3,386 research outputs found
Approaches for the Development of Low-Budget Analyzers of the Spectrum Sensor Networks 2.4–2.5 GHz
In Ukraine, more and more new home and industrial networks are being built with full or partial use of wireless technologies. Over the past few years, such technologies have become the de facto standard. The number of networks is increasing because of their affordability and ease of use, the emergence of industrial roaming systems, a wide range of antenna equipment and permissions fixed at the legislative level. When designing a wireless network, it is not possible to anticipate all the nuances: re-reflection, shading, directionality of the antennas of the receivers, etc., so after the construction of a real system, you need to check it and reduce the impact of negative factors. Spectrum analyzers help solve this problem
Rational Choice of Machining Tools Using Prediction Procedures
Introducing the methods and procedures for predictive analysis into the design process contours of a variety of machining tools (MT) of metal cutting machines is the main aim of this article. A sequence of realization of prediction object (PO) choice as an initial stage of search of perspective designs is offered. Effective in this regard is the "Tree of objectives" apparatus, on the basis of which many ways of improving MT are formed, selecting progressive (reducing the dimension of the problem) at each level of the hierarchy of the constructed graph-tree. The procedure for selecting the prediction method (PM) as a means of generating the forecast data is developed. The task of choosing a method is structured in detail and uses "Information supply"as the main criterion. To this end, assessment scales of choice criteria have been formed, on the basis of which it is possible to evaluate their effectiveness for the PM selection process. The rules forPOcoding are introduced by a three-element information code, including information source classes – static data, expert estimates and patent data. The process of forecasting the MT components by the method of engineering forecasting on the basis of a representative patent fund is realized. The General Definition Table has been built (GDT "Machining tools") and estimates of the prospects of design solutions have been obtained. A fragment of the database of 3D models of promising MT designs in the integrated computer-aided design KOMPAS-3D is proposed
Quantum Resonances and Regularity Islands in Quantum Maps
We study analytically as well as numerically the dynamics of a quantum map
near a quantum resonance of an order q. The map is embedded into a continuous
unitary transformation generated by a time-independent quasi-Hamiltonian. Such
a Hamiltonian generates at the very point of the resonance a local gauge
transformation described the unitary unimodular group SU(q). The resonant
energy growth of is attributed to the zero Liouville eigenmodes of the
generator in the adjoint representation of the group while the non-zero modes
yield saturating with time contribution. In a vicinity of a given resonance,
the quasi-Hamiltonian is then found in the form of power expansion with respect
to the detuning from the resonance. The problem is related in this way to the
motion along a circle in a (q^2-1)-component inhomogeneous "magnetic" field of
a quantum particle with intrinsic degrees of freedom described by the SU(q)
group. This motion is in parallel with the classical phase oscillations near a
non-linear resonance. The most important role is played by the resonances with
the orders much smaller than the typical localization length, q << l. Such
resonances master for exponentially long though finite times the motion in some
domains around them. Explicit analytical solution is possible for a few lowest
and strongest resonances.Comment: 28 pages (LaTeX), 11 ps figures, submitted to PR
Integrable quadratic Hamiltonians on so(4) and so(3,1)
We investigate a special class of quadratic Hamiltonians on so(4) and so(3,1)
and describe Hamiltonians that have additional polynomial integrals. One of the
main results is a new integrable case with an integral of sixth degree.Comment: 16 page
How Well a Chaotic Quantum System Can Retain Memory of Its Initial State?
In classical mechanics the local exponential instability effaces the memory
of initial conditions and leads to practical irreversibility. In striking
contrast, quantum mechanics appears to exhibit strong memory of the initial
state. We relate the latter fact to the low (at most linear) rate with which
the system's Wigner function gets during evolution more and more complicated
structure and establish existence of a critical strength of external influence
below which such a memory still survives.Comment: 5 pages, 4 figure
Analysis of Recent Attacks Based on Social Engineering Techniques
This paper attempts to strengthen the pursued research on social engineering (SE) threat identification, and control, by means of the author’s illustrated classification, which includes attack types, determining the degree of possible harm to each types of possible, known attacks, countermeasures by types of threats that leads to loss of personal or corporate confidential information (user id, passwords, closed documentation). Further, this analytical study will become the starting point for deeper, practically oriented and tested research
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