The laplacian operator applied to the coordinates of a manifold provides the mean curvature vector. Manipulating the metric of the manifold or interpreting its coordinates in various ways provide useful tools for shape and image processing and representation. We will review some of these tools focusing on scale invariant geometry, curvature flow with respect to an embedding of the image manifold in a high dimensional space, and object segmentation by active contours defined via the shape laplacian...

We consider the problem of minimizing ${\int }_0^{\ell }\sqrt{{\xi }^2+K^2\left(s\right)}\mathrm{d}s$ ∫ 0 ℓ ξ 2 + K 2 ( s )   d s for a planar curve having fixed initial and final positions and directions. The total lengthℓ is free. Here s is the arclength parameter, K(s) is the curvature of the curve and ξ > 0 is a fixed constant. This problem comes from a model of geometry of vision due to Petitot, Citti and Sarti. We study existence of local and global minimizers for this problem. We prove that if for a certain choice of boundary conditions there...

We explore the borderline between decidability and undecidability of the following question: “Let C be a class of codes. Given a machine $𝔐$ of type X, is it decidable whether the language $L\left(𝔐\right)$ lies in C or not?” for codes in general, ω-codes, codes of finite and bounded deciphering delay, prefix, suffix and bi(pre)fix codes, and for finite automata equipped with different versions of push-down stores and counters.

In the last decade, formal methods have proved their interest when analyzing security protocols. Security protocols require in particular to reason about the attacker knowledge. Two standard notions are often considered in formal approaches: deducibility and indistinguishability relations. The first notion states whether an attacker can learn the value of a secret, while the latter states whether an attacker can notice some difference between protocol runs with different values of the secret. Several...

In the last decade, formal methods have proved their interest when analyzing security protocols. Security protocols require in particular to reason about the attacker knowledge. Two standard notions are often considered in formal approaches: deducibility and indistinguishability relations. The first notion states whether an attacker can learn the value of a secret, while the latter states whether an attacker can notice some difference between protocol runs with different values of the secret. Several...

The paper investigates the possibility of decomposing vibration signals into deterministic and nondeterministic parts, based on the Wold theorem. A short description of the theory of adaptive filters is presented. When an adaptive filter uses the delayed version of the input signal as the reference signal, it is possible to divide the signal into a deterministic (gear and shaft related) part and a nondeterministic (noise and rolling bearings) part. The idea of the self-adaptive filter (in the literature...

A method of geometrical characterization of multidimensional data sets, including construction of the convex hull of the data and calculation of the volume of the convex hull, is described. This technique, together with the concept of minimum convex hull volume, can be used for detection of influential points or outliers in multiple linear regression. An approximation to the true concept is achieved by ordering the data into a linear sequence such that the volume of the convex hull of the first...

A movement analysis of objects contained in visual scenes can be performed by means of linear multidimensional filters, which have already been analyzed in the past. While the soundness of the results was convincing, interest in those systems declined due to the limited computational power of contemporary computers. Recent advances in design and implementation of integrated circuits and hardware architectures allow realizing velocity filters if the n-D system is carefully adapted to the analyzed...

Here, we present determinants of some square matrices of field elements. First, the determinat of 2 * 2 matrix is shown. Secondly, the determinants of zero matrix and unit matrix are shown, which are equal to 0 in the field and 1 in the field respectively. Thirdly, the determinant of diagonal matrix is shown, which is a product of all diagonal elements of the matrix. At the end, we prove that the determinant of a matrix is the same as the determinant of its transpose.

Let A, D, K, k ∈ ℕ with D square free and 2 ∤ k,B = 1,2 or 4 and ${\mu }_i\in -1,1(i=1,2)$, and let $h(-2^{1-e}D)(e=0or1)$ denote the class number of the imaginary quadratic field $\mathbb{Q}\left(\surd (-2^{1-e}D)\right)$. In this paper, we give the all-positive integer solutions of the Diophantine equation Ax² + μ₁B = K((Ay² + μ₂B)/K)ⁿ, 2 ∤ n, n > 1 and we prove that if D > 1, then $h(-2^{1-e}D)\equiv 0\left(modn\right)$, where D, and n satisfy $kⁿ-2^{e+1}=Dx²$, x ∈ ℕ, 2 ∤ n, n > 1. The results are valuable for the realization of quadratic field cryptosystem.