Skocz do pozycji: 1.

Tytuł:

Measuring Exposure to High-Frequency Electromagnetic Fields Experienced by a Helicopter Crew During Flight

Autorzy:

Michałowska, Joanna
Puzio, Łukasz
Tofil, Arkadiusz
Pytka, Jarosław

Powiązania:

https://bibliotekanauki.pl/articles/36453924.pdf

Data publikacji:

2022

Wydawca:

Sieć Badawcza Łukasiewicz - Instytut Lotnictwa

Tematy:

electromagnetic
helicopter
exposure
high-frequency

Opis:

High-frequency electromagnetic fields (EMF) can have a negative effect on both the human body and electronic devices. Monitoring and measurement of the electromagnetic field generated by devices is important from the point of view of environmental protection, the human body and electromagnetic compatibility. In this study, we tested the value of the electromagnetic field strength determined by the NHT3DL by Microrad with measurement probes during flights in the Robinson R44 helicopter. The reference point for the results obtained were the normative limits of the electromagnetic field permitted to affect the crew and passengers during flight. The maximum RMS values recorded during the measurements were E = 4.399 V/m in the 100 kHz-6.5 GHz frequency band and for the magnetic component H = 2.829 A/m in the 300 kHz-30 MHz frequency band. These results were passed to the Statistica 13.3 software for a detailed stochastic analysis of the values tested.

Źródło:

Transactions on Aerospace Research; 2022, 1 (266); 59-65
0509-6669
2545-2835

Pojawia się w:

Transactions on Aerospace Research

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 2.

Tytuł:

On the Noise Hazard Assessment within the Intermediate Range of the High Audible and the Low Ultrasonic Frequencies

Autorzy:

Śliwiński, A.

Powiązania:

https://bibliotekanauki.pl/articles/177315.pdf

Data publikacji:

2016

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

ultrasonic noise assessment
high frequency audiometry

Opis:

In parallel to the ultrasonic noise assessment procedures and research activity in the field there have appeared several papers in the domain of so called high-frequency audiometry which covers the range of frequencies 8–20 kHz. They are important for recognizing the harmfulness and hazard of the audible high frequency sound components in the same range as the one of the low frequency ultrasonic noise. On the other hand there exists a certain inconsequent situation in the general approach to the problem of ultrasonic noise hazard assessment in work places environment which concerns the convention to include the frequency range of 10–20 kHz to the domain of ultrasonics. The range consists of one third octave bands of central frequencies: 10, 12.5, 16, 20 kHz and conventionally is called low frequency ultrasonic noise though at least the components of the two lowest bands are naturally audible by a majority of population (mainly young people).The paper presents a discussion related to some achievements of the two domains and some conclusions which could be useful for a more consequent description of the subject and could be taken into account in the future regulations for the ultrasonic noise assessment in work places environment.

Źródło:

Archives of Acoustics; 2016, 41, 2; 331-338
0137-5075

Pojawia się w:

Archives of Acoustics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 3.

Tytuł:

Extended High Frequency Hearing Thresholds in Tinnitus Patients with Normal Hearing

Autorzy:

Ristovska, Lidija
Jachova, Zora

Powiązania:

https://bibliotekanauki.pl/articles/31339952.pdf

Data publikacji:

2022

Wydawca:

Polska Akademia Nauk. Czasopisma i Monografie PAN

Tematy:

extended high frequency
hearing loss
tinnitus

Opis:

The aim of the study was to compare the extended high-frequency (EHF) hearing thresholds (10–16 kHz) in tinnitus and non-tinnitus ears, in a group of 98 patients with unilateral tinnitus and normal hearing at standard audiometric frequencies, in a 0.125–8 kHz range. It was found that a total of 65 patients (66%) had a hearing loss (a threshold shift >20 dB HL) in the EHF range and the EHF hearing loss occurred more frequently in the tinnitus ear than in the non-tinnitus ear. The data also indicate that the EHF thresholds increased with the patient’s age and were in most patients higher in the tinnitus ear than in the non-tinnitus ear.

Źródło:

Archives of Acoustics; 2022, 47, 4; 449-455
0137-5075

Pojawia się w:

Archives of Acoustics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 4.

Tytuł:

Comparative analysis of methods for hourly electricity demand forecasting in the absence of data - a case study
Analiza porównawcza metod prognozowania godzinnego zapotrzebowania na energię elektryczną przy brakach w danych - studium przypadku

Autorzy:

Zawadzki, Jan

Powiązania:

https://bibliotekanauki.pl/articles/2194900.pdf

Data publikacji:

2023

Wydawca:

Akademia Bialska Nauk Stosowanych im. Jana Pawła II w Białej Podlaskiej

Tematy:

forecasting
missing data
time series
high frequency

Opis:

Scope and purpose of work: This paper examines the impact of the number of gaps in data, the analytical form, and the model type selection criterion on the accuracy of interpolation and extrapolation forecasts for hourly data. Materials and methods: Forecasts were developed on the basis of predictors that are based on: classical time series forecasting models and regression time series forecasting models, hybrid time series forecasting models and hybrid regression forecasting models for uncleared series, and exponential smoothing models for cleared series of two or three types of seasonal fluctuations, with minimum estimates of errors in interpolation or extrapolation forecasts. Results: Adaptive and hybrid regression models have proved to have the most favorable predictive properties. Most hybrid time series models for systematic and non-systematic gaps and for both analytical forms are single models that generally describe fluctuations within a 24-hour cycle. Conclusions: The lowest estimators of prediction errors involving interpolation were obtained for exponential smoothing models, followed by hybrid regression models. A reverse sequence was obtained for extrapolative forecasting.

Źródło:

Economic and Regional Studies; 2023, 16, 1; 34-50
2083-3725
2451-182X

Pojawia się w:

Economic and Regional Studies

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 5.

Tytuł:

Comparative investigation of SiC and Si power electronic devices operating at high switching frequency

Autorzy:

Zymmer, K.
Mazurek, P.

Powiązania:

https://bibliotekanauki.pl/articles/200057.pdf

Data publikacji:

2011

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

semiconductor devices
silicon carbide
high frequency converters

Opis:

The paper presents results of measurements of the reverse recovery current and dynamic forward voltage of the silicon carbide (SiC) Schottky diodes operating at a 500 A/ěs current slope. These data were compared with the corresponding parameters determined for ultrafast silicon (Si) diodes. Results of power losses measurement in SiC Schottky diodes operating at switching frequency range of (10–200) kHz are presented and compared with corresponding data of ultrafast Si diodes. Also, results of power losses measurements in transistors of dc voltage switch are shown. Investigations were conducted with a SiC and the ultrafast Si freewheeling diode at the transistor switching frequency of 100 kHz. The results of measuring power losses dissipated in the dc converter with a SiC Schottky diode and the ultrafast silicon diode are also presented.

Źródło:

Bulletin of the Polish Academy of Sciences. Technical Sciences; 2011, 59, 4; 555-559
0239-7528

Pojawia się w:

Bulletin of the Polish Academy of Sciences. Technical Sciences

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 6.

Tytuł:

An analysis of the performance of genetic programming for realised volatility forecasting

Autorzy:

Yin, Z.
O’Sullivan, C.
Brabazon, A.

Powiązania:

https://bibliotekanauki.pl/articles/91765.pdf

Data publikacji:

2016

Wydawca:

Społeczna Akademia Nauk w Łodzi. Polskie Towarzystwo Sieci Neuronowych

Tematy:

realised volatility
genetic programming
high frequency data

Opis:

Traditionally, the volatility of daily returns in financial markets is modeled autoregressively using a time-series of lagged information. These autoregressive models exploit stylised empirical properties of volatility such as strong persistence, mean reversion and asymmetric dependence on lagged returns. While these methods can produce good forecasts, the approach is in essence atheoretical as it provides no insight into the nature of the causal factors and how they affect volatility. Many plausible explanatory variables relating market conditions and volatility have been identified in various studies but despite the volume of research, we lack a clear theoretical framework that links these factors together. This setting of a theory-weak environment suggests a useful role for powerful model induction methodologies such as Genetic Programming (GP). This study forecasts one-day ahead realised volatility (RV) using a GP methodology that incorporates information on market conditions including trading volume, number of transactions, bid-ask spread, average trading duration (waiting time between trades) and implied volatility. The forecasting performance from the evolved GP models is found to be significantly better than those numbers of benchmark forecasting models drawn from the finance literature, namely, the heterogeneous autoregressive (HAR) model, the generalized autoregressive conditional heteroscedasticity (GARCH) model, and a stepwise linear regression model (SR). Given the practical importance of improved forecasting performance for realised volatility this result is of significance for practitioners in financial markets.

Źródło:

Journal of Artificial Intelligence and Soft Computing Research; 2016, 6, 3; 155-172
2083-2567
2449-6499

Pojawia się w:

Journal of Artificial Intelligence and Soft Computing Research

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 7.

Tytuł:

A High-Efficient Low-Voltage Rectifier for CMOS Technology

Autorzy:

Jendernalik, W.
Jakusz, J.
Blakiewicz, G.
Kłosowski, M.

Powiązania:

https://bibliotekanauki.pl/articles/220356.pdf

Data publikacji:

2016

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

CMOS rectifier
high frequency rectifier
wireless power transmission

Opis:

A new configuration of rectifier suiting CMOS technology is presented. The rectifier consists of only two n-channel MOS transistors, two capacitors and two resistors; for this reason it is very favourable in manufacturing in CMOS technology. With these features the rectifier is easy to design and cheap in production. Despite its simplicity, the rectifier has relatively good characteristics, the voltage and power efficiency, and bandwidth greater than 89%, 87%, and 1 GHz, respectively. The performed simulations and measurements of a prototype circuit fully confirmed its correct operation and advantages.

Źródło:

Metrology and Measurement Systems; 2016, 23, 2; 261-268
0860-8229

Pojawia się w:

Metrology and Measurement Systems

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 8.

Tytuł:

Modele hierarchiczne w prognozowaniu zmiennych o wysokiej częstotliwości obserwowania w warunkach braku pełnej informacji
Hierarchical models in forecasting of the high-frequency variables in the conditions of lack of full information

Autorzy:

Szmuksta-Zawadzka, Maria
Zawadzki, Jan

Powiązania:

https://bibliotekanauki.pl/articles/425235.pdf

Data publikacji:

2014

Wydawca:

Wydawnictwo Uniwersytetu Ekonomicznego we Wrocławiu

Tematy:

high-frequency data
hierarchical models
incomplete time series

Opis:

The paper presents a procedure of application of regular hierarchical models in forecasting missing data in high-frequency time series with cyclical fluctuations. Annual, weekly and daily cycles of seasonal fluctuation have additive character. Separately regular hierarchical models have been built for even length cycles.Theoretical considerations are illustrated with an empirical example.

Źródło:

Econometrics. Ekonometria. Advances in Applied Data Analytics; 2014, 4(46); 72-84
1507-3866

Pojawia się w:

Econometrics. Ekonometria. Advances in Applied Data Analytics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 9.

Tytuł:

Experimental Study of Identifying Emission Sources of Acoustic Signals on the Cylinder Body of a Two-Stroke Marine Diesel Engine

Autorzy:

Dong, Xuan Thin
Nguyen, Manh Hung

Powiązania:

https://bibliotekanauki.pl/articles/1953513.pdf

Data publikacji:

2021

Wydawca:

Polska Akademia Nauk. Czasopisma i Monografie PAN

Tematy:

acoustic emission
two-stroke marine diesel engine
experimental method
low-to-high frequency ranges
medium-to-high frequency ranges
vibration

Opis:

In this paper, an experimental method was utilized to investigate acoustic emission (AE) characteristics and to identify emission sources of the nonlinear AE signal on the cylinder body of a large low-speed two-stroke marine diesel engine in real-working conditions on the sea in misfiring and normal firing modes. Measurements focused on the AE signal acquired in a transverse direction in low-frequency (20-80 kHz), medium-frequency (100-400 kHz) and high-frequency (400-900 kHz) ranges. The collected signals were analyzed on the crank angle and crank angle-frequency domains. The results showed that all potential sources of the nonlinear AE signal could be mapped in the low-frequency range. However, only the AE signal caused by the combustion process at around the top dead center could be well-observed in the medium-to-high-frequency range. The findings also revealed that in normal firing conditions, the AE energy radiated by friction in the down-stroke period was smaller than in the up-stroke process due to gas-sealing forces. Moreover, the AE energy in the misfiring condition was higher than in the normal firing state. These outcomes considerably contributed understandings to characteristics of friction and wear around the mid-stroke area of the cylinder on a two-stroke marine diesel engine.

Źródło:

Archives of Acoustics; 2021, 46, 1; 105-119
0137-5075

Pojawia się w:

Archives of Acoustics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 10.

Tytuł:

ON LOW-FREQUENCY ESTIMATION OF BID-ASK SPREAD IN THE STOCK MARKET

Autorzy:

Kociński, Andrzej Marek

Powiązania:

https://bibliotekanauki.pl/articles/453684.pdf

Data publikacji:

2014

Wydawca:

Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Katedra Ekonometrii i Statystyki

Tematy:

high-frequency data
low-frequency data
Roll estimator
Corwin-Schultz estimator

Opis:

In the article two popular low-frequency methods od bid-ask spread estimation are presented and applied to the stocks quoted on the Warsaw Stock Exchange (WSE): the Roll method [Roll 1984] and Corwin-Schultz method [Corwin and Schultz 2012]. The widely available data on average spreads published by WSE are used as benchmark and proxy of information, usually received from difficult to access and limited high-frequency financial data

Źródło:

Metody Ilościowe w Badaniach Ekonomicznych; 2014, 15, 2; 135-143
2082-792X

Pojawia się w:

Metody Ilościowe w Badaniach Ekonomicznych

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 11.

Tytuł:

Trading volume and volatility patterns across selected Central European stock markets from microstructural perspective

Autorzy:

Gurgul, H.
Syrek, R.

Powiązania:

https://bibliotekanauki.pl/articles/1201257.pdf

Data publikacji:

2017

Wydawca:

Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH

Tematy:

high frequency data
flexible Fourier form regression
intraday patterns

Opis:

In this paper, the intraday patterns of trading volumes and volatilities as well as autocorrelations are investigated using high-frequency data. The analysis is performed for companies listed in the main German, Austrian, and Polish indices with the aid of Flexible Fourier Form regression. We have found some similarities to prior investigations in light of stylized facts about intraday patterns. We noted the differences in intraday patterns and autocorrelations across markets, which depend on the maturity level of the market. The most-regular patterns are observed for DAX companies. Additionally, using day-of-the-week dummies, we discover some peaks that can be associated with macroeconomic announcements in Germany and the US. This leads to conclusions that the day of the week and announcements should be taken into account in modeling volatilities (returns) and volumes from high-frequency data.

Źródło:

Managerial Economics; 2017, 18, 1; 87-101
1898-1143

Pojawia się w:

Managerial Economics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 12.

Tytuł:

Comparison of acoustical and optical zooplankton measurements using an acoustic scattering model: A case study from the Arctic frontal zone

Autorzy:

Szczucka, Joanna
Błachowiak-Samołyk, Katarzyna
Trudnowska, Emilia
Hoppe, Łukasz

Powiązania:

https://bibliotekanauki.pl/articles/2046858.pdf

Data publikacji:

2016

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

Arctic
Svalbard
zooplankton
high−frequency echosounding
sound scattering model

Źródło:

Polish Polar Research; 2016, 37, 1; 67-88
0138-0338
2081-8262

Pojawia się w:

Polish Polar Research

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 13.

Tytuł:

Palatalization as a Non-Uniform Process Affecting Grammatical Words: A Comparison of Data from Dialectally Identified and Unidentified Late Middle English Texts

Autorzy:

Kocel, Agnieszka

Powiązania:

https://bibliotekanauki.pl/articles/888650.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Warszawski. Wydawnictwa Uniwersytetu Warszawskiego

Tematy:

palatalization
high frequency lemmas
Middle English
dialects
lexical diffusion

Opis:

The process of palatalization has exerted much influence on the forms of four highfrequency lemmas, EACH, MUCH, SUCH, WHICH, revealing significant heterogeneity in terms of palatalized and non-palatalized variants being used in the close vicinity of each other both in the Northern and Southern dialects as well as in the texts of unknown origin. Such unpredictability of the process, accounted for by the operation of lexical diffusion, raises questions concerning the manner of how palatalization, being one of the major phonological changes, affected the lexis and phonological system of Middle English, proving to be much less consistent than expected.

Źródło:

Anglica. An International Journal of English Studies; 2013, 22/2; 5-25
0860-5734

Pojawia się w:

Anglica. An International Journal of English Studies

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 14.

Tytuł:

Dehydration of no flotation size coal's slimes on the deck of high-frequency screen with multislopes area's working surface
Оbezvozhivanie ugolnogo shlama na site vysokochastotnogo vibracionnogo grokhota s raznonaklonnymi uchastkami rabochejj poverkhnosti

Autorzy:

Eremejev, I.
Polulyakh, A.
Polulyakh, D.
Grachyov, O.

Powiązania:

https://bibliotekanauki.pl/articles/791890.pdf

Data publikacji:

2014

Wydawca:

Komisja Motoryzacji i Energetyki Rolnictwa

Tematy:

coal
dehydration
physical model
working surface
high-frequency screen

Źródło:

Teka Komisji Motoryzacji i Energetyki Rolnictwa; 2014, 14, 2
1641-7739

Pojawia się w:

Teka Komisji Motoryzacji i Energetyki Rolnictwa

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 15.

Tytuł:

High power microwave for knocking out programmable suicide drones

Autorzy:

Chaari, Mohamed Zied

Powiązania:

https://bibliotekanauki.pl/articles/1311126.pdf

Data publikacji:

2021

Wydawca:

Akademia Sztuki Wojennej

Tematy:

high power microwave
conical horn antenna
errant drone
kill drone
high frequency

Opis:

The primary research objective is to reduce the dangers of rogue drones in our lives and the consequences of extremist groups, drug dealers, and organised criminals using them. The growing number of incidents involving modified drones proves the weakness of existing technology in stopping and neutralising errant drones such as the hand-held gun jammer, trained eagle, R.F. jammer, and others. This technology is not very likely to able to knock out a rogue drone and is incapable of stopping programmable drones. This article aims to examine the directed energy of HPM (high power microwaves) in using the electromagnetic field strength energy to damage the drone’s structure or burn its PCB board electronics. It goes on to analyse electronic attack using microwave power with high frequency to immediately switch off drones. The effectiveness of high microwave power for disrupting drones at different distances and in different weather conditions is evaluated. A study of the conical horn antenna of the magnetron coupling system, which has an operating frequency of 2.45 GHz, is also included.

Źródło:

Security and Defence Quarterly; 2021, 34, 2; 68-84
2300-8741
2544-994X

Pojawia się w:

Security and Defence Quarterly

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 16.

Tytuł:

Palatalization in Grammatical Words as Reflected in Unclassified Late Middle English Sources

Autorzy:

Kocel, Agnieszka

Powiązania:

https://bibliotekanauki.pl/articles/888843.pdf

Data publikacji:

2012

Wydawca:

Uniwersytet Warszawski. Wydawnictwa Uniwersytetu Warszawskiego

Tematy:

palatalization
Late Middle English
dialects
unclassified
corpora
high-frequency items

Opis:

Although palatalization changing [k] into [tS] was most widespread in Southumbria, the previous examination (Kocel 2009, 2010) has already proved that on no account can it be perceived as a homogeneous process. This lack of consistency is reflected in many instances of palatal forms found in the North alongside many nonpalatal ones encountered in the East Midlands and London. Consequently, the substantial number of such “odd” forms seems to defy the existence of clear-cut boundaries between the above mentioned areas, allowing for an unhindered influx and amalgamation of ostensibly dialect-specific variants. The problem appears even more complex, taking into account the vast collection of dialectally unidentified Middle English texts which, containing both palatal and nonpalatal forms, only corroborate the fact that palatalization could not be dialect or even area specific. The multitude of variants present in those texts, a result of the Scandinavian influence and dialectal borrowing, point to the process of the lexical diffusion of these forms across the whole English territory, affecting in particular such high-frequency items as the grammatical words each, much, such and which. The aim of the study, thus, will be to determine the extent of palatalization affecting these grammatical words, through the analysis of the spelling/phonological discrepancies and the distribution of each, much, such and which in unclassified Late Middle English sources. The data come from the Innsbruck Corpus of Middle English Prose, The Middle English Dictionary and A Linguistic Atlas of Late Mediaeval English.

Źródło:

Anglica. An International Journal of English Studies; 2012, 21/2; 4-15
0860-5734

Pojawia się w:

Anglica. An International Journal of English Studies

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 17.

Tytuł:

The potential for real-time testing of high-frequency trading strategies through a developed tool during volatile market conditions

Autorzy:

Vaitonis, Mantas
Korovkinas, Konstantinas

Powiązania:

https://bibliotekanauki.pl/articles/30148245.pdf

Data publikacji:

2023

Wydawca:

Polskie Towarzystwo Promocji Wiedzy

Tematy:

high frequency trading
cryptocurrencies
algorithmic trading
multidimensional matrice
parallelization
simulation

Opis:

This study presents a method for testing high-frequency trading (HFT) for algorithms on GPUs using kernel parallelization, code vectorization, and multidimensional matrices. The research evaluates HFT strategies within algorithmic cryptocurrency trading in volatile market conditions, particularly during the COVID-19 pandemic. The study's objective is to provide an efficient and comprehensive approach to assessing the efficiency and profitability of HFT strategies. The results show that the method effectively evaluates the efficiency and profitability of HFT strategies, as demonstrated by the Sharp ratio of 2.29 and the Sortino ratio of 2.88. The authors suggest that further study on HFT testing methods could be conducted using a tool that directly connects to electronic marketplaces, enabling real-time receipt of high-frequency trading data and simulation of trade decisions. Finally, the study introduces a novel method for testing HFT algorithms on GPUs, offering promising results in assessing the efficiency and profitability of HFT strategies during volatile market conditions.

Źródło:

Applied Computer Science; 2023, 19, 2; 63-81
1895-3735
2353-6977

Pojawia się w:

Applied Computer Science

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 18.

Tytuł:

Connectivity Solutions in Automated Trading

Autorzy:

Popławski, P.

Powiązania:

https://bibliotekanauki.pl/articles/226896.pdf

Data publikacji:

2015

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

telecommunications
digital systems
systems architecture
automated trading
high frequency trading

Opis:

The study analyzes the architecture and deployment of direct market access (DMA) solutions for automated trading of securities. It provides an overview of automated trading systems including: trading floor architecture, trading environment connectivity, and DMA solutions. Among a range of factors influencing operational capacities, round-trip latency has been recognized as the key quality differentiator of an automated trading floor. The study identifies potential opportunity costs due to latency levels as a major driver of technological progress in trading in highly liquid market conditions.

Źródło:

International Journal of Electronics and Telecommunications; 2015, 61, 4; 403-408
2300-1933

Pojawia się w:

International Journal of Electronics and Telecommunications

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 19.

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

/5

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Skocz do pozycji: 20.

Tytuł:

Measurement and Analysis of Partial Discharge using an Ultra-High Frequency Sensor for Gas Insulated Structures

Autorzy:

Wang, G.
Kil, G.-S.

Powiązania:

https://bibliotekanauki.pl/articles/221519.pdf

Data publikacji:

2017

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

gas insulated structures
partial discharge
ultra-high frequency sensor
conversion

Opis:

Although the gas insulated structures have a high degree of reliability, the unavoidable defects are primary reason of their failures. Partial discharge (PD) has been regarded as an effective indication for condition monitoring and diagnosis of gas insulated switchgears (GISs) to ensure their reliable and stable operation. Among various PD detection methods, the ultra-high frequency (UHF) technique has the advantages of on-line motoring and defect classification. In this paper, there are presented 7 types of artificial electrode systems fabricated for simulation of real insulation defects in gas insulated structures. A real-time measurement system was developed to acquire defect patterns in a form of phase-resolve partial discharge (PRPD) intensity graph, using a UHF sensor. Further, the discharge distribution and statistical characteristics were extracted for defect identification using a neural network algorithm. In addition, a conversion experiment was proposed by detecting the PD pulse simultaneously using a non-induction resistor and a UHF sensor. A relationship between the magnitude of UHF signal and the amplitude of apparent charge was established, which was used for evaluation of PD using the UHF sensor.

Źródło:

Metrology and Measurement Systems; 2017, 24, 3; 515-524
0860-8229

Pojawia się w:

Metrology and Measurement Systems

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 21.

Tytuł:

Power quality enhancement of three-phase front-end rectifier of UPS system using current injection technique

Autorzy:

Dhomane, G. A.
Suryawanshi, H.

Powiązania:

https://bibliotekanauki.pl/articles/262756.pdf

Data publikacji:

2008

Wydawca:

Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

Tematy:

high frequency current injection
high power factor
soft transition
power factor correction circuit

Opis:

Power Quality, in terms of power factor and harmonics, is greatly hampered by a three-phase rectifier used as a front-end ac-to-dc converter in many systems including a UPS. This paper presents the high power factor operation of the converter with reduced total harmonic distortion up to 4%. The power quality up gradation is due to high-frequency current injection, at the input of the front-end rectifier. A small filter is required at the output for filtering the high-frequency content. Sinusoidal PWM technique is used for controlling the output voltage. DSP is used for generating the desired gate pulses. The converter has high efficiency, low EMI emissions, high power packing density and suitable for UPS system. A Simulation and experimentation is carried out on a 3 kW converter and experimental results are in good agreement with simulation results.

Źródło:

Electrical Power Quality and Utilisation. Journal; 2008, 14, 2; 35-39
1896-4672

Pojawia się w:

Electrical Power Quality and Utilisation. Journal

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 22.

Tytuł:

Practical application of high resolution ground penetrating radar method inside buildings

Autorzy:

Mazurek, E.
Łyskowski, M.

Powiązania:

https://bibliotekanauki.pl/articles/184545.pdf

Data publikacji:

2012

Wydawca:

Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH

Tematy:

GPR
sleeve
high frequency GPR antenna
foundations of buldings
reinforced concrete

Opis:

An infrastructure development requires a precise indoor localization plan of cables, pipes or reinforcing elements. Due to the age of many buildings in Poland such plans often do not exist or do not contain the evidence of numerous activities carried out over years like repairs or modifications. Due to this situation demands for application of geophysical methods grow, especially with respect to the Ground Penetrating Radar (GPR) method. A possibility of precise localization of hidden objects arises with the use of high frequency antennas together and with precise measuring grid. Research carried out at the request of one of the departments of AGH University of Science and Technology in building B2 showed great potential of GPR methods in this field. The study was devoted to recognition of structure of the concrete floor. The obtained results gave very precise location of numerous objects of interest and they became a good sample of high resolution investigations. The survey was performed with ProEx unit, produced by a Swedish company - Mala Geoscience, which is in the possession of the Department of Geophysics, Faculty of Geology, Geophysics and Environmental Protection.

Źródło:

Geology, Geophysics and Environment; 2012, 38, 4; 439-448
2299-8004
2353-0790

Pojawia się w:

Geology, Geophysics and Environment

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 23.

Tytuł:

Statistical investigations of fast changeable processes occurring in ship piston combustion engine

Autorzy:

Chłopek, Z.
Piaseczny, L.

Powiązania:

https://bibliotekanauki.pl/articles/259250.pdf

Data publikacji:

2005

Wydawca:

Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa

Tematy:

piston combustion engine
fast changeable processes
stochastic processes
high frequency noise

Opis:

Combustion piston engine is one of the devices in which fast changeable processes occur in operational conditions. In this paper are presented basic problems associated with research on fast changeable processes occurring in diesel engines, exemplified by the processes of indicated pressure and fuel pressure injected to engine's cylinder. Dynamical characteristics of the investigated processes were analyzed and problems of synchronous averaging of pseudo-periodical signals were considered in order to limit high frequency noise content in useful signal. Some limitations of elimination effectiveness of high frequency noise from tested signals have been revealed.

Źródło:

Polish Maritime Research; 2005, 2; 10-16
1233-2585

Pojawia się w:

Polish Maritime Research

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 24.

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

/5

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Skocz do pozycji: 25.

Tytuł:

Improving sensitivity of residual current transformers to high frequency earth fault currents

Autorzy:

Czapp, S.
Dobrzyński, K.
Klucznik, J.
Lubosny, Z.
Kowalak, R.

Powiązania:

https://bibliotekanauki.pl/articles/141169.pdf

Data publikacji:

2017

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

current transformers
earth fault currents
electric devices
electromagnetic couplings
high frequency

Opis:

For protection against electric shock in low voltage systems residual current devices are commonly used. However, their proper operation can be interfered when high frequency earth fault current occurs. Serious hazard of electrocution exists then. In order to detect such a current, it is necessary to modify parameters of residual current devices, especially the operating point of their current transformer. The authors proposed the modification in the structure of residual current devices. This modification improves sensitivity of residual current devices when high frequency earth fault current occurs. The test of the modified residual current device proved that the authors’ proposition is appropriate.

Źródło:

Archives of Electrical Engineering; 2017, 66, 3; 485-494
1427-4221
2300-2506

Pojawia się w:

Archives of Electrical Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 26.

Tytuł:

Modelling Foreign Exchange Realized Volatility Using High Frequency Data: Long Memory versus Structural Breaks

Autorzy:

Maatoug, Abderrazak Ben
Lamouchi, Rim
Davidson, Russell
Fatnassi, Ibrahim

Powiązania:

https://bibliotekanauki.pl/articles/2076275.pdf

Data publikacji:

2018

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

foreign exchange markets
realized volatility
high-frequency data,long memory
structural change

Opis:

In this study, we model realized volatility constructed from intra-day highfrequency data. We explore the possibility of confusing long memory and structural breaks in the realized volatility of the following spot exchange rates: EUR/USD, EUR/JPY, EUR/CHF, EUR/GBP, and EUR/AUD. The results show evidence for the presence of long memory in the exchange rates’ realized volatility. From the Bai–Perron test, we found structural breakpoints that match significant events in financial markets. Furthermore, the findings provide strong evidence in favour of the presence of long memory.

Źródło:

Central European Journal of Economic Modelling and Econometrics; 2018, 1; 1-25
2080-0886
2080-119X

Pojawia się w:

Central European Journal of Economic Modelling and Econometrics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 27.

Tytuł:

System pomiarowy sygnałów HPEM w badaniach zabezpieczeń systemów teleinformatycznych
A measurement system of HPEM signals in investigations of teleinformatic system security

Autorzy:

Biaduń, M.
Berczyński, R.
Kuchta, M.

Powiązania:

https://bibliotekanauki.pl/articles/156906.pdf

Data publikacji:

2014

Wydawca:

Stowarzyszenie Inżynierów i Techników Mechaników Polskich

Tematy:

HPEM
sygnał szybkozmienny
przetwornik A/C
high-frequency signal
converter A/C

Opis:

W referacie przedstawiono system akwizycji danych pomiarowych z bardzo szybkim przetwornikiem analogowo-cyfrowym AD9484 Analog Devices. Stanowi on końcowy stopień systemu pomiarowego do identyfikacji i pomiarów wybranych parametrów impulsów elektromagnetycznych o bardzo dużej mocy [4]. Układ pomiarowy pozwala na przeprowadzenie badań związanych z bezpieczeństwem systemów teleinformatycznych narażonych na sygnały HPEM (ang. High Power Electromagnetics), czyli ekstremalnie wysokomocowych impulsów promieniowania elektromagnetycznego. Technologia opiera się na wykorzystaniu pola elektromagnetycznego o bardzo dużym natężeniu, powodując uszkodzenia lub zniszczenia urządzeń elektronicznych. Impulsy elektromagnetyczne HPEM charakteryzują się szczególnymi parametrami: wysoką mocą emitowanych impulsów, bardzo krótkim czasem trwania impulsów oraz prędkością propagacji równą prędkości światła, które sprawiają, że broń elektromagnetyczna jest niezwykle skuteczna w działaniach wojennych czy terrorystycznych. Rejestrację i analizę sygnałów wspomaga oprogramowanie VisualAnalog, zawierające bogaty zestaw do symulacji, przetwarzania danych oraz przeprowadzania licznych testów na zgromadzonych danych pomiarowych. Przedstawiono przykładowe charakterystyki amplitudowoczasowe oraz amplitudowo-częstotliwościowe sygnałów HPEM.
The paper presents a data acquisition system with a very fast analogtodigital converter Analog Devices AD9484. It is the final stage of a measurement system for identification and measurement of selected parameters of electromagnetic pulses of very high power [4]. The measurement system allows for tests connected with the security of ICT systems exposed to HPEM (High Power Electromagnetics) signals, which are extremely high power pulses of electromagnetic radiation. The technology is based on the use of the electromagnetic field of very high intensity, causing damage or destroying electronic devices. HPEM electromagnetic pulses are characterized by specific parameters: a high power of the emitted pulses, a very short duration of pulses and the propagation velocity equal to the speed of light which makes electromagnetic weapon extremely effective in warfare or terrorism. Recording and analyzing signals supports the VisualAnalog software, including a rich set of simulation, data processing, and performing a big number of tests on the collected measurement data. Examples of the amplitude-time and amplitude-frequency characteristics of HPEM signals are presented in Section 3 of the paper.

Źródło:

Pomiary Automatyka Kontrola; 2014, R. 60, nr 9, 9; 753-755
0032-4140

Pojawia się w:

Pomiary Automatyka Kontrola

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 28.

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

/5

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Skocz do pozycji: 29.

Tytuł:

Silicon carbide based DC-DC converter – operating analysis

Autorzy:

Niewiara, Ł.
Tarczewski, T.
Grzesiak, L. M.

Powiązania:

https://bibliotekanauki.pl/articles/377549.pdf

Data publikacji:

2016

Wydawca:

Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej

Tematy:

DC\DC converter
SiC MOSFETS
high switching frequency

Opis:

In this paper operating analysis of DC-DC converter is presented. Silicon Carbide based DC-DC converter is investigated. SiC power switches (i.e. MOSFETs and diodes) were used. Synchronous buck topology is applied for converter structure. The DC-DC converter mathematical model is also presented. The parameters of LC circuit were calculated using shown equations. Working conditions determine the values of output LC circuit (inductance and capacitance). The analysis of working conditions is presented for different switching frequencies. The size of passive components (LC) is compared for different operating points. Experimental tests results were presented. Waveforms of voltage and current signals were also shown.

Źródło:

Poznan University of Technology Academic Journals. Electrical Engineering; 2016, 88; 109-119
1897-0737

Pojawia się w:

Poznan University of Technology Academic Journals. Electrical Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 30.

Tytuł:

Symulacja numeryczna rzeczywistej baterii kondensatorowej pracującej w układach wielkiej częstotliwości w zastosowaniu do falowników. Część I. Kondensatory dla baterii wielkiej częstotliwości
Numerical simulation of the actual capacitor bank working in high frequency systems for use in inverters. Part I. Capacitors for high frequency banks

Autorzy:

Gąsiorski, A.
Posyłek, Z.
Roman, A.

Powiązania:

https://bibliotekanauki.pl/articles/103791.pdf

Data publikacji:

2017

Wydawca:

Uniwersytet Humanistyczno-Przyrodniczy im. Jana Długosza w Częstochowie. Wydawnictwo Uczelniane

Tematy:

kondensator
wielka częstotliwość
układ rezonansowy falowników
capacitors
high frequency
resonant systems of inverters

Opis:

W części I pracy pokazano rzeczywiste problemy związane z zastosowaniem kondensatorów wielkiej częstotliwości w układach rezonansowych falowników oraz przedstawiono kondensator jako element obwodu. Pokazano historyczne początki budowy pierwszych kondensatorów oraz pierwsze ich zastosowania w Częstochowie. Omówiono również sposób budowy i wielkości materiałowe stosowane do produkcji pojedynczych kondensatorów, zwłaszcza wykonanych z tworzyw, łączonych w baterie dla układów wielkiej częstotliwości stosowanych w wykonawczych (roboczych) układach rezonansowych falowników.
Part I of the paper shows the real problems associated with the use of high frequency capacitors in resonance systems of inverters and the capacitor is shown as a circuit element. The historical beginnings of the construction of the first capacitors and the first historical applications in Czestochowa are shown. The method of construction and material sizes used for the production of single capacitors, especially plastic, are combined in banks for high frequency circuits used in executive (working) resonant systems of inverters.

Źródło:

Prace Naukowe Akademii im. Jana Długosza w Częstochowie. Technika, Informatyka, Inżynieria Bezpieczeństwa; 2017, T. 5; 209-222
2300-5343

Pojawia się w:

Prace Naukowe Akademii im. Jana Długosza w Częstochowie. Technika, Informatyka, Inżynieria Bezpieczeństwa

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 31.

Tytuł:

Effect of High Frequency Heat Treatment on the Microstructure and Macroscopic Properties of WC-50Ni+Stellite 1 Coating Layer Fabricated by HVOF Spray Process

Autorzy:

Ham, Gi-Su
Wi, Dong-Yeol
Park, Sun-Hong
Lee, Kee-Ahn

Powiązania:

https://bibliotekanauki.pl/articles/354654.pdf

Data publikacji:

2020

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

HVOF spray
WC-50Ni
Stellite 1
composite coating
high frequency heat treatment

Opis:

The microstructure and macroscopic properties of WC-50Ni+stellite 1(Co-Cr-W, ST1) coating layer fabricated by HVOF spray have been investigated. WC-50Ni powder and ST1 powders were mixed in the ratio of 1:0 and 5:5 wt.%, respectively. Argon heat treatment (Ar) and high-frequency heat treatment (H.F.) were conducted on the coating materials. WC was decomposed in the Ar heat treatment specimen, but decomposition of WC was not observed in the H.F. heat treatment specimen. Hardness was measured for as-sprayed WC-50Ni (821.5Hv) and as-sprayed WC-50Ni+ST1 (668.1 Hv). Hardness of Ar heat treatment specimen was reduced by about 14~18% than that of the as-sprayed coating layers. However, when the H.F. heat treatment was performed, the hardness inversely increased by about 6~10% than the as-sprayed coating layer. Based on these results, the method to improve the mechanical property of HVOF sprayed WC-50Ni+ST1 coating layer has also been also discussed.

Źródło:

Archives of Metallurgy and Materials; 2020, 65, 3; 1087-1092
1733-3490

Pojawia się w:

Archives of Metallurgy and Materials

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 32.

Tytuł:

Analysis of the EUR/USD exchange rate in binary-temporal representation

Autorzy:

Stasiak, Michał Dominik

Powiązania:

https://bibliotekanauki.pl/articles/692587.pdf

Data publikacji:

2017

Wydawca:

Uniwersytet Ekonomiczny w Poznaniu

Tematy:

foreign exchange market
high frequency econometrics
technical analysis
modeling of currency exchange rates

Opis:

An exchange rate between two currencies can be described in a binary representation. The binarization algorithm transforms the exchange rate represented by tick data into a binary string. Each course change equal to a given discretization unit is assigned a binary value indicating the direction of the change. The performed statistical analysis confirms the existence of a correlation between previous course changes and the probability of future direction of the changes. In order to conduct a more detailed analysis of the exchange rate in a binary representation, each shift in the trajectory can be assigned a parameter representing the duration of the change. Depending on the current market dynamics, course trajectory changes may occur at different moments in time. The main goal of the presented research is to verify the existence of any dependences between the duration of a change and the probability of future direction of the change.

Źródło:

Research Papers in Economics and Finance; 2017, 2, 2; 39-45
2543-6430

Pojawia się w:

Research Papers in Economics and Finance

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 33.

Tytuł:

Wyznaczanie właściwości uziemień metodami statycznymi, wysokoczęstotliwościowymi i udarowymi
Determination of earthing properties using static, high frequency and impulse methods

Autorzy:

Wołoszyk, M.
Wojtas, S.

Powiązania:

https://bibliotekanauki.pl/articles/157090.pdf

Data publikacji:

2008

Wydawca:

Stowarzyszenie Inżynierów i Techników Mechaników Polskich

Tematy:

uziemienie
metoda udarowa
rezystancja
metoda wysokoczęstotliwościowa
earthing
resistance
impulse method
high frequency method

Opis:

Podstawowym parametrem charakteryzującym skuteczność działania uziemienia jest jego rezystancja, a niekiedy rezystancja udarowa lub impedancja. Parametry te stosowane są często zamiennie chociaż wyznacza się je różnymi metodami i często mają one różne wartości liczbowe dla tego samego uziemienia. W artykule przedstawiono różne metody pomiaru tych parametrów oraz zaprezentowano wyniki badań porównawczych wykonanych przy użyciu metody statycznej, wysokoczęstotliwościowej oraz udarowej. Omówiono obszary zastosowań oraz ograniczenia omawianych metod, a także typowe błędy związane z interpretacją wyników i błędy w dobrze metody.
The basic parameter for evaluating the earthing is usually its resistance. Sometimes the earthing properties are described by means of its impulse resistance or impedance. These parameters are determined by different methods and they often have different numerical values for the same earthing. The paper presents different methods for measuring the earthing parameters mentioned above and the results of comparative investigations obtained from the static, high frequency and impulse procedures. The aplication areas and limitations of all the described measurement methods as well as typical mistakes are described. The main reasons for the mistakes are usually wrong interpretations of the obtained results and wrong choice of the measurement method.

Źródło:

Pomiary Automatyka Kontrola; 2008, R. 54, nr 12, 12; 836-838
0032-4140

Pojawia się w:

Pomiary Automatyka Kontrola

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 34.

Tytuł:

Research into properties of power electronics devices made of silicon carbide sic, in conditions of commutating current with high frequency
Badania właściwości przyrządów energoelektronicznych wykonanych na bazie węglika krzemu w warunkach komutacji prądu z wysoką częstotliwością

Autorzy:

Michalski, A.
Zymmer, K.

Powiązania:

https://bibliotekanauki.pl/articles/158856.pdf

Data publikacji:

2011

Wydawca:

Sieć Badawcza Łukasiewicz - Instytut Elektrotechniki

Tematy:

przyrząd półprzewodnikowy
węglik krzemu
wielka częstotliwość
semiconductor devices
silicon carbide
high frequency convertes

Opis:

The paper presents results of measurements of the reverse recovery current and dynamic forward voltage of the SiC Schottky diodes at a current variation slope in a device, of 500 A/ s. These data were compared with the corresponding parameters determined for ultrafast silicon diodes. Results of tests of power losses in diodes made of silicon carbide, at a current commutation frequency of (10 200) kHz are presented, comparing them with corresponding data determined for ultrafast silicon diodes. Test results of power losses in transistors constituting elements of d.c. voltage controllers are also shown. Investigations were conducted with an ultrafast SiC diode and with an ultrafast silicon diode at the transistor switching frequency of 100 kHz.
W artykule przedstawiono wyniki pomiarów przejściowego prądu wstecznego oraz dynamicznego napięcia przewodzenia diod Schottky`ego wykonanych na bazie węglika krzemu - SiC. Pomiary przeprowadzono przy stromości zmian prądu wynoszącej 500 A/žs. Wyniki te porównano z odpowiednimi rezultatami uzyskanymi dla ultraszybkiej diody krzemowej o takich samych parametrach napięciowo-prądowych. Przedstawiono także wyniki pomiarów strat mocy generowanych w tych diodach w warunkach komutacji prądu z częstotliwością zmienianą w granicach (10 ÷ 200) kHz. Artykuł zawiera również wyniki badań strat mocy wydzielanych w tranzystorze kluczującym z częstotliwością 100 kHz. Wyniki te dotyczą przypadków współpracy tranzystora w procesie komutacji prądu z ultraszybką diodą krzemową oraz z diodą SiC.

Źródło:

Prace Instytutu Elektrotechniki; 2011, 253; 61-71
0032-6216

Pojawia się w:

Prace Instytutu Elektrotechniki

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 35.

Tytuł:

Impact of very high-frequency sound and low-frequency ultrasound on people – the current state of the art

Autorzy:

Pawlaczyk-Łuszczyńska, Małgorzata
Dudarewicz, Adam

Powiązania:

https://bibliotekanauki.pl/articles/2116587.pdf

Data publikacji:

2020-06-16

Wydawca:

Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi

Tematy:

low-frequency airborne ultrasound
high-frequency sound
occupational exposure
impact on humans
auditory effects
non-auditory effects

Opis:

For several decades, low-frequency ultrasound (<100 kHz) has been widely used in industry, medicine, commerce, military service and the home. The objective of the study was to present the current state of the art on the harmful effects of low-frequency airborne ultrasound on people, especially in occupational settings. The scientific literature search was performed using accessible medical and other databases (WOS, BCI, CCC, DRCI, DIIDW, KJD, MEDLINE, RSCI, SCIELO and ZOOREC), and the obtained results were then hand-searched to eliminate non-relevant papers. This review includes papers published in 1948–2018. The potential effects of the low-frequency airborne ultrasound have been classified as auditory and non-auditory effects, including subjective, physiological, and thermal effects. In particular, already in the 1960–1970s, it was demonstrated that ultrasonic exposure, when sufficiently intense, appeared to result in a syndrome involving nausea, headache, vomiting, disturbance of coordination, dizziness, and fatigue, and might cause a temporary or permanent hearing impairment. However, since that time, not too much work has been done. Further studies are needed before any firm conclusions can be drawn about the auditory and non-auditory effects of low-frequency airborne ultrasound.

Źródło:

International Journal of Occupational Medicine and Environmental Health; 2020, 33, 4; 389-408
1232-1087
1896-494X

Pojawia się w:

International Journal of Occupational Medicine and Environmental Health

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 36.

Tytuł:

Which Option Pricing Model Is the Best? HF Data for Nikkei 225 Index Options

Autorzy:

Kokoszczyński, Ryszard
Sakowski, Paweł
Ślepaczuk, Robert

Powiązania:

https://bibliotekanauki.pl/articles/1357377.pdf

Data publikacji:

2019-04-01

Wydawca:

Uniwersytet Warszawski. Wydział Nauk Ekonomicznych

Tematy:

Option pricing models
high-frequency data
realized volatility
implied volatility
stochastic volatility
emerging markets

Opis:

In this study, we analyse the performance of option pricing models using 5-minutes transactional data for the Japanese Nikkei 225 index options. We compare 6 different option pricing models: the Black (1976) model with different assumptions about the volatility process (realized volatility with and without smoothing, historical volatility and implied volatility), the stochastic volatility model of Heston (1993) and the GARCH(1,1) model. To assess the model performance, we use median absolute percentage error based on differences between theoretical and transactional options prices. We present our results with respect to 5 classes of option moneyness, 5 classes of option time to maturity and 2 option types (calls and puts). The Black model with implied volatility (BIV) comes as the best and the GARCH(1,1) as the worst one. For both call and put options, we observe the clear relation between average pricing errors and option moneyness: high error values for deep OTM options and the best fit for deep ITM options. Pricing errors also depend on time to maturity, although this relationship depend on option moneyness. For low value options (deep OTM and OTM), we obtained lower errors for longer maturities. On the other hand, for high value options (ITM and deep ITM) pricing errors are lower for short times to maturity. We obtained similar average pricing errors for call and put options. Moreover, we do not see any advantage of much complex and time-consuming models. Additionally, we describe liquidity of the Nikkei225 option pricing market and try to compare the results we obtain here with a detailed study for Polish emerging option market (Kokoszczyński et al. 2010b).

Źródło:

Central European Economic Journal; 2017, 4, 51; 18 - 39
2543-6821

Pojawia się w:

Central European Economic Journal

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 37.

Tytuł:

A novel circuit topology of modified switched boost hybrid resonant inverter fitted induction heating equipment

Autorzy:

Bhattacharya, A.
Sit, K.
Sadhu, P. K.
Pal, N.

Powiązania:

https://bibliotekanauki.pl/articles/140770.pdf

Data publikacji:

2016

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

modified switched boost
high frequency
hybrid resonant inverter
induction heating
controllability
VSI and PSIM

Opis:

A novel circuit topology of modified switched boost high frequency hybrid resonant inverter fitted induction heating equipment is presented in this paper for efficient induction heating. Recently, induction heating technique is becoming very popular for both domestic and industrial purposes because of its high energy efficiency and controllability. Generally in induction heating, a high frequency alternating magnetic field is required to induce the eddy currents in the work piece. High frequency resonant inverters are incorporated in induction heating equipment which produce a high frequency alternating magnetic field surrounding the coil. Previously this high frequency alternating magnetic field was produced by voltage source inverters. But VSIs have several demerits. So, in this paper, a new scheme of modified switched boost high frequency hybrid resonant inverter fitted induction heating equipment has been depicted which enhances the energy efficiency and controllability and the same is validated by PSIM.

Źródło:

Archives of Electrical Engineering; 2016, 65, 4; 815-826
1427-4221
2300-2506

Pojawia się w:

Archives of Electrical Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 38.

Tytuł:

Filtry sinusoidalne jako skuteczna ochrona wysokoobrotowych silników w układach napędowych o podwyższonej częstotliwości
Sinewave filters as an effective protection of high-speed motor in high frequency drives

Autorzy:

Czornik, Jarosław
Haltof, Maciej
Jasiński, Leszek

Powiązania:

https://bibliotekanauki.pl/articles/2142538.pdf

Data publikacji:

2022

Wydawca:

Sieć Badawcza Łukasiewicz - Instytut Napędów i Maszyn Elektrycznych Komel

Tematy:

filtr sinusoidalny
napęd o podwyższonej częstotliwości
silnik wysokoobrotowy
sine wave filters
high frequency drive
high-speed motor

Opis:

Układy napędowe o podwyższonej częstotliwości to grupa urządzeń, która w ostatnich latach najmocniej zaznaczyła swoją obecność na rynku Oil & Gas. Podwyższona częstotliwość napięcia wyjściowego przekształtnika umożliwia regulację prędkości obrotowych w szerszym zakresie. Zwiększa to wydajność i uniwersalność całego napędu, ale jednocześnie powoduje dodatkowe zagrożenia dla izolacji kabli zasilających, transformatora podwyższającego jak i samego silnika. Niezbędnym elementem takiego układu staje się filtr sinusoidalny, który zapewnia ochronę i niezawodność całego napędu. W artykule przedstawiono analizę doboru elementów składowych filtru sinusoidalnego LC i ich parametrów względem podwyższonej częstotliwości pracy i częstotliwości przełączeń. Przedstawiono wyniki badań wpływu tych parametrów na pracę filtru oraz na przebieg napięcia wyjściowego i współczynnik odkształcenia THDu.
Drive systems with increased frequency are a group of devices that has made a significant presence in the Oil & Gas industry in recent years. Increased frequency of the converter output voltage allows speed changes in a wider range. This increases the efficiency and versatility of the entire drive, but at the same time causes additional stresses for the insulation of the power cables, the step-up transformer and the motor itself. Therefore, an indispensable element of such a system is a sinusoidal filter, which ensures protection and reliability of the entire drive. The article presents an analysis of the selection of components of a sinusoidal LC filter and its parameters in a relation to the increased operating frequency and switching frequency. The results of the research on the influence of these parameters on the filter operation, output voltage and the THDu coefficient have been presented.

Źródło:

Maszyny Elektryczne: zeszyty problemowe; 2022, 3, 1 (127); 89--94
0239-3646
2084-5618

Pojawia się w:

Maszyny Elektryczne: zeszyty problemowe

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 39.

Tytuł:

Characteristics and Applications of Silicon Carbide Power Devices in Power Electronics

Autorzy:

Kondrath, N.
Kazimierczuk, M. K.

Powiązania:

https://bibliotekanauki.pl/articles/226774.pdf

Data publikacji:

2010

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

silicon carbide (SiC)
SiC properties
high voltage
high-temperature
high-frequency applications
high-temperature electronics
wide energy band-gap semiconductors

Opis:

Silicon carbide materials, with its high mechanical strength, high thermal conductivity, ability to operate at high temperatures, and extreme chemical inertness to most of the electrolytes, are very attractive for high-power applications. In this paper, properties, advantages, and limitations of SiC and conventional Si materials are compared. Various applications, where SiC power devices are attractive, are discussed.

Źródło:

International Journal of Electronics and Telecommunications; 2010, 56, 3; 231-236
2300-1933

Pojawia się w:

International Journal of Electronics and Telecommunications

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 40.

Tytuł:

Wykorzystanie modeli wyrównywania wykładniczego w prognozowaniu zmiennych o wysokiej częstotliwości w warunkach braku pełnej informacji
Application of exponential smoothing models in forecasting high frequency time series in the condition of lack of full information

Autorzy:

Szmuksta-Zawadzka, Maria
Zawadzki, Jan

Powiązania:

https://bibliotekanauki.pl/articles/425251.pdf

Data publikacji:

2015

Wydawca:

Wydawnictwo Uniwersytetu Ekonomicznego we Wrocławiu

Tematy:

forecasting
high frequency time series
complex seasonality
exponential smoothing models
systematic gaps in the data

Opis:

The paper will present the results of the application of the modified additive and multiplicative exponential smoothing models (Brown, Holt and Holt-Winters) in the interpolation and extrapolation forecasting of demand for power energy in the agglomeration A in hour periods, based on time series with systematic gaps. The basis for the construction of forecasts will be time series, from which twelve month, weekly and twenty-four hour fluctuation cycles have been eliminated. Additionally the comparative analysis of accuracy of forecasts built for classical time series models with complex seasonal fluctuations will be conducted. There also will be presented an assess of the criteria for selecting the optimal values of the smoothing constants in terms of building an ex ante forecasts.

Źródło:

Econometrics. Ekonometria. Advances in Applied Data Analytics; 2015, 4 (50); 228-239
1507-3866

Pojawia się w:

Econometrics. Ekonometria. Advances in Applied Data Analytics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 41.

Tytuł:

Bayesian optimization for solving high-frequency passive component design problems

Autorzy:

Baranowski, Michal
Fotyga, Grzegorz
Lamecki, Adam
Mrozowski, Michal

Powiązania:

https://bibliotekanauki.pl/articles/2173688.pdf

Data publikacji:

2022

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

high-frequency design
machine learning
Bayesian optimization
optymalizacja bayesowska
konstrukcja o wysokiej częstotliwości
nauczanie maszynowe

Opis:

In this paper, the performance of the Bayesian Optimization (BO) technique applied to various problems of microwave engineering is studied. Bayesian optimization is a novel, non-deterministic, global optimization scheme that uses machine learning to solve complex optimization problems. However, each new optimization scheme needs to be evaluated to find its best application niche, as there is no universal technique that suits all problems. Here, BO was applied to different types of microwave and antenna engineering problems, including matching circuit design, multiband antenna and antenna array design, or microwave filter design. Since each of the presented problems has a different nature and characteristics such as different scales (i.e. number of design variables), we try to address the question about the generality of BO and identify the problem areas for which the technique is or is not recommended.

Źródło:

Bulletin of the Polish Academy of Sciences. Technical Sciences; 2022, 70, 4; art. no. e141595
0239-7528

Pojawia się w:

Bulletin of the Polish Academy of Sciences. Technical Sciences

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 42.

Tytuł:

Zastosowanie drapieżnych strategii w handlu o wysokiej częstotliwości

Autorzy:

Lenczewski Martins, Carlos Jorge

Powiązania:

https://bibliotekanauki.pl/articles/610061.pdf

Data publikacji:

2017

Wydawca:

Uniwersytet Marii Curie-Skłodowskiej. Wydawnictwo Uniwersytetu Marii Curie-Skłodowskiej

Tematy:

High-Frequency Trading
predatory strategies
algorithmic trading
handel o wysokiej częstotliwości
strategie drapieżne
handel algorytmiczny

Opis:

The development of High-Frequency Trading since the 1990s has been so dynamic, that one may say it certainly will be present in every country, sooner or later. Most of the research dedicated to High-Frequency Trading is dedicated to show how detrimental it may be to the financial system, other present business models and integration with other entities of the financial market, some try to research how profitable this type of trading may be, and finally some research is dedicated to the risk analysis – although these papers are very limited. This paper is aimed to expand the topic of business models by showing selected strategies of High-Frequency Trading. This is very important since these strategies may be also implemented in conditions of lower liquidity and have a direct influence on the stability of large institutions.
Rozwój handlu o wysokiej częstotliwości, który powstał w latach 90. XX w., jest tak dynamiczny, że można stwierdzić, iż z pewnością będzie obecny w każdym kraju. Większość opracowań poświęconych handlowi o wysokiej częstotliwości można podzielić na: starające się wykazać, jak szkodliwy jest on dla systemu finansowego; opisujące modele biznesowe i współdziałanie z pozostałymi podmiotami rynku finansowego; wykazujące opłacalność handlu i podmiotów stosujących ten rodzaj handlu; poświęcone zagadnieniom zarządzania ryzykiem transakcji o wysokiej częstotliwości, chociaż ich liczba jest bardzo ograniczona. Niniejsze opracowanie ma na celu rozwijać zagadnienia związane z modelami biznesowymi, omawiając wybrane drapieżne techniki w handlu o wysokiej częstotliwości. Jest to dość istotne, ponieważ mogą one być zastosowane w warunkach o niskiej płynności oraz mogą wpływać bezpośrednio na działalność i stabilność pojedynczych, a także znaczących instytucji finansowych.

Źródło:

Annales Universitatis Mariae Curie-Skłodowska, sectio H – Oeconomia; 2017, 51, 4
0459-9586

Pojawia się w:

Annales Universitatis Mariae Curie-Skłodowska, sectio H – Oeconomia

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 43.

Tytuł:

Current dependence of resistances and capacitances in a vertical-cavity surface-emitting laser
Prądowa zależność rezystancji i pojemności w laserze o emisji powierzchniowej z pionową wnęką rezonansową

Autorzy:

Komar, P.
Śpiewak, P.
Gębski, M.
Lott, J. A.
Wasiak, M.

Powiązania:

https://bibliotekanauki.pl/articles/296617.pdf

Data publikacji:

2017

Wydawca:

Politechnika Łódzka. Wydawnictwo Politechniki Łódzkiej

Tematy:

high-frequency modulation
capacitance
modelling of semiconductor lasers
modulacja wysokiej częstotliwości
pojemność
modelowanie laserów półprzewodnikowych

Opis:

Based on the model of impedance and modulation time constants for vertical-cavity surface-emitting lasers (VCSELs) we study the resistances and capacitances of an equivalent circuit as a function of the current flowing through the VCSEL. We observe reduction of some components of the resistance and the capacitance, as well as the modulation time constants for increasing current.
W oparciu o model impedancji i stałych czasowych modulacji dla laserów o emisji powierzchniowej z pionową wnęką rezonansową (VCSEL) badamy opory i pojemności równoważnego obwodu w funkcji prądu przepływającego przez laser. Obserwujemy, że wraz ze wzrostem prądu przepływającego przez urządzenie, niektóre ze składowych rezystancji i pojemności w elektrycznym układzie zastępczym ulegają zmniejszeniu. Wraz ze wzrostem prądu zmniejsza się również stała czasu modulacji.

Źródło:

Scientific Bulletin. Physics / Technical University of Łódź; 2017, 38; 53-60
1505-1013
2449-982X

Pojawia się w:

Scientific Bulletin. Physics / Technical University of Łódź

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 44.

Tytuł:

EM emission of ICs implementated in FPGA : influence of floor plan and electric function

Autorzy:

Szczęsny, J.
Kołodziejski, J. F.

Powiązania:

https://bibliotekanauki.pl/articles/378429.pdf

Data publikacji:

2007

Wydawca:

Sieć Badawcza Łukasiewicz - Instytut Technologii Elektronowej

Tematy:

FPGA
emisja elektromagnetyczna
prąd wysokiej częstotliwości
Xilinx
electromagnetic emission
high frequency current
near-field disturbances

Opis:

In the paper some investigations are presented aiming to check the influence of IC floor plan and the circuit function on its electromagnetic emissions. As the test vehicle Xilinx FPGA XCV800 type was used, in which two types of multiplicators were implemented. To compare the effects, high frequency currents in supply and ground pins of the circuits as well as near field disturbances were measured over the circuits.

Źródło:

Electron Technology : Internet Journal; 2007, 39, 4; 1-7
1897-2381

Pojawia się w:

Electron Technology : Internet Journal

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 45.

Tytuł:

Effect of High-Frequency Electric Resistance Welding (HF-ERW) Parameters on Metallurgical Transformations and Tensile Properties of API X52 Microalloy Steel Welding Joint

Autorzy:

Sabzi, M.
Kianpour-Barjoie, A.
Ghobeiti-Hasab, M.
Dezfuli, S. M.

Powiązania:

https://bibliotekanauki.pl/articles/353144.pdf

Data publikacji:

2018

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

High Frequency Electric Resistance Welding
HF-ERW
frequency
compression force
Vee angle
mechanical behavior
API X52 microalloyed steel

Opis:

This study investigates the effects of frequency, compression force and Vee angle parameters of High-Frequency Electric Resistance Welding (HF-ERW) process on mechanical properties of API X52 microalloy steel welding joint. Therefore, API X52 microalloy steel sheets having thickness of 8 mm was provided to manufacture pipes with the diameter of 16”. with direct weld seams using the HF-ERW method. During the manufacturing process, frequency values of 150, 200 and 250 kHz, compression forces of 2, 4 and 6 mark and Vee angles of 3°, 5°, and 7° were adopted. After changing the welding parameters, from the welded pipes, tensile and Charpy impact test samples prepared to macroscopically evaluate the weld metal flow and examine the effects of these parameters on mechanical properties of the welded joints. According to the results, it was concluded that frequency of 150 kHz, the compression force of 4 mark and Vee angle of 5° yields best mechanical properties in the HF-ERW joint of API X52 microalloy steel.

Źródło:

Archives of Metallurgy and Materials; 2018, 63, 4; 1693-1699
1733-3490

Pojawia się w:

Archives of Metallurgy and Materials

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 46.

Tytuł:

Wartość zagrożona portfela inwestycyjnego szacowana na podstawie danych wysokiej częstotliwości − badania empiryczne
Value at risk of the investment portfolio based on high frequency data − empirical studies

Autorzy:

Iskra, Daniel
Czernik, Tadeusz

Powiązania:

https://bibliotekanauki.pl/articles/586363.pdf

Data publikacji:

2015

Wydawca:

Uniwersytet Ekonomiczny w Katowicach

Tematy:

Dane wysokiej częstotliwości
Optymalny portfel inwestycyjny
Wartość zagrożona
High frequency data
Optimal portfolio
Value at Risk

Opis:

W opracowaniu zaprezentowano wyniki szacowania wartości zagrożonej spółek oraz optymalnych portfeli inwestycyjnych. Badania przeprowadzono na minutowych notowaniach spółek wchodzących w skład indeksu S&P100. W symulacjach uwzględniono dwa podejścia konstrukcji empirycznych rozkładów logarytmicznej stopy zwrotu użytych do wyznaczania wartości zagrożonej. W pierwszym z nich rozpatrywany szereg zawierał kolejne notowania cen akcji. W podejściu drugim w konstrukcji rozkładów empirycznych dokonano podziału dni na części i wyznaczano rozkład na podstawie danych z wybranych części dnia sesyjnego (np. z jednej godziny) z kilku, kilkunastu dni. W wyniku przeprowadzonych badań wykazano, iż w pewnych przypadkach (użyte podejście, zakres parametrów) zgodność oszacowanej wartości zagrożonej z realnymi stratami była wysoka.
Paper presents results of estimating Value at Risk for stocks and the optimal investment portfolios. Study was conducted at the minute quotations of companies included in the S&P100 index. The simulations included two design approaches of empirical distributions of the logarithmic rate of return used to determine the value at risk. The first one takes into account consecutive price quotations. In the second price quotations were divided into empirical distributions days were divided into six groups (quotations which come from time interval e.g. 10 am-11 am from each consecutive day were transferred to the same data set). The research has shown that in certain cases the accuracy of the estimated value at risk of real loss was high.

Źródło:

Studia Ekonomiczne; 2015, 221; 32-49
2083-8611

Pojawia się w:

Studia Ekonomiczne

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 47.

Tytuł:

Hearing status of people occupationally exposed to ultrasonic noise

Autorzy:

Dudarewicz, Adam
Zamojska-Daniszewska, Małgorzata
Zaborowski, Kamil
Pawlaczyk-Łuszczyńska, Małgorzata

Powiązania:

https://bibliotekanauki.pl/articles/2084911.pdf

Data publikacji:

2022-06-08

Wydawca:

Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi

Tematy:

noise
pure-tone audiometry
otoacoustic emissions
noise-induced hearing loss
ultrasonic noise
extended high-frequency audiometry

Opis:

ObjectivesThe aim of the study was to evaluate the hearing status of operators of low-frequency ultrasonic devices compared to employees exposed to audible noise at a similar A-weighted sound pressure level (SPL) but without ultrasonic components.Material and MethodsStandard pure-tone audiometry, extended high-frequency audiometry (EHFA), transient-evoked otoacoustic emissions (TEOAE), and distortion-product otoacoustic emissions (DPOAE), as well as questionnaire surveys were conducted among 148 subjects, aged 43.1±10.8 years, working as ultrasonic device operators for 18.7±10.6 years. Their exposure to noise within the ultrasonic and audible frequency range was also evaluated. The control group comprised 168 workers, adjusted according to gender, age (±2 years), tenure (±2 years), and the 8-hour daily noise exposure level (LEX,8h) of ±2 dB.ResultsThe ultrasonic device operators and the control group were exposed to audible noise at L_EX,8h of 80.8±3.9 dB and 79.1±3.4, respectively. The Polish maximum admissible intensity (MAI) values for audible noise were exceeded in 16.8% of the ultrasonic device operators, while 91.2% of them were exposed to ultrasonic noise at SPL>MAI values. There were no significant differences between the groups in terms of the hearing threshold levels (HTLs) up to 3 kHz, while the ultrasonic device operators exhibited significantly higher (worse) HTLs, as compared to the control group, in the range of 4–14 kHz. The results of the DPOAE and TEOAE testing also indicated worse hearing among the ultrasonic device operators. However, the differences between the groups were more pronounced in the case of EHFA and DPOAEs.ConclusionsThe outcomes of all hearing tests consistently indicated worse hearing among the ultrasonic device operators as compared to the control group. Both EHFA and DPOAE seem to be useful tools for recognizing early signs of hearing loss among ultrasonic device operators.

Źródło:

International Journal of Occupational Medicine and Environmental Health; 2022, 35, 3; 309-325
1232-1087
1896-494X

Pojawia się w:

International Journal of Occupational Medicine and Environmental Health

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 48.

Tytuł:

Symulacja numeryczna rzeczywistej baterii kondensatorowej pracującej w układach wielkiej częstotliwości w zastosowaniu do falowników. Część II. Modele elektryczne rzeczywistych kondensatorów tworzących baterie. I symulacja pracy wybranych połączeń elementów tych baterii
Numerical simulation of the actual capacitor bank working in high frequency systems for use in inverters Part II. Electrical models of the actual capacitors forming the banks and simulating the operation of selected connections of the components of these banks

Autorzy:

Gąsiorski, A.
Posyłek, Z.
Roman, A.

Powiązania:

https://bibliotekanauki.pl/articles/103422.pdf

Data publikacji:

2017

Wydawca:

Uniwersytet Humanistyczno-Przyrodniczy im. Jana Długosza w Częstochowie. Wydawnictwo Uczelniane

Tematy:

kondensator
obwody wielkiej częstotliwości
symulacja numeryczna
pomiary praktyczne
capacitors
high frequency circuits
numerical simulation
practical measurements

Opis:

W części II pracy przedstawiono stosowane modele elektryczne rzeczywistych kondensatorów od prostych do bardziej skomplikowanych oraz dokonano wyboru modelu pięcioelementowego, niezbyt skomplikowanego, ale odzwierciedlającego w sposób najprostszy w swoim schemacie istotę problematyki obwodów wielkiej częstotliwości. Zastosowano wybrany model do utworzenia baterii równolegle połączonych pięciu kondensatorów, działanie baterii zostało opisane równaniami, które były podstawą do przeprowadzenia symulacji numerycznej. Symulacja pokazała zachowanie się elementarnych rzeczywistych kondensatorów wchodzących w skład baterii w funkcji częstotliwości i pozwoliła na wyciągnięcie wniosków. Wszelkie pomiary praktyczne zostały wykonane w Laboratorium Badawczym Elektrycznym Wydziału Elektrycznego Politechniki Częstochowskiej.
Part II of the paper presents the applied electrical models of real capacitors from simple to more complex and has chosen a five-element model that is not too complicated but reflects the essence of the problem of high frequency circuits in the simplest way. The selected model was used to create a bank in parallel with five capacitors connected, the bank was described by the equations that were the basis for the numerical simulation. The simulation showed the behavior of the elementary real capacitors in the bank as a function of frequency and allowed to extract and record the conclusions. All practical measurements were performed at the Electrical Testing Laboratory of the Czestochowa University of Technology.

Źródło:

Prace Naukowe Akademii im. Jana Długosza w Częstochowie. Technika, Informatyka, Inżynieria Bezpieczeństwa; 2017, T. 5; 223-236
2300-5343

Pojawia się w:

Prace Naukowe Akademii im. Jana Długosza w Częstochowie. Technika, Informatyka, Inżynieria Bezpieczeństwa

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 49.

Tytuł:

Zastosowanie ultrasonografii w medycynie estetycznej i kosmetologii - doświadczenia własne
The usefulness of ultrasonography in aesthetic medicine and cosmetology - own experiences

Autorzy:

Mlosek, R.
Jakubowski, W.

Powiązania:

https://bibliotekanauki.pl/articles/261451.pdf

Data publikacji:

2011

Wydawca:

Politechnika Wrocławska. Wydział Podstawowych Problemów Techniki. Katedra Inżynierii Biomedycznej

Tematy:

kosmetologia
medycyna estetyczna
ultrasonografia klasyczna
ultrasonografia wysokich częstotliwości
cosmetology
aesthetic medicine
classical ultrasonography
high-frequency ultrasonography

Opis:

Badania ultrasonograficzne stają się coraz bardziej popularne w medycynie estetycznej i kosmetologii. W badaniach skóry użyteczna jest ultrasonografia klasyczna oraz ultrasonografia wysokich częstotliwości. W ultrasonografii klasycznej wykorzystywane są głowice o częstotliwości do 20 MHz, natomiast w ultrasonografii wysokich częstotliwości głowice 20-100 MHz. Ta druga umożliwia szczegółowe obrazowanie naskórka, skóry właściwej oraz górnej części tkanki podskórnej. Ultrasonografia klasyczna pozwala uwidocznić całą tkankę podskórną. W kosmetologii i medycynie estetycznej ultrasonografia stosowana jest do oceny stanu skóry oraz do monitorowania przebiegu terapii poprawiających jej wygląd.
Ultrasound examinations of skin are more and more popular in aesthetic medicine and cosmetology. In the examinations of skin, the classical ultrasonography and high-frequency ultrasonography, are useful. In the classical ultrasonography, the transducers characterized by the frequency up to 20 MHz are applied, while in the high-frequency ultrasonography these values are in the range of 20 MHz to 100 MHz. High-frequency ultrasonography allows for the detailed imaging of the epidermis, dermis and the upper part of subcutaneous tissue. The classical ultrasonography enables the visualization of the entire subcutaneous tissue. In the cosmetology and aesthetic medicine ultrasonography is used to evaluate skin condition and to monitor the results of the therapy applied to improve its appearance.

Źródło:

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna; 2011, 17, 3; 227-230
1234-5563

Pojawia się w:

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 50.

Tytuł:

Antireflux surgery is required after endoscopic treatment for Barrett’s esophagus

Autorzy:

Tyselskyi, Volodymyr
Poylin, Vitaliy
Tkachuk, Olga
Kebkalo, Andrey

Powiązania:

https://bibliotekanauki.pl/articles/1391513.pdf

Data publikacji:

2021

Wydawca:

Index Copernicus International

Tematy:

antireflux operation
argonoplasmic coagulation
Barrett’s esophagus
gastroesophageal reflux disease
high-frequency welding of living tissues

Opis:

Introduction: Barrett’s esophagus is an acquired condition that develops as a result of transformation of normal stratified squamous epithelium in the lower part of the esophagus into columnar epithelium. Barrett’s esophagus is considered to be a complication of gastroesophageal reflux disease (GERD). Various endoscopic techniques have been shown to be successful in the treatment of this condition. However, long-term success in preventing further esophageal dysplasia is not clear. Biological welding consists in the application of controlled high-frequency current on living tissues and has been used to stop gastrointestinal bleeding, similarly to the APC technique which involves ablation of small intestinal metaplasia of the esophageal mucosa. Aim: The goal of this study was to evaluate the effectiveness of endoscopic techniques in the treatment of Barrett’s esophagus and verify the need for a subsequent surgical intervention in patients with GERD complicated by Barrett’s esophagus. Material and methods: Patients with Barrett’s esophagus C1-3M2-4 (Prague classification from 2004) and high dysplasia without nodules, as well as patients with confirmed GERD without hiatal hernia, were included in this study. Endoscopic treatment was performed with the use of argonoplasmic coagulation (APC) and high-frequency welding of living tissues (HFW). After the examination the patients were re-examined. Patients with recurrence of metaplasia and high DeMeester score (˃ 100) underwent antireflux surgery – crurography and Nissen fundoplication with creation of a soft and short cuff.Results: A total of 89 patients were included in the study, 81 of whom were reexamined after ablation of Barrett’s esophagus.In 12 patients, a recurrence of intestinal metaplasia resembling the small intestine was identified. Implementation of two-stage treatment was required for 9 patients – it involved a second procedure of ablation of the esophagus, followed by antireflux surgery. Surgical treatment was refused by 3 patients, who underwent only the second ablation procedure. All patients received drug therapy, consisting of prokinetics and proton pump inhibitors. Esophageal pH monitoring was repeated 3 months after surgery, showing normalization of the DeMeester score. As a result, the patients experienced no complaints such as heartburn, chest pain or dysphagia, which significantly improved their quality of life. Esophagogastroduodenoscopy and biopsy of the mucous membrane of the lower third of the esophagus were performed in accordance with the Seattle Protocol. After examining histological specimens, no regions of metaplasia were identified. Conclusion: Antireflux surgery is required as a part of the treatment for Barrett’s esophagus, which prevents further dysplasia and development of esophageal cancer.

Źródło:

Polish Journal of Surgery; 2021, 93, 5; 1-5
0032-373X
2299-2847

Pojawia się w:

Polish Journal of Surgery

Dostawca treści:

Biblioteka Nauki

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