Papers by Keyword: FDTD

Abstract: The dye-sensitized solar cell is one of the most promising solar cells as an alternative to conventional silicon-based solar cells. The advantages of DSSC compared to conventional silicon-based solar cells are the easy fabrication process and low cost. In general, DSSC consists of semiconductor materials and dye as a photoanode, a catalyst at the counter electrode, and an electrolyte. The problem is that the DSSC performance is not optimal in the light utilization process. One of the ways to improve DSSC performance is by increasing photon absorption. A method that can increase photon absorption on DSSC is by adding a light scattering layer (LSL) using TiO₂ microparticles. The technique used in this study for the optical model is the scattering theory and numerical methods using the Finite Differential Time Domain (FDTD). The scattering intensity and incident photon intensity are used for the electron generation process. The result of electron generation is used to model electrically to obtain the value of the short circuit current density and the open-circuit voltage with the diffusion differential equation. DSSC with LSL has higher efficiency than DSSC without LSL. The results obtained from this study DSSC with LSL has an efficiency of 5.5%, Jsc 16 mA/cm², and an open-circuit voltage of 0.6184 volts. DSSC without LSL has an efficiency of 4.9%, Jsc of 14.5 mA/cm², and an open-circuit voltage of 0.6073 Volt.

Abstract: Finite difference time domain (FDTD) method is a grid-based, robust and straightforward method to model and study the optical properties of metal nanoparticles (MNPs). However, high computational costs of FDTD including simulation time and memory demand mitigate the interest in this algorithm. In this paper, FDTD algorithm is reviewed and reasons of high computational cost requirement in FDTD are investigated. Computational costs are directly characterised by the resolution and size of FDTD grid (known as Yee grid). High FDTD grid resolution is essentially required in MNPs plasmonic modelling to achieve promising accuracy. This results in increasing the dimension of FDTD operational parameters (stored in FDTD matrices) which increases memory and simulation time required and consumed by the algorithm.

Abstract: Among noble metal nanoparticles (MNPs), plasmonic effect of gold and silver nanoparticles (Au NPs and Ag NPs) is interesting to study due to their high near-field energy. This makes them excellent particles to absorb and scatter incident radiation in optical applications such as coupling them to fluorescent emitters to enhance their radiative decay and emission rate. This paper reviews and studies the methodology required for tuning the doping concentration and modelling plasmonic optical properties of Au NPs and Ag NPs by using finite difference time domain (FDTD) method. The frequency-dependent optical behaviour of MNPs is discussed. Plasmonic optical properties of MNPs can be characterised by their dimension, shape and doping concentration. Dimension and shape of MNPs can be simply defined in FDTD space grid (known as Yee grid). However, tuning MNPs doping concentration is more challenging which is undertaken by changing the spacing between MNPs and lateral boundaries of FDTD Yee grid. This can be vastly useful in Au NPs and Ag NPs optical optimization and applications to estimate plasmonic resonance based on doping concentration of particles.

Abstract: In order to get the low transmission rate in both mid infrared atmospheric window and far infrared atmospheric window, an infrared frequency selective surface composed of two layers based on hexagonal ring structure was designed. Simulation analysis using CST electromagnetic software shown that the frequency selective surface had two stopbands in both 3μm~5μm and 8μm~15μm regions, of which the average transmittance is lower than 2.5%. Therefore, this frequency selective surface realized two stopbands in infrared wavebands; This paper analyzed the filtering mechanism of the frequency selective surface based on the effective medium theory. In the end, this paper researched the effect of electromagnetic wave polarization mode, incident angle and dielectric layer thickness on the transmission properties of the frequency selective surface. The results revealed that the transmission of frequency selective surface is insensitive to polarization mode and incident angle, while the dielectric layer thickness is an important factor to the transmittance of frequency selective surface.

Abstract: It is well known that the occurrence of partial discharge phenomena within switchgears can lead to their destruction. Early detection can avoid failures of electrical equipment. The work of this paper mainly provides theoretic foundation for precise partial discharge (PD) location in switchgears. Hyperboloid method and spatial grid search method are proposed to locate PD source with transient earth voltage (TEV) test. Finite-difference time-domain (FDTD) is used to simulate the propagation process of TEV signal and validate the proposed method. Laboratory test on operating switchgear was conducted and the test results were in consistent with the simulation.

Abstract: This paper presents two methods for electromagnetic nondestructive evaluation (eNDE) of composite materials reinforced with carbon woven fibers using a sensor with orthogonal coils and a sensor with metamaterials lens. The samples were impacted with low energy in order to study delamination influence. The electromagnetic behavior of composite was simulated by finite-difference time-domain (FDTD) software, showing a very good concordance with eNDE tests.

Abstract: Mie scattering theory is used in this paper to analyze the forward scattered light intensity distribution of an air bubble in the subsurface of optical glass, shining by a monochrome laser with a wavelength of 632.8um. The scattering process can be classified as uncorrelated single scattering .according to the properties of optical media. The finite difference time domain (FDTD) software is used to establish a 3-d simulation model to calculate for forward scattered intensity distribution of different sized air bubbles. Moreover, according to the relationship between Mie scattering intensity pattern and the size of bubbles, the size of bubbles are figured out with the help of neural network algorithm. The errors are lower than 10%. The simulation results can improve the precision of defects detection in optical glass.

Abstract: The portable grounding system plays an important role in the lightning protection system of mobile equipments. But the traditional earth electrodes composed of vertical rods wouldn’t work well or would take a long time to set up in some conditions such as frozen soil, hard clay and so on. In this paper, a new type of portable grounding system which can be quickly spread and folded has been designed. To analyze the TGR’s (Transient Grounding Resistance) time-domain characteristics, the grounding systems have been modeled and simulated with FDTD (Finite Difference Time Domain). The influence rule of electrodes’ number and down-lead’s position to TGR has been studied with numerical analysis and validated with experiments. The results show that the new grounding system works well even on cement floor.

Abstract: Defects inside the gas-insulated switchgear (GIS) will produce ultra-high frequency (UHF) electromagnetic waves. The waves will be affected by the shell of GIS when propagating inside the GIS cavity. In the 0-3GHz frequency range, propagation characteristic of electromagnetic which is excited by partial discharge in GIS is simulated based on the method of finite difference time domain (FDTD). This paper designs the GIS simulation models with and without insulator according to the size of a 220kV single phase GIS bus and sets a metal protrusion defect on the bus as the PD source. The transmission characteristics of model waves inside typical GIS structures, and the influence of the insulator to the propagation of electromagnetic wave was studied via setting the different directions of electromagnetic, comparing the time and frequency domain results of electromagnetic wave in different structures and measurement angles.

Abstract: The near-field characteristics of the ideal electric dipole are analyzed in this paper. A practical ultrafast band antenna near field FDTD is made and the near field distribution of the antenna is studied by numerical simulation. The calculation results show that the FDTD method is used for the analysis of feasibility and reliability of the near-field communication antenna.