| Summary: | 碩士 === 國立中正大學 === 物理系 === 92 === In this thesis, how the feedback mechanism affects an self-organized critical (SOC)system was investigated by several kinds of sandpile models.First, we derived some analytic results of a dissipative sandpile,which only loses grains during toppling processes, for the critical exponents on square lattices.Comparing the obtained results from analytic works with the numberical simulations,we found they are very close.Furthermore, we widely simulate sandpile models with other dissipative ways and ondifferent kinds of lattice, for example, scale-free network.Finally, we distinguished the critical exponents into two classes:
(1).the overall exponent which will keep the same value for differentdissipative ways.
(2).the detailed exponent which depends on the dissipative ways.
In summary,this investigation suggests the dissipative way occupies an important position in an SOC system.Besides, because the critical exponet is an index to describe the universality,this study also provides us a deeper understanding for the universality.
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