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87 results on '"Edwardson, S. P."'

12. Converting Television Standards

Author

Edwardson, S. M.

Abstract

Discusses converting television standards, primarily in terms of the various converters available. (LS)

Published
1969

13. The influences of particle number on hot spots in strongly coupled metal nanoparticles chain.

Author

Wang, Z. B., Luk'yanchuk, B. S., Guo, W., Edwardson, S. P., Whitehead, D. J., Li, L., Liu, Z., and Watkins, K. G.

Subjects
NANOPARTICLES, GOLD, SILVER, RAMAN effect, DIMERS, ELECTROMAGNETIC fields
Abstract

In understanding of the hot spot phenomenon in single-molecule surface enhanced Raman scattering (SM-SERS), the electromagnetic field within the gaps of dimers (i.e., two particle systems) has attracted much interest as it provides significant field amplification over single isolated nanoparticles. In addition to the existing understanding of the dimer systems, we show in this paper that field enhancement within the gaps of a particle chain could maximize at a particle number N>2, due to the near-field coupled plasmon resonance of the chain. This particle number effect was theoretically observed for the gold (Au) nanoparticles chain but not for the silver (Ag) chain. We attribute the reason to the different behaviors of the dissipative damping of gold and silver in the visible wavelength range. The reported effect can be utilized to design effective gold substrate for SM-SERS applications. [ABSTRACT FROM AUTHOR]

Published
2008
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15. NUV femtosecond laser inscription of volume Bragg gratings in poly (methyl) methacrylate with linear and circular polarizations

Author

Ye, L, Perrie, Walter, Allegre, Olivier, Jin, Y, Kuang, Z., Scully, Patricia, Fearon, E, Eckford, D, Edwardson, S P, and Dearden, Geoff

Abstract

Large, high efficiency, volume Bragg gratings with dimensions of 5 mm× 5 mm and thickness between 1 and 7 mm with 20 μm pitch have been inscribed in poly (methyl) methacrylate (PMMA) with 180 fs, 387 nm parallel beams using both linear and circular polarizations. Linear polarization (perpendicular to the scan direction) produced the highest refractive index contrast, while circular polarization produced the lowest. The measured first-order diffraction efficiency with grating thickness L agrees well with theoretical expectations, and reached a maximum of 94% near L= 4 mm, the highest yet observed in pure PMMA. The source of the variation in refractive index contrast was investigated, and it was found to be due to the polarization-dependent nonlinear filamentation, the first such observation in a pure polymer.

Published
2013
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33. Optical trapping for engineering manufacture

Author

Edwardson, S. P., primary, Perrie, W., additional, Sharp, M., additional, Dearden, G., additional, Wang, Z. B., additional, Whitehead, D., additional, Crouse, P., additional, Lui, Z., additional, Li, L., additional, and Watkins, K. G., additional

Published
2007
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39. Iterative 3D laser forming of continuous surfaces

Author

Edwardson, S. P., primary, Moore, A. J., additional, Abed, E., additional, McBride, R., additional, French, P., additional, Hand, D. P., additional, Dearden, G., additional, Jones, J. D. C., additional, and Watkins, K. G., additional

Published
2004
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47. Laser Forming of Aerospace Alloys

Author

Watkins, K. G., primary, Edwardson, S. P., additional, Magee, J., additional, Dearden, G., additional, French, P., additional, Cooke, R. L., additional, Sidhu, J., additional, and Calder, N. J., additional

Published
2001
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49. Ultrashort Pulse Periodic Structuring of Metallic Surfaces.

Author

MELLOR, L. F., EDWARDSON, S. P., PERRIE, W., DEARDEN, G., and WATKINS, K. G.

Subjects
*ULTRA-short pulsed lasers, *METALLIC surfaces, *LASERS in engineering, *OPTICAL polarization, *WAVELENGTHS, *LIGHT propagation
Abstract

A detailed study has been conducted into the effect of laser process parameters on the production of laser induced periodic surface structures in 316L stainless steel using a pulsed picosecond fibre laser. Periodic structures were produced via scanning of the incident beam at varying speeds in order to control the pulse overlap. Feature depth and uniformity were found to rely heavily upon both the scan speed and pulse energy. Inhomogeneous feature production across the track cross-section was observed and attributed to the Gaussian nature of the incident beam. Features were observed oriented perpendicularly to the direction of polarization for linearly polarized light with a period approximately equal to the incident light wavelength. This period was observed to alter with incident angle and a dependency on laser scan direction was also found. A threshold intensity value for the production of laser induced surface ripples was calculated from a Gaussian analysis of measured track width. The threshold value when machining at 200 kHz, 750 mm/s, and 2 µJ was calculated to be 2.35 x 1014 W/m². [ABSTRACT FROM AUTHOR]

Published
2012

50. Finite Element Modelling of the Laser Forming of AISI 1010 Steel.

Author

Griffiths, J., Edwardson, S. P., Boegelein, T., Prandina, M., Dearden, G., and Watkins, K. G.

Subjects
*FINITE element method, *THERMAL stresses, *ABSORPTION, *INDUSTRIAL lasers, *STEEL, *GRAPHITE, *THERMAL expansion
Abstract

Laser forming offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, correction of design shape or distortion and precision adjustment applications. In order to fulfil this promise in a manufacturing environment the process must have a high degree of controllability, which can be achieved through a better understanding of its underlying mechanisms. One area of limited understanding is that of the variation in bend angle per pass observed during multi-pass laser forming along a single irradiation track, notably the decrease in bend angle per pass after many irradiations. Finite element (FE) modelling can be used to ascertain which of the various process parameters (such as graphite burn-off, geometrical effects, variation in absorption, etc.) contribute towards this phenomenon and subsequently the magnitude of their contribution. [ABSTRACT FROM AUTHOR]

Published
2012

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