Shumin Li

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For the solution to ∂ 2 t u(x, t) − △u(x, t) + q(x)u(x, t) = δ(x1)δ ′ (t) and u|t<0 = 0, we consider an inverse problem of determining q(x), x ∈ Ω from data f = u|S T and g = ∂u ∂ν T > 0. For suitable T > 0, we prove an L 2 (Ω)-size estimation of q: q L 2 (Ω) ≤ C n f H 1 (S T) + g L 2 (S T) o , provided that q satisfies a priori uniform boundedness(More)
Let u = u(q) satisfy a hyperbolic equation with impulsive input: ∂ 2 t u(x, t) − u(x, t) + q(x)u(x, t) = δ(x 1)δ (t) and let u| t<0 = 0. Then we consider an inverse problem of determining q(x), x ∈ Ω from data u(q)| S T and (∂u(q)/∂ν) | S T. Here Ω ⊂ {(x 1 ,. .. , x n) ∈ R n |x 1 > 0}, n ≥ 2, is a bounded domain, S T = {(x, t); x ∈ ∂Ω, x1 < t < T + x1}, ν =(More)
By using the bifurcation theory of planar dynamical systems and the method of detection functions , the bifurcations of limit cycles in a Z 2-equivariant planar perturbed Hamiltonian polynomial vector fields of degree 7 are studied. An example of a special Z 2-equivariant vector field having 50 limit cycles with a configuration of compound eyes are given.
The properties and characteristics of voltage-fed AC-DC single-stage PWM converters are reviewed in this paper. This is done with respect to the primary-side DC bus voltage, which is a critical parameter in these types of converters. The operation of two single-stage converters - a forward converter and a full-bridge converter - is examined in detail.(More)
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