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Wyświetlanie 1-15 z 414
Tytuł:
Prediction of flow boiling heat transfer data for R134a, R600a and R290 in minichannels
Autorzy:
Mikielewicz, D.
Jakubowska, B.
Powiązania:
https://bibliotekanauki.pl/articles/240780.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
flow boiling
natural refrigerants
minichannels
wrzenie w przepływie
naturalne czynniki chłodnicze
minikanały
Opis:
In the paper presented is the analysis of the results of calculations using a model to predict flow boiling of refrigerants such as R134a, R600a and R290. The latter two fluids were not used in the development of the model semiempirical correction. For that reason the model was verified with present experimental data. The experimental research was conducted for a full range of quality variation and a relatively wide range of mass velocity. The aim of the present study was also to test the sensitivity of developed model to a selection of the model of two-phase flow multiplier and the nonadiabatic effects. For that purpose two models have been analysed namely the one due to Müller-Steinhagen and Heck, and Friedel. In addition, the work shows the importance of taking surface tension into account in the calculation of the flow structure.
Źródło:
Archives of Thermodynamics; 2014, 35, 4; 97-114
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A 100 W SiC MESFET Amplifier for L-band T/R Module of APAR
Autorzy:
Wojtasiak, W.
Gryglewski, D.
Powiązania:
https://bibliotekanauki.pl/articles/226539.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
high power amplifier
SiC
MESFET
T/R module
APAR
Opis:
In the paper, a 100W SiC MESFET amplifier design dedicated for a L-band T/R module of APAR is presented. The output power higher than 100 W has been achieved by combining in a balanced configuration two single stages with Cree's 60 W CRF24060 SiC MESFETs. The amplifier design methodology is based on the small-signal model and DC characteristics of SiC MESFET. The model is extracted using the transistor Sparameters at three operating points for On-state, Off-state and normally biased. The measurements and simulations prove usefulness of the proposed design method. The amplifier was excited with pulsed and cw signals for the case temperature ranging from 60°C to 140°C. As a result of the case temperature changes the output power drop was lower than 0.5 dB at the level of 150 W.
Źródło:
International Journal of Electronics and Telecommunications; 2011, 57, 1; 135-140
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Implementation of factitious force method for control of 5R manipulator with skid-steering platform REX
Autorzy:
Mazur, A.
Cholewiński, M.
Powiązania:
https://bibliotekanauki.pl/articles/202350.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
underactuated system
nonholonomic constraint
kinematics
dynamics
kinematyka
dynamika
ograniczenia nieholonomiczne
Opis:
In the paper implementation of the factitious force concept for a controlling complex mobile manipulator has been presented. As the nonholonomic constraint only lack of longitudinal slippage of wheels has been chosen - in skid-steering platforms lateral slippage is necessary to change orientation of such a platform. From a control theory point of view such a system is dynamically underactuated. As a solution to a underactuation problem a method of factitious force has been proposed. This method assumes extension on the dynamics level, in the form of an additional control inputs uv, which values are equal to zero equivalently. For a mobile manipulator, consisting of platform REX and 5R robotic onboard arm, a cascaded control law has been proposed. A simulation study was conducted for a mathematical model of a considered object with real values of physical parameters, i.e. lengths, masses, inertia moments etc. obtained from the 3D model. Results obtained in simulations have shown a proper action of the control system and convergence of tracking errors, occurring in a platform and in joints of a manipulator, to zero.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2016, 64, 1; 71-80
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigations on mixture preparation for two phase adiabatic pressure drop of R134a flowing in 5 mm diameter channel
Autorzy:
Muszyński, T.
Andrzejczyk, R.
Dorao, C. A.
Powiązania:
https://bibliotekanauki.pl/articles/240440.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
adiabatic flow
frictional pressure drop
two-phase flow
flow pattern map
R134a
przepływ adiabatyczny
tarciowy spadek ciśnienia
przepływ dwufazowy
mapy przepływu
Opis:
The article presents detailed two-phase adiabatic pressure drops data for refrigerant R134a. Study cases have been set for a mass flux varying from 200 to 400 kg/m2s, at the saturation temperature of 19.4°C. Obtained experimental data was compared with the available correlations from the literature for the frictional pressure drop during adiabatic flow. Influence of mixture preparation on pressure drop was investigated, for varying inlet subcooling temperature in the heated section. The flow patterns have also been obtained by means of a high-speed camera placed in the visualization section and compared with literature observations.
Źródło:
Archives of Thermodynamics; 2017, 38, 3; 101-118
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The theoretical model of the transient behaviour for the micro combined heat and power organic Rankine cycle
Teoretyczny model ciągły dla obiegu kogeneracyjnego ORC
Autorzy:
Matysko, R.
Mikielewicz, J.
Ihnatowicz, E.
Powiązania:
https://bibliotekanauki.pl/articles/172873.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
układ mikro CHP
obieg ORC
modelowanie dynamiczne
wymiana ciepła
micro CHP system
ORC cycle
dynamical modelling
heat transfer
Opis:
W pracy przedstawiono wyniki obliczeń obiegu ORC w warunkach eksploatacyjnych. Przeprowadzone obliczenia umożliwiają określenie bezwładności układu podczas zmiany obciążeń cieplnych parownika i skraplacza. Z obliczeń uzyskano czasy bezwładności oraz parametry temperatury na dolocie do turbiny i skraplacza dla czynnika R123. Bardzo zbliżone wyniki obliczeń parametrów uzyskanych z własnego modelu obiegu ORC do przeprowadzonego niezależnie eksperymentu dają podstawy do stwierdzenia, że model dobrze odzwierciedla układy rzeczywiste. Podkreślić należy fakt, że obliczenia dynamiki obiegu za pomocą tego modelu przeprowadzono dla różnych czynników roboczych (R123, HFE7100, propan) uzyskując dobre jakościowo wyniki, co pozwala poszerzyć zakres jego stosowalności również na inne czynniki robocze. Wyniki własnych obliczeń porównano z badaniami eksperymentalnymi obiegu ORC innych autorów uzyskując dobrą zgodność.
This article presents results of calculations of the organic Rankine cycle (ORC) in working conditions. The calculations make it possible to define the inertia of the evaporator and condenser while the heat loads change occurs. Calculations allow to get the inertia of the system, and the parameters of temperature at the inlet to the turbine and condenser for the R123 refrigerant. Very similar calculations results of the parameters were obtained from own model for ORC cycle, and experiment results performed independently gave basis to conclude that the model well reflects the real systems. It should be emphasized that the dynamics calculations for the cycle prepared by this model was conducted for different working fluids (R123, HFE7100, propane). Good quality of the results from these calculations, allows to expand the scope of the model applicability to other working fluids. Our own results of calculations were compared with other authors experimental studies of the ORC cycle obtaining a good compliance.
Źródło:
Archiwum Energetyki; 2012, 42, 2; 93-102
0066-684X
Pojawia się w:
Archiwum Energetyki
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sensitivity of robust estimators applied in strategy for testing stability of reference points. EIF approach
Wykorzystanie empirycznych funkcji wpływu do badania wrażliwości odpornych estymatorów zastosowanych w strategii badania stabilności punktów nawiązania
Autorzy:
Duchnowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/145444.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
stabilność
deformacja
estymatory
displacement
stability
R-estimation
empirical influence function
Opis:
In deformation analyses, it is important to find a stable reference frame and therefore the stability of the possible reference points must be controlled. There are several methods to test such stability. The paper's objective is to examine one of such methods, namely the method based on application of R-estimation, for its sensitivity to gross errors. The method in question applies three robust estimators, however, it is not robust itself. The robustness of the method depends on the number of unstable points (the fewer unstable points there are, the more robust is the proposed method). Such property makes it important to know how the estimates applied and the strategy itself respond to a gross error. The empirical influence functions (EIF) can provide necessary information and help to understand the response of the strategy for a gross error. The paper presents examples of EIFs of the estimates, their application in the strategy and describes how important and useful is such knowledge in practice.
Ważnym etapem badania deformacji jest wyznaczenie stabilnej bazy odniesienia a wiec także badanie stabilności potencjalnych punktów odniesienia. Istnieje kilka metod badania stabilności, jedna z nich jest metoda wykorzystująca R-estymatory. Celem niniejszej pracy jest zbadanie wrażliwości na błędy grube estymatorów stosowanych w wymienionej metodzie. Jakkolwiek zastosowane estymatory są odporne, to sama metoda nie ma tej własności a jej odporność zależy w dużej mierze od liczby punktów niestabilnych (ogólnie mówiąc, im mniej jest punktów niestabilnych tym strategia jest odporniejsza na błędy grube). Z tego powodu ważnym jest by rozumieć w jaki sposób błędy grube wpływają na zastosowane estymatory i na wyniki samej strategii. Powyższy problem może być rozwiązany z zastosowaniem empirycznych funkcji wpływu (EIF). W pracy przedstawiono przykładowe funkcje EIF, ich zastosowanie w strategii oraz omówiono jak pozyskane informacje mogą być ważne i przydatne w praktyce.
Źródło:
Geodesy and Cartography; 2011, 60, 2; 123-134
2080-6736
2300-2581
Pojawia się w:
Geodesy and Cartography
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of the possibility of using transmission in the lte system on a selected railway line for the purpose of running railway traffic
Autorzy:
Chrzan, Marcin
Powiązania:
https://bibliotekanauki.pl/articles/1833612.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
GSM-R
LTE system
open systems
railway line
railway traffic control
system LTE
linia kolejowa
kontrola ruchu kolejowego
Opis:
The railway and the Rail Traffic Control Systems installed on it in Poland have recently experienced rapid technological development. This is undoubtedly due to the funds that Poland receives from the European Union for the modernization of railway infrastructure. The development of modern railway infrastructure means not only stations, modern rolling stock, but also safe and reliable train control systems based on the latest telecommunications and information technologies. For a longer time, radio communication based on the GSM-R (GSM for Railways) standard is being introduced on PKP. For this purpose, dedicated infrastructure is being built in order to use this technology for railway traffic. This is associated with huge investment costs. Since the beginning of its existence, research has been conducted worldwide on the use of LTE (Long Term Evolution) technology for conducting railway traffic. For economic and technological reasons, it is necessary to study other possibilities of using modern telecommunications infrastructure not yet dedicated to railway tasks in these open networks. The article will present research on the use of open radio communication network based on LTE standard for rail traffic and passenger comfort. It will discuss the research method and selected results of measurements made on railway line no. 4. The choice of this railway line was dictated by two factors. The first one resulted from the maximum train speed, the second one is the variety of rolling stock used on this line (compartmental and non-compartmental wagons). The part of research concerning collection of measurement material was performed within the framework of completed research work PBS3/A6/29/2015. As a result of conducted in-depth literature analysis as well as performed measurements and calculations, it allowed to develop a model and software for simulating system operation in real conditions. This system allows to send railway telegrams on appropriate safety level defined in standardization documents. The research proved the possibility of using an open system in the LTE standard for the transmission of signals for railway traffic control and passengers while maintaining an appropriate level of safety. The only limitations which were indicated by the tests are improper radio interface coverage of railway lines. Appropriate planning of radio coverage of railway areas by radio communication operators (so far ignored) with proper cooperation of infrastructure manager can lead to launching efficient communication system without necessity to build specialized infrastructure for railway.
Źródło:
Archives of Transport; 2021, 57, 1; 91-101
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
SocialRouting : The social-based routing algorithm for Delay Tolerant Networks
Autorzy:
Schoeneich, R. O.
Surgiewicz, R.
Powiązania:
https://bibliotekanauki.pl/articles/963900.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
routing protocols
MANET
DTN
Opis:
Delay and Disruptive Tolerant Networks (DTN) are relatively a new networking concept that could provide a robust communication in wide range of implementations from the space to battlefield or other military usage. However in such dynamic networks, which could be considered as a set of intermittently connected nodes, message forwarding strategy is a key issue. Existing routing solutions concentrate mainly on two major routing families flooding and knowledge based algorithms. This paper presents SocialRouting - the social-based routing algorithm designed for DTN. The use of the social properties of wireless mobile nodes is the novel way of message routing that is based on message ferrying between separated parts of the network. Proposed idea has been extensively tested using simulation tools. The simulations were made based on especially designed for measurements in DTN scenarios and compared with popular solutions.
Źródło:
International Journal of Electronics and Telecommunications; 2016, 62, 2; 167-172
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
All fiber THz spectrometer for plastics industry
Autorzy:
Wilk, R.
Powiązania:
https://bibliotekanauki.pl/articles/200188.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
fiber THz spectrometer
plastic industry
Opis:
In this paper we present an all-fiber THz spectrometer based on novel OSCAT technique. We investigate its application to non-destructive testing in the polymer industry. A set of polypropylene samples with different contents of TiO2 as a filler is examined using THz waves.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2011, 59, 3; 283-285
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy Coder for Audio Signals
Autorzy:
Ulacha, G.
Stasinski, R.
Powiązania:
https://bibliotekanauki.pl/articles/226974.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
lossless audio coding
entropy coding
OLS
Opis:
In the paper an effective entropy coder designed for coding of prediction errors of audio signals is presented. The coder is implemented inside a greater structure, which signal modeling part is a lossless coding backward adaptation algorithm consisting of cascaded Ordinary Least Squares (OLS), three Normalized Least Mean Square (NLMS), and prediction error bias correction sections. The technique performance is compared to that of four other lossless codecs, including MPEG-4 Audio Lossless (ALS) one, and it is shown that indeed, on the average the new method is the best. The entropy coder is an advanced context adaptive Golomb one followed by two context adaptive arithmetic coders.
Źródło:
International Journal of Electronics and Telecommunications; 2015, 61, 2; 219-224
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Development of a Committee of Artificial Neural Networks for the Performance Testing of Compressors for Thermal Machines in Very Reduced Times
Autorzy:
Coral, R.
Flesch, C. A.
Penz, C. A.
Borges, M. R.
Powiązania:
https://bibliotekanauki.pl/articles/221092.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
refrigeration compressor
artificial neural networks
performance test
Opis:
This paper presents a new test method able to infer - in periods of less than 7 seconds - the refrigeration capacity of a compressor used in thermal machines, which represents a time reduction of approximately 99.95% related to the standardized traditional methods. The method was developed aiming at its application on compressor manufacture lines and on 100% of the units produced. Artificial neural networks (ANNs) were used to establish a model able to infer the refrigeration capacity based on the data collected directly on the production line. The proposed method does not make use of refrigeration systems and also does not require using the compressor oil.
Źródło:
Metrology and Measurement Systems; 2015, 22, 1; 79-88
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bimetallic Micro-Punches for Micro-Blanking Processes
Autorzy:
Presz, W.
Cacko, R.
Powiązania:
https://bibliotekanauki.pl/articles/355478.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
microforming
micro-blanking
bimetallic micro-punches
Opis:
Rapid development of micro-machines, which partly needs metallic micro-parts, is nowadays a fact. A very promising way of micro-parts manufacturing is micro-blanking. For a quite complicated 2D shapes, like micro-gears, dies might be rather easy manufactured by wire-cutting. Production of micro-punches seems to be much more difficult. In this article a solution of manufacturing of micro-punches consisting of two components: punch body based on standard micro-punches and mechanically joined end – bimetallic micro-punch – is proposed. Joining process is based on the extrusion, after which a shaped end must be hardened and finally sharpened. Within this work an experimental stack-up equipped with a special measuring system and unique flexible micro-tools was developed. Simplified processes of bimetallic micro-punch manufacturing was completed as well as FEM analysis.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 1; 29-34
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 414

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