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- ItemAerosol number size distributions from 3 to 500 nm diameter in the arctic marine boundary layer during summer and autumn(Copenhagen : Blackwell Munksgaard, 1996) Covert, D.S.; Wiedensohler, A.; Aalto, P.; Heintzenberg, J.; Mcmurry, P.H.; Leck, C.Aerosol physics measurements made onboard the Swedish icebreaker Oden in the late Summer and early Autumn of 1991 during the International Arctic Ocean Expedition (IAOE-91) have provided the first data on the size distribution of particles in the Arctic marine boundary layer (MBL) that cover both the number and mass modes of the size range from 3 to 500 nm diameter. These measurements were made in conjunction with atmospheric gas and condensed phase chemistry measurements in an effort to understand a part of the ocean-atmosphere sulfur cycle. Analysis of the particle physics data showed that there were three distinct number modes in the submicrometric aerosol in the Arctic MBL. These modes had geometric mean diameters of around 170 nm. 45 nm and 14 nm referred to as accumulation, Aitken and ultrafine modes, respectively. There were clear minima in number concentrations between the modes that appeared at 20 to 30 nm and at 80 to 100 nm. The total number concentration was most frequently between 30 and 60 particles cm-3 with a mean value of around 100 particles cm-3, but the hourly average concentration varied over two to three orders of magnitude during the 70 days of the expedition. On average, the highest concentration was in the accumulation mode that contained about 45% of the total number, while the Aitken mode contained about 40%. The greatest variability was in the ultrafine mode concentration which is indicative of active, earby sources (nucleation from the gas phase) and sinks; the Aitken and accumulation mode concentrations were much less variable. The ultrafine mode was observed about two thirds of the time and was dominant 10% of the time. A detailed description and statistical analysis of the modal aerosol parameters is presented here.
- ItemSelf-stabilization of the biosphere under global change: A tutorial geophysiological approach(Abingdon : Taylor and Francis Ltd., 1997) Von Bloh, W.; Block, A.; Schellnhuber, H.J.A 2-dimensional extension of the simple Lovelock-Watson model for geosphere-biosphere feed-back is introduced and discussed. Our enriched version also takes into account various pertinent physical, biological, and civilisatory processes like lateral heat transport, species competition, mutation, germination, and habitat fragmentation. The model is used as a caricature of the Earth System, which allows potential response mechanisms of the biosphere to environmental stress (as generated, e.g., by global warming or anthropogenic land-cover change) to be investigated qualitatively. Based on a cellular automaton representation of the system, extensive calculations are performed. They reveal a number of remarkable and, partially, counter-intuitive phenomena: our model biosphere is able to control almost perfectly the geophysical conditions for its own existence. If the environmental stress exceeds certain thresholds, however, life breaks down on the artificial planet via a first-order phase transition, i.e., in a non-reversible way. There is a close connection between self-stabilizing capacity, biodiversity and geometry of habitat fragmentation. It turns out, in particular, that unrestricted Darwinian competition, which reduces the number of co-existing species, is the best guarantee for survival of the artificial ecosphere as a whole.
- ItemGeometry of heteroclinic cascades in scalar parabolic differential equations(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 1998) Wolfrum, MatthiasWe investigate the geometrical properties of the attractor for semilinear scalar parabolic PDEs on a bounded interval with Neumann boundary conditions. Using the nodal properties of the stationary solutions which are determined by an ordinary boundary value problem, we obtain crucial information about the long-time behavior for the full PDE. Especially, we prove a criterion for the intersection of strong- stable and unstable manifolds in the finite dimensional Morse-Smale flow on the attractor.
- ItemThe feedback of midlatitude waves onto the Hadley cell in a simple general circulation model(Milton Park : Taylor & Francis, 1996) Becker, E.; Schmitz, G.; Geprägs, R.We present self-consistent comparisons of axissymmetric and 3-dimensional simulations of the tropospheric circulation under idealized physical conditions. These reveal a feedback of transient eddies onto the Hadley circulation which, first, strongly depends on equatorial heating and, second, is in case of realistic heating quite different from prescribed eddy forcing. A quantitative estimation for the eddy-induced mixing of vorticity into the poleward flow of the Hadley cell is given. The proposed relation is in accordance with observations. It is derived from the computational result that eddy momentum flux convergence is of the same order as the equatorward flux of relative vorticity generated by the Hadley circulation. Evaluation of the local budgets of sensible heat gives rise to a clear picture of how the poleward heat transports due to Hadley circulation and transient eddies interlock. This mechanism is found to be essential for an interpretation of the eddy feedback.
- Itemstudy of structural modification in extruded and heat-treated lithium disilicate glasses by the method of radiation color centers chronospectroscopy(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Arbuz, Valerii I.; Carl, Gunter; Rüssel, Christian; Durschang, BernhardSamples of extruded and non-extruded lithium disilicate glasses were studied. Extruded glass samples were cut out along and across the extrusion axis of fmished cylindrical rods. For all the samples, spectra of radiation-induced absorption, Δα(E), were measured for various time instants after the cessation of X-irradiation. On the data basis obtained, kinetic dependences. Δα = f(t), were plotted and analyzed. In the diagram "Δα versus lgt", they are represented by straight hnes. Each of them is falling down with its own constant slope a. These a's are rate parameters of the decay of radiation color centers (CCs). They appear to be functions of average distances between recombinating electron and hole CCs. The above α-parameter decreases when passing from the longitudinal cut extruded glass sample to the sample of the non-extruded glass and finally to the transversely cut extruded glass sample. These data mean that, in the course of extrusion, the glass structure becomes less dense in the axial direction of extruded glass rods and more dense in the radial one. Α 4-hour heat treatment at 465 °C (≈5°C above the glass transformation temperature, Tg) eliminated the above anisotropy of radiation properties in extruded glasses and forced their anisometric structures to return to the isometric State characteristic of the non-extruded glass.
- ItemLaser glass level measurement - Possibilities and perspectives using the Horn System(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Meindl, Stephan[no abstract available]
- ItemChemical surface and thin film analysis in glass coating(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Oechsner, HansAfter a short overview of recent analytical techniques for compositional surface analysis and the determination of concentration depth profiles, the principle, the Instrumentation and the Performance of the routinely used electron spectroscopic and mass spectrometric methods, namely photo- and Auger electron spectroscopy as well as secondary ion and secondary neutral mass spectrometry, are described. The application of these techniques to electrically insulating surfaces and layer structures is particularly emphasized by corresponding practical examples. Secondary neutral mass spectrometry is specifically addressed with regard to the potentialities of the novel high-frequency mo d e of electron-gas secondary neutral mass spectrometry for quantitative composition analysis and high-resolution depth profiling of electrically nonconducting sample structures.
- ItemChemical composition of medieval glass from excavations in West Germany(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Wedepohl, K. HansInvestigations of excavated glass fragments from the Roman-Frankish cemetery at Krefeld-Gellep, the Carolingian imperial palace with glassworks at Paderborn, the monasteries and towns of Corvey, Höxter and Brunshausen-Gandersheim and several glassworks in the Bramwald, Hils, Spessart and Eichsfeld areas allow conclusions on the sequence of major medieval glass types. Exhaustion of Imports of trona-soda or soda raw glass and increased needs caused the introduction of woodash as domestic alkali and earth alkali source for glass manufacture at about 800 AC. Early woodash glass from 800 to 1000, woodash glass from about 1000 to 1400 and woodash-lime glass from about 1400 to post-medieval times were the major glass types. They were accompanied by minor Imports of soda-lime and soda-ash glass objects, the latter since about 1300. From about 1100 to 1400 woodash-lead and lead glass have been produced from the P bO byproducts of the silver metallurgy. Galena from the Harz Mountains was a major source of lead for lead glass in northwestern Europe. The average production of a medieval glassworks was in the order of 15 t glass per year and its requirements for ash and fuel about 30001 wood. The number of glassworks in Germany during the late medieval period (moving after 5 to 30 years from one to another location) is tentatively estimated to be in the order of 40. Their main furnaces were constructed for about 1400 C working temperature. The occurrence of the medieval chemical glass types in a sequence allows some rough dating of glass fragments.
- ItemÖfen zur vollelektrischen Schmelze von Glas in Deutschland(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Fleischmann, BernhardDie HVG verschickte im November 1993 einen Fragebogen an alle Betreiber von vollelektrischen Wannen in Deutschland mit einem Durchsatz von mehr als 10 t/d. 24 ausgefüllte Fragebögen wurden der HVG bis zum April 1994 zurückgesandt. Auch 6 vollelektrische Öfen von Nichtmitgliedern sind in die Auswertung mit aufgenommen. Ausgewertet wurden die Wannengröße (Durchmesser und Badtiefe), Art und Material der Heizelektroden, Gemengeeinlage, Gesamtscherbenanteil, Glasart und gefertigtes Erzeugnis, Schmelzleistung und spezifischer Wärmeverbrauch. In 8 Wannen wird Borosilicatglas erschmolzen, in 6 Kalk-Natronsilicatglas, in 4 Bleikristall- und in 2 Kristallglas, in 2 weiteren C-Glas und in einer Opalglas. Gefertigt werden Glasbehälter, Rohre, Wirtschaftsglas, Fasern, Streuscheiben und Beleuchtungsglas. Sowohl bei der Wannenfläche als auch bei der Badtiefe läßt sich in Abhängigkeit von der maximalen Tagestonnage eine gemeinsame Tendenz bei fast allen Öfen erkennen. Der spezifische Wärmeverbrauch sinkt mit steigendem Durchsatz bzw. größerem Wannenvolumen, da das Verhältnis von Oberfläche zu Wanneninhalt besser wird damit die Wandverluste anteilmäßig geringer werden. An 20 Wannen werden Molybdänelektroden und an 4 Wannen Zinnoxidelektroden eingesetzt. Diese Heizelektroden sind an 9 Wannen als Seiten- und Bodenelektroden eingebaut, an 7 Wannen als Seitenelektroden, an 5 Wannen als Bodenelektroden und an 3 Wannen als Topelektroden.
- ItemModelling of time strength behaviour of soda-lime-silica glass in moist environments(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Höhne, Lutz; Ullner, ChristianThe time strength behaviour of alkali silicate glasses depends on the environmental media and external stresses during aging as well as on the type of initial crack (kind of damage). An extended crack growth model based on the competing processes of crack growth and its retardation due to stress-enhanced alkali leaching in moist media has been implemented on a computer. Considering residual contact stresses, this model is able to simulate crack arrest, strength increase (or decrease, respectively) during aging under load, static and dynamic fadgue including strength distribudons of various soda-lime-silica glass applicadons. Lifetime predicdon of static fatigue can be improved up to about 10 years.