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During ground-based solidification, buoyancy flow can develop by the density difference in the hypoeutectic type of the alloys, such as Al-7 wt% Si alloy. Buoyancy flow can affect the thermal field, solute distribution in the melt, and the position and amount of the new grains. As solidification is a very complex process, it is not very easy to separate the different effects. Under microgravity conditions, natural convection does not exist or is strongly damped due to the absence of the buoyancy force. Therefore, experiments in microgravity conditions provide unique benchmark data for pure diffusive solidification conditions. Compared to the results of the ground-based and microgravity experiments, it is possible to get information on the effect of gravity (buoyancy force). In the framework of the CETSOL project, four microgravity solidification experiments were performed on grain refined (GF) and non-grain refined Al-7 wt% Si alloy onboard the International Space Station in the Materials Science Laboratory. These experiments aimed to study the effect of the solidification parameters (solid/liquid front velocity vSL, temperature gradient GSL) on the grain structure and dendritic microstructures. The microgravity environment eliminates the melt flow, which develops on Earth due to gravity. Four ground-based (GB) experiments were performed under Earth-like conditions with the same (similar) solidification parameters in a vertical Bridgman-type furnace having four heating zones. The detailed analysis of the grain structure, amount of eutectic, and secondary dendrite arm spacing (SDAS) for different process conditions is reported and compared with the results of the microgravity experiments. GB experiments showed that the microstructure was columnar in the samples that do not contain GF material or in case the solid/liquid (vSL front velocity was slow (0.02 mm/s)). In contrast, in the sample which contained GF material, progressive columnar/equiaxed transition (PCET) was observed at vSL = 0.077 mm/s and GSL = 3.9 K/mm. The secondary (SDAS) dendrite arm spacing follows the well-known power law, S D A S = K [ t 0 ] 1 3 , where K is a constant, and t0 is the local solidification time for both GB and µg experiments. [ABSTRACT FROM AUTHOR]

For the future market potential of parabolic trough power plants with direct steam generation (DSG), it is beneficial to integrate a thermal storage system. Heat storage media based on phase change materials offer heat transfer at constant temperatures needed for the evaporation process. Different options for a plant layout are presented and discussed. The interactions between the three subsystems--solar field, power block, and thermal storage--are analyzed, and boundary conditions arising from the thermal storage system are identified. Compared with a system without storage the number of operating points increases significantly since different combinations of storage charge and discharge operations go along with a varying power output of the solar field. It is shown that the large number of theoretical operating points can be reduced to a subset with practical relevance. Depending on the live steam parameters a reheat is necessary within the power block. Compared with parabolic trough fields with a single phase heat transfer medium such as oil, a special heat exchanger configuration is needed for a DSG plant. Different alternatives based on available technologies are presented and evaluated. [DOI: 10.1115/1.4001563] Keywords: solar thermal power plant, direct steam generation, thermal storage

During the solidification of hypoeutectic Al–7% Si alloy, density differences develop in the melt due to variations in concentration and temperature. On Earth, melt flow can occur due to gravity, which then affects the solidification process. The microgravity environment strongly eliminates convection in the melt and allows investigation of the solidification process in purely diffusive circumstances. In this study, four solidification experiments were performed on grain-refined and non-grain-refined Al–7 wt% Si alloy on-board the International Space Station (ISS) in the Materials Science Lab (MSL) to study the effect of solidification parameters (solid/liquid front velocity (v) and temperature gradient (G)) on the grain structure and dendritic microstructure. The grain structure has been analyzed in detail in some earlier studies. The aim of this work was to carry out detailed analysis of the macrosegregation caused by the diffusion of Si from the initial mushy zone during the homogenization step and the subsequent solidification phase of the experiments as well as the correlated distribution of eutectic along the solidification direction. The secondary dendrite arm spacing (SDAS) for different process conditions was also studied. For these two issues, microgravity experimental results were compared to simulation results. The macrosegregation was calculated by the finite difference method. Because the steady-state solidification conditions were never reached, the solidification process was characterized by the average front velocity and temperature gradient. Considering the actual liquidus temperature (TL) caused by macrosegregation, the SDAS was calculated as a function of the average processing parameters and the actual liquidus temperature with the classical Kirkwood's equation. As a result, good agreement was obtained between the calculated and measured SDAS. [ABSTRACT FROM AUTHOR]

Many Fusarium head blight (FHB) [caused by Fusarium graminearum Schw. and F. culmorum (W.G. Sm.) Sacc.] quantitative trait loci (QTL) have been detected in both spring and winter wheat (Triticum aestivum L:). However, a QTL validation has not been performed in winter wheat. We report on the verification of resistance QTL in winter wheat, which had been previously mapped in a Dream/Lynx population. The QTL intervals of chromosomes 7BS, 6AL, and 2BL were enriched with amplified fragment length polymorphism (AFLP) markers. For a more precise estimation of the QTL effects and their influence on plant height and heading date, [BC.sub.2][F.sub.4] lines were created by marker-assisted selection and examined for FHB resistance. The phenotypic effects of the two main QTL on chromosomes 6AL and 7BS confirmed the previous results of the original mapping population. In the backcross population, QTL6AL and QTL7BS reduced FHB severity individually by 27% each relative to lines without resistance alleles. Both QTL had an effect on plant height, resulting in taller plants being more resistant. The combination of both QTL decreased disease severity most effectively (36%). The successfully validated QTL on chromosomes 6AL and 7BS are designated Qfhs.lfl-6AL and Qfhs. lfl-7BS, respectively. The best genotypes carried one or both of the major QTL, displaying their importance for disease resistance. In contrast to spring wheat, where QTL have been identified in an exotic genetic background, the resistance QTL validated in this study already reside in an adapted genetic background with excellent agronomic performance.

This article introduces a new graph-based modeling methodology called heat flow modeling (HFM) for the purpose of mapping building information model (BIM) of HVAC systems automatically into fault detection and diagnosis (FDD) systems that can be integrated into HVAC control systems. The goal is an efficient and effective support of the maintenance of HVAC systems to detect and locate faults that may reduce energy efficiency, user comfort, or system lifetime. The nodes of the HFM model have a one-to-one relationship with HVAC system components and related building entities. The nodes are connected by arcs that model the flows in the HVAC systems, e.g., air, water, and information flows. The functionality of the nodes includes state variable estimations and failure rule evaluations. The failure rule outputs can be fed to an associative network based diagnosis engine to locate the faults. Since HFM nodes are instances of generic classes derived from small libraries, HVAC FDD systems can be automatically generated. The simulation result has shown the effectiveness of a proposed FDD approach and two software prototypes demonstrating the reduced engineering effort of fault detection for a small bank HVAC system. [ABSTRACT FROM AUTHOR]

The article discusses the microstructure formation in aluminum-silicon alloy which are directionally solidified in a rotating magnetic field. Accordingly, aluminum-silicon7Mg (AlSi7Mg) alloys are used in order to produce high stressed automotive components such as engine frames and cylinder heads in foundry industry. Various processes have been used in order to investigate the microstructure formation in AlSi7Mg0.3 and AlSi7Mg0.6 alloys during directional solidification.

Multielement isotope ratio analysis was checked for its suitability as a means for the discrimination between agricultural products from integrated/conventional or organic production, respectively. Differences were mainly found for δ 15 N-values. Paprika and tomatoes from organic production in greenhouses showed δ 15 N-values above+7 ‰, whereas corresponding products from conventional cultivation had δ 15 N-values near 0 ‰. Lettuce, onions, cabbage and Chinese cabbage from field production had δ 15 N-values in the range of+5 to+6 and+5.5 to+7.5 ‰, respectively (conventional and organic production); these overlapping differences do not permit a reliable discrimination. The same is true for wheat, showing average δ 15 N-values of+2.3±1.0 and+3.6±1.6 ‰, respectively. The unexpected relative high 15 N-enrichments of vegetables from integrated production are discussed as originating, at least partially, from 15 N-enrichment in the soil by NH 3 evaporation and denitrification. [ABSTRACT FROM AUTHOR]