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101.
Janez Pirnat Janko Lunik Vojko Jazbinek Veselko
agar Janez Seliger Thomas M. Klaptke Zvonko Trontelj 《Chemical physics》2009,364(1-3):98-104
14N NQR frequencies and spin–lattice relaxation times were measured in technologically important 5-aminotetrazole and 5-aminotetrazole monohydrate at different temperatures between 77 K and 300 K. Five NQR triplets ν+, ν− and ν0 were found for the five inequivalent nitrogen atoms in each compound between 0.7 MHz and 4 MHz. Carr-Purcell based multipulse sequences were used to accumulate quadrupole echo signals before the FFT analysis. Assignment of the frequencies to atomic positions was made and the results are analysed in relation to the molecular chemical bonds and possible H-bonds in the crystal structures. The new NQR frequencies are reasonably related to the previously published NQR spectrum of the third family member, 1H-tetrazole. 相似文献
102.
Summary: The cohesive zone model is used for the numerical simulation of crack growth in homogeneous specimens made of two different grades of polyethylene (PE) as well as in PE-bimaterials. The material data and the shapes of the cohesive function are deduced from experimental data by Ivankovic et al., Eng. Fract. Mech. 71, 2004, 657–668 and Ting et al., Polym. Eng. Sci. 46, 2006, 763–777. Fracture toughness parameters are evaluated from the simulated load versus displacement curves. The results show a significant influence of the arrangement of the two PE-grades in the bimaterial specimens, caused by both the different material properties and the different characteristic parameters of the cohesive function. 相似文献
103.
Optimising calibration and measurement capabilities in terms of economics in conformity assessment 总被引:1,自引:0,他引:1
Gaber Beges Janko Drnovsek Leslie R. Pendrill 《Accreditation and quality assurance》2010,15(3):147-154
Calibration measurement capabilities (CMC) are key factors in declaring the metrological performance of national metrology
institutes (NMIs). Different countries have different CMC capabilities, reflecting both the existing measurement science competence
as well as the perceived national needs for traceable calibration. This paper deals with increasing interest in decision-making
in conformity assessment in terms of effective costs associated with measurement, testing and incorrect decision-making. The
work examines the CMCs of calibration laboratories and NMIs with economic decision theory, in particular, in terms of customer
satisfaction and with respect to conformity assessment issues. Optimal strategies for calibration costs, maintenance of national
measurement standards, testing and production costs are illustrated in practical examples. CMCs are an essential instrument
to enable conformity assessment both for product safety, legal metrology, quality requirements as well as scientific research.
The newly defined term “target measurement uncertainty”, introduced in the latest international metrology vocabulary (VIM),
should be therefore always related to appropriate CMCs and related dissemination paths in the whole conformity assessment
procedure. These requirements are clear and transparent justification for the development of required national metrological
infrastructures, in order to fulfil the requirements of target measurement uncertainty for intended use or application in
the particular conformity assessment procedure. 相似文献
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107.
Summary The extraction of iron(III) from aqueous HCl, H2SO4, HClO4, HNO3 solutions by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone (HA) dissolved in CHCl3 has been studied. Quantitative extraction of iron(III) is achieved if the concentration of the acids does not exceed 1N. The composition of the iron (III)—HA complex formed in the organic phase was investigated spectrophotometrically, radiometrically and by analysis of the isolated species. In the aqueous phase iron (III) and HA form three different complexes, depending on the initial iron: HA concentration ratio and the pH of the solution. They are the violet FeA2+, the orange-red FeA2
+ and the orange-yellow FeA3. The latter is identical with the complex found in the organic phase, which was isolated as a solid crystalline material and characterized by elemental analysis and infrared spectroscopy. A spectrophotometric method for the determination of iron(III) in the aqueous phase and in the chloroform solution, by extraction with HA, is described.
Zusammenfassung Die Extraktion von Fe(III) aus wäßrigen Lösungen von HCl, H2SO4, HClO4 oder HNO3 mit 2-Carbäthoxy-5-hydroxy-1-(4-tolyl)-4-pyridon (HA) in chloroformischer Lösung wurde untersucht. Sie verläuft quantitativ, wenn die Konzentration der Säure nicht größer ist als 1-n. Die Zusammensetzung des Fe(III)-HA-Komplexes in der organischen Phase wurde spektrophotometrisch, radiometrisch und durch Analyse der isolierten Substanz untersucht. In wäßrigem Milieu bilden Eisen(III) und HA drei verschiedene Komplexe je nach dem anfänglichen Konzentrationsverhältnis Fe(III): HA und je nach dem pH der Lösung. FeA2+ ist violett, FeA2 + ist orange-rot und FeA3 orangegelb. Diese Verbindung ist mit dem in der organischen Phase gefundenen Komplex identisch, der in kristallisierter Form isoliert und durch Elementaranalyse und IR-Spektrometrie charakterisiert wurde. Eine spektrophotometrische Methode zur Eisen(III)-Bestimmung in wäßriger Phase und in chloroformischer Lösung durch Extraktion mit HA wurde beschrieben.相似文献
108.
Summary Extraction of zirconium, niobium and tantalum from oxalic and hydrofluoric acid solutions, by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone (HA) dissolved in chloroform was studied. Extraction mechanism for the extraction of zirconium from oxalate solutions and of niobium from fluoride solutions is proposed. Separation of zirconium and niobium from oxalate solution as well as from fluoride solution and tantalum and niobium from fluoride solution is described. Back-extraction of these metals is possible by hydrofluoric and oxalic acid. Results obtained show that the efficiency of extraction by HA decreases in the sequence tantalum > niobium > zirconium.
Zusammenfassung Die Extraktion von Zirkonium, Niob und Tantal aus oxalsauren und fluorwasserstoffsauren Lösungen mit Hilfe einer chloroformischen Lösung von 2-Carbäthoxy-5-hydroxy-(4-tolyl)-4-pyridon wurde untersucht. Ein Extraktionsmechanismus für Zirkonium aus Oxalatlösungen und für Niob aus Fluoridlösungen wurde vorgeschlagen. Die Trennung von Zirkonium und Niob aus einer Oxalatlösung oder aus einer Fluoridlösung sowie von Tantal und Niob aus einer Fluoridlösung wurde beschrieben. Die Rückextraktion dieser Metalle mit Flußsäure und Oxalsäure ist möglich. Die Ergebnisse zeigen, daß die Effizienz der Extraktion in der Reihenfolge Tantal > Niob > Zirkonium abfällt.相似文献
109.
Roman Drnovsek 《Proceedings of the American Mathematical Society》1997,125(8):2391-2394
The following generalization of Lomonosov's invariant subspace theorem is proved. Let be a multiplicative semigroup of compact operators on a Banach space such that for every finite subset of , where denotes the Rota-Strang spectral radius. Then is reducible.
This result implies that the following assertions are equivalent:
(A) For each infinite-dimensional complex Hilbert space , every semigroup of compact quasinilpotent operators on is reducible.
(B) For every complex Hilbert space , for every semigroup of compact quasinilpotent operators on , and for every finite subset of it holds that .
The question whether the assertion (A) is true was considered by Nordgren, Radjavi and Rosenthal in 1984, and it seems to be still open.
110.
Maja Milivojevic Fir Andrej Smidovnik Luka Milivojevic Janko Zmitek Mirko Prosek 《Journal of inclusion phenomena and macrocyclic chemistry》2009,64(3-4):225-232
The complexes of coenzyme Q10 with β- and γ-cyclodextrin in aqueous solutions were prepared in order to improve the water solubility, thermo- and photo-stability of coenzyme Q10. Complex formation resulted in an increase in water solubility at room temperature and pH 6.5 by a factor at least 102. The solubility of coenzyme Q10 in the presence of cyclodextrins linearly increases with temperature and pH. The UV light (λ = 254) and temperature together have a great effect on coenzyme Q10 stability. After 120 min of exposure at 80 °C and UV light about 72.3% of pure coenzyme Q10 was degraded. Thermo- and photo-stability was strongly improved by complex formation; more than 64% of coenzyme Q10 remained unchanged. The formation of complexes was evaluated using IR spectrometry, X-ray diffractometry and TGA/DSC analysis. 相似文献