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Wyświetlanie 1-15 z 237
Tytuł:
Gigacycle fatigue at high-frequency loading
Autorzy:
Bokůvka, O.
Nový, F.
Chalupová, M.
Nicoletto, G.
Powiązania:
https://bibliotekanauki.pl/articles/329118.pdf
Data publikacji:
2008
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
materiał strukturalny
zmęczenie materiału
właściwości
gigacycle fatigue
high-frequency loading
structural material
Opis:
In this work there are information about an experimental high-frequency testing apparatus and specimens enable to determine the fatigue properties in the ultra-high-cycles region (gigacycle fatigue) and the rates of long fatigue cracks growth in near-threshold areas. The selected characteristic examples about fatigue resistance of various structural materials are presented. The results are utilizable in the field of material engineering and threshold states of material.
Źródło:
Diagnostyka; 2008, 4(48); 53-56
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Laboratory model of high frequency sonar
Autorzy:
Buszman, K.
Szymczak, W.
Powiązania:
https://bibliotekanauki.pl/articles/331519.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
laboratory model
sonars
hydroacoustic
Opis:
This article contains the construction and laboratory application of high frequency sonar model. In view of working in laboratory conditions, they must be fulfilled succeeding parametric cases: very narrow beam, low level of side lobes and low acoustic power of transmitted impulse sounding. When all of these conditions are fulfilled, it makes possible the explanation to students some terms like depth, angular resolution and making clear, that water is the best environment to acoustic waves transmission. Furthermore, there is used automatic component, namely rotary antenna, which make possibility to precision area scanning.
Źródło:
Hydroacoustics; 2008, 11; 39-46
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High-Frequency Susceptibilities of Inhomogeneous Magnetoelastic Medium
Autorzy:
Ignatchenko, V. A.
Erementchouk, M. V.
Powiązania:
https://bibliotekanauki.pl/articles/1964778.pdf
Data publikacji:
1997-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.30.+d
75.80.+q
61.43.Er
Opis:
A response of an inhomogeneous magnetoelastic medium with the zero-mean magnetostriction to high-frequency elastic and electromagnetic fields is studied. It is shown that diagonal susceptibilities have the resonance anomalies in the vicinity of the frequency of the magnetoelastic resonance, while the coefficients of crossing excitations are equal to zero.
Źródło:
Acta Physica Polonica A; 1997, 92, 2; 415-418
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High-Frequency Noise Sources in Quantum Wells
Autorzy:
Ardaravičius, L.
Liberis, J.
Matulionis, A.
Powiązania:
https://bibliotekanauki.pl/articles/2035523.pdf
Data publikacji:
2002-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.Ht
72.70.+m
73.40.Kp
Opis:
Hot-electron noise is investigated for InGaAs and InAs quantum wells containing a two-dimensional electron gas channel in a pulsed electric field applied parallel to the interfaces. Noise sources resulting from hot-electron "thermal" motion, electron temperature fluctuations, and real-space transfer are observed. The experimental results on hot-electron "thermal" noise are used to estimate energy relaxation time in the field range where other sources do not play any important role. Measurements of noise anisotropy in the plane of electron confinement are used to discuss real-space-transfer noise. High-frequency noise technique is used to study hot-electron trapping, and trap location in InAlAs/InGaAs/InAlAs heterostructure channels is determined.
Źródło:
Acta Physica Polonica A; 2002, 102, 2; 329-335
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Overheat protection circuit for high frequency processors
Autorzy:
Frankiewicz, M.
Kos, A.
Powiązania:
https://bibliotekanauki.pl/articles/200992.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
PTAT
overheat
CMOS
VLSI
full-custom design
Opis:
The paper describes design and structure of the overheat protection circuit based on the PTAT sensors. The digital core of the system is driven by a 3-bit information generated by the structure. As a result, behaviour of the core differs for each temperature. The circuit was designed in LF CMOS 0.15 ěm technology using full-custom technique. The presented paper focuses especially on the structure of the overheat protection circuit and simulations results of the functional blocks of the system. Layout and some parameters of the circuit are also considered.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2012, 60, 1; 55-59
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of low and high frequency fatigue tests
Autorzy:
Vasko, A.
Belan, J.
Kucharikova, L.
Powiązania:
https://bibliotekanauki.pl/articles/111844.pdf
Data publikacji:
2017
Wydawca:
Stowarzyszenie Menedżerów Jakości i Produkcji
Tematy:
fatigue test
low frequency cyclic loading
high frequency cyclic loading
nodular cast iron
test zmęczeniowy
cykliczne obciążenie niskoczęstotliwościowe
cykliczne obciążenie o wysokiej częstotliwości
żeliwo sferoidalne
Opis:
The paper presents the results of low and high frequency fatigue tests carried out on nodular cast iron. The specimens of synthetic nodular cast irons from three different melts were studied in the high cycle fatigue region (from 105 to 108 cycles) using fatigue experimental equipments for low and high frequency cyclic loading. Low frequency fatigue tests were carried out at frequency f ≈ 120 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100; high frequency fatigue tests were carried out at frequency f ≈ 20 kHz using the ultrasonic fatigue testing device KAUP-ZU. Both fatigue tests were realised at sinusoidal cyclic push-pull loading (stress ratio R = –1) at ambient temperature (T = 20 ± 5 °C).
Źródło:
Production Engineering Archives; 2017, 17; 15-18
2353-5156
2353-7779
Pojawia się w:
Production Engineering Archives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High frequency ship radiated noise in shallow water
Autorzy:
Carbó, R.
Molero, A. C.
Powiązania:
https://bibliotekanauki.pl/articles/332483.pdf
Data publikacji:
1999
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The stationary acoustic field in a two pIane parallel medium, sea surface and sea boftom, when a source near to the sea surface radiates, is characterized by the thickness of the medium and the reflectivity of the boundary surfaces. It is known that the maxima and minima of pressure are produced at same given depths depending on the radiated frequency and distance. Considering the ship noise as an acoustical source, the frequency spectrum of the acoustic pressure at certain depth, is nof only the spectrum of the acoustic ship noise but it is also modified by the wave field originated by consecutive reflections at the boundary surfaces. As a consequence, over the free field spectrum of (he ship noise, a series of minima appears. The corresponding frequencies are those for which the receiver is located at the nodes of the stationary wave field.
Źródło:
Hydroacoustics; 1999, 2; 213-218
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thick Film Transducers for High Frequency Coded Ultrasonography
Autorzy:
Nowicki, A.
Lewandowski, M.
Wójcik, J.
Tymkiewicz, R.
Lou-Moller, R.
Wolny, W.
Zawada, T.
Powiązania:
https://bibliotekanauki.pl/articles/176939.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
transducers
thick film
high frequency ultrasound
pulse compression
Golay codes
Opis:
Recently a new technology of piezoelectric transducers based on PZT thick film has been developed as a response to a call for devices working at higher frequencies suitable for production in large numbers at low cost. Eight PZT thick film based focused transducers with resonant frequency close to 40 MHz were fabricated and experimentally investigated. The PZT thick films were deposited on acoustically engineered ceramic substrates by pad printing. Considering high frequency and nonlinear propagation it has been decided to evaluate the axial pressure field emitted (and reflected by thick metal plate) by each of concave transducer differing in radius of curvature – 11 mm, 12 mm, 15 mm, 16 mm. All transducers were activated using AVTEC AVG-3A-PS transmitter and Ritec diplexer connected directly to Agilent 54641D oscilloscope. As anticipated, in all cases the focal distance was up to 10% closer to the transducer face than the one related to the curvature radius. Axial pressure distributions were also compared to the calculated ones (with the experimentally determined boundary conditions) using the angular spectrum method including nonlinear propagation in water. The computed results are in a very good agreement with the experimental ones. The trans- ducers were excited with Golay coded sequences at 35–40 MHz. Introducing the coded excitation allowed replacing the short-burst transmission at 20 MHz with the same peak amplitude pressure, but with almost double center frequency, resulting in considerably better axial resolution. The thick films exhibited at least 30% bandwidth broadening comparing to the standard PZ 27 transducer, resulting in an increase in matching filtering output by a factor of 1.4–1.5 and finally resulting in a SNR gain of the same order.
Źródło:
Archives of Acoustics; 2011, 36, 4; 945-954
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal Characterization of High-Frequency Flyback Power Transformer
Autorzy:
Kasikowski, R.
Gołaszewski, J.
Więcek, B.
Farrer, M.
Powiązania:
https://bibliotekanauki.pl/articles/114581.pdf
Data publikacji:
2015
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
IR thermography
power losses
H-F flyback transformer
thermal impedance
Opis:
This paper presents preliminary thermographic measurements and a simple thermal analysis of power losses in high-frequency (H-F) transformers used in AC-DC power converters. The analysis is based on complex thermal impedance and time constant distribution. The main aim of this research was to consider quantitatively the contribution of different power losses in the H-F transformer, including fringing flux effect.
Źródło:
Measurement Automation Monitoring; 2015, 61, 6; 237-241
2450-2855
Pojawia się w:
Measurement Automation Monitoring
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High Frequency Traders - destrukcyjna czy poprawiająca funkcjonowanie innowacja rynku finansowego?
High Frequency Traders - Destructive or Improving Innovation of Capital Market?
Autorzy:
Gorczyńska, Alina
Powiązania:
https://bibliotekanauki.pl/articles/593602.pdf
Data publikacji:
2014
Wydawca:
Uniwersytet Ekonomiczny w Katowicach
Tematy:
Innowacje
Inwestor giełdowy
Programy komputerowe
Rynki finansowe
Computer programs
Financial markets
Innovations
Stock exchange investor
Opis:
Technological advances and legal conditions in investments in the financial market have created many innovations at the turn of the century. One of the innovations in the financial market are High Frequency Traders (HFT) that have existed since 2005, and since then rapidly have developed its activity, affecting functioning of financial market. As the positive effects of their activities is acknowledged: possibility to increase liquidity and transparency of financial market, as well as enhancing competition between trading venues, which in turn can lead to lower transaction costs. However, the functioning HFT is also connected with dangers associated with the possibility of a decrease in liquidity on the market (in terms of variation), the collapse of the market as a result of a failure or an error on the handling of orders and restriction of competition among financial market investors.
Źródło:
Studia Ekonomiczne; 2014, 186 cz 2; 188-187
2083-8611
Pojawia się w:
Studia Ekonomiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An accurate prediction of high-frequency circuit behaviour
Autorzy:
Yoshitomi, S.
Kimijima, H.
Kojima, K.
Kokatsu, H.
Powiązania:
https://bibliotekanauki.pl/articles/308807.pdf
Data publikacji:
2005
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
electro-magnetic simulation
SPICE
circuit test structure
RF CMOS
EKV2.6-MOS model
spiral inductor
CMOS VCO
Opis:
An accurate way to predict the behaviour of an RF analogue circuit is presented. A lot of effort is required to eliminate the inaccuracies that may generate the deviation between simulation and measurement. Efficient use of computer-aided design and incorporation of as many physical effects as possible overcomes this problem. Improvement of transistor modelling is essential, but there are many other unsolved problems affecting the accuracy of RF analogue circuit modelling. In this paper, the way of selection of accurate transistor model and the extraction of parasitic elements from the physical layout, as well as implementation to the circuit simulation will be presented using two CMOS circuit examples: an amplifier and a voltage controlled oscillator (VCO). New simulation technique, electro-magnetic (EM)-co-simulation is introduced.
Źródło:
Journal of Telecommunications and Information Technology; 2005, 1; 47-62
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High frequency metrology for intracardiac ablation: in-vivo results
Autorzy:
Rouane, A.
Bru, P.
Powiązania:
https://bibliotekanauki.pl/articles/221888.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
impedance matching
voltage measurement cell
current measurement cell
high frequency energy
Opis:
Cardiac Radiofrequency (RF) ablation is a commonly used clinical procedure for treating many cardiac arrhythmias. However, the efficacy of RF ablation may be limited by two factors: small ventricular lesions and impedance rise, leading to coagulum formation and desiccation of tissue. In this paper, a high frequency (HF) energy ablation system operating at 27.12 MHz based on an automated load matching system was developed. A HF energy matched probe associated to the automated impedance matching device ensures optimal transfer of the energy to the load. The aim of this study was to evaluate this energy for catheter ablation of the atrioventricular junction. In vivo studies were performed using 10 sheep to characterize the lesions created with the impedance matching system. No cardiac perforation was noted. No thrombus was observed at the catheter tip. Acute lesions ranged from 3 to 45 mm in diameter (mean šSD = 10.3š10) and from 1 to 15 mm in depth (6.7š3.9), exhibiting a close relationship between HF delivered power level and lesion size. Catheter ablation using HF current is feasible and appears effective in producing a stable AV block when applied at the AV junction and large myocardial lesions at ventricular sites.
Źródło:
Metrology and Measurement Systems; 2012, 19, 3; 603-610
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of high frequency vibration of tram monobloc wheel
Autorzy:
Sowiński, B.
Powiązania:
https://bibliotekanauki.pl/articles/224110.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
noise
tram wheel
FEM analysis
hałas
koła
tramwaj
analiza MES
Opis:
European Environmental Agency estimates that about 120 million people in the EU (over 30% of the total population) are exposed to traffic noise above 55 Ldn dB. It is estimated that 10% of the EU population is exposed to noise associated with the rail traffic. The two main sources of traffic noise comes from vehicles engines and the noise generated in the contact between the wheel and the road. In the latter the considerable part the noise is due to phenomena occurring in a wheel tram – rail system. Therefore, the problem of reducing the noise generated by railway vehicles is the subject of many studies, both experimental and theoretical. Commonly used wheel trams so called "resilient wheels" are equipped with layer made of a resilient material, e.g. rubber, between the tread and the wheel disc. But the monobloc tram wheel is the standard design against which should be carried out the studies on reduction of noise in wheel-rail system. This paper presents the results of calculations related to eigenforms, eigenfrequencies and Frequency Response Function of a three-dimensional model of a monobloc tram wheel. The calculations were carried out using the finite element method. Vibration analysis was performed for the range to 5 kHz. Analysis carried out has shown that the wheel tread plays a more important role in the generation of high-frequency vibrations.
Źródło:
Archives of Transport; 2016, 39, 3; 65-75
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PC-based high frequency imaging system with coded excitation
Autorzy:
Lewandowski, M.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/331588.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
coded transmission
SNR
FPGA
Opis:
Coded transmission is a technique that gives significant improvement in SNR and enables higher contrast imaging without sacrificing the resolution. A novel HF (20-35 MHz) ultrasound real-time imaging system for research and evaluation of the coded transmission was developed. The digital programmable coder-digitizer module based on the field programmable gate array (FPGA) chip supports arbitrary waveform coded transmission and RF echoes sampling up to 200 MSPS. A novel balanced software architecture supports real-time RF processing and display at rates up to 30 frames/sec. The system was used to gather data for sine burst and 16-bit Golay code excitation using a single element scanning head with thick film focused spherical transducer 25 MHz center frequency and 56% system bandwidth. SNR gain for the Golay codes (referenced to single burst) of 15 dB for 20 MHz and 16 dB for 35 MHz were obtained. In water the axial resolution for both single burst and the Golay codes was the same FWMH=20 ns at 20 MHz and FWMH=15 ns at 35 MHz. The presented system is a practical and low cost implementation of coded excitation technique in HF ultrasound imaging.
Źródło:
Hydroacoustics; 2008, 11; 239-247
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 237

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