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  • Wiley-Blackwell  (47)
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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Dynamic strength variationThe Weibull probability function or the arcsin √P distribution suffices for description purposes provided that considerations are confined to failure or survival probabilities between 20 and 80%. Beyond these limits more sophisticated analysis of the test results - as too in the case of the design engineer when estimating the statistically induced component of the safety margin - must make use of more realistic distribution functions.
    Notes: Zu ihrer Beschreibung genügt die Weibullsche Wahrscheinlichkeitsfunktion oder auch die arcsin P-Verteilung nur, solange man sich auf Ausfall- oder Überlebenswahrscheinlichkeiten zwischen 20 und 80% beschränkt. Jenseits dieser Grenzen muß sich die anspruchsvollere Analyse der Versuchsergebnisse - wie auch der Konstrukteur bei der Abschätzung der statistisch bedingten Komponente der Sicherheitsspanne - wirklichkeitsnäherer Verteilungsfunktionen bedienen.
    Additional Material: 5 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Valve Materials for Combustion EnginesAn overview is being given on production numbers, requirements and properties of valve materials. Their development from the beginning till today's state of the art is reviewed with a focus on Chromium-Manganese-Nitrogen-alloys. Valve materials are grouped by the criteria of density - heavy, lightweight - and alloying elements. The multiple stresses of the material in the valve are being met with a few standardised grades and specific ways of manufacture. The path of the material from bar stock to the finished valve is being followed. Engine development in the past decades increased the load on the valves which could be met by continuously developing their structural strength. Also the strength of all valve materials could be raised to nominal strength above 1100 Mpa by applying specific methods. Higher strength at the surface is being effectuated by work hardening effects. The technology to increase reliability of hollow valves and new aspects of valve seat facing including residual stress is explicitly discussed. General aspects of alloy utilisation is followed by a discussion of lightweight valve materials as Titanium alloys, intermetallic Titaniumaluminide alloys and ceramic materials, spec. Silicon Nitride, which all have a potential as forthcoming valve materials capable of reducing fuel consumption of the engines.
    Notes: Nach einem Überblick über Produktionszahlen, allgemeine Anforderungen und Eigenschaften von Ventilen für Verbrennungsmotoren, wird in einem Rückblick die Werkstoffentwicklung für die Ventilstähle von den ersten Anfängen bis zum heutigen Stand aufgezeigt. Schwerpunktmäßig wird die Gruppe der Chrom-Mangan-Stickstoff-Stähle behandelt. Daneben werden die Ventilwerkstoffe geordnet nach schweren und leichten und innerhalb dieser Gruppen nach Legierungsmerkmalen beschrieben. Es wird über die vielfältigen Werkstoffanstrengungen am Ventil informiert, die mit wenigen genormten Werkstoffgüten und speziellen Fertigungsverfahren problemlos mit niedrigsten Fehlerraten beherrscht werden. Der Weg des Werkstoffes vom Halbzeug bis zum fertigen Ventil wird in allen Schritten verfolgt. Die in den letzten Dekaden forcierte Motorenentwicklung führte zu verschärften Betriebsbedingungen auch für die Ventile, die mit einer kontinuierlichen Weiterentwicklung bestehender Werkstoffgüten und Verbesserungen der Gestaltsfestigkeit der Ventile aufgefangen wurden. In diesem Zusammenhang werden spezielle Lösungen zur Festigkeitssteigerung aller Ventilwerkstoffe bis in den Bereich von über 1100 MPa erläutert, die nach bekannten metallkundlichen Gesetzen ermöglicht wurden. Als wesentliches Prinzip werden ortsabhängig, besonders an der Oberfläche, erhöhte Festigkeits- und Verschleißeigenschaften zur Optimierung der Gestalts- und Betriebsfestigkeit eingesetzt. Über Entwicklungen zur Technologie der Hohlventile und von erweiterten Lösungen beim Auftragschweißen von Ventilsitzen im Zusammenhang mit Eigenspannungen wird ausführlich berichtet. Einer kurzen allgemeinen Betrachtung zum Legierungsaufwand der wichtigsten Ventilwerkstoffe folgt ein Kapitel über Titan, Intermetallische Verbindungen und Keramik, die möglicherweise als zukünftige leichte Ventilwerkstoffe Verwendung finden können.
    Additional Material: 38 Ill.
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  • 3
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Microbial deterioration of materials - biofilm and biofouling: Biofilms in industrial water circuits. Case history: Process water system in a paper factory
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: The Gradient of the S, N-curve. The classical two-parameter basic equations of Wöhler and Basquin and also the four-parameter equation of Palmgren/Weibull approximate the Wöhler curve in certain ranges only. They fail in particular when one attempts to use them to convert a service life increase into the appropriate gain in strength. For a more exacting analysis these approximations must be replaced by models of the Wöhler curve which are nearer to actual reality.
    Notes: Die klassischen Zwei-Parameter-Ansätze von Wöhler und Basquin, aber auch der Vier-Parameter-Ansatz von Palmgren/Weibull approximieren die S, N-Kurve nur bereichsweise; vor allem versagen sie, wenn man sich ihrer bedienen will, um eine erzielte Lebensdauersteigerung in den entsprechenden Festigkeitsgewinn umzurechnen: Bei anspruchsvolleren Analysen müssen diese Approximationen durch wirklichkeitsnähere Modelle der Wöhlerkurve ersetzt werden.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: polypropylene ; spherulite ; cocrystallization ; lamellae ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: During spherulitic crystallization of polymers, there is a tendency for low molecular weight and other less crystallizable entities to be rejected from the body of the spherulites. This rejection process causes a segregation of these species to those areas where spherulites impinge. As a result of this segregation, lamellar and spherulite boundaries have a tendency to become weak, often resulting in premature mechanical failure. The objective of this work, anthropomorphically speaking, is to develop a melt miscible blend system in which a propylene copolymer “fools” a polypropylene homopolymer into rejecting the copolymer to the spherulite boundaries as an impurity. However, once the copolymer arrives at these boundaries, the copolymer subsequently connects adjacent spherulites through cocrystallization of the propylene copolymer segments. It was found that addition of either a random ethylene-propylene copolymer or an isotactic-atactic block copolymer was able to yield the desired effect. Cocrystallization was confirmed by calorimetry, and segregation of copolymer and subsequent reinforcement at the spherulite boundaries was directly observed microscopically. Using this approach, toughness was increased with little loss in stiffness. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2047-2056, 1998
    Additional Material: 8 Ill.
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  • 6
    ISSN: 0006-3592
    Keywords: chlorobenzoic acid ; methylbenzoic acid ; genetically modified strain ; Pseudomonas sp. B13 FR1 SN45P ; batch cultivation ; chemostat ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Degradation of 3-chlorobenzoic acid (3CB), 4-chlorobenzoic acid (4CB), and 4-methylbenzoic acid (4MB) as single substrates (carbon sources) and as a substrate mixture were studied in batch and continuous culture using the genetically modified microorganism Pseudomonas sp. B13 FR1 SN45P. The strain was able to mineralize the single compounds as well as the substrate mixture completely. Conversion of the three compounds in the substrate mixture proceeded simultaneously. Maximum specific substrate conversion rates were calculated to be 0.9 g g-1 h-1 for 3 CB and 4CB and 1.1 g g-1 h-1 for 4MB. Mass balances indicated the transient accumulation of pathway intermediates during batch cultivations. Hence, the rate limiting step in the degradative pathway is not the initial microbial attack of the original substrate or its transport through the cell membrane. Degradation rates on 3CB were comparable to those of the parent strain Pseudomonas sp. B13. The stability of the degradation pathways of strain Pseudomonas sp. B13 FR1 SN45P could be demonstrated in a continuous cultivation over 3.5 months (734 generation times) on 3CB, 4MB, and 4CB, which were used as single carbon sources one after the other.
    Additional Material: 8 Ill.
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  • 7
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Pyrolyse-Felddesorptions-Massenspektrometrie ist zur Untersuchung verschiedener Polyamide wie Nylon 6,8,12 und Nylon 66 verwendet worden. Das pyrolytische Verhalten dieser Verbindungen hängt stark vom Lösungsmittel und vom Temperatur-programm ab. Ameisensäure als Lösungsmittel ruft starke thermische Fragmentierung hervor, während mit 1,1,1,3,3,3-Hexafluoro-2-propanol fast ausschließlich Molekülionen oder kationisierte Moleküle gebildet werden. Mit zunehmender Temperatur entstehen größere Cluster der polymeren Untereinheit (Mn + Na)+, aber gleichzeitig nimmt die thermische Fragmentierung auf der Emitteroberfläche zu. Die kationisierten Moleküle sind in allen Spektren dominant. Sie werden von M3 bis M5 oder M15 gebildet, je nach Kettenlange der polymeren Untereinheit. Mit zunehmender Temperatur verschiebt sich der Basispeak des Spektrums zu höheren Massen, und schwache Signale bis m/z 2000 und darüber werden registriert. Thermische Produkte werden hauptsächlich gebildet durch Wassereliminierung (-18 mu), Verlust der Säureamid-Gruppe (-44 mu) nach Umlagerung und von längeren Polyamiden durch Verlust von Methylengruppen (-42 oder 56 mu) durch cis-Eliminierung.Diese thermische Fragmentierung der Polymeren auf der Emitteroberfläche kann durch geeignete Emitterheizung kontrolliert werden und stimmt direkt mit der allgemeinen chemischen Kenntnis von diesen Substanzen in flüssiger und fester Phase überein. Zusammen mit den Vorteilen der integrierten Registrierung, der hohen Massenauflösung und der direkten Isotopenbestimmung ist die Kombination von Pyrolyse und Felddesorptions-Massenspektrometrie hervorragend geeignet zur Charakterisierung von synthetischen Polymeren anhand ihrer Untereinheiten und deren Sequenzen im hohen Massenbereich.
    Notes: Pyrolysis field desorption mass spectrometry has been performed from various polyamides such as nylon 6, 8, 12, and nylon 66. The pyrolytic behaviour of these compounds depends strongly on the solvent and the temperature program employed. Using formic acid as solvent strong thermal fragmentation is observed, while with 1,1,1,3,3,3-hexafluoro-2-propanol almost exclusively molecular ions or cationized molecules of the monomer building block M are produced. With increasing temperature larger clusters of polymeric subunits (Mn + Na)+ are generated, but thermal fragmentation on the emitter surface also increases. The cationized molecules dominate all spectra. They are found from M3 to M5 or M15 depending on the chain length of the polymer subunit. With increasing temperature, the base peak of the spectrum is shifted to the higher mass end and small signals up to m/z 2000 and above are recorded. Thermal products are mainly formed by water elimination (-18 mu), loss of the acid amide group (-44 mu) after rearrangement and from longer polyamides by loss of the methylene groups (- 42 or 56 mu) by cis-elimination.These thermal fragmentations of the polymeric substances on the emitter surface can be controlled by appropriate emitter heating and correlate directly with the common chemical knowledge of these materials in the liquid or solid phase. Together with the options of integrating recording, high mass resolution and direct isotope determination, the combination of pyrolysis and field desorption mass spectrometry offers a unique tool for characterization of building blocks and high mass sequences in synthetic polymers.
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  • 8
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The viscosity level in the range of the Newtonian viscosity η0, as well as in the shear rate dependent range (non-Newtonian-viscosity, η = f(\documentclass{article}\pagestyle{empty}\begin{document}$$ \mathop \gamma \limits^. $$\end{document})) of polymer solutions can be determined on the basis of a molecular modelling. Prerequisite is the information about the molecular parameters of the individual molecules  -  found in most cases in handbooks  -  and the result of the one-point measurement of η0 in the concentrated range.In addition, a criterium for shear stability was obtained, predicting the boundary range between a stable and a degraded polymer solution. This criterium holds for the laminar as well as for the turbulent flow. So, answers could be given to technologically interesting questions about the stability of the solutions.Under modified considerations, these results may be applied to polymer melts.
    Notes: Das Viskositätsniveau im Bereich der Ruhescherviskosität η0 (Newtonscher Bereich) sowie im schergeschwindigkeitsabhängigen Bereich (nicht-Newtonscher Bereich (η = f(\documentclass{article}\pagestyle{empty}\begin{document}$$ \mathop \gamma \limits^. $$\end{document})) von Polymerlösungen kann auf der Basis molekularer Modellierungen bestimmt werden. Voraussetzung hierfür ist die Kenntnis der molekularen Parameter des Einzelmoleküls, welche in vielen Fällen Handbüchern entnommen werden könen, und das Ergebnis einer Einpunktmessung von η0 in konzentrierter Lösung. Darüber hinaus wurde ein Stabilitätskriterium erarbeitet, das den Grenzbereich zwischen einer scherstabilen und einer degradierten Polymerlösung vorhersagt. Dieses Kriterium ist sowohl für den laminaren als auch für den turbulenten Strömungszustand verwendbar, wodurch anwendungstechnologisch bedeutsame Fragestellungen bezüglich der Stabilität beantwortet werden können.Die Ergebnisse sind unter einer modifizierten Betrachtungsweise auf Polymerschmelzen übertragbar.
    Additional Material: 11 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 108 (1858), S. 1-7 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 10
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reactions of ground state oxygen atoms with trans-2-butene, cis-2-butene, 2-methylpropene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene was investigated in the temperature range 200 to 370K. In this range, the rate constants are (in units 10-11 cm3 s-1): (1.1 ± 0.1) exp[+(180 ± 24)K/T]; (0.98 ± 0.09) exp[+(149 ± 23)K/T]; (1.14 ± 0.13) exp[+(128 ± 33)K/T]; (2.34 ± 0.16) exp[+(250 ± 16)K/T]; and (3.31 ± 0.50) exp[+(257 ± 36)K/T], respectively. The atoms were generated by the H2 laser photolysis of NO and detected by the time resolved chemiluminescence in the presence of NO. The concentrations of the O(3P) atoms were kept so low that secondary reactions with products are unimportant. © 1995 John Wiley & Sons, Inc.
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