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  • 1
    Call number: SR 90.0002(838)
    In: Professional paper
    Type of Medium: Series available for loan
    Pages: VI, 34 S. + 1 pl.
    Series Statement: U.S. Geological Survey professional paper 838
    Language: English
    Location: Lower compact magazine
    Branch Library: GFZ Library
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  • 2
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract In order to test gas-phase reaction schemes for the production of small oxides of carbon in cold, dense interstellar clouds, we have searched for the radical CCO and for propadienone (H2C3O) in Taurus Molecular Cloud 1, a nearby cloud which exhibits a rich organic chemistry. The radical CCO has been detected with a fractional abundance some two orders of magnitude less than that of CCS, about one order of magnitude less than that of H2CCO, and slightly less than that of C3O. An upper limit has been obtained on the abundance of propadienone which is slightly less than that of its isomer propynal (HC2CHO).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Nonlinear dynamics 5 (1994), S. 421-432 
    ISSN: 1573-269X
    Keywords: Chaos ; unbalance ; journal ; bearings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The behaviour of non-linear systems often yield unexpected phenomena which are extremely sensitive to initial conditions. The hydrodynamic journal bearing is a common machine element which is strongly nonlinear for large excursions within the clearance space. A simple model of a rigid journal, supported hydrodynamically using a short bearing theory is shown to behave chaotically when the rotating unbalance force exceeds the gravitational load. At these values of the force ratio the time history of the response is very sensitive to initial conditions and a spectral analysis demonstrates a significant broadening from the expected peak at the rotational frequency. A once per revolution sampling of the time history (Poincaré plot) revealed an apparent aperiodic pattern. An estimate of the fractal dimension using the Grasberger-Procaccia algorithm resulted in a lower bound of 2.15, a typical result for low dimensional systems with significant dissipative action. The required levels of unbalance are only an order of magnitude greater than acceptable levels for rotating machinery and thus could be achieved with in-service erosion or minor damage. The subsequent non-synchronous response could result in fatigue and potential shaft failure.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An increase by over three orders of magnitude from 0.58 mΩ to 1.17 Ω was observed at 4.0 K in the 3 GHz microwave surface resistance of ceramic YBa2Cu3O7−δ following exposure to neutrons. The transport resistivity of an unirradiated pellet was linear in temperature down to Tc with a room-temperature value of 2.13 mΩ cm and a resistivity extrapolated to 4.0 K of 0.53 mΩ cm. Following irradiation, the resistivity rose with decreasing temperature from a room-temperature value of 1.5 Ω cm to a maximum at around 45 K with little change evident at Tc . These results, in conjunction with eddy current, susceptibility, iodometric titration, and thermally stimulated luminescence measurements on irradiated and unirradiated samples, collectively suggest that the effect of neutron irradiation has been to decrease intergranular coupling without the development of an insulating phase.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sintered samples of EuBa2Cu3Ox and GdBa2Cu3Ox with x(approximately-equal-to)7 have been irradiated at 90 °C with 800 MeV protons. The superconducting transition temperature decreases 1.7 K/1017 pcm−2 for both materials. The critical magnetization current density, characterizing intragranular conduction, increases a factor of 3 at zero field and relatively larger factors for finite magnetic fields at 7 and 75 K for fluences on the order of 1017 pcm−2. No and only minor differences between irradiated and unirradiated specimens were seen in calorimetric and transmission electron microscopy analyses, respectively.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An analysis is presented of extratropical cyclone frequency, the 500 hPa height standard deviation field and the monthly 700 hPa height field in the Northern Hemisphere, together with precipitation in the Mackenzie basin and the Mackenzie River runoff. Spatial and temporal variability in the data are examined for the period 1965 to 1989, and a cross-correlation analyses is performed to determine the relationship between the runoff and the precipitation variations, and between the precipitation and the atmospheric circulation anomalies. It is found that precipitation fluctuations in the Mackenzie River drainage basin are strongly linked to variations in the Mackenzie River runoff and in the North Pacific storm tracks, with the time scale of variability ranging from interannual to decadal. The results are discussed in relation to the interdecadal Arctic climate cycle proposed by Mysak, Manak and Marsden, and revised by Mysak and Power. In particular, the latter authors hypothesized that, as part of this cycle, air-sea interactions and synoptic scale processes over the northwestern North Atlantic influenced, via cyclone movements in the Labrador Sea and Baffin Bay, precipitation in northern Canada and hence river runoff into the Arctic. The results of this study indicate that such influences on the precipitation in the Mackenzie basin are small, and hence that the Mysak-Power feedback loop which describes this climate cycle needs further revision.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1254
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract A mathematical model to estimate outdoor thermal comfort for humans from micrometeorological data has been formulated using the energy balance concept and the simultaneous satisfaction of four criteria for comfort from the literature: (a) a comfortable perspiration rate, (b) a comfortable core body temperature, (c) a comfortable skin temperature, and (d) a near-zero energy budget. A cylindrical modification of the globe thermometer is proposed as a simple monitor of outdoor radiation absorption for a person, and the effect of windspeed on the thermal resistance of clothing is considered. Results show a correlation coefficient of 0.91 between model output and subjective comfort ratings of 59 different situations with a variety of temperatures, insolations and windspeeds.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 16 (1970), S. 278-290 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Eine Reihe von Berechnungen für das Sulfat-Ion wird beschrieben, die dazu dienen sollen, die Verwendbarkeit verschiedener MO-Methoden unter Einschluß aller Valenz-Elektronen und verschiedener Verfahren zur Berechnung von Parametern entsprechend den vorhergehenden Arbeiten zu prüfen. Die CNDO- und die Mulliken-Methode ergeben einander ähnliche Resultate, während die MCZDO-Resultate eng mit denjenigen der komplizierten NDDO- und der Rüdenberg-Methode übereinstimmen. Daraus folgt, daß die MCZDO-Methode sich als die im allgemeinen am meisten geeignete Näherungsmethode für theoretische Untersuchungen von polyatomaren Systemen erweisen mag, die größere Atome enthalten oder aus anderen Gründen jenseits des Bereiches der ab inito Berechnungen liegen. Es wird gezeigt, daß die ZDO Technik — geeignet angewendet — annehmbare numerische Ergebnisse liefert. Vorzüge des Gebrauchs der Orbitalexponenten von Burns gegenüber denjenigen von Slater und die Wichtigkeit des Gebrauchs der transformierten Rumpfwechselwirkungs-Matrixelemente bei voller Überlappung in ZDO-Berechnungen werden gezeigt.
    Abstract: Résumé Une série de calculs sur l'ion sulfate a servi à tester un certain nombre de méthodes d'orbitales moléculaires pour tous les électrons de valence ainsi que plusieurs procédés d'évaluation des paramètres décrits dans les articles précédents. Les méthodes CNDO et Mulliken fournissent des résultats semblables alors que les résultats fournis par MCZDO sont en accord étroit avec ceux des calculs plus complexes selon NDDO et Ruedenberg. Ceci suggère que la méthode MCZDO peut s'avérer la méthode approchée la plus convenable pour l'étude théorique de systèmes contenant des atomes lourds ou de systèmes hors de portée pour un calcul ab-initio. La technique du recouvrement différentiel nul, convenablement appliquée, est numériquement acceptable. Les avantages de l'emploi des exposants orbitaux de Burns à la place de ceux de Slater et l'importance de l'emploi de l'hamiltonien de coeur total transformé dans un calcul ZDO sont illustrés dans ce travail.
    Notes: Abstract A series of calculations on the sulphate ion is reported, serving to test the viability of several all-valence-electron molecular orbital methods and several procedures for evaluating parameters described in preceding papers. The CNDO and Mulliken methods yield similar results while the MCZDO results are in close accord with those of the more complex NDDO and Ruedenberg calculations. This suggests that the MCZDO method may prove to be the most generally suitable approximate method for theoretical studies of polyatomic systems containing larger atoms, or otherwise beyond the scope of ab inito calculations. The zero differential overlap technique, properly applied, is shown to be numerically acceptable. Advantages of using Burns rather than Slater orbital exponents and the importance of using the transformed full overlap core hamiltonian in ZDO calculations are illustrated.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 16 (1970), S. 291-302 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Bekanntlich hat die Elektronenkorrelation einen wichtigen Einfluß auf die Resultate von MO-Berechnungen. Sie wird jedoch gewöhnlich nicht direkt in solche Berechnungen mit einbezogen. Eine Analyse der allgemeinen Theorie der Elektronenkorrelationen führt zu einer Paar-Korrelationshypothese, die als Grundlage für die Ableitung einer Methode dient, um die Elektronenkorrelation explizit in der LCAOMO-Energie zu berücksichtigen. Die abgeleiteten Ausdrücke wirken sich stark auf semi-empirische Parameter-Schemata von Methoden unter Einschluß aller Valenzelektronen aus, woraus folgt, daß diese keine korrekte Berücksichtigung der Korrelationskorrekturen enthalten. Es ist also vorzuziehen, theoretisch begründete Parameter-Schemata in Näherungs-MO Berechnungen anzustreben, die zu Näherungs-Hartree-Fock-Molekül-Funktionen führen sollen. Die Elektronenkorrelationskorrektur kann dann bei dem Ausdruck für die totale Valenzelektronen-Energie angewendet werden, wie es in der vorliegenden Arbeit dargestellt wird.
    Abstract: Résumé La corrélation électronique a une influence importante sur les résultats des calculs d'orbitales moléculaires mais n'est pas d'ordinaire incluse dans ces calculs. Une analyse de la théorie générale de la corrélation électronique conduit à une hypothèse de corrélation de paire que l'on utilise pour trouver un moyen explicite de tenir compte de la corrélation électronique dans l'énergie LCAOMO. Les expressions que l'on obtient contiennent des implications significatives pour les schéma semiempiriques des méthodes à électrons de valence, montrant que ces méthodes ne contiennent pas la corrélation électronique sous une forme correcte. Ceci indique l'intérêt d'un schéma paramétrique théoriquement fondé dans les méthodes Hartree-Fock approchées. La correction de corrélation électronique peut alors être appliquée à l'énergie totale des électrons de valence ainsi que cela est exposé dans cet article.
    Notes: Abstract Electron correlation is known to have an important influence on the results of molecular orbital calculations, but is not usually directly included in such calculations. An analysis of the general theory of electron correlation leads to a pair correlation hypothesis, which serves as a basis for the subsequent derivation of a way of explicitly allowing for electron correlation in the LCAOMO energy. The derived expressions carry significant implications for the semi-empirical parameter schemes of all-valence-electron methods, implying that they cannot be regarded as incorporating the correct form of correlation correction. This points to the advantage of aiming at a theoretically founded parameter scheme in approximate molecular orbital calculations, designed to produce approximate Hartree-Fock molecular wave functions. The electron correlation correction can then be applied to the expression for the total valence electron energy as developed in the present paper.
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  • 10
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Nach dem Verfahren von Ewald wurde der Einfluß des elektrostatischen Beitrages des Kristallgitters auf die MO's und spektroskopische Zustände des Permanganat- und Chromat-Anions berechnet. Eine rohe Abschätzung der Faktorgruppen-Aufspaltung legt die Vermutung nahe, daß auch dieser Effekt beobachtbar ist. Jedoch sind die Energieverschiebungen und Aufspaltungen infolge der Umgebung des Kristallgitters wahrscheinlich größer als die Faktorgruppen-Aufspaltung. Es wird besonders auf den bedeutenden Einfluß des Gitterfeldes auf die MO-Energien hingewiesen, die das oberste besetzte Orbital des Grundzustandes stark bindend machen, ganz im Gegensatz zur Situation für die isolierten Anionen.
    Abstract: Résumé La méthode d'Ewald a été utilisée pour calculer l'effet de l'environnement électrostatique (réseaux cristallins) sur les orbitales moléculaires et les états spectroscopiques des oxyanions permanganate et chromate. L'estimation de la séparation du groupe facteur sur la base d'un modèle grossier suggère que cet effet peut être observé dans les ions moléculaires dans les cristaux. Cependant les déplacements et les séparations des bandes dûs à l'effet électrostatique du réseau sont prédits comme étant plus grands que les séparations du groupe facteur. On attire l'attention sur l'effet significatif du champ du réseau sur les énergies des orbitales moléculaires, la plus haute orbitale occupée devenant fortement liante, contrairement à ce qui a lieu dans les anions isolés.
    Notes: Abstract The Ewald method has been used to calculate the effect of electrostatic environments (crystal lattices) on the molecular orbitals and spectroscopic state levels of the oxyanions, permanganate and chromate. An estimate of factor group splitting based on a crude model suggests that it may be an observable effect in molecular ions in crystals. However the shifts in energy and the splitting of bands due to electrostatic effect of the lattice are predicted to be more important than the factor group splittings. Attention is drawn to the significant effect of the lattice field on the molecular orbital energies, making the uppermost filled orbital of the ground state strongly bonding, in contrast to the situation in the isolated anions.
    Type of Medium: Electronic Resource
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