Yahoo奇摩 網頁搜尋

  1. Exxon Valdez oil spill - Wikipedia

    en.wikipedia.org › wiki › Exxon_Valdez_oil_spill

    The Exxon Valdez oil spill occurred in Prince William Sound, Alaska, on March 24, 1989, when Exxon Valdez, an oil tanker owned by Exxon Shipping Company that was bound for Long Beach, California struck Prince William Sound's Bligh Reef, 1.5 ...

  2. Yangmingshan - Wikipedia

    en.wikipedia.org › wiki › Yangmingshan
    • History
    • Landscape and Geology
    • Xiaoyoukeng
    • Flora and Fauna
    • Historical and Cultural Sites
    • Gallery
    • See Also
    • External Links

    This mountain range was originally called "Grass Mountain" (Chinese: 草山; Pe̍h-ōe-jī: Chháu-soaⁿ) during the Qing Dynasty, in reference to the Datun Mountain (大屯山; Tōa-tūn-soaⁿ).Officials during this period were worried about thieves stealing sulfur from the rich sulfur deposits in the area, so they would regularly set fire to the mountain. Thus, only grass and no trees could be seen. Daiton National Park[ja], Taiwan's first national park, was established on 27 December 1937. It was one of three national parks designated by Governor-General of Taiwan Seizō Kobayashi during Japanese rule. In 1950, President Chiang Kai-shek renamed Grass Mountain to Yangmingshan to commemorate the Ming Dynasty scholar Wang Yangming. In 1962, the then Taiwan Provincial Bureau of Public Works began to plan the Yangmingshan National Park. The initial planning area was 28,400 hectares, including Mount Kwan-in and the Tatun Volcano Group.

    Different from the high mountain national parks, Yangmingshan National Park has a lower elevation. Even though mountain elevations range from only 200–1120 meters, beautiful landscapes such as ridges, valleys, lakes, waterfalls and basins are abundant. Andesite rocks make up most of the area's geology.

    Xiaoyoukeng is a post-volcanic geological landscape area located in the north of Taiwan in Yangmingshan National Park at the northwestern foot of Seven Star Mountain. It is approximately 805 meters above sea level and is famed for the fumaroles, sulfur crystals, hot springsand spectacular 'landslide terrain' formed by post-volcanic activity. Hiking trails to Seven Star Mountain are accessible from the Xiaoyoukeng parking lot. The top of the trail is 1,120 meters above sea level, which is the highest peak of Taipei City. The Xiaoyoukeng trail can connect to Qixing Park, Menghuan Pond, and Lengshuikeng. The trail also connects to visitor center, Yangmingshan Second Parking Lot and the Yangmingshan Bus Station.

    Due to the effects of post-volcanic activity and precipitation, soil in the region is highly acidic. With the influence of the northeast monsoon and the area's microclimates, winter temperatures are much lower than the surrounding areas. The above factors cause the vegetation to differ from those in other regions at the same latitude. Some medium and high altitude plants can be found here such as bird-lime tree and hairy Japanese maple. Vegetation groups can be divided into subtropical monsoon rain forests, temperate evergreen broadleaf forests and mountain ridge grasslands. There are 1360 species of vascular bundle plants in the region. Some of the common ones are red nanmu, large-leaved machilus, Formosan sweet gum, Taiwan cherry, Mori cleyera and dark spotted cherry. The most famous is Taiwan isoetes in Menghuan pond, an aquatic fern only found in Taiwan. Mt. Datun is one of the most well known places to see some of the 168 species of butterflies in northern Taiwan. The best time...

    Chinese Culture University

    The school was founded in 1962. The founder Dr. Zhang Qiyun and the Chinese Culture Foundation Committee originally proposed the school to be called "Far Eastern University". After a letter from the previous President Jiang Gong, he suggested that it be changed to "Chinese Cultural Institute". In 1963, 15 departments of the day department of the University Department began to enroll students, and then 4 departments of the night department were established and renamed "Chinese Culture College"...

    Chung-Shan Building - Meeting place of the now defunct National Assembly of the Republic of China

    During the administration of President Chiang Kai-shek, the Chung-Shan Building in Yangmingshan National Park was built in 1965 to honor the centenary birthday of Sun Yat-sen, the country's founding father. Ms. Xiu Zelan, a well-known architect, designed it. It is surrounded by mountains and is surrounded by flora. The exterior is a typical Chinese classical structure with exquisite and precise interior décor. It was once the home of the National Assembly and a popular location for heads of s...

    Grass Mountain Chateau - Summer residence of Chiang Kai-shek

    Grass Mountain is a valley area surrounded by Datun Mountain, Qixing Mountain, and Shamao Mountain, but it is not a mountain. The Grass Mountain Hotel was formerly the guest home of Taiwan Sugar Corporation, and Jiang Gong moved in when the Nationalist Government moved to Taiwan in 1949. The hotel is positioned on a strategic high point of a grassy mountain and is quiet and pleasant. In front of you, the Keelung River and the Danshui River meet. The natural splendor may be seen from the Guand...

    • 113.38 km² (43.78 sq mi)
    • Taiwan
    • September 16, 1985
    • Taipei (majority of park within city limits)
  3. Electric generator - Wikipedia

    en.wikipedia.org › wiki › Electric_generator
    • Terminology
    • History
    • Specialized Types of Generator
    • Common Use Cases
    • Equivalent Circuit

    Electromagneticgenerators fall into one of two broad categories, dynamos and alternators. 1. Dynamos generate pulsing direct current through the use of a commutator. 2. Alternators generate alternating current. Mechanically a generator consists of a rotating part and a stationary part: 1. Rotor: The rotating part of an electrical machine. 2. Stator: The stationary part of an electrical machine, which surrounds the rotor. One of these parts generates a magnetic field, the other has a wire winding in which the changing field induces an electric current: 1. Field winding or field (permanent) magnets: The magnetic field-producing component of an electrical machine. The magnetic field of the dynamo or alternator can be provided by either wire windings called field coils or permanent magnets. Electrically-excited generators include an excitation system to produce the field flux. A generator using permanent magnets (PMs) is sometimes called a magneto, or a permanent magnet synchronous gene...

    Before the connection between magnetism and electricity was discovered, electrostatic generators were invented. They operated on electrostatic principles, by using moving electrically charged belts, plates, and disks that carried charge to a high potential electrode. The charge was generated using either of two mechanisms: electrostatic induction or the triboelectric effect. Such generators generated very high voltage and low current. Because of their inefficiency and the difficulty of insulating machines that produced very high voltages, electrostatic generators had low power ratings, and were never used for generation of commercially significant quantities of electric power. Their only practical applications were to power early X-ray tubes, and later in some atomic particle accelerators.

    Direct current

    A dynamo uses commutators to produce direct current. It is self-excited, i.e. its field electromagnets are powered by the machine's own output. Other types of DC generators use a separate source of direct current to energize their field magnets.

    Power station

    A power station, also referred to as a power plant or powerhouse and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Most power stations contain one or more generators, a rotating machine that converts mechanical power into three-phase electric power. The relative motion between a magnetic field and a conductor creates an electrical current. The energy source harnessed to turn the generator varies widely. Most power stations in...

    Genset

    An engine-generator is the combination of an electrical generator and an engine (prime mover) mounted together to form a single piece of self-contained equipment. The engines used are usually piston engines, but gas turbines can also be used, and there are even hybrid diesel-gas units, called dual-fuel units. Many different versions of engine-generators are available - ranging from very small portable petrolpowered sets to large turbine installations. The primary advantage of engine-generator...

    Human powered electrical generators

    A generator can also be driven by human muscle power (for instance, in field radio station equipment). Human powered electric generators are commercially available, and have been the project of some DIY enthusiasts. Typically operated by means of pedal power, a converted bicycle trainer, or a foot pump, such generators can be practically used to charge batteries, and in some cases are designed with an integral inverter. An average "healthy human" can produce a steady 75 watts (0.1 horsepower)...

    An equivalent circuit of a generator and load is shown in the adjacent diagram. The generator is represented by an abstract generator consisting of an ideal voltage source and an internal impedance. The generator's V G {\\displaystyle V_{\\text{G}}} and R G {\\displaystyle R_{\\text{G}}} parameters can be determined by measuring the winding resistance (corrected to operating temperature), and measuring the open-circuit and loaded voltage for a defined current load. This is the simplest model of a generator, further elements may need to be added for an accurate representation. In particular, inductance can be added to allow for the machine's windings and magnetic leakage flux,but a full representation can become much more complex than this.

  4. Microscope - Wikipedia

    en.wikipedia.org › wiki › Microscope
    • History
    • Types
    • External Links

    Although objects resembling lenses date back 4,000 years and there are Greek accounts of the optical properties of water-filled spheres (5th century BC) followed by many centuries of writings on optics, the earliest known use of simple microscopes (magnifying glasses) dates back to the widespread use of lenses in eyeglasses in the 13th century. The earliest known examples of compound microscopes, which combine an objective lens near the specimen with an eyepiece to view a real image, appeared in Europe around 1620. The inventor is unknown although many claims have been made over the years. Several revolve around the spectacle-making centers in the Netherlands including claims it was invented in 1590 by Zacharias Janssen (claim made by his son) and/or Zacharias' father, Hans Martens, claims it was invented by their neighbor and rival spectacle maker, Hans Lippershey (who applied for the first telescope patent in 1608), and claims it was invented by expatriate Cornelis Drebbel who was...

    Microscopes can be separated into several different classes. One grouping is based on what interacts with the sample to generate the image, i.e., light or photons (optical microscopes), electrons(electron microscopes) or a probe (scanning probe microscopes). Alternatively, microscopes can be classified based on whether they analyze the sample via a scanning point (confocal optical microscopes, scanning electron microscopes and scanning probe microscopes) or analyze the sample all at once (wide field optical microscopes and transmission electron microscopes). Wide field optical microscopes and transmission electron microscopes both use the theory of lenses (optics for light microscopes and electromagnet lenses for electron microscopes) in order to magnify the image generated by the passage of a wave transmitted through the sample, or reflected by the sample. The waves used are electromagnetic (in optical microscopes) or electron beams (in electron microscopes). Resolutionin these mic...

  5. Transformer - Wikipedia

    en.wikipedia.org › wiki › Transformer
    • Principles
    • Construction
    • Classification Parameters
    • Applications
    • History
    • Bibliography

    Ideal transformer

    An ideal transformer is a theoretical linear transformer that is lossless and perfectly coupled. Perfect coupling implies infinitely high core magnetic permeability and winding inductances and zero net magnetomotive force (i.e. ipnp - isns = 0).[c] A varying current in the transformer's primary winding attempts to create a varying magnetic flux in the transformer core, which is also encircled by the secondary winding. This varying flux at the secondary winding induces a varying electromotive...

    Transformer EMF equation

    If the flux in the core is purely sinusoidal, the relationship for either winding between its rms voltage Erms of the winding, and the supply frequency f, number of turns N, core cross-sectional area a in m2 and peak magnetic flux density Bpeak in Wb/m2or T (tesla) is given by the universal EMF equation: 1. E rms = 2 π f N a B peak 2 ≈ 4.44 f N a B peak {\\displaystyle E_{\\text{rms}}={\\frac {2\\pi fNaB_{\\text{peak}}}{\\sqrt {2}}}\\approx 4.44fNaB_{\\text{peak}}}

    Polarity

    A dot convention is often used in transformer circuit diagrams, nameplates or terminal markings to define the relative polarity of transformer windings. Positively increasing instantaneous current entering the primary winding's ‘dot’ end induces positive polarity voltage exiting the secondary winding's ‘dot’ end. Three-phase transformers used in electric power systems will have a nameplate that indicate the phase relationships between their terminals. This may be in the form of a phasordiagra...

    Cores

    Core form = core type; shell form = shell type Closed-core transformers are constructed in 'core form' or 'shell form'. When windings surround the core, the transformer is core form; when windings are surrounded by the core, the transformer is shell form. Shell form design may be more prevalent than core form design for distribution transformer applications due to the relative ease in stacking the core around winding coils. Core form design tends to, as a general rule, be more economical, and...

    Windings

    The electrical conductor used for the windings depends upon the application, but in all cases the individual turns must be electrically insulated from each other to ensure that the current travels throughout every turn. For small transformers, in which currents are low and the potential difference between adjacent turns is small, the coils are often wound from enamelled magnet wire. Larger power transformers may be wound with copper rectangular strip conductors insulated by oil-impregnated pa...

    Cooling

    It is a rule of thumb that the life expectancy of electrical insulation is halved for about every 7 °C to 10 °C increase in operating temperature (an instance of the application of the Arrhenius equation). Small dry-type and liquid-immersed transformers are often self-cooled by natural convection and radiation heat dissipation. As power ratings increase, transformers are often cooled by forced-air cooling, forced-oil cooling, water-cooling, or combinations of these. Large transformers are fil...

    Transformers can be classified in many ways, such as the following: 1. Power rating: From a fraction of a volt-ampere (VA) to over a thousand MVA. 2. Duty of a transformer: Continuous, short-time, intermittent, periodic, varying. 3. Frequency range: Power-frequency, audio-frequency, or radio-frequency. 4. Voltage class: From a few volts to hundreds of kilovolts. 5. Cooling type: Dry or liquid-immersed; self-cooled, forced air-cooled;forced oil-cooled, water-cooled. 6. Application: power supply, impedance matching, output voltage and current stabilizer, pulse, circuit isolation, power distribution, rectifier, arc furnace, amplifier output, etc.. 7. Basic magnetic form: Core form, shell form, concentric, sandwich. 8. Constant-potential transformer descriptor: Step-up, step-down, isolation. 9. General winding configuration: By IEC vector group, two-winding combinations of the phase designations delta, wye or star, and zigzag; autotransformer, Scott-T 10. Rectifier phase-shift winding c...

    Various specific electrical application designs require a variety of transformer types. Although they all share the basic characteristic transformer principles, they are customized in construction or electrical properties for certain installation requirements or circuit conditions. In electric power transmission, transformers allow transmission of electric power at high voltages, which reduces the loss due to heating of the wires. This allows generating plants to be located economically at a distance from electrical consumers.All but a tiny fraction of the world's electrical power has passed through a series of transformers by the time it reaches the consumer. In many electronic devices, a transformer is used to convert voltage from the distribution wiring to convenient values for the circuit requirements, either directly at the power line frequency or through a switch mode power supply. Signal and audio transformers are used to couple stages of amplifiers and to match devices such...

    Discovery of induction

    Electromagnetic induction, the principle of the operation of the transformer, was discovered independently by Michael Faraday in 1831 and Joseph Henry in 1832. Only Faraday furthered his experiments to the point of working out the equation describing the relationship between EMF and magnetic flux now known as Faraday's law of induction: 1. | E | = | d Φ B d t | , {\\displaystyle |{\\mathcal {E}}|=\\left|{{\\mathrm {d} \\Phi _{\\text{B}}} \\over \\mathrm {d} t}\\right|,} where | E | {\\displaystyle |{\\m...

    Induction coils

    The first type of transformer to see wide use was the induction coil, invented by Rev. Nicholas Callan of Maynooth College, Ireland in 1836. He was one of the first researchers to realize the more turns the secondary winding has in relation to the primary winding, the larger the induced secondary EMF will be. Induction coils evolved from scientists' and inventors' efforts to get higher voltages from batteries. Since batteries produce direct current (DC) rather than AC, induction coils relied...

    First alternating current transformers

    By the 1870s, efficient generators producing alternating current (AC) were available, and it was found AC could power an induction coil directly, without an interrupter. In 1876, Russian engineer Pavel Yablochkov invented a lighting system based on a set of induction coils where the primary windings were connected to a source of AC. The secondary windings could be connected to several 'electric candles'(arc lamps) of his own design. The coils Yablochkov employed functioned essentially as tran...

    Beeman, Donald, ed. (1955). Industrial Power Systems Handbook. McGraw-Hill.
    Calvert, James (2001). "Inside Transformers". University of Denver. Archived from the original on May 9, 2007. Retrieved May 19, 2007.
    Coltman, J. W. (Jan 1988). "The Transformer". Scientific American. 258 (1): 86–95. Bibcode:1988SciAm.258a..86C. doi:10.1038/scientificamerican0188-86. OSTI 6851152.
    Coltman, J.W. (Jan–Feb 2002). "The Transformer [Historical Overview]". IEEE Industry Applications Magazine. 8 (1): 8–15. doi:10.1109/2943.974352. S2CID 18160717.
  6. Light-emitting diode - Wikipedia

    en.wikipedia.org › wiki › Light-emitting_diode

    A bulb-shaped modern retrofit LED lamp with aluminum heat sink, a light diffusing dome and E27 screw base, using a built-in power supply working on mains voltage. A light-emitting diode ( LED) is a semiconductor light source that emits light ...

  7. Russia - Wikipedia

    en.wikipedia.org › wiki › Russia

    Russia (Russian: Россия, Rossiya, Russian pronunciation: [rɐˈsʲijə]), or the Russian Federation, [b] is a country spanning Eastern Europe and Northern Asia.It is the largest country in the world by area, covering over 17 million square ...

  8. Robot - Wikipedia

    en.wikipedia.org › wiki › Robot

    Machine capable of carrying out a complex series of actions automatically. This article is about mechanical robots. For software agents, see Bot. For other uses of the term, see Robot (disambiguation). ASIMO (2000) at the Expo 2005. Articulated ...