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  • 1
    Electronic Resource
    Electronic Resource
    Voronoi network model of ZnO varistors with different types of grain boundaries (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6516-6522 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical transport in zinc oxide varistors is simulated using two-dimensional Voronoi networks. The networks are assumed to contain randomly distributed grain boundaries of three electrical types: (1) high nonlinearity (i.e., "good'') junctions; (2) poor nonlinearity (i.e., "bad'') junctions; and (3) linear with low-resistivity (i.e., ohmic) junctions. These type classifications are those found in experimental measurements. By varying the type concentrations, the simulated current density versus electric field (J–E) characteristics can be made to conform to the different experimentally observed characteristics of ZnO varistors. These characteristics include the sharpness of switching at the transition between ohmic and nonlinear J–E response (i.e., knee region), as well as the degree of nonlinearity. It is shown that the reduction of the nonlinearity coefficient of bulk varistors, relative to that of isolated grain boundaries, can be explained only by the presence of "bad'' varistor junctions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363645
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  • 2
    Electronic Resource
    Electronic Resource
    Radio-frequency antenna studies for high-current, high-duty-cycle, H− volume sources (abstract) : Papers from the Ninth International Conference on Ion Sources (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1007-1007 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Spallation Neutron Source requires an ion source capable of delivering a high-current (∼50 mA) H− beam with a 6% duty cycle continuously for the three weeks between the scheduled maintenance periods. The cesium-enhanced, multicusp volume ion source under development on the integrated test facility at LBNL delivers H− ion currents up to 50 mA, increasing approximately linearly with the rf power. Initial experience using porcelain-coated copper antennas, however, indicates lifetimes will fall below the desired three-week period, mostly limited by antenna failures. In an effort to improve our understanding of the antenna limitations, we are in the process of developing an antenna test dome, which will allow us to visually observe and study the rf-initiated discharge at low-power levels. We hope to be able to test antennas for invisible defects by observing and measuring the onset of the discharge. In addition, we are planning to test different antennas. Results will be presented at the meeting. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1432464
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  • 3
    Electronic Resource
    Electronic Resource
    USE OF CHEMICAL SENSOR ARRAYS FOR FOOD AND FRAGRANCE ANALYSIS (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of sensory studies 5 (1990), S. 0 
    Details
    ISSN: 1745-459X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many workers have recently developed and demonstrated the use of gas sensor arrays to detect and recognize a variety of compounds. In general, a pattern recognition approach is used in which the signature of an unknown sample is compared to a library of signatures of known substances. All of these efforts have shown varying degrees of success when applied to pure compounds. Unfortunately, flavors and fragrances are never pure compounds. A prototype gas sensor array has been constructed and tested with various mixtures of interest. The results are discussed in terms of their implication to the food and fragrance industry.Early experiments on gasoline-alcohol mixtures demonstrated that the signatures do not follow a rule of mixing, but were more strongly influenced by the more volatile and/or more reactive component. This led us to examine the behavior of alcohol-water mixtures for possible quality control in the distilling industry. We discovered that the signature of alcohol dominated even at concentrations as low as ten percent. Preliminary experiments were also performed to see if the prototype sensor array could be used to automatically detect rancidity in dairy products.Flavorings and essential oils are in many cases even more complex mixtures. The behavior of representative classes of these substances were characterized in an attempt to understand their signatures on the basis of their constituents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-459X.1990.tb00485.x
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