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On Semicontinuity in Impulsive Dynamical Systems

Krzysztof Ciesielski (2004)

Bulletin of the Polish Academy of Sciences. Mathematics

In the important paper on impulsive systems [K1] several notions are introduced and several properties of these systems are shown. In particular, the function ϕ which describes "the time of reaching impulse points" is considered; this function has many important applications. In [K1] the continuity of this function is investigated. However, contrary to the theorem stated there, the function ϕ need not be continuous under the assumptions given in the theorem. Suitable examples are shown in this paper....

On solutions of differential equations with ``common zero'' at infinity

Árpád Elbert, Jaromír Vosmanský (1997)

Archivum Mathematicum

The zeros c k ( ν ) of the solution z ( t , ν ) of the differential equation z ' ' + q ( t , ν ) z = 0 are investigated when lim t q ( t , ν ) = 1 , | q ( t , ν ) - 1 | d t < and q ( t , ν ) has some monotonicity properties as t . The notion c κ ( ν ) is introduced also for κ real, too. We are particularly interested in solutions z ( t , ν ) which are “close" to the functions sin t , cos t when t is large. We derive a formula for d c κ ( ν ) / d ν and apply the result to Bessel differential equation, where we introduce new pair of linearly independent solutions replacing the usual pair J ν ( t ) , Y ν ( t ) . We show the concavity of c κ ( ν ) for | ν | 1 2 and also...

On solving systems of differential algebraic equations

Marian Kwapisz (1992)

Applications of Mathematics

In the paper the comparison method is used to prove the convergence of the Picard iterations, the Seidel iterations, as well as some modifications of these methods applied to approximate solution of systems of differential algebraic equations. The both linear and nonlinear comparison equations are emloyed.

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