General




Find answers to all kinds of questions through these sites.





1. InfoPlease: Visitors to this site will be treated to an almanac, atlas, encyclopedia, dictionary and much more, which should be more than enough to find information on just about anything you’d need.
2. Ask Deb: Professional researchers and writers answer questions on various subjects, including dating, careers, personal finance, and beauty.
3. About.com: This site provides articles on a huge variety of subjects, many of which provide useful information or can link you to sites that have what you’re looking for.
4. Refdesk.com: Billed as a "fact check for the Internet," this site provides a range of resources that make it easy to search the web, check an encyclopedia or dictionary, read the news and much more.
5. Reference.com: Part of the Dictionary.com site, this online resource provides access to many encyclopedia articles, as well as the accompanying dictionary and thesaurus.
6. Answers.com: Answers.com provides visitors with access to articles from sites and journals all over the Web.
7. Factbites: Called a cross between a search engine and an encyclopedia, this site is designed to make searching for information easier by filtering out information and only giving you the most relevant results.

Library and Reference




Search through library archives and do academic research on these sites.





8. Oxford Journals: Look through all the journals published by Oxford and find many articles that are free to read and download.
9. eBrary: Many libraries give full access to eBrary’s collections, but if you don’t have one near to you that does, you can use this page and still enjoy looking through loads of books and journals.
10. ibiblio: This site is full of public domain information including maps, books, pictures and much more that you can use in your next research project.
11. LibrarySpot: Find a myriad of library resources on this site as well as links to other authoritative sites and encyclopedias online.
12. WorldCat: Save yourself a trip to the library and find out if a library has the information you need before you go. This site allows users to find libraries in their area that have the books and materials they need.
13. Internet Public Library: This site puts together a great repository of links to authoritative sites all over the Web on topics like history, law, computers and more.

3D wireframe is basically an extension of 2D drafting. Each line has to be manually inserted into the drawing. The final product has no mass properties associated with it and cannot have features directly added to it, such as holes. The operator approaches these in a similar fashion to the 2D systems, although many 3D systems allow using the wireframe model to make the final engineering drawing views.

3D "dumb" solids (programs incorporating this technology include AutoCAD and Cadkey 19) are created in a way analogous to manipulations of real world objects. Basic three-dimensional geometric forms (prisms, cylinders, spheres, and so on) have solid volumes added or subtracted from them, as if assembling or cutting real-world objects. Two-dimensional projected views can easily be generated from the models. Basic 3D solids don't usually include tools to easily allow motion of components, set limits to their motion, or identify interference between components.

3D parametric solid modeling (programs incorporating this technology include Pro/ENGINEER, NX, the combination of UniGraphics and IDeas, CATIA V5, Autodesk Inventor, Alibre Design, TopSolid, T-FLEX CAD, SolidWorks, and Solid Edge) require the operator to use what is referred to as "design intent". The objects and features created are adjustable. Any future modifications will be simple, difficult, or nearly impossible, depending on how the original part was created. One must think of this as being a "perfect world" representation of the component. If a feature was intended to be located from the center of the part, the operator needs to locate it from the center of the model, not, perhaps, from a more convenient edge or an arbitrary point, as he could when using "dumb" solids. Parametric solids require the operator to consider the consequences of his actions carefully.

Some software packages provide the ability to edit parametric and non-parametric geometry without the need to understand or undo the design intent history of the geometry by use of direct modeling functionality. This ability may also include the additional ability to infer the correct relationships between selected geometry (e.g., tangency, concentricity) which makes the editing process less time and labor intensive while still freeing the engineer from the burden of understanding the model’s design intent history. These kind of non history based systems are called Explicit Modellers. The first Explicit Modeling system was introduced to the world at the end of 80's by Hewlett-Packard under the name SolidDesigner. This CAD solution, which released many later versions, is now sold by PTC as "CoCreate Modeling"

Draft views are able to be generated easily from the models. Assemblies usually incorporate tools to represent the motions of components, set their limits, and identify interference. The tool kits available for these systems are ever increasing; including 3D piping and injection mold designing packages.

Mid range software are integrating parametric solids more easily to the end user: integrating more intuitive functions (SketchUp), using the best of both 3D dumb solids and parametric characteristics (VectorWorks), making very real-view scenes in relative few steps (Cinema4D) or offering all-in-one (form•Z).

Top end systems offer the capabilities to incorporate more organic, aesthetics and ergonomic features into designs (Catia, GenerativeComponents). Freeform surface modelling is often combined with solids to allow the designer to create products that fit the human form and visual requirements as well as they interface with the machine.

• Sweeping
  
  • An area feature is "swept out" by moving a primitive along a path to form a solid feature. These volumes either add to the object ("extrusion") or remove material ("cutter path").
  • Also known as 'sketch based modeling'.
  • Analogous to various manufacturing techniques such as extrusion, milling, lathe and others.
  • Boundary representation (BRep)
    
    • A solid object is represented by boundary surfaces and then filled to make solid.
    • Also knowing as 'surfacing'.
    • Analogous to various manufacturing techniques; Injection moulding, casting, forging, thermoforming, etc.
    • Parameterized primitive instancing.
      
      • An object is specified by reference to a library of parameterized primitives.
      • For example, a bolt is modeled for a library, this model is used for all bolt sizes by modifying a set of its parameters.
      • Spatial occupancy enumeration (voxel)
        
        • The whole space is subdivided into regular cells, and the object is specified by the set of cells it occupies.
        • Models described this way lend themselves to Finite difference analysis.
        • This is usually not done after a model is made, as part of automated pre-processing for analysis software.

In computer science, computational geometry is the study of algorithms to solve problems stated in terms of geometry. Some purely geometrical problems arise out of the study of computational geometric algorithms, and the study of such problems is also considered to be part of computational geometry.

The main impetus for the development of computational geometry as a discipline was progress in computer graphics, computer-aided design and manufacturing (CAD/CAM), but many problems in computational geometry are classical in nature.

Other important applications of computational geometry include robotics (motion planning and visibility problems), geographic information systems (GIS) (geometrical location and search, route planning), integrated circuit design (IC geometry design and verification), computer-aided engineering (CAE) (programming of numerically controlled (NC) machines).

The three main branches of computational geometry are:



• Combinatorial computational geometry, also called algorithmic geometry, which deals with geometric objects as discrete entities.
• Numerical geometry, also called machine geometry, computer-aided geometric design (CAGD), or geometric modelling, which deals primarily with representing real-world objects in forms suitable for computer computations in CAD /CAM systems. This branch may be seen as a further development of descriptive geometry and is often considered a branch of computer graphics and/or CAD, whereas the former branch is often called simply computational geometry.
• Non-numerical geometry, which studies and develops non-numerical geometrical algorithms. This is the oldest branch of computational geometry which goes back to geometric constructions with the help of ruler and compass. Algorithms of geometric constructions are the soul and the origin of geometry and are not numerical in nature. Although until recently such constructions could be performed with the help of a ruler and compass only, two decades ago new means of geometric constructions emerged. These were various optical devices capable of manipulating images of geometrical figures, such as mirrors, beam splitters, holograms, etc. The observation that geometric constructions can be performed optically rather than with the help of ruler and compass laid in the foundation of "Optical Computational Geometry" put forward by Yevgeny Karasik in 1990.

Computational geometry is a branch of computer science devoted to the study of algorithms which can be stated in terms of geometry. Some purely geometrical problems arise out of the study of computational geometric algorithms, and such problems are also considered to be part of computational geometry.

The main impetus for the development of computational geometry as a discipline was progress in computer graphics, computer-aided design and manufacturing (CAD/CAM), but many problems in computational geometry are classical in nature.

Other important applications of computational geometry include robotics (motion planning and visibility problems), geographic information systems (GIS) (geometrical location and search, route planning), integrated circuit design (IC geometry design and verification), computer-aided engineering (CAE) (programming of numerically controlled (NC) machines).

The main branches of computational geometry are:



• Combinatorial computational geometry, also called algorithmic geometry, which deals with geometric objects as discrete entities. A groundlaying book in the subject by Preparata and Shamos dates the first use of the term "computational geometry" in this sense by 1975.^[1]
• Numerical computational geometry, also called machine geometry, computer-aided geometric design (CAGD), or geometric modeling, which deals primarily with representing real-world objects in forms suitable for computer computations in CAD/CAM systems. This branch may be seen as a further development of descriptive geometry and is often considered a branch of computer graphics or CAD. The term "computational geometry" in this meaning has been in use since 1971.^[2]

Main aspects of study are:



• Constructing digitized representations of objects, with the emphasis on precision and efficiency (either by means of synthesis, see, for example, Bresenham's line algorithm or digital disks, or by means of digitization and subsequent processing of digital images).
• Study of properties of digital sets; see, for example, Pick's theorem, digital convexity, digital straightness, or digital planarity.
• Transforming digitized representations of objects, for example (A) into simplified shapes such as (i) skeletons, by repeated removal of simple points such that the digital topology of an image does not change, or (ii) medial axis, by calculating local maxima in a distance transform of the given digitized object representation, or (B) into modified shapes using mathematical morphology.
• Reconstructing "real" objects or their properties (area, length, curvature, volume, surface area, and so forth) from digital images.
• Study of digital curves and surfaces
• Designing tracking algorithms for digital objects

In 3D computer graphics, 3D modeling is the process of developing a mathematical, wireframe representation of any three-dimensional object (either inanimate or living) via specialized software. The product is called a 3D model. It can be displayed as a two-dimensional image through a process called 3D rendering or used in a computer simulation of physical phenomena. The model can also be physically created using 3D Printing devices.

Models may be created automatically or manually. The manual modeling process of preparing geometric data for 3D computer graphics is similar to plastic arts such as sculpting.

Green Building XML Modeling Software



• Bentley Systems Bentley Architecture
• Autodesk Revit
• Green Building Studio[1] Green Building Studio Inc
• Ecotect[2] Square One research [3]

Behavioral modeling in computer-aided design






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In computer-aided design, behavioral modeling is a high-level circuit modeling technique where behavior of logic is modeled.




The Verilog-AMS and VHDL-AMS languages are widely used to model logic behavior.







[edit] Other modeling approaches




• RTL Modeling : logic is modeled at register level.
• Structural Modeling : logic is modeled at both register level and gate level.







[edit] References




Analog Behavioral Modeling with the Verilog-A Language by Dan FitzPatrick, Ira Miller.