Search results for "Operator"

HyperWall: A Hypervisor for Detection and Prevention of Malicious Communication

2020

Malicious programs vary widely in their functionality, from key-logging to disk encryption. However, most malicious programs communicate with their operators, thus revealing themselves to various security tools. The security tools incorporated within an operating system are vulnerable to attacks due to the large attack surface of the operating system kernel and modules. We present a kernel module that demonstrates how kernel-mode access can be used to bypass any security mechanism that is implemented in kernel-mode. External security tools, like firewalls, lack important information about the origin of the intercepted packets, thus their filtering policy is usually insufficient to prevent c…

On the continuous and discontinuous maximal operators

2018

Abstract In the first part of this paper we study the regularity properties of a wide class of maximal operators. These results are used to show that the spherical maximal operator is continuous W 1 , p ( R n ) ↦ W 1 , p ( R n ) , when p > n n − 1 . Other given applications include fractional maximal operators and maximal singular integrals. On the other hand, we show that the restricted Hardy–Littlewood maximal operator M λ , where the supremum is taken over the cubes with radii greater than λ > 0 , is bounded from L p ( R n ) to W 1 , p ( R n ) but discontinuous.

Three solutions for a two-point boundary value problem with the prescribed mean curvature equation

2015

The existence of at least three classical solutions for a parametric ordinary Dirichlet problem involving the mean curvature operator are established. In particular, a variational approach is proposed and the main results are obtained simply requiring the sublinearity at zero of the considered nonlinearity.

Better numerical approximation by Durrmeyer type operators

2018

The main object of this paper is to construct new Durrmeyer type operators which have better features than the classical one. Some results concerning the rate of convergence and asymptotic formulas of the new operator are given. Finally, the theoretical results are analyzed by numerical examples.

Estimates for the differences of positive linear operators and their derivatives

2019

The present paper deals with the estimate of the differences of certain positive linear operators and their derivatives. Oxur approach involves operators defined on bounded intervals, as Bernstein operators, Kantorovich operators, genuine Bernstein-Durrmeyer operators, and Durrmeyer operators with Jacobi weights. The estimates in quantitative form are given in terms of the first modulus of continuity. In order to analyze the theoretical results in the last section, we consider some numerical examples.

Frames and weak frames for unbounded operators

2020

In 2012 G\u{a}vru\c{t}a introduced the notions of $K$-frame and of atomic system for a linear bounded operator $K$ in a Hilbert space $\mathcal{H}$, in order to decompose its range $\mathcal{R}(K)$ with a frame-like expansion. In this article we revisit these concepts for an unbounded and densely defined operator $A:\mathcal{D}(A)\to\mathcal{H}$ in two different ways. In one case we consider a non-Bessel sequence where the coefficient sequence depends continuously on $f\in\mathcal{D}(A)$ with respect to the norm of $\mathcal{H}$. In the other case we consider a Bessel sequence and the coefficient sequence depends continuously on $f\in\mathcal{D}(A)$ with respect to the graph norm of $A$.

Hilbert space operators with two-isometric dilations

2021

A bounded linear Hilbert space operator $S$ is said to be a $2$-isometry if the operator $S$ and its adjoint $S^*$ satisfy the relation $S^{*2}S^{2} - 2 S^{*}S + I = 0$. In this paper, we study Hilbert space operators having liftings or dilations to $2$-isometries. The adjoint of an operator which admits such liftings is characterized as the restriction of a backward shift on a Hilbert space of vector-valued analytic functions. These results are applied to concave operators (i.e., operators $S$ such that $S^{*2}S^{2} - 2 S^{*}S + I \le 0$) and to operators similar to contractions or isometries. Two types of liftings to $2$-isometries, as well as the extensions induced by them, are construct…

Le ragioni e il cuore. L’abuso e il lavoro di cura.

2008

Tipologie di parenting disfunzionale e multiplo: un’indagine nei contesti extrafamiliari

2009

CONTESTO La famiglia d’origine intesa come luogo di cura e di sostegno, affettivo e materiale, a volte può presentare una significativa inadeguatezza delle relazioni o, ancora, episodi di maltrattamento o abuso. Situazioni, queste, per le quali è importante che gli adulti assolvano il dovere di tutelare l’infanzia a rischio, garantendo ambiti protettivi (Petrillo, 2005). I progetti di tutela dell’infanzia, infatti, previo allontanamento del minore dalla famiglia, prevedono l’inserimento dello stesso in comunità atte a garantire non solo l’assistenza quotidiana dell’utenza ma anche l’opportunità di rivedere la propria storia personale . OBIETTIVI Analisi delle tipologie di parenting stabilit…

Metabolic signatures across the full spectrum of non-alcoholic fatty liver disease.

2022

Funder: European Commission