transfer cases, added to militarized a civilian truck. The Timken transfer case was the first part-time design, that allowed the driver to engage or disengage four-wheel drive using a lever inside the cab. In spite of the limited 1930s U.S. military budgets, the '34 truck was liked well-enough that a more modern  ton truck was developed, and 1,700 RF-40-X-4(USA) trucks were produced in 1938, and 292 TF-40-X-4(USA) in 1939.

Starting in 1936, Japanese company Tokyu Kurogane Kogyo built roughly 4,700 four-wheel-drive roadsters, called the Kurogane Type 95 reconnaissance car, used by the Imperial Japanese Army from 1937 until 1944, during the Second Sino-Japanese War. Three different bodystyles were manufactured – a two-door roadster, a two-door pickup truck, and a four-door phaeton, all equipped with a transfer case that engaged the front wheels, powered by a 1.3-litre, two-cylinder, air-cooled OHV V-twin engine.

The 1937 Mercedes-Benz G5 and BMW 325 4×4 featured full-time four-wheel drive, four-wheel steering, three locking differentials, and fully independent suspension. They were produced because of a government demand for a four-wheel-drive passenger vehicle. The modern G-series/Wolf such as the G500 and G55 AMG still feature some of the attributes, with the exception of fully independent suspension, since it can compromise ground clearance. The Unimog is also a result of Mercedes 4x4 technology.

The first Russian-produced four-wheel-drive vehicle, also in part for civilian use, was the GAZ-61, developed in the Soviet Union in 1938. "Civilian use" may be a bit of a misnomer, as most, if not all, were used by the Soviet government and military (as command cars), but the GAZ-61-73 version is the first four-wheel-drive vehicle with a normal closed sedan body. Elements of the chassis were used in subsequent military vehicles such as the 1940 GAZ-64 and the 1943 GAZ-67, as well as the postwar GAZ-69, and the properly civilian GAZ-M-72, based on the rear-wheel drive GAZ-20 "Victory" and built from 1955 to 1958. Soviet civilian life did not allow the proliferation of civilian products such as the Jeep in North America, but through the 1960s, the technology of Soviet 4×4 vehicles stayed on par with British, German, and American models, even exceeding it in some aspects, and for military purposes just as actively developed, produced, and used.

World War II – a leap in AWD proliferation

Until "go-anywhere" vehicles were needed for the military on a large scale, four-wheel drive and all-wheel-drive vehicles had not found their place. The World War II Jeep, originally developed by American Bantam, but mass-produced by Willys and Ford, became the best-known four-wheel-drive vehicle in the world during the war. The American Dodge WC series and Chevrolet G506 4x4 variants were also produced by the hundreds of thousands, as well as the Canadian Military Pattern trucks, of which 4x4s were by far the most prevalent of their various driveline configurations. All told, North America built about  million 4x4 driven vehicles during the war,

Availability of certain critical components, such transfer cases and especially constant-velocity joints affected development. Though not used much on commercial vehicles, all-wheel drive vehicles all needed these; and they would use two or three times the number of driven axles, meaning more gears to cut for all the differentials. Produced up to the war by a few specialized firms with limited capacity, from spring 1942, Ford, Dodge, and Chevrolet joined in fabricating these in a quantity more than a 100-fold greater than in 1939.

Although Russia had their own jeep-like vehicle (the GAZ-64) up and running in 1940, a year earlier than the American jeep, in the early years of the war, they relied significantly on Lend-Lease vehicles, provided by the western allies. In 1943, they launched a further-developed version: the GAZ-67.

By contrast, the Axis powers' closest equivalent to the jeep, the VW Kübelwagen, of which only some 50,000 were built, though being equipped with portal gear hubs, only had rear-wheel drive.

1945–1960s

Willys introduced the model CJ-2A in 1945, the first full-production four-wheel-drive vehicle for sale in the general marketplace. Due to the ubiquitous World War II Jeep's success, its rugged utilitarianism set the pattern for many four-wheel-drive vehicles to come. Hot on its heels, Dodge also started production of the civilian 4WD Power Wagon trucks, for the 1946 model year. Both the Willys and the Dodge were developed directly from their WW II predecessors.

Equally boxy to the Jeep, and also inline-four powered, the Land Rover appeared at the Amsterdam Motor Show in 1948. Originally conceived as a stop-gap product for the struggling Rover car company, despite chronic underinvestment, it succeeded far better than their passenger cars. Inspired by a Willys MB – the ubiquitous WWII "jeep" – that was frequently run off-road on the farm belonging to chief engineer Maurice Wilks, Land Rover developed the more refined yet still off-road capable luxury 4WD Range Rover in the 1970s.

With the acquisition of the "Jeep" name in 1950, Willys had cornered the brand. Its successor, Kaiser Jeep, introduced a revolutionary 4WD wagon called the Wagoneer in 1963. Not only was it technically innovative, with independent front suspension and the first automatic transmission coupled to 4WD, but also it was equipped and finished as a regular passenger automobile. In effect, it was the ancestor of the modern SUV. The luxury AMC or Buick V8-powered Super Wagoneer produced from 1966 to 1969 raised the bar even higher.

Jensen applied the Formula Ferguson (FF) full-time all-wheel-drive system to 318 units of their Jensen FF built from 1966 to 1971, marking the first time 4WD was used in a production GT sports car. While most 4WD systems split torque evenly, the Jensen split torque roughly 40% front, 60% rear by gearing the front and rear at different ratios.

1970s–1990s
American Motors Corporation (AMC) acquired Kaiser's Jeep Division in 1970 and quickly upgraded and expanded the entire line of off-road 4WD vehicles. With its added roadworthiness, the top-range full-sized Grand Wagoneer continued to compete with traditional luxury cars. Partially hand-built, it was relatively unchanged during its production through 1991, even after Chrysler's buyout of AMC.

Subaru introduced the category-expanding Leone in 1972, an inexpensive compact station wagon with a light-duty, part-time four-wheel-drive system that could not be engaged on dry pavement. In September, AMC introduced Quadra Trac full-time AWD for the 1973 model year Jeep Cherokee and Wagoneer. Due to full-time AWD, which relieved the driver of getting out to lock hubs and having to manually select between 2WD and 4WD modes, it dominated all other makes in FIA rally competition. Gene Henderson and Ken Pogue won the Press-on-Regardless Rally FIA championship with a Quadra Trac-equipped Jeep in 1972.

American Motors introduced the innovative Eagle for the 1980 model year. These were the first American mass-production cars to use the complete front-engine, four-wheel-drive system. The AMC Eagle was offered as a sedan, coupe, and station wagon with permanent automatic all-wheel drive passenger models. The new Eagles combined Jeep technology with an existing and proven AMC passenger automobile platform. They ushered a whole new product category of "sport-utility" or crossover SUV. AMC's Eagles came with the comfort and high-level appointments expected of regular passenger models and used the off-road technology for an extra margin of safety and traction.

The Eagle's thick viscous fluid center differential provided a quiet and smooth transfer of power that was directed proportionally to the axle with the greatest traction. This was a true full-time system operating only in four-wheel drive without undue wear on suspension or driveline components. No low range was used in the transfer case. This became the forerunner of the designs that followed from other manufacturers. The automobile press at the time tested the traction of the Eagles and described it as far superior to the Subaru's and that it could beat many so-called off-road vehicles. Four Wheeler magazine concluded that the AMC Eagle was "The beginning of a new generation of cars."

The Eagles were popular (particularly in the snowbelt), had towing capacity, and came in several equipment levels including sport and luxury trims. Two additional models were added in 1981, the subcompact SX/4 and Kammback. A manual transmission and a front axle-disconnect feature were also made available for greater fuel economy. During 1981 and 1982, a unique convertible was added to the line. The Eagle's monocoque body was reinforced for the conversion and had a steel targa bar with a removable fiberglass roof section. The Eagle station wagon remained in production for one model year after Chrysler acquired AMC in 1987. Total AMC Eagle production was almost 200,000 vehicles.

Audi also introduced a permanently all-wheel-driven road-going car, the Audi Quattro, in 1980. Audi's chassis engineer, Jörg Bensinger, had noticed in winter tests in Finland that a vehicle used by the West German Army, the Volkswagen Iltis, could beat any high-performance Audi. He proposed developing a four-wheel-drive car that would also be used for rallying to improve Audi's conservative image. The Audi quattro system became a feature on production cars.

In 1987, Toyota also developed a car built for competition in rally campaigns. A limited number of road-going FIA Homologation Special Vehicle Celica GT-Four (known as Toyota Celica All-Trac Turbo in North America) were produced. The All-Trac system was later available on serial production Toyota Camry, Toyota Corolla, and Toyota Previa models.

Some of the earliest mid-engined four-wheel-drive cars were the various road-legal rally cars made for Group B homologation, such as the Ford RS200 made from 1984 to 1986. In 1989, niche maker Panther Westwinds created a mid-engined four-wheel drive, the Panther Solo 2.

2000–present
In the United States, as of late 2013, AWD vehicles comprised 32% of new light vehicle sales, up 5% since 2008. This is in large part due to the popularity of the crossover. Most crossovers offer the popular technology, in spite of it increasing vehicle price and fuel consumption. Car manufacturers have inundated consumers with marketing proclaiming AWD as a safety feature, although the advantage of AWD over FWD occurs in accelerating, not braking or steering. Tests have shown that though AWD gives improved acceleration in wintery conditions, it does not help with braking.

In 2008, Nissan introduced the GT-R featuring a rear-mounted transaxle. The AWD system requires two drive shafts, one main shaft from the engine to the transaxle and differential and a second drive shaft from the transaxle to the front wheels.

Uses

Road racing
Spyker is credited with building and racing the first four-wheel-drive racing car, the Spyker 60 HP in 1903.

Bugatti created a total of three four-wheel-drive racers, the Type 53, in 1932, but the cars were notorious for having poor handling.

Miller produced the first 4WD car to qualify for the Indianapolis 500, the 1938 Miller Gulf Special.

Ferguson Research Ltd. built the front-engined P99 Formula One car that actually won a non-World Championship race with Stirling Moss in 1961. In 1968, Team Lotus raced cars in the Indy 500 and three years later in Formula 1 with the Lotus 56, that had both turbine engines and 4WD, as well as the 1969 4WD-Lotus 63 that had the standard 3-litre V8 Ford Cosworth engine. Matra also raced a similar MS84, and McLaren entered their M9A in the British Grand Prix, while engine manufacturers Cosworth produced their own version, which was tested but never raced. All these F1 cars were considered inferior to their RWD counterparts, as the advent of aerodynamic downforce meant that adequate traction could be obtained in a lighter and more mechanically efficient manner, and the idea was discontinued, though Lotus tried repeatedly.

Nissan and Audi had success with all-wheel drive in road racing with the former's advent of the Nissan Skyline GT-R in 1989. So successful was the car that it dominated the Japanese circuit for the first years of production, going on to bigger and more impressive wins in Australia before weight penalties eventually levied a de facto ban on the car. Most controversial was the win pulled off at the 1990 Macau Grand Prix, where the car led from start to finish. Audi's dominance in the Trans-Am Series in 1988 was equally controversial, as it led to a weight penalty midseason and to a rule revision banning all AWD cars; its dominance in Super Touring eventually led to a FIA ban on AWD system in 1998.

New  24 Hours of Le Mans regulations may revive AWD/4WD in road racing, though such systems are only allowed in new hybrid-powered Le Mans prototypes. One example is the Audi R18 e-tron quattro (winner of  race, the first hybrid/4WD to win Le Mans), using an electric motor in the front axle with the gasoline engine in the rear.

In heavy trucks
Medium-duty and heavy-duty trucks have recently adopted 4×4 drivetrains; 4×4 medium-duty trucks became common after Ford began selling Ford Super Duty trucks. These trucks shared many parts between the light-duty and medium-duty, reducing production costs. The Dana 60 front axle is used on both medium- and light-duty Super Duty trucks. Furthermore, the Big Three share/shared parts between the companies, reducing costs. The Dana S 110 is currently being used for the rear drive, under Ford and Ram's medium-duty trucks. The Dana 110 was also used on the General Motors 4×4s. Ram Trucks began selling medium-duty trucks, 4×4 and 4×2, in 2008. General Motors sold a 4×4 for model years 2005–2009.

In construction equipment

Volvo introduced the Model 646 four-wheel-drive backhoe loader in 1977. Case Corporation followed suit in the U.S. in 1987.

Terminology
In engineering terms, "four-wheel drive" designates a vehicle with power delivered to four wheel ends spread over at least two axles. The term "4×4" (pronounced four by four) was in use to describe North American military four-wheel-drive vehicles as early as the 1940s, with the first number indicating the number of wheel ends on a vehicle and the second indicating the number of driven wheels.

Trucks with dual tires on the rear axle and two driven axles are designated as 4×4s despite having six wheels, because the paired rear wheels behave as a single wheel for traction and classification purposes. True 6×6 vehicles, which have three powered axles, are classified as 6×6s regardless of how many wheels they have. Examples of these with two rear, one front axle are the six-wheeled Pinzgauer, which is popular with defense forces around the globe, and 10-wheeled GMC CCKW made famous by the U.S. Army in World War II.

Four-wheeler is a related term applying to all-terrain vehicles, and not to be confused with four-wheel drive. The "four" in the instance referring to the vehicle having four wheels, not necessarily all driven.

Unusual systems
Prompted by a perceived need for a simple, inexpensive all-terrain vehicle for oil exploration in North Africa, French motor manufacturer Citroën developed the 2CV Sahara in 1958. Unlike other 4×4 vehicles, which use a conventional transfer case to drive the front and rear axles, the Sahara had two engines, each independently driving a separate axle, with the rear engine facing backwards. The two throttles, clutches, and gear-change mechanisms could be linked, so the two   engines could run together, or they could be split and the car driven solely by either engine. Combined with twin fuel tanks and twin batteries (which could be set up to run either or both engines), the redundancy of two separate drive trains meant that they could make it back to civilization even after major mechanical failures. Only around 700 of these cars were built, and only 27 are known to exist today.

BMC experimented with a twin-engined Mini Moke (dubbed the "Twini Moke") in the mid-1960s, but never put it into production. This made advantage of the Mini's 'power pack' layout, with a transverse engine and the gearbox in the engine sump. Simply by fitting a second engine/gearbox unit across the rear, a rudimentary 4×4 system could be produced. Early prototypes had separate gear levers and clutch systems for each engine. Later versions sent for evaluation by the British Army had more user-friendly linked systems.

In 1965, A. J. M. Chadwick patented a 4WD system, GB 1113068, that used hemispherical wheels for an all-terrain vehicle. Twenty years later, B. T. E. Warne, patented, GB 2172558, an improvement on Chadwick's design that did not use differential gear assemblies. By using near-spherical wheels with the provision to tilt and turn each wheel co-ordinatively, the driven wheels maintain constant traction. Furthermore, all driven wheels steer, and as pairing of wheels is not necessary, vehicles with an odd number of wheels are possible without affecting the system's integrity. Progressive deceleration is made possible by dynamically changing the front-to-rear effective wheel diameter ratios.

Suzuki Motors introduced the Suzuki Escudo Pikes Peak Edition in 1996. Earlier Suzuki versions were twin-engined; from 1996 on, the engine is a twin-turbocharged 2.0-L V6, mated to a sequential six-speed manual transmission.

Nissan Motors has developed a system called E-4WD, designed for cars that are normally front-wheel drive; however, the rear wheels are powered by electric motors. This system was introduced in some variants of the Nissan Cube and Tiida. (This is similar to the system used on the Ford Escape Hybrid AWD.)

Chrysler's Jeep Division debuted the twin-engined,  Jeep Hurricane concept at the 2005 North American International Auto Show in Detroit. This vehicle has a unique "crab crawl" capability, which allows it to rotate 360° in place. This is accomplished by driving the left wheels as a pair and the right wheels as a pair, as opposed to driving the front and rear pairs. A central gearbox allows one side to drive in the opposite direction from the other. It also has dual Hemi V8s.

Some hybrid vehicles such as the Lexus RX400h provide power to an AWD system through a pair of electric motors, one to the front wheels and one to the rear. In the case of the AWD model version of the Lexus RX400h (and its Toyota-branded counterpart, the Harrier hybrid), the front wheels can also receive drive power directly from the vehicle's gasoline engine, as well as via the electric motors, whereas the rear wheels derive power only from the second electric motor. Transfer of power is managed automatically by internal electronics based on traction conditions and need, making this an all-wheel-drive system.

The 4RM system used in the Ferrari FF in 2011 is unique in that it has a rear transaxle with a secondary front transaxle connected directly to the engine. The car operates primarily as a rear-wheel drive vehicle. Clutches in the front transaxle engage when the rear wheels slip. Drive to the front wheels is transmitted through two infinitely variable clutch packs that are allowed to 'slip' to give the required road wheel speeds. The front transaxle has three gears, two forward, and reverse. The two forward gears of the front transmission match the lower four forward gears of the rear transmission. It is not used in higher gears. The connection between this gearbox and each front wheel is via independent Haldex-type clutches, without a differential. Due to the difference in ratios, the clutches continually slip and only transmit, at most, 20% of the engine's torque.

Systems by design type

Center differential with mechanical lock
 Alfa Romeo 164 Q4 (central viscous coupling, epicyclic unit and Torsen rear differential)
 Alfa Romeo 155 Q4 (central epicyclic unit, Ferguson viscous coupling and Torsen rear differential)
 AMC Eagle (central viscous coupling)
 Audi – Quattro Coupé, 80, 90, 100 & 200 (locking center and rear differentials) – up to 1987
 Audi Q7 -double pinion 50/50 with lockup clutch pack
 BMW 3 series and 5 series in the 1980s – planetary center differential with a 37–63 (front-back) torque split and viscous lock (also in rear differential but not front differential)
 Chevrolet Rounded-Line K Fleetside, K Stepside, K Blazer, and K Suburban – permanent four-wheel-drive (1973–1979) two-speed New Process 203 transfer case, center differential with 50:50 torque split and lock. An Eaton Automatic Differential Lock was optional for the rear hypoid differential.
 Ford Escort RS (RS 2000 16v 4×4 models and RS Cosworth), Sierra Cosworth, Sierra and Granada 4×4 models,
 Dodge Power Wagon – permanent four-wheel-drive (1974–1979) two-speed New Process 203 transfer case, center differential with 50:50 torque split and lock.
 Ford Expedition (1997–present) and Expedition EL/Max (2007–present) – automatic ControlTrac four-wheel drive with two-speed dual range BorgWarner transfer case and intelligent locking center multi-disc differential
 Ford Explorer (1995–2010) – automatic ControlTrac four-wheel drive with two-speed dual range BorgWarner transfer case and intelligent locking center multi-disc differential
 Ford F-Series – permanent four-wheel-drive (1974–1979) two-speed New Process 203 transfer case, center differential with 50:50 torque split and lock.
 GMC Rounded-Line K Wideside, K Fenderside, K Jimmy, and K Suburban – permanent four-wheel-drive (1973–1979) two-speed New Process 203 transfer case, center planetary differential with 50:50 torque split and lock. An Eaton Automatic Differential Lock was optional for the rear hypoid differential.
 H1 & Humvee NVG 242HD AMG open center differential, locked center differential, Neutral, low range locked. Also Torsen1 differential at the front and rear axle, The H1 moved to Torsen2 when ABS was added. The H1 Alpha had optional locking differentials in place of torsens.
 Hummer H2, H3 40/60 planetary with lock
 Jeep Grand Cherokee, Commander (except models equipped with Quadra-Trac I)
 Jeep Liberty, Jeep Cherokee (XJ), Dodge Durango (Select-Trac) – NV 242 transfer case- rear drive, open center differential, locked center differential, Neutral, low range
 Full size Jeeps with Borg Warner QuadraTrac: limited-slip center differential, 50/50 locked center differential. Low range could be used in locked or unlocked mode, allowing for use of the low range on pavement.
 Land Rover Defender (and Series III V8 models)
 Land Rover Discovery/LR3
 Land Rover Freelander
 Lada Niva (VAZ-2121) – full-time 4WD using open center differential. Transfer case with high/low range and manual central diff lock. Low range selectable in locked or unlocked mode, allowing use on pavement.
 Lexus RX300 -viscous coupling across the otherwise open center differential.
 Lincoln Navigator (1998–2006) – automatic ControlTrac four-wheel drive with two-speed dual range BorgWarner transfer case and intelligent locking center multi-disc differential
 Navigator and Navigator L (2007–present) use a one-speed single range transfer case, no reduction gearing
 Mercedes-Benz Unimog (locking center and rear with up to 10 low range gears).
 Mercedes-Benz G-Class (locking center and lockers on both front- and rear axle)
 Mercedes-Benz GL-Class – 4Matic all-wheel-drive system
 Mitsubishi Pajero (also known as Montero or Shogun)
 Porsche Cayenne – 38/62 planetary with lockup clutch pack
 Range Rover Classic 1970–1995 all full-time 4WD either plate LSD, manual lock or Ferguson viscous center differential.
 Range Rover 2nd Gen. 1994–2002 full-time 4WD Ferguson viscous center differential
 Suzuki Grand Vitara/Escudo (2005 and later models, excepting the XL-7) -full-time 4WD using limited-slip center differential, off-road 4WD with selectable center differential lock and low range transfer case 4 mode (4h, 4h lock, 4l n), traction control and electronic stability control
 Subaru – manual transmissions come with 50/50 viscous-type center differential; performance models include a planetary differential with computer-regulated lockup; automatic transmission models have an electronically controlled variable transfer clutch.
 Toyota Land Cruiser
 Toyota Sequoia (Multi-mode)
 Volkswagen Touareg -double pinion 50/50 with lockup clutch pack

Torsen center differential
 Alfa Romeo Q4s – with (Torsen T-3):
 156 Crosswagon and Sportwagon
 159
 Brera, Spider
 Audis with quattro – various iterations of Torsen, the T-3 starting from the 2007 B7 RS4
 80, 90 & Coupé (Typ 89)
 100 & 200
 A4, S4, RS4
 A5 & S5
 A6, S6, RS6
 A8, S8
 Q5, Q7
 Bentley Continental GT, Bentley Continental Flying Spur (2005) initially Torsen T-2, current have T-3
 Chevrolet Trailblazer SS Torsen T-3
 Lexus GX470, Toyota Land Cruiser Prado 120 Torsen T-3
Range Rover 3rd Gen. 2002–2009
 Toyota 4Runner (Only 2003-2009 model and 2010+ Limited V6 model) Torsen T-3 with lock
 Toyota FJ Cruiser (only manual models) Torsen T-3 with lock
 Toyota Hilux Surf Torsen T-3 with lock
 Toyota Land Cruiser 200/2008/V8 Torsen T-3 with lock
 Toyota Sequoia (only 2005–07 Models)
 Volkswagen Passenger Cars with 4motion:
 Volkswagen Passat Torsen T-2 (B5.5 model, not latest B6 model with transverse engine)
 Volkswagen Phaeton Torsen T-2

Non-locking center differential
 BMW 3-series and X5 between 2001 and xDrive – planetary center differential with permanent 38–62 (front-back) torque split #
 Cadillac Escalade, STS AWD, SRX AWD (The first two generations had a viscous clutch on the center differential) #
 Chrysler 300C AWD#
 Dodge Ramcharger 1974–1981 – NP203 FullTime 4WD Transfer Case
 Dodge Magnum, Charger AWD #
 GMC Yukon Denali, XL Denali, Sierra Denali #
 Mercedes 4MATIC cars, R class, and ML class (note some MLs had low range) #
 Plymouth Trail Duster 1974–1981 – NP203 FullTime 4WD Transfer Case
 Toyota Highlander #
 Toyota Sienna AWD (−2010 only) #

The above systems ending with "#" function by selectively using the traction control system (via ABS) to brake a slipping wheel.

Multiple-clutch systems
 Acura RL, RDX (SH-AWD) Right and left axle shaft
 Acura MDX SH-AWD & VTM4
 Ford Explorer – Ford's full-time shift-on-the-fly Intelligent 4WD System (I-4WD) on the 2011 Explorer with Terrain Management System and RSC (Roll Stability Control), Curve Control functionality, HDC (Hill Descent Control) and HAA (Hill Ascent Assist).
 Honda Ridgeline
 Honda Pilot
 Infiniti FX (ATTESA E-TS)
 Mercedes-Benz 1st generation 4MATIC (normally rear-drive, automatic clutch in transfer case engages 4WD on demand)
 Mitsubishi GTO MR/3000GT VR-4
 Mitsubishi Lancer Evolution Series S-AWC
 2010 Mitsubishi Outlander GT S-AWC
 Mitsubishi Outlander (2003–2006) independent front and rear axle coupling, and Active Center Differential.
 Nissan GT-R (ATTESA E-TS)
 Nissan Skyline GT-R (ATTESA E-TS and ATTESA E-TS-PRO) front axle coupling, rear differential locking
 Nissan Skyline GTS4 (ATTESA E-TS)
 Nissan A31 Cefiro SE4 (ATTESA E-TS)
 Porsche 959 PSK front axle coupling, rear differential locking
 Saab 9-3, Saab 9-5, Saab 9-4X (Saab XWD)

Multi-plate clutch coupling
 Audi A3 quattro, Audi S3, Audi TT quattro, Audi R8 (with Haldex Traction)
 BMW xDrive: latest 3 Series, latest 5 series, X3, latest X5 series
 Chevrolet Equinox (GMPCA)
 Chrysler Pacifica (BorgWarner ITM3e) (on 2007 model)
 Dodge Nitro (Quadra-Trac 1)
 Dodge Caliber
 Ford: Escape, Freestyle, Edge, Fusion, Five Hundred (Freestyle, FiveHundred Haldex Traction based) (Escape Control Trac II, based)
 Honda CR-V, HR-V, Element
 Hyundai Santa Fe, Hyundai Tucson Borg-Warner ITM 3e magnetic multi-plate clutch coupling
 Hyundai Veracruz IMJ magnetic multi-plate clutch coupling
 Infiniti: G35x, M35x
 Jeep Compass (Freedom Drive)
 Jeep Grand Cherokee and SRT8 NVG 249, 247
 Land Rover Freelander 2/LR2 (also Haldex Traction)
 Lamborghini: AWD variants VT series (viscous traction)
 Lincoln: MKS, MKZ
 Mazdaspeed6 (a power takeoff unit linked to clutch pack with torque sensitive rear differential)
 Mazda: Mazda3, Mazdaspeed6, Tribute, CX-3, CX-30, CX-5, CX-50, CX-60, CX-7, CX-8, CX-9 (tribute Control Trac II, based)
 Mercury: Milan, Montego, Mariner (Montego Haldex Traction–based)
 Mitsubishi Outlander (current generation)
 Nissan Murano automatic with manual lockup switch
 Porsche 911 AWD variants (a version of BorgWarner ITM3e) — excluding the 964-series Porsche 911 Carrera 4 31/69 planetary center differential
 Pontiac Torrent (GMPCA)
 Subaru low powered automatic transmission models
 Subaru Legacy, Outback, Impreza, Forester, Tribeca automatic transmission models: mechanical front drive, clutch coupled rear axle
 Suzuki: SX4, XL7, Aerio, Swift/Cultus based Subaru Justy. (viscous clutch)
 Toyota RAV4 – from 2005 (third generation only)
 Toyota Sienna AWD (2011 and newer only)
 Volkswagen Golf 4motion, Volkswagen Jetta 4motion, Volkswagen Tiguan 4motion, Volkswagen Passat (B6) 4motion (initially viscous coupling, later with Haldex Traction)
 Volvo: S40, S60, S80, V50, V70, XC70, XC90 (Visco system until 2003; then all Haldex Traction–based)

Note: the above all function like 2WD when the multi-plate clutch coupling is not engaged (with exception of Subaru models), and like 4WD high-range in a part-time 4WD system when the clutch is engaged (usually by computer although some allow manual control). Some in this category have varying degrees of control in the torque distribution between front and rear by allowing some of the clutches in a multi-plate clutch coupling to engage and slip varying amounts. An example of a system like this is the BorgWarner i-Trac(TM) system.
Note: the Haldex Traction-based car list was created from the list on Haldex Traction corporate website: Haldex Cars. A version of the BorgWarner ITM3e system is used on 2006 and up Porsche 911TT's. The Borg-Warner ITM 3e is also used in the 2006-now Hyundai Santa Fe and the Hyundai Tucson. In the Hyundais, the ITM 3e acts like a full-time AWD with 95:5 normal torque split. In extreme conditions, the system can be locked in a 50:50 split via the 4WD LOCK button.

Part-time
These are vehicles that have no center differential. Since there is no center differential to allow for speed differences between the front and rear wheels when turning, a small amount of tire slippage must occur during turns. When used on slick surfaces, this is not a problem, but when turning on dry pavement, the tires grip, then are forced to slip, then grip again, and so on, until the turn is completed. This causes the vehicle to exhibit a 'hopping' or 'binding' sensation. Using an engaged part-time 4WD system on a hard surface is not recommended, as damage to the drive-line eventually occurs. Part-time transfer cases are the industry standard transfer case for the 4x4 truck market. Any other transfer case can be considered more robust, however more moving parts and complexity can, sometimes, make other transfer cases less durable.

See also

 4WS
 Dune bashing
 Four-wheel drive in Formula One
 Limited slip differential
 Off-road vehicle
 Rock crawling
 Sport utility vehicle
 Transfer case
 Driveline windup

Footnotes

References

Off-road vehicles
Car layouts
Drivetrain

All-wheel-drive vehicles
English inventions
British inventions

af:Motordryfuitleg

Four-wheel drive


زيدكي (Зідьки) هي مدينة في مقاطعة كاركيفسكا في أوكرانيا.

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زيدكي (كاركيفسكا)


Gulklukka (fræðiheiti: Campanula thyrsoides). er tvíær tegund af klukkuættkvísl (Campanulaceae). Hún vex í Alpafjöllum og Júrafjöllum austur í Balkanskaga.

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الحياة خارج الأرض هي الحياة الافتراضية خارج كوكب الأرض والتي لم تنشأ عليه. يتراوح مجال هذه الحياة من بدائيات النوى (أو أشكال الحياة المشابهة) إلى كائنات تملك حضارة أكثر تقدمًا من الحضارة البشرية. تتكهن معادلة دريك بوجود حياة ذكية في مكان ما آخر في الكون. يُعرف علم الحياة خارج الأرض بجميع أشكاله بعلم الأحياء الفلكي (الأستروبيولوجي).

بدأ البحث المستمر الدؤوب منذ منتصف القرن العشرين للبحث عن علامات للحياة خارج كوكب الأرض. يشمل هذا البحث الحياة خارج الأرض الموجودة في الوقت الحالي والقديمة، بالإضافة إلى تضييق نطاق البحث إلى البحث عن حياة ذكية خارج الأرض. تتنوع الطرق حسب نوع البحث، فهي تمتد من تحليل بيانات التلسكوب والعينات، إلى استعمال الأجهزة الراديوية لاكتشاف إشارات الاتصال وإرسالها.

كان لمفهوم الحياة خارج كوكب الأرض، وخاصة الحياة الذكية، تأثيرًا ثقافيًا رئيسيًا، وبشكل خاص في أعمال الخيال العلمي. قدّم الخيال العلمي على مدار السنين عددًا من الأفكار النظرية تتميز كل منها بمجموعة واسعة من الاحتمالات. أثار الكثير منها اهتمام المتلقين من الشعب فيما يخص الحياة خارج كوكب الأرض. أحد الأمور المهمة بشكل خاص هو التعقّل في محاولة التواصل مع حياة خارج الأرض. يشجع البعض على استخدام طرق عدوانية في التواصل مع الحياة الذكية خارج الأرض. يجادل البعض بأن الإفصاح عن موقع الأرض، سيقود لغزو محتمل في المستقبل في حال وجود حضارات ذكية في كواكب أخري.

بشكل عام
افتُرض وجود حياة فضائية مثل الميكروبات في النظام الشمسي وفي كل أنحاء الكون. تعتمد هذه الفرضية على الحجم الشاسع للكون المرصود والقوانين الفيزيائية المتناغمة فيه. تبعًا لهذا الطرح الذي قدمه علماء مثل كارل ساغان وستيفن هوكينغ، بالإضافة إلى شخصيات بارزة مثل وينستون تشرشل، سيكون من غير المحتمل عدم وجود حياة في مكان آخر غير الأرض. يتجسد هذا الطرح في مبدأ كوبرنيكوس الذي ينص أنّ الأرض لا تشغل مكانًا مميزًا في الكون، وفي مبدأ العادية الذي ينص أنه لا يوجد شيء مميز فيما يخص الحياة على كوكب الأرض. قد تكون كيمياء الحياة بدأت بعد الانفجار العظيم بوقت قصير، قبل 13.8 مليار عام، في الفترة الصالحة للحياة عندما كان عمر الكون بين 10 إلى 17 مليون عامًا فقط. ربما برزت الحياة في عدة أماكن منفصلة في الكون. أو عوضًا عن ذلك، يمكن أن تكون الحياة قد تشكلت بتواتر أقل، ومن ثم انتشرت –بواسطة النيازك– إلى الكواكب الصالحة للحياة في عملية تدعى التبذّر الشامل. وعلى أي حال، يمكن أن تكون جزيئات عضوية معقدة قد تشكلت في قرص كوكبي أولي من حبيبات الغبار التي تحيط بالشمس قبل تشكّل الأرض. وفقًا لهذه الدراسات، قد تحدث هذه العملية خارج الأرض على كواكب متعددة وعلى الأقمار في النظام الشمسي وعلى كواكب تدور حول نجوم أخرى.

التطور
تشير دراسة نشرت عام 2017 أنه نظرًا للتطور المعقد في الأنواع على كوكب الأرض، فإن مستوى إمكانية التنبؤ بتطور حياة فضائية في أماكن أخرى سيجعلها تبدو مشابهة للحياة على كوكبنا. كتب سام ليفين أحد مؤلفي الدراسة «نتوقع أن يكونوا مثل البشر، عبارة عن تسلسل من الكيانات، التي تتعاون جميعها لخلق حياة فضائية. يوجد في كل مستوى من الكائن الحي آليات لإزالة التناقض، والحفاظ على التعاون، والحفاظ على أداء الكائن الحي لوظائفه. يمكننا حتى أن نقدّم بعض الأمثلة لما ستكون عليه هذه الآليات». هنالك بحث أيضًا يدور حول تحديد قدرة الحياة على تنمية الذكاء. أُشير إلى ارتباط نشوء هذه القدرة بعدد البيئات الملائمة المحتملة التي يتضمنها الكوكب، وأنّ تعقيد الحياة نفسها ينعكس في كثافة المعلومات في البيئات الكوكبية، والذي يمكن تقديره من خلال البيئات الملائمة.

اللمحة التاريخية

كانت فكرة المخلوقات الفضائية تأتي من أفلام الخيال العلمي التي كانت تصورها بأن لها تكنولوجيا تفوق تكنولوجيا البشر كما يعتقد أن كوكب المريخ قد توجد فيه حضارات متقدمة كما كانت سينما الخيال العلمي تصور الفضائيين يسكنون جوارنا في القمر لكن مع أول هبوط حققه الإنسان على القمر تغيرت الآراء تمامآ فوجدوا أن القمر مجرد كتلة صخرية تدور حول كوكب الأرض أي لا توجد فيه حياة.

أطلقت ناسا أول مشروع للبحث عن الحياة خارج الأرض في عام 1964 ومن وقتها حتى الآن قامت بالعديد من المشاريع أهمها إطلاق مسبار كيبلر للبحث عن كواكب صالحة للحياة.

تطور البحث عن المخلوقات الفضائية
بعد تبني وكالة ناسا مشروع البحث عن الحياة خارج الأرض 1964 بدأت تطلق المشروع تلو الآخر أملاً إما في استقبال اتصال ما من حضارة أخرى أو إرساله.

أول الرحلات أطلق في 1972 (باسم بيونير 10) حيث أرسلت صور تحوي على أشخاص وذكر وأنثى وأشكال هندسية وصور تم انتقائها شخصيا من قبل (كارل ساغان).

في عام 1974 أطلقت الوكالة إِشارات مشفرة ومرمزة كانت تحوي (لمحة عن علوم الرياضيات والحساب على الأرض ) وهي العلم التي يعتقد أن كل الحضارات الذكية من الممكن أن تفهمها وتفهم أنها من صنع حضارة أخرى.

وفي عام 1977 أطلقت ناسا مشروع أصوات الأرض (ضمن مشروع فوياجر) وهو عبارة عن مسبارين فضائيين جهزا بإسطوانة صوت ذهبية (لوحة فوياجر الذهبية) سجل عليها العديد من أصوات البشر الذين أرسلوا تحياتهم ب55 لغة كما سجل بعض الأصوات التي تسمع على الأرض كأصوات البراكين والبحار والحيوانات وغيرها وحتى بعض الموسيقى لموسيقيين مشهورين على الأرض كموتزارت أو بيتهوفن وبثت هذه الرسالة في أرجاء الفضاء التي استطاع المسبار الوصول إليها وأطلقا باتجاه كوكبي فوياجر1 وفوياجر2 واللذان يعتقد بوجود حياة فيهما.(تفاصيل الرحلة: فوياجر).

بدأ تطور البحث في عام 1990م، حيث اكتشف فريق من علماء الفلك أول كوكب يقع خارج المجموعة الشمسية، أطلقوا عليه اسم كوروت-7ب، واُكْتُشِف عن طريقه فعندما يمر كوكب بجوار النجم يحجب ضوء النجم كما أن جاذبية الكوكب تشد النجم قليلا، ولكن لم يغير هذا الاكتشاف شيئاً بالنسبة للبحث عن الحياة خارج كوكب الأرض، فهذه الكواكب لا تدعم الحياة لأن معظمها كواكب غازية مثل كوكبي المشتري وزحل.

في عام 1993 توقف السيناتور الأمريكي براين عن دعم وتمويل مشاريع ناسا وخصص هذه الميزانية فقط للبحث عن الحياة خارج الأرض.

في عام 2007 بدأ معهد سيتي المختص بأبحاث الحياة خارج الأرض بنشر 350 هوائي استقبال لاستقبال أية إشارات من الفضاء وسرعة تحليلها ثم تطور المشروع إلى مشروع سيتي أت هوم (SETI @ HOME) والذي مكن المواطنين من أنحاء العالم بالمشاركة في البحث عبر الإنترنت وتقديم المعلومات التي ترد (في حال الورود) إلى الهوائيات وهو مشروع لاقى تفاعل الملايين خاصة في دول العالم المتقدم.

وفي عام 2009م، أطلقت وكالة ناسا لأبحاث الفضاء تلسكوبا شديد الحساسية يحتوي على مرايا عالية الدقة، في مهمة اسمها مهمة كبلر، على اسم العالم يوهانس كيبلر، للبحث عن النجوم التي يبهت ضوءها.

وفي عام 2012 أرسلت وكالة ناسا للفضاء مركبة كيوريوسيتي روفر إلى المريخ للبحث عن الحياة على سطح الكوكب، فكانت خيبة أمل حيث لم تجد المركبة أية أشكال حياة على المريخ، فهو كوكب ميت لا يوجد فيه ماء. كما بدأ العلماء باستخدام أكبر المراصد على الأرض، وهو مرصد كيك، والذي يمكنه تحديد كتلة الكوكب وبعده عن النجم، فيجب أن يكون الكوكب في منطقة متوسطة البعد كي يستطيع دعم الحياة. والبحث عن الحياة خارج الأرض أشبه بالبحث عن إبرة في كومة قش فعلى بعد آلاف السنين الضوئية تضيع الكواكب في ضوء النجوم المجاورة.

الاكتشاف
في يوم 15 آب من عام 1977 تلقى مرصد لاسيتي إشارة من خارج الأرض على شكل موجة كانت أقوى ب30 مرة عن الإشارة الاعتيادية التي ترد من الكون واستمرت لمدة 72 ثانية قبل أن تختفي سميت فيما بعد هذه الإشارة بإشارة الواو وعند قيام الحواسيب بترجمة الإشارة رقمياً نتجت أحرف وأرقام غير مفهومة المعنى، ولم يستطع العلماء معرفة مصدر الإشارة إلا أنه يعتقد أنها من كوكب يبعد حوالي 20 سنة ضوئية عن الأرض حيث يظن أنه توجد حضارة ذكية ما!.

سبب هبوط مسباركيوريوسيتي روفركانت خيبة أمل كبرى بسبب عدم وجود حياة على كوكب المريخ لكن مع هذا حفر مسبار كيريوسيتي، بضعة أمتار في المريخ حيث وجد طبقة بيضاء ظن العلماء أنها عبارة عن أملاح لكن بعد مرور بعض الوقت بدأت هذه الطبقة البيضاء بالذوبان في التربة، وهو ما أثار جدلاً عن وجود ماء في المريخ، لكن في عام 2015 اكتشفت وكالة ناسا مياها على المريخ وبدأت التساؤلات عن احتمالية وجود حياة عليه.

معادلة رياضية
حدد العلماء حديثاً معادلة لا تزال غير قابلة للحل، وهي تحدد عدد الأماكن في المجرة التي من الممكن أن تحوي حضارة ذكية (N) وكانت على الشكل التالي:

N=R* x fp x ne x fL x fi x fc x L
 حيث تدل R* على معدل ولادة النجوم الجديدة في المجرة سنوياً.
وتدل كل أحرف f على كسور (وهي أقل من الواحد) حيث:
 تدل fp على نسبة النجوم التي تحوي كواكب.
 تدل fL على نسبة الكواكب التي تحوي حياة.
 تدل fi على نسبة جميع أنماط الحياة.
 تدل fc على نسبة الكائنات التي تستخدم التكنلوجيا وتطلق إشارات في الفضاء كالبشر.
 و تدل ne على متوسط عدد الكواكب القابلة للحياة.
 وأخيراً تدل L على طول مدة بقاء هذه الكائنات (وهو الأهم فوجود البشر هو مدة قصيرة جداً جداً في عمر الكون).
فيما بعد قام العلماء باعتبار أن كل هذه النسب f هي نسبة صغيرة جداً كما هو R* و ne ولذلك أعتبر تقريبياً أن: NL

مفارقة فيرمي
.
معروفة باسم: أين الجميع؟ وهي مفارقة أطلقها العالم إنريكو فيرمي حيث اعتبر أنه وفقاً للمعطيات فإنه لا شيء مميز يحتويه عالمنا حتى يحوي حياة (فالشمس نجم عادي يوجد مثله ملايين) ومعظم هذه النجوم تحوي كواكب مثلها تماماً ومن الممكن أن يشبه العديد من هذه الكواكب الأرض ومهما كان عدد الحضارات التي تعيش هنا أو هناك فإن احتمال وصول إحداها لتحقيق (ما نعتبره مستحيلاً) وهو السفر عبر النجوم موجود، وبالتالي لابد وأن تكون إحداها قد وصلت إلينا أو تركت أثراً ما أو كانت هنا من قبل وهذا الكلام منطقي ورياضي لكن فعليا لم يحدث هذا على الإطلاق! ولهذا سميت مفارقة.

بعض الحلول لمفارقة فيرمي والتي اقترحها العلماء:
 هم موجودون لكنهم لا يتواصلون معنا.
 هم موجودون ويتواصلون معنا ولكن لا يمكننا سماعهم.
 هم كانوا موجودون في وقت لم نكن نحن فيه (ليس بالضرورة مروا على الأرض).
 هم موجودون لكن معظم الناس لا تدرك ذلك حتى الآن.
 اختفوا! (أي دمروا أنفسهم أو دمرهم شيء ما، كما قد يحصل مع البشر في حال نشوب حرب نووية !).
 قد نكون غير مهمين بالنسبة لهم (فقد يكونوا متطورين لمراحل قد تجعلنا بنظرهم كالنحل مثلاً بالنسبة للبشر، فهل فكر البشر يوما ما بالتواصل مع النحل؟ رغم أنهم أمامنا يعملون طوال الوقت وينظمون أنفسهم!).

في علم الأحياء
بالنسبة للحياة خارج الأرض يجب أن توجد عناصر مهمة هي أوكسجين وهيدروجين ونيتروجين وكاربون والأحماض الامينية فإنها مهمة جدا لبناء مركبات حيوية وتكوين حامض نووي.

كانت الأفلام الخيالية العلمية تعتبر أقصر وسيلة لتصور الحياة في الفضاء الخارجي وأيضا تصورها من ناحية تطور المخلوقات الفضائية في التفكير وتصور حضارتهم المتقدمة، ومن أهم الأفلام حرب النجوم (فيلم) وحرب العوالم (فيلم 2005) وستار تريك وغيرها من الأفلام.

نظرية بانسبرميا
أساس نظرية بانسبيرميا التي تنسب إلى العالم بانسبيرميا حيث تنص على أن النيازك أو الكويكبات تحتوي على المواد اللازمة للحياة وتسمى ببذور الحياة.

وسميت هذه النظرية أيضا بالتبذر الشامل وتنص على أن بذور الحياة تنتقل في الفضاء حيث ما اصطدمت بكوكب ما بدأت المواد بالانتشار، وتعتبر هذه النظرية من النظريات المهمة في الدراسات الخاصة بالحياة خارج كوكب الأرض.

فرضية الأرض النادرة

تعتبر هذه النظرية من النظريات المعارضة لوجود المخلوقات في كوكب غير الأرض أي تنص على أن كوكب الأرض هو الكوكب الوحيد الصالح للحياة، وتعتبر هذه النظرية أكثر قبولا عند الأشخاص المعارضين لوجود فكرة المخلوقات الفضائية.

قابلية السكن للكواكب
تعتبر من أهم الدراسات في البحث عن الحياة خارج كوكب الأرض، ودراسة الشروط الملائمة للحياة ومن هذه الشروط:

 البعد عن النجم: يجب أن يكون الكوكب في مجال متوسط في البعد لكي يسمح بظهور الحياة عليه أو يسمح بظهور مركب الماء عليه، لأن الكوكب إذا كان قريباً من النجم سيصبح حاراً جداً والماء سوف يتبخر، وإذا كان بعيداً عنه سوف يكون كوكباً جليدياً أي متجمداً لا حياة طبيعية فيه كمثل الحياة على كوكبنا.

أما إذا كان متوسط البعد فسيمكن ذلك من ظهور الماء السائل على سطحه.
 وفرة الماء: تحتاج الكواكب الصالحة للحياة إلى ماء.

 نوع الكوكب: يجب الاهتمام بنوعية الكوكب لأنه ليس كل الكواكب صالحة للحياة لأن هناك كواكب غازية أي متكونة من الغازات مثل المشتري وزحل.

انظر أيضاً

أحداث وأجسام
 غليزا 581 سي، ودي، وإي
 ترابيست-1
 نيزك تلال ألان 84001

مواضيع
 علم الأحياء الفلكي
 قابلية السكن في الكواكب
 فرضية الأرض النادر

نظريات
 معادلة دريك
 مبدأ العادية
 بانسبيرميا
 مقياس كارداشيف Kardashev scale
 المنطقة المجرية الصالحة للحياة

أماكن
 المنطقة 51
 كيبلر-22b

المراجع

البحث عن كائنات ذكية خارج الأرض
تخمينات علمية
خلافات علمية
خلافات فلكية
رسائل بين نجمية
علم الأحياء الفلكي
فرضيات علم الأحياء
مسائل غير محلولة في علم الأحياء
مسائل غير محلولة في علم الفلك

الحياة خارج الأرض