220 research outputs found
Multi-Elliptical Geometry of Scatterers in Modeling Propagation Effect at Receiver
In the proposed chapter, the authors present a geometric-statistical propagation model that defines three groups of received signal components, i.e., direct path, delayed scattering, and local scattering components. The multi-elliptical propagation model, which represents the geometry of scatterer locations, is the basis for determining the delayed components. For the generation of the local components, a statistical distribution is used. The basis for this model is a power angular spectrum (PAS) of the received signal, which is closely related to a type of propagation environment and transmitter-receiver spatial positions. Therefore, we have an opportunity to evaluate the influence of the environment type and an object motion direction on the basic characteristics such as envelope distribution, PAS, autocorrelation function, and spectral power density. The multi-elliptical model considers the propagation phenomena occurring in the azimuth plane. In the chapter, we will also show the 3D extension of modeling effects of propagation phenomena
Interference in Multi-beam Antenna System of 5G Network
Massive multiple-input-multiple-output (MIMO) and beamforming are key technologies, which significantly influence on increasing effectiveness of emerging fifth-generation (5G) wireless communication systems, especially mobile-cellular networks. In this case, the increasing effectiveness is understood mainly as the growth of network capacity resulting from better diversification of radio resources due to their spatial multiplexing in macro- and micro-cells. However, using the narrow beams in lieu of the hitherto used cell-sector brings occurring interference between the neighboring beams in the massive-MIMO antenna system, especially, when they utilize the same frequency channel. An analysis of this effect is the aim of this paper. In this case, it is based on simulation studies, where a multi-elliptical propagation model and standard 3GPP model are used. We present the impact of direction and width of the neighboring beams of 5G new radio gNodeB base station equipped with the multi-beam antenna system on the interference level between these beams. The simulations are carried out for line-of-sight (LOS) and non-LOS conditions of a typical urban environment
Estimation of the Reception Angle Distribution Based on the Power Delay Spectrum or Profile
The paper presents an estimation of the reception angle distribution based on temporal characteristics such as the power delay spectrum (PDS) or power delay profile (PDP). Here, we focus on such wireless environment, where the propagation phenomenon predominates in azimuth plane. As a basis to determine probability density function (PDF) of the angle of arrival (AOA), a geometrical channel model (GCM) in form of the multielliptical model for delayed scattering components and the von Mises’ PDF for local scattering components are used. Therefore, this estimator is called the distribution based on multielliptical model (DBMM). The parameters of GCM are defined on the basis of the PDS or PDP and the relative position of the transmitter and the receiver. In contrast to the previously known statistical models, DBMM ensures the estimation PDF of AOA by using the temporal characteristics of the channel for differing propagation conditions. Based on the results of measurements taken from the literature, DBMM verification, assessment of accuracy, and comparison with other models are shown. The results of comparison show that DBMM is the only model that provides the smallest least-squares error for different environments
Methodology of Testing Shot Blasting Machines in Industrial Conditions
Shot blasting machines are widely used for automated surface treatment and finishing of castings. In shot blasting processes the stream of shots is generated and shaped by blasting turbines, making up a kinetic and dynamic system comprising a separating rotor, an adapting sleeve and a propelling rotor provided with blades. The shot blasting performance- i.e. the quality of shot treated surfaces depends on the actual design and operational parameters of the unit whilst the values of relevant parameters are associated with the geometry of turbine components and the level of its integration with the separator system. The circulation of the blasting medium becomes the integrating factor of the process line, starting from the hopper, through the propeller turbine, casting treatment, separation of contaminated abrasive mixture, to its recycling and reuse.Inferior quality of the abrasive agent (shot) and insufficient purity of the abrasive mixture are responsible for low effectiveness of shot blasting. However, most practitioners fail to fully recognise the importance of proper diagnostics of the shot blasting process in industrial conditions. The wearing of major machine components and of the blasting agent and quality of shot treated surfaces are often misinterpreted, hence the need to take into account all factors involved in the process within the frame of a comprehensive methodology.This paper is an attempt to formulate and apply the available testing methods to the engineering practice in industrial conditions
Gravitational wave background from binary systems
Basic aspects of the background of gravitational waves and its mathematical
characterization are reviewed. The spectral energy density parameter
, commonly used as a quantifier of the background, is derived for an
ensemble of many identical sources emitting at different times and locations.
For such an ensemble, is generalized to account for the duration of
the signals and of the observation, so that one can distinguish the resolvable
and unresolvable parts of the background. The unresolvable part, often called
confusion noise or stochastic background, is made by signals that cannot be
either individually identified or subtracted out of the data. To account for
the resolvability of the background, the overlap function is introduced. This
function is a generalization of the duty cycle, which has been commonly used in
the literature, in some cases leading to incorrect results. The spectra
produced by binary systems (stellar binaries and massive black hole binaries)
are presented over the frequencies of all existing and planned detectors. A
semi-analytical formula for is derived in the case of stellar
binaries (containing white dwarfs, neutron stars or stellar-mass black holes).
Besides a realistic expectation of the level of background, upper and lower
limits are given, to account for the uncertainties in some astrophysical
parameters such as binary coalescence rates. One interesting result concerns
all current and planned ground-based detectors (including the Einstein
Telescope). In their frequency range, the background of binaries is resolvable
and only sporadically present. In other words, there is no stochastic
background of binaries for ground-based detectors.Comment: 30 pages, 16 figure
The formation of the double neutron star pulsar J0737--3039
We find that the orbital period (2.4 hours), eccentricity (0.09), dipole
magnetic field strength (6.9 x 10^9 Gauss) and spin period (22 ms) of the new
highly relativistic double neutron star system PSR J0737-3039 can all be
consistently explained if this system originated from a close helium star plus
neutron star binary (HeS-NS) in which at the onset of the evolution the helium
star had a mass in the range 4.0 to 6.5 M_sun and an orbital period in the
range 0.1 to 0.2 days. Such systems are the post-Common-Envelope remnants of
wide Be/X-ray binaries (orbital period ~ 100 to 1000 days) which consist of a
normal hydrogen-rich star with a mass in the range 10 - 20 M_sun and a neutron
star. The close HeS-NS progenitor system went through a phase of mass transfer
by Roche-lobe overflow at a high rate lasting a few times 10^4 years; assuming
Eddington-limited disk accretion onto the neutron star this star was spun up to
its present rapid spin rate. At the moment of the second supernova explosion
the He star had a mass in the range 2.3 to 3.3 M_sun and in order to obtain the
present orbital parameters of PSR J0737-3039 a kick velocity in the range 70 -
230 km/s must have been imparted to the second neutron star at its birth.Comment: accepted by MNRA
On the orbital and physical parameters of the HDE 226868/Cygnus X-1 binary system
In this paper we explore the consequences of the recent determination of the
mass m=(8.7 +/- 0.8)M_Sun of Cygnus X-1, obtained from the Quasi-Periodic
Oscillation (QPO)-photon index correlation scaling, on the orbital and physical
properties of the binary system HDE 226868/Cygnus X-1. By using such a result
and the latest spectroscopic optical data of the HDE 226868 supergiant star we
get M=(24 +/- 5)M_Sun for its mass. It turns out that deviations from the third
Kepler law significant at more than 1-sigma level would occur if the
inclination i of the system's orbital plane to the plane of the sky falls
outside the range 41-56 deg: such deviations cannot be due to the first
post-Newtonian (1PN) correction to the orbital period because of its smallness;
interpreted in the framework of the Newtonian theory of gravitation as due to
the stellar quadrupole mass moment Q, they are unphysical because Q would take
unreasonably large values. By conservatively assuming that the third Kepler law
is an adequate model for the orbital period we obtain i=(48 +/- 7) deg which
yields for the relative semimajor axis a=(42 +/- 9)R_Sun. Our estimate for the
Roche's lobe of HDE 226868 is r_M = (21 +/- 6)R_Sun.Comment: Latex2e, 7 pages, 1 table, 4 figures. To appear in ApSS (Astrophysics
and Space Science
EEG Correlates of Attention Concentration in Successful Amateur Boxers
Parameters of EEG activities that could be related to a better attention concentration were
compared in two groups of young men, one of which included adequately coached amateur
boxers and another consisted of students that were not involved in boxing. The EEG signals
were registered from the Cz point in accordance with the 10-20 system; the theta/beta and
theta/sensorimotor rhythm (SMR) ratios proved to be especially important for purposes of
analysis. Research media included a FlexComp Infinity coder and an EEG-Z sensor with an
automatic impedance function. The results were evaluated by means of BioGraph Infinity.
The obtained results allow us to conclude that adequately coached amateur boxers who are
successful achieve lower theta/beta ratio and theta/SMR ratios than control group students
not involved in boxing. One can suggest this is due to the better attention concentration in the
boxers (despite posible head injuries) compared to the control group.Ми порівнювали показники ЕЕГ-активності, які могли мати
відношення до кращої концентрації уваги, в двох групах
молодих чоловіків. Одна з груп складалася з боксерівлюбителів із високими спортивними показниками, а друга –
із студентів-спортсменів, які не займалися боксом. ЕЕГсигнали відводилися від локусу Cz (відповідно системі
10–20); особливу увагу при аналізі приділяли відношенням
потужностей тета/бета та тета/сенсомоторного (СМР)
ритмів. До комплексу апаратури входили кодер FlexComp Infinity та сенсор EEG-Z із функцією автоматичного контролю
імпедансу. Результати оцінювали за допомогою програми
„BioGrapf Infinity”. Отримані результати дозволяють дійти
висновку, що в адекватно тренованих боксерів-любителів
(котрі досягали високих результатів на змаганнях) значення
відношень тета/бета та тета/СМР у середньому є вищими,
ніж такі у студентів з іншою спортивною спеціалізацією
(група контролю). Незважаючи на можливі наслідки
неминучих травм голови, для студентів-боксерів, вірогідно,
є характерною краща концентрація сенсомоторної уваги,
ніж для суб’єктів групи контролю
Black hole mass estimation from X-ray variability measurements in AGN
We propose a new method of estimation of the black hole masses in AGN based
on the normalized excess variance, sigma_{nxs}^2. We derive a relation between
sigma_{nxs}^2, the length of the observation, T, the light curve bin size,
Delta t, and the black hole mass, assuming that (i) the power spectrum above
the high frequency break, f_{bf}, has a slope of -2, (ii) the high frequency
break scales with black hole mass, (iii) the power spectrum amplitude (in
'frequency x power' space) is universal and (iv) sigma_{nxs}^2 is calculated
from observations of length T < 1/f_{bf}. Values of black hole masses in AGN
obtained with this method are consistent with estimates based on other
techniques such as reverberation mapping or the Mbh-stellar velocity dispersion
relation. The method is formally equivalent to methods based on power spectrum
scaling with mass but the use of the normalized excess variance has the big
advantage of being applicable to relatively low quality data.Comment: 5 pages, 1 figure, 1 table, accepted for publication in MNRAS Letter.
Added minor change on page 5 - corrected mistake (1/T 1/T > nu
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