220 research outputs found

    Multi-Elliptical Geometry of Scatterers in Modeling Propagation Effect at Receiver

    Get PDF
    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

    Get PDF
    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

    Get PDF
    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

    Get PDF
    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

    Full text link
    Basic aspects of the background of gravitational waves and its mathematical characterization are reviewed. The spectral energy density parameter Ω(f)\Omega(f), 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, Ω(f)\Omega(f) 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 Ω(f)\Omega(f) 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

    Full text link
    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

    Full text link
    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

    No full text
    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

    Full text link
    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
    corecore