Annealing
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The word anneal has several meanings:
- In metallurgy and materials science annealing is a heat treatment wherein the microstructure of a material is altered, causing changes in its properties such as strength and hardness. Typically, this results in softening of the metal through removal of crystal defects and the internal stresses which they cause. In the semiconductor industry, silicon wafers are annealed, so that dopant atoms (usually, boron, phosphorus, or arsenic) can be incorporated into substitutional positions in the crystal lattice, resulting in drastic changes in the electrical properties of the semiconducting material.
- In glass (glassblowing and lampworking), annealing is heating a piece until its temperature reaches a stress-relief point, that is, a temperature at which the glass is still too hard to deform, but is soft enough for internal stresses to ease. The piece is then allowed to heat-soak until its temperature is even throughout; the time necessary for this varies depending on the type of glass and thickness of the thickest section. The piece is then slowly cooled at a predetermined rate until its temperature is below a critical point, at which it can no longer generate internal stresses, and then the temperature can safely be dropped to room temperature. This relieves the internal stresses, resulting in a piece which should last for many years. Glass which has not been annealed will crack or even shatter when subjected to a relatively small temperature change or other shock.
- In biology (genetics) to anneal means for DNA or RNA to pair by hydrogen bonds to a complementary sequence, forming a double-stranded polynucleotide. The term is often used to describe the binding of a DNA probe, or the binding of a primer to a DNA strand during polymerase chain reaction.
- In computer science, simulated annealing is a technique for searching for a solution in a space otherwise too large for "ordinary" search methods to yield results. It is a probabilistic technique based on formulas from physics describing an annealing process. See the book Numerical Recipes for a good treatment.
- In library and information science, knowledge or information annealing is a network-based information system or body of knowledge in which all users of the system are permitted to change the system at will. Over time, the system is said to become better structured and more correct, as knowledgeable users correct existing mistakes and add new content. The original Information annealing software called MaxThink was introduced by Neil Larsen in the early 1980s.