Aircraft landing gear system Essay Example | Topics and Well Written Essays - 1750 words

Aircraft landing gear system - Essay Example twisted, shielded pair with shield grounded at both ends Source (transmitter) must be able to handle 400 ? at the maximum. Receivers must have minimum effective input impedance of 8 ? Normally designed for range of less than 175 ft (or 50+ meters) A data â€Å"one† is created when the rising edge goes from 0 to 10+/- 1 positive volts; a data â€Å"zero† is created when the falling edge goes down from 0 to 10+/- 1 negative volts Error Checking ARINC 429 uses the odd parity bit to detect error and ensure that data that is being received is accurate. It is the last bit in a message transmission constantly changing with label and data change always resulting in â€Å"Odd Parity† always containing the number ‘1.’ Data Word Format An ARINC message is usually a single data word that is 32-bit long and includes five fields: Label; SDI; Data; SSM, and; Parity. Label identifies the kind of data that being transmitted and has a value of 8. SDI (or Source Destin ation Identifier), specifies the value of the intended receiver. In a system with multiple receivers, each receiver is assigned a value. Data, the actual message of the transmission, uses two kinds of format: the BCD (short for Binary Coded Decimal), uses four bits, and; the BNR (short for Binary encoding). Both define units, resolution, range, number of bits used and frequency of the label. SSM (or Status/Sign Matrix) assists in the interpretation of numeric values in the data field with values such as ‘north,’ ‘east,’ ‘plus,’ ‘minus,’ etc. Finally, P, for parity bit, is the last bit transmitted (Cook et al 462). c) Comparison of ARINC 429, ARINC 629 and MIL 1553B Databuses 1. Encoding Method ARINC 429 uses a bipolar return to 0 type of encoding; MIL 1553B uses the Manchester II biphase where a logic one (1) is transmitted as a bipolar coded signal I/O and a logic zero (0) as a bipolar coded signal I/O (TSCM 9-6.2). ARINC 629 also uses binary encoding. 2. Bus Coupling Method The ARINC 429 has integrated line transmitter/receivers that software can program to receive (Rx) or transmit (Tx) and operate at specific transmission rate independently of other channels. On the other hand, ARINC 629 incorporates bus controllers into every unit and coupling is made using current transformers without cutting off wires. Meanwhile, MIL 1553B uses the transformer and direct method of bus coupling. 3. Data Word Format ARINC 429 uses a 32-bit data format. Fig. 2 illustrates the allocation of bits in the fields. It also shows the numbering of bits from 1, or the LSB (Least Significant Bit), to 32, or the MSB (Most Significant Bit). In the order of transmission, the Label is transmitted first, with the MSB going out before the LSB, but in all other fields, the LSB is transmitted first. Fig. 2 shows the order of transmission by field (label, SDI, Data, SSM and P) within every field. MSB LSB Fig. 2 ARINC 429 32-bit Word Format ( AIM GmbH p. 15) Fig. 3 ARINC 429 Word Transfer Order (AIM GmbH p. 15) On the other hand, ARINC 629 uses a 20-bit date format, where the first three bits are allocated to word time synchronisation, the next 16 bits to data content and the last bit as parity bit. Fig. 4 illustrates the bit allocation in an ARINC 629 data bus system and shows that it has only three fields as opposed to the ARINC 429 that may have as

Colonial America & American Art Research Paper Example | Topics and Well Written Essays - 2500 words

Colonial America & American Art - Research Paper Example What is most striking is their approach to social, economic and political inequality, a theme that has run deep throughout American history, and continues to do so today. Zinn begins his account of American history, predictably, with the first expeditions of Columbus to the New World. Some pages later, the author gives a clear excursus on his approach to and conception of history, and his view on the role of the historian. Zinn explains that he has rejected history which involves a grand narrative of political events, of war and of conquest; in short, he has rejected the history of the nation. He quotes Kissinger’s assertion that ‘History is the memory of the State’ in order to reject it (19). Kissinger, by contrast, was most interested in a model of history based on the nation-state, and relations between nation-states. He penned several works on theories of power relations, and on the history of European state relations in the 19th century. Zinn suggests a diffe rent approach – an attempt to view history from the perspective of ‘the people’: ‘the story of the discovery of America from the viewpoint from the viewpoint of the Arawaks, of the Constitution from the standpoint of the slaves, of Andrew Jackson as seen by the Cherokees’, and so forth (10). ... This is in contrast to the more conventional view of history taken by Craven. Craven’s book is essentially a catalogue of the styles and trends in art and architecture which have developed and flourished at different stages in American history. The historical summaries given at the beginning of each major section (i.e. Colonial America, Federal America etc.) are essentially a narrative of high political developments. The historical introduction given to the Federal period is a particularly good example. Having mentioned that the newly-independent colonies were troubled by their squabbling Congress, Craven goes on to emphasize that America was ‘also the home of a large number of exceptional men – George Washington, Thomas Jefferson, John Adams, James Madison, Benjamin Franklin, and Alexander Hamilton, to mention but a few’ (110). This presentation of the ‘great men’ view of history, explored in some detail by the great 19th century historian and essayist Thomas Carlyle, could not be more different from the presentation of the so-called ‘Founding Fathers’ in Zinn’s account. In a chapter entitled ‘Tyranny is Tyranny’, in which he charts the beginnings of the American Revolution, Zinn interprets events in a framework which could easily be called Marxist (59). He sees the events leading to the War of Independence as a struggle between the working class and a landowning, wealthy class for control of political power in the nascent country. The initial skirmishes may have been the work of commoners, but, as Zinn sees it, ‘certain important people in the English colonies’ the seized control of the convulsions (59). By creating a