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821.
Until now there are almost no results on the precise geometric location of minimal enclosing balls of simplices in finite-dimensional real Banach spaces. We give a complete solution of the two-dimensional version of this problem, namely to locate minimal enclosing discs of triangles in arbitrary normed planes. It turns out that this solution is based on the classification of all possible shapes that the intersection of two norm circles can have, and on a new classification of triangles in normed planes via their angles. We also mention that our results are closely related to basic notions like coresets, Jung constants, the monotonicity lemma, and d-segments. 相似文献
822.
Partha Sarkar R.K. Roy A. Mitra A.K. Panda Margarita Churyukanova Sergey Kaloshkin 《Journal of magnetism and magnetic materials》2012
Rapidly quenched microwires with a nominal composition of Fe39Co39Si8B14 (#AO), Fe37Co37Nb4Si8B14 (#AN) and Fe36Co36Nb4Cr2Si8B14 (#ANC) have been investigated. Devitrification of as-quenched microwires showed that crystallization temperatures increased with simultaneous incorporation of Nb and Cr as in #ANC alloy. Addition of these elements also contributed to an increase in activation energy in #AN and #ANC alloys. Nb addition reduced the particle size, which became much finer in the case of the Cr-containing alloy. Although Nb addition did not have much effect on lowering the Curie temperature TC of the amorphous phase, Cr substitution lowered TC to 698 K from high values of 785 K and 787 K observed in the #AO and #ANC alloys, respectively. However, the Cr addition revealed a better Giant magneto-impedance (GMI) response compared to the other alloys. Such improved GMI properties in the Cr-containing alloy are attributed to lower values of the coercivity and magnetostriction in the alloy containing both Nb and Cr. 相似文献
823.
S Rummel M Herrmann M Wahren SM Yunusov MA Ilatovskaya YB Isaev ND Lapkina YN Novikov VB Shur 《Isotopes in environmental and health studies》2012,48(3):391-392
Potassium graphite intercalation compounds are able to activate C-H bonds of hydrocarbons at room temperature. In this paper, the hydrogen-deuterium exchange of CHD(3) in the presence of C(8)K, C(24)K and C(36)K is described. 相似文献
824.
Ivalina Trendafilova Manuel Ojeda John M. Andresen Alenka Risti Momtchil Dimitrov Nataa Novak Tuar Genoveva Atanasova Margarita Popova 《Molecules (Basel, Switzerland)》2023,28(1)
Transition metals as catalysts for total VOC oxidation at low temperatures (150–280 °C) are a big challenge nowadays. Therefore, iron-modified SBA-15, AlSBA-15, and ZrSBA-15 materials with 0.5 to 5.0 wt.% Fe loading were prepared and tested for toluene oxidation. It was found that increasing Fe loading significantly improved the rate of oxidation and lowered the temperature of achieving 100% removal of toluene from above 500 °C for the supports (AlSBA-15 and ZrSBA-15) to below 400 °C for 5FeZrSBA-15. The formation of finely dispersed iron oxide active sites with a particle size less than 5 nm was observed on all the SBA-15, AlSBA-15, and ZrSBA-15 supports. It was found that the surface properties of the mesoporous support due to the addition of Al or Zr predetermined the type of formed iron oxide species and their localization on the support surface. Fe-containing SBA-15 and AlSBA-15 showed activity in total toluene oxidation at higher temperatures (280–450 °C). However, 5 wt. % Fe-containing ZrSBA-15 showed excellent activity in the total oxidation of toluene as a model VOC at lower temperatures (150–380 °C) due to the synergistic effect of Fe-Zr and the presence of accessible and stable Fe2+/Fe3+ active sites. 相似文献
825.
Lara P Paneque M Poveda ML Salazar V Santos LL Carmona E 《Journal of the American Chemical Society》2006,128(11):3512-3513
2,6-Dimethyl-substituted anisoles can be converted into the corresponding 2-ethyl-6-methylphenols in a several-step reaction mediated by a TpMe2Ir(III) complex; use of the 13C-enriched anisoles, ArO13CH3, shows that the 13C label distributes across the two ethyl sites with a preference for the terminal position. 相似文献
826.
Alessandro Berarducci Marcello Mamino Margarita Otero 《Israel Journal of Mathematics》2010,180(1):143-161
It is known that a definably compact group G is an extension of a compact Lie group L by a divisible torsion-free normal subgroup. We show that the o-minimal higher homotopy groups of G are isomorphic to the corresponding higher homotopy groups of L. As a consequence, we obtain that all abelian definably compact groups of a given dimension are definably homotopy equivalent,
and that their universal covers are contractible. 相似文献
827.
Melquizedeque B. Alves Vianney O. Santos jr. Valerio C. D. Soares Paulo A. Z. Suarez Joel C. Rubim 《Journal of Raman spectroscopy : JRS》2008,39(10):1388-1395
Anionic species formed in mixtures of 1‐n‐butyl‐3‐methylimidazolium chloride (BMICl) with different amounts of niobium pentachloride (NbCl5) or zinc dichloride (ZnCl2) were investigated by Raman spectroscopy. In the BMICl and NbCl5 ionic mixtures the presence of the anion NbCl6− was detected for all compositions (molar fraction, X) and a mixture of this anion and the neutral Nb2Cl10 in acid ones. Two different anions were observed for basic mixtures of BMICl and ZnCl2: ZnCl42−(0 < X < 0.35) and Zn2Cl62−(X > 0.3), whereas for acidic ones three species were detected: Zn2Cl62−(X < 0.7), Zn3Cl82−(X > 0.7) and Zn4Cl102−(X > 0.7). It has also been observed that in both cases, the formation of larger anions causes a shift of the C H stretching modes to higher wavenumbers as the result of a decrease in the hydrogen bond between Cl and the hydrogens from the cation. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
828.
In this paper we introduce a new type of orthogonality for real normed planes which coincides with usual orthogonality in the Euclidean situation. With the help of this type of orthogonality we derive several characterizations of the Euclidean plane among all normed planes, all of them yielding also characteristic properties of inner product spaces among real normed linear spaces of dimensions d ⩾ 3. 相似文献
829.
830.
Gerald Gerlach Margarita Guenther Gunnar Suchaneck Joerg Sorber Karl-Friedrich Arndt Andreas Richter 《Macromolecular Symposia》2004,210(1):403-410
In the present work, pH-sensitive poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blends as well as hydrogels based on poly(N-isopropylacrylamide) (PNIPAAm), which are sensitive to organic solvent concentration in aqueous solutions, were used in silicon micromachined sensors. A sensitivity of approximately 15 mV/pH was obtained for a pH sensor with a 50 μm thick PVA/PAA hydrogel layer in a pH range above the acid exponent of acrylic acid (pKa=4.7). The output voltage versus pH-value characteristics and the long-term signal stability of hydrogel-based sensors were investigated and the measurement conditions necessary for high signal reproducibility were determined. The influence of the preparation conditions of the hydrogel films on the sensitivity and response time of the chemical and pH sensors is discussed. 相似文献