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151.
This work focuses on models suitable for taking into account the spectral properties of combustion gases in computationally demanding applications, such as computational fluid dynamics. One such model, which is often applied in combustion modelling, is the weighted-sum-of-grey-gases (WSGG) model. The standard formulation of this model uses parameters fitted to a wide range of temperatures, but only for specific ratios of H2O to CO2. Then, the model is limited to gases from fuels with a given composition of hydrogen and carbon, unless several sets of fitted parameters are used. Here, the WSGG model is modified to account for various ratios of H2O to CO2 concentrations. The range of molar ratios covers both oxy-fuel combustion of coal, with dry- or wet flue gas recycling, as well as combustion of natural gas. The non-grey formulation of the modified WSGG model is tested by comparing predictions of the radiative source term and wall fluxes in a gaseous domain between two infinite plates with predictions by a statistical narrow-band model. Two grey approximations are also included in the comparison, since such models are frequently used for calculation of gas radiation in comprehensive combustion computations. It is shown that the modified WSGG model significantly improves the estimation of the radiative source term compared to the grey models, while the accuracy of wall fluxes is similar to that of the grey models or better. 相似文献
152.
Jindrich Hala Martin Luxa David Simurda Marek Bobcík Ondrej Novák Bartoloměj Rudas Jaroslav Synác 《热科学学报(英文版)》2018,27(2):95-102
This study presents the comparison of aerodynamic performances of two successive designs of the root profiles for the ultra-long rotor blade equipped with a straight fir-tree dovetail. Since aerodynamic and strength requirements laid upon the root section design are contradictory, it is necessary to aerodynamically optimize the design within the limits given by the foremost strength requirements. The most limiting criterion of the static strength is the size of the blade cross-section, which is determined by the number of blades in a rotor and also by the shape and size of a blade dovetail. The aerodynamic design requires mainly the zero incidence angle at the inlet of a profile and in the ideal case ensures that the load does not exceed a limit load condition. Moreover, the typical root profile cascades are transonic with supersonic exit Mach number, therefore, the shape of a suction side and a trailing edge has to respect transonic expansion of a working gas. In this paper, the two variants of root section profile cascades are compared and the aerodynamic qualities of both variants are verified using CFD simulation and two mutually independent experimental methods of measurements (optical and pneumatic). 相似文献
153.
Stanislav Haviar Jiří Čapek Šárka Batková Nirmal Kumar Filip Dvořák Tomáš Duchoň Markéta Fialová Petr Zeman 《International Journal of Hydrogen Energy》2018,43(50):22756-22764
Magnetron-based gas aggregation cluster source (GAS) was used to prepare high-purity CuO (cupric oxide) nanoclusters on top of sputter-deposited thin film of tungsten trioxide (WO3). The material was assembled as a conductometric hydrogen gas sensor and its response was tested and evaluated. It is demonstrated that addition of CuO clusters noticeably enhances the sensitivity of the pure WO3 thin film. With an increasing amount of CuO clusters the sensitivity of CuO/WO3 system rises further. When CuO clusters form a sufficiently thick and compact layer, the resistance response is reversed. Based on the sensorial behavior, conventional and near-ambient pressure X-Ray photoemission spectroscopies, and resistivity measurements, we propose that the sensing mechanism is based on the formation of nano-sized p-n junctions in between p-type CuO and n-type WO3. The advantages of the GAS technique for preparing sensorial and/or catalytically active materials are emphasized. 相似文献
154.
155.
Zdravko Šumić Aleksandra Tepić Senka Vidović Jelena Vladić Branimir Pavlić 《Sensing and Instrumentation for Food Quality and Safety》2016,10(3):425-433
Optimization of shiitake mushroom vacuum drying process was the objective of this research. In order to produce dried sample with satisfactory shelf life, response surface methodology was used. Vacuum drying used to accomplish the task was previously described by the authors. The samples were dried at 46–74 °C and 20–580 mbar. As quality indicators of dried product, total solids, water activity, total phenolics, IC50 and total color change were used. Response surface methodology resulted in optimal conditions of 57.1 °C and 100 mbar. In order to verify predictions and adequacy of the second-order polynomial models, separate validation experiments were conducted at optimum conditions. The predicted amount of total solids was 85.40 %, while aw value was 0.615. 相似文献
156.
ZdenĚK Slanina Chihiro Miyajima Xiang Zhao Filip Uhlík Ludwik Adamowicz Eiji Obarsawa 《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(4-5):385-402
Abstract Semiempirical quantum-chemical PM3 calculations are reported for a relatively new class of exohedral metallo-fullerenes - metal-coated or metal-covered fullerenes: C60Mn. The exohedral species were recently observed, however, their geometrical and electronic structure is not known yet. In this paper, relatively-even metal-atom distributions over the fullerene rings are considered - such regular forms are computed for M= Be, Mg, Al. Three selected stoichiometrics are treated: C60M12, C60M20, and C60M32. The stoichiometrics correspond to the location of the metal atoms above the twelve pentagons, above the twenty hexagons, and above each of the thirty two rings of C60 This interesting arrangement over the rings is possible only for some types of atoms, while other elements are localized above bonds or atoms, or inside the cage, or even react and destroy the cage. Other limitation comes from the parametrization of the computational methods - the computations are performed with the PM3 semiempirical method and metal-layer atomization heats are used as a stability measure. Structural characteristics are presented, too. Considerable reductions of the cage symmetry are reported and their relationships to Jahn-Teller effect are discussed, too (no case of the icosahedral symmetry is found). 相似文献
157.
ZdenĚK Slanina Filip Uhlík Jean-Pierre François Eiji Obarsawa 《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(4-5):403-415
Abstract Owing to the three-fold degeneracy of the LUMO in C60, its hexa-anion is not subjected to Jahn-Teller distortions. In contrast to the accepted presumptions, however, computations at the MNDO, AMI, PM3, SAM1, HF/STO-3G, HF/3-21G, and HF/4-31G levels show that the completely relaxed, non-icosahedral cage of C6? 60is lower in energy. The computed energy gain varies between 60 and 150 kJ/mol and thus, it is consistently significant (the most sophisticated approach, HF/4-31G, yields 93 kJ/mol). The longest C-C bond in the relaxed structures is at most computed 0.05 Å longer compared to the 5/6 bond in the icosahedral C6? 60The symmetry of C6? 60is relaxed to D2 A C2v, isomer is discussed, too. 相似文献
158.
Yang W Liu J Zheng R Liu Z Dai Y Chen G Ringer S Braet F 《Nanoscale research letters》2008,3(11):468-472
In this report, a novel chemical synthesis of polyaniline/gold nanocomposite is explored using ionic liquid (IL) 1-Butyl-3-methylimidazolium
hexafluorophosphate. The direct chemical synthesis of polyaniline/gold nanocomposite was initiated via the spontaneous oxidation
of aniline by AuCl4
− in IL. A nearly uniform dispersion of polyaniline/Au particles with a diameter of 450 ± 80 nm was produced by this method,
which indicates that this method is more suitable for controlling particle dimensions. It was also found that the electrical
conductivity of the polyaniline/gold nanocomposite was more than 100 times higher than that of the pure polyaniline nanoparticles.
The polyaniline/gold nanocomposite displays superior function in the biocatalytic activation of microperoxidase-11 because
of the high surface area of the assembly and the enhanced charge transport properties of the composite material. We also report
the possible application of polyaniline/gold nanocomposite as a H2O2 biosensor. 相似文献
159.
Sobotník J Hanus R Kalinová B Piskorski R Cvacka J Bourguignon T Roisin Y 《Journal of chemical ecology》2008,34(4):478-486
The behavioral and electroantennographic responses of Prorhinotermes canalifrons to its soldier frontal gland secretion, and two separated major components of the secretion, (E)-1-nitropentadec-1-ene and (E,E)-α-farnesene, were studied in laboratory experiments. Behavioral experiments showed that both the frontal gland secretion
and (E,E)-α-farnesene triggered alarm reactions in P. canalifrons, whereas (E)-1-nitropentadec-1-ene did not affect the behavior of termite groups. The alarm reactions were characterized by rapid walking
of activated termites and efforts to alert and activate other members of the group. Behavioral responses to alarm pheromone
differed between homogeneous and mixed groups, suggesting complex interactions. Antennae of both soldiers and pseudergates
were sensitive to the frontal gland secretion and to (E,E)-α-farnesene, but soldiers showed stronger responses. The dose responses to (E,E)-α-farnesene were identical for both soldiers and pseudergates, suggesting that both castes use similar receptors to perceive
(E,E)-α-farnesene. Our data confirm (E,E)-α-farnesene as an alarm pheromone of P. canalifrons. 相似文献
160.
Zhang Y Ronning F Gofryk K Mara NA Haberkorn N Zou G Wang H Lee JH Bauer E McCleskey TM Burell AK Civale L Zhu YT Jia Q 《Nanoscale》2012,4(7):2268-2271
Highly aligned carbon nanotube (CNT) ribbons were sandwiched in epitaxial superconducting NbC films by a chemical solution deposition method. The incorporation of aligned long CNTs into NbC film enhances the normal-state conductivity and improves the superconducting properties of the assembly. 相似文献