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    Wyświetlanie 1-21 z 21
    Tytuł:
    Design and testing of a low cost peak-power tracking controller for a fixed blade 1.2 kVA wind turbine
    Autorzy:
    Gitano, H.
    Taib, S.
    Khdeir, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/262657.pdf
    Data publikacji:
    2008
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
    Tematy:
    wind turbine
    DC-DC converter
    peak power tracking
    power controller
    Opis:
    Wind turbines are a common source of electrical power generation in rural sites around the world. The power generated by a wind turbine at a given wind speed is a non-linear function of rotor speed. This results in a specific rotor speed for maximum power production at each wind speed. A control system incorporating a Pulse Width Modulated DC -DC converter has been designed to vary the load on the wind turbine thereby forcing it to operate at its maximum power point. Another important feature of the controller is the application of electrical stall-breaking of the turbine. The circuit was then tested on a turbine test bed simulating various wind speeds, and the “peak-power tracking” capability and electrical breaking capability were verified. The system gave an overall efficiency of 70 to 80% over a wide range of wind speeds and PWM duty cycles.
    Źródło:
    Electrical Power Quality and Utilisation. Journal; 2008, 14, 1; 95-101
    1896-4672
    Pojawia się w:
    Electrical Power Quality and Utilisation. Journal
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of power on agility, linear speed and change of direction deficit in female soccer players
    Autorzy:
    Fischerova, Patricia
    Krosta, Roksana
    Gołaś, Artur
    Terbalyan, Artur
    Nitychoruk, Magdalena
    Maszczyk, Adam
    Powiązania:
    https://bibliotekanauki.pl/articles/1933017.pdf
    Data publikacji:
    2021-06-23
    Wydawca:
    PPHU Projack Jacek Wąsik
    Tematy:
    COD deficit
    change of direction
    power
    strength
    agility
    straight linear speed
    soccer
    female
    peak power
    Opis:
    Introduction: The aim of the study was to examine relationships between power of the lower limb and agility, speed, and change of direction (COD) deficit in professional female soccer players. Material and methods: Thirty-three elite Polish Extraliga league soccer players (aged 22 ±5 years; body height 166 ± 4 cm; body weight 58 ± 8 kg) performed the following fitness tests: lower limb muscle power (Leg Press, Half Squat, Counter Movement Jump), straight linear speed (SLS 20 m), and COD speed ( Zig-Zag test, COD deficit). Using the median value as a reference, the players were subdivided into two groups (n=17; n=16) according to their LP, HS 60% 1RM, CMJ (High values below median = stronger group and Low = weaker group ). Results: The COD deficit was calculated as the difference between the 20m speed and the Zig-Zag test. The stronger group was better than the weaker group in SLS 20m (p<0.05; ES=1.23; 0.83; 0.93), but in the Zig-Zag agility test, the difference in the results was not statistically significant (p>0.05; ES=0.48; 0.34; 0.34) and this affected the COD deficit, which was higher (p<0.05; ES=0.9; 0.73; 0.72). The most important finding was that the stronger group had a higher COD deficit and its improvement (reduction) occurs only if the results of the agility test are improved (through agility training) [Ydeficit All groups=0.10+0.87* 20m - 0.83* Zig-Zag]. Increasing power (HS, LP) lead to the improvement in SLS p<0.05, not to COD abilities. Conclusion: This can be useful for coaches during agility training and to improve COD deficit in soccer players and women in general.
    Źródło:
    Physical Activity Review; 2021, 1, 9; 109-116
    2300-5076
    Pojawia się w:
    Physical Activity Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ocena długoterminowych prognoz zużycia energii i mocy szczytowych w systemach elektroenergetycznych
    The problem of assessing long-term forecasts of energy consumption and peak power in the Power Systems
    Autorzy:
    Dąsal, K.
    Popławski, T.
    Rusek, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/283058.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Instytut Gospodarki Surowcami Mineralnymi i Energią PAN
    Tematy:
    systemy elektroenergetyczne
    modelowanie
    prognoza długoterminowa
    moc szczytowa
    zużycie energii
    power systems
    modeling
    long-team forecasting
    peak power
    energy consumption
    Opis:
    W artykule skoncentrowano się na zagadnieniu dotyczącym oceny wykonywanych prognoz w dłuższych horyzontach. Przeprowadzono analizę kilku prognoz wykonanych w różnych instytucjach. Dokonano oceny prognoz energii i mocy szczytowych na podstawie kształtowania się rocznych stopni obciążeń.
    The article focuses on the issue concerning the assessment carried out at longer forecast horizons. An analysis of several forecasts made in different institutions. The assessment of forecasts of energy and peak power on the basis of formation of the annual load levels.
    Źródło:
    Polityka Energetyczna; 2011, 14, 2; 35-48
    1429-6675
    Pojawia się w:
    Polityka Energetyczna
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ekonomiczne uwarunkowania pracy elektrowni szczytowej na paliwa gazowe w Krajowym Systemie Elektroenergetycznym
    Economic condition for the operation of gas peak load power plant in Polish Power System
    Autorzy:
    Niewiński, Grzegorz
    Rajewski, Adam
    Powiązania:
    https://bibliotekanauki.pl/articles/548133.pdf
    Data publikacji:
    2018
    Wydawca:
    Uniwersytet Rzeszowski. Wydawnictwo Uniwersytetu Rzeszowskiego
    Tematy:
    elektrownia szczytowa,
    turbiny gazowe,
    silniki tłokowe,
    zapotrzebowanie na energię elektryczną
    peak power plant,
    gas turbines,
    reciprocating engines,
    electricity demand
    Opis:
    Celem pracy było przeanalizowanie ekonomicznych uwarunkowań eksploatacji elektrowni szczytowej opalanej paliwem gazowym w Krajowym Systemie Elektroenergetycznym. W pracy przeanalizowano strukturę zapotrzebowania na energię elektryczną oraz sposoby jej zaspokojenia ze szczególnym uwzględnieniem źródeł szczytowych. Niedobory mocy można pokryć zarówno przez jej import, redukcję zapotrzebowania u odbiorców końcowych, jak również przez dedykowane jednostki szczytowe. W artykule podjęto próbę wyznaczenia ceny energii elektrycznej, produkowanej przez elektrownię szczytową o mocy ok. 200 MW, przy której inwestycja byłaby opłacalna. Do porównania wybrano dwie technologie bazujące na gazowych turbinach lotniczopochodnych oraz silnikach tłokowych. W każdym z przypadków przeprowadzono analizę techniczno-ekonomiczną zaproponowanego rozwiązania wraz z uproszczoną analizą wrażliwości wybranych parametrów. Dodatkowo uwzględniono możliwości pełnienia usług systemowych takich jak Praca Interwencyjna oraz Operacyjna Rezerwa Mocy. Z przeprowadzonych obliczeń wynika, że jednostkowe koszty produkcji energii elektrycznej w rozpatrywanych elektrowniach znacznie przekraczają osiągalne na rynku ceny energii elektrycznej, jednakże dopłaty, jakie należałoby ponieść na rzecz źródeł szczytowych są znacznie niższe niż koszt redukcji zużycia energii (negawaty), czy też koszty ponoszące przez przemysł na skutek ograniczenia dostaw energii. Dodatkowo świadczenie usług systemowych, w tym regulacji wtórnej częstotliwości znacząco ekonomikę i funkcjonalność zaproponowanych rozwiązań.
    The goal of the presented study was analyzing the economic conditions for the operation of a gas-fired power plant in the National Power System (KSE). The paper was analyzing electricity demand and methods of covering that demand with special focus on peaking sources. Shortages of power in the National Power System may be covered by import, reduction of consumer loads and by dedicated peaking sources. The authors have attempted to determine sales prices of electricity produced by peak power plant with a power of approx. 200 MW, at which the project is feasible. Two plant technologies were compared: aeroderivative gas turbines and reciprocating engines. For each of those cases a techno-economic analysis was performed along with a simplified analysis of sensitivity to selected parameters. Abilities to provide ancillary services such as emergency operation and operational capacity reserve were also taken into account. Calculations reveal that the specific costs of generating electricity at investigated plants greatly exceed electricity prices achieved in the market. However extra payments which would be required by peaking sources are at the same time much lower than the cost of load reduction (negawatts) or costs suffered by the industry due to restrictions in power supply. In addition, the provision of ancillary services, including secondary frequency regulation, significantly improves the economics and functionality of the proposed peak load power plant.
    Źródło:
    Nierówności Społeczne a Wzrost Gospodarczy; 2018, 54; 403-424
    1898-5084
    2658-0780
    Pojawia się w:
    Nierówności Społeczne a Wzrost Gospodarczy
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hybrid PAPR reduction schemes for different OFDM-based VLC systems
    Autorzy:
    El-Ganiny, Mohamed Y.
    Khalaf, Ashraf A. M.
    Hussein, Aziza I.
    Hamed, Hesham F. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2174839.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    visible light communication
    peak-to-average power ratio
    bit error rate
    Opis:
    Orthogonal frequency division multiplexing has been widely used in many radio frequency wireless communication standards as a preferable multicarrier modulation scheme. The modulated signals of a conventional orthogonal frequency division multiplexing system are complex and bipolar. In intensity-modulated direct detection optical wireless communications, transmitted signals should be real and unipolar due to non-coherent emissions of an optical light emitting diode. In this paper, different hybrid optical systems have been proposed to satisfy real and unipolar signals. Peak-to-average power ratio is one of the biggest challenges for orthogonal frequency division multiplexing-based visible light communications. They are based on a combination of non-linear companding techniques with spreading or precoding techniques. Simulation evaluation is performed under direct current-biased optical orthogonal frequency division multiplexing, asymmetrically clipped optical orthogonal frequency division multiplexing, and Flip-orthogonal frequency division multiplexing systems in terms of peak-to-average power ratio, bit error rate, and spectral efficiency. The proposed schemes are investigated to determine a scheme with a low peak-to-average power ratio and an acceptable bit error rate. MATLABTM software has been successfully used to show the validity of the proposed schemes.
    Źródło:
    Opto-Electronics Review; 2022, 30, 3; art. no. e141951
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hybrid PAPR reduction schemes for different OFDM-based VLC systems
    Autorzy:
    El-Ganiny, Mohamed Y.
    Khalaf, Ashraf A. M.
    Hussein, Aziza I.
    Hamed, Hesham F. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2174840.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    visible light communication
    peak-to-average power ratio
    bit error rate
    Opis:
    Orthogonal frequency division multiplexing has been widely used in many radio frequency wireless communication standards as a preferable multicarrier modulation scheme. The modulated signals of a conventional orthogonal frequency division multiplexing system are complex and bipolar. In intensity-modulated direct detection optical wireless communications, transmitted signals should be real and unipolar due to non-coherent emissions of an optical light emitting diode. In this paper, different hybrid optical systems have been proposed to satisfy real and unipolar signals. Peak-to-average power ratio is one of the biggest challenges for orthogonal frequency division multiplexing-based visible light communications. They are based on a combination of non-linear companding techniques with spreading or precoding techniques. Simulation evaluation is performed under direct current-biased optical orthogonal frequency division multiplexing, asymmetrically clipped optical orthogonal frequency division multiplexing, and Flip-orthogonal frequency division multiplexing systems in terms of peak-to-average power ratio, bit error rate, and spectral efficiency. The proposed schemes are investigated to determine a scheme with a low peak-to-average power ratio and an acceptable bit error rate. MATLABTM software has been successfully used to show the validity of the proposed schemes.
    Źródło:
    Opto-Electronics Review; 2022, 30, 3; art. no. e141951
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    PAPR reduction using a combination between precoding and non-liner companding techniques for ACO-OFDM-based VLC systems
    Autorzy:
    Mohammed, Nazmi A.
    Elnabawy, M. M.
    Khalaf, Ashraf A. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1818212.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    visible light communication
    light emitting diode
    peak-to-average power ratio
    bit error rate
    Opis:
    Peak-to-average power ratio reduction techniques for visible light communication broadcasting systems are designed, simulated, and evaluated in this work. The proposed techniques are based on merging non-linear companding techniques with precoding techniques. This work aims to nominate an optimum novel scheme combining the low peak-to-average power ratio with the acceptable bit error rate performance. Asymmetrically clipped optical orthogonal frequency division multiplexing with the low peak-to-average power ratio performance becomes more attractive to real-life visible light communication applications due to non-linearity elimination. The proposed schemes are compared and an optimum choice is nominated. Comparing the presented work and related literature reviews for peak-to-average power ratio reduction techniques are held to ensure the proposed schemes validity and effectiveness.
    Źródło:
    Opto-Electronics Review; 2021, 29, 2; 59--70
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    PAPR reduction using a combination between precoding and non-liner companding techniques for ACO-OFDM-based VLC systems
    Autorzy:
    Mohammed, N. A.
    Elnabawy, M. M.
    Khalaf, A. A. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1818214.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    visible light communication
    light emitting diode
    peak-to-average power ratio
    bit error rate
    Opis:
    Peak-to-average power ratio reduction techniques for visible light communication broadcasting systems are designed, simulated, and evaluated in this work. The proposed techniques are based on merging non-linear companding techniques with precoding techniques. This work aims to nominate an optimum novel scheme combining the low peak-to-average power ratio with the acceptable bit error rate performance. Asymmetrically clipped optical orthogonal frequency division multiplexing with the low peak-to-average power ratio performance becomes more attractive to real-life visible light communication applications due to non-linearity elimination. The proposed schemes are compared and an optimum choice is nominated. Comparing the presented work and related literature reviews for peak-to-average power ratio reduction techniques are held to ensure the proposed schemes validity and effectiveness.
    Źródło:
    Opto-Electronics Review; 2021, 29, 2; 59--70
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    PAPR reduction using a combination between precoding and non-liner companding techniques for ACO-OFDM-based VLC systems
    Autorzy:
    Mohammed, N. A.
    Elnabawy, M. M.
    Khalaf, A. A. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1818217.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    visible light communication
    light emitting diode
    peak-to-average power ratio
    bit error rate
    Opis:
    Peak-to-average power ratio reduction techniques for visible light communication broadcasting systems are designed, simulated, and evaluated in this work. The proposed techniques are based on merging non-linear companding techniques with precoding techniques. This work aims to nominate an optimum novel scheme combining the low peak-to-average power ratio with the acceptable bit error rate performance. Asymmetrically clipped optical orthogonal frequency division multiplexing with the low peak-to-average power ratio performance becomes more attractive to real-life visible light communication applications due to non-linearity elimination. The proposed schemes are compared and an optimum choice is nominated. Comparing the presented work and related literature reviews for peak-to-average power ratio reduction techniques are held to ensure the proposed schemes validity and effectiveness.
    Źródło:
    Opto-Electronics Review; 2021, 29, 2; 59--70
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prognozy długoterminowe energii elektrycznej w KSE – wybrane problemy
    Long-term forecasts of electric energy consumpti on in the domestic power engineering system – selected issues
    Autorzy:
    Dąsal, K.
    Popławski, T.
    Rusek, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/282367.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Instytut Gospodarki Surowcami Mineralnymi i Energią PAN
    Tematy:
    prognozowanie
    model ekonometryczny
    system elektroenergetyczny
    metoda doboru zmiennych
    prognoza długoterminowa
    moc szczytowa
    zużycie energii
    forecasting
    econometric model
    power engineering system
    method of choice of variables
    long-term forecast
    peak power
    energy consumption
    Opis:
    Istnieje wiele czynników mających znaczenie w procesie prognozowania. Do najważniejszych zaliczyć należy wybór modelu oraz dobór zmiennych objaśniających w przypadku wielowymiarowego modelu ekonometrycznego. W artykule skoncentrowano się na doborze zmiennych, który odgrywa kluczową rolę. Spośród wielu istniejących i znanych algorytmów doboru zmiennych, w artykule przedstawiono autorsko wybrane trzy metody: metodę pojemności integralnej Hellwiga, metodę współczynnika korelacji cząstkowej oraz metodę współczynnika korelacji wielorakiej. Dla każdej z zastosowanych metod podano syntetyczny opis wyjaśniający istotę jej działania. Wybór modelu do opracowania prognoz potraktowano jako mniej istotny, ponieważ dla każdej metody doboru model jest ten sam. Obliczenia wykonano modelem MRK (Model Rozk?adu Kanonicznego), zamieszczając syntetyczny opis modelu. Wykazano na rzeczywistych danych jak zastosowana metoda doboru zmiennych objaśniających wpływa na uzyskane wyniki prognozy zużycia energii elektrycznej na poziomie kraju. W przykładzie obliczeniowym dysponowano potencjalnym zbiorem z siedmioma zmiennymi objaśniającymi. W opracowaniu zawarto 14 różnych prognoz otrzymanych w wyniku zastosowanych 3 metod wyboru zmiennych. Wyniki dopasowania modeli (prognoz wygasłych) oraz prognoz do 2030 roku, przedstawiono w tabelach i na wykresach. We wnioskach zawarto uwagi dotyczące prognoz długoterminowych podstawowych wielkości dotyczących Krajowego Systemu Elektroenergetycznego, mogące mieć wpływ na poprawność ocen tych prognoz. Zwrócono uwagę na problem poprawności oceny prognoz długoterminowych dotyczącej zużycia energii czy mocy szczytowych. Wskazanie prognoz o mniejszym ryzyku pope?nienia dużych błędów umożliwia równoległa analiza prognozy zużycia energii elektrycznej, prognozy szczytów obciążeń z jednoczesnym wyznaczeniem wielkości umożliwiających realność prognoz. Może to przykładowo być wyznaczenie rocznych stopni obciążenia, dla których mamy ściśle określony zakres zmienności. W przypadku dysponowania jedynie prognozę zużycia energii elektrycznej możliwe są inne analizy, przykładowo porównania energochłonności PKB, energochłonności produktów czy gałęzi gospodarki w wybranych krajach. Jeszcze innym, powszechnie stosowanym wskaźnikiem jest roczne zużycie energii elektrycznej na osobę. Prognozy ludności są jednymi z dokładniejszych, stąd ten wskaźnik może być dobrym odniesieniem przy porównywaniu prognoz.
    There exist a number of important factors in forecasting processes. The most significant in the case of a multi-dimensional econometric model are the choice of the model and the explanatory variables. This paper focuses on the choice of variables, which plays a crucial role. Among many existing and recognized algorithms for the selection of variables, the following three chosen arbitrarily by the authors are presented: the method of integral capacity by Hellwig, the partial correlation coefficient, and multiple correlation coefficient. For each considered method, a synthetic description explaining its action is given. The choice of the model for making forecasts was treated as less significant because, for each method, the same model is used. Calculations were made using the MRK (Model of Canonical Distribution) model. The synthetic description of the model is also provided. Using real-life data, the analysis demonstrates how the method applied in choosing explanatory variables influences the obtained forecast results concerning the consumption of electric energy on a national scale. In the example calculation, a potential dataset of seven explanatory variables was used. The paper summarizes fourteen different forecasts obtained from three methods of variables selection. The results of model fittings (extinct forecasts) and forecasts until 2030 are presented in the form of tables and charts. Concluding remarks concern long-term forecasts of fundamental quantities related to the Domestic Power Engineering System, which may influence the correctness of these forecasts. Particular attention was paid to the issue of the correctness of long-term forecasts related to energy consumption and peak power. An analysis of the forecast of energy consumption, processed parallel to the determination of quantities assessing the reality of these forecasts, makes it possible to indicate the forecasts endowed with the lowest risk of making excessive errors. For example, it may be possible to consider the determination of annual load levels for which a pre-determined, exact level of variability is given. In situations where only the forecast of electric energy consumption is available, it is possible to develop further analyses such as a comparison of energy consumption for a Domestic Brutto Product, energy consumption for products, or economic branches in selected countries. Yet another indicator in common use is annual energy consumption per capita. Forecasts per capita are among the most exact; therefore, this indicator may be a useful tool for comparison of different forecasts.
    Źródło:
    Polityka Energetyczna; 2012, 15, 4; 71-83
    1429-6675
    Pojawia się w:
    Polityka Energetyczna
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Suitable Spreading Sequences for Asynchronous MC-CDMA Systems
    Autorzy:
    Addad, M.
    Djebbari, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/307793.pdf
    Data publikacji:
    2018
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    BER
    crest factor
    multiple access interference
    MC-CDMA
    peak-to-average power ratio
    zero correlation zone
    Opis:
    In order to meet the demand of high data rate transmission with good quality maintained, the multi-carrier code division multiple access (MC-CDMA) technology is considered for the next generation wireless communication systems. However, their high crest factor (CF) is one of the major drawbacks of multi-carrier transmission systems. Thus, CF reduction is one of the most important research areas in MC-CDMA systems. In addition, asynchronous MC-CDMA suffers from the effect of multiple access interference (MAI), caused by all users active in the system. Degradation of the system’s bit error rate (BER) caused by MAI must be taken into consideration as well. The aim of this paper is to provide a comparative study on the enhancement of performance of an MC-CDMA system. The spreading sequences used in CDMA play an important role in CF and interference reduction. Hence, spreading sequences should be selected to simultaneously ensure low CF and low BER values. Therefore, the effect that correlation properties of sequences exert on CF values is investigated in this study. Furthermore, a numerical BER evaluation, as a function of the signal-to-noise ratio (SNR) and the number of users, is provided. The results obtained indicate that a trade-off between the two criteria is necessary to ensure good performance. It was concluded that zero correlation zone (ZCZ) sequences are the most suitable spreading sequences as far as the satisfaction of the above criteria is concerned.
    Źródło:
    Journal of Telecommunications and Information Technology; 2018, 3; 9-13
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance analysis of DFT-S-OFDM waveform for Li-Fi systems
    Autorzy:
    Hussin, S.
    Shalaby, E. Mansour
    Powiązania:
    https://bibliotekanauki.pl/articles/2063891.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    light-fidelity
    visible light communications
    orthogonal frequency division multiplexing
    discrete Fourier transform spread
    peak-to-average power ratio
    Opis:
    In this paper, the effect of an indoor visible light communication channel is studied. Moreover, the analysis of the received power distribution of the photodiode in the line of sight and the first reflection of the channel without line of sight with several parameters is simulated. Two different waveforms are explained in detail. Orthogonal frequency division multiplexing has been widely adopted in radio frequency and optical communication systems. One of the most important disadvantages of the orthogonal frequency division multiplexing signal is the high peak-to-average power ratio. Therefore, it is important to minimize the peak-to-average power ratio in the visible light communication systems more than in radio-frequency wireless applications. In the visible light communication systems, the high peak-to-average power ratio produces a high DC bias which reduces power efficiency of the system. A discrete Fourier transform spread orthogonal frequency division multiplexing is proposed to be used in wireless communication systems; its ability to minimize peak-to-average power ratio has been tested. The analysis of two different subcarrier allocation methods for the discrete Fourier transform-spread subcarriers, as well as the examination of two distinct subcarrier allocation strategies, distributed and localized mapping, are investigated and studied. The effects of an accurate new sub-band mapping for the localized discrete Fourier transform spread orthogonal frequency division multiplexing scheme are presented in this paper. The light-fidelity system performance of the orthogonal frequency division multiplexing and discrete Fourier transform spread orthogonal frequency division multiplexing with different sub-mapping techniques are simulated with Matlab™. A system performance size of bit error rate and peak-to-average power ratio are obtained, as well.
    Źródło:
    Opto-Electronics Review; 2021, 29, 4; 167--174
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance evaluation of UFMC-based VLC systems using a modified SLM technique
    Autorzy:
    Mansour Shalaby, E.
    Dessouky, M.
    Hussin, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1818194.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    universal filtered multi-carrier
    orthogonal frequency division
    multiplexing
    peak-to-average power ratio
    selected-mapping
    discrete Hartley transform precoding
    Opis:
    Universal filtered multi-carrier (UFMC) is being studied as the favourable waveforms supporting the visible light communication broadcasting systems. However, the UFMC system faces a serious performance degradation on the transmitter side due to its high peak-to-average power ratio (PAPR). High PAPR of the signal is an analytical intention parameter for mobile networks, and it is necessary to minimize it as much as possible. This paper focuses on the PAPR reduction of the UFMC scheme. An efficient hybrid method of the PAPR reduction has been proposed and analysed through the Matlab™ simulation. The proposed hybrid scheme consists of a mixture of the selected-mapping method and the discrete Hartley transform precoding for a UFMC system (SLM-DHT-P-UFMC). The simulation results show that the proposed hybrid system has a better PAPR reduction performance compared to traditional SLM-UFMC and DHT-P-UFMC systems. Hence, LM-DHT-P-UFMC is considered to be the suggested scheme in visible light communication broadcasting systems.
    Źródło:
    Opto-Electronics Review; 2021, 29, 3; 85--90
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance evaluation of UFMC-based VLC systems using a modified SLM technique
    Autorzy:
    Mansour Shalaby, E.
    Dessouky, M.
    Hussin, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1818201.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    universal filtered multi-carrier
    orthogonal frequency division
    multiplexing
    peak-to-average power ratio
    selected-mapping
    discrete Hartley transform precoding
    Opis:
    Universal filtered multi-carrier (UFMC) is being studied as the favourable waveforms supporting the visible light communication broadcasting systems. However, the UFMC system faces a serious performance degradation on the transmitter side due to its high peak-to-average power ratio (PAPR). High PAPR of the signal is an analytical intention parameter for mobile networks, and it is necessary to minimize it as much as possible. This paper focuses on the PAPR reduction of the UFMC scheme. An efficient hybrid method of the PAPR reduction has been proposed and analysed through the Matlab™ simulation. The proposed hybrid scheme consists of a mixture of the selected-mapping method and the discrete Hartley transform precoding for a UFMC system (SLM-DHT-P-UFMC). The simulation results show that the proposed hybrid system has a better PAPR reduction performance compared to traditional SLM-UFMC and DHT-P-UFMC systems. Hence, LM-DHT-P-UFMC is considered to be the suggested scheme in visible light communication broadcasting systems.
    Źródło:
    Opto-Electronics Review; 2021, 29, 3; 85--90
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A complexity efficient PAPR reduction scheme for FBMC-based VLC systems
    Autorzy:
    Roshdy, Radwa A.
    Hussein, Aziza I.
    Mabrook, Mohamed M.
    Salem, Mohammed A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2204164.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    visible light communication
    filter bank multicarrier
    peak-to-average power ratio reduction
    computational complexity
    cube satellite communication link
    inter-satellite communications
    Opis:
    Visible light communication based on a filter bank multicarrier holds enormous promise for optical wireless communication systems, due to its high-speed and unlicensed spectrum. Moreover, visible light communication techniques greatly impact communication links for small satellites like cube satellites, and pico/nano satellites, in addition to inter-satellite communications between different satellite types in different orbits. However, the transmitted visible signal via the filter bank multicarrier has a high amount of peak-to-average power ratio, which results in severe distortion for a light emitting diode output. In this work, a scheme for enhancing the peak-to-average power ratio reduction amount is proposed. First, an algorithm based on generating two candidates signals with different peak-to- average power ratio is suggested. The signal with the lowest ratio is selected and transmitted. Second, an alternate direct current-biased approach, which is referred to as the addition reversed method, is put forth to transform transmitted signal bipolar values into actual unipolar ones. The performance is assessed through a cumulative distribution function of peak-to-average power ratio, bit error rate, power spectral density, and computational complexity. The simulation results show that, compared to other schemes in literature, the proposed scheme attains a great peak-to-average power ratio reduction and improves the bit the error rate performance with minimum complexity overhead. The proposed approach achieved about 5 dB reduction amount compared to companding technique, 5.5 dB compared to discrete cosine transform precoding, and 8 dB compared to conventional direct current bias of an optical filter bank multicarrier. Thus, the proposed scheme reduces the complexity overhead by 15.7% and 55.55% over discrete cosine transform and companding techniques, respectively.
    Źródło:
    Opto-Electronics Review; 2023, 31, 1; art. no. e144919
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Operation of a power unit as a peak unit and its impact on the economy and reliability of the power system
    Praca bloku energetycznego w charakterze jednostki szczytowej i jej wpływ na ekonomię i niezawodność systemu elektroenergetycznego
    Autorzy:
    Rusin, A.
    Wojaczek, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/181706.pdf
    Data publikacji:
    2018
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Metalurgii Żelaza im. Stanisława Staszica
    Tematy:
    power unit
    wind power plants
    peak unit
    reliability of power system
    blok energetyczny
    siłownia wiatrowa
    jednostka szczytowa
    niezawodność systemu
    Opis:
    Wind power plants are at the forefront of the development of renewable energy sources (RES) but their operation depends on changing weather conditions. Favouring energy obtained from renewable sources forces the operation of conventional energy as a regulator balancing the system’s demand. Coal-fired power units were designed for continuous operation and their efficiency decreases if they are used as peak units. The increased number of start-ups and frequent fluctuations in the generated power lead in the long run to the accumulation of consumption processes such as thermal fatigue and cracking. Another noticeable effect is also the decrease in reliability indicators and increased operating costs associated with expensive start-ups. The paper presents an estimation of operating costs related to more frequent start-ups of a power unit. The impact of the deterioration of reliability indicators on the production capacity of a single power plant as well as the reliability of the entire system was also analysed.
    Siłownie wiatrowe stoją na czele rozwoju odnawialnych źródeł energii (OZE), lecz ich praca zależy od zmiennych warunków pogodowych. Faworyzowanie energii uzyskanej z odnawialnych źródeł wymusza pracę konwencjonalnej energetyki jako regulatora bilansującego zapotrzebowanie systemu. Bloki węglowe projektowane były do pracy ciągłej i ich sprawność spada, jeżeli użytkowane są jako jednostki szczytowe. Zwiększona liczba rozruchów i częste fluktuacje mocy generowanej prowadzą w dłuższej perspektywie do kumulacji procesów zużycia takich jak zmęczenie cieplne i pękanie. Innym zauważalnym efektem jest również spadek wskaźników niezawodności i zwiększone koszty eksploatacji związane z drogimi rozruchami. W artykule przedstawiono oszacowanie kosztów eksploatacji związanych z częstszymi rozruchami bloku energetycznego. Analizowano również wpływ pogorszenia się wskaźników niezawodności na możliwości produkcyjne pojedynczej elektrowni jak i na niezawodność całego systemu.
    Źródło:
    Prace Instytutu Metalurgii Żelaza; 2018, T. 70, nr 3, 3; 46-50
    0137-9941
    Pojawia się w:
    Prace Instytutu Metalurgii Żelaza
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Temporal patterns of pollen shedding for longleaf pine (Pinus palustris) at the Escambia Experimental Forest in Alabama, USA
    Autorzy:
    Chen, X.
    Brockway, D.G.
    Guo, Q.
    Powiązania:
    https://bibliotekanauki.pl/articles/2078205.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Instytut Dendrologii PAN
    Tematy:
    accumulated air temperature
    accumulated pollen density
    peak pollen shedding
    pollen phenology
    power-law
    Opis:
    Longleaf pine is an important tree species in the southeastern United States and studying the temporal patterns of pollen shedding is crucial to a better understanding of its phenology and seed production. In this study, field observation data on the timing of pollen shedding from 1958 to 2013 were analyzed with reference to local weather conditions. Our results indicated that the time of peak pollen shedding after January 1 (TPPS) ranged from 53 days (about February 22) to 95 days (around April 5). There was no significant trend of decreasing TPPS. The number of days with the maximum air temperature above 0 °C was close to the TPPS. The accumulated maximum daily air temperature for the TPPS approximated an average of 1,342 °C. The TPPS declined with an increase in the average air temperature during winters. The time of 80% accumulated pollen density (TAPD) varied from 5 to 32 days, with an average of 13 days. Taylor’s power-law was evident in the TAPD data, with the time group of 10–15 days having an interval time of 2 years. Winter weather was not correlated with the TAPD. These results provide new information concerning the pollen phenology for longleaf pine trees
    Źródło:
    Dendrobiology; 2020, 84; 30-38
    1641-1307
    Pojawia się w:
    Dendrobiology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Problems related to balancing peak power on the example of the Polish National Power System
    Autorzy:
    Majchrzak, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/141127.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    cost of energy deliver failure
    peak demand of system
    system services
    power grids
    Opis:
    The article discusses issues related to ensuring secure operation of the National Power System. The tasks of transmission system operators in that scope were presented and the power demand of the Polish National Power System on critical days in terms of power generation and demand was characterized. The article also presents the causes and course of events which took place in August 2015 when there was a critical imbalance in the Polish National Power System leading to the introduction of limitations. Then, the possibilities and types of costs connected with the possibilities of balancing the system in the periods of peak loads were characterized. The summary of the article contains the presentation of conclusions related to power balancing in the power system and reduction of related costs.
    Źródło:
    Archives of Electrical Engineering; 2017, 66, 1; 207-221
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wyznaczanie obciążeń szczytowych w wiejskich sieciach elektroenergetycznych
    Determination of the peak loads in rural power network
    Autorzy:
    Trojanowska, M.
    Nęcka, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/238567.pdf
    Data publikacji:
    2007
    Wydawca:
    Instytut Technologiczno-Przyrodniczy
    Tematy:
    wiejska sieć elektroenergetyczna
    zużycie energii elektrycznej
    obciążenie szczytowe
    rural power network
    electrical energy consumption
    peak load
    Opis:
    W pracy przedstawiono modele przydatne do wyznaczania rocznego obciążenia szczytowego wiejskiej stacji transformatorowej 15/0,4 kV, w postaci regresyjnych zależności pomiędzy obciążeniem szczytowym stacji, a zużyciem energii elektrycznej przez odbiorców zasilanych za jej pośrednictwem. Praca zawiera także analizę dobowej, tygodniowej i rocznej zmienności obciążeń odbiorców wiejskich oraz wyniki obliczeń rocznego czasu użytkowania mocy szczytowej, dokonanych w oparciu o wyniki ciągłej rejestracji poboru mocy czynnej w wybranych wiejskich stacjach transformatorowych.
    Paper presents the models useful to determination of annual peak load of a 15/0.4 kV rural transformer station, in form of regression dependences between the station peak load and consumption of electrical energy by the customers being supplied with energy through that station. Paper includes also an analysis of daily, weekly and annual variations in rural consumers' loads, as well as the calculations of yearly peak power use duration, based on the results of continuous recording of active power consumption in selected rural transformer stations.
    Źródło:
    Problemy Inżynierii Rolniczej; 2007, R. 15, nr 2, 2; 139-144
    1231-0093
    Pojawia się w:
    Problemy Inżynierii Rolniczej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Homoscedasticity test for the linear trend
    Testy homoskedastycznośd dla modelu liniowego
    Autorzy:
    Domański, Czesław
    Powiązania:
    https://bibliotekanauki.pl/articles/905620.pdf
    Data publikacji:
    2002
    Wydawca:
    Uniwersytet Łódzki. Wydawnictwo Uniwersytetu Łódzkiego
    Tematy:
    F-test
    peak test
    Goldfeld-Quandt test
    Kendal statistic homoscedasticity
    heteroscedastidty
    Fc statistic test power
    quantiles
    Opis:
    W literaturze statystycznej i ekonometrycznej bardzo wyraźnie podkreśla się znaczenie i metody weryfikacji podstawowych założeń dotyczących modelu ekonometrycznego, chociaż w praktyce niezbyt często postulat ten jest realizowany.
    Abstract. In this paper we consider single parameter models of heteroscedastidty: linear, square, exponential, group. A significant predominance of the parametric tests over the peak tests is shown using the variability coefficient as the most natural measure of homosccdasticity and the summary Kendal statistic as a measure of a test power. Another suggestion is that it is worth using the Goldfeld-Quandt parametric test, when the growth in the variance is quite „smooth” (in other case - the classical F-lesl is better). Prevalence of the F-test over the peak test is much smaller.
    Źródło:
    Acta Universitatis Lodziensis. Folia Oeconomica; 2002, 156
    0208-6018
    2353-7663
    Pojawia się w:
    Acta Universitatis Lodziensis. Folia Oeconomica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Leg strength and power in Polish striker soccer players
    Autorzy:
    Buśko, K.
    Górski, M.
    Nikolaidis, P. T.
    Mazur-Różycka, J.
    Łach, P.
    Staniak, Z.
    Gajewski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/307478.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    izokinetyka
    moment siły
    moc
    force sense
    height of jump
    isokinetic
    peak torque
    power
    striker soccer players
    Opis:
    The main goal of the present study was to examine muscle strength and power of dominant and non-dominant leg, knee extensors and flexors, and their correlations with jumping performances in soccer players. A secondary aim was to evaluate muscle sense. Methods: 31 male professional strikers (age 20.9 ± 2.3 years, body mass 75.1 ± 6.6 kg, body height 179.5 ± 4.7 cm) participated in the study. The power output of lower extremities and the height of rise of the body mass centre during vertical jumps were measured using a force plate. The maximum muscle torque of the flexors and extensors of the knee were measured under isometric conditions using a special isometric torquemeter. Force sense was measured in isometric conditions in two tests: (a) fifty percent of the maximal voluntary contraction was set as a value of target force and the participants were instructed to reproduce the target force, (b) the participants attempted to develop a torque reproducing a sine course within the range of 10 to 50% of MVC performed. Results: A direct relationship was observed between the peak muscle torque in knee extensors developed during isokinetic contraction at all velocities and power and height of three types of vertical jumps ( p < 0.05). No correlation was observed between jumping performance and muscle torque under isometric condition. No differences were found in strength and jumping abilities as well as in force sense between dominant and non-dominant legs. Conclusions: This study offered a comprehensive and complete evaluation of leg muscle strength, sense and power, with the use of using force plate and isokinetic dynamometry.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2018, 20, 2; 109-116
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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