Temat: propagation - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Waves in elastic materials and structures
Autorzy:: Wesołowski, Z.
Tematy:: wave propagation
discontinuity
reflection and propagation speed; Pokaż więcej
Data publikacji:: 2015
Powiązania:: https://bibliotekanauki.pl/articles/332103.pdf Link otwiera się w nowym oknie
Źródło:: Hydroacoustics; 2015, 18; 167-179
1642-1817
Pojawia się w:: Hydroacoustics
Opis:: The mathematical description of waves propagation in elastic materials and structures is presented. Particularly, the considerations concern the water as a transmission medium for acoustic waves. The following issues are discussed: discontinuity, reflection, and propagation speed, among others.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 2.

Tytuł:: An Empirical Propagation Model for Corridors in Office Buildings
Autorzy:: Kosz, P.
Tematy:: wireless systems
radio wave propagation
propagation model
propagation path loss
indoor environment
test stand; Pokaż więcej
Data publikacji:: 2017
Powiązania:: https://bibliotekanauki.pl/articles/227038.pdf Link otwiera się w nowym oknie
Źródło:: International Journal of Electronics and Telecommunications; 2017, 63, 1; 5-10
2300-1933
Pojawia się w:: International Journal of Electronics and Telecommunications
Opis:: This paper presents an empirical propagation path loss model for corridors in office buildings. The proposed model estimates changeable character of radio signal attenuation, based on a special approach as a combination of the simple free-space model with the author’s model. The measurement stand and measurement scenario are described. The propagation path loss research have been made in corridor for different frequencies in range 30 MHz to 290 MHz. A significant number of measurement results were allowed an analysis of the radio wave propagation conditions in the environment. In general, the propagation path loss increases for each measurement frequencies with length of propagation route. Based on measurement data, the new empirical propagation path loss model was developed. For this purpose, the regression analysis was made. The novelty of this model is that it could be used for estimate propagation path loss in measured environment for different radio wave frequencies. At the end, in order to justification the practical usefulness of described method for estimate a radio wave attenuation, the statistical evaluation was made. Thus, the results of the statistical analysis (ME, SEE and R2 values) are satisfactory for each measured radio wave frequency.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 3.

Tytuł:: Key fault propagation path identification of CNC machine tools based on maximum occurrence probability
Autorzy:: Zhang, Yingzhi
Zhou, Yutong
Yang, Fang
Wang, Zhiqiong
Sun, Mo
Tematy:: fault propagation
CNC machine tools
key fault propagation path
improved Pagerank
fault propagation probability; Pokaż więcej
Data publikacji:: 2023
Powiązania:: https://bibliotekanauki.pl/articles/27312788.pdf Link otwiera się w nowym oknie
Źródło:: Eksploatacja i Niezawodność; 2023, 25, 3; art. no. 169887
1507-2711
Pojawia się w:: Eksploatacja i Niezawodność
Opis:: In order to revise the deviation caused by ignoring the dynamic character of fault propagation in traditional fault propagation path identification methods, a method based on the maximum occurrence probability is proposed to identify the key fault propagation path. Occurrence probability of fault propagation path is defined by dynamic importance, dynamic fault propagation probability and fault rate. Taking the fault information of CNC machine tools whichsubject to Weibull distribution as an example, this method has been proven to be reasonable through comparative analysis. Result shows that the key fault propagation path of CNC machine tools is not unique, but changes with time. Before 1000 hours, key fault propagation path is electrical component (E) to mechanical component (M); after 1000 hours, key fault propagation path is auxiliary component (A) to mechanical component (M). This change should be taken into account when developing maintenance strategies and conducting reliability analysis.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 4.

Tytuł:: The Uncertainty of Noise Composed of Separate Sound Events
Autorzy:: Makarewicz, R.
Gołębiewski, R.
Tematy:: noise propagation; Pokaż więcej
Data publikacji:: 2016
Powiązania:: https://bibliotekanauki.pl/articles/176332.pdf Link otwiera się w nowym oknie
Źródło:: Archives of Acoustics; 2016, 41, 1; 133-138
0137-5075
Pojawia się w:: Archives of Acoustics
Opis:: Transportation noise is a main source of noise pollution. It is assumed that it consists of recognizable noise events which come from moving aircrafts, trains and boats. The noise of an isolated sound event is assessed by the sound exposure level, LAE. Much legislation and many regulations and guidelines employ the A-weighted time-average sound level, LAeq,T, with the time interval T of one hour or longer. LAE measurements enable an approximation of LAeq,T. The key point is the uncertainty of this approximation. It has been shown that an increase in the number of LAE categories brings about a decrease in uncertainty. For illustrative purposes, LAE measurements of aircrafts taking off and landing were carried out.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 5.

Tytuł:: Influence of number of step reactions on flame parameters under quenching conditions
Autorzy:: Gutkowski, A.
Tematy:: flame propagation
quenching diameter
flame propagation velocity
numerical simulation; Pokaż więcej
Data publikacji:: 2011
Powiązania:: https://bibliotekanauki.pl/articles/242109.pdf Link otwiera się w nowym oknie
Źródło:: Journal of KONES; 2011, 18, 2; 153-159
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Opis:: Last decade, construction and using of microscale gas-turbines and internal combustion engines is collecting growing attention. However, the flame propagation limitations impede the development of micro and mesoscale combustion devices. Due to its small scale, increasing effect of flame-wall interaction causes a large heat loss and in consequence flame quenching. Both, fundamental experimental work and numerical simulations are conducted in order to overcome quenching issues. The most basic analysis concerns flame behaviour in small scale devices are premixed flame propagation in narrow tubes. There are two possibilities of flame-flow configurations: flame moving in a stationary mixture and a stationary flame in mowing mixture. These configurations have influence on flame shape, flame propagation velocity and quenching diameter. Most of numerical investigation assumes single-step reaction. It means that for flames propagating in propane-air mixtures C3H8 reacts directly with oxygen and leads to CO2 and H2O. This chemical kinetics mechanism omits existence of CO in reaction zone and in combustion products. Therefore it is interesting to use two-step reactions mechanism and compare the results with those obtained from single-step reaction model. The purpose of this analysis is to find influence of number of reaction steps on flame behaviour under quenching conditions for flames propagating in stationary lean propane-air mixtures. Quenching diameter, flame propagation velocity are determined and analyzed.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 6.

Tytuł:: Modeling the phenomenon of ultrasonic wave propagation in selected fluids using COMSOL - a case study
Autorzy:: Nowak, Konrad W.
Wielkopolan, Agata
Tematy:: ultrasound
modeling of wave propagation
acoustic propagation
fluid
COMSOL; Pokaż więcej
Data publikacji:: 2024
Powiązania:: https://bibliotekanauki.pl/articles/59123627.pdf Link otwiera się w nowym oknie
Źródło:: Technical Sciences / University of Warmia and Mazury in Olsztyn; 2024, 27; 341-356
1505-4675
2083-4527
Pojawia się w:: Technical Sciences / University of Warmia and Mazury in Olsztyn
Opis:: The aim of this study was to model the propagation of acoustic waves with frequencies in the ultrasound range in three selected fluids. Ultrasonic wave propagation in the studied fluids was tested in a laboratory to validate the model. The laboratory tests involved simple measurements of the time of flight of an ultrasonic wave with a frequency of 5 MHz in fluids with different parameters: demineralized water, rapeseed oil, and gelatinized potato starch colloid. In the second part of the study, the COMSOL Multiphysics program was used to develop a model of ultrasonic wave propagation in the same fluids. The model was developed using the Transient analysis type in the Pressure Acoustics application mode of the Acoustics Module. The modeling results were somewhat different from those obtained in laboratory tests; therefore, they did not meet the research assumptions in this stage of research. The limitations of the presented model were discussed. The study demonstrated that medium density was a parameter that exerted the greatest influence on the modeling process.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 7.

Tytuł:: Investigation of the underwater noise produced by ships by means of intensity method
Autorzy:: Kozaczka, E.
Domagalski, J.
Gloza, I.
Tematy:: energy
propagation
hydroacoustics; Pokaż więcej
Data publikacji:: 2010
Powiązania:: https://bibliotekanauki.pl/articles/258726.pdf Link otwiera się w nowym oknie
Źródło:: Polish Maritime Research; 2010, 3; 26-36
1233-2585
Pojawia się w:: Polish Maritime Research
Opis:: This paper presents results of research on spectral structure of underwater noise acoustic field radiated into water by selected ships moving in shallow waters. Underwater acoustic field of ships in motion is associated with acoustic activity of ship mechanisms and equipment under work. Vibration energy radiated by the mechanisms and devices is transmitted by ship structural elements to surrounding water where it is propagated in the form of acoustic waves of a wide frequency band. In this paper are presented results of the research on propagation of energy of acoustic waves in the near fiel, obtained from acoustic pressure measurements by means of two sensors located close to each other.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 8.

Tytuł:: Identification of hydroacoustic wave sources of ship in motion
Autorzy:: Kozaczka, E.
Domagalski, J.
Tematy:: identification
propagation
hydroacoustics; Pokaż więcej
Data publikacji:: 2010
Powiązania:: https://bibliotekanauki.pl/articles/259355.pdf Link otwiera się w nowym oknie
Źródło:: Polish Maritime Research; 2010, 4; 64-71
1233-2585
Pojawia się w:: Polish Maritime Research
Opis:: This paper deals with results of identification tests of acoustic field spectrum of underwater noise generated by ship in motion. The field is connected with acoustic activity of ship mechanisms and devices in operation. Vibration energy generated by the mechanisms and devices is transferred through ship structural elements to surrounding water where it propagates in the form of acoustic waves of a broad band of frequencies. In the publication results of identification tests of underwater noise generated by a ship in motion, are presented.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 9.

Tytuł:: Identification of hydro-acoustic waves emitted from floating units during mooring tests
Autorzy:: Kozaczka, E.
Domagalski, J.
Grelowska, G.
Gloza, I.
Tematy:: identification
propagation
hydroacoustics; Pokaż więcej
Data publikacji:: 2007
Powiązania:: https://bibliotekanauki.pl/articles/260463.pdf Link otwiera się w nowym oknie
Źródło:: Polish Maritime Research; 2007, 4; 40-46
1233-2585
Pojawia się w:: Polish Maritime Research
Opis:: Measurements of hydro-acoustic noise emitted from vessels are a.o. a subject of the tests carried out in the control measurement ranges of the Navy. The measurements are performed both on anchored and floating vessels. Acoustic field of vessels is changing along with their speed changing and is associated with acoustic activity of wave sources installed in vessel’s hull (main engines, electric generating sets, reduction gears, pumps, shaft-lines, piping, ventilating ducts etc) as well as hydro-dynamic sources such as screw propellers and water flow around the hull [5, 7]. Vibration energy generated by the onboard devices is transferred through ship structural elements to water where it propagates in the form of hydro-acoustic waves of a wide frequency band.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 10.

Tytuł:: An Optimized Propagation Model based on Measurement Data for Indoor Environments
Autorzy:: Morocho-Yaguana, M.
Ludeňa-González, P.
Sandoval, F.
Poma-Vélez, B.
Erreyes-Dota, A.
Tematy:: indoor
ITU model
log-distance model
loss measurement
one-slope model
path loss
propagation measurements
propagation models
radio propagation; Pokaż więcej
Data publikacji:: 2018
Powiązania:: https://bibliotekanauki.pl/articles/308451.pdf Link otwiera się w nowym oknie
Źródło:: Journal of Telecommunications and Information Technology; 2018, 2; 69-75
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Opis:: Propagation is an essential factor ensuring good coverage of wireless communications systems. Propagation models are used to predict losses in the path between transmitter and receiver nodes. They are usually deﬁned for general conditions. Therefore, their results are not always adapted to the behavior of real signals in a speciﬁc environment. The main goal of this work is to propose a new model adjusting the loss coeﬃcients based on empirical data, which can be applied in an indoor university campus environment. The Oneslope, Log-distance and ITU models are described to provide a mathematical base. An extensive measurement campaign is performed based on a strict methodology considering different cases in typical indoor scenarios. New loss parameter values are deﬁned to adjust the mathematical model to the behavior of real signals in the campus environment. The experimental results show that the model proposed oﬀers an attenuation average error of 2.5% with respect to the losses measured. In addition, comparison of the proposed model with existing solutions shows that it decreases the average error signiﬁcantly for all scenarios under evaluation.
Dostawca treści:: Biblioteka Nauki

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