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In this paper we consider the inverse minimum flow (ImF) problem, where lower and upper bounds for the flow must be changed as little as possible so that a given feasible flow becomes a minimum flow. A linear time and space method to decide if the problem has solution is presented. Strongly and weakly polynomial algorithms for solving the ImF problem are proposed. Some particular cases are studied and a numerical example is given. 相似文献
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L. Seetha Lakshmi V Sridharan DV Natarajan V Sankara Sastry T S Radhakrishnan 《Pramana》2002,58(5-6):1019-1026
Mn site is substituted with closed shell ions (Al, Ga, Ti, Zr and a certain combination of Zr and Al) and also with Fe and
Ru ions carrying the magnetic moment (S=5/2 and 2 respectively) at a fixed concentration of 5 at %. Substitution did not change either the crystal symmetry or the
oxygen stoichiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures
(T
p(ρ) and T
C, respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising
due to difference in the ionic radii between the substituent (r
M) and the Mn3+ ion (r
Mn
3+) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and
that of the neighboring Mn ion. 相似文献
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Summary The results obtained for halogen absorption with different preparations of lead chromates are discussed. It has been found that pure lead chromate is a poor external absorbent for microanalytical determinations of halogens. Differences in the absorption properties of lead chromates of various origins can be explained by the presence of PbO · PbCrO4 and by its different mechanical structures.
Absorptionseigenschaften handelsüblicher Bleichromate
Zusammenfassung Die Ergebnisse der Halogenabsorption an Bleichromat verschiedener Herkunft werden diskutiert. Dabei wurde festgestellt, daß reines Bleichromat für mikroanalytische Halogenbestimmungen unzureichend ist. Unterschiedliche Absorptionseigenschaften dieser Verbindung können durch das Vorhandensein von PbO · PbCrO4 sowie durch die verschiedene mechanische Struktur erklärt werden.相似文献
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Synthesis of a key precursor for orienticin C and model study on ruthenium-mediated macrocyclization
A tripeptido--arene--ruthenium complex was prepared as a key precursor for the projected synthesis of orienticin C, demonstrating that the cyclopentadienylruthenium moiety can be attached to a chloroarene in the presence of multiple functionality. The ruthenium-mediated intramolecular SNAr reaction for formation of the required diaryl ether linkage was successfully tested on a model system. 相似文献
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A new, very sensitive reagent is proposed for the colorimetric determination of uranium(VI), namely 1-phenyl-3-methyl-4-(3'-carboxy-4'-hydroxyphenyl-azo)-pyrazol-5-one. 相似文献
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Ionel Stavarache Ana-Maria Lepadatu Nicoleta G. Gheorghe Ruxandra M. Costescu George E. Stan Dan Marcov Adrian Slav Gheorghe Iordache Tionica F. Stoica Vladimir Iancu Valentin S. Teodorescu Cristian M. Teodorescu Magdalena Lidia Ciurea 《Journal of nanoparticle research》2011,13(1):221-232
Transmission electron microscopy and X-ray photoelectron spectroscopy analyses are performed to investigate Ge nanoparticles embedded in an amorphous SiO2 matrix. GeSiO thin films are prepared by two methods, sol?Cgel and radio frequency magnetron sputtering. After the deposition, the sol?Cgel films are annealed in either N2 (at 1 atm and 800 °C) or H2 (at 2 atm and 500 °C), and the sputtered films in H2 (at 2 atm and 500 °C), to allow Ge segregation. Amorphous Ge-rich nanoparticles (3?C7 nm size) are observed in sol?Cgel films. Crystalline Ge nanoparticles in the high pressure tetragonal phase (10?C50 nm size) are identified in the sputtered films. The size of the nanoparticles increases with Ge concentration in the volume of the film. At the film surface, the Ge concentration is much larger that in the volume for both sol?Cgel and sputtered films. At the same time, at the film surface, only oxidized Ge is observed. 相似文献
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