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Reduction Compass
The reduction compass or proportional dividers is a geometry tool with asymmetric-length branches to allow performing homothetic transformations, reproducing a pattern while enlarging or reducing its size and conserving angles. It was invented by Fabrizio Mordente before 1567. Use and principle The reduction compass is made of two branches, with two points each. Several types exist, including the following: * simple reduction compass: the pivot is fixed, and the enlargement factor is determined by the length difference between the small and long end of the branches; * mobile-headed reduction compass: the pivot is mounted on a slide, and its position determines the enlargement factor. File:Reduction compass-MHS 1880-IMG 3829-gradient.jpg, Simple reduction compass on display at the Musée d'Histoire des Sciences de la ville de Genève. File:Reduction compass-MHS 1914-IMG 3834-gradient.jpg, Sliding-pivot reduction compass by Nairne on London, 18th century. On display at the Musé ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homothetic Transformation
In mathematics, a homothety (or homothecy, or homogeneous dilation) is a transformation of an affine space determined by a point ''S'' called its ''center'' and a nonzero number ''k'' called its ''ratio'', which sends point X to a point X' by the rule : \overrightarrow=k\overrightarrow for a fixed number k\ne 0. Using position vectors: :\mathbf x'=\mathbf s + k(\mathbf x -\mathbf s). In case of S=O (Origin): :\mathbf x'=k\mathbf x, which is a uniform scaling and shows the meaning of special choices for k: :for k=1 one gets the ''identity'' mapping, :for k=-1 one gets the ''reflection'' at the center, For 1/k one gets the ''inverse'' mapping defined by k. In Euclidean geometry homotheties are the similarities that fix a point and either preserve (if k>0) or reverse (if k<0) the direction of all vectors. Together with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Musée D'histoire Des Sciences De La Ville De Genève
The ''Musée d'histoire des sciences de la Ville de Genève'' (Museum of the History of Science of the City of Geneva) is a small museum in Switzerland dedicated to the history of science. Location The museum is located in the ''Villa Bartholoni'', designed by Félix-Emmanuel Callet, built in 1830 as a summer residence for Parisian bankers, Constant and Jean-François Bartholoni and extensively restored between 1985 and 1992. It is situated in the park ''La Perle du Lac'', overlooking Lake Geneva, adjacent to the Conservatory and Botanical Garden of the City of Geneva. Both the Villa and the museum itself are listed in the Swiss Inventory of Cultural Property of National and Regional Significance. Access The Museum is open daily from 10am to 5pm, except for 25 December and 1 January and admission is free. The museum receives over 250,000 visitors per year. History The museum was established in 1964 by the enthusiasm of ' (the Museum and review of the History of Science Associa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Technical Drawing Tools
Drafting tools may be used for measurement and layout of drawings, or to improve the consistency and speed of creation of standard drawing elements. Tools such as pens and pencils mark the drawing medium. Other tools such as straight edges, assist the operator in drawing straight lines, or assist the operator in drawing complicated shapes repeatedly. Various scales and the protractor are used to measure the lengths of lines and angles, allowing accurate scale drawing to be carried out. The compass is used to draw arcs and circles. A drawing board was used to hold the drawing media in place; later boards included drafting machines that sped the layout of straight lines and angles. Tools such as templates and lettering guides assisted in the drawing of repetitive elements such as circles, ellipses, schematic symbols and text. Other auxiliary tools were used for special drawing purposes or for functions related to the preparation and revision of drawings. The tools used for manual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drawing Aids
Drawing is a form of visual art in which an artist uses instruments to mark paper or other two-dimensional surface. Drawing instruments include graphite pencils, pen and ink, various kinds of paints, inked brushes, colored pencils, crayons, charcoal, chalk, pastels, erasers, markers, styluses, and metals (such as silverpoint). Digital drawing is the act of drawing on graphics software in a computer. Common methods of digital drawing include a stylus or finger on a touchscreen device, stylus- or finger-to-touchpad, or in some cases, a mouse. There are many digital art programs and devices. A drawing instrument releases a small amount of material onto a surface, leaving a visible mark. The most common support for drawing is paper, although other materials, such as cardboard, wood, plastic, leather, canvas, and board, have been used. Temporary drawings may be made on a blackboard or whiteboard. Drawing has been a popular and fundamental means of public expression throughout human ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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