http://hdl.handle.net/10204/918 Tue, 21 May 2013 07:28:08 GMT 2013-05-21T07:28:08Z http://hdl.handle.net/10204/6693 Title: Fingerprint pores extractor Authors: Mngenge, NA; Nelufule, NN; Nelwamondo, FV; Msimang, M Abstract: Automatic Fingerprint Recognition Systems (AFRSs) rely on minutiae position and orientation within the fingerprint image for matching. Minutiae information is highly accurate provided that the fingerprint image matched is of high quality. However, this is not always the case because of diseases and hash working conditions that affect fingerprints. In order to maintain high level of security independent of varying fingerprint image quality research suggests the use of other fingerprint features to compliment minutiae. These are things like ridge contours, sweat pores, dots, and incipient ridges. Sweat pores have been proven as one of the most distinctive among these feature. Thus in order to improve accuracy of AFRSs pores can be fused with minutiae or used alone. Sweat pores have been less utilized in the past due to constraints imposed by fingerprint scanning devices and resolution standards. Recently, progress has been made on both scanning devices and resolution standards to support the use of pores in AFRSs. However, very few techniques exist for extracting, matching and fusing them with minutiae. Matching and fusion can only be possible if pores are available. Some techniques have been proposed to reliable extract pores. However, existing techniques can only work on one resolution i.e. an algorithm proposed and tested on 500dpi cannot work on 1000dpi without minor modifications because pores size change if resolution changes. In addition, existing pore extraction techniques are computationally expensive. In this paper an algorithm to extract feature level 3 (pores) is proposed. The algorithm uses Laplacian of Gaussian (LoG) in Fourier domain in order to reduce computation. The performance of the proposed algorithm is tested on two distinct databases with different resolutions in order to validate its accuracy. The accuracy of the proposed algorithm is further measured using false detection rate (FDR) and true detection rate (TDR). Results show that FDR ranges from 10-35% while TDR ranges from 65-90%. Description: 2012 National Conference on Computing and Communication Systems, Durgapur, West Bengal, India, 21- 22 November 2012. To be published in IEEE Xplore Thu, 01 Nov 2012 00:00:00 GMT http://hdl.handle.net/10204/6693 2012-11-01T00:00:00Z http://hdl.handle.net/10204/6665 Title: An investigation of Laser Induced Breakdown Spectroscopy for use as a control in the laser removal of rock from fossils found at the Malapa hominin site, South Africa Authors: Roberts, DE; Du Plessis, A; Steyn, J; Botha, LR; Pityana, S; Berger, LR Abstract: Laser Induced Breakdown Spectroscopy (LIBS) was used to study the spectra from fossils and surrounding rock recovered from the Cradle of Mankind site at Malapa, South Africa. The objective was to find a suitable spectral line(s), specific to fossils, which could be used as a control signal to limit damage to fossils during high speed laser removal of the encasing rock. The calcified clastic matrix (rock) encasing the fossils was found to emit a variety of complex LIBS spectra. Nevertheless, it was found possible to distinguish fossils in a single LIBS pulse, and without significant damage to the fossil, using spectral lines of neutral phosphorus. Description: Copyright: 2012 Elsevier. This is an ABSTRACT ONLY. The definitive version is published in Spectrochimica Acta Part B: Atomic Spectroscopy, vol. 73, pp 48- 54 Sun, 01 Jul 2012 00:00:00 GMT http://hdl.handle.net/10204/6665 2012-07-01T00:00:00Z http://hdl.handle.net/10204/6592 Title: Modal decomposition without a priori scale information Authors: Schulze, C; Ngcobo, S; Duparre, M; Forbes, A Abstract: The modal decomposition of an arbitrary optical field may be done without regard to the spatial scale of the chosen basis functions, but this generally leads to a large number of modes in the expansion. While this may be considered as mathematically correct, it is not efficient and not physically representative of the underlying field. Here we demonstrate a modal decomposition approach that requires no a priori knowledge of the spatial scale of the modes, but nevertheless leads to an optimised modal expansion. We illustrate the power of the method by successfully decomposing beams from a diode-pumped solid state laser resonator into an optimised Laguerre-Gaussian mode set. Our experimental results, which are in agreement with theory, illustrate the versatility of the approach. Description: Copyright: 2012 Optical Society of America. Published in Optics Express, vol. 20(25), 27866-27873 Sat, 01 Dec 2012 00:00:00 GMT http://hdl.handle.net/10204/6592 2012-12-01T00:00:00Z http://hdl.handle.net/10204/6584 Title: Efficient sorting of Bessel beams Authors: Dudley, A; Mhlanga, T; Lavery, M; McDonald, A; Roux, FS; Padget, M; Forbes, A Abstract: We demonstrate the efficient sorter of Bessel beams separating both the azimuthal and radial components. This is based upon the recently reported transformation of angular to transverse momentum states. We separately identify over forty azimuthal and radial components, with a radial spacing of 1588 m-1, and outline how the device could be used to identify the two spatial dimensions simultaneously. Description: Copyright: 2013 Optical Society of America. Published in Optics Express, vol. 21(1), pp 165-171 Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10204/6584 2013-01-01T00:00:00Z