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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 24 (1978), S. 817-830 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A system of equations based on the ionic atmosphere theory of Debye and Huckel, Born model contribution, and local compositions of the nonrandom two-liquid (NRTL) model is developed to represent isothermal activity coefficients, in the whole range of concentrations, for solutions in an undissociated solvent of a partially or completely dissociated electrolyte.The physical constants and the four adjustable parameters necessary to represent the osmotic coefficient, for fifteen strong aqueous electrolytic solutions, are given at 298.15°K and atmospheric pressure. Vapor-liquid equilibrium, for the hydrochloric acid-water system at 298.15°K, is represented for acid compositions ranging from infinite dilution to 18 M using a known dissociation constant and six parameters.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 1143-1150 
    ISSN: 1040-0397
    Keywords: Stripping voltammetry ; Metal complexation ; Latex ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differential pulse anodic stripping voltammetry (DPASV) was applied to the study of the binding of ZnII, CdII and PbII by two kinds of polystyrene latex particles at different pH values and at different electrolyte concentrations. For the calculation of stability constants, the criterion of consistency between current and potential data was applied. For CdII and PbII, the application of DPASV yields qualitatively good results (in agreement with those previously found by DPP). However, from a quantitative point of view, the consistency criterion often reduces the applicability of the technique to quite narrow pH ranges, which increases the error in some calculations. In the case of ZnII, certain anomalies were found, rendering quantitative considerations impossible.
    Additional Material: 6 Ill.
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  • 3
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complex formation of Zn(II) and Cd(II) with polymethacrylic acid (PMA) and polyacrylic acid (PAA) is studied by sampled direct current, normal pulse, reverse pulse, and differential pulse polarography and by differential pulse anodic stripping voltammetry (DPASV). Titrations of Zn(II) or Cd(II) with partially neutralized PMA or PAA by DPASV allow the precise determination of the apparent formation constant K of the four systems. The two Zn(II) systems appear to be labile on the different time scales of the several techniques, without remarkable complications due to secondary phenomena. Their K values, determined by all techniques, agree satisfactorily. The two Cd(II) systems, and especially the Cd/PAA system, show rather involved behavior, which tends to normality when the degree of neutralization αn of the polycarboxylates increases. Both slow kinetics and ligand adsorption coupled with induced Cd(II) adsorption (evidenced by maxima on the normal pulse polarograms) seem to be present. For all αn values, DPASV yields higher estimates of K than do polarographic techniques.
    Additional Material: 10 Ill.
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  • 4
    Publication Date: 2016-02-26
    Description: The broadband albedo values retrieved from satellite sensors are usually compared directly to ground measurements. Some authors have noted the necessity of high spatial resolution albedo estimates to fill the gap between ground measurements and satellite retrievals. In this respect, hyperspectral airborne data with high spatial resolution is a powerful tool. Here, a new operational method for the calculation of airborne broadband apparent albedo over the spectral range of 350–2500 nm is presented. This new method uses the Hemispherical Directional Reflectance Factor (HDRF) as a proxy for the narrowband albedo, assuming a Lambertian approximation. The broadband apparent albedo obtained is compared to that estimated using theapparent albedo equation devised for the Moderate Resolution Imaging Spectroradiometer (MODIS). Airborne data were collected using the Airborne Hyperspectral Scanner (AHS). Field data were acquired at three sites: a camelina field, a green grass field, and a vineyard.  The HDRF can be used to approximate the narrowband albedo for all View Zenith Angle (VZA) values for flights parallel to the solar principal plane (SPP); for flights orthogonal to the SPP, discrepancies are observed when the VZA approaches −45°. Root Mean Square Error (RMSE) values in the range 0.009–0.018 were obtained using the new method, improving upon previous results over the same area (RMSEs of 0.01–0.03). The relative error in the albedo estimation using the new method is 12% for −36.2° 〈 VZA 〈 40.8° in the case of flights parallel to the SPP and less than 15% for −13° 〈 VZA 〈 45° and 45% for VZA = −45° for flights orthogonal to the SPP. The good performance of the new method lies in the use of the at-surface solar irradiance and the proposed integration method.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by MDPI Publishing
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  • 5
    Publication Date: 2017-05-21
    Description: The heliostat field of solar central receiver systems (SCRS) is formed by hundreds, even thousands, of working heliostats. Their adequate configuration and control define a currently active research line. For instance, automatic aiming methodologies of existing heliostat fields are being widely studied. In general, control techniques require a model of the system to be controlled in order to obtain an estimation of its states. However, this kind of information may not be available or may be hard to obtain for every plant to be studied. In this work, an innovative methodology for data-based analytical heliostat field characterization is proposed and described. It formalizes the way in which the behavior of a whole field can be derived from the study of its more descriptive parts. By successfully applying this procedure, the instantaneous behavior of a field could be expressed by a reduced set of expressions that can be seen as a field descriptor. It is not intended to replace real experimentation but to enhance researchers’ autonomy to build their own reliable and portable synthetic datasets at preliminary stages of their work. The methodology proposed in this paper is successfully applied to a virtual field. Only 30 heliostats out of 541 were studied to characterize the whole field. For the validation set, the average difference in power between the flux maps directly fitted from the measured information and the estimated ones is only of 0.67% (just 0.10946 kW/m2 of root-mean-square error, on average, between them). According to these results, a consistent field descriptor can be built by applying the proposed methodology, which is hence ready for use.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 6
    Publication Date: 2018-01-26
    Description: Energies, Vol. 11, Pages 291: Solar Ray Tracing Analysis to Determine Energy Availability in a CPC Designed for Use as a Residential Water Heater Energies doi: 10.3390/en11020291 Authors: Miguel Terrón-Hernández Manuel Peña-Cruz Jose Carrillo Ulises Diego-Ayala Vicente Flores Compound parabolic concentrators are relevant systems used in solar thermal technology. With adequate tailoring, they can be used as an efficient and low-cost alternative in residential water heating applications. This work presents a simulation study using a ray tracing analysis. With this technique, we simulate the interaction between solar rays and solar concentrator to quantify the amount of energy that impinges on the receiver at a particular time. Energy availability is evaluated in a comparison of two configurations throughout the year: static setup at 21° and multi-position setup; tilted with respect to the horizontal, depending on three seasonal positions: 0° for summer, 16° for spring/autumn, and 32° for winter, with the aim to evaluate the amount of available energy in each season. The fact that a tracking system can be dispensed with also represents an economical option for the proposed application. The results showed that at 21°, the proposed solar Compound Parabolic Concentrator (CPC) works satisfactorily; however, by carrying out the selected angular adjustments, the overall energy availability increased by 22%, resulting in a more efficient option. The most effective design was also built and analyzed outdoors. The obtained thermal efficiency was of ~43%. The optical design and its evaluation developed herein proved to be a valuable tool for prototype design and performance evaluation.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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