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11.
Abstract— Measurements from sensors designed to measure erythemal UV irradiance were used to relate the UV incident on a horizontal surface to that incident on a surface maintained normal to the sun throughout the day at Lauder, New Zealand. These UV measurements were also related to variations in global radiation, total column ozone and atmospheric pressure at the surface. Strong correlations were found between these variables over the 37 day observation period in the summer of 1995/1996. Results from these cross-calibrated UV sensors show that the irradiance incident on a surface normal to the sun can be significantly different from that on a horizontal surface. On clear days, the normal-incidence signal can be 30-40% greater for solar zenith angles in the range 60-70Ao . Consequently, the risk of UV damage can be greater than reported by measurements or models that assume horizontal incidence (e.g. UV index). On cloudy days the normal-incidence UV can be less than 50% of the horizontal-incidence UV. Averaged over a day, any enhancements in normal-incidence UV over horizontal-incidence UV are smaller. The effects were strongly dependent on cloud conditions. Under clear skies the enhancements are generally less than 10%, and the integrated excess over horizontal-incidence UV is usually less than 5%. However, under cloudy skies the reductions can still be large. 相似文献
12.
Homogenization in open sets with holes 总被引:1,自引:0,他引:1
Doina Cioranescu Jeannine Saint Jean Paulin 《Journal of Mathematical Analysis and Applications》1979,71(2):590-607
Let Qr be a cylindrical bar with r cylindrical cavities having generators parallel to those of Qr. Let Ω be the cross-section of the bar, Ω1 the cross-section of the domain occupied by the material and the cross- sections of the cavities: . The study of the elastic torsion of this bar leads to the following problem [see 2., 3., 267–320)]: (1) where μ is the shear modulus of the material, α is the angle of twist and represents the stress function. In this paper the problem (1) with an increasing number of holes which are distributed periodically is considered. One would like to know if has a limit , and if so, the equation satisfied by this limit. This is an “homogenization” problem — the heterogeneous bar Qr is replaced by a homogeneous one, the response of which under torsion approximates as closely as possible that of Qr. A more general problem will be studied and the case of elastic torsion will be obtained as an application. The proof uses the energy method [see Lions (Collège de France, 1975–1977), Tartar (Collège de France, 1977)] and extension theorems. A related problem is the homogenization of a perforated plate [cf. Duvaut (to appear)]. 相似文献
13.
Larsen EH Hansen M Paulin H Moesgaard S Reid M Rayman M 《Journal of AOAC International》2004,87(1):225-232
This study investigated the speciation and bioavailability of selenium in yeast-based intervention agents from multiple manufacturers from several time points. Sources of selenized yeast included Nutrition 21 (San Diego, CA), which supplied the Nutritional Prevention of Cancer (NPC) Trial from 1981-1996; Cypress Systems (Fresno, CA; 1997-1999); and Pharma Nord (Vejle, Denmark; 1999-2000), which supplied the Prevention of Cancer by Intervention by Selenium (PRECISE) Trial pilot studies. The low-molecular-selenium species were liberated from the samples by proteolytic hydrolysis followed by separation by ion exchange liquid chromatography and detection by inductively coupled plasma-mass spectrometry. The results for the NPC tablets showed that selenomethionine, together with 3 unidentified selenium compounds, were predominant in the sample hydrolysates. The relative amounts of the 4 selenium species varied (p < 0.05) among several of the 7 tablet batches used during the course of the NPC Trial. In comparison, 5 batches of more recently produced selenized yeasts, which were used as a source of selenium in the PRECISE and other trials, contained less of the unknown compounds and more selenomethionine at 54-60% of the total selenium in the yeasts. One batch of yeast, however (from 1985), which originated from the same producer as the yeast used in the NPC tablets, contained only 27% of selenium in the sample as selenomethionine. Human subjects receiving 200 microg selenium/day in the UK PRECISE Pilot Trial showed a higher concentration (p < 0.01) and higher increase from baseline in plasma selenium than did the same dosage used in the NPC Trial. Differences in intake, speciation, or bioavailability of selenium from the yeast-based supplements in the population groups studied may explain this. Furthermore, the selenium concentration in whole blood from the Danish PRECISE Pilot Trial was higher (p < 0.001) than that obtained with synthetic L-selenomethionine in a comparable group of Danes, both groups having been treated with 300 microg selenium/day. 相似文献
14.
Maurice Tchuente Paulin Melatagia Yonta Jean-Michel Nlong II Yves Denneulin 《Acta Appl Math》2008,102(2-3):219-236
Given an undirected and connected graph G, with a non-negative weight on each edge, the Minimum Average Distance (MAD) spanning tree problem is to find a spanning tree of G which minimizes the average distance between pairs of vertices. This network design problem is known to be NP-hard even when the edge-weights are equal. In this paper we make a step towards the proof of a conjecture stated by A.A. Dobrynin, R. Entringer and I. Gutman in 2001, and which says that the binomial tree B n is a MAD spanning tree of the hypercube H n . More precisely, we show that the binomial tree B n is a local optimum with respect to the 1-move heuristic which, starting from a spanning tree T of the hypercube H n , attempts to improve the average distance between pairs of vertices, by adding an edge e of H n -T and removing an edge e′ from the unique cycle created by e. We also present a greedy algorithm which produces good solutions for the MAD spanning tree problem on regular graphs such as the hypercube and the torus. 相似文献
15.
Initial oxidation of duplex stainless steel 总被引:1,自引:0,他引:1
?rtomir Donik Aleksandra Kocijan Irena Paulin Boris Pihlar 《Applied Surface Science》2009,255(15):7056-7061
Three different techniques were used to produce thin oxide layers on polished and sputter-cleaned duplex stainless-steel samples. These samples were exposed to 10−5 mbar of pure oxygen inside the vacuum chamber, exposed to ambient conditions for 24 h, and plasma oxidized. The oxide layers thus produced were analysed using XPS depth profiling in order to determine the oxide layers’ compositions with depth. We found that all the techniques produce oxide layers with different traces of metallic components and with the maximum concentration of chromium oxide shifted towards the oxide-layer-bulk-metal interface. A common characteristic of all the oxide layers investigated is a double-oxide stratification, with regions closer to the surface exhibiting higher concentrations of iron oxide and those more in-depth exhibiting higher concentrations of chromium oxide. A simple non-destructive Thickogram procedure was used to corroborate the thickness estimates for the thinnest oxide layers. 相似文献
16.
The aim of this paper is to give a geometric approach to Tits' amalgam method to construct buildings and to initiate a study of hyperbolic buildings, i.e. whose types are reflexion systems of the real hyperbolic space. We construct lots of examples and study their cohomology at infinity. We construct CAT(–1) polyhedral complexes having big discrete parabolic groups of isometries. 相似文献
17.
Paulin Nkolo Gérard Audran Paul Bremond Raphaël Bikanga Sylvain R.A. Marque Valérie Roubaud 《Tetrahedron》2017,73(23):3188-3201
Solvent effects in β-phosphorylated nitroxides show that nitrogen and phosphorus hyperfine coupling constants aN and aP, increase and decrease with increasing polarity, polarizity, and Hydrogen Bond Donor effects of solvents, respectively. In a series of articles, it was shown that the driving interaction controlling the change in aP is the maximization of the N+?—O– … ???+PO– dipole – dipole interaction. In this work, we show that the steric strain in spiro β-phosphorylated nitroxides affords the opposite trend for aP, that is, aP increases with increasing solvent properties features. 相似文献
18.
Positron mass absorption coefficients in 18 elemental and 6 compound solids are directly measured from implantation profiles. Their dependences on sample atomic number and positron mean energ are correlated to the forbiddenness of β+ transitions. 相似文献
19.
Alexander G. M. Paulin 《manuscripta mathematica》2012,137(1-2):129-157
If π f is a cuspidal automorphic representation of ${GL_{2/\mathbb{Q}}}$ associated to a modular form f, the local and global Langlands correspondences are compatible at all finite places of ${\mathbb{Q}}$ . On the p-adic Coleman–Mazur eigencurve this principle can fail (away from p) under one of two conditions: on a generically principal series component where monodromy vanishes; or on a generically special component where the ratio of the Satake parameters degenerates. We prove, under mild restrictive hypotheses, that such points are the intersection of generically principal series and special components. This is a geometric analogue of Ribet’s level raising and lowering theorems. 相似文献
20.
We investigate the stability constants of convex sets in linear spaces. We prove that the stability constants of affinity
and of the Jensen equation are of the same order of magnitude for every convex set in arbitrary linear spaces, even for functions
mapping into an arbitrary Banach space. We also show that the second Whitney constant corresponding to the bounded functions
equals half of the stability constant of the Jensen equation whenever the latter is finite. We show that if a convex set contains
arbitrarily long segments in every direction, then its Jensen and Whitney constants are uniformly bounded. We prove a result
that reduces the investigation of the stability constants to the case when the underlying set is the unit ball of a Banach
space. As an application we prove that if D is convex and every δ-Jensen function on D differs from a Jensen function by a bounded function, then the stability constants of D are finite. 相似文献