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Tytuł:
Decomposition of Acoustic and Entropy Modes in a Non-Isothermal Gas Affected by a Mass Force
Autorzy:
Leble, S.
Perelomova, A.
Powiązania:
https://bibliotekanauki.pl/articles/177555.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
non-uniform media
acoustics of non-uniform media
hydrodynamic field
initialization of hydrodynamic field
Opis:
Diagnostics and decomposition of atmospheric disturbances in a planar flow are considered in this work. The study examines a situation in which the stationary equilibrium temperature of a gas may depend on the vertical coordinate due to external forces. The relations connecting perturbations are analytically established. These perturbations specify acoustic and entropy modes in an arbitrary stratified gas affected by a constant mass force. The diagnostic relations link acoustic and entropy modes, and they are independent on time. Hence, they provide an ability to decompose the total vector of perturbations into acoustic and non-acoustic (entropy) parts, and to establish the distribution of energy between the sound and entropy modes, uniquely at any instant. The total energy of a flow is hence determined in its parts which are connected with acoustic and entropy modes. The examples presented in this work consider the equilibrium temperature of a gas, which linearly depends on the vertical coordinate. Individual profiles of acoustic and entropy parts for some impulses are illustrated with plots.
Źródło:
Archives of Acoustics; 2018, 43, 3; 497-503
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear phenomena of small-scale sound in a gas with exponential stratification
Autorzy:
Perelomova, A.
Powiązania:
https://bibliotekanauki.pl/articles/1940705.pdf
Data publikacji:
2017
Wydawca:
Politechnika Gdańska
Tematy:
sound propagation
non-uniform media
nonlinear acoustics
Opis:
The nonlinear dynamics of perturbations, quickly varying in space, with comparatively large characteristic wavenumbers k: k > 1/H, is considered. H is the scale of density and pressure reduction in unperturbed gas, as the coordinate increases (H is the so-called height of the uniform equilibrium gas). Coupling nonlinear equations which govern the sound and the entropy mode in a weakly nonlinear flow are derived. They describe the dynamics of the gas in the leading order, with an accuracy up to the terms k(H)-1. In the field of the dominative sound mode, other induced modes contain parts which propagate approximately with their own linear speeds and the speed of the dominative mode. The scheme of successive approximations of nonlinear links between perturbations in the progressive mode is established. The numerical calculations for some kinds of impulses confirm the theory.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2017, 21, 2; 135-147
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Relationship between thermal and ultrasound fields in breast tissue in vivo
Autorzy:
Gambin, B.
Kruglenko, E.
Wójcik, J.
Powiązania:
https://bibliotekanauki.pl/articles/332806.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
backscattered ultrasonic signal
non-uniform temperature field
Opis:
The study shows the direct relationship between the temperature field and the parallel changes that are taking place in backscattered ultrasonic signals from the breast tissue in vivo when heated to the temperature of approximately 42 deg. C. The non-uniform temperature field inside the heating tissue was determined by the numerical model using FEM. It is shown that the spatial distribution of intensities of the backscattered signals coincides with the temperature distribution field predicted by the numerical model in some areas. The result indicates the possibility of the indirect measurement of the temperature rise in the breast tissue in vivo by measuring the intensity variations of the ultrasound echo.
Źródło:
Hydroacoustics; 2015, 18; 53-58
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Standing Waves in One-Dimensional Resonator Containing an Ideal Isothermal Gas Affected by the Constant Mass Force
Autorzy:
Perelomova, A.
Powiązania:
https://bibliotekanauki.pl/articles/177416.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
acoustic resonator
non-uniform media
standing waves
Opis:
The study is devoted to standing acoustic waves in one-dimensional planar resonator which containing an ideal gas. A gas is affected by the constant mass force. Two types of physically justified boundary conditions are considered: zero velocity or zero excess pressure at both boundaries. The variety of nodal and antinodal points is determined. The conclusion is that the nodes of pressure and antinodes of velocity do not longer coincide, as well as antinodes of pressure and nodes of velocity. The entropy mode may contribute to the total field in a resonator. It is no longer isobaric, in contrast to the case when the external force is absent. Examples of perturbations inherent to the entropy mode in the volume of a resonator are discussed.
Źródło:
Archives of Acoustics; 2017, 42, 2; 263-271
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An approach to free vibration analysis of axially graded beams
Autorzy:
Kukla, S.
Rychlewska, J.
Powiązania:
https://bibliotekanauki.pl/articles/281723.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
axially graded beam
non-uniform beam
free vibration
Opis:
In this study, the solution to the free vibration problem of axially graded beams with a non-uniform cross-section has been presented. The proposed approach relies on replacing functions characterizing functionally graded beams by piecewise exponential functions. The frequency equation has been derived for axially graded beams divided into an arbitrary number of subintervals. Numerical examples show the influence of the parameters of the functionally graded beams on the free vibration frequencies for different boundary conditions.
Źródło:
Journal of Theoretical and Applied Mechanics; 2016, 54, 3; 859-870
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New Synchronization Method for Transmission Systems with Variable Length of Bits
Autorzy:
Godek, J.
Golański, R.
Kołodziej, J.
Stępień, J.
Powiązania:
https://bibliotekanauki.pl/articles/226590.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
delta modulation
adaptation
non-uniform sampling
synchronization
codec
Opis:
Based on the Spartan 3E evaluation module, a flexible platform for the implementation of different algorithms for A/D conversion was developed. The aim of presented work was to improve the concept of the sampling rate adaptation to the input signal rate of change in terms of practical issues including synchronization of delta codecs. The new, original synchronization method, useful in systems dedicated for transmission of variable duration of bits was proposed and experimentally verified. Performed measures and observations have shown elimination of the synchronization lose phenomenon.
Źródło:
International Journal of Electronics and Telecommunications; 2015, 61, 1; 31-36
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Transformation of Long Gravitational Waves in a Region of Variable Water Depth: a Comparison of Theory and Experiment
Autorzy:
Szmidt, K.
Powiązania:
https://bibliotekanauki.pl/articles/241424.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
shallow water
nonlinear waves
non-uniform water depth
Opis:
The paper describes investigations on transformation of long gravitational waves in water of variable depth with reflection of the waves from a shelf barrier. In the model considered, a long water wave arrives from an area of constant water depth to an area of constant, smaller water depth, where it reflects at a vertical wall. The analysis is confined to a finite fluid domain, relevant to experimental investigations in a laboratory flume. In theoretical analysis of the phenomenon, we follow a non-linear shallow water approximation to the problem considered. The fundamental equations of fluid motion are derived with the help of a standard variational procedure in a material system of coordinates. The equations proved to be a reasonable approximation to a description of the long waves propagating in fluid with small variation of its depth. In the discussed case of reflection of such waves from a vertical barrier, however, the motion of the fluid is more complicated and therefore the long water wave theory does not deliver as good results as in the case of pure propagation of the waves. The primary objective of this paper is thus to compare the theoretical solution proposed with data obtained in experiments, and to answer the question about accuracy and applicability of the theoretical model in the description of the problem investigated.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2007, 54, 2; 137-158
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low-Complexity Non-uniform Constellation Demapping Algorithm for Broadcasting System
Autorzy:
Wang, Chen
Wang, Fang
Li, Mingqi
Tian, Jinfeng
Powiązania:
https://bibliotekanauki.pl/articles/226497.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
non-uniform constellation
soft demapping
complexity
QAM
NGB-W
Opis:
This paper presents a novel low-complexity soft demapping algorithm for two-dimensional non-uniform spaced constellations (2D-NUCs) and massive order one-dimensional NUCs (1D-NUCs). NUCs have been implemented in a wide range of new broadcasting systems to approach the Shannon limit further, such as DVB-NGH, ATSC 3.0 and NGB-W. However, the soft demapping complexity is extreme due to the substantial distance calculations. In the proposed scheme, the demapping process is classified into four cases based on different quadrants. To deal with the complexity problem, four groups of reduced subsets in terms of the quadrant for each bit are separately calculated and stored in advance. Analysis and simulation prove that the proposed demapper only introduces a small penalty under 0.02dB with respect to Max-Log-MAP demapper, whereas a significant complexity reduction ranging from 68.75% to 88.54% is obtained.
Źródło:
International Journal of Electronics and Telecommunications; 2019, 65, 3; 413-420
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimum design of non-uniform symmetrical linear antenna arrays using a novel modified invasive weeds optimization
Autorzy:
Kenane, E.
Djahli, F.
Powiązania:
https://bibliotekanauki.pl/articles/140370.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
invasive weeds optimization
non uniform linear array
optimization
synthesis
Opis:
This paper presents a new modified method for the synthesis of non-uniform linear antenna arrays. Based on the recently developed invasive weeds optimization technique (IWO), the modified invasive weeds optimization method (MIWO) uses the mutation process for the calculation of standard deviation (SD). Since the good choice of SD is particularly important in such algorithm, MIWO uses new values of this parameter to optimize the spacing between the array elements, which can improve the overall efficiency of the classical IWO method in terms of side lobe level (SLL) suppression and nulls control. Numerical examples are presented and compared to the existing array designs found in the literature, such as ant colony optimization (ACO), particle swarm optimization (PSO), and comprehensive learning PSO (CLPSO). Results show that MIWO method can be a good alternative in the design of non-uniform linear antenna array.
Źródło:
Archives of Electrical Engineering; 2016, 65, 1; 5-18
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Packetizing of non-uniform telemedical data with use of nested report structures
Autorzy:
Augustyniak, P.
Powiązania:
https://bibliotekanauki.pl/articles/333542.pdf
Data publikacji:
2011
Wydawca:
Uniwersytet Śląski. Wydział Informatyki i Nauki o Materiałach. Instytut Informatyki. Zakład Systemów Komputerowych
Tematy:
telemedycyna
niejednolite dane
telemedicine
non-uniform data
adaptive ECG interpretation
Opis:
This paper presents an effective solution of packetizing of non-uniform data for the purpose of reporting in telemedical surveillance systems with adaptive interpretation. Unlike the regular systems, where the data continuity is guaranteed by the common reporting interval and unified report content, the adaptive systems must implement a reservation procedure in order to proper data delivery, accordingly to sampling rates set individually for each of the diagnostic parameters. This procedure combines the content of every packet with respect to changes in data flow from particular diagnostic data, caused by time-variable requirements for the update rate of their time series. Our approach postulates appending to the information structure of two auxiliary data attributes, the validity period and the priority. The proposed solution was implemented and tested in a prototype cardiology-oriented monitor using two alternative reporting modes following the monitoring requisites. In immediate mode diagnostic packets are transmitted immediately accordingly to the time requirements, what allows the telediagnostic system to respond in short time in case of emergency. In delayed mode the transmission is deferred until packets are entirely filled with valid data, what limits the usage of data carrier for long-time regular reporting.
Źródło:
Journal of Medical Informatics & Technologies; 2011, 18; 9-17
1642-6037
Pojawia się w:
Journal of Medical Informatics & Technologies
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Modified Penetration Model for Copper-Tungsten Shaped Charge Jets with Non-uniform Density Distribution
Autorzy:
Elshenawy, T.
Elbeih, A.
Li, Q. M.
Powiązania:
https://bibliotekanauki.pl/articles/358894.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
shaped charge
jet penetration
virtual origin
non-uniform density distribution
Opis:
The penetration of a shaped charge jet with non-uniform density distribution was studied. The virtual origin model, which assumes a constant jet density, was modified to include the situation where the jet density deficit/reduction of an un-sintered copper-tungsten powder jet causes a non-uniform jet density distribution. A relation between the relative density ratio and the normalised jet velocity is proposed, based on which an analytical solution of the modified virtual origin model is obtained. The validity of the modified virtual origin model was demonstrated by its largely improved prediction in comparison with experimental and numerical results. It showed that the density reduction term reduces the penetration depth by 16.58% for an un-sintered copper-tungsten powder jet.
Źródło:
Central European Journal of Energetic Materials; 2016, 13, 4; 927-943
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesizing Non-Uniformly Excited Antenna Arrays Using Tiled Subarray Blocks
Autorzy:
Mohammed, Jafar Ramadhan
Powiązania:
https://bibliotekanauki.pl/articles/27312954.pdf
Data publikacji:
2023
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
antenna arrays
non-uniform amplitudes
performance optimization
tiled subarray blocks
Opis:
Conventionally, non-uniformly excited antenna arrays are synthesized by independently determining the excitation amplitude and phase of each single element. Such an approach is considered to be the most expensive and complex design method available. In this paper, the tilling technique is harnessed to synthesize non-uniformly excited antenna arrays. To apply this technique, the array elements are first divided into different subarray shapes, such as rectangles or squares known as tiles. The use of rectangular tile blocks instead of a single element architecture greatly simplifies the array design process and reduces array complexity. Next, the problem concerned with synthesizing sub-arrays comprising rectangular tile blocks is formulated and solved by using horizontal and vertical orientations of tiles having different shapes and sizes, and their larger integer expansions. The third approach to tiled design is a mixture of both previous tile architectures. A genetic algorithm is used to design such tiled arrays offering optimum sidelobe levels, beam width, directivity and taper efficiency. Simulation results demonstrated the effectiveness of the proposed tiled arrays.
Źródło:
Journal of Telecommunications and Information Technology; 2023, 4; 25--29
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Local scour in non-uniform bed material below a horizontal solid apron
Autorzy:
Zawadzki, P.
Błażejewski, R.
Powiązania:
https://bibliotekanauki.pl/articles/240972.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
two-dimensional mathematical model
local scour
horizontal solid
non-uniform bed material
Opis:
A two-dimensional mathematical model of local scour in non-uniform non-cohesive soil below a horizontal solid apron is presented. The model parameters were identified on the basis of own experimental laboratory data. Verification of the model, accomplished using other laboratory data, showed fairly good conformity, however, additional verification under field conditions is needed.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2001, 48, 1; 3-17
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Use of Combinatorial Methods for Sound Scanning of Objects
Autorzy:
Tsmot, I.
Riznyk, O.
Rabyk, V.
Powiązania:
https://bibliotekanauki.pl/articles/411064.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Oddział w Lublinie PAN
Tematy:
ideal ring bundle
non-uniform structure
sound diagnostic
sound generator
sound scanning
Opis:
In article considers application of combinatorial methods for research of sound images scan by the medium of integer sequences – ideal ring bundles as comfortable mathematical models for synthesis and optimization of systems with non-uniform structure. By using combinatorial approaches quality of methods based on the passage of sound signals through the tissues can be significantly improved. Studies show that the use of integer sequences based on the ideal ring bundles in information conversion tasks ensures simplicity of hardware application.
Źródło:
ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes; 2018, 7, 3; 59-62
2084-5715
Pojawia się w:
ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-uniform illumination correction based on the retinex theory in digital image correlation measurement method
Autorzy:
Gu, G.
She, B.
Xu, G.
Xu, X.
Powiązania:
https://bibliotekanauki.pl/articles/173506.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
digital image correlation (DIC)
non-uniform illumination correction
retinex theory
deformation measurement
Opis:
Digital image correlation is a well-known optical measurement method for full-field deformation and strain measurements. The quality of speckle images used in digital image correlation calculation can directly affect the measurement accuracy of digital image correlation. In most practical measurement circumstances, a uniform illumination environment is usually required to illuminate the detected object in order to capture speckle images upon different deformed states with uniform background intensity. However, the tested object becomes so large that the adopted light source cannot cover all the interested area with uniform illumination, and the speckle images acquired by CCD camera may have non-uniform background intensity distributions. In this paper, the influence of non-uniform illumination is first analyzed in detail by means of a comparison of experimental results of digital image correlation using speckle patterns with both uniform and non-uniform intensity distributions. Then, a new correctional method based on the combination of the basic retinex theory and the illumination formulae of a point light source is proposed. Finally, a real experiment with non-uniform illumination is implemented to verify the effectiveness of this method.
Źródło:
Optica Applicata; 2017, 47, 2; 199-208
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 49

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