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  • Artikel  (77)
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  • 1
    Digitale Medien
    Digitale Medien
    Mathematical modeling of high-power transferred arcs (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7757-7767 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The behavior of an argon arc in a transferred arc furnace with a cold cathode and anode has been investigated using an elliptic model with emphasis on a high-current, long arc (L=100–200 mm, I=500 A). Conservation equations for the laminar arc column are written assuming local thermodynamic equilibrium. The governing equations are solved by employing an efficient finite difference method. The anode is included in the calculation domain. Numerical calculations performed for a transferred argon arc show good agreement with temperature measurements obtained by emission spectroscopy. The results also indicate that, except in regions close to the anode, the arc behavior is parabolic. © 1994 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357953
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  • 2
    Digitale Medien
    Digitale Medien
    Nonequilibrium effects in supersonic induction plasma (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2622-2630 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Supersonic plasma jets find applications in plasma chemistry and plasma processing, metallurgy, experimental physics, and space technology. Usually the plasma in these jets deviates from chemical and thermal equilibrium. To optimize the industrial process detailed study of nonequilibrium effects in supersonic flow is required. In the article we apply numerical simulation to study the supersonically accelerated argon plasma flow downstream of the induction plasma torch. We compare the jets exhausting from two different convergent-divergent nozzles by means of a two-temperature model. The results show that the axial electron number density is rather convective flux controlled than recombination-ionization reaction controlled in both cases. However, the recombination resulting in electron gas heating is more essential in the jet flowing from the nozzle with a higher outlet Mach number. The composition of the jet exhausting from the nozzle with a lower outlet Mach number remains almost unchanged ("frozen") until the end of the first expansion zone. These results confirm that the chamber pressure and the nozzle design changing leads to the induction plasma jets with different chemical conditions. For low-pressure supersonic plasma, these conditions vary from frozen to recombining. The conclusion is that depending on the industrial process, one can choose the proper torch nozzle geometry to have nonequilibrium plasma with the required properties. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1432478
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  • 3
    Digitale Medien
    Digitale Medien
    A turbulent flow model for the rf inductively coupled plasma (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4178-4185 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A mathematical representation is given for the turbulent fluid flow and energy transfer in an rf induction plasma. The flow and temperature fields are obtained through the solution of the two-dimensional rotationally symmetric turbulent Navier–Stokes equations along with the energy and the one-dimensional Maxwell's equations for the electric and magnetic fields. The turbulent viscosity is determined using the standard k-ε model. Results are given for an argon plasma under atmospheric conditions. Different aspects of turbulent flows and their implications in rf plasmas are discussed. The results indicate the presence of both laminar and turbulent regimes in the same flow field. The effect of swirl in the plasma gas is to increase the overall turbulence level in the torch.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.343297
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  • 4
    Digitale Medien
    Digitale Medien
    Mathematical modeling of a free-burning arc in the presence of metal vapor (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3065-3070 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The transfer of energy between the plasma and the iron anode and the evaporation of metal were taken into account in modeling a short free-burning arc in argon at atmospheric pressure. The presence of metal vapor in the plasma modifies the electrical conductivity and the radiated power and leads to arc cooling in the anode region. In return, the arc cooling modifies the rate of vaporization of the anode and thus the calculated concentration of iron vapor in the arc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354624
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  • 5
    Digitale Medien
    Digitale Medien
    GIS in Public Health Practice (2005)
    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 20 (2005), S. 0 
    Details
    ISSN: 1477-9730
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1477-9730.2005.00333_1.x
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  • 6
    Digitale Medien
    Digitale Medien
    Effect of the presence of iron vapors on the volumetric emission of Ar/Fe and Ar/Fe/HZ plasmas (1994)
    Springer
    Plasma chemistry and plasma processing 14 (1994), S. 301-315 
    Details
    ISSN: 1572-8986
    Schlagwort(e): Volumetric emission ; argon plasma ; iron emission ; atmospheric plasma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract The net volumetric emission coefficient was calculated using the escape factor method for Ar/Fe and Ar/H2/Fe plasmas, at atmospheric pressure, over the temperature range from 3000 K to 30,000 K. The calculation involved 712 lines for Ar I, Ar II, and Ar III, 3481 lines for Fe I, Fe II, and Fe III, and 230 lines for H in the Ar/H2/Fe case. A semiempirical method was used for the determination of line profiles and line broadening. The results show a strong influence of the presence of even traces of iron vapors at low temperatures where the volumetric emission increases by several orders of magnitude. Special attention is given to self-absorption of the argon resonance lines which prevents the radiation from escaping within a few millimeters from the emission source.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01447083
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  • 7
    Digitale Medien
    Digitale Medien
    Acute toxicity of organophosphorus and organochlorine insecticides in laboratory animals (1979)
    Springer
    European journal of nutrition 18 (1979), S. 258-268 
    Details
    ISSN: 1436-6215
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Medizin
    Notizen: Summary The influence of acute poisoning with Dursban (O.P.I.) and D.D.T. (O.cl.I.) on serum enzymes and histopathological examination of the liver, kidney and testes was investigated in albino rats. Two repeated i.p. injections of Dursban in a dose of half the LD 50 resulted in a significant increase in serum GOT, GPT and alkaline phosphatase activity and a decrease of cholinesterase. In case of DDT, two doses of 150 mg/kg orally resulted in a significant increase in the activity of serum GPT only, while three doses increased serum GOT and GPT. No significant change was observed in serum alkaline phosphatase and cholinesterase activity. Regarding the pathological examination it was found that in animals treated with Dursban there was liver necrosis of mid-zonal type and fatty change at the periphery. In case of DDT the liver cells lost their radial arrangements and showed fatty change. There was cellular infiltration in the centre, mostly mononucleolar cells. In both insecticides there was necrosis of some of the seminiferous tubules of the testes and cloudy swelling of the convoluted tubules of the kidney. Histochemical study of the liver in animals treated with Dursban showed that glycogen was deposited at one side of the cell. However, there was depletion of glycogen around the central vein. In liver treated with DDT there were large globules of fat inside the liver cells, indicating increased fat content compared to control liver, where there were tiny minute droplets of fat.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02020516
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  • 8
    Digitale Medien
    Digitale Medien
    Morphological study of hydroxyapatite nanocrystal suspension (2000)
    Springer
    Journal of materials science 11 (2000), S. 523-531 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract Nanometer size hydroxyapatite (HA) crystals are prepared by a wet chemical precipitation method at different synthesis temperatures and with various reactant addition rates. The resulting aqueous suspensions are studied in terms of morphology (transmission electron microscope, specific surface area), phase (X-ray diffraction, electron diffraction and infrared spectroscopy) and rheological properties. This work shows that shape, size and specific surface area of the HA nanoparticles are very sensitive to the reaction temperature and also to the reactant addition rate. The measured pH at the end of synthesis, which is strongly linked with the reactant addition rate, is a key parameter which can be used to determine the purity of the synthesized HA nanocrystal and also for the stabilization (dispersion) of the suspension. HA nanoparticles synthesized at low temperature (T 〈 6°C) are monocrystalline. A transition temperature (T=60 °C) can be defined as a limit for the synthesis of monocrystalline HA nanocrystals, above this critical temperature nanocrystals become polycrystalline. HA monocrystals adopt a needle shape and are oriented following the c-axis of the hexagonal HA structure. The as-synthesized suspension is then concentrated and the effect of a dispersing agent addition, which is needed to get a high solid/liquid ratio coupled with good flowability of the suspension, is also shown, because this suspension is used in the suspension plasma spraying process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008918110156
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  • 9
    Digitale Medien
    Digitale Medien
    Influence of plasma modification of titanium carbide powder on its sintering properties (1995)
    Springer
    Journal of materials science 14 (1995), S. 1694-1697 
    Details
    ISSN: 1573-4811
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00422678
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  • 10
    Digitale Medien
    Digitale Medien
    Laser Doppler anemometry under plasma conditions. Part II. Measurements in an inductively coupled r.f. plasma (1988)
    Springer
    Plasma chemistry and plasma processing 8 (1988), S. 133-144 
    Details
    ISSN: 1572-8986
    Schlagwort(e): Laser Doppler anemometry ; induction plasma ; particle trajectory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Laser Doppler anemometry is used for the measurements of the plasma and particle velocity profiles in the coil region of an inductively coupled r.f. plasma. Results are reported for a 50 mm i.d. induction plasma torch operated at atmospheric pressure with argon as the plasma gas. The oscillator frequency is 3 MHz and the plate power is varied between 4.6 and 10.5 kW. Plasma velocity measurements are obtained using a fine carbon powder as a tracer. Measurements are also given for larger silicon particles ( $$\bar d_p = {\text{ }}33{\text{ }}\mu m and \sigma = 13 \mu m$$ ) centrally injected into the discharge under different operating conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01016153
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