1.
Athens Metro
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The Athens Metro is a rapid-transit system in Greece which serves the Athens conurbation and parts of East Attica. It incorporates the former Athens-Piraeus Electric Railways, which opened as a steam railway in 1869. Beginning in 1991, Attiko Metro constructed and extended Lines 2 and 3, the metro network merged in 2011 when the Greek government created the Urban Rail Transport Company, a subsidiary of the Athens Urban Transport Organisation. First Chairman and CEO of the company became Kostas Vassiliadis. The system is noted for being modern and efficient, in its own right and it has drastically changed Athens by providing a much-needed solution to the citys traffic and air pollution problem, as well as revitalising many of the areas it serves. An extension of Line 3 is under construction towards Piraeus and also extensions of existing lines. The Athens Metro is actively connected with the means of public transport, such as buses, trolleys, the Athens Tram. The Athens Metro is hailed for its modernity and many of its stations feature works of art, exhibitions, until 28 January 2000, Line 1 was the only rapid-transit line in Athens and Piraeus. The Athens and Piraeus Railway Company opened the line on 27 February 1869 as a railway between Piraeus and Thiseio. It was electrified in 1904, and extended in stages to Kifisia in 1957, from 1976 to 16 June 2011, the Athens-Piraeus Electric Railway Company operated Line 1 independently from the rest of the metro and tram networks. Unlike Lines 2 and 3, it runs almost entirely above ground, since the current Line 1 opened the government has proposed many expansions to the subway network, including a 1963 plan for a fourteen-line subway network. Construction of Lines 2 and 3 began in November 1992 to decrease traffic congestion, Lines 2 and 3, built by Attiko Metro and operated until 2011 by Attiko Metro Operations Company, are known respectively as the red and blue lines and were inaugurated in January 2000. Line 3 was extended to the Eleftherios Venizelos International Airport in summer 2004, the Greek government attempted to absorb ISAP into Attiko Metro under Law 2669/1998 so the latter would be responsible for the whole network, but this initiative failed. Athens Metro operations were consolidated when the Greek government enacted Law 3920/2011, replacing AMEL, ISAP and Athens Tram with Urban Rail Transport, the modern incarnation of Line 1 is 25. 6-kilometre long, and serves 24 stations. Together, Lines 2 and 3 are 58. 9-kilometre long, the three-line Athens Metro network serves 61 stations. It owns and operates 57 of them, and OSE owns the remainder on the airport section, the network has four metro interchanges, enabling the lines to interchange with each other at least once. Line 2 and the Attiko Metro portion of Line 3 is entirely underground, Line 1 is primarily in the open, with a tunnel section in central Athens. The airport section of Line 3, east of the tunnel portal near Doukissis Plakentias, is open, in the tunnel sections up and down lines share a common tunnel, except for approaches to stations with an island platform
2.
Track gauge
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In rail transport, track gauge is the spacing of the rails on a railway track and is measured between the inner faces of the load-bearing rails. All vehicles on a network must have running gear that is compatible with the track gauge, as the dominant parameter determining interoperability, it is still frequently used as a descriptor of a route or network. There is a distinction between the gauge and actual gauge at some locality, due to divergence of track components from the nominal. Railway engineers use a device, like a caliper, to measure the actual gauge, the nominal track gauge is the distance between the inner faces of the rails. In current practice, it is specified at a distance below the rail head as the inner faces of the rail head are not necessarily vertical. In some cases in the earliest days of railways, the company saw itself as an infrastructure provider only. Colloquially the wagons might be referred to as four-foot gauge wagons, say and this nominal value does not equate to the flange spacing, as some freedom is allowed for. An infrastructure manager might specify new or replacement track components at a variation from the nominal gauge for pragmatic reasons. Track is defined in old Imperial units or in universally accepted metric units or SI units, Imperial units were established in United Kingdom by The Weights and Measures Act of 1824. In addition, there are constraints, such as the load-carrying capacity of axles. Narrow gauge railways usually cost less to build because they are lighter in construction, using smaller cars and locomotives, as well as smaller bridges, smaller tunnels. Narrow gauge is often used in mountainous terrain, where the savings in civil engineering work can be substantial. Broader gauge railways are generally expensive to build and require wider curves. There is no single perfect gauge, because different environments and economic considerations come into play, a narrow gauge is superior if ones main considerations are economy and tight curvature. For direct, unimpeded routes with high traffic, a broad gauge may be preferable, the Standard, Russian, and 46 gauges are designed to strike a reasonable balance between these factors. In addition to the general trade-off, another important factor is standardization, once a standard has been chosen, and equipment, infrastructure, and training calibrated to that standard, conversion becomes difficult and expensive. This also makes it easier to adopt an existing standard than to invent a new one and this is true of many technologies, including railroad gauges. The reduced cost, greater efficiency, and greater economic opportunity offered by the use of a common standard explains why a number of gauges predominate worldwide
3.
Railway electrification system
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A railway electrification system supplies electric power to railway trains and trams without an on-board prime mover or local fuel supply. Electrification has many advantages but requires significant capital expenditure, selection of an electrification system is based on economics of energy supply, maintenance, and capital cost compared to the revenue obtained for freight and passenger traffic. Different systems are used for urban and intercity areas, some electric locomotives can switch to different supply voltages to allow flexibility in operation, Electric railways use electric locomotives to haul passengers or freight in separate cars or electric multiple units, passenger cars with their own motors. Electricity is typically generated in large and relatively efficient generating stations, transmitted to the railway network, some electric railways have their own dedicated generating stations and transmission lines but most purchase power from an electric utility. The railway usually provides its own lines, switches and transformers. Power is supplied to moving trains with a continuous conductor running along the track usually takes one of two forms. The first is a line or catenary wire suspended from poles or towers along the track or from structure or tunnel ceilings. Locomotives or multiple units pick up power from the wire with pantographs on their roofs that press a conductive strip against it with a spring or air pressure. Examples are described later in this article, the second is a third rail mounted at track level and contacted by a sliding pickup shoe. Both overhead wire and third-rail systems usually use the rails as the return conductor. In comparison to the alternative, the diesel engine, electric railways offer substantially better energy efficiency, lower emissions. Electric locomotives are usually quieter, more powerful, and more responsive and they have no local emissions, an important advantage in tunnels and urban areas. Different regions may use different supply voltages and frequencies, complicating through service, the limited clearances available under catenaries may preclude efficient double-stack container service. Possible lethal electric current due to risk of contact with high-voltage contact wires, overhead wires are safer than third rails, but they are often considered unsightly. These are independent of the system used, so that. The permissible range of voltages allowed for the voltages is as stated in standards BS EN50163. These take into account the number of trains drawing current and their distance from the substation, railways must operate at variable speeds. Until the mid 1980s this was only practical with the brush-type DC motor, since such conversion was not well developed in the late 19th century and early 20th century, most early electrified railways used DC and many still do, particularly rapid transit and trams
4.
Volt
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The volt is the derived unit for electric potential, electric potential difference, and electromotive force. One volt is defined as the difference in potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. It is also equal to the difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can also be expressed as amperes times ohms, watts per ampere, or joules per coulomb, for the Josephson constant, KJ = 2e/h, the conventional value KJ-90 is used, K J-90 =0.4835979 GHz μ V. This standard is typically realized using an array of several thousand or tens of thousands of junctions. Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc. in the water-flow analogy sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage is likened to difference in water pressure. Current is proportional to the diameter of the pipe or the amount of water flowing at that pressure. A resistor would be a reduced diameter somewhere in the piping, the relationship between voltage and current is defined by Ohms Law. Ohms Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems, the voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell. Cells can be combined in series for multiples of that voltage, mechanical generators can usually be constructed to any voltage in a range of feasibility. High-voltage electric power lines,110 kV and up Lightning, Varies greatly. Volta had determined that the most effective pair of metals to produce electricity was zinc. In 1861, Latimer Clark and Sir Charles Bright coined the name volt for the unit of resistance, by 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. In 1881, the International Electrical Congress, now the International Electrotechnical Commission and they made the volt equal to 108 cgs units of voltage, the cgs system at the time being the customary system of units in science. At that time, the volt was defined as the difference across a conductor when a current of one ampere dissipates one watt of power. The international volt was defined in 1893 as 1/1.434 of the emf of a Clark cell and this definition was abandoned in 1908 in favor of a definition based on the international ohm and international ampere until the entire set of reproducible units was abandoned in 1948. Prior to the development of the Josephson junction voltage standard, the volt was maintained in laboratories using specially constructed batteries called standard cells
5.
Athens Olympic Sports Complex
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The Athens Olympic Park, is a sport facilities complex located at Marousi, northeast Athens, Greece. The complex consists of five major venues as well as other sport facilities. The Olympic Athletic Center of Athens has hosted the Mediterranean Games in 1991, the most significant event the Athens Olympic Sports Complex has hosted, was the Olympic Games. OACA was the venue for the Athens Olympic Games in 2004. The complex was revamped for the games under a design produced by the Spanish architect Santiago Calatrava and it is currently used as the home ground of AEK Athens F. C. one of the biggest football clubs in Greece. The Nikos Galis Olympic Indoor Hall was completed in 1995, and was the largest indoor venue in use for sporting events at the 2004 Summer Olympics in Athens and it is part of the Athens Olympic Sports Complex, in the suburb of Maroussi. The arena was used for gymnastics and trampolining and also hosted the finals of the basketball matches at the games. On May 18 and 20,2006, the Olympic Indoor Hall hosted the 51st Eurovision Song Contest, the Athens Olympic Sports Complex can be reached by Metro, by suburban train, or by direct bus lines [A7,602,550. The table below illustrates how the Athens Olympic Sports Complex facilities are used today,2004 Summer Olympics official report, pp.201,207,227,231,242,273,303,324,329,346,409. Media related to Athens Olympic Sports Complex at Wikimedia Commons Official site Olympic Indoor hall info and pictures at stadia. gr
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- Line 1
& 
- Line 3 & Line 4
- Line 3
- Line 2
