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  • 1
    Electronic Resource
    Electronic Resource
    On-line state estimation and control in glutamic acid production (1991)
    Springer
    Bioprocess and biosystems engineering 7 (1991), S. 35-39 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An automatic computer control system for glutamic acid production has been developed. A method based on empirical reaction subspace and singular value decomposition was presented for on-line estimation of cell concentration, glutamic acid, and total sugar. The only on-line measured state variable was the oxygen uptake rate. The estimated cell concentration was used as an index for the addition of penicillin. The estimated total sugar concentration was used for system identification. Adaptive control was then applied to manipulate the substrate feeding rate. The total sugar concentration was maintained at a given value during the period of fed-batch culture for glutamic acid production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00383576
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effective minority-carrier hole confinement of Si-doped, n+-n GaAs homojunction barriers (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 273-277 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical performance of Si-doped n+-n GaAs homojunction barriers grown by molecular-beam epitaxy (MBE) is characterized and analyzed. We employed a successive etch technique to study hole injection currents in GaAs n+-n-p+ solar cells. The results of the analysis show that minority-carrier holes in our MBE-grown material have a mobility of 293 cm2/V s for an n-type Si-doping level of 1.5×1016 cm−3 at 300 K. The interface recombination velocity for these homojunction barriers is estimated to be less than 1×103 cm/s, and it appears to be comparable to that recently observed for Si-doped n+-n GaAs homojunction barriers grown by metalorganic chemical vapor deposition. We present evidence that these n+-n GaAs homojunctions, unlike p+-p GaAs homojunctions, are almost as effective as AlGaAs heterojunctions in minority-carrier confinement, and that their electrical performance is not degraded by heavy doping effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343868
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence for band-gap narrowing effects in Be-doped, p-p+ GaAs homojunction barriers (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6361-6364 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical performance of Be-doped, p-p+ GaAs homojunction barriers is characterized and analyzed. The results of the analysis show that minority-carrier electrons, at 300 K, have a mobility of 4760 cm2/V s at a hole concentration of 2.3×1016 cm−3, and that the effective recombination velocity for these homojunction barriers is about 6×104 cm/s. We present evidence that this unexpectedly high recombination velocity is a consequence of an effective reduction in band gap due to the heavy impurity doping. The effective band-gap shrinkage in this Be-doped material grown by molecular-beam epitaxy appears to be comparable to that already observed for Zn-doped GaAs grown by metalorganic chemical vapor deposition. This work demonstrates that so-called band-gap narrowing effects significantly influence the electrical performance of GaAs devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342102
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  • 4
    Electronic Resource
    Electronic Resource
    Surface passivation effects of As2S3 glass on self-aligned AlGaAs/GaAs heterojunction bipolar transistors (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2113-2115 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A recently developed As2S3 chemical treatment was used to passivate the perimeters of self-aligned heterojunction bipolar transistors (HBTs). The As2S3 chemical treatment significantly lowered the base current resulting in a two order of magnitude reduction in the collector current density at which dc current gain was observed (β=1). No degradation with time has been observed in the electrical characteristics of the chemically treated HBTs. This absence of degradation is attributed to the impermeability to oxygen of the As2S3 glass which coats the perimeter of the HBT after chemical treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104114
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    Paper (German National Licenses)
    Fulltext
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