SUMMARY / RELATED TOPICS

Wave

In physics and related fields, a wave is a disturbance of one or more fields such that the field values oscillate about a stable equilibrium value. If the relative amplitude of oscillation at different points in the field remains constant, the wave is said to be a standing wave. If the relative amplitude at different points in the field changes, the wave is said to be a traveling wave. Waves can only exist in fields; the types of waves most studied in physics are mechanical and electromagnetic. In a mechanical wave and strain fields oscillate about a mechanical equilibrium. A traveling mechanical wave is a local deformation in some physical medium that propagates from particle to particle by creating local stresses that cause strain in neighboring particles too. For example, sound waves in air are variations of the local pressure that propagate by collisions between gas molecules. Other examples of mechanical waves are seismic waves, gravity waves and shock waves. In an electromagnetic wave the electric and magnetic fields oscillate.

A traveling electromagnetic wave consists of a combination of variable electric and magnetic fields, that propagates through space according to Maxwell's equations. Electromagnetic waves can travel through a vacuum. Other types of waves include gravitational waves, which are disturbances in a gravitational field that propagate according to general relativity. Mechanical and electromagnetic waves transfer energy and information, but they do not transfer particles in the medium. In mathematics and electronics waves are studied as signals. On the other hand, some waves do not appear to move at all, like hydraulic jumps. Some, like the probability waves of quantum mechanics, may be static. A physical wave is always confined to some finite region of space, called its domain. For example, the seismic waves generated by earthquakes are significant only in the interior and surface of the planet, so they can be ignored outside it. However, waves with infinite domain, that extend over the whole space, are studied in mathematics, are valuable tools for understanding physical waves in finite domains.

A plane wave seems to travel in a definite direction, has constant value over any plane perpendicular to that direction. Mathematically, the simplest waves are the sinusoidal ones in which each point in the field experiences simple harmonic motion. Complicated waves can be described as the sum of many sinusoidal plane waves. A plane wave can be a transverse, if its effect at each point is described by a vector, perpendicular to the direction of propagation or energy transfer. While mechanical waves can be both transverse and longitudinal, electromagnetic waves are transverse in free space. A wave can be described just like a field, namely as a function F where x is a position and t is a time; the value of x is a point of space in the region where the wave is defined. In mathematical terms, it is a vector in the Cartesian three-dimensional space R 3. However, in many cases one can ignore one dimension, let x be a point of the Cartesian plane R 2; this is the case, for example. One may restrict x to a point of the Cartesian line R — that is, the set of real numbers.

This is the case, for example, when studying vibrations in recorder. The time t, on the other hand, is always assumed to be a scalar; the value of F can be any physical quantity of interest assigned to the point x that may vary with time. For example, if F represents the vibrations inside an elastic solid, the value of F is a vector that gives the current displacement from x of the material particles that would be at the point x in the absence of vibration. For an electromagnetic wave, the value of F can be the electric field vector E, or the magnetic field vector H, or any related quantity, such as the Poynting vector E × H. In fluid dynamics, the value of F could be the velocity vector of the fluid at the point x, or any scalar property like pressure, temperature, or density. In a chemical reaction, F

Australian Surf Life Saving Championships

The Australian Surf Life Saving Championships known as The Aussies is the national Surf lifesaving championships for Australia. It is the largest event of its kind in the world, it is organised by the Surf Life Saving Australia, is held annually since 1915. The first Australian Surf Life Saving Championships were held at Bondi Beach, New South Wales in March 1915. During the 2015 Championships 7,000 surf lifesavers, representing 311 Surf Life Saving Clubs, will be competing in over 380 events in Youth Championships, Masters Championships and Open Championships; the 2019 Championships will be held at Gold Coast, Queensland. Held at the Australian Surf Life Saving Championships every year, the Australian Ironman Title is awarded to the winner of this event; the format is the same as for typical surf carnivals, a 10-to-20-minute race with a field of 150 competitors, which over several rounds of will be reduced to a final of 16 athletes. It is the blue ribbon event the Championships, the one that attracts the most attention in terms of television and spectators on the beach.

It is one of the last events on the program, raced on a final day of competition.. Ironman World Life Saving Championships The Aussies webpage

Pedro Francisco BonĂ³

Pedro Francisco Bonó y Mejía was a Dominican politician and intellectual. He is credited with being the first Dominican sociologist, he was the president of the Senate of the Dominican Republic in 1858. Bonó was born to Joseph Bonó and Inés Mejía y Port, his maternal grandmother, Doña Eugénie Port, a native of Brittany who had large plantations and fortune in the Saint-Domingue until the outbreak of the Haitian Revolution, taught him the French language and fashioned him intellectually. A metro station in Santo Domingo is named after him. El Montero Apuntes para los Cuatro Ministerios de la República Apuntes sobre las Clases Trabajadoras Dominicanas Congreso Extraparlamentario Epistolario Ensayos Sociohistóricos Actuación Pública Papeles de Pedro Francisco Bonó