bitvortex

Shogi & Go

2007-07-13T17:04:00.000-03:00

soroban e suan pan

2007-02-14T16:27:00.000-03:00

ábacos:

muitas informações sobre o ábaco em geral (soroban e suan pan):
www.ee.ryerson.ca/~elf/abacus/

soroban:

programa simulando um soroban gratuito pra baixar:
http://www.sorobanbrasil.com.br/index.html

informações gerais sobre o soroban:
www.soroban.org

ensino em sampa ( tambem onde comprei o meu soroban):
http://www.cpsoroban.com.br/

site da maior fabricante de sorobans:
http://www.soroban.com/

suan pan:

breve introdução ao ábaco (suan pan nesse caso):
http://www.ee.ryerson.ca/~elf/abacus/portugues/intro.html

o lee abacus(uma versão diferente do suan pan):
http://www.ee.ryerson.ca:8080/~elf/abacus/leeabacus/bagley/

sobre a história e modo de funcionamento do ábaco (em alemão):
www.benjaminwrightson.de/abakus.htm

Computação e Linux

2007-02-14T01:59:00.000-03:00

computação geral:

site de dicas da unicamp(muito bom):
http://www.dicas-l.com.br/

o melhor editor de texto do mundo(pra mim ;-) )
http://www.vim.org/

teclado muito interessante(pena que não tem no brasil):
http://typematrix.com/

teclado dvorak:
http://www.mwbrooks.com/dvorak/

linux:

o site principal, informações gerais:
http://www.linux.org/

excelente repositório de informações:
http://focalinux.cipsga.org.br/

http://www.linuxdicas.com.br/

site do slack:
http://www.slackware.org/

mb:
http://www.slackwarezine.com.br/

mb: portugues
http://www.slacklife.com.br/

http://www.slackware-brasil.com.br/

http://br-linux.org/

muito bom:
http://www.vivaolinux.com.br/

excelente site do carlos e. morimoto:
http://www.guiadohardware.net/

site de compras de produtos relacionados ao linux:
http://www.linuxmall.com.br/

site da debian:

site da debian brasil:
http://www.debian.org.br/

bash cures cancer:
http://bashcurescancer.com/

Sites para aprender japonês/chinês

2007-01-28T02:26:00.000-03:00

The Japanese Page:
http://www.thejapanesepage.com/

Japanese Learning:
http://www.japaneselearning.com/

Outro site muito bom (com RSS feeds):
http://www.yookoso.com/index.php

E-Kanji:
http://www.geocities.com/easykanji/

Guia da gramática japonesa:
http://www.guidetojapanese.org/

Online Japanese Study:
http://u-biq.org/magazine.htm

Testes de japonês:
http://test.u-biq.org/

Active Chinese, é comercial, mas tem uma versão demo sobre conversação em mandarim:
http://www.activechinese.com/index.jsp

Esse mostra a genealogia dos caracteres chineses(muito bom):
http://www.zhongwen.com/

Dicionários online (entre outros)

2007-01-15T18:00:00.000-03:00

dicionário inglês-inglês:
http://wordnet.princeton.edu/

dicionário alemão-inglês/francês/espanhol
http://dict.leo.org/

dicionário inglês-latim e latim-inglês:
http://catholic.archives.nd.edu/cgi-bin/words.exe

banco de dicionários :
http://www.dict.org/

the internet public library:
http://www.ipl.org/

outro site com links para muitos outros dicionarios:
http://www.fazfacil.com.br/Dicionarios.htm

Abacus

2007-01-15T15:50:00.001-03:00

An abacus is a calculation tool, often constructed as a wooden frame with beads sliding on wires. It was in use centuries before the adoption of the written Hindu-Arabic numeral system and is still widely used by merchants and clerks in the China, Japan, Hong Kong, Africa, and elsewhere.

[hide]

[edit] Origins

The origins of the abacus are disputed, as many different cultures have been known to have used similar tools. It is known to have existed in Babylonia and in China, with invention to have taken place between 1000 BCE and 500 BCE.^{[citation needed]} The first abacus was almost certainly based on a flat stone covered with sand or dust. Lines were drawn in the sand and pebbles used to aid calculations. From this, a variety of abaci were developed; the most popular were based on the bi-quinary system, using a combination of two bases (base-2 and base-5) to represent decimal numbers.

The use of the word abacus dates back to before 1387 when a Middle English work borrowed the word from Latin to describe a sandboard abacus. The Latin word came from abakos, the Greek genitive form of abax ("calculating-table"). Because abax also had the sense of "table sprinkled with sand or dust, used for drawing geometric figures," it is speculated by some linguists that the Greek word may be derived from a Semitic root, ābāq, the Hebrew word for "dust." Though details of the transmission are obscure, it may also be derived from the Phoenician word abak, meaning "sand". The plural of abacus is abaci.

[edit] Earlier numeral systems

Before the invention of the Chinese abacus, counting rods, other symbolic methods such as tally sticks, notches on bones, and the like, were undoubtedly used as a tool for counting and calculation.

[edit] Babylonian abacus

A tablet found on the Greek island Salamis in 1846 dates back to 300 BCE making it the oldest counting board discovered so far. It was originally thought to be a gaming board.

Its construction is a slab of white marble measuring 149 cm in length, 75 cm in width and 4.5 cm thick, on which are 5 groups of markings. In the center of the tablet are a set of 5 parallel lines equally divided by a vertical line, capped with a semi-circle at the intersection of the bottom-most horizontal line and the single vertical line. Below these lines is a wide space with a horizontal crack dividing it. Below this crack is another group of eleven parallel lines, again divided into two sections by a line perpendicular to them but with the semi-circle at the top of the intersection; the third, sixth and ninth of these lines are marked with a cross where they intersect with the vertical line

[edit] Roman abacus

Main article: Roman abacus

Reconstructed Roman Abacus

The Late Empire Roman abacus shown here in reconstruction contains eight long grooves containing up to five beads in each and eight shorter grooves having either one or no beads in each.

The groove marked I indicates units, X tens, and so on up to millions. The beads in the shorter grooves denote fives—five units, five tens, etc., essentially in a bi-quinary coded decimal system, obviously related to the Roman numerals. The short grooves on the right may have been used for marking Roman ounces.

Computations are made by means of beads which would probably have been slid up and down the grooves to indicate the value of each column.

[edit] Chinese abacus

Main article: Chinese abacus

Before the invetion fo Chinese abacus,they used Counting rods as calculation tool.

The suanpan (Simplified Chinese: 算盘; Traditional Chinese: 算盤; pinyin: suànpán, lit. "Counting tray") of the Chinese is similar to the Roman abacus in principle, though has a different construction, and it was designed to do both decimal and hexadecimal arithmetics.

The Chinese abacus is typically around 20 cm (8 inches) tall and it comes in various widths depending on the application. It usually has more than seven rods. There are two beads on each rod in the upper deck and five beads each in the bottom for both decimal and hexadecimal computation. The beads are usually rounded and made of a hard wood. The beads are counted by moving them up or down towards the beam. The abacus can be reset to the starting position instantly by a quick jerk along the horizontal axis to spin all the beads away from the horizontal beam at the center.

A Chinese bookkeeper using an abacus to calculate his accounts

Chinese abaci can be used for functions other than counting. Unlike the simple counting board used in elementary schools, very efficient suanpan techniques have been developed to do multiplication, division, addition, subtraction, square root and cube root operations at high speed.

Bead arithmetic is the calculating technique used with various types of abaci, in particular the Chinese abacus. The similarity of the Roman abacus to the Chinese one suggests that one could have inspired the other, as there is some evidence of a trade relationship between the Roman Empire and China. However, no direct connection can be demonstrated, and the similarity of the abaci may be coincidental, both ultimately arising from counting with five fingers per hand. Where the Roman model (like most modern Japanese) has 4 plus 1 bead per decimal place, the standard Chinese abacus has 5 plus 2, allowing less challenging arithmetic algorithms, and also allowing use with a hexadecimal numeral system. Instead of running on wires as in the Chinese and Japanese models, the beads of Roman model runs in groves, presumably making arithmetic calculations much slower. Possibly the Roman abacus was used primarily for simple counting.^{[dubious — see talk page]}In a contest between the Chinese abacus and the electric calculator on November 12, 1946, the abacus won 4 to 1.

[edit] Japanese abacus

Japanese soroban

Soroban (算盤, lit. "Counting tray") is a Japanese abacus, modified Chinese abacus (算盤). Traditional Chinese weighing units used a hexadecimal system which necessitated two beads on the upper deck. The Japanese first eliminated one bead from the upper deck and later another bead from the lower deck in each column of the Chinese abacus, making the Japanese abacus purely for the decimal system. The Japanese also eliminated the use of the Qiuchu (Chinese division table). However, the Chinese division table was still used when there were 5 lower beads. There came the debate of the multiplication table versus the division table, with the school of multiplication table prevailing in the 1920s. The rods (number of digits) usually increase to 21, 23, 27 or even 31, thus allowing calculation for more digits or representations of several different numbers at the same time.

Soroban is taught in primary schools as a part of lessons in mathematics because the decimal numerical system can be demonstrated visually. When teaching the soroban, a song-like instruction is given by the teacher. The soroban is about 8 cm (3 inches) tall. The beads on a soroban are usually shaped as a double cone (bi-cone) to facilitate ease of movement. Often, primary school students may bring along with them two sorobans, one with 1 upper bead and 5 lower beads, the other with 1 upper bead with 4 lower beads. Despite the advent of handheld calculators, some parents send their children to private tutors to learn soroban because proficiency in soroban calculation can be easily converted to mental arithmetic at a highly advanced level.

[edit] Russian abacus

Russian abacus

The Russian abacus, the schoty (счёты), usually has a single slanted deck, with ten beads on each wire (except one wire which has four beads, for quarter-ruble fractions). This wire is usually near the user. (Older models have another 4-bead wire for quarter-kopeks, which were minted until 1916.) The Russian abacus is often used vertically, with wires from left to right in the manner of a book. The wires are usually bowed to bulge upward in the center, in order to keep the beads pinned to either of the two sides. It is cleared when all the beads are moved to the right. During manipulation, beads are moved to the left. For easy viewing, the middle 2 beads on each wire (the 5th and 6th bead) usually have a colour different from the other 8 beads. Likewise, the left bead of the thousands wire (and the million wire, if present) may have a different color.

The Russian abacus is still in use today in shops and markets throughout the former Soviet Union, although it is no longer taught in most schools.

[edit] School abacus

School abacus used in Danish elementary school. Early 20th century.

Around the world, abaci have been used in pre-schools and elementary schools as an aid in teaching the numeral system and arithmetic. In Western countries, a bead frame similar to the Russian abacus but with straight wires has been common (see image). It is still often seen as a plastic or wooden toy.

The type of abacus shown here is often used to represent numbers without the use of place value. Each bead and each wire has the same value and used in this way it can represent numbers up to 100.

The most significant educational advantage of using an abacus, rather than loose beads or counters, when practicing counting and simple addition is that it gives the student an awareness of the groupings of 10 which are the foundation of our number system. Although adults take this base 10 structure for granted, it is actually difficult to learn. Many 6 year olds can count to 100 by rote with only a slight awareness of the patterns involved.

[edit] Uses by the blind

Abaci are still commonly used by individuals who are blind. They use an abacus to perform the mathematical functions multiplication, division, addition, subtraction, square root and cubic root. A piece of soft fabric or rubber is placed behind the beads so that they do not move inadvertently. This keeps the beads in place while the user feels or manipulates them.

Recently, abaci have been replaced to some extent by electronic calculators with speech, but only in those countries where they are easily available and affordable. However, even when they are available, many blind people still prefer to use the abacus. In addition, many blind children educated at schools for the blind are required to learn how to use the abacus before they are permitted the use of a talking calculator or similar device. This can be compared to sighted children being required to learn how to solve mathematical problems on paper before they are allowed the use of a calculator, although using a braille-writer is comparable.

[edit] Native American abaci

This section is a stub. You can help by expanding it.

Representation of an Inca quipu

Some sources mention the use of an abacus called a nepohualtzintzin in ancient Aztec culture. This Mesoamerican abacus uses the 5-digit base-20 system.

The quipu of the Incas was a system of knotted cords used to record numerical data (some think that it may have been used as an alphabet tool) - like advanced tally sticks—but was not used to perform calculations. Calculations were carried out using a yupana (quechua for "counting tool"; see figure) which was still in use after the conquest of Peru. The working principle of a yupana was unknown up to very recent years (2001) when an explanation of the mathematical basis of these instruments has been proposed: comparing the form of several yupanas, it appears that calculations were based using the Fibonacci sequence 1,1,2,3,5 and powers of 10, 20 and 40 as place values for the different fields in the instrument. The Fibonacci sequence is useful to keep the number of grains within any one field at minimum.

[edit] See also

[edit] Further reading

Pullan, J. M. (1968). The History of the Abacus. London: Books That Matter. ISBN 0-09-089410-3.
Menninger, Karl W. (1969). Number Words and Number Symbols: A Cultural History of Numbers. MIT Press. ISBN 0-262-13040-8.
Kojima, Takashi (1954). The Japanese Abacus: its Use and Theory. Tokyo: Charles E. Tuttle. ISBN 0-8048-0278-5.

[edit] External links

Find more information on Abacus by searching Wikipedia's sister projects:

Dictionary definitions from Wiktionary
Textbooks from Wikibooks
Quotations from Wikiquote
Source texts from Wikisource
Images and media from Commons
News stories from Wikinews
Learning resources from Wikiversity

[edit] Tutorials

[edit] Abacus curiosities

Links sobre física/ciência em geral

2007-01-13T04:16:00.001-03:00

um ótimo blog universitário de física:
http://universitariodefisica.blogspot.com/

experimentos simples e interessantes sobre várias áreas:
http://www.feiradeciencias.com.br/

como as coisas funcionam.... muito material mesmo!
http://www.howstuffworks.com

página do prof. lang do if - ufrgs
http://www.if.ufrgs.br/mpef/Lang/

revista scientific american:
http://www.sciam.com/

science daily:
http://www.sciencedaily.com/

contém uma vasta coleção de conteúdos (das ciências em geral, inclusive) :
http://scienceworld.wolfram.com/physics/

Scientific Electronic Library Online - BR
http://www.scielo.br/

humor na ciência:
http://www.humornaciencia.hpg.ig.com.br/

periódicos da capes:
http://www.periodicos.capes.gov.br

Portal para periódicos de livre acesso na Internet:
http://livre.cnen.gov.br/Inicial.asp

animação em flash explicando as dez dimensões:
http://www.tenthdimension.com/flash2.php

Revista electrónica de ciencia, tecnología, sociedad y cultura:
http://www.tendencias21.net

Consejo Superior de Investigaciones Científicas:
http://www.csic.es

ebook de física:
http://instruct.tri-c.edu/fgram/web/..%5Cphysics.htm

links semelhantes em outro site:
http://www.fazfacil.com.br/Revistas.htm

Sites interessantes sobre xadrez

2007-01-09T02:24:00.000-03:00

o melhor site de jogo online gratuito que conheço:
www.freechess.org

o melhor site de material didático que encontrei(muita coisa mesmo!):
http://www.exeterchessclub.org.uk/

o melhor site com material ditático de xadrez em português que ja encontrei:
www.cex.org.br

xadrez por email:
http://www.itsyourturn.com/

tópicos gerais interessantes sobre xadrez:
chess.about.com

o chess publisher, animação em flash do jogo criada a partir de algum pgn:
http://chess.maribelajar.com/chesspublisher/index.php

begin chess, dicas gerais(incluindo training schedule) :
http://www.beginchess.com/

chess for blood, outro blog, só que focalizado exclusivamente ao xadrez:
http://chessforblood.blogspot.com/

gerador de diagramas enxadrísticos:
http://chessup.net/

dejascacchi - táticas em pdf
http://dejascacchi.altervista.org/exercises.htm

chess puzzles by GMs
http://www.wtharvey.com/

boletim informativo :
http://xeque.net

confederação brasileira de xadrez:
www.cbx.org.br

federação gaúcha de xadrez:
http://www.fgx.org.br/

variantes de xadrez:
http://www.chessvariants.org/Gindex.html

recreational mathematics:
http://mathworld.wolfram.com/topics/Chess.html

Paradise Lost - John Milton

2007-01-01T19:06:00.000-03:00

Of Man's first disobedience, and the fruit
Of that forbidden tree whose mortal taste
Brought death into the world, and all our woe,
With loss of Eden, till one greater Man
Restore us, and regain the blissful seat,
Sing, Heav'nly Muse, that, on the secret top
Of Oreb, or of Sinai, didst inspire
That shepherd who first taught the chosen seed
In the beginning how the Heav'ns and Earth
Rose out of Chaos; or, if Sion hill
Delight thee more, and Siloa's brook that flow'd
Fast by the oracle of God, I thence
Invoke thy aid to my advent'rous song,
That with no middle flight intends to soar
Above th' Aonian mount, while it pursues
Things unattempted yet in prose or rhyme.
And chiefly thou, O Spirit, that dost prefer
Before all temples th' upright heart and pure,
Instruct me, for thou know'st; thou from the first
Wast present, and, with mighty wings outspread,
Dovelike sat'st brooding on the vast abyss,
And mad'st it pregnant: what in me is dark
Illumine; what is low, raise and support;
That, to the height of this great argument,
I may assert Eternal Providence,
And justify the ways of God to men.

Paradise Lost - a poem by John Milton