Use of chloroflurocarbons as internal standards for the measurement of atmospheric non-methane volatile organic compounds sampled onto solid adsorbent cartridges

Solid adsorbents have proven useful for determining the vertical profiles of volatile organic compounds (VOCs) using sampling platforms such as balloons, kites, and light aircraft, and those profiles provide valuable information about the sources, sinks, transformations, and transport of atmospheric VOCs. One of the largest contributions to error in VOC concentrations is the estimation of the volume of air sampled on the adsorbent cartridge. These errors arise from different sources, such as variations in pumping flow rates from changes in ambient temperature and pressure with altitude, and decrease in the sampling pump battery power. Another significant source for sampling rate variations are differences in the flow resistance of individual sampling cartridges. To improve the accuracy and precision of VOC measurements, the use of ambient chlorofluorocarbons (CFCs) as internal standards was investigated. A multibed solid adsorbent, AirToxic (Supelco), was chosen for its wide sampling range (C3-C12). Analysis was accomplished by thermal desorption and dual detection GC/FID/ECD, resulting in sensitive and selective detection of both VOCs and CFCs in the same sample. Long-lived chlorinated compounds (CFC-11, CFC-12, CFC-113, CCl4 and CH3CCl3) banned by the Montreal Protocol and subsequent amendments were studied for their ability to predict sample volumes using both ground-based and vertical profiling platforms through the boundary layer and free troposphere. Of these compounds, CFC-113 and CCl4 were found to yield the greatest accuracy and precision for sampling volume determination. Use of ambient CFC-113 and CCl4 as internal standards resulted in accuracy and precision of generally better than 10% for the prediction of sample volumes in ground-, balloon-, and aircraft-based measurements. Consequently, use of CFCs as reference compounds can yield a significant improvement of accuracy and precision for ambient VOC measurements in situations where accurate flow control is troublesome.     

Attitudes towards computers and information technology at three universities in Germany, Belgium, and the U.S.

Students' interest in computers and information technology is both a prerequisite and a goal of successful qualification programs. The present study was conducted to search for intercultural differences or cross-cultural consistency of attitudes in this field, based on the Computer and Information Technology Attitude Inventory (CITAI; Weinsier & Leutner, 1988). This instrument was developed to overcome theoretical and methodological problems of usual Likert-type questionnaires by (a) hiding the object of measurement from the responding student and (b) by using a factorial or facet design for constructing 72 items (titles of university short courses with and without reference to computers or information technology). Data on 529 students were collected at three universities in Germany, Belgium, and the U.S. Multidimensional scalings indicated high similarity of the interitem correlation structures across the three samples based on both point-to-point correspondences and facet theoretic regional analysis of the spaces. This cross-cultural consistency underlines the construct validity of the questionnaire design. However, some intercultural differences were found — for instance, that European students have a strong preference/or noncomputer as opposed to computer courses, whereas U.S. students do not have any preference. The results are discussed with regard to the initial hypothesis that an object loses its feature of being a controversial theme with strong effects on attitudes if that object becomes more and more a component of the normal environment.     

Drawing as a generative activity and drawing as a prognostic activity.

In this study, 9th-grade students (N = 196) with a mean age of 14.7 years read a scientific text explaining the chemical process of doing laundry with soap and water and then took 3 tests. Students who were instructed to generate drawings during learning scored higher than students who only read on subsequent tests of transfer (d = 0.91), retention (d = 0.87), and drawing (d = 2.00). For students who were instructed to generate drawings during learning, those who generated high-accuracy drawings (according to a median split) scored higher than students who generated low-accuracy drawings on subsequent tests of transfer (d = 0.99), retention (d = 0.79), and drawing (d = 1.87); furthermore, drawing-accuracy scores during learning correlated with learning-outcome scores on transfer (r = .57), retention (r = .50), and drawing (r = .82). Results suggest that drawing can serve as a generative activity and as a prognostic activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detection of Melting Temperatures and Sources of Errors Using Two-Color Pyrometry During In-flight Measurements of Atmospheric Plasma-Sprayed Particles

Growing demands on the quality of plasma-sprayed coatings require reliable methods to monitor and optimize the spraying processes. As the coating microstructures are dependent on the characteristics of the powder feedstock, particle in-flight diagnostics is of great importance. In particular, the melting status of the particles is critical in this regard. Thus, the accurate determination of the particle temperature is necessary. In-flight particle temperature measurements during atmospheric plasma spraying (APS) of tungsten, molybdenum, and yttria-stabilized zirconia by two-color pyrometry were analyzed statistically. The diagnostic tool applied is the DPV-2000 (Tecnar). The particle temperature distributions allow for assessment of the melting status of the particles as well as the identification of the melting temperature and particle fractions in the molten and solidification state. Furthermore, the relevant systematic and material-dependent sources for measurement errors using two-color pyrometry were investigated. Their influence was carefully estimated and corrected. As long as there are reliable data available on the emissivity of the powder material, good agreement between the corrected measured melting temperatures and the reference data can be expected.     

Plasma_sprayed components for SOFC applications

The major challenge in the development of plasma sprayed components for SOFC was the fabrication of dense electrolytes by atmospheric plasma_spraying (APS) avoiding cracks typically generated during the spraying process. Compared to conventional plasma_sprayed ceramics both the number of micro_cracks and segmentation cracks have to be reduced considerably to achieve sufficiently low leakage rates.Based on a detailed understanding of the formation of plasma_sprayed coatings appropriate process conditions have been established to reach the target values. The major influencing factors are the particle properties in the plasma jet, the substrate temperature, the kind of movement of the gun during deposition, the particle size distribution of the used YSZ powder, and the powder feeding rate. In addition, also the used APS gun plays a major role. With the Triplex II gun it was possible to produce rather thin (≤ 40 μm) YSZ layers with sufficiently low leakage rates without any thermal post_treatment.As substrates tape_casted ferritic steel sheets have been used. The anode was also sprayed by APS using a separate injection of NiO and YSZ. Electrochemical performance was measured after wet_chemically applying a LSCF cathode. The values of the measured open circuit voltage (OCV) were comparable to the ones of sintered cells, indicating the high density of the produced electrolytes. The optimized cells showed at 0.7 V cell voltage a power density of 500 mW/cm² @ 1073 K.     

Influence of three-dimensional cloud effects on satellite derived solar irradiance estimation—First approaches to improve the Heliosat method

Three-dimensional (3D) cloud effects which influence the surface solar irradiance are investigated by using the radiative transfer model SHDOM (spherical harmonics discrete ordinate method). The calculations are motivated by improving the Heliosat method which is used for the estimation of surface solar irradiance from satellite data. The modelled results lead to the assumption that it is possible to find a correction for moderate viewing and solar geometries for the current Heliosat method. Based on these results an empirical study has been done, comparing ground measurements with Heliosat derived data. It will be shown that a correction of the current Heliosat method for 3D cloud effects is possible. For two out of four sites the proposed corrections decrease the relative root mean square error (rRMSE) of the irradiance derived by the Heliosat method in a range of about 2%. The use of a site specific correction for different locations shows that the adaptability of the corrections depend on the dominant local cloud regimes, which governs e.g. the existence of certain cloud types.     

Improving Powder Injection in Plasma Spraying by Optical Diagnostics of the Plasma and Particle Characterization

Powder injection parameters such as gas flow, injection angle, and injector position strongly influence the particle beam and thus coating properties. The interaction of the injection conditions on particle properties based on DPV-2000 measurements using the single-cathode F4 torch is presented. Furthermore, the investigation of the plasma plume by emission computer tomography is described when operating the three-cathode TriplexPro? torch. By this imaging technology, the three-dimensional shape of the radiating plasma jet is reproduced based on images achieved from three CCD cameras rotating around the plume axis. It is shown how the formation of the plasma jet changes with plasma parameters and how this knowledge can be used to optimize particle injection.     

Standardisierte Charakterisierung optischer Komponenten

Standardized Characterization of Optical Components The scope of the present contribution is to present a plain review on prominent measurement techniques for the determination of quality parameters for optical coatings and laser components. Emphasis is imposed on standardized test methods for the spectral transfer characteristics, the optical losses induced by scattering and absorption, as well as for laser induced damage thresholds of coated optics. The fundamental principles of the measurement methods are considered und illustrated by examples selected from typical applications. This contribution is intended to introduce the measurement principles on a practical basis and to give indications for a deeper insight into the topic