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    Wyświetlanie 1-14 z 14
    Tytuł:
    Elastic Enhancement Factor: Mesoscopic Systems versus Macroscopic 2D Electromagnetic Analogue Devices
    Autorzy:
    Sokolov, V.
    Zhirov, O.
    Powiązania:
    https://bibliotekanauki.pl/articles/1400563.pdf
    Data publikacji:
    2015-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    05.45.Gg
    24.60.Lz
    05.45.Mt
    Opis:
    Excess of probabilities of the elastic processes over the inelastic ones is a common feature of the resonance phenomena described in the framework of the random matrix theory. This effect is quantitatively characterized by the elastic enhancement factor $F^{(β)}$ that is the typical ratio of elastic and inelastic cross-sections. Being measured experimentally, this quantity can supply us with information on specific features of the dynamics of the intermediate complicated open system. We discuss properties of the enhancement factor in a wide scope from mesoscopic systems to macroscopic analogue electromagnetic resonators and demonstrate essential qualitative distinction between the elastic enhancement factor's peculiarities in these two cases. Complete analytical solution is found for the case of systems without time-reversal symmetry and only a few open equivalent scattering channels.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 6; 990-993
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical and Experimental Studies of the Elastic Enhancement Factor for 2D Open Systems
    Autorzy:
    Ławniczak, M.
    Białous, M.
    Yunko, V.
    Bauch, S.
    Sirko, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1400561.pdf
    Data publikacji:
    2015-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    05.45.Mt
    03.65.Nk
    Opis:
    We present the results of numerical and experimental studies of the elastic enhancement factor W for microwave rough and rectangular cavities simulating two-dimensional chaotic and partially chaotic quantum billiards in the presence of moderate absorption. We show that for the frequency range ν=15.0-18.5 GHz, in which the coupling between antennas and the system is strong enough, the values of W for the microwave rough cavity lie below the predictions of random matrix theory and on average above the theoretical results of V. Sokolov and O. Zhirov, Phys. Rev. E 91, 052917 (2015). We also show that for the partially chaotic rectangular billiard the enhancement factor W calculated by applying the Potter-Rosenzweig model with κ=2.8±0.5 is close to the experimental one.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 6; 974-978
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of linewidth enhancement factor (LEF) on routes to chaos in optically injected semiconductor lasers
    Autorzy:
    Al-Hosiny, N. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2033881.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    injection locking
    chaos
    linewidth enhancement factor
    routes to chaos
    Opis:
    The effect of the linewidth enhancement factor (LEF) or α-factor on two common routes to chaos (mainly period-doubling and quasi-periodic routes) in optically injected semiconductor laser is theoretically investigated using bifurcation diagrams. The value of the LEF is slightly modified to examine the sensitivity of routes to chaos to any variation in the LEF. Despite the fact that LEF enhances chaos in the system, both routes are found to be highly insensitive to the variation in the LEF.
    Źródło:
    Optica Applicata; 2021, 51, 4; 621-632
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of the dose enhancement factor of high intensity low mono-energetic X-ray radiation with labeled tissues by gold nanoparticles
    Autorzy:
    Ranjbar, H.
    Shamsaei, M.
    Ghasemi, M. R.
    Powiązania:
    https://bibliotekanauki.pl/articles/148638.pdf
    Data publikacji:
    2010
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    radiation therapy
    energy optimization
    dose enhancement factor
    dose absorption
    gold nanoparticles
    MCNPX code
    Opis:
    The aim of radiotherapy is to maximize the dose applied to the tumor while keeping the dose to the surrounding healthy tissue as low as possible. To further enhance dose to a tumor, techniques to radiosensitization of the tumor, using high atomic number elements, have been proposed. The aim of this study was to investigate the influence of using gold nanoparticles as a contrast agent on tumor dose enhancement when the tissue is irradiated by a typical mono energy X-ray beam. To improve the conventional radiotherapy enhancement of the absorbed dose in a tumor tissue and to spare the skin and normal tissues during irradiation in the presence of concentration agent, a model based on a Monte Carlo N-Particle eXtended (MCNPX) computer code has been designed to simulate the depth dose in a phantom containing an assumed tumor. Test was carried out in two phases. In phase 1, verification of this model using the MCNPX was evaluated by comparing the obtained results with those of the published reports. In phase 2, gold was introduced into assumed tumor inside the phantom at different depths in the simulation program. Simulation was performed for four different concentrations of gold nanoparticles using a low mono-energetic parallel beam of synchrotron radiation. The obtained results show that the optimum energy for dose enhancement is found to be around 83–90 keV for all gold concentrations. The dose enhancement factor is increased linearly with concentration and diminished in depth along the central beam in the tumor. This approach of introducing contrast agents in conventional radiotherapy could hopefully prepare new treatment planning and improve the efficiency of tumor therapy.
    Źródło:
    Nukleonika; 2010, 55, 3; 307-312
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental and numerical study of the heat transfer and pressure drop in triangular chevron channels
    Autorzy:
    Dolatabadi, H.
    Aghdam, A. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/949298.pdf
    Data publikacji:
    2018
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    heat transfer
    pressure drop
    thermal enhancement factor
    phase shift
    Opis:
    Experimental and Numerical studies were carried out on turbulent heat transfer and friction factor loss through a triangular chevron channel. For uniform wall heat flux equal 1350 (W/m²) using air as a working fluid. Reynolds number varied from 3000 to 10000, phase shifted at the range of 0≤ϕ≤180, with variation distance between chevron surfaces (5 ≤ D ≤ 35 mm). Nu increased and TEF decreased in increasing of Re. The TEF and Nu increased with closing to channel phase shift angle 90˚, the best performance was noticed on phase shift, ϕ=90º. At the end of this paper effect of distance between chevron surfaces presented, The TEF and Nu increased with decreasing to channel distance and the best performance was noticed on closing to D=5(mm).
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2018, 56, 3; 751-763
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Badania szybkości absorpcji CO2 w wodnych roztworach węglanów potasowych z dodatkiem 2-etyloaminoetanolu
    Investigations of the rate of CO2 absorption into aqueous potash solutions with 2-ethylaminoethanol
    Autorzy:
    Moniuk, Wł.
    Pohorecki, R.
    Nosewicz, M.
    Szczepańska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2071147.pdf
    Data publikacji:
    2010
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    ditlenek węgla
    2-etyloaminoetanol
    proces Benfield
    absorpcja z reakcją chemiczną
    współczynnik przyspieszania wnikania masy
    carbon dioxide
    2-ethylaminoethanol
    BENFIELD process
    absorption with chemical reaction
    enhancement factor
    Opis:
    W pracy przedstawiono wpływ stężenia cząstek na częstość obrotów mieszadła niezbędną dla wytworzenia drobnoziarnistej zawiesiny całkowitej. Pompujące ku dołowi pojedyncze mieszadło z sześcioma pochylonymi łopatkami o stosunku średnicy zbiornika do średnicy mieszadła Did = 3 użyto do mieszania zawiesiny kredy. Pomiary przeprowadzono w zbiorniku cylindrycznym (średnica 200 i 300 mm) z przegrodami. Średnia średnica objętościowa cząstek wynosiła 4,6 μm, a ich stężenie zmieniano w granicach od 2,5 do40%obj.
    The effect of particle concentration on impeller speed necessary for fine suspension mixing is presented in the paper. A single down pumping pitched six-blade impeller with the vessel to impeller diameter ratio Did = 3 was used for mixing of chalk suspension. Measurements were carried out in cylindrical baffled vessels with diameters of 200 and 300 mm. The mean volumetric diameter of particles was 4.6 μm and the mean volumetric concentration changed in the range from 2.5% to 40%.
    Źródło:
    Inżynieria i Aparatura Chemiczna; 2010, 3; 75-76
    0368-0827
    Pojawia się w:
    Inżynieria i Aparatura Chemiczna
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of protrusions on the initiation of partial discharges in XLPE high voltage cables
    Autorzy:
    AlShaikh Saleh, Mohammad
    Refaat, Shady S.
    Olesz, Marek
    Abu-Rub, Haitham
    Guziński, Jarosław
    Powiązania:
    https://bibliotekanauki.pl/articles/2090691.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    FEA
    finite elements analysis
    protrusions
    XLPE
    water trees
    partial discharge
    void
    space charge
    stress enhancement factor
    analiza elementów skończonych
    kable XLPE
    polietylen kablowy
    polietylen sieciowany
    wyładowanie niezupełne
    ładunek przestrzenny
    Opis:
    This paper is focusing on 3D Finite Elements Analysis (FEA) based modelling of protrusions as defects or imperfections in the XLPE high voltage cable. This study is aiming to examine the impact protrusions have on the initiation of partial discharges. Spherical and ellipsoidal protrusions with different sizes at the conductor screen of the high voltage cable is an essential content of this paper. In addition, a spherical gas-filled void is placed inside and outside the protrusions, and a water tree produced from protrusions is under consideration. The partial discharge influence taking place at the protrusions and the stress enhancement factor is determined for all the variations mentioned to quantify the rise in the inception of partial discharges due to the protrusions.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; e136037, 1--9
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of protrusions on the initiation of partial discharges in XLPE high voltage cables
    Autorzy:
    AlShaikh Saleh, Mohammad
    Refaat, Shady S.
    Olesz, Marek
    Abu-Rub, Haitham
    Guziński, Jarosław
    Powiązania:
    https://bibliotekanauki.pl/articles/2173562.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    FEA
    finite elements analysis
    protrusions
    XLPE
    water trees
    partial discharge
    void
    space charge
    stress enhancement factor
    analiza elementów skończonych
    kable XLPE
    polietylen kablowy
    polietylen sieciowany
    wyładowanie niezupełne
    ładunek przestrzenny
    Opis:
    This paper is focusing on 3D Finite Elements Analysis (FEA) based modelling of protrusions as defects or imperfections in the XLPE high voltage cable. This study is aiming to examine the impact protrusions have on the initiation of partial discharges. Spherical and ellipsoidal protrusions with different sizes at the conductor screen of the high voltage cable is an essential content of this paper. In addition, a spherical gas-filled void is placed inside and outside the protrusions, and a water tree produced from protrusions is under consideration. The partial discharge influence taking place at the protrusions and the stress enhancement factor is determined for all the variations mentioned to quantify the rise in the inception of partial discharges due to the protrusions.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; art. no. e136037
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Enhancement of speech communication technology performance using Adaptive-Control Factor based Spectral Subtraction method
    Autorzy:
    Alim, I. A.
    Kolawole, M. O.
    Powiązania:
    https://bibliotekanauki.pl/articles/309098.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    Adaptive-Control Factor
    MBSS
    musical noise
    subbands
    Opis:
    This paper presents speech enhancement technique based on Spectral Subtraction (SS) method. SS is a renowned noise reduction technique that works on the principle that noise spectrum estimate over the entire speech spectrum can be subtracted from the noisy signal. On the contrary, most of the noise encountered in the real-world conditions is majorly colored. Unlike Additive White Gaussian Noise (AWGN), colored noise does not affect the speech signal uniformly over the entire spectrum. To mitigate effects of colored noise on the processed signal, we propose a Multi-Band Spectral Subtraction (MBSS) method using novel Adaptive-Control Factor (ACF). The spectrum is divided into frequency sub bands based on a nonlinear multi-band frame and various signal-to-noise ratios (SNRs) are considered. The proposed scheme results in better system performance with quality signal and unlike the basic SS method. It mitigates the effects of anomaly known as “musical” tones artifacts in the processed signal that result in residual noise and speech distortion. The computational complexity involved is minimal. Furthermore, simulation results show that the proposed algorithm removes more colored noise without removing the relatively low amplitude speech signal over the entire speech spectrum. Subjective listening tests, with clean speech signals and different noise levels, show discernable performance of our proposed method when compared with the conventional SS approach.
    Źródło:
    Journal of Telecommunications and Information Technology; 2013, 2; 35-39
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    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
    Artykuł
    Tytuł:
    Evaluation of thermal performance factor for solar air heaters with artificially roughened channels
    Autorzy:
    Siddique, Waseem
    Raheem, Aneeq
    Aqeel, Muhammad
    Qayyum, Sualeh
    Salamen, Tareq
    Waheed, Khalid
    Qureshi, Kamran
    Powiązania:
    https://bibliotekanauki.pl/articles/1845043.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    turbulence promoter
    solar air heater
    heat transfer enhancement
    thermal performance factor
    słoneczny grzejnik powietrzny
    intensyfikacja wymiany ciepła
    współczynnik wydajności cieplnej
    Opis:
    Heat transfer augmentation has become the utmost industrial desire. Turbulence promoters seems to be a better option for better heat transfer but at the expense of enormous pressure drop. In the current study, experimental optimization of heat transfer and pressure drop in various configurations of ribbed and corrugated surfaces on the bottom wall of the Solar Air Heater channel, having aspect ratio of 26:5 was performed. The results were evaluated in terms of enhancement in heat transfer (Nu/Nu s), friction factor ratio (f/f s) and thermal performance factor ( η). Three different cases and nine configurations with a pitch to rib/corrugation height ratio of 4.0 were studied. Case A consists of a smooth, continuous square rib, inline and staggered broken ribs. Case B comprises 30°, 45°, 60° and 90° trapezoidal corrugated geometries while Case C is the comparison of smooth, wavy corrugated and the best configurations of cases A and B. The results show that rectangular duct with staggered broken ribs and trapezoidal corrugation at 45° are the best configurations for case A and B, respectively. The 45° corrugated configuration is the best one amongst all, with values of 1.53, 1.5 and 1.33% for Nu/Nu s, f/f s and η respectively.
    Źródło:
    Archive of Mechanical Engineering; 2021, LXVIII, 2; 195-225
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Współdziałanie nauczycieli jako czynnik ich rozwoju osobowego i poprawy jakości procesów edukacyjnych (Teachers’ interaction as a factor in their personal development and in the enhancement of the quality of school educational processes)
    Autorzy:
    Kochanowska, Ewa
    Powiązania:
    https://bibliotekanauki.pl/articles/707241.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Źródło:
    Rocznik Komisji Nauk Pedagogicznych; 2014, LXVII
    0079-3418
    Pojawia się w:
    Rocznik Komisji Nauk Pedagogicznych
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance Enhancement of Cooperative MIMO-NOMA Systems Over Sub-6 GHz and mmWave Bands
    Autorzy:
    Saleh, Ahmed A.
    Ahmed, Mohamad A.
    Powiązania:
    https://bibliotekanauki.pl/articles/24200732.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    error probability
    MIMO
    mmWave
    NOMA
    out-age probability
    power allocation factor
    successive-interference cancellation (SIC
    Opis:
    In this paper, two radio links with different frequency bands are considered for base stations (BS) serving users via decode-and-forward (DF) cooperative relays. Backhaul and access links are proposed with sub-6 GHz and millimeter wave (mmWave) bands, respectively. Non-orthogonal multiple access (NOMA) is employed in the backhaul link to simultaneously transmit a superposed signal in the power domain, using the same band. The superposed signals, containing two signals that differ in terms of power allocation factors (PAFs), are designed for two selected DF relays in the BS. The two relays are chosen from several relays to be serviced by the BS based on a pairing algorithm that depends on different users’ circumstances. The furthest DF relay detects the incoming NOMA signal directly, while the nearest one applies successive interference cancellation (SIC) before extracting its signal. Each DF relay forwards the detected signals toward their intended users over mmWave channels. Three performance metrics are utilized to evaluate the system’s performance: outage probability, achievable throughput, and bit error rate. Comparisons between two mmWave bands in the access link (28 and 73 GHz) are made to demonstrate the superiority of the 28 GHz band in terms of the three performance-related metrics.
    Źródło:
    Journal of Telecommunications and Information Technology; 2023, 2; 70--77
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study of an adaptive accelerated model and a data transfer method based on a Reliability Enhancement Test
    Badania adaptacyjnego modelu przyspieszonego oraz metody transferu danych w oparciu o test poprawy niezawodności
    Autorzy:
    Tao, J.
    Yu, Z.
    Ren, Z.
    Yi, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/301882.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
    Tematy:
    test poprawy niezawodności
    model Arrheniusa
    model Duane’a
    adaptacyjny model przyspieszony
    współczynnik przyspieszenia
    reliability enhancement test
    Arrhenius model
    Duane model
    adaptive accelerated model
    acceleration factor
    Opis:
    Aby ocenić niezawodność produktu za pomocą testu poprawy niezawodności (Reliability Enhancement Test, RET), w badaniach najpierw rozważano proces zmiany parametrów modelu Arrheniusa poprzez połączenie modelu Arrheniusa z modelem Duane'a oraz przedstawiono adaptacyjny model przyspieszony i metodę oceny parametrów. Następnie, na podstawie adaptacyjnego modelu przyspieszonego opisano metodę transferu danych z RET do badań przy normalnym oddziaływaniu czynników zewnętrznych. Wreszcie, omówiono różnice obserwowane przy zastosowaniu RET do badań identyfikacyjnych niezawodności i badań wzrostu niezawodności. Na przykładzie zagadnienia inżynierskiego przedstawiono także metodę obliczania wskaźnika niezawodności produktu za pomocą RET.
    To assess the reliability of a product using a Reliability Enhancement Test (RET), this study first considers the change process of the Arrhenius model parameters by combining the Arrhenius model with the Duane model and gives an adaptive accelerated model and a parameter estimation method. Then, the data transfer method from the RET to normal test stress are described based on the adaptive accelerated model. Finally, the differences observed when the RET is used for a reliability identity test or a reliability growth test are discussed, and an engineering case demonstrates a method for obtaining the reliability index of a product using the RET.
    Źródło:
    Eksploatacja i Niezawodność; 2014, 16, 1; 128-132
    1507-2711
    Pojawia się w:
    Eksploatacja i Niezawodność
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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