previous description
The most significant steps in the cryopreservation of cattle embryos in more recent times inclued the aiblity to freeze and transfer embryos in straws without dilution and the development of the open-pulled-straw(OPS) method for efficient vitrification of embryos and ooctyes. Although vitrification appeared on the scene of embryo cryopreservation in the mid 1980s as an alteranticve to traditional slow-rate freezing of cattle embryos, its possible advantages( simplicity, speed, low cost) had little impact on commercial cattle Et operations and its application was generaly confined to research studies. In vitrification, ice-crystal formation is prevented by using high concentrations of cryoprotectants and high cooling and warming rates.
no previous description
new description
Penetrant testing is a means of aiding visual inspection for surface defectys such as cracks. The process operates on the principle that penetrant dyes are absorbed into surface-breaking defectys and can thus be utilized to make the defects more visible. The first step of the penetrant inspection procedure is a careful cleaning of the test object to remove all surface oils and contamination. Next, the dye is applied to the surface and allowed to soak into whatever defects may be present. The dye is then removed from the surface, leaving only the dye that has become trapped in surface cracks. Finally, a powdew-like developer is applied to the test object. The developer draws residual dye out of cracks, making their presence highly visible. The visibility of dyes is often further enchanced via ultraviolet flourescance.
(National Materials Advisory Board (U.S.). Committee on Nondestructive Evaluation of Metal Matrix Composites,Nondestructive evaluation of metal matrix composites, p11)
4 - Flow Forming ( Manufacture Method )
no previous description
new description
Flow forming is shown schematically in figure 5.8. This shows forward flow forming; the direction in which the roller moves is the same as the material. In practice, two or three rollers would be used, acting as 90 degrees to the centre-line and radially fed, axially, to a pre-set distange from the mandrel. Starting with a flat blank is not common; it is more usual to start with a pre-formed cup-which can be produced by spinning on the same machine (figure 5.9). In flow forming of course, Tf = T0 . sin (Q) also applies and for accurate flow forming of high strenght materials destined for the aerospace industry for example, the forming machine would be fitted with four-axis computer numerical control, giving independent control of three work rolls in conjunction with the longitudinal slide (fourth axis)
Although a relatively slow process, flow forming can produce a large thickness reduction and the resulting parts exhibit close tolerances, good surface finish and high strength, due to straing hardening.
( Roger Pearce, Sheet Metal Forming, pp 67,68)
5 - Deoxidizing ( Contamination removal process )
previous description
Deoxidizing is the process of removing metal oxides,particullarly on aluminium components. A caustic soda (%5) solution in water is quite effective in removing ozide on aluminium parts. The deoxidized parts are later immersed in a bath having 20 to 50 % nitric acid solution in water to clean up the surface completely.
(Manufacturing Processes Second Edition, J.P. Kaushish, pg. 891)
(Ian R. Gordon, Laboratory production of Cattle Embryos,p. 279)
new description (better)
new description (better)
At very high cooling rate, water molecules can be brought to rest, or close to it, before they have time to nucleate crystal. Water becomes solid while remaining in an amorphous state that can be preserved indefinitely, provided the temperature is kept cold enough. The process is called vitrification. In fact, nobody knows for sure what vitrification is. There are fundamental theoritical questions that are not answered and experimental results that are not understood. A discussion, which should be accessible to nonspecialists, is presented elsewhere (Duboched, 2006). For lack of certainity as to what vitrification is, we choose the simplest solution, while keeping in mind that our views may need to be revisited.
(J. Richard McIntosh,Cellular Electron Microscopy, p17)
2 - Versatility ( usage capability )
(J. Richard McIntosh,Cellular Electron Microscopy, p17)
2 - Versatility ( usage capability )
no previous description
new description
Versatility means that the aspect design can be reused across a range of different applications. The opposite of versatility is inflexibility i.e., the inability to refine the abstractions of aspect to a broad range of application requirements. Typically, the cause of such inflexibility is that certain design choices, that are fixed by the aspect, conflict with the requirements of the application. As a result, the application developer has to workaround this problem by reimplementing the aspect functionality, leading to duplicated code.
(Shmuel Katz,Mira Mezini,Christine Schwanninger,Wouter Joosen, Transactions on Aspect-Oriented Software Development VIII, pp49,50)
3 - Penetrant Testing ( Non-Destructive Testing Method )
3 - Penetrant Testing ( Non-Destructive Testing Method )
previous description
A typical penetrant testing involves use of a variety of materials for cleaning and developing as well as the penetrant material itself.In general, the fluids involved in the penetrant process are either petroleum-or-water-based and the solvents or cleaners are selected according to the type of penetrant.Penetrant material consists of the indicating dye plus the carrier fluid. The indicating dye may give a colour contrast with respect to the suroundings, as is the case for visible dye penetrant methods, or a brightness contrast for the flourescent penetrants, the dye appears bright yellow green under ultraviolet light.
new description ( better )
Penetrant testing is a means of aiding visual inspection for surface defectys such as cracks. The process operates on the principle that penetrant dyes are absorbed into surface-breaking defectys and can thus be utilized to make the defects more visible. The first step of the penetrant inspection procedure is a careful cleaning of the test object to remove all surface oils and contamination. Next, the dye is applied to the surface and allowed to soak into whatever defects may be present. The dye is then removed from the surface, leaving only the dye that has become trapped in surface cracks. Finally, a powdew-like developer is applied to the test object. The developer draws residual dye out of cracks, making their presence highly visible. The visibility of dyes is often further enchanced via ultraviolet flourescance.
(National Materials Advisory Board (U.S.). Committee on Nondestructive Evaluation of Metal Matrix Composites,Nondestructive evaluation of metal matrix composites, p11)
4 - Flow Forming ( Manufacture Method )
no previous description
new description
Flow forming is shown schematically in figure 5.8. This shows forward flow forming; the direction in which the roller moves is the same as the material. In practice, two or three rollers would be used, acting as 90 degrees to the centre-line and radially fed, axially, to a pre-set distange from the mandrel. Starting with a flat blank is not common; it is more usual to start with a pre-formed cup-which can be produced by spinning on the same machine (figure 5.9). In flow forming of course, Tf = T0 . sin (Q) also applies and for accurate flow forming of high strenght materials destined for the aerospace industry for example, the forming machine would be fitted with four-axis computer numerical control, giving independent control of three work rolls in conjunction with the longitudinal slide (fourth axis)
Although a relatively slow process, flow forming can produce a large thickness reduction and the resulting parts exhibit close tolerances, good surface finish and high strength, due to straing hardening.
( Roger Pearce, Sheet Metal Forming, pp 67,68)
5 - Deoxidizing ( Contamination removal process )
previous description
Deoxidizing is the process of removing metal oxides,particullarly on aluminium components. A caustic soda (%5) solution in water is quite effective in removing ozide on aluminium parts. The deoxidized parts are later immersed in a bath having 20 to 50 % nitric acid solution in water to clean up the surface completely.
(Manufacturing Processes Second Edition, J.P. Kaushish, pg. 891)
new
Deoxidizing and etching are both done with either caustic or acid solutions. Deoxidizing may use both, in series, if the metal to be anodized or alodized is badly oxidized. The purpose of deoxidizing is to remove oxides that have formed naturally, but in an undersirable manner.
(Frank Woodard, Industrial Waste Treatment Handbook, p101)
(Frank Woodard, Industrial Waste Treatment Handbook, p101)
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