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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Vacuum refining of copper matte

Allaire, André. January 1986 (has links)
No description available.
72

Superconducting fault current limiter with integrated vacuum interrupter

Pei, Xiaoze January 2012 (has links)
Fault current levels in land-based power systems are generally rising because of the increase in renewable generation capacity. Once the fault current level exceeds the capacity of the existing protection equipment, expensive upgrades become necessary. In order to avoid excessively expensive equipment upgrades, many fault current limitation techniques have been investigated. This thesis presents the work conducted on the design, manufacture and testing of a resistive superconducting fault current limiter (SFCL) with an integrated fast-acting vacuum interrupter. The practical application of magnesium diboride (MgB2) in round wire form was also investigated. A single-strand MgB2 SFCL coil was investigated and demonstrated repeatable and reliable current-limiting action. In practical power system applications, the development of SFCLs needs a considerable scale-up of the current-carrying capability of the MgB2 wire samples. One option is to use parallel wires in order to carry current levels in the kA range. The behaviour of a prototype three-strand MgB2 SFCL coil was assessed, which showed that each of the three wire strands shared the current approximately equally and demonstrated reliable and repeatable behaviour during testing. The MgB2 SFCL coil with multiple wire strands in parallel shows considerable potential as a practical method for scaling-up the current levels required for power system applications. One of the significant operational issues for resistive SFCLs is the temperature recovery time after a fault is cleared. A vacuum interrupter was integrated therefore into the SFCL system to quickly remove the superconducting coil from the circuit during a fault condition and allow the superconducting coil to recover whilst a bypass resistor acted as a current limiting resistor. A fast-acting actuator and its control circuit were designed and manufactured to control the operation of the vacuum interrupter. The SFCL with a prototype vacuum interrupter was successfully tested to validate the design process. The energy dissipated in the superconducting coil was significantly reduced by the fast operation of the vacuum interrupter and the recovery time significantly reduced. This research demonstrates the potential of a cost-effective and compact SFCL for the power system applications.
73

Vacuum refining of copper matte

Allaire, André January 1986 (has links)
No description available.
74

The effect of vacuum cleaning upon household atmospheric dust

Brethour, Sylvia Gay. January 1966 (has links)
LD2668 .T4 1966 B75 / Master of Science
75

Fabrication and characterization of ultrasmall tunnelling devices

Wong, Terence Kin Shun January 1992 (has links)
No description available.
76

ANALYTICAL MASS SPECTROMETRY WITH A SELECTIVE VACUUM ULTRAVIOLET PHOTOIONIZATION SOURCE.

HUTH, THOMAS CARL. January 1986 (has links)
The vacuum ultraviolet molecular hydrogen laser is evaluated as a selective ion source for analytical mass spectrometry of easily-ionized compounds. The types of compounds ionized below the photon energy of 7.8 eV include polynuclear aromatic hydrocarbons, and many amines and nitrogen-containing heterocycles. The latter two categories encompass a large number of pharmaceuticals and drugs of abuse. H₂ laser photoionization produces parent molecular ions only, for all compounds studied thus far. Selectivity of the threshold photoionization process is very high, as compounds within as little as 0.2 eV above the threshold are completely rejected. The ability of the technique to discriminate against interfering matrix components is demonstrated for both simple synthetic and complex "real world" mixtures. Easily interpreted spectra are obtained from simple extracts of spiked coffee, beer, soy sauce, urine and blood serum. The most important interference is shown to be electron impact ionization arising from acceleration of stray electrons in the ion source. Most of this ionization is caused by low-energy secondaries generated when stray primaries are collected by the ion source electrodes. The primaries are produced mainly by interaction of scattered laser radiation with metal surfaces. This interference can be controlled through proper instrumental design.
77

UHV studies of the adsorption of small adsorbate molecules on low index platinum single crystals

Baily, Christopher John January 2003 (has links)
No description available.
78

Thermally enhanced colloidal processing of #alpha#-alumina

Murfin, Alice M. January 1995 (has links)
No description available.
79

The theory of vacuum tube oscillators and an analysis of a high power signal generator

Kendall, Harry W. Unknown Date (has links)
No description available.
80

Gauge invariant calculation of vacuum polarization phenomena in quantum electrodynamics

Herrera, John Chardon January 1964 (has links)
Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / A technique capable of describing in detail the various phenomena arising in the limit of low energy photons because of the polarization of the vacuum is obtained by quantizing the gauge invariant effective interaction Lagrangian. This approach then permits the use of the standard covariant calculational tools of Quantum Electro-dynamics. We first apply this technique to the computation of the differential cross section for low energy photon-photon scattering. The well known Euler cross section is thereby derived in a direct manner. As a second example, the probability of the triple breakup of a free photon because of vacuum polarization is explicitly shown to vanish. This, however, is primarily due to the kinematics of the photon breakup. For a third application we calculate the differential cross section for the scattering of a low energy photon from the Coulomb field of a nucleus, that is, Delbruck scattering. Here the exact low energy differential cross section is obtained. However, though the present technique determines completely the angular dependence, it is necessary to introduce a momentum cutoff in the Coulomb field in order to obtain a finite value for the coefficient in front of the angular dependence. A comparison of the resulting expression for the cross section with that for forward scattering given by Rohrlich and Gluckstern (1952) gives the numerical value of this coefficient. A brief comparison between the angular distribution for Delbruck scattering and that for a combination of an electric and magnetic dipole radiator is presented. / 2031-01-01

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