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21.
In this work we display a numerical comparison, under statistical and computational point of view, between semi-analytical Eulerian and Lagrangian dispersion models to simulate the ground-level concentration values of a passive pollutant released from a low height source. The Eulerian approach is based on the solution of the advection–diffusion equation by the Laplace transform technique. The Lagrangian approach is based on solution of the Langevin equation through the Picard’s Iterative Method. Turbulence inputs are calculated according to a parameterization capable of generating continuous values in all stability conditions and in all heights of the Planetary Boundary Layer (PBL). Numerical simulations and comparisons show a good agreement between predicted and observed concentrations values. The comparison reveals the main advantages and disadvantages between the models. 相似文献
22.
Anders Björner Andreas Paffenholz Jonas Sjöstrand Günter M. Ziegler 《Discrete and Computational Geometry》2005,34(1):71-86
In 1992 Thomas Bier presented a strikingly simple method to produce a
huge number of simplicial (n – 2)-spheres on 2n vertices, as deleted
joins of a simplicial complex on n vertices with its combinatorial
Alexander dual.
Here we interpret his construction as giving the poset of all the
intervals in a boolean algebra that “cut across an ideal.” Thus we
arrive at a substantial generalization of Bier’s construction: the
Bier posets Bier(P, I) of an arbitrary bounded poset P of
finite length. In the case of face posets of PL spheres this yields
cellular “generalized Bier spheres.” In the case of Eulerian or
Cohen–Macaulay posets P we show that the Bier posets Bier(P, I)
inherit these properties.
In the boolean case originally considered by Bier, we show that all the
spheres produced by his construction are shellable, which yields “many
shellable spheres,” most of which lack convex realization.
Finally, we present simple explicit formulas for the g-vectors of
these simplicial spheres and verify that they satisfy a strong form of
the g-conjecture for spheres. 相似文献
23.
In this paper, we consider the closure property of a random convolution $ \sum\nolimits_{n = 0}^\infty {{p_n}{F^*}^n} $ , where F is a heavy-tailed distribution on [0, ??), and p n (n?=?0, 1, . . . ) are the local probabilities of a nonnegative integer-valued random variable. We obtain conditions under which the fact that distribution F belongs to the dominatedly varying-tailed class, long-tailed class, or to the intersection of these classes implies that $ \sum\nolimits_{n = 0}^\infty {{p_n}{F^*}^n} $ is in the same class. 相似文献
24.
25.
Jonas Söderberg 《Journal of Pure and Applied Algebra》2006,207(2):417-432
We prove that a sequence of positive integers (h0,h1,…,hc) is the Hilbert function of an artinian level module of embedding dimension two if and only if hi−1−2hi+hi+1≤0 for all 0≤i≤c, where we assume that h−1=hc+1=0. This generalizes a result already known for artinian level algebras. We provide two proofs, one using a deformation argument, the other a construction with monomial ideals. We also discuss liftings of artinian modules to modules of dimension one. 相似文献
26.
Valente DL Braasch J Myrbeck SA 《The Journal of the Acoustical Society of America》2012,131(1):205-217
Despite many studies investigating auditory spatial impressions in rooms, few have addressed the impact of simultaneous visual cues on localization and the perception of spaciousness. The current research presents an immersive audiovisual environment in which participants were instructed to make auditory width judgments in dynamic bi-modal settings. The results of these psychophysical tests suggest the importance of congruent audio visual presentation to the ecological interpretation of an auditory scene. Supporting data were accumulated in five rooms of ascending volumes and varying reverberation times. Participants were given an audiovisual matching test in which they were instructed to pan the auditory width of a performing ensemble to a varying set of audio and visual cues in rooms. Results show that both auditory and visual factors affect the collected responses and that the two sensory modalities coincide in distinct interactions. The greatest differences between the panned audio stimuli given a fixed visual width were found in the physical space with the largest volume and the greatest source distance. These results suggest, in this specific instance, a predominance of auditory cues in the spatial analysis of the bi-modal scene. 相似文献
27.
28.
Torto N Mmualefe LC Mwatseteza JF Nkoane B Chimuka L Nindi MM Ogunfowokan AO 《Journal of chromatography. A》2007,1153(1-2):1-13
Africa as a continent has its unique challenges for analytical chemists in sample preparation for chromatographic analyses. The areas of agriculture, environment, food and health provide formidable challenges when it comes to method development, for example, drought can result in inadequate supplies of good quality water. The testing of water quality necessitates the development of assay methods that can be employed to not only determine the quantities of pesticides associated with malaria and tsetse fly eradication programmes, but also to monitor mycotoxins or neurotoxins. Urbanisation has also meant that endocrine disruptors such as phthalate esters need to be monitored. This review will profile some of the activities by analytical chemists practising in the African continent, who seek to address some of the challenges in sample preparation for chromatographic analyses. 相似文献
29.
30.
Dr. Jonathan Rittle Prof. Jonas C. Peters 《Angewandte Chemie (International ed. in English)》2016,55(40):12262-12265
Nitrogenase enzymes mediate the six‐electron reductive cleavage of cyanide to CH4 and NH3. Herein we demonstrate for the first time the liberation of CH4 and NH3 from a well‐defined iron cyanide coordination complex, [SiPiPr3]Fe(CN) (where [SiPiPr3] represents a tris(phosphine)silyl ligand), on exposure to proton and electron equivalents. [SiPiPr3]Fe(CN) additionally serves as a useful entry point to rare examples of terminally‐bound Fe(CNH) and Fe(CNH2) species that, in accord with preliminary mechanistic studies, are plausible intermediates of the cyanide reductive protonation to generate CH4 and NH3. Comparative studies with a related [SiPiPr3]Fe(CNMe2) complex suggests the possibility of multiple, competing mechanisms for cyanide activation and reduction. 相似文献