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Wyświetlanie 1-15 z 583
Tytuł:
Flexible spectrum use and laws of physics
Autorzy:
Strużak, R.
Powiązania:
https://bibliotekanauki.pl/articles/317656.pdf
Data publikacji:
2013
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
radio frequency spectrum
spectrum management
flexible spectrum use
Opis:
This note refers to flexible-use spectrum rights that would allow the radio frequency spectrum to be traded, aggregated, divided and freely used for a wide range of user-selected services. So far, discussions on that approach have largely focused on economic aspects, without due consideration of physical realizability. We argue here that additional spectrum management rules are required to assure compatible coexistence of radio systems in congested environments.
Źródło:
Telekomunikacja i Techniki Informacyjne; 2013, 3; 67-72
1640-1549
1899-8933
Pojawia się w:
Telekomunikacja i Techniki Informacyjne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectrum management. Part 1
Autorzy:
Strużak, R.
Powiązania:
https://bibliotekanauki.pl/articles/317730.pdf
Data publikacji:
2013
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
spectrum management
radio frequency spectrum resources
Opis:
As preparations for the Year 2000 World Radiocommunication Conference continue in earnest, ITU News will bring you in-depth analyses of what is at stake in the complex radio world. Indeed, how the spectrum/orbit resources are used and managed has a profound impact on society, its prosperity, security, culture, and education. This article takes you back in history on the use, management and regulation of the radio frequency spectrum resources. It then discusses current trends.
Źródło:
Telekomunikacja i Techniki Informacyjne; 2013, 3; 53-57
1640-1549
1899-8933
Pojawia się w:
Telekomunikacja i Techniki Informacyjne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Radio-Frequency Spectrum Management
Autorzy:
Strużak, R.
Tjelta, T.
Borrego, J. P.
Powiązania:
https://bibliotekanauki.pl/articles/308539.pdf
Data publikacji:
2016
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
radio frequency spectrum
spectrum management
wireless system
Opis:
This article review lessons learned from the uses of radio-frequency (RF) spectrum at national and international scales. Its main purpose is to stimulate debate on how to allow new wireless systems to operate, and to reduce the chronic apparent shortage of RF spectrum. The article aims at a better understanding of the mechanisms behind spectrum management and their pertinence to the public interest. The main contributions if the article are: • Considering RF spectrum management as a construct that structures radio services and, at the same time, distributes wealth and power; • Highlighting major doctrines of RF spectrum management; • Promoting spectrum management directly by its users; • Promoting cooperation and transparency. The several parts of the paper include the evolution of spectrum exploitation, and a foreseeable future by taking a closer look at major dilemmas and challenges. The paper ends with general comments and conclusions.
Źródło:
Journal of Telecommunications and Information Technology; 2016, 3; 108-130
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Perturbation of the spectrum οf an essentially selfadjoint operator
Autorzy:
Pokrzywa, Andrzej
Powiązania:
https://bibliotekanauki.pl/articles/1340681.pdf
Data publikacji:
1993
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
crossnorm
spectrum
Opis:
The aim of this paper is to find estimates of the Hausdorff distance between the spectra of two nonselfadjoint operators. The operators considered are assumed to have their imaginary parts in some normed ideal of compact operators. In the case of the classical Schatten ideals the estimates are given explicitly.
Źródło:
Applicationes Mathematicae; 1993-1995, 22, 1; 75-89
1233-7234
Pojawia się w:
Applicationes Mathematicae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the axiomatic theory of spectrum
Autorzy:
Kordula, V.
Müller, V.
Powiązania:
https://bibliotekanauki.pl/articles/1287568.pdf
Data publikacji:
1996
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
axiomatic theory of spectrum
local spectrum
semiregular operators
Opis:
There are a number of spectra studied in the literature which do not fit into the axiomatic theory of Żelazko. This paper is an attempt to give an axiomatic theory for these spectra, which, apart from the usual types of spectra, like one-sided, approximate point or essential spectra, include also the local spectra, the Browder spectrum and various versions of the Apostol spectrum (studied under various names, e.g. regular, semiregular or essentially semiregular).
Źródło:
Studia Mathematica; 1996, 119, 2; 109-128
0039-3223
Pojawia się w:
Studia Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Trends in Use of RF Spectrum
Autorzy:
Strużak, R.
Powiązania:
https://bibliotekanauki.pl/articles/308169.pdf
Data publikacji:
2009
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
radio communication hyperspace
radio frequency spectrum resources
radio regulations
spectrum engineering
spectrum management
Opis:
This paper reviews possible improvements in the use of radio waves for carrying information from an engineering viewpoint. A few new concepts are proposed, which reduce the problem to an arrangement of solids in a multidimensional space.
Źródło:
Journal of Telecommunications and Information Technology; 2009, 4; 95-100
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The importance of FFT and BCS spectrums analysis for diagnosis and prediction of rolling bearing failure
Autorzy:
Nadabaică, D. C.
Nedeff, V.
Radkowski, S.
Mączak, J.
Powiązania:
https://bibliotekanauki.pl/articles/328404.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
FFT spectrum
BCS spectrum
rolling bearings
diagnose
prediction
Opis:
Dynamic equipments, in their vast majority, have rolling bearings in their components. Measurement and analysis of the values of rolling bearings vibration, on time, represent a safe and effective measure for identifying the state of wear of bearings, and to predict the evolution of their technical condition and of the entire equipment. This paper presents the detection of causes which lead to the damage of rolling bearing by using FFT (Fast Fourier Transformation) and BCS (Bearing Condition Signature) spectrums, by measuring its housing vibrations (self-aligning ball bearing, ZKL 1205K type) mounted in a test rig. The results presents the analysis mode of FFT and BCS spectrums in order to obtain beneficial information for the detection of that unbalance caused by loading, of the implemented defect on rolling bearing raceway and of bearing damage mode under the action of these causes.
Źródło:
Diagnostyka; 2013, 14, 4; 3-12
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Spectral Characterizations of Graphs
Autorzy:
Huang, Jing
Li, Shuchao
Powiązania:
https://bibliotekanauki.pl/articles/31341668.pdf
Data publikacji:
2017-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Laplacian spectrum
adjacency spectrum
cospectral graphs
spectral characterization
Opis:
Several matrices can be associated to a graph, such as the adjacency matrix or the Laplacian matrix. The spectrum of these matrices gives some informations about the structure of the graph and the question “Which graphs are determined by their spectrum?” is still a difficult problem in spectral graph theory. Let $ \mathcal{U}_p^{2q} $ be the set of graphs obtained from $ C_p $ by attaching two pendant edges to each of $ q (q \le p) $ vertices on $ C_p $, whereas $ \mathcal{V}_p^{2q} $ the subset of $ \mathcal{U}_p^{2q} $ with odd $p$ and its $q$ vertices of degree 4 being nonadjacent to each other. In this paper, we show that each graph in $ \mathcal{U}_p^{2q} $, $p$ even and its $q$ vertices of degree 4 being consecutive, is determined by its Laplacian spectrum. As well we show that if $G$ is a graph without isolated vertices and adjacency cospectral with the graph in $ \mathcal{V}_p^{p−1} = \{ H \} $, then $ G \cong H $.
Źródło:
Discussiones Mathematicae Graph Theory; 2017, 37, 3; 729-744
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on Noise Attenuation Characteristics of Hydrofoil with Specific Cavitation Number
Autorzy:
Xiaohui, He
Zhongle, Liu
Chao, Yang
Zhiyong, Yuan
Powiązania:
https://bibliotekanauki.pl/articles/31339799.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
sound pressure spectrum
noise
sound power spectrum
numerical prediction
Opis:
In this study, the modified Sauer cavitation model and Kirchhoff-Ffowcs Williams and Hawkings (K-FWH) acoustic model were adopted to numerically simulate the unsteady cavitation flow field and the noise of a three-dimensional NACA66 hydrofoil at a constant cavitation number. The aim of the study is to conduct and analyze the noise performance of a hydrofoil and also determine the characteristics of the sound pressure spectrum, sound power spectrum, and noise changes at different monitoring points. The noise change, sound pressure spectrum, and power spectrum characteristics were estimated at different monitoring points, such as the suction side, pressure side, and tail of the hydrofoil. The noise characteristics and change law of the NACA66 hydrofoil under a constant cavitation number are presented. The results show that hydrofoil cavitation takes on a certain degree of pulsation and periodicity. Under the condition of a constant cavitation number, as the attack angle increases, the cavitation area of the hydrofoil becomes longer and thicker, and the initial position of cavitation moves forward. When the inflow velocity increases, the cavitation noise and the cavitation area change more drastically and have a superposition tendency toward the downstream. The novelty is that the study presents important calculations and analyses regarding the noise performance of a hydrofoil, characteristics of the sound pressure spectrum, and sound power spectrum and noise changes at different monitoring points. The article may be useful for specialists in the field of engineering and physics.
Źródło:
Archives of Acoustics; 2023, 48, 3; 359-372
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Weak invertibility and strong spectrum
Autorzy:
Meyer, Michael J.
Powiązania:
https://bibliotekanauki.pl/articles/1292680.pdf
Data publikacji:
1993
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
radical
norm
spectrum
Opis:
A notion of weak invertibility in a unital associative algebra A and a corresponding notion of strong spectrum of an element of A is defined. It is shown that many relationships between the Jacobson radical, the group of invertibles and the spectrum have analogues relating the strong radical, the set of weakly invertible elements and the strong spectrum. The nonunital case is also discussed. A characterization is given of all (submultiplicative) norms on A in which every modular maximal ideal M ⊆ A is closed.
Źródło:
Studia Mathematica; 1993, 105, 3; 255-269
0039-3223
Pojawia się w:
Studia Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Matrices defined by frames
Autorzy:
Ambroziński, Z.
Rudol, K.
Powiązania:
https://bibliotekanauki.pl/articles/255955.pdf
Data publikacji:
2009
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
frames
operators
spectrum
Opis:
Matrix representations of bounded Hilbert space operators are considered. The matrices in question are defined with respect to frames, rather than bases. The frames, a generalisation of bases, used extensively in applied harmonic analysis, are overcomplete sequences. We consider some properties related to tight frames, where, up to some multiplicative constant, a form of Parseval Identity takes place. We also describe parts of spectra of operators in terms of their matrices.
Źródło:
Opuscula Mathematica; 2009, 29, 4; 365-375
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Graphs with All But Two Eigenvalues In [−2, 0]
Autorzy:
Abreu, Nair
Alencar, Jorge
Brondani, André
de Lima, Leonardo
Oliveira, Carla
Powiązania:
https://bibliotekanauki.pl/articles/31804163.pdf
Data publikacji:
2020-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph spectrum
complete multipartite graph
graph determined by its spectrum
Opis:
The eigenvalues of a graph are those of its adjacency matrix. Recently, Cioabă, Haemers and Vermette characterized all graphs with all but two eigenvalues equal to −2 and 0. In this article, we extend their result by characterizing explicitly all graphs with all but two eigenvalues in the interval [−2, 0]. Also, we determine among them those that are determined by their spectrum.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 2; 379-391
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis and anticancer evaluation of some coumarin and azacoumarin derivatives
Autorzy:
Bakare, Safyah B.
Powiązania:
https://bibliotekanauki.pl/articles/1849302.pdf
Data publikacji:
2021
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
Coumarin
azacoumarin
1H-NMR spectrum
13C-NMR spectrum
anticancer
Opis:
Coumarin and its nitrogen analogue 1-aza coumarin are a class of lactones and lactams, respectively, which are indispensable heterocyclic units to both chemists and biochemists. 1-Aza coumarin derivatives, which ultimately metabolize as the corresponding 8-hydroxy coumarins in the biological system are therefore found to be very good anti-inflammatory, anti-cancer, and analgesic agents. A series of hybrid substituted coumarin and azacoumarin-3-carboxylic acid derivatives (8-methoxycoumarin-3-carboxylic acid (4a), 8-methoxyazacoumarin-3-carboxylic acid (4b), 5-bromo-8-methoxycoumarin-3-carboxylic acid (5a), 5-bromo-8-methoxyazacoumarin-3-carboxylic acid (5b), 2-acetoxy-5-bromo-8-methoxyquinoline-3-carboxylic acid (6), and 5,7-di(phenylazo)-8-methoxycoumarin-3-carboxylic acid (7) were synthesized and structurally proved using spectral and elemental analysis data. Substituted coumarin-3-carboxylic acid (4a and 5a) and Substituted azacoumarin-3-carboxylic acid (4b, 5b and 6) were tested for their in vitro cytotoxic activity against MCF-7 and HepG-2 cell lines.
Źródło:
Polish Journal of Chemical Technology; 2021, 23, 2; 27-34
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 583

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