Weisheng Qiu

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Let (K,+, ∗) be an odd order presemifield with commutative multiplication. We show that the set of nonzero squares of (K, ∗) is a skewHadamard difference set or a Paley type partial difference set in (K,+) according as q is congruent to 3modulo 4 or q is congruent to 1 modulo 4. Applying this result to the Coulter–Matthews presemifield and the Ding–Yuan(More)
We show that a Lipschitz domain can be expanded solely near a part of its boundary, assuming that the part is enclosed by a piecewise C curve. The expanded domain as well as the extended part are both Lipschitz. We apply this result to prove a regular decomposition of standard vector Sobolev spaces with vanishing traces only on part of the boundary. Another(More)
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