Background History

The use of biaxial rotation and heat for materials fabrication dates to R. Peters of Britain in 1855 for the manufacture of hollow artillery shells [41,42]. Rotational molding of polyethylene started in the early 1950s. 

Rotational molding is especially useful for the manufacture of very large parts and containers. For example, container volume is limited in the blowmolding process by the size and weight of the parison which is formed during the process. A very heavy parison is subject to sagging before the application of the blowing step, which will cause a non-uniform part thickness. 

Some of the important variables that need to be carefully monitored during the rotational molding process are  

Molds need to provide a smooth, nonporous surface with good heat conductivity to allow for controlled heating and cooling. Two-piece molds manufactured from cast aluminum or sheet-metal are common. 

Although the rotational molding process is carried out with very little shear on the polymer melt, the cooling rate of the polyethylene after the fabrication step remains important in order to avoid excessive shrinkage and warpage. This is due to the crystallization process that takes place as the polymer melt cools from an amorphous, less dense state to a solid, semicrystalline state, higher density solid. 

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Why/ whether policy is needed demand needs and reality decarbonization ofworld metabolic cycle general background history role of energy in development, etc. 

The quality manual shall be a written document including the scope of the Quality System. Information about the construction organization, such as name, location, and means of communication, shall be included, as well as additional information, such as its line of business and a brief description of its background, history, and size. 

There was a background history of cardiovascular disease in 40% of the patients at baseline, and myocardial infarction was reported in 1.5% of those who took finasteride and 0.5% of those who took placebo, a significant difference. 

All reactions under study have their background history. There may be a reasonable mechanism suggested, or at least there are some hypotheses at the... 

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Leonardo da Vinci Drawings History of Science Friction, http / /www.tribol-ogie.nl/backgrounds/history/historyhtm. 

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Relevant background history - stick to issues affecting diagnosis or management ... 

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