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Inhalt:
-Ottmar Ette: Unterwegs zum Weltbewußtsein. Alexander von Humboldts Wissenschaftsverständnis und die Entstehung einer ethisch fundierten Weltanschauung
-Ulrike Leitner: Humboldt’s works on Mexico
-Herbert Pieper: „Ungeheure Tiefe des Denkens, unerreichbarer Scharfblick und die seltenste Schnelligkeit der Kombination“. Zur Wahl Alexander von Humboldts in die Königliche Akademie der Wissenschaften zu Berlin vor 200 Jahren
-Ingo Schwarz: „Es ist meine Art, einen und denselben Gegenstand zu verfolgen, bis ich ihn aufgeklärt habe“. Äußerungen Alexander von Humboldts über sich selbst
-Petra Werner: Übereinstimmung oder Gegensatz? Zum widersprüchlichen Verhältnis zwischen A. v. Humboldt und F. W. J. Schelling
Laser beam melt ablation - a contact-free machining process - offers several advantages compared to conventional processing mechanisms: there exists no tool wear and even extremely hard or brittle materials can be processed. During ablation the workpiece is molten by a CO2-laser beam, this melt is then driven out by the impulse of a process gas. The idea behind laser ablation is rather simple, but it has a major limitation in practical applications: with increasing ablation rates surface quality of the workpiece processed declines rapidly. At high ablation rates, depending on the process parameters different periodic-like structures can be observed on the ablated surface. These structures show a dependence on the line energy, which has been identified as a fundamental control parameter. In dependence on this parameter several regimes with different behaviours of the process have been separated. These regimes are distinguishable as well in the surfaces obtained as in the signals gained by the measurement of the process emissions. Further aim is to identify the different modes of the system and reach a deeper understanding of the dynamics of the molten material in order to understand the formation of these surface structures. With this it should be possible to influence the system in the direction of avoiding structure formation even at high ablation rates. Relying on the results on-line monitoring and control of the process should be studied.
Towards a better understanding of laser beam melt ablation using methods of statistical analysis
(2002)
Laser beam melt ablation, as a contact free machining process, offers several advantages compared to conventional processing mechanisms. Although the idea behind it is rather simple, the process has a major limitation: with increasing ablation rate surface quality of the workpiece processed declines rapidly. The structures observed show a clear dependence of the line energy. In dependence of this parameter several regimes of the process have been separated. These are clearly distinguishable as well in the surfaces obtained as in the signals gained by the measurement of the process emissions which is the observed quantity chosen.
Inhalt:
- Kristian Köchy: Das Ganze der Natur – Alexander von Humboldt und das romantische Forschungsprogramm
- Gerhard Kortum: „Alexander von Humboldt“ als Name für Forschungsschiffe vor dem Hintergrund seiner meereskundlichen Arbeiten
- Ulrike Leitner: „Anciennes folies neptuniennes!“ Über das wiedergefundene „Journal du Mexique à Veracruz“ aus den mexikanischen Reisetagebüchern A. v. Humboldts
- Oliver Lubrich: „Egipcios por doquier“. Alejandro de Humboldt y su visión ‘orientalista’ de América
- Jose Alberto Navas Sierra: Humboldt y el ‘Área de Libre Comercio de las Américas (ALCA)’ – Un ejercicio de ‘ciencia humboldtiana
- Miguel Ángel Puig-Samper und Sandra Rebok: Un sabio en la meseta. El viaje de Alejandro de Humboldt a España en 1799
- Ingo Schwarz: Nachruf – Zur Erinnerung an Kurt-R. Biermann
As a non-contact process laser beam melt ablation offers several advantages compared to conventional processing mechanisms. During ablation the surface of the workpiece is molten by the energy of a CO2-laser beam, this melt is then driven out by the impulse of an additional process gas. Although the idea behind laser beam melt ablation is rather simple, the process itself has a major limitation in practical applications: with increasing ablation rate surface quality of the workpiece processed declines rapidly. With different ablation rates different surface structures can be distinguished, which can be characterised by suitable surface parameters. The corresponding regimes of pattern formation are found in linear and non-linear statistical properties of the recorded process emissions as well. While the ablation rate can be represented in terms of the line-energy, this parameter does not provide sufficient information about the full behaviour of the system. The dynamics of the system is dominated by oscillations due to the laser cycle but includes some periodically driven non-linear processes as well. Upon the basis of the measured time series, a corresponding model is developed. The deeper understanding of the process can be used to develop strategies for a process control.
As a non-contact process laser beam melt ablation offers several advantages compared to conventional processing mechanisms. During ablation the surface of the workpiece is molten by the energy of a CO2-laser beam, this melt is then driven out by the impulse of an additional process gas. Although the idea behind laser beam melt ablation is rather simple, the process itself has a major limitation in practical applications: with increasing ablation rate surface quality of the workpiece processed declines rapidly. With different ablation rates different surface structures can be distinguished, which can be characterised by suitable surface parameters. The corresponding regimes of pattern formation are found in linear and non-linear statistical properties of the recorded process emissions as well. While the ablation rate can be represented in terms of the line-energy, this parameter does not provide sufficient information about the full behaviour of the system. The dynamics of the system is dominated by oscillations due to the laser cycle but includes some periodically driven non-linear processes as well. Upon the basis of the measured time series, a corresponding model is developed. The deeper understanding of the process can be used to develop strategies for a process control.
We apply linear and nonlinear methods to study the properties of surfaces generated by a laser beam melt ablation process. As a result we present a characterization and ordering of the surfaces depending on the adjusted process parameters. Our findings give some insight into the performance of two widely applied multifractal analysis methods-the detrended fluctuation analysis and the wavelet transform modulus maxima method-on short real world data
HiN : Alexander von Humboldt im Netz = Festschrift für Margot Faak zu Ehren ihres 80. Geburtstages
(2006)
Inhalt:
- Die Mitarbeiter der Avh-Forschungsstelle: Margot Faak zum 80. Geburtstag
- Marie-Noëlle Bourguet: La fabrique du savoir. Essai sur les carnets de voyage d'Alexander von Humboldt
- Ottmar Ette: Unterwegs zu einer Weltwissenschaft? Alexander von Humboldts Weltbegriffe und die transarealen Studien
- Eberhard Knobloch: Erkundung und Erforschung - Alexander von Humboldts Amerikareise
- Herbert Pieper: Die Geognosie der Vulkane
- Christian Suckow: Prinz Humboldt
- Ursula Thiemer-Sachse: ¡Qué arte es comprender el arte ...! La visión del arte indígena de América por Alejandro de Humboldt
- Margot Faak: G. W. Leibniz im Urteil Alexander von Humboldts
- Regina Mikosch, Ingo Schwarz: Bibliographie zu Margot Faak