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In this paper, we investigate an original way to deal with the problems generated by the limitation process of high-order finite volume methods based on polynomial reconstructions. Multi-dimensional Optimal Order Detection (MOOD) breaks away from classical limitations employed in high-order methods. The proposed method consists of detecting problematic situations after each time update of the solution and of reducing the local polynomial degree before recomputing the solution. As multi-dimensional MUSCL methods, the concept is simple and independent of mesh structure. Moreover MOOD is able to take physical constraints such as density and pressure positivity into account through an “a posteriori” detection. Numerical results on classical and demanding test cases for advection and Euler system are presented on quadrangular meshes to support the promising potential of this approach. 相似文献
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A fiber is usually used as a probe in visible and near-infrared diffuse spectra measurement. However, the use of different fiber probes in the same measurement may cause data mismatch problems. Our group has researched the influence of the parameters of fiber probe, including the aperture angle, on the diffuse spectrum by a modified Monte Carlo model. To eliminate the influence of the aperture angle, we proposed a fitted equation of correction coefficient to correct its difference in practical range. However, we did not discuss the limitation of this method. In this work, we explored the collection efficiency in different optical environment with Monte Carlo simulation method, and find the suitable conditions—weak absorbing and strong scattering media, for the proposed collection efficiency. Furthermore, we tried to explain the stability of the collection efficiency in this condition. This work gives suitable conditions for the collection efficiency. The use of collection efficiency can help reduce the influence of different measurement systems and is also helpful to the model translation. 相似文献
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The Mannich reaction of various 5-substituted and N-acyl substituted chiral hydantoins with a series of aldimines smoothly occurred with full stereochemical control. These Mannich adducts have been cleaved by alcoholysis to afford several synthetically useful chiral building blocks like β-amino esters and β-lactams in good yields and in enantiopure form. 相似文献
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Regina Benveniste 《Mathematical Programming》1982,22(1):261-287
This paper introduces the use of stochastic models for the evaluation of relative computational efficiency of algorithms. Such an approach is used for the comparison of computational efficiency of three algorithms for quadratic programming. 相似文献
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红外光谱差减技术在扣除背景组份干扰方面得到广泛应用,但其扣除空气中水汽效果却不尽如人意。研究了不同湿度的水汽光谱与光谱差减效果的关系,以探究光谱差减技术在水汽扣除领域局限性的原因。结果表明:(1)相对湿度改变,水汽的红外光谱也发生变化,不管如何小心地选择比例系数f,从相对湿度x%的水汽光谱Ax,也不能完全扣除相对湿度为y%的水汽光谱Ay,即fAx≠Ay。(2)相对湿度改变,水分子团簇(H2O)n的相对组成也会发生变化,这是导致光谱差减技术局限性的主要原因。(3)将湿度为x%和y%的两水汽光谱Ax和Ay进行线性组合,则可以高度近似地模拟出介于两者之间的湿度的水汽光谱。比如用40%水汽谱和30%水汽谱,可以模拟得到32%或35%或37%的水汽谱。实验结果表明这是扣除水汽干扰效果更好的路径。(4)论证了水汽补偿湿度滴定法具有高效性的原因。 相似文献
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《Journal of Macromolecular Science: Physics》2013,52(3-4):833-846
Growth rates of PPS and PVDF spherulites in very thin films were measured. The growth rates change by about four orders of magnitude within the crystallization temperature ranges examined in this work. Film thickness at the position of the spherulite for which growth rates were determined was measured; the film thickness was deduced from retardation in the spherulite. In the light of the criterion we proposed, film thicknesses more than several tens of microns are required for the growth rate to change by four orders of magnitude. However, the thickness of the thinnest film examined experimentally was less than 1 μm. This discrepancy between theory and experiment is large and violates the framework of the traditional growth model unrecoverably. 相似文献
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Jianshuo Zhang Yuki Nakaya Prof. Dr. Ken-ichi Shimizu Prof. Dr. Shinya Furukawa 《Angewandte Chemie (International ed. in English)》2023,62(18):e202300744
Electric field catalysis using surface proton conduction, in which proton hopping and collision on the reactant are promoted by external electricity, is a promising approach to break the thermodynamic equilibrium limitation in endothermic propane dehydrogenation (PDH). This study proposes a catalyst design concept for more efficient electroassisted PDH at low temperature. Sm was doped into the anatase TiO2 surface to increase surface proton density by charge compensation. Pt−In alloy was deposited on the Sm-doped TiO2 for more favorable proton collision and selective propylene formation. The catalytic activity in electroassisted PDH drastically increased by doping an appropriate amount of Sm (1 mol % to Ti) where the highest propylene yield of 19.3 % was obtained at 300 °C where the thermodynamic equilibrium yield was only 0.5 %. Results show that surface proton enrichment boosts alkane dehydrogenation at low temperature. 相似文献
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