If A is a finite set of cardinality n ≥ 1, 2 is the set of all subsets of A, and S is a nonempty subset of 2, we say that S has the odd-intersection property if there exists a subset N of A such that the cardinality of N ∩S is odd for each S ∈ S. Let OIP (n) denote the set of all subsets of 2 with the odd-intersection property. A nonempty set S of nonempty subsets of A is an obstruction (to the...

We consider the nonconvex problem minimizing the ratio of two quadratic functions over finitely many nonconvex quadratic inequalities. Relying on the homogenization technique we establish a sufficient condition that warrants the attainment of an optimal solution. Our result allows to extend and recover known conditions for some interesting special instances of the problem and to derive further ...

In this paper we answer certain questions posed by V.I. Arnold, namely, we study periods of continued fractions for solutions of quadratic equations in the form x + px = q with integer p and q, p + q ≤ R. Our results concern the average sum of period elements and Gauss–Kuzmin statistics as R → ∞.

Quadratic regularizers are used in nonparametric registration to ensure that the registration problem is well posed and to yield solutions that exhibit certain types of smoothness. Examples of popular quadratic regularizers include the diffusion, elastic, fluid, and curvature regularizers. Two important features of these regularizers are whether they account for coupling of the spatial componen...

In 1997, Lin [1] proposed a dynamic key management scheme using user hierarchical structure. After that, Lee [2] brought to two comments on Lin’s method. In 2002, Lin [3] proposed a more efficient hierarchical key management scheme based on Elliptic Curve. Lin’s efficient scheme solves the weaknesses appearing in Lee’s scheme in [1]. In this paper, we further use Quadratic Residues (Q.R.) theor...

In this paper we discuss problems with quadratic objective function, one or two quadratic constraints, and, possibly, some additional linear constraints. In particular, we consider cases where the Hessian of the quadratic functions are simultaneously diagonalizable, so that the objective and constraint functions can all be converted into separable functions. We give conditions under which a sim...