Browsing by Issue Date, starting with "1995"
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- O Estado do "Eloquente" (1411-1438)Publication . Freitas, Judite A. Gonçalves de
- Progressive ladder network topology combining interferometric and intensity fiber-optic-based sensorsPublication . Lobo Ribeiro, Antonio B.; Caleya, R. F.; Santos, J. L.Progressive ladder topology is studied by consideration of its properties of power budget and coupler tailoring. Optimization criteria are addressed for lossless and real systems, and their basic characteristics are compared with other topologies. Numerical results are presented, and an experiment is described for the case in which the network supports interferometric and intensity (with referentiation) fiber-optic-based sensors.
- Interlaboratory comparisons of petrography of liquefaction residues from three Argonne Premium coalsPublication . Hower, J. C.; Anderson, K. B.; Mackay, G.; Pinheiro, H. J.; Flores, Deolinda; Lemos de Sousa, M. J.Three Argonne Premium coal samples, the Beulah-Zap lignite (North Dakota), the high volatile A bituminous Stockton (West Virginia), and the low volatile Pocahontas No. 3 (Virginia), were ground to three initial sizes: -20 mesh, -100 mesh, and "micronized". The samples were each subjected to liquefaction at 673 K for 30 min at a 2:1 tetralin :coal ratio and in an H 2 atmosphere at 13.79 MPa (~ 2000 psi). Polished pellets of the unconverted residues were circulated to three laboratories for a study designed to determine, albeit on a limited scale, the interlaboratory consistency in constituent identification and the problem areas in maceral/neo-maceral/mineral recognition. Within broad categories, the agreement for the Beulah-Zap and Pocahontas No. 3 residues is good. The high volatile A bituminous Stockton coal was the most plastic and most altered, resulting in a residue lending itself to more subjective interpretations. The biggest discrepancy between the laboratories is in the distinction of granular residue and mineral matter and in the transitions between "partially reacted macerals" and "vitroplast" and between "vitroplast" and "granular residue". The initial size of the feed coal appears to influence the recognition of material in the residue.
- Combined spatial- and time-division-multiplexing scheme for fiber grating sensors with drift-compensated phase-sensitive detectionPublication . Rao, Y. J.; Zhang, L.; Bennion, I.; Lobo Ribeiro, Antonio B.; Jackson, D. A.A combined spatial- and time-division-multiplexing topology with drift-compensated high-resolution wavelength-shift detection is reported for fiber Bragg grating sensors. An eight-element grating sensor array is demonstrated based on this topology. A resolution of ~1.2 microepsilon over a range of ~1.5 mepsilon with a measurement bandwidth of 30 Hz (~0.22 microepsilon/ radicalHz) has been achieved for quasi-static strain measurement.
- Referencing technique for intensity-based sensors using fibre optic Bragg gratingsPublication . Cavaleiro, P.M.; Lobo Ribeiro, Antonio B.; Santos, J.L.An all-optical fibre referencing scheme for intensity based sensors which uses two identical fibre Bragg gratings is described. It provides a general and simple miniature sensor design with referencing directiveness against system power fluctuations. The concept is demonstrated for a reflective-type displacement sensing cavity, and its potential for simultaneous measurand and temperature evaluation is evaluated.
- Intercomparison of two meso-meteorological models applied to the Lisbon regionPublication . Borrego, C.; Coutinho, M.; Barros, NelsonIn this paper two mesoscale meteorological models are applied to the Lisbon region. A special concern is directed to the initial conditions and input parameterization in order to assure that equal simulation constraints were imposed to both models. Results obtained for 4 August 1992 (a typical summer day) are compared to meteorological data acquired in three monitoring stations. Both simulations show similar reactions to the mesoscale forcings that occur in the modelling region. The minor differences found between simulation and reality for the meteorological situation can cause major errors in predicting air quality.
- A mechanistic model of the effects of light and temperature on algal primary productivityPublication . Duarte, PedroIn this work a model of algal primary productivity combining a mechanistic light function with a temperature Arrhenius function is presented. Data on primary productivity obtained with algae acclimated to different environmental conditions was used to test the model. A simple method for model parameter estimation based on regression analysis is described. The parameter estimates can be improved by a non-linear least-squares method (e.g. the Gauss-Newton method) resulting in a significant fit to the observed data as tested by regression analysis. According to the present model, the initial slope of the productivity/light curves is temperature dependent whilst the optimal light intensity is temperature independent. These model predictions were validated by the obtained experimental results.
- Source rock/dispersed organic matter characterization-TSOP research subcommitee resultsPublication . Teerman, S. C.; Cardott, B. J.; Harding, R. W.; Lemos de Sousa, M. J.; Logan, D. R.; Pinheiro, H. J.; Reinhardt, M.; Thompson-Rizer, C. L.; Woods, R. A.Because sedimentary organic matter consists of a diverse mixture of organic components with different properties, a combination of chemical and petrographic results offers the most complete assessment of source rock properties. The primary purpose of this Society for Organic Petrology (TSOP) subcommittee is to contribute to the standardization of kerogen characterization methods. Specific objectives include: (1) evaluation of the applications of different organic matter (petrographic) classifications and terminology, and (2) integration of petrographic and geochemical results. These objectives were met by completing questionnaires, and petrographic, geochemical and photomicrograph round-robin exercises. Samples that were selected for this study represent different petrographic and geochemical properties, and geologic settings to help identify issues related to the utilization of different classifications and techniques. Petrographic analysis of the organic matter was completed using both a prescribed classification and the individual classification normally used by each participant. Total organic carbon (TOC), Rock-Eval pyrolysis and elemental analysis were also completed for each sample. Significant differences exist in the petrographic results from both the prescribed and individual classifications. Although there is general agreement about the oil- vs gas-prone nature of the samples, comparison of results from individual classifications is difficult due to the variety of nomenclature and methods used to describe an organic matter assemblage. Results from the photomicrograph exercise document that different terminology is being used to describe the same component. Although variation in TOC and Rock-Eval data exists, geochemical results define kerogen type and generative potential. Recommendations from this study include: (1) A uniform organic matter classification must be employed, which eliminates complex terminology and is capable of direct correlation with geochemical parameters. (2) A standardized definition and nomenclature must be used for the unstructured (amorphous) organic matter category. Subdivisions of this generalized amorphous category are needed to define its chemical and environmental properties. (3) Standardized techniques including multimode illumination, types of sample preparations and data reporting will help eliminate variability in the type and amount of organic components reported.