Gani Can Öz (12th Week Unanswered Terms)

ASHBY PLOT: Of more importance to us in materials selection processes is the availability of data upon which to base our decisicion. The nature of data needed in early stages differs greatly in its level of precision and breadh from that needed in later stages. At the conceptual stage, the designer requires approximate property velues for the widest possible range of materials. It is an this stage that the materials selection charts of Ashby are particularly useful. Such a plot assists the designer in selecting an apprppriate class of material for consideration. The specific plot to use depends upon the design criteria; for example modulus versus densitymay be important for one application, whereas thermal conductivity versus tensile strength is important for another. (An introduction to materials engineering and science for chemical and material engineers. Brian S. Mitchell)
UTILITY MODEL: Some countries for example Japan, Germany nad Korea allow utility model patents, which can be thougt of small, more specific utility patents. Utility models typically have a shorter life that a utility patent and were originally intended to provide some quick, inexpensice legal protection fr small invnetor. From a practial stand point, utility models are normally very narrowly claimed, or very specific to a particular product or machine. (Patent strategy for researchers and research managers, H. Jackson Knight)
SEMICONDUCTOR: A semiconductor material has a resistivity lying between that of a conductor and that of an insulator. However, in contrast to the granular materials used for resistors, a semiconductor establishes its conduction properties through a complex quantum mechanical behavior within a periodic array of semiconductor atoms, i.e., within a crystalline structure. For appropriate atomic elements, the crystalline structure leads to a disallowed energy band between the energy level of electrons bound to the crystal's atoms and the energy level of electrons free to move within the crystalline structure (i.e., not bound to an atom). This \energy gap" fundamentally impacts the mechanisms through which electrons associated with the crystal's atoms can become free and serve as conduction electrons. The resistivity of a semiconductor is proportional to the free carrier density, and that density can be changed over a wide range by replacing a very small portion (about 1 in 10^6) of the base crystal's atoms with di®erent atomic species (doping atoms). The majority carrier density is largely pinned to the net dopant impurity density. By selectively changing the crystalline atoms within small regions of the crystal, a vast number of small regions of the crystal can be given different conductivities. (Semiconductor Materials S. K. Tewksbury)
SUN KINK: Under extreme heat or heat fluctuations, rail expansion can cause rail buckling or a sun kink. The buckling occurs due to the expansion as a result of high rail temperatures. Buckling causes the track to shift laterally and sometimes vertically, resulting in a deformation that deviates from the normal track alignment. Buckling usually occurs in the afternoon and early evening hours, over the course of a hot day when rail stresses are highest. (Heat Order Issues Technical Memorandum December 15, 2008 Prepared by: Virginia Department of Rail and Public Transportation)


Gani Can Öz
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