Informacja

Drogi użytkowniku, aplikacja do prawidłowego działania wymaga obsługi JavaScript. Proszę włącz obsługę JavaScript w Twojej przeglądarce.

Wyszukujesz frazę "high-frequency" wg kryterium: Temat


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
Artykuł
Tytuł:
Development of the power supply and control system for the hemodialysis machine
Rozwój układu zasilania i sterowania urządzenia do hemodializy
Autorzy:
Yaskiv, Volodymyr
Yaskiv, Anna
Powiązania:
https://bibliotekanauki.pl/articles/27315436.pdf
Data publikacji:
2023
Wydawca:
Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
Tematy:
hemodialysis
power supply and control system
rectangular hysteresis loop
high-frequency magnetic amplifier
hemodializa
układ zasilania i sterowania
prostokątna pętla histerezy
wzmacniacz magnetyczny wysokiej częstotliwości
Opis:
The article describes new approaches to creating an autonomous compact system with automatic control for hemodialysis. It is proposed to organize a closed circuit for cleaning the dialysis solution using an electrolytic regenerator as a function of the concentration of urea in it. The functional diagram of the created system is presented and described. To power the regenerator, ensure thermal stabilization of the solution, and power auxiliary electronic and electrical equipment, a multi-channel power supply and control system for the hemodialysis machine based on high-frequency magnetic amplifiers has been developed and researched. The advantages of power switches based on high-frequency magnetic amplifiers in comparison with transistor switches, including in the construction of controlled power sources, are given. The principle of operation of the voltage regulator on high-frequency magnetic amplifiers is described. Theoretical and experimental oscillograms are given. Photographs of the experimental unit as well as an industrial sample of the multi-channel power supply and control system of the hemodialysis machine are provided. Their main technical characteristics are given. Conclusions to the conducted work are formulated. Carrying out the regeneration of the dialysis solution significantly reduces its costs – 2 liters of solution, which is suitable for use for 6 months, is enough for the operation of the device. Existing hemodialysis machines are a stationary open system using a single-use dialysis solution at a rate of up to 35 l/h, which ties the machine to stationary clinical conditions. Introducing feedback on the concentration of urea in the dialysis solution allows you to automate the blood purification procedure, as well as automatically complete hemodialysis at the necessary time, and also eliminates the dependence of the device on the conditions of the hospital.
Do zasilania regeneratora, stabilizacji termicznej roztworu oraz zasilania pomocniczych urządzeń elektronicznych i elektrycznych opracowano i zbadano wielokanałowy układ zasilania i sterowania aparatu do hemodializy oparty na wzmacniaczach magnetycznych wysokiej częstotliwości. Przedstawiono zalety wyłączników mocy opartych na wzmacniaczach magnetycznych wysokiej częstotliwości w porównaniu z wyłącznikami tranzystorowymi, w tym w budowie sterowanych źródeł prądu. Opisano zasadę działania regulatora napięcia we wzmacniaczach magnetycznych wysokiej częstotliwości. Podano oscylogramy teoretyczne i eksperymentalne. Przedstawiono fotografie jednostki doświadczalnej oraz próbkę przemysłową wielokanałowego układu zasilania i sterowania aparatu do hemodializy. Podano ich główne parametry techniczne. Sformułowano wnioski z przeprowadzonej pracy. Przeprowadzenie regeneracji płynu do dializy znacząco obniża jego koszty – do pracy urządzenia wystarczają 2 litry płynu, który wystarcza na 6 miesięcy. Istniejące aparaty do hemodializy to stacjonarne systemy otwarte wykorzystujące roztwór do dializy jednorazowego użytku z szybkością do 35 l/h, co wiąże urządzenie ze stacjonarnymi warunkami klinicznymi. Wprowadzenie informacji zwrotnej o stężeniu mocznika w płynie dializacyjnym pozwala zautomatyzować procedurę oczyszczania krwi, a także automatycznie zakończyć hemodializę w wymaganym czasie, a także eliminuje zależność urządzenia od warunków panujących w szpitalu.
Źródło:
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska; 2023, 13, 3; 23--28
2083-0157
2391-6761
Pojawia się w:
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Expiration day effects of stock and index futures on the Warsaw Stock Exchange before and in the initial phase of the COVID-19 pandemic
Autorzy:
Suliga, Milena
Powiązania:
https://bibliotekanauki.pl/articles/24201282.pdf
Data publikacji:
2023
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
COVID-19
event study
expiration day effects
futures market
high-frequency data
stock market
Warsaw Stock Exchange
Opis:
This paper examines the existence of expiration day effects of stock and index derivatives on the Warsaw Stock Exchange. Event study analysis is employed to high-frequency data to check the occurrence of four types of anomalies: abnormal increase in trading volume and in intraday volatility of underlying stocks, price reversal and price shock. The study confirms that on expiration days trading volume of underlying stocks increase unusually during the time when final settlement prices of expiring futures are being calculated. Intraday volatility of stock prices is also abnormally high on expiration days. However, before 2020 this price effect occurred on expiration days during triple withing hour, while in the initial phase of COVID-19 pandemic it has been visible on expiration days only at the close and additionally at the beginning of the next trading session. The analysis of price reversal and price shock effects revealed that only the second anomaly is a phenomenon which constantly appears after futures expiration, indicating the distortion of stock prices on expiration days and their return to normal levels at the beginning of the next trading session. Division of the research period (2018-2020) into two parts allow to find out that after the outbreak of the pandemic, when the importance of hedgers’ activity on the futures market have increased, some of the analyzed anomalies have weakened and their duration have been shortened. However, distortions of underlying stock prices have been still visible at the close of the trading session on expiration days. This suggests that as long as the final settlement prices of stock future are equal to closing prices of underlying stocks, expiration day effects will occur on the WSE.
Źródło:
Managerial Economics; 2023, 23, 1; 39--82
1898-1143
Pojawia się w:
Managerial Economics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on the influence of power frequency electric field of pantograph on passengers’ health in high-speed EMU
Autorzy:
Tian, Rui
Zhang, Jia-Qi
Lu, Mai
Powiązania:
https://bibliotekanauki.pl/articles/24202736.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
induced current density
induced electric field intensity
high-speed EMU
pantograph
power frequency electric field
Opis:
In this work we discussed the safety of the electric field environment in the No. 3 carriage where the pantograph is located. DSA380 pantograph, CRH5 EMU carriage and passengers’ models were established to study the electric field exposure of passengers at different positions. The results showed that Emax in the carriage without passengers is 1.173 x 10 6 mV/m. Then we set the passengers’ positions according to the electric field distribution in the carriage without passengers and obtained that Emax in the carriage with passengers is 3.195 x 10 6 mV/m. It can be seen that the maximum induced electric field intensity of passengers at different positions appears on the soles of shoes, the maximum value is 3.028 x 105 mV/m, the maximum induced current density occurs at the ankle, its maximum value is 3.476 x 10 -5 A/m 2. It can be concluded that the maximum induced electric field intensity of passenger’s head appears in the cerebrospinal fluid area, with a maximum value of 202.817 mV/m, and the maximum induced electric field intensity of passenger’s head at the door is larger than that in the middle of the carriage. The maximum values of the induced electric field intensity in all tissues of passengers are much smaller than the basic limits of electromagnetic exposure to the public set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). This study indicated that the pantograph has little influence on the electric field environment in the carriage under working state, and will not cause any health hazard to the passengers in this working frequency electric field environment.
Źródło:
Archives of Electrical Engineering; 2023, 72, 2; 483--501
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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 LEX,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
Artykuł
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
Artykuł
Tytuł:
Noise exposure and hearing status among employees using communication headsets
Autorzy:
Pawlaczyk-Łuszczyńska, Małgorzata
Dudarewicz, Adam
Zaborowski, Kamil
Zamojska-Daniszewska, Małgorzata
Powiązania:
https://bibliotekanauki.pl/articles/2153012.pdf
Data publikacji:
2022
Wydawca:
Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:
noise-induced hearing loss
pure-tone audiometry
otoacoustic emissions
communication headsets
occupational exposure to noise
extended high-frequency audiometry
Opis:
Objectives The objective of this study was to assess the hearing of employees using communication headsets with regard to their exposure to noise. Material and Methods The study group comprised 213 employees, including 21 workers of the furniture industry, 15 court transcribers and 177 call center operators, aged 19–55 years, working with headsets for a period of up to 25 years. All the participants underwent a standard puretone audiometry, extended high-frequency audiometry (EHFA) as well as transient-evoked otoacoustic emissions (TEOAEs) and distortion-product otoacoustic emissions (DPOAEs). Noise exposure from headsets was evaluated using the microphone in a real ear technique according to PN-EN ISO 11904-1:2008. Results Personal daily noise exposure levels ranged 57–96 dB and exceeded 85 dB only in 1.4% of the call center operators. Forty-two percent of the participants had bilateral normal hearing in the standard frequency range of 250–8000 Hz, and 33% in the extended highfrequency range of 9–16 kHz. It was found that DPOAEs were present bilaterally in 59% of the participants. Reproducibility of TEOAE at >70% and signal-to-noise ratio at >6 was exhibited by 42% and 17% of them, respectively. The 3 subgroups of workers differed in age, gender, noise exposure and type of headsets in use. However, after adjusting for age and gender, significant differences between these subgroups in terms of hearing were mostly visible in EHFA. A significant impact of age, gender, daily noise exposure level and current job tenure on hearing tests results was also noted among the call center operators and the transcribers. The most pronounced were the effects of age and gender, whereas the impact of the daily noise exposure level was less evident. Conclusions It seems that EHFA is useful for recognizing early signs of noise-induced hearing loss among communication headset users. However, further studies are needed before any firm conclusions concerning the risk of hearing impairment due to the use of such devices can be drawn.
Źródło:
International Journal of Occupational Medicine and Environmental Health; 2022, 35, 5; 585-614
1232-1087
1896-494X
Pojawia się w:
International Journal of Occupational Medicine and Environmental Health
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An approach to suppress high-frequency resonance using model predictive and selective harmonic elimination combined strategy
Autorzy:
Chen, Sitong
Chen, Xiaoqiang
Wang, Ying
Xiong, Ye
Powiązania:
https://bibliotekanauki.pl/articles/1841300.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
CRH5 EMUs and traction power supply coupled system
high-frequency oscillation
high speed railway
model predictive control (MPC)
selective harmonic elimination pulse-width modulation (SHEPWM)
CRH5 EMU i system sprzężony z zasilaniem trakcyjnym
oscylacja wysokiej częstotliwości
kolej dużych prędkości
kontrola predykcyjna modelu (MPC)
selektywna eliminacja harmoniczna modulacja szerokości impulsu (SHEPWM)
Opis:
High-frequency resonance is a prominent phenomenon which affects the normal operation of the high-speed railway in China. Aiming at this problem, the resonance mechanism is analyzed first. Then, model predictive control and selective harmonic elimination pulse-width modulation (MPC-SHEPWM) combined control strategy is proposed, where the harmonics which cause the resonance can be eliminated at the harmonic source. Besides, the MPC is combined to make the current track the reference in transients. The proposed control has the ability to suppress the resonance while has a faster dynamic performance comparing with SHEPWM. Finally, the proposed MPC-SHEPWM is tested in a simulation model of CRH5 (Chinese Railway High-speed), EMUs (electric multiple units) and a traction power supply coupled system, which shows that the proposed MPC-SHEPWM approach can achieve the resonance suppression and shows a better dynamic performance.
Źródło:
Archives of Electrical Engineering; 2021, 70, 2; 415-430
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł
Tytuł:
Assessment of the Change in the Tin Concentration in Bronzes to the Basic Components of the Sound of Bells
Autorzy:
Cekus, Dawid
Nadolski, Maciej
Powiązania:
https://bibliotekanauki.pl/articles/2049724.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
high-tin bronze
components of the sound of bell
frequency analysis
mechanical properties
velocity of sound
Opis:
The subject of the study was to determine the impact of changes in mechanical properties of high-tin bronzes on the basic components of the sound of a bell. Change in the tin concentration in the range of about 7.5 to 20 parts wt. in a casting alloy significantly affects the mechanical properties of the alloy such as Young’s modulus or hardness. The free vibrations of bells were obtained with the help of the finite element method. In the numerical analyses the mechanical properties of standard alloys were adopted. The obtained natural frequencies of the bell made of a bronze with different tin concentration in copper were compared with the acoustic properties of a real bell casted on the basis of the same ribs. A significant effect of the increase in the alloying share of tin on the obtained results was stated. In addition, the acoustic analysis of aluminum bronze C95500 have been performed. Based on the obtained results, authors stated that this material can replace the commonly used high tin bronze C91300 for the unit production of bells.
Źródło:
Archives of Metallurgy and Materials; 2021, 66, 2; 531-535
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
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
Artykuł

Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies