este tema que escoji es la carrera que quiero estudiar y mi futuro, y quiero dar a conocer las diferentes clases de especializaciones que hay y su historia
Un Wiki (del hawaiano wiki wiki, «rápido») es un sitio web colaborativo quepuede ser editado por varios usuarios.
Los usuarios de una wiki pueden así crear, editar, borrar o modificar el contenido de una página web, de una forma interactiva, fácil y rápida; dichas facilidades hacen de una wiki una herramienta efectiva para la escritura colaborativa. (definición tomada deWikipedia) (eninglés, enfranjes)
Principales característicasde los Wikis. En generalpermiten:
- Lapublicación de forma immediatausando sólo el navegador web (ej. Explorer, Firefox, Mozilla, etc.)
- Elcontroldel accesoy de permisos de edición. Pueden estar abiertos a todo el mundo o sólo a aquellos que invitemos .
- Que quede registrado quién y cuándo se ha hecho la modificación en las páginas del wiki, por lo que es muy fácil hacer unseguimiento de intervenciones .
-El acceso a versiones previasa la última modificación así como su restauración, es decir queda guardado y con posible acceso todo lo que se va guardando en distintas intervenciones y a ver los cambios hechos .
-Subir y almacenar documentos y todo tipo de archivosque se pueden enlazar dentro del wiki para que los alumnos los utilicen (imágenes, documentos pdf, etc.ejemplo de documento pdf alojado en el wiki).
-Enlazarpáginas exteriores e insertar audios, vídeos, presentaciones, etc.
Unwikio unawiki(delhawaianowiki, ‘rápido’)1es unsitio webcuyaspáginaspueden ser editadas por múltiplesvoluntariosa través del navegador. Losusuariospueden crear, modificar o borrar un mismo texto que comparten. Los textos o «páginas wiki» tienen títulos únicos. Si se escribe el título de una «página wiki» en algún lugar del wiki entre doblescorchetes([[...]]), esta palabra se convierte en un «enlace web» a la página wiki.
En una página sobre «alpinismo», por ejemplo, puede haber una palabra como «piolet» o «brújula» que esté marcada como palabra perteneciente a un título de página wiki. La mayor parte de las implementaciones de wikis indican en elURLde la página el propio título de la página wiki (en Wikipedia ocurre así:http://es.wikipedia.org/wiki/Alpinismo), facilitando el uso y comprensibilidad del link fuera del propio sitio web. Además, esto permite formar en muchas ocasiones una coherenciaterminológica, generando una ordenaciónnaturaldel contenido.
La aplicación de mayor peso y a la que le debe su mayor fama hasta el momento ha sido la creación deenciclopediascolectivas, género al que pertenece laWikipedia. Existen muchas otras aplicaciones más cercanas a la coordinación de informaciones y acciones, o la puesta en común de conocimientos o textos dentro de grupos.
La mayor parte de los wikis actuales conservan un historial de cambios que permite recuperar fácilmente cualquier estado anterior y ver qué usuario hizo cada cambio, lo cual facilita enormemente el mantenimiento conjunto y el control de usuarios nocivos. Habitualmente, sin necesidad de una revisión previa, se actualiza el contenido que muestra la página wiki editada.
Las ventajas son:
La principal utilidad de un wiki es que permite crear y mejorar las páginas de forma instantánea, dando una gran libertad al usuario, y por medio de una interfaz muy simple. Esto hace que más gente participe en su edición, a diferencia de los sistemas tradicionales, donde resulta más difícil que los usuarios del sitio contribuyan a mejorarlo.
Dada la gran rapidez con la que se actualizan los contenidos, la palabra «wiki» adopta todo su sentido. El «documento» de hipertexto resultante, denominado también «wiki» o «WikiWikiWeb», lo produce típicamente una comunidad de usuarios. Muchos de estos lugares son inmediatamente identificables por su particular uso de palabras enmayúsculas, o textocapitalizado- uso que consiste en poner en mayúsculas las iniciales de las palabras de una frase y eliminar los espacios entre ellas - como por ejemplo enEsteEsUnEjemplo. Esto convierte automáticamente a la frase en un enlace. Estewiki, en sus orígenes, se comportaba de esa manera, pero actualmente se respetan los espacios y sólo hace falta encerrar el título del enlace entre dos corchetes.
See also: History of rail transport, Category:Early steam locomotives
The earliest railways employed horses to draw carts along railed tracks.
As the development of steam engines progressed through the 18th century, various attempts were made to apply them to road and railway use.[1] In 1784, William Murdoch, a Scottish inventor, built a prototype steam road locomotive.[2] An early working model of a steam rail locomotive was designed and constructed by steamboat pioneer John Fitch in the United States probably during the 1780s or 1790s.[3] His steam locomotive used interior bladed wheels guided by rails or tracks. The model still exists at the Ohio Historical Society Museum in Columbus.[4]
The first full scale working railway steam locomotive was built by Richard Trevithick in the United Kingdom and, on 21 February 1804, the world's first railway journey took place as Trevithick's unnamed steam locomotive hauled a train along the tramway of the Penydarren ironworks, near Merthyr Tydfil in south Wales[5][6] Accompanied with Andrew Vivian, it ran with mixed success.[1] Then followed the successful twin cylinder locomotive Salamanca by Matthew Murray for the edge railedrack and pinionMiddleton Railway in 1812.[7] In 1825 George Stephenson built the Locomotion for the Stockton and Darlington Railway, north east England, which was the first public steam railway in the world. In 1829, he built The Rocket which was entered in and won the Rainhill Trials. This success led to Stephenson establishing his company as the pre-eminent builder of steam locomotives used on railways in the United Kingdom, United States and much of Europe.[8] The Liverpool and Manchester Railway opened a year later making exclusive use of steam power for both passenger and freight trains.
The United States started developing steam locomotives in 1829 with the Baltimore and Ohio Railroad's Tom Thumb. This was the first locomotive to run in America, although it was intended as a demonstration of the potential of steam traction, rather than as a revenue-earning locomotive. The first successful steam railway in the US was the South Carolina Railroad whose inaugural train ran on 25 December 1830 hauled by the Best Friend of Charleston.[citation needed] Many of the earliest locomotives for American railroads were imported from Great Britain, including the Stourbridge Lion and the John Bull, but a domestic locomotive manufacturing industry was quickly established, with locomotives like the DeWitt Clinton being built in the 1830s.[8]
The first railway service in Continental Europe (or for that matter, anywhere outside the United Kingdom and the United States) was opened on 5 May 1835 in Belgium, between Mechelen and Brussels. The name of the locomotive used was The Elephant.
In Germany the first working steam locomotive was a rack-and-pinion engine, similar to the Salamanca, designed by the British locomotive pioneer John Blenkinsop. Built in June 1816 by Johann Friedrich Krigar in the Royal Berlin Iron Foundry (Königlichen Eisengießerei zu Berlin), the locomotive ran on a circular track in the factory yard. It was the first locomotive to be built on the European mainland and the first steam-powered passenger service, because curious onlookers could ride in the attached coaches for a fee. It is portrayed on a New Year's badge for the Royal Foundry dated 1816. Another locomotive was built using the same system in 1817. They were to be used on pit railways in Königshütte and in Luisenthal on the Saar (today part of Völklingen), but neither could be returned to working order after being dismantled, moved and reassembled. On 7 December 1835 the Adler ran for the first time between Nuremberg and Fürth on the Bavarian Ludwig Railway. It was the 118th engine from the locomotive works of Robert Stephenson and stood under patent protection.
In 1837 the first steam railway started up in Austria on the Emperor Ferdinand Northern Railway between Vienna-Floridsdorf and Deutsch-Wagram. The oldest continually working steam engine in the world also runs in Austria: the GKB 671 built in 1860 has never been taken out of service and is still used for special excursions.
In 1838 the third steam locomotive to be built in Germany, the Saxonia, was manufactured by the Maschinenbaufirma Übigau near Dresden, built by Prof. Johann Andreas Schubert. The first independently designed locomotive in Germany was the Beuth built by August Borsig in 1841. In 1848 the first locomotive produced by Henschel-Werke in Kassel, the Drache, was delivered.
The first railway line over Swiss territory was the Strasbourg–Basle line opened in 1844. Three years later, in 1847, the first fully Swiss railway line, the Spanisch Brötli Bahn, from Zürich to Baden was opened.
Boiler
The typical steam locomotive employs a steel fire-tube boiler that contains pressurized water and steam. A firebox is normally located in the rear of the boiler (chimney in front). The firebox has a water filled steel chamber surrounding the top and sides of the flame in the firebox. If wood or coal is used to make the fire in the firebox it is built on a set of grates where ashes may be separated from the burning fuel. These ashes must periodically be removed from the engine. If wood or coal are the fuel used in the firebox there is a door at the rear of the firebox that is opened to add more fuel. If oil is used there nearly always is a door for adjusting the air flow, maintenance or for cleaning the oil jets. To extract even more heat, the smoke and hot air from the combustibles in the firebox travel horizontally through a bundle of parallel tubes submerged in the water in the boiler from the front of the firebox to the front of the boiler. The heat extracted in the firebox and tubes in the boiler converts the water to pressurized steam in the boiler. To minimize heat loss from the boiler it is normally surrounded with layers of insulation. The water and steam in the boiler are kept pressurized to raise the boiling temperature of the water and generate high pressure steam. The amount of pressure in the boiler is monitored by the engineer or fireman by a gauge mounted in the cab. Excess steam pressure can be released manually or may blow a safety valve. Too much pressure may cause the boiler to burst, potentially killing the crew as well as disabling the engine.
At the front of the boiler is the smokebox, where steam is ejected into the chimney (US: "smoke stack") drawing the smoke and hot air through the fire tubes in the boiler and out the top of the chimney. The combustion in a typical steam engine is not very complete leading to a prodigious amount of smoke and often sparks being produced. This made these engines very dirty to live around as well as being an acute hazard while passing through a forest, tunnel or snow shed.
The steam generated in the boiler is used to drive the locomotive and also for other purposes (whistles, brakes, pumps, air flow, etc.). This constant use of steam requires the boiler to have water continually pumped (usually automatically) into it. The source of this water is an unpressurized tank, which is periodically topped up at water stops. The water level is normally monitored with a transparent tube or gauge. If the boiler runs out of water the fire may melt a hole in it, possibly causing an explosion. In a wreck or accident the boiler may burst, potentially hurting or killing the crew. Scale may build up in boiler to prevent proper heat transfer, and corrosion eventually degrades the boiler's material to the point where it needs to be rebuilt or replaced. Start up on a large engine may take an hour or more of preliminary heating of the water in the boiler before it is ready to go. The steam engine in locomotives was a novel invention that took advantage of readily available fuels such as wood and coal. As new sources of energy were discovered such as petroleum, the steam engine was replaced by more efficient, less maintenance intensive internal combustion engines.
The boiler is typically placed horizontally. For locomotives designed to work on steep slopes, it may be placed vertically or mounted at an angle instead.
The steam generated in the boiler fills the steam space above the water in the partially-filled boiler. Its maximum working pressure is limited by spring-loaded safety valves. It is then collected either in a perforated tube fitted above the water level or from a dome that often houses the regulator valve, or throttle, the purpose of which is to control the amount of steam leaving the boiler. The steam then either travels directly along and down a steam pipe to the engine unit or may first pass into the wet header of a superheater, the role of the latter being to improve thermal efficiency and eliminate water droplets suspended in the "saturated steam", the state in which it leaves the boiler. On leaving the superheater, the steam exits the dry header of the superheater and passing down a steam pipe entering the steam chests adjacent to the cylinders of a reciprocating engine. Inside each steam chest is a sliding valve that distributes the steam via ports that connect the steam chest to the ends of the cylinder space. The role of the valves is twofold: admission of each fresh dose of steam and exhaust of the used steam once it has done its work.
The cylinders are double acting, with steam admitted to each side of the piston in turn. In a two-cylinder locomotive, one cylinder is located on each side of the locomotive. The cranks are set 90° out of phase. During a full rotation of the driving wheel, steam provides four power strokes; each cylinder receives two injections of steam per revolution. The first stroke is to the front of the piston and the second stroke to the rear of the piston; hence two working strokes. Consequently two deliveries of steam onto each piston face in two cylinders generates a full revolution of the driving wheel. Each piston is connected to the driving axle on each side by a connecting rod, the driving wheels are connected together by coupling rods to transmit power from the main driver to the other wheels. Note that at the two "dead centres", when the connecting rod is on the same axis as the crankpin on the driving wheel, the connecting rod applies no torque to the wheel. Therefore, if both cranksets could be at "dead centre" at the same time, and the wheels should happen to stop in this position, the locomotive could not be started moving. Therefore the crankpins are attached to the wheels at a 90° angle to each other, so only one side can be at dead centre at a time.
Each piston transmits power directly through a connecting rod (US: main rod) and a crankpin (US: wristpin) on the driving wheel (US main driver) or to a crank on a driving axle. The movement of the valves in the steam chest is controlled through a set of rods and linkages called the valve gear, actuated from the driving axle or else from the crankpin; the valve gear includes devices that allow reversing the engine, adjusting valve travel and the timing of the admission and exhaust events. The cut-off point determines the moment when the valve blocks a steam port, "cutting off" admission steam and thus determining the proportion of the stroke during which steam is admitted into the cylinder; for example a 50% cut-off admits steam for half the stroke of the piston. The remainder of the stroke is driven by the expansive force of the steam. Careful use of cut-off provides economical use of steam and, in turn, reduces fuel and water consumption. The reversing lever (US: Johnson bar), or screw-reverser, (if so equipped) that controls the cut-off therefore performs a similar function to a gearshift in an automobile - maximum cut-off, providing maximum tractive effort at the expense of efficiency, is used to pull away from a standing start, whilst a cut-off as low as 10% is used when cruising, providing reduced tractive effort with lower fuel/water consumption.[9]
Nadie sabía exactamente qué iba a pasar el 20 de julio de 1810, pero se podía percibir una atmósfera de que algo ocurriría. Fue un viernes, día de mercado y todo el pueblo caminaba por las calles de Santa Fe.
Después de la abdicación del monarca español Fernando VII tras la invasión francesa a España en 1808, llevada a cabo por parte de Napoleón Bonaparte, en España se organizaron juntas de gobierno a nivel local para resistir al invasor y, a la vez, gobernar en ausencia del rey depuesto. Estas juntas pronto uniéndose organizaron un gobierno "alterno" al gobierno de ocupación impuesto por Napoleón.
Este gobierno alterno tenía representantes de todas las provincias de toda España y también de sus colonias. Sin embargo, la representación de las colonias era inferior a la de los reinos españoles. En el caso de las colonias americanas había sólo 9 representantes en contraste con los 36 de la península. Esto hizo que en América se buscara o una mayor representación o una mayor autonomía, e incluso Independencia de la metrópoli.
Ya en 1809 se habían producido los primeros gritos de libertad en la América española, en lo que hoy es Ecuador y Bolivia. En la Nueva Granada se habían gestado de manera similar, y ciudades como Cartagena y Mompos habían conformado juntas independentistas que buscaban mayor autonomía e incluso una independencia absoluta de España
En la provincia de Santa fe se había creado una junta de notables integrada por autoridades civiles e intelectuales criollos. Los principales personeros de la oligarquía criolla que conformaban la junta eran: José Miguel Pey, Camilo Torres, Acevedo Gómez, Joaquín Camacho, Jorge Tadeo Lozano, Antonio Morales, entre otros.
Estos comenzaron a realizar reuniones sucesivas en las casas de los integrantes y luego en el observatorio astronómico, cuyo director era Francisco José de Caldas. En estas reuniones empezaron a pensar en la táctica política que consistía en provocar una limitada y transitoria perturbación del orden público y así aprovechar para tomar el poder.
La junta de notables propuso entonces crear un incidente con los españoles, a fin de crear una situación conflictiva que diera salida al descontento potencial que existía en Santafé contra la audiencia española. Lo importante era conseguir que el Virrey, presionado por la perturbación del orden, constituyera ese mismo día la Junta Suprema de Gobierno integrada por los regidores del Cabildo de Santafé.
Don Antonio Morales manifestó que el incidente podía provocarse con el comerciante peninsular don José González Llorente y se ofreció "gustoso" a intervenir en el altercado. Los notables criollos aceptaron la propuesta y decidieron ejecutar el proyecto el viernes, 20 de julio, fecha en que la Plaza Mayor estaría colmada de gente de todas las clases sociales, por ser el día habitual de mercado.
Se convino que un grupo de criollos (encabezados por Pantaleón Santamaría y los hermanos Morales) fueran el día indicado a la tienda de Llorente a pedirle prestado un florero o cualquier clase de adorno que les sirviera para decorar la mesa de un anunciado banquete en honor a otro criollo destacado, Antonio Villavicencio. En el caso de una negativa, los hermanos Morales procederían a agredir al español.
A fin de garantizar el éxito del plan, si Llorente entregaba el florero o se negaba de manera cortés, se acordó que don Francisco José de Caldas pasara a la misma hora por frente del almacén de Llorente y le saludara, lo cuál daría oportunidad a Morales para reprenderlo por dirigir la palabra a un "chapetón" enemigo de los americanos y dar así comienzo al incidente.
Se ocupa del diagnóstico, pronóstico, tratamiento, y prevención de las enfermedades que afectan a los animales domésticos, de experimentación, exóticos, silvestres y salvajes. Se incluyen igualmente todos aquellos perfiles médicos que se centran en la salud individual, tales como la identificación, la etología, el control sanitario, y la prevención de zoonosis.
Este material es de :http://ciencianet.com/treaccion.html
Material necesario:
-una regla de 50cm
Procedimiento:
pidele a un amigo que sostenga la punta superior de la regla y que la deje caer sin avisarte
situa los dedos en el sero y cuando la veas caer, sierra los dedos sobre ella
anota la distancia que a caido la regla. vendra indicada por la división que se encuentre debajo de tus dedos.
Repítelo varias veces hasta que obtengas valores similares :
Explicacion:
La distancia que ha caido la regla depende de tu tiempo de reaccion. si no se tiene en cuenta el rozamiento con el aire, un cuerpo que cae libremente, partiendo del reposo, recorre una distancia vertical que viene dada por:
d:distancia recorrida
g:aceleracion de la gravedad (9,8 m/s2)
t:tiempo que dura la caida
Despejando de la exprecion anterior, el tiempo de reaccion sera:
Si se expresa la distancia (d) en centímetros y se tiene en cuenta que la aceleración de la gravedad (g) vale 980 cm/s2. El tiempo de reacción expresado en segundos será :
