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  • 1
    Electronic Resource
    Electronic Resource
    Two-dimensional analysis of electrical breakdown in a nonuniform gap between a wire and a plane (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 41-50 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical breakdown of a gap between a wire (modeled as a hyperboloid) and a plane has been investigated numerically by solving the two-dimensional form of the diffusion flux equations for the charged particle number densities and Poisson's equation for the self-consistent electric field. Electron impact ionization, thermal ionization, and three-body recombination have been considered as the charged particle production and loss mechanisms. The electrode surfaces are considered to be absorbing and the initial density of the particles is small, but nonzero. A gap length of 0.5 mm is investigated and the gas medium is air or argon at atmospheric pressure. The temporal development of the profiles of ion and electron number densities, potential and electric field, and current growth on both the electrodes are presented when the applied voltage is 1500 and 2500 V for both positive and negative wires. When the wire is negatively biased, the peaks in the radial distribution of both of the charged particle densities near the wire occur off the axis except during the very early part of the breakdown. With positive polarity, the electron density maximum always occurs on the discharge axis, while for ions it moves away from the axis, later in the transient, due to the reverse particle drift in the electric field from the negative polarity case. The discharge spreads farther out into the ambient (almost two times the gap length) when the wire is negatively biased than with positive polarity. The effect of charge separation on the externally applied electric field is significant at voltages 2500 V and higher. Ionization is greater in argon than in air for a fixed potential difference between the electrodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343373
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  • 2
    Electronic Resource
    Electronic Resource
    Extended two-dimensional analysis of electrical breakdown between a wire and a plane (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4132-4138 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of a discharge between a wire and a plane has been simulated numerically through the development of large electron and positive ion number densities. When the number densities grow sufficiently large and equal a new region within the computational model is formed, within which the governing equations of the quasi-neutral region are solved for the common ion and electron number density and electric potential. Results for the temporal development of the quasi-neutral region, radial profiles of charged particle number density, electric potential, and electric field strength from discharge initiation to program termination are described. The quasi-neutral region is shown to develop first off of the discharge axis, above the wire-to-plane gap. Near the quasi-neutral region the electric field strength and electric potential are highly distorted and within the quasi-neutral region are greatly diminished.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349135
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of negative ions on electrical breakdown in a nonuniform air gap between a wire and a plane (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1349-1358 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical breakdown of an axisymmetric, atmospheric pressure air gap between a wire and a plane has been investigated for a gap length of 0.5 mm. O− and O−2 have been identified as the negative ions affecting the discharge development in air, besides electrons and positive ions, and have been included in the electrical breakdown model. Five coupled two-dimensional transient partial differential equations describing the discharge evolution in the air gap have been solved using a finite difference algorithm developed earlier. Temporal development of the charged particle number densities, electrostatic potential, electric field, and current at both the electrodes is presented when the wire is negatively biased at 2500 V. The impact of negative ions on gap breakdown has been assessed by comparing the results of analyses with and without negative ions. It is concluded that the negative ions have negligible effect during the early stages of the discharge development. However, as the discharge evolves, the negative ions cause a net loss of electrons from the discharge. The effect is most pronounced away from the discharge axis, where peaks in the electron density occur as breakdown proceeds. Radial spread of discharge and current growth rate are relatively unaffected by the presence of negative ions, but the magnitude of total current at the electrodes has been found to decrease by a decade when the negative ions are present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870734
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  • 4
    Electronic Resource
    Electronic Resource
    Breakdown of a wire-to-plane discharge: Transient effects (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 3532-3536 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A wire-to-plane discharge during the early phases of breakdown has been studied. The discharge has been modeled in a prolate spheroidal coordinate system with the wire shape taken as a hyperboloid of revolution. Four simultaneous coupled, time-dependent, nonlinear partial differential equations describe the electrical discharge. These are the conservation equations for ion and electron densities, the energy equation for electron temperature, and Poisson's equation for the self-consistent electric field. By solving this formulation subject to appropriate initial and boundary conditions, charged particle densities and temperature variations have been obtained as the ionization progresses in the discharge. The results show that both the electron temperature and the charged particle densities increase with the progress of ionization. The effect of different wire polarities is also examined. With a positive wire polarity, the increases in electron temperature and charged particle densities are confined to regions of the discharge in the vicinity of the wire tip. With a negative wire polarity, the breakdown occurs in the entire gap at a faster rate than with a positive wire polarity. The wire polarity affects the magnitude of energy transfer between the particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859732
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  • 5
    Electronic Resource
    Electronic Resource
    Electrode heating in a wire-to-plane arc (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 465-472 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A steady wire-to-plane electric discharge has been modeled in a prolate spheroidal coordinate system with the wire shape taken as a hyperboloid of revolution. A set of continuum conservation equations for the charged particle densities and temperatures together with Poisson's equation for the self-consistent electric potential describe the steady electric discharge process. These equations have been solved numerically to obtain ion and electron densities, temperature distribution, and electrode heat fluxes. Particle densities show the main body of the arc is quasineutral bounded by space charge sheaths at both electrodes. The temperature is greatest in a region around the discharge axis about one-third of the distance from the wire to the plane. Strong electric fields are concentrated in the electrode sheaths. The heat flux to the wire is sharply peaked near the tip but on the plane it decays slowly away from the discharge axis. The knowledge of heat transfer from the arc to the electrodes is useful in determining arc parameters that govern the ball formation process used in wire bonding of microelectronic semiconductor chips as well as welding processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860297
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  • 6
    Electronic Resource
    Electronic Resource
    Long-term clonidine effects on autonomic function in essential hypertensive man (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 25-32 
    Details
    ISSN: 1432-1041
    Keywords: clonidine ; hypertension ; baroreceptor reflex ; mode of action ; sympathetic activity ; urinary catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Acute studies of clonidine suggest that it lowers blood pressure by central enhancement of baroreflex sensitivity coupled with diminished evidence of sympathetic outflow, but longterm clonidine data have not been conclusive. We examined effects of one month of low dose clonidine (0.4 ± 0.15 mg/day) alone in 13 essential hypertensive men, assessing several biochemical indices of sympathetic function, as well as physiologic parameters, including baroreflex sensitivity, the cold pressor test, and the hypotensive response to alpha adrenergic blockade. Clonidine diminished mean arterial pressure (from 104±5 to 84±3 mmHg;p〈0.01), without associated changes in several biochemical parameters of sympathetic outflow (urinary excretion of catecholamines, metanephrines, and vanillylmandelic acid; allp〉0.1). Circulatory baroreflex function was not enhanced by clonidine, during either the amylnitrite test or the phenylephrine test, before or after parasympathetic blockade with atropine. The cold pressor test, an index of efferent sympathetic pressor function, was also unaltered. The enhanced mean arterial pressure response to phentolamine during clonidine therapy (from a fall of 14.8±4.3 to 39.4±5.2 mmHg,p〈0.01), suggested an increase in alpha adrenergic vascular tone, perhaps mediated by clonidine's alpha agonist properties in vascular smooth muscle. The antihypertensive mechanism of longterm low dose clonidine cannot reliably be ascribed either to baroreflex enhancement or to suppression of sympathetic outflow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558378
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  • 7
    Electronic Resource
    Electronic Resource
    Analytical importance of some secondary and threshold reactions induced in nuclear reactors (1991)
    Springer
    Journal of radioanalytical and nuclear chemistry 148 (1991), S. 155-161 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The feasibility of threshold and secondary reactions as analytical alternatives for some special elements is discussed. Examples of applications, at the author's laboratory for determination of lithium, fluorine, titanium and thallium are presented. The importance of threshold reactions as interferences of capture reactions is also discussed. The pairs of elements where the interference was experimentally evaluated were calcium and titanium, scandium and titanium; manganese and iron; copper and zinc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02060557
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  • 8
    Electronic Resource
    Electronic Resource
    Contribution of neutron activation analysis to a geochemical study of contamination by arsenic, antimony, selenium and molybdenum (1993)
    Springer
    Journal of radioanalytical and nuclear chemistry 170 (1993), S. 225-233 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A method for arsenic, antimony, selenium and molybdenum determination in water, loess and volcanic glasses, by radiochemical neutron activation analysis based on coprecipitation with Bi2S3 in hydrochloric medium, is described. The results of application to a study of natural contamination in the south-eastern region of the province of Córdoba, Republic of Argentina, are presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02134594
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of70Ge(n,p)70Ga and74Ge(n,p)74Ga reaction cross sections for a fission neutron spectrum (1996)
    Springer
    Journal of radioanalytical and nuclear chemistry 212 (1996), S. 353-359 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The fission neutron spectrum averaged cross-sections for the reactions70Ge(n,p)70Ga and74Ge(n,p)74Ga have been determined. The averages of four determinations are, respectively, (3.10±0.30) mb and (0.00938±0.00059) mb. The present values are, to the authors' knowledge, the first experimental data on the fission averaged cross-section for these reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02162650
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  • 10
    Electronic Resource
    Electronic Resource
    Use of the Absolute Parametric Method to Evaluate the Analytical Significance of Threshold Reactions on P, Si, Al and Mg by NAA (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 244 (2000), S. 417-423 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We investigated the use of threshold reactions on magnesium, aluminum, silicon and phosphorus to determine elemental concentrations and also to correct analytical interferences, using the parametric method. The reactor neutron spectrum averaged cross sections of the threshold reactions on these elements were referred to the (111±3) mb value for the 58Ni(n,p)58g+mCo reaction cross section. The results of the cross section measurements are: 25Mg(n,p)25Na, 1.57±0.12 mb; 28Si(n,p)28Al, 5.68±0.25 mb; 29Si(n,p)29Al, 3.02±0.15 mb; 30Si(n,α)27Mg, 0.1346±0.0090 mb; and 31P(n,α)28Al, 1.912±0.083 mb. The values for the cross sections of the following reactions: 24Mg(n,p)24Na, 1.441±0.092 mb; 27Al(n,p)27Mg, 3.84±0.18 mb; and 27Al(n,α)24Na 0.721±0.028 mb were re-measured to check the methodology. We present the application of these values to the analysis of some reference materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006760314629
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