A hardware solution for real-time intelligent fingerprint acquisition

The first step in any fingerprint recognition system is the fingerprint acquisition. A well-acquired fingerprint image results in high-resolution accuracy and low computational effort of processing. Hence, it is very useful for the recognition system to evaluate recognition confidence level to request new fingerprint samples if the confidence level is low, and to facilitate recognition process if the confidence level is high. This paper presents a hardware solution to ensure a successful and friendly acquisition of the fingerprint image, which can be incorporated at low cost into an embedded fingerprint recognition system due to its small size and high speed. The solution implements a novel technique based on directional image processing that allows not only the estimation of fingerprint image quality, but also the extraction of useful information (in particular, singular points). The digital architecture of the module is detailed and their features in terms of resource consumption and processing speed are illustrated with implementation results into FPGAs from Xilinx. Performance of the solution has been verified with fingerprints from several standard databases that have been acquired with sensors of different sizes and technologies (optical, capacitive, and thermal sweeping).     

Application specific integrated circuit solution for multi‐input multi‐output piecewise‐affine functions

This paper presents a fully digital architecture and its application specific integrated circuit implementation for computing multi‐input multi‐output (MIMO) piecewise‐affine (PWA) functions. The work considers both PWA functions defined over regular hyperrectangular and simplicial partitions of the input domains and also lattice PWA representations. The proposed architecture is able to implement PWA functions following different realization strategies, using a common structure with a minimized number of blocks, thus reducing power consumption and hardware resources. Experimental results obtained with application specific integrated circuit (ASIC) integrated in a 90‐nm complementary metal‐oxide semiconductor standard technology are provided. The proposed architecture is compared with other digital architectures in the state of the art habitually used to implement model predictive control applications. The proposal is superior in power consumption (saving up to 86%) and economy of hardware resources (saving up to 40% in comparison with a mere replication of the three representations) to other proposals described in literature, being ready to be used in applications where high‐performance and minimum unitary cost are required. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of the electrical and rheological behavior of different processed CNF/PMMA nanocomposites

Carbon nanofiber (CNF)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared via melt-compounding, solvent casting and in situ polymerization. Mechanical properties, rheological behavior and electrical resistivity were investigated in specimens with varying CNF loadings. The three processing techniques were compared. Improved properties were obtained in the solvent processed and in situ polymerized composites. The rheological and electrical percolation of these nanocomposites appeared in the same concentration set (between 1 and 5 wt%). No changes were found in melt-compounding, even by the addition of 10 wt% of CNFs. Electrical resistivity of the samples prepared by solvent casting was measured before and after pressing in the hot plate press. It is remarkable that in the non-pressed samples the CNFs formed an efficient 3-D conductive network, yielding composites with percolation thresholds even six orders of magnitude lower than after pressing, where this 3-D network was destroyed.     

CMOS Design of a Current-Mode Multiplier/Divider Circuit with Applications to Fuzzy Controllers

Multiplier and divider circuits are usually required in the fields of analog signal processing and parallel-computing neural or fuzzy systems. In particular, this paper focuses on the hardware implementation of fuzzy controllers, where the divider circuit is usually the bottleneck. Multiplier/divider circuits can be implemented with a combination of A/D-D/A converters. An efficient design based on current-mode data converters is presented herein. Continuous-time algorithmic converters are chosen to reduce the control circuitry and to obtain a modular design based on a cascade of bit cells. Several circuit structures to implement these cells are presented and discussed. The one that is selected enables a better trade-off speed/power than others previously reported in the literature while maintaining a low area occupation. The resulting multiplier/divider circuit offers a low voltage operation, provides the division result in both analog and digital formats, and it is suitable for applications of low or middle resolution (up to 9 bits) like applications to fuzzy controllers. The analysis is illustrated with Hspice simulations and experimental results from a CMOS multiplier/divider prototype with 5-bit resolution. Experimental results from a CMOS current-mode fuzzy controller chip that contains the proposed design are also included.     

Waterbirds and nutrient enrichment in Mar Menor Lagoon, a shallow coastal lake in southeast Spain

The Mar Menor, a 135‐km² saline lake, is the largest water surface on the western Mediterranean coast, and an internationally important bird area. It is surrounded by a large irrigated agricultural plain, with dense tourism developments. Although the impacts of these activities on water quality are locally evident, their effects on waterbird populations are poorly known. In the winter 2004–2005, we studied the distribution of four waterbird species (Podiceps cristatus, Podiceps nigricollis, Phalacrocorax carbo and Fulica atra) around the main drainage channel that discharges into the lake, where it was feasible to infer spatial patterns of eutrophication (alongshore and shore centre) from previous environmental surveys. Waterbirds were counted along a stretch of undeveloped shoreline extending southwards from the channel outlet, in contiguous sections, and in bands parallel to the shoreline. Linear mixed models (LMM) indicated the population density increased only markedly for grebes (Podiceps cristatus, Podiceps nigricollis) and coot (Fulica atra) in littoral bands qualifying as eutrophic, but not an alongshore response, with their finescale alongshore distribution being apparently unrelated to nutrient sources. Considering the whole lake, however, the temporal trends and distribution of the wintering populations indicated that waterbirds respond numerically, in a guild‐specific way, to nutrient inputs. Grebes and coot could be a useful ‘two‐stage’ warning signal for potential problem areas affected by similar influences.     

Effect of solvent nature in casting-based carbon nanofiber/poly(methyl-methacrylate) nanocomposites

Eight different solvents, of different polarities, were used to prepare carbon nanofiber (CNF)/poly(methyl methacrylate nanocomposites by solvent casting. Selected solvents ranged from organic acetone to nonpolar toluene, passing through N-containing solvents. In addition, pristine and oxygen and nitrogen-functionalized CNFs were used. Two objectives were pursued: (1) the role of the solvent in the dispersion of the CNFs and (2) the benefit of the functionalization on the dispersion through the stability in the solvent and compatibility with the matrix. The dispersion analysis of the materials leads to the conclusion that solvents containing oxygen groups work better with the oxidized CNFs, similarly solvents containing nitrogen groups with the nitrogen-functionalized CNFs. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012