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Graphite Mold Casting

Graphite is used in making moulds to receive alloys such as titanium, which can be poured only into inert moulds. The casting process must be performed in a vaccum to eliminate aany possibility of contaminating the metal. The graphite moulds can be made either by machining a block of graphite to create the desired mould cavityor by compacting a graphite base aggregate around the pattern and then sintering the obtained mould at a temperature 1800 to 2000 F in reducing atmosphere. In fact, graphite mould liners have found widespread industrial applications in the centrifugal casting of brass and bronze.

(Product design and manufacturing, Yazar: A.K. Chitale, R.C. Gupta, Page 93)

Natural Rubber (28,04 20,25)

Natural rubber occurs as a latex that may be tapped or removed from the rubber bearing plant or tree. The latex is subsequently coagulated and the precipitated material collected. Originally, natural rubber was harvested in its wild state from South America, especially from Hevea brasileanus trees. The Hevea tree is not a unique source of rubber. Mant other plants from the South American regions produce rubbery as well as plastic materials. It is very possible that the hull balls obtained by Columbus and the conQuistadors did not derive from Hevea. Most efforts toward commercially producing natural rubber from other plants have focused on the Guayule bushes of the Mexican desert.

(Rubber processing: technology, materials, principles, Yazar: James lindsay White)

Syntetic Rubber (Synthetic Rubber) (28,04 20,43)

Today, the tonnage of synthetic rubbers is more than three times that of natural rubber. Development of these synthetic materials was motivated largely by the world wars when NR was difficult to obtain. The most important of the synthetics is styrene-butadiene rubber (SBR), a copolymer of butadiene and styrene. As with most other polymers, the predominant raw material fofr the synthetic rubbers is petroleum. Only the synthetic rubbers of greatest commercial importance are discussed here. Market share data are for total volume of natural and synthetic rubbers. About 10% of total volume of rubber production is reclaimed; thus, total tonnages do not sum to 100%.

(Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, Yazar: Mikell P. Groover, Page 178-179)

Feedback Linearization Technique

Most physical systems operations are nonlinear in nature and hence they should be described by means of nonlinear mathematical models. Since nonlinear models are not convenient for control purposes, due to both theoretical and computational reasons, they are often linearized by using appropriate exact or approximate linearization techniques. Among them, feedback linearization control law and a state variable transformation (diffeomorphism) such that the closed loop system model becomes linear, in the new coordinate variables. However, feedback linearization requires some strong constraints to be satisfied by the original nonlinear system, and thus its applicability is quite restricted. If, in addition, the original system is characterized by uncertain parameters, external disturbances and unmeasured state variables, as is the case of bioprocess control systems, the linearization problem becomes particularşy complex and almost inextricable.

(Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2003 (ICCMSE 2003),Yazar:T.E. Simos, Page 90)