Search results for "Chemical engineering"
showing 10 items of 5892 documents
Obituary for Prof. Dr. Jun-ichi Yoshida
2019
New insights in the metabolic behaviour of PAO under negligible poly-P reserves
2017
[EN] In a previous study the authors confirmed the ability of PAOs to perform GAO metabolism in short-term experiments. However, what happens when PAOs are exposed to poly-P shortage for an extended period of time? The answer to this question was the aim of this work from a macroscopic and microscopic point of view. Therefore, the poly-P was removed from a PAO enriched SBR and maintained without poly-P during five solid retention time. The PAOs were found to quickly change their metabolism to a clear GAO performance and remained without GAO colonization for the entire experimental period, even though GAO was present (around 5%) at the beginning of the experiment. Unlike the results obtained…
Unraveling the Structure and Properties of Layered and Mixed ReO3–WO3 Thin Films Deposited by Reactive DC Magnetron Sputtering
2022
Tungsten trioxide (WO3) is a well-known electrochromic material with a wide band gap, while rhenium trioxide (ReO3) is a “covalent metal” with an electrical conductivity comparable to that of pure metals. Since both WO3 and ReO3 oxides have perovskite-type structures, the formation of their solid solutions (ReO3–WO3 or RexW1–xO3) can be expected, which may be of significant academic and industrial interest. In this study, layered WO3/ReO3, ReO3/WO3, and mixed ReO3–WO3 thin films were produced by reactive DC magnetron sputtering and subsequent annealing in air at 450 °C. The structure and properties of the films were characterized by X-ray diffraction, optical spectroscopy, Hall conductivity…
Photophysical and Electrical Properties of Highly Luminescent 2/6-Triazolyl-Substituted Push-Pull Purines.
2021
This work is supported by the ERDF 1.1.1.1. activity project No. 1.1.1.1/16/A/131. The authors thank Dr. sc. ing. Jānis Zicāns and Dr. sc. ing. Remo Merijs Meri for DSC analyses.
Inelastische Lichtstreuung von Polymeren in Lösung, Schwerpunktstransport und Polymolekularität
1979
Mittels der inelastischen Lichtstreuung wurden zwei Polystyrol-Praparate mit M = 200000 und 670000 und vier aus diesen Substanzen zusammengesetzte Mischungen in Toluol bei 20 °C vermessen. Die im Winkelbereich 11° ≤ ϑ≤40° aufgenommenen Autokorrelationsfunktionen wurden dazu benutzt, verschiedene Bestimmungsverfahren von z-Mitteln von Potenzen des Reibungs- und Diffusionskoeffizienten zu testen. Experimentell gelang es bei den Mischungen lediglich die ersten Potenzen dieser Grosen zu ermitteln. Diese werden zusammen mit den Reibungs- bzw. Diffusionskoeffizienten der einzelnen Komponenten zur Charakterisierung der Parameter der Molekulargewichtsverteilung der Mischungen benutzt. Inelastic lig…
Convective mass transfer to partially recessed and porous electrodes
2003
Abstract The diffusional problem of a rotating porous electrode has been analysed based on the mass transfer equations for a partially blocked electrode. It is shown that the porous geometry leads to a dependence of the current on rotation rate identical to that corresponding to a coupled diffusion-activated electron transfer mechanism. The apparent rate constant, however, is related only to the geometry of the porous surface. It is shown that the characteristic diffusional length corresponds to the pore dimension modified by a term including the transition from linear to spherical diffusional geometry at the pore entrance. The theory is compared with experimental results for the reduction …
Local electrochemical impedance measurements on inclusion-containing stainless steels using microcapillary-based techniques
2009
MnS inclusions are good precursor sites for pitting corrosion of stainless steel. The objective of this paper was to quantify the passive properties of resulfurized stainless steel after immersion in chloride media. This was done by combining microcapillary techniques with electrochemical impedance spectroscopy and numerical analysis (specific equivalent circuit). It was shown that sulfur species produced in the electrolyte during the dissolution of inclusions react with the native passive film to CrS and FeSO 4 . Local electrochemical impedance spectroscopy measurements provided data describing the behaviour of the affected matrix at the microscale. For example, the value of the charge tra…
Electro-optical and laser spectrofluorimetry study of coumarins 7 and 30: evidence for the existence of the close-lying electronic states and conform…
1997
Our experiments and calculations reveal a set of anomalous and interesting properties of coumarin 7 (CU7) and coumarin 30 (CU30) in solution. The spectral dependence of electro-optical coefficients and, consequently, dipole moments indicates that the absorption band is a superposition of several (at least two) electronic transitions. Probably, there are two close-lying π,π* singlet electronic excited states which contribute to the first absorption band. The calculations using the MM2 program show that both dyes in the ground state have two stable plane anti conformers. From time-resolved spectrofluorimetric measurements we obtained evidence for the existence of conformers in paraffin oil so…
Die Fällungschromatographie als exakte Methode zur Bestimmung der Molekulargewichtsverteilung von Hochpolymeren Zur Theorie der Fällungschromatograph…
1965
Bei der Fallungschromatographie wird ein Gemisch Hochpolymerer durch kombinierte Wirkung eines Losungsmittel-Fallungsmittel- und eines Temperaturgradienten in Fraktionen zerlegt, aus denen man nach einem fruher beschriebenen Verfahren die Verteilungskurve der Molekulargewichte erhalt. Eine so bestimmte Verteilungsfunktion ist dann exakt, wenn die Uneinheitlichkeit der Fraktionen (Ufr) klein gegen die Uneinheitlichkeit des zu analysierenden Polymeren (U) ist. Die Uneinheitlichkeit der bei der Fallungschromatographie erhaltenen Fraktionen ist nach Gleichung (20) durch drei Grosen bestimmt: 1 Die Breite der idealisierten Fraktionen, gemessen durch den Abstand ΔP der mittleren Polymerisationsgr…
Convective electrodiffusion processes through graft-modified charged porous membranes
1999
Convective diffusion and electrophoresis across a charged porous membrane showing variable permeability properties were studied. The membrane used was prepared by grafting poly(acrylic acid) (PAA) onto a porous polyvinylidene fluoride (PVDF) membrane. The degree of grafting was selected to be relatively low, 18 wt%, to compromise between the ion selectivity and hydraulic permeability of the membrane. The possible electric field induced effects on the membrane permselectivity were examined after the membrane had been characterized by convective diffusion and concentration cell potential measurements. The measured electrophoresis data, however, could be modelled using the extended Teorell–Mey…