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Wyświetlanie 1-5 z 5
Tytuł:
Light Fidelity (Li-Fi) overview and investigation into connection speed
Autorzy:
Sharma, Mithun
Sharma, Shilpi
Powiązania:
https://bibliotekanauki.pl/articles/1818970.pdf
Data publikacji:
2021
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
Light Fidelity
Li-Fi
Six-Sigma
defect reduction
wireless communication
redukcja wad
komunikacja bezprzewodowa
Opis:
The overarching aim was to reduce the frequency of connection failures that occur due to the connection speed and reliability, and identify, characterise and optimise the key process input variables (KPIVs). An experimental research approach with an inbuilt planned manipulation to one or more variables in the experimental data set was adopted. Key elements of the Six-Sigma methodology were applied to resolve the issue of high failures due to connection speed and reliability between two Li-Fi transceivers. KPIVs were successfully identified, characterised and optimised to implement a permanent corrective action to ensure a reduction in connection failures from 17% to 0%. The alignment between two Li-Fi transceivers along with Li-Fi cut-out was found to be critical in achieving good connection speed and reliability. The interference due to ambient visible spectrum lighting found to be statistically insignificant. This study explored the application and benefits of accessible wireless data communication technologies. Moreover, it sheds light on the probable factors that may influence Li-Fi connection speed and areas for future research. The current research provides a Six- Sigma based solution to high connection failure rates while using an infrared-based Li-Fi transceiver. Results also offer insights into the analytical tools that were found to be effective during the problem-solving process.
Źródło:
Engineering Management in Production and Services; 2021, 13, 1; 63--73
2543-6597
2543-912X
Pojawia się w:
Engineering Management in Production and Services
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:
Calcium alginate/activated carbon/humic acid tri-system porous fi bers for removing tetracycline from aqueous solution
Autorzy:
Sun, Qinye
Zheng, Heng
Li, Yanhui
Li, Meixiu
Du, Qiuju
Wang, Cuiping
Sui, Kunyan
Li, Hongliang
Xia, Yanzhi
Powiązania:
https://bibliotekanauki.pl/articles/949364.pdf
Data publikacji:
2020
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
Sodium alginate
Humic acid
Activated carbon
Adsorption
Tetracycline
Opis:
In this study, activated carbon and humic acid powder were fixed by the cross-linking reaction of sodium alginate. Calcium alginate/activated carbon/humic acid (CAH) tri-system porous fibers were prepared by the wet spinning method and freeze-dried for the removal of tetracycline in aqueous solution. Subsequently, the morphology and structure of CAH fibers were measured by scanning electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method. The effect of pH, contact time, temperature and other factors on adsorption behavior were analyzed. The Langmuir and Freundlich isotherm models were used to fit tetracycline adsorption equilibrium data. The dynamics data were evaluated by the pseudo-second-order model, the pseudo-second-order model and the intraparticle diffusion model. Thermodynamic study confirmed that the adsorption of tetracycline on CAH fibers was a spontaneous process.
Źródło:
Polish Journal of Chemical Technology; 2020, 22, 3; 9-16
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Complex Signal Mapping for Improving Spectral Efficiency of Li-Fi Systems
Autorzy:
Sileh, Ibrahim K.
Abdulkafi, Ayad A.
Hussein, Mohammed K.
Hardan, Saad M.
Powiązania:
https://bibliotekanauki.pl/articles/958061.pdf
Data publikacji:
2019
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
Li-Fi
OFDM
signal mapping
PAPR
BER
Opis:
Light fidelity (Li-Fi) systems based on the orthogonal frequency division multiplexing (OFDM) scheme have gained more attention in the communications circles, as a means to provide high spectral efficiency and ensure stricter data rate requirements for visible light communication (VLC) systems. However, common OFDM schemes employ Hermitian symmetry to obtain a real-valued signal which is necessary in intensity modulation and direct detection (IM/DD) optical systems, at the expense of doubling the required bandwidth. In this paper, a novel transmission scheme for an OFDM-based Li-Fi system is proposed to tackle the issue in question. A new approach to complex signal mapping (CSM), based on the pairing function method, has been developed for Li-Fi systems. It does not require Hermitian symmetry and, hence, saves about 50% of the required bandwidth. Unlike existing OFDM-based VLC approaches, the proposed scheme employs CSM to ensure a real and positive signal without Hermitian symmetry in order to fully utilize the bandwidth available to Li-Fi networks. Simulation results show that the proposed scheme significantly outperforms other systems in terms of spectral efficiency. The CSM-OFDM based Li-Fi system also achieves a good peak-to-average power ratio (PAPR) reduction with acceptable bit-error-rate (BER) performance, compared to conventional approaches.
Źródło:
Journal of Telecommunications and Information Technology; 2019, 3; 58-62
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Matter-Wave Bright Solitons of $\text{}^7Li$ Gas in an Expulsive Potential
Autorzy:
Golam Ali, Sk.
Talukdar, B.
Roy, S.
Powiązania:
https://bibliotekanauki.pl/articles/1814020.pdf
Data publikacji:
2007-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.75.Fi
05.45.Yv
Opis:
A Lagrangian based method is used to derive an analytical model for studying the dynamics of matter-wave bright soliton created in a harmonic potential which is attractive in the transverse direction and expulsive in the longitudinal direction. By means of sech trial functions and a Ritz optimization procedure, evolution equations are constructed for width, amplitude and nonlinear frequency chirp of the propagating soliton of the atomic condensate. Our equation for the width is an exact agreement with that of Carr and Castin, obtained by more detailed analysis. In agreement with the experiment of Paris group, the expulsive potential is found to cause the soliton to explode for N|$a_s$|=0.98, N being the number of atoms in the condensate and $a_s$ -- the scattering length of the atom-atom interaction.
Źródło:
Acta Physica Polonica A; 2007, 112, 6; 1165-1170
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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