Modelling and simulation of the utilization of a PEM fuel cell in the rural sector of Venezuela

We studied the use of Proton Exchange Membrane (PEM) fuel cells in rural villages of Venezuela lacking a permanent and reliable energy supply. For this purpose, we formulated a semi-empirical mathematical model representing the main technical and economic features involved in the operation of the PEM cells. The simulation of the resulting non-linear model spans a 20-year time horizon, considering how costs are affected by the expected increase in the energy demand of the rural population, to which it is applied and the decrease in the unit costs of the cell on account of technological improvements and mass production of the cell. These villages are located in the parish of Trinidad de la Capilla, in the central-west part of the country. They were selected on the basis of various social and economic factors involving percentage of rural population and the Human Development Index. The results show that the main operating variables, current density, efficiency and generated voltage, show the typical behaviour of this type of cell, whereas, from the economic point of view, the cost of the electricity produced by the cell stack decreases to constant values, both for the same year and interanually, due to the economy of scale and because the investment costs and the costs of the hydrogen used offset one another. The use of PEM cells, besides meeting the energy requirements of this Venezuelan rural parish, is viable in principle, as it contributes in a large way to improving the quality of life and sustainable development of these isolated and depressed regions, which, due to their distance from the electrical grid and their surface area, are not covered by it, and probably will not be in the near future.     

Analytical assessment of destoned and organic-destoned extra-virgin olive oil

Outcomes related with the concentrations of bioactive compounds in new functional virgin olive oil kinds (destoned or organic-destoned) are referred to in this research paper. We paid attention to their nutraceutical metabolome and noticeably to their concentration in biophenolics and vitaminic antioxidants (tocopherols, tocotrienols and β-carotene) and to their sensory and hedonistic traits. There was evidence that the innovative destoning technique, owing to its soft action during olive processing, meaningfully affected the profile of the non-glyceryl-containing components and noticeably the levels of phytochemicals more related to human health and nutrition. We observed that the profile of the major lipidome (triacylglycerols and ω₉, ω₆ and ω₃ fatty acids) of the new natural produces did not differ significantly from that of the reference ones. But they were richer in biophenols (oleuropein and ligstroside aglycons, lignans, flavonoids, phenol acids and phenol alcohols) as well as in α- and γ-tocopherol and α- and γ-tocotrienol. Moreover, they stood out for their harmonic flavour and aroma, higher levels of green volatiles and more marked fragrance. They also had excellent hedonistic properties, higher stability/endurance to oxidation, and longer shelf-life. Their bionutritional traits were further enhanced when organic olives were submitted to destoning during processing. They can thus contribute to reduce risks concerning several current human pathologies (including mainly cardiovascular diseases and cancer types).     

Linear viscoelasticity,probe tack,and extrusion flow results of SEBS copolymers

Microphase‐separated poly(styrene‐b‐ethylene‐co‐butylene‐ b‐styrene) copolymers of different molecular weights with polystyrene (PS) volume fraction ? = 0.30 are investigated. Linear dynamic viscoelastic data reveal the blocking effect of the ordered PS microdomains, which produces a predominantly elastic response at low frequencies, associated with a mechanical relaxation. These results are correlated with tack and extrusion flow measurements, which involve polymer/metal adhesion processes. Nonlinearity implied in some experiments alters the ordered morphology of low molecular weight samples producing a viscous dominant behavior. Dissipation is reflected in viscous‐like adhesion and lack of viscoplastic response in extrusion flow experiments. For the highest molecular sample, only a rubbery or entangled state (G′ > G″ and G′ > 10⁵ Pa) is observed in the linear viscoleastic regime. This is associated with the lack of adhesion seen in both, probe tack experiments and capillary flow measurements. This lack of adhesion gives rise to a plug‐flow as the polymer slips in the capillary wall. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Design criteria for high-frequency RC-active sinusoidal oscillators

High-frequency RC-active sinusoidal oscillators using two op amps are surveyed from a unified viewpoint. Information about their performance is obtained using linear and non-linear approaches. As a consequence of this analysis, two main criteria are proposed to optimize these systems and to select the best configuration for a given application. the first criterion is related to the feasibility of obtaining an oscillation frequency independent of the op amps used in the design. the second criterion is connected with the level of harmonic distortion present in the signal. Experimental measurements obtained agree closely with the theoretical analysis carried out.     

Low-Voltage CMOS Nonlinear Transconductors and Their Application to Companding Current-Mode Filters

Two novel nonlinear CMOS transconductors that can be employed for building CMOS current-mode filters are presented and their performances compared to formerly proposed topologies aimed at the same goal. The first one is based on a previous topology proposed by the authors, where a new biasing procedure leads to an improved performance for low supply voltages. The second one follows a novel approach, based on cascading a transresistor and a transconductor. The analysis is complemented with a more general approach based on the identification of translinear loops present in the circuit. Both nonlinear transconductors can operate at supply voltages as low as one V _GS plus two V _DS of a saturated MOSFET. CMOS current-mode filters based on these blocks are built following companding techniques, and their correct operation is validated by simulation and experimental results.     

HCV inhibits antigen processing and presentation and induces oxidative stress response in gastric mucosa

Productive hepatitis C virus (HCV) infection appears to be primarily confined to the liver. However, a wide variety of extrahepatic disease manifestations are associated with the infection and HCV RNA has been frequently detected in gastric mucosa. The present study aims to determine molecular alterations present in vivo in the stomach where HCV expression does not induce a carcinoma but a lymphoma, thus extending the knowledge of alterations in intracellular pathways consequent to HCV infection. We compared, by 2-D DIGE, the gastric protein expression profile from six HCV positive and six HCV negative samples lacking neoplastic or dysplastic conditions. In HCV positive tissue we observed a down regulation of proteins involved in MHC maturation and assembly, antigen processing and presentation and ER stress, in addition to an up regulation of proteins involved in cellular oxidative stress responses. Ubiquinol-cytochrome-C-reductase (UQCRFS1), part of the mitochondrial respiratory chain complex-III, was identified as the most up regulated protein. Data were confirmed by Western blot and immunohistochemistry. Our results demonstrate a HCV negative influence on the different pathways that determine antigen processing and presentation via MHC-I and the cellular attempts to counteract HCV induced oxidative stress. Both these processes facilitate immune escape and cell survival and probably contribute to HCV chronicization.     

Audio scrambling technique based on cellular automata

Scrambling is a process that has proved to be very effective in increasing the quality of data hiding, watermarking, and encryption applications. Cellular automata are used in diverse and numerous applications because of their ability to obtain complex global behavior from simple and localized rules. In this paper we apply cellular automata in the field of audio scrambling because of the potential it holds in breaking the correlation between audio samples effectively. We also analyze the effect of using different cellular automata types on audio scrambling and we test different cellular automata rules with different Lambda values. The scrambling degree is measured and the relation between the robustness and the scrambling degree obtained is studied. Experimental results show that the proposed technique is robust to data loss attack where 1/3 of the data is lost and that the algorithm can be applied to music and speech files of different sizes.     

Visual quality evaluation of large LED displays based on subjective sensory perception

Large light-emitting diode (LED) displays have undergone a great deal of development in recent years. One of their main characteristics is their potential for great diversity in their physical parameters (size, brightness, power consumption, etc.) and in the configuration of the LED pixel arrays. The physical parameters can vary by several orders of magnitude, while the matrix can be organized in discrete real RGB pixels or in several types of virtual pixel distributions such as Bayer, Hexagonal and Diagonal. For this reason, it is particularly difficult to make a complete and exhaustive evaluation of any type of displays based only on objective parameters. In this paper we have developed and used a subjective method for evaluating the image quality of various types of LED displays. The results obtained show that there is not a perfect display solution and that for each particular project it is possible to find an optimal LED matrix solution based on quality performance and the number and distribution of LEDs used (that marks pixel resolution, overall manufacturing cost and power consumption). For displays with the same number of LEDs the array of emitters formed by real pixels are desirable for applications viewed at short distances and for predominantly alphanumeric content, while virtual pixels arrays are advantageous in applications requiring greater viewing distances and a higher content of complex images.     

Mapping coffee plantations with Landsat imagery: an example from El Salvador

Considering the potential of shaded coffee plantations mixed with natural vegetation for promoting biodiversity conservation, this project assessed the utility of multi-date Landsat Thematic Mapper (TM) satellite imagery for the characterization of natural vegetation versus coffee plantations in western El Salvador. For assembling a multi-temporal Landsat TM data set, we applied a regression analysis model to remove cloud cover and cloud shadows. Then, through a hybrid classification approach, a nine-class land use/land cover (LULC) map was generated. We identified two types of coffee plantations (‘open-canopy’ and ‘close-canopy’) along with natural forest/shrubland, mangrove, water bodies, sandy coastal soils, bare soil, urban areas and agriculture. Notwithstanding the small sample size of the accuracy data, our assessment revealed an overall accuracy of 76.7% (Kappa coefficient?=?0.68), considering only the four classes with independent field data. The overall classification accuracy for distinguishing coffee plantations from non-mangrove natural forest was 81.6% and the classification accuracy for distinguishing ‘open-canopy’ from ‘close-canopy’ coffee plantations was 85.7%. We are encouraged by the results of this prototype study. They indicate that remote-sensing techniques can be used to distinguish different classes of coffee production systems and to differentiate coffee from natural forest.