Temat: finite-difference time-domain

Skocz do pozycji: 1.

Tytuł:: Gold nano-elliptic arrays used in plasmonic waveguides in near infrared spectrum
Autorzy:: Nurmohammadi, T.
Yadipour, R.
Abbasian, K.
Tematy:: loss coefficient
group velocity
finite-difference time-domain; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/174404.pdf Link otwiera się w nowym oknie
Opis:: In this paper, we investigated plasmonic waveguides in near infrared spectrum, especially at original (λ = 1310 nm) and also communication bands (λ = 1550 nm) using gold nano-elliptic rings. It is possible to shift localized surface plasmon resonance, by appropriate geometrical properties, to the desired wavelength. Three-dimensional simulations utilizing the finite-difference time-domain algorithm are used to determine the set of geometrical parameters of gold nano-elliptic rings for exciting localized surface plasmon resonance at 1310 and 1550 nm. Employing different configurations of gold nano-elliptic rings chains, waveguides are designed, with–3 dB transmission loss coefficients and group velocities calculations for different modes. In comparison with circular nanorings, elliptic rings showed better characteristics, such as high electric field enhancements and low loss transmission coefficients.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Modelling and analysis of fibre microlenses with ray-tracing and finite-difference methods
Autorzy:: Śliwak, Adam
Jeleń, Mateusz
Patela, Sergiusz
Tematy:: Finite-difference time-domain method
knife-edge method
microlens
raytracing; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Powiązania:: https://bibliotekanauki.pl/articles/2063899.pdf Link otwiera się w nowym oknie
Opis:: Fibre optic microlenses are small optical elements formed on the end-faces of optical fibres. Their dimensions range from a few tens to hundreds of micrometres. In the article, four optical fibre microlenses are modelled and analysed. Microlenses are used for light beam manipulation and quantitative metrics are needed to evaluate the results, for example, the size of focusing spot or intensity distribution. All four lenses tested are made of rods of the same refractive index; they were welded to a single-mode fibre. Two modelling methods were used to analyse the lenses: ray-tracing and finite-difference time-domain. The ray-tracing algorithm moves rays from one plane to another and refracts them on the surfaces. Finite-difference time-domain consists of calculating Maxwell’s equations by replacing spatial and temporal derivatives by quotients of finite differences. In this paper, the results of the microlenses analyses obtained from ray-tracing and finite-difference timedomain methods were compared. Both mets of analysis showed the presence of undesirable side lobes related to lens design, namely rods too long for lens fabrication. The test results were compared with the measurements made with the knife-edge method. The use of a single tool to determine parameters of an optical fibre lens does not allow for precise determination of its properties. It is necessary to use different tools and programs. This allows a complete analysis of the beam parameters, letting us find the causes of technical issues that limit the performance of the lenses.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Study on Chinese Speech Intelligibility Under Different Low-Frequency Characteristics of Reverberation Time Using a Hybrid Method
Autorzy:: Huang, Wuqiong
Peng, Jianxin
Xie, Tinghui
Tematy:: low frequency
speech intelligibility
classroom
finite-difference time-domain method; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/31339871.pdf Link otwiera się w nowym oknie
Opis:: Reverberation time (RT) is an important indicator of room acoustics, however, most studies focus on the mid-high frequency RT, and less on the low-frequency RT. In this paper, a hybrid approach based on geometric and wave methods was proposed to build a more accurate and wide frequency-band room acoustic impulse response. This hybrid method utilized the finite-difference time-domain (FDTD) method modeling at low frequencies and the Odeon simulation at mid-high frequencies, which was investigated in a university classroom. The influence of the low-frequency RT on speech intelligibility was explored. For the low-frequency part, different impedance boundary conditions were employed and the effectiveness of the hybrid method has also been verified. From the results of objective acoustical parameters and subjective listening experiments, the smaller the low-frequency RT was, the higher the Chinese speech intelligibility score was. The syllables, consonants, vowels, and the syllable order also had significant effects on the intelligibility score.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: A simple model of the scanning near-field optical microscopy probe tip for electric field enhancement
Autorzy:: Wang, Y.
Cai, W.
Yang, M.
Liu, Z.
Shang, G.
Tematy:: near-field tip
electromagnetic field enhancement
finite-difference time-domain
FDTD; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/174091.pdf Link otwiera się w nowym oknie
Opis:: In this paper, we present a simple near-field probe model that is composed of an elongated ellipsoid and a finite metal truncated cone. The elongated ellipsoid has been shown to act as a protrusion or separate particle near a truncated cone apex with strong near-field enhancement under laser excitation. By controllably varying the length of the ellipsoid protrusion from the truncated cone, the truncated cone-ellipsoid probes can be adapted to the suitability of near-field probes. The effects of substrate material and excitation wavelength on the near field enhancement for different tip apexes are also discussed. In addition, we compared the properties of the truncated cone-ellipsoid probe with the widely used hemisphere conical tip by launching surface plasmon polaritons on plasmonic waveguides to prove the suitability of the truncated cone-ellipsoid probes as high performance near-field probes. The present simple model would provide a theoretical basis for the actual construction of probes.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: The 100 W class A power amplifier for L-band T/R module
Autorzy:: Wojtasiak, W.
Gryglewski, D.
Sędek, E.
Tematy:: modelling
MESFETs
finite difference time domain method
power transistors
microwave transistors; Pokaż więcej
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Powiązania:: https://bibliotekanauki.pl/articles/308787.pdf Link otwiera się w nowym oknie
Opis:: In the paper a balanced high power amplifier with class A silicon bipolar transistors for L-band T/R module is described. The amplifier was designed for maximum power and minimum transmitance distortions. The obtained parameters of the amplifier are as follow: output power at 1 dB compression P(1dB)>49 dBm, linear gain IS21I>10 dB, and transmitance deviations during the RF pulse: phase delta arg(S2)<0.9° and deltaP(out)<0.2 dB.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Finite-difference time-domain solution of second-order photoacoustic wave equation
Autorzy:: Rahimzadeh, A.
Chen, S.-L.
Tematy:: photoacoustic tomography
numerical simulation
finite-difference time-domain
second-order photoacoustic equation; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/173969.pdf Link otwiera się w nowym oknie
Opis:: A finite-difference time-domain numerical solution is presented for solving a single second-order photoacoustic equation, instead of solving three coupled first-order equations. In this way, we are able to insert the heating function to the simulation directly instead of initial pressure. Results are validated using k-Wave simulation and show a good agreement for future development. The perfectly matched layer boundary condition has been implemented for a second-order photoacoustic equation and results are compared to Dirichlet, Neumann and Mur boundary conditions.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Simulation of optical properties of Si photonic crystals
Autorzy:: Gamalath, K. A. I. L. W.
Settinayake, W. A. S. C.
Tematy:: photonic crystal
waveguides
power divider
finite difference time domain method
yee lattice approach; Pokaż więcej
Wydawca:: Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Powiązania:: https://bibliotekanauki.pl/articles/412423.pdf Link otwiera się w nowym oknie
Opis:: To investigate optical properties of Si photonic crystal waveguides, a mathematical model was set up. Finite difference time domain method was used to calculate the Maxwell’s equations numerically. For the evolution of the electromagnetic fields in the photonic crystals, simulations were done for a small lattices using Yee lattice approach. The properties of a waveguide and a power divider were investigated for 3λx 3λ photonic crystal formed from Si circular rods in air for telecommunication wavelength 1.55 μm. The model developed was satisfactory in predicting the behaviour of light in linear photonic crystals.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Heterostructure photonic crystal multichannel drop filter based on microcavities and ring resonators
Autorzy:: Amirkhani-Shahraki, A
Shahraki, M N
Mosavi, M.R.
Tematy:: finite difference time domain method
ring resonators
heterostructure
microcavities
photonic crystal integrated circuits; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/174469.pdf Link otwiera się w nowym oknie
Opis:: In this paper, a heterostructure photonic crystal multichannel drop filter based on ring resonators and microcavities is presented. This structure has been made in the form of a two-dimensional square lattice with two regions with refractive indexes of 3.464 and 3.86. The refractive indexes are so chosen as to allow the easy and practical fabrication of the device. The presented heterostructure photonic crystal multichannel drop filter consists of a waveguide, two ring resonators and a microcavity. This microcavity is placed at the end of the bus waveguide. The ring resonators have been installed in two regions with different refractive indexes. These ring resonators act as energy couplers, and at their resonance frequencies, they capture the electromagnetic energy which is transmitted in the bus waveguide. Filter characteristics have been obtained by using the finite difference time domain method. Finally, we will demonstrate that in the optimal structure, at ports B and D (vertical), drop efficiencies close to 90% and 67%, respectively, can be obtained within the third communication window, and at port C (horizontal), an efficiency of almost 80% can be achieved within the second communication window.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Using FDTD method to the analysis of electric field intensity inside complex building constructions
Autorzy:: Choroszucho, Agnieszka
Stankiewicz, Jacek Maciej
Tematy:: finite-difference time-domain method (FDTD)
wireless communications
systems
electromagnetic wave propagation
building materials; Pokaż więcej
Wydawca:: Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Powiązania:: https://bibliotekanauki.pl/articles/378245.pdf Link otwiera się w nowym oknie
Opis:: The aim of this article is to make a detailed analysis of the influence of the reinforcement diameter, the number of rows of reinforcing bars and the spacing between them for the values of the electric field intensity. The subject of the research is a model containing a wall made of concrete (dielectric) and reinforcement (conductor). Four reinforcement systems commonly used in building construction have been analysed. In addition, the influence of symmetry and asymmetry in the structure of bars on the values of field intensity determined for non-homogeneous material structures (reinforced concrete) was considered. For comparison, a concrete wall, without reinforcement (homogeneous material) was also analysed. Using FDTD method, the maximum electric field values generated by the Wi-Fi operating at the f = 2.4 GHz were calculated.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Basic Logic Gates in Two Dimensional Photonic Crystals for All Optical Device Design
Autorzy:: Sonth, Mahesh V
Srikanth, Gimmadi
Agrawal, Pankaj
Premalatha, B.
Tematy:: basic gates
photonic crystals
finite difference time domain
plane wave expansion
photonic band gap; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/1844637.pdf Link otwiera się w nowym oknie
Opis:: The research carried out in the field of optics and photonics with an idea to design and develop the all optical logic devices in the fascinating material known as photonic crystals (PhCs). The structural investigation reveals that the two dimensional (2-D) PhCs is more suitable for fabrication of optoelectronic components. In this article we have designed basic logic gates in 2-D PhCs as they are the building blocks for the construction of optical devices and in these, refractive index is periodically modulated with the wavelength. The understanding of light behaviour in complex PhCs helps in creating photonic band gap (PBG) that can prevent light of certain wavelength propagating in crystal lattice structure. For the selected geometry structure, three PBG bands will exists out of which two of them are transverse electric (TE) and one is transverse magnetic (TM) mode. The PBG bands in the TE mode ranges from 0.31( α λ ) to 0.46( α λ ), 0.61( α λ ) to 0.63( α λ ) and TM mode ranges from 0.86( α λ ) to 0.93( α λ ). The free space wavelength of 1550 nm is set for the finite difference time domain (FDTD) simulation of the structure. The response time and computational overhead required for the proposed OR gate is 0.128ps and 4.4MB is obtained. Also we calculated the extinction ratio for AND gate and NOT gate as 6.19 dB and 10.21 dB respectively.
Dostawca treści:: Biblioteka Nauki

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