Observations from the moderate resolution imaging spectroradiometer (MODIS) were used in combination with a large data set of field measurements to map woody above-ground biomass (AGB) across ...tropical Africa. We generated a best-quality cloud-free mosaic of MODIS satellite reflectance observations for the period 2000–2003 and used a regression tree model to predict AGB at 1 km resolution. Results based on a cross-validation approach show that the model explained 82% of the variance in AGB, with a root mean square error of 50.5Mgha−1 for a range of biomass between 0 and 454Mgha−1. Analysis of lidar metrics from the Geoscience Laser Altimetry System (GLAS), which are sensitive to vegetation structure, indicate that the model successfully captured the regional distribution of AGB. The results showed a strong positive correlation (R2 = 0.90) between the GLAS height metrics and predicted AGB.
The corrosion behaviour of bulk metallic glasses is greatly related to their microstructures. The microstructures in bulk metallic glasses of the same chemical composition are represented to a ...certain extent by their atomic mobility. Evolution of the microstructure and mechanical properties of Zr58Nb3Cu16Ni13Al10 bulk metallic glass after annealing were studied with X-ray diffraction, dynamic mechanical analysis and Vickers hardness tests. Polarization curve, open circuit potential, electrochemical impedance spectroscopy and Mott-Schottky analysis were performed to investigate the effect of atomic mobility on the corrosion behaviour in 1 mol/L de-aerated H2SO4 at 333 K. Dynamic mechanical analysis indicated that the atomic mobility of Zr58Nb3Cu16Ni13Al10 bulk metallic glass was reduced by structural relaxation and crystallization. All electrochemical measurements showed that the passivation ability decreased and the corrosion resistance of Zr58Nb3Cu16Ni13Al10 bulk metallic glass deteriorated as the annealing temperature increased. Mott-Schottky analysis revealed that the defect concentration in the passive films increased and the flat-band potential shifted to a negative potential with a decrease in the atomic mobility. X-ray photoelectron spectroscopy results proved that the main chemical compositions of the passive films were ZrO2, Al2O3 and Nb2O5. The formation of a passive film was suppressed because the atomic mobility of strong passivating elements (Zr, Al and Nb) decreased. In addition, the precipitation of crystals (Zr2Cu and Cu10Zr7) accelerated the corrosion of the bulk metallic glass in H2SO4.
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Electrophoretic deposition of bioactive glass (BG) coatings reinforced by whisker hydroxyapatite (WHA) particles was investigated in this work. Different BG powders as freeze dried (FBG) with fine ...particle size and calcined (CBG) with coarse particle size were used. Hydroxyapatite with whisker morphology reinforced microstructure of BG composite coatings and improved their mechanical properties. CBG and FBG coatings with 50 and 75 wt% WHA respectively, showed the highest bonding strength and bioactivity response as optimum coatings. Combination of WHA and BG particles had synergistic effect on the generation of apatite layer on the coatings during bioactivity test. Cellular behavior was influenced by surface roughness and environment alkalinization generated by BG dissolution. Finer particle size of FBG compared to CBG had positive effect on bioactivity and antibacterial characteristics of the coatings due to its rapid dissolution. FBG powder calcination conducted simultaneously with sintering of corresponding coated samples without negative effect on BG characteristics.
•Whisker hydroxyapatite reinforces the mechanical properties of bioglass coatings.•Bioglass powder stabilization can happen with sintering of coating simultaneously.•Bioglass with hydroxyapatite show better biological reaction due to synergism.•Fine particle size of bioglass shows better response to some biological properties.
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485.
Basics Glasbau Achilles, Andreas
2017, 2008, 2017-05-22
eBook
Der Glasbau ist eines der innovativsten und abwechslungsreichsten Gebiete der Baukonstruktion. Glas verbindet Außen- und Innenräume - gleichzeitig schützt es den Innenraum vor der Außenwelt. Die ...konstruktiven Möglichkeiten des Materials reichen weit über klassische Fensterkonstruktionen hinaus. So verfügen spezielle Gläser über erstaunliche physikalische Eigenschaften und lassen sich so vielfältig und kreativ einsetzen. Themen: Baustoff Glas Verarbeitung und Veredelung Anwendungsbereiche Konstruktionsarten Anschlüsse / Befestigungen
Carbon nanotube–ZnO composite powders, which act as high-temperature electromagnetic wave absorbents, are prepared by homogeneous precipitation. Carbon nanotube–ZnO/glass composites are fabricated by ...pressureless sintering. ZnO nanoparticles are assembled on the surface of carbon nanotubes, which produces heterostructure and enhances polarization at heterogeneous interface. Owing to the consumption of an amorphous carbon layer on the outer surface of carbon nanotubes and the generation of oxygen vacancies in ZnO during sintering, a higher concentration of charge carriers is produced in ZnO, which causes more relaxation polarization and dielectric loss in electromagnetic field. Owing to the shortened relaxation time, and the increase of relaxation polarization, permittivity and dielectric loss increases with the increase in testing temperature. Reflection coefficient of the obtained composite reaches −70dB. The special integration of multiwalled carbon nanotubes modified with some metal oxide semiconductor nanoparticles provides an effective approach to design high-temperature electromagnetic absorbing materials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Bernard Perrot produced sophisticated glass objects from ~1666–1709 in Orléans, particularly white enamelled artefacts and ruby glass. We present here the first non‐invasive Raman study of 16 ...polychrome and white enamelled glass artefacts that are assigned to Bernard Perrot or his followers. These glasses belong to the museum collections at Orléans and Sèvres in France. The prominent characteristic of these artefacts is their white bodies that were produced in imitation of porcelain. The small thickness of enamel applied to these glasses imposes the use of a high magnification (×200) long working distance microscope objective for Raman analysis. Pigments and opacifiers were identified, and the production technology was discussed. White opacification was found to be obtained by three compounds: calcium phosphate (bone opacification) for blown utensils, calcium antimonate for figurines, and cassiterite for thin enamels. The use of characteristic arsenic‐rich European cobalt was identified in the blue enamels with the characteristic Raman signature of lead arsenate apatite as observed for the 17th and 18th century French soft‐paste porcelains and Limoges enamels. The easy Raman detection of arsenic‐rich phases also allows on‐site identification of ruby glasses produced according to Perrot's technique (formation of Au° colloids by reaction initiated with an arsenic salt). The amount and crystallinity of calcium phosphate being variable appears to be a potential tool to discriminate between different production periods or workshops.
As a non‐invasive method, on‐site Raman analysis competes very well for the characterization of enamelled glass artefacts with ion beam techniques, which are not mobile and much more expensive. The potential of Raman analysis for the identification of Perrots recipe in ruby glass is thus an important outcome of the present study. The amount and crystallinity of calcium phosphate being variable appears to be a potential tool to discriminate between different production periods or workshops.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Currently, one of the major methodological gaps in the observation of glaciers from space is the measurement of volume changes of mountain glaciers and ice caps. In this paper, we present a case ...study of comparing a digital elevation model derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite optical stereo, elevation data derived from Ice, Cloud, and land Elevation Satellite Geoscience Laser Altimeter System (GLAS) laser altimetry, and contour lines from a topographic map from the 1970s. For two ice caps in Eastern Svalbard, Kvalpyntfonna and Digerfonna, we obtain an overall elevation change of -0.55 or -0.61 m/year between 1970 and 2002 (ASTER) or GLAS (2006), respectively. From comparison of different methods and from different quality checks, we estimate the error of this numbers to be on the order of 5%. This paper demonstrates that and on how long-term glacier volume changes can be observed from space over a large number of ice caps and glaciers.
Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) inherently suffers from various errors. Many previous works employed Geoscience Laser Altimeter System onboard the Ice, Cloud, ...and land Elevation Satellite (ICESat/GLAS) data to assess and enhance SRTM DEM accuracy. Nevertheless, data coregistration between the two datasets was commonly neglected in their studies. In this paper, an automated and simple three dimensional (3D) coregistration method (3CM) was introduced to align the 3-arc-second SRTM (SRTM3) DEM and ICESat/GLAS data over Jiangxi province, China. Then, accuracy evaluation of the SRTM3 DEM using ICESat/GLAS data with and without data coregistration was performed on different classes of terrain factors and different land uses, with the purpose of evaluating the importance of data coregistration. Results show that after data coregistration, the root mean square error (RMSE) and mean bias of the SRTM3 DEM are reduced by 14.4% and 97.1%, respectively. Without data coregistration, terrain aspects with a sine-like shape are strongly related to SRTM3 DEM errors; nevertheless, this relationship disappears after data coregistration. Among the six land uses, SRTM3 DEM produces the lowest accuracy in forest areas. Finally, by incorporating land uses, terrain factors and ICESat/GLAS data into the correction models, the SRTM3 DEM was enhanced using multiple linear regression (MLR), back propagation neural network (BPNN), generalized regression NN (GRNN), and random forest (RF), respectively. Results exhibit that the four enhancement models with data coregistration obviously outperform themselves without the coregistration. Among the four models, RF produces the best result, and its RMSE is about 3.1%, 2.7% and 11.3% lower than those of MLR, BPNN, and GRNN, respectively. Moreover, 146 Global Navigation Satellite System (GNSS) points over Ganzhou city of Jiangxi province were used to assess the accuracy of the RF-derived SRTM3 DEM. It is found that the DEM quality is improved and has a similar error magnitude to that relative to the ICESat/GLASS data.
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Volcanic flank collapses and explosive eruptions are among the largest and most destructive processes on Earth. Events at Mount St. Helens in May 1980 demonstrated how a relatively small (<5 km
) ...flank collapse on a terrestrial volcano could immediately precede a devastating eruption. The lateral collapse of volcanic island flanks, such as in the Canary Islands, can be far larger (>300 km
), but can also occur in complex multiple stages. Here, we show that multistage retrogressive landslides on Tenerife triggered explosive caldera-forming eruptions, including the Diego Hernandez, Guajara and Ucanca caldera eruptions. Geochemical analyses were performed on volcanic glasses recovered from marine sedimentary deposits, called turbidites, associated with each individual stage of each multistage landslide. These analyses indicate only the lattermost stages of subaerial flank failure contain materials originating from respective coeval explosive eruption, suggesting that initial more voluminous submarine stages of multi-stage flank collapse induce these aforementioned explosive eruption. Furthermore, there are extended time lags identified between the individual stages of multi-stage collapse, and thus an extended time lag between the initial submarine stages of failure and the onset of subsequent explosive eruption. This time lag succeeding landslide-generated static decompression has implications for the response of magmatic systems to un-roofing and poses a significant implication for ocean island volcanism and civil emergency planning.
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