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  1. 疫苗涵蓋率 相關
  1. List of states and union territories of India by vaccination coverage - Wikipedia › wiki › List_of_states_and_union_territories

    List of states and union territories of India by vaccination coverage. This is a list of the States of India ranked in order of percentage of children between 12–23 months of age who received all recommended vaccines. This information was ...

  2. Influenza - Wikipedia › wiki › Influenza

    Influenza, commonly called " the flu ", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These ...

  3. Uruguay - Wikipedia › wiki › Uruguay

    Uruguay is a representative democratic republic with a presidential system. The members of government are elected for a five-year term by a universal suffrage system. Uruguay is a unitary state: justice, education, health, security, foreign ...

  4. Rec. 709 - Wikipedia › wiki › Rec
    • Technical Details
    • Standards Conversion
    • Relationship to sRGB
    • See Also
    • External Links

    The standard is freely available at the ITU website, and that document should be used as the authoritative reference. The essentials are summarized below.

    Conversion between different standards of video frame rates and color encoding has always been a challenge for content producers distributing through regions with different standards and requirements. While BT.709 has eased the compatibility issue in terms of the consumer and television set manufacturer, broadcast facilities still use a particular frame rate based on region, such as 29.97 in North America, or 25 in Europe meaning that broadcast content still requires at least frame rate conversion.

    sRGB was created after the early development of Rec.709. The creators of sRGB chose to use the same primaries and whitepoint as Rec.709, but changed the tone response curve (sometimes referred to as gamma) to better suit the intended use in offices and brighter conditions than television viewing in a dark living room.

    Rec. 601, a comparable standard for standard-definition television(SDTV)
    Rec. 2020, a standard for ultra high definition television (UHDTV) with Wide Color Gamut(WCG)
    Rec. 2100, a standard for high dynamic rangetelevision (HDR-TV) with FHD and UHD resolution
  5. Lithuania - Wikipedia › wiki › Lithuania

    Lithuania covers an area of 65,300 km 2 (25,200 sq mi), with a population of 2.8 million. Its capital and largest city is Vilnius; other major cities are Kaunas and Klaipėda. Lithuanians belong to the ethno-linguistic group of the Balts and ...

  6. Facebook - Wikipedia › wiki › Facebook

    Facebook's initial public offering came on May 17, 2012, at a share price of US$38. The company was valued at $104 billion, the largest valuation to that date. The IPO raised $16 billion, the third-largest in U.S. history, after Visa Inc. in ...

  7. Tainan - Wikipedia › wiki › Tainan

    Tainan, officially Tainan City, is a special municipality in southern Taiwan facing the Taiwan Strait on its western coast. Tainan is the oldest city on the island and also commonly known as the "Capital City" for its over 200 years of ...

  8. Semiconductor - Wikipedia › wiki › Semiconductor
    • Properties
    • Materials
    • Physics of Semiconductors
    • Early History of Semiconductors
    • See Also
    • Further Reading
    • External Links

    Variable electrical conductivity

    Semiconductors in their natural state are poor conductors because a current requires the flow of electrons, and semiconductors have their valence bands filled, preventing the entire flow of new electrons. Several developed techniques allow semiconducting materials to behave like conducting materials, such as doping or gating. These modifications have two outcomes: n-type and p-type. These refer to the excess or shortage of electrons, respectively. An unbalanced number of electrons would cause...


    Heterojunctions occur when two differently doped semiconducting materials are joined together. For example, a configuration could consist of p-doped and n-doped germanium. This results in an exchange of electrons and holes between the differently doped semiconducting materials. The n-doped germanium would have an excess of electrons, and the p-doped germanium would have an excess of holes. The transfer occurs until an equilibrium is reached by a process called recombination, which causes the...

    Excited electrons

    A difference in electric potential on a semiconducting material would cause it to leave thermal equilibrium and create a non-equilibrium situation. This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion. Whenever thermal equilibrium is disturbed in a semiconducting material, the number of holes and electrons changes. Such disruptions can occur as a result of a temperature difference or photons, which can enter the system and create electrons...

    A large number of elements and compounds have semiconducting properties, including: 1. Certain pure elements are found in Group 14 of the periodic table; the most commercially important of these elements are silicon and germanium. Silicon and germanium are used here effectively because they have 4 valence electrons in their outermost shell which gives them the ability to gain or lose electrons equally at the same time. 2. Binary compounds, particularly between elements in Groups 13 and 15, such as gallium arsenide, Groups 12 and 16, groups 14 and 16, and between different group 14 elements, e.g. silicon carbide. 3. Certain ternary compounds, oxides, and alloys. 4. Organic semiconductors, made of organic compounds. 5. Semiconducting Metal-organic frameworks. The most common semiconducting materials are crystalline solids, but amorphous and liquid semiconductors are also known. These include hydrogenated amorphous silicon and mixtures of arsenic, selenium and tellurium in a variety of...

    Energy bands and electrical conduction

    Semiconductors are defined by their unique electric conductive behavior, somewhere between that of a conductor and an insulator. The differences between these materials can be understood in terms of the quantum states for electrons, each of which may contain zero or one electron (by the Pauli exclusion principle). These states are associated with the electronic band structure of the material. Electrical conductivity arises due to the presence of electrons in states that are delocalized (exten...

    Charge carriers

    The partial filling of the states at the bottom of the conduction band can be understood as adding electrons to that band. The electrons do not stay indefinitely (due to the natural thermal recombination) but they can move around for some time. The actual concentration of electrons is typically very dilute, and so (unlike in metals) it is possible to think of the electrons in the conduction band of a semiconductor as a sort of classical ideal gas, where the electrons fly around freely without...


    The conductivity of semiconductors may easily be modified by introducing impurities into their crystal lattice. The process of adding controlled impurities to a semiconductor is known as doping. The amount of impurity, or dopant, added to an intrinsic (pure) semiconductor varies its level of conductivity. Doped semiconductors are referred to as extrinsic.By adding impurity to the pure semiconductors, the electrical conductivity may be varied by factors of thousands or millions. A 1 cm3 specim...

    The history of the understanding of semiconductors begins with experiments on the electrical properties of materials. The properties of the time-temperature coefficient of resistance, rectification, and light-sensitivity were observed starting in the early 19th century. Thomas Johann Seebeck was the first to notice an effect due to semiconductors, in 1821. In 1833, Michael Faraday reported that the resistance of specimens of silver sulfide decreases, when they are heated. This is contrary to the behavior of metallic substances such as copper. In 1839, Alexandre Edmond Becquerel reported observation of a voltage between a solid and a liquid electrolyte, when struck by light, the photovoltaic effect. In 1873, Willoughby Smith observed that selenium resistors exhibit decreasing resistance, when light falls on them. In 1874, Karl Ferdinand Braun observed conduction and rectification in metallic sulfides, although this effect had been discovered much earlier by Peter Munck af Rosenschold...

    A. A. Balandin & K. L. Wang (2006). Handbook of Semiconductor Nanostructures and Nanodevices (5-Volume Set). American Scientific Publishers. ISBN 978-1-58883-073-9.
    Sze, Simon M. (1981). Physics of Semiconductor Devices (2nd ed.). John Wiley and Sons (WIE). ISBN 978-0-471-05661-4.
    Turley, Jim (2002). The Essential Guide to Semiconductors. Prentice Hall PTR. ISBN 978-0-13-046404-0.
    Yu, Peter Y.; Cardona, Manuel (2004). Fundamentals of Semiconductors : Physics and Materials Properties. Springer. ISBN 978-3-540-41323-3.
    Calculator for the intrinsic carrier concentrationin silicon
    Semiconductor OneSource Hall of Fame, Glossary
  9. Hughes H-4 Hercules - Wikipedia › wiki › Hughes_H-4_Hercules
    • Design and Development
    • Operational History
    • Display
    • Specifications
    • See Also
    • References
    • External Links

    In 1942, the U.S. War Department needed to transport war materiel and personnel to Britain. Allied shipping in the Atlantic Ocean was suffering heavy losses to German U-boats, so a requirement was issued for an aircraft that could cross the Atlantic with a large payload. Wartime priorities meant the aircraft could not be made of strategic materials (e.g., aluminum). The aircraft was the brainchild of Henry J. Kaiser, a leading Liberty ship builder and manufacturer. Kaiser teamed with aircraft designer Howard Hughes to create what would become the largest aircraft yet built. It was designed to carry 150,000 pounds (68,000 kg), 750 fully equipped troops or two 30-ton M4 Sherman tanks.The original designation "HK-1" reflected the Hughes and Kaiser collaboration. The HK-1 aircraft contract was issued in 1942 as a development contract and called for three aircraft to be constructed in two years for the war effort. Seven configurations were considered, including twin-hull and single-hull...

    Hughes returned to California during a break in the Senate hearings to run taxi tests on the H-4.On November 2, 1947, the taxi tests began with Hughes at the controls. His crew included Dave Grant as copilot, two flight engineers, Don Smith and Joe Petrali, 16 mechanics, and two other flight crew. The H-4 also carried seven invited guests from the press corps and an additional seven industry representatives. In total, thirty-six people were on board. Four reporters left to file stories after the first two taxi runs while the remaining press stayed for the final test run of the day. After picking up speed on the channel facing Cabrillo Beach, the Hercules lifted off, remaining airborne for 26 seconds at 70 ft (21 m) off the water at a speed of 135 miles per hour (217 km/h) for about one mile (1.6 km). At this altitude, the aircraft still experienced ground effect.Nevertheless, the brief flight proved to detractors that Hughes' (now unneeded) masterpiece was flight-worthy—thus vindica...

    Ownership of the H-4 was disputed by the U.S. government, which had contracted for its construction. In the mid-1970s, an agreement was reached whereby the Smithsonian Institution's National Air and Space Museum would receive the Hughes H-1 Racer and section of the H-4's wing, the Summa Corporationwould pay $700,000 and receive ownership of the H-4, the U.S. government would cede any rights, and the aircraft would be protected "from commercial exploitation." In 1980, the H-4 was acquired by the Aero Club of Southern California, which later put the aircraft on display in a very large geodesic dome next to the Queen Mary ship exhibit in Long Beach, California. The large dome facility became known as the Spruce Goose Dome. The very large enclosed indoor dome area around the H-4 consisted of meeting and special event space, elaborate audio-visual displays about Howard Hughes and the aircraft itself, and dining areas for tourists. Many convention groups held large dinners, sales meetings...

    Performance specifications are projected. General characteristics 1. Crew:3 2. Length:218 ft 8 in (66.65 m) 3. Wingspan:320 ft 11 in (97.82 m) 4. Height:79 ft 4 in (24.18 m) 5. Fuselage height:30 ft (9.1 m) 6. Empty weight:250,000 lb (113,398 kg) 7. Powerplant: 8 × Pratt & Whitney R-4360 Wasp Major28-cylinder air-cooled radial piston engines, 3,000 hp (2,200 kW) each 8. Propellers: 4-bladed Hamilton Standard, 17 ft 2 in (5.23 m) diameter constant-speed propellers Performance 1. Cruise speed:250 mph (400 km/h, 220 kn) 2. Range:3,000 mi (4,800 km, 2,600 nmi) 3. Service ceiling:20,900 ft (6,400 m)


    1. Francillon, René J. McDonnell Douglas Aircraft since 1920: Volume II. Annapolis, Maryland: Naval Institute Press, 1990. ISBN 1-55750-550-0. 2. McDonald, John J. Howard Hughes and the Spruce Goose. Blue Ridge Summit, Pennsylvania: Tab Books Inc., 1981. ISBN 0-8306-2320-5. 3. Odekirk, Glenn E. Spruce Goose (Title inside cover: HK-1 Hercules: A Pictorial History of the Fantastic Hughes Flying Boat). Long Beach, California: Glenn E. Odekirk and Frank Alcantr, Inc., 1982. No ISBN. 4. Parker, Da...

    Evergreen Aviation & Space Museum, home of the Spruce Goose
    Vintage photos of Spruce Goose's construction
  10. Unicode font - Wikipedia › wiki › Unicode_font

    Background The Unicode standard does not specify or create any font (), a collection of graphical shapes called glyphs, itself.Rather, it defines the abstract characters as a specific number (known as a code point) and also defines the required ...

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  1. 疫苗涵蓋率 相關