A tunnel is an underground passageway, dug through the surrounding soil/earth/rock and enclosed except for entrance and exit at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods. A tunnel may be for rail traffic, or for a canal; the central portions of a rapid transit network are in the tunnel. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment. Secret tunnels are built for military purposes, or by civilians for smuggling of weapons, contraband, or people. Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human-made barriers safely. Tunnels can be connected together in tunnel networks. A tunnel is long and narrow; the definition of what constitutes a tunnel can vary from source to source.

For example, the definition of a road tunnel in the United Kingdom is defined as "a subsurface highway structure enclosed for a length of 150 metres or more." In the United States, the NFPA definition of a tunnel is "An underground structure with a design length greater than 23 m and a diameter greater than 1,800 millimetres."In the UK, a pedestrian, cycle or animal tunnel beneath a road or railway is called a subway, while an underground railway system is differently named in different cities, the "Underground" or the "Tube" in London, the "Subway" in Glasgow, the "Metro" in Newcastle. The place where a road, canal or watercourse passes under a footpath, cycleway, or another road or railway is most called a bridge or, if passing under a canal, an aqueduct. Where it is important to stress that it is passing underneath, it may be called an underpass, though the official term when passing under a railway is an underbridge. A longer underpass containing a road, canal or railway is called a "tunnel", whether or not it passes under another item of infrastructure.

An underpass of any length under a river is usually called a "tunnel", whatever mode of transport it is for. In the US, the term "subway" means an underground rapid transit system, the term pedestrian underpass is used for a passage beneath a barrier. Rail station platforms may be connected by pedestrian footbridges. Much of the early technology of tunneling evolved from military engineering; the etymology of the terms "mining", "military engineering", "civil engineering" reveals these deep historic connections. Predecessors of modern tunnels were adits to transport water for irrigation or drinking, sewerage; the first Qanats are known from before 2000 B. C; the Tunnel of Eupalinos is a tunnel aqueduct 1,036 m long running through Mount Kastro in Samos, built in the 6th century BC to serve as an aqueduct. It is the second known tunnel to have been excavated from both ends, after the Siloam tunnel in the Palestinian neighbourhood of Silwan in eastern Jerusalem. A major tunnel project must start with a comprehensive investigation of ground conditions by collecting samples from boreholes and by other geophysical techniques.

An informed choice can be made of machinery and methods for excavation and ground support, which will reduce the risk of encountering unforeseen ground conditions. In planning the route, the horizontal and vertical alignments can be selected to make use of the best ground and water conditions, it is common practice to locate a tunnel deeper than otherwise would be required, in order to excavate through solid rock or other material, easier to support during construction. Conventional desk and preliminary site studies may yield insufficient information to assess such factors as the blocky nature of rocks, the exact location of fault zones, or the stand-up times of softer ground; this may be a particular concern in large-diameter tunnels. To give more information, a pilot tunnel may be driven ahead of the main excavation; this smaller tunnel is less to collapse catastrophically should unexpected conditions be met, it can be incorporated into the final tunnel or used as a backup or emergency escape passage.

Alternatively, horizontal boreholes may sometimes be drilled ahead of the advancing tunnel face. Other key geotechnical factors: Stand-up time is the amount of time a newly excavated cavity can support itself without any added structures. Knowing this parameter allows the engineers to determine how far an excavation can proceed before support is needed, which in turn affects the speed and cost of construction. Certain configurations of rock and clay will have the greatest stand-up time, while sand and fine soils will have a much lower stand-up time. Groundwater control is important in tunnel construction. Water leaking into a tunnel or vertical shaft will decrease stand-up time, causing the excavation to become unstable and risking collapse; the most common way to control groundwater is to install dewatering pipes into the ground and to pump the water out. A effective but expensive technology is ground freezing, using pipes which are inserted into the ground surrounding the excavation, which are cooled with special refrigerant fluids.

This freezes the ground around each pipe until the whole space is surrounded with frozen soil, keeping water out until a permanent structure can be bui

Canh line

The Canh line was the fifteenth dynasty of Hùng kings of the Hồng Bàng period of Văn Lang. Starting 754 B. C. the line refers to the rule of his successors. It is best known as the period when the Lạc Việt made their appearance in Văn Lang and whose influence was an important one on Vietnamese history. Cảnh Chiêu Lang took the regnal name of Hùng Triệu Vương upon becoming Hùng king; the series of all Hùng kings following Cảnh Chiêu Lang took that same regnal name of Hùng Triệu Vương to rule over Văn Lang until 661 B. C. During this period, at a regional level, Văn Lang was divided into as many as 15 administrative regions called bộs each still governed by a Lạc tướng. Hùng Vương became a form of address for a person, king; the Hùng kings of this line restored a single strong kingship as part of the Đông Sơn period, initiating another glorious chapter in Vietnamese history, as the Vietnamese people identified with the Đông Sơn culture. The 7th century BC witnessed the process of migration of Lạc Việt refugees who fled the Spring and Autumn period to Văn Lang.

The Lạc Việt were a people from East Asia. The migrant people settled in the Red River Delta; the Lạc Việt settlers would grasp power over Văn Lang. Đào Duy Anh. Đất nước Việt Nam qua các đời. NXB VHTT, 2005. Hauptly, Denis J. In Vietnam, New York. Nguyễn Khắc Thuần. Thế thứ các triều vua Việt Nam. Giáo Dục Publisher. Sloper, David W. Higher Education in Vietnam: Change and Response. Institute of Southeast Asian, 1995 - 20c

Elizabeth McCord (character)

Elizabeth "Bess" Adams McCord is a fictional character and the protagonist of the CBS TV series Madam Secretary portrayed by Téa Leoni. Elizabeth is the President of the United States and former United States Secretary of State. Born in Virginia, Elizabeth attended Houghton Hall Boarding School, where she was co-captain of the debate team alongside Bahrainian Crown Prince Yousif Obaid, she attended the University of Virginia, one of her professors was future Chief Justice of the United States Frawley. It was where she met her future husband. In 1990, Elizabeth married Henry McCord, they have two daughters, Stephanie "Stevie" and Alison, a son, Jason. She has a brother, Dr. Will Adams, married to Sophie Adams, with whom he has a 5-year-old daughter, Annie, she speaks fluent French, Arabic, Persian and "a year of high school Spanish". Elizabeth worked for the CIA as an analyst for 20 years until she resigned from her position due to an ethical dilemma, just as she was being considered for promotion to Station Chief, Baghdad.

She taught at the University of Virginia as a Political Science Professor. After the death of Vincent Marsh in a plane crash, President Conrad Dalton asked her to be the US Secretary of State. Not a natural politician, Elizabeth clashes with the White House Chief of Staff Russell Jackson; as the Secretary of State, her first year in office was spent investigating her predecessor's death. In "Tamerlane", Elizabeth is in the home of Iranian Foreign Minister Zahed Javani when a coup d'état orchestrated by Secretary Marsh, CIA Director Andrew Munsey, CIA analyst Juliet Humphrey, is attempted. In the aftermath, Elizabeth was left with some post-traumatic stress and has been seeing Russell Jackson's personal therapist. In "The Show Must Go On", during a communications blackout on Air Force One with both the President and the Speaker of the House on board, with the Vice President in surgery and President pro tempore of the Senate found to be incompetent after a series of mini-strokes earlier in the year, Elizabeth is sworn in as Acting President for a number of hours.

In "You Say You Want a Revolution", Elizabeth and her Cuban counterpart are instrumental in the restoration of Cuba–United States relations, including the opening of the Cuban embassy in Washington and the U. S. embassy in Havana and the repeal of the embargo against Cuba. This has been viewed as a significant milestone in the Dalton presidency. During the first half of the second season, Elizabeth was instrumental in preventing a potential United States-Russia War. In "Vartius", due to the failing health and impending resignation of Mark Delgado, President Dalton offered the position of Vice President of the United States to Elizabeth, she accepted, but when President Dalton lost his party's primary, she advised him to run as an independent candidate and ask a popular senator, Teresa Hurst, from Pennsylvania to be his Vice President instead, as winning Pennsylvania would increase his chances of ensuring neither major party candidate would achieve a majority in the Electoral College. On election night, Dalton won the key states of Florida and Pennsylvania, guaranteeing that neither major-party candidate would secure a majority.

Thanks to the efforts of Russell Jackson, Dalton was re-elected by the House of Representatives. In season 4, Secretary McCord is considered to be a favorite to run for president over Vice President Teresa Hurst. Russell Jackson tells her that President Dalton would prefer to leave the Oval Office to her, his longtime mentee, instead of his Vice President, who has her own presidential ambitions. In the last episode of season 4, Elizabeth stated. In season 5, Secretary McCord offered her resignation to President Dalton, he accepted. In the season 5 episode "Better Angels", Elizabeth was holding a public gathering at her family farm, when she announced her candidacy to be President of the United States; the first episode of season 6, "Hail to the Chief", reveals that Elizabeth McCord won her bid to become the first female POTUS. The sixth season opens with accusations that the McCord campaign conspired with Iran to win the election; the second episode, "The Strike Zone", features former campaign manager turned Senior Counselor to the President Mike B. testifying in front of the Senate Intelligence Committee.

With the exception of her personal assistant, Blake Moran, new policy advisor Kat Sandoval Elizabeth inherited her entire senior staff from her predecessor, Vincent Marsh. Her personal staff while Secretary of State consists of: Nadine Tolliver – Chief of Staff to the Secretary Jay Whitman – Policy Advisor. – Acting White House Chief of Staff Daisy Grant – Spokesperson for the US Department of State.