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41.
Reverse ray-tracing model for the performance evaluation of stationary solar concentrators 总被引:1,自引:0,他引:1
The yearly energy collection efficiency of stationary solar concentrators can be evaluated using reverse ray-tracing, and a solar radiation model. In reverse ray-tracing, rays originating at the receiver of the concentrator are traced towards the surrounding hemisphere. The method allows for the evaluation of the absolute energy collection: new concentrators may be optimized for location and tilt, requiring one-time ray-tracing. The tilt of existing concentrators is optimized. Only possible solar incidence is considered by our model. The method is fast and realistic; it can be modified for concentrators in tilt operation. 相似文献
42.
Obermaier H Mohring J Deines E Hering-Bertram M Hagen H 《IEEE transactions on visualization and computer graphics》2012,18(2):270-282
Crease surfaces describe extremal structures of 3D scalar fields. We present a new region-growing-based approach to the meshless extraction of adaptive nonmanifold valley and ridge surfaces that overcomes limitations of previous approaches by decoupling point seeding and triangulation of the surface. Our method is capable of extracting valley surface skeletons as connected minimum structures. As our algorithm is inherently mesh-free and curvature adaptive, it is suitable for surface construction in fields with an arbitrary neighborhood structure. As an application for insightful visualization with valley surfaces, we choose a low frequency acoustics simulation. We use our valley surface construction approach to visualize the resulting complex-valued scalar pressure field for arbitrary frequencies to identify regions of sound cancellation. This provides an expressive visualization of the topology of wave node and antinode structures in simulated acoustics. 相似文献
43.
Hans Michael Egon Pabst Franz Ledl und Hans-Dieter Belitz 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1985,181(5):386-390
Summary In addition to the mono- and dipyrrolidinohexosereductones described recently (Z Lebensm Unters Forsch (1984) 178:356) two further bittertasting compounds were isolated from heated mixtures of proline and sucrose (molar ratio 3: 1, 190 °C, 30 min) and also synthesized, namely 2,3-bis-(1-pyrrolidinyl)2-cyclopenten-l-one and 2,3-bis(1-pyrrolidinyl)-5methyliden-2-cyclopenten-l-one. The recognition thresholds (mmol/1) are 0.15–0.25 and 0.06–0.12 respectively. Both compounds have a burning bitter taste character. From a maltose-proline reaction mixture 2--glucosyl-5-hydroxy-5-methyl-4-piperidinyl-2-cyclopenten-1-one was isolated. When the dihydroxypyranone VI was heated with proline, 2,5-dihydroxy-5-methyl-4-prohnyl-2-cyclopenten-1-one and the cyclopent(b)azepinones XI and XII were among the compounds formed. These compounds also have a bitter taste character.Zusammenfassung Zusätzlich zu den kürzlich beschriebenen Mono- and Dipyrrolidinohexosereduktionen (Z Lebensm Unters Forsch (1984) 178:356) wurden zwei weitere bittere Verbindungen aus erhitzten Mischungen von Prolin and Saccharose (Molverhältnis 3:1, 190 °C, 30 min) isoliert and synthetisiert. Es handelt sich um 2,3-Bis-(1-Pyrrolidinyl)-2-cyclopenten-1-on und 2,3-Bis-(1-Pyrrolidinyl)-5-methyliden-2-cyclopenten-1-on. Die Erkennungsschwellenwerte (mmol/1) sind 0,15-0,25 and 0,06-0,12. Beide Verbindungen haben einen brennend-bitteren Geschmack. Aus einem Maltose-Prolin-Umsetzungsgemisch gelang die Isolierung des 2--Glucosyl-5-hydroxy-5-methyl-4-piperidinyl-2-cyclopenten-1-ons. Bei der Reaktion des Dihydropyranons VI mit Prolin wurden u. a. das 2,5-Dihydroxy-5-methyl-4-prolinyl2-cyclopenten-1-on sowie die Cyclopent(b)azepinone XI and XII gebildet. Diese Verbindungen sind ebenfalls mehr oder weniger stark bitter. 相似文献
44.
Hui Gu Rowland M. Cannon Hans J. Seifert Michael J. Hoffmann Isao Tanaka 《Journal of the American Ceramic Society》2002,85(1):25-32
The nitrogen solubility in the SiO2 -rich liquid in the metastable binary SiO2 -Si3 N4 system has been determined by analytical TEM to be 1%–4% of N/(O + N) at 1973–2223 K. Analysis of the near edge structure of the electron energy loss peak indicates that nitrogen is incorporated into the silicate network rather than being present as molecular N2 . A regular solution model with a positive enthalpy of mixing for the liquid was used to match the data for the metastable solubility of N in the presence of crystalline Si3 N4 and to adjust the computed phase diagram. The solubility of Si3 N4 in fused SiO2 is far less than reported in liquid silicates also containing Al, Mg, and/or Y. Apparently, these cations act as modifiers that break anion bridges in the silicate network and, thereby, allow further incorporation of Si3 N4 without prohibitive amounts of network cross-linking. Finally, indications emerged regarding the diffuse nature of the Si3 N4 -SiO2 interface that leads to amorphous regions of higher N content. 相似文献
45.
Summary Dynamic mechanical measurements on polystyrene — poly(vinylmethylether) blends are demonstrating that the relaxation processes in the blends are mainly connected with the motions of the poly(vinylmethylether) chain.Concerning the effect of mixing on topological properties of the blends, an increase of the polydispersity of the relaxation processes is detected in blends with high molecular weight polystyrene while low molecular weight polystyrene exerts an effect of dilution upon the relaxation of the high molecular poly(vinylmethylether) chains.From these measurements as well as from thermoanalytical data it results that the energetic interaction is more pronounced in the blends with oligomeric than with high molecular weight polystyrene. The glass transition temperature shows a larger deviation from additivity for blends with high molecular polystyrene than for those with oligomeric polystyrene.Herrn Prof. Dr. M. Kryszewski zum 60. Geburtstag herzlichst gewidmet 相似文献
46.
Benno Krachler Mats Eliasson Hans Stenlund Ingegerd Johansson G?ran Hallmans Bernt Lindahl 《Nutrition journal》2006,5(1):34
Background
Body mass, as well as distribution of body fat, are predictors of both diabetes and cardiovascular disease. In Northern Sweden, despite a marked increase in average body mass, prevalence of diabetes was stagnant and myocardial infarctions decreased. A more favourable distribution of body fat is a possible contributing factor. 相似文献47.
Hans Schott 《Journal of the American Oil Chemists' Society》1988,65(5):816-819
Foaming of solutions of the nonionic surfactant, octoxynol 9, was investigated in the concentration range of 0.010 to 5.00%
and in the temperature range of 7–37 C, well below the cloud point of 65 C, by measuring the height and stability of foams
generated by pouring thin streams of surfactant solutions into a glass column. All foams were fast-thinning. Their height
increased monotonically with surfactant concentration. The rate of change of foam height with log surfactant concentration
underwent no change at the CMC of 0.018%, but was four times lower above 0.146% than below 0.146%. Foams at lower temperatures
generally thinned somewhat more slowly and were stronger or more cohesive and more stable than foams generated at higher temperatures
by surfactant solutions of comparable concentrations. Oxidative degradation reduced foam height somewhat. Octoxynol 9 and
sodium lauryl sulfate, rated as a good foamer, produced foams of comparable volume and stability. 相似文献
48.
Hans Schott 《Journal of the American Oil Chemists' Society》1988,65(10):1658-1663
The effect of electrolytes and other additives on the foaming of solutions of the nonionic surfactant octoxynol 9 (Triton
X-100) was investigated and correlated with their effect on the cloud point. Foams were generated by pouring solutions as
a thin stream into a vertical tube. The height of the generally fast-draining foam columns was measured as a function of time,
and their stability was rated according to the damage sustained within 13 min. The surfactant concentrations used, 0.050,
0.100 and 2.00%, were above the critical micelle concentration. Increasing concentrations increased foam height but not foam
stability.
The electrolytes NaCl and Na2SO4 salted the surfactant out. They reduced its cloud point in proportion to their concentration. They also reduced the foam
height, albeit to a lesser extent than the cloud point, but hardly reduced the foam stability below the cloud point. 相似文献
49.
50.
Hans Kockelmann 《化学,工程师,技术》1996,68(3):219-227
Flow theories can help in determining the fundamental interrelationships between the leak rate of gaskets for flange connections and the relevant influencing parameters. The basic rule for the transfer of results obtained for special boundary conditions to other conditions can be derived. In this way the effort involved in gasket testing can be reduced. This paper gives the interrelations between the leak rate of gaskets on the one hand and the internal pressure, the temperature, the medium, and the gasket thickness on the other and discusses them with aid of measured results. The effect of the gasket stress and thickness can be determined only of experimental investigations. Furthermore, the requirements placed on gaskets, the leak rate related gasket characteristics defined in various standards and the measuring techniques for their determination are discussed. 相似文献