الفهرس 
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Abstract
A reductive perturbation theory has been applied to investigate the propagation of nonlinear dustionacoustic waves (DIAWs) in a collisionless, unmagnetized three component dusty plasma, consisting of negatively charged warm dust particles, warm ions and isothermal electrons. The perturbation theory leads to a Kortewegde Vries (KdV) equation. The soliton solution of the KdV equation is obtained. It is found that, both compressive and rarefactive solitons can exist in the system. The effects of various plasma parameters on the features of the compressive and rarefactive solitons are investigated. At the critical phase velocity, where the coefficient of the nonlinear term in the KdV equation vanishes, a new set of stretched variables is used to derive a modified Kortewegde Vries (mKdV) equation. However, in the vicinity of the critical phase velocity neither KdV nor mKdV equation is adequate for describing the system and so a further modified Kortewegde Vries (fmKdV) equation is derived. The soliton solutions of both mKdV and fmKdV equations are obtained. The effects of plasma parameters on the amplitude and the width of the compressive and rarefactive solitary waves have been studied. We also deduced Sagdeev potential from the basic set of fluid equations using a pseudopotential method. It is found that, for small perturbed potential, the Sagdeev potential is exactly the same as that obtained by the reductive perturbation theory. The effects of trapped electron temperature, dust charge variation and dust grain radius on the nonlinear DIAWs in dusty plasmas having trapped electrons are investigated. The behavior of the nonlinear DIAWs is governed by mKdV equation. It is found that, only compressive DIAWs can propagate in a dusty plasma with trapped electrons and both the amplitude and width of DIAWs depend mainly on the trapped electron temperature, dust charge variations and grain radius.