Preform

Preform

A preform is material that has undergone preliminary shaping but is not yet in its final form.

Fiber optics

In fiber optics, a preform is a piece of glass used to draw an optical fiber.The preform may consist of several pieces of a glass with different refractive index,to provide the core and cladding of the fiber. The shape of the preform may be circular, although for some applications such as double-clad fibers another form is preferred.cite journal|title=Highly efficient, high-gain, short-length, and power-scalable incoherent diode slab-pumped fiber amplifier/laser| author= Kouznetsov, D.| coauthors=Moloney, J.V.| journal=IEEE Journal of Quantum Electronics| url=http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=1242365&isnumber=27838|volume=39 | year=2003 | issue=11 | pages=1452–1461 | doi=10.1109/JQE.2003.818311] In fiber lasers based on double-clad fiber, an asymmetric shape improves the filling factor for laser pumping.

Due to the surface tension, the shape is smoothed during the drawing process, and the shape of the resulting fiber does not reproduce the sharp edges of the preform.Nevertheless, the careful polishing of the preform is important, any defects of the preformsurface affect the optical and mechanical properties of the resulting fiber. In particular, the preformfor the test-fiber shown in the figure was not polished well, and the cracks are seen with confocal optical microscope.

Archeology

In archeology, a preform is the rough, incomplete and unused basic form of a stone tool formed by lithic reduction. Typically, a preform is the shaped remnant of a lithic core. Larger and thicker than the intended tool, it lacks the final trimming and refinement that is present in the completed artifact. Sometimes basic features such as stems and notches have been initiated. In most cases, the term refers to incomplete projectile point.

oldering

A solder preform is a specially designed shape of solder adjusted to the application where it is used. Although there are many methods that are used to manufacture the solder preform, stamping is probably the most common method. The solder preform can be manufactured including the solder flux needed for the soldering process. This can be an internal flux, inside the solder preform, or external, where the solder preform is coated.

See also

*Blank (archeology)

References


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Look at other dictionaries:

  • Preform — Pre*form , v. t. [L. praeformare. See {Pre }, and {Form}.] To form beforehand, or for special ends. Their natures and preformed faculties. Shak. [1913 Webster] …   The Collaborative International Dictionary of English

  • preform — [prē fôrm′] vt. to form in advance …   English World dictionary

  • preform — v. /pree fawrm /; n. /pree fawrm /, v.t. 1. to form beforehand. 2. to determine or decide beforehand: to preform an opinion. 3. to shape or fashion beforehand: to preform a mold. n. 4. biscuit (def. 5). 5. any of various uncompleted objects of… …   Universalium

  • preform — transitive verb Etymology: Latin praeformare, from prae + formare to form, from forma form Date: 1601 1. to form or shape beforehand 2. to bring to approximate preliminary shape and size • preform noun …   New Collegiate Dictionary

  • preform — ruošinys statusas T sritis automatika atitikmenys: angl. preform vok. Vorform, f rus. заготовка, f pranc. préforme, f …   Automatikos terminų žodynas

  • preform — rėmelis statusas T sritis radioelektronika atitikmenys: angl. frame; preform vok. Rahmen, m rus. рамка, f pranc. cadre, m …   Radioelektronikos terminų žodynas

  • preform — ruošinys statusas T sritis fizika atitikmenys: angl. blank; preform; stab vok. Ausgangserzeugnis, n rus. заготовка, f pranc. pièce brute, f; préforme, f …   Fizikos terminų žodynas

  • preform — 1. noun a) An object that has undergone preliminary shaping but is not yet in its final form. b) The rough, incomplete and unused basic form of a stone tool. 2. verb To shape something before some other operation …   Wiktionary

  • preform — prɪː fÉ”rm / fɔːm v. mold beforehand, form in advance; shape in advance; assemble beforehand …   English contemporary dictionary

  • preform — perform …   Anagrams dictionary

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