The Experts below are selected from a list of 1749 Experts worldwide ranked by ideXlab platform
Akiyoshi Tatematsu - One of the best experts on this subject based on the ideXlab platform.
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a technique for representing lossy thin wires and coaxial cables for fdtd based surge simulations
IEEE Transactions on Electromagnetic Compatibility, 2018Co-Authors: Akiyoshi TatematsuAbstract:To protect power equipment and electronic devices in low-voltage control circuits in power plants and substations from abnormal voltages such as lightning or switching surges, it is necessary to design effective protection measures based on the prediction of surge phenomena. Nowadays, full-wave numerical approaches have become effective tools for analyzing electromagnetic transient phenomena in three-dimensional or grounding structures. To apply the finite-difference time-domain (FDTD) method to surge analysis, several techniques for representing thin wires and coaxial cables have been developed. In this study, to simulate lossy wires and cables in FDTD-based surge simulations, first, we propose a technique for taking into account the effect of the conductor internal impedances of thin wires and Metal Sheath of coaxial cables by using a series of lumped-parameter frequency-dependent impedances on the conductors. Second, we propose a technique for simulating the effect of the surface transfer impedances of coaxial cables in the FDTD method while representing the Metal Sheath directly by a lossy thin wire in the FDTD method and solving surge phenomena inside the coaxial cables on the basis of transmission line theory. The proposed techniques are validated by circuit-theory-based simulations.
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a technique for representing coaxial cables for fdtd based surge simulations
IEEE Transactions on Electromagnetic Compatibility, 2015Co-Authors: Akiyoshi TatematsuAbstract:The finite-difference time-domain (FDTD) method is a very effective tool for predicting surge phenomena in 3-D structures such as buildings and transmission line towers and in grounding systems such as grounding grids. In this paper, we propose a new technique for representing a coaxial cable for FDTD-based surge simulations. In this technique, the Metal Sheath of the cable and the electromagnetic field outside the Metal Sheath are simulated in the FDTD method, while the surge phenomena inside the Metal Sheath are solved on the basis of transmission line theory. Therefore, this technique can take into account the effect of the Metal Sheath of the coaxial cable, the traveling wave inside the cable, and wires connected to the internal conductor of the cable at the same time. Using the proposed technique, we predicted the surge phenomena in a coaxial cable and compared them with measured results for the purpose of validation.
S M Prokes - One of the best experts on this subject based on the ideXlab platform.
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plasmonic coupling on dielectric nanowire core Metal Sheath composites
Nanotechnology, 2010Co-Authors: Dimitri A Alexson, O J Glembocki, S M ProkesAbstract:We have developed dielectric core/Metal Sheath nanowire (NW) composites for surface-enhanced Raman scattering (SERS), in which an electroless (EL) Ag plating approach was employed. The NW surface was uniformly covered with a high density of 3D silver islands, having a diameter in the 20–30 nm range and spaced less than ≈10 nm apart. In comparison with the silver deposition via e-beam evaporation, the EL coating approach has the advantage of full Metal coverage of the NWs. This approach also provides a fast and simple way to completely cover any nanostructures with Ag, including nanowires, regardless of the orientation or shape. SERS measurements were performed using benzene thiol and the SERS signal strength of the EL-coated NW composites was significantly greater than expected, since the surface plasmon resonance (SPR) of 20 nm Ag nanospheres is weak and in the UV, while our measurements were performed using a 514.5 nm laser line. However, we have modeled this system using our electric field calculations and the results indicate that the strong SERS signal is due to plasmonic coupling of neighboring closely spaced islands, as well as an enhanced substrate effect. In addition, the nanowire core serves as a template for the formation of these small, closely spaced Ag islands, resulting in the strong SERS signal.
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effect of crossing geometry on the plasmonic behavior of dielectric core Metal Sheath nanowires
Applied Physics Letters, 2009Co-Authors: S M Prokes, Dimitri A Alexson, O J Glembocki, H D Park, R W RendellAbstract:We have shown that dielectric/Metal composite nanowires exhibit very strong surface enhanced Raman spectroscopy (SERS) signals when arranged in a random three-dimensional geometry. Since the intersections of the nanowires are critical in generating the high electric fields necessary for this enhancement, we are investigating this effect under more controlled conditions. We examined nanowire arrays formed by e-beam lithography and we have examined the plasmonic effects, both longitudinal and transverse, due to changes in crossing geometry by specific placements of dielectric/Metal nanowires on these arrays. Results indicate significant angular effects on the SERS enhancement supported by electric field calculations.
Dimitri A Alexson - One of the best experts on this subject based on the ideXlab platform.
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plasmonic coupling on dielectric nanowire core Metal Sheath composites
Nanotechnology, 2010Co-Authors: Dimitri A Alexson, O J Glembocki, S M ProkesAbstract:We have developed dielectric core/Metal Sheath nanowire (NW) composites for surface-enhanced Raman scattering (SERS), in which an electroless (EL) Ag plating approach was employed. The NW surface was uniformly covered with a high density of 3D silver islands, having a diameter in the 20–30 nm range and spaced less than ≈10 nm apart. In comparison with the silver deposition via e-beam evaporation, the EL coating approach has the advantage of full Metal coverage of the NWs. This approach also provides a fast and simple way to completely cover any nanostructures with Ag, including nanowires, regardless of the orientation or shape. SERS measurements were performed using benzene thiol and the SERS signal strength of the EL-coated NW composites was significantly greater than expected, since the surface plasmon resonance (SPR) of 20 nm Ag nanospheres is weak and in the UV, while our measurements were performed using a 514.5 nm laser line. However, we have modeled this system using our electric field calculations and the results indicate that the strong SERS signal is due to plasmonic coupling of neighboring closely spaced islands, as well as an enhanced substrate effect. In addition, the nanowire core serves as a template for the formation of these small, closely spaced Ag islands, resulting in the strong SERS signal.
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effect of crossing geometry on the plasmonic behavior of dielectric core Metal Sheath nanowires
Applied Physics Letters, 2009Co-Authors: S M Prokes, Dimitri A Alexson, O J Glembocki, H D Park, R W RendellAbstract:We have shown that dielectric/Metal composite nanowires exhibit very strong surface enhanced Raman spectroscopy (SERS) signals when arranged in a random three-dimensional geometry. Since the intersections of the nanowires are critical in generating the high electric fields necessary for this enhancement, we are investigating this effect under more controlled conditions. We examined nanowire arrays formed by e-beam lithography and we have examined the plasmonic effects, both longitudinal and transverse, due to changes in crossing geometry by specific placements of dielectric/Metal nanowires on these arrays. Results indicate significant angular effects on the SERS enhancement supported by electric field calculations.
O J Glembocki - One of the best experts on this subject based on the ideXlab platform.
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plasmonic coupling on dielectric nanowire core Metal Sheath composites
Nanotechnology, 2010Co-Authors: Dimitri A Alexson, O J Glembocki, S M ProkesAbstract:We have developed dielectric core/Metal Sheath nanowire (NW) composites for surface-enhanced Raman scattering (SERS), in which an electroless (EL) Ag plating approach was employed. The NW surface was uniformly covered with a high density of 3D silver islands, having a diameter in the 20–30 nm range and spaced less than ≈10 nm apart. In comparison with the silver deposition via e-beam evaporation, the EL coating approach has the advantage of full Metal coverage of the NWs. This approach also provides a fast and simple way to completely cover any nanostructures with Ag, including nanowires, regardless of the orientation or shape. SERS measurements were performed using benzene thiol and the SERS signal strength of the EL-coated NW composites was significantly greater than expected, since the surface plasmon resonance (SPR) of 20 nm Ag nanospheres is weak and in the UV, while our measurements were performed using a 514.5 nm laser line. However, we have modeled this system using our electric field calculations and the results indicate that the strong SERS signal is due to plasmonic coupling of neighboring closely spaced islands, as well as an enhanced substrate effect. In addition, the nanowire core serves as a template for the formation of these small, closely spaced Ag islands, resulting in the strong SERS signal.
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effect of crossing geometry on the plasmonic behavior of dielectric core Metal Sheath nanowires
Applied Physics Letters, 2009Co-Authors: S M Prokes, Dimitri A Alexson, O J Glembocki, H D Park, R W RendellAbstract:We have shown that dielectric/Metal composite nanowires exhibit very strong surface enhanced Raman spectroscopy (SERS) signals when arranged in a random three-dimensional geometry. Since the intersections of the nanowires are critical in generating the high electric fields necessary for this enhancement, we are investigating this effect under more controlled conditions. We examined nanowire arrays formed by e-beam lithography and we have examined the plasmonic effects, both longitudinal and transverse, due to changes in crossing geometry by specific placements of dielectric/Metal nanowires on these arrays. Results indicate significant angular effects on the SERS enhancement supported by electric field calculations.
R W Rendell - One of the best experts on this subject based on the ideXlab platform.
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effect of crossing geometry on the plasmonic behavior of dielectric core Metal Sheath nanowires
Applied Physics Letters, 2009Co-Authors: S M Prokes, Dimitri A Alexson, O J Glembocki, H D Park, R W RendellAbstract:We have shown that dielectric/Metal composite nanowires exhibit very strong surface enhanced Raman spectroscopy (SERS) signals when arranged in a random three-dimensional geometry. Since the intersections of the nanowires are critical in generating the high electric fields necessary for this enhancement, we are investigating this effect under more controlled conditions. We examined nanowire arrays formed by e-beam lithography and we have examined the plasmonic effects, both longitudinal and transverse, due to changes in crossing geometry by specific placements of dielectric/Metal nanowires on these arrays. Results indicate significant angular effects on the SERS enhancement supported by electric field calculations.