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  • 1
    Digitale Medien
    Digitale Medien
    Unsteady heating of metallic particles in a rarefied plasma (1995)
    Springer
    Plasma chemistry and plasma processing 15 (1995), S. 199-219 
    Details
    ISSN: 1572-8986
    Schlagwort(e): Metallic particles ; unsteady heating ; free-molecule regime ; analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Analytical results are presented concerning the unsteady heating of a metallic spherical particle innnersed in a rarefied plasma. The results show that the tinte periods required for the solid-phase heating, melting, liquid-phase heating, and evaporation are all proportional to the particle radius. For estimating the time needed for the solid-phase heating and that for the melting, the additional heat transfer rmechanism due to the thermionic emission front the particle surface is usually negligible since the surface temperatures of the particle heated in the plasma are, in general, compartively low during those heating steps. Thermionic emission assumes its effect only as the higher surface temperatures of the heated particle are involved (e.g., higher than 4000 K), while radiation loss shows its effects at much lower wall temperatures. As the plasma temperature is comparatively low, radiation heat loss may restrict the surface temperature of a particle to such a low value that the effect of thermionic emission on the overall heating time can he neglected and complete evaporation of refractor y metallic particles becomes impossible. The uncertainty in the calculation of the effect of thermionic emission is associated with the choice of the value of the effective work function for the particle material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01459696
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  • 2
    Digitale Medien
    Digitale Medien
    Drag force acting on an evaporating particle immersed in a rarefied plasma flow (1995)
    Springer
    Plasma chemistry and plasma processing 15 (1995), S. 1-23 
    Details
    ISSN: 1572-8986
    Schlagwort(e): Drag force ; evaporating particle ; free-molecule regime ; analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Analytical expressions are presented for the drag force acting on an evaporating or nonevaporating particle immersed in a plasma flow for the extreme case of free-molecule flow regime and thin plasma .sheath. It is shown that the drag force on a spherical particle is proportional to the square of the particle radius and to the relative velocity between the particle and the bulk plasma at low speed ratios. The existence of a relative velocity between the particle and the plasma results in a nonuniform heat flux distribution with its rnaximum value at the frontal stagnation point of tire sphere. This nonuniform distribution of the local heat fux density causes a nonuniforrn distribution of the local evaporated-mass flux and vapor reaction force around the surface of an evaporating particle, and thus induces an additional force on the particle. Consequently, the drag force acting on art evaporating particle is always greater than that on a nonevaporating one. This additional drag force due to particle evaporation is more significant for nonmetallic particles and for particle materials with lower latent heat of evaporation and lower vapor molecular mass. It increases with increasing plasma temperature and with decreasing gas pressure at the high plasma temperatures associated with appreciable gas ionization. The drag ratio increases with increasing electron/heavy-particle temperature ratio at high electron temperatures for a two-temperature plasma.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01596679
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  • 3
    Digitale Medien
    Digitale Medien
    Plasma-particle momentum transfer under conditions of great knudsen numbers and thin plasma sheath (1995)
    Springer
    Plasma chemistry and plasma processing 16 (1995), S. S71 
    Details
    ISSN: 1572-8986
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Particle drag force and thermophoresis results previous obtained are revised by including modified expressions for ion and electron components of the surface pressure. The present analysis shows that there is almost no difference between non-evaporating metallic and nonmetallic particles in their drags and there is only a little difference between those particles in their thermophoretic forces. The effect of evaporation on thermophoretic and drag forces is still marked, but the drag or thermophoretic force ratio with to without accounting for evaporation assumes somewhat different values from those obtained previously and depends notably on whether the particle is metallic or nonmetallic at high plasma temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01512628
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  • 4
    Digitale Medien
    Digitale Medien
    Thermophoretic Force on a Small Particle Suspended in a Plasma with a Combined Specular and Diffuse Reflection at the Particle Surface (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 33-51 
    Details
    ISSN: 1572-8986
    Schlagwort(e): Thermophoresis ; nonevaporating or evaporating particle ; free-molecule regime ; combined specular and diffuse reflection ; sphere
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Additional kinetic-theory analytical results are presented concerning the thermophoretic force acting on a spherical nonmetallic or metallic, nonevaporating or evaporating particle suspended in a plasma for the extreme case of free-molecule regime and thin plasma sheath. A combined specular and diffuse reflection of the atoms incident on or formed in the ion–electron recombination process at the particle surface has been taken into account in this analysis as an extension of the previous paper (Xi Chen, J. Phys. D: Appl. Phys. 30, 826–841, 1997). It has been shown that the specular reflection fraction of gas particles at the surface does not affect the thermophoretic force acting on a nonevaporating, metallic or nonmetallic, spherical particle, but they affect significantly the evaporation-added thermophoretic force. The evaporation-added thermophoretic force decreases linearly with the increase of the specular reflection fraction, and the decreasing rate for a nonmetallic evaporating particle is much greater than that for a metallic one at high plasma temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021851815657
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  • 5
    Digitale Medien
    Digitale Medien
    On the Focussing and Transmission Properties of Electron Beam in High Power Microwave Sources Filled with Plasma (1999)
    Springer
    International journal of infrared and millimeter waves 20 (1999), S. 305-315 
    Details
    ISSN: 1572-9559
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Based on the electron movement principles the beam paraxial trajectory and space trajectory equation in drifting space filled with plasma are given in this paper. The space is divided into two areas(α and β, β contains β1 and β2), the behavior of electrons in these areas is studied. The equations are theoretically or numerically solved, the focussing and transmission properties are studied and some parameters affecting these properties are discussed in detail. The relativistic effect is also taken into account. The study shows that with plasma filled the beam can be focused efficiently and transmitted with high quality by optimally choosing the plasma filling fraction and the voltage. Plasma microwave electronics stemmed from 1949, however, it developed rapidly in recent years. In the process of high power microwave study, plasma is more and more introduced into microwave source. Because of the neutralization effect of plasma, the beam can transmit with high quality, even under weak or without magnetic field, it can propagate through drifting tube or slow wave structure by its self magnetic focusing force[1–2]. By making full use of this property, microwave devices without magnetic field system can be made, this leads to a decrease in volume and weight of the device. Some experiments show that this kind of device can promote the output power and efficiency obviously. However, because of the presence of plasma, the beam's behavior changes greatly compared to those under vacuum condition. It is important to study the properties of the beam in drifting space or slow wave structure filled with plasma for the development of the device.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021724022230
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  • 6
    Digitale Medien
    Digitale Medien
    On the Dispersion Properties of a Plasma Filled Rippled Boundary Resonator (1999)
    Springer
    International journal of infrared and millimeter waves 20 (1999), S. 559-566 
    Details
    ISSN: 1572-9559
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Under the condition of considering the plasma electrons redistribution and ion channel and the transverse oscillating of the beam after the REB incident, the dispersion equation of corrugated waveguide filled with plasma was obtained in this paper, its expressions under several conditions were also given. The results showed that whether consider these factors or not, the results would be quite different.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022680203679
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  • 7
    Digitale Medien
    Digitale Medien
    Cloning, expression and characterization of a UDP-galactose 4-epimerase from Escherichia coli (1999)
    Springer
    Biotechnology letters 21 (1999), S. 1131-1135 
    Details
    ISSN: 1573-6776
    Schlagwort(e): cloning ; E. coli ; expression ; α 1,3-galactosyltransferase ; UDP-galactose 4-epimerase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The gene galE encoding UDP-galactose 4-epimerase was cloned into E. coli BL21(DE3) from the chromosomal DNA of E. coli strain K-12. High expression of the soluble recombinant epimerase was achieved in the cell lysate. In order to evaluate the use of this epimerase in enzymatic synthesis of important α-Gal epitopes (oligosaccharides with a terminal Galα1,3Gal sequence), a new radioactivity assay (α1,3-galactosyltransferase coupled assay) was established to characterize its activity in producing UDP-galactose from UDP-glucose. Approximately 2700 units (100 mg) enzyme with a specific activity of 27 U mg−1 protein could be obtained from one liter of bacterial culture. The epimerase was active in a wide pH range with an optimum at pH 7.0. This expression system established a viable route to the enzymatic production of α-Gal oligosaccharides to support xenotransplantation research.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005678225031
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