Analog computer

An analog computer or analogue computer is a type of computer that uses the continuously changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved. In contrast, digital computers represent varying quantities symbolically and by discrete values of both time and amplitude. Analog computers can have a wide range of complexity. Slide rules and nomograms are the simplest, while naval gunfire control computers and large hybrid digital/analog computers were among the most complicated. Systems for process control and protective relays used analog computation to perform control and protective functions. Analog computers were used in scientific and industrial applications after the advent of digital computers, because at the time they were much faster, but they started to become obsolete as early as the 1950s and 1960s, although remained in use in some specific applications, such as aircraft flight simulators, the flight computer in aircraft, for teaching control systems in universities.

More complex applications, such as aircraft flight simulators and synthetic aperture radar, remained the domain of analog computing well into the 1980s, since digital computers were insufficient for the task. This is a list of examples of early computation devices considered precursors of the modern computers; some of them may have been dubbed as'computers' by the press, though they may fail to fit modern definitions. The Antikythera mechanism was an orrery and considered an early mechanical analog computer, according to Derek J. de Solla Price. It was designed to calculate astronomical positions, it was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, has been dated to circa 100 BC during the Hellenistic period of Greece. Devices of a level of complexity comparable to that of the Antikythera mechanism would not reappear until a thousand years later. Many mechanical aids to calculation and measurement were constructed for astronomical and navigation use.

The planisphere was first described by Ptolemy in the 2nd century AD. The astrolabe was invented in the Hellenistic world in either the 1st or 2nd centuries BC and is attributed to Hipparchus. A combination of the planisphere and dioptra, the astrolabe was an analog computer capable of working out several different kinds of problems in spherical astronomy. An astrolabe incorporating a mechanical calendar computer and gear-wheels was invented by Abi Bakr of Isfahan, Persia in 1235. Abū Rayhān al-Bīrūnī invented the first mechanical geared lunisolar calendar astrolabe, an early fixed-wired knowledge processing machine with a gear train and gear-wheels, circa 1000 AD; the castle clock, a hydropowered mechanical astronomical clock invented by Al-Jazari in 1206, was the first programmable analog computer. The sector, a calculating instrument used for solving problems in proportion, trigonometry and division, for various functions, such as squares and cube roots, was developed in the late 16th century and found application in gunnery and navigation.

The planimeter was a manual instrument to calculate the area of a closed figure by tracing over it with a mechanical linkage. The slide rule was invented around 1620–1630, shortly after the publication of the concept of the logarithm, it is a hand-operated analog computer for doing division. As slide rule development progressed, added scales provided reciprocals and square roots and cube roots, as well as transcendental functions such as logarithms and exponentials and hyperbolic trigonometry and other functions. Aviation is one of the few fields where slide rules are still in widespread use for solving time–distance problems in light aircraft. Mathematician and engineer Giovanni Plana devised a Perpetual Calendar machine, though a system of pulleys and cylinders and over, could predict the perpetual calendar for every year from 0 AD to 4000 AD, keeping track of leap years and varying day length; the tide-predicting machine invented by Sir William Thomson in 1872 was of great utility to navigation in shallow waters.

It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location. The differential analyser, a mechanical analog computer designed to solve differential equations by integration, used wheel-and-disc mechanisms to perform the integration. In 1876 James Thomson had discussed the possible construction of such calculators, but he had been stymied by the limited output torque of the ball-and-disk integrators. In a differential analyzer, the output of one integrator drove the input of the next integrator, or a graphing output; the torque amplifier was the advance. Starting in the 1920s, Vannevar Bush and others developed mechanical differential analyzers; the Dumaresq was a mechanical calculating device invented around 1902 by Lieutenant John Dumaresq of the Royal Navy. It was an analog computer that related vital variables of the fire control problem to the movement of one's own ship and that of a target ship, it was used with other devices, such as a Vickers range clock to generate range and deflection data so the gun sights of the ship could be continuously set.

A number of versions of the Dumaresq were produced of increasing complexity as development proceeded. By 1912 Arthur Pollen had developed an electrically driven mechanical analog computer for fire-control systems, based on the differential analyser, it was used by the Imperial Russian Navy in World War I. Starting in 1929, AC network analyzers were constructed to solve calculation problems related to electrical power systems that were too l

Maria Beatrice of Savoy

Maria Beatrice of Savoy was a Princess of Savoy and Duchess of Modena by marriage. She was the eldest daughter of Victor Emmanuel, Duke of Aosta and his wife Maria Teresa of Austria-Este, her father became King of Sardinia unexpectedly in 1802. Her maternal grandparents were Archduke Ferdinand of Austria-Este and Maria Beatrice Ricciarda d'Este. Ferdinand was the third son of Maria Theresa of Austria. Maria Beatrice was the eldest daughter of Princess of Carrara. In December 1798, Maria Beatrice left Turin with her parents and uncles to escape the French Revolutionary and Napoleonic wars, they fled to Parma Florence, settled at Sardinia, the last dominion held by Kingdom of Sardinia. Maria Beatrice spent most of her time at Cagliari in the following thirteen years. On 20 June 1812, Maria Beatrice married her maternal uncle Archduke of Austria-Este. Maria Beatrice's husband became Francis IV, Duke of Modena and Mirandola on 14 July 1814, thereby elevating Maria Beatrice to the rank of Duchess of Modena.

The marriage beget four children: Maria Theresa, Archduchess of Austria-Este, married Henri, Count of Chambord. Francis V, Duke of Modena, married Princess Adelgunde of Bavaria. Ferdinand Karl Viktor, Archduke of Austria-Este, married Archduchess Elisabeth Franziska of Austria. Archduchess Maria Beatrix of Austria-Este, married Count of Montizón; the couple left Sardinia on 15 July 1813 for Zakynthos Island, sailed to Trieste off the east shore of Adriatic Sea reaching Vienna by land. On the invasion of Joachim Murat during The Hundred Days, they fled Modena until 15 May 1815. On the outbreak of revolution, Maria Beatrice had to flee Modena again with her family on 5 February 1831, but with Austrian military assistance the Ducal family was able to return within a year. Maria Beatrice died of a heart condition on 15 September 1840 at Castello del Catajo, her remains were kept in the Chiesa di San Vincenzo in Modena. She was a Lady of the Austrian Order of the Starry Cross. Through her father, she inherited the Jacobite claim to the thrones of England and Ireland, but like other non-Stuart pretenders, she never asserted her claim.

Had she gained the throne she would have been Mary II. Mary III and II


Bridgetown is the capital and largest city of Barbados. The Town of Saint Michael, the Greater Bridgetown area is located within the parish of Saint Michael. Bridgetown is sometimes locally referred to as "The City", but the most common reference is "Town"; as of 2014, its metropolitan population stands at 110,000. The Bridgetown port, found along Carlisle Bay lies on the southwestern coast of the island. Parts of the Greater Bridgetown area, sit close to the borders of the neighbouring parishes Christ Church and St. James; the Grantley Adams International Airport for Barbados, is located 16 kilometres southeast of Bridgetown city centre, has daily flights to major cities in the United Kingdom, United States and the Caribbean. There is no longer a local municipal government, but it is a constituency of the national Parliament. During the short-lived 1950s-1960s Federation of the British West Indian Territories, Bridgetown was one of three capital cities within the region being considered to be the Federal capital of region.

The present-day location of the city was established by English settlers in 1628. Bridgetown is a major West Indies tourist destination, the city acts as an important financial, convention centre, cruise ship port of call in the Caribbean region. On 25 June 2011, "Historic Bridgetown and its Garrison" was added as a World Heritage Site of UNESCO. Although the island was abandoned or uninhabited when the British landed there, one of the few traces of indigenous pre-existence on the island was a primitive bridge constructed over the Careenage area's swamp at the centre of Bridgetown, it was thought that this bridge was created by a people indigenous to the Caribbean known as the Tainos. Upon finding the structure, the British settlers began to call what is now the Bridgetown area Indian Bridge. Scholars believe that the Tainos were driven from Barbados to the neighbouring island of Saint Lucia, during an invasion by the Kalinagos, another indigenous people of the region. After 1654 when a new bridge was constructed over the Careenage by the British, the area became known as The Town of Saint Michael and as Bridgetown, after Sir Tobias Bridge.

Bridgetown is the only city outside the present United States. Two of Washington's ancestors and Gerrard Hawtaine, were early planters on the island, their grandmother was Mary Washington of Sulgrave, England. In 2011, historic buildings in Bridgetown were designated as a protected area by UNESCO. English settlement of Bridgetown began on 5 July 1628 under Charles Wolverstone, who brought with him 64 settlers to these lands formally claimed by James Hay, the Earl of Carlisle. Wolverstone had been sent by a group of London merchants, headed by Sir Marmaduke Rawdon, they had been granted a lease to 10,000 acres of land by the Earl of Carlisle in settlement of debts. Wolverstone granted each of the settlers 100 acres of land on the northern side of the Careenage waterway for the purpose of general settlement; the southern shore on Needham's Point was claimed by Carlisle's agents in October 1628. In 1631, many acres of land directly facing Carlisle Bay were passed to Henry Hawley, the new Governor.

An investigation by a Commission in 1640 found that much of Hawley's land transactions were legitimate and properly showed these lands as being attributed to the Earl of Carlisle. Bridgetown was built with a street layout resembling early English medieval or market towns, with its narrow serpentine street and alley configuration. In 1824, Barbados became the seat of the Anglican Diocese of the Leeward Islands; the St Michael's Parish Church became a Cathedral. In 1842, Trinidad, Grenada, Saint Vincent, Saint Lucia were split into separate dioceses by Royal Letters Patent which decreed that the Town of Bridgetown should be called the City of Bridgetown. From 1800 until 1885, Bridgetown was the main seat of Government for the former British colonies of the Windward Islands. During this period, the resident Governor of Barbados served as the Colonial head of the Windward Islands. After the Government of Barbados exited from the Windward Islands union in 1885, the seat was moved from Bridgetown to St. George's on the neighbouring island of Grenada.

In December 1925, a committee sought to petition the King for a Royal Charter of Incorporation to provide local government in the city, proposed to consist of a mayor, 8 aldermen, 12 common councillors, a town clerk, a head-borough or chief constable, such other officers as would be deemed necessary. It was proposed that the island's House of Assembly should seek to incorporate the city instead of using a Royal Charter; this proposal did not succeed. This provided a separate administration with a mayor. On 20 September 1960, the College of Arms in London granted arms to the City of Bridgetown; the armorial bearings were designed by the late Neville Connell, the director of the Barbados Museum and Historical Society, H. W. Ince, the Honorary Secretary of the Society. Local